Cp2Ti(κ2-tBuNCNtBu): A Complex with an Unusual κ2 Coordination Mode of a Heterocumulene Featuring a Free Carbene
Cp2Ti(κ2-tBuNCNtBu): A Complex with an Unusual κ2 Coordination Mode of a Heterocumulene Featuring a Free Carbene
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DOI：
10.1021/jacs.0c02487
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发表时间：
2020-04-29
影响因子：
15
通讯作者：
Tonks, Ian A.
中科院分区：
文献类型：
--
作者：
Beaumier, Evan P.;Gordon, Christopher P.;Tonks, Ian A.
虽然杂累积多烯与金属中心的结合方式多种多样，但mono kappa（2）-ECE（E = O，S，NR）配位方式尚未见报道。本文描述了带有游离卡宾的应变4元金属配合物Cp 2 Ti-（kappa（2）-tBuNCl 11 ′ Bu）（3）（Cp = N，tBu =叔丁基）的合成、分离和物理表征。计算（DFT、CASSCF、QT-AIM、ELF）和固态CP-MAS C-13 NMR光谱分析表明，3最好被描述为具有部分Ti-C-β键的游离卡宾，所述部分Ti-C-β键由弯曲的N-C-N骨架的Ti-N π键与N-C-N σ键混合而产生。3的反应性研究证实了其类似卡宾的性质：用[LutH]I质子化可形成钛甲脒基（4），而用S-8氧化可生成钛硫脲基（5）。此外，还报道了一种相关的桥连二钛酰胺卡宾（Cp 2 Ti）（2）（μ-η（1），η（1）-CyNCNCy）（10）（Cy =环己基）。两者合计，这项工作表明，2-电子还原的heterocumulene部分可以允许访问到不寻常的自由卡宾配位几何形状，从还原过渡金属片段适当的稳定配位环境。
Although there are myriad binding modes of heterocumulenes to metal centers, the monometallic kappa(2)-ECE (E = O, S, NR) coordination mode has not been reported. Herein, the synthesis, isolation, and physical characterization of Cp2Ti- (kappa(2)-tBuNCI\I`Bu) (3) (Cp = cyclopentadienyl, tBu = tert-butyl), a strained 4-membered metallacycle bearing a free carbene, is described. Computational (DFT, CASSCF, QT-AIM, ELF) and solid-state CP-MAS C-13 NMR spectroscopic analysis indicate that 3 is best described as a free carbene with partial Ti-C-beta bonding that results from Ti-N pi-bonding mixing with N-C-N sigma-bonding of the bent N-C-N framework. Reactivity studies of 3 corroborate its carbene-like nature: protonation with [LutH]I results in the formation of a Ti-formamidinate (4), while oxidation with S-8 yields a Ti-thioureate (5). Additionally, a related bridged dititanamidocarbene, (Cp2Ti)(2)(mu-eta(1),eta(1)--CyNCNCy) (10) (Cy = cyclohexyl) is reported. Taken together, this work suggests that the 2-electron reduction of heterocumulene moieties can allow access to unusual free carbene coordination geometries given the proper stabilizing coordination environment from the reducing transition metal fragment.