ABSTRACT
The employment of the hexyl-substituted anion [HexCB11 Cl11 ]- allowed the synthesis of a ZnII species, Zn[HexCB11 Cl11 ]2 , 3, in which the Zn2+ cation is only weakly coordinated to two carborate counterions and that is soluble in low polarity organic solvents such as bromobenzene. DOSY NMR studies show the facile displacement of at least one of the counterions, and this near nakedness of the cation results in high catalytic activity in the hydrosilylation of 1-hexene and 1-methyl-1cyclohexene. Fluoride ion affinity (FIA) calculations reveal a solution Lewis acidity of 3 (FIA=262.1â kJ mol-1 ) that is higher than that of the landmark Lewis acid B(C6 F5 )3 (FIA=220.5â kJ mol-1 ). This high Lewis acidity leads to a high activity in catalytic CO2 and Ph2 CO reduction by Et3 SiH and hydrogenation of 1,1-diphenylethylene using 1,4-cyclohexadiene as the hydrogen source. Compound 3 was characterized by multinuclear NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, and DFT studies.
ABSTRACT
An original multi-cooperative catalytic approach was developed by combining metal-ligand cooperation and Lewis acid activation. The [(SCS)Pd]2 complex featuring a non-innocent indenediide-based ligand was found to be a very efficient and versatile catalyst for the Conia-ene reaction, when associated with Mg(OTf)2. The reaction operates at low catalytic loadings under mild conditions with HFIP as a co-solvent. It works with a variety of substrates, including those bearing internal alkynes. It displays complete 5-exo vs. 6-endo regio-selectivity. In addition, except for the highly congested t Bu-substituent, the reaction occurs with high Z vs. E stereo-selectivity, making it synthetically useful and complementary to known catalysts.
ABSTRACT
Cycling between Au(i) and Au(iii) is challenging, so gold-catalyzed cross-couplings are rare. The (MeDalphos)AuCl complex, which we showed was prone to undergo oxidative addition, is reported here to efficiently catalyze the C-N coupling of aryl iodides and amines. The transformation does not require an external oxidant or a directing group. It is robust and works with a wide scope of aryl iodides and N-nucleophiles under mild conditions. Mechanistic studies, including the NMR and MS characterization of a key aryl amido Au(iii) complex, strongly support a 2e redox cycle in which oxidative addition precedes transmetalation and reductive elimination is the rate-determining step.
