Transition Metal Complexes# Flashcards
What is a complex?
A central metal ion surrounded by ligands.
What are ligands?
Ligands are uncharged or negatively charged ions with at least one lone pair of electrons which they donate to an unfilled metal orbital to form a dative covalent bond.
What is a dative covalent bond?
A covalent bond where both the electrons come from the same atom instead of one from each.
What are ligands which donate one pair of electrons called?
Monodenate ligands.
What are ligands which donate 2 pairs of electrons called?
Bidenate ligands.
What is EDTA?
Ethylenediaminetetraacetic acid is a hexadenate ligand which is often used in volumetric analysis.
What is a coordination number?
The total number of bonds from the ligand to the central metal ion. e.g. for EDTA it is 6.
What are the rules for writing the formular of a complex?
The symbol of the metal is written first, followed by the negatively charged ligands and then the neutral ligands. The formula is enclosed in square brackets and the charge is written outside the bracket.
What are the rules for naming complexes?
1) Ligands are named first in alphabetical order, followed by the name of the metal and its oxidation state.
2) If the ligand is a negative ion ending in ‘ide’ it now ends in ‘o’.
3) If the ligand is ammonia, it becomes ammine.
4) If the ligand is water it becomes aqua.
5) If the complex is negatively charged overall, the name of the metal ends in ‘ate’ (e.g. cobaltate). Copper becomes cuprate and iron becomes ferrate.
What happens to the d orbitals when a complex is formed?
The ligands repel the electons in the d orbitals that lie on the axes. This means the d orbitals are no longer degenerate and the orbitals that lie on the axes now have a higher energy than the orbitals lying between the axes. This is called splitting of the d orbitals and the energy difference depends on the postition of the ligand in the spectrochemical series.
What is the spectrochemical series?
A series that puts ligands into order of their ability to split the d orbitals. Strong field ligands create a large difference in energy and weak field ligands create a smaller difference in energy.
What colours make up white light?
Red, green and blue.
What colour do you see in a coloured compound?
White light minus the colour that was absorbed. e.g. if red light was absorbed you would see cyan (green and blue light).
What is a transition metal compound?
A transition metal that has had its d orbitals split by ligands.
Why can transition metal compounds absorb light?
Because the photons in the light are able to excite electrons in the lower energy d orbitals to higher energy d orbitals. This is called a d-d transition. If the light absorbed is in the visible part of the electromagnetic spectrum the compound will be coloured.
