Tp*Sn(Cl)Bu-2 as a convenient reagent for the preparation of hydrotris(3,5-dimethylpyrazolyl)borate complexes of niobium, tantalum, and zirconium

Organotin complexes bearing a Tp* ligand, Tp*Sn(Cl)(n)Bu3-n (1, n = 1; 2, n = 2; Tp* = hydrotris-(3,5-dimethylpyrazolyl)borate), were found to be useful reagents for introducing a Tp* ligand on niobium and tantalum as well as zirconium. The reactivities of these organotin compounds together with Tp*SnCl3 (3) were compared directly by using the reaction with ZrCl4, which affords Tp*ZrCl3(4), as a test case. The reaction rate was in the order 1 > 2 much greater than 3. Thus, complex 1 was used for the preparation of Tp*NbCl3 (5) and [Tp*TaCl3]-[TaCl6] (6), whose structures mere confirmed by X-ray analysis. X-ray analysis of 1 indicated that one of the three Sn-N bonds in 1 was cleaved and that the Sn atom adopted a five-coordinate square pyramidal geometry that made complex 1 more reactive than the six-coordinate complexes 2 and 3.