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Quinoxaline 1,4-dioxide complexes with 3 d metal perchlorates[1]
Journal article

Quinoxaline 1,4-dioxide complexes with 3 d metal perchlorates[1]

D.E. Chasan, L.L. Pytlewski, C. Owens and N.M. Karayannis
Journal of inorganic & nuclear chemistry, v 40(6), pp 1019-1026
1978

Abstract

A series of 3 d metal perchlorate complexes with quinoxaline 1,4-dioxide(L) were synthesized and characterized by means of IR and electronic spectral and magnetic susceptibility (at 297-143 or 80°K) studies. With the exception of a 4:1 LCu(ClO 4) 2 complex, which is apparently monomeric, pentacoordinated of the type [CuL 4(OClO 3)](ClO 4), the spectral and magnetic evidence is in favor of bi- or polynuclear structures, involving terminal (L t ) and bridging quinoxaline 1,4-dioxide, aqua and unidentate perchlorato ligands, as well as ionic ClO 4 − and lattice water. The magnetic data point to significant spin-spin interactions in these bi- or polynuclear complexes; this is suggestive of coordination of the bridging L groups through only one of their NO oxygens, which acts as a bridge between neighboring metal ions (M ▪M or M(L b ) 2M bridging) rather than functioning as bidentate, with each of the NO oxygens coordinating to a different metal ion (M( b L b )M bridges). Proposed structural types are as follows for the binuclear, hexacoordinated new complexes: [(H 2O)(O 3ClO) 2(L t )Cr(L b ) 2Cr(L t )(OClO 3) 2(OH 2)](ClO 4) 2·6H 2O; (H 2O)(O 3ClO)(L t ) 2Fe(L b ) 2Fe(L t ) 2(OClO 3)(OH 2)](ClO 4) 4·8H 2O; and [(H 2O)(O 3ClO)(L t ) 2M(L b ) 2M(L t ) 2(OClO 3)(OH 2)](ClO 4) 2· 10H 2O (M = Mn, Fe, Co, Ni, Zn). For a second Cu(II) complex, involving a 3:2 L to Cu ratio, the relatively small μ eff decrease (0.29 μB) in the 295-82°K range, favors an oligomeric pentacoordinated structure, comprising both possible kinds of bridging L (i.e. characterized by −Cu(L b ) 2Cu( b L b )- sequences).

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