A heterobimetallic complex featuring a Ti–Co multiple bond and its application to the reductive coupling of ketones to alkenes

To explore metal–metal multiple bonds between first row transition metals, Ti/Co complexes supported by two phosphinoamide ligands have been synthesized and characterized. The Ti metalloligand Cl(2)Ti(XylNP(i)Pr(2))(2) (1) was treated with CoI(2) under reducing conditions, permitting isolation of the Ti/Co complex [(μ-Cl)Ti(XylNP(i)Pr(2))(2)CoI](2) (2). One electron reduction of complex 2 affords ClTi(XylNP(i)Pr(2))(2)CoPMe(3) (3), which features a metal–metal triple bond and an unprecedentedly short Ti–Co distance of 2.0236(9) Å. This complex is shown to promote the McMurry coupling reaction of aryl ketones into alkenes, with concomitant formation of the tetranuclear complex [Ti(μ(3)-O)(NXylP(i)Pr(2))(2)CoI](2) (4). A cooperative mechanism involving bimetallic C[double bond, length as m-dash]O bond activation and a cobalt carbene intermediate is proposed.