The interaction of dihydridotetrakis(triphenylphosphine)ruthenium(II), RuH2(PPh3)4, with the following compounds has been studied: 2,2′-bipyridyl, o-dicyanobenzene, 2-hydroxypyridine, 8-hydroxyquinoline, 2-aminopyridine, 2-mercaptopyridine, o-phenylenediamine, 2-aminothiophenol, 2-aminophenol, pyrocatechol, resorcinol, and hydroquinone. The products have been characterised by i.r. and n.m.r. (1H and 31P) spectroscopy, and structures for new compounds proposed.