Cyclopentadienylthallium

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 and main group cyclopentadienyl complexes, as well as organic cyclopentadiene derivatives.^[1]

Cyclopentadienylthallium

Names
IUPAC name Thallium(I) cyclopentadienide
Other names Thallium cyclopentadienide (η5-Cyclopentadienyl)thallium
Identifiers
CAS Number	34822-90-7
3D model (JSmol)	Interactive image
ChemSpider	24721800 Y
ECHA InfoCard	100.047.466
EC Number	252-229-2
PubChem CID	97304
InChI InChI=1S/C5H5.Tl/c1-2-4-5-3-1;/h1-5H;/q-1;+1 Key: CVEQRUADOXXBRI-UHFFFAOYSA-N InChI=1/C5H5.Tl/c1-2-4-5-3-1;/h1-5H;/q-1;+1 Key: CVEQRUADOXXBRI-UHFFFAOYAE
SMILES [cH-]1cccc1.[Tl+]
Properties
Chemical formula	C5H5Tl
Molar mass	269.48 g·mol−1
Appearance	Light yellow solid
Melting point	300 °C (572 °F; 573 K)
Solubility in water	Insoluble
Hazards
GHS labelling:
Pictograms
Signal word	Danger
NFPA 704 (fire diamond)	3 0 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation and structure

Cyclopentadienylthallium is prepared by the reaction of thallium(I) sulfate, sodium hydroxide, and cyclopentadiene:^[2]

Tl₂SO₄ + 2 NaOH → 2 TlOH + Na₂SO₄

TlOH + C₅H₆ → TlC₅H₅ + H₂O

The compound adopts a polymeric structure, consisting of infinite chains of bent metallocenes. The Tl---Tl---Tl angles are 130°.^[3] Upon sublimation, the polymer cracks into monomers of C_5v 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.