Transition Metal Chemistry, Coordination Nomenclature, Ligand Theory, and Molecular Symmetry

Comprehensive vocabulary flashcards covering transition metal chemistry, coordination nomenclature, ligand classifications, macrocycles, molecular symmetry elements, point groups, and matrix representations.

Haber-Bosch Process

An industrial exothermic reaction disfavoured by entropy ($N_2 + 3H_2 \rightleftharpoons 2NH_3$, $\Delta H^\circ_{298K} = -92.28\,kJ\,mol^{-1}$) that produces ammonia using inorganic heterogeneous catalysts such as $FeO$, $Al_2O_3$, $K_2O$, and $CaO$.

Cisplatin

A platinum-based coordination complex containing two ammine ligands and two chloride ligands ($\text{cis-}[PtCl_2(NH_3)_2]$) used as a medical cancer therapeutic.

Ammine

The IUPAC coordination chemistry name for an uncharged ammonia ($NH_3$) ligand.

Aqua

The IUPAC coordination chemistry name for a neutral water ($H_2O$) ligand.

Ferrate

The IUPAC name ending used for iron when it is located in an anionic coordination complex.

Cuprate

The IUPAC name ending used for copper when it is located in an anionic coordination complex.

Bis / Tris / Tetrakis

Numerical prefixes used to indicate multiple identical ligands when the ligand's name already contains a simple numerical prefix (such as ethylenediamine).

Ligand

A molecule or ion that binds to a central metal ion in a coordination complex, classified by charge (anionic X-type or neutral L-type) and the number of coordination sites occupied.

Monodentate Ligand

A ligand that forms a single bond to a central metal ion using one donor atom, occupying a single coordination site.

Chelating Ligand

A ligand with multiple donor atoms that binds to a central metal ion at more than one coordination site, forming a ring structure that incorporates the metal.

Ethylenediamine (en)

A neutral bidentate amine ligand ($1,2\text{-diaminoethane}$, $NH_2CH_2CH_2NH_2$) that coordinates to metal ions via two nitrogen atoms to form a 5-membered chelate ring.

1,2-bis(diphenyl)phosphinoethane (diphos)

A neutral bidentate phosphine ligand containing two phosphorus donor atoms that forms 5-membered chelate rings with metal centers.

2,2'-Bipyridine (bipy)

A neutral bidentate nitrogen-donor ligand composed of two connected pyridine rings that forms 5-membered chelate rings with transition metals.

Acetylacetonate (acac)

An anionic bidentate oxygen-donor ligand that coordinates to metal ions to form 6-membered chelate rings.

Diethylenetriamine (deta)

A tridentate nitrogen-donor ligand that occupies three facial ($fac$) coordination sites on an octahedral metal center.

Terpyridine (terpy)

A tridentate aromatic nitrogen-donor ligand that occupies three meridional ($mer$) coordination sites in a plane on an octahedral metal center.

Macrocyclic Ligand

A cyclic molecule with at least three donor atoms that completely encircled a central metal ion in a coordination complex.

Cyclam

A tetradentate nitrogen-containing macrocyclic ligand that binds transition metals in a square planar geometry.

Metal Templation

A synthetic strategy where coordination to a central metal ion controls the directional condensation and polymerization of reactants (such as in Schiff base formation) to yield macrocyclic ligands.

Porphyrin

An 18-electron aromatic macrocyclic ligand synthesized from pyrroles and aldehydes that loses two protons ($H^+$) to coordinate $M^{2+}$ metal ions, vital in biological systems like hemoglobin and chlorophyll.

Crown Ether

A macrocyclic polyether ligand composed of repeating $-\text{OCH}_2\text{CH}_2\text{O}-$ units that selectively encapsulates alkali and alkaline earth metal cations based on ring cavity size.

18-Crown-6 (18C6)

An 18-membered macrocyclic crown ether containing 6 oxygen atoms whose cavity size provides an optimal fit specifically for potassium cations ($K^+$).

Cryptand

A 3D macrobicyclic ligand containing polyethylene glycol chains attached to apical nitrogen atoms that encapsulates metal cations within a three-dimensional cavity.

Symmetry Element

A geometrical point, line, or plane (such as an axis or mirror plane) about which a symmetry operation is performed.

Symmetry Operation

A spatial movement (such as rotation, reflection, or inversion) performed relative to a symmetry element that produces an orientation indistinguishable from the original.

Identity Operation ($E$)

A fundamental symmetry operation that leaves the molecule completely unchanged, mathematically equivalent to multiplication by 1.

Proper Rotation Axis ($C_n$)

A symmetry element around which a counter-clockwise rotation by an angle of $\frac{360^\circ}{n}$ leaves the molecule indistinguishable.

Principal Axis

The proper rotation axis in a molecule that possesses the highest order of rotational symmetry (largest $n$).

Horizontal Mirror Plane ($\sigma_h$)

A mirror plane that is oriented perpendicular to the principal rotation axis of a molecule.

Vertical Mirror Plane ($\sigma_v$)

A mirror plane that runs parallel to and contains the principal rotation axis of a molecule.

Dihedral Mirror Plane ($\sigma_d$)

A vertical mirror plane that runs parallel to the principal axis and bisects the angle between adjacent perpendicular $C_2$ axes.

Center of Inversion ($i$)

A symmetry element at the center of a molecule through which every atom is projected an equal distance in the opposite direction, transforming coordinates $(x, y, z)$ to $(-x, -y, -z)$.

Improper Rotation Axis ($S_n$)

A roto-reflection operation consisting of a rotation by $\frac{360^\circ}{n}$ followed by a reflection through a plane perpendicular to the rotation axis.

Point Group

A set of symmetry operations describing a molecule's overall symmetry, where all operations leave at least one central point fixed in space.

Chirality Symmetry Requirement

The structural condition stating that a molecule is chiral if and only if it lacks an improper rotation axis ($S_n$, which includes $S_1 = \sigma$ and $S_2 = i$), restricting chiral molecules to the $C_1$, $C_n$, or $D_n$ point groups.

Transformation Matrix

A $3 \times 3$ matrix that operates on a column matrix of Cartesian coordinates $(x, y, z)$ to generate new coordinates $(x', y', z')$ resulting from a symmetry operation.

Character ($\chi$)

The trace, or sum of the diagonal elements, of a transformation matrix representing a symmetry operation.

Reducible Representation ($\Gamma$)

A set of characters combined from the transformation matrices of all symmetry operations in a point group, which can be further simplified into irreducible representations.