Synthesis and molecular structure of [Fe2Cl2(μ-S-tBu)2(η 1-η1-μ-dppe)] (dppe = Ph2P(CH2)2PPH2)

Article abstract of DOI:10.1515/znb-2003-0418

The red title compound was synthesized by the metathesis reaction of [FeCl₂(dppe)] (dppe = Ph₂PCH₂)₂PPh₂) and NaS-tBu in THF. The X-ray structure analysis revealed a dinuclear complex with two iron(II) centers coordinated in a distorted tetrahedral fashion by two bridging thiolates, one bridging dppe molecule and one terminal chloro ligand.

Full text of DOI:10.1515/znb-2003-0418

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Synthesis and Molecular Structure of
[Fe2Cl2(µ-S-tBu)2(η1-η1-µ-dppe)]: A suspension
of 526 mg (1 mmol) of [Fe(Cl)2(dppe)] in 50 ml
THF was treated with a mixture of 225 µl
(2 mmol) of tert-butylthiol und 48 mg (2 mmol) of
NaH in 10 ml of THF. The brown reaction mixture
was stirred for 2 h at ambient temperature. Subse-
quently the solvent was stripped in vacuo. The
solid residue was suspended in toluene (60 ml) and
filtered through celite. The filtrate was concen-
trated to 30 ml and n-hexane (30 ml) was added.
A red precipitate formed immediately which was
isolated by filtration and washed with n-hexane.
Red crystals suitable for an X-ray diffraction
analysis were obtained from a concentrated to-
luene/n-hexane solution (3:1, v:v) at Ð20 ∞C. Yield:
410 mg (0.54 mmol, 54 %). Ð C34H42Cl2Fe2P2S2
(759.34): calcd. C 53.78, H 5.57; found C 53.99,
H 5.38.
[Fe2Cl2(µ-S-tBu)2(η1-η1-µ-dppe)]
(dppe = Ph2P(CH2)2PPh2)
Han Vinh Huynha, Roland Fröhlichb,
and F. Ekkehardt Hahna
a
Institut für Anorganische und Analytische
Chemie, Westfälische Wilhelms-Universität
Münster, Wilhelm-Klemm-Straße 8,
D-48149 Münster
b
Organisch-Chemisches Institut,
Westfälische Wilhelms-Universität Münster,
Corrensstraße 40, D-48149 Münster
Reprint requests to Prof. Dr. F. E. Hahn.
E-mail: fehahn@uni-muenster.de
Z. Naturforsch. 58b, 359Ð361 (2003);
received January 16, 2003
The red title compound was synthesized by the
metathesis reaction of [FeCl2(dppe)] (dppe =
Ph2PCH2)2PPh2) and NaS-tBu in THF. The X-ray
structure analysis revealed a dinuclear complex
with two iron(II) centers coordinated in a dis-
torted tetrahedral fashion by two bridging thio-
lates, one bridging dppe molecule and one termi-
nal chloro ligand.
X-ray
structure
determination:
Formula
C34H42Cl2Fe2P2S2, M = 759.34, red crystal 0.30 ¥
0.25 ¥ 0.25 mm3, a = 9.785(1), b = 21.733(1), c =
3
˚
˚
17.428(1) A, ꢀ = 96.06(1)∞, V = 3685.5(5) A ,
ρcalcd = 1.369 g cmÐ3, µ = 11.54 cmÐ1, empirical
absorption correction (0.723 Յ θ Յ 0.761), Z = 4,
monoclinic, space group P21/n (No. 14), λ =
Key words: Dinuclear Complexes, Iron, Thiolates
˚
0.71073 A, T = 198 K, ω and ꢁ scans, 33670 reflec-
Ð1
˚
Introduction
tions collected (ðh, ðk, ðl), [(sinθ)/λ] = 0.71 A
,
10923 independent (Rint = 0.037) and 8771 ob-
served reflections [I Ն 2 σ(I)], 385 refined parame-
ters, R = 0.042, wR2 = 0.100, max. residual electron
In our search for model compounds for the
Fe(µ-S)2Fe ferredoxine [1] we explored the reac-
tivity of [Fe(Cl)2(dppe)] towards thiolates. Expect-
ing that the reaction with simple alkylthiolato salts
NaSR would lead to complexes of the type
[Fe(SR)2(dppe)]. Next it was planned to substitute
the dppe ligand by a functionalized bidentate ben-
zenedithiolato ligand [2] or a bridging bis(ben-
zenedithiolato) ligand [3]. However, the reaction
of [Fe(Cl)2(dppe)] with NaS-tBu does not proceed
with substitution of both chloro ligands but
instead yields the novel dinuclear complex
[Fe2Cl2(µ-S-tBu)2(η1-η1-µ-dppe)].
density 1.07 (Ð0.64) e AÐ3, hydrogens calculated
˚
and refined as riding atoms. The data set was col-
lected with a Nonius KappaCCD diffractometer,
equipped with a rotating anode generator Nonius
FR591. Programs used: data collection COLLECT
[5], data reduction Denzo-SMN [6], absorption
correction SORTAV [7], structure solution
SHELXS-97 [8], structure refinement SHELXL-
97 [9] , graphics SCHAKAL [10]. Crystallographic
data (excluding structure factors) have been de-
posited with the Cambridge Crystallographic Data
Centre as supplementary publication no. CCDC-
201201. Copies of the data can be obtained free of
charge on application to The Director, CCDC, 12
Union Road, CambridgeCB2 1EZ, UK [fax: int.
code +44(1223)336-033,
Experimental Section
All manipulations were performed in an atmo-
sphere of dry argon by standard Schlenk tech-
niques. Solvents were dried by standard methods
und freshly distilled prior to use. [Fe(Cl)2(dppe)]
was prepared according to a literature procedure
[4].
e-mail: deposit@ccdc.cam.ac.uk].
0932Ð0776/03/0400Ð0359 $06.00 ” 2003 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com
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Results and Discussion
the same side of the roughly planar Fe(µ-S)2Fe
ring. Steric interactions between these alkyl
groups lead to almost identical small FeÐSÐFe
angles (Fe1ÐS1ÐFe2 73.94(2)∞, Fe1ÐS2ÐFe2
74.08(2)∞) and larger SÐFeÐS angles (S1ÐFe1ÐS2
106.11(2)∞, S1ÐFe2ÐS2 105.81(2)∞). The other an-
gles around the iron centers deviate strongly from
the value expected for tetrahedral coordination.
Due to steric requirements of the bridging dppe
ligand the SÐFeÐP angles are smaller than ex-
pected for tetrahedral coordination (range
97.30(2)∞Ð100.54(2)∞) while the ClÐFeÐS angles
are larger (range 117.14(3)∞Ð124.70(3)∞).
The reaction of [FeCl2(dppe)] with two equiva-
lents of NaS-tBu yields the title compound
[Fe2Cl2(µ-S-tBu)2(η1-η1-µ-dppe)] as a red solid.
The complex is air sensitive and turns to a black
solid upon decomposition. Crystals suitable for an
X-ray structure determination were obtained from
a
concentrated toluene/n-hexane solution at
Ð20 ∞C.
The X-ray structure analysis reveals a dinuclear
complex (Fig. 1). The iron(II) centers are coodi-
nated in a distorted tetrahedral fashion by two
bridging thiolato sulfur atoms, a terminal chloro
ligand and a phosphorus atom from a bridging
dppe ligand. The dppe ligand forms together with
the two iron(II) centers and one µ-S atom a seven-
membered ring next to a four- membered Fe(µ-
S)2Fe ring. Both tBu substituents are located on
˚
The FeÐS bond distances (range 2.3197(6) AÐ
˚
2.3426(6) A) are comparable to equivalent dis-
tances observed in the FeII phosphine-thiolato
complexes [Fe2(SR)4(dppe)2], [Fe(SR)2(dppp)]
and [Fe(SR)2(PMePh2)] [11] and in the thiourea-
thiolato complex [Fe(SR)2(SC(NMe2)2)2] [12].
They even fall in the range found for homoleptic
FeII tetrathiolates [Fe(SR)4]2- [13].
Substitution of a chloro ligand in [Fe(Cl2(dppe)]
by a thiolato ligand and the subsequent rearrange-
ment to the dinuclear [Fe2Cl2(µ-S-tBu)2(η1-η1-µ-
dppe)] leaves the FeÐCl and FeÐP distances virtu-
ally unchanged as can be seen by comparison to
the molecular structure of [FeCl2(dippe)] [14].
Surprisingly, the reaction of [FeCl2(dppe)] with
NaSÐtBu leads to the substitution of only one
chloro ligand and a rearrangement to the di-
nuclear [Fe2Cl2(µ-S-tBu)2(η1-η1-µ-dppe)]. The ste-
ric bulk of the tert-butylthiolato ligand together
with that of the phosphine ligand are apparently
sufficient to prevent the substitution of the second
chloro ligand. The mononuclear complex
[Fe(SR)2(dppp)] (dppp = Ph2P(CH2)3PPh2) is
known [11]. However, in this complex the thiolato
ligand ist sterically less demanding and the biden-
tate phosphane ligand forms with the iron(II) cen-
ter a six-membered ring. Complexes of the type
[X2Fe(η1-η1-µ-dppe)2FeX2] (X = IÐ, RSÐ) have
also been described [11]. However, the coordina-
tion of only one bridging dppe ligand and two
bridging thiolato ligands together with a terminal
chloro ligand has not been observed in FeII coordi-
nation chemistry so far.
S1
Cl1
Cl2
Fe1
Fe2
S2
P1
P2
C2
C1
Fig. 1. Molecular structure of [Fe2Cl2(µ-S-tBu)2(η1-η1-µ-
dppe)]. Hydrogen atoms have been omitted. Selected
˚
bond lengths [A] und angles [∞]: Fe1ÐCl1 2.2096(7),
Fe1ÐS1 2.3197(6), Fe1ÐS2 2.3341(6), Fe1ÐP1 2.4355(6),
Fe2ÐCl2 2.2133(6), Fe2ÐS1 2.3426(6), Fe2ÐS2
2.3206(6), Fe2ÐP2 2.4345(6); Cl1ÐFe1ÐS1 124.70(3),
Cl1ÐFe1ÐS2 117.14(3), Cl1ÐFe1ÐP1 106.21(3), S1Ð
Fe1ÐS2 106.11(2), S1ÐFe1ÐP1 98.66(2), S2ÐFe1ÐP1
99.22(2), Cl2ÐFe2ÐS1 120.30(2), Cl2ÐFe2ÐS2 121.94(2),
Cl2ÐFe2ÐP2 106.17(2), S1ÐFe2ÐS2 105.81(2), S1ÐFe2Ð
P2 100.54(2), S2ÐFe2ÐP2 97.30(2), Fe1ÐS1ÐFe2
73.94(2), Fe1ÐS2ÐFe2 74.08(2).
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