Dynamic 15N NMR studies of iron phosphine complexes containing coordinated dinitrogen

Abstract

AbstractThe 15N‐labelled iron dinitrogen complexes trans‐[FeH(N2)(PP)2]+[BPh4]− (PP = dppe, depe, dmpe) and cis‐[FeH(N2)(PP3)]+[BPh4]− were prepared in situ by exchange of unlabelled coordinated dinitrogen with 15N2. 15N NMR chemical shifts and coupling constants are reported. The 15N spectra exhibit separate signals for the metal‐bound and terminal nitrogen atoms of the coordinated N2. The 15N resonances display 15N, 15N coupling as well as 31P, 15N coupling and long‐range 15N, 1H coupling when there is a metal‐bound hydrido ligand. Exchange between free and coordinated dinitrogen was monitored by magnetization transfer between 15N‐labelled sites using an inversion–transfer–recovery experiment. Exchange between the metal‐bound and terminal nitrogen atoms of coordinated N2 was also monitored by magnetization transfer and this could proceed by N2 dissociation or by an intramolecular process. Copyright © 2003 John Wiley & Sons, Ltd.