Chem 124 Ch.23(3-4) Flashcards
Cis-trans isomers, enantiomers. Crystal field theory, spectrochemical series
Two coordination compounds that have the same ligands arranged differently in space around the central metal ion, but are not mirror images of one another, are called____isomers. If the identical ligands are next to each other, the isomer is described as____ while the isomer with identical ligands across from each other is the____ isomer.
geometric/cis-trans; cis; trans
What is the difference btwn cis and trans geometric isomers?
- Cis has compounds or molecules next to each other (w/ the middle being across from each other) w/ different dashes
- Trans has compounds or molecules across from each other with diff dashes (the metal cation is inbtwn).
If two compounds are mirror images of one another, but are not superimposable (lay over one another), they are called____ isomers or enantiomers. These isomers have____ physical properties except for the direction in which each rotates the plane of polarized light.
optical; identical
An object appears to be red. What can correctly explain this observation?
- absorbs only blue light
- absorbs only green light
- absorbs only red light
- absorbs all wavelengths of light except red.
- absorbs all colors that are similar to red.
- absorbs all wavelengths of light except red.
- absorbs only green light
Reason: Green is its complementary color-> if it absorbs green the it will show as red
What correctly describe geometric isomers of coordination compounds?
- A coordination compound might have geometric isomers of the ligands can be arranged differently in space relative to the central metal ion.
- The isomer that has identical ligands adjacent to each other is called the cis isomer.
- A coordination compound will have geometric isomers if all possible arrangements of the ligands give the same compound.
- Geometric isomers are diff compounds and have diff physical prop.
- The isomer that has diff ligands across from each other is called the trans isomer
- A coordination compound might have geometric isomers of the ligands can be arranged differently in space relative to the central metal ion.
- The isomer that has identical ligands adjacent to each other is called the cis isomer.
- Geometric isomers are diff compounds and have diff physical prop.
Which of the following complex ions can exist as a pair of cis-trans isomers? Select all that apply.
- [Pd(NH3)3Cl]+
- [Pd(CN)2(OH)2]2–
- [Pt(NH3)4Br2]2+
- [Fe(CN)6]3–
- [Pd(CN)2(OH)2]2–
Reason: A complex ion of Pd with a coordination number of 4 is square planar. The CN ligands in this ion could be adjacent to each other or across from each other, so [Pd(CN)2(OH)2]2– exists as a pair of cis-trans isomers. - [Pt(NH3)4Br2]2+
Reason: Pt with a coordination number of 6 is octahedral. [Pt(NH3)4Br2]2+ exists as a pair of cis-trans isomers because the 2 Br ligands could either be next to each other or across from each other.
Match the color given w/ the color and wavelength of light absorbed
Blue->
Red->
Violet->
- Yellow-green:570nm
- Orange:600nm
- Blue-green:490 nm
Blue-> Orange:600nm
Red-> Blue-green:490 nm
Violet-> Yellow-green:570nm
What statements correctly describe a pair of optical isomers?
- Optical isomers rotate plane polarized light in opposite directions.
- The mirror image of any compound is called it’s optical isomer.
-Optical isomers exist for all octahedral coordination complexes. - Optical isomers have identical melting and boiling points.
- Optical isomers are mirror-image compounds that cant be superimposed.
- Optical isomers have identical melting and boiling points.
- Optical isomers rotate plane polarized light in opposite directions.
- Optical isomers are mirror-image compounds that cant be superimposed.
An object has a particular color if it ____ light of that color, or if it absorbs only ____ color.
- Reflects; supplementary
- Reflects; complementary
- absorbs; supplementary
- absorbs; complementary
- Reflects; complementary
What is the color of a complex ion that absorbs light primarily in the 450 nm range?
- blue
- orange
- white
- black
- orange
What statements correctly describe the crystal field model as it applies to the formation of an octahedral complex?
- As ligands approach the metal ion, there is repulsion between the ligand electrons and the metal ion electrons.
- After bonding, the d orbitals of the metal ion are split into 2 groups of different energies.
- Before bonding the d orbitals of the metal ion are identical in energy and shape.
- The ligands interact equally with all five d orbitals of the metal ion.
- Ligand-metal ion repulsions are not the same for all the d orbitals of the metal ion.
- As ligands approach the metal ion, there is repulsion between the ligand electrons and the metal ion electrons.
- Ligand-metal ion repulsions are not the same for all the d orbitals of the metal ion.
- After bonding, the d orbitals of the metal ion are split into 2 groups of different energies.
When a metal cation forms an octahedral complex the ligands approach directly along the x, y, and z axes. The two d orbitals with lobes along the axes will experience a _____ repulsion than the three d orbitals with lobes between the axes. The d orbitals will be split into two groups; the higher energy group has _____ orbitals and the lower energy group has _____ orbitals.
- lower; three; two
- lower; two; three
- greater; two; three
- greater; three; two
- greater; two; three
The splitting of d-orbital energies into two groups by the interaction of a metal ion with a group of ligands is called the crystal field____, and the energy difference between the two groups of d orbitals is the crystal field____ energy of that field.
effect; splitting
Match each type of ligand w/ the correct description of the crystal field.
strong-field ligands->
weak-field ligands ->
- smaller crystal field splitting energy
- larger crystal field splitting energy
strong-field ligands-> larger crystal field splitting energy
weak-field ligands ->smaller crystal field splitting energy
Why do the ligands cause splitting of the metal ion d-orbital energies when a complex ion is formed?
- the 5 d orbitals have diff orientations and are not all repelled equally by the approaching ligands.
- The 5 d orbitals repel each other as well as the approaching ligands.
- the d orbitals are not all the same energy before bonding occurs.
- the 5 d orbitals have diff orientations and are not all repelled equally by the approaching ligands.
When a coordination complex absorbs light, a d electron moves from a____energy d orbital to a ____energy one. The wavelength of light absorbed, and hence the color observed, depends on the energy____ between the orbitals, which is equal to the crystal field____ energy (Δ).
low;high,gap;splitting
What statements describe the arrangement of the d orbitals in a metal cation after the formation of an octahedral complex?
- “There will be” 3 higher energy d orbitals designated eg orbitals.
- ”..” 2 higher energy d orbitals designated eg orbitals.
- “…” 3 lower energy d orbitals designated t2g orbitals.
- All 5 d orbitals will have the same splitting an thus will have the same energy.
- ”..” 2 higher energy d orbitals designated eg orbitals.
- “…” 3 lower energy d orbitals designated t2g orbitals.
How do you know (given the complex ion) will appear a certain color?
Orange: if it has a larger Δ
Which of the following options correctly describe the magnetic properties of transition metal complexes? Select all that apply.
- A strong-field ligand has a large Δ, leading to more unpaired electrons.
- A weak-field ligand will have the same number of unpaired electrons as the free ion.
- A low-spin complex contains fewer unpaired electrons than a high-spin complex.
- The number of unpaired electrons depends both on the metal ion and on the ligands.
- A strong-field ligand forms a high-spin complex.
- A weak-field ligand will have the same number of unpaired electrons as the free ion.
- A low-spin complex contains fewer unpaired electrons than a high-spin complex.
- The number of unpaired electrons depends both on the metal ion and on the ligands.
Which of the following statements correctly describe the factors affecting the color of a particular coordination complex? Select all that apply.
- The color depends only on the nature of the ligands.
- The splitting energy of the complex determines the wavelengths of light absorbed and hence the color.
- For a given metal ion, the color depends on the ligand.
- For a given ligand, the color depends on the oxidation state of the metal ion.
- For a given ligand, the color depends on the oxidation state of the metal ion.
- The splitting energy of the complex determines the wavelengths of light absorbed and hence the color.
- For a given metal ion, the color depends on the ligand.
Which of the following complex ions will have only one unpaired electron? Select all that apply.
- [MnCl6]4–
- [Mn(CO)6]2+
- [Mn(CN)6]4–
- [Mn(en)6]2+
- [Mn(H2O)5Cl]+
- [Mn(CO)6]2+
- [Mn(CN)6]4–
- [Mn(en)6]2+
The difference in splitting of d-orbital energies for ______ complexes is simply the reverse of that for the ______ complexes.
- square-planar; octahedral
- square-planar; square-pyramidal
- tetrahedral; octahedral
- tetrahedral; square-planar
- tetrahedral; octahedral
Electrons in the d orbitals of a complex ion may enter the higher energy d orbitals once the lower energy d orbitals are half filled if the value of Δ is _____. Electrons will completely fill the lower energy d orbitals before entering the higher energy d orbitals if the value of Δ is _____.
- small;large
- large;small
- small;large
Match each complex ion w/ the correct # of unpaired e-.
Mn(CN)64– ->
Co(en)33+ ->
FeCl42– ->
Co(H2O)62+ ->
- 0 unpaired e-
- 1 unpaired e-
- 4 unpaired e-
- 3 unpaired e-
Mn(CN)64– -> 1
Co(en)33+ -> 0
FeCl42– -> 4
Co(H2O)62+ -> 3
Which of the following statements correctly describe the differences between octahedral, square planar, and tetrahedral complexes? Select all that apply.
- Square planar complexes tend to be low-spin complexes.
- Tetrahedral complexes have smaller splitting energies than octahedral complexes.
- Square planar complexes are usually diamagnetic.
- A square planar complex has 2 lower energy d orbitals and three higher energy d orbitals.
- Tetrahedral complexes are all low-spin complexes.
- Square planar complexes are usually diamagnetic.
- Square planar complexes tend to be low-spin complexes.
- Tetrahedral complexes have smaller splitting energies than octahedral complexes.
