Molecular Thorium Trihydrido Clusters Stabilized by Cyclopentadienyl Ligands

Hydrogenolysis of alkyls 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( u -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( u -H) 2 ] 4 ( u - p -CH-C 6 H 4 -Me) 2 (Cp ttt = C 5 H 2 ( t Bu) 3 ) ( 11 ) was also isolated. All the complexes were characterized by NMR spectroscopy and single-crystal X-ray analysis. Hydride positions in [(Cp Me4 )Th( u -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 .