- Bis-imine-cyclometalated macrocycles: Synthesis, characterization and observation of solution behaviour
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A novel class of cyclometalated macrocycles [(Cp*Ir) 2(R-NC-C6H2-CN-R)2] 2(pyrazine)2·(OTf)4 [R = Ph (4a), p-MeOC6H4 (4b), p-MeC6H4 (4c), p-ClC6H4 (4d), Me (4e)]; [(Cp*Rh) 2(R-NC-C6H2-CN-R)2] 2(pyrazine)2·(OTf)4 [R = Ph (4a′), p-MeOC6H4 (4b′), p-MeC6H4 (4c′)] and [(Cp*Ir)2(R-CN-C6H 4-NC-R)2]2(pyrazine)2·(OTf) 4 [R = Ph (5a), p-MeOC6H4 (5b)] was stepwise constructed through the double-site C-H activation of aromatic bis-imine substrates. The structures of binuclear complexes and tetranuclear macrocycles were confirmed by single-crystal X-ray diffraction. Isomers were found both in binuclear species and macrocyclic complexes. Flexible substrates led to the existence of isomers for binuclear species, yet gave no isomers after macrocyclic constructions; rigid ones, in contrast, led to isomers only for macrocyclic species. The isomers of tetranuclear macrocycles were thermodynamically stable to reversible transformation on a scale of days. Robust bonding and a certain degree of rigidity were invoked to explain the existence of isomers. This is the first example, to our knowledge, in which coordinated macrocycles containing half-sandwich Cp*M (M = Ir, Rh) fragments have been constructed, without a dynamic reversible process.
- Li, Hao,Han, Ying-Feng,Jin, Guo-Xin
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p. 4982 - 4993
(2011/08/02)
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