Thallium—chlorine bonds

In 1962, Sugano showed that the Seitz model (115) could be interpreted as a molecular orbital model (123), an interpretation that clarifies analysis of these systems. In this interpretation, the absorption bands observed in the TI(I) doped alkali halide system come from the electronic transition aigf a g) hu), but the excited states are still calculated assuming an ionic interaction between the metal and the hgand. Since the thallium-chlorine bond is actually largely covalent, Bramanti et al. (118) modified the approach and used a semiempirical molecular orbital (MO) calculation to describe the energy levels of T1(I) doped KCl. Molecular orbitals were constructed by the linear combination of atomic orbitals (LCAO) method from the 6s and 6p metal orbitals and the 3p chlorine orbitals. Initial calculations were conducted with the one-electron approximation the method was then expanded to include Coulomb and spin-orbit interactions. The results of Bramanti et al. were consistent with experimental... 

Main and subgroup elements of the earlier rows often exhibit a dynamic equilibrium between different coordination numbers. Elements such as fluorine, chlorine, oxygen, etc., can donate one or two free electron pairs to vacant lower energy orbitals of these metal atoms. Fluorine can therefore act as a bifunctional bridging atom, and oxygen can even be mono- to tetrafunctional, according to its bond partner. In all these cases the coordination number is increased above normal. In the case of fluorine, fluorine bridge bonds exist, for example, in the anion of the complex between thallium fluoride and aluminum fluoride ... 

Trichloro-(l,10-phenanthroline)thallium(m) exists as a weak chlorine-bridged dimer. The Tl-N distances are 2.348 and 2.380 A, whilst the terminal Tl-Cl distances are 2.443 and 2.457 A. The bridging chlorine atoms form one short (2.500 A) and one long (3.236 A) bond to each thallium atom. 

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