Binuclear pentalene titanium carbonyls involved in the deoxygenation of carbon dioxide
| Autor: | Luana-Flavia Radu, R. Bruce King, Amr A. A. Attia, Alexandru Lupan |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Pentalene
010304 chemical physics Organic Chemistry Metal carbonyl 010402 general chemistry Photochemistry 01 natural sciences Biochemistry Bond-dissociation energy 0104 chemical sciences Inorganic Chemistry chemistry.chemical_compound Crystallography chemistry 0103 physical sciences Materials Chemistry Density functional theory Singlet state Physical and Theoretical Chemistry Deoxygenation Carbonylation Cis–trans isomerism |
| Zdroj: | Journal of Organometallic Chemistry. 867:201-207 |
| ISSN: | 0022-328X |
| DOI: | 10.1016/j.jorganchem.2017.11.006 |
| Popis: | The complete series of binuclear pentalene titanium carbonyls Pn2Ti2(CO)n and Pn†2Ti2(CO)n (Pn = pentalene; Pn† = 1,4-(iPr3Si)2C8H4; n = 0, 1, 2, 3, 4), including Pn†2Ti2(CO)2 obtained experimentally from Pn†2Ti2 and carbon dioxide, have been investigated by density functional theory. For the carbonyl-free Pn2Ti2 system the singlet structure is found to lie 22.5 and 18.5 kcal/mol in energy below the isomeric triplet and quintet structures, respectively. However, for the experimentally known Pn†2Ti2 system (Pn† = 1,3-(iPr3Si)2C8H4) the singlet, triplet, and quintet spin state structures have essentially equal energies within 0.3 kcal/mol suggesting the possibility of complicated magnetic behavior. The Ti–Ti distance of 2.399 A found in crystalline Pn†2Ti2 by X-ray crystallography is closest to the 2.415 A Ti-Ti distance predicted for the triplet spin state structure. Carbonylation of Pn2Ti2 results in successive lengthening of the Ti-Ti distance as CO groups are added. Three CO groups are the maximum number that can be introduced into a viable Pn2Ti2(CO)n derivative as indicated by the predicted exothermic CO dissociation energy of the tetracarbonyl Pn2Ti2(CO)4. The lowest energy structure for the monocarbonyl Pn2†Ti2(CO) has a four-electron donor bridging η2-μ-CO group in accord with the experimental structure. The lowest energy structure for the dicarbonyl Pn†2Ti2(CO)2 has exclusively terminal CO groups in a cis configuration, again in accord with the experimental Pn†2Ti2(CO)2 structure. Two terminal CO groups are accompanied by a third highly unsymmetrical semibridging CO group in the lowest energy structures for the tricarbonyls Pn2Ti2(CO)3 and Pn†2Ti2(CO)3. However, the lowest energy structures for the tetracarbonyls Pn2Ti2(CO)4 and Pn†2Ti2(CO)4 have exclusively terminal CO groups. |
| Databáze: | OpenAIRE |
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