Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal, Metalloid, and Metal Combinations (An=U, Th; Pn=P, As, Sb, Bi)

The synthesis and characterisation is presented of the compounds [An(Tren DMBS ){Pn(SiMe 3 ) 2 }] and [An(Tren TIPS ){Pn(SiMe 3 ) 2 }] [Tren DMBS =N(CH 2 CH 2 NSiMe 2 Bu t ) 3 , An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren TIPS =N(CH 2 CH 2 NSiPr i 3 ) 3 , An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U−Sb and Th−Sb moieties are unprecedented examples of any kind of An−Sb molecular bond, and the U−Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th−Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U−Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An−An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U−Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.