DOCSLIB.ORG

Chemistry of Transition Metals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Chemistry of Transition Metals Chemistry of Transition Metals Part 1. General Considerations 1 •Filling of 3d, 4d, and 5d shells •In s- and p-block, electrons added to outer shell. •In d-block, electrons added to penultimate shell expanding it from 8-18 2 •Most elements have incompletely filled d-shell (interesting properties) Transition elements 1. Metals 2. Almost all: HARD, STRONG, High m.p., b.p. 3. Conduct heat & electricity 4. Form Alloys 5. Show variable oxidation states 6. At least one of the ions & compounds colored. 7. Form paramagnetic species because of partially filed shells 8. Form coordination compounds (complexes) and organometallic compounds. 3 Variable oxidation state 1. Increase in the number of oxidation states from Sc to Mn. All possible states exhibited by only Mn. Sc +3 2. Decrease in the number of Ti +1 +2 +3 +4 oxidation states from Mn to Zn, V +1 +2 +3 +4 +5 due to the pairing of d- electrons occurs after Mn Cr +1 +2 +3 +4 +5 +6 (Hund's rule). Mn +1 +2 +3 +4 +5 +6 +7 3. Stability of higher oxidation Fe +1 +2 +3 +4 +5 +6 states decreases along Sc to Zn. Mn(VII) and Fe(VI) are Co +1 +2 +3 +4 +5 powerful oxidizers. Ni +1 +2 +3 +4 4. Down the group, the stability of high oxidation states Cu +1 +2 +3 increases (easier availability of Zn +2 both d and s electrons for ionization). 4 Variable oxidation state 5 Color 1. The d-orbitals of the metal interact with the electron cloud of the ligands in such a manner that the d-orbitals become non-degenerate. When the d-level is not completely filled, it is possible to promote and electron from a lower energy d-orbital to a higher energy d- orbital by absorption of a photon of electromagnetic radiation having an appropriate energy (d-d transitions). 2. Metal to Ligand and Ligand to Metal Charge Transfer (LMCT and MLCT) transitions (KMnO4) 3. Electromagnetic radiations in the visible region of the spectrum often possess the appropriate energy for the above transitions. 6 Color 7 8 9 10 11 12 13 14 Self Study Isomerism Naming of complexes 15 Self Study 16 Part 2. Theories / Concepts Bonding in transition metal compounds -Werner Coordination Theory 18 electron rule -Valence Bond Theory -Crystal field theory -Molecular orbital approach High spin and low spin complexes Spectrochemical series CFSE 17 Jahn-Teller distortions Werner Coordination Theory Werner : 1893 (electron was discovered in 1896) Nobel prize in 1913. In complexes, metal ions show two different types of valency: Primary Valency: Non-directional, is the number of charges on the complex ion. 1. Secondary Valency: Directional, equals to the number of ligands coordinated to the metal. 18 18 electron rule (based on earlier EAN Rule: Sidgwick) Stable low oxidation state complexes are found to have a total of 18 bonding electrons metal electrons + lone pairs from ligands = 18 2 8 ! Ni(CO)4 -4s3d and 4 lone pairs 2 6 ! Fe(CO)5 -4s3d and 5 lone pairs 2 4 ! Cr(CO)6 -4s3d and 6 lone pairs The stability of these 18 electron species can be explained using MO theory. Corresponds to filling all the molecular bonding orbitals and none of the antibonding orbitals However, is rule only works for species with metals in a low oxidation state NOT FOR MOST COMPLEXES 19 Valence Bond Theory The idea that atoms form covalent bonds by sharing pairs of electrons was first proposed by G. N. Lewis in 1902. In 1927, Walter Heitler and Fritz London showed how the sharing of pairs of electrons holds a covalent molecule together. The Heitler-London model of covalent bonds was the basis of the VBT. The last major step in the evolution of this theory was the suggestion by Linus Pauling that atomic orbitals mix to form hybrid orbitals, such as the sp, sp2, sp3, 3 2 3 dsp , and d sp orbitals. 20 VBT – Assumptions / Features Coordination compounds contain metal ions, in which ligands form covalent-coordinate bonds to the metal. Ligands must have a lone pair of electrons. Metal should have an empty orbital of suitable energy available for bonding. Atomic orbitals are used for bonding (rather than molecular orbitals) This theory is useful to predict the shape and stability of the metal comples. Limitations: (1) Does not explain why some complexes are colored and others are not; (2) Does not explain 21 the temp. dependence of the magnetic properties. VBT – Example Co: 3d74s2 Co3+ : 3d64s0 3d 4s 4p 4d Outer sphere complex xx xxxx xx xx xx Reactive / labile High spin Paramagnetic sp3d2 3d 4s 4p 4d Inner sphere complex xx xx xx xxxx xx Stable Low spin Diamagnetic d2sp3 22 Crystal Field Theory (Text : JD Lee; pp.204-222) •This theory (CFT) largely replaced VB Theory for interpreting the chemistry of coordination compounds. •It was proposed by the physicist Hans Bethe in 1929. •Subsequent modifications were proposed by J. H. Van Vleck in 1935 to allow for some covalency in the interactions. These modifications are often referred to as Ligand Field Theory. •For a review on the evolution of bonding models see: C. J. Ballhausen, J. Chem. Ed. 1979 56 194-197, 215-218, 357-361. 23 CFT-Assumptions •The interactions between the metal ion and the ligands are purely electrostatic (ionic). •The ligands are regarded as point charges •If the ligand is negatively charged: ion-ion interaction. If the ligand is neutral : ion-dipole interaction •The electrons on the metal are under repulsive from those on the ligands •The electrons on metal occupy those d-orbitals farthest away from the direction of approach of ligands 24 Symmetric Field •The 5Xd orbitals in an isolated gaseous metal are degenerate. •If a spherically symmetric field of negative charges is placed around the metal, these orbitals remain degenerate, but all of them are raised in energy as a result of the repulsion between the negative charges on the ligands and in the d orbitals. E metal ion in a spherical negative field Mn+ metal ion spherical in free state negative field (vacuum) 25 Octahedral Field •If rather than a spherical field, discrete point charges (ligands) are allowed to interact with the metal, the degeneracy of the d orbitals is removed (or, better said, lifted). The splitting of d orbital energies and its consequences are at the heart of crystal field theory. eg E n+ M t2g •Not all d orbitals will interact to the same extent with the six point charges located on the +x, -x, +y, -y, +z and -z axes respectively. •The orbitals which lie along these axes (i.e. x2-y2, z2) will be destabilized more that 26 the orbitals which lie in-between the axes (i.e. xy, xz, yz). Octahedral Complexes 27 CFT-Octahedral Complexes 2 2 2 •For the Oh point group, the x -y , z orbitals belong to the Eg irreducible representation and xy, xz, yz belong to the T2g representation. ∆ •The extent to which these two sets of orbitals are split is denoted by 0 or alternatively 10Dq. As the baricenter must be conserved on going from a spherical field to an octahedral field, the t2g set must be stabilized as much as the eg set is destabilized. ∆ = + 0.6 o = − 0.4 ∆ o 28 Illustration of CFSE 3+ 1 − [Ti(H2O)6] : a d complex and the e occupies the lowest energy orbital, i.e. one of the three degenerate t2g orbitals. The purple colour is a result of the absorption of light which results in the 1 0 0 1 promotion of this t2g electron into the eg level. t2g eg –> t2g eg The UV-Vis absorption spectrum reveals that this transition occurs with a maximum at 20300 cm-1 which ∆ corresponds to o 243 kJ/mol. (1000 cm-1 = 11.96 kJ/mol or 2.86 kcal/mol or 0.124 eV.) 29 ∆ Typical 0 values are of the same order of magnitude as the energy of a chemical bond. •What happens for more than 1 electron in d orbitals? •The electron-electron interactions must be taken into account. •For d1-d3 systems: Hund's rule predicts that the electrons will not pair and occupy the t2gset. •For d4-d7 systems ( there are two possibilities): Either put the electrons in the t2g set and therefore pair the electrons (low spin case or strong field situation. Or put the electrons in the eg set, which lies higher in energy, but the electrons do not pair (high spin case or weak field situation). •Therefore, there are two important parameters to consider: The Pairing energy (P), and the eg -t2g Splitting (referred ∆ to as 0, 10Dq) •For both the high spin (h.s.) and low spin (l.s.) situations, it is possible to compute the CFSE. 30 ∆ o vs Pairing Energy ∆ 1 -1 Complex Config. o, cm- P, cm spin-state 2+ 6 [Fe(OH2)6] d 10,400 17,600 high-spin 4- 6 [Fe(CN)6] d 32,850 17,600 low-spin 3- 7 [CoF6] d 13,000 21,000 high-spin 3- 7 [Co(NH3)6] d 23,000 21,000 low-spin 31 ∆ o is dependent on: •Nature of the ligands •The charge on the metal ion •Whether the metal is a 3d, 4d, or 5d element Ligands which cause a small splitting are Weak field ligands -1 (∆ο in the range 7000 - 30000 cm ) and those cause a large splitting are Strong field ligands (CFSE typically > 30000 cm-1) Spectrochemical Series − − 2− − − − − − 2− I < Br < S < SCN < Cl < N3 , F < urea, OH < ox, O < − − − − H2O < NCS < py, NH3 < en < bpy, phen < NO2 < CH3 , C6H5 < CN− < CO.
Load more

Recommended publications
  • CHEM 250 (4 Credits): Reactions of Nucleophiles and Electrophiles (Reactivity 1)
    CHEM 250 (4 credits): Reactions of Nucleophiles and Electrophiles (Reactivity 1): Description: This course investigates fundamental carbonyl reactivity (addition and substitution) in understanding organic, inorganic and biochemical processes. Some emphasis is placed on enthalpy, entropy and free energy as a basis of understanding reactivity. An understanding of chemical reactivity is based on principles of Lewis acidity and basicity. The formation, stability and reactivity of coordination complexes are included. Together, these topics lead to an understanding of biochemical pathways such as glycolysis. Enzyme regulation and inhibition is discussed in the context of thermodynamics and mechanisms. Various applications of modern multi-disciplinary research will be explored. Prerequisite: CHEM 125. Course Goals and Objectives: 1. Students will gain a qualitative understanding of thermodynamics. A. Students will develop a qualitative understanding of enthalpy and entropy. B. Students will predict the sign of an entropy change for chemical or physical processes. C. Students will understand entropy effects such as the chelate effect on chemical reactions. D. Students will use bond enthalpies or pKas to determine the enthalpy change for a reaction. E. Students will draw or interpret a reaction progress diagram. F. Students will apply the Principle of Microscopic Reversibility to understand reaction mechanisms. G. Students will use Gibbs free energy to relate enthalpy and entropy changes. H. Students will develop a qualitative understanding of progress toward equilibrium under physiological conditions (the difference between G and Go.) I. Students will understand coupled reactions and how this can be used to drive a non- spontaneous reaction toward products. J. Students will apply LeChatelier’s Principle to affect the position of anequilibrium by adding or removing reactants or products.
    [Show full text]
  • Nobel Lecture, 8 December 1981 by ROALD HOFFMANN Department of Chemistry, Cornell University, Ithaca, N.Y
    BUILDING BRIDGES BETWEEN INORGANIC AND ORGANIC CHEMISTRY Nobel lecture, 8 December 1981 by ROALD HOFFMANN Department of Chemistry, Cornell University, Ithaca, N.Y. 14853 R. B. Woodward, a supreme patterner of chaos, was one of my teachers. I dedicate this lecture to him, for it is our collaboration on orbital symmetry conservation, the electronic factors which govern the course of chemical reac- tions, which is recognized by half of the 1981 Nobel Prize in Chemistry. From Woodward I learned much: the significance of the experimental stimulus to theory, the craft of constructing explanations, the importance of aesthetics in science. I will try to show you how these characteristics of chemical theory may be applied to the construction of conceptual bridges between inorganic and organic chemistry. FRAGMENTS Chains, rings, substituents - those are the building blocks of the marvelous edifice of modern organic chemistry. Any hydrocarbon may be constructed on paper from methyl groups, CH 3, methylenes, CH 2, methynes, CH, and carbon atoms, C. By substitution and the introduction of heteroatoms all of the skeletons and functional groupings imaginable, from ethane to tetrodotoxin, may be obtained. The last thirty years have witnessed a remarkable renaissance of inorganic chemistry, and the particular flowering of the field of transition metal organo- metallic chemistry. Scheme 1 shows a selection of some of the simpler creations of the laboratory in this rich and ever-growing field. Structures l-3 illustrate at a glance one remarkable feature of transition metal fragments. Here are three iron tricarbonyl complexes of organic moie- ties - cyclobutadiene, trimethylenemethane, an enol, hydroxybutadiene - which on their own would have little kinetic or thermodynamic stability.
    [Show full text]
  • Copyrighted Material
    1 INTRODUCTION 1.1 WHY STUDY ORGANOMETALLIC CHEMISTRY? Organometallic chemists try to understand how organic molecules or groups interact with compounds of the inorganic elements, chiefl y metals. These elements can be divided into the main group, consisting of the s and p blocks of the periodic table, and the transition elements of the d and f blocks. Main-group organometallics, such as n -BuLi and PhB(OH)2 , have proved so useful for organic synthesis that their leading characteristics are usually extensively covered in organic chemistry courses. Here, we look instead at the transition metals because their chemistry involves the intervention of d and f orbitals that bring into play reaction pathways not readily accessible elsewhere in the periodic table. While main-group organometallics are typically stoichiometric reagents, many of their transition metal analogs are most effective when they act as catalysts. Indeed, the expanding range of applications of catalysis is a COPYRIGHTEDmajor reason for the continued MATERIAL rising interest in organo- metallics. As late as 1975, the majority of organic syntheses had no recourse to transition metals at any stage; in contrast, they now very often appear, almost always as catalysts. Catalysis is also a central prin- ciple of Green Chemistry 1 because it helps avoid the waste formation, The Organometallic Chemistry of the Transition Metals, Sixth Edition. Robert H. Crabtree. © 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc. 1 2 INTRODUCTION for example, of Mg salts from Grignard reactions, that tends to accom- pany the use of stoichiometric reagents. The fi eld thus occupies the borderland between organic and inorganic chemistry.
    [Show full text]
  • Mineral Formation and Sorption Mechanisms in Marine Ferromanganese-Rich Sediments
    Mineral Formation and Sorption Mechanisms In Marine Ferromanganese-rich Sediments Amy Leanne Atkins Submitted in accordance with the requirements for the degree of Doctor of Philosophy The University of Leeds School of Earth and Environment October 2014 The candidate confirms that the work submitted is her own, except where work, which has formed part of jointly authored publications has been included. The contributions of the candidate and the other authors to this work have been indicated overleaf. The candidate confirms that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from this thesis may be published without proper acknowledgement. ii Declaration Chapter 4 is a reproduction of a peer-reviewed publication in the journal Geochimica et Cosmochimica Acta as: Atkins A. L., Shaw S., Peacock C. L. (2014) Nucleation and growth of todorokite: Implications for trace-metal cycling in marine sediments. Geochim. Cosmochim. Acta. 144, 109-125. TEM images presented in chapter 4 were collected by Michael Ward at the Leeds Electron Microscopy and Spectroscopy centre with the guidance of the candidate. All other experimental work has been conducted by the candidate. The interpretation of the experimental data, and preparation of the manuscript has been undertaken by the candidate with the help and guidance of her supervisors: Caroline L. Peacock and Sam Shaw. Chapter 5 is a reproduction of a manuscript currently in the final stages of preparation for submission to the journal Geochimica et Cosmochimica Acta as: Atkins A.
    [Show full text]
  • Crystallographic Determination of Wild Type, Mutant and Substrate
    Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. Crystallographic Determination of Wild Type, Mutant and SubstrateSubstrate---- Analogue Inhibited Structures of Bacterial Members of a Family of Superoxide Dismutases bybyby Simon Hardie Oakley Submitted as part of the requirements for the degree of Doctor of Philosophy Institute of Fundamental Sciences, Chemistry Massey University, New Zealand 2009 i "Part of the inhumanity of the computer is that, once it is competently programmed and working smoothly, it is completely honest." Isaac Asimov (1920-92), author, inventor of the word “robotics”. ii 0.1 Abstract Crystallographic Determination of Wild Type, Mutant and Substrate-Analogue Inhibited Structures of Bacterial Members of a Family of Superoxide Dismutases The iron and manganese superoxide dismutases are a family of metallo-enzymes with highly conserved protein folds, active sites and dimer interfaces. They catalyse the elimination of the cytotoxic free radical superoxide to molecular oxygen and hydrogen peroxide by alternate reduction then oxidation of the active- site with the concomitant transfer of protons from the solvent. There are many key aspects of enzymatic function that lack a structural explanation. The focus of this study is on three crystal structures. The iron-substituted manganese superoxide dismutase from Escherichia coli complexed with azide, a substrate-mimicking inhibitor, was solved to 2.2 Å. This “wrong” metal form shows a binding pattern seen previously in the manganese superoxide dismutase from Thermus thermophilus.
    [Show full text]
  • Ligand Field Theory Continued Chapter 10
    Coordination Chemistry II: Ligand Field Theory Continued Chapter 10 Wednesday, November 25, 2015 Adding Metal Electrons * t1u Metal ions typically have some valence electrons that can be accommodated in the metal d orbitals * a1g • d0 ions – Ti4+, Zr4+, V5+, Ta5+, Cr6+, Mo6+, etc. 1 3+ 4+ 4+ 5+ 5+ * • d ions – Ti , V , Ta , Cr , Mo , etc. eg • d2 ions – V3+, Ta3+, Cr4+, Mo4+, etc. • d3 ions – V2+, Ta2+, Cr3+, Mo3+, Mn4+, etc. t2g • d4-d7 – hold on • d8 ions – Co1+, Ni2+, Cu3+, etc. t1u • d9 ions – Ni1+, Cu2+, etc. a1g 10 1+ 2+ eg • d ions – Cu , Zn , etc. High Spin and Low Spin Complexes * * t1u The situation is a little more t1u complicated for d4-d7 metals: * * a1g a1g •d4 ions – Cr2+, Mo2+, Mn3+, Fe4+, Ru4+, etc. * * eg eg •d5 ions – Mn2+, Re2+, Fe3+, Ru3+, etc. LOW SPIN •d6 ions – Fe2+, Ru2+, Co3+, Rh3+, Pt4+, etc. t2g t2g HIGH SPIN •d7 ions – Fe1+, Ru1+, Co2+, Rh2+, Ni3+, etc. t t 1u For d4-d7 electron counts: 1u a1g a1g • when ∆o > Πtotal ➙ low spin eg eg • when ∆o < Πtotal ➙ high spin High Spin and Low Spin n+ Electron configurations for octahedral complexes, e.g. [M(H2O)6] . Only the d4 through d7 cases can be either high-spin or low spin. Δ< Π Δ> Π Weak-field ligands: Strong-field ligands: - Small Δ, High spin complexes - Large Δ, Low spin complexes Electron Pairing Energy The total electron pairing energy, Πtotal, has two components, Πc and Πe • Πc is a destabilizing energy for the Coulombic repulsion associated with putting two electrons into the same orbital • Πe is a stabilizing energy for electron exchange associated with
    [Show full text]
  • Surface Geochemistry of the Clay Minerals
    Proc. Natl. Acad. Sci. USA Vol. 96, pp. 3358–3364, March 1999 Colloquium Paper This paper was presented at the National Academy of Sciences colloquium ‘‘Geology, Mineralogy, and Human Welfare,’’ held November 8–9, 1998 at the Arnold and Mabel Beckman Center in Irvine, CA. Surface geochemistry of the clay minerals GARRISON SPOSITO*†,NEAL T. SKIPPER‡,REBECCA SUTTON*, SUNG-HO PARK*, ALAN K. SOPER§, AND JEFFERY A. GREATHOUSE¶ *Earth Sciences Division, Mail Stop 90y1116, Ernest Orlando Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720; ‡Department of Physics and Astronomy, University College, Gower Street, London WC1E 6BT, United Kingdom; §ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, United Kingdom; and ¶Department of Chemistry, University of the Incarnate Word, 4301 Broadway, San Antonio, TX 78209 ABSTRACT Clay minerals are layer type aluminosilicates (6) and in the construction of environmental liners (7). Major that figure in terrestrial biogeochemical cycles, in the buff- impact on industrial organic synthesis comes in the many ering capacity of the oceans, and in the containment of toxic designed catalysts developed from clay minerals with adsorbed waste materials. They are also used as lubricants in petroleum polymeric cations (8). extraction and as industrial catalysts for the synthesis of many Certain clay minerals are isostructural with mica (1, 2) but organic compounds. These applications derive fundamentally are not as well crystallized because of random isomorphic from the colloidal size and permanent structural charge of cation substitutions in their structure (9, 10). These cation clay mineral particles, which endow them with significant substitutions lead to a negative net surface charge that induces surface reactivity.
    [Show full text]
  • Organometallics Study Meeting H.Mitsunuma 1
    04/21/2011 Organometallics Study Meeting H.Mitsunuma 1. Crystal field theory (CFT) and ligand field theory (LFT) CFT: interaction between positively charged metal cation and negative charge on the non-bonding electrons of the ligand LFT: molecular orbital theory (back donation...etc) Octahedral (figure 9-1a) d-electrons closer to the ligands will have a higher energy than those further away which results in the d-orbitals splitting in energy. ligand field splitting parameter ( 0): energy between eg orbital and t2g orbital 1) high oxidation state 2) 3d<4d<5d 3) spectrochemical series I-< Br-< S2-< SCN-< Cl-< N -,F-< (H N) CO, OH-< ox, O2-< H O< NCS- <C H N, NH < H NCH CH NH < bpy, phen< NO - - - - 3 2 2 2 5 5 3 2 2 2 2 2 < CH3 ,C6H5 < CN <CO cf) pairing energy: energy cost of placing an electron into an already singly occupied orbital Low spin: If 0 is large, then the lower energy orbitals(t2g) are completely filled before population of the higher orbitals(eg) High spin: If 0 is small enough then it is easier to put electrons into the higher energy orbitals than it is to put two into the same low-energy orbital, because of the repulsion resulting from matching two electrons in the same orbital 3 n ex) (t2g) (eg) (n= 1,2) Tetrahedral (figure 9-1b), Square planar (figure 9-1c) LFT (figure 9-3, 9-4) - - Cl , Br : lower 0 (figure 9-4 a) CO: higher 0 (figure 9-4 b) 2. Ligand metal complex hapticity formal chargeelectron donation metal complex hapticity formal chargeelectron donation MR alkyl 1 -1 2 6-arene 6 0 6 MH hydride 1 -1 2 M MX H 1 -1 2 halogen 1 -1 2 M M -hydride M OR alkoxide 1 -1 2 X 1 -1 4 M M -halogen O R acyl 1 -1 2 O 1 -1 4 M R M M -alkoxide O 1-alkenyl 1 -1 2 C -carbonyl 1 0 2 M M M R2 C -alkylidene 1 -2 4 1-allyl 1 -1 2 M M M O C 3-carbonyl 1 0 2 M R acetylide 1 -1 2 MMM R R C 3-alkylidine 1 -3 6 M carbene 1 0 2 MMM R R M carbene 1 -2 4 R M carbyne 1 -3 6 M CO carbonyl 1 0 2 M 2-alkene 2 0 2 M 2-alkyne 2 0 2 M 3-allyl 3 -1 4 M 4-diene 4 0 4 5 -cyclo 5 -1 6 M pentadienyl 1 3.
    [Show full text]
  • Metal Ligand Bonding
    METAL LIGAND BONDING DR. ALKA GUPTA DEPARTMENT OF CHEMISTRY BRAHMANAND COLLEGE, KANPUR METAL LIGAND BONDING Three modern theories have been suggested to explain the nature of metal-ligand bonding in transition metal complexes. Valence Bond Theory, VBT (due to L. Pauling and J. L. Slater, 1935). Crystal Field Theory, CFT (due to H. Bethe, 1929 and J. Van Vleck, 1932) Ligand Field Theory, LFT or Molecular Orbital Theory, MOT (due to J. Van Vleck, 1935). Valence Bond Theory (VBT) Assumptions: The central metal atom provides a number of empty s, p and d atomic orbitals equal to it’s co- ordination number for the formation of co- ordinate bond with ligand orbitals. Each ligand has at least one s-orbital containing a lone pair of electrons. The empty orbitals of the metal ion hybridise together to form hybrid orbitals which are equal in number as the atomic orbitals taking part in hybridisation. These are vacant, equivalent in energy and have definite geometry. Different types of hybridisation in co- ordination compounds C.N. Hybridisation Geometry Examples + 2 sp Linear or diagonal [Ag (NH3)2] 2 – 3 sp Trigonal planar [Hg I3] 3 0 2- 4 sp Tetrahedral [Ni(CO)4] , [Ni X4] , ( X= Cl–, Br–, I– ) 2 2- 4 d sp Square planar [Ni (CN)4] 3 o 3- 5 d sp Trigonal [Fe (CO)5] , [Cu Cl5] bipyramidal 3 2- 5 sp d Square pyramidal [Sb F5] , IF5 2 3 3- 3+ 6 d sp Octahedral [Fe (CN)6] , [Co(NH3)6] 3 2 3- 3- 6 sp d Octahedral [CoF6] , [FeF6] • Empty hybrid orbital of the metal atom or ion overlap with the filled orbitals of the ligand to form ligandmetal coordinate bonds.
    [Show full text]
  • Arsenic Adsorption Onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations
    Minerals 2014, 4, 208-240; doi:10.3390/min4020208 OPEN ACCESS minerals ISSN 2075-163X www.mdpi.com/journal/minerals Article Arsenic Adsorption onto Minerals: Connecting Experimental Observations with Density Functional Theory Calculations Heath D. Watts 1,*, Lorena Tribe 2 and James D. Kubicki 1,3,* 1 Department of Geosciences, The Pennsylvania State University, University Park, PA 16802, USA 2 Division of Science, The Pennsylvania State University, Berks, Reading, PA 19610, USA; E-Mail: [email protected] 3 Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA 16802, USA * Authors to whom correspondence should be addressed; E-Mails: [email protected] (H.D.W.); [email protected] (J.D.K.); Tel.: +1-814-865-3951 (J.D.K.); Fax: +1-814-867-2378 (J.D.K). Received: 24 December 2013; in revised form: 25 February 2014 / Accepted: 6 March 2014 / Published: 27 March 2014 Abstract: A review of the literature about calculating the adsorption properties of arsenic onto mineral models using density functional theory (DFT) is presented. Furthermore, this work presents DFT results that show the effect of model charge, hydration, oxidation state, and DFT method on the structures and adsorption energies for AsIII and AsV onto Fe3+-(oxyhydr)oxide cluster models. Calculated interatomic distances from periodic planewave and cluster-model DFT are compared with experimental data for AsIII and AsV adsorbed to Fe3+-(oxyhydr)oxide models. In addition, reaction rates for the adsorption of AsV on α-FeOOH (goethite) (010) and Fe3+ (oxyhydr)oxide cluster models were calculated using planewave and cluster-model DFT methods. Keywords: arsenic; density functional theory (DFT); kinetics; thermodynamics; adsorption; computational chemistry; planewave DFT; reaction rates; As—Fe bond distances Minerals 2014, 4 209 1.
    [Show full text]
  • Curriculum & Syllabus for M.Sc. CHEMISTRY
    M.Sc. Chemistry Regulations 2016 Curriculum & Syllabus for M.Sc. CHEMISTRY (Four Semesters/ Full Time) CURRICULUM SEMESTER I S. No. Course Course Title L T P C Code 1. CHC6101 Organic Chemistry 3 0 0 3 2. Thermodynamics and CHC6102 3 0 0 3 Electrochemistry 3. CHC6103 Inorganic Chemistry 3 0 0 3 4. CHC6104 Analytical Chemistry 3 1 0 4 5. Elective 3* 6. CHC6105 Organic Chemistry Practical 0 0 4 2 7. CHC6106 Inorganic Chemistry Practical -I 0 0 4 2 8. CHC6107 Physical Chemistry Practical - I 0 0 4 2 CHC6108 Seminar 2 1 Total credits 23 SEMESTER II S. No. Course Course Title L T P C Code 1 GEC6202 Research Methodology 3 0 0 3 2. CHC6201 Synthetic Organic Chemistry 3 1 0 4 3. CHC6202 Quantum Chemistry 3 1 0 4 4. CHC6203 Coordination Chemistry 3 0 0 3 5. Elective 3 1 0 4 7 Synthetic Organic Chemistry CHC6204 0 0 4 2 Practical 8. CHC6205 Inorganic Chemistry Practical-II 0 0 4 2 9 CHC6206 Physical Chemistry Practical -II 0 0 4 2 Total Credits 24 B.S. Abdur Rahman Crescent Institute of Science & Technology 1 M.Sc. Chemistry Regulations 2016 SEMESTER III S. No. Course Course Title L T P C Code 1. CHC7101 Advanced Organic Chemistry 3 0 0 3 2. CHC7102 Physical Chemistry 3 0 0 3 3. CHC7103 Advanced Inorganic Chemistry 3 0 0 3 Elective 11** CHC7104 Internship (during summer vacation) 1 7 CHC7201 Project Phase -1 2*** Total Credits 21 SEMESTER IV S. No. Course Course Title L T P C Code 1.
    [Show full text]
  • Lecture 28: Transition Metals: Crystal Field Theory Part I
    5.111 Lecture #28 Wednesday, November 19, 2014 Reading For Today: 16.8-16.11 in 4th and 5th editions Reading for Lecture #29: same as above Topic: I. Introduction to Crystal Field Theory II. Crystal Field Theory: Octahedral Case III. Spectrochemical Series I. Introduction to Crystal Field Theory Crystal field and ligand field theories were developed to explain the special features of transition metal coordination complexes, including their beautiful colors and their magnetic properties. Coordination complexes are often used as contrast agents for magnetic resonance imaging (MRI) and other types of imaging. Basic idea behind theories: When a metal ion with a given oxidation number (Mn+, where M is a metal and n+ is its oxidation number) is placed at the center of a coordination sphere defined by a set of ligands, the energy levels of the d orbitals housing the metal electrons are from those in the free metal ion. Crystal field theory is based on an ionic description of the metal-ligand bond. Ligand field theory includes covalent and ionic aspects of coordination. It is a more powerful description of transition metal complexes. It is, however, beyond the scope of this course. (Take 5.03 if you are interested in this topic). Crystal Field Theory considers ligands as point charges and considers the repulsion between the negative point charges and the d-orbitals, and even though this theory is simple, a number of properties of transition metals can be explained. L- L- L- Mn+ L- - L L- © W.H.Freeman & Co Ltd. All rights reserved. This content is excluded from our Creative Commons license.
    [Show full text]