TRANSITION-METAL-CATALYZED OXIDATIONS, 7 - SPECTROSCOPIC EVIDENCE FORINTRAMOLECULAR 2)CENTER-DOT-CENTER-DOT-CENTER-DOT-CENTER-DOT-HO-C HYDROGEN-BONDING IN SOLUTION

The ring-opening reaction of epoxycyclohexane with 2-[3(5)-pyrazolyl]p yridine results in the formation of racemic trans-2-[3-(2-pyridyl)-1-p yrazolyl)cyclohexanol (1). Kinetic resolution with Lipase B from candi da antarctica gives the (1S,2S) enantiomer of 1, the solid-state struc ture of which was determined by X-ray crystallography, as an enantiome rically pure tridentate ligand. Investigation by NMR spectroscopy of t he corresponding oxodiperoxomolybdenum complex 2, where 1 acts as a bi dentate chelate, proves the formation of a weak intramolecular Mo-VI(O -2).... HO-C bridge in CHCl3 solution. This H bonding is broken by sol vents such as acetone, THF or DMF, which are capable of forming hydrog en bonds to alcohols. Intermolecular hydrogen bonds between the OH gro ups and molybdenum peroxo moieties are also found in the solid-state s tructure of 2, leading to a helical arrangement of the peroxo complexe s.