SYNTHESIS AND STRUCTURE OF SOME PALLADIUM(I) CLUSTER COMPOUNDS CONTAINING ISOCYANIDE LIGANDS

The reaction of [Pd4(mu-CO)4(mu-O2CCH3)4] with C8H9NC has been shown t o occur with substitution of CO by C8H9NC to give [Pd4(mu-CO)2(mu-CNC8 H9)2(mu-O2CCH3)4] (1) with two equivalents of isocyanide and [Pd4(mu-C NC8H9)4(mu-O2CCH3)4] (2) with four equivalents of isocyanide. The stru cture of [Pd4(mu-CNC8H9)4(mu-O2CCH3)4].CH2Cl2 has been determined by s ingle crystal X-ray diffractometry. The structure is based on a rectan gular unit of palladium atoms with the two shorter edges, which have P d-Pd distances of 2.6572(5) and 2.6668(4) angstrom, bridged by isocyan ide ligands, and the two longer edges, with Pd-Pd distances of 2.8888( 4) and 2.9369(4) angstrom, bridged by two acetate ligands. The bridgin g isocyanide groups are nearly linear, with C-N-C angles of between 16 1.2(4) and 169.3(5)-degrees. This leads to relatively high values for the nu(NC) stretching frequencies in the IR spectrum. Compound 1 has a lso been synthesised by carbon monoxide reduction of palladium(II) ace tate in the presence of isocyanide.