Structure Of Transition Metal Complexes Research Articles

Valence bond concepts applied to the molecular mechanics description of molecular shapes. 4. Transition metals with pi-bonds.

We have developed a model for understanding the shapes of transition metal complexes containing multiple bonds. This model, which focuses on Lewis-like structures and the balance of forces arising from sigma- and pi-bond frameworks, provides a simple method for predicting the structures of transition metal complexes with pi-bonds. Potential energy expressions suitable for implementation in molecular mechanics computations have been derived from consideration of orbital hybridizations and coded into our UFF2-based molecular mechanics program, VALBOND. The VALBOND method correctly predicts the structures for a wide variety of experimentally and computationally characterized compounds containing metal-ligand multiple bonds.

Intramolecular Metal Ligand Aromatic Cation−π Interactions in Crystal Structures of Transition Metal Complexes

Cation−π interactions between ligands coordinated to a metal cation and aromatic groups have been predicted by theoretical calculations, and have been found in crystal structures of metalloproteins from the Protein Data Bank (PDB). We proposed metal ligand aromatic cation−π (MLACπ) interaction as intramolecular interactions in transition metal complexes. Searching crystal structures of transition metal complexes from the Cambridge Structural Database (CSD) reveals that there are quite a number of metal complexes, where an aromatic ring interacts with a hydrogen atom from a ligand in the same complex. The hydrogen atom is separated from the metal center by a few bonds and gains positive charge from the metal atom. In the complexes there are various metal atoms and various ligands. In the most of the complexes, the aromatic ring is separated from the metal center by two or four bonds, and interacts with the hydrogen atom of another ligand. In complexes where the aromatic ring is separated from the metal center by four or five bonds, there are examples of aromatic groups interacting with the hydrogen atom in the same ligand. By quantum chemical computations it was evaluated for the model systems of cationic cobalt(III) complexes with a charge of +1, that the energy of this intramolecular MLACπ interaction is about 4 kcal/mol.

Effective Hamiltonian approach to catalytic activity of transition metal complexes

AbstractThe application of an effective electron Hamiltonian approach to the description of the electronic structure of transition metal complexes with chemically active ligands is analyzed. This approach is implemented in a computational code. The evolution of the electronic structure along a path of isomerization of quadricyclane to norbornadiene in the coordination sphere of Co‐tetraphenylporphyrin is considered. In addition, the electronic states of atomic oxygen coordinated to transition metal oxides and metal porphyrins are studied. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 99–109, 2001

Spatial structure of transition metal complexes in solution determined by EXAFS spectroscopy

CdK EXAFS, ZnK and CuK EXAFS and XANES spectra were measured for solutions of cadmium, zinc and copper dialkyldithiocarbamates in organic solvents with varying donating abilities: tributylphosphine, methylene chloride, benzene, dibutylsulfide, pyridine, dimethylsulfoxide and for some model compounds. The parameters of the local surroundings of the Cd, Zn and Cu atoms for complex forms in solutions were determined using EXAFS spectroscopy. Spatial structure models of the complex forms in a metal chelate – nonaqueous solvent system are suggested.

Coordination chemistry of some low-coordinate organophosphorus compounds

Abstract

ChemInform Abstract: Crystal and Molecular Structures of Transition Metal Complexes with N‐ and C‐Bonded Diazoalkane Ligands

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Crystal and molecular structures of transition metal complexes with N- and C-bonded diazoalkane ligands

The review covers structural and physicochemical studies on diazoalkanes N-coordinated to transition metals and encompasses all collected crystal structures. Our goal is to provide a classification of the complexes based on the metal, ranging from early to late transition metals, the nuclearity of the complex (mono, dinuclear, clusters), the electronic configuration of the metal (d 0 to d 10) and the bonding mode of the diazoalkanes. Interestingly, the variety of structures may be rationalized within the valence bond formalism, the reactions being essentially oxidative addition of diazoalkane on the metal complexes giving hydrazonido (-2- ligand). C-coordinated diazoalkyl complexes are still restricted to a few metals and a few diazosubstituents and their chemistry is not well developed.

Coordination Chemistry of Some Low Coordinate Organophosphorus Compounds of Coordination Number 2

Abstract The structures of transition metal complexes with low coordinate organophosphorus compounds are described; these compounds involve diphosphenes, phosphaethenes, phosphaallenes, phosphabutatrienes, and so on of coordination number 2. They are discussed in terms of X-ray crystallographic analysis and 31P NMR analysis.

Basis sets for transition metals: Optimized outer p functions.

Although the (n + 1)p orbital is unoccupied in transition-metal ground-state configurations which are all nd(x) (n + 1)s(y) , these (n + 1)p functions play a crucial role in the structure of transition metal complexes. As we show here, the usual solution, adding one or more diffuse functions, can be insufficient to create an orbital of the correct energy. The major problem appears to be due to the incorrect placement of the (n + 1)p orbital's node. Even splitting the most diffuse component of the np orbital and adding a second diffuse function does not completely solve this problem. Although one can usually solve this deficiency by further uncontracting of the np function, here we offer a set of properly optimized (n + 1)p functions that offer a more compact and satisfactory solution to the proper placements of the node. We show an example of the common deficiencies seen in typical basis sets, including standard basis sets in GAUSSIAN94, and show that the new optimized (n + 1)p function performs well compared to a fully uncontracted basis set. © 1996 by John Wiley & Sons, Inc.

Force field calculation on the structure of transition metal complexes: Application to schiff-base complexes of Ti(IV)

Force field calculation on the structure of transition metal complexes: Application to schiff-base complexes of Ti(IV)

ChemInform Abstract: Correlation Between the Composition and Structure of Transition Metal Complexes and Their RF Values Obtained by Planar Chromatography

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Force Field Calculations on the Structures of Transition Metal Complexes. 1. Application to Copper(II) Complexes in Square-Planar Coordination

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTForce Field Calculations on the Structures of Transition Metal Complexes. 1. Application to Copper(II) Complexes in Square-Planar CoordinationF. Wiesemann, S. Teipel, B. Krebs, and U. HoewelerCite this: Inorg. Chem. 1994, 33, 9, 1891–1898Publication Date (Print):April 1, 1994Publication History Published online1 May 2002Published inissue 1 April 1994https://doi.org/10.1021/ic00087a027RIGHTS & PERMISSIONSArticle Views341Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (813 KB) Get e-Alerts Get e-Alerts

Use of semi-empirical molecular orbital theory for study of electronic structures of transition metal complexes

Abstract

Phosphorus and proton nuclear magnetic resonance studies of transition-metal complexes of triphosphate and pyrophosphate in aqueous solution

The structures of transition-metal complexes of triphosphate and pyrophosphate have been examined in aqueous solution by phosphorus 31P and water proton n.m.r. For pyrophosphate, 1:1 bidentate complexes containing four water molecules are formed with Ni2+, Co2+ and Mn2+ in the pH range 7–10, but the Cu2+ complex contains two pyrophosphate molecules. 1:1 complexes are also formed between triphosphate and Ni2+, Co2+ and Mn2+ but there exists a dynamic equilibrium between bidentate and tridentate forms, the former being favoured by Mn2+ and the latter by Ni2+ and Co2+. A further equilibrium involving a complex containing two triphosphate molecules becomes important for Cu2+ and this predominates in alkaline media. The lifetimes for triphosphate bound to transition metals, Cu2+, Mn2+, Co2+, Ni2+ and Fe3+, have been determined as a function of temperature, and activation energies for ligand exchange are 4.6, 23.4, 32.1, 34.4 and 25.8 kJ mol–1, respectively. The rotational correlation times determined for triphosphate complexes of Mn2+ and Cu2+ are 5.6 × 10–10 and 4.0 × 10–10 s determined from 31P n.m.r., but the effective correlation times determine from water-proton n.m.r. are 4.5 × 10–11 and 5.0 × 10–11 s, respectively. The electronic relaxation time for Mn2+ decreases from 1.5 × 10–8 to 5 × 10–9 s on complexation with equimolar amounts of tripolyphosphate.

On the electronic structure of transition metal complexes. I. An INDO‐MO investigation of some octahedral complex ions

AbstractMolecular‐orbital calculations within the INDO framework are reported for the hexafluoro, hexachloro, and hexaaquo metallate (II) ions of the first transition series. The parameterization scheme and choice of orbital exponents have been detailed. The results indicate that the method in its present form gives fairly satisfactory predictions of molecular properties.

On the electronic structure of transition‐metal complexes II. Bonding characteristics in titanium chloride systems

AbstractThe electronic structure of [TiCl4]n systems (n = 0, −1, −2, −3, and −4) has been investigated by the INDO method. Calculations show the stability of the tetrahedral structure over the square‐planar one, for any value of n, in accord with experimental observation. The occupation of the 4p orbitals of the titanium atom was found to increase regularly as the dihedral angle decreases and reaches a maximum at the square‐planar conformation. Energy partitioning analysis enabled much deeper understanding of bonding characteristics of the studied systems. It has been shown that the one‐atom energy component may be a very sensitive measure of the stability of the central metal atom in its various oxidation states.

Principles of electronic structure in transition metal complexes. Additive ligand electronic effects and core–valence ionization correlations for Mo(CO)6−n(PMe3)n where n=0, 1, 2, 3

Gas phase core photoelectron spectroscopic (XPS) results are reported for a series of trimethylphosphine substituted molybdenum carbonyls: Mo(CO)6, Mo(CO)5(PMe3), cis-Mo(CO)4(PMe3)2, trans-Mo(CO)4(PMe3)2, and fac-Mo(CO)3(PMe3)3. Core ligand additivity, defined as a constant shift in core ionizations with each successive step of ligand substitution, is indicated by these data. The shift per phosphine substitution is −0.65±0.10 eV for the molybdenum 3d5/2 ionization, −0.75±0.11 eV for the carbon (carbonyl) 1s ionization, and −0.78±0.09 eV for the oxygen 1s ionization. Comparison of core and valence data sets for these complexes illustrates a second principle, core–valence ionization correlation. The ratio of the Coulombic valence metal d level shifts to the core metal shifts is 0.74±0.06. This trend, in a system with extensively delocalized metal orbitals, shows that core and valence photoelectron spectroscopies are intimately related and that key additional understanding of electron distributions and bonding can be obtained from correlating the information of these techniques. Simple models for both the ligand additivity and core–valence ionization correlation principles are presented to demonstrate the fundamental features and possible limitations of these principles.

ChemInform Abstract: ELECTRONIC STRUCTURE OF TRANSITION METAL COMPLEXES. IV. D‐D* TRANSITIONS

Chemischer InformationsdienstVolume 14, Issue 36 Physical Inorganic Chemistry ChemInform Abstract: ELECTRONIC STRUCTURE OF TRANSITION METAL COMPLEXES. IV. D-D* TRANSITIONS E. KAI, E. KAISearch for more papers by this authorT. ARAKAWA, T. ARAKAWASearch for more papers by this authorK. NISHIMOTO, K. NISHIMOTOSearch for more papers by this author E. KAI, E. KAISearch for more papers by this authorT. ARAKAWA, T. ARAKAWASearch for more papers by this authorK. NISHIMOTO, K. NISHIMOTOSearch for more papers by this author First published: September 6, 1983 https://doi.org/10.1002/chin.198336001Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue36September 6, 1983 RelatedInformation

A program for calculating the electronic structure of transition metal complexes by the Mulliken-Wolfsberg-Helmholtz method

A program for calculating the electronic structure of transition metal complexes by the Mulliken-Wolfsberg-Helmholtz method

ChemInform Abstract: SPECTRA AND STRUCTURE OF TRANSITION METAL COMPLEXES WITH TETRADENTATE MACROCYCLIC LIGANDS

Chemischer InformationsdienstVolume 12, Issue 5 Reviews ChemInform Abstract: SPECTRA AND STRUCTURE OF TRANSITION METAL COMPLEXES WITH TETRADENTATE MACROCYCLIC LIGANDS K. B. YATSIMIRSKII, K. B. YATSIMIRSKIISearch for more papers by this authorYA. D. LAMPEKA, YA. D. LAMPEKASearch for more papers by this author K. B. YATSIMIRSKII, K. B. YATSIMIRSKIISearch for more papers by this authorYA. D. LAMPEKA, YA. D. LAMPEKASearch for more papers by this author First published: February 3, 1981 https://doi.org/10.1002/chin.198105349AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume12, Issue5February 3, 1981 RelatedInformation