Coordination Compounds PART TWO

Bonding Theories, Isomerism. I've skipped colour and organometallic complexes because I really can't lol. Check out my other flashcards too! Answer mode: Answer with Definition

What does Werner’s Theory postulate?

Each central metal ion/atom in a coordination sphere shows two types of valences: primary valency and secondary valency.

What does the primary valency of a central metal atom/ion represent?

the oxidation state of that metal atom/ion

What does the secondary valency of a central metal atom/ion represent

the coordination number of that metal atom/ion.

Is the primary valency of a central metal atom/ion directional or non-directional?

non-directional what the fuck even is this btw

Is the secondary valency of a central metal atom/ion directional or non-direction

directional

Which valency of the central metal atom/ion is ionisable? (primary/secondary valency)

primary

Which valency of the central metal atom/ion is NOT ionisable? (primary/secondary valency)

secondary

What is the coordination number of $Fe^{2+}$?

6

What is the coordination number of $Fe^{3+}$?

6

What is the coordination number of $Co^{3+}$?

6

What is the coordination number of $Pt^{4+}$?

6

What is the coordination number of $Cr^{3+}$?

6

What is the coordination number of $Ru^{2+}$?

6

What is the coordination number of $Os^{3+}$?

6

What is the coordination number of $Pt^{2+}$?

4

What is the coordination number of $Ni^{2+}$?

4

What is the coordination number of $Cu^{2+}$?

4

What is the coordination number of $Zn^{2+}$?

4

What is the coordination number of $Au^{3+}$?

4

What is the coordination number of $Hg^{2+}$?

4

What is the coordination number of $Ag^{1+}$?

2

What is the coordination number of $Mo^{3+}$?

8

What sort of molecules can satisfy a central metal atom’s primary valency?

(anions, cations, neutral molecules)

only anions

What sort of molecules can satisfy a central metal atom’s secondary valency?

(anions, cations, neutral molecules)

anions and neutral molecules

If a central metal atom has a coordination number of 2, what is its hybridisation?

$$sp$$

linear

If a central metal atom has a coordination number of 4, what are its possible hybridisations?

$sp³$ (tetrahedral)

$dsp²$ (square planar)

If a central metal atom has a coordination number of 6, what are its possible hybridisations?

$sp³d²$ (octahedral)

$d²sp³$ (octahedral)

If a central metal atom has a coordination number of h, what is its hybridisation?

$dsp³$ (trigonal bipyramidal)

What are inner orbital complexes / low spin complexes?

complexes where the central metal atom has its inner $(n-1)d$ orbital participating in hybridisation

What are outer orbital complexes / high spin complexes?

complexes where the central metal atom has its outer $nd$ orbital participating in hybridisation

What are Weak Field Ligands?

Ligands that cannot force electrons to pair up in the central metal atoms/ions.

What are the three main groups for donor atoms of Weak Field Ligands?

$S$ulphur

$H$alogens

$O$xygen

What are the three main groups for donor atoms of Strong Field Ligands?

$N$itrogen

$C$arbon

$P$hosphorus

What is the formula for calculating the magnetic moment of a complex?

$$\sqrt{n(n+2)}$$

where $n$ is the number of unpaired electrons

What is the hybridisation of $[Fe(CN)_6]^{3+}$?

$$d²sp³$$

What is the hybridisation of $[FeF_6]^{3-}$?

$$sp³d²$$

What is the hybridisation of $[Ni(CN)_4]^{2-}$?

$$dsp²$$

What is the hybridisation of $[NiCl_4]^{2-}$?

$$sp³$$

What is the hybridisation of $[Ni(CO)_4]$?

(special case)

$$sp³$$

this is because the $s$ orbital must be empty always for hybridisation.

What is the hybridisation of $[Cu(NH_3)_4]^{2+}$?

(special case)

$$dsp²$$

this is because $dsp²$ is more stable than $sp³$ with one unpaired electron.

What does the Effective Atomic Number of a metal ion denote?

It tells us about the number of electrons in a central metal ion after making coordinate bonds with ligands.

What is EAN’s rule?

Complexes having an Effective Atomic Number equal to the atomic number of the next noble gas are found to be extra stable.

What is the formula for calculating Effective Atomic Number of a central metal ion/atom?

$$EAN=Z-OS+2CN$$

$EAN = \text{atomic number of metal} - \text{oxidation state of metal} + \text{the number of electrons provided by ligands through coordinate bonds}$.

What is the main postulate of Crystal Field Theory?

When a ligand approaches the central metal ion, the degenerate $d$ orbitals of the metal ion undergo splitting into two sets ($e_g$ and $t_{2g}$).

What is crystal field splitting energy?

The energy difference between the two split sets of $d$ orbitals under Crystal Field Theory.

How does the Crystal Field strength of a ligand affect $\Delta$ i.e. the Crystal Field Splitting Energy of a metal atom/ion’s $d$ orbitals?

$\Delta \propto \text{crystal field strength of ligand}$.

What does the $d_{xy}$ orbital look like?

What does the $d_{yz}$ orbital look like?

What does the $d_{zx}$ orbital look like?

What does the $d_{x²-y²}$ orbital look like?

What does the $d_{z²}$ orbital look like?

Which $d$ orbitals are axial orbitals?

$d_{x²-y²}$ and $d_{z²}$

Which $d$ orbitals are non-axial orbitals?

$d_{xy}$, $d_{yz}$ and $d_{zx}$

What are axial orbitals called?

($t_{2g}$ / $e_g$)

$$e_g$$

What are non-axial orbitals called?

($t_{2g}$ / $e_g$)

$$t_{2g}$$

How does the diagram of the splitting of $d$ orbitals look in the presence of SFLs and WFLs in an octahedral complex?

What is pairing energy?

The energy required to force two unpaired electrons into one orbital is called pairing energy.

In the presence of Strong Field Ligands, which one is greater; Crystal Field Splitting Energy or Pairing Energy?

Crystal Field Splitting Energy

In the presence of Weak Field Ligands, which one is greater; Crystal Field Splitting Energy or Pairing Energy?

Pairing Energy

What is Crystal Field Stabilisation Energy?

It is the energy by which complex compounds get stable due to the splitting of $d$ orbitals.

What is the formula for calculating Crystal Field Stabilisation Energy in an octahedral complex?

$$CFSE = (0.6\times\Delta_o\times n_{e_g})+(-.04\times\Delta_o\times n_{t_{2g}})+np$$

Where:

$\Delta_o$ is the crystal field splitting energy in an octahedral complex

$n_{e_g}$ is the number of electrons in the $e_g$ orbitals

$n_{t_{2g}}$ is the number of electrons in the $t_{2g}$ orbitals

$n$ is the number of pairing done by SFLs ($\therefore$ in WFLs this value is 0)

$p$ is the pairing energy

The low spin complex of a $d^6$ cation in an octahedral complex will have what Crystal Field Stabilization Energy? (in terms of $\Delta_o$ and $p$)

$$CFSE = (0.6\times\Delta_o\times0)+(-0.4\times\Delta_o\times6)+3p$$

$$CFSE = -2.4\Delta_o + 3p$$

In an octahedral complex, which orbitals have more energy, $e_g$ or $t_{2g}$?

$$e_g$$

In a tetrahedral complex, which orbitals have more energy, $e_g$ or $t_{2g}$?

$$t_{2g}$$

How does the diagram of the splitting of $d$ orbitals look in the presence of SFLs and WFLs in a tetrahedral complex?

What is the formula for calculating Crystal Field Stabilisation Energy in an octahedral complex?

$$CFSE = (0.4\times\Delta_t\times n_{e_g})+(-0.6\times\Delta_t\times n_{t_{2g}})+np$$

Where:

$\Delta_t$ is the crystal field splitting energy in an tetrahedral complex

$n_{e_g}$ is the number of electrons in the $e_g$ orbitals

$n_{t_{2g}}$ is the number of electrons in the $t_{2g}$ orbitals

$n$ is the number of pairing done by SFLs ($\therefore$ in WFLs this value is 0)

$p$ is the pairing energy

What is the relationship between $\Delta_o$ and $\Delta_t$?

$\Delta_o$ is the crystal field splitting energy in an octahedral complex

$\Delta_t$ is the crystal field splitting energy in an tetrahedral complex

$$\Delta_o=\dfrac94\Delta_t$$

$\Delta_o$ is greater

List the spectrochemical series as best as you can.

(good luck 💀)

Weak Field Ligands:
I⁻ < Br⁻ < S²⁻ < SCN⁻ < Cl⁻ < NO₃⁻ < N₃⁻ < F⁻ < OH⁻ < C₂O₄²⁻ < H₂O

Strong Field Ligands:

NCS⁻ < CH₃CN < py < NH₃ < en < bipy < phen < NO₂⁻ < PPh₃ < CN⁻ < CO

How does the oxidation state of the central metal ion affect the stability of the complex?

the greater the oxidation state, the more stable the complex

For a group complexes with the same oxidation number (of metal ion), same ligands, and same coordination number, how would you determine which one is more stable?

Greater the $Z_{\text{eff}}$, more stable the complex

How does chelation affect the stability of a complex?

Chelating ligands are more stable than non-chelating ligands.

Which ligands make the complex more stable; SFLs or WFLs?

SFLs

How does the number of rings in a complex affect the stability of the complex?

the more the number of rings, the more stable the complex.

What is Ionisation isomerism?

Coordination compounds that have the same composition but different ions in solution.

What sort of isomerism do these two show?

• $$[Co(NH_3)_5Cl]Br$$

• $$[Co(NH_3)_5Br]Cl$$

Ionisation isomerism

What is hydrate/solvate isomerism?

The coordination compounds that have the same composition but a different number of $H_2O$ molecules present as ligands?

What sort of isomerism do these two show?

• $$[Cr(H_2O)_5Cl]Cl_2\cdot H_2O$$

• $$[Cr(H_2O)_4Cl_2]Cl\cdot 2H_2O$$

hydrate/solvate isomers

What sort of isomers give different confirmative tests?

ionisation isomers

What is coordination isomerism?

Isomerism caused by the interchange of ligands and metal ions between two complex ions of the same complex

(yeah both the anion and cation in the compound are complex)

What sort of isomerism do these two show?

• $$[Pt(NH_3)_3Cl][CuCl_3(NH_3)]$$

• $$[Pt(NH_3)_4][CuCl_4]$$

coordination isomerism

What is linkage isomerism?

The coordination compounds that have the same composition but differ in mode of attachment of ligand to metal ion.

(i.e. ambidentate ligands must be present)

What sort of isomerism do these two show?

• $$[Co(NH_3)_5NO_2]Cl_2$$

• $$[Co(NH_3)_5B(ONO)]Cl_2$$

linkage isomerism

What are stereoisomers?

Isomers that have the same formula, same composition, but differ in the orientation of ligands around the metal atom.

What are geometrical isomers?

Isomers of compounds where ligands occupy different positions around the central metal ion.

What are cis-isomers?

Isomers where two identical ligands are coordinated to the central metal ion from the same side.

What are trans-isomers?

Isomers where two identical ligands are coordinated to the central metal ion from opposite sides.

What is the characteristic of optically active isomers?

Isomers are due to lack of center/plane of symmetry

What is the characteristic of optically inactive isomers?

Isomers are due to existence of center/plane of symmetry

What sort of geometry must a 4-coordinated complex have for it to definitely not show geometrical isomerism?

tetrahedral geometry

Under what condition can 4-coordinated tetrahedral complexes show optical isomerism?

If all 4 ligands are different, it can show optical isomerism.

Depict the cis and trans isomers of a complex with the general formula $[Ma_2b_2]$.

($a$ and $b$ are both monodentate)

Depict the cis and trans isomers of a complex with the general formula $[Ma_2bc]$.

($a$ and $b$ and $c$ are both monodentate)

Can a complex with the general formula $[Ma_4]$ show geometrical isomerism?

no

Can a complex with the general formula $[Ma_2b_2]$ show geometrical isomerism?

yes

Can a complex with the general formula $[Ma_2bc]$ show geometrical isomerism?

yes

Can a complex with the general formula $[Ma_3b]$ show geometrical isomerism?

no

Depict the geometrical isomers of a complex with the general formula $[Mabcd]$.

($a$ and $b$ and $c$ and $d$ are both monodentate)

Can a complex with the general formula $[M(AA)bc]$ show geometrical isomerism?

($AA$ is bidentate with the same donor atom, $b$ and $c$ are monodentate)

no

Can a complex with the general formula $[M(AB)cd]$ show geometrical isomerism?

($AB$ is bidentate with different donor atoms, $c$ and $d$ are monodentate)

yes

Can a complex with the general formula $[M(AA)_2]$ show geometrical isomerism?

($AA$ is bidentate with the same donor atom)

no