8032
Stereochemistry of Carbonylmetalloporphyrins. The Structure of (Pyridine)(carbonyl)(5,10,15,20tetraphenylporphinato)iron( 11) Shie-Ming Peng and James A. Ibers* Contribution from the Department of Chemistry, Northwestern University, Evanston, Illinois 60201. Received May 17, 1976
Abstract: The six-coordinate carbon monoxide complex of an iron(I1) porphyrin, Fe(TPP)(CO)(Py) ( T P P = 5,10,15,20-tetraphenylporphyrin dianion, Py = pyridine), has been prepared and its structure determined from three-dimensional x-ray diffraction data. The linear ( I 7 9 (2)") Fe-C-0 arrangement found here is to be contrasted with the bent F e - C - 0 arrangements reported for three carbon monoxide hemoproteins. The Fe-C and C - 0 distances are 1.77 (2) and 1.12 (2) A, respectively. The average Fe-N(porphyrin) distance is 2.02 (3) A, somewhat shorter than the Fe-N(Py) distance of 2.10 ( I ) A trans to the C O group in this octahedral complex. The Fe atom is displaced only 0.02 A from the porphyrin N4 plane toward the CO group. The porphyrin core is nearly planar and all bond parameters in the core agree well with those found in other porphyrins. The complex crystallizes with four formula units and eight benzene molecules in the monoclinic space group Clh 5-P2 I/c with a = 13.246 (17), b = 19.555 (26), c = 19.822 (25) A, and p = 105.49 (3)". The final agreement indices on Fo2, based on the leastsquares refinement of 205 variables for 3161 observations (including Foi 5 0), are R = 0.18 and R , = 0.23. The conventional R index on F , for reflections with Fo2 t 3u(Fo2) is 0.090.
Crystallographic studies of several carbon monoxide hemoproteins, for example erythrocruorin,' the bloodworm Glycera dibranchiata, and myoglobin3 have been interpreted in favor of bent Fe-C-0 bonds of approximately 1 3 5 - 1 4 5 O . Insofar as we are aware there are no precedents for this angular arrangement in any transition metal complexes containing terminal CO goups. In view of the utility of model compounds for understanding the bonding of small molecules to hemo p r o t e i n ~and ~ because of the surprising absence of structural studies on model carbon monoxide complexes of iron(I1) porphyrin^,^ the present study of Fe(TPP)(CO)(Py) was undertaken.
Experimental Section Preparation of Fe(TPPXC0XPy). All reactions were carried out under dinitrogen using modified Schlenk tubes. All solvents were thoroughly saturated with dry N2. Tetraphenylporphyrin free base (500 mg) was dissolved in a mixed solvent of 20 ml of pyridine and 50 ml of chloroform. To the solution was quickly added about 130 ml of a saturated solution of iron(l1) acetate in acetic acid, prepared by refluxing iron powder in acetic acid. The mixture was stirred for 2 h at 50-60 "C. Then carbon monoxide was bubbled into the solution for 20 min and the solution was kept at 5 " C overnight under a C O atmosphere to yield lustrous purple crystals of Fe(TPP)(CO)(Py). Anal. Calcd for CsoH33FeN50: C, 77.42; H, 4.26; N, 9.03. Found: C, 78.04; H, 4.26; N , 8.87. Crystallographic Data. Crystals of Fe(TPP)(CO)(Py) more suitable for x-ray study were grown by slow cooling of a saturated benzene solution of Fe(TPP)(CO)(Py) under a C O atmosphere. This procedure yields material of formula Fe(TPP)(CO)(Py).2CsH6. Preliminary precession photographs of the crystals displayed monoclinic symmetry and systematic absences consistent with the centrosymmetric space group C2h 5 - P 2l/c. These photographs also indicated that the crystals are highly mosaic. This mosaicity does not result from loss of solvent of crystallization, as all crystals examined had been sealed under dry nitrogen in capillaries. On the basis of an examination of a number of crystals one was selected as being least mosaic. This crystal, which was mounted with the [loo] direction approximately along the spindle axis, displayed faces of the forms (0 2 11 and { 1 101and had a calculated volume of 0.033 mm3. The lattice parameters, obtained as previously described7 by hand centering 20 reflections in the range 16" < 20 < 25" on a FACS-I diffractometer using Mo K a l radiation (A 0.709 30 A), are a = 13.246 (17) A, b = 19.555 (26) A, and c = 19.822 (25) A, and = 105.49 (3)'. The calculated density, based on four Fe(TPP)(CO)(Py) and eight benzene molecules per unit cell is 1.25 g/cm3 and agrees well with an observed value of 1.24 (2) g/cm3, as measured by flotation in aqueous zinc chloride solution.
Journal of the American Chemical Society
/ 98:25 /
Based on w scans using a narrow source and open counter the width at half height of trial reflections was found to be 0.5 to 1 '. Accordingly, data were collected in shells of 20 by the w-scan method, using graphite monochromatized Mo Ka radiation. The scan range in w was 2.0'. The takeoff angle was 3.2'. A fully open aperture (6 X 6 mm) was positioned 24 cm from the crystal. In order to minimize x-ray exposure of the crystal a step-scan mode was employed, with the 2.0" scan broken up into 40 steps of I-s counting duration each. Background counts of 20-s duration were taken at each end of the scan range. I f a reflection failed to obey the condition I > 3a(I), the peak was rescanned and the background counting time was increased from 20 to 40 s . The ~ results of the two peak scans and separate background counts were summed. In the processing of the data these rescanned reflections were brought to the same scale as singly scanned reflections by division by 2. Data were collected in the range 2 < 20 I35". Beyond 35" there appeared to be less than 10% of the measured reflections statistically observable. During the course of data collection six standards were measured every 100 reflections. The deviations of these standards were all within counting statistics. Thus our initial expectation that the crystals might be x-ray sensitive, based on the known photosensitivity of iron porphyrin carbon monoxide complexes, was unfounded. The data were processed in the usual manner,7 using a value of p of 0.05. Of the 351 9 reflections measured, 3 I61 are unique after exclusion of equivalent reflections and systematically absent reflections and these were used in subsequent calculations. Based on trial calculations employing a linear absorption coefficient of 3.48 cm-l no absorption correction was deemed necessary. Solution and Refinement of Structure. The Fe atom and the atoms of the porphyrin core were located in an origin-removed, sharpened Patterson synthesis. Subsequent refinements and difference Fourier syntheses led to the location of all non-hydrogen atoms. The structure was refined by full-matrix, least-squares techniques. The usual procedures, computer programs, atomic scattering factors, and anomalous terms were employed.x The quantity minimized was Zw(F,* - F,*)l with w = l/a2(Fo2). All the data (including Fo2 < 0) were used. The agreement indices for the refinement on FO2are
R = Z I F o 2 - FC2I/ZFo2 R , = [ Z w ( F o 2- F c 2 ) 2 / 2 ~ F o 4 ] ' / 2
In all of the refinements, the four phenyl rings of the T P P moiety and the two benzene rings were treated as rigid g r o ~ p s All . ~ other individual, non-hydrogen atoms were refined isotropically. The hydrogen atoms were included as a fixed contribution before the last cycle, their positions being idealized assuming a trigonal, planar geometry and using a C-H distance of 0.95 A. Each hydrogen atom was assigned a thermal parameter of 1.O A* greater than the isotropic thermal parameter of the carbon atom to which it is attached. The
December 8. 1976
8033 Table I. Positional and Thermal Parameters for the Nongroup Atoms of Fe(TPP)(C0)(Py).2C,H6 ATOM
X
A
2
V
I , A
2
ATOM
X
2
1
etA
2
FE
2.23792121l
J . 12643 1 1 3 1
0.326071131
2.64171
c5
G.357L1131
0.13314l941
0.1657419Cl
2.771401
0
0.23G111ZI
2.274761751
0.32455173)
6,551371
C6
0.2019113)
0.13003I92l
0.16241 I 8 0 I
2.411381
N1
0.37741111
5.13161177l
0.293511681
1.~21331
c7
0.12111131
0 . 1 3 2 1 9 196)
0.098791841
3.141421
N2
0.162451961
5.12368 ( 7 2 1
0.218701611
2.49131)
C8
0. 112891 121
0.13334 1 871
0,11483 177)
3.011381
N3
3.152431961
0.12056 I 7 1 1
0.34649 ( 6 3 1
2.901301
c9
0.j5331121
0~13046190l
0.19c311771
2.58138l
N4
C.316901971
5.12567 1711
0.422281611
2.521311
Cllj
0.129921931
0.22827 1781
2.57140)
N5
3e242kl13l
0. 21Y431721
3 . 311781771
3.371371
c11
0.12646198l
0.3OO68 I 7 7 1
2.37 1 3 7 1
C
0.2334 1171
~.21711131
0.32311101
5.00 1501
c12
-0.0729113)
0~1258l1Ol
0.34125 I 8 4 1
2.781421
CPVl
0.154Gllrl
-3.~13371961
0.281921881
3.61 145)
C13
-G.J215114I
0.1220110l
0.408201851
3.721441
CPVZ
0.15601181
-L.395JIiZl
0.2C7C I111
4.491631
C14
0. i i 8 9 4 I 1 2 1
0.12041l88)
0.41272(771
2.30 ( 3 6 )
CP13
G.25iZ 1171
-u.ll8~llll
0.282161971
5.56154)
C15
0.16741131
0.11729( 8 9 1
0 . 4 7 4 1 7 1771
2.47139)
CPY4
2.3394 1 1 8 1
-0.;8321131
0.3151112)
4.781701
C16
0.2739 I 1 4 1
0.11779l941
0.478481851
3.161421
CP15
11.33311181
-0.J141112I
0.3291110l
3.971571
C17
C.35631141
0.1156019EI
0.54132 ( e 8 1
5.591471
Cl
5.47r1114l
0.13231101
0.341781891
2.821441
cia
0.44711121
0~11802189l
0 e 52434 I781
2.541401
CZ
11.55161131
J a 135** I981
0.29977051
3.751431
C19
0.4245 I 1 3 1
0.12 307 197 I
0.449831821
3.041411
c3
0.49801131
0.13593 I 9 3 1
0.232131781
2.431411
c20
0.50141121
0.12898190)
0.413661781
2.74(371
c4
0~3892112l
0,13233 1 8 8 1
0.226801791
2.20 (381
-G.D195112I C.lj5211121
a Estimated standard deviations in the least significant figure(s) are given in parentheses in this and all subsequent tables.
Table 11. Derived Parameters for the Rigid Group Atoms of Fe(TPP)(CO)(Py).2C6H6 )TOM
X
1
2
2
891
CPll
0.33656l811
a.
CP12
0.359701951
0.196581591
CP13
0.386751961
0.19775 1571
CP14
G.390671841
0.137371E5l
-0.02946145)
CP15
0.367531961
0.07531 I 5 9 1
CP16
0.34048 1941
CPZl CP22 CP23
1 3 4 0 2 1841
X
ATOM
2
V
0.A
2
0.096901451
4.271471
CP41
0.611591661
0.1300e1831
0.45259151l
2.791431
0.07008 170 I
5.00 ( 5 3 )
CP42
0.66021111
0. ~ l 7 0 8 7 1 5 6 1
0.411443 I 6 9 1
5.081551
0~006901741
6.701591
CP43
0.76331111
0 e 0 7 3 3 1 158 I
0.525621631
5.041521
5,641511
CP44
0.817741661
0.13495184)
0.534971531
4,6614111
-0. 5 0 2 6 4 1 7 0 1
5.951531
CP45
0.7691111l
0 a 19416 I 5 6 1
0 . 5 0 3 1 3 1711
5.85156)
0. ir7363 1 5 7 )
0.06054174)
5.88156)
CP46
6.666ClllI
0.191721591
0.461941631
4.661561
-0.13491 I 6 9 1
0.12970 1951
0.188331521
4 . 2 0 1441
CBl
0.075L6181l
0.3796l12l
0.39631 164)
6.261621
-0.1923
3.069*61611
0.173271691
6.50 I 6 2 1
CB2
0~0291116l
0.43980 176)
0.411131731
8.611741
-0~29601121
0.07123167l
0.13316l741
7.15 1591
CB3
-G.06931161
0.438011821
0.42381170l
9.271131
CP24
-0.34235169)
0,13342 I 9 9 1
O.lG8121551
7.651571
C84
-0.121721821
0.3761 I13 1
0 ~42166 168)
9.441691
CP25
-2.2850
J.
O.i2319(731
9.36 I 6 7 1
CB5
-0.0758(161
0.31589 I 7 8 1
0.406831771
7.91 I 7 6 1
CP26
-2.1812113l
3.19159 1641
J . l E 3 2 9 1751
7.16(601
C86
O.O~ZEll6l
0.31768 I EO I
0.594151721
8.12(681
(131
I131
193731651
CP31
0.134991761
2 . 1 1 9 8 1 I7n1
0.54144140)
3.24 I 3 9 1
CB ' I
0.56640 I 9 9 1
0.4018111l
0.33597 164)
10.98 1741
CP32
5.129271911
0.18219 ( 5 5 )
0.574C1167l
3.90 1491
CB '2
0.49411161
0.451981611
0.30548 1951
10.971791
CP33
J.10616(921
0.18335 I 5 7 1
0.638491671
4.351491
CB ' 3
C.40171131
0.S3388193l
0.25675 1 8 8 )
8.551791
CP34
G.08E761791
0.123331841
0.67041 1411
4.781b51
CB ' 4
c.3~0~119ni
0.36561111
0.238511631
9.081691
CP35
0.094471961
O.J609j ( 5 9 1
0.63785l7Cl
5.55 I 5 7 1
c9 '5
0.4529 I 1 6 1
0. 315381641
0.269001431
E .83 ( 7 2 1
CP36
3.117581951
is 55313 I 5 3 1
095733617t:
5.251541
CB '6
C.54591131
0.33348(871
0 e31773 1961
9.95 1 7 = l
Q I G I O G R O U P PA.74UETEQj GROUP
A
2
Y
X
C
C
B DELTA
EPSILON
ETA
CPI
3.353621411 -0.238631651
0.13569145) 0.131 59 1 4 8 1
G. 0 3372 1 3 8 1
CP2
G.148231351
3.039518Cl -5.OF91lZl
CP3
0.11187145l
0 . 1 2 1 57 1451
5.63593 1351
-3.ZC35
0.71466 I 6 2 1
0.13252 1441
0.493781341
-2.5121101
-3.3364182)
-2.E043166l
-0.023331731 0.47353 17.31
0.377 851551 0.383681571
0.4i898135l
-3.1761151
-3.2721111
-2.6925178)
6.287241451
-2.964 I 1 3 1
CP4
CB CB'
18iI
3.0911101
1.32391641
3.04311901
0.31421E8l
-3.12971951
-1.7855159)
3.1E71111
2.6658 I 8 2 1
a x c , y , , and z c are the fractional coordinates of the origin of the rigid group. bTlie rigid group orientation angles delta, epsilon, and eta (radians) have been defined previously: S. J. La Placa and J . A. Ibers,Acta Crysrullogr.,1 8 , 5 1 1 (1965).
final agreement indices on Fu2for the 3 161 reflections and 205 variables are R = 0.18 and R , = 0.23. The conventional agreement indices on F , for the 1223 reflections with FU22 3u(FU2)are R = 0.090 and R , = 0.094. An analysis of Xw(FU2- F c 2 ) 2as a function of FU2,setting angles, and Miller indices shows no unusual trends. The standard deviation of an observation of unit weight is 1.37 e2. A final difference Fourier map is essentially featureless with the highest peak equal to 0.75 (12) e/@ around the N(5) atom. Remaining peaks have electron densities less than 0.6 (1) e/A3. The featureless difference Fourier map and especially the limited number of observations discouraged us from carrying out refinements based on anisotropic vibrations of the atoms. There is no reason to believe that the metrical details obtained are significantly affected by the absence of an anisotropic model. The final positional and thermal parameters for the nongroup atoms
appear in Table 1. Derived positional parameters and thermal parameters for the rigid group atoms are given in Table 11. The calculated positions and estimated thermal parameters for the hydrogen atoms are given in Table III.'O A listing of the observed and calculated structure amplitudes appears in Table IV.'O Entries with F, < 0 are for those reflections having FO2< 0.
Description of the Structure and Discussion The crystal structure consists of four discrete molecules of Fe(TPP)(CO)(Py) and eight molecules of benzene. The contents of a unit cell are shown in Figure 1, and a view of the Fe(TPP)(CO)(Py) molecule with the numbering scheme used is shown in Figure 2. In Table V the bond distances and angles in the Fe(TPP)(CO)(Py) molecule are presented.
Peng, Ibers / (PyridineJ(carbonyIJ(5, IO,IS.20-tetraphenyIporphinatoJiron(1I)
8034
Figure 1. Stereoscopic view of the contents of one unit cell of Fe(TPP)(CO)(Py).2CsHh. The z axis is horizontal to right; they axis is almost vertical, and the x axis is about perpendicular to the paper going away from the reader. Vibrational ellipsoids are drawn at the 20% level. Hydrogen atoms have been omitted. A
4
central iron atom is that of an axially distorted octahedron. The four equivalent Fe-N(pyrro1e) distances average 2.02 (3) A, comparing well with those in low spin iron porphyrin structures: 2.004 (4) 8, for Fe(TPP)(piperidine)2,13 2.001 (3) 8, for Fe(NO)(TPP),I4 and 2.008 (4) A for Fe(NO)(TPP)(NMeIm).I5 The axial Fe-N(pyridine) bond distance is 2.10 (1) 8,. This bond length may be compared with the Fe-N(axia1) distances of 2.088 (3) A found in Fe(I)(CO)(Py),16 2.122 (5) 8, in Fe(I)(CO)(NH2NH2),16-172.180 (4) A in F e ( N 0 ) -
Figure 2. A drawing of the Fe(TPP)(CO)(Py) molecule with the numbering sequence. Hydrogen atoms have been omitted.
I
I (TPP)(N-MeIm),15 and 2.127 (3) 8, in Fe(TPP)(piperidine)2.I3 All these bond lengths exceed that of 2.00 8, expected for a low-spin Fe-N distance. The long Fe-N distances in the first two structures have been attributed to the strong trans effect of the C O ligand.I6 A similar trans effect has been observed in the ruthenium(I1) carbonyl porphyrin complexes, Ru(TPP)(CO)(Py).l .5C7H8I8 and Ru(TPP)(CO)(EtOH).19 The Ru-N(Py) and Ru-O(Et0H) distances are 2.193 (4) and 2.21 (2) A, respectively, as compared with the Ru-N(porphyrin) distance of 2.052 (9) A, but in the last two iron structures, the long Fe-N bond lengths are attributed to the steric interactions between nitrogen atoms of the porphinato core and the hydrogen atoms of the imidazole or piperidine
ligand^.^^,^^ Figure 3. Diagram giving the averaged ( D 4 h ) bond distances (A) and angles (deg) in the porphyrin skeleton of the Fe(TPP)(CO)(Py) molecule.
In this porphyrin complex the geometry of the TPP moiety is very similar to that found in other metalloporphyrins.6s' The averaged bond distances and angles for the four crystallographically nonequivalent pyrrole rings are presented in Figure 3. They agree within experimental error with those found for other low spin iron(I1) porphyrin structures.6 The deviations from planarity of the porphyrin skeleton are given in Table VI. They are significant, but comparable with those found in other metalloporphyrins.6,1l , I 2 The inner coordination sphere of the complex, with selected bond parameters, is shown in Figure 4. The environment of the Journal of the American Chemical Society
/ 98:25 /
The pyridine ring is not exactly perpendicular to the plane of the porphyrin (interplanar angle = 100.4'). It is oriented such that the normal to the ring bisects the N( 1)-Fe-N(2) and N(3)-Fe-N(4) angles, thereby minimizing the steric interactions between porphyrin nitrogen atoms and pyridine hydrogen atoms. The nonbonded contacts between the ortho H atoms and the porphyrin ring are HCPY(5)-N(1), 2.59 A; HCPY(l)-N(3), 2.55 8,. The Fe-C(carbony1) distance is 1.77 (2) 8, and is slightly longer than the bond distances observed in Fe(I)(CO), 1.694 (4) in Fe(I)(CO)(NH2NH2), 1.751 (6) 8,,lh3l7and in Fe(I)(CO)(Py), 1.730 (3) This observation may represent a stronger binding of CO to iron(I1) complexes of ligand I than to iron(I1) porphyrin complexes, consistent with the lower C O stretching frequencies in these complexes: 192 1 - 1940 cm-' in Fe(I)(CO)XI6 vs. 1980 cm-I in Fe(TPP)(CO)(Py).
December 8, 1976
8035 Table V. Bond Distances (A) and Angles (deg) for Fe(TPP)(CO)(Py).2C6H, Fe-C Fe-N(l) Fe-N(2) Fe-N(3) Fe-N(4) Fe-N(5)
c-0
N(l)-C(l) N(l)-C(4) N(2) -C (6) N(2)-C(9) N(3)-C(ll) N(3)-C(14) N(4)-C(16) N(4)-C(19) C(l)-C(2) C(3)-C(4) C(6)-C(7) C(8)-C(9) C(ll)-C(12) C(13)-C(14) C(16)-C(17) C(18)-C(19) C(2)-C(3) C (7) -C (8) C(12)-C( 13) C(17)-C(18) C(l)-C(20) C(4)-C(5) C(5)-C(6) C(9)-C(10) C(lO)-C(ll) C(14)-C(15) C( 15)-C( 16) C (19 ) -C (2 0) C(S)-CP( 11) C(1O)-CP(2 1) C(15)-CP(31) C(20)-CP(4 1) N(5)-CPY(1) N(5)-CPY(5) CPY (l)-CPY (2) CPY (2)-CPY(3) CPY (3) -CPY(4) CPY (4)-CPY(5) 0-C-Fe C-Fe-N(l) C-Fe-N(2) C-Fe-N(3) C-Fe-N(4) C-Fe-N(5) N(l)-Fe-N(2) N(2)-Fe-N(3) N(3)-Fe-N(4) N(4)-Fe-N(1) N(l)-Fe-N(3) N(2)-Fe-N(4) N(l)-Fe-N(S) N(2)-Fe-N(5) N(3)-Fe-N(5) N(4)-Fe-N(5)
1.77 (2) 2.05 (1) 1.99 (1) 2.00 (1) 2.02 (1) 2.10 (1) 1.12 (2) 1.38 (2) 1.37 (2) 1.35 (2) 1.40 (2) 1.40 (2) 1.37 (2) 1.38 (2) 1.38 (2) 1.48 (2) 1.42 (2) 1.42 (2) 1.45 (2) 1.44 (2) 1.45 (2) 1.42 (2) 1.43 (2) 1.34 (2) 1.34 (2) 1.32 (2) 1.33 (2) 1.38 (2) 1.39 (2) 1.38 (2) 1.37 (2) 1.39 (2) 1.37 (2) 1.39 (2) 1.40 (2) 1.51 (2) 1.52 (2) 1.51 (2) 1.46 (2) 1.33 (2) 1.33 (2) 1.43 (3) 1.37 (3) 1.36 (3) 1.40 (3) 179 (2) 90.0 (8) 89.4 (7) 90.5 (9) 92.0 (7) 177.5 (8) 89.1 ( 5 ) 91.3 ( 5 ) 89.7 ( 5 ) 90.0 ( 5 ) 179.4 (6) 178.3 (6) 89.0 (7) 88.3 (6) 90.5 (7) 90.3 (6)
Fe- N(pyrro1e)
N-C,
I
1
2.02 (3)O
1.38 (2)
ca-cb
1.44 (2)
cb-cb
1.33 (2)
Ca-Cm
1.39 (2)
Cm-Cp
1.50 ( 3 )
C- Fe- N,
90.5 (11)
N,-Fe-N,
90.0 (9)
N,-Fe-N(S)
89.5 (11)
Fe-N( l)-C(l) Fe-N( 1)-C(4) Fe-N(2)-C(6) Fe-N(2)-C(9) Fe-N(3)-C(11) Fe-N( 3)-C( 14) Fe- N(4)-C (16) Fe-N(4)-C(19) C(l)-N(l)-C(4) C(6)-N(2)-C(9) C( 1 1)-N( 3)-C (14) C(16)-N(4)-C(19) N ( 1) -C (1)-C( 2) N(l)-C(4)-C(3) N(2) -C (6)-C(7) N(2)-C(9)-C(8) N(3)-C(ll)-C(12) N(3)-C(14)-C(13) N(4)-C(16)-C(17) N(4)-C(19)-C(l8) c (1)-C(2) -C(3) C(2)-C(3)-C(4) C(6)-C(7)-C( 8) C(7)-C(8)-C(9) C ( l l)-C(l2)-C(13) C(12)-C(13)-C(14) C(16)-C(17)-C( 18) C(17)-C(18)-C( 19) N ( 1)-C( 1)-C( 20) N (1)-C(4) -C (5) N(2)-C(6)-C(5) N(2)-C(9)-C(10) N(3)-C(1 l)-C(lO) N(3)-C(14)-C(15) N(4)-C( 16)-C( 15 ) N(4)-C(19)-C(20) C(4)-C(5)-C(6) C(9)-C(10)-C(11) C(14)-C(lS)-C(16) C(19)-C(20)-C(1) C(4)-C (5)-CP( 11) C (6)-C(5) -CP( 11) c (9 )-c (1O)-CP(2 1) C(1 l)-C(lO)-CP(21) C(14)-C(15)-CP(31) C(16)-C(15)-CP(31) C(19)-C(20)-CP(41) C(l)-C(20)-CP(41) C(20)-C(l )-C(2) C(3)-C(4)-C(5) C(5)-C(6)-C(7) C (8)-C(9) -C( 10) C(10)-C(11)-C(12) C( 13)-c(14)-c( 15) C(15)-C(16)-C(17) C (18)-C (19) -C( 2 0) CPY (5)-N(S)-CPY(l) N(5)-CPY (1)-CPY(2) CPY (l)-CPY (2)-CPY (3) CPY (2)-CPY(3)-CPY(4) CPY (31--CPYI4)-CPY (51 . . CPY(~~-CPY~S~-N(S)
124 (1) 126 (1) 129 (1) 126 (1) 126 (1) 127 (1) 127 (1) 127 (1) 110 (1) 105 (1) 106 (1) 107 (1) 105 (1) 108 (1) 111 (1) 110 (1) 108 (1) 109 (1) 109 (2) 108 (1) 108 (1) 109 (2) 108 (2) 106 (1) 108 (1) 108 (2) 108 (2) 108 (1) 131 (2) 125 (2) 125 (1) 125 (1) 125 (2) 126 (2) 126 (1) 128 (1) 126 (2) 126 (1) 124 (2) 121 (1) 117 (1) 117 (1) 118 (1) 116 (1) 117 (1) 118 (1) 120 (1) 120 (1) 124 (1) 127 (2) 124 (2) 125 (1) 127 (1) 125 (2) 126 (2) 124 (1) 120 (2) 120 (2) 119 (2) 120 (2) 119 (2) 121 i 2 j
Fe-N,-C,
126 (1)
Ca-N4-Ca
107 (2)
N4-Ca-Cb
109 (2)
N4-Ca-Cm
126 (2)
Ca-Cm-C,
124 (2)
Ca-Cm-Cp
118 (1)
The value in parentheses is the standard deviation of a single observation, taken to be the larger of that estimated from the inverse matrix or that obtained from the values averaged on the assumption that they are from the same population.
The displacement of the iron atom in the complex Fe(TPP)(CO)(Py) toward the CO group is small and not significant (0.02 8, for the Nq plane and 0.00 8, for the orphyrin plane). The comparable displacements are 0.1 1 in Fe(I)(CO)(NH*NH*) (0.00 8, after correction for the displacement of the Fe in the four-coordinate complex Fe(I)),*O 0.07 8, in Fe(NO)(TPP)(N-MeIm),l5 and 0.08 8, in Ru(TPP)(CO) (Py).' The most significant feature of the present structure is the linear Fe-C-0 bond (179 (2)'). While such a linear bond is
8:
*
Peng, Ibers
to be expected on the basis of the extensive literature on transition metal carbonyl complexes, the result is nonetheless highly significant since bent Fe-C-0 bonds with bond angles of 1 3 5 - 1 4 5 O appear to be the rule in various carbon monoxide The fact that in the present complexes of structure, a close analogue of the carbon monoxide complexes of the hemoproteins, the Fe-C-0 linkage is linear strongly suggests that another interpretation of the results of the protein studies is in order. The allegedly bent Fe-C-0 linkage in these proteins is derived from Fourier maps on which the C and 0
/ (PyridineJ(carbony1)(5,10,15,20-tetraphenylporphinato)iron(II)
8036 Table VI. Deviations (A, X 10') from Weighted Least-Squares Planes and Angles between Planes0 Atom
Plane 1
Fe 0
Plane 2
-2 --292
Plane 3
0 -290 -177 21 1
Figure 4. Drawing illustrating the inner coordination sphere of the carbonyl complexes with selected metrical details. The 50% ellipsoids are displayed.
in our opinion, to expect that owing to the fixed nature of the globin pocket bending will occur a t the Fe atom, leading to a linear Fe-C-0 bond which is not perpendicular to the porphyrin plane. The resolution of the Fourier maps of the carbon monoxide complexes of hemoproteins is not sufficient to eliminate this chemically more reasonable possibility.
Acknowledgment. This research was supported by the National Institutes of Health through Grant HL-13 157. Plane A
Angles between Normals t o the Planes Plane B
2 (porphyrin) 2 2 2 2 2 2 2 3 3 3 3 3 3 CB Plane 1 2
Angle, deg
1 (four N atoms) 3 (pyridine) CP1 (phenyl 1) CP2 (phenyl 2) CP3 (phenyl 3) CP4 (phenyl 4) CB (benzene) CB' (benzene) CP 1 CP2 CP3 CP4 CB CB' CB'
1.39 100.4 83.8 80.9 86.8 76.2 84.6 93.4 98.5 22.3 96.0 27.2 147.5 20.8 128.0
Coefficients of the Plane Equation A + B y + Cz = Db A B C 0.5 39 0.271 4.916 11.434 7.215 11.697 7.423 2.328 8.844
-19 .SO9 -19.534 4.441 -2.172 -2.181 -1.133 -3.774 -2.585 2.034
D
-1.273 -0.912 -19.164 4.838 -18.760 4.223 -18.351 17.705 -17.615
-2.729 -2.705 3 -4.710 CP1 4.026 CP2 -4.789 CP3 3.729 CP4 -4.257 CB 6.210 CB' -0.091 0 The entries for which an error is not indicated are for atoms which were not included in the calculation of the plane. b The plane is in crystal coordinates as defined by W. C. Hamilton, Acta CrystalQY, 18, 502 (1965).
atoms remain unresolved. These maps have apparently been interpreted on the assumption that the Fe-C vector is perpendicular to the porphyrin plane. It is much more reasonable, Journal of the American Chemical Society
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98:25
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Supplementary Material Available: Table 111, hydrogen atom coordinates, and Table IV, structure amplitudes (24 pages). Ordering information is given on any current masthead page.
References and Notes (1)R. Huber, 0.Epp, and H. Formanek. J. Mol. Biol., 52,349 (1970). (2)E. A. Padian and W. E. Love, J. Biol. Chem., 249,4067 (1974). (3)J. C. Norvell, A. C. Nunes, and B. P. Schoenborn, Science, 190, 568 (1975). (4)F. Basolo, B. M. Hoffman, and J. A. Ibers, Acc. Chem. Res., 8, 364 (1975). (5)J. P. Collman, R. R . Gagne. T. R . Halbert, J. L. Hoard, C. A. Reed, and A. A. Sayler have unpublished results on an approximate structure for Fe(TpivalPP)(CO)(1-Melm) (Tpival PP = meso-tetra(a,a,a,a-epivalamidophenylporphyrin, 1-Melm = 1-methylimidazole). Although they conclude that the Fe-C-0 linkage appears to be strictly linear they suggest that the accurate determination of the position of the carbon atom in the multiply bonded Fe-C-0 linkage demands x-ray data of much higher resolution than currently available.6 (6)J. L. Hoard in "Porphyrins and Metalloporphyrins". K. M. Smith, Ed.. Elsevier. Amsterdam, 1975,pp 317-380. (7)P. W. R. Corfield, R. J. Doedens,and J. A. Ibers, horg. Chem., 6,197 (1967); R. J. Doedens and J. A. Ibers, ibid., 8,204 (1967).The diffractometer was run under a new version of the Vanderbilt disk-oriented control system: P. G. Lenhert, J. Appl. Crystallogr., 8,568 (1975). (8)See, for example, B. A. Averill, T. Herskovitz, R. H. Holm, and J. A. Ibers, J. Am. Chem. SOC.,95,3523(1973). (9)S.J. La Placa and J. A. Ibers, Acta Crystal/ogr., 18,51 1 (1965). (10)Supplementary material; see paragraph at end of paper regarding supplementary material. (11)E. B. Fleischer, Acc. Chem. Res., 3, 105 (1970). (12)J. L. Hoard, Science, 174,1295 (1971). (13)L. J. Radonovich, A. Bloom, and J. L. Hoard, J. Am. Chem. Soc., 94,2073
(1972). (14)W. R. Scheidt and M. E. Frisse, J. Am. Chem. Soc., 97,17 (1975). (15)W. R. Scheidt and P. L. Piciulo. J. Am. Chem. SOC.,98, 1913 (1976). (16)V. L. Goedken. S . 4 . Peng. J. Norris. and Y. Park, J. Am. Chem. Soc.. in press.
(17)V. L. Goedken, J. Norris, and Y. Whang, J. Chem. Soc., Chem. Commun.. 337 (1973). (18)R. G. Little and J. A. Ibers, J. Am. Chem. SOC.,95,8583 (1973). (19)J. J. Bonnet, S.S.Eaton. G. R . Eaton, R. H. Holm, and J. A. Ibers. J. Am. Chem. SOC..95,2141 (1973). (20) V. L. Goedken, J. J. Pluth, S.-M. Peng, and B. Bursten, J. Am. Chem. SOC., in press.
December 8, 1976
