Formation and structural properties of 1,1′,2,2′-tetra(terf-butyl-carbamoyl)-ferrocene and -ruthenocene

Article abstract of DOI:10.1039/a906553i

Sodium cyclopentadienide adds two molar equivalents of tert-butylisocyanate to yield the 1,2-bis(N-tert-butylcarbamoyl)cyclopentadienide reagent 1. This reacts with RuCl₂(PPh₃)₄ 3 in a 2:1 stoichiometry to yield the metallocene [η⁵-C₅H₃(CONHCMe₃) ₂]₂Ru 5. Complex 5 was characterized by an X-ray crystal structure analysis. It shows a near to eclipsed C₂-symmetric metallocene conformation with the carboxamide substituents pairwise connected by intramolecular hydrogen bridges between -CONHR groups attached to different Cp ligands. The intermediate of the substitution reaction sequence, the complex [η⁵-C₅H₃(CONHCMe₃) ₂]RuCl(PPh₃)₂ 4, was also isolated and characterized by X-ray diffraction. Treatment of 1 with FeCl₂ (2:1) yields 1,1′,2,2′-tetra(N-tert-butylcarbamoyl)ferrocene 6. The X-ray crystal structure analysis of 6 features a staggered C_i metallocene conformation. The Royal Society of Chemistry 1999.

Full text of DOI:10.1039/a906553i

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Formation and structural properties of 1,1Ј,2,2Ј-tetra(tert-butyl-
carbamoyl)-ferrocene and -ruthenocene†
Katrin Klaß, Roland Fröhlich and Gerhard Erker*
Organisch-Chemisches Institut der Universität Münster, Corrensstr. 40, D-48149 Münster,
Germany. E-mail: erker@uni-muenster.de, fax: ϩ49(251)83 36503
Received 12th August 1999, Accepted 28th October 1999
Sodium cyclopentadienide adds two molar equivalents of tert-butylisocyanate to yield the 1,2-bis(N-tert-
butylcarbamoyl)cyclopentadienide reagent 1. This reacts with RuCl2(PPh3)4 3 in a 2:1 stoichiometry to yield the
metallocene [η5-C5H3(CONHCMe3)2]2Ru 5. Complex 5 was characterized by an X-ray crystal structure analysis.
It shows a near to eclipsed C2-symmetric metallocene conformation with the carboxamide substituents pairwise
connected by intramolecular hydrogen bridges between –CONHR groups attached to different Cp ligands. The
intermediate of the substitution reaction sequence, the complex [η5-C5H3(CONHCMe3)2]RuCl(PPh3)2 4, was also
isolated and characterized by X-ray diffraction. Treatment of 1 with FeCl2 (2:1) yields 1,1Ј,2,2Ј-tetra(N-tert-
butylcarbamoyl)ferrocene 6. The X-ray crystal structure analysis of 6 features a staggered Ci metallocene
conformation.
ligand system. This was confirmed by treatment of the reagent
1 with Group 8 metal halides.
Introduction
1,2-Disubstituted acyl- or carboxylate-substituted metallocenes
are not easy to synthesize selectively by means of electrophilic
aromatic substitution1 or related arene substitution reactions at
the intact metallocene nucleus.2 Therefore, other pathways that
introduce the required substituent pattern at the stage of the
ligand synthesis, prior to its attachment to the transition metal,
are of value for this synthetic target.3 We have recently shown4
that the two-fold addition of an alkylisocyanate to cyclopent-
adienide directly leads to the selective formation of a 1,2-
carboxamide-substituted cyclopentadienyl anion reagent.5
Thus treatment of CpNa with two molar equivalents of tert-
butylisocyanate resulted in the formation of 1. Its subsequent
reaction with Group 4 metal halides did not, however, lead
to the formation of the respective η5-C5H3(CONHR)2 metal
complexes.6 The formation of strong metal to oxygen bonds7
was found to be favored, resulting e.g. in the clean synthesis of
the respective [κ2-O,O-C5H3(CONHR)2]Zr-chelate complexes
(i.e. 2 from 1 and ZrCl4)4,5 (see Scheme 1).
Results and discussion
The reagent 1 was prepared as described previously4 by
treatment of sodium cyclopentadienide with two molar equiv-
alents of tert-butylisocyanate in tetrahydrofuran at 0 ЊC.
After workup at ambient temperature sodium-1,2-bis(tert-
butylcarbamoyl)cyclopentadienide 1 was isolated as an off-
white solid in 96% yield. It shows characteristic 1H NMR
signals at δ 7.90 (NH), 6.73 (d, 2H) and 6.25 (t, 1H, 3JHH = 3.6
Hz, C5H3), and at 1.44 (s, tert-butyl, CMe3, in benzene-d6–
THF-d8, 10:1.5). The 13C NMR signals of the C5H3-core of 1
appear at δ 116.4 (ipso-C), 115.1 and 108.8 (C-2, C-3). The
reagent 1 was then reacted with RuCl2(PPh3)4 3 (see Scheme 2).
Scheme 1 Synthesis and reactions of the ligand system 1.
Scheme 2 Syntheses of the 1,1Ј,2,2Ј-tetracarbamoylmetallocenes 5
and 6.
We expected that metal–oxygen bond formation would
probably not be dominant in the related chemistry of late
transition metals in combination with the [C5H3(CONHR)2]Ϫ
The reaction required stirring overnight at elevated temperature
(40 ЊC in toluene) to go to completion. Under these con-
ditions both chloride ligands at ruthenium are replaced by the
ligand system 1 with formation of sodium chloride. During
† Supplementary data available: rotatable 3-D crystal structure diagram
in CHIME format. See http://www.rsc.org/suppdata/dt/1999/4457/
J. Chem. Soc., Dalton Trans., 1999, 4457–4461
This journal is © The Royal Society of Chemistry 1999
4457

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Fig. 1 A view of the molecular structure of 5 (with non-systematic
atom numbering scheme). Selected bond lengths (Å) and angles (Њ): Ru–
C4 2.160(6), Ru–C5 2.172(5), Ru–C3 2.172(6), Ru–C1 2.182(5), Ru–C2
2.182(6), C5–C6 1.503(7), C6–O6 1.230(6), C6–N7 1.344(7), N7–C8
1.473(7), C4–C9 1.505(8), C9–O9 1.236(6), C9–N10 1.328(7), N10–C11
1.475(7); C5–C6–O6 118.3(5), C5–C6–N7 117.8(5), O6–C6–N7
123.9(5), C6–N7–C8 125.0(5), C4–C9–O9 120.1(5), C4–C9–N10
114.9(5), O9–C9–N10 124.9(6), C9–N10–C11 126.0(5).
Fig. 2 Comparison of the molecular geometries of 5 (Ru, top) and 6
(Fe, bottom).
the reaction all four triphenylphosphine ligands are also
eliminated from the metal center; they were removed from
the reaction mixture during the workup process by washing
with pentane. This left a clean product of composition
[C5H3(CONHCMe3)2]2Ru 5 that was isolated in >60% yield.
In the IR spectrum (KBr) complex 5 exhibits sharp NH
bands at ν = 3313 and 3254 cmϪ1 and the typical carboxamide
features at ν = 1631 and 1544 cmϪ1 (see for a comparison, 2:
1585 and 1529 cmϪ1). In the 1H NMR spectrum the resonances
of the –CONHC(CH3)3 moiety are found at δ 8.16 (NH) and
1.39 (tert-butyl). The C5H3 signals show a similar pattern as
observed for 2, but they are found at markedly lower δ values:
Fig.
3
Metallocene conformations and intramolecular hydrogen
bonding pattern of 5 and 6 found in the solid state.
3
5.12 (d) and 4.60 (t, JHH = 2.6 Hz) (see for a comparison, 2:
6.43, 6.36). This trend is even more pronounced in the 13C
NMR spectrum of 5 [C5H3-part: δ 83.0 (ipso-C), 79.2, 76.3
(C-2, C-3); see 2 for a comparison: δ 122.7, 114.4, 114.0]. These
spectroscopic data already indicated principally different
framework structures for the early metal complex 2 and the late
transition metal complex 5 of the ligand system 1. This was
confirmed by the X-ray crystal structure analysis of the new
complex 5.
Single crystals of 5 were obtained by slowly concentrating a
solution of the product in dichloromethane. The X-ray crystal
structure analysis has revealed that a metallocene was formed.
The central ruthenium atom is coordinated only to the C5H3-
core of the C5H3(CONHR)2 ligand system. Very different from
the situation encountered in the early transition metal complex
2 and its congeners, the carboxamide substituents in 5 are not
directly connected to the metal center at all. They solely func-
tion as Cp-bonded substituents (Fig. 1).
worthy. In the crystal complex 5 exhibits a chiral C2-symmetric
conformation with a close to eclipsed arrangement of the
Cp-rings along the Cp(centroid)–Ru–Cp(centroid) vector.10 In
the projection, two of the –CONHCMe3 substituents eclipse
(vectors C4–C9 and C4*–C9*), whereas their adjacent
–CONHCMe3 neighbors reside in the lateral ends of the
w-shaped projection enforced by the overall C2-symmetric
conformational arrangement (see Fig. 2). The angle between
the respective projections of the vectors C5–C6 and C4–C9
amounts to ca. 65Њ, that between the projections of the C5–C6
and C5*–C6* vectors is ca. 140Њ. The carboxamido substituents
at each Cp ring are substantially rotated from the cyclopent-
adienyl plane [dihedral angles C5–C4–C9–O9 Ϫ139.7(7)Њ, C4–
C5–C6–O6 Ϫ138.7(6)Њ]. The C(6)᎐O(6) carbonyl group [and its
᎐
symmetry equivalent C(6*)᎐O(6*) counterpart] is oriented
᎐
toward the “outside” of the metallocene whereas the C(9)᎐O(9)
᎐
In the tetra-carboxamide-substituted metallocene both
C5H3(CONHR)2 rings are η5-coordinated to ruthenium.8 The
substituted cyclopentadienyl ligands are oriented nearly
parallel to each other. The decrease of symmetry introduced
by the Cp-substituents and their specific conformational
arrangement (see below) has only resulted in a marginal tilting
of the η5-Cp rings:9 the Ru–C(Cp) distances are between
2.160(6) and 2.182(6) Å.
carbonyl group of the adjacent carboxamido substituent is
oriented “inwards”. Moreover, the two pairs of –CONHCMe3
substituents are located very close to each other at one sector of
the metallocene. This is probably due to intramolecular hydro-
gen bonding between the C(9)᎐O(9) carbonyl group and the
᎐
N(7*)–H hydrogen donor [and their symmetry-equivalent
counterparts C(9*)᎐O(9*) and N(7)–H, see Fig. 3] [N(7*)–
᎐
H(7*) 0.80(5) Å, H(7*) ؒ ؒ ؒ O(9) 2.26(6) Å, N(7*) ؒ ؒ ؒ O(9)
3.030(6) Å, angle N(7*)–H(7*) ؒ ؒ ؒ O(9) 162(6)Њ]11 (see Fig. 1
and Fig. 3). Intermolecular hydrogen bonding between N(10)–
The conformational arrangement of the substituents at
the 1,1Ј,2,2Ј-tetra-substituted metallocene framework is note-
4458
J. Chem. Soc., Dalton Trans., 1999, 4457–4461

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Fig. 5 Molecular structure of 6 (with non-systematic atom numbering
scheme). Selected bond lengths (Å) and angles (Њ): Fe–C1 2.033(2), Fe–
C2 2.038(2), Fe–C3 2.043(2), Fe–C5 2.046(2), Fe–C4 2.052(2), C1–C10
1.495(2), C10–O11 1.239(2), C10–N12 1.341(2), N12–C13 1.479(2),
C2–C20 1.501(2), C20–O21 1.240(2), C20–N22 1.336(2), N22–C23
1.481(2); C1–C10–O11 121.9(1), C1–C10–N12 114.6(1), O11–C10–N12
123.5(2), C10–N12–C13 124.6(1), C2–C20–O21 118.7(1), C2–C20–N22
116.7(1), O21–C20–N22 124.7(2), C20–N22–C23 125.7(2).
Fig. 4 A view of the molecular structure of 4.
H and O(6**) then results in the formation of supramolecular
strands of
5 in the crystal [N(10)–H(10) 0.81(5) Å,
H(10) ؒ ؒ ؒ O(6**) 2.23(6) Å, N(10) ؒ ؒ ؒ O(6**) 2.943(6) Å, angle
N(10)–H(10) ؒ ؒ ؒ O(6**) 148(6)Њ].
Chloride substitution at the RuCl2(PPh3)4 starting material 3
and triphenylphosphine elimination takes place sequentially
upon treatment with the [C5H3(CONHCMe3)2Ϫ] reagent. A
likely intermediate of the overall reaction sequence could be
observed and isolated by the reaction between 3 and 2 in a
1:1 stoichiometry. After a reaction time of 14 h at 40 ЊC in
toluene an almost quantitative conversion to the ruthenium
half-sandwich complex [η5-C5H3(CONHCMe3)2]RuCl(PPh3)2 4
(see Scheme 2) was monitored, and this product was isolated in
ca. 90% yield. Complex 4 shows the presence of two remaining
PPh3 ligands at ruthenium (31P NMR: δ 38.7 in benzene-d6),
and it exhibits the typical 1H and 13C NMR resonances of
the η5-C5H3(CONHR)2 ligand system [1H NMR: δ 8.80 (NH),
4.14 and 3.83 (C5H3); 13C NMR: δ 94.8, 81.0, 80.9 (C5H3), both
in toluene-d8].
The X-ray crystal structure analysis reveals the presence of
a three-legged piano-stool structure of the half-sandwich
complex 4 (Fig. 4). The C5H3(CONHR)2 ligand is η5-co-
ordinated to ruthenium. Both carboxamide functionalities
are arranged almost coplanar with the Cp-ring system. The
unsaturated functional groups appear to be in π-conjugation
with the adjacent Cp-π-system. The coplanar conformational
arrangement of the carboxamido groups is supported, or
probably even dominated by intramolecular hydrogen bond-
the metallocene framework. Within each –CONHCMe3 pair
there seems to be an intramolecular hydrogen bond interaction
(see Fig. 3) [N(22)–H(22) 0.87(2) Å, H(22) ؒ ؒ ؒ O(11) 1.93(2) Å,
N(22) ؒ ؒ ؒ O(11) 2.764(2) Å, angle N(22)–H(22) ؒ ؒ ؒ O(11)
162(2)Њ]. An additional intermolecular close hydrogen bridging
contact is observed between N(12)–H(12) [0.84(2) Å] and
O(21*) [H(12) ؒ ؒ ؒ O(21**) 2.22(2) Å, N(12) ؒ ؒ ؒ O(21**)
3.047(2) Å, angle N(12)–H(12) ؒ ؒ ؒ O(21**) 168(2)Њ (see Fig. 5)]
that leads to the formation of µ-H bridged chains of molecules
of 6 in the solid state.
Conclusions
We 6 and others12 had shown that a single ester or carbox-
amide substituent at a Cp ligand does not substantially change
its coordination behavior toward a Group 4 transition metal:
η5-C5H4X coordination is still observed. This situation is
drastically changed when two such electron-withdrawing
carbonyl substituents are jointly removing electron-density
from the Cp ligand core. It was shown that the 1,2-
C5H3(COX)2-type ligands prefer bonding through their sub-
stituent heteroatoms at the oxophilic Group 4 metals.4,5 Chelate
zirconium complexes of these ligands exhibiting the uncom-
plexed Cp-ring systems were observed. This present study
has now revealed that there is a subtle balance for these easily
available ligands between κ2-O,O-chelate and η5-cyclopent-
adienyl coordination that may be tipped by a selective choice of
the central transition metal. Apparently, the metal–oxygen
bond energy in the case of the late transition elements iron and
ruthenium is too low to compensate for the π-ligand/metal
combination and consequently the conventional metallocene
structure is favored in this case.
ing between the CONHR moieties [C(1)᎐O(1) ؒ ؒ ؒ H–N(2)
᎐
interaction, see Fig. 4]. Due to disorder problems of cocrystal-
lized solvent details of the crystal structure of 4 will not be
discussed.
The reaction of [C5H3(CONHCMe3)2]Na 1 with FeCl2 pro-
duced the corresponding 1,1Ј,2,2Ј-tetracarbamoyl-ferrocene
system 6 (Scheme 2 and Fig. 5). In this case we did not observe
or isolate a mono-cyclopentadienyl iron intermediate corre-
sponding to the Ru-system 4. Single crystals of the ferrocene 6
were obtained from dichloromethane by slow evaporation of
the solvent at ambient temperature.
The X-ray crystal structure analysis of 6 shows the presence
of a metallocene structure with two symmetry-equivalent η5-
C5H3(CONHCMe3)2 ligands at the central Fe-atom. The Fe–
C(Cp) distances range uniformly between 2.033(2) and 2.052(2)
Å. The metallocene conformation in the crystal is staggered
with an inversion symmetry. Thus the two pairs of carb-
oxamido-substituents occupy sectors opposite to each other at
Our route makes 1,1Ј,2,2Ј-tetra-functionalized metallocene
systems very readily available. To our knowledge the reactions
shown in Scheme 2 represent the first examples of simple
synthetic entries to ferrocene and ruthenocene 1,1Ј,2,2Ј-
tetracarboxamides. Systems, such as 5 and 6, show an interest-
ing hydrogen-bonding pattern. The resulting close spatial
concentration of polar functional groups may lead to an inter-
esting coordination behavior and resulting redox properties
which we have begun to investigate in our laboratory.
J. Chem. Soc., Dalton Trans., 1999, 4457–4461
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O4RuؒC6H6, M = 705.89, 0.40 × 0.05 × 0.05 mm, a = 12.458(4),
Experimental
b = 15.758(3), c = 18.019(2) Å, β = 96.61(2)Њ, V = 3513.9(14) Å3,
µ = 4.89 cmϪ1, Z = 4, monoclinic, space group C2/c (No. 15),
T = 223 K, 3194 reflections collected ( h, ϩk, Ϫl), 3090
independent (Rint = 0.085) and 1799 observed reflections
[I ≥ 2σ(I)], R = 0.056, wR2 = 0.113.
Most reactions were carried out in an inert atmosphere (argon)
using Schlenk-type glassware or in a glovebox. Solvents were
dried and distilled under argon prior to use. For additional
general information including a compilation of the instru-
mentation used for spectroscopic and physical characterization
of the compounds, see refs. 4 and 6. RuCl2(PPh3)4 3 was used as
purchased, the reagent 1 was prepared as previously described
in the literature.4
Preparation of 1,1Ј,2,2Ј-tetra(N-tert-butylcarbamoyl)ferrocene
6
A mixture of FeCl2 (100 mg, 0.79 mmol) and [C5H3(CONHC-
Me3)2]Na 1 (451 mg, 1.58 mmol) was suspended in tetrahydro-
furan at Ϫ78 ЊC. The reaction mixture was slowly allowed
to warm to room temperature and was then stirred overnight.
The solvent was removed in vacuo and 20 mL of dichloro-
methane was added. The precipitate was filtered off and the
solvent was removed in vacuo from the clear filtrate. The residue
was suspended in pentane, isolated on a frit, washed with
pentane until the washings were colorless (2 × 10 mL), and
dried in vacuo to yield 298 mg (66%) of 6, mp 274 ЊC. (Found:
C, 60.93; H, 7.96; N, 9.44%. C30H46N4O4Fe (582.6) requires C,
61.85; H, 7.96; N, 9.62%). HRMS (ESI): Found m/z = 605.2740,
(C30H46N4O4Fe ϩ Naϩ) requires 605.2766. IR (KBr): ν = 3276,
3072 (NH), 1650, 1644, 1591 (CONH) cmϪ1. δH(200.1 MHz,
Preparation of [1,2-bis(N-tert-butylcarbamoyl)cyclopentadi-
enyl]bis(triphenylphosphine)chlororuthenium 4
A solution containing 500 mg (0.41 mmol) of RuCl2(PPh3)4 3
and 117 mg (0.41 mmol) of the [C5H3(CONHCMe3)2]Na reagent
1 in 50 mL of toluene was stirred for 14 h at 40 ЊC. After cool-
ing to room temperature a precipitate was filtered off and the
solvent was removed from the clear filtrate in vacuo. The result-
ing light brown solid was stirred in pentane, collected by filtra-
tion and washed with pentane (2 × 10 mL) to remove most of
the liberated triphenylphosphine. The product was then dried in
vacuo to yield 340 mg (90%) of 4, mp 254 ЊC. A sample was
recrystallized from benzene; the obtained microcrystalline
3
1
chloroform-d) 8.49 (br s, 4H, NH), 4.81 (d, 4H, J = 2.7 Hz),
material contained 1.5 equiv. of the solvent as analyzed by H
4.21 (t, 2H, 3J = 2.7 Hz, C5H3), 1.45 (s, 36H, tert-butyl). δC(50.3
NMR. (Found: C, 70.09; H, 6.29; N, 2.57%. C51H53N2O2P2-
ClRuؒ1.5C6H6 (M 719.9) requires C, 69.19; H, 6.00; N, 2.69%).
δH(599.9 MHz, toluene-d8) 8.80 (br s, 2H, NH), 7.52 (m, 12H,
m-Ph), 6.87 (m, 18H, o-, p-Ph), 4.14 (br, 2H), 3.83 (br, 1H,
C5H3), 1.37 (s, 18H, tert-butyl). δC(150.8 MHz, toluene-d8):
MHz, chloroform-d) 168.6 (C᎐O), 77.9, 74.9 (C H ), 51.8, 28.7
᎐
5
3
(tert-butyl), ipso-C of C5H3 not detected. X-Ray crystal struc-
ture analysis of 6: C30H46N4O4Fe, M = 582.56, a = 6.793(1),
b = 10.902(1), c = 11.208(1) Å, α = 92.05(1), β = 99.78(1),
γ = 107.58(1)Њ, V = 776.4(2) Å3, µ = 5.24 cmϪ1, Z = 1, triclinic,
1
3
165.2 (C᎐O), 138.1 (dd, JPC, JPC = 21.3, 20.1 Hz, ipso-Ph),
᎐
134.8 (pt, 3JPC = 5JPC = 4.8 Hz, m-Ph), 128.4 (d, 4JPC = 11.9 Hz,
¯
space group P1 (No. 2), λ = 0.71073 Å, T = 198 K, 6015 reflec-
p-Ph), 127.6 (pt, JPC = 4JPC = 4.4 Hz, o-Ph), 94.8 (ipso-C of
2
tions collected ( h, k, l), 3538 independent (Rint = 0.022) and
3309 observed reflections [I ≥ 2σ(I)], R = 0.036, wR2 = 0.097.
Data sets were collected with Nonius MACH3 or KappaCCD
diffractometers, using a rotating anode generator FR591.13
CCDC reference number 186/1719.
C5H3), 81.0, 80.9 (C5H3), 51.6, 28.8 (CMe3). δP(81.0 MHz,
benzene-d6): 38.7, ν1/2 = 3.1 Hz. δC/H correlation (GHSQC,
150.8/599.9 MHz, toluene-d8) 134.8/7.52 (m-Ph), 128.4/6.87
(p-Ph), 127.6/6.87 (o-Ph), 81.0/3.83 (C3/3-H of C5H3), 80.9/
4.14 (C2/2-H of C5H3), 28.8 /1.37 (tert-butyl). δC/H correlation
See http://www.rsc.org/suppdata/dt/1999/4457/ for crystallo-
graphic files in .cif format.
(GHMBC, 150.8/599.9 MHz, toluene-d ) 165.2/8.80 (C᎐O),
᎐
8
138.1/7.52 (ipso-Ph/m-Ph), 134.8/7.52, 6.87 (m-Ph/o-, m-, p-Ph),
128.4/7.52 (p-Ph/m-Ph), 127.6/6.87 (o-Ph/o-, p-Ph), 94.8/4.14,
3.83 (C1/2-H, 3-H of C5H3), 81.0/4.14 (C3/2-H of C5H3),
80.9/3.83 (C2/3-H of C5H3), 51.6/1.37 (tert-butyl). X-Ray
crystal structure analysis of 4: C51H53N2O2P2ClRuؒ1/2C7H8,
M = 970.48, a = 11.511(1), b = 13.315(1), c = 18.735(1) Å,
α = 70.27(1), β = 73.87(1), γ = 72.15(1)Њ, V = 2523.6(4) Å3,
Acknowledgements
Financial support from the Fonds der Chemischen Industrie
and the Deutsche Forschungsgemeinschaft is gratefully
acknowledged.
µ = 4.68 cmϪ1, Z = 2, triclinic, space group P1 (No. 2), T =
¯
References
223 K, 6996 reflections collected (ϩh, k, l), 6601 indepen-
dent (Rint = 0.066) and 4263 observed reflections [I ≥ 2σ(I)],
R = 0.086, wR2 = 0.221, disordered solvent molecule refined
with restraints.
1 Gmelin, Handbook of Inorganic and Organometallic Chemistry, 8th
edn., ed. A. Slawisch, Organoiron Compounds, Part A8 (Ferrocene),
Springer-Verlag, Berlin, 1986, pp. 323–345; Part A11 (Ferrocene),
1995, pp. 1–33 and references cited therein. See also: A. F.
Cunningham, Jr., Organometallics, 1994, 13, 2480.
2 For selected examples see e.g. L. Westman and K. L. Rinehart, Jr.,
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Preparation of 1,1Ј,2,2Ј-tetra(N-tert-butylcarbamoyl)-
ruthenocene 5
A reaction mixture containing 1.00 g (0.82 mmol) of 3 and 938
mg (3.28 mmol) of 1 in 50 mL of toluene was stirred overnight
at 40 ЊC, then cooled to room temperature and filtered. Solvent
was removed from the filtrate in vacuo. The residue was
suspended in pentane with stirring, collected by filtration and
washed with pentane (4 × 20 mL) to remove PPh3. After drying
in vacuo 330 mg of 5 (64%) was obtained. Mp 237 ЊC. (Found:
C, 60.44; H, 7.50; N, 6.97%. C30H46N4O4RuؒC7H8 (M 719.9)
requires C, 61.73; H, 7.56; N, 7.79%). HRMS (ESI): Found
m/z = 651.2454, (C30H46N4O4Ru ϩ Naϩ) requires 651.2453. IR
4 K. Klaß, L. Duda, N. Kleigrewe, G. Erker, R. Fröhlich and
E. Wegelius, Eur. J. Inorg. Chem., 1999, 11.
5 N. Etkin, C. M. Ong and D. W. Stephan, Organometallics, 1998, 17,
3656.
6 In contrast, the [C5H4–CONHR]Ϫ ligands add to Zr or Ti centers
to form the respective [η5-C5H4–CONHR] metal complexes:
M. Oberhoff, L. Duda, J. Karl, R. Mohr, G. Erker, R. Fröhlich and
M. Grehl, Organometallics, 1996, 15, 4005.
(KBr): ν = 3313, 3254 (NH), 1631, 1544 (CONH) cmϪ1
δH(200.13 MHz, dichloromethane-d2) 8.16 (br s, 4H, NH),
.
3
3
5.12 (d, 4H, J = 2.6 Hz), 4.60 (t, 2H, J = 2.6 Hz, C5H3), 1.39
(s, 36H, tert-butyl). δC(50.3 MHz, dichloromethane-d2) 167.7
7 J. K. Kochi, in Organometallic Mechanisms and Catalysis, Academic
Press, New York, 1978, pp. 237–245; J. A. Connor, Top. Curr.
Chem., 1977, 71, 71.
(C᎐O), 83.0 (ipso-C of C H ), 79.2, 76.3 (C H ), 51.9, 28.8
᎐
5
3
5
3
(tert-butyl). X-Ray crystal structure analysis of 5: C30H46N4-
4460 J. Chem. Soc., Dalton Trans., 1999, 4457–4461

View Article Online
8 Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials
Science, ed. A. Togni and T. Hayashi, VCH, Weinheim, 1995 and
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13 Programs used. Data collection: EXPRESS: Nonius B.V., 1994.
Collect, Nonius B.V., 1998. Data reduction: MolEN: K. Fair, Enraf
Nonius B.V., 1990. Denzo-SMN: Z. Otwinowski and W. Minor, in
Methods Enzymol., 1997, 276, 307. Absorption Correction for CCD
data: SORTAV: R. H. Blessing, Acta Crystallogr., Sect. A, 1995,
51, 33; J. Appl. Crystallogr., 1997, 30, 421. Structure Solution:
SHELXS-97: G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46,
467. Structure refinement: SHELXL-97: G. M. Sheldrick,
Universität Göttingen, 1997. Graphics: SCHAKAL: E. Keller,
Universität Freiburg, 1997.
Paper 9/06553I
J. Chem. Soc., Dalton Trans., 1999, 4457–4461
4461