柠檬酸镍(Ⅱ)配合物的合成、光谱和晶体结构

SYNTHESIS, STRUCTURE AND SPECTROSCOPIC PROPERTIES OF NICKEL(Ⅱ) CITRATO COMPLEXES

在弱酸性介质中，氯化镍和柠檬酸铵反应可得到镍水合离子与二聚柠檬酸镍配离子的加合配合物（ＮＨ４）［Ｎｉ（Ｈ２Ｏ）６］［Ｎｉ（Ｈｃｉｔ）（Ｈ２Ｏ）２］４·１０Ｈ２Ｏ１。该配合物的晶体属三斜晶系，空间群为Ｐ１，晶胞参数：ａ＝９．７２７３（９），ｂ＝１２．０３４（２），ｃ＝１３．３４８（２），α＝６３．５４（２），β＝８８．４５（１），γ＝８６．２８（１）°，Ｖ＝１３９５．９（３）３，Ｚ＝１，配合物的阳离子为两个铵离子和一个六水合镍离子，阴离子由两个二聚柠檬酸镍［Ｎｉ（Ｈｃｉｔ）（Ｈ２Ｏ）２］２－２组成。在不对称的配阴离子中，两个柠檬酸分别以羟基、α－羧基和一个β－羧基同第一个镍配位，剩下的β－羧基作为桥基同另一个镍配位形成二聚体。

? The complex (NH 4) 2[Ni(H 2O) 6][Ni(Hcit)(H 2O) 2] 4·10H 2O1 was separated from the reaction of nickel chloride and ammonium citrate at pH 3. Its crystal structure was determined by Xray methods . Compound 1 is triclinic, space group P1, with a=9.7273(9), b=12.034(2), c=13.348(2), α=63.54(2), β=88.45(1), γ=86.28(1)°, V=1395.9(3) 3, Z=1, R=0.0729, R W=0.0798 for 2760 observed reflections. The structure consists of ammonium cation, hexahydrate nickel(Ⅱ) cation and two centrosymmetric tetradentate citrato nickel(Ⅱ) dimeres, [Ni(Hcit)(H 2O) 2] 2- 2. The average principal NiO dimensions are: NiO(hydroxy), 2.070(8), NiO(αcarboxy), 2.041(8), NiO(βcarboxy), 2.055(8), NiO(water), 2.053(8). It is deduced that the complex is formed by the coprecipitation of dimeric citrato nickel(Ⅱ) anion and hexahydrate nicke(Ⅱ), in which the later is produced from the decomposition of dimeric citrato nickel(Ⅱ) or dicitrato nickel(Ⅱ) anion.