Hooper Thomas N, Weller Andrew S, Beattie Nicholas A, Macgregor Stuart A
Department of Chemistry , Chemistry Research Laboratories , University of Oxford , Mansfield Road , Oxford , OX1 3TA , UK . Email:
Institute of Chemical Sciences , Heriot Watt University , Edinburgh , EH14 4AS , UK . Email:
Chem Sci. 2016 Mar 1;7(3):2414-2426. doi: 10.1039/c5sc04150c. Epub 2015 Dec 21.
We report a detailed, combined experimental and computational study on the fundamental B-H and P-H bond activation steps involved in the dehydrocoupling/dehydropolymerization of primary and secondary phosphine-boranes, HB·PPhR'H (R = Ph, H), using [RhCp*(PMe)Me(ClCHCl)][BAr], to either form polyphosphino-boranes [HB·PPhH] ( ∼ 15 000 g mol, PDI = 2.2) or the linear diboraphosphine HB·PPhBH·PPhH. A likely polymer-growth pathway of reversible chain transfer step-growth is suggested for HB·PPhH. Using secondary phosphine-boranes as model substrates a combined synthesis, structural (X-ray crystallography), labelling and computational approach reveals: initial bond activation pathways (B-H activation precedes P-H activation); key intermediates (phosphido-boranes, α-B-agostic base-stabilized boryls); and a catalytic route to the primary diboraphosphine (HB·PPhHBH·PPhH). It is also shown that by changing the substituent at phosphorus (Ph or Cy Bu) different final products result (phosphido-borane or base stabilized phosphino-borane respectively). These studies provide detailed insight into the pathways that are operating during dehydropolymerization.
我们报告了一项详细的、结合实验与计算的研究，该研究针对伯膦硼烷和仲膦硼烷（HB·PPhR'H，R = Ph、H）在脱氢偶联/脱水聚合过程中涉及的基本B-H和P-H键活化步骤展开，使用[RhCp*(PMe)Me(ClCHCl)][BAr]，以形成聚膦硼烷[HB·PPhH]（~15000 g/mol，PDI = 2.2）或线性二硼膦HB·PPhBH·PPhH。对于HB·PPhH，提出了一种可能的可逆链转移逐步增长的聚合物生长途径。以仲膦硼烷作为模型底物，通过合成、结构（X射线晶体学）、标记和计算相结合的方法揭示了：初始键活化途径（B-H活化先于P-H活化）；关键中间体（磷硼烷、α-B-配位体稳定的硼基）；以及通往伯二硼膦（HB·PPhHBH·PPhH）的催化路线。研究还表明，通过改变磷上的取代基（Ph或Cy Bu）会得到不同的最终产物（分别为磷硼烷或碱稳定的膦硼烷）。这些研究为脱水聚合过程中起作用的途径提供了详细的见解。
