Synthesis and structure of some palladium(I) cluster compounds containing isocyanide ligands

Abstract

The reaction of [Pd 4(μ-CO) 4(μ-O 2CCH 3) 4] with C 8H 9NC has been shown to occur with substitution of CO by C 8H 9 NC to give [Pd 4(μ-CO) 2(μ-CNC 8H 9) 2(μ-O 2CCH 3) 4] ( 1 with two equivalents of isocyanide and [Pd 4(μ-CNC 8H 9) 4(μ-O 2CCH 3) 4] ( 2) with four equivalents of isocyanide. The structure of [Pd 4(μ-CNC 8H 9) 4(μ-O 2CCH 3) 4]· CH 2Cl 2 has been determined by single crystal X-ray diffractometry. The structure is based on a rectangular unit of palladium atoms with the two shorter edges, which have PdPd distances of 2.6572(5) and 2.6668(4) åA, bridged by isocyanide ligands, and the two longer edges, with PdPd distances of 2.8888(4) and 2.9369(4) åA, bridged by two acetate ligands. The bridging isocyanide groups are nearly linear, with CNC angles of between 161.2(4) and 169.3(5)°. This leads to relatively high values for the v(NC) stretching frequencies in the IR spectrum. Compound 1 has also been synthesised by carbon monoxide reduction of palladium(II) acetate in the presence of isocyanide.