189754-84-5Relevant academic research and scientific papers
Preparation, Characterization, and Solid State Thermal Studies of Nickel(II) Squarate Complexes of 1,2-Ethanediamine and Its Derivatives
Das, Debasis,Ghosh, Ashutosh,Chaudhuri, Nirmalendu Ray
, p. 789 - 797 (1997)
[NiL3]C4O4 [L=1,2-ethanediamine (en) and 1,2-N,N'-dimethylethanediamine (N,N'-dmen)], [NiL3]C4O4·nH2O (for L=1,2-N-methylethanediamine (meen) and 2-methyl-1,2-propanediamine (pn); n=1, and for L=1,2-propanediamine (pn); n=21, and |NiL2C4O4]·2H2O [L= 1,2-N-ethylethanediamine (eten), 1,2-N-propylethanediamine (pren), 1,2-N,N-dimethylethanediamine (N,N-dmen) and 1,2-N,N'-diethylethanediamine (N,N'-deten)] have been synthesized by the addition of the respective diamines to finely powdered nickel(II)squarate dihydrate, NiC4O4·2H2O. All of the tris-species, except for [Ni(N,N'-dmen)3)C4O4 were also prepared by adding diamines to NiC4O4·2H2O dissolved in aqueous ammonia (25%). When the latter method was followed, the bis-species [NiL2C4O4] [L = eten, pren, 1,2-N-isopropylethanediamine (ipren), N,N'-dmen, N,N'-dmen, and N,N'-deten] were also obtained. [NiL2C4O4] (L = en, meen, N,N'-dmen, pn, and ibn) were also prepared from their corresponding tris(diamine) species upon heating in the solid state. [Ni(ibn)3]C4O4·nH2O after dehydration underwent an irreversible endothermic (145 - 160 °C; ΔW = 6.5 kJ mol-1) phase transition without showing any visual color change. [Ni(ipren)2C4O4] exhibited a reversible phase transition (78 - 107 °C; ΔH = 1.4 kJ mol-1 for heating and 105 - 72°C; ΔH = -1.3 kJ mol-1 for cooling). The phase transitions are considered to have been due to conformational changes of the diamine chelate rings. All of the tris as well as bis(diamine) complexes possess an octahedral geometry, except for |Ni(ibn)2]C4O4, which is square-planar. The bis-species [NiL2C4C4] (L = eten, pren, N,N-dmen, and N,N'-deten) exists in two isomeric forms.
