Non-innocent Ligand - Redox Non-Innocent Ligands in Organometallic Chemistry and Catalysis

Redox Non-Innocent Ligands in Organometallic Chemistry and Catalysis

In paramagnetic organometallic complexes of Rh and Ir (metallo-radicals), ethene ligands, amido ligands, and (reactive) carbene ligands are sometimes also behaving as 'redox non-innocent' ligands:

• Solvent coordination to some metallo-radical IrII(ethene) species transfers the spin-density from the metal to the redox non-innocent ethene ligand, after which direct radical coupling reactions with the olefinic ligand radical become possible.

• Oxidation of certain RhI-amido and IrI-amido complexes does not lead to the expected MII-amido species. Instead the unexpected MI-aminyl radical complexes are formed.

• Carbene formation from diazo compounds at metallo-radical IrII species unexpectedly leads to formation of 'carbene radicals'. This is a result of the redox non-innocent character of Fischer-type carbenes, where one-electron reduction of the carbene ligand by IrII leads to formation of carbon centered 'carbene radicals' coordinated to IrIII. These 'carbene radicals' reveal interesting radical-type reactivities.

• The application of redox non-innocent ligands in homogeneous catalysis was recently reviewed.