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

Three novel iron dinitrogen hydrides, [FeH(iPr-PSiMeP)(N2)(PMe3)] (1), [FeH(iPr-PSiPhP)(N2)(PMe3)] (2), and [FeH(iPr-PSiPh)(N2)(PMe3)] (3), supported by silyl ligand are synthesized for the first time by changing the electronic effect and steric hindrance of the ligands through the reaction of ligand L1 - L3 with Fe(PMe3)4 in a nitrogen atmosphere. The ligands containing electro-donating group with large steric hindrance on the phosphorus atom are beneficial for formation of the dinitrogen complexes. A penta-coordinate iron hydride [FeH(iPr-PSiPh)(PMe3)2] (4) was formed through the reaction of ligand L3 with Fe(PMe3)4 in a argon atmosphere under the same conditions. The reactions between complex 1 - 3 with an atmospheric pressure of dihydrogen gas resulted in the Fe(II) dihydrides, [(iPr-PSiMe(μ-H)P)Fe(H)2(PMe3)] (5), [(iPr-PSiPh(μ-H)P)Fe(H)2(PMe3)] (6) and [(iPr-PSiPh(μ-H))Fe(H)2(PMe3)2] (7), with an η2-(Si−H) coordination. The isolation of dihydrides 5 - 7 demonstrates 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 silylation of dinitrogen under ambient conditions and among them 3 is the best catalyst.