Syntheses, structures, and nonlinear optical properties of heteroselenometallic W-Se-Ag cluster compounds containing phosphine ligands.

Treatment of [Et4N]2[WSe4] with a 1:1 mixture of AgNO3 and PCy3 (Cy = cyclohexyl) in the absence of iodide afforded a linear trinuclear compound [(mu-WSe4)(AgPCy3)2] (1). A similar reaction in the presence of iodide gave rise to the isolation of the cubanelike compound [(mu3-WSe4)Ag3(PCy3)3(mu3-I)] (2). Treatment of [Et4N]2[WSe4] with AgI in the presence of bidentate phosphine ligands bis(diphenylphosphino)amine (dppa) and bis(diphenylphosphino)methane (dppm) afforded the tetranuclear compounds [(mu3-WSe4)Ag3(mu-I)(mu-dppa)2] (3) and [(mu3-WSe4)Ag3(mu3-I)(mu-dppm)2] (4), respectively, which exhibit an open butterfly configuration. A novel hexanuclear cluster compound [(mu3-WSe4)2Ag4(mu-dppm)3] (5) was obtained from interaction of [Et4N]2[WSe4] with AgNO3 and dppm in the absence of iodide source. The above cluster compounds are electrically neutral and air-stable in both solution and the solid state and have been characterized by electronic, infrared, mass, and NMR spectroscopies. The solid-state structures of five cluster compounds have been established by X-ray crystallography. The nonlinear optical properties of compounds 4 and 5 were examined by z-scan techniques with 7 ns pulses at 532 nm. The optical limiting effects of compounds 1, 2, 4, and 5 were determined and compared with related argentoselenometallic compounds.