The synthesis and reactions of palladium–iron carbonyl complexes containing bridging Ph2PCH2PPh2 ligands

Abstract

Treatment of a tetrahydrofuran solution of Fel₂, with two equivalents of Ph₂PCH₂PPh₂(dppm), under an atmosphere of CO, gave trans,mer-[Fel₂(CO)(dppm-PP′)(dppm-P)](1b) in high yield. The bromide analogue was prepared similarly but was unstable. Treatment of compound (1b) with [Pd(dba)₂](dba = dibenzylideneacetone) in benzene, under an atmosphere of CO, gave the bimetallic iron(I)–palladium(I) complex [lFe(CO)₂(µ-dppm)₂Pdl](2c). Complex (2c) was protonated by HBF₄·OEt₂, to give the cationic hydride [lFe(CO)₂(µ-dppm)₂(µ-H)Pdl]BF₄, which was characterised only in solution. Treatment of (2c) with MeNC caused displacement of both iodide and carbonyl ligands from iron to give [(MeNC)₃Fe(µ-dppm)₂PdI]I, whereas treatment of (2c) with the bulky isocyanide Bu^tNC displaced only iodide to give [(Bu^tNC)(OC)₂Fe(µ-dppm)₂PdI]I. N.m.r. (¹H- and ³¹P-{¹H}) and i.r. data are reported.