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

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