33988-34-0Relevant academic research and scientific papers
Correlation of rate, spectroscopic, and structural data for (pyridine)- or (triphenylphosphine)-bis(dimethylglyoximato)organocobalt complexes
Randaccio, Lucio,Bresciani-Pahor, Nevenka,Orbell, John D.,Calligaris, Mario,Summers, Michael F.,Snyder, Barry,Toscano, Paul J.,Marzilli, Luigi G.
, p. 469 - 478 (1985)
The crystal and molecular structures of the complexes trans-bis(dimethylglyoximato)(R)(triphenylphosphine)cobalt(III) [R = CH2CH3 (1), 2-C4H9 (2), CH2C(CH3)(CO2C2H5) 2 (3)] and trans-bis(dimethylglyoximato)(CH2C(CH3)(CO 2C2H5)2(pyridine)cobalt(III) (4) are reported. Crystal data for 1: P21/n; a = 10.346 (1) ?, b = 15.310 (2) ?, c = 18.516 (3) ?, β = 103.10 (1)°; Z = 4; R = 0.043 for 4698 independent reflections. Crystal data for 2: P21/n, a = 11.157 (5) ?, b = 11.285 (4) ?, c = 24.356 (9) ?, β = 101.86 (8)°; Z = 4, R = 0.059 for 2612 independent reflections. Crystal data for 3: P1, a = 10.998 (5) ?, b = 10.564 (5) ?, c = 16.085 (8) ?, α = 104.92 (4)°, β = 96.25°, γ = 94.74 (5)°; Z = 2; R = 0.033 for 5084 independent reflections. Crystal data for 4: P21/n, a = 13.597 (9) ?, b = 22.47 (1) ?, c = 8.748 (5) ?, β = 93.98 (5)°; Z = 4; R = 0.035 for 2237 independent reflections. The rate constants, k1, of PPh3 dissociation for 1-3 above and other structurally characterized compounds with R = CH2CN, CH(CH3)CN, CH2CF3, CH2Br, CH3, i-C3H7, and neo-C5H11 were determined. Trends in 31P and 1H NMR spectra were examined for these and related acido (X = Cl, Br, I, NO2) complexes. Good correlations were found between Co-P bond length, the sum of the CPC angles, log k1, and 1H NMR parameters. The 31P NMR shifts were attenuated by opposing contributions from several different effects and did not correlate with other parameters. Distortions in the planarity of the bis(climethylglyoximato)cobalt moiety appear to reflect both the bulk of the axial ligands and lattice effects. For 4, the dihedral angle between the dioximato moieties (12.3°) is toward the pyridine and is the largest such angle in a pyridine complex of this type. No unusual distortions are observed in the alkyl group of 3 or 4.
