Characterization and reactivity of some electrochemically generated products of Rh2(μ-dppp)2(μ-CO)Cl2 (dppp = 2-(diphenylphosphino)pyridine)

Abstract

Abstract The reaction of the dirhodium(I) complex Rh 2 (μ-dppp) 2 (μ-CO)Cl 2 , 1 , (dppp = 2- (diphenylphosphino)pyridine) with Cl − in the presence of CO leads to the monomeric species Rh(dppp) 2 (CO)Cl and Rh(CO) 2 Cl − 2 . In the absence of CO no chemical reaction occurs. Electrochemical oxidation of 1 in the presence of Cl − at + 0.90 V (vs SCE) affords a new dirhodium(II) complex Rh 2 (μ-dppp) 2 (CO)Cl 4 , 4 , whose fluxional behaviour at room temperature is demonstrated using variable temperature 31 P NMR. The 31 P NMR is interpreted with the aid of the complex containing 13 CO. Complex 4 reacts with CO to produce Rh 2 (μ-dppp) 2 (CO) 2 Cl 4 , 5 , and with (CH 3 ) 3 CNC ( t -BuNC) to form Rh 2 (μ-dppp) 2 ( t -BuNC) 2 Cl 4 , 6 . Complex 6 appears to partially dissociate to give [Rh 2 (μ-dppp) 2 (μ-Cl) ( t -BuNC) 2 Cl 2 ]Cl. When the equilibrium mixture is treated with NH 4 PF 6 the equilibrium is driven in the direction of the ionic species and the complex [Rh 2 (μ-dppp) 2 (μ-Cl) ( t -BuNC) 2 Cl 2 ]PF 6 is isolated.