Elementary Organometallic Reactions
|
|
- Kelley Douglas
- 6 years ago
- Views:
Transcription
1 Elementary eactions CE 966 (Tunge) Elementary rganometallic eactions All mechanisms are simply a combination of elementary reactions. 1) Coordination -- issociation 2) xidative Addition -- eductive Elimination 3) σ-bond metathesis 4) Atom abstraction 5) Addition -- Elimination 6) Alkyl-Acyl ntercoversion (C migratory insertion) igand Substitution eactions ' ' issociative (like S 1) elative rates of substitution at 25 o Cin 2 2 t 2 2 u rel rate pyr pyr 57 pyr 0.5 Trans effect : (kinetic) strong σ-donors or π-acceptors accelerate substitution of substituents that are trans to themselves. elative rates of substitution of chloride Et 3 t Et 3 rel rate 1 40 C Et ,500 (C) 6 Cr coordinatively saturated 130 o C (C)5 Cr slow 3 fast open coordination site (C) 5 Cr 3 General order:,, alkene, C >> 3 > > > pyr > 3 > - Example: elmchen G.; T Associative chanisms Very common for square planar complexes! Associative u u intermediate nterchange (like S 2) u u tr ansition state u u ac(c 2 ) 2 Ac i r 2 [r(c)] 2 TF 2 r u 95% (91% ee) 5% ucleophilic attack occurs trans to phosphorus Trans influence: (thermodynamic) strong σ-donors weaken the bonds to atoms that are trans to themselves. General order:, > 3 > () 3, 2 > pyr >C, olefin,
2 Elementary eactions CE 966 (Tunge) Example: ippard, S. J. JACS S -C 2 =2.08Å -C 2 =2.21Å 2 C C 2 C 3 nverse electron demand associative substitution Stahl, S. S. JACS ; Stahl, S. S.; andis, C.. JACS egenerate exchange Eyring equation: -ΔG k = k bt h e T To determine activation parameters ondegenerate exchange = -Δ ΔS k b T h e T e ln k T = -Δ T ln k b h ΔS slope intercept 2 2 k f k r onitor the rate of approach to equilibrium. 2 2 F 3 C F 3 C CF 3 CF 3 ρ = 2.2 (exchange is faster with electron deficient alkenes) 1 line-broadening measures rates from s -1 Exchange rate gives: Δ = 7.3 kcal/mol ΔS = -24 eu. so k(25 o C) = s -1 exchange rate = k = π(w obs -W nat ) W = peak width at ½ height. Coalescence of peaks occurs when k = π(δν)/1.414 where Δν is the peak separation in z. "ormal" associative substitution U U "nverse elctron demand" U U
3 Elementary eactions CE 966 (Tunge) ntramolecular ligand/substrate activation is common 2 2 ote: Substitutions are also possible via a radical chain mechanism, but these processes are not as prevalent in catalysis. xidative addition Concerted n Stepw ise n n F 3 C n n n Cooperative ( radical) 2 n n n 2 - U 3 3 r xidative addition to radicals Example: Wayland, B. B. JACS s s h s s 2(T)h C 4 h() (T)h r 2 (T)h C 3 (T)h h() h(t) xidative addition can be accelerated by ligand dissociation Example: artwig, J. F. JACS 1995, (o-tol) 3 (o-tol) 3 - k (o-tol) 3 (o-tol) 3 rate is inverse firstorder in (o-tol) 3! Concerted (cis) Stepwise (trans) (o-tol) 3-3 r C 3 Vaska's complex 3 C r 2 3 r cis-addition C 3 C r r 3 C 3 C 3 trans-addition cis-addition kinetic thermodynamic or ligand association ate complexes: Amatore, C. Acc. Chem. es. 2000, k app (20 o C) -1 s
4 Elementary eactions CE 966 (Tunge) lefin coordination: ovis, T. JACS i i i i Et 2 Zn Et 2 Zn Et 4% ee Et 65% ee i r 2 ca. 4 times faster eductive Elimination: the microscopic reverse of oxidative addition. igand association can induce reductive elimination 3 3 eductive elimination can be stimulated by oxidation. 3 3 via C 3 C C C 3 C 3 C C 3 C 3 rate = k[][c 3 ] C 3 3 Z Z 2 fastest reverse reaction is difficult (C- activation) slowest reverse is unusual igand dissociation can induce reductive elimination Stille, J. K. JACS C C 3 C 3 rel rate C 3 1 C 3 3 C C 3 C C 3 solv C 3 reductive elimination requires dissociation σ-bond tathesis : Very common for early transition metals Bercaw, J. E. JACS Sc 2-80 o C hexane Sc Sc t is often difficult to tell whether late transition metals undergo σ- bond metathesis or oxidative addition/reductive elimination, but generally the latter is favored.
5 Elementary eactions CE 966 (Tunge) igratory nsertion Alkyl-acyl interconversion (a 1,1-insertion) oes methyl migrate or C insert? (Flood, T. C. JACS ) C C * n C C C () 3 Stereochemistry - retention C Fe C 3 C () 3 C C * C C * n n C () 3 C C C thy migration (observed) Fe Whitesides G.. JACS tbu retention C insertion (T observed) not: sonitriles and carbenes are isoelectronic with C. Fe tbu ydrometallation (a 1,2-insertion, very common) Almost always syn-addition Zr 3 h 3 Zr 3 h 3 pre-coordination 3 3 h β-ydride elimination (reverse of hydrometallation) ydrometallation is often reversible. C C like C and C Zr Zr Example: Whitby,. J. T t Bu C 2 5mol% dppf 10 mol% atbu (1.3 eq) Bu toluene, 109 o C 60% See: Gibson, T. T 1982, 157. Zr Zr n t Bu n α-ydride elimination (reverse of migratory insertion) much more rare than β-ydride elimination 3 C 3 C 3 C Ta 2 i C 3 3 C 3 C 3 C Ta C 3 C 3 3 C 3 C 3 C Ta C 3
6 Elementary eactions CE 966 (Tunge) Carbometallation Slower than hydrometallation but still very facile for early transition metals (and too) Casey, C.. JACS 2003, o C eterometalation Similar to carbometalation, but often thought to be more difficult. eactions that proceed by aminopalladation have been the subject of much recent investigation. See: Wolfe, J.. JACS eview: uniz, K. Chem. Soc. ev n n Carbometallation with late transition metals is normally slower Example: Amatore, C. Chem. Eur. J C 2 Ac F 25 o C k obs ~1.5x10-6 s -1 eductive coupling of ligands. C 2 C 2 The reductive coupling of alkenes and alkynes to form metallacycles is a common theme in catalysis. t is a specific subset of carbometallation reactions. Ti( 3 ) 2 probably better described as a carbometallation ntramolecular bicyclization: see ugent, W. A. JACS Ti Ti Ti Cycloaddition is a common way for aminometalation. ote: [22] is thermally allowed. Bergman,. G. JACS TF Zr ucleophilic attack on coordinated ligands. Zr Very common: ewis acids promote nucleophilic attack of most π- electrophiles. Attack on cationic π-complexes is very common. ibeskind,. rgmet C o C 2 Cu(C)i 2 TF -78 o C 89% o C C avies-green-ingos ules: 1) ucleophilic attack at even polyenes is preferred 2) ucleophilic attack at open polyenes is preferred 3) Even-open polyenes attacked at terminal C
7 Elementary eactions CE 966 (Tunge) 4) dd-open attacked at terminal C if is very electrophilic Attack on C: a useful synthesis of Fischer carbenes n C C C i n C C 3 BF 4 - n C C An alternative open transition state explains cases where inversion of configuration is observed (i.e. with S 2-activated alkyl halides) Sn ' Sn ' ' Electrophilic soft metals activate alkynes. ozaki,. eterocycles 1987, 297. Au Au Au 3 irect observation of transmetalation. artwig, J. F. JACS Et 3 TS h Et 3 TS B() 2 Et 3 TF, rt Et 3 Et 3 h B Et 3 Et 3 (4 equiv) C o C Et 3 Et 3 h Et 3 Transmetalation Catalysis Transmetallation is likely not a unique class of elementary reactions. Such processes most likely occur by standard ligand substitutions sequences or by σ-bond metathesis. onetheless, transmetalation is extremely important in catalysis and it requires some unique considerations. any transmetalations exploit the transfer of C to softer less electrophilic metals. Thus, a wide variety of organometallics can be prepared by treatment of metal halides with i or g. Examples: Transmetalation in Stille couplings Espinet,. JACS 1998, 8978; JACS recoordination of the transmetalating agent is important. Sn 3 associative substitution Sn 3 Sn 3 cyclic TS The cyclic transition state gives retention of configuration at C. Catalysis is a wholly kinetic phenomenon. Stability is often inversely proportional to activity. ther important concepts 1) recatalyst vs. Catalyst 2) esting State 3) ate-limiting step Calibrations ates always increase with temperature but What activation energy does a given temperature supply? (Assume a reaction that is completed in 4 hours t 1/2 = 1 h; k = 1.9 x 10-4 s -1 ) What is the activation energy of that reaction? -78 o C -50 o C 0 o C 25 o C 100 o C 16.5 kcal/mol 18.6 kcal/mol 20.6 kcal/mol 22.5 kcal/mol 29.1 kcal/mol
8 Elementary eactions CE 966 (Tunge) What is the effect of temperature on a reaction with a free energy of activation of 25 kcal/mol? (Assuming the activation energy is T independent) T 0 o C 25 o C 35 o C 45 o C 55 o C 65 o C k obs 5.5 x 10-8 s x 10-6 s x 10-5 s x 10-5 s x 10-4 s x 10-4 s -1 rxn time 583 d 11 d 2.7 d 18 h 5.2 h 1.6 h ow does temperature affect competing reaction pathways? ΔS =15eu ΔS =-30eu T igher temps disfavor bimolecular reaction paths.
Chem 634. Introduction to Transition Metal Catalysis. Reading: Heg Ch 1 2 CS-B 7.1, , 11.3 Grossman Ch 6
Chem 634 Introduction to Transition etal Catalysis eading: eg Ch 1 2 CS-B 7.1, 8.2 8.3, 11.3 Grossman Ch 6 Announcements Problem Set 1 due Thurs, 9/24 at beginning of class ffice our: Wed, 10:30-12, 220
More informationOrganometallic Chemistry and Homogeneous Catalysis
rganometallic hemistry and omogeneous atalysis Dr. Alexey Zazybin Lecture N8 Kashiwa ampus, December 11, 2009 Types of reactions in the coordination sphere of T 3. Reductive elimination X-L n -Y L n +
More informationReaction chemistry of complexes Three general forms: 1. Reactions involving the gain and loss of ligands a. Ligand Dissoc. and Assoc. (Bala) b.
eaction chemistry of complexes Three general forms: 1. eactions involving the gain and loss of ligands a. Ligand Dissoc. and Assoc. (Bala) b. Oxidative Addition c. eductive Elimination d. Nucleophillic
More informationCHEM 251 (4 credits): Description
CHEM 251 (4 credits): Intermediate Reactions of Nucleophiles and Electrophiles (Reactivity 2) Description: An understanding of chemical reactivity, initiated in Reactivity 1, is further developed based
More informationThree Type Of Carbene Complexes
Three Type f arbene omplexes arbene complexes have formal metal-to-carbon double bonds. Several types are known. The reactivity of the carbene and how it contributes to the overall electron counting is
More informationO CH 3. Mn CH 3 OC C. 16eelimination
igratory Insertion igratory Insertion/Elimination 1 A migratory insertion reaction is when a cisoidal anionic and neutral ligand on a metal complex couple together to generate a new coordinated anionic
More informationSome Hartwig Chemistry Experimental Approaches and Detailed Mechanistic Analysis
Some artwig Chemistry Experimental Approaches and Detailed chanistic Analysis b. 1964 1986 A.B. Princeton U, Maitland Jones 1990.D. UC Berkeley, obert Bergman and ichard Anderson 1990-92 Post-doc, MIT,
More informationLecture 6: Transition-Metal Catalysed C-C Bond Formation
Lecture 6: Transition-Metal Catalysed C-C Bond Formation (a) Asymmetric allylic substitution 1 u - d u (b) Asymmetric eck reaction 2 3 Ar- d (0) Ar 2 3 (c) Asymmetric olefin metathesis alladium π-allyl
More informationVI. Metal alkyls from oxidative addition / insertion
V. Metal alkyls from oxidative addition / insertion A. Carbonylation - C insertion very facile, metal acyls easily cleaved, all substrates which undergo oxidative addition can in principle be carbonylated.
More informationChapter 2 The Elementary Steps in TM Catalysis
hapter 2 The Elementary Steps in TM atalysis + + ligand exchange A oxidative addition > n + A B n+2 reductive elimination < B n n+2 oxidative coupling + M' + M' transmetallation migratory insertion > (carbo-,
More informationCourse 201N 1 st Semester Inorganic Chemistry Instructor: Jitendra K. Bera
andout-9 ourse 201N 1 st Semester 2006-2007 Inorganic hemistry Instructor: Jitendra K. Bera ontents 3. rganometallic hemistry xidative Addition, Reductive Elimination, Migratory Insertion, Elimination
More informationOrganometallics Study Meeting Part 4. Reactions of Organometallic Complexes
rganometallics Study eeting art 4. eactions of rganometallic Complexes 1. asics 2011/4/28 oshino(d1).10 1-1. igand Exchange Dissosiative echanism ' n n-1 ' n-1 Fe(C) 5 (18e):hoto-promoteddissociationofigand
More informationσ Bonded ligands: Transition Metal Alkyls and Hydrides
σ Bonded ligands: Transition Metal Alkyls and Hydrides Simplest of organo-transitionmetal species Rare until and understanding of their stability in the 60 s and 70 s Metal alkyls can be considered as
More informationInsertion Reactions. 1) 1,1 insertion in which the metal and the X ligand end up bound to the same (1,1) atom
Insertion Reactions xidative addition and substitution allow us to assemble 1e and 2e ligands on the metal, respectively. With insertion, and its reverse reaction, elimination, we can now combine and transform
More informationRepeated insertion. Multiple insertion leads to dimerization, oligomerization or polymerization. κ 1: mainly dimerization κ
Repeated insertion ultiple insertion leads to dimerization, oligomerization or polymerization. k prop Et Key factor: k CT / k prop = κ κ 1: mainly dimerization κ 0.1-1.0: oligomerization (always mixtures)
More informationChiral Catalyst II. Palladium Catalysed Allylic Displacement ( -allyl complexes) 1. L n Pd(0) 2. Nuc
Chiral Catalyst II ast lecture we looked at asymmetric catalysis for oxidation and reduction Many other organic transformations, this has led to much investigation Today we will look at some others...
More informationRecapping where we are so far
Recapping where we are so far Valence bond constructions, valence, valence electron counting, formal charges, etc Equivalent neutral classification and MLX plots Basic concepts for mechanism and kinetics
More informationCarbenes and Carbene Complexes I Introduction
Carbenes and Carbene Complexes I Introduction A very interesting (honest) class of radical-like molecules Steadily becoming more important as they find far more synthetic applications We will primarily
More informationCH 3 TMG, DMF N H 3 CO 2 S. (PPh 3 ) 2 Pd 0
1. (a) rovide a reasonable mechanism for the following transformation. I S 2 C 3 C 3 ( 3 ) 2 2, CuI C 3 TMG, DMF 3 C 2 S TMG = Me 2 Me 2 ICu ( 3 ) 2 0 I S 2 C 3 S 2 C 3 Cu I 3 3 3 C 2 S I 3 3 3 C 2 S 3
More informationZr-Catalyzed Carbometallation
-Catalyzed Carbometallation C C C C ML n C C ML n ML n C C C C ML n ML n C C ML n Wipf Group esearch Topic Seminar Juan Arredondo November 13, 2004 Juan Arredondo @ Wipf Group 1 11/14/2004 Carbometallation
More informationStrained Molecules in Organic Synthesis
Strained Molecules in rganic Synthesis 0. Introduction ~ featuring on three-membered rings ~ Tatsuya itabaru (M) Lit. Seminar 08068 for cyclobutadienes : see Mr. Yamatsugu's Lit. Sem. 069 eat of Formation
More informationOxidative Addition/Reductive Elimination 1. Oxidative Addition
Oxidative Addition Oxidative Addition/Reductive Elimination 1 An oxidative addition reaction is one in which (usually) a neutral ligand adds to a metal center and in doing so oxidizes the metal, typically
More informationOrganometallic Study Meeting#11 Chapter 5. Ligand Substitution Reactions
rganometallic Study eeting#11 Chapter 5. igand Substitution Reactions 5.1 Introdution 011/6/18 K.isaki igand Substitution = A reaction in which a free ligand replaces a coordinated ligand Dissociative
More informationOrganometallic Rections 1: Reactions at the Metal
E Organometallic Rections 1: Reactions at the Metal Three major classes of reactions: 1 Ligand Substitution associative (cf. S N 2) dissociative (cf. S N 1) interchange (not dealt with in this course)
More informationOxidative Addition and Reductive Elimination
xidative Addition and Reductive Elimination red elim coord 2 ox add ins Peter.. Budzelaar xidative Addition Basic reaction: n + X Y n X Y The new -X and -Y bonds are formed using: the electron pair of
More informationAn Overview of Organic Reactions. Reaction types: Classification by outcome Most reactions produce changes in the functional group of the reactants:
An Overview of Organic Reactions Reaction types: Classification by outcome Most reactions produce changes in the functional group of the reactants: 1. Addition (forward) Gain of atoms across a bond Example:
More informationCHEM Core Chemistry 3. Reaction Mechanisms in Organometallic Chemistry
E3012 - ore hemistry 3 eaction echanisms in Organometallic hemistry In an earlier section of this lecture course we considered the mechanisms of substitution reactions in organometallic species, and noted
More informationFunctionalization of terminal olefins via H migratory insertion /reductive elimination sequence Hydrogenation
M.C. White, Chem 153 verview -282- Week of ovember 11, 2002 Functionalization of terminal olefins via migratory insertion /reductive elimination sequence ydrogenation ML n E ydrosilylation Si 3 Si 3 ML
More informationSonogashira: in situ, metal assisted deprotonation
M.C. White, Chem 253 Cross-Coupling -120- Week of ctober 11, 2004 Sonogashira: in situ, metal assisted deprotonation catalytic cycle: ' (h 3 ) n d II The first report: h Sonogashira T 1975 (50) 4467. h
More informationOrgano-transition Metal Chemistry
Prof. Dr. Burkhard König, nstitut für rganische Chemie, Universität egensburg 1 rgano-transition tal Chemistry 1. Some Basics Chemistry involves intermediates containing transition-metal carbon bonds tal-carbon
More informationReductive Elimination
Reductive Elimination Reductive elimination, the reverse of oxidative addition, is most often seen in higher oxidation states because the formal oxidation state of the metal is reduced by two units in
More informationAdditions to Metal-Alkene and -Alkyne Complexes
Additions to tal-alkene and -Alkyne Complexes ecal that alkenes, alkynes and other π-systems can be excellent ligands for transition metals. As a consequence of this binding, the nature of the π-system
More informationA Summary of Organometallic Chemistry
A Summary of Organometallic Chemistry Counting valence electrons (v.e.) with the ionic model 1. Look at the total charge of the complex Ph 3 P Cl Rh Ph 3 P PPh 3 OC CO 2 Fe OC CO Co + charge:0 charge:
More informationConjugated Systems, Orbital Symmetry and UV Spectroscopy
Conjugated Systems, Orbital Symmetry and UV Spectroscopy Introduction There are several possible arrangements for a molecule which contains two double bonds (diene): Isolated: (two or more single bonds
More informationdeactivation or decomposition is therefore quantified using the turnover number.
A catalyst may be defined by two important criteria related to its stability and efficiency. Name both of these criteria and describe how they are defined with respect to stability or efficiency. A catalyst
More informationChapter 4 Electrophilic Addition to Carbon Carbon Multiple Bonds 1. Addition of H X 2. Addition of H OH and addition of Y X 3. Addition to allene and
Chapter 4 Electrophilic Addition to Carbon Carbon Multiple Bonds 1. Addition of X 2. Addition of and addition of Y X 3. Addition to allene and alkyne 4. Substitution at α-carbon 5. eactions via organoborane
More informationNuggets of Knowledge for Chapter 17 Dienes and Aromaticity Chem 2320
Nuggets of Knowledge for Chapter 17 Dienes and Aromaticity Chem 2320 I. Isolated, cumulated, and conjugated dienes A diene is any compound with two or C=C's is a diene. Compounds containing more than two
More informationModule 10 : Reaction mechanism. Lecture 1 : Oxidative addition and Reductive elimination. Objectives. In this lecture you will learn the following
Module 10 : Reaction mechanism Lecture 1 : Oxidative addition and Reductive elimination Objectives In this lecture you will learn the following The oxidative addition reactions. The reductive elimination
More informationInorganic Chemistry Year 3
Inorganic Chemistry Year 3 Transition Metal Catalysis Eighteen Electron Rule 1.Get the number of the group that the metal is in (this will be the number of d electrons) 2.Add to this the charge 1.Negative
More informationElectrophilic Carbenes
Electrophilic Carbenes The reaction of so-called stabilized diazo compounds with late transition metals produces a metal carbene intermediate that is electrophilic. The most common catalysts are Cu(I)
More informationReductive Elimination
Reductive Elimination Reductive elimination, the reverse of oxidative addition, is most often seen in higher oxidation states because the formal oxidation state of the metal is reduced by two units in
More informationMetal Hydrides, Alkyls, Aryls, and their Reactions
Metal Hydrides, Alkyls, Aryls, and their Reactions A Primer on MO Theory σ-bonding in Organotransition Metal Complexes M-C Bond Energies in Organotransition Metal Complexes Thermodynamic Predictions
More informationTHE ORGANOMETALLIC CHEMISTRY OF THE TRANSITION METALS
THE ORGANOMETALLIC CHEMISTRY OF THE TRANSITION METALS Second Edition ROBERT H. CRABTREE Yale University New Haven, Connecticut A Wiley-Interscience Publication JOHN WILEY & SONS New York / Chichester /
More informationsp 3 C-H Alkylation with Olefins Yan Xu Dec. 3, 2014
sp 3 C-H Alkylation with Olefins, Yan Xu Dec. 3, 2014 1) sp 3 C-H Alkylation via Directed C-H activation 2) Hydroaminoalkylation (still via C-H activation) 3) Hydrohydroxyalkylation (via radical chemistry)
More informationChapter 5. Nucleophilic aliphatic substitution mechanism. by G.DEEPA
Chapter 5 Nucleophilic aliphatic substitution mechanism by G.DEEPA 1 Introduction The polarity of a carbon halogen bond leads to the carbon having a partial positive charge In alkyl halides this polarity
More informationN-Heterocyclic Carbenes (NHCs)
N-Heterocyclic Carbenes (NHCs) In contrast to Fischer and Schrock type carbenes NHCs are extremely stable, inert ligands when complexed to a metal centre. Similar to phosphine ligands they are electronically
More informationTransition Metal Chemistry
Transition Metal Chemistry 2 2011.12.2 Ⅰ Fundamental Organometallic Reactions Following four reactions are important formal reaction patterns in organotransition metal complexes, which would conveniently
More informationOC 2 (FS 2013) Lecture 3 Prof. Bode. Redox Neutral Reactions and Rearrangements
C 2 (F 203) Lecture 3 Prof. Bode edox eutral eactions and earrangements Types of edox eutral rganic eactions. eactions with no external reducing or oxidizing agent In this case, one part of the starting
More informationCarbenes and Olefin Metathesis
arbenes and Olefin etathesis Peter H.. Budzelaar etal-carbon multiple bonds any transition metals form not only - single bonds but also = and (more rare) even bonds. omplexes containing an = bond are called
More informationAsymmetric Nucleophilic Catalysis
Asymmetric ucleophilic Catalysis Chiral catalyst X 2 Chiral catalyst X = alkyl, X 1 2 1 Vedejs, E.; Daugulis,. J. Am. Chem. Soc. 2003, 125, 4166-4173 Shaw, S. A.; Aleman,.; Vedejs, E. J. Am. Chem. Soc.
More informationRadical Reactions. Radical Stability!!! bond dissociation energies X Y X + Y. bond BDE (kcal/mol) bond BDE (kcal/mol) CH 3 CH 3 CH 2 95 O H R 2 C H
adical eactions adical Stability!!! bond dissociation energies X Y X Y bond BDE (kcal/mol) bond BDE (kcal/mol) C 3 104 108 C 3 C 2 98 110 95 2 C 102 (-) 93 (C-) 92 C 3 C 3 36 89 85 C 3 C 3 80 adical eactions
More informationCHEM Lecture 7
CEM 494 Special Topics in Chemistry Illinois at Chicago CEM 494 - Lecture 7 Prof. Duncan Wardrop ctober 22, 2012 CEM 494 Special Topics in Chemistry Illinois at Chicago Preparation of Alkenes Elimination
More information1.13 Acid-Base Reactions: Lone-Pair Donors & Acceptors
1.13 Acid-Base Reactions: Lone-Pair Donors & Acceptors I, Cl, N 3, 3 P 4 pka 10 to 5 Super strong acids 3 + pka 1.7 RC 2 pka ~ 5 acids Ph pka ~ 10 get 2, R pka ~ 16 weaker RCC (alkynes) pka ~ 26 RN 2 pka
More information( ) Thermodynamic selectivity (reversible reactions)
II. Reactivity A) General Principles Fundamental Equations G o Ea / RT = "RT ln K eq k = Ae 1) Kinetics vs Thermodynamics Kinetic selectivity (irreversible reactions) [ P 1 ] [ ] = ln k 1 P 2 ( ) = " #G
More informationInsertion and elimination. Peter H.M. Budzelaar
Peter H.. Budzelaar Insertion reactions If at a metal centre you have a) a σ-bound group (hydride, alkyl, aryl) b) a ligand containing a π-system (olefin, alkyne, C) the σ-bound group can migrate to the
More informationOrganometallics: Hard to define usefully and completely at the same time, but generally: Compounds containing metal-carbon bond(s).
eady; Catalysis rganometallics: Definitions rganometallics: ard to define usefully and completely at the same time, but generally: Compounds containing metal-carbon bond(s). C C C C C C K 3 o question:????
More informationAcid-Base -Bronsted-Lowry model: -Lewis model: -The more equilibrium lies to the right = More [H 3 O + ] = Higher K a = Lower pk a = Stronger acid
Revision Hybridisation -The valence electrons of a Carbon atom sit in 1s 2 2s 2 2p 2 orbitals that are different in energy. It has 2 x 2s electrons + 2 x 2p electrons are available to form 4 covalent bonds.
More informationThe Mechanistic Studies of the Wacker Oxidation. Tyler W. Wilson SED Group Meeting
The Mechanistic Studies of the Wacker xidation Tyler W. Wilson SE Group Meeting 11.27.2007 Introduction xidation of ethene by (II) chloride solutions (Phillips, 1894) -First used as a test for alkenes
More informationModule 6 : General properties of Transition Metal Organometallic Complexes. Lecture 2 : Synthesis and Stability. Objectives
Module 6 : General properties of Transition Metal Organometallic Complexes Lecture 2 : Synthesis and Stability Objectives In this lecture you will learn the following Understand the role lead by ligands
More informationNickel-Catalyzed Reductive Cross-Electrophile-Coupling Between Aryl and Alkyl Halides
ickel-catalyzed Reductive Cross-Electrophile-Coupling Between Aryl and Alkyl Halides Eunjae Shim Zakarian Group Literature Talk / Dec 13 th, 2018 University of California, Santa Barbara Table of Contents
More informationLearning Guide for Chapter 17 - Dienes
Learning Guide for Chapter 17 - Dienes I. Isolated, conjugated, and cumulated dienes II. Reactions involving allylic cations or radicals III. Diels-Alder Reactions IV. Aromaticity I. Isolated, Conjugated,
More informationSupporting Information
Supporting Information Formation of Ruthenium Carbenes by gem-hydrogen Transfer to Internal Alkynes: Implications for Alkyne trans-hydrogenation Markus Leutzsch, Larry M. Wolf, Puneet Gupta, Michael Fuchs,
More informationAdvanced Organic Chemistry
D. A. Evans, G. Lalic Question of the day: Chemistry 530A TBS Me 2 C Me toluene, 130 C 70% TBS C 2 Me H H Advanced rganic Chemistry Me Lecture 16 Cycloaddition Reactions Diels _ Alder Reaction Photochemical
More informationand Ultraviolet Spectroscopy
Organic Chemistry, 7 th Edition L. G. Wade, Jr. Chapter 15 Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy 2010, Prentice all Conjugated Systems Conjugated double bonds are separated
More informationHydrides and Dihydrogen as Ligands: Lessons from Organometallic Chemistry. Lecture 9
ydrides and Dihydrogen as Ligands: Lessons from Organometallic Chemistry Lecture 9 Inorganic Chemistry Chapter 1: Figure 10.1 2009 W.. Freeman Synthesis of Organometallic Complex ydrides Reaction of MCO
More informationOrganic Chemistry Laboratory Summer Lecture 6 Transition metal organometallic chemistry and catalysis July
344 Organic Chemistry Laboratory Summer 2013 Lecture 6 Transition metal organometallic chemistry and catalysis July 30 2013 Summary of Grignard lecture Organometallic chemistry - the chemistry of compounds
More informationMetal Catalyzed Outer Sphere Alkylations of Unactivated Olefins and Alkynes
Metal Catalyzed uter Sphere Alkylations of Unactivated lefins and Alkynes Stephen Goble rganic Super-Group Meeting Literature Presentation ctober 6, 2004 1 utline I. Background Introduction to Carbometallation
More informationOrganometallic Catalysis
Organometallic Catalysis The catalysts we will study are termed homogeneous catalysts as they are dissolved in th e same solvent as the substrate. In contrast, heterogeneous catalysts, such as palladium
More informationCuI CuI eage lic R tal ome rgan gbr ommon
Common rganometallic eagents Li Et 2 Li Mg Et 2 Li alkyllithium rignard Mg Mg Li Zn TF ZnCl 2 TF dialkylzinc Zn 2 2 Zn Li CuI TF ganocuprate CuI 2 2 CuI common electrophile pairings ' Cl ' '' ' ' ' ' '
More information14-1 Reactions Involving Gain or Loss of Ligands Reactions Involving Modification of Ligands
Organometallic Reaction and Catalysis 14-1 Reactions Involving Gain or Loss of Ligands 14-2 Reactions Involving Modification of Ligands 14-3 Organometallic Catalysts 14-4 Heterogeneous Catalysts Inorganic
More informationLecture 9: Addition to σ*
hemistry 201: rganic eaction chanisms Lecture 9: Addition to σ* B fast A not so fast σ* π* δ - δ δ - E M p Addition to σ* orbital leads to bond cleavage ydrogen atoms are always attached to something.
More informationStable gold(iii) catalysts by oxidative addition of a carboncarbon
Stable gold(iii) catalysts by oxidative addition of a carboncarbon bond Chung-Yeh Wu, Takahiro oribe, Christian Borch Jacobsen & F. Dean Toste ature, 517, 449-454 (2015) presented by Ian Crouch Literature
More informationThere are only two important things in chemistry, kinetics and thermodynamics. And, exp(-δg/rt) = k 1 /k -1, so there s really only one thing.
Ready; Catalysis Kinetics-1 There are only two important things in chemistry, kinetics and thermodynamics. And, exp(-δg/rt) = k 1 /k -1, so there s really only one thing. Kinetics provides information
More informationEPIC LIGAND SURVEY: METAL ALKYLS - I
EPIC LIGAND SURVEY: METAL ALKYLS - I With this post we finally reach the defining ligands of organometallic chemistry, alkyls. Metal alkyls feature a metal-carbon σ bond and are usually actor ligands,
More informationSuggested solutions for Chapter 40
s for Chapter 40 40 PBLEM 1 Suggest mechanisms for these reactions, explaining the role of palladium in the first step. Ac Et Et BS () 4 2 1. 2. K 2 C 3 evision of enol ethers and bromination, the Wittig
More informationLigand Substitution Reactivity of Coordinated Ligands
Reactivity of Coordinated Ligands 2 C 2 H 4 (0) + H + + + 2 2 e (Cu 2 Cu) H CH 3 CH H "βh elim" ins βh elim H Peter H.M. Budzelaar Why care about substitution? Basic premise about metalcatalyzed reactions:
More informationCatalysis by Group IV Elements CHEM 966 (Tunge) Good reference: Titanium and Zirconium in Organic Synthesis Ilan Marek Ed., 2002.
Catalysis by Group IV Elements CEM 966 (Tunge) Good reference: Titanium and Zirconium in rganic Synthesis Ilan Marek Ed., 2002. Electronegativity: Ti(1.54); (1.33); f(1.3) Much of the chemistry is dominated
More informationHYDROGENATION. Concerned with two forms of hydrogenation: heterogeneous (catalyst insoluble) and homogeneous (catalyst soluble)
YDGEATI Concerned with two forms of hydrogenation: heterogeneous (catalyst insoluble) and homogeneous (catalyst soluble) eterogeneous Catalysis Catalyst insoluble in reaction medium eactions take place
More informationOrganic Chemistry CHM 314 Dr. Laurie S. Starkey, Cal Poly Pomona Alkyl Halides: Substitution Reactions - Chapter 6 (Wade)
rganic Chemistry CM 314 Dr. Laurie S. Starkey, Cal Poly Pomona Alkyl alides: Substitution Reactions - Chapter 6 (Wade) Chapter utline I. Intro to RX (6-1 - 6-7) II. Substitution Reactions A) S N 2 (6-8,
More informationDirect, Catalytic Hydroaminoalkylation of Unactivated Olefins with N-Alkyl Arylamines
Current Literature - May 12, 2007 Direct, Catalytic ydroaminoalkylation of Unactivated lefins with -Alkyl ylamines ' '' Ta[ 2 ] 5 (4-8 mol%), 160-165 o C 24-67h 66-95% ' '' S. B. erzon and J. F. artwig,
More informationNegishi Coupling of Secondary Alkylzinc Halides with Aryl Bromides and Chlorides
Negishi Coupling of Secondary Alkylzinc alides with Aryl Bromides and Chlorides X X = Br, Cl 2 1 ZnBr 1, 2 = Alkyl Cat. Pd(OAc) 2 Ligand TF/Toluene rt or 60 o C 1 2 J. Am. Chem. Soc. 2009, ASAP Article
More informationM.C. White, Chem 253 Mechanism -43- Week of September 27th, 2004
M.C. White, Chem 253 Mechanism -43- Week of September 27th, 2004 igand Exchange Mechanisms Associative ligand substition: is often called square planar substition because16 e-, d8 square planar complexes
More informationNucleophilic attack on ligand
Nucleophilic attack on ligand Nucleophile "substitutes" metal hapticity usually decreases xidation state mostly unchanged Competition: nucleophilic attack on metal usually leads to ligand substitution
More informationLoudon Chapter 18 Review: Vinyl/Aryl Reactivity Jacquie Richardson, CU Boulder Last updated 2/21/2016
Chapter 18 covers leaving groups that are directly attached to double-bonded sp 2 carbons. These molecules don t do most of the regular alkyl halide chemistry from Ch. 9 (S N1/ S N2/E1), but they can do
More informationOrganometallic Chemistry and Homogeneous Catalysis
Organometallic Chemistry and Homogeneous Catalysis Dr. Alexey Zazybin Lecture N6 Kashiwa Campus, November 27, 2009 Group VIB: Cr, Mo, W -Oxidation states from -2 to +6 -While +2 and +3 for Cr are quite
More informationHybridization of Nickel Catalysis and Photoredox Catalysis. Literature seminar#1 B4 Hiromu Fuse 2017/02/04(Sat)
Hybridization of Nickel Catalysis and Photoredox Catalysis Literature seminar#1 B4 Hiromu Fuse 2017/02/04(Sat) Introduction Novel cross coupling was reported! Highly selective sp 3 C-H functionalization!
More informationJACS ASAP Article: Published 3/12/08. Lei Jiao, Changxia Yuan and Zhi-Xiang Yu. Current Literature: 3/29/08. David Arnold
Tandem h(i)-catalyzed [(5+2)+1] Cycloaddition/Aldol eaction for the Construction of Linear Triquinane Skeleton: Total Syntheses of (+)-irsutene and (+)-1- Desoxyhypnophilin JACS ASAP Article: Published
More informationChem 253 Problem Set 7 Due: Friday, December 3, 2004
Chem 253 roblem Set 7 ue: Friday, ecember 3, 2004 Name TF. Starting with the provided starting material, provide a concise synthesis of. You may use any other reagents for your synthesis. It can be assumed
More informationReactions. Reactions. Elimination. 2. Elimination Often competes with nucleophilic substitution. 2. Elimination Alkyl halide is treated with a base
eactions 1 eactions 2 2. limination Alkyl halide is treated with a base B: 2. limination ften competes with nucleophilic substitution LIMINATIN Nu: SUBSTITUTIN Nu Bimolecular B: limination B * * 3 Kinetics
More informationOlefin Metathesis ROMP. L n Ru= ROMP n RCM. dilute
lefin Metathesis MP: ing-opening metathesis polymerization Thermodynamically favored for 3,4, 8, larger ring systems Bridging groups (bicyclic olefins) make ΔG polymerization more favorable as a result
More informationAnswers To Chapter 7 Problems.
Answers To Chapter Problems.. Most of the Chapter problems appear as end-of-chapter problems in later chapters.. The first reaction is an ene reaction. When light shines on in the presence of light and
More informationThe following molecules are related:
Isolobal Analogy Inclusion of the ligand η-c 5 H 5 - which, as a donor of 3 π-electron pairs formally occupies 3 coordination sites, yields the analogies: The following molecules are related: 1 Isolobal
More informationChapter 20 Carboxylic Acid Derivatives. Nucleophilic Acyl Substitution
ucleophilic Acyl Substitution hapter 20 arboxylic Acid Derivatives ucleophilic Acyl Substitution Y (1) need to have Y as a u Y u u + Y (2) could not happen with aldehydes or ketones as : and : are poor
More information1. Addition of HBr to alkenes
eactions of Alkenes I eading: Wade chapter 8, sections 8-1- 8-8 tudy Problems: 8-47, 8-48, 8-55, 8-66, 8-67, 8-70 Key Concepts and kills: Predict the products of additions to alkenes, including regiochemistry
More informationHighlights of Schmidt Reaction in the Last Ten Years
ighlights of Schmidt eaction in the Last Ten Years Dendrobates histrionicus Jack Liu ov. 18, 2003 Introduction Classical Schmidt reaction of aldehydes and carboxylic acids Classical Schmidt reaction of
More informationOChem 1 Mechanism Flashcards. Dr. Peter Norris, 2018
OChem 1 Mechanism Flashcards Dr. Peter Norris, 2018 Mechanism Basics Chemical change involves bonds forming and breaking; a mechanism describes those changes using curved arrows to describe the electrons
More informationChapter 3. Alkenes And Alkynes
Chapter 3 Alkenes And Alkynes Alkenes ydrocarbons containing double bonds C C double bond the functional group center of reactivity Molecular Formula of Alkene Acyclic alkene: C n 2n Cyclic alkene: C n
More informationReaction Mechanisms - Ligand Substitutions. ML n-x P x + xl
Reaction chanisms - igand Substitutions igand Substitutions 1 A substitution reaction is one in which an existing ligand on a metal center is replaced by another ligand. Exactly how this occurs depends
More informationChapter 7 Substitution Reactions 7.1 Introduction to Substitution Reactions Substitution Reactions: two reactants exchange parts to give new products
hapter 7 Substitution eactions 7.1 Introduction to Substitution eactions Substitution eactions: two reactants exchange parts to give new products A-B + -D A-D + B- 3 2 + Br 3 2 Br + Elimination eaction:
More informationOChem 1 Mechanism Flashcards. Dr. Peter Norris, 2015
OChem 1 Mechanism Flashcards Dr. Peter Norris, 2015 Mechanism Basics Chemical change involves bonds forming and breaking; a mechanism describes those changes using curved arrows to describe the electrons
More information