Halo-carbonyl complexes of platinum(II) and palladium(II)

Abstract

The mononuclear and binuclear square-planar complexes of palladium(II) and platinum(II) cis-PtCl 2(CO) 2 ( 1), trans- Pt 2Cl 4(CO) 2 ( 2), cis-PtBr 2(CO) 2 ( 3), and cis-Pd 2Cl 4(CO) 2 ( 4), have been prepared by new synthetic procedures and some of them ( 2, 3, and 4) structurally characterised by X-ray diffraction methods. In the mononuclear platinum derivatives, cis-PtX 2(CO) 2, X=Cl, Br, the molecules are arranged in columns, the Pt ⋯Pt separation being 3.378 Å (X=Cl) or 3.65 Å (av., X=Br). The chloride-bridged dinuclear chloro-carbonyl complexes M 2Cl 4(CO) 2, M=Pd, Pt, contain terminal chloride and carbonyl groups, trans for the platinum derivative 2, but, unexpectedly, cis for the corresponding palladium compound 4. Packing is based on intermolecular C ⋯X or Pt ⋯Pt interactions, as a function of the nature of the halide. The carbonylation at atmospheric pressure and room temperature of the tetrahalo complexes of platinum(II) in the presence of AlX 3 as halide scavenger leads to [PtX 3(CO)] − or PtX 2(CO) 2, depending on the Pt/AlX 3 molar ratio. The crystal and molecular structural data of [NBu 4][PtBr 3(CO)] ( 5), show the anion to have substantially identical Pt–Br bond distances, the CO ligand performing no trans influence.