Assembly of hexa- and trinuclear monoorganostannoxanes: hemi-labile nature of intramolecular N→Sn coordination in RSnCl3 (R = 2-phenylazophenyl)

Abstract

The reactions of RSnCl₃ [R = 2-(phenylazo)phenyl] with phosphonic acids, RPO₃H₂ (R = t-Bu, C₆H₁₁) or (ArO)₂PO₂H (Ar = 4-NO₂-C₆H₅O) in refluxing THF afforded hexatin cages, [(RSn)₆(μ-OH)₆(μ₃-O)₂(t-BuPO₃)₄]·5THF (1), [(RSn)₆(μ-OH)₆(μ₃-O)₂(C₆H₁₁PO₃)₄]·THF (2) and [(RSn)₆(μ-OH)₄(μ₃-O)₂{(NO₂C₆H₄O)PO₃}₄]·THF (3), respectively. On the other hand, the reactions of RSnCl₃ with 1,1,2,3,3-pentamethylene phosphinic acid [cycPO₂H] or Ph₂P(O)OH under similar reaction conditions afforded trinuclear O-capped clusters [(RSn)₃(μ₃-O) (μ₂-OH)₃ (μ-cycPO₂)₃] [cycPO₂]·CH₃CN·H₂O (4) and [(RSn)₃(μ₃-O) (μ₂-OH)₃ (μ-Ph₂PO₂)₃] [Ph₂PO₂]·CH₃CN·CH₂Cl₂ (5) respectively. Molecular structures of 1–3 reveal that the intramolecular N→Sn coordination found in RSnCl₃ is hemilabile; 1–3 do not contain such a feature and the tin atoms in these compounds are six coordinate, possessing a 1C, 5O coordination environment in a distorted octahedral geometry. The cage structures in 1–3, containing two trinuclear sub-units, are formed as a result of the coordination action of several ligands: 4 μ₃-(η¹η¹η¹)[RPO₃]²⁻, 2 μ₃-O²⁻ and 6 μ-OH. The molecular structures of 4–5 reveal them to be cationic trinuclear complexes where 3 tin and 4 oxygen atoms occupy the vertices of a distorted cube while one of the vertices is unoccupied. The molecular structures of 4–5 also reveal that the intramolecular N→Sn coordination present in RSnCl₃ is absent in these compounds attesting to the hemilabile nature of this interaction.