Complexes are assemblies of a central metal ion bonded to surrounding ligands. Common ligands include NH3, CN-, OH-, and CO. Transition metals can form complexes with varying coordination numbers and oxidation states. Complex ions undergo ligand substitution and acid-base decomposition reactions in solution.

1. Chapter ____

2. Complexes: assemblies of a central metal ion bonded to a group of surroundings molecules or ions. Ex. [Ag(NH 3 ) 2 ] + Complex Ion: If the complex carries a charge Coordination Compounds: Compounds that contain complexes

3. Ligands: the molecules or ions that surround the metal ion in a complex and usually have at least one lone pair of electrons Ex. The 2 NH 3 ligands bonded to the Ag + Coordination Number: The number of donor atoms attached to a metal

4. Form one or more stable ions that have a complete d orbitals Recall how to write electron configurations for d orbital elements. Block 2B will not be considered because its only common oxidation state has a complete d orbital ‘ S’ electrons are the first to be removed when these metals form ions Atomic radius: decreases across the period because the 3d electrons shield the 4s electrons

5. Electronegativity & Ionization energy: increases slightly Closed packed structure and a very small atomic radii Results in a very strong metallic bond Leads to transition metals have higher densities, melting points, and boiling points. Form a variety of oxidation states in their compounds

6. Metal +1 +2 +3 +4 +5 +6 +7 Sc Colorless Ti Violet Colorless V Violet Green blue Yellow Cr Blue Green Yellow (CrO 4 2- ) orange (Cr 2 O 7 2- Mn Pale pink Brown Dark green (MnO 4 2- ) Intense purple (MnO 4 - ) Fe Pale green Yellow or brown Co Pink Orange/yellow Ni Green Cu Blue Zn colorless

7. They are either polar or anions Because ligands have lone pairs, they can function as Lewis bases This makes the metal a Lewis acid Ligand coordiante to the metal Ex. [Cu(NH 3 ) 4 ]SO 4 [Cu(NH 3 ) 4 ] 2+ CATION SO 4 2- ANION

8. The charge of a complex is the sum of the charges on the central atom on its surrounding ligands. Try these: What is the oxidation number of the central atom in [Co(NH 3 ) 5 Cl](NO 3 ) 2 [Ru(NH 3 ) 5 (H 2 O)]Cl 2 [Cr(NH 3 ) 6 ](NO 3 ) 3 K 4 [Fe(CN) 6 ]

9. The atom of the ligand bound directly to the metal is called the donor atom Ex. [Ag(NH 3 ) 2 ] + N is the donor atom The coordination number (the number of donor atoms attached to the metal) in the above example is 2. Dependent on the number of donor atoms present, ligands are classified as monodentate, bidentate, or polydentate Ex. Monodentate: H 2 O Bidentate: ethylenediamine: H 2 N-CH 2 –CH 2 –NH 2 Bidentate and polydentate ligands are called chelating agents : They hold the metal atom like a claw.

10. In naming salts, the name of the cation is given before the name of the anion. Ex. In [Co(NH 3 ) 5 Cl]Cl 2 , we name the [Co(NH 3 ) 5 Cl] 2+ and then Cl - . Within a complex ion or molecule, the ligands are named before the metal. Prefixes that give the number of ligands are not considered part of the ligand name in determining alphabetical order. In [Co(NH 3 ) 5 Cl] 2+ ion, the ammonia ligands are named first, then the chloride, then the metal: Pentaaminechlorocobalt (III)

11. 3. The names of anionic ligands end in the letter O, whereas neutral ones ordinarily bears the name of the molecule. Number of Ligands Prefix 1 Mono 2 Di 3 Tri 4 Tetra 5 Penta 6 Hexa Ligand Name Cl - Chloro OH - Hydroxo NO 2 - Nitrito CN - Cyano SO 4 2- Sulfato H 2 O Aquo or aqua NH 3 Ammine CO Carbonyl NO Nitrosyl

12. A Greek prefix is used to indicate the number of each kind of ligand when more than one is present. If the name of the ligand itself contains a Greek prefix, such as mono- or di-, the name of the ligand is enclosed in parentheses and alternate prefixes are used, Bis-, Tris-, tetrakis-,hexakis Ex. [Co(en) 3 ]Cl 3 tris(ethylenediamine)cobalt (III) chloride If the complex is an anion, its name ends in –ate. Ex. K 4 [Fe(CN) 6 ] hexocyanoferrate (II) ion Others: Copper: Cuprate Silver: Argenate

13. The oxidation number of the metal is given in parentheses in Roman numerals following the name of the metal. Try naming these: [Cr(H 2 O) 4 Cl 2 ]Cl [Co(NH 3 ) 4 (H 2 O)CN]Cl 2 Na[Al(OH) 4 ] K 2 [Ni(CN) 4 ] (NH 4 ) 2 [CuBr 4 ] [Ni(H 2 O) 6 ]SO 4 [CoCl 3 (NH 3 ) 3 ] 1- [Co(NH 3 ) 6 ]Cl 3 K 3 [Fe(CN) 6 ] K 4 [Fe(CN) 6 ]

14. ☺ Central ion is first ☺ Ligands second ☺ Neutral molecules first ☺ Negative ions second ☺ Neutral molecules and polyatomic ions are always surrounded by (parentheses) , even if only 1 present ☺ Entire complex ion formula surrounded by [brackets]

15. Write the formula for the diamminepalladium(II) ion ☺ Central ion – palladium (Pd) ☺ Ligands – NH 3 (2) ☺ Written in parentheses ☺ Neutral charge ☺ Brackets around entire formula ☺ Calculate the net charge [Pd(NH 3 ) 2 ] 2+

16. Write the formula for the carbonylpentacyanoferrate(II) ion ☺ Central ion – iron (Fe) ☺ Ligands ☺ CN (5) 1- charge Written in parentheses ☺ CO (1) Neutral Written in parentheses ☺ Brackets around entire formula ☺ Calculate the net charge [Fe(CO)(CN) 5 ] 3-

17. Tetraammineplatinum(II) ion [Pt(NH 3 ) 4 ] 2+ Tetraiodoaurate(III) ion [AuI 4 ] - Pentacarbonylnitrosyliron(II) ion [Fe(CO) 5 (NO)] 2+

18. Ligand Exchange Reactions of Transition Metals (and Al 3+ ) Complex ions undergo ligand substitution reactions in solutions Ex. [Ni(H 2 O) 6 ] 2+ + NH 3 -> [Ni(NH 3 ) 6 ] 2+ + H 2 O or Ni 2+ + NH 3 -> [Ni(NH 3 ) 6 ] 2+ How do you know the number of ligands that are in the product? Hint: Often, not all the time!!, the number of ligands is twice the cation charge. Also, helpful to know the following table

19. Metal Ion Ligand Number of Ligands Fe 3+ SCN - 1 Ni 2+ NH 3 Any between 1 and 6 Ag + CN - 2 Ag + NH 3 1 or 2 Zn 2+ NH 3 4 Al 3+ OH - 3 or 4 Zn 2+ OH - 4 Cu 2+ NH 3 4 Co 2+ Cl _ 4

20. Decomposition of complex by acid-base neutralization Complexes containing NH 3 can be broken down by acid base decomposition by adding an acid Ex. [Cu(NH 3 ) 4 ] 2+ + H + -> Cu 2+ + NH 4 + The NH 3 acts as a base (accepts H + ions to form NH 4 + ). The rest of the complex is broken down. Go over sheet from the “Ultimate Chemical Equation Handbook.” Responsible for all the reactions listed in the transition metal section.