The quest for PdII-PdII interactions: Structural and spectroscopic studies and ab initio calculations on dinuclear [Pd2(CN)4(μ-diphosphane)2] complexes

Abstract

Structural and spectroscopic properties of and theoretical investigations on dinuclear [Pd2(CN)4(P-P)2] (P - P = bis(dicyclohexylphosphanyl)-methane (1), bis(dimethylphosphanyl)-methane (2)) and mononuclear trans-[Pd(CN)2(PCy3)2] (3) complexes are described. X-ray structural analyses reveal Pd ⋯ Pd distances of 3.0432(7) and 3.307(4) Å in 1 and 2, respectively. The absorption bands at λ > 270 nm in 1 and 2 have 4dσ* →5pσ electronic-transition character. Calculations at the CIS level indicate that the two low-lying dipole-allowed electronic transition bands in model complex [Pd2(CN)4(μ-H2- PCH2PH2)2] at 303 and 289 nm are due to combinations of many orbital transitions. The calculated interaction-energy curve for the skewed dimer [{trans-[Pd(CN)2(PH3)2]}2] is attractive at the MP2 level and implies the existence of a weak PdII-PdII interaction.