Mixed sandwich thorium complexes incorporating bis(tri-isopropylsilyl)cyclooctatetraenyl and pentamethylcyclopentadienyl ligands: synthesis, structure and reactivity

Abstract

The Th(IV) mixed-sandwich halide complexes Th(COT^TIPS2)Cp*X (where COT^TIPS2 = 1,4-{SiⁱPr₃}₂C₈H₆, X = Cl, I) have been synthesised, and structurally characterised. When Th(COT^TIPS2)Cp*I is reduced in situ in the presence of CO₂, a mixture of dimeric carboxylate and oxalate complexes {Th(COT^TIPS2)Cp*}₂(μ-κ¹:κ²-CO₃) and {Th(COT^TIPS2)Cp*}₂(μ-κ²:κ²-C₂O₄) are formed, possibly via a transient Th(III) species. Th(COT^TIPS2)Cp*Cl is readily alkylated to yield the benzyl complex Th(COT^TIPS2)Cp*CH₂Ph, which reacts with CO₂ to form a carboxylate and with H₂ to form a hydride; the latter inserts CO₂, giving the bridging formate complex {Th(COT^TIPS2)Cp*(μ-κ¹:κ¹-O₂CH)}₂.