Coordination Compunds Flashcards
(17 cards)
What are ligands in coordination chemistry?
Ligands are ions or molecules bound to the central atom/ion in a coordination entity. They donate electron pairs to the metal ion.
What are examples of ligands?
Simple ions like Cl⁻, small molecules like H₂O or NH₃, larger molecules like ethane-1,2-diamine (en), or macromolecules like proteins.
What is a unidentate ligand?
A ligand that binds to a metal ion through a single donor atom, e.g., Cl⁻, H₂O, NH₃.
What is a bidentate ligand? Give examples.
A ligand that binds through two donor atoms. Examples: ethane-1,2-diamine (H₂NCH₂CH₂NH₂) (en), oxalate ion (C₂O₄²⁻).
What is a polydentate ligand?
A ligand with several donor atoms, e.g., N(CH₂CH₂NH₂)₃. tris(2-aminoethyl)amine. It is also often abbreviated as tren. It can coordinate with multiple sites on the metal ion.
What is a hexadentate ligand?
A ligand that can bind through six donor atoms, e.g., EDTA⁴⁻.
What is a chelate complex?
A complex where di- or polydentate ligands bind through multiple donor atoms simultaneously to the same metal ion.
Why are chelate complexes more stable than others?
Because the ligand forms a ring structure with the metal ion, which provides extra stability.
What is an ambidentate ligand? Give examples.
A ligand with two different donor atoms and either of the two ligetes in the complex is called ambidentate ligand. Example: NO₂⁻ (can bind through N or O), SCN⁻ (can bind through S or N).
What is the coordination number of a metal ion?
The number of ligand donor atoms directly bonded to the central atom/ion via sigma bonds.
Does coordination number depend on pi bonds?
No, it depends only on the number of sigma bonds.
What is the coordination sphere?
The central atom/ion and ligands enclosed in square brackets. Ions outside are called counter ions.
What is a coordination polyhedron?
The spatial arrangement of ligands around the central metal atom. Shapes include octahedral, tetrahedral, square planar, trigonal bipyramidal, and square pyramidal.
What is the oxidation number of the central atom in a complex?
The charge the atom would carry if all ligands were removed as neutral species.
How is oxidation number represented in coordination compounds?
Using Roman numerals in parentheses after the complex name.
What are homoleptic and heteroleptic complexes?
Homoleptic: Metal bound to only one kind of donor group, e.g., [Co(NH₃)₆]³⁺. Heteroleptic: Metal bound to more than one kind of donor group, e.g., [Co(NH₃)₄Cl₂]⁺.
