Oxy- and thio-phosphorus acid derivatives of tin. Part 12. A Mössbauer spectroscopic investigation of the structures and polymorphic behaviour of diorganotin(IV) phenyl-phosphonates and -arsonates

Abstract

The phenylphosphonate and phenylarsonates Me₂Sn[PhPO₃], Me₂Sn[PhAsO₃], and Buⁿ₂Sn[PhAsO₃] are isolated as their α-modifications from the reaction of dimethyl- or di-n-butyl-tin dichloride with the monosodium salt of the appropriate acid. β-Modifications are obtained by removal of water from the monohydrates Me₂Sn[PhPO₃]·H₂O, Me₂Sn[PhAsO₃]·H₂O, and Buⁿ₂Sn[PhAsO₃]·H₂O, obtained in turn from the reaction of the diorganotin dichloride with the disodium salt of the appropriate acid. Only one form of Ph₂Sn[PhPO₃] was isolated; this can be obtained either from the direct reaction of diphenyltin dichloride with phenylphosphonic acid or by removal of water from Ph₂Sn[PhPO₃]·H₂O. On the basis of i.r. and variable-temperature Mössbauer spectroscopic and X-ray powder diffraction data it is suggested that the structures of the β-modifications and of Ph₂Sn[PhPO₃] consist of infinite chains, and that chains with similar backbone structures occur in solid-state forms of their hydrate precursors. The α-modifications of Me₂Sn[PhAsO₃] and Buⁿ₂Sn[PhAsO₃] appear to have two-dimensional sheet structures in which tin achieves five-co-ordination, but the data do not preclude the possibility that α-Me₂Sn[PhPO₃] has a more associated three-dimensional network structure, with tin in highly distorted octahedral sites. The complexes Me₂Sn[PhAs(OH)O₂]₂, Buⁿ₂Sn[PhAs(OH)O₂]₂, and Buⁿ₂Sn[PhP(OH)O₂]₂, obtained by the reaction of a diorganotin dihalide with the appropriate acid, have structures in which tin is in octahedral sites. It is suggested that these are chain structures in which chains are linked by strong hydrogen bonds.