VINYLIDENE-TRANSITION-METAL COMPLEXES .8. STEPWISE TRANSFORMATION OF ALKYNEIRIDIUM(I) COMPLEXES TO ALKYNYL(HYDRIDO)IRIDIUM(III) AND VINYLIDENEIRIDIUM(I) COMPLEXES

Square-planar vinylidene iridium(I) complexes trans-[IrCl(CCHR)(PPr3i)2] (XIa-c) have been prepared in two steps from trans-[IrCl(HCCR)(PPr3i)2] (VIIIa-c) via the isolated (for R Me, Ph) alkynyl(hydrido) iridium(III) isomers [IrH(C2R)Cl(PPr3i)2] (IXb, c). The reaction of [IrCl(C8H14)2]2 and PPr3i with HCCSiPh3 leads directly to the formation of [IrH(C2SiPh3)Cl(PPr3i)2] (IXe). The vinylidene complexes XIa-c react with HBF4 to give first [IrHCl(CCHR)(PPr3i)2]+ (XIIa-c) and then by intramolecular rearrangement to give the BF4 salts of the carbyne iridium cations trans-[IrCl(CCH2R)(PPr3i)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(CCHR)(PPr3i)2] (X OH: XVa-c; X I : XVIa-c; X CH3 : XVIIa, c), are prepared from XIa-c by ligand displacement using KOH, NaI and LiCH3 as reagents. trans-[IrI(CCH2)(PPr3i)2] (XVIa) reacts with CO to give the octahedral alkynyl(hydrido)iridium(III) complex [IrH(C2H)I(PPr3i)2(CO)] (XVIII). From XIc and XIa as starting materials, the vinyl iridium(III) compounds [IrH2(CHCHPh)(PPr3i)2(CO)] (XIX) and [Ir(CMeCH2)Cl(I)(PPr3i)2] (XX) have also been obtained. © 1990.