Structural studies on an iron(III) complex containing (Z)-2-(2-aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide, a model compound for a cephalosporin antibiotic Cefdinir
作者:Shuhei Deguchi、Mamoru Fujioka、Yoshihiko Okamoto、Tsutomu Yasuda、Nobuhumi Nakamura、Kazuya Yamaguchi、Shinnichiro Suzuki
DOI:10.1039/dt9960001967
日期:——
(Z)-2-(2-Aminothiazol-4-yl)-N-(2-hydroxyethyl)-2-(hydroxyimino)acetamide (HL) has been employed as a model compound for a cephalosporin antibiotic, Cefdinir. A trinuclear iron(III) complex [Fe3L6]Cl[OH]21 has been obtained from a methanol solution containing HL and FeCl3 and its structure determined by X-ray crystallography: monoclinic, space group P21/n, a= 15.559(1), b= 19.295(2), c= 10.963(1)Å, β= 101.29(1)°, Z= 2. The molecular structure contains a linear Fe(1)–Fe(2)–Fe(1′) arrangement, the central atom Fe(2) being an inversion centre. Atom Fe(1) is co-ordinated to three molecules of L through the thiazole and oximate nitrogen atoms to form Fe(1)L3, and Fe(2) to six oximate oxygen atoms of the two Fe(1)L3 units. The two Fe(1)L3 units are bridged by the central iron atom Fe(2). The Mössbauer spectrum of 1 gave an apparent doublet signal consisting of two doublets, A and B, assigned to Fe(1) and Fe(2), respectively. The isomer shifts δ of these doublets are the same (0.26 mm s–1), and are typical for high-spin iron(III). In addition, the reflectance spectrum did not show any intervalence bands. These spectral data indicate that the three iron atoms are high-spin iron(III). The compound co-ordinates to iron(III)via the thiazole ring nitrogen atom and the oximate nitrogen atom (2N mode) in methanol which is different from that in water, where L prefers to co-ordinate to an iron(III) through the oximate oxygen atom and the amide oxygen atom (2O mode).
(Z)-2-(2-氨基噻唑-4-基)-N-(2-羟乙基)-2-(羟基亚氨基)乙酰胺(HL)被用作头孢菌素类抗生素头孢地尼的模型化合物。从含有 HL 和 FeCl3 的甲醇溶液中得到了三核铁(III)复合物 [Fe3L6]Cl[OH]21,并通过 X 射线晶体学确定了其结构:单斜,空间群 P21/n,a= 15.559(1),b= 19.295(2),c= 10.963(1)埃,β= 101.29(1)°,Z= 2。分子结构包含线性的 Fe(1)-Fe(2)-Fe(1′) 排列,中心原子 Fe(2) 是一个反转中心。原子 Fe(1) 通过噻唑和氧化氮原子与三个 L 分子配位形成 Fe(1)L3,Fe(2) 与两个 Fe(1)L3 单元的六个氧化氧原子配位。两个 Fe(1)L3 单元由中心铁原子 Fe(2) 桥接。1 的摩斯鲍尔光谱显示出一个明显的双特信号,由两个双特信号 A 和 B 组成,分别归属于 Fe(1) 和 Fe(2)。这些双重信号的同分异构体移位 δ 相同(0.26 mm s-1),是典型的高自旋铁(III)信号。此外,反射光谱没有显示任何间隔带。这些光谱数据表明,这三个铁原子是高自旋铁(III)。该化合物在甲醇中通过噻唑环氮原子和氧化物氮原子(2N 模式)与铁(III)配位,这与在水中的情况不同,在水中 L 更喜欢通过氧化物氧原子和酰胺氧原子(2O 模式)与铁(III)配位。