Study of new mononuclear platinum group metal complexes containing η5 and η6 – Carbocyclic ligands and nitrogen based derivatives and formation of helices due to NH⋯Cl interactions

A quite general approach for the preparation of η5- and η6-cyclichydrocarbon platinum group metal complexes is reported. The dinuclear arene ruthenium complexes [(η6-arene)Ru(μ-Cl)Cl]2 (arene = C6H6, C10H14 and C6Me6) and η5-pentamethylcyclopentadienyl rhodium and iridium complexes [(η5-C5Me5)M(μ-Cl)Cl]2 (M = Rh and Ir) reacts with two equivalents of the ligands 2-chloro-3-(pyrazolyl)quinoxaline (L1) and di-(2-pyridyl)amine (L2) in presence of NH4PF6 to afford the corresponding mononuclear complexes of the type [(η6-arene)Ru(L1)Cl]PF6 {arene = C6H6 (1), C10H14 (2) and C6Me6 (3)}, [(η6-arene)Ru(L2)Cl]PF6 {arene = C6H6 (4), C10H14 (5) and C6Me6 (6)}, and [(η5-C5Me5)M(L1)Cl]PF6 {M = Rh (7), Ir (8)} and [(η5-C5Me5)M(L2)Cl]PF6 {M = Rh (9), Ir (10)}. However the mononuclear η5-cyclopentadienyl analogues such as [(η5-C5H5)Ru(PPh3)2Cl], [(η5-C5H5)Os(PPh3)2Br], [(η5-C5Me5)Ru(PPh3)2Cl] and [(η5-C9H7)Ru(PPh3)2Cl] complexes react in presence of one equivalent of ligands 2-chloro-3-(pyrazolyl)quinoxaline (L1) and di-(2-pyridyl)amine (L2) and one equivalent of NH4PF6 in methanol yielded mononuclear complexes [(η5-C5H5)Ru(PPh3)(L1)]PF6 (11), [(η5-C5H5)Os(PPh3)(L1)]PF6 (12), [(η5-C5Me5)Ru(PPh3)(L1)]PF6 (13) and [(η5-C9H7)Ru(PPh3)(L1)]PF6 (14) and [(η5-C5H5)Ru(PPh3)(L2)]PF6 (15), [(η5-C5H5)Os(PPh3)(L2)]PF6 (16), [(η5-C5Me5)Ru(PPh3)(L2)]PF6 (17) and [(η5-C9H7)Ru(PPh3)(L2)]PF6 (18) respectively. These compounds have been systematically characterized by IR, NMR and mass spectrometry. The molecular structures of 2, 4 and 15 have been established by single crystal X-ray diffraction study and some of the representative complexes have also been studied by UV–visible spectroscopy. The crystal packing diagram of complex 4 reveals that the cation [(η6-C6H6)Ru(L2)Cl]+ is engaged in non-covalent interaction. This compound gives rise to a 1D helical architecture along the ‘a’ axis via intermolecular NH⋯Cl hydrogen bonds.