Dimethylzinc and sulfur dioxide give the products (CH3)2Zn•SO2 and (CH3)2Zn•2SO2 for which the formulations CH3ZnO.SO•CH3 and (CH3SO•O)2Zn are proposed. With dimethylmercury, sulfur dioxide gives products best formulated as (CH3Hg)2SO2 and CH3HgSO•OCH3.