(Neocuproin)zinc Thiolates: Attempts at Modeling Cobalamin‐Independent Methionine Synthase

Abstract

Abstract Several new complexes [(neo)Zn(SR) 2 ] [neo = neocuproin (2,9‐dimethylphenanthroline)] have been synthesized and structurally characterised. They react in a stepwise fashion with the alkylating agents CH 3 I and (CH 3 ) 2 SO 4 to afford the thioethers CH 3 SR and first the mixed complexes [(neo)Zn(SR)X] (X = I, CH 3 SO 4 ) and then [(neo)ZnX 2 ]. Similar alkylations occur with benzyl iodide, but not with trimethyl phosphate in nonpolar media. Under these conditions, thiolate exchange with [PPN]SR does not occur which indicates that the alkylations take place at the zinc‐bound thiolates. In polar solvents (methanol, DMSO), thiolate exchange occurs readily, and at higher temperatures (CH 3 ) 3 PO 4 also acts as an alkylating agent which indicates that under these conditions free thiolate is available in solution. Qualitative kinetic data support the associative alkylation mechanism in nonpolar media and the change of mechanism in polar media. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)