Metal and ligand substitution of the aluminium tris-pyridyl ligands [RAl(2-py′)3]− (R = Et, nBu, sBu, tBu; 2-py′ = 2-pyridyl, 3-methyl-2-pyridyl, 5-methyl-2-pyridyl, 6-methyl-2-pyridyl)

Abstract

A series of tris-pyridyl complexes [RAl(2-py)₃]Li·thf [2-py = 2-pyridyl; R = Et (1); ⁿBu (2); ^sBu (3), ^tBu (4)] were prepared by the sequential reaction of AlCl₃ with RLi then 2-Li-py in thf. The related complexes [MeAl{2-(3-Me)py}₃]Li(μ-Br)Li(thf)₃ (5), [MeAl{2-(5-Me)py}₃]Li·thf (6) and [MeAl{2-(6-Me)py}₃]Li·thf (7) are obtained similarly from MeAlCl₂ and the appropriate lithio-pyridine (2-Li-py′). The synthetic approaches used provide the means for extensive elaboration of the [RAl(2-py′)₃]⁻ ligand frameworks, and potentially broad access to a large range of new anionic tris-pyridyl ligands of this type. Fundamental insights into how the ligand bites and coordination environments offered are modified by substituents at the Al bridgehead and pyridyl rings are given by the solid-state structures of 1–7.