T: +27(0)51 401 9111 | info@ufs.ac.za | www.ufs.ac.za

CHPC: 2013 National Meeting and Conference

2–6 December

Cape Town International

Convention Centre

Jeanet Conradie+27(0)51 401 2194 | ConradJ@ufs.ac.za | www.ufs.ac.za

Density Functional Theory calculations with High Performance Computing predicts chemical reactivity.

Catalytic Application1.

This StudyRh(I)--diketonato

complexes

Monsanto Process[Rh(CO)2(I)2]

rate determining

1 electrochemical oxidation 2 substitution3 chemical oxidation

RhI

RhIII

The complexes

O

R'O

RhI

R

CO

PX3

PX3 = P(OCH2)3CCH3PX3 = PPh3

O

R'O

RhI

R

CO

CO

O

R'O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3

2.

CF3 (3.01) > CCl3 (2.76) > CH3 (2.34) > Ph (2.21) > Fc (1.87)

(high ) (low )

e- withdrawing e- donating

more electron donating

in terms ofsum of group

electronegativities R + R’

donate electron density via conjugation to Rh

FeIIFc =

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

FcCCl3 (6)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

O

R'O

RhI

R

X

Y

3.The complexes

O

R'

O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3O

R'O

RhI

R

CO

COO

R'O

RhI

R

CO

PR3

(3): PX3 = P(OCH2)3CCH3(4): PX3 = PPh3

(1)(2)(5)

Experimental: Electrochemical oxidation

electrochemical oxidation 1

electrochemical oxidation 3 and 4

electrochemical oxidation 5

electrochemical oxidation 2

4.

(7)

(10)

(11)

more electron donating

Rh(I) easier oxidized to Rh(III)

oxidation

-2eRhI RhIII

Experimental: Electrochemical oxidation 1

O

RO

RhIP(OPh)3

P(OPh)3

R'

one electro-active center

more electron donating

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

5.

J.J.C. Erasmus, J. Conradie, Electro Chim. Acta 56 (2011) 9287.

[RhI(RCOCHCOFc)(P(OPh)3)2] -2e-[RhIII(RCOCHCOFc)(P(OPh)3)2]2+ -1e-

[RhIII(RCOCHCOFc+)(P(OPh)3)2]3+

two electro-active centers

(3)

(8)

oxidation

-2eRhI RhIII

Experimental: Electrochemical oxidation 1

O

RO

RhIP(OPh)3

P(OPh)3

FeII

more electron donating

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

6.

J.J.C. Erasmus, J. Conradie, Electro Chim. Acta 56 (2011) 9287.

oxidation

-2eRhI RhIII

[RhI(RCOCHCOFc)(P(OPh)3)2] -2e-[RhIII(RCOCHCOFc)(P(OPh)3)2]2+ -1e-

[RhIII(RCOCHCOFc+)(P(OPh)3)2]3+

two electro-active centers

(3)

(8)

Experimental: Electrochemical oxidation 1

O

RO

RhIP(OPh)3

P(OPh)3

FeII

more electron donating

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

(1) has three electro-active centers

7.

J.J.C. Erasmus, J. Conradie, Electro Chim. Acta 56 (2011) 9287.

(1)

(3)

(8)

oxidation

-2eRhI RhIII

[RhI(RCOCHCOFc)(P(OPh)3)2] -2e-[RhIII(RCOCHCOFc)(P(OPh)3)2]2+ -1e-

[RhIII(RCOCHCOFc+)(P(OPh)3)2]3+

two electro-active centers

more electron donating

Rh(I) easier oxidized to Rh(III)

Experimental: Electrochemical oxidation 1

O

RO

RhIP(OPh)3

P(OPh)3

FeII

more electron donating

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

(1) has three electro-active centers

8.

J.J.C. Erasmus, J. Conradie, Electro Chim. Acta 56 (2011) 9287.

J.J.C. Erasmus, J. Conradie, Electro Chim. Acta 56 (2011) 9287.

oxidation

-2eRhI RhIII

more electron donating

Rh(I) easier oxidized to Rh(III)

[RhI(RCOCHCOR')(P(OPh)3)2] [RhIII(RCOCHCOR')(P(OPh)3)2]2+-2e-

Experimental: Electrochemical oxidation 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3

more electron donating

CF3CF3 (11)

CH3CF3 (10)

PhCF3 (9)

FcCF3 (8)

CH3CH3 (7)

PhCH3 (5)Ph Ph (4)

CH3Fc (3)Fc Ph (2)Fc Fc (1)R R'

9.

LUMO

HOMO

oxidation

more electron donating

Rh(I) easier oxidized to Rh(III)

higher energy HOMO – electrons easier removed – easier oxidized

-2e-RhI RhIII

Oxidation of Rh(I) to Rh(III) corresponds to the removal of 2 electrons from the highest molecular orbital, the HOMO of the complex.

DFT and Electrochemical oxidation 110.

Gaussian 09 with B3LYP functional and 6-311G(d,p) basis set for C, H, O, F, P, Fe and Lanl2dz for Rh

LUMO

HOMO

oxidation

-2e-RhI RhIII

Oxidation of Rh(I) to Rh(III) corresponds to the removal of 2 electrons from the highest molecular orbital, the HOMO of the complex.

DFT and Electrochemical oxidation 1

more electron donating

Rh(I) easier oxidized to Rh(III)

higher energy HOMO – electrons easier removed – easier oxidized

11.

J. Conradie, Electro Chim. Acta 110 (2013) 718.

Experimental: Electrochemical oxidation 2

Rh Fc

y = 7.826x + 2.710

R2 = 0.963

2

3

4

5

6

0.0 0.1 0.2 0.3 0.4 0.5

E pa(Rh) / V

1+ 2

(Go

rdy

scal

e)

y = 8.053x + 2.193

R2 = 0.954

2

3

4

5

6

0.0 0.1 0.2 0.3 0.4 0.5

E 0/(Fc) / V

1+ 2

(G

ord

y sc

ale)

more electron donating

O

FcO

RhIII

R

O

R'O

RhI

R

O

R'O

RhIII

R

- 2e-

- e-+ e-

+

2+

3+

For R' = Fc

12.

CV data from: Conradie J. and Swarts J.C., Dalton Trans., 2011, 40, 5844-5851

DFT and Electrochemical oxidation 2

LUMO

HOMO

HOMO-1

• First oxidation: 2e- from HOMO (RhI to RhIII)

• Second oxidation: e- from HOMO-1 (Fc to Fc+)

-2e- -e-

O

FcO

RhIII

R

O

R'O

RhI

R

O

R'O

RhIII

R

- 2e-

- e-+ e-

+

2+

3+

For R' = Fc

CV data from: Conradie J. and Swarts J.C., Dalton Trans., 2011, 40, 5844-5851DFT: von Eschwege, K.G. and Conradie, J., S. Afr. J. Chem., 2011, 64, 203-209.

13.

DFT and Electrochemical oxidation 2

LUMO

HOMO

HOMO-1

• First oxidation: 2e- from HOMO (RhI to RhIII)

• Second oxidation: e- from HOMO-1 (Fc to Fc+)

-2e- -e-

O

FcO

RhIII

R

O

R'O

RhI

R

O

R'O

RhIII

R

- 2e-

- e-+ e-

+

2+

3+

For R' = Fc

higher energy HOMO – electrons easier removed – easier oxidized

14.

DFT and Electrochemical oxidation 3

O

R'

O

RhI

R

CO

P(OCH2)3CCH3

O

R'O

RhIII

R

CO

P(OCH2)3CCH3

- 2e-

2+

higher energy HOMOelectrons easier removed

easier oxidized

Erasmus, J.J.C. and Conradie, J., Dalton Transactions, 2013, 42, 8655–8666.

15.

DFT and Electrochemical oxidation 4

O

R'O

RhI

R

CO

PPh3

O

R'

O

RhIII

R

CO

PPh3

- 2e-

2+

Ferreira, H., Conradie, M.M. and Conradie, J., Electrochim. Acta, 2013, 113, 519-526.

higher energy HOMOelectrons easier removed

easier oxidized

16.

DFT and Electrochemical oxidation 5

CV data from: Conradie, J., et. al., Inorg. Chim. Acta., 358, 2005, 2530-2542.

O

FcO

RhI

R

CO

CO

O

Fc

O

RhI

R

CO

CO

O

FcO

RhIII

R

CO

CO

+

+ e- - e-

- 2e-

+

1+

3+

• HOMO on ferrocene

• First oxidation: e- from HOMO (Fc to Fc+)

17.

DFT and Electrochemical oxidation 5

CV data from: Conradie, J., et. al., Inorg. Chim. Acta., 358, 2005, 2530-2542.

O

FcO

RhI

R

CO

CO

O

Fc

O

RhI

R

CO

CO

O

FcO

RhIII

R

CO

CO

+

+ e- - e-

- 2e-

+

1+

3+

• HOMO on ferrocene

• First oxidation: e- from HOMO (Fc to Fc+)

18.

DFT and Electrochemical oxidation 5

CV data from: Conradie, J., et. al., Inorg. Chim. Acta., 358, 2005, 2530-2542.

higher energy HOMOelectrons easier removed

easier oxidized

O

FcO

RhI

R

CO

CO

O

Fc

O

RhI

R

CO

CO

O

FcO

RhIII

R

CO

CO

+

+ e- - e-

- 2e-

+

1+

3+

19.

DFT and Electrochemical oxidation: Summary20.

Experimental: Substitution reactions

O

R'

O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3O

R'O

RhI

R

CO

COO

R'O

RhI

R

CO

PR3

PX3 P(OPh)3

2CO

PX3 = P(OCH2)3CCH3PX3 = PPh3

21.

Experimental: Substitution reactions

• Experimental1 V# and large negative S#: – associative mechanism involving the formation of a 5-c species.

• The FMO Theory simplifies reactions to interactions between frontier orbitals. 1 J.G. Leipoldt, E.C. Steynberg, R. van Eldik, Inorg. Chem. 26 (1987) 3068.

O

R'

O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3O

R'O

RhI

R

CO

COO

R'O

RhI

R

CO

PX3

N

N

N

N

Rh

+

PX3 P(OPh)3

2CO

PX3 = P(OCH2)3CCH3PX3 = PPh3 substitution 3 substitution 1

substitution 2

22.

Experimental and DFT: Substitution reaction 1

k2 from J.G. Leipoldt, G.J. Lamprecht and E.C. Steinberg, J. Organomet. Chem. 397 (1990) 239DFT from Conradie, J. Inorg. Chim. Acta, 2013, 406, 211-216.

• DFT calculated TS:– Associative mechanism– 5-coordinate TS – Rh is electron acceptor (electrophile)– electron withdrawing groups stabilize TS, more reactive

O

R'O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3

P(OPh)3

HOMOP(OPh)3

HOMORh()(cod)

TS

23.

Experimental and DFT: Substitution reaction 1

y = -0.125x - 3.728

R2 = 0.979

-5.0-4.9-4.8-4.7-4.6-4.5-4.4-4.3-4.2-4.1-4.0

0 5 10

lnk 2

EH

OM

O(c

alc)

/ eV

k2 from J.G. Leipoldt, G.J. Lamprecht and E.C. Steinberg, J. Organomet. Chem. 397 (1990) 239DFT from Conradie, J. Inorg. Chim. Acta, 2013, 406, 211-216.

• DFT calculated TS:– Associative mechanism– 5-coordinate TS – Rh is electron acceptor (electrophile)– electron withdrawing groups stabilize TS, more reactive

lower energy HOMOelectrons easier accepted

larger substitution k

O

R'O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3

P(OPh)3

24.

Experimental and DFT: Substitution reaction 2

k2 from J.G. Leipoldt and E. C. Grobler, Trans. Met. Chem. 11 (1986) 110 and T.G. Vosloo, W.C. Du Plessis, J.C. Swarts, Inorg. Chim. Acta 331 (2002) 188.DFT from Conradie, J. J. Organomet. Chem. 2012, 719, 8-13

y = -0.074x - 3.963

R2 = 0.978

-5.0

-4.8

-4.6

-4.4

-4.2

-4.0

0 5 10 15

lnk 2E

HO

MO(c

alc)

/ e

V

O

R'O

RhI

R

N

N

N

N

Rh

+

lower energy HOMOelectrons easier accepted

larger substitution k

25.

Experimental and DFT: Substitution reaction 3

k2 from J.G. Leipoldt, S.S. Basson, J.J.J. Schlebush and, E.C. Grobler Inorg. Chim. Acta., 1982, 62, 113–115.DFT from Conradie, S. Afr. J. Chem; 2013, 66, 54-59

O

R'O

RhI

R

O

R'O

RhI

R

CO

CO

lower energy HOMOelectrons easier accepted

larger substitution k

26.

Experimental: Oxidative addition

chemical oxidation 2

and 3

chemical oxidation 1

O

R'

O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3O

R'O

RhI

R

CO

COO

R'O

RhI

R

CO

PR3

P(OPh)3PX3

2CO

PX3 = P(OCH2)3CCH3PX3 = PPh3

CH3I

O

R'O

RhIII

CO

PX3

R

CH3

I

CH3I

O

R'O

RhIII

P(OPh)3

P(OPh)3R

CH3

I

27.

M.M. Conradie, J. Conradie, J. Organomet. Chem. 695 (2010) 2126.

Experimental and DFT: Oxidative addition 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3

O

RO

RhP(OPh)3

R'

CH3

I

P(OPh)3

+CH3Ik2

• DFT calculated TS:– Associative mechanism

28.

M.M. Conradie, J. Conradie, J. Organomet. Chem. 695 (2010) 2126.

Experimental and DFT: Oxidative addition 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3

O

RO

RhP(OPh)3

R'

CH3

I

P(OPh)3

+CH3Ik2

• DFT calculated TS:– Associative mechanism

29.

M.M. Conradie, J. Conradie, J. Organomet. Chem. 695 (2010) 2126.

Experimental and DFT: Oxidative addition 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3

O

RO

RhP(OPh)3

R'

CH3

I

P(OPh)3

+CH3Ik2

• DFT calculated TS:– Associative mechanism– Rh nucleophile– electron donating groups makes Rh more electron rich,

i.e more reactive towards o.a.

higher energy HOMOelectrons easier donated

larger oxidative addition k

29.

more electron donating

Rh(I) easier oxidized to Rh(III)

k2 from: G.J. Van Zyl, G.J. Lamprecht, J.G. Leipoldt, T.W. Swaddle, Inorg. Chim. Acta 143 (1988) 223-227M.M. Conradie, J.J.C. Erasmus, J. Conradie, Polyhedron 30 (2011) 2345.DFT from Conradie, J., Electrochimica Acta; 2013, 110, 718-725

Experimental and DFT: Oxidative addition 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3

O

RO

RhP(OPh)3

R'

CH3

I

P(OPh)3

+CH3Ik2

higher energy HOMOelectrons easier donated

larger oxidative addition k

30.

Experimental and DFT: Oxidative addition 2

O

RO

RhCO

R'

CH3

I

P(OCH2)3CCH3

O

R'

O

RhI

R

CO

P(OCH2)3CCH3

+CH3Ik2

Erasmus, J.J.C. and Conradie, J., Inorg. Chim. Acta; 2011, 375, 128-134 Erasmus, J.J.C. and Conradie, J., Cent. Eur. J. Chem. 2012, 10(1) 256-566. Erasmus, J.J.C., Conradie, M.M. and Conradie, J., Reac. Kinet. Cat. Lett. 2012, 105(2) 233-249. Erasmus, J.J.C. and Conradie, J., Dalton Transactions, 2013, 42, 8655–8666.

more electron donating

Rh(I) easier oxidized to Rh(III)

higher energy HOMOelectrons easier donated

larger oxidative addition k

31.

2

Experimental and DFT: Oxidative addition 3

O

RO

RhCO

R'

CH3

I

PPh3

O

R'O

RhI

R

CO

PPh3

+CH3Ik2

more electron donating

Rh(I) easier oxidized to Rh(III)

higher energy HOMOelectrons easier donated

larger oxidative addition kk2 from:Basson, S. S.; Leipoldt, J. G.; Roodt, A.; Venter, J. A.; van der Walt, T. J. Inorg. Chim. Acta, 1986, 119, 35.Conradie, J., Lamprecht, G.J., Roodt, A. and Swarts, J.C. Polyhedron, 23, 2007, 5075-5087.Conradie, M.M. and Conradie, J. Inorg. Chim. Acta., 2008, 361, 208-218 and 2008, 361, 2285-2295.Stuurman, N.F. and Conradie, J. J Organomet. Chem., 2009, 694, 259-268.Conradie, J. and Swarts, J.C. Organometallics, 2009, 28 (4), 1018-1026.DFT Conradie, J., unpublished

32.

Experimental and DFT: Summary kinetics33.

• The stability/reactivity of the HOMO of [Rh(RCOCHCOR')(XY)] complexes is related to the electronic influence of R and R' on Rh – more electron donating, higher HOMO energy

• The energy of the HOMO of [Rh(RCOCHCOR')(XY)] relates to: – experimental electrochemical oxidation potential– experimental substitution kinetic rate constants – experimental oxidative addition kinetic rate constants

• Close correlation between the experimental and the theoretical descriptors enable the design of related rhodium complexes with a particular reactivity.

Conclusion

O

R'O

RhI

R

X

Y

34.

The Chemistry Department at the UFSfor available facilities

HPC Warehouse Facility of the UFS for computational facilities

The National Research Foundationfor financial support

CTCC and the University of Tromsøfor computational facilities

+27(0)51 401 2194 | ConradJ@ufs.ac.za | www.ufs.ac.za

Experimental: Chemical- and Electrochemical oxidation and Substitution reactions

substitution 1 substitution 2

substitution 3chemical

oxidation 1 and 2

chemical oxidation 3

electrochemical oxidation 1

electrochemical oxidation 3 and 4

electrochemical oxidation 2

electrochemical oxidation 2

O

R'

O

RhI

R

O

R'O

RhI

R

P(OPh)3

P(OPh)3O

R'O

RhI

R

CO

COO

R'O

RhI

R

CO

PR3

PX3 P(OPh)3

2CO

PX3 = P(OCH2)3CCH3PX3 = PPh3

O

R'O

RhIII

CO

PX3

R

CH3

I

CH3I

N

N

N

N

Rh

+

O

R'O

RhIII

P(OPh)3

P(OPh)3R

CH3

I

CH3I

Experimental parameters related to oxidation potential of [Rh(RCOCHCOR')(P(OPh)3)2] 1 oxidation potential (Epa) of Rh2 kinetic rate constant (k2) of oxidative addition reaction

Calculated parameter related to oxidation potential of [Rh(RCOCHCOR')(P(OPh)3)2] 3 energy of HOMO (EHOMO)4 calculated NPA charge on Rh(P(OPh)3)2

Parameters used to describe electron donating power (RCOCHCOR’)

5 group electronegativity () of R and R’ groups6 Hammett values (meta) of R and R’ groups7 pKa of the -diketone (RCOCH2COR’)

Empirical relationship describing redox potential 8 Lever ligand parameter Eredox (vs. SHE) = SM X ΣEL + IM

(ΣEL=sum of the values of the ligand EL parameter for all the ligands )

DFT and Electrochemical oxidation 1

O

R'O

RhI

R

P(OPh)3

P(OPh)3