Chemistry of unsaturated group 6 metal complexes with bridging hydroxy and methoxycarbyne ligands. 4. Carbonyl, isocyanide, and diphosphine derivatives of the complexes [M2(η5-C5H5) 2(μ-COMe)(μ-PR2)2]BF4 (M = W, R = Ph; M = Mo, R = Et)

Article abstract of DOI:10.1021/om8002152

The unsaturated complexes [M₂Cp₂(M-COMe)(μ-PR ₂)₂]BF₄ [M = W, R = Ph (1a); M = Mo, R = Et (1b); Cp = η⁵-C₅H₅] react with CO under pressure [ca. 4 atm (1a) or ca. 60 atm (1b)] to give the corresponding electron-precise dicarbonyl derivatives [M₂Cp₂(-COMe) (μ-PR₂)₂(CO)₂]BF₄, which display a parallel arrangement of the carbonyl ligands (W-W = 2.9020(5) A for the ditungsten complex). The reactions with CN^tBu take place rapidly at room temperature to give analogously the corresponding derivatives with parallel isocyanide ligands, cis-[M₂Cp₂(μ-COMe)(μ-PR ₂)₂(CN^tBu)₂]BF₄. At low temperature, however, a less stable isomer can be detected, which in the ditungsten system is identified as the isomer having a transoid arrangement of isocyanide groups, trans-[M₂Cp₂(μ-COMe)(M-PR ₂)₂(CN^tBu)₂]BF₄, while for the dimolydenum system that isomer is identified as the ketenylimine complex [Mo₂Cp₂{μ-η¹:η¹-C(OMe) C(N^tBu)}(μ-PEt₂)₂(CN^tBu)]BF ₄, a product resulting from the C-C coupling between carbyne and isocyanide ligands; these products rearrange slowly at room temperature to yield the corresponding and more stable cis isomers. The reactions of compounds 1a,b with the diphosphine Me₂PCH₂PMe₂ (dmpm) yield analogously addition derivatives of formula [M₂Cp₂(μ- COMe)(μ-PR₂)₂(μ-dmpm)]BF₄, with the diphosphine ligand being placed preferentially either trans to the carbyne or trans to a diphenylphosphide bridge depending on the experimental conditions. The structure of the first isomer was confirmed through an X-ray study on the ditungsten complex (W-W = 2.917(1) A). Diazoalkanes N ₂CRR′ (R = H, R′ = SiMe₃; R = R' = Ph) react with the ditungsten carbyne complex la without loss of dinitrogen nor coupling to the methoxycarbyne ligand to yield, after spontaneous demethylation of the latter, the neutral diazoalkane complexes [W₂Cp₂(μ- PPh₂)₂(κ¹-N₂CRR′)(CO)]. Carbonylation of the isocyanide complex cis-[W₂Cp₂(μ- COMe)(μ-PPh₂)₂(CN^tBu)₂]BF ₄ does not induce any coupling process but just partial substitution to give the carbonyl isocyanide derivative cis-[W₂Cp ₂(M-COMe)(μ-PPh₂)₂(CO)(CN ^tBu)]BF₄, whereas its reduction with sodium amalgam induces an N-C(^tBu) bond cleavage, yielding the cyanide derivative cis-[W₂Cp₂(μ-COMe)(μ-PPh₂) ₂(CN)(CN^tBu)]. The latter complex can be methylated with [Me₃O]BF₄ to give the methylisocyanide derivative Cis-[W₂Cp₂(M-COMe)(μ-PPh₂) ₂(CN^tMe)(CN^tBu)]BF₄, and this reduction/methylation sequence can be repeated once more to give the bis(isocyanide) complex cis-[W₂Cp₂(μ-COMe)(μ- PPh₂)₂(CNMe)₂]BF₄ via the corresponding cyanide intermediate.

Full text of DOI:10.1021/om8002152

Organometallics 2008, 27, 3879–3891
3879
Chemistry of Unsaturated Group 6 Metal Complexes with Bridging
Hydroxy and Methoxycarbyne Ligands. 4. Carbonyl, Isocyanide,
and Diphosphine Derivatives of the Complexes
[M2(η5-C5H5)2(µ-COMe)(µ-PR2)2]BF4 (M ) W, R ) Ph;
M ) Mo, R ) Et)
M. Esther Garc´ıa,† Daniel Garc´ıa-Vivo´,† Miguel A. Ruiz,*,† and Patrick Herson‡
Departamento de Qu´ımica Orga´nica e Inorga´nica/IUQOEM, UniVersidad de OViedo,
E-33071 OViedo, Spain, and Laboratoire de Chimie Inorganique et Materiaux Moleculaires,
UniVersite´ Pierre et Marie Curie, 75252 Paris, Cedex 05, France
ReceiVed March 7, 2008
The unsaturated complexes [M2Cp2(µ-COMe)(µ-PR2)2]BF4 [M ) W, R ) Ph (1a); M ) Mo, R ) Et
(1b); Cp ) η5-C5H5] react with CO under pressure [ca. 4 atm (1a) or ca. 60 atm (1b)] to give the
corresponding electron-precise dicarbonyl derivatives [M2Cp2(µ-COMe)(µ-PR2)2(CO)2]BF4, which display
a parallel arrangement of the carbonyl ligands (W-W ) 2.9020(5) Å for the ditungsten complex). The
reactions with CNtBu take place rapidly at room temperature to give analogously the corresponding
derivatives with parallel isocyanide ligands, cis-[M2Cp2(µ-COMe)(µ-PR2)2(CNtBu)2]BF4. At low tem-
perature, however, a less stable isomer can be detected, which in the ditungsten system is identified as
the isomer having a transoid arrangement of isocyanide groups, trans-[M2Cp2(µ-COMe)(µ-
PR2)2(CNtBu)2]BF4, while for the dimolydenum system that isomer is identified as the ketenylimine
complex [Mo2Cp2{µ-η1:η1-C(OMe)C(NtBu)}(µ-PEt2)2(CNtBu)]BF4, a product resulting from the C-C
coupling between carbyne and isocyanide ligands; these products rearrange slowly at room temperature
to yield the corresponding and more stable cis isomers. The reactions of compounds 1a,b with the
diphosphine Me2PCH2PMe2 (dmpm) yield analogously addition derivatives of formula [M2Cp2(µ-
COMe)(µ-PR2)2(µ-dmpm)]BF4, with the diphosphine ligand being placed preferentially either trans to
the carbyne or trans to a diphenylphosphide bridge depending on the experimental conditions. The structure
of the first isomer was confirmed through an X-ray study on the ditungsten complex (W-W ) 2.917(1)
Å). Diazoalkanes N2CRR′ (R ) H, R′ ) SiMe3; R ) R′ ) Ph) react with the ditungsten carbyne complex
1a without loss of dinitrogen nor coupling to the methoxycarbyne ligand to yield, after spontaneous
demethylation of the latter, the neutral diazoalkane complexes [W2Cp2(µ-PPh2)2(κ1-N2CRR′)(CO)].
Carbonylation of the isocyanide complex cis-[W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4 does not induce
any coupling process but just partial substitution to give the carbonyl isocyanide derivative cis-[W2Cp2(µ-
COMe)(µ-PPh2)2(CO)(CNtBu)]BF4, whereas its reduction with sodium amalgam induces an N-C(tBu)
bond cleavage, yielding the cyanide derivative cis-[W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNtBu)]. The latter
complex can be methylated with [Me3O]BF4 to give the methylisocyanide derivative cis-[W2Cp2(µ-
COMe)(µ-PPh2)2(CNMe)(CNtBu)]BF4, and this reduction/methylation sequence can be repeated once
more to give the bis(isocyanide) complex cis-[W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)2]BF4 via the corre-
sponding cyanide intermediate.
centers, and it is on these substrates that the reactivity of the
alkoxycarbyne ligand has been mostly investigated.2 Thus,
complexes 1a,b are attractive substrates to study the reactivity
Introduction
Recently we reported the synthesis of the 30-electron
complexes [M2Cp2(µ-COMe)(µ-PR2)2]BF4 [M ) W, R ) Ph
(1a); M ) Mo, R ) Et (1b); Cp ) η5-C5H5] (Chart 1), with a
methoxycarbyne ligand bridging a triple metal-metal bond.1
This is an unusual situation, since most of the alkoxycarbyne
(COR) complexes described so far contain the COR ligand
acting as a bridging group (in a µ2 or µ3 fashion) over single
metal-metal bonds at electron-precise di- or trinuclear metal
(2) (a) Hersh, W. H.; Fong, R. H. Organometallics 2005, 24, 4179. (b)
Peters, J. C.; Odon, A. L.; Cummins, C. C. Chem. Commun. 1997, 1995.
(c) Bronk, B. S.; Protasiewicz, J. D.; Pence, L. E.; Lippard, S. J.
Organometallics 1995, 14, 2177. (d) Seyferth, D.; Ruschke, D. P.; Davis,
W. H. Organometallics 1994, 13, 4695. (e) Chi, Y.; Chuang, S. H.; Chen,
B.-F.; Peng, S.-M; Lee, G.-H J. Chem. Soc., Dalton Trans. 1990, 3033. (f)
Friedman, A. E.; Ford, P. C. J. Am. Chem. Soc. 1989, 111, 551. (g) Keister,
J. B. Polyhedron 1988, 7, 847. (h) Friedman, A. E.; Ford, P. C. J. Am.
Chem. Soc. 1986, 108, 7851. (i) Farrugia, L. J.; Miles, A. D.; Stone, F. G. A.
J. Chem. Soc., Dalton Trans. 1985, 2437. (j) Beanan, L. R.; Keister, J. B.
Organometallics 1985, 4, 1713. (k) Nuel, D.; Dahan, F.; Mathieu, R. J. Am.
Chem. Soc. 1985, 107, 1658. (l) Shapley, J. R.; Yeh, W.-Y.; Churchill,
M. R.; Li, Y.-J Organometallics 1985, 4, 1898. (m) Green, M.; Mead, K. A.;
Mills, R. M.; Salter, I. D.; Stone, F. G. A.; Woodward, P. J. J. Chem. Soc.,
Chem. Commun. 1982, 51.
* To whom correspondence should be addressed. E-mail: mara@
uniovi.es.
† Universidad de Oviedo.
‡ Universite´ Pierre et Marie Curie.
(1) Garc´ıa, M. E.; Garc´ıa-Vivo´, D.; Ruiz, M. A.; Aullo´n, G.; Alvarez,
S. Organometallics 2007, 26, 4930.
10.1021/om8002152 CCC: $40.75
2008 American Chemical Society
Publication on Web 07/02/2008

3880 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
Chart 1
Chart 2
of the alkoxycarbyne ligand at unsaturated binuclear centers and
to explore the unusual transformations that might be induced
or allowed by the coexistence of different multiple bonds
(metal-metal and metal-carbon bonds) in the same molecule.
In this respect, our recent study on the reactivity of the
isoelectronic bis(alkoxycarbyne) complexes [Mo2Cp2(µ-COMe)(µ-
COR)(µ-PCy2)]+ (R ) Me, Et) revealed some unusual trans-
formations, most remarkably the occurrence of reversible C-C
coupling between both alkoxycarbyne ligands induced by the
uptake/release of simple ligands such as CO, isocyanides, or
diphoshines.3 We thus decided to examine the possibility of
coupling the methoxycarbyne group to these simple ligands by
using isoelectronic substrates having just one alkoxycarbyne
group. In this paper we report our study on the reactions of the
unsaturated cations 1a,b toward CO, CNtBu, and some diphos-
phines and diazoalkanes. As it will be seen, most of these
reactions led to the coordination of the added ligand, as expected
for an organometallic complex having a triple intermetallic bond,
but coupling to the methoxycarbyne group was observed in only
one case. Since C-C coupling between carbyne ligands might
be also induced by electron uptake,4 we then examined the
reduction reactions of some of the new isocyanide derivatives
synthesized. This led to no coupling to the carbyne ligand either,
but unexpectedly to selective C-N bond cleavage processes,
these rendering the corresponding cyanide derivatives in high
yield.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for compound
2a
W(1)-W(2)
W(1)-C(1)
2.9020(5)
2.021(1)
2.023(1)
2.001(9)
2.02(1)
C(1)-W(1)-C(100)
C(2)-W(2)-C(100)
C(1)-W(1)-W(2)
131.8(4)
131.2(4)
88.0(3)
88.0(3)
84.5(3)
84.1(3)
85.5(3)
83.1(3)
70.7(3)
65.0(3)
71.0(3)
65.1(3)
145.7(8)
121.8(7)
122.2(1)
W(2)-C(2)
W(1)-C(100)
W(2)-C(100)
C(100)-O(100)
O(100)-C(101)
W(1)-P(12)
W(1)-P(21)
W(2)-P(12)
W(2)-P(21)
C(2)-W(2)-W(1)
P(12)-W(1)-C(1)
P(21)-W(1)-C(1)
P(12)-W(2)-C(2)
P(21)-W(2)-C(2)
P(12)-W(2)-C(100)
P(21)-W(2)-C(100)
P(12)-W(1)-C(100)
P(21)-W(1)-C(100)
W(1)-C(100)-O(100)
W(2)-C(100)-O(100)
C(100)-O(100)-C(101)
1.407(8)
1.431(9)
2.429(2)
2.459(3)
2.428(3)
2.451(3)
Results and Discussion
displays two WCp(CO) fragments in a cisoid arrangement
bridged by three groups, one methoxycarbyne and two diphe-
nylphosphide ligands, with the P and Mo atoms placed almost
in the same plane, while the carbyne ligand is placed trans to
the carbonyl ligands, the latter being almost parallel to each
other. The structure is thus comparable to those determined
recently for the unsaturated hydride complexes [W2Cp2(µ-H)(µ-
Carbonylation of Compounds 1a,b. As expected for orga-
nometallic complexes having multiple metal-metal bonds,5
compounds 1a,b react with CO to give the corresponding
addition products. Thus, the overnight stirring of solutions of
these complexes under CO pressure [ca. 4 atm (1a) or ca. 60
atm (1b)] gives the corresponding electron-precise dicarbonyl
derivatives [M2Cp2(µ-COMe)(µ-PR2)2(CO)2]BF4 (2a,b) (Chart
2). However, while the reaction of compound 1a cleanly affords
complex 2a, the carbonylation of 1b showed lower selectivity
and gave compound 2b only as the major component of a
complex mixture that could not be purified. Despite this, the
spectroscopic data obtained from these mixtures were informa-
tive enough to give full support to the proposed structure for
the major product. The dicarbonyls 2a,b are unstable com-
pounds, which progressively decompose upon manipulation. In
fact, complex 2a is unstable in donor solvents such as THF or
even dichloromethane/toluene mixtures, to yield complex
mixtures of products that could not be separated or identified.
Solid-State and Solution Structure of Compounds 2. The
structure of compound 2a was confirmed through a single-crystal
X-ray diffraction study (Table 1 and Figure 1). The cation
(3) Garc´ıa, M. E.; Garc´ıa-Vivo´, D.; Ruiz, M. A. Organometallics 2008,
27, 543.
(4) Okazaki, M.; Ohtani, T.; Ogino, H. J. Am. Chem. Soc. 2004, 126,
4104.
(5) (a) Collman, J. P.; Boulatov, R. Angew. Chem., Int. Ed. 2002, 41,
3948. (b) Winter, M. J. AdV. Organomet. Chem. 1989, 29, 101. (c) Curtis,
M. D. Polyhedron 1987, 6, 759. (d) Cotton, F. A.; Walton, R. A. Multiple
Bonds Between Metal Atoms, 2nd ed.; Oxford University Press: Oxford,
1993.
Figure 1. ORTEP diagram (30% probability) of the cation in
compound 2a, with H atoms and Ph rings (except the C1 atoms)
omitted for clarity.

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3881
Table 2. Selected IRa and NMRb Data for Carbonyl and Isocyanide Complexes
ν(CX)
δ(P) [JPW
]
δ(µ-COMe) [JCP]
[W2Cp2(µ-COMe)(µ-PPh2)2(CO)2]BF4 (2a)
[Mo2Cp2(µ-COMe)(µ-PEt2)2(CO)2]BF4 (2b)
[W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4 (cis-3a)
[W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4 (trans-3a)
[Mo2Cp2(µ-COMe)(µ-PEt2)2(CNtBu)2]BF4 (cis-3b)
[Mo2Cp2{µ-κ1:κ1-C(OMe)C(NtBu)}
2009 (vs), 1962 (w)
1998 (vs)c
2123 (vs), 2100 (w, sh)
2101 (vs)
2118 (vs), 2098 (w, sh)
2097 (vs)
-50.2 [217]
13.4
-15.4 [229]
-22.4 [264, 200]
47.5
132.5
383.8[40]d
375.9
410.5 [54]
239.5 [15]
(µ-PEt2)2(CNtBu)]BF4 (4)
[W2Cp2(µ-PPh2)2{κ1-N2CH(SiMe3)}(CO)] (7)
[W2Cp2(µ-PPh2)2(κ1-N2CPh2)(CO)] (8)
1800 (vs)e
107.3 [380, 318]
109.7 [380, 319]
-31.6 [224, 229]f
-0.3 [234]
1795 (vs)e
[W2Cp2(µ-COMe)(µ-PPh2)2(CO)(CNtBu)]BF4 (9)
[W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNtBu)] (10)
[W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)(CNtBu)]BF4 (11)
[W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNMe)] (12)
[W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)2]BF4 (13)
2153 (s, CN), 1955 (vs, CO)
2133 (vs), 2094 (w)
2137 (vs), 2109 (m)
2152 (vs), 2091 (w)
2163(vs), 2141(w, sh)
377.9 [41]
380.9 [39]
-16.2 [229]
-1.4 [232]
-15.7 [227]
385 [40]
a Recorded in dichloromethane solution, ν(CX) in cm-1 (X ) O, N) for carbonyl, isocyanide, and cyanide ligands. b Recorded in CD2Cl2 solutions at
290 K and 121.50 (31P) or 75.48 (13C) MHz, unless otherwise stated; δ in ppm relative to internal TMS (13C) or external 85% aqueous H3PO4
(
31P), J
d
in Hz. c The expected weak band at lower frequency could not be identified unambiguously in the IR spectra of the crude product. JCW ) 64 Hz.
e ν(CO). f CDCl3 solution.
PPh2)2(CO)2]+ and [Mo2Cp2(µ-H)(µ-PCy2)2(CO)(CNtBu)]+,6
with the hydride ligand being here replaced by the carbyne
group. The latter ligand, however, provides the dimetal center
with three (instead of one) electrons, and therefore a single
metal-metal bond must be formulated for 2a according to the
EAN rule. In agreement with this, the intermetallic separation
in 2a (2.9020(5) Å) is longer than that measured for the above
ditungsten hydride (2.7589(8) Å) and comparable to those
determined for related cations with single M-M bonds such as
[W2Cp2(µ-F)(µ-CO)(CO)2(µ-dmpm)]+(2.945(1)Å)7and[Mo2Cp2(µ-
CH2PPh2)(µ-I)(µ-PPh2)(CO)2]+ (3.001(2) Å).8 The slight short-
ening of the intermetallic length in 2a, when compared to the
mentioned electron-precise cations, is doubtlessly caused by the
presence of three, rather than two, monodentate bridging ligands,
a situation that has been also found to cause a systematic
decrease of intermetallic distances in related thiolate-bridged
systems.9 The methoxycarbyne ligand bridges the metal atoms
in 2a quite symmetrically, with W-C distances (ca. 2.02 Å)
similar to those previously found by us for other complexes
bearing methoxycarbyne ligands such as [W2Cp2(µ-COMe)(µ-
PPh2)2]+ (1.97(1) Å)10 and [Mo2Cp2(µ-COMe)2(µ-PCy2)]+ (ca.
2.00 Å),11 and the methoxyl group lies in the W2C(carbyne)
plane, as usually found for all these complexes. As for the
bonding within the carbyne ligand, the C(100)-O(100) distance,
1.407(8) Å, is longer than the corresponding distances measured
in related dimolybdenum methoxycarbyne complexes (ca. 1.32
Å),1,11,12 and this points to only a small residual multiplicity in
that particular C-O bond.1,13 Interestingly, we note that similar
C-O distances within the methoxycarbyne ligand were previ-
ously found in the ditungsten complexes [W2Cp2(µ-COMe)(µ-
Ph2PCH2PPh2)(CO)2]+ (1.42(5) Å)14 and [W2Cp2(µ-COMe)(µ-
PPh2)2]+ (1.390(9) Å).10 It is thus tempting to conclude that
the elongation effect observed for the C-O distance within the
methoxycarbyne ligand of these complexes can be associated
with the presence of electron-rich (compared to molybdenum)
tungsten atoms, but further structural data will be needed to
validate this trend.
Spectroscopic data in solution for compound 2a (Table 2 and
Experimental Section) are fully consistent with its solid-state
structure, after assuming the presence of fast rotation, on the
NMR time scale, around the C-OMe bond of the methoxy-
carbyne ligand, a common dynamic process previously studied
in detail for other alkoxycarbyne complexes.1,13–15 The retention
of the carbonyl arrangement of the solid is clearly denoted by
the appearance of two C-O stretching bands in the IR spectrum
[2009 (vs), 1962 (w) cm-1], with the typical pattern of cisoid
M2(CO)2 oscillators having almost parallel CO ligands.16 Rather
unexpectedly for a metal-metal bonded species,17 the 31P NMR
spectrum of 2a exhibits a quite shielded 31P resonance (δP )
-50.2 ppm). This shielding effect has been also found for the
structurally related cations [M2Cp2(µ-H)(µ-PR2)2(CO)2]+ (R)
Ph, Cy, Et; M ) Mo, W)6 and seems to be characteristic of
binuclear Mo2 or W2 cyclopentadienyl cations displaying flat
M2P2 cores. In addition, compound 2a exhibits a reduced W-P
coupling (217 Hz) compared to its precursor 1a (363 Hz), an
effect consistent with the increase in the coordination number
of the tungsten atoms that occurred upon carbonylation.18
The available spectroscopic data for the dimolybdenum
complex 2b (Table 2 and Experimental Section) are very similar
to those just discussed for complex 2a, and then a detailed
analysis is not needed. The most significant difference concerns
the 31P NMR spectrum, which exhibits a single resonance (δP
) 13.4 ppm) some 60 ppm downfield from the corresponding
resonance in 2a. This great difference, however, can be mainly
(6) Alvarez, M. A.; Garc´ıa, M. E.; Martinez, M. E.; Ramos, A.; Ruiz,
M. A.; Sa´ez, D.; Vaissermann, J. Inorg. Chem. 2006, 45, 6965.
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Lanfranchi, M.; Tiripicchio, A. Organometallics 1999, 18, 4509.
(8) Riera, V.; Ruiz, M. A.; Villafan˜e, F.; Bois, C.; Jeannin, Y. J.
Organomet. Chem. 1989, 375, C23.
(9) Pe´tillon, F. Y.; Schollhammer, P.; Talarmin, J.; Muir, K. W. Coord.
Chem. ReV. 1998, 178-180, 203.
(10) Garc´ıa, M. E.; Riera, V.; Rueda, M. T.; Ruiz, M. A. J. Am. Chem.
Soc. 1999, 121, 1960.
(15) (a) Bavaro, L. M.; Keister, J. B. J. Organomet. Chem. 1985, 287,
357. (b) Keister, J. B.; Payne, M. W.; Muscatella, M. J. Organometallics
1983, 2, 219. (c) Johnson, B. F. G.; Lewis, J.; Orpen, A. G.; Raithby, P. R.;
Su¨ss, G. J. Organomet. Chem. 1979, 173, 187. (d) Keister, J. B. J. Chem.
Soc., Chem. Commun. 1979, 214. (e) Gavens, P. D.; Mays, M. J. J.
Organomet. Chem. 1978, 162, 389.
(11) Alvarez, C. M.; Alvarez, M. A.; Garc´ıa, M. E.; Garc´ıa-Vivo´, D.;
Ruiz, M. A. Organometallics 2005, 24, 4122.
(12) Garc´ıa, M. E.; Melo´n, S.; Ramos, A.; Riera, V.; Ruiz, M. A.;
Belletti, D.; Graiff, C.; Tiripicchio, A. Organometallics 2003, 22, 1983.
(13) Garc´ıa, M. E.; Garc´ıa-Vivo´, D.; Ruiz, M. A.; Aullo´n, G.; Alvarez,
S. Organometallics 2007, 26, 5912.
(16) Braterman, P. S. Metal Carbonyl Spectra; Academic Press: London,
U.K., 1975.
(17) Carty, A. J.; MacLaughlin, S. A.; Nucciarone, D. In Phosphorus-
31 NMR Spectroscopy in Stereochemical Analysis; Verkade, J. G., Quin,
L. D, Eds.; VCH: Deerfield Beach, FL, 1987; Chapter 16.
(18) Jameson, C. J. In Phosphorus-31 NMR Spectroscopy in Stereo-
chemical Analysis; Verkade, J. G., Quin, L. D., Eds.; VCH: Deerfield Beach,
FL, 1987; Chapter 6.
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tallics 1999, 18, 634.

3882 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
attributed to the distinct shielding effect of the metals involved
(molybdenum vs tungsten).6,19
Chart 2).22 Third, because of the electronic unsaturation of the
dimetal center in 1b (as opposed to the electron-precise nature
of the above diiron substrate), the incoming isocyanide ligand
coordinates to the metal center and not just to the carbyne atom,
thus yielding, after coupling, a ketenylimine derivative bound
to the dimetal center through both carbon atoms (instead of one),
then behaving as a full three-electron donor. Finally, and this
being perhaps the most unusual feature in the formation of 4,
the C-C coupling process leading to this complex is reversible,
since it slowly transforms into the carbyne-bis(isocyanide)
isomer 3b at room temperature. To our knowledge, all previ-
ously reported carbyne-isocyanide coupling reactions are
irreversible in nature. At this point we should note that the
ditungsten complex trans-3a also has the right geometry to allow
for a similar C-C coupling, so the fact that such a coupling is
not observed in this case must be interpreted as a thermodynamic
effect, perhaps derived from the higher strength (compared to
molybdenum) of the W-C bonds involved.
Solution Structure of the Isocyanide Derivatives 3 and
4. As stated above, only the cis isomers cis-3a,b could be
isolated as pure compounds. Spectroscopic data for these species
(Table 2 and Experimental Section) are comparable to those
already discussed for the cis-dicarbonyls 2a,b and then need
not be discussed in detail. The most relevant data are the
appearance in the IR spectra of two C-N stretching bands with
the pattern (strong and weak, in order of decreasing frequencies)
expected for M2(CNtBu)2 oscillators with almost parallel
arrangement of the isocyanide ligands, and the presence of
highly deshielded 13C NMR resonances [δC ) 383.8 (cis-3a),
410.5 (cis-3b)], these being indicative of the retention of the
bridging methoxycarbyne ligands. The latter also undergo fast
rotation around the corresponding C-OMe bonds on the NMR
time scale, as usually observed. Finally we note that the 31P
nuclei of these cations are considerably shielded, as observed
for the dicarbonyls 2a,b.
The available spectroscopic data for trans-3a indicate that
this isomer retains an intact methoxycarbyne ligand (δC ) 375.9
ppm) and has inequivalent WCp(CNtBu) moieties but equivalent
diphenylphosphide groups. Therefore, its structure must be
similar to that of cis-3a, but with a transoid arrangement of the
WCp(CNtBu) moieties (Chart 2). This implies that, while one
metal center exhibits the usual four-legged piano stool coordina-
tion geometry, the second metal center displays a pseudotrigonal
pyramidal environment. Although this is not a common ar-
rangement in binuclear cyclopentadienyl complexes of the group
6 metals, we can quote some structurally characterized prece-
dents, as is the case of the trans-dicarbonyls [Mo2Cp2{µ-η1,κ:
η2-C(CO2Me)CH(CO2Me)}(µ-PCy2)(CO)2]23 and [Mo2Cp2(µ-
CH2PPh2)2(µ-I)(µ-PPh2)(CO)2]+.8
The NMR data for 4 reveal that this compound also displays
inequivalent metal environments, but the most relevant spec-
troscopic feature is the lack of a strongly deshielded 13C NMR
resonance, denoting that a methoxycarbyne ligand is no longer
present in this molecule. Instead, the 13C NMR resonance for
the former carbyne atom is now located at 239.5 ppm, which is
consistent with the occurrence of a coupling between COMe
and CNtBu ligands to give a ketenylimine ligand. The chemical
shift of this resonance is comparable to those of some mono-
nuclear alkoxy- and aminocarbene molybdenum complexes,24
while that of the former isocyanide ligand does not change its
Reaction of Compounds 1a,b with CNtBu. The ditungsten
complex 1a reacts readily with tert-butyl isocyanide (2 equiv)
at room temperature to give a mixture of two isomers of the
complex [W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4 (cis-3a and
trans-3a) (Chart 2) in a ratio cis/trans of ca. 5. These isomers
could not be separated by chromatographic techniques or
crystallization; moreover, the ratio of these products turned out
to be highly dependent on the reaction temperature and, to some
extent, on the method of addition of the isocyanide. Thus, the
isomer cis-3a can be selectively obtained by the slow addition
of an isocyanide solution into a dichloromethane solution of
1a at room temperature. Unfortunately, the isomer trans-3a
could not be selectively prepared, although it can be obtained
as an equimolar mixture with its cis isomer when a solution of
1a is added slowly into another solution containing an excess
of CNtBu at 213 K. Finally, a separate experiment proved that
complex trans-3a rearranges to the cis isomer slowly at room
temperature and in just 45 min at 333 K.
The reaction of the dimolybdenum substrate 1b with CNtBu
(2 equiv) proceeds similarly to that just discussed for the
ditungsten complex 1a, to yield a mixture of two isomers in a
ca. 2:1 ratio. The major and most stable isomer can be
characterized as cis-[Mo2Cp2(µ-COMe)(µ-PEt2)2(CNtBu)2]BF4
(cis-3b), which is the molybdenum analogue of cis-3a, but the
second isomer is not the corresponding trans isomer, but the
ketenylimine complex [Mo2Cp2{µ-η1:η1-C(OMe)C(NtBu)}(µ-
PEt2)2(CNtBu)]BF4 (4) (Chart 2), resulting from the C-C
coupling between an isocyanide molecule and the methoxycar-
byne ligand in an hypothetical trans isomer of 3b. As it was
the case with the isomers of 3a, the above dimolybdenum
isomers could not be separated, and the cis isomer could be
quantitatively obtained under similar experimental conditions
to those described above for the ditungsten analogue cis-3a.
Unfortunately, complex 4 could not be prepared selectively,
although it can be obtained at 243 K as the major component
of a 2:1 mixture with its isomer cis-3b (see Experimental
Section). Most interestingly, complex 4 is thermally unstable
in solution, rearranging progressively at room temperature to
yield almost cleanly the thermodynamically more favored cis-
3b, thus proving that the C-C coupling leading to compound
4 is a reversible process.
The formation and properties of compound 4 are remarkable
in several aspects. First, we note that the coupling of isocyanide
to carbyne ligands is not as common as the carbonyl-carbyne
coupling leading to ketenyl derivatives.20 In fact, sometimes
this coupling occurs only after some kind of activation, such as
the protonation of the isocyanide ligand.21 Second, earlier
isocyanide-carbyne couplings have been generally observed
only at mononuclear complexes, the only reported precedent
involving a binuclear substrate being the reaction of the electron-
precise carbyne complexes [Fe2Cp2(µ-CR)(µ-CO)(CO)2]+ with
CNtBu to give the corresponding η1-coordinated ketenylimine
derivatives [Fe2Cp2{µ-C(CNtBu)R}(µ-CO)(CO)2]+ (R ) H, Et;
(19) Garc´ıa, M. E.; Riera, V.; Ruiz, M. A.; Rueda, M. T.; Sa´ez, D.
Organometallics 2002, 21, 5515.
(20) (a) Fischer, H.; Hoffmann, P.; Kreissl, F. R.; Schrock, R. R.;
Schubert, U.; Weiss, K. Carbyne Complexes; VCH: Weinheim, Germany,
1988. (b) Heesook, K. P.; Angelici, R. J. AdV. Organomet. Chem. 1987,
27, 51. (c) Mayr, A.; Hoffmeister, H. AdV. Organomet. Chem. 1991, 32,
227.
(21) (a) Filippou, A. C.; Lungwitz, B.; Kociok-Ko¨hn, G. Eur. J. Inorg.
Chem. 1999, 1905. (b) Filippou, A. C. Polyhedron 1990, 9, 727.
(22) Casey, C. P.; Crocker, M.; Niccolai, G. P.; Fagan, P. J.; Konings,
M. S. J. Am. Chem. Soc. 1988, 110, 6070.
(23) Alvarez, M. A.; Garc´ıa, M. E.; Ramos, A.; Ruiz, M. A.; Lanfranchi,
M.; Tiripicchio, A. Organometallics 2007, 26, 5454.
(24) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: London, U.K., 1981.

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3883
specifically the cis-dicarbonyl derivatives.19 We also note that
the rearrangement of a COMe ligand from a bridging to an
almost terminal position upon addition of ligands has been
observed previously in the unsaturated complex [Mo2Cp2(µ-
COMe)(µ-PCy2)(µ-CO)] upon carbonylation.13 The approach
of the second isocyanide molecule is then expected to occur on
the metal atom bearing the carbyne ligand and trans to it, since
this allows an easy and concerted rearrangement of the meth-
oxycarbyne ligand back to the bridging position. This gives
specifically the trans isomer, which is a stable structure in the
ditungsten substrate (trans-3a). For the dimolybdenum substrate,
however, this structure would represent an intermediate (not
observed) that would rapidly undergo C-C coupling between
the carbyne and isocyanide ligands, thus yielding the kete-
nylimine complex 4. These complexes, therefore, are the kinetic
products of the corresponding reactions, thus explaining their
prevalence when the reactions are carried out at low tempera-
tures and using high relative proportions of isocyanide.
To explain the preferential formation of the cis isomers at
ambient temperatures and lower isocyanide concentrations, we
assume that a cis/trans isomerization at the intermediate A might
take place prior to further addition of isocyanide. This would
occur rapidly at ambient temperature but only to some extent
at 213 K. The addition of the second isocyanide molecule on
this new intermediate (trans-A) would then render specifically
the cis isomers of compounds 3, which are the thermodynamic
products. We recall here that related cis to trans isomerization
processes involving the dicarbonyls [M2Cp2(µ-PR2)(µ-
PR′2)(CO)2] have been previously reported by us, exhibiting
different isomerization rates depending on the particular com-
plex.6
Scheme 1. Pathways in the Reactions of Compounds 1a,b
with tBuNC (M ) WCp, MoCp; P ) PPh2, PEt2; L )
tBuNC; positive charges in all complexes omitted for clarity)
chemical shift significantly (δC 159.7 or 155.7 ppm, see
Experimental Section), which is consistent with its transforma-
tion into a sort of iminoacyl ligand (cf. δC 155.5 ppm for
[MoCp(CO)2{P(OPh)3}{η1-C(Me)NPh}]).25 All the above data
are therefore suggestive of a coordination of the ketenylimine
ligand through both carbon atoms. As a result, a symmetry plane
relating the phosphorus atoms is retained, and a double Mo-Mo
must be formulated for this cation according to the EAN rule
(Chart 2). All this is in agreement with the presence of a single
resonance in the 31P NMR of 4, considerably more deshielded
than the one in the electron-precise isomer cis-3b. The alterna-
tive coordination of the ketenylimine ligand through just one
carbon atom, as observed for the diiron complexes mentioned
above (Chart 2), can be safely excluded here since that would
render two different environments for the P atoms in 4. To our
knowledge, the asymmetric coordination mode of the kete-
nylimine ligand proposed for 4 has not been previously
described in the literature and has to be taken here as a direct
consequence of the unsaturated nature of the carbyne precursor
1b.
The above steps account for the fast formation of either the
cis or trans isomers of compounds 3. It should be kept in mind
that there is also a slower process whereby both 4 and trans-3a
eventually rearrange into the thermodynamic products cis-3a,b
at room temperature or above (not shown in Scheme 1).
However, we have not studied the kinetics of this final
transformation in detail.
Reactions of Compounds 1a,b with Diphosphines. Phos-
phine ligands are known to attack the electrophilic carbon atom
of the carbyne ligand in several mononuclear complexes,20
a
behavior also shown by some binuclear complexes such as the
cation [Fe2Cp2(µ-CH)(µ-CO)(CO)2]+.26 Due to the unsaturated
nature of the methoxycarbyne complexes 1a,b, we decided to
examine the reactions of these substrates with some diphos-
phines rather than using simple phosphines, in order to reduce
both the unsaturation at the dimetal center and the number of
possible isomers. No reaction was observed when using the
diphosphine Ph2PCH2PPh2, either at room temperature or in
refluxing dichloroethane solutions. However, when using the
smaller and more basic diphosphine Me2PCH2PMe2 (dmpm),
ligand coordination occurs at room temperature, although no
coupling to the methoxycarbyne ligand takes place.
The reaction of the ditungsten complex 1a with dmpm gives
a mixture of the diphosphine derivatives [W2Cp2(µ-COMe)(µ-
PPh2)2(µ-dmpm)]BF4 (trans-5a and cis-5a) and the hydride
complex [W2Cp2(H)(µ-PPh2)2(µ-dmpm)]BF4 (6) (Chart 3), with
cis and trans here describing the relative position of the carbyne
and diphosphine ligands. The relative amount of the above
isomers is dependent on the experimental conditions; thus, the
Pathways in the Reactions with CNtBu. As it has been
shown in the preceding sections, the reactions of the unsaturated
methoxycarbyne complexes 1a,b with CNtBu can lead, depend-
ing on the experimental conditions, to mixtures having different
relative amounts of the isocyanide derivatives 3 as either cis or
trans isomers and, in the case of the molybdenum substrate, to
the ketenylimine derivative 4. Moreover, all these complexes
eventually transform into the cis isomers, which are the
thermodynamic products. Although we have detected no
intermediate species in these reactions, the above results can
be rationalized on the basis of the elementary steps collected
in Scheme 1.
It is first assumed that the first isocyanide molecule should
approach the unsaturated metal center at the less hindered
position, which is that between the PPh2 and COMe bridging
ligands. This leaves the COMe and CNtBu ligands arranged in
a cis relative position (intermediate A), thus paralleling the
carbonylationreactionsofthebis(phosphide)complexes[M2Cp2(µ-
PR2)(µ-PR′2)(µ-CO)] (M ) Mo, W; R ) alkyl, aryl) to give
(26) (a) Churchill, M. R.; Keil, K. M.; Janik, T. S.; Willoughby, M. C.
J. Coord. Chem. 2001, 52, 229. (b) Churchill, M. R.; Janik, T. S. J. Coord.
Chem. 1997, 27, 667. (c) Churchill, M. R.; Korzenski, M. B.; Janik, T. S.
J. Coord. Chem. 1996, 26, 683.
(25) Adams, R. D.; Chodosh, D. F. Inorg. Chem. 1978, 17, 41.

3884 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
Chart 3
Table 3. Selected Bond Lengths (Å) and Angles (deg) for compound
cis-5a
W(1)-W(2)
W(1)-C(1)
W(2)-C(1)
W(1)-P(1)
W(2)-P(2)
C(1)-O(1)
O(1)-C(2)
W(1)-P(3)
W(1)-P(4)
W(2)-P(3)
W(2)-P(4)
2.917(1)
2.09(2)
2.08(2)
2.496(4)
2.516(4)
1.34(2)
P(1)-W(1)-C(1)
P(2)-W(2)-C(1)
P(1)-W(1)-W(2)
P(2)-W(2)-W(1)
P(1)-W(1)-P(3)
P(2)-W(2)-P(3)
P(1)-W(1)-P(4)
P(2)-W(2)-P(4)
C(1)-W(1)-P(3)
C(1)-W(2)-P(3)
C(1)-W(1)-P(4)
C(1)-W(2)-P(4)
W(1)-C(1)-O(1)
W(2)-C(1)-O(1)
C(1)-O(1)-C(2)
79.9(5)
83.1(5)
89.8(1)
92.4(1)
89.2(2)
89.2(2)
142.5(2)
145.2(2)
98.0(4)
97.9(4)
70.1(5)
70.1(5)
141(1)
Figure 2. ORTEP diagram (30% probability) of the cation in
compound cis-5a, with H atoms and Ph rings (except the C1 atoms)
omitted for clarity.
than the corresponding ones in 2a (ca. 2.022(1) Å), while the
C-O length (1.34(2) Å) is slightly shorter. While this could be
a genuine consequence of the change in the ligands trans to it
(carbonyls vs PPh2), we will not enter into detailed comparisons
due to the low precision of the data involving the diphosphine
complex.
1.42(2)
2.442(4)
2.428(4)
2.452(4)
2.432(4)
Solution Structure of Compounds 5 and 6. The spectro-
scopic data in solution for compounds 5 (Table 4 and Experi-
mental Section) are fully consistent with the structures proposed
(Chart 3) and, in the case of cis-5a, with the structure found in
the crystal. The data for the trans isomers are indicative of their
higher symmetry, which implies the equivalence of the pairs
of Cp (assuming fast rotation around the C-OMe bond), PPh2,
and PMe2 groups. In fact these isomers are the structural
analogues of the dicarbonyls 2a,b or the isocyanide complexes
cis-3a,b. Thus, these diphosphine complexes also exhibit
strongly shielded 31P NMR resonances for the PR2 ligands (δP
) -21.4 ppm (trans-5a), 36.1 ppm (trans-5b), which is a
characteristic of phosphide complexes having flat M2P2 skel-
etons, as noted above. The rotation of the methoxycarbyne
ligand in trans-5a can be slowed enough below 213 K to render
spectroscopic features in agreement with the static structure of
these complexes, that is, with the COMe group placed in the
W2C(carbyne) plane, this causing the inequivalence of the Cp
and PMe2 groups (Chart 2). Indeed, at 213 K two Cp resonances
130(1)
119(1)
trans isomer is the major product when the reaction is carried
out in dichloromethane solutions and using normal diphosphine
concentrations, while the use of acetone as solvent and large
ligand concentration favors the formation of the cis isomer.
Unfortunately, the hydride complex 6 was obtained always as
a very minor product and could not be isolated as a pure
material. In contrast, both trans-5a and cis-5a could be obtained
as pure materials after crystallization or chromatographic
workup, thus allowing their full structural characterization.
The reaction of the dimolybdenum complex 1b with dmpm
takes place also at room temperature to give a mixture of
products. Unfortunately, we have been able to isolate and
characterize only the major product in these mixtures, identified
as the isomer diplaying a transoid arrangement of the diphos-
phine and methoxycarbyne ligands (trans-5b). All attempts to
further modify the selectivity of this reaction were unsuccessful.
Solid-State Structure of Compound cis-5a. The structure
of this complex was confirmed through a single-crystal X-ray
diffraction study (Table 3 and Figure 2). The cation displays
two WCp fragments bridged by four groups, methoxycarbyne,
diphosphine, and two diphenylphosphide ligands, with the P
atoms of the diphosphine trans to one of the PPh2 ligands (Mo
and P atoms almost in the same plane), while the second
phosphide ligand is placed trans to the methoxycarbyne group
(with the P, C, and Mo atoms defining a plane almost
perpendicular to the former plane, and the methoxyl group lying
in this plane as usual). The structure is thus comparable to that
of the dicarbonyl complex 2a, except that the PPh2 groups are
now arranged in mutually cis positions, so they are the
diphosphine and the carbyne ligands. Yet, the interatomic
distances are comparable to those measured for the dicarbonyl
cation, particularly the intermetallic length, 2.917(1) Å, con-
sistent with the formulation of a single W-W bond for this
electron-precise cation. The W-C lengths involving the meth-
oxycarbyne ligand in cis-5a (ca. 2.08(2) Å) are slightly longer
1
are present in the H NMR spectrum, while at 193 K the 31P
NMR multiplets now clearly correspond to an ABC2 (instead
of A2B2) spin system. Finally, the presence of an unperturbed
methoxycarbyne ligand is readily apparent in the 13C NMR
spectrum of trans-5b, which displays a characteristic resonance
at 403.0 ppm for the carbyne atom. The corresponding resonance
for the ditungsten complex trans-5a could not be located in the
13C NMR spectrum, perhaps as a result of its coupling to four
31P nuclei.
The spectroscopic data for cis-5a are in full agreement with
the asymmetric structure found in the crystal. Actually, even at
room temperature the rotation of the methoxyl group around
the C-OMe bond is slow enough to give distinct (but still broad)
resonances for the Cp and PMe2 groups, which become sharper
and better resolved at low temperature. Moreover, the PPh2
groups are also inequivalent, so the 31P NMR spectrum displays
four distinct resonances. Full assignment of these resonances
(Table 4) can be made in the low-temperature spectra by
considering the number of P-W couplings observed for each
resonance (one for the diphosphine P atoms, two for the PPh2

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3885
Table 4. Selected 31P NMR Data for Diphosphine Complexesa
δ(P) [JPW
]
J(P,P)
compound
P1
P2
P3
P4
1,2
20
1,3
14
1,4
2,3
2,4
3,4
[W2Cp2(µ-COMe)(µ-PPh2)2(µ-dmpm)]BF4 (trans-5a)b
-20.5
[222]
32.2
[287, 250]
36.1
62.0
-17.7
[212]
-13.6
[212]
37.7
-20.3
[182]
-15.8
[226]
161
[W2Cp2(µ-COMe)(µ-PPh2)2(µ-dmpm)]BF4 (cis-5a)
-62.2
[129, 112]
21
21
0
55
12
161
5
0
[Mo2Cp2(µ-COMe)(µ-PEt2)2(µ-dmpm)]BF4 (trans-5b)c
[W2Cp2(H)(µ-PPh2)2(µ-dmpm)]BF4 (6)
29
0
-13.9
[256]
-32.4
[214]
60.3
96
14
24
[190, 144]
a Recorded in CD2Cl2 solutions at 233 K and 161.99 MHz, unless otherwise stated; δ in ppm relative to external 85% aqueous H3PO4 (31P), J in Hz;
labels for P atoms (P1 to P4) are given according to the drawings below the title; the assignment for compounds 5 of P2 as that P atom closer to the
methoxyl group is arbitrary. b Recorded at 193 K. c Recorded at 293 K.
Scheme 2. Pathways in the Reactions of Compounds 1a,b
groups) and the fact that P-P couplings between phosphine
with dmpm (M ) WCp, MoCp; P ) PPh2, PEt2; P--P )
and phosphide P atoms are expected to be higher for ligands
Me2PCH2PMe2 or dmpm; positive charges in all complexes
2
arranged cis, following the trends established for JXY in
omitted for clarity)
complexes of the type [MCpXYL2].18,27 The most striking
spectroscopic feature is the huge difference in the chemical shifts
and P-W couplings of the two PPh2 ligands, with that
positioned trans to the carbyne ligand (δP ) 32.2 ppm, JPW
)
287, 285 Hz) being ca. 95 ppm more deshielded than that
positioned trans to the diphosphine ligand (δP ) -62.2 ppm,
JPW ) 122, 112 Hz). While the differences in the corresponding
P-W couplings could be rationalized by considering the
different number of donor atoms trans to each PPh2 group (one
vs two), we can give no clear justification for the largely
different shielding of these P atoms.
As stated above, rotation of the methoxyl group around the
C-OMe bond of a bridging methoxycarbyne ligand is usually
a fast process on the NMR time scale at room temperature.1,13–15
The fact that this process is relatively slow in the case of cis-
5a is here interpreted as an effect of the severe steric crowding
in this molecule, with the methoxyl group being forced to
approach the Me groups of the dmpm ligand upon the mentioned
rotation, a circumstance absent in the case of the isomer trans-
5a.
Although we could not obtain a pure sample of compound
6, the available spectroscopic data (Table 4 and Experimental
Section) for this product reveal the presence of an essentially
terminal hydride ligand (δH ) -6.20 ppm) along with two PPh2
groups and a diphosphine bridge. This leaves a very asymmetric
structure with four inequivalent P donor atoms and different
coordination number in the W atoms. Full assignment of the
31P resonances can be made as done for cis-5a, and the results
are shown in Table 4. This yields chemical shifts for the PPh2
groups that are now quite similar to each other and not
particularly shielded, in agreement with the proposed puckered
(rather than flat) central W2P2 skeleton.
opening of the carbyne bridge to give an intermediate B having
a cis arrangement of the dmpm and carbyne ligands. Coordina-
tion of the pendant P atom, however, here cannot take place
trans to the carbyne ligand, but cis to it, then leading in a
concerted way to the isomer displaying the diphosphine and
carbyne ligands close to each other (cis-5a). The formation of
the more symmetric isomer can be explained by assuming a
cis/trans isomerization at the intermediates B (as proposed for
the isocyanide reaction), which then allows for the coordination
of the pendant P atom of the diphosphine trans to the carbyne
ligand, thus leading in a concerted way to the isomers trans-
5a,b. The influence of the solvent, with acetone (compared to
dichloromethane) favoring the formation of cis-5a, could thus
be explained by considering that the more polar solvent (acetone)
would thermodynamically favor the more polar intermediate B
(cis isomer) due to stronger intermolecular (dipole-dipole)
interactions.
The formation of the hydride complex 6 is unexpected,
although we will not discuss in detail the possible pathways to
explain its formation, due to its low proportion under all
conditions examined. We note, however, that an independent
experiment revealed that the hydroxycarbyne complex [W2Cp2(µ-
COH)(µ-PPh2)2]BF4 (a potential contaminant of complex 1a)10
was not the source of 6, since the reaction of this complex with
dmpm results in the deprotonation of the hydroxycarbyne ligand
to give its neutral precursor [W2Cp2(µ-PPh2)2(µ-CO)]. Therefore,
we trust that the actual source of the hydride ligand in 6 is the
Pathways in the Reactions with dmpm. The formation of
the main products in the reactions of the carbyne complexes
1a,b with dmpm can be rationalized by considering elementary
steps similar to those discussed previously for the reactions with
CNtBu, as shown in the Scheme 2. The initial attack of the
P-donor molecule would occur analogously with simultaneous
(27) Wrackmeyer, B.; Alt, H. G.; Maisel, H. E. J. Organomet. Chem.
1990, 399, 125.

3886 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
Table 5. Selected Bond Lengths (Å) and Angles (deg) for
Compound 8 (data for the molecule depicted in Figure 3)
Chart 4
W(3)-W(4)
W(3)-C(2)
W(4)-N(3)
N(3)-N(4)
N(4)-C(160)
C(2)-O(2)
W(3)-P(3)
W(3)-P(4)
W(4)-P(3)
W(4)-P(4)
2.906(1)
1.907(11)
1.786(10)
1.309(14)
1.281(14)
1.195(13)
2.340(3)
2.330(3)
2.438(3)
2.431(3)
C(2)-W(3)-W(4)
N(3)-W(4)-W(3)
C(2)-W(3)-P(3)
C(2)-W(3)-P(4)
N(3)-W(4)-P(3)
N(3)-W(4)-P(4)
P(3)-W(3)-P(4)
P(3)-W(4)-P(4)
W(4)-N(3)-N(4)
N(3)-N(4)-C(160)
85.6(4)
113.1(3)
89.4(3)
93.9(3)
98.4(3)
102.6(3)
107.4(1)
101.3(1)
173.9(7)
123.4(9)
methyl group of the methoxycarbyne ligand. This would require
at some stage the migration of the Me group to the metal, an
elementary step previously proposed for a bridging methoxy-
carbyne ligand,2a then followed by the pertinent C-H and W-C
bond cleavage steps.
completed with one terminal ligand in each case (CO and
N2CPh2), arranged in a transoid position. The carbonyl ligand
is placed almost perpendicular to the average W2P2 plane
(C-W-W ca. 85-90°), while the diazoalkane ligand is
terminally bound in an end-on fashion to the second W atom,
pointing away from the dimetal center (W-W-N angles ca.
111-114°), possibly to minimize steric repulsions. The inter-
atomic distances involving the diazoalkane ligand [ca. 1.79 Å
(W-N), 1.30 Å (N-N), and 1.28 Å (N-C)] suggest a strong,
four-electron (imido-like) coordination of the ligand,31 which
implies almost triple W-N, single N-N, and double N-C
bonds, respectively. In agreement with this, the W-N-N (ca.
172-174°) and N-N-C angles (ca. 119-124°, respectively)
are close to the ideal figures of 180° and 120°, respectively,
and a single metal-metal bond must be formulated for this
electron-precise complex, which is consistent with the inter-
metallic separations of 2.88-2.95 Å. Another piece of evidence
for the strong binding of the diazoalkane molecule in 8 is the
elongation caused on the W-P lengths of the same metal atom
(ca. 2.43 Å), these being some 0.1 Å longer than those involving
the tungsten atom bearing the carbonyl ligand.
Reaction of Compound 1a with Diazoalkanes. Carbyne-
bridged complexes are known to react with diazoalkanes to give
alkenyl and related ligands resulting from the C-C coupling
between carbyne and alkylidene groups after N2 evolution.28
This behavior has been also observed by us for the 32-electron
methoxycarbyne
complex
[W2Cp2(µ-COMe)(CO)2(µ-
Ph2PCH2PPh2)]BF4.29 It was thus unexpected to find out that
the substituted diazoalkanes N2CRR′ (R ) H, R′ ) SiMe3; R
) R′ ) Ph) would react with the ditungsten carbyne complex
1a in a completely different way. In fact, this reaction takes
place very slowly at room temperature using a 2-fold excess of
the reagent to give in each case a single organometallic product,
identified as the corresponding diazoalkane complex [W2Cp2(µ-
PPh2)2(κ1-N2CRR′)(CO)] (7, 8, Chart 4). Attempts to increase
the rate of the above reactions by working at higher temperatures
caused substantial decomposition of the diazoalkane, without
significant improvement in the formation of the organometallic
complex. We also note that the dimolybdenum complex 1b
reacts with N2CH(SiMe3) in a similar way, but the corresponding
diazoalkane complex was quite unstable and no further attempts
were made to fully characterize it.
Spectroscopic data in solution for 7 and 8 are fully consistent
with the structure found in the crystal for the latter complex. In
particular the substantial asymmetry introduced by the strongly
bound diazoalkane ligand is reflected in the noticeably different
couplings of the P nuclei to the inequivalent tungsten atoms
(δP ca. 110 ppm, JPW ca. 380 and 320 Hz). On the other side,
both the 31P chemical shifts and the P-W couplings of these
complexes are comparable to those measured for the isoelec-
tronic oxocomplex cis-[W2Cp2(O)(µ-PPh2)2(CO)],10 despite the
different arrangement of their terminal ligands. A closer
structural relationship might also be established with the
dimolybdenum oxocomplex trans-[Mo2Cp2(O)(µ-PPh2)2(CO)],32
one having the same transoid arrangement of the terminal
ligands. The C-O stretching frequency of the carbonyl in this
The formation of compounds 7 and 8 from 1a requires the
incorporation of a diazoalkane molecule and further demethy-
lation. A separate experiment showed that the neutral complex
[W2Cp2(µ-PPh2)2(µ-CO)] (which is the demethylation product
of 1a) does not react with N2CH(SiMe3) either at room
temperature or in refluxing dichloroethane solution, thus proving
that demethylation is not the initial step in the formation of our
diazoalkane complexes. Instead, coordination of the diazoalkane
must occur first, a fact itself not surprising when considering
the high unsaturation of the dimetal center in 1a. Actually,
N-coordination of diazoalkane molecules has been previously
observed in the reactions of other triply bonded group 6 metal
complexes such as the cation [W2Cp2(µ-Ph2PCH2PPh2)(µ-
CO)(CO)2]2+ 30 or even the neutral dimer [Mo2Cp2(CO)4].5c
The structure of compound 8 has been confirmed through an
X-ray study (Table 5 and Figure 3), which reveals the presence
of three independent molecules in the unit cell, not very different
from each other. The complex displays two transoid WCp
fragments bridged by two diphenylphosphide bridges defining
an almost flat W2P2 skeleton (dihedral P-W-W-P angles ca.
170°), with the coordination sphere of the metals being
(28) (a) Garc´ıa, M. E.; Tran-Huy, N. H.; Jeffery, J. C.; Sherwood, P.;
Stone, F. G. A. J. Chem. Soc., Dalton Trans. 1987, 2201. (b) Delgado, E.;
Hein, J.; Jeffery, J. C.; Raterman, A. L.; Stone, F. G. A. J. Chem. Soc.,
Dalton Trans. 1987, 1191.
(29) Alvarez, M. A.; Garc´ıa, M. E.; Riera, V.; Ruiz, M. A.; Robert, F.
Organometallics 2002, 21, 1177.
(30) Alvarez, M. A.; Anaya, Y.; Garc´ıa, M. E.; Riera, V.; Ruiz, M. A.
Organometallics 2004, 23, 433.
(31) Dartiguenave, M.; Menu, M. J.; Deydier, E.; Dartiguenave, Y.;
Siebald, H. Coord. Chem. ReV. 1998, 178-180, 623.
(32) Adatia, T.; McPartlin, M.; Mays, M. J.; Morris, M. J.; Raithby,
P. R. J. Chem. Soc., Dalton Trans. 1989, 1555.
Figure 3. ORTEP diagram (30% probability) of compound 8 (only
one of the three independent molecules shown), with H atoms and
Ph rings (except the C1 atoms) omitted for clarity.

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3887
Chart 5
Scheme 3. Reduction Reactions of Isocyanide Derivatives (M
) WCp; P ) PPh2)
complex is 1824 cm-1 (CH2Cl2 solution), to be compared to
ca. 1800 cm-1 in the case of compounds 7 and 8. Even after
accounting for the expected reduction in frequency when
replacing Mo by W (ca. 10 cm-1), the above data suggest that
the diazoalkane ligands in our complexes behave effectively as
stronger donors than a terminal oxo ligand. Other spectroscopic
features of these complexes are as expected and deserve no
further comments.
Carbonylation and Reduction Reactions of the Isocya-
nide Complex cis-3a. Since the formation of compound 4
proves the feasibility of the carbyne-isocyanide coupling
processes in our binuclear substrates, we further attempted to
induce this sort of coupling by adding ligands (carbonylation
reactions) or electrons (reduction reactions) to the stable
bis(isocyanide) complex cis-3a.
Compound cis-3a does not react with CO at atmospheric
pressure, but does it readily at 333 K under a moderate
overpressure (ca. 4 atm) to give the carbonyl isocyanide
derivative [W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)(CO)]BF4 (9) in
good yield (Chart 5). The spectroscopic data for 9 (Table 2 and
Experimental Section) are intermediate between those for the
dicarbonyl 2a and the bis(isocyanide) complex cis-3a, and thus
we assume that the carbonyl and isocyanide ligands in 9 are
arranged in cis position. There is no doubt, in any case, that
this complex retains a methoxycarbyne ligand, as evidenced by
the appearance in the 13C NMR spectrum of a strongly
deshielded resonance at 377.9 ppm, corresponding to the
bridgehead carbyne atom.
frequency of the 1840 cm-1 band might be indicative of the
presence of either bridging or bent-terminal isocyanide ligands
in C.33 We favor the second possibility, since this would require
a minimum rearrangement, it would perhaps relieve some steric
pressure at the dimetal center, and above all, it might imply the
weakening of the N-C bond as a result of the rehybridization
(from sp to sp2) at the N atom (Scheme 3). We note that the
cleavage of the N-C(R) bond in metal-bound isocyanide ligands
is well documented, most often being induced thermally.34
A
closer precedent to the reactions here discussed can be found
in the reaction of the thiolate complex [Mo2Cp2(µ-
SMe)3(CNtBu)2]BF4 with nBuLi to give the corresponding
cyanide derivative [Mo2Cp2(µ-SMe)3(CN)(CNtBu)].35
The spectroscopic data for the bis(isocyanide) complexes 11
and 13 (Table 2 and Experimental Section) are very similar to
those of the precursor cis-3a and thus support the retention of
the cis arrangement of the terminal ligands in all these cations.
This must be therefore extended to the cyanide complexes 10
and 12, since the methylation steps relating these species are
not expected to modify the overall stereochemistry of the
complexes. The presence of the terminal cyanide ligand in
compounds 10 and 12 is denoted in their IR spectra by the
appearance of a weak band at ca. 2090 cm-1, a value not far
from those reported for the above dimolybdenum complex (2075
Compound cis-3a is reduced rapidly by a sodium amalgam
in THF to give with good yield the neutral cyanide derivative
[W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNtBu)] (10) as the result of
a C-N bond cleavage in one of the isocyanide ligands (Chart
5). The terminal cyanide ligand in 10 is nucleophilic enough to
be methylated at the N atom by [Me3O]BF4, to give the
cm-1 35 or for the mononuclear cation [W(CNtBu)5(CN)]+
)
(2045 cm-1).36 In addition, the 13C NMR spectrum of 10
displays a broad resonance at 154 ppm, which can be assigned
to the metal-bound carbon atom of the cyanide ligand.
methylisocyanide
derivative
[W2Cp2(µ-COMe)(µ-
PPh2)2(CNMe)(CNtBu)]BF4 (11) almost quantitatively. This
C-N bond cleavage/formation sequence can be repeated once
more to give the cyanide complex [W2Cp2(µ-COMe)(µ-
PPh2)2(CN)(CNMe)] (12) and then the bis(methylisocyanide)
derivative [W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)2]BF4 (13), with
this proving that the C-N bond cleavage that occurs after
reduction takes place selectively so as to remove the tBu (rather
than Me) group (Scheme 3). Moreover, IR monitoring of the
reaction mixture now allowed the detection of the precursor of
12. This intermediate species (C in Scheme 3) has no detectable
NMR resonances and is associated with the presence of a broad
and strong IR band at 1840 cm-1, as well as a second band in
the usual region of terminal isocyanide ligands, overlapping with
the C-N stretching bands of 12. Full disappearance of C is
best achieved by increasing the temperature, to finally give
compound 12 in good yield. Intermediate C is thus proposed
to be the paramagnetic species resulting from the initial one-
electron reduction of 11, still keeping both isocyanide ligands,
then slowly undergoing the selective homolytic cleavage of the
N-C(tBu) bond to yield a diamagnetic product. The low
Concluding Remarks
The unsaturated methoxycarbyne complexes [M2Cp2(µ-
COMe)(µ-PR2)2]BF4 (1a,b) react with CO, CNtBu, and dmpm
mainly to give electron-precise derivatives of the type [M2Cp2(µ-
COMe)(µ-PR2)2L2]BF4, having an intact methoxycarbyne ligand
and almost parallel ligands (L), both placed away from the
methoxycarbyne ligand. In the CNtBu reaction, a kinetic product
(33) Singleton, E.; Oosthuizen, H. E. AdV. Organomet. Chem. 1983,
22, 209.
(34) For some examples, see: (a) Poszmik, G.; Carrol, P. J.; Wayland,
B. B. Organometallics 1993, 12, 3410. (b) Adachi, T.; Sasaki, N.; Ueda,
T.; Kaminaka, M.; Yoshida, T. J. Chem. Soc., Chem. Commun. 1989, 1320.
(c) Jones, W. D.; Kosar, W. P. Organometallics 1986, 5, 1823. (d) Tetrick,
S. M.; Walton, R. A. Inorg. Chem. 1985, 24, 3363.
(35) Cabon, N.; Paugam, E.; Pe´tillon, F. Y.; Schollhammer, P.; Talarmin,
J.; Muir, K. W. Organometallics 2003, 22, 4178.
(36) Giandomenico, C. M.; Hanau, L. H.; Lippard, S. J. Organometallics
1982, 1, 142.

3888 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
Carbonylation of Compound 1b. A solution of 1b (0.050 g,
0.080 mmol) in dichloromethane (10 mL) was stirred at room
temperature in a high-pressure reactor under a CO atmosphere (60
bar) for 12 h. After depressurization of the reactor, the resulting
yellowish solution was transferred into a Schlenk flask. Petroleum
ether was then added, the solvents were removed under vacuum,
and the residue was then washed with petroleum ether (3 × 5 mL)
to yield a solid containing compound 2b as the major component.
Further purification of this solid was not possible. νCO (CH2Cl2):
1998 (vs) cm-1. The expected weak band at lower frequency could
not be identified unambiguously in the IR spectra of the crude
product. 1H NMR: δ 5.49 (s, 10H, Cp), 3.87 (s, 3H, OMe), 2.1-1.9
(m, 8H, CH2), 1.2-1.0 (m, 12H, Me). 31P{1H} NMR: δ 13.4 (s).
having a transoid arrangement of isocyanide ligands is also
formed, which in the case of the dimolybdenum substrate
undergoes a spontaneous and reversible C-C coupling reaction
between the carbyne and a close isocyanide group to yield a
ketenylimine ligand coordinated to the dimetal center in a novel
µ-C:C-fashion. Diazoalkanes react with the ditungsten carbyne
complex 1a without loss of dinitrogen or coupling to the
methoxycarbyne ligand to yield, after spontaneous demethylation
of the latter, neutral derivatives having a strongly bound, end-
on-coordinated (imido-like) diazoalkane ligand. The isocyanide
derivative cis-[W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4 is also
reluctant to undergo carbyne-isocyanide coupling: its reaction
with CO causes displacement of only one isocyanide ligand,
while its reduction with sodium amalgam induces the cleavage
of an N-C(tBu) bond to give the corresponding cyanide
derivative, which is able to generate new isocyanide ligands
through alkylation at the N atom.
Preparation of cis-[W2Cp2(µ-COMe)(µ-PPh2)2(CNtBu)2]BF4(cis-
3a). A dichloromethane (2 mL) solution of CNtBu (3.25 mL of a
0.05 M solution in petroleum ether, 0.176 mmol) was placed into
a dropping funnel and then added very slowly into a solution of
compound 1a (0.080 g, 0.080 mmol) in dichloromethane (10 mL).
The mixture was stirred at room temperature for 10 min and the
solvent then removed under vacuum. The residue was afterward
washed with petroleum ether (2 × 5 mL) and dried under vacuum
to give compound cis-3a as an orange powder (0.086 g, 92%). Anal.
Calcd for C46H51BF4N2OP2W2: C, 47.45; H, 4.41; N, 2.40. Found:
C, 47.31; H, 3.98; N, 2.35. νCN (CH2Cl2): 2123 (vs), 2100 (w, sh)
cm-1. 1H NMR: δ 7.6-7.0 (m, 20H, Ph), 5.39 (s, 10H, Cp), 3.43
(s, 3H, OMe), 0.98 (s, 18H, tBu). 31P{1H} NMR: δ -15.4 (s, JPW
) 229). 13C{1H} NMR: δ 383.8 (t, JCP ) 40, JCW ) 64, µ-COMe),
Experimental Section
General Procedures and Starting Materials. All manipulations
and reactions were carried out under a nitrogen (99.995%)
atmosphere using standard Schlenk techniques. Solvents were
purified according to literature procedures and distilled prior to
use.37 Petroleum ether refers to that fraction distilling in the range
338-343 K. The compounds [W2Cp2(µ-COMe)(µ-PPh2)2]BF4
(1a),1 [Mo2Cp2(µ-COMe)(µ-PEt2)2]BF4 (1b),1 and diphenyldiaz-
omethane38 were prepared as described previously. All other
reagents were obtained from the usual commercial suppliers and
used as received. Chromatographic separations were carried out
using jacketed columns cooled by tap water (ca. 288 K) or by a
closed 2-propanol circuit, kept at the desired temperature with a
cryostat. Commercial aluminum oxide (Aldrich, activity I, 150
mesh) was degassed under vacuum prior to use. The latter was
afterward mixed under nitrogen with the appropriate amount of
water to reach the activity desired. IR stretching frequencies were
measured in solution or Nujol mulls, are referred to as ν (solvent)
or ν (Nujol), respectively, and are given in wavenumber units
(cm-1). Nuclear magnetic resonance (NMR) spectra were routinely
recorded at 300.13 (1H), 121.50 (31P{1H}), or 75.47 (13C{1H}) at
290 K in CD2Cl2 solutions unless otherwise stated. Chemical shifts
(δ) are given in ppm, relative to internal tetramethylsilane (1H, 13C)
or external 85% aqueous H3PO4 (31P). Coupling constants (J) are
given in Hz, and “ft” in second-order multiplets stands for “false
or apparent triplet”.
Preparation of [W2Cp2(µ-COMe)(µ-PPh2)2(CO)2]BF4 (2a). A
1,2-dichloroethane solution (10 mL) of compound 1a (0.100 g,
0.100 mmol) was placed in a bulb equipped with a Young’s valve.
The bulb was cooled at 77 K, evacuated under vacuum, and then
refilled with CO. The valve was then closed, and the solution was
allowed to reach room temperature and further stirred at 333 K for
14 h to give a brown solution. After removal of solvents under
vacuum, dichloromethane (10 mL) and then petroleum ether (15
mL) were added. Removal of the solvents from the latter mixture
under vacuum and washing of the residue with petroleum ether (2
× 5 mL) gave compound 2a as a brown powder (0.095 g, 90%).
The crystals used in the X-ray diffraction study were grown by
slow diffusion of a layer of petroleum ether into a dichloromethane
solution of the complex at 253 K. Compound 2a is a rather unstable
and air-sensitive complex for which no satisfactory elemental
analysis could be obtained. νCO (CH2Cl2): 2009 (vs), 1962 (w) cm-1.
1H NMR: δ 7.5-7.0 (m, 20H, Ph), 5.73 (s, 10H, Cp), 4.09 (s, 3H,
OMe). 31P{1H} NMR: δ -50.2 (s, JPW ) 217).
154.2 (t, JCP ) 10, JCW ) 45, CNtBu), 143.3 [m, AXX′, |JCP
+
JCP′| ) 51, C1(Ph)], 141.6 [m, AXX′, |JCP + JCP′| ) 21, C1(Ph)],
134.6 [ft, AXX′, |JCP + JCP′| ) 10, C2(Ph)], 132.4 [ft, AXX′, |JCP
+ JCP′| ) 8, C2(Ph)], 129.0 [s, C4(Ph)], 128.1 [ft, AXX′, |JCP
+
JCP′| ) 10, C3(Ph)], 127.9 [m, C3(Ph)], 127.5 [s, C4(Ph)], 88.6 (s,
Cp), 67.0 (s, OMe), 58.9 [s, C1(tBu)], 30.6 [s, C2(tBu)].
Preparation of Solutions of trans-[W2Cp2(µ-COMe)(µ-
PPh2)2(CNtBu)2]BF4(trans-3a). Using a dropping funnel, a dichlo-
romethane (5 mL) solution containing 0.050 g (0.050 mmol) of 1a
was added very slowly into a Schlenk tube containing a dichlo-
romethane solution (2 mL) of CNtBu (6 mL of a 0.05 M solution
in petroleum ether, 0.3 mmol) cooled at 213 K. The mixture was
stirred at 213 K for 20 min and the solvent removed under vacuum.
The residue was afterward washed with petroleum ether (3 × 5
mL) and dried under vacuum, to give a mixture of complexes cis-
3a and trans-3a, in a ratio cis/trans ) 1. All attempts to separate
these isomers were unsuccessful. Moreover, the trans isomer
progressively converts into the cis isomer in solution at room
1
temperature. νCN (CH2Cl2): 2101 (vs) cm-1. H NMR: δ 7.5-7.1
(m, 20H, Ph), 5.72 (s, 5H, Cp), 4.60 (t, JHP ) 2, 5H, Cp), 2.60 (s,
t
3H, OMe), 1.64, 1.13 (2 × s, 2 × 9H, 2 × Bu). 31P{1H} NMR:
δ -22.4 (s, JPW ) 264, 200). 13C{1H} NMR: δ 375.9 (s, µ-COMe),
164.0 (s, CNtBu), 144-127 (m, Ph), 89.3 (s, Cp), 88.8 (s, Cp),
66.8 (s, OMe), 58.4 [s, C1(tBu)], 31.5, 30.5 [2 × s, 2 × C2(tBu)].
Some of the 13C resonances of trans-3a could not be unambiguously
identified due to superimposition with those of cis-3a.
Preparationofcis-[Mo2Cp2(µ-COMe)(µ-PEt2)2(CNtBu)2]BF4(cis-
3b). Using a dropping funnel, a dichloromethane (2 mL) solution
of CNtBu (4.8 mL of a 0.05 M solution in petroleum ether, 0.240
mmol) was added very slowly into another solution containing
compound 1b (0.050 g, 0.080 mmol) in 10 mL of dichloromethane
at 273 K. The mixture was stirred for 10 min at 273 K and the
solvent then removed under vacuum. The residue was afterward
washed with petroleum ether (2 × 5 mL) and dried under vacuum,
to give compound cis-3b as an orange powder (0.058 g, 92%). Anal.
Calcd for C30H51BF4Mo2N2OP2: C, 45.25; H, 6.45; N, 3.51. Found:
C, 45.45; H, 6.67; N, 3.64. νCN (CH2Cl2): 2118 (vs), 2098 (w, sh)
cm-1. 1H NMR: δ 5.15 (s, 10H, Cp), 3.84 (s, 3H, OMe), 1.95 [m,
(37) Amarego, W. L. F.; Chai, C. Purification of Laboratory Chemicals.,
5th ed.; Butterworth-Heinemann: Oxford, U.K., 2003.
(38) Miller, J. B. J. Org. Chem. 1959, 24, 560.
t
4H, CH2], 1.58 [m, 4H, CH2], 1.50 (s, 18H, Bu), 1.17 [m, 12H,
CH3]. 31P{1H} NMR (CDCl3): δ 47.5 (s). 13C{1H} NMR (CDCl3):

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3889
δ 410.5 (t, JCP ) 54, µ-COMe), 169.4 (t, JCP ) 16, CNtBu), 88.2
ABMX, JPP ) 161, 21, 5, JPW ) 212, µ-dmpm), -15.8 (dd, ABMX,
JPP ) 161, 21, JPW ) 226, µ-dmpm), -62.2 (dd, JPP ) 55, 5, JPW
(s, Cp), 66.9 (s, OMe), 59.1 [s, C1(tBu)], 30.3 [s, C2(tBu)], 24.7
[ft, AXX′, |JCP + JCP′| ) 21, C1(Et)], 24.4 [ft, AXX′, |JCP + JCP′
) 21, C1(Et)], 13.1, 12.9 [2 × s, 2 × C2(Et)].
|
) 129, 112, µ-PPh2). H NMR (300.12 MHz, 293 K): δ 7.6-7.0
1
(m, 20H, Ph), 5.60 (s, br, 5H, Cp), 5.31 (s, br, 5H, Cp), 3.73 (s,
Preparation of [Mo2Cp2µ-η1:η1-C(OMe)C(NtBu)}(µ-PEt2)2-
(CNtBu)]BF4(4). Using a dropping funnel, a dichloromethane (5
mL) solution containing 0.050 g (0.080 mmol) of 1b was added
very slowly into a Schlenk tube containing a dichloromethane
solution (2 mL) of CNtBu (6 mL of a 0.05 M solution in petroleum
ether, 0.3 mmol) cooled at 243 K. The mixture was then allowed
to reach room temperature and the solvent removed under vacuum.
The residue was afterward washed with petroleum ether (3 × 5
mL) and dried under vacuum, to give a mixture of complexes cis-
3b and 4, with the ratio 4/cis-3b ) 2. All attempts to separate these
isomers were unsuccessful. Besides, compound 4 progressively
converts into the cis isomer in solution at room temperature. νCN
3H, OMe), 1.50 (m, br, 12H, PMe), -0.18 (dt, JHP, JHH ) 14, 11,
1
1H, CH2). H NMR (400.13 MHz, 233 K): δ 7.6-7.0 (m, 20H,
Ph), 5.66 (s, 5H, Cp), 5.31 (s, 5H, Cp), 3.67 (s, 3H, OMe), 1.61
(d, JHP ) 8, 3H, PMe), 1.56 (d, JHP ) 7, 3H, PMe), 1.45 (d, JHP
)
7, 6H, PMe), -0.27 (dt, JHP, JHH ) 14, 10, 1H, CH2); the other
resonance of the CH2 group could not be identified in the different
spectra, being possibly obscured by those of the methyl groups.
13C{1H} NMR (100.63 MHz, 213 K): δ 391.0 (s, br, µ-COMe),
150-128 (m, Ph), 87.4, 84.0 (2 × s, Cp), 73.3 (s, OMe), 24.4 (d,
JCP ) 33, PMe), 20.9 (d, JCP ) 31, PMe), 19.6 (dd, JCP ) 25, 13,
PMe), 17.9 (dd, JCP ) 25, 12, PMe); the resonance for the CH2
group could not be identified in the spectrum. Spectroscopic data
for 6: 31P{1H} NMR (161.99 MHz, 233 K): δ 62.0 (d, JPP ) 12,
JPW ) 190, 144, µ-PPh2), 60.3 (ddd, JPP ) 24, 14, 12, µ-PPh2),
1
(CH2Cl2): 2097 (vs) cm-1. H NMR (CDCl3, 243 K): δ 5.26 (s,
5H, Cp), 5.18 (s, 5H, Cp), 3.76 (s, 3H, OMe), 2.32 [m, 2H, CH2],
2.14 [m, 2H, CH2], 1.26, 1.19 (2 × s, 2 × 9H, tBu), the resonances
of some CH2 groups, as well as those of the Me groups, could not
be identified unambiguously, due to superimposition with those of
cis-3b. 31P{1H} NMR (233 K): δ 132.5 (s). 13C{1H} NMR (CDCl3,
243 K): δ 239.5 [t, JCP ) 15, C(OMe)], 159.7, 155.7 (2 × m,
C(NtBu) and CNtBu], 91.8, 86.3 (2 × s, Cp), 62.3 (s, OMe), 58.4,
57.9 [2 × s, C1(tBu)], 30.1, 29.4 [2 × s, C2(tBu)], 27.7, 24.8 [2 ×
m, AXX′, 2 × C1(Et)], 13.9, 13.3 [2 × s, 2 × C2(Et)].
-13.9 (dd, JPP ) 96, 14, JPW ) 256, µ-dmpm), -32.4 (dd, JPP
)
1
96, 24, JPW ) 214, µ-dmpm). H NMR (400.13 MHz, 233 K): δ
5.50 (s, 5H, Cp), 5.18 (s, 5H, Cp), 1.96 (d, JHP ) 10, 3H, PMe),
1.71 (d, JHP ) 8, 3H, PMe), 0.33 (q, JHP ) JHH ) 11, 1H, CH2),
-6.20 (ddd, JHP ) 34, 28, 11, 1H, W-H); other resonances for
this complex were masked by those of the major product. 13C{1H}
NMR (100.63 MHz, 213 K): δ 86.2, 81.3 (2 × s, 2 × Cp); other
resonances for this isomer were masked by those of the major
species present in the reaction mixture.
Preparation
of
trans-[W2Cp2(µ-COMe)(µ-PPh2)2(µ-
Preparation
of
trans-[Mo2Cp2(µ-COMe)(µ-PEt2)2(µ-
dmpm)]BF4(trans-5a). A dichloromethane solution (5 mL) of
compound 1a (0.100 g, 0.100 mmol) was stirred with an excess of
dmpm (32 µL, 0.200 mmol) overnight. After removal of the
solvents, the residue was chromatographed on alumina (activity IV)
at 253 K. Elution with dichloromethane/THF (4:1) gave first a
yellow fraction, which yielded, after removal of the solvents under
vacuum, compound trans-5a as a yellow powder (0.035 g, 31%).
A green band could then be collected, this containing a mixture of
compounds cis-5a (major), trans-5a (minor), and 6 (very minor).
Anal. Calcd for C41H47BF4OP4W2: C, 43.42; H, 4.18. Found: C,
dmpm)]BF4(trans-5b). Compound 1b (0.050 g, 0.080 mmol) and
dmpm (32 µL, 0.200 mmol) were stirred in dichloromethane (10
mL) overnight in a bulb equipped with a Young’s valve. After
removal of the solvent under vacuum the residue was then
chromatographed on alumina (activity IV) at 278 K. Elution with
dichloromethane/THF (5:1) gave a yellow fraction, which yielded,
after removal solvents under vacuum, compound trans-5b as a
yellow powder (0.033 g, 54%). Anal. Calcd for C25H47BF4Mo2OP4:
C, 39.19; H, 6.18. Found: C, 39.29; H, 6.33. 1H NMR (CDCl3): δ
5.07 (s, 10H, Cp), 3.87 (s, 3H, OMe), 2.12 [t, JHP ) 10, 2H,
CH2(dmpm)], 1.60-1.10 (m, 32H, PEt and PMe). 31P{1H} NMR:
δ 37.7 (t, A2B2, JPP ) 29, µ-dmpm), 36.1 (t, A2B2, JPP ) 29,
µ-PEt2). 13C{1H} NMR (CDCl3): δ 403.0 (s, br, µ-COMe), 87.1
(s, Cp), 64.2 (s, OMe), 29.2 [m, CH2(dmpm)], 25.4 (s, br, PMe),
24.2 [m, 2 × C1(Et)], 12.4, 12.2 [2 × s, 2 × C2(Et)].
1
43.46; H, 4.23. H NMR (293 K): δ 7.7-7.0 (m, 20H, Ph), 5.56
(s, 10H, Cp), 2.89 (s, 3H, OMe), 1.48 (t, JHP ) 10, 2H, CH2), 1.29
1
(ft, AnAn’XX′, |JHP + JHP′| ) 16, 12 H, PMe). H NMR (400.13
MHz, 193 K): δ 7.8-7.0 (m, 20H, Ph), 5.83 (s, 5H, Cp), 5.35 (s,
5H, Cp), 2.88 (s, 3H, OMe), 1.47 (m, br, 2H, CH2), 1.28 (d, JHP
)
)
12, 12H, PMe). 31P{1H} NMR (293 K): δ -20.5 (t, A2B2, JPP
16, µ-dmpm), -21.4 (t, A2B2, JPP ) 16, JPW ) 222, µ-PPh2).
31P{1H} NMR (161.99 MHz, 213 K): δ -18.5 (br, µ-dmpm), -20.3
(br, µ-dmpm), -20.8 (ft, ABC2, JPP ) 17, µ-PPh2). 31P{1H} NMR
Preparation of [W2Cp2(µ-PPh2)2{µ1-N2CH(SiMe3)}(CO)] (7).
A dichloromethane solution (10 mL) of compound 1a (0.060 g,
0.060 mmol) was stirred with N2CH(SiMe3) (60 µL of a 2 M
solution in hexane, 0.120 mmol) for 5 days to give a purple solution.
The solvent was then removed under vacuum, and the residue was
chromatographed on alumina (activity IV) at 278 K. Elution with
dichloromethane/petroleum ether (1:2) gave a purple fraction, which
yielded, after removal of solvents, compound 7 as a purple powder
(0.039 g, 64%). Anal. Calcd for C39H40N2OP2SiW2: C, 46.36; H,
3.99; N, 2.77. Found: C, 46.28; H, 4.11; N, 2.71. νCO (CH2Cl2):
(161.99 MHZ, 193 K): δ -17.7 (dt, ABC2, JPP ) 161, 20, JPW
)
212, µ-dmpm), -20.3 (dt, ABC2, JPP ) 161, 14, JPW ) 182,
µ-dmpm), -20.5 (ft, ABC2, JPP ) 16, JPW ) 224, µ-PPh2). 13C{1H}
NMR: 142.7 [s, br, C1(Ph)], 134.2 [ft, AXX′, |JCP + JCP′| ) 20,
C1(Ph)], 135-127 (m, Ph), 87.2 (s, Cp), 65.8 (s, OMe), 33.2 (t,
JPP ) 25, CH2), 23.4 (ft, AXX′, |JCP + JCP′| ) 32, PMe).
Reaction of 1a with dmpm in Acetone. An acetone solution
(10 mL) of compound 1a (0.100 g, 0.100 mmol) was stirred at
273 K with an excess of dmpm (32 µL, 0.200 mmol) for 24 h. The
solvent was then removed under vacuum and the residue washed
with petroleum ether (3 × 5 mL) to give a solid shown (by NMR)
to be a mixture of the isomers cis-5a and trans-5a (0.080 g, ca.
71%; ratio cis/trans ) 10) with a very minor proportion of
compound 6. The green crystals of cis-5a used in the X-ray
diffraction study were grown by slow diffusion of a layer of
petroleum ether into an acetone solution of the complex at 293 K.
Spectroscopic data for cis-5a: 31P{1H} NMR (293 K): δ 31.9 (dt,
JPP ) 55, 21, JPW ) 269, µ-PPh2), -14.9 (dd, br, JPP ) 161, 21,
µ-dmpm), -15.6 (dd, br, JPP ) 161, 21, µ-dmpm), -60.3 (dd, JPP
) 55, 5, JPW ) 126, µ-PPh2). 31P{1H} NMR (161.99 MHz, 233
K): δ 32.2 (dt, JPP ) 55, 21, JPW ) 287, 250, µ-PPh2), -13.6 (ddd,
1
1800 (vs) cm-1. H NMR: δ 8.1-7.9 (m, 20H, Ph), 6.51 (s, 1H,
CH), 4.87, 4.85 (2 × s, 2 × 5H, Cp), 0.06 (s, 9H, SiMe3). 31P{1H}
NMR: δ 107.3 (s, JPW ) 380, 318). 13C{1H} NMR: δ 229.1 (s,
CO), 151.5 [d, JCP ) 41, C1(Ph)], 149.2 (s, CHSi), 141.6 [d, JCP
)
49, C1(Ph)], 136.2 [m, AXX′, C2(Ph)], 133.2 [m, AXX′, C2(Ph)],
129.0 [s, C4(Ph)], 128.2 [m, AXX′, C3(Ph)], 127.6 [m, AXX′,
C3(Ph)], 127.3 [s, C4(Ph)], 99.7, 85.1 (2 × s, Cp), -2.5 (s, SiMe3).
Preparation of [W2Cp2(µ-PPh2)2(µ1-N2CPh2)(CO)] (8). A
dichloromethane solution (10 mL) of compound 1a (0.060 g, 0.060
mmol) was stirred with freshly prepared N2CPh2 (ca. 0.231 g, 1.191
mmol) for 5 days to give a deep blue solution. The solvent was
then removed under vacuum, and the residue was chromatographed
on alumina (activity IV) at 278 K. Elution with dichloromethane/
petroleum ether (1:1) gave a blue fraction, which yielded, after

3890 Organometallics, Vol. 27, No. 15, 2008
Garc´ıa et al.
removal solvents, compound 8 as a blue powder (0.043 g, 66%).
The crystals used in the X-ray diffraction study were grown by
slow diffusion of layers of toluene and petroleum ether into a
dichloromethane solution of the complex at 253 K. Anal. Calcd
for C48H40N2OP2W2: C, 52.87; H, 3.70; N, 2.57. Found: C, 52.43;
H, 3.40; N, 2.18. νCO (CH2Cl2): 1795 (vs) cm-1. 1H NMR (400.13
MHz): δ 7.8-6.4 (m, 30H, Ph), 4.80, 4.64 (2 × s, 2 × 5H, Cp).
31P{1H} NMR (162.01 MHz): δ 109.7 (s, JPW ) 380, 319).
5H, Cp), 3.43 (s, 3H, OMe), 2.84 (s, 3H, NMe), 0.84 (s, 9H, tBu).
31P{1H} NMR: δ -16.2 (s, JPW ) 229).
Preparation of [W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNMe)] (12).
A tetrahydrofuran (10 mL) solution of compound 11 (0.040 g, 0.036
mmol) was stirred with an excess of Na(Hg) (ca. 0.25 mL of a
0.5% amalgam) for 10 min to give a yellowish solution, which
was filtered using a canula. The solvent was removed under vacuum,
the residue dissolved in dichloromethane (10 mL), and the solution
then refluxed for 2 h. After removal of the solvent the residue was
chromatographed on an alumina column (activity IV) at 278 K.
Elution with dichloromethane gave a yellow fraction, which yielded,
after removal of the solvent under vacuum, compound 12 as a
yellow powder (0.022 g, 62%). Anal. Calcd for C39H36N2OP2W2:
C, 47.88; H, 3.71; N, 2.86. Found: C, 47.69; H, 3.92; N, 2.89. νCN
P r e p a r a t i o n
o f
[ W 2 C p 2 ( µ - C O M e ) ( µ -
PPh2)2(CO)(CNtBu)]BF4(9). A 1,2-dichloroethane solution (8 mL)
of compound cis-3a (0.060 g, 0.052 mmol) was placed in a bulb
equipped with a Young’s valve. The bulb was cooled at 77 K,
evacuated under vacuum, and then refilled with CO. The valve was
then closed and the solution was allowed to reach room temperature
and further stirred at 333 K for 2 h. Solvent was then removed
under vacuum, and the residue was dissolved in dichloromethane.
Addition of petroleum ether to this solution and partial evaporation
of solvents under vacuum caused the precipitation of a solid, which
was separated from the mother liquor and further washed with
petroleum ether to yield compound 9 as a brown powder (0.051 g,
88%). Anal. Calcd for C42H42BF4NO2P2W2: C, 45.47; H, 3.81; N,
1.26. Found: C, 45.53; H, 3.91; N, 1.18. IR (CH2Cl2): 2153 (s,
(CH2Cl2): 2152 (vs, CNMe), 2091 (w, CN) cm-1 1H NMR: δ
.
7.8-7.0 (m, 20H, Ph), 5.37, 5.20 (2 × s, 2 × 5H, Cp), 3.27 (s,
3H, OMe), 2.57 (s, 3H, NMe). 31P{1H} NMR: δ -1.4 (s, JPW
232).
)
Preparation of [W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)2]BF4(13).
A dichloromethane solution (10 mL) of compound 12 (0.030 g,
0.031 mmol) was stirred with an excess of [Me3O]BF4 (ca. 0.050
g, 0.34 mmol) for 20 min to give an orange solution, which was
filtered. Petroleum ether (15 mL) was added to the filtrate, the
solvents were then removed under vacuum, and the residue was
washed with petroleum ether to yield compound 13 as an orange
powder (0.031 g, 94%). Anal. Calcd for C40H39BF4N2OP2W2: C,
44.47; H, 3.64; N, 2.59. Found: C, 44.32; H, 3.23; N, 2.49. νCN
(CH2Cl2): 2163 (vs), 2141 (w, sh) cm-1. 1H NMR: δ 7.9-7.0 (m,
20H, Ph), 5.42 (s, 10H, Cp), 3.50 (s, 3H, OMe), 2.67 (s, 6H, NMe).
31P{1H} NMR: δ -15.7 (s, JPW ) 227). 13C{1H} NMR: δ 385.0
(t, JCP ) 40, µ-COMe), 158.6 (t, JCP ) 10, CNMe), 142.8 [m,
AXX′, |JCP + JCP′| ) 49, C1(Ph)], 140.8 [m, AXX′, |JCP + JCP′| )
23, C1(Ph)], 134.9 [ft, AXX′, |JCP + JCP′| ) 10, C2(Ph)], 132.8 [ft,
AXX′, |JCP + JCP′| ) 9, C2(Ph)], 128.7-128.4 [m, C4(Ph) and
C3(Ph)], 128.2 [ft, AXX′, |JCP + JCP′| ) 9, C3(Ph)], 127.9 [s,
C4(Ph)], 88.3 (s, Cp), 67.4 (s, OMe), 30.2 (s, NMe).
X-ray Structure Determination for Compound 2a. Suitable
crystals of 2a were stuck on a glass fiber and mounted on an Enraf-
Nonius automatic diffractometer. Accurate cell dimensions and
orientation matrix were obtained by least-squares refinements of
25 accurately centered reflections. No significant variations were
observed in the intensities of two checked reflections during data
collection. The data were corrected for Lorentz and polarization
effects. Computations were performed by using the PC version of
CRYSTALS.39 Scattering factors and corrections for anomalous
absorption were taken from ref 40. The structure was solved by
direct methods (SHELXS),41 completed by Fourier techniques, and
refined by full-matrix least-squares. An empirical absorption
correction (DIFABS)42 was applied. All non-hydrogen atoms were
anisotropically refined. All hydrogen atoms were introduced in
calculated positions in the last cycles of refinements and were
allocated an overall isotropic thermal parameter.
ν
CN), 1955 (vs, νCO) cm-1. 1H NMR (CDCl3): δ 7.6-7.1 (m, 20H,
Ph), 5.82, 5.42 (2 × s, 2 × 5H, Cp), 3.66 (s, 3H, OMe), 0.70 (s,
9H, Bu). 31P{1H} NMR (CDCl3): δ -31.6 (s, JPW ) 224, 219).
t
13C{1H} NMR: δ 377.9 (t, JCP ) 41, µ-COMe), 230.4 (t, JCP ) 8,
CO), 143.6 (t, JCP ) 7, CNtBu), 140.6 [m, AXX′, |JCP + JCP′| )
50, C1(Ph)], 139.6 [m, AXX′, |JCP + JCP′| ) 28, C1(Ph)], 134.3 [ft,
AXX′, |JCP + JCP′| ) 2, C2(Ph)], 132.4 [ft, AXX′, |JCP + JCP′| ) 4,
C2(Ph)], 129.5 [s, C4(Ph)], 128.4 [m, AXX′, 2 × C3(Ph)], 128.2
[s, C4(Ph)], 89.5, 89.2 (2 × s, Cp), 68.8 (s, OMe), 59.1 [s, C1(tBu)],
28.7 [s, C2(tBu)].
Preparation of [W2Cp2(µ-COMe)(µ-PPh2)2(CN)(CNtBu)] (10).
A tetrahydrofuran (10 mL) solution of compound cis-3a 0.100 g
(0.086 mmol) was stirred with an excess of Na(Hg) (ca. 0.5 mL of
a 0.5% amalgam) for 10 min to give a yellowish solution, which
was then filtered using a canula and further stirred for 2 h. Solvent
was then removed under vacuum, and the residue was chromato-
graphed on an alumina column (activity IV) at 278 K. Elution with
dichloromethane/petroleum ether (4:1) gave a yellow fraction, which
yielded, after removal of solvents under vacuum, compound 10 as
a yellow powder (0.061 g, 69%). All the spectroscopic data for
this compound were recorded after stirring the corresponding
solutions with KOH for 10 min. Anal. Calcd for C42H42N2OP2W2:
C, 49.43; H, 4.15; N, 2.74. Found: C, 49.26; H, 3.98; N, 2.77. νCN
(CH2Cl2): 2133 (vs, CNtBu), 2094 (w, CN) cm-1
.
1H NMR: δ
7.7-7.0 (m, 20H, Ph), 5.40, 5.21 (2 × s, 2 × 5H, Cp), 3.18 (s,
t
3H, OMe), 0.63 (s, 9H, Bu). 31P{1H} NMR: δ -0.3 (s, JPW
)
234). 13C{1H} NMR: δ 380.9 (t, JCP ) 39, µ-COMe), 153.9 (s, br,
CN), 141.3 (t, JCP ) 12, CNtBu), 146.9 [m, AXX′, |JCP + JCP′| )
56, C1(Ph)], 142.4 [ft, AXX′, |JCP + JCP′| ) 18, C1(Ph)], 135.5 [ft,
AXX′, |JCP + JCP′| ) 9, C2(Ph)], 132.9 [ft, AXX′, |JCP + JCP′| ) 8,
C2(Ph)], 127.7 [s, C4(Ph)], 127.3 [m, 2 × C3(Ph)], 126.5 [s, C4(Ph)],
87.5, 87.0 (2 × s, Cp), 65.0 (s, OMe), 56.7 [s, C1(tBu)], 28.9 [s,
C2(tBu)].
X-ray Structure Determination for compound cis-5a. The
X-ray intensity data for cis-5a were collected on a Smart-CCD-
1000 Bruker diffractometer using graphite-monochromated Mo KR
radiation at 120 K. Cell dimensions and orientation matrixes were
initially determined from least-squares refinements on reflections
measured in 3 sets of 30 exposures collected in 3 different ω regions
and eventually refined against all reflections. The software
Preparation of [W2Cp2(µ-COMe)(µ-PPh2)2(CNMe)(CNtBu)]-
BF4(11). A dichloromethane solution (10 mL) of compound 10
(0.050 g, 0.049 mmol) was stirred with an excess of [Me3O]BF4
(ca. 0.050 g, 0.34 mmol) for 20 min to give an orange solution,
which was filtered. Petroleum ether (15 mL) was added to the
filtrate, the solvents were then removed under vacuum, and the
residue was washed with petroleum ether to yield compound 11 as
an orange powder (0.051 g, 93%). Anal. Calcd for
C43H45BF4N2OP2W2: C, 46.02; H, 4.04; N, 2.50. Found: C, 46.21;
H, 4.20; N, 2.43. νCN (CH2Cl2): 2137 (vs), 2109 (s) cm-1. 1H NMR
(300.08 MHz): δ 8.0-7.3 (m, 20H, Ph), 5.46, 5.38 (2 × s, 2 ×
(39) Watkin, D. J.; Prout, C. K.; Carruthers, J. R.; Betteridge, P. W.
Crystals Issue 10; Chemical Crystallography Laboratory, University of
Oxford: Oxford, U.K., 1996.
(40) Cromer, D. T. International Tables for X-ray Crystallography;
Kynoch Press: Birmingham, U.K., 1974; Vol. IV.
(41) Sheldrick, G. M. SHELXS86, Program for Crystal Structures
Solution; University of Go¨ttingen: Go¨ttingen, Germany, 1986.
(42) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.

Chemistry of Unsaturated Group 6 Metal Complexes
Organometallics, Vol. 27, No. 15, 2008 3891
Table 6. Crystal Data for Compounds 2a, cis-5a, and 8
2a
cis-5a
8
mol formula
mol wt
cryst syst
space group
radiation (λ)
a, Å
C38H33BF4O3P2W2
1054.13
monoclinic
P21/n
C45H53BF4OP4W2 · 2 C3H6O
3C48H40N2OP2W2 · CH2Cl2 · 1/2C6H14
1250.31
3399.34
triclinic
monoclinic
C2/c
0.71073
35.173(11)
14.162(4)
20.128(6)
90
110.453(5)
90
j
P1
0.71073
1.54184
9.656 (1)
22.715 (3)
17.005 (2)
90
103.061 (9)
90
12.7468(3)
21.5175(7)
25.9987(7)
70.188(3)
80.796(2)
78.514(2)
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
3633.5(8)
4
9394(5)
8
6541.3(3)
2
Z
calcd density, g cm-3
absorpt coeff, mm-1
temperature, K
θ range, deg
index ranges (h, k, l)
no. of reflns collected
no. of indep reflns
no. of reflns with I > nσ(I)
R indexes
1.930
6.472
293
1.768
5.086
120(1)
1.726
10.973
100(2)
2.2-27.5
-12, 8; -29, 29; -21, 22
26 749
8138 [Rint ) 0.11]
4127 (n ) 3)
R1 ) 0.040
wR2 ) 0.039a
1.141
1.24-26.49
-43, 44; -17, 17; -25, 25
39 602
9603 [Rint ) 0.07]
7394 (n ) 2)
R1 ) 0.0646
wR2 ) 0.1675bc
1.212
3.28-73.93
-15, 15; -22, 26; -32, 29
75 304
24 252 [Rint ) 0.09]
13 625(n ) 2)
R1 ) 0.0432
wR2 ) 0.1065bd
0.934
[data with I > nσ(I)]
GOF
no. of restraints/params
∆(max,min), e Å-3
0/452
1.32, -1.01
0/545
4.90, -2.92
0/1490
0.21, -1.70
a wR ) [∑w(|Fo| - |Fc|)2/∑wFo2 1/2, with w ) w′[1 - ((|Fo| - |Fc|)/6σ(Fo))2]2 with w′ ) 1/ΣrArTr(X) with coefficients 0.341, 0.246, and 0.237 for a
]
2 2
Chebyshev series for which X ) Fc/Fc(max). b wR ) 1/[∑w(|Fo|2 - |Fc|2)/∑w|Fo|2]1/2, with w ) 1/[σ2(Fo)2 + (aP)2 + bP], where P ) (Fo + 2Fc )/3.
c a ) 0.0375, b ) 815.0623. d a ) 0.052, b ) 0.000.
SMART43 was used for collecting frames of data, indexing
reflections, and determining lattice parameters. The collected frames
were then processed for integration by the software SAINT,43 and
a multiscan absorption correction was applied with SADABS.44
Using the program suite WinGX,45 the structure was solved by
Patterson interpretation and phase expansion and refined with full-
matrix least-squares on F2 with SHELXL97.46 All non-hydrogen
atoms were refined anisotropically, with the exception of C(14),
which was refined isotropically because it was persistently non-
positive definite. All hydrogen atoms were geometrically located,
and they were given an overall isotropic thermal parameter. The
final refinement on F2 proceeded by full-matrix least-squares
calculations. The lattice contains two molecules of acetone per
formula of the complex.
X-ray Structure Determination for Compound 8. Data col-
lection for this compound was carried out at 100 K on a Oxford
Diffraction Xcalibur Nova single-crystal diffractometer, using Cu
KR radiation (λ ) 1.5418 Å). Images were collected at a 65 mm
fixed crystal-detector distance, using the oscillation method, with
1° oscillation and variable exposure time per image (10-40 s). Data
collection strategy was calculated with the program CrysAlis Pro
CCD.47 Data reduction and cell refinement was performed with
the program CrysAlis Pro RED.47 An empirical absorption cor-
rection was applied using the SCALE3 ABSPACK algorithm as
implemented in the program CrysAlis Pro RED.47 Using the
program suite WinGX,45 the structure was solved by Patterson
interpretation and phase expansion and refined with full-matrix least-
squares on F2 with SHELXL97.46 Most of the non-hydrogen atoms
were refined anisotropically, but some carbon atoms were found
to exhibit persistently nonpositive definite anisotropic temperature
factors and, therefore, were refined isotropically. All the hydrogen
atoms were fixed at calculated positions, and neither their position
nor their isotropic factors were refined in order to avoid an increase
of the parameters in the least-squares routine. The unit cell contains
six molecules of the complex (three independent ones), two
molecules of dichloromethane, and one molecule of hexane. In
addition, during the last cycles of refinement some residual peaks,
corresponding to a highly disordered nonidentified solvent, were
found near a special position of the unit cell. Crystallographic data
for 2a, cis-5a, and 8 are collected in Table 6.
Acknowledgment. We thank the MEC of Spain for a grant
(to D.G.) and financial support (Projects BQU2003-05471
and CTQ2006-01207) and the Unidad de Rayos X at the
Universidad de Santiago de Compostela and at the Univer-
sidad de Oviedo (Spain) for the adquisition of the diffraction
data for compounds cis-5a and 8, respectively.
(43) SMART & SAINT Software Reference Manuals, Version 5.051
(Windows NT Version); Bruker Analytical X-ray Instruments: Madison, WI,
1998.
(44) Sheldrick, G. M. SADABS, Program for Empirical Absortion
Correction; University of Go¨ttingen: Go¨ttingen, Germany, 1996.
(45) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837.
(46) Sheldrick, G. M. SHELXL97: Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(47) CrysAlis Pro; Oxford Diffraction Ltd.: Oxford, U.K., 2006.
Supporting Information Available: CIF file giving the crystal-
lographic data for the structural analysis of compounds 2a, cis-5a,
and 8. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM8002152