Acetylene, insertion into molybdenum

A sintered clay boat is charged with pure CaCNg, either alone or with an added amount (somewhat below the calculated value) of well-charred sugar charcoal or acetylene black. The boat is inserted into a ceramic tube (inside diameter 30 mm., length 500 mm.). The tube is provided with a groimd stopper at one end and sealed at the other. It is connected to a high-vacuum system and heated by means of an electric furnace with a molybdenum wire winding to temperatures above 1350°C. 

As part of a study of the reactions of metallacyclic y-ketovinyl complexes of molybdenum and tungsten with acetylenes, directed toward the synthesis of complexed -/-lactones, Stone has reported92 the isolation of several vinyl-ketene complexes. When complex 72 was heated with 2-butyne, one molecule of the alkyne was incorporated into the complex with concomitant carbonylation. X-ray analysis of the product (73) has shown unequivocally that the C-l to C-4 vinylketene fragment is bonded in a planar, rj4-configu-ration. In contrast to the thermal reaction, ultraviolet irradiation of 72 or 74 in the presence of 2-butyne affords the complexes 75 and 76, respectively, where the lone carbonyl remaining after alkyne insertion had been replaced by a third molecule of the alkyne. 

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