Reactivity of the carbyne complexes [W2(μ-COR)(η5-C5H5)2 (CO)2(μ-Ph2PCH2PPh2)]+ (R = H, Me) toward diazomethane

Article abstract of DOI:10.1021/om010725r

Reaction of [W₂(μ-COH)Cp₂(CO)₂(μ-dppm)]BF₂ (Cp = η⁵-C₅H₅; dppm = Ph₂PCH₂PPh₂) with CH₂N₂ in the presence of CuCl at -75 °C leads to the methoxycarbyne cluster [CuW₂Cl(μ₃-COMe)Cp₂(CO)₂(μ-dpp m)]BF₄. Copper(I) chloride can be cleanly removed from the latter upon addition of PPh₃, thus giving the methoxycarbyne complex [W₂(μ-COMe)Cp₂(CO)₂(μ-dppm)]-BF₄ . In the absence of CuCl, either the hydroxy or the methoxycarbyne ditungsten cations react with CH₂N₂ to give a mixture of the μ-methylene, μ-alkenyl compound [W₂(μ-CH₂){μ-η¹:η²-C(O Me)=CH₂}Cp₂(CO)₂(μ-dppm)]BF₄, which has been characterized through an X-ray study, and the μ-alkyne, μ-alkenyl species [W₂{μ-η¹:η²-C(OMe)CH}{μ-η ¹:η²-C(OMe)CH₂}Cp₂-(CO)(μ-dpp m)]BF₄, the latter being the result of the addition of four molecules of CH₂N₂ to the starting hydroxycarbyne compound. The influence of experimental conditions on the above reactions has been analyzed through separate experiments. For example, the use of tetrahydrofuran as solvent almost suppresses the formation of the alkyne product, whereas the use of a noncoordinating anion such us [B{3,5-C₆H₃(CF₃)₂}₄] ^- instead of BF₄^- as counterion precludes the reaction to occur beyond the methoxycarbyne compound. The solution structures of the new compounds are analyzed in the light of the IR and NMR spectra, and plausible reaction pathways are proposed in order to explain the formation of the reaction products.

Full text of DOI:10.1021/om010725r

Organometallics 2002, 21, 1177-1183
1177
Rea ctivity of th e Ca r byn e Com p lexes
[W2(µ-COR)(η5-C5H5)2(CO)2(µ-P h 2P CH2P P h 2)]+ (R ) H, Me)
tow a r d Dia zom eth a n e
M. Angeles Alvarez, M. Esther Garc´ıa, V´ıctor Riera, and Miguel A. Ruiz*
Departamento de Quı´mica Orga´nica e Inorga´nica/ IUQOEM, Universidad de Oviedo,
E-33071 Oviedo, Spain
Francis Robert
Laboratoire de Chimie des Me´taux de Transition, UACNRS 419, Universite´ P. et M. Curie,
4 Place J ussieu, 75252 Paris, Cedex 05, France
Received August 9, 2001
Reaction of [W2(µ-COH)Cp2(CO)2(µ-dppm)]BF4 (Cp ) η5-C5H5; dppm ) Ph2PCH2PPh2) with
CH2N2 in the presence of CuCl at -75 °C leads to the methoxycarbyne cluster [CuW2Cl(µ3-
COMe)Cp2(CO)2(µ-dppm)]BF4. Copper(I) chloride can be cleanly removed from the latter upon
addition of PPh3, thus giving the methoxycarbyne complex [W2(µ-COMe)Cp2(CO)2(µ-dppm)]-
BF4. In the absence of CuCl, either the hydroxy or the methoxycarbyne ditungsten cations
react with CH2N2 to give a mixture of the µ-methylene, µ-alkenyl compound [W2(µ-CH2){µ-
η1:η2-C(OMe)dCH2}Cp2(CO)2(µ-dppm)]BF4, which has been characterized through an X-ray
study, and the µ-alkyne, µ-alkenyl species [W2{µ-η1:η2-C(OMe)CH}{µ-η1:η2-C(OMe)CH2}Cp2-
(CO)(µ-dppm)]BF4, the latter being the result of the addition of four molecules of CH2N2 to
the starting hydroxycarbyne compound. The influence of experimental conditions on the
above reactions has been analyzed through separate experiments. For example, the use of
tetrahydrofuran as solvent almost suppresses the formation of the alkyne product, whereas
-
the use of a noncoordinating anion such us [B{3,5-C6H3(CF3)2}4]- instead of BF4 as
counterion precludes the reaction to occur beyond the methoxycarbyne compound. The
solution structures of the new compounds are analyzed in the light of the IR and NMR
spectra, and plausible reaction pathways are proposed in order to explain the formation of
the reaction products.
In tr od u ction
The Fischer-Tropsch reaction involves the transfor-
mation of CO at the metallic surface into surface-bound
methyne, methylene, or even methyl groups.8 There is
general agreement that the final products (mainly linear
aliphatic alkanes and alkenes) are formed through
The formation of C-C bonds at transition metal
centers is a fundamental process that attracts consider-
able attention, not only because it can lead to new and
useful synthesis of organic compounds but also because
complexes experiencing these processes can act as
models for the surface species involved in heteroge-
neously catalyzed related reactions.1 In this context,
metal complexes containing coordinated hydrocarbons
susceptible to transformation through C-C coupling
reactions are of interest as molecular models for pro-
cesses such as the Fischer-Tropsch synthesis.2 Among
the most attractive candidates for modeling the elemen-
tal steps involved in the latter we note several di- and
polynuclear complexes containing µ-carbyne,3 µ-meth-
ylene,4 methyl,5 µ-alkenyl,6 or µ-alkylidene7 ligands, all
of which have been found to experience coupling to other
hydrocarbon groups.
(3) (a) Garc´ıa, M. E.; J effery, J . C.; Sherwood, P.; Stone, F. G. A. J .
Chem. Soc., Dalton Trans. 1988, 2443. (b) Garc´ıa, M. E.; J effery, J .
C.; Sherwood, P.; Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1988,
2431. (c) Garc´ıa, M. E.; Tran-Huy, N. H.; J effery, J . C.; Sherwood, P.;
Stone, F. G. A. J . Chem. Soc., Dalton Trans. 1987, 2201. (d) Delgado,
E.; Hein, J .; J effery, J . C.; Ratermann, A. L.; Stone, F. G. A.; Farrugia,
L. J . J . Chem. Soc., Dalton Trans. 1987, 1191.
(4) (a) Royo, E.; Royo, P.; Cuenca, T.; Galakhov, M. Organometallics
2000, 19, 5559. (b) Nishioka, T.; Isobe, K.; Kinoshita, I.; Ozawa, Y.;
Va´zquez de Miguel, A.; Nakai, T.; Miyajima, S. Organometallics 1998,
17, 1637. (c) Akita, M.; Hua, R.; Knox, S. A. R.; Moro-oka, Y.;
Nakanishi, S.; Yates, M. I. J . Organomet. Chem. 1998, 569, 71. (d)
Wang, Z.-Q.; Mart´ınez, J .; Maitlis, P. M. Inorg. Chim. Acta 1998, 280,
62.
(5) (a) Torkelson, J . R.; McDonald, R.; Cowie, M. J . Am. Chem. Soc.
1998, 120, 4047. (b) Beringhelli, T.; D’Alfonso, G.; Panigati, M.; Porta,
F.; Mercandelli, P.; Moret, M.; Sironi, A. J . Am. Chem. Soc. 1999, 121,
2307.
* E-mail: mara@sauron.quimica.uniovi.es.
(1) Somarjai, G. A. Introduction to Surface Chemistry and Catalysis;
Wiley-Interscience: New York, 1994.
(2) (a) Muetterties, E. L.; Stein, J . Chem. Rev. 1979, 19, 479. (b)
Rofer De Poorter, C. K. Chem. Rev. 1981, 81, 447. (c) Beanan, L. R.;
Keister, J . B. Organometallics 1985, 4, 1713. (d) Maitlis, P. M. J .
Organomet. Chem. 1995, 500, 239. (e) Maitlis, P. M.; Long, H. C.;
Quyoum, R.; Turner, M. L.; Wang, Z.-Q. J . Chem. Soc., Chem. Commun.
1996, 1.
(6) (a) Glushove, D.; Hogarth, G.; Lavender, M. H. J . Organomet.
Chem. 1997, 528, 3. (b) Brady, L. A.; Dyke, A. F.; Garner, S. E.;
Guerchais, V.; Knox, S. A. R.; Maher, J . P.; Nicholls, S. M.; Orpen, A.
G. J . Chem. Soc., Chem. Commun. 1992, 310.
(7) Nucciarone, D.; Taylor, N. J .; Carty, A. J .; Tiripicchio, A.;
Triripicchio Camellini, M.; Sappa, E. Organometallics 1988, 7, 118,
and references therein.
(8) Kamisnsky, M. P.; Winograd, N.; Geoffroy, G. L. J . Am. Chem.
Soc. 1986, 108, 1315.
10.1021/om010725r CCC: $22.00 © 2002 American Chemical Society
Publication on Web 02/19/2002

1178 Organometallics, Vol. 21, No. 6, 2002
Alvarez et al.
stepwise polymerization of methylene groups.1 For this
reason, the controlled addition of methylene groups to
metal complexes is a process of interest. Although
diazocompounds have been extensively used as a source
of alkylidene ligands in organometallic chemistry,9 there
are only a few examples of controlled and stepwise
addition of methylene groups to a single metal complex
by using diazomethane.3c,10
Sch em e 1. Ch em ica l Tr a n sfor m a tion s betw een
Ca r byn e Com p lexes
Recently we reported the synthesis of the thermally
stable hydroxy and alkoxycarbyne complexes [W2(µ-
COR)Cp2(CO)2(µ-dppm)]+ [R ) H (1), Me (2); Cp ) η5-
C5H5; dppm ) Ph2PCH2PPh2].11 These complexes re-
acted with BH3‚THF to yield the methylidyne-borane
complex [W2(µ-CHBH3)Cp2(CO)2(µ-dppm)]+. The latter
transformation completed an unusual CO to CH reduc-
tion via the hydroxycarbyne intermediate 1, a signifi-
cant observation in the general context of the Fischer-
Tropsch synthesis. Apart from the carbyne atom as a
reaction center, compounds 1 and 2 have formal double
metal-metal bonds, so they seemed very suitable
substrates to explore stepwise addition reactions of
methylene groups. In this paper we describe the reac-
tivity of compounds 1 and 2 toward diazomethane under
different conditions, which allows some control over the
products. These result from several transformations
induced by methylene groups, such as insertion of CH2
into O-H bonds or coupling to carbyne or carbonyl
ligands.
room temperature, this reaction being illustrative of the
donor ability of the methoxycarbyne ligand in 2 and its
potential in the synthesis of heterometallic clusters.12
The addition of group 11 metal halides to carbyne
complexes has been previously observed.14 Thus it is
perhaps surprising that the hydroxycarbyne complex 1
does not react with CuCl even after long stirring times.
In all, the above results reveal the way by which
compound 1 is transformed into 3. It is evident that the
hydroxycarbyne 1 experiences an insertion reaction of
CH2 into the O-H bond, thus giving the methoxycar-
byne 2. The latter then reacts with the Lewis acid CuCl
to yield the acid-base adduct 3. Although compound 2
was originally prepared through O-methylation at a
terminal CO ligand on the complex [W2Cp2(CO)4(µ-
dppm)],11 the above reactions (conversion of 1 into 3
followed by treatment with PPh3) offer an alternative,
more efficient, preparative route to the methoxycarbyne
2. The presence of CuCl is critical in this synthesis, as
we will discuss later, because this precludes further
additions of CH2N2.
The arrangement of terminal ligands and bridging
diphosphine in 3 does not differ greatly from that of 2.11
Its IR spectrum exhibits in the νst(CO) region two bands
and a shoulder with relative intensities similar to those
of 2, but shifted to slightly higher frequencies. The 31P-
{1H} NMR spectrum at 238 K shows two doublets (11.6
and 6.1 ppm, J PP ) 44 Hz), thus indicating that addition
of the CuCl fragment to 2 proceeds with retention of
the chemical inequivalence of the two phosphorus atoms
and hence the tungsten atoms. By contrast, the 13C
resonance of the carbyne ligand (332.7 ppm at 238 K)
is strongly shifted (by ca. 40 ppm) upfield with respect
to that of 2. This shielding effect is characteristic when
changing the coordination mode of the carbyne ligands
from µ2 to µ3.12a,c Overall, the above data justify the
formulation of compound 3 as a triangular cluster
CuW2, with the methoxycarbyne ligand bridging the
three metallic atoms.
Resu lts a n d Discu ssion
Rea ction of Com p ou n d s 1 a n d 2 w ith CH 2N2 in
th e P r esen ce of Cu Cl. Copper(I) chloride is well
known to catalyze the decomposition of CH2N2, thus
releasing the methylene fragment.13 For this reason, we
first carried out the reaction of the carbyne complexes
1 and 2 with CH2N2 in the presence of CuCl. Surpris-
ingly, however, the product was the same in both cases.
Thus, the reaction of either 1 or 2 in CH2Cl2 with an
excess of an ethereal solution of CH2N2 at low temper-
ature (-75 °C), in the presence of stoichiometric amounts
of CuCl, leads to the trimetallic cluster [CuW2Cl(µ3-
COMe)Cp2(CO)2(µ-dppm)]+ (3) in very good yield. Cop-
per(I) chloride is easily removed from the latter cluster
by treatment with a base such as PPh3 at room tem-
perature, whereby the methoxycarbyne 2 is obtained in
excellent yield along with [CuCl(PPh3)]4 (Scheme 1). As
expected, 3 can be obtained by treating 2 with CuCl at
(9) For reviews see: (a) Herrmann, W. A. Adv. Organomet. Chem.
1982, 20, 159. (b) J . E. Hahn. Prog. Inorg. Chem. 1984, 31, 205.
(10) (a) Trepanier, S. J .; Sterenberg, B. T.; McDonald, R.; Cowie,
M. J . Am. Chem. Soc. 1999, 121, 2613. (b) Dell’Anna, M. M., Trepanier,
S. J .; McDonald, R.; Cowie, M. Organometallics 2001, 20, 88. (c) Akita,
M.; Hua, R.; Knox, S. A. R.; Moro-oka, Y.; Nakanishi, S.; Yates, M. I.
J . Chem. Soc., Chem. Commun. 1997, 51. (d) Holmgren, J . S.; Shapley,
J . R.; Wilson, S. R.; Pennington, W. T. J . Am. Chem. Soc. 1986, 108,
508. (e) Nucciarone, D.; Taylor, N. J .; Carty, A. J . Organometallics
1984, 3, 177. (f) Nucciarone, D.; MacLaughlin, S. A.; Taylor, N. J .;
Carty, A. J . Organometallics 1988, 7, 106.
(11) (a) Alvarez, M. A.; Bois, C.; Garc´ıa, M. E.; Riera, V.; Ruiz, M.
A. Angew. Chem., Int. Ed. Engl. 1996, 35, 102. (b) Alvarez, M. A.;
Garc´ıa, M. E.; Riera, V.; Ruiz, M. A. Organometallics 1999, 18, 634.
(12) (a) Stone, F. G. A. Angew. Chem., Int. Ed. Engl. 1984, 23, 89.
(b) Kreissl, F. R. In Carbyne Complexes; Fischer, H., Hofmann, P.,
Kreissl, F. R., Schrock, R. R., Schubert, U., Weiss, K., Eds.; VCH:
Weinheim, Germany, 1988; p 100. (c) Stone, F. G. A. Adv. Organomet.
Chem. 1990, 31, 53.
In solution, compound 3 seems to experience a dy-
namic process equalizing the chemical environment of
(13) (a) Hoel, E. L.; Ansell, G. B.; Leta, S. Organometallics 1984, 3,
1633, and references therein. (b) Casey, C.; Austin, E. A. Organome-
tallics 1986, 5, 584.
(14) (a) Clark, G. R.; Cochrane, C. M.; Marsden, K.; Roper, W. R.;
Wright, L. J . J . Organomet. Chem. 1986, 315, 211. (b) J effery, J . C.;
Ruiz, M. A.; Stone, F. G. A. J . Organomet. Chem. 1988, 355, 231.

Reactivity of Carbyne Complexes with Diazomethane
Organometallics, Vol. 21, No. 6, 2002 1179
Ch a r t 1
both tungsten atoms. This is indicated by the fact that
the 31P resonances broaden severely when raising the
temperature, although coalescence is not yet reached
at 293 K. In agreement with this, the 1H NMR spectrum
at that temperature exhibits a single resonance for the
cyclopentadienyl groups. All these observations are
indicative of the presence of a dynamic process similar
to that found for 2, which we have discussed in detail
previously11 and needs then not be reproduced here.
Rea ction of Com p ou n d s 1 a n d 2 w ith CH 2N2 in
th e Absen ce of Cu Cl. When copper(I) chloride is not
present, the reaction between CH2N2 and either 1 or 2
becomes more dependent on experimental conditions.
Thus, addition of an excess of an ethereal solution of
CH2N2 to a dichloromethane solution of compound 1 or
2 cooled at -75 °C leads in both cases to a mixture con-
taining the alkyne alkenyl complex [W2{µ-η1:η2-C(OMe)-
CH}{µ-η1:η2-C(OMe)CH2}Cp2(CO)(µ-dppm)](BF4) (5) as
major product, along with significant amounts of the
alkenyl methylene compound [W2(µ-CH2){µ-η1:η2-C(OMe)-
CH2}Cp2(CO)2(µ-dppm)](BF4) (4) (Chart 1). In contrast
with this, the methylene complex 4 becomes the major
product formed when the addition of CH2N2 is carried
out on a THF solution of compound 2 (this reaction
cannot be tested on the hydroxycarbyne complex 1
because this compound is unstable in donor solvents).11
The temperature has no significant influence on the
relative amounts of 4 and 5, although we have noticed
that when the reaction is performed at higher temper-
atures, a variety of other uncharacterized products start
to appear. The relative amount of CH2N2 has little effect
either. For example, reaction of 1 with a slight excess
of diazomethane in CH2Cl2 gives expectedly 2 as the
major compound, with small amounts of complexes 4
and 5. However, the ratio 4:5 in that mixture is roughly
the same (ca. 1:2) as that obtained when using a large
excess of reagent. Finally, we must note that treatment
of a pure sample of 4 with excess of diazomethane leads
to no reaction, an observation implying that 4 is not an
intermediate in the formation of 5.
F igu r e 1. CAMERON drawing of the molecular structure
of the cation in compound 4. Ellipsoids represent 30%
probability.
nearly in the average plane defined by the Cp centroids
and CO ligands, with the diphosphine bridge placed
almost perpendicular to it and the µ-vinyl ligand placed
trans to the dppm bridge. The relative position of the
bridging groups in this cation is analogous to those
found for the bridging ligands in the isoelectronic
complexes [W2(µ-X)Cp(µ-CO)(CO)2(µ-dppm)]+ (X ) F,
Cl).15 According to the 18-electron rule, a single metal-
metal bond should be formulated for this cation, in
agreement with the intermetallic distance, 2.965(1) Å,
which is very close to those measured in the above-
mentioned halide complexes.15
The tungsten atoms of the cation are not equivalent,
and the methylene group is trans to the carbonyl ligand
on W(1) but cis with respect to the carbonyl on W(2).
Despite this, this methylene ligand bridges symmetri-
cally the dimetallic unit (W-C distances 2.19(2) and
2.22(2) Å). The intrinsically asymmetric bridging al-
kenyl ligand in 4 displays some unexpected interatomic
lengths. An inspection of the corresponding figures in
related Mo16 or W17 alkenyl complexes reveals the
following general trends: (a) the bridgehead carbon
atom displays similar M-C lengths, in the range 2.10-
2.20 Å, the shortest one being frequently that corre-
sponding formally to the π interaction; (b) the second
carbon atom, π bonded to the metal, exhibits longer
C-M lengths, in the range 2.20-2.30 Å; (c) the C-C
bond length within the alkenyl group, in the range
Unfortunately, we have not been able to isolate
compound 5 from the corresponding reaction mixture
as a pure solid, and all attempts to obtain X-ray quality
single crystals have been unsuccessful. Nevertheless,
the NMR and IR data allow us to establish quite
precisely the structure of 5 in solution, as we will discuss
later. The structure of 4 has been determined through
an X-ray study. A view of the cation is shown in Figure
1, and selected bond lengths and angles are listed in
Table 2. The ditungsten center is bridged by dppm, a
roughly symmetrical methylene ligand, and a methoxy-
vinyl group. The coordination spheres are completed by
terminal cyclopentadienyl and carbonyl ligands, ar-
ranged trans to each other. The methylene group lies
(15) (a) Alvarez, M. A.; Garc´ıa, G.; Garc´ıa, M. E.; Riera, V.; Ruiz,
M. A.; Bois, C.; J eannin, Y. Angew. Chem., Int. Ed. Engl. 1993, 32,
1156. (b) Alvarez, M. A.; Garc´ıa, G.; Garc´ıa, M. E.; Riera, V.; Ruiz, M.
A.; Lanfranchi, M.; Tiripicchio, A. Organometallics 1999, 18, 4509.
(16) (a) Conole, G.; Hill, K. A.; McPartlin, M.; Mays, M. J .; Morris,
M. J . J . Chem. Soc., Chem. Commun. 1989, 688. (b) Doel, G. R.; Feasey,
N. D.; Knox, S. A. R.; Orpen, A. G.; Webster, J . J . Chem. Soc., Chem.
Commun. 1986, 542. (c) Adams, H.; Biebricher, A.; Gay, S. R.;
Hamilton, T.; McHugh, P. E.; Morris, M. J .; Mays, M. J . J . Chem. Soc.,
Dalton Trans. 2000, 2983. (d) Bamber, M.; Froom, S. F. T.; Green, M.;
Schulz, M.; Werner, H. J . Organomet. Chem. 1992, 434, C19.
(17) (a) Finnimore, S. R.; Knox, S. A. R.; Taylor, G. E. J . Chem. Soc.,
Dalton Trans. 1982, 1783. (b) Ahmed, K. J .; Chisholm, M. H.; Folting,
K.; Huffmann, J . C. J . Chem. Soc., Chem. Commun. 1985, 152. (c)
Mays, M. J .; Reinisch, P. F.; Solan, G. A.; McPartlin, M.; Powell, H. R.
J . Chem. Soc., Dalton Trans. 1995, 1597.

1180 Organometallics, Vol. 21, No. 6, 2002
Ta ble 1. IR a n d 31P {1H} NMR Da ta for New Com p ou n d s
Alvarez et al.
) J PP
b
compd
νst(CO)a/cm-1
δ P(J PW
18.3 (br)
17.7c
[W2(µ-COH)Cp2(CO)2(µ-dppm)](TFPB) (1′)
1892 (m), 1857 (mf)
1952 (vs), 1838 (s)
1961 (s), 1927 (sh, w), 1846 (vs)
1955 (vs), 1875 (s br)
1879 (vs)
[W2(µ-COMe)Cp2(CO)2(µ-dppm)](TFPB) (2′)
[CuW2Cl(µ3-COMe)Cp2(CO)2(µ-dppm)](BF4) (3)
[W2(µ-CH2){µ-C(OMe)CH2}Cp2(CO)2(µ-dppm)](BF4) (4)
[W2{µ-C(OMe)CH}{µ-C(OMe)CH2}Cp2(CO)(µ-dppm)](BF4) (5)
12.5 (br), 7.0 (v br)d,e
11.1 (248), 6.2 (218)d
10.6, 9.6
56
81
a
b
Recorded in CH2Cl2 solution. Recorded at 121.50 MHz and 291 K in acetone-d6 solution, unless otherwise stated; δ in ppm relative
to external 85% aqueous H3PO4; J in hertz. c Recorded at room temperature in CH2Cl2/D2O. Recorded at 161.98 MHz. δ ) 11.6 (400),
6.1 (350), J PP ) 44, when recorded at 238 K.
d
e
(µ-η1:η2-CHCHPh)(CO)4]18b or [Mo2Cp2(µ-η1:η2-C(Me)-
CHMe)(µ-PMe2)(CO)3].18c The unusual feature in the
bridging alkenyl ligand in 4 is that the quite large
π-type W-C lengths (W(2)-C(71) ) 2.39(2), W(2)-C(72)
) 2.43(2) Å) are indicative of a relatively weak π
interaction, but do not correlate with the C(71)-C(72)
length of 1.48(3) Å, almost corresponding to a single
bond. At present, we cannot offer a rationale for this
geometric feature.
Ta ble 2. Cr ysta l Da ta for Com p ou n d 4‚1/2CH2Cl2
mol formula (4‚1/2CH2Cl2)
mol wt
C41.5H40BClF4O3P2W2
1138.68
a, Å
10.714(3)
b, Å
15.405(3)
c, Å
24.875(7)
R, deg
90
90.27(2)
90
4116(2)
â, deg
γ, deg
V, Å3
Z
4
The spectroscopic data in solution for 4 are consistent
with its solid-state structure. The inequivalent carbonyl
ligands give rise to two strong νst(CO) bands at 1955
(vs) and 1875 (s, br) cm-1 in the IR spectrum in
dichloromethane and to two 13C NMR resonances in the
cryst syst
space group
systematic absences
cryst shape/color
monoclinic
P21/c
h0l, l ) 2n+1, 0k0, k ) 2n+1
parallelepiped/red
59.03
1.837
linear abs coeff µ (cm-1
)
density calcd (g cm-3
diffractometer
temp, K
)
1
region of terminal carbonyls. In the H NMR spectrum,
CAD4-Enraf-Nonius
293
the inequivalent protons of the µ-CH2 ligand appear as
doublets of triplets at 3.02 and 4.44 ppm, and the
corresponding carbon atom gives rise to a triplet at 89.9
ppm in the 13C NMR spectrum. These data are not
unusual for a methylene bridging ligand.9 The µ-alkenyl
ligand also gives rise to 13C{1H} and 1H NMR reso-
nances in the expected regions.19-21 A typical set of two
weakly coupled resonances in the 1H spectrum is
observed for the geminal CH2 group,3c while the two
metal-bonded carbon atoms of the alkenyl group give
resonances at 192.1(CR) and 68.1 (CH2) ppm.
The structure proposed for compound 5 is depicted
in Chart 1 and is in full agreement with all spectroscopic
data available. The monocarbonylic nature of 5 is
deduced from the presence of a single band in the
νst(CO) region of the IR spectrum (1879 cm-1 in CH2-
Cl2) and a doublet at 228.1 ppm in the 13C NMR
spectrum, a chemical shift consistent with its terminal
nature. The presence of a methoxyvinyl ligand similar
to that found for 4 is deduced from the appearance of
characteristic NMR resonances. This ligand gives rise
to two P-coupled resonances in the 13C NMR spectrum,
at 188.3 (CR) and 77.0 (CH2) ppm, these chemical shifts
being similar to those for 4. The presence of this alkenyl
ligand is also deduced from the appearance of two
weakly coupled resonances at 0.75 and 3.33 ppm
(J HH ) 4 Hz), similar to those found for 4 and other vinyl
ligands.19,20
radiation
scan type
Mo KR (λ ) 0.71069 Å)
ω/2θ
scan range, deg
θ limits, deg
octants collected
no. of data collected
0.8 + 0.345 tan θ
1-25
0, 12; 0, 18; -29, 29
7964
no. of unique data collected
no. of unique data used for
refinement
7231
3768 (Fo)2 > 3σ(Fo)2
R (int)
0.075
decay of standards reflns %
R ) ∑|Fo| - |Fc|/∑|Fo|
Rw ) ∑w(|Fo| - |Fc|)2/∑w(Fo)2
abs corr
<1
0.046
0.053, w ) 1.0
DIFABS (min ) 0.94,
max ) 1.10)
506
no. of variables
∆Fmin/∆Fmax (e/Å3)
-1.64/1.70
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p ou n d 4
W(1)-W(2)
W(1)-P(2)
W(1)-C(20)
W(1)-C(72)
W(1)-C(51)
C(71)-C(72)
C(74)-O(73)
2.965(1)
2.480(5)
2.19(2)
2.17(2)
1.94(2)
1.48(3)
1.46(2)
W(2)-C(71)
W(2)-P(1)
W(2)-C(20)
W(2)-C(72)
W(2)-C(61)
C(72)-O(73)
2.39(2)
2.546(5)
2.22(2)
2.43(2)
1.96(2)
1.29(2)
P(1)-W(2)-C(72)
P(1)-W(2)-C(71)
P(1)-W(2)-W(1)
C(20)-W(2)-C(61)
135.6(4) P(2)-W(1)-C(72)
147.9(5) P(2)-W(1)-W(2)
146.5(5)
92.8(1)
89.6(1) C(20)-W(1)-C(51) 122.2(7)
78.9(7) W(1)-C(20)-W(2) 84.5(6)
1.40-1.45 Å, is intermediate between that correspond-
ing to a single and a double bond. Thus, the description
of the metal to ligand interaction in terms of a σ bond
(C to M) and a π bond (CdC to M) is generally
satisfactory. Under this view, it is expected that an
increase of the π bond strength should cause a C-C
elongation and vice versa. This is actually observed, for
example, for the dimolybdenum complex [Mo2Cp2(µ-
SPh)(µ-η1:η2-C(Me)dCHMe)(CO)2], which displays quite
long Mo-C (π type) distances of ca. 2.37 Å, which is
consistent with a short C-C distance (1.384(11) Å).18a
A similar effect is found in the complexes [Mo2Cp2Cl-
The NMR data for 5 clearly show that, in addition to
the alkenyl group, the molecule contains a second
(18) (a) Schollhammer, P.; Pe´tillon, F. Y.; Poder-Guillou, S.;
Talarmin, J .; Muir, K. W.; Yufit, D. S. J . Organomet. Chem. 1996, 513,
181. (b) Acum, G. A.; Mays, M. J .; Raithby, P. R.; Solan, G. A. J .
Organomet. Chem. 1995, 492, 65. (c) Conole, G.; Henrick, K.; McPartlin,
M.; Horton, A. D.; Mays, M. J . New J . Chem. 1988, 12, 559.
(19) (a) Raithby, P. R.; Rosales, M. J . Adv. Inorg. Chem. Radiochem.
1985, 29, 168. (b) Sappa, E.; Tiripicchio, A.; Braunstein, P. Coord.
Chem. Rev. 1985, 65, 219. (c) Holton, J .; Lappert, M. F.; Pearce, R.;
Yarrow, P. I. W. Chem. Rev. 1983, 83, 135.
(20) Evans, J .; McNulty, G. S. J . Chem. Soc., Dalton Trans. 1984,
79.
(21) Fong, R. H.; Hersh, W. H. J . Am. Chem. Soc. 1987, 109, 2843.

Reactivity of Carbyne Complexes with Diazomethane
Organometallics, Vol. 21, No. 6, 2002 1181
hydrocarbon ligand which can be unambiguously identi-
fied as a bonded methoxyacetylene molecule. The metal-
bonded carbon atoms give 13C resonances at 253.6
(COMe) and 147.3 (CH) ppm. The large chemical shift
difference between these resonances suggests a very
asymmetric coordination of the alkyne to the dimetallic
unit, while the quite high chemical shift of the internal
resonance suggests substantial multiple-bond character
in the corresponding W-C interaction. Similar high 13C
chemical shifts (ca. 260 ppm) have been recently de-
scribed for both carbon atoms of the bridging alkyne
ligand in the molybdenum cations [Mo2Cp2(µ-SMe)3-
(RCCH)]+.22 Actually, the chemical shifts found for the
alkyne group in 5 are similar to those exhibited by the
bridging aminoalkyne ligand in the clusters [M3(CO)9-
(µ3-S)(µ3-MeC2NMe2)] (M ) Fe, Ru, Os).23 Structural
data for aminoalkyne ligands bridging either trimetallic
clusters23 or dinuclear compounds24,25 support a view
of these ligands as bis-carbene (one terminal, one
bridging) donor groups, which is consistent with the
corresponding 13C chemical shifts and is also supported
on MO calculations26 and reactivity.25,27 In summary,
we believe that the methoxyalkyne ligand in 5 is very
similar to a dialkylaminoalkyne group and is thus
bonded as a terminal alkylidene through the internal
carbon atom, thus effectively replacing the lost carbonyl
group, and as a bridging alkylidene through the termi-
nal (CH) carbon atom.
Role of Ca tion -An ion In ter a ction s in th e Rea c-
tivity of th e Ca r byn e Com p lexes. The results dis-
cussed above seem to prove that there are independent
pathways for the generation of either 4 or 5 from the
carbyne complexes and diazomethane. As we have found
strong differences in the relative amounts of 4 and 5
when changing the donor properties of the reaction
solvent (from CH2Cl2 to tetrahydrofuran), we suspected
that interactions between the cation 2 and its counterion
and/or the solvent might influence the course of the
reaction. We must note that cation-anion interactions
occur for salt 2 in poorly solvating solvents, as deduced
from IR data.11 Thus, a change in the solvent modifies
not only any cation-solvent interaction but also any
cation-anion interaction being present.
attempts to isolate this new salt were made. Spectro-
scopic data for 1′ (Table 1) are similar to those of 1, but
now the IR spectrum for 1′ in dichloromethane solution
displays just two strong bands in the νst(CO) region,
instead of the four ones exhibited by 1. This indicates
that the cation-anion interaction likely responsible for
the observed splitting of the νst(CO) bands in 111 is
eliminated when replacing BF4- for the less coordinat-
ing TFPB-, as expected.
Compound 2′ was prepared by reaction of a dichlo-
romethane solution of 1′ and CH2N2 (in Et2O). However,
even when using a large excess of CH2N2, the major
organometallic product formed is still 2′, along with
large amounts of polymethylene as a white insoluble
solid. The IR spectrum of 2′ in dichloromethane solution
displays just two νst(CO) bands instead of the three
bands observed for 2.11 This again indicates that the
anion/cation interaction present in 2 has been largely
eliminated after replacement of BF4- by TFPB-. In all,
however, the use of the TFPB ion in the diazomethane
reactions under discussion is not useful for elucidating
the reaction pathways in operation: it allows the
hydroxy to methoxycarbyne transformation, but makes
the latter complex an efficient catalyst for the decom-
position of diazomethane, which in turn precludes the
formation of significant amounts of products (like 4 or
5) incorporating more methylene units. Decomposition
of diazomethane catalyzed by transition metal com-
plexes is not an unusual reaction.29
Rea ction P a th w a ys in th e F or m a tion of Com -
p ou n d s 4 a n d 5. The results discussed above reveal
that the reactions of the carbyne complexes 1 and 2 with
diazomethane are not simple processes, as they involve
the addition of up to four methylene groups to the
starting substrates. The surroundings of the carbyne
cation are also important, so that changing the solvent
or the counterion has a strong influence on the distribu-
tion of products. Although the information obtained is
not complete enough so as to define all elemental steps
involved, we can get a general picture of the reaction
pathways under operation (Scheme 2).
In the first place, it is clear that the initial step is
the formal insertion of methylene into the O-H bond
of the hydroxycarbyne ligand in 1, thus yielding the
methoxycarbyne 2. The fact that the same distribution
of products is obtained starting from 1 or 2 supports
this view. On the other hand, the insertion of methylene
into O-H bonds is well documented.3c,30 Compound 2
has two reactive sites for further methylene addition,
the W-W bond and the W-C(carbyne) bond, both of
them with double-bond character. These type of meth-
ylene additions are well known, the first one being the
classical metallacyclopropanation process9a and the
second one leading to bridging alkenyl CRdCH2 lig-
ands.3c,d In fact, compound 4 is the result of both types
of methylene addition to the methoxycarbyne complex
2, but we cannot tell in which order this double addition
is actually occurring. By recalling that the methoxyvinyl
ligand is present in both 4 and 5, we propose that
methylene addition to the bridging carbyne occurs first
to give the alkenyl intermediate A, which is still
To study the role of the counterion in the above
reactions, we have prepared the hydroxycarbyne (1′) and
methoxycarbyne (2′) cations as salts of the TFPB anion
(TFPB ) [B{3,5-C6H3(CF3)2}4]-). The latter is a rather
inert, noncoordinating anion that has been found to be
useful in the stabilization of highly reactive cationic
species.28 Compound 1′ was prepared similarly to 1,11
but using H(TFPB)‚2Et2O28b instead of HBF4‚OEt2. No
(22) Schollhammer, P.; Cabon, N.; Capon, J . F.; Pe´tillon, F. Y.;
Talarmin, J . Organometallics 2001, 20, 1242.
(23) Adams, R. D.; Chen, G.; Tanner, J . F.; Yin, J . Organometallics
1990, 9, 595.
(24) Adams, R. D.; Chen, G.; Yin, J . Organometallics 1991, 10, 1278.
(25) Cabrera, E.; Daran, J . C.; J eannin, Y.; Kristiansson, O. J .
Organomet. Chem. 1986, 310, 367.
(26) Nomikon, Z.; Halet, J . F.; Hoffmann, R.; Tanner, J .; Adams, R.
D. Organometallics 1990, 9, 588.
(27) Cabrera, E.; Daran, J . C.; J eannin, Y. Organometallics 1988,
7, 2010.
(28) (a) Nishida, H.; Takada, N.; Yoshhimura, M.; Sonoda, T.;
Kobayashi, H. Bull. Chem. Soc. J pn. 1984, 57, 2600. (b) Brookhart,
M.; Grant, B.; Volpe, A. F., J r. Organometallics 1992, 11, 3920. (c)
Butts, M. D.; Scott, B. L.; Kubas, G. J . J . Am. Chem. Soc. 1996, 118,
4746. (d) Heinekey, D. M.; Radzewich, C. E. Organometallics 1998,
17, 51, and references therein.
(29) Hamilton, D. H.; Shapley, J . R. Organometallics 2000, 19, 761.
(30) Hayashi, T.; Kato, T.; Kaneko, T.; Asai, T.; Ogoshi, H. J .
Organomet. Chem. 1994, 473, 323.

1182 Organometallics, Vol. 21, No. 6, 2002
Alvarez et al.
Sch em e 2. P r op osed P a th w a ys for th e Rea ction s
of Dia zom eth a n e w ith Com p ou n d 1 [W-W )
W2Cp 2(µ-d p p m )]
however, that the reverse process has been proposed in
order to explain the formation of the ketene complex
[Ru2(η5-C5Me5)2(µ-CO)(CO)2{µ-C(O)CH2}].33 Finally, a
further insertion of methylene into the O-H bond in
intermediate D gives the alkyne product 5.
To obtain further support for our proposal on the
formation of compounds 4 and 5, we carried out the
reaction of 1 with an excess of CD2N2 in CH2Cl2 at -65
°C. This led to a mixture of compounds 4 and 5
deuterated as expected, i.e., containing a µ-C(OCHD2)-
CD2 vinyl group. This itself implies that there is no
H-exchange involving the hydroxycarbyne ligand. The
most important observation was, however, that the 4:5
ratio was then 1:1, to be compared with a 1:2 ratio when
using the normal, nondeuterated reagent. This kinetic
isotope effect in the formation of 5 is in agreement with
the transformation C/D proposed (Scheme 2), the latter
requiring the cleavage of a C-H bond.
In summary, by combining rational elemental steps
we can give a satisfactory explanation for the formation
of compounds 4 and 5. Yet, some speculation is unavoid-
able and some questions remain to be answered, for
example, the precise role of the solvent and the coun-
terion, both of which can almost suppress the formation
of some of the methylene derivatives of the carbyne
complexes 1 and 2.
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were carried out under
an atmosphere of nitrogen. Solvents were purified according
to standard procedures34 and distilled under nitrogen prior to
use. Petroleum ether refers to that fraction distilling in the
range 60-65 °C. Compound 1,11 H(TFPB)‚2Et2O,28b CuCl,35
and diethyl ether solutions of CH2N236 were prepared according
to literature procedures. Diethyl ether solutions of CD2N2 were
prepared analogously, but using NaOD/D2O solutions and
EtOD instead of the nondeuterated reagents. All other re-
agents were purchased from the usual commercial suppliers
and used as received. Filtrations were carried out using dry
diatomaceous earth under nitrogen. Low-temperature reac-
tions were performed using jacketed Pyrex Schlenk tubes,
refrigerated by a closed 2-propanol circuit kept at the desired
temperature with a cryostat.
NMR spectra were recorded at 400.13 (1H), 161.98 (31P{1H}),
or 100.61 (13C{1H}) MHz in acetone-d6 solution at room
temperature, unless otherwise indicated. Chemical shifts (δ)
are given in ppm, relative to internal TMS (1H, 13C), or external
85% H3PO4 aqueous solution (31P), with positive values for
frequencies higher than that of the reference. Coupling
constants (J ) are given in hertz. 13C{1H} NMR spectra were
recorded on solutions containing a small amount of tris-
(acetylacetonato)chromium(III) as a relaxation reagent. The
assignments of the 13C resonances were routinely verified
through standard DEPT experiments.
unsaturated. Further methylene addition to the double
W-W bond would yield complex 4, thus completing one
of the reaction pathways. Alternatively, the methylene
addition can give a terminal methylene group, with
displacement of a terminal CO to a bridging position,
then yielding a new intermediate B. Precedents for this
type of addition to a doubly bonded binuclear center can
also be found on related complexes. For example, tBuNC
adds to the doubly bonded [Mo2Cp′2(µ-CH2PPh2)(µ-
PPh2)(CO)2] to give [Mo2Cp′2(µ-CH2PPh2)(µ-PPh2)(µ-
CO)(CO)(CNtBu)] (Cp′ ) η5-C5H4Me).31 Intermediate B
has now methylene and carbonyl groups which can
couple to each other to give a bonded ketene group, also
a known process.10d,32 An H migration in the unsatur-
ated ketene intermediate C to give the hydroxy acety-
lene species D is then proposed, thus providing the two
extra electrons needed for electronic saturation of the
molecule. This is the elemental step for which we have
not found clear precedents in the literature. We note,
P r ep a r a tion of Solu tion s of Com p ou n d 1′. A dichlo-
romethane solution (30 mL) of compound [W2Cp2(CO)4(µ-
dppm)] (0.1 g, 0.1 mmol) was stirred with H(TFPB)‚2Et2O (100
mg, 0.1 mmol) for 45 min at -40 °C to give a brown solution.
Solvent was then removed under vacuum and the residue
(31) Garc´ıa, G.; Garc´ıa, M. E.; Melo´n, S.; Riera, V.; Ruiz, M. A.;
Villafan˜e, F. Organometallics 1997, 16, 624.
(33) Doherty, N. M.; Filders, M. J .; Forrow, N. J .; Knox, S. A. R.;
Macpherson, K. A.; Orpen, A. G. J . Chem. Soc., Chem. Commun. 1986,
1335.
(34) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: Oxford, U.K., 1988.
(35) Brauer, G. Handbuch der Pra¨parativen Anorganischen Chemie;
Ferdinand Enke Verlag: Stuttgart, Germany, 1978; Vol. 2, p 972.
(36) Vogel, A. I. Textbook of Practical Organic Chemistry, 4th ed.;
Longmans: London, U.K., 1978; p 291.
(32) (a) Gao, Y.; J ennings, M. C.; Puddephatt, R. J . Organometallics
2001, 20, 1882. (b) Morrison, E. D.; Geoffroy, G. L. J . Am. Chem. Soc.
1985, 107, 3541. (c) Yang, Y.-L.; Wang, L. J .-J .; Lin, Y.-Ch.; Huang,
S.-L.; Chen, M.-C.; Lee, G.-H.; Wang, Y. Organometallics 1997, 16,
1573. (d) Geoffroy, G. L.; Bassner, S. L. Adv. Organomet. Chem. 1988,
28, 1, and references therein. (e) Lin, Y. C.; Calabrese, J . C.; Wreford,
S. S. J . Am. Chem. Soc. 1983, 105, 1679.

Reactivity of Carbyne Complexes with Diazomethane
Organometallics, Vol. 21, No. 6, 2002 1183
washed with petroleum ether (2 × 5 mL) to give compound 1′
as an oily solid. The latter was redissolved in CH2Cl2 and was
then ready for further use.
CH2N2 (5 mL, ca. 3 mmol) was added to a dichloromethane
solution (12 mL) of compound 2 (0.01 g, 0.09 mmol) at -65
°C. The solution was stirred for 45 min and allowed to reach
room temperature slowly. Solvent was then removed under
vacuum, and the residue washed with toluene (5 × 5 mL),
extracted with CH2Cl2, and filtered. Removal of solvent from
the filtrate under vacuum gave a solid containing complex 5
as major species. Attempts to further purify this product were
unsuccessful. 1H NMR: δ 7.96 (s, 1H, CH), 7.94-7.01 (m, 20H,
Ph), 5.24 (s, 5H, Cp), 5.16 (s, 5H, Cp), 3.80 (s, 3H, OMe), 3.67
(br q, J HH = J HP = 13, 1H, PCH2), 3.64 (s, 3H, OMe), 3.33 [d,
J HH ) 4, 1H, µ-C(OMe)dCH2], 2.63 [dt, J HP ) 10, J HH ) 14,
1H, PCH2], 0.75 [d, J HH ) 4, 1H, µ-C(OMe)dCH2] ppm. 13C-
{1H} NMR: δ 253.6 [t, J CP ) 4, J CW ) 135, µ-C(OMe)tCH),
228.1 [d, J CP ) 8, WCO], 188.3 [t, J CP ) 4.5, µ-C(OMe)dCH2],
147.3 (s, µ-C(OMe)tCH), 143.0-129.0 (Ph), 98.7, 94.1 (2 × s,
2 x Cp), 77.0 [t, J CP ) 5, µ-C(OMe)dCH2], 61.8, 60.2 (2 × s,
2 × OMe), 23.4 [dd, J CP ) 29, 24, PCH2] ppm.
P r ep a r a tion of Solu tion s of Com p ou n d 2′. A diethyl
ether solution of CH2N2 (5 mL, ca. 3 mmol) was added to a
dichloromethane solution (8 mL) of compound 1′ (0.165 g, 0.09
mmol) at -65 °C. The mixture was stirred for 45 min, and
solvent was then removed under vacuum. The oily residue was
extracted with CH2Cl2 (3 × 5 mL) and filtered. Removal of
solvent from the filtrate under vacuum gave a residue contain-
ing compound 2′ as the major species present. Attempts to
further purify this product were unsuccessful due to its
progressive decomposition upon manipulation.
P r ep a r a tion of [Cu W2Cl(µ3-COMe)Cp 2(CO)2(µ-d p p m )]-
(BF 4) (3). A diethyl ether solution of CH2N2 (5 mL, ca. 3 mmol)
and 0.01 g (0.09 mmol) of CuCl were added to a dichlo-
romethane solution (15 mL) containing compound 1 (0.094 g,
0.09 mmol) at - 75 °C. The mixture was stirred for 45 min
and allowed to reach room temperature slowly. Solvent was
then removed under vacuum and the residue extracted with
CH2Cl2 (3 × 5 mL) and filtered. Removal of solvent from the
filtrate under vacuum yielded compound 3 as a brown micro-
crystalline powder (0.087 g, 83%). Anal. Calcd for C39BClCu-
F4H35O3P2W2: C, 40.10; H, 3.00. Found: C, 40.18; H, 3.05. 1H
NMR (200.13 MHz): δ 7.80-7.10 (m, 20H, Ph), 5.60 (s, 10H,
Cp), 5.17 (t, J HP ) 11, 2H, CH2), 4.91 (s, 3H, OCH3). 31P{1H}
NMR (238 K): δ 11.6 (d, J PP ) 44, J PW ) 400, 1P, µ-dppm),
6.1 (d, J PP ) 44, J PW ) 350, 1P, µ-dppm). 13C{1H} NMR (238
K): δ 332.7 (s, µ3-COMe), 247.8 (s, CO), 220.7 (s br, CO),
140.1-126.5 (Ph), 99.8 (s, Cp), 92.6 (s, Cp), 73.1 (s, OCH3),
48.9 (t, J CP ) 31, CH2).
X-r a y St r u ct u r e Det er m in a t ion for Com p ou n d
4‚1/2CH2Cl2. A selected crystal was set up on an automatic
diffractometer. Unit cell dimensions with estimated standard
deviations were obtained from least-squares refinements of the
setting angles of 25 well-centered reflections. Two standard
reflections were monitored periodically; they showed no change
during data collection. Corrections were made for Lorentz and
polarization effects. Empirical absorption correction (Difabs)37
was applied. An extinction correction was unnecessary.
Computations were performed by using the PC version of
CRYSTALS.38 Atomic form factors for neutral atoms were
taken from ref 39. Real and imaginary parts of anomalous
dispersion were taken into account. The structures were solved
by direct methods (SHELXS)40 and successive Fourier maps.
Hydrogen atoms could not be found on difference maps and
were not introduced in the calculations. Other atoms were
anisotropically refined. Full matrix least-squares refinements
were carried out by minimizing the function ∑w(|Fo| - |Fc|)2
where Fo and Fc are the observed and calculated structure
factors. Models reached convergence with R ) ∑(|Fo| - |Fc|)/∑
|Fo| and Rw ) [∑w(|Fo| - |Fc|)2/∑w(Fo)2]1/2 having values listed
in Table 2; each reflection was assigned a weight unity.
Criteria for a satisfactory complete analysis were the ratios
of rms shift to standard deviations being less than 0.2 and no
significant features in the last difference map. The asymmetric
unit contains a half molecule of CH2Cl2. Figure 1 represents
a CAMERON41 view of the cation, with the numbering scheme.
P r ep a r a tion of [W2(µ-COMe)Cp 2(CO)2(µ-d p p m )](BF 4)
(2). Solid PPh3 (0.020 g, 0.078 mmol) was added to a dichlo-
romethane solution (8 mL) of compound 3 (0.087 g, 0.075
mmol) at room temperature. The mixture was stirred for 10
min and the solvent removed under vacuum. The residue was
washed with toluene (5 × 5 mL), extracted with CH2Cl2, and
filtered. Removal of solvent from the filtrate under vacuum
yielded compound 3 as a dark brown powder (0.075 g, 83%).
P r epar ation of [W2(µ-CH2){µ-η1:η2-C(OMe)CH2}(CO)2Cp2-
(µ-d p p m )]BF 4 (4). A diethyl ether solution of CH2N2 (5 mL,
ca 3 mmol) was added to a tetrahydrofuran solution (12 mL)
of compound 2 (0.01 g, 0.09 mmol) cooled at 0 °C. The mixture
was stirred for 30 min, and solvent was then removed under
vacuum. The residue was extracted with CH2Cl2 (3 × 5 mL)
and filtered. Removal of solvent from the filtrate under vacuum
gave a solid containing compound 4 as major product. Recrys-
tallization at room temperature from CH2Cl2/diethyl ether/
petroleum ether yielded compound 4 (0.053 g, 52%) as orange
crystals. Suitable crystals for the X-ray study were grown by
slow diffusion of a concentrated CH2Cl2 solution of a pure
sample of the complex into a layer of petroleum ether at room
temperature. Anal. Calcd for C41H39BF4O3P2W2: C, 44.92; H,
3.59. Found: C, 45.21; H, 3.70. 1H NMR (300.13 MHz): δ
7.62-6.98 (m, 20H, Ph), 5.86 (td, J HP ) 13, J HH ) 12, 1H,
PCH2), 5.12 (d, J HP ) 3, 5H, Cp), 4.95 (d, J HP ) 1.5, 5H, Cp),
4.44 (td, J HP ) 26, J HH ) 12, 1H, µ-CH2), 3.89 (dt, J HP ) 14,
11, J HH ) 11, 1H, PCH2), 3.85 [d, J HH ) 4, 1H, CdCH2], 3.70
(s, 3H, OMe), 3.02 (q, J HP ) J HH ) 12, 1H, µ-CH2), 2.36 [dd,
J HH ) 4, J HP ) 1, 1H, CdCH2] ppm. 13C{1H} NMR (50.32
MHz): δ 229.0 (d, J CP ) 7, CO), 218.0 (d, J CP ) 6, CO), 192.1
[d, J CP ) 9, µ-C(OMe)dCH2], 138.5-128.1 (Ph), 94.2 (s, Cp),
89.9 (t, J CP ) 8, µ-CH2), 88.4 (s, Cp), 68.1 [dd, J CP ) 9, 3,
µ-C(OMe)dCH2], 60.8 (s, OMe), 41.8 (dd, J CP ) 19, 23, PCH2)
ppm.
Ack n ow led gm en t. We thank the DGES of Spain
for financial support (Projects PB96-0317 and BQU2000-
0944). We also thank Estefan´ıa Llamas for the prepara-
tion of compound 1′, and Felipe Garc´ıa for experimental
assistance in the diazomethane reactions.
Su p p or tin g In for m a tion Ava ila ble: Tables of fractional
atomic coordinates, anisotropic thermal parameters, and bond
lengths and angles for compound 4. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM010725R
(37) Walker, N.; Stuart, D. Acta Crystallogr., A 1983, 39, 158.
(38) Watkin, D. J .; Carruthers, J . R.; Betteridge, P. W. CRYSTALS,
An Advanced Crystallographic Computer Program; Chemical Crystal-
lography Laboratory: Oxford, U.K., 1988.
(39) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham, U.K., 1974; Vol. IV.
(40) Sheldrick, G. M. SHELXS 86, Program for Crystal Structure
Solution; University of Go¨ttingen: Go¨ttingen, 1986.
(41) Pearce, L. J .; Watkin, D. J . CAMERON; Chemical Crystal-
lography Laboratory: Oxford, U.K., 1989.
P r epa r a tion of [W2{µ-η1:η2-C(OMe)CH}{µ-η1:η2-C(OMe)-
CH2}Cp 2(CO)(µ-d p p m )]BF 4 (5). A diethyl ether solution of