Transition-metal derivatives of the functionalized cyclopentadienyl ligand. XVI. Synthesis of the bridged complexes [(μ-η5-C5H4PPh2)M(CO) 2]2 (M = Cr, Mo, W). X-Ray crystal structure of the dihydride derivative [μ-η5-C5H4PPh2W(CO) 2H]2

Article abstract of DOI:10.1039/a706746a

Four synthetical methods, implying basically the oxidation of the anionic species [(η⁵-C₅H₄PPh₂)M(CO) ₃]^- [M = Cr, (2a^-), Mo (2b^-), W (2c^-)] to produce the new homobimetallic derivatives [(μ,η⁵-C₅H₄PPh₂)M(CO) ₂]₂ (M-M), [M = Cr (1a), Mo (1b), W (1c)] of the heterodifunctional diphenylphosphinocyclopentadienyl bridging ligand, have been investigated. The first approach proceeds in two steps: thus the electrochemical oxidation of the complexes 2a^- and 2b^- leads to the metal-metal bonded dimetallic complexes [(η⁵-C₅H₄PPh₂)M(CO) ₃]₂ (M-M), [M = Cr (5a), Mo (5b)]; the irradiation of these complexes 5a and 5b with a high-pressure Hg lamp affords the corresponding decarbonylated bridged complexes 1a and 1b. The second method, using silver tetrafluoroborate as the oxidant of the anions 2a^- to 2c^-, leads to the formation of tetrametallic cyclic complexes of silver and Group 6 transition metals [(μ-η⁵-C₅H₄PPh₂[M(CO) ₃Ag]₂, [M = Cr (6a), Mo (6b), W (6c)] but the splitting of these compounds into bimetallic complexes 1a-c and metallic silver appears neither easy nor selective. As a third procedure, the hydrido complexes (η⁵-C₅H₄PPh₂)M(CO)₃H [M = Cr (3a), Mo (3b), W (3c)] are irradiated with a high-pressure Hg lamp. This procedure is useful to prepare 1b but is non-selective in the two other cases, affording mainly bimetallic dihydrido-bridged complexes [(μ-η⁵-C₅H₄PPh₂)M(CO) ₂H]₂ [M = Mo (7b), W (7c)] and 1a or 1b, as a result of the expected competition between the dehydrogenation and the decarbonylation processes. The X-ray molecular structure of 7c points out the transoid disposition of the hydrido ligands, which could well be a factor of its inertness in a spontaneous dehydrogenation process towards 1c. Finally, the most efficient method requires the preliminary preparation of the iodo complexes (η⁵-C₅H₄PPh₂)M(CO)₃I [M = Cr (4a), Mo (4b), W (4c)], which are reacted in toluene with their anionic parents 2^-. This last method is particularly useful for preparing 1a and 1c.

Full text of DOI:10.1039/a706746a

View Article Online / Journal Homepage / Table of Contents for this issue
Transition-metal derivatives of the functionalized cyclopentadienyl
ligand. XVI. Synthesis of the bridged complexes [(l-g5-
C H PPh )M(CO) ] (M = Cr, Mo, W). X-Ray crystal structure of
5 4
2
2 2
the dihydride derivative [(l-g5-C H PPh )W(CO) H]
5 4
2
2
2
Brigitte Brumas-Soula, Francoise Dahan and Rene Poilblanc*
L aboratoire de chimie de coordination du CNRS,¤ 205 route de Narbonne, 31077 T oulouse cedex,
France
Four synthetical methods, implying basically the oxidation of the anionic species [(g5-C H PPh )M(CO) ]~
5
4
2
3
[M \ Cr, (2a~), Mo (2b~), W (2c~)] to produce the new homobimetallic derivatives [(l,g5-
C H PPh )M(CO) ] (MwM), [M \ Cr (1a), Mo (1b), W (1c)] of the heterodifunctional
5
4
2
2 2
diphenylphosphinocyclopentadienyl bridging ligand, have been investigated. The Ðrst approach proceeds in two
steps: thus the electrochemical oxidation of the complexes 2a~and 2b~ leads to the metalÈmetal bonded
dimetallic complexes [(g5-C H PPh )M(CO) ] (MwM), [M \ Cr (5a), Mo (5b)]; the irradiation of these
5
4
2
3 2
complexes 5a and 5b with a high-pressure Hg lamp a†ords the corresponding decarbonylated bridged
complexes 1a and 1b. The second method, using silver tetraÑuoroborate as the oxidant of the anions 2a~ to 2c~,
leads to the formation of tetrametallic cyclic complexes of silver and Group 6 transition metals [(l-g5-
C H PPh [M(CO) Ag] , [M \ Cr (6a), Mo (6b), W (6c)] but the splitting of these compounds into bimetallic
5
4
2
3
2
complexes 1aÈc and metallic silver appears neither easy nor selective. As a third procedure, the hydrido
complexes (g5-C H PPh )M(CO) H [M \ Cr (3a), Mo (3b), W (3c)] are irradiated with a high-pressure Hg
5
4
2
3
lamp. This procedure is useful to prepare 1b but is non-selective in the two other cases, a†ording mainly
bimetallic dihydrido-bridged complexes [(l-g5-C H PPh )M(CO) H] [M \ Mo (7b), W (7c)] and 1a or 1b, as
5
4
2
2
2
a result of the expected competition between the dehydrogenation and the decarbonylation processes. The X-ray
molecular structure of 7c points out the transo•d disposition of the hydrido ligands, which could well be a factor
of its inertness in a spontaneous dehydrogenation process towards 1c. Finally, the most efficient method requires
the preliminary preparation of the iodo complexes (g5-C H PPh )M(CO) I [M \ Cr (4a), Mo (4b), W (4c)],
5
4
2
3
which are reacted in toluene with their anionic parents 2~. This last method is particularly useful for preparing
1a and 1c.
Complexes des metaux de transition avec les ligands cyclopentadienyles fonctionnalises. XVI. Synthese des
complexes dimetalliques [(l-g5-C H PPh )M(CO) ] (M = Cr, Mo, W). Structure moleculaire du derive
5
4
2
2 2
dihydrure [(l-g5-C H PPh )W(CO) H] . AÐn dÏacceder a la serie des complexes homobimetalliques pontes
5
4
2
2
2
[(l-g5-C H PPh )M(CO )] (MwM), [M \ Cr (1a), Mo (1b), W (1c)] du ligand heterodifonctionnel pontant
diphenylphosphinocyclopentadienyle, quatre possibilites de preparations ont ete etudiees. Elles impliquent
5
4
2
2 2
fondamentalement lÏoxydation des anions [(g5-C H PPh )M(CO) ]~ [M \ Cr (2a~), Mo (2b~), W (2c~)]. La
5
4
2
3
premiere approche met dÏabord en jeu lÏoxydation electrochimique de 2a~ et 2b~ conduisant aux complexes a
liaison metalÈmetal [(g5-C H PPh )M(CO )] (MwM), [M \ Cr (5a), Mo (5b)] dont lÏirradiation sous UV
5
4
2
3 2
conduit aux derives recherches 1a et 1b. La deuxieme, utilisant comme oxydant le tetraÑuoborate dÏargent,
conduit a la formation de complexes tetrametalliques cycliques [(l-g5-C H PPh )M(CO) Ag] [M \ Cr (6a),
5
4
2
3
2
Mo (6b), W (6c)]. La troisieme voie met en jeux lÏirradiation UV des hydrures (g5-C H PPh )M(CO) H,
5
4
2
3
[M \ Cr (3a), Mo (3b), W (3c)]. Celle-ci se traduit par la deshydrogenation de 3b en 1b, mais la decarbonylation
de 3c, conduit au complexe dihydrure ponte [(l-g5-C H PPh )W(CO) H] , 7c dont la structure a ete
5
4
2
2
2
determinee. Finalement, la quatrieme methode exige la preparation prealable des iodures (g5-
C H PPh )M(CO) I [M \ Cr (4a), Mo (4b), W (4c)] qui reagissent aisement avec les anions correspondants
5
4
2
3
2a~È2c~.
We are currently involved in the synthesis of various dinuclear
compounds in which two functionalized cyclopentadienyls,
acting as eight-electron ligands, bridge the two metallic
centers. This bridging forces the metallic atoms to remain in
close proximity and has been shown, specially in the case of
rhodium(I) complexes,1 to promote reactions in which the two
metal centers cooperate.2 In extending these studies to metalÈ
metal bonded dimers of the Group 6 transition metals, we
anticipated that bridging might stabilize new dimetallic
species and modify the course of reactions in which homolytic
or heterolytic splittings of the metalÈmetal bond play a promi-
nent part.3 In the present paper, we shall describe and
compare synthetic processes a†ording the dinuclear complexes
of the general formula [(l-g5-C H PPh )M(CO) ] [M \ Cr
5
4
2
2 2
(1a), Mo (1b), W (1c)].
Using the monometallic anionic complexes [(g5-
C H PPh )M(CO) ]~[M \ Cr (2a~), Mo (2b~), W (2c~)] as
5
4
2
3
starting materials, four synthetic attempts implying basically
oxidative processes were investigated, namely: (i) electro- and
photo-chemical transformations of the anions 2a~, 2b~ and
2c~; (ii) chemical oxidation of the anions 2a~, 2b~ and 2c~ by
¤ UPR 8241 liee par convention a lÏUniversite Paul Sabatier et a
l“Institut National Polytechnique de Toulouse.
New J. Chem., 1998, Pages 15È23
15

View Article Online
silver tetraÑuoroborate; (iii) photochemical dehydrogenation
of the hydrides (g5-C H PPh )M(CO) H [M \ Cr (3a), Mo
5
4
2
3
(3b), W (3c)]; and (iv) metalÈmetal bond formation by reaction
of the lithium salts [Li][2] with the corresponding iodo com-
plexes (g5-C H PPh )M(CO) I [M \ Cr (4a), Mo (4b), W
5
4
2
3
(4c)].
Interestingly, the Ðrst process includes the primary forma-
tion of metalÈmetal bonded complexes [(g5-
1a–1c
C H PPh )M(CO) ] [M \ Cr (5a), Mo (5b)], the second one
5
4
2
3 2
a†ords novel tetrametallic MwAg cyclic complexes [(l-g5-
C H PPh )M(CO) Ag] [M \ Cr (6a), Mo (6b), W (6c)] and
Scheme 1
5
4
2
3
2
of a symmetry plane in the C H wP fragment as shown in
the third one also leads to novel dimetallic dihydrides [(l-g5-
C H PPh )M(CO) H] [M \ Mo (7b), W (7c)]. The X-ray
5
4
Scheme 1. From the values of the J coupling constants, it is
HvP
5
4
2
2
2
also suggested that the two signals at higher Ðeld in the three
molecular structure of the dihydride 7c is also presented and
discussed in comparison with the already known parent com-
pounds [(g5-C H )W(CO) (l-H)] (W xW ), related to the
complexes 1aÈ1c correspond to the protons in the a positions
to the phosphorus atoms. Noticeably, the four cyclo-
pentadienyl signals exhibit an important solvent e†ect (see
Experimental). This last phenomena is most clearly observed
with 1a and 1b. A last argument in favor of the equivalency of
the two [(g5-C H PPh )M(CO) ] fragments in 1aÈ1c is pro-
5
5
2
2
series of non-bridged complexes.4
Preparations of the molybdenum complex 1b and its X-ray
crystal structure, together with that of one of the tetrametallic
cyclic complexes [(l-g5-C H PPh )Mo(CO) Ag] , have
5
4
2
2
5
4
2
3
2
vided by the 31PM1HN NMR spectra, which exhibit only one
signal (Table 1). In all three cases, the chemical shifts appear
as characteristic of the coordination of the phosphorus atom
to the metal atom. In compound 1c, each 31P nucleus is
coupled with one 183W leading to a low intensity doublet that
brackets the uncoupled singlet; the isotopic Ðgure corresponds
to the isotopic ratio 183W/W (14.28%).
already been reported in two preliminary communications5,6
Results
The complex [(l-g5-C H PPh )Mo(CO) ] , 1b, is an inter-
5
4
2
2 2
esting example of a dinuclear complex having a metalÈmetal
bond supported by “ÑexibleÏ bridging ligands. As described
hereafter chromium and tungsten analogs have now been pre-
pared. Beside elemental analysis data, the three compounds
Preparation of the diphenylcyclopentadienyl monometallic
starting materials
1aÈ1c have been identiÐed by their mass spectra (DCI/NH ),
3
which are in good agreement with the expected isotopic
Fig. 1 sums up the various synthetic pathways used to prepare
the three dimetallic complexes 1aÈ1c via four methods, each
pattern calculated for dimetallic complexes. In addition, they
were also easily characterized by spectroscopic methods as
shown below.
starting
from
the
anionic
complexes
[(g5-
C H PPh )M(CO) ]~, 2a~È2c~. These anions were prepared
As shown in Table 1, the most evident analogies appear in
the IR spectra in the CwO stretching frequency region, where
5
4
2
3
from the lithium diphenylphosphinocyclopentadienyde using
tricarbonyl metal derivatives since the reactions with the
hexacarbonyl complexes produce largely the monomeric pen-
tacarbonyl anion [(g1-PPh C H )M(CO) ]~ (in which the
the observation of four bands agrees with the expected C
symmetry. Moreover, comparison of these spectra with that of
2v
the centrosymmetric metalÈmetal bonded complex [(g5-
2 5
4
5
phosphorus atom is bonded to the metal).
C H )Mo(CO) PPh ] 7 [1850 (s), 1831(vs) cm~1] suggests
5
5
2
3 2
By using the heptatrienyl tricarbonyl complexes (g6-
C H )M(CO) (M \ Cr, Mo) in reÑux with THF, the anions
the assignment of the two higher frequency bands of the C
2v
bridged complexes 1aÈ1c, to the in-phase stretching modes.
The observed spectra of 1aÈ1c are also comparable with that
exhibited by the [l-(Ph P)CH ][M(g5-C H )(CO) ] com-
plexes, which nevertheless, interestingly show a low frequency
shift [1919(s), 1882(vs), 1848(m), 1828(s) for M \ Mo8a and
1911(s), 1875(vs), 1837(m), 1815(s) for M \ W8b] in the same
solvent.
7
8
3
2a~ and 2b~ were obtained in good yield (99 and 91%,
respectively, with respect to (g6-C H )M(CO) ).9 Neverthe-
7
8
3
2
2
5
5
2 2
less, the synthesis of (g6-C H )Cr(CO) itself is slow (it needs
about 20 h of reÑux); in addition the substitution reaction of
7
8
3
(g6-C H )Cr(CO) with Li(C H PPh ) needs a three-day
7
8
3
5
4
2
period of reÑux to reach completeness. Moreover, the product
[Li][2a] was formed along with a pyrophoric compound
whose separation is awkward and decreases its yield (60%).
These constraints prompted us to use the complex
(CH CH CN) Cr(CO) as the starting material. In our hands,
In the 1H NMR spectra, the four protons of each cyclo-
pentadienyl ligand are non-equivalent, conÐrming the absence
3
2
3
3
the preparation of this complex following the published
procedure10 also gave a modest yield (60%), but its reaction in
toluene with a suspension of Li(C H PPh ) very conveniently
a†ords [Li][2a], which precipitated in high purity and good
yield [99% with respect to (CH CH CN) Cr(CO) ].
Table 1 Spectral characteristics of the bridged complexes 1a-1c
IR/cm~1 a 31PM1HN NMR/ppm
5
4
2
[(l-g5-C H PPh )Cr(CO) ]
1941 vs
1890 vs
1864 w
1844 s
88.5b
5
4
2
2 2
1a
3
2
3
3
The preparation of 2c~, starting from the cycloheptatrienyl
complex (g6-C H )W(CO) , has also been tested. In addition
7
8
3
to the slowness of the preparation of this starting material, its
reaction with Li(C H PPh ) in THF reÑux is accompanied by
[(l-g5-C H PPh )Mo(CO) ]
2 2
1943 vs
1888 vs
1868 w
1846 s
68.2c
5
4
2
1b
5
4
2
decomposition. Therefore a second method of preparation
was preferred using (CH CN) W(CO) as the starting
material.11 As in the case of the chromium compound, the use
of suspensions in toluene of the reactants (CH CN) W(CO)
and Li(C H PPh ) a†ords easily a precipitate of the product
[Li][2c] in high purity and good yield with respect to
(CH CN) W(CO) (97%).
3
3
3
[(l-g5-C H PPh )W(CO) ]
2 2
1938 vs
1892 vs
1863 w
1838 s
39.9 (J
35.0 (J
\ 140 Hz)b
\ 164 Hz)c
5
4
2
PvW
PvW
1c
3
3
3
5
4
2
a In toluene solution. b 81.015 MHz, [2H ]acetone c 32.40MHz,
3
3
3
6
The lithium salts [Li][2a], [Li][2b] and [Li][2c] were
identiÐed in 31PM1HN NMR by signals at chemical shifts (2a~,
[2H ]benzene.
6
16
New J. Chem., 1998, Pages 15È23

View Article Online
Fig. 1 The four synthetic reaction paths a†ording the bridged homobimetallic derivatives [(l-g5-C H PPh )M(CO) ] [M \ Cr (1a), Mo (1b),
5
4
2
2 2
W (1c)]
d [ 17.0(s); 2b~, d [ 18.2 (s); 2c~, d [ 17.2 (s ] d, 2J \ 41
4aÈ4c were easily identiÐed, namely in 31PM1HN NMR spectra,
PvW
Hz) in [2H ]benzene, consistent with a non-coordinated phos-
6
which show singlets at d [14.0 and [12.8 in [2H ]acetone,
6
phorus arm and in the infrared, surprisingly, by four CwO
respectively, for 4a and 4b and at [16.1 (s ] d, J \ 71 Hz)
PvW
stretching bands. The occurrence of four bands instead of the
three normally expected for tricarbonyl compounds has been
attributed to the formation of a species in which an inter-
action occurs between the CO groups and a lithium cation.12
The new hydrido complexes (g5-C H PPh )M(CO) H
in [2H ]benzene for 4c, fully consistent with a pendant phos-
6
phorus atom.
Electro- and photo-chemical processes leading to the bridged
dinuclear complexes 1a and 1b: method A
5
4
2
3
[M \ Cr (3a), Mo (3b), W (3c)] were readily prepared by
adding one equivalent of glacial acetic acid to toluene solu-
tions of the lithium salts [Li][2]. The solutions (from orange
for chromium to yellow for the tungsten derivatives) instanta-
neously turned red (from bright red for chromium to orange
red for the tungsten derivatives) together with the formation
of a light precipitate of lithium acetate. The hydrido complex-
es were identiÐed in 31PM1HN NMR spectra by singlets at
chemical shifts consistent with a dangling phosphino group
(3a, d [ 19.8; 3b, d [ 19.5; 3c, d [ 19.8), in 1H NMR spectra
by their hydride signals at high Ðeld [3a, d [ 5.39(s); 3b,
The transformation of the mononuclear anionic complexes
2a~È2c~, into the dinuclear neutral complexes 1aÈ1c can be
regarded as the succession of two processes, the oxidative
coupling of the anions, then the substitution of a carbonyl
ligand bonded to one of the metal centers by the phosphino
group bonded to the other metal center. We have already
reported our observations in the case of the molybdenum com-
plexes.6 We mention that in this case, the primary formation
of a dimetallic neutral species [(g5-C H PPh )Mo(CO) ]
5
4
2
3 2
(MwM), 5b (Fig. 1), resulted directly from the electrochemical
oxidation of the mononuclear anionic complexes 2b~.
d [ 5.26(s); 3c, d [ 7.28 (s ] d, 1J
\ 36 Hz)] and in infra-
HvW
red by two bands that compare quite well with those of their
We have attempted to apply the same processes to the chro-
mium compounds. An oxidative electrolysis of 2a~ was per-
formed at 0 mV on a platinum-gauze electrode in acetone
with 0.1 M Et NBF . Noticeably, as in the case of the molyb-
denum compounds, a phenomenum of saturation of the elec-
trode occurred, limiting the number of electrons exchanged
per mole of 2a~ during the exhaustive electrolysis. Therefore,
for purposes of electron counting and electrosynthesis, an elec-
trolytic cell without a frit was used. After the electrolysis, the
acetone solution showed complicated infrared and
parent compounds (g5-C H )M(CO) H. The formation of
5
5
3
byproducts was also observed and will be discussed further.
The three complexes 3aÈ3c have been obtained as crystalline
solids by concentrating and cooling their solutions in toluene
(or THF) to [18 ¡C.
4
4
The transformation of the preceding anionic compounds
2a~È2c~ into the iodo derivatives (g5-C H PPh )M(CO) I,
5
4
2
3
(4aÈ4c) has been easily performed, by simply adding iodine to
a toluene solution of 2a~È2c~. The three new complexes
New J. Chem., 1998, Pages 15È23
17

View Article Online
31PM1HNNMR spectra, from which the bridged complex 1a
was easily identiÐed. Additionally, a peak at d [ 19.0 suggests
the presence of a complex bearing a dangling phosphine arm.
To this signal observed in the 31PM1HN NMR spectra, one can
associate, in respect of the concomitant intensity variations
during various essays, two bands in the infrared spectra at
1978 and 1908 cm~1. These data were Ðnally assigned to the
metalÈmetal bonded complex 5a resulting probably from the
dimerization of the electrogenerated radical M(g5-
C H PPh )Cr(CO) N.13 Attempts to transform 5a into 1a
complex the reaction of [Li][2b] with acetic acid a†ords simi-
larly the hydrido complex (g5-C H PPh )Mo(CO) H, 3b, but
5
4
2
3
in addition gives noticeable amounts of a compound 7b that
was characterized in 1H NMR spectra by a high-Ðeld signal at
d [ 5.29 and in 31PM1HN NMR spectra by a singlet at d 59.37,
suggesting the coordination of the phosphine arm. In the tung-
sten case, analogous mixtures were obtained, from which the
hydrido complex (g5-C H PPh )W(CO) H, 3c, was easily
5
4
2
3
identiÐed by its IR and 1H NMR spectra. Moreover, by slow
evaporation of an acetone solution of 3c, crystals of the com-
pound 7c were obtained, suggesting the occurrence of a substi-
tution process, even in absence of irradiation:
5
4
2
3
failed, leading to the precipitation of an unidentiÐed green
powder.
We have also tried to use the considered two-phase electro-
photochemical process to get the tungsten compound 1c. In
this case the electrolysis, performed at 600 mV, also on a
platinium-gauze electrode in acetone with 0.1 M Et NBF ,
stopped after the consumption of only 0.5 Faraday mol~1.
The absence in the infrared spectra of any band in the 2000È
1800 cm~1 region where 5b was characterized and the pres-
ence in the 31PM1HN NMR spectra of peaks without the
characteristic satellites due to the coupling with 183W show
that the expected products, 5c and 1c, do not form. Consider-
ing this result, we thought it useless to perform further photo-
chemical experiments.
*, ~CO
(g5-C H PPh )W(CO) H ÈÈÈ
5
4
2
3
3c
4
4
1[(l-g5-C H PPh )W(CO) H]
2
5
4
2
2
2
7c
The crystals of 7c were suitable for X-ray analysis which
conÐrmed the dimetallic phosphino-bridged molecular struc-
ture [(l-g5-C H PPh )W(CO) H] (see below).
5
4
2
2
2
To support the discussion of the photochemical transform-
ation of the preceding compound, it is worth summarizing
some aspects of the photoreactivity of the parent complexes
(g5-C H )M(CO) H (M \ Cr, Mo, W). Fig. 2 recalls part of
5
5
3
the published observations in this Ðeld.4b,c The various path-
ways postulated for the photolysis of these complexes di†er
essentially, depending on the experimental conditions (in CO
matrice, in gas phase, in n-pentane solution, . . .), in the nature
of the dihydrogen elimination processes. They are postulated
to occur either (i) from monometallic or (ii) from bimetallic
species. Therefore, the CO dissociationÈassociation equi-
librium (iii) can be regarded as dispatching the system into
one or the other process. Interestingly, the hydrido-bridged
complexes [(g5-C H )M(CO) (l-H)] 8 can lose H reversibly
An attempt to oxidize the anion by silver tetraÑuoroborate:
method B
A further possibility to get the dimeric complexes 1aÈ1c is
chemically to oxidize the anionic complexes 2a~È2c~. Con-
sidering the value of the oxidation potential of 2b~ (E \ 100
p
mV), it is advisable to use ferrocenium as an oxidizing
reagent; unfortunately we were unable to get a clean reaction.
For this reason, we extended the investigation using silver
cation as the oxidant.
5
5
2
2
2
upon UV irradiation, forming the dimers [(g5-
C H )M(CO) ] (M \ Mo and W). These dimers are known
As already reported in the case of the molybdenum com-
pounds,5 when 1 equiv of silver tetraÑuoroborate crystals was
added to a toluene solution of one of anions 2a~È2c~, a grey
precipitate of lithium tetraÑuoroborate appeared, which was
easily removed. In each case one can obtain from the resulting
solution, in moderate yield, yellow crystals of the crown-like
complexes [(l-g5-C H PPh )M(CO) Ag] [M \ Cr (6a), Mo
5
5
2 2
to add CO in a dark reaction, forming the saturated [(g5-
C H )M(CO) ] complexes.
5
5
3 2
5
4
2
3
2
(6b), W (6c)]. These complexes have been fully characterized
by elemental analysis, MS, IR and NMR spectroscopies and
their crystal structures have been solved.14 The scheme shown
in Fig. 1 is based on the results of this study.
As far as the synthesis of the complexes 1aÈ1c is concerned,
it was e†ectively possible to observe their formation by
heating at reÑux the toluene solutions of their respective silver
derivatives 6aÈ6c. But these reactions are non-selective and
unidentiÐed products form through a decomposition process.
Concerning the presently studied hydrido complexes 3aÈ3c,
the presence of a pendant ligand PPh led us to anticipate
2
photoprocesses notably di†erent from those described in Fig.
2. Because of the spontaneous decarbonylation of 3b into 7b
(or of 3c into 7c), it was not expected to be easy to get signiÐ-
cant data for the separate pathways. Therefore we restricted
Synthesis of the hydrido complexes (g5-C H PPh )M(CO) H
5
4
2
3
[M = Cr (3a), Mo (3b), W (3c)] and [(l-g5-
C H PPh )M(CO) H] [M = Mo (7b), W (7c)] : some
5
4
2
2
2
observations on the photochemical dehydrogenation processes:
method C
The hydrido complexes (g5-C H PPh )M(CO) H [M \ Cr
5
4
2
3
(3a), Mo (3b), W (3c)] were expected to be the direct precur-
sors of the dimeric compounds 1aÈ1c and lead to efficient
pathways for their dehydrogenation and decarbonylation
reactions. The preparation of these hydrido compounds was
attempted from the lithium salt [Li][2] through reaction with
acetic acid. In the case of the chromium complex, the reaction
in toluene at room temperature a†ords mainly the mono-
metallic hydrido complex 3a, but the formation of small quan-
Fig. 2 Photoreactivity in the parent series of non-bridged cyclo-
pentadienyl hydrido tricarbonyl complexes (g5-C H )M(CO) H
tities of 1a suggests also
a
spontaneous multistep
5
5
3
transformation of 3a into 1a. In the case of the molybdenum
(M \ Mo and W) as summarized from references 4
18
New J. Chem., 1998, Pages 15È23

View Article Online
ourself to preliminary experiments. Thus the solutions con-
taining both 3b and 7b (or 3c and 7c) have been irradiated
with a UV high-pressure lamp. The mixture of molybdenum
complexes transformed in toto into complex 1b, a†ording no
additional observations. In contrast, in the case of the tungsten
complexes, monitoring by infrared spectroscopy of the
progress of the photoreaction showed the characteristic CwO
stretching bands of the complexes 1c and 5c [this compound
being identiÐed by its bands at 1963(s) and 1906(s) cm~1,
similar to those of 5b at 1959 and 1913 cm~1]. The appear-
ance of 5c shows that the irradiation of 3c induces a dehydro-
Table 2 Selected bond lengths (Ó) and angles (deg) with e.s.d.s in
parentheses for the complex [(l-g5-C H PPh )W(CO) H] (7c)
5
4
2
2
2
WÉ É ÉW@
WwP
4.5408(6)
2.413(2)
2.004(8)
1.65(5)
2.294(7)
2.323(7)
2.358(9)
2.367(8)
2.312(8)
1.145(13)
WwC(1)
WwC(2)
1.923(10)
1.942(10)
WwCp
WwH(1)
WwC(3)
WwC(4)
WwC(5)
WwC(6)
WwC(7)
C(1)wO(1)
C(3)wC(4)
C(4)wC(5)
C(5)wC(6)
C(6)wC(7)
C(7)wC(3)
C(2)wO(2)
1.443(10)
1.421(12)
1.372(13)
1.400(11)
1.360(10)
1.195(12)
genation process, which ends with the formation of
a
metalÈmetal bonded complex:15
PwWwCp
125.4(2)
103.2(3)
79.4(3)
66(2)
CpwWwC(2)
CpwWwH(1)
C(1)wWwC(2)
C(1)wWwH(1)
C(2)wWwH(1)
125.6(4)
119(2)
77.7(4)
61(2)
hl, ~H2
PwWwC(1)
PwWwC(2)
PwWwH(1)
CpwWwC(1)
(g5-C H PPh )W(CO) H ÈÈÈ
5
4
2
3
3c
127.5(4)
116(2)
1[(g5-C H PPh )W(CO) ] (W wW )
2
5
4
2
3 2
@ denotes the 1 [ x, [y, 1 [ z symmetry operation. Cp is the centroid
5c
of the C(3)C(4)C(5)C(6)C(7) cyclopentadienyl ring.
Finally in the case of the chromium compounds, the irradia-
tion of 3a (in fact of a mixture containing in addition small
amounts of 1a) a†orded a light green powder. This green
product, which apparently from its ponderal analysis, does
not contain the diphenylphosphinocyclopentadienyl ligand,
was not considered for further studies. To sum up, as regards
the efficiency, the preparation of compounds 1aÈ1c by the
irradiation of the hydrido complexes (method C) appears
limited to the previously described case of the molybdenum
compound 1b, which was obtained with high yield (90%).6
each (g5-C H w)W(CO) (Ph Pw)H moiety conforms to the
5
4
2
2
“four-legged piano stoolÏ description with the four “legsÏ
including one phosphine, two carbonyl ligands and the
hydride ligand. The two carbonyl groups are in ciso•d posi-
tions. Those two moieties are related by centrosymmetry and,
in particular, the two MwH bonds occupy transo•d positions
with respect to the molecular center of symmetry. The metalÈ
metal distance, 4.5408(6) Ó, is long enough to prevent any
metalÈmetal interaction.
The X-ray molecular structure of
There have been numerous studies of the cyclopentadienyl
complexes that adopt a “four-legged piano stoolÏ geometry
but, among the hydrido-substituted complexes of the type (g5-
C R )M(CO) LH, whose structures are similar to the frag-
[(l,g5-C H PPh )W(CO) H] , 7c
5
4
2
2
2
The noticeable stability of the dihydrido complex 7c with
respect to the dehydrogenation process led us to try to obtain
a better understanding of its structure. Therefore an X-ray
crystallographic investigation of a suitable crystal of 7c was
carried out.
The molecular geometry and atomic numbering scheme of
7c are shown in Fig. 3 and selected bond lengths and angles
are given in Table 2. In a perspective view the most prominent
features are the dinuclear nature of the complex and the head-
to-tail disposition of the bridging ligands. The geometry of
5 5
2
ment (g5-C H w)W(CO) (Ph Pw)H of 7c, only the structure
5
4
2
2
of the chromium derivative (g5-C H )Cr(CO) (PPh Cy)H
5
5
2
2
(Cy \ cyclohexyl)16 and of the molybdenum derivatives (g5-
C Me )Mo(CO) (CNBut)H 17 and (g5-C Me )Mo(CO) H 18
5
5
2
5
5
3
have been reported. In the former molybdenum compound a
MowH distance of 1.63(4) Ó was observed while the neutron
di†raction study of the latter a†ords 1.789(7) Ó. Our determi-
nation of a WwH distance of 1.65(5) Ó is coherent with the
former observation as the covalent radius of tungsten is only
0.01 Ó longer than that of molybdenum; nevertheless the
lower precision of our result precludes any comparison with
the latter neutron di†raction determination.
C(18)
C(17)
C(11)
C(19)
To our knowledge, 7c is the Ðrst reported structure of a
C(12)
C(16)
C(10)
C(14)
tungsten derivative of the type (g5-C R )M(CO) LH, and this
5 5
2
limits therefore the comparisons that can be made. The
average WwCO distance of 1.93 Ó in 7c appears, as expected,
some 0.05 Ó shorter than the values generally observed in
[(g5-C R R@)W(CO) ] complexes (R \ R@ \ Me; R \ H,
C(13)
C(9)
C(15)
C(3′)
C(8)
H(1)
P
5 4
3
R@ \ various groups).19 Concerning the CwO distances, it
would be unwise, in view of their e.s.d.s, to try a precise com-
parison; we will just consider that they lie in the normal
range. The angles between the “legsÏ and the (Cp)wW axis
and also between them indicate no signiÐcant deviations
worth mention.
O(1)
C(1)
W
W′
C(6)
C(2)
C(7)
O(2)
Considering the dehydrogenation processes in 7c, it is
worth noticing the transo•d geometry of the hydrido ligands.
Such a mutual position could well be a considerable ender-
gonic hindrance to a reductive elimination process of dihydro-
gen and it was surprising that both complexes 3c and 7c
disappear when they are irradiated. Nevertheless, the existence
of a facile pathway to the ciso•d isomer, based on the cisÈ
trans rearrangement observed20 in the related mono-
metallic hydride (g5-C H )W(CO) (PMe )H, is not excluded
Cp
C(3)
C(5)
P′
C(4)
5
5
2
3
and could provide a reasonable explanation of the observ-
ations reported above in the description of ““method CÏÏ.
Fig. 3 Perspective view of the dihydrido complex [(l-g5-
C H PPh )W(CO) H] , 7c
5
4
2
2
2
New J. Chem., 1998, Pages 15È23
19

View Article Online
Formation of metal–metal bonds by reaction of the lithium
salts [Li] [2] with the corresponding iodo complexes (g5-
C H PPh )M(CO) I [M = Cr (4a), Mo (4b), W (4c)] :
1890 (vs), 1864 (w), 1844 (s) cm~1; MS (DCI/NH ), m/z 714
3
[MH`] showing an isotopic pattern characteristic for a
dichromium compound. Anal. calcd for Cr C
2 38 28 4 2
63.87; H, 3.95. Found: C, 63.45; H, 3.69.
H O P : C,
5
4
2
3
method D
Such syntheses of some dinuclear metalÈmetal bonded com-
plexes of molybdenum and tungsten, bridged by one or two
heterodifunctional ligands C H PPh , have already been
Li[(g5-C H PPh )Cr(CO) ], [Li] [2a]. First method: To a
5
4
2
3
yellow solution of 1.20 g (4.68 mmol) of Li(C H PPh ) in 130
5
4
2
mL of THF was added 1.07 g of (g6-C H )Cr(CO) (4.68
5
4
2
7
8
3
reported.21 Following this method, T HF was used as solvent.
Thus, by heating at reÑux solutions of 2b~ with one equiva-
lent of (g5-C H )M(CO) I (M \ Mo, W) for 16 h, the mono-
mmol). The resulting red solution was reÑuxed for 3 days,
giving an orange solution that was cooled to room tem-
perature. The solvent was removed in vacuo to give a brown
yellow residue, which was washed with pentane to give 1.82 g
of [Li][2a] as a beige solid (99% yield). Second method: To a
heterogeneous yellow solution of 0.128 g (0.5 mmol) of
Li(C H PPh ) in 15 mL of toluene was added a green solu-
5
5
3
bridged (CO) Mo(l-g5-C H PPh )M(g5-C H ) (M \ Mo,
3
5
4
2
5 5
W) were obtained but in low yield. Following this process
using 2b~ with one equivalent of 4b, the dibridged complex 1b
was obtained, also in a low yield (32%). Overall this method
appears to be non-selective and all products need to be puri-
Ðed by column chromatography.
5
4
2
tion of 0.150 g (0.5 mmol) of (CH CH CN) Cr(CO) in 15 mL
3
2
3
3
of toluene. The heterogeneous mixture was heated and when
the reÑux temperature was obtained the solution became
homogeneous. A white precipitate rapidly appeared. The new
mixture was cooled to room temperature and the suspension
was Ðltered and washed with pentane. [Li][2a] was obtained
as 0.160 g of a dried white product (82% yield). 1H NMR (200
MHz, C D ): d 7.84 (2m, 4H, ortho), 7.66 to 7.08 (m, 6H, meta
We have used the above principle to synthesize the three
complexes 1aÈ1c, in toluene solution. First, iodo complexes
4aÈ4c were obtained with a good yield from solutions of
anionic complexes 2a~È2c~ with one equivalent of iodine.
4aÈ4c were added to the corresponding anionic species
2a~È2c~ and the resulting toluene solutions were reÑuxed
during 16 h for the chromium and molybdenum complexes
and 24 h for the tungsten complex. This method appears quite
selective, the three complexes 1a, 1b and 1c are obtained as
crystalline powders without puriÐcation, with excellent yields
of 95, 95 and 99%, respectively.
6
6
and para), 5.02 (s, 4H, C H ); 31P M1HN NMR (32.40 MHz,
C D ): d [17.0 (s); IR (THF, m ): 1903 (vs), 1811 (vs), 1788
5
4
6
6
CO
(s), 1725 (s) cm~1. Anal. calcd for LiCrC
H
O P: C, 61.24;
20 14
3
H, 3.57. Found: C, 60.82; H, 4.28.
(g5-C H PPh )Cr(CO) H, 3a. To a dark orange solution of
5
4
2
3
Experimental
General methods and materials
0.12 g (0.31 mmol) of [Li][2a] in 30 mL of toluene was added
18 lL of glacial acetic acid (0.31 mmol, one equivalent). The
solution, which had turned bright red, was stirred for 10 min.
All reactions of water- or air-sensitive compounds were con-
ducted under a dry argon atmosphere using Schlenck tech-
niques. Solvents were puriÐed as follows: toluene, diethyl
ether and tetrahydrofuran were distilled under nitrogen over
After Ðltration and elimination of CH COOLi, the solution
3
was concentrated and cooled to [18 ¡C. A red solid precipi-
tated and the suspension was Ðltered. 3a was obtained as 0.11
g of a dried red powder (92% yield). 1H NMR (200 MHz,
C D ): d 7.70 and 7.45 (2m, 4H, ortho), 7.20 (m, 6H, meta and
Na/benzophenone. Dichloromethane was distilled over CaH .
2
6
6
Starting materials (g6-C H )M(CO)
(M \ Cr, Mo),9
para), 4.98 (s, 2H, C H ), 4.74 (s, 2H, C H ), [5.39 (s,
7
8
3
5
4
5 4
(CH CH CN) Cr(CO) 10 and (CH CN) W(CO) ,11 as well
hydride); 31P M1HN NMR (32.40 MHz, C D ): d [19.8 (s); IR
3
2
3
3
3
3
3
6
6
as the cyclopentadienide Li(C H PPh ),22 were prepared as
(toluene, m ): 2012 (vs), 1927 (vs) cm~1. Anal. calcd for
5
4
2
CO
3
described in the literature.
CrC
H
O P: C, 62.18; H, 3.91. Found: C, 62.34; H, 3.79.
20 15
All irradiations were performed by a 500-watt, high-
pressure, water-cooled, mercury lamp with a Hanau power
supply. Infrared spectra were obtained on a 1725 X Perkin
Elmer FT-IR spectrometer. 1H, 13C and 31P NMR spectra
were recorded using 80-, 200-, or 250-MHz Bruker instru-
ments. Mass spectra were recorded on a Nermag R10 instru-
ment. Elemental analyses (%) were performed by the
Microanalytical Laboratory of the Coordination Chemistry
Laboratory (Toulouse, France).
[(g5-C H PPh )Cr(CO) I], 4a. To an orange solution of
5
4
2
3
1.78 mmol of 2a~ in 40 mL of toluene was added 0.451 g of I
2
(1.78 mmol). The resulting red solution was stirred for 10 min.
After Ðltration, the solution was concentrated and cooled to
[18 ¡C. An orange solid precipitated, and the suspension was
Ðltered. 4a was obtained as 0.738 g of a dried orange powder
(81% yield). 1H NMR (200 MHz, C D ): d 7.98 to 7.30 (m,
6
6
10H, ortho, meta and para), 5.82 (s, 2H, C H ), 5.38 (s, 2H,
5
4
C H ); 31P M1HN NMR (32.40 MHz, C D ): d [16.1 (s); 31P
5
4
6 6
Syntheses
M1HN NMR (81.015 MHz, [2H ]acetone): d [14.0 (s); IR
6
(toluene, m ): 2029 (vs), 1975 (vs) with a shoulder at 1955 (s)
Only the selected methods of preparation of compounds 1 are
described hereafter in detail.
CO
cm~1. Anal. calcd for CrC
H
O PI: C, 46.90; H, 2.76.
20 14
3
Found: C, 46.77; H, 2.81.
[(l-g5-C H PPh )Cr(CO) ] , 1a. Method D: To an
5
4
2
2 2
orange solution of 1.44 mmol of 2a~ in 20 mL of toluene was
added a red solution of 1.44 mmol of 4a in 20 mL of toluene.
The resulting violet solution was reÑuxed for 16 h, then cooled
to room temperature. After concentration and Ðltration, dark
metallic crystals were obtained, giving 0.977 g of 1a (95%
yield). 1H NMR (200 MHz, C D ): d 7.90 and 7.75 (2m, 8H,
[(l-g5-C H PPh )Mo(CO) ] , 1b. Method A: The hydride
5
4
2
2 2
3b (in fact a mixture also containing 7b can be used) was dis-
solved in 30 mL of toluene and the solution was irradiated
with a low-pressure Hg lamp for 5 h. The red solution was
then concentrated and cooled to [18 ¡C. A red solid precipi-
tated and the suspension was Ðltered. The product was
washed with pentane and dried under vacuum. 1b was
obtained as 0.17 g of a dried red powder (99% yield). Method
B: After linear voltametry of Li[(g5-C H PPh )Mo(CO) ],
6
6
ortho), 7.13 (m, 12H, meta and para), 4.64 (s, 2H, C H ), 4.38
5
4
(s, 2H, C H ), 3.81 (s, 2H, C H ), 3.34 (s, 2H, C H ); 1H NMR
5
4
5
4
5 4
(200 MHz, [2H ]acetone): d 8.05 and 7.70 (2m, 8H, ortho),
6
5
4
2
3
7.65 (m, 12H, meta and para), 5.15 (s, 2H, C H ), 4.48 (s, 2H,
[Li][2b], on a platinum-gauze electrode in acetone with 0.1 M
5
4
4
C H ), 3.58 (m, 2H, C H ), 3.41 (s, 2H, C H ); 31P M1HN
Et NBF electrolyte, electrolysis at 100 mV was performed.
5
4
5
6
4
5
4
4
NMR (32.40 MHz, C D ): d 83.6 (s); 31P M1HN NMR (81.015
The bright orange solution turned progressively dark red
when one electron/mol of 2b~ was exchanged. The supporting
electrolyte was eliminated through two cycles of evaporation
6
MHz, [2H ]acetone): d 88.5 (s); IR (CH Cl , m ): 1940 (vs),
6
2
2
CO
CO
1889 (vs), 1864 (w), 1842 (s) cm~1; IR (toluene, m ): 1941 (vs),
20
New J. Chem., 1998, Pages 15È23

View Article Online
to dryness and redissolution in di†erent solvents, from acetone
to THF in which Et NBF is not soluble, and then from THF
tration, the solution was concentrated and cooled to [18 ¡C.
An orange solid precipitated and the suspension was Ðltered.
4b was obtained as 0.500 mg of a dried orange product (90%
4
4
to toluene. The 31P M1HN NMR (32,40 MHz, C D ) spectrum
6
6
shows the presence of [(g5-C H PPh )Mo(CO) ] , 5b, at d
yield). 1H NMR (200 MHz, [2H ]acetone): d 7.57 to 7.45 (m,
5
4
2
3 2
6
[17.0 (s), of 1b at d 68.1 (s) and of unidentiÐed species at d
10H, ortho, meta and para), 6.24 (m, 2H, C H ), 5.81 (m, 2H,
5
4
62.5 (s); in IR (THF, m ) the bands at 1959(s), 1913 (s) cm~1
C H ); 31P M1HN NMR (81.015 MHz, [2H ]acetone): d [12.8
CO
5
4
6
were assigned to 5b (main product) by comparison with [(g5-
(s); IR (THF, m ): 2039 (vs), 1964 (vs) cm~1. Anal. calcd for
CO
C H )Mo(CO) ] for which m are at 1960(s), 1914 (s) cm~1
MoC
H
O PI: C, 43.19; H, 2.54. Found: C, 43.01; H, 2.65.
5
5
3 2
CO
20 14
3
in CCl . The red solution was irradiated with a high-pressure
4
[(l-g5-C H PPh )W(CO) ] , 1c. Method D: To a solu-
Hg vapor lamp for 3 h. It was then concentrated, Ðltered, and
5
4
2
2 2
tion of 0.120 g of [Li][2c] (0.23 mmol) in 15 mL of toluene
was added a red solution of 0.147 g of 4c (0.23 mmol) in 15
mL of toluene. The solution was reÑuxed for 16 h. and then
cooled to room temperature. After concentration and Ðl-
tration, a red powder was obtained, giving 0.224 g of 1c (99%
yield). Red crystals of 1c were obtained by slow di†usion of
diethyl ether in a saturated dichloromethane solution. 1H
NMR (200 MHz, C D ): d 7.92 and 7.41 (2m, 8H, ortho), 7.23
cooled to [18 ¡C. The precipitate was washed with pentane
and dried under vacuum. A dried red powder of 1b was
obtained with a 40 to 50% yield for electrolysis and irradia-
tion. Method D: To an orange solution of 1 mmol of 2b~ in
50 mL of toluene was added a red solution of 1 mmol of 4b in
50 mL of toluene. The dark solution was reÑuxed for 16 h and
then cooled to room temperature. After concentration and Ðl-
tration, 0.761 g of 1b were obtained (95% yield). 1H NMR
(200 MHz, C D ): d 7.90 and 7.75 (2m, 8H, ortho), 7.13 (m,
6
6
to 7.09 (m, 12H, meta and para), 4.64 (s, 2H, C H ), 4.38 (s,
5
4
6
6
2H, C H ), 3.81 (s, 2H, C H ), 3.34 (s, 2H, C H ); 1H NMR
12H, meta and para), 4.89 (s, 2H, C H ), 4.42 (s, 2H, C H ),
5
4
5
4
5 4
5
4
5 4
(200 MHz, [2H ]acetone): d 8.08 and 7.81 (2m, 8H, ortho),
7.67 to 7.30 (m, 12H, meta and para), 5.45 (s, 2H, C H ), 5.00
3.73 (s, 2H, C H ), 3.15 (s, 2H, C H ); 31P M1HN NMR (32.40
6
5
4
5 4
MHz, C D ): d 68.2 (s); 13C M1HN NMR (50.323 MHz, C D ):
5
4
6
6
6 6
(s, 2H, C H ), 4.19 (s, 2H, C H ), 3.89 (s, 2H, C H ); 31P M1HN
d 244.5 (d, 1J \ 27 Hz, 2CO), 232.3 (s, 2CO), 140.4 (d,
5
4
5
4
5 4
CP
NMR (32.40 MHz, C D ): d 35.0 (s ] d, J \ 328 Hz); IR
PvW
1J \ 41 Hz, 4C, ipso), 134.3 and 133.4 (2s, 4C, para), 135.2
6
6
CP
(CH Cl , m ): 1940 (vs), 1889 (vs), 1864 (w), 1842 (s) cm~1; IR
and 132.2 (2d, 1J \ 10 Hz, 8C, ortho), 131.6 and 130.7 (2s,
2
2
CO
CP
(toluene, m ): 1938 (vs), 1892 (vs), 1863 (w), 1838 (s) cm~1; IR
8C, meta), 94.1 and 88.2 (2s, 4C of C H P), 91.8 and 88.6 (2d,
CO
3
5 4
(THF, m ): 1936 (vs), 1890 (vs), 1862 (w), 1835 (s) cm~1; MS
1J \ 11 Hz, 4C of C H P), 53.6 (d, 1J \ 41 Hz, 2C of
CP CP
C H P); IR (THF, m ): 1941 (vs), 1896 (vs), 1865 (w), 1843 (s)
CO
2
5
4
1
(DCI/NH ), m/z 978 [MH`] showing an isotopic pattern
3
5
4
CO
characteristic for a ditungsten compound. Anal. calcd for
cm~1; IR (toluene, m ): 1943 (vs), 1898 (vs), 1868 (w), 1846 (s)
CO
W C
H O P : C, 46.65; H, 2.89. Found: C, 46.20; H, 3.00.
cm~1; MS (DCI/NH ), m/z 802 [MH`] showing an isotopic
2 38 28 4 2
3
pattern characteristic for a dimolybdenum compound. Anal.
Li[(g5-C H PPh )W(CO) ], [Li] [2c]. To a yellow solu-
calcd for Mo C
H, 3.56.
H O P : C, 56.87; H, 3.52. Found: C, 57.0;
5
4
2
3
tion of 0.835 g (3.26 mmol) of Li(C H PPh ) in 50 mL of
2 38 28 4 2
5
4
2
toluene was added a solution of 1.275 g of (CH CN) W(CO)
3
3
3
(3.26 mmol) in 50 mL of toluene. The heterogeneous mixture
was heated and when the reÑux temperature was obtained, the
solution became homogeneous. After 15 min a beige precipi-
tate appeared. The new mixture was cooled to room tem-
perature and the suspension was Ðltered. [Li][2c] was
obtained as 1.655 g of a dried white powder (97% yield). 1H
Li[(g5-C H PPh )Mo(CO) ], [Li] [2b]. To a yellow solu-
5
4
2
3
tion of 2.40 g (9.37 mmol) of Li(C H PPh ) in 275 mL of THF
5
4
2
was added 2.55 g of (g6-C H )Mo(CO) (9.37 mmol). The red
7
8
3
solution was reÑuxed for 3 h and the resulting yellow solution
was cooled to room temperature. The solvent was removed in
vacuo to give a brown yellow residue, which was washed with
pentane to give 3.72 g of [Li][2b] as a beige solid (91% yield).
1H NMR (200 MHz, C D ): d 7.70 and 7.46 (2m, 4H, ortho),
NMR (200 MHz, [2H ]acetone): d 7.56 to 7.48 (m, 4H, ortho),
6
7.45 to 7.38 (m, 6H, meta and para), 5.25 (s, J \ 2.3 Hz, 2H,
HvP
C H ), 5.04 (s, J \ 1.9 Hz, 2H, C H ); 31P M1HN NMR
6
6
7.14 (m, 6H, meta and para), 5.50 (br s, 4H, C H ); 31P M1HN
5
4
HvP
6
5 4
(32.40 MHz, C D ): d [17.2 (s ] d, 2J \ 41 Hz); IR
5
4
NMR (32.40 MHz, C D ): d [18.2 (s); IR (THF, m ): 1909
6
PvW
(THF, m ): 1903 (vs), 1808 (vs), 1786 (s), 1724 (s) cm~1. Anal.
6
6
CO
(vs), 1813 (vs), 1790 (s), 1724 (s) cm~1; IR (KBr, m ): 1980 (s),
CO
calcd for LiWC
H, 3.27.
H
O P: C, 45.84; H, 2.69. Found: C, 46.12;
CO
1901 (vs), 1789 (vs), 1763 (s) cm~1. Anal. calcd for
20 14
3
LiMoC
H
O P: C, 55.1; H, 3.2. Found: C, 52.2; H, 3.9.
20 14
3
(g5-C H PPh )W(CO) H, 3c. To a yellow solution of 0.290
5
4
2
3
(g5-C H PPh )Mo(CO) H,
3b
and
[(l-g5-
g (0.55 mmol) of [Li][2c] in 30 mL of THF was added 30 lL
of glacial acetic acid (0.55 mmol). The resulting red solution
was stirred for 10 min. After Ðltration and elimination of
5
4
2
3
C H PPh )Mo(CO) H] , 7b. An orange solution of 0.21 g
5
4
2
2
2
(0.48 mmol) of [Li][2b] in 30 mL of toluene was treated with
28 lL of glacial acetic acid (0.48 mmol, one equivalent). The
bright orange solution was stirred for 10 min. After Ðltration
CH COOLi, the solution was concentrated and cooled to
3
[18 ¡C. An orange solid precipitated, and the suspension was
and elimination of CH COOLi, the solution was concentrated
Ðltered. 3c was obtained as 0.275 g of a dried orange powder
3
and cooled to [18 ¡C. An orange solid precipitated and the
(96% yield). 1H NMR (200 MHz, [2H ]acetone): d 7.57 to
6
suspension was Ðltered. A dried orange powder (0.18 g) was
obtained. Spectroscopic analyses showed that the mono-
metallic hydride compound 3b and the dimetallic dihydride
compound 7b were present in an approximate ratio of 6 : 1.
1H NMR (200 MHz, C D ): d 7.70 and 7.45 (2m, 32H, ortho),
7.37 (m, 10H, C H ), 6.03 (s, 2H, C H ), 5.75 (s, 2H, C H ),
6
5
5
4
5 4
[7.23 (s ] d, hydride, J
\ 36 Hz); 1H NMR (200 MHz,
CDCl ): d 7.45 to 7.25 (m, 10H, C H ), 5.59 (s, 2H, C H ),
HvW
3
6
5
5 4
5.40 (s, 2H, C H ), [7.28 (s ] d, hydride, 1J
\ 36 Hz); 31P
5
4
HvW
M1HN NMR (32.40 MHz, C D ): d [ 19.8 (s ] d, 2J \ 63
6
6
6
6
PvW
7.20 (m, 48H, meta and para), 4.98 (s, 24H, C H of 3b) and
Hz); IR (THF, m ): 2019 (vs), 1926 (vs) cm~1. Anal. calcd for
5
4
CO
4.74 (s, 8H, C H of 7b), [5.26 (s, 6H, hydride of 3b) and
WC
H
O P: C, 62.18; H, 3.91. Found: C, 62.34; H, 3.79.
5
4
20 15
3
[5.29 (s, 2H, hydrides of 7b); 31P M1HN NMR (32.40 MHz,
C D ): d [19.5 (s, 3b) and 59.4 (s, 7b); IR (toluene, m ): 2024
(g5-C H PPh )W(CO) I, 4c. To a yellow solution of 0.315
6
6
CO
5
4
2
3
(s), 1937 (s) cm~1. Anal. calcd for 6 MoC
H
O P and 1
g (0.60 mmol) of [Li][2c] in 30 mL of THF was added 0.152 g
20 15
3
Mo C
H
O P : C, 53.4; H, 3.4. Found: C, 54.1; H, 3.9.
of I (0.60 mmol). The resulting red solution was stirred for 10
min. After Ðltration, the solution was concentrated and cooled
2 36 30 4 2
2
(g5-C H PPh )Mo(CO) I, 4b. To an orange solution of 1
to [18 ¡C. An orange solid precipitated and the suspension
was Ðltered. 4c was obtained as 0.314 g of a dried orange
powder (81% yield). 1H NMR (200 MHz, C D ): d 7.40 and
5
4
2
3
mmol of 2b~ in 30 mL of THF was added 0.254 g of I (1
2
mmol). The red solution was stirred for 10 min. After Ðl-
6
6
New J. Chem., 1998, Pages 15È23
21

View Article Online
X-Ray crystallography for 7c
Table 3 Crystal Data for [(l-g5-C H PPh )W(CO) H] 7c
5
4
2
2
2
Di†raction data were collected on an Enraf-Nonius CAD-4
di†ractometer at room temperature using MoKa graphite-
monochromated radiation (k \ 0.71073 Ó). Accurate unit cell
parameters were obtained from least-squares reÐnement of 25
reÑections in the 11È15¡ h range. The intensities were cor-
rected for Lorentz and polarization e†ects and for a slight
([6.3%) linear decay.23 Empirical absorption corrections24
were made from w scans. The structure was solved by Pat-
terson techniques.25a Relevant crystallographic data for 7c are
listed in Table 3. Full-matrix least-squares reÐnement25b mini-
mizing &w(o F o [ o F o)2 was performed with non-hydrogen
atoms anisotropic but those of phenyl rings reÐned as iso-
tropic rigid groups. The hydride ligand H(1) was located on a
di†erence-Fourier map. Its position agreed with that obtained
by seeking sites of potential energy minima.26 It was reÐned
isotropically. All other H atoms were introduced in calculated
positions. Final atomic coordinates are given in Table 4.
CCDC reference number 440/002.
Chemical formula
FW
Crystal system
Space group
a/Ó
b/Ó
c/Ó
U/Ó3
F(000)
Z
C H O P W
980.3
38 30 4 2
2
Orthorhombic
Pbca (no.61)
12.042(1)
16.535(2)
16.871(2)
3359(1)
1872
4
q
/g cm~3
1.938
calc
Radiation
MoKa (j \ 0.71073 Ó)
c
c
l(MoKa)/mm~1
6.70
T
ÈT
0.922È1.000
3È46
&
'
2h range/deg
Scan mode
x [ 2h
No. of data collected
No. of observed data
No. of variable params
S
2328 (all unique)
1193 [F2 [ 3r(F2)]
o
o
128
1.093
w
[r2(F ) ] 0.0011F2]~1
o
o
(*/r)
0.008
0.030
0.034
Conclusions
max
R \ &[(o F o [ o F o)/& o F o
o
c
o
The possibility to obtain in very good yields a series of
bridged metalÈmetal bonded complexes now opens
opportunities to study comparatively the structures and physi-
cal properties in that series. Chemical properties, in particular
the electrochemical behavior, are currently extended from the
case of the molydenum complex5 to the chromium and tung-
sten ones.
Rw \ [&w(o F o [ o F o)2/&w o F o2]1@2
o
c
o
(*/q)
/e Ó~3
0.55, [0.53
max, min
7.31 (2m, 4H, ortho), 7.17 to 7.12 (m, 6H, meta and para), 5.07
(quint., 2H, C H ), 4.87 (t, 2H, C H ); 31P M1HN NMR (32.40
5
4
5 4
PvW
MHz, C D ): d [16.1 (s ] d, 2J \ 71 Hz); IR (THF, m ):
Acknowledgements
6
6
CO
O PI: C,
3
2033 (vs), 1951 (vs) cm~1. Anal. calcd for WC
37.30; H, 2.19. Found: C, 37.52; H, 2.24.
H
20 14
The authors would like to express their gratitude to Suzy
Richelme and Dr. D. de Montauzon for helpful contributions
and comments on the mass spectra and electrochemical deter-
minations, respectively and to Dr. Andre Maisonnat for
helpful discussions.
Formation of the complex [(l-g5-C H PPh )W(CO) H] ,
5
4
2
2
2
7c. In the 1H NMR tube of a 3c solution in [2H ]acetone,
6
orange crystals of 7c were obtained by slow concentration
[2H ]acetone. MS (DCI/NH ), m/z 980 [MH`] showing an
References
6
3
isotopic pattern characteristic for a ditungsten compound.
1 (a) A. Iretskii, M. C. Jennings and R. Poilblanc, Inorg. Chem.,
1996, 35, 1266. (b) J. B. Tommasino, D. de Montauzon, X. He, A.
Maisonnat, R. Poilblanc, J. N. Verpeaux and C. Amatore,
Organometallics, 1992, 11, 4150.
Anal. calcd for W C
46.42; H, 3.01.
H O P : C, 46.56; H, 3.08. Found: C,
2 38 30 4 2
2 (a) M. J. Hostetler, M. D. Butts and R. G. Bergman, J. Am. Chem.
Soc., 1993, 115, 2743. (b) D. Baudry, A. Dormond and A. HaÐd,
New J. Chem., 1993, 17, 465. (c) M. Visseaux, A. Dormond, M. M.
Kubichi, C. Mo•se, D. Baudry and M. Ephritikine, J. Organomet.
Chem., 1992, 433, 95. (d) M. Ogasa, M. D. Rausch and R. D.
Rogers, J. Organomet. Chem., 1991, 403, 279. (e) X. He, A. Maison-
nat, F. Dahan and R. Poilblanc, Organometallics, 1991, 10, 2443.
( f ) A. Dormond, P. Hepiegne, A. HaÐd and C. Mo•se, J.
Organomet. Chem., 1990, 398, C1. (g) M. El Amane, R. Mathieu
and R. Poilblanc, New J. Chem., 1988, 12, 661. (h) G. K. Anderson
and M. Lee, Organometallics, 1988, 7, 2285. (i) K. W. Lee, W. T.
Pennington, A. W. Cordis and T. L. Brown, J. Am. Chem. Soc.,
1985, 107, 631. (j) F. Faraone, S. Lo Schiaoo, G. Bruno and G.
Bombieri, J. Chem. Soc., Chem. Commun., 1984, (k) G. Bruno, S. Lo
Schiavo, P. Priraino and F. Faraone, Organometallics, 1985, 4,
1098. (l) P. Kalk, J.-M. Frances, P. M. PÐster, T. G. Southern and
A. Thorez, J. Chem. Soc., Chem. Commun., 1983, 510. (m) M. El
Amane, R. Mathieu and R. Poilblanc, Organometallics, 1983, 2,
1618.
3 (a) J. R. Knorr and T. L. Brown, J. Am. Chem. Soc., 1993, 115,
4087. (b) S. C. Tenhae†, K. J. Covert, M. P. Castellani, J. Grunke-
meier, C. Kunz, T. J. R. Weakley, T. Koenig and D. R. Tyler,
Organometallics, 1993, 12, 5000. (c) S. L. Scott, J. H. Espenson and
W.-J. Chen, Organometallics, 1993, 12, 4077. (d) Q. Yao, A. Bakac
and J. H. Espenson, Organometallics, 1993, 12, 2010. (e) W. C.
Watkins, T. Jaeger, C. E. Kidd, S. Fortier, M. C. Baird, G. Kiss,
G. C. Roper and C. D. Ho†, J. Am. Chem Soc., 1992, 114, 907. ( f )
S. Fortier, M. C. Baird, K. F. Preston, J. R. Morton, T. Ziegler, T.
J. Jaeger, W. C. Watkins, J. H. MacNeil, K. A. Watson, K. Hensel,
Y. Le Page, J.-P. Charland and A. J. Williams, J. Am. Chem. Soc.,
1991, 113, 542. (g) S. J. McLain, J. Am. Chem. Soc., 1988, 110, 643.
(h) R. H. Hooker, K. A. Mahmoud and A. J. Rest, J. Organomet.
Table 4 Atomic coordinates for 7c
Atom
x/a
y/b
z/c
W
H(1)
P
0.51845(2)
0.4614(62)
0.3671(2)
0.4576(7)
0.4262(7)
0.4224(8)
0.3677(6)
0.6529(6)
0.6857(6)
0.7071(7)
0.6919(7)
0.6581(5)
0.2335(4)
0.1480(4)
0.0452(4)
0.0277(4)
0.1131(4)
0.2160(4)
0.3631(4)
0.4514(4)
0.4450(4)
0.3502(4)
0.2618(4)
0.2683(4)
0.12256(2)
0.1285(41)
0.0294(1)
0.2245(6)
0.2885(5)
0.1510(6)
0.1747(4)
0.0465(4)
0.1301(4)
0.1596(7)
0.0962(5)
0.0283(5)
0.0803(3)
0.0638(3)
0.1015(3)
0.1557(3)
0.1722(3)
0.1345(3)
[0.0301(4)
[0.0297(4)
[0.0748(4)
[0.1204(4)
[0.1209(4)
[0.0757(4)
0.44077(2)
0.3522(21)
0.4198(1)
0.4072(6)
0.3940(5)
0.5289(6)
0.5832(4)
0.5018(4)
0.5089(5)
0.4313(5)
0.3800(5)
0.4233(4)
0.4119(3)
0.4654(3)
0.4567(3)
0.3946(3)
0.3411(3)
0.3498(3)
0.3289(3)
0.2754(3)
0.2057(3)
0.1895(3)
0.2430(3)
0.3127(3)
C(1)
O(1)
C(2)
O(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
22
New J. Chem., 1998, Pages 15È23

View Article Online
Chem., 1983, 254, C25. (i) R. J. Kazlauskas and M. S. Wrighton, J.
Am. Chem. Soc., 1982, 104, 6005. (j) D. S. Ginley, C. R. Bock and
M. S. Wrighton, Inorg. Chim. Acta, 1977, 23, 85. (k) R. M. Laine
and P. C. Ford, Inorg. Chem., 1977, 16, 388. (l) M. S. Wrighton and
D. S. Ginley, J. Am. Chem. Soc., 1975, 97, 4246. (m) J. L. Hughey
IV, C. R. Bock and T. J. Meyer, J. Am. Chem. Soc., 1974, 97, 4440.
(n) R. D. Adams, D. E. Collins and F. A. Cotton, J. Am. Chem.
Soc., 1974, 96, 749.
15 In addition, a species characterized by two low frequency stretch-
ing bands at 1753 and 1728 cm~1, whose concentration increased
with the duration of the experiment, was attributed to the forma-
tion of CO-bridged dimetallic species.
16 W. C. Watkins, K. Hensel, S. Fortier, D. H. Macartney, M. C.
Baird and S. J. MacLain, Organometallics, 1992, 11, 2418.
17 H. G. Alt, H. E. Engelhardt, T. Frister and R. D. Rogers, J.
Organomet. Chem., 1989, 366, 297.
18 L. Brammer, D. Zhao, R. M. Bullock and R. K. McMullan, Inorg.
Chem., 1993, 32, 4819.
19 (a) H. G. Alt, J. S. Han and R. D. Rogers, J. Organomet. Chem.,
1993, 454, 165. (b) T. J. R. Weakley, A. Avey Jr. and D. R. Tyler,
Acta Crystallogr., Sect. C, 1992, 48, 154. (c) A. L. Rheingold and
J. R. Harper, Acta Crystallogr., Sect. C, 1991, 47, 184. (d) T. E.
Bitterwolf and A. L. Rheingold, Organometallics, 1991, 10, 3856. (e)
A. Avey, S. C. Tende†, T. J. R. Weakley and D. R. Tyler,
Organometallics, 1991, 10, 3607. ( f ) I. R. Lyatifov, T. K. Casanov,
T. K. Kurbanov, A. N. Shnulin and V. K. ShilÏnikov, Koord.
Khim., 1990, 16, 1343 (Chem. Abstr., 1991, 114(15), 336k). (g) W.
Abriel and J. Heck, J. Organomet. Chem., 1986, 302, 363.
20 B. Wrackmeyer, H. G. Alt and H. E. Maisel, J. Organomet. Chem.,
1990, 399, 125.
21 T. J. Duckworth, M. J. Mays, G. Conole and M. McPartlin, J.
Organomet. Chem., 1992, 439 327.
22 F. Mathey and J.-P. Lampin, J. Organomet. Chem., 1975, 31, 2685.
23 C. K. Fair, MolEn Molecular Structure Procedures, Enraf-Nonius,
Delft, Holland 1990
4 (a) H. G. Alt, T. Frister, E. E. Trapl and H. E. Engelhardt, J.
Organomet. Chem., 1989, 362, 125. (b) K. A. Mahmoud, A. J. Rest
and H. G. Alt, J. Chem. Soc., Dalton T rans., 1984, 187. (c) H. G.
Alt, K. A. Mahmoud and A. J. Rest, Angew. Chem., Int. Ed. Engl.,
1983, 22, 544.
5 B. Brumas, F. Dahan, D. de Montauzon and R. Poilblanc, J.
Organomet. Chem., 1993, 453, C13.
6 B. Brumas, D. de Caro, F. Dahan, D. de Montauzon and R. Poil-
blanc, Organometallics, 1993, 12, 1503.
7 M. A. Bennett, L. Pratt and G. Wilkinson, J. Chem. Soc., 1961,
2037.
8 (a) A. Alvarez, E. Garcia, V. Riera, M. A. Ruiz, C. Bois, Y. Jeannin,
V. Riera and M. A. Ruiz, Angew. Chem., Int. Ed. Engl., 1993, 32,
1156. (b) V. Riera, M. A. Ruiz and F. Villafane, Organometallics,
1992, 11, 2854.
9 (a) R. B. King and A. Fronzaglia, Inorg. Chem., 1966, 5, 1837. (b)
E. W. Abel, M. A. Bennett, R. Burton and G. Wilkinson, J. Chem.
Soc., 1958, 919, 4559. (c) E. W. Abel, M. A. Bennett and G. Wilkin-
son, Proc. Chem. Soc., 1958. 152.
10 G. J. Kubas, L. S. van der Sluys, R. A. Doyle and R. J. Angelici,
Inorganic Syntheses, ed. R. J. Angelici, Wiley, vol. 28, p. 32.
11 (a) T. J. McNeese, J. Chem. Educ., 1991, 68, 678. (b) R. B. King,
Organomet. Synth., 1965, 1, 109.
24 A. C. T. North, D. C. Phillips and F. S. Mathews, Acta Crystal-
logr., Sect. A, 1968, 21, 351.
25 (a) G. M. Sheldrick, SHEL XS86 Program for Crystal Structure
Solution, University of Gottingen, Gottingen, 1986. (b) G. M. Shel-
drick, SHEL X76 Program for Structure Determination, University
of Cambridge, Cambridge, 1976.
12 M. Y. Darensbourg, Prog. Inorg. Chem., 1985, 33, 221.
13 (a) Following the suggestion of Baird et al., brace brackets will be
used to distinguish the 17-electron species from the closed-shell
compounds of similar formulae. (b) T. A. Huber, D. H. Macerney
and M. C. Baird, Organometallics, 1993, 12, 4715.
26 A. G. Orpen, J. Chem. Soc., Dalton T rans., 1980, 2509.
14 B. Brumas-Soula, G. Commenges, F. Dahan and R. Poilblanc
unpublished results.
Received 29th January 1997; Paper 7/06746A
New J. Chem., 1998, Pages 15È23
23