f-Block complexes of a m-terphenyl dithiocarboxylate ligand

Straightforward syntheses are provided for the m-terphenyl dithiocarboxylic acid 2,6-(C₆H₄-4-^tBu)₂C₆H₃CS₂H (TerphCS₂H, 2) and its lithium and potassium salts, TerphCS₂Li(Et₂O)₂ and TerphCS₂K (1·Et₂O and 4, respectively). These compounds can be isolated in good yields on multi-gram scales starting from Terph–I without isolating intermediates. Salt metathesis and protonolysis reactions provided access to the homoleptic actinide(IV) complexes (TerphCS₂)₄An (An = Th (5) and U (6)). Electrochemical and reactivity studies revealed that the dithiocarboxylate ligand is incompatible with U(III). The homoleptic lanthanum(III) complex (TerphCS₂)₃La and its η⁶-toluene adduct (7 and 7·tol, respectively) were also structurally characterized. Binding of toluene to 7 was shown to displace intramolecular La–C_arene close contacts that are facilitated by a distortion from the usual geometry of bound dithiocarboxylate ligands.