Pentamethylcyclopentadienyl iridium dichloride dimer

Pentamethylcyclopentadienyl iridium dichloride dimer
IUPAC name Di-µ-chloro-bis[chloro(pentamethylcyclopentadienyl)iridium(III)]
Other names Dichloro(pentamethylcyclopentadienyl)iridium(III)
Identifiers
CAS number	12354-84-6 Y
Properties
Molecular formula	C20H30Cl4Ir2
Molar mass	796.71 g/mol
Appearance	orange solid
Melting point	>230 °C
Y iridium dichloride dimer (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Pentamethylcyclopentadienyl iridium dichloride is an organometallic compound with the formula [(C₅(CH₃)₅IrCl₂)]₂, commonly abbreviated [Cp*IrCl₂]₂ This bright orange air-stable diamagnetic solid is a reagent in organometallic chemistry.^[1]

Preparation, structure, reactions

The compound has C_2h symmetry. Each metal is pseudo-octahedral. It was first prepared by the reaction of hydrated iridium trichloride with hexamethyldewar benzene.^[2] More conveniently, iridium trihydrate and pentamethylcyclopentadiene consistently gives the product in both high yield and purity according to this idealized equation:^[1]

2 Cp*H + 2 IrCl₃(H₂O)₃ → [Cp*IrCl₂]₂ + 2 HCl + 6 H₂O

The two Ir-μ-Cl bonds are labile and can be cleaved to give a variety of adducts of the general formula Cp*IrCl₂L. Such adducts undergo further substitution to afford cations [Cp*IrClL₂]⁺ and [Cp*IrL₃]²⁺. The chloride ligands can also be replaced by other anions such as carboxylates, nitrite, and azide.

Reduction of [Cp*IrCl₂]₂ under an atmosphere of CO affords the dicarbonyl Cp*Ir(CO)₂], which can be decarbonylated to give the unsaturated derivative [Cp*Ir(CO)]₂.^[3] Treatment of [Cp*IrCl₂]₂ with borohydride under an atmosphere of H₂ gives the iridium(V) derivative Cp*IrH₄.

[Cp*IrCl₂]₂ is a precursor to catalysts for the asymmetric transfer hydrogenation of ketones.^[4]

References

1. ^ ^{a b} White, C.; Yates, A.; Maitlis, P. M. (1992). "(η⁵-Pentamethylcyclopentadienyl)Rhodium and -Iridium Compounds". Inorganic Syntheses 29: 228–234. doi:10.1002/9780470132609.ch53. 
2. ^ Jung W. Kang; K. Moseley; Peter M. Maitlis (1969). "Pentamethylcyclopentadienylrhodium and -iridium halides. I. Synthesis and properties". Journal of the American Chemical Society 91: 5970. doi:10.1021/ja01050a008. 
3. ^ R. G. Ball; W. A. G. Graham; D. M. Heinekey; J. K. Hoyano; A. D. McMaster; B. M. Mattson; S. T. Michel (1990). "Synthesis and structure of dicarbonylbis(.eta.-pentamethylcyclopentadienyl)diiridium". Inorganic Chemistry 29: 2023. doi:10.1021/ic00335a051. 
4. ^ Ikariya, T.; Blacker, A. J. (Dec 2007). "Asymmetric transfer hydrogenation of ketones with bifunctional transition metal-based molecular catalysts". Accounts of Chemical Research 40 (12): 1300–8. doi:10.1021/ar700134q. ISSN 0001-4842. PMID 17960897.