HOMODINUCLEAR AND HETERODINUCLEAR ALPHA-PYRIDONATE-BRIDGED PLATINUM AND PALLADIUM COMPLEXES WITH BIS(N-METHYLIMIDAZOL-2-YL)KETONE (BMIK) - CRYSTAL-STRUCTURES OF [(BMIK)PT(ALPHA-PYRIDONATE)2PT(BMIK)](NO3)2.4H2O, [(BMIK)PD(ALPHA-PYRIDONATE)2PD(BMIK)](NO3)2.4H2O, AND [(BMIK)PD(ALPHA-PYRIDONATE)2PT/PD(BMIK)](NO3)2.4H2O

The isotypic dinuclear complexes [(BMIK)Pt(alpha-pyridonate)2Pt(BMIK)](NO3)2 . 4H2O (1) (P1BAR; a = 12.197(5) angstrom, b = 12.505(5) angstrom, c = 12.866(5) angstrom, alpha = 88.17(3)-degrees, beta = 73.55(3)-degrees, gamma = 69.84(3)-degrees; Z = 2) and [(BMIK)Pd(alpha-pyridonate)2Pd(BMIK)](NO3)2 . 4H2O (2) (a = 12.408(3) angstrom, b = 12.660(3) angstrom, c = 12.913(3) angstrom, alpha = 89.55(3)-degrees, beta = 74.59(2)-degrees, gamma = 68.68(2)-degrees) were prepared by reaction of [Pt(BMIK)(H2O)2](NO3)2 or [Pd(BMIK)(H2O)2](NO3)2 with alpha-pyridone in aqueous solutions at 40-degrees-C and were isolated as red air-stable crystals (BMIK = bis(N-methylimidazol-2-yl)ketone). For the synthesis of mixed crystals of 2 with the heterometal complex [(BMIK)Pd(alpha-pyridonate)2Pt(BMIK)](NO3)2: 4H2O (3) (a = 12.430(4) angstrom, b = 12.648(3) angstrom, c = 12.907(4) angstrom, alpha = 89.64(2)-degrees, beta = 74.57(2)-degrees, gamma = 68.65(2)-degrees) alpha-pyridone was reacted with [Pd(BMIK)(H2O)2](NO3)2 in a molar ratio of 2:1 followed by addition of [Pt(BMIK)(H2O)2](NO3)2. The dinuclear cations consist of two M(BMIK) moieties (M = Pt, Pd) bridged by the N- and O-atoms of alpha-pyridonate, forcing the heterocylic ring into head-head-orientation. Within the dinuclear cation, the two metal atoms are between 2.840 angstrom and 2.860 angstrom apart. The intermolecular distances are between 4.762 angstrom and 4.837 angstrom. The coordination geometry of both metal atoms is square-planar with the metal atoms being diplaced slightly from their respective coordination planes toward each other. H-1 and Pt-195 NMR spectra are reported for the complexes.