Cr(I)Cl as well as Cr+ are stabilised between two cyclic alkyl amino carbenes

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Chemical Science, 6 (5): 3148--3153 (2015)
DOI: 10.1039/C5SC00646E


Cr(I)Cl is a very unstable species. The present work describes the stabilization of Cr(I)Cl in the low coordinate environment of cyclic alkyl(amino) carbene ligands and its synthetic application to yield an unprecedented cationic complex with a two coordinate Cr(I). One electron redn. of (cAAC)2CrCl2 (1) with equiv. amt. of KC8 results in the formation of (cAAC)2CrCl (2), with a distorted trigonal planar configuration at the metal center. SQUID, EPR and theor. studies reveal a Cr(I) center with S = 5/2 spin ground state for 2. It represents the first example of a mononuclear Cr complex showing slow relaxation of magnetization under an applied magnetic field. The chlorine atom in 2 is expected to be prone to further reactions with appropriate reagents. This qualifies 2 as a promising precursor for the prepn. of various interesting complexes with Cr(I) in a low coordinate environment. The first example of this metathesis reaction is obsd. when 2 is treated with NaB(C6H3(CF3)2)4 resulting in (cAAC)2Cr+B(C6H3(CF3)2)4-, a linear cationic complex with two coordinate Cr(I) and an S = 5/2 spin ground state. on SciFinder(R)



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