A Tripodal Benzylene-Linked Trisamidophosphine Ligand Scaffold: Synthesis and Coordination Chemistry with Group(IV) Metals

A new tripodal trisamidophosphine ligand (<b>1</b>) based on the trisbenzylphosphine backbone has been synthesized in three steps starting from NaPH₂ and phthaloyl-protected 2-aminobenzyl bromide. At elevated temperatures, <b>1</b> reacts directly with M­(NMe₂)₄ (M = Zr, Hf) to afford the dimethylamido complexes [PN₃]­M­(NMe₂) (M = Zr, Hf) (<b>2</b>), which are easily converted into the corresponding triflates [PN₃]­MOTf (M = Zr, Hf) (<b>3</b>) via reaction with triethylsilyl trifluoromethanesulfonate. The related titanium chloro complex [PN₃]­TiCl (<b>4-Ti</b>) is obtained from <b>1</b> and Bn₃TiCl via protonolysis. Triple deprotonation of <b>1</b> with <i>n</i>-butyllithium affords the tris-lithium salt Li₃­[PN₃] (<b>1-Li</b>), which serves as a common starting material for the preparation of all the group­(IV) chlorides [PN₃]­MCl (M = Ti, Zr, Hf) (<b>4</b>). Upon treatment of <b>4-Ti</b> with Bn₂Mg­(thf)₂, formation of a benzyltitanium species is observed, which is converted cleanly into a ligand-CH-activated species (<b>5-Ti</b>)