Scheme 3. Possible reaction sequences responsible for the rapid exchange of the ruthenium hydride and coordinated borane groups in (POBOP)Ru(H)(PPh3). Chelating ligand arms are not shown for clarity. (a) The pathway involving the Ru(0) diborane complex 4-1 as an intermediate. (b) The pathway involving the Ru(iv) BB–carboryne dihydride complex 4-2 as an intermediate. Note “walking” of the metal center on the carborane cage in both cases.
