Department of Chemistry, Tulane University, 6400 Freret Street, New Orleans, Louisiana 70118-5698, USA.
Inorg Chem. 2013 Jun 3;52(11):6743-51. doi: 10.1021/ic4009174. Epub 2013 May 15.
An expanded set of compounds of the type W(S2C2Me2)2L1L2 (n = 0: L1 = L2 = CO, 1; L1 = L2 = CN(t)Bu, 2; L1 = CO, L2 = carbene, 3; L1 = CO, L2 = phosphine, 4; L1 = L2 = phosphine, 5. n = 2-: L1 = L2 = CN(-), 6) has been synthesized and characterized. Despite isoelectronic formulations, the compound set reveals gradations in the dithiolene ligand redox level as revealed by intraligand bond lengths, υ(CCchelate), and rising edge energies in the sulfur K-edge X-ray absorption spectra (XAS). Differences among the terminal series members, 1 and 6, are comparable to differences seen in homoleptic dithiolene complexes related by full electron transfer to/from a dithiolene-based MO. The key feature governing these differences is the favorable energy of the CO π* orbitals, which are suitably positioned to overlap with tungsten d orbitals and exert an oxidizing effect on both metal and dithiolene ligand via π-backbonding. The CN(-) π* orbitals are too high in energy to mix effectively with tungsten and thus leave the filled dithiolene π* orbitals unperturbed. This work shows how, and the degree to which, the redox level of a noninnocent ligand can be modulated by the choice of ancillary ligands(s).
已合成并表征了一组扩展的 W(S2C2Me2)2L1L2（n=0：L1=L2=CO，1；L1=L2=CN(t)Bu，2；L1=CO，L2=卡宾，3；L1=CO，L2=膦，4；L1=L2=膦，5。n=2-：L1=L2=CN(-)，6) 型化合物。尽管具有等电子结构，但化合物系列揭示了二硫烯配体的氧化还原水平存在梯度，这表现为配体内键长、υ(CCchelate)和硫 K 边 X 射线吸收光谱（XAS）的上升边缘能量的变化。终端系列成员 1 和 6 之间的差异与通过与二硫烯基 MO 之间的完全电子转移相关的同系物二硫烯配合物中观察到的差异相当。控制这些差异的关键特征是 CO π轨道的有利能量，CO π轨道适当地与钨轨道重叠，并通过π-backbonding 对金属和二硫烯配体产生氧化作用。CN(-) π轨道的能量太高，无法与钨有效混合，从而使充满的二硫烯 π轨道不受干扰。这项工作表明了，并且在何种程度上，可以通过选择辅助配体来调节非无辜配体的氧化还原水平。
