Neuartige basische Liganden für die homogenkatalytische Methanolcarbonylierung, XXVI. Dynamisches und reaktives Verhalten von (Ether‐Phosphan)ruthenium(II)‐Komplexen in Abhängigkeit von der O‐Basizität

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 Ph 2 PCH 2 C 4 H 7 O 2 ( 3a ) with Cl 2 Ru(PPh 3 ) 3 ( 2 ) results in the formation of the bis(chelate) complex trans ‐Cl 2 Ru(PˆO) 2 ( 4a ). (P∼O = η 1 P ‐coordinated; PˆO = η 2 O,P ‐coordinated). With CO both Ru–O bonds are cleaved to give all‐trans ‐Cl 2 Ru(CO) 2 (P∼O) 2 ( 7a ). At 35°C 7a is transformed into the monocarbonyl ruthenium complex trans ‐Cl 2 (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 ‐Cl 2 (OC) 2 Ru( 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 CH 2 OCH 3 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 .