Aharonovich Sinai, Botoshanski Mark, Eisen Moris S
Schulich Faculty of Chemistry and Institute of Catalysis Science and Technology, Kyriat Hatechnion, Haifa, 32000, Israel.
Inorg Chem. 2009 Jun 15;48(12):5269-78. doi: 10.1021/ic9002065.
When N-trimethylsilylpentafluoro aniline reacts with BuLi in the presence of THF or TMEDA, the corresponding THF (2) or TMEDA (4) lithium anilides are obtained. Complex 4 is monomeric in the solid state, with a distorted trigonal pyramidal coordination geometry at the lithium center. The strong C-F-->Li interaction in this complex is also accompanied by the elongation of the C-F bond. Mild heating of complex 4 with 2-cyanopyridine results in rapid evolution of Me(3)SiF to quantitatively yield the tetrafluoro-2-(2-pyridyl)benzimidazolate lithium complex (6). From the reaction mixture of complex 4 the asymmetric N-trimethylsilyl, N'-pentafluorophenyl-2-pyridylamidinate lithium complex (5) was isolated as a dormant intermediate. Complex 5 possesses several unusual bonding features with the most notably being a very short Si-N bond length and a rare kappa(1)-Z-syn amidinate bonding mode. A mechanism that includes silicon assisted C-F bond activation is proposed for the cyclization reaction based on the structural parameters of complexes 5 and 6, and on (1)H, (19)F, and (13)C NMR studies.
当N - 三甲基硅基五氟苯胺在四氢呋喃（THF）或N,N,N',N'',N''-四甲基乙二胺（TMEDA）存在下与丁基锂（BuLi）反应时，可得到相应的四氢呋喃（2）或N,N,N',N'',N''-四甲基乙二胺（4）锂苯胺盐。配合物4在固态时为单体，锂中心具有扭曲的三角锥配位几何结构。该配合物中强烈的C - F→Li相互作用还伴随着C - F键的伸长。配合物4与2 - 氰基吡啶温和加热会导致三甲基硅基氟（Me(3)SiF）快速逸出，定量生成四氟 - 2 -（2 - 吡啶基）苯并咪唑锂配合物（6）。从配合物4的反应混合物中分离出了不对称的N - 三甲基硅基，N'-五氟苯基 - 2 - 吡啶脒锂配合物（5）作为休眠中间体。配合物5具有几个不寻常的键合特征，最显著的是非常短的Si - N键长和罕见的κ(1)-Z-顺式脒键合模式。基于配合物5和6的结构参数以及（1）H、（19）F和（13）C核磁共振研究，提出了一种包括硅辅助C - F键活化的环化反应机理。
