Immobilization and Characterization of RuCl₂(PPh₃)₃ Mesoporous Silica SBA-3

The five-fold coordinated ruthenium (II) catalyst RuCl₂(PPh₃)₃ is heterogenized on the surface of amine functionalized mesoporous silica material SBA-3 and studied by BET, XRD and ³¹P CP-MAS solid-state NMR. The spectra indicate the replacement of one or two of the triphenyl-phosphine groups in the course of the grafting. To distinguish between both possibilities two-dimensional J-resolved ³¹P MAS solid-state NMR combined with quantum chemical calculations is employed. The changes of the scalar coupling pattern between the neat catalyst and the immobilized catalyst suggest the replacement of two of the PPh₃-groups by coordinative bonds to the amine-functions of the linker. DFT calculations reveal the absence of two chemically and magnetically equivalent phosphines and confirm the replacement of two PPh₃-groups. This finding is similar to the results observed for the binding of the rhodium in the Wilkinson’s catalyst, despite the different coordination of the metals (four-fold versus five-fold), the presence of two chlorine ligands and the different transition metal.