The Role of Ligand Steric Bulk in New Monovalent Aluminum Compounds
| Autor: | Warren Tomlinson, Dennis H. Mayo, Rebecca M. Wilson, Joseph P. Hooper |
|---|---|
| Přispěvatelé: | Physics |
| Rok vydání: | 2017 |
| Předmět: |
Steric effects
chemistry.chemical_classification 010405 organic chemistry Ligand Atoms in molecules 010402 general chemistry 01 natural sciences 0104 chemical sciences Delocalized electron chemistry Cyclopentadienyl complex Computational chemistry Thermochemistry Non-covalent interactions Density functional theory Physical and Theoretical Chemistry |
| Popis: | The article of record as published may be located at https://doi.org/10.1021/acs.jpca.7b02075 The tetrameric Al(I) cyclopentadienyl compound Al4Cp*4 (Cp* = C5Me5) is a prototypical low-valence Al compound, with delocalized bonding between four Al(I) atoms and η5 ligands bound to the cluster exterior. The synthesis of new [AlR]4 (R = C5Me4Pr, C5Me4iPr) tetramers is presented. Though these systems failed to crystallize, comparison of variable-temperature 27Al NMR data with density functional theory (DFT) calculations indicate that these are Al4R4 tetramers analogous to Al4Cp*4 but with increased ligand steric bulk. NMR, DFT, and Atoms in Molecules analyses show that these clusters are enthalpically more stable as tetramers than the Cp* variant, due in part to noncovalent interactions across the bulkier ligand groups. Thermochemistry calculations for the low-valence metal interactions were found to be extremely sensitive to the DFT methodology used; the M06-2X functional with a cc-pVTZ basis set is shown to provide very accurate values for the enthalpy of tetramerization and 27Al NMR shifts. This computational method is then used to predict geometrical structures, noncovalent ligand interactions, and monomer/tetramer equilibrium in solution for a series of Al(I) cyclopentadienyl compounds of varying steric bulk. |
| Databáze: | OpenAIRE |
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