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Stereochemistry of 5-and 6-coordinate high-spin manganese(III) porphyrins and their structural analogues
INORG.
NUCL.
CHEM. LETTERS
Vol.
11,
pp.
505-509,
1975.
Pergamon
Press. Printed
in
Great
Britain.
STEREOCHEMISTRY OF 5-AND 6-COORDINATE HIGH-SPIN MANGANESE(Ill) PORPHYRINS AND THEIR STRUCTURAL ANALOGUES Victor W. Day , B. Ray Stults, Emmett L. Tasset, Robert S. Marianelli Department of Chemistry University of Nebraska Lincoln, Nebraska 68508 and Laurence J. Boucher Department of Chemistry Carnegie-Mellon University Pittsburgh, Pennsylvania 15213 (Received10March1975)
The critical roles played by many biological macromolecules which incorporate metalloporphyrins (or the related corrins) as prosthetic groups have stimulated considerable interest recently in understanding the interplay and relative importance of the various components of metalloporphyrins in determining their biological mode of action.
To this end, a series of
chemical and solid-state structural studies for Mn(III) porphyrins and related compounds were recently begun in this laboratory.
Preliminary
results which dramatically demonstrate the stereochemical effect of having an occupied dz2 orbital in octahedral high-spin Mn(III) complexes (including a Mn(III) porphyrin) have already appeared (I).
The present work describes
solid-state structural studies of two 5-coordinate high-spin Mn(III) complexes which demonstrate the stereochemical effect of removing a neutral Lewis base (methanol) from the octahedral coordination polyhedron of Mn(TPP)(N3)(CH30H ) and the effect of replacing the dianionic ~,B,y,~-tetraphenylporphinato(TPP) macrocycle with a somewhat less constrained dianionic N, N'-ethylynebisacetylacetoniminato (acyn) Schiff base ligand (2). Two different crystalline forms of Mn(TPP)(N3) were obtained by 505
506
5- and 6-Coordinate High-spin Manganese(Ill) Polphyrins
recrystallizing
Mn(TPP)(N3)(CH3OH).CH30H
The major product,
an unsolvated
structure determination
Vol. 11 No 7/8
from benzene/heptane
solution.
form of Mn(TPP)(N3) , was shown by a
to be statistically
disordered in the solid state
with the manganese atom coincident with or very near the crystallographic inversion
center at the origin of a monoclinic
= 12.612(3),
! = 13.193(2)~,
unit cell with a = 13.272(3),
$ = 128.50(1) ° , and Z = 2 (space group,
P21/c ; R = 0.114 for 3567 reflections).
The structure of the minor product,
a benzene solvate of Mn(TPP)(N3) , was also determined and is reported at this time with the structure of Mn(acyn)Cl. molecules
approximate
the coordination
The coordination
idealized C4v geometry.
polyhedron
for Mn(TPP)(N3)
polyhedra of both
Whereas the "square" base of
is S4-ruffled with each pyrolle
nitrogen atom being displaced by 0.037~ from the 4-atom mean plane, atoms comprising the "square" base for Mn(acyn)Cl 0.002~.
The Mn(acyn)Cl molecule approximates
the four
are coplanar to within
quite closely its maximum
possible symmetry of C -m. s Three-dimensional
diffraction data on both compounds were collected
on a computer-controlled Nb-filtered
four-circle
or graphite monochromated
Syntex PI Autodiffractometer
using
MoK~ radiation and e-20 scans.
Both structures were solved using the heavy-atom technique and the structural parameters have been refined to convergence full-matrix parameters
least-squares
in cycles of unit-weighted
refinement which employed isotropic thermal
for all hydrogen atoms but was otherwise anisotropic.
Crystal data and refinement Mn(N4C44H28)(N3).C6H6,
results are as follows:
Mn(TPP)(N3).C6~ ,
monoclinic, ~ = 17.514(3), ~ = 11.089(3), ~ =
21.881(3)~,
B = 113.62(1) ° , Z = 4; space group P21/c; R = 0.050 for 3979
independent
reflections having 2 @MoK~-<43° and I>o(I)
continuing with a data set twice as large).
(refinement
Mn(acyn)Cl,
monoclinic, ~ = 7.220(i),b = 24.350(3), ~ = 8.067(i)~, space group P21/n ; R = 0.034 for 1491 independent
is
Mn(O2N2CI2HI6)CI,
~ = 101.37(1) ° , Z = 4;
reflections having 2eMoK~
Vol. 11, No. 7/8
5- and 6-Coordinate High-spin Manganese(Ill) Porphyrins
507
(b)
o
Oa
N
~
(c)
FIG. 1
Perspective ORTEP molecular drawings of: Mn(TPP)(Nq)(CHqOH), (a); ~ ( T P P ) ( N 3 ) , (b); and Mn(acyn)(Cl), (c); all fionhydrogen atoms are represented by thermal vibration ellipsoids which .encompass 50% of their electron density. For clarity, hydrogen atoms in (b) and (c) are represented by arbitrarily small spheres which in no way represent their true thermal motion. Solvent molecules of crystallization in (a) and (b) are not included.
<43 ° and l>o(I)(refinement is continuing with a data set four times as large). ORTEP molecular drawings of Mn(TPP) (N3) (CH30H) , Mn(TPP) (N3) , and Mn (acyn)Cl are shown in Figure I.
Comparisons of pertinent stereochemical
parameters for these compounds with those of two different crystalline forms of 5-coordinate Mn(TPP)CI (3,4) are given in Table I.
Conversion of
6-coordinate Mn(TPP)(N3)(CH3OH ) into 5-coordinate Mn(TPP)(N 3) by removal of the coordinated methanol has resulted in a shorter (and more "normal") Mn-toazide bond and a larger (by 0.183~) displacement of the Mn atom from the mean plane of the 24-atom porphine skeleton.
The data in Table I indicate
508
5- anal 6-Coordinate High-spin Manganese(Ill) Porphyrins
Vol. 11, No. 7/8
TABLE I Stereochemical Parameters of Coordination Polyhedron for Square-Pyramidal and Octahedral High-Spin Manganese(Ill) Porphyrins and Related Complexes Compound
Bond a
Average Length,~ b
&M~ ~c
Mn (TPP) (N3) (CH30H)
Mn-N
2.031(7,10,15)
0.085
i
0.234
d
0.273
3
0.26
4
0.343
d
Mn(TPP)(N3)'C6H 6
Mn(TPP)CI'CH3COCH 3
Mn(TPP)CI.CHCI 3
Mn(acyn)Cl
Reference
P Mn-N a
2.176(9)
Mn-O
2.329(8)
M~-N
2.005(3,6,9)
P Mn-N a
2. 045 (4)
Mm-N
2.008(-,13,16)
P Mn-CI
2.363
Mn-Np
2.02
Mn-CI
2.38
Mn-O
1.901(3,5,5)
Mm-N
1.971(3,7,7)
Mn-CI
2.379(1)
aThe four crystallographically independent pyrolle nitrogen atoms in each porphyrin complex are designated colle~tively as N . Coordinated azide nitrogen atoms are designated as N a . -The first n~mber in parentheses following a given bond length is the r.m.s, estimated standard deviation of an individual datum. The second and third numbers, when included, are the average and maximum deviations from the average value, respectively, cThis number represents the displacement of th~ metal from the "square" base or girdle of the coordination polyhedron. This work.
that a value of 2.38~ can probably be assigned to apical Mn-CI bonds in sterically non-hindered 5-co0rdinate Mn(lll) complexes.
A value of ~0.25~
for the displacement of the Mn atom from the mean plane of four pyrolle nitrogen atoms of the porphine skeleton seems to be a standard value for sterically non-hindered 5-coordinate Mn(lll) porphyrins.
A somewhat larger
displacement of the metal atom can be accomplished with ligands which are less constrained than the porphyrin macrocycle.
The porphine skeletons of
Vol. 11, No. 7/8
5- and 6-Coordinate High-spin Manganese(Ill) Porphyrins
509
all three 5-coordinate porphyrin complexes are quite nonplanar, being ruffled in accord with approximate S 4 symmetry.
The acyn ligand is even less planar
with both of its essentially planar (to within 0.02~) 7-atom acetylaeetonimine (ONCs) skeletal groupings being folded along the O...N polyhedral edges by 15.2 ° and 19.2 ° away from the CI atom and out of the plane of the "square" base.
With the 4-atom ethylyne (N-C=C-N) grouping being similarly folded
along the N..-N polyhedral edge by 9.0 ° toward the CI atom, the distortion of the acyn ligand from planarity is seen to have a pattern similar to the S4 ruffling of porphine skeletons.
The rigid stereoehemical requirements of the
porphyrin macrocycle are therefore seen to produce coordination polyhedra with unique stereochemical parameters for 5-coordinate high-spin Mm(lll) porphyrin complexes.
ACKNOWLEDGEMENTS
We thank the University of Nebraska Computing Center for a generous allocation of computer time and the donors of the Petroleum Research Fund administered by the American Chemical Society for partial financial support.
REFERENCES
1.
V. W. Day, B. R. Stults, E. L. Tasset, R. O. Day, and R. S. Marianelli, J. Amer. Chem. Soc., 96, 2650 (1974); B. R. Stults, V. W. Day, E. L. Tasset, and R. S. Marianelli, Inor$. Nucl. Chem. Letters, 9, 1259 (1973).
2.
L. J. Boucher and V. W. Day, submitted for publication.
3.
B. M. Chen and A. Tulinsky, unpublished data; B. M. Chen, Ph.D. Thesis, Michigan State University, 1970.
4.
L. J. Radonovich and J. L. Hoard, private communication.
NUCL.
CHEM. LETTERS
Vol.
11,
pp.
505-509,
1975.
Pergamon
Press. Printed
in
Great
Britain.
STEREOCHEMISTRY OF 5-AND 6-COORDINATE HIGH-SPIN MANGANESE(Ill) PORPHYRINS AND THEIR STRUCTURAL ANALOGUES Victor W. Day , B. Ray Stults, Emmett L. Tasset, Robert S. Marianelli Department of Chemistry University of Nebraska Lincoln, Nebraska 68508 and Laurence J. Boucher Department of Chemistry Carnegie-Mellon University Pittsburgh, Pennsylvania 15213 (Received10March1975)
The critical roles played by many biological macromolecules which incorporate metalloporphyrins (or the related corrins) as prosthetic groups have stimulated considerable interest recently in understanding the interplay and relative importance of the various components of metalloporphyrins in determining their biological mode of action.
To this end, a series of
chemical and solid-state structural studies for Mn(III) porphyrins and related compounds were recently begun in this laboratory.
Preliminary
results which dramatically demonstrate the stereochemical effect of having an occupied dz2 orbital in octahedral high-spin Mn(III) complexes (including a Mn(III) porphyrin) have already appeared (I).
The present work describes
solid-state structural studies of two 5-coordinate high-spin Mn(III) complexes which demonstrate the stereochemical effect of removing a neutral Lewis base (methanol) from the octahedral coordination polyhedron of Mn(TPP)(N3)(CH30H ) and the effect of replacing the dianionic ~,B,y,~-tetraphenylporphinato(TPP) macrocycle with a somewhat less constrained dianionic N, N'-ethylynebisacetylacetoniminato (acyn) Schiff base ligand (2). Two different crystalline forms of Mn(TPP)(N3) were obtained by 505
506
5- and 6-Coordinate High-spin Manganese(Ill) Polphyrins
recrystallizing
Mn(TPP)(N3)(CH3OH).CH30H
The major product,
an unsolvated
structure determination
Vol. 11 No 7/8
from benzene/heptane
solution.
form of Mn(TPP)(N3) , was shown by a
to be statistically
disordered in the solid state
with the manganese atom coincident with or very near the crystallographic inversion
center at the origin of a monoclinic
= 12.612(3),
! = 13.193(2)~,
unit cell with a = 13.272(3),
$ = 128.50(1) ° , and Z = 2 (space group,
P21/c ; R = 0.114 for 3567 reflections).
The structure of the minor product,
a benzene solvate of Mn(TPP)(N3) , was also determined and is reported at this time with the structure of Mn(acyn)Cl. molecules
approximate
the coordination
The coordination
idealized C4v geometry.
polyhedron
for Mn(TPP)(N3)
polyhedra of both
Whereas the "square" base of
is S4-ruffled with each pyrolle
nitrogen atom being displaced by 0.037~ from the 4-atom mean plane, atoms comprising the "square" base for Mn(acyn)Cl 0.002~.
The Mn(acyn)Cl molecule approximates
the four
are coplanar to within
quite closely its maximum
possible symmetry of C -m. s Three-dimensional
diffraction data on both compounds were collected
on a computer-controlled Nb-filtered
four-circle
or graphite monochromated
Syntex PI Autodiffractometer
using
MoK~ radiation and e-20 scans.
Both structures were solved using the heavy-atom technique and the structural parameters have been refined to convergence full-matrix parameters
least-squares
in cycles of unit-weighted
refinement which employed isotropic thermal
for all hydrogen atoms but was otherwise anisotropic.
Crystal data and refinement Mn(N4C44H28)(N3).C6H6,
results are as follows:
Mn(TPP)(N3).C6~ ,
monoclinic, ~ = 17.514(3), ~ = 11.089(3), ~ =
21.881(3)~,
B = 113.62(1) ° , Z = 4; space group P21/c; R = 0.050 for 3979
independent
reflections having 2 @MoK~-<43° and I>o(I)
continuing with a data set twice as large).
(refinement
Mn(acyn)Cl,
monoclinic, ~ = 7.220(i),b = 24.350(3), ~ = 8.067(i)~, space group P21/n ; R = 0.034 for 1491 independent
is
Mn(O2N2CI2HI6)CI,
~ = 101.37(1) ° , Z = 4;
reflections having 2eMoK~
Vol. 11, No. 7/8
5- and 6-Coordinate High-spin Manganese(Ill) Porphyrins
507
(b)
o
Oa
N
~
(c)
FIG. 1
Perspective ORTEP molecular drawings of: Mn(TPP)(Nq)(CHqOH), (a); ~ ( T P P ) ( N 3 ) , (b); and Mn(acyn)(Cl), (c); all fionhydrogen atoms are represented by thermal vibration ellipsoids which .encompass 50% of their electron density. For clarity, hydrogen atoms in (b) and (c) are represented by arbitrarily small spheres which in no way represent their true thermal motion. Solvent molecules of crystallization in (a) and (b) are not included.
<43 ° and l>o(I)(refinement is continuing with a data set four times as large). ORTEP molecular drawings of Mn(TPP) (N3) (CH30H) , Mn(TPP) (N3) , and Mn (acyn)Cl are shown in Figure I.
Comparisons of pertinent stereochemical
parameters for these compounds with those of two different crystalline forms of 5-coordinate Mn(TPP)CI (3,4) are given in Table I.
Conversion of
6-coordinate Mn(TPP)(N3)(CH3OH ) into 5-coordinate Mn(TPP)(N 3) by removal of the coordinated methanol has resulted in a shorter (and more "normal") Mn-toazide bond and a larger (by 0.183~) displacement of the Mn atom from the mean plane of the 24-atom porphine skeleton.
The data in Table I indicate
508
5- anal 6-Coordinate High-spin Manganese(Ill) Porphyrins
Vol. 11, No. 7/8
TABLE I Stereochemical Parameters of Coordination Polyhedron for Square-Pyramidal and Octahedral High-Spin Manganese(Ill) Porphyrins and Related Complexes Compound
Bond a
Average Length,~ b
&M~ ~c
Mn (TPP) (N3) (CH30H)
Mn-N
2.031(7,10,15)
0.085
i
0.234
d
0.273
3
0.26
4
0.343
d
Mn(TPP)(N3)'C6H 6
Mn(TPP)CI'CH3COCH 3
Mn(TPP)CI.CHCI 3
Mn(acyn)Cl
Reference
P Mn-N a
2.176(9)
Mn-O
2.329(8)
M~-N
2.005(3,6,9)
P Mn-N a
2. 045 (4)
Mm-N
2.008(-,13,16)
P Mn-CI
2.363
Mn-Np
2.02
Mn-CI
2.38
Mn-O
1.901(3,5,5)
Mm-N
1.971(3,7,7)
Mn-CI
2.379(1)
aThe four crystallographically independent pyrolle nitrogen atoms in each porphyrin complex are designated colle~tively as N . Coordinated azide nitrogen atoms are designated as N a . -The first n~mber in parentheses following a given bond length is the r.m.s, estimated standard deviation of an individual datum. The second and third numbers, when included, are the average and maximum deviations from the average value, respectively, cThis number represents the displacement of th~ metal from the "square" base or girdle of the coordination polyhedron. This work.
that a value of 2.38~ can probably be assigned to apical Mn-CI bonds in sterically non-hindered 5-co0rdinate Mn(lll) complexes.
A value of ~0.25~
for the displacement of the Mn atom from the mean plane of four pyrolle nitrogen atoms of the porphine skeleton seems to be a standard value for sterically non-hindered 5-coordinate Mn(lll) porphyrins.
A somewhat larger
displacement of the metal atom can be accomplished with ligands which are less constrained than the porphyrin macrocycle.
The porphine skeletons of
Vol. 11, No. 7/8
5- and 6-Coordinate High-spin Manganese(Ill) Porphyrins
509
all three 5-coordinate porphyrin complexes are quite nonplanar, being ruffled in accord with approximate S 4 symmetry.
The acyn ligand is even less planar
with both of its essentially planar (to within 0.02~) 7-atom acetylaeetonimine (ONCs) skeletal groupings being folded along the O...N polyhedral edges by 15.2 ° and 19.2 ° away from the CI atom and out of the plane of the "square" base.
With the 4-atom ethylyne (N-C=C-N) grouping being similarly folded
along the N..-N polyhedral edge by 9.0 ° toward the CI atom, the distortion of the acyn ligand from planarity is seen to have a pattern similar to the S4 ruffling of porphine skeletons.
The rigid stereoehemical requirements of the
porphyrin macrocycle are therefore seen to produce coordination polyhedra with unique stereochemical parameters for 5-coordinate high-spin Mm(lll) porphyrin complexes.
ACKNOWLEDGEMENTS
We thank the University of Nebraska Computing Center for a generous allocation of computer time and the donors of the Petroleum Research Fund administered by the American Chemical Society for partial financial support.
REFERENCES
1.
V. W. Day, B. R. Stults, E. L. Tasset, R. O. Day, and R. S. Marianelli, J. Amer. Chem. Soc., 96, 2650 (1974); B. R. Stults, V. W. Day, E. L. Tasset, and R. S. Marianelli, Inor$. Nucl. Chem. Letters, 9, 1259 (1973).
2.
L. J. Boucher and V. W. Day, submitted for publication.
3.
B. M. Chen and A. Tulinsky, unpublished data; B. M. Chen, Ph.D. Thesis, Michigan State University, 1970.
4.
L. J. Radonovich and J. L. Hoard, private communication.