Synthesis, characterisation and thermal studies of ruthenium(II) carbonyl complexes of functionalised tripodal phosphine chalcogen donor ligands, [CH3C(CH2P(X)Ph2)3], where X = Se, S, O

The polymeric ruthenium(II) carbonyl complex, [Ru(CO)2Cl2]n reacts with 1,1,1-tris-(diphenylphosphinomethyl)ethane trichalcogenide ligands, [CH3C(CH2P(X)Ph2)3], where X = Se(a), S(b) and O(c) in 1:1 (metal:ligand) molar ratio to afford hexa-coordinated complexes of the type η2-(X,X)-[Ru(CO)2Cl2P3X3] (1a–c). The complexes 1a–c exhibit two equally intense ν(CO) bands in the range 1979–2060 cm−1 indicating cis-disposition of the two terminal carbonyl groups. The values of ν(CO) frequencies containing different ligands, in general, follow the order: P3O3 > P3S3 > P3Se3 which may be explained in terms of ‘Soft–Hard’ (Ru(II)–O) and ‘Soft–Soft’ (Ru(II)–S/Se) interactions. The complexes have been characterized by elemental analyses, mass, 1H, 31P, 77Se and 13C NMR spectroscopy. The thermal stability of the complexes has also been studied.