The photolytic reactions of AlX (X = F, Cl, and Br) with O(2) in solid argon matrixes are shown to yield the peroxo species XAlO(2), all exhibiting C(2)(v)() symmetry. The species were identified and characterized by means of IR spectroscopy allied with quantum mechanical calculations. In addition to singlet XAlO(2) as the main product of the reaction of AlX, the experiments give clear evidence for the formation of XAl(mu-O)(2)AlX, by the reaction of the dimer (AlX)(2), which is also known to be present in the matrixes upon deposition. Finally, weak IR absorptions were tentatively assigned to XAlO(2) in its triplet electronic state. According to our calculations, the singlet-triplet gap amounts to about 40 kJ mol(-1) for all species. The properties of the peroxide species invite comparison with previously investigated dioxygen complexes, as well as the superoxide species XAlOO and various possible products of the reaction of (AlX)(2) dimers.

The spontaneous and photolytically induced reactions of AlF and AlCl in the presence of HCl and HBr in solid argon matrices were followed and the products identified and characterized by means of IR spectroscopy. Quantum mechanical calculations allow for a further evaluation of the properties of the reaction products. These are the adducts AlF.HCl, AlF.HBr, and AlCl.HBr, representing the products of spontaneous reactions, and the trivalent Al(III) hydrides HAlFCl, HAlFBr, and HAlClBr, which were formed upon photoactivation of these complexes. All three hydrides are planar molecules (C(s)() symmetry) with bond angles in agreement with the predictions of the VSEPR theory. In addition, the mixed halides AlFCl(2), AlFBr(2), and AlClBr(2) were formed upon photolysis. The bisadducts AlF.(HCl)(2) and AlF.(HBr)(2) are likely to be the precursors to these species.

Durch eine photolytisch induzierte Reaktion von AlF mit O2 in einer Argonmatrix gelang die Synthese der ersten Peroxo‐ und Bis‐Superoxokomplexe des Aluminiums: FAlO2 und FAl(O2)2 (siehe Bild). Die Verbindungen wurden anhand ihrer IR‐Spektren sowie durch DFT‐ und Ab‐initio‐Rechnungen identifiziert und strukturell charakterisiert.

Matrix isolation has been used to study the photolytically induced reaction of AlX (X = F, Cl, or Br) with O(2). The peroxo and bisperoxo compounds XAlO(2) and XAl(O(2))(2) are found to be the products of these reactions. While the peroxo species XAlO(2) were already addressed in a separate work, we concentrate herein on the bissuperoxo complexes XAl(O(2))(2), which are to our knowledge the first examples of such complexes with Al centers. Our IR spectroscopic results taking in the effect of isotopic substitution ((16)O/(18)O) allied with quantum chemical calculations show that the O(2) moieties in these complexes are side-on coordinated, leading to an overall C(2)(v)() symmetry of the complexes and a spin multiplicity of 3. The O-O distance of about 1.366 A argues for the presence of superoxide units. The force constants are, however, somewhat smaller than expected for a superoxide anion and indicate that the bonding in the complexes cannot be described simply on the basis of an ionic model. Interestingly a photoinduced intramolecular isotopic scrambling process is observed for the compounds resulting in partial conversion of the XAl((16)O(2))((18)O)(2) isotopomer into XAl((16)O(18)O)((16)O(18)O). The properties of the complexes will be compared to those of complexes to transition metal centers.

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