סמינר בכימיה אורגנית: Nitrene and Carbene Chemistry at Middle and Late Metals in Bis(alkoxide) Ligand Environments

Prof. Stanislav Groysman, Department of Chemistry, Wayne State University, USA

23 ביוני 2024, 16:00 
בניין שנקר, אולם מלמד 006 
סמינר בכימיה אורגנית

 

Abstract:

Our research focuses on the design of first-row transition metal complexes in weak-field alkoxide ligand environments for C-N, N-N, and C-C bond formation. We prepared a series of mononuclear middle and late metal complexes featuring bulky bis(alkoxide) ligation M(OR)2(THF)2 (OR = OCtBu2Ph, OCtBu2(3,5-Ph2Ph);  M = Cr-Co) and are currently investigating their reactivity in nitrene and carbene transfer. Related complexes with chelating bis(alkoxide)  ligands are also being studied. The iron(II) complex Fe(OR)2(THF)2 undergoes facile reaction with aliphatic and aromatic azides. Treatment of Fe(OR)2(THF)2 with aliphatic azides leads to the reductive coupling of azides to form iron(III) hexazene complex (RO)2Fe(μ-κ2:κ2-RNNNNNNR)Fe(OR)2. In contrast, the reaction of Fe(OR)2(THF)2 with aromatic azides (ArN3) results in the catalytic formation of azoarenes ArNNAr, with concomitant liberation of dinitrogen. Mechanistic studies demonstrate that the reaction proceeds via reactive metal-nitrene and metal-tetrazene intermediates [Fe(OR)2(NAr)] and [Fe(OR)2(N(Ar)NNNAr)], respectively. The reaction of Co(OR)2(THF)2 with diphenyldiazomethane produces high-valent Co(OR)2(=CPh2), which undergoes carbene transfer to isocyanides to yield ketenimines. The reaction of Fe(OR)2(THF)2 with diazoalkanes or diazoesters results in rare reductive coupling through the terminal nitrogens to yield tetrazene-bridged dinucleating ligands. In contrast, the reaction of Fe(OR)2(THF)2 with iodonium ylides forms a reactive metal-carbene that undergoes efficient cyclopropanation. Spectroscopic, theoretical, and reactivity studies will be presented. 

 

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