Redetermination of chlorido(2,2′:6′,2′′-terpyridine-κ3 N,N′,N′′)gold(I) dichloride trihydrate at 173 K

The redetermined structure of the title compound, [AuCl(C15H11N3)]Cl2·3H2O, at 173 (2) K is reported. The structure displays O—H⋯Cl and O—H⋯O hydrogen bonding. The distance of one of the chloride ions from the gold(I) atom [5.047 (1) Å] differs from that determined previously.

The redetermined structure of the title compound,  H 11 N 3 )]Cl 2 Á3H 2 O, at 173 (2) K is reported. The structure displays O-HÁ Á ÁCl and O-HÁ Á ÁO hydrogen bonding. The distance of one of the chloride ions from the gold(I) atom [5.047 (1) Å ] differs from that determined previously.

Related literature
For the previous determination of the crystal structure of the title compound, see: Hollis & Lippard (1983).
A search of the literature revealed that the crystal structure of this compound was previously reported by Hollis & Lippard (1983). The reported structure possesses almost identical crystal parameters to the structure reported here in terms of space group, and unit-cell dimensions and angles. In addition, the coordination sphere parameters appear to closely match those obtained previously. However, the collection of data at 173 K, in comparison to 296 K as reported by Hollis & Lippard, results in some notable conclusions in addition to yielding more accurate data.
The water molecules and chloride ions are involved in extensive intermolecular hydrogen bonding. Additionally, Cl3 is orientated differently here than in the previously determined structure. With reference to the gold centre, Cl3 is found 5.047 (1) Å from the metal atom while the structure reported by Hollis & Lippard shows this distance to be 5.016 Å.

Experimental
A mixture of AuCl 4 .3H 2 O (0.100 g, 0.29 mmol) and terpyridine (0.072 g, 0.31 mmol) was placed in 10 ml of deionized water in a round-bottom flask. The solution pH was adjusted to 3.0 with 1 M NaOH, and the resulting mixture refluxed at 100°C for 24 h. The red mixture was then cooled to room temperature and filtered to remove small amounts of a purple solid. The filtrate obtained was allowed to stand at room temperature to induce precipitation of the crystalline product. The crystals were filtered off and air-dried to yield the title compound. (0.013 g, 7.5%), mp 503 K. 1 8, 151.5, 146.8, 141.5, 139.7, 126.0, 122.8, 122.7.

Refinement
Hydrogen atoms were positioned geometrically and allowed to ride on their respective parent atoms, with C-H bond lengths of 0.93 Å (CH) in a riding model with U iso (H) = 1.2U eq (X) for X = CH.  Fig. 1. The asymmetric unit of I. Displacement ellipsoids are drawn at the 40% probability level. The labelling of atoms is as shown, and is identical to that of Hollis & Lippard. The two chloride counter ions and the three water molecules associated with I are evident, present above and below the plane of the molecule.