SYNTHESES OF SOME HYDROTRIS(3,5-DIMETHYLPYRAZOL-1-YL)-BORATO(ARYLOXO)ZIRCONIUM(IV) COMPLEXES AND THE X-RAY CRYSTAL-STRUCTURES OF [ZRL(OC6H4NO2-4)3], [ZRL(OC6H3ME2-2,6)3] AND [ZRL(CL)(OC6H3ME2-2,6)2] (L = 3,5-ME2C3N2H)

The compound [ZrLCl3] [L = HB(3,5-Me2C3N2H)3] reacts with the sterically undemanding phenol derivatives HOC6H4Z (Z = H, 2-F, 3-F, 4-F, 3-NO2, 4-NO2 or 4-Bu(t)) to give only the tris(aryloxo) complexes [ZrL(OC6H4Z)3], even when [ZrLCl3] is present in excess. When sterically demanding phenol derivatives are used it is possible to obtain mixed chloro-aryloxo zirconium complexes so that [ZrL(Cl)(OC6H3Me2-2,6)2], [ZrL(Cl)(OC6H4Ph-2)2], [ZrLCl2(OC6H3Me2-2,6)] and [ZrLCl2(OC6H3Ph2-2,6)] have been isolated in addition to [ZrL(OC6H3Me2-2,6)3] and [ZrL(OC6H4Ph-2)3]. X-Ray crystallographic studies of [ZrL(OC6H4NO2-4)3], [ZrL(OC6H3Me2-2,6)3] and [ZrL(Cl)(OC6H3Me2-2,6)2] reveal that, in each case, the zirconium ion has a distorted-octahedral co-ordination geometry. The respective Zr-O(aryl) distances for these complexes are 1.978(1), 1.973(3) (mean) and 1.948(1) angstrom (mean); while the respective Zr-O-C(aryl) angles are 161.4(1), 175(1) (mean) and 174(2)-degrees (mean). In all of these structures the aryl group is found to be oriented towards the ligand L and interposed between neighbouring 3,5-Me2C3N2H moieties.