Molecular Thorium Trihydrido Clusters Stabilized by Cyclopentadienyl Ligands.

Hydrogenolysis of alkyl-substituted cyclopentadienyl (Cp ) ligated thorium tribenzyl complexes [(Cp )Th(p-CH -C H -Me) ] (1-6) afforded the first examples of molecular thorium trihydrido complexes [(Cp )Th(μ-H) ] (Cp =C H ( Bu) or C H (SiMe ) , n=5; C Me SiMe , n=6; C Me , n=7; C Me H, n=8; 7-10 and 12) and [(Cp ) Th H ] (Cp =C H SiMe ; 13). The nuclearity of the metal hydride clusters depends on the steric profile of the cyclopentadienyl ligands. The hydrogenolysis intermediate, tetra-nuclear octahydrido thorium dibenzylidene complex [(Cp )Th(μ-H) ] (μ-p-CH-C H -Me) (Cp =C H ( Bu) ) (11) was also isolated. All of the complexes were characterized by NMR spectroscopy and single-crystal X-ray analysis. Hydride positions in [(Cp )Th(μ-H) ] (Cp =C Me H) were further precisely confirmed by single-crystal neutron diffraction. DFT calculations strengthen the experimental assignment of the hydride positions in the complexes 7 to 12.