Novel mixed-valence Cu compounds formed by Cuii dimers with double oximato bridges: in situ formation of anionic layer [Cu2(SCN)3]nn−

Abstract

Two new N3O donor ketoxime Schiff bases (HL(1) and HL(2)) have been synthesized by condensing N,N-dimethylethylenediamine with diacetylmonoxime and benzilmonoxime, respectively in a 1:1 ratio. Reaction of Cu(ClO4)2·6H2O with HL(1) resulted in a discrete oximato-bridged dinuclear Cu(II) complex [Cu2(L(1))2(H2O)2](ClO4)2 (1). The same reaction in presence of NaSCN affords the complex {[Cu(II)2(L(1))2][Cu(I)4(μ(1,3)-SCN)4(μ(1,1,3)-SCN)2]}n (2), where partial Cu(II)→Cu(I) reduction is observed. In 2, arrays of [Cu(II)2(L(1))2](2+) cationic units are inserted in between 2D {[Cu(I)4(SCN)6](2-)}n layers and connected via μ(1,1,3)-SCN(-) links, thus forming a 3D network. On the other hand, reaction of Cu(CH3COO)2 and HL(2) in the presence of NaSCN gave rise to a mixed-valence pentanuclear cluster {[Cu(II)2(L(2))2(NCS)]2[Cu(I)(SCN)(μ(1,1)-SCN)(μ(1,3)-SCN)]} (3) where Cu(II) is also partly reduced to Cu(I). In compound 3, two cationic [Cu(II)2(L(2))2(NCS)](+) units are bridged by the anionic [Cu(I)(SCN)3](2-) unit through long Cu-SCN linkages. The ligands and the complexes have been characterized by elemental analysis, UV/Vis and IR spectroscopy. The complexes are further characterized by single crystal X-ray diffraction and variable temperature magnetic (VTM) studies. Finally a complete magneto-structural correlation has been established between compounds 1-3 and all the characterized Cu dimers with a double NO bridge.

Mixed ligand complexes of copper(II), cobalt(II), nickel(II) and zinc(II) with thiocyanate and pyrazole based tetradentate ligand: Syntheses, characterizations and structures

“…Various types of tripodal ligands with aromatic or aliphatic amine and their metal complexes have been synthesized and characterized [18][19][20][21]. Thiocyanate is an ambidentate pseudohalide and can coordinate with metal ions as terminal or bridging ligand to give monomeric, dimeric and polymeric complexes [22][23][24][25][26][27][28][29][30][31]. It has great potential in building up of coordination networks of varied dimensionalities when it acts as bridging ligand [32][33][34].…”

Antiferromagnetic Mixed-Valence Cu(I)–Cu(II) Two-Dimensional Coordination Polymers Constructed by Double Oximato Bridged Cu(II) Dimers and CuISCN Based One-Dimensional Anionic Chains

“…On the other hand, the reaction of copper perchlorate with either HL 1 or HL 2 in the presence of SCN – at room temperature leads to in situ Cu­(II) to Cu­(I) partial reduction generating two mixed-valence Cu­(I/II) 2D coordination polymers 2 ∞ [{(Cu II 2 L 1 2 )}­{Cu I 4 (μ 1,3 -SCN) 2 ­(μ 1,1,3 -SCN) 4 }] n ( 2 ) and 2 ∞ [{(Cu II 2 L 2 2 )}­{Cu I 2 (μ 1,3 -SCN) 2 ­(μ 1,1,3 -SCN) 2 }] n ( 3 ) with different frameworks. Complex 2 , in which the Cu I SCN based infinite chain is formed in an unprecedented manner, represents a unique example of “supramolecular isomers” of a previously reported 3D mixed-valence coordination polymer . The structures and variable-temperature magnetic susceptibility measurement of complexes 1 – 3 are presented here in detail.…”

“…The mixed-valence copper complexes which are reported to date can largely be grouped into four categories: (i) complexes containing Cu­(II) cation and Cu­(I) anion, (ii) bi- and polynuclear complexes in which Cu­(II) and Cu­(I) centers bridged by polydentate ligands, (iii) complexes containing Cu­(II) and Cu­(I) centers bridged by CN – /SCN – /SeCN – pseudohalides, and (iv) complexes with Cu­(I) and Cu­(II) ions enclosed in a cluster. The general method for the synthesis of cyano, thiocyanato, and selenocyanato Cu­(II)–Cu­(I) complexes is the partial reduction of Cu­(II) salts in the presence of a ligand (CN – /SCN – /SeCN – ), which serves both as a ligand and as a reducing agent. − Such in situ Cu­(II) to Cu­(I) reduction is a usual phenomenon when Cu­(II) salts are subjected to high energy closed vessel solvothermal reactions in the presence of the ligand, , but is a rare case at room temperature open pot synthesis. − The reduction leads to the formation of Cu I X (where X – = CN – /SCN – /SeCN – ) based species which generates a mixed-valence polymeric coordination framework with the help of Cu­(II) and other ancillary ligands attached to the Cu­(II) ion.…”

“…First, the different binding modes of both thiocyanato and ancillary ligands furnish different coordination environments around both Cu­(I) and Cu­(II) ions, and this leads to the formation of various frameworks. , Second, the different dimensionalities of Cu I SCN based species influence the structure of polymers. For example, Cu I SCN based 1D chains are connected by Cu­(II) moieties to construct 2D polymers, whereas Cu I SCN based 2D layers are associated with Cu­(II) moieties to produce three-dimensional (3D) polymers. ,, Finally, the nature, size, and structure of the ancillary ligands attached to the Cu­(II) ion can also influence the resulting structure …”

Double azido/cyanato bridged copper(II) dimers incorporating tridentate nitrogen donors Schiff base: Structure, EPR and magnetic studies

“…The synthesis and characterization of di-and polynuclear first row transition metal Schiff base complexes achieved considerable interest primarily because of their significance as biologically relevant model complexes [1,2], magnetic materials [3][4][5], nonlinear optics [6], electrical materials [7] and catalysts [8]. Among them divalent transition metal Schiff base complexes with bridging pseudohalide have been comprehensively studied due to their unique structural diversities [9,10] and fascinating applications in biology [1,2] and material science [11].…”