Unusual reactivity of the unsaturated dimolybdenum complex [Mo2(η5-C5H5)2 {μ-OP(OEt)2}{μ-P(OEt)2} {μ-P(OEt)2}(CO)2]

Article abstract of DOI:10.1021/om0301886

Reaction of the doubly metal-metal bonded compound [Mo₂Cp₂{μ-OP(OEt)₂}{μ- P(OEt)₂}(CO)₂] with [Fe₂(CO)₉] leads to the 46 e^- cluster [FeMo₂Cp₂ {μ-OP(OEt)₂}{μ-P(OEt)₂}(CO)₅]. By contrast, reaction of [Mo₂Cp₂{μ-OP(OEt)₂} {μ-P(OEt)₂}(CO)₂] with SnCl₂ leads to the incorporation of two molecules of reagent: one molecule inserts into the Mo-O bond, and the other one adds to the Mo=Mo double bond to finally yield the tetranuclear compound [Mo₂Cp₂{μ-(EtO)₂ POSnCl₂}{μ-P(OEt)₂}(μ-SnCl₂) (CO)₂] as confirmed by an X-ray diffraction study. Complex [Mo₂Cp₂{μ-OP(OEt)₂}{μ-P(OEt)₂} (CO)₂] reacts with HCC(p-C₆H₄Me) to give a mixture of the alkyne-bridged compound [Mo₂Cp₂ {μ-η²:η²HCC(p-C₆H₄Me)} {μ-(EtO)₂POP(OEt)₂}(CO)₂] and the alkenyl-bridged [Mo₂Cp₂{μ-η¹, κ¹:η²-OP(OEt)₂ CH=C(p-C₆H₄Me)}{μ-P(OEt)₂}(CO)₂] (structure confirmed through an X-ray diffraction study). This requires either P-O reductive elimination between phosphonate and phosphido ligands or insertion of the incoming alkyne into the Mo-P (phosphonate) bond, all these uncommon processes occurring at room temperature. The solution structure of the new compounds is analyzed on the basis of their IR and NMR data and X-ray diffraction studies, and the reaction pathways prevalent for the title compound are discussed on the basis of the data available.

Full text of DOI:10.1021/om0301886

Organometallics 2003, 22, 2741-2748
2741
Un u su a l Rea ctivity of th e Un sa tu r a ted Dim olybd en u m
Com p lex [Mo2(η5-C5H5)2{µ-OP (OEt)2}{µ-P (OEt)2}(CO)2]
Celedonio M. 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
Claudette Bois
Laboratoire de Chimie Inorganique et Materiaux Moleculaires, Universite´ P. et M. Curie,
75252, Paris, Cedex 05, France
Received March 11, 2003
Reaction of the doubly metal-metal bonded compound [Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}-
(CO)2] with [Fe2(CO)9] leads to the 46 e- cluster [FeMo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)5].
By contrast, reaction of [Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)2] with SnCl2 leads to the
incorporation of two molecules of reagent: one molecule inserts into the Mo-O bond, and
the other one adds to the ModMo double bond to finally yield the tetranuclear compound
[Mo2Cp2{µ-(EtO)2POSnCl2}{µ-P(OEt)2}(µ-SnCl2)(CO)2] as confirmed by an X-ray diffraction
study. Complex [Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)2] reacts with HCC(p-C6H4Me) to give
a mixture of the alkyne-bridged compound [Mo2Cp2{µ-η2:η2-HCC(p-C6H4Me)}{µ-(EtO)2POP-
(OEt)2}(CO)2] and the alkenyl-bridged [Mo2Cp2{µ-η1,κ1:η2-OP(OEt)2CHdC(p-C6H4Me)}{µ-
P(OEt)2}(CO)2] (structure confirmed through an X-ray diffraction study). This requires either
P-O reductive elimination between phosphonate and phosphido ligands or insertion of the
incoming alkyne into the Mo-P (phosphonate) bond, all these uncommon processes occurring
at room temperature. The solution structure of the new compounds is analyzed on the basis
of their IR and NMR data and X-ray diffraction studies, and the reaction pathways prevalent
for the title compound are discussed on the basis of the data available.
In tr od u ction
several intramolecular oxidative additions such as those
from the C-H (cyclopentadienyl) or backbone P-C and
P-O bonds in the bridging phosphorus ligands. During
these studies we found that the thermal cleavage of a
backbone P-O bond in the molybdenum complex [Mo2-
Cp2{µ-(EtO)2POP(OEt)2}(CO)4] gave the unsaturated
compound [Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)2] (1) in
high yield.3d There were two points of interest in the
chemical behavior of 1. First, this compound was found
to carbonylate readily to give either [Mo2Cp2{µ-OP-
(OEt)2}{µ-P(OEt)2}(CO)4] or the starting complex [Mo2-
Cp2{µ-(EtO)2POP(OEt)2}(CO)4], depending on the reac-
tion conditions (Scheme 1), thus providing the first
example of reversibility of the P-O cleavage in this type
of bridging diphosphite ligand. Second, compound 1
combines the presence of a double MdM bond with a
bridging alkoxyphosphido group, itself a poorly studied
ligand. We therefore decided to explore the reactivity
of compound 1 in some more detail. By taking into
account the significant differences in the bridging
ligands, we could anticipate a chemical behavior quite
different from that shown by the isoelectronic di-
phenylphosphido complex [Mo2Cp2(µ-CH2PPh2)(µ-PPh2)-
(CO)2].3b,4 In this paper we report some reactions of
The reactivity of complexes having multiple metal-
metal bonds has been a lively research area during the
last years,1 and much effort has been dedicated to the
understanding of the many factors governing the chemi-
cal behavior of the dimetal center in these species. Some
of the most important factors are the electronic and
steric properties of the coordinated ligands, their influ-
ence being more critical when these ligands act as
bridges between the metals involved in the multiple
M-M bond. The unsaturated cyclopentadienyl carbon-
yls of general formula [M2Cp2(CO)x] (M ) transition
metal, Cp ) η5-C5H5, x ) 2-5) form an important class
within the organometallic complexes having multiple
intermetallic bonds, because of both their electronic
structure and wide reactivity, which makes them useful
synthetic reagents.2 We have previously studied the
decarbonylation reactions of the complexes [M2Cp2(CO)4-
(µ-L2)] [M ) Mo or W; L2 ) Ph2PCH2PPh2, Me2PCH2-
PMe2, (EtO)2POP(OEt)2]3 as a synthetic approach to
diphosphine-stabilized unsaturated cyclopentadienyl
compounds. From these studies we have concluded that
the formation of multiple M-M bonds competes with
* To whom correspondence should be addressed. E-mail: mara@
sauron.quimica.uniovi.es.
(1) Cotton, F. A.; Walton, R. A. Multiple Bonds Between Metal Atoms,
2nd ed.; Oxford University Press: Oxford, U.K., 1993.
(2) (a) Winter, M. J . Adv. Organomet. Chem. 1989, 29, 101. (b)
Curtis, M. D. Polyhedron 1987, 6, 759.
(3) (a) Alvarez, M. A.; Garc´ıa, M. E.; Riera, V.; Ruiz, M. A.; Falvello,
L.; Bois, C. Organometallics 1997, 16, 354. (b) Garc´ıa, G.; Garc´ıa, M.
E.; Melo´n, S.; Riera, V.; Ruiz, M. A.; Villafan˜e, F. Organometallics 1997,
16, 626. (c) Alvarez, C.; Garcia, M. E.; Riera, V.; Ruiz, M. A.
Organometallics 1997, 16, 1378. (d) Alvarez, C.; Alvarez, M. A.; Garcia,
M. E.; Riera, V.; Ruiz, M. A.; Bois, C. Organometallics 1997, 16, 2581.
10.1021/om0301886 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 05/28/2003

2742 Organometallics, Vol. 22, No. 13, 2003
Alvarez et al.
clusters,6,7 while CO ligands bonded to molybdenum
atoms give rise to resonances at higher chemical shifts
and exhibit informative PC couplings [243.8 ppm (d, J CP
) 12 Hz) and 238.1 ppm (dd, J CP ) 24, 17 Hz)]. From
the multiplicity of the latter we conclude that the 238.1
ppm resonance corresponds to the carbonyl bonded to
the molybdenum atom bearing both phosphorus atoms,
its chemical shift and PC couplings being similar to the
corresponding values for compound 1 [239.3 ppm (dd,
J CP ) 24, 17 Hz)].3d By contrast, the resonance at 243.8
ppm has shifted 12.3 ppm downfield with respect to the
corresponding one in compound 1 (231.5 ppm).3d This
is taken as an indication of a coordination change of a
CO ligand from terminal to bridging (or semibridging)
between the iron and molybdenum nuclei bonded to a
single phosphorus atom. The IR spectrum of 2 (Table
1) shows five signals in the CO stretching region. The
first three bands (2026, 1964, and 1948 cm-1) have the
typical pattern of compounds having [Fe(CO)3] frag-
ments.6-8 The other two bands correspond essentially
to the carbonyls bonded to the molybdenum atoms (1880
and 1804 cm-1). By comparing these two frequencies
with those in the starting compound 1 (1882 and 1839
cm-1) we can appreciate a substantial red-shift in the
low-frequency band. This could be indicative of bridging
or semibridging coordination of one of the CO ligands
in compound 2, in agreement with the 13C{1H} NMR
data. This coordinative behavior of CO is not unusual,
and it has been observed in other 46 e- clusters such
as [FeM2Cp2{µ3-C2(C6H4Me-4)2}(CO)6]7 and [M2RhCp3-
(µ-CO)2(CO)3]9 (M ) Mo, W). In these molecules, the
bridging CO ligands seem to contribute to a more
equitative distribution of the electronic deficiency (2 e-)
of the trimetal cores. We must remark, however, that
even when compound 2 is formally unsaturated, it does
not react with simple Lewis bases such as CO or PPh3
under ordinary conditions. This thermodynamic prefer-
ence for unsaturated (46 e-) rather than saturated (48
e-) structures was also observed for the above-men-
tioned cluster [FeMo2Cp2{µ3-C2(C6H4Me-4)2}(CO)6]7 and
might be both steric and electronic in origin.
Syn th esis a n d Str u ctu r e of [Mo2Cp 2{µ-(EtO)2P O-
Sn Cl2}{µ-P (OEt)2}(CO)2(µ-Sn Cl2)] (3). When a solu-
tion of 1 is transferred over 3 equiv of SnCl2, a color
change is progressively observed and compound [Mo2-
Cp2{µ-(EtO)2POSnCl2}{µ-P(OEt)2}(CO)2(µ-SnCl2)] (3)
(Chart 1) is obtained as the major product after 1 h.
The formation of 3 requires the incorporation of 2 equiv
of SnCl2 to the molecule, one being inserted at the
Mo-O bond and the other being added to the double
ModMo bond. Although some intermediate species are
likely to be involved in the slow formation of 3, reaction
of compound 1 with just 1 equiv of SnCl2 failed to detect
any of them, but led instead to 3 and unspecific
decomposition of the starting compound. Thus, there
seems to be a strong preference for the addition of two
rather than single tin atoms to the unsaturated 1.
The structure of 3 has been solved through an X-ray
study, and it is depicted in Figure 1, while Table 2 lists
Sch em e 1. Ca r bon yla tion /Deca r bon yla tion
Rea ction s of Com p ou n d 13d
Ch a r t 1
compound 1 aimed at the formation of new Mo-C or
Mo-metal bonds. As it will be shown, the reactivity of
1 is quite unusual, because it involves not only the
expected additions to the ModMo bond but also some
easy insertion reactions into Mo-P or Mo-O bonds as
well as reductive elimination of P-O bonds, all occur-
ring under very mild conditions.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of [F eMo2Cp 2-
{µ-OP (OEt)2}{µ-P (OEt)2}(CO)5] (2). Compound 1 is
a highly reactive molecule due to its unsaturated nature,
this being both electronic (it is a 32 e- complex) and
coordinative (CpML3 environment around Mo) in origin.
In the first place we studied the reactions of 1 with some
16 e- metal fragments in order to obtain heterometallic
clusters (the metallic cyclopropanation reaction, by
following the isolobal relationship).5 Indeed, compound
1 reacts slowly with [Fe2(CO)9] in toluene to give the
46 e- cluster [FeMo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)5]
(2) (Chart 1), along with small amounts of the trinuclear
cluster [Fe3(CO)12]. The 31P{1H} NMR spectrum of 2
exhibits two signals (Table 1). That at high chemical
shift (356.0 ppm) is assigned to the phosphorus atom of
the alkoxyphosphido ligand, while the other one (129.0
ppm) is assigned to the phosphorus atom of the phos-
phonate ligand. The 13C{1H} NMR spectrum of 2 shows
five signals of equal intensity in the carbonyl region,
and it does not experience appreciable changes with
temperature, which indicates that the molecule behaves
as rigid on the NMR time scale. Three of these signals
(δ ) 214.9, 213.2, and 202.7 ppm) appear within the
chemical shift region characteristic of CO ligands coor-
dinated to iron atoms in Fe-group 6 mixed metal
(6) J effery, J . C.; Ruiz, M. A.; Stone, F. G. A. J . Organomet. Chem.
1988, 355, 231.
(7) Garc´ıa, M. E.; J effery, J . C.; Sherwood, P.; Stone, F. G. A. J .
Chem. Soc., Dalton Trans. 1987, 1209.
(8) Borg, G. J . Organomet. Chem. 1975, 94, 181.
(9) Winter, G.; Schulz, B.; Trunschke, A.; Miessner, H.; Bo¨ttcher,
H. C.; Walther, B. Inorg. Chim. Acta 1991, 184, 27.
(4) Riera, V.; Ruiz, M. A.; Villafan˜e, F. Organometallics 1993, 12,
124.
(5) (a) Hoffmann, R. Angew. Chem., Int. Ed. Engl. 1982, 21, 711.
(b) Stone, F. G. A. Angew. Chem., Int. Ed. Engl. 1984, 23, 89.

Unusual Reactivity of a Dimolybdenum Complex
Organometallics, Vol. 22, No. 13, 2003 2743
Ta ble 1. IR a n d NMR Da ta for Com p ou n d s 1-5
compound
νst(CO)/cm-1
δ P/ppm
J
PP/Hz
[Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)2] (1)a
[FeMo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}(CO)5] (2)
1882(m), 1839(vs)b
2026(vs), 1964(s), 1948(s)
1880(s), 1804(m)b
347.0, 139.9c
356.0, 129.0d
9
3
[Mo2Cp2{µ-(EtO)2POSnCl2}{µ-P(OEt)2}(µ-SnCl2)(CO)2] (3)
1978(vs), 1933(w)e
357.5f,g
22
22
139.9f,h
[Mo2Cp2{µ-HCC(p-tol)}{µ-(EtO)2POP(OEt)2}(CO)2] (4)
[Mo2Cp2{µ-OP(OEt)2CHdC(p-tol)}{µ-P(OEt)2}(CO)2] (5)
1929(s), 1857(vs)I
1899(w), 1886(vs)i
175.7f
356.4, 68.9c
4
a
b
d
Data from ref 3d. Recorded in toluene. c Recorded in C6D6. Recorded in toluene-d8. e Recorded in CH2Cl2. f Recorded in CD2Cl2.
g
h
i
119Sn
117Sn
119Sn
117Sn
J P
) 399, 108, J P
) 382, 103. J P
) 531, 455, J P
) 498, 437. Recorded in petroleum ether.
disposition with respect to the µ-(EtO)2POSnCl2 ligand.
We note that the CO ligands in compound 3 adopt a cis
relative geometry, while they are mutually trans in the
starting compound, so an isomerization must occur at
some step of the reaction between 3 and SnCl2. This cis
arrangement of CO ligands has been observed before
for the isoelectronic compounds [W2Cp2(µ-X)(µ-CO)-
(CO)2(µ-Ph2PCH2PPh2)](PF6) (X ) F, Cl),10 and it is
considered to be the result of an important thermody-
namic preference for this geometry. The Mo-Mo dis-
tance in 3 [3.412(6) Å] is consistent with the presence
of a formally single Mo-Mo bond, it being somewhat
longer than those found at the related neutral com-
pounds [Mo2Cp2(CO)4(µ-Ph2PCH2PPh2)] [3.327(1) Å]11
and [W2Cp2(CO)4{µ-(EtO)2POP(OEt)2}] [3.2731(6) Å].3d
The alkoxyphosphido ligand exhibits a symmetric co-
ordination with respect to the molybdenum atoms
[d(Mo-P) 2.40(1) and 2.41(1) Å]. However, the µ-SnCl2
group displays an asymmetric coordination [d(Mo-Sn)
2.683(5) and 2.731(5) Å], surely due to the intrinsic
asymmetry of the phosphonate-stannyl bridging ligand
(EtO)2POSnCl2. A similar effect has been previously
observed at the Mn2Zn cluster [Mn2(CO)6{µ-Zn(bipy)}-
{µ-OP(OEt)2}{µ-P(OEt)2}(CO)6],12 which contains three
closely related bridging ligands. Although a few com-
plexes displaying SnX2 groups bonded to two metal
fragments have been structurally characterized, such
as the neutral [{MoCp(CO)3}2(µ-SnX2)]13a,b or the anions
[{Mo(CO)5}2(µ-SnX2)]2- (X ) Cl, Br, I),13c they all show
open-chain trimetal cores. Thus, compound 3 seems to
be the first one having a SnCl2 group incorporated as
part of a metal triangle. The resulting interaction seems
to be particularly strong, as deduced from the values of
the Mo-Sn distances in 3 (ca. 2.70 Å on average), which
are considerably shorter than those found in open Mo2-
Sn chains (i.e., 2.9831(10) and 3.0186(11) Å for [{MoCp-
(CO)3}2(µ-SnI2)]).13a Other internuclear distances in
compound 3 have normal values.
F igu r e 1. CAMERON diagram of the molecular structure
of compound 3. Ellipsoids represent 30% probability.
Ta ble 2. Selected Bon d Dista n ces a n d An gles for 3
d (Å)
θ (deg)
Mo(1)-Mo(2)
Mo(1)-P(1)
Mo(1)-Sn(1)
Mo(1)-P(2)
Mo(2)-Sn(1)
Mo(2)-P(1)
Mo(2)-Sn(2)
Sn(2)-O(3)
Mo(1)-C(1)
Mo(2)-C(2)
P(1)-O(4)
3.412(6)
2.41(1)
2.683(5)
2.47(2)
2.731(5)
2.40(1)
2.680(5)
2.11(3)
1.92(7)
1.91(5)
1.61(3)
1.62(3)
1.52(3)
1.59(4)
2.38(1)
2.37(1)
2.35(2)
2.36(1)
Sn(1)-Mo(1)-P(1)
Sn(1)-Mo(1)-P(2)
Sn(1)-Mo(1)-C(1)
Sn(1)-Mo(2)-Sn(2)
Sn(1)-Mo(2)-P(1)
Sn(1)-Mo(2)-C(2)
Sn(1)-Mo(2)-P(1)
P(1)-Mo(1)-P(2)
Mo(1)-Sn(1)-Mo(2)
P(1)-Mo(2)-Sn(2)
Mo(1)-Mo(2)-Sn(2)
Mo(2)-Sn(2)-O(3)
Sn(2)-O(3)-P(2)
Mo(1)-P(2)-O(3)
Cl(1)-Sn(1)-Cl(2)
Cl(3)-Sn(2)-Cl(4)
75.9(3)
82.7(4)
130.0(18)
82.2(2)
75.1(3)
133.7(14)
75.1(3)
135.8(5)
78.1(2)
126.1(4)
83.3(1)
115.1(9)
123.1(19)
123.9(15)
92.9(5)
Spectroscopic data in solution for 3 are consistent with
the structure found in the crystal. In the first place, the
relative intensities of the CO stretching bands (strong
and weak, in order of decreasing frequency) are indica-
tive of their mutual, almost parallel, cis arrangement.14
Second, the relative arrangement of the three bridging
P(1)-O(5)
P(2)-O(3)
P(2)-O(6)
Sn(1)-Cl(1)
Sn(1)-Cl(2)
Sn(2)-Cl(3)
Sn(2)-Cl(4)
95.6(6)
(10) (a) Alvarez, M. A.; Garc´ıa, G.; Garc´ıa, M. E.; Riera, V.; Ruiz,
M. A.; Lanfranchi, M.; Tiripicchio, A. Organometallics 1999, 18, 4509.
(b) 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.
(11) Azam, K. A.; Deeming, A. J .; Felix, M. S. B.; Bates, P. A.;
Hurthouse, M. B. Polyhedron 1988, 7, 1793.
(12) Liu, X. Y.; Riera, V.; Ruiz, M. A.; Tiripicchio, A.; Tiripicchio-
Camellini, M. Organometallics 1996, 15, 974.
(13) (a) Veith, M.; Mathur, S.; Mathur, C.; Huch, V. Organometallics
1998, 17, 1044. (b) Flo¨rke, U.; Haupt, H. J . Z. Kristallogr. 1992, 202,
147. (c) Schiemenz, B.; Antelmann, B.; Huttner, G.; Zsolnai, L. Z.
Anorg. Allg. Chem. 1994, 620, 1760.
the most relevant bond distances and angles. The
coordination geometry around each metal center can be
considered of the “four-legged piano stool” type, if we
exclude the metal-metal bond, where the µ-SnCl2
ligand has a trans disposition with respect to the CO
ligands, whereas the µ-P(OEt)2 ligand exhibits a trans

2744 Organometallics, Vol. 22, No. 13, 2003
Alvarez et al.
Ch a r t 2
ligands seems to be retained in solution, as deduced
from the P-Sn couplings. Thus, the phosphido group
displays quite different couplings to each of the tin
atoms (ca. 400 and 100 Hz), in agreement with their
quite different bond angles [P(1)-Mo(2)-Sn(1) ) 75.1-
(3)° and P(1)-Mo(2)-Sn(2) ) 126.1(4)°, or cis and trans,
respectively]. Analysis of P-Sn couplings in the phos-
phonate-stannyl resonance cannot be done easily, as
they involve both P-Mo-Sn and P-O-Sn bond path-
ways, even if ignoring three-bond pathway contribu-
tions.
Rea ction of Com p ou n d 1 w ith HCC(p-C6H4Me-
4). We have also used the isolobal5 relationship between
multiple M-M and C-C bonds in order to examine the
potential of compound 1 to form new Mo-C bonds. First,
the reaction with CH2N2 was examined, but that was
found to lead to complex mixtures of compounds that
could not be characterized. We then examined the
reactions with some simple olefins and alkynes, the 2+2
organic addition being its model. Although no reaction
was observed at room temperature between olefins or
internal alkynes and 1, reaction of the latter with a
terminal alkyne such as HCC(p-tol) [p-tol ) C6H4Me-
4] proceeds smoothly at room temperature to give a
mixture of isomers [Mo2Cp2{µ-η2:η2-HCC(p-tol)}{µ-
(EtO)2POP(OEt)2}(CO)2] (4) and [Mo2Cp2{µ-η1,κ1:η2-
OP(OEt)2CHdC(p-tol)}{µ-P(OEt)2}(CO)2] (5) (Chart 2),
in a 1:4 ratio. Surprisingly, this ratio was rather
insensitive to experimental conditions such as temper-
ature or excess of alkyne used. Reactions with other
terminal alkynes HCCR having nonaromatic R groups
were tried, but no reaction was observed at room
temperature in these cases.
Compound 4 is the result of a P-O bond reductive
elimination between phosphido and phosphonate ligands
at the starting substrate and coordination of the incom-
ing alkyne as a 4 e- ligand to the resulting tetraethyl-
pyrophosphite-bridged fragment. The presence of two
carbonyl ligands in the molecule is denoted by the
presence of two absorptions in the CO stretching region
of the IR spectrum (1929 and 1857 cm-1, Table 1). These
bands present almost the same intensity, this being
indicative of CO ligands arranged at approximately 90°
angles.14 The 31P{1H} NMR of 4 exhibits a single
resonance at 175.7 ppm (Table 1), with a chemical shift
compatible with the presence of a tetraethylpyrophos-
phite group bridging a dimolybdenum cyclopentadienyl
center.3d,15 The presence of the new ligand allows the
metal centers to be symmetry-related, which implies the
chemical equivalence of both Cp or carbonyl ligands.
F igu r e 2. CAMERON diagram of the molecular structure
of compound 5. Ellipsoids represent 30% probability.
This is clearly apparent in the 1H or 13C{1H} NMR
spectra, which exhibit single resonances for these
ligands (an AXX′ multiplet is observed for the carbonyl
groups). As for the alkyne ligand, it gives rise to a triplet
1
resonance in the H NMR spectrum (δ ) 5.32 ppm, J )
5 Hz), while the metal-bonded carbon atoms give
resonances at 90.8 (singlet, internal acetylenic carbon)
and 86.7 ppm (triplet, J PC ) 16 Hz, terminal acetylenic
carbon), in the region observed for similar compounds
of the type [Mo2Cp2(µ-η2:η2-RCCR′)(CO)4].2b Both the
observed PH and PC couplings are structurally infor-
mative. In the first place, because these couplings are
equal to both phosphorus atoms, a coordination mode
of the alkyne ligand perpendicular to the intermetallic
bond must be proposed for 4. Second, it is known that
PC couplings in cyclopentadienyl complexes of the type
[MCpX(CO)2(PR3)] (M ) Mo, W; X ) halogen, alkyl,
2
2
hydride, etc.) follow the order | J cis | > | J trans|,16 where
cis and trans refer to angles between ligands around
80° and 120°, respectively. On the basis of this informa-
tion, we then propose that the internal acetylenic carbon
is coordinated trans with respect the phosphorus atoms,
which leaves the terminal acetylenic carbon cis to them,
thus explaining its higher PC coupling. This conforma-
tion would be also expected on the basis of steric
considerations, if the repulsive interaction between the
alkyne and bridging diphosphite is to be minimized.
The structure of 5 has been solved through an X-ray
study, and it is depicted in Figure 2, while Table 3 lists
the most relevant bond distances and angles. The
molecule displays two cyclopentadienyl carbonyl mo-
lybdenum moieties arranged so that the carbonyl ligands
(14) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:
London, U.K., 1975.
(15) Riera, V.; Ruiz, M. A.; Villafan˜e, F. Organometallics 1992, 11,
2854.
(16) (a) Wrackmeyer, B.; Alt, H. G.; Maisel, H. E. J . Organomet.
Chem. 1990, 399, 125. (b) Todd, L. J .; Wilkinson, J . R.; Hickley, J . P.;
Beach, D. L.; Barnet, K. W. J . Organomet. Chem. 1978, 154, 151.

Unusual Reactivity of a Dimolybdenum Complex
Organometallics, Vol. 22, No. 13, 2003 2745
Ta ble 3. Selected Bon d Dista n ces a n d An gles for 5
C-P(O)(OR)2 bonds, such as 1.785(3) Å for [Fe2(CO)6-
(µ-PPh2){µ-C(Me)dC(H)P(O)(OMe)2}].19
d (Å)
θ (deg)
Spectroscopic data for 5 indicate that this compound
retains in solution its solid state structure. The IR
spectrum of 5 has two absorptions in the carbonyl region
[1899 (w), 1886 (vs) cm-1, Table 1] with relative intensi-
ties characteristic of M2(CO)2 oscillators with a transoid
geometry.14 The 31P{1H} NMR spectrum of 5 exhibits
two resonances at 356.4 and 68.9 ppm (Table 1). The
first one, due to the diethoxyphosphido bridge, appears
at a chemical shift almost identical to that of compound
1 (356.0 ppm).3d On the other hand, the signal at 68.9
ppm is out of the range found for our previous dimo-
lybdenum phosphonate compounds (125-200 ppm), in
agreement with its coordination to the C atom of the
alkyne. Indeed, the chemical shift of this resonance is
close to the values for the phosphonium salts of phos-
phites [RP(OR)3]+ (ca. 50 ppm).20 The 1H NMR spectrum
of 5 shows a doublet at 2.00 ppm [J HP ) 31 Hz] due to
the terminal acetylenic proton, which was not detected
by the X-ray study. The high PH coupling for this H
atom at 5 (31 Hz) is considerably higher than that
observed at 4 (5 Hz), in agreement with the smaller
number of bonds between the proton and the phospho-
rus atom. The assignment of that high coupling to the
P (phosphonate) nucleus was confirmed through a
Mo(1)-Mo(2)
Mo(1)-P(1)
Mo(1)-C(3)
Mo(1)-C(4)
Mo(2)-C(3)
Mo(2)-P(1)
P(2)-C(4)
C(3)-C(4)
Mo(1)-C(1)
Mo(2)-C(2)
Mo(2)-O(3)
C(3)-C(30)
P(2)-O(3)
P(2)-O(6)
P(2)-O(7)
P(1)-O(4)
P(1)-O(5)
2.991(1)
2.366(3)
2.154(9)
2.214(9)
2.245(9)
2.350(3)
1.702(9)
1.46(1)
1.90(1)
1.95(1)
2.230(6)
1.48(1)
1.491(7)
1.570(7)
1.566(7)
1.628(6)
1.617(7)
Mo(2)-C(3)-Mo(1)
C(3)-Mo(1)-P(1)
C(3)-Mo(2)-P(1)
C(3)-Mo(1)-C(1)
C(3)-Mo(2)-C(2)
C(4)-Mo(1)-P(1)
O(3)-Mo(2)-P(1)
O(3)-Mo(2)-C(3)
C(1)-Mo(1)-Mo(2)
C(2)-Mo(2)-Mo(1)
Mo(1)-P(1)-Mo(2)
Mo(2)-O(3)-P(2)
O(3)-P(2)-C(4)
85.6(3)
78.8(2)
77.4(2)
78.8(4)
125.5(4)
115.3(2)
134.9(2)
79.0(3)
115.3(3)
84.3(4)
78.72(8)
117.6(3)
108.4(4)
118.7(8)
115.1(6)
68.3(5)
C(30)-C(3)-C(4)
C(3)-C(4)-P(2)
C(3)-C(4)-Mo(1)
P(2)-C(4)-Mo(1)
117.9(5)
are in a transoid disposition. Both metal atoms are
bridged by two ligands. The first one is the diethoxy-
phosphido group already present in the starting com-
pound. The other one is a phosphonoalkenyl ligand
formed by insertion of the terminal acetylenic carbon
into the P-Mo bond of the former phosphonate ligand,
which retains its coordination through the oxygen atom,
thus formally providing a total of 5 e- to the dimetal
center. The alkenyl end of the ligand is σ bonded to the
molybdenum atom O-bonded [Mo(2)], and it displays π
coordination to the other metal atom [Mo(1)]. In a formal
sense, compound 5 is a 34 e- complex, so that a single
Mo-Mo bond must be formulated for this molecule. This
is in agreement with the intermetallic separation, which
displays a quite short value, 2.991(1) Å, comparable to
those in related singly bonded binuclear cations of the
group 6 metals, such as the halide complexes [W2Cp2-
(µ-X)(µ-CO)(CO)2(µ-Ph2PCH2PPh2)]+ (X ) F, Cl) [2.945-
(1) and 3.040(3) Å]10 or the alkenyl [W2Cp2{µ-C(OMe)d
CH2}(µ-CH2)(CO)2(µ-Ph2PCH2PPh2)]+ [2.965(1) Å].17 The
interatomic distances involving the alkenyl moiety in 5
[relatively short Mo-C lengths, around 2.20 Å, and a
relatively large C-C length, 1.46(1) Å] are indicative
of strongly σ and π binding of the ligand to the
molybdenum atoms.17 Although there are only a few
structural studies on complexes bearing related zwit-
terionic PX3-substituted alkenyl bridges (X ) R or OR)18
to be compared with, and none of them involve Mo or
W complexes, this seems to be a general feature for this
type of alkenyl ligand. In the case of compound 5, the
considerable strength of the π interaction is deduced
from the low value of the Mo(1)-C(4) separation, 2.214-
(9) Å, in the lower part of the range (2.20-2.30 Å) found
for µ-η1:η2-alkenyl dimolybdenum complexes.17 This can
be understood by considering the increased electronic
charge in the carbon atoms, resulting from the donor-
acceptor interaction between the P and C atoms of the
former phosphonate and alkyne groups. This is also
consistent with the short P(2)-C(4) length in 5 [1.702-
(9) Å], considerably shorter than those found for normal
1
selectively decoupled H{31P} NMR experiment.
Rea ction P a th w a ys P r eva len t for Com p ou n d 1.
Compound 1 has a coordinative and electronic unsat-
uration and expectedly behaves as a good ligand accep-
tor, as confirmed through the experiments discussed
above. All reagents examined in this work are them-
selves (or act as source of) at least 2 e- donors that
might first coordinate to the double metal-metal bond
to reduce those coordinative and electronic unsatura-
tions (intermediates A and A′, Schemes 2 and 3). Then,
these intermediates would evolve differently in each
case. The synthesis of 2 just requires ejection of a CO
molecule after the addition of the Fe(CO)4 fragment,
thus giving a 46 e- cluster. As stated before, this
thermodynamic preference for an unsaturated rather
than saturated 48 e- trimetal cluster has been observed
previously. The formation of compound 3 can be under-
stood by starting at the same intermediate A, followed
by reductive elimination of a Sn-O bond to give a
second intermediate B. This is not an expected isomer-
ization, because it forms an unsaturated intermediate,
but there is some precedent for such a process. In fact,
we have found previously that the anion [Mn2{µ-OP-
(OEt)2}{µ-P(OEt)2}(CO)6]2- reacts with Cl2SnPh2 to give
first the expected derivative having a µ-SnPh2 bridge,
which then evolves spontaneously to the complex [Mn2{µ-
(EtO)2POSnPh2}{µ-P(OEt)2}(CO)7], characterized through
an X-ray study.21 In both cases it is reasonable to
assume that the driving force for these Sn-O reductive
eliminations would be the fact that a strong Sn-O bond
is formed. The formation of compound 3 is then com-
pleted by addition of a second molecule of SnCl2 to the
double ModMo bond in intermediate B. As stated
(17) Alvarez, M. A.; Garc´ıa, G.; Garc´ıa, M. E.; Riera, V.; Ruiz, M.
A.; Robert, F. Organometallics 2002, 21, 1177.
(19) Doherty, S.; Elsegood, M. R. J .; Ward, M. F.; Waugh, M.
Organometallics 1997, 16, 4251.
(20) Tebby, J . C. In Phosphorous-31 NMR spectroscopy in Stereo-
chemical Analysis; Verkade, J . G., Guin, L. D., Eds.; VCH: Deerfield,
1987, Chapter 1.
(21) Liu, X. Y.; Riera, V.; Ruiz, M. A.; Tiripicchio, A. Unpublished
results.
(18) (a) Takats, J .; Washington, J .; Santarsiero, D. B. Organome-
tallics 1994, 13, 1078. (b) Doherty, S.; Elsegood, M. R. J .; Clegg, W.;
Mampe, D.; Rees, N. H. Organometallics 1996, 15, 5002, (c) Tanase,
T.; Begum, R. A. Organometallics 2001, 20, 106. (d) Doel, G. R.; Feasey,
N. D.; Knox, S. A. R.; Orpen, A. G.; Webster, J . J . Chem. Soc., Chem.
Commun. 1986, 542.

2746 Organometallics, Vol. 22, No. 13, 2003
Alvarez et al.
Sch em e 2. P r op osed Rea ction P a th w a ys in th e
F or m a tion of Com p ou n d s 2 a n d 3
F igu r e 3. Reactivity patterns exhibited by compound 1.
to the phosphonate P atom can lead to the formation of
5 by reductive elimination of a P-C bond, by first giving
a new intermediate B′. There are some precedents for
the insertion of alkynes into M-P bonds of phosphine
complexes. This is the case of the reactions leading to
the alkenyl-bridged cation [Pt2Pd(µ-dpmp){µ-dpmp-CHd
C(CO2Et)}(XylNC)2]2+ (dpmp ) Ph2PCH2 P(Ph)CH2-
PPh2)18c or the mononuclear complexes [PdCl2(µ-Ph2-
PCH2P(Ph)2CHdC(Ph)]23 and [Mo(η3-CHCHPPh2CH2-
CH2PPh2-C,C′,P)(NCMe)2(Ph2PCH2CH2PPh2)]2+ 24
To
.
our knowledge, the formation of 5 is the first example
of akyne insertion into a metal-P (phosphonate) bond.
The η1-vinyl intermediate B′ thus formed would finally
give the electron-precise 5 after coordination of its Cd
C bond, a rearrangement expected to be facile.
The formation of compound 4 can also be understood
starting from A′ (whichever of the possible isomers)
after reductive elimination of a P-O bond to generate
an unsaturated diphosphite-bridged intermediate C′,
which then would experience alkyne rearrangement
from the µ-η1:η1 to the µ-η2:η2 mode so as to achieve a
saturated structure. The above P-O bond reductive
elimination has been observed previously in one in-
stance, this requiring some thermal activation (ca. 90-
100°). The novel feature of the P-O bond formation here
disclosed is that it occurs readily at room temperature.
From the above considerations it can be concluded
that the key step in the reactions of 1 is the evolution
of the 34 e- intermediates (A and A′) formed after the
initial addition process. Starting at this point, either
P-C, O-Sn, or P-O reductive eliminations induce the
formation of a wide range of compounds. We notice that
the only precedent for a related P-O bond reductive
elimination was postulated to occur at a 34 e- interme-
diate, the tricarbonyl [Mo2Cp2{µ-OP(OEt)2}{µ-P(OEt)2}-
(µ-CO)(CO)2]. Why is it that these saturated interme-
diates experience rather unexpected reductive elimination
processes to give unsaturated compounds is not clear
at present, but further studies will hopefully bring new
data so as to understand this unusual behavior.
Sch em e 3. P r op osed 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
Con clu sion
Compound 1 experiences under mild conditions a wide
variety of processes (Figure 3). As expected for a
substrate having a double metal-metal bond, addition
of donors to the dimetal center occurs readily, thus
reducing the metal-metal bond order to one (Fe(CO)4)
or even to zero (CO), but this is generally followed by
other reactions. Further processes include the insertion
of the incoming molecule into the Mo-O bond (SnCl2)
or Mo-P [HCC(p-tol)] bond of the phosphonate ligand,
giving unusual bridging groups. A final process involves
before, this double addition of SnCl2 on compound 1 is
strongly favored, irrespective of the available amount
of SnCl2 in the reaction mixture.
The formation of compounds 4 and 5 is also likely to
be initiated by addition of 1 equiv of HCC(p-tol) to the
double ModMo bond in 1 to obtain the intermediate A′,
proposed to have an alkyne molecule coordinated in the
µ-η1:η1-fashion (Scheme 3). This coordination mode has
been frequently found upon insertion of alkynes into
metal-metal bound A-frame dimers and related spe-
cies.22 Intermediate A′ could display two different
structures (isomers) depending on the position of the
organic residue, but only that with the CH group close
(22) Puddephatt, R. J . Chem. Soc. Rev. 1983, 12, 99.
(23) Allen, A.; Lin, W. Organometallics 1999, 18, 2922.
(24) Ishino, H.; Kuwata, S.; Ishii, Y.; Hidai, M. Organometallics
2001, 20, 13.

Unusual Reactivity of a Dimolybdenum Complex
Organometallics, Vol. 22, No. 13, 2003 2747
Ta ble 4. Cr ysta l Da ta for Com p ou n d s 3 a n d 5
the diethoxyphosphido/phosphonate P-O reductive elimi-
nation [observed in the reaction with HCC(p-tol)] to give
a diphosphite-bridged derivative at room temperature.
In summary, the chemical behavior of compound 1 is
quite different from that of the isoelectronic [Mo2Cp2(µ-
CH2PPh2)(µ-PPh2)(CO)2], a complex unreactive toward
16 e- metal fragments, alkynes, or CO.3b,4 This differ-
ence can be attributed to the smaller size and higher
electron-withdrawing power of the phosphonate and
alkoxyphosphido ligands in 1, when compared to the
related phosphinomethyl and diphenylphosphido bridges,
respectively.
3
5
mol formula
mol wt
C
20H30Cl4Mo2O7P2Sn2
C
29H38Mo2O7P2
1015.47
752.44
cryst syst
orthorhombic
Pbca
orange
parallelepiped
Mo KR (λ )
0.71069 Å)
20.608(8)
18.696(9)
17.154(5)
triclinic
P1h
space group
cryst color
cryst shape
radiation (λ, Å)
orange
parallelepiped
Mo KR (λ )
0.71069 Å)
10.706(2)
10.886(2)
15.432(4)
70.57(2)
79.17(2)
69.55(1)
1584(11)
2
1.58
9.1
Nonius CAD4
293
ω/2θ
1-25
0.8 + 0.345 tan θ
5791
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
Exp er im en ta l Section
6609(8)
4
Gen er a l Com m en ts. All manipulations and reactions were
carried out using standard Schlenk techniques under an
atmosphere of dry, oxygen-free nitrogen. Solvents were puri-
fied according to standard literature procedures25 and distilled
under nitrogen prior to use. Petroleum ether refers to that
fraction distilling in the range 65-70 °C. Compound 1 was
prepared by literature methods.3d Other reagents were ob-
tained from the usual commercial suppliers and used without
further purification. Filtrations were carried out using diato-
maceous earth, and alumina for column chromatography was
deactivated by appropriate addition of water to the commercial
material (Aldrich, neutral, activity I). NMR spectra were
recorded at 400.13 (1H), 81.03 (31P{1H}), or 100.62 MHz (13C-
{1H}), at room temperature unless otherwise stated. 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 routinely recorded on solutions containing a small
amount of tris(acetylacetonate)chromium(III) as a relaxation
reagent.
calcd density, g cm-3 2.04
µ(Mo KR), cm-1
diffractometer
temperature, K
scan type
26.82
Philips-PW 1100
293
ω/2θ
1-25
0.8 + 0.345 tan θ
6429
θ limits, deg
scan width
total no. of data
collected
no. of unique total
data
5830
5561
no. of unique data
used
1038
2721
[(Fo)2>2.5σ(Fo)2]
0.057
[(Fo)2>3σ(Fo)2]
0.041
Ra
Rw
b
0.065
0.045
abs coeff corr
(min., max.)
no. of variables
∆Fmin (e/Å3)
0.94, 1.14
0.76, 1.21
199
-0.76
0.75
362
-0.39
0.63
∆Fmax (e/Å3)
a
b
2 1/2
R ) ∑|Fo - |Fc||/∑Fo. Rw ) [∑w(Fo - |Fc|)2/∑wFo
] .
X-ray diffraction study were grown by slow diffusion of
petroleum ether into a CH2Cl2 solution of 3 at room temper-
ature. Anal. Calcd for C20H30O7P2Cl4Mo2Sn2: C, 23.66; H, 2.98.
P r ep a r a tion of [F eMo2Cp 2{µ-OP (OEt)2}{µ-P (OEt)2}(µ-
CO)(CO)4] (2). A toluene solution (10 mL) of compound 1
(0.046 g, 0.07 mmol) was treated with [Fe2(CO)9] (0.030 g, 0.08
mmol) and the mixture stirred at room temperature for 20 h.
Solvent was then removed under vacuum and the residue
dissolved in a minimum of toluene and chromatographed on
a tap-water refrigerated alumina column (activity II, 15 × 2.5
cm) prepared in petroleum ether. Elution with toluene gave
two green fractions. The first fraction contained [Fe3(CO)12]
and was discarded. The second fraction gave, after removal of
solvent under vacuum, compound 2 as a green powder (0.040
g, 74%). Anal. Calcd for C23H30O10P2FeMo2: C, 35.59; H, 3.90.
1
Found: C, 23.59; H, 2.95. H NMR (200.13 MHz, CD2Cl2): δ
5.22 (s, 5H, Cp), 5.18 (d, J HP ) 1, 5H, Cp), 4.20-3.55 (m, 8H,
CH2), 1.37, 1.26, 1.24, 1.15 (4 × t, J HH ) 7, 4 × 3H, Me). 31P-
{1H} NMR (161.98 MHz, CD2Cl2): δ 357.5 (d, J PP ) 22, J P
119
Sn
117
119
) 399, 108, J P
) 521, 455, J P
) 382, 103, µ-P), 138.9 (d, J PP ) 22, J P
) 498, 437, µ-OPSn).
Sn
Sn
117
Sn
Rea ction of Com p ou n d 1 w ith HCC(p-tol). A toluene
solution (12 mL) of compound 1 (0.090 g, 0.14 mmol) was
treated with HCC(p-tol) (40 µL, 0.14 mmol), and the mixture
was stirred at room temperature for 24 h. Solvent was then
removed under vacuum, and the residue was dissolved in a
minimum of petroleum ether and chromatographed on a tap-
water refrigerated alumina column (activity II, 15 × 2.5 cm)
prepared in petroleum ether. Elution with CH2Cl2/petroleum
ether (1:4) gave two red fractions. Removal of the solvent under
vacuum from the first fraction gave 0.016 g (15%) of [Mo2Cp2-
{µ-η2:η2-HCC(p-tol)}{µ-(EtO)2POP(OEt)2}(CO)2] (4) as an or-
ange solid. Anal. Calcd for C29H38O7P2Mo2: C, 46.29; H, 5.09.
Found: C, 46.12; H, 4.97. 1H NMR (CD2Cl2): δ 7.25, 7.04 (2 ×
d, J HH ) 8, 2 × 2H, C6H4Me), 5.32 (t, J HP ) 5, 1H, CH), 4.85
(s, 10H, Cp), 4.15-3.85 (m, 4H, CH2), 3.75-3.65 (m, 4H, CH2),
2.22 (s, 3H, C6H4Me), 1.16, 0.96 (2 × t, J HH ) 7, 2 × 6H, Me).
31P{1H} NMR (CD2Cl2): δ 175.7 (s, µ-POP). 13C{1H} NMR
(75.47 MHz, CD2Cl2): δ 234.6 (false t, (AXX′), J AX + J AX′ ) 19,
CO), 149.9, 132.9, 130.4, 128.5 (4 × s, C6H4Me), 90.8 (s, HCCR),
88.2 (s, Cp), 86.7 (t, J CP ) 16, HCCR), 61.6 (s, CH2), 59.8 (s,
CH2), 21.0 (s, C6H4Me), 16.5, 16.4 (s, OCH2Me). Removal of
the solvent under vacuum from the second fraction gave
1
Found: C, 35.46; H, 3.79. H NMR (300.13 MHz, toluene-d8):
δ 5.12 (d, J HP ) 1, 5H, Cp), 4.99 (s, 5H, Cp), 4.24 (m, 1H, CH2),
4.07-3.87 (m, 2H, CH2), 3.87-3.50 (m, 4H, CH2), 3.42 (m, 1H,
CH2), 1.32, 1.20, 1.19, 1.09 (4 × t, J HH ) 7, 4 × 3H, Me). 31P-
{1H} NMR (121.5 MHz, toluene-d8): δ 356.0 (d, J PP ) 3, µ-P),
129.0 (d, J PP ) 3, µ-OP). 13C{1H} NMR (CD2Cl2): δ 243.8 (d,
J CP ) 12, µ-CO), 238.1 (dd, J CP ) 24, 17, MoCO), 214.9 (dd,
J CP ) 10, 6, FeCO), 213.2 (d, J CP ) 8, FeCO), 202.7 (t, J CP
)
4, FeCO), 93.9, 87.0 (2 × s, Cp), 65.7 (d, J CP ) 11, CH2), 64.2
(d, J CP ) 9, CH2), 58.8 (d, J CP ) 10, CH2), 58.6 (s, CH2), 16.6
(d, J CP ) 7, Me), 16.3 (d, J CP ) 4, Me), 16.2 (d, J CP ) 7, Me),
15.7 (d, J CP ) 9, Me).
P r epar ation of [Mo2Cp2{µ-(EtO)2P OSn Cl2)}{µ-P (OEt)2}-
(CO)2(µ-Sn Cl2)] (3). A toluene solution (8 mL) of compound
1 (0.046 g, 0.07 mmol) was treated with SnCl2 (0.040 g, 0.21
mmol), and the mixture was stirred at room temperature for
1 h and then filtered through diatomaceous earth. Removal
of solvent under vacuum from the filtrate gave compound 3
as an orange powder (0.044 g, 75%). The crystals used in the
compound
[Mo2Cp2{µ-η1,κ1:η2-OP(OEt)2CHdC(p-tol)}{µ-P-
(OEt)2}(CO)2] (5) (0.072 g, 68%) as an orange solid. The crystals
used in the X-ray diffraction study were grown by slow
(25) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: Oxford, U.K., 1988.

2748 Organometallics, Vol. 22, No. 13, 2003
Alvarez et al.
diffusion of petroleum ether into a solution of 5 in CH2Cl2 at
-20 °C. Anal. Calcd for C29H38O7P2Mo2: C, 46.29; H, 5.09.
reflections, in the case of 3, hydrogen atoms were not found
on difference maps nor introduced in calculations, and only
Sn, Mo, Cl, and P atoms were anisotropically refined. For
compound 5, almost all hydrogen atoms could be found on
difference maps, others were geometrically located, and all of
them were given an overall isotropic thermal parameter, while
non-hydrogen atoms were anisotropically refined.
1
Found: C, 46.17; H, 4.93. H NMR (CD2Cl2): δ 7.40 (br, 2H,
C6H4Me), 7.00 (d, J HH ) 8, 2H, C6H4Me), 5.20 (s, 5H, Cp), 4.77
(d, J HP ) 1, 5H, Cp), 4.10-3.99 (m, 1H, CH2), 3.98-3.75 (m,
5H, CH2), 3.71-3.64 (m, 2H, CH2), 2.30 (s, 3H, C6H4Me), 2.00
(d, J HP ) 31, 1H, CH), 1.33, 1.31 (2 × t, J HH ) 7, 2 × 3H,
OCH2Me), 1.29 (t, J HH ) 7, 6H, OCH2Me). 31P{1H} NMR
(C6D6): δ 356.4 (d, J PP ) 4, µ-P), 68.9 (d, J PP ) 4, µ-OP).
X-r a y Str u ctu r e Deter m in a tion for Com p ou n d s 3 a n d
5. A selected crystal was set up on an automatic diffractometer
in each case. 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. Crystallographic data and other infor-
mation are summarized in Table 4. Corrections were made for
Lorentz and polarization effects. Empirical absorption correc-
tion (Difabs)26 were applied. A secondary extinction correction
was unnecessary.
Refinements were carried out in three blocks by minimizing
the function ∑w(|Fo| - |Fc|)2 where Fo and Fc are the observed
and calculated structure factors. Models reached convergence
with R and Rw having values defined and listed in Table 4.
The weighting scheme was unity. Figures 2 and 3 represent
CAMERON30 views of compounds 3 and 5 respectively.
Ack n ow led gm en t. We thank the Ministerio de
Ciencia y Tecnolog´ıa of Spain for financial support
(Projects BQU2000-0220 and BQU2000-0944) and the
Universidad de Oviedo for a grant to C.M.A.
Computations were performed by using the PC version of
CRYSTALS.27 Atomic form factors for neutral Sn, Mo, P, Cl,
O, C, and H were taken from ref 28. Real and imaginary parts
of anomalous dispersion were taken into account. The struc-
tures were solved by direct methods (SHELXS 86)29 and
successive Fourier maps. Because of the few number of
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates for non-hydrogen atoms, for hydrogen atoms,
anisotropic thermal parameters and bond lengths and angles
for compounds 3 and 5. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM0301886
(26) Walker, N.; Stuart, D. Acta Crystallogr. A 1983, 39, 158.
(27) Watkin, D. J .; Carruthers, J . R.; Betteridge, P. W. CRYSTALS,
An Advanced Crystallographic Computer Program; Chemical Crystal-
lography Laboratory: Oxford, UK, 1988.
(29) Sheldrick, G. M. SHELXS 86, Program for Crystal Structure
Solution; University of Go¨ttingen: Go¨ttingen, 1986.
(28) International Tables for X-Ray Crystallography; Kynoch
Press: Birmingham, U.K., 1974; Vol. IV.
(30) Pearce, L. J .; Watkin, D. J . CAMERON; Chemical Crystal-
lography Laboratory: Oxford, U.K., 1989.