J . Am. Chem. SOC. 1982, 104, 3715-3721
3715
Structure of the Iron( 111)-“Capped” Porphyrin, FeCl( C,-Cap), [ 5,10,15,20-[ Pyrromellitoyltetrakis( 0-(oxyethoxy )phenyl) ] porphyrinato]chloroiron( 111) M. Sabat and James A. Ibers* Contribution from the Department of Chemistry, Northwestern University, Evanston, Illinois 60201. Received November 12, 1981
Abstract: The structure of the iron(II1) “capped” porphyrin, [5,10,15,20-[pyrromellitoyltetrakis(o-(oxyethoxy)phenyl)]porphyrinato]chloroiron(III),FeCI( C2-Cap), has been determined from single-crystal, X-ray diffraction data collected at -1 50 O C . The material crystallizes as the trichloroform solvate, FeCI( C2-Cap).3CHCl3, in space group G h - P 2 , / c of the monoclinic system with four formula units in a cell of dimensions a = 14.473 (5) A, b = 19.514 (9) A, c = 22.830 (11) A, p = 101.61 (2)O, V = 6316 A3. The structure was described by 396 variables, and at convergence of the full-matrix, least-squares refinement the values of R and R, (on F,9897 data having Fo2 > 3u(Fo2))are 0.065 and 0.078. The chloro ligand is outside the “cap” and the iron atom is above the mean plane of the porphyrin core away from the “cap”. The geometry about the iron atom is typical for FeCl(porphyrin) systems, with Fe-C1 = 2.242 (1) 8, and with Fe 0.46 8, above the mean N4 plane and 0.47 8, above the mean 24-atom porphyrin plane. The porphyrin itself is slightly nonplanar, with the mean displacement from the least-squares plane being 0.076 8, and the maximum displacement being 0.208 8,. Although the conformations of the side chains that link porphyrin to “cap” are distinctly different from those found in the related free-base porphyrin, H2(C2-Cap), the “cap” to porphyrin distances are very similar in the two structures. The separations between the centroids of the phenyl “cap” and respectively those of the four pyrrole nitrogen atoms and the 24-atom porphyrin skeleton are 4.03 and 4.01 8, in FeCI(C,-Cap) and 3.86 and 3.96 8, in H2(C2-Cap). These separations are too small to accommodate O2 or CO within the cap and imply considerable flexibility of these “capped” porphyrins in solution where binding of O2 or C O to Fe“(C2-Cap) systems occurs.
To elucidate structurefunction relationships in hemoproteins requires knowledge of the intrinsic properties of the heme group-its affinities for bases and for axial ligands-together with a precise sterochemical knowledge of the structures involved. Owing t o the size and complexity of protein crystal structure analyses, it is presently only through the use of model compounds that we can obtain a t least in part such information.1*2 Among t h e well-characterized model systems the “chelated-heme”,) “picket-fen~e”,~ and “ ~ a p p e d porphyrins ”~ are of particular interest owing to their ability t o bind dioxygen reversibly. T h e ligation of small molecules, including O2 a n d CO, to these modified porphyrins has been studied extensively.610 But structural studies on these molecules have not kept pace with the ligation studies, owing in large measure t o the difficulty of growing suitable crystals. In particular, there a r e no structural results on the “chelated-heme” systems and only one structural result on a “capped” system, namely the structure of the free-base “capped” porphyrin, 5,10,15,20- [pyrromellitoyltetrakis(o-(oxyethoxy)phenyl)Jporphyrin, H2(C2-Cap).ll In this paper we present
(1) Ibers, J. A,; Holm, R. H. Science (Washington, D.C.) 1980, 209, 223-235. (2) Jameson, G . B.; Robinson, W. T.; Ibers, J. A. In ‘Hemoglobin and Oxygen Binding“; Ho, C . Ed., Elsevier North Holland, Amsterdam, 1982; pp 25-35. (3) Traylor, T. G . Acc. Chem. Res. 1981, 14, 102-109 and references therein. (4) Collman, J. P.; Gagne, R. R.; Halbert, T. R.; Marchon, J.-C.; Reed, C. A. J . Am. Chem. SOC.1973, 95, 7868-7870. (5) Almog, J.; Baldwin, J. E.; Huff, J. J . Am. Chem. SOC.1975, 97, 227-228. (6) Traylor, T. G.; Berzinis, A. P. Proc. Nail. Acad. Sci. U.S.A. 1980, 77,
3171-3175. (7) Collman, J. P.; Brauman, J. I.; Collins, T. J.; Iverson, B.; Sessler, J. L. J . Am. Chem. SOC.1981, 103, 2450-2452. (8) Collman, J. P.; Brauman, J. I.; Doxsee, K. M.; Halbert, T. R.; Suslick, K. S . Proc. Natl. Acad. Sci. U.S.A. 1975, 75, 564-568. (9) (a) Ellis, P. E., Jr.; Linard, J. E.; Szymanski, T.; Jones, R. D.; Budge, J. R.; Basolo, F. J . Am. Chem. SOC.1980,102, 1889-1896. (b) Hashimoto, T.; Dyer, R. L.; Crossley, M. J.; Baldwin, J. E.; Basolo, F. Ibid. 1982, 104, 2101-2109.
(10) Linard, J. E.; Ellis, P. E., Jr.; Budge, J. R.; Jones, R. D.; Basolo, F. J . Am. Chem. SOC.1980, 102, 1896-1904.
0002-7863/82/1504-3715$01.25/0
Table I. Crystal Data and Data Collection Procedures for FeC1(C2Cap).3CHCl,
formula formula weight, amu space group a, A
b, A c,
a
0,deg
v,A’
Z
temp, “c crystal volume, mm3 radiation linear absorption coefficient, cm-’ transmission factors detector aperture
takeoff angle, deg scan speed A-1 sin e limits, A-l background scan range data collected
P
all data, including systematic absences unique data, with Fo2 > 30(F,*)
’Reference 13. 5 68-5 70.
C65H45C110FeN4012
1484.5 CihP2 ,I C 14.473 (5) 19.5 14 (9) 22.830 (11) 101.61 (2) 6316 4 -150’ 0.0896 graphite-monochromated Mo Kor (A(Mo Kor,) = 0.7093 A) 7.29 0.696-0.872 4.5 mm wide, 6 mm high, 32 cm from crystal 3.4 2.0” in 2e per min 0.0431-0.6291 (3.5” < 20(Mo Kor,) < 53.0”) 10 s a t each end of scan with rescan optionb 0.8” below Kcu, to 0.9” above KorZ +h,k,l 0.04 13835 9897
Lenhert, P. G . J. A p p l . Crystallogr. 1975,8,
structural results for FeC1(C2-Cap). As we shall see, the “cap”-to-porphyrin separation in this molecule is very close to that in H2(C2-Cap)and is far too small to accommodate a CO or O2 molecule. (1 I ) Jameson, G. B.; Ibers, J. A. J . Am. Chem. Soc. 1980,102,2823-2831.
0 1982 American Chemical Societv
3716 J . Am. Chem. Soc.. Vol. 104, No. 13, 1982
Sabat and Ibers
Table 11. Positional and Thermal Parameters for FeCl(CZCap)~3CHCI,
...... ............:..............I......*~!!~?~.~~~*..~55 P
FE
-0.331597 137)
0.257582126)
CL I
-0.283567 I 7 2 1
01
177Y60 ( 4 9 1
...... ....**........ ~!5.*.....**.~~~..I....*~~~.*..*
2
i:?:... i..
a33
*.
0 175618 122)
15 m 28 I 2 6 I
7.16113)
4.03110~
-0.32 I151
I .69 112)
0.245926 142)
31.57 I541
10.711251
-0.10129)
1-60 I251
2.25117) -3,13128)
-0.48 19 I
CLll
O.LO547 ( 1 I I
0.215673 171)
0.267349165)
7 0 ~ 6 196) 6
2 1 - 3 7 1381
6,871181 20.74 (331
CLl2
0.16274i121
0.168137 163)
86.3 I 1 0 I
25.95 ( 4 2 )
18.15(31)
-8.91 153)
CL13
O.U1897(10)
0. I 1 9 6 9 4 ( 7 5 ) 0.156809 166 I
13.2 3 ( 4 5 I 20.04 I 4 6 1
0.234043161)
54.46181)
20.47 (35)
18.521301
7.45142)
4.48 I 3 9 1
6.23 I 2 6 I
CL21
0.U6313 I 1 1 1
0.239091176)
0.487373 (831
63.72 1931
23.92i42)
43.37150)
8.96150)
33.13 (561
8.98 ( 3 7 1
CL22
-0.06826 I 1 0 1
0.129227 1 8 6 )
0 - 4 9 I 178 I 6 6 I
43.78 I 7 8 1
43.15(54)
18.941321
-9.78 I521
6.47(40)
0.791341
CL23
-0.03525(181
0.174470l901
0.378243 I 6 9 1
37.09 155)
17.44132)
59.06 I 8 9 1
39.31 168)
9.51134)
238.3i21)
-9.05
148)
-3.48129)
CL3lA
0.16501(441
0.37316 ( 4 1 )
0109198 I 2 9 1
35.0 I151
56.7 i 171
16.24 ( 7 5 )
-1*7i15)
6.08181)
-10,93197)
CL32A
0.2140 ( 1 1 1
0.43184i631
0.20979i72)
37.7(241
48.2 ( 2 5 1
10.59i66)
20.2 (231
7.251911
-1.0115)
CL3S
0.2426112)
0.50950(201
0.11053 ( 2 1)
35.4 I 1 I I
27.89 I 8 6 1
I 1 -4i221
34.0 122 )
CL318
0.1528 1 1 U )
0.4017112)
0.08411 166)
38.8142)
83.4152)
18.3i18)
4.9i201
CL328
0.213112*1
0.4395 ( 1 4 )
0.2053iL61
66.5155)
66.91561
12.2i201
-5,4143) 18.0150)
-1.8i22)
-6.7133)
CL338
0.283361101
0.51317i361
0.11108i29)
55.31471
31.8116)
27.0i131
10.1i171
14.4i151
11.1110)
-0.08201 ( L O 1
0.49795 I141
0 -22179 i12)
1.87i5)
02
-0,14558 II 9 1
0~446621141
0.10262i12)
1.76 I51
03
-0,18387
1201
0.540591151
0.04585 i 1 3 )
2117i51
04
0.214691151
-0.05358113)
0.32279 I141
-0.08698
I e87 I51
C13
-0.445081271
0~11700l201
0*03488117)
1.5616)
0.26352 I 1 5 1
-0 0 3542 I13 I
2.3715)
C14
1.3016)
0.010171151
3.02161
C15
0.16581l191 0.17773i191
0.080631171
0.22549117)
-0.453551261 -0.53589126)
0~102271161
C16
-0.54522 127)
0.22716119)
0*144791171
1.31 16) 1 36 I61
012
-0.275891201
0.55343(151
N1
-0.31176i211
0.34857 115)
N2
-0,20552121)
0.27671 115)
N3
-0.36897121)
0.20021t15)
112) 0.06067il4) 0.23147 113) 0.342081123 0.15355 1131 0.22268i141 0.15001l13) 0.09862114)
1.7715)
011
-0,25402 120) 0. J7832 I 1 9 1 -0.47073i211 -0.67151 1 2 3 ) -0,61822 i I Y I -0.b223li211 -0,50371 ( 2 0 1 -0.434671191
N4
-0,47371 122)
0.27049116)
c1
-0.37469
c2
-0.325351281
c3
-0.23355i271 -O.L2425(261
0.42955119)
c4 c5
-0.13945
C6
-0.132211261
c7
01
05 06 07 08 09 010
-
0.35451 (141
0.36552 i 161 0.506361151 0.55871Il41
239.111)
:!P:*.
202015)
II 2 1
-0.03705
10 - 5 8 176) -10.9127)
....*.~.....**.*.*..* :.... .... I....*...*...**..*.. *.*
0.A
2
2.47161
C17
-0.631511281
0.24250 121)
0.16365 I181
I .72 ( 7 1
2.23i5)
C18
-0.61377128)
0.294981201
0.20310118)
1.78171
1.43 I 6 1
1.92i5)
C19
-0.51625127)
0*31270(191
0.20946117)
2.12151
c20
-0~670191261
0.36561 (191
Oe246061161
1 36 ( 6 )
1 - 22 15)
C27
-0.04585
0.52409l221
0~171651201
2119i8) 2.03171
I311
1.19151
C28
-0.050181301
0.47221 ( 2 1 )
0~122721193
1.24 151
C29
0.48784120)
0.06698 I 1 8 1
0.17361114)
I . 34 (51
C36
-0.205141281 -0.27627130)
0.38143 i 1 9 )
0.25140 i 171
1.44(6)
c37
-0.374471311
0.43260 121)
0~291501181
1 - 7 1 17)
C38
-0.42552128)
0.288231171 0.245771161
1.51 ( 6 ) 1.30161
c45
0.377451191 0.35902i19)
0.22955i171
1.36161
c47
0~31368l191 0.30193i201
0.183561171
1.35i61
c54
-0.U4761128)
0~161091171
1.59 17)
c55
C8
-0.O6950
0.25922120)
0~114251171
1.6117)
C56
-0 I 70646 I 3 1 I -0 s I 1146 129) -0 158095 1281 -0,50937 130) -0.4273602) -0.35415iL71
0.534741201
0 I 12955 117)
1.61 17)
c9
-0.167891L71
0.24160i19)
0.10807l17)
1 a35 I 6 1
C63
0.14166 ( 3 6 )
0.14182126)
o ,23894
3.1519)
c10
-0.21530i261
0.19306119)
0.06779 I 1 7 1
1.3316)
C64
0.u1720i421
0016274 i301
0.45371 127)
6-19ill)
c11
-0.J0933 ( 2 6 )
0.17392 ( 1 9 )
0.06440 I 1 7 I
1 37 ( 6 1
C651
0.24375(El I
0.42361(641
0,13775 I 5 2 1
3.371261
c12
-0.35686i2n)
0~121941201
0.02489 i 1 8 )
1.64171
lL7 I
I261
I281
C46
1.60171
0,23547122)
-0.115091191
2.08171
0,26373122) 0.31361 ( 2 1 )
-01 12577 I 1 9 1 -0~042491181
2.17i81 1.74 ( 7 )
0.24771 122)
-0,04928
(201
2.21 ( 8 1
0.32417i21)
-0.04903
118)
1.94 I71
02020 117)
1.71 171
0.36917(201
01
0*578961221
0.22328119)
2.13171
0.598961231
0.19624 1201
2.40181
1231
Estimated standard deviations in the least significant figure(s) are given in parentheses in this and all subsequent tables. The form of the anisotropic thermal ellipsoid is: exp[-(Bllh2 + B22kZ + 8331’ + 2812hk + 2 B 1 3 h l + 2B23kI)I. The quantities given in the table are the thermal coefficients X lo4. 23
42 Y
Figure 1. Crystal packing diagram for FeC1(C2-Cap)-3CHC13.The view is down the b axis.
Experimental Section A powder sample of FeC1(C2-Cap),prepared by the reaction of FeC1,
46’
37
Figure 2. Molecular geometry and atomic numbering scheme for with H2(C2-Cap)in THF, was kindly supplied by Dr. John R. Budge and FeCI(C2-Cap). Hydrogen atoms are omitted for clarity. Professor Fred Basolo. The H2(C2-Cap)had been prepared by Dr. T. Szymanski from the literature method of Baldwin and c o - w o r k e r ~ . ~ ~ ’ ~ over a period of 18 months. On the basis of the crystal structure deHexane was diffused into a chloroform solution of FeC1(C2-Cap)at 5 OC termination, the material formed is FeCI(C2-Cap).3CHCI3. Preliminary film photographs showed symmetry and systematic absences consistent with the monoclinic space group C$,-P2,/c and also (12) Almog, J.; Baldwin, J. E.; Dyer, R. L.; Peters, M. J . Am. Chem. SOC. 1975, 97, 226-227. provided evidence for rapid solvent loss from the crystals. The crystals
J . Am. Chem. Soc., Vol. 104, No. 13, 1982 3717
Structure of Iron(III)-"Capped" Porphyrin
Figure 3. Stereodiagram of FeCI(C,-Cap). Probability ellipsoids are drawn at the 50%level. Hydrogen atoms are omitted for clarify.
Table 111. Derived Parameters for the Rigid Group Atoms for FeC1(C,Cap).3CHC13
!!::.........:..............:.............. .............::.......,:!:? .........:..............!.................................. ~~~
~
f
c21 c22 CL3 c24 C25 C26 HlC22 HlC23 HlC24 WlC25 c30 C3 I C32 c33
c 34 c35 HlC31 HlC32 H1C33 W1C34 c39 c40 c4 1 C42
-0.04812i15) O.Ul083i19l 0.09521(171 0.12063ilbI 0.06168(19) -O.U2269(171 -0.00653 (261 0.13544 (241 0,17822 1 2 0 ) 0.07904 126) -0.15968(171 -0.08541118) -0.U3046 116) -0.04977118) -0.12403119) -0.178991161 -0,07223 I261 0,02023 (221 -0,01226 (241 -0.13721(271 -0.62098(161 -0.63151117) -0.70615 I191 -0.77025 1171
0.38752 i 121 U1J63b07 198) 0.36798 1131 0.43627 1141 0.48019ilO) 0.45581112) 0.29700 I 1 1 ) 0.33802 117) 0.45291 ti91 0.52679 i 1 1 ) 0.15881113) 0.11546 1141 0.08596 ( 131 0.09983 1141 0.14318114l 0.17268 i 131 0,10599 (20) 0.05637(1ai 0.07970(20) 0.15264(201 0 13470 ( 121 0.06896t133 0.02787 i 1 0 1 0.05251 (131
0.264861111 0 e 30354 112 ) 0*33750112) 0.33278 112) 0.29410113) 0.26014 ( 1 1 ) 0*30675118) 0~36390116l 0.35596 117) 0.29088 1181 0.02688 I 1 0 I 0.051 179 (821 0.01440 I 1 1 ) -0.04668ilOI -0.070976 (82) -0,03420 ( 1 I ) 0,092860 1861 0.03098ilS) -0.07178~34~ -0,112657 I861 0.07508111)
0 09654 I 10 ) 0*06870112) 0.01939112)
B
2
2
0.11824 ( 1 3 I 0.1593411Ol 0.05215 i 17 I -0.01699i12l 0.02446 i 171 0.13506 1181 0.40606i121 0.372415 195) 0.40868 i 13 I 0.47858112l 0.512228i94l 0.475971121 0.324711101 0.38572 i 171 0.50333 (17) 0 . 5 5 9 9 3 1101 0.37427112l 0.39723i131 0.450171131 O.480151121 0.45719i13l 0.40425i131 0.46584 i 191 0,38858 ( 191
1-48(61
1.91 ( 7 1 2-41 iBI 2.44i81 2.89181 1.6717) 2.9 3.3 3.4
3.2 1.44161 1.7717) 2.0517) 2.0517l 2.02171 1-15(71 2.8 J.0
3.0 3.0 1.37 (6) 1.98i71 2.22(81 2.02i71
B*AL
2.31 I81
-0.00207~111 0.02577 1121 0.13019114) 0.08334117l 0.00038117) -0.03573114) 0.283521111 0.328771121 0.36488 I 1 I I 0.3557S i 1 1 I 0.31050i12l 0.27438 I 10 I 0.33500i17l 0.39576 i 151 0.38039 1161 0.30426118) -0.00052 i 1 1 I 0,02829 I 1 2 I 0.06985 I 1 I ) 0,08261 I 1 I I 0.053801121 0.01223 I 1 1 I 0,08951 1161 -0.007431161
1.85i71
2.8 3.2 3.0 3.3 1.52i6l I .98 17) 2.26i8) 2.22181 2.02(71 1.72 ( 7 1 3.0 3.1 3.3 3.0 1.60 171 1.6217) 1.63i7l 1.sai71 1.61 ( 7 1 1.76171
2.6 2.7
X,, Y,, and Z, are the fractional coordinates of the origin of the rigid group. The rigid group orientation angles delta, epsilon, and eta(radians) have been defined previously: La Placa, S . J.; Ibers, J. A. Acta Crystallogr. 1965,18, 511-519. Table VI. Geometry of the Coordination Sphere in High-Spin Fe(II1)-Porphyrin Complexes, FeX(porphyrin) Fe-N, A
Fe-X, A
N-Fe-N, deg
ANd, .+laADorDh, Ab
ref
1.792 (3) FeF (TPP)C 2.072 (l)d 86.99 (1) 0.47 0.47 16 FeCI(TPP) 2.192 (12) 2.049 (9) 0.38 17 0.38 FeBr(TPP) 2.348 (2) 2.069 (9) 86.8 0.49 0.5 6 18 FeI(TPP) 2.554 (2) 2.066 (11) 87.2 (2) 0.46 0.5 3 19 2.062 (10) FeCl(Proto IX)e 2.218 (6) 0.55 20 87.0 0.48 Fe(SPhNO,)(Proto-IX) 2.064 (18) 2.324 (2) 87.5 (6) 0.43 0.45 21 Fe(OCH,)(MesoP)f 2.073 (6) 1.842 (4) 86.7 (2) 0.46 0.43 22 0.47 this work FeC1(C,Cap)g 2.063 (3) 2.242 (1) 87.2 (4) 0.46 Distance of the Fe atom from the least-squares plane through the 4 N atoms of the porphyrin core. Distance of the Fe atom from the least-squares plane through the 24-atom porphyrin in core. TPP = 5,10,15,2O-tetraphenylporphyrinato. Estimated standard deviation of a single observation is given in parentheses. e Proto-IX = protoporphyrin IX dimethyl ester dianion. MesoP = mesoporphyrin IX dimethyl ester dianion. g Structure determined at -150 "C; all other structures were determined at room temperature.
used for the collection of intensity data was cut from a larger crystal contained in a glovebag saturated with CHCI3 vapor. The crystal was quickly transferred to the cold streamL3of a Picker diffractometer. The cold stream ( t = -150 OC at the crystal) provided complete protection of the crystal from desolvation during the period of data collection. (13) Huffman, J. C. Ph.D. Thesis, Indiana University, 1974.
Intensity data were collected by methods standard in this 1ab0ratory.l~ Crystal data and details of data collection are given in Table I. The structure was solved by direct methods (MULTANSO). Refinement of the structure proceeded along lines standard in this 1ab0ratory.l~In (14) See,for example: Waters, J. M.; Ibers, J. A. Inorg. Chem. 1977, 16, 3273-3217.
3718
Sabat and Ibers
J . Am. Chem. Soc., Vol. 104, No. 13, 1982
Table VII. Bond Distances (A) for FeC1(C2Cap).3CHC1, 0(1)-U27) 0(4)-W6) 0(7)-U45) O( lO)C(5 4)
1.444 (5) 1.435 (5) 1.418 (6) 1.429 (5)
C(27)€(28) C(36)€(37) C(45 ) C ( 4 6 ) C(5 41435 5 )
1.500 (6) 1.498 (6) 1.494 (6) 1.496 (6)
1.384 (5) 1.395 (5)
C(28)-0(2) C(37)-O(5) C(46)-0(8) C(55)-0(11)
1.453 (5) 1.461 (5) 1.448 (5) 1.451 (5)
1.430 (5) 1.438 (6)
0(2)-W9) 0(5)-W8) 0(8)-(347) 0(11)€(5 6)
1.330 ( 5 ) 1.345 (5) 1.341 (5) 1.339 (5)
C(29)-0(3) C(38)-0(6) c(4 71-0 (9 C(56)-0(12)
1.203 (5) 1.205 (5) 1.200 (5) 1.211 (5)
C(29)€(57) C(38)€(59) C(47)€(60) C(5 6)€(62)
1.517 (5) 1.511 (5) 1.514 (5) 1.497 (5)
C(63)Cl(ll) C(63)€1( 12) C(63)C1(13) C(64)€1(21) C(64)€1(22) C(64)€1(23)
1.762 (5) 1.759 (6) 1.778 (6) 1.746 (6) 1.765 (6) 1.752 (7)
C(65A)CC1(31A) C(65 A)C1(32A) C(65 A)-C1(3 3A) C(65 B)C1(3 le) C(65B)C1(32B) C(65B)C1(33B)
1.70 (1) 1.79 (2) 1.79 (1) 1.83 (2) 1.71 (4) 1.66 (2)
Fe-N 2.063 (3)a
NC,b 1.384 (7)
caCb
1.437 (6)
1.437 (5) 1.432 (6)
CbCb
1.347 (6)
CaCm 1.398 (5)
C m G 1.514 (7)
1.431 (11)
1 1. 1 1
1.497 (6)
1.45 3 (6)
1.339 (6)
1.205 (5)
1.510 (9)
1.760 (11)
1.365 (4)
Here, and elsewhere, the estimated standard deviation given in parentheses following a mean value is the larger of that calculated for an individual observation on the assumption that the values averaged are from the same population or of that calculated for an individual parameter from the inverse of the least-squares matrix. The nomenclature is that of: Hoard, J. L. Science (Washington, D.C.)1971,174, 12951302. The chloroform solvate composed of atoms (365). Cl(31). C1(32), and Cl(33) is disordered over sites A and B with a distribution of 0.75:0.25. the refinement only the Fe and CI atoms were refined anisotropically; all other nonhydrogen atoms were refined isotropically, with the phenyl groups restricted to their idealized geometry (D6,J. The only complication in the refinement was the disorder of one of the three chloroform groups. Refinement of both alternative positions with a variable occupancy factor was carried out. Prior to the final cycle of refinement on F, all hydrogen atoms, except those for the disordered chloroform molecule, were idealized and included as fixed contributions. The final cycle, involving 396 variables and 9897 observations, converged to values of the usual R and R, indices of 0.065 and 0.078 and to an error in an observation of unit weight of 2.47 e. Elaboration of the model, e.g., anisotropic refinement of the carbon atoms, was not attempted owing to the expense involved with minimal expectation of dramatic changes in porphyrin parameters derived from these low-temperature data. Moreover, an analysis of xw(lF,,I - I F, as a function of IF& setting angles, and Miller indices revealed no unusual trends. In the final difference electron density map, the three highest peaks (0.9-1.2 e/A3) were in the vicinity of the disordered solvent molecule. Neither in this map nor throughout the refinement process was there any indication of disorder in the side chains. The final parameters of the atoms are listed in Tables I1 and 111. Table 1Vt5lists the idealized positions of the H atoms, while Table VI5 presents the values of lO]F,,I vs. 10lFJ for those reflections used in the refinement. (15) Supplementary material.
-045-033
I
\
\
I
067-407
Figure 4. Displacements (XlO’) of atoms from the least-squares plane of the 24-atom porphyrin skeleton. The estimated standard deviations are 0.003 A for nitrogen atoms and 0.004 for carbon atoms. Displacements in parentheses were not included in the calculation of the least-squares plane.
Results The crystal structure of FeC1(C2-Cap).3CHC1, consists of the packing of discrete monomeric molecules of FeCl( C2-Cap) and
J . Am. Chem. SOC.,Vol. 104, No. 13, 1982 3719
Structure of Iron(III)-"Capped" Porphyrin Table VIII. Bond Angles (deg) for FeCl(C2€ap).3CHCl, 103.5 (1) 99.4 (1) 103.0 (1) 105.3 (1)
C(25)4(26)-0(1) C(34)C(35)-0(4) C(43)C(44)-0(7) C(5 2 ) C ( 5 3)-O(10)
121.2 (2) 124.6 (2) 124.4 (2) 123.0 (2)
C(21)€(26)-0(1) C(30)C(35)-0(4) C( 39)
