Lithium Aluminum Hydride-(2,2-Bipyridyl)(1,5-cyclooctadiene)nickel1

(LiAlH4)

[16853-85-3]  · AlH4Li  · Lithium Aluminum Hydride-(2,2-Bipyridyl)(1,5-cyclooctadiene)nickel  · (MW 37.96) ((bipy)(cod)Ni)

[55425-72-4]  · C18H20N2Ni  · Lithium Aluminum Hydride-(2,2-Bipyridyl)(1,5-cyclooctadiene)nickel  · (MW 323.09)

(reagent for desulfurization)1

Physical Data: see entry for Lithium Aluminum Hydride. A crystal structure of (2,2-bipyridyl)(cod)Ni has been reported.3d

Solubility: sol THF.

Preparative Methods: as a red-violet solution1a by addition of an equimolar quantity of LiAlH4 to a solution of the nickel complex in THF at rt with production of a mole of hydrogen. The nickel complex can be prepared according to literature procedures.2

Handling, Storage, and Precautions: highly flammable hydrogen is liberated during the formation of the complex. Solutions should be protected from open flames, moisture, and oxygen under an atmosphere of argon. Nickel and nickel salts are reputed to be carcinogenic and should be handled with due precautions. LiAlH4 is highly flammable as the solid or in solution.

Homogeneous Desulfurizing Agent.

LiAlH2-(THF)n-C10H8N2-Ni (1), resulting from addition of LiAlH4 to (2,2-bipyridyl)(1,5-cyclooctadiene)Ni, is a powerful desulfurizing agent for some aromatic sulfur heterocycles. For example, desulfurization3 of dibenzothiophene was achieved with two molar equivalents of the reagent (1) (eq 1).1a

Phenothiazine (X = NH), phenoxathiine (X = O), and thianthrene (X = S) can be desulfurized under the same conditions (eq 2).1a Note that for thianthrene, good chemoselectivity is obtained as only one sulfur atom is removed.

The use of LiAlD4 resulted in only minor incorporation of deuterium, while quenching with DOAc provided almost no incorporation of the label. Other amine ligands such as ethylenediamine, HMPA, TMEDA, or pyridine (2 equiv), instead of 2,2-bipyridyl, proved equally effective. Only the limited number of systems described above1a have been studied and the generality of this reagent has not been demonstrated. Other reports of homogeneous desulfurizing agents related to (1) have appeared in the literature and show broader applicability.3


1. (a) Eisch, J. J.; Hallenbeck, L. E.; Han, K. I. JACS 1986, 108, 7763. (b) Luh, T.-Y.; Ni, Z.-J. S 1990, 89. (c) Ganem, B.; Osby, J. O. CRV 1986, 86, 763.
2. (a) Eisch, J. J.; Hallenbeck, L. E.; Han, K. I. JOC 1983, 48, 2963. (b) Binger, P.; Doyle, M. J.; McMeeking, J.; Krüger, C.; Tsay, Y.-H. JOM 1977, 135, 405. (c) Jpn. Patent 70 28 574, 1970 (CA 1970, 74, 3729). (d) Dinjus, E.; Walther, D.; Kaisen, J.; Sieler, J.; Thanh, N. N. JOM 1982, 236, 123.
3. (a) Becker, S. R.; Fort, Y.; Caubère, P. JOC 1990, 55, 6194. (b) Becker, S. R.; Fort, Y.; Vanderesse, R.; Caubère, P. JOC 1989, 54, 4848. (c) Chan, M. C.; Cheng, K.-M.; Li, M. K.; Luh, T.-Y. CC 1985, 1610. (d) Ho, K. M.; Lam, C. H.; Luh, T.-Y. JOC 1989, 54, 4474. (e) Ho, N.-F.; Mak, T. C. W.; Luh, T.-Y. JCS(D) 1990, 3591. (f) Pörschke, K. R.; Wilke, G. JOM 1988, 358, 519.

Julien G. Doyon

The Ohio State University, Columbus, OH, USA



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