A Linear Two‐Coordinate Cr(II) Complex: Synthesis, Characterization, and Reactivity

Abstract

The synthesis and characterization of a linear two‐coordinate Cr(II) amido complex, Cr{N(tBu)Dipp}2 (Dipp = 2,6‐diisopropylphenyl), from the reaction of 1 molar equivalent (equiv) of CrCl2 and 2 equiv of LiN(tBu)Dipp is reported. Single‐crystal X‐ray diffractometry (SC‐XRD) analysis revealed that it has a short Cr−N bond distance of 1.8878(9) Å, which could be attributed to the relatively less bulky nature of the amido ligand compared with reported systems. Furthermore, the oxidation reaction of the two‐coordinate Cr(II) complex was explored. The oxidation reaction of Cr{N(tBu)Dipp}2 with the one‐electron oxidants AgOTf and [FeCp2][BArF4] (BArF4− = [B{C6H3‐3,5‐(CF3)2}4]−) afforded the trigonal planar three‐ and bent two‐coordinate Cr(III) complexes Cr{N(tBu)Dipp}2(OTf) and [Cr{N(tBu)Dipp}2][BArF4], respectively. The reaction of Cr{N(tBu)Dipp}2 with 1 equiv of the organic azides AdN3 (Ad = 1‐adamantyl) and PhN3 afforded the three‐coordinate Cr(IV) imido complexes Cr{N(tBu)Dipp}2(NAd) and Cr{N(tBu)Dipp}2(NPh), respectively. The reaction of Cr{N(tBu)Dipp}2 and two equiv of Me3NO afforded the Cr(VI) dioxo complex Cr{N(tBu)Dipp}2(O)2. The reaction of Cr{N(tBu)Dipp}2 with 1 equiv of CyN=C=NCy resulted in the insertion of the carbodiimide into the Cr−N bond, with the formation of a three‐coordinate Cr(II) complex. Finally, density functional theory (DFT) calculations were used to elucidate the electronic structure of these complexes.