Rh(I) and Rh(III) silyl PMe3 complexes.: Syntheses, reactions and 103Rh NMR spectroscopy

Synthetic approaches to Rh(I) silyls are described. The complexes LnRhSiR3 (L=PMe3; 6, n = 4, R-3 = (OEt)(3); 7, n = 4 R-3 = Me(OMe)(2); 21, n = 3, R-3 = Ph-3) resulted from the reactions of MeRhL4 (1) with the corresponding silanes HSiR4. Complex 21 was prepared alternatively from PhRhL3 (2) and HSiPh3, while analogous reactions of HSi(OEt)(3), HSiMe(OMe)(2) and HSiMe(OMe)(2) led to the bis(silyl)hydrides fac-L3Rh(SiR3)(2)(H) (8, R-3 = (OEt)(3); 9, R-3 = Me(OMe)(2); 13, R-3 = (OMe)(3)). Like in analogous iridium-based systems, the outcome of these reactions largely depends on the nature of substituents at the silicon atom. Synthesis of Rh(I) silyls inaccessible by this route, namely those with alkyl substituents at the silicon, LnRhSiR3 (19, n = 3, R-3 = PhMe2; 22, n = 4, R-3 = Me-3), was achieved utilizing nucleophilic attack of the corresponding silyllithiums at [L4Rh]Cl. The solid-state structure of 19 was determined by X-ray crystallography. C17H38P3SiRh, Fw = 466.38 monoclinic, C2/m, a = 13.304(3) Angstrom: b = 13.814(2) Angstrom, c = 13.123(4) Angstrom, beta = 110.66(3) deg, V = 2257(1) Angstrom(3), Z = 4, d(calcd) = 1.373 g cm(-3), mu = 1.019 mm(-1). A series of di(hydrido)silyls fac-L3Rh(H)(2)(SiR3) (10, R-3 =(OEt)(3); 15, R-3 = PhMe3; 16, R-3 = Ph-3) was synthesized using oxidative additions of HSiR3 to HRhL4 (3). Complexes 10, 15, 16 we thermodynamically stable with respect to H-H and SI-H reductive-elimination reactions at ambient conditions. Complex 8 reductively eliminates HSi(OEt), reversibly at room temperature and complex 13 is capable upon heating of mediating dehydrogenative Si-Si coupling of HSi(OMe), and redistribution of [(MeO)(3)Si](2). Rh-103 NMR data obtained for MeRhL4 (1), HRhL4 (3), L3RhSiPhMe2 (19), L3RhSiPh3 (21) and for the di(hydrido) silyls (10, 15, 16) allowed to qualitatively evaluate steric and electronic effects of methyl, silyl, and hydride ligands on the Rh-103 chemical shift. (C) 1998 Elsevier Science S.A.