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Rhodium phosphine complexes immobilized on silica as active catalysts for 1-hexene hydroformylation and arene hydrogenation.
Autorzy
Rok wydania
2004
Czasopismo
Journal of Molecular Catalysis A-Chemical
Numer woluminu
210
Strony
179-187
DOI
10.1016/j.molcata.2003.09.012
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
In immobilizing the rhodium complexes [Rh(acac)(CO)(P)] (1) and [Rh(acac)(P)2] (2) (P = Ph2PCH2CH2Si(OMe)3) onto SiO2, acetylacetone is found to be released through protonation of the acac ligand by the acidic silica-OH groups. The resulting complexes [Rh(O-{SiO2}(HO-{SiO2})(CO)(P-{SiO2})] (1a) and [Rh(O-{SiO2})(HO-{SiO2})(P-{SiO2})2] (2a) were successfully tested with respect to their catalytic action on 1-hexene hydroformylation as well as benzene and toluene hydrogenation. The reaction outcome, viz. the formation of aldehydes versus isomerization, depends strongly on the presence and concentration of a phosphine co-catalyst. Thus, while 1a gave only a 17% yield of aldehyde in the absence of phosphines, the yield is increased to 54% in the presence of phosphinated silica P-{SiO2} or even 94% if PPh3 is added to the solution. Without extra added phosphine, both 1a and 2a effect mainly the isomerization of 1-hexene to 2-hexene. Pre-catalyst 1a catalyzes also the hydrogenation of benzene at 10.5 atm H2 and 90 °C to give cyclohexane with a TOF of 608 h−1.Rhodium complexes [Rh(acac)(CO)(Ph2PCH2CH2Si(OMe)3)] and [Rh(acac)(Ph2PCH2CH2Si(OMe)3)2] were immobilized at silica as [Rh(O-{SiO2}(HO-{SiO2})(CO)(P-{SiO2})] (1a) and [Rh(O-{SiO2})(HO-{SiO2})(P-{SiO2})2] (2a), respectively, after removal of acac ligands protonated by acidic proton of silica-OH group. Complexes 1a and 2a were characterized with -CP/MAS, XPS and IR methods and used as pre-catalysts in hydroformylation of 1-hexene. The pre-catalyst 1a produced up to 54% of aldehydes with Ph2PCH2CH2Si-{SiO2} co-catalyst and up to 94% with PPh3 and it was found more active compared to 2a. Additionally 1a catalyzes hydrogenation of aromatic hydrocarbons (benzene and toluene).
Słowa kluczowe
Rhodium complexes, Surface confined catalysts, Hydroformylation, Hydrogenation, Alkylsiloxanes
Adres publiczny
https://doi.org/10.1016/j.molcata.2003.09.012
Strona internetowa wydawcy
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