Crystal structure of {[1′-(diphenylphosphino)ferrocenyl]methyl}dimethylammonium chloride monohydrate

The molecular structure of {[1′-(diphenylphosphino)ferrocenyl]methyl}dimethylammonium chloride monohydrate is presented. Individual ions and the solvating water molecule assemble into dimeric units located around crystallographic inversion centers via N—H⋯Cl and O—H⋯Cl hydrogen bonds.

The protonated aminomethyl chain is directed away from the ferrocene core, with the angle between the C1-N bond and the axis of the ferrocene unit, Cg1Á Á ÁCg2, being 148.99 (11) . The phosphine substituent at the other cyclopentadienyl ring is oriented so that one of its pivotal P-C(Ph) bonds lies nearly in the plane of the bonding five-membered ring C6-C10, while the other is roughly parallel with the axis of the ferrocene unit. The angle at which the P-C18 bond intersects the C6-C10 plane is 13.17 (10) , whereas the angle subtended by the P-C12 bond and the Cg1Á Á ÁCg2 line is only 8.68 (5) .

Supramolecular features
Each [Ph 2 PfcCH 2 NHMe 2 ] + cation in the structure of the title compound is involved in an N-HÁ Á ÁCl hydrogen bond to a proximal chloride anion (for hydrogen-bond parameters, see Table 1). The anions further act as hydrogen-bond acceptors for a pair of inversion-related water molecules, which in turn results in the formation of charge-neutral, closed dimeric arrays {(Ph 2 PfcCH 2 NHMe 2 ) 2 Cl 2 (H 2 O) 2 } around the crystallographic inversion centers. These discrete units are further interlinked into chains along the a axis via the weaker C-HÁ Á ÁO and C-HÁ Á ÁCl interactions, as shown in Fig. 2.

Database survey
A search in the Cambridge Structural Database (Version 5.38 with the latest update from May 2017; Groom et al., 2016) for structurally related compounds resulted in the structures of two similar (ferrocenylmethyl)ammonium salts, namely N-(ferrocenylmethyl)dimethylammonium chloride (Winter & Wolmershä user, 1998) and its dihydrate (Guo et al., 2006), and two complexes obtained from Ph 2 PfcCH 2 NMe 2 featuring a protonated (dimethylamino)methyl side chain, viz.

Synthesis and crystallization
The 'amine' Ph 2 PfcCH 2 NMe 2 regenerated from the synthesis of the phosphinoferrocene betaine Ph 2 PfcCH 2 NMe 2 -(CH 2 ) 3 SO 3 (Zá branský et al., 2015) (ca 100 mg) was dissolved in acetic acid (10 mL) and the solution was evaporated under reduced pressure. After this procedure was repeated twice using chloroform as a solvent, the residue was dissolved in a minimum amount of hot ethyl acetate. The solution was filtered and layered with hexane. Crystallization by liquidphase diffusion over several days afforded orange crystals of the title compound. The yield was not determined.

Figure 2
Section of the hydrogen-bonded chains in the structure of the title compound. For clarity, hydrogen atoms not involved in hydrogen bonding are omitted.

Refinement
Relevant crystallographic data and structure refinement parameters are summarized in Table 2. All non-hydrogen atoms were refined freely with anisotropic displacement parameters. The hydrogen atoms of the water molecule and the NH proton were located on a difference electron-density map and refined as riding atoms with U iso (H) set to 1.2U eq of their bonding atom. Hydrogen atoms bonded to carbons were included in their theoretical positions and refined as riding atoms with U iso (H) = 1.2U eq (C).  (Bruker, 2015); cell refinement: SAINT (Bruker, 2015); data reduction: SAINT (Bruker, 2015); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: PLATON (Spek, 2009

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.