Structures and Reactivity Patterns of Group 9 Metallocorroles
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Abstract
Group 9 metallocorroles 1-M(PPh(3)) and 1-M(py)(2) [M = Co(III), Rh(III), Ir(III); 1 denotes the trianion of 5,10,15-tris-pentafluorophenylcorrole] have been fully characterized by structural, spectroscopic, and electrochemical methods. Crystal structure analyses reveal that average metal-N(pyrrole) bond lengths of the bis-pyridine metal(III) complexes increase from Co (1.886 A) to Rh (1.957 A)/Ir (1.963 A); and the average metal-N(pyridine) bond lengths also increase from Co (1.995 A) to Rh (2.065 A)/Ir (2.059 A). Ligand affinities for 1-M(PPh(3)) axial coordination sites increase dramatically in the order 1-Co(PPh(3)) < 1-Rh(PPh(3)) < 1-Ir(PPh(3)). There is a surprising invariance in the M(+/0) reduction potentials within the five- and six-coordinate corrole series, and even between them; the average M(+/0) potential of 1-M(PPh(3)) is 0.78 V vs Ag/AgCl in CH(2)Cl(2) solution, whereas that of 1-M(py)(2) is 0.70 V under the same conditions. Electronic structures of one-electron-oxidized 1-M(py)(2) complexes have been assigned by analysis of electron paramagnetic resonance spectroscopic measurements: oxidation is corrole-centered for 1-Co(py)(2) (g = 2.008) and 1-Rh(py)(2) (g = 2.003), and metal-centered for 1-Ir(tma)(2) (g(zz) = 2.489, g(yy) = 2.010, g(xx) = 1.884, g(av) = 2.128) and 1-Ir(py)(2) (g(zz) = 2.401, g(yy) = 2.000, g(xx) = 1.937, g(av) = 2.113).