Chlorido{N-[(E)-2-(diphenylphosphanyl)benzylidene]-2-(thiophen-2-yl)ethanamine-κP}gold(I)

The title compound, [AuCl(C25H22NPS)], crystallizes with two independent molecules in the asymmetric unit in which the thiophene fragments are disordered over two sets of sites with 0.537 (10):0.463 (10) and 0.701 (9):0.299 (9) occupancy ratios. In both cases, the thiophene ring is rotated by approximately 180° for the second component. Important geometrical parameters include Au—P = 2.235 (2) and 2.237 (2) Å, Au—Cl = 2.286 (2) and 2.292 (2) Å, and P—Au—Cl = 177.39 (8) and 172.63 (7)°. Weak intermolecular C—H⋯Cl interactions are observed in the crystal structure.


Experimental
Crystal data [AuCl(C 25  238 restraints H-atom parameters constrained Á max = 1.63 e Å À3 Á min = À1.24 e Å À3 Table 1 Hydrogen-bond geometry (Å , ). Financial assistance from the South African National Research Foundation (SA NRF), the Research Fund of the University of Johannesburg and SASOL is gratefully acknowledged.

Comment
There is a growing interest in the coordination chemistry of iminophosphine ligands containing both hard (N donor) and soft (P donor) Lewis acids. Studies of gold(I) complexes have been related to anti-arthritic (Shaw, 1999), anti-tumor (Barnard et al., 2004 and antimicrobial physiological activities (Nomiya et al., 2003).
The asymmetric unit consists of two crystallographically independent molecules of the title compound, each having distinct features such as P1-Au1-Cl1 = 177.38 (9) and P2-Au2-Cl2 = 172.62 (8)°, respectively (Fig. 1). Bond lengths in the metal coordination environment are comparable and listed in the supplementary material for comparison. The thiophene fragments of each unit also show different packing behavior and had to be treated differently with independent disorder refinements [0.463 (10):0.537 (10) and 0.299 (9):0.701 (9) occupancy ratios]. In both cases the thiophene ring rotated approximately 180° for the second component. Conformational differences between the two independent molecules are highlighted in Figure 2 using Mercury (Macrae et al., 2006;Weng et al., 2008a;Weng et al., 2008b), with the root mean squared deviation (RMSD) calculated as 0.3274 Å. Weak intermolecular C-H···Cl interactions are observed in the crystal structure (Table 2).

Experimental
To a dry CH 2 Cl 2 (10 ml) solution of the precursor [Au(tht)Cl] (tht = tetrahydrothiophene) was added an equimolar amount of N-{(E)- [2-(diphenylphosphanyl)phenyl]methylidene}-2-thiophen-2-ylethanamine in CH 2 Cl 2 (10 ml), and stirred at room temperature for 2 hrs. The solvent was reduced and the complex precipitated out on addition of hexane, filtered off, washed with Et 2 O (2 × 5 ml) and dried under vacuum for 4 hrs affording a white precipitate in 55% yield. Crystals suitable for X-ray structure determination were obtained by recrystallization from a CH 2 Cl 2 -hexane mixture at room temperature.

Refinement
All H atoms were positioned in geometrically idealized positions with C-H = 0.99 Å and 0.95 Å for methylene and aromatic H atoms, respectively. All H atoms were allowed to ride on their parent atoms with U iso (H) = 1.2U eq (C). Disorder refinement models for two sites were applied to the thiophenes of each independent molecule in the asymmetric unit (hereafter referred to as molecule 1 and 2 for the unit containing Au1 and Au2, respectively). For the first molecule the disorder was more severe and C20/21 attached to the thiophene also had to be split. Geometrical (FLAT) restraints were applied to keep the rings C22A/B-C23A/B-C24A/B-C25A/B-S1A/B and C47A/B-C48A/B-C49A/B-C50A/B-S2A/B planar.
Bond distance (DFIX) and 1,3 distance similarity restraints (SADI) were applied to obtain reasonable geometries. Ellipsoid displacement (SIMU and DELU) restraints were also applied to the disordered moieties. Free variables were connected to each disordered component to add to unity, respectively. Occupation parameters of the disordered atoms refined 0.537 (10) and 0.701 (9) for the major components of molecule 1 and 2, respectively. All the above restraints were applied with the default standard deviations for molecule 1. In the case of molecule 2 ellipsoid displacement restraints had to be adjusted supplementary materials sup-2 to 0.02 and 0.005 for SIMU and DELU, respectively. Several reflections were omitted (as suggested by the checkCIF procedure) during refinement and can be found from the attached instruction file. The highest residual electron density of 1.63 e.Å -3 is 0.92 Å from Au2, representing no physical meaning. Fig. 1. View of the asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 30% probability level. For clarity: a) hydrogen atoms are omitted, b) bonds in part B of the disordered parts are indicated with dotted lines.