Synthesis and coordination properties of chelating dithiophenolate ligands

Chelating 3,3'-R(1)-5,5'-R(2)-2,2'-dithiobiphenyl ligands (R(1) = R(2) = Cl, 4a; R(1) = R(2) = (t)Bu, 4b; R(1) = allyl, R(2) = H, 4c) and the 2,2'-methylenedibenzenethiol ligand (4d) were synthesized from the corresponding diols (1a-1d) via a three-step procedure involving a Miyazaki-Newman-Kwart rearrangement. Zinc complexes and a tin complex (for 4c) have been prepared to explore their coordination potential, and the substitution pattern, as well as the chelate ring size, is shown to severely effect their ligating properties. Four of the complexes have been characterized crystallographically in the solid state, and the nuclearity of the zinc complexes in solution has been studied by diffusion-ordered NMR spectroscopy. Depending on the ligand, zinc complexes [(4)Zn(4,4'-(t)Bu-bipyridine)](n) (5a-d) are monomeric (n = 1; 4b, 4c), monomeric in solution and dimeric in the solid state (n = 1, 2; 4a), or dimeric overall (n = 2; 4d). The tin complex (4c)SnPh(2) (6c) was additionally synthesized to prove the coordinating abilities of the allyl substituted ligand 4c.