The racemic and meso diastereomers of an electron-rich binucleating tetraphosphine ligand have been used to prepare homobimetallic rhodium norbornadiene complexes. The racemic bimetallic Rh complex is an excellent hydroformylation catalyst for 1-alkenes, giving both a high rate of reaction and high regioselectivity for linear aldehydes, whereas the meso complex is considerably slower and less selective. A mechanism involving bimetallic cooperativity between the two rhodium centers in the form of an intramolecular hydride transfer is proposed. Mono- and bimetallic model complexes in which the possibility for bimetallic cooperativity has been reduced or eliminated are very poor catalysts.

https://science.sciencemag.org/content/sci/260/5115/1784.full.pdf

A bimetallic hydroformylation catalyst: high regioselectivity and reactivity through homobimetallic cooperativity.

The electronic effect in the rhodium diphosphine catalyzed hydroformylation was investigated. A series of electronically modified thixantphos ligands was synthesized, and their effects on coordination chemistry and catalytic performance were studied. Phosphine basicity was varied by using p-(CH3)2N, p-CH3O, p-H, p-F, p-Cl, or p-CF3 substituents on the diphenylphosphine moieties. X-ray crystal structure determinations of the complexes (thixantphos)Rh(CO)H(PPh3) and (p-CH3O-thixantphos)Rh(CO)H(PPh3) were obtained. The solutions structures of the (diphosphine)Rh(CO)H(PPh3) and (diphosphine)Rh(CO)2H complexes were studied by IR and NMR spectroscopy. IR and 1H NMR spectroscopy showed that the (diphosphine)Rh(CO)2H complexes consist of dynamic equilibria of diequatorial (ee) and equatorial−apical (ea) isomers. The equilibrium compositions proved to be dependent on phosphine basicity; the ee:ea isomer ratio shifts gradually from almost one for the p-(CH3)2N-substituted ligand to more than nine for the p-CF3-subs...

Electronic Effect on Rhodium Diphosphine Catalyzed Hydroformylation: The Bite Angle Effect Reconsidered

The hydroformylation of decene-1 was studied in the presence of the fluorous-soluble P[CH2CH2(CF2)5CF3]3 modified rhodium catalyst at 100 °C and 1.1 MPa of CO/H2 (1:1) in a 50/50 vol % toluene/C6F11CF3 solvent mixture, which forms a homogeneous liquid phase at and above 100 °C. P[CH2CH2(CF2)5CF3]3 was selected on the basis of a semiempirical calculation of the electronic properties of P[(CH2)x(CF2)yCF3]3 (x = 0, y = 2, 4 and x = 0−5, y = 2) and prepared by the reaction of PH3 with CH2CH(CF2)5CF3. The solution structure of HRh(CO){P[CH2CH2(CF2)5CF3]3}3 (1) in C6F11CF3 is similar to that of HRh(CO)(PPh3)3 (2) in toluene and HRh(CO){P(m-C6H4SO3Na)3}3 (3) in water. High-pressure NMR of 1 under 2.1−8.3 MPa of CO/H2 (1:1) revealed that 1 is in equilibrium with HRh(CO)2{P[CH2CH2(CF2)5CF3]3}2 (4). Kinetic studies show that the reaction is first order in both rhodium and decene-1. While the reaction is inhibited by P[CH2CH2(CF2)5CF3]3, the normal/iso (n/i) ratio of the aldehyde increases with increasing phosphine ...

Molecular Engineering in Homogeneous Catalysis: One-Phase Catalysis Coupled with Biphase Catalyst Separation. The Fluorous-Soluble HRh(CO){P[CH2CH2(CF2)5CF3]3}3 Hydroformylation System

Ionic Phosphine Ligands with Cobaltocenium Backbone: Novel Ligands for the Highly Selective, Biphasic, Rhodium-Catalyzed Hydroformylation of 1-Octene in Ionic Liquids†

The metal-catalyzed isomerization–hydroformylation tandem reaction is of great importance for the production of linear aldehydes starting from internal olefins, but also, the shift of the double bond from a terminal position into the interior of an alkyl chain and the subsequent hydroformylation can be of interest. This review aims to summarize problems and achievements in this area under particular consideration of results published by the Leibniz-Institut fur Katalyse (LIKAT) in the past two decades. A main focus is given to the variation of metals (Co, Rh, Ru, Pd, Pt, Fe) and phosphorus ligands used for the tandem reaction.

Ronald A. Duwell

Papers

The mechanism of phosphine-modified rhodium-catalyzed hydroformylation studied by CIR-FTIR