Organische Synthesen mit Übergangsmetallkomplexen, 42 Allene als Liganden in zweikernigen Eisencarbonyl‐Komplexen; Carbonylierungen von Allenen sowie deren Kupplung mit Alkinen und Allenen; dynamische “Keten‐Scheibenwischer”‐Komplexe

Abstract

On photochemically induced metallation with pentacarbonyl NMR measurements. The ketene unit is moving back and forth iron allenes H2C = C = CHR 1 (R = H, C6H5) give dinuclear like a windshield wiper. Thermolysis of 5 under normal presacyl iron complexes 2, in which the central carbon of the sure affords ferracyclopentadiene iron complexes 6 (by 1,3-C = C = C unit is attached to a carbonyl group. 2 on warming hydrogen shifts) and 4-methylene-2-cyclopenten-1-one ? (by yield n-ally1,o complexes 3 by loss of carbon monoxide. The cyclocarbonylation). Thermolysis of 5 under CO pressure gives reaction 2 e 3 + CO is reversibel. 3 add alkynes R1 -C = C -RZ 7 as the sole products. Complexes 3 also add allenes 1 with 4 (R' = C6H5, CH20CH3; R2 = H, C,H5) with insertion of the insertion into the M -C a-bond and formation of a C -C bond C = C triple bond into the M -C o-bond to give dinuclear between the central carbon atoms of both allene units to give ketene complexes 5. The latter are fluxional, as was shown by dinuclear bis(ally1) complexes 8 and 8'.