When tungsten hexacarbonyl is refluxed in butyronitrile, C3H7CN, product X is formed fir...

When tungsten hexacarbonyl is refluxed in butyronitrile, C₃H₇CN, product X is formed first. Continued reflux converts X to Y , and very long reflux (several days) converts Y to Z . However, even refluxing for several weeks does not convert compound Z into another product. In addition, in each reaction step, a colorless gas is liberated. The following infrared bands are observed (cm^-1):

a. Propose structures of X , Y , and Z . Where more than one isomer is possible, determine the isomer that is the best match for the infrared data. (Note: a weak band in Y may be obscured by other bands.)

b. Account for the trend in the position of the infrared bands in the sequence .

c. Suggest why Z does not react further when refluxed in butyronitrile. (See G. J. Kubas, Inorg. Chem. 1983 , 22 , 692.)