Oxygen radical character in group 11 oxygen fluorides

Infrared Spectroscopic and Theoretical Investigations of Group 13 Oxyfluorides OMF2 and OMF (M=B, Al, Ga, In)

Group 13 oxyfluorides OMF2 were produced by the reactions of laser-ablated group 13 atoms M (M=B, Al, Ga and In) with OF2 and isolated in excess neon or argon matrices at 5 K. These molecules were characterized by matrix-isolation infrared spectroscopy and isotopic substitution experiments in conjunction with quantum-chemical calculations. The calculations indicate that the OMF2 molecules have a 2 B2 ground state with C2v symmetry. The computed molecular orbitals and spin densities show that the unpaired electron is mainly located at the terminal oxygen atom. Oxo monofluorides OMF were only observed in solid argon matrices and exhibit a linear structure in the singlet ground state. The M-O bonding in the OMF molecules can be rationalized as highly polar multiple bonds based on the calculated bond lengths and natural resonance theory (NRT) analyses. In particular, the molecular orbitals of OBF exhibit the character of a triple bond B-O resulting from two degenerate electron-sharing π bonds and an O→B dative σ bond formed by the oxygen 2p lone pair which donates electron density to the boron empty 2p orbital.

Terminal Au-N and Au-O Units in Organometallic Frames

Since gold is located well beyond the oxo wall, chemical species with terminal Au-N and Au-O units are extremely rare and limited to low coordination numbers. We report here that these unusual units can be trapped within a suitable organometallic frame. Thus, the terminal auronitrene and auroxyl derivatives [(CF₃ )₃ AuN]^- and [(CF₃ )₃ AuO]^- were identified as local minima by calculation. These open-shell, high-energy ions were experimentally detected by tandem mass spectrometry (MS² ): They respectively arise by N₂ or NO₂ dissociation from the corresponding precursor species [(CF₃ )₃ Au(N₃ )]^- and [(CF₃ )₃ Au(ONO₂ )]^- in the gas phase. Together with the known fluoride derivative [(CF₃ )₃ AuF]^- , they form an interesting series of isoleptic and alloelectronic complexes of the highly acidic organogold(iii) moiety (CF₃ )₃ Au with singly charged anions X^- of the most electronegative elements (X=F, O, N). Ligand-field inversion in all these [(CF₃ )₃ AuX]^- species results in the localization of unpaired electrons at the N and O atoms.

Molecular oxofluorides OMFn of nickel, palladium and platinum: oxyl radicals with moderate ligand field inversion

High-valent late transition metal oxo compounds attracted attention because of their peculiar metal–oxygen bond. Their oxo ligands exhibit an electrophilic and distinct radical oxyl (O˙⁻) rather than the more common nucleophilic (O²⁻) character.

σ-Noninnocence: Masked Phenyl-Cation Transfer at Formal NiIV

Reductive elimination is an elementary organometallic reaction step involving a formal oxidation state change of -2 at a transition-metal center. For a series of formal high-valent NiIV complexes, aryl-CF3 bond-forming reductive elimination was reported to occur readily (Bour et al. J. Am. Chem. Soc. 2015, 137, 8034-8037). We report a computational analysis of this reaction and find that, unexpectedly, the formal NiIV centers are better described as approaching a +II oxidation state, originating from highly covalent metal-ligand bonds, a phenomenon attributable to σ-noninnocence. A direct consequence is that the elimination of aryl-CF3 products occurs in an essentially redox-neutral fashion, as opposed to a reductive elimination. This is supported by an electron flow analysis which shows that an anionic CF3 group is transferred to an electrophilic aryl group. The uncovered role of σ-noninnocence in metal-ligand bonding, and of an essentially redox-neutral elimination as an elementary organometallic reaction step, may constitute concepts of broad relevance to organometallic chemistry.