Synthesis and characterization of tetranuclear hydroxcarbonyl complexes of molybdenum and tungsten, [Et4N]4[Mo(CO)3(η3-OH)]4 and [Et4N]4[W(CO)3(η3-OH)]4

Journal of Organometallic Chemistry, 361 (1989) 89-99

Ekvier Sequoia !%A., Lausanne - printed in The Netherlands

Synthesis and characterization of tetranuclear hydroxocarbonyl

complexes of molybdenum and tungsten,

Jiann T. Lii *, Show K. Yeh,

Institute of Chemistv, Academia Sinica, Nankang Taipei, Taiwan (Republic of China)

Gene EL Lee, and Yu Wang *

Department of Chemistry, National Taiwan University, Taipei, Taiwan (Republic of China)

(Received May 31st, 1988)

Abstract

Reaction of M(CO),(PMTA) (M = W, MO; PMTA = 1,1,4,7,7-pentamethyldieth- ylenetriamine) with a stoichiometric amount of hydroxide ion in aqueous THF solution yields [M(CO),(~~-OH)]44- (1, M = W; 2, M = MO). These tetranuclear metal carbonyl complexes were isolated as their Et,N+ salts. The crystal structures of both complexes have been determined. Compounds 1 and 2 are isostructural; the crystals are monoclinic, space group C2/c, Z= 4, with unit cell dimensions a 23.86(3), b 12.317(7), c 23.21(l) A, /3 1238(2)O for 1; and a 23.888(7), b 12.300(2), c 23.254(3) A, j3 123.85(2)” for 2. The anions consist of a distorted cubic A4B4 (A = metal, B = oxygen) core with triply hedging hydroxide groups and M(CO), units. The M-M distances (average 3.59(6) A for 1 and 3.58(6) A for 2) within the

M404 core clearly show non-bonding between metal atoms which is consistent with a closed-shell metal configuration.

lntroduclion

Transition-metal oxide compounds are of fundamental importance in the cata- lytic oxidation of hydrocarbons, and in the polymerization and metathesis of olefins [l]. The catalytic activities of the metal oxides are thought to depend on their acid-base properties [2]. Polynuclear organometallic complexes containing hydroxyl groups are interesting not only because they could serve as models for the acid-base character of metal oxides, but also because they are closely related to the recently developed oxide-supported organometallic catalysts [3], such as Mo(CO), + ahunina + Mo(CO),(ads) + 3C0. Polynuclear carbonyl clusters containing hydroxyl ligands

are not very common. Of these complexes, [Re(CO),(OH)], [4], [Mo(CO),(NO)- (OH)], 151, and [Cr(CO),(OH)1,4- [6] all consist of four tetrahedral arrays of M(CO),L (L = CO or NO) units held together by four triply-bridging OH groups. This cubic tetranuclear structure has also been observed in some closely related complexes containing organo-oxo or organo-thio ligands such as [Cr(CO),(OC,H,)],

[61,

[Cr(CO),(OMe)144- 171, and ]Re(CO),(SMe)l, 181.

Protonation of the tri(p-hydroxo) trianion [M2(~-OH),(CO),]3- (M = MO, W) [9] results in the formation of Hieber’s acid, [HM(C0)3(p3-OH)]4, originally formulated as H, M, (p-OH) 3 (CO),. The presence of four triply bridging hydroxo groups and the tetrahedral array of M(CO), units in Hieber’s acids has been confirmed on the basis of the structural characterization of the tungsten derivatives [HW(CO),(OH)(PPh,O)], [lo]. It is surprising that the “conjugate base” of Hieber’s acid,

PfWO)3(~3-OH)144-,

being iso-electronic with [ Re(C0) 3 ( p 3-OH)] 4, remains

elusive in the literature. There is no reaSon why these anions should not exist. The chromium cognate in this family, [CI(CO),(~~-OH)]~~-, has recently been success- fully isolated [6]. Here we report our successful synthesis, and the characterization of the conjugate bases of two compounds, [Et4N]4[M(CO)3(~3-OH)]4 (M = W, MO).

Experimental

All manipulations were carried out under purified N, using standard Schlenk techniques, or in a Vacuum Atmosphere DL-08/85 drybox. THF was distilled from blue Na-benzophenone ketyl solution before use. Acetonitrile and methanol were purged thoroughly with dry N,, refluxed over P,Os and Mg/I,, respectively, and distilled under N,. All other solvents were stored over 4 A molecular sieves and purged with N, before use. Mo(CO), and W(CO), were purchased from Strem Chemicals Inc. ; 1,1,4,7,7-pentamethyldiethylenetriamine (PMTA) was purchased

from Eastman Kodak; tetraethylammonium hydroxide (20 wt.% in H,O) from Merck. M(CO),(PMTA) (M = MO, W) was prepared by a published procedure [l]. The IR spectra were recorded on a Perkin-Elmer 880 spectrometer. The NMR spectra were recorded on a Bruker MSL 200 spectrometer. Melting points were determined in N,-filled capillaries using a Buchi 520 apparatus and are uncorrected. Elemental analyses were performed by Taipei Regional Instrumental Center.

[Er4N]q[W(CO)3(~3-OH)/4 (2). To a solution of W(CO),(PMTA) (2.10 g, 4.76 mmol) in 60 ml of THF was added 40 ml of H,O and 3.5 ml (4.76 mmol) of aqueous Et,NOH (20 wt.%). The contents of the flask were heated at 85 o C for 5 h. The solution separated into two layers during the reaction. After cooling, the solution was evaporated to dryness. The yellow crystals so obtained were washed with MeOH (2 x 20 ml), THF (2 x 20 ml), and dried in vacua. Yield: 1.74 g, 89% based on W(CO),(PMTA). IR: (v(CO), CH,CN) 1868(s), 1727(vs) cm-‘; (Y(OH), Nujol mull) 3676(m) cm-‘. i3 C NMR (6 0 ppm for TMS): (6(CO), CD&N) 231 ppm. ‘H NMR (CD,CN): 6 3.28 (q, J(H-H) 7.2 Hz, 8H, CH,), 1.31(tt, J(H-N) 1.7 Hz, 12H, CH,), 0.96 ppm (s, lH, OH). The compound decomposes at 181°C. Anal. Found: C, 31.55; H, 5.23; N, 3.09. C,H,,N,O,,W, calcd.: C, 31.82; H, 5.10; N, 3.37%. The p3-OD derivative of 1 was prepared similarly, except that Et,NOD, D,O, and CD,OD were used in the reaction. Et4NOD was prepared as follows: The solid Et,NOH obtained by removal of water from the commercial aqueous Et,NOH

was stirred with a lOO-fold excess of D,O. The process was repeated three times to ensure maximal H/D exchange. The p,-OD derivative of 1 has a v(OD) band at 2712 cm-‘.

[Et4N]q[Mo(CO)~~~3-OH)14 (2). To a solution of Mo(CO),(PMTA) (500 mg, 1.42 mmol) in 25 ml of THF was added 25 ml of H,O and aqueous Et,NOH (1.0 ml, 1.42 mmol). The solution was heated at 85 o C for 2 h. After cooling, the solution was evaporated to dryness and the yellow crystals obtained were washed with MeOH (2 x 20 ml), THF (2 x 20 ml), and then dried in vacua. Yield: 300 mg, 65% based on Mo(CO),(PMTA). IR: (v(CO), CH,CN) 1871(s), 1736(vs) cm-‘; (v(OH), Nujol mull) 3691(m) cm -I. 13C NMR: (S(CO), CD,CN) 234 ppm. ‘H NMR (CD&N): S 3.28 (q, J(H-H) 7.2 Hz, 8H, CH,), 1.31 (tt, J(H-N) 1.7 Hz, 12H, CH,), - 0.27 ppm(s, lH, OH). The compound decomposes at 189 o C. Anal. Found: C, 40.13; H, 6.68; N, 4.23. C,H,,Mo4N,0,, calcd.: C, 40.38; H, 6.47; N, 4.28%. The p,-OD derivative of 2 was prepared similarly. It has a v(OD) band at 2712 cm-‘.

Crystallographic studies. Crystals of 1 and 2 suitable for X-ray diffraction

measurements were -grown by slow diffusion of THF into a concentrated solution of 1 or 2 in CH,CN. Crystals were coated with Nujol and mounted in the thin-walled glass capillary tubes under nitrogen. Diffraction measurements were made on an Enraf-Nonius CAD-4 diffractometer using graphite-monochromated MO-K, radia- tion (X 0.7107 A) with the 8-28 scan mode. Unit cells were determined from

Table 1

Crystal data for compound 1 and 2

Formula Formula wt a,A b,A 0 T;, :eg Cryst syst spa= group Z v, K ddtiV g/cm3 Cryst sire, mm Radiation II (cm-‘) Transmission factors (ma% mini 28 range octants

No. of unique reflns Reflns with Z > 30 No. of variables R; R, Extinction coeff 1 2 CU~-~LWN~%W~ C&f~4N&sMo.+ 1660.6 1308.9 23.86(3) 23.888(7) 12.317(7) 12.300(2) 23.21(l) 23.254(3) 123.8(2) 123.84(2) monoclinic monoclinic c2/c c2/c 4 4 5668.21 5674.37 1.946 1.532 0.65 x 0.65 x 0.65 0.35 x 0.35 x 0.43 Mo-AK, (A = 0.7107 A) Mo-K, 83.3 9.0 1.00; 0.79 1.00; 0.94 O-50 O-50 *h,+k,+I f h,+k,+l -28-28,0-14,0-27 -28-28,0-14,0-27 4978 4979 4147 3907 288 288 0.038; 0.046 0.041; 0.061 2.7(4)x 1O-4 5.4(4)X 1o-4

92 Table 2

Atomic coordinates and B_, for [W(CO)&,-0H)14(NEt,), esd’s refer to the last digit

W(l) W(2) c(1) c(2) C(3) c(4) c(5) C(6) o(1) o(2) o(3) o(4) o(5) o(6) o(7) O(8) NlA ClA C2A C3A C4A C5A C6A C7A C8A NIB ClB ClB’ C2B C3B C3B’ C4B C5B C5B’ C6B C7B C7B’ C8B C8B’ HO(7) HO@) X _Y z

_B-l

a

0.591436(18) 0.02476( 3) 0.313239(U) 2.458(19) O&5650(18) 0.6719(5) 0.6549(5) 0.6052(6) 0.5402(5) 0.4082(5) 0.486q5) 0.7242(4) 0.6943(4) 0.6159(5) 0.5710(4) 0.3608(4) 0.4855(4) 0.4906(3) 0.5631(3) 0.2735(4) 0.2015(6) 0.1586(6) 0.3061(7) 0.3801(6) 0.2827(7) 0.2511(9) 0.308q6) 0.3056(7) 0.4086(5) 0.4213(19) O&23(10) O&76(7) 0.4005(18) 0.4089(15) 0.3664(U) 0.3336(18) 0.3422(14) 0.2835(12) O&9(3) 0.4499(13) 0.524(3) 0.5213(20) 0.494(3) 0.406(4) - 0.17166(3) 0.0179(10) 0.0223(8) 0.1774(9) -0.1711(8) - 0.1678(9) -0.3253(g) 0.0161(9) 0.0227(8) 0.2725(7) - 0.1740(8) - 0.1691(7) - 0.4164(6) 0.0047(5) - 0.1514(5) 0.4148(7) 0.4451(11) 0.3901(14) 0.478qll) 0.4518(12) 0.2955(12) 0.2500(12) 0.4445(13) 0.5672(14) 0.6886(7) 0.786(3) 0.7687(17) 0.8833(11) 0.599(3) 0.577(3) 0.4899(17) 0.709( 3) 0.7163(23) 0.7345(20) 0.649(5) 0.6934(21) 0.639(4) 0.679(3) 0.052(6) 0.219(6) 0.319909(M) 0.3151(5) 0.4117(5) 0.3174(6) 0.4199(5) 0.3249(5) 0.3349(5) 0.3186(5) 0.4726(4) 0.3201(5) 0.4796(4) 0.3277(4) 0.3493(4) 0.2986(3) 0.2951(3) 0.6689(4) 0.6283(6) 0.6517(7) 0.6392(6) 0.6732(7) 0.6649(8) 0.5931(8) 0.7445(6) 0.7562(8) 0.5117(5) 0.5523(19) 0.4919(10) 0.5173(7) 0.5481(18) 0.4813(15) 0.4988(11) 0.4314(18) 0.5001(14) 0.4356(12) 0.487(3) 0.5973(13) 0.568(3) 0.6371(20) 0.344(3) 0.681(4) 2.372(18) 4.2(6) 3.8(6) 4.4(7) 3.4(6) 3.5(6) 3.6(6) 7.1(7) 6.9(6) 6.9(7) 5.9(5) 5.3(5) 5.7(5) 2.5(3) 2.3( 3) 3.9(5) 5.7(8) 7.1(10) 5.8(9) 6.1(9) 6.9(10) 8.4(12) 6.4(9) 8.5(12) 4.4(6) 9.9(10) 3.8(4) 6.2(3) 9.2(9) 7.1(7) 11.4(6) 9.3(9) 6.3(6) 13.7(7) 17.6(20) 5.7(6) 15.2(16) 10.2(11) 6.3 6.3

u B_ is the mean of the principal axes of the thermal ellipsoid occupancy of ClB, ClB’, C3B, C3B’, C5B, C5B’, C7B, C7B’. C8B, C8B’ = 0.5.

centering 25 reflections in the 28 range 16.96-23.80° for 1 and 23.34-27.14O for 2. Other relevant experimental details are listed in Table 1. Absorption corrections according to JI scans of three reflections were applied. All the data processing was carried out on a PDP 11 and VAX 780 using the NRCC SDP program [12]. The

coordinates of the tungsten or molybdenum atoms were obtained from Patterson syntheses. The coordinates of all the remaining atoms were obtained from a series of structure factor calculations and Fourier syntheses. The structures were refined by

Table 3

Atomic coordinates and Beq for [Mo(CO),(p3-OH),(NEt4)4 eds’s refer to the last digit.

X Y z _Bea

o

MW) MW) c(l) c(2) c(3) c(4) C@) c(6) o(l) o(2) o(3) o(4) o(S) o(6) o(7) o(8) NlA ClA C2A C3A C4A CSA C6A C7A C8A NlB ClB C2B C3B C4B CSB C6B C7B C8B ClB’ C3B’ CSB’ C7B’ C8B’ H0(7) H0(8)

D B_ is the mean of the principal axes of the thermal ellipsoid occupancy of ClB, ClB’, C3B, C3B’, CSB, CSB’, C7B, C7B’, C8B, C8B’ = 0.5. 0.591188(23) 0.485675(23) 0.6718(3) 0.6542(3) 0.6055(3) 0.5391(3) 0.4089(3) 0.4847(3) 0.7243(3) 0.6960(3) 0.6185(3) 0.5706(3) O-36207(24) ‘0.4841(3) 0.49037(17) 0.56425(17) 0.27299(25) 0.2016(4) 0.1585(4) 0.3069(4) 0.3804(4) 0.2831(4) 0.2531(S) 0.3074(4) 0.3051(5) 0.4096(3) 0.4225(11) 0.4478(4) 0.3972(11) 0.3709(6) O-3377(12) 0.2845(7) 0.4555(13) 0.5292(13) O&41(7) 0.4107(9) 0.3421(9) 0.4510(8) 0.5235(12) 0.494(3) 0.594(4) 0.02546(4) -0.17021(4) 0.0193(6) 0.0229(S) 0.1794(S) -0.1707(S) -0.1662(S) -0.3221(S) 0.017q6) 0.0233(S) 0.2722(4) -0.1778(S) -0.1686(S) -0.4135(4) 0.0072(3) -0.1523(3) 0.4143(S) 0.4460(7) 0.3882(9) 0.4767(7) 0.4512(g) 0.2919(g) 0.2495(g) 0.4415(8) 0.5643(9) 0.6889(S) 0.7896(19) 0.8844(8) 0.5960(21) 0.4890(10) 0.7094(21) 0.7327(12) 0.6564(23) O&411(23) 0.7704(12) 0.5773(16) 0.7174(15) 0.6975(14) 0.6731(19) 0.052(6) - 0.219(6) O-312875(24) 0.319647(23) 0.3147(3) 0.4110(3) 0.3171(4) 0.418q3) 0.3255(3) 0.3348(3) 0.3200(3) 0.47107(24) 0.3212(3) 0.47951(23) 0.32%(3) 0.3517(3) 0.29974(17) 0.29593( 18) 0.6685(3) 0.627q4) 0.6507(S) 0.6395(4) 0.673q4) 0.6664(S) 0.5936(S) 0.7446(4) 0.7564(S) 0.5129(3) 0.5492(12) 0.5180(S) 0.5473(12) 0.499q6) O-4345(13) 0.4333(g) O&381(14) 0.5743(14) 0.4920(7) 0.4843(9) O.SOOS(9) 0.5980(9) 0.6340(12) 0.344(3) 0.319(4) 2.422(23) 2.342(23) 4-o(4) 3.6(4) 3.9(4) 3.3(3) 3.3(3) 3.4(3) 6.9(4) 6.8(4) 6.8(4) 5.9(3) SS(4) 5.6(3) 2.42(19) 2.34(19) 3.7(3) 5.8(S) 6.8(6) 5.6(S) 6-o(6) 6.q6) 7.7(7) 5.9(S) 7.5(7) 4.1(3) 8.7(6) 6.42(20) 9.q6) 9.6(3) 9.9(6) 12.5(4) 11.6(8) llS(8) 4.2(3) 6.7(4) 6.1(4) 5.6(4) 9.0(6) 6.3 6.3

nlinhkng

c;wi(~ob” - lyq2,

where wi was calculated from the counting statis-

tics. The atomic scattering factors

f.

and anomalous dispersion terms f ‘, f” were taken from ref. 13. All the non-hydrogen atoms, except the ethyl carbon atoms of NIB, were refined anisotropically. Hydrogen atoms in the anions were located in the final difference Fourier maps and refined. A secondary extinction correction was included in the refinement. One of the cations (NIB) was found to have some disorder atoms; namely all the a-carbon atoms and one of the &carbon atoms. The disordered atoms, listed in Tables 2 and 3, are marked with an apostrophe (‘)_

Reaction of M(CO),(PMTA) (PMTA = 1,1,4,7,7-pentamethyldiethylenetriamine) with one equivalent of Et,NOH in aqueous THF at 85 O C, gave the yellow crystalline compound, [Et4N]4[M(CO),(pC13-OH)]d (1, M = W; 2, M = MO). The infrared carbonyl region of 1 and 2 exhibited the two-band pattern (Y(CO) 1868(s), 1727(vs) cm-’ for 1, and 1871(s), 1736(vs) cm-’ for 2) characteristic of a M(CO), moiety. Only one carbonyl signal (6 231 ppm for 1 and 234 ppm for 2) in the 13C NMR spectra was observed, indicating that all the carbonyl groups are equivalent in the solution. A Y(OH) band of medium intensity observed at 3676 cm-’ for compound 1, and at 3691 cm - ’ for compound 2 is indicative of the presence of a bridging hydroxide ligand. Peaks assignable to the p3-OH resonance appeared at S 0.96 (compound 1) and at - 0.27 ppm (compound 2) in the ‘H NMR spectra. In order to characterize these species fully, single crystal structural determinations of 1 and 2 were undertaken. The structure of [Mo(CO) 3( P~-OH)]~~- is shown in Fig. 1. Atomic parameters are given in Table 2 and 3. Selected bond distances and angles are collected in Tables 4 and 5.

Fig. 1. ORTEP drawing of [Mo(CO)3(~3-OH)]4 4- Thermal . ellipsoids are drawn with 50% probability boundaries.

Table 4

Selected interatomic distances (A) and angles (deg) with esd’s for [W(CO),(~,-OH)]s4- a

Distances W(l)-W(l)a W(l)-W(2)a W(l)-C(l) W(l)-C(3) W(2)-c(5) W(l)-o(7) W(l)-o(8) W(2)-o(8) c(l)-o(l) C(3)-o(3) C(5)-o(5) O(7)-0(7)a O(7)-O(8)a Angles WWWl-W(l)a W(l)a-0(7)-W(2) W(l)-O(8)-W(2)a 0(7)-W(l)-Oa 0(7)a-W(l)-0(8) 0(7)-W(2)-0(8)a W(l)-C(l)-o(l) W(l)-C(3)-o(3) W(2)-C(5)-o(5) 3.661(9) 3.530(4) 1.899(10) 1.902(11) 1.915(10) 2.25q6) 2.241(6) 2.236(6) 1.205(13) 1.193(14) 1.169(12) 2.535(11) 2.639(8) W(l)-W(2) W(2)-W(2)a W(lhc(2) W(2)-c(4) W(2)=(6) W(l)-0(7)a W(2)-o(7) W(2)-0(8)a cX2)-0(2) c(4)-o(4) c(6)-o(6) 0(7)-o(8) o(8)-o(8)a 3.5616(24) 3.6709(24) 1.915(11) 1.928(10) 1.924(10) 2.231(8) 2.245(6) 2.254(6) 1.184(13) 1.152(11) 1.172(12) 2.618(8) 2.537(12) 109.6(3) 104.13(24) 103.47(22) 68.91(24) 72.32(21) 71.81(20) 177.4(9) 177.6(10) 177.8(10) WbWbY2) W(l)-0(8)-W(2) W(2)-O(8)-W(2)a o(7)-W(l)-o(8) o(7)-W(2)-o(8) O(8)-W(2)-O(8)a W(l)-c(2)-o(2) W(2)-C(4)-o(4) W(2)-c(6)-o(6) 104.83(23) 105.41(23) 109.7(3) 71.32(21) 71.52(20) 68.8q24) 178.9(9) 177.1(9) 173.4(9) a Atoms, W(l)a, W(2)a, 0(7)a, 0(8)a, are symmetry equivalent.

Complexes 1 and 2 are isostructural, and have the same structure as the chromium analogue. Thus they ah crystaIIize in the same space group *. The anions of 1 and 2 are composed of four [M(CO),(OH)]- units in a cubane-Iike arrangement with metal and hydroxide oxygen atoms located at alternate comers of a distorted M404 cube. In 1, the average W-W distance is 3.59(6) A, and the ayerage O-O distance is 2.60(5) A. In 2, the fverage MO-MO distance is 3.58(6) A while the average O-O distance is 2.65(5) A. The coordination geometry of each metal is a distorted octahedron. Each metal is bonded to three cis-CO Iigands and three 0 atoms of the hydroxide groups. Each p3-oxygen atom is bonded to three metal atoms and a hydrogen atom. Although such hydrogen atom positions cannot be ascertained from X-ray diffraction, the IR spectra (vide supra) do indicate the existence of hydroxide groups.

Other relevant bond distances and angles are as follows. The average

W-O(P~)-W,

Pfo-O(~~)-Mol ad W+W-o(&

[O(P~)-MO-O(P~)I bond

angles are 106(3) o [105(3) “1 and 71(l) O [72(2) O 1, respectively. Within the tungsten

(molybdenum) coordination sphere, the W-O@,) distant is 2.24(l) A (2.25(l) A) and the W-C,, (MO-C,,) distance is 1.92(l) A (1.91(l) A). The terminal carbonyl

* 12/a in ref. 6 can be transformed into C2/c, a correction has to be made for 2 = 4 according to the formula given.

96

Table 5

Selected interatomic distances (A) and angles (deg) with esd’s for [Mo(CO)s(ps-OH)]44- u Distances Ma(l)-Mo(l)a Me(l)-Mo(2)a Ma(l)-C(1) Me(l)-C(3) Mo(2w5) Ma(l)-O(7) Ma(l)-0(8) Mo(2)-0(8) C(l)-o(l) C(3)-O(3) C(5)-O(5) O(7)-O(7)a O(7)-0(8)a Angles Ma(l)-O(7)-Mo(l)a Mo(l)a-O(7)-Mo(2) Ma(l)-O(S)-Mo(2)a O(7)-Ma(l)-O(7)a 0(7)a-Ma(l)-O(8) O(7)-Mo(2)-O(8)a MO(~)-C(l)-O(1) Ma(l)-C(3)-0(3) Mo(2)-C(5)-0(5) 3.6524(17) 3.5153(9) 1.905(7) 1.917(7) 1.912(6) 2.264(4) 2.251(4) 2.243(4) 1.188(8) 1.172(8) 1.177(7) 2.598(7) 2.695(5) 108.36(15) 103.17(14) 102.28(14) 70.43(13) 73.74(13) 73.40(13) 175.9(6) 175.7(6) 177.0(6) Mo(l)-Mo(2) Mo(2)-Mo(2)a Ma(l)-C(2) Mo(2)-C(4) Mo(2)-C(6) Ma(l)-0(7)a Mo(2)-O(7) Mo(2)-O(8)a C(2)-O(2) C(4)-O(4) C(6)-O(6) 0(7)-o(8) 0(8)-0(8)a Mo(lWWMti2) Mo(l)-W)-Mti2) Mo(2)-O(8)-Mo(2)a 0(7)-Ma(l)-0(8) 0(7)-Mo(2)-0(8) o(8)-Mvro(2)-o(8)a Ma(l)-C(2)-O(2) Mo(2)-C(4Fq4) Mo(2)-C(6)-0(6) 3.5513(9) 3.6644(10) 1.910(6) 1X8(6) 1.903(6) 2.241(3) 2.246(4) 2.264(3) 1.181(8) 1.183(7) 1.195(8) 2.672(5) 2.585(7) 103.91(14) 104.44(14) 108.83(14) 72.59(13) 73.08(13) 70.01(13) 176.1(6) 175.6(6) 171.3(6) a Atoms, Mo(l)a, Mo(Z)a, 0(7)a, 0(8)a, are symmetry equivalent.

ligands have an average W-C-O (MF-C-O) bond angle of 177(2) o (175(2) o ) and a C-O distance of 1.18(2) A (1.18(l) A).

Discussion

The structures observed for [W(CO),(P~-OH)]~~- and for [Mo(CO),(~,-OH)]44- are the same as that of [Cr(CO),(~3-OH)]44- [6]. The symmetry of the anion is C,, which coincides with the crystallographic 2-fold axis. Other polynuclear complexes of the alternating A4B4 type have similar symmetry or even more symmetric geometries, e.g. [ Cr(C0) 3( p ,-OMe)] 44- has & 171 and

[Mo(COM~OWH)14 161

has T,. The observed W-W (MO-MO) mean distance of 3.59(6) A (3.58(6) A) indicates the absence of metal-metal bonds in such anions, since it is much longer than the W-W single bonds reported elsewhere 3.222(l) A in [C,H,W(CO),], [14], 3.155 A in I,Wz(CO), [15], and 3.0256(4) A in W,(CO),(p-PPh,), [16]. The non-bonding between the metal atoms or ions are also formally in accord with the l&electron rule, where /.t3-OH group is normally considered to be a five-electron donor. The obtuse M-O-M angles of 106(3) o for 1 and 105(3)O for 2, and the acute O-M-O angles of 71(l) O for 1 and 72(2)O for 2 as well as the large metal separation are similar to those found for a series of cubane-like A4B4 complexes [17]. The average core bond angles and non-bonding M-M distances of these complexes are listed in Table 6 for comparison. In contrast, shorter metal-metal

98

However, our ‘H NMR spectroscopic data strongly disfavor the existence of (p-H)W,(CO),,- [27], HW(CO),- [28], and W,(~-OH)3(C0)63- [9,29]. These com- plexes were reported to form from reaction of W(CO), with OH- under different conditions. We presently do not know why no discernible M,(F-OH),(CO),~- were detected in our case. When M(CO),(PMTA) was allowed to react with an excess (more than five-fold) of Et,NOH or KOH, the tetrameric [M(CO)3(OH)],4- was contaminated with unidentified materials. No peaks assignable to M2( CL-

ow,m,3- [291 were detected, however. A speculative mechanism for the forma-

tion of 1 and 2 from M(CO),(PMTA) involves a reversible ring opening (with scission at the M-N bond) followed by nucleophilic attack by OH-. Such a mechanism has been proposed in the reaction of Mo(CO),(PNP) (PNP = Ph,PCH,CH,N(Et)CH,CH,PPh,) with CO [30].

The large upfield shift of the hydroxide ligand in the ‘H NMR spectra is consistent with their basic character, i.e., the hydrogen atoms in [M(CO)3(~3-OH)]44- are readily replaced by deuterium with D,O (lo-fold excess) within 30 minutes, the reaction product being [ M(C0) 3 (p 3-OD)] 44-. Our preliminary results indicate that 1 reacts with electrophiles such as NO+BF,-, Ph,PAuCl and iodine. Further studies on the reactions of 1 and 2, as well as the extension of similar synthetic strategy to other cubane type complexes are in progress.

Supplementary material available: Tables SI and SII listing anisotropic temper-

ature factors and hydrogen atom coordinates and isotropic thermal parameters (6 pages); tables of calculated and observed structure factors (66 pages); Table SIII listing all bond distances and angles (6 pages), are all available from the authors.

Acknowledgement

The authors express their appreciation to the Institute of Chemistry, Academia Sinica, and to the National Science Council, Republic of China, for support of this work.

References

1 (a) R.A. Sheldon and J.K. Kochi, Metal-Catalyzed Oxidations of Organic Compounds, Academic Press, New York, 1981; (b) C.N. Satterfield, Heterogeneous Catalysis in Practice., McGraw-Hill Inc., New York, 1980; (c) R. Higgins, P. Hayden, in C. KernbalI (Ed.), Catalysis, The Chemical Society, 1977, Vol 1, Chapter 5.

2 K. Tanabe, in J.R. Anderson and M. Boudart (Eds.), Catalysis, Springer-Verlag, Berlin, 1981, Vol 2, Chapter 5.

3 (a) H. Kn&inger, in B.C. Gates, L. Guczi and H. Knozinger (Eds.), Metal Clusters in Catalysis, Elsevier, Amsterdam, 1986, Chapter 6; (b) J.M. Basset and A. Choplin, J. Mol. Catal., 21 (1983) 95; (c) Y.J. Yermakov, J. Mol. Catal., 21 (1983) 35; (d) R. Barth, B.C. Gates, Y. Zhao, H. Kntinger and J. Hulse, J. Catal., 82 (1983) 147; (e) A. Brenner and D.A. Hucul, J. Am. Chem. Sot., 102 (1980) 2484. 4 (a) M. Herberhold and G. Slim, Angew. Chem., Int. Ed. Engl., 14 (1975) 700; (b) M. Herberhold; G.

Stiss, J. Ellermann and H. Gabelein, Chem. Ber., 111 (1978) 2931.

5 V. Albano, P. BeIIon, G. Ciani and M. Manassero, J. Chem. Sot., Chem. Commun., (1969) 1242. 6 T.J. McNeese, T.E. Mueller, D.A. Wierda and D.J. Darensbourg, Inorg. Chem., 24 (1985) 3465. 7 T.J. McNeese, M.B. Cohen and B.M. Foxman, Organometalhcs, 3 (1984) 552.

8 E.W. Abel, W. Harrison, R.A. McLean, W.C. Marsh and J. Trotter, J. Chem. Sot., Chem. Commun., (1970) 1531.

9 (a) W. Hieber, K. Englert and K. Rieger, Z. Anorg. Allg. Chem., 300 (1959) 295, and 304. 10 V.G. Albano, G. Ciani, M. Manassero and M. Sansoni, J. Grganomet. Chem., 34 (1972) 353.

11 J.E. ElIis and G.L. Rochfort, Grganometalhcs, 1(1982) 682.

12 (a) E.J. Gabe and F.L. Lee, Acta CrystaBogr., 37 (1981) S339; (b) E.J. Gabe, Y. LePage, P.S. White and F.L. Lee, ibid., 43 (1987) C294.

13 International Tables for X-ray Crystallography: Kynoch, Birmingham, England, 1974, Vol IV and Vol III, p. 276.

14 RD. Adams, D.M. CoBins and F.A. Cotton, Inorg. Chem., 13 (1974) 1086.

15 M.C. G&dwell, J. Simpson and W.R. Robinson, J. Grganomet. Chem., 107 (1976) 323. 16 S.G. Shyu, M. CaIligaris, G. Nardin and A. Wojcicki, J. Am. Chem. Sot., 109 (1987) 3617. 17 A.S. Faust and L.F. DahI, J. Am. Chem. Sot., 92 (1970) 7337.

18 B. Nuber, F. Oberdorfer and M.L. ZiegIer, Acta Crystallogr. B, 37 (1981) 2062. 19 W. Harrison, W.C. Marsh and J. Trotter, J. Chem. Sot., Dalton Trans., (1972) 1009. 20 D. Bright, Chem. Commun., (1970) 1169.

21 T.G. Spiro, D.H. Templeton and A. ZaIkin, Inorg. Chem., 7 (1968) 2165. 22 F. Bottom@, D.E. Paea and P.S. White, J. Am. Chem. Sot., 104 (1982) 5651. 23 (a) R.S. Gail, CT.-W Chu, F.Y.-K Lo and L.F. Dahl, ibid., 104 (1982) 3409.

24 L.L. Nelson, F. Yip-kwaiIo, D. Rae and L.F. DahI, J. Grganomet. Chem., 225 (1982) 309.

25 (a) F.A. Cotton and R.M. Wing, Inorg. Chem., 4 (1965) 314; (b) D.E. Koshland, S.E. Myers and J.P. Cheswick, Acta CrystaIlogr. B, 33 (1977) 2013; (c) W.H. Hersh, J. Am. Chem. Sot., 107 (1985) 4599. 26 M. Herberhold, F. Wehrmann, D. Neugebauer and G. Huttner, J. Grganomet. Chem., 152 (1978) 329. 27 M.D. Grilbone and B.B. Kedzia, J. Grganomet. Chem., 140 (1977) 161.

28 (a) D.J. Darensbourg and A. Rokicki, ACS Symp. Ser., 152 (1981) 107; (b) D.J. Darensbourg and A. Rokicki, Grganometalhcs, 1 (1982) 1685.

29 (a) U. SartoreIIi, L. GarlascheIli, G. Ciani and G. Bonora, Inorg. Chim. Acta, 5 (1971) 191; (b) V.G. Albano and G. Ciani, M. Manassero, J. Grganomet. Chem., 25 (1970) C55.