Migratory insertion of acetylene in N-heterocyclic carbene complexes of ruthenium: Formation of (ruthenocenylmethyl)imidazolium salts

Article abstract of DOI:10.1021/om060990i

With the parent acetylene and [RuCp(IPr)(CH₃CN) ₂]PF₆ (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2- ylidene) an unusual C-C coupling process takes place involving three acetylene molecules and migration of the NHC ligand to give the formal [2 + 2+ 1] cycloaddition product [RuCp(η⁴-C₅H₅- η¹-CH-IPr)]-PF₆. This complex undergoes a facile 1,2-H shift to afford the (ruthenocenylmethyl)imidazolium salt [RuCp(η ⁵-C₅H₄-CH₂-IPr)]PF₆. The same reaction takes place with [RuCp(SIPr)(CH₃CN)₂]PF ₆ (SIPr = 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2- ylidene), giving [RuCp(η⁵-C₅H₄-CH ₂-SIPr)]PF₆. A conceivable mechanism for this reaction sequence is established by means of DFT/B3LYP calculations. The key step is the facile insertion of acetylene into the Ru-C bond of the NHC ligand, requiring merely 4.1 kcal/mol with 1,3-dimethylimidazol-2-ylidene but 17.2 kcal/mol with 1,3-diphenylimidazol-2-ylidene as model NHC ligands.

Full text of DOI:10.1021/om060990i

Organometallics 2007, 26, 1531-1535
1531
Migratory Insertion of Acetylene in N-Heterocyclic Carbene
Complexes of Ruthenium: Formation of
(Ruthenocenylmethyl)imidazolium Salts
Eva Becker,† Verena Stingl,† Georg Dazinger,† Kurt Mereiter,‡ and Karl Kirchner*,†
Institute of Applied Synthetic Chemistry and Institute of Chemical Technologies and Analytics, Vienna
UniVersity of Technology, Getreidemarkt 9, A-1060 Vienna, Austria
ReceiVed October 26, 2006
With the parent acetylene and [RuCp(IPr)(CH3CN)2]PF6 (IPr ) 1,3-bis(2,6-diisopropylphenyl)imidazol-
2-ylidene) an unusual C-C coupling process takes place involving three acetylene molecules and migration
of the NHC ligand to give the formal [2 + 2 + 1] cycloaddition product [RuCp(η4-C5H5-η1-CH-IPr)]-
PF6. This complex undergoes a facile 1,2-H shift to afford the (ruthenocenylmethyl)imidazolium salt
[RuCp(η5-C5H4-CH2-IPr)]PF6. The same reaction takes place with [RuCp(SIPr)(CH3CN)2]PF6 (SIPr )
1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), giving [RuCp(η5-C5H4-CH2-SIPr)]PF6. A
conceivable mechanism for this reaction sequence is established by means of DFT/B3LYP calculations.
The key step is the facile insertion of acetylene into the Ru-C bond of the NHC ligand, requiring merely
4.1 kcal/mol with 1,3-dimethylimidazol-2-ylidene but 17.2 kcal/mol with 1,3-diphenylimidazol-2-ylidene
as model NHC ligands.
Introduction
N-heterocyclic carbenes (NHC) play an important role as
“noninterfering” supporting ligands in many stoichiometric and
catalyzed reactions of transition-metal complexes.1 The role of
the carbene ligands is similar to that of tertiary phosphine
ligands, but they are in general much more strongly bound to a
metal center than phosphines and thus less likely to be replaced
by other ligands.2 On the other hand, due to the obvious
electronic differences between NHC ligands and tertiary phos-
phines, it is not surprising that NHC ligands are much more
likely to participate in rearrangement reactions within the metal
coordination sphere. In fact, several recent reports clearly show
that NHC-metal bonds are kinetically not inert and are able to
participate in various intramolecular reactions.3 This includes
migration of a methyl group to a coordinated NHC ligand3c and
the reductive elimination of alkylimidazolium salts from NHC
alkyl complexes.3f Our recent studies of the interactions between
the [RuCp(IPr)]+ (IPr ) 1,3-bis(2,6-diisopropylphenyl)imidazol-
2-ylidene) moiety, derived from labile [RuCp(IPr)(CH3CN)2]+,
and various terminal alkynes have revealed that the IPr ligand
rapidly migrates onto the carbene carbon atom of a highly
electrophilic bis(carbene) intermediate, affording allyl carbene
complexes (Scheme 1).4
Figure 1. Structural view of [RuCp(η5-C5H4-CH2-IPr)]PF6 (3a)
-
showing 40% thermal ellipsoids (PF6 and hydrogen atoms
omitted for clarity). Selected bond lengths (Å): Ru-C(1-5)av
)
2.183(2), Ru-C(6-10)av ) 2.178(2), C(6)-C(11) ) 1.594(2),
C(11)-C(12) ) 1.501(2), C(12)-N(1) ) 1.349(2), C(12)-N(2)
) 1.349(2), C(13)-C(14) ) 1.354(2).
IPr and SIPr (SIPr ) 1,3-bis(2,6-diisopropylphenyl)-4,5-dihy-
droimidazol-2-ylidene). This behavior strongly contrasts that of
tertiary phosphines, where such reactions are, to our knowledge,
unknown.
Herein we report the first example of a facile migratory
insertion of acetylene into the Ru-C bond of the NHC ligands
† Institute of Applied Synthetic Chemistry.
‡ Institute of Chemical Technologies and Analytics.
(3) For recent examples of the “noninnocent” behavior of NHC ligands
see: (a) Galan, B. R.; Gembicky, M.; Dominiak, P. M.; Keister, J. B.; Diver,
S. T. J. Am. Chem. Soc. 2005, 127, 15702. (b) Allen, D. P.; Crudden, C.
M.; Calhoun, L. A.; Wang, R. Y. J. Organomet. Chem. 2004, 689, 3203.
(c) Danopoulos, A. A.; Tsoureas, N.; Green, J. C.; Hursthouse, M. B. Chem.
Commun. 2003, 756. (d) Dorta, R.; Stevens, E. D.; Hoff, C. D.; Nolan, S.
P. J. Am. Chem. Soc. 2003, 125, 10490. (e) Jazzar, R. F. R.; Macgregor, S.
A.; Mahon, M. F.; Richards, S. P.; Whittlesey, M. K. J. Am. Chem. Soc.
2002, 124, 4944. (f) McGuiness, D. S.; Saendig, N.; Yates, B. F.; Cavell,
K, J. J. Am. Chem. Soc. 2001, 123, 4029. (g) McGuiness, D. S.; Cavell, K.
J. Organometallics 2000, 19, 4918.
(1) For reviews see: (a) Arduengo, A. J., III. Acc. Chem. Res. 1999, 32,
913. (b) Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem. ReV.
2000, 100, 39. (c) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34,
18. (d) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290. (e) Hillier,
A. C.; Grasa, G. A.; Viciu, M. S.; Lee, H. M.; Yang, C.; Nolan, S. P. J.
Organomet. Chem. 2002, 653, 69. (f) Perry, M. C.; Burgess, K. Tetrahe-
dron: Asymmetry 2003, 14, 951.
(2) (a) Titcomb, L. R.; Caddick, S.; Cloke, F. G. N.; Wilson, D. J.;
McKerrecher, D. Chem. Commun. 2001, 1388; (b) Simms, R. W.; Drewitt,
M. J.; Baird, M. Organometallics 2002, 21, 2958.
10.1021/om060990i CCC: $37.00 © 2007 American Chemical Society
Publication on Web 02/17/2007

1532 Organometallics, Vol. 26, No. 6, 2007
Becker et al.
Scheme 1
Scheme 2
Scheme 3
one C-C triple bond into a C-C single bond. A similar reaction
has been described recently for the reaction of various terminal
acetylenes and [Ru(η5-C5H4CH2CH2-κ1P-PPh2)(CH3CN)2]PF6,
Results and Discussion
Upon treatment of [RuCp(IPr)(CH3CN)2]+ (1a)5 with HCt
CH in CH2Cl2 for 10 min at room temperature, [RuCp(η4-C5H5-
η1-CH-IPr)]PF6 (2a) is obtained in 94% isolated yield (Scheme
2). This compound is air-stable both in solution and in the
1
featuring a tethered phosphine.6b The H NMR spectroscopic
data for 2a include characteristic multiplets in the range of 5.50-
3.48 ppm assignable to the diene protons H3-6 of the coordinated
η4-cyclopentadiene unit and resonances at 2.18 and 1.83 ppm
which correspond to H2 and the Ru-CH proton H1. In the 13C-
{1H} NMR spectrum the resonance of the sp3 carbon C1
is diagnostic, giving rise to an unusually high field shifted
resonance at -39.9 ppm. The coordinated sp2 carbon atoms C3,
C4, C5, and C6 of the cyclopentadiene moiety exhibit resonances
at 42.4, 85.2, 85.1, and 69.5 ppm, respectively, while the
noncoordinated sp3 carbon C2 gives rise to a singlet at 54.4 ppm.
1
solid state and was characterized by H and 13C{1H} NMR
spectroscopy as well as by elemental analysis. In the course of
the overall [2 + 2 + 1] cyclotrimerization6 the Ru-C(IPr) bond
is cleaved and four new C-C bonds are formed, thereby
converting two C-C triple bonds into C-C double bonds and
(4) Becker, E.; Stingl, V.; Dazinger, G.; Puchberger, M.; Mereiter, K.;
Kirchner, K. J. Am. Chem. Soc. 2006, 128, 6572.
(5) Becker, E.; Stingl, V.; Mereiter, K.; Kirchner, K. Organometallics
2006, 25, 4166.

N-Heterocyclic Carbene Complexes of Ruthenium
Organometallics, Vol. 26, No. 6, 2007 1533
Figure 2. Reaction profile of the computed relative Gibbs free energies (in kcal/mol) for the reaction of the ruthenacyclopentatriene (A)
with acetylene to give the formal [2 + 2 + 1] cycloadition product (E) (bond distances in Å) with 1,3-dimethylimidazol-2-ylidene as the
model NHC ligand.
If a solution of 2a is kept at 40 °C for 12 h, the (rutheno-
cenylmethyl)imidazolium salt [RuCp(η5-C5H4-CH2-IPr)]PF6 (3a)
is formed in essentially quantitative yield as a result of a facile
1,2-hydrogen shift. The driving force for this rearrangement is
obviously ligand aromatization. A structural view of 3a is
depicted in Figure 1. The same reaction takes place with
acetylene and [RuCp(SIPr)(CH3CN)2]PF6 (1b) (a structural view
of this compound is given in the Supporting Information),
bearing the slightly more basic saturated NHC ligand 1,3-bis-
(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene. In this
case, however, no intermediate could be detected and only the
formation of the imidazolinium salt [RuCp(η5-C5H4-CH2-SIPr)]-
PF6 (3b) was observed (a structural view of 3b is given in the
Supporting Information).
In this context it has to be mentioned that Ru(p-cymene)-
(NHC)Cl2 (NHC ) 1-butyl-3-methylimidazol-2-ylidene) was
found to catalyze the oligomerization of HCtCPh, where the
linear oligomers contain a positively charged imidazolium end-
group.7 This observation seems to be related to our observations
and may suggest that insertion of HCtCPh into the Ru-C bond
of the NHC ligand initiates the oligomerization process.
DFT/B3LYP calculations have been performed to shed light
on the mechanism of this unusual transformation. The result of
this study is shown in Scheme 3. A free energy profile for the
conversion of A to the [2 + 2 + 1] cycloaddition product 2 (E
in the model) is depicted in Figure 2 with 1,3-dimethylimidazol-
2-ylidene (R ) Me) as the model NHC ligand. Additionally,
the free energy profile for the most crucial conversion of A to
C has been calculated with the bulkier NHC ligand 1,3-
diphenylimidazol-2-ylidene (R ) Ph) (Figure 3), since it has
been shown that that aromatic and aliphatic imidazolium
compounds exhibit different electronics and particularly sig-
nificant steric differences.8 On the basis of our experimental
findings, the starting point and key intermediate is the ruthena-
cyclopentatriene complex A, which is able to accommodate a
third acetylene molecule to afford the metallacyclopentadiene
acetylene complex B. This is the rate-determining step both for
R ) Me and for R ) Ph. The most remarkable step is the
insertion of acetylene into the Ru-C bond of B, resulting in
the formation of the novel metallacyclopentadiene 1-metalla-
cyclopropene complex C. The free activation energy for this
intramolecular process is very low for R ) Me, requiring merely
4.1 kcal/mol, but 17.2 kcal/mol is needed for R ) Ph, which
may be largely attributed to the increased steric bulk of the 1,3-
diphenylimidazol-2-ylidene ligand. In fact, Nolan et al. have
demonstrated that the electronic differences for NHC ligands
are relatively small when moving from alkyl- to aryl-substituted
ligands, especially in comparison to the substantial electronic
differences seen in phosphine ligands.8 It should be noted that
coupling reactions between a coordinated alkyne and coordinated
phosphines to yield 1-metallacyclopropenes have been reported
in the literature.9,10 In all of these cases, however, the “formal”
(6) For [2 + 2 + 1] cyclotrimerization reactions of alkynes see: (a)
Han, W. S.; Lee, S. W. Organometallics 2005, 24, 997. (b) Becker, E.;
Mereiter, K.; Puchberger, M.; Schmid, R.; Kirchner, K.; Doppiu, A.; Salzer,
A. Organometallics 2003, 22, 3164. (c) O’Connor, J. M.; Closson, A.;
Hiibner, K.; Merwin, R.; Gantzel, P. K.; Roddick, D. M. Organometallics
2001, 20, 3710. (d) Xi, Z.; Li, P. Angew. Chem., Int. Ed. 2000, 39, 2950.
(e) Radhakrishnan, U.; Gevorgyan, V.; Yamamoto, Y. Tetrahedron Lett.
2000, 41, 1971. (f) Kim, H. J.; Choi, N. S.; Lee, S. W. J. Organomet. Chem.
2000, 616, 67. (g) O’Connor, J. M.; Hiibner, K.; Merwin, R.; Gantzel, P.
K.; Fong, B. S.; Adams, M;, Rheingold, A. L. J. Am. Chem. Soc. 1997,
119, 3631. (h) Lee, G. C. M.; Tobias, B.; Holmes, J. M.; Harcourt, D. A.;
Garst, M. E. J. Am. Chem. Soc. 1990, 112, 9330. Moran, G.; Green, M.;
Orpen, A. G. J. Organomet. Chem. 1983, 250, C15. (i) Moreto, J.; Maruya,
K.; Bailey, P. M.; Maitlis, P.M. J. Chem. Soc., Dalton Trans. 1982, 1341.
(j) Liebeskind, L. S.; Chidambaram, R. J. Am. Chem. Soc. 1987, 109, 5025.
(7) Csabai, P.; Joo, F.; Trzeciak, A. M.; Ziolkowski, J. J. J. Organomet.
Chem. 2006, 691, 3371.
(8) Dorta, R.; Stevens, E. D.; Scott, N. M.; Costabile, C.; Cavallo, L.;
Hoff, C. D.; Nolan, S. P. J. Am. Chem. Soc. 2005, 127, 2485.
(9) Ishino, H.; Kuwata, S.; Ishii, Y.; Hidai, M. Organometallics 2001,
20, 13.

1534 Organometallics, Vol. 26, No. 6, 2007
Becker et al.
Figure 3. Reaction profile of the computed relative Gibbs free energies (in kcal/mol) for the reaction of the ruthenacyclopentatriene (A)
with acetylene to give the 1-metallacyclopropene intermediate (C) (bond distances in Å) with 1,3-diphenylimidazol-2-ylidene as the model
NHC ligand.
insertion of alkynes into metal-P bonds appears to be a
nucleophilic addition at the coordinated alkyne, requiring prior
dissociation of the phosphine. In fact, intermolecular nucleo-
philic additions of phosphines and phosphites to alkyne ligands
are feasible and well established.11 Complex C is prone to C-C
coupling between the carbene carbon atom of the 1-metallacy-
clopropene moiety and the R-carbon of the metallacyclopenta-
diene unit to give D. This reaction requires a free activation
energy of 13.4 kcal/mol and is energetically very favorable,
releasing 35.0 kcal/mol. The final and rate-determining step is
the insertion of the vinyl moiety into the η2-olefin unit to give
E, thus completing the [2 + 2 + 1] cyclotrimerization. The
overall reaction from A to E is strongly exergonic by -63.0
kcal/mol.
N-heterocyclic carbene ligand is not necessarily just a spectator
ligand. This behavior is in contrast with that of related phosphine
systems.
Experimental Section
General Techniques. All manipulations were performed under
an inert atmosphere of argon by using Schlenk techniques. All
chemicals were standard reagent grade and were used without
further purification. The solvents were purified according to standard
procedures.12 The deuterated solvents were purchased from Aldrich
and dried over 4 Å molecular sieves. [RuCp(CH3CN)2(IPr)]PF6 (1a)
was prepared according to the literature.13 1H and 13C{1H} NMR
spectra were recorded on a Bruker AVANCE-250 spectrometer
operating at 250.13 and 62.86 MHz, respectively, and were
referenced to SiMe4. 1H and 13C{1H} NMR signal assignments were
In conclusion, our experimental and theoretical data provide
for the first time clear evidence that acetylene is able to undergo
facile migratory insertion into the Ru-C bond of NHC ligands,
which has not been observed before in N-heterocyclic carbene
complexes. This process is accompanied by Ru-C bond
cleavage and is another example of the finding that an
1
confirmed by H-COSY, 135-DEPT, and HSQC(1H-13C) experi-
ments.
[RuCp(CH3CN)2(SIPr)]PF6 (1b). A suspension of SIPr‚HCl
(692 mg, 1.62 mmol) in 20 mL of toluene was cooled to -40 °C,
and n-BuLi (0.65 mL of a 2.6 M solution in n-hexane) was added
via syringe. The mixture was stirred for 30 min at room temperature.
LiCl was removed by filtration. This solution was then slowly added
to a stirred solution of [RuCp(CH3CN)3]PF6 (350 mg, 0.81 mmol)
in THF (10 mL). The solution was stirred at room temperature for
30 min. After removal of the solvent under vacuum the remaining
brown solid was dissolved in 2 mL of acetonitrile and purified by
(10) O’Connor, J. M.; Bunker, K. D. J. Organomet. Chem. 2003, 671,
1.
(11) For phosphine attack on coordinated alkynes see: (a) Cadierno, V.;
Gamasa, M. P.; Gonzalez-Bernardo, C.; Perez-Carreno, E.; Garcia-Granda,
S. Organometallics 2001, 20, 5177 and references therein. (b) Davidson, J.
L. J. Chem. Soc., Dalton Trans. 1986, 2423. (c) Davidson, J. L.; Vasapollo,
G.; Manojlovic-Muir, L.; Muir, K. W. J. Chem. Soc., Chem. Commun. 1982,
1025. (d) Allen, S. R.; Beevor, R. G.; Green, M.; Norman, N. C.; Orpen,
A. G. J. Chem. Soc., Dalton Trans. 1985, 435. (e) Morrow, J. R.; Tonker,
T. L.; Templeton, J. L.; Kenan, W. R. J. Am. Chem. Soc. 1985, 107, 6956.
(12) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: New York, 1988.
(13) Becker, E.; Stingl, V.; Mereiter, K.; Kirchner, K. Organometallics
2006, 25, 4166.

N-Heterocyclic Carbene Complexes of Ruthenium
Organometallics, Vol. 26, No. 6, 2007 1535
column chromatography (neutral Al2O3, eluent CH3CN). 1b was
isolated as a yellow microcrystalline solid. Yield: 76% (480 mg).
Anal. Calcd for C36H49F6N4PRu: C, 55.16; H, 6.30; N, 7.15.
refined anisotropically. Hydrogen atoms were inserted in idealized
positions and were refined riding with the atoms to which they
were bonded. For 1b and 3b see Supporting Information.
1
Found: C, 55.09; H, 6.40; N, 7.25. H NMR (δ, CD2Cl2, 20 °C):
Crystal data for 3a: C38H47F6N2PRu, Mr ) 777.82, triclinic, space
group P1h (No. 2), T ) 100(2) K, a ) 10.3126(9) Å, b ) 10.9150-
(10) Å, c ) 16.9277(15) Å, V ) 1776.2(3) Å,3 Z ) 2, µ ) 0.548
mm-1. Of 16 177 reflections collected, 10 035 were independent.
Final R indices: R1 ) 0.036 (all data), wR2 ) 0.081 (all data).
7.46-7.26 (m, 6H, Ar4), 3.99 (s, 4H, SIPr CH2), 3.80 (s, 5H, Cp),
3.33 (m, JHH ) 6.8 Hz, 4H, Pri CH), 2.09 (s, 6H, CH3CN), 1.34
(d, JHH ) 6.8 Hz, 12H, Pri CH3), 1.33 (d, JHH ) 6.8 Hz, 12H, Pri
CH3). 13C{1H} NMR (δ, CD2Cl2, 20 °C): 214.7 (NCN), 147.0
(Ar2,6), 138.8 (Ar1), 131.6 (Ar4), 126.3 (CN), 124.4 (Ar3,5), 74.4
(Cp), 54.9 (SIPr CH2), 28.5 (Pri CH), 25.9 (Pri CH3), 23.1 (Pri CH3),
4.2 (CH3CN).
Computational Details. All calculations were performed using
the Gaussian03 software package on the Silicon Graphics Origin
2000 computer of the Vienna University of Technology.16 The
geometry and energy of the model complexes and the transition
states were optimized at the B3LYP level17 with the Stuttgart/
Dresden ECP (SDD) basis set18 to describe the electrons of the
ruthenium atom. For the C, N, and H atoms the 6-31g** basis set
was employed.19 A vibrational analysis was performed to confirm
that the structures of the model compounds have no imaginary
frequency. Frequency calculations were performed to confirm the
nature of the stationary points, yielding one imaginary frequency
for the transition states and none for the minima. The vibrational
eigenvectors corresponding to the reaction coordinate (with imagi-
nary frequency) of all transition states were visually checked to
confirm the connectivity of transition states with the reactants and
the products. Crucial transition states (TSBC) have been confirmed
by IRC calculations. All geometries were optimized without
symmetry constraints.
[RuCp(η4-C5H5-η1-CH-IPr)]PF6 (2a). A solution of 1a (100
mg, 0.13 mmol) in 5 mL of CH2Cl2 was stirred under an atmosphere
of acetylene for 10 min at room temperature. Then the solvent was
removed and 2a was isolated as a pure, air-stable red-brown solid.
Yield: 94% (93 mg). Anal. Calcd for C38H47F6N2PRu: C, 58.68;
H, 6.09; N, 3.60. Found: C, 58.83; H, 6.19; N, 3.53. 1H NMR (δ,
CD2Cl2, 20 °C): 7.75-7.38 (m, 6H, Ar), 7.21 (s, 2H, IPr CH),
5.50 (m, 1H, H5), 5.37 (m, 1H, H6), 5.24 (m, 1H, H4), 4.59 (s, 5H,
Cp), 3.48 (m, 1H, H3), 2.87-2.63 (m, 4H, Pri CH), 2.18 (m, 1H,
H2), 1.78 (m, 1H, H1), 1.39 (d, JHH ) 6.7 Hz, 12H, Pri CH3), 1.23
(d, JHH ) 6.5 Hz, 12H, Pri CH3). 13C{1H} NMR (δ, CD2Cl2, 20
°C): 163.9 (NCN), 145.8 (Ar2,6), 145.1 (Ar2,6), 132.3 (Ar4), 132.2
(Ar1), 132.0 (Ar4), 125.5 (Ar3,5), 125.2 (Ar3,5), 124.8 (IPr CH), 123.6
(IPr CH), 85.2 (C4), 85.1 (C5), 78.2 (Cp), 69.5 (C6), 54.4 (C2), 42.4
(C3), 29.5 (Pri CH), 29.3 (Pri CH), 26.9 (Pri CH), 25.2 (Pri CH),
22.3 (Pri CH3), 21.6 (Pri CH3), -39.9 (C1).
[RuCp(η5-C5H4-CH2-IPr)]PF6 (3a). A solution of 2a (90 mg,
0.12 mmol) in CH2Cl2 (1 mL) was heated to 40 °C for 12 h. After
the solvent was removed, the remaining solid was purified by
column chromatography (neutral Al2O3, eluent 1/1 Et2O/CH2Cl2).
Yield: 96% (86 mg). Anal. Calcd for C38H47F6N2PRu: C, 58.68;
H, 6.09; N, 3.60. Found: C, 58.77; H, 6.11; N, 3.72. 1H NMR (δ,
CD2Cl2, 20 °C): 7.41-7.72 (m, 8H, Ar, IPr CH), 4.33 (s, 5H, Cp),
4.29 (bs, 2H, H3,4), 3.78 (bs, 2H, H2,5), 3.54 (s, 2H, CH2), 2.48 -
2.17 (m, 4H, Pri CH), 1.29 (d, JHH ) 6.0 Hz, 12H, Pri CH3), 1.23
(d, JHH ) 5.7 Hz, 12H, Pri CH3). 13C{1H} NMR (δ, CD2Cl2, 20
°C): 146.2 (NCN), 145.0 (Ar2,6), 132.7 (Ar4), 129.2 (Ar1), 125.4
(Ar3,5), 124.8 (IPr CH), 78.5 (C1), 71.7 (C2,5), 71.3 (Cp), 70.9 (C3,4),
29.3 (Pri CH), 29.1 (Pri CH), 26.6 (CH2), 25.2 (Pri CH3), 22.4 (Pri
CH3).
Acknowledgment. Financial support by the “Fonds zur
Fo¨rderung der wissenschaftlichen Forschung” is gratefully
acknowledged (Project No. P16600-N11).
Supporting Information Available: CIF files giving complete
crystallographic data and technical details for 1b, 3a, and 3b and
text, figures, and tables giving additional details of the crystal
structures of 3a and 3b. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM060990I
[RuCp(η5-C5H4-CH2-SIPr)]PF6 (3b). A solution of 1b (100 mg,
0.13 mmol) in 5 mL of CH2Cl2 was stirred under an atmosphere
of acetylene for 30 min at room temperature. Then the solvent was
removed and 3b was isolated as a pure, air-stable brown solid.
Yield: 96% (96 mg). Anal. Calcd for C38H49F6N2PRu: C, 58.53;
H, 6.33; N, 3.59. Found: C, 58.60; H, 6.24; N, 3.52. 1H NMR (δ,
(16) 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.;
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CD2Cl2, 20 °C): 7.60 (t, JHH ) 7.5 Hz, 2H, Ar4), 7.39 (d, JHH
)
7.5 Hz, 4H, Ar3,5), 4.56 (bs, 2H, H3,4), 4.40 (s, 4H, SIPr CH2),
4.27 (s, 5H, Cp), 4.84 (bs, 2H, H2,5), 3.26 (s, 2H, CH2), 2.85 (m,
JHH ) 6.8 Hz, 4H, Pri CH), 1.36 (d, JHH ) 6.8 Hz, 12H, Pri CH3),
1.34 (d, JHH ) 6.8 Hz, 12H, Pri CH3). 13C{1H} NMR (δ, CD2Cl2,
20 °C): 167.7 (NCN), 146.0 (Ar2,6), 131.8 (Ar4), 129.2 (Ar1), 125.6
(Ar3,5), 77.2 (C1), 72.0 (C2,5), 71.3 (Cp), 70.9 (C3,4), 52.8 (SIPr CH),
29.3 (Pri CH), 28.0 (CH2), 25.8 (Pri CH3), 23.2 (Pri CH3).
X-ray Structure Determination. X-ray data were collected on
a Bruker Smart CCD area detector diffractometer using graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å) and 0.3° ω-scan
frames. Corrections for absorption, λ/2 effects, and crystal decay
were applied.14 The structures were solved by direct methods using
the program SHELXS97.15 Structure refinement on F2 was carried
out with the program SHELXL97.4 All non-hydrogen atoms were
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(14) Bruker programs: SMART, version 5.625; SAINT, version 6.36;
SADABS, version 2.10; SHELXTL, version 6.1 (Bruker AXS Inc., Madison,
WI, 2003).
(15) Sheldrick, G. M. SHELX97: Program System for Crystal Structure
Determination; University of Go¨ttingen, Go¨ttingen, Germany, 1997.