IS RUH4(PPH3)3 IN SOLUTION INDEED A NONCLASSICAL HYDRIDE

A novel systematic investigation of temperature dependences of H-1, H-2, P-31 NMR spectra and H-1 T1, T2 and H-2 T1 relaxation times has been carried out for solutions of RuH4(PPh3)3 (5) and its isotopomers in toluene. The linewidth of the H-ligands of 5 in the 180-310 K temperature range is governed by T2 and J(H-P), the chemical shift does not depend on the temperature and the character of the T1 change is the same for all protons of the complex. It has been shown that the H-1 T1(T) dependences are not consistent with the theoretical data, but the T1min value can be used to calculate the distances between H-ligands. The calculated distances under the assumption of the classical and non-classical models of 5, the found quadrupole coupling constant of D-ligands (68 +/- 3 kHz) and J(H-D) (c. 2.7 Hz) have revealed an inadequacy of those models by a whole set of experimental data. A dynamic structure involving fast pairwise approachment-detachment of the H-ligands is suggested and discussed.