New routes to low-coordinate iron hydride complexes: The binuclear oxidative addition of H2

The oxidative addition and reductive elimination reactions of H-2 on unsaturated transition-metal complexes are crucial in utilizing this important molecule. Both biological and man-made iron catalysts use iron to perform H-2 transformations, and highly unsaturated iron complexes in unusual geometries (tetrahedral and trigonal planar) are anticipated to give unusual or novel reactions. In this paper, two new synthetic routes to the low-coordinate iron hydride complex [(LFe)-Fe-tBu(mu-H)](2) are reported. Et3SiH was used as the hydride source in one route by taking advantage of the silaphilicity of the fluoride ligand in three-coordinate (LFeF)-Fe-tBu. The other synthetic method proceeded through the binuclear oxidative addition of H-2 or D-2 to a putative Fe(I) intermediate. Deuteration was verified through reduction of an alkyne and release of the deuterated alkene product. Mossbauer spectra of [(LFe)-Fe-tBu(mu-H)](2) indicate that the samples are pure, and that the iron(II) centers are high-spin. (C) 2009 Elsevier B.V. All rights reserved.