Molecular structures of Sn(II) and Sn(IV) compounds with di-, tri- and tetramethylene bridged salen* type ligands

Abstract

Six tin complexes of the type (O,N,N,O)Sn and (O,N,N,O)SnCl2 (L1Sn, L2Sn, L3Sn, L1SnCl2, L2SnCl2, L3SnCl2) with di-anionic salen type tetradentate O,N,N,O chelators were synthesized and characterized by 1H, 13C, 119Sn NMR spectroscopy, single-crystal X-ray diffraction, and elemental analysis (L1Sn, L2Sn, L1SnCl2, L2SnCl2, L3SnCl2) or 119Sn solid state NMR spectroscopy and elemental analysis (L3Sn). The length of the oligomethylene bridge of the ligands (L1)2-, (L2)2- and (L3)2- (which are the anions of di-, tri- and tetramethylene-α,ω-N,N′-bis(2-hydroxyacetophenoneimine, respectively) was found to have significant influence on the configuration of the tin coordination sphere. In detail, the Sn atom in L1Sn occupies the apex of a (O,N,N,O) square pyramid, whereas L2Sn resembles a see-saw setup of the tin coordination sphere, and L3Sn appears to be of oligomeric nature concluded from its distinctly lower solubility and different 119Sn NMR shift. In the monomolecular Sn(IV) compounds the Cl atoms are trans-disposed in L1SnCl2, and cis-arrangements of the Cl atoms in combination with a mer-fac-arrangements of the (O,N,N,O) ligands are found in L2SnCl2 and L3SnCl2.

Keywords

• chelate
• nmr
• salen
• tin
• x-ray