The Electron Transfer Series [Mo^III(bpy)₃]ⁿ (n=3+, 2+, 1+, 0, 1−), and the Dinuclear Species [{Mo^IIICl(^Mebpy)₂}₂(μ₂‐O)]Cl₂ and [{Mo^IV(tpy^.)₂}₂(μ₂‐MoO₄)](PF₆)₂⋅4 MeCN

Abstract

The electronic structures of the five members of the electron transfer series [Mo(bpy)3](n) (n = 3+, 2+, 1+, 0, 1-) are determined through a combination of techniques: electro- and magnetochemistry, UV/Vis and EPR spectroscopies, and X-ray crystallography. The mono- and dication are prepared and isolated as PF6 salts for the first time. It is shown that all species contain a central Mo(III) ion (4d(3)). The successive one-electron reductions/oxidations within the series are all ligand-based, involving neutral (bpy(0)), the π-radical anion (bpy·)(1-), and the diamagnetic dianion (bpy(2-))(2-): [Mo(III)(bpy(0))3](3+) (S = 3/2), [Mo(III)(bpy·)(bpy(0))2](2+) (S = 1), [Mo(III)(bpy·)2(bpy(0))](1+) (S = 1/2), [Mo(III)(bpy·)3] (S = 0), and [Mo(III)(bpy·)2(bpy(2-))](1-) (S = 1/2). The previously described diamagnetic dication "[Mo(II)(bpy(0))3](BF4)2" is proposed to be a diamagnetic dinuclear species [{Mo(bpy)3}2(μ2-O)](BF4)4. Two new polynuclear complexes are prepared and structurally characterized: [{Mo(III)Cl((Me)bpy(0))2}2(μ2-O)]Cl2 and [{Mo(IV)(tpy·)2}2(μ2-Mo(VI)O4)](PF6)2⋅4 MeCN.

Structure of Electronically Reduced N-Donor Bidentate Ligands and Their Heteroleptic Four-Coordinate Zinc Complexes: A Survey of Density Functional Theory Results

“…35 This structural signature, which has also been studied in other non-innocent ligands such as substituted bipyridine, [37][38][39] phenanthroline, 40 terpyridine, 38,39,41 pyridine-2,6-diimine 40 or quinones 42 is a good indicator of both the electronic population of the coordinated ligands and the electronic structure of the complexes. [43][44][45][46][47] If high resolution X-ray crystallographic structures can be obtained, accurate bond lengths and the way in which they change upon varying the oxidation level can allow the redox state of the ligands in their coordination complexes to be determined unambiguously. Alternatively, a good correlation has been recently established between the 13 C NMR chemical shifts and the relevant bond lengths in non-innocent ligands at different levels of reduction.…”

Structure of Electronically Reduced N-Donor Bidentate Ligands and Their Heteroleptic Four-Coordinate Zinc Complexes: A Survey of DFT Results

“…35 This structural signature, which has also been studied in other non-innocent ligands such as substituted bipyridine, [37][38][39] phenanthroline, 40 terpyridine 38,39,41,42 or pyridine-2,6-diimine, 40 is a good indicator of both the electronic population of these coordinated ligands and of the electronic structure of the complexes. [43][44][45][46][47] High resolution X-ray crystallography structures are required to obtain accurate bond lengths as well as their change upon varying oxidation level, and these can allow the redox state of the ligands in their coordination complexes to be determined unambiguously. Alternatively, a good correlation has been recently established between the 13 C NMR chemical shifts and the relevant bond lengths in non-innocent ligands at various reduction levels.…”