2-Organoselenomethyl-1H-benzimidazole Complexes of Copper(II) and Copper(I)
Résumé
Abstract. 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•2 MeOH crystallizes in an approximately mixed square-pyramidal/trigonal-bipyramidal structure ( = 0.52) with the second and third row atoms Cl and Se in the equatorial plane, the related [Cu(msbi)2(MeOH)](BF4)2 = [2](BF4)2 exhibits a closer to square-pyramidal arrangement with = 0.36 for that complex dication 22+. In both cases, the Cu-N bonds are short at about 1.94 Å while 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)o, less straightened than the ca. 170o in comparable CuI complexes with thioether-1H-benzimidazole ligands. A copper(I) compound [Cu(psbi)2][Cu(psbi)(psbi-H+)](PF6) = [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)o, 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.
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