137465-32-8Relevant articles and documents
Separating the Re-H and H-H dipole-dipole contributions to the 1H NMR spin-lattice relaxation rate of the hydride ligand in mer,trans-ReH(CO)3(PPh3)2 by deuteration
Luo, Xiao-Liang,Liu, Hong,Crabtree, Robert H.
, p. 4740 - 4742 (2008/10/08)
The reaction of mer,trans-ReCl(CO)3(PPh3)2 with LiAlH4 in THF at room temperature gives mer,trans-ReH(CO)3(PPh3)2 (1). The temperature dependence of the 1H NMR spin-lattice (T1) relaxation rate of the hydride resonance of 1 is studied to try to understand the excess T1 relaxation often found for rhenium hydride complexes. Our previous assumption that the dipole-dipole relaxation mechanism is dominant is confirmed. Two main dipole-dipole contributions are identified. One is from the usual proton-proton dipole-dipole (HHDD) relaxation between the hydride ligand and the protons of the phosphine ligands, and the other from the rhenium-hydride dipole-dipole (ReHDD) relaxation. The two contributions can be separated by studying mer,trans-ReH(CO)3(PPh3-d15)2 (1-d30). The two components come to a minimum T1 value at different temperatures. The T1(min) value observed for the ReHDD relaxation in 1-d30 is consistent with an Re-H bond distance of 1.75 ?, which is in satisfactory agreement with those determined by neutron diffraction studies on other rhenium hydride complexes.
