Lecture 21 February 24, 2010 Bonds to MH + ; CH4 CH3OH catalysis

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1 Lecture 21 February 24, 2010 Bonds to M + ; C4 C3 catalysis ature of the Chemical Bond with applications to catalysis, materials science, nanotechnology, surface science, bioinorganic chemistry, and energy William A. Goddard, III, wag@wag.caltech.edu 316 Beckman Institute, x3093 Charles and Mary Ferkel Professor of Chemistry, Materials Science, and Applied Physics, California Institute of Technology Teaching Assistants: Wei-Guang Liu <wgliu@wag.caltech.edu> Ted Yu <tedhyu@wag.caltech.edu> 1

2 Remaining Course schedule Wednesday Feb. 24, 2pm L21, normal, TDAY Friday Feb. 26, 2pm L22, move to 115BI Friday Feb. 26, 3pm L23, move to 115BI (make up for Mar. 1) Monday, Mar. 1 no class (wag at IST/AS review in Maryland) Wednesday, Mar. 3 no class (wag at IST/AS review Maryland) Friday Mar. 5, 2pm, L24 (make up for March 3) Friday Mar 5 3pm L25 (catching up to March 5) Monday, Mar. 8 2pm L26, caught up, normal Wednesday, Mar. 10 no class (wag at conference in Chicago) Thursday Mar. 11, 2pm, L27 Last lecture (make up for Mar. 10) Final available Thursday March 11 Final due back Friday March 19 2

3 Last time 3

4 Mysteries from experiments on oxidative addition and reductive elimination of C and CC bonds on Pd and Why are Pd and so different 4

5 energetics ot agree with experiment 5

6 Possible explanation: kinetics 6

7 Consider reductive elimination of, C and CC from Pd Conclusion: no barrier C modest barrier CC large barrier 7

8 Consider oxidative addition of, C, and CC to Conclusion: no barrier C modest barrier CC large barrier 8

9 Summary of barriers This explains why CC coupling not occur for while C and coupling is fast But why? 9

10 ow estimate the size of barriers (without calculations) 10

11 Examine coupling at transition state Can simultaneously get good overlap of with Pd sd hybrid and with the other Thus get resonance stabilization of TS low barrier 11

12 Examine CC coupling at transition state Can orient the C 3 to obtain good overlap with Pd sd hybrid R can orient the C 3 to obtain get good overlap with the other C 3 But CAT D BT SIMULTAEUSLY, thus do T get resonance stabilization of TS high barier 12

13 Examine C coupling at transition state can overlap both C 3 and Pd sd hybrid simultaneously but C 3 cannot thus get ~ ½ resonance stabilization of TS 13

14 ow we understand chemistry But what about Pd? Why are and Pd so dramatically different 14

15 goes from s 1 d 9 to d 10 upon reductive elimination thus product stability is DECREASED by 12 kcal/mol Using numbers from QM 15

16 Pd goes from s 1 d 9 to d 10 upon reductive elimination thus product stability is ICREASED by 20 kcal/mol Using numbers from QM Pd and would be ~ same 16

17 Thus reductive elimination from Pd is stabilized by an extra 32 kcal/mol than for due to the ATMIC nature of the states The dramatic stabilization of the product by 35 kcal/mol reduces the barrier from ~ 41 () to ~ 10 (Pd) This converts a forbidden reaction to allowed 17

18 Summary energetics Conclusion the atomic character of the metal can control the chemistry 18

19 Examine bonding to all three rows of transition metals Use M+ as model because a positive metal is more representative of organometallic and inorganic complexes M0 usually has two electrons in ns orbitals or else one M+ generally has one electron in ns orbitals or else zero M2+ never has electrons in ns orbitals 19

20 Ground states of neutral atoms Sc (4s)2(3d) Sc + (4s)1(3d)1 Sc ++ (3d)1 Ti (4s)2(3d)2 Ti + (4s)1(3d)2 Ti ++ (3d)2 V (4s)2(3d)3 V + (4s)0(3d)3 V ++ (3d)3 Cr (4s)1(3d)5 Cr + (4s)0(3d)5 Cr ++ (3d)4 Mn Fe Co i Cu (4s)2(3d)5 (4s)2(3d)6 (4s)2(3d)7 (4s)2(3d)8 (4s)1(3d)10 Mn + Fe + Co + i + Cu + (4s)1(3d)5 (4s)1(3d)6 (4s)0(3d)7 (4s)0(3d)8 (4s)0(3d)10 Mn ++ Fe ++ Co ++ i ++ Cu ++ (3d)5 (3d)6 (3d)7 (3d)8 (3d)10 20

21 Bond energies M+ Re Mo Au Cr Cu Ag 21

Exchange energies: Mn+: s 1 d 5 For high spin (S=3) A[(d 1 a)(d 2 a)(d 3 a)(d 4 a)(d 5 a)(sa)] Get 6*5/2=15 exchange terms 5Ksd + 10 Kdd Responsible for und s rule Ksd Kdd Mn+ 4.8 19.8 kcal/mol Tc+ 8.

22 Exchange energies: Mn+: s 1 d 5 For high spin (S=3) A[(d 1 a)(d 2 a)(d 3 a)(d 4 a)(d 5 a)(sa)] Get 6*5/2=15 exchange terms 5Ksd + 10 Kdd Responsible for und s rule Ksd Kdd Mn kcal/mol Tc Re Form bond to, must lose half the exchange stabilization for the orbital bonded to the A{(d 1 a)(d 2 a)(d 3 a)(d 4 a)(sd b a)[(sd b )+(sd b )](ab-ba)} sd b is a half the time and b half the time 22

23 Ground state of M + metals Mostly s1dn-1 Exceptions: 1 st row: V, Cr-Cu 2 nd row: b-mo, Ru-Ag 3 rd row: La,, Au 23

24 Size of atomic orbitals, M + Valence s similar for all three rows, 5s biggest Big decrease from La(an 57) to f(an 72 Valence d very small for 3d 24

25 Charge transfer in M + bonds electropositive 1 st row all electropositive 2 nd row: Ru,Rh,Pd electronegative 3 rd row:, Au, g electronegative electronegative 25

26 26

27 1 st row 27

28 28

29 Schilling 29

30 30

31 31

32 ew material 32

33 2 nd row 33

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35 35

36 36

37 37

38 38

39 39

40 3 rd row 40

41 41

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49 Catalyst Challenges for the Selective Chemistry needed for Sustainable Development Challenge: improved catalysts for industrial applications including Low temperature conversion of methane to fuels and organic feedstocks igh selectivity and activity for converting alkanes to organic feedstocks Fuel cell cathode catalysts for the oxygen reduction reaction (RR) with decreased overpotential, much less, and insensitive to deactivation Fuel cell anode catalysts capable of operating with a variety of fuels but insensitive to C and to deactivation A methane fuel cell (C C 2 + power [8 (+ and e-)] Efficient catalysts for photovoltaic production of energy and 2 Efficient catalysts for storing and recovering hydrogen Catalysts for high performance Li ion and F ion batteries Enormous experimental efforts have been invested in solving these problems but better solutions are needed more quickly I claim that Theory and Modeling are poised to provide guidance to achieve these goals much more quickly 49

Projects in Catalysis: First establish mechanism then use mechanism to design improved catalyst Propane ammoxidation - structure of new phases in Mixed Metal xide (Mitsubishi, BP) catalysts:

50 Projects in Catalysis: First establish mechanism then use mechanism to design improved catalyst Propane ammoxidation - structure of new phases in Mixed Metal xide (Mitsubishi, BP) catalysts: MoVbTaTex TUESDAY butane MA over VP and D over V 2 5 Fuel Cell cathode electrocatalysis: non and Co,i alloys Direct methanol fuel cell: Ru-Ruy at anode CuSi x catalysis of Me to Si(Me) 2 2 and role additives rganometallic Catalysts C 4 to liquids:,, s, Re, Rh, Ru TDAY Pd-mediated activation of molecular oxygen Mechanism of the Wacker reaction E in aqueous solution (kcal/mol) Single Site Polymerization catalysts for A polar C monomers copyright 2010 William A. Goddard III, all rights reserved Al i Al 50

51 Role of Theory in Developing Catalysts 1. Establish Mechanism of current catalysts: Use QM to predict all plausible reaction paths, Determine transition states (TS) and stable reaction intermediates (RI) Calculate vibrational frequencies (vf) to prove TS (one negative curvature) and RI Use frequencies to calculate entropy, Cp. Use QM and Poisson-Boltzmann to get free solvation energy. Get free energy at reaction temperatures G = E elec + ZPE + vib (T) + lib (T) TS vib TS lib + G solv Use to estimate rates This provides the conceptual framework to interpret experiments 2. Validation: Predict new experiments to test mechanism 3. Lead discovery: Combinatorial Computational Rapid Prototyping In silico search for new lead candidates for Ligands, Metals, Solvents 4. Experiments: optimize best predicted ligands and reaction conditions. Continue theory and simulation in collaboration with experiments Critical to new role of theory: accuracy and reliability for novel systems Must trust the theory well enough to do only 1 to 10% of the systems Focus experiments on these 1% to 10% predicted to be best copyright 2010 William A. Goddard III, all rights reserved = 51

52 as theory ever contributed to catalysis development? ver last 30 years quantum mechanics (QM) theory has played an increased role in analyzing and interpreting experimental results on catalytic systems But has QM led to new catalysts before experiment and can we count on the results from theory to focus experiments on only a few systems? Case study: ew catalysts for low temperature activation of C 4 and functionalization to form liquids (C 3 ) 53

Motivation: The enormous stranded methane gas reserves, huge opportunity for new technology World Gas (C 4 ) Reserves are estimated at 5000-6000 tcf

53 Motivation: The enormous stranded methane gas reserves, huge opportunity for new technology World Gas (C 4 ) Reserves are estimated at tcf equivalent to 600 billion barrels of liquid fuel, comparable to total petroleum reserves To transport as gas is too expensive, must transform to liquid, e.g. C 3 Current technology: high temperature (800C) Sasol process, requires huge capital investments ($billion) Much of remaining methane is associated gas that must be flared as the petroleum is removed Required: Low temperature (250C) process to selectively convert C 4 to C 3 and other liquids 54

Experimental discovery: Periana 3 et al., Science, 1998 3 3 ( 3 ) 2 2 TF: 1x10-2 s -1 t ½ = 15 min Rate ok, but decompose far too fast. Why?

compounds (out of laaarge number examined) catalyze conversion of methane to methylbisulfate in fuming sulphuric acid (102%) C 4 + 2 S 4 + S 3 C 3 S 3 + 2 + S 2 C 3 S 3

54 Experimental discovery: Periana 3 et al., Science, ( 3 ) 2 2 TF: 1x10-2 s -1 t ½ = 15 min Rate ok, but decompose far too fast. Why? (bpim) 2 TF: 1x10-3 s -1 t ½ = >200 hours ot decompose but rate 10 times too slow Also poisoned by 2 product ow improve rate and eliminate poisoning Two Platinum compounds (out of laaarge number examined) catalyze conversion of methane to methylbisulfate in fuming sulphuric acid (102%) C S 4 + S 3 C 3 S S 2 C 3 S C S 4 S 2 + ½ 2 S 3 3 Catalytica: Many $$$ trying to solve these problems experimentally, failed, cancelled project. Periana came to USC, teamed up with Goddard, Chevron funded. Found success 55

55 Quantum Mechanics for rganometallic reactions Density Functional Theory (B3LYP or M06) More recently M06 Includes Generalized Gradient Approximation (nonlocal) exact exchange (hybrid). M06 has KE functional Basis Set: Gaussian functions C,,,, S: All electron, 6-31G**(+) or cc-pvtz(-f) Triple zeta basis for C,,, (includes diffuse functions) Metals:,, etc : Replace (1s) through (4f) shells with onlocal PsuedoPotentials Thus for treat 18 electrons explicitly [(5s) 2 (5p) 6 (5d) 9 (6s) 1 ] Basis set: LACVP**(+) (polarization + diffuse functions) Periodic 2D slabs: Sequest with PBE DFT using Psuedopotentials and Gaussian basis sets based on PBE DFT We have used this level of theory for studying reaction mechanisms of over 20 organometallic reaction systems. Always find good agreement with experimental observations, but seldom is there a clear-cut experimental measurement for comparison. 56

Extremely important for these systems (p from -10 to +30) in very highly polar solvents: accuracy of predicting Solvation effects in QM The Poisson-Boltzmann Continuum Model in Jaguar/Schrödinger is

56 Extremely important for these systems (p from -10 to +30) in very highly polar solvents: accuracy of predicting Solvation effects in QM The Poisson-Boltzmann Continuum Model in Jaguar/Schrödinger is extremely accurate Calculate Solvent Accessible Surface of the solute by rolling a sphere of radius R solv over the surface formed by the vdw radii of the atoms. Calculate electrostatic field of the solute based on electron density from the orbitals Calculate the polarization in the solvent due to the electrostatic field of the solute (need dielectric constant ) This leads to Reaction Field that acts back on solute atoms, which in turn changes the orbitals. Iterated until selfconsistent. Calculate solvent forces on solute atoms Use these forces to determine optimum geometry of solute in solution. Can treat solvent stabilized zwitterions Difficult to describe weakly bound solvent molecules interacting with solute (low frequency, many local minima) Short cut: ptimize structure in the gas phase and do single point solvation calculation. Some calculations done this way Solvent: = 99 R solv = A Implementation in Jaguar (Schrodinger Inc): pk organics to ~0.2 units, solvation to ~1 kcal/mol (p from -20 to +20) 57

57 Comparison of Jaguar pk with experiment pka: Jaguar (experiment) 6.9 (6.7) (-52.35) E_sol: zero (+) 5.8 (5.8) (-49.64) 6.1 (6.0) (-55.11) 5.3 (5.3) (-57.94) 5.0 (4.9) (-51.84) 58

58 l/mol K) = l/mol S 3 8 First Step: ature of (Bpym) 2 S 3 catalyst 8 8 Is + on the Catalytica catalyst in fuming 2 S 4 (p~-10)? (16.5) 2+ 2S - 4 (at ) 0 K) = (0 K) = 2S - 4 (at ) 2 S 4 S 3 kcal/mol kcal/mol S 3 - S (0 K) = (+4.9) 53 K) = S +6.3 kcal/mol 3 G(453 K) = 2 S 4 S 3 kcal/mol +5.2 kcal/mol (10.6) 2 S 4 (10.8) S 3 G(453 K) = S kcal/mol S - 2S - 4 (at ) 4 (at ) 2 S 4 S 3 2 S 4 (at ) -7.6 S 3 - S - kcal/mol 2S - 4 (at ) 4 (at ) (0 (-7.8) -5.4 S 3 - ( G kcal/mol) K) = (0 K) = 2 S 4 (at ) 2 S kcal/mol kcal/mol (-8.7) C 2 S 4 (0 K) = (11.7) (0 K) = -8.9 S kcal/mol G(453 K) = +6.3 S kcal/mol 3 G(453 K) = kcal/mol +5.2 kcal/mol S S 3 G(453 K) = S 3 G(453 K) = S S 4 2 S kcal/mol +5.2 kcal/mol S S 4 (at ) S - 2S - 4 (at ) 59 4 ( In (15.5) 2+ acidic media bpym(bpym) 2 2 has (15.8) one proton bpym

59 Why is (Bpym) 2 Stable? Mixing metal with bpym in 2 S 4 dissolves the metal to form the catalyst, thus quite stable Most favorable species (bpym) 2 is stable due to chelation and presence of backside protonation sites Energetics are G in kcal/mol 60

60 Why is ( 3 ) 2 2 catalyst unstable? Most favorable species ( 3 ) 2 2 quickly protonated to form 4+, losing the 3 ligands, leading to precipitation of inorganic. 61

61 Mechanisms for C activation To discuss kinetics of C- activation for ( 3 ) 2 2 and (bpym) 2 eed to consider the mechanism C L X L C X oxidative addition xidative addition Form 2 new bonds in TS L L X X C X L L X X L L X C L L X C L L X C L L X C X X Sigma metathesis (2 s + 2 s ) X Concerted, keep 2 bonds in TS L X L X L C L C X X copyright electrophilic 2010 substitution William A. Goddard III, all rights reserved Electrophilic addition Stabilize ccupied rb. in TS 62

62 Use QM to determine mechanism: C- activation step. Requires high accuracy (big basis, good DFT) xidative addition Theory led to new mechanism, formation of ion pair intermediate, proved with D/ exchange 38.0, TS , TS 2a 40.5, TS 2b 36.0, TS 2c -bond metathesis Electrophilic addition 1. Form Ion-Pair intermediate 2. Rate determining step is C 4 ligand association T C activation! 32.1; B C 4 complex 27.0; C ; C ; C 3 (bpym) 2 Start 0.0; A 1 (sol, 0K) kcal/mol 3. Electrophilic Addition wins C 3 complex 63

63 C- Activation Step for (bpym + )()(S 3 ) Solution Phase QM (Jaguar) RDS is C 4 ligand association T C activation! ( kcal/mol Start C 2 3 S 0.0 A C 4 S 3 3 S C T B S 3 C 2 T2b T2 Electrophilic Substitution Electrophilic substitution C 4 complex Form Ion-Pair intermediate xidative Addition C C 3 2 S 4 3 S C 3 xidative addition C 3 complex Differential of =0.7 kcal/mol confirmed with detailed /D exchange experiments 64

64 Theory based mechanism: Catalytic Cycle Start here 1 st turnover Catalytic step L 2 -C 4 +C 4 Adding C 4 leads to ion pair with displaced anion After first turnover, the catalyst is (bpym) (S 3 ) not (bpym) 2 L 2 S 3 +C 4 -C 4 L 2 C 4 + X - 2 S 4 C 3 S 3 functionalization methane complex C- activation X + S 3 - S 3 X =, S 3 L 2 C 3 S 3 (IV) complex oxidation S S S 4 L 2 C 3 (II)-C 3 complex 65

interaction of C water 2 with reactant, catalysis, transition state or 3 S product? (a) C 3 ( kcal/mol S 3 (0 K) = -6.8 kcal/mol 0.0 A S 3 +33.1 T1 +27.4 S 3 2 C 2 T2b +32.

65 b 4 lic n C xidative Addition C 3 2 S 4 C 3 3 S L 2 2 Water Inhibition 3 S Experimental bservation: Reaction strongly inhibited B by water, shuts off as solvent goes from 102% to 96% Is this because of interaction of C water 2 with reactant, catalysis, transition state or 3 S product? (a) C 3 ( kcal/mol S 3 (0 K) = -6.8 kcal/mol 0.0 A S T S 3 2 C 2 T2b T2 Electrophilic Substitution C xidative Addition C 3 2 S 4 Barrier 33.1 kcal/mol (b) Theory: Complexation of water to activated catalyst is 7 kcal/mol S (0 K) = 3 exothermic, making barrier kcal/mol kcal/mol higher. Product formation 0 Thus inhibition is a ground state effect Challenge: since (at ) 2 S 4 (at ) 2 is a product of the reaction, must make the catalyst (c) less attractive copyright to William but still A. Goddard attractive III, all rights to C reserved 4 2 (at ) 8 8 C 4 S 4 - (at ) 8 Barrier 39.9 kcal/mol 8 66

66 Quantum Mechanical Rapid Prototyping QMRP: computational analogue of combinatorial chemistry Three criteria for C 4 activation: 1. Thermodynamic Criterion: Energy cost for formation of R-C 3 must be less than 10 kcal mol -1. Fast to calculate because need only minimize stable M-C 3 Reaction Intermediate 2. Poisoning Criterion: Species must be resistant to poisoning from water (i.e. water complexation is endothermic) Fast to calculate because minimize only M- 2 intermediate. 3. Kinetic Criterion: Barrier to product formation must be less than 35 kcal mol -1. Test for minimized M-(C 4 ). Barrier only a few kcal/mol higher. Slower to calculate because of weakly bound anion and C 4, but minimize only intermediate. 4. Do real barriers only when 3 is less than 35 kcal/mol Many cases of Metal, ligand, solvent exper pilot Small set systems for lab experiment Muller, Philipp, Goddard Topics in Catalysis 2003, 23, 81 67

67 A few of the prototype ligand/metal sets evaluated by QMRP Au Au s s s s s 68

68 More exotic ligand/metal sets evaluated by QMRP. Since calculations are fast, a couple of hours, can try wild guesses X X X X S X S X S X X X X X F 3 C CF 3 F F F F F F X F X copyright 2010 William X A. Goddard III, all rights reserved F F X F 69

69 QMRP: II C and ligands, reject (C)(II) ()(II) + C = = +51.3* kcal/mol C C C 3 kcal/mol C C C A * (0)=49.0, G(298)=49.9 C A C 3 E(A-C) too high for both complexes 70

QMRP: s II C and IV ligands, reject (C)s(II) (C)(IV) C s = s C = kcal/mol 0.0 C 3 +32.7 C kcal/mol +39.

70 QMRP: s II C and IV ligands, reject (C)s(II) (C)(IV) C s = s C = kcal/mol 0.0 C C kcal/mol C C(2) C 3 C A 3 C C s 0.0 A s C E(A-C) too high for (C)s(II), but acceptable for (C)(IV) C 4 C +8.0 C(1) C 3 71

71 C kcal/mol QMRP: III C, passes 1,3, fails 2, reject C W C + 2 = A C 4 C 0.0 A' C + C 4 3 C B C 3 C T2 + C C' C 3 C + C 3 C'' C C C 3 (C)(III) system passes QM-RP tests 1 and 3, but is not resistant to water (test 2) 72

72 QMRP: I, passes 1,2,3 examine further ()(I) = kcal/mol 3 C T W 0.0 A' C B 3 C C' C 3 C 4 ()(I) system passes all three tests! ()(I) picked as focal point for more detailed studies 73

QMRP: further examination of I. ot stable in acid media, reject + 3 + - 2 + 2 0.0-28.7-32.7 2 + 2 2 4.

73 QMRP: further examination of I. ot stable in acid media, reject (I) not compatible with acidic media protonation to (III) predicted to be rapid and irreversible. xidation state of I too low move to III 74

QMRP: III C 40 Even though (C) I failed QC-RP tests, could (C) III () 2 be viable? 30 20 18.

74 QMRP: III C 40 Even though (C) I failed QC-RP tests, could (C) III () 2 be viable? Solvated in ( 2 ) Very slight water inhibition, low ligand lability, Both good 75

QMRP: Further examine III - C 60 50 3 C? 46.1? C3 40 30 20 10 0 20.

75 QMRP: Further examine III - C C? 46.1? C C 4 C 3 Unfavorable to have covalent 3 C -C 3 bond trans to -Ph bond 10.6 xidative addition Thermodynamically Inaccessible. Thus reject Solvated ( 2 ) 76

Switch from III C to III C 40 30 Eliminate trans-effect by switching ligand central C to Get some

76 Switch from III C to III C Eliminate trans-effect by switching ligand central C to Get some water inhibition, but low ligand lability Continue C C C Solvated (2) 77

Further examine III C 40 30 20 10 0 C 4 activation by Sigma bond metathesis - eutral species - Kinetically

77 Further examine III C C 4 activation by Sigma bond metathesis - eutral species - Kinetically accessible with total barrier of 28.9 kcal/mol C C 3 C 28.9 C 3 C 2 C Passes Test Solvated (2) 78

Examine Functionalization for III - C 50 40 Reductive Elimination to form C 3 Kinetically inaccessible 44.

78 Examine Functionalization for III - C Reductive Elimination to form C 3 Kinetically inaccessible 44.3 C 2 C C C 3 C C Solvated ( 2 ) Maybe problem is that III -> I unfavorable eed to xidize to V prior to functionalization? C 2 C 79

xidize with 2 prior to Functionalization 30 20 III - C Passes Test 24.

79 xidize with 2 prior to Functionalization III - C Passes Test 24.5 C 3 C C C C C Solvated ( 2 ) - 2 xidation by 2 Kinetically accessible C 2 C 80

Re-examine Functionalization for III C Passes Test 20 10 0 3 C C 3 C 8.3 C -10-2.1-11.2-20 -19.

80 Re-examine Functionalization for III C Passes Test C C 3 C 8.3 C C 2 Solvated ( 2 ) C 3 C C Thus reductive elimination from V Is kinetically accessible C 3 C 81

81 C activation xidation 3 C C C C 2 Experimental ligand C C C C +C C 24.5 C 3 C C C C 3 C Functionalization C 4 C 3 3 C C C C C 3 C Predicted: Muller, Philipp, Goddard Topics in Catalysis 2003, 23, 81 C A solution III C To avoid 2 poisoning, work in strong base instead of strong acid. Use lower oxidation states, e.g. III and I QM optimum ligands (Goddard) 2003 Tested experimentally (Periana) 2009 It works C C C 3 C 82

82 Experimental Synthesis of III C system Experimental realization of catalytic C 4 hydroxylation predicted for an iridium C pincer complex, demonstrating thermal, protic, and oxidant stability; Young, KJ; xgaard, J; Ess, D; Meier SK, Stewart T, Goddard WA, Periana RA; Chem. Comm., (22): (2009) 83

83 Xray of III C Experimental realization of catalytic C 4 hydroxylation predicted for an iridium C pincer complex, demonstrating thermal, protic, and oxidant stability; Young, KJ; xgaard, J; Ess, D; Meier SK, Stewart T, Goddard WA, Periana RA; Chem. Comm., (22): (2009) bond lengths (Å): (1)-(2) 2.017(6), (1)-C(16) 2.078(8), (1)-C(27) 2.174(9), (1)- (1) 2.164(6), (1)-C(29) 2.081(11), (1)-(1) 2.207(6). bond angles (deg): (2)-(1)-C(16) 78.7(3), (2)-(1)-C(27) 161.0(3), (2)-(1)-(1) 76.8(2), C(16)-(1)-(1) 155.4(3), C(27)-(1)-(1) 84.2(3), C(29)-(1)-(1) 171.1(5). Thermal ellipsoid plot of 1-TFA with 50% probability. ydrogens, and benzene co-solvent removed for clarity. bond lengths (Å): bond angles (deg): 84

Periana persisted only because he was confident it would work.

84 Final step: QM for Experimental Ligand Message: it took 2 years of experiments to synthesize the desired ligand and incorporate the in the correct ox. state. Periana persisted only because he was confident it would work. ot practical to do this for the 1000 s of cases examined in QMRP Chem. Comm., (22): (2009) enthalpy solvent corrections in kcal mol -1 (453K) for TFA ( = 8.42 radius = Å). 85

Lecture 17, March 3, 2015 Organometallic catalysis: CH4 CH 3 OH

Lecture 17, March 3, 2015 Organometallic catalysis: CH4 CH 3 OH Lecture 17, March 3, 2015 rganometallic catalysis: C4 C 3 Elements of Quantum Chemistry with Applications to Chemical Bonding and Properties of Molecules and Solids Course number: Ch125a; Room 115 BI ours: