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- Title
Electronic Influences on the Stability and Kinetics of Cp Rhodium(III) Azide Complexes in the iClick Reaction with Electron-Poor Alkynes.
- Authors
Waag‐Hiersch, Luisa; Mößeler, Jan; Schatzschneider, Ulrich
- Abstract
Rhodium(III) azide half-sandwich complexes of general formula [Rh(Cp*)(N3)(bpyR,R)]CF3SO3 with R = H, OCH3 were prepared in three steps in an overall yield of 55-65 %. Their stability strongly depends on the 4,4'-substituent on the 2,2'-bipyridine (bpy) ligand and increases in the order COOCH3 < H < OCH3. Consequently, no stable product could be isolated for the complex with the methyl ester substituent. The title compounds easily underwent cycloaddition reactions with ethyl 4,4,4-trifluoro-2-butynoate in acetonitrile at room temperature in the absence of catalyst. The resulting triazolate products were simply isolated by precipitation in 65-75 % yield. The trifluoromethyl group enabled facile monitoring of the reaction by 19F NMR spectroscopy. Kinetic studies with solution IR spectroscopy revealed pseudo-first-order rate constants of 2.4 to 3.8 × 10-3 s-1, and the reactions were accelerated by the presence of electron-donating groups at the 4,4'-position of the bpy coligand. These values are of a similar magnitude as those for the Staudinger ligation utilized for bio(macro)molecule functionalization.
- Subjects
RHODIUM chloride; RING formation (Chemistry) kinetics; ALKYNES; METHYL formate; BIPYRIDINE analysis
- Publication
European Journal of Inorganic Chemistry, 2017, Vol 2017, Issue 24, p3024
- ISSN
1434-1948
- Publication type
Article
- DOI
10.1002/ejic.201700199