A Dramatic Steric Effect on the Rate of Migratory CO Insertion on Rhodium

Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine–phosphine monoselenide ligands

“…45 On the other hand, in view of high trans influencing nature, the acyl group favors apical position trans to the vacant coordination site. 6,13 Thus, the most probable structure of the intermediates and the acyl complexes are represented in Scheme 1. In the complexes 4a and 8b-d, iodine prefers to coordinate to the metal centers at trans to each other.…”

Carbon Monoxide as a Chemical Feedstock: Carbonylation Catalysis

“…A comparative study of PS, PO and PP ligands able to form five-membered chelate rings (51 [107], 52 [108] and 18) showed that the corresponding [RhI(CO)(PX)] complexes react between 35 and 50 times faster with MeI than 43 -an activity similar to the one observed with PEt 3 [109,110]. This enhancement in activity is attributed to the good donor properties of the ligands.…”

“…When using dppeo [110], Ph 2 P(CH 2 ) 2 P(O)Ph 2 (58), a ligand quite active for methanol carbonylation under mild conditions (80 8C, 50 psig CO, TOF = 400 mol mol -1 h -1 ), the same type of "closing-opening" mechanism is thought to be operative. This is in contrast with dppmo, which forms a five-membered chelate ring, and the ligand acts as a bidentate chelate during the entire catalytic cycle.…”

Dicarbonylrhodium(I) complexes of aminophenols and their catalytic carbonylation reaction

“…37 On the other hand, the high trans influencing nature of the acetyl group favours the epical position trans to the vacant site. 40,41 Therefore, based on the IR and NMR data, the proposed structure of the complexes is shown in the Scheme 2. However, our attempt to isolate suitable crystals for X-ray crystal structure determination was not successful.…”

“…On the other hand, for 1b and 1c the electronic factors play a key role as the substituents on the ligands are away from their coordination site and subsequently away from the active Rh centre. Thus, the high philicity of the Rh centre in complex 1b makes it more prone towards OA of CH 3 I, which in contrast might tend to reduce the migratory insertion reaction 41 and might lead to initial equilibrium between 1 b and 1b. After a certain reaction time when a major portion of 1b was reacted, the equilibrium was disturbed and the rate of decay of 1 b became faster.…”