Synthesis, Reactivity Investigation, and X-ray Diffraction Structures of New Platinum(II) Compounds Containing Redox-Active Diphosphine Ligands

Abstract

Substitution of the 1,5-cyclooctadiene (cod) ligand in PtCl2(cod) (1) by the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) yields PtCl2(bpcd) (2). Knoevenagel condensation of 2 with 9-anthracenecarboxaldehyde leads to the functionalization of the bpcd ligand and formation of the corresponding 2-(9-anthracenylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (abpcd) substituted compound PtCl2(abpcd) (3), which is also obtained from the direct reaction of 1 with the abpcd ligand in near quantitative yield. The reaction of 3 with disodium maleonitriledithiolate (Na2mnt) affords the chelating dithiolate compound Pt(mnt)(abpcd) (4). Compounds 2�C4 have been fully characterized in solution by IR and NMR spectroscopies (1H and 31P), and their molecular structures established by X-ray crystallography. The electrochemical properties of 2�C4 have examined by cyclic voltammetry, and the nature of the HOMO and LUMO levels in these systems has been established by MO calculations at the extended H��ckel level, the results of which are discussed with respect to electrochemical data and related diphosphine derivatives.