Selenium interatomic distance

From elemental sulfur to selenium and tellurium, intermolecular interactions (,secondary bonds, soft-soft interactions) play an increasing role. According to N. W. Alcock,1 the term secondary bond describes interatomic distances longer than covalent single bonds but shorter than van der Waals interatomic distances.1 In many cases secondary bonds can also be described as coordinative Lewis base - Lewis acid or charge transfer (donor-acceptor) types of interactions. 

Structure type ErsCuPbaSen (Gulay et al., 2006i) (Figure 98, Table 48). SG Cmcm, Z = 4, fl = 0.40710, h = 1.3480, c = 3.8092 run. The erbium and copper atoms are located in distorted octabedra and tetrahedra, respectively. The shortest interatomic distances among these coordination spheres are d(Er-Se) = 0.2795 nm and d(Cu-Se) = 0.240 nm. The selenium atoms create mono- and bicapped trigonal prismatic arrangements around the Pbl and Pb2 atoms, respectively, and the shortest Pb-Se distance is 0.2877 nm. The Sel and Se6 atoms are located in octahedra... 

This class can be illustrated by the dimers [(Bu CH2)2lnSCH2Bu ]2 (In-S 2.618 and 2.623 A), [(Bu CH2)2lnSeCH2But]2 (In-Se 2.705 and 2.719 A) [215], [(Me3CCH2)2lnSePh]2, and polymeric [Me(PhSe)In(//-SePh)] j [285]. The compounds have been reviewed [113]. Some interatomic distances for other indium-sulfur and indium-selenium supermolecules are collected in Table 3.8. 

Mercury is a soft metal and as such it is expected to form secondary bonds, most readily with sulfur, selenium, and other heavy non-metals. The situation is, however, more complex and secondary interactions with other electronegative atoms have also been observed in the solid state. Interatomic distances longer than the expected van der Waals distances are, moreover, sometimes observed between molecules orientated such that weak interactions lead to particular arrangements in the crystal [69]. The are numerous examples of secondary bonds in organomercury chemistry although most are intramolecular there are several examples of inter-molecular secondary bonds leading to supramolecular self assembly. A review has been published on this subject [70] and many new examples have subsequently been reported. 

---