Reactions of halogeno(phenyl)alkynes with complexes of platinum(0), palladium(0), rhodium(I), and iridium(I). The preparation of [1—2-η-chloro(phenyl)ethyne]bis(triphenylphosphine)platinum(0) and chloro-[1—2-η-chloro(phenyl)ethyne]bis(triphenylphosphine)rhodium(I) and the kinetics of isomerisation of the former to an alkynyl complex

Abstract

Hydrazine hydrate reduction of cis-[PtCl₂(PPh₃)₂] in the presence of PhCCCl gives the 1—2-η-halogenoalkyne complex [Pt(η²-PhCCCl)(PPh₃)₂]. Similar reaction with PhCCX (X = Br or I) give the alkynyls trans-[PtX(CCPh)(PPh₃)₂]. Treatment of [PtCl₂(Ph₂PCH₂CH₂PPh₂)] with Na[BH₄] in the presence of PhCCCl gives [Pt(η²-PhCCCl)(Ph₂PCH₂CH₂PPh₂)]. The reactions of PhCCX (X = Cl, Br, or I) with [Pt(trans-PhHCCHPh)-(PPh₃)₂] in diethyl ether give cis-[PtX(CCPh)(PPh₃)₂] which isomerise to the trans complexes in benzene solution. The complex [RhCl(PPh₃)₃] reacts with PhCCCl to give [RhCl(η²-PhCCCl)(PPh₃)₂], and the reaction of PhCCCl with trans-[IrCl(CO)(PPh₃)₂] affords a mixture containing the complexes [IrCl(η²-PhCCCl)(CO)-(PPh₃)₂] and [IrCl₂(CCPh)(CO)(PPh₃)₂], but other alkynes PhCCX (X = Br or I) give only alkynyl complexes of iridium. The alkynyl complexes trans-[PdX(CCPh)(PPh₃)₂] are formed in reactions of [Pd(PPh₃)₄] with PhCCX. The kinetics and mechanism of isomerisation of [Pt(η²-PhCCCl)(PPh₃)₂] to [PtCl(CCPh)(PPh₃)₂] in a range of monohydroxylic alcohols are reported and discussed.