Computational Spectroscopy Lab

Immobilisation of rhodium acetonitrile complexes in ordered mesoporous silica.

Abstract

Rhodium acetonitrile complexes have been immobilised in the mesoporous silica MCM-41 by pore volume impregnation of a solution of the compound [Rh2(CH3CN)10](BF4)4 in acetonitrile. Powder XRD and N2 adsorption–desorption analysis of the derivatised material confirmed that the textural properties of the hexagonally ordered host were preserved during the grafting experiment and that the channels remained accessible. The BET specific surface area decreased from 1047 to 820 m2 g−1, while the specific total pore volume decreased from 0.85 to 0.64 cm3 g−1. The functionalised material was also characterised by MAS NMR (11B, 13C and 29Si), FTIR and Raman spectroscopy, Rh K-edge EXAFS spectroscopy, UV–Vis and luminescence spectroscopy. These studies revealed the existence of surface-attached dimeric species, with a rhodium–rhodium interatomic distance (2.58 Å) similar to that in the compound [Rh2(CH3CN)10](BF4)4 (2.61 Å). Exposure of this material to light promotes irreversible photodissociation of the dimeric species to give immobilised monomeric species.

M. Pillinger, C. D.Nunes, P. D.Vaz, A. A.Valente, I. S.Goncalves, Paulo Ribeiro-Claro, J. Rocha, L. D.Carlos F. E.Kuhn.