Modulating the Steric, Electronic, and Catalytic Properties of Cp* Ruthenium Half-Sandwich Complexes with β-Diketiminato Ligands

Phillips, Andrew D.Thommes, KatrinScopelliti, RosarioGandolfi, ClaudioAlbrecht, MartinSeverin, KaySchreiber, Dominique F.Dyson, Paul J.2011-11-232011-11-23201110.1021/om2006479https://infoscience.epfl.ch/handle/20.500.14299/72787WOS:000297090200010Five different types of β-diketiminate ligands, bearing electron-donating to strongly electron-withdrawing substituents, were synthesized and used in the synthesis of Cp* ruthenium complexes (Cp* = η5-C5Me5). One series consists of complexes with a covalent RuIII–Cl bond, and the other series features a reduced RuII center, where the chloride is abstracted by treatment of the corresponding RuIII compounds with Zn or Mg. All compounds were characterized by single-crystal X-ray diffraction, UV–visible spectroscopy, and cyclic voltammetry. In the case of RuII complexes, solution NMR techniques provided key information regarding the electronic and structural differences induced by the different β-diketiminate ligands employed. Capitalizing on the facile reduction–oxidation cycle of the Cp* ruthenium β-diketiminato complexes, catalytic atom transfer radical addition (ATRA) and cyclization (ATRC) reactions were performed on relevant substrates. The turnover rates are strongly dependent on the type of β-diketiminate used, where ligands with electron-withdrawing substituents, i.e., trifluoromethyl groups, provided complexes that efficiently catalyze the addition of CCl4 or toluenesulfonyl chloride to styrene. In contrast, complexes with electron-donating substituents on the β-diketiminate promoted efficient ATR cyclization of N-allyl-N-phenyltrichloroacetamide and 2,2,2-trichloroethyl ether. Thus, the overall product conversion and yield are dependent on matching the ligand substitution pattern of the catalyst to the type of substrate.Transfer Radical-AdditionOlefin Metathesis CatalystsH Bond ActivationCyclization Atrc ReactionsEnol-Ester SynthesisSchiff-Base LigandsKharasch AdditionEthylene PolymerizationOrganic-SynthesisStructural-CharacterizationModulating the Steric, Electronic, and Catalytic Properties of Cp* Ruthenium Half-Sandwich Complexes with β-Diketiminato Ligandstext::journal::journal article::research article