title: Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions.
abstract: To fully characterize the Co(III)-'nitrene radical' species that are proposed as intermediates in nitrene transfer reactions mediated by cobalt(II) porphyrins, different combinations of cobalt(II) complexes of porphyrins and nitrene transfer reagents were combined, and the generated species were studied using EPR, UV-vis, IR, VCD, UHR-ESI-MS, and XANES/XAFS measurements. Reactions of cobalt(II) porphyrins 1(P1) (P1 = meso-tetraphenylporphyrin (TPP)) and 1(P2) (P2 = 3,5-Di(t)Bu-ChenPhyrin) with organic azides 2(Ns) (NsN3), 2(Ts) (TsN3), and 2(Troc) (TrocN3) led to the formation of mono-nitrene species 3(P1)(Ns), 3(P2)(Ts), and 3(P2)(Troc), respectively, which are best described as [Co(III)(por)(NR″(•-))] nitrene radicals (imidyl radicals) resulting from single electron transfer from the cobalt(II) porphyrin to the 'nitrene' moiety (Ns: R″ = -SO2-p-C6H5NO2; Ts: R″ = -SO2C6H6; Troc: R″ = -C(O)OCH2CCl3). Remarkably, the reaction of 1(P1) with N-nosyl iminoiodane (PhI═NNs) 4(Ns) led to the formation of a bis-nitrene species 5(P1)(Ns). This species is best described as a triple-radical complex [(por(•-))Co(III)(NR″(•-))2] containing three ligand-centered unpaired electrons: two nitrene radicals (NR″(•-)) and one oxidized porphyrin radical (por(•-)). Thus, the formation of the second nitrene radical involves another intramolecular one-electron transfer to the "nitrene" moiety, but now from the porphyrin ring instead of the metal center. Interestingly, this bis-nitrene species is observed only on reacting 4(Ns) with 1(P1). Reaction of the more bulky 1(P2) with 4(Ns) results again in formation of mainly mono-nitrene species 3(P2)(Ns) according to EPR and ESI-MS spectroscopic studies. The mono- and bis-nitrene species were initially expected to be five- and six-coordinate species, respectively, but XANES data revealed that both mono- and bis-nitrene species are six-coordinate O(h) species. The nature of the sixth ligand bound to cobalt(III) in the mono-nitrene case remains elusive, but some plausible candidates are NH3, NH2(-), NsNH(-), and OH(-); NsNH(-) being the most plausible. Conversion of mono-nitrene species 3(P1)(Ns) into bis-nitrene species 5(P1)(Ns) upon reaction with 4(Ns) was demonstrated. Solutions containing 3(P1)(Ns) and 5(P1)(Ns) proved to be still active in catalytic aziridination of styrene, consistent with their proposed key involvement in nitrene transfer reactions mediated by cobalt(II) porphyrins.
authors.forename: Monalisa
authors.initials: M
authors.lastname: Goswami
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Lyaskovskyy
authors.forename: Sérgio R
authors.initials: SR
authors.lastname: Domingos
authors.forename: Wybren Jan
authors.initials: WJ
authors.lastname: Buma
authors.forename: Sander
authors.initials: S
authors.lastname: Woutersen
authors.affiliation: §Lehrstuhl für Bioanorganische Chemie, Department Chemie und Pharmazie, Universität Erlangen-Nürnberg. Egerlandstraße 1, D-91058 Erlangen, Germany.
authors.forename: Oliver
authors.initials: O
authors.lastname: Troeppner
authors.affiliation: §Lehrstuhl für Bioanorganische Chemie, Department Chemie und Pharmazie, Universität Erlangen-Nürnberg. Egerlandstraße 1, D-91058 Erlangen, Germany.
authors.forename: Ivana
authors.initials: I
authors.lastname: Ivanović-Burmazović
authors.affiliation: ⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.
authors.forename: Hongjian
authors.initials: H
authors.lastname: Lu
authors.affiliation: ⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.
authors.forename: Xin
authors.initials: X
authors.lastname: Cui
authors.affiliation: ⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.
authors.forename: X Peter
authors.initials: XP
authors.lastname: Zhang
authors.affiliation: ∥Max Planck Institut für Chemische Energiekonversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Edward J
authors.initials: EJ
authors.lastname: Reijerse
authors.affiliation: ∥Max Planck Institut für Chemische Energiekonversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Serena
authors.initials: S
authors.lastname: DeBeer
authors.affiliation: ∥Max Planck Institut für Chemische Energiekonversion, Stiftstraße 34-36, 45470 Mülheim an der Ruhr, Germany.
authors.forename: Matti M
authors.initials: MM
authors.lastname: van Schooneveld
authors.affiliation: #Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany.
authors.forename: Florian Felix
authors.initials: FF
authors.lastname: Pfaff
authors.affiliation: #Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straße 2, 12489 Berlin, Germany.
authors.forename: Kallol
authors.initials: K
authors.lastname: Ray
authors.forename: Bas
authors.initials: B
authors.lastname: de Bruin
mesh_terms: D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D007097:Imines / Q000737:chemistry*; D008024:Ligands; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013057:Spectrum Analysis
chemical_list: D007097:Imines; D008024:Ligands; D008665:Metalloporphyrins; C017621:phenylnitrene; D003035:Cobalt
references.citation: J Org Chem. 2004 May 28;69(11):3610-9
references.pmid: 15152988
references.citation: Org Lett. 2005 Jun 23;7(13):2787-90
references.pmid: 15957947
references.citation: Org Biomol Chem. 2005 Jan 7;3(1):107-11
references.pmid: 15602604
references.citation: Angew Chem Int Ed Engl. 2006 Oct 6;45(39):6422-5
references.pmid: 16969883
references.citation: Nat Chem Biol. 2006 Jun;2(6):284-7
references.pmid: 16710330
references.citation: J Am Chem Soc. 2008 Jan 9;130(1):343-50
references.pmid: 18072775
references.citation: Chemistry. 2014 Aug 25;20(35):11035-47
references.pmid: 25066508
references.citation: J Am Chem Soc. 2011 Nov 23;133(46):18785-801
references.pmid: 22047035
references.citation: Chem Rev. 1997 Dec 18;97(8):2879-2932
references.pmid: 11851481
references.citation: Angew Chem Int Ed Engl. 2013 Nov 25;52(48):12510-29
references.pmid: 24214688
references.citation: J Org Chem. 2006 Aug 18;71(17):6655-8
references.pmid: 16901165
references.citation: Angew Chem Int Ed Engl. 2013 May 10;52(20):5309-13
references.pmid: 23589338
references.citation: Org Lett. 2010 Mar 19;12(6):1248-51
references.pmid: 20184343
references.citation: Chem Rev. 1998 Apr 2;98(2):911-936
references.pmid: 11848918
references.citation: Chem Commun (Camb). 2009 Jul 14;(26):3952-4
references.pmid: 19662263
references.citation: Science. 2010 Feb 12;327(5967):794-5
references.pmid: 20150476
references.citation: Chem Soc Rev. 2013 Feb 21;42(4):1440-59
references.pmid: 22975722
references.citation: J Am Chem Soc. 2007 Jun 20;129(24):7500-1
references.pmid: 17523647
references.citation: J Am Chem Soc. 2008 May 7;130(18):5844-5
references.pmid: 18402447
references.citation: Chemistry. 2013 Aug 19;19(34):11320-31
references.pmid: 23818419
references.citation: Inorg Chem. 2000 Jun 26;39(13):2936-47
references.pmid: 11232835
references.citation: J Am Chem Soc. 2012 Sep 12;134(36):14710-3
references.pmid: 22928636
references.citation: Nature. 2002 May 30;417(6888):507-14
references.pmid: 12037558
references.citation: J Am Chem Soc. 2011 Jun 15;133(23):8858-61
references.pmid: 21598972
references.citation: Chem Sci. 2014 Jun 1;5(6):2422-2427
references.pmid: 25071929
references.citation: Angew Chem Int Ed Engl. 2008;47(44):8460-3
references.pmid: 18825766
references.citation: J Org Chem. 2008 Sep 19;73(18):7260-5
references.pmid: 18710285
references.citation: Org Lett. 2012 Oct 5;14(19):5158-61
references.pmid: 22998175
references.citation: J Am Chem Soc. 2010 Sep 22;132(37):12796-9
references.pmid: 20735129
references.citation: Inorg Chem. 2011 Oct 17;50(20):9896-903
references.pmid: 21520926
references.citation: J Am Chem Soc. 2008 Apr 16;130(15):5042-3
references.pmid: 18357991
references.citation: Chem Commun (Camb). 2014 Oct 9;50(78):11440-53
references.pmid: 24912622
references.citation: J Am Chem Soc. 2005 Nov 30;127(47):16629-40
references.pmid: 16305252
references.citation: J Am Chem Soc. 2006 Oct 11;128(40):13175-83
references.pmid: 17017797
references.citation: J Am Chem Soc. 2006 Oct 18;128(41):13340-1
references.pmid: 17031930
references.citation: Spectrochim Acta A Mol Biomol Spectrosc. 2005 Jul;61(9):2089-93
references.pmid: 15911396
references.citation: Dalton Trans. 2011 Apr 14;40(14):3435-44
references.pmid: 21279237
references.citation: J Am Chem Soc. 2010 Aug 11;132(31):10891-902
references.pmid: 20681723
references.citation: Org Biomol Chem. 2010 Sep 7;8(17):3831-46
references.pmid: 20617243
references.citation: Chem Commun (Camb). 2005 Nov 7;(41):5175-7
references.pmid: 16228026
references.citation: J Am Chem Soc. 2013 May 15;135(19):7194-204
references.pmid: 23634746
references.citation: J Am Chem Soc. 2008 Mar 12;130(10):3181-97
references.pmid: 18284242
references.citation: J Am Chem Soc. 2010 Oct 27;132(42):15046-59
references.pmid: 20882992
references.citation: J Am Chem Soc. 2013 Sep 4;135(35):13168-84
references.pmid: 23968297
references.citation: Angew Chem Int Ed Engl. 2008;47(6):1138-40
references.pmid: 18163374
references.citation: J Chem Theory Comput. 2008 Dec 9;4(12):2057-66
references.pmid: 26620478
references.citation: J Am Chem Soc. 2006 Sep 13;128(36):11784-91
references.pmid: 16953617
references.citation: Inorg Chem. 2012 Mar 19;51(6):3718-32
references.pmid: 22424275
references.citation: Chem Soc Rev. 2011 Apr;40(4):1899-909
references.pmid: 21088785
references.citation: J Am Chem Soc. 2007 Oct 10;129(40):12074-5
references.pmid: 17877352
references.citation: J Am Chem Soc. 2007 Nov 21;129(46):14106-7
references.pmid: 17967011
references.citation: Angew Chem Int Ed Engl. 2011 Sep 12;50(38):8839-43
references.pmid: 21905177
references.citation: J Am Chem Soc. 2011 Aug 10;133(31):12264-73
references.pmid: 21711027
references.citation: Angew Chem Int Ed Engl. 2007;46(27):5184-6
references.pmid: 17535005
references.citation: Dalton Trans. 2011 Jun 7;40(21):5697-705
references.pmid: 21483935
references.citation: Org Lett. 2008 May 15;10(10):1995-8
references.pmid: 18422325
references.citation: Nature. 2008 Jan 24;451(7177):417-24
references.pmid: 18216847
references.citation: Angew Chem Int Ed Engl. 2008;47(27):5056-9
references.pmid: 18512215
references.citation: Chem Commun (Camb). 2009 Jul 28;(28):4266-8
references.pmid: 19585042
references.citation: Acc Chem Res. 2007 Jul;40(7):522-31
references.pmid: 17469792
references.citation: Science. 2006 Apr 7;312(5770):67-72
references.pmid: 16601184
references.citation: J Am Chem Soc. 2011 Jun 8;133(22):8518-21
references.pmid: 21563829
references.citation: Inorg Chem. 2011 Sep 5;50(17):8630-5
references.pmid: 21797263