CoCl2 complexes with 4-substituted

Martin and Stewart1199 first described the preparation of the deep-violet complex [Co(SacSac)2] (363 R = Me) from the reaction of CoCl2 with acetylacetone (acacH) and H2S. A similar synthesis1200 where CF,acac is substituted for acac yields [Co(CF3SacSac)2] (363 R = CF3). The preparation of [Co(PhSacSac)2] via BHf reduction of the dithiolium salt (364) in the presence of CoCl2 has also been reported.1201... 

A common problem associated with the use of metal carbonyls as synthetic reagents is the drastic conditions required to induce CO dissociation. Catalytic amounts of a variety of transition metal complexes have been found to induce stepwise CO substitution (35). Thus Fe(CO)5 reacts with 2,6-dimethylphenyl isocyanide only in the presence of catalytic CoCl2 to give Fe(RNC)(CO)4. The data are consistent with the mechanisms presented in Scheme 3. 

Smith °" have demonstrated asymmetric interactions in stereospecific substitution reactions. An estimate of the magnitude of the asymmetric interaction in the case of the d and / form of d.s-[CoCl2(en)2] with the solvent (—)-2,3-butanedioF °, from solubility product measurements, suggests that antiracemisationin systems where solvolytic interference is less important (perhaps with m-[Co(N02)2(en)2] ), will lead to interesting kinetics. In this solvent, as well as 1,2-propanediol, such studies, when compared with the racemisation rates of the resolved complexes in the racemic or meso forms of the solvents, must lead to a greater understanding of the role of the solvent in a class of reactions whose precise mechanism has proved difficult to define. 

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