Cyclooctadiene rhodium chloride dimer
{{chembox
|Watchedfields = changed
|verifiedrevid = 477163428
|ImageFile = Cyclooctadiene-rhodium-chloride-dimer-2D-skeletal.png
|ImageFile1 = Cyclooctadiene-rhodium-chloride-dimer-3D-balls.png
|IUPACName = di-μ-chlorido-
|OtherNames = Cyclooctadiene rhodium chloride dimer
|Section1={{Chembox Identifiers
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 21171524
|PubChem = 6436379
|EC_number = 235-157-6
|InChI = 1/2C8H12.2ClH.2Rh/c2*1-2-4-6-8-7-5-3-1;;;;/h2*1-2,7-8H,3-6H2;2*1H;;/q;;;;2*+1/p-2/b2*2-1-,8-7-;;;;/r2C8H12.2ClRh/c2*1-2-4-6-8-7-5-3-1;2*1-2/h2*1-2,7-8H,3-6H2;;/b2*2-1-,8-7-;;
|SMILES = Cl1[Rh]Cl[Rh]1.C=1CC\C=C/CCC=1.C/1C\C=C/CC\C=C\1
|InChIKey = QSUDXYGZLAJAQU-PXXGERDABU
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/2C8H12.2ClH.2Rh/c2*1-2-4-6-8-7-5-3-1;;;;/h2*1-2,7-8H,3-6H2;2*1H;;/q;;;;2*+1/p-2/b2*2-1-,8-7-;;;;
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = QSUDXYGZLAJAQU-MIXQCLKLSA-L
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 12092-47-6
}}
|Section2={{Chembox Properties
|Formula = C16H24Cl2Rh2
|MolarMass = 493.0806 g/mol
|Density = 1.93 g/cm3
|SolubleOther = dichloromethane
|MeltingPtC = 243
}}
|Section7 ={{Chembox Hazards
|GHSPictograms = {{GHS07}}{{GHS09}}
|GHSSignalWord = Warning
|HPhrases = {{H-phrases|302|315|317|319|335|411}}
|PPhrases = {{P-phrases|261|264|270|271|272|273|280|301+312|302+352|304+340|305+351+338|312|321|330|332+313|333+313|337+313|362|363|391|403+233|405|501}}
}}
}}
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.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}}
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:{{cite journal|title=Olefin Complexes of Rhodium|author1=Chatt, J. |author2=Venanzi, L. M. |journal=Nature|year=1956|volume=177|issue=4514|pages=852–3|doi=10.1038/177852b0|bibcode=1956Natur.177..852C|s2cid=4296682}}
: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 + {{mvar|n}}L → [L{{mvar|n}}Rh(COD)]+Cl− (where L = PR3, alkene, etc. and {{mvar|n}} = 2 or 3)
In this way, chiral phosphines can be attached to Rh. The resulting chiral complexes are capable of asymmetric hydrogenation.{{cite journal | author = W. S. Knowles | title = Asymmetric Hydrogenations (Nobel Lecture 2001) | journal = Advanced Synthesis & Catalysis | year = 2003 | volume = 345 | issue = 1–2 | doi = 10.1002/adsc.200390028 | pages = 3–13}} 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,"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}} in contrast to the highly bent structure of cyclooctadiene iridium chloride dimer where the dihedral angle is 86°.
References
{{Reflist}}
External links
- {{Commons category-inline}}
{{Rhodium compounds}}
Category:Organorhodium compounds
Category:Homogeneous catalysis