Electronic structure of tris(pyrazolyl)hydroborato [Tp] gallium complexes: density functional studies of monovalent Ga[Tp], terminal chalcogen complexes, Ga(Tp)E (E = O, S, Se or Te) and a GaI_3 adduct, Ga_2[Tp]I_3

摘要

Density functional theory calculations have been made on gallium complex supported by the tris(pyrazolyl)-hydroborato ligand [Tp], Ga[Tp] I, Ga[Tp]E II (E = O a, S b, Se c or Te d) and Ga_2[Tp]I_3 III aimed at modelling the bonding in the recently reported tris (3, 5-di-tert-butylpyrazolylhydroborato ([Tp~(But_2)]) gallium complexes, Ga[Tp~(But_2)] 1, the terminal chalcogen complexes Ga[Tp~(But_2)] E 2 (E = S b, Se c or Te d), and the adduct Ga_2[Tp~(But_2)]I_3 3. The calculated and observed structures are in good agreement. The gallium "lone pair" in Ga[Tp] has Ga-N antibonding character. The decrease in Ga-N bond lengths between Ga[Tp] and its adducts is associated with relief of this antibonding character. The bonding in Ga[Tp]E (E = O, S, Se or Te) is found to be almost entirely semipolar [[Tp]Ga~+-E~-] irrespective of the nature of the chalcogen element although the polarisation of charge decreases on descending the group. The GaI_3 adduct is also best described by the resonance structure [Tp]Ga~+-Ga~-I_3.