Chlorobis(cyclooctene)rhodium dimer explained

Chlorobis(cyclooctene)rhodium dimer is an organorhodium compound with the formula Rh₂Cl₂(C₈H₁₄)₄, where C₈H₁₄ is cis-cyclooctene. Sometimes abbreviated Rh₂Cl₂(coe)₄, it is a red-brown, air-sensitive solid that is a precursor to many other organorhodium compounds and catalysts.

The complex is prepared by treating an alcohol solution of hydrated rhodium trichloride with cyclooctene at room temperature.^[1] The coe ligands are easily displaced by other more basic ligands, more so than the diene ligands in the related complex cyclooctadiene rhodium chloride dimer.

Catalyst for C-H activation

C-H activation is often catalyzed by chlorobis(cyclooctene)rhodium dimer as demonstrated in the synthesis of a strained bicyclic enamine.^[2]

The synthesis of a mescaline analogue involves enantioselective annulation of an aryl imine via a C-H activation.^[3] The total synthesis of lithospermic acid employs "guided C-H functionalization" late stage to a highly functionalized system. The directing group, a chiral nonracemic imine, is capable of performing an intramolecular alkylation, which allows for the rhodium-catalyzed conversion of imine to the dihydrobenzofuran.^[4]

References

1. Van der Ent, A.; Onderdelinden, A. L. "Chlorobis(cyclooctene)rhodium(I) and di-μ-chlorobis[bis(cryclooctene)iridium] (I) complexes" Inorganic Syntheses 1973, volume 14, pp. 92-5.
2. Yotphan . Sirilata . Bergman . Robert G. . Ellman . Jonathan A. . The Stereoselective Formation of Bicyclic Enamines with Bridgehead Unsaturation via Tandem C–H Bond Activation/Alkenylation/ Electrocyclization . . 2008 . 130 . 8. 2452–2453 . 10.1021/ja710981b . 18247623 . 3062933 .
3. Synthesis of a Tricyclic Mescaline Analogue by Catalytic C−H Bond Activation. Organic Letters. 2003-04-01. 1523-7060. 1301–1303. 5. 8. 10.1021/ol034228d. Kateri A.. Ahrendt. Robert G.. Bergman. Jonathan A.. Ellman. 12688744.
4. Total Synthesis of (+)-Lithospermic Acid by Asymmetric Intramolecular Alkylation via Catalytic C-H Bond Activation . J. Am. Chem. Soc. . 2005 . 127 . 39 . 13496–13497 . O'Malley . S. J. . Tan . K. L. . Watzke . A. . Bergman . R. G. . Ellman . J. A. . 10.1021/ja052680h . 16190703.