Di-μ-thiocyanato-bis[bis(tri-p-tolylphosphine)silver(I)] 0.35-hydrate

In the binuclear centrosymmetric title compound, [Ag2(NCS)2(C21H21P)4]·0.35H2O, a pseudo-polymorph of [Ag2(NCS)2(C21H21P)4]·2CH3CN, the Ag atom is coordinated by two phosphine ligands and two bridging thiocyanate ligands in a distorted tetrahedral configuration. The crystal structure exhibits intermolecular C—H⋯π interactions.

Cg1 and Cg6 are the centroids of the C111-C116 and C231-C236 benzene rings, respectively. Comment Silver(I) complexes of the type [AgLnX] (L is a tertiary phosphine or arsine, n = 1-4 and X is a coordinating or noncoordinating anion) were first prepared by Mann et al. (1937) and were the first crystallographic examples of metal phosphine complexes. These compounds display a rich diversity of structural types due to the interplay of parameters such as the geometric flexibility of Ag(I), the bite angle, the electronic properties of the group 15 donor ligand, the coordination of the supporting ligand, etc. (Meijboom et al., 2009).
As part of work that was aimed at the identification of roles the above mentioned properties play during the crystallization of simple silver(I) salts with Group 15 donor ligands with initial focus on tri-p-tolylphosphine complexes (Meijboom et al., 2006;Meijboom, 2006;Meijboom & Muller, 2006;Venter et al., 2006;Meijboom, 2007), we present here a pseudo-polymorph of the previously reported [Ag 2 (NCS) 2 (C 21 H 21 P) 4 ]2CH 3 CN (Venter et al., 2007), [Ag 2 (NCS) 2 (C 21 H 21 P) 4 ]0.35H 2 O (I). Complex (I) was left standing on the bench top in the lab for a long period of time during which it supposedly absorbed moisture into its structure.
The asymmetric unit of the title compound, Fig. 1, comprises half a unit of the Ag I complex (the other half generated by the symmetry operator -x+1, -y+1, -z+1) and 0.35 molecule of H 2 O. The bond lengths (Allen et al., 1987) and angles (Table 1)  The geometry around the Ag(I) atom is a slightly distorted tetrahedral which is coordinated by the two SCN anions and two phosphine ligands resulting in a dimeric species in which the two Ag(I) centres are bridged by the SCN anions (Table 1).
The crystal structure is stabilized by pairs of C-H···π intermolecular interactions along the crystallographic a and c axes supplementary materials sup-2 Refinement All hydrogen atoms were positioned geometrically, with C-H = 0.95 Å for aromatic hydrogens and 0.98 Å for methyl hydrogens, and allowed to ride on their parent atoms with U iso (H) = 1.2U eq (C).

CheckCif Alerts explanations
Applying restraints does not seem to remove Hirshfeld Test Diff. There is partial occupation of the O atom. EADP restaraints were applied. The su's on the Cell Angles are true values. The Solvent Disorder fraction too small.

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.