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RESEARCH PRODUCT

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

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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 A, whereas the Cu–Se distances vary between 2.62 A for 1+ and ca. 2.54 A 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) A, an N–CuI–N angle of 157.5(3)°, a Se···Se interaction at 3.6237(3) A, 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.