Cyclooctadiene iridium chloride dimer

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.

Cyclooctadiene iridium chloride dimer
Names
Other names
Bis(1,5-cyclooctadiene)diiridium(I) dichloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.961
EC Number
  • 235-170-7
  • C1/C=C\CC/C=C\C1.C1/C=C\CC/C=C\C1.[Cl].[Cl].[Ir].[Ir]
Properties
C16H24Cl2Ir2
Molar mass 671.70
Appearance red-orange solid
Density 2.65 g/cm3 (red polymorph)
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H302, H312, H315, H319, H335
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

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]

See also

References
  1. J. Hartwig, "Organotransition Metal Chemistry: From Bonding to Catalysis" University Science Books, 2009. ISBN 978-1891389535.
  2. Herdé, J. L.; Lambert, J. C.; Senoff, C. V. (1974). "Cyclooctene and 1,5-Cyclooctadiene Complexes of Iridium(I)". Inorganic Syntheses. Inorganic Syntheses. Vol. 15. p. 18–20. doi:10.1002/9780470132463.ch5. ISBN 9780470132463.
  3. 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
  4. 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
  5. 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. p. 173–176. doi:10.1002/9780470132555.ch50. ISBN 9780470132555.
  6. 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.
  7. 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.
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