(Z)-N-(1-Ethoxyethylidene)-2,6-bis(propan-2-yl)anilinium chloride hemihydrate

In the title compound, C16H26NO+·Cl−·0.5H2O, the asymmetric unit consists of two independent cations, their respective chloride anions and a solvent water molecule. Together they form a discrete crescent-shaped entity linked by hydrogen bonds from the central water atom to two Cl− ions and from the latter to two protonated imine groups. The geometries of the two independent cations are essentially the same. The planar N=C(O)CH3 groups in each (r.m.s. deviations = 0.0011 and 0.0026 Å) form dihedral angles of 75.28 (5) and 79.10 (4)° with the benzene rings. In one cation, the methyl atoms of one of the isopropyl groups were modeled as disordered over two sets of sites, with refined occupancies of 0.589 (17) and 0.411 (17).

In the title compound, C 16 H 26 NO + ÁCl À Á0.5H 2 O, the asymmetric unit consists of two independent cations, their respective chloride anions and a solvent water molecule. Together they form a discrete crescent-shaped entity linked by hydrogen bonds from the central water atom to two Cl À ions and from the latter to two protonated imine groups. The geometries of the two independent cations are essentially the same. The planar N C(O)CH 3 groups in each (r.m.s. deviations = 0.0011 and 0.0026 Å ) form dihedral angles of 75.28 (5) and 79.10 (4) with the benzene rings. In one cation, the methyl atoms of one of the isopropyl groups were modeled as disordered over two sets of sites, with refined occupancies of 0.589 (17) and 0.411 (17).

Comment
The structure of the two independent cations in (I) is shown in Fig. 1. In one cation (b) the isopropyl group was refined with a two component disorder model (C31,C32, C31A & C32A). In the structure of 5-(2-((1-ethoxyethylidene)ammonio)-2-methylpropyl)thianthrenium diperchlorate (II) (Shine et al., 2004), which is the only other compound with an ethoxyiminium group that we could locate in the Cambridge Structural Database (Allen, 2002; WebCSD June 2012) (refcode: FARCAD), the geometry about the iminium bond is also Z.
The H-bonded cluster, shown in Fig. 2, is the asymmetric unit in the crystal. Both imino nitrogen atoms N1 and N2 are protonated and form strong hydrogen bonds (Table 1)

Experimental
The title compound (I) was obtained as a side product of the reaction of (2,6-diisopropylphenyl)phosphine with N-[2,6bis(1-methylethyl)phenyl]-2,2-dimethylmethanimidoyl chloride (Boeré et al., 1998) in THF solution (24 h reflux). While the main product precipitated after cooling, the filtrate was evaporated and treated with ethanol. On cooling this mixture to 243 K for an extended period, crystals of (I) formed as colourless blocks. Presumably, (I) forms by the direct nucleophilic addition of ethanol to unreacted imidoyl chloride. It crystallizes as a hemi-hydrate.

Refinement
During refinement, the methyl groups of one isopropyl group on each of the cations, specifically C8 & C9 and C31 & C32, evidenced large anisotropic displacements. Attempts to define a two-position disorder model for C8 & C9 failed, so these atoms have been treated by a straightforward anisotropic refinement. However, a very reasonable chemical model ensued from a two-position disorder model for C31 and C32 (refined occupancy ratio of 0.589 (17):0.411 (17)). Attempts to include C30 within the disorder model did not lead to a stable refinement, so the second methine carbon was supplementary materials geometrically defined by a dummy atom to ensure the generation of the disordered H atoms on this atom. Hydrogen atoms attached to carbon were treated as riding, with C-H = 0.98 Å and U iso (H) = 1.5U eq (C) for methyl, C-H = 1.00 Å and U iso (H) = 1.2U eq (C) for methine and C-H = 0.95 Å and U iso (H) = 1.2U eq (C) for aromatic H atoms. The NH and OH hydrogen positions are freely refined with isotropic displacements.

Figure 1
The two independent cations of the title compound with ellipsoids drawn at the 50% probability level. H atoms bonded to C atoms are not shown. Atoms labeled C31/C32/C31A/C32A are the components of disorder.