Metal Pyrazolato Complexes. Synthesis, Characterization, and X-ray Powder Diffraction Studies of Group 12 Coordination Polymers

A number of polymeric pyrazolato complexes have been prepared and characterized by spectroscopy, thermal analyses (DSC and TGA), and X-ray powder diffraction (XRPD) methods. Ab initio XRPD studies showed that the (isomorphous) [Zn(pz)(2)](n)() and [Cd(pz)(2)](n)() species (Hpz = pyrazole) are 1-D polymers containing tetrahedrally coordinated metals and M(-pz)(2)M (M = Zn, Cd) bridges, much alike [Cu(pz)(2)](n)() [orthorhombic, Ibam, a = 7.4829(4), b = 14.3844(6), c = 7.3831(3) Å (Zn) and a = 7.8591(6), b = 13.652(1), c = 7.9165(4) Å (Cd)]; differently, Hg(pz)(2) [triclinic, P, a = 7.4097(3), b = 9.4474(3), c = 5.8345(3) Å, alpha = 96.310(2), beta = 96.752(3), and gamma = 73.694(2) degrees ] is best described as a mononuclear complex, containing two monodentate pyrazolato ligands loosely interacting, through long(er) Hg.N contacts with neighboring molecules. During the synthesis of the latter, an intermediate phase was obtained, and characterized as Hg(pz)NO(3), which contains a polymeric polycation, [Hg(pz)](n)()(n)()(+), based on Hg(-pz)Hg bridges, and uncoordinated NO(3)(-) groups (orthorhombic, Pcmn, a = 17.2985(9), b = 5.2538(3), c = 7.3912(4) Å). All structures were ultimately refined by the Rietveld method.