Isomers of Cyclometalated Macrocycles Constructed through Olefinic C–H Activation

A new series of dinuclear complexes [(Cp*M)2{(2-pyridyl)-CC-(2-pyridyl)}Cl2] (M = Rh (1a), Ir (1b)) and tetranuclear metallamacrocycles [{(Cp*M)2{(2-pyridyl)-CC-(2-pyridyl)}(pyrazine)}2](OTf)4 (M = Rh (2a), Ir (2b)), [{(Cp*M)2{(2-pyridyl)-CC-(2-pyridyl)}(bpy)}2](OTf)4 (M = Rh (3a), Ir (3b); bpy = 4,4′-bipyridine), and [{(Cp*M)2{(2-pyridyl)-CC-(2-pyridyl)}(bpe)}2](OTf)4 (M = Rh (4a), Ir (4b); 4,4′-bpe = trans-1,2-bis(4-pyridyl)ethylene) were constructed stepwise through double-site C–H activation on the olefinic CC bond of 1,2-bis(2-pyridyl)ethylene. Isomers were observed in both the dinuclear species and tetranuclear macrocyclic complexes and were confirmed by single-crystal X-ray diffraction. The molecular structures of 1a–c, (R,R)-(S,S)-3b, (R,R)-(S,S)-4a, (R,R)-(R,R)-/(S,S)-(S,S)-4a, and (R,R)-(S,S)-4b were characterized by single-crystal X-ray crystallography. All complexes were fully characterized by 1H NMR spectroscopy, ESI-MS, and elemental analysis.