New Route to Polynuclear Ni(II) and Cu(II) Complexes with Bridging Oxime Groups That Are Inaccessible by Conventional Preparations


A series of new polynuclear complexes of divalent Ni and Cu with 2-cyano-2-oximino-acetic acid (later AACO 2 -) were obtained as the result of the ligand modification reaction in the process of complexation, using 2-cyano-2-oximino-acetates such as methyl- (later as MeCO), and ethyl- (as ECO later on). Synthesized compounds were characterized by spectroscopic methods, thermal analysis, magnetochemistry, and X-ray crystallography. Crystal data revealed the formation of the dimeric [Ni(AACO)(H 2 O) 3 ] 2 ·H 2 O (1), trimeric K 2 [Ni 3 (AACO) 4 (H 2 O) 4 ]·4H 2 O (2), and K 2 [Cu 3 (AACO) 4 (H 2 O) 4 ]·4H 2 O (3) complexes, with bridging NO-groups cyanoxime dianions. In the latter two compounds, the AACO 2- anions adopt cis-arrangements around metal centers. One mononuclear complex of K 2 [Cu(AACO) 2 (H 2 O)]·2H 2 O (4) composition was isolated and characterized as well, where the cyanoxime forms the trans-complex 4. There is moderate-to-strong antiferromagnetic coupling between metal centers in polynuclear complexes. Data of thermal analysis studies revealed high-energy properties for dehydrated complexes 3 and 4, which violently decompose at ∼200 °C. These compounds may be viewed as room temperature completely safe, but heat-triggered actuators, because of their pronounced mechanical action upon leaving the system (crucible). Final products of thermal decomposition are Ni and NiO for 1, and the mixture of NiO and K 2 O for 2, with metallic copper for 3 and 4.


Chemistry and Biochemistry

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Crystal Growth and Design