PYRAZINE BRIDGED ORGANODICOBALOXIMES - A CONVENIENT ONE-POT SYNTHESISAND CIS INFLUENCE STUDIES

Twenty six complexes, pyrazine bridged organodicobaloximes of the type RCo(L-2)-pyrazine-Co(L-2)R where R is alkyl group and L is dmgH(-)/dp gH(-) have been synthesised. It was found that one could synthesise su ch complexes in one pot directly from the alkyl(aquo)cobaloximes witho ut converting it to the alkylcobaloxime dimer, as reported in the lite rature. H-1-NMR studies have revealed that the pyrazine ring protons e xperience considerably more cis influence than the H-alpha protons of the pyridine in simple alkylcobaloximes. This is presumably because th e pyrazine ring protons are in close proximity to two metallabicycles while the H-alpha protons of the simple alkylcobaloximes are influence d by only one metallabicycle. The trends in the Co-C charge transfer t ransition and N-O, N-O' frequencies are similar to the alkyl (pyridine ) cobaloximes. Low resolution x-ray crystal structure of one of the di cobaloximes, [EtCo(dpgH)(2)] mu-Pz indicates that the two subunits of the molecule rotate around the two Co-N single bonds with the result t hat the two metallabicycles are completely staggered with respect to e ach other. (C) 1998 Elsevier Science S.A. All rights reserved.