Reactivity of a low-valent chromium dinitrogen complex

(NniPrCr)2(μ2-κ2:κ2-N2) (1, NniPr = bis(2,6-diisopropylphenyl)pentane-2,4-ketiminato), formally a chromium(I) complex, was exposed to a variety of small molecules possessing hetero- or homo-atomic single, double, or triple bonds. Reaction of 1 with adamantyl azide yielded complexes in various higher oxidation states, such as (NniPrCrII)2(μ2-NAd) (2), NniPrCrIII(κ2-N4Ad2) (3), or NniPrCrV(NAd)2 (4). Compound 1 was found to reductively couple 3-pentanone to form NniPrCr(κ2-O2C2Et4) (5) and reductively couple benzylidene aniline to form both NniPrCrIII(cis-κ2-C28H22N2) (6a) an NniPrCrIII(trans-κ2-C28H22N2) (6b). Reaction with a stochiometric amount of benzylidene aniline yielded the imine complex NniPrCr(η2-NPhCHPh) (7). Exposure of 1 to a bulky isocyanide formed the octahedral NniPrCrI[CN(C6H4(Me)2]4 (9). Complex 1 was also found to break the O–O, NO, and S–S bonds in various small molecules to form NniPrCrII(OCMe3) (11), NniPrCrV(O)(NPh) (8), and [NniPrCrII(μ-SPh)]2 (10).

The chromium dinitrogen complex (Nn−iPrCr)2(μ2-κ2:κ2-N2) is a readily accessible Cr(I) synthon. Its substitutional lability and great reducing power facilitate the binding and activation of a wide range of organic molecules.Figure optionsDownload as PowerPoint slideResearch highlights
► A dinuclear Cr(I) dinitrogen complex (1) is a reactive low-valent chromium synthon.
► Compound 1 couples ketones and imines.
► Compound 1 cleaves single and multiple heteroatom bonds.