Penta- and hexaorganostannate(iv) complexes based on O-heterocyclic ligands

In the present study, the synthesis of homoleptic five- and six-coordinate heteroaryl tin(iv) compounds using two O-heterocyclic substituents, 2-furyl (2-fu) and 2-benzofuryl (2-fu^Bz) ligands is described. The compounds were obtained as their lithium salts [Li₂(OEt₂)₂Sn(2-fu)₆] (1), [Li(tmeda)₂][Sn(2-fu)₅] (tmeda = N,N,N',N'-tetramethylethylenediamine) (2) and [Li(thf)₄][Sn(2-fu^Bz)₅] (3), featuring both an intramolecular coordination of the counterions by the anionic hypercoordinate tin(iv) species found in 1 as well as solvent separated cation/anion pairs for compounds 2 and 3. In addition, the co-crystalline complex [K₂(thf)₆Sn(2-fu^Bz)₆]·[K₂(thf)₄Sn(2-fu^Bz)₆] (4a·4b) was achieved. The characterization of all compounds by various spectroscopic methods and X-ray structural analysis complemented by density functional computations provided insights into the diversity of complex formation.