Crystal structures of the 2:2 complex of 1,1′-(1,2-phenyl­ene)bis­(3-m-tolyl­urea) and tetra­butyl­ammonium chloride or bromide

The title compounds both comprise a tetra­butyl­ammonium cation, a halide anion and an ortho-phenyl­ene bis-urea mol­ecule. Each halide ion shows four N—H⋯X (X = Cl or Br) inter­actions with two urea receptor sites of different bis-urea moieties. A crystallographic inversion centre leads to the formation of a 2:2 arrangement of two halide anions and two bis-urea mol­ecules.
The title compounds, tetra­butyl­ammonium chloride–1,1′-(1,2-phenyl­ene)bis­(3-m-tolyl­urea) (1/1), C16H36N+·Cl−·C22H22N4O2 or [(n-Bu4N+·Cl−)(C22H22N4O2)] (I) and tetra­butyl­ammonium bromide–1,1′-(1,2-phenyl­ene)bis­(3-m-tolyl­urea) (1/1), C16H36N+·Br−·C22H22N4O2 or [(n-Bu4N+·Br−)(C22H22N4O2)] (II), both comprise a tetra­butyl­ammonium cation, a halide anion and an ortho-phenyl­ene bis-urea mol­ecule. Each halide ion shows four N—H⋯X (X = Cl or Br) inter­actions with two urea receptor sites of different bis-urea moieties. A crystallographic inversion centre leads to the formation of a 2:2 arrangement of two halide anions and two bis-urea mol­ecules. In the crystals, the dihedral angle between the two urea groups of the bis-urea mol­ecule in (I) [defined by the four N atoms, 165.4 (2)°] is slightly smaller than that in (II) [167.4 (2)°], which is probably due to the smaller ionic radius of chloride compared to bromide.