Cyclooctadiene iridium chloride dimer

Cyclooctadiene iridium chloride dimer
Names



Other names Bis(1,5-cyclooctadiene)diiridium(I) dichloride
Identifiers
CAS Number	12112-67-3
3D model (JSmol)	Interactive image
ChemSpider	21171240
ECHA InfoCard	100.031.961
EC Number	235-170-7
PubChem CID	5365616 PubChem has wrong formula
CompTox Dashboard (EPA)	DTXSID00923689
SMILES C1/C=C\CC/C=C\C1.C1/C=C\CC/C=C\C1.[Cl].[Cl].[Ir].[Ir]
Properties
Chemical formula	C₁₆H₂₄Cl₂Ir₂
Molar mass	671.70
Appearance	red-orange solid
Density	2.65 g/cm³ (red polymorph)
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H302, H312, H315, H319, H335
Precautionary statements	P261, P264, P270, P271, P280, P301+P312, P302+P352, P304+P340, P305+P351+P338, P312, P321, P322, P330, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Chemical compound

Cyclooctadiene iridium chloride dimer is an organoiridium compound with the formula [Ir(μ²-Cl)(COD)]₂, where COD is the diene 1,5-cyclooctadiene (C₈H₁₂). It is an orange-red solid that is soluble in organic solvents. The complex is used as a precursor to other iridium complexes, some of which are used in homogeneous catalysis.^[1] The solid is air-stable but its solutions degrade in air.

Preparation, structure, reactions

The compound is prepared by heating hydrated iridium trichloride and cyclooctadiene in alcohol solvent. In the process, Ir(III) is reduced to Ir(I).^[2]

In terms of its molecular structure, the iridium centers are square planar as is typical for a d⁸ complex. The Ir₂Cl₂ core is folded with a dihedral angle of 86°. The molecule crystallizes in yellow-orange and red-orange polymorphs; the latter one is more common.^[3]^[4]

The complex is widely used precursor to other iridium complexes. A notable derivative is Crabtree's catalyst.^[5] The chloride ligands can also be replaced with methoxide to give cyclooctadiene iridium methoxide dimer, Ir₂(OCH₃)₂(C₈H₁₂)₂.^[6] The cyclooctadiene ligand is prone to isomerize in cationic complexes of the type [(C₈H₁₂)IrL₂]⁺.^[7]

References

^ J. Hartwig, "Organotransition Metal Chemistry: From Bonding to Catalysis" University Science Books, 2009. ISBN 978-1891389535.
^ Herdé, J. L.; Lambert, J. C.; Senoff, C. V. (1974). "Cyclooctene and 1,5-Cyclooctadiene Complexes of Iridium(I)". Inorganic Syntheses. Vol. 15. pp. 18–20. doi:10.1002/9780470132463.ch5. ISBN 9780470132463.
^ F. Albert Cotton, Pascual Lahuerta, Mercedes Sanau, Willi Schwotzer "Air oxidation of Ir₂(Cl)₂(COD)₂ revisited. The structures of [Ir(μ²-Cl)(COD)]₂ (ruby form) and its oxidation product, Ir₂Cl₂(COD)₂(μ₂-OH)₂(μ²-O)" Inorganica Chimica Acta, 1986 vol. 120, Pages 153–157. doi:10.1016/S0020-1693(00)86102-2
^ Tabrizi, D., Manoli, J. M., Dereigne, A., "Etude radiocristallographique de μ-dichloro-bis (π cyclooctadiène-1,5) diiridium: [(COD-1,5)IrCl]₂, variété jaune-orange", Journal of the Less Common Metals 1970, vol. 21, pp. 337. doi:10.1016/0022-5088(70)90155-4
^ Crabtree, Robert H.; Morehouse, Sheila M. (1986). "[η4 -1,5-Cyclooctadiene)(Pyridine)-(Tricyclohexylphosphine)Iridium(I)Hexafluorophosphate". [η⁴-1,5-Cyclooctadiene)(Pyridine)(Tricyclohexylphosphine)Iridium(I)Hexafluorophosphate. Inorganic Syntheses. Vol. 24. pp. 173–176. doi:10.1002/9780470132555.ch50. ISBN 9780470132555.
^ Uson, R.; Oro, L. A.; Cabeza, J. A. (1985). "Dinuclear Methoxy, Cyclooctadiene, and Barrelene Complexes of Rhodium(I) and Iridium(I)". Inorganic Syntheses. Vol. 23. pp. 126–130. doi:10.1002/9780470132548.ch25. ISBN 9780470132548.
^ Martín, Marta; Sola, Eduardo; Torres, Olga; Plou, Pablo; Oro, Luis A. (2003). "Versatility of Cyclooctadiene Ligands in Iridium Chemistry and Catalysis". Organometallics. 22 (26): 5406–5417. doi:10.1021/om034218g.