VINYLIDENE TRANSITION-METAL COMPLEXES .27. REACTIONS OF ALKYNYLSILANES WITH [RHCL(PIPR3)2] - THE SYNTHESIS OF 4-COORDINATE (ALKYNE)IDENERHODIUM(I), ALKYNYLIDENERHODIUM(I), AND VINYLIDENERHODIUM(I) AND 5-COORDINATE AND 6-COORDINATE ALKYNYLHYDRIDORHODIUM(III) COMPLEXES FROM RC-EQUIVALENT-TO-CSIME3, ME3SIC-EQUIVALENT-TO-CSIME3, AND HC-EQUIVALENT-TO-CSIME3

Treatment of [RhCl(PiPr3)2] (1) with the alkynylsilanes RC=CSiMe3 leads to the formation of the alkyne complexes trans-[RhCl(RC=CSiMe3)(PiPr3)2] (R = Me (2), Ph (3), CO2Et (4), CO2SiMe3 (5), CH2OH (6), C(O)CHPh2 (7)) or the corresponding vinylidenerhodium(I) derivatives trans-[RhCl(=C=C(SiMe3)R)(PiPr3)2](R=SiMe3(8), nPr(9), nBu(10), tBu(11)). Compounds 2-5 rearrange either thermally or photochemically to give the isomeric rhodium vinylidenes 12-15. Whereas the reaction of 1 with HMe2SiC=CSiMe2H affords the dinuclear hydrido-(silyl)rhodium(III) complex [{RhHCl(PiPr3)212(mu-Me2SiC=CSiMe2)] (16), the five-coordinate alkynlhydrido compound [RhH(C=CSiMe3)Cl(PiPr3)2] (18) is obtained from 1 and HC=CSiMe3. 18 rearranges smoothly to yield trans-[RhCl(=C=CHSiMe3)(PiPr3)2] (19), and it reacts with pyridine to give [RhH(C=CSiMe3)Cl(py)(PiPr3)2] (20). Treatment of 20 with Na[N(SiMe3)2] as a strong base affords the square-planar alkynyl derivative trans-[Rh(C=CSiMe3)(py)(PiPr3)2] (21). The corresponding ethene complex trans-[Rh(C=SiMe3)(C2H4)(PiPr3)2](22) is similarly obtained from 18 and Na[N(SiMe3)2] under a C2H4 atmosphere. The Rh-C2H4 bond in 22 is rather labile and therefore displacement reactions with alkynes occur readily. With HC=SiMe3, the bis(alkynyl)hydridorhodium(III) compounds [RhH(C=CSiMe3)2(PiPr3)2] (23) and [RhH(C=CSiMe3)2(py)(PiPr3)2] (24) and with RC=CSiMe3 the alkyne((alkynyl)rhodium(I) derivatives trans-[Rh(C=CSiMe3)(R=CSiMe3)(PiPr3)2] (R = CO2Et (25), CO2SiMe3 (26)) are obtained. The X-ray crystal structure of 24 (orthorhombic, space group Pna2(1) (No. 33) with a = 19.109(7) angstrom, b = 17.397(4) angstrom, c = 12.329(3) angstrom, and Z = 4) reveals a trans disposition of the two alkynyl, the two phosphine, and the hydride and the pyridine units. The synthesis of some cyclopentadienylrhodium complexes containing alkynylsilane ligands will also be described.