Cationic Diiron and Diruthenium μ-Allenyl Complexes: Synthesis, X-Ray Structures and Cyclization Reactions with Ethyldiazoacetate/Amine Affording Unprecedented Butenolide- and Furaniminium-Substituted Bridging Carbene Ligands

Article abstract of DOI:10.1039/c0dt00697a

The novel cationic diiron μ-allenyl complexes [Fe₂Cp ₂(CO)₂(μ-CO){μ-η¹: η²_α,β-C_α(H)C _βC_γ(R)₂}]⁺ (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe₂Cp₂(CO)₄]. The solid state structures of [4a][CF₃SO₃] and of the diruthenium analogues [Ru ₂Cp₂(CO)₂(μ-CO){μ-η¹: η²_α,β-C_α(H)C _βC_γ(R)₂}][BPh₄] (R = Me, [2a][BPh₄]; R = Ph, [2c][BPh₄]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Bronsted bases result in formation of the μ-allenylidene compound [Ru₂Cp ₂(CO)₂(μ-CO){μ-η¹:η¹- C_αC_βC_γ(Ph)₂}] (5) and of the dimetallacyclopentenone [Fe₂Cp₂(CO)(μ-CO) {μ-η¹:η³-C_α(H)C _β(C_γ(Me)CH₂)C(O)}] (6), respectively. The nitrile adducts [Ru₂Cp₂(CO)(NCMe)(μ- CO){μ-η¹:η²-C_α(H)C _βC_γ(R)₂}]⁺ (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me₃NO, react with N₂CHCO₂Et/NEt₃ at room temperature, affording the butenolide-substituted carbene complexes [Ru₂Cp ₂(CO)(μ-CO){μ-η¹:η³-C _α(H)C_βC_γ(R) ₂OC(O)C(H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru₂Cp₂(CO)(μ-CO){μ-η¹: η³-C_α(H)C_βC _γ(Me)₂OC(OEt)C(H)]⁺ (9) has been detected in the course of the reaction leading to 10a. The addition of N ₂CHCO₂Et/NHEt₂ to 7a gives the 2-furaniminium-carbene [Ru₂Cp₂(CO)(μ-CO){μ- η¹:η³-C_α(H)C _βC_γ(Me)₂OC(OEt)C(H)]⁺ (11). The X-ray structures of 10a, 10b and [11][BF₄] have been determined. The reactions of 4a,b with MeCN/Me₃NO result in prevalent decomposition to mononuclear iron species. The Royal Society of Chemistry 2010.

Full text of DOI:10.1039/c0dt00697a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Cationic Diiron and Diruthenium l-Allenyl Complexes: Synthesis, X-Ray
Structures and Cyclization Reactions with Ethyldiazoacetate/Amine
Affording Unprecedented Butenolide- and Furaniminium-Substituted
Bridging Carbene Ligands†
Adriano Boni,a,b Fabio Marchetti,‡a Guido Pampaloni*a and Stefano Zacchinic
Received 22nd June 2010, Accepted 26th August 2010
DOI: 10.1039/c0dt00697a
1
2
The novel cationic diiron m-allenyl complexes [Fe2Cp2(CO)2(m-CO){m-h :h a,b-Ca(H) Cb Cg (R)2}]+
(R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from
[Fe2Cp2(CO)4]. The solid state structures of [4a][CF3SO3] and of the diruthenium analogues
1
2
[Ru2Cp2(CO)2(m-CO){m-h :h a,b-Ca(H) Cb Cg (R)2}][BPh4] (R = Me, [2a][BPh4]; R = Ph, [2c][BPh4])
have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Brønsted bases
1
1
result in formation of the m-allenylidene compound [Ru2Cp2(CO)2(m-CO){m-h :h -Ca Cb Cg (Ph)2}]
1
3
(5) and of the dimetallacyclopentenone [Fe2Cp2(CO)(m-CO){m-h :h -Ca(H) Cb(Cg (Me)CH2)C( O)}]
1
2
(6), respectively. The nitrile adducts [Ru2Cp2(CO)(NCMe)(m-CO){m-h :h -Ca(H) Cb Cg (R)2}]+ (R =
Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me3NO, react with N2CHCO2Et/NEt3
at room temperature, affording the butenolide-substituted carbene complexes
1
3
[Ru2Cp2(CO)(m-CO){m-h :h -Ca(H)CbCg (R)2OC( O)C(H)] (R = Me, 10a; R = Ph, 10b). The
1
3
intermediate cationic compound [Ru2Cp2(CO)(m-CO){m-h :h -Ca(H)CbCg (Me)2OC(OEt)C(H)]+ (9) has
been detected in the course of the reaction leading to 10a. The addition of N2CHCO2Et/NHEt2 to 7a
1
3
gives the 2-furaniminium-carbene [Ru2Cp2(CO)(m-CO){m-h :h -Ca(H)CbCg (Me)2OC(OEt)C(H)]+ (11).
The X-ray structures of 10a, 10b and [11][BF4] have been determined. The reactions of 4a,b with
MeCN/Me3NO result in prevalent decomposition to mononuclear iron species.
[–C(R) C(R¢)C N(Me)(R¢¢)]+, held by the frame [Fe2Cp2(CO)2].
These metal compounds have been shown to be convenient starting
materials for the preparation of unusual “organic architectures”,
by stepwise functionalization of the C3 chain.4
Introduction
The addition of organic reactants to unsaturated hydrocarbyl
fragments, promoted by transition metal species, is a topic
arousing great interest, due to the wide applications both in
organic synthesis and in industrial processes.1 In this context, the
activation of hydrocarbyl units, bridge-coordinated in dinuclear
iron or ruthenium complexes bearing ancillary cyclopentadienyl
and/or carbonyl ligands, has been widely investigated.2 Indeed,
dinuclear metal species often provide unconventional reactivity
patterns to bridging ligands, as consequence of the cooperativity
effects due to the two metal centers working in concert.3 Therefore,
metal-bound hydrocarbyl groups may be converted into unusual
organic species, which could not be attainable through common
organic procedures. Furthermore, the bimetallic core may play a
key role in the stabilization of the new species, offering the pos-
sibility of different coordination fashions. As a notable example,
several papers have appeared in the last decade on the chemistry
of diiron complexes containing a bridging vinyliminium ligand,
Among the unsaturated hydrocarbyl species, allenyl ligands
[–C(H)
C CRR¢] in polynuclear complexes have attracted in-
creasing attention, since their coupling reactions with unsaturated
organics may provide interesting derivatives.5 Having considered
that the large majority of the reported allenyl complexes are
neutral, we have decided to focus our attention on the cationic
[M2Cp2(CO)2(m-CO){m-C(H)
C
CRR¢}]+ (M = Fe, 4; M = Ru,
2), whose positive charge should basically enhance the reactivity
with nucleophiles.
The diruthenium compounds 2 are known in the form of
tetrafluoroborato salts, nevertheless no crystallographic descrip-
tion has been reported heretofore and only limited information
have appeared on the reactivity.6 Such diruthenium species can
be prepared in good yields by a three-step route, see Scheme 1,
starting with photolytic insertion of diphenylacetylene into the
Ru–CO bond of [Ru2Cp2(CO)4],7 affording the cyclopentenone
1
3
[Ru2Cp2(CO)(m-CO){m-h :h -C(Ph) C(Ph)C( O)}]. Successive
aUniversita` di Pisa, Dipartimento di Chimica e Chimica Industriale,
Via Risorgimento 35, I-56126, Pisa, Italy. E-mail: pampa@dcci.unipi.it;
Fax: +39 050 2219246; Tel: +39 050 2219219
alkyne-exchange reactions result in formation of [Ru2Cp2(CO)2(m-
1
3
CO){m-h :h -C(H) C(C(R)(R¢)(OH))C( O)}] (R = R¢ = Me, 1a;
R = Ph, R¢ = Me, 1b), that yield the final products 2a,b upon
treatment with HBF4.6
bScuola Normale Superiore, Piazza dei Cavalieri, I-56126, Pisa, Italy
cUniversita` di Bologna, Dipartimento di Chimica Fisica e Inorganica, Viale
Risorgimento 4, I-40136, Bologna, Italy
We report herein the synthesis of the new diiron m-allenyl com-
† CCDC reference numbers 781673–781678. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt00697a
‡ Born in 1974. fabmar@dcci.unipi.it
1
2
plexes [Fe2(Cp)2(CO)2(m-CO){m-h :h a,b-C(H)
C
C(R)2}] [BF4]
(R = 4a; R = Ph, 4b), together with the X-ray characterization
10866 | Dalton Trans., 2010, 39, 10866–10875
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literature procedure (see Introduction), we have synthesized
1
2
the diruthenium allenyl [Ru2(Cp)2(CO)2(m-CO){m-h :h
-
a,b
Ca(H) Cb Cg (Me)2}][BF4] ([2a][BF4])6 and the unreported
1
2
diphenyl
derivative
[Ru2(Cp)2(CO)2(m-CO){m-h :h
-
a,b
Ca(H) Cb Cg (Ph)2}][BF4] ([2c][BF4]). The new complexes
4a,b and 2c have been fully characterized by IR and NMR
spectroscopy, and elemental analysis. Anion-exchange reactions
were performed to obtain the crystalline salts [2a][BPh4],
[2c][BPh4] and [4a][SO3CF3], whose solid state structures have
been ascertained by X-ray diffraction studies. The ORTEP
representations of the cations are shown in Fig. 1–3, whereas
relevant bond lengths and angles are reported in Table 1. All
cations consist of a cis-[M2(Cp)2(CO)2(m-CO)] core, to which the
1
2
bridging m-h :h -C(H)
C
C(R)2 allenyl ligand is coordinated.
The bonding parameters of the latter are as expected for
this class of ligands,5c with C(14)–C(15)–C(16) considerably
bent [154.8(10)◦ for 2a; 151.7(4)◦ and 151.5(4)◦ for the two
independent molecules of 2c; 152.0(8)◦ for 4a; usual values
for reported structures are in the range 143 ∏ 157◦] and both
Scheme 1 Preparation of dinuclear ruthenium allenyl derivatives.
of both diiron and diruthenium species. Hence, the chemistry of
2 and 4 will be discussed, showing that the reactions of 2 with
ethyldiazoacetate in the presence of amines afford unprecedented
heterocycle-substituted carbene ligands.
˚
˚
˚
C(14)–C(15) [1.390(13) A for 2a; 1.355(6) A and 1.360(6) A for
˚
the two independent molecules of 2c; 1.332(11) A for 4a] and
˚
˚
˚
C(15)–C(16) [1.328(13) A for 2a; 1.326(6) A and 1.329(5) A for the
˚
two independent molecules of 2c; 1.339(11) A for 4a] displaying
Results and Discussion
considerable p-character (usual values for reported structures are
Synthesis and X-ray structures of diiron and diruthenium cationic
l-allenyl complexes
˚
˚
in the ranges 1.36 ∏ 1.40 A and 1.31 ∏ 1.35 A, respectively). The
bridging CO ligand is substantially asymmetric in all structures,
1
showing the shorter contact toward M(2), that is h -coordinated
1
2
The diiron–allenyl complexes [Fe2Cp2(CO)2(m-CO){m-h :h
-
a,b
to the allenyl ligand.
Ca(H) Cb Cg (R)2}][BF4] (R = Me, [4a][BF4]; R = Ph, [4b][BF4])
were prepared by a two-step procedure, consisting of photolytic
CO displacement and insertion of the alkynol HC CCR2OH into
a Fe–CO bond,7 followed by protonation of the –OH group and
H2O removal (see Scheme 2).
Fig. 1 Structure of the cation 2a in [2a][BPh4]·CH2Cl2. The H-atoms,
except H(14), have been omitted for clarity. Thermal ellipsoids are at the
30% probability level. Only the main images of the two disordered Cp
ligands are drawn.
Scheme 2 Preparation of cationic diiron m-allenyl complexes.
Coherently with the solid state features, the IR spectra (in
CH2Cl2 solution) of 2 and 4 display three absorptions ascribable
to two terminal carbonyl ligands and one semi-bridging carbonyl
(e.g. for 4a at 2036, 2011 and 1864 cm-1, respectively). The
NMR spectra of 2, 4 at room temperature show broad signals,
as result of an exchange process. This process probably consists
of s–p “windshield wiper” motion of the allenyl moiety, in
accord with what observed formerly in analogous bridged-allenyl
dinuclear complexes.5f,8 Readable 1H-NMR spectra (single sets of
resonances) could be recorded at -40 ◦C in CD3CN solution.
Relevant features are represented by the CaH resonances, falling
The
intermediate
dimetallacyclopentenone
species
1
3
[Fe2Cp2(CO)2(m-CO){m-h :h -C(H)C(CR2OH)C( O)}] (R
=
Me, 3a; R = Ph, 3b) have been isolated and fully characterized by
analytical and spectroscopic techniques (see Experimental). The
successive generation of the allenyl moiety is accompanied by the
cleavage of a C–C bond and the conversion of the acyl group into
a terminal carbonyl ligand (see Scheme 2).
Compounds 4a,b have been isolated in good yields
after filtration on alumina. Similarly, by following the
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◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for 2a, 2c and 4a in [2a][BPh4]·CH2Cl2, [2c][BPh4]·0.5THF, [4a][CF3SO3]
2a
2c (I)a
2c (II)a
4a
M(1)–M(2)
M(1)–C(11)
M(2)–C(11)
M(1)–C(13)
M(2)–C(12)
M(1)–C(14)
M(2)–C(14)
M(1)–C(15)
C(11)–O(11)
C(12)–O(12)
C(13)–O(13)
C(14)–C(15)
C(15)–C(16)
2.7801(10)
2.187(14)
1.946(12)
1.829(13)
1.845(13)
2.138(9)
2.015(11)
2.199(10)
1.200(12)
1.159(12)
1.184(12)
1.390(13)
1.328(13)
2.7793(6)
2.185(5)
1.979(5)
1.901(5)
1.883(5)
2.154(4)
2.039(5)
2.184(4)
1.155(5)
1.127(5)
1.126(5)
1.355(6)
1.326(6)
2.7819(6)
2.175(5)
1.972(5)
1.895(5)
1.875(5)
2.168(4)
2.049(4)
2.182(4)
1.156(5)
1.138(5)
1.124(5)
1.360(6)
1.329(5)
2.6063(14)
2.152(8)
1.815(9)
1.761(9)
1.766(10)
2.026(8)
1.940(8)
2.061(7)
1.178(9)
1.141(10)
1.147(9)
1.332(11)
1.339(11)
M(1)–C(11)–M(2)
M(1)–C(11)–O(11)
M(2)–C(11)–O(11)
M(1)–C(14)–M(2)
M(2)–C(14)–C(15)
C(14)–C(15)–C(16)
C(14)–C(15)–M(1)
M(1)–C(15)–C(16)b
84.3(5)
83.6(2)
84.10(18)
129.6(4)
146.0(4)
82.50(15)
122.9(3)
151.5(4)
71.2(2)
81.7(3)
130.0(10)
145.5(11)
84.0(4)
126.0(8)
154.8(10)
68.9(6)
130.2(4)
146.0(4)
82.98(16)
126.4(4)
151.7(4)
70.6(3)
126.1(7)
152.2(8)
82.1(3)
124.7(6)
152.0(8)
69.6(5)
136.1(8)
137.7(3)
137.3(3)
137.7(6)
a Two independent molecules are present within the unit cell. b Sum angles at C(16): 2a, 360.0(17); 2c (I)a, 360.0(7); 2c (II)a, 355.9(7); 4a, 359.9(14).
Fig. 2 Structure of the cation 2c in [2c][BPh4]·0.5THF. The H-atoms,
Fig. 3 Structure of the cation 4a in [4a][SO3CF3]. The H-atoms, except
except H(14), have been omitted for clarity. Thermal ellipsoids are at the
30% probability level. Only one of the two independent cations present
within the unit cell is represented.
H(14), have been omitted for clarity. Thermal ellipsoids are at the 30%
probability level.
Ca(H) Cb(Cg (Me)CH2)C( O)}] (6) were obtained and identified
by spectroscopy and elemental analysis (see Scheme 3). Best yields
were reached by using NaH for the synthesis of 5, and NHEt2
for that of 6 (see Experimental). The reactions of 2a with sodium
hydride and of 4b with diethylamine gave complicated mixtures
of products; [Fe2Cp2(CO)4] was clearly identified in the mixture
derived from 4b.
at typical high-frequency, in accordance with the m-alkylidene
character [e.g. in the case of 4a: d(1H) = 11.77 ppm; d(13C) = 147.2
ppm].6,7 The allenyl carbons Cb and Cg are found at ca. 150 and
125 ppm, respectively.
Deprotonation reactions of diiron and diruthenium l-allenyl
complexes
Compound 5 is the result of Ca–H deprotonation, and belongs
to the family of group 8 m-allenylidene dinuclear adducts.9 The
NMR spectra (in CDCl3) show unique peaks for the two Cp
rings, in accordance with the symmetry exhibited by the molecule.
The allenylidene-chain carbon atoms can been seen at 192.0 (Ca),
201.4 (Cb) and 105.8 ppm (Cg ), in agreement with results reported
previously for similar compounds.9a
On the other hand, compound 6 results from single depro-
tonation of one Cg -bound methyl group in 4a, and successive
cyclization consisting of carbon–carbon bond formation between
The chemistry of the cationic species 2 and 4 with a variety of com-
pounds (i.e. NaH, NaBH4, KCN, lithium alkyls, lithium acetylides,
alkynes, alkenes, amines, phosphines and isocyanides) was ex-
plored. All the neutral reactants except amines did not give any
reaction even at high temperature. However, ionic reactants and
amines acted as Brønsted bases towards 2c and 4a at room temper-
ature, resulting in deprotonation reactions. Thus, the allenylidene
1
1
compound [Ru2Cp2(CO)2(m-CO){m-h :h -Ca Cb Cg (Ph)2}] (5)
1
3
and the dimetallacyclopentenone [Fe2Cp2(CO)(m-CO){m-h :h -
10868 | Dalton Trans., 2010, 39, 10866–10875
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coordination to the [Fe2Cp2(CO)2] framework (see Introduction),
starting from 4, unattainable.
As consequence, we focused our attention on the chemistry
of the diruthenium species 2a,c. Thus, the complexes
1
2
[Ru2Cp2(CO)(NCMe)(m-CO){m-h :h -Ca(H) Cb Cg (R)2}]+
(R = Me, 7a; R = Ph, 7b) have been prepared from 2a,c according
to the known procedure,6 and have been used in situ for subsequent
reactions. According to former observations, 7a,b probably exist
in solution as mixtures of interconverting isomers, allowing
NCMe to be bound at either ruthenium atom.6 Displacement
of the nitrile ligand by a chloride ion takes place to give the
1
2
neutral [Ru2Cp2(CO)(Cl)(m-CO){m-h :h -Ca(H) Cb Cg (R)2}]
(R = Me, 8a; R = Ph, 8b), see Scheme 4. The X-ray structure of
8a was previously determined, showing the chloride bound to the
ruthenium s-connected with Ca.6 The newly synthesized 8b has
1
been characterized by elemental analysis, IR and H NMR (one
set of resonances). In principle, both types of compounds 7–8
are potential precursors of coordinatively unsaturated species:
acetonitrile is a labile ligand and may be easily replaced in 7,
whereas the chloride ligand in 8 could be efficiently removed by
AgSO3CF3.13
Scheme 3 Deprotonation reactions of the allenyl complexes 2c and 4a.
the Cb and one carbonyl ligand. The spectroscopic features of 6
agree with the structure shown in Scheme 3: the IR spectrum (in
CH2Cl2) shows four bands at 1975, 1796, 1748 and 1611 cm-1,
attributed respectively to the terminal carbonyl ligand, the bridg-
1
ing carbonyl, the acyl group and the C C fragment. The H
NMR spectrum displays the singlet related to the Ca–H proton at
typical high frequency (d 12.29 ppm), whereas the resonances due
to Cg , CH3 and Csp2-H2 are as expected for a propenyl fragment
[–C(CH3) CH2]. Furthermore, the 13C NMR resonances for Ca,
Cb and acyl-CO are in accordance with those reported for similar
diiron cyclopentenone compounds.7
Synthesis of unprecedented heterocycle-substituted carbene ligands
via reactions of the allenyl unit with ethyldiazoacetate/amine
The reactions leading to 5, 6 show the presence of acidic sites
within the m-allenyl unit in the cationic complexes 2, 4. This fact
prevents the possibility of the addition of nucleophiles, which
are also Brønsted bases, to the allenyl ligand. On the other
hand, neutral species (e.g. alkynes, alkenes) are almost unreactive
towards 2, 4 (see above). In fact, the availability of a vacant metal
site in a dinuclear compound is an essential requirement for the
successive intramolecular coupling between the incoming reactant
and the bridging hydrocarbyl ligand.2c,d,i,4e,10 The vacancy may be
generated upon replacement of one carbonyl with a labile ligand,
and acetonitrile has often been used to the purpose.
Scheme 4 Preparation of nitrile- and chloro-derivatives.
We decided to study the reactivity of the nitrile adduct 7a with
ethyldiazoacetate, N2CHCO2Et. The reaction, which proceeds
smoothly in dichloromethane solution at room temperature, has
been monitored by IR spectroscopy. Progressive consumption of
the starting metal compound has been observed, whereas two new
carbonylic bands have appeared at 1980 and 1812 cm-1. These have
been attributed to the cationic adduct [Ru2Cp2(CO)(m-CO){m-
1
3
Unfortunately, our attempts to obtain dinuclear nitrile deriva-
tives of 4a and b have failed. In reality the reactions with
MeCN/Me3NO result in fragmentation to give complicated
mixtures of non identified mononuclear iron species, together with
minor amounts of [Fe2Cp2(CO)4]. The easy cleavage of the Fe–Fe
bond in 411 is confirmed by the room temperature formation of
h :h -Ca(H)CbCg (Me)2OC(OEt)C(H)]+ (9) (Scheme 5). The latter
could not be isolated in the solid state, however it was identi-
1
fied via H NMR in CDCl3 solution (see Experimental). After
few hours, new bands came along at lower wavenumbers (1963,
1792 and 1735 cm-1), suggesting the conversion of 9 into a neutral
product. We have seen that the addition of a molar excess of
NEt3 makes the conversion quantitative. The resulting product,
6
[FeCp(h -PhBPh3)],12 identified by X-ray diffraction analysis, in
1
3
an attempt to prepare [4a][BPh4] by addition of NaBPh4 to an
acetonitrile solution of [4a][BF4]. The combination of the acidic
properties of 4 with the instability of the dinuclear system makes
the idea of building functionalized organic fragments stabilized by
i.e. [Ru2Cp2(CO)(m-CO){m-h :h -Ca(H)CbCg (Me)2OC( O)C(H)]
(10a), has been isolated as a crystalline solid after work-up. By fol-
lowing an analogous procedure, we have prepared [Ru2Cp2(CO)(m-
1
3
CO){m-h :h -Ca(H)CbCg (Ph)2OC( O)C(H)] (10b), see Scheme 5.
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Fig. 4 Molecular structure of 10a. The H-atoms, except H(13) and H(15),
have been omitted for clarity. Thermal ellipsoids are at the 30% probability
level.
Scheme
5
Coupling reaction of the m-allenyl ligand with
diethyldiazoacetate.
The new complexes 10a,b have been fully characterized by IR
and NMR spectroscopy, elemental analysis and X-ray diffraction.
The ORTEP representations are shown in Fig. 4 and 5, whereas
relevant bond lengths and angles are reported in Table 2.
The molecular structures of 10a,b consist of
a bridg-
ing 5-dimethyl(diphenyl)-2-furanone-4-carbene ligand [m-
1
3
h :h -Ca(H)CC(R2)OC( O)C(H)] coordinated to the cis-
[Ru2Cp2(CO)(m-CO)] core. The carbene ligand possesses partial
◦
˚
Table 2 Selected bond lengths (A) and angles ( ) for 10a, 10b and 11 in
[11][BF4]·CH2Cl2
a
10a
10b
11
Fig. 5 Molecular structure of 10b. The H-atoms, except H(13) and H(15),
have been omitted for clarity. Thermal ellipsoids are at the 30% probability
level.
Ru(1)–Ru(2)
Ru(1)–C(11)
Ru(2)–C(11)
Ru(2)–C(12)
Ru(1)–C(13)
Ru(2)–C(13)
Ru(1)–C(14)
Ru(1)–C(15)
C(11)–O(11)
C(12)–O(12)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–X(1)
C(16)–O(2)
C(17)–O(2)
C(14)–C(17)
2.7544(6)
2.005(5)
2.049(5)
1.871(5)
2.145(4)
2.032(4)
2.164(5)
2.194(4)
1.186(6)
1.124(6)
1.404(6)
1.411(7)
1.487(7)
1.205(6)
1.358(6)
1.479(6)
1.527(6)
2.7375(3)
2.020(2)
2.0628(19)
1.856(2)
2.1197(17)
2.0387(18)
2.1636(17)
2.1879(18)
1.172(2)
1.143(3)
1.406(2)
1.433(2)
1.461(3)
1.205(2)
1.376(3)
1.461(2)
1.533(2)
2.7386(6)
2.012(5)
2.064(5)
1.855(6)
2.149(5)
2.043(5)
2.169(4)
2.189(4)
1.176(6)
1.148(7)
1.400(6)
1.429(6)
1.439(7)
1.313(6)
1.330(6)
1.502(6)
1.520(6)
bridging allylidene character, hence two main resonance formulas
may be drawn for its representation (see Scheme 6).14 Indeed
˚
˚
both C(13)–C(14) [1.406(2) A and 1.404(6) A for 10a and
˚
10b, respectively] and C(14)–C(15) interactions [1.433(2) A
and 1.411(7) A] show appreciable p-character. Conversely, the
C(15)–C(16) [1.461(3) A and 1.487(7) A] and C(14)–C(17)
[1.533(2) A and 1.527(6) A] are characteristic for Csp –Csp and
˚
˚
˚
2
2
˚
3
˚
2
˚
Csp –Csp single bonds. Similarly, C(16)–O(1) [1.205(2) A and
˚
1.205(6) A] is a C O double bond, whereas both C(16)–O(2)
˚
˚
˚
˚
[1.376(3) A and 1.358(6) A] and C(17)–O(2) [1.461(2) A and
2
3
1.479(6) A] are in agreement with Csp –O and Csp –O single
bonds. The C(14)–C(15)–C(16)–O(2)–C(17) ring is almost planar
Ru(1)–C(11)–Ru(2)
Ru(1)–C(11)–O(11)
Ru(2)–C(11)–O(11)
Ru(1)–C(13)–Ru(2)
C(13)–C(14)–C(15)
C(14)–C(15)–C(16)
C(15)–C(16)–O(2)
C(16)–O(2)–C(17)
O(2)–C(17)–C(14)
C(17)–C(14)–C(15)
85.60(18)
138.6(4)
135.5(4)
82.46(15)
123.8(4)
106.3(4)
109.8(4)
110.6(3)
102.4(4)
109.2(4)
84.20(7)
84.41(18)
139.8(4)
135.5(4)
81.55(16)
123.1(4)
104.9(4)
113.7(4)
109.2(4)
101.9(3)
109.3(4)
139.37(17)
136.14(17)
82.32(6)
122.82(16)
106.91(17)
109.98(16)
110.65(14)
103.35(14)
107.65(15)
a Sum angles at C(16): [10a], 360.0(3); [10b], 359.9(8); [11]+]+, 360.0(7).
Scheme 6 Resonance formulas for compounds 10.
10870 | Dalton Trans., 2010, 39, 10866–10875
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[mean deviations from the least squares plane are 0.0469 and
The cationic complex 11 contains an unprecedented 2-
furaniminium substituted carbene ligand. It has to be noted that
2-furaniminium rings are essential constituents of a large number
of natural products and pharmaceuticals.21
Complex 11 has been characterized by spectroscopic and
analytical techniques, and by an X-ray diffraction study. The
structure of 11 (see Fig. 6) is closely related to those of 10a and
10b, once the acyl C O group is replaced by a cationic iminium
[C NEt2]+ fragment. Therefore, the bridging hydrocarbyl ligand
in 11 may be alternatively described in terms of allylidene, as we
have discussed above for 10a,b (see Scheme 6). Since the most
relevant bonding parameters of 11 are similar to those of 10a,b
(see Table 2), they will not be discussed further.
˚
0.0494 A, respectively].
The IR spectra of 10a,b (CH2Cl2) clearly show two bands due
to a terminal carbonyl ligand and a bridging one (e.g. for 10b at
1965 and 1795 cm-1), and another absorption related to the acyl
group at ca. 1740 cm-1. The salient NMR features are represented
by the CaH resonances [e.g. for 10a: d(1H) = 10.04 ppm; d(13C) =
137.9 ppm]. Coupling along the Ca–C–C(O) chain is evident in
1
the H NMR spectrum of 10a, where CaH and CH(O) protons
resonate as doublets (4JHH = 1.47 Hz). Furthermore, the 13C NMR
resonances of the Cb and of the CbCC(O) carbon atoms fall at
ca. 115 and 40 ppm respectively, while the 13C resonance of the
lactone C O carbon is seen at ca. 180 ppm.
The formation of the novel compounds 10a,b deserves further
comment. It has to be remarked that the parent complexes
2a,c are inert towards N2CHCO2Et. This means that the cy-
clization reaction involving the diazocompound and the allenyl
moiety cannot proceed in the absence of the weakly coordinated
NCMe ligand. In other words, the initial coordination of the
[:CHCO2Et] unit is required in order to have subsequent coupling
with the m-allenyl (see above). Unfortunately, we could not
collect evidences for the formation of any intermediate species
containing the [Fe CH(CO2Et)] frame. The coupling takes place
regiospecifically through formation of new Cb–C and Cg –O bonds,
at room temperature. The final compounds 10a,b are probably
obtained (see Scheme 5) via [Et+] abstraction by the tertiary
amine NEt3 behaving as a Brønsted base, although different
pathways (e.g. hydrolysis due to adventitious water) should not
be excluded in principle. Compounds 10a,b contain a a,b-
butenolide (g-crotonolactone) substituted carbene. Interestingly,
the a,b-butenolide ring represents the substructure of numerous
biologically important natural and synthetic products, including
terpenoidal lactone pheromones,15 antileukaemic lignans,16 and
prostacycline analogues:17 there is still great interest in the
development of new synthetic protocols.18 Examples are not
lacking of carbon ligands bearing a a,b-butenolide substituent,19
however we present here the first case of a crystallographically
characterized a,b-butenolide-substituted carbene bridged in a
dinuclear complex.20
Fig. 6 Structure of the cation 11 in [11][BF4]·CH2Cl2. The H-atoms,
except H(13) and H(15), have been omitted for clarity. Thermal ellipsoids
are at the 30% probability level.
The IR spectrum of 11 (CH2Cl2 solution) displays two absorp-
tions at 1975 and 1806 cm-1, related to the terminal and the
bridging carbonyl groups, respectively. In addition, a medium
intensity band at 1644 cm-1 accounts for the iminium C NEt2
fragment. The iminium carbon is seen (in CDCl3) at 181.0 ppm in
the 13C NMR spectrum. The resonances of Ca, Cb and Cg fall at
141.3, 114.3 and 97.2 ppm, in the order given, resembling those
found for 10a. The m-alkylidene nature of Ca is confirmed by the
high-frequency chemical shift (d 10.35 ppm) of the related proton
in the 1H NMR spectrum.
The presence of the [OEt] moiety, in the supposed intermediate
cationic complex 9 (see Scheme 5), gives the opportunity of
alternative derivatization of the five-membered cycle. Indeed, the
treatment of a dichloromethane solution of 9 with the amine
NHEt2, instead of NEt3, yielded the stable [Ru2Cp2(CO)(m-CO){m-
Conclusions
1
3
h :h -Ca(H)CbCg (Me)2OC(NEt2)C(H)]+ (11), in admixture with
minor amounts of 10a (Scheme 7). The formation of 11 is the
result of the nucleophilic attack of the secondary amine NHEt2 to
replace the alkoxo group (–OEt) in 9.
Unprecedented carbene ligands bearing heterocyclic substituents,
that represent the skeleton of several natural products and/or
pharmaceuticals, have been obtained by straightforward reaction
of cationic diruthenium m-allenyl complexes with ethyldiazoac-
etate/amine. The reaction proceeds with regiospecific [3+2] cy-
clization, assisted by the [Ru2Cp2(CO)2] framework, involving the
diazocompound and the allenyl unit.
Novel cationic m-allenyl diiron complexes have been prepared
by a two-step procedure from the commercially available
[Fe2Cp2(CO)4]. The X-ray structure of [Fe2Cp2(CO)2(m-
1
2
CO){m-h :h -C(H)
of the diruthenium analogues [Ru2Cp2(CO)2(m-CO){m-h :h -
C(H)
C
C(Me)2}][CF3SO3],
likewise
those
1
2
C
C(R)2}][BPh4] (R = Me, Ph), has been determined and
discussed. The substitution of one carbonyl ligand with the labile
acetonitrile, in the case of the diruthenium complexes, is required
Scheme 7 Formation of the 2-furaniminium-carbene 11.
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in order to allow the coupling allenyl-ethyldiazoacetate. The same
process is not viable on the diiron complexes, as a consequence of
the weakness of the Fe–Fe bond.
1H NMR (CD3CN, 238 K) d 11.00 (s, 1 H, CaH); 7.49∏7.20 (10
1
H, Ph); 6.04, 5.72 (s, 10 H, Cp). 13C{ H} NMR (CD3CN, 238 K)
d 216.7 (m-CO); 195.5, 193.6 (CO); 155.0 (Cb); 139.8 (ipso-Ph);
130.9 (Ca); 130.1, 129.0, 128.4 (Ph); 127.6 (Cg ); 94.2, 92.0 (Cp).
Crystals suitable for X-ray analysis were obtained as follows: a
large excess of NaBPh4 (0.500 g, 1.46 mmol) was added to a stirred
acetonitrile solution of [2c][BF4] (0.145 mmol in 20 mL). The
mixture was stirred overnight, and then filtered on a Celite pad in
order to remove insoluble salts. The resulting solution was dried
under vacuo, affording a yellow microcrystalline solid. X-Ray
quality crystals of [2c][BPh4] were collected from CH2Cl2–Et2O at
-30 ◦C.
Experimental
General
All reactions were carried out under nitrogen atmosphere, using
standard Schlenk techniques. Solvents were distilled immediately
before use under nitrogen from appropriate drying agents. Pho-
tolysis reactions were carried out in silica glass tubes by using a
150 W mercury lamp. Chromatography separations were carried
out on columns of alumina (Fluka, Brockmann Activity I) for
neutral compounds and deactivated alumina (6% w/w water)
for ionic compounds, respectively. Glassware was oven-dried
before use. Infrared spectra were recorded at 298 K on a FT-
IR Perkin–Elmer Spectrometer equipped with a UATR sampling
accessory (solid samples). NMR measurements were performed
on a Varian Mercury Plus 400 instrument. The chemical shifts for
1H and 13C were referenced to the non-deuterated aliquot of the
solvent. The spectra were fully assigned via DEPT experiments
and 1H,13C correlation measured through gs-HSQC and gs-
HMBC experiments.22 Unless otherwise stated, NMR spectra were
recordedat298K. Allorganicreactants, includingHC CCR2OH
(R = Me, Ph), HBF4 (54% w/w in Et2O), NHEt2, NEt3, LiCl
and N2CHCO2Et, were commercial products (Aldrich) of the
highest purity available and used as received. [Fe2Cp2(CO)4] was
purchased from Strem and used as received, while [Ru2Cp2(CO)4]
was prepared by published procedure.23
Crystals of [2a][BPh4], suitable for X-ray analysis, were obtained
from [2a][BF4] by the same procedure described above.
Synthesis of [Fe2Cp2(CO)(l-CO){l-g1:g3-C(H) C(CR2OH)
C( O)}] (R
=
Me, 3a;
R
=
Ph, 3b).
A solution of
HC CCMe2OH (8.00 mL, 82.6 mmol) and [Fe2Cp2(CO)4] (15.0 g,
42.4 mmol), in THF (160 mL), was irradiated with UV light for
180 h. Then the volatile materials were removed under vacuo, and
the brown residue was dissolved in CH2Cl2 and charged on an
alumina column. Elution with neat acetone afforded a brown–
green band corresponding to 3a. The product was obtained as a
brown microcrystalline solid upon removal of the solvent. Yield:
10.8 g, 62%. Anal. Calcd. for C18H18Fe2O4: C, 52.73; H, 4.42.
Found: C, 52.31; H, 4.57. IR (solid state): n(OH) 3307 (m-br),
1
n(CO) 1961 (vs), 1766 (s), 1740 (m) cm-1. H NMR (CDCl3) d
12.58 (s, 1 H, CH); 5.03, 4.75 (s, 10 H, Cp); 3.34, 1.50 (s, 6 H, Me);
1.99 (br, 1 H, OH).
Compound 3b was prepared by the same procedure described
for 3a, by irradiating a solution of HC CCPh2OH (8.20 g,
39.4 mmol) and [Fe2Cp2(CO)4] (6.40 g, 18.1 mmol) in THF
(180 mL) for 215 h. Yield: 6.28 g, 65%. Anal. Calcd. for
C28H22Fe2O4: C, 62.96; H, 4.15. Found: C, 62.29; H, 4.19. IR
(CH2Cl2): n(OH) 3298 (m-br), n(CO) 1973 (vs), 1752 (s), 1705
Synthesis of [Ru2Cp2(CO)(l-CO){l-g1:g3-C(H) C(CPh2OH)
1
3
C( O)}]
(1c). Compound
[Ru2Cp2(CO)(m-CO){m-h :h -
C(Ph) C(Ph)C( O)}] (1.25 g, 2.10 mmol), in solution of THF
(25 mL), was treated with HC CCPh2OH (2.20 g, 10.6 mmol).
The mixture was stirred at boiling temperature for 4 h, then it
was allowed to cool to room temperature and filtered through an
1
(m) cm-1. H NMR (CDCl3) d 12.26 (s, 1 H, CH); 7.40∏7.20 (10
H, Ph); 5.01, 4.62 (s, 10 H, Cp); 1.60 (br, 1 H, OH).
1
3
alumina column. Thus, the product [Ru2Cp2(CO)(m-CO){m-h :h -
C(H) C(CPh2OH)C( O)}] (1c) was obtained as an orange
microcrystalline solid upon removal of the solvent under vacuo.
Yield: 1.15 g, 88%. Anal. Calcd. for C28H22O4Ru2: C, 53.84; H,
3.55. Found: C, 53.68; H, 3.39. IR (CH2Cl2): n(CO) 1976 (vs),
1804 (s), 1738 (m) cm-1. 1H NMR (CDCl3) d 10.51 (s, 1 H, CH);
Synthesis of [Fe2Cp2(CO)2(l-CO){l-g1:g2a,b-Ca(H) Cb Cc-
(R)2}][BF4] (R = Me, [4a][BF4]; R = Ph, [4b][BF4]). Compound 3a
(2.50 g, 6.10 mmol), prepared according to the procedure described
above, was dissolved in THF (50 mL). The solution was cooled to
-50 ◦C, and then treated with a solution of HBF4 in Et2O (1.74 mL,
6.90 mmol). The resulting mixture was allowed to warm to room
temperature, and stirred overnight. Subsequent removal of the
volatile materials and chromatography of the residue on alumina
gave a red fraction which was collected by using neat acetonitrile.
Thus compound [4a][BF4] was obtained as a red microcrystalline
solid upon removal of the solvent under vacuo. Yield: 2.58 g,
88%. Anal. Calcd. for C18H17BF4Fe2O3: C, 45.06; H, 3.57. Found:
C, 44.52; H, 3.68. IR (CH2Cl2): n(CO) 2036 (vs), 2011 (s), 1864
(m) cm-1. 1H NMR (CD3CN, 238 K) d 11.77 (s, 1 H, CaH); 5.58,
1
7.42∏7.20 (10 H, Ph); 5.37, 4.98 (s, 10 H, Cp). 13C NMR{ H}
(CDCl3) d 223.0 (m-CO); 221.3 (C O); 198.9 (CO); 153.2 (CH);
145.4, 144.7 (ipso-Ph); 127.8, 127.7, 127.6, 127.5, 127.3 (Ph); 89.3,
87.7 (Cp); 79.1 (CPh2OH); 58.6 (C-CPh2OH).
Synthesis
of
[Ru2Cp2(CO)2(l-CO){l-g1:g2a,b-Ca(H)
Cb Cc(Ph)2}][BF4] ([2c][BF4]) and characterization of [Ru2Cp2-
(CO)2(l-CO){l-g1:g2a,b-Ca(H) Cb Cc(Me)2}][BPh4]
([2a]-
[BPh4]). A solution of HBF4 in Et2O (3.53 mL, 14.0 mmol)
was added dropwise to a solution of 1c (0.880 g, 1.48 mmol)
in THF (20 mL). The resulting mixture was stirred for 2 h at
room temperature. The solvent was removed under vacuo and the
residue was dissolved in CH2Cl2 (10 mL). Subsequent addition
of diethyl ether (60 mL) caused precipitation of [2c][BF4], as
air-stable orange microcrystalline solid. Yield: 0.862 g, 84%. Anal.
Calcd. for C27H21BF4O3Ru2: C, 48.43; H, 3.05. Found: C, 47.86;
H, 3.21. IR (CH2Cl2) n(CO) 2048 (vs), 2026 (m), 1881 (m) cm-1.
1
5.36 (s, 10 H, Cp); 2.28, 1.94 (s, 6 H, Me). 13C NMR{ H} (CD3CN,
238 K) d 242.0 (m-CO); 210.6, 206.3 (CO); 149.1 (Cb); 147.2 (Ca);
121.4 (Cg ); 92.3, 89.1 (Cp); 27.7, 23.2 (Me). Crystals suitable for
X-ray analysis were obtained as follows: to a solution of [4a][BF4]
(0.25 mmol) in THF (20 mL), CF3SO3Na (2.30 mmol) was added.
The mixture was stirred overnight, then it was filtered through a
Celite pad. The resulting solution was layered with diethyl ether,
10872 | Dalton Trans., 2010, 39, 10866–10875
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in a Schlenk tube. Crystals of [4a][SO3CF3] were collected after
48 h at -30 ◦C.
C27H21ClO2Ru2: C, 52.73; H, 3.44; Cl, 5.76. Found: C, 52.50; H,
1
3.58; Cl, 5.56. IR (CH2Cl2) n(CO) 1992 (vs), 1883 (s) cm-1. H
Complex [4b][BF4] was prepared by a procedure analogous to
that described for [4a][BF4], by treating 3b (2.40 g, 4.49 mmol)
with HBF4/Et2O (1.24 mL, 4.90 mmol). Yield: 2.23 g, 82%. Anal.
Calcd. for C28H21BF4Fe2O3: C, 55.68; H, 3.50. Found: C, 55.33;
H, 3.46. IR (CH2Cl2): n(CO) 2042 (vs), 2017 (s), 1870 (m) cm-1.
1H NMR (CD3CN, 238 K) d 12.30 (s, 1 H, Ca); 7.78∏7.02 (10 H,
Ph); 5.74, 5.38 (s, 10 H, Cp).
NMR (CDCl3) d 10.06 (s, 1 H, CaH); 7.66∏7.23 (10 H, Ph); 5.19,
5.02 (s, 10 H, Cp).
Synthesis
of
[Ru2Cp2(CO)(l-CO){l-g1:g3-Ca(H)-
CbCc(R)2OC( O)C(H)], (R = Me, 10a; R = Ph, 10b).
A
dichloromethane solution of [7a][BF4], freshly prepared from
[2a][BF4] (0.189 g, 0.331 mmol) and Me3NO/MeCN (0.350 mmol
in 3.50 mL), was treated with N2CHCO2Et (0.18 mL, 1.67 mmol).
The mixture was stirred for 4 h, during which progressive
colour turning from orange to red was observed. IR spectrum
(CH2Cl2) indicated the disappearance of the starting ruthenium
compound and the clean formation of [Ru2Cp2(CO)(m-CO){m-
Synthesis of [Ru2Cp2(CO)2(l-CO){l-g1:g1-Ca Cb Cc(Ph)2}]
(5). Sodium hydride (0.052 g, 2.17 mmol) was added to a solution
of complex [2c][BF4] (0.420 g, 0.615 mmol) in THF (15 mL). The
mixture was stirred for 4 h, then it was filtered on a Celite pad
in order to remove insoluble salts. The solvent was eliminated
under vacuo, thus the residue was dissolved in CH2Cl2 (5 mL)
and chromatographed on alumina. A red band was collected by
using neat CH2Cl2 as eluent, hence microcrystalline 5 was obtained
upon removal of the solvent. Yield: 0.302 g, 81%. Anal. Calcd. for
C28H20O3Ru2: C, 55.44; H, 3.32. Found: C, 55.21; H, 3.50. IR
1
3
h :h -Ca(H)CbCg (Me)2OC(OEt)C(H)][BF4] (9) [n(CO) 1980,
1812 cm-1]. Hence NEt3 (0.14 mL, 1.00 mmol) was added to the
solution, resulting in immediate turning to orange. The mixture
was charged on a alumina column and chromatographed. Elution
with CH2Cl2/THF (1 : 1 v/v) gave an orange fraction: compound
10a was obtained as an orange microcrystalline solid upon
removal of the solvent under vacuo. Yield: 0.134 g, 79%. Anal.
Calcd. for C19H18O4Ru2: C, 44.53; H, 3.54. Found: C, 44.36; H,
1
(CH2Cl2) n(CO), 1954 (vs), 1803 (s) cm-1. H NMR (CDCl3) d
1
7.70∏7.25 (10 H, Ph); 5.31 (s, 10 H, Cp). 13C NMR{ H} (CDCl3)
1
d 242.9 (m-CO); 201.4 (Cb); 198.4, 197.9 (CO); 192.0 (Ca); 141.0
(ipso-Ph); 128.9, 128.6, 127.5, 126.3 (Ph); 105.8 (Cg ); 89.9 (Cp).
3.63. IR (CH2Cl2) n(CO) 1963 (vs), 1792 (s), 1735 (m) cm-1. H
NMR (CDCl3) d 10.04 (d, 1 H, 4JHH = 1.47 Hz, CaH); 5.31, 4.94
(s, 10 H, Cp); 1.66, 1.35 (s, 6 H, Me); 1.50 (d, 1 H, 4JHH = 1.47 Hz,
Synthesis of [Fe2Cp2(CO)(l-CO){l-g1:g3-Ca(H) Cb(Cc(Me)
CH2)C( O)}] (6). A solution of complex [4a][BF4] (1.40 g,
2.92 mmol), in CH2Cl2 (15 mL), was treated with NHEt2 (0.36 mL,
3.5 mmol). The mixture was stirred overnight at room temperature.
Then the final mixture was charged on an alumina column. A
brown fraction was collected by using a mixture of CH2Cl2 and
THF (1 : 1 v/v) as eluent. Yield: 0.940 g, 82%. Anal. Calcd. for
C18H16Fe2O3: C, 55.15; H, 4.11. Found: C, 54.70; H, 4.31. IR
(CH2Cl2) n(CO) 1975 (vs), 1796 (s), 1748 (m), n(C C) 1611
1
CH). 13C NMR{ H} (CDCl3) d 238.2 (m-CO); 200.8 (CO); 179.3
(C O); 137.9 (Ca); 116.9 (Cb); 91.3 (Cg ); 89.1, 85.4 (Cp); 41.9
(CH); 32.2, 25.0 (Me).
Compound 10b was prepared by the same procedure described
for 10a, by reacting [7b][BF4], freshly prepared from [2c][BF4]
(0.310 mmol) and Me3NO/MeCN, with N2CHCO2Et/NEt3.
Chromatography: CH2Cl2 100%. Colour: yellow. Yield: 0.162 g,
82%. Anal. Calcd. for C29H22O4Ru2: C, 54.71; H, 3.48. Found:
C, 54.34; H, 3.61. IR (CH2Cl2) n(CO) 1965 (vs), 1795 (s), 1746
(m) cm-1. 1H NMR (CDCl3) d 10.35 (s, 1 H, CaH); 7.59∏7.33 (10
1
(m) cm-1. H NMR (CDCl3) d 12.29 (s, 1 H, CaH); 5.40, 5.23
(m, 2 H, CH2); 5.06, 4.62 (s, 10 H, Cp); 2.09 (s, 3 H, Me). 13C
1
H, Ph); 5.37, 4.55 (s, 10 H, Cp); 1.59 (s, 1 H, CH). 13C NMR{ H}
1
NMR{ H} (CDCl3) d 261.9 (m-CO); 232.7 (C O); 210.5 (CO);
(CDCl3) d 238.0 (m-CO); 201.2 (CO); 178.3 (C O); 145.0, 142.2
(ipso-Ph); 141.6 (Ca); 128.4, 127.9, 125.9 (Ph); 112.4 (Cb); 89.2,
85.4 (Cp); 61.5 (Cg ); 43.8 (CH).
173.2 (Ca); 139.8 (Cg ); 116.9 (CH2); 87.9, 87.3 (Cp); 31.2 (Cb); 20.8
(Me).
Synthesis of [Ru2Cp2(CO)(NCMe)(l-CO){l-g1:g2-Ca(H)
Cb Cc(Ph)2}][BF4] (7b). A solution of [2c][BF4] (0.280 g,
0.410 mmol) in CH2Cl2 (15 mL) was treated with Me3NO (0.040 g,
0.533 mmol) in solution of MeCN (5.3 mL). The resulting mixture
was stirred at room temperature for 1 h. Hence the mixture
was filtered through a Celite pad and the volatile materials were
removed under vacuo. Compound [7b][BF4] was obtained as a
red microcrystalline solid. Yield: 0.258 g, 89%. Anal. Calcd. for
C29H24BF4NO2Ru2: C, 49.23; H, 3.42; N, 1.98. Found: C, 49.76;
H, 3.38; N, 2.05. IR (CH2Cl2) n(CO) 2008 (vs), 1861 (s) cm-1.
Crystals of 10a and 10b suitable for X-ray analyses were
collected from dichloromethane solutions layered with pentane,
at -30 ◦C.
In a different experiment, compound [7a][BF4] (0.250 mmol)
was dissolved in CDCl3 (0.65 mL) and treated with N2CHCO2Et
in a NMR tube. Then the tube was sealed and after 2 h 1H NMR
1
spectroscopy indicated the prevalent formation of [9][BF4]. H
NMR (CDCl3) d 10.50 (d, 1 H, 4JHH = 1.2 Hz, CaH); 5.59, 5.35 (s,
10 H, Cp); 4.27 (q, 2 H, 3JHH = 7.0 Hz, OCH2); 2.27 (t, 3 H, 3JHH
7.0 Hz, OCH2CH3); 1.96, 1.82 (s, 6 H, Me); 1.67 (d, 1 H, 4JHH
1.2 Hz, CH).
=
=
Synthesis
of
[Ru2Cp2(CO)(Cl)(l-CO){l-g1:g2-Ca(H)
Cb Cc(Ph)2}] (8b).
A
dichloromethane solution (20 mL)
Synthesis
of
[Ru2Cp2(CO)(l-CO){l-g1:g3-Ca(H)-
of [7b][BF4], freshly prepared from 2c (0.239 g, 0.350 mmol)
and Me3NO/MeCN (0.380 mmol in 3.80 mL), was treated with
LiCl (0.140 g, 3.30 mmol). The resulting mixture was stirred at
room temperature for 3 h. Then, the mixture was charged on
an alumina column. An orange band was collected by using a
mixture of CH2Cl2 and THF (1 : 1 v/v) as eluent. Compound
8b was obtained as a microcrystalline solid upon removal of
the solvent under vacuo. Yield: 0.185 g, 86%. Anal. Calcd. for
CbCc(Me)2OC(NEt2)C(H)] [BF4] ([11][BF4]). The treatment
of 9, prepared from 2a (0.350 mmol) in CH2Cl2 (20 mL),
with NHEt2 (1.80 mmol) gave an orange mixture which was
chromatographed on alumina. Compound 10a was recovered
in 33% yield by using CH2Cl2/THF (1 : 1 v/v) as eluent. Then,
elution with acetonitrile gave a second yellow band which
afforded [11][BF4] in the form of yellow microcrystalline solid
after removal of the solvent. Yield: 0.110 g, 48%. Anal. Calcd. for
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Table 3 Crystal data and experimental details for [2a][BPh4]·CH2Cl2, [2c][BPh4]·0.5THF, [4a][CF3SO3], 10a, 10b and [11][BF4]·CH2Cl2
Complex
[2a][BPh4]·CH2Cl2 [2c][BPh4]·0.5THF [4a][CF3SO3]
10a
10b
[11][BF4]·CH2Cl2
Formula
Fw
C43H39BCl2O3Ru2 C54H45BO3.5Ru2
C19H17F3Fe2O6S
542.09
294(2)
0.71073
Orthorhombic
P212121
10.6193(15)
21.194(3)
9.5464(14)
90
2148.5(5)
4
1.676
1.506
1096
C19H18O4Ru2
512.47
295(2)
0.71073
Orthorhombic
P212121
9.9279(16)
11.5719(18)
15.274(2)
90
1754.8(5)
4
1.940
1.741
1008
C29H22O4Ru2
636.61
294(2)
C24H30BCl2F4NO3Ru2
740.34
295(2)
887.59
294(2)
962.85
294(2)
T/K
˚
l/A
0.71073
Orthorhombic
P212121
9.9707(18)
14.798(3)
27.089(5)
90
0.71073
Monoclinic
C2/c
56.255(6)
9.6487(10)
36.085(4)
114.9470(10)
17759(3)
16
0.71073
Monoclinic
P21/c
10.5647(9)
14.6934(13)
16.2336(14)
105.4060(10)
2429.4(4)
4
0.71073
Monoclinic
P21/n
16.280(3)
10.5976(18)
16.662(3)
92.275(2)
2872.5(9)
4
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
b/◦
3
˚
Cell Volume/A
Z
3996.9(12)
4
Dc/g cm-3
m/mm-1
F(000)
1.475
0.927
1.441
0.725
1.741
1.277
1264
1.712
1.290
1472
1792
7840
Crystal size/mm
0.19 ¥ 0.16 ¥ 0.12 0.18 ¥ 0.12 ¥ 0.11
0.18 ¥ 0.15 ¥ 0.11 0.25 ¥ 0.21 ¥ 0.16 0.22 ¥ 0.15 ¥ 0.14 0.25 ¥ 0.24 ¥ 0.21
1.92–25.99
16383
q limits/◦
1.50–25.03
28799
1.24–26.00
89261
2.21–26.00
18166
1.90–28.00
27425
1.72–27.00
31061
Reflections collected
Independent reflections 7059 [Rint = 0.1210] 17412 [Rint = 0.0600] 4221 [Rint = 0.0748] 3457 [Rint = 0.0349] 5676 [Rint = 0.0200] 6266 [Rint = 0.0444]
Data/restraints/
parameters
7059/544/555
17412/620/1096
4221/86/286
3457/98/234
5676/2/322
6266/134/344
Goodness on fit on F2 1.035
1.017
0.0400
0.0983
0.701/-0.429
1.083
0.0517
0.1325
0.604/-0.409
1.090
0.0296
0.0774
0.878/-0.363
1.058
0.0202
0.0531
0.286/-0.584
1.058
0.0477
0.1422
1.017/-0.725
R1 (I > 2s(I))
wR2 (all data)
0.0586
0.1474
Largest diff. peak and 0.602/-0.322
-3
˚
hole/e A
C23H28BF4NO3Ru2: C, 42.15; H, 4.31; N, 2.14. Found: C, 42.63;
H, 4.26; N, 2.27. IR (CH2Cl2) n(CO) 1975 (s), 1806 (m), n(C N)
1644 (m) cm-1. 1H NMR (CDCl3) d 10.35 (s, H, CaH); 5.52, 5.05
(s, 10 H, Cp); 3.77∏3.55 (m, 4 H, CH2CH3); 1.83, 1.68 (s, 6 H,
using the TWIN refinement routine of SHELXTL. The two Cp
ligands in [2a][BPh4]·CH2Cl2 are disordered: disordered atomic
positions were split and refined using one occupancy parameter
per disordered group.
CCDC reference numbers 781673, 10a, 781674, [11][BF4]·
CH2Cl2, 781675, [2c][BPh4]·0.5THF, 781676, 10b, 781677,
[4a][CF3SO3], 781678, [2a][BPh4]·CH2Cl2, contain the supplemen-
tary crystallographic data for this paper.†
1
Cg Me); 1.46, 1.30 (m, 6 H, CH2CH3); 1.20 (s, 1 H, CH). 13C{ H}
NMR (CDCl3) d 238.1 (m-CO); 200.8 (CO); 181.0 (C N); 141.3
(Ca); 114.3 (Cb); 97.2 (Cg ); 90.2, 85.3 (Cp); 47.7, 44.8 (CH2CH3);
38.4 (CH); 31.2, 25.3 (Cg Me); 13.3, 13.2 (CH2CH3). Crystals
suitable for X-ray analysis were obtained from a dichloromethane
solution layered with diethyl ether, at -30 ◦C.
Acknowledgements
The authors wish to thank the Ministero dell¢Istruzione,
dell¢Universita` e della Ricerca (project: ‘New strategies for the
control of reactions: interactions of molecular fragments with
metallic sites in unconventional species’) for financial support and
Prof. Giuseppe Fachinetti, University of Pisa, for the generous gift
of Ru3(CO)12.
X-Ray Crystallographic Study. Crystal data and collection
details for [2a][BPh4]·CH2Cl2, [2c][BPh4]·0.5THF, [4a][CF3SO3],
10a, 10b and [11][BF4]·CH2Cl2 are reported in Table 3. The
diffraction experiments were carried out on a Bruker Apex II
diffractometer equipped with a CCD detector using Mo-Ka
radiation. Data were corrected for Lorentz polarization and
absorption effects (empirical absorption correction SADABS).24
Structures were solved by direct methods and refined by full-
matrix least-squares based on all data using F2.25 The unit
cell of [2c][BPh4]·0.5THF contains two independent molecules
which display very similar bonding parameters. Non-H atoms
were refined anisotropically. H-atoms were placed in calculated
positions, except H(14) and H(44) in [2c][BPh4]·0.5THF, H(14) in
[4a][CF3SO3], H(13) and H(15) in 10a, 10b and [11][BF4]·CH2Cl2
which were located in the Fourier map. H-atoms were treated
isotropically using the 1.2 fold Uiso value of the parent atom
except methyl protons, which were assigned the 1.5 fold Uiso
value of the parent C-atom. Similar U restraints were applied as
follow: all C atoms of [2a][BPh4]·CH2Cl2, [2c][BPh4]·0.5THF and
10b; all C and O atoms of [4a][CF3SO3] and [11][BF4]·CH2Cl2.
The crystals of [4a][CF3SO3] are racemically twinned with refined
Flack parameters of 0.46(4);26 the structure was therefore refined
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