Dicarbonyl(acetylacetonato) Rhodium(I)

[14874-82-9]  · C7H7O4Rh  · (258.04)

(catalyst (precatalyst) for various carbonylation reactions, silylcarbocyclizations, conjugate additions to enones, carbamoylstannation, and reduction of aromatic nitro compounds)

Physical Data: mp 155°C1; IR (CCl4) 2990, 2911, 1553, 1513, 1429, 1374, 1276, 1193, 1126, 1019, 933, 782 cm-1; 1H NMR (CCl4) d 5.52 (1H), 2.11 (6H).

Solubility: soluble in acetone, benzene, chlorinated solvents; sparingly soluble in MeOH, ether, aliphatic hydrocarbons.

Form Supplied in: dark green crystalline solid; commercially available.

Analysis of Reagent Purity: NMR, IR, mp.

Preparative Methods: prepared from tetracarbonyl-m-dichlorodirhodium(I).1

Purification: vacuum sublimation at ca. 90°C.1

Handling, Storage, and Precautions: stable in air; best stored in a dry atmosphere.

Hydroformylation

Dicarbonyl(acetylacetonato) rhodium(I) [Rh(acac)(CO)2] is a common precatalyst for the hydroformylation of alkenes.2 In combination with ligands, alkenes are hydroformylated to aldehydes under mild conditions (eq 1). Chemo-, regio-, and stereoselectivity depend upon the nature of the substrate and upon the ligands employed.

Silylformylation

The Rh(acac)(CO)2-catalyzed intermolecular silylformylation of terminal alkynes with dimethyl(phenyl)silane and carbon monoxide affords (Z)-1-silyl-2-formylalk-1-enes with complete regio- and stereoselectivity (eq 2).3

Triethylsilane and tert-butyldimethylsilane also participate in intermolecular silylformylation.4 The regioselectivity is completely reversed in the intramolecular silylformylation of alkynes (eq 3).5 Internal and terminal alkynes are silyformylated with complete regio- and stereoselectivity, with exclusive formation of products arising from exo-cyclization.

The intramolecular silylformylation of alkenes affords b-silyl aldehydes with exclusive formation of aldehydes arising from exo-cyclization (eq 4).6 When the phenyl groups on silicon are replaced with allyl groups, tandem silyformylation-allylsilylation occurs to afford, after oxidation of the carbon-silicon bond, 1,3,5-syn-triols (eq 5).7

Carbocyclizations

Rh(acac)(CO)2 catalyzes the intramolecular silylcarbocyclization of triynes,8 enynes,9 and ynals.10 The silylcarbotricylization of enediynes affords bis-cyclopentyl products (eq 6).11 This cascade carbometallation sequence proceeds stereospecifically, and complements traditional Heck chemistry.

The carbonylative carbotricyclization of enediynes is catalyzed by Rh(acac)(CO)2 to afford fused 5-7-5 tricyclic products (eq 7).12 In a reaction that complements the Pauson-Khand reaction, Rh(acac)(CO)2 catalyzes the carbonylative bicyclization of 1,6-diynes to afford bicyclo[3.3.0]octenones.13

Conjugate Additions

The conjugate addition of aryl- and alkenylboronic acids to enones is catalyzed by Rh(acac)(CO)2 (eq 8).14

The asymmetric conjugate addition of a-cyano phosphonates15 and a-cyano Weinreb amides16 to enones and enals is catalyzed by Rh(acac)(CO)2 in the presence of chiral ligands (eq 9).

Other Transformations

Carbamoylstannation of terminal alkynes is catalyzed by Rh(acac)(CO)2 to afford 3-trimethylstannyl-2-enamides (eq 10).17

In the presence of phosphine18 and amine19 ligands, Rh(acac)(CO)2 catalyzes the reduction of aromatic nitro compounds to anilines with CO/H2O. Rh(acac)(CO)2 catalyzes the addition of aryl- and alkenylboronic acids to aldehydes,20 and catalyzes the formylation of organomercurial chlorides (eq 11).21


1. Wilkinson, G.; Donati, F., J. Chem. Soc. 1964, 3156.
2. Breit, B.; Seiche, W., Synthesis 2001, 1.
3. Ojima, I.; Donovan, R. J.; Eguchi, M.; Shay, W. R.; Ingallina, P.; Korda, A.; Zeng, Q., Tetrahedron 1993, 49, 5431.
4. Bonafoux, D.; Ojima, I., Org. Lett. 2001, 3, 1303.
5. Ojima, I.; Vidal, E.; Tzamarioudaki, M.; Matsuda, I., J. Am. Chem. Soc. 1995, 117, 6797.
6. Leighton, J. L.; Chapman, E., J. Am. Chem. Soc. 1997, 119, 12416.
7. Zacuto, M. J.; Leighton, J. L., J. Am. Chem. Soc. 2000, 122, 8587.
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11. Ojima, I.; McCullagh, J. V.; Shay, W. R., J. Organomet. Chem. 1996, 521, 421.
12. Ojima, I.; Lee, S.-Y., J. Am. Chem. Soc 2000, 122, 2385.
13. Ojima, I.; Zhu, J.; Vidal, E. S.; Kass, D. F., J. Am. Chem. Soc. 1998, 120, 6690.
14. Sakai, M.; Hayashi, H.; Miyaura, N., Organometallics 1997, 16, 4229.
15. Sawamura, M.; Hamashima, H.; Ito, Y., Bull. Chem. Soc. Jpn 2000, 73, 2559.
16. Sawamura, M.; Hamashima, H.; Shinoto, H.; Ito. Y., Tetrahedron Lett. 1995, 36, 6479.
17. Hua, R.; Onozawa, S.; Tanaka, M., Organometallics 2000, 19, 3269.
18. Nomura, K.; Ishino, M.; Hazama, M., J. Mol. Cat. A 1991, 66, L19.
19. Nomura, K.; Ishino, M.; Hazama, M., Bull. Chem. Soc. Jpn 1991, 64, 2624.
20. Sakai, M.; Ueda, M.; Miyaura, N., Angew. Chem., Int. Ed. Engl. 1998, 37, 3279.
21. Sarraf, S. T.; Leighton, J. L., Org. Lett. 2000, 2, 3205.

Michael J. Zacuto & James L. Leighton

Columbia University, New York, NY, USA



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