Direct observation of metalated N,N-dimethylbenzylamines by ft NMR spectroscopy

Chelated aryllithium reagent: ortho- and para-pyrrolidinomethylphenyllithium

“…Both lithium reagents were prepared in ether by Li/Sn exchange (using 6 and 7), and the lithium reagent was purified by crystallization from diethyl or dimethyl ether before solutions were prepared for spectroscopic study, using solvent mixtures containing THF, dimethyl ether, and/or ether. 6 Li/ 7 Li NMR spectra of aryllithium reagents in THF/ether (M = monomer, D = dimer, for A/B/C see Figure 2). [7b] Chemical shifts are referenced to external 0.3 M LiCl in methanol.…”

“…(a) 13 C and 6 Li NMR spectra of a variable concentration study of 5- 6 Li in THF at - 13 C NMR spectra by line shape simulation.…”

“…[4,5] The X-Ray structure of crystals grown from ether-hexane showed 2 to be tetrameric, with each lithium vertex coordinated by a nitrogen. [4a] It resembles the structure of tetrameric PhLi [6] except that the amino group replaces the coordinated ether molecule on each Li atom. Solution studies on the more soluble 3 showed that in toluene or diethyl ether the tetrameric structure and Nchelation remains intact, but addition of a small amount of THF (1 equiv) gave a dimeric structure as evidenced by C-Li coupling and 13 C chemical shifts.…”

“…The 13 C and 6 Li NMR spectra from the variable temperature experiment of 5 in THF together with a DNMR simulation overlay is shown in Figure 5. The monomer and dimer signals of the ortho, meta, and para carbons coalesced between -68 °C and -100 °C.…”

“…C and 6 Li NMR spectra of a variable temperature study of 0.09 M 5- 6 Li in THF as well as line shape simulations [7d] (upper line, in red) of carbon signals.…”