Spectroscopic detection of organolanthanide dihydrogen and olefin complexes

Although dihydrogen complexes are frequently invoked along the reaction coordinate for lanthanide-centered, actinide-centered, and d{sup 0} transition element-centered hydrogenolytic processes, existence of such species remains highly speculative. A significant question concerns the viability of metal-dihydrogen coordination at an electron-deficient center not likely to engage in extensive, perhaps requisite, metal {yields} H{sub 2} backbonding. The authors report here the first spectroscopic detection of an organolanthanide dihydrogen complex utilizing a coordinatively unsaturated, paramagnetic NMR probe selected for high sensitivity to complexation and thermodynamic unfavorability of oxidative addition or metal-ligand bond hydrogenolysis.