Syntheses, molecular structures and optical nonlinearities of heteroselenometallic W-Se-Pd compounds containing bidentate phosphine ligands

Reaction of [NEt4]2[WSe4] with [Pd2(dppm)2Cl2] afforded the hexanuclear windmill-shaped compound [(WSe4)2Pd4(dppm)2] (1) {dppm = bis(diphenylphosphino)methane}. Treatment of [NEt4]2[WSe4] with [Pd(P∧P)Cl2] gave the dinuclear compounds [(WSe4)Pd(P∧P)] {P∧P = dppe, 1,2-bis(diphenylphosphino)ethane (2); dppp, 1,3-bis(disphenylphosphino)propane (3)}. The crystal structures of these heteroselenometallic W-Se-Pd compounds have been determined and their nonlinear optical properties were studied with an 8 ns pulsed laser at 532 nm. It was found that compounds 1-3 show predominantly nonlinear refraction and negligible nonlinear absorption. Compound 1 exhibits a considerable self-defocusing properties with the nonlinear refractivity (n2) value estimated to be -3.74 × 10-10 cm2 W-1 M-1. The optical limiting thresholds of compounds 1, 2 and 3 were determined to be ca. 3.1, 6.5 and 7.2 J cm-2, respectively.