CuII-mediated Controllable Creation of Tertiary and Quaternary Carbon Centers: Designed Assembly and Structures of a New Class of Copper Complexes Supported by in Situ Generated Substituted 1-Pyridineimidazo[1,5-a]pyridine Ligands
Yanmei Chen (陈砚美), Lei Li (李磊), Yanyuan Cao (曹燕媛), Jian Wu (吴健), Qian Gao (高倩), Yahong Li (李亚红)*, Hailiang Hu (胡海良), Wei Liu (刘玮), Yonglu Liu (刘勇路), Zhenhui Kang (康振辉), Jingping Li (李金平)
CrystEngComm2013, 15, 2675–2681.
Hydrothermal reaction of CuCl2·2H2O, 3-(pyridin-2-yl)imidazo[1,5-a]pyridine (HPIP) and formaldehyde, yielded a novel mixed-valence CuI/CuII complex [L1Cu2Cl2][Cu2Cl4]·2EtOH (1·2EtOH; L1 = tetrakis(3-(pyridin-2-yl)imidazo[1,5-a]pyridin-1-yl)methane). The in situ generated quaternary carbon-containing ligand L1 was derived from CuII-mediated quadruple coupling of HPIP and formaldehyde, where the three bonds of formaldehyde were totally cleaved. 1·2EtOH can also be prepared by replacing formaldehyde by formic acid, N,N-dimethylformamide, and glyoxal, respectively. When acetic acid, which usually serves as a radical reaction inhibitor, was introduced into the reaction systems, two CuI complexes [(L2)2Cu3](CuCl2)3·2EtOH (2·2EtOH) and L3Cu2Cl2 (3) (L2 = tris(3-(pyridin-2-yl)imidazo[1,5-a]pyridin-1-yl)methane, and L3 = 1,1,2,2-tetrakis(3-(pyridin-2-yl)imidazo[1,5-a]pyridin-1-yl)ethane) were afforded. The tertiary carbon-bearing ligands L2 and L3 were generated in situ via CuII-mediated controllable cleavage of two bonds of formaldehyde, N,N-dimethylformamide and glyoxal, respectively. The plausible mechanisms for the formation of the ligands L1–L3 were proposed.
