Synthesis, characterization and catalytic activity of a cobalt catalyst: Silica-supported, bis(1,5-diphenyl-1,3,5-pentanetrionato)dicobalt(II) [Co2(dba)2]

Abstract

Models of silica supported cobalt catalysts were formed by decorating the surface of Cab-O-Sil with the dinuclear cobalt complex, bis(1,5-diphenyl-1,3,5-pentanetrionato) dicobalt(II), [Co 2 (dba) 2 ]. To confirm the formation of a monolayer and multilayer of the complex on Cab-O-Sil, various loadings of [Co 2 (dba) 2 ] were combined with Cab-O-Sil by batch impregnation. The supported samples were characterized by elemental analysis, DRIFTS, and TGA to show that the Co 2 (dba) 2 complex was adsorbed on the silica surface intact and DRIFTS confirmed the loading of the Co 2 (dba) 2 as a monolayer on the Cab-O-Sil up to a loading < 2.09 wt% Co. This experimental monolayer loading confirmed the predicted loading (2.06 wt% Co metal) based on the surface area of the support, 200 m 2 /g, and the footprint area of the complex (1.866 nm 2). When this precatalyst was decomposed in air and reduced in hydrogen, the morphology of the resulting particles depended upon the initial disposition of the metal complex on the support. Monolayer films of the metal complex decomposed into metal or metal oxide particles which are too small to give XRD reflections (2.09 wt% Co); whereas, catalyst derived from a multilayer film (4.1 wt% Co) showed large metal particles developing a very sharp XRD reflection from the Co(111) index. Both catalysts were active for the Fischer-Trøpsch reaction at 350 o C with the catalyst derived from the multilayers of complex showing an activity, as characterized by first order rates constants, about 33 times that of the catalyst derived from a monolayer of the complex:71.4 vs 2.16 (mol Co-hour)-1. The selectivity to liquid hydrocarbons showed a remarkably narrow distribution of molecular weights, comprised of mainly iso-and cycloalkanes having 6-8 carbons.

Highly effective organometallic‐mediated radical polymerization of vinyl acetate using alumina‐supported Co(acac)2 catalyst: A case study of adsorption and polymerization

“…Two states of hydroxyl groups are capable of coordinating the transition metal as well as their complexes such as Co(acac) 2 . The mechanism of this reaction includes the connection of hydroxyl groups' oxygen on the surface of alumina supporter to metal in the complex . The possible mechanism of the adsorption of Co(acac) 2 catalyst on the surface of alumina support is shown in Scheme .…”

Synthetic Tuning of CoII-Doped Silica Nanoarchitecture Towards Electrochemical Sensing Ability

“…Silica nanoparticles provide a good platform for uploading of metal ions and complexes through different synthetic approaches, including doping into silica matrix or deposition at a surface of nanoparticles [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. Such hybrid silica nanoparticles uploaded by transition d-metal ions exhibit electrochemical behavior controlled by both inner-sphere environments of the metal ions and nano-architecture of the nanoparticles [ 14 , 15 , 17 , 18 ].…”