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O2activation at a chromium(II) siloxide complex in propionitrile leads to a chromium(III) complex with an end-on bound superoxide ligand, while the reaction in tetrahydrofuran leads to a side-on peroxo chromium(IV) compound. The superoxide reacts faster with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl hydroxylamine while the peroxide, unlike the superoxide, proved capable of deformylating aldehydes. The system was found to represent a unique case, where even a switching between the two structures can be achieved via the solvent; its ability to coordinate at the position transto the O2ligand is decisive, as supported by density functional theory studies. Altogether, the results show that subtle changes can determine for an initially formed metal-dioxygen adduct, whether it exists as a superoxide or a peroxide, which thus merits consideration in discussions on mechanisms and possible reaction routes.

The behavior of a xanthene derivative with one bismuthane and one phosphane function, Xan(PPh2)(BiPh2), as a ligand toward group 11 metal cations was investigated. It was found that contact with [Cu(MeCN)4]OTf, AgOTf, [Au(PPh3)OTf], in all three cases leads to a transformation of Xan(PPh2)(BiPh2) into a tridentate PBiP system, where a BiPh unit connects two phosphinoxanthyl moieties. In the resulting compounds, [PhBi(Xan(PPh2))2Cu]OTf, 1, [PhBi(Xan(PPh2))2Ag]OTf, 2, and [PhBi(Xan(PPh2))2AuPPh3]OTf, 3, the metal cations are coordinated tetrahedrally by two phosphane donors, one bismuthane donor and a fourth ligand, corresponding to OTf–in case of 1and 2, or PPh3in the case of 3. DFT calculations in combination with NBO analysis showed that the bismuth atoms in these PBiP ligands act as σ-donors. 3thus corresponds to the first known AuI← BiIIIcomplex.