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Bent Phosphaallenes With "Hidden" Lone Pairs as Ligands
Xiaodan Chen1, Zhongshu Li2,3, Gernot Frenking4,5
1College of Chemistry and Materials Science, Jinan University, 510632, Guangzhou, P. R. China.
Chemistry (Weinheim an Der Bergstrasse, Germany)
|March 31, 2019
Summary
Phosphaheteroallenes, a novel class of phosphorus compounds, act as ligands for coinage metals. These molecules exhibit unique carbene-like reactivity due to a hidden electron pair at their central carbon atom.
Area of Science:
- Organophosphorus chemistry
- Coordination chemistry
- Computational chemistry
Background:
- Phosphaheteroallenes (R-P=C=L) featuring N-heterocyclic carbenes (NHCs) can be conceptualized as NHC-stabilized phosphaisonitriles (R-P=C:←L).
- Their potential as ligands in coordination chemistry remains largely unexplored.
Purpose of the Study:
- To investigate the coordination behavior of phosphaheteroallenes with NHC ligands towards coinage metal ions.
- To explore the electronic structure and reactivity of these unique phosphorus compounds.
Main Methods:
- Synthesis and characterization of phosphaheteroallenes.
- Coordination experiments with coinage metal ions (e.g., gold, silver, copper).
- Spectroscopic analyses (NMR, IR, X-ray crystallography).
- Density Functional Theory (DFT) calculations.
Main Results:
- Phosphaheteroallenes effectively coordinate to coinage metal centers, primarily through the central carbon atom.
- Experimental and computational data reveal a formally "hidden" electron lone pair at the central carbon.
- Evidence of intramolecular C-H bond insertion by this lone pair, demonstrating carbene-type reactivity.
Conclusions:
- Phosphaheteroallenes are versatile ligands for coinage metals, coordinating via the central carbon.
- The presence of a reactive lone pair on the central carbon atom imparts carbene-like behavior.
- These findings expand the scope of organophosphorus chemistry and ligand design.