Journal of Organometallic Chemistry 598 (2000) 353 – 358
Syntheses, characterization and structures of chromium group
carbonyl complexes containing a multifunctional
Ph
2P(o-C
6H
4)CH
N(CH
2)
2(o-C
6H
4N) ligand
Ching-Chao Yang
a, Wen-Yann Yeh
a,*, Gene-Hsiang Lee
b, Shie-Ming Peng
baDepartment of Chemistry, National Sun Yat-Sen Uni6ersity, Kaohsiung804, Taiwan bDepartment of Chemistry, National Taiwan Uni6ersity, Taipei106, Taiwan
Received 24 September 1999; received in revised form 15 November 1999; accepted 22 November 1999
Abstract
Reactions of the phosphine – imine – pyridine-containing ligand Ph2P(o-C6H4)CHN(CH2)2(o-C6H4N) (PNN) with
M(CO)3(NCMe)3 (M = Cr, Mo, W) produce the tridentate complexes fac-M(CO)3(h3-PNN). On the other hand, treating
W(CO)4(NCMe)2with PNN results in the bidentate complex W(CO)4(h2-PNN), which converts to fac-W(CO)3(h3-PNN) upon
heating, but no facialmeridional isomerism is evidenced. The new compounds have been characterized by elemental analysis and mass, IR, and NMR spectroscopy. The molecular structures of W(CO)4(h2-PNN), fac-W(CO)3(h3-PNN) and
fac-Mo(CO)3(h3-PNN) are determined by an X-ray diffraction study. © 2000 Elsevier Science S.A. All rights reserved.
Keywords:Chromium group; Multifunctional ligand
1. Introduction
The multifunctional compound Ph2
P(o-C6H4)CHN(CH2)2(o-C6H4N) (PNN), which contains a phosphine, an imine and a pyridyl electron-donating groups, was prepared by Lavery and Nelson from
co-condensation of Ph2P(o-C6H4)C(O)H and
H2N(CH2)2(o-C6H4N) [1]. Due to its flexible structure, this molecule can act either as a monodentate P, a bidentate PN or a tridentate PNN ligand, which is applicable to the design of new catalytic re-actions [2 – 5]. For instance, the hemilabile property of
the pyridyl group has made the [(PNN)Pd(allyl)]+
complexes very active in allylic alkylation reactions [6].
We recently found the reactions of PNN with trios-mium carbonyl clusters to afford complexes containing chelate and bridging PNN ligands as well as leading to
CH and CP bond activation of the PNN ligand [7].
In the present research, we explore the reactions of PNN with mononuclear chromium group carbonyl complexes.
2. Results and discussion
2.1. Syntheses
Reactions of M(CO)3(NCMe)3 with the PNN
molecule at room temperature result in a facile substi-tution of the labile acetonitrile ligands to afford
fac-M(CO)3(h3-PNN) in 52, 70 and 72% yields for
M = Cr, Mo and W, respectively (Eq. (1)). On the
other hand, treating W(CO)4(NCMe)2 with PNN
pro-duces the phosphine – imine bidentate complex
W(CO)4(h2-PNN), which transforms to
fac-W(CO)3(h3-PNN) upon heating (Eq. (2)). The Pd(0),
Pd(II) and Pt(II) complexes containing h1–h3-PNN
ligands were prepared previously by Vrieze and
co-workers [4,8], while the Mo(CO)4 complexes with the
related PN and PNNP ligands were reported by Rauchfuss [9].
* Corresponding author. Fax: + 886-7-5253908.
E-mail address:wenyann@mail.nsysu.edu.tw (W.-Y. Yeh)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved. PII: S 0 0 2 2 - 3 2 8 X ( 9 9 ) 0 0 7 3 4 - 2
(2) Attempts to synthesize the tungsten poly(PNN)
com-plexes, such as W(CO)4(PNN)2, W(CO)3(PNN)2 or
W(CO)3(PNN)3, have been unsuccessful. It was found
that treating W(CO)3(NCMe)3 with an excess amount
of PNN, heating or photolysis of W(CO)4(h2-PNN) in
the presence of PNN, or pyrolysis of W(CO)6and PNN
at high temperature led only to fac-W(CO)3(h3-PNN).
Since both the PN and NN sets of the ligand can
form a stable six-membered chelate ring upon coordina-tion, it is probable that the chelate effect [10] is govern-ing the products yielded.
The d6 metal tricarbonyl complexes M(CO)
3L3 ex-hibit facial ( fac) and meridional (mer) isomers. When
L is a good s donor and poor p acceptor relative to
CO, the fac isomer is expected to be more stable electronically to achieve stronger M – CO back dona-tion. On the other hand, the mer isomer is less sterically encumbered and is favored when L contains bulky
groups [11,12]. For example, only fac-W(CO)3(PMe3)3
is existent while both fac-W(CO)3(PPh3)3 and
mer-W(CO)3(PPh3)3 are present [13]. We were unable to
convert fac-W(CO)3(h3-PNN) into mer-W(CO)3(h3
-fragments resulting from successive loss of three CO groups. The IR spectra in the carbonyl-stretching re-gion for these complexes are similar, suggesting great resemblance of their structures.
The 1H-NMR spectrum of free PNN in CDCl
3
pre-sents a doublet resonance at 9.01 ppm (JPH= 5 Hz) for
the CHN proton and two 2H triplets at 3.93 and 3.04
ppm (JHH= 7 Hz) for the (CH2)2 protons, while its
31P{1H}-NMR spectrum shows a singlet at − 13.08
ppm for the phosphine group. In the fac-M(CO)3(h3
-PNN) complexes, the phosphine 31P resonances are
shifted downfield to 50.94, 36.13 and 31.73 ppm for M = Cr, Mo and W, respectively, and the imine CHN 1H resonances are shifted slightly to ca. 9.5 ppm. It has been noted that, for the metal phosphine complexes of a similar structure, one generally observes a high-field
shift of the 31P resonance as one descends in a given
group [14]. Furthermore, the (CH2)2 proton resonances
are split into four 1H multiplets in the range 4.30 – 1.13 ppm to indicate asymmetric coordination of the PNN ligand, leading to diastereotopic methylene groups.
W(CO)4(h2-PNN) forms orange – red crystals. Its
FAB mass spectrum displays a molecular ion peak at
m/z = 690 for 184W, which is 28 more than that of
fac-W(CO)3(h3-PNN), and fragments corresponding to successive loss of four carbonyls. Apparently, either the PN or the NN set of PNN ligand is bonded to the W atom to satisfy the 18-electron rule. On the basis of the
31P-NMR spectrum, which displays a resonance at
24.19 ppm with 183W satellites (1J
WP= 238 Hz), the
PN coordination mode is preferred. The IR spectra of
W(CO)4(h2-PNN) and fac-W(CO)
3(h3-PNN) in the carbonyl region are shown in Fig. 1; it appears that the absorptions are shifted to lower energy with increasing substitution, consistent with the stronger net donor capability of the PNN ligand compared with CO.
2.3. Molecular structures
Crystals of W(CO)4(h2-PNN), fac-W(CO)3(h3-PNN)
and fac-Mo(CO)3(h3-PNN) contain an ordered array of
mutu-Fig. 1. IR spectra in the carbonyl region for (a) W(CO)4(h2-PNN) and (b) fac-W(CO)3(h3-PNN) obtained in CH2Cl2solvent.
Fig. 3. Molecular structure of fac-W(CO)3(h3-PNN). Thermal ellip-soids are drawn at 30% probability. The hydrogen atoms have been artificially omitted for clarity.
1.955(4) A, to C(1). Enhancement of WCO
back-do-nation for the latter two bondings is consistent with
good s donor and poor p acceptor of the phosphine
(and imine) ligand relative to CO. The PNN ligand chelates the tungsten atom through the phosphine – imine groups with the bite angle P(1)WN(1)=
80.74(2)°. The uncoordinated C(11)N(1) bond
(1.275(5) A, ) retains a CN double-bond character.
The molecular structures of fac-W(CO)3(h3-PNN)
and fac-Mo(CO)3(h3-PNN) are essentially identical,
where the coordination about the central metal atom is a distorted octahedron with the PNN ligand capping a triangular face. Three terminal carbonyl ligands are
linked to W and Mo atoms with the MCO distances in
the range 1.927(5) – 1.976(6) A, and the MCO angles
in the range 175.3(6) – 178.8(4)°. The P(1)MN(1), P(1)MN(2) and N(1)MN(2) angles are 79.1(1), 94.2(1) and 82.8(1)° for M = W, and 78.5(1), 94.55(9) ally separated by normal van der Waals distances.
TheirORTEPdiagrams are shown in Figs. 2 – 4. Selected
bond distances and bond angles for W(CO)4(h2-PNN)
are given in Table 1, and for fac-W(CO)3(h3-PNN) and
fac-Mo(CO)3(h3-PNN) are collected in Table 2.
W(CO)4(h2-PNN) is associated with four terminal
carbonyls with the WCO angles in the range
174.7(4) – 178.2(4)°. The WCO distances are 2.024(4) A,
to C(2) and 2.007(4) A, to C(4), while those distances
trans to the phosphine and imine groups are slightly but
significantly shorter, being 1.982(4) A, to C(3) and
Fig. 2. Molecular structure of W(CO)4(h2-PNN). Thermal ellipsoids are drawn at 30% probability. The hydrogen atoms have been artifi-cially omitted for clarity.
Fig. 4. Molecular structure of fac-Mo(CO)3(h3-PNN). Thermal ellip-soids are drawn at 30% probability. The hydrogen atoms have been artificially omitted for clarity.
80.74(7) P(1)WN(1) C(1)WN(1) 173.2(1) 175.6(1) C(3)WP(1) C(2)WC(4) 172.2(2) C(11)N(1)C(12) 113.9(3) 3.1. General methods
All manipulations were carried out under an atmo-sphere of purified dinitrogen with standard Schlenk
techniques [15]. Cr(CO)6, Mo(CO)6 and W(CO)6 from
Strem were used as received. Anhydrous Me3NO was
obtained from Me3NO·2H2O (Aldrich) by sublimation
under vacuum twice. Ph2P(o-C6H4)CHN(CH2)2
(o-C6H4N) was synthesized from condensation of Ph2
P(o-C6H4)C(O)H and NH2(CH2)2(o-C6H4N) (Aldrich) as described in the literature [1]. Solvents were dried over appropriate reagents under dinitrogen and distilled im-mediately before use [16]. Infrared spectra were
recorded with a 0.1 mm-path CaF2 solution cell on a
Hitachi I-2001 IR spectrometer. 1H- and 31P-NMR
spectra were obtained on a Varian VXR-300 spectrom-eter at 300 and 121.4 MHz, respectively. Fast-atom-bombardment (FAB) mass spectra were recorded by using a VG Blotch-5022 mass spectrometer. Elemental analyses were performed at the National Science Coun-cil Regional Instrumentation Center at National Chung-Hsing University, Taichung, Taiwan.
3.2. Synthesis of fac-Cr(CO)3(h3-PNN)
A 50 ml Schlenk flask was equipped with a magnetic stir bar and a reflux condenser connected to an oil
bubbler. Cr(CO)6(101 mg, 0.45 mmol) and acetonitrile
(15 ml) were introduced into the flask under dinitrogen, and the solution was heated to reflux for 72 h, at which
point the IR spectrum indicated Cr(CO)6 was
com-pletely transformed to Cr(CO)3(NCMe)3. The
acetoni-trile solvent was then removed under vacuum. A
solution of PNN (181 mg, 0.45 mmol) in
dichloromethane (10 ml) was added to the flask by a syringe and the reaction mixture was stirred at ambient temperature for 1 h, resulting a solution color change from bright yellow to deep red. The solution was then dried under vacuum, and the crude product was crystal-lized from dichloromethane – hexane to afford dark red
crystals of fac-Cr(CO)3(h3-PNN) (124 mg, 0.23 mmol,
52%). IR (CH2Cl2, nCO): 1914 s, 1810 s, 1788 s cm− 1. and 83.1(1)° for M = Mo. The P(1), C(4), C(9), C(10)
and N(1) atoms are planar to within 90.1 A, for both
compounds. The C(10)N(1) double-bond distances are
1.281(7) and 1.276(6) A, for the W and Mo complexes,
Table 2
Selected bond distances (A, ) and bond angles (°) for fac-M(CO)3(h3 -PNN) (M = W and Mo) M = W M = Mo Bond distances MP(1) 2.484(1) 2.494(1) 2.228(4) MN(1) 2.243(4) 2.341(4) MN(2) 2.364(4) 1.976(6) MC(1) 1.970(5) MC(2) 1.938(5) 1.931(4) 1.940(5) MC(3) 1.927(5) 1.144(6) C(1)O(1) 1.150(6) 1.171(6) C(2)O(2) 1.166(5) 1.163(6) C(3)O(3) 1.168(5) 1.837(5) P(1)C(4) 1.834(4) 1.410(7) C(4)C(9) 1.403(6) 1.456(8) C(9)C(10) 1.454(7) 1.281(7) 1.276(6) C(10)N(1) 1.461(7) 1.475(6) N(1)C(11) 1.508(8) C(11)C(12) 1.503(7) 1.492(8) C(12)C(13) 1.496(7) 1.345(6) 1.351(5) C(13)N(2) Bond angles MC(1)O(1) 175.3(6) 175.6(5) MC(2)O(2) 178.8(4) 178.2(4) 177.2(4) MC(3)O(3) 176.2(4) 79.1(1) 78.5(1) P(1)MN(1) 94.2(1) P(1)MN(2) 94.55(9) N(1)MN(2) 82.8(1) 83.1(1) P(1)MC(1) 168.3(2) 168.6(2) 177.8(2) C(3)MN(2) 177.9(2) C(2)MN(1) 175.6(2) 175.9(2) 115.4(4) C(10)N(1)C(11) 115.9(4) 127.1(5) N(1)C(10)C(9) 126.2(4)
1H-NMR (C 6D6, 20°C): 9.56 (d, CHN), 8.07–5.90 (m, Ph, Py), 4.30 (m, 1H), 2,95 (m, 1H), 2.10 (m, 1H), 1.13 (m, 1H, CH2) ppm. 31P{1H}-NMR (C 6D6, 20°C): 50.94 ppm. MS (FAB) m/z: 530 (M+, 52Cr), 530 – 28n (n = 1 – 3).
3.3. Synthesis of fac-Mo(CO)3(h3-PNN)
Mo(CO)6 (100 mg, 0.37 mmol) and acetonitrile (15
ml) were refluxed under dinitrogen for 12 h to produce
Mo(CO)3(NCMe)3. The reaction of Mo(CO)3(NCMe)3
and PNN (150 mg, 0.37 mmol) was then carried out and worked up in a fashion identical with that above.
fac-Mo(CO)3(h3-PNN) (149 mg, 0.26 mmol, 70%) was obtained as dark red crystals after crystallization from
dichloromethane – hexane. IR (CH2Cl2, nCO): 1920 s, 1816 s, 1794 s cm− 1. 1H-NMR (C 6D6, 20°C): 9.40 (d, CHN), 8.05–5.95 (m, Ph, Py), 4.08 (m, 1H), 2,81 (m, 1H), 2.12 (m, 1H), 1.20 (m, 1H, CH2) ppm. 31P{1 H}-NMR (C6D6, 20°C): 36.13 ppm. MS (FAB) m/z: 574
(M+,96Mo), 574 – 28n (n = 1 – 3). Anal. Found C, 55.53; H, 3.65; N, 4.25. C30H25Cl2N2O3PMo (containing a
CH2Cl2 crystal solvent) Anal. Calc. C, 54.64; H, 3.82;
4.24%.
3.4. Synthesis of fac-W(CO)3(h3-PNN)
W(CO)6(90 mg, 0.25 mmol) and acetonitrile (20 ml)
were refluxed under dinitrogen for 72 h to produce
W(CO)3(NCMe)3. The reaction of W(CO)3(NCMe)3
and PNN (101 mg, 0.25 mmol) was then carried out and worked up in a fashion identical with that above.
fac-W(CO)3(h3-PNN) (119 mg, 0.18 mmol, 72%) was obtained as dark red crystals after crystallization from
dichloromethane – hexane. IR (CH2Cl2, nCO): 1912 s, 1808 s, 1786 s cm− 1. 1H-NMR (C 6D6, 20°C): 9.45 (d, CHN), 8.07–5.92 (m, Ph, Py), 4.03 (m, 1H), 3.93 (m, 1H), 2.89 (m, 1H), 1.20 (m, 1H, CH2) ppm. 31P{1 H}-NMR (C6D6, 20°C): 31.73 (s, with 183W satellites, JWP= 227 Hz) ppm. MS (FAB) m/z: 662 (M+,184W), 662 – 28n (n = 1 – 3). Anal. Found C, 47.96; H, 3.54; N, 3.75. C30H25Cl2N2O3PW (containing a CH2Cl2 crystal solvent) Anal. Calc. C, 48.19; H, 3.34; 3.74%.
3.5. Synthesis of W(CO)4(h2-PNN)
W(CO)6 (100 mg, 0.28 mmol) and dichloromethane
(5 ml) were placed in a 50 ml Schlenk flask under
dinitrogen. A solution of Me3NO (45 mg, 0.60 mmol)
in acetonitrile (7 ml) was added dropwise into the flask by a syringe over a period of 20 min. The mixture was stirred at ambient temperature for 2 h, at which point
the IR spectrum indicated the presence of W(CO)4
-(NCMe)2. The acetonitrile solvent was then removed
under vacuum. A solution of PNN (112 mg, 0.28
mmol) in dichloromethane (7 ml) was added to the flask by a syringe and the reaction mixture was stirred at ambient temperature for 1 h, resulting a solution color change from bright yellow to orange red. The volatile materials were removed under vacuum, and the residue was crystallized from dichloromethane – hexane
to afford orange red crystals of W(CO)4(h2-PNN) (99
mg, 0.14 mmol, 50%). IR (CH2Cl2,nCO): 2008 s, 1894 s, 1856 s cm− 1.1H-NMR (C 6D6, 20°C): 8.52 (d, CHN), 8.07 – 6.85 (m, Ph, Py), 4.35 (t, 2H, CH2), 3.11 (t, 2H, CH2) ppm.31P{1H}-NMR (C6D6, 20°C): 24.19 (s, with 183W satellites, J WP= 238 Hz) ppm. MS (FAB) m/z: 690 (M+, 184W), 690 – 28n (n = 1 – 4). Anal. Found C, 52.12; H, 3.44; N, 4.00. C30H23N2O4PW; Anal. Calc. C, 52.19; H, 3.35; 4.05%. 3.6. Thermolysis of W(CO)4(h2-PNN)
A solution of W(CO)4(h2-PNN) (9 mg) in n-octane
(4 ml) was heated to reflux under dinitrogen for 2 h, resulting in a solution color change from orange red to deep red. The octane solvent was removed under vac-uum, and the residue crystallized from
dichloro-methane – hexane to yield fac-W(CO)3(h3-PNN) (6 mg).
Similar results were obtained by heating W(CO)4(h2 -PNN) in the presence of PNN ligand. There was no
evidence for the formation of W(CO)3(PNN)2 or
W(CO)4(PNN)2.
3.7. Attempts to isomerize fac-W(CO)3(h3-PNN) to
mer-W(CO)3(h3-PNN) thermally
A solution of fac-W(CO)3(h3-PNN) (5 mg) in toluene solvent (3 ml) was heated to reflux under dinitrogen for 12 h. The reaction monitored by IR showed no new CO
absorptions to indicate the formation of
mer-W(CO)3(h3-PNN).
3.8. Co-pyrolysis of W(CO)6 and PNN in a sealed
tube
W(CO)6 (23 mg) and PNN (21 mg) were mixed,
ground, and sealed in a Pyrex glass tube under vacuum (0.01 torr). The tube was placed in a silicon oil bath at 125°C for 1 h, removed from oil bath and cooled to ambient temperature, and opened in air. The products were extracted with dichloromethane and crystallized
by adding n-hexane. fac-W(CO)3(h3-PNN) (10%) and
W(CO)4(h2-PNN) (23%) were obtained.
3.9. Structural determination for fac-W(CO)3(h3-PNN),
fac-Mo(CO)3(h3-PNN) and W(CO)4(h2-PNN)
Crystals of fac-W(CO)3(h3-PNN) (ca. 0.60×0.50×
0.20 mm3), fac-Mo(CO)
90 a (°) 80.58(2) 90 102.02(1) 86.52(2) 102.34(2) b (°) 68.73(2) g (°) 90 90 1361.0(5) V (A,3) 2917.3(6) 2937(1) 4 2 4 Z 1.685 Dcalc.(g cm−3) 1.701 1.491 1464 676 1336 F(000) 4.232 m (mm−1) 4.341 0.717 0.0290/0.0759 0.0197/0.0477 0.0421/0.1079 R1/wR2a Goodness-of- 1.062 1.077 1.053 fit on F2 aR1= F o − Fc / Fo ; wR2= {[w( Fo 2− F c 2)2]/ w F o 4]}1/2.
We are grateful for support of this work by the National Science Council of Taiwan.
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0.20 mm3) and W(CO)
4(h2-PNN) (ca. 0.60 × 0.50 ×
0.50 mm3) were each mounted in a thin-walled glass
capillary and aligned on the Nonius CAD-4
diffrac-tometer with graphite-monochromated Mo – Ka
radia-tion (l=0.71073 A,). The data were collected using the
u/2u scan technique with u ranging from 1.94 to 25.00°
for fac-W(CO)3(h3-PNN), 1.93 to 25.00° for
fac-Mo(CO)3(h3-PNN) and 1.29 to 25.00° for W(CO)4(h2 -PNN). All data were corrected for Lorentz and polarization effects and for the effects of absorption. The structures were solved by the heavy-atom method
and refined by full-matrix least-square cycles on F2 on
the basis of 4232 observed reflections [I\2s(I)] for
fac-W(CO)3(h3-PNN), 3612 observed reflections for
fac-Mo(CO)3(h3-PNN) and 4438 observed reflections
for W(CO)4(h2-PNN). The non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included but not refined. All calculations were performed using theSHELXTLpackage. A summary of relevant crystallo-graphic data is provided in Table 3.
