Dioxo-, Oxo-imido-, and Bis-imido-Molybdenum(VI) Complexes with a Bis-phenolate-NHC Ligand,Organometallics

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Dioxo-, Oxo-imido-, and Bis-imido-Molybdenum(VI) Complexes with a Bis-phenolate-NHC Ligand
Organometallics ( IF 2.5 ) Pub Date : 2019-09-24 , DOI: 10.1021/acs.organomet.9b00472
Marc Baltrun ₁ , Fabian A. Watt ₁ , Roland Schoch ₁ , Stephan Hohloch ₁

Affiliation

We report the facile synthesis of five rare high-valent Mo(VI)-NHC complexes with a dianionic OCO-pincer benzimidazolylidene ligand (L¹) with the general formula L¹MoO₂ (1), L¹Mo(O)(N^tBu)(THF) (2), L¹Mo(N^tBu)(NH^tBu)Cl (3), L¹Mo(N^tBu)₂ (4), and L¹ Mo(NMes)₂ (5). These complexes represent a complete series of high-valent molybdenum(VI) complexes, obtained by consecutive exchange of the oxo for imido ligands from the dioxo complex (1) to the bis-imido complexes (4 and 5). The complexes can be synthesized in high yields following a simple deprotonation protocol, using either triethylamine or lithium diisopropylamide (LDA) as a base. All complexes have been characterized by various techniques, including ¹H, ¹³C{¹H}, and ¹⁵N NMR spectroscopy, IR spectroscopy, and X-ray diffraction analysis. Except for the dioxo complex 1, all complexes adopt monomeric structures in the solid state. Compounds 1, 4, and 5 are rare examples of five-coordinated molybdenum(VI) complexes in the solid state, while 2 is six-coordinated, having a weakly bound THF ligand in the axial position. The dioxo complex 1 was found to be stable under air and moisture in the solid state as well as in solution for several days. Furthermore, preliminary reactivity studies and an approximate determination of the pK_a value of the imido ligands in 4 are presented.

中文翻译：

具有双酚盐-NHC配体的二氧-，氧-亚氨基-和双-亚氨基-钼（VI）配合物

我们报告5罕见的高价的Mo（VI）-NHC络合物与双阴离子OCO-钳形benzimidazolylidene配体（L的简便合成¹与通式L）^1层的MoO ₂（1）中，L ¹的Mo（O）（N ^t Bu）（THF）（2），L ¹ Mo（N ^t Bu）（NH ^t Bu）Cl（3），L ¹ Mo（N ^t Bu）₂（4）和L ¹ Mo（NMes）₂（5）。这些配合物代表了高价钼（VI）配合物的完整系列，这些配合物是通过连续地将oxo的亚胺配体的交换从dioxo配合物（1）转变为bi-imido配合物（4和5）而获得的。使用三乙胺或二异丙基氨基化锂（LDA）作为碱，可以按照简单的去质子化方案以高收率合成配合物。所有配合物已通过多种技术进行了表征，包括¹ H，¹³ C { ¹ H}和¹⁵ N NMR光谱，IR光谱和X射线衍射分析。二氧杂配合物1除外，所有配合物均采用固态单体结构。化合物1，4和5是五配位钼（VI）在固体状态下复合物的罕见例子，而2是六配位，具有在轴向位置的弱结合的THF配位体。发现二氧杂配合物1在空气和湿气中以固态以及在溶液中稳定数天。此外，提出了初步的反应性研究和4个亚胺基配体的p K _a值的近似测定。

更新日期：2019-09-25

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