Dimolybdenum and ditungsten cyclopentadienyl carbonyls with electron-rich phosphide bridges

Article abstract of DOI:10.1021/om020573f

New hydrido complexes of the type [M₂Cp₂(μ-H)(μ-PRR′)(CO)₄] (M = Mo, W) have been prepared through the thermal reaction of [Mo₂Cp₂(CO)₆] with HPCy₂, H₂PCy, or HPEt

Full text of DOI:10.1021/om020573f

Organometallics 2002, 21, 5515-5525
5515
Dim olybd en u m a n d Ditu n gsten Cyclop en ta d ien yl
Ca r bon yls w ith Electr on -Rich P h osp h id o Br id ges.
Syn th esis of th e Hyd r id o P h osp h id o Com p lexes
[M2Cp 2(µ-H)(µ-P RR′)(CO)4] a n d Un sa tu r a ted
Bis(p h osp h id o) Com p lexes [M2Cp 2(µ-P R2)(µ-P R′R′′)(CO)x]
t
(x ) 1, 2; R, R′, R′′ ) Et, Cy, Bu )
M. Esther Garc´ıa, V´ıctor Riera, Miguel A. Ruiz,* M. Teresa Rueda, and
David Sa´ez
Departamento de Quı´mica Orga´nica e Inorga´nica/ IUQOEM, Universidad de Oviedo,
E-33071 Oviedo, Spain
Received J uly 16, 2002
New hydrido complexes of the type [M2Cp2(µ-H)(µ-PRR′)(CO)4] (M ) Mo, W) have been
prepared through the thermal reaction of [Mo2Cp2(CO)6] with HPCy2, H2PCy, or HPEt2 or
the thermal reaction of [W2Cp2(CO)4] with HPR2 (R ) Cy, Et, Ph). In contrast, UV irradiation
of [M2Cp2(CO)6] and HPRR′ leads with good yield to the bis(phosphido) complexes [M2Cp2-
(µ-PRR′)2(µ-CO)] (R ) R′ ) Cy, Et, Ph; R ) Cy, R′ ) H). Related complexes having different
t
t
phosphido groups, [M2Cp2(µ-PR2)(µ-PR′R′′)(µ-CO)] (R ) Cy, Bu, Ph; R′ ) Cy, Bu, Et; R′′ )
t
Cy, Bu, Et, H), can be prepared in high yield through the photochemical reaction of [M2-
Cp2(µ-PR2)(µ-H)(CO)4] and HPR′R′′ or [M2Cp2(µ-H)(µ-PR′R′′)(CO)4] and HPR2. All triply
bonded compounds react easily with carbon monoxide at room temperature or under moderate
heating to finally yield the corresponding trans-dicarbonyl complexes [M2Cp2(µ-PRR′)2(CO)2]
or [M2Cp2(µ-PR2)(µ-PR′R′′)(CO)2]. Some of the intermediates in these carbonylation reactions
have been identified, including the cis-dicarbonyl complex [Mo2Cp2(µ-PPh2)(µ-PtBu2)(CO)2]
and the tricarbonyl complex [Mo2Cp2(µ-PEt2)2(CO)3]. The structures of the new complexes
are analyzed on the basis of the corresponding IR and NMR (1H, 31P, 13C) data, and the
reaction pathways operative in these highly efficient syntheses of bis(phosphido) complexes
is discussed on the basis of the available data and some cross-experiments.
In tr od u ction
the ditungsten analogues with L ) PHPh,10 PH2,6,7
PC4H2Ph2.11 The triply bonded precursors [M2Cp2(µ-
PR2)2(µ-CO)] are even more scarce. In fact, before our
ditungsten diphenylphosphido complex2 only two other
related complexes had been reported, these being the
molybdenum monocarbonyls [Mo2Cp2(µ-RPC6H4PR)(µ-
CO)] (R ) Ph,12a tBu12b) and [Mo2Cp2(µ-PPh2)2(µ-CO)].13
Thus, the search for related complexes with either equal
or different bridging phosphido groups was itself a
synthetic target. Recently, Mays and co-workers have
reported the synthesis of the mixed-phosphide com-
Recently we have shown that the diphenylphosphido
ligand is an useful bridging group able to stabilize
highly reactive dinuclear cyclopentadienyl species such
as the paramagnetic1 [Mo2Cp2(µ-PPh2)(CO)4] or the
hydroxycarbyne2 [W2Cp2(µ-COH)(µ-PPh2)2]BF4. To tune
the reactivity of the unsaturated dimetal center in the
above species, we must be able to modify the steric and
electronic properties of the bridging phosphido ligand.
This can be done, provided that suitable precursors
having different substituents on phosphorus, [M2Cp2-
(µ-H)(µ-PRR′)(CO)4] or [M2Cp2(µ-PR2)(µ-PR′2)(µ-CO)],
are available. Surprisingly, since the first report on
[Mo2Cp2(µ-H)(µ-PMe2)(CO)4] by Hayter,3 relatively few
related complexes have been described. These include
the dimolybdenum complexes [Mo2Cp2(µ-H)(µ-L)(CO)4]
with L ) PPh2,4 PtBu2,5 PH2,6,7 PHMe,6 PHPh,8,9 and
(5) J ones, R. A.; Schwab, S. T.; Stuart, A. L.; Whittlesey, B. R.;
Wright, T. C. Polyhedron 1985, 4, 1689.
(6) Ebsworth, E. A. V.; Mcintosh, A. P.; Schro¨der, M. J . Organomet.
Chem. 1986, 312, C41.
(7) Davies, J . E.; Mays, M. J .; Raithby, P. R.; Shields, G. P.;
Tompkin, P. K. J . Chem. Soc., Chem. Commun. 1997, 361.
(8) Henrick, K.; McPartlin, M.; Horton, A. D.; Mays, M. J . J . Chem.
Soc., Dalton Trans. 1988, 1083.
(9) Woodward, S.; Curtis, M. D. J . Organomet. Chem. 1992, 439,
319.
(10) Grobe, J .; Haubold, R. Z. Anorg. Allg. Chem. 1985, 145.
(11) Mercier, M.; Ricard, L.; Mathey, F. Organometallics 1993, 12,
98.
(12) (a) Kyba, E. P.; Mather, J . D.; Hassett, K. L.; McKennis, J . S.;
Davis, R. E. J . Am. Chem. Soc. 1984, 106, 5371. (b) Kyba, E. P.; Kerby,
M. C.; Kashyap, R. P.; Hassett, K. L.; Davis, R. E. J . Organomet. Chem.
1988, 346, C19.
(13) Adatia, T.; McPartlin, M.; Mays, M. J .; Morris, M. J .; Raithby,
P. R. J . Chem. Soc., Dalton Trans. 1989, 1555.
* To whom correspondence should be addressed. E-mail: mara@
sauron.quimica.uniovi.es.
(1) Garc´ıa, M. E.; Riera, V.; Rueda, M. T.; Ruiz, M. A.; Lanfranchi,
M.; Tiripicchio, A. J . Am. Chem. Soc. 1999, 121, 4060.
(2) Garc´ıa, M. E.; Riera, V.; Rueda, M. T.; Ruiz, M. A.; Halut, S. J .
Am. Chem. Soc. 1999, 121, 1960.
(3) (a) Hayter, R. G. Inorg. Chem. 1963, 2, 1031. (b) Petersen, J . L.;
Dahl, L. F.; Williams, J . M. J . Am. Chem. Soc. 1974, 96, 6610.
(4) Treichel, P. M.; Dean, W. K.; Douglas, W. M. J . Organomet.
Chem. 1972, 42, 145.
10.1021/om020573f CCC: $22.00 © 2002 American Chemical Society
Publication on Web 11/09/2002

5516 Organometallics, Vol. 21, No. 25, 2002
Garc´ıa et al.
Sch em e 1. Syn th esis of Hyd r id o P h osp h id o
Com p lexes
in good overall yields (ca. 60% based on [W2Cp2(CO)6]).
This second method is also more convenient than the
first one when using volatile phosphines, due to the
lower operating temperature. Thus, HPEt2 must be
reacted with [Mo2Cp2(CO)6] below 80 °C, and even so,
important evaporation of phosphine takes place, requir-
ing an excess of reagent to be added. This inconvenience
is avoided when reacting HPEt2 with [Mo2Cp2(CO)4],
which yields compound 1b at 60 °C in ca. 1 h.
Str u ctu r a l Ch a r a cter iza tion of Com p ou n d s 1
a n d 2. Spectroscopic data for the new compounds 1a -c
and 2a ,b,d (Table 1 and Experimental Section) indicate
that all these compounds have the same structure
(Chart 1), it being the transoid one crystallographically
characterized for [Mo2Cp2(µ-H)(µ-PRR′)(CO)4] (R ) R′
) Me,3b tBu;5 R ) Ph, R′ ) Et14b). This is particularly
clear when the corresponding IR or NMR data are
compared with those reported for related complexes3-11
and need not be discussed in detail.
pound [Mo2Cp2(µ-PPh2)(µ-PHPh)(CO)2] through the re-
action of Li[Mo2Cp2(µ-PHPh)(CO)4] with ClPPh2 and
that of [Mo2Cp2(µ-PPh2)(µ-PPhEt)(CO)2] from the phos-
phaalkene complex [Mo2Cp2(µ-PPhCHMe)(CO)4] and
PPh2H.14b
14a
The 13C NMR spectra of compounds 1 and 2 exhibit
the expected CO resonances. By recalling that 2J (PC)
couplings in complexes of the type [MCpX(CO)2(PR3)]
(M ) Mo, W; X ) halogen, alkyl, hydride, etc) usually
15,16
In this paper we report the synthesis of new bis-
(phosphido) complexes of the type [M2Cp2(µ-PR2)(µ-
PR2′)(CO)x] (M ) Mo, W; x ) 1-3) having basic and
follow the order J cis > J trans
,
we expect for the
carbonyl ligand trans to the phosphido bridge a PC
coupling lower than that for the carbonyl trans to the
hydrido bridge. Accordingly, compounds 1a ,b exhibit
only two CO resonances, appearing as a singlet and as
a doublet, respectively. In the case of 1c, the C2 axis
relating both metal centers is no longer an element of
symmetry, and this renders both cyclopentadienyls and
all four carbonyls inequivalent (two doublets and two
singlets as expected).
t
bulky groups such as Et, Cy, and Bu. These can be
conveniently accessed through the reaction of primary
or secondary phosphines with suitable hydrido phos-
phido precursors of the type [M2Cp2(µ-H)(µ-PR2)(CO)4].
Resu lts a n d Discu ssion
Syn t h esis of H yd r id o P h osp h id o Com p lexes.
There are two well-established methods to generate
dimolybdenum or tungsten phosphido complexes of the
type [M2Cp2(µ-H)(µ-PRR′)(CO)4] starting from phos-
phines having P-H bonds (Scheme 1). The first one
involves the thermal reaction of [Mo2Cp2(CO)6] and the
corresponding phosphine and has been successfully used
The above data are in excellent agreement with those
reported for [Mo2Cp2(µ-H)(µ-PRPh)(CO)4] at -40 °C (R
) H, Ph).8,9 The latter complexes were found to experi-
ence a fluxional process rendering all carbonyl and both
cyclopentadienyl ligands equivalent, so that just very
broad 13C carbonyl resonances were observed at room
temperature. Obviously, our dimolybdenum complexes
1a -c are more rigid, as they exhibit NMR spectra at
room temperature consistent with their static structure.
The same can be said of the ditungsten derivatives with
diethyl- or dicyclohexylphosphido bridges 2a ,b, which
also display two carbonyl resonances at room temper-
ature, as expected. The diphenylphosphido derivative
2d , however, is fluxional and gives a single, very broad
13C carbonyl resonance at 229.0 ppm, which at 233 K
transforms into a doublet (232.2 ppm) and a singlet
(224.2 ppm), as expected. Thus, it is concluded that,
irrespective of the metal, the dynamic behavior of this
family of compounds is strongly dependent on the
hydrocarbon substituents on phosphorus. From the
abundant studies on the steric17 and electronic18 influ-
ence of substituents on phosphines, we can estimate for
5
for HPtBu2 and HPPh2 or H2PPh.8 The second method
involves the rapid addition of phosphine to the triply
bonded [M2Cp2(CO)4] to yield intermediates of the type
[M2Cp2(CO)4(PRR′H)2]. The latter then experience elimi-
nation of 1 equiv of HPRR′ (either spontaneously or
under moderate heating) to yield the final hydrido
phosphido complexes, and this method has been suc-
cessfully used for PH3, PH2Me, and PHMe2 (M ) Mo,
W)6 and PH2Ph (M ) Mo).9 We have found that the first
method also works well for HPCy2, HPEt2, and H2PCy.
Thus, refluxing toluene solutions of [Mo2Cp2(CO)6] with
the above phosphines (T ) 80 °C for HPEt2 due to its
low boiling point) gives the corresponding hydridoderiv-
atives 1a -c in good yield. Ditungsten complexes, how-
ever, cannot be prepared in this way, due to the low
decarbonylation rate of [W2Cp2(CO)6], and the second
method must be used instead. Thus, addition of 2 equiv
of HPR2 (R ) Cy, Et, Ph) to [W2Cp2(CO)4] (prepared in
situ from [W2Cp2(CO)6]) followed by further stirring at
room temperature (Cy), 40 °C (Et), or 60 °C (Ph) gives
the corresponding phosphido complexes [W2Cp2(µ-H)-
(µ-PR2)(CO)4] (2a ,b,d : a , R ) Cy; b, R ) Et; d , R ) Ph)
(15) Todd, L. J .; Wilkinson, J . R.; Hickley, J . P.; Beach, D. L.;
Barnett, K. W. J . Organomet. Chem. 1978, 154, 151.
(16) Wrackmeyer, B.; Alt, H. G.; Maisel, H. E. J . Organomet. Chem.
1990, 399, 125.
(17) (a) Tolman, C. A. Chem. Rev. 1977, 77, 33. (b) Stahl, L.; Ernst,
R. D. J . Am. Chem. Soc. 1987, 109, 5673. (c) Brown, T. L. Inorg. Chem.
1992, 31, 1286. (d) Muller, T. E.; Mingos, D. M. P. Transition Met.
Chem. 1995, 20, 533. (e) Smith, J . M.; Taverner, B. C.; Coville, N. J .
J . Organomet. Chem. 1997, 530, 131 and references therein.
(18) (a) Dias, P. B.; Minas de Piedade, M. E.; Martinho-Simoe´s, J .
A. Coord. Chem. Rev. 1994, 135, 737. and references therein. (b) Drago,
R. S. Organometallics 1995, 14, 3408.
(14) (a) Davies, J . E.; Feeder, N.; Gray, C. A.; Mays, M. J .; Woods,
A. D. J . Chem. Soc., Dalton Trans. 2000, 1695. (b) Bridgeman, A. J .;
Mays, M. J .; Woods, A. D. Organometallics 2001, 20, 2076.

Mo2 and W2 Complexes with Phosphido Bridges
Organometallics, Vol. 21, No. 25, 2002 5517
Ta ble 1. Selected IR a n d NMR Da ta for New [M2Cp 2(µ-H)(µ-P RR′)(CO)4] Com p ou n d s
M
R
R′
compd
ν(CO)a
δ(CO)b (J PC
)
δ(P)b (J PW
)
δ(µ-H)b [J PH] (J HW
)
Mo
Mo
Mo
Cy
Et
Cy
Cy
Et
H
1a
1b
1c
1945 (w,sh),1928 (vs), 1860 (s)
1942 (w,sh), 1930 (vs), 1866 (s)
1953 (w, sh), 1935 (vs), 1871 (s)
244.1 (19), 235.9
243.5 (24), 235.9
242.8 (19), 237.1
242.2 (20), 236.7
232.2 (br), 223.4 (br)
233.8 (20), 225.6
232.2 (17), 224.2e
218.8c
179.8c
152.6c
-13.2 [34]
-12.3 [35]c
-12.4 [35]
W
W
W
Cy
Et
Ph
Cy
Et
Ph
2a
2b
2d
1918 (vs), 1841 (s)
139.6 (182)c
99.6 (197)c
109.2 (209)
-16.4 [24] (40)
-14.9 [25] (39)
-14.8 [27] (39)
1919 (vs), 1846 (s)
1959 (w, sh), 1926 (vs), 1853 (s)d
a
b
Recorded in toluene solution, unless otherwise stated. ν in cm-1
.
Recorded in CD2Cl2 solutions at 290 K and 300.13 (1H), 121.50
(
31P), or 75.47 MHz (13C) unless otherwise stated. δ in ppm relative to internal TMS (1H, 13C) or external 85% aqueous H3PO4; J in hertz.
c In toluene-d8 solution. In dichloromethane solution. e At 233 K; when recorded at 290 K, only a broad resonance at 229 ppm is observed.
d
Ch a r t 1
Ch a r t 2
the groups involved here that the electron-donor influ-
ence on the phosphido ligand would follow the sequence
Cy > Et > Ph > H, whereas the relative size would
decrease in the order Cy > Ph ≈ Et > H. Thus, taking
into account that the complexes exhibiting fluxional
behavior at room temperature are those with PPh2 or
PHPh bridges, whereas those with similar overall size
but more electron-releasing groups PEt2 (1b, 2b) and
PHCy (1c) behave as more rigid molecules, we conclude
that electronic effects seem to be prevalent in these
compounds, with the electron-withdrawing substituents
on the phosphido ligand increasing the rate of the
fluxional process.
Syn th esis of Bis(ph osph ido) Com plexes. As stated
above, before our photochemical synthesis of [W2Cp2(µ-
PPh2)2(µ-CO)] from [W2Cp2(µ-H)(µ-PPh2)(CO)4] and HP-
Ph2 only two other related monocarbonyls had been
reported, these being prepared through prolonged ther-
mal12 or photochemical13 treatment of suitable precur-
sors. The interesting point of our method was 2-fold.
First, it was fast, with reaction times around 1 h at room
temperature. Second, it allowed the synthesis of mixed
bis(phosphido) derivatives, by appropriate choice of
substrate and phosphine. Indeed, we have found that
this synthetic approach is quite general, and a large
number of mixed bis(phosphido) derivatives can be
synthesized in this rational way. Apparently, this
preparative route to mixed phosphido complexes has not
been explored in detail previously, although we can
quote a precedent in the synthesis of [Fe2(µ-PCy2)(µ-
PPh2)(CO)4(µ-dppm)] from [Fe2(µ-PCy2)(µ-H)(µ-CO)-
(CO)4(µ-dppm)] and HPPh2.19 Moreover, we have found
that symmetric bis(phosphido) complexes can be syn-
thesized in a one-pot reaction from [M2Cp2(CO)6] and
the corresponding HPR2 under photochemical condi-
tions, a process expectedly involving the corresponding
hydrido compounds 1 and 2 as intermediate species.
Irradiation of toluene solutions of [Mo2Cp2(CO)6] with
UV light in the presence of ca. 3 equiv of HPCy2 or
HPEt2 gives the corresponding monocarbonyls [Mo2Cp2-
(µ-PR2)2(µ-CO)] (3a ,b: a , R ) Cy; b, R ) Et) (Chart 2).
When the smaller H2PCy is used, the stoichiometry
must be fixed to 2 equiv of phosphine in order to avoid
further additions of the ligands. The corresponding
monocarbonyl complex [Mo2Cp2(µ-PHCy)2(µ-CO)] (3c) is
obtained as a mixture of two isomers (see later). In a
similar way, UV irradiation of [W2Cp2(CO)6] with HPEt2
or HPPh2 gives the related monocarbonyls [W2Cp2(µ-
PR2)2(µ-CO)] (4b,d ) in good yields (d , R ) Ph).
IR and 31P NMR monitoring of the above reactions
indicates that several species are involved as intermedi-
ates in the formation of monocarbonyls 3 and 4. Apart
from the corresponding hydrido complexes 1 and 2, we
have also identified the corresponding dicarbonyl com-
pounds [M2Cp2(µ-PR2)2(CO)2] as intermediates in these
reactions, these being observed in larger amounts for
the smaller phosphines H2PCy and HPEt2. As expected,
these dicarbonyl complexes can be formed from 3 or 4
and CO, as we will discuss later.
Irradiation of toluene solutions of the hydrido com-
plexes 1 or 2 and the appropriate primary or secondary
phosphine proceeds rapidly, presumably with H2 elimi-
nation, to give with good yields the corresponding mixed
bis(phosphido) monocarbonyls 5 and 6, analogous to the
“symmetric” compounds 3 and 4 (Scheme 2). The
method is quite general, and reaction times are ca. 1 h
on a 0.1 g scale. For example, 1a and PH2Cy give [Mo2-
Cp2(µ-PCy2)(µ-PHCy)(µ-CO)] (5e), while 1c and PHtBu2
give [Mo2Cp2(µ-PHCy)(µ-PtBu2)(µ-CO)] (5f) and [Mo2Cp2-
(µ-H)(µ-PPh2)(CO)4] reacts with PHCy2, PHEt2, or PH2-
Cy to yield respectively [Mo2Cp2(µ-PPh2)(µ-PR′R′′)(µ-
CO)] (5g-i: g, R′ ) R′′ ) Cy; h , R′ ) R′′ ) Et; i, R′′ )
H; R′ ) Cy). As for ditungsten species, compound 2a
and PH2Cy give [W2Cp2(µ-PCy2)(µ-PHCy)(µ-CO)] (6e),
while 2b and PHPh2 lead expectedly to [W2Cp2(µ-PEt2)-
(19) Hogarth, G.; Lavender, M. H.; Shukri, K. Organometallics 1994,
14, 2325.

5518 Organometallics, Vol. 21, No. 25, 2002
Garc´ıa et al.
Ta ble 2. Selected IR a n d NMR Da ta for New [M2Cp 2(µ-P RR′)2(µ-CO)] a n d [M2Cp 2(µ-P R2)(µ-P R′R′′)(µ-CO)]
Com p ou n d s
M
R
R′
R′′
compd
ν(CO)a
δ(CO)b [J PC
]
δ(P)b
J PP
J PW
Mo
Mo
Mo
Cy
Et
Cy
Cy
Et
H
3a
3b
3c
1689
1693
1703
307.0 [7]
298.0 [7]c
263.7c
212.3c
167.3
304.7 [7] (A)d
303.2 [7] (B)
305.0
167.8, 165.3
27
W
W
Mo
Et
Ph
Cy
Et
Ph
Cy
4b
4d
5e
1654
1635e
1694
147.1c
376
389
303.9
144.7
H
306.7 (D)f
(E)
240.9 (PCy2), 166.9
238.7 (PCy2), 166.7
280.6 (PtBu2), 179.5c
243.4 (PCy2), 194.5c
222.5 (PEt2), 192.7
193.3 (PPh2), 168.2c
288.9 (PtBu2), 198.6
201.5 (PHtBu), 196.9
181.2 (PCy2), 111.8
182.1 (PCy2), 107.4
152.9 (PEt2), 136.5
27
22
27
23
26
28
22
27
<1
9
Mo
Mo
Mo
Mo
Mo
Mo
W
tBu
Ph
Ph
Ph
Ph
Ph
Cy
Cy
Cy
Et
Cy
tBu
tBu
Cy
H
5f
5g
5h
5i
5j
5k
6e
1695
1692
1696
1702
1694
1702
1655
297.8g
Cy
Et
H
306.3 [7]
304.9
304.4 [7]
306.2 [7]
304.1 [7]
307.5 (D)
306.2 (E)f
304.4
tBu
H
H
358, 368
358, 370
374, 392
W
Ph
Et
Et
6h
1657
6
a
b
Recorded in toluene solution, unless otherwise stated. ν in cm-1
.
Recorded in CD2Cl2 solutions at 290 K and 300.13 (1H), 121.50
(
31P), or 75.47 MHz (13C) unless otherwise stated. δ in ppm relative to internal TMS (1H, 13C) or external 85% aqueous H3PO4; J in hertz.
d g
c In toluene-d8 solution. Ratio A:B ) 6:4. e In dichloromethane solution. f Ratio D:E ) 7:3. In benzene-d6 solution.
of a P-tBu moiety into a P-H one. This must occur at
Sch em e 2. Syn th esis of Bis(p h osp h id o)
the intermediate steps leading to 5k , as the µ-PtBu2
ligand, once formed, is stable under these reaction
conditions (i.e., 5j does not transform into 5k ). Although
we have not been able to find any precedent for this
degradation of a HPtBu2 molecule upon coordination to
a metal complex, several reasonable proposals can be
envisaged, as we will discuss later on.
Com p lexes
Str u ctu r a l Ch a r a cter iza tion of Com p ou n d s 3-6.
Spectroscopic data for compounds 3-6 are all similar
(Table 2) and indicative of the presence of two bridging
phosphido groups and a bridging carbonyl. The struc-
ture is therefore the same as that crystallographically
determined for [Mo2Cp2(µ-PhPC6H4PPh)(µ-CO)]12a and
[Mo2Cp2(µ-PPh2)2(µ-CO)],13 for which the short inter-
metallic distances (ca. 2.5 Å) are consistent with the
formulation of a triple metal-metal bond.
The bridging carbonyl in complexes 3-6 gives rise to
a C-O stretching band at ca. 1700 cm-1 (M ) Mo) or
1655 cm-1 (M ) W) and to characteristic 13C resonances
at ca. 305 ppm. Assignment of 31P NMR resonances in
the mixed-phosphido complexes 5 and 6 can be unam-
biguously done by comparison with the chemical shifts
of the “symmetric” compounds 3 and 4 and analysis of
the one-bond P-H couplings when necessary. For
compound 6h , as chemical shifts for PEt2 or PPh2 groups
are quite similar, assignment of the 31P resonances is
based on the measured P-W couplings, expected to be
higher for P atoms bearing better electron acceptor
groups.
Chemical shifts for the phosphorus atoms in com-
pounds 3-6 follow the same general trend observed for
the tetracarbonylic complexes 1 and 2, i.e., PtBu2 > PCy2
> PEt2 = PPh2 > PHCy. Thus, they rather seem to be
following the steric demands of the hydrocarbon groups
attached to the phosphorus bridge. We note, however,
that chemical shifts of phosphido bridges are quite
sensitive to many structural features (C-P-C and
M-P-M angles, M-M, M-P lengths, etc.);20,21 there-
fore, we will not attempt to correlate these shifts with
(µ-PPh2)(µ-CO)] (6h ). In some cases, intermediate di-
carbonyl species can be detected during the formation
of these mixed-metal compounds, as we have noted also
for the “symmetric” monocarbonyls 3 and 4.
From the above reactions it can be concluded that, to
combine two different phosphido ligands, it is not
important which ligand is first incorporated into the
substrate (i.e., the one present in the phosphido hydrido
complex). However, this cannot be assumed in all cases.
For example, when the relatively bulky PPh2 and PtBu2
groups are combined, the order of incorporation of
ligands becomes critical. Thus, the photochemical reac-
tion of [Mo2Cp2(µ-H)(µ-PtBu2)(CO)4] with HPPh2 leads
expectedly to [Mo2Cp2(µ-PtBu2)(µ-PPh2)(µ-CO)] (5j),
but the reaction between [Mo2Cp2(µ-H)(µ-PPh2)(CO)4]
and HPtBu2 leads instead to a ca. 1:1:1 mixture of
5j, [Mo2Cp2(µ-PPh2)2(µ-CO)],13 and [Mo2Cp2(µ-PPh2)(µ-
PHtBu)(µ-CO)] (5k ). While the formation of the bis-
(diphenylphosphido) complex is due to slow photochemi-
cal decomposition of the starting substrate (we note that
the reaction time in this case is substantially longer,
ca. 3 h), the formation of 5k requires the transformation
(20) Carty, A. J .; McLaughin, S. A.; Nucciarone, D. in Phosphorus-
31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J . G., Quin,
L. D., Eds.; VCH: New York, 1987; Chapter 16.

Mo2 and W2 Complexes with Phosphido Bridges
Organometallics, Vol. 21, No. 25, 2002 5519
Ch a r t 3
detect in some cases intermediate species likely to be
the dicarbonyl compounds, analogous to the well-
characterized doubly bonded complex [Mo2Cp2(µ-PPh2)2-
(CO)2].13 We then decided to study the reactions of CO
with the triply bonded complexes 3-6 as a synthetic
route to the mentioned dicarbonyl compounds. There
were two further points of interest in these reactions.
First, they would provide us some insight on the
reaction pathways operative in the photochemical syn-
thesis of monocarbonyl compounds 3-6. Second, they
would represent a first check on the ligand-acceptor
ability of these highly unsaturated molecules having
double or triple intermetallic bonds.
All compounds 3-6 react with CO at atmospheric
pressure to yield the corresponding dicarbonyl deriva-
tives 7-10, which are selectively obtained as trans
isomers (Chart 3). The rate of carbonylation appears to
be dominated by the steric (rather than electronic)
properties of the bridging groups. Thus, all complexes
combining PEt2, PPh2, or PHCy bridges are rapidly
carbonylated at room temperature within a few min-
utes, while those incorporating PCy2 or PtBu2 groups
require several hours and/or higher temperatures for
complete carbonylation (for example, 3 h at 80 °C for
3a ).
We have been able to detect and characterize two
intermediate species in some of these carbonylation
reactions. In the first place, IR and 31P NMR monitoring
of the slow carbonylation of 5j at 80 °C reveals that a
cis isomer of the final product, cis-[Mo2Cp2(µ-PPh2)(µ-
PtBu2)(CO)2] (11), is first formed, which then slowly
transforms into 9j. It is important to note that in the
absence of CO compound 11 does not transform into its
trans isomer 9j at either room temperature or 80 °C and
that it gives back the monocarbonyl 5j under UV
irradiation within a few minutes. Incidentally, com-
pound 11 appears to be the first example of a bis-
(phosphido) species of the type [M2Cp2(µ-X)(µ-Y)(CO)2]
(X, Y ) 3e donor groups) exhibiting a cis-dicarbonyl
geometry. We note, however, that both cis and trans
geometries are well-known for the related bis(thiolate)
complexes [Mo2Cp2(µ-SR)2(CO)2].23 More importantly,
we trust that compound 11 represents the first stage
in the carbonylation reactions of triply bonded com-
plexes 3-6, as we will discuss later on.
F igu r e 1. Possible structures of monocarbonyl complexes
having P-H bonds, viewed along the M-M bond (Cp
groups omitted).
any single geometric or electronic property of the
phosphido bridge.
Complexes with bridging PHCy or PHtBu groups can
exist as several isomers depending on the orientation
of the H atom (Figure 1). This is the case for the
molybdenum complexes 3c and 5e,f,i,k and the ditung-
sten compound 6e. Complex 3c displays two isomers in
solution, one having equivalent P atoms (δP 167.3 ppm)
and one having non equivalent P atoms (δP 167.8, 165.3
ppm). The latter must be therefore the unique asym-
metric conformer B, while the former is presumably
conformer A and not C, on the basis of steric grounds.
Species with a single PHR bridge can exist as isomers
of types D and E, but complexes 5f,i,k display single
isomers in solution. Presumably, these compounds adopt
the less sterically demanding structure D. However,
compounds 5e and 6e display two isomers in solution
with similar ratios (ca. 70:30). On steric grounds, we
would expect for the major isomer a structure of type
D, while the minor isomer would adopt structure E. This
3
is in agreement with J (P-H) values measured for the
P-H hydrogens in compounds 5e and 6e. These three-
bond couplings are strongly dependent on the dihedral
angle (φ) defined by the bonds involved.22 On this basis,
we expect for structure D (φ(H-P-M-P) close to 90°)
a
3J (P-H) value smaller than that for structure E
(φ(H-P-M-P) close to 180°). Indeed, the major isomer
in these compounds displays a 3J (P-H) value of 2-3
Hz for the P-bonded hydrogen, to be compared to
3J (P-H) ) 7 Hz for the corresponding hydrogen in the
minor isomer.
Ca r bon yla tion Rea ction s of Tr ip ly Bon d ed Com -
p lexes 3-6. As noted above, during the synthesis of
the monocarbonylic complexes 3-6 we were able to
(21) (a) Carty, A. J .; Fyfe, C. A.; Lettinga, M.; J ohnson, S.; Randall,
L. H. Inorg. Chem. 1989, 28, 4120. (b) Eichele, K.; Wasylishen, R. E.;
Corrigan, J . F.; Taylor, N. J .; Carty, A. J .; Feindel, K. W.; Bernard, G.
M. J . Am. Chem. Soc. 2002, 124, 1541.
(22) Bentrude, W. G.; Setzer, W. N. In Phosphorus-31 NMR Spec-
troscopy in Stereochemical Analysis; Verkade, J . G., Quin, L. D., Eds.;
VCH: New York, 1987; Chapter 11.
(23) Pe`tillon, F. Y.; Schollhammer, P.; Talarmin, J .; Muir, K. W.
Coord. Chem. Rev. 1998, 178-180, 203.

5520 Organometallics, Vol. 21, No. 25, 2002
Garc´ıa et al.
Ta ble 3. Selected IR a n d NMR Da ta for New [M2Cp 2(µ-P RR′)2(CO)2] a n d [M2Cp 2(µ-P R2)(µ-P R′R′′)(CO)2]
Com p ou n d s
M
R
R′
R′′
compd
ν(CO)a
δ(CO)b [J PC
]
δ(P)b
J PP
J PW
Mo
Mo
Mo
Mo
W
Cy
Et
Et
Cy
Et
Ph
Cy
tBu
Ph
Ph
Ph
Ph
Ph
Ph
Cy
Ph
Cy
Et
Et
H
Et
Ph
Cy
Cy
Cy
Et
Cy
tBu
tBu
tBu
Cy
Et
7a
1851 (d, sh), 1833 (s)
1860 (d, sh), 1840 (s)
1930 (vs), 1863 (s), 1817 (s)
1872 (d, sh), 1849 (s)
1863 (d, sh), 1838 (s)
1882 (d, sh), 1852 (s)e
1865 (d, sh), 1839 (s)
1867 (d, sh), 1837 (s)
1874 (d, sh), 1848 (s)g
1880 (d, sh), 1851 (s)
1878 (d, sh), 1857 (s)
1865 (d, sh), 1853 (s)
1926 (s), 1871 (m)
95.4
78.7
194.7c
45.4
16.7
34.7
7b
12
7cd
8b
8d
9e
237.3 [13]
241 [4], 237.9c
236.4
228.2 [4]
291
301
W
Mo
Mo
Mo
Mo
Mo
Mo
Mo
Mo
W
H
H
238.0 [12], 237.4 [15]
109.9 (PCy2), 41.7f
170.6 (PtBu2), 52.7f
107.4 (PCy2), 83.3
85.6, 85.2
9
<1
7
9
8
4
14
8
9f
Cy
Et
H
9g
9h
9i
96.4 (PPh2), 48.1f
174.1 (PtBu2), 94.7f
213.0 (PtBu2), 148.0f
91.6 (PPh2), 83.5
44.7 (PCy2), -20.1
32.7 (PPh2), 20.0
tBu
tBu
H
9j
11
9k
10e
10h
248.7[7]
1882 (d, sh), 1856 (s)
1860 (d, sh), 1837 (s)
1873 (d, sh), 1849 (s)
H
Et
225.3 [5], 224.6
225.3 [4]
6
6
284, 276
305, 287
W
a
b
Recorded in toluene solution, unless otherwise stated. ν in cm-1
.
Recorded in CD2Cl2 solutions at 290 K and 300.13 (1H), 121.50
(
31P), or 75.47 MHz (13C) unless otherwise stated. δ in ppm relative to internal TMS (1H, 13C) or external 85% aqueous H3PO4; J in hertz.
c Recorded at 193 K. Data for the anti isomer; δP 46.2 for the syn isomer. e In dichloromethane solution. f In toluene-d8. g In tetrahydrofuran
d
solution.
Ch a r t 4
Carbonylation of the bis(diethylphosphido) derivative
3b is fast at room temperature. When this reaction is
carried out at -50 °C, it can be shown that the
tricarbonyl intermediate [Mo2Cp2(µ-PEt2)2(CO)3] (12) is
first formed. Compound 12 can be spectroscopically
characterized but was not isolated, as it transforms
progressively at room temperature into the correspond-
ing trans-dicarbonyl complex 7b. Tricarbonyl complexes
frequency).25 This arrangement implies the presence of
such as 12 are rare species, placed midway between the
a C2 axis passing through the phosphorus atoms, which
makes equivalent both hydrocarbon groups R on the PR2
bridges, easily denoted by the appearance of single
resonances for P-C atoms in the 13C NMR spectra (see
Experimental Section). This symmetry element is ab-
sent in those complexes with PRR′ bridges, which then
exhibit separated resonances for the carbonyl or cyclo-
pentadienyl ligands (Table 3 and Experimental Section).
The structure of compounds 7-10 is therefore the same
as that crystallographically determined for [Mo2Cp2(µ-
PPh2)2(CO)2],13 for which the short intermetallic dis-
tance of ca. 2.71 Å justifies the formulation of a double
intermetallic bond.
usually more stable tetracarbonylic or dicarbonylic
structures ([M2Cp2(µ-X)(µ-Y)(CO)n], n ) 4, 2). In fact,
previous examples of stable group 6 complexes related
to 12 are limited to cases where a restricted cis-type
conformation is imposed by the bridging ligands, as it
is in the case of [Mo2Cp2(µ-PhPC6H4PPh)(CO)3]12a or
[M2(µ-η5:η5-C5H4SiMe2C5H4)(µ-PMe2)2(CO)3] (M ) Mo,
W).24 The relevance of complex 12 in the present context
is derived from its spontaneous thermal decay to the
corresponding trans-dicarbonyl derivative 7b, as this
allows us to propose it as a general intermediate in the
carbonylation pathway of the triply bonded complexes
3-6, as we will discuss later on.
The 31P spectra of trans-dicarbonyl complexes 7-10
reveal two characteristic features: first, a strong shield-
ing of the P nucleus (100-160 ppm) relative to the
corresponding triply bonded monocarbonyls and, second,
a low J (PP) coupling (when observed, 4-9 Hz). These
spectroscopic features have been also recognized for
the related complexes [Mo2L2(µ-CH2PPh2)(µ-PPh2)(CO)2]
(L ) C5H5, C5H4Me)26 and [Mo2Cp2(µ-PPh2)(µ-PPhH)-
(CO)2],14a and they seem to be characteristic of these
trans-dicarbonylic structures with an essentially planar
M2P2 core. In this context, it is interesting to note that
the cis-dicarbonyl 11, which possibly has a somewhat
puckered Mo2P2 core (Chart 4), exhibits 31P shifts 40-
50 ppm higher than those corresponding to the trans
isomer 9j. Thus, a simple conformational change, rather
than a modification of the intermetallic bond order (and
the M-M length), accounts for about half the shielding
observed between triply and doubly bonded complexes.
The above results indicate that, despite the formal
unsaturation of all complexes 7-10, these doubly bonded
species are stable toward carbonylation. To this we must
add the knowledge that Hayter’s compound [Mo2Cp2(µ-
PMe2)2(CO)4] does not decarbonylate in refluxing
toluene,3a whereas [Mo2Cp2(µ-PPh2)(µ-PPhH)(CO)4] does
it slowly to give the corresponding dicarbonyl [Mo2Cp2-
(µ-PPh2)(µ-PPhH)(CO)2],14a a close analogue of com-
plexes 9. All this seems to clearly indicate that the
stability of the unsaturated dicarbonyls 7-10 and
related bis(phosphido) complexes toward CO addition
is mainly steric in origin.
Str u ctu r al Ch ar acter ization of Com pou n ds 7-12.
Spectroscopic data for dicarbonylic complexes 7-10 are
all similar and indicative of the presence of two bridging
phosphido groups and two terminal carbonyl ligands
(Table 3). The relative trans geometry of the latter is
derived from the relative intensities of the C-O stretch-
ing bands (weak and strong, in order of decreasing
(25) Braterman, P. S. Metal Carbonyl Spectra; Academic Press:
London, 1975.
(24) (a) Heck, J . J . Organomet. Chem. 1986, 311, C5. (b) Abriel, W.;
Baum, G.; Burdorf, H.; Heck, J . Z. Naturforsch. 1991, 46b, 841.
(26) Garc´ıa, G.; Garc´ıa, M. E.; Melo´n, S.; Riera, V.; Ruiz, M. A.;
Villafan˜e, F. Organometallics 1997, 16, 624.

Mo2 and W2 Complexes with Phosphido Bridges
Organometallics, Vol. 21, No. 25, 2002 5521
Sch em e 3. P h otoch em ica l Syn th esis of th e Tr ip ly
Bon d ed Com p lexes 3-6
F igu r e 2. Schematic view of the isomers observed for
compound 7c along the Mo-Mo bond (CO groups omitted).
The structure of compound 11 is firmly supported on
spectroscopic data. The cis arrangement of the carbonyl
ligands is clearly denoted by the relative intensities of
the C-O stretching bands (strong and medium, in order
of decreasing frequencies).25 The phosphido bridges are
now placed on a symmetry plane rather than along the
C2 axis present in the trans isomers. This implies that
both R groups attached to the phosphorus bridges are
not equivalent, in agreement with the observation of two
P-C(Ph) or P-C(tBu) 13C resonances.
Compound 7c is obtained as a mixture of two isomers,
presumably differing in the relative orientation of both
PHCy groups (syn and anti isomers; see Figure 2).
Crystallization of the mixture allows the isolation of the
minor isomer as a pure solid, which can be unambigu-
ously identified as the anti isomer. This is derived from
1
the observation of single 13C or H resonances for both
carbonyl and cyclopentadienyl ligands of the molecule.
In contrast, the major isomer exhibits separated 1H
resonances for both Cp ligands, and it is thus identified
as the syn isomer. These assignments also lead to the
reasonable suggestion that the relative conformation of
the phosphido bridges is preserved during the carbonyl-
ation/decarbonylation processes connecting compounds
3 and 7, so that monocarbonyl isomers A would lead to
dicarbonyl syn isomers while isomers B would lead to
anti isomers and vice versa.
The tricarbonylic nature of compound 12 is clearly
denoted by the presence of three strong C-O stretching
bands in its IR spectrum. The frequencies and intensi-
ties are very similar to those found for [Mo2(µ-η5:η5-
C5H4SiMe2C5H4)(µ-PMe2)2(CO)3], for which an X-ray
study revealed the presence of a plane of symmetry
containing the metal atoms and relating the phosphido
bridges and the carbonyl ligands of the dicarbonylic
moiety.24 We then conclude that compound 12 adopts a
similar structure (Chart 4). In agreement with this, the
CO ligands give rise to two 13C resonances in the
terminal region, with relative intensities 1:2, and the
Cp or Et groups exhibit two chemical environments in
each case. The 31P chemical shift of the phosphido
bridges in 12 (194.7 ppm) is similar to that of the
monocarbonyl complex 3b (212.3 ppm), and both values
are much higher than that of the trans-dicarbonyl 7b
(81.3 ppm). This again illustrates the very anomalous
low shift of the doubly bonded dicarbonyls, so that the
observed values can be hardly correlated in a simple
way with the intermetallic bond order or other geometric
parameter related to it as, for example, M-M lengths
or M-P-M angles.
fore, we can give a general picture of the main reaction
pathways operating in this highly efficient photochemi-
cal preparation of bis(phosphido) complexes (Scheme 3).
The photochemical route from [M2Cp2(CO)6] to the
phosphido hydrido complexes 1 and 2 is possibly not
very different from the thermal route (Scheme 1) and
will not be discussed. The photochemical reaction of the
latter with a second molecule of phosphine having a
P-H bond is a critical step toward the bis(phosphido)
derivatives and would be surely initiated by simple
carbonyl substitution to yield the tricarbonyl intermedi-
ate A. It has been shown previously that the photo-
chemical reaction of [Mo2Cp2(µ-H)(µ-PPh2)(CO)4] with
tertiary phosphines or phosphites affords slowly (ca. 24
h) the tricarbonyl derivatives [Mo2Cp2(µ-H)(µ-PPh2)-
(CO)3(PR3)] (as a mixture of two isomers).8 This is in
contrast with the short reaction times required in our
reactions (ca. 1 h). This difference can be explained by
considering the coupling to the substitution step of an
irreversible process such as hydrogen elimination. In-
deed, a further decarbonylation on intermediate A could
promote the oxidative addition of the P-H bond in the
incoming phosphine to give dihydride B, which, upon
H2 elimination, would yield the trans-dicarbonyl com-
plexes 7-10 (experimentally observed as intermediate
species in some cases). The latter in turn would rapidly
decarbonylate under the UV light to finally yield the
triply bonded monocarbonyls 3-6. In the case of the
reaction of [Mo2Cp2(µ-H)(µ-PPh2)(CO)4] with HPtBu2,
the elimination of one of the tBu groups leading to
compound 5k must occur at the intermediate A (i.e.,
before a bridging PtBu2 is formed). This can occur in
several reasonable ways. For example, a â-elimination
t
Rea ction P a th w a ys in th e F or m a tion of Bis-
(p h osp h id o) Com p lexes. Although the present work
is mainly synthetic in nature and no mechanistic studies
have been attempted, we have recognized some trends
and have identified intermediates in some cases; there-
of the Bu group on P would liberate 2-methylpropene
t
to generate a bonded PH2 Bu ligand, which then would
transform (via the corresponding intermediate B) into
a bridging PHtBu group. Alternatively, the bonded
t
PHtBu2 ligand can eliminate BuH to generate a phos-

5522 Organometallics, Vol. 21, No. 25, 2002
Garc´ıa et al.
Sch em e 4. Ca r bon yla tion Rea ction s of th e Tr ip ly
However, spectroscopic data for 12 suggest that the Cp
ligands are in a relative cis geometry (Chart 4). There-
fore, we must assume that these tricarbonyl intermedi-
ates can experience some cis-trans rearrangement (to
give D′) before CO is lost and the final trans-dicarbonyls
7-10 are formed. In this context, it is interesting to note
that similar proposals have been made in order to
account for the CO-catalyzed cis-trans isomerization
of the related thiolate complexes [Mo2Cp2(µ-SMe)2(CO)2]
and the reduction products of the cations [Mo2Cp2(µ-
SR)2(CO)3(MeCN)]2+ (R ) Me, Ph).23
Bon d ed Com p lexes 3-6
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations and reactions were
carried out under a nitrogen (99.9995%) atmosphere using
standard Schlenk techniques. Solvents were purified according
to literature procedures28 and distilled prior to use. Petroleum
ether refers to that fraction distilling in the range 65-70 °C.
Compounds [W2Cp2(CO)x] (x ) 6,29 430) and [Mo2Cp2(µ-H)(µ-
t
PR2)(CO)4] (R ) Bu,5 Ph8) were prepared as described previ-
ously. All other reagents were obtained from the usual
commercial suppliers and used as received. Photochemical
experiments were performed using jacketed quartz Schlenk
tubes, refrigerated by tap water (ca. 15 °C). A 400 W mercury
lamp (Applied Photophysics) placed ca. 1 cm away from the
Schlenk tube was used for these experiments. Chromato-
graphic separations were carried out using jacketed columns
refrigerated by tap water. Commercial aluminum oxide (activ-
ity I, 150 mesh) was degassed under vacuum prior to use. The
latter was mixed afterward under nitrogen with the appropri-
ate amount of water to reach the activity desired. Carbonyl-
ation experiments were carried out using Schlenk tubes
equipped with Young valves. Filtrations were performed using
diatomaceous earth. NMR spectra were routinely recorded at
300.13 (1H), 121.50 (31P{1H}) or 75.47 MHz (13C{1H}) at 290
K on CD2Cl2 solutions unless otherwise stated. Chemical shifts
(δ) are given in ppm, relative to internal TMS or external 85%
aqueous H3PO4 solutions (31P). Coupling constants (J ) are
given in hertz.
P r ep a r a tion of [Mo2Cp 2(µ-H)(µ-P Cy2)(CO)4] (1a ). A
toluene solution (35 mL) of [Mo2Cp2(CO)6] (0.625 g, 1.28 mmol)
and HPCy2 (260 µL, 1.28 mmol) was refluxed for 1 h 15 min
to yield a dark orange solution, which was filtered. Petroleum
ether was then added, and the mixture was allowed to
crystallize at -20 °C to give compound 1a 0.532 g, 84%) as a
dark orange microcrystalline solid. Anal. Calcd for C26H33O4-
PMo2 (1a ): C, 49.38; H, 5.22. Found: C, 49.57; H, 5.15. 1H
NMR: δ 5.32 (s, 10H, Cp), 2.81-0.79 (m, 22H, Cy), -13.2 (d,
J HP ) 34, 1H, µ-H). 13C{1H} NMR: δ 244.1 (d, J CP ) 19, 2 ×
CO), 235.9 (s, 2 × CO), 90.4 (s, Cp), 41.1 (d, J PC ) 15, C1(Cy)),
32.2, 30.2 (2 × s, C2 and C6(Cy)), 28.2, 27.6 (2 × s, C3 and
C5(Cy)), 27.15 (s, C4(Cy)).
phinidene (PtBu) intermediate which, upon insertion
into the hydrido bridge, would also lead to a bridging
PHtBu group. Although we have not found any prece-
dent for this degradation of a bonded PHtBu2 ligand,
there are precedents of related (P-C into P-H) trans-
formations for phosphorus ligands having very sterically
demanding groups.27
The fast photochemical transformation of the dicar-
bonyls 7-10 into the triply bonded complexes 3-6
cannot be reproduced thermally even under severe
heating. In contrast, the latter are rapidly carbonylated
at room temperature, except for those complexes incor-
porating the bulky PCy2 or PtBu2 groups, which require
a moderate heating of the solution (up to 80 °C) if
carbonylation is to be completed in a reasonable time.
Actually, the transformation of monocarbonyls 3-6 into
the trans-dicarbonyls 7-10 does not seem to be a simple
process. The reactions of carbon monoxide with the di-
tert-butylphosphido complex 5j and the diethylphos-
phido complex 3b are especially revealing in this respect
and allow us to draw a general reaction pathway for all
these reactions (Scheme 4). As we have shown above,
complex 5j reacts with CO at 80 °C to yield first the
cis-dicarbonyl complex 11. We assume that similar cis
complexes (C in Scheme 4) are formed in all cases but
are not detected. Separate experiments have shown that
complex 11 does not transform into its trans isomer 9j
unless CO is present (and even so, it does it slowly at
80 °C). We trust this is because the cis-trans isomer-
ization requires the formation of the tricarbonylic
intermediate D, which we assume to be the next general
intermediate in these reactions. Complex 12 is, of
course, the representative example of such an interme-
diate and decays specifically to the corresponding trans-
dicarbonyl complex 7b , as we have shown above.
P r ep a r a tion of [Mo2Cp 2(µ-H)(µ-P Et2)(CO)4] (1b). A tolu-
ene solution (25 mL) of [Mo2Cp2(CO)6] (0.300 g, 0.61 mmol)
and HPEt2 (83 µL, 0.71 mmol) was heated at 80 °C for 1 h 20
min. Then, a further 50 µL (0.43 mmol) of HPEt2 was added,
and heating was continued for 20 min. Solvent was then
removed under vacuum, the residue was dissolved in
a
minimum amount of toluene, and this solution was chromato-
graphed on alumina (activity IV). Elution with dichloromethane/
petroleum ether (1:3) gave an orange band. Removal of
solvents from the latter yielded compound 1b as an orange
microcrystalline solid (0.192 g, 61%). Anal. Calcd for C18H21O4-
PMo2 (1b): C, 41.23; H, 4.00. Found: C, 41.35; H, 3.95. 1H NMR
(28) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: Oxford, U.K., 1988.
(29) Manning, A. R.; Hackett, P.; Birdwhistell, R.; Soye, P. Inorg.
Synth. 1990, 28, 148.
(27) Stephan, D. W.; Ho, J . Inorg. Chem. 1994, 33, 4595.
(30) Curtis, M. D.; Hay, M. S. Inorg. Synth. 1990, 28, 152.

Mo2 and W2 Complexes with Phosphido Bridges
Organometallics, Vol. 21, No. 25, 2002 5523
(toluene-d8): δ 4.73 (s, 10H, Cp), 2.82 (m, 2H, CH2), 1.05 (dt,
J HP ) 16, J HH ) 7, 6H, CH3), 0.78 (m, 2H, CH2), -12.3 (d, J HP
purple band. Removal of solvents from the latter yielded
compound 3a as a purple microcrystalline solid (0.177 g, 60%).
Anal. Calcd for C35H54OP2Mo2 (3a ): C, 56.46; H, 7.26. Found:
C, 56.39; H, 7.21. 1H NMR: δ 5.57 (s, 10H, Cp), 1.90-1.10 (m,
44H, Cy). 13C{1H} NMR: δ 307.0 (t, J PC ) 7, µ-CO), 90.5 (s,
Cp), 44.4 (AA′X multiplet, J CP + J CP′ ) 15, C1(Cy)), 34.5, 30.8
(2 × s, 2 × C2(Cy)), 28.2(AA′X multiplet, J CP + J CP′ ) 10,
C3(Cy)), 27.8 (AA′X multiplet, J CP + J CP′ ) 11, C3(Cy)), 26.52,
26.46 (2 × s, 2 × C4(Cy)). The second resonance of the C1(Cy)
carbon atoms was obscured by that from the solvent.
P r ep a r a tion of [Mo2Cp 2(µ-P Et2)2(µ-CO)] (3b). [Mo2Cp2-
(CO)6] (0.300 g, 0.61 mmol) and HPEt2 (230 µL, 2.00 mmol)
were reacted for 3 h as described for 3a . After workup,
compound 3b was obtained as a purple microcrystalline solid
(0.275 g, 87%). Anal. Calcd for C19H30OP2Mo2 (3b): C, 43.19;
H, 5.68. Found: C, 42.95; H, 5.70. 1H NMR: δ 5.48 (s, 10H,
Cp), 1.82 (dq, J HP ) 16, J HH ) 8, 4H, CH2), 1.70 (m, 4H, CH2),
0.97 (dt, J HP ) 16, J HH ) 8, 6H, CH3), 0.46 (dt, J HP ) 19, J HH
) 8, 6H, CH3). 13C{1H} NMR: δ 298.0 (t, J PC ) 7, µ-CO), 90.0
(s, Cp), 36.8, 31.8 (2 × m, 2 × CH2), 13.3, 11.1 (2 × s, 2 ×
CH3).
) 35, 1H, µ-H). 13C{1H} NMR (toluene-d8): δ 243.5 (d, J CP
)
19, 2 × CO), 235.9 (s, 2 × CO), 90.3 (s, Cp), 28.8 (d, J CP ) 19,
CH2), 11.4 (d, J CP ) 5, CH3).
P r ep a r a tion of [Mo2Cp 2(µ-H)(µ-P CyH)(CO)4] (1c). The
procedure is completely analogous to that described for 1a .
By using [Mo2Cp2(CO)6] (0.35 g, 0.71 mmol) and H2PCy (96
µL, 0.71 mmol) (reaction time 1 h) compound 1c is obtained
as a yellow microcrystalline solid (0.325 g, 85%). Anal. Calcd
for C20H23O4PMo2 (1c): C, 43.65; H, 4.18. Found: C, 43.50;
H, 4.25. 1H NMR: δ 5.35 (dd, J PH ) 325, J HH ) 4, 1H, PH),
5.20 (s, 5H, Cp), 5.12 (s, 5H, Cp), 2.11-1.08 (m, 11H, Cy),
-12.4 (d, J HP ) 35, 1H, µ-H). 13C{1H} NMR: δ 242.8 (d, J PC
)
19, CO), 242.2 (d, J PC ) 20, CO), 237.1 (s, CO), 236.7 (s, CO),
90.6, 90.1 (2 × s, 2 × Cp), 42.8 (d, J PC ) 22, C1(Cy)), 36.3, 35.9
(2 × s, C2 and C6(Cy)), 27.9, 27.8 (2 × d, J PC ) 12.5, C3 and
C5(Cy)), 26.5 (s, C4(Cy)).
P r ep a r a tion of [W2Cp 2(µ-H)(µ-P Cy2)(CO)4] (2a ). A di-
glyme solution (30 mL) of [W2Cp2(CO)4] (ca. 0.75 mmol,
prepared in situ) and HPCy2 (155 µL, 0.766 mmol) was stirred
at room temperature for 16 h under a N2 purge to give a dark
orange mixture. Solvent was then removed under vacuum, the
residue was dissolved in a minimum amount of toluene, and
this solution was chromatographed on silica gel (Aldrich,
70-230 mesh). Elution with dichloromethane/petroleum
ether (2:5) gave an orange band. Removal of solvents from the
latter yielded compound 2a as an orange microcrystalline solid
(0.355 g, 58%). Anal. Calcd for C26H33O4PW2 (2a ): C, 38.63;
H, 4.08. Found: C, 38.93; H, 4.12. 1H NMR: δ 5.44 (s, 10H,
Cp), 2.70-0.89 (m, 22H, Cy), -16.40 (d, J HP ) 24, J HW ) 40,
1H, µ-H). 13C{1H} NMR: δ 232.2 (br, 2 × CO), 224.4 (br, 2 ×
CO), 88.0 (s, Cp), 39.2 (d, J PC ) 23, C1(Cy)), 30.8, 30.1 (2 × s,
br, C2 and C6(Cy)), 27.1, 26.5 (2 × s, br, C3 and C5(Cy)), 26.2
(s, C4(Cy)).
P r ep a r a tion of [W2Cp 2(µ-H)(µ-P Et2)(CO)4] (2b). The
procedure is analogous to that described for 2a , but with HPEt2
(90 µL, 0.785 mmol) instead and a reaction time of 5 h at 50
°C. After chromatography on silica, compound 2b was obtained
along with a small amount of [W2Cp2(CO)6]. Filtration of the
mixture through alumina (activity IV) and removal of solvents
under vacuum yielded compound 2b as a pure orange micro-
crystalline solid (0.320 g, 61%). Anal. Calcd for C18H21O4PW2
(2b): C, 30.87; H, 3.00. Found: C, 30.81; H, 3.01. 1H NMR: δ
5.30 (s, 10H, Cp), 3.07 (br, 2H, CH2), 1.04 (br, 2H, CH2), 1.32
P r ep a r a tion of [Mo2Cp 2(µ-P CyH)2(µ-CO)] (3c). [Mo2Cp2-
(CO)6] (0.150 g, 0.31 mmol) and H2PCy (100 µL, 0.75 mmol)
were reacted for 7.5 h as described for 3a . After workup
(elution with dichloromethane/petroleum ether (1:1)), com-
pound 3c was obtained as a blue greenish microcrystalline
solid (0.123 g, 69%). This material was shown by NMR to be
a mixture of two isomers (A and B, see text; ratio A:B ) 6:4).
Anal. Calcd for C23H34OP2Mo2 (3c): C, 47.60; H, 5.86. Found:
C, 47.45; H, 5.83. Isomer A: 1H NMR δ 7.33 (dd, J HP ) 334,
J HH ) 2, 2H, PH), 5.51 (s, 10H, Cp), 1.80-0.70 (m, 22H, Cy);
13C{1H} NMR δ 304.7 (t, J PC ) 7, µ-CO), 90.3 (s, Cp), 43.5
(AA′X multiplet, J CP+J CP′ ) 27, C1(Cy)), 32.8-25.2 (Cy). Isomer
B: 1H NMR δ 7.42 (dd, J HP ) 336, 2, 1H, PH), 7.22 (dd, J HP
)
326, 4, 1H, PH), 5.51 (s, 10H, Cp); 13C{1H} NMR δ 303.2 (t,
J PC ) 7, µ-CO), 90.0 (s, Cp), 45.9 (d, J CP ) 28, C1(Cy)), 44.0 (d,
J CP ) 26, C1(Cy)), 32.8-25.2 (Cy).
P r ep a r a tion of [W2Cp 2(µ-P Et2)2(µ-CO)] (4b). [W2Cp2-
(CO)6] (0.100 g, 0.150 mmol) and HPEt2 (45 µL, 0.39 mmol)
were reacted for 1 h 15 min as described for 3a . After workup,
compound 4b was isolated as a purple microcrystalline solid
(0.086 g, 82%). Anal. Calcd for C19H30OP2W2 (4b): C, 32.40;
H, 4.26. Found: C, 32.32; H, 4.19. 1H NMR: δ 5.31 (s, 10H,
Cp), 1.90 (m, 8H, CH2), 0.89 (dt, J HP ) 17, J HH ) 7, 6H, CH3),
0.41 (dt, J HP ) 18, J HH ) 8, 6H, CH3). 13C{1H} NMR: δ 305.0
(s, µ-CO), 88.8 (s, Cp), 46.2 (AA′X multiplet, J CP + J CP′ ) 23,
CH2), 33.7 (AA′X multiplet, J CP + J CP′ ) 25, CH2), 13.0, 9.1 (2
× s, 2 × CH3).
(dt, J PH ) 17, J HH ) 7, 6H, CH3), -14.93 (d, J HP ) 25, J HW
)
39, 1H, µ-H). 13C{1H} NMR: δ 233.8 (d, J PC ) 20, 2 × CO),
225.6 (s, 2 × CO), 89.6 (s, Cp), 28.1 (d, J PC ) 26, CH2), 12.2 (d,
J PC ) 4, CH3).
P r ep a r a tion of [W2Cp 2(µ-P P h 2)2(µ-CO)] (4d ). [W2Cp2-
(CO)6] (0.150 g, 0.225 mmol) and HPPh2 (78 µL, 0.45 mmol)
were reacted in tetrahydrofuran (25 mL) for 1 h 40 min as
described for 3a . After workup, compound 4d was isolated as
a purple microcrystalline solid (0.157 g, 78%). Anal. Calcd for
P r ep a r a tion of [W2Cp 2(µ-H)(µ-P P h 2)(CO)4] (2d ). The
procedure is completely analogous to that described for 2a .
[W2Cp2(CO)4] (ca. 2 mmol) in diglyme (40 mL) and HPPh2 (350
µL, 2.01 mmol), were reacted for 2 h at 60 °C under a N2 purge.
After workup, compound 2d was obtained as an orange
microcrystalline solid (0.996 g, 63%). Anal. Calcd for C26H21O4-
PW2 (2d ): C, 39.21; H, 2.64. Found: C, 39.30; H, 2.71. 1H
NMR: δ 7.90-7.10 (m, 10H, Ph), 5.00 (s, 10H, Cp), -14.83 (d,
J HP ) 27, J HW ) 39, 1H, µ-H). 13C{1H} NMR (233 K): δ 232.3
(d, J PC ) 17, 2 × CO), 224.2 (s, 2 × CO), 140.7 (d, J PC ) 44,
C1(Ph)), 133.0-126.0 (m, Ph), 90.1 (s, Cp).
P r ep a r a tion of [Mo2Cp 2(µ-P Cy2)2(µ-CO)] (3a ). A toluene
solution (30 mL) of [Mo2Cp2(CO)6] (0.200 g, 0.41 mmol) and
HPCy2 (260 µL, 1.28 mmol) was irradiated with UV-visible
light at 15 °C for 2 h 30 min while nitrogen was gently bubbled
through the solution, to give a black-green mixture. Solvent
was then removed under vacuum, the residue was dissolved
in a minimum amount of toluene, and this solution was
chromatographed on alumina (activity IV). Elution with
petroleum ether gave a yellow-green fraction containing
unidentified phosphorus side products, which were discarded.
Elution with dichloromethane/petroleum ether (2:1) gave a
C
35H30OP2W2 (4b): C, 46.89; H, 3.35. Found: C, 47.01; H, 3.24.
1H NMR: δ 7.80-6.55 (m, 20H, Ph), 5.80 (s, 10H, Cp). 13C-
{1H} NMR: δ 303.9 (s, µ-CO), 154.1 (d, J CP ) 42, C1(Ph)), 144.0
(d, J CP ) 48, C1(Ph)), 131.5-125.0 (m, Ph), 91.0 (s, Cp).
P r ep a r a tion of [Mo2Cp 2(µ-P Cy2)(µ-P CyH)(µ-CO)] (5e).
Compound 1a (0.090 g, 0.14 mmol) and H2PCy (20 µL, 0.15
mmol) were reacted for 40 min as described for 3a . After
workup, compound 5e was isolated as a purple microcrystalline
solid (0.078 g, 84%). Anal. Calcd for C29H44OP2Mo2 (5e): C,
52.58; H, 6.65. Found: C, 52.25; H, 6.53. This material was
shown by NMR to be a mixture of two isomers (D and E, see
text; ratio D:E ) 7:3). Pure isomer D could be isolated by
fractional crystallization of the mixture, thus allowing the
unequivocal assignment of NMR resonances. Isomer D: 1H
NMR δ 7.40 (ddd, J HP ) 333, 2, J HH ) 2, 1H, PH), 5.54 (s,
10H, Cp), 1.90-0.41 (m, 33H, Cy); 13C{1H} NMR δ 306.7 (s,
br, µ-CO), 91.0 (s, Cp), 46.0-26.5 (Cy). Isomer E: 1H NMR δ
6.88 (dd, J HP ) 322, 7, 1H, PH), 5.61 (s, 10H, Cp).

5524 Organometallics, Vol. 21, No. 25, 2002
Garc´ıa et al.
Found: C, 52.15; H, 4.93. H NMR: δ 7.11 (d, J HP ) 333, 1H,
P r ep a r a tion of [Mo2Cp 2(µ-P tBu 2)(µ-P CyH)(µ-CO)] (5f).
Compound 1c (0.035 g, 0.06 mmol) and HPtBu2 (15 µL, 0.08
mmol) were reacted for 1 h as described for 3a . After workup,
compound 5f was obtained as a purple solid (0.031 g, 81%).
Anal. Calcd for C25H40OP2Mo2 (5f): C, 49.19; H, 6.56. Found:
1
PH), 7.37-6.86 (m, 10H, Ph), 5.52 (s, 10H, Cp), 0.91 (d, J HP
)
16, 9H, CH3). 13C{1H} NMR: δ 304.1 (t, J CP ) 7, µ-CO), 151.2
(d, J CP ) 33, C1(Ph)), 144.2 (d, J CP ) 40, C1(Ph)), 138.4-127.3
(Ph), 91.9 (s, Cp), 37.0 (d, J CP ) 26, C1(tBu)), 31.3 (d, J CP ) 5,
CH3).
C, 48.98; H, 6.51. 1H NMR (toluene-d8): δ 7.15 (ddd, J HP
337, 4, J HH ) 1, 1H, PH), 5.53 (s, 10H, Cp), 1.74-0.55 (m, 11H,
)
P r ep a r a tion of [W2Cp 2(µ-P Cy2)(µ-P CyH)(µ-CO)] (6e).
Compound 2a (0.075 g, 0.093 mmol) and H2PCy (14 µL, 0.105
mmol) were reacted for 45 min as described for 3a . After
workup, compound 6e was obtained as a black-blue micro-
crystalline solid (0.060 g, 75%). Anal. Calcd for C29H44OP2W2
(6e): C, 41.54; H, 5.25. Found: C, 41.32; H, 5.21. This material
was shown by NMR to be a 7:3 mixture of two isomers (D and
E, respectively; see text). Isomer D: 1H NMR δ 9.14 (ddd, J HP
) 348, 3, J HH ) 1.6, 1H, PH), 5.77 (s, 10H, Cp), 1.80-0.31 (m,
33H, Cy); 13C{1H} NMR δ 307.5 (s, µ-CO), 90.7 (s, Cp), 49.2-
t
t
Cy), 0.93 (d, J HP ) 14, 9H, Bu), 0.77 (d, J HP ) 13, 9H, Bu).
13C{1H} NMR (benzene-d6): δ 297.8 (s, µ-CO), 90.1 (s, Cp), 44.2
(d, J CP ) 28, C1(Cy)), 43.6 (d, J CP ) 8, C1(tBu)), 43.0 (d, J CP
)
10, C1(tBu)), 33.4 (d, J CP ) 4, C2(tBu)), 32.7 (s, C2(Cy)), 32.1
(d, J CP ) 2, C2(tBu), 26.2 (d, J CP ) 13, C3(Cy)), 25.1 (s, C4(Cy)).
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P Cy2)(µ-CO)] (5g).
[Mo2Cp2(µ-H)(µ-PPh2)(CO)4] (0.100 g, 0.16 mmol) and HPCy2
(35 µL, 0.17 mmol) were reacted for 1 h as described for 3a .
After workup, compound 5g was obtained as a black micro-
crystalline powder (0.093 g, 79%). Anal. Calcd for C35H42OP2-
Mo2 (5g): C, 57.39; H, 5.74. Found: C, 57.23; H, 5.69. 1H
NMR: δ 7.31-6.62 (m, 10H, Ph), 5.58 (s, 10H, Cp), 2.00-0.40
(m, 22H, Cy). 13C{1H} NMR: δ 306.3 (t, J CP ) 7, µ-CO), 153.9
(d, J CP ) 31, C1(Ph)), 145.2 (d, J CP ) 40, C1(Ph)), 133.1-126.6
(Ph), 91.6 (s, Cp), 52.9 (d, J CP ) 17, C1(Cy)), 44.0 (d, J CP ) 13,
C1(Cy)), 34.3-26.0 (Cy).
26.4 (Cy). Isomer E: 1H NMR δ 8.61 (dd, J HP ) 341, 7, J HW
)
6, 1H, PH), 5.83 (s, 10H, Cp); 13C{1H} NMR δ 306.2 (s, µ-CO),
91.0 (s, Cp).
P r ep a r a tion of [W2Cp 2(µ-P P h 2)(µ-P Et2)(µ-CO)] (6h ).
Compound 1b (0.150 g, 0.242 mmol) and HPPh2 (112 µL, 0.644
mmol) were reacted for 1 h as described for 3a . After workup
(elution with dichloromethane), compound 6h was obtained
as a dark purple microcrystalline solid (0.225 g, 79%). Anal.
Calcd for C27H30OP2W2 (6h ): C, 40.52; H, 3.75. Found: C,
40.74; H, 3.74. 1H NMR: δ 7.35-7.06 (m, 10H, Ph), 5.76 (s,
10H, Cp), 1.98 (dq, J HP ) 11, J HH ) 8, 2H, CH2), 1.36 (dq, J HP
) 9, J HH ) 8, 2H, CH2), 0.59 (dt, J HP ) 17, J HH ) 8, 3H, CH3),
0.43 (dt, J HP ) 19, J HH ) 8, 3H, CH3). 13C{1H} NMR: δ 304.4
(s, J CW ) 133, µ-CO), 154.8 (d, J CP ) 40, C1(Ph)), 147.4 (d, J CP
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P Et2)(µ-CO)] (5h ).
Complex [Mo2Cp2(µ-H)(µ-PPh2)(CO)4] (0.150 g, 0.242 mmol)
and HPEt2 (56 µL, 0.49 mmol) were reacted for 45 min as
described for 3a . After workup, compound 5h was obtained
as a purple microcrystalline solid (0.125 g, 83%). Anal. Calcd
for C27H30OP2Mo2 (5h ): C, 51.93; H, 4.81. Found: C, 51.65; H,
1
4.90. H NMR: δ 7.27-6.68 (m, 10H, Ph), 5.53 (s, 10H, Cp),
) 46, C1(Ph)), 131.5-125.8 (Ph), 89.9 (s, Cp), 37.2 (d, J CP
26, CH2), 33.0 (d, J CP ) 24, CH2), 13.0 (s, CH3), 8.9 (d, J CP
5, CH3).
)
)
1.70 (dq, J HP ) 11, J HH ) 8, 2H, CH2), 1.23 (dq, J HP ) J HH
)
8, 2H, CH2), 0.66 (dt, J HP ) 17, J HH ) 8, 3H, CH3), 0.47 (dt,
J HP ) 19, J HH ) 8, 3H, CH3). 13C{1H} NMR: δ 304.9 (s, µ-CO),
153.0 (d, J CP ) 31, C1(Ph)), 145.8 (d, J CP ) 40, C1(Ph)), 132.3-
P r ep a r a tion of [Mo2Cp 2(µ-P Cy2)2(CO)2] (7a ). A toluene
solution (6 mL) of compound 3a (0.075 g, 0.100 mmol) was
placed in a Schlenk tube equipped with a Young valve and
was frozen by immersion into liquid N2. After vacuum evacu-
ation, CO was allowed to fill the tube, the valve was closed,
and the tube was allowed to reach room temperature. The
solution was then further stirred at 80 °C for 3 h to give a
dark green solution. Removal of solvents under vacuum and
washing of the residue with petroleum ether yielded compound
7a as a green powder (0.073 g, 93%). Anal. Calcd for C36H54O2P2-
Mo2 (7a ): C, 55.97; H, 7.00. Found: C, 55.76; H, 7.13. 1H
NMR: δ 5.37 (s, 10H, Cp), 2.01-0.78 (m, 44H, Cy).
126.9 (Ph), 91.5 (s, Cp), 34.6 (d, J CP ) 21, CH2), 31.6 (d, J CP
17, CH2), 13.2 (s, CH3), 10.0 (d, J CP ) 6, CH3).
)
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P CyH)(µ-CO)] (5i).
[Mo2Cp2(µ-H)(µ-PPh2)(CO)4] (0.125 g, 0.200 mmol) and H2PCy
(35 µL, 0.26 mmol) were reacted for 2 h 15 min as described
for 3a . After workup, compound 5i was obtained as a purple
solid (0.085 g, 65%). A small amount of [Mo2Cp2(µ-PPh2)2(µ-
CO)] can be also separated in the chromatography. Anal. Calcd
for C29H32OP2Mo2 (5h ): C, 53.55; H, 4.92. Found: C, 53.33; H,
1
5.01. H NMR: δ 7.51-6.59 (m, 10H, Ph), 7.01 (d, br, J HP
)
339, 1H, PH), 5.51 (s, 10H, Cp), 2.05-0.59 (m, 11H, Cy). 13C-
{1H} NMR: δ 304.4 (t, J CP ) 7, µ-CO), 151.1 (d, J CP ) 33,
C1(Ph)), 144.4 (d, J CP ) 40, C1(Ph)), 138.4-127.7 (Ph), 91.9 (s,
P r ep a r a tion of [Mo2Cp 2(µ-P Et2)2(CO)2] (7b). Compound
3b (0.100 g, 0.190 mmol) was reacted with CO for 1 h 10 min
at room temperature as described for 7a . After workup,
compound 7b was obtained as a brown-green solid (0.095 g,
90%). Anal. Calcd for C20H30O2P2Mo2 (7b): C, 43.17; H, 5.40.
Cp), 44.6 (d, J CP ) 26, C1(Cy)), 34.1 (s, C2(Cy)), 27.6 (d, J CP
)
13, C3(Cy)), 26.5 (s, C4(Cy)).
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P tBu 2)(µ-CO)] (5j).
[Mo2Cp2(µ-H)(µ-PtBu2)(CO)4] (0.070 g, 0.120 mmol) and HPPh2
(21 µL, 0.12 mmol) were reacted for 45 min as described for
3a . After workup, compound 5j was obtained as a red solid
(0.085 g, 65%). A small amount of [Mo2Cp2(µ-PPh2)2(µ-CO)] can
be also separated in the chromatography. Anal. Calcd for
1
Found: C, 43.34; H, 5.49. H NMR: δ 5.21 (s, 10H, Cp), 2.66
(m, 4H, CH2), 1.42 (m, 4H, CH2), 1.28 (dt, J HP ) 16, J HH ) 7,
12H, CH3). 13C{1H} NMR: δ 237.3 (t, J CP ) 13, CO), 86.4 (s,
Cp), 25.5 (AA′X multiplet, J CP + J CP′ ) 21, CH2), 12.1 (s, CH3).
P r ep a r a tion of [Mo2Cp 2(µ-P CyH)2(CO)2] (7c). [Mo2Cp2-
(CO)6] (0.150 g, 0.310 mmol) and H2PCy (100 µL, 0.75 mmol)
were reacted for 1 h 15 min as described for 3a . After workup
(elution with dichloromethane/petroleum ether (1:3)) com-
pound 7c was obtained as a dark green solid (0.158 g, 84%).
This material was shown by NMR to be a 6:4 mixture of two
isomers (syn and anti; see text). The anti isomer could be
separated by fractional crystallization from toluene/petroleum
ether. Anal. Calcd for C24H34O2P2Mo2 (7c): C, 47.38; H, 5.59.
Found: C, 47.35; H, 5.61. Anti isomer: 1H NMR (benzene-d6)
δ 5.55 (dd, J HP ) 336, 6, 1H, PH), 5.19 (s, 10H, Cp), 2.45-
1.20 (m, 22H, Cy); 13C{1H} NMR δ 236.4 (s, CO), 88.3 (s, Cp),
42.5 (d, J CP ) 29, C1(Cy)), 36.0, 35.3 (2 × s, C2(Cy) and C6(Cy)),
28.0, 27.9 (2 × d, J CP ) 10, C3(Cy) and C5(Cy)), 26.6 (s, C4(Cy)).
P r ep a r a tion of [W2Cp 2(µ-P Et2)2(CO)2] (8b). Complex 4b
(0.086 g, 0.122 mmol) was reacted with CO for 10 min at room
temperature as described for 7a . After workup, compound 8b
C
31H38OP2Mo2 (5j): C, 55.69; H, 5.59. Found: C, 55.39; H, 5.55.
1H NMR: δ 7.35-6.45 (m, 10H, Ph), 5.69 (s, 10H, Cp), 0.82
(d, J HP ) 14, 9H, Bu), 0.66 (d, J HP ) 14, 9H, Bu). 13C{1H}
NMR: δ 306.2 (t, J CP ) 7, µ-CO), 155.3 (d, J CP ) 33, C1(Ph)),
143.7 (d, J CP ) 37, C1(Ph)), 133.4-126.4 (Ph), 92.8 (s, Cp), 45.4
t
t
(d, J CP ) 10, C1(tBu)), 41.9 (d, J CP ) 8, C1(tBu)), 34.7 (d, J CP
3, CH3)), 33.4 (d, J CP ) 5, CH3).
)
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P tBu H)(µ-CO)] (5k ).
[Mo2Cp2(µ-H)(µ-PPh2)(CO)4] (0.200 g, 0.320 mmol) and
HPtBu2 (90 µL, 0.49 mmol) were reacted for 3 h as described
for 3a . Column chromatography of the reaction mixture with
1:1, 2:1, and 3:1 dichloromethane/petroleum ether mixtures
gave fractions containing [Mo2Cp2(µ-PPh2)2(µ-CO)), compound
5k , and compound 5j, respectively. Removal of solvents from
the second band yielded complex 5k as a black solid (0.055 g,
28%). Anal. Calcd for C27H30OP2Mo2 (5k ): C, 51.93; H, 4.81.

Mo2 and W2 Complexes with Phosphido Bridges
Organometallics, Vol. 21, No. 25, 2002 5525
was obtained as a green solid (0.081 g, 90%). Anal. Calcd for
11 along with some 9j and unreacted 5j. Compound 9j: 1H
NMR δ 7.55-7.15 (m, 10H, Ph), 5.35 (s, 10H, Cp), 1.35 (d, J HP
) 13, 18H, CH3). Compound 11: 1H NMR δ 7.55-7.05 (m, 10H,
Ph), 5.13 (s, 10H, Cp), 1.47 (d, J HP ) 14, 9H, CH3), 1.06 (d,
J HP ) 13, 9H, CH3); 13C{1H} NMR δ 248.7 (t, J CP ) 7, 2 ×
CO), 155.2 (d, J CP ) 33, C1(Ph)), 153.6 (d, J CP ) 27, C1(Ph)),
135.1-125.6 (Ph), 86.0 (s, Cp), 42.7 (d, J CP ) 17, C1(tBu)), 40.9
(d, J CP ) 10, C1(tBu)), 35.2 (d, J CP ) 5, CH3), 34.0 (d, J CP ) 4,
CH3).
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P tBu H)(CO)2] (9k ).
Complex 5k (0.055 g, 0.088 mmol) was reacted with CO for
10 min at room temperature as described for 7a . After workup,
compound 9k was obtained as a gray-green solid (0.051 g,
89%). Anal. Calcd for C28H30O2P2Mo2 (9k ): C, 51.54; H, 4.60.
Found: C, 51.50; H, 4.65. 1H NMR: δ 7.75-7.05 (m, 10H, Ph),
5.73 (br, d, J HP ) 336, 1H, PH), 5.45, 5.35 (2 × s, 2 × 5H, 2 ×
Cp), 1.43 (d, J HP ) 16, 9H, CH3). 13C{1H} NMR: δ 132.8-126.3
(Ph), 87.9, 87.6 (2 × s, 2 × Cp), 33.7 (d, J CP ) 36, C1(tBu)),
31.1 (d, J CP ) 5, CH3).
C
20H30O2P2W2 (8b): C, 32.80; H, 4.10. Found: C, 32.90; H, 4.15.
1H NMR: δ 5.31 (s, 10H, Cp), 2.80 (m, 4H, CH2), 1.37 (m, 16H,
CH2 and CH3). 13C{1H} NMR: δ 228.2 (t, J CP ) 4, CO), 85.1
(s, Cp), 29.2 (AA′X multiplet, J CP + J CP′ ) 30, CH2), 13.5 (s,
CH3).
P r ep a r a tion of [W2Cp 2(µ-P P h 2)2(CO)2] (8d ). Complex 4d
(0.090 g, 0.100 mmol) was reacted with CO for 10 min at room
temperature as described for 7a . After workup, compound 8d
was obtained as a green solid (0.075 g, 81%). Anal. Calcd for
C36H30O2P2W2 (8d ): C, 46.77; H, 3.25. Found: C, 46.66; H, 3.19.
1H NMR: δ 7.80-7.15 (m, 20H, Ph), 5.43 (s, 10H, Cp).
P r ep a r a tion of [Mo2Cp 2(µ-P Cy2)(µ-P CyH)(CO)2] (9e).
Complex 5e (0.080 g, 0.120 mmol) was reacted with CO for 45
min at room temperature as described for 7a . After workup,
compound 9e was obtained as a microcrystalline green powder
(0.065 g, 79%). Anal. Calcd for C30H44O2P2Mo2 (9e): C, 52.18;
1
H, 6.38. Found: C, 52.25; H, 6.33. H NMR: δ 5.40, 5.35 (2 ×
s, 2 × 5H, 2 × Cp), 5.03 (ddd, J HP ) 339, 6, J HH ) 2, 1H, PH),
2.51-1.08 (m, 33H, Cy). 13C{1H} NMR: δ 238.0 (t, J CP ) 12,
CO), 237.4 (t, J CP ) 15, CO), 88.2 (s, Cp), 88.0 (s, Cp), 45.7-
26.7 (Cy).
P r ep a r a tion of [W2Cp 2(µ-P Cy2)(µ-P CyH)(CO)2] (10e).
Complex 6e (0.060 g, 0.072 mmol) was reacted with CO for 18
h at room temperature as described for 7a . After workup,
compound 10e was obtained as a gray-green solid (0.047 g,
76%). Anal. Calcd for C30H44O2P2W2 (10e): C, 41.58; H, 5.08.
P r ep a r a tion of [Mo2Cp 2(µ-P tBu 2)(µ-P CyH)(CO)2] (9f).
Complex 5f (0.035 g, 0.06 mmol) was reacted with CO for 1.5
h at 60 °C as described for 7a . After workup, compound 9f
was obtained as a green solid (0.031 g, 86%). Anal. Calcd for
C26H40O2P2Mo2 (9f): C, 48.91; H, 6.27. Found: C, 48.75; H, 6.22.
1
Found: C, 41.65; H, 5.15. H NMR: δ 6.33 (d, J HP ) 353, 1H,
PH), 5.43, 5.39 (2 × s, 2 × 5H, 2 × Cp), 2.41-1.05 (m, 33H,
Cy). 13C{1H} NMR: δ 225.3 (t, J CP ) 5, CO), 224.6 (s, br, CO),
84.6, 84.4 (2 × s, 2 × Cp), 46.8 (d, J CP ) 26, C1(Cy)), 45.9 (d,
J CP ) 27, C1(Cy)), 42.5 (d, J CP ) 35, C1(Cy)), 34.6-25.5 (Cy).
P r ep a r a t ion of [W2Cp 2(µ-P P h 2)(µ-P E t 2)(CO)2] (10h ).
Complex 6h (0.200 g, 0.250 mmol) was reacted with CO at
room temperature for 3 h as described for 7a . After workup,
compound 10h was isolated as a gray-green solid (0.165 g,
80%). Anal. Calcd for C28H30O2P2W2 (10h ): C, 40.84; H, 3.62.
Found: C, 40.62; H, 3.59. 1H NMR: δ 7.58-7.10 (m, 10H, Ph),
5.34 (s, 10H, Cp), 2.85 (m, 2H, CH2), 1.52 (m, 2H, CH2), 1.40
(dt, J HP ) 14, J HH ) 7, 6H, CH3). 13C{1H} NMR: δ 225.3 (t,
J CP ) 4, J CW ) 196, CO), 148.1 (d, J CP ) 46, C1(Ph)), 133.1 (d,
J CP ) 10, C2(Ph)), 126.6 (d, J CP ) 10, C3(Ph)), 126.4 (s, C4(Ph)),
85.0 (s, Cp), 27.6 (d, J CP ) 29, CH2), 12.1 (d, J CP ) 5, CH3).
P r ep a r a tion of [Mo2Cp 2(µ-P Et2)2(CO)3] (12). Complex 3b
(0.100 g, 0.190 mmol) was reacted with CO at -50 °C for 15
min as described for 7a , but using CD2Cl2 (1 mL) as solvent.
The resulting red solution was shown by NMR to contain
compounds 12 and 7b as major species. Complex 12, however,
transforms readily into the dicarbonyl 7b, the transformation
being complete in ca. 1 h at room temperature. 1H NMR: δ
5.01, 4.96 (2 × s, 2 × 5H, Cp), 2.44, 1.82 (2 × m, 2 × 4H, CH2),
1.40, 0.98 (2 × m, 2 × 6H, CH3). 13C{1H} NMR (193 K): δ
241.2 (s, br, CO), 237.9 (s, br, 2 × CO), 88.0, 87.5 (2 × s, 2 ×
Cp), 29.5 (d, J CP ) 9, CH2), 27.1 (s, CH2), 12.0 (CH3).
1H NMR: δ 5.40, 5.32 (2 × s, 2 × 5H, 2 × Cp), 1.30 (d, J HP
)
13, 9H, CH3), 1.27 (d, J HP ) 14, 9H, CH3), 2.30-1.20 (m, 11H,
Cy).
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P Cy2)(CO)2] (9g).
Complex 5g (0.075 g, 0.102 mmol) was reacted with CO for 45
min at 50 °C as described for 7a . After workup, compound 9g
was obtained as a green solid (0.072 g, 95%). Anal. Calcd for
C
36H42O2P2Mo2 (9g): C, 56.85; H, 5.53. Found: C, 56.64; H,
1
5.58. H NMR: δ 7.65-7.18 (m, 10H, Ph), 5.38 (s, 10H, Cp),
2.00-1.05 (m, 22H, Cy).
P r ep a r a t ion of [Mo2Cp 2(µ-P P h 2)(µ-P E t 2)(CO)2] (9h ).
Complex 5h (0.040 g, 0.064 mmol) was reacted with CO for
30 min at room temperature as described for 7a . After workup,
compound 9h was isolated as a black-green solid (0.038 g,
90%). Anal. Calcd for C28H30O2P2Mo2 (9h ): C, 51.54; H, 4.60.
Found: C, 51.69; H, 4.69. 1H NMR: δ 7.57-7.05 (m, 10H, Ph),
5.25 (s, 10H, Cp), 2.73, 1.57 (2 × m, 2 × 2H, 2 × CH2), 1.35
(m, 6H, CH3).
P r ep a r a t ion of [Mo2Cp 2(µ-P P h 2)(µ-P CyH )(CO)2] (9i).
Complex 5i (0.090 g, 0.138 mmol) was reacted with CO for 5
min at room temperature as described for 7a . After workup,
compound 9i was obtained as a green solid (0.082 g, 88%).
Anal. Calcd for C30H32O2P2Mo2 (9i): C, 53.11; H, 4.72. Found:
1
C, 52.98; H, 4.63. H NMR: δ 7.75-7.10 (m, 10H, Ph), 5.39,
5.31 (2 × s, 2 × 5H, 2 × Cp), 5.36 (d, br, J HP ) 339, 1H, PH),
2.01-0.83 (m, 11H, Cy).
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 for
a grant to D.S. We also thank the FICYT of Asturias
for a grant to M.T.R.
P r ep a r a tion of [Mo2Cp 2(µ-P P h 2)(µ-P tBu 2)(CO)2] (9j and
11). Complex 5j (0.050 g, 0.073 mmol) was reacted with CO
for 8 h 30 min at 80 °C as described for 7a . After workup,
compound 9j was isolated as a gray-green solid (0.038 g, 76%).
Anal. Calcd for C32H38O2P2Mo2 (9j): C, 54.25; H, 5.37. Found:
C, 54.39; H, 5.29. If the above carbonylation is carried out for
3 h 30 min, the reaction mixture then contains the cis isomer
OM020573F