Metal complexes containing redox-active ligands in oxidation of hydrocarbons and alcohols: A review

Ligands are innocent when they allow oxidation states of the central atoms to be defined. A noninnocent (or redox) ligand is a ligand in a metal complex where the oxidation state is not clear. Dioxygen can be a noninnocent species, since it exists in two oxidation states, i.e., superoxide (O2 −) and peroxide (O2 2−). This review is devoted to oxidations of C–H compounds (saturated and aromatic hydrocarbons) and alcohols with peroxides (hydrogen peroxide, tert-butyl hydroperoxide) catalyzed by complexes of transition and nontransition metals containing innocent and noninnocent ligands. In many cases, the oxidation is induced by hydroxyl radicals. The mechanisms of the formation of hydroxyl radicals from H2 O2 under the action of transition (iron, copper, vanadium, rhenium, etc.) and nontransition (aluminum, gallium, bismuth, etc.) metal ions are discussed. It has been demonstrated that the participation of the second hydrogen peroxide molecule leads to the rapture of O–O bond, and, as a result, to the facilitation of hydroxyl radical generation. The oxidation of alkanes induced by hydroxyl radicals leads to the formation of relatively unstable alkyl hydroperoxides. The data on regioselectivity in alkane oxidation allowed us to identify an oxidizing species generated in the decomposition of hydrogen peroxide: (hydroxyl radical or another species). The values of the ratio-of-rate constants of the interaction between an oxidizing species and solvent acetonitrile or alkane gives either the kinetic support for the nature of the oxidizing species or establishes the mechanism of the induction of oxidation catalyzed by a concrete compound. In the case of a bulky catalyst molecule, the ratio of hydroxyl radical attack rates upon the acetonitrile molecule and alkane becomes higher. This can be expanded if we assume that the reactions of hydroxyl radicals occur in a cavity inside a voluminous catalyst molecule, where the ratio of the local concentrations of acetonitrile and alkane is higher than in the whole reaction volume. The works of the authors of this review in this field are described in more detail herein. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Oxidations By The System "hydrogen Peroxide-dinuclear Manganese(iv) Complex-carboxylic Acid": Part 5. Epoxidation Of Olefins Including Natural Terpenes

Dinuclear manganese(IV) complex [LMn(O) 3MnL](PF 6) 2 (L = 1,4,7-trimethyl-1,4,7-triazacyclononane) efficiently catalyzes epoxidation of sterically accessible olefins, including natural compounds by hydrogen peroxide in acetonitrile at room temperature if a small amount of a carboxylic acid (for example, oxalic acid) is present in the solution.. Dinuclear manganese(IV) complex [LMn(O) 3MnL](PF 6) 2 (1, L = 1,4,7-trimethyl-1,4,7-triazacyclononane) efficiently catalyzes epoxidation of sterically accessible olefins, including natural compounds by hydrogen peroxide in acetonitrile at room temperature if a small amount of a carboxylic acid is present in the solution. The kinetics of dec-1-ene epoxidation and accompanying dioxygen evolution (catalase activity) under the action of this system in the presence of acetic acid has been studied. The initial rates of both epoxidation and O 2 evolution are proportional to the catalyst initial concentration. First order has been found for catalyst 1 for both processes, whereas the rate dependences of the dec-1-ene epoxidation is first order and the O 2 evolution is second order for H 2O 2. The epoxidation rate increases and the O 2 evolution rate decreases with growing of acetic acid concentration. Zero order has been found for dec-1-ene in its epoxidation. The reaction proceeds with an induction period for a few minutes during which changes in the electronic spectra of the reaction solution are observed. It has been proposed that the processes of the alkane oxidation and dioxygen evolution on the one hand and of the olefin epoxidation on the other hand are induced by different intermediate species. An assumption has been made that the epoxidation occurs with participation of oxo-hydroxy Mn(V) derivative [LMn V(O)(O) 2(HO)Mn IVL] 2+, whereas di(hydroperoxy) complex [LMn III(OOH)(O) 2(HOO)Mn IVL] + is responsible for the alkane oxidation with simultaneous dioxygen evolution. The following equations for the initial rates were proposed for [CH 3CO 2H] = 0.25 mol dm -3: d[epoxide]/dt = k eff(epoxide)[1][H 2O 2] with k eff(epoxide) = 2.8-3.7 mol -1 dm 3 s -1; d[CyOOH]/dt = k eff(CyOOH)[1][H 2O 2] 2[CyH] with k eff(CyOOH) = 4.1-6.2 mol -3 dm 9 s -1; d[O 2]/dt = k eff(O 2)[1][H 2O 2] 2 with k eff(O 2) = 2.8-7.0 mol -2 dm 6 s -1. Many different carboxylic acids were checked as cocatalysts and it has been found that oxalic acid acts with the highest efficiency in the epoxidation whereas the accompanying catalase activity of the system is very low in this case. It has been also demonstrated that complex 1 is unique catalyst because similar compounds containing only one Mn(IV) center (2) or dinuclear complex with bridging phenylboronic acid (3) are very poor catalysts in the olefin epoxidation. No epoxidation has been found when hydrogen peroxide was replaced by tert-butyl hydroperoxide. The system based on 1, H 2O 2 and acetic and/or oxalic acid was employed for the efficient epoxidation of terpenes limonene, citral, carvone and linalool, while other terpenes containing sterically hindered double bonds (citronellal, α- and β-isomers of pinene) were epoxidized only with <15% yield. Using limonene as example, it has been demonstrated that regioselectivity of the epoxidation (predominant formation of product with addition of the O atom either to internal ring or external double bond) can be controlled by replacing acetic acid by oxalic acid. © 2004 Elsevier B.V. All rights reserved.2221-2103119Wieghardt, K., Bossek, U., Nuber, B., Weiss, J., Bonvoisin, J., Corbella, M., Vitols, S.E., Girerd, J.J., (1988) J. Am. Chem. Soc., 110, pp. 7398-7411Bossek, U., Weyhermüller, T., Wieghardt, K., Nuber, B., Weiss, J., (1990) J. Am. Chem. Soc., 112, pp. 6387-6388Koek, J.H., Russell, S.W., Van Der Wolf, L., Hage, R., Warnaar, J.B., Spek, A.L., Kerschner, J., Delpizzo, L., (1996) J. Chem. Soc., Dalton Trans., pp. 353-362Pulacchini, S., Shastri, K., Dixon, N.C., Watkinson, M., (2001) Synthesis, pp. 2381-2383Hage, R., Iburg, J.E., Kerschner, J., Koek, J.H., Lempers, E.L.M., Martens, R.J., Racherla, U.S., Krijnen, B., (1994) Nature, 369, pp. 637-639Quee-Smith, V.C., Delpizzo, L., Jureller, S.H., Kerschner, J.L., Hage, R., (1996) Inorg. Chem., 35, pp. 6461-6465Gilbert, B.C., Kamp, N.W.J., Lindsay Smith, J.R., Oakes, J., (1997) J. Chem. Soc., Perkin Trans., 2, pp. 2161-2165Gilbert, B.C., Kamp, N.W.J., Lindsay Smith, J.R., Oakes, J., (1998) J. Chem. Soc., Perkin Trans., 2, pp. 1841-1844Barton, D.H.R., Li, W., Smith, J.A., (1998) Tetrahedron Lett., 39, pp. 7055-7058Koek, J.H., Kohlen, E.W.M.J., Russell, S.W., Van Der Wolf, L., Ter Steeg, P.F., Hellemons, J.C., (1999) Inorg. Chim. Acta, 295, pp. 189-199Zondervan, C., Hage, R., Feringa, B.L., (1997) Chem. Commun., pp. 419-420Cui, Y., Chen, C.-L., Gratzl, J.S., Patt, R., (1999) J. Mol. Catal. A: Chem., 144, pp. 411-417Bolm, C., Meyer, N., Raabe, G., Weyhermüller, T., Bothe, E., (2000) Chem. Commun., pp. 2435-2436Brinksma, J., Hage, R., Kerschner, J., Feringa, B.L., (2000) Chem. Commun., pp. 537-538Brinksma, J., Schmieder, L., Van Vliet, G., Boaron, R., Hage, R., De Vos, D.E., Alsters, P.L., Feringa, B.L., (2002) Tetrahedron Lett., 43, pp. 2619-2622Lindsay Smith, J.R., Shul'Pin, G.B., (1998) Russ. Chem. Bull., 47, pp. 2313-2315Gilbert, B.C., Lindsay Smith, J.R., Newton, M.S., Oakes, J., Prats, R.P.I., (2003) Org. Biomol. Chem., 1, pp. 1568-1577De Vos, D.E., Meinershagen, J.L., Bein, T., (1996) Angew. Chem. Int. Ed., 35, pp. 2211-2213De Vos, D.E., Bein, T., (1996) Chem. Commun., pp. 917-918De Vos, D.E., Bein, T., (1996) J. Organomet. Chem., 520, pp. 195-200Subba Rao, Y.V., De Vos, D.E., Bein, T., Jacobs, P.A., (1997) Chem. Commun., pp. 355-356Knops-Gerrits, P.-P., De Vos, D.E., Jacobs, P.A., (1997) J. Mol. Catal. A: Chem., 117, pp. 57-70De Vos, D.E., De Wildeman, S., Sels, B.F., Grobet, P.J., Jacobs, P.A., (1999) Angew. Chem. Int. Ed., 38, pp. 980-983Bolm, C., Kadereit, D., Valacchi, M., (1997) Synlett, pp. 687-688Vincent, J.-M., Rabion, A., Yachandra, V.K., Fish, R.H., (1997) Angew. Chem. Int. Ed., 36, pp. 2346-2349De Vos, D.E., Sels, B.F., Reynaers, M., Subba Rao, Y.V., Jacobs, P.A., (1998) Tetrahedron Lett., 39, pp. 3221-3224Grenz, A., Ceccarreli, S., Bolm, C., (2001) Chem. Commun., pp. 1726-1727Berkessel, A., Sklorz, C.A., (1999) Tetrahedron Lett., 40, pp. 7965-7968Brinksma, J., La Crois, R., Feringa, B.L., Donnoli, M.I., Rosini, C., (2001) Tetrahedron Lett., 42, pp. 4049-4052Bennur, T.H., Sabne, S., Deshpande, S.S., Srinivas, D., Sivasanker, S., (2002) J. Mol. Catal. a, 185, pp. 71-80Shul'Pin, G.B., Lindsay Smith, J.R., (1998) Russ. Chem. Bull., 47, pp. 2379-2386Shul'Pin, G.B., Süss-Fink, G., Lindsay Smith, J.R., (1999) Tetrahedron, 55, pp. 5345-5358Shul'Pin, G.B., Süss-Fink, G., Shul'Pina, L.S., (2001) J. Mol. Catal. a, 170, pp. 17-34Shul'Pin, G.B., Nizova, G.V., Kozlov, Y.N., Pechenkina, I.G., (2002) New J. Chem., 26, pp. 1238-1245Lindsay Smith, J.R., Shul'Pin, G.B., (1998) Tetrahedron Lett., 39, pp. 4909-4912Shul'Pin, G.B., (2001) Petrol. Chem., 41, pp. 405-412Mandelli, D., Woitiski, C.B., Schuchardt, U., Shul'Pin, G.B., (2002) Chem. Nat. Comp., 38, pp. 243-245Nizova, G.V., Bolm, C., Ceccarelli, S., Pavan, C., Shul'Pin, G.B., (2002) Adv. Synth. Catal., 344, pp. 899-905Süss-Fink, G., Patent USA, 2002. WO 2,002,088,063 (to Lonza A.-G., Switzerland), priority: US 2001-286539EP 2001-111776Renaud, J.-P., Battioni, P., Bartoli, J.F., Mansuy, D., (1985) J. Chem. Soc., Chem. Commun., pp. 888-889Anelli, P.L., Banfi, S., Montanari, F., Quici, S., (1989) J. Chem. Soc., Chem. Commun., pp. 779-780Anelli, P.L., Banfi, S., Legramandi, F., Montanari, F., Pozzi, G., Quici, S., (1993) J. Chem. Soc., Perkin Trans., 1, pp. 1345-1357Campbell, L.A., Kodadek, T., (1996) J. Mol. Catal. a, 113, pp. 298-310Berkessel, A., Frauerkron, M., Schwenkreis, T., Steinmetz, A., Baum, G., Fenske, D., (1996) J. Mol. Catal. a, 113, pp. 321-342Berkessel, A., Frauenkron, M., Schwenkreis, T., Steinmetz, A., (1997) J. Mol. Catal. a, 117, pp. 339-346Baciocchi, E., Boschi, T., Cassioli, L., Galli, C., Lapi, A., Tagliatesta, P., (1997) Tetrahedron Lett., 38, pp. 7283-7286Tsuda, Y., Takahashi, K., Yamaguchi, T., Matsui, S., Komura, T., Nishiguchi, I., (1999) J. Mol. Catal. a, 138, pp. 145-153Wang, R.-M., Hao, C.-J., Wang, Y.-P., (1999) Synth. Commun., 29, pp. 1409-1414Krishnan, R., Vancheesan, S., (1999) J. Mol. Catal. a, 142, pp. 377-382Canali, L., Sherrinton, D.C., (1999) Chem. Soc. Rev., 28, pp. 85-93Merlau, M.L., Grande, W.J., Nguyen, S.T., Hupp, J.T., (2000) J. Mol. Catal. a, 156, pp. 79-84Hubin, T.J., McCormick, J.M., Collinson, S.R., Buchalova, M., Perkins, C.M., Alcock, N.W., Kahol, P.K., Busch, D.H., (2000) J. Am. Chem. Soc., 122, pp. 2512-2522Bartoli, J.-F., Mouries-Mansuy, V., Le Barch-Ozette, K., Palacio, M., Battioni, P., Mansuy, D., (2000) Chem. Commun., pp. 827-828Kholdeeva, O.A., Vanina, M.P., (2001) React. Kinet. Catal. Lett., 73, pp. 83-89Kureshy, R.I., Khan, N.H., Abdi, S.H.R., Patel, S.T., Jasra, R.V., (2001) Tetrahedron: Asymmetry, 12, pp. 433-437Hoogenraad, M., Kooijman, H., Spek, A.L., Bouwman, E., Haasnoot, J.G., Reedijk, J., (2002) Eur. J. Inorg. Chem., 2897, pp. 2897-2903Pietikäinen, P., Haikarainen, A., (2002) J. Mol. Catal. a, 180, pp. 59-65Patel, S.A., Sinha, S., Mishra, A.N., Kamath, B.V., Ram, R.N., (2003) J. Mol. Catal. a, p. 192Brulé, E., De Miguel, Y.R., (2002) Tetrahedron Lett., 43, pp. 8555-8558Garcia, M.-A., Meou, A., Brun, P., (1996) Synlett, pp. 1049-1050Martins, R.R.L., Neves, M.G.P.M.S., Silvestre, A.J.D., Silva, A.M.S., Cavaleiro, J.A.S., (1999) J. Mol. Catal. a, 137, pp. 41-47Borocci, S., Marotti, F., Mancini, G., Monti, D., Pastorini, A., (2001) Langmuir, 17, pp. 7198-7203Martins, R.R.L., Neves, M.G.P.M.S., Silvestre, A.J.D., Simões, M.M.Q., Silva, A.M.S., Tomé, A.C., Cavaleiro, J.A.S., Crestini, C., (2001) J. Mol. Catal. a, 172, pp. 33-42Maraval, V., Ancel, J.-E., Meunier, B., (2002) J. Catal., 206, pp. 349-357Louloudi, M., Kolokytha, C., Hadjiliadis, N., (2002) J. Mol. Catal. a, 180, pp. 19-24Quici, S., Banfi, S., Pozzi, G., (1993) Gazz. Chim. Ital., 123, pp. 597-612Tetard, D., Verlhac, J.-B., (1996) J. Mol. Catal. a, 113, pp. 223-230Bansai, V., Sharma, P.K., Banerji, K.K., (1999) J. Chem. Res. (S), pp. 480-481Mirkhani, V., Tangestaninejad, S., Moghadam, M., (1999) J. Chem. Res. (S), pp. 722-723Matsushita, T., Sawyer, D.T., Sobkowiak, A., (1999) J. Mol. Catal. a, 137, pp. 127-133Cammarota, L., Campestrini, S., Carrieri, M., Di Furia, F., Ghiotti, P., (1999) J. Mol. Catal. a, 137, pp. 155-160Avdeev, M.V., Bagrii, E.I., Maravin, G.B., Korolev, Y.M., Borisov, R.S., (2000) Petrol. Chem., 40, pp. 391-398Banfi, S., Cavazzini, M., Pozzi, G., Barkanova, S.V., Kaliya, O.L., (2000) J. Chem. Soc., Perkin Trans., 2, pp. 871-877Gonsalves, A.M.d'A.R., Serra, A.C., (2000) J. Porphyrins Phthalocyanines, 4, pp. 599-604Doro, F.G., Lindsay Smith, J.R., Ferreira, A.G., Assis, M.D., (2000) J. Mol. Catal. a, 164, pp. 97-108Chatterjee, D., Mukherjee, S., Roy, B.C., (2001) J. Mol. Catal. a, 169, pp. 41-45Blay, G., Fernández, I., Giménez, T., Pedro, J.R., Ruiz, R., Pardo, E., Lloret, F., Muñoz, M.C., (2001) Chem. Commun., pp. 2102-2103Huang, J.-W., Mei, W.-J., Liu, J., Ji, L.-N., (2001) J. Mol. Catal. a, 170, pp. 261-265Vinhado, F.S., Prado-Manso, C.M.C., Sacco, H.C., Iamamoto, Y., (2001) J. Mol. Catal. a, 174, pp. 279-288Pan, J.-F., Chen, K., (2001) J. Mol. Catal. a, 176, pp. 19-22Brinksma, J., Rispens, M.T., Hage, R., Feringa, B.L., (2002) Inorg. Chim. Acta, 337, pp. 75-82Carrell, T.G., Cohen, S., Dismukes, G.C., (2002) J. Mol. Catal. a, 187, pp. 3-15Mohajer, D., Rezaeifard, A., (2002) Tetrahedron Lett., 43, pp. 1881-1884Xiang, S., Zhang, Y., Xin, Q., Li, C., (2002) Chem. Commun., pp. 2696-2697Larsen, A.S., Wang, K., Lockwood, M.A., Rice, G.L., Won, T.-J., Lovell, S., Sadilek, M., Mayer, J.M., (2002) J. Am. Chem. Soc., 124, pp. 10112-10123Lane, B.S., Vogt, M., Derose, V.J., Burgess, K., (2002) J. Am. Chem. Soc., 124, pp. 11946-11954Richardson, D.E., Yao, H., Frank, K.M., Bennet, D.A., (2000) J. Am. Chem. Soc., 122, pp. 1729-1739Yao, H., Richardson, D.E., (2000) J. Am. Chem. Soc., 122, pp. 3220-3221Bossek, U., Hummel, H., Weyhermüller, T., Wieghardt, K., Russell, S., Van Der Wolf, L., Kolb, U., (1996) Angew. Chem., Int. Ed., 35, pp. 1552-1554Duboc-Toia, C., Hummel, H., Bill, E., Barra, A.-L., Chouteau, G., Wieghardt, K., (2000) Angew. Chem., Int. Ed., 39, pp. 2888-2890Shul'Pin, G.B., Druzhinina, A.N., (1992) React. Kinet. Catal. Lett., 47, pp. 207-211Shul'Pin, G.B., Nizova, G.V., (1992) React. Kinet. Catal. Lett., 48, pp. 333-338Shul'Pin, G.B., Druzhinina, A.N., (1993) Petrol. Chem., 33, pp. 247-251Shul'Pin, G.B., Druzhinina, A.N., Shul'Pina, L.S., (1993) Petrol. Chem., 33, pp. 321-325Shul'Pin, G.B., Bochkova, M.M., Nizova, G.V., (1995) J. Chem. Soc., Perkin Trans., 2, pp. 1465-1469Shul'Pin, G.B., Nizova, G.V., Kozlov, Yu.N., (1996) New J. Chem., 20, pp. 1243-1256Shul'Pin, G.B., (2002) J. Mol. Catal. A: Chem., 189, pp. 39-66Shilov, A.E., Shul'pin, G.B., (2000) Activation and Catalytic Reactions of Saturated Hydrocarbons in the Presence of Metal Complexes, , Kluwer, Dordrecht/Boston/London Chapter 10 (Homogeneous catalytic oxidation of hydrocarbons by peroxides and other oxygen atom donors)Shilov, A.E., Shul'Pin, G.B., (1997) Chem. Rev., 97, pp. 2879-2932Shul'Pin, G.B., (2003) Comptes Rendus - Chim., 6, pp. 163-178Jørgensen, K.A., (1989) Chem. Rev., 89, pp. 431-458Bryliakov, K.P., Babushkin, D.E., Talsi, E.P., (2000) J. Mol. Catal. a, 158, pp. 19-35Barkanova, S.V., Makarova, E.A., (2001) J. Mol. Catal. a, 174, pp. 89-105Nam, W., Kim, I., Lim, M.H., Choi, H.J., Lee, J.S., Jang, H.G., (2002) Chem. Eur. J., 8, pp. 2067-2071Linde, C., Koliaï, N., Norrby, P.-O., Åkermark, B., (2002) Chem. Eur. J., 8, pp. 2568-2573Brandt, P., Norrby, P.-O., Daly, A.M., Gilheany, D.G., (2002) Chem. Eur. J., 8, pp. 4299-4307Gonsalves, R., A.m.d'A., A.C., Serra, A.M., (2002) J. Chem. Soc., Perkin Trans., 2, pp. 715-719Mandimutsira, B.S., Ramdhanie, B., Todd, R.C., Wang, H., Zareba, A.A., Czernuszewicz, R.S., Goldberg, D.P., (2002) J. Am. Chem. Soc., 124, pp. 15170-15171Hsieh, W.-Y., Pecoraro, V.L., (2002) Inorg. Chem. Acta, 341, pp. 113-117Cavallo, L., Jacobsen, H., (2003) Eur. J. Inorg. Chem., pp. 892-902Boelrijk, A.E.M., Dismukes, G.C., (2000) Inorg. Chem., 39, pp. 3020-3028Palopoli, C., González-Sierra, M., Robles, G., Dahan, F., Tuchagues, J.-P., Signorella, S., (2002) J. Chem. Soc., Dalton Trans., pp. 3813-3819Triller, M.U., Hsieh, W.-Y., Pecoraro, V.L., Rompel, A., Krebs, B., (2002) Inorg. Chem., 41, pp. 5544-5554Ashur, I., Brandis, A., Greenwald, M., Vakrat-Haglili, Y., Rosenbach-Belkin, V., Scheer, H., Scherz, A., (2003) J. Am. Chem. Soc., 125, pp. 8852-8861Anand, R., Dorrestein, P.C., Kinsland, C., Begley, T.P., Ealick, S.E., (2002) Biochemistry, 41, pp. 7659-7669Reinhardt, L.A., Svedruzic, D., Chang, C.H., Cleland, W.W., Richards, N.G.J., (2003) J. Am. Chem. Soc., 125, pp. 1244-1252Mehn, M.P., Fujisawa, K., Hegg, E.L., Que Jr., L., (2003) J. Am. Chem. Soc., 125, pp. 7828-784

Redox interaction of Mn–bicarbonate complexes with reaction centres of purple bacteria

It is found that dark reduction of photooxidized primary electron donor P870+ in reaction centres from purple anoxygenic bacteria (two non-sulphur Fe-oxidizing Rhodovulum iodosum and Rhodovulum robiginosum, Rhodobacter sphaeroides R-26 and sulphur alkaliphilic Thiorhodospira sibirica) is accelerated upon the addition of Mn2+ jointly with bicarbonate (30–75 mM). The effect is not observed if Mn2+ and HCO3− have been replaced by Mg2+ and HCO2−, respectively. The dependence of the effect on bicarbonate concentration suggests that formation of Mn2+–bicarbonate complexes, Mn(HCO3)+ and/or Mn(HCO3)2, is required for re-reduction of P870+ with Mn2+. The results are considered as experimental evidence for a hypothesis on possible participation of Mn–bicarbonate complexes in the evolutionary origin of oxygenic photosynthesis in the Archean era

Palanquin-like Cu 4 Na 4 silsesquioxane synthesis (via oxidation of 1,1-bis(diphenylphosphino)methane), structure and catalytic activity in alkane or alcohol oxidation with peroxides

The self-assembly synthesis of copper-sodium phenylsilsesquioxane in the presence of 1,1-bis(diphenylphosphino)methane (dppm) results in an unprecedented cage-like product: [(PhSiO 1,5 ) 6 ] 2 [CuO] 4 [NaO 0.5 ] 4 [dppmO 2 ] 2 1. The most intriguing feature of the complex 1 is the presence of two oxidized dppm species that act as additional O-ligands for sodium ions. Two cyclic phenylsiloxanolate (PhSiO 1,5 ) 6 ligands coordinate in a sandwich manner with the copper(II)-containing layer of the cage. The structure of 1 was established by X-ray diffraction analysis. Complex 1 was shown to be a very good catalyst in the oxidation of alkanes and alcohols with hydrogen peroxide or tert-butyl hydroperoxide in acetonitrile solution. Thus, cyclohexane (CyH), was transformed into cyclohexyl hydroperoxide (CyOOH), which could be easily reduced by PPh 3 to afford stable cyclohexanol with a yield of 26% (turnover number (TON) = 240) based on the starting cyclohexane. 1-Phenylethanol was oxidized by tert-butyl hydroperoxide to give acetophenone in an almost quantitative yield. The selectivity parameters of the oxidation of normal and branched alkanes led to the conclusion that the peroxides H 2 O 2 and tert-BuOOH, under the action of compound (1), decompose to generate the radicals HȮ and tert-BuȮ which attack the C-H bonds of the substrate. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Copper(ii) complexes with 2,2′:6′,2′′-terpyridine, 2,6-di(thiazol-2-yl)pyridine and 2,6-di(pyrazin-2-yl)pyridine substituted with quinolines. Synthesis, structure, antiproliferative activity, and catalytic activity in the oxidation of alkanes and alcohols with peroxides

A series of 2,2′:6′,2′′-terpyridine (terpy), 2,6-di(thiazol-2-yl)pyridine (dtpy) and 2,6-di(pyrazin-2-yl)pyridine (dppy) derivatives with n-quinolyl substituents (n = 2 and 4) was used to synthesize five-coordinate complexes [CuCl2(n-quinolyl-terpy)] (1-2), [CuCl2(n-quinolyl-dtpy)] (3-4) and [CuCl2(n-quinolyl-dppy)] (5-6), respectively. The main emphasis of the research was to investigate the impact of the triimine skeleton (terpy, dtpy and dppy) and n-quinolyl pendant substituent on the antiproliferative and catalytic properties of 1-6. The obtained Cu(ii) compounds were studied as antiproliferative agents against human colorectal (HCT116) and ovarian (A2780) carcinoma, and they were used as catalysts for the oxidation of alkanes and alcohols with peroxides under mild conditions. The kinetic characteristics of the oxidizing species generated by the catalytic system Cu(ii) complex-H2O2 in CH3CN were obtained from the dependence of the alkane oxidation rate on its initial concentration. A model of competitive interaction of hydroxyl radicals with CH3CN and RH in the catalyst cavity has been proposed which is based on the simultaneous study of kinetics and selectivity in alkane oxidations. 2019 © The Royal Society of Chemistry

New oxidovanadium(IV) complexes with 2,2′-bipyridine and 1,10-phenathroline ligands: Synthesis, structure and high catalytic activity in oxidations of alkanes and alcohols with peroxides

Reactions of [VCl 3 (thf) 3 ] or VBr 3 with 2,2′-bipyridine (bpy) or 1,10‐-phenanthroline (phen) in a 1:1 molar ratio in air under solventothermal conditions has afforded polymeric oxidovanadium(IV) four complexes 1‒4 of a general formula [VO(L)X 2 ] n (L = bpy, phen and X = Cl, Br). Monomeric complex [VO(DMF)(phen)Br 2 ] (4a) has been obtained by the treatment of compound 4 with DMF. The complexes were characterized by IR spectroscopy and elemental analysis. The crystal structures of 3 and 4a were determined by an X‐-ray diffraction (XRD) analysis. The {VOBr 2 (bpy)} fragments in 3 form infinite chains due to the V = O…V interactions. The vanadium atom has a distorted octahedral coordination environment. Complexes 1‒4 have been tested as catalysts in the homogeneous oxidation of alkanes (to produce corresponding alkyl hydroperoxides which can be easily reduced to alcohols by PPh 3 ) and alcohols (to corresponding ketones) with H 2 O 2 or tert‐-butyl hydroperoxide in MeCN. Compound 1 exhibited the highest activity. The mechanism of alkane oxidation was established using experimental selectivity and kinetic data and theoretical DFT calculations. The mechanism is of the Fenton type involving the generation of HO • radicals. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

The first tris-heteroleptic copper cage, ligated by germsesquioxanes, 2,2′-bipyridines and 3,5-dimethylpyrazolates. Synthesis, structure and unique catalytic activity in oxidation of alkanes and alcohols with peroxides

Self-assembly reaction of copper(II) ions and triple set of ligands (phenylgermaniumsesquioxane, 2,2′-bipyridine, 3,5-dimethylpyrazolate) results in the formation of the first example of tris-heteroleptic copper cage product (PhGeO2)10Cu6(2,2′-bipy)2(3,5-Me2Pz)2 (1). The ligation styles of complex’ components are different and includes (i) O-coordination from two cyclic pentamembered germsesquioxanes, (ii) N-coordination from two deprotonated 3,5-dimethylpyrazoles, (iii) N-ligation from two 2,2′-bipyridines. These features as well as other details of structure of 1 were established by X-day diffraction study. Analysis of the regioselectivity parameters found for the oxidation of linear and branched alkanes led to a conclusion that the reaction mechanism includes the formation of HO• radicals. However, the kinetic peculiarities of the cyclohexane oxidation with H2O2 in acetonitrile allowed to assume that the oxidation proceeds predominantly in a cavity generated inside of the tris-heteroleptic copper cage but not in the solution volume. © 2019 Elsevier B.V

New Cu4Na4-and Cu5-based phenylsilsesquioxanes. Synthesis via complexation with 1,10-phenanthroline, structures and high catalytic activity in Alkane oxidations with peroxides in acetonitrile

Self-assembly of copper(II)phenylsilsesquioxane assisted by the use of 1,10-phenanthroline (phen) results in isolation of two unusual cage-like compounds: (PhSiO1,5)12 (CuO)4 (NaO0.5)4 (phen)4 1 and (PhSiO1,5)6 (PhSiO1,5)7 (HO0.5)2 (CuO)5 (O0.25)2 (phen)3 2. X-Ray diffraction study revealed extraordinaire molecular architectures of both products. Namely, complex 1 includes single cyclic (PhSiO1,5)12 silsesquioxane ligand. Four sodium ions of 1 are additionally ligated by 1,10-phenan throlines. In turn, “sodium-less” complex 2 represents coordination of 1,10-phenanthrolines to copper ions. Two silsesquioxane ligands of 2 are: (i) noncondensed cubane of a rare Si6-type and (ii) unprecedented Si7-based ligand including two HOSiO1.5 fragments. These silanol units were formed due to removal of phenyl groups from silicon atoms, observed in mild conditions. The presence of phenanthroline ligands in products 1 and 2 favored the π–π stacking interactions between neighboring cages. Noticeable that in the case of 1 all four phenanthrolines participated in such supramolecular organization, unlike to complex 2 where one of the three phenanthrolines is not “supramolecularly active”. Complexes 1 and 2 were found to be very efficient precatalysts in oxidations with hydroperoxides. A new method for the determination of the participation of hydroxyl radicals has been developed. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

New Cu₄Na₄-and Cu₅-based phenylsilsesquioxanes. Synthesis via complexation with 1,10-phenanthroline, structures and high catalytic activity in Alkane oxidations with peroxides in acetonitrile

Self-assembly of copper(II)phenylsilsesquioxane assisted by the use of 1,10-phenanthroline (phen) results in isolation of two unusual cage-like compounds: (PhSiO1,5)12 (CuO)4 (NaO0.5)4 (phen)4 1 and (PhSiO1,5)6 (PhSiO1,5)7 (HO0.5)2 (CuO)5 (O0.25)2 (phen)3 2. X-Ray diffraction study revealed extraordinaire molecular architectures of both products. Namely, complex 1 includes single cyclic (PhSiO1,5)12 silsesquioxane ligand. Four sodium ions of 1 are additionally ligated by 1,10-phenan throlines. In turn, “sodium-less” complex 2 represents coordination of 1,10-phenanthrolines to copper ions. Two silsesquioxane ligands of 2 are: (i) noncondensed cubane of a rare Si6-type and (ii) unprecedented Si7-based ligand including two HOSiO1.5 fragments. These silanol units were formed due to removal of phenyl groups from silicon atoms, observed in mild conditions. The presence of phenanthroline ligands in products 1 and 2 favored the π–π stacking interactions between neighboring cages. Noticeable that in the case of 1 all four phenanthrolines participated in such supramolecular organization, unlike to complex 2 where one of the three phenanthrolines is not “supramolecularly active”. Complexes 1 and 2 were found to be very efficient precatalysts in oxidations with hydroperoxides. A new method for the determination of the participation of hydroxyl radicals has been developed