BIOINORGANIC CHEMISTRY A Short Course Second Edition

CYTOCHROME P450 : A MONOOXYGENASE 381

The [Fe IV (O)(TMCS)] + complex was synthesized at 90% yield starting with
[Fe II (TMCS)] + and using one equivalent of m - chloroperbenzoic acid ( m CPBA)
as oxidant in the presence of excess base. The deep blue complex is stable at
− 60 ° C but decays slowly as the temperature is raised. M ö ssbauer data ( ΔEQ =
0.22 mm/s and δ = 0.19 mm/s) support the Fe(IV) oxidation state assignment as
do X - ray absorption spectroscopy experiments. Extended X - ray absorption
fi ne structure (EXAFS) indicates one oxygen atom at 1.70(2) Å , three nitrogen/
oxygen atoms at 2.09(2) Å , one sulfur atom at 2.33(2) Å , and four carbons at
2.95(2) Å. The supposed Fe = O bond distance is longer than that found for other
characterized Fe = O species. For instance, the Fe = O bond distance in PDB:
1DZ9 (Section 7.4.4), believed to contain a Fe IV = O compound I - type moiety is
1.67 Å. The Fe = S distance is signifi cantly shorter than that computed for cyto-
chrome P450 compounds I (2.6 Å ) and II (2.5 Å )^70 but are close to those found
for PDB: 1DZ9. (See Section 7.4.4 and Figure 7.17 .) The researchers found that

Figure 7.23 Reactions of (A) [Fe IV (O)(TMCS)] + and (B) [Fe IV (O)(TMC)] 2+.

N N

N N

FeIV

O

S

+

P

Ph

Ph Ph

PPh 3 = triphenylphosphine

PPh^3

N N

N N

NCCH 3

FeIV

O

PPh^3

P

Ph

Ph

Ph

O

OPPh 3

N N

N N

FeII

2 +

H

H

CH 3 OH solvent

cis-1,2 dihydroanthracene

N.R.

N N

N N

FeIII

OCH 3

S

+

H

H

B

A

2 +

[FeIV(O)(TMCS)]+

TMCS = monoanion of 1-mercaptoethyl-

4,8,11-trimethyl-1,4,8,11-tetraaza

cyclotetradecane

CH 3 OH solvent

[FeIII(TMCS)(OCH 3 )]+

cis-1,2 dihydroanthracene

deep blue

one-electron reduced species

red

+

[FeII(TMC)]2+

N. R.

[FeIV(O)(TMC)]2+

complex 1 complex 2

complex 3