Tetracarbonyl trifluorosilyl cobalt

In a nitrogen-filled glove bag 10 g. of antimony trifluoride are placed into a 30-ml. glass reactor which is then evacuated and pumped on for 24 hours to provide a final drying at room temperature. The reactor is then cooled to liquid-nitrogen temperature, and 3 g. of hydrogen-chloride-free trichlorosilane is added to the reactor. The Teflon stopcock is then closed 

Quite often additional trifluorosilane can be obtained by simply returning the unreacted silane to the reaction vessel and allowing additional reaction time. A single reaction period yields about 1.5 g. (65% based on HSiCl3 employed) of product having an observed molecular weight of 86.9 (calcd. 86.1) and an infrared spectrum consistent with pure trifluorosilane.11 However, on some occasions the product is contaminated with silicon tetra-fluoride due to a reaction of the antimony compounds with the trifluorosilane. The silicon tetrafluoride impurity does not interfere with the preparation of tetracarbonyl(trifluorosilyl)cobalt. 

Next 2 g. of dicobalt octacarbonyl is placed in a 20-ml. glass reactor in a nitrogen-filled glove bag. After evacuation of the reactor, 1.8 g. of trifluorosilane is condensed and the Teflon stopcock closed. The reaction is allowed to proceed for 24 hours 

Cool the reactor to —196° and remove the noncondensable materials by pumping. Allow the reactor to warm to 0° and remove the excess trifluorosilane, tetracarbonyl(trifluorosilyl)-cobalt, and any cobalt carbonyl hydride formed by pumping the volatile products through a — 78° (Dry Ice-acetone mixture) trap into a —196° trap. A dark residue will remain in the reactor consisting of unreacted dicobalt octacarbonyl and decomposition products. Unreacted trifluorosilane will be in the —196° trap. 

The —78° trap will contain both the triflu or osilyl carbonyl and any carbonyl hydride formed. These arc then condensed into a clean 20-ml. glass reactor cooled to —196°. About 1.0 g. trifluorosilane is then condensed into the reactor at —196°, and the mixture is allowed to stand at room temperature for about 2 hours. 

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The reactor is then cooled to —196°, and any hydrogen formed is removed by pumping. The reactor is allowed to warm to. 0°, and the contents are then pumped through traps cooled to — 78 and —196°. The trap cooled to —78° will contain the transparent amber crystals of tetracarbonyl(trifluorosilyl)cobalt which melt at 19.4-19.5° to form an amber liquid. Yield is 60% based on Co2(CO)8 employed. 

Tetracarbonyl(trifluorosilyl)cobalt is a white solid which upon vacuum sublimation forms transparent amber crystals which melt at 19.5° with decomposition. This compound is kept at 0° with an ice bath and sublimed in the vacuum system to minimize decomposition. For example, in manipulating this compound in the vacuum line, distillation traps should be at 0° or lower. Gaseous samples, however, are not observed to undergo decomposition at temperatures up to 80°. The gas-... 

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