Monocyclopentadienylhydride derivatives of ruthenium: Stereoselective proton transfer and proton-hydride exchange in an extremely short dihydrogen bond

Article abstract of DOI:10.1021/ja031926k

Diastereomerically pure complexes of formula CpRuCl(PP*) and CpRuH(PP*) with chiral ferrocenyl diphosphines were prepared and the selectivity of proton-transfer processes over the monohydride compounds with different acids was studied. With 1 equiv of HBF₄ the cis-dihydrogen and trans-dihydride complexes were formed while with 3 equiv of CF ₃CO₂H the trans-dihydride derivative was the only product. However, the use of 1 equiv of CF₃CO₂H led to a dihydrogen bonded complex with an extremely short RuH...HO ₂CF₃ interaction that exhibits proton-hydride exchange. Using the labeled acid CF₃CO₂D, a stereoselective transference of the deuteron was demonstrated that implies the previous epimerization of the monohydride and the subsequent attack of the acid in the position previously occupied by the hydride.

Full text of DOI:10.1021/ja031926k

Published on Web 05/15/2004
Monocyclopentadienylhydride Derivatives of Ruthenium:
Stereoselective Proton Transfer and Proton-Hydride Exchange
in an Extremely Short Dihydrogen Bond
Ester Cayuela,† Fe´lix A. Jalo´n,*,† Blanca R. Manzano,† Gustavo Espino,‡
Walter Weissensteiner,§ and Kurt Mereiter
Contribution from the Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica,
Facultad de Qu´ımicas, UniVersidad de Castilla-La Mancha, AVda. Camilo J. Cela 10,
13071 Ciudad Real, Spain; Departamento de Qu´ımica, Facultad de Ciencias,
Plaza Misael Ban˜uelos s/n, 09001 Burgos, Spain; Faculty of Chemistry, UniVersity of Vienna,
Wa¨hringer Strasse 38, A-1090 Vienna, Austria; and Faculty of Technical Chemistry,
Vienna UniVersity of Technology, Getreidemarkt 9/164-SC, A-1060 Vienna, Austria
Received December 23, 2003; E-mail: felix.jalon@uclm.es
Abstract: Diastereomerically pure complexes of formula CpRuCl(PP*) and CpRuH(PP*) with chiral ferrocenyl
diphosphines were prepared and the selectivity of proton-transfer processes over the monohydride
compounds with different acids was studied. With 1 equiv of HBF4 the cis-dihydrogen and trans-dihydride
complexes were formed while with 3 equiv of CF3CO2H the trans-dihydride derivative was the only product.
However, the use of 1 equiv of CF3CO2H led to a dihydrogen bonded complex with an extremely short
RuH‚‚‚HO2CF3 interaction that exhibits proton-hydride exchange. Using the labeled acid CF3CO2D, a
stereoselective transference of the deuteron was demonstrated that implies the previous epimerization of
the monohydride and the subsequent attack of the acid in the position previously occupied by the hydride.
Introduction
through a stereoselective attack cis to the hydride with kinetic
control. The cis species slowly evolves to the thermodynamically
Monocyclopentadienylhydride derivatives of ruthenium have
received special attention in recent years, particularly with
respect to their chemistry and properties as hydride transition
metal complexes. New concepts have been introduced and
important advances have been made in the study of these
systems. For instance, such complexes were some of the first
transition metal systems in which quantum mechanical exchange
between the hydrides was observed and studied.1 Interesting
cis to trans isomerism, involving dihydrogen-dihydride trans-
formation, has also been demonstrated.2 Furthermore, the acid
character of the cationic dihydride derivatives has been used to
build a large acidity scale in organic solvents.3
stable trans dihydride. The nonclassical dihydride derivatives
are, in some cases, stable at room temperature, mainly when
diphosphine ligands with small bite angle are used.2a,4 In some
rare examples, both cis and trans dihydrides are in equilibrium
at room temperature.2 In other examples, it has been theoretically
studied5 and experimentally demonstrated5c,6 that the proton
transfer occurs through a prior step in which a dihydrogen bond
Ru-H‚‚‚H-A is formed. Interesting ideas concerning the
noninnocent role of the conjugated base (A-) of the proton donor
agent (AH) have recently been suggested,5c,7 but many aspects
concerning the kinetic control of this counteranion remain
unknown. In this work, our aim was to gain further insights
into the protonation process of monohydridediphosphine ruth-
enium derivatives. To achieve this goal, we used two different
but complementary approaches: (i) to use chiral diphosphine
ligands. This would create an asymmetric environment in the
Studies concerning proton transfer to the neutral monohydride
derivatives, mainly with systems containing two phosphorus
donor atoms, have demonstrated that the process proceeds
† Departamento de Qu´ımica Inorga´nica, Orga´nica y Bioqu´ımica, Facultad
de Qu´ımicas, Universidad de Castilla-La Mancha.
(4) Conroy-Lewis, F. M.; Simpson, S. J. J. Chem. Soc., Chem. Commun. 1987,
1675.
(5) (a) Orlova, G.; Scheiner, S. J. Phys. Chem. A. 1998, 102, 4813-4818. (b)
Orlova, G.; Scheiner, S. J. Phys. Chem. A. 1999, 103, 514. (c) Belkova, N.
V.; Besora, M.; Epstein, L. M.; Lledo´s, A.; Maseras, F.; Shubina, E. S. J.
Am. Chem. Soc. 2003, 125, 7715-7725.
(6) (a) Ayllo´n, J. A.; Gervaux, C.; Sabo-Etienne, S.; Chaudret, B. Organome-
tallics 1997, 16, 2000. (b) Shubina, E. S.; Belkova, N. V.; Bakhmutova,
E. V.; Vorontsov, E. V.; Backhmutov, V. I.; Ionidis, A. V.; Bianchini, C.;
Marvelli, L.; Peruzzini, M.; Epstein, L. M. Inorg. Chim. Acta 1998, 280,
302. (c) Gruendeman, S.; Ulrich, S.; Limbach, H.-H.; Golubev, N. S.;
Denisiov, G. S.; Epstein, L. M.; Sabo-Etienne, S.; Chaudret, B. Inorg. Chem.
1999, 38, 2550. (d) Chu, H. S.; Xu, Z.; Ng, S. M.; Lau, C. P.; Lin, Z. Eur.
J. Inorg. Chem. 2000, 993.
‡ Departamento de Qu´ımica, Facultad de Qu´ımicas y CyTA.
§ Faculty of Chemistry, University of Vienna.
Faculty of Technical Chemistry, Vienna University of Technology.
(1) (a) Heinekey, D. M.; Hinkle, A. S.; Close, J. D. J. Am. Chem. Soc. 1996,
118, 5353-5361. (b) Sabo-Etienne, S.; Chaudret, B. Chem. ReV. 1998,
98, 2077-2091. (c) Maseras, F.; Lledo´s, A.; Clot, E.; Eisenstein, O. Chem.
ReV. 2000, 100, 601-636.
(2) (a) Chinn, M. S.; Heinekey, D. M. J. Am. Chem. Soc. 1990, 112, 5166-
5175. (b) Jia G.; Lough, A. J.; Morris R. H. Organometallics 1992, 11,
161-171.
(3) (a) Jia, G.; Morris, R. H. J. Am. Chem. Soc. 1991, 113, 875-883. (b) Abdur-
Rashid, K.; Fong, T. P.; Greaves, B.; Gusev, D. G.; Hinman, J. G.; Landau,
S. E.; Lough, A. J.; Morris, R. H. J. Am. Chem. Soc. 2000, 122, 9155-
9171. (c) Berming D. E.; Noll, B. C.; DuBois, D. L. J. Am. Chem. Soc.
1999, 121, 1432.
(7) Basallote, M. G.; Dura´n, J.; Ferna´ndez-Trujillo, M. J.; Ma´n˜ez, M. A.
Organometallics 2000, 19, 695-698.
9
10.1021/ja031926k CCC: $27.50 © 2004 American Chemical Society
J. AM. CHEM. SOC. 2004, 126, 7049-7062
7049

A R T I C L E S
Cayuela et al.
Chart 1
Scheme 1
Scheme 2
coordination sphere that could give valuable information regard-
ing the stereoselectivity of the transfer; (ii) to analyze the proton
transfer process using not only the strong acid HBF4, but also
a weaker acid such as CF3CO2H. Given that the cis species that
could be initially formed can be quite acidic, it was envisaged
that a similarity in acidity with the proton-transfer agent could
allow the observation of intermediates in this process. The fact
that the kinetic acidity of one acid changes with its concentration
in the reaction medium has also been used to modulate the
degree of the transference.
Ligands and precursors indicated in Scheme 1 were charac-
terized as optically active compounds by polarimetry and as
pure species by mass spectrometry and NMR. The elemental
analyses were in accordance with their chemical formula. In
general, if the signals are not obscured by other resonances,
the 1H and 13C{1H} NMR spectra showed the expected signals
for the Cp and the alkylic interannular chain. The PPh2 and
PR2 groups showed complex patterns due to the diastereotopic
character of the phosphine substituents. PPh2 and PR2 groups
exhibited the characteristic resonances in the respective 31P-
{1H} NMR spectra that are mutually coupled in the case of the
diphosphine derivatives.
The existence of the interannular alkylic chain makes these
ligands conformationally rigid,8 which is especially convenient
for our structural studies because of the simplification that this
feature causes in the NMR spectra at low temperature due to
the existence of only one conformation (see below). In the sole
conformation of these ligands, the PPh2 group attached to the
interannular chain is slightly above the disubstituted Cp ring
and, as a consequence, the C2′′ carbon of the chain points toward
the C1-C5′ axis as indicated in Chart 1. Previous nOe studies
on palladium9 and ruthenium10 complexes with related ligands
demonstrated that the stated conformation persists when the
diphosphine is coordinated to metallic centers.
Results and Discussion
A. Synthesis and Structural Characterization of Ligands
and Complexes 1-6. The racemic 1-diphenylphosphino-2,1′-
(1-diphenylphosphinopropanediyl)-ferrocene, PPPhPF (see Chart
1) was prepared according to methods previously reported by
some of us.8 The enantiomerically pure ligands [(Sc,Sp)-1-
dicyclohexylphosphino-2,1′-(1-diphenylphosphinopro-
panediyl)ferro-cene, (Sc,Sp)-PCyPPhPF and (Sc,Sp)-1-diisopropy-
lphosphino-2,1′-(1-diphenylphosphinopropanediyl)-ferrocene,
(Sc,Sp)-PipPPhPF] were synthesized for the first time.
To prepare them, two new chiral ferrocenylaminophosphine
derivatives were also obtained as the respective precursors:
(Sc,Sp)-1-dicyclohexylphosphino-2,1′-[1-(N,N-dimethylamino)-
1,3-propanediyl]-ferrocene, (Sc,Sp)-PCyAPF and (Sc,Sp)-1-diiso-
propylphosphino-2,1′-[1-(N,N-dimethylamino)-1,3-propanediyl]-
ferrocene, (Sc,Sp)-PipAPF (see Scheme 1). These ferrocenylamino-
phosphine derivatives were obtained by a previous ortho-
lithiation of the chiral ferrocenylamine (S)-1,1′-[1-(N,N-
dimethylamino)-1,3-propanediyl]-ferrocene with n-buthyllithium.
The known8 high diastereoselectivity of this lithiation allows,
by quenching with PClCy2 or PCliPr2, the preparation of the
enantiomericaly pure aminophosphines (Sc,Sp)-PCyAPF and
(Sc,Sp)-PipAPF, respectively. The reaction of (Sc,Sp)-PCyAPF or
(Sc,Sp)-PipAPF with PHPh2 in acetic acid (see Scheme 1) gave
the diphosphines (Sc,Sp)-PCyPPhPF and (Sc,Sp)-PipPPhPF respec-
tively in a type of reaction where, as it has been reported,8a the
configuration of the chiral center is retained (See Experimental
Section for more details).
The halide complexes 1-3 were prepared by thermally
induced substitution reactions in toluene (Scheme 2) in an
analogous way to procedures previously described for other
similar monocyclopentadienyldiphosphines.11
The reaction of 1-3 with an excess of LiAlH4 in THF
allowed the isolation of the monohydride complexes 4-6 by
metathetical exchange of chloride by hydride (Scheme 3). In
(9) Go´mez-de la Torre, F.; Jalo´n, F. A.; Lo´pez-Agenjo, A.; Manzano, B. R.;
Rodr´ıguez, A.; Sturm, T.; Weissensteiner, W.; Mart´ınez-Ripoll, M. Orga-
nometallics 1998, 17, 4634-4644.
(10) Jalo´n, F. A.; Lo´pez-Agenjo, A.; Manzano, B. R.; Moreno-Lara, M.;
Rodr´ıguez, A.; Sturm, T.; Weissensteiner, W. J. Chem. Soc., Dalton Trans.
1999, 4031-4039.
(8) (a) Sturm, T.; Weissensteiner, W.; Spindler, F.; Mereiter, K.; Lo´pez-Agenjo,
A. M.; Manzano, B. R.; Jalo´n, F. A. Organometallics 2002, 21, 1766. (b)
Mernyi, A.; Kratky, Ch.; Weissensteiner, W.; Widhalm, M. J. Organomet.
Chem. 1996, 508, 209-218.
(11) (a) Ashby, G. S.; Bruce, M. I.; Tomkins, I. B.; Wallis, R. C. Aust. J. Chem.
1979, 32, 1003-1016. (b) Blackmore, T.; Bruce, M. I.; Stone, F. G. A. J.
Chem. Soc. A 1971, 2376-2382.
9
7050 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
Scheme 3
Chart 2
epimerization and the relatively high velocity of this process.
According to these data, the formation of the exo isomer
probably occurs under kinetic control. The epimerization process
of monocyclopentadienyl ruthenium derivatives has hardly been
studied and the examples that have been investigated are
centered on halide or pseudohalide derivatives. This process is
considered to be difficult in phosphine derivatives14a,15 but is
feasible in complexes bearing ligands that are prone to allowing
a reversible and partial dissociation.16 The dramatic effect of
the methanol in our experiments can be understood by taking
into account the known solvolysis effect of this solvent. This
solvent probably favors the partial dissociation of the diphos-
phine, allowing the epimerization process to give the thermo-
dynamically more stable form (endo H, RRu). In addition to the
aforementioned process, a slow incorporation of deuterium into
the hydride group of 6 was observed in the acetone-d6/methanol-
d4 solution. After 12 h, the D/H ratio was 8/2. The other groups
in the complex were not deuterated in this time and only the
OH group of the solvent incorporated protium. This process
was reversible and when the solution of 6 + 6-d was evaporated
to dryness and wet acetone-d6 was used to dissolve the complex,
the deuterium was almost totally removed from this complex.
As discussed below, an acid-base process is probably the
mechanism involved in this isotopic exchange.
The monohalide complexes 1-3 exhibit in the IR spectra
only one small vibration band in the 270-290 cm-1 region and
this is characteristic of the Ru-Cl stretching mode. The more
characteristic vibration of the monohydride complexes 4-6 is
the Ru-H stretching, which appears in the range 1950-2000
cm-1 and is observed as a small band.17
The 31P{1H} NMR spectra of 1-6 show two doublets with
a JPP of about 54 Hz for the halide and JPP ) 41.5-50.7 Hz for
the hydride derivatives. These values are in the range usually
found for diphosphine coordinated in three-legged piano-stool
compounds14a,15,18 (see data in the Experimental Section). The
shift of these resonances to higher frequency with respect to
the free ligand provides evidence of the coordination of the
diphosphines.
contrast with other similar reactions, in which the trihydride
derivatives were formed in addition to the monohydrides,12 in
this case the reaction leads selectively to the monohydride
complexes.
All of the neutral complexes 1-6 are soluble in polar solvents
such as acetone and THF while the monohydride compounds
are more soluble in nonpolar solvents such as toluene. The
monohydride complexes 4-6 undergo hydride/chloride meta-
thesis with chlorocarbon solvents.13
Complexes 1-6 were characterized by NMR and IR spec-
troscopy. The molecular structure of 4 was determined by X-ray
diffraction (see below). Elemental analyses are consistent with
the proposed formulas.
The observation of consistent NMR resonances confirms that
complexes 1-5 exist in solution as single species, despite the
fact that two diastereomers are possible given the stereogenic
character of the Ru center due to the asymmetry of the
diphosphine ligands (see Chart 2). The absolute configuration
of the ruthenium center was determined according to the method
described below. The asymmetry and rigidity of the diphosphine
ligands probably impose an energetic difference that is suf-
ficiently high to see only one of the diastereomers in solution
by NMR methods. This diastereospecificity contrasts with the
results found by other authors in the preparation of chiral
monocyclopentadienyl derivatives.14 However, for complex 6
the two diastereomeric forms were observed in acetone or
toluene solutions in a 100:6 ratio even though only the major
component (RRu, endo H) in solution was obtained after
crystallization. To study the possible existence of an equilibrium
between the exo and endo stereoisomers of 6, solutions in
acetone-d6 and toluene-d8 were monitored by NMR spectroscopy
over a period of several hours at room temperature and in
toluene-d8 at 80 °C. The ratio between these isomers did not
change. However, when methanol-d4 was added to an acetone-
d6 solution of this complex at room temperature (1:1 v/v ratio
of solvents), the signals due to the minor component of the
mixture (exo H, SRu) disappeared immediately from the spectra,
showing the effect of the solvent in the equilibrium constant of
1H NMR data are compiled in the Experimental Section and
the 13C{1H} NMR information is given in the Supporting
Information. The assignment of the resonances was carried out
on the basis of information extracted from 1H 1H COSY,
1
selectively decoupled H{31P} NMR spectra, nOe and DEPT
experiments. For 4-6, a doublet of doublets or an apparent
triplet is observed in the high field region of the 1H NMR spectra
(15) Morandini, F.; Consiglio, G.; Straub, B.; Ciani, G.; Sironi, A. J. Chem.
Soc., Dalton Trans. 1983, 2293-2298.
(16) (a) Onitsuka, K.; Ajioka, Y.; Matsushima, Y.; Takahashi, S. Organometallics
2001, 20, 3274-3282. (b) Carmona, D.; Vega, C.; Lahoz, F. J.; Atencio,
R.; Oro, L. A.; Lamata, P.; Viguri, F.; San Jose´, E. Organometallics 2000,
19, 2273-2280. (c) Slugovc, Ch.; Simanko, W.; Mereiter, K.; Schmid, R.;
Kirchner, K.; Xiao, L.; Weissensteiner, W. Organometallics, 1999, 18,
3865-3872. (d) Brunner, H.; Neuhierl, T.; Nuber, B. J. Organomet. Chem
1998, 563, 173-178. (e) Mezzetti, A.; Consiglio, G.; Morandini, F. J.
Organomet. Chem. 1992, 430, C15-C18.
(12) Davies, S. G.; Moon, S. D.; Simpson, S. J. J. Chem. Soc., Chem. Commun.
1983, 1278-1279.
(13) The same property has been reported for CpRuH(PMe3)2: Lemke, F. R.;
Brammer, L. Organometallics 1995, 14, 3980-3987.
(14) (a) Consiglio, G.; Morandini, F.; Bangerter, F. Inorg. Chem. 1982, 21, 455-
457. (b) Morandini, F.; Consiglio, G.; Lucchini, V. Organometallics 1985,
4, 1202-1208.
(17) Bruce, M. I.; Butler, I. R.; Cullen, W. R.; Koutsantonis, G. A.; Snow, M.
R.; Tiekink, E. R. T. Aust. J. Chem. 1988, 41, 963-969.
(18) Torres-Lubia´n, R.; Rosales-Hoz, M. J.; Arif, A. M.; Ernst, R. D.; Paz-
Sandoval, M. A. J. Organomet. Chem. 1999, 585, 68-82.
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7051

A R T I C L E S
Cayuela et al.
Table 1. Details for the Crystal Structure Determinations of
CpRuH(PPPhPF), 4, and CpRu(CF3CO2)(PPPhPF), 13
CpRuH(PPPhPF), 4
CpRu(CF CO )(PPPhPF), 13
3 2
formula
fw
space group
a, Å
b, Å
c, Å
C42H38FeP2Ru
761.58
P1h (no. 2)
11.318(4)
11.675(4)
13.253(5)
93.94(2)
97.22(2)
106.93(2)
1651.8(9)
2
C44H37F3FeO2P2Ru
873.60
P1h (no. 2)
11.350(5)
11.543(5)
16.084(7)
82.07(2)
88.66(2)
62.05(2)
1841.6(14)
2
1.575
297(2)
0.945
888
R, deg
â, deg
γ, deg
V, Å3
Z
F
calc, g cm-3
T, K
1.531
297(2)
1.024
780
µ, mm-1
F(000)
θ
max, deg
30.0
24309
9439
7923
30.0
33751
10525
8557
478
0.0328
0.0449
0.0901
no. of reflns measured
no. of unique reflns
no. of reflns I > 2σ(Ι)
no. of params
419
R1 (I > 2σ(Ι))a
R1 (all data)
wR2 (all data)
diff Four. Peaks
min/max, e Å-3
0.0329
0.0431
0.0880
-0.97/0.66
Figure 1. Molecular structure of complex 4 in the crystalline state showing
20% thermal ellipsoids. Hydrogen atoms of the aromatic rings have been
omitted for clarity. Only the SRu,Rc,Rp enantiomer is represented.
-0.57/0.65
(-12.75 to -14.15 ppm). These signals correspond to the
resonance of the hydride ligand coupled to the two chemically
2
2
2
a R1 ) Σ||Fo| - |Fc||/Σ|Fo|, wR2 ) [Σ(w(Fo - Fc )2)/Σ(w(Fo )2)]1/2
.
different phosphorus atoms. The coupling constants (JHP
)
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
CpRuH(PPPhPF), 4, and CpRu(CF3CO2)(PPPhPF), 13
34.1-34.9 Hz) are consistent with the expected structure for
these complexes.3b,12
4
13
B. Stereochemical Studies of 4. The structure of complex 4
was studied both in the solid state (X-ray diffraction) and in
solution (nOe experiments) in order to demonstrate the absolute
configuration of this complex.
1. X-ray Study of 4. Compound 4 crystallized as a racemic
and contains in its lattice both SRu-Rc-Rp and RRu-Sc-Sp forms
of the complex. Only one of the two enantiomers existing in
the unit cell of space group P1h is shown in Figure 1 (see Table
1 for salient crystal data). The hydride hydrogen could be located
from the diffraction data and was refined in positional param-
eters yielding a chemically reasonable structure.
As expected, the complex exhibits a three-legged piano stool
structure (see Figure 1). A selection of bond distances and bond
angles is compiled in Table 2. Bond distances around the
ruthenium center can be considered as normal.13,19 The relative
disposition of the CpRuH moiety with respect to the ferrocenyl
ligand shows that the absolute configuration of the metal is S,20
when (Rc,Rp)-PPPhPF is the coordinated enantiomer (endo H
in Chart 2). The bite angle of the diphosphine is 87.94(5)°,
smaller than observed in comparable derivatives bearing diphos-
phines with three spacer carbons that are in the range of 90-
97°.21 The bond angles between the donor atoms (P-Ru-H )
81 and 87°, H-Ru-Cpc, ) 122° and P-Ru-Cpc ) 130.6 and
132.0° (Cpc ) Cp centroid)) are in the range of this type of
<Ru-(C(71)-C(75))>
Ru-P(1)
2.247(3)
2.2277(12)
2.2348(11)
1.51(2)
2.196(2)
2.343(1)
2.305(1)
2.183(2)
2.045(2)
2.038(2)
1.825(2)
1.837(2)
1.843(2)
1.866(2)
1.847(2)
1.840(2)
1.504(3)
1.548(3)
1.534(3)
1.501(3)
92.03(4)
93.78(5)
86.41(5)
Ru-P(2)
Ru-H(1)/Ru-O(1)
<Fe-(C(11)-C(15)>
<Fe-(C(21)-C(25))>
P(1)-C(22)
2.032(3)
2.032(2)
1.811(2)
1.841(2)
1.839(2)
1.862(2)
1.837(2)
1.838(2)
1.512(3)
1.550(3)
1.526(3)
1.492(4)
87.94(5)
80.6(9)
P(1)-C(31)
P(1)-C(41)
P(2)-C(1)
P(2)-C(51)
P(2)-C(61)
C(1)-C(21)
C(1)-C(2)
C(2)-C(3)
C(3)-C(11)
P(1)-Ru-P(2)
P(1)-Ru-H(1)/Ru-O(1)
P(1)-Ru-H(1)/Ru-O(1)
87.1(9)
monohydrides.13 One of the most important aspects to be
discussed in this structure is the conformation of the diphosphine
ligand. As it can be observed in Figure 1, two of the phenyl
groups have practically parallel Cipso-Cpara axis with a pseudo-
axial orientation in the six-member coordination metallacycle.
These two phenyl groups block the position trans to the Ru-H
bond that is one of the possible directions of attack in the proton-
transfer process (trans attack). The other two phenyl groups are
situated in a pseudoequatorial position in the coordination
metallacycle. According with the conformational rigidity of this
ligand, very probably this conformation persists in solution but
nOe experiments have been carried out in order to demonstrate
this statement.
(19) Brammer, L.; Klooster, W. T., Lemke, F. R. Organometallics 1996, 15,
1721-1727.
(20) The Cahn-Ingold-Prelog criteria extended to π-bonded ligands have been
considered in this assignment. Priority order of the ligands, Cp > PPh2Cp
> PPh2R > H. Lecomte, C.; Dusausoy, Y.; Protas, J.; Tirouflet, J.;
Dormond, A. J. Organomet. Chem. 1974, 73, 67. Brunner, H. Enantiomer
1997, 2, 133. Brunner, H. Angew. Chem., Int. Ed. 1999, 38, 1194-1208.
(21) (a) Chang, Ch. W.; Lin, Y. Ch.; Lee, G. H.; Wang, Y. Organometallics
2000, 19, 3692. (b) Hung, M. Y.; Ng, S. M. Organometallics 2000, 19,
3692. (c) Zanetti, N. C.; Spindler, F.; Spencer, J.; Togni, A.; Rihs, G.
Organometallics 1996, 15, 860. (d) Lister, S. A.; Redhouse, A. D.; Simpson,
S. J. J. Acta Crystallgr. 1992, C48, 1661.
2. Stereochemical nOe Studies for 4. Bidimensional (NOE-
SY) and monodimensional nOe studies have proven to be
successful methods to determine the single or more populated
9
7052 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
Scheme 4
Chart 3
bond (cis attack) by kinetic control. The cis isomers have a non-
classical nature for these Ru derivatives. However, unless L2 is
a bidentate ligand with a small bite angle, a slow cis to trans
isomerization usually occurs that irreversibly transforms these
dihydrides into the classical trans species (see Scheme 4).
The cis to trans isomerization in this type of dihydride has
been explained in terms of the formation of trigonal bipyramidal
intermediates,2a dissociative processes with the partial breaking
of Ru-L bonds26 or the deprotonation of the cis isomer with
subsequent attack at the trans position.27 This last mechanism
seems to be more probable in the case of acidic cis dihydrogen
complexes.
With this information in mind, we carried out the reactions
of our monohydrides 4-6 with acids of different strength such
as HBF4 or CF3CO2H (also CF3CO2D). The corresponding
transfer reactions were monitored by NMR at low temperature
(-80 or -70 °C) in NMR tubes using acetone-d6 as solvent.
To compare the results, some of the reactions were followed
during a slow increase in the temperature or were carried out
directly at room temperature.
1. Proton Transfer from HBF4. Initially, we used HBF4 as
a donor in the proton transfer, with 4 acting as the acceptor.
The choice of this strong acid was based on the fact that the
majority of examples where the cis-dihydride has been stabilized
have involved the use of this acid.2a,28 The reaction carried out
at -70 °C in acetone-d6, using a slight excess of acid with
respect the 1:1 ratio of reactants, led to a mixture of three
hydride derivatives in which, besides 4, signals for two new
species appeared in the 1H and 31P{1H} spectra (see Figure 2a).
The major component of this mixture, 8, shows hydride
resonances as two doublets of doublets at -7.90 and -8.36
ppm, whereas the other new component, 7, exhibits a broad
signal at -8.3 ppm (obscured by one of the hydride resonance
of 8). The 1H{31P}NMR spectrum showed that the multiplicity
of the hydride signals of 8 was due to JHP coupling constants.
The T1(min) of the hydride resonances of the three derivatives
was calculated and showed clearly different values: 4 (188 ms,
209 K), 7 (15 ms, 225 K) and 8 (320 ms, 243 K). The low
value obtained for 7 allows the assignment of this resonance to
the dihydrogen molecule coordinated in the cis-[CpRu(η2-
H2)(PPPhPF)]BF4, 7. A H-H distance of 1.13 Å (low rotation
regime) or 0.90 Å (rapid rotation regime)29 was calculated for
this coordinated molecule and is in accordance with that
expected for this type of complexes.30 The T1(min) value, the
chemical shift, the JPH coupling constants of the hydride
configuration of molecules in solution.22 We and others have
demonstrated that the assignment of resonances of the ortho
phenyl protons and the determination of the nOe’s of these
protons with their neighboring groups is a very effective way
to show the conformation of ferrocenylaminophosphine9,23 and
ferrocenyldiphosphine ligands24 coordinated to metallic centers.
We assigned the resonances of the ortho protons of 4 by
examining selectively decoupled 1H{31P} NMR spectra. In this
way, irradiation of the 31P NMR resonances induces decoupling
in the resonances at 7.78, 7.89 (PA) and 6.73, 8.45 (PB) ppm
(see Chart 3a). In the corresponding monodimensional nOe
spectra, an nOe is observed between the resonance at 6.73 and
the Cp resonances at 2.58, 3.30 (Cpdown) and 3.93 ppm (Cpup)
and between the resonance at 8.45 and the Cp resonance at 3.93
ppm. The Cp resonance at 2.58 is substantially more shielded
to lower frequency than the rest of the Cp resonances. This
situation is due to the shielding effect of phenyl B2 on H5′.10
On the basis of this information, the resonance at 6.73 can be
assigned to the ortho proton of phenyl B2 in Chart 3a. In
agreement with this assignment, an nOe between this resonance
and the hydride signal is also observed and all this evidence
supports the (RRu, endo H) absolute configuration of 4 when
the (Sc-Sp)-PPPhPF enantiomer is coordinated (see Chart 3a).
We can conclude that the configuration determined in the solid-
state persists in solution. The short distances between H5′ and
one of the ortho protons of phenyl B2 (2.78 Å) and between
this ortho proton and the hydride (2.50 Å), as seen in the X-ray
structure of 4, support the nOe results. The 1H NMR spectrum
of 4 at low temperature does not show signs of the existence of
other conformations or other stereoisomers, a situation that
reflects the rigidity of the diphosphine in 4 and the existence
of a single configuration.
Analogous experiments were carried out with the major
isomer of 6 and an endo orientation for the hydride ligand (RRu-
Sc-Sp diastereomer) was also found.
C. Proton-Transfer Processes. The reaction of monohy-
drides CpRuHL2 with Bro¨nsted acids (HA) leads to cationic
dihydrides through proton-transfer reactions.25 The mechanism
of such reactions is assumed to start with attack at the Ru-H
(26) De los Rios, I.; Jime´mez-Tenorio, M.; Padilla, J.; Puerta, M. C.; Valerga,
P. Organometallics 1996, 15, 4565-4574.
(27) Ryan, O. B.; Tilset, M. J. Am. Chem. Soc. 1991, 113, 9554.
(28) (a) Chinn, M. S.; Heinekey, D. M. J. Am. Chem. Soc. 1987, 109, 5865-
5867. (b) Esteruelas, M. A.; Go´mez, A. V.; Lahoz, F. J.; Lo´pez, A. M.;
On˜ate, E.; Oro, L. A. Organometallics 1996, 15, 3423. (c) Gamasa, M. P.;
Gimeno, J.; Gonza´lez-Bernardo, C.; Martin-Vaca, B. M.; Borge, J.; Garc´ıa-
Granada, S. Inorg. Chim. Acta 2003, 347, 181-188. (d) Mathew, N.;
Jagirdar, B. R.; Ranganathan, A. Inorg. Chem. 2003, 42, 187-197. (e)
Aneetha, H.; Tenorio, M. J.; Puerta, M. C.; Valerga, P. J. Organomet. Chem.
2002, 663, 151-157. (f) Mathew, N.; Jagirdar, B. R. Organometallics 2000,
19, 4506-4517.
(22) (a) Pregosin, P. S.; Trabesinger, G. J. Chem. Soc., Dalton Trans. 1998,
727-734. (b) Friedbolin, H. Basic One- and Two-Dimensional NMR
Spectroscopy; John Wiley & Sons: New York, 1999.
(23) Hess, A.; Sehnert, J.; Weyhermuller, T.; Metzler-Nolte, N. Inorg. Chem.
2000, 39, 5437-5443.
(24) (a) Abbenhuis, H. C. L.; Burkhard, U.; Gramlich, V.; Koellner, C.; Pregosin,
P. S. Organometallics 1995, 14, 759-766. (b) Manzano, B. R.; Jalo´n, F.
A.; Go´mez-de la Torre, F.; Lo´pez-Agenjo, A.; Rodr´ıguez, A. M.; Mereiter,
K.; Weissensteiner, W.; Sturm, T. Organometallics 2002, 21, 789-802.
(25) Jessop, P. G.; Morris, R. H. Coord. Chem. ReV. 1992, 121, 155-248.
(29) (a) Hamilton, D. G.; Crabtree, R. H. J. Am. Chem. Soc. 1988, 110, 4126-
4133 (b) Bautista, M. T.; Earl, K. A.; Maltby, P. A.; Morris, R. H.;
Schweitzer, C. T.; Sella, A. J. Am. Chem. Soc. 1988, 110, 7031-7036. (c)
Desrosiers, P. J.; Cai, L.; Lin, Z.; Richards, R.; Halpern, J. J. Am. Chem.
Soc. 1991, 113, 4173-4184.
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7053

A R T I C L E S
Cayuela et al.
Figure 2. High field 1H and 31P{1H} NMR spectra (acetone-d6) at -70 °C after the adition of a stoichiometric amount of HBF4 to 4, showing the hydride
resonances of 4 (starting material), 7 and 8 (products of the protonation). (a) without CF3CO2Na. (b) after the adition of this salt. Empty arrows indicate the
increase or decrease of the resonance intensities of 4.CF3CO2H and 7.
Scheme 5
resonances and other structural aspects, which will be discussed
below, show that 8 is the isomer trans-[CpRuH2(PPPhPF)]BF4.
When the temperature was increased to room temperature, the
resonance of 7 practically disappeared and 8 was the major
component. This effect is consistent with the expected behavior
in the proton transfer to the monohydride 4, with the formation
of a dihydrogen compound under kinetic control (7) that evolves
irreversibly to the trans isomer, 8, when the temperature is
increased.
On the basis of this information, it can be concluded that the
protonation of 4 with HBF4 is not complete and the reaction
sequence reflected in Scheme 5 is established. An estimated
value of the equilibrium constant of the process 4 + HBF4 T
7, K(-70 °C) ) 43.3 L mol-1, has been evaluated on the basis
of the spectrum integrations.
To obtain initial information about the effect that the presence
of a weaker acid has on this system, a solution of CF3CO2Na
in acetone-d6 (see Experimental Section) was added to this
mixture of hydrides at -70 °C (the amount of CF3CO2Na was
approximately the stoichiometric). After the addition, the
resonances due to the nonclassical dihydride 7 disappeared
completely in the 1H and 31P NMR spectra increasing those of
4, whereas the signals of 8 were practically unaffected (See
Figure 2). The initial incomplete protonation of 4, and the
complete transformation of 7 to 4 when the counteranion
-
CF3CO2 is added, suggests a relatively high thermodynamic
acidity of the H2 molecule in 7 that can be estimated higher
than that of CF3CO2H and lower, but close, than the acidity of
HBF4. Although in this description of the deprotonation experi-
-
ment of 7 with the anion CF3CO2 we have referred to the
formation of 4 as the product, in the next section, we will see
that 4 is very much associated to the CF3CO2H acid resulting
(30) See Jia, G.; Lau, C. P. J. Organomet. Chem. 1998, 565, 37-48 and
references therein.
9
7054 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
Scheme 6
from this deprotonation leading to the concatenate (4‚CF3CO2H)
we will number as 9 (see below and Scheme 6).
In an effort to better evaluate the effect of CF3CO2H in our
proton-transfer studies and to analyze the possible role of the
counteranion, we used this acid in conjunction with 4 in two
different molar ratios.
2. Proton Transfer with a Stoichiometric Amount of
CF3CO2H. Proton-Hydride Exchange. When a stoichiometric
amount of the acid was used at -70 °C, new hydride resonances,
1
similar to those of 8, appeared in the H NMR spectrum. It
seems reasonable that these new signals correspond to the trans-
dihydride with CF3CO2 as a counteranion, i.e., trans-[CpRuH2-
(PPhPhPF)]CF3CO2, 10. In addition, other resonances were
observed due to a new product, 9, and these appeared to be
similar to those of the starting monohydride 4. A signal due to
the proton of the acid (around 4 ppm) was also observed. In
Scheme 6, the products formed in this proton transfer are
indicated. As the temperature was increased, only the resonances
of the acid proton and the hydride of 9 broadened, whereas those
of 10 remained sharp (see Figure 3). The broadening of these
two resonances is reversible and when the temperature was
decreased they became sharp. As expected, an increase in the
intensity of the resonances of the dihydride 10 was also observed
when the temperature was raised.
The reversible broadening of the resonances of the acid and
the hydride of 9 suggests the existence of a proton-hydride
exchange. The participation of 10 in this exchange can be ruled
out and its formation seems to be irreversible. The exchanging
resonances in the spectrum are too far apart (about 5000 Hertz)
to observe clearly a state of coalescence. However, an ap-
proximate value of 57 kJ/mol at 0 °C for the free energy of
activation for this exchange can be estimated from the broaden-
ing of the resonances.31 Although the aforementioned protium-
deuterium exchange observed in the hydride group of 4 in
methanol-d4 clearly has a lower rate, it could follow a similar
mechanism.
As far as the mechanism of the proton-hydride exchange
observed in our system is concerned, the most reasonable
explanation would be the participation of a dihydrogen complex
as an intermediate. However, the chemical shift and JHP coupling
constants of the monohydride 9 remained practically unchanged
when the temperature was raised. This allows us to rule out a
rapid equilibrium between 9 and a significant amount of the
cis-dihydrogen compound (the δ value of this dihydrogen
complex should be very similar to that of 7 and differs from
that found in 9). However, the participation of a dihydrogen
complex as a short-living intermediate cannot be excluded. It
is necessary to consider that in some cases where dihydrogen
Figure 3. Variable temperature 1H NMR study in the high field region
after the addition of a stoichiometric amount of CF3CO2H to 4, showing
the hydride resonances of the products of protonation 9 and 10.
bonds have been found, a parallel process of proton-hydride
exchange has also been observed.32 The formation of a dihy-
drogen bond could not alter the δ value of the starting
hydride32a,33 but an additional relaxation would be expected.
In our case, the T1(min) for the hydride of complex 4 before
the addition of the acid was calculated to be 188 ms at 209 K,
whereas after the addition of CF3CO2H, that is in 9, the value
was reduced to 49 ms at 234 K. The T1 values for the proton
resonance of the acid (at about 4 ppm) are similar to those of
the hydride of 9 at each temperature. This situation is a
consequence of the proton-hydride exchange described above.
(32) (a) Caballero, A.; Jalo´n, F. A.; Manzano, B. R. Chem. Commun. 1998,
1879-1880. (b) Ayllo´n, J. A.; Sayers, S. F.; Sabo-Etienne, S.; Donnadieu,
B.; Chaudret, B., Clot, E. Organometallics 1999, 18, 3981-3900. (c) Lee,
J. C Jr.; Peris, E.; Rheingold, A. L.; Crabtree, R. H. J. Am. Chem. Soc.
1994, 116, 11 014-11 019.
(31) To calculate this value, k was previously estimated according with k )
πW, being W the broadening in excess of the natural line width and then
the activation free energy was calculated with the following equation: ∆GT‡
) aT[10.319 + log(T/k)] (a ) 1.914 × 10-2). Sandstrom, J. Dynamic NMR
Spectroscopy; Academic Press: New York, 1982.
(33) (a) Shubina, E. S.; Belkova, N. V.; Krylov, A. N.; Vorontsov, E. V.; Epstein,
L. M.; Gusev, D. G.; Niedermann, M.; Berke, H. J. Am. Chem. Soc. 1996,
118, 1105-1112. (b) Belkova, N. V.; Ionidis, A. V.; Epstein, L. M.;
Shubina, E. S.; Gruendemann, S.; Golubev, N. S.; Limbach, H.-H. Eur. J.
Inorg. Chem. 2001, 1753-1761.
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7055

A R T I C L E S
Cayuela et al.
Scheme 7
Scheme 8
In contrast, the value for the dihydride 10 does not change in
the presence of free CF3CO2H acid (320 ms at 243 K).
the properties of a nonclassical dihydrogen compound were
preserved. Chaudret and Crabtree et al.35 described pronounced
hydride relaxation in Cp′RuH(PPh3)2 complexes when weak
acids are present. As in 9, evidence for the existence of a proton-
hydride interaction was observed in these systems. However,
in these examples the proton-hydride exchange was not ob-
served. The T1(min) measured for one of these complexes was
too short to be attributed solely to a dipole-dipole relaxation
and other ancillary groups of the complex were also relaxed. A
dependence of the relaxation with the concentration of the acid
was also observed for one of the complexes. In our opinion,
the behavior of 9, although probably related with the observa-
tions of these authors, offers more information about the
chemical characteristics of strong dihydrogen bonds.
If we consider the final steps in Scheme 7, the liberated free
acid (HA) could attack at the trans position in the monohydride
4 and give the trans isomer 10. This path would explain the
observed transformation of 9 into 10 when the temperature was
raised. However, the participation of a dihydrogen complex in
equilibrium with 9 as a transient in the proton-hydride exchange,
as previously stated, and also responsive of the cis to trans
isomerization cannot be excluded.
3. Proton Transfer with an Excess of CF3CO2H or
CF3CO2D. Synthesis of Complexes 10-13. Stereoselectivity
of the Process. It has been reported that a higher concentration
of the acid CF3CO2H increases its acidity due to the formation
of homoconjugated pairs5c and that an increase in the concentra-
tion accelerates the proton-transfer process.7 Given this informa-
tion, we decided to analyze the results of the proton transfer
when an excess of this acid was used. An acid:complex ratio
of 3:1 was used in the protonation of the monohydrides 4-6.
The only products from these reactions, both at -80 °C and at
room temperature, were the trans-dihydride derivatives repre-
sented in Scheme 8.
Such species have not been isolated but have been character-
ized by 1H and 31P NMR spectroscopy. In accordance with the
asymmetric environment, these complexes show two different
resonances both for the phosphorus atoms and for the two
hydrides. The two hydride resonances of each complex differ
As stated in the previous section, 4 was present in the solution,
as a minor product, after a slight excess of HBF4 was added
and is apparently regenerated from 7 when CF3CO2Na was
added. However, the T1(min) calculated for 4 in the presence
of the residual H+ and after the addition of the CF3CO2 salt is
45 ms, a value similar to that of 9 and clearly lower than the
value found for 4 before the addition of the salt. We propose
that the observed excess of relaxation is due not only to the
presence of H+ but mainly to the association of 4 with CF3-
CO2H to form 9 as it is indicated in Scheme 6. According to
the approximate method described by Morris,29 the additional
relaxation found for 9 supposes that the average proton-hydride
distance is 1.43 Å. This value is substantially lower than that
normally expected for a dihydrogen bond (around a minimum
of 1.70 Å) and higher than that in a dihydrogen compound (1.13
Å in 8). Short proton-hydride bonds of about 1.50 Å have been
theoretically calculated5a,32b and theoretical studies have also
suggested that in “CpRu” systems strong dihydrogen bonds can
be formed depending on the donor character of the acid.5a
However, to the best of our knowledge, these species with short
proton-hydride interactions have never been found previously
and complex 9 represents the first example. This system could
be considered as a step, described here for the first time, in the
proton-transfer process, e.g., an intermediate state between a
dihydrogen bond and a coordinated dihydrogen molecule. In
-
this system, the counteranion CF3CO2 could change between
the two hydrogen atoms of the dihydrogen bond, thus changing
the nature of both in the way represented in Scheme 7, which
explains the observed proton-hydride exchange. In this way,
this extremely short dihydrogen bond behaves as a dihydrogen
molecule polarized by the counteranion. Such a term has been
proposed previously but was not experimentally demonstrated
by Norton34 to explain the proton-hydride exchange in one
dihydrogen-bonded complex.32b
Shubina and Limbach33b demonstrated the existence of a
hydrogen-bonded ion-pair adduct in the complex CpRu(CO)L-
(η2-H2)‚‚‚CF3CO2. In contrast with our system, in this example
(35) Castellanos, A.; Ayllo´n, J. A.; Sabo-Etienne, S.; Donnadieu, B.; Chaudret,
B.; Yao, W. B.; Kavallieratos, K.; Crabtree, R. H. C. R. Acad. Sci. Ser. II
C, 1999, 2, 359-368.
(34) Papish, E. T.; Magee, M. P., Norton, J. R. in Recent AdVances in Hydride
Chemistry; Peruzzini, M., Poli, R., Ed.; Elsevier: Amsterdam, 2001, 45.
9
7056 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
Chart 4
slightly in their chemical shifts and are markedly different to
those of the corresponding starting monohydrides (see Experi-
mental Section). As expected for these types of complexes, the
2JHP coupling constants of the hydrides are slightly smaller that
2
those of the monohydrides. The same is true for JPP, which
decreases to very small values. The 2JHH values are practically
zero and are undetectable in the spectra.
We assigned both the phosphorus (PA and PB) and the hydride
resonances (Hexo and Hendo) for 10-12 (see Experimental
Section) using an analogous procedure to that described for the
monohydrides 4-6. The nOe experiments were found to be of
special value in this respect. As a representative example, the
main nOe’s observed for 10 are shown in Chart 3b.
The formation of the trans isomers 10-12 as the only species
does not exclude a possible prior attack at the Ru-H bond, as
occurred when a stoichiometric amount of the acid was used.
However, comparing the results when a stoichiometic amount
or an excess of the acid was used, a clear increase in the form-
ation rate of the trans-dihydrides was observed in the latter case.
To obtain information about the stereochemistry of the proton-
transfer process we carried out an identical reaction with 4, but
in this case CF3CO2D was used as the acid (at -70 °C). It can
be seen from Figure 4a that the deuterium is selectively
incorporated in the endo position to give 10-Dendo. Surprisingly,
this is the position where the hydride was situated in the starting
complex 4 and, as a consequence, a simple trans-attack does
not explain this result. A cis-attack, with the subsequent
formation of a dihydrogen intermediate, followed by a very
selective deuterium/protium migration could explain this result,
although such an isotopic effect is unexpected.
1
Figure 4. (a) High field H NMR spectrum of 10 (down) and 10-D (up)
at -70 °C showing a selective distribution of deuterium in the endo-hydride
position of 10-D. (b) evolution of the isotopic distribution (protium-
deuterium) in 10-D at 25 °C as a function of time (seconds).
An isotopic redistribution at -70 °C is not apparent (identical
integrations were obtained after 1 h). However, when the tem-
perature was raised to 25 °C the isotopic populations slowly
equilibrated (see Figure 4b). This redistribution of isotopes
follows an apparent first-order Arrhenius plot (k ) 2.1 × 10-3
s-1).
To understand this selective attack, we propose the mecha-
nism depicted in Chart 4. First, complex 4 must be in
epimerization equilibrium with the exo-hydride isomer. As stated
previously, we have demonstrated the existence of an epimer-
ization equilibrium for 6. The CF3CO2H would play the same
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7057

A R T I C L E S
Cayuela et al.
Scheme 9
Chart 5
role in 4 as CD3OD did in 6. The latter isomer could be a minor
species that is not observed in the NMR spectra. The observed
selectivity can be explained if we consider that the proton
transfer must follow a trans-attack that is substantially more
rapid for the exo than for the endo-epimer.
As stated previously, both in the solid state and in solution,
4 presents an endo orientation of the hydride ligand. It is
noteworthy that in this epimer the region trans to the hydride is
blocked by two phenyl rings of the PPh2 groups (see Figure 1).
Such a situation could make this position less prone to undergo
attack by the acid, the difficulty being maximized by the low
dissociation degree of the acid and the possible formation of
the homoconjugated pairs: [CF3CO2H]2.36
Figure 5. Molecular structure of complex 13 in the crystalline state showing
20% thermal ellipsoids. Hydrogen atoms of the aromatic rings have been
omitted for clarity. Only the SRu,Rc,Rp enantiomer is represented.
Complex 13 was characterized by X-ray diffraction and NMR
spectroscopy. To the best of our knowledge the cis to trans
transformation of these systems has always been considered as
being irreversible. Our results, however, clearly support a
situation where, although shifted to the trans form, the cis and
trans isomers are in a slow equilibrium.
The isotope redistribution with temperature can be explained
by proposing that the proton transfer reaction is reversible, but
this would imply that the cationic trans dihydride 10 should be
sufficiently acidic when compared with CF3CO2H; a situation
that is very unlikely. Another possible pathway would involve
the existence of a reversible trans to cis isomerization for 10,
as indicated in Chart 5. In this way, the formation of a cis form
of 10-D (dihydrogen compound) would open the door to a
deprotonation that would regenerate the monohydride 4 (4-D
in the chart). A new epimerization and proton-transfer process
could then convert 4-D into the isotopomer of the starting trans-
The results obtained when excess of CF3CO2H (or CF3CO2D)
was used as the acid agent in the transference appear to support
a single trans-attack - a process in marked contrast to the
normally accepted cis-attack for these sorts of reactions under
kinetic control and also with our results using HBF4 as the acid.
However, on considering all of our results, it would be possible
the initial participation of a species with a cis contact, but labile
enough not to allow the proton-hydride exchange. Otherwise,
the selective attack of the CF3CO2D would not be possible.
Probably, the increase in the acidity and in the rate of the proton
transfer when an excess of acid is used (due to the formation
of homoconjugated pairs) makes this transfer occur finally
through a trans attack.
dihydride, e.g., to 10-Dexo
.
The possible existence of the trans to cis isomerization
equilibrium described above was supported by an additional and
fortuitous experience. Although the trans dihydride complex 10
appears to be stable in acetone-d6, when this solution was used
to obtain crystals of this complex a new complex of formula
CpRu(CF3CO2)(PPPhPF), 13, was obtained. This can be ex-
plained by the reaction indicated in Scheme 9, and confirms
the existence of the trans to cis transformation.
D. X-ray Structure of 13. The structure determination of
13 revealed it crystallized as a racemic in the triclinic P1h space
group. Ru shows the usual three-legged piano stool coordination
with two P atoms of the PP-ligand and a weakly bonded O from
the CF3COO group (See Figure 5). The CF3COO group exhibits
usual dimensions; it shows relatively large thermal motion
parameters for its free oxygen atom O(2) and for the CF3 group.
Tables 1 and 2 compiles the main crystallographic and structural
data. The Ru-Fe-complex differs distinctly in conformation
from the corresponding to 4. Whereas in 13, the Cp rings of
(36) The formation of such sort of homoconjugated pairs has been observed in
secondary amines and alcohols: (a) Castaneda, J. P.; Denisov, G. S.;
Shreiber, V. M. J. Mol. Structure 2001, 560, 151. (b) Drichko, N. V.;
Kerenskaya, G. I.; Shreiber, V. M. Chem. Phys. Lett. 1999, 304, 73. (c)
Yuchnevich, G. V.; Tarakanova, E. G.; Maiorov, V. D.; Librovich, N. B.
J. Mol. Structure 1992, 265, 237.
9
7058 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
thermodynamically stable although it is noteworthy that a slow
transformation into CpRu(CF3CO2)(PPPhPF), 13, suggest that
a trans to cis transformation is also possible.
Experimental Section
General Comments. All manipulations were carried out under an
atmosphere of dry oxygen-free nitrogen using standard Schlenk
techniques. Solvents were distilled from the appropriate drying agents
and degassed before use. Elemental analyses were performed with a
Perkin-Elmer 2400 CHN microanalyzer. IR spectra were recorded as
Nujol mulls on a Perkin-Elmer PE 883 IR spectrometer (w ) weak).
Mass spectra were recorded on a Finningan MAT 8230 spectrometer
(EI). Optical rotations were measured on a Perkin-Elmer 241 polarim-
eter. Chromatographic separations were performed under gravity either
on silica gel (Merck, 40-62µ) on alumina (Merck, activity II-III,
0.063-0.200 mm). Petroleum ether with a boiling range of 55-65 °C
was used for chromatography. 1H, 13C{1H} and 31P{1H} NMR spectra
were recorded on a Varian Unity 300 spectrometer. See Chart 1 for
numbering scheme. Chemical shifts (ppm) are relative to TMS (1H,
13C NMR) or 85% H3PO4 (31P NMR) (s ) singlet, d ) doublet, t )
triplet, pq ) apparent quartet, pt ) apparent triplet, m ) multiplet).
Unless specified otherwise, the 13C resonances are singlets. 13C
information is included into the Supporting Information. COSY
spectra: standard pulse sequence, acquisition time 0.214 s, pulse width
10 µs, relaxation delay 1 s, 16 scans, 512 increments. The nOe
difference spectra were recorded with 5000 Hz, acquisition time 3.27
s, pulse width 90°, relaxation delay 4 s, and irradiation power 5-10
dB. For the variable temperature spectra, the temperature of the probe
((1 K) was controlled by a standard unit calibrated with a methanol
Figure 6. Wire Frame representation of complexes 4 and 13 exhibiting
the elevation of the CpRu(O2CCF3) fragment in the last and the consequent
opening of the trans position to the Ru-X bond.
Ru and ferrocene are mutually inclined by about 45°, they are
inclined in 4 by about 90°. This contrasting rearrangement is
probably due to the different steric requirements of the hydride
(4) and the CF3CO2 anion (13) and this last pushes away the
ferrocenyl moiety to liberate a part of the steric hindrance. As
a consequence, in 13 when compared with 4, both the P-C(Cp)
and P-C(chain) bonds turn elevating the CpRuO2CCF3 unit
over the ferrocenyl group which separates the two phenyl groups
that blocked the trans-hydride position in 4 (Figure 6).
Conclusions
Organometallic compounds with three stereogenic centers of
formula CpRuX(PP*) (X ) Cl, H) bearing enantiomericaly pure
or racemic ferrocenyldiphosphine ligands (PP*) have been
prepared. In five of the isolated complexes only one diastereo-
mer was observed by NMR spectroscopy. This diastereomer is
very probably, as unambiguously demonstrated in the case of
4, the X-endo form. The product of the proton-transfer reactions
of the monohydrides was dependent on the acid used, its
concentration and the temperature. When HBF4 was used with
CpRuH(PPPhPF), 4, the expected cis isomer (nonclassical
dihydride) was obtained by kinetic control. This isomer evolved
slowly into the trans isomer when the temperature was increased.
In contrast, when CF3CO2H was used the cis isomer was not
observed because it is more acidic than the transfer agent. When
an acid:complex ratio of 1:1 was used, a new derivative, [CpRu-
(H‚‚‚HO2CCF3)(PPPhPF)]BF4 9, with an extremely short dihy-
drogen bond was formed. Complex 9 represents a new and
previously unreported step in the proton-transfer process to
transition metal hydrides. A fast and reversible proton-hydride
exchange is one of the most relevant properties of this hydrogen
bond. This short hydrogen bond is reminiscent of the term
introduced by Norton of a coordinated dihydrogen molecule
reference. T1 values were obtained on the basis of the inversion recovery
37
method. CpRuCl(PPh3)2
and the racemic ligand PPPhPF,8a were
prepared according to literature methods. This last was used as racemic
to improve the crystallization of the complexes. HBF4, CF3CO2H, and
CF3CO2D were used as supplied from Aldrich.
Preparation of (Sc,Sp)-1-Dicyclohexylphosphino-2,1′-[1-(N,N-di-
methylamino)-1,3-propanediyl]-ferrocene, (Sc,Sp)-PCyAPF. In a 150-
mL Schlenk tube, a 2-g portion (7.43 mmol) of (S)-1,1′-[1-(N,N-
dimethylamino)-1,3-propanediyl]-ferrocene8b ([R]D ) -32°, (c ) 1,
20
MeOH)) was dissolved under argon in 45 mL of dry diethyl ether. To
the degassed solution, 5.1 mL of n-butyllithium (8.2 mmol, 1.6 M in
hexane) was added dropwise. After being stirred for 16 h at room
temperature, 1.8 mL (8.2 mmol) of chlorodicyclohexylphosphine was
added dropwise at 0 °C, and the mixture was stirred for additional 24
h at room temperature. The reaction mixture was quenched at 0 °C
with 30 mL of saturated aqueous NaHCO3 solution. The organic layer
was separated, and the aqueous layer was extracted with diethyl ether
(4 × 30 mL). The combined organic layers were washed with 60 mL
of brine and dried with MgSO4, the solvent was removed under reduced
pressure. The crude product was purified by chromatography on silica
gel (40-63 µm, eluent: CHCl3/CH3OH 8/2) followed by a chroma-
tography on alumina under argon (eluent: petroleum ether/Et2NH 99/
1). Yield: 1.106 g (2.38 mmol, 32%). Anal. Calcd for C27H40FeNP:
-
polarized by the counteranion (CF3CO2 in our case). This
original species evolved to the trans isomer. For this evolution,
we propose a first step involving rupture of the dihydrogen bond
that regenerates the monohydride 4 and subsequent trans attack
of the liberated acid, although the participation of a dihydrogen
complex in equilibrium with 9 as a transient in the proton-
hydride exchange cannot be excluded. Using CF3CO2D in
excess, we have demonstrated that the trans-attack is stereose-
lective into the endo position of the complex, probably due to
steric protection of the exo region of the complex. Because this
position is occupied by the hydride in the starting complex, an
epimerization of the monohydride 4 is necessary before the trans
attack takes place. The feasibility of such epimerization has been
demonstrated for 6. The trans-dihydride, trans-[CpRuH2(PPPh-
PF)]CF3CO2 (classical species), 10, can be considered as
C, 69.67; H, 8.66; N, 3.01. Found: C, 69.65; H, 8.63; N, 3.06. MS (EI
20
140 °C) m/z (rel%): 465 (86, M+), 422 (38), 339 (47), 257 (100). [R]λ
:
+64.0 (589 nm), +77.4 (578 nm), +163 (546 nm), (c ) 0.5, CHCl3).
1H NMR (300 MHz, chloroform-d): δ 4.10, 4.01, 3.99, 3.94, 3.92,
3.87, 3.85 (s, 1H, CpFe), 2.90 (pq, 1H, H2′′ax), 2.2 (s, 6H, N(CH3)2),
2.60-0.92 (m, Cy + protons of the interannular chain). 31P {1H} NMR
(121 MHz, chloroform-d): δ -1.16 (s).
Preparation of (Sc,Sp)-1-Diisopropylphosphino-2,1′-[1-(N,N-di-
methylamino)-1,3-propanediyl]-ferrocene, (Sc,Sp)-PipAPF. In a 150
mL Schlenk tube was dissolved under argon 1.4 g (5.22 mmol) of (S)-
20
1,1′-[1-(N,N-dimethylamino)-1,3-propanediyl]-ferrocene8b ([R]D
)
(37) Bruce, M. I.; Hameister, C.; Swinger, A. G.; Wallis, R. C. Inorg. Synth.
1982, 21, 78.
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7059

A R T I C L E S
Cayuela et al.
-32°, (c ) 1, MeOH)) in 35 mL of dry diethyl ether. To the degassed
solution was added dropwise 4.1 mL of n-butyllithium (6.56 mmol,
1.6 M in hexane). After stirring for 16 h at room temperature 1.2 mL
(7.54 mmol) of chlorodiisopropylphosphine was added dropwise at 0
°C and the mixture was stirred for additional 24 h at room temperature.
The reaction mixture was quenched at 0 °C with 30 mL of saturated
aqueous NaHCO3 solution. The organic layer was separated and the
aqueous layer was extracted with diethyl ether (4 × 30 mL). The
combined organic layers were washed with 60 mL of brine and dried
with MgSO4, the solvent was removed under reduced pressure. The
crude product was purified by chromatography on silica gel (40-63
µm, eluent: CHCl3/CH3OH 8/2) followed by a chromatography on
alumina under argon (eluent: petroleum ether/Et2NH 99/1). Yield. 1.065
g (2.77 mmol, 53%). Anal. Calcd for C21H32FeNP: C, 65.46; H, 8.37;
N, 3.64. Found: C, 69.89; H, 8.67; N, 3.60. MS (EI 60 °C) m/z
(rel%): 385 (99, M+), 342 (62), 299 (99), 257 (80). [R]λ20: +63.9
(589 nm), +77.9 (578 nm), +169 (546 nm), (c ) 0.5, CHCl3). 1H NMR
(300 MHz, chloroform-d): δ 4.10, 4.02, 4.00, 3.97, 3.95 (s, 1H, CpFe),
3.90 (s, 2H, CpFe), 3.05 (pq, 1H, H2′′ax), 2.61 (dd, 1H, H1′′ax), 2.30 (m,
1H, H2′′eq), 2.30 (dd, 1H, H3′′eq), 1.85 (pt, 1H, H3′′ax), 2.15 (s, 6H,
N(CH3)2), 2.20-2.10 (m, 2H, CH(CH3)2), 1.40 (dd, 3H, CH(CH3)2),
1.20-1.10 (m, 6H, CH(CH3)2), 0.95 (m, 3H, CH(CH3)2). 31P {1H} NMR
(121 MHz, chloroform-d): δ -1.12 (s).
(65.3 mg, 0.11 mmol) in 8 mL of toluene was added to the first solution.
The reaction mixture was heated at 95-105 °C with continuous stirring
for 13 h. The solution was evaporated to dryness and the resulting solid
was passed through a chromatography column filled with alumina.
Toluene was used as the first eluent and PPh3 was removed as a
colorless solution. An orange solution of complex 1 was obtained when
THF was used as eluent. The solvent was evaporated to dryness and 1
was isolated as an orange powder. Yield: 67.7 mg (0.085 mmol, 88%.
For 2, the amounts were as follows: CpRuCl(PPh3)2 (435 mg, 0.59
mmol), (Sc,Sp)-PCyPPhPF (350 mg, 0.60 mmol). An orange product was
obtained. Yield: 391 mg (0.48 mmol, 82%). For 3, the amounts were
as follows: CpRuCl(PPh3)2 (536 mg, 0.74 mmol), (Sc,Sp)-PipPPhPF (450
mg, 0.78 mmol). An orange product was obtained. Yield: 458 mg (0.63
mg, 85%). 1: Anal. Calcd for C42H37ClFeP2Ru: C, 63.55; H, 4.52.
1
Found: C, 63.59; H, 4.63. IR (cm-1) 286 (w, ν(Ru-Cl)). H NMR
(300 MHz, chloroform-d): δ 8.8-6.7 (m, 20H, Ph), ortho protons
assigned: 8.15 (m, 2H, PAPhdown), 8.15 (m, 2H, PAPhup), 8.75 (m, 2H,
PBPhdown), 6.78 (m, 2H, PBPhup), 3.98 (s, 5H, CpRu), 4.43 (s, 1H, CpFe),
4.35 (s, 1H, CpFe), 4.31 (s, 1H, CpFe), 3.99 (s, 1H, CpFe), 3.87 (s,
1H, CpFe), 3.17 (s, 1H, CpFe), 2.21 (s, 1H, CpFe-H5′), 3.15 (t, JHP
)
6 Hz, H1′′), 2.46 (pq, H2′′ax), 2.20 (m, H2′′ec), 1.45 (t, H3′′ax), 1.85 (dd,
H3′′ec). 31P {1H} (121 MHz, chloroform-d): 65.21 (d, JPP ) 56.8 Hz,
PAPh2), 35.52 (d, PBPh2). 2: Anal. Calcd for C42H49ClFeP2Ru: C, 62.49;
H, 5.95. Found: C, 62.32; H, 5.98. IR (cm-1) 275 (w, ν(Ru-Cl)). 1H
NMR (300 MHz, chloroform-d): δ 8.2-7.0 (m, 10H, Ph), ortho protons
assigned: 8.16 (m, 2H, PAPhdown), 4.52 (s, 5H, CpRu), 4.43 (m, 2H,
CpFe), 4.29 (m, 2H, CpFe), 4.07 (m, 2H, CpFe), 4.04 (s, 1H, CpFe),
3.15-2.0 (m, 5H, interanular chain), 3.15-0.84 (m, 22H, Cy). 31P {1H}
(121 MHz, chloroform-d): 62.05 (d, JPP ) 54.2 Hz, PAPh2), 46.28 (d,
PBCy2). 3: Anal. Calcd for C36H41ClFeP2Ru: C, 59.46; H, 5.50.
Preparation of (Sc,Sp)-1-Dicyclohexylphosphino-2,1’-(1-diphen-
ylphosphino propanediyl)-ferrocene, (Sc,Sp)-PCyPPhPF. To a degassed
solution of (+)-(Sc,Sp)-aminophosphine PCyAPF (0.650 g, 1.40 mmol)
in freshly distilled acetic acid (12 mL) was added diphenylphosphine
(0.35 mL, 2 mmol). The solution was stirred at 100 °C for 16 h. The
reaction mixture was cooled to room temperature and CH2Cl2 (15 mL)
and saturated NaHCO3 solution (20 mL) were added (vigorous evolution
of CO2). The organic layer was separated and the aqueous layer was
extracted three times with CH2Cl2. The combined organic layers were
washed until neutral with saturated NaHCO3 solution and water and
dried over MgSO4. The solvent was evaporated and the residue was
purified by chromatography on alumina (eluent: petroleum ether
followed by petroleum ether/CHCl3 8/2). Yield: 0.348 g (0.57 mmol,
41%). Anal. Calcd for C37H44FeP2: C, 73.27; H, 7.31. Found: C, 73.38;
H, 7.20. MS (EI 140 °C) m/z (rel%): 606 (100, M+), 523 (68), 440
(10), 255 (19). [R]λ20: -105 (589 nm), -87.8 (578 nm), +22.2 (546
1
Found: C, 59.47; H, 5.46. IR (cm-1) 273 (w, ν(Ru-Cl)). H NMR
(300 MHz, chloroform-d): δ 8.2-7.0 (m, 10H, Ph), ortho protons
assigned: 8.10 (m, 2H, PAPhdown), 6.99 (m, 2H, PAPhup), 4.39 (s, 5H,
CpRu), 4.38 (s, 1H, CpFe), 4.22 (m, 3H, CpFe), 3.97 (m, 2H, CpFe),
3.94 (s, 1H, CpFe), 3.02 (ddd, JHP ) 6 Hz, H1′′), 2.80 (m, 2H, JHH
)
7 Hz, CHCH3), 2.70 (m, H2′′ax), 2.20 (dd, H3′′ax), 1.35 (m, H2′′ec), 1.32
(pt, H3′′ec), 1.66 (dd, JH-PB ) 17.0 Hz, 3H, CHCH3), 1.63 (dd, JH-PB
)
17.8 Hz, 3H, CHCH3), 1.13 (dd, JH-PB ) 14,1 Hz, 3H, CHCH3), 0.34
(dd, JH-PB ) 15.1 Hz, 3H, CHCH3). 31P {1H} (121 MHz, chloroform-
1
i
nm), (c ) 0.5, CHCl3). H NMR (300 MHz, chloroform-d): δ 7.62-
d): 62.86 (d, JPP ) 54.8 Hz, PAPh2), 54.34 (d, PB Pr2).
Preparation of CpRuH(PPPhPF) 4, CpRuH((Sc,Sp)PCyPPhPF) 5
and CpRuH((Sc,Sp)PipPPhPF) 6. Complexes 4-6 were prepared by a
similar method. As a representative example, complex 4 was prepared
as follows: CpRuCl(PPPhPF) (70 mg, 0.88 mmol) was dissolved in 8
mL of THF. An excess of LiAlH4 (60 mg, 1.58 mmol) was then added.
The reaction mixture was stirred for 4 h at room temperature and the
solvent was then evaporated to dryness. The resulting solid was
extracted with toluene (3 × 10 mL). Degassed water (10 mL) was added
to the resulting solution. After separation of the two phases, the organic
solvent was evaporated to dryness and 4 was obtained as a pale-yellow
solid. Yield: 402 mg (0.528 mmol, 60%). For 5, the amounts were as
follows: CpRuCl(PPCyPPhF) (100 mg, 0.124 mmol), LiAlH4 (60 mg,
1.58 mmol). An orange-yellow product was obtained. Yield: 43 mg
(0.056 mmol, 45%). For 6, the amounts were as follows: CpRuCl-
(PPipPPhF) (100 mg, 0.17 mmol), LiAlH4 (70 mg, 1.84 mmol). A pale-
yellow product was obtained. Yield: 50 mg (0.071 mmol, 42%). 4:
Anal. Calcd for C42H38FeP2Ru: C, 66.30; H, 4.80. Found: C, 66.15;
H, 4.82. IR (cm-1) 1961 (w, ν(Ru-H)). 1H NMR (300 MHz, acetone-
d6): δ 8.5-6.6 (m, 20H, Ph), ortho protons assigned: 7.89 (m, 2H,
PAPhdown), 7.78 (m, 2H, PAPhup), 8.45 (m, 2H, PBPhdown), 6.73 (m, 2H,
PBPhup), 4.33 (s, 5H, CpRu), 4.33 (s, 1H, CpupFe), 4.01 (s, 1H, Cpup-
7.10 (m, 10H, Ph), 3.98 (s, 2H, CpFe), 4.05, 4.01, 3.95, 3.90, 3.80 (s,
1H, CpFe), 2.90 (pq, 1H, H2′′ax), 2.65 (dd, 1H, H1′′ax), 2.40 (m, 1H,
H2′′eq), 2.35 (dd, 1H, H3′′eq), 2.00-0.85 (m, 23H, Cy + H3′′ax). 31P {1H}
NMR (121 MHz, chloroform-d): δ -5.54, -6.25 (AB, JPP ) 43.1
Hz).
Preparation of (Sc,Sp)-1-Diisopropylphosphino-2,1’-(1-diphen-
ylphosphino propanediyl)-ferrocene, (Sc,Sp)-PipPPhPF. The prepara-
tion procedure followed exactly that of diphosphine (Sc,Sp)-PCyPPhPF.
The following amounts were used: (+)-(Sc,Sp)-aminophosphine, Pip-
APF, (0.673 g, 1.75 mmol), acetic acid (15 mL), diphenylphosphine
(0.4 mL, 2.3 mmol). Yield: 0.471 g (0.89 mmol, 51%). Anal. Calcd
for C31H36FeP2: C, 70.73; H, 6.89. Found: C, 70.56; H, 6.65. MS (EI
140 °C) m/z (rel%): 526 (5, M+), 483 (100), 440 (47), 255 (63).
[R]λ20:-43.9 (589 nm), -33.0 (578 nm), +40.1 (546 nm), (c ) 0.5,
CHCl3). 1H NMR (300 MHz, chloroform-d): δ 7.6-7.1 (m, 10H, Ph),
4.03, 4.01, 3.95, 3.92, 3.89, 3.87, 3.86 (s, 1H, CpFe), 2.95 (pq, 1H,
H2′′ax), 2.60 (dd, 1H, H1′′ax), 2.30 and 2.05 (m, 1H, H3′′eq and H2′′eq),
1.60 (pt, 1H, H3′′ax), 1.5 (dd, 3H, CH(CH3)2, 1.45-1.23 (m, 6H, CH-
(CH3)2), 1.60 (m, 2H, CH(CH3)2), 0.85 (pt, 3H, CH(CH3)2). 31P {1H}
NMR (121 MHz, chloroform-d): δ -5.15 (d, JPP ) 45.7 Hz, PPh2),
-13.6 (d, PiPr2).
Preparation of CpRuCl(PPPhPF) 1, CpRuCl((Sc,Sp)-PCyPPhPF) 2
and CpRuCl((Sc,Sp)-PipPPhPF) 3. Complexes 1-3 were prepared
following a similar method. As a representative example, complex 1
was prepared as follows: a sample of CpRuCl(PPh3)2 (72.5 mg, 0.1
mmol) was dissolved in 12 mL of toluene. Another solution of PPPhPF
Fe), 3.93 (s, 1H, CpupFe), 3.92 (s, 1H, CpdownFe), 3.73 (s, 1H, Cpdown-
Fe), 3.30 (s, 1H, CpdownFe), 3.00 (ddd, JHP ) 6 Hz, H1′′), 2.58 (s, 1H,
CpdownFe-H5′), 2.58 (pq, H2′′ax), 2.11 (m, H2′′ec), 1.65 (t, H3′′ax), 1.86
(dd, H3′′ec), -12.75 (dd, 1H, JHP ) 34.9, Ru-H). 31P {1H} (121 MHz,
acetone-d6): 91.46 (d, JPP ) 50.7 Hz, PAPh2), 57.71 (d, PBPh2). 5:
9
7060 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004

Derivatives of Ruthenium
A R T I C L E S
Anal. Calcd. for C42H50FeP2Ru: C, 65.27; H, 6.30. Found: C, 64.87;
H, 6.33. IR (cm-1) 1989 (w, ν(Ru-H)). 1H NMR (300 MHz, acetone-
d6): δ 7.9-6.9 (m, 10H, Ph), ortho protons assigned: 7.90 (m, 2H,
PAPhdown), 7.76 (m, 2H, PAPhup), 4.97 (s, 5H, CpRu), 4.28 (s, 1H, CpFe),
4.06 (s, 1H, CpFe), 3.91 (s, 1H, CpFe), 3.86 (s, 1H, CpFe), 3.82 (s,
1H, CpFe), 3.78 (s, 1H, CpFe), 3.75 (s, 1H, CpFe), 2.21 (pt, 1H, H1′′),
Formation of [CpRu(H‚‚‚HO2CCF3)(PPPhPF)]BF4, 9 (short di-
hydrogen bond). This reaction was carried out in an NMR tube at
-70 °C. A solution of complex 4 (15 mg, 0.019 mmol) in 0.5 mL of
acetone-d6 was introduced into the NMR tube. The solution was cooled
to -70 °C and a stoichiometric amount of CF3CO2H (1.4 µL, 0.019
mmol) was added. The reaction was monitored by NMR spectroscopy
by introducing the tube into the probe, which had been cooled to the
appropriate temperature. While monitoring the reaction, the temperature
2.9-0.9 (m, Cy + protons of the interannular chain), -13.40 (t, JHP
)
34.5 Hz, 1H, Ru-H). 31P {1H} (121 MHz, benzene-d6): 90.60 (d, JPP
) 41.5 Hz, PAPh2), 65.49 (d, PBCy2). 6: Anal. Calcd for C36H42FeP2-
Ru: C, 62.40; H, 5.90. Found: C, 62.02; H, 5.89. IR (cm-1) 1977 (w,
ν(Ru-H)). 1H NMR (300 MHz, acetone-d6): δ, 6M 8.2-7.1 (m, 10H,
Ph), ortho protons assigned: 8.18 (m, 2H, PAPhdown), 7.25 (m, 2H, PA-
Phup), 4.55 (s, 1H, CpFe), 4.51 (s, 1H, CpFe), 4.48 (s, 5H, CpRu),
4.32 (s, 1H, CpFe), 4.27 (s, 1H, CpFe), 4.14 (s, 1H, CpFe), 4.04 (s,
1H, CpFe), 4.03 (s, 1H, CpFe), 2.80 (spt, JHH ) 7 Hz, 2H, CHMe2),
2.59 (pt, JHP ) 9.0 Hz, H1′′), 2.56 (m, H2′′ax), 2.15 (m, H3′′ec), 1.72 (m,
H2′′ec), 1.75 (dd, JHP ) 14 Hz, 3H, CHCMe2), 1.68 (dd, JHP ) 14 Hz,
3H, CHCMe2),1.56 (pt, H3′′ax), 1.20 (dd, JHP ) 14 Hz, 3H, CHCMe2),
0.36 (dd, JHP ) 14 Hz, 3H, CHCMe2), -13.57 (t, JHP ) 34.1 Hz, Ru-
H). 6m: 8.2-7.1 (m, 10H, Ph), ortho protons assigned: 7.80 (m, 2H,
PAPhdown), 4.73 (s, 5H, CpRu), 4.40 (s, 1H, CpFe), 4.15 (s, 1H, CpFe),
4.10 (s, 1H, CpFe), 4.05 (s, 1H, CpFe), 3.94 (m, 3H, CpFe), 3.05 (m,
2H, CHMe2), 1.55 (dd, JHP ) 14 Hz, 3H, CHMe2), 1.40 (dd, JHP ) 14
was increased and the NMR recorded at 10° intervals. The 1H and 31
P
NMR data were very similar to those of 4. 1H NMR (300 MHz, acetone-
d6, -70 °C): several resonances non overlapped with those of complex
10 could be assigned, δ 8.4-6.6 (m, 20H, Ph), ortho protons
assigned: 8.35 (m, 2H, PBPhdown), 6.63 (m, 2H, PBPhup), 4.33 (s, 5H,
CpRu), 4.33 (s, 1H, CpupFe), 3.98 (bs, 1H, CF3CO2H), 3.27 (s, 1H,
CpFe), 3.09 (ddd, JHP ) 6 Hz, H1′′), 2.52 (pq, H2′′ax), 2.30 (s, 1H, Cpdown
-
Fe-H5′), 2.05 (m, H2′′ec), 1.80 (dd, H3′′ec), 1.61 (t, H3′′ax), -12.74 (dd,
1H, JHP ) 34.8, Ru-H) 31P {1H} (121 MHz, acetone-d6, -80 °C):
91.14 (d, JPP ) 45.2 Hz, PAPh2), 57.40 (d, PBPh2).
Preparation of trans-[CpRuH2(PPPhPF)]CF3CO2 10, trans-
[CpRuH2((Sc,Sp)-PCyPPhPF)]CF3CO2 11 and trans-[CpRuH2((Sc,Sp)-
PipPPhPF)]CF3CO2 12. These reactions were carried out in NMR tubes
at -80 °C. The reactions were monitored by NMR spectroscopy by
introducing the tubes into the NMR probe, which had been cooled to
the appropriate temperature. While monitoring the reaction, the
temperature was increased and the NMR spectra recorded at 10°
intervals. As a representative example: a sample of 25 mg of 4 (0.033
mmol) was dissolved in 0.5 mL of acetone-d6 and the solution
introduced into an NMR tube, closed and introduced into a thermo-
statised bath at -80 °C. After several minutes this tube was introduced
in a Schlenck porta-tube and then CF3CO2H was added (8 µL, 0.1
mmol). The tube was shaken and rapidly introduced in the NMR probe,
which had been cooled to -80 °C. The corresponding products were
Hz, 3H, CHMe2), 0.96 (dd, JHP ) 14 Hz, 3H, CHMe2), 0.16 (dd, JHP
)
14 Hz, 3H, CHMe2), -14.15 (t, JHP ) 34.5 Hz, Ru-H). 6M or 6m:
3.25 (pt, H1′′), 2.82 (m, H2′′ec), 2.10 (dd, H3′′ec). 31P {1H} (121 MHz,
i
acetone-d6), 6M 90.16 (d, JPP ) 42.8 Hz, PAPh2), 71.80 (d, PB Pr2).
i
6m: 84.39 (d, JPP ) 42.8 Hz, PAPh2), 71.80 (d, PB Pr2).
Formation of cis-[CpRu(η2-H2)(PPPhPF)]BF4 7 and trans-[CpRuH2-
(PPPhPF)]BF4 8. The reaction was carried out in an NMR tube at -70
°C. A solution of complex 4 (15 mg, 0.019 mmol) in 0.5 mL of acetone-
d6 was introduced into the NMR tube. The solution was cooled to -70
°C and a stoichiometric amount of a solution of HBF4 (54% wt. in
diethyl ether, 2.6 µL, 0.019 mmol) was added. The reaction was
monitored by NMR spectroscopy by introducing the tube into the probe,
which had been previously cooled to the appropriate temperature. While
monitoring the reaction, the temperature was increased and the NMR
recorded at 10° intervals. At -70 °C, complex 4 and two other hydride
derivatives were present in the solution (see discussion). One of the
reaction products is 7. Another reaction product is 8 and this was
practically the only product observed at room temperature (see
discussion). The 1H and 31P NMR structural data for 8 are very similar
to those described for 10 (see below). 7: 1H NMR (300 MHz, acetone-
d6, -70 °C): δ 8.5-6.6 (m, 20H, Ph), ortho protons assigned: 8.26
(m, 2H, PBPhdown), 6.47 (m, 2H, PBPhup), 5.41 (s, 5H, CpRu), 4.79 (s,
1H, CpFe), 4.16 (s, 1H, CpFe), 3.89 (s, 1H, CpFe), 3.50 (s, 1H, CpFe),
3.08 (m, H1′′), 2.81 (s, 1H, CpdownFe-H5′), 2.48 (m, H2′′ax), 2.05 (m,
H2′′ec), 1.86 (m, H3′′ec), 1.70 (m, H3′′ax), -8.3 (bs, Ru-H). 31P {1H}
(MHz, acetone-d6, -90 °C): 74.91 (d, JPP ) 43.29 Hz, PAPh2), 43.01
(d, PBPh2).
1
characterized by H and 31P{1H} NMR spectroscopy. 10: 1H NMR
(300 MHz, acetone-d6): δ 8.8-7.0 (m, 20H, Ph), ortho protons
assigned: 8.53 (m, 2H, PAPh), 8.80 (m, 2H, PBPhdown), 6.98 (m, 2H,
PBPhup), 3.99 (s, 5H, CpRu), 4.54 (s, 1H, CpFe), 4.31 (s, 1H, CpFe),
4.24 (s, 1H, CpFe), 4.09 (s, 1H, CpFe), 3.92 (s, 1H, CpFe), 3.09 (s,
1H, CpFe), 3.08 (pq, H2′′ax), 2.82 (m, H2′′ec), 1.90 (m, H3′′ax), -7.75
(dd, JH-PA ) 29.5 Hz, JH-PB ) 22.0 Hz, 1H, Ru-H), -8.21 (t, JH-PA
) 29.5 ) JH-PB ) 26.9 Hz, 1H, Ru-H). 31P {1H} (121 MHz, acetone-
d6): 73.08 (d, JPP ) 7.0 Hz, PAPh2), 54.47 (d, PBPh2). 11: 1H NMR
(300 MHz, acetone-d6): δ 7.9-7.1 (m, 10H, Ph), ortho protons
assigned: 7.84 (m, 4H, PAPhdown and PAPhup), 5.70 (s, 5H, CpRu), 4.85
(s, 1H, CpFe), 4.58 (s, 1H, CpFe), 4.40 (s, 1H, CpFe), 4.35 (s, 1H,
CpFe), 4.30 (s, 1H, CpFe), 4.19 (s, 1H, CpFe), 4.12 (t, H1′′), 3.1-0.8
(Cy), -8.87 (t, JH-PA ) JH-PB ) 26.2 Hz, 1H, Ru-H), -8.83 (t, JH-PA
) JH-PB ) 28.6 Hz, 1H, Ru-H). 31P {1H} (121 MHz, acetone-d6):
74.13 (s, PAPh2), 63.88 (s, PBCy2). 12: 1H NMR (300 MHz, acetone-
d6): δ 8.9-6.6 (m, 10H, Ph), ortho protons assigned: 8.04 (m, 4H,
PAPhdown and PAPhup), 5.67 (s, 5H, CpRu), 4.80 (s, 1H, CpFe), 4.71 (s,
1H, CpFe), 4.31 (s, 1H, CpFe), 4.25 (s, 1H, CpFe), 3.42 (s, 1H, CpFe),
3.89 (s, 1H, CpFe), 3.35 (t, H1′′), 2.8-2.5 (m, 2H, CHMe2), 1.63 (dd,
JHP ) 19.0 Hz, 3H, CHMe2), 1.52 (dd, JHP ) 18.5 Hz, 3H, CHMe2),
1.07 (dd, JHP ) 17.5 Hz, 3H, CHMe2), 0.73 (dd, JHP ) 17.8 Hz, 3H,
CHMe2), -8.97 (t, JH-PA ) JH-PB ) 27.4 Hz, 1H, Ru-H), -8.82 (t,
JH-PA ) JH-PB ) 28.3 Hz, 1H, Ru-H). 31P {1H} (121 MHz, acetone-
Deprotonation Reaction of 7 at Low Temperature. A comparable
experiment to that described in the formation of 7 and 8 was carried
out at -70 °C. In this way a solution of 4 (6.6 mg, 8.7 × 10-3 mmol)
was prepared in 0.5 mL of acetone-d6. This solution was cooled to
-70 °C and a slight excess of a 0.26 M solution of HBF4.Et2O in
acetone-d6 (35 µL, 9.1 × 10-3 mmol) was added. The tube was
introduced in the NMR probe previously cooled at -70 °C and
i
d6): 74.53 (s, PAPh2), 71.64 (s, PB Pr2).
1
monitored by H and 31P NMR. The corresponding resonances of the
Preparation of CpRu(CF3CO2)(PPPhPF), 13. To obtain mono-
crystals of complex 10, a sample was dissolved in acetone in a Schlenk-
tube. A tube containing diethyl ether was also introduced into the
Schlenk tube in order to produce slow evaporation of this solvent and
condensation over the acetone solution. After several days, orange
complexes 4, 7, and 8 were observed and their ratio was determined
by the relative integrations of the hydride resonances (17:21:62
respectively). This tube was extracted from the NMR probe and
introduced in a thermostatized bath at -70 °C. A 0.073 M CF3CO2Na
solution (100 µL, 7.3 × 10-3 mmol) was added into the tube that was
introduced again in the NMR probe. According with the relative
integrations, the amount of 8 kept practically unchanged whereas 7
completely disappeared in favor of 9 (relative ratio of 9:8 ) 40:60).
1
monocrystals were obtained that were found to be of complex 13. H
NMR (300 MHz, acetone-d6, -70 °C): δ 8.5-6.8 (m, 20H, Ph), ortho
protons assigned: 8.05 (m, 2H, PAPhdown), 8.32 (m, 2H, PBPhdown), 6.80
(m, 2H, PBPhup), 4.17 (s, 5H, CpRu), 4.69 (s, 1H, CpFe), 4.33 (s, 1H,
9
J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004 7061

A R T I C L E S
Cayuela et al.
CpFe), 4.16 (s, 1H, CpFe), 4.09 (s, 1H, CpFe), 2.99 (s, 1H, Cpdown
-
positions and were refined riding with the atoms to which they were
bonded. Selected crystallographic and geometric data are given in Tables
1 and 2. More details are reported in the supporting.
Fe-H5′), 3.53 (m, H1′′), 2.30 (m, H2′′ax), 1.95 (m, H2′′ec), 1.60 (m, H3′′ax),
1.86 (m, H3′′ec).31P {1H} (121 MHz, acetone-d6): 67.36 (d, JPP ) 57.4
Hz, PAPh2), 38.47 (d, PBPh2).
Acknowledgment. Dedicated to Prof. Karl Schlo¨gl on the
occasion of his 80th birthday. Authors from the UCLM thank
the D.G.E.S. for financial support (Grant nï. PB2002-00286)
and the Consejer´ıa de Ciencia y Tecnolog´ıa de la Junta de
Comunidades de Castilla-La Mancha (Grant no. PBI-02-002).
X-ray Structure Determination for 4 and 13. X-ray data of suitable
cystals were collected on a Bruker Smart CCD area detector diffrac-
tometer (graphite-monochromated Mo KR radiation, λ ) 0.71073 Å)
using 0.3° ω-scan frames that covered complete spheres of the reciprocal
space. Data processing included a correction for absorption by the
multiscan method.38 The structures were solved with direct methods
using the program SHELXS97.39 Structure refinements on F2 were
carried out with the program SHELXL97.39 Non-hydrogen atoms were
refined anisotropically. The hydride H atom was refined in x, y, and z
without restraints. All other hydrogen atoms were inserted in idealized
Supporting Information Available: Tables and CIF’s of
X-ray structural data, including data collection parameters,
positional and thermal parameters, bond distances and angles
for complexes, and additional structural views of 4 and 13. 13C-
{1H} NMR information of ligands and complexes 1-6. This
material is available free of charge via the Internet at
http://pubs.acs.org.
(38) Bruker, Programs SMART, version 5.054; SAINT, version 6.2.9; SADABS
version 2.03; XPREP, version 5.1; SHELXTL, version 5.1; Bruker AXS
Inc.: Madison, WI, 2001.
(39) Sheldrick, G. M. SHELX97: Program System for Crystal Structure
Determination; University of Go¨ttingen: Germany, 1997.
JA031926K
9
7062 J. AM. CHEM. SOC. VOL. 126, NO. 22, 2004