Characterization of Hexameric and Octameric sec-Butyllithium/sec-Butoxide Mixed Aggregates

• Published in: European journal of inorganic chemistry Vol. 2013; no. 24; pp. 4136 - 4141
• Main Authors: Su, Chicheung, Hopson, Russell, Williard, Paul G.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 12.08.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Aggregates; Aggregation; Butyllithium; Hydrocarbons; Lithium; Mixed aggregates; NMR; NMR spectroscopy; Nuclear magnetic resonance; Organolithium reagents; Polymers; Solvents; Spectroscopic analysis; Spectrum analysis
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201300749

Solution‐state characterization of sec‐butyllithium in [D8]toluene was conducted by utilizing a variety of NMR spectroscopic experiments including diffusion‐ordered NMR spectroscopy (DOSY) with diffusion‐coefficient–formula‐weight correlation analyses and other one‐ and two‐dimensional NMR spectroscopic techniques. These results suggest that sec‐butyllithium exists primarily as a tetramer/hexamer mixture in hydrocarbon solvents. However, the presence of roughly 2–5 % (by mol ratio) lithium sec‐butoxide in both commercially available and laboratory‐synthesized sec‐butyllithium solutions due to the reaction with adventitious dioxygen will lead to the formation of a 1:5 sec‐butoxide/sec‐butyllithium mixed hexamer. A sec‐butoxide/sec‐butyllithium mixed octamer will emerge when the proportion of butoxide to butyllithium increases. Solutions of sec‐butyllithium in [D8]toluene and the aggregates in them were characterized by a variety of methods including diffusion‐ordered NMR spectroscopy (DOSY) and other one‐ and two‐dimensional NMR spectroscopic techniques.