title: Temperature-independent catalytic two-electron reduction of dioxygen by ferrocenes with a copper(II) tris[2-(2-pyridyl)ethyl]amine catalyst in the presence of perchloric acid.
abstract: Selective two-electron plus two-proton (2e(-)/2H(+)) reduction of O(2) to hydrogen peroxide by ferrocene (Fc) or 1,1'-dimethylferrocene (Me(2)Fc) in the presence of perchloric acid is catalyzed efficiently by a mononuclear copper(II) complex, [Cu(II)(tepa)](2+) (1; tepa = tris[2-(2-pyridyl)ethyl]amine) in acetone. The E(1/2) value for [Cu(II)(tepa)](2+) as measured by cyclic voltammetry is 0.07 V vs Fc/Fc(+) in acetone, being significantly positive, which makes it possible to use relatively weak one-electron reductants such as Fc and Me(2)Fc for the overall two-electron reduction of O(2). Fast electron transfer from Fc or Me(2)Fc to 1 affords the corresponding Cu(I) complex [Cu(I)(tepa)](+) (2), which reacts at low temperature (193 K) with O(2), however only in the presence of HClO(4), to afford the hydroperoxo complex [Cu(II)(tepa)(OOH)](+) (3). A detailed kinetic study on the homogeneous catalytic system reveals the rate-determining step to be the O(2)-binding process in the presence of HClO(4) at lower temperature as well as at room temperature. The O(2)-binding kinetics in the presence of HClO(4) were studied, demonstrating that the rate of formation of the hydroperoxo complex 3 as well as the overall catalytic reaction remained virtually the same with changing temperature. The apparent lack of activation energy for the catalytic two-electron reduction of O(2) is shown to result from the existence of a pre-equilibrium between 2 and O(2) prior to the formation of the hydroperoxo complex 3. No further reduction of [Cu(II)(tepa)(OOH)](+) (3) by Fc or Me(2)Fc occurred, and instead 3 is protonated by HClO(4) to yield H(2)O(2) accompanied by regeneration of 1, thus completing the catalytic cycle for the two-electron reduction of O(2) by Fc or Me(2)Fc.
authors: Department of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea.
authors: Dipanwita
authors: D
authors: Das
authors: Yong-Min
authors: YM
authors: Lee
authors: Kei
authors: K
authors: Ohkubo
authors: Wonwoo
authors: W
authors: Nam
authors: Kenneth D
authors: KD
authors: Karlin
authors: Shunichi
authors: S
authors: Fukuzumi
mesh_terms: D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010472:Perchlorates / Q000737:chemistry*; D013696:Temperature
chemical_list: D000588:Amines; D056831:Coordination Complexes; D005296:Ferrous Compounds; D000075163:Metallocenes; D010472:Perchlorates; D003300:Copper; D010100:Oxygen; C004998:ferrocene
references: Proc Natl Acad Sci U S A. 2004 Sep 7;101(36):13105-10
references: 15340147
references: Nature. 2001 Nov 15;414(6861):345-52
references: 11713541
references: J Org Chem. 2006 Sep 1;71(18):7007-15
references: 16930056
references: Chem Rev. 1996 Nov 7;96(7):2541-2562
references: 11848836
references: J Phys Chem B. 2006 Jun 15;110(23):11180-7
references: 16771381
references: J Am Chem Soc. 2008 Jul 23;130(29):9459-73
references: 18582059
references: Inorg Chem. 1998 Sep 21;37(19):4838-4848
references: 11670647
references: J Am Chem Soc. 2008 Jan 16;130(2):434-5
references: 18085783
references: Inorg Chem. 2011 Jul 4;50(13):6158-62
references: 21627090
references: J Am Chem Soc. 2011 Feb 16;133(6):1859-69
references: 21218824
references: Science. 2004 May 7;304(5672):864-7
references: 15131304
references: Inorg Chem. 2008 Dec 15;47(24):12032-9
references: 18998628
references: J Biol Chem. 2006 Feb 10;281(6):3013-6
references: 16301310
references: Chem Rev. 1996 Nov 7;96(7):2889-2908
references: 11848844
references: Science. 1998 Jun 12;280(5370):1723-9
references: 9624044
references: J Am Chem Soc. 2009 Sep 23;131(37):13453-9
references: 19715275
references: Angew Chem Int Ed Engl. 2001 Dec 17;40(24):4570-4590
references: 12404359
references: Chem Commun (Camb). 2003 Nov 7;(21):2700-1
references: 14649818
references: Chem Rev. 2007 Oct;107(10):3904-51
references: 17850115
references: J Am Chem Soc. 2003 Mar 5;125(9):2629-40
references: 12603151
references: Angew Chem Int Ed Engl. 2009;48(1):165-7
references: 19035597
references: J Am Chem Soc. 2009 Apr 15;131(14):5034-5
references: 19317484
references: Nature. 2010 May 6;465(7294):115-9
references: 20410881
references: Chem Rev. 2004 Feb;104(2):1047-76
references: 14871149
references: Chem Commun (Camb). 2010 Oct 21;46(39):7334-6
references: 20820513
references: J Phys Chem A. 2005 Feb 17;109(6):1105-13
references: 16833419
references: Faraday Discuss. 2011;148:11-39; discussion 97-108
references: 21322475
references: Inorg Chem. 2008 Aug 4;47(15):6726-37
references: 18582035
references: Science. 1993 Aug 6;261(5122):701-8
references: 7688141
references: J Am Chem Soc. 2009 Apr 8;131(13):4657-63
references: 19290629
references: J Am Chem Soc. 2010 May 26;132(20):6874-5
references: 20443560
references: J Am Chem Soc. 2011 Jun 1;133(21):8114-7
references: 21539366
references: Chem Rev. 2004 Feb;104(2):1013-45
references: 14871148
references: J Am Chem Soc. 2011 Mar 23;133(11):3696-9
references: 21366244
references: Science. 1995 Aug 25;269(5227):1069-74
references: 7652554
references: J Am Chem Soc. 2010 Oct 6;132(39):13733-41
references: 20828124
references: Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):13990-4
references: 21808032
references: Chem Rev. 1996 Nov 7;96(7):2563-2606
references: 11848837
references: J Am Chem Soc. 2010 Mar 3;132(8):2655-62
references: 20131825
references: Chemistry. 2012 Jan 23;18(4):1084-93
references: 22237962
references: Chemistry. 2010 Jan 4;16(1):354-61
references: 19937616
references: J Biol Inorg Chem. 2004 Sep;9(6):669-83
references: 15311336
references: Chem Commun (Camb). 2007 May 7;(17):1710-2
references: 17457416
references: Chemistry. 2009;15(10):2335-40
references: 19156806
references: Chem Rev. 2004 Feb;104(2):651-97
references: 14871138
references: Angew Chem Int Ed Engl. 2010 Mar 29;49(14):2622-5
references: 20229541
references: Electrochim Acta. 2012 Nov 1;82:493-511
references: 23457415
references: Biochim Biophys Acta. 2001 Jun 1;1505(2-3):185-208
references: 11334784
references: Acc Chem Res. 2007 Jul;40(7):543-53
references: 17595052
references: Proc Natl Acad Sci U S A. 2009 May 5;106(18):7320-3
references: 19380725
references: J Am Chem Soc. 2004 Aug 18;126(32):10013-20
references: 15303875
references: Inorg Chem. 2009 Mar 16;48(6):2571-82
references: 19215120
references: Science. 2007 Mar 16;315(5818):1565-8
references: 17363671
references: J Am Chem Soc. 2012 Apr 25;134(16):7025-35
references: 22462521
references: Inorg Chem. 2003 Mar 24;42(6):1807-24
references: 12639113
references: Angew Chem Int Ed Engl. 1998 Apr 3;37(6):798-799
references: 29711401
references: J Am Chem Soc. 2011 Jan 12;133(1):131-40
references: 21142043
references: Chem Rev. 2008 Jul;108(7):2439-61
references: 18620369
references: J Am Chem Soc. 2001 Aug 8;123(31):7715-6
references: 11481001
references: Chem Rev. 1996 Nov 7;96(7):2239-2314
references: 11848828
references: J Am Chem Soc. 2002 Sep 18;124(37):10974-5
references: 12224933
references: Acc Chem Res. 2008 Aug;41(8):969-79
references: 18605740
references: Inorg Chem. 2001 May 7;40(10):2312-22
references: 11327908
references: Chemphyschem. 2010 Sep 10;11(13):2979-84
references: 20607710