Transition metal Schiff-base complexes as ligands in tin chemistry. Part 2. A tin-119 Mössbauer spectroscopic investigation of the adducts SnBunxCl3–x(OR)·ML (x= 0 or 1; R = H or alkyl; M = CuII or NiII; L = quadridentate Schiff-base ligand)

Abstract

The compound SnCl₃(OEt)·EtOH reacts with the complexes ML [M = Cu^II or Ni^II; H₂L =N,N′-ethylene-bis(salicylideneimine), N,N′-o-phenylenebis(salicylideneimine), or derivatives of these] to give the adducts SnCl₃(OEt)·ML. Hydrolysis of the ethoxo adducts in chloroform under ambient conditions yields the adducts SnCl₃(OH)·ML. Chloroform solutions of the adducts SnCl₄·ML gives similar hydroxo adducts under ambient conditions when M = Cu^II but not when M = Ni^II. The compound SnBuⁿCl₂(OH)·H₂O reacts with ML at –10 °C to give 1 : 1 adducts, but at higher temperatures SnBuⁿCl(OH)₂·H₂O and SnBuⁿCl₃·ML are formed. The compound SnBuⁿCl₂(OMe)·MeOH reacts with ML in chloroform to yield the adducts SnBuⁿCl₂(OMe)·ML. The replacement of chloride by hydroxide or alkoxide in either SnBuⁿCl₃ or SnCl₄ results in a reduction of the Lewis acidity at tin. Mössbauer quadrupole-splitting data for SnBuⁿCl₂(OH)·ML and SnBuⁿCl₂(OMe)·ML were analysed in terms of the point-charge model from which it was established that the donor oxygen and carbon atoms practically always adopt fac geometry about tin; this contrasts with the mer geometry preferred by many adducts SnBuⁿCl₃·ML.