Chiral and achiral phosphine derivatives of alkylidyne tricobalt carbonyl clusters as catalyst precursors for (asymmetric) inter- and intramolecular Pauson–Khand reactions

Abstract

Phosphine derivatives of alkylidyne tricobalt carbonyl clusters have been tested as catalysts/catalyst precursors in intermolecular and (asymmetric) intramolecular Pauson–Khand reactions. A number of new phosphine derivatives of the tricobalt alkylidyne clusters [Co₃(μ₃-CR)(CO)₉] (R = H, CO₂Et) were prepared and characterised. The clusters [Co₃(μ₃-CR)(CO)_9−x(PR′₃)_x] (PR′₃ = achiral or chiral monodentate phosphine, x = 1–3) and [Co₃(μ₃-CR)(CO)₇(P–P)] (P–P = chiral diphosphine; 1,1′- and 1,2-structural isomers) were assayed as catalysts for intermolecular and (asymmetric) intramolecular Pauson–Khand reactions. The phosphine-substituted tricobalt clusters proved to be viable catalysts/catalyst precursors that gave moderate to very good product yields (up to ∼90%), but the enantiomeric excesses were too low for the clusters to be of practical use in the asymmetric reactions.