Influence of 1,2,4-Tri-tert-butylcyclopentadienyl Ligand on the Reactivity of the Thorium Bipyridyl Metallocene [η⁵‑1,2,4-(Me₃C)₃C₅H₂]₂Th(bipy)]

The thorium bipyridyl metallocene (Cp^3tBu)₂Th(bipy) (1; Cp^3tBu = η⁵-1,2,4-(Me₃C)₃C₅H₂) shows a rich reactivity toward a series of small molecules. For example, complex 1 may act as a synthon for the (Cp^3tBu)₂Th(II) fragment as illustrated by its reactivity toward to CuI, hydrazine derivative (PhNH)₂, Ph₂E₂ (E = S, Se), elemental sulfur (S₈) and selenium (Se), organic azides, CS₂, and isothiocyanates. Moreover, in the presence of polar multiple bonds, such as those in ketones Ph₂CO and (CH₂)₅CO, aldehydes p-MePhCHO and p-ClPhCHO, seleno-ketone (p-MeOPh)₂CSe, nitriles PhCN, Ph₂CHCN, C₆H₁₁CN, and p-(NC)₂Ph, and benzoyl cyanide PhCOCN, C–C coupling occurs to furnish (Cp^3tBu)₂Th[(bipy)(Ph₂CO)] (10), (Cp^3tBu)₂Th[(bipy)((CH₂)₅CO)] (11), (Cp^3tBu)₂Th[(bipy)(p-MePhCHO)] (12), (Cp^3tBu)₂Th[(bipy)(p-ClPhCHO)] (13), (Cp^3tBu)₂Th[(bipy){(p-MeOPh)₂CSe}] (14), (Cp^3tBu)₂Th[(bipy)(PhCN)] (16), (Cp^3tBu)₂Th[(bipy)(Ph₂CHCN)] (17), (Cp^3tBu)₂Th[(bipy)(C₆H₁₁CN)] (18), [(Cp^3tBu)₂Th]₂{μ-(bipy)[p-Ph(CN)₂](bipy)} (20), and (Cp^3tBu)₂Th{(bipy)[PhC(CN)O]} (21), respectively. Nevertheless, ketazine (PhCHN)₂ or benzyl nitrile PhCH₂CN forms the dimeric complexes [(Cp^3tBu)Th]₂[μ-NC(Ph)(bipy)]₂ (15) and (Cp^3tBu)₂Th[(bipy){C(CHPh)NH}] (19), respectively. In contrast, C–N bond cleavage and C–C coupling processes occur upon addition of isonitriles Me₃CNC and C₆H₁₁NC to 1 to yield the thorium isocyanido amido complexes (Cp^3tBu)₂Th[4-(Me₃C)bipy](NC) (22) and (Cp^3tBu)₂Th[4-(C₆H₁₁)bipy](NC) (23), respectively. Furthermore, a single-electron transfer (SET) process ensues when 1 equiv of CuI is added to 1 to yield the Th(VI) bipyridyl iodide complex (Cp^3tBu)₂Th(I)(bipy) (3).