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首页> 外文期刊>Organometallics >A New Way to Scorpionate Niobium Complexes:Terminal Alkyne,Imido,and Oxo Complexes and the Rearrangement of a-Agostic Ethyl Complexes
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A New Way to Scorpionate Niobium Complexes:Terminal Alkyne,Imido,and Oxo Complexes and the Rearrangement of a-Agostic Ethyl Complexes

机译：蝎化铌配合物的新方法：末端炔，亚胺基和氧代配合物以及α-乙基乙基配合物的重排

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This paper describes an efficient,straightforward synthesis of new hydrotris(pyrazolyl)-borate(Tp')niobium terminal alkyne complexes and some reactions of these complexes.Reduction of the niobium(IV)complexes Tp'NbCl_3(Tp' = TpMe_2(1),Tp~(Me2,4C1)(1-CD)with zinc in the presence of a terminal alkyne HC(ident to)CR gives good yields(ca.75%)of the new alkyne complexes Tp'NbCl_2(HC(ident to)CR)(2-R)(R = H,Ph,C_6H_4-4-Me,CH_2Ph,CF_3)and 2-C1-Ph.The strategy is significant since the previously reported synthesis of Tp'NbCl_2(RC(ident to)CR')was possible only with internal alkynes.NMR data indicate that the four-electron donor alkyne sits in the molecular mirror plane.Restricted alkyne rotation is observed by NMR in solution.The more abundant rotamer has the large substituent located distal to the Tp' ligand,thereby alleviating steric interactions.Only this rotamer is observed in the crystal structures of 2-R(R = Ph,C_6H_4-4-Me,CH_2Ph).In the crystal structure of 2-CF_3,however,three independent molecules are observed with both alkyne orientations.The one that has the CF_3 group proximal to TpMe_2 exhibits H...F bridges between the alkyne CF_3 group and the methyl group at the 3-position of the Tp~(Me2)ligand.Oxo and imidoniobium complexes are also available via the same synthetic procedure.alpha-C-H agostic ethyl complexes Tp~(Me2)-NbCl(mu-H-CHCH_3)(HC(ident to)CR)(4-R)(R = Ph,C_6H_4-4-Me,CH_2Ph)have been synthesized.Their thermolyses have been studied with the goal of observing the Nb-CH_2CH_3/H-C(ident to)CR exchange leading to the putative TpMe_2NbCl(H)(CH_3CH_2C(ident to)CR).This reaction mainly gives decomposition products,although spectrocopic data suggest that it occurs.This reaction is significant in the context of comparing kinetic and thermodynamic data for M-H versus M-C stability and reactivity.
机译：本文描述了一种高效，直接合成新型氢三（吡唑基）-硼酸酯（Tp'）铌末端炔烃配合物以及这些配合物的反应的方法。铌（IV）配合物的还原Tp'NbCl_3（Tp'= TpMe_2（1）末端炔烃HC（与CR相同）存在下，Tp〜（Me2,4C1）（1-CD）与锌的合成可得到新炔烃配合物Tp'NbCl_2（HC ）CR）（2-R）（R = H，Ph，C_6H_4-4-Me，CH_2Ph，CF_3）和2-C1-Ph。由于先前报道的Tp'NbCl_2（RC（ NMR数据表明四电子供体炔位于分子镜面上，通过NMR在溶液中观察到炔的旋转受到限制，旋转异构体越丰富，位于其远端的取代基就越大。 Tp'配体，从而减轻了空间相互作用。仅在2-R（R = Ph，C_6H_4-4-Me，CH_2Ph）的晶体结构中观察到该旋转异构体。但是在2-CF_3的晶体结构中观察到三个在两个炔烃方向上都观察到分子.CF_3基团接近TpMe_2的分子在TCF〜（Me2）配体3位的炔烃CF_3基团和甲基之间表现出H ... F桥。也可以通过相同的合成方法获得亚氨基铌络合物。α-CH原子乙基络合物Tp〜（Me2）-NbCl（mu-H-CHCH_3）（HC（与）CR）（4-R）（R = Ph，已经合成了C_6H_4-4-Me，CH_2Ph。为了观察Nb-CH_2CH_3 / HC（ident to）CR交换导致推定的TpMe_2NbCl（H）（CH_3CH_2C（ident to）CR）的目的已经研究了它们的热解。该反应主要产生分解产物，尽管分光光度数据表明它发生了。在比较MH与MC的稳定性和反应性的动力学和热力学数据的背景下，该反应非常重要。

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