Synthesis and Structure of [η⁵‑1,2,4-(Me₃Si)₃C₅H₂]₂Th(bipy) and Its Reactivity toward Small Molecules

Halide exchange of (Cp^3tms)₂ThCl₂ (1; Cp^3tms = η⁵-1,2,4-(Me₃Si)₃C₅H₂) with Me₃SiI furnishes (Cp^3tms)₂ThI₂ (2), which is then reduced with potassium graphite (KC₈) in the presence of 2,2′-bipyridine to give the thorium bipyridyl metallocene (Cp^3tms)₂Th(bipy) (3) in good yield. Complex 3 was fully characterized and readily reacted with various small molecules. For example, 3 may serve as a synthetic equivalent for the (Cp^3tms)₂Th(II) fragment when exposed to CuI, Ph₂S₂, organic azides, and CS₂. Moreover, upon the addition of thiobenzophenone Ph₂CS, p-methylbenzaldehyde (p-MeC₆H₄)CHO, benzophenone Ph₂CO, amidate PhCONH(p-tolyl), seleno-ketone (p,p′-dimethoxy), selenobenzophenone (p-MeOPh)₂CSe, di(p-tolyl)methanimine (p-tolyl)₂CNH, 1,2-di(benzylidene)hydrazine (PhCHN)₂, and nitriles PhCN, PhCH₂CN, and Ph₂CHCN C–C coupling results to give (Cp^3tms)₂Th[(bipy)(Ph₂CS)] (8), (Cp^3tms)₂Th[(bipy)(p-MePhCHO)] (9), (Cp^3tms)₂Th[(bipy)(Ph₂CO)] (10), (Cp^3tms)₂Th[(bipy){(p-tolylNH)(Ph)CO}] (11), (Cp^3tms)₂Th[(bipy){(p-MeOPh)₂CSe}] (12), (Cp^3tms)₂Th[(bipy){(p-tolyl)₂CNH}] (13), (Cp^3tms)₂Th[(bipy)(PhCHNNCHPh)] (14), (Cp^3tms)₂Th[(bipy)(PhCN)] (16), (Cp^3tms)₂Th[(bipy)(PhCH₂CN)] (17), and (Cp^3tms)₂Th[(bipy)(Ph₂CHCN)] (18), respectively. However, when thiazole is added to 3, the dimeric sulfido complex [(Cp^3tms)₂Th]₂[μ-(bipy)CH₂NCHCHS]₂ (15) can be isolated. Moreover, the addition of isonitriles such as Me₃CNC and PhCH₂NC to 3 results in C–N bond cleavage and C–C coupling processes to form the thorium isocyanido amido complexes (Cp^3tms)₂Th[4-(Me₃C)bipy](NC) (19) and (Cp^3tms)₂Th[4-(PhCH₂)bipy](NC) (20), respectively. Nevertheless, upon exposure of 3 to (trimethylsilyl)diazomethane Me₃SiCHN₂, the bis-amido complex (Cp^3tms)₂Th[5,6-(Me₃SiCH)bipy] (21), concomitant with N₂ release, is isolated.