EPR spectroscopic study of the reaction of ground-state aluminium atoms with acyclic alcohols in a rotating cryostat

Abstract

Ground-state aluminium atoms have been reacted with methanol, ethanol and 2-methylpropan-2-ol, in an adamantane matrix, in a rotating cryostat at 77 K. We found no electron paramagnetic resonance (EPR) evidence under these experimental conditions for aluminium atom insertion into the C–C, C–H or O–H bonds of these alcohols. There are, however, several mononuclear aluminium species formed with large aluminium hyperfine interactions (hfi) (1206–1537 MHz). A comparison of the magnetic parameters with those determined for similar systems suggests that in the aluminium–methanol reaction, Al(OCH₃)₂ is the major product. In addition, our results suggest that HOAlOCH₃ and Al(OH)₂ are present in the reaction mixture. We have calculated the aluminium hfi for these species using density functional theory (DFT) methods and the results are in close agreement with the experimental values. The aluminium–ethanol reaction gives Al(OCH₂CH₃)₂ and HOAlOCH₂CH₃ while only HOAlOC(CH₃)₃ is observed from reaction of aluminium atoms with 2-methylpropan-2-ol.