Synthesis and Reactivity of Terminal Gold(I) Amides and Phosphides

Miles W. Johnson, Sophia L. Schevick, Robert G. Bergman,* and F. Dean Toste*

Department of Chemistry, University of California, Berkeley, CA 94720-1460

Gold Amide Synthesis Gold Phosphide Synthesis

Acknowledgments

Conclusions

Evaluating Gold(I) Amides as Catalytic Intermediates Background

Goals of Investigation

Reactivity of Gold(I) Amides Reactivity of Gold(I) Phosphides

- Both aryl- and alkyl-substituted amides are tolerated.

- All complexes are isolable with the exception of the t-butyl amide.

-These represent the first examples of terminal gold(I) amides with a strongly coordinated amido moiety.

- Prepare terminal gold(I) amides and phosphides, and confirm their identity crystallographically - Test their potential as catalysts and their fundamental reactivity

- Evaluate the potential of amides as catalytic intermediates in gold catalysis

- Compare the reactivity of gold pnictogenides to that of other transition metal amide and phosphide complexes.

- The first example of gold catalysis resulting in C-P bond formation

-All intermediates in a plausible catalytic cycle have been isolated or observed spectroscopically:

- Terminal gold(I) amides are highly nucleophilic and basic. - A gold carbamate was synthesized and characterized spectroscopically using its 13CO2-enriched isotopologue.

- The dimesityl phosphide represents the first terminal Group 11 phosphide characterized crystallographically. - Less hindered phosphides form the corresponding μ-phosphide.

Au—N: 1.967(4) Å Σ angles at N: 360°

Au—P: 1.967(4) Å Σ angles at P: 317°

Gold amides are often proposed as catalytic intermediates but none have been isolated until now.

- No reaction is observed between the di-isopropyl gold amide and alkyne. -This suggests that an outersphere mechanism for amination is operative and not insertion.

- No exchange is seen between the gold anilide and free aniline. - This result suggests that these amido moieties are unlikely to dissociate and then attack a ligated olefin or alkyne.

- The first terminal gold(I) amides and phosphides have been synthesized and characterized crystallographically. - Gold amides are reactive toward a number of electrophiles.

- Homogenous gold catalysis using a phosphorous nucleophile has been accomplished. - Gold amides have been shown to be unlikely intermediates in traditional gold catalysis.

Inertness toward alkynes

Strong ligation of amido ligand

Thanks to Drs. Neal Mankad, Jürgen Koller, and Antonio DiPasquale for helpful discussion and assistance with X-ray crystallography. Financial support was provided in the form of a grant from the U. S. Air Force, and as pre-doctoral research fellowships from the National Science Foundation and UC Berkeley.

Gold(III) anilides exist but their reactivity is unexplored.

Cinellu Group

Eur. J. Inorg. Chem. 2003, 2304-2310.

Numerous inert, polymetallic phosphides have been prepared.

Glueck Group

Inorg. Chem. 2003, 42, 8891-8901.

The triflimidate complex is a surrogate for cationic gold.

Gagosz Group

Org. Lett. 2005, 7, 4133-4136. Organometallics 2007, 26, 4704-4707.

Gold silylamides are polymerization initiators.

Nolan Group

Organometallics 2011, 30, 2650-2653.

Isolated gold amides and phosphides

Proposed amide intermediates

Hydroamination of allenes

Yamamoto Group Angew. Chem. Int. Ed. 2006,

45, 3314-3317.

Hydroamination of alkynes

Bertrand Group Angew. Chem. Int. Ed. 2008,

47, 5224-5228. Angew. Chem. Int. Ed. 2011,

50, 5560-5563.