RH(I) AND RH(III) SILYL PME3 COMPLEXES - SYNTHESES, REACTIONS AND RH-103 NMR-SPECTROSCOPY

Synthetic approaches to Rh(I) silyls are described. The complexes LnRh SiR3 (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 fr om PhRhL3 (2) and HSiPh3, while analogous reactions of HSi(OEt)(3), HS iMe(OMe)(2) and HSiMe(OMe)(2) led to the bis(silyl)hydrides fac-L3Rh(S iR3)(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 react ions largely depends on the nature of substituents at the silicon atom . Synthesis of Rh(I) silyls inaccessible by this route, namely those w ith alkyl substituents at the silicon, LnRhSiR3 (19, n = 3, R-3 = PhMe 2; 22, n = 4, R-3 = Me-3), was achieved utilizing nucleophilic attack of the corresponding silyllithiums at [L4Rh]Cl. The solid-state struct ure of 19 was determined by X-ray crystallography. C17H38P3SiRh, Fw = 466.38 monoclinic, C2/m, a = 13.304(3) Angstrom: b = 13.814(2) Angstro m, 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 d i(hydrido)silyls fac-L3Rh(H)(2)(SiR3) (10, R-3 =(OEt)(3); 15, R-3 = Ph Me3; 16, R-3 = Ph-3) was synthesized using oxidative additions of HSiR 3 to HRhL4 (3). Complexes 10, 15, 16 we thermodynamically stable with respect to H-H and SI-H reductive-elimination reactions at ambient con ditions. Complex 8 reductively eliminates HSi(OEt), reversibly at room temperature and complex 13 is capable upon heating of mediating dehyd rogenative Si-Si coupling of HSi(OMe), and redistribution of [(MeO)(3) Si](2). Rh-103 NMR data obtained for MeRhL4 (1), HRhL4 (3), L3RhSiPhMe 2 (19), L3RhSiPh3 (21) and for the di(hydrido) silyls (10, 15, 16) all owed to qualitatively evaluate steric and electronic effects of methyl , silyl, and hydride ligands on the Rh-103 chemical shift. (C) 1998 El sevier Science S.A.