Instability of Square Planar N3-Ligand Iridium(I) Ethene Complexes

New, five-coordinate, iridium(I) bis-ethene complexes [ fac -(bpa-R)Ir I (ethene) 2 ] + ( 1 +: R = H, 2 +: R = Me, 3 +: R = Bz; bpa-H = N, N -di(2-pyridylmethyl)amine, bpa-Me = N -methyl- N, N -di(2-pyridylmethyl)amine, bpa-Bz = N -benzyl- N, N -di(2-pyridylmethyl)amine) were prepared. In contrast to their previously reported rhodium analogues, these iridium species do not readily lose one of their two ethene fragments to form square planar mono-ethene complexes [ mer- (bpa-R)Ir I (ethene)] + . Heating complex 1 + results in N−H activation at the bpa-H ligand and formation of the dinuclear iridium(III) species [{( mer -μ 2 -bpa # )Ir III (ethyl)(MeCN)} 2 ] 2+ ( 4 2+ ) with bridging amides (bpa # = bpa-H deprotonated at NH amine ). Heating bpa-Bz complex 3 + results in aromatic C−H activation of the ligand benzyl group to form dinuclear iridium(III) species [{(bpa-Bz # )Ir III (μ 2 - H)} 2 ] 2+ ( 5 2+ ) with unsupported hydride bridges (bpa-Bz # = bpa-Bz cyclometalated at the benzylic C2-position). The dimeric structure of 5 2+ easily breaks up in MeCN, giving the mononuclear species [(bpa-Bz # )Ir III (H)(MeCN)] + ( 6 + ). Complex 5 2+ is also light-sensitive: glass-filtered daylight converts it to a geometrical isomer, 7 2+, in which the cyclometalated benzyl functionality of one of the two ligands has switched its position with a pyridyl donor.