Synthesis and structure of the bis(tetramethylcyclopentadienyl)uranium metallocenes (C5Me4H)2UMe2, (CMe4H)2UMeCl, [(C5Me4H)2U][(μ-η6:η1-Ph)(μ-η1:η1-Ph)BPh2], and [(C5Me4)SiMe2(CH2CH=CH2)]2UI(THF)

Although bis(pentamethylcyclopentadienyl)uranium metallocene chemistry has been extensively explored, relatively little is known about the reactivity of the bis(tetramethylcyclopentadienyl) analogues. To provide the essential (C5Me4H)(2)U-containing complexes for comparison with (C5Me5)(2)U-containing species, a series of bis(tetramethylcyclopentadienyl)uranium complexes has been prepared. The recently isolated (C5Me4H)(2)UCl2 (1) reacts with MeLi to form the methyl complexes (C5Me4H)(2)UMe2 (2) and (C5Me4H)(2)UMeCl (3), both of which were characterized by X-ray crystallography. Complex 3 can also be synthesized by ligand redistribution between 1 and 2. Complex 2 is easily reduced with potassium to form (C5Me4H)(2)UMe2K (4), which provides entry into unsolvated bis(tetramethylcyclopentadienyl) U(III) chemistry. Complex 4 reacts with 2 equiv of Et3NHBPh4 to form the trivalent cationic complex [(C5Me4H)(2)U] [(mu-Ph)(2)BPh2] (5), which has a structure differing from that of [(C5Me5)(2)U] [(mu-Ph)(2)BPh2] in that one arene ring in 5 approaches the uranium ion in an eta(6) mode and the other in an eta(1) orientation. Attempts to make unsolvated bis(tetramethylcyclopentadienyl) U(III) complexes with the tethered olefin ligand [(C5Me4)SiMe2(CH2CH=CH2)](-) - by reacting [(C5Me4)SiMe2(CH2CH=CH2)]K with UI3(THF)(4) led to the formation Of [(C5Me4)SiMe2(CH2CH=CH2)](2)UI(THF) (6). Although solvated, 6 readily loses THF and is the first example of an actinide complex that contains a tethered olefin functionality.