Unless otherwise stated, all images in this file have been reproduced from:

1. Unless otherwise stated, all images in this file have been reproduced from: Blackman, Bottle, Schmid, Mocerino and Wille,Chemistry, 2007 (John Wiley)     ISBN: 9 78047081 0866

2. CHEM1002 [Part 2] Dr Michela Simone Lecturer BSc (I Hons), MSc, D.Phil. (Oxon), MRSC, MRACI Weeks 8 – 13 Office Hours: Monday 3-5, Friday 4-5 Room: 412A (or 416) Phone: 93512830 e-mail:michela.simone@sydney.edu.au

3. Summary of Last Lecture • Solubility Equilibria II • The solubility of a salt MmXn is reduced by the addition or presence in solution of either Mn+ or Xm- from another source – the common ion effect • The solubility of hydroxides is very sensitive to pH since this controls [OH-(aq)] • The solubility of a salt in the presence of a common ion can be calculated from the solubility product as this gives the maximum concentrations of the ions that are allowed

4. Complexes I • Lecture 12 • Hydrolysis of Metal Ions • Metal Complexes • Ligands • Blackman Chapter 13, Sections 13.1-13.4 • Lecture 13 • Isomerism • Stability • Blackman Chapter 13, Sections 13.1-13.4

5. Hydrolysis of Metal Ions + M(H2O)42+(aq) M2+ H2O(l) adduct • Metal cations act as Lewis acids (electron pair acceptor) • Water is the Lewis base (electron pair donor)

6. Acidity of Aqueous Transition Metal Ions [Fe(OH2)5(OH)]2+ + H+ [Fe(OH2)6]3+

7. ACID STRENGTH Metal Ion Hydrolysis • The higher the metal charge, the greater the hydrolysis • The smaller the metal ion, the greater the hydrolysis

8. The Coordination Bond L L Mn+ • A ligand donates an electron pair to the metal ion to form a coordinate or dative bond. • All ligands have at least one lone pair • some ligands have more than one lone pair and can bond to two or more metal ions • Usually more than one ligand binds to the metal ion • commonly 4 or 6 ligands coordinate to a metal

9. Metal Complexes • A coordination compound: • a complex ion (the metal and its ligands) • counter ions to balance its charge • The metal ion has a positive charge (Co3+, Fe2+, Cu2+ etc) • The ligands can be: • neutral (NH3, OH2, pyridine, amines etc), giving rise to positively charged complexes (e.g. [Co(NH3)6]3+) • negatively charged (Cl-, OH-, CN- etc), giving rise to negatively charged complexes (e.g. [Co(CN)6]3-) • a mixture of these, giving rise to positive, negative or neutral complexes (e.g. [Co(NH3)3(CN)3]

10. Metal Complexes [Co(NH3)6]Cl3 • Square brackets indicate the complex ion: • [Co(NH3)]3+ • Co3+ with six neutral NH3ligands • Three Cl- counter ions to balance the charge • When dissolved in water, the complex ions and counter ions are separate [Co(NH3)6]Cl3 [Co(NH3)6]3+(aq) + 3Cl-(aq)

11. Typical coordination number for some metal ions. M+ CN M2+ CN M3+ CN Cu+ 2,4 Mn2+ 4,6 Sc3+ 6 Ag+ 2 Fe2+ 6 Cr3+ 6 Au+ 2,4 Co2+ 4,6 Co3+ 6 Ni2+ 4,6 Au3+ 4 Cu2+ 4,6 Zn2+ 4,6 Coordination Number • The number of ligands bonded to the metal ion • varies from 2 - 8 depending on the metal and ligand sizes and charges • 4 and 6 are the most common

12. Complex Geometry

13. Chelate Ligands • Unidentate or monodentate) ligand – forms one bond • Bidentate ligand – can form two bonds • Polydentate ligand – can form > two bonds • tridentate • tetradentate • pentadentate • hexadentate • etc ... CHELATE LIGANDS • Chelate effect: complexes with chelate ligands are usually more stable than those with monodentate ligands of the same type:

14. Some Chelate Ligands • Bidendate • ethane-1,2-diamine (en)

15. Some Chelate Ligands • Hexadendate • ethane-1,2-diaminetetraacetic acid(H4EDTA) EDTA4- [Co(EDTA)]- • EDTA is used to treat severe lead poisoning...and to soften water in shampoo and soaps

16. Summary: Complexes I • Learning Outcomes - you should now be able to: • Complete the worksheet • Explain why solutions of metal ions are acidic • Identify the complex ion and ligands in a coordination compound • Draw representations of octahedral, tetrahedral and square planar complexes using tapered bonds • Answer review problems 13.51-13.58 in Blackman • Next lecture: • Isomerism and stability of complexes

17. Practice Examples • What are the possible geometries of a metal complex complex with a coordination number of 4? • square planar or tetrahedral or octahedral • square planar or tetrahedral • octahedral only • tetrahedral only • square planar only

18. Naming Metal Complexes: (i) Ligands • The normal chemical name is used unless the ligand is negatively charged in which cases “o” is used as the suffix Special Cases

19. Naming Metal Complexes: (i) Ligands • The number of ligands of any one type is indicated with the appropriate Greek prefix • monodentate: di, tri, tetra, penta, hexa, etc e.g. dichlorido, tetraaqua, hexaamine • polydentate: bis, tris, tetrakis etc • If there is more than one ligand type • Listed in alphabetical order with no space between them! • Prefixes do not affect the order diamminedichloridodifluorido A < C < F triamminedichloridofluorido A < C < F

20. Naming Metal Complexes: (ii) Metal • If the complex is neutral or positively charged the normal metal name is used • If the complex is negatively charged, ‘ate’ is added to the metal name • Co: cobaltate • Zn: zincate • Exceptions (historic):

21. Naming Metal Complexes: (iii) Metal • Metal is named after ligands with no space between them! • The oxidation state of the metal is indicated by Roman numerals • Fe3+ is given as iron(III) • Mn7+ is given as manganese(VII)

22. Naming Metal Complexes • Counter ions are named as separate words and are not numbered • cations before the complex ion K3[Co(CN)6] potassium hexacyandidocobaltate(III) • anions after the complex ion [Co(NH3)4Cl2]Cl tetraamminedichloridocobalt(III) chloride

23. Naming Metal Complexes • Indicating the presence of solvent molecules • Water of crystallisation (hydration) is indicated separately at the end of the name • [Co(NH3)4Cl2]Cl·2H2O tetraamminedichlorocobalt(III) chloride-2-water