A trithiol protio-ligand and its fixation to the periphery of a carbosilane dendrimer as scaffolds for polynuclear rhodium and iridium complexes and metallodendrimers

Article abstract of DOI:10.1021/om0504957

Tris(methylenethiol)methane derivatives containing an allyl or benzyl linker (ROCH₂C(CH₂-SH)₃; R = Bn(6a), CH ₂=CHCH₂(6b)), which could allow their fixation to carbosilane dendrimers, were synthesized through a multistep synthesis. Grafting the periphery of the core dendrimer Si[(CH₂)₃Si(Me) ₂H]₄ was achieved with the tosyl derivative CH ₂=CHCH₂OCH₂-C(CH₂OTs)₃ by a hydrosilylation reaction to give selectively Si[(CH₂) ₃Si(Me)₂(CH₂)₃OCH ₂-C(CH₂OTs)₃]₄ (G(0) _OTs-12). This dendrimer was converted into the thiol-functionalized carbosilane dendrimer Si[(CH₂)₃Si(Me)₂(CH ₂)₃OCH₂C(CH₂SH)₃] ₄ (G(0)_SH-12) by reduction of the thiocyanate intermediate Si[(CH₂)₃Si(Me)₂(CH₂) ₃OCH₂C(CH₂SCN)₃]₄ with LiAlH₄. The trithiol compounds 6a and 6b protonated the complexes [Rh(μ-OMe)(cod)]₂ and [Rh(acac)-diolefin] (M = Rh, diolefin = cod, nbd, tfb) to give the corresponding trinuclear complexes [Rh ₃{μ-ROCH₂c(ch₂s)₃}(diolefin) ₃] (7-9). Their structure can be described as an adamantane-like entity, in which the metals are held together by the thiolate arms of the ligand, with the sulfurs bridging the metal atoms in a μ₂ fashion, as shown for [Rh₃{μ-BnOCH₂C(CH₂S) ₃}-(nbd)₃] by X-ray diffraction methods. Carbonylation of 7-9 under atmospheric pressure gave the carbonyl complexes with the thiolate tripod ligands [M₃{μ-ROCH₂C(CH₂S) ₃}(CO)₆] (M = Rh, Ir), which were reacted with phosphorus donor ligands (PR₃ = PPh₃, P(OMe)₃) to give [M₃{μ-ROCH₂C(CH₂S)₃}(CO) ₃(PR)₃] as a sole isomer of averaged C_3v symmetry. The functional dendrimers were metalated by reaction of the core molecule Si[(CH₂)₃Si(Me)₂-(CH₂) ₃OCH₂C(CH₂SH)₃]₄ (G(0)_SH-12) by applying the synthetic protocols above-described for trinuclear complexes. Thus, the reactions of G(0)_SH-12 with the complexes [M(acac)(diolefin)] (M = Rh, Ir; diolefin = cod, nbd, tfb) gave the metallodendrimers Si[(CH₂)₃Si(Me)₂(CH ₂)₃-OCH₂C(CH₂S) ₃{M(diolefin)}₃]₄ (G(0) _{M(dioiefin)-12}) as insoluble solids. Soluble metallodendrimers, Si[(CH₂)₃Si(Me)₂(CH₂) ₃OCH₂C(CH₂S)₃{Rh(CO) ₂}₃]₄ (G(0)_Rh(CO)2-12) and Si[(CH₂)₃-Si(Me)₂(CH₂) ₃OCH₂C(CH₂S)₃{M(CO)(PPh ₃)}₃]₄ (G(0)_{M(co)(PPh3)-12}) were obtained either by carbonylation of the diolefin compounds or by the reaction of G(0)_SH-12 with [M(acac)(CO)₂] (M = Rh, Ir), and by further reaction with PPh₃, respectively.

Full text of DOI:10.1021/om0504957

Organometallics 2005, 24, 5147-5156
5147
A Trithiol Protio-Ligand and Its Fixation to the
Periphery of a Carbosilane Dendrimer as Scaffolds for
Polynuclear Rhodium and Iridium Complexes and
Metallodendrimers
Jose´ A. Camerano,† Miguel A. Casado,*,†,‡ Miguel A. Ciriano,*,†
Fernando J. Lahoz,† and Luis A. Oro†,‡
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain, and Instituto Universitario de
Cata´lisis Homoge´nea, Universidad de Zaragoza, 50009 Zaragoza, Spain
Received June 15, 2005
Tris(methylenethiol)methane derivatives containing an allyl or benzyl linker (ROCH2C(CH2-
SH)3; R ) Bn(6a), CH2dCHCH2(6b)), which could allow their fixation to carbosilane den-
drimers, were synthesized through a multistep synthesis. Grafting the periphery of the core
dendrimer Si[(CH2)3Si(Me)2H]4 was achieved with the tosyl derivative CH2dCHCH2OCH2-
C(CH2OTs)3 by a hydrosilylation reaction to give selectively Si[(CH2)3Si(Me)2(CH2)3OCH2-
C(CH2OTs)3]4 (G(0)OTs-12). This dendrimer was converted into the thiol-functionalized
carbosilane dendrimer Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SH)3]4 (G(0)SH-12) by reduction of
the thiocyanate intermediate Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SCN)3]4 with LiAlH4. The
trithiol compounds 6a and 6b protonated the complexes [Rh(µ-OMe)(cod)]2 and [Rh(acac)-
diolefin] (M ) Rh, diolefin ) cod, nbd, tfb) to give the corresponding trinuclear complexes
[Rh3{µ-ROCH2c(ch2s)3}(diolefin)3] (7-9). Their structure can be described as an adamantane-
like entity, in which the metals are held together by the thiolate arms of the ligand, with
the sulfurs bridging the metal atoms in a µ2 fashion, as shown for [Rh3{µ-BnOCH2C(CH2S)3}-
(nbd)3] by X-ray diffraction methods. Carbonylation of 7-9 under atmospheric pressure gave
the carbonyl complexes with the thiolate tripod ligands [M3{µ-ROCH2C(CH2S)3}(CO)6]
(M ) Rh, Ir), which were reacted with phosphorus donor ligands (PR3 ) PPh3, P(OMe)3) to
give [M3{µ-ROCH2C(CH2S)3}(CO)3(PR)3] as a sole isomer of averaged C3v symmetry. The
functional dendrimers were metalated by reaction of the core molecule Si[(CH2)3Si(Me)2-
(CH2)3OCH2C(CH2SH)3]4 (G(0)SH-12) by applying the synthetic protocols above-described for
trinuclear complexes. Thus, the reactions of G(0)SH-12 with the complexes [M(acac)(diolefin)]
(M ) Rh, Ir; diolefin ) cod, nbd, tfb) gave the metallodendrimers Si[(CH2)3Si(Me)2(CH2)3-
OCH2C(CH2S)3{M(diolefin)}3]4 (G(0)M(diolefin)-12) as insoluble solids. Soluble metalloden-
drimers, Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)2}3]4 (G(0)Rh(CO)2-12) and Si[(CH2)3-
Si(Me)2(CH2)3OCH2C(CH2S)3{M(CO)(PPh3)}3]4 (G(0)M(CO)(PPh3)-12) were obtained either by
carbonylation of the diolefin compounds or by the reaction of G(0)SH-12 with [M(acac)(CO)2]
(M ) Rh, Ir), and by further reaction with PPh3, respectively.
Introduction
features make metallodendrimers valuable materials to
develop a number of applications that have already been
used in catalysis,3 redox processes,4 host-guest chem-
istry,5 electronics,6 and light-harvesting.7
The success of the preparation of such materials often
relies on a suitable design of the ligand systems grafted
to the dendritic surfaces, so that the coordination of the
Metallodendrimers are an evolving class of dendritic
macromolecules that incorporate metals in their struc-
tures.1 The main attraction about this class of archi-
tectures relies in their intrinsic properties,2 which
include a globular shape, a defined and known location
of the metallic centers within the dendritic structure, a
high solubility, and usually an elevated concentration
of metallic sites around their peripheries. All these
(3) (a) Smith, G. S.; Mapolie, S. F. J. Mol. Catal. A: Chem. 2004,
213, 187. (b) Niu, Y.; Crooks, R. M. R. C. R. Chem, 2003, 6, 1049. (c)
Reek, J. N. H.; de Groot, D.; Oosterom, G. E.; Kamer, P. C. J.; van
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(e) Rodr´ıguez, G.; Lutz, M.; Spek, A. L.; van Koten, G. Chem. Eur. J.
2002, 8, 45. (f) Oosterom, G. E.; Reek, J. N. H.; Kamer, P. C. J.; van
Leeuwen, P. W. N. M. Angew. Chem., Int. Ed. 2001, 40, 1828. (g)
Astruc, D.; Chardac, F. Chem. Rev. 2001, 101, 2991. (h) Kleij, A. W.;
Gossage, R. A.; Gebbink, R. J. M. K.; Brinkmann, N.; Reijerse, E. J.;
Kragl, U.; Lutz, M.; Spek, A. L.; van Koten, G. J. Am. Chem. Soc. 2000,
122, 12112. (i) Caminade, A. M.; Maraval, V.; Laurent, R.; Majoral, J.
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* E-mail: mcasado@ unizar.es (Casado); mciriano@ unizar.es
(Ciriano).
† Instituto de Ciencia de Materiales de Arago´n.
‡ Instituto Universitario de Cata´lisis Homoge´nea.
(1) Newkome, G. R.; He, E.; Moorefield, C. N. Chem. Rev. 1999, 99,
1689.
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Weinheim, Germany, 2001.
10.1021/om0504957 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 09/08/2005

5148 Organometallics, Vol. 24, No. 21, 2005
Camerano et al.
Chart 1
metallic fragments, which commonly is carried out in
the last synthetic step, must be very efficient in order
to avoid cross-linking or oligomerization processes.8
Given the number of papers dedicated to metalloden-
drimers, it is surprising that there are only a few reports
on dendrimers peripherally adapted with hydrosulfido
groups,9 functionalities that have the potential to
stabilize complexes with virtually every metal from the
periodic table.10 Moreover, interaction of thiols with
metallic nanoparticles is a topic of current interest.
Recent examples are a versatile approach to stabilize
gold nanoparticles of a specific size with R-functionalized
thiols from a single precursor,9a,11 and the condensation
of bifunctionalized thiol-ferrocene dendrons around gold
nanoparticles to form redox-active dendrimers.12
Scheme 1. Synthesis of the Tripod
Protio-Ligandsa
We have reported recently8a a method to prepare
different generations of carbosilane dendrimers func-
tionalized on their peripheries with hydrosulfido groups,
more specifically with propanethiol chains attached to
the ending silicon atoms. The goal of this project was
to prepare thiolate complexes on the surface of discrete
metallodendrimers with a high potential as catalytic
precursors in hydroformylation of olefins.13 However,
the intrinsic architecture of these dendritic assemblies
led to polymeric metallodendrimers, in which the den-
dritic cores remained glued to one another through the
“M(L2)” (M ) Rh, Ir) metal fragments, forming insoluble
tridimensional networks. To overcome this unwanted
situation for homogeneous catalysis purposes, the ar-
chitecture of the hydrosulfido periphery of the den-
drimer should be designed in such a way that discrete
metallodendrimers result. With this aim we have de-
a i ) RBr, KOH (R ) C6H4CH2, CH2dCHCH2); ii ) HCl (aq);
iii ) TsCl, py; iv ) KSCN, v ) LiAlH4.
veloped the synthesis of tripod-based thiol protio-ligands
appropriate for their attachment to the periphery of
carbosilane dendrimers. One of them incorporates an
olefin side able to undergo hydrosilylation with den-
drimers functionalized with Si-H peripheral bonds and
also bears three arms terminated with hydrosulfido
groups able to form discrete complexes of transition
metals (Chart 1). A related ligand with a consequent
iridium complex was reported by Maissonat and Poil-
blanc.14 We also describe herein some of their rhodium
and iridium complexes, the successful attachment of the
ligand to preformed carbosilane dendrimers, and de-
rived rhodium and iridium discrete metallodendrimers.
(4) (a) Daniel, M. C.; Ba, F.; Aran˜ases, J. R.; Astruc, D. Inorg. Chem.
2004, 43, 8649. (b) Daniel, M. C.; Ruiz, J.; Astruc, D. J. Am. Chem.
Soc. 2003, 125, 1150. (c) Astruc, D. Pure Appl. Chem. 2003, 75, 461.
(d) Daniel, M. C.; Ruiz, J.; Blais, J. C.; Daro, N.; Astruc, D. Chem.
Eur. J. 2003, 9, 4371. (e) Ruiz, J.; Pradet, C.; Varret, F.; Astruc, D.
Chem. Commun. 2002, 1108. (f) Cheng, L.; Cox, J. A. Chem. Mater.
2002, 14, 6. (g) Chow, H. F.; Chan, I. Y. K.; Fung, P. S.; Mong, T. K.
K.; Nongrum, M. F. Tetrahedron 2001, 57, 1565. (h) Astruc, D.; Blais,
J. C.; Cloutet, E.; Djakovitch, L.; Rigaut, S.; Ruiz, J.; Sartor, V.; Vale´rio,
C. Top Curr. Chem. 2000, 210, 228. (i) Astruc, D. Acc. Chem. Res. 2000,
33, 287.
(5) Newkome, G. R. Pure Appl. Chem. 1998, 70, 2337.
(6) (a) Astruc, D.; Blais, J. C.; Daniel, M. C.; Gatard, S.; Nlate, S.;
Ruiz, J. R. C. R. Chem. 2003, 6, 1117. (b) MacDonnell, F. M.; Wouters,
K. L.; Kirk, W. P.; Basir, N. A. Polym. Prepr. 2003, 44, 350. (c) Alonso,
B.; Astruc, D.; Blais, J. C.; Nlate, S.; Rigaut, S.; Ruiz, J.; Sartor, V.;
Vale´rio, C. C. R. Chim. 2001, 4, 173.
(7) (a) Tyson, D. S.; Luman, C. R.; Castellano, F. N. Inorg. Chem.
2002, 41, 3578. (b) Murfee, H. J.; Thoms, T. P. S.; Greaves, J.; Hong,
B. Inorg. Chem. 2000, 39, 5209.
(8) (a) Camerano, J. A.; Casado, M. A.; Ciriano, M. A.; Tejel, C.; Oro,
L. A. Dalton Trans. 2005, 3092. (b) Gatard, S.; Kahlal, S.; Me´ry, D.;
Nlate, S.; Cloutet, E.; Saillard, J. Y.; Astruc, D. Organometallics 2004,
23, 1313. (c) Becker, J. J.; Gagne´, M. R. Organometallics 2003, 22,
4984. (d) Kleij, A. W.; Gebbink, J. M. K.; van den Nieuwenhuijzen, P.
A. J.; Kooijman, H.; Lutz, M.; Spek, A. L.; van Koten, G. Organome-
tallics 2001, 20, 634.
(9) (a) Schmid, G.; Emmrich, E.; Majoral, J. P.; Caminade, A. M.
Small 2005, 1, 73. (b) Emmrich, E.; Franzka, S.; Schmid, G.; Majoral,
J. P. Nano Lett. 2002, 2, 1239. (c) Satoh, K.; Yoshimura, T.; Esumi, K.
J. Colloid Interface Sci. 2002, 255, 312. (d) Cadierno, V.; Zablocka,
M.; Donnadieu, B.; Igau, A.; Majoral, J. P.; Skowronska, A. Chem. Eur.
J. 2001, 7, 221. (e) Schmid, G.; Meyer-Zaika, W.; Pugin, R.; Sawitowski,
T.; Majoral, J. P.; Caminade, A. M.; Turrin, C. O. Chem. Eur. J. 2000,
6, 1693.
Results and Discussion
Synthesis of the Tripod Protio-Ligands ROCH2C-
(CH2SH)3 (R ) C6H5CH2 (Bn), 6a; CH2dCHCH2, 6b).
The starting material was pentaerythol, C(CH2OH)4, an
inexpensive chemical that was transformed into the
known compound HOCH2C(CH2O)3CCH3 (1).15 The api-
cal hydroxyl group in 1 was etherified with selected
benzyl (Bn) or allyl bromides to give the corresponding
ether derivatives ROCH2C(CH2O)3CCH3 (R ) Bn (2a),
R ) CH2dCHCH2 (2b)) in excellent yields (Scheme 1).
Once the apical functionalization was achieved, the
protecting orthoacetate group in 2 was hydrolyzed to
the corresponding triol derivatives ROCH2C(CH2OH)3
(R ) Bn (3a), R ) CH2dCHCH2 (3b)), which were
isolated as analytically pure oils. Protection of the free
hydroxylic functionalities with tosylate groups gave
ROCH2C(CH2OTs)3 (R ) Bn (4a), R ) CH2dCHCH2
(10) (a) Stephan, D. G.; Nadasdi, T. T. Coord. Chem. Rev. 1996, 147,
2171. (b) Torrens, H. Coord. Chem. Rev. 2000, 196, 331. (c) Dance, I.
G. Polyhedron 1986, 5, 1037.
(11) Woehrle, G. H.; Brown, L. O.; Hutchinson, J. E. J. Am. Chem.
Soc. 2005, 127, 2171.
(14) Maisonnat, A.; Devillers, J.; Poilblanc, R. Inorg. Chem. 1987,
26, 1502.
(15) Dunn, T. J.; Neumann, W. L.; Rogic, M. M.; Woulfe, S. R. J.
Org. Chem. 1990, 55, 6368.
(12) Astruc, D.; Daniel, M. C.; Ruiz, J. Chem. Commun. 2004, 2367.
(13) Bayo´n, J. C.; Claver, C.; Masdeu-Bulto´, A. M. Coord. Chem.
Rev. 1999, 193-195, 73.

Trithiol Protio-Ligand
Organometallics, Vol. 24, No. 21, 2005 5149
Scheme 2. Preparation and Structures of the
Trinuclear Complexesa
a i ) [Rh(acac)(diolefin)]; R ) Bn, allyl.
(4b)), which were reacted with potassium thiocyanate
to give the expected sulfur-containing derivatives
ROCH2C(CH2SCN)3 (R ) Bn (5a), R ) CH2dCHCH2
(5b)) in good yields. The final step to achieve the desired
hydrosulfido tripodal systems involved the chemical
reduction of the thiocyanate compounds 5 with lithium
aluminum hydride in diethyl ether to give the com-
pounds ROCH2C(CH2SH)3 (R ) Bn (6a), R ) CH2d
CHCH2 (6b)) as malodorous oils. All the intermediates
involved in the syntheses were completely characterized
by elemental analyses and multinuclear NMR and mass
spectra (see Experimental Section).
Synthesis and Structural Characterization of
Trinuclear Rhodium Diolefin Complexes. The com-
pounds ROCH2C(CH2SH)3 (R ) Bn, 6a; allyl, 6b) bear
three hydrosulfide groups acidic enough to protonate
acetylacetonate (acac) and methoxo or hydroxo ligands
in rhodium and iridium complexes to produce thiolate
tripod-based complexes. Thus, treatment of 6a with 3
equiv of [Rh(acac)(cod)] gave a dark red colored solution
within a few seconds, from which the compound [Rh3-
{µ-BnOCH2C(CH2S)3}(cod)3] (7) was isolated as a dark
red microcrystalline solid in excellent yield. Alterna-
tively, reactions of 6a with the dinuclear complexes [Rh-
(µ-OR)(cod)]2 (R ) H, Me) gave complex 7 in similar
yield. In a different approach, compound 6a was depro-
tonated with n-BuLi in THF to give the soluble lithium
salt of the ligand, which afforded cleanly complex 7 upon
reaction with [Rh(µ-Cl)(cod)]2. The related diolefin
rhodium complexes [Rh3{µ-BnOCH2C(CH2S)3}(diolefin)3]
(8a, 9a) and those derived from 6b, [Rh3{µ-CH2dCHCH2-
OCH2C(CH2S)3}(diolefin)3] (8b, 9b) (diolefin ) nor-
borna-2,5-diene (nbd) 8, tetrafluorobenzo[5,6]bicyclo-
[2.2.2]octa-2,5,7-triene (tfb) 9), were also isolated in good
yields as violet (nbd) and dark red (tfb) microcrystalline
solids, respectively, by reaction of the complexes [Rh-
(acac)(diolefin)] with the appropriate compounds 6a and
6b (Scheme 2).
Figure 1. Molecular representation of the trinuclear
complex 8a.
Table 1. Selected Bond Distances (Å) and Angles
(deg) for the Complex 8a
Rh(1)-S(1)
Rh(1)-S(2)
Rh(1)-M(1)* a
Rh(1)-M(2)*
Rh(2)-S(1)
Rh(2)-S(3)
Rh(2)-M(3)*
Rh(2)-M(4)*
Rh(3)-S(2)
Rh(3)-S(3)
Rh(3)-M(5)*
Rh(3)-M(6)*
S(1)-C(22)
2.3161(8)
2.3539(7)
S(1)-Rh(2)-M(3)* 159.05(9)
S(1)-Rh(2)-M(4)* 100.41(9)
2.0498(33) S(3)-Rh(2)-M(3)* 96.22(9)
2.0284(33) S(3)-Rh(2)-M(4)* 160.19(9)
2.3587(8)
2.3145(7)
2.0023(31) S(2)-Rh(3)-M(6)* 93.30(10)
2.0433(31) S(3)-Rh(3)-M(5)* 99.33(10)
2.3222(7)
2.3803(8)
2.0538(32) Rh(1)-S(1)-C(22) 111.43(11)
2.0046(32) Rh(2)-S(1)-C(22) 113.62(11)
1.825(3)
1.823(3)
1.824(3)
94.94(3)
S(2)-Rh(3)-S(3)
96.85(3)
S(2)-Rh(3)-M(5)* 163.78(9)
S(3)-Rh(3)-M(6)* 162.84(9)
Rh(1)-S(1)-Rh(2) 92.12(3)
Rh(1)-S(2)-Rh(3) 97.68(3)
Rh(1)-S(2)-C(23) 111.23(11)
Rh(3)-S(2)-C(23) 111.08(11)
Rh(2)-S(3)-Rh(3) 87.59(3)
S(2)-C(23)
S(3)-C(24)
S(1)-Rh(1)-S(2)
S(1)-Rh(1)-M(1)* 166.96(10) Rh(2)-S(3)-C(24) 114.81(11)
S(1)-Rh(1)-M(2)* 96.21(9)
S(2)-Rh(1)-M(1)* 98.08(9)
S(2)-Rh(1)-M(2)* 164.57(9)
Rh(3)-S(3)-C(24) 110.27(11)
S(1)-C(22)-C(25) 121.86(22)
S(2)-C(23)-C(25) 121.79(22)
S(3)-C(24)-C(25) 122.09(22)
S(1)-Rh(2)-S(3)
96.61(3)
a M* represents the midpoints of the olefinic double bonds.
The structure of complex 8a consists of three “Rh-
(nbd)” fragments held together by the three thiolate
arms of the ligand, with the sulfurs bridging the
rhodium atoms in a µ2 fashion. The structure can be
described as an adamantane-like entity that nearly
incorporates a C3 axis passing through the C(25) and
C(26) atoms. The rhodium atoms complete a typical
square-planar coordination with an nbd molecule in-
teracting through the two olefinic bonds in a η2 mode.
The separation between the adjacent rhodium centers
is too long (Rh(1)‚‚‚Rh(2) 3.3663(4) Å, Rh(1)‚‚‚Rh(3)
3.5207(3) Å, Rh(1)‚‚‚Rh(4) 3.2494(3) Å) to consider any
kind of interactions between the metals.16 The Rh-S
bond distances (2.3145(7)-2.3803(8) Å) compare well
with those found in some dinuclear rhodium thiolate
complexes such as [Rh2[µ-S(CH2)3S](cod)2]17 or the
mononuclear tripod-based complex [(CH3C(CH2PPh2)3-
Rh(CH3C(CH2S)3)].18 The molecular structure of com-
Complexes 7-9 are trinuclear, showing the molecular
ions in accordance with the calculated m/z values. They
are very soluble in chlorinated solvents, THF, and
toluene, which allowed their study by NMR methods in
solution. To establish the coordination of the tridentate
ligand and to obtain accurate geometrical parameters
for one of them, an X-ray diffraction study on a mono-
crystal of the complex [Rh3{µ-BnOCH2C(CH2S)3}(nbd)3]
(8a) was carried out. Figure 1 shows the molecular
structure along with the atom-labeling scheme used,
and Table 1 displays selected bond distances and angles
of 8a.
(16) (a) Ciriano, M. A.; Pe´rez-Torrente, J. J.; Viguri, F.; Lahoz, F.
J.; Oro, L. A.; Tiripicchio, A.; Tiripicchio-Camellini, M. J. Chem. Soc.,
Dalton Trans. 1990, 1493. (b) Bonnet, J. J.; Kalck, P.; Poilblanc, R.
Inorg. Chem. 1977, 16, 1514.
(17) Masdeu, A. M.; Ruiz, A.; Castillo´n, S.; Claver, C.; Hitchcock, P.
B.; Chaloner, P. A.; Bo´, C.; Poblet, J. M.; Sarasa, P. J. Chem. Soc.,
Dalton Trans. 1993, 2689.

5150 Organometallics, Vol. 24, No. 21, 2005
Camerano et al.
Scheme 3
plex 8a resembles that found for the complex [Ir3(µ-
CH3C(CH2S)3(CO)6],14 whose basic organic framework
is similar to that described in this work.
The diolefin complexes 7-9 display in solution a
structure similar to that found for 8a in the solid state
and behave in a similar way, judging from their 1H and
13C{1H} NMR spectra. The 1H NMR spectra showed
sharp signals for the bridging ligand, while the signals
for diolefin are broad at room temperature, still showing
two environments for the olefinic protons as predicted
for a species that possesses an effective C3v symmetry.
The nbd complexes 8, however, showed a broad band
for the olefin protons at room temperature. This broad-
ening of the signals is indicative of a fluxional process
that can be frozen at low temperature. Thus the 1H
NNR spectra of complexes 8 in the slow exchange
showed a singlet for the three equivalent CH2S groups
and two signals for the olefin protons, as expected.
Therefore, the structure in solution of complexes 7-9
corresponds to that found in the solid state for 8a
without the symmetry restraint imposed by the allyl or
benzyl groups.
Trinuclear Rhodium and Iridium Carbonyl and
Phosphine Complexes. Treatment of ROCH2C(CH2-
SH)3 (R ) Bn, 6a; allyl, 6b) with 3 molar equiv of [Rh-
(acac)(CO)2] gave the complexes [Rh3{µ-ROCH2C(CH2-
S)3}(CO)6] (R ) Bn, 10a; allyl, 10b) cleanly as black
microcrystalline solids in very good yields. An alterna-
tive route to these compounds consists of the carbonyl-
ation of the diolefin complexes 7-9 in dichloromethane
under atmospheric pressure (Scheme 2). The initial
trinuclear framework is maintained in the reactions, as
confirmed by the mass spectra of both complexes 10,
which showed the molecular ions along with the se-
quential loss of six carbonyl ligands. In addition, the
IR spectra of complexes 10 in toluene showed three
intense bands in the carbonyl region, which agrees with
the predicted 1A1 and 2E active stretching modes under
C3v symmetry.
from the replacement of one sole carbonyl ligand at each
metallic center (Scheme 3). In this way, the complexes
[M3{µ-BnOCH2C(CH2S)3}(PR3)3(CO)3] (M ) Rh; R ) Ph,
12; OMe, 13; M ) Ir, R ) Ph, 14) were isolated as brown
solids in excellent yields. While 12 and 13 can be
obtained alternatively by the reactions of [Rh(acac)(CO)-
(PPh3)] and [Rh(acac)(CO)(P(OMe)3)] with 6a, respec-
tively, the reaction of [Ir(acac)(CO)(PPh3)] with 6a gave
a mixture of complexes that was not analyzed further.
The trinuclear nature of complexes 12-14 was con-
firmed by their mass spectra. These complexes exhibit
one band in the IR spectra, which is in accordance with
the presence of only one carbonyl ligand per metal
center. A sole isomer, the most symmetrical of C3
symmetry, resulted from these reactions, since the 31P-
{1H} NMR spectra of complexes 12-14 showed a
doublet for the rhodium complexes and a singlet for the
iridium one. These rhodium and iridium complexes
resemble in structure and selectivity in the replacement
reactions the early-late complexes [CpTi(µ3-S)3{Rh(CO)-
(PR3)}3], formed by addition of phosphine or phosphite
ligands to the hexacarbonyl precursor.19,20 However, the
iridium complex does not follow the behavior of [CpTi-
(µ3-S)3{Ir(CO)2}3], for which the complexes [CpTi(µ3-S)3-
Ir3(µ-CO)(CO)3(PR3)3] with one tetrahedral iridium cen-
ter and a bridging carbonyl were isolated, probably
because of the interaction of the iridium center with the
early transition metal.21
Attachment of the Tripod System to Carbosilane
Peripheries. The methodology to graft the tripod
ligand to carbosilane dendrimers relies on a hydrosi-
lylation step, in which the olefin involved is already
incorporated in the ligand system and the Si-H bonds
are located at specific sites on the periphery of the
carbosilane dendrimer, whose preparation has been
reported elsewhere.22 However, the direct coupling of
the trithiol protio-ligand or their complexes to the
dendrimer by hydrosilylation was not obvious, since
some functional groups were found to be incompatible
with the reaction conditions used. Thus, the platinum-
catalyzed hydrosilylation of the allyl-containing tri-
nuclear complexes [Rh3{µ-CH2dCHCH2OCH2C(CH2S)3}-
(L-L)3] (L-L ) nbd, 8b; tfb, 9b; (CO)2, 10b) with the
Complexes 10 are very soluble in diethyl ether, THF,
and chlorinated solvents and insoluble in hexanes and
methanol. Solutions of 10 are intensively colored and
exhibit black-orange dichroism, which is indicative of
intermolecular metal-metal interactions, as reported
for the complex [Ir3{µ-CH3C(CH2S)3}(CO)6] in the solid
state.14 The equivalence of all the carbonyl groups and
of all the CH2S moieties in the 13C{1H} NMR spectra is
consistent with the structure proposed in Scheme 2.
In a similar way, reaction of BnOCH2C(CH2SH)3 (6a)
with 3 molar equiv of [Ir(acac)(CO)2] gave the complex
[Ir3{µ-BnOCH2C(CH2S)3}(CO)6] (11) in excellent yield
as a dark blue microcrystalline solid, which in solution
turns to a deep red color. The trinuclear nature of
complex 11 was confirmed by the mass spectrum, and
the IR spectrum in toluene showed three ν(CO) bands
expected for a C3v symmetry. The structure of 11 is
similar to that proposed for complex [Rh3{µ-BnOCH2C-
(19) Casado, M. A.; Pe´rez-Torrente, J. J.; Ciriano, M. A.; Oro, L. A.;
Orejo´n, A.; Claver, C. Organometallics 1999, 18, 3035.
(20) Atencio, R.; Casado, M. A.; Ciriano, M. A.; Lahoz, F. J.; Pe´rez-
Torrente, J. J.; Tiripicchio, A.; Oro, L. A. J. Organomet. Chem. 1996,
514, 103.
(21) Casado, M. A.; Ciriano, M. A.; Edwards, A. J.; Lahoz, F. J.; Oro,
L. A.; Pe´rez-Torrente, J. J. Organometallics 1999, 18, 3025.
(22) (a) Chai, M.; Pi, Z.; Tessier, C.; Rinaldi, P. L. J. Am. Chem.
Soc. 1999, 121, 273. (b) Cuadrado, I.; Mora´n, M.; Losada, J.; Casado,
M. C.; Pascual, C.; Alonso, B.; Lobete, F. Adv. Dendritic Macromol.
1996, 3, 151. (c) Seyferth, D.; Son, D. Y. Organometallics 1994, 13,
2682. (d) Majoral J. P.; Caminade, A. M. Chem. Rev. 1999, 99, 845.
1
(CH2S)3}(CO)6] (10a), since their H NMR spectra are
virtually identical, while a singlet was observed for the
carbonyl ligands in the 13C{1H} NMR spectrum of 11.
The carbonyl complexes 10a and 11 reacted with
phosphine or phosphite donor ligands to give the product
(18) Ghilardi, C. A.; Midollini, S.; Orlandini, A.; Scapacci, G. Inorg.
Chim. Acta 1997, 266, 113.

Trithiol Protio-Ligand
Organometallics, Vol. 24, No. 21, 2005 5151
Scheme 4. Attachment of a Tripod Ligand Precursor to Carbosilane Dendrimersa
a i ) Karstedt’s catalyst, THF; ii ) KSCN, DMF; iii ) LiAlH4, Et2O.
core dendrimer Si[(CH2)3Si(Me)2H]4 (G(0)SiH-4) did not
follow the expected manifold. Instead, we observed that
the allyl group of the bridging ligand underwent an
isomerization process under the reaction conditions to
give a mixture of the trans- and cis-1-propenyl deriv-
atives. For example, by monitoring the reaction of
the complex [Rh3{µ-CH2dCHCH2OCH2C(CH2S)3}(CO)6]
(10b) with G(0)SiH-4 by 1H NMR techniques in the
presence of the Karstedt’s catalyst, [{O(SiMe2CHd
CH2)2}3Pt2], the transformation of the allyl moiety to
the corresponding mixture of isomers (cis:trans ) 2:1)
[Rh3{µ-CH3-CHdCHOCH2C(CH2S)3}(CO)6] was found
to be complete in 21 h at room temperature in benzene.
It was clear at this point that the attachment of the
tripod ligand to the dendrimer had to be carried out
using organic-based materials. However, the hydrosi-
lylation of the compounds CH2dCHCH2OCH2C(CH2-
SCN)3 (5b) and CH2dCHCH2OCH2C(CH2SH)3 (6b) with
the dendritic core Si[(CH2)3Si(Me)2H]4 (G(0)SiH-4) also
failed, presumably because of the poisoning of the Pt0
catalyst by the sulfur donor atoms. Nevertheless, we
found that the reaction of CH2dCHCH2OCH2C(CH2-
OTs)3 (4b) with G(0)SiH-4 using the Karstedt’s catalyst
gave cleanly the desired product of the anti-Markovni-
kov addition of the silane along the olefin, Si[(CH2)3Si-
(Me)2(CH2)3OCH2C(CH2OTs)3]4 (G(0)OTs-12), in quan-
titative yield (Scheme 4). Neither the starting material
nor the Markovnikov isomer was observed in the
product, which indicated that the hydrosilylation pro-
tocol to attach the tosylate derivative to the dendritic
core is an excellent way to perform the coupling.
Moreover, this methodology involves the formation of
Si-C bonds between the core dendrimer and the pre-
cursor of the ligand, which led to very robust and
thermally stable constructs. Parallel strategies23 have
been used to couple a tripod-based phosphine ligand to
carbosilane dendrimers, although some of these relied
on the formation of Si-O bonds,24 which are more
susceptible to the hydrolysis.
[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SH)3]4 (G(0)SH-12) as
an oil, which was purified by column chromatography.
The purity and the identity of the target dendrimer
G(0)SH-12 was confirmed by the MALDI-TOF spectrum,
which showed a sharp signal at m/z 1327.5 correspond-
ing to the molecular ion Si[(CH2)3Si(Me)2(CH2)3OCH2-
+
C(CH2SH)3]4 minus two protons, with the expected
pattern for the isotopic distribution. The dendritic
intermediates involved in this multistep synthesis have
been unambiguously characterized by multinuclear
NMR spectroscopy and elemental analyses.
Preparation of Dodecanuclear Metallodendri-
mers of Rhodium and Iridium. The synthesis of
metallodendrimers using the core molecule Si[(CH2)3-
Si(Me)2(CH2)3OCH2C(CH2SH)3]4 (G(0)SH-12) as support
is straightforward by applying the synthetic protocols
above-described for trinuclear complexes. For instance,
the reactions of G(0)SH-12 with the complexes [Rh(acac)-
(diolefin)] (diolefin ) cod, nbd, tfb) in a 1:12 molar ratio
in THF or CH2Cl2 gave dark red or violet solutions from
which dark solids analyzing as Si[(CH2)3Si(Me)2(CH2)3-
OCH2C(CH2S)3{Rh(diolefin)}3]4 (G(0)Rh(diolefin)-12) pre-
cipitated within a few minutes. Monitoring these reac-
1
tions by H NMR showed clearly the release of acetyl-
acetone, but no peaks from either the dendritic skele-
ton or the diolefinic ligands were observed as a conse-
quence of the low solubility of the resulting metallo-
dendrimers. Despite the insolubility of the above diolefin
dendrimers in organic solvents, their carbonylation
under atmospheric pressure gave the soluble com-
pound Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)2}3]4
(G(0)Rh(CO)2-12), which was fully characterized.
A
direct synthesis of the carbonylmetalloden-
drimer G(0)Rh(CO)2-12 and the analogous iridium com-
pound Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Ir(CO)2}3]4
G(0)Ir(CO)2-12 consisted in the reaction of G(0)SH-12 with
[M(acac)(CO)2] (M ) Rh, Ir) in a 1:12 molar ratio
(Scheme 5). These compounds were isolated as black
and dark red solids, respectively, in excellent yields.
Both showed three ν(CO) intense bands in the IR
spectrum, which agrees with a local C3v symmetry.
While the iridium compound is insoluble in organic
solvents, G(0)Rh(CO)2-12 was soluble enough in CDCl3
to observe the 13C{1H} NMR spectrum that is in
accordance with the proposed metallodendritic struc-
ture. In particular, the carbonyl groups gave a doublet
at δ 182.2 ppm (1JC-Rh ) 67 Hz) and the Si-Me moiety
at δ -3.4 ppm, a chemical shift typical for CH3-Si
A further reaction of G(0)OTs-12 with potassium
thiocyanate in refluxing DMF gave cleanly the dendritic
derivative Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SCN)3]4
(G(0)SCN-12), isolated as a heavy oil in quantitative
yield. The final step involved the reduction of G(0)SCN-12
with LiAlH4, which afforded the target dendrimer Si-
(23) Findeis, R. A.; Gade, L. H. Eur. J. Inorg. Chem. 2003, 99.
(24) Findeis, R. A.; Gade, L. H. J. Chem. Soc., Dalton Trans. 2002,
3952.

5152 Organometallics, Vol. 24, No. 21, 2005
Scheme 5. Formation of Metallodendrimers of Rhodium and Iridiuma
Camerano et al.
a M ) Rh, Ir; P or PR3 ) PPh3, P(OMe)3.
groups. Moreover, the incorporation of the Rh(CO)2
moieties to the dendrimer was indicated by the MALDI-
TOF spectrum of G(0)Rh(CO)2-12, which showed peaks
at m/z corresponding to the molecular ion minus 5, 16,
and 24 carbonyl groups.
(G(0)Ir(CO)(PPh3)-12) resulted from the one-pot reaction
of G(0)SH-12 with [Ir(acac)(CO)2] followed by the addi-
tion of 12 molar equiv of PPh3. The 31P{1H} NMR
spectrum of G(0)Ir(CO)(PPh3)-12 showed a sole singlet at
δ -24.2 ppm, indicating that the isomer of local sym-
metry C3 was formed selectively.
Soluble metallodendrimers were obtained by reacting
mononuclear rhodium complexes of the type [Rh-
(acac)(CO)(PR3)] (R ) Ph, OMe) with G(0)SH-12, which
gave the compounds Si[(CH2)3Si(Me)2(CH2)3OCH2-
C(CH2S)3{Rh(CO)(PPh3)}3]4 (G(0)Rh(CO)(PPh3)-12) and
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)(P(O-
Me)3)}3]4 (G(0)Rh(CO)(P(OMe)3)-12) (Scheme 5). The 1H
NMR spectrum of G(0)Rh(CO)(PPh3)-12 in C6D6 is not very
significant, since broad bands were observed, suggesting
a fluxional process that could not be frozen even at -90
°C in CD2Cl2. However the 13C{1H} NMR spectrum in
CD2Cl2 gave signals of the tripod frameworks compa-
rable to those shown by complex [Rh3{µ-BnOCH2C-
(CH2S)3}(CO)3(PPh3)3] (12), and the signals from the
dendritic skeleton agreed with the structure proposed
for G(0)Rh(CO)(PPh3)-12. Noteworthy, the 31P{1H} NMR
Experimental Section
General Procedures. All manipulations were performed
under a dry argon atmosphere using Schlenk-tube techniques.
Solvents were dried by standard methods and distilled under
argon immediately prior to use. Standard literature procedures
were used to prepare the starting materials [Rh(acac)(diolefin)]
(diolefin ) cod, nbd),25 [Rh(acac)(CO)2],26 [Rh(acac)(CO)-
(PPh3)],25 and [Ir(acac)(cod)].27 The core dendrimer Si[(CH2)3-
Si(Me)2H]4 (G(1)SiH-4)
22 and the compound HOCH2C(CH2O)3-
CCH3 (1)15 were synthesized according to literature procedures.
All the other chemicals used in this work have been purchased
from Aldrich Chemicals and used as received.
Carbon and hydrogen analyses were performed with a
Perkin-Elmer 2400 microanalyzer. Mass spectra were recorded
in a VG Autospec double-focusing mass spectrometer operating
in the FAB+ mode for the metal complexes and in the EI mode
for the organic compounds. Ions were produced with the
standard Cs+ gun at ca. 30 kV; 3-nitrobenzyl alcohol (NBA)
was used as matrix. 1H, 31P{1H}, and 13C{1H} spectra were
recorded on Varian Unity, Bruker ARX 300, and Varian
Gemini 300 spectrometers operating at 299.95, 121.42, and
75.47 MHz, 300.13, 121.49, and 75.47 MHz, and 300.08,
121.48, and 75.46 MHz, respectively. Chemical shifts are
reported in ppm and referenced to Me4Si using the residual
signal of the deuterated solvent (1H and 13C) and H3PO4 as
external reference (31P). Molecular weights were determined
with a Knauer osmometer using a chloroform solution of the
complexes. MALDI-TOF spectra were recorded in a Reflex
MALDI spectrometer operating in the linear and reflector
modes.
spectra of G(0)Rh(CO)(PPh3)-12 and (G(0)Rh(CO)(P(OMe)3)-12
)
showed a sole doublet, indicating the coordination of the
four trinuclear tripod entities in the dendrimers is
similar to the monomer version.
Treatment of G(0)SH-12 with [Ir(acac)(CO)2] yielded
a deep red solution, which within 5 min resulted in a
red insoluble solid, whose analytical data fit with those
calculated for the iridium metallodendrimer Si[(CH2)3-
Si(Me)2(CH2)3OCH2C(CH2S)3{Ir(CO)2}3]4 (G(0)Ir(CO)2-12).
The 1H NMR spectrum of the reaction in situ in CDCl3
showed the release of acetylacetone, the disappearance
of the SH triplet, and the shift of 0.22 ppm of the CH2S-
tripod signals of the species in solution relative to
G(0)SH-12. In addition, the IR spectrum of the in situ
reaction showed three bands in the carbonyl region
that agree with a local C3v symmetry. Despite the
insolubility of G(0)Ir(CO)2-12 that precluded a further
characterization, the derived metallodendrimer Si-
[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Ir(CO)(PPh3)}3]4
(25) Bonati, F.; Wilkinson, G. J. Chem. Soc. 1964, 3156.
(26) Hernandez-Gruel, M. A. F.; Torrente, J. J.; Ciriano, M. A.; Oro,
L. A. Inorg. Synth. 2004, 34, 127.
(27) Robinson, S. R.; Shaw, B. L. J. Chem. Soc. 1965, 4997.

Trithiol Protio-Ligand
Organometallics, Vol. 24, No. 21, 2005 5153
Synthesis of the Compounds. BnOCH2C(CH2O)3CCH3
(2a). Solid HOCH2C(CH2O)3CCH3 (1) (7.67 g, 47.9 mmol) was
added to a stirred suspension of finely powdered KOH (12.63
g, 225.2 mmol) and benzyl bromide (9.56 g, 6.65 mL, 55.6
mmol) in DMSO (50 mL). The resulting mixture was stirred
for 45 min at room temperature, and then water (100 mL) was
added. The solution thus obtained was extracted with diethyl
ether (3 × 50 mL). The combined organic extracts were washed
with a saturated solution of NaCl, then dried over Na2SO4,
and finally filtered through a pad of Celite. After removal of
the solvent by distillation under vacuum, a heavy colorless oil
iced water. The precipitate thus obtained was filtered off,
washed with cold diethyl ether, and dried under vacuum to
yield 4a as a white solid (29.61 g, 72%). H NMR (CDCl3, 22
1
°C) δ: 7.86 (d, 3J ) 8.24 Hz, 6H, C6H4CH3), 7.46 (m, 11H, C6H5
+ C6H4CH3), 4.43 (s, 2H, PhCH2O), 4.08 (s, 6H, CCH2OTs),
3.47 (s, 2H, PhCH2OCH2), 2.60 (s, 9H, CH3). 13C{1H} NMR
(CDCl3, 22 °C) δ: 145.3 (s, Cipso Ts), 131.7 (s, Cipso Bn), 130.0
(s, Cm+Cp Ts), 128.3 (s, Cm Bn), 127.9 (s, Co Ts), 127.7 (s, Cp
Bn), 127.2 (s, Co Bn), 73.2 (s, PhCH2OCH2), 66.6 (s, CH2OTs),
66.2 (s, PhCH2), 43.6 (s, C(CH2OTs)3), 21.4 (s, CH3). MS (EI):
m/z ) 517 (M+ - 2 OTs, 15%). Anal. Calcd for C33H36O10S3:
C, 57.54; H, 5.27. Found: C, 57.78; H, 5.13.
1
was isolated (11.0 g, 92%). H NMR (CDCl3, 22 °C) δ: 7.26-
7.39 (m, 5H, C6H5), 4.58 (s, 2H, PhCH2O), 4.02 (s, 6H,
C(CH2O)3), 3.20 (s, 2H, PhCH2OCH2), 1.47 (s, 3H, CH3). 13C-
{1H} NMR (CDCl3, 22 °C) δ: 137.5 (s, Cipso), 128.5 (s, Cm), 127.8
(s, Co), 127.4 (s, Cp) (Bn), 108.4 (s, CCH3), 73.3 (s, PhCH2OCH2),
69.3 (s, C(CH2O)3), 68.1 (s, PhCH2), 34.6 (s, C(CH2O)3), 23.2
(s, CH3). Anal. Calcd for C14H18O4: C, 67.18; H, 7.24. Found:
C, 67.20; H, 7.20.
CH2dCHCH2OCH2C(CH2OTs)3 (4b). This complex was
prepared as described for 4a starting from 3b (3.96 g, 22.5
mmol) in pyridine (20 mL) and p-toluenesulfonyl chloride
(17.15 g, 89.9 mmol) to yield 4b as a white solid (10.3 g, 72%).
3
1H NMR (CDCl3, 22 °C) δ: 7.69 (d, J ) 8.2 Hz, 6H), 7.36 (d,
3J ) 8.0 Hz 6H) (C6H4CH3), 5.59 (m, 1H, dCH), 5.05 (m, 2H,
dCH2), 3.88 (s, 6H, CH2OTs), 3.69 (d, 3J ) 1.4 Hz, 2H, CH2d
CHCH2O), 3.28 (s, 2H, CH2OCH2C), 2.44 (s, 9H, CH3). 13C-
{1H} NMR (CDCl3, 22 °C) δ: 140.9 (s, Cipso Ts), 129.3 (s, d
CH), 127.4 (s, Cp Ts), 125.6 (s, Cm Ts), 123.5 (s, Co Ts), 112.8
(s, dCH2), 67.6 (s, CH2dCHCH2O), 62.3 (s, CH2OTs), 61.5 (s,
CH2OCH2C), 39.1 (s, C(CH2OTs)3), 17.0 (s, CH3). MS (EI): m/z
) 366 (M+ - 3 C6H5CH3), 309 (M+ - 3 C6H5CH3 - OCH2CHd
CH2). Anal. Calcd for C29H34O10S3: C, 54.53; H, 5.37. Found:
C, 55.05; H, 5.57.
BnOCH2C(CH2SCN)3 (5a). A mixture of 4a (2.02 g, 2.93
mmol) and KSCN (3.70 g, 38.1 mmol) in dry DMF (15 mL)
was stirred at 140 °C for 6 h. The resulting dark solution was
poured into cold water and left overnight at 5 °C. The tan
precipitate formed was separated by decantation, washed with
water, and then dissolved in methylene chloride (3 × 20 mL).
The combined organic fractions were washed with a saturated
NaCl solution, dried over Na2SO4, filtered, and then vacuum-
dried, yielding a brownish oil (870 mg, 85%). 1H NMR (CDCl3,
22 °C) δ: 7.31-7.35 (m, 5H, C6H5), 4.55 (s, 2H, PhCH2O), 3.60
(s, 2H, PhCH2OCH2), 3.29 (s, 6H, CH2SCN). 13C{1H} NMR
(CDCl3, 22 °C) δ: 136.3 (s, Cipso), 128.6 (s, Cm), 128.5 (s, Co),
128.2 (s, Cp) (Bn), 111.4 (s, SCN), 73.4 (s, PhCH2OCH2), 69.1
(s, PhCH2), 45.8 (s, C(CH2SCN)3), 35.8 (s, CH2SCN). Anal.
Calcd for C15H15N3OS3: C, 51.55; H, 4.33. Found: C, 51.23;
H, 4.21.
CH2dCHCH2OCH2C(CH2O)3CCH3 (2b). This complex was
prepared as described for 2a starting from HOCH2C(CH2O)3-
CCH3 (2.57 g, 12.8 mmol) (1), KOH (3.38 g, 60.3 mmol), and
allyl bromide (1.86 g, 1.33 mL, 15.4 mmol) in DMSO (15 mL)
and isolated as a heavy colorless oil (2.18 g, 85%). 1H NMR
(CDCl3, 22 °C) δ: 5.77 (m, 1H, dCH), 5.17 (s, 2H, dCH2), 3.97
(m, 6H, C(CH2O)3), 3.87 (d, 3J ) 1.37 Hz, 2H, OCH2CHdCH2),
3.14 (s, 2H, CH2OCH2CHdCH2), 1.41 (s, 3H, CH3). 13C{1H}
NMR (CDCl3, 22 °C) δ: 133.9 (s, dCH), 117.1 (s, dCH2), 108.3
(s, CCH3), 72.1 (s, CH2dCHCH2OCH2), 68.1 (s, C(CH2O)3), 42.0
(s, CH2dCHCH2), 34.5 (C(CH2O)3), 23.0 (s, CH3). Anal. Calcd
for C10H16O4: C, 59.98; H, 8.05. Found: C, 59.85; H, 8.01.
BnOCH2C(CH2OH)3 (3a). Aqueous HCl (23.8 mmol, 2 mol
L-1, 12 mL) was added to a solution of 2a (3.68 g, 14.7 mmol)
in methanol (40 mL), and the resulting mixture was stirred
for 6 h. Solid Na2CO3 (1.80 g, 17.0 mmol) was carefully added
in small portions, and the suspension formed was vigorously
stirred for an additional 3 h at room temperature. The volatiles
were removed by distillation (90 °C) under reduced pressure,
leaving a thick oil as residue, which was dissolved in meth-
ylene chloride and then filtered through a pad of Celite. Upon
removal of the solvent under vacuum, the resulting oil was
purified by column chromatography on silica gel using a
mixture of CH2Cl2/MeOH (1:1) as eluent to yield 3a as a
1
colorless oil (3.08 g, 93%). H NMR (CDCl3, 22 °C) δ: 7.27-
CH2dCHCH2OCH2C(CH2SCN)3 (5b). This complex was
prepared as described for 5a starting from 4b (6.96 g, 10.90
mmol), KSCN (13.77 g, 141.7 mmol), and dry DMF (30 mL) to
7.38 (m, 5H, C6H5), 4.49 (s, 2H, PhCH2O), 3.69 (s, 6H, CH2-
OH), 3.47 (s, 2H, PhCH2OCH2), 3.19 (br s, 3H, OH). 13C{1H}
NMR (CDCl3, 22 °C) δ: 137.7 (s, Cipso), 128.4 (s, Cm), 127.8 (s,
Cp), 127.4 (s, Co) (Bn), 73.5 (s, PhCH2OCH2), 72.0 (s, PhCH2),
63.5 (s, CH2OH), 44.9 (s, C(CH2OH)3). MS (EI): m/z ) 227 (M+,
12%). Anal. Calcd for C12H18O4: C, 63.70; H, 8.02. Found: C,
63.48; H, 7.97.
1
give a brownish oil (2.21 g, 68%). H NMR (CDCl3, 22 °C) δ:
5.81 (m, 1H, dCH), 5.19 (m, 2H, dCH2), 4.02 (d, 3J ) 5.0 Hz,
2H, CH2dCHCH2O), 3.55 (s, 2H, CH2OCH2C), 3.30 (s, 6H, CH2-
SCN). 13C{1H} NMR (CDCl3, 22 °C) δ: 133.8 (s, dCH), 118.6
(s, dCH2), 112.6 (s, SCN), 72.0, 71.8 (s, CH2O), 55.8 (s, C(CH2-
SCN)3), 45.8 (s, CH2SCN). Anal. Calcd for C11H13N3OS3: C,
44.12; H, 4.38. Found: C, 44.38; H, 4.35.
CH2dCHCH2OCH2C(CH2OH)3 (3b). This complex was
prepared as described for 3a starting from aqueous HCl (56
mmol, 2 mol L-1, 28.0 mL), 2b (6.91 g, 34.5 mmol) in methanol
(40 mL), and solid Na2CO3 (4.22 g, 39.7 mmol). The residual
oil was purified by column chromatography on silica gel using
a mixture of CH2Cl2/MeOH (1:1) as eluent to yield 3b as a
colorless oil (5.88 g, 96%). 1H NMR (CDCl3, 22 °C) δ: 5.82 (m,
1H, dCH), 5.21 (m, 2H, dCH2), 3.96 (d, 3J ) 4.35 Hz, 2H,
CH2dCHCH2O), 3.70 (s, 6H, CH2OH), 3.48 (s, 2H, CH2OCH2C),
2.89 (br s, 3H, OH). 13C{1H} NMR (CDCl3, 22 °C) δ: 134.1 (s,
dCH), 117.5 (s, dCH2), 72.6 (s, CH2dCHCH2O), 72.5 (s,
CH2OCH2C), 64.3 (s, CH2OH), 45.0 (s, C(CH2OH)3). MS (GC-
MS): m/z ) 127 (M+ - 3OH). Anal. Calcd for C8H16O4: C,
54.53; H, 9.15. Found: C, 54.19; H, 8.85.
BnOCH2C(CH2OTs)3 (4a). To a solution of 3a (13.47 g,
59.52 mmol) in pyridine (60 mL) cooled at -5 °C was added
p-toluenesulfonyl chloride (43.59 g, 238.1 mmol) in small
portions to keep the reaction temperature below 0 °C. After
stirring at 0 °C for 2 h and then at room temperature for 24
h, the pink-colored reaction mixture was poured into crushed-
BnOCH2C(CH2SH)3 (6a). A solution of 5a (2.10 g, 6.01
mmol) in a mixture of diethyl ether/THF (1:1, 10 mL) was
added to a stirred suspension of LiAlH4 (0.46 g, 12.0 mmol) in
diethyl ether (15 mL) under an argon atmosphere. The
resulting suspension was stirred for 3 h and then carefully
hydrolyzed with a saturated solution of NH4Cl until two phases
were clearly separated. The aqueous layer was extracted with
diethyl ether (3 × 50 mL), and then the combined organic
factions were dried over Na2SO4 and filtered. After removal
of volatiles under reduced pressure the residual pale yellow
oil was purified by column chromatography on silica gel eluting
with a mixture of hexanes/ethyl acetate, 9:1 (1.30 g, 79%). 1H
NMR (CDCl3, 22 °C) δ: 7.35-7.29 (m, 5H, C6H5), 4.48 (s, 2H,
PhCH2O), 3.34 (s, 2H, PhCH2OCH2), 2.62 (d, 3J ) 8.5 Hz, 6H,
3
CH2SH), 1.14 (t, J ) 8.93 Hz, 3H, SH). 13C{1H} NMR (C6D6,
22 °C) δ: 138.9 (s, Cipso), 129.0 (s, Cm), 128.3 (s, Co), 128.2 (s,
Cp) (Bn), 73.6 (s, PhCH2OCH2), 70.0 (s, PhCH2), 27.4 (s, CH2-

5154 Organometallics, Vol. 24, No. 21, 2005
Camerano et al.
SH), 43.6 (s, C(CH2SH)3). MS (EI): m/z ) 272 (M+ - 2 H).
Anal. Calcd for C12H18OS3: C, 52.51; H, 6.61. Found: C, 52.75;
H, 6.71.
mmol) and [Rh(acac)(nbd)] (0.56 g, 1.89 mmol) (0.47 g, 92%).
1H NMR (C6D6, 22 °C) δ: 5.52 (m, 1H, CH), 4.88 (m, 2H, d
CH2) (allyl), 4.21 (m, 12H, dCH), 3.73 (m, 6H, CH) (nbd), 3.41
(dm, 2H, CH2 allyl), 2.53 (s, 6H, CH2S), 2.39 (s, 2H, OCH2),
1.37 (s, 12H, CH2 nbd). 13C{1H} NMR (C6D6, 22 °C) δ: 130.2
(s, CH), 111.3 (s, dCH) (allyl), 84.2 (s, OCH2), 79.3 (s, CH2,
allyl), 59.0, 58.9 (s, CH nbd), 58.0, 52.5 (br s, dCH nbd), 46.0
(s, CH2 nbd), 41.2 (s, C(CH2S)3, 24.9 (s, CH2S). MS (FAB+):
m/z ) 806 (M+, 5), 613 (M+ - Rh - nbd, 35%). Anal. Calcd for
C29H37ORh3S3: C, 43.19; H, 4.61. Found: C, 43.36; H, 4.81.
[Rh3{µ-BnOCH2C(CH2S)3}(tfb)3] (9a). To a solution of
[Rh(acac)(tfb)] (0.24 g, 0.33 mmol) in THF (10 mL) at 0 °C was
added a solution of 6a (60 mg, 0.22 mmol) in THF (4 mL),
giving a dark red solution within a few seconds. The solution
was stirred for 30 min. After evaporation of the solvent under
reduced pressure, the oily residue was washed repeatedly with
cold methanol to give a dark red solid (0.26 g, 93%). 1H NMR
(CDCl3, 22 °C) δ: 7.21-7.14 (m, 5H, C6H5), 5.68 (m, 3H, CH),
5.22 (m, 3H, CH) (tfb), 4.07 (s, 2H, PhCH2OCH2), 4.00 (m, 6H,
dCH), 3.46 (m, 6H, dCH) (tfb), 2.55 (s, 2H, PhCH2OCH2), 2.52
(s, 6H, CH2S). 13C{1H} NMR (C7D8, 22 °C) δ: 139.7 (dm,
1JC-F ) 265 Hz), 138.6 (dm, 1JC-F ) 252 Hz) (CF tfb), 140.1 (s,
Cipso Bn), 138.0, 136.8 (m, CF tfb), 128.4 (s, Cm), 127.6 (s, Cp),
127.4 (s, Co) (Bn), 83.2 (s, PhCH2OCH2), 73.2 (s, PhCH2), 63.9,
57.6 (br s, dCH) (tfb), 41.4 (s, C(CH2S)3), 41.0, 40.2 (br s, CH)
(tfb), 29.9 (s, CH2S). Anal. Calcd for C48H33OF12Rh3S3: C,
45.74; H, 2.64. Found: C, 45.50; H, 2.64.
[Rh3{µ-CH2dCHCH2OCH2C(CH2S)3}(tfb)3] (9b). Com-
plex 9b was isolated as a red microcrystalline solid following
the procedure described for 9a starting from 6b (51 mg, 0.23
mmol) and [Rh(acac)(tfb)] (0.25 g, 0.34 mmol) (0.27 g, 99%).
1H NMR (CDCl3, 22 °C) δ: 5.63 (m, 4H, CH allyl + CH tfb),
5.16 (m, 3H, CH, tfb), 4.99 (m, 2H, dCH2 allyl), 3.96 (m, 6H,
dCH), 3.46 (d, 2H, CH2 allyl), 3.41 (m, 6H, dCH) (tfb), 2.47
(s, 6H, CH2S), 2.44 (s, 2H, PhCH2OCH2). MS (FAB+): m/z )
1208 (M+, 30%). Anal. Calcd for C44H31OF12Rh3S3: C, 43.73;
H, 2.59. Found: C, 43.89; H, 2.66.
[Rh3{µ-BnOCH2C(CH2S)3}(CO)6] (10a). To a solution of
[Rh(acac)(CO)2] (0.42 g, 1.64 mmol) in diethyl ether (30 mL)
at -78 °C was added a solution of 6a (0.10 g, 0.55 mmol) in
diethyl ether (4 mL) to give a dark blue solution within a few
seconds. The solution was stirred for 30 min, filtered under
argon via cannula, and then evaporated to dryness to yield a
dark blue, microcrystalline solid (0.36 g, 89%). 1H NMR (C6D6,
22 °C) δ: 7.13-6.94 (m, 5H, C6H5), 3.87 (s, 2H, PhCH2O), 2.07
(s, 2H, PhCH2OCH2), 1.67 (s, 6H, CH2S). 13C{1H} NMR (CDCl3,
22 °C) δ: 183.8 (d, 1JC-Rh ) 66 Hz, CO), 138.2 (s, Cipso), 129.1
(s, Cm), 128.2 (s, CP), 128.2 (s, CO) (Bn), 82.9 (s, PhCH2OCH2),
73.4 (s, PhCH2) 41.2 (s, C(CH2S)3), 21.3 (s, CH2S). MS
(FAB+): m/z ) 748 (M+, 35), 720 (M+ - 1 CO, 100), 692
(M+ - 2 CO, 60), 664 (M+ - 3 CO, 40), 636 (M+ - 4 CO, 35),
608 (M+ - 5 CO, 70), 578 (M+ - 6 CO, 60%). IR (toluene, cm-1):
ν(CO), 2085 (s), 2058 (s), 2015 (s). Anal. Calcd for C18H15O7-
Rh3S3: C, 28.89; H, 2.02. Found: C, 29.10; H, 1.92.
CH2dCHCH2OCH2C(CH2SH)3 (6b). This complex was
prepared as described for 6a, starting from 5b (2.34 g, 7.81
mmol) in THF (50 mL) and LiAlH4 (0.22 g, 5.72 mmol) in
diethyl ether (75 mL). The resulting pale yellow oil was
purified by column chromatography on silica gel eluting with
a mixture of hexanes/ethyl acetate, 9:1 (1.40 g, 80%). 1H NMR
(CDCl3, 22 °C) δ: 5.83 (m, 1H, dCH), 5.19 (m, 2H, dCH2), 4.02
(d, 3J ) 1.1 Hz, 2H, CH2dCHCH2O), 3.32 (s, 2H, CH2OCH2C),
2.61 (s, 6H, CH2SH), 1.23 (br s, 3H, SH). 13C{1H} NMR (C6D6,
22 °C) δ: 134.5 (s, dCH), 117.1 (s, dCH2), 72.1 (s, CH2d
CHCH2O), 69.3 (s,CH2OCH2C), 43.1 (s, C(CH2SH)3), 26.8 (s,
CH2SH). MS (GC-MS): m/z ) 222 (M+ - 2 H). Anal. Calcd
for C8H16OS3: C, 42.82; H, 7.19. Found: C, 42.78; H, 7.15.
[Rh3{µ-BnOCH2C(CH2S)3}(cod)3] (7). Method A: To a
solution of [Rh(µ-OH)(cod)]2 (0.19 g, 0.41 mmol) in THF (6 mL)
at 0 °C was added a solution of 6a (0.074 g, 0.27 mmol) in
THF (4 mL) to give a dark red solution within a few seconds.
The solution was stirred for 30 min, allowing it to reach room
temperature. After evaporation of the solvent under reduced
pressure, the oily residue was washed repeatedly with cold
methanol to give a dark red solid (0.23 g, 84%). Method B: To
a solution of [Rh(acac)(cod)] (0.30 g, 0.96 mmol) in THF (6 mL)
was added a solution of 6a (87 mg, 0.32 mmol) in THF (4 mL)
to give a dark red solution within a few seconds. The solution
was stirred for 30 min and then filtered via cannula to a
Shlenk tube. After evaporation of the solvent under reduced
pressure, the oily residue was washed repeatedly with cold
methanol to give a dark red solid (0.25 g, 86%). Method C: To
a solution of 6a (52 mg, 0.19 mmol) in THF (4 mL) at -78 °C
was added n-BuLi (0.36 mL, 1.6 mol L-1, 0.57 mmol) via
syringe to render a yellow solution, which was stirred for 10
min. Solid [Rh(µ-Cl)(cod)]2 (0.14 g, 0.28 mmol) was then added
to the resulting mixture at -78 °C to give a dark red solution,
which was allowed to gradually reach room temperature. The
solvent was evaporated under vacuum, and the residue was
extracted with toluene (10 mL) and filtered through a pad of
Celite under argon. After removal of volatiles a red solid was
isolated (0.15 g, 88%). 1H NMR (C6D6, 22 °C) δ: 7.62-7.14 (m,
5H, C6H5), 4.87 (m, 6H, dCH), 4.45 (m, 6H, dCH) (cod), 3.75
(s, 2H, PhCH2O), 2.62 (s, 2H, PhCH2OCH2), 2.58 (s, 6H, CH2S),
2.49 (m, 6H), 2.32 (m, 6H), 2.07 (m, 6H), 1.86 (m, 6H) (CH2,
cod). 13C{1H} NMR (C6D6, 22 °C) δ: 140.0 (s, Cipso), 129.0 (s,
1
Cm), 128.1 (s, Cp), 127.8 (s, Co) (Bn), 82.4 (d, JC-Rh ) 11 Hz,
1
dCH) (cod), 81.8 (s, PhCH2OCH2), 80.0 (d, JC-Rh ) 10 Hz,
dCH) (cod), 74.1 (s, PhCH2O), 46.5 (s, C(CH2S)3), 32.0 (s,
CH2S), 31.9, 31.8 (s, CH2, cod). MS (FAB+): m/z ) 904 (M+,
87), 578 (M+ - 3 cod, 69%). Anal. Calcd for C36H51ORh3S3: C,
47.79; H, 5.68. Found: C, 47.80; H, 5.21.
[Rh3{µ-BnOCH2C(CH2S)3}(nbd)3] (8a). To a solution of
[Rh(acac)(nbd)] (0.24 g, 0.82 mmol) in toluene (7 mL) was
added a solution of 6a (75 mg, 0.27 mmol) in toluene (4 mL)
to give a dark violet solution within a few seconds. The solution
was stirred for 30 min, and the volatiles were evaporated
under reduced pressure to give a violet solid, which was
washed with methanol and vacuum-dried (0.21 g, 87%). 1H
NMR (CDCl3, -60 °C) δ: 7.16-6.94 (m, 5H, C6H5), 4.50 (m,
6H, dCH), 3.97 (m, 6H, dCH), 3.77 (m, 3H, CH) (nbd), 3.68
(s, 2H, PhCH2OCH2), 3.52 (m, 3H, CH) (nbd), 2.60 (s, 6H,
CH2S), 2.22 (s, 2H, PhCH2OCH2), 1.33 (m, 6H, CH2 nbd). 13C-
{1H} NMR (C7D8, 22 °C) δ: 130.0-128.0 (all s, Ph), 84.2 (s,
PhCH2OCH2), 73.2 (s, PhCH2), 63.9, 63.8 (s, CH), 62.3, 56.6
(br s, dCH) (nbd), 50.9 (s, CH2 nbd), 46.1 (s, C(CH2S)3, 29.9
(s, CH2S). MS (FAB+): m/z ) 674 (M+ - 2 nbd, 25), 579
(M+ - 3 nbd, 35%). Anal. Calcd for C33H39ORh3S3: C, 46.27;
H, 4.59. Found: C, 46.78; H, 4.11.
[Rh3{µ-CH2dCHCH2OCH2C(CH2S)3}(CO)6] (10b). Com-
plex 11b was isolated as a black, microcrystalline solid
following the procedure described for 10a starting from 6b
(0.15 g, 0.67 mmol) and [Rh(acac)(CO)2] (0.52 g, 2.00 mmol)
(0.44 g, 94%). 1H NMR (CDCl3, 22 °C) δ: 5.63 (m, 1H, CH),
4.94 (m, 2H, dCH2), 3.33 (dm, 2H, dCH) (allyl), 2.05 (s, 2H,
OCH2), 1.68 (s, 6H, CH2S). 13C{1H} NMR (CDCl3, 22 °C) δ:
1
183.7 (d, JC-Rh ) 66 Hz, CO), 134.7 (s, CH), 117.4 (s, dCH)
(allyl), 83.3 (s, OCH2), 72.5 (s, CH2 allyl), 41.5 (s, C(CH2S)3),
21.7 (s, CH2S). MS (FAB+): m/z ) 698 (M+, 20), 670 (M+ - 1
CO, 70), 642 (M+ - 2 CO, 35), 614 (M+ - 3 CO, 25), 586
(M+ - 4 CO, 15), 558 (M+ - 5 CO, 10), 530 (M+ - 6 CO, 16%).
IR (toluene, cm-1): ν(CO), 2084 (s), 2056 (s), 2015 (s). Anal.
Calcd for C14H13O7Rh3S3: C, 24.09; H, 1.87. Found: C, 24.05;
H, 1.77.
[Rh3{µ-CH2dCHCH2OCH2C(CH2S)3}(nbd)3] (8b). Com-
plex 8b was isolated as a violet microcrystalline solid following
the procedure described for 8a, starting from 6b (0.14 g, 0.63
[Ir3{µ-BnOCH2C(CH2S)3}(CO)6] (11). To a solution of [Ir-
(acac)(CO)2] (0.57 g, 1.64 mmol) in THF (6 mL) at -78 °C was

Trithiol Protio-Ligand
Organometallics, Vol. 24, No. 21, 2005 5155
added a solution of 6a (0.15 g, 0.55 mmol) in diethyl ether (4
mL) to give a dark blue solution within a few seconds. The
solution was stirred for 30 min and then concentrated to ca. 3
mL. Upon addition of hexanes, a black solid precipitated. The
supernatant solution was decanted, and the dark blue solid
was vacuum-dried (0.36 g, 89%). 1H NMR (CDCl3, 22 °C) δ:
7.22-7.00 (m, 5H, C6H5), 3.94 (s, 2H, PhCH2O), 1.95 (s, 2H,
PhCH2OCH2), 1.90 (s, 6H, CH2S). 13C{1H} NMR (CDCl3, 22
°C) δ: 173.1 (s, CO), 129.1 (s, Cipso), 129.1 (s, Cm), 128.7 (s,
Cp), 128.4 (s, Co) (Bn), 83.5 (s, PhCH2OCH2), 73.4 (s, PhCH2),
42.3 (s, C(CH2S)3), 20.3 (s, CH2S). MS (FAB+): m/z ) 1017
(M+, 87), 989 (M+ - 1 CO, 100), 961 (M+ - 2 CO, 34), 933
(M+ - 3 CO, 29), 905 (M+ - 4 CO, 34), 876 (M+ - 5 CO, 60),
849 (M+ - 6 CO, 22%). IR (toluene, cm-1): ν(CO), 2080 (s),
2049 (s), 2004 (s). Anal. Calcd for C18H15O7Ir3S3: C, 21.27; H,
1.49. Found: C, 21.51; H, 1.52.
THF (10 mL) was added 8 drops of a 2.1-2.3% solution of
Karstedt’s catalyst in xylene. The reaction mixture was stirred
for 48 h at room temperature, and then the volatiles were
removed under reduced pressure to give a thick oil. This was
purified by column chromatography on silica gel (hexanes/ethyl
acetate, 9:1) and then eluted with methylene chloride to afford
a thick, colorless oil (14.05 g, 99%). 1H NMR (CDCl3, 22 °C) δ:
7.73 (d, 3J ) 7.8 Hz, 24H, C6H4CH3), 7.29 (d, 3J ) 7.4 Hz, 24H,
C6H4CH3), 3.88 (s, 24H, CH2OTs), 3.22 (s, 8H, OCH2), 3.11 (t,
3JH-H ) 6.9 Hz, 8H, CH2O), 2.44 (s, 36H, C6H4CH3), 1.30 (m,
16H, CH2), 0.55 (m, 16H, CH2), 0.31 (m, 8H, CH2), -0.07 (s,
24 H, SiCH3). 13C{1H} NMR (CDCl3, 22 °C) δ: 145.3 (s, Cipso),
132.0 (s, Cp), 130.0 (s, Co), 127.9 (s, Cm) (Ts), 74.4 (s, OCH2),
66.8 (s, CH2OTs), 66.5 (s, CH2O), 43.6 (s, C(CH2)3), 23.4 (s,
CH2), 21.5 (C6H4CH3), 19.9, 18.3, 17.3, 10.9 (s, CH2), -3.7 (s,
SiCH3). Anal. Calcd for C136H188O40S12Si5: C, 54.67; H, 6.34.
Found: C, 54.92; H, 5.95.
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SCN)3]4 (G(0)SCN-12).
A mixture of G(0)OTs-12 (14.05 g, 4.71 mmol) and KSCN (68.80
g, 708 mmol) in dry DMF (125 mL) was heated at 150 °C in
an oil bath for 24 h. The resulting cool solution was poured
into ice and then left at 5 °C overnight. The tan precipitate
formed was separated by decantation, washed with water, and
extracted with methylene chloride (3 × 20 mL). The combined
organic fractions were washed with a saturated solution of
NaCl, dried over Na2SO4, and then filtered. Upon removal the
volatiles under reduced pressure, a thick brownish oil was
obtained (7.56 g, 98%). 1H NMR (CDCl3, 22 °C) δ: 3.26 (s, 24H,
CH2SCN), 3.23 (s, 8H, OCH2), 3.06 (m, 8H, CH2O), 1.53 (m,
8H, CH2), 1.29 (m, 8H, CH2), 0.53 (m, 16H, CH2), 0.46 (m, 8H,
CH2), -0.24 (s, 24 H, SiCH3). 13C{1H} NMR (CDCl3, 22 °C) δ:
111.1 (s, SCN), 74.4 (s, OCH2), 72.6 (s, CH2O), 46.0 (s, CH2-
SCN), 37.2 (s, C(CH2)3), 23.7, 19.4, 18.4, 17.4, 11.2 (s, CH2),
-3.5 (s, SiCH3). Anal. Calcd for C64H104N12O4S12Si5: C, 47.14;
H, 6.43. Found: C, 47.25; H, 5.91.
[Rh3{µ-BnOCH2C(CH2S)3}(CO)3(PPh3)3] (12). To a solu-
tion of [Rh3{µ-BnOCH2C(CH2S)3}(CO)6] (10a) (0.20 g, 0.27
mmol) in THF (10 mL) at 0 °C was added a solution of PPh3
(0.21 g, 0.81 mmol) in THF (3 mL). A color change was
observed along with the evolution of carbon monoxide. After
stirring for 30 min, the solvent was evaporated under vacuum,
affording a brown solid, which was washed with methanol and
1
then vacuum-dried (0.37 g, 95%). H NMR (CDCl3, 22 °C) δ:
7.99-7.05 (m, 50H, C6H5), 3.87 (s, 2H, PhCH2O), 2.36 (s, 2H,
PhCH2OCH2), 2.32 (s, 6H, CH2S). 13C{1H} NMR (CDCl3, 22
°C) δ: 189.2 (dd, 1JC-Rh ) 70 Hz, 2JC-P ) 19 Hz, CO), 140.7-
122.3 (C6H5), 83.9 (s, PhCH2OCH2), 73.7 (s, PhCH2), 43.6 (s,
C(CH2S)3), 20.1 (s, CH2S). 31P{1H} NMR (CDCl3, 22 °C) δ: 36.3
1
(d, JP-Rh ) 154 Hz). MS (FAB+): m/z ) 1424 (M+ - CO, 5),
1104 (M+ - 3 CO-PPh3, 7%). IR (toluene, cm-1): ν(CO), 1976
(s). Anal. Calcd for C69H60O4P3Rh3S3: C, 57.11; H, 4.17.
Found: C, 56.94; H, 4.63.
[Rh3{µ-BnOCH2C(CH2S)3}(CO)3(P(OMe)3)3] (13). To a
solution of [Rh3{µ-BnOCH2C(CH2S)3}(CO)6] (10a) (0.79 g, 0.11
mmol) in THF (6 mL) at 0 °C was added a solution of P(OMe)3
(0.39 g, 0.32 mmol, 37 µL) in THF (3 mL). A color change to
brown was observed together with the evolution of carbon
monoxide. After stirring for 30 min, the solvent was evaporated
under vacuum, affording a brown solid, which was washed
with methanol and then vacuum-dried (950 mg, 87%). 1H NMR
(CDCl3, 22 °C) δ: 7.48-7.10 (m, 5H, C6H5), 4.07 (s, 2H,
PhCH2O), 3.77 (d, 3JH-P ) 12 Hz, 27H, P(OMe)3), 3.70 (s, 2H,
PhCH2OCH2), 2.52 (s, 6H, CH2S). 13C{1H} NMR (CDCl3, 22
°C) δ: 187.5 (dd, 1JC-Rh ) 69 Hz, 2JC-P ) 25 Hz, CO), 139.0 (s,
Cipso), 128.9 (s, Cm), 128.6 (s, Cp), 128.0 (s, Co) (Bn), 84.5 (s,
PhCH2OCH2), 73.6 (s, PhCH2), 52.5 (s, (P(OMe)3)), 42.5 (s,
C(CH2S)3), 26.5 (s, CH2S). 31P{1H} NMR (CDCl3, 22 °C) δ:
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2SH)3]4 (G(0)SH-12). To
a well-stirred suspension of LiAlH4 (2.02 g, 53.2 mmol) in
diethyl ether (20 mL) was added dropwise a solution of
G(0)SCN-12 (10.84 g, 6.65 mmol) in a mixture (1:1) of diethyl
ether and THF (40 mL). The reaction mixture was stirred for
15 h and then was carefully hydrolyzed with a saturated NH4-
Cl solution until two layers separated. The aqueous phase was
extracted with diethyl ether (3 × 50 mL), and the combined
organic fractions were dried over Na2SO4 and filtered. Then
the volatiles were removed under reduced pressure to afford
a brown oil. This was purified by chromatography on silica
gel using a mixture of hexanes/ethyl acetate (9:1), obtaining a
clear, malodorous oil (7.05 g, 65%). 1H NMR (CDCl3, 22 °C) δ:
3.47 (m, 8H, CH2O), 3.33 (s, 8H, OCH2), 2.64 (s, 24H, CH2-
1
135.7 (d, JP-Rh ) 240.3 Hz). MS (FAB+): m/z ) 1036 (M+,
17), 1008 (M+ - CO, 38), 980 (M+ - 2 CO, 38), 952 (M+ - 3
CO, 100%). IR (toluene, cm-1): ν(CO), 1982 (s). Anal. Calcd
for C24H42O13P3Rh3S3: C, 27.81; H, 4.08. Found: C, 27.67; H,
4.13.
3
SH), 1.54 (m, 8H, CH2), 1.30 (m, 8H, CH2), 1.22 (t, J ) 7.1
Hz, 12H, CH2SH), 0.54 (m, 16H, CH2), 0.47 (m, 8H, CH2),
-0.02 (s, 24 H, SiCH3). 13C{1H} NMR (CDCl3, 22 °C) δ: 74.5
(s, OCH2), 70.2 (s, CH2O), 46.0 (s, C(CH2)3), 27.1 (s, CH2SH),
30.0, 20.1, 18.5, 15.3, 11.4 (s, CH2), -3.4 (s, SiCH3). MALDI-
TOF: calcd 1330; found, 1327.5. Anal. Calcd for C52H116O4S12-
Si5: C, 46.94; H, 8.79. Found: C, 47.09; H, 8.43.
[Ir3{µ-BnOCH2C(CH2S)3}(CO)3(PPh3)3] (14). To a solu-
tion of [Ir3{µ-BnOCH2C(CH2S)3}(CO)6] (11) (0.16 g, 0.16 mmol)
in THF (6 mL) at 0 °C was added a solution of PPh3 (0.12 g,
0.47 mmol) in THF (3 mL). A color change to brown was
observed together with the evolution of carbon monoxide. After
stirring for 30 min, the solvent was evaporated to ca. 2 mL,
and after addition of hexanes a brown solid precipitated. The
remaining solution was cannulated off, and the solid was
washed with hexanes and then vacuum-dried (0.23 g, 86%).
1H NMR (CDCl3, 22 °C) δ: 7.87-7.68 (m, 18H, PPh3), 7.13-
6.89 (m, 32H, C6H5), 3.82 (s, 2H, PhCH2O), 1.90 (s, 2H, PhCH2-
OCH2), 0.99 (s, 6H, CH2S). 31P{1H} NMR (CDCl3, 22 °C) δ: -8.1
(s). MS (FAB+): m/z ) 1718 (M+, 35). IR (toluene, cm-1): ν-
(CO), 2009 (s). Anal. Calcd for C69H60Ir3O4P3S3: C, 48.21; H,
3.52. Found: C, 48.11; H, 3.47.
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)2}3]4 (G-
(0)Rh(CO)2-12). To a solution of G(0)SH-12 (71 mg, 0.053 mmol)
in dichloromethane (10 mL) was added solid [Rh(acac)(CO)2]
(0.16 g, 0.635 mmol) to give a black solution, which was stirred
for 30 min. The solution was evaporated to ca. 2 mL, and after
addition of hexanes a black solid precipitated. The solid was
filtered, washed with hexanes, and then vacuum-dried (0.16
g, 94%). 1H NMR (CDCl3, 22 °C) δ: 3.25 (t, 3J ) 6.63 Hz, 8H,
CH2O), 2.89 (s, 8H, OCH2C), 2.22 (s, 24H, CH2S), 1.45 (m, 8H),
1.27 (m, 8H), 0.50 (m, 16H), 0.35 (m, 8H) (CH2), -0.16 (s, 24H,
1
CH3). 13C{1H} NMR (CDCl3, 22 °C) δ: 182.2 (d, JC-Rh ) 67
Hz, CO), 84.0 (s, OCH2), 74.6 (s, CH2O) 41.5 (s, C(CH2S)3), 23.7
(s, CH2), 21.6 (s, CH2S), 20.0, 18.5, 17.5, 11.3 (s, CH2), -3.4 (s,
CH3). IR (toluene, cm-1): ν(CO), 2085 (s), 2060 (s), 2014 (s).
Anal. Calcd for C76H104O28S12Si5Rh12: C, 28.30; H, 3.25.
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2OTs)3]4 (G(0)OTs-12).
To a mixture of Si[(CH2)3Si(Me)2H]4 (2.05 g, 4.72 mmol) and
CH2dCHCH2OCH2C(CH2OTs)3 (4b) (12.07 g, 18.9 mmol) in

5156 Organometallics, Vol. 24, No. 21, 2005
Camerano et al.
Found: C, 28.13; H, 3.69. MALDI-TOF: 3085 (M+ - 5CO),
2778 (M+ - 16CO), 2554 (M+ - 24CO).
monoxide. After stirring for 10 min the solution was evapo-
rated to ca. 1 mL, and addition of hexanes gave an orange solid,
which was washed with hexanes and then vacuum-dried (59
mg, 85%). 1H NMR (CDCl3, 22 °C) δ: 7.25-7.62 (set of m,
180H, C6H5), 2.92 (t, 3J ) 6.60 Hz, 8H, CH2O), 2.23 (s, 8H,
OCH2), 1.86 (br s, 24H, CH2S), 1.45 (m, 8H), 1.22 (m, 8H), 0.53
(m, 16H), 0.27 (m, 8H) (CH2), -0.06 (s, 24H, CH3). 13C{1H}
NMR (C6D6, 22 °C) δ: 177.4 (s, CO), 136.0-130.9 (C6H5), 84.1
(s, OCH2), 74.9 (s, CH2O), 53.6 (s, C(CH2S)3), 25.1 (s, CH2S),
21.0, 19.6, 18.5, 15.9, 12.0 (s, CH2), -2.7 (s, CH3). 31P{1H} NMR
(CDCl3, 22 °C) δ: -24.2 (s). IR ν(CO), 2010.0 (s). Anal. Calcd
for C280H284Ir12O16P12S12Si5: C, 47.31; H, 4.03. Found: C, 47.17;
H, 4.24.
X-ray Structural Determination of Compound 8a.
Suitable crystals for the X-ray diffraction experiments were
obtained by slow evaporation of hexane into a concentrated
toluene solution of 8a at 5 °C. Intensity data were collected at
low temperature (100(2) K) on a CCD Bruker SMART APEX
diffractometer with graphite-monochromated Mo KR radiation
(λ ) 0.71073 Å) by using ω rotations (0.3°). Instrument and
crystal stability were evaluated by measuring equivalent
reflections at different times; no significant decay was ob-
served. Data were corrected for Lorentz and polarization
effects, and a semiempirical absorption correction was ap-
plied.28 The structure was solved by Patterson and difference
Fourier methods.29 Anisotropic displacement parameters were
applied for all non-hydrogen atoms. Hydrogen atoms were
found in subsequent difference Fourier maps and included as
free isotropic atoms; five of them were refined with a riding
thermal parameter. Refinements were carried out by full-
matrix least-squares on F2 (SHELXL-97).29 The highest re-
siduals were found in the proximity of metal centers and have
no chemical sense.
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Ir(CO)2}3]4 (G-
(0)Ir(CO)2-12). An NMR tube was charged with G(0)SH-12 (10
mg, 0.007 mmol), [Ir(acac)(CO)2] (31 mg, 0.090 mmol), and
CDCl3 (0.5 mL). The mixture was shaken for 5 min, and the
resulting deep red solution was analyzed by IR and NMR
techniques. After 10 min a red solid precipitated, and this was
collected and subjected to elemental analysis. 1H NMR (CDCl3,
22 °C) δ: 3.24 (t, 3J ) 6.61 Hz, 8H, CH2O), 2.77 (s, 8H,
OCH2C), 2.49 (s, 24H, CH2S), 1.44 (m, 8H), 1.23 (m, 8H), 0.55
(m, 16H), 0.33 (m, 8H) (CH2), -0.25 (s, 24H, CH3). IR (toluene,
cm-1): ν(CO), 2065 (s), 2053 (s), 2002 (s). Anal. Calcd for
C76H104Ir12O28S12Si5: C, 21.24; H, 2.44. Found: C, 21.12; H,
2.36.
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)(P-
Ph3)}3]4 (G(0)Rh(CO)(PPh3)-12). To a solution of G(0)SH-12 (0.17
g, 0.13 mmol) in toluene (10 mL) at -78 °C was added a
solution of [Rh(acac)(CO)(PPh3)] (0.77 g, 1.55 mmol) in toluene
(10 mL) via cannula under argon. A slight color change to deep
yellow was observed, and upon reaching room temperature,
the color turned to dark red gradually. After stirring for 30
min at room temperature, the solvent was evaporated under
vacuum to give a dark red oil, which was washed with diethyl
ether to afford a red solid, which was dried under vacuum (0.69
g, 89%). 1H NMR (CD2Cl2, -90 °C) δ: 7.25-7.63 (set of m,
180H, C6H5), 3.11 (br s, 8H, CH2O), 2.72 (br s, 8H, OCH2), 2.15
(br s, 24H, CH2S), 1.45-0.50 (set of m, 40H, CH2), -0.11 (br
s, 24H, CH3). 13C{1H} NMR (C6D6, 22 °C) δ: 189.0 (dd,
1JC-Rh ) 71 Hz, 2JC-P ) 19 Hz, CO), 136.5-130.1 (C6H5), 84.7
(s, OCH2), 75.2 (s, CH2O), 43.6 (s, C(CH2S)3), 30.1 (s, CH2S),
27.5, 21.0, 19.6, 18.6, 12.0 (s, CH2), -2.7 (s, CH3). 31P{1H} NMR
1
(CD2Cl2, -90 °C) δ: 36.1 (d, JP-Rh ) 152.9 Hz). IR (toluene,
cm-1): ν(CO), 1967 (s). Anal. Calcd for C280H284O16P12Rh12S12-
Si5: C, 55.70; H, 4.74. Found: C, 55.53; H, 5.00.
Crystal data for 8a: C33H39ORh3S3, M ) 856.55; crystal
size 0.235 × 0.130 × 0.109 mm3; orthorhombic, P212121; a )
13.6332(7) Å, b ) 14.4891(7) Å, c ) 14.9966(8) Å; Z ) 4; V )
2962.3(3) Å3; Dc ) 1.921 g/cm3; µ ) 1.891 mm-1, minimum and
maximum transmission factors 0.665 and 0.820; 2θmax ) 56.4°;
19 394 reflections collected, 6769 unique [R(int) ) 0.0251];
number of data/restraints/parameters 6769/0/512; final GoF
1.053, R1 ) 0.0224 [6594 reflns I > 2σ(I)], wR2 ) 0.0502 for
Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Rh(CO)(P(O-
Me)3)}3]4 (G(0)Rh(CO)(P(OMe)3)-12). To a solution of G(0)SH-12
(0.13 g, 0.10 mmol) in toluene (10 mL) at -78 °C was added a
solution of [Rh(acac)(CO)(P(OMe)3)] (0.42 g, 1.20 mmol) in
toluene (10 mL) via cannula under argon. A drastic color
change from pale yellow to a dark-colored solution was
observed upon reaching room temperature. After stirring for
2 h at room temperature, the solvent was evaporated under
vacuum to give a black oil, which was washed with cold diethyl
ether, affording a black solid, which was dried under vacuum
(0.33 g, 84%). 1H NMR (CD2Cl2, 22 °C) δ: 3.61 (m, 108H,
P(OCH3)3), 2.94 (br s, 8H, CH2O), 2.43 (br s, 24H, CH2S), 2.40
(br s, 8H, OCH2), 1.53-0.60 (set of m, 40H, CH2), 0.00 (br s,
24H, CH3). 13C{1H} NMR (C6D6, 22 °C) δ: 185.6 (m, CO), 83.6
(s, OCH2), 73.4 (s, CH2O), 50.5 (s, (P(OMe)3)), 40.6 (s, C(CH2S)3),
24.7 (s, CH2S), 22.8, 19.1, 17.9, 16.7, 10.4 (s, CH2), -4.5 (s,
all data; largest diff peak 0.68 e‚Å-3
.
Acknowledgment. The financial support from Min-
isterio de Ciencia y Tecnolog´ıa (MCyT(DGI)/FEDER)
Project BQU2002-0074 is gratefully acknowledged. J.A.C.
thanks Ministerio de Educacio´n y Ciencia for a fellow-
ship.
Supporting Information Available: Details of the X-ray
crystallographic study of 8a (as a crystallographic information
file). This material is available free of charge via the Internet
at http://pubs.acs.org.
1
CH3). 31P{1H} NMR (C6D6, 22 °C) δ: 133.7 (d, JP-Rh ) 179.4
Hz). IR: ν(CO), 1996 (s). Anal. Calcd for C100H212O28P12Rh12S12-
Si5: C, 27.43; H, 4.88. Found: C, 27.32; H, 4.72.
Synthesis of Si[(CH2)3Si(Me)2(CH2)3OCH2C(CH2S)3{Ir-
(CO)(PPh3)}3]4 (G(0)Ir(CO)(PPh3)-12). To a solution of G(0)SH-12
(13 mg, 0.01 mmol) in dichloromethane (10 mL) was added a
solution of [Ir(acac)(CO)2] (41 mg, 0.12 mmol) in dichlo-
romethane (5 mL) via cannula under argon, to give a deep red
solution within a few seconds. Then PPh3 (31 mg, 0.12 mmol)
was added to give a red solution with evolution of carbon
OM0504957
(28) SAINT+ Software for CCD difractometers; Bruker AXS:
Madison, WI, 2000. Sheldrick, G. M. SADABS Program for Correction
of Area Detector Data; University of Go¨ttingen: Go¨ttingen, Germany,
1999.
(29) Sheldrick, G. M. SHELXS-97: Program for Crystal Structure
Solution; University of Go¨ttingen: Go¨ttingen, Germany, 1997.