trans-Bis(benzoato-O)tetrakis(methanol-O)iron(II): ligand bulk is not structure-determining

The title compound, [Fe(C₇H₅O₂)₂(CH₄O)₄], is a centrosymmetric six-coordinate Fe^II complex coordinated by two axial monodentate benzoate ligands and four methanol ligands in the equatorial plane [Fe-O_benzoate 2.0935 (7) Å, and Fe-O_methanol 2.1310 (7) and 2.1290 (7) Å]. The benzoate ligands adopt monodentate ligation, rather than a bridged polymeric structure, because of strong intra- and intermolecular hydrogen bonds to the methanol ligands. This structure is nearly identical to that obtained with a much bulkier carboxyl­ate ligand [Chavez, Que & Tolman (2001). Chem. Commun. pp. 111-112].

S1. Comment

A recent report of an Fe^II complex having the same core structure as the title compound, but with a bulky trisubstituted benzoate, attributed the atypical structure to the extreme steric bulk of the carboxylate (Chavez et al., 2001). We demonstrate here that the structure can also be obtained using unsubstituted benzoic acid (Fig. 1).

The core geometry in the title complex, (I), is very similar to that in the complex [Fe^II(HOMe)₄] Query abbreviation, (III), where HOMe is 4-tert-butyl-2,6-bis[2,2'',6,6''-tetramethyl-m-terphenyl-2'-yl)methyl]phenyl carboxylate, (II). The Fe-carboxylate bonds are slightly shorter in (I) [Fe—O1 2.0935 (7) Å] than in (III) [2.13 (2) Å], while the Fe-methanol bonds are comparable [Fe—O3 2.1310 (7) and Fe—O4 2.1290 (7) Å in (I), and 2.162 (2) and 2.091 (2) Å in (III)]. The charge on the benzoate ligand is delocalized over the carboxylate group [C1—O1 1.260 (1) and C1—O2 1.266 (1) Å]. Both methanol ligands in (I) are hydrogen bonded to the uncoordinated O atom of the benzoate [intramolecular O2···O3 2.623 (1) Å and intermolecular O4···O2ⁱ 2.634 (1) Å; Table 1; symmetry code: (i) x, 1/2 - y, 1/2 + z]. These intermolecular hydrogen bonds link the molecules into layers parallel to the bc plane, and the phenyl rings in adjacent layers interleave. The short Fe—O bond in (III) involves the methanol that forms a strong hydrogen bond to the uncoordinated carboxylate O atom [O···O 2.582 (3) Å], whereas the longer bond involves a methanol that forms a weaker hydrogen bond to a solvate methanol [intramolecular O···O 3.199 (3) Å]. This difference can be attributed to the bulky carboxylate in (III). \sch

The most closely related metal carboxylate complexes with four additional coordinated alcohol ligands are the isomorphous Ca²⁺ and Cd²⁺ complexes of a natural product, Griseocheline, from Streptomyces griseus (Scharfenberg-Pfeiffer & Czugler, 1991). Each of two tridentate ligands are coordinated to the metal through one carboxylate and two alcohols. However, the complexes have pseudo twofold symmetry with a cis arrangement of the two carboxylates. More common structures with simpler ligands are generally centrosymmetric with amine donors in the equatorial plane. A related structure is trans-[bis(4-bromobenzoato-O)(2-dimethylaminoethanol-N,O)]copper(II), in which the free O atom on the benzoate forms a hydrogen bond to the coordinated alcohol (Turpeinen et al. 1996). The centrosymmetric structures are also preferred with the Fe^II and Co^II acetate and trifluoroacetate complexes, [M(RCOO)₂(NH₂CH₂py)₂], with the diamine 2-aminomethylpyridine (Payne, 1998).

S2. Experimental

Compound (I) was crystallized from a methanol solution containing Fe(BPh₄)₂ (0.25 mmol), benzoic acid (1.0 mmol) and triethylamine (1 mmol). Crystals of triethylammonium tetraphenylborate, (Et₃NH)(BPh₄), were also isolated from this solution.

S3. Refinement

The H-atom parameters were freely refined, giving C—H = 0.86 (3)–0.98 (2) Å and U_iso = 0.029 (4)–0.10 (1) Ų.

Computing details

Data collection: SMART (Bruker, 2001); cell refinement: SMART and SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 1997); software used to prepare material for publication: SHELXTL.

Figures

Fig. 1. A view of the molecular structure of (I) with 50% probability displacement ellipsoids. H atoms are drawn as small spheres of arbitrary radii and intra- and intermolecular hydrogen bonds are indicated by dotted lines.

trans-Bis(benzoato-O)tetrakis(methanol-O)iron(II)

Crystal data

[Fe(C7H5O2)2(CH4O)4]	F(000) = 448
Mr = 426.24	Dx = 1.411 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 9.863 (1) Å	Cell parameters from 9801 reflections
b = 12.065 (2) Å	θ = 2.7–32.9°
c = 8.605 (1) Å	µ = 0.79 mm^−1
β = 101.45 (1)°	T = 100 K
V = 1003.5 (3) Å^3	Block, colourless
Z = 2	0.40 × 0.25 × 0.15 mm

Data collection

Bruker SMART-APEX CCD on D8 diffractometer	2922 independent reflections
Radiation source: fine-focus sealed tube	2731 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
Detector resolution: 8.333 pixels mm^-1	θmax = 30.0°, θmin = 2.1°
ω scans	h = −13→13
Absorption correction: multi-scan (SADABS; Blessing, 1995; Sheldrick, 2001)	k = −16→16
Tmin = 0.79, Tmax = 0.89	l = −12→12
11390 measured reflections

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)] = 0.027	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.078	All H-atom parameters refined
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0495P)^2 + 0.2157P] where P = (Fo^2 + 2Fc^2)/3
2922 reflections	(Δ/σ)max = 0.001
176 parameters	Δρmax = 0.58 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	Uiso*/Ueq
Fe1	0.5000	0.0000	0.5000	0.01320 (7)
O1	0.67049 (7)	0.04085 (6)	0.40014 (9)	0.01874 (15)
O2	0.60217 (8)	0.19438 (6)	0.26267 (9)	0.02054 (15)
O3	0.39268 (8)	0.14316 (6)	0.39495 (9)	0.01811 (15)
H1	0.4489 (18)	0.1732 (14)	0.349 (2)	0.034 (4)*
O4	0.59133 (8)	0.09086 (6)	0.70638 (8)	0.02078 (16)
H2	0.5979 (17)	0.1587 (15)	0.7091 (19)	0.031 (4)*
C1	0.68961 (10)	0.11862 (8)	0.30922 (11)	0.01524 (17)
C2	0.82386 (10)	0.11968 (8)	0.25182 (11)	0.01584 (17)
C3	0.92079 (11)	0.03605 (10)	0.29936 (13)	0.0228 (2)
H3	0.9015 (19)	−0.0227 (14)	0.366 (2)	0.030 (4)*
C4	1.04542 (12)	0.03587 (12)	0.24770 (16)	0.0305 (3)
H4	1.113 (2)	−0.0209 (16)	0.279 (2)	0.041 (5)*
C5	1.07343 (12)	0.11922 (11)	0.14676 (15)	0.0296 (2)
H5	1.1585 (18)	0.1194 (15)	0.111 (2)	0.038 (4)*
C6	0.97772 (11)	0.20244 (10)	0.09859 (13)	0.0254 (2)
H6	0.9944 (16)	0.2597 (17)	0.032 (2)	0.037 (5)*
C7	0.85335 (10)	0.20335 (9)	0.15155 (12)	0.02016 (19)
H7	0.7864 (16)	0.2600 (14)	0.1187 (18)	0.029 (4)*
C8	0.31935 (11)	0.22182 (9)	0.47091 (14)	0.0230 (2)
H8B	0.3826 (18)	0.2680 (14)	0.5435 (19)	0.033 (4)*
H8A	0.2596 (17)	0.2673 (15)	0.3905 (19)	0.034 (4)*
H8C	0.2617 (18)	0.1824 (15)	0.533 (2)	0.039 (4)*
C9	0.59115 (19)	0.05311 (10)	0.86254 (14)	0.0345 (3)
H9B	0.525 (3)	0.083 (3)	0.898 (4)	0.102 (10)*
H9A	0.656 (3)	0.081 (2)	0.933 (3)	0.074 (7)*
H9C	0.586 (2)	−0.0266 (18)	0.864 (2)	0.040 (5)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Fe1	0.01604 (11)	0.00979 (11)	0.01447 (11)	0.00015 (6)	0.00472 (7)	0.00021 (5)
O1	0.0199 (3)	0.0169 (3)	0.0207 (3)	0.0017 (3)	0.0073 (3)	0.0052 (3)
O2	0.0214 (3)	0.0155 (3)	0.0263 (4)	0.0029 (3)	0.0086 (3)	0.0057 (3)
O3	0.0208 (3)	0.0136 (3)	0.0215 (3)	0.0028 (2)	0.0080 (3)	0.0016 (2)
O4	0.0326 (4)	0.0135 (3)	0.0164 (3)	−0.0041 (3)	0.0054 (3)	−0.0015 (2)
C1	0.0175 (4)	0.0134 (4)	0.0149 (4)	−0.0016 (3)	0.0036 (3)	−0.0009 (3)
C2	0.0159 (4)	0.0166 (4)	0.0149 (4)	−0.0020 (3)	0.0029 (3)	0.0002 (3)
C3	0.0206 (5)	0.0231 (5)	0.0259 (5)	0.0024 (4)	0.0072 (4)	0.0082 (4)
C4	0.0208 (5)	0.0343 (6)	0.0385 (6)	0.0078 (5)	0.0108 (4)	0.0142 (5)
C5	0.0190 (5)	0.0377 (6)	0.0342 (6)	0.0007 (4)	0.0101 (4)	0.0104 (5)
C6	0.0212 (5)	0.0298 (6)	0.0260 (5)	−0.0035 (4)	0.0072 (4)	0.0097 (4)
C7	0.0185 (4)	0.0201 (5)	0.0219 (4)	−0.0013 (3)	0.0038 (3)	0.0050 (3)
C8	0.0240 (5)	0.0178 (5)	0.0284 (5)	0.0051 (4)	0.0082 (4)	−0.0021 (4)
C9	0.0677 (9)	0.0194 (5)	0.0161 (5)	−0.0048 (5)	0.0077 (5)	−0.0009 (4)

Geometric parameters (Å, º)

Fe1—O1	2.0933 (7)	C3—C4	1.388 (2)
Fe1—O1^i	2.0933 (7)	C3—H3	0.95 (2)
Fe1—O4	2.1288 (8)	C4—C5	1.392 (2)
Fe1—O4^i	2.1288 (8)	C4—H4	0.95 (2)
Fe1—O3^i	2.1310 (7)	C5—C6	1.384 (2)
Fe1—O3	2.1310 (7)	C5—H5	0.95 (2)
O1—C1	1.260 (1)	C6—C7	1.391 (2)
O2—C1	1.266 (1)	C6—H6	0.93 (2)
O3—C8	1.428 (1)	C7—H7	0.95 (2)
O3—H1	0.82 (2)	C8—H8B	0.97 (2)
O4—C9	1.419 (1)	C8—H8A	0.98 (2)
O4—H2	0.82 (2)	C8—H8C	0.98 (2)
C1—C2	1.502 (1)	C9—H9B	0.86 (3)
C2—C3	1.394 (1)	C9—H9A	0.86 (3)
C2—C7	1.396 (1)	C9—H9C	0.96 (2)
O1—Fe1—O1^i	180.00 (2)	C4—C3—C2	120.4 (1)
O1—Fe1—O4	88.84 (3)	C4—C3—H3	119 (1)
O1^i—Fe1—O4	91.16 (3)	C2—C3—H3	121 (1)
O1—Fe1—O4^i	91.16 (3)	C3—C4—C5	119.8 (1)
O1^i—Fe1—O4^i	88.84 (3)	C3—C4—H4	121 (1)
O4—Fe1—O4^i	180.0	C5—C4—H4	119 (1)
O1—Fe1—O3^i	89.61 (3)	C6—C5—C4	120.2 (1)
O1^i—Fe1—O3^i	90.39 (3)	C6—C5—H5	120 (1)
O4—Fe1—O3^i	88.35 (3)	C4—C5—H5	120 (1)
O4^i—Fe1—O3^i	91.65 (3)	C5—C6—C7	120.1 (1)
O1—Fe1—O3	90.39 (3)	C5—C6—H6	122 (1)
O1^i—Fe1—O3	89.61 (3)	C7—C6—H6	118 (1)
O4—Fe1—O3	91.65 (3)	C6—C7—C2	120.2 (1)
O4^i—Fe1—O3	88.35 (3)	C6—C7—H7	120.8 (9)
O3^i—Fe1—O3	180.0	C2—C7—H7	119.0 (9)
C1—O1—Fe1	131.44 (6)	O3—C8—H8B	111 (1)
C8—O3—Fe1	126.78 (6)	O3—C8—H8A	110 (1)
C8—O3—H1	112 (1)	H8B—C8—H8A	111 (1)
Fe1—O3—H1	104 (1)	O3—C8—H8C	109 (1)
C9—O4—Fe1	123.01 (7)	H8B—C8—H8C	107 (1)
C9—O4—H2	108 (1)	H8A—C8—H8C	109 (1)
Fe1—O4—H2	124 (1)	O4—C9—H9B	110 (2)
O1—C1—O2	123.91 (9)	O4—C9—H9A	114 (2)
O1—C1—C2	117.44 (8)	H9B—C9—H9A	96 (2)
O2—C1—C2	118.65 (8)	O4—C9—H9C	110 (1)
C3—C2—C7	119.34 (9)	H9B—C9—H9C	112 (2)
C3—C2—C1	119.68 (9)	H9A—C9—H9C	115 (2)
C7—C2—C1	120.99 (9)
O4—Fe1—O1—C1	−94.37 (9)	Fe1—O1—C1—C2	−176.55 (6)
O4^i—Fe1—O1—C1	85.63 (9)	O1—C1—C2—C3	0.3 (1)
O3^i—Fe1—O1—C1	177.27 (9)	O2—C1—C2—C3	−178.92 (9)
O3—Fe1—O1—C1	−2.73 (9)	O1—C1—C2—C7	−179.62 (9)
O1—Fe1—O3—C8	−133.21 (8)	O2—C1—C2—C7	1.2 (1)
O1^i—Fe1—O3—C8	46.79 (8)	C7—C2—C3—C4	0.0 (2)
O4—Fe1—O3—C8	−44.36 (8)	C1—C2—C3—C4	−179.9 (1)
O4^i—Fe1—O3—C8	135.64 (8)	C2—C3—C4—C5	−0.5 (2)
O1—Fe1—O4—C9	−138.4 (1)	C3—C4—C5—C6	0.3 (2)
O1^i—Fe1—O4—C9	41.6 (1)	C4—C5—C6—C7	0.3 (2)
O3^i—Fe1—O4—C9	−48.8 (1)	C5—C6—C7—C2	−0.8 (2)
O3—Fe1—O4—C9	131.2 (1)	C3—C2—C7—C6	0.6 (2)
Fe1—O1—C1—O2	2.6 (2)	C1—C2—C7—C6	−179.47 (9)

Symmetry code: (i) −x+1, −y, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H1···O2	0.82 (2)	1.83 (2)	2.623 (1)	161 (2)
O4—H2···O2^ii	0.82 (2)	1.83 (2)	2.634 (1)	166 (2)

Symmetry code: (ii) x, −y+1/2, z+1/2.