482323-03-5Relevant academic research and scientific papers
Stabilization of β-Diketiminato Nickel(I) with Alkaline Metal Halide Entities for Small Molecule Activation
Holze, Patrick,Braun-Cula, Beatrice,Mebs, Stefan,Limberg, Christian
, p. 973 - 981 (2018/05/30)
The reduction of the β-diketiminato nickel(II) halide complex [LtBuNiIIBr] [LtBu = CH(CtBuNdipp)2–, dipp = 2,6-diisopropylphenyl] with potassium sources proceeds via the initial formation of [(LtBuNiI)x(μ-Br)xKx] aggregates, which could be isolated and characterized for x = ∞ and 6. The KBr equivalents readily give way to external donors or substrates to be activated at the central nickel(I) atoms. To test, in how far the steric bulk induced by the residues at [LtBu]– influences the formation of the KBr adducts β-diketiminato ligands with less steric congestion, namely LMe6 and LMe7 [LMe6 = CH(CMeNdmp)2–, LMe7 = CMe(CMeNdmp)2–, dmp = 2,6-dimethylphenyl] were employed. Through deprotonation of HLMe6 with nBuLi followed by treatment with NiBr2(dme) the nickel(II) precursor compound [LMe6NiII(μ-Br)2Li(THF)2] was prepared and shown to enter an equilibrium with [(LMe6NiIIBr)2] and LiBr in solution; [(LMe6NiIIBr)2] could be accessed also independently. Syntheses of the complexes [LMe7NiII(μ-Br)2Li(THF)2] and [(LMe7NiIIBr)2] could be achieved analogously. To test the potential of nickel complexes with the LMe6 and LMe7 ligands for the activation of N2 the thf-free [(LMe6/7NiIIBr)2] complexes were reduced with potassium in an N2 atmosphere. This led neither to a KBr adduct nor to an N2 complex but to the dimer [(LMe6NiI)2], as the smaller ligands allow an efficient interaction of the central nickel atoms with the aryl rings.
Modulating the steric, electronic, and catalytic properties of Cp* ruthenium half-sandwich complexes with β-diketiminato ligands
Phillips, Andrew D.,Thommes, Katrin,Scopelliti, Rosario,Gandolfi, Claudio,Albrecht, Martin,Severin, Kay,Schreiber, Dominique F.,Dyson, Paul J.
, p. 6119 - 6132 (2012/01/04)
Five 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.
