Reaction of di- and tri-valent chromium amides with O2 †

Dioxygen Activation by Siloxide Complexes of Chromium(II) and Chromium(IV)

“…Chromium(II) compounds have been shown to be capable of dioxygen activation. Early work brought evidence for this spectroscopically,1, 2 and in the late 1990s the first chromium(IV) oxo complexes were structurally characterized 3. 4 Within the last years it has been shown, in particular by Nam and Theopold, that molecular chromium(II) centers, ligated by nitrogen donors, in contact with dioxygen formed reactive species featuring superoxido, peroxido, and oxido ligands 5–9.…”

Encouraging Chromium(III) Ions to Form Larger Clusters: Syntheses, Structures, Magnetic Properties and Theoretical Studies of Di‐ and Octametallic Cr Clusters

“…In fact, only two such dinuclear complexes and one dodecanuclear Cr III complex exist. [17,29,30] For the dinuclear complexes there are no reported magnetic measurements and for the Cr 12 cluster the measurements have not been analysed due to the complexity of the system. The crystal structures of two Cr III dimers displaying a linear or quasi-linear [Cr 2 O] 4+ core are known, [24,25] but, as is often the case, there are no studies of the magnetic properties, meaning we have no way to check the validity of our theoretical results.…”

“…[15][16][17][18][19][20][21][22][23] Moreover, there exists little magnetic characterisation of these species and/or their magnetic properties have not been quantitatively analysed because the complexity of the system. [24][25][26][27][28][29][30] Thus, it is very difficult to compare and contrast any results with other Cr III complexes. In addition, in such complicated multiple J systems it is usually possible to find several sets of J values that can reproduce the experimental magnetic behaviour equally well.…”

Dioxygen Activation by Siloxide Complexes of Chromium(II) and Chromium(IV)

“…The Cr1ÀO1/Cr1'ÀO1' distances of 1.698(3) are in the range of bond lengths reported for Cr IV =O double bonds. [8,19,20] In contrast, the Cr1···O1'/Cr1'···O1 distances of 1.955(3) are considerably longer and thus argue against a bis-m-oxido core, the structural motif that previously has been observed [3,4] to form after O 2 activation at Cr II complexes (apart from mononuclear complexes [4][5][6][7][8] ). DFT calculations (see the Supporting Information) reproduced the solid-state structure and thus confirmed that the asymmetry is not circumstantial but has electronic reasons.…”

“…Early work brought evidence for this spectroscopically, [1,2] and in the late 1990s the first chromium(IV) oxo complexes were structurally characterized. [3,4] Within the last years it has been shown, in particular by Nam and Theopold, that molecular chromium(II) centers, ligated by nitrogen donors, in contact with dioxygen formed reactive species featuring superoxido, peroxido, and oxido ligands. [5][6][7][8][9] We believed that siloxide surroundings could lead to novel reactivity in this regard, as chromium(II) sites embedded in a silica matrix are known to have rather special electronic properties, that therefore guarantee the activity of the Phillips catalyst [10,11] employed for the industrial polymerization of ethylene.…”