Synthesis and structural characterisation of the isotypic complexes MIIL2(py)2•2H2O (M = Cu, Zn);: the interplay of lattice imposed ligand disposition and Jahn-Teller distortions [HL = 5-(4-methoxyphenyl)pyrazole-3-carboxylic acid]

The mononuclear complexes of general formula ML2(H2O)(2) (M = Zn, Cu, Ni, Co) and ML2(py)(2). 2H(2)O (M = Zn, Cu, Co) have been prepared [HL = 5-(4-methoxyphenyl)pyrazole-3-carboxylic acid, py = pyridine]. The crystal structures of ZnL2(py)(2). 2H(2)O and CuL2(py)(2). 2H(2)O have been determined and are isotypic. Two independent molecules are present in the structures, both of which are pseudo-octahedral with mutually tuans stereochemistries. In the zinc case the two metal coordination environments differ only slightly and these differences are probably due to packing forces, but for copper the differences are greater and indicate that the direction of the Jahn-Teller distortion observed is dependent upon the subtle constraints imposed by the lattice. The occurrence of such molecular forms is unique for such donor sets and allows a special opportunity to observe the interplay of Jahn-Teller effects and packing forces.