Reaction of polynuclear acetylide clusters. Synthesis of pentanuclear heterometallic clusters by addition of [M(CO)3(CCPh)(-C5H5)] to [MOs3(CO)11(CCPh)(-C5H5)](M = Mo or W). Crystal structures of [Mo2Os3(CO)11(CCPhCCPh)(-C5H5)2]?2H2O and [MoWOs3(CO)8(?4-C

(1)

Rotation of Coordinated Acetylide Ligands on the Triangular

Surface of Trinuclear Heterometallic Clusters

Der-Kweng Hwang and Yun

Chi'

Department of Chemistry, National Tsing Hua University, Hsinchu 30043, Taiwan, Republic of China

Shie-Ming Pengt and Gene-Hsiang Lee

Department of Chemistry, National Taiwan University, Taipei 10764, Taiwan, Republic of China Received February 26, 1990

Convenient and widely applicable synthetic routes to the trinuclear heterometallic acetylide complexes

LMM',(CO),(C=CR) have been developed. These routes involve the reaction of metal acetylides LM-

(CO),(C=CR) (L

=

Cp and Cp*; M

=

W and Mo; R

=

Ph, C5H4F, C5H,0Me, tBu, and "Pr) with

Os,-

(CO),&NCMe), and with RU,(CO)~~.

For the W0s2 derivatives prepared (1-31,

the acetylide ligand adopts

an asymmetric arrangement in which the acetylide C-C vector is coordinated to one of the W-Os bonds.

For all the WRu2 derivatives

(4-91,

the acetylide ligand adopts both the asymmetric (with its C-C bond

orthogonal to one of the W-Ru bonds) and the symmetric arrangement (with its C-C bond orthogonal

to the unique Ru-Ru bond) and undergoes rapid interconversion in solution. For the MoRu2 derivatives

(10,

1 l ) ,

the acetylide favors the asymmetric form in both solution and the solid state; however, when the

**substituent R and the ligand L are replaced by a bulky tert-butyl group and Cp* ligand, respectively (13),**

the symmetric form becomes the dominant species. The dynamic 13C NMR studies suggest that the acetylide

ligand of the W0s2 derivatives is static but, in the asymmetric MoRu2 derivatives (10,

111,

the acetylide

is fluxional and undergoes migration from one Mo-Ru edge to the other. The preference of the site selectivity

for the acetylide ligand has also been studied by variation of the transition-metal atoms (M and M'), the

accessory ligand (L), and the substituent (R). The structures of the complexes CpWOs2(CO),(C=CPh)

(l),

CpWRu2(CO),(C*Ph)

(4),

and CpMoRu2(CO),(C=CPh) (10) have been determined by single-crystal

X-ray diffraction studies. Crystal data for 1: space group

PZ1/c;

a = 8.332 (3)

A,

b

= 14.543 (4)

A,

c =

17.819 (5)

A,

0

= 94.46 (3)O, 2 = 4;

final

R

= 0.068, R, = 0.090,

and GOF

= 1.768.

Crystal data for

4:

space

group

P2,/n;

a = 12.476 (1)

A,

b

=

13.216 (4)

A,

c = 13.395 (4)

A, 0

= 97.99 (2)O,

2

= 4;

final R

= 0.029,

R

= 0.027,

and GOF

= 1.583.

Crystal data for

10:

space group P 2 J c ;

a = 12.770 (4)

A,

b = 8.188 (4)

AYc = 21.313 (4)

A,

0

= 91.26 (2)O, 2 = 4;

final R

= 0.030,

R,

= 0.031,

and GOF =

2.34.

Introduction

The C2 hydrocarbyl ligands occupy a key position in the

development of dinuclear, trinuclear, and polynuclear

organometallic chemistry. This position results partially

from the belief that the chemistry of the Cz hydrocarbyl

ligands in the organometallic complexes is analogous to

that of small hydrocarbon intermediates adsorbed on metal

surfaces. Among the many interesting properties of the

C2 ligands is their mobility on the coordination sphere of

the transition-metal complexes. Related studies on the C2

hydrocarbyl moieties have attracted the attention of many

theoretical and synthetic chemists.

Schilling and Hoffmann have reported the extended

Huckel calculation of some hydrocarbons on the face of

trinuclear homometallic transition-metal comp1exes.l

For

the trinuclear

C2

vinylidene complexes, Norton and Mislow

have reported the disrotatory correlated rotation about the

Co3(CO),-C vector

and

C-CHR bond in Co3(CO),(CCHR)+

by variable-temperature 13C NMR studiesS2 The motion

of

the

vinylidene

ligand

in

H30~3(C0)9[C=

CCHzCH2CH2]+

has also been de~cribed.~

For the related

C2 alkyne complexes, the migration of the perpendicular

alkyne ligand

(l.~~-77~-1

mode) to the parallel position

( ~ ( ~ - 7 ~ -

I(

mode) upon electrochemical reduction has been

documented for some trinuclear c l u ~ t e r s , ~

whereas the

alkyne ligand of the dinuclear heterometallic complexes

CpNiCo(CO),(RC=CR')

undergoes rotational motion

about the Ni-Co bond ~ e c t o r . ~

In addition, both Stone

and co-worker@ and Shapley and co-workers' have de-

scribed the "windscreen-wiper" type of motion for the

coordinated alkyne ligand on a W20s triangular face.

I

'To whom inquiries concerning the X-ray crystallographic work should be addressed.

0276-7333/90/2309-2709$02.50/0

Rosenberg and co-workers have reported the similar free

rotation of the alkyne on the phosphine-substituted tri-

osmium fragments.8

Recently, there has been growing research activity in the

area of syntheses of acetylide cluster c o m p l e x e ~ . ~

How-

ever,

to

our knowledge, only a few papers have focused on

the fluxional behavior of the acetylide ligand.l0 The

reason is that, in the past, only the homometallic trinuclear

acetylide complexes have been prepared. Therefore,

it

is

difficult to distinguish whether the fluxional behavior of

a target molecule is due to the rotation of acetylide or to

(1) Schilling, B. E. R.; Hoffmann, R. J. Am. Chem. SOC. 1979, 101,

(2) Edidan, R. D.; Norton, J. R.; Mislow, K. Organometallics 1982, I ,

4687.

561

--_.

(3) Koridze, A. A.; Kizas, 0. A.; Kolobova, N. E.; Petrovskii, P. V.;

Fedin. E. I. J. Ormnomet. Chem. 1984.265. C33: 1984.272. C31.

(4) 'Osella, D.; Coberto, R.; Montangero, P.; Zanello,

P.;

Cinquantini,

(5) Jaouen, G.; Marinetti, A.; Saillard, J.-Y.; Sayer, B. G.; McGlinchey,

A. Organometallics 1986, 5, 1247.

M. J. Organometallics 1982, I, 225.

(6) Busetto, L.; Green, M.; Hesser, B.; Howard, J. A. K.; Jeffery, J. C.;

Stone, F. G. A. J. Chem. SOC., Dalton Trans. 1983, 519.

(7) Shapley, J. R.; Park, J. T.; Churchill, M. R.; Bueno, C.; Wasserrnan,

H. J. J. Am. Chem. SOC. 1981,103, 7385.

(8) Rosenberg,

E.;

Bracker-Novak, J.; Gellert, R. W.; Aime, S.; Go-

betto, R.; Osella, D. J. Organornet. Chem. 1989, 365, 163.

(9) (a) Carty, A. J. Pure Appl. Chem. 1982, 54, 113. (b) Aime, S.;

Osella, D.; Deeming, A. J.; Lanfredi, A. M. M.; Tiripicchio, A. J. Orga-

nomet. Chern. 1983,244, C47. (c) Dawoodi, Z.; Maya, M. J.; Henrick, K.

J. Chem. SOC., Dalton Trans. 1984,1769. (d) Deeming, A. J.; Donovan-

Mtunzi, S.; Hardcastle, K. J. Chem. SOC., Dalton Trans. 1986, 543. (e)

Boyar,

E.;

Deeming, A. J.; Kabir, S. E. J. Chem. SOC., Chem. Commun.

1986, 577. (f) Nucciarone, D.; MacLaughlin, S. A.; Taylor, N. J.; Carty,

A. J. Organometallics 1988, 7,106. (9) Galindo, A.; Mathieu, R.; Cami-

nade, A.-M.; Majoral, J.-P. Organometallics 1988, 7, 2198. (h) Chi, Y.;

Hwang, D.-K.; Chen, S.-F.; Liu, L.-K. J. Chem. SOC., Chem. Commun.

1989, 1540. (i) Farrugia, L. J. Organometallics 1990, 9, 105. (10) (a) Jangala, C.; Rosenberg, E.; Skinner, D.; Aime, S.; Milone, L.;

Sappa, E. Inorg. Chem. 1980,19, 1571. (b) Predieri, G.; Tiripicchio, A,;

Vignali, C.; Sappa, E. J. Organornet. Chem. 1988, 342, C33.

0

1990

American Chemical Society

Downloaded by NATIONAL TAIWAN UNIV on August 12, 2009

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2710

Organometallics, Vol. 9, No.

IO,

1990

Hwang et al.

the mobility of another accessory ligand, such as inter-

metallic CO scrambling."

In this paper, we report the

preparation and crystal structure of a series of trinuclear

WOs,,

WRu2, and MoRuz acetylide complexes. Varia-

ble-temperature lH and 13C NMR studies indicate that the

acetylide ligand in some complexes undergoes rotation on

the face of the heterometallic triangle. Furthermore,

a

systematic analysis of the preference of site selectivity and

fluxional behavior of the acetylide ligand has been achieved

by varying the transition-metal atom, the accessory ligand,

and the substituent

of

the acetylide ligand.

A portion of

these results has appeared in a preliminary report.12

Experimental Procedure

General Information. Infrared spectra were recorded on a Perkin-Elmer 580 spectrometer or on a Bomen M-100 FT-IR spectrometer. 'H and 13C NMR spectra were recorded with Bruker AM-400 (400.13 MHz) or Varian Gemini-300 (300 MHz) instruments. Mass spectra were obtained on a JEOL-HX110

instrument operating in electron impact or fast atom bombard-

ment modes. All reactions were performed under a nitrogen atmosphere with use of deoxygenated solvents dried by an appropriate reagent. The progress of reactions was monitored by analytical thin-layer chromatography (5735 Kieselgel60 F254, E. Merck), and the products were separated on preparative thin-layer

chromatographic plates (Kieselgel60 FaM, E. Merck). Elemental

analyses were performed by the staff of the NSC Regional In- strument Center a t National Cheng Kung University, Tainan, Taiwan.

Materials. Metal carbonyl complexes and pentamethylcyclopentadiene were purchased from Strem Chemicals, Inc. Carbon monoxide enriched with 99% 13C was purchased from Cambridge Isotope Laboratories. Phenylacetylene, 1-hexyne, and 1-pentyne were supplied by Aldrich Chemical Co., Inc. (4-

fluoropheny1)acetylene and (4-methoxy)phenylacetylene was

prepared from 4-fluoroacetophenone and 4-vinylanisole, respec-

tively, according to the published p r o ~ e d u r e s . ' ~ J ~ CPW(CO)~H

was prepared by protonation of the sodium salt of the CpW(CO),- anion with acetic acid a t ambient temperature, whereas Cp*W- (CO)3H was prepared by the reaction of pentamethylcyclopentadiene with W(CO),(NCEt), in toluene a t 100 OC.15 On the other hand, the molybdenum hydride complexes Cp*Mo(CO),H and CpMo(CO),H were prepared from the reaction of (p-xyl-

ene)Mo(CO), with pentamethylcyclopentadiene and cyclo-

pentadiene monomer, respectively.16 Metal carbonyl chloride complexes LM(CO)&I were generated from the reactions of the

respective hydrides with CCl, under nitrogen." The metal

acetylides LM(CO),C=CR and the triosmium acetonitrile com-

plex Os3(CO)lo(CH3CN)2 were prepared according to literature

13CO-enriched acetylide complexes were prepared by equilibrating the acetylide complexes in a seal tube (25 mL) equipped with a Rotaflo stopcock under approximately 1 atm of 99% 13C0 a t 100 OC in toluene overnight.

Preparation of CpWOs,(CO),(C=CPh). As all the reactions

of the metal acetylides LM(CO),C=CR with O S ~ ( C O ) ~ ~ were

performed under similar conditions, the experimental details of

(11) Rosenberg, E.; Milone, L.; Aime, S. Inorg. Chim. Acta 1975, 15, 33.

(12) Chi, Y.; Liu, B.-J.: Lee, G.-H.; Peng, S.-H. Polyhedron 1989, 8,

2003.

(13) Lambert, J. B.; Larson, E. G.; Bosch, R. J.; TeVrucht, M. L. E.

J. Am. Chem. SOC. 1985, 107, 5443.

(14) (a) Newman, M. S.; Dhawan, B.; Hashem, M. M.; Khanna, V. K.;

Springer, J. M. J. Org. Chem. 1976,41, 3925. (b) Vaughn, T. H.; Vogt,

R. R.; Nieuwland, J. A. J. Am. Chem. SOC. 1934,56, 2120.

(15) Kubas, G. L.; Wasserman, H. J.; Ryan, R. R. Organometallics 1985,4, 2012. (b) Kubas, G. J. Inorg. Chem. 1983,22,692.

(16) Nolan, S. P.; Hoff, C. D. In Organometallic Syntheses; King, R.

B., Eisch, J. J., Eds.; Elsevier: New York, 1989; Vol. 4, p 58.

(17) Piper, T. S.; Wilkinson, G. J. Inorg. Nucl. Chem. 1956, 3, 104.

(18) Bruce, M. I.; Humphrey, M. G.; Matisons, J. G.; Roy, S. K.;

Swincer, A. G. Aust. J. Chem. 1984, 37, 1955.

(19) Johnson, B. F. G.; Lewis, J.; David, A. P. J. Chem. Soc., Dalton Trans. 1981, 407.

only one reaction are reported here.

In a 100-mL round-bottom reaction flask, O S ~ ( C O ) , ~ (456 mg,

0.503 mmol) was treated with sublimed Me3N0 (91 mg, 1.04 mmol) in a mixture of dichloromethane (50 mL) and acetonitrile (20 mL) a t ambient temperature for 60 min. After evaporation of the solvent in vacuo, the acetylide complex CpW(CO),C=CPh (240 mg, 0.553 mmol) was added, and the reaction mixture was

then dissolved in a toluene solution (30 mL) and brought to reflux

for 30 min. Finally the solvent was evaporated, and the residue was separated by thin-layer chromatography (silica gel, di- ch1oromethane:hexane = l:l), giving 90 mg of C ~ W O S ~ ( C O ) ~ ~ - (CECPh) as a red crystalline solid (0.073 mmol, 15%) and 35 mg

of CpWOs2(CO),(C=CPh) (la) as a yellow crystalline solid (0.003

mmol, 8%). Crystals of la suitable for an X-ray diffraction study were obtained from a layered solution of dichloromethane- methanol a t room temperature. Spectroscopic data for complex

la: MS (FAB, '=Os, le4W) m / z 956 (M'); IR (C6H12) u(C0) 2077

(s), 2043 (vs), 2005 (vs), 1995 (s), 1965 (s), 1924 (m) cm-'; 'H NMR

(CD2C12, 294 K) 6 7.68 (d, 2 H), 7.37 (t, 2 H), 7.20 (t, 1 H), 5.29

(s, 5 H); 13C NMR (CD2C12, 294 K) 6 208.3

( J w x

= 165 Hz,

W-CO), 204.1

( J w x

= 157 Hz, W-CO), 179.4 (OS-CO), 137.5

(CCPh), 73.8

(Jwx

= 16 Hz, CCPh). Anal. Calcd for

C21Hlo08WOsz: C, 26.42; H, 1.06. Found: C, 26.40; H, 1.10. Carbonylation of CpWOs3(CO),,(C=CPh). Toluene (40 mL) and the red tetrametallic acetylide complex CpWOs3- (CO)ll(C=CPh) (58 mg, 0.047 mmol) were combined in a 200-mL

pressure bottle. A partial vacuum was drawn over the toluene

solution; then the bottle was charged with carbon monoxide to

a pressure of 30 psi. The bottle was then placed in a preheated

oil bath, and the solution was stirred a t 120 "C for 6 h. After the solvent was evaporated, the residue was separated by thin-layer

chromatography (silica gel, dichloromethane:hexane =

l:l),

giving

38 mg of C ~ W O S , ( C O ) ~ ( C = C P ~ ) (0.040 mmol, 85%) in addition

to a trace amount of Os3(CO)12 (not determined).

Preparation of Cp*WOsZ(CO),(C=CPh). The title complex (yield 2%) was prepared under conditions similar to those for complex l a , in addition to 10% of the red tetrametallic acetylide

complex C ~ * W O S , ( C O ) ~ ~ ( C = C P ~ ) . Spectral data for complex

2a: MS (FAB, lg20s, lMW) m / z 1026 (M'); IR (C&12) u(C0) 2076

(s), 2041 (vs), 2004 (vs), 1991 (s), 1963 (m), 1905 (w) cm-l; 'H

NMR

(s, 15 H). Anal. Calcd for C26Hzo08WOs2: C, 30.48; H , 1.97.

Found: C, 30.38; H , 1.99.

Preparation of C ~ W O S ~ ( C O ) ~ ( C = C " B U ) . The title complex

(yield 11%) was prepared under conditions similar to those for complex l a , in addition to 19% of the red tetranuclear acetylide complex CpWOs3(CO)ll(C=CnBu). Spectroscopic data for com-

plex 3a: MS (FAB, 1920s, le4W)

m / z

936 (M'); IR (CsH12) u(C0)

2075 (s), 2040 (vs), 2003 (vs), 1991 (s), 1975

(vw),

1961 (m), 1924

(w) cm-'; 'H NMR (CDC13, 294 K) 6 5.33 (s, 5 H), 3.04 (m, 2 H),

1.73 (m, 1 H), 1.61 (m, 1 H), 1.39 (m, 2 H), 0.93 (t, 3 H). Anal. Calcd for ClgH,,08WOs2: C, 24.42; H, 1.51. Found: C, 24.33; H, 1.48.

In a 50-mL round-bottom reaction flask, the metal acetylide CpW(CO)3C=

CPh (37 mg, 0.039 mmol) and R u ~ ( C O ) ~ ~ (37 mg, 0.039 mmol) in

toluene (35 mL) were heated to reflux for 30 min. After evaporation of the solvent in vacuo, the residue was separated by thin-layer chromatography (silica gel, hexane:dichloromethane = 1:l) and recrystallization, giving 20 mg of C ~ W R U ~ ( C O ) ~ ( C =

CPh) (4) as a n orange crystalline material (0.018 mmol, 46%).

Crystals of 4 suitable for X-ray structural determination were obtained by recrystallization from a layered solution of dichloromethane-methanol. Spectroscopic data for complex 4: MS

(FAB, lo2Ru, le4W) m / z 778 (M+); IR (C6H12) u(C0) 2076 (s), 2069

(m), 2044 (vs), 2033 (vs), 2010 (vs), 2003 (m), 1994 (m), 1975 (m),

1966 (w), 1952

(vw),

1930

(vw),

1918

(vw)

cm-'; 'H NMR (CDCl,,

294 K) 6 7.64-7.24 (m, P h ) , 5.56 (s, Cp, 4b), 5.25 (s, Cp, 4a); 13C

NMR (THF-d,, 294 K) 6 210.8 (Jw4 = 160 Hz, W-CO, 4a), 210.7

( J w x = 165 Hz, W-CO, 4a), 207.6 ( J w x = 169 Hz, W-CO, 4b),

197.0 (Ru-CO, 4b), 196.6 (Ru-CO, 4a), 168.9 ( J w x = 139 Hz,

CCPh, 4b), 168.6 (CCPh, 4a), 98.3

(Jw.c

= 22 Hz, CCPh, 4b), 85.6

(JW4 = 2 1 Hz, CCPh, 4a). Anal. Calcd for C2,Hl0O8WRu2: C ,

32.49; H, 1.30. Found: C, 32.37; H, 1.35.

P r e p a r a t i o n of C p * w R ~ ~ ( C o ) ~ ( c ~ P h ) . The toluene so-

lution of a mixture of Ru3(C0),2 (100 mg, 0.156 mrnol) and

(CDC13, 294 K) 6 7.62 (d, 2 H), 7.31 (t, 2 H), 7.20 (t, 1 H), 1.93

P r e p a r a t i o n of CpWRu,(CO),(C=CPh).

(3)

Cp*W(CO),C=CPh (90 mg, 0.178 mmol) was heated a t reflux for 30 min. After TLC separation and recyrstallization, the

acetylide complex Cp*WRu2(CO)8(C~CPh) (5); 86 mg, 0.10

mmol) was obtained in 57% yield. Spectroscopic data for complex

5: MS (FAB, loZRu, law)

m / z

848 (M'); IR (C6H12) u(C0) 2071

(m), 2064 (vs), 2038 (s), 2024 (vs), 2005 (s), 2001 (vs), 1986 (m),

1970 (w), 1965 (w), 1955 (w), 1936

(vw),

1913 (vw) cm-'; 'H NMR

(CD2C12, 273

K)

6 7.65-7.27 (m, Ph), 2.30 (s, Me, 5b), 1.93 (s, Me,

5a); 13C NMR (THF-d8, 226

K)

6 218.5 (W-CO, 5a), 217.3

(W-CO, Sa), 214.5

(Jw4

= 169 Hz, W-CO, 5b), 175.3 (CCPh,

5b), 173.0

(Jwc

= 141 Hz, CCPh, 5a), 100.1

(Jw4

= 23 Hz, CCPh,

5b), 90.2 (CCPh, 5a). Anal. Calcd for C~,J&O~WRU~: C, 36.89;

H, 2.38. Found:

C,

36.86; H, 2.42.

P r e p a r a t i o n

of

C p W R u 2 ( C O ) 8 ( C ~ C 6 H , F ) . The toluene

solution of a mixture of R U , ( C O ) ~ ~ (75 mg, 0.117 mmol) and

CpW(C0)3C=CC6H4F (80 mg, 0.177 mmol) was heated a t reflux

for 30 min. After TLC separation and recrystallization, the

acetylide complex C ~ W R U , ( C O ) ~ ( C I C C ~ H ~ F ) (6; 73 mg, 0.091

mmol) was obtained in 52% yield. Spectroscopic data for complex

6: MS (FAB, lo2Ru, le4W) m / z 796 (M'); IR (C6HlZ) u(C0) 2075

(s), 2069 (s), 2042 (vs), 2032 (vs), 2009 (vs, br), 1994 (m), 1979

(vw),

1972 (m), 1963 (w), 1949 (vw), 1928

(vw),

1914

(vw)

cm-'; 'H NMR

(CDC13, 294 K) 6 7.63 (m, 1 H), 7.52 (m, 1 H), 7.02 (m, 2 H), 5.57

(s, Cp, 6b), 5.25 (s, Cp, 6a); 13C NMR (CDC13, 294

K)

6 211.3

(W-CO, 6a), 210.8 (W-CO, 6a), 207.7

( J w x

= 169 Hz, W-CO,

6b), 196.9 (Ru-CO, 6b), 196.5 (Ru-CO, 6a), 88.4 (Cp, 6a), 86.2 (Cp, 6b). Anal. Calcd for C2,HSFO8WRu2: C, 31.76; H , 1.14. Found: C, 31.68; H, 1.13.

Preparation

of

C p W R u 2 ( C 0 ) 8 ( ~ C 6 H 4 0 M e ) . The toluene

solution of a mixture of R U , ( C O ) ~ ~ (165 mg, 0.248 mmol) and

CpW(CO),C=CC6H40Me (180 mg, 0.388 mmol) was heated a t reflux for 30 min. After TLC separation and recrystallization,

the acetylide complex C ~ W R U ~ ( C O ) ~ ( C ~ C ~ H ~ ~ M ~ ) (7; 162 mg,

0.200 mmol) was obtained in 52% yield. Spectroscopic data for

complex 7: MS (FAB, lo2Ru, le4W) m / z 808

(M');

IR (C&12)

u(C0) 2077 (s), 2070 (s), 2043 (vs), 2033 (vs), 2011 (vs, br), 1991

(m), 1972 (m), 1964 (w), 1948 (vw), 1928 (vw), 1913

(vw)

cm-';

'H

NMR (toluene-d8, 244

K)

6 7.95 (d, 1.18 H , 7b), 7.84 (d, 0.82

H, 7a), 6.90 (d, 0.82 H, 7a), 6.78 (d, 1.18 H, 7b), 4.63 (s, 2.95 H,

Cp, 7b), 4.45 (s, 2.05 H , Cp, 7a), 3.52 (s, 2.05 H , OMe, 7a), 3.41

(s, 2.95 H, OMe, 7b); 13C NMR (CDCl,, 244

K)

6 211.3 (W-CO,

7a), 210.8 (W-CO, 7a), 207.7

( J w c

= 178 Hz, W-CO, 7b), 196.7

(br, Ru-CO), 166.1 (CCAr, 7b), 165.1 (CCAr, 7a), 98.6 (CCAr, 7b), 84.6 (CCAr, 7a), 88.4 (Cp, 7a), 86.0 (Cp, 7b). Anal. Calcd

for C22H120sWR~2: C, 32.77; H, 1.50. Found: C, 32.72; H, 1.47.

of

C ~ W R U ~ ( C O ) ~ ( C ~ ~ B U ) . The toluene so-

lution of a mixture of R u ~ ( C O ) ~ ~ (189 mg, 0.296 mmol) and

CpW(C0)3C=CtBu (184 mg, 0.443 mmol) was heated a t reflux for 40 min. After TLC separation and recrystallization, the

acetylide complex C ~ W R U ~ ( C O ) ~ ( C = C ~ B U ) (8); 223 mg, 0.294

mmol) was obtained in 66% yield. Selected spectroscopic data

for complex 8: MS (FAB, lo2Ru, law) m / z 758 (M'); IR (C6H12)

u(C0) 2074 (w), 2068 (vs), 2039 (w), 2031 (vs), 2005 (vs), 1991 (s),

1981 (w), 1971 (w), 1961 (m), 1928 (w, br) cm-'; 'H NMR (CDCl,,

294

K)

6 5.47 (s, 4.8 H, 8b), 5.38 (s, 0.2 H, 8a), 1.42 (s, 0.36 H,

8a), 1.35 (a, 8.64 H, 8b). 13C NMR (CD2C12, 294

K)

6 211.8

(W-CO, 8a), 209.9 (W-CO, 8a), 208.0

( J w x

= 172 Hz, W - C O ,

8b), 197.6 (Ru-CO, 8b), 196.9 (Ru-CO, 8a), 87.1 (Cp, 8a), 86.1 (Cp, 8b). Anal. Calcd for CI9Hl4O8WRu2: C, 30.17; H, 1.87. Found: C, 30.08; H, 1.86.

of

C~WRU~(CO)~(C=C!"P~). The toluene so-

lution of a mixture of R U , ( C O ) ~ ~ (223 mg, 0.349 mmol) and

CpW(CO),C=C"Pr (210 mg, 0.524 mmol) was heated a t reflux for 30 min. After TLC separation and recrystallization, the acetylide complex CpWRuz(CO)8(C=CnPr) (9; 221 mg, 0.298 mmol) was isolated in 57% yield. Selected spectroscopic data

for complex 9 MS (FAB, lo2Ru,

law)

m/z 744 (M'); IR (C6H12)

u(C0) 2074 (w), 2068 (s), 2040 (m), 2030 (vs), 2005 (vs), 1998 (m), 1991 (s), 1980 (vw), 1970 (w), 1960 (m), 1924

(vw,

br) cm-'; 'H NMR (CDCl,, 294 K) 6 5.49 (s, 4 H, 9b), 5.31 (s, 1 H , 9a), 2.93 (t, 0.4 H, 9a), 2.84 (t, 1.6 H, 9b), 1.81 (m, 0.4 H, 9a), 1.68 (m, 1.6 H, 9b), 1.00 (t, 0.6 H, 9a), 0.98 (t, 2.4 H, 9b); 13C NMR (CD2C12, 294

K)

6 211.6

(Jw4

= 163 Hz, W-CO, 9a), 210.1

(Jw4

= 166

Hz, W-CO, 9a), 208.2 (Jwx = 170 Hz, W-CO, 9b), 197.2

(Ru-CO, 9b), 196.8 (Ru-CO, 9a), 163.1 (CC"Pr, 9a), 161.9 ( J w ~

= 139

Hz,

CCnPr, 9b), 97.9

(Jwx

= 22 Hz, CC"Pr, 9b), 87.7 (Cp,

9a), 87.0 (CC"Pr, 9a), 86.2 (Cp, 9b). Anal. Calcd for

C18H1208WRu2: C, 29.11;

H,

1.62. Found: C, 29.10; H, 1.59.

P r e p a r a t i o n of CpMoRu2(CO)8(C=CPh). The toluene so-

lution of a mixture of R U , ( C O ) ~ ~ (357 mg, 0.559 mmol) and

CpMo(CO),C=CPh (290 mg, 0.838 mmol) was heated a t reflux for 40 min. After TLC separation and recrystallization, the acetylide complex CpMoRu2(CO)&C=CPh) (loa; 244 mg, 0.353 mmol) was isolated in 42% yield. Selected spectroscopic data

for complex loa: MS (FAB, ' q u , %Mol m / z 692 (M');

IR

(C6H12)

u(C0) 2078 (vs), 2045 (vs), 2012 (vs), 2005 (s), 1978 (m), 1948 (w),

1920 (vw, br) cm-'; 'H NMR (CDCl,, 294

K)

6 7.64 (d, 2 H), 7.35

(t, 2 H), 7.26 (t, 1 H), 5.14 (s, 5 H); 13C NMR (CDC13, 294

K)

6

226.8 (Mo-CO, 1 C), 225.3 (Mo-CO, 1 C), 197.9 (Ru-CO, 3 C),

196.4 (Ru-CO, 3C, broad), 91.0 (Cp, 5 C). Anal. Calcd for

C 2 1 H 1 0 0 8 M ~ R ~ 2 : C, 36.64; H, 1.46. Found: C, 36.51; H, 1.46.

P r e p a r a t i o n of C ~ * M ~ R U ~ ( C O ) ~ ( C = C P ~ ) . The toluene

solution of a mixture of Ru,(CO),~ (300 mg, 0.469 mmol) and Cp*Mo(CO),C=CPh (293 mg, 0.704 mmol) was heated a t reflux for 30 min. After TLC separation and recrystallization, the

acetylide complex C ~ * M O R U ~ ( C O ) ~ ( C = C P ~ ) (1 la; 304 mg, 0.399

mmol) was isolated in 57% yield. Selected spectroscopic data

for complex lla: MS (FAB, ' q u , %Mo)

m/z

762 (M+);

IR

(C6H12)

v(C0) 2072 (vs), 2040 (vs), 2007 (vs), 1999 (s), 1971 (s), 1972 (w,

br), 1885 (w, br) cm-'; 'H NMR (CDCl,, 294 K) 6 7.59 (d, 2 H),

7.31 (t, 2 H), 7.22 (t, 1 H), 1.76 (s, 15 H); 13C NMR (CDCI,, 244

K)

6 230.0 (Mo-CO, 1 C), 229.4 (Mo-CO, 1 C), 201.4 (Ru-CO,

1 C), 197.6 (Ru-CO, 3C), 193.7 (Ru-CO, 1 C), 192.8 (Ru-CO,

1 C), 175.3 (CCPh), 94.5 (CCPh), 103.1 (C5Me5). Anal. Calcd for

C26H2008MoRu2:

c,

41.17; H, 2.66. Found:

c,

41.13; H, 2.66.

P r e p a r a t i o n of C ~ M O R ~ ~ ( C O ) ~ ( C ~ Y B U ) . The toluene

solution of a mixture of Ru,(CO),~ (131 mg, 0.205 mmol) and

C~MO(CO)~C=C*BU (104 mg, 0.319 mmol) was heated a t reflux

acetylide complex C ~ M O R U ~ ( C O ) ~ ( C = C ~ B U ) (12; 80 mg, 0.119

for complex 1 2 MS (FAB, '%u, %Mo)

m / z

672 (M'); IR (C6Hld

u(C0) 2076 (s), 2070 (w), 2041 (vs), 2032 (m), 2010 (vs), 1999 (s),

1974 (m), 1951

(vw),

1917

(vw)

cm-'; 'H NMR (CDCl,, 244

K)

6 5.43 (s, 5 H, 12a), 5.34 (s, 12b), 1.38 (s, 12b), 1.33 (s, 9 H, 12a);

13C NMR (CD2C12, 205

K)

6 225.9 (Mo-CO, 1 C, 12a), 225.5

(Mo-CO, 1 C, 12a), 223.0 (Mo-CO, 2 C, 12b), 204.0 (Ru-CO,

1 C, 12a), 202.4 (Ru-CO, 1 C, 12a), 200.1 (Ru-CO, 6 C, 12b),

197.4 (Ru-CO, 1 C, 12a), 196.4 (Ru-CO, 1 C, 12a), 194.8

(Ru-CO, 1 C, 12a), 194.3 (Ru-CO, 1 C, 12a). Anal. Calcd for ClSHl4O8MoRu2: C, 34.14; H, 2.11. Found: C, 33.92; H , 2.04.

P r e p a r a t i o n of C ~ * M O R U ~ ( C O ) ~ ( C = C ~ B U ) . The toluene

solution of a mixture of R u ~ ( C O ) ' ~ (43 mg, 0.067 mmol) and

Cp*Mo(CO),C=CtBu (40 mg, 0.101 mmol) was heated a t reflux for 60 min. After TLC separation and recrystallization, the

acetylide complex C ~ * M ~ R U ~ ( C O ) ~ ( C = C ~ B U ) (13b; 27 mg, 0.036

for complex 1 3 b MS (FAB, ' q u , %Mo) m / z 742 (M');

IR

(C6H12)

u(C0) 2062 (s), 2023 (vs), 1999 (vs), 1986 (s), 1963 (w), 1951 (w),

1912

(vw,

br) cm-'; 'H NMR (CDCl,, 294

K)

6 2.08 (s, 15 H), 1.38

(s, 9

H);

13C NMR (CDC13, 294

K)

6 227.3 (Mo-CO), 199.1

(Ru-CO), 186.8 (CCtBu), 115.8 (CCtBu), 103.9 ((&Me5), 35.5

(CMe3), 34.8 (5 Me), 11.6 (3 Me); 13C NMR (CD2C12, 200

K)

6 227.0

(Mo-CO, 2 C), 207.0 (Ru-CO, broad, 2 C), 200.6 (Ru-CO,

broad, 2 C), 191.0 (Ru-CO, broad, 2 C). Anal. Calcd for

C 2 4 H 2 4 0 8 M ~ R ~ 2 : C, 39.03; H, 3.28. Found: C, 38.99; H, 3.25.

P r e p a r a t i o n of C ~ M O R U ~ ( C O ) ~ ( C = C C ~ H ~ F ) . The toluene

solution of a mixture of R U ~ ( C O ) ' ~ (193 mg, 0.302 mmol) and

C ~ M O ( C ~ ) ~ C = C C ~ H , F (165 mg, 0.453 mmol) was heated a t reflux

acetylide complex C ~ M O R U ~ ( C ~ ) ~ ( C E C C ~ H ~ F ) (14a; 127 mg,

0.179 mmol) was isolated in 40% yield. Selected spectroscopic

data for complex 14a: MS (FAB, lo2Ru, s8M0) m / z 710 (M'); IR

(C6H12) u(C0) 2077 (vs), 2044 (vs), 2011 (vs), 2004 (S), 1986 (W),

1976 (s), 1948 (m), 1914 (w) cm-I; 'H NMR (CDCl,, 294 K) 6 7.62

(m, 2 H), 7.04 (m, 2 H), 5.15 (s, 5 H); 13C NMR (CDC13, 294 K)

6 226.7 (Mo-CO, 1 C), 225.1 (Mo-CO, 1 C), 197.8 (Ru-CO, 3

C), 196.4 (Ru-CO, broad, 3 C), 171.8 (CCAr), 91.6 (CCAr), 90.8 (Cp, 5 C). Anal. Calcd for C2,HSFO8MoRu2: C, 35.71; H, 1.28. Found: C, 35.63; H, 1.28.

X-ray Crystallography. Diffraction measurements were carried out on a Nonius CAD-4 fully automatic four-circle dif-

(4)

2712

Organometallics, Vol.

9,

No.

10, 1990

Hwang et al.

Table I. Experimental Data for the X-ray Diffraction Studies of Complexes 1.4, and 10'

compd 1 4 10

formula C21H10080SZW CZ1H1008RU2W C2IHloOBMoRu2

space group p 2 1 l C R 1 l n R I / C

mol wt 1104.27 776.29 688.39

cryst syst monoclinic monoclinic monoclinic

a,

A

8.332 (3) 12.476 (1) 12.770 (4) b, A 14.543 (4) 13.216 (4) 8.188 (4) c,

A

17.819 (5) 13.395 (4) 21.313 (4) P, deg 94.46 (3) 97.99 (2) 91.26 (2)

v,

A3 2153 (1) 2187 (1) 2228 (1) Z 4 4 4

4,

g/cm3 2.945 2.358 2.052 F(000) 1703.33 1447.68 1319.70 temp, K 297 297 297

scan method 8/28 scan mode 0/28 scan mode 8/28 scan mode

28(max), deg 49.8 49.8 49.8

scan param 0.65

+

0.35 tan 0

scan speed (variable), deg/min 16.48110-16.4812 16.481 10-16.48/2 16.48/10-16.4812

cryst size, mm

abs cor

IC.

scan $ scan $ scan

transmissn factors: max, min 0.998, 0.371 0.997, 0.796 1.000, 0.839

variation of std rflns, 90

no. of unique rflns 3777 3840 3907

no. of data with I

>

2 a ( n 2980 2851 3089

no. of atoms and params refined 42, 145 42, 290 42, 290

max A / u ratio 0.043 0.467 2.484

R; RWb 0.068; 0.090 0.029; 0.027 0.030; 0.031

GOF' 1.768 1.583 2.34

max/min residual electron density, e/A3 2.30-1.35 0.8W.58 0.42-0.65

[ ~ W ~ F ~ - F , ~ ~ / / ~ W ~ F ~ ~ ~ ) " ~ .

CGOF

= [x:wlF, - Fc12/(No-Nv)]1'2 ( N o = number of observations; N , = number of variables).

0.65

+

0.35 tan 0 0.65

+

0.35 tan 8

h,k,E ranges -9 to 9, 0-17, 0-21 -14 to 14,O-15,0-15 -15 to 15, 0-9,0-25

0.25 X 0.40 X 0.50 0.20 X 0.20 X 0.25 0.08 X 0.18 X 0.55

~ ( M o K a ) , mm-' 17.28 6.74 1.90

<3 (every 3600 s) <2 (every 7200 s) <2 (every 7200 s)

weighting scheme unit weight l / a 2 (counting statistic)

112

OFeatures common to all determinations: X(Mo K a ) = 0.70930

A;

Nonium CAD-4 diffractometer. b R = x l F o - FJ/)JF,I; R, =

fractometer. In general, the space group and parameters of unit

cell dimensions were determined and refined from 25 randomly

selected reflections, with a 20 angle about 20°, obtained by using the CAD-4 automatic search, center, index, and least-squares routines. All data reduction and structural refinement were

performed by using the NRCC-SDP-VAX software packages. T h e

structures were solved by the heavy-atom method and refined by least-squares cycles. For complex 1, the tungsten and the osmium metal atoms were refined anisotropically and the rest of the non-hydrogen atoms were refined isotropically. For com-

plexes 4 and 10, all non-hydrogen atoms were refined with an-

isotropic thermal parameters; the hydrogen atoms of the phenyl group and the cyclopentadienyl ligand were added a t the idealized positions and included in the structure factor calculations. The data collection and refinement parameters for complexes 1,4, and

10 are summarized in Table

I.

Atomic positional parameters for

complex 1 are found in Table 11, whereas some selected bond

angles and lengths are given in Table

V.

The corresponding

parameters for complex 4 are given in Tables

I11

and VI and for

complex 10 in Tables IV and VII, respectively.

Results and Discussion

Preparation

of the WOsz Acetylide Complexes.

Treatment of LW(CO),C=CR (R = Ph,

L

=

Cp, Cp*;

R

=

"Bu, L

= C p )

with the lightly stabilized triosmium

complex

OS,(CO)~&H~CN)~

in refluxing toluene (110

"C,

30 min) provided a pale yellow trinuclear heterometallic

acetylide complex (1,

L

=

Cp,

R

=

Ph; 2,

L

=

Cp*,

R

=

Ph; 3,

L

= Cp, R = "Bu) in low yield (2-ll%), in addition

to the red tetrametallic complex LWOS,(CO)~~(C=CR)

(10-19%

Thermolysis of the tetrametallic acetylide

complexes under a CO atmosphere induced cluster frag-

mentation and produced the trinuclear WOsz acetylide

complexes in high yield (78435%). The latter has been

considered as an alternative, complementary method to

(20) Chi, Y.; Lee, G.-H.; Peng, S.-H.: Wu, C.-H. Organometallics 1989,

8, 1574.

generate large quantities of the WOs, acetylide complexes

in our laboratory. Furthermore, other chemistry of these

WOs3

acetylide complexes, such as the reactions with di-

substituted alkynesz1 and with mononuclear metal ace-

tylide complexes,2z has also been developed.

The structural information of these WOsz acetylide

complexes was initially provided by a 13C NMR study. The

l3CI1H)

NMR spectrum of

1 showed two signals at 6 137.5

and 73.8, reminiscent of those reported for the two ace-

tylide carbon nuclei (6 172.9 and 112.7) in the WFe, ana-

logue CpWFez(CO)8(C=CTol).23 The latter is a hetero-

metallic cluster in which the acetylide ligand functions as

a five-electron donor, a-bonded to the tungsten atom while

employing its two orthogonal alkyne a-bonds to bridge the

unique Fe-Fe edge. However, since the color as well as

the IR spectra of these osmium complexes in the region

of CO absorption differs substantially from those of the

WFe2 derivatives, an X-ray diffraction study was carried

out on complex 1 to determine the location of the acetylide

ligand in the WOsz derivatives.

Description of the Structure of C ~ W O S ~ ( C O ) ~ ( C =

CPh)

(1).

As

indicated in Figure 1, this molecule has

a

triangular WOsz core structure with distances W-Os(1)

=

2.830 (2)

A,

W-042)

=

2.916 (2)

A,

and Os(l)-Os(2) =

2.814 (2)

A,

in which the tungsten atom is associated with

a Cp ring and two CO ligands, while each of the osmium

atoms is linked to three, mutually orthogonal, terminal CO

ligands. The acetylide moiety is coordinated to the WOsz

triangular face with its a-carbon bound to all three metal

atoms with bond distances W-C(15)

=

2.20 (3)

A,

Os-

(21) Wu, C.-H.; Chi, Y.; Peng, S.-H.; Lee, G.-H. Organometallics, in (22) Wu, C.-H.; Chi, Y.; Pew, S.-H.: Lee. G.-H. J. Chem. Soc..Dalton

press.

Trans., in press.

P. J . Chem. Soc., Chem. Commun. 1983, (23) Green, M.; Marsden, K.; Salter, I. D.; Stone, F. 446. G. A.; Woodward,

(5)

Organometallics,

Vol.

9,

No.

10, 1990

2713

Table 11. Atomic Coordinates and Equivalent Isotropic

Displacement Coefficients for CpWOs,(CO),(C=CPh) (1)

X Y z B;,,"

A'

0.48889 (14) 0.26829 (15) 0.22595 (14) 0.416 (4) 0.619 (4) 0.654 (4) 0.105 (5) 0.154 (4) 0.393 (4) 0.314 (4) 0.113 (4) 0.118 (4) 0.188 (4) 0.118 (5) -0.012 (5) -0.014 (4) 0.491 (5) 0.405 (3) 0.589 (4) 0.648 (4) 0.753 (5) 0.793 (6) 0.736 (5) 0.630 (5) 0.360 (3) 0.702 (4) 0.754 (4) 0.002 (3) 0.079 (4) 0.464 (4) 0.358 (3) 0.036 (4) 0.149 0.285 0.151 -0.089 -0.091 0.617 0.786 0.877 0.762 0.587 0,81811 (8) 0.96203 (8) 0.83355 (8) 0.7582 (21) 0.7191 (21) 0.8829 (23) 1.043 (3) 0.9141 (24) 1.046 (3) 0.7106 (21) 0.7723 (23) 0.8041 (24) 0.8884 (24) 0.947 (3) 0.900 (3) 0.8120 (24) 0.891 (3) 0.9351 (19) 0.8897 (22) 0.978 (3) 0.985 (3) 0.908 (4) 0.826 (3) 0.813 (3) 0.7252 (20) 0.6553 (23) 0.9247 (22) 1.0919 (19) 0.8846 (22) 1.0962 (21) 0.6360 (20) 0.7365 (21) 0.748 0.909 1.013 0.928 0.759 1.034 1.049 0.913 0.768 0.752 0.16703 (6) 0.13507 (6) 0.25760 (6) 0.0798 (17) 0.2004 (17) 0.1258 (19) 0.1568 (21) 0.0470 (19) 0.0810 (20) 0.2740 (17) 0.1687 (19) 0.3731 (20) 0.3791 (19) 0.3249 (22) 0.2848 (21) 0.3133 (20) 0.2734 (21) 0.2272 (15) 0.3458 (18) 0.3692 (21) 0.434 (3) 0.475 (3) 0.4554 (23) 0.3874 (21) 0.0233 (16) 0.2167 (19) 0.1005 (18) 0.1733 (16) -0.0045 (18) 0.0514 (17) 0.2923 (16) 0.1219 (17) 0.405 0.415 0.315 0.244 0.296 0.337 0.453 0.520 0.487 0.370 1.35 (5) 1.55 (5) 1.24 (4) 1.6 (5) 1.6 (5) 2.2 (6) 2.9 7) 2.3 (6) 2.6 (6) 1.8 (5) 2.3 (6) 2.4 (6) 2.4 (6) 3.2 (7) 2.9 (7) 2.5 (6) 3.0 (7) 1.0 (4) 2.0 (5) 2.8 (7) 4.1 (9) 4.9 (10) 3.6 (8) 3.0 (7) 3.9 (6) 4.9 (7) 4.5 (6) 3.6 (5) 4.6 (6) 4.2 (6) 3.7 (5) 4.3 (6) 3.6 3.4 3.9 3.6 3.6 3.7 4.9 5.5 4.4 3.7

Bi,

is the mean of the principal axes of the thermal ellipsoid.

/-.

c 2 0

b

\

Figure 1. ORTEP diagram of CpWOs2(CO)&C=CPh) (1).

(1)-C(15) = 2.16 (3)

A,

and Os(2)-C(15)

=

1.96 (3) 8, and

with its &carbon linked to W and Os(1) atoms with dis-

tances Os(l)-C(14) = 2.17

(4)

A

and W-C(14) = 2.36 (4)

A. The acetylide C-C bond distance (1.23 (5)

A)

in this

compound is only a little longer than the average C-C

Table 111. Atomic Coordinates and Equivalent Isotropic Displacement Coefficients for CpWRu,(CO),(CdPh) (4)

W 0.06565 (3) 0.152711 (25) 0.232915 (24) 2.226 (14) X Y z B b :

A'

Ru(1) 0.01359 (5) Ru(2) -0.06312 (5) C(1) 0.1463 (7) C(2) 0.0384 (7) C(3) -0.0590 (8) C(4) -0.1360 (7) C(5) 0.0559 (7) C(6) -0.1425 (8) C(7) 0.1303 (7) C(8) 0.1938 (8) C(9) 0.0571 (11) C(10) -0.0335 (9) C(l1) 0.0016 (9) C(12) 0.1128 (8) C(13) 0.1507 (9) C(14) -0.1503 (7) C(15) -0.0687 (7) C(16) -0.2617 (6) C(17) -0.3468 (7) C(18) -0.4510 (8) C(19) -0.4724 (8) C(20) -0.3890 (9) C(21) -0.2823 (7) O(1) 0.2222 (6) O(2) 0.0583 (6) O(3) -0.1027 (7) O(4) -0.1778 (6) O(5) 0.1245 (6) O(6) -0.1908 (8) O(7) 0.1733 (6) O(8) 0.2736 (6) H(9) 0.055 H(10) -0.113 H(11) -0.047 H(12) 0.160 H(13) 0.227 H(17) -0.331 H(18) -0.515 H(19) -0.550 H(20) -0.406 H(21) -0.221 0.25009 (5) 0.33911 (5) 0.3217 (6) 0.1407 (7) 0.3353 (8) 0.3451 (7) 0.4236 (6) 0.4459 (7) 0.0634 (7) 0.2410 (7) 0.0034 (7) 0.0565 (10) 0.1431 (8) 0.1409 (8) 0.0560 (9) 0.2249 (6) 0.1789 (5) 0.2087 (6) 0.2556 (7) 0.2338 (8) 0.1642 (8) 0.1175 (8) 0.1390 (7) 0.3666 (6) 0.0838 (5) 0.3884 (7) 0.3511 (6) 0.4739 (5) 0.5078 (6) 0.0066 (5) 0.2861 (6) -0.062 0.038 0.198 0.196 0.032 0.310 0.268 0.149 0.065 0.104 0.42250 (5) 0.24900 (5) 0.4574 (6) 0.5210 (6) 0.5028 (7) 0.1146 (7) 0.2284 (7) 0.3009 (7) 0.3440 (7) 0.2635 (7) 0.1469 (7) 0.1074 (7) 0.0610 (7) 0.0721 (7) 0.1232 (7) 0.3243 (6) 0.2912 (6) 0.3451 (6) 0.2886 (7) 0.3003 (8) 0.3706 (9) 0.4289 (7) 0.4179 (7) 0.4774 (5) 0.5830 (5) 0.5503 (6) 0.0335 (5) 0.2174 (6) 0.3305 (6) 0.3995 (5) 0.2734 (6) 0.186 0.111 0.025 0.046 0.140 0.237 0.257 0.381 0.482 0.464 2.57 (3) 2.53 (3) 3.0 (4) 3.3 (4) 4.4 (5) 3.6 (4) 3.6 (4) 4.3 (5) 3.7 (4) 3.9 (4) 5.0 (6) 5.1 (6) 4.4 (5) 4.1 (5) 4.7 (5) 2.6 (4) 2.4 (3) 2.4 (3) 3.6 (4) 4.6 (5) 4.7 (5) 4.6 (5) 3.8 (4) 5.7 (4) 5.5 (4) 7.6 (5) 5.5 (4) 6.4 (4) 7.6 (5) 5.4 (4) 6.1 (4) 5.1 5.4 4.8 4.6 5.1 4.4 5.2 4.9 5.3 4.5

Bi,

is the mean of the principal axes of the thermal ellipsoid.

distance of acetylene molecules (1.20

The most salient feature of the structure is the orien-

tation of the acetylide moiety, which

is

a-bonded to an

Os

atom and a t the same time forms a transverse bridge acros9

the second

W-Os

bond. Therefore, the structure of 1 is

related to the CpWFe2(CO)8(C=CTol) by a

120°

rotation

of the acetylide ligand. The heterometallic acetylide

cluster CpNiFe2(CO)6(C=CtBu) also shows a similar

asymmetric

arrange men^?^

Description of the Solution Dynamics of the W 0 s 2

Complexes.

The acetylide ligand of these

WOsp

com-

plexes is static on the time scale of

'3c

NMR spectroscopy.

The

13C

NMR spectrum of a 13CO-enriched sample of

complex 1 exhibits two W-CO signals a t 6 208.6 and 204.0,

a sharp O S ( C O ) ~

signal a t 6 179.7, and two very broad

O s 4 0 signals a t 6 178.8 and 173.4 a t 295

K

in toluene-ds.

When the temperature was increased to 350

K,

the Os(C-

O ) ,

signal a t

6

179.7 remained unchanged but the broad

Os-CO signals a t

6

178.8 and 173.4 merged into a sharp

signal a t 6 176.5. This behavior is consistent with the

presence of two, independent, localized 3-fold exchanges

of

the CO ligands of the OS(CO)~

unit. One %fold rotation,

( 2 4 ) March, J. Aduanced Organic Chemistry, 3rd ed.; Wiley: New (25) Martinetti, A.; Sappa, E.; Tiripicchio, A.; Camellini, M. T. J .

York, 1985; Chapter 1.

Organomet. Chem. 1980, I97, 335.

(6)

2714 Organometallics, Vol.

9,

No.

10, 1990

Table IV. Atomic Coordinates and Equivalent Isotropic Disolacement Coefficients for CDMORU.(CO).(C=(

Hwang et al.

Table VII. Relevant Bond Distances

(A)

and Angles (deg) of CDMoRu,(CO).(C=CPh) (10) X Y 2 Bi,," A2 Ru(1) 0.71869 (4) 0.46159 (7) 0.070708 (25) 2.403 (22) Ru(2) 0.87172 (4) 0.22655 (8) 0.09524 (3) 2.97 (3) 0.73598 (5) 0.34163 (8) 0.5996 (6) 0.6026 (10) 0.7169 (6) 0.4012 (9) 0.8218 (6) 0.6254 (10) 0.8887 (6) 0.1398 (9) 0.9978 (6) 0.3537 (12) 0.9385 (6) 0.0524 (11) 0.8640 (6) 0.4783 (10) 0.6627 (6) 0.5566 (10) 0.7400 (12) 0.0920 (12) 0.8106 (7) 0.1975 (14) 0.7576 (9) 0.3200 (12) 0.6509 (9) 0.2983 (16) 0.6412 (9) 0.1552 (17) 0.7203 (5) 0.2079 (8) 0.6274 (5) 0.2643 (8) 0.5142 (5) 0.2296 (8) 0.4394 (5) 0.3283 (9) 0.3339 (5) 0.2930 (10) 0.3015 (6) 0.1626 (10) 0.3744 (6) 0.0641 (10) 0.4796 (6) 0.0917 (9) 0.5275 (5) 0.6812 (8) 0.7181 (4) 0.3595 (7) 0.8822 (5) 0.7242 (8) 0.8967 (4) 0.0877 (7) 1.0699 (5) 0.4355 (9) 0.9347 (4) 0.5666 (8) 0.6222 (5) 0.6797 (7) 0.756 -0.012 0.886 0.181 0.787 0.413 0.589 0.370 0.57s 0.104 0.461 0.420 0.282 0.363 0.22; 0.132 0.352 -0.026 CI.Fix0 0.012

the mean of the principal 0.9755 (5) -0.0548 (8) 0.19495 (3) 2.62 (3) 0.0627 (4) 3.8 (4) -0.0146 (3) 3.3 (3) 0.0594 (4) 4.2 (4) 0.0139 (4) 3.6 (4) 0.0937 (4) 5.3 (5) 0.1400 (4) 4.7 (4) 0.1937 (3) 3.9 (4) 0.1956 (3) 4.0 (4) 0.2470 (4) 7.1 (6) 0.2767 (4) 5.4 (5) 0.3024 (4) 5.4 (5) 0.2889 (5) 7.5 (6) 0.2538 (4) 7.4 (6) 0.1044 (3) 2.4 (3) 0.1149 (3) 2.2 (3) 0.1100 (3) 2.4 (3) 0.1362 (3) 3.8 (3) 0.1280 (4) 4.0 (4) 0.0942 (4) 4.1 (4) 0.0681 (4) 4.9 (4) 0.0764 (3) 3.8 (3) 0.0572 (3) 6.6 (3) -0.06550 (23) 5.0 (3) 0.0516 (3) 7.0 (4) -0.0349 (3) 5.5 (3) 0.0903 (3) 8.8 (4) 0.1667 (3) 7.7 (4) 0.2014 (3) 6.2 (3) 0.2035 (3) 6.1 (3) 0.225 6.0 0.278 5.1 0.327 5.5 0.300 6.7 0.238 6.0 0.163 4.1 0.147 4.4 0.089 4.8 0.041 5.2 0.060 4.3

axes of the thermal ellipsoid. Table V. Relevant Bond Distances (A) and Angles (deg) of

(A) Bond Distances

W-OS(l) 2.830 (2) W-Os(2) 2.916 ( 2 )

Os(l)-Os(2) 2.814 (2) W-C(15) 2.20 (3)

O~(l)-C(14) 2.17 (4) W-C(14) 2.36 (4)

W-CO (mean) 1.97 (3) Os-CO (mean) 1.87 (3)

(B) Bond Angles

W-c-0 (mean) 172 (3) Os-C-0 (mean) 176 (3)

Table VI. Relevant Bond Distances (A) and Angles (deg) of CpWOsi(CO)s(Cd!Ph) ( 1 )

Os(l)-C(15) 2.16 (3) 0~(2)-C(15) 1.96 (3)

C(14)-C(15) 1.23 (5) C(16)-C(14) 1.47 (5)

0~(2)-C(15)-C(14) 159 (3) C(15)-C(14)-C(16) 148 (4)

CDWRU,(CO)*(C*Ph) (4) (A) Bond Distances

w-Rul1) 2.998 (1) W-Ru(2) 2.965 (1)

Ru(l)-Ru(2) 2.661 (1) W-C(15) 1.976 (8)

R ~ ( l ) - C ( 1 5 ) 2.128 (8) Ru(2)-C(15) 2.195 (7)

Ru(l)-C(14) 2.297 (8) R~(2)-C(14) 2.188 (8)

C(14)-C(15) 1.31 (1) C(16)-C(14) 1.47 (1)

W-CO (mean) 1.979 (9) Ru-CO (mean) 1.910 (9)

(B) Bond Angles

W-C-0 (mean) 172.1 (8) Ru-C-0 (mean) 177.6 (9)

having a lower energy barrier, produces the sharp signals

a t 6 179.7 a t room temperature; the second, having a rel-

atively greater activation barrier, reaches the limit of fast

W-C(15)-C(14) 162.5 (6) C(15)-C(14)-C(16) 142.5 (8)

(A) Bond Distances

Mo-Ru(l) 2.828 (1) Mo-Ru(2) 2.927 (1)

Ru(l)-Ru(2) 2.784 (1) Mo-C(l4) 2.223 (6)

Ru(l)-C( 15) 2.214 (6) Mo-C(l5) 2.265 (6)

Mo-CO (mean) 1.988 (8) Ru-CO (mean) 1.902 (8)

(B) Bond Angles

Mo-C-0 (mean) 171.0 (7) Ru-C-0 (mean) 177.6 (7)

Ru(l)-C(14) 2.198 (6) Ru(2)-C(14) 1.954 (6)

C( 14)-C( 15) 1.296 (9) C(15)-C(16) 1.475 (9)

Ru(2)-C(14)-C(15) 154.2 (5) C(14)-C(15)-C(16) 144.9 (6)

Table VIII. Numbering Scheme and the Relative Abundance of the Acetylide Derivatives of Type

LMM',(CO)B(C4R)

re1 abundance of each isomer L M M' R c p W os Cp* W

os

Cp W

os

Cp W Ru Cp* W Ru Cp W Ru Cp W Ru Cp W Ru Cp W Ru Cp Mo Ru Cp* Mo Ru Cp Mo Ru Cp* Mo Ru Cp Mo Ru Ph la Ph 2a "Bu 3a Ph 4a Ph 5a CBHIF 6a C6H40Me 7a 'Bu 8a "Pr 9a Ph 1 Oa Ph l l a tBu 12a tBu C6H4F 14a 100% 100% 100% 45 % 15% 45 % 41 % 4% 20 % 100% 100% 95 90 100% 4b 5b 6b 7b 8b 9b 12b 13b 55 % 85% 55% 59% 96% 80 7'0 5 90 100%

exchange a t higher temperature. In contrast, rotation of

the CpW(CO), unit cannot be observed because the two

CO ligands on the tungsten atom are diastereotopic. The

coalescences of the two W-CO signals and of the two

O S ( C O ) ~

signals were not observed even a t 370

K,

sug-

gesting that the racemization of 1 has not occurred a t this

temperature.

Preparation a n d Characterization

of the

WRu,

Complexes. In order to investigate the preferred orien-

tation of the acetylide ligand over the triangular face of

the heterometallic complexes, we have carried out the

syntheses of several WRu, derivatives. Complexes

(4,

L

=

Cp, R

=

Ph; 5,

L

=

Cp*, R

=

Phi 6,

L

=

Cp, R = C&&F;

7,

L

=

Cp, R

=

C&OMe; 8,

L

=

Cp, R

=

t B ~ ;

9, L

= Cp,

R

=

nPr)

were obtained in good yield from the reaction

between Ru,(CO),, and the corresponding tungsten ace-

tylide in a 2:3 molar ratio.

For these WRuz derivatives,

the

'H

NMR spectra and IR spectra in the region of CO

absorption suggest the presence of two isomers in solution

(Table VIII). The assignment of each isomer is further

confirmed by their characteristic 13C NMR data.

In order to prove that the isomerization is due to the

acetylide rotation, we have carried out the structural de-

termination on complex

4.

Crystals suitable for X-ray

experiments were obtained by recrystallization from

CH2Clz-hexane a t room temperature. Its molecular

structure is shown in Figure 2, and selected bond angles

and distances are summarized in Table VI. The WRu2

triangle is nearly isosceles with the bond distances W-

Ru(1)

=

2.998 (1)

A,

W-Ru(2)

=

2.965

(1)

A,

and Ru-

(lkRu(2)

=

2.661 (1)

A. The tungsten atom is associated

with two slightly bent CO ligands (LW-C-O(mean)

=

172.1

(8)")

in addition to a Cp ligand, and each ruthenium atom

is

linked to three linear CO ligands (LRu-C-O(mean)

=

177.6

(9)").

Most interesting, the acetylide moiety is now

u-bonded to the W atom and, quasi-symmetrically,

K -

bonded to the two Ru atoms. Therefore, we conclude that

the WRu, derivatives

in

the solid state are isostructural

(7)

- -

I

Figure 2. ORTEP

diagram

of

CpWRuz(CO)B(C=CPh)

(4). Scheme I

I " " " ~ ~ " " ' ~ " " ' " ' ~ " ~ ' 210.0 200.0 1 9 0 . 0

PPm

Figure 3.

Variable-temperature

13C

NMR

spectra (CD2C1J of 4,

showing

the region of GO resonances.

a b

not with the WOsz derivatives but rather with the WFez

derivatives.

The heterometallic acetylide clusters

CpWFe2(CO)8(C=CTol)23

and C O F ~ ~ ( C O ) ~ ( C * S ~ M ~ ~ ) ~ ~

also exhibit a similar symmetric arrangement.

Description of the

13C

N M R

Spectra of the WRu2

Complexes.

Both the lH NMR and IR v(C0) spectra

suggest the presence of two isomers in solution. The so-

lution dynamics of these WRuz complexes are of particular

interest. On the basis of the structural information es-

tablished, we propose that the isomerization is caused by

a 360' rotation of the acetylide ligand over the WRuz

triangle (Scheme

I).

Before we proceed to discuss the

rotation of the acetylide ligands, it is important to un-

derstand the assignment of each isomer and their relative

abundance

a/b

in solution. The 'H NMR and IR spectra

failed to provide adequate information. Fortunately, 13C

NMR spectra in the region of CO resonances can reveal

information on the overall molecular symmetry that allows

us to assign the structure unambiguously.

The 13C NMR spectrum of 4 a t 205

K

exhibits three

W-CO signals a t 6 210.8, 210.5, and 207.3 in the ratio

1:1:2.4 (Figure 3). Therefore, the

first

two resonance lines

are assigned to the "asymmetric" isomer

(4a,

the acetylide

C-C bond bisects the W-Ru bond) and the third one to

the "symmetric" isomer

(4b,

the acetylide C-C bond is

orthogonal to the Ru-Ru bond). This assignment is rea-

(26) Seyferth, D.; Hoke, J. B.; Rheingold, A. L.; Cowie, M.; Hunter, A. D. Organometallics 1988, 7, 2163.

sonable because the CO ligands of the CpW(CO), unit in

the asymmetric isomer

4a

are diastereotopic, whereas in

isomer

4b

the rotation of the CpW(CO)z fragment, having

a relatively smaller activation barrier, would average the

chemical environment of the CO ligands. Furthermore,

five signals a t 6 202.5,200.8, 196.0, 194.2, and 192.4 with

an intensity ratio of 1:1:1:1:2 are assigned to the Ru-CO

resonances of

4a;

the signal at 6 192.4 is double the in-

tensity of the other four signals and therefore corresponds

to two coincident signals. The Ru-CO signals of

4b

were

not observed at this temperature. However, when the

temperature was decreased

to

190 K,

the W-CO signal of

4b

broadened and collapsed slightly, suggesting the slowing

down of the CpW(CO)z rotation, and three very broad

Ru-CO signals at 6 203.0, 198.5, and 189.0 appeared in the

spectrum, consistent with the symmetric nature of

4b.

On

the other hand, when the temperature was increased to

240 K,

isomer 4b showed a broad Ru-CO signal at 6 197.1,

indicating the presence of a rapid 3-fold rotation of the

R u ( C O ) ~

unit. The other three weak Ru-CO signals a t 6

202.9, 194.6, and 192.7 are assigned to isomer

4a.

Again,

the localized Ru(CO)~

rotation in

4a

is responsible for the

observed NMR spectra.

Similar 13C NMR spectra were also observed for other

WRu2 derivatives. The 13C NMR spectrum of 8 at 294

K

exhibits one W-CO signal at 6 208.4 and one Ru-CO signal

at

6

198.0 in the ratio 1:3 assigned to isomer

8b,

in addition

to two weak W-CO signals a t

6

212.2 and

209.3

and one

weak Ru-CO signal a t 6 197.3 assigned to

8a

(Figure 4).

Between 213 and 205

K

the Ru-CO signals assigned to

8b

collapsed to the base line and six relatively weak Ru-CO

signals of equal intensity at 6 204.6, 202.1, 198.0, 196.2,

194.4, and 193.6 emerged from the base line. We assign

these six distinct Ru-CO signals to the asymmetric isomer

8a.

When the temperature was decreased to 178

K,

one

broad W-CO signal at

6

208.9 and three broad Ru-CO

(8)

2716 Organometallics, Vol.

9,

No.

10, 1990

Hwang et al.

k

355K

--

340K / 337K ---w---,---u- IICK 2i6 2 ; ~ 208 I 20.1 I " 2 0 0 I ' 196 / " ' /1 9 2 " ' l1 8 8 ' ~ ppm ' '

Figure

4. Variable-temperature 13C

NMR

spectra

(CD2C12)

of

8, showing the region of

CO

resonances.

signals at 6 205.1,200.2, and 191.0 of isomer

8b

were clearly

observed. Further decreasing of the temperature to 156

K

produced the splitting of these four signals, giving two

W-CO signals at 6 211.6 and 206.7 and six Ru-CO signals

a t 6 207.2, 203.3, 200.8,

200.0,

193.1, and 189.1. We at-

tribute the dynamic motion occurring between 178 and 156

K

to the rotational motion of the CPW(CO)~

unit. This

rotational motion could be of a "pinwheel" type similar to

the localized

R u ( C O ) ~

rotationz7 or a "swinging" motion

with the bulky

Cp

ligand staying away from the acetylide.

Both types of movements would average the environment

of W-CO ligands and exhibit the observed fluxional be-

havior; unfortunately, our data are unable to distinguish

them. From the coalescence temperature (178

K)

of the

W-CO signals, the activation free energy

**(AG*)**

for the

rotation

of

the CpW(CO)z unit was estimated to be close

to 3 kJ/mol.

Assignment of the 13C NMR data of other WRuz de-

rivatives is

also

based on the generalized experimental

observation that the symmetric isomers

b

give one W-CO

signal but the asymmetric isomers

a

give a pair of dia-

stereotopic W-CO signals. After the major isomer in so-

lution is established from the 13C NMR data, the relative

intensities of the corresponding Cp signals

or

the Cp*

signals in the

'H

NMR spectrum reveal a more accurate

ratio

a/b.

These data are listed in Table

VIII. Rotation of the Acetylide Ligand

on

the WRu,

Triangle.

The 'H NMR spectrum of 4 in toluene-d,

(Figure 5) shows two Cp signals a t 6 4.78 and 4.58 in the

ratio 1.2:l a t ambient temperature assigned to isomers

4b

and

4a,

respectively. When the system is warmed to 340

K, both Cp signals coalesce to a broad signal at

d

4.86,

suggesting the beginning of the interconversion between

4a

and

4b.

The exchange observed is consistent with a

120' rotation

(or

the so-called edge hopping)28

of

the

(27) Rosenberg, E.; Thoreen-Thorsen, B.; Milone, L.; Aime, S. Inorg. Chem. 1985, 24, 231.

l I l 1 l 1 1 1 1 1 1 1 l

5.00 4.90 4.80 4 . 1 0 4 . 6 0 4 . 5 0 4.40 ppm

Figure 5. Variable-temperature

'H

NMR

spectra (toluene-d8)

of 4 in the region of Cp resonances.

Table

IX.

Free Energy

(AG')

Data for the Acetylide

Isomerization of WRuz Derivatives and Racemerization of

MoRut Derivatives

comdex L R T,. K Av, Hz AG' kJ/mol

WRuz Derivatives 4

CP

Ph 337 80.00 68 6 CP C.5H.J 334 89.0" 67 7 Cp CBH,OMe 300 72.90 61 9 Cp "Pr 353 75.? 72 MoRuz Derivatives 10 Cp Ph 338 163.0b 67 11 Cp* Ph 303 46.4b 63

"The chemical shift difference between the Cp signals. 4The chemical shift difference between the diastereotopic W-CO signals.

C h a r t I

acetylide from a W-Ru edge to the Ru-Ru edge

(a

*

b

or

a'

Q

b,

Scheme

I).

From the coalescence temperature

of 337

K

for the Cp signals with chemical shift difference

(Av

**= 80.0 Hz), an estimate for AG* of 66 kJ/mol is ob-**

tained for the barrier of rotation. The kinetic parameters

of other WRu2 derivatives for this process, calculated from

the data of the variable-temperature 'H NMR studies, are

summarized in Table

IX. However, the second rotational process, racemization of

4a (a

*

a'),

consisting of a 120° rotation of the acetylide

over the tungsten atom, cannot be examined by 'H NMR

studies. On the other hand, the appropriate evidence is

deduced from the variable-temperature 13C NMR data.

The

13C

NMR spectrum of 4 in toluene-d, at 310

K

(Figure

S1 of the supplementary material) exhibits two W-CO

signals at 6 212.0 and 211.5 for isomer

4a

and one W-CO

signal a t

6

208.5 for isomer 4b. These three signals merge

to

the base line simultaneously on warming to 355

K

and

coalesce to a single line a t 6 209.5 on further warming to

373 K,

indicating that both the racemization

(a

*

a')

and

isomerization

(a

-

b)

occur at the same or about the same

rate.29 These observations indicate that the racemization

may either (i) involve a 240' rotation of the tilted acetylide

(28) Rosenberg, E.; Wang, J.; Gellert, R. W. Organometallics 1988, 7 ,

1093.

(29) The calculated chemical shift of the averaged W-CO signals (based on the chemical shifts at 310 K) for the exchange of the symmetric

and the unsymmetric isomers is at 6 210.0. We believe that the smell

difference (0.5 ppm) is caused by the temperature dependence of the

chemical shifts.

(9)

Vol. 9,

No.

10, 1990

2717

@

C13

un

W

Figure

6. ORTEP

diagram

of

CpMoRu,(CO)B(C=CPh)

(10).

(0

<

180") over both ruthenium atoms

(a

Q

b

-

a') or

(ii)

involve a common transition state in which the acetylide

C-C bond

is

perpendicular to the WRu2 triangle (Chart

I).

The third possibility involving a direct 120" rotation

of the tilted acetylide

(0

<

180") over the tungsten atom

(a

(=$

a')

is presumably a process with a slightly greater

barrier because of the repulsion imposed by the bulky Cp

ligand. Finally, although we are unable to eliminate the

first and third possibilities involving the titled acetylide

moiety, the second pathway involving the vertical acetylide

moiety is preferred. The participation of a similar inter-

mediate containing a vertical C2 vinylidene moiety has

been claimed to account for the isomerization of the eth-

oxyvinylidene ligands of the osmium cluster

H20s3-

Preparation and Characterization of the

MoRu2

Complexes.

The related MoRu2 derivatives

(10,

L

= Cp,

R = Ph;

11,

L

=

Cp*, R = Ph;

12,

L

= Cp, R = tBu; 13,

L

**= Cp*, R = tBu; 14,**

L

= Cp, R = C6H4F) were syn-

thesized from reactions between R U ~ ( C O ) ~ ~

and the re-

spective molybdenum acetylide under similar conditions.

The X-ray structural determination on phenyl derivative

10 suggests that it has a structure similar to those of

complex

1 and complex 12,28 both possessing the asym-

metric arrangement (Figure 6).

Consistent with the

solid-state structure, its 13C NMR spectrum at 215

K

ex-

hibits two Mo-CO signals at 6 226.4 and 225.3 and six

Ru-CO signals a t 6 202.6, 202.0, 196.6, 196.2, 194.3, and

193.7 (Figure

S2).

When the sample is warmed to 275

K,

the signals at 6 202.6,194.3, and 193.7 and at 6 202.2,196.6,

and 196.2 each coalesce to a singlet a t 6 196.4 and a broad

signal at 6 197.8, indicating the onset of the localized Ru-

(CO), rotation. A similar structure was proposed for the

**respective Cp* derivative 11; further support comes from**

the 13C NMR spectrum at 244

K,

which shows two Mo-CO

singlets a t

6

230.0 and 229.5 in the intensity ratio 1:l and

four Ru-CO signals a t 6 201.4, 197.6, 193.7, and 192.8 in

the ratio 1:3:1:1.

Although the assignment of complexes

10 and 11 in

solution is straightforward, the assignment of the tert-butyl

derivatives

12 and 13 is quite different. First, the IR

spectrum of

12 in the region of CO absorptions indicates

the existence of two isomers. The identity of each isomer

is then confirmed by the 13C NMR studies at 205

K,

which

(CO)g(C=CHOEt).30

cJz_

)k

360K n 338K I " " I " " I ' " I ' " ' I ~ ' ' ~ I ~ ' ' ' 205 200 195 ppm 230 225 220

Figure 7.

Variable-temperature

13C

NMR spectra (toluene-d8)

of 10 in

the

region of

CO resonances.

Scheme I1

a a'

show the expected eight-line pattern (two Mo-CO and six

Ru-CO signals) at 6 225.9,225.5, 204.0, 202.4, 197.4, 196.4,

194.8, and 194.3 assigned

to

isomer

12a

and the two-line

pattern of isomer

12b

(one Mo-CO and Ru-CO signal) at

6 223.0 and 200.1 in the ratio 1:3. From the intensity ratio

of 13C NMR integration, the abundance

12a:12b

is calcu-

lated to be 19:l. This assignment is in contrast with that

of the recently published report on

12,%

and the incorrect

deduction

was

probably made because of the low concen-

tration of

12b

in solution. Furthermore, the 13C NMR

spectrum

of 13a

at 200

K

exhibits one sharp Mo-CO signal

at 6 227.0 and three broad Ru-CO signals at 6 207.0,200.6,

and 191.9 in the ratio l:l:l:l, consistent with the adoption

of a symmetric arrangement.

Description of the Solution Dynamics of the

MoRu,

Complexes.

The acetylide ligand of the MoRu2 complexes

10 and 11 is associated with one of the Mo-Ru bonds;

therefore, its fluxional motion (Scheme

11)

can be exam-

ined by 13C NMR studies. The 13C NMR spectrum of

10 at 294

K

(Figure 7) exhibits two Mo-CO signals a t

b

226.8 and 225.2, a sharp Ru(CO), signal a t 6 198.4, and a broad

Ru(CO), signal at 6 196.9. When the temperature is in-

creased gradually, the sharp Mo-CO signals start to

broaden and the broad Ru(CO), signals start to sharpen.

However, both the Mo-CO and the R~(CO)~.signals

col-

lapse in a pairwise manner at 338

K,

indicating that the

molecule begins to acquire a time-averaged mirror plane.

This observation cannot be explained according to the

concept of intermetallic Ru-CO scrambling proposed

for

the RU,(CO)~(C"L~BU)-

anion.31 Thus, we propose that

a further fluxional process, i.e. migration of the acetylide

(30) Boyar, E.; Deeming, A. J.; Felix, M. S. B.; Kabir, S. E.; Adatia, T.; Bhusate, R.; McPartlin, M.; Powell, H. R. J. Chem. Soc., Dalton Trans. 1989, 5.

(31) Barner-Thonen, C.; Harcastle, K. I.; Rosenberg, E.; Siege], J.; Manotti Landfredi, A. M.; Tiripicchio, A.; Tiripicchio Cammellini, M.

Inorg. Chem. 1981,20, 4306.