PREPARATION AND TIN-119M MOSSBAUER-SPECTRA OF DIORGANOTIN(IV) COMPLEXES OF PICOLINIC-ACID AND PICOLINIC-ACID N-OXIDE

Two types of complexes of diorganotin picolinates (i) R2Sn(Pic)2 [2:1] and (ii) [R2SnPic]2O [1:1] and of diorganotinpicolinate N-oxides (i) R2Sn(PicO)2 [2:1] and (ii) [R2SnPicO]2O [1:1] (R = CH3, n-C4H9, n-C8H17, C6H5CH2) have been prepared by reacting picolinic acid and picolinic acid N-oxide with diorganotin oxide in 2:1 and 1:1 ligand:metal molar ratio. The methyl and benzyl derivatives are less soluble in organic solvents whereas the butyl and octyl derivatives are more soluble. A unidentate carboxylate is present in all the complexes. However, a weak interaction such as C = O --> Sn cannot be ruled out in the less soluble complexes. In the picolinates the ring nitrogen coordinates to tin(IV) intramolecularly in the butyl and octyl derivatives and intra- and intermolecularly in the methyl and benzyl derivatives. Mossbauer parameters show a distorted trans octahedral structure for the 2:1 derivatives and a distorted trans trigonal bipyramidal structure for the 1:1 picolinates with an Sn-O-Sn bridge. A mixed distorted trans octahedral tin atom geometry and a distorted trans trigonal bipyramidal tin with an Sn-O-Sn bridge are found in the same molecule in the 1:1 complexes of picolinic acid N-oxide.