Synthesis, structures, and linkage isomerism of (allylbenzylmalonate)platinum(II) complexes

Abstract

New platinum(II) complexes A(2)Pt(ABM) (A = triethylphosphine (TEP); A(2) = 2,2-dimethyl-1,3-propanediamine (DMPDA), trans-(+/-)-1,2-diaminocyclohexane (DACH); ABM = allylbenzylmalonate) have been synthesized in aqueous solution and characterized by means of X-ray analysis and multinuclear NMR spectroscopy. The crystal structures of cis-(TEP)(2)Pt(ABM) (monoclinic P2(1)/n, a = 12.179(3), b = 16.869(7), c = 12.870(3) Angstrom, beta = 93.27(2)degrees, V = 2757(1) Angstrom(3), Z = 4, R = 0.0390) and (DACH)Pt(ABM). 2H(2)O (triclinic P (1) over bar, a = 7.649(3), b = 14.064(2), c = 19.190(8) Angstrom, alpha = 98.98(2), beta = 90.05(3), gamma = 105.73(2)degrees, V = 1961(1) Angstrom(3), Z = 2, R = 0.0455) have been solved. The platinum atom in both complexes adopts a typical square planar arrangement with each coligand in cis positions. In the solid state, the ABM ligand exhibits different chelation modes depending on the coligands: (O,O')-chelation in the phosphine analog and (O,alkene)-chelation in the amine analogs. For the phosphine complex, the (O,O')-chelation mode of the ABM ligand is impregnable even in solutions at variable temperatures, probably due to the strong pi-bonding between the phosphorus and platinum atoms. However, (diamine)platinum(II) complexes have shown interesting linkage isomerism between the (O,O')- and (O,alkene)-chelation modes in solutions depending on solvent and temperature. (C) 1999 Elsevier Science S.A. All rights reserved.