Molecular Thorium Trihydrido Clusters Stabilized by Cyclopentadienyl Ligands

Hydrogenolysis of alkyl‐substituted cyclopentadienyl (Cp R ) ligated thorium tribenzyl complexes [(Cp R )Th(p‐CH 2 ‐C 6 H 4 ‐Me) 3 ] ( 1 – 6 ) afforded the first examples of molecular thorium trihydrido complexes [(Cp R )Th(μ‐H) 3 ] n (Cp R =C 5 H 2 ( t Bu) 3 or C 5 H 2 (SiMe 3 ) 3 , n=5; C 5 Me 4 SiMe 3 , n=6; C 5 Me 5 , n=7; C 5 Me 4 H, n=8; 7 – 10 and 12 ) and [(Cp # ) 12 Th 13 H 40 ] (Cp # =C 5 H 4 SiMe 3 ; 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 ttt )Th(μ‐H) 2 ] 4 (μ‐p‐CH‐C 6 H 4 ‐Me) 2 (Cp ttt =C 5 H 2 ( t Bu) 3 ) ( 11 ) was also isolated. All of the complexes were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. Hydride positions in [(Cp Me4 )Th(μ‐H) 3 ] 8 (Cp Me4 =C 5 Me 4 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 .