Chelate and macrocycle effects in the 2,2' -Bipyridine N,N' -Dioxide complexation of Alkyltin Trichlorides.

The synthesis of macrocyclic ligands(3, 4, and 7) for alkyltin trichloride (RSnCl3) encapsulation is described. Key reactions were the condensation of p-MeOCH2C6H4MgBr with 6,6'-dibromo- 2,2'-bipyridine, ring closures in dimethylformamide containing Cs2CO3, and oxidation of a bipyridyl precursor (5) to its N,N'- dioxide with buffered aqueous H2O2 in AcOH. The preparation of 4,4'-di-tert-butyl-2,2'-bipyridine 1,1'-dioxide (8) is also reported. The affinity of 8 for MeSnCl3 was greater than that of 4-tert-butylpyridine 1 -oxide, while the affinity of 7 was less than that of 5.