Ethyl and isopropyl 4-ferrocenylbenzoate

The title compounds, [Fe(C₅H₅)(C₁₄H₁₃O₂)] and [Fe(C₅H₅)(C₁₅H₁₅O₂)], respectively, contain the ferrocenyl η⁵(C₅H₄) and phenyl­ene –C₆H₄– rings in a nearly coplanar arrangement, with interplanar angles of 6.88 (12) and 10.5 (2)°, respectively. Molecules of the ethyl ester form dimers through η⁵(C₅H₅)C—H...O=C hydrogen bonds, with graph set R(20), and, together with Csp³—H...π(C₅H₅) interactions, generate a one-dimensional column (irregular ladder). Molecules of the iso­propyl ester aggregate through η⁵(C₅H₅)C—H...π(C₆H₄) interactions.

S1. Comment

The design of new redox-active ligands for application in diverse research areas, such as medicinal chemistry and materials science, has engrossed scientists in recent years. Ferrocene derivatives, which are efficient redox systems, have been studied extensively in charge-transfer chemistry, hydrogen bonding and molecular-recognition science, peptide chemistry, nonlinear optical materials and liquid crystal research (Chesney et al., 1998; Glidewell et al., 1997; Zakaria et al., 2002; Kraatz et al., 1999; Gallagher et al., 1999a,b; Hudson, Asselsbergh et al., 2001; Hudson, Manning et al., 2001; Even et al., 2001; Seo et al., 2001). Our interest in ferrocenylbenzoyl derivatives stems from their use as precursors to ferrocenylbenzoyl amino acid ester and dipeptide derivatives. We have recently reported the crystal structure of methyl 4-ferrocenylbenzoate, (I) (Savage et al., 2002).

An understanding of the interactions present in a given crystal structure can provide valuable information on the hydrogen bonding and aggregation modes, not just in the solid state but also in the liquid-crystalline state. The structures of ethyl 4-ferrocenylbenzoate, (II), and the isopropyl analogue, (III), are reported herein for comparison with the methyl ester, (I), and our on-going research on longer chain alkyl derivatives. \sch

The Fe1—C bond lengths for the η⁵(C₅H₄) ring of (II) are in the range 2.0341 (16)–2.0452 (14) Å, similar to the η⁵(C₅H₅) ring, with a range of 2.0315 (18)–2.0407 (17) Å. For (III), these values are 2.024 (3)–2.044 (3) Å and 2.023 (4)–2.033 (4) Å, respectively. In (II), the Fe1···Cg1 and Fe1···Cg2 distances are 1.6425 (8) and 1.6463 (9) Å, respectively, and Cg1···Fe1···Cg2 is 179.49 (5)°, where Cg1 and Cg2 are the centroids of the η⁵(C₅H₄) and η⁵(C₅H₅) rings; in (III), these values are 1.6413 (15) and 1.643 (2) Å, and 178.88 (9)°, respectively. In (II), the cyclopentadienyl C—C bond-length ranges are small, at 1.413 (3)–1.435 (2) and 1.398 (3)–1.420 (3) Å for the η⁵(C₅H₄) and η⁵(C₅H₅) rings, respectively. In (III), these ranges are 1.407 (5)–1.428 (4) and 1.389 (6)–1.410 (6) Å, respectively. These results are as expected and highlight the similarity in the ferrocenyl bond lengths and angles in the esters (I) (Savage et al., 2002), and (II) and (III), described herein.

The cyclopentadienyl rings deviate slightly from eclipsed geometry in (II), as evidenced by the C1n···Cg1···Cg2···C2n (n = 1–5) torsion angles of −2.87 (14) to −3.61 (14)°. In (III), the angles are in the range 6.1 (3)–7.0 (3)°, similar to the eclipsed geometry in (I), where the range is 0.8 (4)–2.3 (4)°. In contrast, the range of angles is 13.7 (2)–15.4 (3)° in para-ferrocenylbenzoyl-L-alanine methyl ester (Savage et al., 2002).

The essentially linear molecular conformations adopted by (II) and (III) are comparable, with interplanar angles of 6.88 (12)° between the η⁵(C₅H₄) and C₆H₄ rings in (II), 10.5 (2)° in (III) and 9.35 (13)° in (I). The major differences are the terminal O1—C1—C34—C33 torsion angles, which are −0.8 (2)° in (II), −18.2 (5)° in (III) and 171.2 (3)° in (I). However, the disposition of the terminal alkoxy group, which gives a C1—O1—C2—C3 torsion angle of 179.76 (16)° in (II) and 112.0 (5)° in (III), means that the methyl groups of the isopropyl moiety in (III) are oriented almost orthogonal to the ester CO₂ plane (Figs. 1 and 3).

Analysis of the hydrogen bonding in (II) shows only two interactions of note, involving the substituted ring and the ester O═C as η⁵(C₅H₄)C—H···O═C interactions (Table 2 and Fig. 2). Molecules of the ethyl ester form dimers through η⁵(C₅H₅)C—H···O═C hydrogen bonds, graph set R₂²(20) (Reference?), and, together with Csp³—H···π(C₅H₅) interactions, these generate a one-dimensional column (irregular ladder). The molecules of the isopropyl ester, (III), aggregate slowly through η⁵(C₅H₅)C—H···π(C₆H₄) interactions (Table 4 and Fig. 4).

Analysis of the April 2002 version of the Cambridge Structural Database using CONQUEST version 1.4 (Allen, 2002), for the mono-substituted para-Fc—C₆H₄—X group, was undertaken for structures which fulfil the three-dimensional coordinates and R < 0.10 criteria (X = any atom). A total of 13 relevant structures were found. The interplanar angle between the C₅H₄ and C₆ rings varies between 2.2 and 29.1° for 17 examples, with a median of 12.8° (11 examples are within the range 7.7–19.3°). Our results above compare favourably with these values.

Tables 2 and 4. Hydrogen bond and short contact parameters, where Cg1 is the centroid of the substituted cyclopentadienyl ring (T2) and where Cg3 is the centroid of the phenylene ring system (T4).

S2. Experimental

Compounds (II) and (III) were prepared according to standard literature procedures. Analytical data for (II): m.p. 358–359 K (uncorrected); IR (KBr, ν, cm⁻¹): 1678 (C═O); UV-VIS, λ_max (CH₃CN): 360 (880), 445 (290) nm; ¹H NMR (400 MHz, CDCl₃, δ, p.p.m.): 7.86 (2H, d, J = 8.4 Hz, Ar—H), 7.66 (2H, d, J = 8.4 Hz, Ar—H), 4.89 [2H, t, J = 1.8 Hz, o-η⁵(C₅H₄)], 4.44 [2H, t, J = 1.8 Hz, m-η⁵(C₅H₄)], 4.32 (2H, q, J = 7 Hz, –OCH₂CH₃), 4.03 [5H, s, η⁵(C₅H₅)], 1.33 (3H, t, –OCH₂CH₃); ¹³C NMR (CDCl₃, δ, p.p.m.): 166.1, 145.5, 129.6, 127.2, 126.0, 83.0, 70.2, 69.9, 67.2, 60.9, 14.6. Analytical data for (III): m.p. 351–352 K (uncorrected); IR (KBr, ν, cm⁻¹): 1710 (C═O); UV-VIS, λ_max (CH₃CN): 360 (1120), 458 (302) nm; ¹H NMR (400 MHz, CDCl₃, δ, p.p.m.): 7.87 (2H, d, J = 8.4 Hz, Ar—H), 7.44 (2H, d, J = 8.4 Hz, Ar—H), 5.18 [1H, m, OCH(CH₃)₂], 4.64 [2H, s, o-η⁵(C₅H₄)], 4.32 [2H, s, m-η⁵(C₅H₄)], 3.96 [5H, s, η⁵(C₅H₅)], 1.30 [6H, t, OCH(CH₃)₂]; ¹³C NMR (CDCl₃, δ, p.p.m.): 166.6, 145.2, 130.0, 128.5, 126.0, 83.9, 70.2, 70.1, 68.5, 67.3, 22.4.

S3. Refinement

For compounds (II) and (III), the space groups P2₁/c and P2₁/a, respectively, were uniquely assigned from the systematic absences and confirmed by the analysis. H atoms were treated as riding atoms, with C—H distances in the range 0.93–0.98 Å.

Computing details

For both compounds, data collection: XSCANS (Siemens, 1994); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996) and PLATON (Spek, 1998); software used to prepare material for publication: SHELXL97 and PREP8 (Ferguson, 1998).

Figures

	Fig. 1. A view of the molecule of (II) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. A stereoview of the interactions in the crystal structure of (II).
	Fig. 3. A view of the molecule of (III) with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 4. A stereoview of the interactions in the crystal structure of (III). For the sake of clarity, the unit-cell box has been omitted.

(II) Ethyl 4-ferrocenylbenzoate

Crystal data

[Fe(C19H18O2)]	F(000) = 696
Mr = 334.18	Dx = 1.425 Mg m^−3
Monoclinic, P21/c	Melting point: 358 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 7.9563 (5) Å	Cell parameters from 80 reflections
b = 16.3464 (11) Å	θ = 5.5–20.7°
c = 12.0088 (10) Å	µ = 0.97 mm^−1
β = 94.128 (5)°	T = 294 K
V = 1557.78 (19) Å^3	Block, orange
Z = 4	0.50 × 0.45 × 0.45 mm

Data collection

Siemens P4 diffractometer	3276 reflections with I > 2σ(I)
Radiation source: X-ray tube	Rint = 0.012
Graphite monochromator	θmax = 28.0°, θmin = 2.1°
ω/2θ scans	h = −10→1
Absorption correction: ψ scan (North et al., 1968)	k = −21→1
Tmin = 0.629, Tmax = 0.646	l = −15→15
4875 measured reflections	4 standard reflections every 296 reflections
3780 independent reflections	intensity decay: +−1%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.079	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.039P)^2 + 0.319P] where P = (Fo^2 + 2Fc^2)/3
3780 reflections	(Δ/σ)max < 0.001
200 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.30 e Å^−3

Special details

Geometry. Cyclopentadienyl details ######################## Cg1—Fe1 1.6425 Cg1—Fe1—Cg2 179.49 Cg2—Fe1 1.6463

Mean plane data ex-SHELXL97 for (II) ####################################

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

5.2156(0.0053)x + 11.4996(0.0103)y − 3.8552(0.0096)z = 7.3838(0.0074)

* −0.0034 (0.0010) C11 * 0.0026 (0.0010) C12 * −0.0008 (0.0011) C13 * −0.0013 (0.0011) C14 * 0.0029 (0.0011) C15 1.6423 (0.0008) Fe1 0.1510 (0.0061) C1 0.3664 (0.0078) C2 0.0887 (0.0067) O1 0.3110 (0.0065) O2

Rms deviation of fitted atoms = 0.0024

5.2747(0.0059)x + 11.2893(0.0116)y − 4.0344(0.0108)z = 10.4919(0.0086)

Angle to previous plane (with approximate e.s.d.) = 1.19 (14)

* −0.0016 (0.0012) C21 * 0.0014 (0.0012) C22 * −0.0007 (0.0012) C23 * −0.0003 (0.0012) C24 * 0.0012 (0.0012) C25 − 1.6462 (0.0009) Fe1 − 3.0245 (0.0069) C1 − 2.7924 (0.0088) C2 − 3.0635 (0.0075) O1 − 2.8711 (0.0075) O2

Rms deviation of fitted atoms = 0.0011

5.8977(0.0039)x + 10.2414(0.0092)y − 3.5255(0.0072)z = 6.8368(0.0048)

Angle to previous plane (with approximate e.s.d.) = 6.42 (12)

* 0.0136 (0.0011) C31 * −0.0077 (0.0012) C32 * −0.0048 (0.0011) C33 * 0.0115 (0.0011) C34 * −0.0055 (0.0012) C35 * −0.0071 (0.0012) C36 1.7029 (0.0027) Fe1 0.0566 (0.0025) C1 0.0811 (0.0037) C2 0.0781 (0.0046) C3 0.0992 (0.0030) O1 0.0619 (0.0027) O2

Rms deviation of fitted atoms = 0.0089

5.8317(0.0048)x + 10.5145(0.0146)y − 3.2855(0.0134)z = 6.9880(0.0057)

Angle to previous plane (with approximate e.s.d.) = 1.54 (13)

* −0.0070 (0.0010) C1 * −0.0071 (0.0016) C2 * 0.0032 (0.0012) C3 * 0.0058 (0.0009) O1 * 0.0051 (0.0011) O2 1.7930 (0.0090) Fe1

Rms deviation of fitted atoms = 0.0058

5.2156(0.0053)x + 11.4996(0.0103)y − 3.8552(0.0096)z = 7.3838(0.0074)

Angle to previous plane (with approximate e.s.d.) = 6.40 (14)

* −0.0034 (0.0010) C11 * 0.0026 (0.0010) C12 * −0.0008 (0.0011) C13 * −0.0013 (0.0011) C14 * 0.0029 (0.0011) C15 1.6423 (0.0008) Fe1 0.1510 (0.0061) C1 0.3664 (0.0078) C2 0.0887 (0.0067) O1 0.3110 (0.0065) O2

Rms deviation of fitted atoms = 0.0024

5.8977(0.0039)x + 10.2414(0.0092)y − 3.5255(0.0072)z = 6.8368(0.0048)

Angle to previous plane (with approximate e.s.d.) = 6.88 (12)

* 0.0136 (0.0011) C31 * −0.0077 (0.0012) C32 * −0.0048 (0.0011) C33 * 0.0115 (0.0011) C34 * −0.0055 (0.0012) C35 * −0.0071 (0.0012) C36 1.7029 (0.0027) Fe1 0.0566 (0.0025) C1 0.0811 (0.0037) C2 0.0781 (0.0046) C3 0.0992 (0.0030) O1 0.0619 (0.0027) O2

Rms deviation of fitted atoms = 0.0089

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Fe1	0.42391 (3)	0.701199 (12)	0.323801 (17)	0.04152 (8)
O1	0.2066 (2)	0.47467 (10)	−0.24288 (12)	0.0796 (4)
O2	0.01774 (14)	0.57520 (8)	−0.25620 (9)	0.0533 (3)
C1	0.1314 (2)	0.52853 (10)	−0.20018 (13)	0.0489 (3)
C2	−0.0149 (2)	0.55551 (11)	−0.37353 (13)	0.0553 (4)
C3	−0.1447 (3)	0.61374 (16)	−0.42061 (18)	0.0815 (6)
C11	0.25972 (18)	0.61258 (9)	0.26420 (13)	0.0460 (3)
C12	0.3909 (2)	0.57835 (10)	0.33805 (13)	0.0501 (3)
C13	0.3854 (2)	0.61604 (11)	0.44385 (14)	0.0569 (4)
C14	0.2530 (2)	0.67385 (13)	0.43741 (14)	0.0594 (4)
C15	0.1753 (2)	0.67255 (12)	0.32731 (14)	0.0539 (4)
C21	0.5276 (3)	0.75038 (13)	0.18930 (15)	0.0647 (5)
C22	0.6552 (2)	0.71840 (12)	0.2659 (2)	0.0700 (5)
C23	0.6436 (2)	0.76025 (12)	0.36839 (18)	0.0663 (5)
C24	0.5119 (3)	0.81687 (11)	0.35455 (17)	0.0637 (5)
C25	0.4411 (3)	0.81077 (11)	0.24453 (17)	0.0636 (5)
C31	0.22186 (18)	0.59141 (9)	0.14605 (12)	0.0430 (3)
C32	0.1031 (2)	0.63437 (10)	0.07822 (14)	0.0505 (3)
C33	0.0705 (2)	0.61497 (10)	−0.03342 (13)	0.0492 (3)
C34	0.15632 (18)	0.55113 (9)	−0.08000 (12)	0.0439 (3)
C35	0.2713 (2)	0.50642 (11)	−0.01278 (14)	0.0532 (4)
C36	0.3035 (2)	0.52601 (10)	0.09854 (14)	0.0531 (4)
H2A	−0.0554	0.4997	−0.3820	0.066*
H2B	0.0875	0.5608	−0.4121	0.066*
H3A	−0.2460	0.6073	−0.3826	0.122*
H3B	−0.1681	0.6028	−0.4987	0.122*
H3C	−0.1038	0.6687	−0.4109	0.122*
H12	0.4669	0.5382	0.3196	0.060*
H13	0.4566	0.6047	0.5068	0.068*
H14	0.2222	0.7071	0.4954	0.071*
H15	0.0852	0.7050	0.3006	0.065*
H21	0.5054	0.7341	0.1155	0.078*
H22	0.7320	0.6776	0.2515	0.084*
H23	0.7117	0.7516	0.4335	0.080*
H24	0.4773	0.8524	0.4089	0.076*
H25	0.3515	0.8417	0.2135	0.076*
H32	0.0443	0.6771	0.1086	0.061*
H33	−0.0089	0.6448	−0.0772	0.059*
H35	0.3274	0.4627	−0.0429	0.064*
H36	0.3809	0.4951	0.1425	0.064*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.04157 (12)	0.04073 (12)	0.04198 (12)	−0.00176 (8)	0.00115 (8)	−0.00168 (8)
O1	0.0926 (10)	0.0868 (10)	0.0588 (8)	0.0393 (8)	0.0003 (7)	−0.0171 (7)
O2	0.0558 (6)	0.0578 (6)	0.0458 (5)	0.0068 (5)	−0.0002 (5)	−0.0047 (5)
C1	0.0460 (8)	0.0502 (8)	0.0507 (8)	−0.0003 (6)	0.0045 (6)	−0.0028 (6)
C2	0.0598 (9)	0.0621 (10)	0.0439 (8)	−0.0032 (8)	0.0024 (7)	−0.0018 (7)
C3	0.0853 (15)	0.0918 (15)	0.0647 (12)	0.0230 (12)	−0.0126 (10)	−0.0023 (11)
C11	0.0421 (7)	0.0465 (8)	0.0494 (8)	−0.0076 (6)	0.0030 (6)	−0.0017 (6)
C12	0.0560 (9)	0.0427 (7)	0.0510 (8)	−0.0060 (6)	−0.0001 (7)	0.0031 (6)
C13	0.0645 (10)	0.0608 (10)	0.0450 (8)	−0.0104 (8)	0.0012 (7)	0.0061 (7)
C14	0.0571 (9)	0.0746 (11)	0.0478 (8)	−0.0076 (9)	0.0121 (7)	−0.0074 (8)
C15	0.0416 (8)	0.0664 (10)	0.0542 (9)	−0.0022 (7)	0.0071 (6)	−0.0078 (8)
C21	0.0750 (12)	0.0662 (11)	0.0544 (9)	−0.0142 (10)	0.0147 (8)	0.0019 (8)
C22	0.0496 (9)	0.0548 (10)	0.1087 (17)	−0.0040 (8)	0.0267 (10)	0.0061 (10)
C23	0.0577 (10)	0.0619 (11)	0.0767 (12)	−0.0182 (9)	−0.0132 (9)	0.0094 (9)
C24	0.0772 (12)	0.0431 (8)	0.0698 (11)	−0.0109 (8)	−0.0002 (9)	−0.0057 (8)
C25	0.0727 (12)	0.0519 (9)	0.0655 (11)	0.0018 (8)	−0.0007 (9)	0.0132 (8)
C31	0.0388 (7)	0.0417 (7)	0.0483 (7)	−0.0062 (6)	0.0022 (5)	−0.0035 (6)
C32	0.0513 (8)	0.0456 (8)	0.0543 (8)	0.0071 (6)	0.0010 (7)	−0.0089 (7)
C33	0.0466 (8)	0.0476 (8)	0.0525 (8)	0.0060 (6)	−0.0025 (6)	−0.0008 (6)
C34	0.0400 (7)	0.0439 (7)	0.0476 (7)	−0.0046 (6)	0.0024 (6)	−0.0034 (6)
C35	0.0506 (8)	0.0518 (8)	0.0567 (9)	0.0108 (7)	−0.0002 (7)	−0.0095 (7)
C36	0.0509 (8)	0.0527 (9)	0.0543 (9)	0.0095 (7)	−0.0058 (7)	−0.0033 (7)

Geometric parameters (Å, º)

Fe1—C11	2.0452 (14)	C24—C25	1.402 (3)
Fe1—C12	2.0341 (16)	C31—C32	1.392 (2)
Fe1—C13	2.0430 (16)	C31—C36	1.394 (2)
Fe1—C14	2.0436 (17)	C32—C33	1.384 (2)
Fe1—C15	2.0358 (16)	C33—C34	1.387 (2)
Fe1—C21	2.0315 (18)	C34—C35	1.384 (2)
Fe1—C22	2.0328 (18)	C35—C36	1.381 (2)
Fe1—C23	2.0343 (17)	C2—H2A	0.9700
Fe1—C24	2.0407 (17)	C2—H2B	0.9700
Fe1—C25	2.0375 (18)	C3—H3A	0.9600
O1—C1	1.200 (2)	C3—H3B	0.9600
O2—C1	1.3282 (19)	C3—H3C	0.9600
O2—C2	1.4503 (19)	C12—H12	0.9300
C1—C34	1.489 (2)	C13—H13	0.9300
C2—C3	1.486 (3)	C14—H14	0.9300
C11—C12	1.434 (2)	C15—H15	0.9300
C11—C15	1.435 (2)	C21—H21	0.9300
C11—C31	1.470 (2)	C22—H22	0.9300
C12—C13	1.416 (2)	C23—H23	0.9300
C13—C14	1.413 (3)	C24—H24	0.9300
C14—C15	1.419 (2)	C25—H25	0.9300
C21—C22	1.420 (3)	C32—H32	0.9300
C21—C25	1.398 (3)	C33—H33	0.9300
C22—C23	1.417 (3)	C35—H35	0.9300
C23—C24	1.399 (3)	C36—H36	0.9300
C1—O2—C2	115.63 (13)	C33—C34—C35	119.07 (14)
O1—C1—O2	123.17 (16)	C1—C34—C33	122.85 (14)
O1—C1—C34	124.07 (15)	C1—C34—C35	118.07 (14)
O2—C1—C34	112.76 (13)	C36—C35—C34	120.74 (15)
O2—C2—C3	107.37 (15)	C35—C36—C31	120.96 (15)
C12—C11—C15	106.70 (14)	C13—C12—H12	125.8
C12—C11—C31	126.47 (14)	C11—C12—H12	125.8
C15—C11—C31	126.81 (14)	C14—C13—H13	125.9
C12—C11—Fe1	69.01 (8)	C12—C13—H13	125.9
C15—C11—Fe1	69.06 (9)	C13—C14—H14	125.8
C31—C11—Fe1	125.85 (10)	C15—C14—H14	125.8
C13—C12—C11	108.47 (15)	C14—C15—H15	125.9
C13—C12—Fe1	70.02 (10)	C11—C15—H15	125.9
C11—C12—Fe1	69.84 (9)	C25—C21—H21	126.1
C14—C13—C12	108.26 (15)	C22—C21—H21	126.1
C14—C13—Fe1	69.80 (10)	C23—C22—H22	126.4
C12—C13—Fe1	69.34 (9)	C21—C22—H22	126.4
C13—C14—C15	108.30 (16)	C24—C23—H23	125.9
C13—C14—Fe1	69.75 (10)	C22—C23—H23	125.9
C15—C14—Fe1	69.35 (9)	C23—C24—H24	125.9
C14—C15—C11	108.26 (16)	C25—C24—H24	125.9
C14—C15—Fe1	69.94 (10)	C21—C25—H25	125.7
C11—C15—Fe1	69.76 (9)	C24—C25—H25	125.7
C25—C21—C22	107.83 (18)	C33—C32—H32	119.2
C25—C21—Fe1	70.14 (11)	C31—C32—H32	119.2
C22—C21—Fe1	69.60 (11)	C32—C33—H33	120.0
C23—C22—C21	107.26 (18)	C34—C33—H33	120.0
C23—C22—Fe1	69.67 (11)	C36—C35—H35	119.6
C21—C22—Fe1	69.51 (11)	C34—C35—H35	119.6
C24—C23—C22	108.13 (17)	C35—C36—H36	119.5
C24—C23—Fe1	70.17 (10)	C31—C36—H36	119.5
C22—C23—Fe1	69.55 (10)	O2—C2—H2A	110.2
C23—C24—C25	108.15 (18)	C3—C2—H2A	110.2
C23—C24—Fe1	69.68 (10)	O2—C2—H2B	110.2
C25—C24—Fe1	69.77 (10)	C3—C2—H2B	110.2
C21—C25—C24	108.62 (17)	H2A—C2—H2B	108.5
C21—C25—Fe1	69.68 (11)	C2—C3—H3A	109.5
C24—C25—Fe1	70.01 (10)	C2—C3—H3B	109.5
C11—C31—C32	121.94 (14)	H3A—C3—H3B	109.5
C11—C31—C36	120.41 (14)	C2—C3—H3C	109.5
C32—C31—C36	117.64 (14)	H3A—C3—H3C	109.5
C31—C32—C33	121.53 (14)	H3B—C3—H3C	109.5
C32—C33—C34	120.00 (14)
C2—O2—C1—O1	1.8 (2)	O1—C1—C34—C35	−1.2 (3)
C2—O2—C1—C34	−178.95 (13)	O2—C1—C34—C35	179.65 (14)
C1—O2—C2—C3	179.76 (16)	O1—C1—C34—C33	178.40 (17)
C12—C11—C31—C36	7.9 (2)	O2—C1—C34—C33	−0.8 (2)
C15—C11—C31—C36	−173.57 (16)	C33—C34—C35—C36	−1.5 (3)
C36—C31—C32—C33	−2.1 (2)	C1—C34—C35—C36	178.07 (16)
C11—C31—C32—C33	178.79 (15)	C34—C35—C36—C31	−0.3 (3)
C31—C32—C33—C34	0.4 (3)	C32—C31—C36—C35	2.0 (2)
C32—C33—C34—C35	1.4 (2)	C11—C31—C36—C35	−178.85 (15)
C32—C33—C34—C1	−178.12 (15)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C22—H22···O1^i	0.93	2.54	3.360 (3)	147
C2—H2A···Cg1^ii	0.97	2.87	3.770 (2)	155

Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x, −y+1, −z.

(III) Isopropyl 4-ferrocenylbenzoate

Crystal data

[Fe(C20H20O2)]	F(000) = 728
Mr = 348.21	Dx = 1.360 Mg m^−3
Monoclinic, P21/a	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yab	Cell parameters from 72 reflections
a = 9.3406 (9) Å	θ = 6.1–15.3°
b = 10.1663 (6) Å	µ = 0.89 mm^−1
c = 17.9072 (10) Å	T = 294 K
β = 90.136 (6)°	Block, red
V = 1700.5 (2) Å^3	0.39 × 0.26 × 0.15 mm
Z = 4

Data collection

Siemens P4 diffractometer	2439 reflections with I > 2σ(I)
Radiation source: X-ray tube	Rint = 0.006
Graphite monochromator	θmax = 26.0°, θmin = 2.3°
ω/2θ scans	h = −11→1
Absorption correction: ψ scan (North et al., 1968)	k = −1→12
Tmin = 0.769, Tmax = 0.875	l = −22→22
4440 measured reflections	4 standard reflections every 296 reflections
3355 independent reflections	intensity decay: +−1%

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.043	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.109	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0468P)^2 + 0.7638P] where P = (Fo^2 + 2Fc^2)/3
3355 reflections	(Δ/σ)max < 0.001
210 parameters	Δρmax = 0.33 e Å^−3
0 restraints	Δρmin = −0.30 e Å^−3

Special details

Geometry. Cyclopentadienyl details ######################## Cg1—Fe1 1.6413 Cg1—Fe1—Cg2 178.88 Cg2—Fe1 1.6431

Mean plane data ex-SHELXL97 for (III) #####################################

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

5.6844(0.0123)x + 7.3778(0.0119)y + 5.7211(0.0272)z = 5.0122(0.0098)

* 0.0022 (0.0018) C11 * −0.0010 (0.0020) C12 * −0.0006 (0.0021) C13 * 0.0020 (0.0022) C14 * −0.0026 (0.0020) C15 − 1.6414 (0.0014) Fe1 0.4305 (0.0113) C1 0.2461 (0.0150) C2 0.6707 (0.0125) O1 0.2609 (0.0123) O2

Rms deviation of fitted atoms = 0.0018

5.5561(0.0150)x + 7.5719(0.0136)y + 5.3895(0.0322)z = 1.5807(0.0116)

Angle to previous plane (with approximate e.s.d.) = 1.72 (3)

* −0.0012 (0.0023) C21 * −0.0016 (0.0024) C22 * 0.0037 (0.0025) C23 * −0.0045 (0.0025) C24 * 0.0035 (0.0024) C25 1.6431 (0.0016) Fe1 3.7432 (0.0136) C1 3.6038 (0.0179) C2 3.9561 (0.0149) O1 3.6110 (0.0147) O2

Rms deviation of fitted atoms = 0.0032

5.9426(0.0086)x + 6.2591(0.0105)y + 8.2988(0.0188)z = 5.7785(0.0046)

Angle to previous plane (with approximate e.s.d.) = 12.2 (2)

* 0.0042 (0.0020) C31 * −0.0099 (0.0021) C32 * 0.0077 (0.0021) C33 * 0.0002 (0.0021) C34 * −0.0058 (0.0022) C35 * 0.0036 (0.0021) C36 0.1005 (0.0043) C11 − 1.4089 (0.0049) Fe1 0.0441 (0.0047) C1 − 0.5081 (0.0076) C2 − 1.9113 (0.0088) C3 0.3926 (0.0054) O1 − 0.3617 (0.0052) O2

Rms deviation of fitted atoms = 0.0061

6.2019(0.0409)x + 7.5402(0.0414)y − 1.7302(0.0387)z = 5.3444(0.0287)

Angle to previous plane (with approximate e.s.d.) = 33.4 (4)

* −0.2297 (0.0029) C1 * 0.5831 (0.0040) C2 * −0.4156 (0.0027) C3 * 0.0118 (0.0039) O1 * 0.0504 (0.0043) O2 − 4.6458 (0.0307) Fe1 − 0.8964 (0.0094) C34

Rms deviation of fitted atoms = 0.3371

5.6844(0.0123)x + 7.3778(0.0119)y + 5.7211(0.0272)z = 5.0122(0.0098)

Angle to previous plane (with approximate e.s.d.) = 24.2 (4)

* 0.0022 (0.0018) C11 * −0.0010 (0.0020) C12 * −0.0006 (0.0021) C13 * 0.0020 (0.0022) C14 * −0.0026 (0.0020) C15 − 1.6414 (0.0014) Fe1 0.0336 (0.0050) C31 0.2714 (0.0090) C34 0.4305 (0.0113) C1 0.2461 (0.0150) C2 0.6707 (0.0125) O1 0.2609 (0.0123) O2

Rms deviation of fitted atoms = 0.0018

5.9426(0.0086)x + 6.2591(0.0105)y + 8.2988(0.0188)z = 5.7785(0.0046)

Angle to previous plane (with approximate e.s.d.) = 10.5 (2)

* 0.0042 (0.0020) C31 * −0.0099 (0.0021) C32 * 0.0077 (0.0021) C33 * 0.0002 (0.0021) C34 * −0.0058 (0.0022) C35 * 0.0036 (0.0021) C36 0.1005 (0.0043) C11 − 1.4089 (0.0049) Fe1 0.0441 (0.0047) C1 − 0.5081 (0.0076) C2 − 1.9113 (0.0088) C3 0.3926 (0.0054) O1 − 0.3617 (0.0052) O2

Rms deviation of fitted atoms = 0.0061

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Fe1	0.20114 (4)	0.01277 (4)	0.37286 (2)	0.04743 (15)
O1	0.8813 (3)	0.0096 (3)	0.10527 (14)	0.0915 (9)
O2	0.7283 (3)	0.1249 (3)	0.03698 (12)	0.0753 (7)
C1	0.7712 (3)	0.0667 (3)	0.09904 (17)	0.0547 (7)
C2	0.8170 (4)	0.1071 (4)	−0.0307 (2)	0.0804 (12)
C3	0.7362 (8)	0.0291 (7)	−0.0831 (3)	0.172 (3)
C4	0.8581 (7)	0.2359 (6)	−0.0577 (3)	0.151 (3)
C11	0.3825 (3)	0.1156 (3)	0.34726 (15)	0.0463 (6)
C12	0.2640 (3)	0.2020 (3)	0.35306 (18)	0.0574 (8)
C13	0.2060 (4)	0.1903 (3)	0.42588 (19)	0.0691 (9)
C14	0.2879 (4)	0.0970 (4)	0.46527 (18)	0.0684 (9)
C15	0.3963 (3)	0.0500 (3)	0.41743 (16)	0.0553 (7)
C21	0.1776 (5)	−0.1321 (4)	0.2955 (2)	0.0777 (10)
C22	0.0633 (4)	−0.0451 (4)	0.2911 (2)	0.0812 (11)
C23	−0.0054 (4)	−0.0437 (5)	0.3611 (3)	0.0921 (13)
C24	0.0682 (5)	−0.1323 (5)	0.4080 (2)	0.0927 (13)
C25	0.1811 (5)	−0.1852 (4)	0.3673 (2)	0.0851 (12)
C31	0.4757 (3)	0.0993 (3)	0.28128 (15)	0.0433 (6)
C32	0.5794 (3)	0.0017 (3)	0.27895 (17)	0.0540 (7)
C33	0.6737 (3)	−0.0072 (3)	0.22028 (17)	0.0550 (7)
C34	0.6649 (3)	0.0798 (3)	0.16006 (16)	0.0484 (7)
C35	0.5602 (3)	0.1759 (3)	0.16179 (16)	0.0553 (7)
C36	0.4682 (3)	0.1859 (3)	0.22122 (16)	0.0537 (7)
H2	0.9038	0.0586	−0.0169	0.096*
H3A	0.6552	0.0787	−0.1005	0.258*
H3B	0.7036	−0.0497	−0.0590	0.258*
H3C	0.7959	0.0064	−0.1247	0.258*
H4A	0.9162	0.2264	−0.1015	0.226*
H4B	0.9116	0.2810	−0.0197	0.226*
H4C	0.7738	0.2856	−0.0698	0.226*
H12	0.2300	0.2571	0.3155	0.069*
H13	0.1276	0.2363	0.4444	0.083*
H14	0.2731	0.0708	0.5144	0.082*
H15	0.4649	−0.0129	0.4295	0.066*
H21	0.2411	−0.1517	0.2572	0.093*
H22	0.0368	0.0037	0.2493	0.097*
H23	−0.0849	0.0064	0.3739	0.110*
H24	0.0454	−0.1519	0.4573	0.111*
H25	0.2477	−0.2457	0.3850	0.102*
H32	0.5853	−0.0589	0.3178	0.065*
H33	0.7441	−0.0719	0.2207	0.066*
H35	0.5520	0.2345	0.1222	0.066*
H36	0.3994	0.2521	0.2213	0.064*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.0414 (2)	0.0550 (3)	0.0459 (2)	−0.00137 (19)	0.00241 (16)	0.0079 (2)
O1	0.0622 (15)	0.142 (3)	0.0707 (15)	0.0412 (16)	0.0177 (12)	0.0218 (16)
O2	0.0735 (15)	0.0969 (18)	0.0556 (13)	0.0313 (13)	0.0205 (11)	0.0155 (13)
C1	0.0513 (17)	0.0596 (17)	0.0533 (17)	0.0003 (15)	0.0056 (14)	0.0005 (15)
C2	0.079 (2)	0.107 (3)	0.055 (2)	0.033 (2)	0.0274 (18)	0.020 (2)
C3	0.222 (8)	0.192 (7)	0.102 (4)	−0.091 (6)	0.083 (5)	−0.056 (4)
C4	0.198 (6)	0.128 (4)	0.125 (4)	−0.057 (4)	0.094 (4)	−0.015 (4)
C11	0.0427 (14)	0.0467 (15)	0.0495 (15)	−0.0013 (12)	−0.0005 (12)	−0.0028 (12)
C12	0.0532 (17)	0.0487 (16)	0.070 (2)	0.0030 (14)	0.0139 (15)	0.0011 (15)
C13	0.070 (2)	0.066 (2)	0.072 (2)	0.0072 (17)	0.0204 (18)	−0.0129 (18)
C14	0.071 (2)	0.087 (3)	0.0464 (17)	−0.0031 (19)	0.0027 (16)	−0.0098 (17)
C15	0.0457 (16)	0.075 (2)	0.0453 (16)	0.0036 (15)	−0.0038 (12)	−0.0052 (14)
C21	0.093 (3)	0.066 (2)	0.073 (2)	−0.022 (2)	−0.002 (2)	−0.0058 (19)
C22	0.078 (2)	0.094 (3)	0.071 (2)	−0.027 (2)	−0.022 (2)	0.015 (2)
C23	0.0449 (19)	0.119 (3)	0.112 (3)	−0.019 (2)	−0.002 (2)	0.005 (3)
C24	0.086 (3)	0.109 (3)	0.084 (3)	−0.043 (3)	0.005 (2)	0.032 (3)
C25	0.098 (3)	0.057 (2)	0.100 (3)	−0.020 (2)	−0.015 (3)	0.020 (2)
C31	0.0369 (13)	0.0453 (15)	0.0476 (15)	−0.0048 (11)	−0.0010 (11)	−0.0010 (12)
C32	0.0574 (16)	0.0500 (16)	0.0545 (16)	0.0072 (14)	0.0068 (13)	0.0109 (14)
C33	0.0505 (16)	0.0540 (17)	0.0606 (17)	0.0123 (14)	0.0043 (13)	0.0026 (15)
C34	0.0404 (14)	0.0513 (16)	0.0535 (16)	−0.0013 (12)	0.0016 (12)	0.0011 (14)
C35	0.0566 (17)	0.0588 (18)	0.0506 (16)	0.0092 (14)	0.0056 (14)	0.0110 (14)
C36	0.0471 (16)	0.0561 (17)	0.0579 (18)	0.0110 (13)	0.0028 (13)	0.0091 (14)

Geometric parameters (Å, º)

Fe1—C11	2.044 (3)	C31—C32	1.387 (4)
Fe1—C12	2.043 (3)	C31—C36	1.392 (4)
Fe1—C13	2.040 (3)	C32—C33	1.375 (4)
Fe1—C14	2.030 (3)	C33—C34	1.397 (4)
Fe1—C15	2.024 (3)	C34—C35	1.383 (4)
Fe1—C21	2.033 (4)	C35—C36	1.373 (4)
Fe1—C22	2.035 (4)	C2—H2	0.9800
Fe1—C23	2.024 (3)	C3—H3A	0.9600
Fe1—C24	2.029 (4)	C3—H3B	0.9600
Fe1—C25	2.023 (4)	C3—H3C	0.9600
O1—C1	1.186 (4)	C4—H4A	0.9600
O2—C1	1.321 (4)	C4—H4B	0.9600
O2—C2	1.481 (4)	C4—H4C	0.9600
C1—C34	1.485 (4)	C12—H12	0.9300
C2—C3	1.440 (7)	C13—H13	0.9300
C2—C4	1.448 (6)	C14—H14	0.9300
C11—C12	1.417 (4)	C15—H15	0.9300
C11—C15	1.428 (4)	C21—H21	0.9300
C11—C31	1.479 (4)	C22—H22	0.9300
C12—C13	1.418 (4)	C23—H23	0.9300
C13—C14	1.407 (5)	C24—H24	0.9300
C14—C15	1.412 (4)	C25—H25	0.9300
C21—C22	1.389 (6)	C32—H32	0.9300
C21—C25	1.395 (5)	C33—H33	0.9300
C22—C23	1.410 (6)	C35—H35	0.9300
C23—C24	1.410 (6)	C36—H36	0.9300
C24—C25	1.391 (6)
C1—O2—C2	117.7 (2)	C14—C15—Fe1	69.86 (18)
O1—C1—O2	124.1 (3)	C11—C15—Fe1	70.20 (16)
O1—C1—C34	123.8 (3)	C22—C21—C25	108.4 (4)
O2—C1—C34	112.1 (3)	C22—C21—Fe1	70.1 (2)
O2—C2—C3	107.9 (4)	C25—C21—Fe1	69.5 (2)
O2—C2—C4	108.2 (3)	C21—C22—C23	107.8 (4)
C3—C2—C4	114.8 (4)	C21—C22—Fe1	70.0 (2)
C25—Fe1—C11	125.06 (16)	C23—C22—Fe1	69.3 (2)
C23—Fe1—C11	155.83 (16)	C22—C23—C24	107.5 (4)
C15—Fe1—C11	41.11 (11)	C22—C23—Fe1	70.1 (2)
C24—Fe1—C11	161.73 (16)	C24—C23—Fe1	69.8 (2)
C14—Fe1—C11	68.75 (12)	C25—C24—C23	107.7 (4)
C21—Fe1—C11	107.83 (14)	C25—C24—Fe1	69.7 (2)
C22—Fe1—C11	120.65 (14)	C23—C24—Fe1	69.4 (2)
C13—Fe1—C11	68.54 (12)	C24—C25—C21	108.5 (4)
C12—Fe1—C11	40.58 (11)	C24—C25—Fe1	70.1 (2)
C25—Fe1—C12	162.70 (15)	C21—C25—Fe1	70.3 (2)
C23—Fe1—C12	121.57 (17)	C11—C31—C32	121.1 (2)
C15—Fe1—C12	68.50 (13)	C32—C31—C36	117.6 (3)
C24—Fe1—C12	156.18 (17)	C11—C31—C36	121.2 (2)
C14—Fe1—C12	68.28 (14)	C31—C32—C33	121.2 (3)
C21—Fe1—C12	126.49 (14)	C32—C33—C34	120.8 (3)
C22—Fe1—C12	109.20 (15)	C33—C34—C35	118.1 (3)
C13—Fe1—C12	40.65 (12)	C1—C34—C33	118.2 (3)
C25—Fe1—C13	154.78 (16)	C1—C34—C35	123.7 (3)
C23—Fe1—C13	108.66 (17)	C34—C35—C36	120.9 (3)
C15—Fe1—C13	68.43 (14)	C31—C36—C35	121.4 (3)
C24—Fe1—C13	120.78 (17)	C3—C2—H2	108.6
C14—Fe1—C13	40.45 (14)	C4—C2—H2	108.6
C21—Fe1—C13	163.79 (15)	O2—C2—H2	108.6
C22—Fe1—C13	127.16 (17)	C2—C3—H3A	109.5
C25—Fe1—C14	119.73 (16)	C2—C3—H3B	109.5
C23—Fe1—C14	125.70 (17)	H3A—C3—H3B	109.5
C15—Fe1—C14	40.75 (12)	C2—C3—H3C	109.5
C24—Fe1—C14	107.28 (16)	H3A—C3—H3C	109.5
C25—Fe1—C15	106.74 (16)	H3B—C3—H3C	109.5
C23—Fe1—C15	162.15 (16)	C2—C4—H4A	109.5
C25—Fe1—C21	40.22 (15)	C2—C4—H4B	109.5
C23—Fe1—C21	67.77 (18)	H4A—C4—H4B	109.5
C15—Fe1—C21	119.97 (15)	C2—C4—H4C	109.5
C24—Fe1—C21	67.63 (17)	H4A—C4—H4C	109.5
C14—Fe1—C21	154.55 (16)	H4B—C4—H4C	109.5
C25—Fe1—C22	67.62 (17)	C11—C12—H12	125.8
C23—Fe1—C22	40.64 (17)	C13—C12—H12	125.8
C15—Fe1—C22	154.92 (15)	C14—C13—H13	126.0
C24—Fe1—C22	68.08 (16)	C12—C13—H13	126.0
C14—Fe1—C22	163.59 (17)	C13—C14—H14	125.8
C21—Fe1—C22	39.94 (16)	C15—C14—H14	125.8
C25—Fe1—C23	67.96 (19)	C14—C15—H15	125.9
C25—Fe1—C24	40.15 (17)	C11—C15—H15	125.9
C23—Fe1—C24	40.73 (17)	C22—C21—H21	125.8
C15—Fe1—C24	124.38 (16)	C25—C21—H21	125.8
C12—C11—C15	107.1 (3)	C21—C22—H22	126.1
C12—C11—C31	126.1 (3)	C23—C22—H22	126.1
C15—C11—C31	126.7 (2)	C22—C23—H23	126.2
C12—C11—Fe1	69.66 (16)	C24—C23—H23	126.2
C15—C11—Fe1	68.69 (16)	C25—C24—H24	126.2
C31—C11—Fe1	127.69 (19)	C23—C24—H24	126.2
C11—C12—C13	108.4 (3)	C24—C25—H25	125.8
C11—C12—Fe1	69.75 (16)	C21—C25—H25	125.8
C13—C12—Fe1	69.56 (18)	C33—C32—H32	119.4
C14—C13—C12	108.0 (3)	C31—C32—H32	119.4
C14—C13—Fe1	69.40 (19)	C32—C33—H33	119.6
C12—C13—Fe1	69.79 (18)	C34—C33—H33	119.6
C13—C14—C15	108.3 (3)	C36—C35—H35	119.5
C13—C14—Fe1	70.14 (19)	C34—C35—H35	119.5
C15—C14—Fe1	69.39 (17)	C35—C36—H36	119.3
C11—C15—C14	108.2 (3)	C31—C36—H36	119.3
C2—O2—C1—O1	5.9 (5)	O1—C1—C34—C35	159.7 (4)
C2—O2—C1—C34	−173.5 (3)	O2—C1—C34—C35	−20.9 (4)
C1—O2—C2—C3	112.0 (5)	O1—C1—C34—C33	−18.2 (5)
C1—O2—C2—C4	−123.2 (4)	O2—C1—C34—C33	161.2 (3)
C36—C31—C32—C33	1.5 (4)	C33—C34—C35—C36	0.4 (5)
C11—C31—C32—C33	−174.8 (3)	C1—C34—C35—C36	−177.5 (3)
C31—C32—C33—C34	−1.9 (5)	C34—C35—C36—C31	−0.7 (5)
C32—C33—C34—C35	0.9 (4)	C32—C31—C36—C35	−0.2 (4)
C32—C33—C34—C1	178.9 (3)	C11—C31—C36—C35	176.1 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···O1	0.98	2.25	2.696 (4)	106
C12—H12···Cg3^i	0.93	2.75	3.658 (3)	167

Symmetry code: (i) x−3/2, −y−1/2, z.