Titanium complexes of amidophosphinimide ligands

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.