Inter- and Intramolecular Thermal Activation of sp3 C-H Bonds with Ruthenium Bisallyl Complexes

Article abstract of DOI:10.1021/om990229r

Complexes of type [{R₂P(CH₂)_nPR₂}Ru(2-Me-all) ₂] (2-Me-all = 2-methylpropenyl; R = Cy, n = 1-3, 5a-c; R = Me, n = 2, 6; R₂ = -(CH₂)₄-, n = 2, 7) have been synthesized from the reaction of the corresponding electron-rich diphosphines with [(cod)Ru(2-Me-all)₂] (4) at 50-70°C. The new complexes were fully characterized by multinuclear NMR spectroscopy and mass spectroscopic techniques. Reacting 4 with Cy₂P(CH₂)_nPCy₂ containing hydrocarbon bridges with n = 3 (1c) and n = 4 (1d) at 95 and 50°C, respectively, led to [κ²P,P′-{(η³-C₆H ₈)CyP(CH₂)_nPCy₂}Ru(η ³-C⁸H¹³)] (n = 3, 4; 8c,d) via intramolecular C-H bond activation and concomitant hydride transfer to cyclooctadiene. The molecular structure of 8c was unambiguously assigned by multinuclear 1D and 2D NMR spectroscopy and confirmed by single-crystal X-ray diffraction. The new complexes were tested as homogeneous catalyst precursors in thermal intermolecular C-H activation processes. In dehydrogenation of cyclooctane (coa), an initial turnover frequency of 1.9 h^-1 was observed using complex 5a under refluxing conditions without the need of a hydrogen scavenger. A maximum total number of 5 catalytic turnovers was achieved after 48 h. Ligand degradation by dehydrogenation was detected under catalytic conditions, presumably initiated via intramolecular C-H activation as in species of type 8. Attempts to utilize complexes 5 for C-H activation in scCO₂ as the reaction medium resulted in insertion of CO₂ into the Ru-allyl moiety, yielding catalytically inactive ruthenium carboxylates.

Full text of DOI:10.1021/om990229r

3316
Organometallics 1999, 18, 3316-3326
In ter - a n d In tr a m olecu la r Th er m a l Activa tion of sp 3
C-H Bon d s w ith Ru th en iu m Bisa llyl Com p lexes
Christian Six,† Barbara Gabor,† Helmar Go¨rls,‡ Richard Mynott,†
Petra Philipps,† and Walter Leitner*,†
Max-Planck-Institut fu¨r Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mu¨lheim/ Ruhr,
Germany, and Institut fu¨r Anorganische und Analytische Chemie,
Friedrich-Schiller-Universita¨t J ena, August-Bebel-Strasse 2, 07743 J ena, Germany
Received April 2, 1999
Complexes of type [{R2P(CH2)nPR2}Ru(2-Me-all)2] (2-Me-all ) 2-methylpropenyl; R ) Cy,
n ) 1-3, 5a -c; R ) Me, n ) 2, 6; R2 ) -(CH2)4-, n ) 2, 7) have been synthesized from the
reaction of the corresponding electron-rich diphosphines with [(cod)Ru(2-Me-all)2] (4) at 50-
70 °C. The new complexes were fully characterized by multinuclear NMR spectroscopy and
mass spectroscopic techniques. Reacting 4 with Cy2P(CH2)nPCy2 containing hydrocarbon
bridges with n ) 3 (1c) and n ) 4 (1d ) at 95 and 50 °C, respectively, led to [κ2P,P′-{(η3-
C6H8)CyP(CH2)nPCy2}Ru(η3-C8H13)] (n ) 3, 4; 8c,d ) via intramolecular C-H bond activation
and concomitant hydride transfer to cyclooctadiene. The molecular structure of 8c was
unambiguously assigned by multinuclear 1D and 2D NMR spectroscopy and confirmed by
single-crystal X-ray diffraction. The new complexes were tested as homogeneous catalyst
precursors in thermal intermolecular C-H activation processes. In dehydrogenation of
cyclooctane (coa), an initial turnover frequency of 1.9 h-1 was observed using complex 5a
under refluxing conditions without the need of a hydrogen scavenger. A maximum total
number of 5 catalytic turnovers was achieved after 48 h. Ligand degradation by dehydro-
genation was detected under catalytic conditions, presumably initiated via intramolecular
C-H activation as in species of type 8. Attempts to utilize complexes 5 for C-H activation
in scCO2 as the reaction medium resulted in insertion of CO2 into the Ru-allyl moiety,
yielding catalytically inactive ruthenium carboxylates.
In tr od u ction
dehydrogenation7-11 and carbonylation/carboxylation
processes.12
Activation and functionalization of C-H bonds of
simple hydrocarbons by organometallic compounds is
an intensively studied area of considerable theoretical
interest1 and potential practical importance.2 Late
transition metal complexes have been addressed as
promising materials to provide approaches to this
ambitious goal.3-5 Since the pioneering work of Shilov
on homogeneously transition-metal-catalyzed alkane
activation in 1969,6 there has been steady progress
especially in the development of efficient systems for
It has been shown that the unfavorable thermody-
namics of alkane dehydrogenation can be overcome by
photoirradiation,7 by hydrogen transfer from alkane to
sacrificial hydrogen acceptors,7b,c,g,8-10 orsmore recentlys
by thermal hydrogen evolution.11 The dehydrogenation
(3) (a) Sakakura, T. In Homogeneous Transition Metal Catalyzed
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Z., Eds.; Wiley: Chichester, 1992; p 653. (c) Selective Hydrocarbon
Activation; Davies, J . A., Watson, P. C., Liebman, J . F., Greenberg,
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of Alkanes; Hill, C. L., Ed.; Wiley: New York, 1989. (e) Shilov, A. E.
Activation of Saturated Hydrocarbons by Transition Metal Complexes;
D. Reidel: Dordrecht, 1984.
* Corresponding author. Fax: +49-208-306 2993. E-mail: leitner@
mpi-muelheim.mpg.de.
† Max-Planck-Institut fu¨r Kohlenforschung.
‡ Friedrich-Schiller-Universita¨t J ena.
(1) (a) Bromberg, S. E.; Yang, H.; Asplund, M. C.; Lian, T.;
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M. C.; Costas, M.; Blomberg, M. R. A.; Siegbahn, P. E. M. J . Chem.
Phys. 1997, 107, 4318. (c) J ime´nez-Catan˜o, R.; Hall, M. B. Organo-
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10.1021/om990229r CCC: $18.00 © 1999 American Chemical Society
Publication on Web 07/21/1999

Thermal Activation of sp3-C-H Bonds
Organometallics, Vol. 18, No. 17, 1999 3317
Sch em e 1
cally removable ligands and cis-bidentate chelating
phosphines for C-H activation of simple alkanes. Our
initial attempts focused on [(P2)Rh(hfacac)] (P2 ) cis-
bidentate phosphine, hfacac ) κ2O,O′-hexafluoroacetyl-
acetonate), which were indeed found to enable thermal
dehydrogenation of coa, but no catalytic turnover could
be achieved.11d In search for thermally more robust, but
structurally similar fragments of type [(P2)M], we
turned to Ru(II) as the coordination center and found
that complexes [(Cy2P(CH2)nPCy2)Ru(2-Me-all)2] (Cy )
cyclohexyl, n ) 1-3; 5a -c) allow intra- and intermo-
lecular thermal C-H activation, resulting in moderate
catalytic turnover in the absence of hydrogen acceptors.11d
In the present contribution, we report details of the
synthesis, characterization, and reactivity of 5a -c and
related bisallyl complexes of ruthenium. Complexes
[κ2P,P′-{(η3-C6H8)CyP(CH2)nPCy2}Ru(η3-C8H13)] (n ) 3,
4; 8c,d ) resulting from intramolecular sp3 C-H activa-
tion of ligand-bound cyclohexyl groups and containing
a novel terdentate ligand system are described, and the
first X-ray crystal structure analysis of such a complex
is presented for 8c. In addition, we provide a complete
summary of the alkane activation results including a
discussion of plausible deactivation mechanisms. Pre-
liminary results on the use of scCO2 as a reaction
medium for catalytic C-H activation are also discussed
briefly.
of cyclooctane (coa) has been established as an ideal test
reaction to probe the ability of an organometallic
compound to achieve catalytic C-H bond activation.7b,e
In a seminal study, Felkin and co-workers have shown
that polyhydride complexes of ruthenium are active in
thermal transfer-dehydrogenation of coa, but a large
excess of the sacrificial hydrogen acceptor tert-butyl-
ethylene (tbe) was required for the formation of ap-
preciable amounts of cyclooctene (coe) A maximum of
55 catalytic cycles was obtained after 7 days.9a Catalytic
thermal dehydrogenation of coa under evolution of
hydrogen (Scheme 1), however, is still rare and has been
hitherto restricted to precious metal complexes based
on iridium and rhodium.11
On the basis of previous experience with the activa-
tion of the H-H bond in the hydrogenation of CO2,13,14
we were interested in the potential of transition metal
catalyst precursors containing thermolabile or chemi-
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Resu lts a n d Discu ssion
Syn th esis a n d Str u ctu r e of Com p lexes [{R2P -
(CH2)n P R2}Ru (2-Me-a ll)2] 5a -c, 6, a n d 7. Bis(allyl)-
ruthenium complexes with phosphorus donor ligands
have recently found numerous useful applications in
organic synthesis and catalysis.15,16 The new com-
plexes 5a -c are obtained from the reaction of [(cod)-
Ru(2-Me-all)2] (cod ) 1,5-cyclooctadiene; 4) with 1 equiv
of the appropriate bis(dicyclohexylphosphino)alkane
1a -c at 50-70 °C in hexane under an inert atmosphere
of argon (Scheme 2). The initially colorless solutions
turn gradually to yellow-orange upon heating, and the
course of reaction can be readily monitored by 31P NMR
spectroscopy on samples taken from septum-sealed
vessels. Under careful temperature control, 1a -c are
converted with high selectivity to 5a -c as the major
phosphorus-containing species (vide infra).
(8) (a) Baudry, D.; Ephritikhine, M.; Felkin, H.; Zakrzewski, J . J .
Chem. Soc., Chem. Commun. 1982, 1235. (b) Baudry, D.; Ephritikhine,
M.; Felkin, H.; Holmes-Smith, R. J . Chem. Soc., Chem. Commun. 1983,
788.
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Zakrzewski, J . Tetrahedron Lett. 1984, 25, 1279; 1984, 25, 1283. (b)
Felkin, H.; Fillebeen-Khan, T.; Holmes-Smith, R.; Lin, Y. Tetrahedron
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Forrow, N. J .; Guittet, E. J . Chem. Soc., Chem. Commun. 1986, 801.
(d) Burk, M. J .; Crabtree, R. H.; Parnell, C. P.; Uriate, R. J .
Organometallics 1984, 3, 816. (e) Maguire, J . A.; Goldman, A. S. J .
Am. Chem. Soc. 1991, 113, 6706. (f) Maguire, J . A.; Petrillo, A.;
Goldman, A. S. J . Am. Chem. Soc. 1992, 114, 9492. (g) Shih, K.-C.;
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1996, 518, 55. (i) Sakakura, T.; Abe, F.; Tanaka, M. Chem. Lett. 1991,
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(10) Efficient transfer-dehydrogenation of coa using Ir and Rh
complexes containing a terdentate pincer ligand with two P-donor
groups in trans-position10a-c or chelating P∩O phosphino enolate
ligands10d has been reported while this work was in progress: (a)
Gupta, M.; Hagen, C.; Flesher, R. J .; Kaska, W. C.; J ensen, C. M. J .
Chem. Soc., Chem. Commun. 1996, 2083. (b) Gupta, M.; Hagen, C.;
Kaska, W. C.; Cramer, R. E.; J ensen, C. M. J . Am. Chem. Soc. 1997,
840. (c) Gupta, M.; Kaska, W. C.; J ensen, C. M. J . Chem. Soc., Chem.
Commun. 1997, 461. (d) Braunstein, P.; Chauvin, Y.; Na¨hring, J .;
DeCian, A.; Fischer, J .; Tiripicchio, A.; Ugozzoli, F. Organometallics
1996, 15, 5551.
(11) (a) Fujii, T.; Saito, Y. J . Chem. Soc., Chem. Commun. 1990,
757. (b) Fujii, T.; Higashino, Y.; Saito, Y. J . Chem. Soc., Dalton Trans.
1993, 517. (c) Aoki, T.; Crabtree, R. H. Organometallics 1993, 12, 294.
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Rosini, G. P.; Gupta, M.; J ensen, C. M.; Kaska, W. C.; Krogh-J espersen,
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Ed. Engl. 1995, 34, 2207.
Complexes 5a -c precipitate from the reaction mix-
ture upon cooling to room temperature and can be
(14) (a) Hutschka, F.; Dedieu, A.; Eichberger, M.; Fornika, R.;
Leitner, W. J . Am. Chem. Soc. 1997, 119, 4432. (b) Angermund, K.;
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C.; Leitner, W.; Lutz, F. Chem. Eur. J . 1997, 3, 755.
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Soc. A 1971, 16. (b) Geneˆt, J . P.; Pinel, C.; Ratovelomanana-Vidal, V.;
Mallart, S.; Pfister, X.; Can˜o De Andrade, M. C.; Laffitte, J . A.
Tetrahedron: Asymmetry 1994, 5, 665. (c) Geneˆt, J . P. Acros Org. Acta
1995, 1, 4.
(16) (a) Holle, S.; J olly, P. W.; Kuhnigk, J . J . Organomet. Chem.
1997, 543, 255. (b) Picquet, M.; Bruneau, C.; Dixneuf, P. H. J . Chem.
Soc., Chem. Commun. 1997, 1201. (c) Bruneau, C.; Dixneuf, P. H. J .
Chem. Soc., Chem. Commun. 1997, 507. (d) Doucet, H.; Ho¨fer, J .;
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133, 939. (e) Doucet, H.; Martin-Vaca, B.; Bruneau, C.; Dixneuf, P. H.
J . Org. Chem. 1995, 60, 7247. (f) Kondo, T.; Ono, H.; Satake, N.;
Mitsudo, T.; Watanabe, Y. Organometallics 1995, 14, 1945. (g) Geneˆt,
J . P.; Pinel, C.; Ratovelomanana-Vidal, V.; Mallart, S.; Pfister, X.;
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1998, 567, 163.

3318 Organometallics, Vol. 18, No. 17, 1999
Six et al.
Sch em e 2
isolated as off-white or pale yellow crystals in 75-80%
total yield by filtration and further concentration of the
mother liquors. All complexes are moderately air-stable
in the solid state and can be stored over months without
decomposition under argon atmosphere at room tem-
perature. 5b and 5c are poorly to moderately soluble
in hydrocarbons and aromatic solvents, whereas 5a is
almost insoluble in most organic solvents at ambient
temperature. The solubility of 5a -c is considerably
higher in chlorinated solvents, but the complexes tend
to decompose in these solutions upon standing.
are shifted downfield, appearing as doublets of virtual
triplets at δ 2.58 for the two syn-allylic protons in cis-
cis position to phosphorus and as apparent doublets at
δ 1.39 for the two anti-congeners. A doublet at δ 1.64
results from the resonances of the two syn-allylic
protons in cis-trans position to phosphorus; the signal
for the two anti-analogues is partly obscured at δ 1.20.
The six methyl protons give rise to a characteristic
sharp singlet at δ 2.21. The signals for the protons of
the methylene units of the diphosphine backbone are
located at δ 1.90 and δ 1.68 for the four protons at the
two outer positions and at δ 1.84 for the two protons at
the middle carbon.
The new complexes 5a -c were fully characterized by
NMR and IR spectroscopy as well as by mass spectro-
scopic (MS) and elemental analysis. The molecular ions
are detectable in the MS spectra of all three complexes
and similar fragmentation patterns are observed, indi-
cating loss of the Me-allyl fragments, cyclohexyl groups,
and PCy2 units. Considerable H-shuffling during the
analysis results in very broad line distributions around
each characteristic mass, making exact assignments im-
possible. Most notably, however, significant amounts of
benzene can be detected in the mass spectra which re-
sult from cyclohexyl dehydrogenation4e,17-19 and subse-
quent P-Caryl cleavage;20 this observation indicates al-
ready a high reactivity of 5a -c for C-H bond activation.
Consistent with a C2 symmetrical molecular struc-
ture, C6D6 solutions of complexes 5a -c give rise to
singlets in the expected region of the 31P{1H} NMR
spectra. The downfield shift compared to the free ligands
1a -c shows the typical dependence on the size of the
P-Ru-P chelate ring.21 The 1H and 13C resonances
were fully assigned on basis of 2D homonuclear and
heteronuclear correlation spectra and selective 31P de-
coupling experiments for 5c as the prototype of com-
plexes [(P2)Ru(2-Me-all)2]. The 1H NMR spectrum is
dominated by an area of overlapping multiplets between
δ 1.0 and 1.9 arising from the cyclohexyl protons,
whereby the definition of Cy1 and Cy2 is arbitrary (see
Scheme 4 for numbering). The allylic proton resonances
Moving from downfield chemical shifts to higher field
in the 13C{1H} spectrum, one first notes a singlet of the
central allylic carbon at δ 93.0, which is absent in the
DEPT spectra. The 2-methyl groups resonate as a
singlet at δ 26.7, whereas the allylic methylene units
give rise to virtual triplets at δ 39.7 in cis,trans position
2
2
to phosphorus (| J P-C + J P′-C| ) 19.5 Hz) and δ 33.8
2
in cis,cis position (| J P-C + 2J P′-C| ) 7.9 Hz). The carbon
atoms of the cyclohexyl rings directly attached to
phosphorus (Cy-C1) appear as the A parts of two
degenerated AXX′ spin systems centered at δ 41.7 and
δ 38.7, respectively. The remaining cyclohexylic carbons
are grouped together as singlets at δ 31.3-30.5 for Cy-
C2 and at δ 27.3 and 27.1 for Cy-C4 and as virtual
triplets at δ 28.9-28.0 for Cy-C3. The bridging meth-
ylene units exhibit the highest field 13C resonances and
give rise to a virtual triplet at δ 21.7 for the two carbons
connected to phosphorus and a singlet at δ 20.4 for the
middle carbon.
Slow crystallization (approximately 12-20 weeks) at
-40 °C of a highly diluted mother liquor of complex 5b
in hexane led to single crystals that were suitable for
single-crystal X-ray diffraction analysis. The molecular
structure of 5b, which was found to crystallize in the
monoclinic crystal system, is shown together with
selected structural parameters in Figure 1. The ruthe-
nium central atom is coordinated to two phosphorus
atoms and two η3-allyl units. The coordination geometry
can be considered distorted tetrahedral (P donor atoms
+ coordination centers of the η3-allyl units) or distorted
octahedral (P donor atoms + outer allylic carbon atoms).
The Ru-P bond distances of 5b (Figure 1) fall within
the range reported for the related complexes.15b,22
Owing to the five-membered chelate ring, the P1-Ru-
P2 angle differs significantly from an ideal tetrahedral
angle, as observed also with the analogous (S,S)-
CHIRAPHOS complex (85.0°)15b and in contrast to the
(17) Dehydrogenation of cyclohexyl groups in monodentate Cy3P to
give η3-cyclohexenyl units: (a) Christ, M. L.; Sabo-EÄ tienne, S.; Chau-
dret, B. Organometallics 1995, 14, 1082. (b) Borowski, A.; Sabo-
EÄ tienne, S.; Christ, M. L.; Donnadieu, B.; Chaudret, B. Organometallics
1996, 15, 1427.
(18) Chaudret, B.; Dagnac, P.; Labroue, D.; Sabo-EÄ tienne, S. New
J . Chem. 1996, 20, 1137.
(19) For dehydrogenation of cyclohexyl phosphine ligands to yield
a coordinated CdC bond see: Hietkamp, S.; Hufkens, D. J .; Vrieze,
K. J . Organomet. Chem. 1978, 152, 347.
(20) (a) Ortiz, J . V.; Havlas, J .; Hoffmann, R. Helv. Chim. Acta 1984,
67, 1. (b) Garrou, P. E. Chem. Rev. 1985, 85, 171. (c) Recent example
for Ru-Ar bond cleavage: Frediani, P.; Faggi, C.; Papaleo, S.; Salvini,
A.; Bianchi, M.; Piacenti, F.; Ianelli, S.; Nardelli, M. J . Organomet.
Chem. 1997, 536-537, 123.
(21) Garrou, P. E. Chem. Rev. 1981, 81, 229.
(22) Smith, A. E. Inorg. Chem. 1972, 11, 2306.

Thermal Activation of sp3-C-H Bonds
Organometallics, Vol. 18, No. 17, 1999 3319
pathway even at lower temperatures if the butylene-
bridged bisphosphane 1d is reacted with the precursor
4 (Scheme 3). After 24 h at 50 °C, complex 8d can be
isolated in pure form by fractional crystallization in 32%
yield. Monitoring the course of reaction by 31P NMR
spectroscopy showed no singlet of significant intensity
in the region expected for complex 5d .24
The tendency for intramolecular H-shuffling under
conditions of mass spectroscopy is even more pro-
nounced with compounds 8c and 8d compared to the
related bisallyl complexes 5-7. Only 8d allows the de-
tection of a weak molecular ion, and in both cases, there
is evidence for the formation of degradation products
containing more than one ruthenium center. Most sig-
nificantly, cyclooctadiene and cyclooctatetraene can be
identified as fragmentation products, and the base peak
under typical EI conditions corresponds to the mass of
benzene. In the case of 8c, a peak at m/e ) 532 (13%)
suggests formation of the fragment [{Cy2P(CH2)3P(Cy)-
Ph}Ru] in which one cyclohexyl group has been dehy-
drogenated completely to a phenyl substituent.
The 31P{1H} NMR spectrum of 8c consists of two
doublets at δ 72.9 and 27.7 (2J P-P′ ) 34.3 Hz), whereby
the strongly downfield shifted resonance results from
the P atom which is part of two chelate rings. Detailed
assignment of the 1H NMR resonances was possible
with the aid of TOCSY and NOESY spectra (see Scheme
4 for numbering). The allylic proton resonances of the
cyclohexenyl group are located at δ 5.56 for the central
hydrogen and at δ 3.66 and δ 1.54 in cis,cis and cis,trans
position to the P atoms, respectively. The allylic moiety
of the cyclooctenyl ligand is characterized by a doublet
of virtual triplets at δ 4.76 for the central proton and
multiplets at δ 3.81 and δ 3.18 for the outer allylic
hydrogen atoms. The highly unsymmetrical coordina-
tion mode of the tridentate ligand leads to six distinct
signals for the diastereotopic protons at each of the
methylene groups in the backbone of the phosphine unit.
In agreement with structure 8c, the 13C{1H} spectrum
shows 35 distinct signals with 25 methylene and 10
methine groups according to DEPT analysis. The allyl
moiety in the cyclohexenyl ring is characterized by three
apparent doublets at δ 75.9 (J ) 1.4 Hz) for the central
carbon and at δ 50.1 (J ) 3.5 Hz) and δ 63.3 (J ) 31.1
Hz) in cis,cis and cis,trans position to the P atoms,
respectively. The phosphorus attached carbon atom of
the cyclohexenyl ring exhibits a chemical shift similar
to those of the other Cy groups, but its coupling constant
1J C-H ) 132 Hz differs significantly from typical values
(122-124 Hz). The allylic carbon atoms of the cycloocte-
nyl ligand give rise to a singlet at δ 83.1 for the central
position and slightly broadened resonances at δ 48.4 in
cis,cis position and δ 47.8 (d, J ) 28 Hz) in cis,trans
position. The methylene groups in R and â position to
the allyl moiety resonate between δ 36.1 and 28.1. The
high-field shift of δ 25.9 for the γ-CH2 group is typical
for a boat conformation of the eight-membered ring,
which is also supported by the large separation of the
F igu r e 1. Molecular structure of [{Cy2P(CH2)2PCy2}Ru-
(2-Me-all)2] (5b) as determined by single-crystal X-ray
diffraction analysis. Heavy atoms are represented as
spheres, and hydrogen atoms have been omitted for clarity.
D(1) and D(2) denote the hypothetical coordinative center
of the two η3-allyl units. Selected bond distances (Å) and
angles (deg): Ru-P(1), 2.335(1); Ru-P(2), 2.333(1); Ru-
D(1) (C1,C2,C3), 1.952(1); Ru-D(2) (C5,C6,C7), 1.946(1);
Ru-C(1), 2.219(4); Ru-C(2), 2.175(4); Ru-C(3), 2.248(5);
Ru-C(5), 2.218(4); Ru-C(6), 2.174(4); Ru-C(7), 2.242(5);
C(1)-C(2), 1.416(6); C(2)-C(3), 1.396(6); C(2)-C(4), 1.512-
(6); C(5)-C(6), 1.415(6); C(6)-C(7), 1.431(7); C(6)-C(8),
1.503(6); P(1)-Ru-P(2), 85.03(4); D(1)-Ru-D(2), 120.10-
(5); C(1)-C(2)-C(3), 118.6(4); C(5)-C(6)-C(7), 117.5(4).
monodentate phosphine coordinated complex [(PPh3)2-
Ru(all)2] (109.9°).22 The angle between the two allylic
moieties is concomitantly widened to approximately
120° in the complexes with the chelating phosphines.
The Ru-C distances follow the typical motive of short
bonds to the outer carbons and longer bonds to the
central carbon of the η3-allyl ligand. The C-C bond
lengths within the 2-Me-allyl fragment are in the
expected range.
The related bisphosphine ruthenium bisallyl com-
plexes 615a and 7 were prepared similarly from 4 and
1,2-bis(dimethylphosphino)ethane (2) or 1,2-bis(1-phos-
pholano)ethane (3), respectively. In the case of ligand
3, the course of reaction differed remarkably from those
observed with other chelating phosphines, but complex
7 could be isolated as a mixture containing small
amounts of 4 according to NMR spectroscopic analyses.
This material was used without further purification for
catalytic tests.
Syn th esis a n d Str u ctu r e of Com p lexes [K2P ,P ′-
{(η3-C6H8)CyP (CH2)n P Cy2}Ru (η3-C8H13)] 8c,d . 31P
NMR monitoring of the reaction of 4 with 1c indicated
formation of a second product at temperatures above
55 °C. This species was formed in a clean reaction on
the expense of 5c. The secondary product precipitated
from hexane at high temperature and could be isolated
in pure form after 10 h at 95 °C in 29% yield by filtering
the hot reaction mixture. The new compound was
unambiguously characterized as the η3-cyclooctenyl
complex 8c (Scheme 3) by one- and two-dimensional
multinuclear NMR spectroscopic techniques and X-ray
crystal structure analysis. The most salient feature of
its structure is a unique terdentate κ2P,P′-(η3-allyl) lig-
and arising from intramolecular cleavage of three ad-
jacent C-H bonds in one of the cyclohexyl rings at-
tached to the phosphorus donor of a chelating bisphos-
phane.17,18,23 The intermolecular C-H-activation leading
to a κ2P,P′-(η3-allyl) ligand becomes the predominant
(23) For intramolecular activation of benzylic sp3 C-H in Ru-allyl
complexes see: Hirano, M.; Kurata, N.; Marumo, T.; Komiya, S.
Organometallics 1998, 17, 501.
(24) A chemical shift in the range of δ 30 ( 10 is estimated for 5d
from the 31P NMR data of 1a -c together with the typical ring
contribution of seven-membered chelates.

3320 Organometallics, Vol. 18, No. 17, 1999
Six et al.
Sch em e 3
Ta ble 1. Ru th en iu m -Med ia ted Th er m a l
Deh yd r ogen a tion of Cycloocta n e (coa )
attached exo- and endo-proton resonances (δ 1.51 and
2.57, respectively).25
complex
c[Ru] [mmol l-1
]
t [h]
Ta [°C]
TONb
The molecular structure of 8c, as unambiguously
derived from NMR measurements in solution, is also
confirmed for the solid state by X-ray crystal structure
analysis. Similar to 5b, complex 8c crystallizes in the
monoclinic crystal system. The solubility properties of
8c allowed only very small crystals to be grown, but the
structure could still be solved with high accuracy and
all hydrogen atoms were located and fully refined. As
in 5c, the ruthenium center in 8c is surrounded by two
allyl fragments and two P-donor atoms and the coordi-
nation geometry can be described in a similar manner.
However, some significant distortions arise from the fact
that one of the allyl ligands is part of a cyclohexenyl
ring attached to a phosphorus donor atom of the
chelating phosphine.
4
12.9
6.5
7.0
7.0
4.6
5.7
6.3
6.1
12.6
5.0
5.4
4.8
4.6
48
48
1
170
170
120
120
170
170
170
170
170
170
170
170
170
0.5
5.2
0.6
1.3
3.2
2.5
4.0
1.4
0.6
0.5
1.3
1.2
5.5
5a
5a
5a
5b
5c
5c
6
49
52
48
168
48
48
48
50
48
48
7
8c
8d
9b
9c
a
b
Bath temperature. Total amount of coe per mole Ru-metal
according to GC analysis.
(Scheme 1). In a standard procedure, carefully purified
coa (g99.993 GC purity) was heated to 170 ( 2 °C for
48 h in the presence of catalytic amounts of the
appropriate ruthenium complex in a small Schlenk tube
equipped with a reflux condenser. An inert atmosphere
was ensured throughout the experiment by passing a
gentle stream of argon over the reaction mixture on top
of the reflux condenser. The refluxing conditions to-
gether with the gas stream were expected to remove any
hydrogen and other gaseous products from the reaction
vessel.11 After cooling and removal of metal-containing
species by passing the solution through a short pad of
silica or by Kugelrohr distillation,26 the liquid phase was
quantitatively analyzed by gas chromatography using
cyclohexane as an internal standard. Results are sum-
marized in Table 1.
The angle at the middle carbon of the cyclohexenyl
fragment, C(14)-C(15)-C(16), is considerably larger
than the corresponding angles in the cylooctenyl ring
or the open allyl ligands in complex 5c. Furthermore,
the cyclohexyl group has to bend toward the ruthenium
atom to be able to act as an additional ligand. This is
reflected in a small angle C(12)-P(1)-Ru below 100°,
whereas the C-P-Ru angles for the nonactivated
cyclohexyl phosphino groups are typically around 120°.
Similarly, the angles between C(13)-C(12)-P(1) and
C(17)-C(12)-P(1) are significantly smaller than the
corresponding angles in the other cyclohexyl rings (113-
115°). At the same time, the phosphorus atom connected
to the activated cyclohexyl ring moves away from
ruthenium, resulting in a Ru-P(1) distances that is ca.
0.48 Å longer than the Cy2P-Ru distances in 8c and
5c. The angle between the two coordination centers of
the two η3-allyl fragments in 8c is 122°, i.e., slightly
larger than the corresponding angle in 5c, although the
larger P-Ru-P angle in 8c would be expected to lead
to a smaller angle if the two allyl moieties were to adopt
their positions without additional constraints.
Complexes 5a -c were indeed found to allow catalytic
formation of coe by thermal dehydrogenation of coa, and
the reaction was shown to occur at homogeneously
dissolved metal species.11d The methylene-bridged com-
plex 5a exhibits the highest reaction rates with a
turnover frequency in the initial state of up to 1.9 h-1
.
The total number of catalytic turnovers (TON) after 48
h reaches a maximum of 5 using 5a as the catalyst
precursor. The length of the -(CH2)n- spacer has only
a small influence on the catalytic efficiency of 5a -c,
whereby the catalytic efficiency decreases somewhat in
the order 5a > 5b > 5c. With all three complexes, a
considerable decrease of the rate of coe formation is
observed within the first 5 h of reaction (Figure 3),
indicating rapid catalyst deactivation by thermal
degradation11d or product inhibition.27
Ca ta lytic Th er m a l In ter m olecu la r Activa tion of
C-H bon d s w ith Ru th en iu m Com p lexes 5-8. The
unexpected isolation of compounds 8 and the results of
the mass spectroscopic investigations of complexes 5
indicated a high activity of the fragment [{Cy2P(CH2)n-
PCy2}Ru] for thermal cleavage of nonactivated sp3 C-H
bonds. This encouraged us to investigate the potential
of ruthenium complexes 5-8 for intermolecular pro-
cesses of this type using the dehydrogenation of coa in
the absence of a hydrogen scavenger as a test reaction
(26) Both methodologies gave consistent results which were identi-
cal to results from direct injection of the mixture in control experi-
ments.
(25) (a) Lange, S.; Wittmann, K.; Gabor, B.; Mynott, R.; Leitner, W.
Tetrahedron: Asymmetry 1998, 9, 475, and references therein. (b) For
a related bisphosphine Ru-cyclooctenyl complex see: Wiles, J . A.; Lee,
C. E.; McDonald, R.; Bergens, S. Organometallics 1996, 15, 3782.
(27) Addition of coe has been shown to retard the dehydrogenation
of coa with Ir complexes containing pincer ligands.11e

Thermal Activation of sp3-C-H Bonds
Organometallics, Vol. 18, No. 17, 1999 3321
complexes 6 and 7 lacking a potentially cleavable C-H
group in close proximity to the metal center give even
lower yields of coe than 5b. Therefore, other thermal
deactivation pathways and/or product inhibition must
also play an important role in limiting the catalytic
efficiency of the ruthenium bisallyl complexes.
Despite their limitations, compounds 5-9 are the first
examples of ruthenium complexes that have been shown
to allow thermal catalytic dehydrogenation of coa in the
absence of external hydrogen acceptors. It cannot be a
priori excluded, however, that the two allylic ligands act
as hydrogen scavengers accounting for up to three
catalytic turnovers. We have therefore analyzed the
liquid phase and the gas phase of typical experiments
for C4 components by GC-MS. After heating 5b in
cyclooctane to 170 °C for 48 h in a closed vessel,
isobutane and isobutene could be detected, but no direct
correlation was found between the amounts of coe and
isobutane.
Figu r e 2. Molecular structureof[κ2P,P′-{(η3-C6H8)CyP(CH2)3-
PCy2}Ru(η3-C8H13)] (8c) as determined by single-crystal
X-ray diffraction analysis. Heavy atoms are represented
as spheres, and hydrogen atoms have been omitted for
clarity. D(1) and D(2) denote the hypothetical coordinative
center of the two η3-allyl units of the cyclooctenyl and
cyclohexenyl ligand, respectively. Selected bond distances
(Å) and angles (deg): Ru-P(1), 2.817(1); Ru-P(2), 2.341-
(1); Ru-D(1) (C4,C5,C6) 1.979(1); Ru-D(2) (C14,C15,C16)
1.981(1); Ru-C(4), 2.270(4); Ru-C(5), 2.151(3); Ru-C(6),
2.311(4); Ru-C(14), 2.261(4); Ru-C(15), 2.141(4); Ru-
C(16), 2.305(5); P(1)-C(12), 1.842(4); C(12)-C(13), 1.530-
(5); C(13)-C(14), 1.519(5); C(14)-C(15), 1.410(5); C(15)-
C(16), 1.413(5); C(16)-C(17), 1.514(5); C(17)-C(12), 1.526(5);
P(1)-Ru-P(2), 92.90(3); D(1)-Ru-D(2) 122.6(2); C(4)-
C(5)-C(6), 122.7(4); C(14)-C(15)-C(16), 116.5(4).
If tert-butylethylene (tbe) was added as a potential
hydrogen acceptor,9a no enhancement of the formation
of coe was observed under various conditions. When a
coa/tbe solution of complex 5b was heated to 120 °C in
a closed system, only 0.8 catalytic turnover for coe
formation was achieved, but almost 4 equiv of tbe were
hydrogenated to tert-butylethane (tba). The excess
hydrogen required for the reduction of tbe is most likely
delivered by dehydrogenative degradation of the ligand’s
cyclohexyl groups. Highly efficient hydrogenation of tbe
occurred without any coe formation when transfer-
dehydrogenation was attempted with 5b in the presence
of H2 under the conditions developed by Goldman.9f
These results led to the conclusion that the reduction
of tbe and the dehydrogenation of coa with complex 5b
are independent reactions, and transfer-dehydrogena-
tion appears to play no significant role for the coe
formation with complexes 5.
Preliminary experiments were carried out to inves-
tigate the possible coupling of the intermolecular C-H
activation at complexes 5 with subsequent reactions
leading to functionalization other than dehydrogenation.
In particular, we were interested in the potential of
formal CO2 insertion into the C-H bond of the alkane
substrate.13 Thus a mixture of a complex of type 5 and
coa was pressurized with CO2 in a window-equipped
stainless steel autoclave and heated to temperatures
that were sufficiently high to allow C-H cleavage in
the absence of CO2. The resulting temperatures and
pressures were well above the critical data of CO2 (Tc
) 31 °C, pc ) 73.8 bar) and homogeneous slightly yellow
solutions were observed in all cases. However, GC
analysis revealed no evidence for the formation of
cyclooctane carboxylic acid or any other functionalized
derivative of coa under various conditions. Furthermore,
dehydrogenation of coa and reduction of tbe were also
suppressed completely in the presence of CO2.
F igu r e 3. Time dependence of the thermal dehydrogena-
tion of cyclooctane (coa) using complexes [{Cy2P(CH2)n-
PCy2}Ru(2-Me-all)2] (5a , n ) 1; 5b, n ) 2; 5c, n ) 3) as
catalysts at 170 °C bath temperature.
Complex 8c is considerably less effective for coa
dehydrogenation than its precursor 5c. Furthermore,
benzene could be detected by GC-MS in the final
reaction mixtures after removal of all metal-containing
species. These findings together with the results de-
scribed above strongly suggest that ligand degradation
via intramolecular C-H activation and subsequent
P-aryl cleavage is one possible pathway for catalyst
deactivation with complexes 5. We have therefore
extended our investigations to related bisallyl complexes
with basic chelating phosphines containing substituents
other than cyclohexyl at phosphorus. The isopropyl-
substituted bisallyl complexes [{iPr2P(CH2)2PiPr2}Ru-
(η3-C3H5)2] (9b ) and [{iPr2P(CH2)3PiPr2}Ru(η3-C4H7)2]
(9c)15a are also catalytically active, with efficiency for
coe formation similar to their congeners of type 5. The
After venting the reaction mixtures, small amounts
of a yellow solid could be isolated from the reactor.
FT-IR spectroscopic analysis of this solid suggested the
presence of a metal complex containing CdO units (two
strong bands at 1652 and 1525 cm-1), indicating the
incorporation of CO2 into the organometallic starting
material 5c. Therefore, NMR studies were carried out
to investigate the reactivity of 5c toward CO2. 31P{1H}

3322 Organometallics, Vol. 18, No. 17, 1999
Six et al.
RTX-1 capillary column with a flame ionization detector. The
identities of alkanes and alkenes were further confirmed by
comparison with authentic samples and GC/MS on a Finnigan
MAT SSQ 7000 using a 60 m OV1 column. Mass spectroscopy
of solid ruthenium phosphine complexes was performed on a
Finnigan MAT 8200 via fractional evaporation/direct injection.
Mass values are given for the 102Ru isotope; [Ru1]+ designates
characteristic fragments containing one Ru center, but cannot
be assigned unambiguously owing to H-shuffling. Elemental
analyses were carried out in the Mikroanalytische Laborato-
rien Dornis und Kolbe, Mu¨lheim/Ruhr. Melting points of the
ruthenium complexes were measured via differential scanning
calorimetry (DSC) on a Mettler Toledo DSC 820.
High -P r essu r e Equ ip m en t. Some of the transfer-dehy-
drogenation experiments and the attempts for functionaliza-
tion reactions with carbon dioxide were performed in two steel
autoclaves of 27 or 225 mL volume, respectively. The reactors
were equipped with two thick-walled glass windows, two
valves, internal thermocouple, pressure gauge, and Teflon-
coated stirring bar. NMR experiments with gaseous CO2 were
performed in a high-pressure 5 mm Wilmad NMR tube with
a PTFE-needle valve.
Ma ter ia ls. Solvents for synthesis and crystallization were
dried and distilled under argon prior to use. Hexane and
pentane were distilled from sodium/potassium alloy, and
benzene was distilled from CaH2.31 Traces of unsaturated
hydrocarbons were removed from cyclooctane by the following
procedure: the cycloalkane was treated with an ice-cooled
mixture of concentrated sulfuric and nitric acids and washed
several times with concentrated sulfuric acid until no further
coloration developed in the acid layer. It was then washed
alternately with water and aqueous Na2CO3 until neutral.31
The organic phase was passed through a column of activated
Al2O3, purified by preparative GC, and distilled from sodium.
The purity of the cyclooctane obtained from this procedure was
verified to be greater than 99.99% by analytical GC prior to
use. tert-Butylethylene (tbe) was distilled and stored under
argon over 3 Å molecular sieves.
The commercial starting materials [(cod)Ru(2-Me-all)2] (4)
and 1,1-bis(dicyclohexylphosphino)methane (1a ) were pur-
chased from Acros Organics and STREM Chemicals, respec-
tively, and used as received. The ligands 1,2-bis(dicyclohexyl-
phosphino)ethane (1b), 1,3-bis(dicyclohexylphosphino)propane
(1c), and 1,4-bis(dicyclohexylphosphino)butane (1d ) were syn-
thesized according to literature procedures.32 1,2-Bis(dimeth-
ylphosphino)ethane (2) was synthesized by the method of
Chatt and Hussain.33 1,2-Bis(1-phospholano)ethane (3) was
obtained in 78% purity by addition of 2,2-dioxo-1,3,2-dioxathie-
pane to H2PCH2CH2PH2 following the procedure of Field.34 The
impurity consisted mainly of the monophospholane, which
could not be separated effectively on the small scale. The
complexes 9b and 9c were kindly provided by Prof. P. W. J olly
and co-workers.16a
NMR spectroscopic monitoring of the reaction of 5c with
13CO2 (5 bar) in C6D6 solution revealed the disappear-
ance of the characteristic signals of the starting complex
under formation of various new, partly broadened
signals. After 36 h at 80-90 °C, the spectrum was
dominated by two sets of signals each consisting of two
sharp doublets (δ 105.5/32.7, 2J PP′ ) 40 Hz; δ 93.3/30.1,
2J PP′ ) 40 Hz) in a 3:1 ratio. Two strong new signals
appeared also in the corresponding 13C{1H} NMR
spectrum at δ 178.3 and 182.6, integrating in the same
ratio. Although no exact structural assignment is pos-
sible on the basis of these data, they are most consistent
with the formation of two isomeric carboxylate com-
plexes formed by insertion of CO2 into the ruthenium
allyl moieties, similar to what has been observed for
related nickel and palladium compounds by Wilke28 and
J olly,29 respectively. The lack of catalytic activity in the
presence of compressed CO2 arises therefore most likely
from the reaction of the precursor molecules 5 with the
heterocumulene, which prevents thermal removal of the
allyl moieties to give the unsaturated species required
for C-H bond cleavage.30
Con clu sion
In conclusion, a series of new ruthenium bismethallyl
complexes [{R2P(CH2)nPR2}Ru(η3-C4H7)2] bearing chelat-
ing bidentate phosphines was synthesized, and it was
shown that these complexes are effective precursors for
thermal cleavage of nonactivated sp3 C-H bonds. The
reaction can proceed catalytically, as demonstrated for
the dehydrogenation of cyclooctane to cyclooctene. In-
tramolecular C-H activation occurs very readily for
complexes containing cyclohexyl-substituted phosphines
with three or more methylene groups in the backbone
of the chelating ligand. The activation of three adjacent
C-H bonds of one cyclohexyl ring leads to unprec-
edented terdentate κ2P,P′-(η3-cyclohexyl) ligands. The
formation of such species must be taken into account
whenever highly coordinately unsaturated fragments of
type [{Cy2P(CH2)nPCy2}M] (n ) 3, M ) platinum group
metal) are formed and may provide a possible low-
energy pathway for catalyst deactivation in catalytic
processes involving such intermediates.
Exp er im en ta l Section
Gen er a l Com m en ts. All manipulations were carried out
in an atmosphere of argon using standard Schlenk techniques
in flame-dried glassware. Some of the experiments involve the
use of closed glass reactors or compressed gases and require
appropriate safety precautions.
An a lytica l Tech n iqu es. NMR spectra were recorded on a
BRUKER AC 200, working at 200.1 MHz (1H), 50.3 MHz (13C),
and 81.0 MHz (31P), unless otherwise noted. Chemical shifts
are given relative to TMS using the solvent resonances as
internal standards for 1H and 13C, and to H3PO4 as external
standard for 31P. Gas chromatographic analyses for dehydro-
genation experiments were performed with a temperature-
programmed Hewlett-Packard 5890 Chem GC using a 60m
The following numbering scheme is used for the assignment
of characteristic NMR resonances in compounds 5a -c and
8c,d . Individual cyclohexyl carbons are denoted with super-
script greek letters, if distinction was possible. Note that the
numbering scheme (Scheme 4) is different from the one used
in X-ray analyses depicted in Figures 1 and 2.
[(1a )Ru (2-Me-a ll)2] (5a ). 4 (311 mg, 0.974 mmol) and 1a
(398 mg, 1 equiv) were dissolved in hexane (40 mL) in a three-
(31) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon: Oxford, 1988.
(32) (a) Issleib, K.; Mu¨ller, D. W. Chem. Ber. 1959, 92, 3175. (b)
Dinjus, E.; Leitner, W. Appl. Organomet. Chem. 1995, 9, 43. (c)
Priemer, H. Ph.D. Thesis, Ruhr-Universita¨t Bochum, 1987.
(33) Burt, R. J .; Chatt, J .; Hussain, W.; Leigh, G. J . J . Organomet.
Chem. 1979, 182, 203.
(34) (a) Field, L. D.; Thomas, I. P. Inorg. Chem. 1996, 35, 2546. (b)
For the solid-state structure of 2,2-dioxo-1,3,2-dioxathiepane see:
Kru¨ger, C.; Kessler, M.; Six, C.; Leitner, W. Acta Crystallogr. 1998,
C54, 389.
(28) Wilke, G. Angew. Chem. 1988, 100, 189; Angew. Chem., Int.
Ed. Engl. 1988, 27, 185.
(29) J olly, P. W. Angew. Chem. 1985, 97, 279; Angew. Chem., Int.
Ed. Engl. 1985, 24, 283.
(30) Supercritical CO2 has been successfully used as an inert solvent
for stoichiometric C-H activation with 16e cyclopentadienyl com-
plexes: J obling, M.; Howdle, S. M.; Healy, M. A.; Poliakoff, M. J . Chem.
Soc., Chem. Commun. 1990, 1287.

Thermal Activation of sp3-C-H Bonds
Organometallics, Vol. 18, No. 17, 1999 3323
Sch em e 4
1
necked flask equipped with argon inlet, reflux condenser, and
a rubber septum. A solid started to precipitate after the
colorless solution was heated to 50 °C (bath temperature) for
5 h. The resulting mixture was stirred at this temperature
until the 31P{1H} NMR spectrum of a sample taken from the
reaction mixture by syringe indicated quantitative consump-
tion of 4 (13 h). After cooling to room temperature, the off-
white precipitate was filtered off, washed with hexane (5 mL)
and dried in vacuo to give almost colorless micorcrystals of
5a . The bright yellow filtrate was concentrated in vacuo to 3
mL, affording a further crop of 5a . Yield: 475 mg (0.766 mmol,
79%). Mp: 200 °C (dec 211 °C). Anal. Found: C, 63.77; H, 9.68;
P, 10.20. Calcd for C33H60P2Ru: C, 63.94; H, 9.76; P, 9.99. EI-
w; 569 w; 554 m; 523 s cm-1. H NMR (C6D6, 300.1 MHz, 302
2
K): δ 2.52 (d, J Hax-Heq ) 8.5 Hz, 2H, Cy1-H2′eq), 2.25 (s, 6H,
η3-CH2C(CH3)CH2), 2.21 (partly obscured d, 2H, η3-CH2C(CH3)-
2
3
CH2 syn, cis,cis to P), 2.15 (d, | J P-H + J P′-H| ) 8.5 Hz, 2H,
PCH2), 2.06 (2H, Cy1-H3′eq), 2.04 (2H, η3-CH2C(CH3)CH2 syn,
cis,trans to P), 2.03 (2H, Cy1-H3eq), 2.01 (2H, Cy1-H1), 1.87
(2H, Cy2-H2eq), 1.83 (2H, Cy2-H1), 1.76 (2H, Cy1-H2eq), 1.74
(2H, Cy1-H3ax), 1.63 (2H, Cy1-H4eq and 2H, Cy2-H2′eq), 1.57
(2H, Cy2-H3eq and 2H, Cy2-H3′eq), 1.51 (2H, η3-CH2C(CH3)-
CH2 anti, cis,cis to P), 1.47 (2H, Cy1-H2′ax and 2H, Cy2-H4eq
and 2H, Cy2-H2ax), 1.35 (2H, Cy2-H2′ax), 1.30 (2H, Cy1-H3′ax
and 2H, η3-CH2C(CH3)CH2 anti, cis,trans to P), 1.21 (2H, Cy1-
H2ax), 1.18 (2H, Cy1-H4ax), 1.09 (2H, PCH2), 1.05 (2H, Cy2-
MS (temperature of vaporization: 165 °C): m/e ) 620 (M•+
,
H
4ax), 1.02 (2H, Cy2-H3ax and 2H, Cy2-H3′ax). 13C{1H} NMR
18), 505 ([Ru1]+, 100), 421 ([Ru1]+, 22), 339 ([Ru1]+, 10), 78
(C6H6+, 13), 56 (C4H8+, 16), 41 (C3H5+, 28). IR (KBr disk): 3044
m; 2991 m; 2926 s; 2846 s; 1718 w; 1443 s; 1366 m; 1348 m;
1331 m; 1292 w; 1263 m; 1224 w; 1196 m; 1171 m; 1117 m;
1068 s; 1022 s; 1001 s; 888 m; 848 s; 836 s; 763 s; 740 s; 674
(C6D6, 75.5 MHz, 302 K): δ 93.4 (s, η3-CH2C(CH3)CH2), 46.9
1
3
1
(vt, | J P-C + J P′-C| ) 26.9 Hz, J C-H ) 121 ( 2 Hz, Cy2-C1),
1
38.0 (partly obscured vt, J C-H ) 124 ( 2 Hz, Cy1-C1), 35.3
(m, | J P-C + 2J P′-C| ) 20.3 Hz, 1J C-H ≈ 150 Hz, η3-CH2C(CH3)-
2
2
CH2 cis,trans to P), 32.2 (vt, | J P-C + 2J P′-C| ) 7.1 Hz, 1J C-H
)
+
≈
m; 558 w; 525 m; 508 m; 466 m cm-1
.
1H NMR (C6D6, 400.1
153 ( 3 Hz, η3-CH2C(CH3)CH2 cis,cis to P), 31.7 (vt, | J P-C
2
MHz, 300 K): δ 3.01 (m, 2H, η3-CH2C(CH3)CH2 syn, cis,cis to
P and 2H, PCH2), 2.36 (d, 2J Hax-Heq ) 13.2 Hz, 2H, Cy1-H2eq),
2.19 (s, 6H, η3-CH2C(CH3)CH2), 1.98-0.85 (48H, cyclohexylic
4J P′-C| ) 4.1 Hz, J C-H ≈ 128 Hz, Cy1-C2′), 31.1 (s, J C-H
1
1
2
4
130 Hz, Cy1-C2), 30.4 (s, Cy2-C2′), 30.2 (vt, | J P-C + J P′-C
|
3
5
1
) 4.1 Hz, Cy2-C2), 28.8 (vt, | J P-C + J P′-C| ) 14.2 Hz, J C-H
1
and remaining η3-CH2C(CH3)CH2). 13C{1H} NMR (C6D6, 100.6
≈ 124 Hz, Cy1-C3′), 28.7 (vt, | J P-C + 2J P′-C| ) 40.7 Hz, PCH2),
MHz, 300 K): δ 93.6 (s, η3-CH2C(CH3)CH2), 43.4 (vt, | J P-C
+
28.3 (vt, | J P-C
+
5J P′-C| ) 10.3 Hz, Cy1-C3), 28.2 (partly
1
3
3J P′-C| ) 15.8 Hz, Cy2-C1), 37.9 (vt, | J P-C + 3J P′-C| ) 5.9 Hz,
obscured vt, 1J C-H ≈ 128 Hz, Cy2-C3′), 28.0 (vt, | J P-C + 5J P′-C
|
1
3
Cy1-C1), 34.9 (vt, | J P-C + J P′-C| ) 20.0 Hz, η3-CH2C(CH3)-
CH2 cis,trans to P), 34.2 (t, 1J P-C ) 27.1 Hz, PCH2), 33.1 (partly
obscured vt, η3-CH2C(CH3)CH2 cis,cis to P), 31.1 (s, Cy1-C2′),
31.0 (s, Cy1-C2), 30.3 (partly obscured vt, Cy2-C2), 29.4 (vt,
) 7.1 Hz, Cy2-C3), 27.2 (s, 1J C-H ) 127 ( 2 Hz, Cy1-C4), 26.8
1 1
2
2
(s, J C-H ) 128 ( 3 Hz, η3-CH2C(CH3)CH2), 26.7 (s, J C-H
)
126 ( 3 Hz, Cy2-C4). 31P{1H} NMR (C6D6, 121.5 MHz, 302
K): δ 63.8 (s).
2
3
| J P-C + 4J P′-C| ) 5.7 Hz, Cy2-C2′), 28.4 (vt, | J P-C + 5J P′-C| )
[(1c)Ru (2-Me-a ll)2] (5c). The synthesis was carried out as
described for 5a reacting 4 (850 mg, 2.66 mmol) with 1c (1.16
g, 1 equiv) in 50 mL of hexane at 50-55 °C (bath temperature)
for 5 h. After cooling, 31P{1H} NMR control of a sample taken
from the orange homogeneous solution indicated quantitative
conversion of the free phosphine with 92% formation of 5c,
4% of 8c, and 4% of other phosphorus-containing impurities.
The solution was evaporated to dryness and the resulting light-
orange solid washed with 3 × 5 mL of pentane, giving
analytically pure 5c as a pale yellow powder after drying in
vacuo. Yield: 1.33 g (2.05 mmol, 77%). Mp: 151 °C (dec 165
°C). Anal. Found: C, 64.74; H, 9.88; P, 9.45. Calcd for C35H64P2-
Ru: C, 64.88; H, 9.96; P, 9.56. EI-MS (temperature of
vaporization: 130 °C): m/e ) 648 (M•+, 0.3%), 532 ([Ru1]+, 8),
450 ([Ru1]+, 3), 365 ([Ru1]+, 2), 78 (C6H6+, 2), 56 (C4H8+, 54),
41 (C3H5+, 100). IR (KBr disk): 3071 m; 3035 m; 2920 s; 2847
s; 1443 s; 1421 m; 1344 w; 1263 w; 1168 m; 1112 m; 1022 s;
1001 m; 967 m; 890 m; 850 m; 829 s; 782 m; 726 m; 638 m;
11.6 Hz, Cy1-C3′), 28.1 (m, Cy1-C3), 28.0 (partly obscured vt,
3
5
Cy2-C3′), 27.8 (vt, | J P-C + J P′-C| ) 10.4 Hz, Cy2-C3), 27.0
(s, Cy1-C4), 26.8 (s, η3-CH2C(CH3)CH2), 26.7 (s, Cy2-C4). 31P-
{1H} NMR (C6D6, 81.0 MHz, 300 K): δ 6.8 (s).
[(1b)Ru (2-Me-a ll)2] (5b). The synthesis was carried out as
described for 5a reacting 4 (582 mg, 1.82 mmol) and 1b (774
mg, 1 equiv) in hexane (60 mL) at 60-70 °C (bath tempera-
ture) for 22 h. The solution was evaporated to dryness, and
the resulting pale yellow solid was washed with 2 × 5 mL
pentane and dried in vacuo. Yield: 878 mg (1.39 mmol, 76%).
Mp: 153 °C (dec 216 °C). Anal. Found: C, 64.43; H, 9.41; P,
9.93. Calcd for C34H62P2Ru: C, 64.42; H, 9.86; P, 9.77.
EI-MS (temperature of vaporization: 137 °C): m/e ) 634
(M•+, 10%), 519 ([Ru1]+, 100), 435 ([Ru1]+, 14), 353 ([Ru1]+, 8),
78 (C6H6+, 4), 56 (C4H8+, 55), 41 (C3H5+, 73). IR (KBr disk):
3069 m; 3035 m; 2926 s; 2845 s; 1444 s; 1420 m; 1341 w; 1265
w; 1173 m; 1120 m; 1068 m; 1047 w; 1020 s; 1000 m; 911 w;
888 m; 871 m; 839 m; 816 m; 783 w; 729 m; 707 w; 682 w; 653
500 m cm-1. H NMR (C6D6, 400.1 MHz, 300 K): δ 2.58 (dvt,
1

3324 Organometallics, Vol. 18, No. 17, 1999
Six et al.
3
3
2J Hsyn-Hanti ) 2.3 Hz, | J P-H + J P′-H| ≈ 5.0 Hz, 2H, η3-CH2C-
phous solid by cooling to -78 °C. This material consisted of
the desired new complex 7 as the only phosphorus-containing
compound, together with small amounts of unreacted 4.
Yield: 482 mg (1.17 mmol, 42%). EI-MS (temperature of
vaporization: 90 °C): m/e ) 414 (M•+, 51%), 410 ([Ru1]+, 100),
357 ([Ru1]+, 45), 301 ([Ru1]+, 71), 268 ([Ru1]+, 56), 241 ([Ru1]+,
24), 55 (C4H7+, 13), 41 (C3H5+, 23). IR (neat): 3018 s; 2934 s;
2858 s; 2823 m; 2716 w; 1446 s; 1410 s; 1366 s; 1347 m; 1176
m; 1109 s; 1022 s; 1001 m; 949 m; 884 s; 864 s; 692 s; 646 s;
2
(CH3)CH2 syn, cis,cis to P), 2.39 (d, J Hax-Heq ) 10.4 Hz, 2H,
Cy1-H2eq), 2.21 (s, 6H, η3-CH2C(CH3)CH2), 2.14 (d, J Hax-Heq
2
) 11.6 Hz, 2H, Cy1-H2′eq), 1.91 (2H, Cy2-H1), 1.90 (2H,
PCH2), 1.84 (2H, PCH2CH2), 1.83 (2H, Cy1-H3eq and 2H, Cy1-
H
H
3′eq), 1.78 (2H, Cy2-H2′eq), 1.76 (2H, Cy1-H1), 1.74 (2H, Cy2-
2eq), 1.69 (2H, Cy1-H4eq), 1.68 (2H, PCH2 and 2H, Cy2-H3′eq),
1.64 (d, | J P-H + J P′-H| ≈ 9.2 Hz, 2H, η3-CH2C(CH3)CH2 syn,
3
3
cis,trans to P), 1.62 (2H, Cy2-H3eq), 1.58 (2H, Cy2-H4eq), 1.39
(d, | J P-H + 3J P′-H| ≈ 14.0 Hz, 2H, η3-CH2C(CH3)CH2 anti, cis,-
3
579 m; 566 m; 518 s cm-1. 1H NMR (C6D6, 200.1 MHz, 300 K):
3
δ 2.87 (partly obscured dvt, | J P-H
+
3J P′-H| ≈ 12.0 Hz, 2H,
cis to P), 1.34 (2H, Cy1-H2ax and 2H, Cy2-H2′ax), 1.32 (2H,
Cy1-H3ax), 1.30 (2H, Cy1-H2′ax), 1.21 (2H, Cy2-H3ax), 1.20 (br,
2H, η3-CH2C(CH3)CH2 anti, cis,trans to P and 2H, Cy2-H2ax
and 2H, Cy1-H3′ax and 2H, Cy1-H4ax), 1.14 (2H, Cy2-H3′ax),
1.07 (2H, Cy2-H4ax). 13C{1H} NMR (C6D6, 100.6 MHz, 300
η3-CH2C(CH3)CH2 syn, cis,cis to P), 2.67 (s, 6H, η3-CH2C(CH3)-
CH2), 2.0-0.8 (m, 26H, heterocyclic, ligand backbone and
allylic protons). 13C{1H} NMR (C6D6, 50.3 MHz, 300 K): δ 93.9
(s, η3-CH2C(CH3)CH2), 40.8 (vt, | J P-C + 2J P′-C| ) 20.1 Hz, η3-
2
K): δ 93.0 (s, η3-CH2C(CH3)CH2), 41.7 (vt, | J P-C + J P′-C| )
1
3
CH2C(CH3)CH2 cis,trans to P), 34.1 (vt, | J P-C + 3J P′-C| ) 25.9
1
20.0 Hz, 1J C-H ) 118 ( 2 Hz, Cy2-C1), 39.7 (vt, | J P-C + 2J P′-C
|
2
Hz, PCH2 cycl.), 33.8 (vt, | J P-C + J P′-C| ) 7.7 Hz, η3-CH2C-
2
2
) 19.5 Hz, η3-CH2C(CH3)CH2 cis,trans to P), 38.7 (vt, | J P-C
+
1
(CH3)CH2 cis,cis to P), 31.6 (vt, | J P-C + 3J P′-C| ) 42.0 Hz, PCH2
1
3J P′-C| ) 6.2 Hz, 1J C-H ) 122 ( 2 Hz, Cy1-C1), 33.8 (vt, | J P-C
2
cycl.), 27.9 (partly obscured vt, PCH2CH2 cycl.), 27.4 (s,
+ 2J P′-C| ) 7.9 Hz, 1J C-H ) 150 ( 2 Hz, η3-CH2C(CH3)CH2 cis,-
PCH2CH2 cycl.), 27.0 (s, η3-CH2C(CH3)CH2), 19.8 (vt, | J P-C
+
1
1
2J P′-C| ) 14.8 Hz, PCH2). 31P{1H} NMR (C6D6, 81.0 MHz, 300
cis to P), 31.3 (s, J C-H ) 127 ( 2 Hz, Cy1-C2′), 31.0 (s, Cy1-
1
C2), 30.9 (s, Cy2-C2), 30.5 (partly obscured vt, J C-H ) 125 (
K): δ 83.0 (s).
3
5
2 Hz, Cy2-C2′), 28.9 (vt, | J P-C + J P′-C| ) 9.0 Hz, Cy1-C3′),
[K2P ,P ′-{(η3-C6H8)CyP (CH2)3P Cy2}Ru (η3-C8H13)] (8c). 4
(1.03 g, 3.23 mmol) and 1c (1.40 g, 1 equiv) were dissolved in
hexane (60 mL), and the almost colorless solution was heated
to 95 °C (bath temperature) for 10 h. After cooling to room
temperature, a pale orange solid precipitated from the red-
brown homogeneous solution. The reaction mixture was
concentrated in vacuo to 10 mL, and the precipitate isolated
by filtration. The solid was washed with cold hexane (2 × 10
mL) and dried in vacuo to give analytically pure 8c. Yield: 599
mg (0.93 mmol, 29%). Mp: 199 °C (dec 206 °C). Anal. Found:
C, 64.91; H, 9.88; P, 9.59. Calcd for C35H60P2Ru: C, 65.29; H,
9.39; P, 9.62. EI-MS (temperature of vaporization: 195 °C):
m/e ) 638 ([Ru1]+, 21), 555 ([Ru1]+, 12), 532 ([Ru1]+, 13), 450
([Ru1]+, 14), 368 ([Ru1]+, 9), 108 (C8H12+, 18), 78 (C6H6+, 100).
IR (KBr disk): 3016 m; 2919 s; 2845 s; 1442 s; 1415 m; 1336
w; 1266 w; 1169 m; 1150 m; 1117 m; 1041 m; 1003 m; 886 m;
28.7 (vt, | J P-C + 5J P′-C| ) 9.4 Hz, Cy1-C3), 28.6 (vt, | J P-C
+
3
3
5J P′-C| ) 5.4 Hz, Cy2-C3′), 28.0 (vt, | J P-C + J P′-C| ) 9.2 Hz,
3
5
1J C-H ) 127 ( 2 Hz, Cy2-C3), 27.3 (s, Cy1-C4), 27.1 (s, Cy2-
C4), 26.7 (s, η3-CH2C(CH3)CH2), 21.7 (vt, | J P-C + 3J P′-C| ) 23.8
1
1
1
Hz, J C-H ≈ 122 ( 2 Hz, PCH2), 20.4 (s, J C-H ) 129 ( 2 Hz,
PCH2CH2). 31P{1H} NMR (C6D6, 162.0 MHz, 300 K): δ 22.1
(s).
[(2)Ru (2-Me-a ll)2] (6). The synthesis was carried out as
described for 5a reacting 4 (1.19 g, 3.71 mmol) with 2 (648
mg, 93% pure, approximately 1 equiv) in 45 mL of hexane at
70 °C (bath temperature). After 15 min the color of the solution
changed from greenish to yellow. The 31P{1H} NMR of a
sample taken after 13 h indicated almost quantitative conver-
sion of 2. The reaction was cooled to room temperature after
15 h and the yellow solution filtered from a small amount of
a gray precipitate. The filtrate was evaporated to dryness and
the resulting pale yellow solid dried in vacuo. Yield: 942 mg
(2.61 mmol, 70%). Anal. Found: C, 46.47; H, 8.57; P, 17.16.
Calcd for C14H30P2Ru: C, 46.53; H, 8.37; P, 17.14. EI-MS
850 m; 829 s; 768 m; 724 m; 639 m; 513 m cm-1 1H NMR
.
(C6D6, 600.2 MHz, 303 K): δ 5.56 (vt, 3J H11-H ≈ 6.4 Hz, 3J H13-H
2
3
≈ 6.4 Hz, 1H, H12), 4.76 (dvt, J P2-H ) 13.4 Hz, J H1-H ≈ 7.6
Hz, 3J H3-H ≈ 7.6 Hz, 1H, H2), 3.81 (m, 3J H2-H ≈ 8.3 Hz, 3J H4-H
≈ 8.3 Hz, 1H, H3, cis,cis to P), 3.66 (m, 1H, H13, cis,cis to P),
3.18 (m, 3J H2-H ≈ 8.2 Hz, 3J H8-H ≈ 8.9 Hz, 1H, H1, cis,trans to
(temperature of vaporization: 30 °C): m/e ) 362 (M•+, 65),
+
345 ([Ru1]+, 16), 307 ([Ru1]+, 87), 251 ([Ru1]+, 100), 57 (C4H9
,
4), 41 (C3H5+, 4). IR (KBr disk): 3033 m; 3011 m; 2963 s; 2897
s; 1414 s; 1365 m; 1272 m; 1023 m; 930 s; 883 s; 831 s; 791 m;
716 m; 692 m; 644 m; 572 w cm-1. 1H NMR (C6D6, 200.1 MHz,
300 K): δ 2.23 (s, 6H, η3-CH2C(CH3)CH2), 2.13 (m, 2J Hsyn-Hanti
3
P), 2.61/1.14 (m/-, | J H-H| ≈ 13.5 Hz/-, 1H each, Cy-H2
adjacent to cyclohexenylic moiety), 2.57 (m, 1H, H6 endo), 2.34
3
(br, 1H, H4), 2.02 (m, 1H, H8), 1.97 (1H, H15), 1.95 (dd, J P1-H
3
) 38.4 Hz, | J H-H| ) 13.3 Hz, 1H, H14), 1.91 (1H, H4), 1.87/
) 2.3 Hz, | J P-H + 3J P′-H| ≈ 5.0 Hz, 2H, η3-CH2C(CH3)CH2 syn,
3
1.22 (1H each, Cy-Hâ2), 1.87 (1H, Cy-Hâ1), 1.86/1.34 (1H
each, Cy-HR), 1.85/1.39 (1H each, Cy-Hâ), 1.81 (1H, H7),
cis,cis to P), 1.50 (partly obscured vt, 2H, η3-CH2C(CH3)CH2
2
3
2
syn, cis,trans to P), 1.27 (d, J P-H ) 8.1 Hz, 6H, PCH3), 1.17
1.75 (1H, H5 and 1H, PCH2CH2), 1.74/1.16 (1H each, Cy-HR),
3
(dd, 2J P-H ) 13.5 Hz/3J P-H ) 1.5 Hz, 4H, PCH2), 1.07 (vt, | J P-H
3
1.72 (1H, Cy-Hγ1), 1.72/1.16 (2H each, Cy-Hδ2,ꢀ), 1.70/1.16
(1H each, Cy-Hδ), 1.69 (1H, H7), 1.69/1.04 (1H each, Cy-Hꢀ),
+ J P′-H| ≈ 12.2 Hz, 2H, η3-CH2C(CH3)CH2 anti, cis,cis to P),
3
0.80 (vt, | J P-H + 3J P′-H| ≈ 15.4 Hz, 2H, η3-CH2C(CH3)CH2 anti,
3
3
3
1.68 (1H, H16), 1.67/1.08 (1H each, Cy-Hγ), 1.67/1.18 (1H
cis,trans to P), 0.56 (d, J P-H ) 6.7 Hz, 6H, PCH3). 13C{1H}
2
3
each, Cy-Hδ3), 1.66/1.13 (1H each, Cy-HR4), 1.64/1.15 (1H
NMR (C6D6, 100.6 MHz, 300 K): δ 94.3 (s, η3-CH2C(CH3)CH2),
each, Cy-Hγ), 1.64 (1H, PCH2CH2), 1.60 (1H, H5), 1.60/1.17
39.9 (vt, | J P-C + 2J P′-C| ) 20.0 Hz, η3-CH2C(CH3)CH2 cis,trans
2
2
(1H each, Cy-Hâ), 1.58/1.07 (1H each, Cy-Hγ), 1.54 (1H, H11
,
to P), 34.2 (vt, | J P-C + 2J P′-C| ) 7.7 Hz, η3-CH2C(CH3)CH2 cis,-
2
4
4
1
3
cis,trans to P and 1H, P1CH2), 1.51 (1H, H6 exo), 1.49 (1H,
cis to P), 31.3 (vt, | J P-C + J P′-C| ) 46.2 Hz, PCH3), 27.0 (s,
P2CH2), 1.43 (1H, Cy-HR), 1.36 (1H, H14), 1.27 (1H, H16),
η3-CH2C(CH3)CH2), 22.5 (vt, | J P-C + 2J P′-C| ) 24.5 Hz, PCH2),
1
1
1.06 (1H, H8), 0.86 (1H, P2CH2), 0.83 (1H, P1CH2). 13C NMR
10.1 (vt, | J P-C + 3J P′-C| ) 17.4 Hz, PCH3). 31P{1H} NMR (C6D6,
1
1
(C6D6, 150.9 MHz, 303 K): δ 83.1 (s, J C-H ) 155 ( 1 Hz, C2),
81.0 MHz, 300 K): δ 48.8 (s).
3
1
75.9 (d, J P1-C ) 1.4 Hz, J C-H ) 164 ( 1 Hz, C12), 63.3 (d,
[(3)Ru (2-Me-a ll)2] (7). The synthesis was carried out as
described for 5a reacting 4 (881 mg, 2.76 mmol) and 3 (522
mg, 78% purity, approximately 1 equiv) at 60-70 °C (bath
temperature) in hexane (15 mL) for 4 h. Upon heating, a solid
precipitated rapidly and the reaction mixture darkened quickly
from yellow to dark brown. The brown solid was filtered off
and found to contain a complex mixture of compounds by 31P-
{1H} NMR analysis. Evaporation of the filtered solution gave
a dark brown viscous material, which solidified to an amor-
2J P1-C ) 31.1 Hz, 1J C-H ) 150 ( 2 Hz, C11, cis,trans to P), 50.1
2
1
(d, J P-C ) 3.5 Hz, J C-H ) 154 ( 1 Hz, C13, cis,cis to P), 48.4
1
2
(m, J C-H ) 142 ( 2 Hz, C3, cis,cis to P), 47.8 (m, | J P1-C
+
2J P2-C| ≈ 28 Hz, J C-H ) 142 ( 2 Hz, C1, cis,trans to P), 45.0
1
(dd, J P-C/3J P-C ) 14.1/2.4 Hz, J C-H ) 122 ( 1 Hz, Cy-CR1),
1
1
40.5 (d, J P-C ) 19.9 Hz, J C-H ) 124 ( 2 Hz, Cy-Câ1), 39.6
(dd, 1J P1-C/3J P2-C ) 23.7/1.9 Hz, 1J C-H ) 132 ( 2 Hz, C15), 39.2
1
1
γ
(d, 1J P-C ) 6.2 Hz, J C-H ) 122 ( 1 Hz, Cy-C1), 36.1 (s, J C-H
1
1

Thermal Activation of sp3-C-H Bonds
Organometallics, Vol. 18, No. 17, 1999 3325
2
) 125 ( 1 Hz, C4), 31.4 (d, C5), 31.0 (d, J P-C ) 2.1 Hz, Cy-
heated to reflux temperature of coa (151 °C) with the oil bath
set at 170 °C for 48 h. After cooling, metal-containing species
were removed by passing the solution through a short pad of
silica or by Kugelrohr distillation.26 The clear colorless liquid
was quantitatively analyzed by gas chromatography using
cyclohexane as an internal standard.
Type II (time-dependence monitoring) was carried out as
for type I, except that the catalyst solution was prepared in a
50 mL three-necked round-bottomed flask equipped with an
argon inlet, a reflux condenser, and a rubber septum seal.
Small samples (0.5 mL) of the reaction mixture were with-
drawn periodically through the septum using a 1 mL gastight
Hamilton syringe and immediately frozen at -78 °C. Workup
and analysis were performed as for type I.
Type III (gas-phase investigations) was carried out as for
type I, except that the Schlenk tube was connected to a gas
sampling tube which was especially designed to fit a modified
Varian MAT CH7 for quantitative GC/MS analyses. The
reaction mixture was frozen at -78 °C and the whole ap-
paratus evacuated before starting the reaction.
Type IV (standard transfer-dehydrogenation) was carried
out as for type I, but the hydrogen acceptor tbe was added in
a molar ratio of 1:5 relative to coa. The resulting mixture was
heated to 120 °C (bath temperature) for 48 h.
Attem p ted C-H Activa tion in th e P r esen ce of Su p er -
cr itica l CO2. The catalyst precursor 5 was dissolved in coa,
and the resulting homogeneous solution was transferred into
a stainless steel autoclave (V ) 225 mL). The autoclave was
pressurized with CO2 and then heated to 100 °C, resulting in
a total pressure of approximately 200 bar. After cooling to room
temperature, the reactor was carefully vented, whereby the
volatiles were passed through a cold trap held at -50 °C. The
collected liquid was quantitatively analyzed by gas chroma-
tography using cyclohexane as an internal standard. In one
experiment using 5c as the precursor, small amounts (<10
mg) of a solid were carefully recovered from the autoclave in
a glovebox and submitted to FT-IR analysis.
X-r a y Cr ysta l Str u ctu r e An a lysis. The crystals were
mounted in a cold nitrogen stream at -90 °C. For the data
collection a Nonius CAD4 diffractometer (compound 5b) and
a Nonius KappaCCD (compound 8c) using graphite-mono-
chromated Mo KR radiation was used. Data were corrected
for Lorentz and polarization effects.35 No absorption correction
was made. The structures were solved by direct methods
(SHELXS36) and refined by full-matrix least-squares tech-
niques against F2 (SHELXL-9337). For 8c all hydrogen atoms
were located by difference Fourier synthesis and refined
isotropically. The hydrogen atoms for 5b were included at
calculated positions with fixed thermal parameters. All non-
hydrogen atoms were refined anisotropically. XP (SIEMENS
Analytical X-ray Instruments, Inc.) was used for structure
representations.
R
4
2
C2), 30.8 (d, J P-C ) 5.8 Hz, C7), 30.6 (d, J P-C ) 4.3 Hz, Cy-
Câ2), 29.4 (d, J P1-C ) 14.6 Hz, C14), 29.3 (d, J P1-C ) 2.7 Hz,
2
2
Cy-C2 adjacent to cyclohexenylic moiety), 28.9 (d, Cy-Cγ2),
δ
2
2
28.6 (d, J P-C ) 5.3 Hz, Cy-C2), 28.5 (d, J P-C ) 2.3 Hz, Cy-
Cꢀ2), 28.4 (d, J P-C ) 11.4 Hz, Cy-C3R), 28.2 (d, J P-C ) 10.5
2
3
Hz, Cy-Câ3), 28.2 (d, 3J P-C ) 10.2 Hz, Cy-Cγ3), 28.1 (d, 3J P-C
)
)
δ
3
3
2.5 Hz, C8), 28.0 (d, J P-C ) 6.5 Hz, Cy-C3), 27.7 (d, J P-C
7.2 Hz, Cy-Cꢀ3), 27.5 (d, J P-C ) 6.4 Hz, Cy-Cδ3), 27.2 (dd,
3
2J P1-C/4J P2-C )11.8/3.1 Hz, C16), 27.1 (s, Cy-CR), 27.0 (s, Cy-
4
Câ4), 26.9 (s, Cy-C4γ), 26.2 (dd, J P2-C/3J P1-C ) 21.8/8.9 Hz,
1
P2CH2), 25.9 (m, C6), 23.1 (dd, 2J P2-C/2J P1-C ) 5.7/2.9 Hz, 1J C-H
1
1
) 128 ( 1 Hz, PCH2CH2), 18.1 (d, J P1-C ) 12.1 Hz, J C-H
)
125 ( 1 Hz, P1CH2). 31P{1H} NMR (C6D6, 243.0 MHz, 303 K):
2
2
δ 72.9 (d, J P1-P2 ) 34.3 Hz, P1), 27.7 (d, J P1-P2 ) 34.3 Hz,
P2).
[K2P ,P ′-{(η3-C6H8)CyP (CH2)4P Cy2}Ru (η3-C8H13)] (8d ). 4
(208 mg, 0.651 mmol) and 1d (295 mg, 1 equiv) were dissolved
in hexane (30 mL) and heated to 50 °C (bath temperature).
The almost colorless solution turned yellow after 10 min and
darkened quickly to brown. After 6 h, the 31P{1H} NMR of a
sample taken from the homogeneous solution still showed the
presence of large amounts of free phosphine. After a total
reaction time of 18 h, 31P{1H} NMR indicated almost quantita-
tive conversion. The reaction mixture was cooled to room
temperature and concentrated in vacuo to 5 mL. The solution
was stored at 4 °C for 10 days, affording a bright orange solid,
which was filtered, washed with hexane (2 × 1 mL), and dried
in vacuo. The filtrate was evaporated to dryness to give a
brown residue from which additional crops of 8d could be
isolated by dissolving it in 2 mL of pentane and storing the
solution at 4 °C for 4 weeks. Yield: 135 mg (0.205 mmol, 32%).
Mp: 150 °C (dec 160 °C). Anal. Found: C, 65.94; H, 9.63; P,
9.49. Calcd for C36H62P2Ru: C, 65.72; H, 9.50; P, 9.42.
EI-MS (temperature of vaporization: 160 °C): m/e ) 658
(M•+, 16), 548 ([Ru1]+, 29), 460 ([Ru1]+, 26), 350 ([Ru1]+, 22),
198 (C6H11)2PH+, 13), 78 (C6H6+, 100), 55 (C4H7+, 76). IR (KBr
disk): 3009 w; 2966 s; 2927 s; 2847 s; 2815 s; 1448 s; 1409 s;
1347 s; 1313 s; 1296 m; 1262 m; 1236 m; 1216 m; 1174 m;
1149 m; 1123 w; 1069 w; 1029 w; 1001 m; 991 w; 888 m; 847
m; 823 m; 807 w; 758 w; 727 w; 667 w; 527 w; 489 m; 466 m
cm-1. 1H NMR (C6D6, 400.1 MHz, 300 K): δ 5.56 (m, 1H, H12),
4.09 (m, J ≈ 6.9 Hz, 2H), 3.90 (m, J ) 9.8/7.3/2.0 Hz, 2H),
3.27 (m, J ≈ 12.9/2.5 Hz, |J | ) 5.8 Hz, 2H), 2.75-0.92 (51H),
0.86 (m, |J | ≈ 11.1, 4H). 13C{1H} NMR (C6D6, 100.6 MHz, 300
K): δ 77.6 (vt, | J P1-C + 3J P2-C| ) 10.7 Hz, 1C), 66.7 (d, J P1-C
3
2
) 7.2 Hz, 1C), 61.2 (dd, J P2-C/3J P1-C ) 11.1/4.7 Hz, 1C), 59.4
1
(dd, J P-C ) 20.4/5.3 Hz, 1C), 56.5 (partly obscured dd, J P-C
6.2 Hz, 1C), 44.2 (dd, J P-C ) 19.5/1.5 Hz, 1C), 41.7 (dd, J P-C
)
)
7.9/3.5 Hz, 1C), 41.5 (dd, J P-C ) 8.5/2.7 Hz, 1C), 41.3 (dd, J P-C
) 13.7/5.5 Hz, 1C), 37.5 (d, J P-C ) 18.6 Hz, 1C), 37.0 (d, 1C),
36.0 (dd, J P-C ≈ 23.7/3.5, 1C), 35.9 (d, J P-C ≈ 2.5 Hz, 1C), 35.2
(d, J P-C ) 7.4 Hz, 1C), 33.8 (dd, J P-C ≈ 6.8/2.2 Hz, 1C and
partly obscured d, 1C), 31.6 (s, 1C), 31.4 (2 d, J P-C ) 3.5 Hz
and J P-C ) 3.8 Hz, 2C), 31.2 (d, J P-C ) 1.8 Hz, 1C), 31.1 (d,
J P-C ) 1.3 Hz, 1C), 30.7 (d, J P-C ) 4.0 Hz, 1C), 30.5 (partly
obscured dd, J P-C ) 3.3 Hz, 1C), 30.2 (d, J P-C ) 5.1 Hz, 1C),
29.8 (d, J P-C ) 2.8 Hz, 1C), 29.6 (d, J P-C ) 2.6 Hz, 1C), 29.2-
27.7 (m, 6C), 27.2 (s, 1C), 27.1 (s, 1C), 27.0 (s, 1C), 26.6 (s,
1C). 31P{1H} NMR (C6D6, 162.0 MHz, 300 K): δ 73.0 (d, J P1-P2
) 29.6 Hz, P1), 9.2 (d, J P1-P2 ) 29.6 Hz, P2).
Catalytic Reaction s. Thermal dehydrogenation or transfer-
dehydrogenation was performed with different reaction sys-
tems. Type I (standard dehydrogenation): 0.015-0.040 mmol
of catalyst precursor was weighed into a Schlenk tube (50 mL)
and dissolved in 5-15 mL of coa. The tube was equipped with
a reflux condenser and connected to a gas bubbler. An inert
atmosphere was ensured throughout the experiment by pass-
ing a gentle stream of argon over the reaction mixture on top
of the condenser. In a typical experiment, the solution was
Cr ysta l Da ta for 5b:38 C34H62P2Ru, Mr ) 633.85 g mol-1
,
colorless prism, size 0.32 × 0.32 × 0.20 mm3, monoclinic, space
group C2/c, a ) 29.992(4) Å, b ) 12.436(3) Å, c ) 18.197(3) Å,
â ) 108.65(1)°, V ) 6430(2) Å3, T ) -90 °C, Z ) 8, Fcalcd
)
1.309 g cm-3, µ (Mo KR) ) 6.08 cm-1, F(000) ) 2720, 7453
reflections in h(-38/0), k(-16/0), l(-22/23), measured in the
range 2.27° e θ e 27.41°, 7316 independent reflections, Rint
)
(35) (a) Otwinowski, Z.; Minor, W. In Methods in Enzymology,
Macromolecular Crystallography, Part A; Carter, C. W., Sweet, R. M.,
Eds.; Academic Press: Orlando, 1997; Vol. 276, p 307. (b) Molen-An
Interactive Structure Solution Procedure; Enraf-Nonius: Delft, The
Netherlands, 1990.
(36) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(37) Sheldrick, G. M. University of Go¨ttingen, Germany, 1993.
(38) Further details of the crystal structure investigations are
available on request from the Fachinformationszentrum Karlsruhe,
Gesellschaft fu¨r wissenschaftlich-technische Information mbH, D-76344
Eggenstein-Leopoldshafen, on quoting the depository number CSD-
410550 (5b) and CSD-410551 (8c), the names of the authors, and the
journal citation.

3326 Organometallics, Vol. 18, No. 17, 1999
Six et al.
0.031, 4574 reflections with Fo > 4σ(Fo), 334 parameters, Robs
) 0.049, wR2obs ) 0.104, GOOF ) 1.129, largest difference peak
and the Fonds der Chemischen Industrie is gratefully
acknowledged. We thank Degussa AG and Hoechst AG
for generous loans of precious metal compounds. We also
thank the MS and GC department of the Max-Planck-
Institut fu¨r Kohlenforschung, namely, Dr. D. Sto¨ckigt
and S. Ruthe, for their valuable assistance. Special
thanks are due to Prof. P. W. J olly for communicating
results prior to publication. C.S. is grateful to S. Holle
for fruitful discussions.
and hole 0.336/-0.599 e Å-3
.
Cr ysta l Da ta for 8c:38 C35H60P2Ru, Mr ) 643.84 g mol-1
,
colorless prism, size 0.20 × 0.20 × 0.20 mm3, monoclinic, space
group P21/c, a ) 15.9384(5) Å, b ) 11.2544(5) Å, c ) 18.8428-
(8) Å, â ) 107.963(2)°, V ) 3215.2(2) Å3, T ) -90 °C, Z ) 4,
Fcalcd ) 1.330 g cm-3, µ (Mo KR) ) 6.1 cm-1, F(000) ) 1376,
8490 reflections in h(-17/17), k(0/12), l(-20/20), measured in
the range 3.15° e θ e 23.25°, 4440 independent reflections,
Rint ) 0.0382, 3388 reflections with Fo > 4σ(Fo), 583 param-
Su p p or tin g In for m a tion Ava ila ble: A listing of crystal
data and positional parameters for complexes 5a and 8c. This
material is available free of charge via the Internet at
http://pubs.acs.org.
eters, Robs ) 0.032, wR2 ) 0.071, GOOF ) 0.988, largest
obs
difference peak and hole 0.336/-0.476 e Å-3
.
Ack n ow led gm en t. Financial support of the Max-
Planck-Society, the Deutsche Forschungsgemeinschaft,
OM990229R