METAL-INDUCED VALENCE ISOMERIZATIONS - GAS-PHASE REACTIONS OF IRON(I) AND COPPER(I) WITH QUADRICYCLANE AND NORBORNADIENE

Metal-promoted valence isomerizations and cycloreversions occur in the gas phase for adducts of norbornadiene (NBD) and quadricyclane (Q) with either Fe(I) or Cu(I). The collisionally activated decomposition (CAD) spectra of the adducts of NBD and Q with each metal indicate that the complexes possess identical structures, although the structures that are formed with Fe(I) are different from those with Cu(I). Both Cu(I) and Fe(I) cause the valence isomerization of Q to NBD. The metal ion then induces a retro Diels-Alder reaction of NBD to form a (C5H6)M+(C2H2) complex. Only the Fe(I) complexes react further to generate a (C5H5)(H)Fe+(C2H2) species. Structures of the adducts of toluene (T) and cycloheptatriene (CHT) with each metal are shown to be similar but non-interconverting with those of NBD and Q. Fourier transform mass spectrometry (FTMS) data provide additional support for the structural assignments. Experimental rate constants for the reactions are nearly equal to each other and to the collision rate constants for each system.