Rhodium(I) fluorothiolate complexes as hydroformylation catalyst precursors. Crystal structure of two polymorphs of trans-[Rh(SC6F5)(CO)(PPh3)(2)]

The perfluorothiolate dinuclear compounds [Rh( mu-SC6F5)(COD)](2) 1 and [Rh( mu-SC6F5)(CO)(2)](2) 2 react with PPh3 to give monomeric and dimeric complexes, the particular product depending upon the PR3/Rh ratio and reaction conditions. Reaction of 2 with 2 moles of PPh, renders cis-7 and trans-[Rh(mu-SC6F5)((CO)(PPh3)](2) 8, while with 4 moles of PPh3 trans[Rh(SC6F5)(CO)(PPh3)2]10a is obtained. This latter product can otherwise be prepared by CI metathesis from trans-[RhCl(CO(PPh3)(2)] in toluene. This same reaction in dichloromethane however yields the cis isomer 10b. When a larger excess of PPh3 is used, a mixture of compounds 11a and 11b is formed. An X-ray crystal structure study shows trans[Rh(SC6F5)(CO)(PPh3)(2)] to exit as two polymorphs. 11a crystallises in the space group P2(1)/n of the monoclinic system with a = 12.489(1), b = 15.430(5), c = 19.719(1) Angstrom, alpha = gamma = 90, beta = 92.84(1)degrees, and 11b is triclinic, space group <P(1)over bar> with a = 9.764(2), b = 12.197(6), c = 17.880 Angstrom, alpha = 100.18(5), beta = 101.92(2), gamma = 113.61(2)degrees. Both PPh3 ligands are mutually trans and the difference in v(CO) stretching frequencies, 1989 and 1939 cm(-1) can be explained in terms of o-phenyl H...CO interactions in the latter. The [Rh( mu-SC6F5)(COD)](2) 1 and [Rh(mu-SC6F5)(CO)(2)](2) 2/nPPh(3) systems have been studied as catalyst precursors for the hydroformylation of 1-heptene in toluene at 30 bar and 343 K. Selectivity towards the Linear aldehyde is enhanced when dimeric complexes are used. (C) 1997 Elsevier Science S.A.