Cationic Ti(IV) and neutral Ti(III) titanocene-phosphinoaryloxide frustrated Lewis pairs: hydrogen activation and catalytic amine-borane dehydrogenation

Titanium-phosphorus frustrated Lewis pairs (FLPs) based on titanocene-phosphinoaryloxide complexes have been synthesised. The cationic titanium(IV) complex [Cp2TiOC6H4P(Bu-t)(2)][B(C6F5)(4)](2) reacts with hydrogen to yield the reduced titanium(III) complex [Cp2TiOC6H4PH(Bu-t)(2)][B(C6F5)(4)] 5. The titanium(III)-phosphorus FLP [Cp2TiOC6H4P(Bu-t)(2)] 6 has been synthesised either by chemical reduction of [Cp2Ti(Cl)OC6H4P(Bu-t)(2)] 1 with [CoCp*(2)] or by reaction of [Cp2Ti{N(SiMe3)(2)}] with 2-C6H4(OH){P(Bu-t)(2)}. Both 2 and 6 catalyse the dehydrogenation of Me2HN center dot BH3.