Reactions of diphosphine-stabilized tetracobalt carbonyl clusters with -Si(OR)3-functionalized alkynes

Article abstract of DOI:10.1021/om030327j

Short-bite ligand cluster stabilization is achieved in the tetrahedral clusters [Co₄(μ-CO)₃ (CO)₇(μ-dppy)] (1a-c), obtained in high yields by reactions of [Co₄(CO)₁₂] with 1 equiv of the diphosphine ligands dppy, Ph₂PCH₂PPh₂ (dppm), Ph₂PNHPPh₂ (dppa), or (Ph₂P)₂N-(CH₂)₃Si(OEt)₃ (dppaSi), respectively. The structure of 1a has been determined by X-ray diffraction, and the P atoms occupy axial positions on the basal face, transoid to a Co-Co bond. Clusters 1a-c were reacted with phenylacetylene to afford the corresponding butterfly clusters [Co₄(μ-CO)₂(CO)₆(μ-dppy)(μ₄ -η²-PhC₂H)] (2a-c) by insertion of the alkyne into a Co-Co bond of the precursor. This was established by an X-ray diffraction study of [Co₄(μ-CO)₂-(CO)₆(μ-dppm) (μ₄-η²-PhC₂H)] (2a). In an alternative synthetic procedure, the alkyne cluster [Co₄(CO)₁₀ (μ₄-η²-PhC₂H)] (3), prepared from [Co₄(CO)₁₂] and phenylacetylene, was reacted with the diphosphines dppy. This led in good yields to butterfly clusters, isomeric with 2a-c in terms of the position of the bridging carbonyls, as revealed by an X-ray diffraction study of the dppa derivative 2′b·0.5CH₂Cl₂. To obtain suitable cluster precursors to sol-gel materials, we have reacted 1a,b with the new trialkoxysilyl alkyne PhC≡CC(O)NH(CH₂)₃-Si(OMe)₃ (L¹) and isolated the corresponding functionalized butterfly clusters [Co₄(μ-CO)₂-(CO)₆(μ-dppy) {μ₄-η²-PhC₂C(O)NH (CH₂)₃Si(OMe)₃}] (4a,b), respectively. Similar reactions between 1a,b and the alkyne HC≡CCH₂NHC(O)NH(CH₂)₃Si(OEt)₃ (L²) afforded the related clusters [Co₄(μ-CO)₂(CO)₆(μ-dppy){μ₄ -η²-HC₂CH₂NHC(O)NH (CH₂)₃Si(OEt)₃}] (5a,b). The cluster [Co₄(μ-CO)₂(CO)₆(μ-dppm){μ₄ -η²-HC₂(CH₂)₂ OC(O)NH(CH₂)₃Si(OEt)₃}] (6a) was obtained by reaction of 1a with HC≡C(CH₂)₂OC(O)NH(CH₂)₃Si(OEt) ₃ (L³). Reaction of [Co₄-(CO)₁₂] with L¹ led to the formation of the dinuclear complex [Co₂(CO)₆{μ-η²-PhC₂C(O)NH-(CH ₂)₃Si(OMe)₃}] (7), which was also prepared by reaction of [Co₂(CO)₈] with L¹. Reaction of 1a with dppaSi afforded the mixed-diphosphine cluster [Co₄(μ-CO)₃(CO)₅(μ-dppm)(μ-dppaSi)] (8), which was characterized by X-ray diffraction. In the course of attempts at linking two molecules of 2a with 1,4-diodobenzene under Sonogashira conditions, the dinuclear complex [Co₂(CO)₄(μ-dppm) {μ-η²-PhC₂H}] (9) was isolated instead. Reaction of 1,4-bis-(trimethylsilyl)butadiyne (L⁴) with [Co₄(CO)₁₂] afforded the known complex [{Co₂ (CO)₆(μ₂-η²-Me₃ SiC_2-)}₂] (10) and with 1a yielded the desired product [Co₄(CO)₈(μ-dppm)(μ₄-η²-Me ₃SiC₂C≡CSiMe₃)] (12), in addition to the known complex [Co₂(CO)₄(μ-dppm)(μ-η²-Me₃ SiC₂C≡CSiMe₃)] (13). Proto-desilylation of 12 using TBAF/THF-H₂O occurred unexpectedly at the cluster core-bound alkyne carbon to afford [Co₄(μ-CO)₂(CO)₆(μ-dppm)(μ₄ -η²-HC₂-C≡CSiMe₃)] (16), instead of the anticipated cluster [Co₄(μ-CO)₂(CO)₆(μ-dppm)(μ₄ -η²-Me₃-SiC₂C≡CH)]. The crystal structure of 16 has been determined by X-ray diffraction.

Full text of DOI:10.1021/om030327j

Organometallics 2003, 22, 4405-4417
4405
Rea ction s of Dip h osp h in e-Sta bilized Tetr a coba lt
Ca r bon yl Clu ster s w ith -Si(OR)3-F u n ction a lized Alk yn es
Aldjia Choualeb,† Pierre Braunstein,*,† J acky Rose´,† Salah-Eddine Bouaoud,‡ and
Richard Welter§
Laboratoire de Chimie de Coordination (UMR 7513 CNRS), Universite´ Louis Pasteur,
4 rue Blaise Pascal, F-67070 Strasbourg Cedex, France, De´partement de Chimie, Faculte´ des
Sciences, Universite´ des Fre`res Mentouri-Constantine, route de Ain el Bey, Algeria, and
Laboratoire DECMET (UMR 7513 CNRS), Universite´ Louis Pasteur, 4 rue Blaise Pascal,
F-67070 Strasbourg Cedex, France
Received May 5, 2003
Short-bite ligand cluster stabilization is achieved in the tetrahedral clusters [Co4(µ-CO)3
(CO)7(µ-dppy)] (1a -c), obtained in high yields by reactions of [Co4(CO)12] with 1 equiv of
the diphosphine ligands dppy, Ph2PCH2PPh2 (dppm), Ph2PNHPPh2 (dppa), or (Ph2P)2N-
(CH2)3Si(OEt)3 (dppaSi), respectively. The structure of 1a has been determined by X-ray
diffraction, and the P atoms occupy axial positions on the basal face, transoid to a Co-Co
bond. Clusters 1a -c were reacted with phenylacetylene to afford the corresponding butterfly
clusters [Co4(µ-CO)2(CO)6(µ-dppy)(µ4-η2-PhC2H)] (2a -c) by insertion of the alkyne into a Co-
Co bond of the precursor. This was established by an X-ray diffraction study of [Co4(µ-CO)2-
(CO)6(µ-dppm)(µ4-η2-PhC2H)] (2a ). In an alternative synthetic procedure, the alkyne cluster
[Co4(CO)10(µ4-η2-PhC2H)] (3), prepared from [Co4(CO)12] and phenylacetylene, was reacted
with the diphosphines dppy. This led in good yields to butterfly clusters, isomeric with 2a -c
in terms of the position of the bridging carbonyls, as revealed by an X-ray diffraction study
of the dppa derivative 2′b‚0.5CH2Cl2. To obtain suitable cluster precursors to sol-gel
materials, we have reacted 1a ,b with the new trialkoxysilyl alkyne PhCtCC(O)NH(CH2)3-
Si(OMe)3 (L1) and isolated the corresponding functionalized butterfly clusters [Co4(µ-CO)2-
(CO)6(µ-dppy){µ4-η2-PhC2C(O)NH(CH2)3Si(OMe)3}] (4a ,b), respectively. Similar reactions
between 1a ,b and the alkyne HCtCCH2NHC(O)NH(CH2)3Si(OEt)3 (L2) afforded the related
clusters [Co4(µ-CO)2(CO)6(µ-dppy){µ4-η2-HC2CH2NHC(O)NH(CH2)3Si(OEt)3}] (5a ,b). The
cluster [Co4(µ-CO)2(CO)6(µ-dppm){µ4-η2-HC2(CH2)2OC(O)NH(CH2)3Si(OEt)3}] (6a ) was ob-
tained by reaction of 1a with HCtC(CH2)2OC(O)NH(CH2)3Si(OEt)3 (L3). Reaction of [Co4-
(CO)12] with L1 led to the formation of the dinuclear complex [Co2(CO)6{µ-η2-PhC2C(O)NH-
(CH2)3Si(OMe)3}] (7), which was also prepared by reaction of [Co2(CO)8] with L1. Reaction
of 1a with dppaSi afforded the mixed-diphosphine cluster [Co4(µ-CO)3(CO)5(µ-dppm)(µ-
dppaSi)] (8), which was characterized by X-ray diffraction. In the course of attempts at linking
two molecules of 2a with 1,4-diodobenzene under Sonogashira conditions, the dinuclear
complex [Co2(CO)4(µ-dppm){µ-η2-PhC2H}] (9) was isolated instead. Reaction of 1,4-bis-
(trimethylsilyl)butadiyne (L4) with [Co4(CO)12] afforded the known complex [{Co2(CO)6(µ2-
η2-Me3SiC2-)}2] (10) and with 1a yielded the desired product [Co4(CO)8(µ-dppm)(µ4-η2-
Me3SiC2CtCSiMe3)] (12), in addition to the known complex [Co2(CO)4(µ-dppm)(µ-η2-
Me3SiC2CtCSiMe3)] (13). Proto-desilylation of 12 using TBAF/THF-H2O occurred unexpectedly
at the cluster core-bound alkyne carbon to afford [Co4(µ-CO)2(CO)6(µ-dppm)(µ4-η2-HC2-
CtCSiMe3)] (16), instead of the anticipated cluster [Co4(µ-CO)2(CO)6(µ-dppm)(µ4-η2-Me3-
SiC2CtCH)]. The crystal structure of 16 has been determined by X-ray diffraction.
In tr od u ction
metal particles whose coalescence into larger, ill-defined
aggregates can thus be prevented. This approach has
obvious relevance to the fabrication of microelectronic
devices1 and to the preparation of new catalyts whose
selectivity will critically depend on the size and disper-
sion of the metal particles and also on the shape of the
The confinement of molecular clusters in the cavities
of meso- or nanoporous inorganic matrixes, followed by
thermal activation under inert atmosphere, has consid-
erable potential for the stabilization of highly dispersed
* To whom correspondence should be addressed. E-mail: braunst@
chimie.u-strasbg.fr.
(1) (a) Simon, U. Adv. Mater. 1998, 10, 1487. (b) Schmid, G.; Chi,
L. F. Adv. Mater. 1998, 10, 515. (c) Simon, U. In Metal Clusters in
Chemistry; Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-
VCH: Weinheim, 1999; Vol. 3, p 1342.
† Laboratoire de Chimie de Coordination, Universite´ Louis Pasteur.
‡ Universite´ des Fre`res Mentouri-Constantine.
§ Laboratoire DECMET, Universite´ Louis Pasteur.
10.1021/om030327j CCC: $25.00 © 2003 American Chemical Society
Publication on Web 09/26/2003

4406 Organometallics, Vol. 22, No. 22, 2003
Sch em e 1. An ch or in g of a Co4 Clu ster in to F u n tion a lized Alu m in a Mem br a n es7
Choualeb et al.
cavity in which they are embedded.2,3 We have shown
that impregnation of a mesoporous xerogel or of MCM-
41 with an organic solution of the heterometallic cluster
[NEt4][Co3Ru(CO)12] and subsequent thermal treatment
lead to highly dispersed magnetic nanoparticles under
milder conditions than when conventional metal salts
are used as precursors.4
prepared the short-bite alkoxysilyl-functionalized diphos-
phine ligands (Ph2P)2N(CH2)3Si(OMe)3, (Ph2P)2N(CH2)4-
SiMe2(OMe), and (Ph2P)2N(CH2)3Si(OEt)3 and used
7,8
them to derivatize the pore walls of nanoporous alumina
membranes.7 The covalent attachment of the diphos-
phine ligands by Si-O bond formation provides a
molecular anchor that allowed subsequent reaction with
the derivative [Co4(CO)10(µ-dppa)] (dppa ) Ph2PNHPPh2),
1b,9 which has a more selective substitution chemistry
than the parent [Co4(CO)12] (Scheme 1).7
We have also used an ordered mesoporous silica of
the type SBA-15 as matrix,10 with (Ph2P)2N(CH2)3Si-
(OMe)3 as anchoring ligand.7 The molecular cluster to
be tethered was again [Co4(CO)10(µ-dppa)], and subse-
quent thermal treatment of the organometallic hybrid
mesoporous silica led to pure nanocrystalline Co2P
particles that were more regular in spatial repartition,
size, and shape than when a silica xerogel, obtained by
the sol-gel process, was used.11
In addition to the impregnation method, and since the
nature of the interactions between the metal cluster and
the host matrix plays a very important role, in particu-
lar but not solely in controling the quantity of metal
incorporated, it appears attractive to develop anchoring
methods that consist in the grafting of molecular metal
clusters into the pores of the matrix5 by using a
bifunctional ligand that would provide a stronger link
between the molecular precursor and the host.6 This
ligand should also lead to a stable molecular species in
order to minimize the risk of breaking the metal-ligand
interaction and thus avoid leaching of the metal com-
plex. We have begun to explore general approaches to
this aim, by attaching first one end of the ligand to the
inorganic matrix and then reacting the other functional
end with the molecular cluster, or first preparing the
functionalized cluster and reacting it with the host
matrix to generate the covalent linkage.7 We have
In such systems, the dative bonding between the
functional ligand and the cluster results from donation
of the phosphorus lone pair to the metal and the
improved stability of the diphosphine system compared
to a monophosphine linkage result from the formation
of a stable MPNPM′ five-membered ring. Generating a
covalent linkage between the metal complex and the
host matrix represents an attractive extension, and we
have already applied the sol-gel process to incorporate
mono- and bimetallic species into an inorganic matrix
by condensation of alkoxysilyl-substituted metal alkyl
complexes with TEOS.12 We became interested in
developing other ligand systems that would form strong,
covalent bonds with the metal cluster and could be
amenable to condensation with an inorganic matrix or
its precursor (e.g., TEOS). Functional alkynes appeared
to us suitable candidates since interaction of their
(2) (a) Braunstein, P.; Devenish, R.; Gallezot, P.; Heaton, B. T.;
Humphreys, C. J .; Kervennal, J .; Mulley S.; Ries, M. Angew. Chem.,
Int. Ed. 1988, 27, 927. (b) Kawi, S.; Gates, B. C. In Clusters and
Colloids. From Theory to Applications; Schmid, G., Ed.; Wiley-VCH:
Weinheim, 1994; Chapter 4, p 298. (c) Lindner, E.; Schneller, T.; Auer,
F.; Mayer, H. A. Angew. Chem., Int. Ed. 1999, 38, 2154. (d) Sasaki,
M.; Osada, M.; Higashimoto, N.; Yamamoto, T.; Fukuoka A.; Ichikawa,
M. J . Mol. Catal. A: Chem. 1999, 141, 223. (e) Hermans, S.; Raja, R.;
Thomas, J . M.; J ohnson, B. F. G.; Sankar, G.; Gleeson, D. Angew.
Chem., Int. Ed. 2001, 40, 1211. (f) Thomas, J . M.; J ohnson, B. F. G.;
Raja, R.; Sankar, G.; Midgley, P. A. Acc. Chem. Res. 2003, 36, 20, and
references cited.
(3) Braunstein, P.; Rose´, J . Heterometallic Clusters in Catalysis.
In Metal Clusters in Chemistry; Braunstein, P., Oro, L. A., Raithby,
P. R., Eds.; Wiley-VCH: Weinheim, Germany, 1999; Vol. 2, pp 616-
677.
(4) Schweyer, F.; Braunstein, P.; Estourne`s, C.; Guille, J .; Kessler,
H.; Paillaud, J .-L.; Rose´, J . Chem. Commun. 2000, 1271.
(5) (a) Brunel, D.; Bellocq, N.; Sutra, P.; Cauvel, A.; Laspe´ras, M.;
Moreau, P.; Di Renzo, F.; Galarneau, A.; Fajula, F. Coord. Chem. Rev.
1998, 180, 1085. (b) Behringer, K. D.; Blu¨mel, J . Inorg. Chem. 1996,
35, 1814.
(7) Braunstein, P.; Kormann, H.-P.; Meyer-Zaika, W.; Pugin, R.;
Schmid, G. Chem. Eur. J . 2000, 6, 4637.
(8) For (Ph2P)2N(CH2)3Si(OEt)3, see: Bachert, I.; Braunstein, P.;
Hasselbring, R. New J . Chem. 1996, 20, 993.
(9) Moreno, C.; Macazaga, M. J .; Marcos, M. L.; Gonzalez-Velasco,
J .; Delgado, S. J . Organomet. Chem. 1993, 452, 185.
(10) Zhao, D.; Feng, J .; Huo, Q.; Melosh, N.; Fredrickson, G. H.;
Chmelka, B. F.; Stucky, G. D. Science 1998, 279, 548.
(11) Schweyer-Tihay, F.; Braunstein, P.; Estourne`s, C.; Guille, J .
L.; Lebeau, B.; Paillaud, J .-L.; Richard-Plouet, M.; Rose´, J . Chem.
Mater. 2003, 15, 57.
(6) (a) Mercier, L.; Pinnavaia, T. J . Adv. Mater. 1997, 9, 500. (b)
Brunel, D. Microporous Mesoporous Mater. 1999, 27, 329. (c) Price, P.
M.; Clark, J . H.; Macquarrie, D. J . J . Chem. Soc., Dalton Trans. 2000,
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Wittig, J . E.; J ones, B. D.; Glosser, R.; Zhu, J . G. J . Organomet. Chem.
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Soc., Chem. Commun. 1995, 229.

Tetracobalt Carbonyl Clusters
Organometallics, Vol. 22, No. 22, 2003 4407
Sch em e 2. Syn th etic Rou tes to Bu tter fly Clu ster s 2a -c a n d Th eir Isom er s 2′a -c
carbon-carbon triple bond with two or more metal
centers can lead to the formation of strong, covalent
metal-carbon σ bonds,13 and we have recently reported
our first results in this direction.14 In this context, we
have focused the present work on the preparation and
characterization of molecular precursors based on tet-
ranuclear cobalt carbonyl clusters, which could give rise
to interesting magnetic materials.4 The cluster [Co4-
(CO)12] has a rich substitution chemistry,15-18 and its
reactions with suitably functionalized alkynes may
afford convenient precursors for subsequent anchoring
processes upon condensation reaction between this
function and surface OH groups. However [Co4(CO)10-
(µ4-η2-alkyne)] clusters, of which the first example
reported in the literature was [Co4(CO)10(µ4-η2-EtC2-
Et)],19 are often prone to decomposition, giving [Co2-
(CO)6(µ-η2-alkyne)] complexes,15b,20 which is consistent
with the greater reactivity of [Co4(CO)10(µ4-η2-alkyne)]
clusters compared to the corresponding dicobalt com-
plexes [Co2(CO)6(µ-η2-alkyne)].21 Stabilization of these
clusters against fragmentation with bi- or polydentate
phosphines is therefore desirable.22
between the metal clusters and alkynes. We have
focused on short-bite diphosphine ligands such as Ph2-
PCH2PPh2 (dppm), Ph2PNHPPh2 (dppa), and the func-
tionalized diphosphine (Ph2P)2N(CH2)3Si(OEt)3 (dppaSi)
known to be suitable for supporting a metal-metal bond
and increasing cluster stability.23 By combining the
beneficial basicity of phosphine donors and the bridging
ability of these diphosphine ligands that results in five-
membered rings, we hoped to obtain functional alkyne-
substituted clusters more stable than when starting
from [Co4(CO)12].
In this paper, we describe the synthesis and X-ray
diffraction studies of diphosphine derivatives of [Co4-
(CO)12] and of two isomers of Co4-alkyne diphosphine
clusters and report an investigation on the substitution
reactions of diphosphine derivatives of [Co4(CO)12] with
new alkynes containing alkoxysilyl functions suitable
to form sol-gel materials. We also undertook an inves-
tigation of the reactions of [Co4(CO)12] and its diphos-
phine derivatives with the conjugated, protected diyne
1,4-bis(trimethylsilyl)butadiyne. Only a few reactions
of [Co4(CO)12] with diynes have been reported.13a,15b,24
Subsequent functionalization of these clusters should
be possible, and studies with nonprotected diynes have
shown that they behave toward the cluster effectively
as two separate alkyne units. Recently, the first example
of tetracobalt metalloligated (or “spiked”) triangular
cluster containing an acetylide ligand, [Co4(CO)10(µ-CO)-
{H2CdCC(Me)2N(Me)C(Me)C(µ4-C)}], was prepared by
It was also hoped that this metal core stabilization
would lead to improved yield and selectivity of reactions
(13) See for example: (a) Sappa, E.; Tiripicchio, A.; Braunstein, P.
Chem. Rev. 1983, 83, 203. (b) Allison, N. T.; Fritch, J . R.; Vollhardt,
K. P. C.; Walborsky, E. C. J . Am. Chem. Soc. 1983, 105, 1384. (c)
Raithby, P. R.; Rosales, M. J . Adv. Inorg. Chem. Radiochem. 1985,
29, 169.
(14) Choualeb, A.; Rose´, J .; Braunstein, P.; Welter, R. Organome-
tallics 2003, 22, 2688.
(15) (a) Chini, P.; Heaton, B. T. Top. Curr. Chem. 1977, 71, 1. (b)
Went, M. J . Adv. Organomet. Chem. 1997, 41, 69. (c) Darensbourg, D.
J .; Incorvia, M. J . Inorg. Chem. 1980, 19, 2585.
(16) Holland, G. F.; Ellis, D. E.; Trogler, W. C. J . Am. Chem. Soc.
1986, 108, 1884.
(17) Wang, J .-Q.; Shen, J . K.; Gao, Y.-C.; Shi, Q.-Z.; Basolo, F. J .
Organomet. Chem. 1991, 417, 131.
(18) Sizun, C.; Kempgens, P.; Raya, J .; Elbayed, K.; Granger, P.;
Rose´, J . J . Organomet. Chem. 2000, 604, 27.
(19) Dahl, L. F.; Smith, D. L. J . Am. Chem. Soc. 1962, 84, 2450.
(20) Dickson, R. S.; Tailby, G. R. Aust. J . Chem. 1970, 23, 229.
(21) Kru¨erke, U.; Hu¨bel, W. Chem. Ber. 1961, 94, 2829.
(22) See for example: Kennedy, J . R.; Selz, P.; Rheingold, A. L.;
Trogler, C. W.; Basolo, F. J . Am. Chem. Soc. 1989, 111, 3615.
(23) (a) Braunstein, P.; Knorr, M.; Stern, C. Coord. Chem. Rev. 1998,
178-180, 903. (b) Bachert, I.; Braunstein, P.; Guillon, E.; Massera,
C.; Rose´, J .; DeCian, A.; Fischer, J . J . Cluster Sci. 1999, 10, 445. (c)
Bachert, I.; Braunstein, P.; McCart, M. K.; Fabrizi de Biani, F.; Laschi,
F.; Zanello, P.; Kickelbick, G.; Schubert, U. J . Organomet. Chem. 1999,
573, 47. (d) Bachert, I.; Bartussek, I.; Braunstein, P.; Guillon, E.; Rose´,
J .; Kickelbick, G. J . Organomet. Chem. 1999, 588, 143. (e) Braunstein,
P.; Durand, J .; Kickelbick, G.; Knorr, M.; Morise, X.; Pugin, R.;
Tiripicchio, A.; Ugozzoli, F. J . Chem. Soc., Dalton Trans. 1999, 4175.
(24) (a) Low, P. J .; Bruce, M. I. Adv. Organomet. Chem. 2002, 48,
71. (b) Dickson, R. S.; Tailby, G. R. Aust. J . Chem. 1969, 22, 1143.

4408 Organometallics, Vol. 22, No. 22, 2003
Choualeb et al.
Ta ble 1. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 1a (estim a ted sta n d a r d d evia tion s
in p a r en th eses)
Co(1)-Co(2)
Co(1)-Co(3)
Co(1)-Co(4)
Co(1)-P(1)
Co(1)-C(1)
Co(1)-C(2)
Co(1)-C(3)
Co(2)-Co(3)
Co(2)-Co(4)
Co(2)-P(2)
Co(2)-C(2)
Co(2)-C(4)
2.4268(8)
2.4565(7)
2.5014(7)
2.190(1)
1.759(5)
1.932(5)
1.929(4)
2.4540(8)
2.5348(8)
2.194(1)
1.923(4)
1.767(5)
Co(2)-C(5)
Co(3)-Co(4)
Co(3)-C(3)
Co(3)-C(5)
Co(3)-C(6)
Co(3)-C(7)
Co(4)-C(8)
Co(4)-C(9)
Co(4)-C(10)
P(1)-C(23)
P(2)-C(23)
1.920(4)
2.528(1)
1.957(4)
1.945(4)
1.789(5)
1.779(5)
1.809(5)
1.830(6)
1.791(5)
1.855(4)
1.843(4)
Co(2)-Co(1)-Co(3)
Co(2)-Co(1)-Co(4)
Co(2)-Co(1)-P(1)
Co(3)-Co(1)-Co(4)
Co(3)-Co(1)-P(1)
Co(4)-Co(1)-P(1)
Co(1)-Co(2)-Co(3)
Co(1)-Co(2)-Co(4)
Co(1)-Co(2)-P(2)
Co(3)-Co(2)-Co(4)
Co(3)-Co(2)-P(2)
Co(4)-Co(2)-P(2)
Co(1)-Co(3)-Co(2)
Co(1)-Co(3)-Co(4)
Co(2)-Co(3)-Co(4)
Co(1)-Co(4)-Co(2)
Co(1)-Co(4)-Co(3)
60.33(2) Co(2)-Co(4)-Co(3)
61.89(2) P(1)-C(23)-P(2)
99.71(4) C(23)-P(1)-Co(1)
61.32(3) C(23)-P(2)-Co(2)
102.84(4) Co(1)-C(1)-O(1)
159.56(4) Co(1)-C(2)-O(2)
60.43(2) Co(2)-C(2)-O(2)
60.50(2) Co(1)-C(3)-O(3)
98.22(4) Co(3)-C(3)-O(3)
60.88(2) Co(2)-C(4)-O(4)
104.17(4) Co(2)-C(5)-O(5)
157.70(4) Co(3)-C(5)-O(5)
59.23(2) Co(3)-C(6)-O(6)
60.22(2) Co(3)-C(7)-O(7)
61.14(2) Co(4)-C(8)-O(8)
57.61(2) Co(4)-C(9)-O(9)
57.98(2)
114.5(2)
110.5(1)
111.3(1)
177.0(4)
142.1(4)
139.9(4)
143.0(3)
138.5(3)
179.2(4)
143.6(4)
137.5(4)
179.2(4)
177.9(4)
178.1(5)
179.1(5)
F igu r e 1. View of the molecular structure of cluster 1a .
Only the ipso carbons of the phenyl groups are shown, and
the hydrogen atoms have been omitted for clarity.
reaction of [Co4(CO)12] with the diacetylenic amine
N(Me)(HCtCCMe2)2.25
58.47(2) Co(4)-C(10)-O(10) 178.4(5)
Resu lts a n d Discu ssion
The P(1)-C(23)-P(2) angle of 114.5(2)° is larger than
in [Co4(CO)8{µ-Me2PCH2PMe2}2] (107.5(4)° and 110.7-
(4)°) taken for comparison in the absence of a dppm
analogue.28a The P-C-P angle in dppm complexes is
generally smaller than the P-N-P angle in the corre-
sponding dppa complexes, with typical values of ca. 107°
and 119°, respectively.23c,d A notable exception was
found in the rectangular cluster [Pd4(µ-Cl)2(µ-dppm)2-
(µ-dppa)2]2+, which displays P-C-P and P-N-P angles
of 118.9(2)° and 113.5(2)°, respectively.23b In the free
ligands, the P-C-P and P-N-P angles in dppm and
dppa are 106.2(3)°28b and 118.9(2)°, respectively.28c,d
The structural similarity between clusters 1a -c is
supported by the pattern of the ν(CO) absorptions in
the IR spectrum and the singlet in the 31P{1H} NMR
spectrum for the two equivalent P nuclei. The broaden-
ing of the 31P{1H} NMR signals for all complexes is
consistent with the rapid relaxation29 induced by the
quadrupolar Co nuclei (I ) 7/2). Best yields of 1a were
obtained with very short reaction times since this
molecule progressively transforms to give the green,
tetrasubstituted cluster [Co4(CO)8(µ-dppm)2]. This latter
cluster is also obtained by reaction of excess dppm with
[Co4(CO)12] or by thermal treatment of [Co2(CO)6(µ-
dppm)].30 Since it did not react with PhCtCH, even
when Me3NO was used as CO activator, it was not
further investigated.
Syn th esis a n d Ch a r a cter iza tion of th e Clu ster s
[Co4(µ-CO)3(CO)7(µ-d p p y)] (1a -c). Reaction of [Co4-
(CO)12] with 1 equiv of dppm, dppa, or dppaSi in CH2-
Cl2 or in hexane at room temperature afforded rapidly
the tetrahedral clusters 1a -c, in which the diphosphine
ligand has substituted two carbonyl ligands and bridges
two basal cobalt atoms (Scheme 2). This has been
previously reported in the case of 1b.9 The structure of
1a has now been determined by X-ray diffraction to
provide more comparative data. A view of the structure
is shown in Figure 1, and selected bond distances and
angles are given in Table 1.
The molecular structure of 1a contains a slightly
distorted tetrahedral Co4 cluster. There is almost a
mirror plane passing through the cluster, which con-
tains the atoms Co(3), Co(4), C(6), C(7), C(10), and C(23).
The basal face Co(1)-Co(3) has three edge-bridging
carbonyl groups, and the P substituents occupy axial
positions at Co(1) and Co(2) with P(1)-Co(1)-Co(4) and
P(2)-Co(2)-Co(4) angles of 159.56(4)° and 157.70(4)°,
respectively. The Co-Co edge bridged by the dppm
ligand (Co(1)-Co(2) ) 2.4268(8) Å) is shorter than the
other two (Co(1)-Co(3) ) 2.4565(7) Å and Co(2)-Co(3)
) 2.4540(8) Å). The remaining seven carbonyl ligands
are essentially linear (Co-C-O ) 177.0(4)-179.2(4)°).
The Co-P bond lengths (Co(1)-P(1) ) 2.190(1) Å and
Co(2)-P(2) ) 2.194(1) Å) are within the range of those
observed in phosphine and phosphite derivatives of [Co4-
(CO)12].26,27 The five-membered ring Co2P2C adopts an
envelope conformation with the CH2 group at the flap.
(28) (a) Mirza, H. A.; Vittal, J . J .; Puddephatt, R. J .; Frampton, C.
S.; Manojlovic-Muir, L.; Xia, W.; Hill, R. H. Organometallics 1993, 12,
2767. (b) Schmidbaur, H.; Reber, G.; Schier, A.; Wagner, F. E.; Mu¨ller,
G. Inorg. Chim. Acta 1988, 147, 143. (c) No¨th, H.; Fluck, E. Z.
Naturforsch. 1984, 39b, 744. (d) For a recent comparison of Pt(II)
complexes with the bridging ligands dppa and dppm, see: J amali, S.;
Rashidi, M.; J ennings, M. C.; Puddephatt, R. J . Dalton Trans. 2003,
2313.
(25) Costa, M.; Gervasio, G.; Marabello, D.; Sappa, E. J . Organomet.
Chem. 2002, 656, 57.
(26) Bahsoun, A. A.; Osborn, J . A.; Voelker, G.; Bonnet, J . J .;
Lavigne, G. Organometallics 1982, 1, 1114.
(27) Darensbourg, D. J .; Zalewski, D. J .; Delord, T. Organometallics
1984, 3, 1210.
(29) Aime, S.; Gobetto, R.; Osella, D.; Milone, L.; Hawkes, G. E.;
Randall, E. W. J . Magn. Reson. 1988, 65, 308.
(30) (a) Huq, R.; Poe¨, A. J . Organomet. Chem. 1982, 226, 277. (b)
Lisic, E. C.; Hanson, B. E. Inorg. Chem. 1986, 25, 812.

Tetracobalt Carbonyl Clusters
Organometallics, Vol. 22, No. 22, 2003 4409
Ta ble 2. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 2a (estim a ted sta n d a r d d evia tion s
in p a r en th eses)
Co(1)-Co(2)
Co(1)-Co(3)
Co(1)-Co(4)
Co(1)-P(1)
Co(1)-C(1)
Co(1)-C(2)
Co(1)-C(9)
Co(2)-Co(3)
Co(2)-P(2)
Co(2)-C(2)
Co(2)-C(3)
Co(2)-C(9)
Co(2)-C(10)
Co(3)-Co(4)
2.410(1)
2.620(1)
2.411(1)
2.218(1)
1.782(4)
1.965(3)
1.988(3)
2.480(1)
2.200(1)
1.845(3)
1.746(4)
2.026(3)
2.091(3)
2.455(1)
Co(3)-C(4)
Co(3)-C(5)
Co(3)-C(6)
Co(3)-C(10)
Co(4)-C(6)
Co(4)-C(7)
Co(4)-C(8)
Co(4)-C(9)
Co(4)-C(10)
P(1)-C(29)
P(2)-C(29)
C(9)-C(10)
C(10)-C(11)
1.791(4)
1.790(4)
1.967(4)
2.007(3)
1.895(4)
1.763(4)
1.756(4)
2.057(3)
2.118(3)
1.856(4)
1.840(3)
1.405(4)
1.484(4)
Co(2)-Co(1)-Co(3)
Co(2)-Co(1)-Co(4)
Co(2)-Co(1)-P(1)
Co(2)-Co(1)-C(9)
Co(3)-Co(1)-Co(4)
Co(3)-Co(1)-P(1)
Co(3)-Co(1)-C(9)
Co(4)-Co(1)-P(1)
Co(4)-Co(1)-C(9)
P(1)-Co(1)-C(9)
Co(1)-Co(2)-Co(3)
Co(1)-Co(2)-P(2)
Co(1)-Co(2)-C(9)
Co(1)-Co(2)-C(10)
Co(3)-Co(2)-P(2)
Co(3)-Co(2)-C(9)
Co(3)-Co(2)-C(10)
P(2)-Co(2)-C(9)
P(2)-Co(2)-C(10)
C(9)-Co(2)-C(10)
Co(1)-Co(3)-Co(2)
Co(1)-Co(3)-Co(4)
Co(1)-Co(3)-C(10)
Co(2)-Co(3)-Co(4)
Co(2)-Co(3)-C(10)
Co(4)-Co(3)-C(10)
Co(1)-Co(4)-Co(3)
Co(1)-Co(4)-C(9)
58.90(3) Co(1)-Co(4)-C(10)
93.80(4) Co(3)-Co(4)-C(9)
98.01(4) Co(3)-Co(4)-C(10)
75.91(9)
74.31(9)
51.42(8)
39.3(1)
112.6(1)
108.0(1)
107.7(1)
73.8(1)
53.8(1)
C(9)-Co(4)-C(10)
58.24(3) P(1)-C(29)-P(2)
156.89(4) Co(1)-P(1)-C(29)
71.6(1)
Co(2)-P(2)-C(29)
128.80(4) Co(1)-C(9)-Co(2)
54.8(1)
94.7(1)
64.78(4) Co(2)-C(9)-Co(4)
99.32(5) Co(2)-C(9)-C(10)
52.4(1)
76.4(1)
F igu r e 2. View of the molecular structure of cluster 2a .
Only the ipso carbons of the phenyl groups of the phosphine
ligand are shown, and the hydrogen atoms have been
omitted for clarity.
Co(1)-C(9)-Co(4)
Co(1)-C(9)-C(10)
73.1(1)
109.7(2)
119.1(2)
72.5(2)
Co(2)-C(10)-Co(3)
Co(2)-C(10)-Co(4) 113.5(1)
74.4(1)
164.03(3) Co(2)-C(10)-C(9)
74.2(1) Co(3)-C(10)-Co(4)
51.23(8) Co(4)-C(10)-C(9)
95.1(1) Co(1)-C(1)-O(1)
126.17(9) Co(1)-C(2)-O(2)
39.9(1) Co(2)-C(2)-O(2)
56.32(3) Co(2)-C(3)-O(3)
56.61(2) Co(3)-C(4)-O(4)
72.97(9) Co(3)-C(5)-O(5)
91.00(3) Co(3)-C(6)-O(6)
54.31(9) Co(4)-C(6)-O(6)
67.6(2)
73.0(1)
68.0(2)
Syn th esis a n d Ch a r a cter iza tion of th e Clu ster s
[Co4(µ-CO)2(CO)6(µ-d p p y)(µ4-η2-P h C2H )] (2a -c).
Clusters 1a -c were reacted with excess phenylacetylene
to afford the green butterfly clusters 2a -c in high yield
(Scheme 2). This was established by an X-ray diffraction
study of 2a , and a view of the structure is shown in
Figure 2. Selected bond distances and angles are given
in Table 2 and discussed below. Insertion of the alkyne
into a Co-Co bond of the precursor has occurred
between one of the phosphine-substituted Co centers of
1a and, most likely, the apical Co atom since it should
be easier to break a Co-Co bond not supported by a
bridging CO ligand. However, the related isoelectronic
cluster [RuCo3(CO)12]-, which has an apical Ru(CO)3
fragment, also reacted with alkynes to afford butterfly
clusters in which a Co-Ru bond forms the hinge of the
butterfly,31 implying that in this case a CO-bridged
Co-Co bond was the site of alkyne insertion.
178.5(3)
136.9(3)
144.7(3)
178.8(3)
178.4(3)
175.8(4)
138.6(3)
142.3(3)
175.8(4)
171.6(4)
55.6(1)
Co(4)-C(7)-O(7)
65.16(2) Co(4)-C(8)-O(8)
52.11(9)
Syn th esis a n d Ch a r a cter iza tion of th e Isom er ic
Clu ster s [Co4(µ-CO)2(CO)6(µ-d p p y)(µ4-η2-P h C2H)]
(2′a -c). In an alternative synthetic procedure, we
reacted the alkyne cluster 3, derived from [Co4(CO)12]
and phenylacetylene,20 with the diphosphines dppy
(Scheme 2, procedure B). Although this led to the
expected carbonyl substitution at the butterfly cluster
in good yields, an X-ray diffraction study of the dppa
derivative 2′b‚0.5CH2Cl2 revealed that an isomer of 2b
has formed. A view of the structure of 2′b is shown in
Figure 3, and selected bond distances and angles are
given in Table 3. Like in 2b, a Co-Co bond connecting
a wing-tip and a hinge atom is supported by the
diphosphine, and the alkyne phenyl group is in a remote
position with respect to the PPh2 group. However,
disubstitution of CO in 3 by dppa has occurred regiospe-
cifically on an unbridged Co-Co edge, and the two
bridging carbonyls do not span the same Co-Co bonds
as established in 2a and assumed in 2b. Clusters 2b
and 2′b are not mirror images of each other. Their IR
spectra are however very similar. Disubstitution of CO
in [Co4(CO)10(µ4-η2-alkyne)] clusters by monophosphines
has been reported to occur regiospecifically on the wing-
tip atoms,32 which is of course impossible with diphos-
phines such as dppy. As was observed for 2b, the
Whereas the 1H NMR spectrum of 1a in CDCl3
showed a broad resonance at 2.85 ppm for the CH2
protons, they appeared as an ABXY spin system (CHA-
CHBP2) in 2a , as expected from the loss of symmetry in
2. At room temperature, the 31P{1H} NMR spectrum of
2b contains two broad resonances at δ 81.2 and 87.4
ppm for the two chemically different P nuclei, in
contrast to 2a and 2c, for which only one broad
resonance was observed, at 28.3 and 81.0 ppm, respec-
tively. We verified for 2a that at 0 °C this resonance
splits into two broad signals with a 1:1 intensity. The
J (PP) coupling could not be resolved owing to the
broadness of the signals. We assume that 2b,c have a
structure analogous to that of 2a . We have no evidence
for the formation of isomeric structures corresponding
to an opposite orientation of the alkyne in the cluster;
the latter would be disfavored for steric reasons, owing
to repulsion between the phenyl groups.
(31) Braunstein, P.; Rose´, J .; Bars, O. J . Organomet. Chem. 1983,
252, C101.

4410 Organometallics, Vol. 22, No. 22, 2003
Choualeb et al.
The alkyne C(9)-C(10) bonds of 1.405(4) Å in 2a and
1.409(4) Å in 2′b‚0.5CH2Cl2 are significantly elongated
when compared to the free alkyne (1.19 Å), consistent
with their 2σ, 2π bonding.13a The Co-Co distances range
from 2.410(1) to 2.620(1) Å in 2a and from 2.419(1) to
2.543(1) Å in 2′b‚0.5CH2Cl2, the shorter bonds being
those supported by the bridging ligands and the longer
being the hinge of the butterfly Co(1)-Co(3). The
differences in Co-C(9) and Co-C(10) distances reflect
the presence of the phenyl group at C(10) and of the
dppy ligand. The dihedral angles between the butterfly
wings of 121.7° in 2a and 117° in 2′b lead to nonbonding
Co(2)‚‚‚Co(4) distances of 3.52 and 3.55 Å, respectively.
The alkyne hydrogen at C(9) was not detected by 1H
NMR spectroscopy (masked by aryl protons), but it was
located by X-ray diffraction in both structures. In the
butterfly cluster [Co4(CO)8(PPh3)2(µ4-η2-HC2H)], the
C-H 1H NMR resonance was observed as a triplet at
7.82 ppm.33 We assume that clusters 2′a -c have a
similar structure, although spectroscopic data in solu-
tion would not allow the identification of minor struc-
tural changes.
F igu r e 3. View of the molecular structure of the cluster
2′b in 2′b‚0.5CH2Cl2. Only the ipso carbons of the phenyl
groups of the phosphine ligand are shown, and the solvent
and hydrogen atoms have been omitted for clarity.
Attempts to functionalize clusters 2b and 2′b by
deprotonation of the NH group using DBU or KH as a
base followed by addition of Cl(CH2)3Si(OEt)3 or
OdCdN(CH2)3Si(OMe)3 failed. Other approaches were
therefore attempted (see below).
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 2′b‚0.5CH2Cl2 (estim a ted sta n d a r d
d evia tion s in p a r en th eses)
Co(1)-Co(2)
Co(1)-Co(3)
Co(1)-Co(4)
Co(1)-P(1)
Co(1)-C(1)
Co(1)-C(8)
Co(1)-C(9)
Co(2)-Co(3)
Co(2)-P(2)
Co(2)-C(2)
Co(2)-C(3)
Co(2)-C(9)
Co(2)-C(10)
Co(3)-Co(4)
2.456(1)
2.543(1)
2.419(1)
2.172(1)
1.785(3)
1.914(3)
1.983(3)
2.448(1)
2.168(1)
1.777(3)
1.833(3)
2.072(3)
2.050(3)
2.456(1)
Co(3)-C(3)
Co(3)-C(4)
Co(3)-C(5)
Co(3)-C(10)
Co(4)-C(6)
Co(4)-C(7)
Co(4)-C(8)
Co(4)-C(9)
Co(4)-C(10)
P(1)-N
2.055(3)
1.795(3)
1.800(3)
2.009(3)
1.759(3)
1.776(3)
1.935(3)
2.050(3)
2.142(3)
1.683(3)
1.694(3)
1.409(4)
1.498(4)
Syn th esis of Alk oxysilyl-F u n ction a lized Alk yn e
Clu ster s. With the objective to incorporate in a Co4
cluster a functional alkyne that could be subsequently
condensed with a silica matrix via the sol-gel method,
we decided to take advantage of the stabilizing effect of
dppm or dppa on the Co4 core to react 1a ,b with the
new alkyne PhCtCC(O)NH(CH2)3Si(OMe)3 (L1) and the
recently reported alkynes HCtCCH2NHC(O)NH(CH2)3-
Si(OEt)3 (L2) and HCtC(CH2)2OC(O)NH(CH2)3Si(OEt)3
(L3).14 Alkyne L1 was prepared in two steps by the
method outlined in eq 1, which involved treatment of
3-phenylpropiolic acid with thionyl chloride followed by
addition of 3-aminopropyl trimethoxysilane. The ligand
was characterized by 1H, 13C, and 29Si NMR and IR
spectroscopy. The infrared spectrum in dichloromethane
contains a strong absorption band at 2220 cm-1 for the
CtC triple bond.
P(2)-N
C(9)-C(10)
C(10)-C(11)
Co(2)-Co(1)-Co(3)
Co(2)-Co(1)-Co(4)
Co(2)-Co(1)-P(1)
Co(2)-Co(1)-C(9)
Co(3)-Co(1)-Co(4)
Co(3)-Co(1)-P(1)
Co(3)-Co(1)-C(9)
Co(4)-Co(1)-P(1)
Co(4)-Co(1)-C(9)
P(1)-Co(1)-C(9)
Co(1)-Co(2)-Co(3)
Co(1)-Co(2)-P(2)
Co(1)-Co(2)-C(9)
Co(1)-Co(2)-C(10)
Co(3)-Co(2)-P(2)
Co(3)-Co(2)-C(9)
Co(3)-Co(2)-C(10)
P(2)-Co(2)-C(9)
P(2)-Co(2)-C(10)
C(9)-Co(2)-C(10)
Co(1)-Co(3)-Co(2)
Co(1)-Co(3)-Co(4)
Co(1)-Co(3)-C(10)
Co(2)-Co(3)-Co(4)
Co(2)-Co(3)-C(10)
Co(4)-Co(3)-C(10)
Co(1)-Co(4)-Co(3)
Co(1)-Co(4)-C(9)
Co(1)-Co(4)-C(10)
Co(3)-Co(4)-C(9)
58.61(3) Co(3)-Co(4)-C(10)
93.60(2) C(9)-Co(4)-C(10)
101.73(3) P(1)-N-P(2)
51.27(8)
39.2(1)
119.9(1)
102.5(1)
104.5(1)
104.8(1)
114.6(1)
73.7(1)
54.40(9) C(17)-P(1)-C(23)
59.28(2) Co(1)-P(1)-N
159.14(3) C(29)-P(1)-C(35)
72.89(9) Co(2)-P(2)-N
120.41(3) Co(1)-C(9)-Co(4)
54.44(9) Co(1)-C(9)-Co(2)
90.19(9) Co(1)-C(9)-C(10)
62.48(2) Co(2)-C(9)-Co(4)
85.22(3) Co(2)-C(9)-C(10)
5 1.10(8) Co(4)-C(9)-C(10)
75.43(9) Co(2)-C(10)-Co(3)
74.5(1)
108.6(2)
119.1(1)
69.2(2)
73.9(2)
74.2(1)
141.59(3) Co(2)-C(10)-Co(4) 115.9(1)
73.66(9) Co(2)-C(10)-C(9)
52.15(8) Co(3)-C(10)-Co(4)
102.89(9) Co(3)-C(10)-C(9)
141.94(9) Co(4)-C(10)-C(9)
70.8(2)
72.5(1)
104.4(2)
66.9(2)
40.0(1)
C(9)-C(10)-C(11)
125.9(3)
178.7(4)
179.1(3)
149.4(3)
132.7(3)
179.0(3)
175.6(4)
173.4(4)
176.3(3)
144.3(3)
137.8(3)
58.90(2) Co(1)-C(1)-O(1)
57.84(2) Co(2)-C(2)-O(2)
74.06(9) Co(2)-C(3)-O(3)
92.86(2) Co(3)-C(3)-O(3)
53.67(8) Co(3)-C(4)-O(4)
56.25(9) Co(3)-C(5)-O(5)
62.89(2) Co(4)-C(6)-O(6)
51.89(8) Co(4)-C(7)-O(7)
74.68(8) Co(1)-C(8)-O(8)
73.84(9) Co(4)-C(8)-O(8)
The reactions of 1a ,b with L1 and L2 afforded the
clusters 4a ,b and 5a ,b, respectively, and 6a was ob-
tained by reaction of 1a with L3. The analytical and
31P{1H} NMR spectrum of 2′b shows two signals, at δ
79.7 and 87.6 ppm.
(32) Raithby, P. R. In Transition Metal Clusters; J ohnson, B. F. G.,
Ed.; Wiley: New York, 1980; Chapter 2.

Tetracobalt Carbonyl Clusters
Organometallics, Vol. 22, No. 22, 2003 4411
Sch em e 3
spectroscopic data confirmed the presence of both the
functional alkyne and the diphosphine in the clusters.
The structures shown for these compounds were de-
duced from their spectroscopic properties and by anal-
ogy with those established by X-ray diffraction for 2a
and 2b.
synthesis of tri- and tetranuclear clusters.34 We are
currently evaluating complex 7 with its Si(OMe)3 func-
tion as a precursor to the synthesis of Co-containing
materials by the sol-gel route.
Syn th esis of [Co4(µ-CO)3(CO)5(µ-d p p m )(µ-d p p a -
Si)] (8). To broaden the scope of possibilities of attach-
ment of a functional Co4 cluster to a silica matrix, we
also examined the incorporation of dppaSi in 1a (eq 2).
This reaction afforded the mixed-diphosphine cluster 8,
which was characterized by X-ray diffraction. A view of
the structure is shown in Figure 4, and selected bond
distances and angles are given in Table 4.
Like in the case of 2b, two broad 31P{1H} NMR
resonances are observed for 4b and 5b at δ 91.1, 103.5
and 78.3, 89.0 ppm, respectively, but only one broad
signal was observed for 4a , 5a , and 6a , like for 2a . The
IR spectrum of all clusters show a characteristic
ν(CdO) band for the amide function in the region 1646-
1720 cm-1 in addition to those for the Co-bound carb-
onyls. All these clusters were obtained in the form of a
paste, which is difficult to purify since column chroma-
tography cannot be applied (presence of the alkoxysilyl
groups). Residual alkyne often contaminates the samples.
It was not possible to prepare the clusters 4a ,b, 5a ,b,
and 6a by first reacting [Co4(CO)12] with the corre-
sponding alkynes followed by the addition of the diphos-
phines because the blue [Co4(CO)10(µ4-η2-alkyne)] clus-
ters rapidly fragment in solution to give i.a. the red
[Co2(CO)6(µ-η2-alkyne)] complexes. The latter can be
obtained directly by reaction of [Co2(CO)8] with the
corresponding alkyne (in the case of L1, see Scheme 3).20
Complex 7 was characterized by IR and NMR 1H
spectroscopy and elemental analysis. These observations
clearly illustrate the advantage of using a diphosphine-
stabilized precursor cluster for subsequent reactions
with functional alkynes.
The molecular structure of 8 can be derived from that
of the parent cluster 1a by substituting an apical and
an equatorial carbonyl group on Co(3) and Co(4),
respectively, with the dppaSi ligand. The two different
diphosphine ligands bridge opposite edges of a distorted
Co4 tetrahedron, and each Co is thus substituted by a
P donor. The structure is similar to those of [Co4(CO)8-
(µ-dmpm)2]28a and [Rh4(CO)8(µ-dppm)2].35 The Co-Co
bond lengths are in the range 2.434(1)-2.543(1) Å and
are comparable with those found in the literature for
Nevertheless, complexes of the type [Co2(CO)6(µ-η2-
alkyne)] may be useful synthons for the subsequent
(34) Adams, H.; Guio, L. V. Y.; Morris, M. J .; Wildgoose, F. A. J .
Organomet. Chem. 2002, 659, 142, and references therein.
(35) Carre´, F. H.; Cotton. F. A.; Frenz, B. A. Inorg. Chem. 1976, 15,
380.
(33) Osella, D.; Ravera, M.; Nervi, C.; Housecroft, C. E.; Raithby,
P. R.; Zanello, P.; Laschi, F. Organometallics 1991, 10, 3253.

4412 Organometallics, Vol. 22, No. 22, 2003
Choualeb et al.
than the Co(3)-C(4) distance of 1.981(4) Å, which
suggests that C(4)O(4) is a bent semibridging carbonyl.37
The refinement of the X-ray data shows that the
CSi(OEt)3 group is disordered over two positions with
occupancy factors of 2/3 and 1/3. The Si-O, C-O, and
C-C distances have been fixed at values of 1.6, 1.45,
and 1.55 Å, respectively.
At room temperature, the 31P{1H} NMR spectrum
contains only two broad resonances at 28.1 and 100.5
ppm, corresponding to the dppm and dppaSi ligands,
respectively, which is not surprising for such clusters.28a
F or m a tion of [Co2(CO)4(µ-d p p m ){µ-η2-P h C2H}]
(9) fr om [Co4(µ-CO)2(CO)6(µ-d p p m )(µ4-η2-P h C2H)]
(2a ). We attempted the linking of two molecules of 2a
with 1,4-diodobenzene under Sonogashira conditions.38
Unfortunately, no coupling reaction was observed, and
instead, fragmentation of 2a afforded the red dinuclear
complex 9 (eq 3).39 Cluster fragmentation was probably
triggered by the base which is necessary for the reaction.
Similar behavior was recently observed with other
alkyne-substituted clusters.14
F igu r e 4. View of the molecular structure of cluster 8.
Only the ipso carbons of the phenyl groups are shown, and
the hydrogen atoms have been omitted for clarity.
Ta ble 4. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 8 (estim a ted sta n d a r d d evia tion s
in p a r en th eses)
Co(1)-Co(2)
Co(1)-Co(3)
Co(1)-Co(4)
Co(1)-P(1)
Co(1)-C(1)
Co(1)-C(2)
Co(1)-C(6)
Co(2)-Co(3)
Co(2)-Co(4)
Co(2)-P(2)
Co(2)-C(2)
Co(2)-C(3)
Co(2)-C(4)
2.434(1)
2.507(1)
2.490(1)
2.184(1)
1.773(5)
1.921(4)
1.936(4)
2.477(1)
2.543(1)
2.219(1)
1.920(4)
1.763(4)
1.897(5)
Co(3)-Co(4)
Co(3)-P(3)
Co(3)-C(4)
Co(3)-C(5)
Co(3)-C(6)
Co(4)-P(4)
Co(4)-C(7)
Co(4)-C(8)
P(1)-C(21)
P(2)-C(21)
P(3)-N
2.535(1)
2.183(1)
1.981(4)
1.757(5)
1.941(4)
2.188(1)
1.775(5)
1.793(5)
1.847(4)
1.847(4)
1.706(4)
1.697(4)
1
Compound 9 was identified by its H NMR data, and
the Co2C2H proton was observed as a triplet at 5.79 ppm
(3J (PH) ) 7.5 Hz), which is in agreement with literature
values for related clusters.40 Compounds of the type
[Co2(CO)4(µ-dppm)(µ-η2-alkyne)] are generally prepared
by reaction of the appropriate alkyne with [Co2(CO)6-
(µ-dppm)]40 or by reaction of dppm with the dinuclear
complexes [Co2(CO)6(µ-η2-alkyne)].41
Reaction of Co4 Clu ster s with a P r otected Diyn e.
With the objective of introducing protected functional-
ities in [Co4(CO)12], we explored its reactivity with 1,4-
bis(trimethylsilyl)butadiyne Me3SiCtCCtCSiMe3 (L4),
also because reactions of diynes with this cluster have
been very little investigated.24 The reaction was per-
formed in hexane or in dichloromethane. TLC indicated
the formation of a blue intermediate, which rapidly
transforms in solution to give the known, green product
[{Co2(CO)6(µ-η2-Me3SiC2-)}2] (10) in 21% yield (Scheme
4). We assume that initial coordination of one of the
triple bonds to [Co4(CO)12] yielded an intermediate of
the type [Co4(CO)10(µ4-η2-Me3SiC2CtCSiMe3)]. The pres-
ence of a second triple bond was suggested to facilitate
further rearrangements and fragmentation into two Co2
units.24
P(4)-N
Co(2)-Co(1)-Co(3)
Co(2)-Co(1)-Co(4)
Co(2)-Co(1)-P(1)
Co(3)-Co(1)-Co(4)
Co(3)-Co(1)-P(1)
Co(4)-Co(1)-P(1)
Co(1)-Co(2)-Co(3)
Co(1)-Co(2)-Co(4)
Co(1)-Co(2)-P(2)
Co(3)-Co(2)-Co(4)
Co(3)-Co(2)-P(2)
Co(4)-Co(2)-P(2)
Co(1)-Co(3)-Co(2)
Co(1)-Co(3)-Co(4)
Co(1)-Co(3)-P(3)
Co(2)-Co(3)-Co(4)
Co(2)-Co(3)-P(3)
Co(4)-Co(3)-P(3)
Co(1)-Co(4)-Co(2)
Co(1)-Co(4)-Co(3)
Co(1)-Co(4)-P(4)
60.18(2) Co(2)-Co(4)-Co(3)
62.20(2) Co(2)-Co(4)-P(4)
98.41(4) Co(3)-Co(4)-P(4)
60.98(2) P(1)-C(21)-P(2)
104.75(4) C(21)-P(1)-Co(1)
159.51(4) C(21)-P(2)-Co(2)
61.37(2) N-P(3)-Co(3)
59.98(2) N-P(4)-Co(4)
96.08(4) P(3)-N-P(4)
60.63(2) Co(1)-C(1)-O(1)
109.01(4) Co(1)-C(2)-O(2)
156.04(4) Co(2)-C(2)-O(2)
58.45(2) Co(2)-C(3)-O(3)
59.18(2) Co(2)-C(4)-O(4)
133.11(4) Co(3)-C(4)-O(4)
60.97(2) Co(3)-C(5)-O(5)
134.51(4) Co(1)-C(6)-O(6)
87.34(4) Co(3)-C(6)-O(6)
57.82(2) Co(4)-C(7)-O(7)
59.84(2) Co(4)-C(8)-O(8)
153.84(4)
58.40(2)
111.56(4)
94.04(4)
108.5(2)
110.1(1)
108.6(1)
116.5(1)
111.0(1)
114.9(2)
178.8(4)
140.4(3)
140.9(3)
178.9(4)
141.2(4)
139.3(4)
177.7(4)
139.8(3)
139.4(3)
177.1(4)
177.2(4)
similar structures.27,28a,36 The five terminal carbonyls
display Co-C-O angles between 177.1(4)° and
178.9(4)°. The Co-C distances range from 1.757(5) to
1.793(5) Å and are substantially shorter than the Co-
(µ-C) distances involving the bridging carbonyls
C(2)O(2) and C(6)O(6) (1.920(4)-1.941(4) Å). The
Co(2)-C(4) distance of 1.897(5) Å is considerably shorter
(37) Crabtree, R. H.; Lavin, M. Inorg. Chem. 1986, 25, 805.
(38) Sonogashira, K. J . Organomet. Chem. 2002, 653, 46.
(39) Spectroscopic data for 9: IR (hexane, νCO): 2028 (s), 2000 (vs),
1976 (vs), 1957 (w). 1H NMR (300.13 MHz, CDCl3) δ: 3.09 (m, 1H,
PCHAHBP, part of an ABX2 spin system), 3.58 (m, 1H, PCHAHBP, part
of an ABX2 spin system), 5.79 (t, 1H, 3J (HP) ) 7.5 Hz), 7.20-7.87 (m,
20H, Ph). 31P{1H} NMR (121.5 MHz, CDCl3) δ: 44.0 (br, w1/2 ) 133
Hz). Anal. Calcd for C37H28Co2O4P2‚1/5 hexane: C, 62.54; H, 4.23.
Found: C, 62.55; H, 4.09.
(40) Snaith, T. J .; Low, P. J .; Rousseau, R.; Puschmann, H.; Howard,
J . A. K. J . Chem. Soc., Dalton Trans. 2001, 292.
(41) Aggarval, R. P.; Connelly, N. G.; Crespo, M. C.; Dunne, B. J .;
Hopkins, P. M.; Orpen, A. G. J . Chem. Soc., Dalton Trans. 1992, 655.
(36) (a) Darensbourg, D. J .; Zalewski, D. J .; Rheingold, A. L.;
Durney, R. L. Inorg. Chem. 1986, 25, 3281. (b) Darensbourg, D. J .;
Incorvia, M. J . Inorg. Chem. 1981, 20, 1911.

Tetracobalt Carbonyl Clusters
Sch em e 4
Organometallics, Vol. 22, No. 22, 2003 4413
F igu r e 5. View of the molecular structure of cluster 16.
Only the ipso carbons of the phenyl groups are shown, and
the hydrogen atoms have been omitted for clarity.
Complex 10 was obtained directly by reaction of [Co2-
(CO)8] with L4, in addition to [Co2(CO)6(µ-η2-Me3SiC2-
CtCSiMe3)] (11),42 or by reaction of the latter with [Co2-
(CO)8]42 (Scheme 4). Complexes 10 and 11 also form by
deprotonation of [Co2(CO)6(µ-η2-Me3SiC2H)], itself pre-
pared by reaction of [Co2(CO)8] with Me3SiCtCH,
followed by intermolecular C-C coupling between two
molecules of the resulting complex.43 Complex 10 has
recently been isolated (in 6% yield) from the reaction of
[Mo2(µ-η2-Me3SiC2CtCSiMe3)(CO)4Cp2] with [Co2(CO)8].44
Preliminary experiments have indicated that 10 exhibits
electrical conductivity.43
We then turned again to the diphosphine-stabilized
cluster 1a and reacted it with L4. Heating the reaction
mixture in dichloromethane for ca. 3 days afforded the
desired product [Co4(CO)8(µ-dppm)(µ4-η2-Me3SiC2-
CtCSiMe3)] (12) in addition to the known, red complex
[Co2(CO)4(µ-dppm)(µ-η2-Me3SiC2CtCSiMe3)] (13) and
other unidentified products (Scheme 5). No reaction was
detected at room temperature. Complex 13, which
results from fragmentation of 12 during reaction, has
also been obtained directly by reaction of [Co2(CO)6-
(µ-η2-Me3SiC2CtCSiMe3)] with dppm.45,46 In hexane at
80 °C, 1a rapidly reacted with L4, but 12 was obtained
in very low yield, whereas 13 was the major product.
Increasing the reaction temperature favors the trans-
formation of 12 to 13. When 12 was exposed to air, it
also transformed to 13.
cussed above. The ν(CtC) absorption was not observed
for 12, whereas it appears at 2115 cm-1 for 13.46
The complex 13 was deprotected at the alkynyl group
using Bu4NF to give 14 (Scheme 5). When stronger
proto-desilylation conditions were used (TBAF, moist
THF, room temperature), complex 15 was obtained
rapidly in high yield.46 The proto-desilylation of 12 using
TBAF/THF-H2O was monitored by TLC and neces-
sitates a few hours to afford a green, air-sensitive
product. We did not observe by 1H NMR the CH
resonance of the expected product [Co4(µ-CO)2(CO)6(µ-
dppm)(µ4-η2-Me3SiC2CtCH)]. The product 16 was char-
acterized by 1H NMR and IR spectroscopy, and its
structure could be established by X-ray diffraction and
shown to be, surprisingly, that of [Co4(µ-CO)2(CO)6(µ-
dppm)(µ4-η2-HC2CtCSiMe3)]. A view of the molecule is
shown in Figure 5, and selected bond distances and
angles are given in Table 5. Unexpectedly, desilylation
occurred at the Co-C-SiMe3 group and not at the
alkynyl carbon. The formation of 16 thus contrasts with
that ofthemixed-metalcluster [RuCo3(CO)10(µ4-η2-Me3SiC2-
CtCH)]-, which is obtained rapidly by proto-desilyla-
tion of [RuCo3(CO)10(µ4-η2-Me3SiC2CtCSiMe3)]-.47
The molecular structure of 16 is thus similar to that
of 2a . The nonbonding Co(2)‚‚‚Co(4) distance is 3.52 Å,
and the dihedral angle between the wings is 117.8°. The
orientation of the C(9)-C(10) bond, which is parallel to
the Co(1)-Co(3) hinge of the metal butterfly, is again
consistent with a minimization of the steric repulsions
with the dppm ligand. To achieve a C-C coupling
analogous to the oxidative coupling of 14 or of [Co2(CO)4-
(µ-dppm)(HCtCC2CtCH)] under standard Eglinton-
Glaser conditions (Cu(OAc)2, pyridine), which afforded
the dimer [Co2(CO)4(dppm)(Me3SiC2CtC-)]245 and the
trimer [Co2(CO)4(µ-dppm)(-CtCC2CtC-)]3,46 respec-
tively, and with the aim of forming clusters linked
through π-delocalized backbones, the isolated cluster 16
was reacted with TBAF, but deprotection at the alkynyl
group was unsuccessful.
Both complexes 12 and 13 were identified by their
1
IR and NMR spectra and elemental analyses. Their H
NMR spectra are very similar, with two different signals
for the -SiMe3 groups. Their PCH2P protons appear as
an ABXY or ABX2 (X ) Y ) P) spin system, respectively.
The identity of 12 was deduced by comparison with
related [Co4(CO)8(µ-dppm)(µ4-η2-alkyne)] clusters dis-
(42) Pannel, K. H.; Crawford, G. M. J . Coord. Chem. 1973, 2, 251.
(43) Magnus. P.; Becker. D. P. J . Chem. Soc., Chem. Commun. 1985,
640.
(44) Bruce, M. I.; Low, P. J .; Werth, A.; Skelton, B. W.; White, A.
H. J . Chem. Soc., Dalton Trans. 1996, 1551.
(45) Rubin, Y.; Knobler, C. B.; Diederich, F. J . Am. Chem. Soc. 1990,
112, 4966.
(46) Diederich, F.; Rubin, Y.; Chapman, O. L.; Goroff, N. S. Helv.
Chim. Acta 1994, 77, 1441.
(47) Choualeb, A.; Braunstein, P.; Rose´, J .; Welter, R. Inorg. Chem.,
accepted for publication.

4414 Organometallics, Vol. 22, No. 22, 2003
Choualeb et al.
Ta ble 5. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for 16 (estim a ted sta n d a r d d evia tion s
in p a r en th eses)
Sch em e 5
Co(1)-Co(2)
Co(1)-Co(3)
Co(1)-Co(4)
Co(1)-P(1)
Co(1)-C(1)
Co(1)-C(2)
Co(1)-C(9)
Co(2)-Co(3)
Co(2)-P(2)
Co(2)-C(2)
Co(2)-C(3)
Co(2)-C(9)
Co(2)-C(10)
Co(3)-Co(4)
2.406(1)
2.594(1)
2.442(1)
2.219(1)
1.776(4)
2.015(4)
1.973(3)
2.483(1)
2.184(1)
1.844(3)
1.751(4)
2.020(3)
2.071(3)
2.441(1)
Co(3)-C(4)
Co(3)-C(5)
Co(3)-C(6)
Co(3)-C(10)
Co(4)-C(6)
Co(4)-C(7)
Co(4)-C(8)
Co(4)-C(9)
Co(4)-C(10)
P(1)-C(28)
P(2)-C(28)
C(9)-C(10)
C(10)-C(11)
C(11)-C(12)
1.809(4)
1.785(4)
1.963(4)
1.988(3)
1.888(3)
1.780(4)
1.760(4)
2.069(3)
2.074(3)
1.847(3)
1.848(3)
1.413(5)
1.437(5)
1.203(5)
Co(2)-Co(1)-Co(3)
Co(2)-Co(1)-Co(4)
Co(2)-Co(1)-P(1)
Co(2)-Co(1)-C(9)
Co(3)-Co(1)-Co(4)
Co(3)-Co(1)-P(1)
Co(3)-Co(1)-C(9)
Co(4)-Co(1)-P(1)
Co(4)-Co(1)-C(9)
P(1)-Co(1)-C(9)
Co(1)-Co(2)-Co(3)
Co(1)-Co(2)-P(2)
Co(1)-Co(2)-C(9)
Co(1)-Co(2)-C(10)
Co(3)-Co(2)-P(2)
Co(3)-Co(2)-C(9)
Co(3)-Co(2)-C(10)
P(2)-Co(2)-C(9)
P(2)-Co(2)-C(10)
C(9)-Co(2)-C(10)
Co(1)-Co(3)-Co(2)
Co(1)-Co(3)-Co(4)
Co(1)-Co(3)-C(10)
Co(2)-Co(3)-Co(4)
Co(2)-Co(3)-C(10)
Co(4)-Co(3)-C(10)
Co(1)-Co(4)-Co(3)
Co(1)-Co(4)-C(9)
59.41(3) Co(1)-Co(4)-C(10)
93.09(3) Co(3)-Co(4)-C(9)
97.56(3) Co(3)-Co(4)-C(10)
74.75(9)
74.7(1)
51.46(9)
39.9(1)
115.8(2)
108.3(1)
108.6(1)
74.1(1)
53.8(1)
C(9)-Co(4)-C(10)
57.89(3) P(1)-C(28)-P(2)
155.77(3) Co(1)-P(1)-C(28)
72.7(1)
Co(2)-P(2)-C(28)
121.67(4) Co(1)-C(9)-Co(2)
54.6(1)
87.9(1)
Co(1)-C(9)-Co(4)
Co(1)-C(9)-C(10)
74.3(1)
107.9(2)
118.8(2)
71.7(2)
64.05(2) Co(2)-C(9)-Co(4)
101.04(3) Co(2)-C(9)-C(10)
52.04(9) Co(2)-C(10)-Co(3)
75.62(9) Co(2)-C(10)-Co(4) 116.2(1)
165.09(3) Co(2)-C(10)-C(9)
75.4(1)
67.9(2)
73.8(1)
69.8(2)
74.5(1)
50.8(1)
96.4(1)
128.0(1)
40.4(1)
56.54(3) Co(2)-C(2)-O(2)
57.95(3) Co(2)-C(3)-O(3)
72.6(1)
Co(3)-C(10)-Co(4)
Co(4)-C(10)-C(9)
C(10)-C(11)-C(12) 176.8(4)
Co(1)-C(1)-O(1)
Co(1)-C(2)-O(2)
178.5(4)
136.4(3)
146.5(3)
178.2(4)
179.7(5)
179.7(4)
138.1(3)
143.2(3)
178.5(4)
171.7(4)
Co(3)-C(4)-O(4)
91.27(2) Co(3)-C(5)-O(5)
53.81(9) Co(3)-C(6)-O(6)
54.71(9) Co(4)-C(6)-O(6)
64.16(2) Co(4)-C(7)-O(7)
51.04(9) Co(4)-C(8)-O(8)
In conclusion, we have shown that prior stabilization
of the Co4 core of [Co4(CO)12] by the short-bite di-
phosphine ligands Ph2PCH2PPh2 (dppm), Ph2PNHPPh2
(dppa), or (Ph2P)2N(CH2)3Si(OEt)3 (dppaSi) is beneficial
and the stabilized tetrahedral clusters 1a -c have been
fully characterized. The butterfly clusters [Co4(µ-CO)2-
(CO)6(µ-dppy)(µ4-η2-PhC2H)] (2a -c) were isolated in
excellent yield by insertion of the alkyne into a Co-Co
bond of the diphosphine-stabilized precursor or by
reaction of [Co4(CO)12] with phenylacetylene followed
by CO substitution with the diphosphines dppy. Isomers
were obtained that differ by the position of the bridging
carbonyls, as established by an X-ray diffraction study
on 2a and 2′b. Reaction of the new alkyne PhCtCC-
(O)NH(CH2)3Si(OMe)3 (L1) with 1a ,b afforded the but-
terfly clusters [Co4(µ-CO)2(CO)6(µ-dppy){µ4-η2-PhC2C(O)-
NH(CH2)3Si(OMe)3}] (4a ,b), respectively. Similar reac-
tions with the alkyne HCtCCH2NHC(O)NH(CH2)3Si-
(OEt)3 (L2) led to [Co4(µ-CO)2(CO)6(µ-dppy){µ4-η2-HC2-
CH2NHC(O)NH(CH2)3Si(OEt)3}] (5a ,b). Cluster [Co4(µ-
CO)2(CO)6(µ-dppm){µ4-η2-HC2(CH2)2OC(O)NH(CH2)3Si-
(OEt)3}] (6a ) was obtained by reaction of 1a with
HCtC(CH2)2OC(O)NH(CH2)3Si(OEt)3 (L3). Reaction of
[Co4(CO)12] with L1 led to the formation of [Co2(CO)6-
{µ-η2-PhC2C(O)NH(CH2)3 Si(OMe)3}] (7), which was also
prepared by reaction of [Co2(CO)8] with L1. Reaction of
1a with dppaSi afforded the mixed-diphosphine cluster
[Co4(µ-CO)3(CO)5(µ-dppm)(µ-dppaSi)] (8). The 1,4-bis-
(trimethylsilyl) butadiyne (L4) afforded with [Co4(CO)12]
the known complex [{Co2(CO)6(µ-η2-Me3SiC2-)}2] (10)
and with 1a gave the desired product [Co4(CO)8(µ-
dppm)(µ4-η2-Me3SiC2CtCSiMe3)] (12), in addition to the
known complex [Co2(CO)4(µ-dppm)(µ2-η2-Me3SiC2Ct
CSiMe3)] (13). Proto-desilylation of 12 using TBAF/
THF-H2O occurred unexpectedly at the cluster core-
bound alkynecarbon toafford thestructurallycharacterized
[Co4(µ-CO)2(CO)6(µ-dppm)(µ4-η2-HC2CtCSiMe3)] (16),
instead of the expected cluster [Co4(µ-CO)2(CO)6(µ-
dppm)(µ4-η2-Me3SiC2CtCH)].
Exp er im en ta l Section
All reactions and manipulations were carried out under an
inert atmosphere of purified nitrogen using standard Schlenk
tube techniques. Solvents were dried and distilled under
nitrogen before use: toluene over sodium, tetrahydrofuran,
hexane, and pentane over sodium-benzophenone, dichlo-
romethane over phosphorus pentoxide. Nitrogen (Air liquide,
R-grade) was passed through BASF R3-11 catalyst and mo-
lecular sieve columns to remove residual oxygen and water.
The ligands Ph2PCH2PPh2 (dppm),48 Ph2PNHPPh2 (dppa),49
and (Ph2P)2N(CH2)3Si(OEt)3 (dppaSi)8 and the clusters [Co4-
(CO)10(µ4-η2-PhC2H)]20 and [Co4(CO)10(µ-dppa)]9 were synthe-
sized by literature methods. Elemental C, H, and N analyses
(48) Sommer, K. Z. Anorg. Chem. 1970, 376, 37.
(49) No¨th, H.; Meinel, L. Z. Anorg. Allg. Chem. 1967, 349, 225.

Tetracobalt Carbonyl Clusters
Organometallics, Vol. 22, No. 22, 2003 4415
Ta ble 6. Cr ysta l Da ta a n d Da ta Collection P a r a m eter s for 1a , 2a , 2′b‚0.5CH2Cl2, 8, a n d 16
1a
2a
2′b‚0.5CH2Cl2
8
16
formula
C
35H22Co4O10P2
C41H28Co4O8P2
C40H27Co4NO8P2
‚0.5CH2Cl2
989.75
green
monoclinic
C2/c
22.045(5)
17.711(5)
21.797(5)
90.000(5)
110.557(5)
90.000(5)
7968(3)
4
1.652
0.71069
1.837
173(2)
-32.30/0.26/0.32
3976
C66H63Co4NO11P4Si
C40H32Co4O8P2Si
fw
900.19
red
triclinic
P1h
10.2475(3)
11.6675(4)
16.3918(7)
74.4260(10)
89.2080(10)
72.497(2)
1795.70(11)
2
1.665
0.71069
1.960
173(2)
-14.14/-16.15/-20.23
900
946.29
green
triclinic
P1h
11.139(5)
11.258(5)
17.036(5)
83.81(2)
77.82(2)
65.28(2)
1896.5(13)
2
1.657
0.71069
1.857
173(2)
0.14/-12.14/-21.22
952
1433.86
green
triclinic
P1h
11.6370(2)
17.9680(3)
18.6170(3)
70.6790(9)
77.3030(9)
73.4500(7)
3487.19(10)
2
1.366
0.71069
1.099
173(2)
-11.15/-21.23/0.24
1472
966.41
green
triclinic
P1h
10.807(5)
12.078(5)
17.196(5)
79.490(5)
74.334(5)
68.537(5)
2002.5(14)
2
1.603
0.71069
1.789
173(2)
-14.15/-16.16/0.20
976
cryst color
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Dcalcd (g‚cm-3
)
wavelength (Å)
µ (mm-1
)
temperature (K)
hkl limits
F(000)
θ limits (deg)
2.50-29.98
12 946
1.22-27.54
8657
6342
0.0388
0.1154
1.039
2.51-32.05
13 817
7360
0.0559
0.1224
1.84-27.46
15 787
12 392
0.0693
0.1978
2.2-30.0
11 653
7930
0.0552
0.1409
0.89
no. of data measd
no. of data (I >2σ(I)) 7210
Ra
Rw
0.1014
a
0.1181
1.172
0.953
GOF
0.819
0.492
1.289
1.948
largest peak in
0.500
0.62
final diff (e Å-3
)
were performed by the Service de Microanalyses du CNRS
(ULP Strasbourg). Infrared spectra (cm-1) were recorded on a
IFS-66 FTIR Bruker or a Perkin-Elmer 1600 series FTIR
CDCl3) δ: 92.8 (br, w1/2 ) 166 Hz). Anal. Calcd for C43H41Co4-
NO13P2Si: C, 46.72; H, 3.74; N, 1.27. Found: C, 46.05; H, 3.68;
N, 1.23.
1
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p m )(µ4-η2-P h C2H)]
(2a /2′a ). Rea ction of [Co4(µ-CO)3(CO)7(µ-d p p m )] (1a ) w ith
P h CtCH. A solution of phenylacetylene (1.11 mL, 10.11
mmol) was added to a solution of 1a (0.471 g, 0.523 mmol) in
80 mL of hexane. The mixture was stirred at room temperature
for 10 days (or 3 h at 80 °C). The reaction was monitored by
TLC (CH2Cl2/hexane, 50/50), which indicated the progressive
formation of a green compound. The solution was filtered, and
the solid was collected, washed with hexane, and recrystallized
from CH2Cl2/hexane at -30 °C to give green, single crystals
of 2a (0.410 g, 0.433 mmol, 83%). IR (CH2Cl2, νCO): 2049 (s),
2007 (vs), 1977 (sh), 1839 (mw), 1785 (sh). IR (KBr, νCO): 2042
spectrometers. The H NMR spectra were recorded at 200.13
or 300.13 MHz, 31P{1H} NMR spectra at 121.5, 161.97, or
202.46 MHz, and 29Si{1H} NMR spectra at 79.48 on Bruker
AC200, AC300, AVANCE 300, AVANCE 400, or AVANCE 500
instruments.
Syn th esis of [Co4(µ-CO)3(CO)7(µ-d p p m )] (1a ). To a solu-
tion of [Co4(CO)12] (0.350 g, 0.612 mmol) in 50 mL of CH2Cl2
was added with stirring a solution of dppm (0.235 g, 0.612
mmol) in 10 mL of CH2Cl2 at room temperature. The color of
the solution changed immediately from black to dark red.
Analytical TLC (CH2Cl2/hexane, 40/60) indicated the formation
of two products. The solvent was immediately evaporated
under reduced pressure, and the residue was chromatographed
on a SiO2 column, with CH2Cl2/hexane (40/60) as eluent,
yielding the green tetrasubstituted [Co4(CO)8(µ-dppm)2] (0.097
g, 0.079 mmol, 13%) and the dark red product 1a (0.380 g,
0.422 mmol, 70%). Recrystallization from hexane afforded after
one week single crystals suitable for X-ray diffraction. IR
(hexane, νCO): 2068 (vs), 2027 (vs), 2019 (vs), 1996 (w), 1989
(m), 1979 (w), 1845 (m), 1830 (sh), 1802 (sh), 1795 (w). 1H NMR
(200.13 MHz, CDCl3) δ: 2.85 (br, 2H, CH2), 7.12-7.45 (m, 20H,
Ph). 31P{1H} NMR (121.5 MHz, CDCl3) δ: 27.8 (br, w1/2 ) 84
Hz). Anal. Calcd for C35H22Co4O10P2: C, 46.7; H, 2.46. Found:
C, 46.99; H, 2.53.
1
(s), 1999 (vs), 1979 (vs), 1847 (m), 1785 (m). H NMR (200.13
MHz, CDCl3) δ: 3.32 (m, 1H, CHACHBP2, part of an ABXY spin
system), 3.93 (m, 1H, CHACHBP2, part of an ABXY spin
system), 6.96-7.55 (m, 25H, Ph), HC2 masked by aryl protons.
31P{1H} NMR (202.46 MHz, CDCl3) δ: (25 °C) 28.3 (br, w1/2
422 Hz); (0 °C) 27.9 (br), 29.0 (br). Anal. Calcd for C41H28
Co4O8P2: C, 52.04; H, 2.98. Found: C, 51.81; H, 3.01.
)
-
Rea ction of [Co4(CO)10(µ4-η2-P h C2H)] (3) w ith d p p m .
A solution of dppm (0.093 g, 0.243 mmol) in 25 mL of CH2Cl2
was added to a solution of 3 (0.150 g, 0.243 mmol) in 25 mL of
CH2Cl2. The mixture was stirred at room temperature, and
the color of the solution changed instantaneously from blue
to green. TLC with CH2Cl2/hexane (50/50) as eluent indicated
the formation of only one product and some decomposition.
The residue was chromatographed on a SiO2 column with CH2-
Cl2/hexane (50/50) as eluent. Recrystallization of the product
from CH2Cl2/hexane at -30 °C afforded a green powder of 2′a
(0.168 g, 0.177 mmol, 73%). IR (CH2Cl2, νCO): 2049 (vs), 2007
(vs), 1983 (vs), 1836 (mw), 1784 (w). IR (KBr, νCO): 2045 (s),
Syn th esis of [Co4(µ-CO)3(CO)7(µ-d p p a Si)] (1c). A solu-
tion of dppaSi (0.083 g, 0.140 mmol) in 10 mL of CH2Cl2 was
added to a solution of [Co4(CO)12] (0.080 g, 0.140 mmol) in 20
mL of the same solvent. The color of the solution changed in
a few minutes from black to dark red, and analytical TLC
(hexane) indicated that all starting material was consumed.
The solution was filtered, the solvent was evaporated under
reduced pressure, and extraction of the product with hexane
followed by recrystallization from hexane afforded 1c (0.097
g, 0.088 mmol, 63%). IR (hexane, νCO): 2068 (vs), 2024 (vs),
2018 (vs), 1999 (sh), 1994 (m), 1980 (sh), 1839 (m), 1793 (m),
1782 (m). 1H NMR (300.13 MHz, CDCl3) δ: -0.45 (m, 2H,
1998 (vs, br), 1828 (m), 1737 (w). Anal. Calcd for C41H28
-
1
Co4O8P2: C, 52.04; H, 2.98. Found: C, 51.91; H, 3.11. The H
and 31P NMR data are the same as for 2a .
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p a )(µ4-η2-P h C2H)]
(2b/2′b). Rea ction of [Co4(µ-CO)3(CO)7(µ-d p p a )] (1b) w ith
P h CtCH. A solution of phenylacetylene (0.37 mL, 3.37 mmol)
was added to a solution of 1b (0.224 g, 0.248 mmol) in 60 mL
of hexane. The mixture was heated to 80 °C for 3 h, and the
3
SiCH2), 0.12 (m, 2H, CH2CH2CH2), 0.98 (t, J (HH) ) 7.14 Hz,
9H, CH3), 2.54 (m, 2H, NCH2), 3.38 (q, 3J (HH) ) 7.14 Hz, 6H,
OCH2), 7.48-7.81 (m, 20H, Ph). 31P{1H} NMR (121.5 MHz,

4416 Organometallics, Vol. 22, No. 22, 2003
Choualeb et al.
reaction was monitored by TLC (CH2Cl2/hexane, 40/60), which
indicated the progressive formation of a green compound. This
latter was treated like 2a , and green crystals of 2b were
obtained after recrystallization for 10 days (0.220 g, 0.232
mmol, 94%). IR (CH2Cl2, νCO): 2050 (vs), 2005 (vs), 1971 (sh),
1832 (m). IR (KBr, νCO): 2041 (vs), 2005 (s), 1990 (vs), 1972
(vs), 1947 (m), 1840 (m), 1810 (m). 1H NMR (300.13 MHz,
CDCl3) δ: 4.11 (br, NH), 6.40-7.68 (m, 25H, Ph), HC2 masked
by aryl protons. 31P{1H} NMR (121.5 MHz, CDCl3) δ: 81.2 br,
87.4 br. Anal. Calcd for C40H27Co4NO8P2‚1/3C6H14: C, 51.68;
H, 3.27; N, 1.44. Found: C, 51.67; H, 3.36; N, 1.57.
R ea ct ion of [Co4(CO)10(µ4-η2-P h C2H )] (3) w it h d p p a .
Similarly to the synthesis of 2′a , reaction of 3 (0.250 g, 0.405
mmol) with dppa (0.156 g, 0.405 mmol) was monitored by TLC,
which indicated the formation of the desired product and some
decomposition. Recrystallization of the product gave green
single crystals of 2′b (0.360 g, 0.379 mmol, 94%), suitable for
X-ray diffraction (see text). IR (CH2Cl2, νCO): 2048 (vs), 2003
(vs), 1987 (sh), 1827 (m). IR (KBr, νCO): 2046 (vs), 2005 (s),
1993 (sh), 1985 (vs), 1922 (m), 1841 (mw), 1819 (m). 31P{1H}
NMR (121.5 MHz, CDCl3) δ: 79.7 br, 87.6 br. Anal. Calcd for
1.70 (m, 2H, CH2CH2CH2), 3.34 (m, 2H, NCH2), 3.51 (s, 9H,
CH3), 6.26 (br, NH), 7.31-7.56 (m, 5H, Ph). 13C{1H} NMR
(100.62 MHz, CDCl3) δ: 6.18 (s, SiCH2), 22.06 (s, CH2CH2CH2),
42.13 (s, NCH2), 50.28 (s, CH3), 83.18 and 84.22 (2s, CtC),
120.28 (s, Cipso of C6H5), 128.46, 129.44, and 132.33 (3s, CH of
C6H5), 153.40 (s, CdO). 29Si{1H} NMR (79.48 MHz, CDCl3) δ:
- 42.7.
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p m ){µ4-η2-P h C2C-
(O)NH(CH2)3Si(OMe)3}] (4a ). A solution of PhCtCC(O)NH-
(CH2)3Si(OMe)3 (L1) (1.256 g, 4.080 mmol) in 5 mL of CH2Cl2
was added to a solution of 1a (0.370 g, 0.411 mmol) in 40 mL
of CH2Cl2. The mixture was heated to reflux, and the reaction
was monitored by TLC (CH2Cl2/hexane, 40/60) and followed
the disappearance of 1a . A green product progressively formed
which did not migrate on the TLC plate, and after 4 h
formation of an other green, unidentified product was ob-
served, which migrates immediately after the precursor. The
reaction was stopped after 7 h. The solution was filtered, and
the solvent was removed under reduced pressure. Purification
from toluene/pentane at -20 °C gave viscous 4a (0.333 g, 0.289
mmol, 71%). IR (CH2Cl2): 2061 (sh), 2054 (s), 2029 (m), 2002
(vs), 1976 (m), 1830 (w), νC≡O, 1646 (vs, νCdO). 1H NMR (300.13
MHz, CDCl3) δ: 0.68 (m, 2H, SiCH2), 1.69 (m, 2H, CH2CH2-
CH2), 3.35 (m, 2H, NCH2), 3.57 (s, 9H, CH3), 6.36 (br, 1H, NH),
7.03-8.35 (m, 25H, Ph). 31P{1H} NMR (121.5 MHz, CDCl3) δ:
39.8 (br, w1/2 ) 83 Hz).
C
40H27Co4NO8P2‚1/2CH2Cl2: C, 50.04; H, 2.90; N, 1.44.
Found: C, 50.42; H, 3.12; N, 1.58. The 1H NMR spectrum is
the same as that for 2b (see above).
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p a Si)(µ4-η2-P h C2H)]
(2c/2′c). Rea ction of [Co4(µ-CO)3(CO)7(µ-d p p a Si)] (1c)
w ith P h CtCH. Cluster 1c (0.100 g, 0.090 mmol) and phen-
ylacetylene (0.098 mL, 0.892 mmol) were refluxed in 20 mL
of CH2Cl2 for 3 h. The color of the solution changed from dark
red to green. The solution was filtered, the solvent was
evaporated, and the residue was recrystallized from CH2Cl2/
hexane to give a green powder of 2c (0.091 g, 0.079 mmol,
88%). IR (CH2Cl2, νCO): 2048 (s), 2000 (vs), 1971 (vs), 1831
(m), 1789 (w). IR (KBr, νCO): 2041 (s), 1997 (vs), 1969 (vs),
1830 (m). 1H NMR (300.13 MHz, CDCl3) δ: -0.045 (m, 2H,
SiCH2), 0.94 (m, 11H, CH2CH2CH2 and CH3), 3.35 (m, 2H,
NCH2), 3.47 (m, 6H, OCH2), 6.81-7.71 (m, 25H, Ph), HC2
masked by aryl protons. 31P{1H} NMR (121.5 MHz, CDCl3) δ:
81.0 (br, w1/2 ) 337 Hz). Anal. Calcd for C49H47Co4NO11P2Si‚
1/3C6H14: C, 51.89; H, 4.41; N, 1.19. Found: C, 51.71; H, 4.77;
N, 1.43.
Rea ction of [Co4(CO)10(µ4-η2-P h C2H)] (3) w ith d p p a Si.
By a procedure similar to that detailed for 2′b, the product
2′c was synthesized by reaction of 3 (0.252 g, 0.408 mmol) with
dppaSi (0.242 g, 0.408 mmol) in CH2Cl2. TLC indicated that
the reaction was instantaneous. Yield of 2′c: 0.422 g, 0.367
mmol, 90%. IR (CH2Cl2, νCO): 2050 (vs), 2001 (vs), 1970 (s),
1834 (m), 1783 (w). IR (KBr, νCO): 2045 (vs), 1995 (vs), 1962
(s), 1839 (m), 1823 (m). Anal. Calcd for C49H47Co4NO11P2Si‚1/
3C6H14: C, 51.89; H, 4.41; N, 1.19. Found: C, 51.93; H, 5.07;
N, 1.64. The 1H and 31P{1H} NMR data are the same as for
2c.
Syn th esis of P h CtCC(O)NH(CH2)3Si(OMe)3 (L1). A
mixture of 3-phenylpropiolic acid (2.00 g, 13.70 mmol) and
thionyl chloride (1.95 g, 1.20 mL, 16.44 mmol) in 50 mL of
toluene was stirred and heated to reflux for 3 h. The orange
reaction mixture was allowed to cool to room temperature, and
the solvent was evaporated to dryness. It was dissolved in 25
mL of freshly distilled toluene, and the mixture was cooled in
an ice bath. A solution of 3-aminopropyltrimethoxysilane (4.82
mL, 27.40 mmol) in 25 mL of toluene was then added dropwise.
After the addition was complete, the ice bath was removed
and the mixture stirred at room temperature for 1 h and then
poured into 100 mL of cold water. The mixture was filtered,
and the solid was discarded. The aqueous phase was separated
and extracted with 50 mL of ethyl acetate, and this extract
was combined with the organic phase. The organic fraction
was dried over MgSO4, and evaporation of the solvent afforded
a viscous, yellow liquid of L1 (1.84 g, 5.97 mmol, 44% (based
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p a ){µ4-η2-P h C2C(O)-
NH(CH2)3Si(OMe)3}] (4b). By a similar procedure, the reac-
tion of 2b (0.157 g, 0.166 mmol) with PhCtCC(O)NH(CH2)3-
Si(OMe)3 (L1) (0.511 g, 1.66 mmol) in 25 mL of CH2Cl2 gave
4b (0.132 g, 0.114 mmol, 69%). IR (CH2Cl2): 2054 (m), 2015
1
(s), 2000 (vs), 1970 (sh), 1832 (mbr), νC≡O, 1646 (m, νCdO). H
NMR (300.13 MHz, CDCl3) δ: 0.42 (m, 2H, SiCH2), 1.70 (m,
2H, CH2CH2CH2), 3.11 (m, 2H, NCH2), 3.46 (s, 9H, CH3), 5.68
(br, NH), 6.53 (m, NH), 7.11-7.51 (m, 25H, Ph). 31P{1H} NMR
(121.5 MHz, CDCl3) δ: 91.1 (br, w1/2 ) 81 Hz), 103.5 (br,
w1/2 ) 648 Hz).
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p m ){µ4-η2-HC2CH2-
NHC(O)NH(CH2)3 Si(OEt)3}] (5a ). A solution of 1a (0.134
g, 0.148 mmol) and HCtCCH2NHC(O)NH(CH2)3Si(OEt)3 (0.445
g, 1.470 mmol) was refluxed in 35 mL of CH2Cl2 for 7 h.
Completion of the reaction was monitored by TLC (CH2Cl2/
hexane, 40/60) to follow the disappearance of 1a . The solvent
was then removed under vacuum, and the product was purified
from toluene/pentane at -20 °C to afford green, viscous 5a
(0.141 g, 0.123 mmol, 83%). IR (CH2Cl2): 2052 (s), 1993 (vs),
1966 (m), 1831 (w) νC≡O; 1679 (vs, νCdO). 1H NMR (300.13 MHz,
CDCl3) δ: 0.62 (m, 2H, SiCH2), 1.21 (m, 9H, CH3), 1.60 (m,
2H, CH2CH2CH2), 2.19 (br, 1H, CHACHBP2, part of an ABXY
spin system), 3.16 (br, 3H, HNCH2CH2 and CHACHBP2, part
of an ABXY spin system), 3.79 (m, 6H, OCH2), 3.96 (m, 2H,
HC2CH2N), 5.14 (m, 2H, NH), 6.91-7.85 (m, 20H, Ph), HC2
masked by aryl protons. 31P{1H} NMR (121.5 MHz, CDCl3) δ:
26.4 (br, w1/2 ) 83 Hz).
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p a ){µ4-η2-HC2CH2-
NHC(O)NH(CH2)3 Si(OEt)3}] (5b). By a similar procedure,
refluxing
a solution of 1b (0.107 g, 0.118 mmol) with
HCtCCH2NHC(O)NH(CH2)3Si(OEt)3 (0.356 g, 1.184 mmol) in
30 mL of CH2Cl2 for 5 h gave 5b (0.109 g, 0.095 mmol, 81%).
IR (CH2Cl2): 2049 (vs), 1998 (vs), 1970 (sh), 1832 (m), νC≡O
;
1
1679 (vs, νCdO). H NMR (300.13 MHz, CDCl3) δ: 0.62 (m, 2H,
SiCH2), 1.21 (m, 9H, CH3), 1.42 (m, 2H, CH2CH2CH2), 3.16
(m, 2H, HNCH2CH2), 3.82 (m, 6H, OCH2), 3.95 (m, 2H, HC2-
CH2N), 4.83 (m, 2H, NH), 7.08-7.80 (m, 20H, Ph), H-C2 and
PNHP masked. 31P{1H} NMR (121.5 MHz, CDCl3) δ: 78.3 (br,
w1/2 ) 331 Hz), 89.0 (br, w1/2 ) 248 Hz).
Syn th esis of [Co4(µ-CO)2(CO)6(µ-d p p m ){µ4-η2-HC2-
(CH2)2OC(O)NH(CH2)3 Si(OEt)3}] (6a ). A solution of 1a
(0.300 g, 0.333 mmol) and HCtC(CH2)2OC(O)NH(CH2)3Si-
(OEt)3 (1.05 g, 3.310 mmol) was refluxed in 40 mL of CH2Cl2
for 9 h. The solvent was removed under reduced pressure, and
on acid)). IR (CH2Cl2): 2220 (s, νC≡C), 1654 (s, νCdO), 1514 (vs,
1
δ
NH). H NMR (300.13 MHz, CDCl3) δ: 0.69 (m, 2H, SiCH2),

Tetracobalt Carbonyl Clusters
Organometallics, Vol. 22, No. 22, 2003 4417
the viscous, green product was extracted with hexane. After
keeping the extract for 3 days at -20 °C, the product
precipitated, the solvent was discarded, and the residue was
triturated with pentane to afford green 6a (0.354 g, 0.304
mmol, 92%). IR (CH2Cl2): 2048 (vs), 2001 (vs), 1975 (sh), 1831
(w), νC≡O; 1720 (m, νCdO). 1H NMR (300.13 MHz, CDCl3) δ: 0.63
3.89 (m, 1H, PCHAHBP, part of an ABX2 spin system), 7.02-
7.47 (m, 20H, Ph). 31P{1H} NMR (121.5 MHz, CDCl3) δ: 37.6
(br, w1/2 ) 133 Hz). Anal. Calcd for C39H40Co2O4P2Si2: C, 57.92;
H, 4.99. Found: C, 57.37; H, 4.65.
The green band gave [Co4(µ-CO)2(CO)6(µ-dppm)(µ4-η2-Me3-
SiC2CtCSiMe3)] (12) (0.081 g, 0.078 mmol, 30%) by extraction
with hexane. The product should be stored at -20 °C in the
solid state. IR (hexane, νCO): 2050 (vs), 2005 (vs), 1994 (m),
3
(m, 2H, SiCH2), 1.22 (t, J (HH) ) 7.15 Hz, 9H, CH3), 1.61 (m,
2H, CH2CH2CH2), 2.50 (m, 1H, CHACHBP2, part of an ABXY
spin system), 3.07 (m, 1H, CHACHBP2, part of an ABXY spin
system), 3.14 (m, 4H, HC2CH2 and HNCH2), 3.85 (m, 8H,
OCH2CH2 and OCH2CH3), 4.74 (br, NH). 31P{1H} NMR (121.5
MHz, CDCl3) δ: 29.8 (br, w1/2 ) 249 Hz).
1
1967 (w), 1843 (m), 1835 (m). H NMR (300.13 MHz, CDCl3)
δ: -0.18 (s, 9H, tCSiMe3), 0.33 (s, 9H, -C2SiMe3), 4.23 (m,
1H, PCHAHBP, part of an ABXY spin system), 5.00 (m, 1H,
PCHAHBP, part of an ABXY spin system), 7.15-7.94 (m, 20H,
Ph). 31P{1H} NMR (121.5 MHz, CDCl3) δ: 25.0 (br, w1/2 ) 498
Hz). Anal. Calcd for C43H40Co4O8P2Si2: C, 49.73; H, 3.88.
Found: C, 50.12; H, 4.51.
Syn th esis of [Co2(CO)6{µ-η2-P h C2C(O)NH(CH2)3Si-
(OMe)3}] (7). A solution of [Co2(CO)8] (0.320 g, 0.940 mmol)
in 30 mL of CH2Cl2 and PhCtCC(O)NH(CH2)3Si(OMe)3 (L1)
(0.298 g, 0.968 mmol) was stirred at room temperature for 50
min. Completion of the reaction was revealed from TLC by
the disappearance of [Co2(CO)8]. The solvent was then removed
under vacuum. Extraction with hexane afforded 7 as red
crystals (0.380 g, 0.640 mmol, 68%). This product was also
obtained, in lower yield (26%), by reaction of L1 with [Co4-
(CO)12]. IR (hexane): 2096 (m), 2064 (vs), 2032 (vs), 1977 (w),
P r oto-d esilyla tion of 12. To a solution of 12 (0.060 g, 0.057
mmol) in 10 mL of THF was added dropwise with stirring
n-Bu4NF (1.0 M in THF/5 wt % H2O; 0.014 mmol, 0.014 mL).
The mixture was stirred at room temperature for 8 h until
TLC indicated complete consumption of the precursor. A
minor, green fraction followed that of the desired product. The
solvent was evaporated under vacuum, and the product was
extracted with CH2Cl2 and filtered through Celite. Separation
by preparative TLC with hexane/CH2Cl2 (50/50) as eluent
afforded [Co4(µ-CO)2(CO)6(µ-dppm)(µ4-η2-HC2CtCSiMe3)] (16)
(0.028 g, 0.028 mmol, 50%). IR (hexane, νCO): 2057 (vs), 2022
ν
C≡O; 1660 (m, νCdO). 1H NMR (300.13 MHz, CDCl3) δ: 0.70
(m, 2H, SiCH2), 1.74 (m, 2H, CH2CH2CH2), 3.44 (m, 2H, NCH2),
3.56 (s, 9H, CH3), 6.17 (br, 1H, NH), 7.33-7.79 (m, 5H, Ph).
Anal. Calcd for C21H21Co2NO10Si: C, 42.51; H, 3.57; N, 2.36.
Found: C, 42.48; H, 3.51; N, 2.31.
1
(vs), 2016 (vs), 1988 (m), 1866 (m), 1838 (w). H NMR (300.13
MHz, CDCl3) δ: 0.15 (s, 9H, SiMe3), 3.22 (m, 1H, PCHAHBP,
part of an ABXY spin system), 3.95 (m, 1H, PCHAHBP, part of
an ABXY spin system), 7.05-7.65 (m, 20H, Ph). 31P{1H} NMR
(121.5 MHz, CDCl3) δ: 30.7 br. Anal. Calcd for C40H32Co4O8P2-
Si: C, 49.71; H, 3.34. Found: C, 50.12; H, 3.55.
Syn th esis of [Co4(µ-CO)3(CO)5(µ-d p p m )(µ-d p p a Si)] (8).
[Co4(µ-CO)3(CO)7(µ-dppm)] (1a ) (0.100 g, 0.111 mmol) and
dppaSi (0.065 g, 0.111 mmol) in 30 mL of CH2Cl2 were mixed
and stirred at room temperature. The reaction was stopped
after ca. 3 h when all starting materials were consumed (TLC).
Separation of the reaction mixture was performed by prepara-
tive TLC (CH2Cl2), giving three green bands. Immediate
extraction with CH2Cl2 of the first and the third band afforded
unidentified products and that of the second band [Co4(CO)8-
(µ-dppm)(µ-dppaSi)] (8) (0.089 g, 0.062 mmol, 56%). Data for
8: IR (CH2Cl2, νCO): 2054 (m), 2005 (s), 1971 (vs), 1955 (sh),
X-r ay Str u ctu r al An alyses of [Co4(µ-CO)3(CO)7(µ-dppm )]
(1a ),
[Co4(µ-CO)2(CO)6(µ-d p p m )(µ4-η2-P h C2H )]
(2a ),
[Co4(µ-CO)2(CO)6(µ-d p p a )(µ4-η2-P h C2H)]‚0.5CH 2Cl2 (2′b ‚
0.5CH2Cl2), [Co4(µ-CO)3(CO)5(µ-d p p m )(µ-d p p a Si)] (8), a n d
[Co4(µ-CO)2(CO)6(µ-d p p m )(µ4-η2-H C2CtCSiMe3)]
(16).
Single crystals were mounted on a Nonius Kappa-CCD area
detector diffractometer (Mo KR, λ ) 0.71073 Å). The complete
conditions of data collection (Denzo software) and structure
refinements are given in Table 6. The cell parameters were
determined from reflections taken from one set of 10 frames
(1.0° steps in phi angle), each at 20 s exposure. The structures
were solved using direct methods (SIR97) and refined against
F2 using the SHELXL97 software.50,51 The absorption was
corrected empirically with Sortav. All non-hydrogen atoms
except those of the disordered CSi(OEt)3 group in 8 were
refined anisotropically. Hydrogen atoms were generated ac-
cording to stereochemistry and refined using a riding model
in SHELXL97.
1
1820 (w), 1791 (m), 1765 (m). H NMR (300.13 MHz, CDCl3)
δ: -0.39 (m, 2H, SiCH2), 0.67 (m, 2H, CH2CH2CH2), 0.94 (m,
9H, CH3), 2.52 (br, 2H, PCH2P), 3.43 (m, 8H, OCH2 and NCH2),
6.90-7.61 (m, 40H, Ph). 31P{1H} NMR (121.5 MHz, CDCl3)
δ: 28.1 (br, w1/2 ) 146 Hz), 100.5 (br, w1/2 ) 219 Hz). Anal.
Calcd for C66H63Co4NO11P4Si: C, 55.28; H, 4.43; N, 0.98.
Found: C, 54.64; H, 4.43; N, 0.95.
Rea ction of [Co4(CO)12] w ith Me3SiCtCCtCSiMe3. To
a solution of [Co4(CO)12] (0.153 g, 0.268 mmol) in 25 mL of
hexane was added
a solution of 1,4-bis(trimethylsilyl)-
butadiyne (0.522 g, 2.680 mmol) in 2 mL of hexane. TLC with
hexane as eluent indicated the formation of a blue product,
which transforms rapidly to a green one, and other secondary
products. The reaction was stopped after 24 h stirring at room
temperature. Chromatographic separation on a SiO2 column
with hexane as eluent afforded green [{Co2(CO)6(µ-η2-Me3-
SiC2-)}2] (10) (0.042 g, 0.055 mmol, 21%). IR (hexane, νCO):
2094 (m), 2076 (s), 2055 (vs), 2027 (vs), 1979 (w). 1H NMR
Ack n ow led gm en t. We are grateful to the CNRS,
the Universite´ Louis Pasteur Strasbourg, and the
Ministe`re de la Recherche (Paris) for financial support.
This project was also supported by the Fonds Interna-
tional de Coope´ration Universitaire-FICU (AUPELF-
UREF, Agence Universitaire de la Francophonie).
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, thermal parameters, bond distances, and angles
for 1a , 2a , 2′b‚0.5CH2Cl2, 8, and 16, respectively. This material
is available free of charge via the Internet at http://pubs.ac-
s.org. This material has also been deposited in CIF format at
http://pubs.acs.org and with the Cambridge Crystallographic
Data Centre as supplementary publication no. CCDC-214676-
214680. Copies of the data can be obtained free of charge on
application to CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: (+44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
(300.13 MHz, CDCl3) δ: 0.12 (s, SiMe3). Anal. Calcd for C22H18
-
Co4O12Si2: C, 34.48; H, 2.37. Found: C, 34.79; H, 1.93.
Rea ction of 1a w ith Me3SiCtCCtCSiMe3. A solution of
1a (0.235 g, 0.261 mmol) in 30 mL of CH2Cl2 and 1,4-bis-
(trimethylsilyl)butadiyne (0.453 g, 2.326 mmol) was heated at
55 °C for 3 days. The reaction was monitored by TLC, which
indicated the formation of two major products (red and green)
and other secondary unidentified products. The solvent was
removed, and the mixture was separated by preparative TLC
with hexane/CH2Cl2 (50/50) as eluent. The red band yielded
[Co2(CO)4(µ-dppm)(µ-η2-Me3SiC2CtCSiMe3)] (13) (0.045 g, 0.055
mmol, 21%) after recrystallization from hexane. IR (hexane,
OM030327J
(50) Kappa CCD Operation Manual; Nonius B.V.: Delft, The
Netherlands, 1997.
(51) Sheldrick, G. M. SHELXL97, Program for the refinement of
crystal structures; University of Gottingen: Germany, 1997.
ν
CO): 2058 (w), 2030 (vs), 2008 (vs), 1982 (vs), 1960 (m). 1H
NMR (300.13 MHz, CDCl3) δ: 0.23 (s, 9H, SiMe3), 0.36 (s, 9H,
SiMe3), 3.33 (m, 1H, PCHAHBP, part of an ABX2 spin system),