1:1 Addition complexes of [Ni(II)L].H2O [HL=N,N'-bis(3-methoxysalicylidene)ethylenediamine (3MeO-H-2salen), N,N'-bis(3-methoxysalicylidene)propane-1,2-diamine (3MeO-H-2salpn) or N,N'-bis(3-methoxysalicylidene)-o-phenylenediamine (30-H-2salphen)] with SnR2Cl2 (R = Me or Ph), SnBunCl3, or SnCl4 have been found to be generally monoaqua adducts of the tin Lewis acids with the water engaged in hydrogen bonding with the methoxy and phenolic oxygen atoms of the Schiff-base ligand. Both water and methoxy oxygen atoms are involved in donor-bond formation to tin in the polymeric structures 2SnMe2Cl2. [Ni(3MeO-salen)]-H2O and SnMe2Cl2.[Ni(3MeO-salphen)].H2O, each of which has two very different tin environments. The two octahedral tin sites in the structure of SnMe2Cl2.2[Ni(3MeO-salphen).H2O] appear to result from two isomeric forms of the adduct co-existing in a lattice as a result of hydrogen-bonding interactions. Crystal-structure determinations revealed that the monoaqua adducts of dimethyltin dichloride which exist in the structures SnMe2Cl2.[Ni(3MeO-salen)]-H2O and SnMe2Cl2. [Ni(3MeO-salpn)].H2O differ in that, in the former tin is in a trigonal-bipyramidal environment, whereas in the latter it is in an octahedral environment as a result of an intermolecular Sn ... Cl contact of 3.61 5 angstrom.