Institution: | Institute of Inorganic and Analytical Chemistry, Place du Château 3, University of Lausanne Switzerland Institute of Organic Chemistry, rue de la Barre 2, University of Lausanne Switzerland Institute of Crystallography, BSP, Dorigny, University of Lausanne Switzerland |
Abstract: | The main product of the thermal reaction between the title oxatetraene (I) and Fe2(CO)9 in ether/pentane is the bimetallic complex (C10H10O)Fe2(CO)6-diexo (II), which has C2υ symmetry both in the solid state (X-ray analysis) and in solution. Whereas the protonation of the free ligand leads usually to polymerisation, the addition of a protic acid such as CF3CO2H to II proceeds cleanly at 0°C giving first a (η 3-allyl)Fe(CO)3O2CCF3 complex (III). The intermediate III adds a second equivalent of acid in a slower step (k2/k1 = 0.1, CF3CO2D/CHCl3, 0°C) giving the trans-bis(η3-allyl) isomer IV with high regioselectivity. The addition of CF3CO2D yields the corresponding deuteriomethylallyliron tricarbonyl trifluoroacetates III′ and IV′. No further deuterium incorporation is observed at 0°C, thus confirming the kinetic control of the regioselective double addition of protic acid to II. |