Pentamethylcyclopentadienyl rhodium dichloride dimer

Pentamethylcyclopentadienyl rhodium dichloride is an organometallic compound with the formula [(C5(CH3)5RhCl2)]2, commonly abbreviated [Cp*RhCl2]2 This dark red air-stable diamagnetic solid is a reagent in organometallic chemistry.[1]

Pentamethylcyclopentadienyl rhodium dichloride dimer
Names
IUPAC name
Di-µ-chloro-bis[chloro(pentamethylcyclopentadienyl)rhodium(III)]
Other names
Dichloro(pentamethylcyclopentadienyl)rhodium(III)
Identifiers
3D model (JSmol)
ChemSpider
Properties
C20H30Cl4Rh2
Molar mass 618.07 g·mol−1
Appearance red solid
dichloromethane, chloroform
Hazards
GHS pictograms
GHS Signal word Danger
GHS hazard statements
 H302, H312, H315, H319, H332, H334, H335
P261, P264, P270, P271, P280, P285, P301+312, P302+352, P304+312, P304+340, P304+341, P305+351+338, P312, P321, P322, P330, P332+313, P337+313, P342+311, P362, P363, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure and preparation

The compound has idealized C2h symmetry. Each metal centre is pseudo-octahedral.

The compound is prepared by the reaction of rhodium trichloride trihydrate and pentamethylcyclopentadiene in hot methanol, from which the product precipitates:[1]

2 Cp*H   +   2 RhCl3(H2O)3     [Cp*RhCl2]2   +   2 HCl   +   6 H2O

It was first prepared by the reaction of hydrated rhodium trichloride with hexamethyl Dewar benzene[2]

Synthesis of [Cp*RhCl2]2 using hexamethyl Dewar benzene.

Reactions

Reductive carbonylation gives [Cp*Rh(CO)2].[3]

The Rh-μ-Cl bonds are labile and cleave en route to a variety of adducts of the general formula Cp*RhCl2L. Treatment with silver ions in polar coordinating solvents causes precipitation of silver(I) chloride, leaving a solution containing dications of the form [Cp*RhL3]2+ (L = H2O, MeCN).

The chemistry is similar to that of the analog pentamethylcyclopentadienyl iridium dichloride dimer.

Further reading (early literature)
  • Kang, Jung W.; Mosley, K.; Maitlis, Peter M. (1968). "Mechanisms of Reactions of Dewar Hexamethylbenzene with Rhodium and Iridium Chlorides". Chem. Commun. (21): 1304–1305. doi:10.1039/C19680001304.
  • Kang, Jung W.; Maitlis, Peter M. (1968). "Conversion of Dewar Hexamethylbenzene to Pentamethylcyclopentadienylrhodium(III) Chloride". J. Am. Chem. Soc. 90 (12): 3259–3261. doi:10.1021/ja01014a063.
  • Criegee, Rudolf; Grüner, H. (1968). "Acid-catalyzed Rearrangements of Hexamethyl-prismane and Hexamethyl-Dewar-benzene". Angew. Chem. Int. Ed. 7 (6): 467–468. doi:10.1002/anie.196804672.
  • Kang, Jung W.; Moseley, K.; Maitlis, Peter M. (1969). "Pentamethylcyclopentadienylrhodium and -iridium halides. I. Synthesis and properties". J. Am. Chem. Soc. 91 (22): 5970–5977. doi:10.1021/ja01050a008.
  • Herrmann, Wolfgang A.; Zybill, Christian (1996). "Bis{(μ-chloro)[chloro(η-pentamethylcyclopentadienyl)rhodium]} — {Rh(μ-Cl)Cl[η-C5(CH3)5]}2". In Herrmann, Wolfgang A.; Salzer, Albrecht (eds.). Synthetic Methods of Organometallic and Inorganic Chemistry – Volume 1: Literature, Laboratory Techniques, and Common Starting Materials. Georg Thieme Verlag. pp. 148–149. ISBN 9783131791610.
  • Heck, Richard F. (1974). "Reactions of Dienes Trienes and Tetraenes with Transition Metal Compounds". Organotransition Metal Chemistry: A Mechanistic Approach. Academic Press. pp. 116–117. ISBN 9780323154703.

References
  1. White, C.; Yates, A.; Maitlis, Peter M. (1992). "(η5-Pentamethylcyclopentadienyl)Rhodium and -Iridium Compounds". Inorg. Synth. 29: 228–234. doi:10.1002/9780470132609.ch53.
  2. Paquette, Leo A.; Krow, Grant R. (1968). "Electrophilic Additions to Hexamethyldewarbenzene". Tetrahedron Lett. 9 (17): 2139–2142. doi:10.1016/S0040-4039(00)89761-0.
  3. Herrmann, Wolfgang A.; Zybill, Christian (1996). "Dicarbonyl(η-pentamethylcyclopentadienyl)rhodium — Rh[η-C5(CH3)5](CO)2". In Herrmann, Wolfgang A.; Salzer, Albrecht (eds.). Synthetic Methods of Organometallic and Inorganic Chemistry – Volume 1: Literature, Laboratory Techniques, and Common Starting Materials. Georg Thieme Verlag. pp. 147–148. ISBN 9783131791610.
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