Activation of C–Cl by ground-state aluminum atoms: an EPR and DFT investigation

Abstract

The reaction of ground-state Al atoms with dichloromethane (CH(2)Cl(2)) in an adamantane matrix at 77 K yielded two mononuclear Al species. The magnetic parameters, extracted from the axial EPR spectrum of Species A/A' (g(1) = 2.0037, g(2) = g(3) = 2.0030, a(Al,1) = 1307 MHz, a(Al,2) = a(Al,3) = 1273 MHz, a(35Cl) = 34 MHz and a(37Cl) = 28 MHz) were assigned to the Al-atom insertion product, ClCH(2)AlCl. Density functional theory (DFT) calculations of the values of the Al and Cl hyperfine interaction (hfi) of the Cl(1)-Cl(2)gauche conformer were in close agreement with the experimental values of ClCH(2)AlCl. The second species, B/B', had identical magnetic parameters to those of ClCH(2)AlCl with the exception that the Al hfi was 15% smaller. Coordination of a ligand, possessing a lone pair of electrons, to the Al atom of the insertion product, [ClCH(2)AlCl]:X, could cause the a(Al) to decrease by 15%. Alternatively, it is possible that the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl is also isolated in the matrix. Support for the spectral assignments is given by calculation of the nuclear hfi of [ClCH(2)AlCl]:H(2)O and the Cl(1)-Cl(2) anti conformer of ClCH(2)AlCl using a DFT method. The potential energy hypersurface for an Al atom approaching CH(2)Cl(2), calculated at the B3LYP level, suggests that Al atom abstraction of Cl forming AlCl and CH(2)Cl is favoured in the gas phase. When produced in a matrix, the close proximity of AlCl and CH(2)Cl could account for the formation of ClCH(2)AlCl. EPR evidence was also found for the formation of the CHCl(2) radical.

Rapid Aluminum Nanoparticle Production by Milling in NH3 and CH3NH2 Atmospheres: An Experimental and Theoretical Study

“…Here, we report a study of nanoparticle production by dry milling aluminum in NH 3 and monomethylamine (MMA) atmospheres, and we compare the results to analogous milling experiments in H 2 , Ar, and N 2 . NH 3 and MMA were chosen because amines are known to bind to and react with aluminum surfaces. − As shown below, nanoparticle production is more efficient in these gases than in reactive liquid milling agents, including alkylamines. Furthermore, the particle size distributions are narrower, without the large concentrations of micron scale particles seen for liquid agents.…”

Aluminum Atom Activation of C–S Bonds: An EPR Study of the Intermediates Formed in the Reaction Between Aluminum Atoms and Dialkyl Sulfides

“…Aluminum atoms activate a number of different bonds including C–H of CH 4 , OH of H 2 O, , SH of H 2 S, SeH of H 2 Se, NH of NH 3 and CpNH 2 , C–O of CH 3 OCH 3 , , C–Br of CpBr, C–Cl of CH 2 Cl 2 , C–N of CpNH 2 , and the H–Cl bond, , under cryogenic conditions, producing divalent mononuclear aluminum species. These aluminum atom insertion products are paramagnetic and have been characterized by electron paramagnetic resonance (EPR) spectroscopy.…”