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Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions.
J Am Chem Soc. 2015 Apr 29; 137(16):5468-79.JA

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+Show Affiliations

No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available§Lehrstuhl für Bioanorganische Chemie, Department Chemie und Pharmazie, Universität Erlangen-Nürnberg. Egerlandstraβe 1, D-91058 Erlangen, Germany.§Lehrstuhl für Bioanorganische Chemie, Department Chemie und Pharmazie, Universität Erlangen-Nürnberg. Egerlandstraβe 1, D-91058 Erlangen, Germany.⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.⊥Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.∥Max Planck Institut für Chemische Energiekonversion, Stiftstraβe 34-36, 45470 Mülheim an der Ruhr, Germany.∥Max Planck Institut für Chemische Energiekonversion, Stiftstraβe 34-36, 45470 Mülheim an der Ruhr, Germany.∥Max Planck Institut für Chemische Energiekonversion, Stiftstraβe 34-36, 45470 Mülheim an der Ruhr, Germany.#Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straβe 2, 12489 Berlin, Germany.#Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Straβe 2, 12489 Berlin, Germany.No affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

25844713

Citation

Goswami, Monalisa, et al. "Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions." Journal of the American Chemical Society, vol. 137, no. 16, 2015, pp. 5468-79.
Goswami M, Lyaskovskyy V, Domingos SR, et al. Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions. J Am Chem Soc. 2015;137(16):5468-79.
Goswami, M., Lyaskovskyy, V., Domingos, S. R., Buma, W. J., Woutersen, S., Troeppner, O., Ivanović-Burmazović, I., Lu, H., Cui, X., Zhang, X. P., Reijerse, E. J., DeBeer, S., van Schooneveld, M. M., Pfaff, F. F., Ray, K., & de Bruin, B. (2015). Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions. Journal of the American Chemical Society, 137(16), 5468-79. https://doi.org/10.1021/jacs.5b01197
Goswami M, et al. Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions. J Am Chem Soc. 2015 Apr 29;137(16):5468-79. PubMed PMID: 25844713.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Characterization of Porphyrin-Co(III)-'Nitrene Radical' Species Relevant in Catalytic Nitrene Transfer Reactions. AU - Goswami,Monalisa, AU - Lyaskovskyy,Volodymyr, AU - Domingos,Sérgio R, AU - Buma,Wybren Jan, AU - Woutersen,Sander, AU - Troeppner,Oliver, AU - Ivanović-Burmazović,Ivana, AU - Lu,Hongjian, AU - Cui,Xin, AU - Zhang,X Peter, AU - Reijerse,Edward J, AU - DeBeer,Serena, AU - van Schooneveld,Matti M, AU - Pfaff,Florian Felix, AU - Ray,Kallol, AU - de Bruin,Bas, Y1 - 2015/04/16/ PY - 2015/4/7/entrez PY - 2015/4/7/pubmed PY - 2016/3/22/medline SP - 5468 EP - 79 JF - Journal of the American Chemical Society JO - J Am Chem Soc VL - 137 IS - 16 N2 - 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. SN - 1520-5126 UR - https://www.unboundmedicine.com/medline/citation/25844713/Characterization_of_Porphyrin_Co_III__'Nitrene_Radical'_Species_Relevant_in_Catalytic_Nitrene_Transfer_Reactions_ L2 - https://doi.org/10.1021/jacs.5b01197 DB - PRIME DP - Unbound Medicine ER -