Question

Inorganic Chemistry Tutorial: Introduction to Coordination Compounds

Answer 1

\({\bf{Definitions:}}\)

complex: central metal atom surrounded by ligands
coordination compounds: neutral complex or ionic compound containing at leaset one complex ion
inner-sphere complex: ligands are attached directly to central metal/ion
outer-sphere complex: cations associate electrostatically w/ anionic ligands
notes: water molecules that are not directly coordinated to cations are equivalent to outer sphere ligands and are called the water of crystallization

monodentate: ligand w/ one lone pair electron and therefore one point of attachment
polydenate: ligands w/ multiple lone pairs of electrons and therefore multiple points of attachment
ambidentate: ligand w/ multiple possible donor atoms, ex; SCN can utilize either S or N to coordinate
chelate: compound in which ligand forms ring around central atom (ligand bonds to central atom at multiple points
notes: cis chelating pattern: the ligand attaches at 2 adjacent coordinating sites
chelate effect: complexes w/ chelating ligands are generally more stable
bite angle: degree of strain in chelating ligand

Answer 2

some illustrations:

Answer 3

\({\bf{Nomenclature:}}\) this can actually get pretty complex but here are some basic principles:
1. ligands are named in alphabetical order
2. the metal, with its oxidation state in parentheses or as a superscript, is next
3. neutral ligands take priority over anionic ligands
4. if the complex is an anion, add -ate to the metal name
5. indicate ligand numbers with prefixes like mono, di, etc. but if ligands already have their own prefixes from the names of their compounds, use bis/tris/tetrakis, etc.
6. anions get the suffix -ido


6. use μ to indicate when a ligand is bridging metal centers

This is a lot easier to understand with some examples so:
Ex 1:\[[PtCl_{2}(NH_{3})_{4}]^{2+}\]
there are 2 anionic Cl ligands, 4 neutral ammine ligands, just going off the scripts, plus our general knowledge of these species. the overall charge is +2 so Pt must have a 4+ charge to balance out.

start with the anion, add "di" since there are 2 chloride ligands, suffix -ido

> dichlorido

then there are 4 ammine ligands, so tetra + ammine. neutrals take priority over anions.

> tetraamminedichlorido

then simply "platinum" followed by its oxidation state 4

> tetraamminedichloridoplatinum(IV)

Answer 4

Ex 2:
\[[Ni(CO)_{3}(py)]\]
pretty simple, you have 2 neutral ligand species (CO = carbonyl, py = pyridine). CO gets a tri prefix since there are three of them.

listing them in alphabetical order:
tricarbonylpyridine

Nickel has an oxidation state 0 since the overall compound is neutral. so simply append nickel(0) at the end.

final name: tricarbonylpyridinenickel(0)

Ex 3: (last example)

\[[CoCl_{2}(en)_{2}]^{+}\]

2 chloride ligands and 2 neutral 1,2-diaminoethane ligands. since "diaminoethane" already has "di" as a prefix, we use "bis" in front of this ligand

> dichloridobis(1,2-diaminoethane)

then simply append the cobalt. overall charge is +1 with 2 neutral ligands, so cobalt has oxidation state 3+

> dichloridobis(1,2-diaminoethane)cobalt(III)

Answer 5

\({\bf{Coordination~Number:}}\) the number of ligands around the central atom

Affected by:
1. size of central atom
2. steric interactions between ligands
3. electronic interactions

Considerations:
1. bulky ligands reduce coordination numbers. (since the ligands are physically taking up more space, it makes sense that there's less room for new ligands to bond)
2. smaller central atoms lead to higher coordination numbers (so basically look towards the upper left of the PT)
3. ligands capable of forming multiple bonds w/ the same central atom generally reduce coordination numbers

Answer 6

Source material is Chapter 7.1-7.2 of Inorganic Chemistry, 7th edition, Weller, et. al.