Primary, secondary, and tertiary alkylrhodoximes 1 were prepared from alkyl bromides and tosylates 4 and the trans-dichlororhodium complex 3. X-ray crystallography of the previously unknown tert-butylrhodoxime 1 k reveals structural features of this terf-o-alkylrhodium compound. Photochemical homolytic cleavage of the Rh-C bond in alkylrhodoximes 1 only occurs in the presence of efficient radical traps which allow further mechanistic studies.
Butanedione dioxime (dimethylglyoxime) complexes of transition metals play an important role in applied coordination chemistry [']. For example photolabile alkyl(dimethylg1yoxime)cobalt complexes 2 (alkylcobaloximes 2) are convenient sources of carbon-centered radicals[21, and a technetium dimethylglyoxime complex (p9"Tc]-Teboroxime) is used for imaging regional myocardial perfusionr3].
Alkylcobaloximes 2 have played a major role in elucidating reaction mechanisms of vitamin BI2 and related alkyl~obalamines[~! 5'-Deoxyadenosylrhodibalamine, the rhodium analog of the cobalamine coenzyme, has been synthesized and tested as a vitamin Bt2 inhibitor in E . coli showing an IC5,, index of 52[51. As part of our studies of alkylcobaloximes as sources offree alkyl radicals in organic synthesis we were interested in photochemical properties of alkylrhodoximes 1 compared to their cobalt analogs 2. Especially the inhibitory effect of 5'-deoxyadenosylrhodibalamine in enzyme reactions led us to the conclusion that carbon-rhodium bonds could be more stable compared to C-Co bonds. Thus tertiary o-alkylrhodium complexes could be in synthetic reach.