Reactivity of [Ru3(CO)12] with a phosphine- functionalized imidazol-2-ylidene and its imidazolium salt

Article abstract of DOI:10.1021/om101021s

The trinuclear cluster [Ru₃(CO)₁₂] reacts at room temperature with the phosphine-functionalized N-heterocyclic carbene (NHC) ligand 1-[2-(diphenylphophino)ethyl]-3-methylimidazol-2-ylidene (dppeImMe), in 1:1 mol ratio, to give the ed

Full text of DOI:10.1021/om101021s

826 Organometallics 2011, 30, 826–833
DOI: 10.1021/om101021s
Reactivity of [Ru3(CO)12] with a Phosphine-Functionalized
Imidazol-2-ylidene and Its Imidazolium Salt
†
a-Alvarez, Alan R. Kennedy, and
~
‡
Javier A. Cabeza,*,† Marina Damonte,† Pablo Garcı
´
Enrique Perez-Carreno
ꢀ
§
ꢀ
†
´
ꢀ
Departamento de Quımica Organica e Inorganica-IUQOEM, Universidad de Oviedo-CSIC,
ꢀ
E-33071 Oviedo, Spain, ‡WestCHEM, Department of Pure and Applied Chemistry,
§
University of Strathclyde, Glasgow G1 1XL, U.K., and Departamento de Quımica Fısica y Analıtica,
Universidad de Oviedo, E-33071 Oviedo, Spain
´
´
´
Received October 29, 2010
The trinuclear cluster [Ru3(CO)12] reacts at room temperature with the phosphine-functionalized
N-heterocyclic carbene (NHC) ligand 1-[2-(diphenylphophino)ethyl]-3-methylimidazol-2-ylidene
(dppeImMe), in 1:1 mol ratio, to give the edge-bridged trinuclear derivative [Ru3(μ-κ2C,P-
dppeImMe)(CO)10] (1). The use of a 1:3 [Ru3(CO)12] to dppeImMe mol ratio leads to the mono-
nuclear derivative [Ru(κ2C,P-dppeImMe)(CO)3] (2), which has a trigonal-bipyramidal ligand
arrangement with the NHC and phosphine fragments of the dppeImMe ligand in axial and equatorial
positions, respectively. Upon gentle heating (refluxing THF), compound 1 is transformed into
the face-capped dihydrido derivative [Ru3(μ-H)2(μ3-κ3C2,P-dppeImCH)(CO)8] (3), which arises
from the oxidative addition of two C-H bonds of the N-methyl group of the dppeImMe ligand.
The trinuclear salt [Ru3(κP-dppeHImMe)3(CO)9][BF4]3 (4[BF4]3), which contains a P-coordinated
1-[2-(diphenylphophino)ethyl]-3-methylimidazolium ligand ([dppeHImMe]þ) on each Ru atom, has
been prepared by treating [Ru3(CO)12] with the salt [dppeHImMe][BF4]. The deprotonation of
4[BF4]3 with three equivalents of K[N(SiMe3)2] is an alternative way to prepare the mononuclear
complex 2.
Introduction
than 30 years ago,3 has been recently continued by us4-10 and
by the research groups of Whittlesey,11,12 Cole,13 and Wang,14
who have reported studies involving triruthenium clusters
derived from 1,3-disubstituted imidazol-2-ylidenes4-9,11-14
(R2Im) and pyrid-2-ylidenes.10
Scheme 1 shows some representative reactions of 1,3-
disubstituted imidazol-2-ylidenes (R2Im) with [Ru3(CO)12].
While 1,3-dimethylimidazol-2-ylidene (Me2Im) and 1,3-di-
mesitylimidazol-2-ylidene (Mes2Im) react with [Ru3(CO)12]
at room temperature to give normal CO-substitution tri-
nuclear products, [Ru3(R2Im)(CO)11],4 analogous reactions
The current interest of the chemical community in the
coordination chemistry of N-heterocyclic carbenes (NHC)1
and in the catalytic properties of many of their complexes2
has recently impelled studies on the synthesis and reac-
tvity of transition metal carbonyl clusters containing NHC
ligands. Within this field and as far as ruthenium carbonyl
cluster complexes are concerned, the pioneering work of
Lappert and Pye, who reported the synthesis of [Ru3(CO)11-
(Et2H2Im)] (Et2H2Im=1,3-diethylimidazolin-2-ylidene) more
*To whom correspondence should be addressed. E-mail: jac@
uniovi.es.
(1) For an excellent review on cyclic carbenes and related species that
cites all review articles and books on NHCs published since 2007, see:
Melaimi, M.; Soleihavoup, M.; Bertrand, G. Angew. Chem., Int. Ed.
2010, 49, 8810.
ꢀ
ꢀ
(7) (a) Cabeza, J. A.; del Rı
´
o, I.; Fernandez-Colinas, J. M.; Sanchez-
o,
Vega, M. G. Organometallics 2009, 28, 1243. (b) Cabeza, J. A.; del Rı
´
I.; Miguel, D.; Sanchez-Vega, M. G. Angew. Chem., Int. Ed. 2008, 47,
1920.
ꢀ
ꢀ
~
(8) Cabeza, J. A.; Perez-Carreno, E. Organometallics 2008, 27, 4697.
ꢀ
´
o, I.; Sanchez-Vega, M. G. Dalton
(2) For recent reviews on catalytic applications of transition metal
NHC complexes, see: (a) Glorius, F. A. Top. Organomet. Chem. 2007,
21, 1. (b) Clavier, H.; Grela, K.; Kirschning, A.; Mauduit, M.;
Nolan, S. P. Angew. Chem., Int. Ed. 2007, 46, 6786. (c) Nolan, S. P.
N-Heterocyclic Carbenes in Synthesis; Wiley-VCH: Weinheim, Germany,
2006. (d) Hahn, F. E. Angew. Chem., Int. Ed. 2006, 45, 1348. (e) Kaufhold,
O.; Hahn, F. E. Angew. Chem., Int. Ed. 2008, 47, 4057.
(9) Cabeza, J. A.; da Silva, I.; del Rı
Trans. 2006, 3966.
(10) (a) Cabeza, J. A.; del Rı
ꢀ
~
ꢀ
´
o, I.; Perez-Carreno, E.; Sanchez-Vega,
ꢀ
M. G.; Vazquez-Garcı
Cabeza, J. A.; del Rı
´
a, D. Angew. Chem., Int. Ed. 2009, 48, 555. (b)
ꢀ
~
ꢀ
´
o, I.; Perez-Carreno, E.; Sanchez-Vega, M. G.;
ꢀ
Vazquez-Garcı
´
a, D. Organometallics 2010, 29, 4464.
(11) (a) Ellul, C. E.; Mahon, M. F.; Saker, O.; Whittlesey, M. K.
Angew. Chem., Int. Ed. 2007, 46, 6343. (b) Critall, M. R.; Ellul, C. E.;
Mahon, M. F.; Saker, O.; Whittlesey, M. K. Dalton Trans. 2008, 4209.
(12) Ellul, C. E.; Saker, O.; Mahon, M. F.; Apperley, D. C.; Whittlesey,
M. K. Organometallics 2008, 27, 100.
(13) Bruce, M. I.; Cole, M. L.; Fung, R. S. C.; Forsyth, C. M.; Hilder,
M.; Junk, P. C.; Konstas, K. Dalton Trans. 2008, 4118.
(14) Zhang, C.; Luo, F.; Cheng, B.; Li, B.; Song, H.; Xu, S.; Wang, B.
Dalton Trans. 2009, 7230.
(3) Lappert, M. F.; Pye, P. L. J. Chem. Soc., Dalton Trans. 1977, 2172.
ꢀ ~ ꢀ
´
o, I.; Miguel, D.; Perez-Carreno, E.; Sanchez-
(4) Cabeza, J. A.; del Rı
Vega, M. G. Organometallics 2008, 27, 211.
(5) (a) Cabeza, J. A.; del Rıo, I.; Miguel, D.; Sanchez-Vega, M. G.
Chem. Commun. 2005, 3956. (b) Cabeza, J. A.; del Rıo, I.; Miguel, D.;
Perez-Carreno, E.; Sanchez-Vega, M. G. Dalton Trans. 2008, 1937.
ꢀ
´
´
ꢀ
~
ꢀ
(6) Cabeza, J. A.; Van der Maelen, J. F.; Garcı
´
metallics 2009, 28, 3666.
a-Granda, S. Organo-
r
pubs.acs.org/Organometallics
Published on Web 01/28/2011
2011 American Chemical Society

Article
Organometallics, Vol. 30, No. 4, 2011 827
Scheme 1
Scheme 3
Scheme 4
Scheme 2
(MeCN)2],19 and some tripalladium20 and mixed-metal
MoNi221 carbonyl clusters have also been described.
On the other hand, although the coordination chemistry of
bi-, tri-, or polydentate ligands constituted by at least one
NHC moiety has already been extensively studied,22 only
two works have hitherto been published involving such
ligands and transition metal carbonyl clusters. They describe
the synthesis of triruthenium and triosmium clusters
containing bidentate NHC-thiolate ligands derived from leva-
milsolium salts9 (Scheme 3) and reactions of NHC-functiona-
lized indenes with [Ru3(CO)12]14 (Scheme 4).
We now describe the preparation of the first [Ru3(CO)12]-
derived complexes containing an imidazol-2-ylidene ligand
functionalized with a phosphine moiety, namely, 1-[2-(diph-
enylphosphino)ethyl]-3-methylimidazol-2-ylidene (dppeImMe).
We have chosen two different synthetic approaches for this
study: (a) to treat [Ru3(CO)12] with different amounts of
dppeImMe and (b) to deprotonate (with a strong base) cationic
[Ru3(CO)12]-derived complexes, previously made by treating
[Ru3(CO)12] with the imidazolium cation [dppeHImMe]þ.
The coordination chemistry of phosphine-functionalized
imidazol-2-ylidenes has already been studied to a significant
extent, but only mononuclear derivatives of these ligands
have hitherto been reported.23
with the very bulky NHCs 1,3-di-tert-butylimidazol-2-yli-
dene (tBu2Im) and 1,3-diadamantylimidazol-2-ylidene
(Ad2Im) afford CO-substitution products that contain an
“abnormally” bound (through C4) NHC ligand, [Ru3(a-
R2Im)(CO)11].11 Mononuclear complexes of the types
[Ru(R2Im)2(CO)3]12 and [Ru(R2Im)(CO)4]13 have been ob-
tained using 1:6 or 1:3 cluster to NHC mole ratios, respectively.
Interestingly, as a consequence of the high basicity of the
NHC ligands, the clusters [Ru3(NHC)(CO)11] (NHC=R2Im,
a-R2Im) undergo easy C-H bond cleavage processes upon
thermal activation to give trinuclear hydrido derivatives that
contain NHC-derived face-capping ligands, such as [Ru3(μ-
H)2(μ3-κ2C2-MeImCH)(CO)9]5 and [Ru3(μ-H)(μ3-κ2C2-R2C3-
N2H)(CO)9]11 (Scheme 2). An AIM theoretical analysis of the
bonding in [Ru3(μ-H)2(μ3-κ2C2-MeImCH)(CO)9]6 as well as
some reactivity7 and a DFT mechanistic study of its synthesis
from [Ru3(Me2Im)(CO)11]8 have been published.
It has been reported that some 1,3-disubstituted imidazol-
2-thiones and imidazolium chlorides react with [Ru3(CO)12]
to give NHC cluster derivatives.13
Concerning other transition metal cluster complexes,
different from triruthenium clusters, NHC derivatives
of [Ru4(μ-H)4(CO)12],15,16 [Os3(CO)12],4,11b [Os3(μ-H)2-
(CO)10],16-18 [Os3(CO)10(MeCN)2],16,18 [Os4(μ-H)4(CO)10-
Results and Discussion
Reactions of [Ru3(CO)12] with dppeImMe. The treatment
of [Ru3(CO)12] with an equimolar amount of dppeHImMe
(prepared in situ by deprotonating [dppeHImMe][BF4] with
K[N(SiMe3)2]) in THF at room temperature led to the
trinuclear cluster [Ru3(μ-κ2C,P-dppeImMe)(CO)10] (1),
which was isolated as a dark orange solid after a chromato-
graphic workup (Scheme 5).
The X-ray structure of compound 1 is shown in Figure 1. A
selection of bond distances is given in Table 1. The structure
can be described as resulting from the substitution of a
ꢀ
ꢀ
(15) Cabeza, J. A.; del Rı
´
o, I.; Fernandez-Colinas, J. M.; Perez-
(18) Cooke, C. E.; Ramnial, T.; Jennings, M. C.; Pomeroy, R. K.;
Clyburne, J. A. C. Dalton Trans. 2007, 1755.
(19) Cooke, C. E.; Jennings, M. C.; Pomeroy, R. K.; Clyburne,
J. A. C. Organometallics 2007, 26, 6059.
(20) Ellul, C. E.; Mahon, M. F.; Whittlesey, M. K. J. Organomet.
Chem. 2010, 695, 6.
~
Carreno, E.; Sanchez-Vega, M. G.; Vazquez-Garcı
2009, 28, 1832.
(16) Cooke, C. E.; Jennings, M. C.; Katz, M. J.; Pomeroy, R. K.;
Clyburne, J. A. C. Organometallics 2008, 27, 5777.
ꢀ
ꢀ
´
a, D. Organometallics
ꢀ ꢀ
(17) Cabeza, J. A.; del Rıo, I.; Fernandez-Colinas, J. M.; Perez-
´
~
Carreno, E.; Sanchez-Vega, M. G.; Vazquez-Garcı
2010, 29, 3828.
ꢀ
ꢀ
´
a, D. Organometallics
(21) Milosevic, S.; Brenner, E.; Ritleng, V.; Chetcuti, M. J. Dalton
Trans. 2008, 1973.

828 Organometallics, Vol. 30, No. 4, 2011
Cabeza et al.
Scheme 5
Figure 1. Structure of compound 1 (ellipsoids set at 20% prob-
ability; phenyl hydrogen atoms omitted for clarity).
dppeImMe ligand for two equatorial CO groups of different
Ru atoms of [Ru3(CO)12], thus spanning an Ru-Ru edge.
The coordination of the dppeImMe ligand does not alter
significantly the Ru-Ru distances with respect to those of
[Ru3(CO)12],24 since in compound 1 they range from
2.8694(4) to 2.8855(4) A. The Ru-Ccarbene distance,
Ru2-C1 2.100(4) A, is a bit shorter than that found in
˚
Table 1. Selected Interatomic Distances (A) in Compound 1
Ru1-Ru2
Ru1-Ru3
Ru2-Ru3
C1-Ru2
C1-N1
2.8855(4)
2.8863(4)
2.8694(4)
2.100(4)
1.365(5)
1.354(4)
1.342(7)
1.395(6)
C3-N1
1.384(5)
1.451(5)
1.528(5)
1.843(4)
1.450(6)
2.3419(9)
1.136(7)
1.92(2)
C4-N1
C4-C5
C5-P1
C6-N2
C1-N2
P1-Ru1
C-O (av)
C(CO)-Ru (av)
(22) For reviews on bi-, tri-, or polydentate ligands containing at least
one NHC moiety, see: (a) Peris, E.; Crabtree, R. H. Coord. Chem. Rev.
2004, 248, 2239. (b) Mata, J. A.; Poyatos, M.; Peris, E. Coord. Chem.
C2-C3
C2-N2
ꢀ
ꢀ
Rev. 2007, 251, 841. (c) Corberan, R.; Mas-Marza, E.; Peris, E. Eur.
J. Inorg. Chem. 2009, 1700. (d) Poyatos, M.; Mata, J. A.; Peris, E. Chem.
[Ru3(Me2Im)(CO)11], 2.115(4) A,4 while the Ru-P distance,
Ru1-P1 2.3419(9) A, is slightly shorter than that of [Ru3-
(PPh3)(CO)11],25 2.379(4) A, but slightly longer than those of
[Ru3(μ-κ2P2-dppe)(CO)10] (dppe = 1,2-bis(diphenylphosphino)-
ethane), 2.330(1) and 2.283(2) A.26
€
Rev. 2009, 109, 3677. (e) Kuhl, O. Chem. Soc. Rev. 2007, 36, 592.
(f) Liddle, S. T.; Edworthy, I. S.; Arnold, P. L. Chem. Soc. Rev. 2007,
36, 1732. (g) Albrecht, M. Chem. Commun. 2008, 3601. (h) Normand,
A. T.; Cavell, K. J. Eur. J. Inorg. Chem. 2008, 2781. (i) Lee, H. M.; Lee,
C.-C.; Cheng, P.-Y. Curr. Org. Chem. 2007, 11, 1491. (j) Pugh, D.;
The solution IR and NMR spectroscopic data of com-
pound 1 are in harmony with its solid-state structure. The
absorptions of terminal CO ligands are the only signals
observed in the stretching carbonyl region of its IR spectrum.
The 13C and 31P NMR spectra of 1 show the resonances of
the Ccarbene and P atoms at 172.8 and 42.3 ppm, respectively.
In an attempt to introduce more than one dppeImMe
ligand into a triruthenium cluster, the parent carbonyl [Ru3-
(CO)12] was treated with three equivalents of dppeImMe in
THF at room temperature. The mononuclear ruthenium(0)
derivative [Ru(κ2C,P-dppeImMe)(CO)3] (2) was the only
product of this reaction (Scheme 5). The use of a 1:2 [Ru3-
(CO)12] to dppeImMe mol ratio led to a mixture of products
that could not be satisfactorily separated.
The composition of compound 2 was established by
analytical and spectroscopic techniques. Its IR spectrum
(recorded in THF) displays a very strong band centered at
1833 cm-1 accompanied by two strong bands at higher fre-
quencies, 1998 and 1909 cm-1. The low wavelengths of these
absorptions provide convincing evidence for the presence of a
strongly basic ligand within the metal coordination shell. This
three-band νCO pattern is coherent with an axial-equatorial
coordination of the ligand in a trigonal-bipyramidal (tbp)
complex (Cs symmetry), as has been observed for [M(κ2P2-
P-P)(CO)3] (M = Fe, Ru; P-P = chelating diphosphine),27
but it gives no hint about what ligand atom (P or C) is in each
coordination site and does not rule out an apical-basal
coordination of the ligand in a square-base pyramidal (sbp)
ꢀ
Danopoulos, A. A. Coord. Chem. Rev. 2007, 251, 610. (k) Cesar, V.;
Bellemin-Laponnaz, S.; Gade, L. H. Chem. Soc. Rev. 2004, 33, 619. (l)
Gade, L. H.; Bellemin-Laponnaz, S. Coord. Chem. Rev. 2007, 251, 718.
(23) For examples of complexes containing NHC-phosphine biden-
tate ligands, see: (a) Hahn, F. E.; Naziruddin, A. R.; Hepp, A.; Pape, T.
ꢀ
Organometallics 2010, 29, 5283. (b) Benhamou, L.; Wolf, J.; Cesar, V.;
Labande, A.; Poli, R.; Lugan, N.; Lavigne, G. Organometallics 2009, 28,
6981. (c) Wolf, J.; Labande, A.; Daran, J. C.; Poli, R. J. Organomet.
Chem. 2006, 691, 433. (d) Wolf, J.; Labande, A.; Natella, M.; Daran,
J. C.; Poli, R. J. Mol. Catal. A: Chem. 2006, 259, 205. (e) Wolf, J.;
Labande, A.; Daran, J. C.; Poli, R. Eur. J. Inorg. Chem. 2007, 5069. (f)
Wolf, J.; Labande, A.; Daran, J. C.; Poli, R. Eur. J. Inorg. Chem. 2008,
ꢀ
3024. (g) Morvan, D.; Capon, J.-F.; Gloaguen, F.; Petillon, F. Y.;
Schollhammer, P.; Talarmin, J.; Yaouanc, J.-J.; Michaud, F.; Kervarec,
N. J. Organomet. Chem. 2009, 694, 2801. (h) Herrmann, W. A.; Kocher,
€
C.; Goossen, L. J.; Artus, G. R. J. Chem.-Eur. J. 1996, 2, 1627. (i)
Tsoureas, N.; Danopoulos, A. A.; Tulloch, A. A. D.; Light, M. E.
Organometallics 2003, 22, 4750. (j) Lee, H. M.; Chiu, P. L.; Zeng, J. Y.
Inorg. Chim. Acta 2004, 357, 4313. (k) Field, L. D.; Messerle, B. A.;
Vuong, K. Q.; Turner, P. Organometallics 2005, 24, 4241. (l) Song, G.;
Wang, X.; Li, Y.; Li, X. Organometallics 2008, 27, 1187. (m) Ho, C.-C.;
Chatterjee, S.; Wu, T.-L.; Chan, K.-T.; Chang, Y.-W.; Hsiao, T.-H.;
Lee, H.-M. Organometallics 2009, 28, 2837. (n) Lee, C.-C.; Ke, W.-C.;
Chan, K.-T.; Lai, C.-L.; Hu, C.-H.; Lee, H. M. Chem.-Eur. J. 2007, 13,
582. (o) Lee, H. M.; Chiu, P. L.; Zeng, J. Y. Inorg. Chim. Acta 2004, 357,
4313. (p) Danopoulos, A. A.; Tsoureas, N.; MacGregor, S. A.; Smith, C.
Organometallics 2007, 26, 253. (q) Stylianides, N.; Danopoulos, A. A.;
Tsoureas, N. J. Organomet. Chem. 2005, 690, 5948. (r) Field, L. D.;
Messerle, B. A.; Vuong, K. Q.; Turner, P. Organometallics 2005, 24,
4241. (s) Nanchen, S.; Pfaltz, A. Helv. Chim. Acta 2006, 89, 1559. (t)
Gischig, S.; Togni, A. Organometallics 2004, 23, 2479. (u) Gischig, S.;
Togni, A. Eur. J. Inorg. Chem. 2005, 2005, 4745. (v) Hahn, F. E.; Jahnke,
M. C.; Pape, T. Organometallics 2006, 25, 5927. (w) Wang, A.-E.;
Zhong, J.; Xie, J.-H.; Li, K.; Zhou, Q.-L. Adv. Synth. Catal. 2004,
346, 595. (x) Seo, H.; Park, H.; Kim, B. Y.; Lee, J. H.; Son, S. U.; Chung,
Y. K. Organometallics 2003, 22, 618. (y) Becht, J.-M.; Bappert, E.;
Helmchen, G. Adv. Synth. Catal. 2005, 347, 1495. (z) Miranda-Soto, V.;
Grotjahn, D. B.; DiPasquale, A. G.; Rheingold, A. L. J. Am. Chem. Soc.
2008, 130, 13200. (aa) Yu, I.; Wallis, C. J.; Patrick, B. O.; Diaconescu,
P. L.; Mehrkhodavandi, P. Organometallics 2010, 29, 6065.
(25) Forbes, E. J.; Goodhand, N.; Jones, D. L.; Hamor, T. A.
J. Organomet. Chem. 1979, 182, 143.
(24) The Ru-Ru distances in [Ru3(CO)12
]
are in the range
(26) (a) Bruce, M. I.; Hambley, T. W.; Nicholson, B. K.; Snow, M. R.
J. Organomet. Chem. 1982, 235, 83. (b) Gallucci, J. C.; Gilbert, K. B.;
Hsu, W.-L.; Shore, S. G. Cryst. Struct. Commun. 1982, 11, 1385.
2.8515-2.8595 A: Churchill, M. R.; Hollander, F. J. Inorg. Chem.
1977, 16, 2655.

Article
Organometallics, Vol. 30, No. 4, 2011 829
complex (also of Cs symmetry). The room-temperature NMR
spectra of 2 confirm the presence of the dppeImMe ligand in
the complex (the resonances of the Ccarbene and P atoms are
observed at 176.3 and 30.0 ppm in their respective spectra) and
also indicate that the complex is fluxional in solution, since only
one resonance, at 214.2 ppm (d, JC-P = 9 Hz), is observed for
the carbonyl ligands in the 13C{1H} spectrum. The fluxionality
could not be frozen out even upon cooling to -80 °C. There-
fore, the IR and NMR spectra of compound 2 do not provide
enough data to unequivocally assign a structure to this
complex.
As we could not get crystals of compound 2 suitable for an
X-ray diffraction study, DFT calculations were carried out
to shed more light on the structure of this complex. Structure
optimization calculations were performed using input mod-
els of tbp and sbp geometries having all possible ligand
arrangements. They all converged to one of the tbp struc-
tures shown in Figure 2, 2ax or 2eq. As the calculations
indicated that structure 2ax is more stable than structure 2eq
(ΔE = 7.2 kcal mol-1, ΔG = 7.1 kcal mol-1, ΔH = 6.9 kcal
mol-1) and as compound 2 is fluxional in solution (even at
very low temperature), we conclude that, in the solid state,
compound 2 should have the structure 2ax, which is a tbp
ligand arrangement with the NHC and phosphine fragments
of the dppeImMe ligand in axial and equatorial positions,
respectively.
Figure 2. DFT-optimized structures, at the B3LYP/LanL2DZ/
6-31G(d,p) level of theory, of the two possible tbp isomers of
compound 2.
With the only exception of [Ru(iPr2Im)2(CO)3] and
[Ru(iPr2ImMe2)2(CO)3], which contain isopropyl groups
on the N atoms and have an axial-equatorial arrangement
of the NHCs in a tbp ligand environment,12 all the remaining
complexes of the types [Ru(NHC)2(CO)3] (NHC = Et2-
ImMe2,12 Mes2Im,28 Cy2Im28) and [Ru(PR3)2(CO)3]29
known at this moment have a tbp axial-axial ligand array
of the non-carbonyl ligands. An analogous tbp axial-axial
ligand arrangement has also been observed in the mixed
NHC phosphine complex [Ru(Mes2Im)(PPh3)(CO)3].30
As far as we are aware, only one work reporting the
synthesis of ruthenium(0) complexes having a bidentate
NHC-phosphine ligand has hitherto been published. It de-
scribes the preparation of [Ru(κ2C,P-dppeImR)(PPh3)-
(CO)2] (R = Mes, Dipp) from dppeImR and the mono-
nuclear complex [Ru(PPh3)3(CO)2], but the structures of
these compounds have not been unambiguously deter-
mined.23b
Figure 3. Structure of compound 3 (ellipsoids set at 30% prob-
ability; phenyl hydrogen atoms omitted for clarity).
˚
Table 2. Selected Interatomic Distances (A) in Compound 3
Ru1-Ru2
Ru1-Ru3
Ru2-Ru3
C1-Ru2
C1-N1
2.8253(3)
2.7931(3)
3.0530(3)
2.063(2)
1.349(3)
1.342(3)
1.348(4)
1.385(3)
1.394(3)
C4-N1
1.457(3)
1.529(3)
1.856(2)
1.453(3)
2.116(3)
2.139(3)
2.3331(6)
1.138(7)
1.92(3)
C4-C5
C5-P1
C6-N2
C6-Ru1
C6-Ru3
P1-Ru2
C-O (av)
C(CO)-Ru (av)
C1-N2
C2-C3
C2-N2
C3-N1
Thermolysis of Compound 1. Heating to reflux a THF
solution of complex 1 for 20 min led to its quantitative
transformation into the face-capped trinuclear derivative
Scheme 6
(27) (a) Manuel, T. A. Inorg. Chem. 1963, 2, 854. (b) Akhtar, M.;
Ellis, P. D.; MacDiarmid, A. G.; Odom, J. D. Inorg. Chem. 1972, 11,
2917. (c) Battaglia, L. P.; Delledonne, D.; Nardelli, M.; Pelizzi, C.;
Predieri, G.; Chiusoli, G. P. J. Organomet. Chem. 1987, 330, 101. (d)
Brookhart, M.; Chandler, W. A.; Pfister, A. C.; Santini, C. C.; White,
P. S. Organometallics 1992, 11, 1263. (e) Whittlesey, M. K.; Perutz,
R. N.; Virrels, I. G.; George, M. W. Organometallics 1997, 16, 268.
(28) (a) Jazzar, R. F. R.; Bhatia, P. H.; Mahon, M. F.; Whittlesey,
[Ru3(μ-H)2(μ3-κ3C2,P-dppeImCH)(CO)8] (3), which was
isolated as an orange solid (Scheme 6).
€
M. K. Organometallics 2003, 22, 670. (b) Burling, S.; Kociok-Kohn, G.;
Mahon, M. F.; Whittlesey, M. K.; Williams, J. M. J. Organometallics
2005, 24, 5868.
(29) See, for example: (a) Collman, J. P.; Roper, W. R. J. Am. Chem.
Soc. 1968, 87, 4008. (b) Jones, R. A.; Wilkinson, G.; Galas, A. M. R.;
Hursthouse, M. B.; Abdul Malik, K. M. J. Chem. Soc., Dalton Trans.
The molecular structure of 3 was determined by X-ray
diffraction (Figure 3, Table 2). The molecule contains a
dppeImCH ligand capping a face of the ruthenium triangle
in such a way that the Ru1-Ru3 edge is spanned by the CH
fragment, while the remaining metal atom, Ru2, is chelated
by the bridging ligand through the carbene C atom and the
phosphine fragment P atom. Two edges of the metal triangle,
Ru1-Ru3 and Ru2-Ru3, are also spanned by hydride
ꢀ
1980, 1771. (c) Espuelas, J.; Esteruelas, M. A.; Lahoz, F. J.; Lopez,
A. M.; Oro, L. A.; Valero, C. J. Organomet. Chem. 1994, 468, 223. (d)
Bodensieck, U.; Vahrenkamp, H.; Rheinwald, G.; Stoeckli-Evans, H.
J. Organomet. Chem. 1995, 488, 85.
(30) Abdur-Rashid, K.; Fedorkiw, T.; Lough, A. J.; Morris, R. H.
Organometallics 2004, 23, 86.

830 Organometallics, Vol. 30, No. 4, 2011
Cabeza et al.
Scheme 7
ligands. The length of the hydride-unbridged edge, Ru1-Ru2
2.8253(3) A, is intermediate between those of the hydride-
bridged edges, Ru1-Ru3 2.7931(3) A, Ru2-Ru3 3.0530(3)
A. The cluster shell is completed by eight carbonyl ligands.
The solution IR and NMR spectra of 3 are in complete
agreement with its solid-state structure. The IR spectrum
clearly shows that this complex has only terminal CO
ligands. The NMR resonances of the Ccarbene and P atoms
of 3 are observed at 173.9 (doublet, JC-P = 13 Hz) and 28.6
ppm in their respective spectra. In addition to the resonances
Figure 4. Structure of the cation of compound 4[BF4]3 viewed
along the C3 symmetry axis (ellipsoids set at 20% probability;
hydrogen atoms omitted for clarity).
˚
Table 3. Selected Interatomic Distances (A) in Compound 4[BF4]3
Ru-Ru
C1-N1
C1-N2
C2-C3
C2-N2
C3-N1
C4-N1
2.858(2)
1.32(2)
1.34(2)
1.31(2)
1.39(2)
1.38(2)
1.46(2)
C4-C5
1.50(2)
1.85(1)
1.46(2)
2.351(4)
1.17(3)
1.89(3)
C5-P1
C6-N2
P1-Ru1
C-O (av)
C(CO)-Ru (av)
1
of the dppmIm fragment, the H NMR spectrum of 3 also
contains the resonances of two hydrides (at -12.19 and -16.76
ppm) and an aliphatic CH proton (at 6.74 ppm).
metal atom, it is not clear whether the chelating ability of
dppeImMe contributes to promote the methyl C-H bond
activation processes because this ligand is not as rigid as
Me2bipy and, in the transformation of 1 into 3, the bridging
to chelating transformation of the ligand may occur before or
after the C-H bond activation processes. The fact that the CO
groups of 1 are fluxional in solution would facilitate the
rearrangement of the dppeImMe ligand over the Ru3 triangle.
Reactions of [Ru3(CO)12] with the Imidazolium-Phosphine
Salt [dppeHImMe][BF4]. No reaction was observed when
[Ru3(CO)12] was treated with various amounts of [dppeHI-
mMe][BF4] in THF at room temperature. However, upon
heating to reflux temperature and regardless of the ratio of
the reactants, the trisubstituted product [Ru3(κP-dppeHI-
mMe)3(CO)9][BF4]3 (4[BF4]3) precipitated out of the solu-
tion as a violet solid (Scheme 7). The use of [dppeHImMe]-
[BF4] to [Ru3(CO)12] ratios smaller than 3 led to mixtures of
[Ru3(CO)12] and 4[BF4]3.
The process that activates two C-H bonds of the N-meth-
yl group of 1 to give 3 should be related to that that trans-
forms the clusters [M3(Me2Im)(CO)11] (M = Ru, Os) into
[M3(μ-H)2(μ3-κ2C2-MeImCH)(CO)9],5 whose mechanism,
which has been studied by DFT methods, proceeds through
an edge-bridged monohydrido intermediate, [M3(μ-H)-
(μ-κ2C2-MeImCH2)(CO)10].8 It is now clear that the high
basicity of the NHCs not only enhances the basicity of the
metal atoms to which they are attached, increasing their
tendency to get involved in oxidative addition processes, but
also facilitates the elimination of one or more CO groups from
the initial cluster under mild conditions. These facts, the high
probability that a ligand C-H bond be placed in close
proximity to a metal atom in a cluster, and the irreversibility
of the CO elimination steps, explain the easy metalation of
C-H,5,10,11 C-C,7b or C-N7b bonds in carbonyl cluster
complexes that contain NHC ligands.
The solid-state structure of 4[BF4]3 was determined by
X-ray diffraction (Figure 4, Table 3). The structure is of poor
quality (see the Experimental Section), but it unequivocally
provides the atom connectivity. The cation has C3 symmetry
and consists of three symmetry-related Ru(κP-dppeHIm-
Me)(CO)3 units interconnected by Ru-Ru bonds. The cat-
ionic [dppeHImMe]þ ligands, which occupy equatorial co-
ordination sites, are coordinated through the P atom. The
NMR spectra of 4[BF4]3 corroborate that these structural
features are maintained in solution. The carbonyl absorp-
tions of the IR spectrum appear at relatively low wave
numbers (2045-1968 cm-1), indicating that the positive
charge of the imidazolium fragment does not affect much
the basicity of the phosphine moiety. A few structures of
The structure of compound 3 resembles that of [Ru3(μ-
H)2(μ3-κ3C,N2-MebipyCH)(CO)8], which arises from the
reaction of [Ru3(CO)12] with 6,60-dimethyl-2,20-bipyridine
(Me2bipy). In this case, the chelation of the rigid Me2bipy
ligand to a cluster metal atom places a ligand methyl group in
close proximity to one or more metal atoms, thus favoring its
metalation.31 Noting that the dppeImMe ligand of com-
pound 1 bridges an Ru-Ru edge whereas the Ccarbene and P
atoms of the dppeImCH ligand of 3 are attached to the same
ꢀ
(31) (a) Cabeza, J. A.; del Rı
´
o, I.; Martı
´
nez-Mendez, L.; Miguel, D.
o, I.;
nez-Mendez, L.; Miguel, D.; Riera, V. Angew. Chem., Int. Ed.
2004, 43, 3464.
Chem.-Eur. J. 2006, 12, 1529. (b) Cabeza, J. A.; da Silva, I.; del Rı
´
ꢀ
Martı
´

Article
Organometallics, Vol. 30, No. 4, 2011 831
neutral triruthenium complexes of the type [Ru3(κP-PR3)3-
(CO)9] have been crystallographically determined, and they
all have a local C3 symmetry.32
processes are also facilitated by the structure of the ligand,
which allows the approach of the N-methyl group to the
metal atoms.
Therefore, the chemical behavior of the cationic [dppeHI-
mMe]þ ligand parallels that of neutral phosphine ligands,
which easily lead to trisubstituted derivatives when they react
with [Ru3(CO)12] upon thermal activation.33
Deprotonation of [Ru3(KP-dppeHImMe)3(CO)9][BF4]3
(4[BF4]3). As the deprotonation of imidazolium salts with
strong bases usually leads to NHC derivatives,1 we reasoned
that the treatment of compound 4[BF4]3 with a strong base
could be either an entry to triruthenium clusters containing
more than one dppeImMe ligand or an alternative way to
synthesize the mononuclear complex 2, which, as described
above, can be prepared from the reaction of [Ru3(CO)12] with
three equivalents of dppeImMe.
As shown in Scheme 7, the reaction of 4[BF4]3 with three
equivalents of K[N(SiMe3)2] led to the immediate forma-
tion of the mononuclear derivative 2 in quantitative yield.
Therefore, Ru-Ru bond cleavage processes accompany the
coordination of the pendant NHC ligand fragments that are
formed by deprotonation of the imidazolium rings of 4-
[BF4]3. Mixtures of products, which were not separated, were
obtained when less than three equivalents of K[N(SiMe3)2]
was used.
It is already known that the great basicity and volume of
monodentate NHC ligands favor the cleavage of Ru-Ru
bonds over Ru-CO bonds in triruthenium clusters
(Scheme 1).12,13 This work now demonstrates that bidentate
NHC-phosphine ligands also follow this trend.
Experimental Section
General Data. Solvents were dried over sodium diphenyl ketyl
(hydrocarbons, diethyl ether, THF) or CaH2 (dichloromethane)
and distilled under nitrogen before use. The reactions were
carried out under nitrogen, using Schlenk-vacuum line techni-
ques, and were routinely monitored by solution IR spectroscopy
(carbonyl stretching region) and spot TLC on silica gel. The
imidazolium bromide [dppeHImMe]Br was prepared as described
elsewhere.23k All remaining starting reagents were purchased from
commercial sources. All reaction products were vacuum-dried for
several hours prior to being weighted and analyzed. IR spectra
were recorded in solution on a Perkin-Elmer Paragon 1000 FT
spectrophotometer. NMR spectra were run on a Bruker DPX-300
instrument, using CH2Cl2 as internal standard for 1H (δ = 5.32),
CD2Cl2 as internal standard for 13C (δ = 53.8), and aqueous 85%
H3PO4 as external standard (δ = 0.00). Microanalyses were
obtained from the University of Oviedo Analytical Service. FAB
~
mass spectra were obtained from the University of A CorunaMass
Spectrometric Service; data given refer to the most abundant
molecular ion isotopomer.
Synthesis of [dppeHImMe][BF4]. A saturated aqueous solu-
tion of Na[BF4] was dropwise added to a solution of [dppeHI-
mMe]Br (5.9 g mg, 0.16 mol) in methanol (25 mL) until
the complete precipitation of a white solid was observed. The
solvent mixture was removed under reduced pressure, and the
residue was extracted into dichloromethane (3 ꢀ 30 mL). The
combined extracts were dried with anhydrous MgSO4, and
the resulting solution was evaporated to dryness to give a white
solid, which was washed with diethyl ether (2 ꢀ 20 mL) and dried
under vacuum (5.5 g, 91%). Anal. Calcd for C18H20BF4N2P
(382.15): C, 56.57; H, 5.28; N, 7.33. Found: C, 56.62; H, 5.38; N,
7.27. 1H NMR (CD2Cl2, 293 K): δ 8.68 (s, 1 H), 7.49 (m, 4 H),
7.32 (m, 6 H), 7.32 (s, br, 1 H), 7.25 (s, br, 1 H), 4.33 (m, 2 H),
3.81 (s, 3 H), 2.73 (m, 2 H). 31P{1H} NMR (CD2Cl2, 293 K):
δ -21.7. 13C{1H} and DEPT NMR (CD2Cl2, 293 K): δ 136.9 (d,
J = 12 Hz, C), 136.5 (s, CH), 133.1 (d, J = 20 Hz, CH), 129.8 (s,
CH), 129.3 (d, J = 7 Hz, CH), 124.1 (s, CH), 122.7 (s, CH), 48.1
(d, J = 24 Hz, CH2), 36.5 (s, CH3), 28.9 (d, J = 16 Hz, CH2).
Synthesis of [Ru3(μ-K2C,P-dppeImMe)(CO)10] (1). A toluene
solution of K[N(SiMe3)2] (500 μL, 0.5 M, 0.250 mmol) was
added to a suspension of [dppeHImMe][BF4] (87 mg, 0.227
mmol) in THF (30 mL). After stirring for 30 min, finely
powdered [Ru3(CO)12] (140 mg, 0.219 mmol) was added. The
mixture was stirred for an additional 1 h. The color changed
from orange to red. The solvent was removed under reduced
pressure and the crude reaction mixture separated by column
chromatography on neutral alumina (activity IV, 2 ꢀ 15 cm).
Hexane eluted a small amount of [Ru3(CO)12]. Hexane-
dichloromethane (3:2) eluted compound 1, which was isolated
as a dark orange solid (94 mg, 49%). Anal. Calcd for C28H19-
N2O10PRu3 (877.65): C, 38.32; H, 2.18; N, 3.19. Found: C,
38.37; H, 2.25; N, 3.05. (þ)-FAB-MS: m/z 879 [M]þ. IR (THF):
Concluding Remarks
In this paper, we have described the synthesis of the first
trinuclear clusters to contain phosphine-functionalized
NHC ligands. We have used dppeImMe as a representative
ligand of this kind. While the dppeImMe ligand prefers to
bridge a cluster edge when it is the only non-carbonyl ligand
in the cluster (as in complex 1), it prefers to chelate a metal
atom when more ligands are attempted to introduce into the
cluster. However, all attempts to prepare triruthenium clus-
ters containing more than one dppeImMe ligand have failed
because the chelation of the dppeImMe ligand induces the
cleavage of Ru-Ru bonds, as indicated by the fact that the
mononuclear derivative 2 was obtained either by treating
[Ru3(CO)12] with three equivalents of dppeImMe or by
deprotonating 4[BF4]3.
The dppeImMe ligand is basic enough to promote its easy
degradation upon mild thermal activation, via an intramo-
lecular cleavage of two C-H bonds of its N-methyl group
(transformation of 1 into 3). These C-H bond activation
ν
CO 2093 (w), 2073 (m), 2038 (w), 2029 (s), 1998 (vs), 1989 (vs),
(32) (a) Bruce, M. I.; Matisons, J. G.; Skelton, B. W.; White, A. H.
J. Chem. Soc., Dalton Trans. 1983, 2375. (b) Darensbourg, D. J.;
Beckford, F. A.; Reibenspies, J. H. J. Cluster Sci. 2000, 11, 95. (c)
Phillips, G.; Hermans, S.; Adams, J. R.; Johnson, B. F. G. Inorg. Chim.
Acta 2003, 352, 110. (d) Bruce, M. I.; Liddell, M. J.; bin Shawkataly, O.;
Hughes, C. A.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1988,
347, 207. (e) Leadbeater, N. E.; Raithby, P. R. J. Coord. Chem. 2001, 53,
1966 (w), 1942 (m). 1H NMR (CD2Cl2, 293 K): δ 7.63-7.44 (m,
5 H), 7.38-7.24 (m, 3 H), 7.11 (d, J = 1.7 Hz, 1 H), 7.06 (d, J =
1.7 Hz, 1 H), 6.77 (d, J = 7.8 Hz, 1 H), 6.75 (d, J = 7.8 Hz, 1 H),
4.36 (m, 1 H), 4.13 (m, 1 H), 3.84 (s, 3 H), 2.40 (m, 1 H), 2.12 (m,
1 H). 31P{1H} NMR (CD2Cl2, 293 K): δ 42.3 (s). 13C{1H} and
DEPT NMR (CD2Cl2, 293 K): δ 212.4 (br, CO), 172.8 (s, C),
132.0-127.2 (m), 124.3 (s, CH), 120.8 (s, CH), 49.2 (d, J = 6 Hz,
CH2), 39.6 (s, CH3), 2.6 (d, J = 24 Hz, CH2).
€
311. (f) Suss-Fink, G.; Godefroy, I.; Ferrand, V.; Neels, A.; Stoeckli-
Evans, H. J. Chem. Soc., Dalton Trans. 1998, 515. (g) Lucas, N. T.;
Cifuentes, M. P.; Nguyen, L. T.; Humphrey, M. G. J. Cluster Sci. 2001,
12, 201. (h) Farrugia, L. J.; Rosenhahn, C.; Whitworth, S. J. Cluster Sci.
1998, 9, 505.
(33) See, for example: (a) Bruce, M. I.; Shaw, G.; Stone, B. F. A.
€
J. Chem. Soc., Dalton Trans. 1972, 2094. (b) Malik, S. K.; Poe, A. Inorg.
Chem. 1978, 17, 1484.
Synthesis of [Ru(K2C,P-dppeImMe)(CO)3] (2). A toluene so-
lution of K[N(SiMe3)2] (4 mL, 0.5 M, 2.000 mmol) was added to
a suspension of [dppeHImMe][BF4] (672 mg, 1.760 mmol) in
THF (30 mL). After stirring for 30 min, finely powdered

832 Organometallics, Vol. 30, No. 4, 2011
Table 4. Crystal, Measurement, and Refinement Data for the Compounds Studied by X-ray Diffraction
Cabeza et al.
1
3
4[BF4]3
formula
fw
cryst syst
space group
a, A
b, A
C28H19N2O10PRu3
877.63
monoclinic
P21/n
11.5695(1),
15.2004(1)
17.9373(1)
90, 105.220(1), 90
3043.83(4)
4
C26H19N2O8PRu3
821.61
orthorhombic
Pbca
14.0159(1)
17.3425(2)
23.5717(2)
90, 90, 90
5729.59(9)
8
C63H60B3F12N6O9P3Ru3
1701.72
trigonal
P-3C1
14.825(1)
14.825(1)
41.080(3)
90, 90, 120
7819.0(9)
4
c, A
R, β, γ, deg
V, A3
Z
F(000)
1712
1.915
3200
1.905
3408
1.446
Dcalcd, g cm-3
μ (Cu KR), mm-1
cryst size, mm
T, K
12.917
0.27 ꢀ 0.20 ꢀ 0.08
13.615
0.10 ꢀ 0.08 ꢀ 0.05
5.920
0.09 ꢀ 0.07 ꢀ 0.03
293(2)
293(2)
293(2)
θ range, deg
min./max. h, k, l
no. collected reflns
no. unique reflns
no. reflns with I > 2σ(I)
no. params/restraints
GOF on F2
R1 (on F, I > 2σ(I))
wR2 (on F2, all data)
max./min. ΔF, e A-3
3.87 to 73.95
-12/14, -18/18, -21/20
11 147
5914
5406
398/0
1.045
0.0374
0.1084
3.15 to 73.88
-17/17, -21/21, -29/27
61 252
5796
5699
369/0
1.096
0.0242
0.0634
3.23 to 73.82
-14/0, 0/16, 0/46
3860
3860
2702
316/83
1.044
0.0962
0.2964
-0.984/1.010
-0.715/0.640
-1.030/1.350
[Ru3(CO)12] (376 mg, 0.588 mmol) was added. The mixture was
stirred for 2 h. The color changed from orange to yellow. The
solid of the resulting suspension was filtered off, and the filtrate
was evaporated to dryness to give a yellow solid, which was
washed with hexane (3 ꢀ 20 mL) and vacuum-dried (695 mg,
82%). Anal. Calcd for C21H19N2O3PRu (479.44): C, 52.61; H,
3.99; N, 5.84. Found: C, 52.68; H, 4.03; N, 5.79. IR (THF): νCO
1998 (s), 1909 (s), 1883 (vs). 1H NMR (CD2Cl2, 293 K): δ 7.68
(m, 4 H), 7.52-7.40 (m, 6 H), 7.02 (d, J = 1.6 Hz, 1 H), 6.93 (d,
J = 1.6 Hz, 1 H), 4.07 (m, 1 H), 4.00 (m, 1 H), 3.97 (s, 3 H), 2.52
(m, 2 H). 31P{1H} NMR (CD2Cl2, 293 K): δ 30.0 (s). 13C{1H}
and DEPT NMR (CD2Cl2, 193 K): δ 214.2 (d, J = 9 Hz, CO),
176.3 (d, J = 16 Hz, C), 139.4 (d, J = 32 Hz, C), 132.4 (d, J = 14
Hz, CH), 129.3 (s, CH), 128.3 (d, J = 10 Hz, CH), 122.6 (s, CH),
121.7 (s, CH), 47.9 (d, J = 10 Hz, CH2), 39.6 (s, CH3), 28.8 (d,
J = 20 Hz, CH2).
vacuum-dried (77 mg, 40%). Anal. Calcd for C63H60B3F12-
N6O9P3Ru3 (1701.75): C, 44.47; H, 3.55; N, 4.94. Found: C,
44.53; H, 3.63; N, 4.88. IR (CH2Cl2): νCO 2045 (w), 2023 (w),
1
1981 (vs), 1968 (vs). H NMR (CD2Cl2, 293 K): δ 8.67 (s, br,
1 H), 7.56-7.45 (m, 10 H), 7.17 (m, 1 H), 7.06 (m, 1 H), 4.09 (m,
2 H), 3.91 (s, 3 H), 3.14 (m, 2 H). 31P{1H} NMR (CD2Cl2, 293
K): δ 21.9 (s). 13C{1H} and DEPT NMR (CD2Cl2, 293 K): δ
136.9 (s, CH), 134.8 (d, J = 43 Hz, C), 132.4 (d, J = 11 Hz, CH),
131.0 (CH), 129.3 (d, J = 10 Hz, CH), 123.9 (CH), 122.4 (CH),
46.1 (d, J = 5 Hz, CH2), 36.7 (CH3), 34.0 (d, J = 20 Hz, CH2).
Deprotonation of 4[BF4]3. A suspension of 4[BF4]3 (616 mg,
0.362 mmol) in THF (30 mL) was treated with a toluene solution
of K[N(SiMe3)2] (2.3 mL, 0.5 M, 1.150 mmol). Immediately, the
solid dissolved to give a yellow solution. An IR analysis of this
solution indicated the complete transformation of 4[BF4]3 into
compound 2.
Synthesis of [Ru3(μ-H)2(μ3-K3C2,P-dppeImCH)(CO)8] (3). A
THF solution (30 mL) of compound 1 (24 mg, 0.029) was stirred
at reflux temperature for 20 min. No color change was observed.
The solvent was removed under reduced pressure, and the solid
residue was washed with hexane (2 ꢀ 15 mL) to give compound 3
as an orange solid (19 mg, 85%). Anal. Calcd for C26H19N2O8-
PRu3 (821.63): C, 38.01; H, 2.33; N, 3.41. Found: C, 38.32; H,
2.47; N, 3.09. (þ)-FAB-MS: m/z 822 [M - H]þ. IR (THF): νCO
2079 (m), 2065 (w), 2038 (vs), 2009 (s), 2000 (s), 1972 (m), 1954
(w). 1H NMR (CD2Cl2, 293 K): δ 7.74-7.64 (m, 3 H), 7.58-7.50
(m, 3 H), 7.48-7.39 (m, 4 H), 7.05 (s, br, 1 H), 6.92 (d, J = 1.6
Hz, 1 H), 6.51 (s, 1 H), 4.22 (ddt, J = 32.1, 14.3, 3.6 Hz, 1 H),
3.98 (m, 1 H), 3.06 (m, 1 H), 1.96 (m, 1 H), -12,19 (s, br, 1 H,
μ-H), -16.76 (s, br, 1 H, μ-H). 31P{1H} NMR (CD2Cl2, 293 K):
δ 28.6 (s). 13C{1H} and DEPT NMR (CD2Cl2, 293 K): δ 206.5
(d, J = 4 Hz, CO); 205.3 (d, J = 7 Hz, CO); 202.4 (s, CO), 202.1
(s, CO); 193.7 (s, CO); 193.6 (s, CO); 188.4 (d, J = 8 Hz, CO);
186.0 (s, CO), 173.9 (d, J = 13 Hz, C); 131.6 (d, J = 12 Hz, CH);
130.0 (d, J = 24 Hz, C); 128.8 (d, J = 9 Hz, CH), 128.5 (d, J =
10 Hz, CH), 118.6 (s, CH), 118.10 (s, CH), 107.2 (s, CH), 47.0 (s,
CH2), 29.4 (d, J = 27 Hz, CH2).
Computational Details. The optimized structures were calcu-
lated by hybrid DFT, within the GAUSSIAN-03 program
suite,34 using Becke’s three-parameter hybrid exchange-
correlation functional35 and the B3LYP nonlocal gradient
correction.36 The LanL2DZ basis set, with relativistic effective
core potentials, was used for the Ru atoms.37 The basis set used
for the remaining atoms was the standard 6-31G with addition of
(d,p)-polarization. To determine the structure of compound 2,
(34) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.;
Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.;
Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson,
G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.;
Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai,
H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.;
Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, E. R.; Yazyev, O.;
Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.;
Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.;
Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas,
O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.;
Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.;
Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.;
Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M.;
Gonzalez, W. C.; Pople, J. A. GAUSSIAN-03 (Revision C2); Gaussian
Inc.: Wallingford, CT, USA, 2004.
Synthesis of [Ru3(KP-dppeHImMe)3(CO)9][BF4]3 (4[BF4]3). A
mixture of [dppeHImMe][BF4] (130 mg, 0.340 mmol) and finely
powdered [Ru3(CO)12] (72 mg, 0.113 mmol) was stirred in THF
(30 mL) at reflux temperature for 1 h. The color changed
from orange to dark violet. After cooling to room temperature,
the solid was filtered, washed with hexane (2 ꢀ 20 mL), and
(35) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
(36) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev., B 1988, 37, 785.
(37) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985, 82, 299.

Article
Organometallics, Vol. 30, No. 4, 2011 833
input models corresponding to all possible tbp and sbp ligand
arrangements were constructed. After optimization, they all con-
verged to either 2ax or 2eq, which were confirmed as energy
minima by calculation of analytical frequencies. The energies
given in this article are potential energies calculated in the gas
phase.
X-ray Diffraction Analyses. Crystals of 1, 3, and 4[BF4]3 were
analyzed by X-ray diffraction methods. A selection of crystal,
measurement, and refinement data is given in Table 4. Diffrac-
tion data were collected on an Oxford Diffraction Xcalibur
Nova single crystal diffractometer, using Cu KR radiation.
Empirical absorption corrections for 1 and 3 were applied using
the SCALE3 ABSPACK algorithm as implemented in the
program CrysAlisPro RED.38 The XABS239 empirical absorp-
tion correction was applied for 4[BF4]3. The structures were
solved by Patterson interpretation using the program
DIRDIF.40 Isotropic and full matrix anisotropic least-squares
refinements were carried out using SHELXL.41 All non-H atoms
were refined anisotropically except for one of the tetrafluorido-
borate units of 4[BF4]3. The positions of the hydride atoms of 3
were calculated with XHYDEX.42 The remaining hydrogen
atoms were set in calculated positions and refined riding on their
parent atoms. The refinement of 4[BF4]3 converged with a high
discrepancy index (R1 = 0.0989), which is attributed to disorder
and high thermal motion of two of the [BF4]- anions and to the
presence of residual electron density arising from a small amount
of disordered solvent (dichloromethane). Most of this residual
electron density was removed with the PLATON SQUEEZE43
routine to give the final model of 4[BF4]3, which, despite its low
resolution, unequivocally provides the atom connectivity. The
molecular plots were made with the PLATON program
package.44 The WINGX program system45 was used throughout
the structure determinations. CCDC deposition numbers: 805137
(1), 805138 (3), and 805139 (4[BF4]3).
(38) CrysAlisPro RED, version 1.171.34.36; Oxford Diffraction Ltd.:
Oxford, UK, 2010.
(39) Parkin, S.; Moezzi, B.; Hope, H. J. Appl. Crystallogr. 1995, 28,
53.
(40) Beurskens, P. T.; Beurskens, G.; de Gelder, R.; Smits,
J. M. M.; Garcıa-Granda, S.; Gould, R. O. The DIRDIF Program
´
System, version 2008.3; Crystallography Laboratory, University of
Nijmegen: Nijmegen, The Netherlands, 2008.
(41) Sheldrick, G. M. SHELXL, version 2008. Acta Crystallogr.
2008, A64, 112.
Acknowledgment. This work has been supported by
the European Union (FEDER grants) and the Spanish
MICINN (projects CTQ2007-60865, CTQ2010-14933,
and DELACIERVA-09-05).
(42) Orpen, A. G. J. Chem. Soc., Dalton Trans. 1980, 2509.
(43) van der Sluis, P.; Spek, A. L. Acta Crystallogr. 1990, A46, 194.
(44) Spek, A. L. PLATON: A Multipurpose Crystallographic Tool,
version 1.15; University of Utrecht: Utrecht, The Netherlands, 2008.
(45) Farrugia, L. J. WinGX, version 1.80.05 (2009). J. Appl. Crystal-
logr. 1999, 32, 837.
Supporting Information Available: Atomic coordinates of the
structures optimized by DFT calculations and crystallographic
data in CIF format for the compounds studied by X-ray
diffraction. This material is available free of charge via the
Internet at http://pubs.acs.org.