NMR Investigations of Noncovalent Carbon Tetrel Bonds. Computational Assessment and Initial Experimental Observation

Abstract

Group IV tetrel elements may act as tetrel bond donors, whereby a region of positive electrostatic potential (σ-hole) interacts with a Lewis base. The results of calculations of NMR parameters are reported for a series of model compounds exhibiting tetrel bonding from a methyl carbon to the oxygen or nitrogen atoms in various functional groups. The (13)C chemical shift (δiso) and the (1c)J((13)C,Y) coupling (Y = (17)O, (15)N) across the tetrel bond are recorded as a function of geometry. The sensitivity of the NMR parameters to the noncovalent interaction is demonstrated via an increase in δiso and in |(1c)J((13)C,Y)| as the tetrel bond shortens. Gauge-including projector-augmented wave density functional theory (DFT) calculations of δiso are reported for crystals that exhibit tetrel bonding in the solid state. Experimental δiso values for solid sarcosine and its tetrel-bonded salts corroborate the computational findings. This work offers new insights into tetrel bonding and facilitates the incorporation of tetrel bonds as restraints in NMR crystallographic structure refinement.

Close contacts involving germanium and tin in crystal structures: experimental evidence of tetrel bonds

“…Most papers on the ability of tetrels to function as electrophiles describe theoretical investigations of interactions involving carbon [38] and silicon [39][40][41], whereas investigations of the heavier group 14 elements are far less frequent [42]. Experimental studies of TBs are quite limited [29,[43][44][45] and, to the best of our knowledge, they have never focused on interactions involving germanium or tin. We therefore decided to analyze structures in the Cambridge Structural Database (CSD) in order to assess whether organic derivatives of these two elements in crystalline solids show the presence of TBs.…”

Ability of IR and NMR Spectral Data to Distinguish between a Tetrel Bond and a Hydrogen Bond

“…Due to the small size of the C atom, coupled with the presence of three non-electron withdrawing substituents, one would not expect the methyl group to readily engage in T-bonding. Yet thorough reviews of a variety of structures yield numerous interactions, on the order of thousands, where a powerful nucleophilic atom is poised in the precise position, near to the extension of the R-C bond axis, that is consistent with a TB [41][42][43][44] .…”

A theoretical NMR study of selected benzazoles: Comparison of GIPAW and GIAO‐PCM (DMSO) calculations

“…At the present time, gauge-including-projected-augmented-wave (GIPAW) calculations are the standard ones to simulate the results obtained by solid-state NMR. [1][2][3][4][5] However, in previous papers, we have been successful in obtaining acceptable results using gauge-invariant atomic orbital/Becke, 3-parameter, Lee-Yang-Parr (GIAO/ B3LYP)/6-311++G(d,p) calculations together with dimethyl sulfoxide (DMSO) and polarizable continuum model (PCM; continuum solvent model). [6][7][8][9][10] Thus, establishing that DMSO is the best solvent to simulate the effects of the solid-state.…”