2366 following these pages in the microfilm edition of this volume of the journal. Photocopies of the supplementary material from this paper only or microfiche (105 X 148 mm, 24X reduction, negatives) containing all of the supplementary material for the papers in this
issue may be obtained from the Journals Department, American Chemical Society, 1155 16th St., N.W., Washington, D. C. 20036. Remit check or money order for $3.00 for photocopy or $2.00 for microfiche, referring to code number JACS-74-2360.
Effect of Ligand Constraints on the Geometry of Two Sulfur-Bridged Binuclear Iron( 11) Complexes. The Structures of Bis {p-[N,N’-dimethyl-N,N’bis(P-mercaptoethyl)ethylenediamine] ] -diiron( 11) and Bis { p-[N,N’-dimethyl-N,N ’-bis(P-mercaptoethy1)1,3-~ropanediamine] ] -diiron( 11) Wei-jen Hu and Stephen J. Lippard” Contribution from the Department of Chemistry, Columbia University, New York, New York 10027. Received October 12, 1973 Abstract: The crystal and molecular structures of two high-spin ferrous complexes, bis { p-[N,N’-dimethyl-N,N’bis(fl-mercaptoethyl)thylenediamine] ] -diiron(II), (FeL)z, and bis { p-[N,N’-dimethyl-N,N’-bis(fl-mercaptoethy1)1,3-propanediamine]}-diiron(II), (FeL’)2, are reported, (FeL’)2 crystalli5es as red-brown parallelepipeds in space group P21/c. The cell parameters are a = 9.538 (1) A, b = 11.636 (1) A, c = 12.248(1) A,and p = 115.54 (1)’. The measured density is 1.497 (2) g/cm3 in agreement with the calculated value of 1.496 (1) g/cm3 for four Fe(C9H20N2S2) formulas in the unit cell, The structure has been refined to R1 = 0.059 and Rz = 0.085 based on 1532 independect observed reflections. The molecule is a dimercapto-bridged dimer with an iron-iron distance of 3.371 (2) A. The coordination geometry about each of the iron :toms is a slightly gistorted trigonal Pipyramid. (FeL)2has the same space group with cell constants a = 9.202 (4) A, b = 11.080 (7) A, c = 12.418 (6) A, and /3 = 112.62 ( 2 ) ” . The measured density is 1.495 ( 5 ) g/cm3 and the calculated density is 1.490 (3) g/cm3 for four Fe(CsHI8N2S2)formulas per unit cell. Its structure was solved based on 738 independent reflections and refined to R values of 0.074 and 0.083. With the same NzSBdonor atom set as (FeL’)?, the coordination geometry of (FeL)2is much more distorted from that of a trigonal bipyramid. Elimination of one methylene group between the two nitrogen donor atoms has caused a 15” decrease of the axial-metal-axial angle !nd deformation of the ye& rhombus. The iron-iron nonbonded distance is shortened significantly from 3.371 (2) A in (FeL’)2to 3.206 ( 5 ) A in (FeL)2, accompanied by a decrease in the bridging angle Fe-S1-Fe’ from 86.91 (8)” in (FeL’)2to 82.7 (2)” in (FeL)2. These results demonstrate that external ligand constraints can influence the geometry of a binuclear Fe2S2 system.
T
he variation of metal-metal distance with electronic configuration has previously been established for low-spin sulfur-bridged iron dimers where strong metal-metal bonding can occur. 1--3 Here we report that the metal-metal distance in binuclear Fe2(SR)2 complexes can also be influenced by geometric constraints when the bridging sulfur atom is part of a tetradentate chelating ligand. This work is part of a continuing investigation of iron-sulfur coordination compounds and proteins. A tetradentate ligand system with an N2S2 donor atom set was employed. Two ligands, N,N’-dimethylN,N’-bis(P-mercaptoethy1)ethylenediamine (LH2) and N,N’-dimethyl-N,N’-bis(P-mercaptoethy1)1,3-propanediamine (L’H2),were ~ynthesized.~As anticipated from (1) L. F. Dahl, E. R. de Gil, and R. D. Feltham, J. Amer. Chem. SOC., 91, 1653 (1969). (2) D. Coucouvanis, S. J. Lippard, and J. A. Zubieta, Inorg. Chem., 9,2775 (1970). (3) N. G. Connelly and L. F. Dahl, J . Amer. Chem, SOC.,92, 7472 (1970). (4) S. J. Lippard, Accounts Chem. Res., 6, 282 (1973), and references therein. (5) The ligands were prepared by a modification of the method of D. D. Reynolds, M. K. Massad, D. L. Fields, and D. J. Johnson, J . Org. Chem., 26, 5109 (1961).
Journal of the American Chemical Society
1 96.8 1 April 17, 1974
LH-
L‘HL
a careful examination of moleculzr models and subsequently demonstrated by the structural analysis of a zinc derivative,6 [ZnzLCl2I22Hz0, complexes of the former ligand are sterically strained. The strain may be judged by anomalously small bond angles imposed by the chelate rings and by other geometric criteria discussed in detail below. In complexes of L’, the strain was expected to be relieved by the presence of the additional methylene group in the N,N chelate ring. The synthesis and chemical and physical properties of the iron derivatives [ F ~ ( C S H I ~ N ~ S ~ )L)2, ] ~ , (and F~ [Fe(C9H20NzSz)]2, (FeL’)z, will be the subject of future communication^.^ Here we report the molecular e
(6) W. J. Hu, D. Barton, and S. I. Lippard, J. Amer. Chem. Soc., 95, 1170 (1973). (7) W. J. Hu, K. D. Karlin, and S. J. Lippard, to be submitted for publication.
2367 where E is the total count in the peak plus background observed for time TE, B1 and BPare the background counts observed for time TB at each end of the scan, and e is an "ignorance factor"lP assumed in this case t o be 0.04. Only reflections which satisfied the condition I > 3 4 were included in the refinement. Determination and Refinement of the Structure. The atomic Experimental Procedure and Results coordinates of the crystallographically independent iron atom and Bis{~-N,N'-dimethyl-N,N'-bis(~-mercaptoethyl)-l,3-propanedi- two sulfur atoms were determined from a three-dimensional Patamine] )-diiron(II), [Fe(CBH20N&)]2. Collection and Reduction of terson synthesis.9 The positional and isotropic thermal paramData. The compound crystallized as red-brown parallelepipeds. eters of these three atoms were refined by least squaress using unit Crystals of both the oxygen-sensitive compounds (FeL'), and weights. The remaining nonhydrogen atoms were located in the (FeL)2 decompose in the air much more slowly than in solution or subsequent electron density difference Fourier map, phased on the as fine powders. This slower decomposition rate permitted three heavy atoms. After refining the scale factor, positional examination on the precession camera to be done in the air. From parameters, and individual isotropic thermal parameters with unit precession photographs taken using Cu K a radiation, the absences weights, subsequent cycles using anisotropic thermal parameters hOI, I # 2i1, and OkO, k # 2t1, established the space group to be and weights w = 4Fo2/u2(FOP)converged to values of 0.075 and P2]/c ( C j 2 h ) . A crystal of approximate dimensions of 0.1 X 0.12 X 0.120 for R1 = Z/IF,, - IF,l//Z/F,I and RP = [Zw(/F,I - IF,/)*/ 0.13 mm was sealed in a glass capillary under a nitrogen atmosphere ZwFo*]'/2, respectively. In these expressions, F , and F, are the and used fo? intensity measurements. Employing Cu K a l radiation observed and calculated structure factor amplitudes and u(Fo2) is (X 1.5405 A) 12 reflections were centered on a FACS-I-DOS difU(Z)l(LP). fractometer and the setting angles were used in a least-squares reAn electron density difference map was then synthesized and finement of the cell constants. Theoresults are a = 9.538 (1) A, revealed the location of the 20 hydrogen atoms which were added b = 11.636 (1) A , c = 12.248 (1) A , and p = 115.54 (1)'. The into the refinement. In the final refinement stage a modification of density measured by flotation in mixtures of bromoform and carbon the weighting scheme was introduced to improve the constancy of tetrachloride was 1.497 (2) g/cm3, in agreement with the calculated the function Zw(lF,I - /Fo1)2for various classes of reflections.13 value of 1.496 (1) g/cm3 for four Fe(CoH20Ns&)formulas in the The empirical funcGon used set _w = (O.llF, 32)-1 and five unit cell. strong reflections (loo), (ZOO), (100), (302), and (111) were reThe mosaicity of the crystal was measured by means of narrowjected because of possible extinction effects.14 source, open counter, w scans. For nine arbitrarily chosen lowIn the refinement of the hydrogen positional parameters (hydroorder, strong reflections, the width at half-height ranged from 0.05 gen isotropic thermal parameters were set at 5.0 A2), H21, H32, to 0.12" (average 0.07') which is acceptably low.8 H61, and HM1115 were found to oscillate about their equilibrium The intensities were measured using Ni-filtered Cu K a radiation positions while all other 16 hydrogen atoms refined well. Thereby the 8-20 scan technique at a takeoff angle of 2.3". At this fore in the final refinement these fo5r hydrogen atoms were fixed in angle the intensity of radiation was about 8 5 % of the maximum idealized positions (C-H = 0.95 A , z ] l " ' individual 10-sec background counts were recorded at both ends of (8) T. C. Furnas, "Single Crystal Orienter Instruction Manual," General Electric Co., Milwaukee, Wis., 1957. (12) (a) G. M. Brown and H. A. Levy, J . Physiol. (Paris), 25, 497 (9) Programs for the IBM 360-91 computer used in this work include, (1964); (b) R. D. Ellison and H. A. Levy, Acta Crysfallogr., 19> 260 in addition to various local data reduction routines, the following: (1965); (c) P . W. R. Corfield, R. J. Doedens, and J. A. Ibers, Inorg. ACAC-4, a revised version of the Prewitt absorption correction program; Chem., 6,197 (1967). XDATA, the Brookhaven Wilson plot and scaling program; FORDAP, (13) D. W. J. Cruickshank in "Computing Methods of Crystallogthe Zalkin Fourier program; CULS, a local version of the Busingraphy," J. S. Rollett, Ed., Pergamon Press, New York, N. Y., 1965. Martin-Levy structure factor calculation and least-squares refinement (14) W. H. Zachariasen, Acta Crysrallogr., Sect. A , 24, 425 (1968). program (ORFLS);ORFFE, the Busing-Martln-Levy molecular geometry (15) Table 11, footnote a. and error function program; ORTEP, the Johnson thermal ellipsoid (16) M. R. Churchill, Inorg. Chem., 12, 1213 (1973). plotting program; MEANPLANE, the Pippy-Ahmed best planes program. (17) In addition to those cited in ref 9 , local versions of MODE-1,the (10) H. P. Hanson, F. Herman, J. D. Lee, and S . Skillman, Acta Brookhaven diffractometer setting and cell constant and orientation reCrjslallogr., 17, 1040 (1964). finement, GSET, the Prewitt diffractometer setting program, and ACAC-3, ( 1 1 ) D. T. Cromer and D. Lieberman, J. Chem. Phys., 53, 1891 a revised version of the Prewitt absorption correction and data reduction ( 1970). program, were used.
structures of these two binuclear, sulfur-bridged FezSz complexes which display quite different metal-metal distances and coordination geometries.
+
+
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Hu, Lippard i Effect o j ' l i g a n d Constraints on Geometry of S-Bridged Fe Cotnplexes
2368 Table I. Final Nonhydrogen Atomic Positional and Thermal Parameters for [ F ~ ( C , H Z , N ~ S Z ) ] ~ ~ ~ ~ Y
X
Fe s1 s2 N1 N2 c1 c2 c3 c4 c5 C6 c7 Me1 Me2 c
0.1206(1) -0,1295 (2) 0.2579(3) -0.0204(8) 0.3455(8) -0.252(1) -0.171 (1) 0,052 (1) 0.209(1) 0.339(1) 0,471 (1) 0.448(1) -0.054(2) 0.386(1)
Z
0.0903(1) 0.1068(1) -0.oO53 (2) 0.0696(2) 0.0162(2) 0.3004(2) 0.2487(6) 0.0642(7) 0.1995(6) 0.1563(6) 0.120(1) 0.006(1) 0,229 (1) 0.067 (1) 0.351 (1) 0.142 (1) 0.388(1) 0.153(1) 0.305(1) 0.224(1) 0.125(1) 0.237(1) 0.079(1) 0.345(1) 0.282(1) -0.063(1) 0.234(1) 0.058(1)
Pll',d
P22
833
PI2
PI3
7.8(2) 9 . 5 (3) 11.8(3) 9.2(10) 9.9(10) 7.2(13) 9 . 6 (15) 16.7 (19) 12.1 (15) 10.9(13) 8.4(13) 11.5(14) 21.8(23) 13.3(16)
4.6(1) 6 . 7 (2) 8 . 1 (2) 5.3(6)
5.2(1) 6 . 3 (2) 6.6(2) 8.2(7) 6.7(6) 12.5(12) 19.7 (17) 13.8 (13) 11.3(11) 8.6(9) 10.1 (10) 7.0(8) 10.6(12) 9.4(10)
0.3(1) -0.8 (2) -1.7(2) 1.0(6) 0.1(6) 0.9(9) 1 . 5 (10) 2 . 8 (11) -1.0(8) -0.7(8) 0.4(8) -0.4(9) 3 7(14) -0.6(10)
1.9(1) 3 . 3 (2) 2.0(2) 2.3(7) 3.6(6) 2.4(10) 5 . 0 (13) 3 . 9 (13) 2.3(10) 1.7(9) 2.6(9) 2.4(9) 4 . 1 (13) 5.5(10)
5.4(5)
8.8(9) 8 . 3 (10) 7 . 7 (9) 4.8(7) 6.5(8) 6.6(7) 6.9(8) lO.O(l1) 8.9(10)
a23
-0.2(1) -0.8 (1) 1.9(2) -1.6(5) 0.3(5) -4.0(9) - 2 . 0 (10) -3.0(9) -0.67) -1.3(7) 0.6(7) - 0 . 1 (7) 2.3(9) 1.3(8
a Atoms are labeled as indicated in Figure 1. Standard deviations, in parentheses, occur in the last significant figure for each parameter. The form of the anisotropic ellipsoid is exp[ -(Pllh2 &k2 &12 2&hk 2p13hl 2@23k/)]. Values reported are X lo3.
+
+
+
Table 11. Final Hydrogen Positional Parameters for
[F~(CIHZONZS~)I~~~~ H11 H12 H21 H22 H31 H32 H41 H42 H51 H52 H61 H62 H7 1 H72 HMll HM12 HM13 HM21 HM22 HM23
X
Y
Z
-0.30 (2) -0.35 (2) -0.16 -0.26 (2) -0.03 (2) 0.07 0.25 (2) 0 . 2 0 (2) 0 . 3 3 (2) 0 . 4 4 (2) 0.49 0 . 6 0 (2) 0.54(2) 0 . 4 6 (2) 0.04 -0.14 (2) -0.15 (2) 0 . 4 1 (2) 0.29 (2) 0 . 5 0 (2)
0.13 (1) 0 . 1 1 (1) 0.22 0.30 (1) 0.43 (1) 0.34 0 . 4 6 (1) 0 . 4 0 (1) 0.27 (1) 0 . 3 4 (1) 0.06 0.17 (1) 0 . 0 3 (1) 0.14 (1) 0.31 0 . 2 0 (1) 0.35 (1) 0 . 1 5 (1) 0 . 2 9 (1) 0.27 (1)
-0.06 (1) 0 . 0 1 (1) 0.15 0 . 0 2 (1) 0.11 (1) . , 0.23 0 . 2 0 (1) 0.07 (1) 0.30 (1) 0 . 2 6 (1) 0.20 0 . 2 7 (1) 0 . 3 8 (1) 0 . 4 0 (1) -0.07 -0.10 (1) -0.09 (1) 0 . 0 3 (1) 0.01 (1) 0 . 0 9 (1)
a In this table, H21, for example, refers to the first hydrogen atom attached to C2; HM13 refers to the third hydrogen atom attached to Mel. See footnote 6, Table I.
Table 111. Root-Mean-Square Amplitudes of Vibration (in A) for [Fe(C9H20N2S~)]~a8b Atom
Min
Int
Max
Fe s1 s2 N1 N2 c1 c2 c3 c4 c5 C6 c7 Me1 Me2
0.166 (2) 0.184 (3) 0.183 (3) 0.168 (11) 0.191 (10) 0 . 1 6 (2) 0.18 (2) 0.19 (2) 0.18 (1) 0.18 (1)
0.175 (2) 0.194 (3) 0.199 (4) 0.186 (10) 0.192 (10) 0.20(1) 0 . 2 4 (1) 0 . 2 5 (1) 0.21 (1) 0 . 2 2 (1) 0.21 (1) 0 . 2 2 (1) 0.29 (2) 0.23 (1)
0.199 (2) 0.221 (3) 0.277 (3) 0.257 (10) 0.205 (10) 0.33 (2) 0.37 (2) 0 . 3 4 (2) 0 , 3 0 (1) 0.27 (1) 0 . 2 7 (1) 0.24(1) 0.32 (2) 0 . 2 6 (1)
0.18 (1)
0.20 (1) 0 . 2 2 (2) 0 . 2 0 (1)
a Taken along the principal axes of the thermal ellipsoids; the orientation of these axes may be seen from Figure 1. See footnotes a and b in Table I.
the scan. A few low order reflections showed structure, indicating some imperfection of the crystal. Several crystals had been examined and they all showed some extent of imperfection so the best one was chosen for data collection. The intensities of four
Joiirnal ofthe American Chemical Society
1 96:8 1 April
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strong and sharp reflections (242), (32i), (411), and (lOG) were measured after every 100 reflections to monitor the crystal and instrument stabilities. There was no systematic decline of these intensities. The last three standards varied randomly within * 4 2 of their mean values and had a combined u (mean) of 3 2 . The first showed up to 7 . 6 2 maximum deviation with a u (mean) of 3 . 6 2 . These variations, while approximately equal to the calculated u(Z)'s for the standards, were somewhat larger than usual, and were probably due either to electronic instability or slight crystal movements. In view of the poor quality of the crystals (cide supra), however, data collection was not interrupted. A total of 1366 reflections was collected, and almost no intensity was observed beyond 20 = 102". The observed intensities were corrected for background, use of attenuators, Lorentz, polarization, and absorption effects (fi = 134.0 c r 1 - 9 . ~ ~The minimum and maximum calculated transmission factors are 0.221 and 0.475, respectively. The agreement factor of the equivalent forms (OkP)and (Oki) based on F,* was improved from 0.210 to 0.100 for 195 reflections after the absorption correction. A Wilson plot subsequently yielded an approximate absolute scale factor.I7 Scattering factors for the zerovalent atoms were obtained from the International Tables.18 The calculated structure factors were corrected for the effects of anomalous dispersion of the iron and sulfur atoms.I* The calculation of u(Z) is the same as for (FeL'),. Reflections which satisfied the condition Z > 3u(Z) were included in the refinement, a total of 738 reflections after averaging. The small number of observable reflections is due t o the poor scattering character of the crystal and results in fairly large standard deviations in the refinement. Determination and Refinement of the Structure. The atomic coordinates of the crystallographically independent iron atom and two sulfur atoms were determined for a Patterson synthesis.17 The positional and isotropic thermal parameters for these three atoms were refined by least squares, with minimization of the function Bw(lF,I - 1 F c / ) 2where , /F,i and lFcl are the observed and calculated structure amplitudes and the weights w were taken as 4Fo2/u2(FO2). A subsequent difference Fourier map yielded the positions of the remaining nonhydrogen atoms. Refinement varying the positional and isotropic thermal parameters led to R, = ZliFol - ~ F c ~ ~ / Z ~ F o ~ of 0.113 and a weighted A factor R2 = [Bw((F,I - (F,1)z/SwFo21'/2 of 0.128. A few cycles using anisotropic thermal parameters converged to R1 = 0.093 and R2 = 0.111. After performing the absorption correction and averaging equivalent reflections, the refinement of all nonhydrogen parameters led to RI = 0.080 and R2 = 0.099. The resulting structure factors were used to compute a dift'erence Fourier map. The 12 methylene hydrogen atoms were located on the Fourier map and were idealized (C-H = 0.95 A , Nl-Fe-N2 (90.3') > S2-Fe-N2 (83.5') shows that the Fe-N2 bond is tilted in the direction of the S 2 . . . N 1 edge of the equatorial plane. This dis(19) M. R. Snow and J. A. Ibers, Inorg. Chem., 12, 249 (1973); edt2- = ethane-1,2-dithiolate.
Hu, Lippard / Effect of Ligand Constraints on Geometry of S-Bridged Fe Complexes
2370 Table VII. Coordination Geometry of the (FeL’)2 and (FeL)2 Bond Angles Compared to Regular Trigonal Bipyramid (TBP) (in deg) Regular TBP
S 1-Fe-N2 S1 ‘-Fe-S2 S1 ’-Fe-Nl S2-Fe-Nl S 1-Fe-S2 SI-Fe-N1 SI-Fe-S1 ’ N2-Fe-S2 N2-Fe-SI ’ N 1-Fe-N2
Table IX. Ligand Geometry of (FeL% and (FeLh Nonbonded Distances, A 3.558 (4) Sl...Sl’ 3.563 (3) Sl...S2 3.144(7) Sl...Nl 4.815 (7) Sl...N2 4.156 (3) S1’. . .S2 3.844 (7) S1’. , .N1 3.477 (7) Sl’...N2 4.014 (7) S2...N1 3.104 (7) S2. . . N 2 3.223(9) Nl...N2
[Fe[Fe(CgH2~NZS2)12a (CsH18NzSz)1zb
180.0 120.0 120.0 120.0 90.0 90.0 90.0 90.0 90.0 90.0
172.0 (2) 122.7 (1) 112.6 (2) 124.7 (2) 95.41 (8) 83.8 (2) 93.09 (8) 83.5 (2) 94.1 (2) 90.3 (3)
157.6 (4) 121.2 (2) 107.3 (5) 130.9 (5) 97.0 (2) 83.7 (4) 97.3 (2) 83.6 (4) 101.5 (4) 79.2 (5)
S1-Cl S2-C7 a See footnotes a and b, Table I. See footnotes a and 6 , Table Nl-C2 IV. Nl-C3 Nl-Me1 N2-C5 N2-C6 Table VIII. Coordination Geometry of the (FeL’)2 and N2-Me2 (FeL)2Bond Length Parameters (in A) Cl-C2 [Fe(CgH~~N~S2)12a [ F ~ ( C E H ~ J N ~ S Z ) I ~ ~
Fe-S 1 Fe-S1 ’ Fe-S2 Fe-N 1 Fe-N2 Fe. . .Fe’ a
2.490 (3) 2.411 (2) 2.325 (2) 2.207 (7) 2.337 (7) 3.371 (2)
See footnotes a and b, Table I.
2.471 (5) 2.379 (5) 2.304 (5) 2.20 (1) 2.32 (1) 3.206 (5)
C6-C7
See footnotes a and b; Table
i:::
Bond Angles, deg 96.2 (4) Fe-SI-Cl 102.2 (4j Fe ‘-S 1-C2 102.0 (3) Fe-S2-C6 Fe-Nl-C2 111.6(6) Fe-Nl-C3 116.6 (6) Fe-N 1-Me1 107.1 (6) C2-N 1-C3 107.1 (8) 106.8 (9) C2-N 1-Me1 107.2 (9) C3-Nl-Mel Fe-N2-C4 109.6 (5) Fe-N2-C5 104,4 (5) Fe-N2-Me2 118.0 (6) C4-N2-C5 109,2 (8) C4-N2-Me2 108.4 (8) C5-N2-Me2 106.9 (7) s1-c 1- c 2 111.4(7) N1-C2-Cl 115.0 (9) N 1-C 3-C4 116.6 (9) N 2-C4-C 3 114.0 (9) N2-C5-C6 115.2(8) 114.3 (8) S2-C6-C5 112.7 (6)
1.81 (2) 1.79(2) 1 . 4 9 (2) 1 .46 (2) 1 . 4 4 (2) 1.47 (2) 1 . 5 5 (3)) 1.49(3) av 1.53 1 . 5 6 (3)/
98.3 (6) 102.5 (7) 101.5 (7) 109 (1) 107 (1) 111 (1) 110 (2) 110 (2) 110 (2) 107 (1) 109 (1) 113 (1) 108 (2) 110 (2) 109 (2) 109 (1) 112 (2) 113 (2) 111 (2) 110 (2) 111 (1)
Magnitude of Torsion Angles, deg Fe-S 1-Cl-C2 Fe-Sl-Cl-C2 35 (11) 33 (1) Sl-Cl-C2-N1 56 (1) S 1-C 1-C2-N 1 60 (2) 44 (1) C 1-C2-Nl-Fe 54 (2) Cl-C2-Nl-Fe 1 4 . 5 (7) C2-Nl-Fe-SI C2-N1-Fe-S1 24 (1) 5 . 1 (7) 1 0 . 5 (4) Nl-Fe-S1-C1 N1-Fe-SI-C1 55 (1) Fe-Nl-C3-C4 49 (2) Fe-Nl-C3-C4 Nl-C3-C4-C5 70 (1) Nl-C3-C4-N2 54 (2) C3-C4-C5-N2 78 (1) C4-C5-N2-Fe 64 (1) C3-C4-N2-Fe 29 (2) CSSN2-Fe-Nl 39.8 (6) C4-N2-Fe-N1 3 (1) N2-Fe-Nl-C3 36.6 (8) N2-Fe-Nl-C3 24 (1) Fe-S2-C7-C6 16.8 (7) Fe-S2-C6-C5 35 (2) S2-C7-C6-N2 49 (1) S2-C6-C5-N2 57 (2) 52.9 (8) C6-C5-N2-Fe C7-C6-N2-Fe 47 (2) 31 . 7 (5) C5-N2-Fe-S2 21 (1) C6-N2-Fe-S2 7 . 6 (8) N2-Fe-S2-C7 7 5 (4) N2-Fe-S2-C6 b See footnotes a and b, Table a See footnotes a and b, Table I. IV.
structurally characterized high-spin irp(I1) sulfur complex, range from 2.339 (3) to 2.380 (3) A . 2 1 The ligand geometry of (FeL’)2 is summarized in Table IX. Atoms C1 and C2 are on the opposite sides of the N1-Fe-S1 plane with distances f0.33 (1) and
(20) P.L. Orioli, Coord. Chem. Rev., 6, 285 (1971).
Journal of the American Chemical Society
1
Fe-S1-Cl Fe’-Sl-Cl Fe-S2-C7 Fe-Nl-C2 Fe-Nl-C3 Fe-N 1-Me1 C2-Nl-C3 C2-N1-Me1 C3-N1-Me2 Fe-N2-C5 Fe-N2-C6 Fe-N2-Me2 C5-N2-C6 C5-N2-Me2 C6-N2-Me2 s 1-Cl-c2 N1-C2-C 1 N 1-C3-C4 c3-c4-c5 N2-C5-C4 N2-C6-C7 S2-C7-C6
IV.
tribution of bond angles is clearly the result of the chelating nature of the ligand since the three smallest bond angles (Sl-Fe-N1, S2-Fe-N2, and NI-Fe-N2) are the bite angles of the three chelating rings. The pattern of metal-ligand bond lengths in this complex can be summarized as follows. (i) The axial bonds are longer than the eoquatorial bonds, i,.e., Fe-S1 (2.490 A) > Ye-Sl’ (2.411 A), Fe-F2 (2.325 A), and Fe-N2 (2.337 A) > Fe-N1 (2.207 A). The differences are on the order of 20-80 times their standard deviations (Table VIII). This result parallels that for the high-spin, trigonal bipyramidal iron(I1) complex [Fe(Me6tren)Br]+, although a good explanation appears to be lacking.20 One reason for the long Fe-N2 bond in the present case might be to minimize nonbonded contacts between its methyl group and the equatorial atoms, especially S I ’ (the S1’. Me2 contact distance is already a short 3.49 (1) A, Figure 1). In the iron(II1) complex [Fe(edt)&*-, the reverse ordering of equatorial > axial bond lengths occurs,1gagain in agreement with structural data on the related d5 high-spin, trigonal bipyramidal complex [Mn(Me6tren)Br]+.2o Th: longer mean Fe-S bond length in (Fe
