4-(1H-2,3-Dihydronaphtho[1,8-de][1,3,2]diazaborinin-2-yl)-1-ethylpyridin-1-ium iodide monohydrate

The cation of the title hydrated salt is a diazaborinane featuring substitution at 1, 2, and 3 positions in the nitrogen–boron six-membered heterocycle. In the crystal, the cations stack along [100] in an alternating head-to-tail manner, while the iodide ion and water molecule form one-dimensional hydrogen-bonded chains beside the cation stack. The cation stacks and I−–water chains are crosslinked by N—H⋯I and N—H⋯O hydrogen bonds.


Structure description
The title compound, C 17 H 17 BN 3 + •I À •H 2 O, is a hydrated diazaborinane derivative featuring substitution at the 1, 2, and 3 positions in the nitrogen-boron six-membered heterocycle (Fig. 1).Diazaborinanes are found to stabilize organic radicals (LaPorte et al., 2023).Recently we reported of the anhydrous polymorph of the title compound (Hashimoto & Okuno, 2024).
In the crystal, the organic cations stack in an alternating head-to-tail manner along the a axis as shown in Fig. 2, where the B1� � �•B1 iv and B1� � �•B1 iii distances are 3.395 (6) and 3.436 (6) A ˚, respectively [symmetry codes: (iv) À x + 1, À y + 2, À z + 1; (iii) À x + 2, À y + 2, À z + 1].The iodide ion accepts three C-H� � �I contacts from adjacent cations and two O-H� � �I links from the water molecules.The iodide anions and water molecules form a one-dimensional hydrogen-bonded chain beside the alternating cation stack and the stacks and hydrogen-bond chains are crosslinked by N-H� � �O and N-H� � �I links.
The geometry of the hydrogen bonds is summarized in Table 1.The contamination of water in acetonitrile is thought to give the hydrated polymorph.Selective formation of the hydrated polymorph has not yet been achieved.

Figure 1
The asymmetric unit of the title compound with displacement ellipsoids drawn at the 50% probability level.

Figure 2
Intermolecular interactions of the title compound.[symmetry codes:

Special details
Geometry.All esds (except the esd in the dihedral angle between two l.s.planes) are estimated using the full covariance matrix.The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry.An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s.planes.Refinement.The positions of the N-bound and O-bound H atoms were obtained from difference Fourier maps and were refined isotropically.The C-bound H atoms were placed at ideal positions and were refined as riding on their parent C atoms.U iso (H) values of the H atoms were set at 1.2U eq (carrier) or 1.5U eq (methyl carrier).

Table 2
Experimental details.