Reactions of acetonitrile di-iron μ-aminocarbyne complexes; synthesis and structure of [Fe2(μ-CNMe2)(μ-H)(CO)2(Cp)2]

Article abstract of DOI:10.1016/S0022-328X(00)00337-5

The complexes [Fe₂{μ-CN(Me)R}(μ-CO)(NCMe)(CO)(Cp)₂]SO ₃CF₃ (R = Me, 2a; 2,6-Me₂C₆H₃, 2b; CH₂Ph, 2c), easily obtained from the corresponding [Fe₂{μ-CN(Me)R}(μ-CO)(CO)₂(Cp)₂]SO ₃CF₃ (1a-c) precursors, react with NBu₄CN affording the cyano complexes [Fe₂{μ-CN(Me)R}(μ-CO)(CN)(CO)(Cp)₂] (3a-c) by displacement of the MeCN ligand. The analogous reaction with NBu₄Cl leads to the formation of [Fe₂{μ-CN(Me)R}(μ-CO)(Cl)(CO)(Cp)₂] (4a-b). The μ-hydride complexes [Fe₂{μ-CN(Me)R}(μ-H)(CO)₂(Cp)₂] (5a-b) have been prepared by reaction of 1a-b with NaBH₄. The corresponding diruthenium compound [Ru₂(μ-CNMe₂)(μ-H)(CO)₂(Cp)₂] (6) has been similarly obtained from [Ru₂(μ-CNMe₂)(μ-CO)(NCMe) (CO)(Cp)₂]SO₃CF₃. The X-ray molecular structure of 5a is that expected for cis isomers of this family of compounds. It shows a chiral conformation of the C₅H₅ ligands and the crystals are a conglomerate of enantiomeric individuals. NMR spectra of the various compounds, which are indicative of the presence of α-α or cis-trans isomeric mixtures, are reported and discussed.

Full text of DOI:10.1016/S0022-328X(00)00337-5

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Journal of Organometallic Chemistry 606 (2000) 163–168
Reactions of acetonitrile di-iron m-aminocarbyne complexes;
synthesis and structure of [Fe2(m-CNMe2)(m-H)(CO)2(Cp)2]
Vincenzo G. Albano b, Luigi Busetto a, Magda Monari b, Valerio Zanotti a,*
a Dipartimento di Chimica Fisica ed Inorganica, Uni6ersita’ di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy
b Dipartimento di Chimica ‘G. Ciamician’, Uni6ersita’ di Bologna, Via Selmi 2, I-40126 Bologna, Italy
Received 17 March 2000; accepted 18 March 2000
Abstract
The complexes [Fe2{m-CN(Me)R}(m-CO)(NCMe)(CO)(Cp)2]SO3CF3 (R=Me, 2a; 2,6-Me2C6H3, 2b; CH2Ph, 2c), easily ob-
tained from the corresponding [Fe2{m-CN(Me)R}(m-CO)(CO)2(Cp)2]SO3CF3 (1a–c) precursors, react with NBu4CN affording the
cyano complexes [Fe2{m-CN(Me)R}(m-CO)(CN)(CO)(Cp)2] (3a–c) by displacement of the MeCN ligand. The analogous reaction
with NBu4Cl leads to the formation of [Fe2{m-CN(Me)R}(m-CO)(Cl)(CO)(Cp)2] (4a–b). The m-hydride complexes [Fe2{m-
CN(Me)R}(m-H)(CO)2(Cp)2] (5a–b) have been prepared by reaction of 1a–b with NaBH4. The corresponding diruthenium
compound [Ru2(m-CNMe2)(m-H)(CO)2(Cp)2] (6) has been similarly obtained from [Ru2(m-CNMe2)(m-CO)(NCMe)
(CO)(Cp)2]SO3CF3. The X-ray molecular structure of 5a is that expected for cis isomers of this family of compounds. It shows
a chiral conformation of the C5H5 ligands and the crystals are a conglomerate of enantiomeric individuals. NMR spectra of the
various compounds, which are indicative of the presence of a–b or cis–trans isomeric mixtures, are reported and discussed.
© 2000 Elsevier Science S.A. All rights reserved.
Keywords: Hydride; Acetonitrile; Carbyne complexes; Crystal structure
1. Introduction
tuted m-aminocarbyne complexes with cyanide, chloride
and hydride anions.
Recent work of our group has focused on the reac-
tions of the dinuclear bridging aminocarbyne complexes
[M2{m-CN(Me)R}(m-CO)(CO)2(Cp)2]SO3CF3 (M=Fe,
Ru; R=Me, CH2Ph; Cp=h5-C5H5) with carbon nu-
cleophiles, aimed at forming carbonꢀcarbon bonds via
addition at the Cp and CO ligands [1].
Continuing our studies on their chemistry [2], we
have become interested in replacing a CO with acetoni-
trile in order to drive the nucleophilic attack at the
metal. In fact, in related di-ruthenium complexes, the
presence of the labile acetonitrile ligand has proved
crucial for a direct involvement of the metal in oxida-
tive additions, substitution reactions and intramolecular
rearrangements thus making those complexes valuable
models for Fischer–Tropsch catalytic processes [3].
Here we report on the reactions of acetonitrile-substi-
2. Results and discussion
A
carbonyl ligand in [Fe2{m-CN(Me)R}(m-
CO)(CO)2(Cp)2]SO3CF3 (R=Me, 1a; 2,6-Me2C6H3, 1b;
CH2Ph, 1c) is readily substituted by MeCN in the
presence of Me3NO, to afford [Fe2{m-CN(Me)R}(m-
CO)(NCMe)(CO)(Cp)2]SO3CF3 (R=Me, 2a; 2,6-
Me2C6H3, 2b; CH2Ph, 2c), in about 95% yield. Their
formulation is based on elemental microanalytical and
spectroscopic data. Replacement of CO by NCMe
makes the two Fe centers non-equivalent; consequently
two Cp singlet signals are observed in the NMR spec-
tra. Unlike 2a, the NMR spectra of compound 2b–c
indicate the presence of two isomeric forms (e.g. for
2c two signals for each of the unequivalent Cp are
observed). Since 2b–c differ from 2a having the asym-
metrically substituted m-CN(Me)R (R=CH2Ph,
2,6-Me2C6H3) ligand in place of the m-CNMe2, these
* Corresponding author. Tel.: +39-51-2093700; fax: +39-51-
6443690.
E-mail address: zanotti@ms.fci.unibo.it (V. Zanotti).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00337-5

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V.G. Albano et al. / Journal of Organometallic Chemistry 606 (2000) 163–168
By addition of NBu4CN to CH2Cl2 solutions of
2a–c the displacement of the coordinated acetonitrile
by cyanide takes place, producing the cyano com-
plexes [Fe2{m-CN(Me)R}(m-CO)(CN)(CO)(Cp)2] (3a–c)
(Scheme 1), which have been isolated in good yields
after column chromatography.
Compound 3a has been identified by comparison of
its spectroscopic data with those previously reported
for the cis isomer [4b]. Compounds 3a–c show an IR
absorption of the w(CN) at about 2091 cm−1, more-
over in the 13C-NMR spectrum the characteristic
downfield resonance of the m-carbyne carbon is ob-
served (at l 339.0 for 3b). As for its precursor 2c,
compound 3c exhibits, in its 1H-NMR spectrum, a
double set of signals for the Cp ligands, indicating the
presence of two isomers (a and b forms) occurring in
comparable amounts. By contrast, 3b shows the large
predominance of one isomeric form.
isomeric forms are presumably due to the different
orientation of Me and R with respect to the non-equiv-
alent Fe atoms (a and b isomers) rather than being
assigned to a cis or trans arrangements of the Cp ligands.
Isomeric a and b forms, are usually found in complexes
of the type [M2{m-CN(Me)R}(m-CO)(L)(CO)(Cp)2]
(M=Fe [1a,4], Ru [1b]). Finally it should be noted that
these isomers are present in comparable amounts for 2c,
whereas one is largely predominant in 2b.
The results here described are to be compared with
those previously obtained in the absence of the labile
CNMe ligand. Cyanide anion has been shown to add
at the bridging carbyne carbon of [Fe2{m-CN(Me)R}(m-
CO)(CO)2(Cp)2]SO3CF3 (R=Me, CH2Ph) yielding the
corresponding m-cyanoaminocarbene complexes [Fe2{m-
C(CN)N(Me)R}(m-CO)(CO)2(Cp)2] [2a]. Therefore re-
placement of CO with NCMe has proved to be quite
effective in directing the nucleophilic attack at the
metal atom.
Scheme 1.
Likewise, treatment of 2a–b with NBu4Cl in
dichloromethane solution results in the displacement of
acetonitrile by chloride leading to the formation of the
complexes
[Fe2{m-CN(Me)R}(m-CO)(Cl)(CO)(Cp)2]
1
(4a–b) (Scheme 1), in moderate yield. The H-NMR
spectrum of 4a has been straightforward with a singlet
for each of the non-equivalent Cp and Me groups (at l
4.75, 4.65 and 4.71, 4.26, respectively). The NMR spec-
tra of 4b reveal the presence, in solution, of only one of
the two possible a and b isomers. A major feature in its
13C-NMR spectrum is the expected low field resonance,
at l 343.3, attributable to the aminocarbyne carbon.
Somewhat unexpectedly, we found that MeCN solu-
tions of 2a–b react with NaBH4 to give the m-hydride
complexes [Fe2{m-CN(Me)R}(m-H)(CO)2(Cp)2] (5a–b)
(Scheme 2).
Scheme 2.
The structure of 5a has been ascertained by X-ray
diffraction and is shown in Fig. 1, together with some
relevant bond parameters. The overall stereochemistry
is that of all the cis isomers of this family of com-
pounds. Although the bond distances conform to an
idealized Cs symmetry the molecule adopts a chiral
conformation in the crystal. The chirality is generated
by the mutually staggered conformation of the C5H5
ligands generated by the optimization of the intraligand
Fig. 1. ORTEP drawing of [Fe2(m-CNMe2)(m-H)(CO)2(Cp)2] (5a) (ther-
mal ellipsoids are drawn at 30% probability). Selected bond lengths:
Fe(1)ꢀFe(2) 2.5877(9), Fe(1)ꢀC(1) 1.864(2), Fe(2)ꢀC(1) 1.860(3),
C(1)ꢀN 1.312(3), NꢀC(2) 1.470(3), NꢀC(3) 1.461(4), Fe(1)ꢀH 1.63(2),
Fe(2)ꢀH 1.59(2), Fe(1)ꢀC(4) 1.736(3), Fe(2)ꢀC(5) 1.730(3), C(4)ꢀO(4)
,
H···H contacts. The FeꢀFe distance [2.588(1) A)] is
1.152(3), C(5)ꢀO(5) 1.157(3), Fe(1)ꢀC(Cpav) 2.118(3), Fe(2)ꢀC(Cpav
)
longer than that found in similar compounds in which
,
2.113(3) A.

V.G. Albano et al. / Journal of Organometallic Chemistry 606 (2000) 163–168
165
,
a bridging CO is in the place of the hydride: 2.504(1) A
in [Fe2(m-CNMe2)(m-CO)(CO){C(O)C4H9}(Cp)2] [1a],
like PPh2 and/or Ph2PCH2PPh2 (dppm), which strongly
contribute to the stability of the dinuclear unit. Exam-
ples include [Fe2(m-PPh2)(m-H)(CO)2(Cp)2] [9], [Fe2(m-
PPh2)(m-H)(m-dppm)(Cp)2] [10], [Fe2(m-PPh2)(m-H)-
(m-dppm)(m-CO)(CO)4] [11] and [Fe2(m-H)(m-dppm)(m-
CO)(CO)6]BF4 [12]. It is noteworthy that these com-
plexes have been obtained by protonation at the metal
or by PꢀH oxidative addition of the diphenylphosphine,
whereas complexes 5a–b result from hydride addition.
In contrast with related m-hydride di-iron complexes,
which readily insert acetylenes into the metal–hydride
functionality [11,12], compound 5a has been found to
be unreactive toward HCꢂCPh and MeOC(O)Cꢂ
CC(O)OMe. Compound 5a is not attacked or deproto-
nated by buthyllithium whereas the reaction with
HSO3CF3, in the presence of MeCN affords 1a in
about 60% yield, confirming that the bridging hydrogen
in 5a is not acidic but hydridic.
,
2.509(2)
A
in [Fe2{m-CN(Me)CH2Ph}(m-CO)(CO)-
,
{C(O)th}¸(C¹p¹)2¹] ¹(ºth=C4H3S) [5], and 2.519(1) A in
[Fe2{m-CN(CH2)4CH2}(m-CO)(CO)2(Cp)2] [6]. The m-
CꢁNMe2 ligand is symmetrically bound [m-CꢀFe 1.86av
,
A] and its geometry does not significantly differ from
that found in the species cited above, in spite of the
substitution of the hydride for a carbonyl ligand. A
similar bonding situation is present in [Fe3(m-H)(m-
CNMe2)(CO)10] [7] in which slightly longer m-CꢀFe
,
distances [1.90(1)av A] should be attributed to the dif-
ferent chemical environment of the Fe atoms. The
m-HꢀFe distances, on the other hand, are in very good
,
agreement in the two species [1.61av A in both
compounds].
The NMR data for compound 5a are in complete
agreement with the structure established in the solid
state. A single Cp resonance (at l 4.64) and one sharp
singlet for the two N bonded Me groups (at l 4.09)
indicate the presence, in solution, of a single species 5a
and the bridging hydride resonance, at −17.75 ppm,
occurs within the expected range [8]. Finally, two IR
w(CO) absorptions (at 1935 and 1891 cm−1, in CH2Cl2
solution) show the typical strong–weak intensity pat-
tern which accounts for the two terminal CO ligands in
a mutual cis position.
In contrast with 5a, two isomers are observed in the
NMR spectra of 5b (e.g. two high field m-H signals are
displayed at l −16.72 and −17.71). Since the Fe
atoms are equivalent in this molecule, a and b isomers
are excluded; therefore the observed forms must be
cis–trans isomers. Unlike 5a, the IR w(CO) band pat-
tern of 5b consists of two absorptions of comparable
intensity (at 1940 and 1901 cm−1), which is consistent
with the presence of both cis and trans isomers.
The formation of 5a–b presumably occurs via the
terminal hydride intermediates [Fe2{m-CN(Me)R}(m-
CO)(CO)(H)(Cp)2] which undergo site exchange with
the bridging CO. Compared to [Fe2(m-CNMe2)(m-
CO)(X)(CO)(Cp)2] (X=CN, 3a; Cl, 4a), in which the
cyanide or chloride ligands steadily occupy the terminal
coordination position, the rearrangement of the hydride
ligand is explained by its tendency to adopt the bridg-
ing coordination whenever a more symmetric structure
can be attained. Again, these results differ from those
previously obtained in the absence of the labile CNMe
ligand. Indeed, H− from NaBH4, has been shown
to add at the bridging carbyne carbon of [Fe2-
Finally we have investigated the reaction of NaBH4
with the diruthenium complex [Ru2(m-CNMe2)(m-
CO)(NCMe)(CO)(Cp)2]SO3CF3 (2d), which was gener-
ated by treatment of [Ru2(m-CNMe2)(m-CO)-
(CO)2(Cp)2]SO3CF3 with Me3NO in CH3CN. The reac-
tion parallels that of the di-iron counterpart 2a, leading
to the formation of [Ru2{m-CN(Me)R}(m-H)-
(CO)2(Cp)2] (6), which has been characterized by ele-
mental analyses, IR and NMR spectroscopy. This re-
sult was somewhat predictable on the basis of the
similar behavior that diruthenium complexes [Ru2{m-
CN(Me)R}(m-CO)(CO)2(Cp)2]SO3CF3 (R=Me,CH2Ph)
and their di-iron counterparts have shown so far [1b,
13]. However 6 differs from the analogous iron com-
pound 5a in its isomeric composition: the w(CO) band
pattern of the former consists of two absorptions, at
1943 and 1907 cm−1 of weak and strong intensity, that
reveal the predominance of the trans isomer.
3. Experimental
3.1. General
All reactions were routinely performed under an inert
atmosphere of nitrogen by using Schlenk techniques.
Solvents were distilled immediately before use under
nitrogen from appropriate drying agents. All the
reagents were commercial products (Aldrich) of the
highest purity available and used as received.
[Ru2(CO)4(Cp)2] was from Strem and used as received.
Instruments employed: IR, Perkin–Elmer Spectrum
2000; NMR, Varian Gemini 200 and 300. Unless other-
wise stated NMR signals due to trace amounts of
second isomeric form are italicized. The compounds
[Fe2{m-CN(Me)R}(m-CO)(CO)2(Cp)2]SO3CF3 (R=Me,
{m-CN(Me)R}(m-CO)(CO)2(Cp)2]SO3CF3
(R=Me,
CH2Ph) causing a rearrangement in which the m-
CHN(Me)R ligand shifts from bridging to terminal
coordination to yield the corresponding aminocarbene
complexes [Fe2(m-CO)2{CHN(Me)R}(CO)(Cp)2] [2a].
A few other di-iron m-hydride complexes are known.
They are also generally bridged by phosphorus ligands

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V.G. Albano et al. / Journal of Organometallic Chemistry 606 (2000) 163–168
1a; 2,6-Me2C6H3, 1b; CH2Ph, 1c) [4] and [Ru2(m-
CNMe2)(m-CO)(CO)2(Cp)2]SO3CF3 [13] were prepared
from the corresponding isocyanide complexes according
to published methods.
(NMe), 19.5, 18.1 (Me2C6H3), and 4.8, 4.6 (MeCN);
signals due to the a form are italicized.
3.4. Synthesis of [Fe2(v-CNMe2)(v-CO)(CO)-
(CN)(Cp)2] (3a), [Fe2{v-CN(Me)Me2C6H3}(v-CO)-
(CN)(CO)(Cp)2] (3b) and [Fe2{v-CN(Me)CH2C6H5}-
(v-CO)(CN)(CO)(Cp)2] (3c)
3.2. Synthesis of [Fe2(v-CNMe2)(v-CO)(NCMe)-
(CO)(Cp)2]SO3CF3 (2a)
Compound [Fe2(m-CNMe2)(m-CO)(CO)2(Cp)2]SO3-
CF3 (152 mg, 0.29 mmol) in MeCN (10 ml) was treated
with anhydrous Me3NO (23 mg, 0.30 mmol). Filtration
on a Celite pad and removal of the solvent gave a
brown residue that was crystallized from CH2Cl2 lay-
ered with n-pentane at −20°C yielding 2a as a brown
microcrystalline solid (143 mg, 96%). Anal. Found: C,
40.31; H, 3.66. C18H19F3Fe2N2O5S requires: C, 39.73;
H, 3.52%. IR (CH2Cl2) wmax (cm−1): 1984vs, 1815s
A mixture of 2a (140 mg, 0.27 mmol) and NBu4CN
(80 mg, 0.30 mmol) was stirred in CH2Cl2 (10 ml) for
60 min. Removal of the solvent and chromatography of
the residue on an alumina column, with 2:1 (v/v)
CH2Cl2–petroleum ether (b.p. 40–60°C) as eluent, gave
a green band which was collected. Crystallization from
CH2Cl2 layered with n-pentane at −20°C yielded 3a
(86 mg, 84%) which was identified by comparison of the
spectroscopic properties with those reported in the liter-
ature [4b]. Compound 3b and 3c were obtained from 2b
and 2c, respectively following the same procedure
above described.
3b: (76%). Anal. Found: C, 58.65; H, 4.71.
C23H22Fe2N2O2 requires: C, 58.76; H, 4.72%. IR
(CH2Cl2) wmax (cm−1): 1982vs, 1804s (CO) and 2091m
(CN). 1H-NMR (CDCl3): l 7.33–7.28 (3 H, m,
Me2C6H3), 5.07, 4.88 (5 H, s, Cp), 4.55, 4.46, (3 H, s,
NMe), 4.20, 4.31 (5 H, s, Cp) and 2.65, 2.54, 2.45, 2.42
(6 H, s, Me2C6H3). 13C-NMR (CDCl3): l 339.0 (m-C),
262.7 (m-CO), 211.8 (CO), 149.1–129.0 (CN and
Me2C6H3), 90.7, 89.3, 91.3, 89.9 (Cp), 54.8 (NMe) and
18.7, 18.4 (Me2C6H3).
1
(CO) and 1584m (CN). H-NMR (CDCl3): l 4.98 (5 H,
s, Cp), 4.86 (5 H, s, Cp), 4.66 (3 H, s, NMe), 4.31 (3 H,
s, NMe) and 1.92 (3 H, s, NCMe). 13C-NMR (CD2Cl2):
l 330.4 (m-C), 266.2 (m-CO), 211.2 (CO), 130.7
(MeCN), 88.7, 87.0 (Cp), 53.2 (NMe, the other NMe
resonance is obscured by the solvent) and 4.4 (MeCN).
3.3. Synthesis of [Fe2{v-CN(Me)Me2C6H3}(v-CO)-
(NCMe)(CO)(Cp)2]SO3CF3 (2b) and [Fe2{v-CN-
(Me)CH2Ph}(v-CO)(NCMe)(CO)(Cp)2]SO3CF3 (2c)
Complexes 2b–c were prepared following the same
procedure described for the synthesis of 2a by treat-
ment of 1b and 1c with Me3NO in MeCN, respectively.
2b: (92%). Anal. Found: C, 47.18; H, 3.94.
C25H25F3Fe2N2O5S requires: C, 47.34; H, 3.97%. IR
(CH2Cl2) wmax (cm−1): 1988vs, 1820s (CO) and 1523m
(CN). 1H-NMR (CDCl3): l 7.42–7.02 (3 H, m,
Me2C6H3), 5.11, 5.00 (5 H, s, Cp), 4.81 (3 H, s, NMe),
4.46, 4.32 (5 H, s, Cp), 2.69, 2.13 (6 H, s, Me2C6H3) and
2.01 (3 H, s, NCMe). 13C-NMR (CDCl3): l 338.9 (m-C),
265.0 (m-CO), 212.1 (CO), 148.5–128.9 (MeCN and
Me2C6H3), 88.4, 88.1 (Cp), 54.8 (NMe), 19.5, 18.1
(Me2C6H3), and 4.8 (MeCN).
3c: (79%). Anal. Found: C, 57.90; H, 4.44.
C22H20Fe2N2O2 requires: C, 57.93; H, 4.42%. IR
(CH2Cl2) wmax (cm−1): 1980vs, 1806s (CO) and 2092m
1
(CN). H-NMR (CDCl3): l 7.61–7.42 (5 H, m, Ph),
6.06 (1H, d JAB=15 Hz, CH2Ph), 5.61 (1H, d JAB=15
Hz, CH2Ph), 4.87 (5 H, s, Cp), 4.72 (5 H, s, Cp), 3.95
(3 H, s, NMe); b isomer: 7.61–7.42 (5 H, m, Ph), 5.80
(1H, d JAB=15 Hz, CH2Ph), 5.54 (1H, d JAB=15 Hz,
CH2Ph), 4.83 (5 H, s, Cp), 4.78 (5 H, s, Cp), 4.11 (3 H,
s, NMe), a/b ratio 0.9.
2c: (95%). Anal. Found: C, 46.44; H, 3.76.
C24H23F3Fe2N2O5S requires: C, 46.47; H, 3.74%. IR
(CH2Cl2) wmax (cm−1): 1987vs and 1820s (CO) and
1566m (CN). 1H-NMR (CDCl3): l (a isomer) 7.45–
7.39 (m, C6H5), 6.37 (1 H, d, J=15 Hz, CH2Ph), 6.21
(1 H, d, J=15 Hz, CH2Ph), 5.04 (5 H, s, Cp), 4.81 (5
H, s, Cp), 4.13 (3 H, s, NMe), 1.83 (3 H, s, NCMe);
(b-isomer) 7.45–7.39 (m, C6H5), 5.89 (1 H, d, J=15
Hz, CH2Ph), 5.74 (1 H, d, J=15 Hz, CH2Ph), 4.96 (5
H, s, Cp), 4.90 (5 H, s, Cp), 4.40 (3 H, s, NMe) and
1.88 (3 H, s, NCMe); a/b isomer ratio 0.8. 13C-NMR
(CDCl3): l 333.4 (m-C), 266.4, 266.2 (m-CO), 212.0,
211.5 (CO), 135.6–127.4 (MeCN and Me2C6H3), 88.4,
88.1, 89.1, 87.5 (Cp), 71.3, 70.9 (CH2Ph), 51.4, 50.5
3.5. Synthesis of [Fe2(v-CNMe2)(v-CO)(CO)(Cl)(Cp)2]
(4a) and [Fe2{v-CN(Me)Me2C6H3}(v-CO)-
(Cl)(CO)(Cp)2] (4b)
A solution of 2a (151 mg, 0.28 mmol) in CH2Cl2 (8
ml) was treated with NBu4Cl (83 mg, 0.30 mmol). The
mixture was stirred for 180 min and the solvent was
then removed under reduced pressure. Chromatography
of the residue on an alumina column, with 1:1 (v/v)
CH2Cl2–petroleum ether (b.p. 40–60°C) as eluent, gave
a brown band which was collected and crystallized
from CH2Cl2–n-pentane mixture yielding 4a (45 mg
41%). Anal. Found: C, 46.10; H, 4.16. C15H16ClFe2NO2

V.G. Albano et al. / Journal of Organometallic Chemistry 606 (2000) 163–168
167
Table 1
50.75; H, 4.78. C15H17Fe2NO2 requires: C, 50.70; H,
Crystal data and experimental details for [Fe2(m-CNMe2)(m-
H)(CO)2(Cp)2] (5a)
4.83%. IR (CH2Cl2) wmax (cm−1): 1935s and 1891w
1
(CO). H-NMR (CDCl3): l 4.64 (10 H, s, Cp), 4.09 (6
H, s, NMe2) and −17.75 (1 H, s, m-H). 13C-NMR
(CD3CN): l 338.4 (m-CNMe2), 217.2 (CO), 81.4 (Cp),
and 51.1 (NMe2).
Formula
M
Temperature (K)
Wavelength (A)
Crystal symmetry
Space group
C15H17Fe2NO2
355.00
293(2)
,
0.71069
Compound 5b was obtained from 2b and NaBH4
following the same procedure described for the synthe-
sis of 5a.
Orthorhombic
P212121 (no. 19)
8.000(2)
,
a (A)
,
b (A)
8.810(3)
5b: (69%). Anal. Found: C, 59.34; H, 5.13.
C22H23Fe2NO2 requires: C, 59.36; H, 5.21%. IR
,
c (A)
20.531(7)
1447.0(8)
4
1.630
2.003
3
,
Cell volume (A )
Z
1
(CH2Cl2) wmax (cm−1): 1940s and 1901s (CO). H-NMR
(CDCl3): l 7.20–6.90 (3 H, m, Me2C6H3), 4.64, 4.61 (5
H, s, Cp), 4.10, 4.07 (5 H, s, Cp) 4.26 (3 H, s, NMe),
2.47, 2.32, 2.27, 2.15 (6 H, s, Me2C6H3), and −16.72,
−17.71, (1 H, s, m-H); signals due to the trans isomer
are italicized (cis/trans isomers ratio 1.4). lC (CDCl3),
cis isomer: 327.8 (m-C), 218.9, 216.9 (CO), 135.1–128.0
(Me2C6H3), 82.8, 81.4 (Cp), 53.1 (NMe) and 18.8, 18.2
(Me2C6H3); trans isomer: 217.8, 217.7 (CO), 82.3, 82.0
(Cp), 18.8, 18.2 (Me2C6H3).
Dcalc (Mg m−3
)
v(MoꢀKa) (mm−1
F(000)
)
728
Crystal size (mm)
q Range (°)
Scan mode
0.15×0.20×0.27
2.5–30
ꢀ
Reflections collected
4561 (9h, +k, +l)
3226
1.031
0.0284, 0.0687
0.03(2)
a=0.0445,
b=0.0381 b
0.31 and −0.39
Unique observed reflections [I\2|(I)]
Goodness of fit on F2
R1 (F)a, wR2 (F2)b
Absolute structure parameter
Weighting scheme
−3
3.7. Synthesis of [Ru2(v-CNMe2)(v-H)(CO)2(Cp)2] (6)
,
Largest difference peak and hole (e A
)
a R1=SꢀꢀFoꢀ−ꢀFcꢀ/SꢀFoꢀ.
A
solution of [Ru2(m-CNMe2)(m-CO)(CO)2(Cp)2]-
b wR2=[Sw(F2o−F2c)2/Sw(Fo2)2]1/2 where w=1/[|2(F2o)+(aP)2+
bP] where P=(F2o+2Fc2)/3.
SO3CF3 (150 mg, 0.24 mmol) in MeCN (10 ml) was
treated with anhydrous Me3NO (21 mg, 0.28 mmol).
The mixture was stirred for 30 min then filtered on a
Celite pad. Removal of the solvent gave a brown oily
residue of [Ru2(m-CNMe2)(m-CO)(CO)(NCMe)(Cp)2]-
SO3CF3 (2d), showing the following spectroscopic data:
IR (CH3CN) wmax (cm−1): 1979vs and 1812s (CO).
1H-NMR (CD3CN): l 5.43 (5 H, s, Cp), 5.20 (5 H, s,
Cp) 3.99 (3 H, s, NMe), 3.92 (3 H, s, NMe). Compound
2d was redissolved in NCMe and treated with NaBH4
(18 mg, 0.47 mmol). The reaction mixture was allowed
to stir for an additional 90 min, then filtered on alu-
mina. Crystallization from CH2Cl2 layered with Et2O at
−20°C yielded 6 (61 mg, 57%). Anal. Found: C, 40.44;
H, 3.86. C15H17NO2Ru2 requires: C, 40.44; H, 3.85%.
IR (CH2Cl2) wmax (cm−1): 1943m and 1907vs (CO).
1H-NMR (CDCl3): l 5.06, 5.02 (10 H, s, Cp), 3.89, 3.86
(6 H, s, NMe2) and −13.29, −13.54 (1 H, s, m-H);
signals due to the cis isomer are italicized (cis/trans
isomer ratio 0.4).
requires: C, 46.26; H, 4.14%. IR (CH2Cl2) wmax (cm−1):
1
1980vs, 1801s (CO). H-NMR (CDCl3): l 4.75 (5 H, s,
Cp), 4.71 (3 H, s, NMe), 4.65 (5 H, s, Cp) and 4.26 (3
H, s, NMe).
Compound 4b was obtained from 2b and NBu4Cl
with the same procedure described for the synthesis of
4a.
4b: (61%). Anal. Found: C, 55.27; H, 4.46.
C22H22ClFe2NO2 requires: C, 55.10; H, 4.62%. IR
(CH2Cl2) wmax (cm−1): 1980vs and 1799s (CO). 1H-
NMR (CDCl3): l 7.35–7.15 (3 H, m, Me2C6H3), 4.85 (3
H, s, NMe), 4.72 (5 H, s, Cp), 4.29 (5 H, s, Cp) and
2.69, 2.13 (6 H, s, Me2C6H3). 13C-NMR (CDCl3): l
343.3 (m-C), 269.0 (m-CO), 213.8 (CO), 148.8–128.9
(Me2C6H3), 87.6, 86.9 (Cp), 54.8 (NMe) and 18.7, 17.6
(Me2C6H3).
3.6. Synthesis of [Fe2(v-CNMe2)(v-H)(CO)2(Cp)2] (5a)
and [Fe2{v-CN(Me)Me2C6H3}(v-H)(CO)2(Cp)2] (5b)
3.8. X-ray crystallographic study of 5a
Complex 2a (160 mg, 0.31 mmol) was stirred with
NaBH4 (15 mg, 0.4 mmol) in MeCN (8 ml) for about
30 min. Removal of the solvent and chromatography
on an alumina column, with 2:1 Et2O–MeCN (v/v) as
eluent, gave a red–orange band which was collected.
Dark-brown crystals of 5a were obtained upon slow
solvent evaporation (70 mg, 64%). Anal. Found: C,
Crystal data and details of the data collection for
[Fe2(m-CNMe2)(m-H)(CO)2(Cp)2] (5a) are given in Table
1. The diffraction experiments were carried out at room
temperature on a fully automated Enraf–Nonius CAD-
4
diffractometer using graphite-monochromated
MoꢀKa radiation. The unit cell parameters were deter-

168
V.G. Albano et al. / Journal of Organometallic Chemistry 606 (2000) 163–168
mined by a least-squares fitting procedure using 25
reflections. Data were corrected for Lorentz and polar-
ization effects. No decay correction was necessary. The
compound crystallized as a racemic conglomerate of
chiral crystals in the space group P212121 and the
absolute configuration of the specimen under investiga-
tion was determined (absolute structure parameter
0.03(2)). The positions of the metal atoms were found by
direct methods using the SHELXS-86 program [14] and all
the non-hydrogen atoms located in electron density
maps. As usual the C5H5 rings were treated as rigid
strategies for the control of reactions: interactions
of molecular fragments with metallic sites in un-
conventional species’) and the University of Bologna
(‘Funds for Selected Research Topics’) for financial
support.
References
[1] (a) V.G. Albano, L. Busetto, C. Camiletti, C. Castellari, M.
Monari, V. Zanotti, J. Chem. Soc. Dalton Trans. (1997) 4671.
(b) V.G. Albano, L. Busetto, C. Camiletti, M. Monari, V.
Zanotti, J. Organomet. Chem. 563 (1998) 153.
,
groups (CꢀC 1.42 A) because they do not contain
information of chemical relevance and both the methyl
and cyclopentadienyl hydrogen atoms were located in
successive Fourier-difference maps but added in calcu-
lated positions. The hydride was located in the Fourier
map and refined with isotropic thermal factor and the
constraint of equal FeꢀH distance. The C5H5 group on
the right of Fig. 1 [C(21)ꢀC(25)] is affected by a higher
thermal motion while the facing methyl group [C(2)]
shows some evidence of a second orientation around the
NꢀC axis (occupation ca. 0.33) almost staggered with
respect to the main image. The final refinement on F2
proceeded by full-matrix least-squares calculations
[2] (a) V. Zanotti, S. Bordoni, L. Busetto, L. Carlucci, A. Palazzi,
R. Serra, V.G. Albano, M. Monari, F. Prestopino, F. Laschi,
P. Zanello, Organometallics 14 (1995) 5232. (b) V.G. Albano,
L. Busetto, L. Carlucci, M.C. Cassani, M. Monari, V. Zanotti,
J. Organomet. Chem. 488 (1995) 133.
[3] (a) N.M. Doherty, J.A.K. Howard, S.A.R. Knox, N.J. Terril,
M.I. Yates, J. Chem. Soc. Chem. Commun. (1989) 638. (b) M.
Akita, R. Hua, S.A.R. Knox, Y. Moro-oka, S. Nakanishi,
M.I. Yates, J. Organomet. Chem. 569 (1998) 71 and references
therein. (c) M. Akita, R. Hua, S. Nakanishi, M. Tanaka, Y.
Moro-oka, Organometallics 16 (1997) 5572.
[4] (a) G. Cox, C. Dowling, A.R. Manning, P. McArdle, D. Cun-
ningham, J. Organomet. Chem. 438 (1992) 143. (b) K. Boss,
C. Dowling, A.R. Manning, J. Organomet. Chem. 509 (1996)
197.
[5] V.G. Albano, S. Bordoni, L. Busetto, C. Camiletti, M. Mon-
ari, A. Palazzi, F. Prestopino, V. Zanotti, J. Chem. Soc. Dal-
ton Trans. (1997) 4665.
(SHELXL-93) [15] using anisotropic thermal parameters
for all non-hydrogen atoms. The methyl and cyclopenta-
dienyl hydrogen atoms were assigned isotropic thermal
parameters 1.2 times Ueq of the pertinent carbon atoms.
[6] V.G. Albano, L. Busetto, C. Castellari, M. Monari, A.
Palazzi, V. Zanotti, J. Chem. Soc. Dalton Trans. (1993) 3661.
[7] F.H. Herbstein, Acta Crystallogr. Sect. B 37 (1981) 339.
[8] (a) D.S. Moore, S.D. Robinson, Chem. Soc. Rev. (1983) 415.
(b) G.G. Hlatki, R.H. Crabtree, Coord. Chem. Rev. 43 (1982)
251.
[9] R.G. Hayter, J. Am. Chem. Soc. 85 (1963) 3120.
[10] H.G. Raubenhaimer, F. Scott, S. Cronje, P.H. van Rooyen, J.
Chem. Soc. Dalton Trans. (1992) 1859.
[11] G. Hogarth, M.H. Lavender, J. Chem. Soc. Dalton Trans.
(1992) 2759.
[12] J. Boothman, G. Hogarth, J. Organomet. Chem. 437 (1992)
201.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 141113. Copies of this informa-
tion may be obtained free of charge from: The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(Fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.ac.
uk or www: http://www.ccdc.cam.ac.uk).
[13] L. Busetto, L. Carlucci, V. Zanotti, V.G. Albano, M Monari,
J. Organomet. Chem. 447 (1993) 271.
[14] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure So-
lution, University of Go¨ttingen, Germany, 1986
Acknowledgements
We thank the Ministero dell’Universita’ e della Ricerca
Scientifica e Tecnologica (M.U.R.S.T.) (project: ‘New
[15] G.M. Sheldrick, SHELXL-93, Program for Crystal Structure
Refinement, University of Go¨ttingen, Germany, 1993
.