2-Organoselenomethyl-1H-benzimidazole Complexes of Copper(II) and Copper(I)

Structurally characterized 2‐methylselenomethyl‐1H‐benzimidazole (msbi) is shown to form complexes in 2:1 ratio with copper(II). Whereas the central cation [Cu(msbi)2Cl]+ = 1+ in [Cu(msbi)2Cl]Cl·2MeOH crystallizes in an approximately mixed square‐pyramidal/trigonal‐bipyramidal structure (τ = 0.52) with the second and third row atoms chlorine and selenium in the equatorial plane, the related [Cu(msbi)2(MeOH)](BF4)2 = [2](BF4)2 exhibits a closer to square‐pyramidal arrangement with τ = 0.36 for that complex dication 22+. In both cases, the Cu–N bonds are short at about 1.94 Å, whereas the Cu–Se distances vary between 2.62 Å for 1+ and ca. 2.54 Å for 22+. Slight differences between the Jahn–Teller influenced species 1+ and 22+ are also apparent from absorption and EPR spectra. Since copper(I) complexes of msbi suitable for crystal structure analysis could not be obtained, the related 1‐methyl‐2‐phenylselenomethyl‐1H‐benzimidazole (mpsbi) was prepared and used to obtain [Cu(mpsbi)2](X) = [3](X) (X = BF4 or PF6). The copper(I) ion in the corresponding cation 3+ shows a DFT‐reproduced distorted tetrahedral configuration with an N–CuI–N angle at 146.7(3)°, less straightened than the ca. 170° in similar CuI complexes with thioether‐1H‐benzimidazole ligands. A copper(I) compound [Cu(psbi)2][Cu(psbi)(psbi‐H+)](PF6) = [4][4′](PF6) with another related ligand, 2‐phenylselenomethyl‐1H‐benzimidazole (psbi), was crystallized in partially benzimidazole‐deprotonated acetonitrile solvate form, showing short Cu–N bonds of 1.898(5) Å, an N–CuI–N angle of 157.5(3)°, a Se···Se interaction at 3.6237(3) Å, and a very small Se–Cu–Se angle of 78.23(4)°. The different responses resulting from thioether and selenoether coordination to copper in the complexes at hand are being discussed.