Bis(dimethylglyoximato)(methyl)(pyridine)cobalt(III)

Abstract

[61754-28-7] C14H22CoN5O4 (MW 383.29) InChI = 1S/C5H5N.2C4H8N2O2.CH3.Co/c1-2-4-6-5-3-1;2*1-3(5-7)4(2)6-8;;/h1-5H;2*7-8H,1-2H3;1H3;/q;;;;+2/p-2/b;2*5-3+,6-4+;; InChIKey = IZQNQFPQEMEGEJ-DVTASQICSA-L (prototype of alkylcobaloximes and model compound for methylcobalamine1) Alternate Names: methyl(pyridine)cobaloxime(III); MeCoIII(dmgH)2py. Physical Data: mp 215–220 °C (dec); d 1.42 g cm−3; polarographic half-wave potentials (acetonitrile solution, vs Ag/AgNO3 electrode): −1.75, −2.44, −3.01 V; λmax = 438 nm (log ɛ = 3.17); 1H, 13C, 59Co NMR, and ESR data,2 FT-IR and Raman spectroscopy,3 polarographic properties (dropping mercury electrode),4 photochemical and radiolytic CCo bond cleavage,5 thermal decomposition,6 and X-ray crystallography7 have been described. Solubility: sol many organic solvents (acetone, methanol, methylene chloride); slightly sol THF, benzene, ethyl acetate; almost insol water. Preparative Method: orange crystals readily available from cobalt(II) chloride, butane-2,3-dione dioxime (dimethylglyoxime, dmgH2), pyridine (py), and dimethyl sulfate or methyl iodide.8 Handling, Storage, and Precautions: requires no special handling procedures. It is less light-sensitive than its solutions, which tend to decompose with loss of methyl and formation of cobaloxime(II), but should be stored in amber colored vials under nitrogen. For some reactions the 4-tert-butylpyridine derivative of methyl(pyridine)cobaloxime(III), i.e. methyl(4-tert-butylpyridine)cobaloxime(III), is easier to handle especially when column chromatography on silica gel (ethyl acetate, orange band, Rf = 0.4) is required, or in applications which require higher concentrations of alkylcobaloxime(III) in solution or use of nonpolar solvents. Samples have been purified with reversed phase HPLC on a chromsil C18 column.9 Methyl(pyridine)cobaloxime is readily recrystallized from methanol/water mixtures under a nitrogen atmosphere.