Synthesis of Dinuclear Mo-Fe Hydride Complexes and Catalytic Silylation of N.

Two transition-metal atoms bridged by hydrides may represent a useful structural motif for N activation by molecular complexes and the enzyme active site. In this study, dinuclear Mo -Fe complexes with bridging hydrides, Cp Mo(PMe )(H)(μ-H) FeCp* (2 a; Cp =Cp*=C Me , 2 b; Cp =C Me H), were synthesized via deprotonation of Cp Mo(PMe )H (1 a; Cp =Cp*, 1 b; Cp =C Me H) by CpFeN(SiMe ) , and they were characterized by spectroscopy and crystallography. These Mo-Fe complexes reveal the shortest Mo-Fe distances ever reported (2.4005(3) Å for 2 a and 2.3952(3) Å for 2 b), and the Mo-Fe interactions were analyzed by computational studies. Removal of the terminal Mo-H hydride in 2 a-2 b by [Ph C] in THF led to the formation of cationic THF adducts [Cp Mo(PMe )(THF)(μ-H) FeCp] (3 a; Cp =Cp*, 3 b; Cp =C Me H). Further reaction of 3 a with LiPPh gave rise to a phosphido-bridged complex CpMo(PMe )(μ-H)(μ-PPh )FeCp (4). A series of Mo-Fe complexes were subjected to catalytic silylation of N in the presence of Na and Me SiCl, furnishing up to 129±20 equiv of N(SiMe ) per molecule of 2 b. Mechanism of the catalytic cycle was analyzed by DFT calculations.