Vinyliden-Übergangsmetallkomplexe: VIII. Die stufenweise Umwandlung von Alkiniridium(I) - in Alkinyl(hydrido)iridium(III)- und Vinylideniridium(I) - Komplexe

Abstract

Square-planar vinylidene iridium(I) complexes trans-[IrCl(CCHR)(PPr 3 i) 2] (XIa–c) have been prepared in two steps from trans-[IrCl(HCCR)(PPr 3 i) 2] (VIIIa–c) via the isolated (for R  Me, Ph) alkynyl(hydrido) iridium(III) isomers [IrH(C 2R)Cl(PPr 3 i) 2] (IXb, c). The reaction of [IrCl(C 8H 14) 2] 2 and PPr 3 i with HCCSiPh 3 leads directly to the formation of [IrH(C 2SiPh 3)Cl(PPr 3 i) 2] (IXe). The vinylidene complexes XIa–c react with HBF 4 to give first [IrHCl(CCHR)(PPr 3 i) 2] + (XIIa–c) and then by intramolecular rearrangement to give the BF 4 salts of the carbyne iridium cations trans-[IrCl(CCH 2R)(PPr 3 i) 2] + (XIIIa–c). In solution, an equilibrium exists between XIIIa–c and XIIa–c which lies almost exclusively towards XIIIa–c. Treatment of XIIIa–c with NaH in benzene regenerates the vinylidene iridium compounds XIa–c. The hydroxo, iodo and methyl derivatives, trans-[IrX(CCHR)(PPr 3 i) 2] (X  OH: XVa–c; X  I : XVIa–c; X  CH 3 : XVIIa, c), are prepared from XIa–c by ligand displacement using KOH, NaI and LiCH 3 as reagents. trans-[IrI(CCH 2)(PPr 3 i) 2] (XVIa) reacts with CO to give the octahedral alkynyl(hydrido)iridium(III) complex [IrH(C 2H)I(PPr 3 i) 2(CO)] (XVIII). From XIc and XIa as starting materials, the vinyl iridium(III) compounds [IrH 2(CHCHPh)(PPr 3 i) 2(CO)] (XIX) and [Ir(CMeCH 2)Cl(I)(PPr 3 i) 2] (XX) have also been obtained.