Substitution of the 1,5-cyclooctadiene (cod) ligand in PtCl ₂(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). The reaction of PtCl₂(bpcd) (2) with 4-methyl-1,2-benzene dithiol under basic conditions affords Pt(tdt)(bpcd) (5). Compounds 2–5 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 2–5 have examined by cyclic voltammetry, and the nature of the HOMO and LUMO levels in systems 2–4 has been established by MO calculations at the extended Hückel level, the results of which are discussed with respect to electrochemical data and related diphosphine derivatives. In addition the new compounds 2–5 have been isolated by column chromatography and characterized by IR, UV-Vis spectroscopy.