SYNTHESIS AND REACTIVITY OF N-ACETYLAMINO ACIDATE(2-) AND RELATED COMPLEXES OF PLATINUM(II)

Treatment of the complexes [PtCl2L2](L = P-donor ligand) with the N-acetyl derivatives of the amino acids glycine, DL-alanine, DL-methionine or L-phenylalanine in the presence of an excess of silver(I) oxide in refluxing dichloromethane affords [Pt{N(COMe)CHRC(O)O}L2] (R = H, Me, CH2CH2SMe or CH2Ph) respectively, and with L-proline the complexes [Pt{NCH2CH2CH2CHC(O)O}L2] are produced, Similar treatment with the N-formyl or N-trifluoroacetyl derivatives of glycine gave the complexes [Pt{N(R)CH2C(O)}2] (R = CHO or COCF3) respectively. An X-ray crystal structure study on the N-acetylglycinato(2-)-N,O complex [Pt{N(COMe)CH2C(O)O}(dppe)] (dppe = Ph2PCH2CH2PPh2) indicated the presence of an almost planar five-membered ring with substantial electron delocalisation within the carboxylate and amide functionalities. Treatment of the complexes [PtCl2L2] with DL-mandelic (alpha-hydroxybenzeneacetic) acid, 2-acetamidophenol, pyrrole-2-carboxylic acid, mercaptoacetic acid or oxamic acid in the presence of an excess of Ag2O in refluxing dichloromethane afforded the complexes [Pt{OC(H)PhC(O)O}L2], [Pt{o-N(COMe)C6H4O}L2], [Pt{NCH = C(H)CH = CC(O)O}L2], [Pt{SCH2C(O)O}L2], [Pt{N(H)C(O)C(O)O}L2] respectively. The cycloocta-1,5-diene (cod) ligand of [Pt{N(COMe)CH2C(O)O}(cod)] and [Pt{N(COMe)CH(CH2Ph)C(O)O}(cod)] is readily displaced by tertiary phosphines. One mole equivalent of Bu(t)NC stereospecifically displaces the PPh3 ligand opposite oxygen in the complex [Pt{N(COMe)CH(CH2Ph)C(O)P}(PPh3)2]. Treatment of [Pt{N(COMe)CH2C(O)O}(PPh3)2] in refluxing ethanol with an excess of either diphenylacetylene or PPh3 leads to the formation of [Pt(PhC = CPh)(PPh3)2] or [Pt(PPh3)4] respectively, in good yield. Treatment of the same metal complex in ethanol at room temperature with either SO2 or CO led to the formation of the bis(ethanesulfonate) or bis(ethoxycarbonyl) complexes respectively. The complex [Pt{NCHCH2CH2CHC(O)O}(PPh3)2] induces the polymerisation of hexaflurobut-2-yne.