Metal-metal interactions in transition metal clusters with π-donor ligands

Lin, Zhenyang; Fan, Man-Fai

doi:10.1007/bfb0018030

Cited by 16 publications

(16 citation statements)

References 218 publications

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“…We notice that here reported values are similar to those observed for 95 [18]. Indeed, both forms of clusters, edge-bridged niobium and facecapped molybdenum are similar, they both are classified as hexanuclear clusters with π-donor ligands [37] and their electronic structure is explained by the same molecular-orbital scheme [37]. A difference is that Nb 6 metal core uses d xy metal orbitals for metal-metal bonding, leaving to metal-halogen bonding, while Mo 6 metal core uses for metal-metal bonding and d xy for metal-halogen bonding [37].…”

Section: Nb Chemical Shiftssupporting

confidence: 87%

“…Although computations of NMR parameters of heavy nuclei such as 79/81 Br of 93 Nb is less obvious than the one of lighter elements from a theoretical point of view (relativistic effects, pseudo-potentials), our results show an overall excellent agreement between experimental and computed NMR parameters. This is all the more impressive since hexanuclear niobium clusters are complex chemical systems where chemical bonding is strongly delocalized over metallic atoms and capping ligands [37,38]. Table S1.…”

Section: Resultsmentioning

confidence: 97%

“…Indeed, both forms of clusters, edge-bridged niobium and facecapped molybdenum are similar, they both are classified as hexanuclear clusters with π-donor ligands [37] and their electronic structure is explained by the same molecular-orbital scheme [37]. A difference is that Nb 6 metal core uses d xy metal orbitals for metal-metal bonding, leaving to metal-halogen bonding, while Mo 6 metal core uses for metal-metal bonding and d xy for metal-halogen bonding [37]. Fragments around metal atom defined by the nearest non-metal atoms in both clusters also have similar features; they are square-pyramid fragments.…”

Section: Nb Chemical Shiftsmentioning

confidence: 99%

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Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds

Perić¹,

Gautier²,

Pickard³

et al. 2014

Solid State Nuclear Magnetic Resonance

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Two hexanuclear niobium halide cluster compounds with a [Nb6X12](2+) (X=Cl, Br) diamagnetic cluster core, have been studied by a combination of experimental solid-state NMR/NQR techniques and PAW/GIPAW calculations. For niobium sites the NMR parameters were determined by using variable Bo field static broadband NMR measurements and additional NQR measurements. It was found that they possess large positive chemical shifts, contrary to majority of niobium compounds studied so far by solid-state NMR, but in accordance with chemical shifts of (95)Mo nuclei in structurally related compounds containing [Mo6Br8](4+) cluster cores. Experimentally determined δiso((93)Nb) values are in the range from 2,400 to 3,000 ppm. A detailed analysis of geometrical relations between computed electric field gradient (EFG) and chemical shift (CS) tensors with respect to structural features of cluster units was carried out. These tensors on niobium sites are almost axially symmetric with parallel orientation of the largest EFG and the smallest CS principal axes (Vzz and δ33) coinciding with the molecular four-fold axis of the [Nb6X12](2+) unit. Bridging halogen sites are characterized by large asymmetry of EFG and CS tensors, the largest EFG principal axis (Vzz) is perpendicular to the X-Nb bonds, while intermediate EFG principal axis (Vyy) and the largest CS principal axis (δ11) are oriented in the radial direction with respect to the center of the cluster unit. For more symmetrical bromide compound the PAW predictions for EFG parameters are in better correspondence with the NMR/NQR measurements than in the less symmetrical chlorine compound. Theoretically predicted NMR parameters of bridging halogen sites were checked by (79/81)Br NQR and (35)Cl solid-state NMR measurements.

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Section: Nb Chemical Shiftssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 97%

Section: Nb Chemical Shiftsmentioning

confidence: 99%

See 1 more Smart Citation

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds

Perić¹,

Gautier²,

Pickard³

et al. 2014

Solid State Nuclear Magnetic Resonance

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“…However, to verify the validity of the BO conservation principle to cluster compounds, we have to compare the calculated BO sum for the TM atoms with the values expected from the electronic structure. Thus, for this study, we used cluster compounds with π-donor ligands, for which the structure of molecular orbitals is well known, and the formal electron bookkeeping is relatively simple. In addition, such compounds form a large number of structural types, with wide range of the TM–TM distances, which ensures more precise fitting of the BV parameters.…”

Section: Calculation Methodsmentioning

confidence: 99%

Bond Order Conservation Principle and Peculiarities of the Metal–Metal Bonding

2018

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Pauling's principles developed later in the bond valence model (BVM) are fundamental in description of bonding in ionic solids and surface phenomena on metals, but applicability of these principles to the metal−metal bonds in the bulk compounds was demonstrated only recently, with a spotlight on the bond valence−bond length correlations. This work is focused on the bond order conservation in cluster compounds and determination of empiric bond valence parameters for the metal−metal bonds, which ensure very simple and reasonably accurate bonding analysis, with zero cost, in any complex cluster compound. Such peculiarities of cluster compounds as matrix effect and nonuniform distribution of the ionic charges (bond valence sums) on the ligands around metal clusters, as well as other important examples of the BVM application to compounds with metal−metal bonds, are discussed.

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“…The MO diagram proposed by Lin and Fan was based on the interaction of the frontier orbitals of individual metal fragments derived from their local ML n coordination. 31 According to their calculations, the nonbonding e g orbitals have the highest energy. Consequently, seven orbitals with the lowest energy should be available for the bonding electrons of Z atoms.…”

mentioning

confidence: 99%

Steric and Electrostatic Effects in Compounds with Centered Clusters Quantified by Bond Order Analysis

Levi

Aurbach

Gatti³

2020

Crystal Growth & Design

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Steric and electrostatic effects affect the strength, energy, and reactivity of chemical bonds, but their quantification by density functional theory is not straightforward, even for simple molecules. In the previous works devoted to compounds with metal–metal bonds, we showed that these effects can be easily and properly described by the difference between formal and effective bond orders, the latter being calculated from the experimental bond lengths using exponential correlations and empirical bond valence parameters. This work applies for the first time the same method to halides with Z-centered M6-clusters (Z represents main group elements like Be, B, C, and N or transition metals like Mn, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt; M = Sc, Zr, Y, and Gd). It was shown that a spatial inconsistency between short M–Z bonds and relatively rigid anion close-packing results in the high strains in the individual bonds, but the total bond order sums calculated for the M atom in most of the halides are close to the number of its valence electrons. This bond order conservation associated with high deformability of electron clouds of M atoms explains the stability of the cluster compounds.

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Metal-metal interactions in transition metal clusters with π-donor ligands

Cited by 16 publications

References 218 publications

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds

Solid-state NMR/NQR and first-principles study of two niobium halide cluster compounds

Bond Order Conservation Principle and Peculiarities of the Metal–Metal Bonding

Steric and Electrostatic Effects in Compounds with Centered Clusters Quantified by Bond Order Analysis

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