Publication details
Synthesis and Crystal Structure of Tetrakis(tetramethylammonium) Bis[decabromotetraselenate(II)]-bis[dibromodiselenate(I)], [(CH3)4N]4[(Se4Br10)2(Se2Br2)2], the Salt of a Mixed-Valence Bromoselenate(II/I) Anion
| Authors | |
|---|---|
| Year of publication | 2010 |
| Type | Article in Periodical |
| Magazine / Source | Zeitschrift für Anorganische und Allgemeine Chemie |
| MU Faculty or unit | |
| Citation | |
| Web | http://dx.doi.org/10.1002/zaac.200900466 |
| Field | Inorganic chemistry |
| Keywords | Bromine; Selenium; Mixed-valent compounds; Solid-state structure; X-ray diffraction |
| Description | Brown crystals of [NMe4]4[(Se4Br10)2(Se2Br2)2] (1) were obtained from the reaction of selenium and bromine in acetonitrile in the presence of tetramethylammonium bromide. The crystal structure of 1 was determined by X-ray diffraction and refined to R = 0.0297 for 8401 reflections. The crystals are monoclinic, space group P21/c with Z = 4 and a = 12.646(3) A, b = 16.499(3) A, c = 16.844(3) A, = 101.70(3)deg (123 K). In the solid-state structure, the anion of 1 is built up of two [Se4Br10]2- ions. Each shows a triangular arrangement of three planar SeBr4 units sharing a common edge through two 3-bridging bromine atoms, and one SeBr2 molecule, which is linked to the SeII atoms of two SeBr4 units; between the Se4Br102- ions a dimerized Se2Br2 molecule (Se4Br4) is situated and one SeI atom of each Se2Br2 molecule has two weak contacts [3.3514(14) A and 3.3952(11) A] to two bromine atoms of one SeBr4 unit. Four SeI atoms of a dimerized Se2Br2 molecule are in a almost regular planar tetraangular arrangement. Contacts between the SeII atom of the SeBr2 molecule and the SeII atoms of two SeBr4 units are 3.035(1) A and 3.115(1) A, and can be interpreted as donor-acceptor type bonds with the SeII atoms of SeBr4 units as donors and the SeBr2 molecule as acceptor. The terminal SeII-Br and 3-Br-SeII bond lengths are in the ranges 2.3376(10) to 2.4384(8) A and 2.8036(9) to 3.3183(13) A, respectively. The bond lengths in the dimerized Se2Br2 molecule are: SeI-SeI = 2.2945(8) A and 3.1398(12), SeI-Br = 2.3659(11) and 2.3689(10) A. |