Rare proximity enforced copper hydrogen interactions in copper(i)-chalcogenones

Abstract

Copper(I) chalcogenones with rare Cu⋯H–C(sp³) hydrogen bonding interactions have been reported. The copper(I) bis(benzimidazole-2-chalcogenone) complexes [Cu(L¹)₄]⁺BF₄⁻ (1) and [Cu(L²)₄]⁺BF₄⁻ (2) (L¹ = bis(1-isopropyl-benzimidazole-2-selone)-3-ethyl; L² = bis(1-isopropyl-benzimidazole-2-thione)-3-ethyl) have been synthesized and characterized. Both complexes possess distorted tetrahedral geometry with a semi-trans arrangement of the benzimidazole-chalcogenone ligands around the Cu(I) center. The structures of 1 and 2 reveal homoleptic coordination with the Cu(I) center with the (sp³)C–H groups of the ethylene linker directed towards the Cu(I) center to maximize the rare proximity-enforced intramolecular Cu⋯H–C interactions. The Cu⋯H–C interactions are found to have a hydrogen bonding nature in the crystalline state, as these interactions are absent in the solution state.