A tale of hydrogen abstraction, initially detected via X-ray diffraction

Acta Crystallogr C Struct Chem. 2014 Mar;70(Pt 3):250-5. doi: 10.1107/S2053229614003234. Epub 2014 Feb 28.

Abstract

Reaction of a bis-tetrazinyl pyridine pincer ligand, btzp, with a vanadium(III) reagent gives not a simple adduct but dichlorido{3-methyl-6-[6-(6-methyl-1,2,4,5-tetrazin-3-yl-κN(2))pyridin-2-yl-κN]-1,4-dihydro-1,2,4,5-tetrazin-1-yl-κN(1)}oxidovanadium(IV) acetonitrile 2.5-solvate, [V(C11H10N9)Cl2O]·2.5CH3CN, a species which X-ray diffraction reveals to have one H atom added to one of the two tetrazinyl rings. This H atom was first revealed by a short intermolecular N...Cl contact in the unit cell and subsequently established, from difference maps, to be associated with a hydrogen bond. One chloride ligand has also been replaced by an oxide ligand in this synthetic reaction. This formula for the complex, [V(Hbtzp)Cl2O], leaves open the question of both ligand oxidation state and spin state. A computational study of all isomeric locations of the H atom shows the similarity of their energies, which is subject to perturbation by intermolecular hydrogen bonding found in X-ray work on the solid state. These density functional calculations reveal that the isomer with the H atom located as found in the solid state contains a neutral radical Hbtzp ligand and tetravalent d(1) V center, but that these two unpaired electrons are more stable as an open-shell singlet and hence antiferromagnetically coupled.

Keywords: crystal structure; hydrogen abstraction; hydrogen bonding; non-innocent; redox; tetrazine; vanadium.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Coordination Complexes / chemistry*
  • Electrons
  • Hydrogen Bonding
  • Ligands
  • Oxidation-Reduction
  • Vanadium / chemistry*
  • X-Ray Diffraction

Substances

  • Coordination Complexes
  • Ligands
  • Vanadium