Chapter 19: Self study Flashcards
Many ligands in complexes have common abbreviations.
Give the full names of the following ligands: en, THF, phen, py, [acac]-, [ox]2-
⦿en: ethylenediamine
⦿THF: tetrahydrofuran
⦿phen: phenanthroline
⦿py: pyridine
⦿[acac]: acetylacetonate
⦿[ox]: oxalato
Draw the structures of the following ligands. Indicate the potential donor atoms in and the denticity of each ligand:
en, [EDTA]4-, DMSO, dien, bpy, phen.
In [Fe(CN)6]3-, a realistic charge distribution results in each ligand carrying a charge of -2/3. In this model, what charge does the Fe centre carry and why is this charge consistent with the electroneutrality principle?
So, that means here each cyanide is carrying a charge of -2/3 and that means we have now 6 cyanate ligands. So, this will be –4. If it is –4, now if you consider Fe 3+ we have 5 electrons, 5 – 4 = +1. So, in this one Fe carries +1 charge. So, according to electroneutrality principle,
the charge carried by iron centre is +1
If the bonding in [CrO4]2- were described in terms of a 100% ionic model, what would be the charge carried by the Cr centre? Explain how this charge distribution can be modified by the introduction of covalent character into the bonds.
If you just look into 100% ionic model, the [CrO4]2– here charge will be –2. In this case the charge will be –2 here, but if you consider covalent model, so 6 electrons are there and these 6 electrons are utilized in making 6 metal to ligand bonds. According to the electroneutrality principle in that case what happens? Number of electrons left and chromium will be zero so that here the charge on chromium will be zero
Draw possible structures for the square planar complexes
[PtBr2(py)2] and [PtCl3(PEt3)]- and give names to distinguish between any isomers that you have drawn.
In [Ru(CO)4(PPh3)], the Ru centre is in a trigonal bipyramidal environment. Draw the structures of possible isomers and give names to distinguish between
them.
Octahedral [RhCl3(OH2)3] has two isomers. Draw their structures and give them distinguishing names.
mer isomer & fac isomer
Explain why cis-[Co(en)2Cl2]+ is chiral while trans-[Co(en)2Cl2]+ is achiral.
Cis-[Co(en)2Cl2]⁺ is chiral because it lacks a plane of symmetry, meaning its mirror image cannot be superimposed onto itself, while trans-[Co(en)2Cl2]⁺ is achiral due to the presence of a plane of symmetry that allows its mirror image to be superimposed on itself;
essentially, the trans isomer has a symmetrical arrangement of ligands, making it non-chiral, whereas the cis isomer has an asymmetrical arrangement, leading to chirality.
A chiral molecule lacks an inversion centre and a plane of symmetry. Use these criteria to show that species belonging to the C2 and D3 point groups are chiral
A molecule is chiral if it lacks a center of inversion, a plane of symmetry, or an improper rotation axis. This means that chiral molecules are dissymmetric, but not always asymmetric.
A molecule is chiral if it does not have the following symmetry elements:
⦿ Inversion center
⦿ Mirror plane
C2:
Symmetry Elements:
⦿E: Identity operation
⦿C2: A twofold rotation axis
D3
Symmetry Elements:
⦿E: Identity operation
⦿2C3: Two threefold rotation axes
⦿3C2: Three twofold rotation axes
Both C2 and D3 point groups lack both an inversion center and a plane of symmetry. Therefore, molecules belonging to these point groups are inherently chiral. This means they will exhibit optical activity and form non-superimposable mirror images, known as enantiomers.
The diagrams below represent two tetrahedral, bischelate
complexes. Explain in terms of symmetry elements why A is achiral, but B is chiral. Draw the structure of the other enantiomer of B
A. Achiral Complex
In complex A, we observe a plane of symmetry bisecting the M-A bond. This plane mirrors the two chelate rings, making the complex superimposable on its mirror image. Therefore, complex A is achiral.
B. Chiral Complex
In complex B, there is no such plane of symmetry. The two chelate rings are arranged in a non-superimposable manner. This lack of symmetry results in the complex being chiral, meaning it exists as two non-superimposable mirror images, or enantiomers.
