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)2ClCl·2MeOH crystallizes in an approx. mixed square-pyramidal/trigonal-bipyramidal structure (t = 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 t = 0.36 for that complex dication 22+. In both cases, the Cu-N bonds are short at about 1.94 \AA, whereas the Cu-Se distances vary between 2.62 \AA for 1+ and ca. 2.54 \AA 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 anal. could not be obtained, the related 1-methyl-2-phenylselenomethyl-1H-benzimidazole (mpsbi) was prepd. 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) compd. Cu(psbi)2Cu(psbi)(psbi-H+)(PF6), 44'(PF6), with another related ligand, 2-phenylselenomethyl-1H-benzimidazole (psbi), was crystd. in partially benzimidazole-deprotonated acetonitrile solvate form, showing short Cu-N bonds of 1.898(5) \AA, an N-CuI-N angle of 157.5(3)°, a Se···Se interaction at 3.6237(3) \AA, 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. on SciFinder(R)
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