Heteroleptic arene ruthenium complexes based on meso-substituted dipyrrins: synthesis, structure, reactivity, and electrochemical studies

Abstract

First examples of heteroleptic arene ruthenium complexes containing dipyrrin ligands with the general formulations [(η⁶-arene)RuCl(L)] [(arene = C₆H₆, C₁₀H₁₄; L = 5-(4-cyanophenyl)-dipyrromethene, cydpm; 5-(4-nitrophenyl)-dipyrromethene, ndpm and 5-(4-benzyloxyphenyl)-dipyrromethene, bdpm] have been synthesized. The complexes [(η⁶-C₁₀H₁₄)RuCl(L)] (L = ndpm and cydpm) reacted with NaN₃ and NH₄SCN to afford neutral mononuclear complexes [(η⁶-C₁₀H₁₄)Ru(N₃)(L)] and [(η⁶-C₁₀H₁₄)Ru(SCN)(L)]. Their reactions with EPh₃ (E = P, As) and exobidentate ditopic P−P and N−N donor ligands, namely, bis-(diphenylphosphino)methane (dppm) and 4,4′-bipyridine (bpy) in the presence of AgSO₃CF₃ afforded cationic mono- and binuclear complexes [(η⁶-C₁₀H₁₄)Ru(L)(EPh₃)]SO₃CF₃, [{(η⁶-C₁₀H₁₄)Ru(L)}₂(μ-dppm)](SO₃CF₃)₂, and [{(η⁶-C₁₀H₁₄)Ru(L)}₂(μ-bpy)](SO₃CF₃)₂, respectively. The reaction products have been characterized by analytical and spectral studies. Molecular structures of the representative complexes [(η⁶-C₁₀H₁₄)RuCl(cydpm)], [(η⁶-C₆H₆)RuCl(cydpm)], [(η⁶-C₁₀H₁₄)RuCl(ndpm)], [(η⁶-C₁₀H₁₄)Ru(N₃)(ndpm)], and [(η⁶-C₁₀H₁₄)Ru(PPh₃)(ndpm)]SO₃CF₃ have been determined crystallographically. Redox behavior of the complexes has been investigated by electrochemical studies. Emission spectral studies at room temperature suggested that the complexes under study are non-emissive.