The first group 4 metal bis(imido) and tris(imido) complexes

Abstract

We report a combined experimental and computational study of the first bis(imido) and tris(imido) complexes of a group 4 metal. Reaction of [Ti(NAr)(NHAr)₂(py)₂] (1, Ar = 2,6-C₆H₃ⁱPr₂) with 3 equivs. of MeLi gave the lithium-stabilised tris(imide) [TiMe(NAr)₃{Li(py)}₃] (2). Reaction of 1 with 2 equivs. of MeLi in the presence of ArNH₂ gave the corresponding bis(imide) [Ti(NAr)₂(NHAr)₂{Li(py)}₂] (3). All three compounds 1, 2 and 3 have substantial Ti–N_imide multiple bond character. Orbital and Mayer bond order analysis show that the formal bond orders are best viewed as ca. 3, 2.5 and 2, respectively, with a further attenuating effect on the multiple bonding by the [Li(py)]⁺ ion coordination. Compounds 2 and 3 are the first examples of any group 4 metal simultaneously containing two or three multiply-bonded ligands.