ABSTRACT
Herein, the synthesis and characterization of bicyclic (alkyl)(amino)carbene (BICAAC)-stabilized phosphinidenes (1-4) are reported. Compounds 1-3 were obtained by reacting trihalophosphine [PX3, X = Cl (1), Br (2), I (3)] with BICAAC in THF. A BICAAC-stabilized bis-phosphinidene (4) was obtained from the reduction of compound 2. All four compounds were characterized by X-ray crystallography and heteronuclear NMR spectroscopy. Theoretical calculations indicated the predominant C(carbene)îP double bond characteristic in compounds 1-4.
ABSTRACT
Examples of air- and water-stable main-group radicals are scarce in the literature due to the higher reactivity of radical compounds as well as several synthetic challenges. Herein, we report two stable structurally characterized glyoxal radical cations (1Ë+ and 2Ë+) stabilized by cyclic(alkyl)(amino)carbene (CAAC) and bicyclic (alkyl)(amino)carbene (BICAAC), respectively. Both 1Ë+ and 2Ë+ are stable under harsh conditions such as strong acids, bases, mild oxidizing agents, and reducing agents, as well as towards bovine serum. Radical (2Ë+) represents the first isolated radical stabilized by a BICAAC ligand.
ABSTRACT
The synthesis and characterization of isolable radicals of main-group elements have been a long-pursued quest. Although there has been considerable progress in this area, particularly in isolating carbon radicals, the isolation of radicals comprising heavier p-block elements is still scarce. Among heavier p-block elements, the radical chemistry involving silicon and phosphorus is explored considerably. This review focuses on isolable phosphorus-centered radicals. Most of the compounds described here have been characterized by single-crystal X-ray analysis and EPR spectroscopy. The cyclic voltammetry study revealed interesting redox chemistry for many of these compounds. Here, we described the synthesis and properties of the radicals and radical ions comprising the phosphorus center.
