DFT Study of the Homogeneous Hydroformylation of Propene Promoted by a Heterobimetallic Pt–Sn Catalyst

Abstract

Full quantum mechanical calculations at the DFT level were carried out to study the full catalytic cycle for the hydroformylation of propene, catalyzed by the heterobimetallic catalyst trans-[HPt(PPh3)2(SnCl3)] with real triphenylphosphine ligands. All intermediates and transition states along the elementary steps of the entire catalytic cycle were located and the energies involved in the catalytic cycle calculated using the BP86 functional. The solvent effects along the entire catalytic cycle were evaluated using the polarizable continuum model. The regioselectivity of the hydroformylation is set at the olefin insertion step, with the aldehyde reductive elimination being the rate-determining step of the entire cycle, with an activation free energy of 18.1 kcal mol–1, in line with the experimental findings. The trans effect of the SnCl3 ligand seems to be pronounced only in the first step of the catalytic cycle, facilitating the insertion of the olefin into the Pt–H bond trans to it. The BP86 calculations predict a diasteroselectivity ratio of 95:5 in favor of the linear aldehyde product, which it is in excellent agreement with the experimental value.

Computational aspects of hydroformylation

“…The mechanism of propene hydroformylation promoted by complex [PtH(SnCl 3 )(PH 3 ) 2 ] was investigated by Rocha et al employing the BP86 functional and solvation corrections. 180 In agreement with previous studies 176, 177 the regioselectity was found to be determined at the olen insertion step. Employing the kinetic model based on concurrent transition states depicted in Fig.…”

Propene Hydroformylation Reaction Catalyzed by HRh(CO)(BISBI): A Thermodynamic and Kinetic Analysis of the Full Catalytic Cycle

“…The formation of linear and branched Rh‐acyl products, ( 6L ) and ( 6B ), are both favorable processes with branched species around 1.3 kcal mol –1 more stable than linear intermediate. Similar behavior was also observed in other computational studies involving the hydroformylation reaction catalyzed by Pt‐Sn [ 55,56 ] and Rh [ 39,57 ] catalysts. The overall analysis of these results shows that the carbonylation step is thermodynamically controlled.…”

“…[ 58 ] Similar results were reported in other studies. [ 25,55,56,59 ] The H 2 oxidative addition step is the rate‐determining of the entire cycle with a Gibbs activation free energy of 26.0 kcal mol –1 for linear pathway relative to the Rh‐acyl ( 6L ) intermediate generated from the CO coordination to metal‐alky complex formed in the propene insertion step. Finally, the overall analysis of the energetic profile in Figure 2 also shows that the formation of the reaction products is thermodynamically quite favorable with a reaction Gibbs free energy of –11.4 kcal mol –1 for the pathway that leads to linear aldehyde.…”

Neue Trends in der homogenen Übergangsmetallkatalyse

“…Diese Regel gilt allerdings nur, wenn andere Metallkomplexe unter denselben Bedingungen verglichen werden, unter denen Rhodium und Cobalt ihre höchsten Aktivitäten zeigen. Inzwischen wurden auch Palladium‐ 44 und Platin‐Katalysatoren 45, 46 näher untersucht. Neuere Arbeiten von M. Beller und R. Franke 47 – 51 zeigen, dass Iridium und das deutlich günstigere Ruthenium bei Einsatz spezieller Liganden ebenfalls in der Lage sind, die Hydroformylierung mit hohen Aktivitäten zu katalysieren.…”