Synthetic Methods of Organometallic and Inorganic Chemistry, Volume 7, 1997

Alternative Procedure

FeI2(CO)4 is also available at CO pressures of only > 6.3 atm from anhydrous Fel2 through an autoclave reaction.

Properties

Iron carbonyl halides are light sensitive. The thermal stability of the complexes decreases in the order I > Br > Cl. The chlorine derivative loses carbon monoxide even at room temperature forming a graycolored product. The compounds can be stored undecomposed for months in an inert gas atmosphere at –35 °C. With water FeCl2 and FeBr2 are formed spontaneously, the iodine complex hydrolyses upon heating. Colors: FeCl2(CO)4 yellow, FeBr2(CO)4 red-brown, FeI2(CO)4 violet-brown. The compounds have cis-configuration. cis-FeI2(CO)4 can be transformed into trans-FeI2(CO)4 photochemically.

IR [X = Cl (C2Cl4)]: v(CO) = 2164, 2124, 2108, 2084 cm–1.

IR [X = Br (C6H4)]: v(CO) = 2150, 2108, 2098, 2074 cm–1.

IR [X = I (C6H14)]: v(CO) = 2131, 2086, 2062, 2047 cm–1.

References

1 W. Hieber, G. Bader, Ber. Dtsch. Chem. Ges. 61, 1717 (1928).

2 W. Hieber, H. Lagally, Z. Anorg. Allgem. Chem. 245, 295 (1940).

3 W. Hieber, A. Wirsching, Z. Anorg. Allgem. Chem. 245, 35 (1940).

•Tetracarbonyl(diiodo)ruthenium — Rul2(CO)4

The carbonylation of ruthenium(III) halides under normal pressure at 210 – 290 °C results in formation of polymeric {RuX2(CO)2}n.1 Mononuclear RuI2(CO)4 is obtained via a high pressure carbonylation of Rul3.

Procedure 2,3

Rigorously dried Rul34 (10.0 g, 20.8 mmol) is thoroughly mixed with approximately 15 g (excess) of fine, acid-free Cu powder* and placed inside the glass inset of a 250-mL rotating autoclave. Some glass balls (diameter 0.5 cm) are added to ensure better mixing of the dust-free material. The autoclave is flushed two times with 100 atm of CO each. For the carbonylation reaction a CO pressure of 240 atm is applied. The operating temperature is 170 °C. After 25 h, the system is cooled down to room temperature and unreacted CO gas is burnt off cautiously. The black, powdery reaction mixture is sublimed under high vacuum at ∼100 °C, which affords RuI2(CO)4 as yellow, needles. Yield: 5.0 – 7.3 g (52 – 75%).

*Fine copper powder is stirred for 3 h with dilute hydrochloric acid, filtered, washed with water and acetone, then dried in an oven at 130 °C.

Properties

The golden, crystalline substance, air-sensitive. Decomposition occurs at >140 °C. The compound has the cis-configuration.

IR (CCl4): v(CO) = 2068 (s), 2097 (s), 2106 (vs), 2119 (s), 2161 cm–1 (m).

References

1 W. Manchot, J. König, Dtsch. Chem. Ges. 57, 2130 (1924).

2 E. R. Corey, M. V. Evans, L. F. Dahl,j. Inorg Chem. 24, 926 (1962).

3 L. F. Dahl, D. L. Wampler, Acta Cryst. 15, 946 (1962).

4 H. L. Grübe, in: Handbuch der Praparativen Anorganischen Chemie, 3rd edn., (G. Brauer, ed.), Vol. III, Enke, Stuttgart, 1981, p. 1749.

Bis{μ-chloro(tricarbonyl)(chloro)ruthenium} — {RuCl2(CO)3}2

The best synthesis for {RuCl2(CO)3}2 seems to be a mechanistically not well understood reaction of Ru3(CO)12 with CHCl3 at temperatures of about 110 °C under a positive N2-pressure.

Procedure 1

A suspension of Ru3(CO)12(2.50 g, 3.91 mmol) in a mixture of 100 mL of CHCl3 and 2 mL of absolute C2H5OH is placed in a 250-mL rolling autoclave with a glass insert. The vessel is put under an initial N2-pressure of ~5 atm and heated for 13 h up to 110° C. After cooling down and relieving the pressure, the white suspension is filtered off through a Bücheer funnel. The residue is washed with a small amount of CHCl3 and dried in a vacuum to furnish the analytically pure product. Yield: ~1.6 – 1.9 g (53 – 63%).

The pale-yellow mother liquor is combined with the washings and concentrated to a volume of ~25 mL under vacuum. Cooling to −10 °C affords a yellowish precipitate which is isolated and recrystallized from a hot mixture of 1,2-dichloroethane and n-hexane. A second crop of 250 – 500 mg of {RuCl2(CO)3}2 is obtained.

Alternative Procedure

A preparation starting from RuCl3 • H2O and formic acid in the presence of HCl is more tedious. Chlorination of Ru3(CO)12 yields a hardly separable mixture of products.2

Properties

The white, air-stable powder changes color to orange-brown on heating above 215 °C, above 315 °C decomposition occurs. The compound is sparingly soluble in CHCl3 and 1,2-dichloroethane, readily soluble in CH3OH and tetrahydrofuran. With the latter solvent, the mononuclear solvent complex RuCl2(CO)3(THF) is formed.3 Single crystal X-ray structure determination: 4 C2h-symmetry, 2 bridging Cl-ligands.

IR (CCl4): v(CO) = 2140 (s), 2081 (s), 2076 cm−1(s).

References

1 A. Mantovani, S. Cenini, Inorg. Synth. 16, 51 (1976).

2 B. F. G. Johnson, R. D. Johnston, J. Lewis, J. Chem. Soc. (A) 729 (1969).

3 M. I. Bruce, F. G. A. Stone,.J. Chem. Soc. (A) 1238 (1967).

4 S. Merlino, G. Montagnoli, Acta Cryst. B24, 424 (1968).

Osmium Carbonyl Chlorides — OsCl2(CO)x (x = 3, 4)

The direct carbonylation of OsCl3 results in the formation of osmium chlorides with varying carbonyl content depending on the reaction conditions (pressure and temperature).

Procedure for Tricarbonyl(dichIoro)osmium 1 — OsCl2(CO)3

A horizontal Pyrex glass tube (diameter 3 cm, length 50 cm) is charged with OsCl3 (2.0 g, 6.7 mmol) and heated to 260 – 270° C for 15 h in a gentle stream of CO. It is convenient to use a furnace which can be opened. During the reaction some white-colored OsCl3 sublimes onto the colder parts of the wall. Near the hot zone, a brownish product appears. The purity of this material normally is sufficient for synthetic purposes. Further purification requires heating at reflux in CCl4 which affords a pure white product. Yield: quantitative.

Properties

The compound is obtained as colorless, air-stable crystals, mp 269 – 273 °C. Decomposition occurs at above 300 º C with formation of Os.

Procedure for Tetracarbonyl(dichloro)osmium 2 — OsCl2(CO)4

In a dry, 100-mL rotating autoclave OsCl3 (5.0 g, 16.9 mmol) is carbonylated at 125 °C (mantel temperature) applying an initial CO pressure of 220 bar. To ensure thorough mixing of the components, glass balls or Raschig rings are placed inside the reaction vessel. Similar to the high pressure carbonylation procedure, the autoclave is purged twice prior to use by applying 50 – 100 bar of CO. During the reaction, a maximum pressure of 285 bar is achieved. After 20 h of reaction time, the vessel is allowed to cool to room temperature, and any unreacted CO is burnt off. The white crystalline content of the autoclave is extracted several times with 50-mL portions of CHCl3. The yellow suspension is filtered through a folded filter paper, and the yellow filter cake is extracted several times with 50-mL portions of dry, hot CHCl3 until all white material has been extracted and a brown filter cake remains. The filtrates are combined and the solvent is removed at 30 °C under vacuum. The product forms a white powder which is pure enough for further synthetic applications. Crude yield: 5.42 – 5.80 g (86 – 92%).

Properties

The compound is obtained as colorless, air-stable crystals. Fast decomposition occurs >250 °C with formation of Os. It is soluble in polar organic solvents (CHCl3, acetone); sublimes in CO at 220 °C swiftly. OsCl2(CO)4 forms a mixture of cis- and trans- isomers.

References

1 W. Manchot, J. König, Ber. Disch. Chem. Ges. 58, 229 (1925).

2 W. Hieber, H. Stallmann, Ber. Dtsch. Chem. Ges. 75, 1472 (1942).

• Bis[(μ-chloro)(dicarbonyl)rhodium] — {RhCl(CO)2}2

Procedure 1

A Pyrex glass tube of approximately 60 cm length (diameter 35 mm) is charged with RhCl3 • 3 H20 (~10 g, 38 mmol). A stream of CO carrying methanol is passed over the rhodium chloride. To keep the methanol concentration low, the gas is cooled in an ice bath using a wash bottle placed before the reaction tube. The furnace used for heating should be easy to open in order to monitor the reaction visually. The reaction tube is slowly heated to 120 – 140 °C. Within 12 h the main quantity of the product forms red, centimeter-long, fine needles. Any H2O formed during the reaction is removed from the entrance of the tube by occasional heating with a heat gun. The compound is analytically pure and does not require any further sublimation. Yield: ~65%.

Particularly large crystals can be obtained by heating the tube to 120 – 140 °C...