Synthesis and Simple Immobilization of Palladium(II) Acyclic Diaminocarbene Complexes on Polystyrene Support as Efficient Catalysts for Sonogashira and Suzuki–Miyaura Cross-Coupling

• Published in: Organometallics Vol. 35; no. 11; pp. 1684 - 1697
• Main Authors: Mikhaylov, Vladimir N, Sorokoumov, Viktor N, Korvinson, Kirill A, Novikov, Alexander S, Balova, Irina A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 13.06.2016
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/acs.organomet.6b00144

Immobilization of palladium­(II) acyclic diaminocarbene (Pd­(II)-ADC) complexes on a resin support surface has been easily performed by metal-mediated addition of amino groups of benzhydrylamine-polystyrene to the coordinated isocyanide ligand of cis-PdCl2(CNR)2 (R = t-Bu, Cy). The investigation of the benzhydrylamine reaction with palladium-coordinated isocyanides in solution has revealed that, depending on the reaction conditions, two carbene-type complexes can be obtained as a result of the addition to the CN triple bond, as well as a third complex which is formed via substitution of the isocyanide ligand by benzhydrylamine. Nucleophilic addition of an amino group to the isocyanide ligand has led to a cis-acyclic diaminocarbene complex or a cationic diaminocarbene complex with trans configuration and an intramolecular hydrogen-bonded chloride anion (the nature of this noncovalent interaction was analyzed by DFT calculations, including AIM analysis). The unsupported and resin-supported palladium catalysts have demonstrated high catalytic activity in both Sonogashira and Suzuki–Miyaura cross-coupling. The supported catalyst can be recovered and repeatedly reused without a significant loss in efficiency. The degree of the palladium binding with polystyrene, the oxidation state, and the palladium leaching level were investigated by XPS and XRF analyses.