Abstract/Summary

Diarylamine-substituted osmanaphthalyne complexes that feature two redox centers linked by the rigid skeleton of the metallacycle (C^C+), specifically, [OsCl2(PPh3)2{(C^C+)NAr2}][BF4 ] (Ar=Ph (1 a), p-MeOPh (1 b)) and their open-ring precursors [OsHCl2(PPh3)2{(CC(PPh3 +)= CHPh)NR2}][BF4 ] (Ar=Ph (2 a), p-MeOPh (2 b)), were successfully synthesized and characterized by 1 H, 13C, and 31P NMR spectroscopy, ESI-MS, and elemental analysis. The solid-state molecular structures of complexes 1 a and 2 a were ascertained by single-crystal X-ray diffraction. The OsC bond length in both complexes 1 a and 2 a fell within the range reported for similar osmanaphthalynes and osmium carbyne complexes, respectively. The structural parameters determined for complex 1 a, which were successfully reproduced by theoretical calculations, point to a p-delocalized metallacycle structure. The purple color of compounds 1 a and b was explained by the diarylamine!Os(metallacycle) chargetransfer absorption in the visible region. The neutral, oneelectron-oxidized and one-electron-reduced states of compounds 1 a, b, and a reference complex that lacked the diarylamine substituent, [OsCl2(PPh3)2{(C^C+)}][BF4] (1’), were investigated by cyclic and square-wave voltammetry, UV/Vis/NIR spectroelectrochemistry, and DFT calculations. The spin density in singly oxidized complexes [1 a]+ and [1 b]+ predominantly resided on the aminyl segment, with osmium involvement controlled by the diphenylamine substitution. Spin density in stable, singly-reduced [1’] was distributed mainly over the osmanaphthalyne metallacycle.