Well-defined imidotitanium alkyl cations: agostic interactions, migratory insertion vs.[2+2] cycloaddition, and the first structurally authenticated AlMe3 adduct of any transition metal alkyl cation

Abstract

The imidotitanium alkyl cations [Ti(N^tBu)(Me₃[9]aneN₃)R]⁺ (R = Me (3⁺) or CH₂SiMe₃ (4⁺)) possess either a very weak α-agostic or β-Si–C agostic interactions, respectively, according to ¹³C and ²⁹Si NMR and DFT studies; reaction of 4⁺ with ⁱPrNCNⁱPr gives totally selective insertion into the Ti–alkyl bond; reaction of 3⁺ with AlMe₃ gives the first structurally characterised AlMe₃ adduct of a transition metal alkyl cation (Me₃[9]aneN₃ = 1,4,7-trimethyltriazacyclononane).