New polar pyrazolylborate ligands and their basic zinc complex chemistry

摘要

By refinement of Trofimenko's procedures, four new tris(pyrazolyl)borate (Tp) ligands bearing pyridyl and carboxamide substituents at the 3-positions of the pyrazole rings, were obtained. Two of them were identified by structure determinations of their potassium salts. Their coordinative properties were explored by preparing Tp(center dot)Zn-X complexes, with X = Cl, Br, I, NO3, OAc, phenolate, thiophenolate and diorganophosphate, including the cationic complexes [Tp(center dot)Zn center dot L](+) with L = methanol and pyrazole. From the spectra and structure determinations of these complexes it has become evident that the polar Tp(center dot) ligands favor coordination numbers higher than four for zinc, either by inducing bidentate coordination of the coligands X and L, using the carboxamide oxygen atoms for coordination, or by linking two Tp(center dot)Zn-X units through the pyridyl nitrogen atoms. As a result, the structural chemistry of these complexes is quite varied, and includes coordination dimers and polymers.