Two polymorphs of aqua[N,N′-ethylenebis(salicylideneaminato-N,O)]oxovanadium(V) nitrate

Abstract

The title compound, aqua[bis(salicylidene)ethylenediaminato-O,N,N H ,O H ]oxovanadium(V) nitrate, [VO(C 16 H 14 N 2 O 2 )-(H 2 O)]NO 3 , crystallizes as two polymorphs in the triclinic and monoclinic crystal systems. In both, the V atom has a distorted octahedral coordination geometry with a long VÐ O water bond trans to V O. The coordinated water molecules are hydrogen bonded to the nitrate ions so that pairs of cations are linked to give neutral centrosymmetric dimers. The V O and VÐO water distances are 1.598 (2) and 2.257 (2) A Ê , respectively, in the triclinic form, and 1.588 (3) and 2.230 (3) A Ê , respectively, in the monoclinic form. In the triclinic form, the dimers pack so that the salen [bis(salicylidene)ethylenediaminate] ligands are parallel to each other, whereas in the monoclinic form, which is the denser, there is a herring-bone arrangement. CommentComplexes of the type [V V O(Schiff base)]Y (Y is Cl, ClO 4 or NO 3 ) can be prepared by oxidizing [V IV O(Schiff base)] with (NH 4 ) 2 Ce(NO 3 ) 6 in acetonitrile, followed by the addition of HY (Nakajima et al., 1990). The structure of [V V O(salen)]-ClO 4 [salen is N,N H -bis(salicylidene)ethylenediaminate] has been studied by X-ray diffraction by Bonadies et al. (1987) and the V atom shown to have a distorted octahedral coordination, with a long [2.456 (3) A Ê ] VÐO perchlorate bond trans to V O. Nakajima et al. (1990) proposed, on the basis of absorption spectra, that their [V V O(Schiff base)]Y complexes had structures analogous to that of the [V V O(salen)]ClO 4 complex. A structural investigation of [V V O(salen)]NO 3 prepared by