Characterization of a Multicomponent Lithium Lithiate from a Combined X‐Ray Diffraction, NMR Spectroscopy, and Computational Approach

Abstract

An unusual lithium lithiate [Li(diglyme)2][(diglyme)Li2(C4H3S)3], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X-ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C4H3S)]2 coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole.

Q.E.COSY: determining sign and size of small deuterium residual quadrupolar couplings using an extended E.COSY principle

“…The model sample used for the pulse sequence development (Fig. ) consists of CDCl 3 in polydimethylsiloxane (PDMS) as alignment medium, [3b] (see also [6b,18] for related apolar gels as alignment media). A 3 mm outer diameter dry PDMS stick, cross‐linked with 200 kGy accelerated electrons, is swollen in 0.5 ml CDCl 3 in a standard 5 mm NMR tube, where 8 mM (1.4 mg) chromium (III) acetylacetonate is added to enhance the relaxation.…”

“…Especially in the latter case, the measurement of residual quadrupolar couplings (RQCs) of Spin 1 nuclei is of particular interest, as the size of RQCs and the typical absence of further interactions in, e.g. 2 H‐spectra or 7 Li‐spectra make them unique tools [5a,6] …”

“…While 7 Li RQCs have been mainly used to characterise the coordination of Li‐compounds, [6a,b] deuterium quadrupolar couplings have been extensively used in specifically deuterated and natural abundance molecules to distinguish enantiomers . As the approximately axially symmetric electric field gradient of deuterons can be assumed to lie along the CD‐bond direction, corresponding RQCs contain structural information that is very similar to residual dipolar couplings.…”

Perspectives in the application of residual dipolar couplings in the structure elucidation of weakly aligned small molecules

“…Apart from the obvious requirements on solubility, the small molecule may also not tolerate the presence of the alignment medium (or vice versa) and decompose (or lead to destabilization or decomposition of the medium). However, after rigorous trials, compatible media were found for moderately unstable compounds like Pd complexes involved in homogeneous catalysis and even very reactive organolithium species …”

Heterobimetallic metallation studies of N,N-dimethylphenylethylamine (DMPEA): benzylic C–H bond cleavage/dimethylamino capture or intact DMPEA complex

“…However, when compared with bonds lengths in monomeric Me 2 Zn, [85] the CZn bonds are shorter by 0.133 Å than that of the Zn1-C11 bond in 6, as would be expected given the linearity of Me 2 Zn and the lower coordination number of its zinc centre (i.e., CN = 2 versus 3). Donor-acceptor complex 6 was also analyzed by a combination of 1 H, 13 C and 7 Li NMR spectroscopy in the deuterated arene solvents benzene and toluene, as well as in the aliphatic hydrocarbon cyclohexane. In its 1 H NMR spectrum in C 6 D 6 solution, the TMP methyl groups appear as two separate resonances (at 1.08 and 1.46 ppm), confirming a difference in the surrounding chemical environment for the two sets of methyl groups (note that the and protons are each also split into separate resonances).…”