Arene displacement, C–H activation and acetonitrile insertion reactions enabled by coordination of a functionalized iminophosphorane to a RuII–p-cymene scaffold

Abstract

Reaction of a sterically demanding iminophosphorano-phosphine, Ph₂PCH₂Ph₂PNAr* (here onwards referred to as PCPNAr*; Ar* = 2,6-dibenzhydryl-4-methylphenyl), (1) with [Ru(η⁶-p-cymene)Cl₂]₂ yielded three different types of complex, [RuCl₂{(η⁶-p-cymene)(PCPNAr*)-κ¹-P}] (2), [RuCl{(P(O)CPNAr*)(κ²-N,C)(C-η⁶-arene)}] (3) and [RuCl{(POCPNAr*)(κ²-N,C-o)(C-η⁶-arene)}] (4), depending on the reaction conditions via CH activation, tethered η⁶-arene coordination, ortho-metallation or PN bond cleavage/rearrangement reactions. Interestingly, a similar reaction in CH₃CN in the presence of AgBF₄ resulted in the insertion of CH₃CN into the PN bond to form a novel metallacycle [Ru(NCMe)₃{(PC₂PN(CH₃)CNAr*)-κ³-N,N,P}][BF₄]₂ (5) containing 4- and 5-membered rings via an aza-Wittig type reaction. Complex 4 showed very good catalytic activity in the transfer hydrogenation of carbonyl compounds.