Abstract Mixed carbamate complexes of dimethyltin(IV) with the formula Me 2 SnLL′ (LL′ = all combinations of Sc(O)NMe 2 , SeC(O)NMe 2 , S 2 CNMe 2 , SSeCNMe 2 and Se 2 CNMe 2 , except for that of S 2 CNMe 2 -Se 2 CNMe 2 reported previously) were prepared and characterized by their melting points and X-ray powdered patterns as well as elemental analyses. Infrared spectra of the complexes in Nujol mulls reveal that all carbamate ligands act in bidentate manners. 1 H NMR spectra indicate that (i) the mixed-carbarmate complex partly disproportionates to the corresponding bis-carbamate complexes, and they exist as an equilibrium mixture with statistical ratios (about 1:2:1) in solution, and (ii) the XYCNMe 2 ligands (XY = SS, SSe, SeSe) coordinated to the tin(IV) are more labile than the XC(O)NMe 2 (X = S, Se). The assignments of each proton signal are also described.