Activation of alkynols by half-sandwich ruthenium complexes: isolation of hydroxyalkynyl(hydrido) and hydroxyvinylidene derivatives

Article abstract of DOI:10.1021/om980970j

The complex [Cp*RuCl(PEt3)2l (Cp= CsMeJ reacts with 2-propyn-l-ol derivatives, HC=CC(OH)RR' (R = R'= H; R = R' = CH3; R = CH3, R' = Ph), in MeOH in the presence of NaBPh4 yielding the metastable 3-hydroxyalkynyl hydrido complexes [Cp*Ru(H)(CCC(OHJRR'XPEt-

Full text of DOI:10.1021/om980970j

950
Organometallics 1999, 18, 950-951
Activa tion of Alk yn ols by Ha lf-Sa n d w ich Ru th en iu m
Com p lexes: Isola tion of Hyd r oxya lk yn yl(h yd r id o) a n d
Hyd r oxyvin ylid en e Der iva tives
Emilio Bustelo, Manuel J ime´nez-Tenorio, M. Carmen Puerta,* and
Pedro Valerga
Departamento de Ciencia de los Materiales e Ingenier´ıa Metalu´rgica y Quı´mica Inorga´nica,
Facultad de Ciencias, Universidad de Ca´diz, Aptdo. 40, 11510 Puerto Real, Ca´diz, Spain
Received December 2, 1998
Summary: The complex [Cp*RuCl(PEt3)2] (Cp* ) C5Me5)
reacts with 2-propyn-1-ol derivatives, HCtCC(OH)RR′
(R ) R′) H; R ) R′ ) CH3; R ) CH3, R′ ) Ph), in MeOH
in the presence of NaBPh4 yielding the metastable
3-hydroxyalkynyl hydrido complexes [Cp*Ru(H)(CtCC-
(OH)RR′)(PEt3)2][BPh4], intermediates in the formation
of the corresponding 3-hydroxyvinylidene complexes, to
which these compounds rearrange both in solution and
in the solid state.
ing hydroxyvinylidene complex.1,8 Recently, Esteruelas
et al. have isolated the η2-alkyne derivative [CpOs(κ1-
OC(O)CH3)(η2-HCtCC(OH)Ph2)(PiPr3)2].9 On the other
hand, Werner et al. have reported formation of rhodium
allenylidenes via (η2-alkyne)- and alkynyl(hydrido)-
rhodium as intermediates.10 Likewise, the interaction
i
of [OsCl(NO)(PiPr2R)2] (R ) Ph, Pr) with HCtC-CR2-
(OH) (R ) CH3, Ph) affords the alkynyl(hydrido)-
osmium(II) complex.11 However, there is no evidence for
ruthenium analogue species, even considering that
allenylideneruthenium(II) complexes constitute the larg-
est group of this sort of compound.
As a continuation of our recent studies on 1-alkyne
activation by [Cp*RuCl(dippe)],12 we report now that the
product of the reaction of [Cp*RuCl(PEt3)2]13 (1) with
2-propyn-1-ol derivatives and NaBPh4 in MeOH is very
sensitive to the order in which the reagents are added.
Thus, if an excess of NaBPh4 and the corresponding
alkynol are dissolved in MeOH at 0 °C, and then the
complex 1 is added, the hydroxyalkynyl hydrido complex
[Cp*Ru(H)(CtCC(OH)RR′)(PEt3)2][BPh4] (R ) R′ ) H
(2); R ) R′) CH3 (3); R ) CH3, R′) Ph (4))14 precipitates
immediately as a white/yellow solid. Any change in this
The discovery of a general method for the preparation
of ruthenium-allenylidene complexes based on the
direct activation of propargyl alcohol derivatives by
electron-rich ruthenium(II) chloride complexes1 has
allowed the study in detail of these highly unsaturated
compounds and of related species.2 This process usually
leads directly to the formation of ruthenium allenylidene
complexes3 which can be stable or undergo further
processes such as the addition of nucleophiles.4 In some
cases, a mixture with the corresponding isomeric vi-
nylvinylidene complex is obtained.5 The initial formation
of an hydroxyvinylidene complex,6 which has been
detected5b or even isolated in some instances,7 has been
postulated. Elimination of water yields the CdCdCRR′
unit in the coordination sphere of a ruthenium center.
The preliminary CtC bond coordination to the metal
complex has been proposed as the first step, followed
by subsequent tautomerization to give the correspond-
(8) Pilette, D.; Ouzzine, K.; Le Bozec, H.; Dixneuf, P. H. Organo-
metallics 1992, 11, 809-817.
(9) Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E. Organome-
tallics 1998, 17, 3141-3142.
(10) Werner, H.; Rappert, T.; Wiedemann, R.; Wolf, J .; Mahr, N.
Organometallics 1994, 13, 2721-2727.
(11) Werner, H.; Flu¨gel, R.; Windmu¨ller, B.; Michenfelder, A.; Wolf,
J . Organometallics 1995, 14, 612-618.
* E-mail address: carmen.puerta@uca.es.
(12) de los R´ıos, I.; J ime´nez Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Chem. Soc., Chem. Commun. 1995, 1757. de los R´ıos, I.; J ime´nez
Tenorio, M.; Puerta, M. C.; Valerga, P. J . Am. Chem. Soc. 1997, 119,
6529-6538.
(1) Selegue, J . P. Organometallics 1982, 1, 217-218.
(2) Crochet, P.; Demerseman, B.; Vallejo, M. I.; Gamasa, M. P.;
Gimeno, J .; Borge J .; Garc´ıa-Granda, S. Organometallics 1997, 16,
5406-5415. Esteruelas, M. A.; Oro, L. A.; Schrickel, J . Organometallics
1997, 16, 796-799. Werner, H. J . Chem. Soc., Chem. Commun. 1997,
903.
(3) Touchard, D.; Pirio, N.; Dixneuf, P. H. Organometallics 1995,
14, 4920-4928. Leung, W.; Chan, E.; Wong, W. Organometallics 1998,
17, 1245-1247.
(4) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J .; On˜ate,
E. Organometallics 1997, 16, 5826-5835. Cadierno, V.; Gamasa, M.
P.; Gimeno, J .; Lo´pez-Gonza´lez, M. C.; Borge, J .; Garc´ıa-Granda, S.
Organometallics 1997, 16, 4453-4463.
(5) (a) Selegue, J . P.; Young, B. A.; Logan, S. L. Organometallics
1991, 10, 1972. (b) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Gonza´lez-
Cueva, M.; Lastra, E.; Borge, J .; Garc´ıa-Granda, S.; Pe´rez-Carren˜o,
E. Organometallics 1996, 15, 2137-2147.
(6) Selegue, J . P. J . Am. Chem. Soc. 1983, 105, 5921-5923. Werner,
H.; Martin, M.; Gevert, O. J . Chem. Soc., Dalton Trans. 1996, 2275-
2283.
(7) Le Lagadec, R.; Roman, E.; Toupet, L.; Mu¨ller, U.; Dixneuf, P.
H. Organometallics 1994, 13, 5030-5039. Werner, H.; Braun, T.;
Steinert, H. J . Organomet. Chem. 1995, 488, 169-176. de los R´ıos, I.;
J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J . Organomet. Chem.
1997, 549, 221-232.
(13) Coto, A.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 1998, 20, 4392-4399.
(14) Experimental procedure for the preparation of complexes
2-4: Complex 1 (127 mg, 0.25 mmol) was added to a solution of the
corresponding alkynol (0.30 mmol) and NaBPh4 (81 mg, 0.50 mmol)
in 10 mL of MeOH at 0 °C (ice bath). The mixture was allowed to warm
until precipitation of a white/yellow solid, which is filtered, washed
with cold EtOH, and hexane, and stored at -20 °C. Yield: 2 194 mg
(91%), 3 210 mg (95%), 4 212 mg (90%). Selected spectral data for 2:
IR (Nujol): ν(OH) not observed, ν(CtC) 2117, ν(Ru-H) 2024 cm-1. 1H
NMR (400 MHz, CDCl3, 273 K): δ -9.25 (t, J HP ) 30.5 Hz, Ru-H),
1.67 (t, J HP ) 1.2 Hz, C5(CH3)5), 4.29 (t, J HP ) 2.7 Hz, Ru-CtC-CH2-
OH). 31P{1H} NMR (161.89 MHz, CDCl3, 273 K): δ 36.8 (s). 3: IR
(Nujol): ν(OH) 3353, ν(CtC) 2120, ν(Ru-H) 2028 cm-1. 1H NMR (400
MHz, CDCl3, 273 K): δ -9.28 (t, J HP ) 30.6 Hz, Ru-H), 1.46 (s, Ru-
CtC-C(CH3)2OH), 1.66 (t, J HP ) 1.2 Hz, C5(CH3)5). 31P{1H} NMR
(161.89 MHz, CDCl3, 273 K): δ 36.8 (s). 4: IR (Nujol): ν(OH) 3312,
ν(CtC) 2104, ν(Ru-H) 2020 cm-1. 1H NMR (400 MHz, CDCl3, 273 K):
δ -9.35 (t, J HP ) 29.9 Hz, Ru-H), 1.65 (t, J HP ) 1.2 Hz, C5(CH3)5),
1.82 (s, Ru-CtC-C(CH3)PhOH), 7.29, 7.37 and 7.55 (m, Ru-CtC-
CMe(C6H5)OH). 31P{1H} NMR (161.89 MHz, CDCl3, 273 K): δ 37.4
and 37.6 (d, J PP′ ) 20.7 Hz).
10.1021/om980970j CCC: $18.00 © 1999 American Chemical Society
Publication on Web 02/25/1999

Communications
Organometallics, Vol. 18, No. 6, 1999 951
Sch em e 1a
the hydroxyalkynyl hydride and/or dehydration prod-
ucts. Solid-state isomerization to hydroxyvinylidene at
30-35 °C allowed the isolation and spectroscopic char-
acterization of these intermediates.15 This process can
be monitored following the ν(CtC) decrease or ν(CdC)
increase by IR spectroscopy. 31P{1H} NMR spectra
consist of one sharp singlet in all cases except for the
complex 7, which, like its precursor, shows an AB
coupling pattern due to the existence of a chiral carbon
on the molecule.
We can conclude that activation of propargyl alcohols
by half-sandwich ruthenium(II) complex 1 occurs through
3-hydroxyalkynyl(hydrido) and 3-hydroxyvinylidene com-
plexes as intermediates, which have been isolated as
stable solids at 0 °C, independently of the propargyl
alcohol used. However, it is known that the formation
and stabilization of the allenylidene moiety by the metal
complex depends on the nature of the substituted
propargyl alcohol and on the ancillary ligands,5b as
inferred from our investigations in progress about
ulterior transformations of compounds 5-7. The η2-
coordination of the propargyl alcohol before the forma-
tion of the hydroxyalkynyl hydride species has not been
detected in these cases, probably due to the steric
influence of the Cp* ligand.
a
Reagents and conditions: (i) HCtC-C(OH)RR′, NaBPh4,
MeOH, 0 °C; (ii) room temperature (spontaneous and irrevers-
ible both in solution and in the solid state).
order may lead to the nondetection of these intermedi-
ates, yielding a mixture of isomerization, dehydration,
and nucleophilic attack products depending on the
alkynol employed, reaction time, etc. These compounds
undergo irreversible isomerization to hydroxyvinylidene,
both in solution and in the solid state at room temper-
ature; hence these products must be handled and stored
at temperatures close to 0 °C, to prevent their isomer-
ization and/or dehydration.
Complexes 2-4 are formally derived from the inser-
tion of the metal atom into the C-H bond of the alkynol,
and therefore must be considered RuIV species. They
display the ν(OH) IR absorption between 3310 and 3355
cm-1, one strong ν(CtC) band at 2100-2120 cm-1, and
one weak ν(Ru-H) at 2020-2030 cm-1. 1H and 31P{1H}
NMR spectra were recorded at 0 °C. The hydride
resonance appears as one high-field triplet in all cases,
whereas the 31P{1H} NMR spectra consist of one sharp
singlet, except for the complex 4, for which two doublet
resonances are observed due to the presence of a chiral
group on the alkynyl ligand that induces the nonequiva-
lence of the phosphorus nuclei.5b These data are con-
sistent with a transoid structure for the complexes 2-4
(Scheme 1). When temperature is raised, the NMR
signals corresponding to [Cp*Ru(H)(CtCC(OH)RR′)-
(PEt3)2][BPh4] decrease, whereas the signals of the
hydroxyvinylidene [Cp*Ru(dCdCHC(OH)RR′)(PEt3)2]-
[BPh4] (R ) R′ ) H (5); R ) R′) CH3 (6); R ) CH3, R′)
Ph (7)) increase their intensity. Thus, after stirring 2
in CH2Cl2 solution several hours, the hydroxyvinylidene
complex 5 was obtained as a stable orange solid.
Attempts made to isolate the hydroxyvinylidene com-
plexes 6 and 7 by controlling the reaction time in
solution afforded a mixture of such species together with
Ack n ow led gm en t. We thank the Direccio´n General
de Ensen˜anza Superior (Project PB97-1357) and the
J unta de Andaluc´ıa (FQM-188) for financial support. We
also thank J ohnson Matthey plc. for including us in
their precious metal loan scheme.
OM980970J
(15) Experimental procedure for the preparation of complexes
5-7: Complexes 2-4 were heated as solids at 35 °C under an inert
atmosphere for 3 h, the color gradually turning from white/yellow to
orange, yielding a quantitative isomerization process. Complex 5 can
also be obtained cleanly starting from a solution of 1 (127 mg, 0.25
mmol) in 15 mL of MeOH to which HCtCCH2OH (14 mg, 0.30 mmol)
was added. After it was stirred for 4 h at room temperature, addition
of NaBPh4 (81 mg, 0.50 mmol) afforded the precipitation of an orange
solid, which was filtered and washed with EtOH and hexane. Selected
spectral data for 5: IR (Nujol): ν(OH) 3459, ν(CdC) 1679 cm-1 1H
.
NMR (400 MHz, CDCl3, 273 K): δ 1.25 (t, J HbHc ) 5.4 Hz, RudCd
CH-CHb2OHc), 1.74 (t, J HP ) 1.8 Hz, C5(CH3)5), 4.05 (dd, J HaHb ) 8.4
Hz, J HbHc ) 5.4 Hz, RudCdCHa-CHb2OHc), 4.21 (tt, J HaHb) 8.4 Hz,
J HP ) 1.6 Hz, RudCdCHa-CHb2OH). 31P{1H} NMR (161.89 MHz,
CDCl3, 273 K): δ 30.6 (s). 6: IR (Nujol): ν(OH) 3543, ν(CdC) 1643
cm-1 1H NMR (400 MHz, CDCl3, 273 K): δ 1.75 (t, J HP ) 1.9 Hz, C5-
.
(CH3)5), 1.37 (s, RudCdCH-C(CH3)2OH), 4.05 (s, RudCdCH-C(CH3)2-
OH). 31P{1H} NMR (161.89 MHz, CDCl3, 273 K): δ 28.9 (s). 7 IR
(Nujol): ν(OH) 3598, ν(CdC) 1633 cm-1 1H NMR (400 MHz, CDCl3,
.
273 K): δ 1.71 (t, J HP ) 1.1 Hz, C5(CH3)5), 1.63 (s, RudCdCH-C(CH3)-
PhOH), 4.38 (s, RudCdCH-CMe(Ph)OH), 7.28, 7.34, 7.36 (m, Rud
CdCH-CMe(C6H5)OH). 31P{1H} NMR (161.89 MHz, CDCl3, 273 K):
δ 28.9 and 29.1 (d, J PP′ ) 35.5 Hz). All new compounds gave satisfactory
C and H elemental analysis.