The structural reorganisation of bis(diethyldithiocarbamato)morpholine–zinc(II) and –copper(II) in the course of solid-state solvation with morpholine and benzene molecules studied by ESR, solid-state 13C and 15N CP/MAS NMR spectroscopy and single-crystal X-ray diffraction

Abstract

Six forms of both non-solvated and solvated adducts of bis(diethyldithiocarbamato)–zinc(II) and –copper(II) with morpholine, of general formulas [M{O(CH 2) 4NH}{S 2CN(C 2H 5) 2} 2] and [M{O(CH 2) 4NH}{S 2CN(C 2H 5) 2} 2]·L (M=Zn(II) ( 1): L=O(CH 2) 4NH ( 2), C 6H 6 ( 3); M=Cu(II) ( 4): L=O(CH 2) 4NH ( 5), C 6H 6 ( 6)), have been prepared and studied by means of ESR, solid-state natural abundance 13C and 15N CP/MAS NMR spectroscopy and single crystal X-ray diffraction data. The existence of two conformers, which are correlated as rotation isomers, was unambiguously established for both zinc(II) and copper(II) non-solvated adducts 1 and 4. These two isomeric forms are characterised by different modes of spatial orientation of the non-planar morpholine ring relative to the two four-membered metallochelate rings. The geometry of the adduct molecules is close to square pyramidal, C 4 v , and therefore the ground state of the unpaired copper(II) electron corresponds to the 3d x 2− y 2 atomic orbital (AO). Solvation of the studied adducts in the solid state leads to their significant structural reorganisation at the molecular level, i.e. their structural unification yielding qualitatively new structural states with: (i) different lengths of the ZnN bond; (ii) reoriented heterocyclic ring of the coordinated morpholine molecule; and (iii) an enhanced contribution of trigonal-bipyramidal character to the geometry of the coordination polyhedra of the central atom (from 7.5 and 22.7% in original adducts to ∼75% in solvated forms). The type of geometry of the coordination polyhedrons in the solvated forms of the adducts (intermediate between trigonal bipyramid D 3 h and square pyramid C 4 v ) correlates with the fact that the ground state of the unpaired copper(II) electron is a mixture of 3d z 2 and 3d x 2− y 2 AOs. All observed ESR and NMR resonances have been assigned and are in agreement with the structures obtained from X-ray diffraction data.