Inorganic Spectroscopy NMR
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Transcript of Inorganic Spectroscopy NMR
����ات ا��آ� ر أ�� ا����ن
1
2Dr. USAMA El-AYAAN
Nuclear Magnetic
Resonance Spectroscopy
� ا�� وي ا������������ ا�� وي ا���������ا����ا��
Introduction
• NMR is the single most widely used physical technique because its wide application.
• It is used to study a wide variety of nuclei:• It is used to study a wide variety of nuclei:– 1H– 13C– 15N– 19F– 31P
4
��ى ��� - �� � أ��اد ��ل آ��� ا��رات���spinً% ��و$ً� و��� ! ن �
quantum numbers �&'��. Iو$'&� ���د ا�)�ل �- ��� � ��ل ا��* ا��رات�� +)�'ًا ��وى�ً�,�-�.(& �&1 أ&0� ذ� . ��&ً
* ا����رو1�2 ا��).�-�,*$56* ه�ا ا���م 1Hا����رو1�2 ��ً �5+ 7��8 5�ت :9�6 +*,�-�.(& '�(+“tiny magnet ” .
Dr. USAMA El-AYAAN
The NMR Spectrometer
5=>
Dr. USAMA El-AYAAN
Nuclear Spin•�� � ن �(� �������� ا�)�دى ا�'�&%ذات ا���د ا�#رى أو ا���د ا '�.
�� /�ل ������� -� ه#+ •���� �.آ�� 1��2'0 ا
• A nucleus with an odd atomic number or an odd mass number has a nuclear spin.
• The spinning charged nucleus generates a magnetic field.
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External Magnetic Field �� ه#ة)4 �6(-��� ���4ض ��9�(� ;�ر:% ������%/�ل �9ى ا
�4?�ف آ������= >��� When placed in an external field, spinning protons act like bar magnets.
7Dr. USAMA El-AYAAN
Two Energy States
�� NMRA4�4:(�ز دا;0�ا
ا��/�ل �� أو 6 ا����B ���Cآ�(�DEF1��2'0 آ�� ا��.
Dr. USAMA El-AYAAN 8
DEF1��2'0 آ�� ا��.
���- G��4 �EE∆ا��H�Fا����
0J��4 )ا��اد� /�ل %9(��ت ا�% αααα ا����� � ا��Eو4
ββββ ا�����
8Dr. USAMA El-AYAAN
∆E and Magnet Strength
• Energy difference is proportional to the
magnetic field strength.
• ∆∆∆∆E = hνννν = γγγγ h B0
2ππππStrength of the applied mag. filed
• Gyromagnetic ratio, γγγγ, is a constant for each
nucleus (26,753 s-1gauss-1 for H).
• In a 14,092 gauss field, a 60 MHz photon is
required to flip a proton.
• Low energy, radio frequency.
9Dr. USAMA El-AYAAN
Magnetic Shielding
• If all protons absorbed the same amount of
energy in a given magnetic field, not much
information could be obtained.
• But protons are surrounded by electrons • But protons are surrounded by electrons
that shield them from the external field.
• Circulating electrons create an induced
magnetic field that opposes the external
magnetic field.
10Dr. USAMA El-AYAAN
Magnetic Shielding
�)= ا��/�ل ا��K9 DEF اذا• ��- �H�Fا� =(���ت ا�?L آ0 ا��Eو4�ت ��H � ��M'6 ا�H �4NMR.
��ت ���� �N2'��و��ت • � ا��/�ل ا��%ا��Eو4- �)E/�4%:ر�Oا� . ��ت ���� �N2'��و��ت • � ا��/�ل ا��%ا��Eو4- �)E/�4%:ر�Oا� .
ل ا�� اة ��P1 -�� /�ل •B ت�� ������%دوران ا�Q'��و.ا��Oر:%-'= ا��/�ل
Dr. USAMA El-AYAAN 11
Shielded Protons
�SBK ز��دة �Rة ا��/�ل )�� ) -&% ا����-����H %9 ب ���B ا��Eو4 ن ا���� �/� آ ن وه#ة اQ�?�ص���ث �'%) -&% ا����ر(- W� ا�C��دة ��ور�� �&��
�ً2 .ا��Eو4 ن �/Magnetic field strength must be increased for a shielded proton to flip at the same frequency.
12Dr. USAMA El-AYAAN
Protons in a Molecule
Depending on their chemical
environment, protons in a molecule
are shielded by different amounts.are shielded by different amounts.
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• The number of signals shows how many different kinds of protons are present.
• The location of the signals shows how shielded or deshieldedthe proton is.
���(4 ��- �&YNMRNMRه��ك دا��Z أر62 أY&� -�� 4)���ه��ك دا��Z أر62 أNMR signalNMR signal
shielded or deshieldedthe proton is.
• The intensity of the signal shows the number of protons of that type.
• Signal splitting shows the number of protons on adjacent atoms. =>
14Dr. USAMA El-AYAAN
���(4 ��- �&YNMRNMRه��ك دا��Z أر62 أY&� -�� 4)���ه��ك دا��Z أر62 أ
� signals ��د -1•�� ����� �� ا ��و����ت ا� ا���اع ا
�%$# �signal"�ن -2• ��&' وا ,*$#و�%�د+ *�ل ا ��و��ن )�
و�� إ � ��د ا ��و����ت �� ��0 ا '�ع signal/�ة -3•
•4- signal splitting ورة�$� و�� إ � ��د ا ��و����ت ��� ا 3رة ا
15Dr. USAMA El-AYAAN
ShieldingDeshielding A/B %&-0أHأ �ًE/B
16Dr. USAMA El-AYAAN
• TMS is added to the sample.
• Since silicon is less electronegative
than carbon, TMS protons are highly
Si
CH3
CH3
CH3
H3C Si
CH3
CH3
CH3
H3C
than carbon, TMS protons are highly
shielded. Signal defined as zero.
• Organic protons absorb downfield (to
the left) of the TMS signal.
17Dr. USAMA El-AYAAN
Chemical Shift
• Measured in parts per million.
• Ratio of shift downfield from TMS (Hz) to
total spectrometer frequency (Hz).
• Same value for 60, 100, or 300 MHz • Same value for 60, 100, or 300 MHz
machine.
• Called the delta scale.
18Dr. USAMA El-AYAAN
�ت TMS إ<�=�ام�� آ���CD F* ���'!� &�ا:�CD Eط -�A ا�@'و �5�F !*ا��=�G�ا� EH�& �.5*ا����C1 ا�H NMR .
Si CH3CH3
CH3
CH
tetramethylsilane
“TMS”
reference compound :را�I�> F�0& Eن �ً@KL *�M7 ا ��� �'و
9��. !* ا�)
TMS
shift in Hz
0
CH3
n
Highly shielded
protons appear
way upfield.
Chemists originally
thought no other
compound would
come at a higher
field than TMS.
downfield
19Dr. USAMA El-AYAAN
11 . .�ً�Z0 آ�����; Aآ�ن K� 0�M 62ً�را�Z0 آ�����; Aآ�ن K� 0�M 62را . .22 . . �^(O� در:� _&��ن `� ���F� 0Z� �^(O� در:� _&��ن `� ���F� 0Z�2626..5 5 ooCC � م اC� إذا `� G&O(0 ا����، �#ا �م ا C� إذا `� G&O(0 ا����ا #� ، . . ة /�ل ������% وا�Bة . . 33H ��- �)���: G��4 `4�� ة /�ل ������% وا�Bة �2و4H ��- �)���: G��4 `4�� أ-&% � /�ل أ-&% � /�ل ) ) �#ا ��)f آ(�� eO% وا��B#ا ��)f آ(�� eO% وا�B((�2و4
�6 ا���&�0 ����&� ��(�Fط ا� FO6 ا���&�0ا�� ����&� ��(�Fط ا� FOل . . ا� %FOا� h�Fا� #;P�ل و %FOا� h�Fا� #;P�وTMS TMS س��J %&- �(< ��ا���د ���Jس ا���J %&- �(< ��ا���د ���Jا�δδδδδδδδد��� وا��% ��C/2 �)�- �Eء � ا��&� ن د��� وا��% ��C/2 �)�- �Eء � ا��&� ن (ppm) (ppm) ..
%F; 6:ن آ��K0 ا����M 62دة را�م �O��4 ذا��� %F; 6:ن آ��K0 ا����M 62دة را�م �O��4 ذا��� h�� ط F; 6Hا �9���� h�� ط F; 6Hا �9���� �(&�Oت ا���� ��ت ا���O&)� ا��Eو4 :: C:NMR NMR��Yت ا�� اد ا��^ �� -�� C: h�� 0�&�4��Yت ا�� اد ا��^ �� -�� h�� 0�&�4 9%9%ا��Eو4
C4�)��2 �)�- ًا�E� ����HHz ����4 اQزا�E� �Bو4 ن �� ة �4دد ا�/(�ز ا�����Oم 9% ا���JسH %&- . 9'&�� آ�ن ا�/(�ز
��E��&� C4�)ام ا��O�ا��1'&� -�� إ��ت � ا �C��ح �&�Eو4- :←←←←
TMS
shift in Hz
0n
downfield
ة �4دد ا�/(�ز ا�����Oم 9% ا���JسH %&- . 9'&�� آ�ن ا�/(�ز. ذو �4دد -��% ��?0 -&% إزا�B أ-&%
Higher frequencies= larger shifts in Hz.
��ت � ا �C��ح �&�Eو4- :←←←←
20 Dr. USAMA El-AYAAN
parts perparts perparts perparts per
millionmillionmillionmillion
��Z����'ا� �BزاQا ))δδδδδδδδ ( (““ف��Fة ا�� H ����2 ����4n `�2�o ���Hف��Fة ا�� H ����2 ����4n `�2�o ���H””
The shifts from TMS in Hz are bigger in higher fiel d: instruments (500 MHz > 400 MHz > 300 MHz > 200 MHz )
We can adjust the shift to a field-independent valu e,the “chemical shift” in the following way:
chemical
shift= δδδδ =
shift in Hz
spectrometer frequency in MHz= ppm
This division gives a number independent
of the instrument used.
���H =(� ��- �)f� م &� Aآ�9% � ة ا����Fف ا�����Oم �2δδδδو4 ن ��H ���4 621 Dr. USAMA El-AYAAN
Delta Scale
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=>Dr. USAMA El-AYAAN
Location of Signals
• More electronegative
atoms deshield more and
give larger shift values.
• Effect decreases with • Effect decreases with
distance.
• Additional
electronegative atoms
cause increase in chemical
shift.
23Dr. USAMA El-AYAAN
���� ����
ل ا�� اة ��AE � ���ف A/�2 ا�� اة � ا���oP ���2/�ل �B ���ز��دة ا�'�9�M ا�Q'��و�` أن �/�h�� 0 ا�� اة �shielding ( ��- �)f(ا��������% ا��Oر:% PR �وه#ا . /�ل ������% -��%
ل ا�� اة ��AE � ���ف A/BK��2 ا�� اة � ا���oP ���2/�ل �B ����GJ ا�'�9�M ا�Q'��و�� �/�h�� 0 ا�� اة �f(� -�� /�ل )deshielding(ا��������% ا��Oر:%
W(O� %������. �downfield (deshielding) = left side of spectrum
upfield (shielding) = right side of spectrum
ا�� ا0 ا���oqة -&% اCB 6Hم اQ�?�صا�� ا0 ا���oqة -&% اCB 6Hم اQ�?�ص
�upfield (shielding) = right side of spectrum�delta values increase from right to left!
CHCl3 CH2Cl2 CH3Cl
7.27 5.30 3.05 ppm
mostdeshielded
� :r�Mل�Aة ا��� H ��oP4
24 Dr. USAMA El-AYAAN
Typical Values
25Dr. USAMA El-AYAAN
12121212C is not NMRC is not NMRC is not NMRC is not NMR----activeactiveactiveactive I = I = I = I = 0000
however….however….however….however…. 13131313C does have spin, I = C does have spin, I = C does have spin, I = C does have spin, I = 1111////2 2 2 2 (odd mass)(odd mass)(odd mass)(odd mass)
4 ا:� ا�(��رو:�� (%1.08)9% ا����EF 13- إ�O)�ض ���E و: د ا�'�2 ن1.1.1.1. �E��2 ��% )100�Jر
��(�Fرات ا��RQ1313اC NMRC NMR ��(�Fرات ا��RQا � h1أ��H NMR AE�2 :
1313C NMR C NMR h��h��
4 ا:� ا�(��رو:�� (%1.08)9% ا����EF 13- إ�O)�ض ���E و: د ا�'�2 ن1.1.1.1. �E��2 ��% )100�Jر�ًE��J4.(
v�B أن “ . 0�&H�Jر�� C���2م ا��������% �� اة ا�(��رو:�� 13- ا��Cم ا��������% �� اة ا�'�2 ن2.2.2.2. L2�Mا�Gyromagnetic constantGyromagnetic constantGyromagnetic constantGyromagnetic constant:γγγγن اة ا�'�2�� �E����2 -13 اة � ���B %9 `���H 62ر
�. ”ا�(��رو:�
h�� 0�/�4 �1313#اC NMR C NMR h�F2 ��ا�#ى 1H NMR�P;# و�Hً� أ� ل ��M'2�Jر).د)1-2 �J�H��w �4/�&� 9% ز� H&�0 :�ًا
%9 ��Z����'ا� �BزاQى ا�1313C NMRC NMR ���B %9 `� �E1أآH NMR
0 - 220 ppm26Dr. USAMA El-AYAAN
“ Typical” 13C NMR
the wave function for the highest occupied molecular orbital for Carbon 60
1313C NMR C NMR h��h��
27
Dr. Richard Smalley
Dr. USAMA El-AYAAN
IFeq
Feq Feq
Feq
Fax IF5 has a square-pyramidal geometry, with one axial fluorine and four equitorial fluorines. Coupling between the inequivalent fluorinesshould give rise to a quintet for the F axresonance and a doublet for the F eqresonance
Feq Feq
28
eqresonance
Fax quintet
Feq doublet
Brisdon, p. 34Dr. USAMA El-AYAAN
31P NMR Spectroscopy
Compound δ (ppm) Compound δ (ppm)
As with As with 1919F NMR spectroscopy, F NMR spectroscopy, 3131P NMR spectroscopy is a fairly routine P NMR spectroscopy is a fairly routine experiment for experiment for phosphinesphosphines, , phosphitesphosphites, , phosphinephosphine oxides,oxides, phosphates, phosphates, and other phosphorus containing compounds, as it is and other phosphorus containing compounds, as it is 100100% abundant. % abundant. The chemical shift is sensitive to the oxidation st ate (P(III) The chemical shift is sensitive to the oxidation st ate (P(III) vsvs P(V))P(V)) and and the nature of the groups attached to the P atom. the nature of the groups attached to the P atom.
PMe3 -62 Me3PO +36
PEt3 -20 Et3PO +48
PBu3 -33 Bu3PO +43
PPh3 -7 Ph3PO +29
[PEt4]+ +40 P(OMe)3 +140
[PF6]- -145 P(OEt)3 +13829Dr. USAMA El-AYAAN
31P NMR for metal phosphine complexes
Cl
M
PR3
ClR3P
R3P ClCl
M
ClPR3R3P
R3P Cl
30
fac-[M(PR3)3Cl3] mer-[M(PR3)3Cl3]
All three PR3 ligands are in the same chemical environment, so the 31P NMR spectrum would have only one resonance
There are two PR3 ligands are in the same chemical environment (trans to each other) and the other in a different environment, so the 31P NMR spectrum would have two resonances, with a 2:1 relative integration
Dr. USAMA El-AYAAN
31P NMR for metal phosphine complexes
Cl
M
PR3
ClR3P
R3P ClCl
M
ClPR3R3P
R3P Cl
fac-[M(PR ) Cl ] mer-[M(PR ) Cl ]
31
fac-[M(PR3)3Cl3] mer-[M(PR3)3Cl3]
All three PR3 ligands are in the same chemical environment, so the 31P NMR spectrum would have only one resonance
There are two PR3 ligands are in the same chemical environment (trans to each other) and the other in a different environment, so the 31P NMR spectrum would have two resonances, with a 2:1 relative integration
Dr. USAMA El-AYAAN
19F and 31P NMR spectra of the PF 6- ion
FF F
-
In the octahedral PF6- ion, all six fluorine
nuclei are identical.
The 19F NMR spectrum would be expected to show coupling of the six equivalent F
P
FF F
F F
32
to show coupling of the six equivalent F nuclei to one P nucleus to give a doubletfor the F resonance
The 31P NMR spectrum would be expected to show coupling of the P nucleus to 6 F nuclei, giving a regular “septet” for the P resonance.
Dr. USAMA El-AYAAN
Coupling
• Consider one H split by one F
33
Brisdon, p. 36
Dr. USAMA El-AYAAN
Coupling
• I = 1/2
34
Brisdon, p. 37
Dr. USAMA El-AYAAN
Coupling• I = 1/2
35
Brisdon, p. 38
Dr. USAMA El-AYAAN
Si(OCH2CH3)2JJ = (= (44..377377-- 44..342342))ppmppm x x 200 200 MHz = MHz = 7 7 Hz
36Dr. USAMA El-AYAAN
19F and 31P NMR spectra of the PF6- ion
1JPF = 709 Hz (typical range is 500-1500 Hz
doublet septet
37
Brisdon, p. 38
Dr. USAMA El-AYAAN
31P NMR spectrum
A doublet of triplets
1JPF(axial)
38
19F NMR spectrum
1JPF(equitorial)
Iggo, NMR Spectroscopy in Inorganic Chemistry, p. 38-40Dr. USAMA El-AYAAN
31P NMR spectrum of [Rh(PPh 3)3Cl]
Wilkinson’sWilkinson’s CatalystCatalyst ((RhRh(PPh(PPh33))33Cl)Cl) hashas threethree PPhPPh33 ligandsligands inintwotwo differentdifferent chemicalchemical environmentsenvironments (( ciscis andand transtrans toto thethe ClCl --
ligandligand)).. InIn additionaddition toto thethe twotwo setssets ofof PP nucleinuclei couplingcoupling totoeacheach other,other, theythey areare alsoalso coupledcoupled toto 103103RhRh (I(I == ½)½)..
39
Iggo, NMR Spectroscopy in Inorganic Chemistry, p. 36Dr. USAMA El-AYAAN
40Dr. USAMA El-AYAAN