Department of Chemistry, University of California, Irvine, California 92697, USA.
Inorg Chem. 2010 Mar 1;49(5):2222-31. doi: 10.1021/ic902101z.
Titanium complexes of N,N'-bis(arylimino)acenaphthylene (BIAN) alpha-diimine ligands with varied steric profiles have been prepared. Coordination of the BIAN ligand derivatives to TiCl(4) afforded the adducts (dpp-BIAN)TiCl(4) (1a), (tmp-BIAN)TiCl(4) (1b), and (dmp-BIAN)TiCl(4) (1c) (dpp = 2,6-diisopropylphenyl; tmp = 2,4,6-trimethylphenyl; dmp = 3,5-dimethylphenyl). While the least sterically crowded complex 1c is robust toward loss of the diimine ligand, the dpp-BIAN and tmp-BIAN ligands are readily displaced by pyridine from the more crowded derivatives 1a and 1b, respectively. The crowded profiles engendered by the tmp-BIAN and dpp-BIAN ligands result in the formation of five-coordinate titanium-imide complexes, (dpp-BIAN)TiCl(2)(=N(t)Bu) (2a) and (tmp-BIAN)TiCl(2)(=N(t)Bu) (2b), upon addition of (t)BuNH(2) to solutions of 1a or 1b, respectively. Single-crystal X-ray diffraction studies reveal a square pyramidal coordination environment with an apical imide ligand and a short Ti-N distance, consistent with a Ti-N triple bond. Conversely, the less crowded dmp-BIAN ligand affords a six-coordinate titanium imido complex, (dmp-BIAN)TiCl(2)(=N(t)Bu)(NH(2)(t)Bu) (4), upon treatment of 1c with (t)BuNH(2). Surprisingly the imido ligand is coordinated trans to one arm of the diimine. This six coordinate species is fluxional in solution, and exchange and variable temperature (1)H NMR experiments suggest dissociation of the coordinated (t)BuNH(2) ligand to generate a five-coordinate imido intermediate analogous to 2a and 2b.
已制备出 N,N'-双（芳基亚氨基）吖啶（BIAN）α-二亚胺配体的钛配合物，其具有不同的空间位阻。BIAN 配体衍生物与 TiCl(4) 的配位作用得到加合物（dpp-BIAN）TiCl(4)（1a）、（tmp-BIAN）TiCl(4)（1b）和（dmp-BIAN）TiCl(4)（1c）（dpp = 2,6-二异丙基苯基；tmp = 2,4,6-三甲基苯基；dmp = 3,5-二甲基苯基）。虽然空间位阻最小的配合物 1c 不易失去二亚胺配体，但 dpp-BIAN 和 tmp-BIAN 配体很容易被吡啶从更拥挤的衍生物 1a 和 1b 中取代。tmp-BIAN 和 dpp-BIAN 配体产生的拥挤轮廓导致在分别向 1a 或 1b 的溶液中加入（t）BuNH(2)时形成五配位钛亚胺配合物（dpp-BIAN）TiCl(2)(=N(t)Bu)（2a）和（tmp-BIAN）TiCl(2)(=N(t)Bu)（2b）。单晶 X 射线衍射研究表明，配位环境为四面体形，其中一个顶点为亚胺配体，Ti-N 距离较短，与 Ti-N 三键一致。相反，空间位阻较小的 dmp-BIAN 配体在与（t）BuNH(2) 反应时，生成六配位钛亚胺配合物（dmp-BIAN）TiCl(2)(=N(t)Bu)(NH(2)(t)Bu)（4）。令人惊讶的是，亚胺配体与二亚胺的一个臂呈反式配位。这种六配位物种在溶液中是动态的，并且交换和变温（1）H NMR 实验表明，与配位（t）BuNH(2) 配体的解离生成类似于 2a 和 2b 的五配位亚胺中间体。
