HYDROGEN-BONDS AND CONFORMATIONS OF ALPHA-CARBINOL DERIVATIVES OF CYCLOPENTADIENYLTRICARBONYLS OF MANGANESE AND RHENIUM

On the basis of IR spectra and molecular mechanics calculations, the conformations stabilized by hydrogen bonding in alpha-carbinol derivatives of cyclopentadienyltricarbonyl manganese and rhenium have been determined. Intramolecular H-bonds with Mn and Re atoms are found in the tertiary carbinols. Relative stability of the OH ... M hydrogen bonds increases in accordance with metal basicity (Mn < Re) and on going from the carbonyl to the triphenylphosphine ligand. The proton-donating ability of these carbinols is quantitatively characterized. Competition exists between intra- and intermolecular H-bonds of different types upon self-association in the crystal.