[59487-85-3]  · C12H10O2Zr  · Dicarbonylbis(cyclopentadienyl)zirconium  · (MW 277.44)

(couples alkynes to form zirconacyclopentadienes3)

Physical Data: subl 70 °C/10-2 mmHg.1a

Solubility: sol hydrocarbons, THF.

Analysis of Reagent Purity: IR, NMR.2

Preparative Method: reduction of Dichlorobis(cyclopentadienyl)zirconium with Magnesium Amalgam under CO atmosphere.2

Purification: hexane solution is filtered through alumina and cooled to -20 °C to induce crystallization; sublimation at 70 °C/10-2 mmHg.2

Handling, Storage, and Precautions: store and handle under an inert atmosphere. Use in a fume hood.

Dicarbonylbis(cyclopentadienyl)zirconium is one of several zirconocene derivatives which give zirconacyclopentadiene complexes when reacted with alkynes (eq 1) (see also Bis(cyclopentadienyl)diphenylzirconium and Dichlorobis(cyclopentadienyl)zirconium).3 Zirconacyclopentadiene complexes may be isolated and purified prior to further manipulations. Significantly, CO insertion usually does not occur, except when the reaction is done in a closed vessel (thereby preventing escape of CO).

A number of reagents, including Hydrogen Chloride, Iodine, and Carbon Monoxide, stereospecifically replace the metal to form substituted 1,3-butadienes.4 For example, the zirconacyclopentadiene (1) reacts with HCl to give (Z,Z)-1,2,3,4-tetrakis(pentafluorophenyl)butadiene (eq 2).3

Zirconacyclopentadiene complexes have also been reported to react with excess alkyne producing expanded zirconacycles, and eventually alkyne oligomers and polymers.5

1. (a) Cardin, D. J. In Dictionary of Organometallic Compounds; Buckingham, J., Ed.; Chapman & Hall: London, 1984; Vol. 2, p 2453. (b) Cardin, D. J.; Lappert, M. F.; Raston, C. L.; Riley, P. I. In Comprehensive Organometallic Chemistry; Wilkinson, G., Ed.; Pergamon: Oxford, 1982; Vol. 3, pp 610-616. (c) Pez, G. P.; Armor, J. N. Adv. Organomet. Chem. 1981, 19, 1. (d) Sikora, D. J.; Macomber, D. W.; Rausch, M. D. Adv. Organomet. Chem. 1986, 25, 317.
2. Sikora, D. J.; Moriarty, K. J.; Rausch, M. D. Inorg. Synth. 1990, 28, 248.
3. Sikora, D. J.; Rausch, M. D. JOM 1984, 276, 21.
4. Most zirconacyclopentadiene complexes have been prepared from the other reagents cited in the text; the interested reader should refer to these sections for methods to form dienes from the zirconacyclopentadiene complexes.
5. (a) Famili, A.; Farona, M. F.; Thanedar, S. CC 1983, 435. (b) Farona, M. F.; Thanedar, S.; Famili, A. J. Polym. Sci. Part A: Polym. Chem. 1986, 24, 3529.

Thomas E. Snead

Emory University, Atlanta, GA, USA

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