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

The Th(IV) mixed-sandwich halide complexes Th(COTTIPS2)Cp*X (where COTTIPS2 = 1,4-{(SiPr3)-Pr-i}(2)C8H6, X = Cl, I) have been synthesised, and structurally characterised. When Th(COTTIPS2)Cp*I is reduced in situ in the presence of CO2, a mixture of dimeric carboxylate and oxalate complexes {Th(COTTIPS2)Cp*}(2)(mu-kappa(1):kappa(2)-CO3) and {Th(COTTIPS2)Cp*}(2)(mu-kappa(2):kappa(2)-C2O4) are formed, possibly via a transient Th(III) species. Th(COTTIPS2)Cp*Cl is readily alkylated to yield the benzyl complex Th(COTTIPS2)Cp*CH2Ph, which reacts with CO2 to form a carboxylate and with H-2 to form a hydride; the latter inserts CO2, giving the bridging formate complex {Th(COTTIPS2)Cp*(mu-kappa(1):kappa 1-O2CH)}(2).