Homoleptic complexes of Ag(I), Cu(I), Pd(II) and Pt(II) with tetrathiafulvalene-functionalized phosphine ligands

Homoleptic complexes of the type [M(L-L)(2)](+/2+) where L-L is a chelating tetrathiafulvalene-based phosphine ligand have been synthesized and fully characterized by X-ray crystallography, P-31{H-1} NMR spectroscopy and electrochemistry. In this study, square-planar cations of Pd(II) and Pt(II) with tetrakis(diphenylphosphino)-tetrathiafulvalene (P4) and tetrahedral cations of Ag(I) and Cu(I) with 3,4-dimethyl-3',4'-bis(diphenylphosphino)tetrathiafulvalene (o-P2) have been isolated. X-Ray studies of six different crystalline compounds revealed that the conformation of the TTF (tetrathiafulvalene) substituents is highly influenced by crystal packing forces. As judged by the remarkable similarity of each Pd/Pt or Cu/Ag pair, the solid-state structures are independent of the identity of the metal. Electrochemical studies indicate that the TTF redox centers on the different phosphine ligands are electronically isolated in these compounds.