Ruthenium Porphyrins with Axial π‐Conjugated Arylamide and Arylimide Ligands

A series of ruthenium porphyrins [Ru IV (por)(NHY) 2 ] and [Ru VI (por)(NY) 2 ] bearing axially coordinated π‐conjugated arylamide and arylimide ligands, respectively, have been synthesized. The crystal structures of [Ru IV (tmp)(NHY) 2 ] (tmp=5,10,15,20‐tetramesitylporphyrinato( 2 −)) with Y=4′‐methoxy‐biphenyl‐4‐yl ( Ar Ar ‐ p ‐OMe), 4′‐chloro‐biphenyl‐4‐yl ( Ar Ar ‐ p ‐Cl), and 9,9‐dibutyl‐fluoren‐2‐yl ( Ar ^ Ar ) show axial RuN(arylamide) distances of 1.978(4), 1.971(6), and 1.985(13) Å, respectively. [Ru IV (tmp)(NH{ Ar ^ Ar }) 2 ] is an example of metalloporphyrins that bind an arylamide ligand featuring a co‐planar biphenyl unit. The [Ru IV (por)(NHY) 2 ] complexes show a quasi‐reversible reduction couple or irreversible reduction wave attributed to Ru IV →Ru III with E pc from −1.06 to −1.40 V versus Cp 2 Fe +/0 and an irreversible oxidation wave with E pa from −0.04 to 0.19 V versus Cp 2 Fe +/0 . Reaction of the [Ru IV (por)(NHY) 2 ] with bromine afforded [Ru IV (por)(NHY)Br]. PhI(OAc) 2 oxidation of the [Ru IV (por)(NHY) 2 ] gave [Ru VI (por)(NY) 2 ]; the latter can be prepared from reaction of [Ru II (por)(CO)] with aryl azides N 3 Y. The crystal structure of [Ru VI (tmp)(N{ Ar Ar ‐ p ‐OMe}) 2 ] features RuN(arylimide) distances of 1.824(5) and 1.829(5) Å. Alkene aziridination and CH amination catalyzed by “[Ru II (tmp)(CO)]+π‐conjugated aryl azides”, or mediated by [Ru VI (por)(NY) 2 ] with Y=biphenyl‐4‐yl ( Ar Ar ) and Ar Ar ‐ p ‐Cl, gave aziridines and amines in moderate yields. The electronic structure of [Ru VI (por)(NY) 2 ] was examined by DFT calculations.