Issue 17, 2019

Reactivity patterns for the activation of CO2 and CS2 with alumoxane and aluminum hydrides

Abstract

Carbon dioxide is readily fixed when reacting with either alumoxane dihydride [{MeLAl(H)}2(μ-O)] (1) or aluminum dihydride [MeLAlH2] (2) (MeL = HC[(CMe)N(2,4,6-Me3C6H2)]2) to produce bimetallic aluminum formates [(MeLAl)2(μ-OCHO)2(μ-O)] (3) and [(MeLAl)2(μ-OCHO)2(μ-H)2] (5), respectively. Furthermore, [(MeLAl)2(μ-OCHO)2(μ-OH)2] (4) is easily obtained upon the reaction of 3 or 5 with H2O. The stability of the unusual dialuminum diformate dihydride core observed in 5 stems from the proximity of the Al centers allowing the formation of two Al–H⋯Al bridges and precluding further hydride transfer to the HCO2 moieties. Contrary to this behavior, 1 and 2 react with CS2 giving cyclic alumoxane and aluminum sulfides [(MeLAl)2(μ-S)(μ-O)] (6) and [{MeLAl(μ-S)}2] (7), respectively. The molecular structures of 3–7 were characterized by IR, Raman, solution or solid-state (MAS) NMR spectroscopy and mass spectrometry and for 4–7 were characterized by X-ray diffraction studies. NMR kinetic studies and DFT calculations suggest that the mechanisms for the formation of 6 and 7 involve the transfer of a hydride group forming transient aluminum thioformate intermediates which proceed to form Al–S–Al moieties through the cleavage of C–S bonds and insertion of a sulfur atom, followed by the elimination of thioformaldehyde.

Graphical abstract: Reactivity patterns for the activation of CO2 and CS2 with alumoxane and aluminum hydrides

Supplementary files

Article information

Article type
Paper
Submitted
01 feb 2019
Accepted
22 mar 2019
First published
05 apr 2019

Dalton Trans., 2019,48, 5595-5603

Reactivity patterns for the activation of CO2 and CS2 with alumoxane and aluminum hydrides

S. González-Gallardo, V. Jancik, D. G. Díaz-Gómez, F. Cortés-Guzmán, U. Hernández-Balderas and M. Moya-Cabrera, Dalton Trans., 2019, 48, 5595 DOI: 10.1039/C9DT00515C

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