Mononuclear bis-chelate and tris-chelate complexes of nickel(II) with selenocyanate.: Molecular structure of [Ni(en)3]cis-[Ni(en)2(NCSe)2]X2 (X = PF6-, ClO4-, and SeCN-) and trans-[Ni(en)2(NCSe)2]

The reaction of Ni(ClO4)(2).aq, ethylenediamine (en) and KSeCN afford mononuclear [Ni(en)(3)][Ni(en)(2)(NCSe)(2)](2)(ClO4)(SeCN) (1) complexes. The same reaction starting with Ni(NO3)(2).aq with or without KPF6 affords two different compounds: [Ni(en)(3)][Ni(en)(2)(NCSe)(2)](2)(PF6)(2) (2) and [Ni(en)(2)(NCSe)(2)] (3). The structures of the three compounds were determined by X-ray crystallography. The structures of compounds (1) and (2) were very similar, consisting of two discrete mononuclear Ni(II) complexes, one tris-chelate and the other cis bis-chelate with the two selenocyanato ligands linked by the nitrogen atoms. The structure of complex (3) is different and consisted of a discrete neutral mononuclear Ni(II) complex trans bis-chelate with the two selenocyanato ligands also linked by the nitrogen atoms. Structures, synthetic trends and magnetic behaviour are discussed. (C) 1998 Elsevier Science Ltd. All rights reserved.