Synthesis of alkyl- and aryl[hydrotris(pyrazolyl)borato]carbonylruthenium complexes by decarbonylation of alcohols. Synthesis of TpRuH(H2)(PPh3) [Tp = hydrotris(pyrazolyl)borate], an observable intermediate in the decarbonylation reaction

Article abstract of DOI:10.1021/om960817u

Treatment of TpRuCl(PPh₃)(CH₃CN) (Tp = hydrotris(pyrazolyl)borate) with NaBH₄ in ethanol did not yield the expected hydride complex TpRuH(PPh₃)(CH₃CN) (2) but rather the methyl carbonyl complex TpRu(CH₃)(CO)(PPh₃) (1b). Formation of Ib was due to decarbonylation of ethanol by 2 generated in situ by NaBH₄ reduction of TpRuCl(PPh₃)(CH₃-CN). Analogous reactions in the presence of other primary alcohols RCH₂OH (R = H, C₂H₅, n-C₃H₅, C₆H₅, C₆H₄CH₃-4, and C₆H₄Cl-4) led to the corresponding σ-organyl complexes TpRuR(CO)(PPh₃). A common feature of the reactions is that the R groups of alcohols RCH₂-OH become the σ-organyl groups in the final metal complexes. A mechanism involving metal-η²-aldehyde and -η²-dihydrogen intermediates is proposed for the decarbonylation reaction. This is supported by the observation of the η²-dihydrogen complex TpRuH(H₂)-(PPh₃) (3) during the decarbonylation reaction. 3 was synthesized independently by heating a THF solution of 2 under 40 atm of H₂ at 60 °C for 48 h or by heating 2 in CH₃OH at 60 °C under 6 atm of H₂ for 5-6 h.

Full text of DOI:10.1021/om960817u

Organometallics 1997, 16, 1241-1246
1241
Syn th esis of Alk yl- a n d
Ar yl[h yd r otr is(p yr a zolyl)bor a to]ca r bon ylr u th en iu m
Com p lexes by Deca r bon yla tion of Alcoh ols. Syn th esis of
Tp Ru H(H2)(P P h 3) [Tp ) Hyd r otr is(p yr a zolyl)bor a te], a n
Obser va ble In ter m ed ia te in th e Deca r bon yla tion
Rea ction
Yu-Zhong Chen, Wai Chung Chan, Chak Po Lau,* Hei Shing Chu, and
Hin Ling Lee
Department of Applied Biology & Chemical Technology, The Hong Kong Polytechnic
University, Hung Hom, Kowloon, Hong Kong
Guochen J ia*
Department of Chemistry, Hong Kong University of Science & Technology, Clear Water Bay,
Kowloon, Hong Kong
Received September 25, 1996X
Treatment of TpRuCl(PPh3)(CH3CN) (Tp ) hydrotris(pyrazolyl)borate) with NaBH4 in
ethanol did not yield the expected hydride complex TpRuH(PPh3)(CH3CN) (2) but rather
the methyl carbonyl complex TpRu(CH3)(CO)(PPh3) (1b). Formation of 1b was due to
decarbonylation of ethanol by 2 generated in situ by NaBH4 reduction of TpRuCl(PPh3)(CH3-
CN). Analogous reactions in the presence of other primary alcohols RCH2OH (R ) H, C2H5,
n-C3H7, C6H5, C6H4CH3-4, and C6H4Cl-4) led to the corresponding σ-organyl complexes
TpRuR(CO)(PPh3). A common feature of the reactions is that the R groups of alcohols RCH2-
OH become the σ-organyl groups in the final metal complexes. A mechanism involving
metal-η2-aldehyde and -η2-dihydrogen intermediates is proposed for the decarbonylation
reaction. This is supported by the observation of the η2-dihydrogen complex TpRuH(H2)-
(PPh3) (3) during the decarbonylation reaction. 3 was synthesized independently by heating
a THF solution of 2 under 40 atm of H2 at 60 °C for 48 h or by heating 2 in CH3OH at 60
°C under 6 atm of H2 for 5-6 h.
In tr od u ction
of TpRuCl(PPh3)(CH3CN) with NaBH4 in EtOH, we
found that TpRu(CH3)(CO)(PPh3) instead of the ex-
pected TpRuH(PPh3)(CH3CN) was produced. Forma-
tion of this product corresponds to decarbonylation of
EtOH during the reaction. Also, reaction of TpRuH-
(PPh3)(CH3CN) with EtOH produces the same complex.
To explore the scope and mechanism of these unusual
reactions, we have studied the reactions of TpRuH-
(PPh3)(CH3CN) with various primary alcohols RCH2OH
and with CH3CHO. The results illustrate that the
decarbonylation reactions are quite general and that
they may involve molecular dihydrogen complexes4 as
intermediates. Incorporation of the R group of RCH2-
OH into the final metal complex is unusual, as the R
group is usually not retained on the metal in most of
the known decarbonylation reactions. Here we report
the synthesis of TpRuR(CO)(PPh3) via these interesting
decarbonylation reactions. The mechanism of the reac-
tions is also discussed.
It is well established that reactions of certain transi-
tion metal complexes with primary alcohols can lead to
decarbonylation of the alcohols.1 Such reactions usually
result in the formation of CO-containing complexes and
degraded fragments of the alcohols, that is, RH from
RCH2OH. While the presence of base is required for
decarbonylation of alcohols in most cases, it is noted that
RuH4(PPh3)3 and RuH(BH4)(PMe2Ph)3 react with eth-
anol to give RuH2(CO)(PPh3)3 and RuH2(CO)(PMe2Ph)3
under neutral condition.
2
3
During our attempts to prepare TpRuH(PPh3)(CH3-
CN) [Tp ) hydrotris(pyrazolyl)borate] from the reaction
X Abstract published in Advance ACS Abstracts, February 15, 1997.
(1) (a) Bennet, M. A.; Bruce, M. I.; Matheson, T. W. In Comprehen-
sive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel,
E. W., Eds.; Pergamon Press: Oxford, U.K., 1982; Vol. 4, pp 721-723.
(b) Chatt, J .; Shaw, B. L.; Field, A. E. J . Chem. Soc. 1964, 3466. (c)
Benedetti, E.; Braca, G.; Sbrana, G.; Salvetti, F.; Grassi, B. J .
Organomet. Chem. 1972, 37, 361. (d) Empsall, H. D.; Hyde, E. M.;
Mentzer, E.; Shaw, B. L.; Uttley, M. F. J . Chem. Soc., Dalton Trans.
1976, 2069. (e) Chaudret, B. N.; Cole-Hamilton, D. J .; Nohr, R. S.,
Wilkinson, G. J . Chem. Soc., Dalton Trans. 1977, 1546. (f) Cole-
Hamilton, D. J .; Wilkinson, G. Nouv. J . Chim. 1977, 1, 142. (g) Gill,
D. F.; Shaw, B. L. Inorg. Chim. Acta 1979, 33, 19. (h) Morton, D.; Cole-
Hamilton, D. J .; Utuk, I. D.; Paneque-Sosa, M. J . Chem. Soc., Dalton
Trans. 1989, 489. (i) Portnoy, M.; Frolow, F.; Milstein, D. Organome-
tallics 1991, 10, 3960.
Resu lts a n d Discu ssion
Syn th eses of Tp Ru R(CO)(P P h 3). Reactions of
TpRuCl(PPh3)(CH3CN) with NaBH4 in alcohols (RCH2-
(2) Van Der Sluys, L. S.; Kubas, G. J .; Caulton, K. G. Organome-
tallics 1991, 10, 1033.
(3) Bruno, J . W.; Huffman, J . C., Caulton, K. G. Inorg. Chim. Acta
1984, 89, 167.
(4) Leading reviews: (a) Crabtree, R. H. Acc. Chem. Res. 1990, 23,
95. (b) J essop, P. G.; Morris, R. H. Coord. Chem. Rev. 1992, 121, 155.
(c) Heinekey, D. M.; Oldham, W. J ., J r. Chem. Rev. 1993, 93, 913. (d)
Crabtree, R. H. Angew. Chem., Int. Ed. Engl. 1993, 32, 789.
S0276-7333(96)00817-5 CCC: $14.00 © 1997 American Chemical Society

1242 Organometallics, Vol. 16, No. 6, 1997
Chen et al.
OH) produce air-stable TpRuR(CO)(PPh3) (R ) H (1a ),
Me (1b), Et (1c), Pr (1d ), Ph (1e), C6H4CH3-4 (1f), C6H4-
Cl-4 (1g)) for which NMR and IR data are collected in
Table 1. For R ) H, the product is only observed if the
reaction is carried out in a sealed tube.
and heating at 60 °C for another 1 h resulted in
disappearance of the two doublets at δ -12.14 and
-12.40 ppm. The hydride peak of TpRuH(PPh3)(CH3-
CN) at δ -13.78 ppm also greatly diminished in
intensity while that of the doublet at δ -9.99 ppm was
greatly enhanced. This NMR study indicates that,
under H2 pressure, TpRuH(PPh3)(CH3CN) and the
species that correspond to the two doublets at δ -12.14
and δ -12.40 ppm are converted to the complex which
shows the doublet at δ -9.99 ppm. Releasing the H2
pressure and further heating the NMR tube eventually
led to disappearance of all the hydride signals, with
appearance of signals due to TpRu(CH3)(CO)(PPh3). The
doublet at δ -12.14 ppm is probably due to the acetal-
dehyde complex TpRuH(PPh3)(CH3CHO), while the
hydrido-dihydrogen complex TpRuH(H2)(PPh3) (3) gives
rise to the doublet at δ -9.99 ppm. The doublet at δ
-12.40 ppm is tentatively assigned to the ethanol
complex TpRuH(PPh3)(EtOH). The assignment of the
signal at δ -12.40 ppm to TpRuH(PPh3)(EtOH) is
supported by the fact that the signal only appears at
the early stage of the reaction and it does not show up
in the reaction of TpRuH(PPh3)(CH3CN) with CH3CHO
(see below).
Several (σ-organyl)ruthenium complexes with hydro-
tris(pyrazolyl)borate have been reported. TpRu(C6H4-
CH3-4)(CO)(PPh3) and a series of σ-vinyl derivatives
have been prepared via the reaction of KTp with Ru-
(C6H4CH3-4)Cl(CO)(PPh3)2 and Ru(CRdCHR)Cl(CO)-
(PPh3)2, respectively.5 The cyanoethyl complex [TpRu-
{CH(CN)CH3}(CO)(PPh3)] was prepared from the chloro-
bridged dimer [Ru2(µ-Cl)2{CH(CN)CH3}2(CO)2(PPh3)4].6
It is worth pointing out that the carbonyl hydride
complex 1a has been prepared previously by treatment
of RuHCl(CO)(PPh3)3 with sodium hydrotris(pyrazolyl)-
borate in refluxing toluene.7 All the (σ-organyl)[hydro-
tris(pyrazolyl)borato]ruthenium complexes reported to
date have been prepared by reacting KTp or NaTp with
ruthenium complex precursors containing the σ-organyl
groups.
Thus, reactions of TpRuCl(PPh3)(CH3CN) with NaBH4
in alcohols provide an alternative simple route to (σ-
organyl)[hydrotris(pyrazolyl)borato]ruthenium complexes.
Formation of TpRuR(CO)(PPh3), instead of TpRuH-
(PPh3)(CH3CN), from the reactions of TpRuCl(PPh3)(CH3-
CN) and NaBH4 in the presence of RCH2OH is unex-
pected, especially in view of the fact that NaBH4
reduction of metal halides in alcoholic solutions is one
of the most common routes to transition metal hydride
complexes.
Rea ction of Tp Ru H(P P h 3)(CH3CN) (2) w ith Ac-
eta ld eh yd e. Dehydrogenation of primary alcohols by
transition metal complexes produce aldehydes,1h,i,8 and
decarbonylation of aldehydes can be affected by transi-
tion metal complexes, yielding metal carbonyls.1i,8b,9
Expulsion of the coordinated CO from the carbonyl
complexes will render the decarbonylation reactions
catalytic.10 A complex formulated as RuH2(η2-HCHO)-
(PPh3)3 was suggested as an intermediate in the decar-
bonylation of methanol with RuHCl(PPh3)3,1e and a well-
characterized η2-formaldehyde complex, WH2(PMe3)4(η2-
HCHO), formed by addition of methanol to WH(η2-
CH2PMe2)(PMe3)4 has been reported.11 Detailed mechan-
istic study of a â-hydride elimination from iridium
alkoxo complexes has been carried out.12 In this pro-
cess, a transient aldehyde complex is suggested as the
immediate product of â-hydrogen elimination. It is thus
reasonable to speculate that our alcohol decarbonylation
proceeds via a metal-aldehyde intermediate. Indeed,
we have been able to prepare TpRu(CH3)(CO)(PPh3) (1b)
by reacting TpRuH(PPh3)(CH3CN) with acetaldehyde.
Syn th esis of Tp Ru H(P P h 3)(CH3CN) (2) a n d Its
Rea ction w ith Eth a n ol. We have attempted to elu-
cidate the mechanism of these interesting decarbony-
lation reactions. As many hydride complexes [e.g.
RuH4(PPh3)3 and RuH(BH4)(PMe2Ph)3] are able to de-
carbonylate alcohols, it was suspected that hydride
species and RCHO were involved in our decarbonylation
reactions. Therefore, we prepared TpRuH(PPh3)(CH3-
CN) (2) and studied its reaction with EtOH and CH3-
CHO. This complex, prepared by NaBH4 reduction of
TpRuCl(PPh3)(CH3CN) in THF, was characterized by
1
elemental analysis and H NMR spectroscopy (CD2Cl2).
2
A doublet at δ -13.91 ppm (d, J PH ) 28 Hz) is
assignable to the hydride ligand cis to the triphen-
ylphosphine, and a singlet at δ 1.69 ppm is assignable
to the coordinated acetonitrile. Complex 2 reacts with
alcohols to afford 1a -g as the final products (eq 1).
1
The H NMR spectrum of a THF-d8 solution of TpRuH-
(PPh3)(CH3CN) and excess acetaldehyde at 70 °C after
10 min showed a small doublet at -12.14 ppm (2J PH
)
1
27 Hz) which was also observed in the H NMR study
TpRuH(PPh3)(CH3CN) + RCH2OH f
(8) (a) Dobson, A.; Robinson, S. D. Inorg. Chem. 1977, 16, 137. (b)
J ung, C. W.; Garrow, P. E. Organometallics 1982, 1, 658. (c) Shinoda,
S.; Itagaki, H.; Saito, Y. J . Chem. Soc., Chem. Commun. 1985, 860.
(d) Morton, D.; Cole-Hamilton, D. J . J . Chem. Soc., Chem. Commun.
1987, 248. (e) Morton, D.; Cole-Hamilton, D. J . J . Chem. Soc., Chem.
Commun. 1988, 1154. (f) Itagaki, H.; Shinoda, S.; Saito, Y. Bull. Chem.
Soc. J pn. 1988, 61, 2291.
(9) (a) Kampmeier, J . A.; Harris, S. H.; Wedegaertner, D. K. J . Org.
Chem. 1980, 45, 315. (b) Ito, T.; Horino, H.; Koshiro, Y.; Yamamoto,
A. Bull. Chem. Soc. J pn. 1982, 55, 504. (c) Collman, J . P.; Hegedus, L.
S.; Norton, J . R.; Finke, R. G. Principles and Applications of Organ-
otransition Metal Chemistry; University Science Book: Mill Valley, CA,
1987; pp 768-775 and references therein. (d) Crabtree, R. H. The
Organometallic Chemistry of The Transition Metals; J ohn Wiley &
Sons: New York, 1994; p 398.
TpRuR(CO)(PPh3) (1)
We have monitored the reaction of TpRuH(PPh3)(CH3-
CN) with ethanol by 1H NMR spectroscopy. Heating of
a THF-d8 solution of TpRuH(PPh3)(CH3CN) and ethanol
in a Wilmad pressure NMR tube at 70 °C for 1 h led to
the emergence of three new hydride signals as doublets
at δ -9.99 ppm (2J PH ) 17.0 Hz), -12.14 ppm (2J PH
)
27.2 Hz), and -12.40 ppm (2J PH ) 29.0 Hz). All three
signals collapsed to singlets upon phosphorus decou-
pling. Pressurizing the NMR tube with 10 atm of H2
(10) (a) Doughty, D. H.; Pignolet, L. H. J . Am. Chem. Soc. 1978,
100, 7083. (b) O’Connor, J . M.; Ma, J . J . Org. Chem. 1992, 57, 5075.
(c) Abu-Hasanayn, F.; Goldman, M. E.; Goldman, A. S. J . Am. Chem.
Soc. 1992, 114, 2520.
(5) Alcock, N. W.; Hill, A. F.; Melling, R. P. Organometallics 1991,
10, 3898.
(6) Hiraki, K.; Ochi, N.; Kitamura, T.; Sasada, Y.; Shinoda, S. Bull.
Chem. Soc. J pn. 1982, 55, 2356.
(7) Sun, N.-Y.; Simpson, S. J . J . Organomet. Chem. 1992, 434, 341.
(11) Green, M. L. H.; Parkin, G.; Moynihan, K. J .; Prout, K. J . Chem.
Soc., Chem. Commun. 1984, 1540.
(12) Blum, O.; Milstein, D. J . Am. Chem. Soc. 1995, 117, 4582.

TpRuH(H2)(PPh3)
Organometallics, Vol. 16, No. 6, 1997 1243
of the reaction between TpRuH(PPh3)(CH3CN) and
ethanol described above. Pressuring the NMR tube
with 10 atm of H2 led to the disappearance of the
doublet at δ -12.14 ppm and the emergence of the
doublet at δ -9.99 ppm. Releasing the H2 pressure and
further heating of the NMR solution eventually led to
the formation of TpRu(CH3)(CO)(PPh3). We assign the
doublet at δ -12.14 ppm to TpRuH(PPh3)(CH3CHO),13
as this signal appears at the early stage in both
reactions of EtOH and CH3CHO with TpRuH(PPh3)(CH3-
CN). Unfortunately we were unable to isolate and to
fully characterize the compound because of its ready
decomposition to give TpRu(CH3)(CO)(PPh3). The ac-
etaldehyde complex TpRuH(PPh3)(CH3CHO) is not un-
usual as there are numerous examples of η1- and η2-
aldehyde complexes.14,15
1
F igu r e 1. Hydride region of the H{31P} NMR spectrum
of a mixture of TpRuH2D(PPh3) (3-d1) and TpRuHD2(PPh3)
(3-d2).
TpRuHD2(PPh3) (3-d2) and a 1:1:1 triplet for TpRuH2D-
(PPh3) (3-d1) (the triplet is partially obliterated by the
quintet). The observed J HD values for both multiplets
are identical at 7.9 Hz. An upfield isotopic shift of 60
ppb is observed for 3-d2 relative to 3-d1. Assuming rapid
fluxionality between hydride and dihydrogen and little
deuterium site preference in 3, the no-exchange coupling
of the (HD) ligand, J HD, is approximately 3J HD/obs and
is therefore equal to 29.7 Hz. This value is typical for
η2-HD coordinated to a transition metal center. It is
noted that the analogous η5-cyclopentadienide complex,
(η5-C5H5)RuH3(PPh3), is a classical trihydride.16 The
reasons for this difference could be the poor electron-
donating ability of hydrotris(pyrazolyl)borate and its
preference for forming octahedral complex. Other ex-
amples of hydrotris(pyrazolyl)borate ligands favoring
dihydrogen coordination have been reported, for ex-
ample, [TpIrH(H2)(PMe3)]+,17 Tp*RhH2(H2)18 [Tp* )
hydrotris(3,5-dimethylpyrazolyl)borate], LRuH(H2)2,19
Syn th esis a n d Ch a r a cter iza tion of Tp Ru H(H2)-
(P P h 3) (3). Heating a THF solution of TpRuH(PPh3)-
(CH3CN) under 40 atm of H2 at 60 °C for 48 h gave
TpRuH3(PPh3) (3). The complex was also prepared by
heating TpRuH(PPh3)(CH3CN) in CH3OH at 60 °C
1
under 6 atm of H2 for 5-6 h in a sealed tube. The H
NMR (THF-d8) spectrum of the compound shows a
doublet (2J PH ) 17.0 Hz) which integrates to three
hydrogens, at δ -9.99 ppm. This doublet shows no sign
of decoalescence down to -110 °C. The 31P{1H} NMR
spectrum shows a singlet at δ 75.31 ppm in CD2Cl2.
2
That J PH (17.0 Hz) in 3 is significantly smaller than
2
those observed for TpRuH(PPh3)(L) (L ) CO, J PH
)
2
26.4 Hz; L ) CH3CN, J PH ) 28.0 Hz) indicates that 3
may contain a dihydrogen ligand. The presence of a
dihydrogen ligand in complex 3 is confirmed by the
small T1min (34 ms at 216 K and 400 MHz) for the
hydride signal at δ -9.99 ppm and J HD for its isoto-
pomer TpRuHxD3-x(PPh3). The HD isotopomers of 3
were generated by heating a methanol-d4 solution of
TpRuH(PPh3)(CH3CN) under 6 atm of H2 for 5 h. As
19
and LRuH(H2)L′ [L ) Tp, Tp*, or hydrotris(3-isopro-
pyl-4-bromopyrazolyl)borate (Tp′); L′ ) PCy3, THT, py,
and NHEt2].
Mech a n ism for Alcoh ol Deca r bon yla tion w ith
Tp Ru H(P P h 3)(CH3CN) (2). Isolation of TpRuR(CO)-
(PPh3) from the reactions of TpRuH(PPh3)(CH3CN) (2)
with primary alcohols reveals that the alcohols are
decarbonylated by TpRuH(PPh3)(CH3CN) in neutral
solutions. A proposed mechanism for the decarbonyla-
tion reactions based on the observations is depicted in
Scheme 1. The dihydrogen complex TpRuH(H2)(PPh3)
(3) observed at the early stage of the reaction of 2 with
ethanol in a sealed NMR tube is probably formed by
substitution of L in TpRuH(PPh3)L (L ) CH3CN, RCH2-
OH, or RCHO) by H2 produced during the reaction.
Intermediates of the ruthenium-alcohol complex (4)
and ruthenium-aldehyde complex (5) are inferred by
the 1H NMR study of the reactions of TpRuH(PPh3)(CH3-
CN) with ethanol and acetaldehyde in sealed NMR
tubes, as described above. The coordinated alcohol in
4 can either undergo oxidative addition to form the
ruthenium alkoxide dihydride intermediate or it can
protonate the metal hydride to generate a ruthenium
alkoxo dihydrogen intermediate. We prefer the alkoxo
1
shown in Figure 1, the H{31P} NMR (THF-d8, 298 K)
shows, in the hydride region, a 1:2:3:2:1 quintet for
(13) The bonding mode of the acetaldehyde is probably η2 because
there is no sign of aldehydic proton of η1-coordinated acetaldehyde in
the low-field region. The aldehydic proton of free acetaldehyde in THF-
d8 appears as a singlet at δ 9.63 ppm; it is expected that the aldehydic
proton of η1-coordinated acetaldehyde will be slightly shifted downfield
from that of the free aldehyde. Aldehydic protons in η2 complexes are
usually shifted significantly upfield, but unfortunately in the present
system, the large number of strong peaks in the 4-8 ppm region
renders observation of the aldehydic proton of η2-coordinated acetal-
dehyde impossible. Usage of 13C NMR measurement to confirm the
coordination mode of the acetaldehyde is excluded because the acquisi-
tion time of such measurement is too long, and TpRuH(PPh3)(CH3-
CN) reacts with acetaldehyde to yield the final product TpRuCH3(CO)-
(PPh3) before the acquisition time is over.
(14) η1-Aldehyde complexes: (a) Schmidt, E. K. G.; Thiel, C. H. J .
Organomet. Chem. 1981, 209, 373. (b) Honeychuck, R. V.; Bonnesen,
P. V.; Farahi, J .; Hersh, W. H. J . Org. Chem. 1987, 52, 5293. (c) Bullock,
R. M.; Rappoli, B. J .; Samsel, E. G.; Rheingold, A. L. J . Chem. Soc.,
Chem. Commun. 1989, 263. (d) Faller, J . W.; Ma, Y. J . Am. Chem.
Soc. 1991, 113, 1579. (e) Huang, Y.-H.; Gladysz, J . A. J . Chem. Educ.
1988, 65, 298 and references therein. (f) Harman, W. D.; Sekine, M.;
Taube, H. J . Am. Chem. Soc. 1988, 110, 2439. (g) Quiro´s Me´ndez, N.
Q.; Arif, A. M.; Gladysz, J . A. Angew. Chem., Int. Ed. Engl. 1990, 29,
1473. (h) Delbecq, F.; Sautet, P. J . Am. Chem. Soc. 1992, 114, 2446.
(15) η2-Aldehyde complexes: (a) Kropps, K.; Skibbe, V.; Erker, G.
J . Am. Chem. Soc. 1983, 105, 3353. (b) Gambarotta, S.; Floriani, C.;
Shiesi-Villa, A.; Guastini, C. J . Am. Chem. Soc. 1985, 107, 2985. (c)
Ferna´ndez, J . M.; Emerson, K.; Larsen, R. H.; Gladysz, J . A. J . Am.
Chem. Soc. 1986, 108, 8268. (d) Buhro, W. E.; Georgiou, S.; Ferna´ndez,
J . M.; Patton, A. T.; Strouse, C. E.; Gladysz, J . A. Organometallics
1986, 5, 956. (e) Garner, C. M.; Quiro´s Me´ndez, N.; Kowalczyk, J . J .;
Ferna´ndez, J . M.; Emerson, K.; Larsen, R. D.; Gladysz, J . A. J . Am.
Chem. Soc. 1990, 112, 5146. (f) Agbossou, F.; Ramsden, J . A.; Huang,
Y.-H.; Arif, A. M.; Gladysz, J . A. Organometallics 1992, 11, 693. (g)
Quiro´s Me´ndez, N.; Seyler, J . W.; Arif, A. M.; Gladysz, J . A. J . Am.
Chem. Soc. 1993, 115, 2323.
(16) Davies, S. G.; Moon, S. D.; Simpson, S. J . J . Chem. Soc., Chem.
Commun. 1983, 1278.
(17) Heinekdy, D. M.; Oldham, W. J ., J r. J . Am. Chem. Soc. 1994,
116, 3137.
(18) Bucher, U. E.; Lengweiler, T.; Nanz, D.; von Philipsborn, W.;
Venanzi, L. M. Angew. Chem., Int. Ed. Engl. 1990, 29, 548.
(19) (a) Halcrow, M. A.; Chaudret, B.; Trofimenko, S. J . Chem. Soc.,
Chem. Commun. 1993, 465. (b) Moreno, B.; Sabo-Etienne, S.; Chaudret,
B.; Rodriguez-Fernandez, A.; J alon, F.; Trofimenko, S. J . Am. Chem.
Soc. 1994, 116, 2635. (c) Moreno, B.; Sabo-Etienne, S.; Chaudret, B.;
Rodriguez, A.; J alon, F.; Trofimenko, S. J . Am. Chem. Soc. 1995, 117,
7441.

1244 Organometallics, Vol. 16, No. 6, 1997
Chen et al.
Sch em e 1. P r op osed Mech a n ism for
Deca r bon yla tion of RCH2OH w ith
Tp Ru H(P P h 3)(CH3CN) (2)
with CH3OH was carried out in an open reactor under
a constant bubbling of dinitrogen. According to the
mechanism depicted in Scheme 1, the intermediate
product of methanol decarbonylation will be formalde-
hyde, which, being very volatile, would escape from the
open system. If the reaction is conducted in a sealed
tube for an extended period of time, the formaldehyde
remains in the system and the reaction sequence in
Scheme 1 is thus followed.
The role of the dihydrogen complexes in the decar-
bonylation reactions is interesting. Formation of TpRu-
(OCH2R)(H2)(PPh3) and TpRu(COR)(H2)(PPh3) facili-
tates the production of RCHO and TpRuR(CO)(PPh3).
However, formation of TpRuH(H2)(PPh3) retards the
decarbonylation. Thus it was observed that the reflux
of a solution of 2 in ethanol under a slow stream of N2
led to the formation of TpRu(CH3)(CO)(PPh3) (1b) at a
faster rate than in a sealed tube. In the former case,
the stream of N2 carries away the H2 and the accumula-
tion of TpRuH(H2)(PPh3) is unlikely; hence, the decar-
bonylation reaction proceeds. In the sealed tube reac-
tion, the H2 accumulates and the decarbonylation
reaction is blocked by the generation of TpRuH-
(H2)(PPh3).
Con clu sion
Reactions of TpRuCl(PPh3)(CH3CN) with NaBH4 in
primary alcohols or TpRuH(PPh3)(CH3CN) (2) with
primary alcohols produce TpRuR(CO)(PPh3) via decar-
bonylation of the primary alcohols. Unlike most transi-
tion metal complex promoted alcohol decarbonylation
reactions, which are usually carried out in basic condi-
tions, decarbonylation of primary alcohols with 2 pro-
ceeds smoothly in nonbasic solutions. Another feature
of our alcohol decarbonylation reactions is that the R
groups of RCH2OH become the σ-organyl groups of the
final metal complexes, instead of forming the usual RH
byproducts in most alcohol decarbonylation reactions.
We propose that the decarbonylation of alcohols by 2
proceeds via metal-η2-aldehyde and -dihydrogen com-
plexes. We have been able to identify a dihydrogen
complex observed in the early stage of the decarbony-
lation reaction, by carrying out its independent synthe-
sis.
dihydrogen intermediate as the fragments [TpRuL-
(PPh3)]0 or 1+ (L ) H, PPh320 or CH3CN20) all form dihy-
drogen complexes with H2. Intramolecular protonation
of TpRuH(PPh3)(RCH2OH) is reasonable as the acidity
of alcohol coordinated on metal is enhanced, and M-H
can be very effective proton acceptor.21 There are
examples of intramolecular and intermolecular proto-
nations of M-H by R-O-H, R-S-H, and RR′N-H.21
For similar reasons, we prefer the formation of the acyl
dihydrogen intermediate over the acyl dihydride from
5. It should be noted that, in the catalytic dehydroge-
nation of alcohols with RuH2(N2)(PPh3)3, the trihydride
intermediate [RuH3(PPh3)3]- was protonated by ethanol
to give the molecular dihydrogen complex RuH2(H2)-
(PPh3)3, which readily lost H2 to generate the unsatur-
ated species RuH2(PPh3)3.8e
Consistent with the mechanism, it was observed that
the decarbonylation product TpRuH(CO)(PPh3) was not
obtainable when the reaction of TpRuH(PPh3)(CH3CN)
Exp er im en ta l Section
Ruthenium trichloride, RuCl3‚3H2O, and lithium tetrafluo-
roborate were obtained from Aldrich. Pyrazole, sodium boro-
hydride, and tetrafluoroboric acid in etheral solution (HBF4‚
Et2O, 54%) were purchased from Fluka. Triphenylphosphine
was obtained from Merck and was recrystallized from ethanol
before use. 4-Methylbenzyl alcohol and 4-chlorobenzyl alcohol
were prepared respectively from reduction of their correspond-
ing 4-substituted benzaldedydes using NaBH4 in ethanol, and
the solid products obtained were recrystallized from petroleum
(20) Chan, W. C.; Lau, C. P.; Chen, Y.-Z.; Fang, Y.-Q.; Ng, S. M.;
J ia, G. Organometallics 1997, 16, 34.
(21) (a) Crabtree, R. H.; Siegbahn, P. E. M.; Eisenstein, O.; Rhein-
gold, A. L.; Koetzle, T. F. Acc. Chem. Res. 1996, 29, 348. (b) Shubina,
E. S.; Belkova, N. V.; Krylov, A. N.; Vorontsov, E. V.; Epstein, L. M.;
Gusev, D. G.; Niedermann, M.; Berke, H. J . Am. Chem. Soc. 1996,
118, 1105. (c) Xu, W.; Lough, A. J .; Morris, R. H. Inorg. Chem. 1996,
35, 1549. (d) Park, S.; Lough, A. J .; Morris, R. H. Inorg. Chem. 1996,
35, 3001. (e) Yao, W.; Crabtree, R. H. Inorg. Chem. 1996, 35, 3007. (f)
Patel, B. P.; Yao, W.; Yap, G. P. A.; Rheingold, A. L.; Crabtree, R. H.
Chem. Commun. 1996, 991. (g) Peris, E.; Lee, J . C., J r.; Rambo, J . R.;
Eisenstein, O.; Crabtree, R. H. J . Am. Chem. Soc. 1995, 117, 3485. (h)
Peris, E.; Wessel, J .; Patel, B. P.; Crabtree, R. H. J . Chem. Soc., Chem.
Commun. 1995, 2175. (i) Wessel, J .; Lee, J . C., J r.; Peris, E.; Yap, G.
P. A.; Fortin, J . B.; Ricci, J . S.; Sini, G.; Albinati, A.; Koetzle, T. F.;
Eisenstein, O.; Rheingold, A. L.; Crabtree, R. H. Angew. Chem., Int.
Ed. Engl. 1995, 34, 2507. (j) Lee, J . C., J r.; Peris, E.; Rheingold, A. L.;
Crabtree, R. H. J . Am. Chem. Soc. 1994, 116, 11014. (k) Lee, J . C.,
J r.; Rheingold, A. L.; Muller, B.; Pregosin, P. S.; Crabtree, R. H. J .
Chem. Soc., Chem. Commun. 1994, 1021. (l) Lough, A. J .; Park, S.;
Ramachandran, R.; Morris, R. H. J . Am. Chem. Soc. 1994, 116, 8356.
(m) Sellmann, D.; Ka¨ppler, J .; Moll, M. J . Am. Chem. Soc. 1993, 115,
1830. (n) Boyd, S. E.; Field, L. D.; Hambley, T. W.; Young, D. J . Inorg.
Chem. 1990, 29, 1496. (o) Baker, M. V.; Field, L. D.; Young, D. J . J .
Chem. Soc., Chem. Commun. 1988, 546.
22
ether (80-100 °C). The complex TpRuCl(PPh3)2 was syn-
thesized according to published procedures. Solvents were
distilled under dry nitrogen atmosphere with appropriate
drying agents (solvent/drying agent): methanol/Mg-I2, aceto-
nitrile/P2O5, dichloromethane/P2O5, tetrahydrofuran/Na-ben-
zophenone, diethyl ether/CaH2, n-hexane/Na.23 All reactions
were performed under an atmosphere of dry nitrogen using
standard Schlenk techniques unless otherwise specified.
(22) Alcock, N. W.; Burns, I. D.; Hill, A. F.; Claire, K. S. Inorg. Chem.
1992, 31, 2906.
(23) Perrin, D. R.; Armanego, W. L. Purification of Laboratory
Chemicals, 2nd ed.; Pergmon: Oxford, U.K., 1980.

TpRuH(H2)(PPh3)
Organometallics, Vol. 16, No. 6, 1997 1245
Ta ble 1. NMR a n d IR Sp ectr oscop ic Da ta for Tp Ru R(CO)(P P h 3)
δ(31P{1H})
ν(CO)
(KBr, cm-1
ν(B-H)
ν(Ru-H)
R
δ(1H) (ppm)a
δ(13C{1H}) (ppm)a
(ppm)a
)
(KBr, cm-1
)
(KBr, cm-1
)
1a b
H
-11.99 (d,2J PH ) 26.4 Hz, 1H, Ru-H);
9H of Tp,c 5.68 (t, 1H), 5.96 (t, 1H),
6.12 (t, 1H), 6.54 (d, 1H), 6.72 (d, 1H),
7.53 (d, 1H), 7.56 (d, 1H), 7.68 (d, 1H),
7.80 (d, 1H); 7.24-7.35 (m, 15H of PPh3)
0.11 (d,3J PH ) 3.0 Hz, 3H, Ru-CH3);
9H of Tp,c 5.82 (t, 1H), 5.87 (t, 1H),
6.15 (t, 1H), 6.65 (d, 1H), 6.73 (d, 1H),
7.57 (d, 1H), 7.60 (d, 1H), 7.65 (d, 1H),
7.68, (d, 1H); 7.17-7.33 (m, 15H
of PPh3)
1.05 (t, J HH ) 6.9 Hz, 3H, Ru-CH2CH3);
0.95, 1.15 (m, 2H, Ru-CH2CH3);
9H of Tp,c 5.79 (t, 1H), 5.81 (t, 1H), 6.10
(t, 1H), 6.69 (d, 1H), 6.73 (d, 1H) 7.51 (d,
1H), 7.57 (d, 1H), 7.59 (d, 1H), 7.69
(d, 1H); 7.09-7.29 (m, 15H of PPh3)
0.75 (t, J HH ) 7.0 Hz, 3H,
Ru-CH2CH2CH3); 0.95-1.76 (m,
4H, Ru-CH2CH2-CH3); 9H of Tp,c
5.86 (t, 1H), 5.89 (t, 1H), 6.17
206.6 (d,2J PC ) 17.1 Hz,
Ru-CO)
68.10 (s)
55.63 (s)
1928 (vs)
2479 (br)
1985 (w)
2
1b Me
1c Et
1d Pr
-5.8 (d, J PC ) 9.2 Hz,
1923 (vs)
2517 (br)
Ru-CH3); 207.9 (d,
2J PC ) 18.0 Hz,
Ru-CO)
2
8.7 (d, J PC ) 9.8 Hz,
55.60 (s)
55.66 (s)
1916 (vs)
1916 (vs)
2494 (br)
2465 (br)
Ru-CH2CH3); 20.8 (s,
Ru-CH2CH3); 8.5 (d,
2J PC ) 19.6 Hz, Ru-CO)
20.3 (s, Ru-CH2CH2CH3)
2
20.5 (d, J PC ) 8.9 Hz,
Ru-CH2CH2CH3; 30.4
(s, Ru-CH2CH2CH3);
2
(t, 1H), 6.79 (d, 1H), 6.83 (d, 1H),
7.53 (d, 1H), 7.64 (d, 1H), 7.66
(d, 1H), 7.72 (d, 1H); 7.12-7.37
(m, 15H of PPh3)
208.0 (d, J PC ) 16.7 Hz,
Ru-CO)
2
1e Ph
9H of Tp,c 5.80 (t, 1H), 5.84 (t, 1H), 5.92
(t, 1H), 6.58 (d, 1H), 6.67 (d, 1H),
7.08 (d, 1H), 7.51 (d, 1H), 7.57 (d, 1H),
7.67 (d, 1H); 6.72-6.77, 6.81-6.87,
7.11-7.17, 7.28-7.33 (m, 15H of
PPh3, 5H of Ph)
163.2 (d, J PC ) 11.1 Hz,
48.87 (s)
52.95 (s)
52.72 (s)
1916 (vs)
1928 (vs)
1933 (vs)
2494 (br)
2468 (br)
2465 (br)
ipso C of Ru-C6H5);
2
206.9 (d, J PC ) 15.7
Hz, Ru-CO)
1f C6H4CH3-4 2.25 [s, 3H, Ru-(C6H4CH3-4)]; 6H of Tp,c
5.86 (t, 1H), 5.90 (t, 1H), 6.00 (t, 1H),
7.58 (d, 1H), 7.63 (d, 1H), 7,74 (d, 1 H);
6.61-6.65, 6.81-6.87, 7.11-7.16,
20.8 [s, Ru-(C6H4CH3-4)];
2
157.5 [d, J PC ) 12.6 Hz,
ipso C of Ru-(C6H4CH3-4)];
2
206.6 (d, J PC ) 15.6 Hz,
7.30-7.32 [m, 3H of Tp, 4H of
Ru-CO)
Ru-(C6H4CH3-4), 15H of PPh3]
2
1g C6H4Cl-4
9H of Tp,c 5.88 (t, 1H), 5.90 (t, 1H), 6.01
(t, 1H), 6.63 (d, 1H), 6.81 (d, 1H), 7.00
(d, 1 H), 7.58 (d, 1H), 7.65 (d, 1H),7.74
(d, 1H); 6.71-6.74, 6.77-6.80,
161.7 [d, J PC ) 12.4 Hz,
ipso C of Ru-(C6H4Cl-4)];
2
206.6 (d, J PC ) 15.6 Hz,
Ru-CO)
6.82-6.87, 7.14-7.17, 7.30-7.34
[m, 4H of Ru-(C6H4Cl-4), 15H of PPh3]
a
b
CDCl3. In CD2Cl2 solution. c All coupling constants for pyrazolyl proton resonances were about 2 Hz.
Infrared spectra were obtained from a Nicolet Magna 750
FT-IR spectrophotometer or a Perkin-Elmer 983 IR spectro-
photometer. 1H NMR spectra were obtained from a Bruker
ARX-300 or a Bruker ARX-400 spectrometer. Chemical shifts
(δ, ppm) were reported relative to tetramethylsilane (TMS).
31P{1H} NMR spectra were recorded on a Bruker ARX-400
instrument at 161.70 MHz or on a Bruker ARX-300 instrument
at 121.49 MHz. 31P chemical shifts were externally referenced
to 10% P(OMe)3 solution in CDCl3 (δ 140.4 ppm). 13C{1H}
NMR spectra were taken on a Bruker ARX-300 instrument
at 75.47 MHz or on a Bruker ARX-400 spectrometer at 100.54
MHz; chemical shifts were internally referenced to CDCl3 (δ
77.0 ppm). Elemental analyses were performed by Butter-
worth Laboratories Ltd., London, U.K., and Institute of
Chemistry, Academia Sinica, Beijing, China.
nances were about 2 Hz); 7.23-7.37 (m, 15 H of PPh3). 31P-
{1H} NMR (CDCl3, 121.49 MHz, 25 °C): δ 51.7 (s).
P r ep a r a tion of Tp Ru H(CO)(P P h 3) (1a ). A 100 mL
Schlenk tube loaded with TpRuCl(PPh3)(CH3CN) (0.20 g, 0.31
mmol) and NaBH4 (0.10 g, 2.6 mmol) was degassed and filled
with nitrogen, for three cycles. Freshly distilled methanol (20
mL) was added, and the tube was then sealed. The mixture
was stirred at 70 °C for 14 h, and then the solvent was removed
by vacuum. The white residue was treated with 10 mL of
1-propanol. A white solid was collected, washed with a few
portions of diethyl ether, and dried in vacuo. Yield ) 0.13 g
(69%). Anal. Calcd for C28H26BN6OPRu: C, 55.54; H, 4.33;
N, 13.88. Found: C, 55.82; H, 4.18; N, 13.65.
P r ep a r a t ion of Tp R u (CH 3)(CO)(P P h 3) (1b). TpRuCl-
(PPh3)(CH3CN) (0.15 g, 0.23 mmol) and sodium borohydride
(0.08 g, 2.3 mmol) were combined in a two-necked round
bottom flask fitted to a condenser. The flask was evacuated
and filled with nitrogen for three cycles. Distilled, degassed
ethanol (40 mL) was added via a cannula, and the resulting
reaction mixture was heated under reflux for 6 h. The solution
was concentrated to ca. 8 mL to give a white solid, which was
then filtered out. The solid was washed with a few 20 mL
portions of ethanol (95%) and diethyl ether and was then
vacuum-dried at room temperature for 6 h. Yield ) 0.07 g
(49%). Anal. Calcd for C29H28BN6OPRu: C, 56.22; H, 4.56;
N, 13.57. Found: C, 55.91; H, 4.42; N, 13.31.
NMR and IR spectroscopic data of TpRuR(CO)(PPh3) (1a -
g) are collected in Table 1.
P r ep a r a tion of Tp Ru Cl(P P h 3)(CH3CN). A 0.50 g (0.59
mmol) amount of TpRuCl(PPh3)2 in a two-necked round bottom
flask fitted with a condenser was evacuated and flushed with
nitrogen. A degassed solution of tetrahydrofuran and aceto-
nitrile (9:1, 30 mL) was added via syringe. The solution was
heated at 60 °C for 6 h with stirring under nitrogen and then
concentrated to a few milliliters. A yellow solid precipitated
out and was collected by filtration and washed with diethyl
ether and then hexane. It was dried under vacuum at room
P r ep a r a tion of Tp Ru (C2H5)(CO)(P P h 3) (1c). This com-
plex was prepared by using the same procedure as for
preparation of 1b, except that 1-propanol (40 mL) was used.
Yield ) 0.10 g (69%). Anal. Calcd for C30H30BN6OPRu: C,
56.87; H, 4.78; N, 13.27. Found: C, 56.50, H, 4.90, N, 13.41.
P r ep a r a tion of Tp Ru (n -C3H7)(CO)(P P h 3) (1d ). This
complex was prepared by the same procedure as for the
temperature. Yield ) 0.26 g (67%). Anal. Calcd for C29H28
-
BClN7PRu: C, 53.35; H, 4.32; N, 15.02. Found: C, 53.80; H,
4.65; N, 14.92. IR (KBr, cm-1): ν(CtN) 2278 (sh, w), ν(B-H)
2474 (br, med). 1H NMR (CDCl3, 300 MHz, 25 °C): δ 2.10 (s,
3H, CH3CN), 5.75 (t, 1H), 5.84 (t, 1H), 6.22 (t, 1H), 6.62 (d,
1H), 6.94 (d, 1H), 7.63 (d, 1H + 1H), 7.64 (d, 1H), 8.07 (d, 1H)
(9H of Tp, all coupling constants for pyrazolyl proton reso-

1246 Organometallics, Vol. 16, No. 6, 1997
Chen et al.
preparation of 1b, except that 1-butanol (40 mL) was used.
Yield ) 0.09 g (60%). Anal. Calcd for C31H32BN6OPRu: C,
57.50; H, 4.98; N, 12.98. Found: C, 57.68; H, 4.82; N, 13.06.
P r ep a r a tion of Tp Ru (C6H5)(CO)(P P h 3) (1e). The prepa-
ration procedures were similar to that for the preparation of
1b, except benzyl alcohol was used in place of ethanol and the
reflux time was extended to 12 h. The yield of the white solid
obtained was 0.100 g (64%). Anal. Calcd for C34H30BN6-
OPRu: C, 59.91; H, 4.45, N, 12.33. Found: C, 60.06; H, 4.55;
N, 12.56.
coupling constants for pyrazolyl proton resonances were about
2 Hz); 7.17-7.36 (m, 15H of PPh3). 31P{1H} NMR (CD2Cl2,
161.70 MHz, 25 °C): δ 75.31 (s). Variable-temperature T1
measurements on the H2 signal were carried out by the
inversion-recovery method using standard 180°-τ-90° pulse
sequences. T1 (400 MHz, CD2Cl2, ms): 86 (293 K), 63 (273
K), 41 (243 K), 34 (223 K), 33 (213 K), 36 (203 K), 41 (193 K).
T1min (34 ms at 216 K and 400 MHz) was obtained from the
“V”-shaped ln T1 vs 1000/T plot.24
Meth od b. Into a 10 mm × 80 mm thick-walled tube fitted
with a threaded vacuum stopcock was loaded 600 mg (0.96
mmol) of TpRuH(PPh3)(CH3CN) (2). The tube was evacuated
and then filled with N2, for three cycles. A 2 mL volume of
methanol was added under N2, and the tube was then
pressurized with 6 atm of H2 and heated at 60 °C. 2, which
was in fine powder form, was not completely dissolved in the
methanol, but as the reaction proceeded, the powder gradually
disappeared and yellow solids started crystallizing out. The
reaction was stopped after 5 h, and more crystals formed as
the tube cooled to room temperature. The tube was vented,
and the solution above the crystals was decanted. The yellow
crystals of TpRuH(H2)(PPh3) (3) were collected and dried in
vacuo. Yield ) 0.21 g (38%).
P r ep a r a tion of Tp Ru (C6H4CH3-4)(CO)(P P h 3) (1f).
A
2-necked pear-shaped flask loaded with TpRuCl(PPh3)(CH3-
CN) (0.30 g, 0.46 mmol), NaBH4 (0.16 g, 4.2 mmol), and
4-methylbenzyl alcohol (5.0 g, 0.041 mol) was degassed and
filled with nitrogen, for three cycles. Freshly distilled THF
(20 mL) was added, and the mixture was stirred under reflux
for 3 days. The mixture was then filtered, and the filtrate was
concentrated to 2-3 mL. A white solid precipitated out after
the addition of ethanol (5 mL). The solid was collected by
filtration and washed with ethanol (5 mL × 2) and then dried
in vacuo for 8 h at 80 °C. Yield ) 0.17 g (53%). Anal. Calcd
for C35H32BN6OPRu: C, 60.43; H, 4.64, N, 12.08. Found: C,
59.92; H, 4.26, N, 12.20.
P r ep a r a tion of Tp Ru (C6H4Cl-4)(CO)(P P h 3) (1g). This
complex was prepared by using a similar procedure as for the
preparation of 1f, except that 4-chlorobenzyl alcohol (6.5 g,
0.046 mol) was used and the reflux time was extended to 5
days. Yield of the white solid obtained: 0.23 g (70%). Anal.
Calcd for C34H29BClN6OPRu: C, 57.03; H, 4.08; N, 11.74.
Found: C, 56,62, H, 4.27; N, 11.40.
P r ep a r a tion of Tp Ru H(P P h 3)(CH3CN) (2). A 50 mL
2-necked pear-shaped flask loaded with TpRuCl(PPh3)(CH3-
CN) (0.30 g, 0.46 mmol) and NaBH4 (0.16 g, 4.2 mmol) was
degassed and then filled with nitrogen, for three cycles.
Freshly distilled dry THF (20 mL) was added, and the mixture
was stirred and refluxed under nitrogen for 3 days. The
mixture was filtered, and to the filtrate was added 5 mL of
acetonitrile; the solution was refluxed for 1 day. The solvent
of the solution was removed, and a yellow powder was
obtained. Dry diethyl ether (10 mL) was added to dissolve
the solid, and the insoluble matter was filtered off. The filtrate
was then concentrated to 1-2 mL, and 10 mL of dry pentane
was added to precipitate out an air-sensitive yellow solid. It
was vacuum-dried and stored under nitrogen. Yield ) 0.18 g
(52%). Anal. Calcd for C29H29BN7PRu: C, 56.32, H, 4.73, N,
15.86. Found: C, 56.70; H; 4.90; N, 15,66. IR (KBr, cm-1):
P r ep a r a tion of Tp Ru HxD3-x(P P h 3) (x ) 2, 3-d 1; x ) 1,
3-d 2). Mixture of the isotopomers, 3-d1 and 3-d2 was prepared
by following method b as for the preparation of 3, except that
methanol-d4 was used. The 1H{31P} NMR spectrum of the
mixture (THF-d8, 400 MHz, 25 °C) showed a 1:2:3:2:1 quintet
at δ -10.11 ppm (due to 3-d2) and a 1:1:1 triplet partially
masked by the quintet, at δ -10.05 ppm (due to 3-d1), J HD/obs
for both the quintet and triplet was identical and was equal
to 7.9 Hz.
1H NMR Stu d y of th e Rea ction of Tp Ru H(P P h 3)-
(CH3CN) (2) w ith C2H5OH. A Wilmad pressure NMR tube
loaded with TpRuH(PPh3)(CH3CN) (∼100 mg) was evacuated
and then filled with N2, for three cycles. Dry THF-d8 (0.3 mL)
was added to the tube under N2, and the tube was then sealed
1
and heated at 70 °C for 1 h. An H NMR spectrum was taken
after cooling the tube to room temperature. Three small
doublets were observed at δ -9.90 (d, 2J PH ) 17.0 Hz), -12.14
(d, 2J PH ) 27.2 Hz), and -12.40 (d, 2J PH ) 29.0 Hz) ppm. The
NMR tube was then pressurized with 10 atm of H2 and heated
at 60 °C for another 1 h. After cooling of the sample to room
temperature, an 1H NMR spectrum was again taken, and it
was observed that the two doublets at δ -12.14 and -12.40
ppm disappeared and the intensity of the one at δ -9.99 ppm
was greatly enhanced.
ν(B-H) 2461 (br, med); ν(CtN) 2258 (w); ν(Ru-H) 1890 (w).
2
1H NMR (CD2Cl2, 400 MHz, 25 °C): δ -13.91 (d, 1H, J PH
)
1H NMR Stu d y of th e Rea ction of Tp Ru H(P P h 3)-
(CH3CN) (2) w ith CH3CHO. A Wilmad pressure NMR tube
loaded with 100 mg of TpRuH(PPh3)(CH3CN) (2) was evacu-
ated and then filled with N2, for three cycles. A 0.3 mL volume
of THF-d8 and 0.1 mL of CH3CHO were added under N2. The
tube was then sealed and heated at 70 °C for 10 min. After
cooling of the sample to room temperature, an 1H NMR
spectrum of the reaction mixture was taken; a small doublet
28.0 Hz, Ru-H); 1.69 (s, 3H, CH3CN); 5.60 (t, 1H), 5.93 (t,
1H), 6.14 (t, 1H), 6.50 (d, 1H), 7.11 (d, 1H), 7.53 (d, 1H), 7.60
(d, 1H), 7.66 (d, 1H), 7.75 (d, 1H) (9H of Tp, all coupling
constants for pyrazolyl proton resonances were about 2 Hz);
7.12-7.28 (m, 15H of PPh3). 31P{1H} NMR (CD2Cl2, 161.70
MHz, 25 °C): δ 77.62 (s).
P r ep a r a tion of Tp Ru H(H2)(P P h 3) (3). Meth od a . The
preparation was carried out in a 250 mL stainless steel
autoclave. A 50 mL round bottom flask, loaded with 200 mg
(0.32 mmol) of TpRuH(PPh3)(CH3CN) (2) and 20 mL of freshly
distilled THF, was put into the autoclave. After the autoclave
was flushed with hydrogen five times, the system was stirred
at 60 °C and under 40 atm of H2. At the end of the reaction
time (48 h), the reactor was cooled rapidly and vented
carefully. The solution was concentrated to 1-2 mL, and 30
mL of hexane was added. The solution was filtered under
nitrogen, and the filtrate was collected. The solvent of the
yellow filtrate was removed in vacuo to produce an air-
sensitive yellow solid. Yield ) 0.12 g (65%). Anal. Calcd for
2
was observed at δ -12.14 ppm (d, J PH ) 27.2 Hz). Further
heating of the tube at 70 °C for another 1 h led to the
disappearance of the doublet at δ -12.14 ppm, and the methyl
peak of TpRu(CH3)(CO)(PPh3) (1b) was observed at δ 0.11
ppm.
Ack n ow led gm en t. This work was supported by the
Hong Kong Research Grant Council Earmarked Grant
HKP 91/94P. We thank Professor Richard Haynes for
helpful discussion and proofreading the manuscript.
OM960817U
C
27H28BN6PRu: C, 55.96; H, 4.87, N, 14.51. Found: C, 56.12;
H, 4.65; N, 14.37. 1H NMR (CD2Cl2, 400 MHz, 25 °C): δ -9.97
(24) (a) Hamilton, D. G.; Crabtree, R. H. J . Am. Chem. Soc. 1988,
110, 4126. (b) Bautista, H. E.; Earl, K. A.; Maltby, P. A.; Morris, R.
H.; Schweitzer, C. T.; Sella, A. J . Am. Chem. Soc. 1988, 110, 7031.
2
(d, J PH ) 17 Hz, 3H, Ru-H3); 5.92 (t, 2H), 6.05 (t, 1H), 6.85
(d, 2H), 7.45 (d, 1H), 7.56 (d, 1H), 7.68 (d, 2H) (9H of Tp, all