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Activation and Photoinduced Release of Alkynes on a Biomimetic Tungsten Center: The Photochemical Behavior of the W−S‐Phoz System
Author(s) -
Peschel Lydia M.,
Vidovič Carina,
Belaj Ferdinand,
Neshchadin Dmytro,
MöschZanetti Nadia C.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201805665
Subject(s) - alkyne , chemistry , ligand (biochemistry) , photodissociation , pyridine , stereochemistry , nuclear magnetic resonance spectroscopy , photochemistry , crystallography , medicinal chemistry , catalysis , organic chemistry , receptor , biochemistry
The synthesis and structural determination of four tungsten alkyne complexes coordinated by the bio‐inspired S,N‐donor ligand 2‐(4′,4′‐dimethyloxazoline‐2′‐yl)thiophenolate (S‐Phoz) is presented. A previously established protocol that involved the reaction of the respective alkyne with the bis‐carbonyl precursor [W(CO) 2 (S‐Phoz) 2 ] was used for the complexes [W(CO)(C 2 R 2 )(S‐Phoz) 2 ] (R=H, 1 a ; Me, 1 b ; Ph, 1 c ). Oxidation with pyridine‐ N ‐oxide gave the corresponding W‐oxo species [WO(C 2 R 2 )(S‐Phoz) 2 ] (R=H, 2 a ; Me, 2 b ; Ph, 2 c ). All W‐oxo‐alkyne complexes ( 2 a , b , c ) were found to be capable of alkyne release upon light irradiation to afford five‐coordinate [WO(S‐Phoz) 2 ] ( 3 ). The photoinduced release of the alkyne ligand was studied in detail by in situ 1 H NMR measurements, which revealed correlation of the photodissociation rate constant ( 2 b>2 a>2 c ) with the elongation of the alkyne C≡C bond in the molecular structures. Oxidation of [WO(S‐Phoz) 2 ] ( 3 ) with pyridine‐ N ‐oxide yielded [WO 2 (S‐Phoz) 2 ] ( 4 ), which shows highly fluxional behavior in solution. Variable‐temperature 1 H NMR spectroscopy revealed three isomeric forms with respect to the ligand arrangement versus each other. Furthermore, compound 4 rearranges to tetranuclear oxo compound [W 4 O 4 (μ‐O) 6 (S‐Phoz) 4 ] ( 5 ) and dinuclear [{WO(μ‐O)(S‐Phoz)} 2 ] ( 6 ) over time. The latter two were identified by single‐crystal X‐ray diffraction analyses.