Studies of metal exchange reactions: The synthesis and structures of heteronuclear metal clusters containing the indenyl ligand (μ3-CR) Co2M(CO)8 (η5-Ind)(R=H,CH3,C6H5, COOC

Article abstract of DOI:10.1016/j.jorganchem.2003.11.028

The novel tetrahedral clusters (μ₃-CR)Co₂M(CO) ₈(η⁵-Ind) (M=Mo,W; R=H, CH₃, C₆H₅, COOC₂H₅) 5-1 containing the indenyl ligand were isolated from reactions of

Full text of DOI:10.1016/j.jorganchem.2003.11.028

Journal of Organometallic Chemistry 689 (2004) 714–721
www.elsevier.com/locate/jorganchem
Studies of metal exchange reactions: the synthesis and structures
of heteronuclear metal clusters containing the indenyl ligand (l3-CR)
Co2M(CO)8(g5- Ind)(R ¼ H,CH3,C6H5,COOC2H5; M ¼ Mo,W)
a,
a
a
a
Wei-Qiang Zhang *, Bao-Hua Zhu , Bin Hu , Yu-Hua Zhang ,
a
Quan-Yi Zhao , Yuan-Qi Yin
a,b,
b
*, Jie Sun
a
State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics,
Chinese Academy of Sciences, Lanzhou 730000, PR China
b
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, PR China
Received 26 July 2003; accepted 7 November 2003
Abstract
The novel tetrahedral clusters (l3-CR)Co2M(CO)8(g5-Ind) (M ¼ Mo,W; R ¼ H, CH3, C6H5, COOC2H5) 5–12 containing the
indenyl ligand were isolated from reactions of tricobalt clusters (l3-CR)Co3(CO)9 (R ¼ H, CH3, C6H5, COOC2H5) and
K(g5-Ind)M(CO)3 (M ¼ Mo,W) under mild conditions. The cluster complex (l3-CC6H5)CoMo2(CO)7(g5-Ind)(g5-Cp
(Cp* ¼ C5H4C(O)CH3) 16 was obtained via the stepwise metal exchange reaction of complex (l3-CC6H5)Co2Mo(CO)8(g5-Ind) 9
with Na(g5-CpMo(CO)3, but the reaction of (l3-CC6H5)Co2Mo(CO)8(g5-Cp*) 15 with K(g5-Ind)Mo(CO)3 yielded only 9. The
crystal structures of compounds 7, 9 and 13 were established by single crystal X-ray diffraction methods and show structural ev-
idence for ‘‘slippage’’ of the indenyl ring.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Tetrahedral cluster; Metal exchange reaction; Ring slippage
1. Introduction
[13], ClM(CO)3Cp [14,15] and NaCpM(CO)3 [6–18]
M ¼ Cr,Mo,W) are excellent precursors for chiral tet-
rahedral-type cluster complexes. However, complexes
containing the indenyl ligand (Ind), in place of the cy-
clopentadienyl (Cp) ligand, have rarely been introduced
into the tetrahedral skeleton by the metal exchange re-
action to date [19].
It is well established that the reactivity of the com-
plexes containing the cyclopentadienyl ligand can be
modified by the use of Ôsubstituted Cp ligandsÕ by using
R groups with different steric and electronic properties.
In this respect, the indenyl ligand (Ind ¼ C9H7) provides
a most interesting opportunity because Rerek and Ba-
solo [20] showed that it can accelerate some substitution
reactions by a factor up to 108 relative to the analogous
complexes containing cyclopentadienyl ligand. This so
called Ôindenyl effectÕ [21–24] suggested to us the possi-
bility of enhancing the reactivity of metal cluster
complexes by introducing indenyl ligands into them. In
order to explore the generality of the synthesis of
Applications of cluster complexes in catalysis has
stimulated great interest in the preparation and prop-
erties of heteronuclear clusters [1–5]. We are interested
in cluster complexes containing a chiral tetrahedral
skeleton because evidence for asymmetric induction by
cluster-catalyzed reactions would provide definitively
the proof that the clusters do not fragment during ca-
talysis [4]. Following the pioneering methods of Vah-
renkamp [6] and Stone [7], the metal exchange reaction
is now the relatively straightforward method for pre-
paring chiral clusters containing a tetrahedral skeleton.
The alkylidyne clusters Co2M(l3-CR) (M ¼ Cr,Mo,W)
synthesized by metal exchange reactions with (l3-CR)
Co3(CO)9 by using various neutral or anionic exchange
reagents such as, Me2AsM (CO)3Cp [8–12], [M(CO)3Cp]2
* Corresponding author. Tel.: 869318277623; fax: 869318277088.
E-mail address: zwqlz@yahoo.com (W.-Q. Zhang).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.11.028

W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
715
complexes containing
a
indenyl ligand by metal
separated by column chromatography on silica gel. Af-
ter a small brown band was eluted with petroleum ether,
petroleum ether/CH2Cl2 (3:1) afforded the main light
green band and a trace of red band. After concentrating
the solvent and crystallization from CH2Cl2–hexane at
)20 °C, the cluster 5 (170 mg, 31% based on cluster 1)
was obtained as black crystals with a byproduct [(g5-
Ind)Mo (CO)3]2 as dark brown solid.
exchange, we recently initiated a study based on the re-
actions of cluster complexes (l3-CR)Co3(CO)9 (1, R ¼ H;
2, R ¼ CH3; 3, R ¼ C6H5; 4, R ¼ COOC2H5) with K(g5-
Ind)M(CO)3 (M ¼ Mo,W). Herein, we report the results
obtained from this study, namely the synthesis and
characterization of the alkylidyne Co2M (M ¼ Mo,W)
cluster complexes containing indenyl ligand (l3-
CR)Co2M(CO)8(g5-Ind) (5–12, M ¼ Mo, W; R ¼ H,
CH3, C6H5, COOC2H5), (l3-CC6H5)CoMo2(CO)7(g5-
Ind)(g5-C5H4C(O)CH3) 16, including the crystal struc-
tures of the compounds 7, 9 and 13 determined by X-ray
diffraction analysis.
For 5. Anal. Found: C,38.18; H,1.45. Calc. for
C24H12O8Co2Mo: C, 38.04; H, 1.42%. IR: m(CO) 2077–
1986 s, 1928 s, 1887 s cmꢀ1; (C9H7) 829 m, 749 m cmꢀ1
.
1H NMR: d 5.61 (s, 1H, C9H7), 6.01 (s, 2H, C9H7), 7.33
(br, 4H, C9H7), 9.88 (s, 1H, lH). For 13. Anal. Found:
C, 48.25; H,2.39. Calc. for C24H14O6Mo2: C, 48.49; H,
2. Experimental
2.38%. IR: m(CO) 2020 w, 1957 s, 1910 s cmꢀ1 1H
.
NMR: d 4.30 (s, 2H, C9H7), 4.65 (s, 4H, C9H7), 6.58,
7.32 (m, 8H, C9H7).
2.1. General information
Compounds 6–12 were prepared similarly.
All reactions were carried out under pure nitrogen
using standard Schlenk techniques. All solvents were
dried and deoxygenated according to standard proce-
dures before use. Chromatographic separations were
performed on 160/200 mesh silica gel. Infrared spectra
were recorded as pressed KBr disks on a Nicolet FTIR
10 DX spectrometer. 1H NMR spectra were recorded on
a Bruker AM-400 MHz spectrometer in CDCl3-deuter-
ated solvent at ambient temperature. Chemical shifts are
given in relative to SiMe4 (0.0 ppm). Elemental analyses
were performed on an 1106-type analyzer. The com-
pounds (l3-CR)Co3(CO)9 (1, R ¼ H; 2, R ¼ CH3; 3,
R ¼ C6H5; 4, R ¼ COOC2H5) [25], (l3-CC6H5)Co2
Mo(CO)8[g5-CpC(O)CH3] [26], Na[CpC(O)CH3] [27],
were prepared according to literature methods.
For (l3-CH)Co2W(CO)8(g5-Ind) (6): A black solid
(150 mg, 24%) and complex 14 as a brown solid. For 6:
Anal. found: C, 33.21; H, 1.18. Calc. for C18H8O8Co2W:
C, 33.04; H, 1.23%. IR: m(CO) 2079–1985 s, 1921 s, 1876
1
s cmꢀ1, (C9H7) 835 m, 750 s cmꢀ1. H NMR d: 5.61 (s,
1H, C9H7), 6.02 (s, 2H, C9H7), 7.33 (br, 4H, C9H7),
10.41(s, 1H, lH). For 14. Anal. found: C, 37.45; H, 1.81;
Calc. for C24H14O6 W2: C, 37.60; H, 1.84%. IR: m(CO)
1
2018 w, 1955 s, 1905 s cmꢀ1. H NMR: d 5.39 (s, 2H,
C9H7), 5.73(s, 4H, C9H7), 7.05,7.46 (m, 8H, C9H7).
For (l3-CCH3)Co2Mo(CO)8(g5-Ind) (7): A black
solid (470 mg, 82%); Anal. found: C, 39.01; H, 1.65.
Calc. for C19H10O8Co2Mo: C, 39.19; H, 1.73%. IR:
m(CO) 2060–1999 s, 1975 s, 1931 s cmꢀ1; (C9H7) 825 m,
1
749 s cmꢀ1. H NMR: d 3.60 (s, 3H, CH3), 5.35 (s, 1H,
C9H7), 5.81 (s, 2H, C9H7), 7.20, 7.52 (br, 4H, C9H7).
For (l3-CCH3)Co2W(CO)8(g5-Ind) (8): A black solid
(480 mg, 73%); Anal. found: C, 33.95; H, 1.47. Calc. for
C19H10O8Co2W: C, 34.14; H, 1.51%. IR: m(CO) 2060–
2.2. Synthesis of complexes 1 and 2
Indene (1.2 mL, 10 mmol) was added dropwise by
syringe to a sample of the potassium sand (390 mg, 10
mmol) dispersed in DME (1,2-dimethoxyethane) (20
mL). The mixture was stirred at 0 °C for 0.5 h, and
turned to bright-yellow during this time. After stirring
for an additional 0.5 h M(CO)6 (10 mmol) (M ¼ Mo
or W) was added while warming to room temperature.
This mixture was then refluxed under nitrogen for 12 h.
A red solution containing K(g5-Ind)M(CO)3 (0.5mol/
mL) (M ¼ Mo,W) was obtained and placed in cold
storage for future use.
2001 s, 1975 s, 1930 s cmꢀ1; (C9H7) 831 m, 750 s cmꢀ1
.
1H NMR: d 3.67 (s, 3H, CH3), 5.36 (s, 1H, C9H7), 5.89
(s, 2H, C9H7), 7.18, 7.49 (br, 4H, C9H7).
For (l3-CC6H5)Co2Mo(CO)8(g5-Ind) (9): Black
crystals (450 mg, 70%). Anal. Found: C, 44.90; H, 1.93.
Calc. for C24H12O8Co2Mo: C, 44.73; H, 1.88%. IR: m(CO)
2078–2005 s, 1921 s, 1873 s cmꢀ1; (C9H7) 817 m, 750 s
cmꢀ1. 1H NMR: d 5.50 (s, 2H, C9H7), 5.63 (s, 1H, C9 H7),
6.93, 7.19 (br, 5H, C6H5), 7.18, 7.31 (br, 4H, C9H7).
For (l3-CC6H5)Co2W(CO)8(g5-Ind) (10): A black
solid (0.540 mg, 75%); Anal. found: C, 39.23; H, 1.60.
Calc. for C24H12O8 Co2W: C, 39.46; H, 1.66%. IR:
m(CO) 2078–2005 s, 1921 s, 1873 s cmꢀ1; (C9H7) 817 m,
2.3. Synthesis of (l3-CH)Co2Mo(CO)8(g5-Ind) (cluster
5)
1
750 s cmꢀ1. H NMR: d 5.48 (s,2H, C9H7), 5.70 (s, 1H,
K(g5-Ind)Mo(CO)3 (2 mL, 1 mmol) in a DME so-
lution was added by syringe to a sample of (l3-
CH)Co3(CO)9 (440 mg, 1 mmol) dissolved in THF(20
mL). The resulting mixture was stirred for 15 min and
the solvent was then removed in vacuo. The residue was
C9H7), 6.88, 7.07 (br, 5H, C6H5), 7.17, 7.29 (br, 4H,
C9H7).
For (l3-CCOOC2H5)Co2MoInd(CO)8(g5-Ind) (11):
A black solid (300 mg,46%); Anal. found: C, 39.15; H
1.84. Calc. for C21H12O10 Co2Mo: C, 39.39; H, 1.89%.

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W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
IR: m(CO) 2081–2003 s, 1921 s, 1873 s cmꢀ1; m(C@O)
CC6H5)Co2Mo(CO)8 (g5-Ind) (320 mg, 0.5 mmol) was
then added and to the mixture and stirred for an addi-
tional 4 h at 60 °C. The solvent was removed under
vacuum. The chromatographic workup (petroleum
ether/CH2Cl2/ether ¼ 4:1:1) gave two green fractions.
The complexes obtained from the two green fractions
were identified as starting material cluster 9 and product
16. Compound 16 was recrystallized from hexane/ben-
zene at )20 °C to give a black crystalline product (120
mg, 33%). Anal. found: C, 47.39; H, 2.48. Calc. for
C30H19 O8CoMo2: C, 47.25; H, 2.51%. IR: m(CO) 2084
s, 2031 s, 1998 s, 1923 s, 1874 s cmꢀ1; m(C@)O) 1684 s
1
1674 s cmꢀ1; (C9H7) 823 m, 752 m cmꢀ1. H NMR: d
1.39 (s, 3H, CH3), 4.38 (s, 2H, CH2), 5.63 (s, 1H, C9H7),
5.84 (s, 2H, C9H7), 7.18, 7.49 (br, 4H, C9H7).
For (l3-CCOOC2H5)Co2W(CO)8(g5-Ind) (12): A
black solid (370 mg, 51%); Anal. found: C, 34.52; H,
1.68. Calc. for C21H12O10Co2W: C, 34.72; H, 1.67%. IR:
m(CO) 2081–2001 s, 1925 s, 1880 s cmꢀ1; m(C@O) 1656 s
1
cmꢀ1; (C9H7) 840 m, 754 m cmꢀ1. H NMR: d 1.36 (s,
3H, CH3), 4.35 (s, 2H, CH2), 5.74 (br, 1H, C9H7), 5.91
(s, 2H, C9H7), 7.18, 7.49 (br, 4H, C9H7).
1
2.4. Metal exchange reactions of (l3-CC6H5)Co3(CO)9
using K(g5-Ind)Mo(CO)3, Na(g5-Cp)Mo(CO)3 and
Na(g5-CpMo(CO)3(Cp* ¼ C5H4C(O)CH3)
cmꢀ1; (C9H7) 804 m, 749 w cmꢀ1. H NMR: d 2.35 (s,
3H, C(O)CH3), 5.64, 5.51, 5.30 (s, 3H, C9H7), 5.15, 5.78
(br, 4H, C5H4), 6.90, 7.22 (br, 5H, C6H5), 7.16, 7.35 (br,
4H, C9H7).
The metal exchange reagent was synthesized by using
appropriate amounts of NaCp, Na[C5H4C(O)CH3],
KInd, with Mo(CO)6 (in order to realize a 0.5 mmol/mL
DME solution) with refluxing overnight, respectively.
To a 10 mL THF solution of (l3-CC6H5)Co3(CO)9 3
(260 mg, 0.5 mmol), was added a solution containing the
metal exchange reagent (1 mL, 0.5 mmol) by syringe.
The mixture was stirred under room temperature and
reaction progress was monitored by TLC.
2.7. Crystallographic analyses
Crystals of 7, 9, 13 were grown by diffusion of a
CH2Cl2 solution of the compounds into pentane at )20
°C. The data crystals were mounted on glass fibers.
Preliminary examination and data collection were per-
ꢀ
formed with Mo Ka (k ¼ 0:71073 A) radiation on a
CCD area detector equipped with graphite monochro-
mator. Data were collected by the x=u scan technique.
Absorption corrections were applied by using SADABS.
The structures were solved by direct method using the
SHELXS 97 program and refined by the full-matrix
least-squares on F 2 by using the SHELXS 97 program.
The non-hydrogen atoms were refined anisotropically.
Hydrogen positions were calculated by using idealized
geometries. The geometrical aspects of the structures
were analyzed by using the PLATON program [28].
2.5. Synthesis of (l3-C6H5)Co2Mo(CO)8(g5-Ind) (clus-
ter 9) (pathway 1)
To
a
sample of (l3-CC6H5) Co2Mo(CO)8[g5-
CpC(O)CH3] (15) (310 mg, 0.5 mmol) dissolved in THF
(20 mL), was added a DME solution containing K(g5-
Ind)Mo(CO)3 (1 mL, 0.5 mol) by syringe. The reaction
was monitored by TLC. The reaction mixture was stir-
red for 2 h at reflux. The solvent was then removed in
vacuo, and the residue was separated by column chro-
matography on silica gel. Chromatographic workup
(petroleum ether/ether/CH2Cl2 ¼ 4:1:1) gave two green
and one red fractions. The complexes obtained from the
two green fractions were identified as the starting ma-
terial 15 and complex 9 (l3-CC6H5)Co2Mo(CO)8 (g5-
Ind). Complex 9 was recrystallized from hexane/CH2Cl2
at )20 °C to give a black crystalline product (150 mg,
47%). Cluster 15. Anal. found: C, 41.63; H, 1.691. Calc.
for C30H19O8CoMo2: C, 41.64; H 1.89%. IR: m(CO)
2069 s, 2019 s, 2008 s, 1992 s, 1973 s cmꢀ1; m(C@O) 1685
3. Results and discussion
3.1. Synthesis and characterization of 5–12 and 16
All of the reactions are summarized in Scheme 1. The
cluster complexes 5–12 were obtained by the displace-
ment of a Co(CO)3 (d9ML3) vertex by using the isolobal
fragments (g5-Ind)M(CO)2 (M ¼ Mo,W) (d5ML5). The
reactions of K(g5-Ind)M(CO)3 (M ¼ Mo,W) with the
alkylidyne tricobalt clusters 1–4 proceed at the room
temperature in moderate yields 50–80%. The byproducts
[(g5-Ind)M(CO)3]2(M ¼ 13, Mo; 14, W) were also fully
characterized. It is found that the substitution at the
apical carbon plays an important role on the metal ex-
change reaction process. When it is a methyl or phenyl
group that is inert to the basicity of K(g5-Ind)M(CO)3
(M ¼ Mo,W), then the reaction follows a simple route
and the products are the corresponding clusters 7–10
and the red by-product [(g5-Ind)M(CO)3]2(M ¼ Mo,W)
in order of elution in the chromatographic separation. If
1
s cmꢀ1. H NMR: d 2.30 (s, 3H, C(O)CH3), 5.17, 5.76
(d, 4H, C5H4), 7.16–7.26 (m, 5H, C6H5).
2.6. (l3-CC6H5)CoMo2(CO)7(g5-Ind)[g5-CpC(O)CH3]
(16) (pathway 2)
Mo(CO)6 (160 mg, 0.6 mmol) was added to a solution
of Na[CpC(O)CH3] (80 mg, 0.6 mmol) in THF (20 mL).
The mixture was heated to reflux for 12 h and then
cooled to room temperature. Cluster
9
(l3-

W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
717
R
R
THF
[IndM(CO)3]2
M Ind
KIndM(CO)3
M=Mo,W
Co
Co
Co
+
+
Co
Co
5.R=H,M=Mo
6.R=H,M=W
1.R=H,
13. M=Mo
14. M=W
2.R=CH3,
7.R=CH3,M=Mo
8.R=CH3,M=W
9.R=C6H5,M=Mo
10.R=C6H5,M=W
3.R=C6H5,
4.R=COOC2H5
11.R=COOC2H5,M=Mo
12.R=COOC2H5,M=W
Scheme 1.
the substitution is an ester group, the products including
the by-product are complicated and include the target
clusters 11 and 12 and two unidentified deep green
bands in trace amounts. Similarly, the products from the
reaction involving ClCCo3(CO)9 are too complicated to
isolate. It is worth to pointing out that if the substitutent
Na[g5-C5H4C(O)CH3]Mo(CO)3 even after stirring for
15 h. Therefore, the metal exchange reactivity of three
reagents decreases in order of K(g5-Ind)Mo(CO)3 ꢁ Na
(g5-Cp)Mo(CO)3 > Na[g5-C5H4C(O)CH3]Mo(CO)3.
In order to investigate the stepwise metal exchange
reaction, we performed the two reactions: (1) reaction of
the cluster complex 15 with K(g5-Ind)Mo(CO)3,
and (2) reaction of cluster complex 9 with Na[g5-
CpC(O)CH3]Mo(CO)3, see Scheme 2. In principle, the
target complex, 16 (l3-CC6H5)CoMo2(CO)7 (g5-
Ind)[g5-CpC(O)CH3] could be obtained by following
both pathways A and B in Scheme 2. Interestingly, in
the pathway A, the (g5-Ind)Mo(CO)2 (d5ML5) unit
displaces the isolobal unit [g5-CpC(O)CH3]Mo(CO)2
(d5ML5) instead of Co(CO)3 (d9ML3, a good leaving
group in many double exchange reactions) to give the
cluster 9. By pathway B the Co(CO)3 (d9ML3) unit is
replaced by the Mo(CO)2[g5-CpC(O)CH3] (d5ML5)
unit, which is consistent with the literature [21]. It is
believed that the metal–metal exchange reaction of the
tricobalt clusters involves fragmentation–reconstruc-
tion, addition–elimination or elimination–addition
mechanisms [29]. The leaving ability of Co(CO)3unit
and the nucleophilicity of the isolobal exchange reagent
is
a ferrocenyl group, the tricobalt cluster (l3-
CFc)Co3(CO)9 decomposes quickly at room tempera-
ture. Generally, the replacement of a cyclopentadienyl
ligand with indenyl ligand will enhance the reactivity of
the complex [21–24]. In order to investigate the reac-
tivity of indenyl metal exchange reagents, the reagents
for the indenyl exchange reactions were compared
with those obtained from the metal exchange reaction
of Na(CpMo(CO)3 (Cp* ¼ C5H5 or C5H4C(O)CH3)
with the tricobalt cluster 3 (l3-CC6H5)Co3(CO)9. We
compared the reactivity of K(g5-Ind)Mo(CO)3, Na(g5-
Cp)Mo(CO)3 and Na[g5-C5H4C(O)CH3]Mo(CO)3 to-
ward tricobalt cluster 3 in THF at room temperature.
The metal exchange reaction, monitored by the disap-
pearance of the tricobalt cluster and the formation of
heteronuclear cluster by TLC, was found require 10–
15 min for the K(g5-Ind)Mo(CO)3, 20–25 min for
Na(g5-Cp)Mo(CO)3 and no reaction was observed for
O
Ph
CH3
Ph
Mo
Mo
Co
Co
Mo Ind
Co
Mo
Cp*
Co
Ph
Co
cluster 9
Ph
cluster 15
Ph
PathwayA.
Co
Co
O
CH3
Mo
Mo
Mo Ind
Co
Mo
Ind
Co
Co
Mo
Cp*
PathwayB.
cluster 9
cluster 16
Scheme 2. Synthesis of the double exchange product (l3-CC6H5)CoMo2(CO)7(g5-Ind)[g5-CpC(O)CH3].

718
W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
is the central feature of these metal–metal exchange re-
actions [12,30–37].
All the new cluster complexes are green in solution
The aromatic protons of indenyl moiety appear as
multiplets in the range d 7.10–7.50 ppm. In addition, for
5 and 6, the H NMR spectra display one singlet at the
1
1
and black in solid state. Elemental analyses, IR and H
range of d 9.88–10.44 ppm for the proton on central
carbon atom. The H NMR spectra of 7 and 8 show a
1
NMR data for these clusters are consistent with the
corresponding structures. All the clusters exhibit a
strong infrared absorption band in the range from 2080
to 1850 cmꢀ1, assigned to terminal carbonyl ligands
coordinated to metal atoms. The absorptions at 2085–
2000 cmꢀ1 and 1980–1820 cmꢀ1 correspond to the car-
bonyl ligands on cobalt atoms and M (M ¼ Mo,W)
atoms, respectively. These characteristic carbonyl ab-
sorption bands indicate the integrity of CCo2M skele-
ton. In the IR spectrum of 16, the different composition
of cluster skeleton (CCoMo2) results in a sharp change
in the position of the carbonyl absorption band. The
vibrational absorptions of these C@O groups appear in
the range 1674–1684 cmꢀ1. Finally, the absorptions of
1
singlet at about d 3.65 ppm for methyl group. The H
NMR spectra of 9 and 10 show multiplets in the range
of d 6.90–7.38 ppm assigned to the C6H4 protons. The
1H NMR spectra of 11 and 12 show broad signals at
around d 1.39 ppm and 4.38 ppm in ratio of 3:2, re-
spectively; assigned to the protons CH3 and CH2
groups. For cluster complex 16, the proton signal of
methyl group appears as singlet at d 2.35 ppm and the
protons of substituted cyclopentadienyl ring appears as
two broad signals which overlap the signals of C9H7
protons in the range of d 5.30–5.78 ppm. It should be
noticed that AA0B type singlets of the protons in the
five-membered ring reveal that the indenyl ligand is lo-
cated in an asymmetric environment, due to the chiral
tetrahedral skeleton CCoMoIndMoCp* [19,39].
indenyl group were observed at 850 and 710 cmꢀ1
,
which is in accord with the literature [38].
1
The H NMR spectra of all complexes show the ex-
pected resonances of the hydrogen atoms on their hy-
drocarbon ligands. The three protons of the C5 ring of
the indenyl moiety of 5–12 display as two broad signals
in ratio of 2:1 in the range d 5.50–5.70 ppm. The reso-
nances (A2B type) of these protons indicate that the
indenyl ligand resides in a symmetric environment.
3.2. The X-ray structure analyses
The complexes (l3-CR)Co2Mo(CO)8(g5-Ind) (7,
R ¼ CH3 and 9, R ¼ C6H5) and [(g5-Ind)Mo(CO)3]2 13
have been characterized by single-crystal X-ray diffrac-
tion studies. The crystallographic data are collected in
Table 1
Summary of the crystallographic data for compounds 7, 9 and 13
Cluster
7
9
13
Empirical formula
Formula weight
Temperature (K)
C19H10O8Co2Mo
580.07
293(2)
C24H12O8Co2Mo
642.14
293(2)
C24H14O6Mo2
590.23
293(2)
ꢀ
Wavelength (A)
0.71073
Triclinic
0.71073
Monoclinic
P21=n
0.71073
Orthorhombic
P212121
Crystal system
Space group
Unit cell dimensions
ꢁ
P1
ꢀ
a (A)
8.7884(6)
9.4183(7)
12.4581(9)
79.969(1)
87.485(1)
87.019(1)
1013.41(13)
2
8.6335(10)
10.0038(11)
27.420(3)
90.00
7.3504(7)
14.4726(14)
19.9447(19)
90.00
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
96.304(2)
90.00
90.00
90.00
3
ꢀ
Volume (A )
2353.9(5)
4
1.812
2121.7(4)
4
1.848
Z
Density (cal.) (g/cm3)
l(Mo Ka) (mmꢀ1
F (000)
1.901
2.271
568
)
1.965
1264
1.222
1160
H range for data collection (°)
Limiting indices
1.66–28.24
ꢀ10 6 h 6 ꢀ 11
ꢀ11 6 k 6 12
ꢀ16 6 l 6 14
6219/4053[Rint ¼ 0:0613]
0.993
2.17–28.31
ꢀ11 6 h 6 10
ꢀ13 6 k 6 13
ꢀ21 6 l 6 35
13936/5464[Rint ¼ 0:1010]
0.913
2.17–28.31
ꢀ9 6 h 6 9
ꢀ19 6 k 6 12
ꢀ26 6 l 6 26
12826/4929[Rint ¼ 0:1084]
0.935
Reflections collected/unique
Goodness-of-fit on F 2
Final R indices, R1
0.0414
0.1003
0.0451
0.0976
0.0440
0.0846
wR2 [I > 2rðIÞ]
ꢀ3
ꢀ
Largest diff. peak and hole (e A
)
1.060 and ꢀ1:072
0.897 and ꢀ0:580
1.128 and ꢀ0:603
P
P
R1 ¼ jjFoj ꢀ jFcj jFoj.
P
P
2
1=2
wR2 ¼ ½ xjFoj ꢀ jFcj = xFo2ꢂ
.

W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
719
Table 1. Selected bond distances and angles are listed in
Tables 2–4. The atomic positional and thermal param-
eters for the two structures are available in the supple-
mentary material. As can be seen in Figs. 1 and 2, the
structures of 7 and 9 both contain tetrahedral CCo2Mo
cluster cores, similar to those found in other carbon
bridged compounds such as (l3-CC6H5)Co2Mo(CO)8
(g5-CpR), where R ¼ H, C(O)CH3, or COOCH3 [26,31].
Compound 7 has tetrahedral skeleton composed of C,
Mo and two Co atoms, a methyl group attached to
carbon atom C(9), two carbonyls coordinated to Mo
atom and two sets of three carbonyls attached to two Co
atoms. The indenyl ligand is connected to the cluster
skeleton through the Mo atom. The carbon atom is
bonded to the two cobalt atoms and one molybdenum
atom with bond lengths 1.911(4), 1.943(4) and 2.091(4)
ꢀ
(A), respectively. The bond angles Mo–Co–Co (62.65°,
62.13° ) in the triangular Co2Mo base are equal and are
larger than the angle Co–Mo–Co (55.20°), making it an
isosceles triangle. The average value of the Mo-C dis-
tances to the five-membered ring of the indenyl ligand is
ꢀ
2.367 A.
Table 2
ꢀ
Selected bond distances (A) and angles (°) for cluster 7
Mo–C9
Mo–C13
2.091(4)
2.304(5)
2.309(4)
2.348(4)
2.424(4)
2.450(4)
2.0411(18)
83.44(15)
45.20(10)
45.89(9)
55.208(16)
50.40(9)
50.94(10)
Mo–Ring(Ind)
Mo–Co1
Mo–Co2
2.0351(3)
2.677(1)
2.690(1)
Mo–C12
Mo–C11
Co1–C9
Co1–Co2
Co2–C9
1.911(4)
2.487(1)
1.943(4)
Mo–C14
Mo–C19
Mo–Cg(Ind)
C1–Mo–C2
C9–Mo–Co1
C9–Mo–Co2
Co1–Mo–Co2
C9–Co1–Co2
C9–Co1–Mo
Co2–Co1–Mo
C9–Co2–Co1
C9–Co2–Mo
Co1–Co2–Mo
Co1–C9–Co2
Co2–C9–Mo
Co1–C9–Mo
62.656(16)
49.24(10)
50.57(10)
62.136(16)
80.36(14)
83.54(14)
83.84(14)
Table 3
ꢀ
Selected bond distances (A) and angles (°) for cluster 9
Mo–C18
Mo–C11
2.086(4)
2.305(7)
2.309(5)
2.349(5)
2.399(4)
2.439(5)
2.0411(18)
82.2(2)
Mo-Ring(Ind)
Mo–Co1
Mo–Co2
2.0351(3)
2.721(1)
2.725(1)
1.928(4)
2.502(2)
1.935(3)
62.74(2)
49.51(10)
49.72(9)
62.56(2)
80.73(14)
85.25(13)
85.24(12)
Mo–C12
Mo–C10
Co1–C18
Co1–Co2
Co2–C18
Mo–C13
Mo–C9
Fig. 1. The molecular structure of 7 showing 50% probability thermal
ellipsoids.
Mo–Cg(Ind)
C1–Mo–C2
C18–Mo–Co1
C18–Mo–Co2
Co1–Mo–Co2
C18–Co1–Co2
C18–Co1–Mo
Co2–Co1–Mo
C18–Co2–Co1
C18–Co2–Mo
Co1–Co2–Mo
Co1–C18–Co2
Co1–C18–Mo
Co2–C18–Mo
44.92(9)
45.04(9)
54.69(2)
49.76(11)
49.83(10)
Table 4
ꢀ
Selected bond distances (A) and angles (°) for complex 13
Mo1–C4
Mo1–C5
2.297(6)
2.341(6)
Mo2–C16
Mo2–C17
2.316(6)
2.334(6)
Mo1–C6
Mo1–C12
Mo1–C7
2.365(6)
2.382(6)
Mo2–C18
Mo2–C24
Mo2–C19
2.375(6)
2.383(6)
2.439(5)
2.426(5)
2.0280
Mo1–Ring(Ind)
Mo1–Mo2
C3–Mo1–C2
C3–Mo1–C1
C2–Mo1–C1
C5–C4–C12
C4–C5–C6
C5–C6–C7
C12–C7–C6
C7–C12–C4
Mo2–Ring(Ind)
C13–Mo2–C15
C13–Mo2–C14
C15–Mo2–C14
C17–C16–C24
C16–C17–C18
C17–C18–C19
C18–C19–C24
C19–C24–C16
2.0355(4)
77.69(24)
104.91(24)
80.20(26)
106.83(48)
110.31(50)
108.07(49)
107.21(48)
107.48(44)
3.2469(6)
104.80(23)
77.71(24)
77.27(25)
108.83(50)
107.95(51)
108.36(50)
107.57(48)
107.14(44)
Fig. 2. solid-state molecular structure of 9 showing 50% probability
thermal ellipsoids.

720
W.-Q. Zhang et al. / Journal of Organometallic Chemistry 689 (2004) 714–721
Table 5
Slippage parameters of the various indenyl ligands
ꢀ
Entry
Compound
D (A)
r (°)
W (°)
X (°)
Reference
1
2
3
4
5
6
7
8
9
7
0.156
0.144
0.100
0.065
0.194
0.120
0.947
0.418
0.043
57.84
49.5
86.9
9.7
4.38
4.05
2.8
5.3
2.6
This work
This work
This work
[42]
9
13
3.8
[MoCp(Ind)(NCMe)(CO)] [BF4]2g5-Cp
[MoCp(Ind)(NCMe)(CO)] [BF4]2g5-Ind
(g5-Cp)(g3-Ind)Mo(CO)2g5-Cp
(g5-Cp)(g3-Ind)Mo(CO)2g3-Ind
[g5-Ind]2Ni
1.9
5.6
None
5.1
2.1
2.6
0.6
[42]
[42]
3.4
6.0
24.1
13.9
2.2
21.4
13.1
0.8
[42]
[43]
13.9
2.2
[g5-Ind]2Fe
[43]
The structure of 9 is similar to 7 except for the sub-
stitution on the apical carbon. The apical carbon atom is
bonded to two cobalt atoms and one molybdenum atom
4. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, deposit numbers CCDC 190825, 190818
and 215773. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge, CB2 1EZ, UK; fax: +44 1223
336033; or deposit@ccdc.cam.ac.uk).
ꢀ
with bond lengths of 1.928(4), 1.935(3) and 2.086(4) A.
Selected bond distances and angles for the cluster
complex (l3-CC6H5)Co2Mo(CO)8(g5-Cp) [31] compare
favorably with those of cluster 9. The molecular struc-
tures of the compounds of 7 and 9 indicate ring slippage
of indenyl ligand. Employing the slip parameters of
Faller, Crabtree and Habib [40], the ‘‘slip’’ parameters
of the indenyl ligand in 7 and 9 listed in Table 5. Both
indenyl ligands in 7 and 9 exhibit ‘‘slip-fold’’ distortion
from ideal pentahapto coordination of the Mo(CO)2
fragment (Table 5, entries 1, 2). These variations are
typical for indenyl ligand coordinated to transition
metals, as comparison with attests of the mixed ring
complex (Table 5, entries 4–6), canonical trihapto (Table
5, entries 7, 8) and pentahapto complexes (Table 5, entry
9).Thus, the indenyl ligands coordinated to the basal
Mo atom of the cluster skeleton exhibit the pentahapto
coordination.
Acknowledgements
We are grateful to the Laboratory of Organometallic
Chemistry at Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences and the National Natural
Science Foundation of China for financial support
(No. 29871061).
The molecular structure of 13 is shown in Fig. 3. The
structure is similar to that of the Cp homologue, [(g5-
Cp)Mo(CO)3]2, 17 [41]. The metal–metal bond distance
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