title: Isotopically enriched 13C diffusion-ordered NMR spectroscopy: analysis of methyllithium.
abstract: We report the development of isotopic-labeled (13)C diffusion-ordered NMR spectroscopy (DOSY) NMR with diffusion coefficient-formula weight (D-FW) analysis and its application in characterizing the aggregation state of methyllithium aggregates and complexes with several widely used diamines. Commercially available (13)C-labeled benzene and several easily synthesized (13)C-labeled compounds using (13)C-labeled iodomethane as the isotopic source are developed as internal references for diffusion-formula weight analysis (D-FW). The technique greatly expands the applicability of DOSY D-FW analysis to a much wider variety of compounds because of isotopic labeling. These results reveal that methyllithium exists as a tetrasolvated tetramer in diethyl ether and exclusively as bis-solvated dimers with chelating diamines.
authors.affiliation: Department of Chemistry, Brown University , Providence, Rhode Island 02912, United States.
authors.forename: Chicheung
authors.initials: C
authors.lastname: Su
authors.forename: Russell
authors.initials: R
authors.lastname: Hopson
authors.forename: Paul G
authors.initials: PG
authors.lastname: Williard