Chapter 22 Flashcards
(18 cards)
1
Q
inner coordination sphere
A
- the ligands that are bound directly to a (central cation of a) metal via coordinate bond
2
Q
coordination number
A
- the number of sites occupied by ligands around a metal ion in a complex
3
Q
coordination compound
A
- a compound made up of at least one complex ion
4
Q
counterion
A
- an ion whose charge balances the charge of a complex ion in a coordination compound
5
Q
coordinate covalent bonds
A
- when ions dissolved in water are hydrated, they are surrounded by water molecs oriented with their pos dipoles directed towards anions and neg dipoles towards cations.
- when these ion-dipole interactions lead to the sharing of lone pair e- with empty valence shell orbitals on the cations, the are coordinate covalent/coordinate bonds
- molecules or anions that function as Lewis bases and form coordinate bonds with metal cations are called ligands
- with metal cations are called ligands. The resulting species, which are composed of central metal ions and the surrounding ligands, are called complex ions or simply complexes
6
Q
monodentate ligand
A
- species that forms only ONE coordinate bond to a metal ion in a complex
- EX: ammonia, water
7
Q
polydentate ligand
A
- a species that forms more than one coordinate bond per molecule
- bidentate(ethylenediamine), tridentate…
- polyamines are polydentate ligands
8
Q
chelation
A
- the interaction of a metal with a polydentate ligand (chelating agent); pairs of electrons on one molecule of the ligand occupy two or more coordination sites on the central metal
- chelating agent: the polydentate ligands that take part in chelation
- sequestering agent: chelating agent that binds metal ions so tightly that they are “sequestered” and prevented from reacting with other substance
- EDTA(forms very stable complex ions)
9
Q
chelate effect
A
- the greater affinity of metal ions for polydentate ligands than for monodentate ligands
- The entropy-driven affinity of metal ions for polydentate ligand
10
Q
crystal field splitting
A
- the separation of a set of d orbitals into subsets with different energies as a result of interactions between electrons in those orbitals and lone pairs of electrons in ligands
- process of changing degenerate (equal-energy) d-orbitals into orbitals with different energies
11
Q
crystal field splitting energy(Δ)
A
- the difference in energy between subsets of d orbitals split by interactions in a crystal field
- the difference in energy created by crystal field splitting
- The size of the energy gap between split d orbitals often corresponds to radiation in the visible region of the electromagnetic spectrum. This means that the colors of solutions of metal complexes depend on the strengths of metal–ligand interactions that affect
12
Q
spectrochemical series
A
- a list of ligands rank-ordered by their ability to split the energies of the d orbitals of transition metal ions.
- Chemists use the parameter field strength to describe the relative magnitude of the split in the energies of the d orbitals in metal ions
- as field strength of ligand inc, crystal field splitting energy(Δ) inc
13
Q
high vs low spin state
A
- EX: Fe3+(has 5 3d e-)
- high spin state: configuration w/ all 5 unpaired e-
- bc spin on all 5 is same direction, so maximum magnetic field is produced
- low-spin state: configuration with only one unpaired e-
- both configurations are paramagnetic bc both have at least one unpaired e-, but high spin is more attracted to external magnets
- whether a transition metal ion is in a high-spin state or a low-spin state depends on whether less energy is needed to promote an electron to a higher-energy orbital or to overcome the repulsion experienced by two electrons sharing the same lower-energy orbital
- small Δo=more likely to be in low-spin states
- higher oxidation #= larger Δo
14
Q
stereoisomers
A
- Coordination compounds that have the same composition and the same connections between parts but differ in the three-dimensional arrangement of those parts are stereoisomers
15
Q
enantiomer
A
- enantiomers: nonsuperimposable steroisomers
- mirror image is not identifcal to the original
16
Q
linkage isomers
A
- occurs in coordination compounds when a ligand can bind to a central metal ion by using either of 2 possible electron-pair–donating atoms
- bc these pairs of molecules have different connectivities, linkage isomers are not stereoisomers. Instead, linkage isomers are a type of constitutional isomer
17
Q
porphyrin
A
- a type of tetradentate macrocyclic ligand
18
Q
macrocyclic ligand
A
- a ring containing multiple electron-pair donors that bind to a metal ion
- literally means big ring
- chorins and porphyrins are members of this category
