PcpA is a hydroquinone ring-cleaving dioxygenase that is specific for ortho-halogenated  hydroquinone substrates and phenol inhibitors (Machonkin, et al., Biochemistry, 2011 , 50, 8899-8913). Metal-halogen secondary bonding has been suggested as a possible source of this specificity. We have synthesized and structurally characterized a series of tris(3,5-diphenylpyrazolyl)borate (TpPh2) complexes of the form (TpPh2)ML, where M = Fe(II), Co(II), or Ni(II) and L = 2,6-dibromo- or 2,6-dichlorophenolate. These complexes exhibit metal-halogen secondary bonding, with M-X distances of 2.56 to 2.88 �. Comparison of solution and mull UV/visible absorption spectra of the Co(II) and Ni(II) complexes suggests that geometry of these complexes in solution resembles that in the crystal structures. Variable temperature NMR studies of the Ni(II) complexes show that the barrier to rotation of the phenolate is low, suggesting that this metal-halogen interaction is relatively weak.

Metal-halogen secondary bonding in iron(II), cobalt(II), and nickel(II) 2,6-dihalophenolate complexes: Insights into the substrate specificity of the hydroquinone dioxygenase PcpA

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.