On the reaction of [(CO)3Fe(μ-Me2NCO) 2Fe(CO)2(NHME2)] with chelating ligands - X-ray structures of new binuclear μ-carbamoyl complexes

Article abstract of DOI:10.1002/zaac.200400054

Reaction of the binuclear μ-carbamoyl complex [(CO)₃Fe(μ- Me₂NCO)₂Fe(CO)₂(HNMe₂)] (1) in toluene with the chelating ligands Ph₂PCH₂PPh₂ (dppm) and Ph₂PCH₂CH₂PPh₂ (dppe) gives different results. With dppm only the complex [(CO)₃Fe(μ- Me₂NCO)₂Fe(CO)₂(dppm)] (3) with a dangling ligand is obtained under replacement of amine, whereas with dppe depending on the reaction conditions up to three compounds are found. A 1:1 mixture of the educts generates the related complex [(CO)₃Fe(μ-Me ₂NCO)₂Fe(CO)₂(dppe)] (4) together with the tetranuclear complex [{(CO)₃Fe(μ-Me₂NCO) ₂Fe(CO)₂}₂(dppe)] (5). 4 slowly converts into [(CO)₃Fe(μ-Me₂NCO)₂Fe(CO)(dppe)] (6) with dppe acting as a chelating ligand. 6 is the first compound in this series in which one of the five CO groups is replaced by another donor. A 2:1 molar ratio of 1 and dppe quantitatively produces 5. Addition of CO to a solution of 6 proceeds under slow reversible conversion of the complex into 4. The compounds were characterized by the usual spectroscopic methods; 3, 5, and 6 were also studied by X-ray diffraction analyses.

Full text of DOI:10.1002/zaac.200400054

On the Reaction of [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(NHMe2)] with Chelating
Ligands ؊ X-Ray Structures of New Binuclear µ-Carbamoyl Complexes
Wolfgang Petz*, Bernhard Neumüller*, and Jens Pudewills
Marburg, Fachbereich Chemie der Philipps-Universität
Received February 25th, 2004.
Professor Werner Massa zum 60. Geburtstag gewidmet
Abstract. Reaction of the binuclear µ-carbamoyl complex
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(HNMe2)] (1) in toluene with the
chelating ligands Ph2PCH2PPh2 (dppm) and Ph2PCH2CH2PPh2
(dppe) gives different results. With dppm only the complex
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(dppm)] (3) with a dangling ligand
is obtained under replacement of amine, whereas with dppe de-
pending on the reaction conditions up to three compounds are
found. A 1 : 1 mixture of the educts generates the related complex
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(dppe)] (4) together with the tetra-
nuclear complex [{(CO)3Fe(µ-Me2NCO)2Fe(CO)2}2(dppe)] (5). 4
slowly converts into [(CO)3Fe(µ-Me2NCO)2Fe(CO)(dppe)] (6) with
dppe acting as a chelating ligand. 6 is the first compound in this
series in which one of the five CO groups is replaced by another
donor. A 2 : 1 molar ratio of 1 and dppe quantitatively produces
5. Addition of CO to a solution of 6 proceeds under slow reversible
conversion of the complex into 4. The compounds were charac-
terized by the usual spectroscopic methods; 3, 5, and 6 were also
studied by X-ray diffraction analyses.
Keywords: Iron; Chelating ligands; Bridging carbamoyl groups;
Crystal structures
Über die Reaktion von [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(NHMe2)] mit Chelatliganden ؊
Kristallstrukturen neuer zweikerniger µ-Carbamoyl Komplexe
Inhaltsübersicht. Die Reaktion des zweikernigen µ-Carbamoylkom-
plexes [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(HNMe2)] (1) mit den Che-
latliganden Ph2PCH2PPh2 (dppm) und Ph2PCH2CH2PPh2 (dppe)
führt zu unterschiedlichen Ergebnissen. Mit dppm entsteht durch
Verdrängung des Amins der Komplex [(CO)3Fe(µ-Me2NCO)2Fe-
(CO)2(dppm)] (3) mit einem frei baumelnden Liganden, wohin-
gegen mit dppe je nach Reaktionsbedingungen bis zu drei Verbin-
dungen gefunden werden. Eine 1 : 1 Umsetzung der Edukte liefert
den zu 3 analogen Komplex [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(dppe)]
(4) zusammen mit dem vierkernigen Komplex [{(CO)3Fe-
(µ-Me2NCO)2Fe(CO)2}2(dppe)] (5). Der Komplex 4 wandelt sich
langsam unter CO-Verlust in [(CO)3Fe(µ-Me2NCO)2Fe-
(CO)(dppe)] (6) um, wobei dppe als Chelatligand fungiert. 6 ist die
erste Verbindung in dieser Serie, in der eine der fünf CO-Gruppen
durch einen Fremddonor ersetzt ist. Ein 2 : 1 Molverhältnis von 1
und dppe liefert quantitativ 5. Einleiten von CO in eine Lösung
von 6 führt langsam zur reversiblen Rückverwandlung in 4. Die
Verbindungen wurden durch die üblichen spektroskopischen
Methoden charakterisiert; 3, 5 und 6 wurden auch durch Kristall-
strukturanalysen bestimmt.
1 Introduction
Recently, we described some new compounds which belong
to a series of unique asymmetrically bridged dinuclear iron
compounds of the type I [1]. These complexes have in com-
mon that only the ligand in the position D, which we have
named the “α” position, has been replaced by other donor
ligands. The labilized position is located trans to Fe(1)
within the symmetry plane of the molecule; D stands for
CO and a variety of N or P donating ligands [2]. The iron
atoms in I are chemically different, and according to the
attached oxygen atoms Fe(2) is in a higher formal oxidation
state than Fe(1) [5].
Scheme 1
The main and typical route to these complexes is the oxi-
dative coupling reaction of anionic carbamoyl, acyl, or al-
koxycarbonyl compounds, [(CO)4FeC(O)R]Ϫ. Recently, we
found that oxidation of the carbamoyl complex [C(NMe2)3-
][(CO)4FeC(O)NMe2] with Agϩ leads to the formation of
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(HNMe2)] (1) with HNMe2
in the α position [1]. Addition of PPh3 to 1 quantitatively
* Prof. Dr. Wolfgang Petz, Prof. Dr. Bernhard Neumüller
Fachbereich Chemie der Philipps Universität
D-35032 Marburg, Hans-Meerwein-Strasse
E-mail: petz@staff.uni-marburg.de, neumuell@chemie.uni-marburg.de
Z. Anorg. Allg. Chem. 2004, 630, 869Ϫ875
DOI: 10.1002/zaac.200400054
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
869

W. Petz, B. Neumüller, J. Pudewills
gives [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(PPh3)] (2) indicating
that HNMe2 is a good leaving group. These properties
prompted us to study the reactivity of 1 more intensively,
and in this contribution we report on the results of the reac-
tion of 1 with the diphosphines Ph2PCH2PPh2 (dppm) and
Ph2PCH2CH2PPh2 (dppe). In choosing chelating ligands,
we also studied the possibility of replacing a further car-
bonyl group additionally to the replacement of a ligand in
the α position with help of the chelating effect. To our
knowledge, no bidentate ligands with N or P donating
atoms have been introduced into I as yet and no com-
pounds with more than one donor ligand instead of CO at
any other position have been obtained. Three of the new
products could be characterized by X-ray analyses.
concentration of 1 mainly 4 is generated and the formation
of 5 is nearly suppressed. However, with time a further pair
of doublets at 88.3 and 65.7 ppm (3J(P,P) ϭ 22.9 Hz) ap-
pears which can be assigned to [(CO)3Fe(µ-Me2NCO)2-
Fe(CO)(dppe)] (6), in which the dppe now acts as a chelat-
ing ligand under replacement of a further CO group at
Fe(2). The ratio of complex 4 to complex 6 under these
conditions was 1:0.3. On heating the NMR tube at about
40 °C for about 30 minutes the signals of 4 decreased in
favor of 6, and a 4:6 ratio of 1:5.4 was recorded. The com-
plex 6 is the first one, in which two positions in I are occu-
pied by a non carbonyl ligand. The signals of 6 increase
with time, and on standing of the reaction mixture at room
temperature for several days the signals of 4 disappeared.
Crystal growth from the solution needs several days and
produces only red crystals of 6. The conversion of 4 into 6
is reversible at room temperature on exposure to an atmos-
phere of CO (1 atm) as shown by 31PNMR experiments.
Thus, stirring a toluene solution of 6 under CO, the 6 to 4
ratio was recorded as 1:0.09 after 3 h and increased to 1:0.4
after 12 h of exposure to CO.
2 Results and Discussion
2.1 Preparation and properties
Similar to the preparation of [(CO)3Fe(µ-Me2NCO)2-
Fe(CO)2(PPh3)] (2) [1], complex 1 reacts with dppm under
substitution of HNMe2 to give quantitatively the complex
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(η1-PPh2CH2PPh2)] (3), in
which the α position is now occupied by one phosphorus
atom of the dppm ligand. The 31P NMR spectrum of 3
exhibits a pair of doublets at 41.5 ppm and Ϫ27.5 ppm
(2J(P,P) ϭ 59.8 Hz). The low field signal is located near the
signal of 2 and the high field signal is close to that of the
free ligand, indicating the presence of a dangling ligand in-
stead of a chelating one. Heating of the reaction mixture or
longer reaction time or addition of another equivalent of 1
do not alter the spectrum, which means that neither a chel-
ating effect occurs with substitution of a further carbonyl
group nor a second diiron fragment can be added to the
free phosphorus atom of the dppm ligand. In contrast to
our findings, the photochemical reaction of dppm with
Fe(CO)5 generates all possible products [8], and similar
pairs of doublets were observed in the complex
[Fe(CO)4(η1-dppm)], however, with a stronger low field
shift of the FePPh2 signal and larger coupling constants [7].
The results completely change if the distance between the
phosphorus atoms is increased e.g. separated by a further
CH2 group as in dppe. In contrast to the dppm ligand, the
results of the reaction of 1 with dppe depend on the ratio
of the reactants, temperature, and reaction time. Thus,
a 1:1 molar ratio of the reactants at room temperature
When a 1:2 ligand to iron complex 1 ratio is allowed to
react, quantitatively the tetranuclear complex 5 is produced
gives
a
mixture of [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(η1-
PPh2CH2CH2PPh2)] (4) with a dangling ligand and the
tetranuclear complex [{(CO)3Fe(µ-Me2NCO)2Fe(CO)2}2-
(dppe)] (5) in which both positions of dppe are occupied by
a diiron fragment; the ratio of 4 to 5 to unreacted dppe was
recorded as 2:1:1, respectively. Similar to 3 the 31P NMR
spectrum of 4 exhibits a pair of doublets at 41.2 ppm and
Ϫ12.2 ppm (3J(P,P) ϭ 36.9 Hz) whereas for 5 a singlet at
41.7 ppm is recorded, which is due to equivalent phos-
phorus atoms. At a threefold excess of dppe and slow ad-
dition of 1 to the solution of dppe to avoid a local high
Scheme 2 (i) 1 equiv. of dppm in toluene, (ii) excess dppe in
toluene, (iii) 1/2 equivalent dppe, (iv) 1 d at room temperature,
(v) 1 atm CO, 3h
870
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Z. Anorg. Allg. Chem. 2004, 630, 869Ϫ875

On the Reaction of [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands
as shown by 31P NMR studies; the singlet at 41.7 ppm was
recorded as the single absorption. Addition of further dppe
to a reaction mixture with a given 4:5 ratio does not change
the initial ratio in favor to 4, which means that phosphine
ligands are bonded stronger than N donating ligands and
ligand exchange does not occur in this case in the α posi-
tion. Thus, only amines such as HNMe2 in the α position
act as excellent leaving groups.
tions around 1500 cmϪ1 where recorded and tentatively as-
signed to the bridging carbamoyl group.
The 1H and 13C NMR spectra of 6 confirm that the
structure of the molecule is rigid on the NMR time scale.
Both spectra exhibit four signals for the NMe2 groups due
to the lack of a molecular symmetry plane and according
to restricted rotation at the CϪNMe2 bond. Compared to
1
3 in the H NMR spectrum of 6 the low field pair at 2.86/
The difference in the reactivity of 3 and 4 towards 1 may
be originated by a steric effect. The free phosphorus atom
in 3 can be considered as a diphenylphosphine with a very
large third substituent and with a large cone angle pre-
venting coordination at a metal atom; in 4, however, the
second phosphorus atom is too far away and free for coor-
dination.
The IR data of 3 and 5 in the carbonyl region are very
similar to those of 2 [1]. Three or four very strong absorp-
tions between 2030 and 1920 cmϪ1 were found for the five
terminal CO groups in the metallacyclic compounds with a
local Cs symmetry. The additional coordination of a phos-
phorus atom as in 6 causes the ν(CO) bands to shift to
lower frequencies according to the increased back donation
of electron density into CO π* orbitals of the remaining
carbonyl groups. For the four CO groups, the loss of the
molecular Cs symmetry gives rise to four strong bands at
1985, 1930, 1919, and 1887 cmϪ1. In all compounds absorp-
2.28 ppm can be attributed to the NMe2 group trans to CO,
whereas the pair 2.68/2.20 ppm belongs to the carbamoyl
group trans to the phosphorus atom. A similar assignment
can be made for the two pairs of NMe2 signals at 39.4/35.2
and 39.0/35.1 ppm in the 13C NMR spectrum of 6. For the
four terminal CO groups and the two carbenoid carbamoyl
carbon atoms six signals were expected; however, the low
solubility of 6 in toluene did not allow to detect the corre-
sponding signals.
If only the α position in the molecular symmetry plane
is occupied by various donor molecules only two absorp-
tions are found for the type I compounds due to the hin-
dered rotation about the CϪN bond. The entrance of the
second dppe phosphorus atom into the coordination sphere
of the metal atom in 6 causes a low field shift of both sig-
nals in the 31P NMR spectrum; the signal at the lowest field
at 88.3 ppm is assigned to the phosphorus atom trans to
the carbamoyl oxygen atom.
Table 1 Crystal data and structure refinement details for 3, 5 and 6
3
5
6
formula
mw (g/mol)
a/pm
b/pm
c/pm
C36H34Fe2N2O7P2
780.31
1200.1(1)
1018.7(1)
2933.4(2)
96.43(1)
0.43 ϫ 0.43 ϫ 0.42
3563.6(5)
4
C48H48Fe4N4O14P2
1190.26
1067.4(2)
1615.9(2)
1524.5(2)
99.11(1)
0.15 ϫ 0.1 ϫ 0.06
2596.3(8)
2
C36H36Fe2N2O6P2
766.33
1212.1(1)
3125.4(2)
961.0(1)
110.58(1)
0.31 ϫ 0.15 ϫ 0.05
3408.2(5)
4
β/°
crystal size/mm
volume/pm3·106
Z
dcalc (g/cm3)
crystal system
space group
diffractometer
radiation
temperature /K
µ/cmϪ1
1.454
1.523
1.493
monoclinic
P21/c (Nr. 14)
IPDS II (Stoe)
Mo-Kα
193
9.5
monoclinic
P21/c (No. 14)
IPDS I (Stoe)
Mo-Kα
193
12.2
monoclinic
P21/n (No. 14)
IPDS II (Stoe)
Mo-Kα
193
9.9
2θmax/°
index range
52.58
52.36
52.39
Ϫ14 Յ h Յ 14
Ϫ12 Յ k Յ 12
Ϫ36 Յ l Յ 36
49398
Ϫ13 Յ h Յ 13
Ϫ19 Յ k Յ 19
Ϫ18 Յ l Յ 18
23051
Ϫ15 Յ h Յ 13
Ϫ38 Յ k Յ 38
Ϫ11 Յ l Յ 11
33126
number of rflns collected
number of indep. rflns (Rint
number of observed rflns with F0 > 4σ(F0)
parameters
)
7189 (0.036)
6198
447
5070 (0.231)
1826
330
6809 (0.0905)
5127
438
absorption correction
structure solution
numerical
direct methods SHELXS-97 [9]
SHELXL-97 [11]
a)
numerical
direct methods SIR-92 [10]
SHELXL-97 [11]
a)
numerical
direct methods SHELXS-97 [9]
SHELXL-97 [11]
a)
refinement against F2
H atoms
R1
0.0323
0.0912
0.40
0.0424
0.0841
0.38
0.042
0.1086
0.53
wR2 (all data)
max. electron density left/e/pm3·10Ϫ6
a) calculated positons with common displacement parameter
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W. Petz, B. Neumüller, J. Pudewills
The NMR data are consistent with the solid state struc-
ture discussed below.
Table 2 Selected bond distances/pm and angles/° in [(CO)3Fe-
(µ-Me2NCO)2Fe(CO)2(PPh2CH2PPh2)] (3)
distances
2.2 Crystal Structures
Fe(1)ϪFe(2)
Fe(1)ϪO(6)
Fe(1)ϪC(1)
Fe(2)ϪC(3)
Fe(2)ϪC(5)
Fe(2)ϪC(7)
P(2)ϪC(8)
O(2)ϪC(2)
O(4)ϪC(4)
O(6)ϪC(6)
N(1)ϪC(6)
256.93(4)
190.0(1)
175.6(2)
178.7(2)
178.4(2)
198.4(2)
185.9(2)
115.0(2)
114.6(3)
128.3(2)
133.4(2)
Fe(1)ϪP(1)
Fe(1)ϪO(7)
Fe(1)ϪC(2)
Fe(2)ϪC(4)
Fe(2)ϪC(6)
P(1)ϪC(8)
O(1)ϪC(1)
O(3)ϪC(3)
O(5)ϪC(5)
O(7)ϪC(7)
N(2)ϪC(7)
227.12(5)
197.7(1)
176.3(2)
179.4(2)
199.4(2)
183.3(2)
115.5(2)
114.8(3)
114.5(3)
128.3(2)
134.5(2)
In order to get a deeper inside into the properties of the
compounds, the structures of 3, 5, and 6 have been deter-
mined by single crystal X-ray diffraction measurements.
Red crystals of the compounds were obtained at room
temperature by layering the filtered toluene solutions with
n-pentane. ORTEP views of the molecules are depicted in
Figures 1 to 3; details of the structure determinations are
collected in Table 1; bond distances and angles are summar-
ized in the Tables 2 (compound 3), 3 (compounds 5), and 4
(compound 6). Molecular structures of similar compounds
with PPh3 in the a position have been determined with R ϭ
mes, NPri2 [2h], NMe2 [1], and OBut [2g]. All compounds
have in common the typical Fe2C2O2 structural motif with
the butterfly arrangement of the carbamoyl ligand.
angles
Fe(2)ϪFe(1)ϪP(1)
Fe(2)ϪFe(1)ϪO(7)
Fe(2)ϪFe(1)ϪC(2)
P(1)ϪFe(1)ϪO(7)
P(1)ϪFe(1)ϪC(2)
O(6)ϪFe(1)ϪC(1)
O(7)ϪFe(1)ϪC(1)
C(1)ϪFe(1)ϪC(2)
Fe(1)ϪFe(2)ϪC(4)
Fe(1)ϪFe(2)ϪC(6)
C(3)ϪFe(2)ϪC(4)
C(3)ϪFe(2)ϪC(6)
C(4)ϪFe(2)ϪC(5)
C(4)ϪFe(2)ϪC(7)
C(5)ϪFe(2)ϪC(7)
Fe(1)ϪP(1)ϪC(8)
157.74(2)
72.91(4)
96.35(6)
89.46(4)
97.96(6)
90.08(7)
173.58(7)
92.20(9)
89.15(7)
68.37(5)
92.4(1)
104.80(8)
95.0(1)
158.20(8)
88.33(9)
113.10(6)
Fe(2)ϪFe(1)ϪO(6)
Fe(2)ϪFe(1)ϪC(1)
P(1)ϪFe(1)ϪO(6)
P(1)ϪFe(1)ϪC(1)
O(6)ϪFe(1)ϪO(7)
O(6)ϪFe(1)ϪC(2)
O(7)ϪFe(1)ϪC(2)
Fe(1)ϪFe(2)ϪC(3)
Fe(1)ϪFe(2)ϪC(5)
Fe(1)ϪFe(2)ϪC(7)
C(3)ϪFe(2)ϪC(5)
C(3)ϪFe(2)ϪC(7)
C(4)ϪFe(2)ϪC(6)
C(5)ϪFe(2)ϪC(6)
C(6)ϪFe(2)ϪC(7)
Fe(1)ϪP(1)ϪC(9)
C(8)ϪP(1)ϪC(9)
C(9)ϪP(1)ϪC(15)
Fe(1)ϪO(6)ϪC(6)
C(6)ϪN(1)ϪC(61)
73.23(4)
102.27(6)
92.01(4)
94.15(6)
84.48(6)
169.58(7)
92.56(7)
173.38(7)
92.82(7)
69.15(5)
93.45(9)
108.92(9)
90.65(8)
160.66(8)
79.85(7)
110.05(6)
104.19(8)
104.21(8)
105.9(1)
124.1(2)
2.2.1 Crystal structure of [(CO)3Fe(µ-Me2NCO)2-
Fe(CO)2(PPh2CH2PPh2)] (3)
The crystal structure of 3 is shown in Figure 1; it is closely
related to that of the corresponding PPh3 derivative 2 [1]
and confirms the presence of only one coordinating P atom
in the molecule. The largest differences are found in a
slightly shorter FeϪFe distance (about 1 pm) and a shorter
FeϪP distance (about 3 pm) in 3; all other parameters are
equal. The position of the dangling free PPh2 group is prob-
ably fixed by packing effects and the distance of the P(2)
atom to the iron moiety is too far away for any interaction.
The dihedral angle between the planes spanned by the
atoms Fe(1), Fe(2), N(1), C(6), O(6) and Fe(1), Fe(2), N(2),
C(7), O(7) is 86°. The PϪCϪP angle amounts to 113° and
is about 3° larger than in [Fe2(CO)7(µ-dppm)] where both
P atoms coordinate and bridge two Fe atoms [3]; however,
if dppm acts as a chelating ligand as in [Fe(CO)3(dppm)],
the corresponding angle is strained to 91° [4].
Fe(1)ϪP(1)ϪC(15) 120.54(6)
C(8)ϪP(1)ϪC(15)
Fe(1)ϪO(7)ϪC(7)
C(6)ϪN(1)ϪC(62)
C(7)ϪN(2)ϪC(71)
103.21(8)
105.5(1)
120.2(2)
120.8(2)
C(61)ϪN(1)ϪC(62) 115.4(2)
C(71)ϪN(2)ϪC(72) 115.6(2)
C(7)ϪN(2)ϪC(72)
Fe(1)ϪC(1)ϪO(1)
Fe(2)ϪC(3)ϪO(3)
Fe(2)ϪC(5)ϪO(5)
Fe(2)ϪC(6)ϪN(1)
Fe(2)ϪC(7)ϪO(7)
O(7)ϪC(7)ϪN(2)
123.4(2
176.5(2)
170.9(2)
178.3(2)
133.1(1)
112.5(1)
115.5(2)
Fe(1)ϪC(2)ϪO(2)
Fe(2)ϪC(4)ϪO(4)
Fe(2)ϪC(6)ϪO(6)
O(6)ϪC(6)ϪN(1)
Fe(2)ϪC(7)ϪN(2)
P(1)ϪC(8)ϪP(2)
178.4(2)
177.7(2)
112.0(1)
114.9(2)
132.0(1)
112.64(9)
2.2.2 Crystal structure of [(CO)3Fe(µ-Me2NCO)2-
Fe(CO)2(PPh2(CH2)2PPh2)Fe(CO)2(µ-Me2NCO)2-
Fe(CO)3] (5)
In the solid state the tetranuclear complex 5 crystallizes in
the centrosymmetric form with the symmetry center in the
middle of the CϪC-bond of dppe; the molecular structure
is depicted in Figure 2. One dimethylamino group is dis-
ordered and only one position is shown. The two planes
containing the atoms Fe(1), Fe(2), O(6), C(6), N(11) and
Fe(1), Fe(2), O(7), C(7), N(2) have a dihedral angle of 86°.
As expected, in both iron moieties the favored α position is
occupied by the phosphorus atoms. Most of the other dis-
tances and angles are identical with the parameters of the
related compounds 2 and 3.
Fig. 1 Structure of 3 (40 % propability for thermal ellipsoids)
zaac.wiley-vch.de Z. Anorg. Allg. Chem. 2004, 630, 869Ϫ875
872
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On the Reaction of [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands
2.2.3 Crystal structure of [(CO)3Fe(µ-Me2NCO)2-
Fe(CO)(PPh2(CH2)2PPh2)] (6)
Table 3 Selected bond distances/pm and angles/° in [(CO)3Fe-
(µ-Me2NCO)2Fe(CO)2(PPh2CH2CH2PPh2)Fe(CO)2(µ-Me2NCO)2-
Fe(CO)3] (5)
The complex 6 is the first one in which two donor atoms
other than CO are bonded in a type I species. In going from
5 to 6 the occupied α position is maintained, which does not
allow the dppe ligand to bridge two Fe atoms but replaces a
CO group at the same atom under loss of the molecular
mirror plane; the molecular structure is shown in Figure 3.
The coordination of the second phosphorus atom increases
the FeϪFe-bond length by about 6 pm; this is the largest
iron iron bond separation found in this series of com-
pounds. As in similar compounds, both iron atoms are ap-
proximately in an octahedral environment. The phosphorus
atom opposite to the FeϪFe bond in the α position is about
three pm further away from Fe(2) than that opposite to
O(5). Also the FeϪO distances are slightly different; as ex-
pected, the oxygen atom trans to CO is closer to Fe(2) than
that trans to P(1). The replacement of one of the two car-
bonyl groups at Fe(2) by a better σ-donor increases d-π*
back donation to the remaining CO group with the effect
of a shortening of the carbon-iron bond distance to about
174 pm. The lack of a symmetry plane induces chirality at
Fe(2) and the unit cell contains the pair of enantiomers.
The corresponding dihedral angle between the two
Fe2CON planes amounts to 83.2°.
distances
Fe(1)ϪFe(2)
Fe(1)ϪC(2)
Fe(1)ϪC(6)
Fe(2)ϪP(1)
Fe(2)ϪO(7)
Fe(2)ϪC(5)
O(1)ϪC(1)
O(3)ϪC(3)
O(5)ϪC(5)
O(7)ϪC(7)
N(11)ϪC(6)
N(11)ϪC(622/1)
257.9(1)
179.3(7)
198.0(6)
228.8(2)
196.9(5)
175.7(8)
115.7(8)
112.9(9)
114.2(8)
127.7(7)
135.0(7)
149(1)
Fe(1)ϪC(1)
Fe(1)ϪC(3)
Fe(1)ϪC(7)
Fe(2)ϪO(6)
Fe(2)ϪC(4)
P(1)ϪC(8)
O(2)ϪC(2)
O(4)ϪC(4)
O(6)ϪC(6)
N(2)ϪC(7)
N(11)ϪC(611/2)
C(8)ϪC(8a)
178.5(7)
179.7(8)
197.3(7)
199.3(3)
174.4(6)
183.8(5)
114.6(7)
116.4(6)
126.0(7)
135.6(9)
147(1)
152(1)
angles
Fe(2)ϪFe(1)ϪC(1)
Fe(2)ϪFe(1)ϪC(3)
Fe(2)ϪFe(1)ϪC(7)
C(1)ϪFe(1)ϪC(3)
C(1)ϪFe(1)ϪC(7)
C(2)ϪFe(1)ϪC(6)
C(3)ϪFe(1)ϪC(6)
C(6)ϪFe(1)ϪC(7)
Fe(1)ϪFe(2)ϪO(6)
Fe(1)ϪFe(2)ϪC(4)
P(1)ϪFe(2)ϪO(6)
P(1)ϪFe(2)ϪC(4)
O(6)ϪFe(2)ϪO(7)
O(6)ϪFe(2)ϪC(5)
O(7)ϪFe(2)ϪC(5)
Fe(2)ϪP(1)ϪC(8)
Fe(2)ϪP(1)ϪC(15)
C(8)ϪP(1)ϪC(15)
Fe(2)ϪO(6)ϪC(6)
C(7)ϪN(2)ϪC(71)
C(71)ϪN(2)ϪC(72)
173.2(3)
91.1(2)
69.0(2)
94.0(3)
105.4(3)
158.7(3)
86.7(3)
80.0(3)
72.5(1)
100.5(2)
93.7(1)
93.4(2)
84.2(2)
90.8(2)
172.8(2)
110.1(2)
115.1(2)
105.3(3)
104.9(3)
119.8(5)
116.8(6)
Fe(2)ϪFe(1)ϪC(2)
Fe(2)ϪFe(1)ϪC(6)
C(1)ϪFe(1)ϪC(2)
C(1)ϪFe(1)ϪC(6)
C(2)ϪFe(1)ϪC(3)
C(2)ϪFe(1)ϪC(7)
C(3)ϪFe(1)ϪC(7)
Fe(1)ϪFe(2)ϪP(1)
Fe(1)ϪFe(2)ϪO(7)
Fe(1)ϪFe(2)ϪC(5)
P(1)ϪFe(2)ϪO(7)
P(1)ϪFe(2)ϪC(5)
O(6)ϪFe(2)ϪC(4)
O(7)ϪFe(2)ϪC(4)
C(4)ϪFe(2)ϪC(5)
Fe(2)ϪP(1)ϪC(9)
C(8)ϪP(1)ϪC(9)
C(9)ϪP(1)ϪC(15)
Fe(2)ϪO(7)ϪC(7)
C(7)ϪN(2)ϪC(72)
90.2(2)
68.6(2)
93.8(3)
107.1(3)
95.7(3)
91.1(3)
159.0(6)
159.50(7)
72.4(1)
101.2(2)
91.5(1)
94.0(2)
172.9(2)
95.1(3)
89.2(3)
117.3(2)
107.0(3)
101.0(3)
106.0(4)
122.7(5)
C(6)ϪN(11)ϪC(611) 120.6(7)
C(6)ϪN(11)ϪC(612) 119.1(7)
C(612)ϪN(11)ϪC(622) 120.4(8)
C(6)ϪN(11)ϪC(622)
Fe(1)ϪC(2)ϪO(2)
Fe(2)ϪC(4)ϪO(4)
Fe(1)ϪC(6)ϪO(6)
Fe(1)ϪC(6)ϪN(12)
O(6)ϪC(6)ϪN(12)
Fe(1)ϪC(7)ϪN(2)
P(1)ϪC(8)ϪC(8a)
120.2(7)
179.7(7)
177.3(6)
114.0(4)
130.3(5)
115.8(5)
132.4(4)
117.6(4)
Fe(1)ϪC(1)ϪO(1)
Fe(1)ϪC(3)ϪO(3)
Fe(2)ϪC(5)ϪO(5)
171.3(7)
176.3(6)
177.6(5)
Fe(1)ϪC(6)ϪN(11) 130.3(5)
O(6)ϪC(6)ϪN(11)
Fe(1)ϪC(7)ϪO(7)
O(7)ϪC(7)ϪN(2)
115.8(5)
112.5(5)
115.0(6)
Fig. 3 Molecular structure of 6 (50 % propability for thermal
ellipsoids)
2.2.4 Conclusion and outlook
In the unique binuclear iron complexes I as yet only the α
position has been replaced by other donating ligands and
the five remaining carbonyl groups are very strongly
bonded. However, it is possible to attack a further CO posi-
tion with the chelating ligands dppe, but at first the easier
attainable α position is occupied serving as an anchoring
position for the chelating ligand. Thus, 6 represents the first
complex in this series containig four CO and two other do-
nor ligands. Starting with one donor atom in the α position
Fig. 2 Molecular structure of 5 (50 % propability for thermal
ellipsoids)
Z. Anorg. Allg. Chem. 2004, 630, 869Ϫ875
zaac.wiley-vch.de
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
873

W. Petz, B. Neumüller, J. Pudewills
3 Experimental Section
Table 4 Selected bond distances/pm and angles/° in [(CO)3Fe-
(µ-Me2NCO)2Fe(CO)(PPh2CH2CH2PPh2)] (6)
All operations were carried out under an argon atmosphere in dried
and degassed solvents using Schlenk techniques. The solvents were
thoroughly dried and freshly distilled prior to use. The IR spectra
were run on a Nicolet 510 spectrometer. For the NMR spectra we
used the instruments Bruker AMX 500 and AC 200. Elemental
analyses were performed by the analytical service of the Fachbe-
reich Chemie der Universität Marburg (Germany). 1 was prepared
according to the literature procedure [1] from [C(NMe2)3][(CO)4-
FeC(O)NMe2] [6] with Agϩ. Commercial available dppm and dppe
were used without further purification.
distances
Fe(1)ϪFe(2)
Fe(1)ϪC(2)
Fe(1)ϪC(5)
Fe(2)ϪP(1)
Fe(2)ϪO(5)
Fe(2)ϪC(4)
P(1)ϪC(9)
P(2)ϪC(8)
P(2)ϪC(27)
O(2)ϪC(2)
O(4)ϪC(4)
O(6)ϪC(6)
N(2)ϪC(6)
263.15(5)
177.9(3)
199.8(3)
221.17(8)
198.4(2)
174.0(3)
183.5(3)
183.3(3)
182.8(3)
115.4(4)
116.3(4)
127.7(3)
134.9(4)
Fe(1)ϪC(1)
Fe(1)ϪC(3)
Fe(1)ϪC(6)
Fe(2)ϪP(2)
Fe(2)ϪO(6)
P(1)ϪC(7)
P(1)ϪC(15)
P(2)ϪC(21)
O(1)ϪC(1)
O(3)ϪC(3)
O(5)ϪC(5)
N(1)ϪC(5)
C(7)ϪC(8)
178.6(3)
177.3(3)
200.4(3)
224.42(8)
196.7(2)
186.9(3)
183.1(3)
182.1(3)
115.6(4)
116.2(4)
126.9(3)
135.7(4)
153.1(4)
[(CO)3Fe(µ-Me2NCO)2Fe(CO)2(dppm)] (3): To a solution of 0.44 g
(0.55 mmol) of 1 in about 10 mL of toluene 0.22 g (0.55 mmol)
of Ph2PCH2PPh2 (dppm) was added at room temperature and the
mixture stirred for 12 h. The mixture was filtered and the clear red
solution layered with pentane. After standing for a week, few small
dark red crystals separated. The solution was decanted from the
crystals. Concentration of the solution to half of its volume and
addition of pentane gave an orange red powder, which was filtered
and dried in vacuum. Yield about 0.30 g (0.39 mol) 70 %. IR
angles
Fe(2)ϪFe(1)ϪC(1)
Fe(2)ϪFe(1)ϪC(3)
Fe(2)ϪFe(1)ϪC(6)
C(1)ϪFe(1)ϪC(3)
C(1)ϪFe(1)ϪC(6)
C(2)ϪFe(1)ϪC(5)
C(3)ϪFe(1)ϪC(5)
C(2)ϪFe(1)ϪC(3)
Fe(1)ϪFe(2)ϪP(2)
Fe(1)ϪFe(2)ϪO(6)
P(1)ϪFe(2)ϪP(2)
P(1)ϪFe(2)ϪO(6)
P(2)ϪFe(2)ϪO(5)
P(2)ϪFe(2)ϪC(4)
O(5)ϪFe(2)ϪC(4)
Fe(2)ϪP(1)ϪC(7)
167.4(1)
95.4(1)
67.17(7)
93.6(2)
105.0(1)
85.5(2)
162.5(1)
85.6(1)
156.38(3)
72.90(6)
86.95(3)
95.10(6)
91.72(6)
96.6(1)
Fe(2)ϪFe(1)ϪC(2)
Fe(2)ϪFe(1)ϪC(5)
C(1)ϪFe(1)ϪC(2)
C(1)ϪFe(1)ϪC(5)
C(2)ϪFe(1)ϪC(3)
C(2)ϪFe(1)ϪC(6)
C(3)ϪFe(1)ϪC(6)
Fe(1)ϪFe(2)ϪP(1)
Fe(1)ϪFe(2)ϪO(5)
Fe(1)ϪFe(2)ϪC(4)
P(1)ϪFe(2)ϪO(5)
P(1)ϪFe(2)ϪC(4)
P(2)ϪFe(2)ϪO(6)
O(5)ϪFe(2)ϪO(6)
O(6)ϪFe(2)ϪC(4)
Fe(2)ϪP(1)ϪC(9)
C(7)ϪP(1)ϪC(9)
C(9)ϪP(1)ϪC(15)
Fe(2)ϪP(2)ϪC(21)
C(8)ϪP(2)ϪC(21)
88.9(1)
67.27(7)
98.7(2)
103.2(1)
97.2(2)
156.1(1)
85.1(1)
108.76(3)
72.37(6)
101.4(1)
178.85(7)
87.8(1)
88.60(6)
84.39(8)
174.2(1)
121.79(9)
101.3(1)
101.2(1)
116.54(9)
105.1(1)
(Nujol): 2025 vs, 1964 vs, 1962 s, 1944 w (sh), 1923 vs ν(CO) cmϪ1
.
31P NMR (toluene): 41.5 (d, FePPh2, 2J(P,P) ϭ 59.8 Hz), Ϫ27.4
(d, PPh2, 2J(P,P) ϭ 59.8 Hz) ppm. Analyses: C 54.93 (calcd. 55.41),
H 4.09 (4.39), N 3.61 (3.59) %.
[{(CO)3Fe(µ-Me2NCO)2Fe(CO)2}2(dppe)] (5): 0.047 g (0.11 mmol)
of 1 and 0.019 g (0.047 mmol) of dppe were placed in an NMR
tube and dissolved in 1 mL of toluene. After agitation in an ultra-
sonic bath (1500 W) for several minutes the 31PNMR spectrum
showed only a singlett at 47.8 ppm. The solution was allowed to
stand at room temperature for several weeks. During this time dark
red crystals separated, which were collected; yield 90 %. IR (Nujol):
2028 vs, 1981 vs, 1925 vs ν(CO). Analyses: C 47.61 (calcd. 48.43),
H 4.00 (4.06), N 4.36 (4.71) %.
92.9(1)
107.35(9)
Fe(2)ϪP(1)ϪC(15) 120.09(9)
C(7)ϪP(1)ϪC(15)
Fe(2)ϪP(2)ϪC(8)
102.1(1)
107.98(9)
Fe(2)ϪP(2)ϪC(27) 115.59(9)
C(8)ϪP(2)ϪC(27)
Fe(2)ϪO(5)ϪC(5)
C(5)ϪN(1)ϪC(51)
105.4(1)
105.0(2)
120.1(3)
C(21)ϪP(2)ϪC(27) 105.2(1)
Fe(2)ϪO(6)ϪC(6)
C(5)ϪN(1)ϪC(52)
C(6)ϪN(2)ϪC(61)
105.6(2)
125.0(3)
120.1(2)
[(CO)3Fe(µ-Me2NCO)2Fe(CO)(dppe)] (6): To a solution of a three-
fold excess of dppe 0.411 g (1.02 mMol) in toluene a solution of
0.150 g (0.34 mMol) of 1 was added dropwise at room temperature
within two hours and the mixture stirred for 20 min. The 31PNMR
spectrum showed the formation of 4 and only small amounts of 6
along with the signal of unreacted ligand. The clear red solution
was filtered, layered with pentane, and allowed to stand at room
temperature. Red crystals of 6 separated after about two weeks,
which were collected and dried in vacuum. 6 is less soluble in tolu-
ene than 2, 3, and 5. IR (Nujol): 1985 vs, 1930 vs, 1919 vs, 1887 s
ν(CO). 1H NMR (toluene-d8): 7.99 to 7.65 (m, Ph), 2.86, 2.68, 2.28,
2.20 (s’s, MeN) ppm; (CDCl3): 3.10, 2.91, 2.72, 2.49 (s’s,
MeN) ppm. 13C NMR (toluene-d8): 39.4, 39.0, 35.2, 35.1 (s’s,
MeN) ppm. 31P NMR (toluene-d8): 88.3 (d, FePPh2, 3J(P,P) ϭ
C(51)ϪN(1)ϪC(52) 114.8(3)
C(6)ϪN(2)ϪC(62)
Fe(1)ϪC(1)ϪO(1)
Fe(1)ϪC(3)ϪO(3)
Fe(1)ϪC(5)ϪO(5)
O(5)ϪC(5)ϪN(1)
Fe(1)ϪC(6)ϪN(2)
123.4(3)
173.4(4)
176.2(3)
114.4(2)
114.6(2)
130.7(2)
C(61)ϪN(2)ϪC(62) 116.6(3)
Fe(1)ϪC(2)ϪO(2)
Fe(2)ϪC(4)ϪO(4)
Fe(1)ϪC(5)ϪN(1)
Fe(1)ϪC(6)ϪO(6)
O(6)ϪC(6)ϪN(2)
178.5(3)
178.6(3)
130.9(2)
114.3(2)
115.0(2)
as in 3 and 4, in no case a symmetric arrangement of the
chelating ligand would be possible. Further, a rearrange-
ment in which the two CO groups out of the symmetry
plane of the diiron fragment either at Fe(1) or Fe(2) are
replaced, is not observed, too.
With I high nuclear dendrimers may be available with
suitable branched phosphines as well as compounds of the
type [LnM(PPh2(CH2)xPPh2)M’Ln] with different transition
metal fragments at both ends of the chelating ligand if a
freshly prepared complex 4 or a similar species [(CO)3Fe-
(µ-Me2NCO)2Fe(CO)2(PPh2(CH2)xPPh2)] (x > 1) is treated
with a 16 electron fragment. However, the question is open,
wether smaller 16 electron fragments than the dinuclear
iron species may be able to occupy the free P position of 3
with x ϭ 1. Additionally, compounds of the type I with a
good leaving group may be interesting for catalytic pur-
poses. Further studies in this area are in progress.
3
22.9 Hz), 65.7 (d, FePPh2, J(P,P) ϭ 22.9 Hz) ppm; (CDCl3): 87.1
(d, FePPh2, 3J(P,P) ϭ 21.6 Hz), 65.6 (d, FePPh2, 3J(P,P) ϭ
21.6 Hz) ppm. Analyses: C 56.09 (calcd. 56.42), H 4.56 (4.74), N
3.58 (3.66) %.
Reaction of 6 with CO: CO gas was bubbled through a solution 6
in toluene of at room temperature. After three hours the ratio of
6:4 was recorded as 1:0.09 and increased to 1:0.4 after 12 hours as
shown by 31P NMR experiments.
Crystallographic data for the structures have been deposited with
the Cambridge Crystallographic Data Center, 12 Union Road,
Cambridge CB21EZ. Copies of the data can be obtained on quot-
ing the depository numbers CCDC 232581 (3), CCDC 232582 (5),
and CCDC 232583 (6), (Fax: (ϩ44)1223-336-033; E-mail:
deposit@ccdc.cam.ac.uk).
874
 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
zaac.wiley-vch.de
Z. Anorg. Allg. Chem. 2004, 630, 869Ϫ875

On the Reaction of [(CO)3Fe(µ-Me2NCO)2Fe(CO)2(NHMe2)] with Chelating Ligands
We thank the Deutsche Forschungsgemeinschaft for financial sup-
port. W. P. is also grateful to the Max-Planck-Society, Munich,
Germany, for financial support.
Anderson, A. F. Hill, A. M. Z. Slawin, A. P. J. White, D. J.
Williams, Inorg. Chem. 1998, 37, 594. i) G. Sundanarajan, J.
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[4] F. A. Cotton, K. I. Hardcastle, G. A. Rusholme, J. Coord.
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 2004 WILEY-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim
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