Structural and electronic studies of substituted m-terphenyl lithium complexes. Issue 2 (21st December 2020)

• Record Type: Journal Article
• Authors: Valentine, Andrew J.; Geer, Ana M.; Taylor, Laurence J.; Teale, Andrew M.; Wood, Katherine E.; Williams, Huw E. L.; Lewis, William; Argent, Stephen P.; McMaster, Jonathan; Kays, Deborah L.
• Is Part Of: Dalton transactions. Volume 50:Issue 2(2020)
• Page Start: 722
• Page End: 728
• Publication Date: 2020-12-21
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d0dt03972a
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Spectroscopic and computational investigation of the effects of para -substituted m -terphenyl lithium complexes reveals significant electronic differences at the metal centre. Abstract : The effect of para -substitution upon the structural and electronic properties of a series of m -terphenyl lithium complexes [R–Ar # –Li]2 (R = t -Bu 1, SiMe3 2, H 3, Cl 4, CF3 5 ; where R–Ar # = 2, 6-{2, 6-Xyl}2 -4-R-C6 H2 and 2, 6-Xyl = 2, 6-Me2 C6 H3 ) has been investigated. X-ray crystallography reveals the complexes to be structurally similar, with little variation in C–M–C bond lengths and angles across the series. However, in-depth NMR spectroscopic studies reveal notable electronic differences, showing a linear correlation between the 7 Li{ 1 H} NMR chemical shifts of the para -substituted complexes and their Hammett constants. The flanking methyl protons exhibit a similar electronic shift in the 1 H NMR spectra, which has been rationalised by the presence of through-space Li⋯H interactions, as evidenced by two-dimensional 7 Li– 1 H heteronuclear Overhauser spectroscopy (HOESY). In both cases, electron-withdrawing substituents are found to cause an upfield peak shift. A computational analysis is employed to account for these trends.