Mononuclear Metal-O2 Complexes~ bearing macrocyclic TMC ligands ~Nam, W et al. Acc. Chem. Res. Early View.

2012. 08. 27. Sonobe (D1)1

Contents
1. Introduction
2. Synthesis & Characterization
2-1. Cr-O2, Ni-O2 complexes
2-2. Mn-O2, Co-O2 complexes
2-3. Fe-O2 complex
3. Reactivity
3-1. Electrophilic oxidation
3-2. Nucleophilic oxidation
4. Summary2

Introduction

transformationofnaturally occuringmolecules

oxidative
metabolism ofxenobiotics

oxidative
phosphoryration

3Introduction
metalloenzymes are well investigatede.g. P450

Ref) I. Schlichting et al. Science 2000, 287, 1615.
4

Introduction
Naphtalene dioxygenaseRef) S. Ramaswamy et al. Science 2003, 299, 1039.

model study of M-O2

We can…
understand the O2 activation mechanisms&apply M-O2 to organic reaction !!
5

Contents
1. Introduction
2. Synthesis & Characterization
2-1. Cr-O2, Ni-O2 complexes
2-2. Mn-O2, Co-O2 complexes
2-3. Fe-O2 complex
3. Reactivity
3-1. Electrophilic oxidation
3-2. Nucleophilic oxidation
4. Summary6

Synthesis of Metal-Superoxo andPeroxo Complexes

JACS, 2010, 132, 5958.

JACS, 2006, 128, 14230.
Nat. Chem. 2009, 1, 568.

7

Cr-O2 complex

8‘End-On’ Cr(III)-Superoxo Complex
characterizationa) UV-vis absorptionspectra&resonance Raman spectra

UV-visrRaman+[Cr(14-TMC)(Cl)][Cr(14-TMC)(O2)(Cl)]+b) ESI-MS analysis

16+18+

16O2[Cr(14-TMC)( O2)(Cl)]

18O2[Cr(14-TMC)( O2)(Cl)]O-O stretching vibration 16 -18 = 66 cm-1 (calculated 16 -18 = 67 cm-1)[CrIII(14-TMC)(O2)(Cl)]+ : 1170 cm-1
reported Raman shift of end-on Cr(III)-superoxo complex

PNAS. 2003, 100, 3635.
[Cr(O2)(H2O)5]2+ = 1166 cm-1

reported Raman shift of side-on Cr(III) complex [TptBuCr(pz'H)(O2)]BARF = 1072 cm-1

9

Ni-O2 complex
JACS. 2006, 128, 14230. O bubbling2or[Ni(14-TMC)](OTf)
H2O2 (10 eq.)
blue
Et3N (10 eq.)O2O2 bubbling

Ni-O-O-Ni
redrRaman; 1131 cm-1
Ni2+-superoxo
ESI-MS; 346.1 (calcd. 346.1 )350.0 18O2

[Ni(14-TMC)(O2)]+ XAS (X-ray absorption spectroscopy)
green-brown
8333.9 eV -> characteristic of Ni2+

DFT optimized structure

EXAFS; Ni-O 1.984 Å -> end-on

H2O2 (5 eq.)Nat. Chem. 2009, 1, 568.
Et3N (2 eq.)Ni(ClO4)2..6H2O + 12-TMC[Ni(12-TMC)(CH3CN)]2+
MeCN, 0 oC
purple solid(1.2 eq.)(1.0 eq.) MeCN, reflux
distorted octahedral geometry
MeMe( O-Ni-O= 43.04o)NN
O-O bond length; 1.386(4) ÅNi-O bond length; 1.889 ÅNN
this complex persist several days at 25 oC!!
MeMeX-ray12-TMC[Ni(12-TMC)(O2)]2+green solid

10

side-on Ni(12-TMC)-O2 complexes
characterization

11

DFT calulation of Ni(nTMC)-O2 complexes

12Synthesis of Metal-Superoxo andPeroxo Complexes
Co complex: Inorg. Chem. 2008, 102, 2155.
JACS, 2010, 132, 16977.

Mn complex: ACIE, 2007, 46, 377.
ACIE, 2009, 48, 4150.

13

‘Side-On’ Mn(III)-peroxo Complex
synthesis & characterization (Mn(14-TMC)(O2)-complex
14-TMC (1.0 eq.)
MnCl2 + TMS(CF3SO3)2.2CH3CN

CH3CN
in Glove Box

Mn(CF3SO3)2.2CH3CN(1.2 eq.)

CH3CN
H2O2 (5.0 eq.)
Et3N (2.5 eq.)
CH3CN, rt
30 secMn(14-TMC)(CF3SO3)2.2CH3CN
70% yield.
[Mn(14-TMC)(O2)]+This complex persisted several hour @ 25 oC !
14‘Side-On’ Mn(III)-peroxido Complex
synthesis & characterization (Mn(14-TMC)(O2)-complex
EPR analysis
2+[Mn(tmc)]

g= 2.0[Mn(tmc)(O2)]+

EPR silent !!

(S= 5/2) Mn(II) species
d 4 species; high-spin (S=2) or low-spin (S=1) ??
determination of spin state by HNMR spectroscopic method(Evans method; J. Chem. Soc. 1959, 2003.; J. Chem. Soc. Dalton Trans. 1998, 2927.)

5.4µµBhigh spin state15

‘Side-On’ Mn(III)-peroxido Complex
synthesis & characterization (Mn(13-TMC)(O2)-complex)16

‘Side-On’ Co(III)-peroxo Complex
synthesis & characterization
Co(OTf)2.6H2O + 14-TMC

CH3CN, Ar

H2O2 (5 eq.) Inorg. Chem. 2008, 102, 2155.
Et3N (2.5 eq.)
CoII(TMC)(CH3CN)2+[CoIII(TMC)(O2)]+o
CH3CN, 0 C
peroxo complex

UV-viscomparable to the reported side-on CoIIIN4O2
max = 436 nm
Inorg. Chem. 2004, 43, 7558.
575 nm801 nmESI-MS[Co(14-TMC)(16O2)]+ ; m/z= 347.1[Co(14-TMC)(18O2)]+ ; m/z= 351.1

EPR & NMR
Co(TMC)(CH3CN)2+ ; g= 7.13, 2.15, 1.51

typical high spin (S=3/2) CoII(d7)[CoIII(TMC)(O2)]+high spin (S(S=2)2) or (S(S=0)0) CoIII(d6); EPR silent !!

H2O2 (5 eq.)
Et3N (2.5 eq.)
CoII(TMC)(CH3CN)2+Co(ClO4)2.6H2O + 12/13-TMC
CH3CN, Ar
CH3CN, 0 oC

JACS, 2010, 132, 16977.
[CoIII(TMC)(O2)]+
peroxo complex

O-O length; 1.438(9) Å (12-TMC)
1.438(4) Å (13-TMC)
Co-O length; 1.866 Å1.856 Å14-TMC-Ni-peoxo;1.386 Å
12/13-TMC-Co; 1.866 Å

12-TMC

13-TMC

12-TMC-Co; 1.889 ÅCoO2 angle ; 45.36o
45.16o17

XAS analysis‘Side-On’ Co(III)-peroxo Complex
synthesis & characterization

rising-edge
7721 eV

7710.1 eV> pre-edge (7710.1 eV)
reflects ligand-field strength> rising-edge (7721 eV)
reflects the charge at the absorbing metal
center -> typical energy for Co3+
> EXAFS
paremeter of both of the complexes are ingood agreement with the crystal structure.

UV-vis[Co(12-TMC)(O[Co(C)(O2)]+max = 350 nm
560 nmshoulders at ~ 500, ~ 700 nm[Co(13-TMC)(O2)]+
max = 348 nm
562 nmshoulders at ~ 500, ~ 710 nm
rRaman (442 nm)
16 18- ; 24 cm-1 = Co-O

ESI-MS[[Co(12-TMC)(()(16O2)]+ ; 319.1 ((calcd 319.2))[Co(12-TMC)(18O2)]+ ; 323.1 (calcd 323.2)[Co(13-TMC)(16O2)]+ ; 333.1 (calcd 333.2)[Co(13-TMC)(18O2)]+ ; 337.1 (calcd 337.3)

Co(III)-O2 complexes exist as superoxo
complexes in solid & solution state.
16-18 ; 22 cm-1 = Co-O

16O218O2-18 ;57 cm-1 = O-O
16[Co(12-TMC)(O2)]+-18 ;56 cm-1 = O-O
16[Co(13-TMC)(O2)]+18

Co-(14-TMC)(O2) is really side-on??
XAS

DFT calculation[Co(12-TMC)(O2)]7709.2 eV

7710.1 eV[Co(12-TMC)(O2)]+[Co(12-TMC)(CH3CN)]

2+7709.3 eV[Co(14-TMC)(O2)]7710.1 eV[Co(14-TMC)(O2)]+2+[ Co(14-TMC)(CH3CN)]

14-TMC and 12-TMC complexes show Co

14-TMC and 12-TMC
complexes are side-on

3+DFT calculation

8331.6 eV
8332.3 eV

11.5 kcal/molhigher[Ni(14-TMC)(O2)][Ni(12-TMC)(O2)]

++Ni
Ni

2+3+19Synthesis of Metal-Superoxo andPeroxo Complexes

Fe complex:
Science 2003, 299, 1038.
Chem. Commun., 2005, 4529.
JACS, 2010, 132, 10668.
Nature 2011, 478, 502.

20

Fe=O Complex
syntheis & charactrization

Science 2003, 299, 1038.

X-ray
UV-vis ; λmax= 820 nm
ESI-MS ; obs 476.9[Fe(IV)(O)(14-TMC)(OTf)] +rRaman ;16O2: 834 cm-1
18
O2: 800 cm-1

[Fe(III)O(L)]2+21

Fe=O & Fe-O2 Complexes
syntheis & charactrization
Chem. Commun., 2005, 4529.

UV-vis; 750 nm
ESI-MS; found 344.1
calculated 344.1
18
O-labeled complex; 348.1
X-band EPR; typical of a high-spin (S=5/2)
Fe(III) species
22

Fe=O & Fe-O2 Complexes
syntheis & charactrization (dioxygen activation)
JACS, 2005, 127, 4178.
JACS, 2009, 131, 13910.

23

Fe=O & Fe-O2 Complexes
syntheis & charactrization
JACS, 2010, 132, 10668.

KIE value; 6.3

24

Fe=O & Fe-O2 Complexes
syntheis & charactrization Nature 2011, 478, 502.
Et3N (2.0 eq.)

Fe(TMC)(OTf)2 + H2O2o(5.0 eq.) CF3CH2OH, 0 C

first report of Fe(III) peroxo structurebond length
O-O ; 1.463(6) ÅFe-O ; 1.910 Ålonger than those of(TMC)-Fe-peroxo complexes.
geometry
all n-Me groups point tothe same side of the peroxo
moiety, as observed inother MIII-peroxo complexes.
No axial ligand binds toFe trans to the peroxo ligand.

Uv-vis (stopped-flow)[Fe(TMC)(O2)]+
UV-visO
III(L)FeOH
t1/2= 60 min(L)FeIIIOO(L)FeIV OO
III(L)FeOH(L)FeIIIOO

782 nm immediately dissapearedbut 526 nm gradualy appeared.

25

Fe=O & Fe-O2 Complexes
charactrization of Fe-OOH
EPR

first shell EXAFS
g= 6.8, 5.2, 1.96

Fe K pre-edge energy and intensity fit values

Fe-O

16O

18

O

O-O

Raman spectrum
O-O stretch ( max= 868 cm-1) of TMC-Fe-OOH is higher than otherhigh-spin FeIII-OOH(R) complexes and much higher than low-spin
FeIII-OOH complexes.
cf) high-spin complex:[Fe(H2bppa)(OOH)]2+ ( max= 830 cm-1)
Inorg. Chem. 2002, 41, 616.
low-spin complex: [Fe(N4Py)(OOH)]2+ ( max= 790 cm-1)
JACS. 2002, 124, 10810.
-1OH
Fe-O stretch ( max= 658 cm ) is higherOthan six-cordinate high-spin complex
NN( max= 621 cm-1), indicating the absence
Feof trans-axial ligand.

NN

high-spin (S=5/2)
FeIII species

26

Fe=O & Fe-O2 Complexes
formong Fe(IV)=O from Fe-OOH

If Fe(IV)=O were in fact product of 1ereduction of Fe(V)=O, the amount ofFe(IV)=O was decrease due to thefast reaction between the highly
reactive Fe(V)=O and the substrates.

27

3. Reactivity28Electrophilic Reaction
with Cr-superoxo/C-H activation
JACS, 2010, 132, 5958.

29Electrophilic Reaction
with Cr-superoxo/O-H activation
NO
CrNO
N

NIII

CrN

NOH
t

Bu

Chem. Sci. 2011, 2, 2057.

OHN

III

NO

t

Bu
substratest

Bu

Cr-O2; pseudo-first order decay & its conctants was dependent on[substrate]. second-order rate constants were determined.
t
Bu (k2= 4.7 x 10-1 ` -40 oC)

O30

NNOO
Ni

Electrophilic Reaction
JACS, 2006, 128, 14230.
with Ni(14-TMC)-O2OH

NN

IINNiNN

PPh3Ph3P OIIN

when Ni-18O2 was used, 18O=PPh3 was obtained.
source of O is Ni-O2
DFT calculation

second-order rate constantk = 6.5 X 10-3 M-1s-1 at 0 oC

Chem. Commun. 2011, 47, 10674.

Eyring analysis

Ni-peroxo complex can oxidaze PPh3, XA, CHD.

H = 6.8 kcal/mol
S = -44 cal mol-1K-1
G = 18.8 kcal

31

O2 transfer reaction
with Ni(12-TMC)-O2

Nat. Chem. 2009, 1, 568.

Mn-O2

Ni-O2

spectral evidence for an intermolecularO2 transfer from N-O2 to Mn.

32

3. Reactivity

33Deformylation(oxidative nucleophilic addition)

MeMeH

YO2-PPAOY2-PPA

Hammet plot; 2-PPA= +1.734

Deformylation
axial ligand effect35

Deformylation
axial ligand effect36

Deformylation
axial ligand effect37

Summary• M-O2 complexes have been synthesized & characterized.
• The coordination mode of O2 are affected by some factors.
(e.g. ring size of ligand; Ni, pH; Fe-O2)• M-O2 reactivity
end-on complexes -> electrophilic oxidation
side-on complexes -> nucleophilic oxidation
catalytic reaction side-on Fe-O2(TON~3)
nucleophilicity is also affected by ring
size & axial ligand
38

Summary of M-O2 & its physical properties

39