FeII complexes supported by an iminophosphorane ligand: synthesis and reactivity

Abstract

The synthesis of iron complexes supported by a mixed phosphine–lutidine–iminophosphorane (PPyNP) ligand was carried out. While bidentate κ²-N,N coordination was observed for FeCl₂, pincer coordination modes were adopted at cationic iron centers, either through dechlorination of [LFe(PPyNP)Cl₂] (1) or direct coordination of PPyNP to Fe(OTf)₂. Reaction with tert-butylisocyanide gave access to the diamagnetic octahedral complex [Fe(PPyNP)(CNtBu)₃]X₂ (X = OTf (4), Cl (4′)). Both 1 and 4 were shown to undergo deprotonation of the phosphinomethyl group, but the resulting complexes were not active for the dehydrogenative coupling of hexan-1-ol. The hydrosilylation of acetophenones was catalyzed at room temperature with 1 mol% of a catalyst generated in situ from cationic PPyNP-supported iron triflate complexes and KHBEt₃.