Investigations into the mechanism of the in situ formation of neutral dinuclear rhodium complexes

The often applied in situ formation of neutral dinuclear rhodium precatalysts of the type [Rh(Diphosphine)(μ2-Cl)]2 with the ligands DPEPhos and DIOP has been mechanistically investigated by NMR spectroscopy. The structural characterization of reaction intermediates [Rh2(μ2-Diphosphine)(COD)2(Cl)2] and [Rh2(Diphosphine)(COD)(μ2-Cl)2] was accomplished using X-ray crystallography. So a new and unexpected intermediate was found, which casts a new light on the mechanism of this ligand exchange. In addition, equilibria could be found which can at least influence the formation of neutral dinuclear rhodium precatalysts.