Phosphines as ligands

Gas-Phase Hydroformylation of Propene over Silica-Supported PPh3-Modified Rhodium Catalysts

“…Here k 7 is the rate coefficient for Reaction 7, K i is the equilibrium constant for Reaction i, P j is the partial pressure of species j, and [PPh 3 ] is the concentration of species , the rate of aldehyde formation is often positive order in alkene, nearly zero order in H 2 and inverse order in CO and PPh 3 [29]. We suggest that the positive order dependences on H 2 and CO seen in this study may reflect the low partial pressures of H 2 and CO used, which result in under-saturation levels of coordinated H and CO.…”

“…More recently, Ding and coworkers [7][8][9][10][11][12] have demonstrated that high activity, near 100% selectivity, and good stability for the hydroformylation of propene to butanal can be achieved with PPh 3 -modified Rh/SiO 2 . Characterization of these catalysts by 1 H, 29 Si, 31 P, and 17 O MAS NMR, suggests that the active species consist of Rh ? species bound to the support via Si-O-Rh bonds, whereas IR spectra of the catalyst exposed to CO suggest that species similar to the homogeneous complex HRh(CO) 2 (PPh 3 ) 2 are formed in situ on the surface of the catalyst.…”

Bis-(thiosemicarbazonato) Zn(ii) complexes as building blocks for construction of supramolecular catalysts

“…This is well documented in the case of phosphites, which display both effects (increase of isomerisation and hydroformylation rate). [63][64][65][66][67][68] In our case, the electronic effects are much smaller than with the phosphites, and we only see a slight increase in conversion. Decreased backdonation to the antibonding CO-orbitals leads to stronger CO bonds of the coordinated CO molecules and as a consequence to higher frequencies of the CO vibrations in the IR spectrum.…”

“…** In type I kinetics, the reaction rate order in respect to the substrate is 1, and the rate-limiting, as well as the rate-determining step are early in the catalytic cycle, while in the type II kinetics the rate order with respect to the substrate is zero and hydrogenolysis is the rate-limiting step. 62,63 † † CO coordinated to Rh or, less probable, to the CO of the Rh-acyl moiety. ‡ ‡ The pipette was previously sealed at the thin end and set within a Schlenk-tube under an inert atmosphere.…”

Asymmetric Hydroformylation

“…In recent years, extensive research into the production of only linear aldehydes has provided impressive results. The application of phosphines with a wide bite angle in the rhodium catalyzed hydroformylation of terminal alkenes enable the regioselectivity to be almost totally controlled [3]. Branched selective hydroformylation, alScheme 1 Asymmetric hydroformylation Asymmetric Hydroformylation 37 though less studied, is a useful tool for organic synthesis [4,5].…”