A study of the coordination ability of 2,5-di(2-pyridyl)phospholes on Ru centres

The coordination behaviour of the readily available 1-phenyl-2,5-di(2-pyridyl)phosphole (NPN) toward Ru centres was investigated. Neutral and ionic compounds of formula [RuCl(p-cymene)(NPN)]TfO (TfO=CF3SO3)… (1), [RuCl(p-cymene)(NPN)]BF4 (2), [RuCl(C6Me6)(NPN)]TfO (3), RuCp′Cl(NPN) [Cp′=C5H5 (4), C5Me5 (5)], Ru(C5Me5)(σ1-C8H13)(NPN) (6), RuCl2(NPN)2 (7) and RuClH(cod)(NPN) (cod=1,5-cyclooctadiene) (8) were obtained. Two diastereomers were obtained for 1, 2 and 4, (a, b) while three were found in the case of 8 (a–c). According to NMR spectroscopy, the 2,5-bis(2-pyridyl)phosphole acts as a 1,4-P,N chelate ligand in all cases. This behaviour was confirmed by an X-ray diffraction study performed on complex 1a. Proton transfer studies on complex 8 demonstrated the influence of the molecular structure on the ability to form dihydrogen bridges.