Dehydrogenative formation and reactivity of the unsaturated benzylidyne-bridged complex [Mo2Cp2(μ-CPh)(μ- PCy2)(μ-CO)]: C-C and C-P coupling reactions

Article abstract of DOI:10.1021/om901053x

The title complex is formed through the photochemical treatment of the benzyl complex [Mo₂Cp₂(μ-CH₂Ph)(μ- PCy₂)(CO)₂] (Cp = η⁵-C₅H ₅). It reacts reversibly with CO to

Full text of DOI:10.1021/om901053x

710 Organometallics 2010, 29, 710–713
DOI: 10.1021/om901053x
Dehydrogenative Formation and Reactivity of the Unsaturated
Benzylidyne-Bridged Complex [Mo2Cp2( μ-CPh)( μ-PCy2)( μ-CO)]:
C-C and C-P Coupling Reactions
ꢀ
M. Angeles Alvarez, M. Esther Garcıa, M. Eugenia Martınez, Sonia Menendez, and
Miguel A. Ruiz*
´ ꢀ ꢀ
Departamento de Quımica Organica e Inorganica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
Received December 9, 2009
Summary: The title complex is formed through the photochemical
treatment of the benzyl complex [Mo2Cp2(μ-CH2Ph)(μ-PCy2)-
(CO)2] (Cp=η5-C5H5). It reacts reversibly with CO to give the
ketenyl complex [Mo2Cp2{μ-C(Ph)CO}(μ-PCy2)(CO)2] and
with methyl triflate to give the mixed-carbyne derivative [Mo2Cp2-
(μ-COMe)(μ-CPh)(μ-PCy2)](CF3SO3), which in turn yields re-
versibly the C-C coupled products [Mo2Cp2{μ-η2:η2-C(OMe)-
CPh}(μ-PCy2)L2](CF3SO3) (L=CO, CNtBu) upon addition of
L. In the presence of [FeCp2](BF4), the title complex adds three
PHEt2 molecules to give the phosphinocarbene derivative
[Mo2Cp2{μ-η1:η1,κ1-C(Ph)PEt2}(μ-PEt2)(CO)(PHEt2)](BF4).
Scheme 1
[Mo2Cp2(μ-COMe)(μ-PCy2)(μ-CO)], a molecule exhibiting a
remarkable multisite reactivity involving both the Mo-Mo and
Mo-C multiple bonds,5 and therefore provides an excellent
opportunity to examine the reactivity of an arylcarbyne ligand at
a highly unsaturated dimetal center while comparing it to that of
the mentioned methoxycarbyne complex. The chemistry of a
carbyne ligand at an unsaturated dimetal center can be consi-
dered as the simplest (if crude) model of the chemical behavior of
related surface species formed in different heterogeneously
catalyzed reactions, notably the Fischer-Tropsch (FT) syn-
thesis of hydrocarbons from syngas (CO þ H2),6 a process of
increasing significance in a scene of high prices and short stocks
for crude oil. Indeed there is increasing evidence that surface
methylidyne groups are important not only in the initial C-C
coupling steps of the FT reaction but also as the propagating
species causing the growth of the hydrocarbon chain.6a As
shown below, our initial studies on the behavior of compound
1 show that the chemistry of this 30-electron carbyne complex
involves different C-C and C-P coupling processes, some of
them being reversible.
Recently we reported the preparation, structure, and bonding
of the unsaturated alkyl-bridged complexes [Mo2Cp2(μ-R)(μ-
PCy2)(CO)2] (Cp=η5-C5H5; R=CH3, CH2Ph), this revealing
that the alkyl ligand in each case is involved in a very weak
R-agostic interaction with the dimetal center both in the solid
state and in solution.1 In a preliminary study on the chemical
behavior of the methyl-bridged complex we found that, while a
molecule of CO could be removed photochemically to yield the
carbonyl derivative [Mo2Cp2(μ-η1:η2-CH3)(μ-PCy2)(μ-CO)]
having a strengthened agostic interaction, its photochemical
treatment in the presence of [Mo(CO)6] or [Fe2(CO)9] would
gave methylidyne-bridged heterometallic clusters, thus revealing
the occurrence of easy dehydrogenation steps after cluster
formation.2 This is an unusual evolution of a bridging agostic
alkyl ligand. Actually, we can quote only a couple of precedents
of related μ-CH3/μ-CH transformations involving agostic
ligands, these reported to occur at room temperature at Ru2
(through dehydrogenation)3a and Fe3 (through double oxidative
addition of C-H bonds) metal centers.3b In addition, related
μ-CH2R/μ-CH/μ-CR transformations (R=CH2Ph) were des-
cribed recently to occur at 120 °C in a Ru3 cluster.4 We here
report that the photochemical treatment of the benzyl complex
[Mo2Cp2(μ-CH2Ph)(μ-PCy2)(CO)2] promotes the full dehydro-
genation of this ligand without the need of a third metal center,
to give the benzylidyne-bridged derivative [Mo2Cp2(μ-CPh)-
(μ-PCy2)(μ-CO)] (1) in good yield (Scheme 1). This unsaturated
compound is isoelectronic with the methoxycarbyne complex
Compound 1 is easily prepared in good yield through the
irradiation with visible-UV light of toluene solutions of the
benzyl complex [Mo2Cp2(μ-CH2Ph)(μ-PCy2)(CO)2], the trans-
formation being complete in ca. 2 h at 288 K.7 Although the
formation of 1 is obviously a multistep process involving the
eventual elimination of H2 and a molecule of CO, no intermedi-
ates could be detected in this reaction through IR and 31P NMR
ꢀ
(5) (a) Alvarez, C. M.; Alvarez, M. A.; Garcıa, M. E.; Garcıa-Vivo,
D.; Ruiz, M. A. Organometallics 2005, 24, 4122. (b) García, M. E.;
García-Vivo, D.; Ruiz, M. A.; Alvarez, S.; Aullon, G. Organometallics
ꢀ
ꢀ
ꢀ
2007, 26, 4930. (c) García, M. E.; García-Vivo, D.; Ruiz, M. A.; Alvarez, S.;
ꢀ
ꢀ
*To whom correspondence should be addressed. E-mail: mara@
uniovi.es.
ꢁ
(1) Garcıa, M. E.; Ramos, A.; Ruiz, M. A.; Lanfranchi, M.; Marchio,
Aullon, G. Organometallics 2007, 26, 5912. (d) García, M. E.; García-Vivo,
D.; Ruiz, M. A. Organometallics 2008, 27, 169. (e) García, M. E.;
ꢀ
García-Vivo, D.; Ruiz, M. A. Organometallics 2009, 28, 4385.
L. Organometallics 2007, 26, 6197.
(2) Alvarez, M. A.; Garcıa-Vivo, D.; Garcıa, M. E.; Martınez, M. E.;
Ramos, A.; Ruiz, M. A. Organometallics 2008, 27, 1973.
(3) (a) Connelly, N. G.; Forrow, N. J.; Gracey, B. P.; Knox, S. A. R.;
Orpen, A. G. J. Chem. Soc., Chem. Commun. 1985, 14. (b) Dutta, T. K.;
Vites, J. C.; Jacobsen, G. B.; Fehlner, T. P. Organometallics 1987, 6, 842.
(4) Temjimbayashi, R.; Murotani, E.; Takemori, T.; Takao, T.;
Suzuki, H. J. Organomet. Chem. 2007, 692, 442.
(6) (a) Maitlis, P. M.; Zanotti, V. Chem. Commun. 2009, 1619. (b) Cho,
H.-G.; Lester, A. J. Phys. Chem. A 2006, 110, 3886. (c) Marsh, A. L.; Becraft,
K. A.; Somorjai, G. A. J. Phys. Chem. B 2005, 109, 13619. (d) Maitlis, P. M.
J. Organomet. Chem. 2004, 689, 4366. (e) Maitlis, P. M. J. Mol. Catal. A
2003, 204-205, 55. (f) Dry, M. E. Catal. Today 2002, 71, 227.
ꢀ
(7) Selected data for 1: ν(CO) (CH2Cl2) 1686 (s) cm-1 31P{1H} NMR
;
(121.52 MHz, CD2Cl2) δ 228.5 (s); 13C{1H} NMR (100.62 MHz,
CD2Cl2) δ 385.2 (d, JCP=15 Hz, μ-CPh), 300.8 (d, JCP=9 Hz, μ-CO).
r
pubs.acs.org/Organometallics
Published on Web 01/15/2010
2010 American Chemical Society

Communication
Organometallics, Vol. 29, No. 4, 2010 711
Figure 2. ORTEP drawing (30% probability) of compound 2,
with H atoms and cyclohexyl rings (except the C1 atoms)
omitted for clarity. Only one of the two independent molecules
Figure 1. ORTEP drawing (30% probability) of compound
1, with H atoms and cyclohexyl rings (except the C1 atoms)
omitted for clarity. Only one of the two disordered positions of
˚
in the crystal lattice is shown. Selected bond lengths (A)
and angles (deg): Mo(1)-Mo(2) = 2.6101(2), Mo(1)-C(1) =
1.939(2), Mo(2)-C(2)=1.957(2), Mo(1)-C(4)=2.238(2), Mo-
(2)-C(4) = 2.255(2), Mo(1)-P(1) = 2.3984(4), Mo(2)-P(1) =
2.3857(4), C(4)-C(3)=1.324(2), C(3)-O(3)=1.177(2); C(1)-
Mo(1)-Mo(2)=75.2(1), C(2)-Mo(2)-Mo(1)=92.3(1).
˚
the phenyl ring is shown. Selected bond lengths (A): Mo(1)-
Mo(2)=2.464(1), Mo(1)-C(1)=2.11(1), Mo(2)-C(1)=2.09(1),
Mo(1)-C(2)=1.97(1), Mo(2)-C(2)=1.99(1), Mo(1)-P(1)=
2.403(2), Mo(2)-P(1)=2.402(2).
monitoring of the corresponding solutions. Moreover, we have
found that the dehydrogenation leading to 1 is irreversible, since
this product does not react with H2 even under pressure (60 bar).
The structure of 1 (Figure 1)8 is quite similar to that determined
previously for the isoelectronic ethoxycarbyne complex
[Mo2Cp2(μ-COEt)(μ-PCy2)(μ-CO)]9 and also displays a very
Scheme 2
˚
short intermetallic length of 2.464(1) A, consistent with the triple
bond to be proposed for these molecules on the basis of the EAN
formalism and DFT calculations,5b and quite short Mo-CPh
lengths of ca. 1.98 A, consistent with the expected formal bond
˚
order (1.5) in a symmetrically bridging carbyne ligand. The
benzylidyne ligand (δC 385.2 ppm), however, seems to behave as
an acceptor group stronger than an alkoxycarbyne ligand, since
the C-O stretching frequency of the bridging carbonyl in 1 is
some 12 cm-1 higher than that in the mentioned alkoxycarbyne
complex. This might be the origin of substantial differences
in the acid-base reactivity of these molecules at their most
active positions, located at the dimetal site, C(carbyne) and
O(carbonyl) atoms, as seems to be the case.
The reactivity of 1 is illustrated through the reactions collected
in Scheme 2. As expected for an unsaturated molecule, com-
pound 1 readily adds CO (ca. 4 bar) at room temperature, but
the reaction involves not just the addition of CO to the dimetal
center (as observed for the methoxycarbyne analogue)5c but also
to the carbyne ligand, to give the ketenyl derivative [Mo2Cp2{μ-
C(Ph)CO}(μ-PCy2)(CO)2] (2) almost quantitatively.10 This pro-
cess is fully reversed by irradiation of toluene solutions of 2 with
visible-UV light at room temperature. Again, although several
steps must be involved in both the forward and back reactions,
no intermediates have been detected by IR monitoring of these
processes. The molecule of 2 (Figure 2)11 features a ketenyl
ligand symmetrically bridging the dimetal center through its C
˚
atom. The intermetallic distance (2.6101(2) A) is intermediate
between that measured for the doubly bonded carbyne complex
12
˚
[Mo2Cp2{μ-C(CO2Me)}(μ-PCy2)(CO)2] (2.656(1) A) and
that for the almost triply bonded phenyl complex [Mo2Cp2(μ-
Ph)(μ-PCy2)(CO)2] (2.557(2) A) and therefore suggests that the
˚
(8) X-ray data for 1: red crystals, monoclinic (C2/c), a=25.741(4) A,
b=12.375(2) A, c=19.531(3) A, β=112.156(2)°, V=5762(2) A , T=120
K, Z=8, R=0.0793 (observed data with I > 2σ(I)), GOF=1.347.
1
˚
3
˚
˚
˚
ꢀ
(9) Garcıa, M. E.; Melon, S.; Ramos, A.; Riera, V.; Ruiz, M. A.;
(11) X-ray data for 2: brown-green crystals, triclinic (P1), a =
˚
˚
˚
Belletti, D.; Graiff, C.; Tiripicchio, A. Organometallics 2003, 22, 1983.
(10) Selected data for 2: ν(CO) (CH2Cl2) 1993 (s), 1895 (s), 1838 (vs)
10.4310(1) A, b=18.4643(3) A, c=19.0331(2) A, R=108.999(1)°, β=
3
˚
104.246(1)°, γ=102.762(1)°, V=3173.12(7) A , T=100 K, Z=4, R=
cm-1
;
31P{1H} NMR (121.52 MHz, CD2Cl2) δ 132.6 (s); 13C{1H} NMR
0.0314 (observed data with I > 2σ(I)), GOF=1.10.
ꢀ
(12) Garcıa, M. E.; Garcıa-Vivo, D.; Ruiz, M. A. Organometallics
2008, 27, 543.
(75.48 MHz, CD2Cl2) δ 249.4 (d, JCP=13 Hz, MoCO), 242.0 (d, JCP=16
Hz, MoCO), 145.0 (s, μ-CCO), 15.8 (d, JCP=1 Hz, μ-CCO).

712 Organometallics, Vol. 29, No. 4, 2010
Alvarez et al.
Chart 1
ketenyl ligand in 2 is effectively providing the dimetal center with
more than one electron. This effect has been previously found in
other ketenyl complexes, such as the heterometallic complex
[FeWCp{μ-C(SiPh3)CO}(CO)5], and can be rationalized by
assuming the contribution of ketenyl (one-electron donor) and
acylium (three-electron donor) resonant forms to the electronic
structure of the bridging ligand (Chart 1).13 Accordingly, the
˚
Mo-C bond distances in 2 (ca. 2.24 A) are significantly shorter
than those measured for the aforementioned phenyl complex
1
(ca. 2.35 A), taken here as a rough model for a one-electron
˚
2
˚
C(sp )-donor ligand, while the C-CO distance (1.324(2) A) is
slightly longer than that expected for a C(sp2)-C(sp) double
bond (ca. 1.31 A). We should note that the presence of the phenyl
Figure 3. ORTEP drawing (30% probability) of compound 4b,
with H atoms, cyclohexyl rings, and tBu groups (except the C1
˚
substituent in the carbyne ligand is critical for the stability of this
ketenyl complex. For instance, the analogous (unknown) meth-
oxyl-substituted complex [Mo2Cp2{μ-C(OMe)CO}(μ-PCy2)-
(CO)2] has been predicted by DFT calculations to sponta-
neously undergo a 1,2-shift of the methoxyl substituent to afford
the (stable) carboxycarbyne isomer [Mo2Cp2{μ-C(CO2Me)}-
(μ-PCy2)(CO)2].12
˚
atoms) omitted for clarity. Selected bond lengths (A) and angles
(deg): Mo(1)-Mo(2)=2.6377(6), Mo(1)-C(1)=2.115(6), Mo-
(2)-C(1) = 2.227(5), Mo(1)-C(3) = 2.269(6), Mo(2)-C(3) =
2.149(6), C(1)-C(3)=1.328(8), Mo(1)-C(20)=2.075(6), Mo-
(2)-C(25) = 2.038(6), Mo(1)-P(1) = 2.379(1), Mo(2)-P(1) =
2.380(2); C(20)-Mo(1)-Mo(2)=98.0(2), C(25)-Mo(2)-Mo-
(1)=87.7(2).
Compound 1 undergoes easy O-alkylation at its bridging
carbonyl with a variety of reagents to give the corresponding
mixed alkoxycarbyne/phenylcarbyne derivatives. Thus, its
reaction with excess CF3SO3Me at room temperature gives
[Mo2Cp2(μ-COMe)(μ-CPh)(μ-PCy2)](CF3SO3) (3) in good
yield,14 along with small and variable amounts of a side
product yet uncharacterized (δP 236.6 ppm). Spectroscopic
data for 3 are comparable to those of the bis(methoxy-
carbyne) cation [Mo2Cp2(μ-COMe)2(μ-PCy2)]þ.5a Of parti-
cular interest is the presence of different carbyne ligands in 3,
denoted by the corresponding 13C NMR resonances at 422.0
(μ-CPh) and 365.6 ppm (μ-COMe). We have previously
shown that the mentioned bis(methoxycarbyne) complex
undergoes an unusually reversible C-C coupling between
its carbyne ligands.5a,12 Analogously, compound 3 re-
date, these taking place invariably at polynuclear (Fe3 and
Fe4) iron clusters.17,18 In fact, the transformations 3/4a prove
for the first time that two metal centers are enough to
accomplish the reversible coupling between alkylidyne and
alkoxycarbyne ligands, the process being triggered by the
uptake and release of CO.
The complexes 4 are formed in the above reactions mainly
as the corresponding trans isomers, along with smaller
amounts of the corresponding cis isomers (two cis isomers
for the less crowded dicarbonyl complex; see the Suppor-
ting Information). An X-ray diffraction study on the
major isomer in 4b confirmed the trans arrangement of the
isocyanide ligands and the coupling of the carbyne ligands to
yield an alkyne molecule bound almost perpendicularly to
the intermetallic bond (twist angle ca. 8°, Figure 3).19
The structure is thus very similar to that of the dimetoxy-
lacetylene complex [Mo2Cp2{μ-η2:η2-C2(OMe)2}(μ-PCy2)-
(CNtBu)2]þ 5a,12 and displays an analogously short interme-
t
acts with CO (290 K, 40 bar) or BuCN (223 K) to give
the corresponding alkyne complexes [Mo2Cp2{μ-η2:η2-C-
(OMe)CPh}(μ-PCy2)L2](CF3SO3) (L = CO (4a), CNtBu
(4b)) resulting from the addition of two molecules of the
ligand and C-C coupling between the carbyne ligands to
yield a bridging phenylmethoxylacetylene molecule, a pro-
cess that can be fully reversed in the case of the dicarbonyl
compound 4a upon photolysis in tetrahydrofuran solu-
tion.15,16 We should note that only a few other reversible
couplings between carbyne ligands have been reported to
˚
tallic length (2.6377(6) A), just below the separation
measured for the mentioned 32-electron carbyne complex
[Mo2Cp2{μ-C(CO2Me)}(μ-PCy2)(CO)2] (2.656(1) A).12 This
˚
suggests the presence of a double intermetallic bond and
therefore indicates that the alkyne molecule can be viewed as
a four-electron donor in this cation. The coupling of the
carbyne ligands is retained in solution, as indicated by
the considerable 13C NMR shielding (relative to those in 3)
of the resonances for the corresponding metal-bound
carbon atoms, now located at ca. 140 (μ-COMe) and 125
(μ-CPh) ppm.
(13) Jeffery, J. C.; Ruiz, M. A.; Stone, F. G. A. J. Organomet. Chem.
1988, 355, 231.
(14) Selected data for 3: 31P{1H} NMR (121.52 MHz, CD2Cl2) δ
265.6 (s); 13C{1H} NMR (75.48 MHz, CD2Cl2) δ 422.0 (s, μ-CPh), 365.6
(d, JCP=14 Hz, μ-COMe).
(15) Selected data for trans-4a: ν(CO) (CH2Cl2) 1986 (m, sh), 1962 (s)
;
cm-1
31P{1H} NMR (121.52 MHz, CD2Cl2) δ 155.3 (s); 13C{1H} NMR
(17) Nuel, D.; Daham, F.; Mathieu, R. Organometallics 1985, 4, 1436.
(18) (a) Okazaki, M.; Takano, M.; Ozawa, F. J. Am. Chem. Soc. 2009,
131, 1684. (b) Okazaki, M.; Ohtani, T.; Ogino, H. J. Am. Chem. Soc. 2004,
126, 4104.
(100.61 MHz, CD2Cl2) δ 218.0 (d, JCP=12 Hz, MoCO), 217.5 (d, JCP
=
11 Hz, MoCO), 138.0 (s, μ-COMe), 125.6 (s, μ-CPh).
(16) Selected data for trans-4b: ν(CN) (CH2Cl2) 2137 (s), 2118 (m, sh)
cm-1 31P{1H} NMR (121.52 MHz, CD2Cl2) δ 170.9 (s); 13C{1H} NMR
;
(19) X-ray data for 4b: red crystals, monoclinic (P21/c), a=9.6041(2)
3
˚
˚
˚
˚
(100.61 MHz, CD2Cl2) δ 184.0, 172.5 (2d, JCP=4 Hz, MoCN),143.6 (s,
μ-COMe), 126.0 (s, μ-CPh).
A, b=15.6382(5) A, c=28.7158(7) A, β=93.126(2)°, V=4306.4(2) A , T=
100 K, Z=4, R=0.060 (observed data with I > 2σ(I)), GOF=1.099.

Communication
Organometallics, Vol. 29, No. 4, 2010 713
coordination of the phosphinocarbene ligand in 50 strongly
resembles that usually observed for μ-η1:η2-alkenyl ligands,
with the bridgehead C atom asymmetrically bound to the
˚
metal centers (Mo-C lengths ca. 2.10 and 2.29 A) and the
phosphorus atom strongly bound to both the C (ca. 1.74 A)
˚
˚
and Mo atoms (ca. 2.45 A). The intermetallic distance
˚
(2.7817(5) A) is significantly longer than expected for a
˚
double metal-metal bond (cf. 2.6377(6) A in 4b), perhaps
as a result of the large number of P-donors in the cation. We
finally note that only three other complexes having a simi-
larly bridging phosphinocarbene ligand appear to have been
previously reported, these being also formed through the
coupling between coordinated phosphide and carbyne li-
gands.22 The formation of 5 is likely to be initiated by an
electron transfer to give the extremely reactive 29-electron
radical [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-CO)]þ (not detected)
rapidly adding up to three PHEt2 molecules, one of them
replacing the dicyclohexylphosphide bridge (itself a very
unusual reaction), another one being coupled to the carbyne
ligand (and being dehydrogenated), and a third one just
being bound in a terminal fashion to alleviate the coordina-
tive unsaturation of the cation so generated. Further work is
now in progress to examine the mechanistic aspects and
synthetic potential of this oxidatively induced reactivity of
the carbyne complex 1.
In summary, we have discovered an efficient synthetic
route to a novel and highly unsaturated benzylidyne-bridged
complex. Our initial research suggests that its reactivity may
involve unusual C-C and C-P coupling processes, with the
first ones being reversibly induced by the addition of simple
two-electron-donor ligands. Further studies are being car-
ried out now to explore in more detail the chemical behavior
of this electron-deficient carbyne complex.
Figure 4. ORTEP drawing (30% probability) of compound 5,
with H atoms (except H(1)) and ethyl groups (except the C1
˚
atoms) omitted for clarity. Selected bond lengths (A) and angles
(deg): Mo(1)-Mo(2)=2.7817(5), Mo(1)-C(1)=1.930(4), Mo-
(2)-P(1) = 2.469(1), Mo(1)-P(3) = 2.344(1), Mo(2)-P(3) =
2.431(1), Mo(1)-C(2)=2.104(4), Mo(2)-C(2)=2.286(4), Mo-
(2)-P(2)=2.446(1), C(2)-P(2)=1.737(4); C(1)-Mo(1)-Mo-
(2) = 84.6(1), P(1)-Mo(2)-Mo(1) = 106.6(1), P(1)-Mo(2)-
P(2)=90.4(1), P(1)-Mo(2)-P(3)=89.1(1), P(2)-Mo(2)-P(3)=
128.0(1).
The reactivity of the carbyne complex 1 can be much
increased through one-electron oxidation. For instance,
although 1 does not react with donor molecules such as
secondary phosphines (HPR2) or thiols (HSR) at room
temperature, it does it instantaneously in the presence of
stoichiometric amounts of the ferrocenium salt [FeCp2]BF4.
The most impressive result is achieved in the reaction with
PHEt2, this leading almost instantaneously to the phos-
phinocarbene derivative [Mo2Cp2{μ-η1:η1,κ1-C(Ph)PEt2}-
(μ-PEt2)(CO)(PHEt2)](BF4) (5) in high yield.20 We have been
able to grow good-quality crystals of the (BAr04)- salt of
this cation (50, Ar0 = 3,5-C6H3(CF3)2; Figure 4).21 The
Acknowledgment. We thank the DGI of Spain (Project
CTQ2006-01207) and the COST action CM0802
‘‘PhoSciNet’’ for supporting this work. We also thank
ꢀ
the Consejerıa de Educacion of Asturias for a grant
to S.M.
Supporting Information Available: Text giving experimental
procedures and spectroscopic data for new compounds and a
CIF file giving crystallographic data for compounds 1, 2, 4b, and
50. This material is available free of charge via the Internet at
http://pubs.acs.org.
(20) Selected data for 5: ν(CO) (CH2Cl2) 1850 (s) cm-1 31P{1H}
;
NMR (162.09 MHz, CD2Cl2) δ 154.2 (d, JPP=18 Hz, μ-P), 41.8 (dd,
JPP=54, 18 Hz, PCPh), -48.9 (d, JPP=54 Hz, PH); 13C{1H} NMR
(100.62 MHz, CD2Cl2): δ 250.6 (d, JCP=10 Hz, MoCO), 129.6 (d, JCP
=
20 Hz, μ-CP).
(21) X-ray data for 5 : brown crystals, triclinic (P1), a=12.9909(6) A,
0
˚
˚
˚
b=13.0073(6) A, c=19.9051(9) A, R=82.299(3)°, β=74.667(3)°, γ=
(22) (a) Davies, S. J.; Howard, J. A. K.; Pilotti, M. U.; Stone, F. G. A.
J. Chem. Soc., Chem. Commun. 1989, 190. (b) El Amin, E. A. E.; Jeffery, J.
C.; Walters, T. M. J. Chem. Soc., Chem. Commun. 1990, 170.
3
˚
86.240(3)°, V=3212.9(3) A , T=100 K, Z=2, R=0.0489 (observed data
with I > 2σ(I)), GOF=1.06.