A process for the production of compounds of the formula ICH.sub.3 (R)SnCl.sub.2 (I)wherein R is C.sub.4 -C.sub.20 alkyl, which process comprises reacting dimethyl tin dichloride and R-Cl, wherein R has the above meaning, in the presence of a catalyst of the formula IIR'(R").sub.3 M.sup..sym. X.sup..crclbar. (II)wherein R' is C.sub.1 -C.sub.20 alkyl which is unsubstituted or substituted by C.sub.1 -C.sub.4 alkoxy, or is C.sub.7 -C.sub.20 aralkyl, the aryl moiety of which can be substituted by halogen or C.sub.1 -C.sub.4 alkoxy, R" has the same meaning as assigned to R' or is phenyl which is unsubstituted or substituted by C.sub.1 -C.sub.4 alkyl, C.sub.1 -C.sub.4 alkoxy or halogen, M.sup..sym. is a cation N, P or Sb, and X is an anion selected from the group consisting of chlorine, SnCl.sub.3, CH.sub.3 -SnCl.sub.4, (CH.sub.3).sub.2 SnCl.sub.3, SnCl.sub.5 or SbCl.sub.4.The compounds of the formula I are intermediates for obtaining stabilizers for halogen-containing thermoplastics.