Synthesis of the donor–acceptor ligand 2-(4-dimethylaminobenzylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (dbpcd) and X-ray diffraction structure of the platinum(II) compound PtCl2(dbpcd)·1.5CH2Cl2

Knoevenagel condensation of 4-(dimethylamino)benzaldehyde with 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd) gives the donor–acceptor ligand 2-(4-dimethylaminobenzylidene)-4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (dbpcd). The reaction of dbpcd with PtCl2(cod) affords the platinum(II) complex PtCl2(dbpcd) in high yield. The free dbpcd ligand and PtCl2(dbpcd) have been isolated and fully characterized in solution by IR and NMR spectroscopies, and the solid-state structure of PtCl2(dbpcd) determined by X-ray diffraction analysis. PtCl2(dbpcd), as the 1.5CH2Cl2 solvate, crystallizes in the triclinic space group P 1 ¯ , a = 11.7412(7) Å, b = 12.0486(7) Å, c = 14.4781(9) Å, α = 82.866(1), β = 75.049(1), γ = 83.905(1), V = 1957.6(2) Å3, Z = 2, and Dcalc = 1.678 mg/m3, R = 0.0291 and wR2 = 0.0723 for 8315 reflections with I > 2σ(I). The molecular structure of PtCl2(dbpcd)·1.5CH2Cl2 consists of a square-planar platinum architecture containing two chlorines and the ancillary dbpcd diphosphine ligand. The redox properties of the dbpcd ligand and PtCl2(dbpcd) have been explored by cyclic voltammetry, and these data are discussed with respect to extended Hückel MO calculations.