NMR Response of the Tetrel Bond Donor

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 Sn-119 and Cl-35 solid-state NMR experiments carried out in applied magnetic fields ranging from 4.7 to 21.1 T. Experimentally measured isotropic (1)J(Sn-119, Cl-35) coupling constants and Cl-35 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 center dot center dot center dot O tetrel bond length. Remarkably, the formation of moderately strong tetrel bonds to Ph3SnCl results in substantial reductions in (1)J(Sn-119, Cl-35) and CQ 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.

Automated summary

Experimental and theoretical studies show that tin atoms can form strong tetrel bonds when acting as tetrel bond donors, leading to significant effects on NMR parameters. The experimental trends in J couplings for tetrel bonds are similar to those for hydrogen bond donors, but NMR parameters are less suitable for measuring tetrel bond strengths.