Synthesis and structural characterization of two interesting sandwich and double sandwich type mixed-valent tellurium-dithiocarbamate complexes;[TeIV {S2CN(C2H5)2}3]2 [TeIV{S2CN(C2H5)2}3](PF6)2 and [TeIV{S2CN(C2H5)2}3] [TeII{S2CN(C2H5)2}2](ClO4)

Abstract Two novel mixed-valent tellurium(II and IV) dithiocarbamate complexes have been prepared and their structures determined by X-ray diffraction studies. Complex 1 , [Te IV (S 2 CNEt 2 ) 3 ] 2 [Te II (S 2 CNEt 2 ) 2 ](PF 6 ) 2 , was obtained from the metathesis reaction of [Te IV (S 2 CNEt 2 ) 3 ClO 4 ] with KPF 6 due to the partial reduction of the primary product [Te IV (SCNEt 2 ) 3 ]PF 6 , which is thermodynamically unstable. The preparation of tellurium(IV) dithiocarbamate in dilute perchloric acid medium results in complex 2 , which has a composition [Te IV (S 2 CNEt 2 ) 3 ][Te II (S 2 CNEt 2 ) 2 ](ClO 4 ). These two complexes represent the first examples of mixed valent complexes of tellurium consisting only the sulphur ligands. Their structural investigation shows that these complexes are stabilized primarily due to the supramolecular Te3.Te interaction, the distance of which is shorter than the earlier known complex. While Te II (S 2 CNEt 2 ) 2 is sandwiched between two Te IV (S 2 CNEt 2 ) 3 molecules in 1 , two such Te(II) molecules are sandwiched in complex 2 .