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Acta Crystallogr C. 2009 November 15; 65(Pt 11): m426–m430.
Published online 2009 October 17. doi:  10.1107/S0108270109034763
PMCID: PMC2773730

Monohalogenated ferrocenes C5H5FeC5H4 X (X = Cl, Br and I) and a second polymorph of C5H5FeC5H4I

Abstract

The structures of the three title monosubstituted ferrocenes, namely 1-chloro­ferrocene, [Fe(C5H5)(C5H4Cl)], (I), 1-bromo­ferrocene, [Fe(C5H5)(C5H4Br)], (II), and 1-iodo­ferrocene, [Fe(C5H5)(C5H4I)], (III), were determined at 100 K. The chloro- and bromo­ferrocenes are isomorphous crystals. The new triclinic polymorph [space group P An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi1.jpg, Z = 4, T = 100 K, V = 943.8 (4) Å3] of iodo­ferrocene, (III), and the previously reported monoclinic polymorph of (III) [Laus, Wurst & Schottenberger (2005 [triangle]). Z. Kristallogr. New Cryst. Struct. 220, 229–230; space group Pc, Z = 4, T = 100 K, V = 924.9 Å3] were obtained by crystallization from ethanolic solutions at 253 and 303 K, respectively. All four phases contain two independent mol­ecules in the unit cell. The relative orientations of the cyclo­penta­dienyl (Cp) rings are eclipsed and staggered in the independent mol­ecules of (I) and (II), while (III) demonstrates only an eclipsed conformation. The triclinic and monoclinic polymorphs of (III) contain nonbonded inter­molecular I(...)I contacts, causing different packing modes. In the triclinic form of (III), the mol­ecules are arranged in zigzag tetra­mers, while in the monoclinic form the mol­ecules are arranged in zigzag chains along the a axis. Crystallographic data for (III), along with the computed lattice energies of the two polymorphs, suggest that the monoclinic form is more stable.

Comment

Once ferrocene had been synthesized, numerous applications were found for the compound and its derivatives. Many ferrocene-based materials were used in the development of bioorganometallic chemistry (Staveren & Metzler-Nolte, 2004 [triangle]), catalysis (Togni & Hayashi, 1995 [triangle]), dendrimers (Astruc et al., 2008 [triangle]), nonlinear optical materials (Kinnibrugh et al., 2009 [triangle]), anti­cancer agents (Jaouen, 2008 [triangle]), etc. For example, ferroquine has been perceived to be extremely active against a chloro­quine-resistant strain CQ(−) of Plasmodium falciparum (Dubar et al., 2008 [triangle]). In this work, we report the first structural study of the monohalogen-substituted ferrocenes 1-chloro­ferrocene, (I), and 1-bromo­ferrocene, (II), and a triclinic form of 1-iodo­ferrocene, (III). It is surprising that the elucidation of the structures of the substituted ferrocenes presented here had not been carried out before, although this is probably due to experimental difficulties related to the low melting points of these compounds. All the title compounds contain two crystallographically independent mol­ecules, denoted A and B, in the unit cell.

An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-scheme1.jpg

Disorder of the Cp rings in ferrocene is a well known phenomenon (Seiler & Dunitz, 1979 [triangle]). Previous workers have found a dynamic type of disorder for the metallocenes Cp2Co and Cp2V (Cp is cyclopentadienyl; Antipin et al., 1993 [triangle]; Antipin & Boese, 1996 [triangle]). Usually, monosubstituted ferrocenes do not show disorder, due to higher rotational barriers compared with unsubstituted Cp rings (Sato, Iwai et al., 1984 [triangle]). Nevertheless, we found that compound (I) has disordered Cp rings for mol­ecule B with equal occupancies over the two orientations at 100 K. A disorder model for the C5H5 and C5H4Cl rings of mol­ecule B was proposed, with the two orientations of each ring differing by rotations in the ring plane of about 20 and 16°, respectively.

The mean values of the Fe—C, C—C, C—X (X = Cl, Br or I) and Fe(...)Cg (Cg is a ring centroid) bond lengths, and the η5-C5H4 X5-C5H5 angles for mol­ecules (I), (II) and (III) are presented in Table 1 [triangle]. The Fe—C and Fe(...)Cg distances to the substituted η5-C5H4 X ring are slightly shorter than those for the η5-C5H5 ring, which is attributed to the substituent in the η5-C5H4 X ring. The shortening of these distances in (I)--(III) is statistically not significant but this trend was observed for all other monosubstituted ferrocenes, whether the substituent is an electron-donating or an electron-withdrawing group (Kaluski & Struchkov, 1966 [triangle]; Sato, Iwai et al., 1984 [triangle]; Sato, Katada et al., 1984 [triangle]; Drouin et al., 1997 [triangle]; Foucher et al., 1999 [triangle]; Lin et al., 1998 [triangle]; Alley & Henderson, 2001 [triangle]; Hnetinka et al., 2004 [triangle]; Nemykin et al., 2007 [triangle]; Gasser et al., 2007 [triangle]).

Table 1
Mean values of the geometric parameters (Å, °) for (I), (II), triclinic (III) and monoclinic (III) at 100 K

The rings of (I) are eclipsed in mol­ecule A, with the torsion angle C1A(Cl)(...)Cg1(...)Cg2(...)C6A = −2.90 (11)°. Mol­ecule B exists in two different conformations. The Cp rings of compound (II) are eclipsed in mol­ecule A and staggered for mol­ecule B; the torsion angles C1A(Br1A)(...)Cg1(...)Cg2(...)C6A and C1B(Br1B)(...)Cg3(...)Cg4(...)C6B are −2.6 (11) and −29.2 (11)°, respectively. The rings of compound (III) are in an eclipsed conformation in both independent mol­ecules; the torsion angles C1A(I1A)(...)Cg1(...)Cg2(...)C6A and C1B(I1B)(...)Cg3(...)Cg4<(...)C6B are −2.2 (11) and −1.9 (11)°, respectively. The η5-C5H4 X and η5-C5H5 rings are almost parallel in the mol­ecules of (I), (II) and (III) (Figs. 1 [triangle], 2 [triangle] and 3 [triangle], and Table 1 [triangle]).

Figure 1
The two independent mol­ecules of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. The second disorder component of mol­ecule ...
Figure 2
The two independent mol­ecules of (II), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
Figure 3
The two independent mol­ecules of (III), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.

Crystals of (I) and (II) obtained from ethanolic solutions are monoclinic and isomorphous. In these crystal structures, four mol­ecules form tetra­mers via inter­molecular C—H(...)X (X = Cl or Br) hydrogen bonds between the C—H groups of mol­ecules with eclipsed conformations and the X atoms of mol­ecules with staggered conformations, and also C—H(...)X hydrogen bonds between mol­ecules with eclipsed conformations (Fig. 4 [triangle] and Table 2 [triangle]). These tetra­mers are, in turn, linked to each other by weak C—H(...)π inter­actions along the a axis.

Figure 4
A view of the tetra­mer in the structure of (II). [Symmetry code: (i) 1 − x, 1 − y, 1 − z.]
Table 2
Intermolecular C—H(...)X (X = Cl, Br or I) hydrogen bonds (Å, °) in (I), (II) and monoclinic (III)

The new triclinic polymorph of (III) [space group P An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi1.jpg, Z = 4, T = 100 K, V = 943.8 (4) Å3] and the previously reported monoclinic polymorph (space group Pc, Z = 4, T = 100 K, V = 924.9 Å3) (Laus et al., 2005 [triangle]) were obtained upon crystallization of ethanol solutions at 253 and 303 K, respectively. Crystals of another previously reported monoclinic polymorph (space group Pc, Z = 4, T = 228 K, V = 953.7 Å3) were grown by vacuum sublimation (Laus et al., 2005 [triangle]). Since this previously reported structure was studied at 228 K, we obtained X-ray diffraction data for both polymorphs of (III) at 100 K and their comparison is based on these data. Both forms contain two crystallographically independent mol­ecules (A and B). The bond lengths and angles in both polymorphs are very similar. The mol­ecular conformations are eclipsed for the triclinic polymorph of (III), and deviate slightly from an eclipsed conformation in the monoclinic polymorph; the torsion angles C1A(I1A)(...)Cg1(...)Cg2(...)C6A and C1B(I1B)(...)Cg3(...)Cg4(...)C6B are −4.8 (11) and 7.0 (11)°, respectively.

The triclinic and monoclinic polymorphs of (III) both contain short nonbonded inter­molecular I(...)I contacts but have different mol­ecular packing modes. The two pairs of independent mol­ecules A and B in triclinic (III) form zigzag tetra­mers via I(...)I contacts [I1A(...)I1B = 4.129 (1) Å and C1A—I1A(...)I1B = 150.78 (10)°; I1B(...) I1B iii = 4.123 (1) Å, C1B—I1B(...)I1B iii = 136.71 (9)° and I1A—I1B(...) I1B iii = 71.07 (10)°; symmetry code: (iii) 1 − x, 2 − y, 1 − z] (Fig. 5 [triangle]). These I(...)I contacts are longer than the sum of spherical van der Waals radii proposed by Bondi (3.96 Å; Bondi, 1964 [triangle]; Rowland & Taylor, 1996 [triangle]), but shorter than the sum of spheroidal van der Waals radii for I (4.26 Å; Nyburg & Faerman, 1985 [triangle]). The I atoms of mol­ecules B demonstrate fork-type I(...)I inter­actions, while the I atoms of mol­ecules A possess only one I(...)I contact. All four I(...)I contacts form an almost planar zigzag tetra­mer.

Figure 5
A view of the tetra­mer in the structure of triclinic (III). Dashed lines indicate the I(...)I contacts. [Symmetry code: (iii) 1 − x, 2 − y, 1 − z.]

Mol­ecules in the monoclinic form of (III) are arranged in chains along the a axis connected by zigzag I(...)I contacts [I1A(...)I1B = 4.183 (1) Å and C1A—I1A(...)I1B = 155.3 (8)°; I1B(...) I1A ii = 3.913 (1) Å, C1B—I1B(...)I1A ii = 93.7 (1)° and I1A—I1B(...)I1A ii = 101.9 (1)°; symmetry code: (ii) −1 + x, y, z] (Fig. 6 [triangle]). The I(...)I contacts between independent mol­ecules A and B are shorter than the sum of the van der Waals radii proposed by Bondi, while the I(...)I contacts which connect pairs of mol­ecules B and A# (Fig. 6 [triangle]) are somewhat longer than the sum of van der Waals radii proposed for spherical and somewhat shorter than for spheroidal I atoms. The lengths of the I(...)I contacts vary for the monoclinic polymorph from those of the triclinic by ca 0.2 Å, while the angles differ significantly.

Figure 6
A view of the zigzag chain for monoclinic (III). Dashed lines indicate the I(...)I contacts and C—H(...)I hydrogen bonds. [Symmetry code: (ii) −1 + x, y, z.]

The tetra­mers in triclinic (III) and the zigzag chains in monoclinic (III) are linked to each other by weak C—H(...)π inter­actions (Table 3 [triangle]). The inter­molecular C—H(...)π(C5H5) contacts for the monoclinic polymorph of (III) are approximately the same as for the triclinic polymorph. In the case of the monoclinic polymorph of (III), there are C—H(...)I hydrogen bonds between neighbouring mol­ecules in the zigzag chains (Table 2 [triangle]), while the I atoms of the triclinic polymorph of (III) do not participate in hydrogen bonding.

Table 3
C—H(...)π(C5H5) short-contact geometry (Å) for the triclinic and monoclinic forms of (III)

We evaluated the crystal energies of the two polymorphs of (III) using the Cerius2 program (Mol­ecular Simulations, 1999 [triangle]). Crystal energies were calculated using the Dreiding force field (Mayo et al., 1990 [triangle]). The initial crystal energies were −16.8 and −18.4 kcal mol−1 (1 kcal mol−1 = 4.184 kJ mol−1) and the energies after minimization were −17.9 and −18.9 kcal mol−1 for the triclinic and monoclinic polymorphs, respectively. These results, along with data on the densities of the polymorphs and their unit-cell volumes, lead us to suggest that the noncentrosymmetric monoclinic polymorph is more stable than the triclinic one.

Experimental

Compounds (I), (II) and (III) were prepared according to standard literature procedures (Fish & Rosenblum, 1965 [triangle]; Perevalova, 1972 [triangle]). Slow evaporation from ethanol solutions produced yellow crystals of (I) and brown crystals of (II). The triclinic and monoclinic polymorphs of (III) were obtained as yellow and orange crystals, respectively, upon crystallization from ethanol solutions at 253 and 303 K, respectively. During crystal selection on the stage of a polarizing microscope, crystals of (I) and (II) melted rapidly due to their low melting points and the heat produced by the microscope lamp. To avoid this problem we used a microscope cooling stage (INSTEC) for crystal selection.

Compound (I)

Crystal data

  • [Fe(C5H5)(C5H4Cl)]
  • M r = 220.47
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi3.jpg
  • a = 7.5068 (16) Å
  • b = 11.303 (3) Å
  • c = 20.444 (4) Å
  • β = 90.041 (5)°
  • V = 1734.6 (7) Å3
  • Z = 8
  • Mo Kα radiation
  • μ = 1.98 mm−1
  • T = 100 K
  • 0.16 × 0.10 × 0.04 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.743, T max = 0.925
  • 18849 measured reflections
  • 4596 independent reflections
  • 3666 reflections with I > 2σ(I)
  • R int = 0.056

Refinement

  • R[F 2 > 2σ(F 2)] = 0.047
  • wR(F 2) = 0.114
  • S = 1.00
  • 4596 reflections
  • 221 parameters
  • 48 restraints
  • H-atom parameters constrained
  • Δρmax = 0.74 e Å−3
  • Δρmin = −0.40 e Å−3

Compound (II)

Crystal data

  • [Fe(C5H5)(C5H4Br)]
  • M r = 264.93
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi3.jpg
  • a = 7.5222 (14) Å
  • b = 11.613 (2) Å
  • c = 20.440 (4) Å
  • β = 90.050 (3)°
  • V = 1785.5 (6) Å3
  • Z = 8
  • Mo Kα radiation
  • μ = 6.10 mm−1
  • T = 100 (2) K
  • 0.16 × 0.10 × 0.04 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: numerical (APEX2; Bruker, 2005 [triangle]) T min = 0.442, T max = 0.793
  • 23171 measured reflections
  • 4504 independent reflections
  • 3816 reflections with I > 2σ(I)
  • R int = 0.052

Refinement

  • R[F 2 > 2σ(F 2)] = 0.031
  • wR(F 2) = 0.078
  • S = 1.02
  • 4504 reflections
  • 217 parameters
  • H-atom parameters constrained
  • Δρmax = 0.60 e Å−3
  • Δρmin = −0.70 e Å−3

Compound (III), triclinic polymorph

Crystal data

  • [Fe(C5H5)(C5H4I)]
  • M r = 311.92
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi5.jpg
  • a = 7.6372 (19) Å
  • b = 11.371 (3) Å
  • c = 11.694 (3) Å
  • α = 72.220 (3)°
  • β = 80.196 (3)°
  • γ = 79.577 (3)°
  • V = 943.8 (4) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 4.81 mm−1
  • T = 100 K
  • 0.40 × 0.30 × 0.20 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.181, T max = 0.373
  • 13091 measured reflections
  • 4676 independent reflections
  • 4314 reflections with I > 2σ(I)
  • R int = 0.031

Refinement

  • R[F 2 > 2σ(F 2)] = 0.030
  • wR(F 2) = 0.083
  • S = 1.01
  • 4676 reflections
  • 217 parameters
  • H-atom parameters constrained
  • Δρmax = 0.66 e Å−3
  • Δρmin = −1.89 e Å−3

Compound (III), monoclinic polymorph

Crystal data

  • [Fe(C5H5)(C5H4I)]
  • M r = 311.92
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi6.jpg
  • a = 6.2918 (10) Å
  • b = 9.7229 (15) Å
  • c = 15.146 (2) Å
  • β = 93.437 (2)°
  • V = 924.9 (2) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 4.91 mm−1
  • T = 100 K
  • 0.14 × 0.11 × 0.09 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003 [triangle]) T min = 0.529, T max = 0.638
  • 8464 measured reflections
  • 3972 independent reflections
  • 3900 reflections with I > 2σ(I)
  • R int = 0.021

Refinement

  • R[F 2 > 2σ(F 2)] = 0.018
  • wR(F 2) = 0.041
  • S = 1.01
  • 3972 reflections
  • 217 parameters
  • 2 restraints
  • H-atom parameters constrained
  • Δρmax = 0.66 e Å−3
  • Δρmin = −0.47 e Å−3
  • Absolute structure: Flack (1983 [triangle]), with 1954 Friedel pairs
  • Flack parameter: 0.003 (18)

All H atoms were positioned geometrically, with C—H = 1.00 Å, and refined in riding mode, with U iso(H) = 1.2U eq(C). The crystals of (I) were found to be twinned. The structure of (I) was refined by the method of Pratt et al. (1971 [triangle]) and Jameson (1982 [triangle]), with a TWIN matrix defined as (100/0An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi16.jpg0/00An external file that holds a picture, illustration, etc.
Object name is c-65-0m426-efi16.jpg), which is the default for a monoclinic twinning type with β close to 90° and a twin fraction of 0.380 (1). A disorder model for the C5H5 and C5H4Cl rings was found with two orientations of the rings with equal occupancies for the two positions, differing by rotations in the ring plane of about 20 and 16°, respectively. The C atoms of the disordered C5H5 and C5H4Cl rings of mol­ecule B of (I) were restrained to be planar within 0.001 Å. The distances between C atoms were fixed in a penta­gon fashion at 1.425 (1) and 2.300 (1) Å for 1,2- and 1,3-distances, respectively. The 33 reflections which did not agree with the ideal model of the disordered mol­ecule were omitted from the refinement.

For all compounds, data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: SAINT-Plus (Bruker, 2001 [triangle]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks global, I, II, III, IV. DOI: 10.1107/S0108270109034763/sf3110sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S0108270109034763/sf3110Isup2.hkl

Structure factors: contains datablocks II. DOI: 10.1107/S0108270109034763/sf3110IIsup3.hkl

Structure factors: contains datablocks III. DOI: 10.1107/S0108270109034763/sf3110IIIsup4.hkl

Structure factors: contains datablocks IV. DOI: 10.1107/S0108270109034763/sf3110IVsup5.hkl

Acknowledgments

The authors are grateful to the NIH for support via the RIMI program (grant No. P20MD001104) and to the NSF for support via grant Nos. CHE-0832622 and DMR-0120967. We thank A. A. Yakovenko for assistance with the X-ray diffraction analysis of compound (I).

Footnotes

Supplementary data for this paper are available from the IUCr electronic archives (Reference: SF3110). Services for accessing these data are described at the back of the journal.

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Articles from Acta Crystallographica Section C: Crystal Structure Communications are provided here courtesy of International Union of Crystallography