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1.
Chem Commun (Camb) ; 58(80): 11240-11243, 2022 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-35735231

RESUMEN

A series of complexes of the general formula [(η6-arene)RuCp][PF6] (where arene = aryl halides or nitroarenes) were synthesised and the arene ring was found to be reactive towards an intermolecular nucleophilic aromatic substitution (SNAr) reaction with a series of cyclic 1,3-diones. Competition experiments indicated that leaving group ability of the aryl halides and nitroarenes went in the order of F ≫ NO2 > Cl > Br. Following SNAr, the arene rings were liberated quantitatively via a rapid photolysis reaction (<15 min).


Asunto(s)
Rutenio , Ácidos Carboxílicos , Dióxido de Nitrógeno
2.
Dalton Trans ; 51(1): 340-351, 2021 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-34897327

RESUMEN

Transfer hydrogenation (TH) is a powerful synthetic tool in the production of secondary alcohols from ketones by using a non-H2 hydrogen source along with metal catalysts. Among homogeneous catalysts, Ru(II) complexes are the most efficient catalysts. In our research, six novel ruthenium(II) complexes bearing bipyridine-based ligands [Ru(L1)Cl2] (1), [Ru(L1)(PPh3)Cl]Cl (2) and [Ru(L2)Cl2] (3) and N-heterocyclic carbene-supported pyridine (NCN) ligands [RuCp(L3)]PF6 (4), [RuCp*(L3)]PF6 (5), and [Ru(p-cymene)(L3)Cl]PF6 (6) (where L1 = 6,6'-bis(aminomethyl)-2,2'-bipyridine, L2 = 6,6'-bis(dimethylaminomethyl)-2,2'-bipyridine and L3 = 1,3-bis(2-methylpyridyl)imidazolium bromide) were synthesised and characterised by NMR spectroscopy, HRMS, and X-ray crystallography. The catalytic transfer hydrogenation of 28 ketones in 2-propanol at 80 °C in the presence of KOtBu (5 mol%) was demonstrated and the effect of ligands is highlighted. The results show that catalyst 1 exhibits improved TH efficiency compared to the commercially available Milstein catalyst and displays higher catalytic activity than 2 due to the steric effect from PPh3. From a combination of kinetic data and Eyring analysis, a zero-order dependence on the acetophenone substrate is observed, implying a rate-limiting hydride transfer step, leading to the proposed inner-sphere hydride transfer mechanism.

3.
Chemistry ; 27(11): 3650-3660, 2021 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-33210827

RESUMEN

π-Coordination of aromatic molecules to metals dramatically alters their reactivity. For example, coordinated carbons become more electrophilic and C-H bonds of coordinated rings become more acidic. For many years, this change in reactivity has been used to trigger reactions that would not take place for uncoordinated arenes, however, there has been a recent resurgence in use of this technique, in part due to the development of catalytic reactions in which π-coordination is transient. In this Minireview, we describe the key reaction chemistry of arenes coordinated to a range of transition metals, including stereoselective reactions and industrially relevant syntheses. We also summarise outstanding examples of catalytic processes. Finally, we give perspectives on the future direction of the field, with respect to both reactions that are stoichiometric in activating metals and those employing catalytic metal.

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