Aluminum-Stabilized Low-Spin Iron(II) Hydrido Complexes of 1,4,7-Trimethyl-1,4,7-triazacyclononane

We investigated herein the reactions of (Me3tacn)­FeCln (1a: n = 3, 1b: n = 2) with common aluminum hydride reagents and a bulky dihydridoaluminate {Li­(ether)2}­{Al­(OC6H3-2,6-tBu2)}­(μ-H)2, which yielded the diamagnetic hydrido complexes 2–4 containing Fe­(II) and Al­(III). In particular, the use of divalent 1b afforded excellent isolated yields. The structures of 2–4 were determined using spectroscopic and crystallographic analyses. The crystal structures showed distorted octahedral Fe centers and fairly short Fe–Al distances [2.19–2.24 Å]. The structures of cation moiety 2 and neutral complex 4 were further probed using DFT calculations, which indicated a stable low-spin Fe­(II) state and strongly electron-donating nature of the (Me3tacn)­FeH3 fragment toward the Al­(III) center.

本研究考察了(Me3tacn)­FeCln（1a：n=3，1b：n=2）与常见氢化铝试剂以及大位阻二氢化铝酸盐{Li­(醚)2}­{Al­(OC6H3-2,6-tBu2)}­(μ-H)2的反应，得到了含Fe(II)和Al(III)的反磁性氢化物配合物2~4。尤为值得注意的是，采用二价前驱体1b可获得优异的分离产率。通过光谱分析与晶体衍射分析确定了配合物2~4的结构。晶体结构显示，铁中心为畸变八面体配位，且Fe-Al键长极短，区间为2.19~2.24 Å。进一步通过密度泛函理论（DFT）计算对阳离子物种2与中性配合物4的结构进行了探究，结果表明体系处于稳定的低自旋Fe(II)态，且(Me3tacn)­FeH3片段对Al(III)中心具有极强的给电子特性。