1,2,3-Triazole-Bridged Binuclear Iridium Pincer Complexes: Comparing Reactivities with Monometallic Analogues

Abstract

Binuclear iridium–pincer complexes bearing metal centers with different coordination spheres could provide a promising platform for new reactivities and enable cooperative catalytic properties. Herein, we report the synthesis of the Ir(III)–Ir(III) pincer complexes [(^tBuPOCN³N²CO^tBuP)Ir₂(H)₂(acac)₂] (3b) and [CF₃–(^tBuPOCN³N²CO^tBuP)Ir₂(H)₂(μ-OAc)(μ-Cl)] (4b). For each complex, a bridging 1,2,3-triazole scaffold in the ligand framework allows for two distinctive Ir–POCN pincer moieties, one having an Ir–N³ bond and the other fragment with a hemilabile Ir–N² coordination. Comparative studies on the structures, reactivity, and catalytic transfer dehydrogenation activity of these complexes with the reactivity of their monomeric analogues─the previously reported [(^tBuPOCN³_Triaz)Ir(H)(acac)] (1b) and independently synthesized [(^tBuPOCN²_Triaz)Ir(H)(acac)] (2b)─are further described. While subsequent reactivity of the mononuclear complexes with CO affords the Ir(I) monocarbonyl complexes, the binuclear complexes instead result in mixed valent Ir(I)–Ir(III) tricarbonyl species. The described binuclear complexes and their reactivity products are the original examples of systems containing nonidentical iridium pincers within the same framework.