Geometry Of Transition Metal Complexes Research Articles

Molecular geometries of transition metal complexes influenced by metal–sulfur interactions

Molecular geometries of transition metal complexes influenced by metal–sulfur interactions

DFT-D4 counterparts of leading meta-generalized-gradient approximation and hybrid density functionals for energetics and geometries.

Previously, we introduced DFT-D3(BJ)ωB97X-V and ωB97M-V functionals and assessed them for the GMTKN55 database [Najibi and Goerigk, J Chem. Theory Comput. 2018, 14, 5725]. In this study, we present DFT-D4 damping parameters to build the DFT-D4 counterparts of these functionals and assess these in comparison. We extend our analysis beyond GMTKN55 and especially turn our attention to enzymatically catalyzed and metal-organic reactions. We find that B97M-D4 is now the second-best performing meta-generalized-gradient approximation functional for the GMTKN55 database and it can provide noticeably better organometallic reaction energies compared to B97M-D3(BJ). Moreover, the aforementioned DFT-D3(BJ)-based functionals have not been thoroughly assessed for geometries and herein we close this gap by analyzing geometries of noncovalently bound dimers and trimers, peptide conformers, water hexamers and transition-metal complexes. We find that several of the B97(M)-based methods-particularly the DFT-D4 versions-surpass the accuracy of previously studied methods for peptide conformer, water hexamer, and transition-metal complex geometries, making them safe-to-use, cost-efficient alternatives to the original methods. The DFT-D4 variants can be easily used with ORCA4.1 and above.

Surprise! It’s a hexagonal planar complex

The geometries of transition-metal complexes are a small clique. The atoms and ligands in such complexes generally take on only a few structures, such as octahedral, trigonal bipyramidal, and square planar shapes. Scientists proposed a hexagonal planar geometry more than 100 years ago, but it has never been captured in crystal form until now. Mark R. Crimmin and coworkers at Imperial College London nabbed the structure with a complex consisting of a palladium atom surrounded by three hydride and three magnesium-diisopropylphenyl ligands (Nature 2019, DOI: 10.1038/s41586-019-1616-2). Scientists know that hexagonal planar compounds can form in condensed metal phases and in the pores of coordination polymers, but a transition-metal complex with this geometry was a surprise, Crimmin says. “The magnesium ligands accept electron density from the palladium,” and, with this geometry, the hydrides overlap well with filled palladium d orbitals to stabilize the compound, he adds. “Not only does this species

Effect of the Structure of Pyridine Ligands and the Substituent in the Carboxylate Anion on the Geometry of Transition Metal Complexes [M2(O2CR)4L2

A series of binuclear tetracarboxylate-linked Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) complexes with 1,2-substituted pyridine, viz., 2,3-cyclododecenopyridine (L), were prepared. Study of the crystal structures of isolated compounds (CIF file CCDC nos. 1575855–1575859) revealed a distortion of the {Ni2(O2CR)4L2} binuclear moiety, manifested as a change in the NiNiN angle (151.67°), in the bridging function of two out of the four carboxylate groups (from μ2- to (κ2,μ2-)), and in the coordination environment of the metal ion (NiO5N). The results were analyzed in comparison with known data. The magnetic properties of copper(II) and nickel(II) complexes were studied. The copper(II) complex is diamagnetic as a result of strong exchange interactions between the unpaired electrons; in the nickel(II) complex antiferromagnetic exchange interactions were detected (JNi–Ni =–25 cm–1).

Vibrational corrections to geometries of transition metal complexes from density functional theory

Zero-point vibrational corrections are computed at the BP86/AE1 level for the set of 50 transition-metal/ligand bonds that have recently been proposed as testing ground for DFT methods, because of the availability of precise experimental gas-phase geometries (Bühl and Kabrede, J Chem Theory Comput 2006, 2, 1282). These corrections are indicated to be transferable to a large extent between various density-functional/basis-set combinations, so that they can be used to estimate zero-point averaged r0g distances from re values optimized at other theoretical levels. Applying this approach to a number of popular DFT levels does not, in general, improve their overall accuracy in terms of mean and standard deviations from experiment. The hybrid variant of the meta-functional TPSS is confirmed as promising choice for computing structures of transition-metal complexes.

Geometries of Transition-Metal Complexes from Density-Functional Theory.

Several levels of density functional theory, i.e., various combinations of exchange-correlation functionals and basis sets, have been employed to compute equilibrium geometries for a diverse set of 32 metal complexes from the first transition row, for which precise gas-phase geometries are known from electron diffraction or microwave spectroscopy. Most DFT levels beyond the local density approximation can reproduce the 50 metal-ligand bond distances selected in this set with reasonable accuracy, as assessed by mean and standard deviations of optimized vs observed values. The ranking of some popular functionals, ordered according to decreasing standard deviation, is BLYP ≈ HCTH > B3LYP > BP86 > TPSS ≈ TPSSh. Together with its hybrid variant, the recently introduced meta-GGA functional TPSS performs best of all tested functionals, with mean and standard deviations of -0.5 and 1.4 pm, respectively. Even smaller errors are found for a more compact but less diverse set of transition-metal mono- and dihalides, for which experimentally derived equilibrium geometries are available.

Geometry of Transition Metal Complexes with Bipyridine in the Excited States

A technique for estimating the changes in the geometrical structural parameters of complex compounds during charge-transfer electron excitations is proposed. The method combines the experimental Raman resonance data, the wave packet dynamics procedure, and quantum-chemical calculations of the geometry and vibrational spectra of relatively small fragments of the complex ion. The technique is used to determine the changes in the geometrical structure of 2,\(2'\)-bipyridine during metal–ligand charge transfer excitations in Ru(II) complexes.

Equilibrium geometries of transition metal complexes. A comparison of approximate molecular orbital theory and experiment

Optimized metal—ligand bond distances have been obtained for fifteen transition metal complexes using PRDDO, an approximate molecular orbital method. Of the twenty-nine unique distances, only six are in error by more than 0.05 Å, and the average error is ≈0.03 Å.

How well does the Hartree–Fock model predict equilibrium geometries of transition metal complexes? Large-scale LCAO–SCF studies on ferrocene and decamethylferrocene

Large scale ab initio LCAO–SCF calculations performed on ferrocene show that the Hartree–Fock model is unable to account for the experimentally observed metal to ring distance. The present results, using basis sets of better than triple zeta quality, show that both the equilibrium geometry and the orbital energies have converged already at the double zeta level (metal-ring distance;1.89 Å, i.e., 15% larger than the experimental value of 1.65 Å). A comparative calculation on decamethylferrocene yields essentially the same results. These findings raise some doubts as to the adequacy of the Hartree–Fock model for predictions of equilibrium geometries of transition metal complexes in general.

Geometry of transition metal complexes with ethylene or allyl groups as the only ligands

Geometry of transition metal complexes with ethylene or allyl groups as the only ligands

Geometries of transition metal complexes containing simple alkenes

Download options Please wait... Article information DOI https://doi.org/10.1039/DF9694700084 Article type Paper Download Citation Discuss. Faraday Soc., 1969,47, 84-92 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Geometries of transition metal complexes containing simple alkenes L. Manojlović-Muir, K. W. Muir and J. A. Ibers, Discuss. Faraday Soc., 1969, 47, 84 DOI: 10.1039/DF9694700084 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Ljubica Manojlović-Muir Kenneth W. Muir James A. Ibers