Fast 1H NMR relaxation in some ruthenium hydrides

We report here the synthesis of the new hydride complexes (C5H4CH(CH2CH2)2NMe)- RuH(PPh3)2 (1) and [(C5H4CH(CH2CH2)2NHMe)-RuH(PPh3)2](BF4) (2), the X-ray crystal structures of 1 and 2, and an unprecedented observation of extremely short relaxation times in a monohydride complex as well as in the reaction of CpRuH(PPh3)2 with a variety of acidic proton donors. The relaxation is much faster than expected for a dipole-dipole process involving the two dihydrogen-bonded protons, but no origin for the effect could be suggested.