The Pseudo-Symmetric Structure of Pb(SPh)2

• Published in: Acta crystallographica. Section B, Structural science Structural science, 1997-06, Vol.53 (3), p.457-465
• Main Authors: Rae, A. D., Craig, D. C., Dance, I. G., Scudder, M. L., Dean, P. A. W., Kmetic, M. A., Payne, N. C., Vittal, J. J.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Miscellaneous; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 0108-7681; 1600-5740
• DOI: 10.1107/S0108768196015819

The crystal structure of Pb(SC 6 H 5 )2 is pseudo- C -centred orthorhombic, a = 54.06 (1), b = 11.468 (1), c = 7.4387 (8) Å, \alpha = \beta = \gamma = 90°, Z = 16, and may be described as a partial ordering of a 1:1 disordered parent structure of symmetry Pmcn , Z = 4 ( a ′ = a /2, b ′ = b /2, c ′ = c ), in which the mirror imposes a 1:1 disorder on two-dimensionally polymeric layers perpendicular to a *. An ideally ordered structure has monoclinic space group C 112 1 / d ( P 2 1 / c using an alternative axis system b , c , [ a + b ]/2), but may also be described as two inversion-related substructures of Cmc 2 1 pseudo- symmetry, where the b -glide planes of one substructure coincide with the mirror planes of the other and vice versa . Moving one substructure by b /2 relative to the other creates a different orientation of the structure. The crystal studied showed a partial disorder of each substructure relative to origins b /2 apart [0.964 (4):0.036 for one substructure and 0.584 (3):0.416 for the other]. This lowers the symmetry of the average structure to C 112 1 with intensities realistically described as K 2 [(1−\delta)| F ( hkl )| 2 + \delta| F ( hkl )| 2 ], where K 2 for h odd, k odd reflections is 0.444 (7) of the value for h even, k even reflections, \delta is 0.325 (5) and F ( hkl ) is the structure factor for an ideally ordered structure. Final values for R of 0.046 and 0.090 were obtained for the 844 h even, k even and 687 h odd, k odd reflections with I ( h ) > 3\sigma( I ( h )) used in refinement. A bond-valence interpretation of the bonding within the polymeric layer structure is given.