Dmitry A. Grishanov

Despite growing interest in the potential applications of p-block hydroperoxo complexes, the chemistry of inorganic hydroperoxides remains largely unexplored. For instance, single-crystal structures of antimony hydroperoxo complexes have not been reported to date. Herein, we present the synthesis of six triaryl and trialkylantimony dihydroperoxides [Me₃Sb(OOH)₂, Me₃Sb(OOH)₂·H₂O, Ph₃Sb(OOH)₂·0.75(C₄H₈O), Ph₃Sb(OOH)₂·2CH₃OH, pTol₃Sb(OOH)₂, pTol₃Sb(OOH)₂·2(C₄H₈O)], obtained by the reaction of the corresponding dibromide antimony(V) complexes with an excess of highly concentrated hydrogen peroxide in the presence of ammonia. The obtained compounds were characterized by single-crystal and powder X-ray diffraction, Fourier transform infrared and Raman spectroscopies, and thermal analysis. The crystal structures of all six compounds reveal hydrogen-bonded networks formed by hydroperoxo ligands. In addition to the previously reported double hydrogen bonding, new types of hydrogen-bonded motifs formed by hydroperoxo ligands were found, including infinite hydroperoxo chains. Solid-state density functional theory calculation of Me₃Sb(OOH)₂ revealed reasonably strong hydrogen bonding between OOH ligands with an energy of 35 kJ/mol. Additionally, the potential application of Ph₃Sb(OOH)₂·0.75(C₄H₈O) as a two-electron oxidant for the enantioselective epoxidation of olefins was investigated in comparison with Ph₃SiOOH, Ph₃PbOOH, t-BuOOH, and H₂O₂.

The synthesis, transformation, and application in catalysis of triphenyllead hydroperoxide, the first dioxygen lead complex, are described. Triphenyllead hydroperoxide is characterized by ²⁰⁷Pb nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and single-crystal X-ray diffraction, revealing the first one-dimensional (1D) coordination peroxo polymer. Photolytic isomorphous transformation of Ph₃PbOOH yields a mixed hydroxo/superoxo crystalline structure, the first nonalkali superoxo crystalline metal salt, which is stable up to 100 °C. Upon further photolysis, another isomorphous transformation of the superoxide to hydroxide is observed. These are the first single-crystal-to-single-crystal hydroperoxide-to-superoxide and then to hydroxide transformations reported to date. Photolysis of triphenyllead hydroperoxide yields two forms of superoxide-doped crystalline structures that are distinguished by widely different characteristic relaxation times. The use of Ph₃PbOOH as an easy-to-handle solid two-electron oxidant for the highly enantioselective epoxidation of olefins is described.

A breakthrough “superoxide colloidal solution route” for low-temperature synthesis of barium and strontium stannate perovskites and their doped analogues was recently introduced. The synthesis starts from hydrogen peroxide-rich stannate solutions and yields a so-called “crystalline superoxide molecular cluster” that is converted by low temperature (3(OOH)(OO) phase (BHHPS). EPR and Raman spectroscopy studies reveal the absence of superoxide in this crystalline phase. FTIR of the deuterated sample, ¹¹⁹Sn NMR, and elemental analysis uncovered the empirical formula, H₄O₇SnBa with two peroxides per each tin element. Rietveld refinement of the XRD confirms the BHHPS cubic phase with replacement of the perovskite oxygen atoms by the OH- and OOH-ligands and peroxobridging groups.

2-Aminobenzimidazole peroxosolvate – the third H ₂ O ₂ crystalline adduct stabilized with the maximum possible number of hydrogen bonds formed by one hydrogen peroxide molecule.

Triphenyl silicon hydroperoxide and its isostructural germanium complex were characterized by single crystal X-ray analysis revealing H-bonding of two triphenylhydroperoxocomplexes, with each hydroperoxo ligand acting as a hydrogen donor and a hydrogen acceptor. Only two other structures with localized protons of hydroperoxo complexes' main group elements (boron and tin) are known (compared to 130 p-block element peroxo compounds) and both exhibit the same hydroperoxo double hydrogen bonding motif. The reaction of the hydroperoxo complexes with triphenylgermanium chloride to give the dinuclear peroxobridged germanium complex demonstrates the higher reactivity of the hydroperoxo moieties compared to the peroxo moiety. DFT calculations provide an estimate of the hydroperoxo double hydrogen bond energies: 62.8 and 63.6 kJ mol⁻¹ for triphenyl silicon, 63.6 and 65 kJ mol⁻¹ for the germanium complex.

Herein, peroxosolvates of the cyclic dipeptides disarcosine (C₆H₁₀N₂O₂·H₂O₂), dialanine (C₆H₁₀N₂O₂·2(H₂O₂)), diglycine (C₄H₆N₂O₂·2(H₂O₂) and C₄H₆N₂O₂·1.786(H₂O₂)·0.214(H₂O)) were synthesized and studied by single crystal X-ray analysis and periodic DFT calculations. The hydrogen bonding networks of cyclic diglycine peroxosolvate and isomorphous hydrate were characterized using Bader analysis of periodic electron density and empirical correlations between enthalpy and metric and spectroscopic parameters of the H-bond. The obtained data for the peroxosolvate of cyclic dipeptides provided a molecular-level insight into the non-redox interaction of hydrogen peroxide with the peptide backbone in aqueous systems. In all structures, H₂O₂ acts as a proton donor in two hydrogen bonds. The carbonyl oxygen atom of the peptide (–CO–NH–) forms a relatively stronger hydrogen bond with the hydrogen peroxide molecule (32–34 kJ mol⁻¹) as compared to that with water in the isomorphous hydrate of cyclic diglycine (26–28 kJ mol⁻¹). The hydrogen atom of the peptide group (–CO–NH–) can form a moderate H-bond with hydrogen peroxide (25 kJ mol⁻¹). The total hydrogen bonding energy of the peroxosolvate is higher than that of the corresponding hydrate (91 vs. 82 kJ mol⁻¹). The stronger hydrogen bonding in peroxosolvates as compared to that in the hydrate and the fact that the intermolecular H-bonds C(O)NH⋯OCNH between cyclic dipeptides are not found in peroxosolvates, despite being prevalent in the structure of nonsolvated dipeptides, imply that hydrogen peroxide can interfere with the secondary structure of proteins via a mechanism that can lead to reversible inhibition or signaling in living systems.

High, nearly 100%, yield synthesis of ammonium peroxogermanate (APG), (NH₄)₆[Ge₆(μ-OO)₆(μ-O)₆(OH)₆]·6H₂O, is presented, and its crystal structure is determined by single crystal X-ray study. It comprises centrosymmetric hexanuclear peroxogermanate anions [Ge₆(μ-OO)₆(μ-O)₆(OH)₆]^6– with six μ-oxo- and six μ-peroxo groups forming negatively charged layers. The space between these layers is filled by ammonium cations and water molecules, forming a highly stable structure due to hydrogen bonding. Highly soluble macroporous amorphous germanium oxide (HSGO) is then synthesized by mild treatment of APG. The compound forms highly oversaturated metastable germanium oxide solution with a solubility of 100 g/L, over 20 times higher than the solubility of amorphous germanium oxide. HSGO solution is a versatile reagent that can react with basic and acidic reagents to give a diverse range of salts including, e.g., germanium sulfide, germanium hydrophosphate, and potassium germanate. In the absence of acid or base, the aqueous HSGO solution yields hexagonal germanium oxide under ambient conditions.