Solution NMR of transition metal complexes

Cook, Tabitha M.

doi:10.1016/b978-0-12-823144-9.00051-0

Cited by 4 publications

(5 citation statements)

References 800 publications

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“…Possibly, this is due to electron density being transferred from the metal centers towards the dinitrogen bridging ligand. The σ iso ( 99 Ru) and σ iso ( 187 Os) are in line with various experimental results [33].…”

Section: Nmr Spectrasupporting

confidence: 90%

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Multimetallic Cooperative Activation of Dinitrogen by All-Metal Trinuclear rings: A DFT Study

Tsipis,

Siskos

2024

Preprint

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The fixation and activation of the dinitrogen molecule, N2 by hexametallic clusters of the general formula {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 (L = CH2-, NH2-, PH2-, OH-, SH-, BH2- and NH2-, M = Ru(II) or Os(II)) were scrutinized by means of density functional theory calculations. In these systems, the dinitrogen molecule, acts as a ligand that bridges the two opposite facing triangular metallic rings, cyclo-M3 of the {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 clusters The hexametallic clusters, that mimick the six Fe cluster of nitrogenase, were found to strongly activate N2, converting it into a hydrazido-like group, N24-. This is substantiated by the calculated N-N bond lengths, Re(N-N) and the stretching frequencies of the N-N bond of dinitrogen, vs(N-N) found in the ranges 1.299 – 1.487 Å and 780 – 1270 cm-1 respectively. Based on the Re(N-N) and vs(N-N) values, the dinitrogen activation depends upon the nature of the hexametallic cluster. Accordingly, the Os(II) clusters were found to activate more strongly the dinitrogen molecule as compared to their Ru(II) counterparts. The nature of the ligand L also affects the extent of the N2 activation by the hexametallic clusters, which follows the order BH2- &lt; NH2- &lt; OH- &lt; CH2- &lt; NH2- &lt; PH2-, SH- for M = Ru(II) and the order BH2- &lt; NH2- &lt; OH- &lt; NH2- &lt; CH2- &lt; PH2- &lt; SH- for M = Os(II). Thus, the strongest N2 activation is observed for the {[(μ2-SH)Os)]6(μ-η1:η3-Ν2)}+6 cluster and the weakest for the {[(μ2-BH)Ru)]6(μ-η1:η3-Ν2)}0 cluster. The calculated Nitrogen-15 NMR isotropic chemical shielding tensors, σiso(15N) exhibit shielding (upfield) upon N2 fixation to the metal centers of the hexametallic clusters, as a results of electron density transfer towards its constituent N nuclei. A multitude of electronic charge distribution partitioning schemes were applied to assist in delineating the bonding properties of the {[(μ2-L)M)]6(μ-η1:η3-Ν2)}0/+6 clusters. Accordingly, it is found that there is a donation/backdonation interaction between the bridging N2 ligand and the two opposing cyclo-M3 rings located on either side. The dinitrogen ligand forms six bonds of mixed covalent/electrostatic nature with the six metal centers of the {[(μ2-L)M)]6)}0/+6 clusters.

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Section: Nmr Spectrasupporting

confidence: 90%

“…NMR spectroscopy has been routinely applied in the study of transition metal complexes [33]. In particular, Nitrogen-15 NMR has proven to be a powerful technique for studying dinitrogen fixation and activation by transition metal complexes [34][35][36][37].…”

Section: Nmr Spectramentioning

confidence: 99%

Multimetallic Cooperative Activation of Dinitrogen by All-Metal Trinuclear rings: A DFT Study

Tsipis,

Siskos

2024

Preprint

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“…NMR is one of the primary techniques to probe chemical or conformational exchanges. ,− EXSY (exchange spectroscopy) has proven useful to observe exchanges slow on the NMR timescale. − , EXSY and NOESY are the same experiment except that, for compounds of low molecular weights, EXSY and NOESY cross-peaks are easily recognized as they have opposite phases . Cross-peaks of EXSY have the same phase of the diagonal peaks, while those of NOESY have the opposite phase.…”

Section: Resultsmentioning

confidence: 99%

Syntheses of Group 5 Amide Amidinates and Their Reactions with Water: Different Reactivities of Nb(V) and Ta(V) Complexes

et al. 2022

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Chemistries of Nb(V) and Ta(V) compounds are essentially identical as a result of lanthanide contraction. Hydrolysis of M(NMe 2 ) 5 (M = Nb, Ta), for example, yields [M(μ 3 -O)(NMe 2 ) 3 ] 4 (M = Nb, 1; Ta, 2) reported earlier. The similar reactivities of Nb(V) and Ta(V) compounds make it challenging, for example, to separate the two metals from their minerals. We have found that the reactions of H 2 O with amide amidinates M(NMe 2 ) 4 [MeC(N i Pr) 2 ] (M = Nb, 3; Ta, 4) show that the niobium and tantalum analogues take different principal paths. For the Nb(V) complex 3, the amidinate and one amide ligand are liberated upon treatment with water, yielding [Nb(μ 3 -O)(NMe 2 ) 3 ] 4 (1). For the Ta(V) complex 4, the amide ligands are released in the reaction with H 2 O, leaving the amidinate ligand intact. [Ta(μ 3 -O)(NMe 2 ) 3 ] 4 (2), the analogue of 1, was not observed as a product in the reaction of 4 with H 2 O. To our knowledge, this is the first example of the formation of two different complexes that maintain the (V) oxidation state in both metals. The new complexes M(NMe 2 ) 4 [MeC(N i Pr) 2 ] (M = Nb, 3; Ta, 4) have been prepared by the aminolysis of M(NMe 2 ) 5 (M = Nb, Ta) with i PrN(H)C(Me)=N i Pr (5). The hydrolysis of 3 and 4 has been investigated by DFT electronic structure calculations. The first step in each hydrolysis reaction involves the formation of a hydrogen-bonded complex that facilitates a proton transfer to the amidinate ligand in 3 and protonation of an axial dimethylamide ligand in 4. Both proton transfers furnish an intermediate metal-hydroxide species. The atomic charges in 3 and 4 have been computed by Natural Population Analysis (NPA), and these data are discussed relative to which of the ancillary ligands is protonated initially in the hydrolysis sequence. Ligand exchanges in 3 and 4 as well as the exchange in i PrN(H)C(Me)=N i Pr (5) were probed by EXSY NMR spectroscopy, giving rate constants of the exchanges: 0.430(13) s −1 (3), 0.033(6) s −1 (4), and 2.23(7) s −1 (5), showing that the rate of the Nb complex Nb(NMe 2 ) 4 [MeC(N i Pr) 2 ] (3) is 13 times faster than that of its Ta analogue 4.

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“…Another advantage of scandium is that 45 Sc NMR is feasible. 45 Sc has 100% natural abundance, an NMR frequency close to that of 13 C and a high receptivity (approximately 0.3 relative to 1 H) [116]. As a quadrupole nucleus with I = 7/2 (Q = −22 fm 2 ) [117], 45 Sc frequently produces NMR spectra with large line widths, particularly for compounds having a low local symmetry around the nucleus.…”

Section: Capped Cube R-ccumentioning

confidence: 99%

Gold-Based Coronands as Hosts for M3+ Metal Ions: Ring Size Matters

Sucena,

Demirer,

Baitullina

et al. 2023

Molecules

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The controlled, self-assembled synthesis of multinuclear coordination compounds can be performed via different approaches. Frequently, steric, geometric and/or electronic factors located at the ligand systems predefine the way in which metal ions can assemble them to large aggregates. For the compounds in the present paper, also the Pearson’s acidities and preferred coordination geometries of the metal ions were used as organization principles. The ligand under study, 2,6-dipicolinoylbis(N,N-diethylthiourea), H2L1ethyl, possesses ‘soft’ sulfur and ‘hard’ nitrogen and oxygen donors. One-pot reactions of this compound with [AuCl(tht)] (tht = tetrahydrothiophene) and M3+ salts (M = Sc, Y, La, Ln, Ga, In) give products with gold-based {Au3(L1ethyl)3}3+ or {Au2(L1ethyl)2}2+ coronands, which host central M3+ ions. The formation of such units is templated by the M3+ ions and the individual size of the coronand rings is dependent on the ionic radii of the central ions in a way that small ions such as Ga3+ form a [Ga⊂{Au2(L1ethyl)2}]+ assembly, while larger ions (starting from Sc3+/In3+) establish neutral [M⊂{Au3(L1ethyl)3}] units with nine-coordinate central ions.

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Solution NMR of transition metal complexes

Cited by 4 publications

References 800 publications

Multimetallic Cooperative Activation of Dinitrogen by All-Metal Trinuclear rings: A DFT Study

Multimetallic Cooperative Activation of Dinitrogen by All-Metal Trinuclear rings: A DFT Study

Syntheses of Group 5 Amide Amidinates and Their Reactions with Water: Different Reactivities of Nb(V) and Ta(V) Complexes

Gold-Based Coronands as Hosts for M3+ Metal Ions: Ring Size Matters

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