Thallium cyclopentadienide
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Cyclopentadienylthallium, also known as thallium cyclopentadienide, is an organothallium compound with formula C5H5Tl. This light yellow solid is insoluble in most organic solvents, but sublimes readily. It is used as a precursor to
transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that ca ...
and main group
cyclopentadienyl complex A cyclopentadienyl complex is a coordination complex of a metal and cyclopentadienyl groups (, abbreviated as Cp−). Cyclopentadienyl ligands almost invariably bind to metals as a pentahapto (''η''5-) bonding mode. The metal–cyclopentadien ...
es, as well as organic cyclopentadiene derivatives.


Preparation and structure

Cyclopentadienylthallium is prepared by the reaction of thallium(I) sulfate, sodium hydroxide, and cyclopentadiene: : Tl2SO4 + 2 NaOH → 2 TlOH + Na2SO4 : TlOH + C5H6 → TlC5H5 + H2O The compound adopts a
polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
ic structure, consisting of infinite chains of bent metallocenes. The Tl---Tl---Tl angles are 130°.Falk Olbrich, Ulrich Behrens "Crystal structure of catena-cyclopentadienylthallium, l(C5H5) Zeitschrift für Kristallographie - New Crystal Structures 1997, 212, 47-47. Upon sublimation, the polymer cracks into monomers of C5v symmetry.


Applications

Compared to other cyclopentadienyl (Cp) transfer reagents, such as cyclopentadienyl sodium, CpMgBr and Cp2Mg, cyclopentadienylthallium is less air sensitive. It is also much less of a reducing agent.


References

{{Cyclopentadiene complexes Cyclopentadienyl complexes Organothallium compounds Half sandwich compounds Thallium(I) compounds