Anchoring of a Ruthenium Complex in Mesoporous Silica Via a Covalent Route

Imobilização de um Complexo de Rutênio em Sílica Mesoporosa Via Rota Covalente

Resumo

Several approaches have been developed focusing on the irreversible attachment of compounds to solid
supports aiming to avoid leaching and consequent loss of activity and recovering. Herein, we discuss the
characterization of a silica-based material modified with cis-[RuCl(ISN)(dppb)(phen)] (RuphenISN),
where ISN = isonicotinic acid, dppb = bis(diphenylphosphine)butane, phen = 1,10-phenanthroline. A
stepwise strategy was adopted in which [RuCl2(dppb)(phen)] was coordinated to ISN previously attached
to silica through an amide coupling reaction forming the mPSi-APTS-ISN-Ruphen material. Scanning
electron microscopy and N2 adsorption/desorption isotherms indicated the prevalence of spherical particles
of 1.5 mm. Solid 13C NMR spectrum of mPSI-APTS-ISN-Ruphen showed chemical shifts in the range
170-120 ppm consistent with sp2 carbons of ISN, dppb and phen moieties. This result along with similar
electrochemical response and vibrational and electronic spectral profiles of mPSi-APTS-ISN-Ruphen
in respect to the non-immobilized RuphenISN complex assure the silica-based material was covalently
modified. Leaching assays performed for 24 h in conditions tipycally applied in hydrogenation catalysis
(basic solution at 100 oC and 2 atm H2 pressure) showed no complex in solution meaning the silica-based
material covalently modified with RuphenISN is robust enough to keep the compound into the silica,
ensuring its recycling and reuse if applied in such processes.