Variable temperature 1H NMR and X-ray diffraction characterisation of [H 5Os 10(CO) 24] − obtained in reproducible and high yields by hydrogenation of silica-supported [Os(CO) 3(OH) 2] n

Abstract

The hydrides localisation in the hydrido carbonyl cluster [H 5Os 10(CO) 24] −, obtained in excellent and reproducible yields by hydrogenation (1 atm, 200 °C) of silica-supported [Os(CO) 3(OH) 2] n , has been investigated by variable temperature 1H NMR and X-ray diffraction of the [(Ph 3P) 2N] + salt. Using both stereochemical and potential energy considerations, three μ 2-H and two μ 3-H have been localised in sites strictly related to those of the parent [H 4Os 10(CO) 24] 2− anion, where hydrides location had been obtained by neutron diffraction of the corresponding [(Ph 3P) 2N] + salt. Such locations are in agreement with low temperature 1H NMR findings. Variable temperature 1H NMR investigation has also shown that μ 2- and μ 3-hydrides have a very different mobility. While μ 2-hydrides exchange easily by an edge-shift process, their exchange with μ 3-hydrides is much more difficult, as the exchange between μ 3-hydrides themselves.