STRUCTURAL BEHAVIOR OF COBALOXIMES - PLANARITY, AN ANOMALOUS TRANSINFLUENCE AND POSSIBLE IMPLICATIONS ON CO-C BOND-CLEAVAGE IN COENZYME-B-12-DEPENDENT ENZYMES

Deviations from planarity of the 17 non-hydrogen atoms forming the equ atorial moiety in cobaloximes can be described by six significant dist ortion modes. No significant correlation has been found between these deformations and changes in the axial Co-C and Co-N distances. Analysi s of the Co-R and Co-B distances reveals that, in a series of related RCo(DH)(2)B complexes, the two distances lengthen or shorten simultane ously but to different degrees. This anomalous structural trans-influe nce is quantified with the help of an additive scheme based on the nat ure of the axial ligands R and B, and is discussed in terms of a simpl e Huckel molecular-orbital model.