One-electron oxidation of [(Me(n)tpa)Ir(I)(ethene)]+ complexes (Me(3)tpa = N,N,N-tri(6-methyl-2-pyridylmethyl)amine; Me(2)tpa = N-(2-pyridylmethyl)-N,N,-di[(6-methyl-2-pyridyl)methyl]-amine) results in relatively stable, five-coordinate Ir(II)-olefin species [(Me(n)tpa)Ir(II)(ethene)](2+) (1(2+): n = 3; 2(2+): n = 2). These contain a "vacant site" at iridium and a "non-innocent" ethene fragment, allowing radical type addition reactions at both the metal and the ethene ligand. The balance between metal- and ligand-centered radical behavior is influenced by the donor capacity of the solvent. In weakly coordinating solvents, 1(2+) and 2(2+) behave as moderately reactive metallo-radicals. Radical coupling of 1(2+) with NO in acetone occurs at the metal, resulting in dissociation of ethene and formation of the stable nitrosyl complex [(Me(3)tpa)Ir(NO)](2+) (6(2+)). In the coordinating solvent MeCN, 1(2+) generates more reactive radicals; [(Me(3)tpa)Ir(MeCN)(ethene)](2+) (9(2+)) by MeCN coordination, and [(Me(3)tpa)Ir(II)(MeCN)](2+) (10(2+)) by substitution of MeCN for ethene. Complex 10(2+) is a metallo-radical, like 1(2+) but more reactive. DFT calculations indicate that 9(2+) is intermediate between the slipped-olefin Ir(II)(CH(2)=CH(2)) and ethyl radical Ir(III)-CH(2)-CH(2). resonance structures, of which the latter prevails. The ethyl radical character of 9(2+) allows radical type addition reactions at the ethene ligand. Complex 2(2+) behaves similarly in MeCN. In the absence of further reagents, 1(2+) and 2(2+) convert to the ethylene bridged species [(Me(n)tpa)(MeCN)Ir(III)(mu(2)-C(2)H(4))Ir(III)(MeCN)(Me(3)tpa)](4+) (n = 3: 3(4+); n = 2: 4(4+)) in MeCN. In the presence of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxo), formation of 3(4+) from 1(2+) in MeCN is completely suppressed and only [(Me(3)tpa)Ir(III)(TEMPO(-))(MeCN)](2+) (7(2+)) is formed. This is thought to proceed via radical coupling of TEMPO at the metal center of 10(2+). In the presence of water, hydrolysis of the coordinated acetonitrile fragment of 7(2+) results in the acetamido complex [(Me(3)tpa)Ir(III)(NHC(O)CH(3)))(TEMPOH)](2+) (8(2+)).

Oxidation induces oxygenation: The first IrII–ethene complex ever (2) was obtained by one‐electron oxidation of the corresponding IrI–ethene complex 1. Whereas 1 reacts with dioxygen to give an IrIII–peroxo‐ethene complex, the IrII–ethene complex 2 activates dioxygen towards CO bond formation and gives the IrIII–formylmethyl complex 3.

New cationic, five-coordinate bis(ethene)iridium(i) complexes [(κ 3 -Me 3 -tpa)Ir I (ethene) 2 ] + (12 + ) and [(κ 3 -Me 2 -dpaMe)Ir I (ethene) 2 ] + (13 + ) have been prepared {Me 3 -tpa = N,N,N-tris[(6-methyl-2-pyridyl)Complexes 12 + and 13 + lose one ethene fragment in solution, yielding the five-coordinate mono(ethene) complex [(κ 4 -Me 3 -tpa)Ir I (ethene)] + (14 + ) and the four-coordinate mono-(ethene) complex [(κ 3 -Me 2 -dpa-Me)Ir I (ethene)] + (15 + ), respectively. [(κ 4 -Me 3 -tpa)Rh I (ethene)] + (11 + ), the rhodium analogue of 14 + , was also prepared. Whereas rhodium complex 11 + is stable in acetonitrile at room temperature, the iridium analogue 14 + converts to the cyclometallated (acetonitrile)(hydrido) complex 16 + within 72 h by dissociation of the

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.

Ethene dissociation from [(Me n tpa)IrII(ethene)]2+, induced by coordination of acetonitrile, causes a rapid and selective M−C coupling between IrII and IrII(ethene), resulting in ethylene-bridged dinuclear iridium(III) complexes of the composition [{(Me n tpa)IrIII(NCMe)}2(μ2-C2H4)]4+ (n = 2, 3).