Transition-Metal Hydrides as Hydrogen Atom Donors: Stronger Metal−Hydrogen Bonds Can Be Advantageous

O’Connor, J. M.; Friese, Seth J.

doi:10.1021/om800551d

Cited by 19 publications

(8 citation statements)

References 16 publications

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“…The formation of H 2 may result either from an homolytic cleavage of the M-H bonds after reduction [32] or from a heterolytic process consisting in the loss of hydride from the19-electron reduced complex to the parent metal hydride. This route is consistent with the diverse reactivity of metal carbonyl hydrides, for which M-H bonds may break as a proton, a hydrogen atom or a hydride [8,9,[59][60][61][62].…”

Section: Electrochemical Studiessupporting

confidence: 70%

Pentabenzylcyclopentadienyl molybdenum and tungsten hydrides: Syntheses, structures and electrochemistry of [MHCpBz(CO)2(L)] (L=CO, PMe3, PPh3)

Antunes¹,

Namorado²,

Azevedo³

et al. 2010

Journal of Organometallic Chemistry

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Section: Electrochemical Studiessupporting

confidence: 70%

Pentabenzylcyclopentadienyl molybdenum and tungsten hydrides: Syntheses, structures and electrochemistry of [MHCpBz(CO)2(L)] (L=CO, PMe3, PPh3)

Antunes¹,

Namorado²,

Azevedo³

et al. 2010

Journal of Organometallic Chemistry

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“…Combining spin-crossover phenomena with appropriate organic ligands is therefore a compelling strategy for generating switchable diradicals. Merging radical-containing ligands with transition metal centers has been an area of active study. − While several metal-containing organic diradicals have been reported in recent years, these examples are largely limited to transient intermediates or pairs of monoradical ligands. − The viability of spin-crossover modulated diradical character remains untested.…”

Section: Introductionmentioning

confidence: 99%

Reversible Switching of Organic Diradical Character via Iron-Based Spin-Crossover

et al. 2020

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Organic diradicals are uncommon species that have been intensely studied for their unique properties and potential applicability in a diverse range of innovative fields. While there is a growing class of stable and well characterized organic diradicals, there has been recent focus on how diradical character can be controlled or modulated with external stimuli. Here we demonstrate that a diiron complex bridged by the doubly oxidized ligand tetrathiafulvalene-2,3,6,7tetrathiolate (TTFtt 2−) undergoes a thermally induced Fe-centered spin-crossover which yields significant diradical character on TTFtt 2−. UV-vis-Near-IR, Mössbauer, NMR, and EPR spectroscopies with magnetometry, crystallography, and advanced theoretical treatments suggest that this diradical character arises from a shrinking TTFtt 2− π-manifold from the Fe(II)-centered spin-crossover. The TTFtt 2− centered diradical is predicted to have a singlet ground state by theory and variable temperature EPR. This unusual phenomenon demonstrates that inorganic spin transitions can be used to modulate organic diradical character. Results and Discussion Synthesis and Structural Parameters Complex 1 was synthesized via reaction with the deprotected proligand 2,3,6,7-tetrakis(2cyanoethylthio)tetrathiafulvalene (TTFtt(C2H4CN)4) in good yield. Complex 1 was insoluble in all solvents we investigated which precluded detailed characterization but is pure as indicated by combustion analysis and behaves as a suitable synthon for subsequent chemistry. Complex 1 can be doubly oxidized with [Cp2Fe][BAr F 4] to form 2 which is more soluble, enabling common solution characterization including 1 H NMR and cyclic voltammetry measurements (Figure S1-S2). Oxidation from 1 to 2 could be ligandcentered (TTFtt 4− →TTFtt 2−), metal-centered (2 Fe(II)→2 Fe(III)), or some intermediate case, but the data acquired for 2 supports a TTFtt 2− structure arising from ligandcentered oxidation (Chart 1B, see below). Compound 2 was structurally characterized via singlecrystal X-ray diffraction (SXRD) at 293 K (2-HT; Figure S3) and 100 K (2-LT; Figure 1). In both structures TTFtt 2− is bridged between two TPA-capped Fe centers with two outer-sphere BAr F 4 − counter anions. The most striking difference between these temperatures is markedly longer Fe bond lengths in 2-HT. The Fe-Npyridine and Fe-Namine bond lengths in 2-LT are 1.958(6)-1.979(6) and 2.017(6) Å (Figure 1), respectively. These values are consistent with Fe-N bonds in other low-spin complexes with a Fe-TPA moiety. 16,17 In 2-HT, these bonds are 0.18-0.19 and 0.244(11) Å longer than their counterparts at 100 K, respectively, and are consistent with high-spin Fe-TPA complexes. The shorter Fe bonds at lower temperature indicate that 2 exhibits a temperature dependent spincrossover as observed in related compounds. 16,21

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“…Moreover, this mechanism would preferentially lead to an E stereochemistry, which is inconsistent with the observed outcome of terminal alkyne insertions. The present insertions could involve a H atom or hydride transfer 2,4,55 as the initial step, although conclusive evidence for either of these possibilities could not be gathered. Further investigations to elucidate the behaviour of hydrides 3 are underway. )]…”

Section: Alkyne Insertion Reactionsmentioning

confidence: 80%

Visible light driven generation and alkyne insertion reactions of stable bis-cyclometalated Pt(iv) hydrides

et al. 2020

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Transition-Metal Hydrides as Hydrogen Atom Donors: Stronger Metal−Hydrogen Bonds Can Be Advantageous

Cited by 19 publications

References 16 publications

Pentabenzylcyclopentadienyl molybdenum and tungsten hydrides: Syntheses, structures and electrochemistry of [MHCpBz(CO)2(L)] (L=CO, PMe3, PPh3)

Pentabenzylcyclopentadienyl molybdenum and tungsten hydrides: Syntheses, structures and electrochemistry of [MHCpBz(CO)2(L)] (L=CO, PMe3, PPh3)

Reversible Switching of Organic Diradical Character via Iron-Based Spin-Crossover

Visible light driven generation and alkyne insertion reactions of stable bis-cyclometalated Pt(iv) hydrides

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