Homoleptic mono-, di-, and tetra-iron complexes featuring phosphido ligands: a synthetic, structural, and spectroscopic study

摘要

We report the first series of homoleptic phosphido iron complexes synthesized by treating either the beta-diketiminato complex [(Dippnacnac)FeCl2Li(dme)(2)] (Dippnacnac = HC[(CMe)N(C6H3-2,6-iPr(2))](2)) or [FeBr2(thf)(2)] with an excess of phosphides R2PLi (R = tBu,tBuPh, Cy, iPr). Reaction outcomes depend strongly on the bulkiness of the phosphido ligands. The use oftBu(2)PLi precursor led to an anionic diiron complex 1 encompassing a planar Fe(2)P(2)core with two bridging and two terminal phosphido ligands. An analogous reaction employing less sterically demanding phosphides,tBuPhPLi and Cy2PLi yielded diiron anionic complexes 2 and 3, respectively, featuring a short Fe-Fe interaction supported by three bridging phosphido groups and one additional terminal R(2)P(-)ligand at each iron center. Further tuning of the P-substrates bulkiness gave a neutral phosphido complex 4 possessing a tetrahedral Fe-4 cluster core held together by six bridging iPr(2)P moieties. Moreover, we also describe the first homoleptic phosphanylphosphido iron complex5, which features an iron center with low coordination provided by three tBu(2)P-P(SiMe3)(-) ligands. The structures of compounds1-5were determined by single-crystal X-ray diffraction and 1-3 by H-1 NMR spectroscopy. Moreover, the electronic structures of1-3were interrogated using zero-field Mossbauer spectroscopy and DFT methods.