An evaluation of microwave-driven stannylation followed by in situ119Sn MAS n.m.r. spectroscopy as a probe for hydroxyl functionality in medium-rank British coals and macerals

Abstract

Stannylation of a range of phenolic compounds with Me 3SnCl, Bu 3SnCl and (Bu 3Sn) 2O (TBTO) was carried out under both microwave-driven and conventional conditions. The degree of stannylation was influenced by the steric environment of the OH group, implying that stannylation in comparison with, say, trimethylsilylation of OH groups could help to map the steric environments of phenolic groups in coals. Good maceral separations of Creswell coal and acceptable separations of Cortonwood coal were achieved. The whole coals and the macerals were stannylated with TBTO under microwave-enhanced conditions and the products were examined by 119Sn MAS n.m.r. and X-ray photoelectron spectroscopy. The reaction was confined to surface regions. Differences were found in the behaviour of the macerals. The crystal and molecular structures of the trimethylstannyl derivative of 2,6-diphenylphenol were determined, to establish the validity of the claim to have stannylated model compounds. Molecular parameters were compared with related systems.