Novel Basic Ligands for the Homogeneous Catalytic Carbonylation of Methanol, XXVIl). -Dynamic and Reactive Behaviour of (Ether-Phosphane)Ruthenium(II) Complexes in Dependence on the 0-Basicity Reaction of the ether-phosphane ligand Ph2PCH2C4H702 (3a) irradiation cis&, trans-6a is retransformed at 40°C into 4a via with C12Ru(PPh3), (2) results in the formation of the bis(che1ate) all-trans-?a and 5a. The latter and the corresponding comcomplex tran~-Cl~Ru(P"O)~ (4a). (P -0 = ql-P-coordinated; plexes 5b, e, containing THF and CH,0CH3 as ether substit-P"0 = q2-0,P-coordinated). With CO both Ru-0 bonds are uents, show fluxional behaviour. The coalescence temperacleaved to give all-tran~-Cl~Ru(CO)~(P-O), (?a). At 35°C 7a is tures (10, 80, and 55"C, resp.) and the estimated AG * values transformed into the rnonocarbonyl ruthenium complex trans-(52, 65, and 59 kJ/mol, resp.) of the exchange process indicate Cl,(PnO)(P-O)RuCO (5a) with elimination of one CO mole-the weakest Ru-0 contact in 5a compared to 5b, c. The lower cule. On heating all-trans-?a to 110°C in toluene the thermo-basicity of the dioxanyl function is also responsible for the dynamically more stable complex cis-C12(OC)2Ru(frans-different reaction behaviour of 4a, 5a, and ?a compared to the P N O )~ (6a) is obtained. All reaction steps are reversible. Upon corresponding complexes with the ligands 3b, c.