Harnessing Chromium(V) Hydrazido Intermediates for N<sub>2</sub> Functionalization to Multisubstituted Hydrazines through Ligand Migration
Xueli Wang, Yue Wu, Yixi Wang, Rong Sun, Junnian Wei, Zhenfeng Xi
Abstract
The direct conversion of N 2 into N-containing organic compounds remains a fundamental challenge in synthetic chemistry. Here, we report a high-valent chromium(V)-mediated strategy for synthesizing multisubstituted hydrazine derivatives via ligand migration, representing ligand migration to N α in a Cr-hydrazido complex. Our approach begins with the oxidation of chromium(IV) hydrazido precursor 1 by benzyl bromide, which replaces the 1,2-bis(diethylphosphino)ethane (depe) ligand with two bromide ions to generate the high-valent chromium(V) dibromide hydrazido complex 2 . Sequential ligand metathesis of 2 with aryl Grignard reagents (ArMgBr, Ar = biphenyl, p -methylphenyl, o -methoxyphenyl), alkenyl or alkyl Grignard reagents (1-phenylvinylmagnesium bromide and isopropylmagnesium bromide), followed by ligand migration from the Cr center to the N α atom and electrophilic trapping (MeOH, PhCH 2 Br), affords structurally diverse hydrazines ( 4a–c, 5a–c, and 6 ). Single-crystal X-ray crystallography, in situ UV–vis spectroscopy, and DFT calculations collectively reveal a ligand migration mechanism in chromium chemistry, directly forging N–C bonds from N 2 without ammonia intermediates. This migration not only constructs new N–C bonds but also enables the direct construction of complex hydrazine structures directly from N 2 .