Inert Pair Effects in Tin and Lead Dihalides: Crystal Structure of Tin(II) Bromide

• Published in: Journal of solid state chemistry Vol. 149; no. 1; pp. 28 - 32
• Main Authors: Abrahams, I., Demetriou, D.Z.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 01.01.2000; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Halides, chalcogenides and analogous compounds of group vb; Inorganic compounds; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Inorganic compounds; Powder pattern; Tin bromides; Binary compounds; XRD; Experimental study; Tin chlorides; Lead bromides; Comparative study; Lead chlorides; Crystal structure
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1999.8489

The crystal structure of stannous bromide, SnBr2, is compared with those of its analogs: SnCl2, PbBr2, and PbCl2. The structure of SnBr2 has been refined by Rietveld analysis of X-ray powder diffraction data in the orthorhombic space group Pbnm, with a=10.5251(7) Å, b=8.3936(5) Å, c=4.2369(2) Å, and Z=4. Refinement terminated with Rwp=11.90% and Rex=19.11%. Sn is in a trigonal-pyramidal coordination with three Br atoms, two of which are bridging and one terminal. The bridging units form polymeric chains, which run parallel to the c-axis. SnBr2 is related to, but is not isostructural with, analogs, PbCl2, PbBr2, and SnCl2. All the structures possess (MX2)n chains (M=Sn or Pb, X=Cl or Br), but those in SnBr2 are shifted with respect to each other, resulting in a difference in the secondary M–X coordination shell. Stereochemical distortions caused by the nonbonding valence electron pairs on the metal atoms are compared using unit cell parameters normalized to take into account differences in covalent radii between the structures.