THE CROWN-ETHER INFLUENCE ON LIGAND-EXCHANGE REACTIONS OF NA2PTCL6 WITH GLYCINE AND D-(-ALANINE - SYNTHESIS AND CHARACTERIZATION OF PLATINUM(IV) AMINO-ACID COMPLEXES())

The reaction of Na2PtCl6 with glycine in water yields cis-[PtCl2(gly)( 2)] (1). [Na(18-cr-6)](2)[PtCl6]. 3H(2)O reacts with glycine and D-(+) -alanine in water to give [Na(18-cr-6)(H2O)(2)][PtCl4(gly)].(18-cr-6) (2) and [Na(18-cr-6)][PtCl4(ala)] (3), respectively. Cis-[PtCl4(glyH)( 2)].4(18-cr-6) (4) and cis-[PtCl4(alaH)(2)].(18-cr-6) (5), respectivel y, are formed when the reaction mixture is irradiated with light from a halogen lamp. All complexes were characterized by microanalysis as w ell as by NMR, IR and Raman spectroscopy revealing that in complexes 1 -3 the glycinato and alaninato ligands act as N,O-chelate ligands wher eas in complexes 4 and 5 the amino acids act as N-donor ligands. The m olecular structure of 1 (orthorhombic, Pbca, a=10.163(2), b=11.028(2), c=16.310(4) Angstrom, Z=8, R-1=0.0413, wR(2)=0.0953) exhibits a disto rted octahedral coordinated Pt atom with a cis-PtCl2 unit and two N,O- coordinated glycinato ligands (OC-6-32). The complex is stabilized by intramolecular hydrogen bonds between the amino group and the C-O grou p as well as the chloro ligand. The crystal structure of 2 (orthorhomb ic, Pnma, a=23.262(9), b=11.149(4), c=15.834(5) Angstrom, Z=4, R-1=0.0 67, wR(2)=0.1644) shows a [PtCl4(gly)](-) unit and an [Na(18-cr-6)(H2O )(2)](+) unit linked via hydrogen bridges with a further crown ether m olecule.