Substitutional lability of diphosphine ligands in tetrahedral iron(II) chloro complexes

Article abstract of DOI:10.1002/ejic.201402859

A series of iron(II) dihalogenide complexes with two different bisphosphinoethane ligands is reported. In the case of 1,2-bis(diphenylphosphanyl)ethane (dppe), depending on the stoichiometry, the tetrahedral [(μ-dppe)FeCl₂]_n and octahedral trans-[(dppe)₂FeCl₂] complexes are formed. The polymeric complex [(μ-dppe)FeCl₂]_n, with iron in a tetrahedral environment, preferentially reacts with chelating amines to give the octahedral diphosphine complex, trans-[(dppe)₂FeCl₂], and different octahedral amine complexes. With the sterically more demanding 1,2-bis(diisopropylphosphanyl)ethane (dippe), the monomeric and tetrahedral halogen complexes [(dippe)FeX₂] are exclusively obtained (X = Cl, Br). These complexes react with chelating amines in a similar manner, to give free ligand and the corresponding octahedral amine complex. The present results suggest that the diphosphines in the investigated iron(II) complexes are bound too weakly to form productive catalyst precursors.

Full text of DOI:10.1002/ejic.201402859

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
FULL PAPER
DOI:10.1002/ejic.201402859
Substitutional Lability of Diphosphine Ligands in
Tetrahedral Iron(II) Chloro Complexes
Robert Langer,*[a,b] Friedrich Bönisch,[a] Leon Maser,[a]
Clemens Pietzonka,[a] Lisa Vondung,[a] and
Thomas Philipp Zimmermann[a]
Keywords: Iron / P ligands / Coordination modes / N ligands / Structure elucidation
A series of iron(II) dihalogenide complexes with two different
bisphosphinoethane ligands is reported. In the case of 1,2-
bis(diphenylphosphanyl)ethane (dppe), depending on the
stoichiometry, the tetrahedral [(μ-dppe)FeCl2]n and octa-
sterically more demanding 1,2-bis(diisopropylphosphanyl)-
ethane (dippe), the monomeric and tetrahedral halogen com-
plexes [(dippe)FeX2] are exclusively obtained (X = Cl, Br).
These complexes react with chelating amines in a similar
hedral trans-[(dppe)2FeCl2] complexes are formed. The poly- manner, to give free ligand and the corresponding octahedral
meric complex [(μ-dppe)FeCl2]n, with iron in a tetrahedral
environment, preferentially reacts with chelating amines to
give the octahedral diphosphine complex, trans-[(dppe)2-
FeCl2], and different octahedral amine complexes. With the
amine complex. The present results suggest that the diphos-
phines in the investigated iron(II) complexes are bound too
weakly to form productive catalyst precursors.
hydrogen,[9] including the hydrogenation of esters to
alcohols.[10] The analogous iron hydrido bromo complex (F)
was later found to be a highly active catalyst for the hydro-
genation of ketones under mild conditions.[11] A similar ob-
servation has been made for the recently reported Ru-
MACHO catalysts for the hydrogenation of esters to
alcohols ([RuHCl(CO)(dpa)], dpa = bis(2-diphenylphos-
phinoethyl)amine),[12] where the corresponding iron(II)
complexes also proved to be active catalysts.[13]
Introduction
The development of iron-based catalysts as substitutes
for noble metals is an important goal on the way to environ-
mentally benign and green chemistry.[1] In recent years, a
growing interest in alternative hydrogenation catalysts has
led to the development of highly active iron catalysts for the
hydrogenation of C–C, C–O, and C–N multiple bonds.[2–4]
For the hydrogenation of C–O double bonds, the most
active catalysts were derived from similar ruthenium coun-
terparts. Casey and Huang, for example, used Knölker’s
complex (B) as catalyst for the hydrogenation of ketones
under mild conditions,[5] whereas the corresponding
ruthenium complex, Shvo’s catalyst (A), appears as a dimer
and has been previously applied for the hydrogenation of
ketones (Scheme 1).[6] Ruthenium complexes featuring four-
dentate diamine diphosphine ligands (C) have been investi-
gated by Morris and Rautenstrauch as catalysts for the
hydrogenation of ketones.[7] In recent years, similar iron(II)
catalysts (e.g., D) for hydrogenation and transfer-hydrogen-
ation reactions have been invented by the Morris group.[8]
Dearomatized pyridine-based ruthenium-pincer complexes
(e.g., E) are able to catalyze various reactions involving
[a] Department of Chemistry, Philipps-University Marburg,
Hans-Meerwein-Str., 35043 Marburg, Germany
E-mail: robert.langer@chemie.uni-marburg.de
Scheme 1. Ruthenium- and analogous iron-based catalysts for the
hydrogenation of ketones.
http://www.uni-marburg.de/fb15/ag-langer
Although different mechanisms are possibly operative for
the corresponding iron and ruthenium complexes, the struc-
tural analogy of these complexes gives rise to the assump-
tion that this concept can be extended. Ruthenium-diamine-
[b] Lehn Institute of Functional Materials (LIFM), Sun Yat-Sen
University (SYSU)
Xingang Road West, Guangzhou 510275, P. R. of China
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201402859.
Eur. J. Inorg. Chem. 0000, 0–0
1
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
diphosphine complexes for example, are highly active and FeCl2/dppe ratios of between 1:1 and 1:2, revealed that the
selective catalysts for the hydrogenation and transfer-hydro- polymeric compound [(dppe)FeCl2]n (1Ј) is always the
genation of C–O double bonds.[14,15] The most prominent major product of the reaction. Furthermore, the elemental
examples are likely the complexes reported by Noyori and and NMR spectroscopic analyses indicate that with increas-
co-workers, who invented chiral ruthenium catalysts with ing FeCl2/dppe ratios, the amount of co-precipitated dppe
binaphthyl-phosphine and diphenylethylenediamine li- increases, whereas complex 1 remains the major product of
gands, which showed high catalytic activity and excellent the reaction. Interestingly, when the same synthetic pro-
regio- and stereoselectivity.[15] Corresponding iron com- cedure is conducted with tetrahydrofuran (THF) instead of
plexes have not been reported so far and would be promis- chloroform, no complexation of iron(II) chloride and
ing candidates. Considering that achiral ruthenium(II) com- iron(II) bromide by dppe is observed. Thus, layering of the
plexes with 1,2-bis(diphenylphosphanyl)ethane (dppe) and reaction mixture with n-hexane results for both precursors
ethylenediamine (en) ligands are active hydrogenation cata- in the formation of colorless crystals, which were identified
lysts,[16] an investigation of the corresponding iron com- as [Fe4Cl8(thf)6] and [FeBr2(thf)2]n, respectively.[20] The for-
plexes would be worthwhile.
mation of THF complexes, which are usually used as solu-
Herein, we present our investigations on the reactivity of ble precursors in complexation reactions, demonstrates that
iron diphosphine complexes towards chelating amine li- dppe is only a weak ligand in the present case. Nonetheless,
gands. Halide complexes of iron with dppe and 1,2-bis- the single-crystal X-ray analysis of the cocrystallized com-
(diisopropylphosphanyl)ethane (dippe) as ligands were syn- pounds 1 and 2 confirms that both octahedral and tetrahe-
thesized and investigated as precursors.
dral complexes with general composition [(dppe)nFeCl2] (n
= 1, 2) can be formed, although the polymeric tetrahedral
complex is preferentially formed under the reaction condi-
tions.
Results and Discussion
In previous studies, contradictory information on the
Compound 1 and 2 cocrystallize in the triclinic space
¯
formation and stability of [(dppe)nFeCl2] (n = 1,2) has been group P1 with one formula unit in the unit cell. The two
reported.[17,18] Mays and co-workers noticed that even in different iron compounds are cocrystallized in a 1:2 ratio
the presence of excess dppe, the monomeric [(dppe)FeCl2] (Figure 1 left). The first one is an octahedral iron(II) com-
is exclusively formed,[17b] the molecular structure of which plex with two dppe and two chloro ligands, adopting a
was not confirmed by single-crystal X-ray diffraction. In trans-configuration. The iron chlorine distance in the cen-
contrast to this observation, a single-crystal X-ray diffrac- trosymmetric complex trans-[(dppe)2FeCl2] is 2.346(1) Å,
tion study of the reaction of FeCl2 and two equivalents of which is in the expected range for octahedral iron(II) com-
dppe with carbon monoxide revealed the formation of plexes, whereas the iron–phosphorus distances are 2.630(1)–
trans-[(dppe)2FeCl2], which crystallizes together with an 2.651(1) Å, which is rather long in comparison to other iron
odd dimer [(κ2C,O-CO)2{FeCl2}2].[18]
dppe complexes.[19] Especially the previously reported com-
By following the procedure of Mays and co-workers, we plex trans-[(dppe)2FeCl2][(κ2C,O-CO)2{FeCl2}2] differs sig-
were able to obtain single crystalline products by simple nificantly in the observed iron–phosphorus distances
layering of the two reactant solutions (Scheme 2). To our (2.322–2.338 Å), whereas the iron–chlorine distances are
surprise, the layering of a chloroform solution containing very similar to those found for 2 (Table 1).[18] This could be
one or two equivalents of dppe with an acetone solution indicative of different spin states for the two trans-[(dppe)2-
of FeCl2 resulted in the formation of different crystalline FeCl2] complexes. The assumption that 2 exhibits a high-
products. The first compound was identified as a mixture spin configuration is supported by the absence of reso-
of two different iron(II) dppe complexes in the crystal struc- nances in the 31P{1H} NMR spectrum of mixtures contain-
ture. In addition to trans-[(dppe)2FeCl2] (2), a chain con- ing complex 2, whereas the previously reported complex
taining [(dppe)FeCl2] (1) as the repeating unit was refined, gives rise to singlet resonance at δ = 55.5 ppm in the
proving that both compositions, with one and two coordi- 31P{1H} NMR spectrum. Unfortunately, we were not able
nated dppe ligands, are possible (Scheme 2). With preferred to synthesize complex 2 in pure form; thus, the electron
bite angles between 82° and 94° in iron complexes, a chelat- configuration could not be proven by magnetic measure-
ing coordination mode of the dppe ligand seems to be disfa- ments.
vored in the tetrahedral 1:1 complexes.[19] A detailed analy-
The second compound is a coordination polymer with
sis of several single crystals that have been obtained with the general composition [(μ-dppe)FeCl2]n, in which the iron
Scheme 2. Reaction of FeCl2 with dppe under different conditions; a/b molar ratios employed in reactions: (i) 1:1.40, (ii) 1:1, and (iii) 1:1.
Eur. J. Inorg. Chem. 0000, 0–0
2
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
larger than in compound 1 [119.07(5)° and 101.51(4)°], indi-
cating a more distorted tetrahedral coordination geometry.
To obtain information on the spin state and possible
magnetic coupling between the different iron atoms in 1,
SQUID measurements were conducted in a temperature
range from 5 to 350 K at a magnetizing field strength of
5000 G. Plotting χ–1 against T results in a linear graph, as
shown in Figure 2. By fitting the χ–1 vs. T plot, the effective
magnetic moment μeff was determined to be 4.87. This
value corresponds reasonably well with the theoretical value
of 4.90 for an iron(II) high-spin species.
Figure 2. Plot of χ–1 vs. T and χ vs. T from the SQUID measure-
ment of 1. The data was collected at a magnetizing field strength
of 5000 G.
Figure 1. Top: ORTEP diagram of the cocrystallized compounds 1
and 2. Bottom: ORTEP diagram of compound 1Ј; thermal ellip-
soids are set at 50% probability (hydrogen atoms are omitted for
clarity).
A closer look at the three-dimensional structure of the
polymeric chains revealed an entirely different arrangement
of 1Ј (Figure 3), which is reflected in the different relative
orientations of the dppe ligands. Whereas the angle between
atoms are tetrahedrally coordinated by two chloro ligands the PCCP-planes of each dppe ligand is 22.30° in com-
and two phosphine groups of two different dppe ligands. pound 1, the corresponding angle in compound 1Ј is 70.94°.
The dppe ligand acts as μ2-bridging ligand between two
Although the dppe ligand seems to be easily replaced in
iron atoms, resulting in a polymeric structure. The iron coordinating solvents, we tried to synthesize iron diphos-
chloride bond lengths in the tetrahedral complex [2.227(1)– phine complexes with common chelating amines, such as
2.230(1) Å] are shorter than in the octahedral complex, as ethane-1,2-diamine and 2-picolylamine (Scheme 3). Ac-
well as the iron–phosphorus bond distances, which were cordingly, 1 was treated with one equivalent of 2-picolylam-
found to be between 2.465(1) and 2.495(1) Å.
ine in dichloromethane, causing an immediate color change
The pure coordination polymer [(μ-dppe)FeCl2]n (1Ј) of the reaction mixture from colorless to yellow, followed
(Figure 1, right) crystallizes in the monoclinic space group by precipitation of a yellow solid. To avoid the precipi-
P21/n with four formula units per unit cell. The iron– tation, we layered the dichloromethane solution of 1 with
chlorine distances (2.236(1)–2.241(1) Å), as well as the one equivalent of 2-picolylamine in tetrahydrofuran, re-
iron–phosphorus distances (2.451(1)–2.486(1) Å), are very sulting in the formation of yellow crystals. These crystals
similar to those found in the cocrystallized coordination were identified as the previously reported [(PicNH2)3Fe]Cl2
polymer. Only the Cl–Fe–Cl and P–Fe–P angles, which are (I),[21] which crystallizes in a new modification with one
126.88(3)° and 111.98(3)°, respectively, are significantly CH2Cl2 molecule in the unit cell. The 31P{1H} NMR spec-
Table 1. Selected bond lengths and angles of iron(II) halide complexes.
From ref.[18]
2
1
1Ј
IV[a]
4
Formula
[(dppe)2FeCl2]
2.322–2.338
2.353
180
83.19
[(dppe)2FeCl2]
2.630–2.651
2.346
180
79.62
[(μ-dppe)FeCl2]n
2.465–2.495
2.227–2.230
119.07
[(μ-dppe)FeCl2]n [(dippe)FeCl2]
[(dippe)FeBr2]
2.425–2.454
2.375–2.384
118.87
Fe–P /Å
2.451–2.486
2.236–2.241
126.88
2.466–2.47
2.22–2.23
118.0
Fe–X[b] /Å
ЄX–Fe–X /°
ЄP–Fe–P /°
101.51
111.98
83.7
84.66
[a] Bond lengths and angles have been taken from Ref.[25] [b] X = Cl, Br.
Eur. J. Inorg. Chem. 0000, 0–0
3
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
We then reacted compound 2 with 2-picolylamine in dif-
ferent solvents and were able to isolate a new crystalline
product from the reaction in MeCN/toluene. The newly
formed complex 3 turned out to be a dimer with a [FeCl4]2–
counterion. The molecular structure of the dimeric cation
in the crystal lattice is shown in Figure 4. Both iron atoms
exhibit octahedral coordination environments with two 2-
picolylamine ligands and two μ2-bridging chloro ligands,
respectively. The iron–nitrogen distances in 3 are very sim-
ilar to those found in complex I, whereas, with distances of
2.462(1)–2.607(2) Å, the Fe–Cl bonds of the complex cation
in 3 appear elongated compared with 1 and 1Ј.
Figure 3. Arrangement of the coordination polymer in the crystal
lattice of (a) 1 and (b) 1Ј; thermal ellipsoids are set at 50% prob-
ability (hydrogen and carbon atoms of the phenyl rings are omitted
for clarity).
trum of the supernatant solution exhibits only a weak sig-
nal, corresponding to uncoordinated dppe. Given that com-
plexes such as trans-[(dppe)2FeCl2] are expected to be para-
magnetic, we added 0.5 equiv. NaHBEt3 to convert iron
dichloro complexes that are potentially present into the
analogous hydride complexes, which are likely diamagnetic
and therewith detectable by NMR spectroscopy. The major
product of this reaction gives rise to a singlet resonance at δ
= 81.7 ppm in the 31P{1H} NMR spectrum. With a quintet
resonance centered at –29.15 ppm (2JP,H = 49.4 Hz) in the
1H NMR spectrum, this complex was unambiguously iden-
tified as trans-[(dppe)2Fe(H)Cl] (II).[22] These observations
provide indirect evidence for the formation of the octa-
hedral complex trans-[(dppe)2FeCl2] (2). In contrast,
ruthenium diphosphine complexes such as [(tol-binap)Ru-
(dmf)4]Cl2 are known to react with picolylamine (PicNH2)
to [(tol-binap)(PicNH2)RuCl2], which is a highly active
hydrogenation precatalyst (tol-binap = 2,2Ј-bis(di-p-tolyl-
phosphanyl)-1,1Ј-binaphthyl).[23]
Figure 4. ORTEP diagram of 3 with thermal ellipsoids set at 50%
probability (carbon-bound hydrogen atoms are omitted for clarity).
Similar observations have been made in the reaction of
1 with ethane-1,2-diamine (en), from which the previously
reported complex trans-[(en)2FeCl2] (III) is assumed as a
reaction product (Scheme 4).[24] As with picolylamine, the
addition of small amounts of NaHBEt3 causes formation
of trans-[(dppe)2Fe(H)Cl] (II),[22] leading to the assumption
that the trans-dichloro complex 2 is a reaction product as
well as trans-[(en)2FeCl2] (III). The ability of iron to form
both stable tetrahedral and octahedral complexes with dppe
and chloro ligands is probably one of the reasons for the
observed reactivity. Furthermore, with iron(II), in contrast
to ruthenium(II), counterions such as [MCl4]2– are easily
formed.
Scheme 4. Reactivity of complex 2 towards ethylenediamine.
As an enhanced stability of the iron(II) diphosphine pre-
cursor could enable the preparation of the desired diphos-
phine amine complexes, dichloride complexes with chelat-
ing diphosphine ligands of the general composition [(di-
phosphine)FeCl2] might be more suitable for the reaction
with chelating amines. Accordingly, a promising compound
for such reactions would be the analogous bis(diisopropyl-
phosphanyl)ethane complex, which appears to be mono-
Scheme 3. Reactivity of 1 towards chelating amine ligands.
Eur. J. Inorg. Chem. 0000, 0–0
4
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
meric with a chelating diphosphine ligand.[25] The corre-
sponding dichloro and dibromo complexes are conveniently
prepared by heating the iron(II) dihalogenide with dippe in
toluene (Scheme 5). The molecular structure of the dibromo
complex 4 has not been reported so far, and single crystals
are easily obtained by layering the reaction mixture with
n-hexane. The [(dippe)FeBr2] complex 4 crystallizes in the
orthorhombic space group Pbca with two independent mol-
ecules in the asymmetric unit. The two molecules are vir-
tually identical in their bond lengths and angles, but they
differ in the orientation of one isopropyl group. The dis-
cussion of the structure in the following will refer to only
one molecule, of which the molecular structure in the crys-
tal lattice is shown in Figure 5.
Scheme 6. Reactivity of complex 4 towards chelating amine ligands.
geometry, in which the central ruthenium atom is stabilized
by one or two agostic interactions to ligand C–H-bonds.[28]
In contrast, the synthesized iron complexes do not seem to
be unsaturated and tend to react under substitution rather
than with the formation of an octahedral complex. Such
behavior of iron might be one of the reasons that, with
mono and bidentate ligands, usually no catalytic activity is
observed in hydrogenation reactions. To prevent the forma-
tion of tetrahedral iron(II) complexes under the reaction
conditions tri- or tetradentate ligands are usually necessary.
Scheme 5. Synthesis of complex 4 and IV.
Conclusions
We have demonstrated that the coordination chemistry
of certain iron diphosphine complexes with chloro or
bromo ligands does not allow for a simple approach to
iron(II) diamine diphosphine complexes. Our study shows
that, with 1,2-bis(diphenylphosphanyl)ethane as L, both the
tetrahedral complex [LFeCl2]n (1) and the octahedral
[L2FeCl2] complex (2), are stable in solution and in the solid
state. Notably, in tetrahedral complex 1, a bridging coordi-
nation mode of the dppe ligand is favored, which is ex-
pected to be less stable towards substitution. Accordingly,
all attempts to react 1 with a chelating amine resulted in
the formation of [L2FeCl2] and amine complexes without
any phosphine in the ligand sphere. Furthermore, with ste-
rically more demanding 1,2-bis(diisopropylphosphanyl)eth-
ane, the monomeric [LFeCl2] complex is formed preferen-
tially, but despite the stronger σ-donation of this ligand, it
is easily replaced in the presence of amines. These observa-
tions suggest that bidentate phosphine ligands are too
weakly bound in iron(II) complexes to be used in active
hydrogenation catalysts and this explains, to some extent,
the high productivity of complexes with tri- and tetra-
dentate ligands. In addition, the ability of iron(II) to form
tetrahedral complexes represents a major difference to the
reactivity of the corresponding ruthenium complexes.
Figure 5. ORTEP diagram of 4 with thermal ellipsoids set at 50%
probability (hydrogen atoms are omitted for clarity).
With a length of 2.425(1)–2.454(1) Å, the iron–phos-
phorus bonds in 4 are similar to those found in the other
tetrahedrally coordinated chloro complexes 1, 1Ј, and IV
(Table 1). Complex 4 possesses iron–bromine distances of
2.425(1)–2.454(1) Å, which are in the expected range. The
P–Fe–P angle of the chelating dippe ligand was found to be
84.66(4)°, which should favor an octahedral coordination
of the iron(II) atom.
Complex 4 was treated with one equivalent of 2-picolyl-
amine and ethane-1,2-diamine in toluene, respectively
(Scheme 6). The dropwise addition of the amine, dissolved
in toluene, led in both cases to the formation of free ligand
after a few drops, as detected by 31P{1H} NMR spec-
troscopy. The isolation of reaction products other than the
free dippe ligand failed. Nevertheless, this result clearly con-
firms that even more σ-donating trialkylphosphino groups
of chelating diphosphine ligand are easily replaced by nitro-
gen-containing donor ligands in iron(II) complexes.
Experimental Section
Materials and Methods: All experiments were carried out under an
atmosphere of purified argon in a Braun Labmaster glove box or
by using standard Schlenk techniques. MeCN and CHCl3 were
dried with CaH2, n-hexane was dried with LiAlH4, toluene and
ethane-1,2-diamine were dried with sodium, THF and diethyl ether
were dried with Na/K alloy. Deuterated solvents were sparged with
The inherent ability of iron(II) to form stable tetrahedral
complexes is well documented and might be the reason for
the observed reactivity of 1. In contrast, tetrahedral ru-
thenium(II) complexes have rarely been reported,[26] and
usually tetracoordinated ruthenium complexes either form
square-planar complexes[27] or they adopt a sawhorse like argon and stored over molecular sieves. The dppe[29] and the
Eur. J. Inorg. Chem. 0000, 0–0
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
dippe[30] ligands were prepared according to a previously reported
procedures. FeCl2, FeBr2, and 2-picolylamine were purchased from
Aldrich and used as received.
solution. After complete diffusion of the two solutions, colorless
crystals were separated by filtration. The crystals were washed three
times with diethyl ether and dried in vacuo, yield 1007 mg
(1.92 mmol, 76%). C26H24Cl2FeP2 (525.17): calcd. C 59.46, H 4.61,
1H and 31P NMR spectra were recorded with Bruker DRX 400 or
DPX 250 NMR spectrometers. IR spectra were recorded by attenu-
ated total reflection of the solid samples with a Bruker Tensor IF37
spectrometer. The intensity of the absorption band is indicated as
vw (very weak), w (weak), m (medium), s (strong), vs (very strong),
and br (broad).
N 0.00; found C 59.14, H 4.60, N 0.00. IR (ATR): ν = 3051 (w),
˜
2903 (w), 1580 (w), 1481 (m), 1434 (w), 1169 (w), 1097 (m), 1024
(w), 996 (w), 992 (w), 847 (w), 742 (m), 718 (s), 690 (vs), 505 (s),
480 (m), 448 (m) cm–1. MS (APCI, pos.): m/z (%) = 399.3 (100)
[dppe + H], 431.3 (21) [dppe(O2) + H], 488.3 (15) [M – Cl].
Formation of I, II and 2: In a typical experiment, [(dppe)FeCl2]n
(1, 40 mg, 0.076 mmol) was dissolved in either CH2Cl2 or toluene
(10 mL) and a solution of 2-picolylamine (1 m in toluene, 76 μL,
0.076 mmol, 1.0 equiv.) was added slowly, causing an immediate
color change to yellow and, in the case of toluene as solvent, the
formation of a yellow solid, which was identified as [(PicNH2)3Fe]-
Cl2·CH2Cl2 (I) after recrystallization from CH2Cl2/n-hexane. Lay-
ering of the CH2Cl2 solution also resulted in the formation of crys-
talline [(PicNH2)3Fe]Cl2·CH2Cl2 (I). The 31P{1H} NMR spectrum
of the supernatant CH2Cl2 or toluene solutions did not show any
resonances. Given that no free dppe ligand could be observed in
the 31P{1H} NMR spectrum, we tried to convert the remaining
paramagnetic chloro phosphine complexes in solution into their
hydrido analogues, which are known to be diamagnetic in the case
of octahedral dppe complexes. For this reason NaHBEt3 (1 m in
toluene, 0.5 equiv.) was added slowly to the supernatant toluene
solution, resulting in a color change from yellow to deep-red. By
31P{1H} and 1H NMR spectroscopic analysis, the major product of
the reaction was identified as trans-[(dppe)2Fe(H)Cl] (II). 31P{1H}
NMR (161 MHz, toluene unlocked, 27 °C): δ = 81.7 (s) ppm. 1H
NMR (400 MHz, toluene unlocked, 27 °C): δ = –29.15 (quint, 2JP,H
= 49.4 Hz, Fe-H) ppm.
HRMS (ESI) were acquired with a LTQ-FT mass spectrometer
(Thermo Fischer Scientific). HRMS (APCI) were acquired with a
LTQ-FT mass spectrometer (Thermo Fischer Scientific). In both
cases the resolution was set to 100,000. Elemental analyses were
performed with a Vario Micro Cube Elemental Analyzer.
Susceptibility measurements were performed with a Quantum De-
sign MPMS SQUID magnetometer.
Preparation of Mixtures Containing Complex 1 and 2: This experi-
ment was conducted according to a procedure originally reported
for [(dppe)FeCl2] by Mays and co-workers.[17b] FeCl2 (100 mg,
0.79 mmol) was heated to reflux in acetone (15 mL), to give a yel-
lowish solution.
A solution of dppe (1000 mg, 2.51 mmol,
1.45 equiv.) in chloroform (10 mL) was layered with the iron chlor-
ide containing acetone solution. After complete diffusion of the
two solutions, a crystalline product formed, which was analyzed by
single-crystal X-ray diffraction, elemental analysis, and mass spec-
trometry. The repeated unit cell refinement of the single crystals
from this mixture revealed that compound 1 is mainly formed un-
der these conditions; the elemental analysis of several batches sup-
ports the formation of a mixture containing 1 and 2.
Synthesis of [(dppe)FeCl2]n (1): FeCl2·4H2O (499 mg, 2.51 mmol)
was heated to reflux in acetone (40 mL), to give a yellowish solu-
tion. A solution of dppe (1000 mg, 2.51 mmol, 1 equiv.) in chloro-
form (4 mL) was layered with the iron chloride containing acetone
Formation of 3: In a typical experiment, [(dppe)FeCl2]n (2, 40 mg,
0.076 mmol) was suspended in MeCN (10 mL) and 2-picolylamine
(0.008 mL, 0.077 mmol, 1.02 equiv.) was added slowly, to give a
Table 2. Crystallographic data for 1–4 and I·CH2Cl2.
1+2·8/5C3H6O·2/5CHCl3
1Ј
I·CH2Cl2
3
4
Empirical formula
C
109.20H106Cl7.20Fe3O1.60P8
C26H24Cl2FeP2
525.14
193(2)
C38H52Cl8Fe2N12
536.11
100(2)
C24H32Cl6Fe3N8
812.83
193(2)
C14H32Br2FeP2
478.01
100(2)
Formula weight [gmol–1
]
2114.49
100(2)
T [K]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
triclinic
P1
monoclinic
P21/n
13.008(3)
11.495(2)
16.800(3)
90
100.08(3)
90
2473.3(9)
4
monoclinic
P21/n
10.995(2)
22.278(5)
11.369(2)
90
118.51(3)
90
2447.2(9)
4
triclinic
P1
orthorhombic
Pbca
23.558(5)
14.932(3)
23.558(5)
90
90
90
8287(3)
16
1.533
¯
¯
10.696(2)
13.970(3)
18.754(4)
86.83(3)
77.37(3)
70.17(3)
2571.7(9)
1
7.572(2)
12.873(3)
16.960(3)
78.86(3)
86.21(3)
88.69(3)
1618.4(6)
2
α [°]
β [°]
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3
]
1.365
0.778
1094
1.410
0.967
1080
1.455
1.071
1104
1.668
1.853
824
μ(Mo-Kα) [mm–1
F(000)
]
4.729
3872
θ range [°]
0.98–26.72
20999
10723, 0.0504
6460
1.83–25.93
18936
4650, 0.0714
2821
1.83–26.79
20632
5183, 0.1105
3113
2.21–25.52
15190
5590, 0.0712
3373
0.989–26.80
42919
8768, 0.1046
6822
Reflections measured
Indep. reflections, RInt
Indep. reflections
[IϾ2σ(I)]
Parameters/restraints
R1 [IϾ2σ(I)]
579/0
0.0495
296/0
0.0288
375/0
0.0656
370/0
0.0380
359/0
0.0461
wR2 (all data)
0.1134
0.0449
0.1715
0.0896
0.0851
GooF (all data)
0.871
1.230/–1.071
0.839
0.303/–0.309
0.973
1.785/–1.264
0.868
0.487/–0.630
1.043
0.586/–0.564
Max. peak/hole [eÅ–3
]
Eur. J. Inorg. Chem. 0000, 0–0
6
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
clear yellow solution. The 31P{1H} NMR spectrum of this mixture
did not show any resonance. For crystallization, the yellow aceto-
nitrile solution was layered on top of pure toluene, resulting in the
formation of yellow crystals, which were identified by single-crystal
X-ray diffraction.
2004, 131, 1394–1395; e) S. Enthaler, B. Hagemann, G. Erre,
K. Junge, M. Beller, Chem. Asian J. 2006, 1, 598–604; f) S.
Zhou, S. Fleischer, K. Junge, S. Das, D. Addis, M. Beller, An-
gew. Chem. Int. Ed. 2010, 49, 1–6; Angew. Chem. 2010, 122,
8298–8302; g) J. Yang, T. D. Tilley, Angew. Chem. Int. Ed. 2010,
49, 1–4; Angew. Chem. 2010, 122, 10384–10386.
C. P. Casey, H. Guan, J. Am. Chem. Soc. 2009, 131, 2499–2507.
a) B. L. Conley, M. K. Pennington-Boggio, E. Boz, T. J. Wil-
liams, Chem. Rev. 2010, 110, 2294–2312, and references cited
therein; b) R. Karvembu, R. Prabhakaran, K. Natarajan, Co-
ord. Chem. Rev. 2005, 249, 911–918, and references cited
therein.
V. Rautenstrauch, X. Hong-Cong, R. Churlaud, K. Abdur-Ra-
shid, R. H. Morris, Chem. Eur. J. 2003, 9, 4954–4967.
C. Sui-Seng, F. N. Haque, A. Hadzovic, A. Pütz, V. Reuss, N.
Meyer, A. J. Lough, M. Zimmer-De Iuliis, R. H. Morris, Inorg.
Chem. 2009, 48, 735–743.
a) C. Gunanathan, D. Milstein, Science 2013, 341, 249 and
references cited therein; b) C. Gunanathan, D. Milstein, Acc.
Chem. Res. 2011, 44, 588–602 and references cited therein.
J. Zhang, G. Leitus, Y. Ben-David, D. Milstein, Angew. Chem.
Int. Ed. 2006, 45, 1113–1115; Angew. Chem. 2006, 118, 1131–
1133.
a) R. Langer, G. Leitus, Y. Ben-David, D. Milstein, Angew.
Chem. Int. Ed. 2011, 50, 2120–2124; Angew. Chem. 2011, 123,
2168–2172; b) R. Langer, M. A. Iron, L. Konstantinovski, Y.
Diskin-Posner, G. Leitus, Y. Ben-David, D. Milstein, Chem.
Eur. J. 2012, 18, 7196–7209; c) R. Langer, Y. Diskin-Posner,
G. Leitus, L. J. W. Shimon, Y. Ben-David, D. Milstein, Angew.
Chem. Int. Ed. 2011, 50, 9948–9952.
a) W. Kuriyama, T. Matsumoto, O. Ogata, Y. Ino, K. Aoki, S.
Tanaka, K. Ishida, T. Kobayashi, N. Sayo, T. Saito, Org. Pro-
cess Res. Dev. 2012, 16, 166–171; b) T. Otsuka, A. Ishii, P. A.
Dub, T. Ikariya, J. Am. Chem. Soc. 2013, 135, 9600–9603.
a) S. Werkmeister, K. Junge, B. Wendt, E. Alberico, H. Jiao,
W. Baumann, H. Junge, F. Gallou, M. Beller, Angew. Chem.
Int. Ed. 2014, 53, 8722–8726; b) P. O. Lagaditis, P. E. Sues, J. F.
Sonnenberg, K. Y. Wan, A. J. Lough, R. H. Morris, J. Am.
Chem. Soc. 2014, 136, 1367–1380; d) S. Chakraborty, H. Dai,
P. Bhattacharya, N. T. Fairweather, M. S. Gibson, J. A. Krause,
H. Guan, J. Am. Chem. Soc. 2014, 136, 7869–7872; e) S. Chak-
raborty, P. O. Lagaditis, M. Förster, E. A. Bielinski, N. Hazari,
M. C. Holthausen, W. D. Jones, S. Schneider, ACS Catal. 2014,
DOI: 10.1021/cs5009656.
[5]
[6]
Synthesis of [(dippe)FeBr2] (4): Bis(diisopropylphosphanyl)ethane
(1.049 g, 3.99 mmol) dissolved in toluene (10 mL) was added drop-
wise to a suspension of FeBr2 (698 mg, 3.24 mmol) in toluene
(20 mL). The resulting suspension was stirred for four days and
then filtered. The volume of the filtrate was reduced in vacuo and
layered with n-hexane (13 mL), to give colorless crystals of the
paramagnetic complex 4 after two days, yield 1.085 mg (2.27 mmol,
70%). C14H32Br2FeP2 (478.01): calcd. C 35.18, H 6.75, N 0.00;
found C 34.87, H 6.66, N 0.00. IR (ATR): 3314 (vw), 3252 (vw),
3049 (vw), 2956 (m), 2930 (m), 2894 (w), 2871 (m), 2371 (vw), 2363
(vw), 2359 (vw), 2353 (vw), 2339 (vw), 2307 (vw), 1576 (vw), 1460
(s), 1435 (w), 1409 (w), 1387 (m), 1368 (m), 1297 (vw), 1260 (w),
1239 (m), 1159(w), 1108 (m), 1096 (m), 1047 (m), 1030 (s), 932 (m),
883 (m), 858 (w), 808 (m), 741 (m), 678 (vs), 667 (vs), 638 (w), 618
(m), 511 (w), 474 (m), 465 (m), 430 (w) cm–1. MS (ESI, pos.): m/z
(%) = 263.3 (80) [dippe + H]+, 317.3 (100) [(dippe)Fe-H]+, 397.1
(2) [M – Br]+, 429.1 (10) [M(O2) – Br]+.
[7]
[8]
[9]
[10]
[11]
Single-Crystal X-ray Analysis: The single-crystal X-ray diffraction
data for the structural analysis of 1–4 was collected by using graph-
ite-monochromated Mo-Kα radiation (λMo-Kα = 0.71073 Å). 1·8/
5C3H6O·2/5CHCl3 and I·CH2Cl2 were measured on the imaging
plate detector system STOE IPDS1, 2 and 3 on the imaging plate
detector system STOE IPDS2T and 4 on the imaging plate detector
system STOE IPDS2. The structures were solved by direct methods
with SHELXS-97 and refined against F2 by full-matrix-least-square
techniques using SHELXL-97.[31] Based on the crystal descriptions,
numerical absorption corrections were applied.[32]
[12]
[13]
CCDC-1023531 (for 1+2), -1023532 (for 1Ј), -1023533 (for 3),
-1023534 (for 4), and -1023535 (for I·CH2Cl2) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Details of
the data collection and the refinement are summarized in Table 2.
[14]
[15]
a) R. M. Bullock, Chem. Eur. J. 2004, 10, 2366–2374; b) R. M.
Bullock, in: Handbook of Homogeneous Hydrogenation (Eds.:
J. G. de Vries, C. J. Elsevier), Wiley-VCH, Weinheim, Germany,
2007, chapter 7; c) N. B. Johnson, I. C. Lennon, P. H. Moran,
J. A. Ramsden, Acc. Chem. Res. 2007, 40, 1291–1299.
a) R. Noyori, T. Ohkuma, Angew. Chem. Int. Ed. 2001, 40,
40–75; Angew. Chem. 2001, 113, 40–75; b) C. A. Sandoval, T.
Ohkuma, K. Munz, R. Noyori, J. Am. Chem. Soc. 2003, 125,
13490–13503; c) C. A. Sandoval, Y. Yamaguchi, T. Ohkuma,
K. Kato, R. Noyori, Magn. Reson. Chem. 2006; 44, 66–75.
a) Y. Ino, A. Yoshida, W. Kuriyama, Eur. Pat. Appl. 2008, EP
1970360 A1 20080917; b) P. D. de Koning, M. Jackson, I. C.
Lennon, Org. Process Res. Dev. 2006, 10, 1054–1058.
a) M. Aresta, P. Giannoccaro, M. Rossi, A. Sacco, Inorg. Chim.
Acta 1970, 5, 115–118; b) M. J. Mays, P. L. Sears, J. Chem.
Soc., Dalton Trans. 1973, 1873, 1873–1875; c) C. B. Unger-
mann, K. G. Caulton, J. Am. Chem. Soc. 1976, 98, 3862–3868;
d) R. A. Henderson, J. Chem. Soc., Dalton Trans. 1988, 509–
514; e) J. E. Barclay, G. J. Leigh, A. Houlton, J. Silver, J. Chem.
Soc., Dalton Trans. 1988, 2865–2870; f) D. J. Evans, P. B. Hitch-
cock, G. J. Leigh, B. K. Nicholson, A. C. Niedwieski, F. S.
Nunes, J. F. Soares, Inorg. Chim. Acta 2001, 319, 147–158.
a) Z.-Z. Zhang, J.-K. Zhang, W.-D. Zhang, H.-P. Xi, H. Cheng,
H.-G. Wang, J. Organomet. Chem. 1996, 515, 1–9.
Acknowledgments
R. L. is grateful to Prof. S. Dehnen and Prof. C. v. Hänisch for
their continuous support. This research is financially supported by
the Deutsche Forschungsgemeinschaft (DFG).
[1] a) S. Enthaler, K. Junge, M. Beller, Angew. Chem. Int. Ed. 2008,
47, 3317–3321; Angew. Chem. 2008, 120, 3363–3367; b) C.
Bolm, J. Legros, J. Le Paih, L. Zani, Chem. Rev. 2004, 104,
6217–6254; c) A. Correa, O. G. Mancheño, C. Bolm, Chem.
Soc. Rev. 2008, 37, 1108–1117.
[2] a) S. C. Bart, E. Lobkovsky, P. J. Chirik, J. Am. Chem. Soc.
2004, 126, 13794–13807; b) S. C. Bart, E. J. Hawrelak, E. Lob-
kovsky, P. J. Chirik, Organometallics 2005, 24, 5518–5527; c)
R. J. Trovitch, E. Lobkovsky, E. Bill, P. J. Chirik, Organometal-
lics 2008, 27, 1470–1478.
[3] a) S. Zhou, S. Fleischer, K. Junge, S. Das, D. Addis, M. Beller,
Angew. Chem. Int. Ed. 2011, 50, 5120–5124; b) W. Zuo, A. J.
Lough, Y. F. Li, R. H. Morris, Science 2013, 342, 1080–1083.
[4] a) R. H. Morris, Chem. Soc. Rev. 2009, 38, 2282–2291; b) S.
Gaillard, J. Renaud, ChemSusChem 2008, 1, 505–509; c) C.
Sui-Seng, F. Freutel, A. J. Lough, R. H. Morris, Angew. Chem.
Int. Ed. 2008, 47, 940–943; Angew. Chem. 2008, 120, 954–957;
d) A. Mikhailine, A. J. Lough, R. H. Morris, J. Am. Chem. Soc.
[16]
[17]
[18]
[19]
a) Y. Matsuura, Y. Tanaka, M. Akita, J. Organomet. Chem.
2009, 694, 1840–1847; b) R. H. Morris, J. F. Sawyer, M. Shiral-
Eur. J. Inorg. Chem. 0000, 0–0
7
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
ian, J. D. Zubkowski, J. Am. Chem. Soc. 1985, 107, 5581–5582; [25] A. R. Hermes, G. S. Girolami, Inorg. Chem. 1988, 27, 1775–
c) M. P. Robalo, A. P. S. Teixeira, M. H. Garcia, M. F. M.
da Piedade, M. T. Duarte, A. R. Dias, J. Campo, W. Wense-
leers, E. Goovaerts, Eur. J. Inorg. Chem. 2006, 2175–2185; d)
S. S. P. R. Almeida, M. F. C. G. da Silva, L. B. Jerzykiewicz, P.
Sobota, A. J. L. Pombeiro, Inorg. Chim. Acta 2003, 356, 259–
266; e) M. F. Meidine, M. A. N. D. A. Lemos, A. J. L. Pom-
beiro, J. F. Nixon, P. B. Hitchcock, J. Chem. Soc., Dalton Trans.
1781.
[26] a) R. A. Sanchez-Delgado, M. Navarro, K. Lazardi, R. Aten-
cio, M. Capparelli, F. Vargas, J. A. Urbina, A. Bouillez, A. F.
Noels, D. Masi, Inorg. Chim. Acta 1998, 275, 528–540; b) P. T.
Bishop, A. R. Cowley, J. R. Dilworth, A. J. Saunders, J. G.
Woollard-Shore, Dalton Trans. 2006, 1267–1270; c) C. L. Ras-
ton, A. H. White, J. Chem. Soc. Dalton Trans. 1975, 2410–2418.
1998, 3319–3324; f) J. Y. Baeg, W. S. Han, S. W. Lee, J. Korean [27] a) X. Yang, A. Walstrom, N. Tsvetkov, M. Pink, K. G. Caul-
Chem. Soc. 2002, 46, 427–431; g) S. S. P. R. Almeida,
M. F. C. G. da Silva, J. J. R. F. da Silva, A. J. L. Pombeiro, J.
Chem. Soc., Dalton Trans. 1999, 467–472; h) J.-G. Lee, B.-S.
Yoo, N.-S. Choi, K. I. Park, S. I. Cho, C. Lee, S. W. Lee, J.
Organomet. Chem. 1999, 589, 138–149; i) J. S. Ricci, T. F. Ko-
etzle, M. T. Bautista, T. M. Hofstede, R. H. Morris, J. F. Saw-
yer, J. Am. Chem. Soc. 1989, 111, 8823–8827; j) J. G. Cordaro,
D. Stein, H. Grützmacher, J. Am. Chem. Soc. 2006, 128, 14962–
14971; k) J. H. Lee, B.-S. Yoo, S. W. Lee, Inorg. Chim. Acta
2001, 321, 75–82; l) B.-S. Yoo, N.-S. Choi, C. Y. Shim, Y. Son,
S. W. Lee, Inorg. Chim. Acta 2000, 309, 137–145; m) S. S. P.
Almeida, M. T. Duarte, L. M. D. Ribeiro, F. Gormley, A. M.
Galvao, J. J. R. F. Da Silva, A. J. L. Pombeiro, J. Organomet.
Chem. 1996, 524, 63–66.
ton, Inorg. Chem. 2007, 46, 4612–4616; b) R. Kumar, A. K.
Singh, R. J. Butcher, P. Sharma, R. A. Toscano, Eur. J. Inorg.
Chem. 2004, 1107–1114; c) B. Askevold, M. M. Khusniyarov,
E. Herdtweck, K. Mayer, S. Schneider, Angew. Chem. Int. Ed.
2010, 49, 7566–7569; d) L. A. Watson, O. V. Ozerov, M. Pink,
K. G. Caulton, J. Am. Chem. Soc. 2003, 125, 8426–8427; e) R.
Flugel, B. Windmuller, O. Gevert, H. Werner, Chem. Ber. 1996,
129, 1007–1013; f) A. Walstrom, M. Pink, H. Fan, J. Tom-
aszewski, K. G. Caulton, Inorg. Chem. 2007, 46, 77047706; g)
A. Walstrom, M. Pink, K. G. Caulton, Inorg. Chem. 2006, 45,
5617–5620; h) Y. Yamamoto, R. Satoh, T. Tanase, J. Chem.
Soc. Dalton Trans. 1995, 307–311.
[28] a) D. Huang, W. E. Streib, J. C. Bollinger, K. G. Caulton, R. F.
Winter, T. Scheiring, J. Am. Chem. Soc. 1999, 121, 8087–8097;
b) S. Lachaize, L. Vendier, S. Sabo-Etienne, Dalton Trans. 2010,
39, 8492–8500; c) R.-M. Catala, D. Cruz-Garritz, P. Terreros,
H. Torrens, A. Hills, D. L. Hughes, R. L. Richards, J. Or-
ganomet. Chem. 1987, 328, C37–C39; d) R.-M. Catala, D.
Cruz-Garritz, P. Sosa, P. Terreros, H. Torrens, A. Hills, D. L.
Hughes, R. L. Richards, J. Organomet. Chem. 1989, 359, 219–
232; e) P. J. Blower, J. C. Jeffery, E. MacLean, V. T. Pinkrah,
F. E. Sowrey, S. J. Teat, M. J. Went, Inorg. Chim. Acta 2004,
357, 4129–4138; f) M. Ogasawara, D. Huang, W. E. Streib, J. C.
Huffman, N. Gallego-Planas, F. Maseras, O. Eisenstein, K. G.
Caulton, J. Am. Chem. Soc. 1997, 119, 8642–8651; g) D. Hu-
ang, W. E. Streib, O. Eisenstein, K. G. Caulton, Organometal-
lics 2000, 19, 1967–1972; h) R. Reguillo, M. Grellier, N. Vau-
travers, L. Vendier, S. Sabo-Etienne, J. Am. Chem. Soc. 2010,
132, 7854–7855; i) M. C. MacInnis, R. McDonald, M. J. Fergu-
son, S. Tobisch, L. Turculet, J. Am. Chem. Soc. 2011, 133,
13622–13633; j) L. Vieille-Petit, X. Luan, M. Gatti, S. Blumen-
tritt, A. Linden, H. Clavier, S. P. Nolan, R. Dorta, Chem. Com-
mun. 2009, 3783–3785.
[20] a) G. Mund, D. Vidovic, R. J. Batchelor, J. F. Britten, R. D.
Sharma, C. H. W. Jones, D. B. Leznoff, Chem. Eur. J. 2003, 9,
4757–2763; b) F. A. Cotton, R. L. Luck, K.-A. Son, Inorg.
Chim. Acta 1991, 179, 11–15; c) V. K. Bel’skii, V. M. Ishchenko,
B. M. Bulychev, A. N. Protskii, G. L. Soloveichik, O. G. Ellert,
Z. M. Seifulina, Y. V. Rakitin, V. M. Novotortsev, Inorg. Chim.
Acta 1985, 96, 123–127; d) H. Zhao, R. Clerac, J.-S. Sun, X.
Ouyang, J. M. Clemente-Juan, C. J. Gomez-Garcia, E. Coro-
nado, K. R. Dunbar, J. Solid State Chem. 2001, 159, 281–292.
[21] a) A. M. Greenaway, E. Sinn, J. Am. Chem. Soc. 1978, 100,
8080–8084; b) B. A. Katz, C. E. Strouse, J. Am. Chem. Soc.
1979, 101, 6214–6221; c) M. Hostettler, K. W. Tornroos, D.
Chernyshov, B. Vangdal, H.-B. Burgi, Angew. Chem. Int. Ed.
2004, 43, 4589–4594; Angew. Chem. 2004, 116, 4689–4695; d)
M. Mikami, M. Konno, Y. Saito, Acta Crystallogr., Sect. B:
Struct. Crystallogr. Cryst. Chem. 1980, 36, 275–287; e) D. Cher-
nyshov, M. Hostettler, K. W. Tornroos, H.-B. Burgi, Angew.
Chem. Int. Ed. 2003, 42, 3825–3830; Angew. Chem. 2003, 115,
3955–3960; f) J. Kusz, D. Schollmeyer, H. Spiering, P. Gutlich,
J. Appl. Crystallogr. 2005, 38, 528–536; g) D. Chernyshov, B. [29] K. Sommer, Z. Anorg. Allg. Chem. 1970, 376, 37–43.
Vangdal, K. W. Tornroos, H.-B. Burgi, New J. Chem. 2009, 33,
1277–1282; h) K. W. Tornroos, M. Hostettler, D. Chernyshov,
B. Vangdal, H.-B. Burgi, Chem. Eur. J. 2006, 12, 6207–6215.
[22] J.-G. Lee, G.-S. Lee, S. W. Lee, Bull. Korean Chem. Soc. 1998,
19, 267–269.
[23] T. Ohkuma, C. A. Sandoval, R. Srinivasan, Q. Lin, Y. Wei, K.
Muñiz, R. Noyori, J. Am. Chem. Soc. 2005, 127, 8288–8289.
[24] F. Calderazzo, U. Englert, G. Pampaloni, E. Vanni, C. R. Acad.
Sci., Ser. IIc: Chim. 1999, 2, 311–319.
[30] M. D. Fryzuk, T. Jones, F. W. B. Einstein, Organometallics
1984, 3, 185–191.
[31] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
[32] a) X-SHAPE, v. 1.06, Crystal Optimisation for Numerical Ab-
sorption Correction Program, Stoe & Cie GmbH, Darmstadt,
Germany, 1999; b) X-RED32, v. 1.01, Data Reduction Program,
Stoe & Cie GmbH, Darmstadt, Germany, 2001.
Received: September 11, 2014
Published Online: ᭿
Eur. J. Inorg. Chem. 0000, 0–0
8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Job/Unit: I42859
/KAP1
Date: 26-11-14 13:08:33
Pages: 9
www.eurjic.org
FULL PAPER
Diphosphine Ligands
R. Langer,* F. Bönisch, L. Maser,
C. Pietzonka, L. Vondung,
T. P. Zimmermann ............................. 1–9
Substitutional Lability of Diphosphine
Ligands in Tetrahedral Iron(II) Chloro
Complexes
The synthesis and reactivity of iron diphos-
phine complexes towards chelating amines
is described. The results illustrate the fun-
damental difference with respect to the cor-
responding ruthenium complexes and dem-
onstrate that the investigated diphosphine
ligands are bound too weakly in iron(II)
complexes to be used for active iron-based
catalysts.
Keywords: Iron / P ligands / Coordination
modes / N ligands / Structure elucidation
Eur. J. Inorg. Chem. 0000, 0–0
9
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim