Synthesis of silyl iron dinitrogen complexes for activation of dihydrogen and catalytic silylation of dinitrogen.

Three novel iron dinitrogen hydrides, [FeH(Pr-PSiP)(N)(PMe)] (1), [FeH(Pr-PSiP)(N)(PMe)] (2), and [FeH(Pr-PSi)(N)(PMe)] (3), supported by a silyl ligand are synthesized for the first time by changing the electronic effect and steric hindrance of the ligands through the reaction of ligands L1-L3 with Fe(PMe) in a nitrogen atmosphere. The ligands containing an electron-donating group with large steric hindrance on the phosphorus atom are beneficial for the formation of dinitrogen complexes. A penta-coordinate iron hydride [FeH(Pr-PSi)(PMe)] (4) was formed through the reaction of ligand L3 with Fe(PMe) in an argon atmosphere under the same conditions. The reactions between complexes 1-3 with an atmospheric pressure of dihydrogen gas resulted in Fe(II) dihydrides, [(Pr-PSi(μ-H)P)Fe(H)(PMe)] (5), [(Pr-PSi(μ-H)P)Fe(H)(PMe)] (6) and [(iPr-PSi(μ-H))Fe(H)(PMe)] (7), with an η-(Si-H) coordination. The isolation of dihydrides 5-7 demonstrates the ability of the dinitrogen complexes 1-3 to realize the activation of dihydrogen under ambient temperature and pressure. The molecular structures of complexes 1-7 were elucidated by single crystal X-ray diffraction analysis. The iron dinitrogen hydrides 1-3 are effective catalysts for the silylation of dinitrogen under ambient conditions and among them 3 is the best catalyst.