NMR Response of the Tetrel Bond Donor

Abstract

The tetrel elements (group 14) have the capacity to act as electrophilic sites and participate in structure-directing noncovalent tetrel bonds. We establish here the experimental response of several NMR interaction tensors to tetrel bonding via a range of 119Sn and 35Cl solid-state NMR experiments carried out in applied magnetic fields ranging from 4.7 to 21.1 T. Experimentally measured isotropic 1 J(119Sn, 35Cl) coupling constants and 35Cl nuclear quadrupolar coupling constants (C Q) in a series of cocrystals of triphenyltin chloride, wherein tin acts as the tetrel bond donor atom, correlate with the experimental Sn···O tetrel bond length. Remarkably, the formation of moderately strong tetrel bonds to Ph3SnCl results in substantial reductions in 1 J(119Sn, 35Cl) and C Q by 27–45 and 20–36%, respectively. The experimental findings are reproduced by periodic gauge-including projector-augmented wave density functional theory (DFT) calculations as well as spin–orbit relativistic zeroth-order regular approximation DFT calculations. The trend established here in J couplings parallels that for hydrogen bond donors, providing experimental evidence for the analogy between the two classes of interactions. Tin chemical shift tensors and computed magnetic shielding tensors correlate less well with structure, suggesting that these are less suitable measures of tetrel bond strength. These results contribute to the elucidation of important analogies and differences between tetrel bonds and related classes of noncovalent interactions such as hydrogen bonds and halogen bonds. This work provides new insights, which should prove to be useful in future studies of related crystalline or amorphous systems featuring tetrel bonds and/or tetrel–halogen moieties such as halide perovskites and related photovoltaic and optoelectronic materials.

Definition of the tetrel bond

“…j. the NMR chemical shifts of nuclei in both R–Tt and TtBA are typically affected (with the former increased or decreased 33 ), as found for R–X⋯A XBs and R–Ch⋯A ChBs; 19,36–39 the isotropic coupling constant of the TtB donor tends to decrease relative to that of the isolated TtB donor, 40,41 as observed for HBs and XBs; 42…”

Influence of Substituents in the Benzene Ring on the Halogen Bond of Iodobenzene with Ammonia

“…For example, the signal of the bridging proton moves downfield by several ppm upon formation of a H-bond, and the degree of this shift is closely related to the strength of the bond. There have been several studies in recent years [43][44][45][65][66][67][68][69][70][71] that suggest that these ideas can be extended to halogen and other related noncovalent bonds.…”

“…There has been a substantial body of past research regarding the relevance of NMR coupling constants to halogen and related noncovalent bonding. [68,72,[74][75][76][77][78] In particular, the coupling constant between the two atoms directly involved in a XB seems to closely track with the strength of the bond. The pertinent coupling constant between I and N in the halogen bonded systems here is delineated by the red curve in Figure 3 (in units of 100 Hz so as to fit into the figure).…”

Characterization of Type I and II Interactions between Halogen Atoms

“…H-bonds have garnered a century’s worth of study over the years. − As corollaries to H-bonds, there are a collection of closely related noncovalent bonds where the bridging H is replaced by any of a wide assortment of other elements. − Given the large number of molecules that contain halogen (X) atoms, it is not surprising that these nuclei are frequently situated in some proximity to one another within the context of crystals and other condensed phases. Indeed, the study of such halogen–halogen interactions has a long and storied literature. − Such X···X interactions, commonly referred to as halogen bonds (XBs), have demonstrated their importance in numerous situations as they can control solid-state structure and represent an important motif for crystal engineering. − As specific examples, XBs can be a crucial ingredient in supramolecular chirality and helical structures, clustering on Cu surfaces, or two-dimensional crystallization at a solid–liquid interface …”