Two trinuclear oxalato tin (IV) adducts have been synthesized and characterized by elemental analyses, infrared and Mössbauer techniques.The suggested structures are discrete, oligomeric or polymeric, the anion behaving as a monochelating and bidentate ligand in one case while being a tetracoordinating ligand in the second one.The environment of the tin centre is trigonal bipyramidal, the SnPh 3 residue being cis or trans coordinated.