15.1.2 Complex Formation

• What is complex formation?

  Central metal ion bonds with ligands
• In complex formation, ligands donate lone pairs of electrons to the central metal ion
• The central metal ion in a complex accepts electron pairs from ligands.
• Ligands donate electron pairs to form coordinate bonds.
• What is the chemical equation for the reaction of copper(II) ions with ammonia to form a complex ion?

  $Cu^{2 + }(aq) +$$4NH_{3}(aq) \rightleftharpoons [Cu(NH_{3})_{4}]^{2 + }(aq)$
• In the reaction of copper(II) ions with ammonia, $NH_{3}$ molecules act as ligands.
• What is the role of the central metal ion in a complex?

  Accepts electron pairs
• What type of bond is formed between a central metal ion and a ligand in a complex ion?

  Coordinate bond
• The coordination number of a complex ion is the number of ligands directly bonded to the central metal ion.
• What is the coordination number of the copper(II) ion in the complex $[Cu(NH_{3})_{4}]^{2 + }$?


  4
• What is the role of a coordination number in a complex ion?

  Determines geometry and stability
• A ligand is an ion or molecule that donates one or more pairs of electrons to form a complex ion.
• Monodentate ligands form only one coordinate bond with the central metal ion.
• What is an example of a bidentate ligand?

  Ethylenediamine
• Ethylenediaminetetraacetate ($EDTA$) is an example of a polydentate ligand.
• What are two common geometries of complex ions with coordination numbers 4 and 6?

  Tetrahedral and octahedral
• What is complex formation in chemistry?

  Metal ion bonds with ligands
• A central metal ion accepts electron pairs from ligands
• What do ligands contribute in complex formation?

  Electron pairs
• A complex ion is the result of bonding between a metal ion and ligands.
• What is the reaction between copper(II) ions and ammonia?

  $Cu^{2 + }(aq) +$$4NH_{3}(aq) \rightleftharpoons [Cu(NH_{3})_{4}]^{2 + }(aq)$
• A central metal ion in a complex ion accepts electron pairs from ligands
• What does the coordination number in a complex ion indicate?

  Number of bonded ligands
• Ligands form coordinate bonds by donating electron pairs to the metal ion.
• What is the coordination number of copper(II) in $[Cu(NH_{3})_{4}]^{2 + }$?


  4
• A complex ion consists of a central metal ion bonded to one or more ligands
• What influences the geometry and stability of a complex ion?

  Coordination number
• Copper(II) is the central metal ion in [Cu(NH_{3})_{4}]^{2 + }</latex>.
• What type of ligand forms one coordinate bond with the metal ion?

  Monodentate
• Ethylenediamine is an example of a bidentate
• Which polydentate ligand is commonly used in complex ions?

  EDTA
• Match the ligand type with its example:

  Monodentate ↔️ $Cl^{ - }$

  Bidentate ↔️ $en$

  Polydentate ↔️ $EDTA$
• What is the coordination number influenced by in complex ions?

  Metal ion size
• Which coordination number is associated with octahedral geometry?

  6
• Steps in naming complex ions according to IUPAC rules

  1️⃣ List ligands before metal ion

  2️⃣ Use prefixes for ligand numbers

  3️⃣ Add "o" to anionic ligand names

  4️⃣ Indicate metal oxidation state in Roman numerals

  5️⃣ Include overall charge in brackets
• What prefix is used for four ligands in complex ion nomenclature?

  Tetra-
• The oxidation state of the metal ion in a complex is indicated in Roman numerals
• What is the systematic name of $[Fe(CN)_{6}]^{4 - }$?


  Hexacyanoferrate(II)