N-Heterocyclic carbene and cyclic (alkyl)(amino)carbene ligated half-sandwich complexes of chromium(II) and chromium(I).

The synthesis and characterization of a series of Cr(II) N-Heterocyclic Carbene (NHC) complexes of the type [{Cr(NHC)Cl(μ-Cl)} 2 ] and [(Cyp)Cr(NHC)X] (Cyp = η 5 -C 5 H 5 , cyclopentadienyl; η 5 -C 5 Me 5 , pentamethylcyclopentadienyl; X = Cl, η 3 -C 3 H 5 ; NHC = IMe Me , IiPr Me , IMes, IDipp) as well as the cyclic (alkyl)(amino)carbene cAAC Me ligated complexes [(η 5 -C 5 H 5 )Cr(cAAC Me )X] (X = Cl, NPh 2 ), [(η 5 -C 9 H 7 )Cr(cAAC Me )Cl] (C 9 H 7 = Ind, indenyl) and [(η 5 -C 13 H 9 )Cr(cAAC Me )Cl] (C 13 H 9 = Fl, fluorenyl) are reported. The reduction of [(η 5 -C 5 Me 5 )Cr(IMe Me )Cl] with KC 8 in the presence of CO afforded the NHC ligated Cr(I) metallo-radical [(η 5 -C 5 Me 5 )Cr(IMe Me )(CO) 2 ]. Quantum chemical calculations performed on [(η 5 -C 5 Me 5 )Cr(IMe Me )(CO) 2 ] confirm for this complex a predominantly chromium centered radical.