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首页> 外文期刊>Organometallics >Reduction of titanium supported by a sigma-/pi-bonded tripyrrole ligand: Ligand C-N bond cleavage and coordination of olefin and arene with an inverse sandwich structure
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Reduction of titanium supported by a sigma-/pi-bonded tripyrrole ligand: Ligand C-N bond cleavage and coordination of olefin and arene with an inverse sandwich structure

机译：减少由sigma / pi键结合的三吡咯配体支撑的钛：配体C-N键的裂解和具有反三明治结构的烯烃和​​芳烃的配位

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摘要

The formally Ti(I)/Ti(II) mixed-valence toluene complex {2,5-[(C4H3N)CPh2](2)[C4H2N(Me)]}Ti (mu,eta(6)-C7H8)Ti[{2,5-[(C4H3N)CPh2](2)[C4H2N(Me)]}][K(DME)(2)]center dot toluene (1) with an inverse sandwich type of structure has been obtained from the reduction of {2,5-[(C4H3N)CPh2](2)[C4H2N(Me)]}TiCl with potassium in toluene. The bridging molecule of toluene in the paramagnetic 1 shows a visible distortion due to a substantial amount of metal-to-ring back-bonding. Complex 1 was always the only detectable product, even in cases when lower than stoichiometric amounts of reductant were employed. DFT calculations have been carried out to elucidate the electronic structure of the mixed-valence 1 in order to clarify the reason for its apparent thermodynamic stability. The most energetically favorable model comprises two divalent Ti centers connected to an organic radical anion. The olefin adducts {2,5-[(C4H3N)CPh2](2)[C4H2N]}Ti(eta(2)-trans-PhHCCHPh)[K(DME)] (2) and {2,5-[(C4H3N)CPh2](2)[C4H2N (Me)]}Ti(eta(2)-trans-PhHCCHPh) (3) were obtained from identical reactions carried out in the presence of trans-stilbene. Complexes 2 and 3 may be regarded as the result of the oxidative addition of a transient divalent species to the trans-stilbene molecule. In the case of 2 however, the reaction is accompanied by the cleavage of the C-N bond of the pi-bound alkylated pyrrole ring.
机译：正式的Ti（I）/ Ti（II）混合价甲苯络合物{2,5-[（C4H3N）CPh2]（2）[C4H2N（Me）]} Ti（mu，eta（6）-C7H8）Ti [从还原中获得了具有逆三明治型结构的{2,5-[（C4H3N）CPh2]（2）[C4H2N（Me）]}] [K（DME）（2）]中心点甲苯（1） {2,5-[（C4H3N）CPh2]（2）[C4H2N（Me）]} TiCl在甲苯中的钾含量。由于大量的金属与环之间的反向键合，顺磁性1中的甲苯桥接分子显示出可见的变形。络合物1始终是唯一可检测到的产物，即使在使用低于化学计量的还原剂的情况下也是如此。为了阐明混合价1的电子结构以阐明其表观热力学稳定性的原因，已经进行了DFT计算。最节能的模型包括两个与有机自由基阴离子连接的二价Ti中心。烯烃加合物{2,5-[（C4H3N）CPh2]（2）[C4H2N]} Ti（eta（2）-trans-PhHCCHPh）[K（DME）]（2）和{2,5-[（C4H3N ）CPh2]（2）[C4H2N（Me）]} Ti（eta（2）-trans-PhHCCHPh）（3）是从在反式二苯乙烯存在下进行的相同反应获得的。络合物2和3可以被认为是将瞬时二价物质氧化加到反式二苯乙烯分子上的结果。然而，在2的情况下，该反应伴随有π-结合的烷基化吡咯环的C-N键的断裂。

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