IR spectral and X-ray single crystal study of hydrogen bonds and structure of nonamethylferrocenyl- and ferrocenylcarbinols in the solid state

The influence of different substituents in the Cp-ring and at the carbinol C atom on the character and stability of H bonds in crystals of FcCHROH and 9 FcCHROH, Fc = C 5 H 5 FeC 5 H 4 ; 9 Fc = C 5 Me 5 FeC 5 Me 4 , (R = H, CH 3 , C 6 H 5 , C 6 F 5 ) was studied by IR spectroscopy specifically in the ν(OH) region. In these crystals, molecules associates predominantly via intermolecular OH⋯O bonds. However, in some of the 9 FcCHROH complexes, the intermolecular OH⋯π H bonds are also formed. The major type of self-association in compounds with R = Mes is OH⋯π(Mes) H-bonding. It was found from the X-ray structural data for the 9 FcCHMesOH that the Mes plane is almost perpendicular to each Cp ring plane. No intermolecular OH⋯O bonds are formed because of intramolecular shielding of the OH group. The stability of the intermolecular hydrogen bonds is determined by steric rather than electronic factors, the most stable intermolecular hydrogen bonds being formed in the case of primary carbinols.