Remarkable Paramagnetically Shifted ¹H and ²H NMR Spectra of Iron(II) Complexes of 2-Aza-21-carbaporphyrin: An Evidence for Agostic Interaction

Abstract

Iron(II) 2-aza-21-carbaporphyrins have been characterized by paramagnetically shifted (1)H and (2)H NMR spectra. The high-spin iron(II) complex (HCTPPH)Fe(II)Br displays the beta-H resonances which reflect the combination sigma and pi routes of spin density delocalization. The uniquely large isotropic shift of the inner H(21) hydrogen (812 ppm, 298 K) indicates an Fe(II)-[C(21)-H] agostic interaction.