Synthese und Reaktivität von Vinyliden-Rhodiumkomplexen mit C=CHtBu und C=CHCO2Me als Liganden [1] / Synthesis and Reactivity of Vinylidene Rhodium Complexes Containing C=CHtBu and C=CHCO2Me as Ligands [1]

Abstract

Square-planar alkyne rhodium complexes trans-[RhCl(RC=CCO2Me)(PiPr3)2] (4-6) bearing at least one electron withdrawing substituent at the C=C triple bond are prepared from [RhCl(PiPr3)2] (3) and RC=CCO2Me. Reaction of 3 with tBuC≡CH gives the isomeric alkyne (7) and alkynyl hydrido (8) rhodium complexes in a stepwise fashion. 8 can be trapped with pyridine to produce [RhH(C2tBu)Cl(PiPr3)2(NC5H5)] (10). Thermal rearrangement of 6 (R = H) and 8 leads to the formation of the vinylidene complexes trans-[RhCl(=C=CHR)(PiPr3)2] (9,12) which react with NaC5H5 in THF to give the cyclopentadienyl derivatives C5H5Rh(=C=CHR)(PiPr3) (13, 14). Reactions of 13 and 14 with sulfur afford the thioketene rhodium compounds C5H5Rh(η2-S=C=CHR)(PiPr3) which on methylation with CF3SO3CH3 in the presence of NH4PF6 give the ionic complexes [C5H5Rh(η2-SCH3=C= CHR)(PiPr3)]PF6 (18,19).