An isolated nitridyl radical-bridged {Rh(N·)Rh} complex.

Area of Science:

• Organometallic Chemistry
• Photochemistry
• Radical Chemistry

Background:

• Rhodium complexes with bipyridine ligands are crucial in catalysis.
• Azido ligands can undergo photochemical transformations, leading to reactive intermediates.
• Understanding radical species in organometallic chemistry is key to reaction mechanisms.

Purpose of the Study:

• To investigate the photochemical activation of a rhodium azide complex.
• To characterize the resulting paramagnetic species and determine its electronic structure.
• To explore the reactivity of the photogenerated radical complex with small molecules like carbon monoxide.

Main Methods:

• Photochemical activation of [(PNNH)Rh(N3)] complex 2.
• Crystallographic characterization of the photoproduct, complex 3.
• Spectroscopic investigation (e.g., EPR) and computational studies to confirm radical character.
• Reaction of complex 3 with carbon monoxide (CO).

Main Results:

• Photochemical activation produced a paramagnetic, nitridyl radical complex [(PNN)Rh=N(·)-Rh(PNN)] (3).
• Complex 3 was successfully characterized crystallographically, revealing its unique structure.
• Spectroscopic and computational data confirmed the predominant nitridyl radical character ((·)N(2-)).
• Complex 3 reacted selectively with CO to yield two equivalents of [(PNN)Rh(I)(CO)] (4).

Conclusions:

• Photochemical activation of rhodium azido complexes can generate stable nitridyl radical species.
• The characterized nitridyl radical complex exhibits unique reactivity, particularly with CO.
• The reaction with CO likely proceeds via a nitridyl radical N,N-coupling mechanism.