Structural isomerism in (p-XC6H4)SeCl3 and (p-XC6H4)SeBr3 (X = F, Cl) compounds. Co-crystallisation of cis- and trans-dimeric forms of (p-ClC6H4)SeCl2(μ-Cl)2(p-ClC6H4)SeCl2. A new structural modification for the “PhSeBr” reagent, Ph2Se2Br2, containing an elongated Se–Se bond
作者:Nicholas A. Barnes、Stephen M. Godfrey、Ruth T. A. Ollerenshaw、Rana Z. Khan、Robin G. Pritchard
DOI:10.1039/c2dt31539d
日期:——
A series of di(para-halophenyl)diselenides, (p-XC6H4)2Se2 (X = F, Cl) have been reacted with three equivalents of SO2Cl2 or Br2, leading to the formation of selenium(IV) RSeX3 compounds. The structures of (p-FC6H4)SeX3 (X = Cl, Br) have been determined, and both exhibit a dimeric RSeX2(μ-X)2RSeX2 structure consisting of two âsaw-horseâ (p-FC6H4)SeX3 units linked by two halide bridges, with an overall square pyramidal geometry at selenium. In both structures all the selenium and halogen atoms are planar, with both aryl rings located on the same side of the Se2X6 plane (cis-isomer). The structure of (p-ClC6H4)SeCl3 also adopts a planar dimeric structure, however both cis- and trans-dimeric molecules are co-crystallised in the unit cell. In contrast, the structure of (p-ClC6H4)SeBr3 adopts a folded cis-dimeric structure due to steric constraints. Secondary Seâ¯X interactions to the âvacantâ sixth coordination site at selenium are a feature of most of these structures, but are most prominent in the folded structure of (p-ClC6H4)SeBr3. A re-examination of the PhSeBr/PhSeBr3 system resulted in the isolation of crystals of a second structural form of âPhSeBrâ. The structure of Ph2Se2Br2 consists of two PhSeBr units linked by an elongated SeâSe bond of 2.832(4) Ã
, and longer secondary Seâ¯Br interactions of 3.333(4) Ã
to form a chain structure. Further weak Seâ¯Br and Brâ¯Br interactions are present, which form loosely linked rippled sheets of selenium and bromine atoms, similar to the sheets observed for the tetrameric form, Ph4Se4Br4.
一系列二(对位卤苯基)二硒化物 (p-XC6H4)2Se2 (X = F, Cl) 与三当量的 SO2Cl2 或 Br2 反应,生成了硒(IV)RSeX3 化合物。(p-FC6H4)SeX3(X = Cl,Br)的结构已经确定,两者都呈现出二聚 RSeX2(δ-X)2RSeX2 结构,由两个 "锯马"(p-FC6H4)SeX3 单元组成,通过两个卤化物桥连接,硒的整体呈方形金字塔几何结构。在这两种结构中,所有的硒原子和卤素原子都是平面的,两个芳基环都位于 Se2X6 平面的同一侧(顺式异构体)。(p-ClC6H4)SeCl3 的结构也采用了平面二聚体结构,但顺式和反式二聚体分子都在单位晶胞中共晶。相反,由于立体限制,(p-ClC6H4)SeBr3 的结构采用了折叠的顺式二聚体结构。与硒的第六配位位点 "空位 "的二次 Seâ¯X 相互作用是大多数这些结构的特征,但在 (p-ClC6H4)SeBr3 的折叠结构中最为突出。通过对 PhSeBr/PhSeBr3 系统的重新研究,我们分离出了第二种结构形式的 "PhSeBr "晶体。Ph2Se2Br2 的结构由两个 PhSeBr 单元组成,通过 2.832(4) à 的拉长 SeâSe 键和 3.333(4) à 的较长次级 Seâ¯Br 相互作用连接,形成链状结构。此外,还存在较弱的 Seâ¯Br 和 Brâ¯Br 相互作用,形成松散连接的硒和溴原子波纹状薄片,类似于在四聚形式 Ph4Se4Br4 中观察到的薄片。