AN INFRARED STUDY OF STRUCTURES OF CYCLOPENTADIENYL COMPOUNDS OF COPPER(I) AND MERCURY(II)

The infrared spectra of the copper(I) compounds (C5H5)CuPR3, R = C2H5, C4H9, and the mercury compounds (C5H5)2Hg and C5H5HgCl have been reinvestigated. Comparisons are made with the spectra of compounds which serve as models for pentahapto- and monohaptocyclopentadienylmetal systems. The following conclusions emerge unequivocally: (1) contrary to the belief which has prevailed since 1956, the copper compounds contain pentahapto (i.e., “sandwich-bonded”) rings, and (2) the mercury compounds contain monohapto (i.e., σ-bonded) rings. The significance of these results is discussed in relation to the physical, chemical, and dynamical properties of the molecules. © 1969, American Chemical Society. All rights reserved.