Advanced Inorganic Chemistry. Alireza Gorji Department of Chemistry, Yazd University. Introduction.

Transcription

1 Advanced Inorganic Chemistry Alireza Gorji Department of Chemistry, Yazd University Introduction 2 1

2 Kinetics vs. Thermodynamics Thermodynamics Kinetics G = H -T S G = H -T S G = -RTlnK G= -RTlnk Large K yield=100% Large k fast reaction G G G G Reaction Coordinate Reaction Coordinate 3 Thermodynamics Kinetics G A A is unstable ناپايدار G<0 B G A G is small A is labile واکنش پذير B G A G>0 A is stable پايدار B G A G is large A is inert بی اثر B Reaction Coordinate Reaction Coordinate 4 2

3 inert G A labile Reaction Coordinate ناپايدار A is unstable 5 Thermodynamics G / H / S / K پايدار Stable ناپايدار Unstable غيرخودبخودی nonspontaneous خودبخودیSpontaneous Kinetics G / H / S / k بی اثر Inert واکنش پذير Labile آهسته Slow سريع Fast Acid Base Electrophile Nucleophile 6 3

4 Reaction Mechanisms Stoichiometry Mechanism Intimate Mechanism 7 G rds Intimate Mechanism Stoichiometry Mechanism Reaction Coordinate 8 4

5 Substitution Reaction ML n X + Y ML n Y + X 9 Stoichiometry Mechanisms 10 5

6 Stoichiometry Mechanisms in Substitution Reaction ML 5 X + Y ML 5 Y + X Dissociative Associative X=Leaving group Y=Entering group Interchange D A I 11 Dissociative Mechanism in Substitution Reaction D rate = k 1 [ML 5 X] k ML 5 X 1 ML 5 + X slow k 2 ML 5 + Y ML 5 Y fast 12 6

7 Associative Mechanism in Substitution Reaction A rate = k 1 [ML 5 X][Y] k ML 5 X + Y 1 ML 5 XY slow k 2 ML 5 XY ML 5 Y + X fast 13 Interchange Mechanism in Substitution Reaction I Fast equilibrium K 1 = k 1 /k -1 k 2 << k -1 For [Y] >> [ML 5 X] 14 7

8 Intimate Mechanisms in Substitution Reaction dissociative activation (d) associative activation (a) 15 Intimate Mechanisms in Substitution Reaction d a D d D a a d A a A d 16 8

9 d a I d I a 17 Mechanisms in Substitution Reactions a d A A a A d D D a D d I I a I d 18 9

10 Determination of Stoichiometry Mechanisms A & D 1. Detection of intermediate by fast spectroscopy and ultrafast spectroscopy. 2. Synthesis and isolation of intermediate. 3. Stereochemistry of reaction. 19 Determination of Intimate Mechanisms Experimental evidence a d Sensitivity to entering group Sensitivity to leaving group trans effect cis effect Increasing of steric hindrance on cis ligands - + Increasing of positive charge on complex + - S > 0 V >

11 21 1- Substitution Reaction in Square Planar Complexes ML 3 X + Y M = Pt ML 3 Y + X 22 11

12 Substitution of square planar Pt 2+ complexes

13 solvent pathway nucleophile pathway rate = k 1 [S][PtA 3 X] + k 2 [Y][PtA 3 X] rate = k 1 [PtA 3 X] + k 2 [Y][PtA 3 X] rate = (k 1 + k 2 [Y])[PtA 3 X] If [Y] >> [PtA 3 X] rate = k obs [PtA 3 X] k obs = (k 1 + k 2 [Y]) 25 rate law for square planar Pt 2+ complexes rate = k 1 [S][PtA 3 X] + k 2 [Y][PtA 3 X] rate = k 1 [PtA 3 X] + k 2 [Y][PtA 3 X] rate = (k 1 + k 2 [Y])[PtA 3 X] If [Y] >> [PtA 3 X] rate = k obs [PtA 3 X] k obs = (k 1 + k 2 [Y]) k 1 = solvent pathway k 2 = nucleophile pathway k obs k 1 slope = k 2 k 2 nucleophile a [Y] 26 13

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15 [PtA 2 Cl 2 ] + Y [PtA 2 ClY] + Cl 29 Y Donor atom n pt Cl - Cl 3.04 C 6 H 5 SH S 4.15 CN - C 7.00 (C 6 H 5 ) 3 P P 8.79 CH 3 OH O 0 I - I 5.42 NH 3 N

16 The trans effect

17 Mechanism of the trans labilization -donor -acceptor G Reaction Coordinate

18 trans labilization 35 Selective synthesis using the trans effect 36 18

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20 39 Steric effect 40 20

21 Activation parameters V / S 41 Stereochemistry 42 21

22 A a or I a

23 2- Substitution Reaction in Octahedral Complexes ML 5 X + Y ML 5 Y + X 45 Characteristic lifetimes for exchange of water molecules in aqua complexes 46 23

24 Lability & Inertness Labile complexes Fast substitution reactions (< few min) Inert complexes Slow substitution reactions (>h) a kinetic concept Labile: s-block elements: Large e.g. Na +, K +, Ba 2+ etc d-block elements: 1 st row, distorted geometries, d 10 f-block Inert: s-block elements (only a few are relatively inert ); Small e.g. Be 2+, Mg 2+ d-block elements: d 3 and d 6 in O h high-field, e.g. Cr III, Co III. Second and third row. 47 Inert! 48 24

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26 The Eigen-Wilkins mechanism K ML 5 X + Y E ML 5 X Y fast k ML 5 X Y ML 5 Y +X slow rate = k[ml 5 X Y] [ML 5 X Y]= K E [ML 5 X][Y] rate = k K E [ML 5 X][Y] if [Y]>>[ML 5 X] [Y] 0 [Y] [ML 5 X] 0 = [ML 5 X]+ [ML 5 X Y]= [ML 5 X](1+ K E [Y]) rate = k K E [ML 5 X] 0 [Y]/ (1+ K E [Y]) rate = k K E [ML 5 X] 0 [Y] 0 / (1+ K E [Y] 0 ) 51 k I d rate = k K E [ML 5 X] 0 [Y] 0 / (1+ K E [Y] 0 ) 52 26

27 The Fuoss-Eigen equation 53 Leaving group effects 54 27

28 Entering group effects Rate is independent of the nature of L Entering group effects Rate is dependent on the nature of L 56 28

29 57 Steric effects 58 29

30 Cone Angle

31 The effect of overall charge [CoL 5 Cl] 2+ + H 2 O [CoL 5 OH 2 ] 3+ + Cl - k 1 [CoL L 4 Cl] + + H 2 O [CoL L 4 OH 2 ] 2+ + Cl - k 2 L = amine k 1 / k 2 =1/ Activation Energetics 62 31

32 Octahedral Substitution and ΔV 63 Octahedral Substitution General Rules 64 32

33 Stereochemistry in Octahedral Substitution

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35 The cis effect

36 71 Base catalyzed hydrolysis of amines 72 36

37 Dissociative Conjugate Base (D CB ) Mechanism D CB

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39 77 39