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Abstract We have explored the structural and energetic properties of a series of RMX3‐NH3(M=Si, Ge; X=F, Cl; R=CH3, C6H5) complexes using density functional theory and low‐temperature infrared spectroscopy. In the minimum‐energy structures, the NH3binds axially to the metal, opposite a halogen, while the organic group resides in an equatorial site. Remarkably, the primary mode of interaction in several of these systems seems to be hydrogen bonding (C‐H‐‐N) rather than a tetrel (N→M) interaction. This is particularly clear for the RMCl3‐NH3complexes, and analyses of the charge distributions of the acid fragment corroborate this assessment. We also identified a set of metastable geometries in which the ammonia binds opposite the organic substituent in an axial orientation. Acid fragment charge analyses also provide a clear rationale as to why these configurations are less stable than the minimum‐energy structures. Matrix‐isolation infrared spectra provide clear evidence for the occurrence of the minimum‐energy form of CH3SiCl3–NH3, but analogous results for CH3GeCl3–NH3are less conclusive. Computational scans of the M‐N distance potentials for CH3SiCl3–NH3and CH3GeCl3–NH3, both in the gas phase and bulk dielectric media, reveal a great deal of anharmonicity and a propensity for condensed‐phase structural change.
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Group 14 Central Atoms and Halogen Bonding in Different Dielectric Environments: How Germanium Outperforms Silicon
Abstract The nature of halogen bonding under different dielectric conditions remains underexplored, especially for inorganic systems. The structural and energetic properties of model halogen bonded complexes (R3M−I—NH3for R=H and F, and M=C, Si, and Ge) are examined computationally for relative permittivities between 1 and 109 using an implicit solvent model. We confirm and assess the exceptionally high maximum potentials at the sigma hole on I (Vs,max) in F3Ge−I relative to cases where M=C or Si. In particular, Ge far outperforms Si in mediating inductive effects. Linear relationships, typically with R2>0.97, are identified betweenVs,max, the full point charge on I in R3M−I, and the interaction energy, and optimized I—N distance in the complexes. An anomalous trend is identified in which, for each M, F3M−I—NH3becomeslessstable as the optimized I—N distance getsshorterin different dielectric environments; it is explained using the F−I—NH3complex as a reference.
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- PAR ID:
- 10292037
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPlusChem
- Volume:
- 86
- Issue:
- 10
- ISSN:
- 2192-6506
- Page Range / eLocation ID:
- p. 1387-1396
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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