Two-electron reductive reactivity of trivalent uranium tetraphenylborate complexes of (C5Me5) and (C5Me4H)

The reductive reactivity of the (BPh₄)¹⁻ ligand in pentamethylcyclopentadienyl (C₅Me₅)₂U](μ-η²:η¹-Ph)₂BPh₂] (1) was compared with that of the tetramethyl analog, (C₅Me₄H)₂U](μ-η⁶:η¹-Ph)(μ-η¹:η¹-Ph)BPh₂] (2) using PhSSPh as a probe to determine if the mode of (BPh₄)¹⁻ bonding affected the reduction. Both complexes act as two-electron reductants to form (C₅Me₄R)₂U(SPh)₂ R = Me, 3; H, 4], but only in the R = H case could the product be crystallographically characterized. An improved synthesis of 1 from (C₅Me₅)₂UH]₂ (5) and Et₃NH]BPh₄] is also reported as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium metallocene (C₅Me₅)₂U(NCMe)₅]BPh₄]₂ (6).