Electronic and Spin-State Effects on Dinitrogen Splitting to Nitrides in a Rhenium Pincer System

Weber, Jeremy E.; Hasanayn, Faraj; Fataftah, Majed S.; Mercado, Brandon Q.; Crabtree, Robert H.; Holland, Patrick L.

doi:10.1021/acs.inorgchem.0c03778

Cited by 16 publications

(14 citation statements)

References 47 publications

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“…Our group has developed a highly reducing rhenium(I) metalate, Na[Re(η 5 -Cp)(BDI)] (Cp = cyclopentadienide, BDI = N , N ′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate), capable of reversibly binding dinitrogen in solution at low temperatures, with the Na + counterion playing a crucial role in the binding and activation process. , Although there is some precedent for dinitrogen functionalization by rhenium complexes, both in monometallic complexes , and via the splitting of dinitrogen by homobimetallic species, ,− we were interested in the unexplored frontier of heterobimetallic dinitrogen functionalization. Through salt elimination reactions between the above-mentioned Na[Re(η 5 -Cp)(BDI)] with either iridium(I) or rhodium(I) reagents, we report the synthesis, characterization, and initial N–C bond formation reactivity of Re-group 9 heterobimetallic dinitrogen species.…”

Section: Introductionmentioning

confidence: 99%

Heterobimetallic-Mediated Dinitrogen Functionalization: N–C Bond Formation at Rhenium-Group 9 Diazenido Complexes

et al. 2022

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We report the synthesis and characterization of rhenium-group 9 heterobimetallic diazenido species (η5-Cp)Re(μ-BDI)(μ-N2)M(η4-COD) (1-M, M = Ir or Rh, Cp = cyclopentadienide, BDI = N,N′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate, COD = 1,5-cyclooctadiene), formed from salt elimination reactions between Na[(η5-Cp)Re(BDI)] and [MCl(η4-COD)]2. Additionally, we find that these same reagents react under an argon atmosphere to instead produce bridging hydride complexes (BDI)Re(μ-η5:η1-C5H4)(μ-H)M(η4-COD) (2-M), which undergo rearrangements upon protonation to form the alternative bridging hydrides [(η5-Cp)Re(μ-BDI)(μ-H)M(η4-COD)][(B(m-C6H3(CF3)2)4)] (3-M). Further, we demonstrate the first example of N–C bond formation at a heterobimetallic dinitrogen complex through reactions of 1-M and methyl triflate, which produces the alkylated species [(η5-Cp)Re(μ-N(Me)N)(μ-BDI)M(η4-COD)][OTf] (4-M, OTf = trifluoromethanesulfonate). A combination of spectroscopic studies, X-ray structural analysis, and computational investigations is discussed as an aid to understanding the modes of dinitrogen activation within these unique heterobimetallic complexes.

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Section: Introductionmentioning

confidence: 99%

Heterobimetallic-Mediated Dinitrogen Functionalization: N–C Bond Formation at Rhenium-Group 9 Diazenido Complexes

et al. 2022

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“…Monometallic rhenium(III) coordination complexes have a variety of applications, including acting as structural models for radiopharmaceutical development, − utility in studying the electronic, magnetic, and photophysical properties of new or exotic ligands, − and the binding and functionalization of dinitrogen. − Within this subset of compounds, numerous octahedral or pseudo-octahedral rhenium(III) complexes have displayed substantial temperature-independent paramagnetism (TIP). ,,,− TIP is a physical phenomenon in which the magnetic susceptibility of a compound does not arise strictly from electron spins of a magnetic ground state according to Curie law but is instead caused by the coupling of an isolated ground state with thermally inaccessible low-lying magnetic excited states through a Zeeman perturbation . Many inorganic complexes exhibit negligible TIP effects; however, metal centers that possess large spin–orbit coupling (SOC), such as rhenium, may enable the presence of low-lying excited states available for effective Zeeman coupling and thus lead to TIP effects worthy of further study .…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic, Magnetic, and Computational Investigations on a Series of Rhenium(III) Cyclopentadienide β-diketiminate Halide and Pseudohalide Complexes

et al. 2021

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The low-valent rhenium(I) salt Na[Re(η5-Cp)(BDI)] (BDI = N,N′-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate) was shown to react with various halide and chalcogenolate reagents, leading to the isolation of a series of rhenium(III)–halide and −pseudohalide complexes: Re(X)(η5-Cp)(BDI) (1-X, X = F, Cl, Br, I; 2, X = OTf) and Re(ER)(η5-Cp)(BDI) (3-ER, ER = SBn, SeBn, TePh). The 1H NMR spectra of these complexes displayed sharp resonances shifted several ppm from typical diamagnetic regions, as well as distinct chemical shift trends down both the halide (with the exception of F) and chalcogenolate series, with both Cp and BDI backbone peaks moving downfield with increasing atomic number. Subsequent magnetic susceptibility measurements of the rhenium(III) halides 1-Cl, 1-Br, and 1-I indicated that these complexes display temperature-independent paramagnetism (TIP), with χTIP values of 7.41(44) × 10–4 to 1.50(51) × 10–3 cm3 mol–1. Multireference complete active space self-consistent field (CASSCF) computations incorporating spin–orbit state mixing revealed small energy separations (1.7–3.0 kcal/mol) between thermally isolated ground states and the first excited spin–orbit states for the rhenium halides, confirming that low-lying excited states are responsible for the observed TIP behavior.

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“…14 Despite the lower ΔBO tot π , the computed energy of the quintet spin state of [1-W] 2 (μ-N 2 ) is only 8.5 kcal/mol higher than the closed shell singlet, suggesting similar energies associated with pairing two in or promoting two electrons to π u *. Indeed, examples of d 4 −d 4 μ-N 2 complexes with open-shell ground states are known, 95,96 and a spin-state change had been proposed to initiate N 2 splitting. 95 The model can therefore be valuable to predict differences in properties or reactivities as a function of spin state.…”

Section: ■ High Spin Complexesmentioning

confidence: 99%

Lewis Structures and the Bonding Classification of End-on Bridging Dinitrogen Transition Metal Complexes

et al. 2023

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The activation of dinitrogen by coordination to transition metal ions is a widely used and promising approach to the utilization of Earth’s most abundant nitrogen source for chemical synthesis. End-on bridging N2 complexes (μ-η1:η1-N2) are key species in nitrogen fixation chemistry, but a lack of consensus on the seemingly simple task of assigning a Lewis structure for such complexes has prevented application of valence electron counting and other tools for understanding and predicting reactivity trends. The Lewis structures of bridging N2 complexes have traditionally been determined by comparing the experimentally observed NN distance to the bond lengths of free N2, diazene, and hydrazine. We introduce an alternative approach here and argue that the Lewis structure should be assigned based on the total π-bond order in the MNNM core (number of π-bonds), which derives from the character (bonding or antibonding) and occupancy of the delocalized π-symmetry molecular orbitals (π-MOs) in MNNM. To illustrate this approach, the complexes cis,cis-[(iPr4PONOP)MCl2]2(μ-N2) (M = W, Re, and Os) are examined in detail. Each complex is shown to have a different number of nitrogen–nitrogen and metal–nitrogen π-bonds, indicated as, respectively: WN–NW, ReNNRe, and Os–NN–Os. It follows that each of these Lewis structures represents a distinct class of complexes (diazanyl, diazenyl, and dinitrogen, respectively), in which the μ-N2 ligand has a different electron donor number (total of 8e–, 6e–, or 4e–, respectively). We show how this classification can greatly aid in understanding and predicting the properties and reactivity patterns of μ-N2 complexes.

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Electronic and Spin-State Effects on Dinitrogen Splitting to Nitrides in a Rhenium Pincer System

Cited by 16 publications

References 47 publications

Heterobimetallic-Mediated Dinitrogen Functionalization: N–C Bond Formation at Rhenium-Group 9 Diazenido Complexes

Heterobimetallic-Mediated Dinitrogen Functionalization: N–C Bond Formation at Rhenium-Group 9 Diazenido Complexes

Spectroscopic, Magnetic, and Computational Investigations on a Series of Rhenium(III) Cyclopentadienide β-diketiminate Halide and Pseudohalide Complexes

Lewis Structures and the Bonding Classification of End-on Bridging Dinitrogen Transition Metal Complexes

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