Synthesis and structural characterization of diorganotin(IV) complexes with heteroditopic pyridyl-ONO′-ligands

Abstract A series of eight novel diorganotin(IV) complexes with heteroditopic pyridyl-ONO′-ligands were prepared viz., [Me2Sn(L1)]2⋅2(H2O) (1), [n-Bu2Sn(L1)]2 (2), [Ph2Sn(L1)] (3), [Me2Sn(L2)]2⋅2(H2L2) (4), [n-Bu2Sn(L2)]2 (5), [Ph2Sn(L2)]⋅0.5(C6H6) (6), [Me2Sn(L3)]2 (7) and [n-Bu2Sn(L3)]2 (8) and structurally characterized. Irrespective of the type of diazo L ligand, the dimethyl- and di-n-butyltin(IV) compounds are dinuclear species with an inversion center in the middle of the {Sn2O2} cores affording metals with coordination number six. The mononuclear compounds 3 and 6, with the bulky phenyl ligands, present the tin cations with highly distorted square pyramid geometries. The detection of a conformation in the (Ln)2- ligand in the solid state structures of 3, 4 and 8 which is different from the one in the remaining compounds suggests that the packing of the molecules conceivably have a greater influence than the imine substituents or the metal co-ligands. The solution 1H and 13C NMR of compounds 4-6 displayed an anisochronous behavior of dimethyl-, di-n-butyl- and diphenyltin parts while those of compounds 1-3 are isochronous. The 119Sn NMR chemical shift displacements of all the compounds are indicative of five-coordinate tin atoms, thus revealing dissociation in solution of the dinuclear 1, 2, 4, 5, 7 and 8 complexes.