A Terminal Iron Nitrilimine Complex: Accessing the Terminal Nitride through Diazo N-N Bond Cleavage

A novel method for the N-N bond cleavage of trimethylsilyl diazomethane is reported for the synthesis of terminal nitride complexes. The lithium salt of trimethylsilyl diazomethane was used to generate a rare terminal nitrilimine transition metal complex with partially occupied d-orbitals. This iron complex 2 was characterized by CHN combustion analysis, ¹ H and ¹³ C NMR spectroscopic analysis, single-crystal X-ray crystallography, SQUID magnetometry, ⁵⁷ Fe Mössbauer spectroscopy, and computational analysis. The combined results suggest a high-spin d ⁶ (S=2) electronic configuration and an allenic structure of the nitrilimine ligand. Reduction of 2 results in release of the nitrilimine ligand and formation of the iron(I) complex 3, which was characterized by CHN combustion analysis, ¹ H NMR spectroscopic analysis, and single-crystal X-ray crystallography. Treatment of 2 with fluoride salts quantitatively yields the diamagnetic Fe^IV nitride complex 4, with concomitant formation of cyanide and trimethylsilyl fluoride through N-N bond cleavage.