Phenyl pyridine cobaloxime

The synthesis of organocobaloximes via Grignard reactions is exemplified in the following preparation of phenyl(pyridine)-cobaloxime. Since the cobalo.ximes contain two acidic oxime protons, the Grignard reagent must be employed in threefold 

Phenyl (pyridine) cobaloxime is stable in air and only sparingly soluble in most organic solvents. The Co—C bond is remarkably stable and difficult to solvolyze, but may be cleaved to produce benzene under reducing conditions in the presence of a noble metal catalyst. 

Shell Development Co., Emeryville, Calif., unpublished data. 

Methods available for the dissolution of ruthenium metal involve alkali fusion under oxidizing conditions. The absence of complete experimental details makes repetition of these methods difficult. The following procedure is a modification of those of Antony and Lucchesi and of Charonnat and, excluding the period of overnight evaporation, takes about 3 hours. The precise stoichiometry of the fused-salt reaction is not known. All procedures must be carried out in a fume hood since chlorine and some ruthenium tetraoxide are produced. 

Potassium hydro-xide (9 g., 0.16 mole) is fused in a silver crucible, using a Bunsen burner as a source of heat, until the water is lost and a quiescent melt is obtained. Ruthenium powder (1.5 g., 0.015 mole) is mixed, without grinding, with 2.3 g. (0.019 mole) of finely ground potassium chlorate. ( Caution. 

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Finally, some successful reductive arylations have been reported via reaction of aryl halides with cobalt(I) nucleophiles. Generally speaking these reactions are only successful when the aryl halide has an electron-withdrawing substituent and yields are generally less than 15% [58,59]. Thus, pyridinecobaloxime(I) reacts with p-bromoacetophenone, methyl-m- and methyl-/>-bromobenzoate, and p-bromo-a,a,a-trifluorotoluene, to produce the expected substituted phenyl(pyridine)cobaloximes in yields of 11.5, 10, 7, and 5% respectively. 

There is at least one confirmed case of concerted cis ehmination of hydridocobalt species from the decomposition of the relatively unstable l-phenyl-2-hydroxyethyl(pyridine)cobaloxime in neutral solution to give phenylacetaldehyde and a cobaloxime(I) species as studied by Naumberg et al. [57]. These workers used the known, rapid cis addition of hydrido(pyridine)cobaloxime to phenylacetylene (Eqn. 14) to form l-phenylvinyl(pyridine)cobaloxime to confirm the formation of hydridocobaloxime during this reaction. When 2-dideuterio-l-phenyl-2-hydroxy(pyridine)cobaloxime was decomposed in the presence of phenylacetylene,... 

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