Redox-induced indenyl slippage in [IndCpMoL2]2+/+/0 complexes

Article abstract of DOI:10.1021/om9808357

The dicationic complexes [IndCpMoL₂]²⁺ (Ind = indenyl; Cp = cyclopentadienyl; 1, L₂ = dppe; 2, L = PMe₃; 4, L₂ = Bipy; 5, L₂ = ^tBu₂bipy; 6, L₂ = H₂

Full text of DOI:10.1021/om9808357

506
Organometallics 1999, 18, 506-515
Red ox-In d u ced In d en yl Slip p a ge in [In d Cp MoL2]2+/+/0
Com p lexes
Carla A. Gamelas,†,‡ Eberhardt Herdtweck,§ J oa˜o P. Lopes,† and
Carlos C. Roma˜o*,†
Instituto de Tecnologia Quı´mica e Biolo´gica da Universidade Nova de Lisboa, Quinta do
Marqueˆs, EAN, Apt 127, 2781-901 Oeiras, Portugal, Escola Superior de Tecnologia, Instituto
Polite´cnico de Setu´bal, 2900 Setu´bal, Portugal, and Anorganisch-chemisches Institut,
Technische Universita¨t Mu¨nchen, D-85478 Garching, Federal Republic of Germany
Received October 6, 1998
The dicationic complexes [IndCpMoL2]2+ (Ind ) indenyl; Cp ) cyclopentadienyl; 1, L2 )
dppe; 2, L ) PMe3; 4, L2 ) Bipy; 5, L2 ) tBu2bipy; 6, L2 ) H2biim; 7, L ) CO and CNMe; 8,
L ) CNMe; 9, L ) CNtBu; 10, L ) NCMe and NMF; 11, L ) NMF) were synthesized from
[IndCpMoL′2]2+ (L′ ) CO, NCMe), [IndCpMo(NCMe)Cl]BF4, or IndCpMoCl2 by ligand
substitution. The neutral complexes (η3-Ind)CpMoL2 (13, L2 ) dppe; 14, L ) PMe3; 15, L2 )
Bipy; 16, L ) CO and CNMe; 17, L ) CNtBu) were obtained upon reduction of the respective
dications with Cp2Co. (η3-Ind)CpMo(dppe) (13) was also prepared by deprotonation of the
cyclopentadiene cation [IndMo(η4-C5H6)(dppe)]BF4 (12) with NEt3. The cyclic voltammograms
of the dications present one reversible 2e reduction step from Mo(IV) to Mo(II) except for 1,
2, and 6, in which cases two reversible 1e waves are observed. The ring-slipped complexes
(η3-Ind)CpMoL2 and the parent dications present similar CV’s. The X-ray crystal structures
of [IndCpModppe][BF4]2 and (η3-Ind)CpMo(dppe) confirm the indenyl ring planar η5
coordination and slip-folded η3, respectively.
In tr od u ction
arene hapticity in the odd-electron intermediate in such
processes. NMR data showed that the Rh(II) intermedi-
ate [Cp*Rh(η-C6Me6)]+ has a planar η6-arene structure
and is, therefore, a 19e complex.7A recent review article
on this problem suggests that the existence of such
hypervalent intermediates is more widespread than is
commonly assumed.8
Ring slippage is a response of a coordinated polyenyl
group to the changes in the electron count at the metal
center. These changes are usually caused by the addi-
tion of two-electron ligands to the metal, as in ligand
substitution associative reactions, but may also arise
from redox processes. This latter aspect was first
experimentally established by Fischer and Elschenbro-
ich, who showed that the 2e reduction of the 18e dication
[Ru(η6-C6Me6)2]2+ with Na produces the neutral complex
Ru(η6-C6Me6)(η4-C6Me6).1 The bending of the benzene
ring in the η4 coordination was confirmed by X-ray
studies.2 Such ring slippages may also be induced
electrochemically, as shown in greater detail by the
groups of Boekelheide3 and Geiger4 for the case of the
[Ru(η-arene)2]2+/+/0 system, as well as by Weaver5 and
Geiger for the isoelectronic group 9 congeners [MCp*-
(η6-arene)]2+/+/0 (M ) Co, Rh, Ir).6 One of the key issues
addressed in these studies was the assignment of the
Given their facile η5 f η3 ring-slippage rearrange-
ments, indenyl complexes may be considered as good
candidates to undergo reversible 2e redox transforma-
tions. The first documented example of this behavior
was reported by Trogler and concerns the electrochemi-
cally reversible stepwise reduction of [(η5-Ind)2V(CO)2]+
to [(η-Ind)2V(CO)2]-,9a for which the intermediate was
structurally characterized by X-ray studies as the ring-
slipped 17e species (η5-Ind)(η3-Ind)V(CO)2.9b The ana-
logues [Cp′2V(CO)2]+ (Cp′ ) Cp, Cp*) show a totally
irreversible decomposition under the same conditions.
More recently, Cooper reported the chemical, spectro-
scopical, and electrochemical study of the system
[IndMn(CO)3]0/-/2-. The expected η3-Ind coordination is
assigned to the dianion (18e species), but the electro-
chemical evidence supports the 19e monoanionic inter-
mediate [IndMn(CO)3]- with η5-Ind coordination.10 In
close parallel, the 2e reduction of [IndFe(CO)3]+ occurs
in a stepwise fashion to give ultimately the anion [(η3-
† Instituto de Tecnologia Qu´ımica e Biolo´gica da Universidade Nova
de Lisboa.
‡ Instituto Polite´cnico de Setu´bal.
§ Technische Universita¨t Mu¨nchen.
(1) Fischer, E. O.; Elschenbroich, C. Chem. Ber. 1970, 103, 162.
(2) Hu¨ttner, G.; Lange, S. Acta Crystallogr., Sect. B 1972, B28, 2049.
(3) (a) Finke, R. G.; Voegeli, R. H.; Langanis, E. D.; Boekelheide, V.
Organometallics 1983, 2, 347. (b) Laganis, E. D.; Voegeli, R. H.; Swann,
R. T.; Finke, R. G.; Hopf, H.; Boekelheide, V. Organometallics 1982,
1, 1415. (c) Plitzko, K.-D.; Wehrle, G.; Gollas, B.; Rapko, B.; Dannheim,
J .; Boekelheide, V. J . Am. Chem. Soc. 1990, 112, 6556.
(4) Pierce, D. T.; Geiger, W. E. J . Am. Chem. Soc. 1992, 114, 6063.
(5) Nielson, R. M.; Weaver, M. J . Organometallics 1989, 8, 1636.
(6) (a) Bowyer, W. J .; Geiger, W. E. J . Am. Chem. Soc. 1985, 107,
5657. (b) Bowyer, W. J .; Geiger, W. E. J . Electroanal. Chem. Interfacial
Electrochem. 1988, 239, 253. (c) Bowyer, W. J .; Merkert, J . W.; Geiger,
W. E.; Rheingold, A. L. Organometallics 1989, 8, 191.
(7) Merkert, J .; Nielson, R. M.; Weaver, M. J .; Geiger, W. E. J . Am.
Chem. Soc. 1989, 111, 7084.
(8) Geiger, W. E. Acc. Chem. Res. 1995, 28, 351.
(9) (a) Miller, G. A.; Therien, M. J .; Trogler, W. C. J . Organomet.
Chem. 1990, 383, 271. (b) Kowaleski, R. M.; Rheingold, A. L.; Trogler,
W. C.; Basolo, F. J . Am. Chem. Soc. 1986, 108, 2460.
(10) Lee, S.; Lovelace, S. R.; Cooper, N. J . Organometallics 1995,
14, 1974.
10.1021/om9808357 CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/20/1999

Indenyl Slippage in [IndCpMoL2]2+/ +/ 0 Complexes
Organometallics, Vol. 18, No. 4, 1999 507
Sch em e 1. H- Abstr a ction a n d H+ Abstr a ction
Sch em e 2
fr om [Cp ′M(η4-C5H6)(CO)2]+
Ind)Fe(CO)3]-.11 Again, the neutral intermediate is
assigned as a 19e species and, therefore, to have
η5-indenyl coordination. On the other hand, the elec-
trochemical evidence obtained on the reduction of (η5-
Ind)Rh(COD) does not allow for a clear distinction
between a 17e and 19e configurations for the anion [(η-
Ind)Rh(COD)]-.12
We have recently characterized the dications [Cp2M-
(CO)2]2+ and [IndCpM(CO)2]2+ (M ) Mo, W) and inde-
pendently synthesized their ring-slipped reduced ana-
logues (η3-Cp)(η5-Cp)M(CO)2 and (η3-Ind)CpM(CO)2, as
shown in Scheme 1.13
Preliminary experiments revealed that the cyclic
voltammogram of [IndCpW(CO)2]2+ presents only a
reversible 2e reduction wave in NCMe, whereas chemi-
cal oxidation of (η3-Ind)CpM(CO)2 forms the dications
[IndCpM(CO)2]2+. These results suggest the possibility
of generating a variety of closely related complexes
which might undergo two successive one-electron redox
steps according to eq 1. This was found to be possible
and we now present the synthesis of a variety of
dications [IndCpML2]2+ and their direct reductions to
the indenyl-slipped neutral complexes (η3-Ind)CpML2.
The choice of the most adequate starting material
depends on its own reactivity toward the nucleophiles
L. The rings of the more accessible dication [IndCpMo-
(CO)2][BF4]2 are very reactive toward strong nucleo-
philes such as phosphines. Therefore, its synthetic use
in this context was limited to the preparation of the
nitrile precursor [IndCpMo(NCMe)2]2+ and isonitrile
complexes 7 and 8, all of which are the result of slow
CO substitutions. Reaction of [IndCpMo(CO)2][BF4]2
with dppe under reflux and visible-light irradiation
gives the analytically pure complex [CpMo(CO)2(dppe)]-
BF4,16 with a Cp signal at δ 4.75 ppm. The weaker
nucleophile P(OMe)3 affords similar results.15 Both
reactions correspond to a loss of the indenyl ring, which
can be interpreted as the result of nucleophilic addition
of the phosphines to the indenyl ring followed by
replacement of the resulting [R3P(Ind)]+ ligand by
excess phosphine, as in eq 2.
Resu lts
Ch em ica l Stu d ies. The synthesis of the dications is
summarized in Scheme 2 and uses the previously
reported precursors [IndCpMo(CO)2]2+, IndCpMoCl2,
and [IndCpMo(NCMe)2]2+ 13
.
Generally speaking, the dications are easily isolated
as analytically pure crystalline materials. The 1H NMR
chemical shifts of the indenyl protons in the η5-
coordination mode assumed for 18e compounds 1-11
(Table 1) follow the reported pattern for similar com-
plexes: two multiplets for H5-8 (δ 8-6.5 ppm), a doublet
for H1/3 (δ 7-5.5 ppm) and a triplet for H2 (δ 6.5-5.5
ppm).14
(11) Pevear, K. A.; Banaszak Holl, M. M.; Carpenter, G. B.; Rieger,
A. L.; Rieger, P. H.; Sweigart, D. A. Organometallics 1995, 14, 512
and references therein.
(12) Amatore, C.; Ceccon, A.; Santi, S.; Verpeaux, J .-N. Chem. Eur.
J . 1997, 3, 279.
(13) (a) Ascenso, J. R.; de Azevedo, C. G.; Gonc¸alves, I. S.; Herdtweck,
E.; Moreno, D. S.; Roma˜o, C. C.; Zu¨hlke, J . Organometallics 1994, 13,
429. (b) Ascenso, J . R.; de Azevedo, C. G.; Gonc¸alves, I. S.; Herdtweck,
E.; Moreno, D. S.; Pessanha, M.; Roma˜o, C. C. Organometallics 1995,
14, 3901. (c) Gonc¸alves, I. S.; Roma˜o, C. C. J . Organomet. Chem. 1995,
48, 155.
A similar attack at the indenyl ring takes place during
the reaction of IndCpMoCl2 with excess PMe3 and TlBF4
(15) Fe´lix, V.; Drew, M., personal communication, 1997.
(16) Green, M. L. H.; Knight, J .; Segal, J . A. J . Chem. Soc., Dalton
Trans. 1977, 2189.
(14) Calhorda, M. J .; Gamelas, C. A.; Gonc¸alves, I. S.; Herdtweck,
E.; Roma˜o, C. C.; Veiros, L. F. Organometallics 1998, 17, 2597.

508 Organometallics, Vol. 18, No. 4, 1999
Gamelas et al.
Ta ble 1. Selected 1H a n d 13C NMR Da ta for [(η5-In d )Cp MoL2][BF 4]2 a n d Rela ted Com p ou n d sa
chem shift of η5-Ind ligand (δ (ppm); room temp)
complex
ligand
dppeb
H5-8
H1/3
H2
C4/9
ref
1
2
4
5
6
7
8
9
7.39; 6.64 m
7.67 s
7.69; 7.34 m
7.52; 7.18 m
7.57; 7.43 m
7.82 m
5.55 m
5.99 m
6.34 d
6.14 d
6.20 d
6.70 c
6.34 d
6.81 d
6.71 d
6.46 d
7.55 d
6.34 m
6.93; 6.22 m
6.27 m
5.45 m
6.63 t
6.43 t
6.57 t
6.32 t
6.05 t
6.37 t
6.65 t
6.53 t
6.98 t
6.29 m
6.39 t
112.4
112.3
116.2
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12
b
(PMe3)2
Bipy
tBu2bipy
H2biim
123.5
(CO)(CNMe)b
b
(CNMe)2
7.70 m
112.8
112.7
(CNtBu)2
7.99; 7.83 m
7.90; 7.73 m
7.66; 7.60 s
8.27; 8.09 m
7.92; 7.80 m
7.85; 7.78 m
10
11
M ) Mo
(NCMe)(NMF)
(NMF)2
(CO)2
(P(OMe)3)2
(CO)(NCMe)
112.4
14
12
M ) W
(NCMe)2
7.59 s
5.92 d
6.65 t
12
a
t
All spectra in CD3COCD3 except as noted. Legend: dppe ) 1,2-bis(diphenylphosphino)ethane, Bipy ) 2,2′-bipyridyl, Bu2bipy ) 4,4′-
di-tert-butyl-2,2′-bipyridine, H2biim ) bis(imidazole), CNtBu ) tert-butyl isocyanide, NMF ) N-methylformamide. The numbering scheme
is as follows:
b
Spectrum in CD3CN.
Sch em e 3
in acetone, affording the cation [CpMo(PMe3)4]BF4 (3).
This reaction is certainly mediated by some cationic
species with a high reactivity toward ring addition. In
the less ionizing solvent CH2Cl2, phosphine attack at
the indenyl ring was prevented and the desired dication
[IndCpMo(PMe3)2][BF4]2 (2) was isolated in 70% yield.
However, these problems are best avoided by the use
of the labile nitrile dication [IndCpMo(NCMe)2][BF4]2,
which proved to be the most convenient synthetic
precursor. Its insolubility in CH2Cl2 was overcome by
adding a small amount of NMF (N-methylformamide)
to the reaction mixture, thereby catalyzing the substitu-
tion reactions when L is 1,2-bis(diphenylphosphino)-
t
ethane (dppe), PMe3, 2,2′-bipyridine (Bipy), Bu2bipy,
2,2′-bis(imidazole) (H2biim), CNMe, and CNtBu. In fact,
in the absence of NMF some of the preparations
reported in this work do not occur (e.g. preparation of
8). Nitrile substitution by NMF occurs readily, and the
trast to its carbonyl analogue [IndMo(η4-C5H6)(CO)2]-
NMF complexes 10 and 11 were isolated and character-
BF4, 12 is not fluxional, as can be concluded by the
ized. The lability of NMF in complex 10 was demon-
1
1
invariance of its H NMR spectrum with temperature
strated by the H NMR observation of its facile conver-
(from -80 °C to room temperature). 12 was assigned
as the endo conformer (bridgehead CH2 cis to the
indenyl ring as in Scheme 3) by comparison of its 1H
NMR spectrum with the one of the known congener
[CpMo(η4-C5H6)(dppe)]BF4.18 In fact, the chemical shifts
of the methylene protons of the C5H6 ring are very
similar to those observed for [CpMo(η4-C5H6)(dppe)]BF4
and, therefore, we assigned Hendo as the higher field
resonance at δ 2.85 ppm and Hexo as the lower field
resonance at δ 3.32 ppm (see Experimental Section). As
expected, Hexo in 12 exhibits a distinct IR stretching
sion into [IndCpMo(NCCD3)2][BF4]2 at room temperature,
immediately after dissolution in NCCD3.
31P coupling to the indenyl protons is evident in the
1H NMR spectra of 1 and 2, H1/3 and H2 appearing as
multiplets (instead of a doublet and a triplet). Concomi-
tantly, the signal of the Cp ring in these complexes
appears as a triplet, as in [Cp2Mo(dppe)]2+ 17,18
.
The crystal structure of [IndCpModppe][BF4]2 (1)
confirms the expected planar η5-coordination mode of
the indenyl ligand (see Crystallography).
In contrast to the above-mentioned addition of the
phosphines to the indenyl ring of [IndCpMo(CO)2]2+, H-
adds to the Cp ring of the dication 1, affording the diene
complex [IndMo(η4-C5H6)(dppe)]BF4 (12). Also, in con-
vibration at 2768 cm-1
.
Hydride addition to 4, 5, 8, and [IndCpMo(NCMe)2]-
[BF4]2 proved to be unsuccessful for the preparation of
the respective diene complexes, probably due to attack
at the non-hydrocarbon unsaturated ligands.
(17) Aviles, T.; Green, M. L. H.; Dias, A. R.; Roma˜o, C. C. J . Chem.
Soc., Dalton Trans. 1979, 1367.
[IndMo(η4-C5H6)(dppe)]BF4 (12) was readly deproto-
nated by NEt3, yielding the neutral species (η3-Ind)-
CpMo(ddpe) (13), as depicted in Scheme 3.
(18) de Azevedo, C. G.; Calhorda, M. J .; de C. T. Carrondo, M. A. A.
F.; Dias, A. R.; Duarte, M. T.; Galva˜o, A. M.; Gamelas, C. A.; Gonc¸alves,
I. S.; da Piedade, F. M.; Roma˜o, C. C. J . Organomet. Chem. 1997, 544,
257.

Indenyl Slippage in [IndCpMoL2]2+/ +/ 0 Complexes
Organometallics, Vol. 18, No. 4, 1999 509
Ta ble 2. Selected 1H a n d 13C NMR Da ta for (η3-In d )Cp MoL2 a n d Rela ted Com p ou n d sa
chem shift of η3-Ind ligand (δ (ppm); room temp)
complex
ligand
H5-8
H1/3
H2
C4/9
ref
13
14
15
16
dppe
(PMe3)2
Bipy
6.46 d
2.96 s (br)
3.03 s (br)
4.77 d
5.96 s (br)
6.26 s (br)
3.44 s (br)
5.50 m
151.5
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6.52 s (br)
6.78; 6.68 m
7.16; 6.88
6.65; 6.51
6.63; 6.50 m
6.56 m
6.54 m
6.68 m
6.56 m
(CO)(CNMe)
4.85; 4.62 t
17
M ) Mo
(CNtBu)2
(CO)2
(P(OMe)3)2
(η3-Ind)(CO)2
(CO)2
4.41 d
5.21 d
3.89 m
5.11 d
4.95 d
6.81 t
6.75 t
3.89 m
4.80 t
7.07 t
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151.1
157.5
12
14
12
18
M ) W
152.0
a
All spectra at room temperature in C6D6. See Table 1 for numbering.
Ta ble 3. Cyclic Volta m m etr y Da ta
complexa
ligand
dppe
Ep,a (V)
Ep,c (V)
Ep/2 (V)
Ia/Ic
η5-Ind
1
2
4
5
6
7
8
-0.30; -0.46
-0.46; -0.74
-0.59
-0.37; -0.52
-0.53; -0.81
-0.67
-0.34; -0.49
-0.50; -0.78
-0.63
1.0; 0.9
1.0; 1.0
0.9
1.0
1.0; 1.1
1.1
(PMe3)2
Bipy
tBu2bipy
-0.60
-0.68
-0.64
H2biim
-0.90; -1.16
-0.15
-0.99; -1.26
-0.22
-0.94; -1.21
-0.19
(CO)(CNMe)
(CNMe)2
(CNCMe3)2
(η4-C5H6)(dppe)
-0.53
-0.49
-0. 61
-0.57
-0.57
-0.53
0.9
1.0
9
12b
+1.27; +0.77
η3-Ind
13
14
15
17
dppe
(PMe3)2
Bipy
(CNCMe3)2
(CO)2
-0.29; -0.46
-0.46; -0.74
-0.59
-0.36; -0.52
-0.53; -0.81
-0.66
-0.33; -0.49
-0.50; -0.78
-0.63
1.0; 0.9
1.0; 1.0
1.0
-0.49
-0.56
-0.53
1.0
M ) Mo
0.19
Ep,c(1) ) 0.12
irrev
E
E
p,c(2) ) -0.26
p,c(3) ) -0.90
a
All the voltammograms were measured in NCMe, except as noted, in ca. 1.0 mM solutions at a scan rate of 200 mV/s and room
temperature. Ep,a, Ep,c, and Ep/2 are referenced to SCE on the basis of a simultaneous measurement of the ferrocene redox potential
(+0.444 V for CH2Cl2 and +0.400 V for NCMe). Ep,a ) anodic sweep (peak potentials). Ep,c ) cathodic sweep (peak potentials). Ep/2
)
b
half-wave potential ((Ep,a + Ep,c)/2). Ia ) anodic current intensity. Ic ) cathodic current intensity. Measured in CH2Cl2.
1H NMR in C6D6 confirms the η3-indenyl coordination
with the H1/3 resonance (a broad singlet at δ 2.96 ppm)
and the H5-8 resonance (a doublet at δ 6.46 ppm) shifted
upfield relative to their usual positions in the η5-indenyl
coordination mode.14 The C5 ring appears at δ 4.48 ppm.
The structure of complex 13 was confirmed by X-ray
diffraction analysis of a single crystal (see Crystal-
lography).
(η3-Ind)CpMo(dppe) (13) proved to be resistant to
electrophilic addition of HCl in Et2O and of MeI in
toluene, at room temperature. Reaction of this neutral
complex with Ph3CBF4 in CH2Cl2 results in oxidation,
affording the dication 1. Conversely, reduction of 1 with
Cp2Co produces 13 in 95% yield.
The dications 2, 4, 7, and 9 also undergo similar
reductions with Cp2Co to give the ring-slipped neutral
species 14-17, as depicted in Scheme 3. However, this
general synthetic procedure does not produce either (η3-
Ind)CpMo(NCMe)2 or (η3-Ind)CpMo(CNMe)2. Unidenti-
fied decomposition products are formed instead.
(16). A second pattern is found for the CNtBu derivative
(17). In this case, the H NMR spectrum is similar to
1
that of (η3-Ind)CpMo(CO)2: a triplet for H2 (ca. δ 6.8
ppm), two multiplets for H5-8 (ca. δ 6.5 ppm), and a
doublet for H1/3 (ca. δ 4.5 ppm).13 The asymmetric
complex (η3-Ind)CpMo(CO)(CNMe) (16) exhibits four
signals for H,5-8 as previously observed in other asym-
metric indenyl molybdenocene derivatives, such as
[IndCpMo(CO)Cl][BF4].13
All 1H NMR peaks in C6D6 are sharp at room
temperature. The rather broad signals observed at room
temperature in the CD2Cl2 spectrum of dppe complex
13 become well-resolved at -70 °C. We did not attempt
any study of this behavior, due to the slow reaction of
the complex with CD2Cl2.
Electr och em ica l Stu d ies. The cyclic voltammo-
grams of the dications [IndCpMoL2]2+ (1-9) and their
reduced ring-slipped counterparts [(η3-Ind)CpMoL2]
(13-17) as well as a few other related complexes were
studied in NCMe and CH2Cl2, and the data are sum-
marized in Table 3 and Figure 1.
The 1H NMR chemical shifts of the protons of the slip-
folded η3-indenyl rings of compounds 13-17 follow two
distinct patterns (Table 2). The most general one has
also been reported for the bis(indenyl) complex (η5-Ind)-
(η3-Ind)Mo(CO)213 and shows the H2 and H1/3 resonances
shifted upfield from their typical positions in the related
η5 coordination mode. This is the case for the complexes
with dppe (13), PMe3 (14), Bipy (15), and (CO)(CNMe)
The cyclic voltammograms of dications 4, 5, and 7-9
show one 2e quasi-reversible wave, as in [IndCpW-
(CO)2]2+ 13
that can be attributed to the two consecutive
,
(19) Gonc¸alves, I. S.; Roma˜o, C. C. J . Organomet. Chem. 1995, 48,
155.
(20) Amatore, C.; Azzabi, M.; Calas, P.; J utand, A.; Lefrou, C.; Rollin,
Y. J . Electroanal. Chem. Interfacial Electrochem. 1990, 288, 45.

510 Organometallics, Vol. 18, No. 4, 1999
Gamelas et al.
Ta ble 4. Cr ysta llogr a p h ic Da ta for
[(η5-In d )Cp Mo(d p p e)]2+[BF 4]-2‚3CH3CN (1) a n d
[(η3-In d )Cp Mo(d p p e)] (13)
1
13
chem formula
fw
C46H45B2F8MoN3P2 C40H36MoP2
971.38
674.61
color/shape
cryst size (mm)
cryst syst
space group
a (pm)
dark red/column
0.69 × 0.25 × 0.25
monoclinic
P21/c
1409.84(5)
1381.67(8)
2237.82(9)
90
95.992(4)
90
4335.3(3)
4
orange/prism
0.28 × 0.20 × 0.13
triclinic
P1h
1092.50(2)
1267.18(4)
1322.68(4)
112.770(1)
94.081(2)
108.926(2)
1555.98(8)
2
b (pm)
c (pm)
R (deg)
â (deg)
γ (deg)
V (106 pm3)
Z
T (K)
193
1.488
4.5
1984
173
1.440
5.5
696
Fcalcd (g cm-3
)
µ (cm-1
F000
)
λ (pm)
71.073
71.073
scan method
imaging plate
2.32-27.75
(16, (18, (29
36 076
9536
9536 (all data)
kappa CCD
2.18-31.35
(12, (18, (18
14 111
7231
7231(all data)
532
θ range (deg)
data collcd (hkl)
no. of rflns collcd
no. of indep rflns
no. of obsd rflns
no. of params refined 571
Rint
0.025
0.0424
0.0905
1.035
0.026
0.0306
0.0709
1.071
R1a
wR2b
GOFc
∆Fmax/min (e Å-3
)
+0.75, -0.50
+0.39, -0.39
R1 ) ∑(||Fo| - |Fc||)/∑|Fo|. b wR2 ) [∑w(Fo2 - Fc2)2/∑w(Fo2)2]1/2
.
a
c GOF ) [∑w(Fo2 - Fc2)2/(NO - NV)]1/2; w t SHELXL-93 weights.
A smaller difference is observed between the two
isonitrile complexes 8 and 9, the latter (L ) CNtBu)
being, as expected, slightly more difficult to reduce than
the former. Particularly striking is the negative poten-
tial of the bis(imidazole) complex 6, clearly more nega-
tive than the potentials of the bipyridyl derivatives 4
and 5.
F igu r e 1. (a, top) Cyclic voltammogram of [IndCpMo-
(dppe)][BF4]2 (1) in NCMe. A similar wave pattern is
observed for 2 and 6 (see Table 3 for CV data). (b, bottom)
Cyclic voltammogram of [IndCpMo(tBu2bipy)][BF4]2 (5) in
NCMe. A similar wave pattern is observed for 4, 7, 8, and
9 (see Table 3 for CV data).
The CO complexes are the easiest to reduce in the
whole series (although irreversibly). This is certainly
due to the high capacity of the CO ligand to withdraw
charge from the reduced metal center by back-donation.
Cr ysta llogr a p h y. 1 and 13 were further character-
ized by single-crystal X-ray diffraction crystallography,
and the corresponding data are given in Table 4. Key
bond distances and angles together with the character-
istic slip parameters of the indenyl ligand are listed in
Table 5.
Both compounds (Figures 2 and 3) are monomeric,
and the geometry around the metal atom is best
described by a distorted tetrahedron. Complex 1 has the
typical structure of a molybdenocene derivative, and 13
has a structure similar to that of many allylic complexes
of the type CpMo(η3-allyl)(CO)2. A projection on the Mo,
P(1), and P(2) plane (Figures 2a and 3a) shows that the
Cp ring adopts an approximately staggered conforma-
tion in 1 and an eclipsed conformation in 13. The
average Mo-P distance in 1 (250.7(1) pm) is signifi-
cantly longer than in complex 13 (242.6(1) pm), which
in turn is very similar to that for the isoelectronic allylic
complex CpMo(η3-C5H7)(dppe) (242.1(2) pm)18 and to
that for the Mo(II) complex (η5-C5Me5)Mo(dppe)Cl (242.8-
(1) pm).21 All intramolecular distances and angles fall
electron transfer reactions from Mo(IV) to Mo(II). The
electron count was performed according to a published
method.20 Cyclic voltammograms of dications 1, 2, and
6 show that these complexes undergo two distinct quasi-
reversible 1e reduction steps. The ring-slipped com-
plexes (η3-Ind)CpMo(dppe) (13), (η3-Ind)CpMo(PMe3)2
(14), and (η3-Ind)CpMo(bipy) (15) present cyclic volta-
mmograms similar to those for the respective dications,
1, 2, and 4. The previously reported congener of complex
1 [Cp2Modppe]2+ presents only irreversible oxidation
waves (at 0.43, 0.78, and 1.28 V).18
In keeping with the chemical observations of the
reductions with Cp2Co, the [IndCpMo(NCMe)2]2+ com-
plex presents irreversible reduction waves. In contrast,
[IndCpMo(CNMe)2]2+, which cannot be chemically re-
duced with Cp2Co to (η3-Ind)CpMo(CNMe)2, shows an
electrochemical reversibility similar to that of the other
dications, for example [IndCpMo(CNtBu)2]2+ (9).
The relative shift of the peak potentials reflects the
variations in the overall donor/acceptor abilities of the
L2 ligands. This is clearly illustrated by comparison of
the potentials of the two phosphine derivatives 1 and
2, the latter (L ) PMe3) being, as expected, more
difficult to reduce than the former (L2 ) dppe), which
bears a weaker σ donor and a better π acceptor.

Indenyl Slippage in [IndCpMoL2]2+/ +/ 0 Complexes
Organometallics, Vol. 18, No. 4, 1999 511
Ta ble 5. Selected In ter a tom ic Dista n ces (p m ),
An gles (d eg), a n d Slip P a r a m eter sa for
[(η5-In d )Cp Mo(d p p e)]2+[BF 4]-2‚3CH3CN (1) a n d
[(η3-In d )Cp Mo(d p p e)] (13)
1b
13c
Mo-C(m1)
Mo-C(m2)
Mo-C(m3)
Mo-C(m4)
Mo-C(m5)
235.7(3)
230.3(3)
228.6(3)
232.1(2)
237.8(3)
236.5(2)
233.7(2)
229.7(2)
230.4(2)
232.2(2)
Mo-C(n1)
Mo-C(n2)
Mo-C(n3)
Mo-C(n3A)
Mo-C(n7A)
229.3(3)
222.6(2)
229.3(2)
242.7(2)
242.9(2)
231.0(2)
218.4(2)
235.1(2)
302.6(2)
305.5(2)
Mo-P(1)
Mo-P(2)
250.83(5)
250.52(5)
242.00(6)
243.12(5)
C(n1)-C(n2)
C(n1)-C(n7A)
C(n2)-C(n3)
C(n3)-C(n3A)
C(n3A)-C(n4)
C(n3A)-C(n7A)
C(n4)-C(n5)
C(n5)-C(n6)
C(n6)-C(n7)
C(n7)-C(n7A)
142.8(3)
142.0(3)
143.0(3)
141.6(3)
142.8(3)
143.4(3)
135.3(3)
142.8(4)
135.2(4)
142.9(3)
142.9(3)
147.5(3)
144.3(4)
146.2(3)
138.5(4)
142.6(3)
140.4(3)
138.5(4)
140.7(4)
137.8(3)
P(1)-Mo-P(2)
P(1)-Mo-C(ind)
P(1)-Mo-Cp
78.53(2)
109.0
105.5
110.3
103.8
135.2
78.26(2)
97.3
115.9
94.7
125.4
130.9
P(2)-Mo-C(ind)
P(2)-Mo-Cp
C(ind)-Mo-Cp
1
13
indenyl
Cp
indenyl
Cp
∆ ) |S| (pm)
σ (deg)
22.2
0.7
6.4
15.7
2.5
9.3
14.2
2.7
6.3
1.7
110.2
7.4
28.5
75.9
25.0
7.0
29.4
2.0
4.3
1.6
F igu r e 2. ORTEP style plots of the dication [(η5-Ind)(Cp)-
Mo(dppe)]2+ (1) with the atomic labeling scheme: (a, top)
top view; (b, bottom) side view. Thermal ellipsoids are
drawn at the 50% probability level. Hydrogen atoms are
omitted for clarity.
Ψ (deg)
∆M-C (pm)
Ω (deg)
a
b
Slip parameters are defined in refs 22 and 37. m ) 5, n )
6: C(ind) denotes the centroid C(61-67A); Cp denotes the centroid
C(51-55). c m ) 2, n ) 1: C(ind) denotes the centroid C(11-13);
Cp denotes the centroid C(21-25).
Complex 1 presents a singular structural feature: it
does not show the alignment of the indenyl ligand
observed for [IndCpMo(CO)(NCMe)]2+ 13
as well as for
,
all other structurally characterized IndCpMIV complexes
(M ) Mo, W) and [Ind2V(CO)2]+.25 On the other hand,
complex 13 shows a vector bisecting both the indenyl
group and the L-M-L angle, as observed in the cases
of IndCpMo(CO)2,13 Ind2W(CO)2,26 and Ind2V(CO)2.9b
within the ranges observed for related compounds, for
example (a) the Mo-P distances, 246.4(2) pm in (d2)-
[(η5-Ind)(Cp)Mo{P(OMe)3}2]2+ and 239.1(2) pm in (d4)-
(η3-Ind)(Cp)Mo{P(OMe)3}2,15 (b) the P(1)-Mo-P(2) angle
of 78.71(4)° in (η5-C5Me5)Mo(dppe)Cl,21 and (c) the bent
angle (η3-Ind)-Mo-(η5-Ind) of 130.4° in (η3-Ind)(η5-Ind)-
Mo(dppe).22 In general, the observed values for the ring-
slippage parameters are typical for η5 coordination (1)
and for η3 coordination (13) and are consistent with
those given in the literature.13b,23,24 The slip-fold angle
Ω of complex 13 (25.0°) is somewhat bigger than that
for IndCpMo(CO)2 (21.4°), probably reflecting its higher
electron density at the metal.13
Discu ssion
Redox-induced ring slippage of the indenyl ligand
between η5 and η3 coordination modes seems to be a
quite general property in the modified molybdenocene
complexes, according to eq 1.
As a matter of fact, this reversible chemical and
electrochemical transformation was shown to occur for
a variety of L2 ligands (CO, CNR, PR3, bipyridyl). In
the case of L2 ) dppe it was possible to characterize
structurally the complexes at both ends of the redox
pair, namely 1 and 13, thereby confirming the hapto-
tropic shift of the indenyl ligand. This is one of the few
examples where such characterization is possible, the
other ones being those described by Elschenbroich,1
Geiger,6 Sweigart,11 Floriani,25 and ourselves ([IndCpMo-
{P(OMe)3}2]2+/0).15 Without this shift such a reduction
is not possible or is totally irreversible, as we have
(21) Abugideiri, F.; Fettinger, J . C.; Keogh, D. W.; and Poli, R.
Organometallics 1996, 15, 4407 and references therein.
(22) Poli, R.; Mattamana, S. P.; and Falvello, L. R. Gazz. Chim. Ital.
1992, 122, 315 and references therein.
(23) Faller, J . W.; Crabtree, R. H.; Habib, A. Organometallics 1985,
4, 929.
(24) Ascenso, J . R.; Gonc¸alves, I. S.; Herdtweck, E.; Roma˜o, C. C. J .
Organomet. Chem. 1996, 508, 169.
(25) Bocarsly, J . R.; Floriani, C.; Chiesi-Villa, A.; Guastini, C. Inorg.
Chem. 1987, 26, 1871 and references therein.
(26) Nesmeyanov, A. N.; Ustynyuk, N. A.; Makarova, L. G.; Andri-
anov, V. G.; Struchkov, Yu. T.; Andrae, S. J . Organomet. Chem. 1978,
159, 189.
shown for [Cp2Modppe]2+
.

512 Organometallics, Vol. 18, No. 4, 1999
Gamelas et al.
evidence for a group 6 bent metallocene in the formal
+3 oxidation state. So far, only [CpCp′MoLn]x+ com-
plexes (M ) Cr, Mo, W; Cp′ ) Cp, Ind, Cp*) in the +2,
+4, +5, and +6 oxidation states have been isolated and/
or spectroscopically or electrochemically observed. This
means that PR3 ligands are effective in stabilizing this
intermediate odd-electron species. The separation be-
tween the waves is 150 mV for 1 and 280 mV for 2. As
argued by Cooper,10 these small potential differences
suggest marked stabilization of the final reduction
products (13 and 14) by an η5 f η3 hapticity shift
concomitant with the second reduction and also sup-
ports η5-indenyl ligation in the first reduction product
[(η3-Ind)CpMo(PR3)2]+.
In the absence of their structural and/or spectroscopi-
cal characterization the actual hapticity of the indenyl
ligand in these complexes remains unknown, and the
fact that they are isoelectronic with the 17e [(η3-Ind)-
(η5-Ind)V(CO)2] is not compelling evidence in favor of a
17e [(η3-Ind)CpMo(PR3)2]+.
To be able to answer this question, we are presently
attempting the isolation of these and related complexes
as well as promoting detailed theoretical and electro-
chemical studies on these redox-induced ring-slippage
transformations.
Exp er im en ta l Section
All experiments were carried out under an atmosphere of
nitrogen by Schlenk techniques. Diethyl ether, THF, and
pentane were dried by distillation from Na/benzophenone.
Acetonitrile was dried over CaH2 and distilled after refluxing
several hours over CaH2 or P2O5. Dichloromethane was
distilled from CaH2. Acetone was distilled and kept over 4 Å
molecular sieves.
Microanalyses and cyclic voltammetric measurements were
1
performed in our laboratories (ITQB). H NMR spectra were
obtained with a Bruker AMX 300 spectrometer. Infrared
spectra were recorded on a Perkin-Elmer 457 and on a Unican
Mattson Mod 7000 FTIR spectrophotometer using KBr pellets.
PMe3,27 H2biim,28 CNMe,29 [IndCpMo(CO)2][BF4]2, [IndCpMo-
(NCMe)2][BF4]2, [IndCpMo(NCMe)Cl]BF4, and IndCpMoCl2
were prepared as described previously.
F igu r e 3. ORTEP style plots of [(η3-Ind)(Cp)Mo(dppe)]
(13) with the atomic labeling scheme: (a, top) top view; (b,
bottom) side view. Thermal ellipsoids are drawn at the 50%
probability level. Hydrogen atoms are omitted for clarity.
13
Electrochemistry. The electrochemical instrumentation con-
sisted of a BAS CV - 50W - 1000 Voltammetric Analyzer
connected to BAS/Windows data acquisition software. All the
electrochemical experiments were run under argon at room
temperature. Tetrabutylammonium hexafluorophosphate (Al-
drich) was used as supporting electrolyte;, it was recrystallized
from ethanol. Cyclic voltammetry experiments were performed
in an MF-1082 glass cell from BAS in a C-2 cell enclosed in a
Faraday cage. The reference electrode was SSC (MF-2063 from
BAS), and its potential was - 44 mV relative to a SCE. The
reference electrode was calibrated with a solution of ferrocene
(1 mM) to obtain a potential in agreement with the literature
value.30
The auxiliary electrode was a 7.5 cm platinum wire (MW-
1032 from BAS) with a gold-plated connector. The working
electrode was a platinum disk (MF-2013 from BAS) with ca.
0.022 cm2 sealed in Kel-F plastic. Between each CV scan the
working electrode was electrocleaned as a routine procedure
and it was polished on 1 µM diamond and subjected to alumina
cleaning with water/methanol and sonicated, according to
The potential at which the electrochemical transfor-
mations take place is dependent on the nature of the
ligands L. This is apparent not only from the value of
these potentials but also from the resolution of the two
one-electron transfers. Better σ donor and weaker π
acceptor ligands L shift the potentials to more negative
values. However, for all ligands tested except phos-
phines and H2biim, the two 1e transfers are not resolved
and a single 2e wave is recorded. In the case of the
phosphines, two separated 1e waves are observed which
correspond to the two one-electron-transfer steps in eq
3.
(27) Wollsberger, W.; Schmidbauer, H. Synth. React. Inorg. Met.-
Org. Chem. 1974, 4, 149.
(28) Calhorda, M. J .; Dias, A. R. J . Organomet. Chem. 1980, 197,
291.
(29) Trofimenko, S. J . Am. Chem. Soc. 1967, 89, 3170.
(30) Nelson, I. V.; Iwamoto, R. T. Anal. Chem. 1963, 35, 867.
The intermediate monocations in eq 3 are stable
within the CV time scale and are the first experimental

Indenyl Slippage in [IndCpMoL2]2+/ +/ 0 Complexes
Organometallics, Vol. 18, No. 4, 1999 513
standard procedures, when necessary. Solvents were dried as
previously described.
2912, 1423, 1300, 1084, 965, 845, 779. 1H NMR (CH3CN-d3,
300 MHz, room temp, δ (ppm)): 7.67 (s, 4H, H5-8); 6.00-5.97
(m, 2H, H1/3); 5.47-5.42 (m, 1H, H2); 5.10 (t, 5H, Cp, [3J PH
)
P r ep a r a tion of [In d Cp Mo(d p p e)][BF 4]2 (1). Meth od a .
A suspension of [IndCpMo(NCMe)2][BF4]2 (0.31 g, 0.58 mmol)
in Me2CO was allowed to react with dppe (0.23 g, 0.58 mmol)
for 5 h at room temperature. The supernatant red solution
was filtered, and the remaining precipitate was further
extracted with the reaction solvent. Upon concentration and
cooling of the Me2CO extracts, the salmon microcrystalline
complex separated. It was washed with CH2Cl2, and red
crystals were obtained by slow diffusion of Et2O into a
concentrated NCMe solution. Yield: 70%.
Meth od b. A solution of [IndCpMo(NCMe)Cl]BF4 (0.22 g,
0.50 mmol) in Me2CO was treated with dppe (0.20 g, 0.50
mmol) and TlBF4 (0.20 g, 0.69 mmol), and this mixture was
refluxed for 1 h. The supernatant solution was filtered, and
the remaining precipitate was further extracted with Me2CO
(3 × 20 mL). The combined extracts were evaporated under
vacuum, and the salmon powder so obtained was washed with
CH2Cl2 until the washings were colorless and recrystallized
from NCMe/Et2O in 40% yield.
Meth od c. A solution of (η3-Ind)CpMo(dppe) (0.05 g, 0.08
mmol) in CH2Cl2 was treated with a solution of Ph3CBF4 (0.05
g, 0.15 mmol) in the same solvent. The reaction mixture
became turbid, and after 3 h of stirring at room temperature
the salmon precipitate was filtered off and washed with CH2-
Cl2. Yield: 80%.
Anal. Found: C, 56.63; H, 4.26. Calcd for C40H36B2F8P2Mo:
C, 56.64, H, 4.28%. Selected IR (KBr, cm-1): ν 3113, 3063,
1483, 1435, 1073, 830, 752, 698. 1H NMR (CH3CN-d3, 300
MHz, room temp, δ (ppm)): 7.64-7.13 (c, 22H, Ph + H5-8);
6.65-6.62 (m, 2H, H5-8); 6.28-6.26 (m, 1H, H2); 5.56-5.53 (m,
2H, H1/3); 5.08 (t, 5H, Cp, [3J PH ) 2.2 Hz]); 3.62-3.20 (c, 4H,
CH2 of dppe). 13C NMR (CH3CN-d3, 75 MHz, room temp, δ
(ppm)): 135.1 (C5/8); 133.4-130.8 (c, dppe); 127.3 (C6/7); 112.4
(C4/9); 99.2 (Cp); 89.2 (C2); 82.3 (C1/3); 28.5 (dppe).
2.1 Hz]); 1.66-1.62 (t, 18H, CH3). 13C NMR (CH3CN-d3, 75
MHz, room temp, δ (ppm)): 134.9 (C5/8); 127.0 (C6/7); 112.3
(C4/9); 97.4 (Cp); 91.6 (C2); 87.4 (C1/3); 21.1 (PMe3).
Rea ction of In d Cp MoCl2 w ith TlBF 4 a n d Excess P Me3
in Aceton e To Affor d [Cp Mo(P Me3)4]BF 4 (3). A suspension
of IndCpMoCl2 (0.24 g, 0.70 mmol) in Me2CO was treated with
excess PMe3 (1.0 mL, 10 mmol) and TlBF4 (0.44 g, 1.5 mmol),
and the mixture was stirred for 1 h at room temperature. The
supernatant solution was separated from the TlCl precipitate
by filtration and taken to dryness under vacuum. The residue
was extracted with CH2Cl2 and air-sensitive complex [CpMo-
(PMe3)4]BF4 obtained as a red powder upon evaporation of the
solvent and washing with Et2O. Yield: 40%.
Anal. Found: C, 24.78; H, 3.97. Calcd for C17H41BF4P4Mo:
C, 25.03, H, 3.97. Selected IR (KBr, cm-1): ν 310, 2980, 2910,
1906, 1423, 1302, 1084, 966, 843. 1H NMR (Me2CO-d6, 300
MHz, room temp, δ (ppm)): 5.66 (s (br), 5H, Cp); 1.88-1.70
(c, 36H, CH3).
P r ep a r a tion of [In d Cp Mo(Bip y)][BF 4]2 (4). A solution
of [IndCpMo(NCMe)2][BF4]2 (0.30 g, 0.56 mmol) in CH2Cl2/
NMF (10/1) was allowed to react with 2,2′-bipyridyl (0.09 g,
0.56 mmol) for 2 h at room temperature. The resulting dark
violet solution was concentrated under vacuum until the only
remaining solvent was NMF. Addition of Et2O/EtOH (30/1)
allowed the precipitation of the violet product. This was
recrystallized from Me2CO/Et2O in 60% yield.
Anal. Found: C, 47.67; H, 3.44; N, 4.46. Calcd for C24H20
-
B2F8N2Mo: C, 47.57, H, 3.33, N, 4.62. Selected IR (KBr, cm-1):
1
ν 3399, 3063, 1601, 1442, 1100, 860, 789. H NMR (Me2CO-
d6, 300 MHz, room temp, δ (ppm)): 8.80 (d (br), 2H, Bipy);
8.50 (t (br), 2H, Bipy); 7.97 (d (br), 2H, Bipy); 7.69 (c, 4H, Bipy
+ H5-8); 7.35-7.32 (m, 2H, H5-8); 6.63 (t, 1H, H2); 6.34 (d, 2H,
H1/3); 6.17 (s, 5H, Cp). 13C NMR (CH3CN-d3, 75 MHz, room
temp, δ (ppm)): 172.6 (Bipy); 158.2 (Bipy); 144.0 (Bipy); 135.2
(C5/8); 129.0 (Bipy); 128.2 (Bipy); 126.3 (C6/7); 116.2 (C4/9); 106.2
(Bipy); 105.6 (Bipy); 104.4 (Bipy); 103.6 (Cp); 96.9 (Bipy); 94.5
(Bipy); 93.6 (C2); 93.1 (C1/3); 27.1 (Bipy); 24.7 (Bipy).
P r ep a r a tion of [In d Cp Mo(tBu 2bip y)][BF 4]2 (5). A sus-
pension of [IndCpMo(NCMe)2][BF4]2 (0.37 g, 0.70 mmol) in
Me2CO was allowed to react with 4,4′-di-(tert-butyl)-2,2′-
bipyridine (0.19 g, 0.70 mmol) for 1 h at room temperature.
The violet solution was taken to dryness, and the resulting
powder was recrystallized from CH2Cl2/Et2O in quantitative
yield.
Rea ction of [In d Cp Mo(CO)2][BF 4]2 w ith d p p e. A sus-
pension of [IndCpMo(CO)2][BF4]2 (0.35 g, 0.70 mmol) in Me2-
CO was treated with dppe (0.28 g, 0.70 mmol), and this
mixture was refluxed and irradiated with a 60 W tungsten
bulb for 4 h. The solvent of the resulting yellow solution was
evaporated under vacuum to yield a powder which was
completely dissolved in CH2Cl2. After concentration to ca. 5
mL and addition of Et2O, [CpMo(CO)2(dppe)]BF4 precipitated
as a yellow powder, in 80% yield. The complex was identified
1
by comparison of its IR and H NMR spectra with those of an
authentic sample.16 Crystals were obtained from a slow CH2-
Cl2/Et2O recrystallization.
Anal. Found: C, 53.05; H, 4.86; N, 4.00. Calcd for C32H36
-
Anal. Found: C, 56.04; H, 4.45. Calcd for C33H29BF4O2P2-
Mo: C, 56.44, H, 4.16%. Selected IR (KBr, cm-1): ν 3055; 1975,
1906 (sv, CO); 1697; 1485; 1437; 1084; 746; 698. 1H NMR (CH3-
CN-d3, 300 MHz, room temp, δ (ppm)): 7.61-7.43 (c, 20H, Ph);
4.75 (s (br), 5H, Cp); 2.93-2.85 (m, 2H, CH2 of dppe); 2.13-
1.99 (m, 2H, CH2 of dppe).
B2F8N2Mo: C, 53.52, H, 5.05, N, 3.90. Selected IR (KBr, cm-1):
ν 3121, 2967, 1618, 1543, 1483, 1415, 1369, 1252, 1060, 845,
768. 1H NMR (Me2CO-d6, 300 MHz, room temp, δ (ppm)): 8.69
t
t
(s (br), 2H, Bu2bipy); 7.76 (d (br), 2H, Bu2bipy); 7.56 (m, 2H,
tBu2bipy); 7.53-7.50 (m, 2H, H5-8); 7.19-7.16 (m, 2H, H5-8);
6.43 (t, 1H, H2); 6.14 (d, 2H, H1/3); 5.98 (s, 5H, Cp); 1.31 (s,
18H, CH3).
P r ep a r a tion of [In d Cp Mo(P Me3)2][BF 4]2 (2). Meth od a .
A suspension of IndCpMoCl2 (0.25 g, 0.71 mmol) in CH2Cl2
was treated with PMe3 (0.16 mL) and TlBF4 (0.41 g, 1.42
mmol). After the mixture was stirred for 12 h, the supernatant
solution was filtered and the remaining precipitate was
extracted with Me2CO (3 × 40 mL). Upon concentration and
cooling the pink microcrystalline complex separated. The
complex was recrystallized from Me2CO/Et2O in 70% yield.
Meth od b. A solution of [IndCpMo(NCMe)2][BF4]2 (0.19 g,
0.36 mmol) in CH2Cl2/NMF (10/1) was allowed to react with
PMe3 (0.07 mL, 0.72 mmol) for 4h at room temperature. The
resulting red solution was concentrated under vacuum until
the only remaining solvent was NMF. Addition of Et2O/EtOH
(30/1) allowed the precipitation of the pink product. This was
washed with CH2Cl2 and Et2O.
P r ep a r a tion of [In d Cp Mo(H2biim )][BF 4]2 (6). A solution
of [IndCpMo(NCMe)2][BF4]2 (0.26 g, 0.50 mmol) in CH2Cl2/
NMF (10/1) was allowed to react overnight with H2biim (0.07
g, 0.50 mmol) under reflux. Upon concentration under vacuum
(until the only remaining solvent was NMF) followed by the
addition of Et2O, the violet microcrystalline complex separated.
The compound was washed with CH2Cl2. Yield: 90%.
Anal. Found: C, 41.15; H, 3.24; N, 9.12. Calcd for C20H18
-
B2F8N4Mo: C, 41.14, H, 3.11, N, 9.59. Selected IR (KBr, cm-1):
ν 3370, 3086, 1665, 1535, 1495, 1427, 1072, 842, 762. 1H NMR
(Me2CO-d6, 300 MHz, room temp, δ (ppm)): 8.11 (s (br), 2H,
N-H); 7.66 (d, 2H, H2biim); 7.59-7.55 (m, 2H, H5-8); 7.44-
7.41 (m, 2H, H5-8); 6.99 (d, 2H, H2biim); 6.57 (t, 1H, H2); 6.20
(d, 2H, H1/3); 5.91 (s, 5H, Cp). 13C NMR (CH3CN-d3, 75 MHz,
room temp, δ (ppm)): 143.6 (H2biim); 133.9 (C5/8); 133.1 (H2-
Anal. Found: C, 24.78; H, 4.25;. Calcd for C20H30B2F8P2-
Mo: C, 25.03, H, 3.97%. Selected IR(KBr, cm-1): ν 3366, 3092,

514 Organometallics, Vol. 18, No. 4, 1999
Gamelas et al.
biim); 127.9 (C6/7); 123.5 (C4/9); 101.9 (Cp); 92.6 (C2); 91.7 (C1/3);
25.2 (H2biim).
P r ep a r a tion of [In d Cp Mo(NMF )2][BF 4]2 (11). A solution
of [IndCpMo(NCMe)2][BF4]2 (0.25 g, 0.47 mmol) in CH2Cl2/
NMF (10/1) was refluxed overnight. The resulting dark green
solution was concentrated under vacuum until the only
remaining solvent was NMF. Addition of Et2O/EtOH (30/1)
allowed the precipitation of the green product. This was
washed with CH2Cl2 and Et2O.
P r ep a r a tion of [In d Cp Mo(CO)(CNMe)][BF 4]2 (7). A
suspension of [IndCpMo(CO)2][BF4]2 (0.35 g, 0.70 mmol) in
CH2Cl2 was treated with excess CNMe (200 µL), and the
reaction mixture was refluxed and irradiated with a 60 W
tungsten bulb for 10 h. The supernatant solution was filtered
and the precipitate washed with CH2Cl2. The dark yellow
complex was recrystallized from NCMe/Et2O in 80% yield.
Anal. Found: C, 39.32; H, 2.83; N, 3.19. Calcd for C17H15B2F8-
NOMo: C, 39.35, H, 2.91, N, 2.70. Selected IR (KBr, cm-1): ν
3079; 2255, 2076 (sv, CO); 1537; 1447; 1416; 1300; 1119; 871;
766. 1H NMR (CH3CN-d3, 300 MHz, room temp, δ (ppm)):
7.88-7.76 (m, 4H, H5-8); 6.72-6.68 (c, 2H, H1/3); 6.32 (t, 1H,
H2); 6.03 (s, 5H, Cp); 3.57 (s, 3H, CH3).
P r ep a r a tion of [In d Cp Mo(CNMe)2][BF 4]2 (8). Meth od
a . A suspension of [IndCpMo(CO)2][BF4]2 (0.35 g, 0.70 mmol)
in CH2Cl2 was treated with a large excess of CNMe (400 µL)
and the reaction mixture refluxed and irradiated with a 60 W
tungsten bulb for 24 h. The supernatant solution was filtered
and the precipitate washed with Me2CO. The yellow complex
was recrystallized from NCMe/Et2O in 40% yield.
Meth od b. Addition of excess CNMe (300 µL) to a solution
of [IndCpMo(NCMe)2][BF4]2 (0.30 g, 0.56 mmol) in CH2Cl2/
NMF (10/1) caused an immediate change of color from violet
to yellow. After 1 h of stirring at room temperature, the
solution was concentrated under vacuum (until the only
remaining solvent was NMF) and Et2O/EtOH (30/1) added to
precipitate the yellow complex. The compound was washed
with CH2Cl2. Yield: 90%.
Anal. Found: C, 38.16; H, 3.93; N, 4.83. Calcd for C18H22
-
B2F8N2O2Mo: C, 38.07; H, 3.90; N, 4.93. Selected IR (KBr,
cm-1): ν 3230, 3052, 1640, 1432, 1350, 1072, 852, 756. 1H NMR
(Me2CO-d6, 300 MHz, room temp, δ (ppm)): 7.66 (s (br), 2H,
H5-8); 7.60 (s (br), 2H, H5-8); 6.53 (t, 1H, H2); 6.46 (d, 2H, H1/3);
6.19 (s, 5H, Cp); 3.74 (s, 6H, CH3).
P r ep a r a t ion of [In d Mo(η4-C5H 6)(d p p e)][BF 4]‚CH 2Cl2
(12). Addition of NaBH4 (7.2 mg, 0.19 mmol) to a solution of
[IndCpMo(dppe)][BF4]2 (0.14 g, 0.16 mmol) in Me2CO caused
an immediate change of color from salmon to dark orange.
After it was stirred for 1 h at room temperature, the reaction
mixture was taken to dryness and the residue was extracted
with CH2Cl2 to give the dark brick red complex in quantitative
yield.
Anal. Found: C, 58.15; H, 4.86. Calcd for C41H39BF4Cl2P2-
Mo: C, 58.12, H, 4.64. Selected IR (KBr, cm-1): ν 3053, 2970,
1
2768, 1697, 1483, 1435, 1084, 748, 698. H NMR (CH2Cl2-d2,
300 MHz, room temp, δ (ppm)): 7.42-6.81 (c, 24H, Ph + H5-8);
6.50 (m, 2H, H1/3); 4.99 (t, 1H, H2); 4.27 (s (br), 2H, H1-2); 3.49
(s (br), 2H, H3-4); 3.32 (s (br), 1H, Hexo); 2.85 (s (br), 1H, Hendo);
2.06 (s, 4H, CH2 of dppe).
Anal. Found: C, 40.61; H, 3.39; N, 5.15. Calcd for C18H18
-
B2F8N2Mo: C, 40.65, H, 3.41, N, 5.27. Selected IR (KBr, cm-1):
ν 3102, 2245, 1537, 1447, 1414, 1304, 1084, 866, 770. 1H NMR
(CH3CN-d3, 300 MHz, room temp, δ (ppm)):7.71-7.68 (m, 4H,
H5-8); 6.34 (d, 2H, H1/3); 6.05 (t, 1H, H2); 5.70 (s, 5H, Cp); 3.59
(s, 6H, CH3). 13C NMR (CH3CN-d3, 75 MHz, room temp, δ
(ppm)): 141.7 (CNMe); 134.7 (C5/8); 127.3 (C6/7); 112.8 (C4/9);
98.1 (Cp); 89.7 (C2); 89.3 (C1/3); 32.9 (CNCH3).
P r ep a r a tion of [In d Cp Mo(CNCMe3)2][BF 4]2 (9). Addi-
tion of excess CNtBu (0.20 mL) to a solution of [IndCpMo-
(NCMe)2][BF4]2 (0.30 g, 0.56 mmol) in CH2Cl2/NMF (10/1)
caused an immediate change of color from violet to light yellow.
After 1 h of stirring at room temperature, the solution was
concentrated under vacuum (until the only remaining solvent
was NMF) and Et2O/EtOH (30/1) added to precipitate the
yellow complex. The compound was washed with CH2Cl2.
Yield: 95%.
P r ep a r a tion of (η3-In d )Cp Mo(d p p e) (13). Meth od a . A
solution of [IndMo(η4-C5H6)(dppe)][BF4] (0.34 g, 0.50 mmol) in
CH2Cl2 was treated with excess NEt3 (0.5 mL). After the
mixture was stirred for 2 h at room temperature, the solvent
of the orange solution was removed under vacuum and the
residue extracted with toluene (3 × 30 mL). The orange powder
obtained upon concentration of the extract was washed with
cold pentane. Yield: 50%.
Meth od b. The addition of an NCMe solution of Cp2Co (0.18
g, 0.95 mmol) to the complex [IndCpMo(dppe)][BF4]2 (0.40 g,
0.48 mmol) dissolved in the same solvent caused an immediate
change in color from salmon to orange together with the
appearance of a precipitate. After the mixture was stirred for
2 h at room temperature, the solvent was removed under
vacuum and the residue extracted with toluene. Upon con-
centration and cooling of the extract the orange microcrystal-
line product separated in 95% yield.
Anal. Found: C, 71.39; H, 5.21. Calcd for C40H36P2Mo: C,
71.22, H, 5.38. Selected IR (KBr, cm-1): ν 3048, 1481, 1433,
1302, 1202, 1092, 1009, 922, 820, 740, 696. 1H NMR (C6H6-d6,
300 MHz, room temp, δ (ppm)): 7.42-6.88 (c, 20H, Ph); 6.46
(d, 4H, H5-8); 4.48 (s (br), 5H, Cp); 2.96 (s (br), 3H, H1/3); 2.17-
1.83 (c, 4H, CH2 of dppe). 13C NMR (CH2Cl2-d2, 75 MHz, room
temp, δ (ppm)): 151.5 (C4/9); 133.4-129.1 (c, dppe + C5/8); 118.0
(C6/7); 114.2 (C2); 86.2 (Cp); 64.99 (C1/3); 29.6 (dppe).
Anal. Found: C, 46.79; H, 4.79; N, 4.56. Calcd for C24H30
-
B2F8N2Mo: C, 46.79, H, 4.91, N, 4.55. Selected IR (KBr, cm-1):
ν 3320, 3055, 2978, 2220, 2200, 1464, 1373, 1200, 1072, 876,
766. 1H NMR (Me2CO-d6, 300 MHz, room temp, δ (ppm)):
8.00-7.98 (m, 2H, H5-8); 7.84-7.81 (m, 2H, H5-8); 6.81 (d, 2H,
H1/3); 6.37 (t, 1H, H2); 6.11 (s, 5H, Cp); 1.66 (s, 18H, CH3). 13C
NMR (CH3CN-d3, 75 MHz, room temp, δ (ppm)): 142.3
(CNCMe3); 134.8 (C5/8); 127.3 (C6/7); 112.7 (C4/9); 98.4 (Cp); 89.6
(C2); 89.3 (C1/3); 62.8 (CNCMe3); 29.7 (CNC(CH3)3).
P r ep a r a tion of [In d Cp Mo(NCMe)(NMF )][BF 4]2 (10). A
solution of [IndCpMo(NCMe)2][BF4]2 (0.25 g, 0.47 mmol) in
CH2Cl2/NMF (10/1) was stirred for 3 h at room temperature.
The resulting dark violet solution was concentrated under
vacuum until the only remaining solvent was NMF. Addition
of Et2O/EtOH (30/1) allowed the precipitation of the violet
product. This was washed with CH2Cl2 and Et2O.
P r ep a r a tion of (η3-In d )Cp Mo(P Me3)2 (14). The addition
of an NCMe solution of Cp2Co (0.24 g, 1.30 mmol) to the
complex [IndCpMo(PMe3)2][BF4]2 (0.39 g, 0.65 mmol) dissolved
in the same solvent caused an immediate change of color from
violet to orange together with the appearance of a fine
precipitate. After the mixture was stirred for 1 h at room
temperature, the solvent was removed under vacuum and the
residue extracted with warm Et2O (3 × 30 mL). Upon
concentration and cooling of the extract the orange micro-
crystalline product separated in 50% yield.
Anal. Found: C, 39.50; H, 3.49; N, 5.11. Calcd for C18H20
-
B2F8N2OMo: C, 39.31; H, 3.67; N, 5.09. Selected IR (KBr,
cm-1): ν 3233, 3052, 2292, 1643, 1421, 1350, 1068, 852, 756.
1H NMR (Me2CO-d6, 300 MHz, room temp, δ (ppm)): 7.91-
7.88 (m, 2H, H5-8); 7.74-7.71 (m, 2H, H5-8); 6.71 (d, 2H, H1/3);
6.65 (t, 1H, H2); 6.19 (s, 5H, Cp); 2.83 (s, 3H, CH3); 2.63 (s,
3H, NCMe).
Anal. Found: C, 56.42; H, 7.39. Calcd for C20H30P2Mo: C,
56.42, H, 5.39. MS (EI; m/z): 430 (M+); 354 (M+ - PMe3); 278

Indenyl Slippage in [IndCpMoL2]2+/ +/ 0 Complexes
Organometallics, Vol. 18, No. 4, 1999 515
(M+ - 2PMe3); 116 (IndH+). Selected IR (KBr, cm-1): ν 3100,
2920, 1416, 1263, 866, 806. 1H NMR (C6H6-d6, 300 MHz, room
temp, δ (ppm)): 6.52 (s (br), 4H, H5-8); 6.26 (s (br), 1H, H2);
4.17 (s (br), 5H,Cp); 3.03 (s (br), 3H, H1/3); 0.68 (t (br), 18H,
PMe3).
P r ep a r a tion of (η3-In d )Cp Mo(Bip y) (15). The addition
of an NCMe solution of Cp2Co (0.24 g, 1.30 mmol) to the
complex [IndCpMo(Bipy)2][BF4]2 (0.23 g, 0.39 mmol) dissolved
in the same solvent caused an immediate change in color from
violet to deep purple. After the mixture was stirred for 1 h at
room temperature, the solvent was removed under vacuum
and the residue extracted with a hexane/ether mixture (1/1)
(2 × 30 mL). Upon concentration and cooling of the extract
the deep purple microcrystalline product separated in 90%
yield.
X-r a y Cr ysta llogr a p h y. Suitable single crystals for the
X-ray diffraction studies were grown by standard techniques
from saturated solutions of 1 in NCCH3/Et2O and of 13 in
n-pentane/n-hexane/(CH3)2O/Et2O at room temperature. Both
structures were solved by a combination of direct methods,
difference Fourier syntheses and refined by full-matrix least-
squares method. Neutral atom scattering factors for all atoms
and anomalous dispersion corrections for the non-hydrogen
atoms were taken from ref 31. All calculations were performed
on a DEC 3000 AXP workstation with the STRUX-V32 system,
including the programs PLATON-92,33 PLUTON-92,33 SIR-
92,34 and SHELXL-93.35
Da ta Collection , Str u ctu r e Solu tion , a n d Refin em en t
for th e Com p lex 1. A summary of the crystal and experi-
mental data is reported in Table 4. Preliminary examination
and data collection were carried out on an imaging plate
diffraction system (IPDS; Stoe&Cie) equipped with a rotating
anode (Nonius FR591; 50 kV; 60 mA; 3.0 kW) and graphite-
monochromated Mo KR radiation. Data collection were per-
formed at 193 K within the θ range of 2.32° < θ < 27.75° with
an exposure time of 1.50 min per image (rotation scan modus
from æ ) 0.0 to 180° with ∆æ ) 1°). A total number of 36 740
reflections were collected; 664 systematic absent reflections
were rejected from the original data set. After merging, a total
of 9536 independent reflections remained and were used for
all calculations. Data were corrected for Lorentz and polariza-
tion effects. Corrections for absorption and decay effects were
applied with the program DECAY.36 The unit cell parameters
were obtained by full-matrix least-squares refinements of 4551
reflections with the program CELL.36 All “heavy atoms” of the
asymmetric unit were anisotropically refined. Hydrogen atoms
were calculated in ideal positions (riding model) and included
in the structure factor calculations but not refined. Full-matrix
least-squares refinements were carried out by minimizing
Anal. Found: C, 67.09; H, 5.04; N, 6.97. Calcd for C24H20N2-
Mo: C, 66.67, H, 4.66, N, 6.48. Selected IR (KBr, cm-1): ν 3048,
1
2928, 1450, 1294, 1240, 1153, 995, 826, 760. H NMR (C6H6-
d6, 300 MHz, room temp, δ (ppm)): 8.54 (d, 2H, Bipy); 7.33
(d, 2H, Bipy); 6.78 (m, 2H, H5-8); 6.68 (m, 2H, H5-8); 6.47 (t,
2H, Bipy); 5.96 (t, 2H, Bipy); 4.77 (d, 2H, H1/3); 4.36 (s, 5H,
Cp); 3.44 (s (br), 1H, H2).
P r ep a r a tion of (η3-In d )Cp Mo(CO)(CNMe) (16). A tolu-
ene solution of Cp2Co (0.06 g, 0.33 mmol) was added to the
complex [IndCpMo(CO)(CNMe)][BF4]2 (0.08 g, 0.16 mmol)
suspended in the same solvent. After the mixture was stirred
for 2 h at room temperature, the solvent was removed under
vacuum and the residue extracted with hexane (2 × 30 mL).
Upon concentration and cooling of the extract the brick red
microcrystalline product separated in 80% yield.
Anal. Found: C, 59.35; H, 3.90; N, 4.42. Calcd for C17H15
-
NOMo: C, 59.14, H, 4.38, N, 4.06. Selected IR (KBr, cm-1): ν
3106, 2131, 1863, 1415, 1201, 1010, 871. 1H NMR (C6H6-d6,
300 MHz, room temp, δ (ppm)): 7.16 (s (br), 1H, H5-8); 6.88
(t, 1H, H5-8); 6.65 (s (br), 1H, H5-8); 6.51 (t, 1H, H5-8); 5.50
(m, 1H, H2); 4.85 (t, 1H, H1/3); 4.69 (s, 5H, Cp); 4.62 (t, 1H,
H1/3); 2.18 (s, 3H, CH3).
2
2 2
∑w(Fo - Fc
) with the SHELXL-93 weighting scheme and
stopped at shift/error < 0.001.
Da ta Collection , Str u ctu r e Solu tion , a n d Refin em en t
for th e Com p lex 13. A summary of the crystal and experi-
mental data is reported in Table 4. Preliminary examination
and data collection were carried out on an Kappa CCD area
detecting diffraction system (NONIUS KCCD) equipped with
a rotating anode (Nonius FR591; 50 kV; 60 mA; 3.0 kW) and
graphite-monochromated Mo KR radiation. Data collection
were performed at 173 K within the θ range of 2.18° < θ <
31.35° with an exposure time of 1.0 min per frame (θ offset
10°, æ-start 0.0°, æ-end 360°, ∆æ ) 1°, repetition 1). A total
number of 14 111 reflections were collected. After merging, a
total of 7231 independent reflections remained and were used
for all calculations. Data were corrected for Lorentz and
polarization effects. The unit cell parameters were obtained
by full-matrix least-squares refinements of 14 653 reflections.
Raw data were reduced and scaled with the programs DENZO
and HKL.37 All “heavy atoms” of the asymmetric unit were
refined anisotropically. All hydrogen atoms were found in the
difference map calculated from the model containing all non-
hydrogen atoms. The hydrogen positions were refined with
individual isotropic displacement parameters. Full-matrix
least-squares refinements were carried out by minimizing
P r ep a r a tion of (η3-In d )Cp Mo(CNCMe3)2 (17). Addition
of a fresh NCMe solution of Cp2Co (0.11 g, 0.59 mmol) to the
complex [IndCpMo(CNCMe3)2][BF4]2 (0.26 g, 0.30 mmol) dis-
solved in the same solvent caused an immediate reaction. After
the mixture was stirred for 1 h at room temperature, the
solvent was removed under vacuum and the residue extracted
with hexane (2 × 30 mL). Upon concentration and cooling of
the extract the yellow complex separated as a powder, in 50%
yield.
Anal. Found: C, 65.59; H, 6.33; N, 5.98. Calcd for C24H30N2-
Mo: C, 65.15, H, 6.83, N, 6.33. Selected IR (KBr, cm-1): ν 3055,
1
2978, 2081, 2047, 1456, 1200, 1033, 793, 746. H NMR (C6H6-
d6, 300 MHz, room temp, δ (ppm)): 6.81 (t, 1H, H2); 6.64-
6.61 (m, 2H, H5-8); 6.51-6.48 (m, 2H, H5-8); 4.80 (s, 5H, Cp);
4.41 (d, 1H, H1/3); 1.04 (s, 18H, CH3).
(31) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C, Tables
6.1.1.4 (pp 500-502), 4.2.6.8 (pp 219-222), and 4.2.4.2 (pp 193-199),
(32) Artus, G.; Scherer, W.; Priermeier, T.; Herdtweck, E. STRUX-
V, A Program System to Handle X-ray Data; TU Mu¨nchen, Mu¨nchen,
Germany, 1997.
(33) Spek, A. L. PLATON-92 - PLUTON-92, An Integrated Tool
for the Analysis of the Results of a Single-Crystal Structure Determi-
nation. Acta Crystallogr., Sect. A 1990, 46, C34.
(34) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; and Camalli, M. SIR-92, University of Bari,
Bari, Italy, 1992.
(35) Sheldrick, G. M. SHELXL-93. In Crystallographic Computing
3; Sheldrick, G. M., Kru¨ger, C., Goddard, R., Eds.; Oxford University
Press: Oxford, England, 1993; pp 175-189.
(36) IPDS Operating System Version 2.8; Stoe&Cie GmbH, Darm-
stadt, Germany, 1997.
2
2 2
∑w(Fo - Fc
) with the SHELXL-93 weighting scheme and
stopped at shift/error < 0.001.
Ack n ow led gm en t. This work was supported by
PRAXIS XXI under projects 2/2.1/QUI/316/94 and PBIC/
C/QUI/220/95. C.A.G. (BD) and J .P.L. (BTL) thank
PRAXIS XXI for a grant.
Su p p or tin g In for m a tion Ava ila ble: Complete listings
of data collection parameters, final fractional atomic coordi-
nates, thermal displacement parameters, bond lengths, and
bond angles for 1 and 13. This material is available free of
charge via the Internet at http://pubs.acs.org.
(37) Otwinowski, Z.; Minor, W. Processing of X-ray Diffraction Data
Collected in Oscillation Mode. In Methods in Enzymology; Carter, W.
C., Sweet, R. M., J r., Eds.; Academic Press: New York, 1996; Vol. 276.
(38) Honan, M. B.; Atwood, J . L.; Bernal, I.; Herrmann, W. A. J .
Organomet. Chem. 1979, 179, 403.
OM9808357