Synthesis and structure of Di-n-butyltin pyridine-2-phosphonate-6-carboxylate

The crystal structure of di-n-butyltin pyridine-2-phosphonate-6-carboxylate, [C14H24NO6PSn](2), features centrosymmetric dimers disposed about a central Sn2O2 core. The phosphonate carboxylate dianion is mu(2)-tetradentate, coordinating one tin atom via one of the phosphonate oxygen atoms, the pyridine nitrogen atom, and one of the carboxylate oxygen atoms; the latter atom also coordinates the second tin atom of the dimer. The remaining positions in the seven-coordinate, distorted pentagonal bipyramidal geometry are occupied by a water molecule and two n-butyl groups that occupy axial positions. The lattice is stabilized by hydrogen-bonding contacts leading to an arrangement of parallel, orthogonally related chains of dimeric units. In methanol solution, the dimer is involved in a dissociation equilibrium that is fast on the NMR time scale.