Transition Metals and Coordination Compounds

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Transition Metals and Coordination Compounds. Presented by: Sudhir Kumar Maingi PGT CHEMISTRY K.V. No. 1 PATHANKOT, JAMMU REGION. Gemstones. the colors of rubies and emeralds are both due to the presence of Cr 3+ ions – the difference lies in the crystal hosting the ion. - PowerPoint PPT Presentation

Text of Transition Metals and Coordination Compounds

  • Transition Metals and Coordination Compounds Presented by: Sudhir Kumar Maingi PGT CHEMISTRY K.V. No. 1 PATHANKOT, JAMMU REGION

  • *Gemstonesthe colors of rubies and emeralds are both due to the presence of Cr3+ ions the difference lies in the crystal hosting the ionSome Al3+ ions in Al2O3 are replaced by Cr3+Some Al3+ ions in Be3Al2(SiO3)6 are replaced by Cr3+

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  • *Properties and Electron Configuration of Transition Metalsthe properties of the transition metals are similar to each otherand very different tot he properties of the main group metalshigh melting points, high densities, moderate to very hard, and very good electrical conductorsin general, the transition metals have two valence electrons we are filling the d orbitals in the shell below the valenceGroup 1B and some others have 1 valence electron due to promotion of an electron into the d sublevel to fill itform ions by losing the ns electrons first, then the (n 1)d

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  • *Atomic Sizethe atomic radii of all the transition metals are very similarsmall increase in size down a column

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  • *Ionization Energythe first ionization energy of the transition metals slowly increases across a seriesthird transition series slightly higher 1st IEtrend opposite to main group elements

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  • *Electronegativitythe electronegativity of the transition metals slowly increases across a seriesexcept for last element in the serieselectronegativity slightly increases down the columntrend opposite to main group elements

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  • *Oxidation Statesoften exhibit multiple oxidation statesvary by 1highest oxidation state is group number for 3B to 7B

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  • *Coordination Compoundswhen a complex ion combines with counterions to make a neutral compound it is called a coordination compoundthe primary valence is the oxidation number of the metalthe secondary valence is the number of ligands bonded to the metalcoordination number coordination number range from 2 to 12, with the most common being 6 and 4CoCl36H2O = [Co(H2O)6]Cl3

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  • *Coordination Compound

  • *Complex Ion Formationcomplex ion formation is a type of Lewis acid-base reactiona bond that forms when the pair of electrons is donated by one atom is called a coordinate covalent bond

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  • *Ligands with Extra Teethsome ligands can form more than one coordinate covalent bond with the metal atomlone pairs on different atoms that are separate enough so that both can reach the metalchelate is a complex ion containing a multidentate ligandligand is called the chelating agent

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  • *EDTAa Polydentate Ligand

  • *Complex Ions with Polydentate Ligands

  • *Geometries in Complex Ions

  • *Naming Coordination Compoundsdetermine the name of the noncomplex iondetermine the ligand names and list them in alphabetical orderdetermine the name of the metal cationname the complex ion by:name each ligand alphabetically, adding a prefix in front of each ligand to indicate the number found in the complex ionfollow with the name of the metal cationwrite the name of the cation followed by the name of the anion

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  • *Common Ligands

  • *Common Metals found in Anionic Complex Ions

  • *IsomersStructural isomers are molecules that have the same number and type of atoms, but they are attached in a different orderStereoisomers are molecules that have the same number and type of atoms, and that are attached in the same order, but the atoms or groups of atoms point in a different spatial direction

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  • *Linkage Isomers

  • *Geometric Isomersgeometric isomers are stereoisomers that differ in the spatial orientation of ligands cis-trans isomerism in octahedral complexes MA4B2 fac-mer isomerism in octahedral complexes MA3B3 cis-trans isomerism in square-planar complexes MA2B2

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  • *Ex. 24.5 Draw the structures and label the type for all isomers of [Co(en)2Cl2]+the ethylenediamine ligand (en = H2NCH2CH2NH2) is bidentateeach Cl ligand is monodentateoctahedralMA4B2

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  • *Optical Isomersoptical isomers are stereoisomers that are nonsuperimposable mirror images of each other[Co(en)3]3+

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  • *Ex 24.7 Determine if the cis-trans isomers of [Co(en)2Cl2]+ are optically activedraw the mirror image of the given isomer and check to see if they are superimposabletrans isomer identical to its mirror imageno optical isomerismcis isomer mirror image is nonsuperimposableoptical isomers

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  • *Bonding in Coordination CompoundsValence Bond Theorybonding take place when the filled atomic orbital on the ligand overlaps an empty atomic orbital on the metal ionexplain geometries well, but doesnt explain color or magnetic properties

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  • *Bonding in Coordination CompoundsCrystal Field Theorybonds form due to the attraction of the electrons on the ligand for the charge on the metal cationelectrons on the ligands repel electrons in the unhybridized d orbitals of the metal ionthe result is the energies of orbitals the d sublevel are splitthe difference in energy depends the complex and kinds of ligandscrystal field splitting energystrong field splitting and weak field splitting

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  • *Splitting of d Orbital Energies due to Ligands in a Octahedral Complex

  • *Strong and Weak Field Splitting

  • *Complex Ion Colorthe observed color is the complimentary color of the one that is absorbed

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  • *Complex Ion Color and Crystal Field Strengththe colors of complex ions are due to electronic transitions between the split d sublevel orbitalsthe wavelength of maximum absorbance can be used to determine the size of the energy gap between the split d sublevel orbitalsEphoton = hn = hc/l = D

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  • *Ligand and Crystal Field Strengththe strength of the crystal field depends in large part on the ligandsstrong field ligands include: CN > NO2 > en > NH3weak field ligands include H2O > OH > F > Cl > Br > Icrystal field strength increases as the charge on the metal cation increases

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  • *Magnetic Properties and Crystal Field Strengththe electron configuration of the metal ion with split d orbitals depends on the strength of the crystal fieldthe 4th and 5th electrons will go into the higher energy dx2-y2 and dz2 if the field is weak and the energy gap is small leading to unpaired electrons and a paramagnetic complexthe 4th thru 6th electrons will pair the electrons in the dxy, dyz and dxz if the field is strong and the energy gap is large leading to paired electrons and a diamagnetic complex

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  • *Low Spin & High Spin Complexesonly electron configurations d4, d5, d6, or d7 can have low or high spin

  • *Tetrahedral Geometry andCrystal Field Splittingbecause the ligand approach interacts more strongly with the planar orbitals in the tetrahedral geometry, their energies are raisedmost high-spin complexes

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  • *Square Planar Geometry andCrystal Field Splittingd8 metalsthe most complex splitting patternmost are low-spin complexes

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  • *Applications of Coordination Compoundsextraction of metals from oressilver and gold as cyanide complexesnickel as Ni(CO)4(g)use of chelating agents in heavy metal poisoningEDTA for Pb poisoningchemical analysisqualitative analysis for metal ionsblue = CoSCN+red = FeSCN2+

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  • *Applications of Coordination Compoundscommercial coloring agentsprussian blue = mixture of hexacyanoFe(II) and Fe(III)inks, blueprinting, cosmetics, paintsbiomoleculesporphyrin ringcytochrome Chemoglobinchlorphyll

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  • Tro, Chemistry: A Molecular Approach*Applications of Coordination Compoundscarbonic anhydrase catalyzes the reaction between water and CO2contains tetrahedrally complexed Zn2+

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  • *Applications of Coordination CompoundsDrugs and Therapeutic Agentscisplatinanticancer drug

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  • * Thank You

    Presented by: Sudhir Kumar Maingi PGT CHEMISTRY K.V. No. 1 PATHANKOT, JAMMU REGION E-MAIL: sudhir.maingi@gmail.com sudhir_maingi@rediffmail.com Phone: 8146832622

    Acknowledgements : Prentice Hall Publications Steven S. Zumdahl

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