Mechanochemical Synthesis of Non-Solvated Dialkylalumanyl Anion and XPS Characterization of Al(I) and Al(II) Species.

A non-solvated alkyl-substituted Al(I) anion dimer was synthesized by a reduction of haloalumane precursor using a mechanochemical method. The crystallographic and theoretical analysis revealed its structure and electronic properties. Experimental XPS analysis of the Al(I) anions with reference compounds revealed the lower Al 2p binding energy corresponds to the lower oxidation state of Al species. It should be emphasized that the experimentally obtained XPS binding energies were reproduced by delta SCF calculations and were linearly correlated with NPA charges and 2p orbital energies.

A meta-Selective C-H Alumination of Mono-Substituted Benzene by Using An Alkyl-Substituted Al Anion through Hydride-Eliminating SN Ar Reaction.

Reaction of an Al-centered anion with toluene proceeded to form C-H cleaved product with a perfect meta-selectivity and a relatively small kinetic isotope effect (KIE, kH /kD =1.51). DFT calculations suggested a two-step reaction mechanism and electronically controlled meta-selectivity arising from the electron-donating methyl group. The reaction with other mono-substituted arenes was also investigated.

An Alumanylyttrium Complex with an Absorption due to a Transition from the Al-Y Bond to an Unoccupied d-Orbital.

The reaction between a dialkyl-substituted alumanyl anion and [Y(CH2 SiMe3 )2 (thf)3 ][BPh4 ] resulted in the formation of (dialkylalumanyl)yttrium complex 2, which exhibits the first 2-center-2-electron (2 c-2 e) Al-Y bond. The 1 H and 13 C NMR spectra of 2 together with an X-ray crystallographic analysis indicated a C2v symmetrical structure. DFT calculations on 2 revealed that its LUMO consists of overlapping 3 p- and 4 d-orbitals of the Al and Y atoms, respectively, and that the HOMO-LUMO gap is narrow. The UV/Vis spectrum of 2 exhibited a visible absorption at 432 nm, which suggests that the strong σ-donating and π-accepting character of the three-coordinate dialkylalumanyl ligand generates a colored d0 -complex that does not contain any π-electrons.

Cycloaddition of Dialkylalumanyl Anion toward Unsaturated Hydrocarbons in (1+2) and (1+4) Modes.

The reactivity of dialkylalumanyl anion (1) towards naphthalene, anthracene, diphenylacetylene, and (E)/(Z)-stilbenes was investigated. The compound 1 reacts with naphthalene and anthracene through (1+4) cyclization, giving Al-containing norbornadiene derivatives. In the reaction of 1 with diphenylacetylene and (E)/(Z)-stilbenes, (1+2) cyclization proceeded to form Al-C-C three-membered rings. Cyclization toward (E)- or (Z)-stilbenes solely gave a trans-cycloadduct. DFT calculations revealed that the cycloaddition of 1 with (Z)-stilbene proceeds via a single transition state with a carbanion character, which results in the selectivity towards the trans-cycloadduct.

Synthesis of Silaphenalenes by Ruthenium-Catalyzed Annulation between 1-Naphthylsilanes and Internal Alkynes through C-H Bond Cleavage.

Ruthenium-catalyzed annulation of 1-naphthylsilanes with internal alkynes afforded silaphenalenes through cleavage of the C-H bond at the 8-position of the naphthalene. [RuH2 (CO){P(p-FC6 H4 )3 }3 ] efficiently catalyzed the reaction. The use of 1-naphthyldiphenylsilane as a substrate resulted in a better yield of the annulation product compared to the use of silanes with alkyl groups on the silicon atom. Internal alkynes with both aryl and alkyl groups were tolerated in this reaction.