Preparation and 119mSn Mössbauer studies of diorganotin(IV) derivatives of nicotinic acid and nicotinic acid N-oxide

Sixteen complexes of nicotinic acid and nicotinic acid N-oxide have been prepared with diorganotin(IV) oxides in 1:1 and 2:1 (ligand:metal) molar ratio. Formulae of diorganotin nicotinates are (i) R2Sn(Nic)2 [2:1] and (ii) [R2SnNic]2O [1:1] and of diorganotin nicotinate N-oxides are (iii) R2Sn(NicO)2[2:1] and (iv) [R2SnNicO]2O[1:1] (R = CH3, nC4H9, nC8H17, C6H5CH2; Nic = anion of nicotinic acid, NicO = anion of nicotinic acid N-oxide). All the butyl- and octylin derivatives are monomeric and are more soluble whereas dimethyl- and dibenzyltin derivatives are polymers and are less soluble or insoluble in common solvents. Mössbauer, 1N NMR and IR spectral studies have been used to assign structures. All the 2:1 complexes possess distorted trans octahedral and all the 1:1 complexes of nicotinic acid have five coordinate distorted trans trigonal bipyramidal structures. However, the 1:1 dinuclear complexes of nicotinic acid N-oxide contain a six coordinated and a five coordinated tin(IV) in the same molecule. A SnOSn bridged structure is present in all the 1:1 complexes. Unlike analogous picolinic acid complexes there is no coordination from ring nitrogen to tin(IV). The carboxylate group is bidentate in all the nicotinic acid complexes whereas it is unidentate in all the picolinic acid complexes as we showed in J. Organomet. Chem., 411 (1991) 89.