The reaction of cyclo-octa-1,5-diene and bicyclo[2,2,1]hepta-2,5-diene with a carbonyl-containing solution has been shown to yield complexes of the type [RuCl2(CO)(diene)]2. Complexes [RuX2(PPh3)2(C7H8)](X = Cl or Br) have been prepared by the reaction of [RuX2(PPh3)4] with bicyclo[2,2,1]hepta-2,5-diene. New complexes of the type [RuCl2(CO)(L)3](L = pyridine, 3-methylpyridine) are described.