Synthesis and Characterization of Quasi-Two-Coordinate Transition Metal Dithiolates M(SAr*)₂ (M = Cr, Mn, Fe, Co, Ni, Zn; Ar* = C₆H₃-2,6(C₆H₂-2,4,6-Prⁱ₃)₂

A sequence of first row transition metal(II) dithiolates M(SAr*)2 (M = Cr(1), Mn(2), Fe(3), Co(4), Ni(5) and Zn(6); Ar* = C6H3-2,6-(C6H2-2,4,6-Pri3)2) has been synthesized and characterized. Compounds 1−5 were obtained by the reaction of two equiv of LiSAr* with a metal dihalide, whereas 6 was obtained by treatment of ZnMe2 with 2 equiv of HSAr*. They were characterized by spectroscopy, magnetic measurements, and X-ray crystallography. The dithiolates 1, 2, and 4−6 possess linear or nearly linear SMS units with further interactions between M and two ipso carbons from C6H2-2,4,6-Pri3 rings. The iron species 3, however, has a bent geometry, two different Fe−S distances, and an interaction between iron and one ipso carbon of a flanking ring. The secondary M−C interactions vary in strength in the sequence Cr2+ ≈ Fe2+ > Co2+ ≈ Ni2+ > Mn2+ ≈ Zn2+ such that the manganese and zinc compounds have essentially two coordination but the chromium and iron complexes are quasi four and three coordinate, respectively. The geometric distortions in the iron species 3 suggested that the structure represents the initial stage of a rearrangement into a sandwich structure involving metal-aryl ring coordination. The bent structure of 3 probably also precludes the observation of free ion magnetism of Fe2+ recently reported for Fe{C(SiMe3)3}2. DFT calculations on the model compounds M(SPh)2 (M = Cr−Ni) support the higher tendency of the iron species to distort its geometry.本研究合成并表征了一系列第一过渡系金属(II)二硫醇盐M(SAr*)₂（其中M=Cr(1)、Mn(2)、Fe(3)、Co(4)、Ni(5)及Zn(6)；Ar*=C₆H₃-2,6-(C₆H₂-2,4,6-Pri₃)₂）。化合物1~5通过2当量LiSAr*与金属二卤化物的反应制得，而化合物6则由ZnMe₂与2当量HSAr*反应得到。所有产物均通过光谱学、磁学测量及X射线晶体学（X-ray crystallography）进行表征。二硫醇盐1、2及4~6具有线性或近似线性的SMS单元，且金属中心M与两个来自C₆H₂-2,4,6-Pri₃环的ipso碳（ipso carbon）之间存在额外相互作用。而铁配合物3则呈现弯曲几何结构，具有两种不同的Fe−S键长，且铁与侧翼环的一个ipso碳存在相互作用。次级M−C相互作用的强度遵循序列Cr²⁺≈Fe²⁺>Co²⁺≈Ni²⁺>Mn²⁺≈Zn²⁺，据此锰与锌配合物的配位数本质上为2，而铬与铁配合物分别为准四配位及准三配位。铁配合物3的几何畸变表明，其结构代表了向涉及金属-芳环配位的三明治结构重排的初始阶段。配合物3的弯曲结构或许也阻碍了Fe²⁺自由离子磁性的观测，而此前已有文献报道Fe{C(SiMe₃)₃}₂中存在该类磁性。对模型化合物M(SPh)₂（M=Cr~Ni）的密度泛函理论（DFT, Density Functional Theory）计算结果证实，铁物种更易发生几何结构畸变。