Mountford Andrew J, Clegg William, Coles Simon J, Harrington Ross W, Horton Peter N, Humphrey Simon M, Hursthouse Michael B, Wright Joseph A, Lancaster Simon J
Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UK.
Chemistry. 2007;13(16):4535-47. doi: 10.1002/chem.200601751.
Treatment of the homoleptic titanium amides [Ti(NR(2))(4)] (R=Me or Et) with the Brønsted acidic reagent H(3)NB(C(6)F(5))(3) results in the elimination of one molecule of amine and the formation of the four-coordinate amidoborate complexes [Ti(NR(2))(3){NH(2)B(C(6)F(5))(3)}], the identity of which was confirmed by X-ray crystallography. The reaction with [Zr(NMe(2))(4)] proceeds similarly but with retention of the amine ligand to give the trigonal-bipyramidal complex [Zr(NMe(2))(3){NH(2)B(C(6)F(5))(3)}(NMe(2)H)]. Cyclopentadienyl (Cp) amidoborate complexes, [MCp(NR(2))(2){NH(2)B(C(6)F(5))(3)}] (M=Ti, R=Me or Et; M=Zr, R=Me) can be prepared from [MCp(NR(2))(3)] and H(3)NB(C(6)F(5))(3), and exhibit greater thermal stability than the cyclopentadienyl-free compounds. H(3)NB(C(6)F(5))(3) reacts with nBuLi or LiN(SiMe(3))(2) to give LiNH(2)B(C(6)F(5))(3), which complexes with strong Lewis acids to form ion pairs that contain weakly coordinating anions. The attempted synthesis of metallocene amidoborate complexes from dialkyl or diamide precursors and H(3)NB(C(6)F(5))(3) was unsuccessful. However, LiNH(2)B(C(6)F(5))(3) does react with the highly electrophilic reagents [MCp(2)Me(mu-Me)B(C(6)F(5))(3)] to give [MCp(2)Me(mu-NH(2))B(C(6)F(5))(3)] (M=Zr or Hf). Comparison of the molecular structures of the Group 4 amidoborate complexes reveals very similar B--N, Ti--N and Zr--N bond lengths, which are consistent with a description of the bonding as a dative interaction between an {M(L)(n)(NH(2))} fragment and the Lewis acid B(C(6)F(5))(3). Each of the structures has an intramolecular hydrogen-bonding arrangement in which one of the nitrogen-bonded hydrogen atoms participates in a bifurcated FHF interaction to ortho-F atoms.
将均配型钛酰胺[Ti(NR₂)₄]（R = Me或Et）与布朗斯特酸性试剂H₃NB(C₆F₅)₃反应，会消除一分子胺并形成四配位的氨基硼酸盐配合物[Ti(NR₂)₃{NH₂B(C₆F₅)₃}]，其结构经X射线晶体学确证。与[Zr(NMe₂)₄]的反应类似，但胺配体得以保留，生成三角双锥配合物[Zr(NMe₂)₃{NH₂B(C₆F₅)₃}(NMe₂H)]。环戊二烯基（Cp）氨基硼酸盐配合物[MCp(NR₂)₂{NH₂B(C₆F₅)₃}]（M = Ti，R = Me或Et；M = Zr，R = Me）可由[MCp(NR₂)₃]和H₃NB(C₆F₅)₃制备，且比不含环戊二烯基的化合物具有更高的热稳定性。H₃NB(C₆F₅)₃与正丁基锂或LiN(SiMe₃)₂反应生成LiNH₂B(C₆F₅)₃，它与强路易斯酸形成包含弱配位阴离子的离子对。尝试从二烷基或二酰胺前体与H₃NB(C₆F₅)₃合成茂金属氨基硼酸盐配合物未成功。然而，LiNH₂B(C₆F₅)₃确实能与高亲电试剂[MCp₂Me(μ-Me)B(C₆F₅)₃]反应生成[MCp₂Me(μ-NH₂)B(C₆F₅)₃]（M = Zr或Hf）。对第4族氨基硼酸盐配合物分子结构的比较显示，B - N、Ti - N和Zr - N键长非常相似，这与{M(L)ₙ(NH₂)}片段与路易斯酸B(C₆F₅)₃之间的配位相互作用的键合描述一致。每个结构都有分子内氢键排列，其中一个与氮键合的氢原子参与与邻位氟原子的分叉FHF相互作用。
