Steric and electronic control of an ultrafast isomerization
| Autor: | Andrew L. Ostericher, Clifford P. Kubiak, Tyler M. Porter |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Steric effects
Denticity 010405 organic chemistry Ligand Chemistry chemistry.chemical_element General Chemistry 010402 general chemistry 01 natural sciences Square pyramidal molecular geometry 0104 chemical sciences Ruthenium Trigonal bipyramidal molecular geometry chemistry.chemical_compound Crystallography Chemical Sciences Isomerization Phosphine |
| Zdroj: | Chemical science, vol 10, iss 34 |
| ISSN: | 2041-6539 2041-6520 |
| DOI: | 10.1039/c9sc02359c |
| Popis: | Synthetic control of the influence of steric and electronic factors on the ultrafast (picosecond) isomerization of penta-coordinate ruthenium dithietene complexes (Ru((CF3)2C2S2)(CO)(L)2, where L = a monodentate phosphine ligand) is reported. Seven new ruthenium dithietene complexes were prepared and characterized by single crystal X-ray diffraction. The complexes are all square pyramidal and differ only in the axial vs. equatorial coordination of the carbonyl ligand. Fourier Transform Infrared (FTIR) spectroscopy was used to study the ν(CO) bandshapes of the complexes in solution, and these reveal rapid exchange between two or three isomers of each complex. Isomerization is proposed to follow a Berry psuedorotation-like mechanism where a metastable, trigonal bipyramidal (TBP) intermediate is observed spectroscopically. Electronic tuning of the phosphine ligands L = PPh3, P((p-Me)Ph)3, ((p-Cl)Ph)3, at constant cone angle is found to have little effect on the kinetics or thermodynamic stabilities of the axial, equatorial and TBP isomers of the differently substituted complexes. Steric tuning of the phosphine ligands over a range of phosphine cone angles (135 < θ < 165°) has a profound impact on the isomerization process, and in the limit of greatest steric bulk, the axial isomer is not observable. Temperature dependence of the FTIR spectra was used to obtain the relative thermodynamic stabilities of the different isomers of each of the seven ruthenium dithietene complexes. This study details how ligand steric effects can be used to direct the solution state dynamics on the picosecond time scale of discrete isomers energetically separated by |
| Databáze: | OpenAIRE |
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