The effects of bulky ortho-aryl substituents in corroles, tested by x-ray crystallography of the rhodium complexes and catalysis thereby

In the present publication we report on the preparation and spectroscopic features of a penta-coordinate rhodium(III) complex of corrole with bulky ortho-phenyl substituents at the meso positions, Rh(tdcc)(PPh₃) [tdcc = tris(2,6-dichlorophenyl)corrole]. Addition of pyridine to Rh(tdcc)(PPh₃), as well as to the closely related complex of tris(pentafluorophenyl)corrole [Rh(tpfc)(PPh₃)] reported earlier, leads to hexa-coordinated rhodium complexes with pyridine and PPh₃ occupying the axial positions. The structures of these two compounds were investigated by NMR and x-ray crystallography. The catalytic potency of Rh(tdcc)(PPh₃) was found significantly lower than that of Rh(tpfc)(PPh₃), which suggests that excess steric crowding prevents efficient carbene-transfer catalysis.