Synthesis and crystal structures of ionic triphenyltin complexes with oxalic and malonic acid

Two ionic triphenyltin complexes (1 and 2) were obtained via condensation of triphenyltin hydroxide with oxalic and malonic acids in the presence of di-isobutylamine. Their structures have been characterized by IR and multinuclear (H-1, C-13, and Sn-119) NMR spectroscopies. The coordinations of tin in the two triphenyltin complexes are confirmed by X-ray crystallographic studies. In the solid state, oxalate complex 1 consists of a di-isobutylammonium cation and an oxalatotriphenylstannate anion. Tin is five-coordinate with a cis-trigonal-bipyramid (TBP) geometry, as the oxalate is a chelating bidentate ligand. Complex 1 is a 1-D polymer via hydrogen bonding between carboxylate oxygen and ammonium nitrogen. The crystallographic studies reveal that 2 is a trinuclear triphenyltin complex formed with the molar ratio of tin, acid, and amine being 3:2:1. A negative charge is delocalized among the three tins in the complex; all tins have trans-TBP geometry with three phenyls in the equatorial plane and two O in axial positions. The malonates in 2 are bridging tridentate with the free carbonyl hydrogen bonded to di-isobutylammonium through an ethanol. This coordination and significant inter- and intramolecular hydrogen bonds between ammonium and malonate result in a 3-D polymeric structure for 2.