BIS(PYRAZOLYLETHYL) ETHER LIGATION TO ZINC AND COBALT - MERIDIONAL VSFACIAL COORDINATION AND THE SUITABILITY OF SUCH LIGANDS IN PROVIDING A NNO DONOR SET FOR MODELING BIOINORGANIC ASPECTS OF ZINC CHEMISTRY

The structures of bis(pyrazolylethyl) ether derivatives of zinc and co balt, namely [eta(3)-O(CH(2)CH(2)pz(Pri2))(2)]Zn(NO3)(2) and [eta(3)-O (CH(2)CH(2)PzMe(2))(2)]CO(NO3)(2), have been determined with a view to addressing the applicability of such ligands in modeling bioinorganic aspects of zinc chemistry. Specific consideration is given to the pos sibility that bis(pyrazolylethyl) ether ligands may provide an NNO don or system which may model aspects of the binding of zinc to protein ba ckbones in enzymes such as thermolysin. The structural studies demonst rate that the bis(pyrazolylethyl) ether ligands do indeed coordinate v ia each of their NNO functionalities but that the relationship to the enzyme is limited by the adoption of meridional rather than facial coo rdination geometries. [eta(3)-O(CH(2)CH(2)Pz(Pri2))(2)]Zn(NO3)(2) is m onoclinic, P2(1)/c (No. 14), with a = 11.619(2) Angstrom, b = 14.380(3 ) Angstrom, c = 16.757(2) Angstrom, beta = 90.44(2)degrees, and Z = 4. [eta(3)-O(CH(2)CH(2)pz(Me2))(2)]Co(NO3)(2) is monoclinic, C2/c (No. 1 5), with a = 17.136(3) Angstrom, b = 10.505(2) Angstrom, c = 11.121(2) Angstrom, beta = 104.62(3)degrees, and Z = 4.