Preparation and tin-119 m Mössbauer spectra of diorganotin(IV) complexes of picolinic acid and picolinic acid N-oxide

Abstract

Two types of complexes of diorganotin picolinates (i) R 2Sn(Pic) 2 [2:1] and (ii) [R 2SnPic] 2O [1:1] and of diorganotinpicolinate N-oxides (i) R 2Sn(PicO) 2 [2:1] and (ii) [R 2SnPicO] 2O [1:1] (R = CH 3, n-C 4H 9, n-C 8H 17, C 6H 5CH 2) 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. Mössbauer 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.