Design of a Highly Active Pd Catalyst with P,N Hemilabile Ligands for Alkoxycarbonylation of Alkynes and Allenes: A Density Functional Theory Study.

Ahmad, Shahbaz; Bühl, Michael

In the palladium‐catalysed methoxycarbonylation of technical propyne, the presence of propadiene poisons the hemilabile Pd(P,N) catalyst. According to density functional theory calculations (B3PW91‐D3/PCM level), a highly stable π‐allyl intermediate is the reason for this catalyst poisoning. Predicted regioselectivities suggest that at least 11 % of propadiene should yield this allyl intermediate, in which the reaction gets stalled under the turnover conditions due to an insurmountable methanolysis barrier of 25.8 kcal mol−1. The results obtained for different ligands and substrates are consistent with the available experimental data. A new ligand, (6‐Cl‐3‐Me‐Py)PPh2, is proposed, which is predicted to efficiently control the branched/linear selectivity, avoiding rapid poisoning (with only 0.2 % of propadiene being trapped as the Pd allyl complex), and to tremendously increase the catalytic activity by decreasing the overall barrier to 9.1 kcal mol−1.

DENSITY functional theory; PALLADIUM compounds; NICKEL phosphide; CATALYST poisoning; ALKYNES; ALLENE; LIGANDS (Chemistry)

Chemistry - A European Journal, 2019, Vol 25, Issue 50, p11625

0947-6539

Academic Journal

10.1002/chem.201902402