Comparative study of 1:1 Lewis acid–base adducts between Cp2M(L)H (M = V, Nb, Ta; L = CO, C2H4, P(CH3)3) and BF3/AlF3

Abstract

Transition metal hydrides play important roles in organometallic catalysis and synthetic reactions. Metallocenes niobium or tantalum hydride derivatives show high reactivities with variety of main group 13 Lewis acids. In this work, the nature of MH···B/Al interaction between Cp2M(L)H(M = V, Nb, and Ta) and BF3/AlF3 in 1:1 Lewis acid–base adducts as well as the influences of different types of ligands on the interactions is investigated. The results show that in Cp2M(L)H···BF3/AlF3, the MH···B interaction belongs to covalent interaction, and MH···Al shows partly covalent character. The covalent character of MH···B/Al bonds decreases with the increasing period of metal atom. The strength of MH···B/Al interaction is related to the type of metal atom (M) and ligand (L) in Cp2M(L)H, and the influences of L are larger than those of M. For the same M, the strength of MH···B/Al bonds is mainly influenced by the type of ligand, and they increase in the sequence of L = CO, C2H4, and P(CH3)3. The formation of Cp2M(L)H···BF3/AlF3 increases the polarity of M–H bond of Cp2M(L)H.