View source for InorganicCompLab yd3717

== EX<sub>3</sub> ==


=== BH<sub>3</sub> ===


==== General information ====

B3LYP / 6-31G(d, p) level

[[File:Bh3_summary_yd3717.PNG|center|thumb|Summary table of BH3 molecule.]]


<pre>
Item               Value     Threshold  Converged?
 Maximum Force            0.000014     0.000450     YES
 RMS     Force            0.000007     0.000300     YES
 Maximum Displacement     0.000053     0.001800     YES
 RMS     Displacement     0.000027     0.001200     YES
</pre>

BH<sub>3</sub> frequency file: [[File:YD3717_BH3_FREQ.LOG]]

<pre>
Low frequencies ---   -7.5936   -1.5614   -0.0054    0.6514    6.9319    7.1055
Low frequencies --- 1162.9677 1213.1634 1213.1661
</pre>

<jmol><jmolApplet>
  <title>Optimized BH3 molecule</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_BH3_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

==== Vibrational spectrum ====



{| class="wikitable"
|+ 
|-
|Wavenumber (cm<sup>-1</sup>) || Intensity (arbitrary units) || Symmetry || IR active? || Type
|-
|1163
|93
|A2
|yes
|out-of-plane bend
|-
|1213
|14
|E
|very slight
|bend
|-
|1213
|14
|E
|very slight
|bend
|-
|2582
|0
|A1
|no
|symmetric stretch
|-
|2716
|126
|E
|yes
|asymmetric stretch
|-
|2716
|126
|E
|yes
|asymmetric stretch
|}


[[File:Bh3_ir_yd3717.PNG|center|thumb|800px|Predicted IR spectrum of BH3 molecule.]]


There are clearly 6 vibrations, but only 3 peaks are seen on the IR spectrum. First reason is that there are two sets of degenerate vibrations, at frequency = 1213 cm<sup>-1</sup> and 2716 cm<sup>-1</sup>. Therefore these four vibrations will only show two different peaks on the spectrum. The vibration at frequency = 2582 cm<sup>-1</sup> is a symmetric stretch, which has no change in dipole moment. So this vibration is IR inactive and will not show on the spectrum. The other peak shown on the spectrum corresponds to the vibration at 1163 cm<sup>-1</sup>.


----

==== MO diagram ====


[[File:full_picture3_yd3717.PNG|center|thumb|800px|MO diagram of BH3 molecule.]]


The predicted LCAO MOs look very similar to the real MOs. They have exactly the same distribution of  phases and nodes. However there are slight differences in phase orientation. For example, the 7th LCAO MO are predicted to have p orbital horizontal. But the real MO shows the p orbital is push downwards a little bit. Similar for the 8th MO, the vertical p orbital is squeezed in between the other phases.

Therefore MO theory can predict most of the MOs correctly, with slight differences on phase orientations. However it is still very useful in learning orbital bondings as it predicts the MO phases and nodes correctly.

[[User:Ng611|Ng611]] ([[User talk:Ng611|talk]]) 13:10, 17 May 2019 (BST) You're totally correct about qualitative MO theory being unable to predict the distortion of MOs off the atoms, well done. However, you should try to be more clear and succinct in your answer. There are also other minor differences that are important, can you spot them?
----

=== NH<sub>3</sub> ===


==== General information ====

B3LYP / 6-31G(d, p) level


[[File:Nh3_summary3_yd3717.PNG|center|thumb|Summary table of NH3 molecule.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000013     0.000450     YES
 RMS     Force            0.000006     0.000300     YES
 Maximum Displacement     0.000040     0.001800     YES
 RMS     Displacement     0.000013     0.001200     YES
</pre>

NH<sub>3</sub> frequency file: [[File:YD3717_NH3_FREQ.LOG]]

<pre>
 Low frequencies ---   -8.5223   -8.4750   -0.0033    0.0335    0.1919   26.4067
 Low frequencies --- 1089.7616 1694.1862 1694.1866
</pre>

<jmol><jmolApplet>
  <title>Optimized NH3 molecule</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_NH3_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

=== NH<sub>3</sub>BH<sub>3</sub> ===


==== General information ====

B3LYP / 6-31G(d, p) level

[[File:Nh3bh3_summary2_yd3717.PNG|center|thumb|Summary table of NH3BH3 molecule.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000114     0.000450     YES
 RMS     Force            0.000063     0.000300     YES
 Maximum Displacement     0.000621     0.001800     YES
 RMS     Displacement     0.000355     0.001200     YES
</pre>

NH<sub>3</sub>BH<sub>3</sub> frequency file: [[File:YD3717_NH3BH3_FREQ.LOG]]

<pre>
 Low frequencies ---   -0.0614   -0.0457   -0.0065   21.6818   21.6877   40.5522
 Low frequencies ---  266.0205  632.3610  640.1375
</pre>

<jmol><jmolApplet>
  <title>Optimized NH3BH3 molecule</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_NH3BH3_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

=== Energy calculation ===

E(NH<sub>3</sub>) = -56.55777 a.u.

E(BH<sub>3</sub>) = -26.61532 a.u.

E(NH<sub>3</sub>BH<sub>3</sub>) = -83.22469 a.u.


ΔE = E(NH<sub>3</sub>BH<sub>3</sub>)-[E(NH<sub>3</sub>)+E(BH<sub>3</sub>)]

= -0.0516 a.u.

= -135 kJ/mol


The normal B-N bond has a strength of 389 kJ/mol <sup>[1]</sup>, while the dative B-N bond strength calculated above is 135 kJ/mol. A very strong bond like N-N triple bond has a energy of 946 kJ/mol <sup>[1]</sup>. Therefore in comparison, this B-N dative bond is only a weak bond.

[[User:Ng611|Ng611]] ([[User talk:Ng611|talk]]) 13:14, 17 May 2019 (BST) Good calculation. I'd avoid using websites as literature sources if you can. Try to use a paper or text/databook if you can. 

----

=== NI<sub>3</sub> ===


==== General information ====

B3LYP / 6-31G(d, p) LANL2DZ level


[[File:Ni3_summary_yd3717.PNG|center|thumb|Summary table of NI3 molecule.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000096     0.000450     YES
 RMS     Force            0.000050     0.000300     YES
 Maximum Displacement     0.001084     0.001800     YES
 RMS     Displacement     0.000616     0.001200     YES
</pre>

NI<sub>3</sub> frequency file: [[File:YD3717_NI3_FREQ.LOG]]

<pre>
 Low frequencies ---  -12.7232  -12.7172   -6.4215   -0.0039    0.0189    0.0620
 Low frequencies ---  101.0767  101.0775  147.4581
</pre>

<jmol><jmolApplet>
  <title>Optimized NI3 molecule</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_NI3_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

==== N-I distance ====


The optimised N-I distance is 2.184 Å.

== Project: Lewis acids and bases ==

=== Five possible structures and symmetry ===

Determine the five possible isomers and identify the symmetry of each isomer of Al<sub>2</sub>Cl<sub>4</sub>Br<sub>2</sub>.


[[File:Structures_yd3717.PNG|center|thumb|600px|Five possible structures and their symmetries of Al2Cl4Br2 molecule.]]


----

=== Two bridging Br ions (Molecule 1) ===

B3LYP / 6-31G(d, p) LANL2DZ level


[[File:molecule1_summary2_yd3717.PNG|center|thumb|Summary table of molecule 1.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000034     0.000450     YES
 RMS     Force            0.000016     0.000300     YES
 Maximum Displacement     0.000687     0.001800     YES
 RMS     Displacement     0.000394     0.001200     YES
</pre>

Molecule 1 frequency file: [[File:YD3717_MOLECULE1_FREQ.LOG]]

<pre>
 Low frequencies ---   -4.9368   -4.7940   -3.2374    0.0019    0.0028    0.0031
 Low frequencies ---   14.9456   63.3281   86.1024
</pre>

<jmol><jmolApplet>
  <title>Optimized molecule 1</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_MOLECULE1_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>



----

=== Bridging Cl ions and trans terminal Br ions (Molecule 2) ===


B3LYP / 6-31G(d, p) LANL2DZ level


[[File:molecule2_summary_yd3717.PNG|center|thumb|Summary table of molecule 2.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000039     0.000450     YES
 RMS     Force            0.000014     0.000300     YES
 Maximum Displacement     0.001287     0.001800     YES
 RMS     Displacement     0.000438     0.001200     YES
</pre>

Molecule 2 frequency file: [[File:YD3717_MOLECULE2_FREQ.LOG]]

<pre>
 Low frequencies ---   -4.2020   -2.2652    0.0037    0.0041    0.0042    1.1849
 Low frequencies ---   17.7423   48.9741   72.9606
</pre>

<jmol><jmolApplet>
  <title>Optimized molecule 2</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_MOLECULE2_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

=== Energy and stability analysis ===


E (molecule 1) = -2352.40631 a.u. = -6175067 kJ/mol

E (molecule 2) = -2352.41629 a.u. = -6175093 kJ/mol


ΔE = E(molecule 1) - E(molecule 2)

= 0.00998 a.u.

= 26 kJ/mol


Molecule 1 with two Br ions bridging has higher energy than molecule 2 with two Cl ions bridging. The energy difference is about 26 kJ/mol.

This is because both Al and Cl are in row 3, while Br is in row 4. The 3p orbitals are similar in energy and sizes, therefore 3p-3p overlap of Al-Cl is better than the 3p-4p overlap of Al-Br. 

Better overlap results in lower energy, which means molecule 2 with Cl bridging is more stable than molecule 1.

[[User:Ng611|Ng611]] ([[User talk:Ng611|talk]]) 13:19, 17 May 2019 (BST) Good calculation and an interesting explanation, although I think it's more likely that steric interactions affect the stability more.  


----

=== AlCl<sub>2</sub>Br ===

B3LYP / 6-31G(d, p) LANL2DZ level


[[File:alcl2br_summary_yd3717.PNG|center|thumb|Summary table of AlCl2Br molecule.]]


<pre>
         Item               Value     Threshold  Converged?
 Maximum Force            0.000081     0.000450     YES
 RMS     Force            0.000042     0.000300     YES
 Maximum Displacement     0.001588     0.001800     YES
 RMS     Displacement     0.000974     0.001200     YES
</pre>

AlCl<sub>2</sub>Br frequency file: [[File:YD3717_ALCL2BR_FREQ.LOG]]

<pre>
 Low frequencies ---    0.0045    0.0048    0.0053    1.3569    3.6367    4.2604
 Low frequencies ---  120.5042  133.9178  185.8950
</pre>

<jmol><jmolApplet>
  <title>Optimized AlCl2Br</title>
  <color>black</color>
  <size>200</size>
  <uploadedFileContents>YD3717_ALCL2BR_FREQ.LOG</uploadedFileContents>
</jmolApplet></jmol>


----

=== Dissociation energy analysis ===


E (molecule 2) = -2352.41629 a.u. = -6175093 kJ/mol

E (AlCl<sub>2</sub>Br) = -1176.19014 a.u. = -3087499 kJ/mol


ΔE = 2 * E(AlCl<sub>2</sub>Br) - E(molecule 2)

= 0.03601 a.u.

= 95 kJ/mol


The reaction of molecule 2 dissociate into 2AlCl<sub>2</sub>Br takes in energy, which means this is an endothermic reaction. The product, i.e. AlCl<sub>2</sub>Br, is higher in energy than the reactant molecule 2.

Therefore, AlCl<sub>2</sub>Br is less stable.


----

=== MO analysis of molecule 2===

==== 40th MO ====

[[File:40MO_full_yd3717.PNG|center|thumb|600px|40th MO of molecule 2.]]


----

==== 41st MO ====

[[File:41MO_full_yd3717.PNG|center|thumb|600px|41st MO of molecule 2.]]


----

==== 43rd MO ====

[[File:43MO_full_yd3717.PNG|center|thumb|600px|43rd MO of molecule 2.]]


[[User:Ng611|Ng611]] ([[User talk:Ng611|talk]]) 13:22, 17 May 2019 (BST) Great LCAO analysis and good description of the key interactions. Well done!

== Reference ==

[1] Bond strength https://labs.chem.ucsb.edu/zakarian/armen/11---bonddissociationenergy.pdf