Rhodium I Chemistry Sébastien Goudreau Rhodium I Literature meeting

Rhodium(I) Chemistry Sébastien Goudreau Rhodium(I) Literature meeting : 13 -02 -2007

Rhodium • Number 45 • [Kr]4 d 85 s 1 • Hard silvery white and durable metal that has a high reflectance. (Use in jewellery) • Does not form an oxide, is not attacked by acids. • Very high melting point : 2236°C • It is the most expensive precious metal. http: //en. wikipedia. org/wiki/Rhodium

Applications • The primary use of this element is as an alloying agent for hardening platinum and palladium. • It is used as an electrical contact material due to its low electrical resistance, low and stable contact resistance, and its high corrosion resistance. • Plated rhodium, made by electroplating or evaporation, is extremely hard and is used for optical instruments. • This metal finds use in jewelry and for decorations. • It is also a highly useful catalyst. http: //en. wikipedia. org/wiki/Rhodium

History • Rhodium was discovered in 1803 by William Hyde Wollaston soon after his discovery of palladium. • Wollaston made this discovery in England using crude platinum ore that he presumably obtained from South America. • His procedure involved dissolving the ore in aqua regia (HCl + HNO 3), neutralizing the acid with Na. OH. • He then precipitated the platinum metal by adding NH 4 Cl, as ammonium chloroplatinate. • The element palladium was removed as palladium cyanide after treating the solution with mercuric cyanide. • William Hyde Wollaston The material that remained was a red rhodium(III) choride. (Greek rhodon meaning "Rose") • Wilkinson’s catalyst : Rh. Cl(PPh 3)3 : 1965 Wilkinson et al. J. Org. Chen. Chem. Commun. , 1965, 7, 131. http: //en. wikipedia. org/wiki/Rhodium Geoffrey Wilkinson Nobel Prize 1973

Rhodium(I) in Organic Chemistry 1) C-H and C-C bond activation 2) Hydrorhodation A) Hydrogenation B) Hydroarylation C) Hydroalkynation D) Hydroacylation E) Hydrosilylation F) Hydroboration 3) Addition A) 1, 4 addition B) 1, 2 addition C) Coupling 4) Sigmatropic Rearrangement A) Cycloaddition B) Alder-ene 5) p-Allyl chemistry 6) b-aryl elimination Square plane

1) C-H and C-C bond activation Prof. David Milstein The Weizmann Institute of Science, Israel (a) Milstein et al. Angew. Chem. Int. Ed. 2007, 46, ASAP. (b) Bergman et al. J. Am. Chem. Soc. 2006, 128, 2452. (c) Milstein et al. J. Am. Chem. Soc. 2003, 125, 11041.

2) Hydrorhodation A) Hydrogenation B) Hydroarylation C) Hydroalkynation D) Hydroacylation E) Hydrosilylation F) Hydroboration

A) Hydrogenation Zassinovich, Mestroni Chem. Rev. 1992, 1051 and references cited therein

Enantioselective Hydrogenation Burk et al. J. Am. Chem. Soc. 1993, 115, 10125.

B) Hydroarylation Pfeffer et al. Chem. Rev. 2002, 1731.

B) Hydroarylation : exemple Pfeffer et al. Chem. Rev. 2002, 1731.

C) Hydroalkynation Pfeffer et al. Chem. Rev. 2002, 1731.

C) Hydroalkynation : exemples Pfeffer et al. Chem. Rev. 2002, 1731.

D) Hydroacylation Pfeffer et al. Chem. Rev. 2002, 1731.

D) Hydroacylation : exemples Pfeffer et al. Chem. Rev. 2002, 1731.

D) Hydroacylation : example Pfeffer et al. Chem. Rev. 2002, 1731.

Intramolecular Hydroacylation Pfeffer et al. Chem. Rev. 2002, 1731.

C) Hydrosilylation

C) Hydrosilylation Pfeffer et al. Chem. Rev. 2002, 1731.

D) Hydroboration Guiry et al. Adv. Synth. Catal. 2005, 347, 609.

Hydrorhodation : Conclusion • Atom efficient • Mild conditions • Good alternative route • Regioselectivity : can be problematic • Enantioselectivity : can be very good

2) Addition reaction A) 1, 4 addition B) 1, 2 addition C) Coupling

A) 1, 4 addition reaction M : Organoboron (organostannate, organosilane, organobismuth) R : Aryl Fagnou, Lautens Chem. Rev. 2003, 169.

A) 1, 4 Addition : exemples Fagnou, Lautens Chem. Rev. 2003, 169.

A) 1, 4 Addition : examples Fagnou, Lautens Chem. Rev. 2003, 169.

Krische’s chemistry

Krische’s chemistry Krische et al. J. Am. Chem. Soc. 2002, 124, 15156.

B) 1, 2 Addition reaction M : Organoboron (organostannate, organosilane, organobismuth) R : Aryl Fagnou, Lautens Chem. Rev. 2003, 169.

B) 1, 2 Addition : exemples Fagnou, Lautens Chem. Rev. 2003, 169.

B) 1, 2 Addition : exemples Ellman et al. J. Am. Chem. Soc. 2005, 127, 1092.

B) 1, 2 Addition : exemples (a) Fagnou, Lautens Chem. Rev. 2003, 169. (b) Iwasawa et al. J. Am. Chem. Soc. 2006, 128, 8706.

Krische’s chemistry Krische et al. J. Am. Chem. Soc. 2006, 128, 718.

C) Coupling Fagnou, Lautens Chem. Rev. 2003, 169.

Addition reaction : Conclusion • Mild conditions : presence of water • Good enantioselectivity • Excess of organoboron needed

4) Sigmatropic rearrangement A) Cycloaddition 2+2+2 2+2+1 (Pauson-Khand) 3+2 4+2 5+2 6+1 4+2+2 B) Alder-ene Paul A. Wender Stanford University, USA

Mecanism : [2+2+2] Lautens et al. Chem. Rev. 1996, 49.

[2+2+1] Cycloaddition : Pauson-Khand Reaction Lautens et al. Chem. Rev. 1996, 49.

[2+2+1] Cycloaddition : Pauson-Khand Reaction Jeong et al. J. Am. Chem. Soc. 2000, 122, 6771.

[3+2] Cycloaddition Wender et al. J. am. Chem. Soc. 2006, 128, 14814.

[4+2] Cycloaddition : Diels Alder Mikami et al. J. Am. Chem. Soc. 2006, 128, 12648.

[5+2] Cycloaddition Saito et al. J. Org. Chem. 2006, 71, 6437.

[6+1] cycloaddition Wender et al. Angew. Chem. Int. Ed. 2006, 45, 3957.

[4+2+2] and [2+2+2+1] cycloaddition Wender et al. J. Am. Chem. Soc. 2006, 128, 5354. Ojima et al. Org. Lett. 2004, 6, 3589.

B) Alder-ene Zhang et al. J. Am. Chem. Soc. 2002, 124, 8198.

Conclusion • Access to a large variety of cycles • Regioselectivity : need linkers

5) Allylic (a) P. A. Evans et al. J. Am. Chem. Soc. 2004, 126, 8642. (b) P. A. Evans et al. J. Am. Chem. Soc. 2003, 125, 8974. (c) P. A. Evans et al. J. Am. Chem. Soc. 2002, 124, 7882.

6) b-aryl elimination John F. Hartwig Yale University, USA

Conclusion 1) C-H and C-C bond activation 2) Hydrorhodation A) Hydrogenation B) Hydroarylation C) Hydroalkynation D) Hydroacylation E) Hydrosilylation F) Hydroboration 3) Addition A) 1, 4 addition B) 1, 2 addition C) Coupling 4) Sigmatropic Rearrangement A) Cycloaddition B) Alder-ene 5) p-Allyl chemistry 6) b-aryl elimination Square plane

Conclusion