Fluorophosphoniums as Lewis acids in organometallic catalysis: application to the carbonylation of β-lactones

Abstract

We describe the synthesis and characterisation of four organic Lewis acids based on fluorophosphoniums, with tetracarbonyl cobaltate as the counter-anion: [R₃PF]⁺[Co(CO)₄]^- (with R = o-Tol, Cy, ⁱPr, and ^tBu). Their catalytic activity was investigated for the carbonylation of β-lactones to succinic anhydrides. In the presence of [^tBu₃PF]⁺[Co(CO)₄]^- IV (3 mol%), 90% of succinic anhydride was afforded from β-propiolactone after 16 h at 80 °C, at a very mild pressure of 2 bar of carbon monoxide. Our study sets the first example of the use of a main-group cation as a Lewis acidic partner in the cobalt-catalyzed carbonylation of β-lactones.