Oxazoline chemistry IX. Synthesis and characterisation of the first Zinc oxazoline dialkyldithiocarbamato complexes; X-ray crystal structure determinations of [Zn(S 2CNR 2-κ 2S) 2(2-R′-4,4-R″-2-oxazoline-κ 1N)] (R = R′ = Me, R″ = H; R = Et, R′ = Me, Et or Ph, R″ = H; R = Bz; R′ = R″ = Me)

Abstract

The synthesis and characterisation (NMR, IR, X-ray diffraction and elemental analysis) of a series of zinc dialkyldithiocarbamato complexes incorporating a monodentate oxazoline ligand are described. These compounds represent the first known examples of oxazolines that are bound to a [Zn(S 2CNR 2) 2] fragment. The syntheses of the title materials involves the treatment of solutions of [Zn(S 2CNR 2) 2] n (R = Me: 1, Et: 2 or benzyl (Bz): 3) with oxazolines (L) of general formula 2-R′-4,4-R″-2-oxazoline (R′ = Me, Et or Ph; R″ = H or Me). The compounds can be isolated in yields ranging from 17% to 82% and all of the complexes are assumed to be mononuclear species of general formula [Zn(S 2CNR 2-κ 2 S) 2(L)]. The nature of the bonding in several examples has been further elucidated in the solid-state by single crystal X-ray diffraction; specifically the cases of R = Me, L = 2-methyl-2-oxazoline: 12; R = Et, L = 2-R′-2-oxazoline: R′ = Me: 9, Et: 10 or Ph: 11 and R = Bz, L = 2,4,4-trimethyl-2-oxazoline: 16. The structurally characterised materials contain two chelating dialkyldithiocarbamato groups and a single oxazoline ligand bound through the N-atom. The disposition of donor atoms around the formally Zn(II) metal centre is best described as distorted trigonal bipyramidal. Complex 16 is the first known N-donor complex of 3 to be fully characterised. In case of the common commercial oxazoline, viz. 4,4-dimethyl-2-phenyl-2-oxazoline, none of the zinc compounds tested forms a stable complex. Some aspects of the steric and electronic effects on oxazoline adduct formation within this series of complexes is discussed. The relationship of these new compounds to other structurally similar and industrially relevant zinc dialkyldithiocarbamate complexes is also detailed.