Organometallics 1983, 2, 83-88
83
Structural Characterization of the Helical Ferrocene (&)-[ (1,2,3,3a,13a,14,15,16,16a,l6f-~)-Diindeno[5,4-c:4',5'-g]phenanthreneliron' John
C.Dewan"
Department of Chemistry, Columbia University, New York, New York 10027 Received September 20, 1982
The crystal structure of the title compound 1 is reported and represents the first ferrocene wherein the two cyclopentadienyl rings are linked by unbroken conjugation. Each of the two terminal cyclopentadienyl rings of the helicene bind iron(I1) in a q5 fashion, and thus the helicene, taken as a whole, binds to the metal in an overall ql0 fashion. The molecule of 1 possesses approximate C2 symmetry but has no crystallographically imposed symmetry. The Fe-C distances range from 2.008 (4) to 2.087 (4) 8, for ring A and from 2.007 (4) to 2.104 (4) A for ring G and the dihedral an le, or angle of tilt, between the terminal cyclopentadienyl rings is 19.8'. The Fe-Q distances are 1.652 if to ring A and 1.655 8, to ring G and the Q(A)-Fe-Q(G) angle is 165.4', where Q represents the centroid of each of the two cyclopentadienyl rings. The angle of twist between the two rings averages 26.7'. Torsion angles around the inner core of the helicene are 15.8, 19.1, 27.8, 17.1, and 15.1' and around the periphery are 10.0,7.4, 14.4,6.3,and 9.0'. The dihedral angles between least-squares planes of consecutive rings are 8.3, 11.7, 12.5, 12.6, 9.5, and 10.2'. Crystal data for 1 are as follows: a = 15.631 (4) A, b = 12.462 (3) A, c = 18.399 (4) A, V = 3584.0 A3, 2 = 8, orthorhombic, space group Pbca, final R = 0.040 for 1837 X-ray diffractometer data with F, > 40(F,).
Introduction Past experiments by Katz and co-workers, using various dicyclopentadienyl dianions and aimed a t synthesizing potential one-dimensional electrical conductors in which conjugated arrays and metal atoms alternate, only resulted in dimer formation.2 A strategy devised to overcome this problem was to synthesize helical dicyclopentadienyl dianions that would force metal ions to bind to opposite faces of the cyclopentadienyl rings in the hope of producing the desired p~lymerization.~Although such polymers have not yet been obtained, it was realized4 that the dianion of helicene 2 would present a unique situation in that the two
85 compounds containing the ferrocene moiety have been reported. Of these, about 14 represent studies on ferrocene it~e1fll-l~ and about 25 represent studies on compounds (1) Given here is the Chemical Abstracts name for the compound which is derived from the fundamental ring system Diindeno[5,4c:4',5'-g]phenanthrene whose structural formula and numbering system system are as
1
8
2
3
cyclopentadienyl rings would lie on top of one another and that reaction of this dianion with iron(I1) might well produce the novel helical ferrocene 1. The synthesis5 and structural characterization6 of 2 have been effected, and its dianion does indeed lead to l5 which represents the first reported ferrocene wherein the two cyclopentadienyl rings are linked by unbroken conjugation. Related molecules are k n o ~ n , but ~ ' ~they contain alternating single and double bonds where adjacent double bonds are not constrained to be parallel. No structural data appear to have been reported for these compounds. An examination of the Cambridge Crystallographic Data FilegJoreveals that the crystal structures of approximately *To whom correspondence should be addressed at the Laboratory of Molecular Biology, Medical Research Council Centre, University Medical School, Cambridge CB2 2QH, England.
7
Note that the numbering scheme used throughout this paper in describing the structure of the title compound, l , is the crystallographic numbering which is depicted in Figure 1. (2) Katz, T. J.; Slusarek, W. J. Am. Chem. SOC. 1980, 102, 1058 and
references cited therein. (3) Katz, T. J.; Slusarek, W. J. Am. Chem. SOC. 1979, 101, 4259. (4) Slusarek, W. Ph.D. Dissertation, Columbia University, New York, 1977.
(5) Katz, T. J.; Pesti, J. J. Am. Chem. SOC.1982, 104, 346. (6) Dewan, J. C. Acta Crystallogr., Sect. B 1981, B37, 1421. (7) Kasahara, A.; Izumi, T.; Shimizu, I. Chem. Lett. 1979, 1119. (8) Tanner, D.; Wennerstrom, 0. Acta Chem. Scand., Ser. B 1980, B34, 529. (9) Allen, F. H.; Bellard, S.; Brice, M. D.; Cartwight, B. A.; Doubleday, A.; Higgs, H.; Hummelink, T.; Hummelink-Peters, B. G.; Kennard, 0.;
Motherwell, W. D. S.; Rodgers, J. R.; Watson, D. G. Acta Crystallogr., Sect B 1979, B35, 2331. (10) Machin, P. A.; Mills, J. N.; Mills, 0. S.; Elder, M. "Crystal Structure Search Retrieval Manual"; SERC Daresbury Laboratory: Warrington, England, 1978. (11) Dunitz, J. D.; Orgel, L. E.; Rich, A. Acta Crystallogr. 1956,9,373. (12) Seiler, P.; Dunitz, J. D. Acta Crystallogr., Sect. B 1979, B35, 1068. (13) Takusagawa, F.; Koetzle, T. F. Acta Crystallogr., Sect B 1979, B35, 1074.
0276-7333/83/2302-0083$01.50/0 0 1983 American Chemical Society
84 Organometallics, Vol. 2, No. I , 1983
Dewan
Table I. Experimental Details of t h e X-ray Diffraction Study of t h e Title Compound, 1 a = 15.631 (4)A b = 12.462 ( 3 ) A c = 18.399 ( 4 ) A V = 3584.0 .+x3
( A ) Crystal Parametersa a t 24 “C mol wt 408.3 space group Pbca 2=8 p(ca1cd) = 1 . 5 1 3 g
( B ) Measurement of Intensity Data instrument radiation detector aperture scan technique scan rate scan width prescan rejection limit prescan acceptance limit max counting time bkgd measurements standards no. of reflections collected reorientation control
reduction to Fo and o ( F o ) absorption correction observed data a
Enraf-Nonius CAD-4F K geometry diffractometer Mo KO ( h , = 0.710 73 A ) graphite monochromated vertical, 4.0 m m ; horizontal, variable (3.0 + tan e ) m m coupled w (crystal)-20 (counter) variable from 1.26 t o 6.71” min-’ in w variable, A w = (0.7 + 0.35 tan e ) ” 10
1000 50 s moving crystal-moving detector, 25% added t o scan width a t both ends of each scan three reflections (200), (222), and (008), measured every 3600 s of X-ray exposure time, showed n o decay [ 3 ” c 20 < 50” ( t h , + k , A I ) ] 3153 unique, non-spacegroup extinguished t h e three reflections (884), (1,11,6), and ( 4 0 9 ) were recentered every 250 data, and if the position of any scattering vector deviated by more than 0.08” from its calculated position, a new orientation matrix was calculated on the basis of the recentering of a further 19 reflections
i~, C ) Treatment of Intensitv Data correction for background, attenuator, and Lorentz-polarization of monochromated X radiation as described previously not applied, p = 8.48 cm ’ 1837 unique reflections with F,, > 40(F,)were used in the structure refinement
From a least-squares fit t o the setting angles of 25 reflections with 28
wherein there is some form of bridge between the two cyclopentadienyl These bridges range from (14) (a) Seiler, P.; Dunitz, J. D. Acta Crystallogr., Sect. B 1979, B35, 2020. (b) Ibid. 1982, B38, 1741. (15) Nesmeyanov, A. N.; Sedova, N. N.; Struchkov, Y. T.; Andrianov, V. G.; Stakheeva, E. N.; Sazonova, V. A. J . Organomet. Chem. 1978,153, 115. (16) Nesmeyanov, A. N.; Struchkov, Y. T.; Sedova, N. N.; Andrianov, V. G.; Volgin, Y. V.; Sazonova, V. A. J. Organomet. Chem. 1977,137,217. (17) McKechnie, J. S.; Maier, C. A.; Bersted, B.; Paul, I. C. J . Chem. Soc., Perkin Trans. 2 1973, 138. (18) Lippard, S. J.; Martin, G. J . Am. Chem. SOC.1970, 92, 7291. (19) Churchill, M. R.; Wormald, J. Inorg. Chem. 1969, 8 , 1970. (20) Osborne, A. G.; Hollands, R. E.; Bryan. R. F.: Lockhart. S. J . Oreanomet. Chem. 1982.224. 129. 721) Osborne, A. G.; Hollhds, R. E.; Howard, J. A. K.; Bryan, R. F. J . Organomet. Chem. 1981,205, 395. (22) Stoeckli-Evans,H.; Osbome, A. G.; Whiteley, R. H. J . Organomet. Chem. 1980,194, 91. (23) Stoeckli-Evans. H.: Osborne. A. G.: Whitelev. R. H. Helu. Chim. Acta 1976. 59. 2402. (24) Abramovitch, R. A.; Atwood, J. L.; Good, M. L.; Lampert, B. A. Inorg. Chem. 1975, 14, 3085. (25) Pierpont, C. G.; Eisenberg, R. Inorg. Chem. 1972, 11, 828. (26) Davis, B. R.; Bernal, I. J . Cryst. Mol. Struct. 1972, 2, 107. (27) Cameron. T. S.: Cordes. R. E. Acta Crvstallogr..Sect. B 1979. B35, 748. (28) Sal’nikova, T. N.; Andrianov, V. I.; Struchkov, Y. T. Koord. Khim. 1977. 3. 768. (29) ’Lecomte, C.; Dusausoy, Y.; Protas, J.; Moise, C. Acta Crystallogr., Sect. B 1973, B29, 1127. (30) Jones, N. D.; Marsh, R. E.; Richards, J. H. Acta Crystallogr. 1965, 19, 330. (31) Hisatome, M.; Kawajiri, Y.; Yamakawa, K.; Mamiya, K.; Harada, Y.; Iitaka, Y. Inorg. Chem. 1982, 21, 1345. (32) Hisatome, M.; Kawaziri, Y.; Yamakawa, K.; Iitaka, Y. Tetrahedron Lett. 1979, 1777. (33) Spaulding, L. D.; Hillman, M.; Williams, G. J. B. J . Organomet. Chem. 1978,155, 109. (34) Hillman, M.; Fujita, E. J. Organomet. Chem. 1978,155,99. Table 6 of this reference summarizes various parameters from a variety of
bridged ferrocenes. (35) Hillman, M.; Fujita, E. J. Organomet. Chem. 1978, 155, 87. (36) Sal‘nikova, T. N.; Andrianov, V. I.; Antipin, M. Y.; Struchkov, Y. T. Koord. Khim. 1977, 3, 939.
> 30”.
Reference 4 8
rather complex arrangements of atoms15J6through heteroatoms such as Si, P, S, Ge, and Se20-26to purely hydrocarbon l i n k ~ . ~ For l - ~ the ~ most part these bridges do not prevent the cyclopentadienyl rings from being parallel, or approximately parallel, to one another. Where the bridge is less than the 3.31-A inter-ring separation observed in ferrocene,12however, significant deviations are observed and an “angle of tilt” is thereby introduced into the molecule. The relatively large number of studies on ferrocene itself12-14has arisen because of the realization that the original room-temperature structure of the monoclinic modification of ferrocenell was in error due to disorder present in the crystals. This original work reported a staggered conformation of the cyclopentadienyl rings (i.e., an “angle of twist” of 36’). The current position, however, is that the cyclopentadienyl rings in ferrocene are either exactly eclipsed or very nearly eclipsed (i.e., an “angle of twist” between 0 and 10’) in all crystals examined, and these extensive studies have been performed a t various temperatures on different crystalline modifications and have used both X-ray and neutron diffraction technique~.’~-’~ Three concerned with various aspects of the (37) Yasufuku, K.; Aoki, K.; Yamazaki, H. Inorg. Chem. 1977, 16, 624. (38) Batail, P.; Grandjean, D.; Astruc, D.; Dabard, R. J . Organomet. Chem. 1976, 110, 91. (39) Batail, P.; Grandjean, D.; Astruc, D.; Dabard, R. J . Organomet. Chem. 1975, 102, 79. (40) Churchill, M. R.; Lin, K.-K. G. Inorg. Chem. 1973, 12, 2274. (41) Lectome, C.; Dusausov, Y.; Protas, J.; Moise, C.; Tiroutlet, J. Acta Crystallogr., Sect B 1973, B i g , 488. (42) Churchill, M. R.; Wormald, J. Inorg. Chem. 1969, 8, 716. Table VI11 of this reference summarizes the configurations of ferrocene derivatives published before ca. 1969. (43) Paul, I. C. J . Chem. Soc., Chem. Commun. 1966, 377. (44) Laing, M. B.; Trueblood, K. N. Acta Crystallogr. 1965, 19, 373. (45) Marr, G.; Rockett, B. W. J . Organomet. Chem. 1982, 227, 373.
Organometallics,Vol. 2, No.I , 1983 85 Table 11. Final Positional Parameters for t h e Atoms of the Title Compound, lash atom
F i g u r e 1. Diagram of the title compound, 1, showing the atom labeling scheme. This does not correspond to the Chemical Abstracts numbering (see ref 1). The 40% probability thermal ellipsoids are depicted for the iron and carbon atoms. Hydrogen atoms have been assigned as arbitrary spheres with B = 1.0 A2 and are labeled according to the carbon atom to which they are bound. The molecule possesses approximate C2 symmetry but has no crystallographically imposed symmetry. The approximate twofold axis is the line joining the midpoints of the C(12)-C(13) and C(26)-C(27) bonds.
chemistry and structure of complexes containing the ferrocene moiety have appeared recently, and they cover the subject in part. This paper presents the results of a crystallographic study on the title compound, 1.
Experimental Section Collection a n d Reduction of X - r a y Data. Crystals of the title compound, 1,were provided by Professor T. J. Katz and Dr. J. Pesti, who have described the synthesis of the compound e l ~ e w h e r e .The ~ dark red crystal used in the diffraction study had approximate dimensions 0.17 mm X 0.13 mm X 0.80 mm and was sealed in a capillary under nitrogen to minimize possible decomposition. Open-counter w scans of several strong low-angle reflections showed that the crystal quality was excellent, the average width of the peaks a t half-height being 0.10’. Further details of the data collection and reduction appear in Table I and ref 48. Determination a n d Refinement of the S t r u c t u r e . Study on the diffractometer showed that the crystal belonged to the orthorhombic system, and the systematic absences Okl when k # 2n, h01 when 1 # 2n, and hkO when h # 2n uniquely define the space group as Pbca (Dii, No. 61).” The structure was solved by using the heavy-atom method. Neutral atom scattering factors and anomalous dispersion corrections for the non-hydrogen atoms were obtained from ref 50. Scattering factors for the hydrogen atoms were those of Stewart et All non-hydrogen atoms were refined anisotropically, and no evidence for disorder was observed in any part of the structure. Hydrogen atoms were placed in calculated positions (C-H = 0.95 A) and were constrained to “ride” on the carbon atom to which they are bound. A common isotropic temperature factor for all the hydrogen atoms converged a t U = 0.039 (3) A2. (46) Cullen, W. R.; Woollins, J. D. Coord. Chem. Reu. 1981, 39, 1. (47) (a) Omae, I. Coord. Chem. Rev. 1982, 42, 31. The references in Table 2 of this review appear to be in error. Structure 45 should be equated with ref 59 and structure 64 with ref 78, and thereafter each reference number incremented by unity and equated with the next structure in the table until, finally, structure 69 equates with ref 84. Also, ref 75 in this review is misprinted and should correspond to ref 23 in this paper. (b) Omae, I., personal communication. (48) Silverman, L. D.; Dewan, J. C.; Giandomenico, C. M.; Lippard, S. J. Inorg. Chem. 1980, 19, 3379. (49) ‘International Tables for X-ray Crystallography”,3rd ed.; Kynoch Press: Birmingham, England, 1976; Vol. I, p 150. (50) “InternationalTables for X-ray Crystallography”;Kynoch Press: Birmingham, England, 1974; Vol. IV, pp 99, 149. (51) Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem. Phys. 1965,42, 3175.
Fe C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C( 20) C(21) C(22) C(23) C(24) C(25) C(26) C(27) C(28) n(A)
n(G) H(2) H(3) H(4) H(6) H(7) H(9) H(10) H(12) H(13) H(15) H(16) H(18) H(19) H(21) H(22) H(23)
X
0.32250 (31 0.4233 ( 2 ) ’ 0.3742 ( 3 ) 0.3735 ( 3 ) 0.4215 ( 3 ) 0.4558 ( 2 ) 0.5147 ( 3 ) 0.5440 ( 3 ) 0.5089 ( 3 ) 0.5407 ( 3 ) 0.5058 ( 3 ) 0.4311 ( 3 ) 0.3977 ( 4 ) 0.3318 ( 3 ) 0.2804 ( 3 ) 0.2053 ( 3 ) 0.1522 ( 3 ) 0.1676 ( 3 ) 0.1116 ( 3 ) 0.1246 ( 3 ) 0.1896 ( 2 ) 0.2124 ( 3 ) 0.2707 ( 3 ) 0.2875 ( 3 ) 0.2403 ( 2 ) 0.2395 ( 3 ) 0.3038 ( 3 ) 0.3911 ( 3 ) 0.4395 ( 2 ) 0.40965 0.24008 0.3465 0.3462 0.4291 0.5327 0.5895 0.5870 0.5321 0.4231 0.3185 0.1913 0.1048 0.0629 0.0928 0.1925 0.2945 0.3234
Y 0.36465 (51 0.4135 ( 4 ) ’ 0.5039 ( 4 ) 0.5044 ( 4 ) 0.4147 ( 4 ) 0.3604 ( 4 ) 0.2737 ( 4 ) 0.2481 ( 4 ) 0.2932 ( 4 ) 0.2603 ( 4 ) 0.2986 ( 4 ) 0.3619 ( 4 ) 0.4067 ( 4 ) 0.4755 ( 4 ) 0.4873 ( 4 ) 0.5492 ( 4 ) 0.5557 ( 4 ) 0.4915 ( 4 ) 0.4998 ( 4 ) 0.4458 ( 4 ) 0.3646 ( 4 ) 0.2855 ( 4 ) 0.2131 ( 3 ) 0.2485 ( 3 ) 0.3450 ( 3 ) 0.4228 ( 3 ) 0.4326 ( 4 ) 0.3868 ( 3 ) 0.3661 ( 4 ) 0.43940 0.29133 0.5546 0.5563 0.3936 0.2347 0.1980 0.2110 0.2827 0.3878 0.5169 0.5872 0.6034 0.5450 0.4624 0.2827 0.1513 0.2136
2
-0.31579 (31 -0.3748 ( 2 ) ’ -0.3503 ( 2 ) -0.2731 ( 3 ) -0.2483 ( 3 ) -0.3103 ( 2 ) -0.3171 ( 3 ) -0.3832 ( 3 ) -0.4495 ( 3 ) -0.5177 ( 3 ) -0.5800 ( 3 ) -0.5786 ( 2 ) -0.6447 ( 3 ) -0.6431 ( 3 ) -0.5785 ( 2 ) -0.5806 ( 3 ) -0.5218 ( 3 ) -0.4600 ( 2 ) -0.3971 ( 3 ) -0.3353 ( 3 ) -0.3338 ( 2 ) -0.2810 ( 3 ) -0.3142 ( 3 ) -0.3858 ( 2 ) -0.3985 ( 2 ) -0.4580 ( 2 ) -0.5140 ( 2 ) -0.5110 ( 2 ) -0.4457 ( 2 ) -0.31136 -0.34266 -0.3808 -0.2433 -0.1991 -0.2754 -0.3875 -0.5195 -0.6253 -0.6898 -0.6849 -0.6238 -0.5222 -0.4006 -0.2928 -0.2323 -0.2917 -0.4201
Atoms are labeled as shown in Figure 1. Estimated standard deviations, in parentheses, occur in t h e last significant figure for each parameter. n (A) and n ( G ) represent the centroids of rings A and G, respectively. bHydrogen atoms are labeled according t o t h e carbon t o which they are bound. Full-matrix least-squares refinement of 263 variables, using R1 = 0.040 and R2 = 0.043. The function minimized in the least squares was Cw(lF,I - lFcl)2,where w = l.0981/[u2(F0)+ O.O00400F~].In the fiial cycles of refinement, no parameter shifted by more than 0.001 of its estimated standard deviation, and the largest peak on the final difference Fourier map was 0.37 e .k3.The average wA2 for groups of data sectioned according to parity group, lFol, (sin e)/x, Ihl, lkl,or 111, showed good consistency, and the weighting scheme was considered to be satisfactory. Final positional parameters, together with their estimated standard deviations, appear in Table 11. Interatomic distances and angles, with estimated standard deviations, are given in Table 111. A listing of final observed and calculated structure factors, a table of anisotropic thermal parameters, and the results of sHELx-7~3;~converged to final residual indices53of
(52) Sheldrick,G. M. In ‘Computing in Crystallography”; Schenk, H., Olthof-Hazekamp, R., van Koningsveld, H., Bassi, G. C., Eds.; Delft University Press: Delft, Holland, 1978; p 34. (53) R1 = m % l- l F c l l / ~ l ~ Rz o l ~= [Z4lF0I- l ~ c 1 ) 2 / ~ : w l ~ 0 1 2 1 ” 2 .
86
Organometallics. Vol 2, No 1 , I983
least-squaresplane calculations are available as supplementary material i n Tables Sl-S3, respectively. Figure 1 depicts the geometrb in 1 along with the atom labeling scheme
Dewan a
Discussion The structure of the title compound, 1, consists of discrete molecules as shown in Figure 1wherein an iron atom is bound in a q5 fashion by each of the two cyclopentadienyl rings at either extremity of the doubly deprotonated C helicene 2. Specifically, the iron is bound to atoms C( 1) through (‘(5) of ring A and to atoms C(20) through C(24) of ring G which means that the helicene, taken as a whole, hinds iron in an overall q10 fashion. The space group, uniquely defined by its systematic absences as P b c a , requires equal numbers of both enantiomers of 1 to be present in each crystal which was also the case for the structure of 2.6 In contrast to the structure of 2, however, in which the molecule has crystallographically required twofold symmetry ii.e., Cz symmetry), the molecule in the present case has no crystallographically imposed symmetry Figure 2. (a) Side view of the title compound, 1. (b) Top view although the approximation to C, symmetry is good. The of 1. (c) Side view of 2. (d) Top view of 2. The 40% probability approximate twofold axis in 1 is the line joining the midthermal ellipsoids are depicted for all iron and carbon atoms while all hydrogen atoms are depicted as arbitrary spheres with B = points of the C(l2)-C(13) and C(26)-C(27) bonds. There 1.0 A’. The structure of 2 has been reported in ref 6. are no unusually short intermolecular contacts in the structure the closest non-hydrogen atom contact being in this case the Fe-R distance is the very short 1.5‘73 3.350 ( 6 ) between (’(2) and C(10),where the latter atom Comparison between 1 and 2 (Figure 2) shows a drais at iI x, 1- y , 1 t- 2 ) . All remaining contacts are greater matic decrease in the dihedral angle between the two than 3.484 (6) A. terminal cyclopentadienyl ring planes upon complexation The angle of tilt, or dihedral angle, between cycloof iron(I1). The angle of tilt in 26 is 69.1’ while that for pentadienyl rings A and G in 1 is 19.8’. As a result of this 1 is 19.8’. The value in 2 is very much larger than that tilt the F e C distances to rings A and G vary systematically normally observed in similar hexahelicenes and heptaand range from 2.008 (4) to 2.087 (4),A for ring A and from helicenes because two methylene hydrogen atoms on either 2.007 (4) tn 2.104 (4) A for ring G with the shorter distances cyclopentadiene ring are projected into the inner core of being closer to the inner core of the molecule. The dethe molecule thus forcing the helix arms apart to prevent viations between equivalent distances to rings A and G are close intramolecular contacts with carbon atoms. The comparable and in no case is this difference greater than dihedral angle between terminal ring planes for hexaca. 4ri, thus maintaining the approximate C2 symmetry of h e l i ~ e n eis~5 8~. 5 O , for 2-methylhexahelicene 54.8O ,55 and the molecule. The range of Fe-C distances in 1 is quite for tribenzo[f,I,r]heptahelicene 33.2°56 and for heptacomparable to that observed in a large number of similar helicene averages 32.3°.57158 It was suggested previously6 complexes.”-44 The complex with which 1 is most comthat helicene 3 should be much less strained than 2 since having an parable is ~1,1’-ferro~enediyl)diphenylsilane,~~ the two methylene hydrogen atoms are now projected away angle of tilt of 19.2’. where the Fe-C distances range from from the inner core of the molecule. This proposal has not 2.01 (1) to 2.11 ( I ) A. The 62-Fe-Q angle in this compound been experimentally verified although, by comparison with is 167.3’ while that in 1 is 165.4’, where R represents the heptahelicene i t ~ e l f , ~ a’ ,dihedral ~~ angle of aroung 30’ centroid of each cyclopentadienyl ring. The Fe-C dismight be expected for 3. The 19.8’ observed in 1 suggests, tances observed in the most recent room-temperature therefore, that the introduction of iron(I1) has served to structure determination of the monoclinic modification of close the helix arms and clamp rings A and G at a distance ferroceneI2 range rather widely from 2.009 to 2.054 A. The closer than might be expected for 3. It was also suggested shorter distance is comparable to the shortest distance previously6 that the dianion of 2, produced by deprotonobserved in 1 although the longer distance in 1 i5 greater ation of both cyclopentadiene rings, should show less strain than that in ferrocene by some 0.05 A. in the helix. While this argument seems sound on steric The Fe-R distance tends to be fairly constant at between grounds, it appears that the two negative charges on the 1.64 and 1.66 A throughout the large range of bridged terminal cyclopentadienyl rings serve to keep the helix ferrocene complexes that have been structurally characarms splayed apart, a fact that is suggested by the exterized. The Fe-R distance in ferrocene“ is 1.655 A which perimental observation5 that deuterated acids attack alcompares well with Fe-Q(A) = 1.652 A and Fe-R(G) = most as often from the inside of the molecule as from the 1.655 A in 1. In certain ferrocene complexes the bridges outside. between the cyclopentadienyl rings are such that the rings The decreased strain in 1, compared to the highly are forced closer together than is usually observed, examples being i4](1,l’)[4](3,3’)[4] (5,5’)[3](4,4’)ferro~enophane,3~ strained helix in 2, can also be seen by comparing the 1,1’,2,2’,3,3’,4,5,4’,5’-pentakis(trimethylene)ferro~ene,~~ 1,1’,%,2’,3,.2,4’,5’-tetrakis(trimethylene)ferro~ene,~~ and (54) de Rango, C.; Tsoucaris, G.; Declercq, J.-P.;Germain, G.; Putzeys, J. P. Cryst. Struct. Commun. 1973, 2, 189. 1,1’,2,2’,4,4’-tri~(trimethylene)ferrocene~~ where the Fe-R ( 5 5 ) Frank, G. W.; Hefelfinger, D. T.; Lightner, D. A. Acta Crystaldistances are, respectively, 1.618, 1.60, 1.616, and 1.573 A. logr., S e c t . B 1973, B29,223. Fe-C‘ distances shorter than ca. 2.0 A are observed, and (56) van den Hark, Th. E. M.; Noordik, J. H.; Beurskens, P. T. Cryst. Struct. Commun. 1974, 3, 443. they tend to be found in these complexes where the cy( 5 7 ) Beurskens, P. T.; Beurskens, C.; van den Hark, Th. E. M. Cryst. clopentadienyl rings have been forced closer together than Struct. Commun. 1976, 5, 241. is usual. One of the shortest Fe-C distances observed is (58) van den Hark, Th. E. M.; Beurskens, P. T. Cryst. Struct. Commiin. 1976. .5. 247. 1 968 (6) in 1,1’,2,2’.4,4’-tris(trimethvIene)ferrocene. and
Organometallics, Vol. 2, No.1, 1983 87
[Diinden0[5,4-~:4',5'-g]phenanthrene]iron
Table 111. Interatomic Distances ( A ) and Angles (deg) for t h e Non-Hydrogen Atoms of t h e Title Compound, 1a Coordination Sphere Fe-C( 1) Fe-C( 2 ) Fe--C(3 ) Fe--C($ )
C( 1)-Fe-C( 2 ) C( 1)-Fe-C( 3 ) C( 1)-Fe-C( 4 ) C( l)-Fe-C( 5 ) C(l)-Fe-C(20) C( 1j-Fe-C( 2 1 ) C( 1)-Fe-C( 22) C(l)-Fe-C(23) C(l)-Fe-C(24) C(2)-Fe-C(3) C( 2 )- Fe-C(4 ) C( 8)-Fe-C( 5 ) C( 2)-Fe-C( 2 0 ) C( 2)-Fe--C( 2 1 ) C( 2)-Fe-C( 2 2 ) C( 2)-Fe-C(23) C( 2)-Fe-C( 2 4 ) C( 3)-Fe-C(4) C( 3)-Fe-C( 5 ) C(3)-Fe-C( 2 0 ) C(3 )--Fe-C(21) C( 3)-Fe-C( 2 2 ) C( 3 )- Fe-C( 2 3 ) C(3)-Fe-C(24)
2.008 2.017 2 070 2.079
(4) (4) (4) (4)
41.8 ( 2 ) 69.3 ( 2 ) 69.4 ( 2 ) 41.5 ( 2 ) 133.6 ( 2 ) 163.2 ( 2 ) 126.6 ( 2 ) 94.9 ( 2 ) 97.4 ( 2 ) 40.6 ( 2 ) 68.4 ( 2 ) 68.7 ( 2 ) 110.3 ( 2 ) 146.6 ( 2 ) 162.4 ( 2 ) 121.8 ( 2 ) 97.1 ( 2 ) 40.1 ( 2 ) 67.5 ( 2 ) 116.1 ( 2 ) 126.9 ( 2 ) 156.9 (2) 162.2 ( 2 ) 129.6 ( 2 )
1.436 ( 6 ) 1.451 ( 6 j 1.454 (6) 1.419 ( 6 ) 1.421 (6) 1.430 ( 6 ) 1.426 (6) 1.338 ( 6 ) 1.451 ( G ) 1.411 ( 6 ) 1.417 ( 6 ) 1.357 ( 6 ) 1.410 (6) 1.436 ( 6 ) 1.428 (6)
Fe-C( 5 ) Fe--C(2 0 ) Fe--C(2 1) Fe--C(2 2 )
Bond Distances 2.087 2.104 2.084 2.055
Fe-C( 23 1 Fe-C( 2 4 ) Fe-n ( A ) Fe-n ( G )
2.013 ( 4 ) 2.007 ( 4 ) 1.652 1.655
Fe-C( 1)-C( 5 ) Fe-C(1)-C(28) Fe-C( 2 )-C( 1) Fe-C( 2)-C( 3 ) Fe-C(3)-C(2) Fe-C( 3 )-C(4 ) Fe-C(4)-C(3) Fe-C(4)-C(5) Fe-C( 5)-C( 1) Fe-C( 5)-C( 4 ) Fe-C( 5)-C(6) Fe-C( 20)-C( 19) Fe-C(20)-C( 21) Fe-C(20)-C( 2 4 ) Fe-C(21)-C(20) Fe-C(21)-C(22) Fe-C(22)-C(21) Fe-C( 22)-C( 23) Fe-C(23)-C( 2 2 ) Fe-C( 23)-C( 2 4 ) Fe-C( 24)-C( 2 0 ) Fe-C( 24)-C( 2 3 ) Fe--C(24)-C( 2 5 )
72.2 ( 2 ) 119.9 (3) 68.8 ( 2 ) 71.7 ( 3 ) 67.7 ( 3 ) 70.3 ( 3 ) 69.6 ( 3 ) 70.2 ( 2 ) 66.3 ( 2 ) 69.6 ( 2 ) 131.3 ( 3 ) 134.6 ( 3 ) 69.3 ( 2 ) 65.8 ( 2 ) 70.8 ( 2 ) 68.8 ( 2 ) 71.0 ( 2 ) 68.1 ( 2 ) 71.3 ( 2 ) 68.9 ( 2 ) 72.9 ( 2 ) 69.4 ( 2 ) 119.4 ( 3 )
(4) (4) (4) (4)
Bond Angles C( 4)-Fe-C( 5 ) 40.1 ( 2 ) C(4)-Fe-C(20) 146.0 ( 2 ) 125.0 ( 2 ) C( 4)-Fe-C( 2 1 ) C(4)-Fe-C(22) 124.1 ( 2 ) C( 4)-Fe-C( 2 3 ) 143.1 ( 2 ) C( 4)-Fe-C( 2 4 ) 165.0 ( 2 ) C( 5)-Fe-C( 2 0 ) 173.6 ( 2 ) C( 5)-Fe-C( 2 1 ) 142.9 ( 2 ) C( 5)-Fe-C( 2 2 ) 111.7 ( 2 ) C( 5)--Fe-C(23) 106.5 ( 2 ) C( 5)-Fe-C( 24 1 132.3 ( 2 ) C(20)-Fe--C(21) 39.9 ( 2 ) C( 20)-Fe-C(22) 67.2 ( 2 ) C( 20)-Fe-C( 23) 68.3 ( 2 ) C( 20)-Fe-C(24) 41.3 (1) C(21)-Fe-C( 2 2 ) 40.1 ( 2 ) C( 21)-Fe-C(23) 68.4 ( 2 ) C( 21 )-Fe-C( 2 4 ) 69.3 ( 2 ) C(22)-Fe-C(23) 40.7 ( 2 ) C(22)-Fe-C(24) 69.3 ( 2 ) C( 23)-Fe-C( 2 4 ) 41.7 ( 2 ) ( A)--Fe--n( G ) 165.4 Fe-C( 1)-C( 2 ) 69.4 ( 2 ) Ligand Geometry Bond Distances C(12)-C( 1 3 ) 1.340 (7) C( 13)-C( 1 4 ) 1.443 (6) C( 14)-C( 1 5 ) 1.406 (6) C( 14)-C( 2 6 ) 1.415 (6) C( 15)-C( 1 6 ) 1.366 ( 6 ) C( 16)-C( 1 7 ) 1.411 (6) C( 17)-C( 1 8 ) 1.455 (6) C( 17)-C( 2 5 ) 1.413 (5) C( 18)-C( 1 9 ) 1.337 ( 6 ) C(19)-C(20) 1.434 ( 6 ) C(2O)-C( 2 1 ) 1.428 ( 6 ) C( 20)-C( 2 4 ) 1.451 (5) C(21)-C( 2 2 ) 1.420 ( 6 ) C(22)-C(23) 1.414 ( 6 ) C( 23)-C( 24) 1.430 ( 5 )
C(24)-C( 25) C(25)-C( 2 6 ) C(26)-C(27) C(27)-C(28) C(l)**.C(23) C( 1)**C(24) C( 2)-.C( 2 0 ) C(2)*..C(24) C(3)*.*C(20) C(3)-.C(21) C( 4)..*C(2 1 ) C(4)..,C(22) C( 5)...C( 2 2 ) C( 5)...C( 23)
1.462 ( 6 ) 1.445 ( 5 ) 1.479 ( 6 ) 1.443 (6) 2.963 ( 6 ) 3.017 ( 5 ) 3.381 ( 6 ) 3.015 ( 6 ) 3.542 ( 6 ) 3.716 ( 6 ) 3.693 ( 6 ) 3.651 ( 6 ) 3.428 ( 6 ) 3.286 ( 6 )
Bond Angles C(2)-C(l)-C(5) C( 2)-C(1 )-C( 28) C(5)-C(l)-C(28) C(l)-C(2)-C(3) C( 2)-C( 3)-C(4) C( 3)-C( 4 )-C( 5 ) C(1 )-C(5)-C(4) C ( 1 )-C( 5 F C ( 6 ) C(4)-C( 5)-C(6) C( 5)-C( 6)-C(7 ) C(6)-C(7)-C(8) C(7)-C(8)-C(9) C(7)-C(8)-C(28) C(9)--C(8)-C( 2 8 ) C(8 k C ( 9 )-C(lO) cis 1-c(10)-C( 1 1 ) C(lO)-C( 11)-C(12) C ( l O ) - C ( l l )-C( 27 )
106.7 ( 4 ) 133.9 ( 4 ) 119.2 ( 4 ) 108.8 ( 4 ) 108.3 ( 4 ) 108.3 ( 4 ) 107.8 ( 4 ) 120.0 (4) 132.2 ( 4 ) 118.8 ( 4 ) 122.8 ( 4 ) 120.1 (4) 119.8 ( 4 ) 1 2 0 . 0 (4) 1 2 0 . 6 (41 121.0 i 4 j 120.2 ( 4 ) 120.0 ( 4 )
C(12)-C( 11)-C( 27 ) C( 11)-C( 12)-C(13) C(12)-C( 1 3 ) - c ( 1 4 ) C(13)-C(14)-C(15) C(13)-C(14)-C(26) C(15)-C( 14)-C( 2 6 ) C( 14)-C( 15)-C(16) C(15)-C( 16)-C(17) C(16)-C( 1 7 )-C( 18) C( 16)-C( 17)-C( 25) C( 18 )-C( 1 7 )-C( 2 5 ) C(17)-C(18)-C(19) C(18)-C(l9)-C(20) C( 19 )--C(2 0 )-C( 2 1) C( 1 9 )-C( 2 0 )-C( 2 4 ) C(21 )-C( 20)-C(24) C(2O)-C( 21 )-C( 2 2 )
119.9 ( 4 ) 120.0 ( 4 ) 120.0 ( 4 ) 123.3 ( 4 ) 118.6 ( 4 ) 132.6 ( 4 ) 119.6 ( 4 ) 120.6 ( 5 ) 120.8 ( 5 ) 119.8 (4) 1 1 9 . 8 (4) 120.3 (4) 121.1 (5) 120.1 ( 4 ) 119.4 ( 4 ) 107.8 ( 4 ) 107.9 ( 4 )
C( 2 1 )-C( 22)-C( 23) C( 22)-c(23)-c(24) C( 20)-C( 24)-c( 2 3 ) C( 20)-C( 2 4 ) - c ( 2 5 ) C(23)-C(24)-C(25) C( 1 7 ) - c ( 2 5 ) - c ( 2 4 ) C( 17)-C( 25)-C( 2 6 ) C( 24)-C( 25)-C( 2 6 ) C( 14)-C(26)-C( 2 5 ) C( 1 4 )-C( 26)-C( 2 7 ) C( 25)-C(26)-C( 2 7 ) C(ll)-C(27)-C(26) C( 11)-C(27 )-C( 2 8 ) C(26)-C( 27)-C(28) C(l)-C(28)-C(8) C( 1)-C( 28)-C( 27 ) C(8)--C(28)-C( 2 7 )
See f o o t n o t e a , Table 11. Values reported have n o t been corrected for thermal motion.
108.7 ( 4 ) 108.6 ( 4 ) 106.8 ( 4 ) 119.8 ( 4 ) 133.2 ( 4 ) 115.4 ( 4 ) 118.9 ( 4 ) 125.7 ( 4 ) 117.3 ( 4 ) 117.1 ( 4 ) 125.5 ( 4 ) 117.0 ( 4 ) 117.2 ( 4 ) 125.8 ( 4 ) 116.0 ( 4 ) 125.6 ( 4 ) 118.4 ( 4 )
88 Organometallics, Vol 2, No I , 1983 terminus to terminus torsion angles around the inner core of the molecules which are 15.8, 19.1, 27.8, 17.1, and 15.1' for the torsion angles C(a)-C(l)-C(28)-C(27), C(1)-C(28)-C(27)-C(26), C(28)-C(27)-C(26)-C(25), C(27)-C(26)-C(25)-C(24), and C(26)-C(25)-C(24)-C(23) in 1. The similar angles for 2, which has crystallographically imposed C2 symmetry, are 4.8, 20.2, 40.8, 20.2, and 4.8'. Thus the strain at the C(28)-C(27)-C(26)-C(25) torsion angle, being 27.8' in 1 compared with 40.8' in 2, is now much more in line with that observed in heptahelicene where this angle averages 25.0" over two independent structure determin a t i o n ~ . The ~ ~ . similar ~ angles in 2-methylhexahelicene5j are 26 and 30' while in 2-bromohe~ahelicene~~ they are 26.6 and 27.9'. Torsion angles around the periphery of the helicene in 1 are 10.0, 7.4, 14.4, 6.3, and 9.0' for the torsion angles C(5)-C(6)-C(7)-C(8), C(8)-C(9)-C(lO)-C(ll),C(11)-C( 12)-C( 13)-C( 14), CI14)-C( 15)-C( 16)-C( 17), and C(17)-C( 18)-C( 19)-C(20). Although in a less dramatic fashion than noted above, the release of helical strain in 1 compared with 2 is also seen in the dihedral angles between consecutive leastsquares planes through rings A t o G which for 1 are 8.3, 11.7, 12.5, 12.6, 9.5, and 10.2' and for 2 are 6.8, 14.1, 17.4, 17.4, 14.1, and 6.8'. The largest deviations from the least-squares planes through rings A to G are 0.023,0.117, 0.100, 0.133, 0.094, 0.111, and 0.028 A in 1, while the comparable deviations in 2 are 0.013, 0.050, 0.124, 0.142, 0.124, 0.050, and 0.013 A. Thus the deviations from planarity are greater in the outer ring planes for 1 when compared with 2. The large helical strain in 2 means, however, that for the inner rings of the helix these deviations become larger in 2, although only by about 0.11 A. The C-C distances in the cyclopentadienyl rings of 1 range from 1.419 (6) to 1.451 (6) .q for ring A (average = 1.431 A) and from 1.414 (6) to 1.451 ( 5 ) A for ring G (average = 1.429 A). These average values agree well with the acceptedm $-cyclopentadienyl C-C bond length of ca. 1.43 A. The cyclopentadienyl distances in 1 are obviously different from those observed in 2 where the nonaromatic nature of the cyclopentadiene rings in this latter compound is reflected in a much larger range of C-C bond lengths. As was noted in the structure of 2,6 and indeed with most helicene structures reported to date, the structure of 1 shows the usual pattern of shortened bond lengths along the periphery of the helix and lengthened bonds around the inner core of the molecule. In 1 these shorter peripheral C-C bond lengths are 1.338 (6), 1.357 (6), 1.340 ( 7 ) , 1.366 (61, and 1.337 (6) A (average = 1.348 A) for the bonds C(6)-C(7), C(9)-C(lO), C(12)-C(13), C(15)-C(16), and C(lS)-C(l9). The average value for the similar bonds in 2 is 1.338 A. The longer inner core C-C bond lengths for 1 are 1.454 (6), 1.443 (61, 1.479 (6), 1.445 (51, and 1.462 (6) A (average = 1.457 A) for the bonds C(l)-C(28), C(27)-C(28), C(26)-C(27), C(25)-C(26). and C(24)-C(25) with the average value for the similar bonds in 2 being 1.437 A. Thus the agreement between these average values for 1 and 2 is quite reasonable. A compilation of the angles of tilt for several bridged ferrocenes appearing in Table 2 of ref 47 suggests that a two-carbon atom bridge induces an angle of tilt of about 24' into the ferrocene molecule while a three-carbon atom bridge produces an angle of tilt of around 10'. The 19.8' observed in 1 suggests, therefore. that the five benzene (59) Lightner, D. A,; Hefelfinger, D. T.; Powers, T. W.; Frank, G. W.; Trueblood. K. N.J. A m . Chem. Soc. 1972. 94. 3492.
Deulan
rings of the helicene, which are effectively bridging the two cyclopentadienyl rings, are behaving somewhere between a two- and three-carbon atom bridge although closer to the former than the latter. The only compound to have an angle of tilt close to that of 1 is the single silicon atom bridged compound ( l,l'-ferrocenediyl)diphenylsilane23 where the angle of tilt is 19.2'. This value in the similar germanium and phosphorus compounds is 16.6 and 26.7', respectively.*2 The angle of twist in 1 (see end of paragraph) averages 26.7' while that in 2 is 24.1'. This difference of 2.6' is probably not a significant deviation especially when one considers that the two structures being compared have angles of tilt differing by some 49.3' and that the cyclopentadienyl rings in 1 are aromatic while those in 2 are not. The conformation of the helicene would seem to be the major factor in determining the angle of twist in 1 and 2, and the helicene appears to be rather rigid in the sense that the closing of the helix arms by the large 49.3' appears to have little effect on values such as the average peripheral bond lengths and inner core bond lengths of the molecules which, as was seen above, agree quite well between 1 and 2. Put alternatively, the top views (Figure 2) reveal few differences between 1 and 2 when compared with the dramatic change revealed by a comparison of the side views of 1 and 2. The angle of twist in 1 was calculated by averaging the five torsion angles C(l)-R(A)-R(G)-C(23) = 27.3', C (2)-0( A)-R (G)-C (24) = 27.3', C (3)-R(A)-R(G)-C(20) = 26.4", C(4)-R(A)-R(G)-C(21) = 26.4', and C (5)-R (A)-Q (G)-C (22) = 26.2'. It is interesting to speculate as to whether complexes that actually require a large angle of tilt between their cyclopentadienyl rings could be formed by the dianion of 2. The R(A)-.R(G) distance in 1 is 3.28 A with an angle of tilt of 19.8", and for 2 the corresponding values are much larger a t 4.44 A and 69.1'. Examination of the recent literature shows that in the uranium complex60 (U[$ICH3)5Cj]2(p-C1))3 the R . 4 distance is 4.47 A with an angle of tilt of 48.4' while these values are 4.82 A and 76.2" in the zirconium complex6' [(q5-C5H4CH3)2ZrH(g-H)],. This suggests that the dianion of 2 should be capable of forming such complexes, certainly in that the R - 4 distance seems to be quite expandable and it may be possible to open this up even further than 4.44 A, thus inducing further distortions into the helicene. It would be of interest to see how far the helicene could be distorted.
Acknowledgment. I thank Professor S. J. Lippard (Columbia University) for the use of his X-ray diffraction facilities, Professor T. J. Katz and Dr. J. Pesti (Columbia University) for providing the crystals of 1, Dr. K. Henrick (Polytechnic of North London) for supplying information from the Cambridge Crystallographic Data Fileg via the Crystal Structure Search Retrievallo system, and Dr. K. L. Loening (Chemical Abstracts Service) for advice concerning nomenclature. Registry No. 1 , 83633-75-4. Supplementary Material Available: Tables S1-S3, listings of final observed and calculated structure factors, anisotropic thermal parameters, and least-squares planes, respectively (11 pages). Ordering information is given on any current masthead page. (60) Fagan, P. J.; Manriquez, J. M.; Marks, T. J.;Day, C. S.; Vollmer, S. H.; Day, V. W. Organometallics 1982, 1, 170. (61) Jones, S. B.; Petersen, J. L. Inorg. Chem. 1981, 20, 2889.
