Zinc−Thiolate Complexes of the Bis(pyrazolyl)(thioimidazolyl)hydroborate Tripods for the Modeling of Thiolate Alkylating Enzymes
datasetposted on 16.05.2005, 00:00 by Mian Ji, Boumahdi Benkmil, Heinrich Vahrenkamp
The new tripod ligands bis(pyrazolyl)(3-tert-butyl-2-thioimidazol-1-yl)hydroborate (L1) and bis(pyrazolyl)(3-isopropyl-2-thioimidazol-1-yl)hydroborate (L2), together with zinc nitrate or zinc chloride and the corresponding thiolates, have yielded a total of 17 zinc−thiolate complexes. These comprise aliphatic as well as aromatic thiolates and a cysteine derivative. Structure determinations have confirmed the tetrahedral ZnN2S2 coordination in the complexes. Upon reaction with methyl iodide, the species L1·Zn−SR are slowly converted to L1·Zn−I and the free thioethers CH3SR. A kinetic analysis has shown these alkylations to be about 1 order of magnitude slower than those of the tris(pyrazolyl)borate complexes TpPh,MeZn−SR. Alkylations with trimethyl phosphate were found to proceed very slowly even in DMSO at 80 °C.