SYNTHETIC PATHWAYS FOR (MU-HO)ZN2 COMPLEXES

The reactions of the 3-substituted kalium hydrotris(pyrazolyl)borates 1 c, d (R = tert-butyl, anisyl) with Zn(ClO4)2 . 6 H2O produce the dinuclear mu-hydroxo complexes [L3Zn-O(H)-ZnL3](ClO4)3 (2a, b; L = 5-tert-butylpyrazole, 5-anisylpyrazole), due to hydrolytic cleavage of the B N bonds. These and similar complexes (2c, d; L = 5-tert-butyl-3-methylpyrazole, 5-phenylpyrazole) are also accessible directly from Zn(ClO4)2. 6 H2O, the substituted pyrazole, and KOH, and in one case (2 b; L = 5-anisylpyrazole) by hydrolytic cleavage of [HB(3-anisylpyrdzoly)3ZnEt] with perchloric acid. With other pyrazole and imidazole ligands, the Zn(ClO4)2/L/KOH reaction produces the simple complexes [ZnL6](ClO4)2 (3a, b; L = pyrazole, 3-methyl-5-phenylpyrazole) and [ZnL4](ClO4)2 (4; L = 2-methylimidazole). The crystal structures of 2a and 4, each containing tetrahedrally coordinated zinc atoms, have been determined.