组会汇报 文献汇报 李满 04/15/2016

文献汇报 Inorg. Chem., 2015, 54, 5043-5052 1

文献汇报 R. A. Baillie and P. Legzdins, Acc. Chem. Res., 2014, 47, 330−340 L. Que et al., J. Am. Chem. Soc., 2003, 126, 472−473 M. J. Burk and R. H. Crabtree, J. Am. Chem. Soc., 1987, 109, 8025−8032 S. Kraft et al., J. Am. Chem. Soc., 2011, 133, 1832−1848 2

文献汇报 Three strategies: (1) the combination of a catalyst responsible for C−H activation with a cocatalyst responsible for dioxygen activation, (2) transition-metal catalysts, which react with both hydrocarbons and molecular oxygen, (3) the introduction of very robust main-group element catalysts for C−H functionalization chemistry. D. Munz and T. Strassner, Inorg. Chem., 2015, 54, 5043-5052 3

Strategy 1 D. Munz and T. Strassner, Inorg. Chem., 2015, 54, 5043-5052

Strategy 1 M. Muehlhofer, T. Strassner, W. A. Herrmann, Angew. Chem. Int. Ed., 2002, 41, 1745−1747 5

Strategy 1 Halogens like chlorine or bromine appear to be good candidates for efficient redox catalysts because they are strong enough oxidants for C−H functionalization chemistry and are well-known to be capable of generating transition-metal complexes in high oxidation states like palladium(IV) or copper(III) by a nonradical two-electron process (Scheme 3). D. Munz and T. Strassner, Angew. Chem. Int. Ed., 2014, 53, 2485−2488 D. Munz and T. Strassner, Chem. Eur. J., 2014, 20, 14872−14879 D. Munz, D. Meyer, T. Strassner, Organometallics, 2013, 32, 3469−3480 6

Strategy 1 D. Munz, D. Meyer, T. Strassner, Organometallics, 2013, 32, 3469−3480 7

Strategy 1 D. Meyer and T. Strassner, J. Organomet. Chem., 2015, 784, 84−87 8

Strategy 1 If 11 is an intermediate in the catalytic cycle it should be as active as 8 in the methane activation (Scheme 1). We therefore tested 11 under our standard conditions (see Methane activation for experimental details) and found a comparable activity (TON 22) as in the case of 8 (TON 24) [19]. D. Meyer and T. Strassner, J. Organomet. Chem., 2015, 784, 84−87 T. Strassner et al., Organometallics, 2006, 25, 5409-5415 9

Strategy 1 D. Meyer and T. Strassner, J. Organomet. Chem., 2015, 784, 84−87 10

Strategy 1 D. Meyer, A. Zeller and T. Strassner, J. Organomet. Chem., 2012, 701, 56−61 11

Strategy 1 Because oleum is produced by the aerobic oxidation of sulfur dioxide in the presence of a vanadium(V) catalyst (contact process), the partial oxidation of methane could be coupled to this cooxidation using sulfur trioxide as the redox mediator. Similar to the catalytic processes in HOFTA,68,165,177 however, a drawback is the formation of the byproduct water, which renders the development of an economic process challenging. This might have kept the authors from demonstrating the possibility for an aerobic cooxidation procedure. R. A. Periana et al., Science, 1998, 280, 560−564 12

Strategy 2 D. Munz and T. Strassner, Inorg. Chem., 2015, 54, 5043-5052 13

Strategy 2 A. B. McQuarters, M. W. Wolf, A. P. Hunt, N. Lehnert, Angew. Chem. Int. Ed., 2014, 53, 4750−4752 14

Strategy 2 The cobalt-catalyzed oxidation of methane to methyl trifluoroacetate by molecular oxygen in trifluoroacetic acid has been studied in detail. Yields of up to 50% based on methane were obtained. Deactivation by precipitation of the cobalt catalyst could be prevented by the addition of trifluoroacetic anhydride. According to an energy-dispersive X-ray analysis, this precipitate contained mainly cobalt fluorides (ca. 20 atom-% cobalt) (cf. CoF2). TFA2O removes water from the reaction mixture. The observation of C−C bond scission processes in the reaction with propane points toward a reaction mechanism involving radicals. T. Strassner et al., Eur. J. Inorg. Chem., 2013, 21, 3659−3663 I. I. Moiseev et al., J. Chem. Soc., Chem. Commun., 1991, 938−939 15

Strategy 3 D. Munz and T. Strassner, Inorg. Chem., 2015, 54, 5043-5052 16

Strategy 3 We could observe that the presence of sodium bromide also led to the formation of minor amounts of propyl trifluoroacetate with NaVO3 under 4 bar of molecular oxygen and 6 bar of propane without the addition of any transition-metal catalyst (Scheme 9). Considering the previous reports on the activation of methane by supposedly Br+ and I+ species and that such types of catalytic systems should be extraordinarily robust with regard to demanding reaction conditions, the development of appropriate and more efficient aerobic cooxidation protocols for methane should become feasible in the near future. D. Munz and T. Strassner, Angew. Chem. Int. Ed., 2014, 53, 2485−2488 D. Munz and T. Strassner, Chem. Eur. J., 2014, 20, 14872−14879 17

Strategy 3 Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate esters is achieved by a homogeneous hypervalent iodine(III) complex in nonsuperacidic (trifluoroacetic acid) solvent. The reaction is highly selective for ester formation (>99%). In the case of ethane, greater than 0.5M EtTFA can be achieved. R. A. Periana et al., Angew. Chem. Int. Ed., 2014, 53, 10490−10494 18

Strategy 3 Calculations identified two low-energy IIII-Et functionalization pathways (Figure 3), which explains the lack of direct observation of the intermediate 6. R. A. Periana et al., Angew. Chem. Int. Ed., 2014, 53, 10490−10494 19

Strategy 3 We describe an efficient system for the direct partial oxidation of methane, ethane, and propane using iodate salts with catalytic amounts of chloride in protic solvents. In HTFA (TFA = trifluoroacetate), >20% methane conversion with >85% selectivity for MeTFA have been achieved. The addition of substoichiometric amounts of chloride is essential, and for methane the conversion increases from <1% in the absence of chloride to >20%. The reaction also proceeds in aqueous HTFA as well as acetic acid to afford methyl acetate. The system is selective for higher alkanes: 30% ethane conversion with 98% selectivity for EtTFA and 19% propane conversion that is selective for mixtures of the mono- and difunctionalized TFA esters. T. B. Gunnoe et al., J. Am. Chem. Soc., 2014, 136, 8393−8401 20

Strategy 3 T. B. Gunnoe et al., J. Am. Chem. Soc., 2014, 136, 8393−8401 21

Strategy 3 It is possible that chloride bonds with the active iodine-based reagent to provide an electronic modulation for the C−H bond-breaking step and/or the C−O bond-forming step. The exact identity of the active iodine species is the subject of ongoing studies. T. B. Gunnoe et al., J. Am. Chem. Soc., 2014, 136, 8393−8401 22

Strategy 3 J. T. Groves, T. B. Gunnoe et al., Dalton Trans., 2015, 44, 5294−5298 23

Conclusion D. Munz and T. Strassner, Inorg. Chem., 2015, 54, 5043-5052 24