ميكانيكية تفاعلات غير عضوية جزء ثانى

1. Rates of Water Exchange
• The rate constants of a given ion are approximately constant, no matter what the
nature of the entering group. (evidence for dissociative activation)
• The substitution rates divide the metal ions into 4-distinct groups
• Class 1.
– Exchange of water is very fast and is essentially diffusion controlled (k >= 108 sec-1) Ions
include Groups 1A , IIA (except Be2+, Mg2+), and IIB (except Zn2+), plus Cr2+, and Cu2+.
• Class 2
– Rate constants are in the range 104 - 108 sec-1. This includes most of the 1st
row T.M divalent ions (except V2+, Cr2+, Cu2+) and Mg2+ and the lanthanide
M3+ ions.
• Class 3.
– Rate constants are in the range 1 - 104 sec-1. This includes Be2+, Al3+, V2+,
and some 1st row T.M. tri-valent ions.
• Class 4.
– Rate constants are in the range 10-3-10-6 sec-1. This includes Cr3+, Co3+, Rh3+,
Ir3+, Pt2+
•
General Comments
‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬1

2. ‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬2

3. • For Class 1 .ionic size, and ionic charge are clearly the
important. As the ion becomes smaller the substitution
rate slows. Reflecting importance of orbital overlap
between metal ion and departing ligand. Group IIA, and
IIB show similar trend, (Be 2+ is anomalous due to
complex hydrolysis reactions.
• For T.M. metals the correlation of rate with size is not
obeyed, e.g. Cr 2+ Ni 2+ and Cu 2+ have identical radii.
• Cu 2+ (d (9 and Cr 2+ (d4( are structurally distorted by the
Jahn-Teller effect, with bond to the axial ligands longer
and weaker than bonds to the equatorial groups.
Therefore the ground state structures are not far
removed from the transition state structures.
• To explain the behavior of the other M 2+ ions we need to
look at the effects of d-electron configuration.
‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬3

4. •‫الفلزات‬ ‫أيونات‬ ‫تقسيم‬ ‫يمكننا‬ ‫االستبدال‬ ‫سرعة‬ ‫بحسب‬ ‫و‬
‫مجموعات‬ ‫أربع‬ ‫إلى‬:
•‫المجموعة‬I:‫للماء‬ ‫االستبدال‬ ‫سرعة‬)1-sec810(k >=
•‫األولى‬ ‫المجموعة‬ ‫عناصر‬ ‫وتشمل‬IA‫الثانية‬ ‫المجموعة‬ ‫وعناصر‬IIA
(‫ماعدا‬Be2+, Mg2+)‫مجموعة‬ ‫و‬(IIB( )‫باستثناء‬Zn2+)‫باإلضافة‬
‫إلى‬Cr2+‫و‬.Cu2
•‫للمجموعة‬ ‫بالنسبة‬IA
•‫أسفل‬ ‫إلى‬ ‫اتجهنا‬ ‫كلما‬ ‫يزداد‬ ‫المجموعة‬ ‫هذه‬ ‫لعناصر‬ ‫اإلحالل‬ ‫معدل‬
•‫االلكترونية‬ ‫الكثافة‬ ‫تقل‬ ‫المجموعة‬ ‫أسفل‬ ‫إلى‬ ‫انتقلنا‬ ‫كلما‬(‫الحجم‬ ‫زيادة‬ ‫بسبب‬)
‫يلي‬ ‫كما‬ ‫المعدل‬ ‫فيزيد‬ ‫األكسجين‬ ‫مع‬ ‫الرابطة‬ ‫كسر‬ ‫يسهل‬ ‫وعليه‬:
Li+ < Na+ < K+ < Cs+
‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬4

5. •‫المجموعة‬II:‫للماء‬ ‫االستبدال‬ ‫سرعة‬)1-sec810-410k (
•‫ثابت‬‫سرعة‬‫التفاعل‬‫يتراوح‬‫ما‬‫بين‬(104-108 sec-1)‫و‬‫تضم‬‫معظم‬‫أأليونات‬
‫الثنائية‬‫للصف‬‫األول‬‫من‬‫العناصر‬‫االنتقالية‬‫ما‬‫عدا‬(V2+ , Cr2+ Cu2+)
‫وتضم‬‫ا‬ً‫ض‬‫أي‬Mg2+‫و‬‫أيونات‬‫الالنثنيدات‬‫ذات‬‫حالة‬‫التأكسد‬‫الثالثية‬M3+.
•‫المجموعة‬III:‫سرعة‬‫االستبدال‬‫للماء‬)1-sec410-1(k
•‫ثابت‬‫سرعة‬‫التفاعل‬‫يتراوح‬‫ما‬‫بين‬(1-104 sec-1)‫وتضم‬‫كل‬‫من‬
Be2+ , Al3+ , V2+‫و‬‫ا‬ً‫ض‬‫بع‬‫من‬‫أيونات‬‫الصف‬‫األول‬‫من‬‫العناصر‬
‫االنتقالية‬‫ذات‬‫حالة‬‫التأكسد‬‫الثالثية‬.
•‫المجموعة‬VI:‫سرعة‬‫االستبدال‬‫للماء‬)1-sec6-10--310(k
•‫ثابت‬‫سرعة‬‫التفاعل‬‫يتراوح‬‫ما‬‫بين‬(10-3-10-6 sec-1)‫وتضم‬Cr3+ ,
Co3+ , Rh3+ ,Ir3+ , Pt2+.‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬5

6. ‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬6

7. ‫تأثير‬(Jahn-Teller)‫يظهر‬ً‫ا‬‫جلي‬‫على‬‫سبيل‬‫المثال‬‫في‬‫كل‬‫من‬Cu2+
(d9)‫و‬Cr2+ (d4)‫حيث‬‫أنهما‬‫مشوهان‬ً‫ا‬‫بنائي‬‫و‬‫ذلك‬‫يرجع‬‫إلى‬‫أن‬
‫الروابط‬‫في‬‫الوضع‬‫العاموي‬(Axial)‫أطول‬‫من‬‫تلك‬‫التي‬‫في‬‫وضع‬
(equatorial)‫مما‬‫يجعلها‬‫أضعف‬‫و‬‫فيسهل‬‫خروج‬‫الليجند‬‫مما‬‫يزيد‬‫من‬
‫معدل‬‫سرعة‬‫التفاعل‬‫و‬‫ذلك‬‫يعود‬‫إلى‬‫التوزيع‬‫الغير‬‫متساوي‬‫لإللكترونات‬
‫في‬eg
‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬7

8. ‫غير‬ ‫ميكانيكية‬ ‫العيان‬ ‫أسامة‬ ‫الدكتور‬ ‫محاضرات‬
‫عضوية‬8

10. Two parallel pathways
L M X
L
L
L
M
L
Y
X
L
L M Y
L
L
+ Y
-X
k2
L
M
L
L
k1
slow
+ Y
very fast
Associative
Dissociative
Rate = (k1 + k2[Y])[ML3X]

11. 18-electron count complexes – first order mechanism
The reactions of coordinatively saturated,
tetrahedral complexes (those with a formal 18
electron count) such as [Ni(CO)2(PR3)2], [Ni(CO)4]
or [Ni{P(OEt)3}4] all exhibit a very simple kinetics:
a first order dependence on the concentration of
the metal complex, and an independence of the
concentration and nature of the reacting
nucleophile.

12. Phosphine exchange of [CoBr2(PPh3)2] (15-electron
species) and halide exchange of [FeBr4]-(13-
electron species) both show second order kinetics:
first order in the concentration of the complex and
the nucleophile.
Second order mechanism
Question
18-electron species [Co(CO)3(NO)] and [Fe(CO)2(NO)2] would react by a
dissociate or associative pathway?

13. Answer

15. Nature 256, 636 - 638 (21 August 1975); doi:10.1038/256636a0
Mechanisms of reactions at square planar metal centres
F. R. HARTLEY* & J. J. PÉRIɆ
*Department of Chemistry, The University, Southampton SO9 5NH, UK
†U.E.R. de Chimie Organique, Université Paul Sabatier, 118 route de Narbonne, 31
Toulouse, France
SQUARE-PLANAR platinum(II) complexes have in the past been found to react by associative
mechanisms (see refs 1 and 2). This has been of some comfort to the proponents3 of the
'16 and 18 electron rules', which state that all stable transition metal complexes and
intermediates in the reactions of such complexes should have either 16 or 18 electrons in
the transition metal's valence shell. We point out here that though substitution reactions at
platinum(II) occur by an associative route, reactions between ligands coordinated to
platinum(II)—here called combination reactions—occur by a dissociative route that violates
the '16 and 18 electron rules'.

16. Rate law and Mechanism
‫أكثر‬ ‫من‬ ‫المسطح‬ ‫المربع‬ ‫الشكل‬ ‫ذات‬ ‫للمتراكبات‬ ‫االستبدال‬ ‫تفاعالت‬ ‫تعتبر‬
‫متراكبات‬ ‫فى‬ ‫وخصوصا‬ ‫دراستها‬ ‫تمت‬ ‫التى‬ ‫الميكانيكيات‬Pt(II).
‫اآلتية‬ ‫األيونات‬ ‫الى‬ ‫باإلضافة‬ ‫هذا‬:
Ni(II) (mainly d8) Rh(I) Pd(II) Ir(I) Pt(II) Au(III)

17. L M X
L
L
L
M
L
Y
X
L L M Y
L
L
+ Y
-X
k2
L
M
L
L
k1
- X
X
S
+ S
L M S
L
L
L
M
L
L
Y
S
-S
+ Y
very fast
Parallel pathways
Rate = (k1(solvent) + k2[Y])[ML3X]

20. ‫في‬ ‫االستبدال‬ ‫سرعة‬ ‫على‬ ‫تؤثر‬ ‫التي‬ ‫العوامل‬Sq-Pl
Factors Which Affect The Rate Of Substitution
1. Role of the Entering Group
2. The Role of The Leaving Group
3. The Nature of the Other Ligands in the Complex
4. Effect of the Metal Centre
‫في‬ ‫االستبدال‬ ‫سرعة‬ ‫على‬ ‫تؤثر‬ ‫التي‬ ‫العوامل‬Pl-Sq
1-‫المستبدلة‬ ‫المجموعة‬
2-‫المغادرة‬ ‫المجموعة‬
3-‫المتراكب‬ ‫في‬ ‫األخرى‬ ‫المرتبطات‬ ‫طبيعة‬
4-‫دور‬‫الفلز‬

21. ‫المستبدلة‬ ‫المادة‬ ‫طبيعة‬(entering group)
‫معدل‬‫اإلحالل‬‫مع‬ ‫يتناسب‬‫المستبدلة‬ ‫المادة‬ ‫قوة‬‫كنيوكلوفيل‬
rate is proportional to the nucleophilicity of entering group
‫المتكون‬ ‫المعقد‬ ‫استقرار‬ ‫مدي‬ ‫علي‬ ‫تعتمد‬(thermodynamic stability)
‫وي‬‫خالل‬ ‫من‬ ‫حدث‬‫لمعقدات‬ ‫تجميعية‬ ‫ميكانيكية‬Pt(II)‫أعاله‬ ‫هو‬ ‫كما‬
Y = H2O, NH3, Cl, Py, CN, PPh3, ….

22. Good nucleophiles are good entering groups
nPt scale is the relative index of nucleophilicity obtained
from the reaction of the standard complex trans-
[Pt(py)2Cl2] in methanol,

23. The graph on the left is drawn for the
reactions of
trans-[Pt(pyridine)2Cl2] with a number of
different nucleophiles in methanol

24. ‫المغادرة‬ ‫المادة‬ ‫طبيعة‬(Leaving group)
[Pt(dien)X]+ + py → [Pt(dien)(py)]2+ + X -
‫عند‬ ‫المائي‬ ‫الوسط‬ ‫في‬ ‫التفاعل‬ ‫هذا‬25، ‫مئوية‬ ‫درجة‬
‫التفاعل‬ ‫سرعة‬ ‫معدل‬ ‫في‬ ‫التالي‬ ‫الترتيب‬ ‫أظهر‬:
X = H2O > Cl-> Br-> I- > N3
- > SCN- > NO2
- > CN-
‫مع‬ ‫تماما‬ ‫يتفق‬ ‫الترتيب‬ ‫هذا‬‫الرابطة‬ ‫قوة‬M―X

25. 1-‫ترانس‬ ‫تأثير‬Trans Effect
2-‫ترانس‬ ‫سطوة‬Trans Influence
3-‫سيس‬ ‫تأثير‬Cis Effect
‫المتراكب‬ ‫فى‬ ‫األخرى‬ ‫المرتبطات‬ ‫طبيعة‬

28. ‫مجموعات‬(‫باي‬)‫المستقبلة‬‫القوية‬‫تقوم‬‫بعملية‬‫زيادة‬‫استقرار‬‫الحالة‬
‫االنتقالية‬‫عن‬‫طريق‬‫اعادة‬‫استقبال‬‫الكثافة‬‫االلكترونية‬‫مما‬‫يؤدي‬‫إلى‬‫تسهيل‬
‫عملية‬‫اإلحالل‬‫للمجموعة‬‫المقابلة‬‫لها‬

29. ‫هذه‬‫المرتبطات‬‫تدفع‬‫بقدر‬‫من‬‫السحابة‬‫االلكترونية‬‫علي‬‫أيون‬‫الفلز‬‫مما‬‫يقلل‬‫من‬
‫ثبات‬‫الحالة‬‫األرضية‬(ground state destabilization)
‫مما‬‫يساعد‬‫علي‬‫إضعاف‬‫ارتباط‬‫المرتبطة‬‫المقابلة‬‫ويسهل‬‫استبدالها‬
σ- donor ligands

38. ‫حركية‬ ‫ظاهرة‬ ‫الترانس‬ ‫تأثير‬ ‫يعتبر‬(‫التفاعل‬ ‫سرعة‬ ‫معدل‬ ‫علي‬ ‫تؤثر‬)

39. ‫تحضير‬ ‫يمكن‬ ‫كيف‬ ‫بين‬cis-, trans-[PtCl2(py)I]-‫من‬
[PtCl4]2-, py , I-
‫تأثير‬ ‫بأن‬ ً‫ا‬‫علم‬‫الترانس‬‫يلي‬ ‫كما‬:I- > Cl- > py

41. ‫ترانس‬ ‫سطوة‬(Trans influence)
The trans influence is purely a thermodynamic phenomenon. That is,
ligands can influence the ground state properties of groups to which they
are trans. Such properties include;
(i) Metal-Ligand bond lengths
(ii) Vibration frequency or force constants
(iii) NMR coupling constants
Trans influence is a change in the bond distance between the
metal and a ligand that is trans to the ligand exerting the
effect through the same d-orbital interaction.

42. The trans influence series based on structural data, has been given as;
R- ~ H- >= PR3 > CO ~ C=C ~ Cl- ~ NH3
‫ترانس‬ ‫سطوة‬(Trans influence)

43. ‫ترانس‬ ‫سطوة‬(Trans influence)
‫األرضية‬ ‫بالحالة‬ ‫يرتبط‬ ‫ثيرموديناميكي‬ ‫عامل‬(‫األساسية‬)‫للجزيء‬
(‫للمركب‬ ‫الحراري‬ ‫المحتوي‬)
‫قوة‬Pt-Cl‫الترتيب‬ ‫حسب‬ ‫تزداد‬:Et3P < H2C=CH2 < Cl

44. ‫ترانس‬ ‫سطوة‬(Trans influence)