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 = CuIIor NiII; L = quadridentate Schiff-base ligand)

Abstract

The compound SnCl3(OEt)·EtOH reacts with the complexes ML [M = CuII or NiII; 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 = CuII but not when M = NiII. 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. Mossbauer 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.