Infrared studies of halide binding with CpMn(CO)2X complexes where X = ligands bearing the O–H or N–H group

Halide ion binding to the OH group of CpMn(CO)2(3-hydroxypyridine) complex has been investigated using infrared absorption spectroscopy via the νCO bands. Fluoride ion interaction in chloroform causes the largest redshift of up to 12 cm−1. The infrared bands of CpMn(CO)2L complexes containing N–H groups are redshifted to a similar extent. The displacement of the 3-hydroxypyridine ligand from the manganese complex by PPh3 is prevented because of a Mn–N bond strengthening effect induced by OH⋯F− binding. Density functional calculations also lend support to the large effect that OH⋯F− interaction has on the magnitude of the νCO redshift and Mn–N bond energy of CpMn(CO)2(3-hydroxypyridine).