The influence of hydrogen bonding on the rate of thiolate alkylation in tripod-zinc thiolate complexes

A series of new thioimidazolylborate zinc thiolate complexes TtixylZnSR (2)–(5) (where R = C6H4-o-OH, C6H4-o-CH2OH, C6H4-o-NH2, and C6H4-p-OH, respectively) have been synthesized and characterized as structural and functional models of the active site of the Ada repair protein. Structural determination of complexes 2–4 reveals intramolecular N/O–H⋯S hydrogen-bonding interactions. The influence of these hydrogen bonding interactions on the methylation of the thiolate ligands is evident from the fact that the rate of methylation for these complexes is reduced ca. 2 orders of magnitude compared to that found in the case of the non-hydrogen bonding-containing complex, TtixylZnSC6H5 (1).