Cobaloximes with Mixed Dioximes of Glyoxime and Diphenylglyoxime: Synthesis, Characterization, CV, X-ray Studies, and Crystal Packing

Syntheses and characterization of organo-group 14 cobaloxime compounds

Reactions of cobaloxime Na[(t-BuPy)Co(DH)2] with Ph3ECl (E = Si, Ge, Sn, and Pb) were investigated. Metal-metal bonded complexes (t-BuPy)Co(DH)2EPh3 were isolated for E = Sn and Pb. (t-BuPy)Co(DH)2SnPh3.(C2H5)2O, C39H52CoN5O5Sn, crystallized in the monoclinic space group P21/c (Z = 4) with unit cell dimensions a = 11.6443(6) A, b = 15.6085(8) A, c = 22.6354(12) A, beta = 96.634(1) degrees , and V = 4086.4(4) A3 at 295(2) K. The structure resembled those of six-coordinate alkyl cobaloxime complexes and had Co-NPy and Co-Sn distances of 2.056(2) and 2.5568(3) A, respectively. (t-BuPy)Co(DH)2PbPh3, C35H42CoN5O4Pb, crystallized in the monoclinic space group P21/n (Z = 4) with unit cell dimensions a = 15.0104(7) A, b = 15.7693(8) A, c = 16.6230(8) A, beta = 114.348(1) degrees , and V = 3584.8(3) A3 at 295(2) K. The complex was nearly isostructural with the Sn analogue and had Co-NPy and Co-Pb distances of 2.049(2) and 2.6191(4) A, respectively. Coupling of the ortho phenyl protons to the spin 1/2 isotopes of Sn and of Pb was a characteristic feature of the 1H NMR spectrum. Additional, longer range couplings were observed for the Pb complex and for both complexes in the 13C NMR. Metal-metal bonded complexes were not obtained for E = Si or Ge. The products isolated in the latter case were the hydride Ph3GeH and the cobalt(II) complex (t-BuPy)Co(DH)2,C17H27CoN5O4, which crystallized in the orthorhombic space group Pbcn (Z = 8). Unit cell dimensions were a = 17.9821(11) A, b = 9.7449(6) A, c = 22.7374(15) A, and V = 3984.4(4) A3 at 295(2) K. The five-coordinate complex had Co-NPy = 2.096(2) A and was dimeric in the lattice.

Kinetics of the reduction of 4-amino and 4-cyanopyridinechlorocobaloximes by iron(II)

Cobaloximes such as trans[Co(dmgH) 2(Py-NH2)Cl] and trans- [Co(dmgH) 2(Py-CN)Cl], where, dmgH = dimethylglyoximato anion, Py-NH 2 = 4-aminopyiridne and Py-CN = 4-cyanopyridine, were prepared and characterized by elemental analysis, UV-VIS, IR and NMR spectroscopy. The kinetics of iron(II) reduction of the complexes were studied spectrophotometrically at 300 nm in 2% (v/v) DMSO-H2O medium at 27?0.1?C and I = 0.25 M (LiClO4) at various hydrogen ion concentrations in the range 2.5 x 10-4 to 5.0x10-2 M under pseudo-first-order conditions using an excess of the reductant. The inverse dependence of rate on [H+] suggests an equilibrium between the protonated and unportonated forms of the complexes, the protonated form reacting slower than the unprotonated form. Computation of the data enabled the evaluation of the rate constants for the protonated and unprotonated from of the complexes, leading to an evaluation of the protonation constant for the complexes. .