Nuclear magnetic resonance study of the bonding and diffusion of CO chemisorbed on Pd

The authors report use of ¹⁷O and ¹³C NMR to study the bonding of CO on Pd particles. By ¹⁷-¹³C double resonance, they measure the CO bond length to be 1.20±{}0.03 A{}. The ¹³C resonance frequency is exceptionally high, 310 ppm above values typical for metal carbonyls. Evidence that the shift arises from electron-spin polarization is given from studies of the magnitude and the dependence on temperature and frequency of the ¹³C spin-lattice relaxation time. A diffusion enegy of 6±{}2 kcal/mole, half that of CO on Pt, is deduced from motional narrowing of the ¹³C NMR line.