Comprehensive Theoretical Study on the Mechanism of Regioselective Hydroformylation of Phosphinobutene Catalyzed by a Heterobinuclear Rhodium(I)−Chromium Complex

Abstract

A concerted mechanism for the hydroformylation of phosphinobutene catalyzed by the heterobinuclear complex (CO)4Cr(μ-PH2)2RhH(CO)(PH3) was elucidated by density functional theory (DFT), with particular emphasis on the catalytic cycle, the regioselectivity, the cooperativity of Cr with Rh, and the interpretation of experimental observations. Four possible mechanisms were investigated, and the results were compared. It is found that the introduction of the Cr(CO)4 moiety remodels the mechanism. The Rh−Cr-catalzyed hydroformylation mechanism includes the following: (a) formation of the chelate acyl species through a chelate associative mechanism including olefin addition, olefin insertion, and carbonyl insertion steps, (b) CO addition to the chelate acyl species with the formation of a monodentate acyl species, and (c) the conversion of the monodentate acyl species to the product aldehyde through H2 coordination, H2 oxidative addition, and aldehyde elimination. Carbonyl insertion is predicted to be the rate-limiting step, with a free energy barrier of 86.76 kJ/mol in benzene solution at 353.15 K and 27.15 atm. The favorability of the branched product is predicted to be nearly 100% both kinetically and thermodynamically. The chromium serves as an orbital reservoir in olefin addition and insertion steps via the variation of the orbital interaction between Rh and Cr atoms. The catalytic activity of the Rh(I)−Cr bimetallic complex is higher than that of the monometallic Rh catalysts. These could explain satisfactorily the reported experimental observations.

The fate of branched and linear isomers in the rhodium-catalyzed hydroformylation of 3,4,4-trimethylpent-1-ene

“…From the superimposition of the profiles Opposite, yet limited, effects are found on the CO addition TS (whose barrier increases) and on the tetracarbonyl intermediate. Similar negligible effects have been obtained with PCM on metal catalyzed reactions by other authors as well using gas phase-optimized geometries either in benzene [64] or in diethyl ether solution [65] with the B3LYP hybrid functionals.…”

Theoretical Study on Mechanism of Hydroformylation of Ethene Catalyzed by a Heterobimetallic Rh(I)‐Cr Complex

“…13 In the following sections, the two mechanisms are firstly discussed in detail. Then, the comparison of the two mechanisms is addressed.…”

“…13 The bond orders of Rh-Cr in 1a and 1b are 0.47 and 0.45, respectively. Initially, the reactant ethene coordinates to catalysts 1a and 1b to generate the η 2 -ethylene complexes 2a and 2b.…”

“…[3][4][5] Scheme 2 The Rh-M (M＝Cr, Mo, and W) heterobimetallic catalyst So far, only the catalytic cycles of hydroformylation catalyzed by monometallic Rh or Co catalysts have been investigated by means of quantum mechanical methods. 11,12 In our previous paper, 13 the mechanism for the hydroformylation of phosphinobutene catalyzed by a heterobinuclear (CO) 4 Cr(μ-PH 2 ) 2 RhH(CO)(PH 3 ) complex was investigated. It was found that the Rh(I)-Crcatalyzed hydroformylation of phosphinobutene included the followings: (a) the formation of the chelate acyl species through the chelate associative mechanism including olefin addition, olefin insertion, and carbonyl insertion steps, (b) the CO addition to the chelate acyl species with the formation of the monodentate acyl species, and (c) the conversion of the monodentate acyl species to the product aldehyde through H 2 coordination, H 2 oxidative addition, and aldehyde elimination.…”

Platinum–alkyl–B(C6F5)3 (or BF3) ‘in situ’ systems as tin(II) halide-free enantioselective hydroformylation catalysts

“…PCM method has been used for numerous studies involving transition metal complexes with reasonable accuracy [43,44]. Thermochemistry corrections were taken from gas-phase frequency calculations at 298.15 K and 1 atm.…”