Oxocyano complexes of molybdenum(IV) and tungsten(IV) with Schiff base ligands derived from salicylaldehyde and aliphatic amines. Crystal structure of [PPh4]2[Mo(CN)3O(ensal)]·5.5H2O (Hensal = N-salicylideneethylenediamine)

Abstract

The reaction of [M(CN)₄O(H₂O)]^2– (M = Mo) with salicylaldehyde and methylamine gave the complex [Mo(CN)₃O(mesal)]^2–, where Hmesal = N-salicylidenemethylamine. If ethylenediamine or propane-1,3-diamine is used in this type of reaction the complexes with singly condensed Schiff bases, N-salicylideneethylenediaminate (ensal) (M = Mo or W) or N-salicylidenepropane-1,3-diaminate (tnsal) (M = Mo), are obtained. X-Ray crystallographic analysis of [PPh₄]₂[Mo(CN)₃O(ensal)]·5.5H₂O showed that the ‘half-unit’ Schiff base co-ordinates in a bidentate manner with a non-coordinated NH₂ group. The complexes were characterised by elemental analysis, electronic absorption, IR and ¹H NMR spectra. The electronic absorption spectra show the presence of solvent dependent MLCT bands. Their solvatochromic effect is comparable with that observed for other complexes of similar structure.