Correlation of rate, spectroscopic, and structural data for (pyridine)- or (triphenylphosphine)-bis(dimethylglyoximato)organocobalt complexes

Article abstract of DOI:10.1021/om00122a007

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.