Dihalide complexes of cobalt(II) have found use as catalysts in a variety of organic transformations. For example, C-N and C-C cross coupling reactions (Buchwald-Hartwig, Susuki, Kumada, Heck), functional group transformations, and polymerization.[1] A source of soluble cobalt(II) dihalide, CoBr2(dme) can be easily synthesized from its anhydrous CoBr2 precursor by stirring in dimethoxyethane.[2][3]
Procedure:[3] In the glovebox, a 150mL one-neck round-bottom flask was charged with anhydrous cobalt(II) bromide (6.52g, 32.7mmol) and approximately 80mL of anhydrous 1,2-dimethoxyethane. The flask was sealed, transferred onto a swivel-frit apparatus attached to a dual-manifold vacuum line (or Schlenk line), and stirred for three days at room temperature under argon (until all the green CoBr2 solids were converted into the blue product. The mixture was subsequently filtered, washed with anhydrous pentane, and dried under vacuum to yield the product complex as a blue powder (reported yield: 7.65g, 83%). The product was then transferred back into the glovebox for storage.
Notes:
- CoBr2(dme) is a paramagnetic, moisture sensitive solid and should be stored under argon/nitrogen to prevent decomposition.
- Anhydrous DME can be dried with molecular sieves for 48h prior to synthesis. Anhydrous cobalt(II) bromide can be purchased from chemical vendors (Millipore-Sigma, TCI, VWR).
[1] Gosmini, C.; Moncomble, A. Cobalt Bromide. EROS, 2011. DOI: 10.1002/047084289X.rn01282.
[2] Fowles, G. W. A.; Rice, D. A.; Walton, R. A. Donor properties of simple ethers. II. Complexes of manganese(II), iron(II), cobalt(II), and nickel(II) halides with tetrahydrofuran and 1,2-dimethoxyethane. J. Inorg. Nucl. Chem. 1969, 31, 3119-3131.
[3] Davis, L. M. Syntheses, Properties, and Reactions of Transition Metal Complexes of Di(tert-butyl)amide and 2,2,6,6-tetramethylpiperidide. Ph.D. Dissertation, University of Illinois: Urbana-Champaign, Urbana, IL, 2014.