Parsons Thomas B, Hazari Nilay, Cowley Andrew R, Green Jennifer C, Mountford Philip
Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, UK.
Inorg Chem. 2005 Nov 14;44(23):8442-58. doi: 10.1021/ic051271j.
The reaction of 1,1-diphenylhydrazine with Ti(NMe2)2Cl2 produced the monomeric terminal titanium hydrazido(2-) species Ti(NNPh2)Cl2(HNMe2)2 (1) in near-quantitative yield. The reaction of Ti(NMe2)2Cl2 with the less sterically demanding ligand precursors 1,1-dimethylhydrazine or N-aminopiperidine gave the dimeric mu-eta2,eta1-bridged compounds Ti2(mu-eta2,eta1-NNMe2)2Cl4(HNMe2)2 (2) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(HNMe2)3 (3). The X-ray structures of 2 and 3 showed the formation of N-H...Cl hydrogen bonded dimers or chains, respectively. The reaction of 1 with an excess of pyridine formed [Ti(NNPh2)Cl2(py)2]n (4, n = 1 or 2). The reaction of the tert-butyl imido complex Ti(N(t)Bu)Cl2(py)3 with either 1,1-dimethylhydrazine or N-aminopiperidine again resulted in the formation of hydrazido-bridged dimeric complexes, namely Ti2(mu-eta2,eta1-NNMe2)2Cl4(py)2 (5, structurally characterized) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(py)2 (6). Compounds 1 and 4 are potential new entry points into terminal hydrazido(2-) chemistry of titanium. Compound 1 reacted with neutral fac-N3 donor ligands to form Ti(NNPh2)Cl2(Me3[9]aneN3) (7), Ti(NNPh2)Cl2(Me3[6]aneN3) (8), Ti(NNPh2)Cl2[HC(Me2pz)3] (9, structurally characterized), and Ti(NNPh2)Cl2[HC(n)Bupz)3] (10) in good yields (Me3[9]aneN3 = trimethyl-1,4,7-triazacyclononane, Me3[6]aneN3 = trimethyl-1,3,5-triazacyclohexane, HC(Me2pz)3 = tris(3,5-dimethylpyrazolyl)methane, and HC((n)Bupz)3 = tris(4-(n)butylpyrazolyl)methane). DFT calculations were performed on both the model terminal hydrazido compound Ti(NNPh2)Cl2[HC(pz)3] (I) and the corresponding imido compounds Ti(NMe)Cl2[HC(pz)3] (II) and Ti(NPh)Cl2[HC(pz)3] (III). The NNPh2 ligand binds to the metal center in an analogous manner to that of terminal imido ligands (metalligand triple bond), but with one of the Ti=N(alpha) pi components significantly destabilized by a pi interaction with the lone pair of the N(beta) atom. The NR ligand sigma donor ability was found to be NMe > NPh > NNPh2, whereas the overall (sigma + pi) donor ability is NMe > NNPh2 > NPh, as judged by fragment orbital populations, Ti-N atom-atom overlap populations, and fragment-charge analysis. DFT calculations on the hydrazido ligand in a mu-eta2,eta1-bridging mode showed involvement of the N=N pi electrons in donation to one of the Ti centers. This TiN2 interaction is best represented as a metallocycle.
1,1 - 二苯基肼与Ti(NMe₂)₂Cl₂反应，以近乎定量的产率生成了单体末端肼基（2 - ）物种Ti(NNPh₂)Cl₂(HNMe₂)₂（1）。Ti(NMe₂)₂Cl₂与空间位阻较小的配体前体1,1 - 二甲基肼或N - 氨基哌啶反应，生成了二聚的μ - η²,η¹ - 桥连化合物Ti₂(μ - η²,η¹ - NNMe₂)₂Cl₄(HNMe₂)₂（2）和Ti₂[μ - η²,η¹ - NN(CH₂)₅]₂Cl₄(HNMe₂)₃（3）。2和3的X射线结构分别显示形成了N - H...Cl氢键二聚体或链。1与过量吡啶反应生成了[Ti(NNPh₂)Cl₂(py)₂]ₙ（4，n = 1或2）。叔丁基亚氨基配合物Ti(N(t)Bu)Cl₂(py)₃与1,1 - 二甲基肼或N - 氨基哌啶反应，再次生成了肼基桥连的二聚配合物，即Ti₂(μ - η²,η¹ - NNMe₂)₂Cl₄(py)₂（5，已进行结构表征）和Ti₂[μ - η²,η¹ - NN(CH₂)₅]₂Cl₄(py)₂（6）。化合物1和4是钛末端肼基（2 - ）化学潜在的新切入点。化合物1与中性面式 - N₃供体配体反应，以良好的产率生成了Ti(NNPh₂)Cl₂(Me₃[9]aneN₃)（7）、Ti(NNPh₂)Cl₂(Me₃[6]aneN₃)（8）、Ti(NNPh₂)Cl₂[HC(Me₂pz)₃]（9，已进行结构表征）和Ti(NNPh₂)Cl₂[HC(n)Bupz)₃]（10）（Me₃[9]aneN₃ = 三甲基 - 1,4,7 - 三氮杂环壬烷，Me₃[6]aneN₃ = 三甲基 - 1,3,5 - 三氮杂环己烷，HC(Me₂pz)₃ = 三（3,5 - 二甲基吡唑基）甲烷，HC((n)Bupz)₃ = 三（（n）丁基吡唑基）甲烷）。对模型末端肼基化合物Ti(NNPh₂)Cl₂[HC(pz)₃]（I）以及相应的亚氨基化合物Ti(NMe)Cl₂[HC(pz)₃]（II）和Ti(NPh)Cl₂[HC(pz)₃]（III）进行了密度泛函理论（DFT）计算。NNPh₂配体与金属中心的结合方式类似于末端亚氨基配体（金属 - 配体三键），但其中一个Ti = N(α) π成分因与N(β)原子的孤对电子发生π相互作用而显著不稳定。通过片段轨道布居、Ti - N原子 - 原子重叠布居和片段电荷分析判断，NR配体的σ供体能力为NMe > NPh > NNPh₂，而总的（σ + π）供体能力为NMe > NNPh₂ > NPh。对处于μ - η²,η¹ - 桥连模式的肼基配体进行的DFT计算表明，N = N π电子参与了向其中一个Ti中心的电子给予。这种TiN₂相互作用最好表示为一个金属环。
