Prospects for ²⁰⁷Pb solid-state NMR studies of lead tetrel bonds

Abstract

The feasibility and value of Pb solid-state NMR experiments on compounds featuring lead tetrel bonds is explored. Although the definition remains to be formalized, lead tetrel bonds may be qualitatively described as existing when there is evidence of a net attractive interaction between an electrophilic region associated with lead in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Unambiguous identification of lead tetrel bonds can be challenging due to the hypervalent tendency of lead. We report here a series ofPb solid-state NMR experiments on five metal-organic frameworks featuring lead coordinated to hydrazone-based ligands. Such frameworks may be held together in part by lead tetrel bonds. The acquisition of Pb solid-state NMR spectra for such materials is feasible and is readily accomplished using a combination of magic-angle spinning and Carr-Purcell-Meiboom-Gill methods in moderate to low applied magnetic fields. The lead centres are characterized byPb isotropic chemical shifts ranging from -426 to -2591 ppm and chemical shift tensor spans ranging from 910 to 2681 ppm. Careful inspection of the structures of the compounds and the literature Pb NMR data may suggest that a tetrel bond to lead results in chemical shift parameters which are intermediate between those which are characteristic of holodirected and hemidirected lead coordination geometries. Challenges associated with DFT computations of thePb NMR parameters are discussed. In summary, the Pb data for the compounds studied herein show a marked response to the presence of non-coordinating electron-rich moieties in close contact with the electrophilic surface of formally hemidirectionally coordinated lead compounds.

Not Only Hydrogen Bonds: Other Noncovalent Interactions

“…Nevertheless, the heavier tetrel atoms (Ge-Pb) participate in noncovalent tetrel bonding interactions when they are in a chemical context avoiding hypervalency, see for instance the SiO 12 (OH) 8 cage in Figure 9 [132,133]. In fact, since the atomic polarizability increases in a given group of the periodic table on going from lighter to heavier elements, the stronger interactions in this group are expected for tin and lead [134][135][136].…”

Tetrel Bonding Interactions in Perchlorinated Cyclopenta- and Cyclohexatetrelanes: A Combined DFT and CSD Study

“…In this regard, the recognition of tetrel-bonding interactions [ 28 ] (i.e., an attractive noncovalent force between a σ-/π-hole present in a group IV atom and a Lewis base) has increased among the scientific community over the past years. In particular, both experimental [ 24 , 29 ] and theoretical [ 30 , 31 ] chemists have contributed to expanding current knowledge by evaluating their impact on solid state, ref. [ 32 ] biological systems [ 33 ] and chemical reactivity [ 34 ].…”

S⋅⋅⋅Sn Tetrel Bonds in the Activation of Peroxisome Proliferator‐Activated Receptors (PPARs) by Organotin Molecules

“…In this regard, tetrel‐bonding interactions (i.e., attractive noncovalent forces between σ‐/π‐holes present in Group 14 atoms and Lewis bases) have increased their recognition among the scientific community over the past years. In particular, both experimental and theoretical chemists have contributed to expanding the current knowledge by evaluating their impact on solid‐state chemistry, chemical reactivity, and biological systems . However, a simple inspection of the literature reveals a lack of biological examples in which tetrel‐bonding interactions play a major role.…”