Benzene chromium tricarbonyl revisited: Theoretical study of the structure and dynamics of (η 6 ‐C 6 H 6 )Cr(CO) 3

The electronic effects of the chromium tricarbonyl fragment on the structure of the benzene ring of (η 6 ‐C 6 H 6 )Cr(CO) 3 is investigated theoretically using ab initio molecular orbital calculations with electron correlation included by using both Møller–Plesset second‐order calculations and density functional theory. The results of the calculations showed that the solid‐state structure of alternating long and short carbon–carbon distances in the benzene ring is a result of the orientation of the Cr(CO) 3 fragment with respect to the benzene ring in which the carbonyl groups lie over the midpoint of alternate carbon–carbon bonds of the benzene ring, called the staggered conformation. A different distortion of the benzene ring is observed even in the eclipsed conformation in which the carbonyls lie over alternate carbon atoms of the benzene ring. The results of these calculations indicate that the distortion of the benzene ring in (η 6 ‐C 6 H 6 )Cr(CO) 3 is a result of the electronic influence of the Cr(CO) 3 fragment on the benzene ring. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 152–160, 2000