Katarzyna Grubel - O2-dependent Aliphatic Carbon-Carbon Bond Cleavage Reactivity in a Ni(II) Enolate Complex Having a Hydrogen Bond Donor Microenvironment; Comparison with a Hydrophobic Analog

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  Grubel, K.; Fuller, A. L.; Chambers; B. M., Arif, A. M; Berreau,   L. M. Inorganic Chemistry 2010,   49, 1071-1081; DOI: 10.1021/ic901981y


  Abstract Image

  A mononuclear Ni(II) complex having an acireductone type ligand,   and supported by the bnpapa   (N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine)   ligand, [(bnpapa)Ni(PhC(O)C(OH)C(O)Ph)]ClO4  (14), has been prepared and characterized by   elemental analysis, 1H NMR, FTIR, and UV−vis. To gain   insight into the 1H NMR features of   14, the air stable analogue complexes   [(bnpapa)Ni(CH3C(O)CHC(O)CH3)]ClO4  (16) and   [(bnpapa)Ni(ONHC(O)CH3)]ClO4  (17) were prepared and characterized by X-ray   crystallography, 1H NMR, FTIR, UV−vis, mass   spectrometry, and solution conductivity measurements. Compounds   16 and 17 are 1:1 electrolyte   species in CH3CN. 1H and 2H NMR   studies of 14, 16, and   17 and deuterated analogues revealed that the   complexes having six-membered chelate rings for the exogenous   ligand (14 and 16) do not have   a plane of symmetry within the solvated cation and thus exhibit   more complicated 1H NMR spectra. Compound   17, as well as other simple Ni(II) complexes of   the bnpapa ligand (e.g.,   [(bnpapa)Ni(ClO4)(CH3CN)]ClO4  (18) and   [(bnpapaNi)2(μ-Cl)2](ClO4)2  (19)), exhibit 1H NMR spectra   consistent with the presence of a plane of symmetry within the   cation. Treatment of   [(bnpapa)Ni(PhC(O)C(OH)C(O)Ph)]ClO4  (14) with O2 results in aliphatic   carbon−carbon bond cleavage within the acireductone-type ligand   and the formation of   [(bnpapa)Ni(O2CPh)]ClO4  (9), benzoic acid, benzil, and CO. Use of   18O2 in the reaction gives high levels of   incorporation (>80%) of one labeled oxygen atom into   9 and benzoic acid. The product mixture and   level of 18O incorporation in this reaction is   different than that exhibited by the analogue supported the   hydrophobic 6-Ph2TPA ligand,   [(6-Ph2TPA)Ni(PhC(O)C(OH)C(O)Ph)]ClO4  (2). We propose that this difference is due to   variations in the reactivity of bnpapa- and   6-Ph2TPA-ligated Ni(II) complexes with triketone   and/or peroxide species produced in the reaction pathway.

  Address (URL): http://pubs.acs.org/doi/abs/10.1021/ic901981y?