New H-bond accepting tris(pyrazolyl)borates: stabilization of metal aquo species as models for the vicinal oxygen chelate enzyme superfamily

The hydrogen-bond accepting ligand K[Tp(2)(CO)(Et,Me)] was prepared and its complexes with divalent Ni, Co, Mn and Cu reveal a stabilization of penta- or hexa-coordinate metal aquo complexes of the general form [Tp(2)(CO)(Et, Me)M(H2O)(x)] (x=2 or 3) which are unprecedented for the alkyl substituted Tp analogs. These complexes make good structural models for many of the enz ymes of the vicinal oxygen chelate superfamily.