Metal-Ligand Multiple Bonding in Thorium Phosphorus and Thorium Arsenic Complexes

The complexes (C₅ Me₅ )₂ Th(EHTipp)₂ , (E=P or As; Tipp=2,4,6-triisopropylphenyl), provide a ligand framework that results in facile access to rare Th-E multiple bonds. The reaction of (C₅ Me₅ )₂ Th(EHTipp)₂ with KN(SiMe₃ )₂ , proceeds cleanly to the desired bridging phosphinidiide or arsinidiide complex, [{(C₅ Me₅ )₂ Th(μ₂ -ETipp)(μ₂ -EHTipp)}K]₂ under ambient conditions. In the absence of a chelating agent, the potassium cation of one monomeric unit interacts with the aryl ring of a second monomer to form a bridged dimer. In the presence of 2,2,2-cryptand, the terminal phosphinidene complex, [(C₅ Me₅ )₂ Th=PTipp(PHTipp)][K(2,2,2-cryptand)] is isolated. Using X-ray crystallographic analysis, we have determined these complexes display the shortest Th-P and Th-As bond lengths reported.