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首页> 外文期刊>Chemistry: A European journal >Chemistry of Guanidinate-Stabilised Diboranes: Transition-Metal-Catalysed Dehydrocoupling and Hydride Abstraction
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Chemistry of Guanidinate-Stabilised Diboranes: Transition-Metal-Catalysed Dehydrocoupling and Hydride Abstraction

机译：胍盐稳定的乙硼烷的化学：过渡金属催化的脱氢偶联和氢化物提取

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摘要

Herein, we analyse the catalytic boron–boron dehydrocoupling reaction that leads from the base-stabilised diborane(6) [H_2B(hpp)]_2 (hpp=1,3,4,6,7,8-hexahydro-2Hpyrimido[1,2-a]pyrimidinate) to the base-stabilised diborane(4) [H2B(hpp)]2. A number of potential transition-metal precatalysts was studied, including transition-metal complexes of the product diborane(4). The synthesis and structural characterisation of two further examples of such complexes is presented. The best results for the dehydrocoupling reactions were obtained with precatalysts of Group 9 metals in the oxidation state of +I. The active catalyst is formed in situ through a multistep process that involves reduction of the precatalyst by the substrate [H_2B(hpp)]_2, and mechanistic investigations indicate that both heterogeneous and (slower) homogeneous reaction pathways play a role in the dehydrocoupling reaction. In addition, hydride abstraction from [H_2B(hpp)]_2 and related diboranes is analysed and the possibility for subsequent deprotonation is discussed by probing the protic character of the cationic boron–hydrogen compounds with NMR spectroscopic analysis.
机译：在这里，我们分析了由碱稳定的乙硼烷（6）[H_2B（hpp）] _ 2（hpp = 1,3,4,6,7,8-hexahydro-2Hpyrimido [1， 2-a]嘧啶酸酯）至碱稳定的乙硼烷（4）[H2B（hpp）] 2。研究了许多潜在的过渡金属预催化剂，包括乙硼烷产物的过渡金属络合物（4）。给出了这种络合物的两个另外的实例的合成和结构表征。用+ I氧化态的第9组金属的预催化剂可获得最佳的脱氢偶联反应结果。活性催化剂是通过多步过程在原位形成的，该过程涉及通过底物[H_2B（hpp）] _ 2还原预催化剂，并且机理研究表明，均相和（较慢的）均相反应途径均在脱氢偶联反应中起作用。此外，分析了从[H_2B（hpp）] _ 2和相关乙硼烷中提取氢化物，并通过NMR光谱分析探查阳离子硼氢化合物的质子传递特性，讨论了随后进行去质子化的可能性。

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