Two-electron reductive reactivity of trivalent uranium tetraphenylborate complexes of (C5Me5)1− and (C5Me4H)1−

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).