Titanium Dinitrogen Complex Catalyzed Hydrophosphination Leveraging the N ₂ ‐Unit Electron Reservoir

Abstract

ABSTRACT Metal dinitrogen complexes, a prominent class of compounds in the mimic of Haber–Bosch NH 3 manufacture, have been prevalently adopted for N 2 functionalization to form N‐X (X = H, C, Si, etc.) bonds through the stoichiometric reactions with acids and electrophilic reagents. The discovery of alternative application of these complexes beyond aforementioned N 2 functionalization is highly desirable but remains elusive. In this work, we demonstrated that a titanium dinitrogen complex exhibits catalytic potential in the hydrophosphination of alkenes with an outstanding substrate compatibility and a turnover number of 743 was achieved. Mechanistic studies showed that the end‐on bridging dinitrogen unit (N 2 ‐unit) of the Ti III complex could be replaced with diphenylphosphine to form a catalytically active Ti II species, with the concurrent extrusion of a free N 2 molecule that was probed by 15 N NMR spectroscopy. Thus, each N 2 ‐unit virtually serves as an electron reservoir providing electrons to metal centers to give catalytically active low‐valent metal species. This reaction represents a rare example of adopting a metal dinitrogen complex as a precatalyst in organic transformations and the introduction of N 2 ‐unit electron reservoir (NER) concept provides a novel and effective strategy for the invoking of low‐valent metal species for catalytic applications.