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.