Synthesis and structural characterization of potassium salts of phosphane-substituted (cyclopentadienyl)iron dicyanides, and their use as bridging ligands for copper(I) phosphane derivatives

Phosphane-substituted CpFe(CN)(2) anions have been synthesized by photochemical decarbonylation of KCpFe(CN)(2)CO in the presence of various mono- and diphosphanes. The synthesis and characterization of uniquely bridged diphosphane derivatives, [KCpFe(CN)(2)](2)-mu-(Ph2P)(2)-(CH2)(n) (n = 2-4), are particularly noteworthy. These phosphane-substituted CpFe(CN)(2)(-) units have afforded stable mixed-metal complexes upon reaction with Cu-I in the presence of tricyclohexylphosphane in acetonitrile solution. X-ray crystallography shows these derivatives to display two-dimensional diamond-shaped structures with copper(I) of the form [Fe(CN)(2)Cu](2), where the Cu-I centers exhibit both trigonal and tetrahedral geometries. Infrared data reveal that the withdrawal of electron density from the iron centers in these mixed metal cyanides via the cyanide ligands is enhanced upon replacing CO in CpFe(CN)(2)CO- with phosphanes. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.