Transmetalation as a route to a cyclic heteronuclear bifunctional Lewis acid containing tin and gallium

The reaction of equimolar quantities of 1,8-bistrimethylstannylnaphthalene (1) and GaCl3 in toluene yields a stannagallacycle, namely, bis(mu-1,8-napthalenediyl) (mu-chloride)methyltin (IV) chlorogallium(III) (2). Compound 2 is insoluble in solvents of low polarity and has been characterized by EA, MSCI, and X-ray analysis. The Latter revealed the existence of a folded eight-membered dimetallacycle as well as the presence of a chloride ligand bridging the two metals. When. treated with pyridine, formation of a soluble bis(pyridine) adduct (3) occurs. Compound 3 has been characterized by EA and H-1, C-13, and S-119, NMR spectroscopy. As shown by X-ray single-crystal analysis of 3, the central eight-membered dimetallacycle of the molecule has remained intact on going from 2 to 3. Compound 3 does not feature a bridging chloride, and its structure is that of a Lewis acid-Lewis base adduct in which two independent pyridine molecules coordinate the metal centers.