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

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 It is a good idea if all lecturers can make an appearance for the first lecture. Remind students we are IT for the rest of the semester. DEMOS for this lecture: EXP 2.3: “Charles law (2.3), EXP 2.1 “CO2 density (2.1)

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

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

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)

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

Metal Ion Hydrolysis Free Ion Hydrated Ion Ka Fe3+ Fe(H2O)63+(aq) 6 x 10-3 Cr3+ Cr(H2O)63+(aq) 1 x 10-4 Al3+ Al(H2O)63+(aq) 1 x 10-5 Be2+ Be(H2O)42+(aq) 4 x 10-6 Cu2+ Cu(H2O)62+(aq) 3 x 10-8 Pb2+ Pb(H2O)62+(aq) Zn2+ Zn(H2O)62+(aq) 1 x 10-9 Co2+ Co(H2O)62+(aq) 2 x 10-10 Ni2+ Ni(H2O)62+(aq) 1 x 10-10 ACID STRENGTH The higher the metal charge, the greater the hydrolysis The smaller the metal ion, the greater the hydrolysis

The Coordination Bond L Mn+ L 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

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]

[Co(NH3)6]Cl3 [Co(NH3)6]3+(aq) + 3Cl-(aq) Metal Complexes [Co(NH3)6]Cl3 Square brackets indicate the complex ion: [Co(NH3)]3+ Co3+ with six neutral NH3 ligands 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)

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 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

Complex Geometry CN Geometry Examples 2 linear [Ag(NH3)2]+ [AuCl2]- 4 square planar [Pd(NH3)4]2+ [PtCl4]2- tetrahedral [Zn(NH3)4]2+ [CuCl4]2- 6 octahedral [Co(NH3)6]3+ [FeCl6]3-

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:

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

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

Summary: Complexes I Complete the worksheet 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

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 The nickel(II) ion exists as the [Ni(OH2)6]2+ complex ion in aqueous solution. Define the term complex. Why is such a solution acidic? Write a balanced equation for the corresponding reaction.

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 Neutral aqua H2O ammine NH3 amine CH3NH2 etc Special Cases Anionic fluorido F- chlorido Cl- bromido Br- iodido I- cyanido CN- hydroxido OH-

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

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): Metal Name in anion not: iron ferrate ironate copper cuprate copperate lead plumbate leadate

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)

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

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