Exclusive C−C Activation and an Apparent α-H Elimination with a Rhodium Phosphinite Pincer Complex

Exclusive C−C bond activation involving the new bisphosphinite ligand {C6H3(CH3)[OP(iPr)2]2} (1) was observed at room temperature, upon reaction with the cationic complex [Rh(COE)2(THF)2]BF4 (COE = cyclooctene) in THF, yielding the Rh(III) complex [(POCOP)Rh(Me)]BF4 (2) (POCOP = C6H3[OP(iPr)2]2). No parallel C−H activation was observed. This preference is assumed to be governed by the better directed phosphinite-bound metal center toward the C−C bond. A single-crystal X-ray diffraction analysis of complex 2 revealed a square pyramidal geometry with the BF4- ion coordinated to the metal center. Complex 2 reacted with H2 at room temperature in THF to yield the Rh(III)-hydrido complex 3 and methane. Deprotonation of 3 with KOtBu yielded the Rh(I) dinitrogen complex [(POCOP)Rh]2(μ-N2) (4), which upon reaction with 1 equiv of CO or ethylene formed (POCOP)Rh(CO) (5) or (POCOP)Rh(C2H4) (6), respectively. Complex 4 readily underwent oxidative addition of MeI, benzyl chloride, and benzyl bromide, forming complexes...