Li2{CH2S(O)Ph}2(TMEDA)2] – An α-sulfinyl-functionalized methyllithium carbenoid

Abstract

The aggregation state of the α-sulfinyl-functionalized methyllithium compound [Li2{CH2S(O)Ph}2(TMEDA)2] (1) in solution and its carbenoid reactivity is presented. Temperature dependent NMR measurements of 1 in THF-d8 revealed the presence of an intermolecular dynamic process (dimer–monomer–dimer equilibrium) with a Gibbs free energy of activation of about 45kJ/mol. 1H DOSY NMR measurements exhibited that in THF-d8 solution the coligand TMEDA is partially cleaved off. Furthermore, the decomposition of 1 in THF-d8 (room temperature, 96h) led to the formation of ethylene and PhSSPh. In refluxing toluene 1 decomposed with formation of ethylene, PhSSPh, xylenes, ethylbenzene, n-propylbenzene and isopropylbenzene. The dimerizing α-elimination yielding ethylene and the C–H insertion reactions observed in boiling toluene give proof of a carbenoid reactivity of 1.