Covalent vs. Dative Bonding in Carbon Monoxide and Other 10-Valence-Electron Diatomics
Valence bond theory (VB) was used to determine the extent and driving forces for covalent vs. dative bonding in 10-valence-electron diatomic molecules N<sub>2</sub>, CO, NO<sup>+</sup>, CN<sup>−</sup>, P<sub>2</sub>, SiS, PS<sup>+</sup>, an...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-11-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/29/22/5396 |
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| Summary: | Valence bond theory (VB) was used to determine the extent and driving forces for covalent vs. dative bonding in 10-valence-electron diatomic molecules N<sub>2</sub>, CO, NO<sup>+</sup>, CN<sup>−</sup>, P<sub>2</sub>, SiS, PS<sup>+</sup>, and SiP<sup>−</sup>. VBSCF calculations were performed at the CCSD(T)/cc-pVDZ optimized geometries. The full triply bonded system included 20 VB structures. A separation of the σ and π space allowed for a subdivision of the full 20 structure set into sets of 8 and 3 for the π and σ systems, respectively. The smaller structure sets allowed for a more focused look at each type of bond. In situ bond energies for σ bonds, individual π bonds, the π system, and triple bonds follow expected trends. Our data shows that N<sub>2</sub> and P<sub>2</sub> have three covalent bonds whereas CO and SiS contain two covalent and one dative bond, and charged species NO<sup>+</sup>, CN<sup>−</sup>, PS<sup>+</sup>, and SiP<sup>−</sup> are a mixture of N<sub>2</sub> and CO type electronic arrangements, resulting in a nearly equal charge distribution. Dative bonds prefer to be in the π position due to enhanced σ covalency and π resonance. Both σ and π resonance energies depend on a balance of ionic strength, orbital compactness, σ constraints, and bond directionality. Resonance energy is a major contributor to bond strength, making up more than 50% of the π bonds in SiS and PS<sup>+</sup> (charge-shift bonds), and is greater than charge transfer in dative bonds. |
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| ISSN: | 1420-3049 |