Multinuclear NMR studies of the products resulting from the reaction of pyridine or 2,2′-bipyridine with [Rh4(CO)12]

Abstract

The progressive addition of anhydrous pyridine, (py), to a solution of [Rh₄(CO)₁₂] in CH₂Cl₂ under CO, even at low temperature, results in immediate disproportionation to give cis-[Rh(CO)₂py₂][Rh₅(CO)₁₅]; further addition of pyridine results in the progressive replacement of CO’s by py on the same apical rhodium in [Rh₅(CO)₁₅]⁻ to give cis-[Rh(CO)₂py₂][Rh₅(CO)_15−xpy_x] (x = 1, 2). The analogous reactions with 2,2′-bipyridine (bipy) give only [Rh(CO)₂bipy][Rh₅(CO)₁₃bipy]. IR and low temperature, multinuclear NMR measurements have been used to establish the structures of all the above anions and the structures of [Rh₅(CO)₁₃(bipy)]⁻ and [Rh₅(CO)₁₃py₂]⁻ are subtly different. Under N₂, [Rh₄(CO)₁₂] reacts with py to give [Rh₆(CO)_16−ypy_y] (y = 1, 2).