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)

Abstract

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)Å(mean); while the respective Zr–O–C(aryl) angles are 161.4(1), 175(1)(mean) and 174(2)°(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.