Syn and Anti Metal Complexes of 24π Antiaromatic Bis(Dicarbonylrhodium(I))Dithiaamethyrin.

From the reaction of sterically less hindered tetrapropyl[24]dithiaamethyrin(1.0.0.1.0.0) 5, with [Rh(CO) 2 Cl] 2 , a unique anti form of the bis(dicarbonylrhodium(I)) complex (6-anti), where two rhodium ions are on the opposite faces of the macrocyclic ligand, was isolated for the first time in 12% yield along with the corresponding syn isomer (6-syn, 61% yield). These structures were characterized in detail by single-crystal X-ray structure analysis. Compound 6-syn exhibited a bowl-shaped structure with the two rhodium atoms separated by a distance of ∼4.5 Å. In contrast, 6-anti contained a wave-shaped macrocycle with a distance of ∼5.3 Å between the two rhodium atoms. Furthermore, the 1 H nuclear magnetic resonance spectra and density functional theory calculation results revealed that 6-anti had a stronger paratropic ring current and a more planar structure than 6-syn. The isolation of both 6-anti and 6-syn enabled detailed discussion of the structure-property relationship.