Alkylaminophosphanyl substituted half-sandwich complexes of vanadium(III) and chromium(III): preparation and reactivity in ethylene polymerisation

[CpR(RPNEt2)]M (CpR=t-BuC5H3, C5(CH3)4, indenyl, fluorenyl; M=Li, K) smoothly react with VCl3(Me3P)2 and CrCl3(THF)3 systems giving paramagnetic complexes [CpR(R1PNEt2)]MCl2 (M=V(Me3P)2, Cr). After reaction with MAO these complexes are active in the polymerisation of ethylene yielding highly crystalline, high-density products of high molecular weight (Mw ranging from 100 000 to 4.5×106 g mol−1, 20≤Tp≤100 °C). Polymerisation with chromium complexes leads to the formation of polyethylenes with broad molecular weight distribution.