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- Title
Synthesis, Structural Characterization and Catalytic Evaluation of Anionic Phosphinoferrocene Amidosulfonate Ligands.
- Authors
Schulz, Jiří; Horký, Filip; Císařová, Ivana; Štěpnička, Petr
- Abstract
Triethylammonium salts of phosphinoferrocene amidosulfonates with electron-rich dialkyphosphino substituents, R2PfcCONHCH2SO3(HNEt3) (4a-c), where fc = ferrocene-1,1'-diyl, and R = i-Pr (a), cyclohexyl (Cy; b), and t-butyl (c), were synthesized from the corresponding phosphinocarboxylic acids-borane adducts, R2PfcCO2H.BH3 (1a-c), via esters R2PfcCO2C6F5.BH3 (2a-c) and adducts R2PfcCONHCH2SO3(HNEt3).BH3 (3a-c). Compound 4b was shown to react with [Pd(μ-Cl)(η-C3H5)]2 and AgClO4 to afford the zwitterionic complex [Pd(η3-C3H5)(Cy2PfcCONHCH2SO3-κ2O,P)] (5b), in which the amidosulfonate ligand coordinates as a chelating donor making use of its phosphine moiety and amide oxygen. The structures of 3b.CH2Cl2, 4b and 5b.CH2Cl2 were determined by single-crystal X-ray diffraction analysis. Compounds 4a-c and their known diphenylphosphino analogue, Ph2PfcCONHCH2SO3(HNEt3) (4d), were studied as supporting ligands in Pd-catalyzed cyanation of aryl bromides with K4[Fe(CN)6] and in Suzuki-Miyaura biaryl cross-coupling performed in aqueous reaction media under mild reaction conditions. In the former reaction, the best results were achieved with a catalyst generated from [PdCl2(cod)] (cod = η2:η2-cycloocta-1,5-diene) and 2 equiv. of the least electron-rich ligand 4d in dioxane-water as a solvent. In contrast, the biaryl coupling was advantageously performed with a catalyst resulting from palladium(II) acetate and ligand 4a (1 equiv.) in the same solvent.
- Subjects
MOLECULAR structure of ligands; ZWITTERIONS; PHOSPHINE
- Publication
Catalysts (2073-4344), 2017, Vol 7, Issue 6, p167
- ISSN
2073-4344
- Publication type
Article
- DOI
10.3390/catal7060167