1 / 19

Nomenclature of Coordination Complexes Ligands Table 21.13 lists common ligands, names, structures, and abbreviations

Chapter 20 Lecture 2 Transition Metals. Nomenclature of Coordination Complexes Ligands Table 21.13 lists common ligands, names, structures, and abbreviations. Naming and Writing Formulas of Coordination Compounds The cation comes first, then the anion(s)

larya
Download Presentation

Nomenclature of Coordination Complexes Ligands Table 21.13 lists common ligands, names, structures, and abbreviations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

    1. Nomenclature of Coordination Complexes Ligands Table 21.13 lists common ligands, names, structures, and abbreviations

    2. Naming and Writing Formulas of Coordination Compounds The cation comes first, then the anion(s) diamminesilver(I) chloride [Ag(NH3)2]Cl potassium hexacyanoferrate(III) K3[Fe(CN)6] Inner Sphere Complex Ion is enclosed in brackets Ligands are named before the metal Metal is written first in the formula Metal oxidation state in Roman Numerals in parenthesis after the metal ion A space only between cation and anion No capitalization is needed tetraamminecopper(II) sulfate [Cu(NH3)4]SO4 hexaamminecobalt(III) chloride [Co(NH3)6]Cl3 Prefixes denote the number of each ligand type. Special prefixes and parentheses are used if the ligand already contains a prefix. 2 di bis 6 hexa hexakis tri tris 7 hepta heptakis tetra tetrakis 8 octa octakis penta pentakis 9 nona nonakis 10 deca decakis

    3. dichlorobis(ethylenediamine)cobalt(III) fluoride [Co(en)2Cl2]F tris(bipyridine)iron(II) chloride [Fe(bipy)3]Cl2 Ligands are named in alphabetical order not counting prefixes. tetraamminedichlorocobalt(III) [Co(NH3)4Cl2]+ amminebromochloromethylamineplatinum(II) [Pt(NH3)BrCl(CH3NH2)] Ligand name alterations: Anionic ligands are given an -o suffix: chloro, flouro, oxo, sulfato Neutral ligands keep their name: methylamine, bipyridine Water becomes aqua NH3 becomes ammine to keep separate from alkylamines How to handle anionic complexes Add ate to the metal name if the complex ion has an overall (-) charge Negatively charged complexes of certain metals use their Latin names: Fe = ferrate Ag = argenate Sb = stibate Pb = plumbate Sn = stannate Au = aurate c) [PtCl4]2- = tetrachloroplatinate(II)

    4. II. Coordination Chemistry Isomers = same ligands arranged differently Hierarchy of isomers

    5. Structural Isomers = different ligands in coordination sphere 1) Coordination Isomers = ratio of ligand:metal same, but ligands are attached to metal ions in different numbers [Pt(NH3)2Cl2] [Pt(NH3)3Cl][Pt(NH3)Cl3] [Pt(NH3)4][PtCl4] 2) Linkage Isomers = depends on which atom of the ligand is attached to metal SCN- Linkage isomers Pb2+SCN = thiocyanate complex Fe3+NCS = isothiocyanate complex NO2- Linkage isomers MONO = nitrito complex MNO2 = nitro complex

    6. C. Stereoisomers = same ligands, but different spatial arrangement Geometric Isomers cis- or trans- isomers possible for MA2B2 Six-coordinate complexes also can have cis and trans isomers Optical Isomers = have opposite effect on plane polarized light

    7. Optical Isomers are non-superimposable mirror images of each other Optical Isomers are called Enantiomers (Many biomolecules/drugs) An object or molecule that has an Enantiomer is called Chiral

    8. III. Coordination Compounds and the Localized Electron Model History Proposed by Pauling in the 1930s Describes bonding using hybrid orbitals filled with e- pairs Extension of Lewis/VSEPR to include d-orbitals Theory Metal ions utilize d-orbitals in hybrids Octahedral complexes require 6 hybrid orbitals d2sp3 hybridization of metal Atomic Orbitals provides new MO Ligand lone pairs fill the hybrid orbitals to produce the bond d-orbitals can come from 3d (low spin) or 4d (high spin)

    9. 3) Coordinate Covalent Bond = Ligand as Lewis Base and Metal as Lewis Acid

    10. Problems with the theory High energy 4d orbitals are unlikely participants in bonding Doesnt explain electronic spectra of transition metal complexes Crystal Field Theory History Developed to describe metal ions in solid state crystals only M+ is surrounded by A- point charges Energies of the d-orbitals are split due to unequal geometric interactions with the point charges Does not take into account covalency and molecular orbitals Has been extended to do so in Ligand Field Theory Theory Place degenerate set of 5 d-orbitals into an octahedral field of (-) charges (L:) The electrons in the d-orbitals are repelled by the (-) charge of the ligands The dz2 and dx2-y2 orbitals are most effected because their lobes point directly along x,y,z axes where the point charges are The dxy, dxz, and dyz orbitals arent destabilized as much

    12. The energy difference between these orbital sets is called delta octahedral = Do The low energy set has t2g symmetry and are stabilized by 0.4 Do each The high energy set has eg symmetry and are destabilized by +0.6 Do each The total energy of the 5 d-orbitals is the same as in the uniform field = 0 (2)(+0.6 Do) + (3)(-0.4 Do) = 0

    13. CFSE = Crystal Field Stabilization Energy = how much energy is gained by the electrons in the 5 d-orbitals due to their splitting Co(III) = d6 low spin (6e-)(-0.4 Do) = -2.4 Do stabilization Cu(II) = d9 (6e-)(-0.4 Do) + (3e-)(+0.6 Do) = -0.6 Do stabilization Cu(I) = d10 (6e-)(-0.4 Do) + (4e-)(+0.6 Do) = 0 Do stabilization

    15. 7) All octahedral metal complexes will have the exact same MO diagram, only the number of d-electrons will change 8) The 6 bonding MOs, with lowered energy for their electron pairs is what holds the metal complex together 9) The d-electrons in the t2g and eg* MOs Determine the Ligand Field Determine the geometry and many characteristics of the metal complex Orbital Splitting and Electron Spin The energy difference between the t2g and eg* MOs = Do = delta octahedral Strong-Field Ligands = ligands whose orbitals interact strongly with metal ion eg* is raised in energy Do is large Weak-Field Ligands = ligands whose orbitals interact weakly with metal ion eg* is raised only slightly in energy Do is small

    16. Electron Spin d0 d3 and d8 d10 octahedral complexes have only one possible arrangement of electrons in the t2g and eg* MOs d4 d7 octahedral complexes have two possible electronic arrangements Low Spin = least number of unpaired electrons; favored by strong field ligands with large Do High Spin = maximum number of unpaired electrons; favored by weak field ligands with small Do

    17. Splittings for other geometries:

    18. The Spectrochemical Series A list of Strong-Field through Weak-Field ligands s-donors only en > NH3 because it is more basic (stronger field ligand) F- > Cl- > Br- > I- (basicity) p-donors Halides field strength is lowered due to p-donor ability For similar reasons H2O, OH-, RCO2- also are weak field ligands p-acceptors increase ligand field strength: CO, CN- > phen > NO2- > NCS- Combined Spectrochemical Series

    19. Electronic Spectra A characteristic of transition metal complexes is color arising from electronic transitions between d-orbitals of different energies Electronic transition in an octahedral d1 complex The UV-Vis Experiment and the spectral result

More Related