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نظرية المجال البلوري. Crystal Field Theory. - PowerPoint PPT Presentation
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الفلرية المعقدات ان على النظرية هذه تفترضايوني ) ( تآصر يعني الكتروستاتيكي تداخل هن عبارة ( موجبة نقطية كشحنة تعتبر المركزية الذرة بين
اوربيتاالت على ( dتحتوي الليكاندات و الخمسة ( نحو تنجذب سالبة نقطية كشحنة بها المحيطة
, هذه فسرت وقد التآصر يحدث و الموجبة الشحناتالطيفي و المغناطيسي السلوك و االلوان النظرية
للمعقدات.
األيون الفلزي وتأثير الليكاندات اقتراب
والتوزيع الفراغي لها على طول Linear combination of اوربيتاالتd المحاور
dz2-dx
2 and dz2-dy
2
d2z2-x
2-y2
Splitting of the d sub-shell in octahedral coordination
dyz dz2 dx2-y2
t2g ألن فصوصهاتتجه مابين االحداثيات
الذين dz2,dx2-y2 أوربيتالييتجهان مباشرة نحو الشحنات السالبة
z z z
اوربيتاالت الليكاند الواهبة eg اوربيتاالت
t2gاوربيتاالت
y y y
x x x
Orbital occupancy for high- and low-spin complexes of d4 through d7 metal ions.
high spin: weak-field
ligand
low spin: strong-
field ligand
high spin: weak-field
ligand
low spin: strong-
field ligand
High and low-spin complexes of d5 ions:
energy
eg eg
t2gt2g
low-spin d5 )[Fe)CN(6]3-(t2gاوربيتاالت تمال أوال بسبب قوة الليكاند
high-spin d5 )[Fe)H2O(6]3+(
تتوزع االلكترونات حسب قاعدة هوند
تكون في اغلب المعقدات طاقة االزدواج عالية لهذا تكون معقدات عالية البرم أما مع الليكاندات القوية
فتنتج طاقة كافية الزدواج االلكترونات وتكوين ايونات d5 معقدات بارامغناطيسية
Δ > P Δ < P
Paramagnetic5 unpaired e’s
paramagneticone unpaired e
[Fe(CN)6]3- Δ = 35,000 cm-1
P = 19,000 cm-1
[Fe(H2O)6]3+ Δ = 13,700 cm-1
P = 22,000 cm-1
energy
eg
t2gCo3+ ion
in gas-phase(d6)
Δ
Co(III) in octahedral
complex
3d sub-shell
d-shellsplit bypresenceof liganddonor-atoms
Splitting of the d sub-shell in an octahedral complex
High and low-spin complexes:
energyeg
eg
t2g t2g
low-spin d6
t2g اوربيتاالت تمال أوال بسبب قوة الليكاند
high-spin d6
تتوزع االلكترونات حسب قاعدة هوند
Δ > P Δ < P
Paramagnetic4 unpaired e’s
diamagneticno unpaired e’s
High and low-spin complexes of some d6 ions:
energy
eg eg
t2gt2g
low-spin d6 )[Co)CN(6]4-( high-spin d5 )[CoF6]3-(
Δ >> P Δ < P
Paramagnetic4 unpaired e’s
diamagneticno unpaired e’s
[Co(CN)6]3- Δ = 34,800 cm-1
P = 19,000 cm-1
[CoF6]3- Δ = 13,100 cm-1
P = 22,000 cm-1
High and low-spin complexes of d7 ions:
energy
eg eg
t2gt2g
low-spin d7 )[Ni)bipy(3]3+(تملئ االوربيتاالت الواطئة
الطاقة ومن ثم االوربيتاالت .العالية الطاقة
high-spin d7 )[Co)H2O(6]3+(تملئ االوربيتاالت
بااللكترونات حسب قاعدة هوند
نفس العدد من االلكترونات و االختالف بحالة التأكسد
Δ > P Δ < P
Paramagnetic3 unpaired e’s
paramagneticone unpaired e
[Ni(bipy)3]3+ [Co(H2O)6]2+ Δ = 9,300 cm-1
Crystal-Field TheoryCrystal-Field Theory
Weak-field ligands (small تمتلك)
االلكترونات تميلإلى االنتقال الىالعالية االوربيتاالتعلى الطاقة
االلكترونات ازدواج .
Strong-field ligands (large تمتلك) في لاللكترونات التدريجي الملئ الى تميل
الطاقة الواطئة االوربيتاالت
dd44, d, d55, d, d66, and d, and d7 7 المعقدات العالية المعقدات العالية في الترتيب االلكترونيفي الترتيب االلكتروني البرم و الواطئة البرم ممكنةالبرم و الواطئة البرم ممكنة
Crystal Field Splitting Energy (CFSE)
• In Octahedral field, configuration is: t2gn eg
n
O = 10 Dq• In weak field: O P, => t2g
3eg1
• In strong field O P, => t2g4
• P - paring energy
CFSE = -0.4 Δo nt2g + 0.6 Δo neg
البلوري المجال استقرار وطاقة لتركيب ملخص التالي الجدول ويبينCFSE) )من للتراكيب المزدوجة االلكترونات حالتي d1→d10وعدد في
القوي : المجال و الضعيف المجال
Example: explain [Fe(CN)6]3- or [Fe(H2O)6]+3 more stable?
energy
eg eg
t2gt2g
CFSE=)3X-0.4Δ₀)+(2X0.6Δ₀) =-1.2Δ₀ + 1.2Δ₀ = 0
Δ > P Δ < P
[Fe)CN(6]3- Δ = 35,000 cm-1
P = 22,000 cm-1
[Fe)H2O(6]3+ Δ = 13,700 cm-1
P = 22,000 cm-1
CFSE=)5X-0.4Δ₀)+(0X0.6Δ₀) +2P =-2.0Δ₀ + 2P
The CFSE for high-spin d5 and for d10 complexes is calculated to be zero:
[ Mn(NH3)6]2+: ] ( )Z n en3[3+
egeg
t2gt2g
Δ = 22,900 cm-1 Δ = not known
CFSE = 10,000(0.4 x 3 – 0.6 x 2) CFSE = Δ(0.4 x 6 – 0.6 x 4)
= 0 cm-1 = 0 cm-1
Crystal Field Stabilization Energy )CFSE( of d5 and d10 ions:
energy
Effect of ligands on the colors of coordination compounds
Slide of 53
• هذه المعقدات لها نفس العدد التناسقي وااليون الفلزي وااليون المرافق
مستويات الطاقة النفصام اوربيتاالت للمعقدات الرباعية
السطوح و المربع المستوي
tetrahedralsquare planar
تمثيل انفصام اوربيتاالت لمعقدات المربع المستوي
dx2-y2
dxy
dz2
dxz dyz
dx2-y2
dxy
dz2
dxz dyz
dxz dyzdxy
dx2-y2 dz2
t2g
eg
square planerZ outoctahedral
d8تكون معقدات مربعة مستوية ايونات
L
M
L
L L
LLM
L L
LL
z
x
y
تجريبيا� وجد إن المربع المستوي هو ناتج من إزالة ليكاندين من
المعقدات الثمانية السطوح
dx2-y2
dz2
dxy
dxz,dyz
dx2-y2
dz2
dxydxz,dyz
Octahedral Square Planar
dn High spin (HS) Low spin (LS) Tetrahedral
d Octahedral
Complexes
Octahedral
complexes
Complexes
d1 0.4- o.4- 0.6-
d2 0.8- 0.8- 1.2-
d3 1.2- 1.2- 0.8-
d4 -o.6 -1.6 o.4-
d5 0 2.0- 0
d6 0.4- 2.4- 0.6-
d7 0.8- 1.8- 1.2-
d8 -1.2 1.2- 0.8-
d9 0.6- 0.6- 0.4-
d10 0 0 0
الرباعية المعقدات في ويالحظاستقرارية اعلي إن السطوح
هي الليـــــكاندي المجال يضفيهانظـــــــــــــــــامي d2,d7(highفي
spin) نظام يتخذ السبب d2 ولهذالرباعي d7 أو المنتظم الشكل
.السطوحااليونين أن تجريبيا� d8 و d3 لوحظ
)Cr3+, Ni2+ كبير حد إلى يفضالنالسطوح الثماني , التناظر
Octahedral
dxz,dyzdxy
dz2
dx2-y2
dxz,dyzdxy
dz2
dx2-y2
TetrahedralSquare Planar
dxz,dyz
dxy
dz2
dx2-y2
OH2
Ni
H2O
OH2
OH2
H2O
H2O
2
Octahedral Coordination number =6
Ni
Cl
ClCl
Cl2-
Tetrahedral (CN=4)
Ni(II) d8 S =1
Ni
C
C
C
C
N
N
N
N
2-
Square Planar (CN=4)
Ni(II) d8 S = 0Ni(II) d8 S = 1
The spectrochemical series:
One notices that with different metal ions the order of increasing Δ with different ligands is always the
same. Thus, all metal ions produce the highest value of Δ in their hexacyano complex, while the hexafluoro
complex always produces a low value of Δ. One has seen how in this course the theme is always a search
for patterns. Thus, the increase in Δ with changing ligand can be placed in an order known as the
spectrochemical series, which in abbreviated form is:
I- < Br- < Cl- < F- < OH- ≈ H2O < NH3 < CN-
The place of a ligand in the spectrochemical series is determined largely by its donor atoms. Thus, all N-donor
ligands are close to ammonia in the spectrochemical series, while all O-donor ligands are close to water. The
spectrochemical series follows the positions of the donor atoms in the periodic table as:
CNOF
PSCl
Br
I
The spectrochemical series:
S-donors ≈between Brand Cl
very littledata onP-donors –may be higherthan N-donors
?
spectrochemicalseries followsarrows aroundstarting at I andending at C
Thus, we can predict that O-donor ligands such as oxalate or acetylacetonate will be close to water in the spectrochemical series. It should be noted that while en and dien are close to
ammonia in the spectrochemical series, 2,2’bipyridyl and 1,10-phenanthroline are considerably higher than ammonia because their sp2 hybridized N-donors are more covalent in
their bonding than the sp3 hybridized donors of ammonia.
O
O-
O
-O O O-
H3C CH3
H2N NH2
H2N NH
NH2N N N N
oxalate acetylacetonate en
dien bipyridyl 1,10-phen
The spectrochemical series:
For the first row of donor atoms in the periodic table, namely C, N, O, and F, it is clear that what we are seeing in the variation of Δ is covalence. Thus, C-
donor ligands such as CN- and CO produce the highest values of Δ because the overlap between the
orbitals of the C-atom and those of the metal are largest. For the highly electronegative F- ion the
bonding is very ionic, and overlap is much smaller. For the heavier donor atoms, one might expect from their low electronegativity, more covalent bonding,
and hence larger values of Δ. It appears that Δ is reduced in size because of π–overlap from the lone
pairs on the donor atom, and the t2g set orbitals, which raises the energy of the t2g set, and so lowers
Δ.
The bonding interpretation of the spectrochemical series:
When splitting of the d sub-shell occurs, the occupation of the lower energy t2g level by electrons
causes a stabilization of the complex, whereas occupation of the eg level causes a rise in energy. Calculations show that the t2g level drops by 0.4Δ, whereas the eg level is raised by 0.6Δ. This means
that the overall change in energy, the CFSE, will be given by:
CFSE =Δ(0.4n(t2g) -0.6n(eg))
where n(t2g) and n(eg) are the numbers of electrons in
the t2g and eg levels respectively.
Crystal Field Stabilization Energy )CFSE(:
The CFSE for some complexes is calculated to be:
[Co(NH3)6]3+: ] ( )C r en3[3+
egeg
t2gt2g
Δ = 22,900 cm-1 Δ = 21,900 cm-1
CFSE = 22,900(0.4 x 6 – 0.6 x 0) CFSE = 21,900(0.4 x 3 – 0.6 x 0)
= 54,960 cm-1 = 26,280 cm-1
Calculation of Crystal Field Stabilization Energy )CFSE(:
energy
For M(II) ions with the same set of ligands, the variation of Δ is not large. One can therefore use the equation for CFSE to calculate CFSE in terms
of Δ for d0 through d10 M(II) ions (all metal ions high-spin):
Ca(II) Sc(II) Ti(II) V(II) Cr(II) Mn(II) Fe(II) Co(II) Ni(II) Cu(II) Zn(II)
d0 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10
CFSE: 0 0.4Δ 0.8Δ 1.2Δ 0.6Δ 0 0.4Δ 0.8Δ 1.2Δ 0.6Δ 0
This pattern of variation CFSE leads to greater stabilization in the complexes of metal ions with high CFSE, such as Ni(II), and lower
stabilization for the complexes of M(II) ions with no CFSE, e.g. Ca(II), Mn(II), and Zn(II). The
variation in CFSE can be compared with the log K1 values for EDTA
complexes on the next slide:
Crystal Field Stabilization Energy )CFSE( of d0 to d10 M)II( ions:
CFSE as a function of no of d-electrons
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1 2 3 4 5 6 7 8 9 10 11
no of d-electrons
CF
SE
in m
ult
iple
s o
f Δ
.
Crystal Field Stabilization Energy )CFSE( of d0 to d10 M)II( ions:
Ca2+ Mn2+ Zn2+
double-humpedcurve
Ni2+
log K1)EDTA( as a function of no of d-electrons
10
12
14
16
18
20
0 1 2 3 4 5 6 7 8 9 10 11
no of d-electrons
log
K1)E
DT
A( .
Log K1)EDTA( of d0 to d10 M)II( ions:
Ca2+
Mn2+
Zn2+
double-humpedcurve
= CFSE
rising baselinedue to ioniccontraction
log K1)en( as a function of no of d-electrons
0
2
4
6
8
10
12
0 1 2 3 4 5 6 7 8 9 10 11
no of d-electrons
log
K1)e
n( .
Log K1)en( of d0 to d10 M)II( ions:
double-humpedcurve
Ca2+Mn2+
Zn2+
rising baselinedue to ioniccontraction
= CFSE
log K1)tpen( as a function of no of d-electrons
0
5
10
15
20
0 1 2 3 4 5 6 7 8 9 10 11
no of d-electrons
log
K1)
tpen
(.
N N NN
N N
Log K1)tpen( of d0 to d10 M)II( ions:
Ca2+
Mn2+
Zn2+
double-humpedcurve
tpen
Irving and Williams noted that because of CFSE, the log K1 values for virtually all complexes of first row d-block metal ions followed the order:
Mn(II) < Fe(II) < Co(II) < Ni(II) < Cu(II) > Zn(II)
We see that this order holds for the ligand EDTA, en, and TPEN on the previous slides. One notes
that Cu(II) does not follow the order predicted by CFSE, which would have Ni(II) > Cu(II). This will
be discussed under Jahn-Teller distortion of Cu(II) complexes, which leads to additional stabilization for Cu(II) complexes over what
would be expected from the variation in CFSE.
The Irving-Williams Stability Order: