Weaving a 2D net of hydrogen and halogen bonds: cocrystal of a pyrazolium bromide with tetra­fluoro­diiodo­benzene

Hydro­halides of Lewis bases may act as halogen bond (XB) acceptors and combine two directional inter­actions, namely, hydrogen bonds (HB) and XBs in the same solid. 3-(1,3,5-Trimethyl-1H-pyrazol-4-yl)acetyl­acetone (C(11)H(16)N(2)O(2), HacacMePz) was protonated with HX (X = Cl or Br) to afford the hydro­halides, C(11)H(17)N(2)O(2) (+)·X (−) or H(2)acacMePz(+)·X (−) (1, X = Cl; 2, X = Br). Hydro­halides 1 and 2 are isomorphous and adopt a classical dipole packing. Consistent with the observation for most β-diketones, the enol form with an intra­molecular HB is observed. Additional noteworthy inter­actions are HBs of the protonated pyrazolium towards the X (−) anion at donor–acceptor distances of 2.9671 (17) Å for 1 and 3.159 (4) Å for 2. Cocrystallization of hydro­bromide 2 with the XB donor tetra­fluoro­diiodo­benzene (TFDIB) leads to the adduct C(11)H(17)N(2)O(2) (+)·Br(−)·0.5C(6)F(4)I(2)·H(2)O or (H(2)acacMePz(+)·Br(−))(2)·(H(2)O)(2)·TFDIB (3), in which the XB donor TFDIB is situated on a crystallographic centre of inversion. Classical HBs link organic cations, water mol­ecules and Br(−) anions into chains along [010]. Almost orthogonal to this inter­action, XBs with Br⋯I = 3.2956 (4) Å connect neighbouring chains along [102] into two-dimensional sheets in the (10 [Image: see text] ) plane. Assisted by their negative charge, halide anions represent particularly good nucleophiles towards XB donors.