Choice of computational protocol for carbon‐lithium spin–spin coupling constants ¹J_CLi

Abstract

In this work, we tested various computational schemes for calculations of 1 J CLi constants with a high accuracy. On the example of six organolithium reagents (phenyllithium monomer and dimer, monomer s-butyllithium, monomers of 1-and 2-lithionaphthalenes, and a methyllithium tetramer), the following aspects are discussed: (i) the role of a model system geometry, (ii) influence of solvent effects, and (iii) the choice of a functional and basis set. Practical recommendations for calculation of 1 J CLi with an accuracy ±2 Hz are formulated.

Recent advances in the liquid‐phase 6,7Li nuclear magnetic resonance

“…The main conclusions reached in the performed study were as follows (taken from the original paper [ 65 ] as they were): Saturation of a lithium atom coordination number is important. It is especially significant for monomeric species, for them the usage of polydentate ligands is suitable. Implicit solvent effects should be taken into account during geometry optimization as well as NMR calculation. The best performing functionals are WP04, LSDA, PBEPBE, B3PW91, and TPSSTPSS. The basis set should include polarization functions. The addition of diffusion function for the well‐balanced basis sets with not the smallest number of primitive Gaussians in its family is not important and should be taken into account only if computational resources allow costly computational schemes. The following basis sets are recommended: 6‐311+G, def2‐TZVP, cc‐pVTZ, aug‐pcseg‐1, aug‐pcsSeg‐1, aug‐pcJ‐0, and pcJ‐1. …”

“…The most recent and most interesting paper in this field is that by Karpov et al, [ 65 ] which deals with the establishing the most convenient computational protocol for carbon–lithium spin–spin coupling constants in six organolithium compounds 31 – 36 and which will be discussed herewith in more detail.…”

“…The deviation of calculated carbon–lithium coupling constants from experiment, evaluated using different computational schemes and reported in that publication, [ 65 ] are shown in graphical form in Figures 29–31. The corresponding experimental values of 1 J C,Li measured in this paper were as follows: 15.6 Hz ( 31 ), 8 Hz ( 32 ), 14 Hz ( 33 ), 36 Hz ( 34 ), 39 Hz ( 35 ), and 14.5 Hz ( 36 ).…”

“…The deviation of carbon–lithium spin–spin coupling constants from experiment calculated with B3LYP functional in combination with Pople, Dunning, Jensen, and Ahlrich families of basis sets of double and triple zeta quality with and without diffuse functions. Reproduced with minor editing privilege from Karpov et al [ 65 ] with the permission of Wiley…”

NMR detection of the strained metallacycles in organolithiums: theoretical study

“…Chemical shifts and 1 J CLi spin-spin coupling constants were calculated for all other complexes using a WP04/aug-pcSseg-1 level of theory, providing the best balance between accuracy and time consumption. 27 Since the experimental investigations of organolithiums are most commonly performed with the use of 6 Li-enriched substrates, 12 the main discussion will be provided for 13 C- 6 Li spin-spin coupling constants. At the same time, the higher natural abundance of the 7 Li isotope (92.41%) makes NMR measurements with this nucleus more convenient (despite its higher quadrupole moment of −0.0406 barn).…”