H-1-NMR AND EPR STUDIES OF [M(NH3)(5)(H2O)](TFMS)(3) (M = RU, OS) - THEORY OF THE PARAMAGNETIC SHIFT FOR STRONG-FIELD D(5) COMPLEXES

The EPR spectra of [Ru(NH3)(5)(H2O)](TFMS)(3) and [Os(NH3)(5)(H2O)](TF MS)(3) (TFMS = trifluoromethanesulfonate) have been measured for a ran ge of temperatures for the solid powders and frozen solutions. The g p arallel to axis for the ''axial'' spectrum observed is shown to be per pendicular to the M-O bond axis, as it is perpendicular to the antibon ding MO that interacts in a pi fashion with the water molecule. The H- 1 NMR of both compounds in 1,2-propanediol carbonate has been obtained over a range of temperatures, and the resonances for axial ammonia, e quatorial ammonia, and the bound water in the complex cation have been identified. Using the experimental g values obtained from EPR and an improved equation that uses all t(2) states, the dipolar component of the shift has been calculated and used to find the contact portion of the paramagnetic shift. An improved equation for the contact shift has been developed which separates the spin contribution into the d(xz), d(yz), and d(xy) portions and this theory applied to the measured cont act shifts. Values for three hyperfine constants have been obtained, t he A(NH3) constant for the MOs that do not pi interact with the water molecule, the A(NH3) constant for the MO that does pi interact, and th e A(H2O) for the MO that does pi interact. The spin transfer for the a mmonia ligand protons is by hyperconjugation giving a positive A, and for the water proton it is mainly by covalent transfer of spin to the nonbonding p orbital with polarization of the spin on the proton givin g a negative A.