1
Chemical shift for a given molecule:Chemical shift for a given molecule:
•• Number of signals = nonequivalent nucleiNumber of signals = nonequivalent nuclei
molecular symmetrymolecular symmetry
•• Relative intensity = number of nucleiRelative intensity = number of nuclei
•• Position in the spectrum = shielding/chemical shiftPosition in the spectrum = shielding/chemical shift
electronic structureelectronic structure
•• MultiplicityMultiplicity = connectivity of atoms and groups= connectivity of atoms and groups
2
MagneticMagnetic CouplingCoupling
The interaction of nuclear spins is composed of two parts:The interaction of nuclear spins is composed of two parts:
1. Dipolar coupling1. Dipolar coupling
direct interaction of magnetic momentsdirect interaction of magnetic moments
solidssolids
oriented phasesoriented phases
NOENOE
relaxationrelaxation
2. Scalar coupling2. Scalar coupling
indirect interaction mediated by electronsindirect interaction mediated by electrons
chemical information about the bondingchemical information about the bonding
BBμμzz ~~ μμ rrAXAX
−−33
(3cos(3cos22
ΘΘ −− 1)1)
3
DipolarDipolar CCouplingoupling
Dipolar coupling constantDipolar coupling constant
DDAXAX ~~ hh γγAA γγXX rrAXAX
−−33
ΔνΔνheterohetero = D= DAXAX(3cos(3cos22
ΘΘ −− 1)1)
ΔνΔνhhomomoo == 1.51.5 DDAXAX(3cos(3cos22
ΘΘ −− 1)1)
DAX
2DAX
4
DipolarDipolar CCouplingoupling
BBμμzz ~~ μμ rrAXAX
−−33
(3cos(3cos22
ΘΘ −− 1)1)
5
ScalarScalar CCouplingoupling
Analysis of the coupling patterns consists ofAnalysis of the coupling patterns consists of
three parts:three parts:
•• number of lines in anumber of lines in a multipletmultiplet
•• relative intensities of lines in therelative intensities of lines in the multipletmultiplet
•• magnitude (and possibly sign) of themagnitude (and possibly sign) of the
coupling constantscoupling constants
6
Scalar (Scalar (SpinSpin--SSpinpin)) CCouplingoupling
The simplest case:
Two magnetically active nuclei
Interacting through bonds (see each other)
Both spins I = ½
0.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0
0.20.40.60.81.01.21.41.61.82.02.22.42.62.83.0
Ha
HbJ = 0
J ≠ 0
7
ScalarScalar CCouplingoupling
A splitting of a signal = more
energy levels involved in the
transitions
Origin = The magnetic moment of
the nucleus Ha produces
polarization at Hb (and vice versa)
Spectrum of Ha
8
TwoTwo SSpinspins I =I = ½½
9
TwoTwo SSpinspins I =I = ½½
10
Homo vs.Homo vs. HHeteroetero CCouplingoupling
11
ScalarScalar CCouplingoupling
CH3-CHCl2
3Hb
Ha
M = 2 n I + 1
12
M = 2 n I + 1
13
14
15
16
ScalarScalar CCouplingoupling
M = 2 n I + 1
17
ScalarScalar CCouplingoupling
18
19
First Order NMR Coupling PatternsFirst Order NMR Coupling Patterns
Spin, IX Polynomial, n = number of nuclei X Examples
1/2 (x + y)n 1H
1 (x2 + xy + y2)n 2H, 6Li, 14N
3/2 (x3 + x2y + xy2 + y3)n 11B, 7Li
2 (x4 + x3y + x2y2 + xy3 + y4)n -
5/2 (x5 + x4y + x3y2 + x2y3 + xy4 + y5)n 17O, 27Al
3 (x6 + x5y + x4y2 + x3y3 + x2y4 + xy5 + y6)n 10B
7/2 (x7 + x6y + x5y2 + x4y3 + x3y4 + x2y5 + xy6 + y7)n 51V, 59Co
Line intensities of the multiplet A are given by the coefficients of
polynomial expansion
AXn
20
SpinSpin ½½ PascalPascal’’s Triangles Triangle
PatternPattern nn Relative Peak HeightRelative Peak Height (x + y)(x + y)nn
SingletSinglet 00 11
DoubletDoublet 11 1 : 11 : 1
TripletTriplet 22 1 : 2 : 11 : 2 : 1
QuartetQuartet 33 1 : 3 : 3 : 11 : 3 : 3 : 1
QuintetQuintet 44 1 : 4 : 6 : 4 : 11 : 4 : 6 : 4 : 1
SextetSextet 55 1 : 5 : 10 : 10 : 5 : 11 : 5 : 10 : 10 : 5 : 1
AndAnd soso onon …………
21
Coupling withCoupling with SSeveraleveral SSpinspins
B
FF3C
F
F3C CF3
CF3
1111
B NMRB NMR
CFCF33 n = 9n = 9
F(2) n = 1F(2) n = 1
F(3) n = 1F(3) n = 1
CFCF33(too far)(too far)
K+
M =M = ΠΠ((22 nnii IIii + 1+ 1))
22
1111
B NMRB NMR SpectrumSpectrum ofof
K[B(CF=CFK[B(CF=CF22))44]]
1111
B NMRB NMR spectrumspectrum ofof K[B(CF=CFK[B(CF=CF22))44] in] in
CDCD33CN:CN: anan overlappingoverlapping quintetquintet ofof
quintetsquintets ofof quintetsquintets
((22
JJB,FB,F = 21.5,= 21.5, 33
JJB,FB,F = 3.2,= 3.2, 33
JJB,FB,F = 2.2= 2.2 HHz).z).
Multiplet overlap
23
K[AgFK[AgF44]]
K[AgFK[AgF44] d] d88 square planarsquare planar
109109Ag I =Ag I = ½½ NA = 48.2%NA = 48.2% γγ == -- 1.2448 101.2448 1077 radrad TT--11 ss--11
107107Ag I =Ag I = ½½ NA = 51.8%NA = 51.8% γγ == -- 1.0828 101.0828 1077 radrad TT--11 ss--11
1199
FF NMRNMR
24
K[AgFK[AgF44]]
M =M = 2nI + 12nI + 1
11J(J(109109AgAg –– F) = 425.8 HzF) = 425.8 Hz
11J(J(107107AgAg –– F) = 370.4 HzF) = 370.4 Hz
110909
AgAg NMRNMR
11J(J(109109AgAg –– F) must have the same value in bothF) must have the same value in both 109109Ag andAg and 1919F spectraF spectra
25
SignalSignal MultiplicityMultiplicity
17O NMR
TcO4
- in 20.1% enriched H2
17O.
H2
17O
26
SignalSignal MultiplicityMultiplicity
CCN
Pt
Tl
NCB
NCC
CAN
CCN
CCN
M =M = ΠΠ((22 nnii IIii + 1+ 1))13C enriched CN-
27
22
J (J (TlTl–– CCCC) <) < 11
J (J (TlTl–– CCBB) <) < 22
J (J (TlTl–– CCAA))
ciscis CCCC 0.45 kHz0.45 kHz
transtrans CCAA 9.71 kHz9.71 kHz
205205
Tl NMRTl NMR
28
ScalarScalar CCouplingoupling
SpinSpin--spinspin couplingscouplings betweenbetween twotwo nucleinuclei willwill bebe
dependentdependent uponupon severalseveral factorsfactors::
•• thethe nucleinuclei involvedinvolved –– magnetogyricmagnetogyric ratioratio
•• thethe distancedistance betweenbetween thethe twotwo nucleinuclei
•• thethe angleangle ofof interactioninteraction betweenbetween thethe twotwo nucleinuclei
•• thethe nuclearnuclear spinspin ofof thethe nucleinuclei
Indirect nuclear spin–spin coupling constants
•through-bond
•through-space
•through hydrogen bonds
29
ScalarScalar CCouplingoupling
The most important contribution to scalar coupling arisesThe most important contribution to scalar coupling arises
from the FERMIfrom the FERMI--CONTACT INTERACTIONCONTACT INTERACTION
which can be described in the Diracwhich can be described in the Dirac--vector model:vector model:
B0 A B
The nuclear spin polarization of nucleus A in a magnetic fieldThe nuclear spin polarization of nucleus A in a magnetic field
polarizes the spins of a bonding electron pair, which in turnpolarizes the spins of a bonding electron pair, which in turn
transfer this polarization to nuclear spin B.transfer this polarization to nuclear spin B.
30
ScalarScalar CCouplingoupling
FERMIFERMI--CONTACT INTERACTION is mediated only by sCONTACT INTERACTION is mediated only by s--
electrons (p, d, f electrons have no contact with the nucleus)electrons (p, d, f electrons have no contact with the nucleus)
ss--electron has definite probability at nucleuselectron has definite probability at nucleus
ee--spin and nuclear spin can interact only when they occupyspin and nuclear spin can interact only when they occupy
same spacesame space
An approximate expression for the scalar coupling constant JAn approximate expression for the scalar coupling constant J
was given by Mc CONNELL:was given by Mc CONNELL:
JJABAB ~~ γγAA γγBB ssAA
22
(0) s(0) sBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
ss22(0) = s(0) = s--electron density at the nucleuselectron density at the nucleus
ααABAB
22 = s= s--character in the Acharacter in the A--B bondB bond
31
Conventions on the NotationConventions on the Notation
of Scalar Coupling Constantsof Scalar Coupling Constants
SpinSpin--spin couplings are generally expressed in terms ofspin couplings are generally expressed in terms of
the COUPLING CONSTANTthe COUPLING CONSTANT nn
JJ
where n denotes the number of bonds between coupled nucleiwhere n denotes the number of bonds between coupled nuclei
DimDimensionension [ J ] = s[ J ] = s−−11 [Hz][Hz]
The magnitude of J depends on theThe magnitude of J depends on the gyromagneticgyromagnetic ratiosratios γγAA,, γγBB
of the coupled nuclei. For comparison of coupling constantsof the coupled nuclei. For comparison of coupling constants
involving different isotopes useinvolving different isotopes use
the REDUCED COUPLING CONSTANT Kthe REDUCED COUPLING CONSTANT K
KKABAB = (4= (4ππ22
/h) (/h) (γγAA γγBB ))−−11
JJABAB
DimDimensionension [ K ] = 10[ K ] = 101919 N AN A22 mm––33
32
Scalar Coupling ConstantsScalar Coupling Constants
To compare substituent influences on coupling for differentTo compare substituent influences on coupling for different
nuclei, usenuclei, use
the EFECTIVE REDUCED COUPLING CONSTANT Kthe EFECTIVE REDUCED COUPLING CONSTANT K’’
KK’’ABAB == KKABAB [[ssAA
22
(0) s(0) sBB
22
(0)](0)]−−11
DimDimensionension [K[K’’ ] = 10] = 104242 N AN A––22 mm33
33
SigSignns of Scalar Coupling Constantss of Scalar Coupling Constants
SiSiggns of scalar coupling may be both POSITIVE or NEGATIVE.ns of scalar coupling may be both POSITIVE or NEGATIVE.
The sign of a coupling constant is defined as follows:The sign of a coupling constant is defined as follows:
KKABAB < 0 if PARALLEL alignment of the spins I(A) and I(B) is< 0 if PARALLEL alignment of the spins I(A) and I(B) is
energetically favoredenergetically favored
KAB < 0
A B
KAB > 0
A B
KKABAB > 0 if ANTIPARALLEL alignment of the spins I(A) and I(B)> 0 if ANTIPARALLEL alignment of the spins I(A) and I(B)
is energetically favoredis energetically favored
34
SiSiggns of Scalar Coupling Constantsns of Scalar Coupling Constants
> 0 if> 0 if γγAA,, γγBB have same signhave same sign
< 0 if< 0 if γγAA,, γγBB have different signhave different sign
KKABAB
JJABAB
NMR spectroscopic measurements in liquids yield generally onlyNMR spectroscopic measurements in liquids yield generally only
information on RELATIVE SIGNS of two couplings,information on RELATIVE SIGNS of two couplings,
i.e. Ki.e. KABAB / K/ KACAC > 0 or K> 0 or KABAB /K/KACAC < 0.< 0.
Determination of absolute signs for KDetermination of absolute signs for KABAB or Kor KACAC requires otherrequires other
experiments (e.g. molecular beam experiments, observation ofexperiments (e.g. molecular beam experiments, observation of
dipolar interactions in the solid state)dipolar interactions in the solid state)
35
SiSiggns of Scalar Coupling Constantsns of Scalar Coupling Constants
The sign ofThe sign of 11KKEHEH isis generally positive.generally positive.
(E = any first to fourth row atom)(E = any first to fourth row atom)
IfIf the relative sign of a coupling constantthe relative sign of a coupling constant nnKKXYXY can becan be
ddeterminedetermined fromfrom nnKKXYXY // 11KKEHEH , it can be translated into an, it can be translated into an
absolute sign.absolute sign.
MMethodsethods for signfor sign determinationdetermination::
analysis of higher order spectraanalysis of higher order spectra
homohomo-- oror heteronuclearheteronuclear 2D2D--ExperimentsExperiments
selective irradiation experimentselective irradiation experiment
Coupling signs may provide useful structural information on:Coupling signs may provide useful structural information on:
the number of bonds connecting two nucleithe number of bonds connecting two nuclei
the oxidation state of elementsthe oxidation state of elements
thethe stereochemicalstereochemical details (conformation and configuration analysis)details (conformation and configuration analysis)
36
Visualization of SpinVisualization of Spin––SpinSpin CouplingCoupling
( ) ( )[ ]↑↓−↑↑== EEKJ ABBAAB
2
1
2
γγ
π
h
the energy splitting between states with parallel
and antiparallel nuclear spins
εAB(r) = the coupling energy density (CED)
integral of CED over all space = KAB
CED is a realspace function, can be visualized in 3D
contains all the information about the propagation of the
nuclear spin–spin interaction throughout a molecule
( ) ( )[ ] ( )∫∫ =−== ↑↓↑↑
dVrdVrrKJ ABBAABBAAB εγγ
π
εεγγ
π 22
1
2
hh
37
Visualization of SpinVisualization of Spin––SpinSpin CouplingCoupling
( ) ( )[ ] ( )∫∫ =−== ↑↓↑↑
dVrdVrrKJ ABBAABBAAB εγγ
π
εεγγ
π 22
1
2
hh
3JHH
through-bond
Benzene
through-space
H2P-CH2-CH2-PH2
3JPP
38
Visualization of SpinVisualization of Spin––SpinSpin CouplingCoupling
( ) ( ) ( )
21λλ
ρρ
ρ
rr
rAB
↑↓↑↑
−
=
3JHH
The coupling electron deformation
density (CDD), the integration of
CDD over space = 0
CDDCED
39
TypesTypes ofof CouplingCoupling
CouplingCoupling betweenbetween twotwo nucleinuclei cancan bebe categorizedcategorized asas followsfollows::
HomonuclearHomonuclear CouplingCoupling
-- couplingcoupling betweenbetween nucleinuclei ofof thethe samesame typetype
11HH--CC--CC--11HH,, 195195PtPt--195195Pt,Pt, 3131PP--CC--3131P,P, 199199HgHg--CC--CC--199199HgHg
HeteronuclearHeteronuclear CouplingCoupling
-- couplingcoupling betweenbetween nucleinuclei ofof differentdifferent typestypes
11HH--1313CC,, 11HH--3311P,P, 205205TlTl--195195Pt,Pt, 1414NN--5151VV
40
Distance DependenceDistance Dependence
TThehe absoluteabsolute valuevalue ofof thethe couplingcoupling constantconstant decreases as tdecreases as thehe numbernumber ofof
intercedinginterceding bondsbonds betweenbetween coupledcoupled nucleinuclei increasesincreases..
TheThe orderorder ofof thethe strengthstrength ofof couplingcoupling isis asas followsfollows:: 11J >J > 22J >J > 33J >J > 44J >J > nnJJ
11
JJ oneone--bondbond oror directdirect
22JJ twotwo--bondbond oror geminalgeminal
33JJ threethree--bondbond oror vicinalvicinal nnJJ longlong--rangerange
41
Distance DependenceDistance Dependence
P
33
JJPCCCPCCC = 14 Hz= 14 Hz
22
JJPCCPCC = 12 Hz= 12 Hz
11
JJPCPC = 55 Hz= 55 Hz
11
J >J > 33
JJ >> 22
JJ
42
LargestLargest HHeteronucleareteronuclear JJ
CN
PtNC CN
CN
CN
Tl
NC
CN
PtNC CN
CN
CN
Tl
CN
PtNC CN
CN
CN
Tl
NC
CN
2 CN
PtNC CN
CN
CN
Tl
NC
CN
3
NC
11
J(J(205205
TlTl--195195
Pt), kHz !!!!Pt), kHz !!!!
7171 5757 4747 3838
43
LargestLargest HHomonuclearomonuclear JJ
11J(J(199199HgHg--199199Hg) =Hg) =
220 300 Hz220 300 Hz
11J(J(199199HgHg--199199Hg) =Hg) =
263 200 Hz in CD263 200 Hz in CD22ClCl22
284 100 Hz in MeOH284 100 Hz in MeOH
44
DDependence onependence on MMagnetogyricagnetogyric RRatioatio
For the same elements, different nuclidesFor the same elements, different nuclides
JJABAB ~~ γγAA γγBB ssAA
22
(0) s(0) sBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
BHBH44
−−
11J(J(1111BB –– H) = 80 HzH) = 80 Hz γγ((1111B) = 8.57 10B) = 8.57 1077 radrad TT−−11ss−−11
11J(J(1010BB –– H) = 28 HzH) = 28 Hz γγ((1100B) = 2.87 10B) = 2.87 1077 radrad TT−−11ss−−11
45
DDependence onependence on MMagnetogyricagnetogyric RRatioatio
*
*
*)(
)(
*)(
)(
B
B
BA
BA
BAJ
BAJ
FBAJ
FBAJ
γ
γ
γγ
γγ
=
−
−
=−
=−
The nuclide with largerThe nuclide with larger γγ has larger coupling constanthas larger coupling constant
JJ((AA--BB))~~ γγAA γγBB ssAA
22
(0) s(0) sBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
46
DDependence onependence on MMagnetogyricagnetogyric RRatioatio
16101610
231231
15051505
11J(J(117117SnSn –– X)X)
HzHz
1685168528.533528.5335nnBuBu33SnSn –– TT
2422424.10644.1064nnBuBu33SnSn –– DD
1575157526.751026.7510nnBuBu33SnSn –– HH
11J(J(119119SnSn –– X)X)
HzHz
γγ (X)(X)
101077
radrad TT−−11
ss−−11
compoundcompound
JJABAB ~~ γγAA γγBB ssAA
22
(0) s(0) sBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
47
Effects ofEffects of EElectronegativelectronegative
SSubstituentsubstituents
1.1. Changes in hybridization: BentChanges in hybridization: Bent’’s rule, more electronegatives rule, more electronegative
substituentssubstituents preferprefer orbitalsorbitals with more pwith more p--character. Remainingcharacter. Remaining
orbitalsorbitals have more shave more s--charactercharacter -- ααABAB
22, hence the, hence the J increasesJ increases
2.2. Removal of electron density increases effective nuclearRemoval of electron density increases effective nuclear
charge, contraction of echarge, contraction of e--cloud, scloud, s--density increasesdensity increases -- ssAA
22(0)(0),,
hence thehence the J increasesJ increases
JJABAB ~~ γγAA γγBB ssAA
22
(0)(0) ssBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
48
Effects ofEffects of EElectronegativitylectronegativity
PAEt3
Pt
Cl
PBEt3Me
PAEt3
Pt
Cl
PBEt3
PAEt3
Pt PBEt3Me
Me
More p-character
More s-character
Cl
11
J(J(195195
PtPt -- PPAA) = 4179 Hz) = 4179 Hz
11
J(J(195195
PtPt -- PPBB) = 1719 Hz) = 1719 Hz
JJABAB ~~ γγAA γγBB ssAA
22
(0)(0) ssBB
22
(0) ((0) (ΔΔE)E)−−11
ααABAB
22
49
Effects ofEffects of EElectronegativitylectronegativity
J increases with increasing sum of substituentJ increases with increasing sum of substituent electronegativityelectronegativity
CO
WOC
CO
PX3
OC
CO
50
Effects ofEffects of CCoordinationoordination NNumberumber
Et3P Pt
Cl
Cl
PEt3
Cl
Cl
Et3P Pt
Cl
Cl
PEt3
11
J(J(195195
PtPt -- P) = 1455 HzP) = 1455 Hz 11
J(J(195195
PtPt -- PPBB) = 2397 Hz) = 2397 Hz
Et3P Pt
PEt3
PEt3
PEt3 PhMe2P Pt
PMe2Ph
PMe2Ph
PMe2Ph
2+
11
J(J(195195
PtPt -- P) = 3740 HzP) = 3740 Hz 11
J(J(195195
PtPt -- PPBB) = 2342 Hz) = 2342 Hz
Increasing coordination numberIncreasing coordination number results in decreasing Jresults in decreasing J
51
Effects ofEffects of CCoordinationoordination NNumberumber
[Cp[Cp22WHWH22]] [Cp[Cp22WHWH33]]++
11J(J(183183WW -- H) =H) = 73.2 Hz73.2 Hz 47.8 Hz47.8 Hz
Increasing coordination numberIncreasing coordination number results in decreasing Jresults in decreasing J
52
Effects ofEffects of ss--CharacterCharacter
B
XPs
XsPs
AXPJ +
−−
=−
)(1
)()%(%
)( 2
1
ss22 (P(P--X) = overlap integral in the PX) = overlap integral in the P--X bondX bond
11J(PJ(P -- X) decreases with increasing coordinationX) decreases with increasing coordination
number and oxidation statenumber and oxidation state
53
Effects of sEffects of s--CCharacterharacter
210210spspalkylidynealkylidyne
120120spsp22
alkylidenealkylidene
8080spsp33
alkylalkyl
11
J(J(183183
WW –– 1313
C), HzC), HzhybridizationhybridizationGroupGroup
W
PMe3H2
C
CH
C
PMe3
t-Bu
t-Bu
t-Bu
W oxidation state
54
Effects of sEffects of s--CCharacterharacter
F
P
F
F
F
F
P
F
F
F
F
P
F
F
F
11
J(J(3131
PP -- C) = 189.2 HzC) = 189.2 Hz 261.1 Hz261.1 Hz 476.0 Hz476.0 Hz
C
H
C
H H
C
11
J(J(1313
CC-- H) = 120 HzH) = 120 Hz 160 Hz160 Hz 250 Hz250 Hz
55
Effects of sEffects of s--CCharacterharacter
11
J(PJ(P--FFaxialaxial) =) = 777777 HzHz
11
J(PJ(P--FFequatequat) =) = 966966 HzHz
F
P
F
F
CF3
F
CF3
P
CF3
NMe2
Cl
F3C
22
J(PJ(P--FFaxialaxial) =) = 5353 HzHz
22
J(PJ(P--FFequatequat) =) = 130130 HzHz
56
Effects of sEffects of s--CCharacterharacter
H
H
H
H 123123
130130
134134
161161
11J (CJ (C--H), HzH), Hz
Increasing J
Intraring angle decreases
More p-character in C-C
More s-character in C-H
57
Effects of sEffects of s--CCharacterharacter
H2
P
B B
PH2
PH2
PH2
H2P
H2P
PH2
11
J(PJ(P--1111
BB) =) = 56.956.9 HzHz
11
J(PJ(P--1111
BB) =) = 26.326.3 HzHz
Explain the difference
58
Effects of sEffects of s--CCharacterharacter
11
J(PJ(P--1111
BB) =) = 56.956.9 HzHz
11
J(PJ(P--1111
BB) =) = 26.326.3 HzHz
LoneLone pairpair = substituent= substituent
withwith zerozero electronegativityelectronegativity
ResidesResides inin orbitalorbital withwith largelarge ss--charactercharacter
P
B
B
P
H2P
H2P
PH2
H
HH
H
59
Effects ofEffects of CCoordinationoordination NNumberumber
F
P
F
F
F
F
F
P
F
F
FF
F
P
F
F
F
H
P
F
F
F
11
J(J(3131
PP -- F)F) negativenegative
−−1400 Hz1400 Hz −−11091109 HzHz −−1080 Hz1080 Hz −−706 Hz706 Hz
Increasing coordination numberIncreasing coordination number results in decreasing Jresults in decreasing J
DilutionDilution ofof ss--charactercharacter intointo moremore bondsbonds
60
Effects ofEffects of OOxidationxidation SStatetate
Cl Pt
Cl
Cl
PBu3
P(OPh)3
Cl
Cl Pt
Cl
P(OPh)3
PBu3Bu3P Pt
Cl
Cl
PBu3
Bu3P
Pt
PBu3
PBu3
PBu3
11
JJ ((195195
PtPt -- 3131
P)P)
3740 Hz 2411 Hz Bu 31593740 Hz 2411 Hz Bu 3159 19211921
OPhOPh 6304 40606304 4060
IncreasingIncreasing oxidationoxidation statestate results in decreasing Jresults in decreasing J
DeDecreasingcreasing electronelectron densitydensity
61
Information from signs of KInformation from signs of KABAB
68685656−−141411J(PJ(P -- C)C)
SnSnIVIVSnSnIVIVSnSnIIII
PPVVPPVVPPIIIIII
−−333939−−38038015515511J(SnJ(Sn -- C)C)
lplp
changeschanges
signsign
P
Me
Me
Me
P
Me
Me
Me
Me
P
Me
Me
Me
O
Sn
Me
Me
Me
Me Sn
Me
Me
Sn
Me
Me
Me
Me
62
Angle DependenceAngle Dependence
TwoTwo typestypes ofof couplingcoupling are mostare most affectedaffected byby bondbond anglesangles::
••geminalgeminal couplingcoupling ((twotwo--bondbond couplingcoupling oror 22JJ))
••vicinalvicinal couplingcoupling ((threethree--bondbond couplingcoupling oror 33JJ))
63
GeminalGeminal CouplingCoupling
GeminalGeminal couplingcoupling oror 22JJ couplingcoupling isis dependentdependent uponupon thethe
bondbond angleangle betweenbetween thethe nucleinuclei..
TThehe smallersmaller thethe angleangle thethe biggerbigger thethe couplingcoupling constantconstant..
64
GeminalGeminal CouplingCoupling
TThehe smallersmaller thethe angleangle thethe biggerbigger thethe couplingcoupling constantconstant..
22
JJ ((11
HH –– 11
HH))
65
Trans/Trans/CCisis CCouplingoupling
H
H
H H
H
H
gemgem 00 –– 33
vicvic ciscis 66 –– 1212
vicvic transtrans 1212 –– 1818
nn
JJ ((11
HH –– 11
HH)), Hz, Hz
66
Trans/Trans/CCisis CCouplingoupling
Ph2
P
Pd
PPh2H
H PPh2H
(OC)4Mn
22
J (J (3131
PPμμ –– PdPd –– 3131
P)P)
ciscis 0 Hz0 Hz
transtrans 213 Hz213 Hz
67
Trans/Trans/CCisis CCouplingoupling
22
J (J (3131
PP –– MM –– 3131
P)P) ciscis < trans< trans
3123125555OhOhMo(CO)Mo(CO)44(PF(PF33))22
−−2828−−3636OhOhCr(CO)Cr(CO)44(PF(PF33))22
567567−−2929OhOhmermer--RhClRhCl33(PMe(PMe33))33
3153153838OhOhW(CO)W(CO)44(PF(PF33))22
1011011212OhOhMo(CO)Mo(CO)44[P(NMe[P(NMe22))33]]22
514514−−1616SPlSPlPtBrPtBr22(PMe(PMe33))22
610610−−88SPlSPlPdClPdCl22(PMe(PMe33))22
22JJ PPPP trans, Hztrans, Hz22JJ PPPP ciscis, Hz, HzCoordCoord..ComplexComplex
68
VicinalVicinal CouplingCoupling
VicinalVicinal couplingcoupling oror 33JJ couplingcoupling isis dependentdependent uponupon thethe dihedraldihedral angleangle
betweenbetween thethe nucleinuclei..
TThehe moremore eclipsedeclipsed oror antiperiplanarantiperiplanar thethe nucleinuclei thethe greatergreater thethe couplingcoupling
constantconstant..
TheThe relationshiprelationship betweenbetween dihedraldihedral angle andangle and couplingcoupling constantconstant isis knownknown
asas thethe KarplusKarplus curvecurve..
C
C
H
H
C
C
H
H C
C
H
H
αα
minimumminimum
αα 23
coscos CBAJ ++=
69
VicinalVicinal CouplingCoupling
αα 23
coscos CBAJ ++=
thethe KarplusKarplus equationequation
70
71
PopulationPopulation AnalAnalyysissis
Z
Hβ2
Hβ1
X
Hα
Y
Hβ2
Hβ1
Z
X
Hα
Y
Hβ1
ZHβ2
X
Hα
Y
p1 p2
p3
)180(
)60(
1321
3212
3211
o
o
t
g
gtg
tgg
J
J
ppp
pJpJpJJ
pJpJpJJ
=++
++=〉〈
++=〉〈
αβ
αβ
from independentfrom independent
measurementsmeasurements
33 inequivalentinequivalent protonsprotons
22 timetime--averagedaveraged vicinalvicinal JJ
(1(1 geminalgeminal J)J)
ppii == populationpopulation ofof rotamersrotamers
g =g = gauchegauche, t = trans, t = trans
experimentexperiment
72
PopulationPopulation AnalAnalyysissis
KOH
OH
HX
HX
HA
HB
HA
HB
Axial Equatorial
p 1 - p
)exp(
1
)1(
)1(
0
RT
G
p
p
K
JppJJ
JppJJ
Equ
BX
Axial
BXBX
Equ
AX
Axial
AXAX
Δ−
=
−
=
−+=〉〈
−+=〉〈
73
DecouplingDecoupling
Heteronuclear broadband decoupling
Selective homonuclear decoupling
74
1515
NN––1515
NN Coupling Across an NHNCoupling Across an NHN
Hydrogen BondHydrogen Bond
CD2Cl2/[d6]DMSO (5:1)
a) 233 K b) 233 K
c) 193 K d) 193 K
22
J(J(1515
NN––1515
N) = 16.5 HzN) = 16.5 Hz
75
66
LiLi––1515
N CouplingN Coupling
6Li I = 1 NA = 7.42 %
15N I = 1/2 NA = 0.37 %
76
66
LiLi––1515
N CouplingN Coupling
6Li NMR:
•two triplets 1:1 δ = 2.15 ppm
(JLiN= 3.7 Hz) a δ = 2.32 ppm
(JLiN= 6.1 Hz)
•triplet δ = 1.63 ppm (JLiN= 4.5 Hz)
77
66
LiLi––1515
N CouplingN Coupling6Li NMR:
•two triplets 1:1 δ = 2.15 ppm
(JLiN= 3.7 Hz) a δ = 2.32 ppm
(JLiN= 6.1 Hz)
•triplet δ = 1.63 ppm (JLiN= 4.5 Hz)