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Crucial Role of Cu-S Bonding for Structural Changes Accompanying the Reversible CuI/CuII Transition in an Unrestrained Cu(N$\cap$S)2 Coordination Arrangement. An Experimental and DFT Study

, , , and . Inorganic Chemistry, 39 (21): 4731--4734 (2000)
DOI: 10.1021/ic000021u

Abstract

The structure of reversibly oxidizable [Cu(mmb)2](BF4) with 1-methyl-2-(methylthiomethyl)-1H-benzimidazole (mmb) as bidentate N,S-donor ligand was detd. and compared with that of the copper(II) species [Cu(mmb)2(h1-ClO4)](ClO4). In the complex ions of the equil. [CuI(mmb)2]+ + ClO4- .dblharw. e- + [CuII(mmb)2(h1-ClO4)]+ the almost linear N-Cu-N backbone is invariant whereas the bonds to the thioether sulfur centers and esp. the changing S-Cu-S angle (145.18(5)° for the CuII species, 109.33(3)° for the CuI form) reflect the metal oxidn. state. In contrast to the perchlorate coordinating copper(II) species, [CuI(mmb)2](BF4) contains a cation with a very large vacant site at the metal center, resulting in elliptical channels within the crystal. DFT calcns. on [CuI(mb)2]+, [CuII(mb)2]2+, and [CuII(mb)2(OClO3)]+ with mb = 2-methylthiomethyl-1H-benzimidazole confirm the essential role of the metal-sulfur bonds in responding to the reversible CuI/II electron transfer process, even in the absence of electronically stronger interacting thiolate sulfur centers or sophisticated oligodentate ligands. [on SciFinder(R)]

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