Über Oxidationszahl‐Obergrenzen in der Chemie

Abstract

The concept of oxidation state OS is based on the Lewis electron-pair picture, assigning all bonding electrons to the more electronegative element. It is useful for bookkeeping the electrons, predicting chemical trends and inspiring synthetic chemists. A survey of experimental and quantum-chemical data reveals a limit near +8 for the highest OS in stable neutral chemical compounds under ambient conditions. OS = +9 was observed for isolated [IrO4] + cations in vacuum. The predicted existence of OS = +10 in a Pt compound is still to be verified experimentally. A high OS may involve the metal becoming electronegative and the O −2 ligands losing their closed-shell character as O −1 .

Homoleptic Trifluoromethyl Derivatives of AgI and AgIII

“…Compound 1 shows ac learly-defined 19 FNMR spectrum at room temperature with well-resolved coupling to the 107 Ag (51.84%)a nd 109 Ag (48.16 %) nuclei ( Figure 1a). This is in con- trast to previous indications on the spectroscopic behavior of the [CF 3 AgCF 3 ] À anion in more complex systems. [11] Exchange processes as outlined in Equation (1) , meaning that, in these isoleptic compounds, silver transmits the magnetic information between nuclei in facing ligands less efficiently than gold.…”

“…Exploring the highest oxidation state available foragiven chemicale lementh as always been and continuest ob eafascinating challenge. [3,4] For the mid coinage-metal, silver,t here appearst ob en ow ell-established speciesi no xidations tate over III. [4,5] As might be expected, this is achieved with the most electronegative elements, fluorinea nd oxygen in the powerful oxidizing species AgF 3 ,[ AgF 4 ] À ,a nd Ag 2 O 3 .…”

“…Since the Ag atom lies acrossa n inversion center, the anion is perfectly linear and the CF 3 groups are staggered about the C-Ag-C line (Figure 2a). Whereas the relatedc omplexa nions[ AgCl 2 ] À are associated in loose dimers in the solid state, [19] no such tendency is observed in the [CF 3 AgCF 3 ] À anions. This denotes little residual electrophilicity for the silver center in the latter organometallic anion.…”

“…[12] This feature is due to relativistic gold contraction, which is especially conspicuous in the Au(I)i on. [22] Crystals of the silver compound 1 are isomorphous with those of the gold complex [PPh 4 ][CF 3 AuCF 3 ] and, because both X-ray diffraction data sets have been measured at the same temperature (100 K), the comparison of the corresponding MÀCb ond distances is particularly meaningful. The MÀCb ond elongation observed for Ag versus Au might be responsible for the decrease in the 3 J( 13 C,F) and 4 J(F,F) values noted above.…”

“…[26] This feature is in line with relativistic contraction being less effective in Au III (d 8 )than in Au I (d 10 ). [27] The equilibrium geometries of the homoleptic anions [CF 3 AgCF 3 ] À and [Ag(CF 3 ) 4 ] À in the gas phase (FigureS5) have been calculated at the DFT/M06/Def2-QZVPD level and their electronic structures have been analyzed (see the Supporting Information for details). The most relevante nergy levels ob- tained fort he [Ag(CF 3 ) 4 ] À species are given in Figure 3w ith propers ymmetry labeling.…”