Module 5- complex ions Flashcards
What is a complex ion
A metal ion/atom surrounded by one or more coordinately bonded ligands
Whats a ligand
A species with a lone pair in its outer shell that it can donate to a central metal ion to form a dative co ordinate bond
Whats a dative co ordinate bond
a covalent bond whereby one atom/ion provides both electrons
What is a co ordination number
Co-ordination number is the number of ligands a central metal ion can bond to/ number of coordinate bonds the central ion forms
Examples of common monodentate ligands
H2O- oxygen has lone pair to donate
NH3- nitrogen has long pair to donate
Cl- ion- has lone pair to donate
CN
Why does Fe(H2O)6 3+ have a coordination number of 6 and what shape and bond angle does the it form
Fe3+ is surrounded by 6 H2O ligands, which means it forms an octahedral shape with bond angles of 90 degrees
What 3 things must be included in the drawing of ligands
- Arrows representing 3D shape are pointing from lone pair on ligand to the central metal ion
- Must make sense in 3D
- Brackets and charge of overall ion
How do orbitals in the central ion change to accommodate the dative bonds of the ligands
The orbitals in ions are hybridised to bring them to the same energy level, which allows them to accept each pair from the dative bond without them splitting up to fill incomplete orbitals
Which ligands mean you can only fit 4 around a central ion
Large ligands like a Cl- ion are too big to fit in an octahedral shape, therefore you can only fit 4 around a central ion, forming either a tetrahedral shape of 109.5 degrees, or a square planar shape of 90 degrees, depending on the central metal ion
How does the size of ions like Ag and Cu+ affect their co ordination number??
Ag+ and Cu+ are very small, so tend to form 180 degree linear structures like [Ag(NH3)2]+
Which 4 metal ions form square planar shapes
Platinum, gold (III), palladium (II) and Nickel
Whats a bidentate ligand and give 2 common examples??
Bidentate ligands are ligands that provide 2 lone pairs of electrons to form co ordinate bonds
-1,2 diaminoethane
-ethandioate ion
They are flexible enough to bend themselves around the central ion to form both bonds
What is the coordination number of the Cr(C2O4)3 3- ion
6 - although only 3 ligands are involved, they are bidentate ligands, so 6 dative bonds are being made altogether
Whats a multidentate ligand and a common example
a ligand forming 3 or more coordinate bonds eg EDTA 4- ion
How do Fe2+, Fe3+ and Mn2+ react with ammonia
All form their respective hydroxide precipitates, and then don’t dissolve in excess
