Iodomanganesecorrole - A stable MnIV-I species

Article abstract of DOI:10.1039/b700411g

The first compound with a Mn^IV-I bond has successfully been prepared by oxidation of a manganese(iii) corrole with molecular iodine and was structurally characterized by X-ray diffraction. The Royal Society of Chemistry.

Full text of DOI:10.1039/b700411g

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Iodomanganesecorrole – a stable MnIV–I species
Martin Bro¨ring,* Christian Hell and Carsten D. Brandt
Received (in Cambridge, UK) 10th January 2007, Accepted 2nd February 2007
First published as an Advance Article on the web 21st February 2007
DOI: 10.1039/b700411g
The first compound with a MnIV–I bond has successfully been
prepared by oxidation of a manganese(III) corrole with
molecular iodine and was structurally characterized by X-ray
diffraction.
which is isolated in 93% yield.{ The composition C47H51N4MnI of
the new compound was proven by elemental analysis while mass
spectra only show the signal at m/z = 726 for the [M 2 I]+ ion.
Thermally, 2 is surprisingly stable and decomposes only above
265 uC.
A well-established reaction of the halogenide anions Cl2, Br2 and
A suitable crystal for a X-ray crystallographic analysis of 2 was
obtained by slow evaporation of a saturated solution of the
compound in a dichloromethane–n-hexane mixture.{ 2 crystallizes
I
2 is their ready oxidation to the corresponding diatomic halogens
and beyond upon contact with MnIV and other high-valent
manganese species. The oxidative power of a Mn ion, however,
can easily be tuned by binding it to a suitable ligand, and several
isolable chloro- and even bromo complexes of manganese in
higher oxidation states have been obtained in the past by this
approach.1,2 In order to prepare iodomanganese(IV) species an
even larger degree of stabilization of the high oxidation state at the
metal atom would be required. However, suitable ligands are rare,
and examples of respective compounds have not yet appeared in
the scientific literature.
¯
in the triclinic system, space group P1, with two formula units in
the unit cell. Fig. 1 shows the molecular structure of 2 and
summarizes selected data.
The iodo ligand is bound to the manganese(IV) atom in a
˚
distance of 2.6626(4) A. As expected this value is smaller than that
found in a related case for a manganese(III) tetraphenylporphyrin
7
(tpp)MnI with 2.767 A. In addition, the iodo ligand in 2 is slightly
˚
tilted towards the bipyrrolic unit by approximately 5u. The Mn–N
˚
bond lengths are found from 1.9200(18) to 1.9447(18) A with the
two bonds to the N atoms of the bipyrrole fragment being shorter
˚
than the other two. The average Mn–N bond length of 1.932 A,
One such ligand capable of stabilizing high oxidation states is
the tetrapyrrolic macrocycle corrole, which deviates from the
porphyrin by the formal loss of one methine carbon.3 Corroles
have often been employed in recent years in order to stabilize
unusually high oxidation states of manganese like +52b,4 and even
+6.5 As we could show earlier manganese(III) corroles are formed
in an oxidative macrocyclization reaction upon treatment of the
open-chain tetrapyrrole 2,29-bidipyrrin with Mn(OAc)2 and
molecular dioxygen in reasonable yields. The manganese ion in
these complexes is easily oxidized to the +4 oxidation state by e.g.
chromatography on silica with dichloromethane in air.6 As shown
below the stabilizing effect of the corrole macrocycle is in fact
sufficiently strong to prepare even the iodo derivative of a
manganese(IV) corrole.
however, is very similar to those found for two chloro- (1.932 and
3
˚
˚
1.934 A) and the one bromomanganese(IV) corrole (1.925 A)
which had been structurally characterized before. The manganese
˚
atom of 2 is displaced 0.3798(4) A from the least-squares plane
formed by the pyrrole nitrogen atoms and displays a domed
square-pyramidal coordination. This displacement value is much
larger than in the MnIII case of (tpp)MnI, but resembles roughly
those found in other halogenomanganese(IV) corroles (Table 1),
for which only insignificantly smaller value have been reported.
As depicted in Scheme 1, the reaction of the MnIII chelate 16
with a slight excess of molecular iodine in dichloromethane results
in a clean transformation to the iodomanganese(IV) corrole 2
˚
Fig. 1 Molecular structure of 2. Selected bond lengths (A) and angles (u):
Scheme 1 Preparation of iodomanganese(IV) corrole 2 by oxidation of
manganese(III) corrole 1 with molecular iodine.
Mn–I 2.6626(4), Mn–N1 1.9447(18), Mn–N2 1.9200(18), Mn–N3
1.9242(18), Mn–N4 1.9441(18); N1–Mn–I 103.71(6), N2–Mn–I 98.71(6),
N3–Mn–I 99.51(6), N4–Mn–I 102.74(6), N1–Mn–N2 88.00(8), N1–Mn–
N3 155.04(8), N1–Mn–N4 95.61(8), N2–Mn–N3 79.50(8), N2–Mn–N4
156.70(8), N3–Mn–N4 88.01(8).
Fachbereich Chemie, Philipps-Universita¨t Marburg, Hans-Meerwein-
Straße, 35043, Marburg, Germany.
E-mail: Martin.Broering@chemie.uni-marburg.de
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blocks, mp 265 uC. Yield: 79 mg, 93%. Anal. Calc. for C47H51N4MnI
(853.78): C 66.12, H 6.02, N 6.56. Found: C 65.88, H 5.99, N 6.37%. MS
(MALDI): m/z 726 ([M 2 I]+).
Table 1 Selected metrical parameters of halogenomanganese corroles
and porphyrins
a
Mn–Ct(N4) /A
˚
Mn–X/A
˚
{ Crystal data for C47H51N4MnI 2: violet blocks, M = 853.76, triclinic,
Compound
¯
˚
space group P1, a = 10.8280(9), b = 13.8006(11), c = 14.7237(11) A, a =
3
(oec)MnIVCl2a
(tpfc)MnIVCl2b
(tpfc)MnIVBr2b
(oedpc)MnIVI 2
(tpp)MnIIII7
a
2.310
2.312
2.428
2.6626
2.767/2.730
0.437
0.43
0.42
0.3798
0.240/0.251
82.033(1), b = 79.093(1), c = 67.676(1)u, V = 1993.1(3) A , Z = 2, Dc =
˚
1.423 g cm23, m(Mo-Ka) = 11.44 cm21, 37720 reflections collected (1.60 ,
h , 26.37u) at 173(2) K, 8157 independent, that are used in the structure
refinement; R1 = 0.0334 [I . 2s(I)], wR2 = 0.0855 (all data), GOF = 1.094
23
.
˚
for 486 parameters, largest difference peak, hole = 0.930, 20.315 e A
CCDC 633171. For crystallographic data in CIF or other electronic format
see DOI: 10.1039/b700411g
Distance between the Mn ion from the mean plane of the four N
atoms.
1 (a) C. Mukherjee, T. Weyhermu¨ller, K. Wieghardt and P. Chaudhuri,
Dalton Trans., 2006, 2169; (b) W. Adam, C. Mock-Knoblauch,
C. R. Saha-Mo¨ller and M. Herderich, J. Am. Chem. Soc., 2000, 122,
9685; (c) L. Kaustov, M. E. Tal, A. I. Shames and Z. Gross, Inorg.
Chem., 1997, 36, 3503; (d) N. A. Law, T. E. Machonkin, J. P. McGorman,
E. J. Larson, J. W. Kampf and V. L. Pecoraro, J. Chem. Soc., Chem.
Commun., 1995, 2015.
The high degree of substitution – ten out of eleven positions of
the corrole ligand of 2 carry alkyl or aryl substituents – does not
influence the macrocycle conformation to a measurable amount.
An almost planar tetrapyrrole is found with deviations of single
atoms of the C19N4 perimeter from the mean plane of a maximum
2 (a) C. Erben, S. Will and K. M. Kadish, in The Porphyrin Handbook, ed.
K. M. Kadish, K. M. Smith and R. Guilard, Academic Press, San Diego,
CA, 2000, vol. 2, 233; (b) G. Golubkov, J. Bendix, H. B. Gray,
A. Mahammed, I. Goldberg, A. J. DiBilio and Z. Gross, Angew. Chem.,
Int. Ed., 2001, 40, 2132; (c) Z. Ou, C. Erben, M. Autret, S. Will, D. Rosen,
J. Lex, E. Vogel and K. M. Kadish, J. Porphyrins Phthalocyanines, 2005,
9, 398.
3 For recent reviews on corroles, see: (a) D. T. Gryko, Eur. J. Org. Chem.,
2002, 1735; (b) D. T. Gryko, J. P. Fox and D. P. Goldberg, J. Porphyrins
Phthalocyanines, 2004, 8, 1091; (c) S. Nardis, D. Monti and R. Paolesse,
Mini-Rev. Org. Chem., 2005, 2, 355.
4 (a) N. Y. Edwards, R. A. Eikey, M. I. Loring and M. M. Abu-Omar,
Inorg. Chem., 2005, 44, 3700; (b) R. A. Eikey, S. I. Khan and M. M. Abu-
Omar, Angew. Chem., Int. Ed., 2002, 41, 3592.
5 G. Golubkov and Z. Gross, J. Am. Chem. Soc., 2005, 127,
3258.
˚
of 0.190(2) A. The steric congestion is however visible at the phenyl
substituents which are rotated by close to 90u with respect to the
tetrapyrrole, so that the three aromatic moieties of 2 are in
orthogonal arrangements throughout.
In summary we have described the preparation and structural
details for the first iodomanganese(IV) complex and shown, that
the concept of ‘‘stabilizing high oxidation states’’ can apply not
only for the metal ion in question, but also for the stability of
redox sensitive co-ligands.
Notes and references
{ Preparation of 2: Manganese(III) corrole 1 (72.6 mg, 0.1 mmol) and
iodine (13 mg, 0.055 mmol) were stirred together in dichloromethane
(100 ml) for 2 h. Subsequently the solution is concentrated in vacuo to 10 ml
and treated with n-hexane (50 ml), whereupon 2 crystallized in violet
6 M. Bro¨ring and C. Hell, Chem. Commun., 2001, 2336.
7 P. Turner, M. J. Gunter, B. W. Skelton and A. H. White, Aust. J. Chem.,
1998, 51, 835.
1862 | Chem. Commun., 2007, 1861–1862
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