Synthesis of new oxy and thiolate [hydro-tris(pyrazol-1-yl)borato] titanium and zirconium(IV) complexes. Molecular structure of [Ti(HB(3,5-Me(2)pz)(3))Cl-3]

The complexes [M(HB(3,5-Me(2)pz)(3))Cl-2(LL)] (pz = pyrazolyl, M = Ti, LL = 2-oxy-6-methylpyridine, 2,4-dimethyl-6-oxypyrimidine; M = Zr, LL = 4,6-dim ethyl-2-thiolatepyrimidine) have been prepared by the reaction of the start ing materials [M(HB(3,5-Me(2)pZ)3)Cl-3] (M = Ti, Zr) and one equivalent of the lithium salt or the protic form of the corresponding hydroxy or thiolat o pyridine or pyrimidine. The complexes were characterized by spectroscopic methods. While the titanium complexes are rigid in solution, the zirconium complex is fluxional at room temperature, although limiting static spectra can be obtained at low temperature. The variable temperature H-1-NMR spect ra indicate that a mechanism involving interchange of both nitrogen atoms o f pyrimidine, in the coordination sphere of the zirconium atom, can explain this dynamic behavior. In addition, the molecular structure of the startin g material [Ti(HB(3,5-Me(2)pz)(3))Cl-3] has been determined by X-ray diffra ction methods. (C) 1999 Elsevier Science S.A. All rights reserved.