Titanium ferrocenyl-phosphinimide complexes

Abstract

Oxidation of [CpFe(η⁵-C₅H₄PtBu₂)] with Me₃SiN₃ gave the phosphinimine [CpFe(η⁵-C₅H₄PtBu₂NSiMe₃)] (1) which was used to prepare [Cp′TiCl₂(NPtBu₂C₅H₄)FeCp] (Cp′ = Cp 2, Cp* 4) and subsequently [Cp′TiMe₂(NPtBu₂C₅H₄)FeCp] (Cp′ = Cp 3, Cp* 5). Similarly, [(η⁵-C₅Ph₅)Fe(η⁵-C₅H₄PtBu₂NSiMe₃)] 6 was converted to [CpTiX₂(NPtBu₂C₅H₄)Fe(η⁵-C₅Ph₅)] (X = Cl 7, Me 8). The bis-phosphinimine [Fe{η⁵-C₅H₄PtBu₂(NSiMe₃)}₂] (9) was prepared and used to obtain [{Fe(η⁵-C₅H₄PtBu₂N)₂}TiCl₂] (10) and [{Fe(η⁵-C₅H₄PtBu₂N)₂}TiMe₂] (11). These species exhibited a temperature dependent conformational change in the chelate geometry on the NMR time scale. Cyclic voltammetry studies showed pseudo reversible redox waves assigned to the Fe²⁺/Fe³⁺ couple for 2 and 4, while 10 exhibited only irreversible oxidations. Compound 9 was also used to prepare [Fe(η⁵-C₅H₄PtBu₂NTiXCl₂)₂] (X = Cl 12, Cp 13, Cp* 15). Compounds 3 and 5 react with B(C₆F₅)₃ or [CPh₃][B(C₆F₅)₃] to generate salts of the formula [Cp′TiMe{(NPtBu₂C₅H₄)FeCp}]X (Cp′ = Cp, X = [MeB(C₆F₅)₃] 17a, [B(C₆F₅)₄] 17b; Cp′ = Cp*, X = [MeB(C₆F₅)₃] 18a, [B(C₆F₅)₄] 18b). Compounds 18 further generated [Cp*TiMe{HNPtBu₂(C₅H₄)Fe(η⁵,η¹-C₅H₄)}]X (X = [MeB(C₆F₅)₃] 19a, [B(C₆F₅)₄] 19b), respectively. The cationic species 17a and 18a are very active polymerization catalysts, giving polyethylene with activities of 2400 and 5000 g mmol⁻¹ h⁻¹ atm⁻¹, respectively at 25 °C.