Multiple Noncovalent Bonding in Halogen Complexes with Oxygen Organics. I. Tertiary Amides

The present work describes the structure
and binding of adducts
of N,N′-diacetylpiperazine
with halogens and interhalogens based on combination of different
experimental methods and quantum chemical calculations. On the basis
of conductometric and spectro-photometric experimental results, behavior
of complexes in the acetonitrile solution was described. The iodine
adduct with N,N′-diacetylpiperazine
fully degrades into components. Adducts of interhalogens I–X
(X = Cl or Br) with N,N′-diacetylpiperazine
in acetonitrile partially dissociate to anionic [X–I–X]− and cationic species. In the solid state, molecules
are connected via CO···I, C–H···I,
and Cl···Cl attractive interactions. N,N′-diacetylpiperazine···dihalogen
complex is stabilized by simultaneous CO···I
and C–H···I interactions. Such binding mode
allows to explain the problems of the direct halogenation of acetyl-containing
compounds with molecular halogens as reagents. We believe that the
observed binding pattern can be used as prototypical for future design
of halogeno complexes.