Cerium(iii) dialkyl dithiocarbamates from [Ce{N(SiMe3)2}3] and tetraalkylthiuram disulfides, and [Ce(κ2-S2CNEt2)4] from the CeIII precursor; TbIII and NdIII analogues

Abstract

The synthesis and characterisation of the first neutral cerium dialkyl dithiocarbamate complexes, using a novel oxidative displacement of the amido ligands of [Ce{N(SiMe₃)₂}₃] by tetraalkylthiuram disulfides [R₂NC(S)S]₂ (R = Me, Et) in thf solution, are reported. In the absence of other donors, the complexes [Ce(κ²-S₂CNMe₂)₃(thf)₂] 2 and Ce(κ²-S₂CNEt₂)₃3 were obtained. The addition of a polypyridyl ligand allowed easy access to a range of complexes of general formula [Ce(κ²-S₂CNR₂)₃(L^∩L)] [R = Me and L^∩L = 2,2′-bipy (4), or 4,7-diphenyl-1,10-phenanthroline (6); or R = Et and L^∩L = 2,2′-bipy (5)]. Brief exposure of the Ce(III) dithiocarbamate 3 to oxygen gas afforded in high yield the diamagnetic, crystalline Ce(IV) dithiocarbamate [Ce(κ²-S₂CNEt₂)₄] 7. The neodymium (8) and terbium (10) complexes, isoleptic with 2, were prepared from the appropriate 4f metal (Ln) bis(trimethylsilyl)amide [Ln{N(SiMe₃)₂}₃] [Ln = Nd or Tb (9)] and [Me₂NC(S)S]₂. The structures of the crystalline complexes 2, 4, 6, 7, 9 and 10 have been determined by X-ray crystallography. Some evidence has been obtained for the formation of the cerium(IV) complex Ce{N(SiMe₃)₂}₂(κ²-S₂CNMe₂)₂. The cerium(IV) complex 7 has the metal coordinated to eight sulfur atoms of four planar chelating S₂CNC₂ moities and its geometry is intermediate between dodecahedral and square prismatic; the mean Ce–S bond length of 2.803 Å in 7 compares with the 2.950 Å in the Ce(III) complex 2.