Unprecedented Reaction Pathway of Sterically Crowded Calcium Complexes: Sequential C-N Bond Cleavage Reactions Induced by C-H Bond Activations

作者：Yang, Yang; Wang, Haobing; Ma, Haiyan^*

来源：Chemistry-An Asian Journal, 2017, 12(2): 239-247.

DOI：10.1002/asia.201601497

• calcium complexes
• C-H activation
• C-N bond cleavage
• N ligands
• ring-opening polymerization

Five bis(quinolylmethyl)-(1H-indolylmethyl)amine (BQIA) compounds, that is, {(quinol-8-yl-CH2)(2)NCH2(3-Br-1H-indol-2-yl)} ((LH)-H-1) and {[(8-R-3-quinol-2-yl)CH2](2)NCH(R-2)[3-R-1-1H-indol-2-yl]} (L2-5H) ((LH)-H-2: R-1=Br, R-2=H, R-3=H; (LH)-H-3: R-1=Br, R-2=H, R-3=iPr; (LH)-H-4: R-1=H, R-2=CH3, R-3=iPr; (LH)-H-5: R-1=H, R-2=nBu, R-3=iPr) were synthesized and used to prepare calcium complexes. The reactions of L1-5H with silylamido calcium precursors (Ca[N(SiMe2R)(2)](2)(THF)(2), R=Me or H) at room temperature gave heteroleptic products (L-1,L-2)CaN(SiMe3)(2) (1, 2), (L-3,L-4)CaN(SiHMe2)(2) (3a, 4a) and homoleptic complexes (L-3,L-5)(2)Ca (D3, D5). NMR and X-ray analyses proved that these calcium complexes were stabilized through Ca center dot center dot center dot C-Si, Ca center dot center dot center dot H-Si or Ca center dot center dot center dot H-C agostic interactions. Unexpectedly, calcium complexes ((L3-5)CaN(SiMe3)(2)) bearing more sterically encumbered ligands of the same type were extremely unstable and underwent C-N bond cleavage processes as a consequence of intramolecular C-H bond activation, leading to the exclusive formation of (E)-1,2-bis(8-isopropylquinol-2-yl)ethane.

• 出版日期2017-1
• 单位华东理工大学