Bond valence sums in coordination chemistry. Sn(II), Sn(III), and Sn(IV) complexes containing SnS and/or SnN bonds

Abstract

A simple method for calculating the oxidation state of Sn in complexes containing SnS and/or SnN bonds is presented. A total of 54 SnS n , 120 SnN n , and 20 mixed Sn(S and N) n fragments with n=2–8 were retrieved from the Cambridge Structural Database and analyzed using the bond valence sum method. New R 0 values of 2.391(14) Å for SnS and 2.058(20) Å for SnN were derived and can be used to calculate the oxidation state of the Sn atom in complexes containing only S and N bonds without any assumptions. The bond valence sum (BVS) results support the existence of the unusual Sn(III) reported recently and confirm postulated Sn⋯phenyl ring and Sn⋯S or Sn⋯O transannular interactions. There are no indications that the lone pair influences the BVS calculation for Sn(II) complexes. Surprisingly, low coordination numbers (CNs) of 2–4 were observed for Sn(II) compared to CNs of 4–8 found for the smaller Sn(IV). A summary of SnS and SnN distances as a function of CN and oxidation state is given.