Versatile reactivity of the bis(dihydrogen) complex RuH2(H2)2(PCy3)2 toward functionalized olefins: Olefin coordination versus hydrogen transfer via the stepwise dehydrogenation of the phosphine ligand

Article abstract of DOI:10.1021/om950888d

Treatment of RuH₂(H₂)₂(PCy₃)₂ (1) with ethylene leads to the formation of [RuH{η³-C₆H₈)-PCy₂}(C ₂H₄)(PCy₃)] (2), which contains an η³-cyclohexenyl ring. Upon addition of 3 equiv of an alkene bearing σ-donor substituents such as CH₂=CH(SiEt₃) or CH₂=CH^tBu, 1 transforms in high yield into the trihydridoruthenium(IV) complex [RuH₃{(η³-C₆H₈)PCy ₂}-(PCy₃)] (3) and the corresponding alkane is obtained quantitatively. Further hydrogen abstraction from 1 can be achieved by using 5 equiv of alkene, leading to the hydridoruthenium(II) complex [RuH{(η³-C₆H₈)PCy₂}{(η ²-C₆H₉)PCy₂}] (4). This is the first complex where C-H activation within two cyclohexyl rings of two tricyclohexylphosphines has occurred. 4 can also be obtained by treatment of 3 with 2 equiv of alkene. The reactions can be reversed by bubbling dihydrogen into a solution of 2-4 yielding 1 at the final stage of hydrogenation. 3 and 4 undergo rapid H-D exchange with the deuterated solvent. Reaction of 1 with alkenes bearing electron-withdrawing substituents such as CH₂=CHCO₂-Me or trans-MeO₂CCH=CHCO₂Me allows the formation of the hydrido dihydrogen complexes [RuH(H₂)(η²-O₂CCH₂CH ₃)(PCy₃)₂] (5) and [RuH(H₂)(η²-O₂CCH₂CH ₂CO₂Me)(PCy₃)₂] (6), respectively. An X-ray structure determination on 5 was carried out. Surprisingly, reaction of 1 with cis-MeO₂CCH=CHCO₂Me yielded the alkene-coordinated complex [RuH₂(η²-CH₃O₂-CCH=CHCO ₂CH₃)(PCy₃)₂] (7). Variable-temperature NMR studies on 7 showed a barrier of rotation for the alkene of 10.5 kcal/mol. 7 was shown to catalyze cis-trans MeO₂-CCH=CHCO₂Me isomerization.

Full text of DOI:10.1021/om950888d

Organometallics 1996, 15, 1427-1434
1427
Ver sa tile Rea ctivity of th e Bis(d ih yd r ogen ) Com p lex
Ru H2(H2)2(P Cy3)2 tow a r d F u n ction a lized Olefin s: Olefin
Coor d in a tion ver su s Hyd r ogen Tr a n sfer via th e Step w ise
Deh yd r ogen a tion of th e P h osp h in e Liga n d
Andrzej F. Borowski,† Sylviane Sabo-Etienne,* M. Lorraine Christ,
Bruno Donnadieu, and Bruno Chaudret
Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne,
31 077 Toulouse Cedex, France
Received November 14, 1995X
Treatment of RuH2(H2)2(PCy3)2 (1) with ethylene leads to the formation of [RuH{η3-C6H8)-
PCy2}(C2H4)(PCy3)] (2), which contains an η3-cyclohexenyl ring. Upon addition of 3 equiv
of an alkene bearing σ-donor substituents such as CH2dCH(SiEt3) or CH2dCHtBu, 1
transforms in high yield into the trihydridoruthenium(IV) complex [RuH3{(η3-C6H8)PCy2}-
(PCy3)] (3) and the corresponding alkane is obtained quantitatively. Further hydrogen
abstraction from 1 can be achieved by using 5 equiv of alkene, leading to the hydridoru-
thenium(II) complex [RuH{(η3-C6H8)PCy2}{(η2-C6H9)PCy2}] (4). This is the first complex
where C-H activation within two cyclohexyl rings of two tricyclohexylphosphines has
occurred. 4 can also be obtained by treatment of 3 with 2 equiv of alkene. The reactions
can be reversed by bubbling dihydrogen into a solution of 2-4 yielding 1 at the final stage
of hydrogenation. 3 and 4 undergo rapid H-D exchange with the deuterated solvent.
Reaction of 1 with alkenes bearing electron-withdrawing substituents such as CH2dCHCO2-
Me or trans-MeO2CCHdCHCO2Me allows the formation of the hydrido dihydrogen complexes
[RuH(H2)(η2-O2CCH2CH3)(PCy3)2] (5) and [RuH(H2)(η2-O2CCH2CH2CO2Me)(PCy3)2] (6), re-
spectively. An X-ray structure determination on 5 was carried out. Surprisingly, reaction
of 1 with cis-MeO2CCHdCHCO2Me yielded the alkene-coordinated complex [RuH2(η2-CH3O2-
CCHdCHCO2CH3)(PCy3)2] (7). Variable-temperature NMR studies on 7 showed a barrier
of rotation for the alkene of 10.5 kcal/mol. 7 was shown to catalyze cis-trans MeO2-
CCHdCHCO2Me isomerization.
In tr od u ction
ligand is weakly coordinated.4 This last result prompted
us to evaluate the catalytic activity of 1 toward hydrosi-
lylation of olefins.
Dihydrogen complexes1 have been postulated as cata-
lytic intermediates in numerous homogeneous processes
such as hydrogenation of alkenes, alkynes, and ketones.1d
The coordinated dihydrogen ligand is further easily
substituted by several molecules and is considered in
these catalytic processes as an intermediate on the way
to oxidative addition. The first stable bis(dihydrogen)
complex, RuH2(H2)2(PCy3)2 (1), was synthesized in our
group 10 years ago,2 and its reactivity has been explored
since then. The presence of two dihydrogen ligands has
allowed the obtention of unusual structures. For ex-
ample, stable 16-electron hydrido dihydrogen complexes
RuHX(H2)(PCy3)2 are obtained by reacting halocarbons
or thiols with 1.3 Substitution of one dihydrogen ligand
by silanes or germanes yields the new complexes RuH2-
(H2)(η2-HER3)(PCy3)2 in which the HER3 (E ) Si, Ge)
We found that treatment of 1 with triethylsilane and
ethylene results in efficient production of vinylsilane.
Dehydrogenative silylation of ethylene is favored over
the hydrosilylation. Mechanistic studies have shown
that 1 serves as a precursor to generate the catalyst
resting state [RuH{(η3-C6H8)PCy2}(C2H4)(PCy3)] (2) by
direct reaction of 1 with ethylene. 2 is the first complex
presenting a dehydrogenated cyclohexyl ligand on a
cyclohexylphosphine bound to the ruthenium in an η3-
mode and was reported in a preliminary communica-
tion.5
Stoichiometric studies are of importance for the
understanding of catalytic processes. The reactivity of
1 toward functionalized alkenes was examined in an
effort to develop other applications in catalytic reactions.
In this paper, we describe the reactivity of the bis-
(dihydrogen) complex 1 toward substituted alkenes and
demonstrate that 1 can cleanly and reversibly transfer
up to 10 hydrogen atoms. We have chosen mono- and
disubstituted alkenes that differ in coordination ability
due to different steric and electronic properties of the
functional groups.
† On leave from the Institute of Coal Chemistry, Polish Academy of
Sciences, 5 Sowinskiego St., 44-101 Gliwice, Poland.
X Abstract published in Advance ACS Abstracts, February 1, 1996.
(1) (a) Kubas, G. J . Acc. Chem. Res. 1988, 21, 120. (b) Crabtree, R.
H. Acc. Chem. Res. 1990, 23, 95. (c) Crabtree, R. H. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 789. (d) J essop, P. G.; Morris, R. H. Coord.
Chem. Rev. 1992, 121, 155. (e) Heinekey, D. M.; Oldham, W. J ., J r.
Chem. Rev. 1993, 93, 913.
(2) (a) Chaudret, B.; Poilblanc, R. Organometallics 1985, 4, 1722.
(b) Arliguie, T.; Chaudret, B.; Morris, R. H.; Sella, A. Inorg. Chem.
1988, 27, 598.
(3) (a) Chaudret, B.; Chung, G.; Eisenstein, O.; J ackson, S. A.; Lahoz,
F. J .; Lopez, J . A. J . Am. Chem. Soc. 1991, 113, 2314. (b) Christ, M.
L.; Sabo-Etienne, S.; Chaudret, B. Organometallics 1994, 10, 3800.
(4) Sabo-Etienne, S.; Hernandez, M.; Chung, G.; Chaudret, B.;
Castel, A. New J . Chem. 1994, 18, 175.
(5) Christ, M. L.; Sabo-Etienne, S.; Chaudret, B. Organometallics
1995, 14, 1082.
0276-7333/96/2315-1427$12.00/0 © 1996 American Chemical Society

1428 Organometallics, Vol. 15, No. 5, 1996
Borowski et al.
Resu lts a n d Discu ssion
5.08, and a broad singlet at δ 4.53 for the allylic protons
at the 4 and 3,5 positions, respectively, of a cyclohexenyl
ligand. The integration ratio for these three signals is
respectively 3:1:2 which indicates the presence of 3
hydrides. Upon phosphorus decoupling, the high-field
triplet is transformed into a singlet and the quartet
pattern into a triplet (J H-H ) 6.2 Hz). The three
hydrides exchange until the temperature limit of 203
K. The observed minimum T1 value is 90 ms at 233 K
(C7D8, 250 MHz) ruling out a hydrido dihydrogen
formulation but not a short contact between the three
hydrides. This complex is therefore formulated as a
trihydridoruthenium(IV) complex, only a limited num-
ber of examples of which are known.6 The presence of
the (η3-cyclohexenyl)(dicyclohexyl)phophine ligand was
supported by the 13C NMR spectrum. The allylic carbon
at the 4 position resonates as a doublet at δ 81.3, while
the two carbons in the 3 and 5 positions give a doublet
at δ 58.9.
(1) Rea ction of Ru H2(H2)2(P Cy3)2 (1) w ith Alk -
en es L (L ) C2H 4, CH 2dCH SiE t3, CH 2dCHt Bu ).
Syn th esis of [Ru H{(η3-C6H8)P Cy2}(C2H4)(P Cy3)] (2).
Treatment of a suspension of 1 in pentane with ethylene
(3 bar) results in evolution of ethane (GC, NMR)) and
formation of a white solid analyzed as [RuH{(η3-C6H8))-
PCy2}(C2H4)(PCy3)] (2) in 87% yield. Key spectroscopic
features include an AB pattern in the 31P{1H} NMR
spectrum with a large J P-P value (283 Hz) indicative of
a trans position for unequivalent phosphines and three
doublets in the 13C NMR spectrum for the allylic C4,
C3, and C5 carbons at δ 77.9 (J C-H ) 161 Hz), 67.0 (J C-H
) 150 Hz), and 45.8 (J C-H ) 156 Hz). The ethylenic
carbons are presumably hidden by the multiplets of the
1
cyclohexyl carbons between δ 27 and 33. The H NMR
spectrum is temperature dependent indicating the flux-
ionality of the molecule and fast rotation of the ethylene
ligand at room temperature. At 297 K (400 MHz, C7D8)
a very broad signal is observed for the hydride at δ
-7.12 which becomes a doublet of doublets (J P-H ) 18.9
and 26.2 Hz) at 223 K. This signal resumes into a
singlet upon phosphorus decoupling. At 297 K, broad
peaks arising from the phosphine protons are observed
between δ 1 and 3.3. The allylic protons appear as two
broad signals at δ 5.13 and 3.52 in a 2:1 ratio. At low
temperature the assignment is rendered difficult due
to very broad resonances of the phosphine protons over
a wide range of chemical shifts (between δ 1 and 3.3).
At 223 K, the three broad signals at δ 5.32, 5.19, and
3.74 can be attributed to the allylic protons and three
additional broad signals can be attributed to the eth-
ylenic protons at δ 4.36, 3.49, and δ 2.73. All these
signals are of equal intensity. The remaining ethylenic
proton is presumably hidden by the phosphine protons.
The addition of 1 equiv of tBuNC to a solution of 2 in
C6D6 in an NMR tube results in ethylene evolution as
evidenced by an intense singlet at δ 5.36 and formation
of a new complex tentatively formulated as [RuH{(η3-
C6H8)PCy2}(PCy3)(tBuNC)]. All attempts to isolate the
complex failed. An AB pattern is observed in the 31P-
As the reaction is virtually instantaneous, it was not
possible to obtain information on the reaction pathway.
1
Monitoring the reaction by H and 31P NMR spectros-
copy did not give any further information (see below:
reactivity of 2-4 toward H2). However, we can propose
that substitution of one dihydrogen ligand by the
competing alkene is followed by alkene insertion into
the Ru-H bond to yield an alkyl hydrido intermediate
which then eliminates the corresponding alkane. Ef-
fective C-H bond activations of one cyclohexyl ring
could allow successive alkene insertion and elimination
of the corresponding alkane.
Syn t h esis of [R u H {(η3-C6H 8)P Cy2}{(η2-C6H 9)-
P Cy2}] (4). We have demonstrated that addition of 3
equiv of a substituted alkene to 1 resulted in hydroge-
nation of the alkene and formation of the trihydride 3.
When 5 equiv of alkene is added to 1, total hydrogena-
tion of the alkene is again achieved and a new hydri-
doruthenium(II) complex [RuH{(η3-C6H8)PCy2}{(η2-
C6H9)PCy2}] (4) is obtained in good yield (74%). As
opposed to the case of 3 where only one cyclohexyl group
of one phosphine has been activated, both phosphine
ligands in 4 exhibit a dehydrogenated cyclohexyl ring
bound to the metal in an η3 and η2 mode, respectively.
This represents the first example of such a double
activation within the same complex. Support for struc-
{1H} NMR spectrum at δ 100.3 and 58.9 with J P-P
)
237 Hz. The 1H NMR spectrum shows a hydride
resonance at δ -8.42 as a doublet of doublets (J P-H
)
28.7 and 22 Hz), a singlet for the protons of tBuNC at δ
1.3, and allylic resonances at δ 5.3, 4.1, and 3.3. These
data are very similar to the ones obtained for the
hydridoruthenium(II) complex 4 (see below).
1
ture 4 is provided by H and 13C NMR spectra.
1
The H NMR spectrum of 4 consists of five separate
signals of equal intensity between δ 5.2 and 3.4 at-
tributed to the two olefinic and the three allylic protons,
a doublet of doublets in the hydride region at δ -7.91
(J P-H ) 26.1 and 20.0 Hz), each of these six signals
integrating for 1, and a complicated multiplet between
δ 2.8 and 1.1 for the remaining cyclohexyl protons.
Upon phosphorus decoupling the hydride signal trans-
forms into a singlet and the multiplet at δ 5.16 simpli-
fies into a triplet which can be assigned to the central
allylic proton. All the other assignments derive from
Syn th esis of [Ru H3{(η3-C6H8)P Cy2}(P Cy3)] (3).
Reaction of 1 with a substituted alkene such as
CH2dCH(SiEt3) or CH2dCHtBu did not result in the
coordination of the alkene.
Addition of 3 equiv of CH2dCH(SiEt3) to a suspension
of 1 in pentane results in immediate dissolution of 1,
and within 20 s, precipitation of a white microcrystalline
solid occurs; this analyzes as RuH3[(η3-C6H8)PCy2]-
(PCy3) (3). This trihydride complex 3 was isolated in
81% yield. GC analysis of the mother liquor reveals the
presence of SiEt4 resulting from the hydrogenation of
the alkene. The same results were obtained by using
CH2dCHtBu instead of CH2dCHSiEt3. The 31P NMR
shows, as for 2, two inequivalent P nuclei with a typical
1
selective H decoupling experiments (see Table 1 and
Scheme 1 for assignments): olefinic hydrogens appear
(6) (a) Arliguie, T.; Border, C.; Chaudret, B.; Devillers, J .; Poilblanc,
R. Organometallics 1989, 8, 1308. (b) Paciello, R. R.; Manriquez, J .
M.; Bercaw, J . E. Organometallics 1990, 9, 260. (c) Baird, G. J .; Davies,
S. G.; Moon, S. D.; Simpson, S. J .; J ones, R. H. J . Chem. Soc., Dalton
Trans. 1985, 1479. (d) Kono, H.; Wakao, N.; Ito, K.; Nagai, Y. J .
Organomet. Chem. 1977, 132, 53.
1
trans coupling (J PP ) 254 Hz). The H NMR spectrum
at 297 K (C7D8) consists of a pseudotriplet at δ -7.57
(J P-H ) 17 Hz) for the hydrides, a quartet pattern at δ

Reactivity of RuH2(H2)2(PCy3)2
Organometallics, Vol. 15, No. 5, 1996 1429
Ta ble 1. Selected NMR Da ta (p p m ) for Com p ou n d s 2-7
complexes
1H NMRa
31P{1H} NMRa
13C NMRa
[RuH{(η3-C6H8)PCy2}(C2H4)(PCy3)] (2)
5.12 (br, 2H, η3-C6H84,3),c
82.2 and 42.2 77.9 (d, J C-H ) 161 Hz, C4),h
3.52 (br, 1H, η3-C6H85),
(J P-P
)
67.0 (d, J C-H ) 150 Hz, C3),
45.8 (d, J C-H ) 156 Hz, C5)
-7.12 (br, Ru-H)
283 Hz)e
[RuH3{(η3-C6H8)PCy2}(PCy3)] (3)
5.05 (m, 1H, η3-C6H84),b
4.51 (br, 2H, η3-C6H83,5),
-7.52 (pst, 3H, J P-H ) 17 Hz, Ru-H3)
109.6 and 61.0 81.3 (d, J C-H ) 163 Hz, C4),g
(J P-P
254 Hz)e
85.5 and 52.7 75.3 (d, J C-H ) 162 Hz, η2-CdC),h
)
58.9 (d, J C-H ) 157 Hz, C3,5
)
[RuH{(η3-C6H8)PCy2}{(η2-C6H9)PCy2}] (4)
5.16 (m, 1H, J H
) 6.8 Hz, η3-C6H84),c
4-H3
4.13 (br, 1H, η3-C6H83),
(J P-P
)
74.3 (d, J C-H ) 151 Hz, C4),
5-H4
3.47 (br, 1H, J H
) 5.3 Hz, η3-C6H85),
268 Hz)f
52.7 (d, J C-H ) 166 Hz, C3,5
)
4.49 (br, 1H, η2-C6H9),
3.93 (br, 1H, η2-C6H9),
-7.91 (dd, 1H, J P-H ) 26.1 and
20.0 Hz, Ru-H)
[RuH(H2)(O2CCH2CH3)(PCy3)2] (5)
2.50 (q, 2H, J H-H ) 7.5 Hz,
51.9 (s)e
182.8 (s, O2CCH2CH3),h
31.3 (t, J C-H ) 126 Hz,
O2CCH2CH3),
O2CCH2CH3),b
1.44 (t, 3H, J H-H ) 7.5 Hz, O2CCH2CH3),
-14.05 (t, 3H, J P-H ) 14.4 Hz,
Ru-H(H2))
9.2 (q, J C-H ) 127 Hz,
O2CCH2CH3)
[RuH(H2)(O2C(CH2)2CO2CH3)(PCy3)2] (6)
3.25 (s, 3H, O2C(CH2)2CO2CH3),b
2.85 (m, 4H, O2C(CH2)2CO2CH3),
-14.19 (t, 3H, J P-H ) 14.4 Hz,
Ru-H(H2))
52.0 (s)e
59.1(s)e
180.5 (s, O2C(CH2)2CO2CH3),i
173.5 (s, O2C(CH2)2CO2CH3),
51.5 (q, J C-H ) 146 Hz,
O2C(CH2)2CO2CH3)
33.1 (m, O2C(CH2)2CO2CH3)
176.5 (s, CH3O2CCHdCHCO2CH3),g
50.6 (q, J C-H ) 145 Hz,
CH3O2CCHdCHCO2CH3),
49.0 (d, J C-H ) 165 Hz,
CH3O2CCHdCHCO2CH3)
[RuH2(Z-CH3O2CCHdCHCO2CH3)(PCy3)2] (7) 3.92 (m, 2H, CH3O2CCHdCHCO2CH3),d
3.44 (s, 6H, CH3O2CCHdCHCO2CH3),
-19.8 (br, 2H, Ru-H2)
a
b
d
g
h
i
C6D6, 296 K. 200.132 MHz. c 400.134 MHz. 250.133 MHz. e 81.015 MHz. f 161.986 MHz. 62.896 MHz. 100.613 MHz. 50.323
MHz.
Sch em e 1
Sch em e 2
It is interesting to note that 4 can also be obtained
upon treatment of 3 with 2 equiv of 3,3-dimethyl-1-
butene: 4 and 2-dimethylbutane are thus quantitatively
at δ 3.93 and 4.49, while allylic hydrogens appear at δ
3.47, 4.13, and 5.16.
1
produced as shown by H and 31P NMR.
The 31P NMR spectrum of 4 shows, as for 2 and 3, an
AB pattern with a typical trans coupling J P-P ) 268
Hz. Evidence for the η3-C6H8 and η2-C6H9 ligands is
verified by 13C NMR: the three allylic carbons resonate
at δ 74.3 and 52.7 for the 4 and 3,5 positions, respec-
tively, while the two olefinic carbons resonate at δ 75.3.
Note that one of us already reported two complexes
[Cp*Ru{(C6H9)PCy2}][BF4] and [Ru{(C6H9)PCy2}(CF3-
COO)]2(µ-CF3COO)2(µ-OH2) where dehydrogenation of
a cyclohexyl ring resulted in the formation of an (η2-
C6H9)PCy2 ligand but presenting in the former case a
strong agostic interaction.7,8
Rea ctivity of 2-4 tow a r d H2. In all these reac-
tions, the alkene serves as an hydrogen acceptor. The
alkene:1 ratios play a crucial role in obtaining 3 and 4,
since 1 is the only source of hydrogen. Thus, a 3-fold
molar excess of the alkene is necessary to achieve total
hydrogenation into the corresponding alkane and quan-
titative formation of 3. In contrast, a 2-fold molar excess
of the alkene affords 3 in the expected yield ca. 63%
and the red dimer Ru2H4(H2)(PCy3)4 characterized by
1H and 31P NMR.2b
Following the same strategy, 4 is prepared either from
1 using 5 equiv of alkene or from 3 using 2 equiv of
(7) Arliguie, T.; Chaudret, B.; J alon, F. A.; Otero, A.; Lopez, J . A.;
Lahoz, F. J . Organometallics 1991, 10, 1888.
(8) Arliguie, T.; Chaudret, B.; Chung, G.; Dahan, F. Organometallics
1991, 10, 2973.

1430 Organometallics, Vol. 15, No. 5, 1996
Borowski et al.
alkene. A further dehydrogenation of the complex 4 is
not observed when a 10-fold excess of the alkene over 1
is used.
Single crystals of 5 were isolated from a benzene
solution, and an X-ray diffraction study is discussed
below.
All the data are consistent with the hydrogenation of
the CdC double bond and demethylation of the ester
group. The 1H NMR spectrum of 5 in C6D6 shows a
triplet at δ -14.05 (J P-H ) 14.4 Hz). No methyl ester
group is observed in the expected region, but ethyl
protons resonances are clearly identified at δ 2.50 as a
quartet and δ 1.44 as a triplet. The relative intensities
of the hydride signal to ethyl protons, using large
relaxation delays (20 s), are in agreement with the
presence of three hydrides. The lowest T1 value found
is 36 ms at 243 K (250 MHz, C7D8) for the hydride signal
and is in favor of a hydrido dihydrogen formulation. The
complex is fluxional since no decoalescence is observed
for the hydride and dihydrogen ligands down to 203 K.
In contrast to 2-4, the 31P{1H} NMR spectrum of 5
in C6D6 shows one singlet at δ 51.9 indicative of two
equivalent phosphines. The IR spectrum of 5 (KBr
disks) shows a very weak band at 2047 cm-1 attributed
to a Ru-H stretch and two bands at 1543 and 1462 cm-1
typical for a bidentate chelating CO2 group. The value
found for ∆ν ) νasymOCO - νsymOCO is in agreement with
those previously reported.9
In order to investigate whether hydrogen abstraction
from the cyclohexyl rings is a reversible process, we
have carried out a series of experiments aimed at a
stepwise hydrogenation of complexes 2-4. When the
reactions of 1 with various amounts of alkene are
carried out in NMR tubes and monitored by 1H and 31P
NMR, no evidence of dihydrogen evolution is found.
Gradual increase of the corresponding saturated alkane
is observed together with the formation of the expected
complexes 2-4.
Bubbling dihydrogen (5 min) into a C6D6 solution of
2 results in the formation of 3 and 1 and evolution of
ethane as monitored by 1H and 31P NMR. Further
hydrogenation results in total conversion to 1. Hydro-
genation of complexes 3 or 4, under the same conditions,
results in the regeneration of the bis(dihydrogen) com-
plex 1. In the case of 4, we assume that hydrogenation
proceeds stepwise via formation of 3 as a short-lived
intermediate.
H-D Exch a n ge. Complexes 3 and 4 undergo H-D
exchange with the deuterated solvent (C6D6 or C7D8).
When 3 is kept in a deuterated solvent over a long
period, two reactions occur: (i) further dehydrogenation
leading to 4 and (ii) H-D exchange between the hy-
drides and the solvent. Deuterium was also incorpo-
rated within the cyclohexyl groups of the phosphine, but
the allylic protons were not exchanged. The reactions
The 13C NMR spectrum of 5 in C6D6 confirms the
presence of the η2-O2CCH2CH3 ligand. A singlet at δ
182.8 is attributed to the quaternary carbon and the
ethyl carbons resonate as a triplet at δ 31.3 (J C-H
)
126 Hz) and as a quartet at δ 9.2 (J C-H ) 127 Hz). The
equivalent cyclohexyl groups of the phosphines are
observed as three triplets at δ 27.1, 28.3, and 30.4
attributed to the methylene carbons and a broad doublet
for the carbons R-bound to the phosphorus at δ 36.1
1
2
were monitored by H, 31P, and H NMR spectroscopy.
1
In the H NMR spectrum the H-D exchange in the
hydride region leads to the appearance of two new
triplets for the isotopomers [Ru]H2D and [Ru]HD2 with
an isotopic shift of 44 and 84 ppb, respectively. After
the NMR tube is kept at room temperature for 3 h, only
the [Ru]HD2 isotopomer is present. Integration of the
hydride and the allylic signals indicates that the [RuD3
1
leading to a sharp triplet with J P-C ) 8.7 Hz upon H
decoupling.
All these spectroscopic data are in agreement with a
hydrido dihydrogen complex containing a chelating
carboxylate ligand and are similar to the data reported
for a series of complexes obtained from the reaction of
1 with carboxylic acids. In particular, RuH(H2)(η2-O2-
CCH3)(PCy3)2 presents a triplet at δ -14.05 (J P-H ) 14.2
Hz) in the hydride region with a T1min value of 35 ms at
243 K (250 MHz) together with a singlet at δ 52.0 in
the 31P NMR spectrum.10 The hydrogenation of the
CdC bond and demethylation of the ester group are
confirmed by the X-ray study. Due to the nucleophilic
character of the hydrides of 1,3 demethylation may
proceed by a mechanism derived from the general base-
catalyzed hydrolysis of esters.11
2
isomer is the major one. The H NMR spectrum (61.4
MHz) confirms the presence of [Ru]D3 and indicates that
some H-D exchange occurs within the cyclohexylphos-
phine protons but that the allylic ones are not affected.
Finally, the 31P{1H} NMR spectrum shows the forma-
tion of two new AB systems isotopically shifted by 160
and 940 ppb from the [Ru]H3 isotopomer and respec-
tively attributed to the [Ru]HD2 and [Ru]D3 isoto-
pomers. The [Ru]D3 isotopomer could also be obtained
by starting from RuD6(PCy3)2 in the presence of 2 equiv
of alkene.
X-r a y Diffr a ction Stu d y of 5. The molecular struc-
ture of 5 is depicted in Figure 1. Crystal data, data
collection, and refinement parameters are reported in
Table 2, and selected bond distances and angles are
listed in Table 3. The structure is approximately
octahedral with two trans phosphine ligands. The
P-Ru-P angle and the Ru-P distances are similar to
those in the hydridodihydrogenbis(tricyclohexyl-
phosphine)ruthenium complex RuH(H2)I(PCy3)2.3a The
(2) Rea ction of Ru H2(H2)2(P Cy3)2 (1) w ith Alk -
en es L (L ) CH2dCHCO2Me, tr a n s- a n d cis-MeO2-
CCHdCHCO2Me). In the preceding section we have
seen that the reactions of 1 with ethylene or substituted
alkenes containing bulky σ-donor ligands cleanly lead
to the formation of a new family of complexes where
one or two cyclohexyl groups of the phosphines have
been dehydrogenated. In this section we present the
results obtained when 1 reacts with substituted alkenes
bearing electron-withdrawing groups.
(9) Nakamoto, K. Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 3rd ed.; J ohn Wiley and Sons: New York,
1978; p 230.
(10) Chung, G.; Arliguie, T.; Chaudret, B. New. J . Chem. 1992, 16,
369.
(11) March, J . Advanced Organic Chemistry, Reactions, Mechanism
and Structure, 4th ed.; Wiley-Interscience: New York, 1992; p 378.
Syn t h esis of [R u H (H 2)(η2-O2CCH 2CH 3)(P Cy3)2]
(5). Addition of 2 equiv of methyl acrylate CH2dCHCO2-
Me to a suspension of 1 in pentane results in gas
evolution and formation of a pale yellow solid analyzed
as [RuH(H2)(η2-O2CCH2CH3)(PCy3)2] (5) in 44% yield.

Reactivity of RuH2(H2)2(PCy3)2
Organometallics, Vol. 15, No. 5, 1996 1431
Ta ble 2. Cr ysta l Da ta , Da ta Collection , a n d
Refin em en t P a r a m eter s
Crystal Data
chem formula
Mr
cryst system
space group
a (Å)
RuC39H74O2P2
736.02
triclinic
P1h
11.750(6)
12.134(6)
14.342(4)
86.13(3)
84.44(4)
82.63(6)
2015(2)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
F(calcd) (Mg‚m-3
radiation type
wavelength (Å)
)
1.213
Mo KR
0.710 73
25
no. of reflcns for cell params
θ range for cell params (deg)
8-10
48.750
789
µ (mm-1
)
F000
temp (K)
293
Data Collection
diffractometer
Enraf-Nonius CAD4
ω/2θ
data collcn method
no. of measd reflcns
no. of indepdt reflcns
no. of obsd reflcns
observn criterion
θmax
3967
3762 (0.023)
2469
[I > 3σ(I)]
20
-11 f h f 11
-11 f k f 11
0 f l f 13
0.8 + 0.35 tg θ
graphite
F igu r e 1. CAMERON view of [RuH(H2)(η2-O2CCH2CH3)-
(PCy3)2] (5).
parameters related to the bidentate carboxylate ligand
are similar to those found for RuH(CO2Me)(PPh3)3. In
particular, the angle O(1)RuO(2) is 57.9° compared to
57.6° in RuH(CO2Me)(PPh3)3.12 Unfortunately, no X-ray
diffraction study could be obtained at low temperature
in order to confirm the hydrido dihydrogen structure
range of h,k,l
scan range θ (deg)
monochromator
scan speed (deg‚min-1
)
2.9-20.1
Refinement
1
established by H NMR. Difference Fourier syntheses
refinement on
F
Ra
0.0483
0.0541
1.17
showed three peaks in the vicinity of the Ru atom.
These peaks could be isotropically refined without any
restraints either on x’s or U(iso)’s as H atoms. The
observed isotropic thermal parameters seem to have
correct values for the H atoms. The large error shifts
on H atoms coordinates prevent any discrimination
between hydride and dihydrogen positions. The H-H
distances are as follows: H(1)-H(2) 2.2(1) Å, H(1)-H(3)
1.2(1) Å, and H(2)-H(3) 1.4(1) Å. Therefore, if we have
proposed in the CAMERON view that the hydrogen
molecule is located in H(1)-H(3), it could also be in
H(2)-H(3).
b
Rw
GOF (S)c
abs corr
semi-empirical ψ-scan
min/max corr
weighting schemed
Ar coeff
no. of reflcns used
no. of params used
0.92-1.07
{w ) w′[1 - (∆F)/6σ(Fo))2]2}
4.50, -2.08, 2.90
2469
230
a
b
R ) ∑(|Fo| - |Fc|)/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w(|Fo|)2]1/2
.
c Goodness of fit ) [∑w(|Fo - Fc|)2/(Nobs - Nparams
]
.
w′ ) 1/∑(r
1/2
d
) 1,3)ArTr(X), where Ar are the coefficients for the Chebyshev
polynomial Tr(X) with X ) Fc/Fc(max)(1).
Syn th esis of [Ru H(H2)(η2-O2CCH2CH2CO2CH3)-
(P Cy3)2] (6). Addition of 2 equiv of dimethyl fumarate,
trans-MeO2CCHdCHCO2Me, to a suspension of 1 re-
sults in the same type of reaction as described above
for the synthesis of 5. A light green colored solid is
obtained in 41% yield and analyzed as [RuH(H2)(η2-O2-
CCH2CH2CO2CH3)(PCy3)2] (6).
The hydride signal appears as a triplet at δ -14.19
(J P-H ) 14.4 Hz) and has the same T1min value as 5 (36
ms at 243 K, 250 MHz, C7D8). The complex is also
fluxional down to 203 K. As shown by 1H and 13C NMR
measurements, the CdC double bond of the starting
alkene has been hydrogenated and one ester group has
lost its methyl group forming a chelate carboxylate
bound to the ruthenium.
in coordination with the metal center as shown by IR
(νCdO at 1735 cm-1) and 13C NMR (δ(CO2Me) 173.5 (s)
and δ(CO2CH3) 50.6 (q)). The 13C NMR spectra show
three triplets at δ 27.5, 28.7, and 30.8 for the methylene
carbons of the cyclohexyl rings at the 4, 3, and 2
positions, respectively. The carbons bound to phospho-
rus appear as a doublet at δ 36.5 leading to a sharp
1
triplet with J P-C ) 8.5 Hz upon H decoupling. Finally,
the two trans phosphine ligands resonate as a singlet
at δ 52.0 in the 31P NMR spectrum. All the spectro-
scopic data are fully consistent with the proposed
structure. The only difference between 5 and 6 is the
presence of the ester group in 6.
Syn th esis of [Ru H2(η2-CH3O2CCHdCHCO2CH3)-
(P Cy3)2] (7). When a pentane suspension of 1 is treated
with
2
equiv of dimethyl maleate, cis-CH3O2-
The two methylene groups give multiplets at δ 2.85
CCHdCHCO2CH3, the originally pale yellow solution
turns deep orange. From that solution, an orange
complex formulated as [RuH2(η2-CH3O2CCHdCHCO2-
CH3)(PCy3)2] (7) is isolated in 77% yield. The formation
of the dihydride 7 formally results from the loss of the
1
and 33.1 in the H and 13C NMR spectra, respectively.
One ester group remains unaffected and is not involved
(12) Skapski, A. C.; Stephens, F. A. J . Chem. Soc., Dalton Trans.
1974, 390.

1432 Organometallics, Vol. 15, No. 5, 1996
Borowski et al.
Ta ble 3. F r a ction a l Atom ic Coor d in a tes a n d
Equ iva len t Th er m a l P a r a m eter s w ith Estim a ted
Sta n d a r d Devia tion s in P a r en th eses
Ta ble 4. Selected In ter a tom ic Bon d Dista n ces (Å)
a n d An gles (d eg) for 5 Wh er e Esd ’s in P a r en th eses
Refer to th e La st Sign ifica n t Digit
a
Ru(1)-P(1)
Ru(1)-P(2)
Ru(1)-O(1)
Ru(1)-O(2)
Ru(1)-H(1)
Ru(1)-H(2)
Ru(1)-H(3)
P(1)-C(111)
P(1)-C(121)
2.327(2)
2.343(2)
2.266(5)
2.213(5)
1.39(6)
1.46(9)
1.5(1)
P(1)-C(131)
P(2)-C(211)
P(2)-C(221)
P(2)-C(231)
O(1)-C(1)
1.862(8)
1.860(7)
1.855(8)
1.841(9)
1.25(1)
1.266(9)
1.50(1)
1.45(2)
atom
x/a
y/b
z/c
Ueq
,
Å2
Ru(1)
P(1)
P(2)
O(1)
O(2)
0.19698(6)
0.2328(2)
0.1784(2)
0.0859(5)
0.2700(5)
0.1725(8)
0.164(1)
0.07932(6)
-0.1055(2)
0.2696(2)
0.0359(5)
0.0362(4)
0.0220(7)
-0.0099(9)
-0.012(1)
-0.1856(6)
-0.1234(6)
-0.1878(7)
-0.3048(8)
-0.3659(8)
-0.3021(7)
-0.1940(6)
-0.2505(7)
-0.3252(8)
-0.2618(9)
-0.2023(9)
-0.1266(8)
-0.1335(6)
-0.0946(8)
-0.1244(8)
-0.0834(9)
-0.1229(8)
-0.0898(7)
0.3355(6)
0.3100(8)
0.3717(9)
0.3452(9)
0.3665(8)
0.3032(7)
0.2990(6)
0.2509(7)
0.2521(8)
0.3685(7)
0.4238(7)
0.4194(6)
0.3591(8)
0.3384(8)
0.402(1)
0.21862(5) 0.0335
0.1789(1)
0.2444(1)
0.3508(4)
0.3548(4)
0.3965(6)
0.4992(7)
0.5468(8)
0.2380(5)
0.2425(6)
0.3086(6)
0.2789(7)
0.2700(7)
0.2052(6)
0.2102(5)
0.3087(6)
0.3238(7)
0.3097(8)
0.2131(8)
0.1986(7)
0.0526(5)
-0.0094(7)
-0.1105(7)
-0.1505(8)
-0.0888(7)
0.0104(6)
0.2916(5)
0.2337(7)
0.2659(7)
0.3682(7)
0.4280(7)
0.3932(6)
0.3336(5)
0.3145(6)
0.4008(7)
0.4361(6)
0.4481(6)
0.3615(6)
0.1384(6)
0.0920(7)
-0.002(1)
-0.019(1)
0.0258(9)
0.125(1))
0.0341
0.0334
0.0510
0.0461
0.0447
0.0700
0.0926
O(2)-C(1)
C(1)-C(11)
C(11)-C(12)
C(1)
1.859(8)
1.886(8)
C(11)
C(12)
C(111)
C(112)
C(113)
C(114)
C(115)
C(116)
C(121)
C(122)
C(123)
C(124) -0.1031(9)
C(125) -0.102(1)
C(126) -0.0053(8)
C(131)
C(132)
C(133)
C(134)
C(135)
C(136)
C(211)
0.268(1)
H(1)-Ru(1)-H(2)
H(1)-Ru(1)-H(3)
H(2)-Ru(1)-H(3)
Ru(1)-P(1)-C(111) 113.1(3)
Ru(1)-P(1)-C(121) 116.8(3)
Ru(1)-P(1)-C(131) 117.8(2)
Ru(1)-P(2)-C(211) 117.2(2)
Ru(1)-P(2)-C(221) 111.5(2)
Ru(1)-P(2)-C(231) 114.3(3)
Ru(1)-O(1)-C(1)
Ru(1)-O(2)-C(1)
P(1)-Ru(1)-P(2)
P(1)-Ru(1)-O(1)
P(1)-Ru(1)-O(2)
P(1)-Ru(1)-H(1)
P(1)-Ru(1)-H(2)
P(1)-Ru(1)-H(3)
104.2(46) C(1)-C(11)-C(12) 116.8(9)
49.5(45) P(2)-Ru(1)-O(1)
54.9(48) P(2)-Ru(1)-O(2)
0.3539(6)
0.4596(7)
0.5434(7)
0.5800(8)
0.4783(8)
0.3935(7)
0.1124(7)
0.1096(7)
0.0127(8)
0.035(2)
0.040(2)
0.053(2)
0.062(3)
0.056(2)
0.044(2)
0.039(2)
0.052(2)
0.058(3)
0.077(3)
0.081(3)
0.059(3)
0.035(2)
0.056(2)
0.066(3)
0.077(3)
0.060(3)
0.049(2)
0.034(2)
0.064(3)
0.071(3)
0.072(3)
0.062(3)
0.055(2)
0.036(2)
0.046(2)
0.058(3)
0.055(2)
0.057(2)
0.040(2)
0.053(2)
0.067(3)
0.119(5)
0.116(5)
0.092(4)
0.117(5)
94.4(2)
91.4(1)
90.3(26)
89.1(37)
93.8(40)
57.9(2)
P(2)-Ru(1)-H(1)
P(2)-Ru(1)-H(2)
P(2)-Ru(1)-H(3)
O(1)-Ru(1)-O(2)
O(1)-Ru(1)-H(1)
O(1)-Ru(1)-H(2) 156.6(40)
O(1)-Ru(1)-H(3) 147.4(44)
O(1)-C(1)-O(2)
99.0(27)
90.4(5)
92.5(5)
119.1(7)
121.8(8)
173.11(8) O(1)-C(1)-C(11)
92.4(1)
91.1(1)
O(2)-Ru(1)-H(1) 156.9(27)
O(2)-Ru(1)-H(2) 98.9(40)
0.2687(6)
0.1707(8)
0.2038(9)
0.3147(9)
0.4096(8))
0.3778(7)
0.0345(6)
90.0(26) O(2)-Ru(1)-H(3) 153.1(44)
84.2(37) O(2)-C(1)-C(11)
119.0(9)
81.1(40)
Hz) for the methylene carbons. The 31P NMR spectrum
(296 K, C6D6) shows a single peak at δ 59.1, which upon
selective decoupling of the protons of the cyclohexyl
groups transforms into a triplet with J P-H ∼ 30 Hz
indicative of the presence of two hydrides.
C(212) -0.0595(8)
C(213) -0.1765(9)
C(214) -0.2098(9)
C(215) -0.1160(8)
C(216)
C(221)
C(222)
C(223)
C(224)
C(225)
C(226)
C(231)
C(232)
C(233)
C(234)
C(235)
C(236)
0.0002(8)
0.2731(6)
0.3998(7)
0.4631(8)
0.4545(8)
0.3312(8)
0.2684(7)
0.2088(8)
0.3279(9)
0.348(1)
The complex is fluxional on the NMR time scale. The
process can be followed by H and 31P NMR spectros-
1
copy. When the 31P NMR spectra in C7D8 are moni-
tored, the single peak observed at room temperature at
δ 64.2 broadens and decoalesces at 243 K. At the slow-
exchange limit, two broad signals are observed and
resolved, at 193 K, as an ill-defined AB pattern at δ 67.9
and 60.7 (J P-P ) 124 Hz). Warming the sample to room
temperature restores the starting singlet at δ 64.2
(observed at 59.1 in C6D6). The fluxional behavior can
0.293(1)
0.173(1)
0.154(1)
0.507(1)
0.528(1)
0.472(1)
1
be also followed by H NMR spectroscopy which shows
a
1/3
Ueq ) (U11U22U33
) .
a change of the hydride and methoxy signals. The very
broad signal observed at δ -19.8 at 296K leads after
decoalescence to two broad signals of equal intensity at
δ -30.9 and -7.4. This last signal appears as an ill-
resolved triplet at 203 K with J P-H ∼ 32 Hz. At low
field the methoxy protons observed at δ 3.58 at 296 K
decoalesces at 223 K and two broad signals are observed
in the slow-exchange limit at δ 3.70 and 3.42.
This behavior could be explained by fast rotation of
the alkene at room temperature. At low temperature,
blocked rotation of the alkene could allow coordination
to ruthenium of one oxygen of the carboxyl group bound
to the ester, rendering the hydrides nonequivalent. The
hydride trans to the oxygen is observed at high field at
δ -30.9. The phosphine ligands are not equivalent as
shown by the AB pattern in the 31P NMR spectrum, and
the rather small J P-P value of 124 Hz indicates that the
phosphines are pushed away from the alkene (see
proposed structure A).
two dihydrogen ligands and the coordination of the
alkene.
The H NMR spectrum of 7 in C6D6 shows, at 296 K,
a very broad resonance in the hydride region at δ -19.8.
A multiplet is observed for the two alkene protons
1
shifted upfield from
δ 5.71 for free cis-MeO2-
CCHdCHCO2Me to δ 3.92 upon coordination to ruthe-
nium. The six protons of the methyl ester groups
resonate as a singlet at δ 3.44 while the cyclohexyl
groups give multiplets between δ 2.7 and 1.2. The
coordination of the CHdCH double bond to the ruthe-
nium is confirmed by the 13C NMR data. 7 shows at
296 K in C6D6 a doublet (J C-H ) 165 Hz) for the alkene
carbons shifted upfield from δ 130.4 for the free alkene
to δ 49.0 upon coordination to the ruthenium. The two
methyl groups of the ester moiety resonate as a quartet
at δ 50.6 (J C-H ) 145 Hz) and a singlet at δ 166.1 for
the quaternary carbons. Thus the alkene proton and
carbon atoms are largely shifted upfield upon coordina-
tion, indicating that there is strong π-back-bonding from
the ruthenium center to the alkene.13 The carbons of
the cyclohexyl groups resonate as a doublet at δ 39.3
We have calculated the rotation barrier of the alkene
using data from the hydride, the methoxy, and the
(13) (a) de Klerk-Engels, B.; Delis, J . G. P.; Vrieze, K.; Goubitz, K.;
Fraanje, J . Organometallics 1994, 13, 3269. (b) Bianchini, C.; Frediani,
P.; Masi, D.; Peruzzini, M.; Zanobini, F. Organometallics 1994, 13,
4616.
(J C-H ) 125 Hz) and three triplets at δ 30.5 (J C-H
127 Hz), 28.5 (J C-H ) 123 Hz), and 27.6 (J C-H ) 128
)

Reactivity of RuH2(H2)2(PCy3)2
Organometallics, Vol. 15, No. 5, 1996 1433
has no precedent. This confirms the nucleophilic be-
havior of 1, as opposed to the electrophilic behavior we
have recently described for the other bis(dihydrogen)-
ruthenium complex Tp*RuH(H2)2.15 The fact that 1
binds dimethyl maleate in an η2 mode to form 7 but not
dimethyl fumarate (synthesis of 6) is most probably due
to steric reasons. The alkenes have both the same
electronic properties but dimethyl fumarate is more
sterically demanding: when dimethyl fumarate ap-
praoches the metal center after substitution of one
dihydrogen ligand, one ester group comes very close to
ruthenium. Activation of the ester group to form a
carboxylate ligand can then occur. The same phenom-
enom can be observed with methyl acrylate.
In contrast to these results, no coordination is ob-
served with alkenes bearing σ-donor substituents. Hy-
drogenation to the corresponding alkane is achieved,
and depending upon the 1/alkene ratios, complex 3 or
4 is obtained. These results indicate that the alkene
serves as hydrogen acceptor. We reasoned that 1 is the
only source of hydrogen and, thus, 3 and 4 formally
result from the loss of respectively 6 and 10 hydrogen
atoms from 1 leading to partial dehydrogenation of the
cyclohexyl groups. 2-4 represent the first members of
a new family of complexes stabilized by η2- and/or η3-
cyclohexenylphosphines.
phosphorus signals (coalescence temperature and fre-
quency difference between the coalescing signals in the
limit of slow exchange). The values obtained for ∆Gq
are equal within experimental error: 10.0, 10.7, and
10.6 kcal/mol, respectively.
When the reaction of 1 with 2 equiv of dimethyl
maleate is performed in a closed NMR tube in C6D6
1
solution and followed by H and 31P NMR, we detect
after 5 min the formation of 7 and of dimethyl succinate,
MeO2CCH2CH2CO2Me, characterized by two singlets at
δ 2.40 and 3.39 as well as traces of 6. After 1.5 h, the
main product of the reaction is 6 as shown by the very
intense triplet in the hydride region at δ -14.2. A sharp
singlet at δ 0.26 may correspond to methane evolution.
By reacting 1 with cis-CH3O2CCHdCHCO2CH3 in
pentane suspensions, we observe the formation of two
different complexes that could be isolated and charac-
terized as 6 and 7. Note that 6 is the main product
obtained by treatment of
1
with trans-CH3O2-
CCHdCHCO2CH3. That fact suggests that an isomer-
ization of the cis- to the trans-diester takes place in
concentrated solutions. Isomerization of cis- to trans-
diester is a well-established reaction, and complexes
containing the two forms were isolated and recently
characterized.14 In order to test whether 7 was active
in isomerization of cis-diester to the thermodynamically
preferred trans isomer, we stirred a pentane suspension
of 7 with cis-diester in a ratio of 1:40 for several days.
A colorless crystalline product precipitated and was
We have already reported that 2 is a powerful catalyst
for the dehydrogenative silylation of ethylene, and we
anticipate that these new structures will lead to the
design of other active catalytic systems.
Exp er im en ta l Section
All reactions were carried out under argon by using Schlenk
glassware and vacuum line techniques. All solvents were
freshly distilled from standard drying agents and thoroughly
degassed under argon before use. Microanalysis were per-
formed by the Laboratoire de Chimie de Coordination Mi-
croanalytical Service. Infrared spectra were obtained as
Voltalef 35 oil mulls or KBr disks on a Perkin-Elmer 1725 FT-
IR spectrometer. NMR spectra were recorded on a Bruker
1
isolated and characterized by H NMR, IR, and mass
spectroscopy as trans-MeO2CCHdCHCCO2Me.
Finally, we have tested the catalytic activity of 1
toward hydrogenation of cis-MeO2CCHdCHCO2Me. The
reaction was run in a Fisher-Porter bottle at room
temperature in C6D6 under 2 bar of H2 with a 1/alkene
ratio of 1:100. Examination of the solution by NMR
spectroscopy, after 2 h stirring, showed total conversion
to dimethyl succinate. 1 and 6 are the only organome-
tallic complexes detected, the former being the major
one.
1
AC200 (at 200.13 MHz for H and at 81.015 MHz for 31P), while
variable-temperature proton spectra and 13C spectra were
obtained by using an AM 250 (at 250.134 and 62.896 MHz,
respectively), all these spectrometers operating on the Fourier
transform mode. RuCl3‚3H2O was purchased from J ohnson
Matthey Ltd, and all other reagents were purchased from
Aldrich and degassed before use.
[Ru H2(H2)2(P (C6H11)3)2] (1). 1 was made by a modified
method based on that described in 1985.2 [Ru(COD)(COT)]
(0.510 g; 1.62 mmol) was introduced into a Fischer-Porter
bottle, and pentane (8 mL) was added. A solution of PCy3
(0.908 g; 3.24 mmol) in pentane (10 mL) was then introduced,
and the resulting yellow solution was degassed before admis-
sion of dihydrogen. The Fischer-Porter bottle was pressurized
to 3 bar, and the stirred yellow solution became orange within
5 min followed by precipitation of a white solid. After 1 h the
solution was filtered off and the cream-white solid was washed
with cold pentane (3 × 3 mL) before drying in a stream of
argon. Yield: 89%.
The same procedure was used to prepare RuD6(PCy3)2 but
using deuterium in place of dihydrogen.
[Ru H{η3-C6H8)P (C6H11)2}(C2H4)P (C6H11)3] (2). A suspen-
sion of 1 (0.500 g; 0.75 mmol) in 30 mL of pentane was placed
in a Fischer-Porter bottle, which was pressurized to 3 bar of
ethylene. Immediate dissolution of 1 was observed with
Con clu sion s
We have described in this paper six new complexes
2-7 resulting from the reactivity of the bis(dihydrogen)
complex 1 toward functionalized alkenes. 2 and 7 are
the only examples in the series where π-coordination
of the alkene is observed. In all the other cases, the
CdC double bonds have been hydrogenated leading to
two different types of complexes, depending on the
nature of the alkene. For alkenes bearing substituents
such as ester groups, coordination to the metal after the
hydrogenation process allows for new reactivity. Namely,
one ester group is dealkylated forming a chelating
carboxylate ligand and complexes 5 and 6 are thus
formed. To our knowledge, this demethylation process
(14) (a) Helliwell, M.; Vessey, J . D.; Mawby, R. J . J . Chem. Soc.,
Dalton Trans. 1994, 1193. (b) Bianchini, C.; Mealli, C.; Melli, A.;
Penizzini, M.; Zanobini, F. J . Am. Chem. Soc. 1988, 110, 8725.
(15) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.; Rodriguez, A.;
J alon, F.; Trofimenko, S. J . Am. Chem. Soc. 1995, 117, 7441.

1434 Organometallics, Vol. 15, No. 5, 1996
Borowski et al.
formation of a red solution. After ca. 5 min, a white solid
precipitated. The mixture was filtered, washed with pentane
(2 × 5 mL), and dried under argon and then under vacuum.
Yield: 87%. Anal. Calcd for C38H68P2Ru: C, 66.3; H, 10.0.
Found: C, 66.4; H, 10.4.
hydrogen atoms attached to it were anisotropically refined.
Difference Fourier syntheses showed up three peaks in the
vicinity of the Ru atom. These peaks could be isotropically
refined without any restraints either on x’s or U(iso)’s as H
atoms.
[Ru H3{(η3-C6H8)P (C6H11)2}P (C6H11)3] (3). To a suspen-
sion of [RuH2(H2)2(PCy3)2] (0.253 g; 0.38 mmol) in 5 mL of
pentane was added H2CdCHSi(C2H5)3 (0.21 mL; 1.14 mmol).
Immediate dissolution of 1 was observed with formation of a
red solution from which after ca. 20 s a white microcrystalline
solid was formed. The mixture was stirred for 1 h, after which
the product was filtered out and washed with pentane (3 ×
1.5 mL) before drying under vacuum. Yield: 81%. Recrys-
tallization from THF/pentane gave thin white needles. Anal.
Calcd for C36H66P2Ru: C, 65.32; H, 10.05. Found: C, 65.47;
H, 10.21.
[Ru H{(η3-C6H8)P (C6H11)2}{(η2-C6H9)P (C6H11)2}] (4). To
a suspension of 1 (0.172 g; 0.26 mmol) in 5 mL of pentane was
added 3,3-dimethyl-1-butene (0.166 mL; 1.3 mmol). The
mixture was stirred for 2.5 h causing a color change from
orange to red-brown. A pink solid was filtered off, washed with
diethyl ether (4 × 2 mL), and dried under vacuum. Yield:
74%. Anal. Calcd for C36H62P2Ru: C, 65.72; H, 9.50. Found:
C, 65.82; H, 9.97.
Refinements were carried out in three blocks approximation
to the normal matrix by minimizing the function ∑w(|Fo| -
|Fc|)2, where Fo and Fc are the observed and calculated
structure factors. Model reached convergence with R and Rw
defined as
R )
||Fo| - |Fc||/ |Fo|
∑
∑
2
Rw ) [ w|(|Fo| - |Fc|)2|/ w|Fo| ]
∑
∑
The criteria for a satisfactory complete analysis were the ratio
of rms shift to standard deviation being less than 0.1 and no
significant features in final difference maps. Further details
of the crystal structure investigation are available on request
from the Director of the Cambridge Crystallographic Data
Centre, 12 Union Road, GB-Cambridge CB21EZ, U.K., on
quoting the full journal citation.
[Ru H(H2)(O2CCH2CH2CO2CH3)(P (C6H11)3)2] (6). To a
suspension of 1 (0.145 g; 0.22 mmol) in 2 mL of pentane was
added E-CH3O2CCHdCHCO2CH3 (63 µL; 0.44 mmol). An
immediate change of color from pale yellow into orange was
observed. After ca. 45 min a homogeneous orange-brown
solution was obtained. Further stirring for 1 h afforded a pale
green solid. The solvent was evaporated under a stream of
argon, and the remaining solid was washed with diethyl ether
(3 × 2 mL)) and then dried under vacuum. Yield: 41%. Anal.
Calcd for C41H76O4P2Ru: C, 61.86; H, 9.62. Found: C, 61.59;
H, 9.65.
4 is moderately stable and may be rapidly handled in air.
It is sparingly soluble in most common solvents.
[Ru H(H2)(O2CCH2CH3)(P (C6H11)3)] (5). To a suspension
of 1 (0.161 g; 0.24 mmol) in 3 mL of pentane was added methyl
acrylate (44 µL; 0.46 mmol). An immediate dissolution of 1
was observed as well as gas evolution. The resulting red
mixture was stirred overnight. A pale-yellow solid that formed
was filtered off, washed with pentane (3 × 1.5 mL), and dried
under vacuum. Yield: 44%. Anal. Calcd for C39H74O2P2Ru:
C, 63.47; H, 10.11. Found: C, 63.18; H, 10.28.
[Ru H2(η2-Z-CH3O2CCHdCHCO2CH3)(P (C6H11)3)2] (7). To
a suspension of 1 (0.29 g; 0.43 mmol) in 7.5 mL of pentane,
warmed to 30 °C, was added Z-CH3O2CCHdCHCO2CH3 (0.109
mL; 0.87 mmol). Slow gas evolution was observed, and the
resulting orange mixture was stirred for 1.5 h. The solvent
was evaporated to dryness, and the residue was washed with
pentane (3 × 1 mL). The orange solid was dried under
vacuum. Yield: 77%. Recrystallization was from diethyl
ether. Anal. Calcd for C42H76O4P2Ru: C, 62.43; H, 9.48.
Found: C, 62.01; H, 9.80.
X-r a y Cr ysta llogr a p h ic An a lyses. A selected crystal was
mounted in Lindemann glass on an automatic CAD4-F Enraf-
Nonius diffractometer. The data were collected at room
temperature (T ) 293 K). Graphite-monochromatized Mo KR
was used. Unit cell dimensions with esd’s were obtained from
least-squares refinement of the setting angles of 25 well-
centered reflections. Three standard reflections were moni-
tored periodically; they showed no change during data collec-
tion. Corrections were made for Lorentz and polarization
effects; absorption corrections (Difabs) were applied.16 Com-
putations were performed by using CRYSTALS adapted on a
PC.17 Atomic form factors for neutral Ru, C, O, P, and H atoms
were taken from ref 18. The structure was solved by direct
methods using SHELXS86.19 Owing to the low ratio (observa-
tions/variable parameters), only the Ru atom and the non-
Ack n ow led gm en t. This work was supported by the
European Union, Brussels, via The Human Capital
Mobility Network “Metal-Mediated and Catalysed Or-
ganic Synthesis”, and the CNRS. M.L.C. thanks the
CONACYT (Mexico) for support.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
data for 5 including tables of bond distances and angles,
fractional atomic coordinates and equivalent isotropic thermal
parameters for H atoms, and anisotropic thermal parameters
(6 pages). Ordering information is given on any current
masthead page.
(16) Sheldrick, G. M. SHELXS86, Program for Crystal Structure
Solution, University of Go¨ttingen, Go¨ttingen, Germany, 1986.
(17) Watkin, D. J .; Carruters, J . R.; Betteridge, P. W. CRYSTALS
User Guide, Chemical Crystallography Laboratory, University of
Oxford, Oxford, U.K., 1985.
(18) Cromer, D. T. International Tables for X-Ray Crystallography;
The Kynoch Press: Birmingham, England, 1974; Vol. IV.
(19) North, A. C. T.; Phillips, D. C.; Mathews, F. S. Acta Crystallogr.
Sect. A 1968, A21, 351.
OM950888D
(20) Pearce, L. J .; Watkin, D. J . CAMERON, Chemical Crystallogr.,
9 Parks Road, Oxford, England.