Kahlert Jan, Böhling Lena, Brockhinke Andreas, Stammler Hans-Georg, Neumann Beate, Rendina Louis M, Low Paul J, Weber Lothar, Fox Mark A
Fakultät für Chemie der Universität Bielefeld, 33615 Bielefeld, Germany.
Dalton Trans. 2015 Jun 7;44(21):9766-81. doi: 10.1039/c5dt00758e.
Two C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes, 1-(BMes2)-2-R-1,2-C2B10H10 (1, R = H, 2, R = Ph), were synthesised by lithiation of 1,2-dicarba-closo-dodecaborane and 1-phenyl-1,2-dicarba-closo-dodecaborane, respectively, with n-butyllithium and subsequent reaction with fluorodimesitylborane. These novel compounds were structurally characterised by X-ray crystallography. Compounds 1 and 2 are hydrolysed on prolonged exposure to air to give mesitylene and boronic acids 1-(B(OH)2)-2-R-1,2-C2B10H10 (3, R = H, 4, R = Ph respectively). Addition of fluoride anions to 1 and 2 resulted in boryl-carborane bond cleavage to give dimesitylborinic acid HOBMes2. UV absorption bands at 318-333 nm were observed for 1 and 2 corresponding to local π-π*-transitions within the dimesitylboryl groups while visible emissions at 541-664 nm with Stokes shifts of 11 920-16 170 cm(-1) were attributed to intramolecular charge transfer transitions between the mesityl and cluster groups. Compound was shown by cyclic voltammetry to form a stable dianion on reduction. NMR spectra for the dianion were recorded from solutions generated by reductions of 2 with alkali metals and compared with NMR spectra from reductions of 1,2-diphenyl-ortho-carborane 5. On the basis of observed and computed (11)B NMR shifts, these nido-dianions contain bowl-shaped cluster geometries. The carborane is viewed as the electron-acceptor and the mesityl group is the electron-donor in C-dimesitylboryl-1,2-dicarba-closo-dodecaboranes.
通过分别用正丁基锂对1,2-二碳-闭式-十二硼烷和1-苯基-1,2-二碳-闭式-十二硼烷进行锂化，随后与氟代二甲基硼烷反应，合成了两种二甲基硼基-1,2-二碳-闭式-十二硼烷，即1-(BMes₂)-2-R-1,2-C₂B₁₀H₁₀（1，R = H；2，R = Ph）。这些新型化合物通过X射线晶体学进行了结构表征。化合物1和2在长时间暴露于空气中时会发生水解，生成均三甲苯和硼酸1-(B(OH)₂)-2-R-1,2-C₂B₁₀H₁₀（分别为3，R = H；4，R = Ph）。向1和2中加入氟离子会导致硼基-碳硼烷键断裂生成二甲基硼酸HOBMes₂。在318 - 333 nm处观察到1和2的紫外吸收带，对应于二甲基硼基内的局部π-π*跃迁，而在541 - 664 nm处的可见发射，斯托克斯位移为11920 - 16170 cm⁻¹，归因于均三甲苯基和簇基团之间的分子内电荷转移跃迁。通过循环伏安法表明该化合物在还原时形成稳定的二价阴离子。二价阴离子[ ]²⁻的核磁共振谱是从用碱金属还原2所产生的溶液中记录的，并与还原1,2-二苯基-邻碳硼烷5所得到的核磁共振谱进行了比较。基于观察到的和计算得到的¹¹B核磁共振位移，这些巢式二价阴离子具有碗状簇几何结构。在二甲基硼基-1,2-二碳-闭式-十二硼烷中，碳硼烷被视为电子受体，均三甲苯基基团为电子供体。
