The chemistry of isocyanide complexes of iridium(1) and iridium (111)

Bedford, Wendy Margaret (1976) The chemistry of isocyanide complexes of iridium(1) and iridium (111). University of Southampton, Doctoral Thesis.

Abstract

The preparation and properties are described of a series of stable five-co-ordinate isocyanide complexes of iridium(i), [Ir(CNR)(LL)2] + [R = Me, p Me.C6H4, But, or R(+)-C6H5.CH(Me); LL = 1,2-bis(diphenylphosphino)ethane (dppe) or cis-1,2-bis(diphenylphosphino)ethylene (dppen)]. The complexes undergo oxidative. addition of halogens, mercuric chloride, and protonic acids (including methanol), without loss of a ligand, to give the dicationic adducts [IrX(CNR)(LL)2]2+ [X = C1, I, HgCl, H] but do not react with alkyl, allyl, or acyl halides. Protonic acids give cis-adducts, under kinetic control, which may then isomerise on heating. Dihydrogen and dioxygen react very slowly, with loss of isocyanide, to give cis- [IrH2(LL)2]+ and [Ir(02)(LL)2]+ respectively and sulphur dioxide gives an unstable sic-co-ordinate adduct which dissociates at room temperature even in liquid sulphur dioxide.The reactions of co-ordinated isocyanides are discussed: nucleophiles may attack the moiety 11-CNR at AI (displacement of BPIC), at C (formation of carbene or imidoyl complexes), or at NR (formation of cyanide complexes).The isocyanide moiety of the six-co-ordinate complexes of iridium(III) is attacked by nucleophiles Y [C1 , I , Me0 , N3-1 , yielding the six-co-ordinate cyanide complexes of iridium(III), [IrX(CN)(LL)2]+ , and RY, rather than carbene complexes. The mechanism of this reaction is discussed, in the light of the results obtained with a complex of the optically active isocyanide R(+)-C6H5.CH(Me).NC. With CN as the nucleophile thi product is [Ir(CN)2(LL)2]+.-1

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