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We have investigated the model system H2S∴SH2 +, i.e., the sulfur−sulfur bound dimer radical cation of H2S, using both density functional theory (LDA, BP86, PW91) and traditional ab initio theory (up to CCSD(T)). Our purpose is to better understand the nature of the three-electron bond. The S−S bond length is 2.886 Å and the bond enthalpy (for 298.15 K) amounts to −40.7 kcal/mol at the BP86/TZ2P level. The best ab initio estimates for the S−S bond strength (our CCSD(T)/6-311++G(2df,2pd)//MP2(full) and literature values) are some 10 kcal/mol weaker than those from nonlocal DFT. It is shown, using an energy decomposition scheme for open-shell systems, that the sulfur−sulfur bond (ΔE = ΔE 2c-3e + ΔE elst) is nearly 60% provided by the three-electron bond (ΔE 2c-3e) between the unpaired sulfur 3p x electron on H2S+• and the sulfur 3p x lone pair on H2S; electrostatic attraction (ΔE elst) is important, too, with a contribution of somewhat more than 40%. We show furthermore that the three-electron bond (ΔE 2c-3e = ΔE 2c- 1e + ΔE Pauli) can be conceived as and quantitatively analyzed in terms of a one-electron bond (ΔE 2c-1e), arising from the β-electron of the H2S lone pair interacting with the corresponding empty β-spin orbital of H2S+•, opposed by the Pauli repulsion (ΔE Pauli) between the α-electrons of the H2S lone pair and H2S+• SOMO.

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An unstable intermediate has been detected and isolated in the reaction of ozone with C60 in solution. On the basis of its UV−vis absorption spectrum, the measured release of O2 in its decay to the epoxide C60O, and the first-order kinetics of this reaction, the intermediate has been identified as C60O3, a primary ozonide. This [6,6]-closed adduct of ozone with C60 thermally dissociates to C60O plus O2 in toluene solution, octane solution, and the solid phase with rate constants (at 23 °C) of 4.6 × 10-2, 1.3 × 10-3, and 3.0 × 10-3 min-1, respectively. The activation energy for dissociation in toluene solution is approximately 89 kJ mol-1. Semiempirical quantum calculations indicate that the formation and subsequent dissociation of C60O3 are both exothermic processes. These findings constitute the first observation of a fullerene ozonide.