KINETISCHE UND MECHANISTISCHE UNTERSUCHUNGEN VON UEBERGANGSMETALL-KOMPLEX-REAKTIONEN XXII. KONKURRENZ ZWISCHEN DISSOZIATIVEM UND ASSOZIATIVEM MECHANISMUS BEI DER REAKTION VON PENTACARBONYL(DIPHENYLCARBEN)WOLFRAM MIT NITRILEN

Article abstract of DOI:10.1016/0022-328X(87)80228-0

The reaction of pentacarbonyl(diphenylcarbene)tungsten, (CO)5W=CPh2 (I), with organyl nitriles, <*> (II) (R = C6H4NMe2-p (a), C6H4OMe-p (b), Ph (c), Me (d), Bu^t (e)), yields the insertion product (CO)5W (III), the nitrile complexes <*> (IV) and <*> (V) and diphenyl ketene, Ph2C=C=O.The product distribution depends on the type and the concentration of the organyl nitrile II.At constant temperature, the yield of III increases and that of IV as well as that of diphenyl ketene decreases with increasing concentration of II and in the order IId, IIc, IIb, IIa.When I reacts with IIb in the presence of 13CO, 13CO is incorporated almost exclusively into IVb.At 50.6 deg C in 1,1,2-trichloroethane, the reaction of I with IIa-d follows an additive rate law: -d/dt = k₁ + k₂.The rate constant k₁ is independent of the type of II and agrees well with the rate constant for the dissociative thermolysis of I in 1,1,2-trichloroethane, however, k₂ clearly increases in the series IId-a.A reaction scheme is proposed consisting of an associative pathway (giving III) and a dissociative pathway leading to the compounds IV, V and diphenyl ketene.