Mono- and bis-amidinate 2,6-xylylimido vanadium chlorides: synthesis, structure, and reactivity

Abstract

Salt metathesis of (2,6-xylylimido) vanadium trichloride (1) with the unsolvated or the TMEDA lithium p-Et benzamidinate complexes (2 and 3, respectively, in 1 : 2 V : Li molar ratio) yields bis[N,N’-bis(trimethylsilyl) p-Et benzamidinate](2,6-xylylimido)VCl (4) as dark brown, diamond-shaped crystals. When equimolar amounts of complexes 1 and 2 are reacted, a mixture of the bis (4) and mono (5) imidovanadium amidinates results. A similar mixture is also obtained by a ligand metathesis reaction of the bis amidinate complex 4 and complex 1. When the synthesis of the mono amidinate 5 is attempted with the TMEDA lithium amidinate complexes 3 or the 3-pyridyl derivative (7) (in 1 : 1 V : Li molar ratio) a redox reaction takes place to produce (κ²-TMEDA)(2,6-xylylimido)V^IVCl₂ (6) as crystalline, mustard-yellow plates. The activity of complex 4 in ethylene polymerization was negligible with MAO or MAO\(CPh₃)⁺[B(C₆F₅)₄]⁻ as co-catalysts.