NOVEL BASIC LIGANDS FOR THE HOMOGENEOUS CATALYTIC CARBONYLATION OF METHANOL .26. DYNAMIC AND REACTIVE BEHAVIOR OF (ETHER-PHOSPHANE)RUTHENIUM(II) COMPLEXES IN DEPENDENCE ON THE O-BASICITY

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 o‐Basicity Reaction of the ether‐phosphane ligand Ph2PCH2C4H7O2 (3a) with Cl2Ru(PPh3)3 (2) results in the formation of the bis(chelate) complex trans‐Cl2Ru(PˆO)2 (4a). (P∼O = η1P‐coordinated; PˆO = η2O,P‐coordinated). With CO both Ru–O bonds are cleaved to give all‐trans‐Cl2Ru(CO)2(P∼O)2 (7a). At 35°C 7a is transformed into the monocarbonyl ruthenium complex trans‐Cl2(PˆO)(P∼O)RuCO (5a) with elimination of one CO molecule. On heating all‐trans‐7a to 110°C in toluene the thermodynamically more stable complex cis‐Cl2(OC)2Ru(trans‐P∼O)2 (6a) is obtained. All reaction steps are reversible. Upon irradiation cis,cis,trans‐6a is retransformed at 40°C into 4a via all‐trans‐7a and 5a. The latter and the corresponding complexes 5b, c, containing THF and CH2OCH3 as ether substituents, show fluxional behaviour. The coalescence temperatures (10, 80, and 55°C, resp.) and the estimated ΔG≢ values (52, 65, and 59 kJ/mol, resp.) of the exchange process indicate the weakest Ru‐O contact in 5a compared to 5b, c. The lower basicity of the dioxanyl function is also responsible for the different reaction behaviour of 4a, 5a, and 7a compared to the corresponding complexes with the ligands 3b, c. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim