四甲基铵Roussin红盐(Me_4N)_2-〔Fe_2S_2(NO)_4〕的分子和晶体结构

四甲基铵Roussin红盐晶体属于单斜晶系,空间群为C_(2h)~5—P2_1/a,晶胞参数为:a=14.804,b=14.086,c=9.382,13=92.2°和Do=1.519g/cm~3,Z=4(Dc=1.508g/cm~3)。在Philips PW1100型四圆衍射仪上用MoKα射线收集了强度数据,共得I_0>2σ(I_0)的独立衍射点2681个。晶体结构用重原子法解出,所有非H原子的坐标和各向异性温度因子经最小二乘对角矩阵修正,最后偏离因子R=O.065。晶胞中4个(Me_4N)_2Fe_2S_2(NO)_4分子分布于两套独立坐标上。阴离子形成双硫桥联的双核Fe络离子。在Fe<>Fe构成的“四元环”菱形平面上,∠S-Fe-S=105.6°,∠Fe-S-Fe=74.4°,Fe—S键长分别为2.247和2.242。此外还有两个NO基与Fe成端基配位且几乎处于与菱形平面垂直的平面上,使Fe原子周围的键大约成四面体分布。Fe—Fe间距为2.714,表明在Fe_2S_2(NO)_4)~(2-)中的Fe—Fe之间存在着直接的M—M作用。{Fe(NO)_2}体系的Fe—N—O角偏离直线形约15°,彼此相向弯成“亲合”形。阳离子(Me_4N)~+中4个CH_3基绕中心N原子成四面体形配置。

The Crystal and Molecular structure of a Typical Red Roussin Salt (Me_4N)_2[Fe_2S_2(NO)_4]

The crystal of Red Roussin salt (Me4N)2Fe2S2(NO)4] was monoclinic belonging to the space group C25h- P21/a with a = 14.804, b = 14.086, c = 9.382A ,β = 92.2°, and D0 = 1.519g/cm3, Z = 4 (Dc = 1.508g/cm3). The intensities were collected on a Philips PW 1100 diffractometer with MoKa radiation.The structure was solved by heavy atom technique and refined by block -diagonal -least-squares with anisotropic temperature factors for 2681 indepen-dent reflections of I0≥2σ(I0) to a discrepancy factor R = 0.065, The results of our investigation show that there are two independent sets of central symmetrical anions in the unit cell with the center of symmetry located at the special positions (a) : (0, 0, 0), (1/2, 1/2, 0) and (d)s (0, 1/2, 1/2),(1/2, 0, 1/2), respectively. Within the anion the dinuclear irons are linked by two bridged sulfur atoms end these four atoms are actually coplanar, forming a Fe2S2 four-member ring rhombus with two angles of Fe-S-Fe = 74.4°, S-Fe-S = 105.6° on the average and Fe-S = 2.247A, 2.242A respectively. Besides, the NO groups are attached in pairs to each iron atom in planes at the angle normal to the rhombus plane. Hence, the bonds about the iron atom are roughly tetrahedral. The Fe-Fe distance of 2.7.14A indicates that there is a direct M-M interaction between the two irons in the anion Fe2S2(NO)4]2-. The angle Fe-N-O of 165° in {Fe(NO)2} system .deviates from the linear line about 15°, bending each other to form an "attracto". The cations (Me4N)+ coordinate with the four methyl groups about the central atom N to form a roughly tetrahedral configuration.