Reactivity of Methoxy Species toward CO on Keggin 12-H₃PW₁₂O₄₀: A Study with Solid State NMR

By using 13 C solid-state NMR, monitoring the reactivity of methoxy species with carbon monoxide has been performed on 12-tungstophosphoric acid, H 3 PW 12 O 40, at 423−473 K. Surface methoxy species have been selectively prepared from methanol at 293−423 K. Almost quantitative conversion of surface methoxy species into acetyl groups bound to the Keggin anion and acetic acid has been observed at 473 K. These data provide unambiguous evidence for the role of methoxy species as the intermediate of methanol and dimethyl ether carbonylation on solid H 3 PW 12 O 40 . The formation of a trimethyloxonium ion has been detected on the surface of heteropolyacid for the first time. The carbonylation of trimethyloxonium proceeds via the analogous mechanism through the methoxy species intermediate.