Enantiospecific C?H Activation Using Ruthenium Nanocatalysts

The activation of C H bonds has revolutionized modern synthetic chemistry. However, no general strategy for enantiospecific C H activation has been developed to date. We herein report an enantiospecific C H activation reaction followed by deuterium incorporation at stereogenic centers. Mechanistic studies suggest that the selectivity for the α‐position of the directing heteroatom results from a four‐membered dimetallacycle as the key intermediate. This work paves the way to novel molecular chemistry on nanoparticles.     

Small Changes Have Consequences: Lessons from Tetrabenzyltitanium and ‐zirconium Surface Organometallic Chemistry

Homoleptic benzyl derivatives of titanium and zirconium have been grafted onto silica that was dehydroxylated at 200 and 700 °C, thereby affording bi‐grafted and mono‐grafted single‐site species, respectively, as shown by a combination of experimental techniques (IR, MAS NMR, EXAFS, and elemental analysis) and theoretical calculations. Marked differences between these compounds and their neopentyl analogues are discussed and rationalized by using DFT. These differences were assigned to the selectivity of the grafting process, which, depending on the structure of the molecular precursors, led to different outcomes in terms of the mono‐ versus bi‐grafted species for the same surface concentration of silanol species. The benzylzirconium derivatives were active towards ethylene polymerization in the absence of an activator and the bi‐grafted species displayed higher activity than their mono‐grafted analogues. In contrast, the benzyltitanium and neopentylzirconium counterparts were not active under similar reaction conditions.     

A comparative study of cupric complexes of dicarboxylic acids and acid-amides ligands

A bis(succinamato)copper(II) complex has been synthetized as well as several cyclic acid-amide ligand complexes. These compounds were characterized by elemental and thermogravimetric analyses, infrared and EPR spectroscopies. Analogous dicarboxylic acids give complexes of 1/1 stoichiometry which are thermally more stable than the acid-amide complexes. All the reported compounds show triplet state EPR spectra similar to cupric acetate. There is no evidence for a participation of the amide functions in cupric ion complexation.     

Magnesium(I) Reduction of Aluminum(III) Hydride Complexes: Generation of Mixed Valence Aluminum (AlI/Al0) Hydride Cluster Compounds, [Al6H8(NR3)2{Mg(β-diketiminate)}4]**

Reduction of a range of amido- and aryloxy-aluminum dihydride complexes, e.g. [AlH₂(NR₃){N(SiMe₃)₂}] (NR₃=NMe₃ or N-methylpiperidine (NMP)), with β-diketiminato dimagnesium(I) reagents, [{(^ArNacnac)Mg}₂] (^ArNacnac=[HC(MeCNAr)₂]⁻, Ar=mesityl (Mes) or 2,6-xylyl (Xyl)), have afforded deep red mixed valence aluminum hydride cluster compounds, [Al₆H₈(NR₃)₂{Mg(^ArNacnac)}₄], which have an average Al oxidation state of +0.66, the lowest for any well-defined aluminum hydride compound. In the solid-state, the clusters are shown to have distorted octahedral Al₆ cores, having zero-valent Al axial sites and mono-valent AlH₂⁻ equatorial units. Several novel by-products were isolated from the reactions that gave the clusters, including the Mg−Al bonded magnesio-aluminate complexes, [(^ArNacnac)(Me₃N)Mg−Al(μ-H)₃[{Mg(^ArNacnac)}₂(μ-H)]]. Computational analyses of one aluminum hydride cluster revealed its Al₆ core to be electronically delocalized, and to possess one unoccupied, and six occupied, skeletal molecular orbitals.