Synthesis and structures of anionic rhenium polyhydride complexes of boron–hydride ligands and their application in catalysis,Chemical Science

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Synthesis and structures of anionic rhenium polyhydride complexes of boron–hydride ligands and their application in catalysis
Chemical Science ( IF 7.6 ) Pub Date : 2020-09-09 , DOI: 10.1039/d0sc03458d
Liam J. Donnelly _{1,

2,

3,

4} , Simon Parsons _{1,

2,

3,

4} , Carole A. Morrison _{1,

2,

3,

4} , Stephen P. Thomas _{1,

2,

3,

4} , Jason B. Love _{1,

2,

3,

4}

Affiliation

The rhenium complex, [K(DME)(18-c-6)][ReH₄(Bpin)(η²-HBpin)(κ²-H₂Bpin)] 1, comprising hydride and boron ligands only, has been synthesized by exhaustive deoxygenation of the commercially available perrhenate anion (ReO₄⁻) with pinacol borane (HBpin). The structure of 1 was analysed by X-ray crystallography, NMR spectroscopy, and DFT calculations. While no hydrides were located in the X-ray crystal structure, it revealed a trigonal arrangement of pinacol boron ligands. Variable-temperature NMR spectroscopy supported the presence of seven hydride ligands but further insight was hindered by the fluxionality of both hydride and boron ligands at low temperature. Further evaluation of the structure by Ab Initio Random Structure Searching (AIRSS) identified the presence of hydride, boryl, σ-borane, and dihydroborate ligands. This complex, either isolated or prepared in situ, is a catalyst for the 1,4-hydroboration of N-heteroaromatic substrates under simple operating procedures. It also acts as a reagent for the stoichiometric C–H borylation of toluene, displaying high meta regioselectivity in the borylated products. Reaction of 1 with 9-BBN resulted in HBpin substitution to form the new anionic tetra(dihydroborate) complex [K(DME)(18-c-6)][Re(κ²-H-9-BBN)₄] 4 for which the hydride positions were clearly identified by X-ray crystallography. The method used to generate these isolable yet reactive boron–hydride complexes is direct and straightforward and has potential utility for the exploitation of other metal oxo compounds in operationally simple catalytic reactions.

中文翻译：

硼氢化物配体的阴离子rh多氢配合物的合成，结构及其在催化中的应用

铼络合物，[K（DME）（18-C-6）] [则热₄（BPIN）（η ² -HBpin）（κ ² -H ₂ BPIN）] 1，其包括氢化物和硼的配体只，已经合成由可商购的高铼酸盐阴离子的详尽脱氧（REO ₄^-）与频哪醇硼烷（HBpin）。1的结构通过X射线晶体学，NMR光谱和DFT计算分析。尽管在X射线晶体结构中没有氢化物，但它显示了频哪醇硼配体的三角排列。可变温度NMR光谱法支持七个氢化物配体的存在，但氢化物和硼配体在低温下的流动性阻碍了进一步的研究。通过从头算随机结构搜索（AIRSS）对结构进行的进一步评估，确定了氢化物，硼基，σ-硼烷和二氢硼酸酯配体的存在。这种复合物，无论是分离的还是原位制备的是在简单的操作程序下将N-杂芳族底物进行1,4-氢硼化的催化剂。它也可作为甲苯化学计量的C–H硼化反应的试剂，在硼化产物中显示出较高的间位选择性。的反应1与9-BBN导致HBpin取代，以形成新的阴离子四（dihydroborate）络合物[K（DME）（18-C-6）] [回复（κ ² -H-9-BBN）₄ ] 4为X射线晶体学清楚地确定了氢化物的位置。生成这些可分离但可反应的硼氢化物配合物的方法是直接而直接的，并且在操作简单的催化反应中具有开发其他金属含氧化合物的潜在用途。

更新日期：2020-09-23

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