CHEM1902 (C10K) Coordination Chemistry.
The transition metals are generally defined as
the elements existing between the Alkali metals and earths
(Groups 1 and 2) and the non-metal elements (Groups 13 - 18).
But note that IUPAC uses the definition that a transition element
is one for which an atom has an incomplete d-subshell, or which gives
rise to a cation with an incomplete d-subshell, so that the elements in
group 12 (which are within the d-block) are not considered transition elements.
For this reason, in the case of the first-row transition metals,
Scandium and Zinc are usually ignored in simple
discussions, since Sc(III) and Zn(II) are their major oxidation
numbers and these are d0 and d10
The oxidation number of a central atom in a coordination
entity is the charge it would bear if all the ligands were removed along with
the electron pairs that were shared with the central atom. It is represented
by a Roman numeral e.g in FeCl3 the oxidation number of iron is Fe(III).
This is often called the
oxidation state and for this course they can be treated
as being the same, however this is not always the case.
A coordination compound, sometimes called a
coordination complex, contains a central metal atom or ion
surrounded by a number of oppositely charged ions or neutral
molecules (possessing lone pairs of electrons) which are known as
If a ligand is capable of forming more than one
bond with the central metal atom or ion, then ring structures are
produced which are known as Metal Chelates, the ring forming
groups are described as chelating agents or polydentate
The coordination number of the central metal
atom or ion is the total number of sites occupied by ligands.
Note: a bidentate ligand uses two sites, a tridentate three sites
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