Vol. 8, No. 1, January 1969
Kh(1) COMPLEXES CONTAINING PHOSPHINES AND ARSINES 119 CONTRIBUTION FROM
THE
DEPARTMENT OF CHEMISTRY,
TULANE UNIVERSITY, NEW ORLEANS, LOUISIANA70118
Rhodium(1) Complexes Containing Mono- and Ditertiary Phosphines and Arsines' BY JOEL T. MAGUE
AND
JOSEPH P. MITCHENER
Received July 30, 1968 Rhodium dicarbonyl chloride dimer, [Rh(C0)2C1]2,reacts with cis- and trans-8-styryldiphenylarsine,cis-o-styryldiphenylphosphine, bis(1-propynyl)phenylphosphine,and tris(ferroceny1)phosphine to give complexes of the type [Rh(CO)ClL2] (L = phosphine or arsine). Using an excess of cis-1,2-bis(diphenylphosphino)ethyleneor bis(diphenylphosphinomethy1) ether, ionic complexes of the type [Rh(L-L)2]X(L-L = diphosphine, X = anion) are obtained. Polymeric complexes of formula [Rh(C0)C1(L-L)ln(L-L = diphosphine) result from the reaction with trans-1,2-bis(dipheny1phosphino)ethylene and bis(dipheny1phosphino)acetylene. By contrast, complexes of the same empirical formula prepared from bis(dipheny1phosphin0)methane and its arsenic analog are dimers. When used in a 2 : 1 molar ratio, cis-1,2-bis(diphenylphosphino)ethylene and [Rh(CO)&l]z give [Rh(L-L)e][Rh(C0)2C12] (L-L = diphosphine). An analogous reaction with the arsenic analog gives [Rh(CO)(L-L)z][Rh(C0)2C12](L-L = diarsine). A number of bromo analogs were also prepared. Conductance and infrared spectral data are presented and the structures of the complexes are discussed.
Introduction To date, only a few scattered reports of Rh(1) complexes of polydentate, tertiary arsines and phosphines have a p ~ e a r e d . ~ -Our ~ current interest in oxidative addition reactions of square-planar, d8, transition metal compounds has required a number of phosphine and arsine complexes of Rh(1). Thus, it appeared that a more thorough study of the reactions of various Rh(1) species with a variety of ditertiary phosphines and arsines would serve both to expand the knowledge of this area and to provide some interesting compounds for further study. We report here the results of this effort together with those of a study on the complexing tendencies of some monotertiary phosphines and arsines containing unsaturated groups. Experimental Section All reactions were carried out in an atmosphere of prepurified nitrogen and the solvents were appropriately dried and distilled before use. Rhodium dicarbonyl chloride dimer, bis(dipheny1phosphino)methane, and bis(dipheny1arsino)methane were purchased from Strern Chemicals, Inc., and hydrated rhodium(II1) chloride was obtained from Alfa Inorganics. 1,2-Bis(diphenylarsino)ethane was purchased from the Aldrich Chemical Co. and the published procedures were used to prepare cis- and trans1,2-bis(diphenylpho~phino)ethylene,~ bis(diphenylphosphin0methyl) ether,e bis(diphenylphosphino)acetylene,' cis-1,2-bis(diphenylarsino)ethylene,8 cis-p-styryldiphenylphosphine,@cisand trans-P-styryldiphenylarsine,l0 tris(ferrocenyl)phosphine," and bis( l-propynyl)phenylphosphine'2 Microanalyses were by Galbraith Microanalytical Laboratory, Knoxville, Tenn. Molecular weights were determined osmo-
(1) Taken in part from the M.S. thesis of J. P. Ltitchener, Tulane University, 1968. (2) A. Sacco and 12. Ugo, J . Chem. Soc., 3274 (1964). (3) R. J. Mawby and L. M . Venanzi, Expevientia, Sufipl., 9, 240 (1964). (4) W. Hieber and H. Lagally, Chem. Be?., 100, 148 (1967). (5) A. M. Aguiar and D. J. Daigle, J . A m . Chem. Soc., 8 6 , 2299 (1964). (6) A. M. Aguiar, K. C. Hansen, and J. T. Mague, J . Org. Chem., 32,2383 (1967). (7) H. Hartmann, C. Beeman, and H. Czempik, Z. Anorg. Allgem. Chem., 287, 261 (1956). (8) A. M, Aguiar, J. T. Mague, H. J. Aguiar, T. G. Archibald, and G. Prejean, J . Ovg. Chem., 33, 1681 (1968). (9) A. M. Aguiar and D. J. Daigle, ibid., 30, 3527 (1965). (10) A. M. Aguiar and T. G. Archibald, ibid., 32, 2627 (1967). (11) G. P. Sollott and E. Howard, Jr., ibid., 27, 4034 (1962). (12) A. M . Aguiar and S. Irelan, t o be submitted for publication.
metrically a t 37". Infrared spectra were obtained on Becknian IR-5A, IR-8, and IR-11 instruments using Nujol mulls unless otherwise specified. All complexes showed bands due to the phosphine or arsine ligand and only significant additional ones are reported. Nmr spectra were obtained on a Varian A-60 spectrometer in deuteriochloroform solution using tetramethylsilane as an internal standard. The conductance data were obtained using a Thomas-Serfass Model RCM15B1 conductance bridge and a cell which had been calibrated with 0.1 M potassium chloride. Measurements were made on acetonitrile (spectrograde) solution in the concentration range 10-4-10-2 M . The X-ray powder data were obtained with a Debye-Scherrer powder camera of !7.296-mm radius using Ni-filtered Cu Ka radiation ( A 1.5418 A). Four general procedures were used for the preparation of the complexes reported in this work. A typical example of each is detailed below. Method A.-To a warm benzene solution (5 ml) of rhodium dicarbonyl chloride dimer (0.1 g, 0.26 mmol) was added 1.04 mmol of the appropriate phosphine or arsine dissolved in 5 ml of benzene. Carbon monoxide was evolved and if precipitation did not readily occur, diethyl ether was added to the cloud point and the solution was cooled a t -5" overnight to obtain the solid product. This was washed with diethyl ether and dried in vacuo. Method B.-To a solution of rhodium dicarbonyl chloride dimer (0.1 g, 0.26 mmol) in absolute ethanol (10 ml) was added 0.52 mmol of the appropriate diphosphine or diarsine in benzene (5 ml). Carbon monoxide was evolved and diethyl ether was then added while the solution was agitated with a nitrogen stream to produce crystals of the product. This was collected, washed with diethyl ether, and dried i n vacuo. Method C.-An aqueous ethanolic solution (20 ml) of hydrated rhodium(II1) chloride (0.1 g, 0.38 mmol) was refluxed for 5 hr under an atmosphere of carbon monoxide. To the resulting pale yellow solution13* (which apparently contains predominantly Rh(CO)zC12-)13b was added 0.38 mmol of the appropriate diphosphine or diarsine in 5 ml of benzene whereupon carbon monoxide evolution occurred. If necessary, precipitation was induced by the addition of diethyl ether. The collected product was then washed with diethyl ether and dried in ~ U C M O . In the cases where method A was also used, identical products were obtained by both routes. Method D.-A benzene solution (5 ml) of the appropriate diphosphine or diarsine (0.36 mmol) was added to 0.2 g (0.36 mmol) of [ ( C ~ H B ) [Rh(CO)2Br2]14 ~N] in absolute ethanol. Carbon mon(13) (a) J. Chatt and B. L. Shaw, J . Chem. SOL, A , 1437 (1966); (b) B. R. James and G . L. Rempel, Chem. Commuiz., 158 (1967). (14) L. M. Vallarino, Inovg. Chenz., 4, 161 (1965).
120
JOEL
T. MAGUE AND
JOSEPH
P. XITCHENER
Inorganic Chemistry
oxide was evolved and the product precipitated upon addition of diethyl ether. This was collected, washed with diethyl ether, and dried in vacuo. Except for the complexes designated in Table I as having insufficient solubility for molecular weight determination, the complexes reported here are generally soluble in polar organic solvents, especially chlorinated ones.
Results and Discussion Analytical, infrared spectral, and X-ray powder data for the complexes are presented in Tables 1-111, respectively. The results of the conductance measurements are given in Figures 1 and 2. The complexes will be discussed according to the type of molecular formula which they were found to possess. In the general formulas to be used in the subsequent discussion, L will represent a monotertiary phosphine or arsine, L-L a ditertiary phosphine or arsine, and X a halogen. [Rh(CO)CIL,] Complexes.-It has been established that phosphines containing unsaturated groups such as vinyl15 and o-allylphenyllGwill react to form transition metal complexes in which both the phosphorus and the double bond are coordinated to the metal atom. Since rhodium forms a considerable number of olefin and acetylene complexes, it was of interest to determine if similar behavior would be shown by this element. Accordingly, the reactions of rhodium dicarbonyl chloride dimer, [Rh(C0)2C1]2, with cis- and trans-pstyryldiphenylphosphine, trans-p-styryldiphenylarsine, and bis (1-propynyl)phenylphosphine were investigated. The crystalline products obtained (1-4) all exhibited a single sharp band in the infrared region characteristic of a terminal carbonyl group bound to rhodium(1) (Table II).13a They analyze as Rh(CO)ClL, and are monomeric and undissociated in benzene solution. A further inspection of their infrared spectra shows that the bands attributable to the carbon-carbon multiple bond stretching frequencies are in the same positions as in the free ligands thus indicating that coordination of these multiple bonds did not occur. The far-infrared spectra of 1-4 were measured over the range 170-350 cm-I. As can be seen from Table 11, a strong band attributable to a terminal Rh-C1 stretching f r e q ~ e n c y was ~ ~ ,found ~ ~ for each. The shoulder observed in 3 is probably due to chlorine isotopic ~ p l i t t i n g . ' ~The complexes thus appear to be strictly analogous to tmns-Rh(CO)C1((CGHj)3P)a1sand have been formulated accordingly. One notable feature of 2 is the high energy of the carbonyl stretching frequency. This would appear to indicate a particularly strong rr-acid character for bis (I -propynyl)phenylphosphine. The reactions of bis( 1-propyny1)phenylphosphine
(15) C. W u and F. J. Welch, J . O?,g. Chenz., SO, 1229 (1965). (16) L. V. Interrante, hl. A. Bennett, and R. S. Nyholm, I n o i g . Chenz., 5, 2212 (1966). (17) M. A. Bennett, I
