Synthesis of Rhodium Complexes Having a Macrocyclic Ligand Based on Two m-Phenylene-Linked Bis(N-heterocyclic carbene) Moieties as a CCC-Pincer Ligand or Two Bis(carbene) Ligand

Abstract

Macrocyclic tetraimidazolium salts 3-PF 6 , 3-TFSI (TFSI = N­(SO2CF3)2), and 4-PF 6 [3: 1,3-bis­(imidazolyl)-2,4-Me2C6H2 core; 4: 1,3-bis­(imidazolyl)­C6H4 core] were synthesized. Treatment of 3-PF 6 and 3-TFSI with AgOAc yielded tetranuclear [(NHC)2Ag]4 complexes 5-PF 6 -A/B and 5-TFSI-A/B having a boxlike structure, respectively, which contained structural isomers arising from staggered and eclipsed configurations of two macrocyclic ligands. The reaction of 5-TFSI-A/B with [RhCl­(coe)2]2 resulted in the formation of a mixture of dinuclear [(CCC-pincer)­Rh]2 complexes 6-TFSI and 7-TFSI with the macrocyclic scaffold through transmetalation and cyclometalation. X-ray crystallographic analysis revealed the flexibility of the butylene linkers of 6-TFSI and 7-TFSI. In contrast, the reaction of 4-PF 6 with [RhCl­(cod)]2 led to the formation of dinuclear [(NHC)2Rh]2 complexes as a mixture of structural isomers 8a-PF 6 and 8b-PF 6 , where the macrocyclic ligand acted as a bidentate NHC ligand for each Rh center.