Synthesis and characterization of pseudotetrahedral N2O and N2S zinc(II) complexes of two heteroscorpionate ligands:: Models for the binding sites of several zinc metalloproteins

Nine new pseudotetrahedral Zn(II) complexes of the heteroscorpionate ligands (3-tert-butyl-2-hydroxy(or thio)-5-methylphenyl)bis(3,5-dimethylpyrazolyl)methane, L1OH or L2SH, have been prepared and characterized (in most cases crystallographically). Complexes isolated include [(L1O)ZnCl]. [(L1O)ZnI], [(L1OH)ZnI2]. [(L1O)-ZnCH3,] [(L1O)ZnOAc], [(L1O)ZnSPh], [(L1O)ZnSBz], [(L2S)ZnCH3], [(L2S)ZnSPh], and [(L2S)(2)Zn]. In conjunction with the widely studied tris(pyrazolyl)borates this new series of heteroscorpionates provides a set of isolobal and isoelectronic ligands differing in donor set, i.e. N-3, N2O, and N2S. Preliminary reactivity studies with HX species, Mel, or trimethyl phosphate suggest differences between the three sets of ligands.