Titanocene pentasulfide

Titanocene pentasulfide is the organotitanium compound with the formula (C5H5)2TiS5, commonly abbreviated as Cp2TiS5. This metallocene exists as a bright red solid that is soluble in organic solvents. It is of academic interest as a precursor to unusual allotropes of elemental sulfur as well as some related inorganic rings.

Titanocene pentasulfide
Names
Other names
titanocene pentasulfide
Identifiers
Properties
C10H10S5Ti
Molar mass 338.382
Appearance red solid
Structure
Dist. tetrahedral
Related compounds
Related compounds
 Zirconocene pentasulfide
Titanocene dichloride
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

Titanocene pentasulfide is prepared by treating Cp2TiCl2 with polysulfide salts:[1] It was first produced by the addition of elemental sulfur to titanocene dicarbonyl:[2]

(C5H5)2Ti(CO)2 + ​5⁄8 S8 → (C5H5)2TiS5 + 2 CO

The complex is viewed as a pseudotetrahedral complex of Ti(IV). The Ti–S distances are 2.420 and 2.446 Å and the S–S bond distances are of a normal range, 2.051–2.059 Å.[3] The molecule exhibits a dynamic NMR spectrum owing to the chair–chair equilibrium of the TiS5 ring which equivalizes the Cp signals at high temperatures.[4]

Reactions

Cp2TiS5 reacts with sulfur and selenium chlorides, ExCl2, to afford titanocene dichloride and various S5+x and S5Sex rings. Illustrative is the synthesis of S7 from disulfur dichloride:[5]

(C5H5)2TiS5 + S2Cl2 → (C5H5)2TiCl2 + S7

It also reacts with alkenes and ketenes to give heterocycles composed of Ti, C and S. With trialkylphosphines, the cycle dimerize into rings of various sizes, depending on the trialkylphosphine used.[6]

Selected reactions of titanocene pentasulfide
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References
  1. Shaver, Alan; McCall, James M.; Marmolejo, Gabriela (1990). "Cyclometallapolysulfanes (and Selanes) of Bis(η5-Cyclopentadienyl) Titanium(IV), Zirconium(IV), Molybdenum(IV), and Tungsten(IV)". Inorg. Synth. 27: 59–65. doi:10.1002/9780470132586.ch11.
  2. "π-Complexes of Group IVA metals with cyclopentadiene, indene, and fluorine". Bull. Soc. Chim. France. 11: 3548–64. 1966.
  3. Epstein, E. F.; Bernal, I. (1970). "Pentachalcogenide dianions in transition-metal complexes: crystal structure of bis-(π-cyclopentadienyl)titanium pentasulphide". J. Chem. Soc. D. 1970: 410–411. doi:10.1039/C29700000410.
  4. Shaver, Alan; McCall, James M. (1984). "Preparation and Variable-Temperature NMR Studies of the Metallacyclosulfanes Cp2MS5 and (MeSCp)MS3, Where M = Ti, Zr, and Hf". Organometallics. 3: 1823–1829. doi:10.1021/om00090a008.
  5. Steudel, Ralf; Eckert, Bodo (2003). "Solid Sulfur Allotropes Sulfur Allotropes". Topics in Current Chemistry. 230: 1–80. doi:10.1007/b12110.
  6. Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999). Advanced Inorganic Chemistry (6th ed.). Wiley. ISBN 978-0471199571.
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