Titanium complexes of amidophosphinimide ligands

Abstract

The tripodal phosphines MeC(CH₂NMe)₃P and N(CH₂CH₂NMe)₃P were converted to the corresponding phosphinimines and the corresponding Ti-complexes MeC(CH₂NMe)₃PNTiCpCl₂ (2) and N(CH₂CH₂NMe)₃PNTiCpCl₂ (5) were prepared. These species were also alkylated to give the corresponding dimethyl derivatives. Preliminary attempts to utilize these species in the polymerization of ethylene with MAO as the activator resulted in all but negligible activity. An alternative synthetic approach utilizing the bis-phosphinimine (CH₂(Me)NPtBu₂)₂ was developed to prepare (CH₂(Me)NP(tBu₂)NSiMe₃)₂ (8), (CH₂(Me)NP(tBu₂)NH)₂ (9) and subsequently [(CH₂(Me)NP(tBu₂)N)₂]Ti(NMe₂)₂ (10), [(CH₂(Me)NP(tBu₂)N)₂]TiCl₂ (11) and [(CH₂(Me)NP(tBu₂)N)₂]TiMe₂ (12). For comparison purposes the related species [tBu₂(Me₂N)PN]₂TiCl₂ (14) and [tBu₂(Me₂N)PN]₂TiMe₂ (15) were also prepared. Compounds (12) and (15), using 2 equiv. of [Ph₃C][B(C₆F₅)₄] as the activator, resulted in moderate to good polymerization activities.