Chemistry:Cyclooctadiene rhodium chloride dimer
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Names | |
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IUPAC name
di-μ-chlorido-
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Other names
Cyclooctadiene rhodium chloride dimer
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Identifiers | |
3D model (JSmol)
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EC Number |
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PubChem CID
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Properties | |
C16H24Cl2Rh2 | |
Molar mass | 493.0806 g/mol |
Density | 1.93 g/cm3 |
Melting point | 243 °C (469 °F; 516 K) |
Solubility | dichloromethane |
Hazards | |
GHS pictograms | ![]() ![]() |
GHS Signal word | Warning |
H302, H315, H317, H319, H335, H411 | |
P261, P264, P270, P271, P272, P273, P280, P301+312, P302+352, P304+340, P305+351+338, P312, P321, P330, P332+313, P333+313, P337+313, P362, P363, P391, 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 | |
Cyclooctadiene rhodium chloride dimer is the organorhodium compound with the formula Rh2Cl2(C8H12)2, commonly abbreviated [RhCl(COD)]2 or Rh2Cl2(COD)2. This yellow-orange, air-stable compound is a widely used precursor to homogeneous catalysts.[1]
Preparation and reactions
The synthesis of [RhCl(COD)]2 involves heating a solution of hydrated rhodium trichloride with 1,5-cyclooctadiene in aqueous ethanol in the presence of sodium carbonate:[1][2]
- 2 RhCl3·3H2O + 2 COD + 2 CH3CH2OH + 2 Na2CO3 → [RhCl(COD)]2 + 2 CH3CHO + 8 H2O + 2 CO2 + 4 NaCl
[RhCl(COD)]2 is principally used as a source of the electrophile "[Rh(COD)]+."
- [RhCl(COD)]2 + nL → [LnRh(COD)]+Cl− (where L = PR3, alkene, etc. and n = 2 or 3)
In this way, chiral phosphines can be attached to Rh. The resulting chiral complexes are capable of asymmetric hydrogenation.[3] A related but still more reactive complex is chlorobis(cyclooctene)rhodium dimer. The dimer reacts with a variety of Lewis bases (L) to form adducts with the stoichiometry RhCl(L)(COD).
Structure
The molecule consists of a pair of square planar Rh centers bound to a 1,5-cyclooctadiene and two chloride ligands that are shared between the Rh centers. The Rh2Cl2 core is also approximately planar,[4] in contrast to the highly bent structure of cyclooctadiene iridium chloride dimer where the dihedral angle is 86°.
References
- ↑ 1.0 1.1 Giordano, G.; Crabtree, R. H. “Di-μ-chloro-bis(η4-1,5-cyclooctadiene)dirhodium(I)” Inorganic Syntheses, 1990, volume 28, pages 88-90. doi:10.1002/9780470132593.ch22
- ↑ Chatt, J.; Venanzi, L. M. (1956). "Olefin Complexes of Rhodium". Nature 177 (4514): 852–3. doi:10.1038/177852b0. Bibcode: 1956Natur.177..852C.
- ↑ W. S. Knowles (2003). "Asymmetric Hydrogenations (Nobel Lecture 2001)". Advanced Synthesis & Catalysis 345 (1–2): 3–13. doi:10.1002/adsc.200390028.
- ↑ "Di-μ-chloro-bis[(cis,cis-η4-1,5-cyclooctadiene)rhodium(I)]: a redetermination" De Ridder, Kirk J. A. Acta Crystallographica, Section C: Crystal Structure Communications 1994, C50, 1569-72. doi:10.1107/S0108270194001459
External links
![]() | Original source: https://en.wikipedia.org/wiki/Cyclooctadiene rhodium chloride dimer.
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