Knoevenagel condensation of the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione with 9-anthracenecarboxaldehyde: Synthesis of the second-generation ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione
Watson, WH; Poola, B; Richmond, MG; ,
The Knoevenangel condensation between 9-anthracenecarboxaldehyde and the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione (bpcd) takes place rapidly in CH2Cl2/MeOH solution in the presence of molecular sieves (4 angstrom) to produce the functionalized ligand 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione. The title compound has been isolated and characterized in solution by IR, NMR, and UV-vis spectroscopies, and the solid-state structure has been established by X-ray diffraction analysis. 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione crystallizes in the triclinic space group P-1, a=10.227(2) angstrom, b=13.865(2) angstrom, c=15.905(2) angstrom, alpha=112.157(2) angstrom, beta=101.424(2) angstrom, gamma=100.065(3) angstrom, V=1968.5(5) angstrom(3), Z=2, and d (calc)=1.101 Mg/m(3); R=0.0873, R (w)=0.2604 for 7452 reflections with I > 2 sigma(I). The cyclic voltammetric behavior for 2-(anthracen-9-ylidene)-4,5-bis(diphenylphosphino)-4-cyclopentene-1,3-dione has been studied, and the observed redox data and results from extended Huckel MO calculations are discussed relative to the parent ligand bpcd.