Di-n-butyltin(IV)-catalyzed dimethyl carbonate synthesis from carbon dioxide and methanol: An in situ high pressure 119Sn{1H} NMR spectroscopic study

The reactivity of five di-n-butyltin(IV) complexes, n-Bu2Sn(OR)(2) (1), n-Bu2SnO (3), [n-Bu2Sn(OR)](2)O (4), (n-Bu2SnO)(2)(CO2) (6) and (n-Bu2SnO)(6)[(n-Bu2SnOR)(2)(CO3)](2) (7) (R = CH3), with CO2, suggested as possible catalyst precursors and key-intermediates for the direct synthesis of dimethyl carbonate from carbon dioxide and methanol, has been investigated using high-pressure Sn-119{H-1} NMR (HP-NMR) spectroscopy. Four of the five precursors studied, i.e. 3, 4, 6 and 7 give rise to an identical Sn-119{H-1} NMR pattern which can be explicitly attributed to the fingerprint of the dimeric form of the 1-methoxy-3-methylcarbonatotetrabutyldistannoxane {5}(2). However, with 1, a new pair of signals is observed in addition to the characteristic Sn-119{H-1} NMR resonances of the dimeric hemicarbonato species {2}(2) and {5}(2), which can be attributed to the in situ formation of an unprecedented species suggested to be the trinuclear carbonato di-n-butyltin(IV) complex, 8. (C) 2011 Elsevier B. V. All rights reserved.