Checked by Hans G. Essler and John H. Richards.
1. Procedure
A
500-ml. three-necked flask is equipped with a
Trubore stirrer,
reflux condenser, and a
pressure-equalizing dropping funnel that carries an inlet for admission of
nitrogen. The system is purged with
nitrogen (Note
1), and
300 ml. of 1,2-dimethoxyethane (Note
2) is added, followed by
7.2 g. (0.312 g. atom) of sodium either as wire or freshly cut small pieces. The solution is stirred, and
31.0 ml. (0.376 mole) of cyclopentadiene (Note
3) is added dropwise. When the evolution of
hydrogen has almost ceased, the mixture is maintained at slightly below the reflux temperature for 1–2 hours. In the event that all the
sodium does not dissolve, the solution is cooled to room temperature, a few milliliters more of
cyclopentadiene added, and the mixture heated again until dissolution of the
sodium is complete.
A mixture of
14.6 g. (0.07 mole) of ruthenium trichloride and
2.4 g. (0.024 g. atom) of ruthenium metal (Note
4) is added, and the reaction mixture is heated and stirred under
nitrogen for 80 hours (Note
5) at slightly below the reflux temperature. With the use of stirring, the solvent is removed at aspirator pressure, and the flask then refilled with
nitrogen. The solid is transferred to a sublimator in a dry-box containing a
nitrogen atmosphere (Note
6) and sublimed at 0.1 mm. pressure with a heating bath at 130° (Note
7). The sublimate is dissolved in
benzene and passed through a
1 × 12-in. column of activated alumina. Evaporation of the
benzene gives
12.2–15.1 g. (
56–69%) of
ruthenocene, m.p.
199–200° (Note
8).
2. Notes
4.
Ruthenium trichloride was prepared by chlorination of powdered
ruthenium at 650–700°
2 with the use of metal obtained from Goldsmith Bros. Smelting and Refining Co., 111. N. Wabash Ave., Chicago 2, Illinois. Complete chlorination could not be effected under these conditions, and on the average about 85% of the metal was converted to trichloride. Consequently, in all the preparations of
ruthenocene, mixtures of trichloride and metal, as obtained from the chlorination reaction, were employed. The equations given for the preparation are idealized; the submitters believe that during the course of reaction the trichloride is gradually reduced to dichloride by
ruthenium metal, and that it is the dichloride which reacts with
sodium cyclopentadienide.
5. Somewhat lower yields than those reported are obtained when the reaction is carried out for a shorter period of time.
6. From this point on, the solid materials are pyrophoric, especially the residual solids from the sublimation process. However, the
ruthenocene obtained by sublimation is not pyrophoric. The checkers found that careful addition of the sublimation residues to water under
nitrogen destroys their pyrophoric character.
7. The checkers found the use of a Dry Ice-cooled sublimation finger advantageous.
8. The yield reported here is based on the total amount of
ruthenium (both Ru
III and Ru
0) available for formation of
ruthenocene. An additional quantity of
ruthenocene may be obtained by extraction of the pyrophoric residue from the sublimation step with
benzene in a Soxhlet extractor under a
nitrogen atmosphere. The
benzene solution is filtered through activated alumina, the solvent evaporated, and the residue sublimed.
3. Discussion
4. Merits of the Preparation
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