The intramolecular M···HO bond in α-metallocenylcarbinols (M = Fe, Ru, Os) and the intermolecular Os···HOH bond in the water complex with osmocene have been studied by extended Hückel (EH) and density functional theory (DFT) methods at the BLYP and B3PW91 levels. There is no evidence that Fe will form such a H-bond. M···HO bonds involve the d-orbitals of the more basic Ru and Os atoms, but otherwise appear to be conventional H-bonds. The approximate intramolecular M···H bond energies are 5.0 and 4.1 kcal/mol for Os and Ru, respectively, as compared to 11.7 kcal/mol for the intermolecular Os···HOH bond. The intermolecular M···H−O bond appears to be of linear type with elongation of the H−O distance. There are steric requirements that accompany these H-bonds. The M−ring distances must be long enough in the intramolecular complexes to permit the carbinal to correctly approach the metal; bulky substituents on the cyclopentadienyl rings inhibit intermolecular bonding.
Published by Organometallics in American Chemical Society.
Inter- and Intramolecular Hydrogen Bonds with Transition Metal Atoms in Metallocenes of the Iron Subgroup G. Orlova, S. Scheiner Organometallics 1998 17 4362-4367.