Organometallics 1986,5, 691-698
691
Acetylene Binding to Triphosphine-Bridged, Trirhodium Chains. The Preparation and X-ray Crystal Structure of the Dimetalated Olefin Complex [Rh3(p- (Ph,PCH,) ,PPh),( p-CO) (CO) (p-CI)CI(p-CH302CC=CCO&H3] [BPh4] Alan L. Balch,’ L. Alan Fossett, John Linehan, and Marilyn M. Olmstead Department of Chemistry, University of California, Davis, California 956 16 Received April 29, 1985
[Rh3(dpmp)z(CO)3C12] [BPhl] (dpmp = bis [ (dipheny1phosphino)methyll phenylphosphine) reacts with dimethyl acetylenedicarboxylate (CH3OZCC~CCO2CH3) to yield major, brown and minor, violet isomers [BPh4]. A similar reaction with diethyl acetylenediof [Rh3(dpmp)z(CO)zClz(~-CH302CC=CCOzCH3)] carboxylate (CH3CHz02CC=CC02CH2CH3)yields only the brown form of [Rh3(dpmp)z(CO)zC1z(pCH3CHzO2CC=CCO2CH2CH3)][BPh4]. With [Rh3(dpma)2(CO)3Clz][BPh4] (dpma = bis[(diphenylphosphino)methyl]phenylarsine) and CH3OzCC~CCO2CH3, the brown form of [Rh,(dpma),(CO),Cl,(pCH3OZCC=CCOzCH3)] [BPh,] is obtained. Spectroscopic data (lH, I3C,and 31PNMR and infrared) indicate that the brown complexes contain a dimetalated olefin, two terminal carbon monoxide ligands, and nonequivalent ends to the triphosphine ligand: a structure with the dimetalated olefin spanning the Rh-Rh [BPh4]undergoes stepwise substitution bond is proposed. [Rh3(dpmp)2(CO)2C12(p-CH302CC=CC0zCH3)] with iodide without major structural change. The minor, violet isomer of [Rh3(dpmp)z(CO)zC1z(~CH302CC=CC02CH3)][BPh4] has been structurally characterized by X-ray crystallography. [Rh3[ ~ ( C ~ H ~ ) ~ P C H ~ ~ ~ P C ~ H ~ ] ~ ( p - ~ ~ ) [B(CsHS)4].3CH2C12 ( ~ ~ ) ( ~ - ~ ~ )crystallizes ~ ~ ( ~ - from ~ ~ 3di-~ z ~ 4 ~ z ~ H 3 ) ] chloromethane/ethyl ether in the triclinic s ace group P1 (no. 2) with two molecules per unit cell of dimensions a = 12.667 (8) A, b = 16.787 (6) c = 23.417 (6) A, CY = 75.60 ( 2 ) O , fl = 81.95 (4)O, and y = 86.31 (4)’ at 140 K. Least-squares refinement of 578 parameters using 7758 reflections yields R = 0.073. The structure consists of a triphosphine-bridged,trirhodium chain with a carbon monoxide: and a dimetalated olefin bridging a nonbonded pair of rhodium ions (Rh-Rh = 3.410 (1)A). This unit is linked to the third rhodium through the phosphine bridge and through a bridging chloride.
82,
Introduction In recent years a substantial body of information has been assembled regarding the reactivity and structural forms of binuclear, phosphine-bridged complexes of the late transition Through the utilization of the small-bite, linear triphosphine, bis[ (diphenylphosphin0)methyllphenylphosphine ( d ~ m p )we , ~ have begun to explore the consequences of extending this area to trinuclear complexes with a nearly linear array of metal c e n t e r ~ . ~ - l ~ The development of this area results from the synthesis and structural characterization of the trirhodium complex 1, which represents the entry point from which all other
(1) Balch, A. L. In “Homogeneous Catalysis with Metal Phosphine Complexes”;Pignollet, L. H., Ed.; Plenum Press: New York, 1983;p 167. (2) Puddephatt, R. J. Chem. SOC.Reu. 1983, 12, 99. (3) Appel, R.; Geizler, K.; Scholer, H.-F. Chem. Ber. 1979, 112, 648. (4) Guimerans, R. R.; Olmstead, M. M.; Balch, A. L. J . Am. Chem. SOC.1983, 105,1677. (5) Olmstead, M. M.; Guimerans, R. R.; Balch, A. L. Inorg. Chem. 1983,22, 2473. (6)Guimerans, R. R.; Olmstead, M. M.; Balch, A. L. Inorg. Chem. 1983,22, 2223. (7) Olmstead, M. M.; Guimerans, R. R.; Farr, J. P.; Balch, A. L. Inorg. Chim. Acta 1983, 75, 199. (8) Balch, A. L.; Guimerans, R. R.; Olmstead, M. M. J . Organomet. Chem. 1984,268, C38. (9) Balch, A. L.; Olmstead, M. M.; Guimerans, R. R. Inorg. Chim. Acta 1984, 84, L21. (10) Balch, A. L.; Guimerans, R. R.; Linehan, J. Inorg. Chem. 1?85, 24, 290. (11) Balch, A. L.;Fossett, L. A.; Guimerans, R. R.; Olmstead, M. M. Organometallics 1985, 4 , 781. (12) Balch, A. L.; Olmstead, M. M. Israel J. Chem. 1985, 25, 189.
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1 (phenyl groups omitted)
trirhodium complexes of this type have been d e r i ~ e d .The ~ Rh3P6cores in these complexes are subject to facile reaction of the ligands lying in the plane perpendicular to the P-Rh-P bonds. For example, substituting different anions (Br-, I-, S2CNR 2a(T) 1758 fication was achieved by dissolving the solid in dichloroR 0.073 methane/methanol (1O:l v/v), filtering, and adding ethyl ether 0.075 Rw no. of parameters 578 slowly. The brown crystalline product (100 mg, 66%) was collected by filtration, washed with ethyl ether, and vacuum dried. Anal. mg (81%). Anal. Calcd for C72H~C11,0,$'6Rh3: c , 47.80; H, 3.56; Calcd for C,HB,As,BC1,06P4Rh3: C, 57.71; H 4.24; C1, 3.46. C1, 1.96; I, 14.03. Found: C, 47.00; H, 3.42; C1, 1.68; I, 14.03. Found: C, 57.87; H, 4.15; C1, 3.46. Spectroscopic Measurements. The 31Pspectra were recorded [Rh3(p-dpmp),(CO),ICl(p-CH30zCC=CCOzCH3)][BP h4] with proton decoupling on a Nicolet NT-200 Fourier transform (5a). A solution of 240 mg (0.126 mmol) of [Rh3(p-dpmp),spectrometer operating a t 81 MHz or on a Nicolet NT-360 (C0)2C12(p-CH302CC=CCOzCH3)] [BPh,] (2a) in 15 mL of dispectrometer a t 145.8 MHz. The 'H and 13C NMR spectra were chloromethane was treated with 1 mL of a saturated methanol recorded a t 360 and 90.5 MHz, respectively, on a Nicolet NT-360 solution of sodium iodide. The brown solution was filtered, and F T spectrometer. The references were as follows: 31P,external 70 mL of methanol was added to the solution within 5 min of the 85% phosphoric acid; 'H and 13C,internal tetramethylsilane. The initial mixing. T h e dark brown solid (largely the iodide salt of high-frequency positive convention, recommended by IUPAC, the desired cation) was separated by filtration from the violet has been used in reporting all chemical shifts. Infrared spectra solution. The solid was suspended in 10 mL of dichloromethane, were recorded from mineral oil mulls by using a Perkin-Elmer and 1 mL of a saturated methanol solution of sodium tetra180 spectrometer. phenylborate was added. The green-brown solution was filtered, X-ray Data Collection, Solution, and Refinement. Welland 70 mL of methanol was added. The fine brown crystalline formed red-brown parallelpipeds were grown by slow vapor difproduct was collected and washed with methanol. Purification fusion of diethyl ether into a dichloromethane solution of 2b. was accomplished by dissolving the solid in dichloromethane, Crystal data, data collection procedures, and refinement of the filtering the solution, and slowly crystallizing the product through structure are summarized in Table VI. T h e lattice was found the gradual addition of ethyl ether. The yield was 180 mg (72%). to be triclinic by standard procedures using the software associated Anal. Calcd for C9fiH84BC1106P6Rh3:c , 57.61; H, 4.23; P, 9.29; with the Syntex P2' diffractometer. The data were collected a t I, 6.34. Found: C, 57.35; H , 4.15; P, 9.30; I, 6.28. ~ ~ ~ s ~ ~ ~ ~ ~ ~ ~ (6).~ ~ 140~K using ~ a ~locally~ modified z ~LT-1zlow-temperature ~ ~ - apparatus ~ ~ ~ ~ on the Syntex P21 diffractometer. Printer plots of several reA solution of 158 mg (0.083 mmol) of Rh3(p-dpmp),(CO),ClZ(pflections using w scans revealed small satellite peaks separate from CH302CC=CC02CH3)] [BPh4] (2a) in 5 mL of dichloromethane but within 2" of the main peaks. Since many of the reflections was treated with 2 mL of a saturated methanol solution of sodium would have had unsymmetrical backgrounds, the data were iodide. On standing for 2 h, the solution gradually turned from collected by scanning the main peak but without making a brown to violet. The solution was filtered, and 70 mL of methanol background measurement. At the end of the data collection, the was gradually added. After the solution was cooled to 5 "C, the crystallographic axes were doubled, and background counts were violet-black crystalline product was collected by filtration and recorded as a function of 28 using odd-numbered indices. These washed with methanol. Purification was effected by dissolving data were curve fit, and a correction was applied to the intensity the product in a minimum of dichloromethane, filtering the sodata in the same manner as a crude absorption correction (as a lution, and adding ethyl ether dropwise to precipitate the product, function of 28 only). In our experience, this method gives satC, 55.09 yield 122 mg (70%). Anal. Calcd for C96HB,B1206P6Rh3: isfactory results in cases such as this or in the instance of cracked H, 4.05; P, 8.88; I, 12.13. Found: C, 55.01; H, 3.84; P, 8.64; I, 11.5. crystals.27 T h e data were also corrected for Lorentz and po[Rh3(p-d~mp),(C0),1Cl(p-CH30,CC=CC0,CH3)]1 (5b). larization effects. One milliliter of a saturated methanol solution of sodium iodide The structure was solved by locating the three rhodium atoms was added to a slurry of 143 mg of [Rh,(p-dpmp),(CO),Cl,(pusing the Patterson method (FMAP 8 routine of SHELXTL, CH302CC=CCO&HJ] [BPh,] (2b) in 15 mL of dichloromethane. version 4, 1984 (Nicolet Instrument Corporation, Madison, WI)). The solid immediately dissolved to produce a rich purple solution. Other atoms were located from successive difference Fourier maps. The solution was filtered, and 60 mL of methanol was gradually Final cycles of refinement were made with anisotropic thermal added. The black crystalline solid was collected by filtration and washed with ethanol. The solid was purified by dissolving it in a minimum volume of dichloromethane, filtering, and precipitating (27) Wood, F. E.; Hvoslef, J.; Hope, H.; Balch, A. L. Inorg. Chem. 1984, the product through the slow addition of ethyl ether; yield 110 23, 4309.
698
Organometallics 1986, 5 , 698-707
parameters for rhodium, phosphorus, chlorine and oxygen and isotropic thermal parameters for all remaining atoms. Hydrogen atoms were not located. Scattering factors and corrections for anomalous dispersion were taken from a standard source.28 An absorption correction (XABS) was applied.29 The atoms of the three dichloromethanemolecules were assigned isotropic U values of 0.05 and were allowed to refine with variable occupancy. The final occupancies were 0.824 (6) for C1(3)C(97)C1(4), 0.774 (6) for (28) “International Tables for X-ray Crystallography”; Kynoch Press: Birmingham, England, 1974; Vol. 4. (29) The method obtains an empirical absorption tensor from an expression relating F, and F,: Hope, H.; Moezzi, B., Department of Chemistry, University of California, Davis, CA. (30) In this paper the periodic group notation (in parentheses) is in accord with recent actions by IUPAC and ACS nomenclature committees. A and B notation is eliminated because of wide confusion. Groups IA and IIA become groups 1 and 2. The d-transition elements comprise groups 3 through 12, and the p-block elements comprise groups 13 through 18. (Note that the former Roman number designation is preserved in the last digit of the new numbering: e.g., 111 3 and 13.)
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C1(5)C(98)C1(6),and 0.859 (6) for C1(7)C(99)C1(8).Two low-angle reflections suffering from extinction were removed from the data set for the final cycles of refinement. A conventional R factor of 0.073 was obtained. The final difference map showed some residual electron density in the vicinity of the dichloromethane molecules, but otherwise no significant features were present.
Acknowledgment. We thank the National Science Foundation (CHE8217954) for financial support. Registry No. 1-BPh4, 84774-75-4; 2a, 100082-53-9; 2b, 100082-55-1; 2b.3CHZC12, 100164-67-8; 3, 100082-57-3; 4, 100082-59-5;5a, 100082-63-1;5b, 100102-33-8;6, 100082-65-3; [Rh3(dpma)2(CO),C12]BPh,,100082-61-9;dimethyl acetylenedicarboxylate, 762-42-5; diethyl acetylenedicarboxylate, 762-21-0; rhodium, 7440-16-6. Supplementary Material Available: Tables of anisotropic thermal parameters, hydrogen atom positions,and structure factor amplitudes (53 pages). Ordering information is given on any current masthead page.
Transposition-A New Rearrangement of a-Silylsilylenes Involving Disilene Intermediates Bong Hyun Boo and Peter P. Gaspar’ Department of Chemistry, Washington University, St. Louis, Missouri 63 130 Received August 28, 7985
Evidence has been found for the rearrangement of Me3Si-Si-H to Me2HSi-Si-Me and for the formation of a Me2Si=SiHMe intermediate. Me,Si-Si-H also rearranges to two isomeric P-silylsilylenes Me2HSiCH2-Si-H and Me-Si-CH2SiH2Me, the latter having been previously overlooked. The question whether methyl shifts occur in the ring opening of disiliranes Me2Si-SiHR-CH2 (R = H, Me) is discussed in light of these findings. An experimental value of 29 kcal/mol is derived for the activation energy for intramolecular C-H insertion by a divalent silicon center to form l-methyl-l,3-disilacyclobutane.
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Introduction Reinvestigation of the gas-phase chemistry of (trimethylsily1)silylene was prompted by the belated recognition that our previous observations on the rearrangements of Me,Si-Si-H (1) underscored a nagging mechanistic question concerning the isomerization of alkylated a-silyl- to @-~ilylsilylenes.~~~ In 1978 Wulff, Goure and Barton both enlivened and revolutionized the study of divalent silicon species by a daring suggestion: that intramolecular C-H insertion by the divalent silicon center of methyl(trimethylsily1)silylene (2) forms a disilirane, 3, whose ring opening by competing hydrogen and methyl shifts completes the conversion of an a-silylsilylene 2 to a pair of isomeric (3-silylsilylenes, 4 and 5.4 Further intramolecular C-H insertions by 4 and 5 can explain the formation of the stable 1,l-and 1,3-di-
Scheme I
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Me2S i
SiHMe
o
2
b
3
a-b or b - a
MI H
/“?
Me-Si
SiHMe2
4
\
b-a
Me
/“Y
MesSi
Si-H
5
I MeHSi
(1) Mo, S.-H.; Holten, J. D., 111; Konieczny, S.; Ma, E. C.-1; Gaspar, P. P. J . Am. Chem. SOC.1982, 104,1424. (2) Boo, B. H.; Gaspar, P. P.; Ghosh, A. K.; Holten, J. D.; Kirmaier, C. R.; Konieczny, S. “Transposition-A New Silylene Rearrangement, and the Laser Photolysis of Polysilanes”, 17th Organosilicon Symposium, North Dakota State University, Fargo, ND, June 1983, abstracts, p 12. (3) .Boo, B. H.; Gaspar, P. P. 187th National Meeting of American Chemical Society, St. Louis, MO, 1984; American Chemical Society: Washington, D.C., 1984; ORGN 227. (4) Wulff, W. D.; Goure, W. F.; Barton, T. J. J. A n .Chem. SOC.1978. 100, 6236.
- /“? -
Me3Si-Si-Me
liHM
\ CH2
6 (15%)
7 ( 28%)
methyl-1,3-disilacyclobutanes 6 and 7, obtained as end products of Scheme I. While a-eliminations of acyclic disilanes forming silylenes and monosilanes by migration of hydrogen, halogen, and alkoxy groups are ~ e l l - k n o w n Davidson ,~ and co‘B 1986 American Chemical Society
