Neutral and cationic methyl complexes of platinum(II) with 6-substituted 2,2 '-bipyridines: Synthesis, characterisation and reactivity with carbon monoxide - Molecular structures of [PtCl(methyl)(6-ethyl-2,2 '-bipyridine)] and of [Pt(methyl)(acetonitrile)(6-ethyl-2,2 '-bipyridine)][BF4]

The complex trans-[PtCl(Me)(SMe2)(2)] reacts with 8-R-substituted 2,2'-bipy ridine, HLn (n = 1, R = H; n = 2, R = Me; n = 3, R = Et; n = 4, R = iPr; n = 5, R = CH2Ph; n = 7, R = Ph), to afford the neutral complexes [PtCl(Me)(H Ln)I. Only one isomer is formed (R cis to Cl) with all the ligands, but one (R = Ph). When R = C(Me)(2)Ph (HL6), only an (N-N-C) cyclometallated speci es is formed. The stereoselectivity observed is interpreted in terms of the nature of the substituent R, and of the hydrogen bond formed between H-C(a lpha) of the R substituent and the chloride ion bound to the platinum cente r. The molecular structure of [PtCl(Me)(HL3)] has been resolved by an X-ray analysis and shows that the above-mentioned hydrogen bond length is 2.28 A ngstrom. The reactivity of three representative complexes (R = H, Et, CH2Ph ) with carbon monoxide has been studied. The reaction affords the ionic spe cies [Pt(Me)(CO)(HLn)](+)[PtCl2(Me)(CO)](-) and the free Ligand. There is e vidence of the formation of an acyl species, which does not contain the bip yridine ligand, only when working at high pressures of CO. The above cation s are also obtained by direct carbonylation of the solvent species, [Pt(Me) (MeCN)(HLn)l[BF4], achieve by halide abstraction from the neutral complexes . The molecular structure of [Pt(Me)(MeCN)(HL3)] [BF4] has been resolved by an X-ray analysis.