Organometallics 1983, 2, 535-538
535
Intermediates in the Associative Phosphine Substitution Reaction of ($-C,H,)Re(CO), Charles P. Casey,' Joseph M. O'Connor, William D. Jones, and Kenneth J. Haller Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706 Received November 8. 1982
The reaction of (q5-C5H5)Re(C0),,11, with P(CH3), produces ~~C-(~'-C~H~)R~(CO),[P(CH~)~]~, 12. The reaction is reversible with Keq = 19 M-2 at 51 "C in benzene. At longer reaction times, the equilibrium mixture of 11 and 12 is converted to (qS-C5H5)Re(C0),[P(CH3),],13. The structure of 12 was determined by X-ray crystallography: monoclinic space group P2'/n, with unit-cell constants a = 8.011 (5) A, b = 14.042 (3) A, c = 16.349 (3) A, 0 = 92.08 (2)O, and 2 = 4.
In 1965, Basolo and Schuster-Woldan noted that the rate of reaction between P(C6H5)3and the coordinatively saturated (q5-C5H5)Rh(C0)2to give (q5-C5H5)Rh(CO)[P(c6H5)3]was unusually fast and depended on the concentration of both the rhodium complex and phosphine.' To explain this associative substitution at a formally coordinatively saturated metal center, they proposed that slippage of the cyclopentadiene ring occurs as phosphine attacks to produce the intermediate shown.
Recently we found structural evidence for cyclopentadiene ring slippage during phosphine substitution reactions a t coordinatively saturated metal centers. The reactions of (q5-C5H5)Re(NO)(CO)(CH3), 1, with 2 equiv of P(CH3)3 a t 25 "C yields the bis(phosphine) adduct (q1-C5H5)Re(NO)(CO)(CH3)[P(CH3)3]2, 2, in which the q5-C5H5ring has slipped all the way to an 7'-C5H5 configuration.2 Upon heating to 90 OC, 1 and 2 equilibrate and are converted to a mixture of phosphine-substituted methyl compound 3 and the phosphine-substituted acetyl compound 4. The rate of formation of 2 depends on the concentration of both 1 and P(CH3), and thus requires a mono(phosphine) adduct 5 as an intermediate. Two possible 18-electron structures for such an intermediate are an q3-C$15linear nitrosyl compound or an v5-C5H5bent nitrosyl compound.
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(t15-C5H5)Re(C0)2[P(CH3)31, 13.
Results Synthesis of ~~C-(~'-C~H~)R~(CO),[P(CH~)~]~. Reaction of (q5-C5H5)Re(C0),,11, with 3.3 M P(CH3)3for 2.5 days in hexane at 64 "C led to the precipitation of light yellow crystals of ~~c-(~'-C~H~)R~(CO)~[P(CH~)~]~, 12, in 85% yield. The hexane solution contained only unreacted 11 and none of the phosphine substitution product (q5C5H5)Re(C0),[P(CH3),],13. Elemental analysis, NMR, and IR data established that 12 was an 9'-C5H5 bis(phosphine) adduct and X-ray analysis defined the cis geometry of the phosphine ligands.
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able at room temperature and decompose to starting material and q5-C5H5mono(phosphine) adducts. The reactions of 6 and 7 with P(CH3)3also show second-order kinetics and require a mono(phosphine) intermediate 10. Since both 6 and 7 contain a nitrosyl ligand, there are again two possible 18-electron formulations for intermediate 10: an q3-C5H5linear nitrosyl compound and an v5-C5H5bent nitrosyl compound. To determine whether a nitrosyl ligand is required for formation of 7'-cyclopentadienyl bis(phosphine) adducts, we have studied the reaction of P(CH3), with the nonnitrosyl-containingcompound (q5-C5H5)Re(C0),,11. Here we report that 11 reach with P(CH3)3to give a very stable 71'-C5H5 bis(phosphine) adduct (q'-C5H5)Re(CO),[P(CH3),I2,12, which we have characterized by spectroscopy and by X-ray crystallography. 11 and 12 were found to equilibrate more rapidly than they were converted to
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The reactions of (q5-C5H5)Mo(C0),(NO),6, and (q5C5H5)W(CO),(NO),7, with P(CH3)3a t -60 "C also give observable bis(phosphine) 7'-cyclopentadienyl compounds (o'-C~H~)MO(CO)~(NO) [P(CH3)312,8, and h1-C5H5)W(CO)Z(NO)[P(CH3)3]2, 9., Compounds 8 and 9 are unst(1) Schuster-Woldan, H.G.; Basolo, F. J . Am. Chem. SOC.1966, 88, 1657-1663. (2) Casey, C. P.;Jones, W. D. J.Am. Chem. SOC.1980,102,6154-6156, and references therein. See also: Werner, H.; Kuhn, A.; Burschka, C. Chem. Ber. 1980,113,2291-2307. Goel, A.B.; Goel, S.; Van Derveer, D.; Clark, H. C. Znorg. Chin. Acta 1981,53, L117-L118.
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The 'H NMR of 12 in benzene-d6 consists of a triplet a t b 6.15 ( J P=~1.5 Hz, 5 H) and a multiplet at 6 1.04 (18 H). The triplet is assigned to the fluxional 77'-C5H5 group of 12; we have been unable to freeze out the fluxionality of the v1-C5H5group of 12 even a t -87 O C in acetone-d6. (3) Caaey, C. P.;Jones, W. D.; Harsy, S. G. J.Organomet. Chem. 1981, 206, C38-C42.
0276-7333/83/2302-0535$01.50/0 0 1983 American Chemical Society
Casey et al.
536 Organometallics, Vol. 2, No. 4, 1983
Re-P( 1) Re-P( 2) Re-C(l) Re-C( 2) Re-C( 3) Re-C(10) pu)-c(4)
Table I. Interatomic Distances ( A ) and Angles (deg) for 12' Distances 1.826 (13) C(3)-0(3) 2.480 (3) w - c (5) C( 10)-C( 11) 1.820 (12) 2.460 (3) P(l)-C(6) C(lO)-C(14) 1.814 (12) 1.910 (13) P( 2)-c(7) 1.772 (13) C(ll)-C(12) 1.944 (14) P(Z)-C(8) C(12)-C(13) 1.798 (14) 1.956 (13) P( 2 )-C( 9) C( 13)-C( 14) 2.360 (10) C(1) - W ) 1.157 (13) 1.812 (13) C(2)-0( 2) 1.154 (13)
1.134 (13) 1.475 (16) 1.448 (14) 1.333 (17) 1.429 (17) 1.363 (16)
Angles
93.54 (10) P(Z),Re,C(lO) 89.49 (27) Re,P(2),C(9) P( 1),Re,P(2) 90.90 (37) C(l),Re,C(Z) 90.82 (49) C(8),P(Z),C(9) p(1),Re,C(1) 90.76 (48) Re,C(lO),C(ll) W),Re,C(3) P(1),Re,C(2) 176.9 (3) 87.46 (35) C(l),Re,C(lO) 176.7 (4) Re,C(lO),C(l4) PW,Re,C(3) 89.95 (46) C(ll),C(lO),C(l4) P(1),Re,C(10) 87.12 (29) C(2),Re,C(3) 88.08 (32) C(Z),Re,C(lO) 91.28 (43) c(lo),c(ll),c(l2) P(2),Re,W) 91.70 (45) C(lZ),C(13),C(14) P(2),Re9C(2) 89.08 (33) C(3),Re,C(10) 112.8 (5) P(2),Re3C(3) 178.5 (4) Re,P( 2),C(8) aThe estimated standard deviation of the least significant digit is given in parentheses. 7.72 I+
120.6 (4) 100.0 (8) 108.5 (7) 110.8 (8) 103.5 (9) 109.9 (10) 109.2 (10)
01
Figure 2. ORTEP diagram of fac-(~'-C~~Re(CO),[P(CH3)J2,12.
deviations from octahedral geometry were observed; the largest deviation is associated with a wider 93.5 (1)" angle between the bulky P(CH3), ligands. The q'-C5H5 ring is nearly planar; the maximum deviation of carbon from the mean plane of the ring is 0.036 A. The q'-C5H5 ring is Figure 1. Signals due tn cis P(CH,), ligands in the 270-MHz oriented over the cis CO ligands and away from the bulky 'H NMR spectrum of foc-(~'-C6H6)Re(CO),[P(CH,),I,, 12. P(CH,), ligands. The angle between rhenium, C(10) of cyclopentadiene ring, and the center of gravity of the C a 5 Similarly, the qL-C5H5groups of 2,8, and 9 are fluxional ring is 120.48". at low temperature. The AX&X9 multiplet at 6 1.04 Formation of (qs-CsH5)Re(CO)z[P(CH3)3]. In the (Figure 1) is assigned to the equivalent cis P(CH,), ligands course of studvine the rate of formation of 12 in aromatic of 12. Analysis' of the spectrum indicates JpH+ JPH,= solvents and equilibration with 11, we observed a side 7.7 HZ (Jp" = 6.6 Hz, J p w = 1.1 Hz) and J p p = -13 f 2 reaction leading to the phosphine substitution product Hz. The magnitude of Jppis consistent with the cis ori(q5-C5H,)Re(C0)z[P(CH,)J, 13. For example, reaction of entation of the P(CH,), ligands hut does not require this 11 (0.44 M) and P(CH,), (2.31 M) in benzene-d6 at 100 OC geometry since there is great variability in the magnitude initially gave 50% starting material 11 and 50% bisof tram P-M-P coupling constants.' For comparison, (phosphine) adduct 12 after 1.5 h. However, after 4.5 h, lJppl= 20 Hz for the cis P(CH,), ligands of 2. In the 13C 2.7% of a new compound identified below as (q5-C,H5)NMR of 12, the fluxional $-C,H, group gives rise to a Re(CO)z[P(CH,),], 13, was observed in addition to 38% singlet at 6 110.8. 11 and 58% 12. After prolonged heating for 90 h, the only 'rhree strong carbonyl bands are seen in the IR spectrum identifiable material in solution was 13, formed in 63% of 12 in CH2Cl2at 200'7,1936, and 1890 c d . This specyield (determined with 1,4-bis(trimethylsilyl)benzeneas trum is consistent with the facial structural assignment an internal NMR standard). of I2 but does not allow exclusion of a meridinal structure. Pure substitution product 13 was obtained as a white X-ray S t r u c t u r e of ~~C-(~'-C~~)R~(CO),[P(CA,),I,. crystalline solid in 57% isolated yield from reaction of The facial configuration of 12 was demonstrated by X-ray (n5-C5H5)Re(CO),with 2.5 M P(CH,), at 102 OC for 43 h crystallographic analysis (Figure 2, Table I). Only minor in toluene. The 'H NMR of 13 consists of a doublet ( J = 0.6 Hz) a t 6 4.56 for the q5-C5H5unit and a doublet (J = 9.4 Hz) at 6 1.20 for the P(CH,), ligand and thus allows (4) Bertrand, R D.: Ogilvie, F. B.:Verkade, J. G. J. Am.Chem. SOC. 1970,92,19091915. its detection in the presence of both 11 and 12. Attempted
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Organometallics, Vol. 2, No. 4, 1983 537
The Phosphine Substitution Reaction of (q5-C&5)Re(C0)5 preparation of 13 by prolonged photolysis (366 nm) of 11 and P(CH3)3in benzene-de a t 40 "C gave only 32% 13 in addition to 28% 11 after 15 days. Equilibration of 11 and 12. The reversibility of the formation of 12 was demonstrated by heating a dilute solution of 12 (0.073 M) in benzene-d, a t 85 "C in a sealed NMR tube in the probe of a Bruker 270-MHz NMR spectrometer. 12 was completely converted to (qS-C5H5)Re(C0)3, 11, and P(CH& upon heating a t 85 "C for 3 h; none ( tungsten compound 7 > rhenium nitrosyl methyl compound 1 > rhenium carbonyl compound 1 l., The similarity of all these relative rate sequences is readily explained since all three reactions are proposed to proceed via the same v3-C6H5mono(phosphine) intermediate. The rate sequence is therefore providing information about the ease of formation of the q3-CsH5intermediate in the various systems. In spite of the fact that (q1-C6H6)Re(CO)(NO)(CH3) [P(CH3)3]2,2,reverts to (q6-C6H,)Re(CO)(NO)(CH3), 1, much more rapidly than (q1-CaH6)Re(Co)3[P(cH3)3]2, 12,revert9 to 11' the equilibrium constant for formation of 2 a t 50 "C (74 M-2) is somewhat larger than the equilibrium constant for formation of 12 (19 Mm2)at the same temperature. No direct comparison of equilibrium constants for the molybdenum and tungsten compounds 6 and 7 is possible since their q'-C& bis(phosphine) adducts are kinetically stable only at low temperatures. However, the fact that 8 and 9 were observable only at high P(CH& concentrations and at low temperature where adduct formation should be more favorable entropically suggests that the formation of adducts 8 and 9 is less thermodynamically favorable than formation of rhenium adducts 2 and 12.
Experimental Section General Data. All reactions were carried out under an atmosphere of dry nitrogen using degassed solvents. NMR spectra were recorded on JEOL FX-200 (13C, 31P)or Brucker WH-270 ('H) spectrometers. Infrared spectra were recorded on a Beckman 4230 infrared spectrometer. Mass spectra were recorded on an AEI-MS-902 spectrometer at 26 eV. fa~-(rl'-c,H,)Re(Co)~[P(CH~)~]~, 12. On a high vacuum line, P(CH3)38(9.8 mmol) was condensed into a tube containing 119 (657 mg, 1.96 mmol) and 3 mL of hexane. The tube was sealed under vacuum at liquid-nitrogen temperature and then heated at 70 O C for 56 h. Large light yellow crystals, which formed in (6)For example, the temperatures a t which these compounds react with P(CH3)3to from bis(phosphine) q1-C6H5derivatives are -60 O C for 6,-60 O C for 7 (5.7times slower than 6),25 "C for 1, and 64 "C for 11. (7)For 2 1, tlIP = 3.1 X 10" s-l at 25.0 "C, whereas 12 is stable for weeks at 25.0 "C. (8) Markham, R. T.; Dietz, E. A,; Martin, D. R. Inorg. Synth. 1976, 16,153.Wolfsberger, W.; Schmidbaur, H. Synth. React. Inorg. Met.-Org. Chem. 1974,4,149. (9)Casey, C. P.; Andrews, M. A.; McAlister, D. R.; Rim, J. E. J. Am. Chem. SOC.1980,102,1927-1933.
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538 Organometallics, Vol. 2, No. 4, 1983 the hot hexane as the reaction progressed, were collected by filtration in an inert-atmosphere box and washed with hexane to give analytically pure 12 (809 mg, 85%): mp (sealed capillary) 133"C dec; 'H NMR (benzene-de)6 6.15, (t, J ~ =H1.47 Hz, 5 H), 1.04 (m, AX&X'e, J p p = -13 k 2 Hz, J p H = 6.6 Hz, J p ~ =t 1.1 Hz, 18 H); 13CNMR (THF-d8,0.09 M Cr(aca&, -30 "C) S 194.4 (br, COS trans to P(CH&), 192.7 (br, CO trans to C5H5), 110.8 (8,C$&, 18.5 (t, Jpc= 14.6 Hz, P(CH,),); 31PNMR (acetone-dJ 6 -42.65 (s) relative to extemal H3P04;IR (CH2C12)2007 (s), 1936 (s), 1890 (8) cm-'. Anal. Calcd for Cl4HZ3O3P2Re: C, 34.49; H, 4.76. Found C, 34.74; H, 4.80. Significant high mass peaks retaining both P(CH& ligands: 423 (M - C5H5)and 395 (M - C5H5- CO); exact mass calcd for 187ReC14Hz3Pz03 488.0677, found 488.0653. (q5-C5H5)Re(CO),[P(CH3)J, 13. On a high vacuum line, was condensed into a tube fitted with a Teflon P(CHJ3 (7.7 "01) needle valve and containing 11 (496 mg, 1.48 mmol) and 3 mL of toluene. The tube was closed off under vacuum at liquidnitrogen temperatures and then heated at 102 "C for 43 h. The solvent and excess P(CH& were pumped off, and the residue was thin layer chromatographed (silica gel-toluene) under a nitrogen atmosphere to give analytically pure 13 (R, = 0.6) as a white crystalline solid (325 mg, 57%): mp (sealed capillary) 95b100 "C dec; 'H NMR (benzene-de,270 MHz) 6 4.56 (d, J = 0.6 Hz, 5 H), 1.20 (d, J = 9.4 Hz, 9 H); 13CNMR (acetone-& 0.09 M Cr(acac)& 6 202.8 (br, CO), 82.76 (s, C,Ha),23.96 (d,J ~ =c36.7 Hz,P(CH&; 31PNMR (acetone-de, 0.09 M Cr(acac)&6 -25.02 (8) relative to external H3P04;IR (THF) 1929 (s), 1859 ( 8 ) cm-'. Anal. Calcd for CloHl4O2PRe:C, 31.33; H, 3.68. Found: C, 31.25; H, 3.71. Conversion of 12 to 11. On a high vacuum line, benzene-de (0.28 mL) was condensed into an NMR tube containing 12 (10 mg, 0.02 mmol) and 1,4-bis(trimethylsilyl)benzene (5 mg, 0.02 mmol). The tube was sealed under vacuum at liquid-nitrogen temperatures and placed in the probe of a Bruker WH-270 spectrometer maintained at 85 "C. The quantitative conversion of 12 to 11 was then monitored by 'H NMR spectroscopy. See Results section. Equilibration of 11 and 12. On a high vacuum line, P(CH& (0.22 mmol) and benzene-dewere condensed into an NMR tube containing 11 (30 mg, 0.089 mmol) to give a total volume of 0.44 mL at 51 f 1 "C. The tube was then sealed under vacuum at liquid-nitrogentemperature and placed in a constant temperature bath at 50.9 0.2 OC. The concentrations of 11 and 12 were periodically monitored by 'H NMR with equilibration occurring after 41 days. The tube was then placed in the probe of the Bruker WH 270 maintained at 51 f 1 OC, and the concentrations of 11, 12, and P(CH& were determined to be 0.101,0.099, and 0.224 M respectively, giving K = [12]/[ll][P(CH3)3]2= 19.5 M-2. Equilibration of 1 and 2. A sealed NMR tube containing 1 (12.3 mg, 0.038 mmol) and P(CH3) (0.076 mmol) in benzene-& (total volume 0.38 mL at 51 f 1 "C) was placed in the probe of a Bruker WH-270 NMR spectrometer maintained at 51 f 1 "C. Equilibration was achieved within 30 min. The concentrations of 1, 2, and P(CH& were found to be 0.058,0.041, and 0.098 M by 'H NMR, giving K = [2]/[1][P(CH3)3]2= 73.6 M-2. X-ray Data Collection. Single crystals of fac-(q1-C5H,)Re(CO)3[P(CH3)3]z, 12, suitable for X-ray diffraction studies were obtained by evaporation of THF. A single crystal of approximate dimensions 0.12 X 0.15 X 0.55 mm was mounted on a SyntexNicolet P i four-circle diffractometer. Preliminary examination of the crystal showed it to be monoclinic. The systematic absences of h01,h + 1 = 2n + 1,and OkO, k = 2n + 1,uniquely determine
*
Casey et al. the space group to be B 1 / n (No. 14). The unit-cell parameters (at 19 f 1 "C; X (Mo Kn) = 0.71073 A) are a = 8.011 (5) A, b = 14.042 (3) A, c = 16.349 (3) A, and 0 = 92.08 ( 2 ) O . These parameters were determined from a least-squaresrefinement utilizing the setting angles of 62 accurately centered reflections from diverse regions of reciprocal space collected at *28 (1281 = 35"). The unit cell volume of 1837.9 A3 led to a calculated density of 1.62 g/cm3 for four formula units of RePzO3Cl4HZ3 per unit cell. A total of 4206 unique intensity data with (sin 8)/X I0.649 A-1 were collected by using a 8-28 step-scan technique with a scan range of 0.65" below 28(Mo KaJ to 0.65" above 28(Mo Ka2)and a variable scan rate (2.0-24.0°/min). Throughout data collection four standard reflections from diverse regions of reciprocal space were monitored every 50 reflections. There were no systematic variations of the intensities of the standard reflections during the time required to collect the data. The intensity data were reduced and standard deviations calculated using methods similar to those described previously.10 Absorption corrections were applied to the data by using an empirical psi curve method (k = 64.9 cm-'). Structure Solution and Refinement. The structure was solved by the standard heavy-atom method from the Patterson map. The rest of the non-hydrogen atoms were located from a series of electron density difference maps. The full-matrix least-squares refinement of the model was based on F, and used the 2712 data with F, > 3a(F0). Atomic form factors for the non-hydrogen atoms were taken from Cromer and Waber" and that for hydrogen from Stewart, Davidson, and Simpson.12 An electron density difference map calculated after isotropic refinement of the non-hydrogen atoms had converged revealed reasonablepositions for most of the hydrogen atoms. AU hydrogen atoms were included in the remaining cycles of refinement as fixed contributors in idealized positions ( ~ C H= 0.95 A; BH = Bc + 1.0). In the final cycles of refinement all non-hydrogen atoms were assumed to vibrate anisotropically. At convergence the discrepancy indices were R1 = xllFol - IFcll/CIFol = 0.045 and Rz = [x.w(lFol- lFc1)2/~w(Fo)2]1/2 = 0,054. The estimated standard deviation of an observation of unit weight was 1.45 with a final data/variable ratio of 15.0. The final electron density difference map had one high peak (about 33% of a typical carbon atom peak) associated with the Re atom. Final atomic coordinates (Table 11),a table of the anisotropic thermal parameters (Table 111),a table of the fixed hydrogen atom parameters (Table IV), and a listing of observed and calculated structure factors ( X l O ) are available as supplementary material.
Acknowledgment. Support from the Division of Basic Energy Sciences of the Department of Energy is gratefully acknowledged. Registry No. 1,38814-45-8;2, 74964-69-5; 11, 12079-73-1;12, 84521-31-3;13, 84521-32-4. Supplementary Material Available: Tables of final atomic coordinates, anisotropic thermal parameters, observed and calculated structure factors, and fixed hydrogen atom parameters (15pages). Ordering information is given on any current masthead page. (10) Haller, K.J.; Enemark, J. H. Inorg. Chem. 1978,17,3552-3558. (11) Cromer. D. T.: Waber. J. T. "International Tables for X-rav C&&ographS;"; Kyn&h Press: Birmingham, England, 1974; Vol. 4,p i 99-101, Table 2.2B. (12) Stewart, R. F.; Davidson, E. R.;Simpson, W. T. J. Chem. Phys. 1965,42, 3175-3187.
