Structure and dynamics of half-sandwich ruthenium(IV) alkynyl hydrido complexes

Article abstract of DOI:10.1021/om020940n

The coordinatively unsaturated complex [Cp*Ru(PMeⁱPr₂)₂][BAr′₄] (1; BAr′₄ = B{3,5-C₆H₃- (CF₃)₂}₄) reacts 1-alkynes in diethyl ether at 0°C, furnishing the Ru^IV alkynyl hydrido derivatives [Cp*RuH(C≡CR)(PMeⁱPr₂)₂] [BAr′₄]. In an analogous fashion, the reaction of 1 with 1-alkyn-3-ols in diethyl ether at 0 °C leads to the 3-hydroxyalkynyl hydrido complexes [Cp*RuH(C≡CC(OH)RR′)(PMeⁱ Pr₂)₂][BAr′₄]. The complexes [Cp*RuH(C≡CCOOMe)(PMeⁱPr₂)₂] [BAr′₄] and [Cp*RuH(C≡CC(OH)Ph₂) (PMeⁱPr₂)₂][BAr′₄]· Et₂O have been structurally characterized, and their crystal structures show a transoid disposition of the hydride and alkynyl ligands. These compounds are stereochemically nonrigid and undergo a rapid equilibrium between possible stereoisomers in solution, which has been studied by variable-temperature NMR spectroscopy and computer simulation. The dynamic NMR study for these processes indicates energy barriers of ca. 11 kcal mol^-1, and moreover the differences in energy for the possible stereoisomers are very small (ca. 1 kcal mol^-1). The akynyl hydrido complexes rearrange to their more stable vinylidene or hydroxyvinylidene tautomers. Spontaneous dehydration of the latter leads to either vinylvinylidene or allenylidene complexes.

Full text of DOI:10.1021/om020940n

Organometallics 2003, 22, 2001-2013
2001
Articles
Str u ctu r e a n d Dyn a m ics of Ha lf-Sa n d w ich
Ru th en iu m (IV) Alk yn yl Hyd r id o Com p lexes†
Halikhedkar Aneetha, Manuel J ime´nez-Tenorio, M. Carmen Puerta, and
Pedro Valerga*
Departamento de Ciencia de Materiales e Ingenier´ıa Metalu´rgica y Quı´mica Inorga´nica,
Facultad de Ciencias, Universidad de Ca´diz, 11510 Puerto Real, Ca´diz, Spain
Kurt Mereiter
Institute of Chemical Technologies and Analytics, Vienna University of Technology,
Getreidemarkt 9, A-1060 Vienna, Austria
Received November 13, 2002
The coordinatively unsaturated complex [Cp*Ru(PMeiPr2)2][BAr′4] (1; BAr′4 ) B{3,5-C6H3-
(CF3)2}4) reacts with 1-alkynes in diethyl ether at 0 °C, furnishing the RuIV alkynyl hydrido
derivatives [Cp*RuH(CtCR)(PMeiPr2)2][BAr′4]. In an analogous fashion, the reaction of 1
with 1-alkyn-3-ols in diethyl ether at 0 °C leads to the 3-hydroxyalkynyl hydrido complexes
[Cp*RuH(CtCC(OH)RR′)(PMeiPr2)2][BAr′4]. The complexes [Cp*RuH(CtCCOOMe)(PMe-
iPr2)2][BAr′4] and [Cp*RuH(CtCC(OH)Ph2)(PMeiPr2)2][BAr′4]‚Et2O have been structurally
characterized, and their crystal structures show a transoid disposition of the hydride and
alkynyl ligands. These compounds are stereochemically nonrigid and undergo a rapid
equilibrium between possible stereoisomers in solution, which has been studied by variable-
temperature NMR spectroscopy and computer simulation. The dynamic NMR study for these
processes indicates energy barriers of ca. 11 kcal mol-1, and moreover the differences in
energy for the possible stereoisomers are very small (ca. 1 kcal mol-1). The alkynyl hydrido
complexes rearrange to their more stable vinylidene or hydroxyvinylidene tautomers.
Spontaneous dehydration of the latter leads to either vinylvinylidene or allenylidene
complexes.
In tr od u ction
ever, the study of the structure of ruthenium alkynyl
hydrido and hydroxyalkynyl hydrido complexes is made
more difficult by their metastable character and the fact
that, in most cases, they rearrange to their more stable
vinylidene isomers in the solid state. In fact, we have
carried out quantitative studies on the solid-state
isomerization to vinylidene of several alkynyl hydrido
complexes using IR spectroscopy as a tool.7 Very re-
cently, the related OsIV alkynyl hydrido complexes
[CpOsH(CtCR)(PiPr3)2][PF6] (R ) Ph, Cy) as well as
the hydroxyalkynyl hydrido derivatives [CpOsH(Ct
CC(OH)RPh)(PiPr3)2][PF6] (R ) Me, Ph) have been
reported.8 These compounds were obtained by reaction
of [CpOsCl(PiPr3)2] with TlPF6 and the appropriate
alkyne or alkynol in acetone/dichloromethane. Other
OsIV alkynyl hydrido complexes of the type [CpOsH(Ct
Since our initial report on the formation of metastable
half-sandwich RuIV alkynyl hydrido complexes [Cp*RuH-
(CtCR)(dippe)]+ (dippe ) 1,2-bis(diisopropylphosphino)-
ethane) as intermediates in the formation of vinylidene
complexes,1,2 we have advanced in the knowledge of the
chemistry of such species. Thus, we have proven that
the previously overlooked hydroxyalkynyl hydrido com-
plexes [Cp*RuH(CtCC(OH)RR′)(PP)]+ (PP ) dippe,
(PEt3)2) are also involved in the formation of hydrox-
yvinylidene complexes and, therefore, in the subsequent
dehydration processes leading to allenylidene, vinylvi-
nylidene, or even hydrido enynyl derivatives.3-6 How-
* To whom correspondence should be addressed. E-mail:
pedro.valerga@uca.es.
† Dedicated to Professor G. J effery Leigh, as recognition of his
career and outstanding contribution to inorganic and organometallic
chemistry.
(5) Bustelo, E.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 1999, 18, 4563.
(6) Bustelo, E.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. Eur.
J . Inorg. Chem. 2001, 2391.
(7) Bustelo, E.; de los R´ıos, I., J ime´nez-Tenorio, M.; Puerta, M. C.;
Valerga, P. Monatsh. Chem. 2000, 131, 1311.
(8) Baya, M.; Crochet, P.; Esteruelas, M. A.; Gutie´rrez-Puebla, E.;
Lo´pez, A. M.; Modrego, J .; On˜ate, E.; Vela, N. Organometallics 2000,
19, 2585.
(1) de los R´ıos, I.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Chem. Soc., Chem. Commun. 1995, 1757.
(2) de los R´ıos, I.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Am. Chem. Soc. 1997, 119, 6529.
(3) de los R´ıos, I.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
J . Organomet. Chem. 1997, 549, 221.
(4) Bustelo, E.; J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P.
Organometallics 1999, 18, 950.
10.1021/om020940n CCC: $25.00 © 2003 American Chemical Society
Publication on Web 04/18/2003

2002 Organometallics, Vol. 22, No. 10, 2003
Aneetha et al.
CPh)(PiPr3)(EPh3)] (E ) Si, Ge) are also known, al-
though these were prepared in a different fashion, by
reaction of [CpOsHCl(PiPr3)(EPh3)] with LiCtCPh in
THF.9 The complex [CpOsH(CtCPh)(PiPr3)2][PF6] was
structurally characterized by X-ray diffraction.8 This
was feasible because, at variance with the case for
ruthenium compounds, osmium alkynyl hydrido deriva-
tives do not undergo isomerization to their vinylidene
tautomers in the solid state or in solution. Furthermore,
they are cleanly deprotonated by strong bases, affording
the neutral OsII alkynyl complexes [CpOs(CtCR)-
(PiPr3)2], which react with HPF6 in Et2O to yield the
corresponding vinylidene complexes [CpOsdCdCHR-
(PiPr3)2][PF6] by protonation at the â-carbon.10 These
results are consistent with the outcome of several theo-
retical studies performed on the acetylene to vinylidene
tautomerization at a d6 metal center.11-16 Since the
initial extended Hu¨ckel calculations carried out by
Silvestre and Hoffmann,11 most studies have concluded
that the intermediacy of alkynyl hydrido complexes
generated by oxidative addition of the alkyne to a d6
metal center is too high in energy and another pathway,
namely a 1,2-H shift, is preferred. This, however, does
not apply to other electronic configurations, and hence,
oxidative addition at a d8 metal center is a feasible step
in the formation of vinylidene complexes of Co,17 Rh,
and Ir.18,19 Very recent DFT studies of the acetylene to
vinylidene isomerization in the d6 complexes [CpMn-
(HCtCH)(CO)2]14 and [CpRu(HCtCR)(PMe3)2]+ (R )
H, Me)15 have successfully located and optimized the
geometries of several possible intermediate complexes
in its pathway to [CpMndCdCH2(CO)2] or [CpRudCd
CHR(PMe3)2]+ (R ) H, Me). Among them, the alkynyl
hydrides [CpMH(CtCR)(L)2]n+, the η2-CH agostic acety-
lene complexes [CpM(η2-HCtCR)(L)2]n+, and the η2-
vinylidene complexes [CpM(η2-CdCH(R))(L)2]n+ (M )
Mn, R ) H, L ) CO, n ) 0; M ) Ru, R ) H, Me, L )
PMe3, n ) 1) are particularly relevant.14,15 Interestingly,
the η2-CH agostic acetylene complexes have been found
to be more stable than alkynyl hydrides and in fact are
considered key intermediates in the isomerization path-
way to vinylidene. However, in the case of [CpRu(HCt
CH)(PMe3)2]+, the energy barriers for the 1,2-hydrogen
shift and for the oxidative addition are almost compa-
rable, so that the oxidative addition process might
become competitive.15 Further theoretical support for
the involvement of alkynyl hydrido complexes as inter-
mediates in the alkyne to vinylidene rearrangement has
been recently found when Cp* is introduced instead of
Cp in the model systems for computation.16
In an attempt to detect intermediates in the formation
of vinylidene complexes, we had previously studied the
direct interaction of 1-alkynes2 and alkynols5,6 at low
temperature with labile complexes such as [Cp*Ru(η2-
C2H4)(dippe)][BPh4]20 and [Cp*Ru(N2)(PEt3)2][BPh4]21
as precursors of the 16e moieties [Cp*Ru(dippe)]+ and
[Cp*Ru(PEt3)2]+. Despite the fact that η2-alkyne species
were identified in some instances, the dissociation rate
of the labile ligand becomes a limiting factor when the
experiments are performed at low temperature, pre-
venting the observation of direct alkyne addition prod-
ucts. The introduction of the noncoordinating anion
[BAr′4]- (BAr′4 ) tetrakis(3,5-bis(trifluoromethyl)phe-
nyl)borate) has recently allowed us to isolate a series
of coordinatively unsaturated cationic complexes
[Cp*Ru(PP)][BAr′4] (PP
)
dippe, PMeiPr2, PEt3,
PPhiPr2, PPh3).22 These compounds offer new possi-
bilities for the study of the addition of 1-alkynes to a
16e metal center, without interference coming from the
need of a preliminary ligand dissociation step. In this
work we describe the structure and dynamic behavior
of a series of half-sandwich RuIV alkynyl hydrido
complexes generated by oxidative addition of 1-alkynes
and alkynols to the 16e complex [Cp*Ru(PMeiPr2)2]-
[BAr′4] (1), as well as their subsequent transformation
into vinylidene or hydroxyvinylidene complexes, and
other products derived from the dehydration of the
latter species.
Exp er im en ta l Section
All synthetic operations were performed under a dry dini-
trogen or argon atmosphere by following conventional Schlenk
techniques. Tetrahydrofuran, diethyl ether, and petroleum
ether (boiling point range 40-60 °C) were distilled from the
appropriate drying agents. Solvents were deoxygenated by
three freeze/pump/thaw cycles and stored under argon. Na-
[BAr′4]23 and [Cp*Ru(PMeiPr2)2][BAr′4] (1)22 were prepared
according to reported procedures. IR spectra were recorded in
Nujol mulls on a Perkin-Elmer FTIR Spectrum 1000 spectro-
photometer. NMR spectra were taken on a Varian Unity 400
MHz or Varian Gemini 200 MHz spectrometer. Chemical shifts
are given in parts per million from SiMe4 (1H and 13C{1H}) or
85% H3PO4 (31P{1H}). Diisopropylmethylphosphine and [BAr′4]-
protons and carbons appeared for all the compounds in the
appropriate shift ranges and are not listed. The 1H NMR
resonance for the OH proton, when observed, appeared be-
tween 2 and 3 ppm, most times overlapping with phosphine
isopropyl signals. Thermodynamic and activation parameters
were obtained by a dynamic NMR line shape fitting simulation
using the program DNMR324 incorporated into SpinWorks
(9) Baya, M.; Esteruelas, M. A.; On˜ate, E. Organometallics 2001,
20, 4875.
(10) Baya, M.; Crochet, P.; Esteruelas, M. A.; Lo´pez, A. M.; Modrego,
J .; On˜ate, E. Organometallics 2001, 20, 4291.
(11) Silvestre, J .; Hoffmann, R. Helv. Chim. Acta 1985, 68, 1461.
(12) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K. J . Am.
Chem. Soc. 1994, 116, 8105.
(13) (a) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Pe´rez-Carren˜o,
E.; Garc´ıa-Granda, S. Organometallics 1999, 18, 2821. (b) Cadierno,
V.; Gamasa, M. P.; Gimeno, J .; Gonza´lez-Bernardo, C.; Pe´rez-Carren˜o,
E.; Garc´ıa-Granda, S. Organometallics 2001, 20, 5177.
(14) De Angelis, F.; Sgamellotti, A.; Re, N. Organometallics 2002,
21, 2715.
(15) De Angelis, F.; Sgamellotti, A.; Re, N. Organometallics 2002,
21, 5944.
(16) Bustelo, E.; Carbo´, J .; Lledo´s, A.; Mereiter, K.; Puerta, M. C.;
Valerga, P. J . Am. Chem. Soc. 2003, 125, 3311.
(17) Bianchini, C.; Peruzzini, M.; Vacca, A.; Zanobini, F. Organo-
metallics 1991, 10, 3697.
(18) Wakatsuki, Y.; Koga, N.; Werner, H.; Morokuma, K. J . Am.
Chem. Soc. 1997, 119, 360.
(19) Wolf, J .; Werner, H.; Serhadli, O.; Ziegler, M. L. Angew. Chem.,
Int. Ed. Engl. 1983, 22, 414. Werner, H.; Ho¨hn, A. J . Organomet. Chem.
1984, 272, 105. Garc´ıa-Alonso, F. J .; Ho¨hn, A.; Wolf, J .; Otto, H.;
Werner, H. Angew. Chem., Int. Ed. Engl. 1985, 24, 406. Dziallas, M.;
Werner, H. J . Chem. Soc., Chem. Commun. 1987, 852. Rappert, T.;
Nu¨rnberg, O.; Mahr, N.; Wolf, J .; Werner, H. Organometallics 1992,
11, 4156.
(20) de los R´ıos, I.; J ime´nez-Tenorio, M.; Padilla, J .; Puerta, M. C.;
Valerga, P. Organometallics 1996, 15, 4565.
(21) J ime´nez-Tenorio, M.; Puerta, M. C.; Valerga, P. J . Organomet.
Chem. 2000, 609, 161.
(22) (a) J ime´nez-Tenorio, M.; Puerta, M. C.; Mereiter, K.; Valerga,
P. J . Am. Chem. Soc. 2000, 122, 11230. (b) Aneetha, H.; J ime´nez-
Tenorio, M.; Puerta, M. C.; Valerga, P.; Sapunov, V. N.; Schmid, R.;
Kirchner, K.; Mereiter, K. Organometallics 2002, 21, 5334.
(23) Brookhart, M.; Grant, B.; Volpe, A. F., J r. Organometallics 1992,
11, 3920.

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Organometallics, Vol. 22, No. 10, 2003 2003
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta for Com p ou n d s 2a , 2i, a n d 3c
2a
2i‚Et2O
3c
formula
fw
T (K)
C
60H65BF24O2P2Ru
C75H83BF24O2P2Ru
1646.23
223(2)
C61H71BF24P2RuSi
1462.09
297(2)
1447.94
297(2)
cryst size (mm)
cryst syst
space group
cell params
a (Å)
0.80 × 0.60 × 0.32
monoclinic
P21/c (No. 14)
0.72 × 0.24 × 0.22
0.76 × 0.64 × 0.58
triclinic
triclinic
P1h (No. 2)
P1h (No. 2)
18.667(4)
19.062(5)
18.852(4)
12.986(3)
14.483(3)
22.235(5)
71.25(1)
79.88(1)
89.36(1)
3894(1)
14.695(3)
14.764(3)
17.085(3)
103.21(1)
107.61(1)
93.00(1)
3410(1)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
99.55(2)
6615(3)
Z
F
4
2
2
calc (g cm-3
)
1.454
1.404
1.424
µ(Mo KR) (cm-1
)
3.93
2944
3.43
1688
3.96
1492
F(000)
max, min transmissn factors
θ range for data collecn (deg)
no. of rflns collected
1.00, 0.78
1.78-25.00
66 842
11 583 (Rint ) 0.045)
8980
889
1.00, 0.93
1.59-25.00
40 655
1.00, 0.93
1.29-30.00
48 863
no. of unique rflns
13 645 (Rint ) 0.028)
19 261 (Rint ) 0.021)
no. of obsd rflns (I > 2σI)
no. of params
11 298
15 697
1011
812
final R1, wR2 values (I > 2σI)
final R1, wR2 values (all data)
residual electron density peaks (e Å-3
0.0497, 0.1231
0.0691, 0.1410
+0.61, -0.76
0.0381, 0.0941
0.0501, 0.1025
+0.46, -0.39
0.0618, 0.1729
0.0749, 0.1915
+1.60, -1.27
)
Ta ble 2. Selected 1H a n d 31P {1H} NMR Da ta for Alk yn yl Hyd r id o Com p lexes 2a -j
31P{1H} NMR at 183 K
1H NMRb
1H NMR at 183 K
2
R, R′
31P{1H NMRa
δ
δ
2J PP Ru-H J HP C5(CH3)5
R
R′
Ru-H
2J HP
2a COOMe
43.1 s
43.5 s (A, 69%)
43.0 br (B, 31%)
42.6 s (A, 69%)
43.3 d, 43.6 d (B, 31%)
41.9 s (A, 68%)
-8.29 t 31.9
-8.56 t 31.9
-8.64 t 31.9
-8.70 t 32.1
1.86
1.84
1.79
1.79
1.82
3.64
-8.71 t (A, 69%) 31.8
-8.30 t (B, 31%) 27.5
-8.93 t (A, 69%) 30.3
-8.52 t (B, 31%) 32.6
-9.01 t (A, 68%) 30.3
-8.63 t (B, 32%) 32.8
-9.03 t (A, 75%) 31.3
-8.62 t (B, 25%) 33.5
2b Ph
42.7 s
42.2 s
42.6 s
42.4 s
6.98, 7.14,
7.25
0.06
15.2
15.4
14.5
2c SiMe3
2d H, H
2e CH3, H
42.4 d, 43.6 d (B, 32%)
42.5 s (A, 75%)
4.36
42.9 d, 43.2 d (B, 25%)
42.1 d, 42.3 d (A, 64%)
42.5 br, 42.9 br (B1, 18%)
42.7 br, 43.4 br (B2, 18%)
42.2 d, 42.6 d (A, 64%)
42.8 d, 43.7 d (B1, 18% ) 13.2
43.0 d, 43.8 d (B2, 18%)
41.9 s (A, 61%)
14.5 -8.61 t 32.0
1.39 d
4.62 -9.04 t (A, 64%) 32.8
-8.65 t 29.7
(B1 + B2, 36%)
5.56 -9.05 t (A, 64%) 32.3
-8.65 t 29.7
(B1 + B2, 36%)
(3J HH ) 6.4)
2f Ph, H
42.6 s
14.8 -8.61 t 31.9
1.78
7.28,7.36,
7.40
14.3
2g CH3, CH3 42.2 s
-8.60 t 32.2
1.82
1.78
1.48
-9.04 t (A, 61%) 30.9
-8.65 t (B, 39%) 32.6
42.5 d, 43.5 d (B, 39%)
14.4
2h Ph, CH3
42.6 d, 42.4 d 42.1 d, 41.7 d (A, 56%)
15.3 -8.61 t 32.5
13.4
7.25, 7.34,
7.45
1.94 -9.08 t (A, 56%) 31.4
(12 Hz)
42.8 s
42.2 s
42.5 d, 44.1 d (B1, 22%)
42.6 d, 44.0 d (B2, 22%)
41.8 s (A, 42%)
42.7 d, 44.7 d (B, 58%)
41.4 s (A1, 29%)
41.7 s (A2, 29%)
42.1 d, 43.5 d (B1, 21%)
42.3 d, 44.3 d (B2, 21%)
-8.68 t
(B1 + B2, 44%)
33.5
14.0
2i Ph, Ph
2j C5H10
-8.58 t 32.1
1.80
1.82
7.28,7.33,
7.54
1.64, 1.95
-9.06 t (A, 42%) 30.4
-8.68 t (B, 58%) 32.6
-9.18 t (A1, 29%) 30.0
-9.09 t (A2, 29%) 29.0
-8.77 t (B1, 21%) 33.3
-8.71 t (B2, 21%) 33.3
14.0
-8.62 t 32.8
14.5
12.5
a
b
Conditions: 161.89 MHz, CD2Cl2, 273 K. δ in ppm, and coupling constants in Hz. Conditions: 400 MHz, CD2Cl2, 273 K. δ in ppm,
and coupling constants in Hz.
1.3.25 Microanalysis was performed by the Serveis Cient´ıfico-
Te`cnics, Universitat de Barcelona.
removed in vacuo. Addition of petroleum ether gave an off-
white crystalline solid, which was filtered, washed with
petroleum ether, dried, and stored at -20 °C. Yield: 80-90%
in all cases. With the exception of compound 2a , microanalysis
was not carried out because these compounds rearrange to
their vinylidene isomers in the solid state. Selected NMR
spectral data for these compounds are given in Tables 2 and
3. 2a : IR ν(CtC) 2112 (s), 2093 (w, sh) cm-1, ν(RuH) 2037
(w) cm-1, ν(CdO) 1677 cm-1. Anal. Calcd for C60H65BF24O2P2-
Ru: C, 49.8; H, 4.49. Found: C, 50.0; H, 4.52. 2b: IR ν(CtC)
Alk yn yl H yd r id o Com p lexes [Cp *R u H (CtCR )-
(P MeiP r 2)2][BAr ′4] (R ) COOMe (2a ), P h (2b), SiMe3 (2c))
a n d 3-Hyd r oxya lk yn yl Hyd r id o Com p lexes [Cp *Ru H{Ct
CC(OH)RR′}(P MeiP r 2)2][BAr ′4] (R, R′ ) H, H (2d ), H, CH3
(2e), H, P h (2f), CH 3, CH3 (2g), CH3, P h (2h ), P h , P h (2i),
C5H10 (2j)). To a solution of 1 (0.272 g, 0.2 mmol) in 5 mL of
CH2Cl2 at 0 °C was added the corresponding alkyne or
hydroxyalkyne (0.2 mmol). The color immediately changed
from blue to colorless or pale yellow. The reaction mixture was
stirred for 10 min at 0 °C. Then, most of the solvent was
2109 cm-1, ν(RuH) 2020 (w) cm-1. 2c: IR ν(CtC) 2038 cm-1
,
ν(RuH) not observed. 2d : IR ν(CtC) 2121 cm-1, ν(RuH) 2025
(w) cm-1, ν(OH) 3625 (w) cm-1. 2e: IR ν(CtC) 2116 cm-1
,
ν(RuH) 2083 (w) cm-1. 2f: IR ν(CtC) 2111 cm-1, ν(RuH) 2037
(w) cm-1, ν(OH) 3608 (w) cm-1. 2g: IR ν(CtC) 2121 cm-1, ν-
(24) Kleier, D. A.; Binsch, G. J . Magn. Reson. 1970, 3, 146.
(25) Marat, K. SpinWorks 1.3; University of Manitoba, 2001.

2004 Organometallics, Vol. 22, No. 10, 2003
Ta ble 3. Selected 13C{1H} NMR Da ta for Alk yn yl Hyd r id o Com p lexes 2a -j
13C{1H} NMRa
Aneetha et al.
R, R′
C5(CH3)5
C5(CH3)5
CR
2J CP
Câ
Cγ
R
R′
2a
2b
2c
2d
2e
2f
2g
2h
2i
COOMe
Ph
SiMe3
H, H
CH3, H
Ph, H
CH3, CH3
Ph, CH3
Ph, Ph
C5H10
10.3
10.3
10.3
10.3
10.3
10.3
10.3
10.3
10.4
10.4
103.1
102.1
102.1
101.9
101.9
102.0
101.9
102.0
102.2
101.9
116.0 t
104.0 t
127.7 t
98.0 t
95.6 t
99.6 t
93.1 t
96.2 t
100.7 t
87.5 t
29.0
28.4
27.3
28.1
27.7
28.2
27.9
27.4
27.3
28.1
109.7
109.7
122.6
113.2
116.3
115.2
119.8
118.8
116.3
119.9
51.9, 153.1
126.4, 128.4,130.2
0.35
53.2
60.1
66.5
66.4
70.0
75.6
72.2
25.5
125.4, 128.0, 128.6
32.1
124.3, 127.0, 128.0
126.1, 127.4, 128.1
22.4, 25.0, 40.3
32.4
2j
a
Conditions: 201.2 MHz, CD2Cl2, 273 K. δ in ppm, and coupling constants in Hz.
Ta ble 4. Th er m od yn a m ic a n d Activa tion P a r a m eter s for th e Equ ilibr iu m betw een Alk yn yl Hyd r id o
Isom er s (A / B), w ith Estim a ted Sta n d a r d Devia tion s in P a r en th eses
thermodynamic params
activation params
186.5
Keq
∆H (kcal mol-1
)
∆S (cal K-1 mol-1
)
∆G298 (kcal mol-1
)
∆Hq (kcal mol-1
)
∆Sq (cal K-1 mol-1
)
∆Gq298 (kcal mol-1
)
2a
2b
2c
2d
2e
2f
2g
2h
2i
0.47
0.48(0.01)
0.75(0.02)
0.97(0.05)
1.70(0.08)
0.70(0.04)
0.66(0.04)
1.10(0.03)
0.70(0.02)
0.27(0.02)
1.68(0.06)
1.13(0.06)
2.74(0.08)
3.9(0.2)
7.1(0.4)
2.6(0.2)
2.4(0.2)
5.0(0.1)
3.3(0.1)
2.0(0.1)
8.3(0.3)
0.14(0.03)
0.07(0.04)
-0.2(0.1)
-0.4(0.2)
-0.1(0.1)
-0.1(0.1)
-0.39(0.06)
-0.28(0.05)
-0.32(0.05)
-0.8(0.1)
6.6(0.1)
6.2(0.1)
6.8(0.3)
6.9(0.5)
6.7(0.4)
6.3(0.3)
7.6(0.6)
7.4(0.4)
6.4(0.3)
7.7(0.7)
-14.2(0.6)
-16.0(0.6)
-14(2)
11.0(0.3)
11.0(0.3)
11.0(0.9)
11(1)
11(1)
11.3(0.9)
11(1)
11(1)
10.9(0.6)
11(2)
0.53
0.51
0.34
0.55
0.57
0.64
0.79
1.36
0.75
-14(2)
-15(2)
-17(2)
-11(3)
-11(2)
-15(1)
2j
-11(3)
Ta ble 5. Selected 1H a n d 31P {1H} NMR Da ta for Hyd r oxyvin ylid en e Com p lexes 3b-j
31P{1H} NMRa
1H NMRb
R, R′
Ph
SiMe3
H, H
CH3, H
Ph, H
CH3,CH3
Ph, CH3
Ph, Ph
C5H10
δ
2J PP′
RudCdCH
4J HP
C5(CH3)5
R
R′
3b
35.7 s
35.9 s
37.1 s
37.1 s
5.40 br
3.39 t
4.34 br
4.12 dt
4.39 d
3.88 br
4.25 br
4.61 br
3.94 br
1.98
1.86
1.76
1.75
1.74
1.76
1.72
1.73
1.75
7.09,7.18, 7.30
0.09
3c
3d
3e
3f
3g
3h
3i
3.1
1.6
4.34 br
1.34 d (3J HH ) 8.7)
7.26, 7.32, 7.37
1.37 s
7.26,7.35, 7.37
7.26,7.29, 7.32
1.26, 1.45
4.77 m
36.9 d, 37.2 d
35.1 s
34.9 d, 35.6 d
35.5 s
31.7
31.7
5.61 d (3J HH ) 8.7)
1.69 s
3j
35.2 s
a
b
Conditions: 161.89 MHz, CDCl3, 273 K. δ in ppm, and coupling constants in Hz. Conditions: 400 MHz, CDCl3, 273 K. δ in ppm, and
coupling constants in Hz.
(RuH) 2024 (w) cm-1, ν(OH) 3615 (w) cm-1. 2h : IR ν(CtC)
2112 cm-1, ν(RuH) 2038 (w) cm-1, ν(OH) 3618 (w) cm-1. 2i:
IR ν(CtC) 2110 cm-1, ν(RuH) 2040 (w) cm-1, ν(OH) 3608 (w)
cm-1. 2j: IR ν(CtC) 2105 cm-1, ν(RuH) 2016 (w) cm-1, ν(OH)
C, 49.8; H, 4.77. 3d : IR ν(CdC) 1643 cm-1. Anal. Calcd for
59H65BF24OP2Ru: C, 49.9; H, 4.58. Found: C, 49.8; H, 4.62.
C
3e: IR ν(CdC) 1643 cm-1. Anal. Calcd for C60H67BF24OP2Ru:
C, 50.3; H, 4.68. Found: C, 50.4; H, 4.75. 3f: IR ν(CdC) 1641
cm-1. Anal. Calcd for C65H69BF24OP2Ru: C, 52.2; H, 4.62.
Found: C, 51.9; H, 4.58. 3g: IR ν(CdC) 1648 cm-1. Anal. Calcd
for C61H69BF24OP2Ru: C, 50.6; H, 4.77. Found: C, 50.5; H,
3608 (w) cm-1
.
Vin ylid en e Com p lexes [Cp *Ru dCdCHR(P MeiP r 2)2]-
[BAr ′4] (R ) P h (3b), SiMe3 (3c)) a n d 3-Hyd r oxyvin yli-
d en e Com p lexes [Cp *Ru {dCdCHC(OH)RR′}(P MeiP r 2)2]-
[BAr ′4] (R, R′ ) H, H (3d ), H, CH3 (3e), H, P h (3f), CH3,
CH3 (3g), CH3, P h (3h ), P h , P h (3i), C5H10 (3j)). A solid
sample of the corresponding alkynyl hydrido derivatives 2b-j
(0.15 g) was heated to 30 °C over a period of 3-6 h. During
this time, the color of the sample changed from off-white or
pale yellow to orange-red. The process can be monitored by
IR spectroscopy, following the decrease in the ν(CtC) band
at ∼2100 cm-1 until its disappearance. Yield: quantitative.
Compound 3i undergoes spontaneous dehydration during this
process, and therefore it was always obtained mixed with the
allenylidene derivative 5i. For this reason, it was not analyzed,
and its NMR characterization was carried out in solutions
containing mixtures of 3i and 5i. Selected NMR spectral data
for these compounds are given in Tables 5 and 6. 2b: IR ν-
(CdC) 1608 cm-1. Anal. Calcd for C64H67BF24P2Ru: C, 52.4;
4.70. 3h : IR ν(CdC) 1642 cm-1. Anal. Calcd for C66H71BF24
-
OP2Ru: C, 52.5; H, 4.71. Found: C, 52.4; H, 4.79. 3i: IR ν-
(CdC) 1638 cm-1. 3j: IR: ν(CdC) 1645 cm-1. Anal. Calcd for
C
64H73BF24OP2Ru: C, 51.7; H, 4.91. Found: C, 51.5; H, 5.03.
Vin ylvin ylid en e Com p lexes [Cp *Ru dCdCHCHdCH2-
(P MeiP r 2)2][BAr ′4] (4e), [Cp *Ru dCdCHC(CH3)dCH2-
(P MeiP r 2)2][BAr ′4] (4g), [Cp*Ru {dCdCHCdCH(CH2)3CH2}-
(P MeiP r 2)2][BAr ′4] (4j). A solution of the corresponding
3-hydroxyvinylidene complex was stirred in 5 mL of CH2Cl2
at room temperature for 8-10 h. The color changed from
yellow-orange to brown. The solvent was evaporated to dryness
to give a brown solid. It was washed twice with petroleum
ether and dried. Yield: Quantitative. 4e: IR ν(CdC) 1627
1
cm-1; H NMR (CDCl3, 298 K) δ 1.76 s (C5(CH3)5), 4.42, 4.97
3
a
b
c
3
b
c
a
b
(d, J H ) 10.2 Hz, RudCdCH CH dCH 2), 4.86 (d, J H
)
H
H
H, 4.57. Found: C, 52.4; H, 4.49. 3c: IR: ν(CdC) 1613 cm-1
Anal. Calcd for C61H71BF24P2RuSi: C, 50.1; H, 4.86. Found:
.
16.8 Hz, RudCdCHaCHbdCHc2), 6.30 (dt, 3J H
Hz,3J H
) 16.8
b
a
H
) 10.2 Hz RudCdCHaCHbdCHc2); 31P{1H} NMR
b
c
H

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Ta ble 6. Selected 13C{1H} NMR Da ta for Hyd r oxyvin ylid en e Com p lexes 3b-j
13C{1H} NMRa
Organometallics, Vol. 22, No. 10, 2003 2005
R, R′
C5(CH3)5
C5(CH3)5
CR
2J CP
Câ
Cγ
R
R′
3b
3c
3d
3e
3f
3g
3h
3i
Ph
SiMe3
H, H
CH3, H
Ph, H
CH3, CH3
Ph, CH3
Ph, Ph
C5H10
H
10.6
10.3
10.7
10.7
10.7
10.7
10.6
10.7
10.7
10.8
103.3
102.2
103.1
103.0
103.2
102.7
102.7
102.9
102.3
103.5
349.5 t
345.0 t
345.4 t
344.3 t
343.8 t
344.8 t
344.7 t
344.3 br
345.9 t
346.5 t
15.5
15.0
14.7
15.5
14.6
14.7
14.3
115.2
116.3
110.2
115.6
114.9
120.9
121.2
120.7
119.6
93.7
126.5, 128.1,128.7
0.64
53.8
61.6
67.5
68.8
72.0
76.4
70.3
-
25.3
125.4, 128.4, 128.9
33.4
123.7, 127.2, 128.4
125.6, 127.8, 128.4
22.3, 24.6, 41.1
34.7
3j
3k
16.2
16.0
a
Conditions: 201.2 MHz, CDCl3, 273 K. δ in ppm, and coupling constants in Hz.
(CDCl3, 298 K) δ 37.3 s; 13C{1H} NMR (CDCl3, 298 K) δ 10.5
s (C5(CH3)5), 103.4 s (C5(CH3)5), 110.6 (Câ), 115.0 (dCH2), 120.9
(Cγ), 353.9 (t, 2J CP ) 15.4 Hz, CR). Anal. Calcd for C60H65BF24P2-
Ru: C, 50.9; H, 4.59. Found: C, 51.1; H, 4.66. 4g: IR ν(CdC)
on a Bruker Smart CCD area detector diffractometer (graphite-
monochromated Mo KR radiation, λ ) 0.710 73 Å, 0.3° ω-scan
frames covering complete spheres of the reciprocal space).
Corrections for Lorentz and polarization effects, for crystal
decay, and for absorption were applied. All structures were
solved by direct methods using the program SHELXS97.26
Structure refinement on F2 was carried out with the program
SHELXL97.26 ORTEP27 was used for plotting.
For the compound 2a seven of the CF3 groups were split,
and the predominantly occupied F sites were refined with
anisotropic Uij values, whereas the subordinate F sites were
refined with a common isotropic U value for all of them. All
other non-hydrogen atoms were anisotropically refined. The
hydride H(1Ru) in 2a was treated with a DFIX restraint.26
All other hydrogens were refined in idealized positions riding
on the atoms to which they were bonded.
For the compound 2i six of the CF3 groups were split, and
the predominantly occupied F sites were refined with aniso-
tropic Uij values, whereas the subordinate F sites were refined
with a common isotropic U value for all of them. Other non-
hydrogen atoms, including those in the solvate molecule Et2O,
were anisotropically refined. The hydride atom H(1Ru) was
localized and isotropically refined. For all other hydrogen
atoms the SHELXL riding model was used.
In the case of compound 3c relatively high anisotropic
thermal displacements were found for the SiMe3 group and
seven CF3 groups. Split refinement was checked, yielding
significantly lower R values, but a nonsplit model was pre-
ferred in this case because of its simplicity. All non-hydrogen
atoms were anisotropically refined. Hydrogen atoms were
refined in idealized positions riding on the atoms to which they
were bonded.
1
1625 cm-1; H NMR (CDCl3, 298 K) δ 1.70 (s, RudCdCHC-
(CH3)dCH2), 1.77 s (C5(CH3)5), 4.52 (br, RudCdCHC(CH3)d
CH2), 4.66, 4.69 (br, RudCdCHC(CH3)dCH2); 31P{1H} NMR
(CDCl3, 298 K) δ 35.4 s; 13C{1H} NMR (CDCl3, 298 K) δ 10.7
s (C5(CH3)5), 24.0 (RudCdCHC(CH3)dCH2), 103.3 s (C5(CH3)5),
2
112.6 (Câ), 116.7 (dCH2), 131.8 (Cγ), 350.4 (t, J CP ) 15.1 Hz,
CR). Anal. Calcd for C61H67BF24P2Ru: C, 51.2; H, 4.69. Found:
C, 51.1; H, 4.58. 4j: IR ν(CdC) 1622 cm-1 1H NMR (CDCl3,
298 K) δ 1.77 s (C5(CH3)5), 1.58, 1.85, 2.13 (m, Ru{dCdCHCd
CH(CH2)3CH2}), 4.46 (br, RudCdCH), 5.46 (br, Ru{dCd
CHCdCH(CH2)3CH2}); 31P{1H} NMR (CDCl3, 298 K) δ 36.0 s;
13C{1H} NMR (CDCl3, 298 K) δ 10.7 s (C5(CH3)5), 21.9, 22.8,
25.6, 30.5 (s, Ru{dCdCHCdCH(CH2)3CH2}), 103.0 s (C5-
2
(CH3)5), 116.8 (Câ), 124.7 (dCH), 125.4 (Cγ), 351.4 (t, J CP
)
15.4 Hz, CR). Anal. Calcd for C64H71BF24P2Ru: C, 52.3; H, 4.83.
Found: C, 52.0; H, 4.69.
Allen ylid en e
Com p lexes
[Cp *R u dCdCdCR R ′-
(P MeiP r 2)2][BAr ′4] (R, R′ ) H, P h (5f), CH3, P h (5h ), P h ,
P h (5i)). The solutions of corresponding 3-hydroxyvinylidene
complexes were stirred for 12 h at room temperature in 5 mL
of CH2Cl2 and then passed through an acidic alumina column
(5 cm height). A brown band was collected in 60-70% yield.
The 3-hydroxyalkynyl hydrido complex of diphenylpropargyl
alcohol spontaneously dehydrated in the solid state to give the
allenylidene complex. 5f: IR ν(CdC) 1919 cm-1 1H NMR
;
(CDCl3, 298 K) δ 1.83 s (C5(CH3)5), 7.37, 7.67, 7.79 (RudCd
CdCHC6H5), 9.39 s (RudCdCdCHC6H5); 31P{1H} NMR (CDCl3,
298 K) δ 38.5 s; 13C{1H} NMR (CDCl3, 298 K) δ 10.9 s (C5-
(CH3)5), 103.2 s (C5(CH3)5), 142.9 (Cγ), 129.7, 130.2, 131.7 (Rud
CdCdCHC6H5), 221.9 (Câ), 301.8 (t, 2J CP ) 18.1 Hz, CR). Anal.
Calcd for C65H67BF24P2Ru: C, 52.8; H, 4.53. Found: C, 52.7;
H, 4.59. 5h : IR ν(CdC) 1914 cm-1; 1H NMR (CDCl3, 298 K) δ
1.45 s (RudCdCdC(CH3)C6H5), 1.84 s (C5(CH3)5), 7.36, 7.65,
7.99 (RudCdCdC(CH3)C6H5); 31P{1H} NMR (CDCl3, 298 K)
δ 39.3 s; 13C{1H} NMR (CDCl3, 298 K) δ 11.1 s (C5(CH3)5), 102.5
s (C5(CH3)5), 30.7 (RudCdCdC(CH3)C6H5), 151.5 (Cγ), 126.1,
129.5, 131.8 (RudCdCdC(CH3)C6H5), 211.1 (Câ), 295.1 (t, 2J CP
) 18.2 Hz, CR). Anal. Calcd for C66H69BF24P2Ru: C, 53.1; H,
Resu lts a n d Discu ssion
The complex [Cp*Ru(PMeiPr2)2][BAr′4] (1) reacts with
1-alkynes HCtCR at 0 °C in dichloromethane, affording
the RuIV alkynyl hydrido derivatives [Cp*RuH(CtCR)-
(PMeiPr2)2][BAr′4] (R ) COOMe (2a ), Ph (2b), SiMe3
(2c)). Likewise, the reaction of 1 with alkynols HCt
CC(OH)RR′ under the same conditions yielded the
corresponding hydroxyalkynyl hydrido derivatives
[Cp*RuH(CtCC(OH)RR′)(PMeiPr2)2][BAr′4] (R, R′ ) H,
H (2d ), H, Me (2e), H, Ph (2f), Me, Me (2g), Me, Ph (2h ),
Ph, Ph (2i), C5H10 (2j)). Compounds 2a -j are off-white
or pale yellow materials, which exhibit characteristic
ν(CtC) and ν(RuH) (weak) bands in their IR spectra.
1
4.63. Found: C, 52.8; H, 4.66. 5j: IR ν(CdC) 1916 cm-1; H
NMR (CDCl3, 298 K) δ 1.80 s (C5(CH3)5), 7.37, 7.64, 7.92 (Rud
CdCdC(C6H5)2); 31P{1H} NMR (CDCl3, 298 K) δ 39.4 s; 13C-
{1H} NMR (CDCl3, 298 K) δ 11.0 s (C5(CH3)5), 102.9 s
(C5(CH3)5), 153.2 (Cγ), 125.9, 128.6, 130.6 (RudCdCdC(C6H5)2),
217.1 (Câ), 294.9 (t, 2J CP ) 18.7 Hz, CR). Anal. Calcd for C71H71
BF24P2Ru: C, 54.9; H, 4.57. Found: C, 55.0; H, 4.69.
-
(26) (a) SHELXS97, Program for Crystal Structure Solution; Uni-
versity of Go¨ttingen, 1990. (b) SHELXL97, Program for Crystal
Structure Refinement; University of Go¨ttingen, 1997.
(27) (a) Farrugia, L. J . ORTEP-3 for Windows, Version 1.07. J . Appl.
Crystallogr. 1997, 30, 565. (b) J ohnson, C. K. ORTEP, A Thermal
Ellipsoid Plotting Program; Oak Ridge National Laboratory, Oak
Ridge, TN, 1965.
X-r a y Str u ctu r e Deter m in a tion s. Crystals of 2a , 2i, and
3c were obtained by slow diffusion of petroleum ether into
diethyl ether solutions at -20 °C. Crystal data and experi-
mental details are given in Table 1. X-ray data were collected

2006 Organometallics, Vol. 22, No. 10, 2003
Aneetha et al.
1
F igu r e 1. Variable-temperature H (hydride region, left) and 31P{1H} (right) NMR spectra of compound 2c in CD2Cl2.
For complexes 2d -j, a weak but sharp band near 3600
cm-1 is also present in most cases, attributable to ν-
(OH) in the hydroxyalkynyl ligand. With the only
exception of compound 2a , which seems to be remark-
ably stable, all the other compounds undergo irrevers-
ible rearrangement to vinylidene complexes at room
temperature in the solid state and in solution. There-
fore, they must be stored at -20 °C as solids and
handled in solution at 0 °C or below if isomerization is
to be avoided. The NMR spectra of these compounds at
0 °C in CD2Cl2 (Tables 2 and 3) match in general the
pattern previously observed for the complexes [Cp*RuH-
(CtCR)(PP)][BPh4] and [Cp*RuH(CtCC(OH)RR′)(PP)]-
[BPh4] (PP ) dippe,2,6 (PEt3)24,5). Thus, the hydride
resonance appears as a high-field triplet, whereas one
singlet is observed in the 31P{1H} NMR in most cases,
except for 2h . In this case, the 31P{1H} NMR spectrum
consists of two overlapping doublets from an AB spin
system, resulting from the magnetic nonequivalence of
the phosphorus atoms due to the presence of the
asymmetric γ-carbon in the alkynyl group, as has been
previously noted for other hydroxyalkynyl hydrido
complexes.4-6,8 This should be also the expected 31P{1H}
NMR pattern for 2e,f, since these compounds also bear
an asymmetric γ-carbon in the alkynyl group, but one
singlet is observed instead. We have reported that the
31P{1H} NMR of [Cp*RuH(CtCC(OH)HPh)(dippe)]-
[BPh4] is temperature dependent, and whereas an AB
double doublet is observed at low temperatures, these
resonances coalesce into one singlet at +15 °C.6 This
has been interpreted in terms of an averaging of the
anisotropy of the phosphorus atom environments through
rapid rotation of the CH(OH)Ph group about the CtC
bond, leading to the accidental coincidence of the
chemical shifts of the two phosphorus atoms, which
remain magnetically inequivalent. This explanation
holds also for 2e,f.
hydrido complexes, i.e., η2-CH agostic alkyne species.
Thus, we monitored by NMR spectroscopy the reactions
of the 16-electron complexes [Cp*Ru(PP)][BAr′4] (PP )
dippe, (PMeiPr2)2) with different alkynes in CD2Cl2 at
1
183 K. At this temperature, the H and 31P{1H} NMR
spectra of the reaction mixture of [Cp*Ru(dippe)][BAr′4]
with HCtCR (R ) COOMe, Ph, SiMe3) revealed exclu-
sively the formation of the corresponding alkynyl hy-
drido derivatives [Cp*RuH(CtCR)(dippe)][BAr′4] at the
expense of [Cp*Ru(dippe)][BAr′4], and no other inter-
mediates were detected. In the case of the reaction of 1
with HCtCR (R ) COOMe, Ph, SiMe3) at 183 K, the
1H NMR spectra showed two distinct triplet hydride
signals, in an approximately 1:2 ratio. The 31P{1H}
NMR spectra consisted of one relatively sharp resonance
for the major component of the mixture and two
doublets from an AM spin system (unresolved in the
case of the HCtCCOOMe reaction) for the minor
component. When the temperature was raised, the two
triplet hydride resonances in the 1H NMR spectra
coalesce into a broad signal, which resolved into one
triplet at 233 K. In a similar fashion, the different
signals in the 31P{1H} spectra coalesce into one broad
feature, which sharpens as the temperature is raised.
1
At 273 K, the H and 31P{1H} NMR spectra of the in
situ reaction of 1 with HCtCR matched exactly those
of 2a -c, respectively. In fact, when the spectra of these
compounds were recorded at 183 K, decoalescence to two
1
triplets was observed for the hydride signals in the H
spectra and to one singlet plus two doublets in the 31P-
{1H} spectra, as shown in Figure 1 for compound 2b,
the original spectra being restored when the tempera-
ture is raised again. Thus, as happens in the case of
the reaction of [Cp*Ru(dippe)][BAr′4] with 1-alkynes, no
intermediates are detected, and the actual species
observed are the alkynyl hydrido complexes 2a -c.
However, this experiment has exposed an unusual
dynamic behavior for the alkynyl hydrido derivatives
generated by reaction of 1 with 1-alkynes, which has
We were interested in detecting possible intermediate
species in the course of the formation of the alkynyl

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Organometallics, Vol. 22, No. 10, 2003 2007
1
F igu r e 2. Variable-temperature H (hydride region, left) and 31P{1H} (right) NMR spectra of compound 2h in CD2Cl2.
1
not been observed for other alkynyl hydrido complexes
such as [Cp*RuH(CtCR)(dippe)]+ 2,6 and [Cp*RuH(Ct
CR)(PEt3)2]+.4,5 This prompted us to undertake detailed
variable-temperature NMR studies of compounds 2a -
j, to clarify the nature of the species observed at low
variance with the H NMR spectra of compounds 2a -i,
which exhibit two triplet hydride resonances when the
temperature is lowered, in the case of 2j four overlap-
ping triplet signals appear. Despite the fact that 2j bears
no chiral center, its variable-temperature 31P{1H} spec-
tra are very complicated, behaving as if indeed a
stereogenic group were present.
1
temperature. Selected H and 31P{1H} NMR data at 183
1
K are also included in Table 2. The H NMR spectra of
complexes 2a -i all exhibit similar behavior, namely
decoalescence of the hydride resonance to two triplet
resonances when the temperature is lowered, corre-
sponding to two different alkynyl hydrido isomers which
coexist in equilibrium. The 31P{1H} NMR spectra of
complexes 2a -d ,g,i also show a parallel behavior and
are consistent with the presence of two isomers, one
with equivalent phosphorus atoms (isomer A) and
another with inequivalent phosphorus atoms (isomer B),
giving rise to the two doublets (AM spin system). In
those cases in which a stereocenter is present at the
γ-carbon (compounds 2e,f,h ), the 31P{1H} NMR spectra
are more complicated, as shown in Figure 2 for com-
pound 2h , for instance. Three different diastereoisomers
are observed at low temperature in these cases. For
isomer A, the phosphorus atoms are now inequivalent
as well, due to the presence of the stereocenter, and an
AB quartet is observed instead of one singlet. The
combination of the inequivalent phosphorus atoms of
isomer B with the two possible enantiomers of the
hydroxyalkynyl ligand gives rise to two different dias-
tereoisomers (B1 and B2), each of them showing two
doublets in the 31P{1H} NMR spectra (two AM spin
systems). The fact that triplet resonances are observed
in all cases for the hydride protons of the possible
isomers, even for those with inequivalent phosphorus
Several possible interpretations can be provided in
order to explain the unprecedented dynamic behavior
of compounds 2a -j. We have observed very recently a
similar pattern for the variable-temperature NMR
spectra of the dihydride complex [Cp*RuH2(PPhiPr2)2]-
[BAr′4].22b These features have been rationalized by
assuming an equilibrium between rotamers of the
phosphine in the transoid dihydride. For each rotational
isomer, one group on each phosphine is pointing away
from Cp*, and the other two are to the sides; hence,
several possible rotamers are possible. If this is also the
case for compounds 2a -j, the species involved should
be all transoid alkynyl hydrides, differing in the relative
orientation of the methyl and isopropyl substituents
around the Ru-P bonds, as shown in Scheme 1. Thus,
A and B should be then more properly referred to as
rotamers or rotameric isomers. Scheme 2 shows the
diastereomeric species, which would result from the
occurrence of rotamers in combination with the presence
of one chiral center at the γ-carbon atom (compounds
2e,f,h ). In case of rotamer A, two enantiomers are
possible, depending on the configuration of the stereo-
genic γ-carbon, but these are not distinguishable by
NMR spectroscopy. At variance with this, for rotamer
B two diastereoisomers, namely B1 and B2, result from
the different configurations of the asymmetric γ-carbon,
and as such they give separate resonances in the 31P-
{1H} NMR spectra. However, the chemical shift for the
hydride resonances of B1 and B2 must coincide, since
only one signal is observed for these isomeric species in
2
atoms, indicates that the coupling constants J HP and
2J HP′ in each case must have very similar values, as has
been found in systems such as [CpRuH(PMeiPr2)(PPh3)]
and [CpRuH2(PMeiPr2)(PPh3)]-[BPh4].21 The variable-
temperature 1H and 31P{1H} NMR spectra of compound
2j (Figure 3) show a slightly different behavior. At
1
their H NMR spectra. The situation of compound 2j is
unique. At 183 K, four hydridic protons appear in the

2008 Organometallics, Vol. 22, No. 10, 2003
Aneetha et al.
1
F igu r e 3. Variable-temperature H (hydride region, left) and 31P{1H} (right) NMR spectra of compound 2j in CD2Cl2.
Sch em e 1. Equ ilibr iu m betw een Rota m er ic Isom er s of Alk yn yl Hyd r id o Com p lexes
1H NMR spectrum, and signals attributable to four
different species are present in the 31P{1H} NMR
spectrum: two singlets and two AM sets of two doublets
each (Figure 3 and Table 2). In this particular case, the
possible conformations of the cyclohexyl ring might be
playing an important stereochemical role. We have
rationalized this in terms of two possible orientations
of the cyclohexyl ring relative to the OH group, namely
exo and endo, for each of the situations A and B, giving
rise to a total of four possible stereoisomers, A1/A2 and
B1/B2, as shown in Scheme 3. Alternatively, isomers
could also arise from the occupation of the OH in axial
and equatorial positions of the cyclohexyl ring, rather
than exo/endo orientations.
Although the assumption of the equilibrium between
phosphine rotamers seems to justify the observed vari-
able-temperature NMR spectra, an alternative explana-
tion can be proposed on the basis of the hypothesis of
stereochemical nonrigidity for the half-sandwich alkynyl
hydrido cations. It must be noted that these complexes
are formally seven-coordinate and that the lack of
stereochemical rigidity is a typical feature of such
species.28 An interesting possibility is therefore to
consider an equilibrium between transoid (isomer A)
and cisoid (isomer B) stereoisomers of complexes 2d -j,
as shown in Scheme 4. Since the cisoid isomers always
have inequivalent phosphorus atoms, these always
appear as two doublets in their 31P{1H} NMR spectra.
The presence of one triplet for the hydride ligand in
these isomers should be again attributed to the ac-
2
2
cidental coincidence of the values of J HP and J HP′
.
Scheme 5 displays the equilibrium between the A and
B types of stereoisomers in the case of hydroxyalkynyl
hydrido complexes bearing an asymmetric γ-carbon. The
pair of enantiomers of the transoid isomer (A1/A2) is not
distinguishable by NMR spectroscopy, giving rise to one
single resonance in their NMR spectra, whereas in case
of the cisoid isomer, the possible configurations of the
asymmetric γ-carbon lead to two different diastereoi-
somers, B1 and B2. The particular case of compound 2j
can be also consistently explained by considering a
transoid/cisoid equilibrium in combination with the
possible exo/endo orientations of the OH group, as
shown in Scheme 6.
(28) Drew, M. G. B., Prog. Inorg. Chem. 1977, 23, 67.

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Organometallics, Vol. 22, No. 10, 2003 2009
Sch em e 2. Equ ilibr iu m betw een Rota m er ic Isom er s of Hyd r oxya lk yn yl Hyd r id o Com p lexes Bea r in g a
Ch ir a l γ-Ca r bon
Sch em e 3. Equ ilibr iu m betw een Rota m er ic a n d Exo/En d o Isom er s of Com p ou n d 2j
In summation, the occurrence of rotameric isomers
and a possible transoid/cisoid equilibrium are both
reasonable proposals that justify the observed dynamic
behavior of complexes 2a -j. The latter is particularly
attractive, in connection with the activation of C-H
bonds and the postulated existence of species containing
a η2-HCtCR ligand.12-14 We have performed a dynamic
1
NMR line shape fitting simulation on the H variable-
temperature NMR spectra of complexes 2a -j. This has
led to the determination of thermodynamic and activa-

2010 Organometallics, Vol. 22, No. 10, 2003
Aneetha et al.
Sch em e 4. Equ ilibr iu m betw een Tr a n soid a n d
Cisoid Isom er s of Alk yn yl Hyd r id o Com p lexes
Sch em e 5. Equ ilibr iu m betw een Tr a n soid a n d
Cisoid Isom er s of Hyd r oxya lk yn yl Hyd r id o
Com p lexes Bea r in g a n Asym m etr ic γ-Ca r bon
F igu r e 4. ORTEP drawing (30% thermal ellipsoids) of the
cation [Cp*RuH(CtCCOOMe)(PMeiPr2)2]+ in complex 2a .
Hydrogen atoms, except hydride, have been omitted.
Selected bond lengths (Å) and angles (deg) with estimated
standard deviations in parentheses: Ru-C(1), 2.264(4);
Ru-C(2), 2.256(4); Ru-C(3), 2.235(2); Ru-C(4), 2.268(4);
Ru-C(5), 2.318(4); Ru-P(1), 2.368(1); Ru-P(2), 2.389(1);
Ru-C(31), 2.006(4); C(31)-C(32), 1.202(5); C(32)-C(33),
1.431(6); C(33)-O(1), 1.186(5); C(33)-O(2), 1.315(5);
H(1Ru)-Ru-C(31), 132; P(1)-Ru-P(2), 106.29(4); Ru-
C(31)-C(32), 177.8(4); C(31)-C(32)-C(33), 175.2(5); O(1)-
C(33)-O(2), 122.9(4).
stool structure with a transoid disposition of hydride
and alkynyl ligands, very similar to that observed for
the complex [Cp*RuH(CtCCOOMe)(dippe)][BPh4].2 The
dimensions of the alkynyl ligand compare well with data
in the literature.2,3,5,8,9,29 The methyl substituents of the
PMeiPr2 ligands point away from Cp* and the iPr groups
to the sides. The torsion angle C(11)-P(1)-P(2)-C(21)
has a value of 21.4°, which corresponds to a slightly
staggered disposition of the phosphine substituents
relative to each other. Therefore, it seems confirmed
that the structure in the solid state for 2a corresponds
to the transoid isomer. We were most interested in the
solid-state structure for compound 2i, which has the
equilibrium shifted in solution toward the B-type iso-
mer. However, this compound readily isomerizes to its
hydroxyvinylidene tautomer at room temperature both
in solution and in the solid state (vide infra). We
managed to grow crystals of 2i at low temperature, and
once isolated, they were immediately subjected to low-
temperature X-ray structure analysis in order to avoid
tautomerization. The complex crystallized as the diethyl
ether solvate. An ORTEP view of the structure of the
complex cation is shown in Figure 5. Again, the cation
has a four-legged piano-stool structure, with a transoid
disposition of hydride and alkynyl ligands: i.e., the same
as in 2a or in [Cp*RuH(CtCCOOMe)(dippe)][BPh4].2
The OH group of the hydroxyalkynyl ligand is clearly
hydrogen-bonded to the oxygen atom of the diethyl ether
solvate molecule, with a bond distance O(1)‚‚‚O(2s) of
2.824(4) Å (calculated H(1OH)‚‚‚O(2s) ) 2.031 Å). In this
case, the disposition of the substituents around the
phosphorus atoms, as well as the relative orientation
tion parameters listed in Table 4 for the equilibrium
between A-type and B-type isomers. With the only
exception of compound 2i, isomer A predominates over
B at low temperature in all cases, as indicated by the
values of Keq being less than 1. ∆G298 has in all cases a
value very close to 0 kcal mol-1, suggesting that the
energy difference between the A and B isomers is indeed
very small. The activation energy ∆Gq298 is close to 11
kcal mol-1 for all compounds, and it is worth mentioning
that the negative values of ∆Sq EW consistent with an
“ordered” transition state in the pathway from isomer
A to isomer B. Changing hydride to deuteride appar-
ently does not affect the thermodynamic and activation
parameters. This is supported by the observation that
the variation with temperature of the 31P{1H} NMR
spectra of the deuterated derivative [Cp*RuD(CtCPh)-
(PMeiPr2)2][BAr′4] (2b-d ) is identical with that of the
nondeuterated complex 2b. Given the fact that com-
pound 2a is stable at room temperature both in the solid
state and in solution and that it does not rearrange to
its vinylidene tautomer, its X-ray crystal structure was
determined. An ORTEP view of the complex cation is
shown in Figure 4. The cation has a four-legged piano-
(29) (a) Bianchini, C.; Frediani, P.; Masi, D.; Peruzzini, M.; Zanobini,
F. Organometallics 1994, 13, 4616. (b) J ime´nez-Tenorio, M.; Puerta,
M. C.; Valerga, P. J . Chem. Soc., Chem. Commun. 1993, 1750.

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Organometallics, Vol. 22, No. 10, 2003 2011
F igu r e 5. ORTEP drawing (30% thermal ellipsoids) of the cation of [Cp*RuH(CtCC(OH)Ph2)(PMeiPr2)2]+ in complex 2i.
Hydrogen atoms, except hydride and OH, have been omitted. Selected bond lengths (Å) and angles (deg) with estimated
standard deviations in parentheses: Ru-H(1Ru), 1.51(3); Ru-C(1), 2.284(3); Ru-C(2), 2.324(3); Ru-C(3), 2.261(3); Ru-
C(4), 2.238(2); Ru-C(5), 2.274(3); Ru-P(1), 2.3589(8); Ru-P(2), 2.3842(9); Ru-C(25), 2.031(3); C(25)-C(26), 1.203(4); C(26)-
C(27), 1.487(4); C(27)-O(1), 1.432(4); C(27)-C(34), 1.536(4); C(27)-C(28), 1.538(4); O(1)-H(1OH), 0.83; H(1Ru)-Ru-
C(25), 133(1); P(1)-Ru-P(2), 106.11(3); Ru-C(25)-C(26), 176.5(2); C(25)-C(26)-C(27), 173.4(3); C(26)-C(27)-O(1),
105.6(2); C(26)-C(27)-C(28), 111.9(2); C(26)-C(27)-C(34), 105.8(2).
Sch em e 6. Equ ilibr iu m betw een Tr a n soid /Cisoid a n d Exo/En d o Isom er s of Com p ou n d 2j
of the phosphine groups, is very similar to that found
in 2a (torsion angle C(11)-P(1)-P(2)-C(18) ) 24.6°).
Thus, also in this case we find the transoid structure
to be the most stable isomer in the solid state.
Having reached this point and taking into consider-
ation all data obtained, we are still not completely
certain of the nature of the species involved in the
fluxional process which affects compounds 2a -j, since
both of the alternatives presented are consistent with
experimental observations. Although the X-ray crystal
structures have shown only transoid cations, we must
note the small differences in energy between the A and
B isomers, which can be easily overcome by the packing
forces in the crystal, leading to only one of the isomers,
namely transoid, to be present. An intramolecular
transoid/cisoid rearrangement does not involve Ru-H
cleavage, and therefore, we should not expect a great
change in the activation parameters of the deuterated
isotopomer. Furthermore, no isotopic effect has been
observed for the tautomerization of [Cp*RuH(CtCPh)-
(dippe)]+ to [Cp*RudCdCHPh(dippe)]+ in solution, even
when this process occurs through
a dissociative
pathway.2 On the other hand, the observed dynamic
behavior has only one recent precedent in the case of

2012 Organometallics, Vol. 22, No. 10, 2003
Aneetha et al.
Sch em e 7
[Cp*RuH2(PPhiPr2)2][BAr′4].22b If we accept as valid the
proposal that invokes phosphine rotamers, we should
expect that this sort of dynamic behavior would have
been observed more often, in other circumstances. For
instance, we have observed decoalescence of the 31P{1H}
NMR resonances in the case of the complexes [TpRuCl-
(PMeiPr2)2]30 and [Cp*RuCl(PMeiPr2)2].21 However, in
these cases, one single resonance gave rise to a partially
resolved AB pattern, rather than to an equilibrium
mixture of isomers. It should have been expected to
observe a similar fluxional behavior in other related
compounds such as [Cp*RuH2(PMeiPr2)2][BPh4]21 or the
vinylidene derivatives 2b-j (vide infra), but this was
not the case. Since this dynamic behavior is rather
exceptional, we are inclined to suggest that the process
responsible for it is actually the rapid equilibrium
between fluxional transoid and cisoid isomers of com-
pounds 2a -j. It is likely that the backbone carbon chain
in the dippe ligand prevents this process from occuring
to any appreciable extent in the [Cp*RuH(CtCR)-
(dippe)][BPh4]2,6 complexes, whereas for [Cp*RuH(Ct
CR)(PEt3)2][BPh4]4,5 derivatives, the activation energy
could be lower than with PMeiPr2 as coligand, and hence
the slow exchange limit is not reached within the
temperature range in which the NMR spectra are
measured. However, given the fact that there is no
rotation around the Ru-P bond in [Cp*RuH(CtCR)-
(dippe)]+ and that the possible rotamers of [Cp*RuH-
(CtCR)(PEt3)2]+ would be identical, the proposal that
invokes hindered rotation around the Ru-P bond can-
not be ruled out in any case.
Vin ylid en e a n d Allen ylid en e Com p lexes. With
the only exception of compound 2a , all the other alkynyl
and hydroxyalkynyl hydrido complexes 2b-j spontane-
ously rearrange to their vinylidene or 3-hydroxyvi-
nylidene isomers, both in solution and in the solid state
(Scheme 7). In fact, the most efficient procedure for the
preparation of the vinylidene and hydroxyvinylidene
complexes 3b-j was the heating of solid samples of the
corresponding alkynyl hydrido derivative 2b-j at 30 °C
for over a period of 3-6 h. The process can be monitored
by IR spectroscopy, following the dissappearance of the
ν(CtC) band near 2100 cm-1 and the concomitant
increase in the ν(CdC) band of the vinylidene ligand in
the range 1620-1640 cm-1. The spectral properties of
the vinylidene and hydroxyvinylidene complexes 3b-j
(Tables 5 and 6) are consistent with data reported in
the literature for related complexes.3-6,13 The X-ray
crystal structure of 3c was determined. An ORTEP view
of the complex cation is shown in Figure 6. The complex
has a three-legged piano-stool structure, with Ru-C(31)
and C(31)-C(32) separations similar to those found in
other vinylidene complexes.2,5,13,31 The dihedral angle
Si-C(32)-Ru-centroid has a value of 84.2°, very close
to perpendicularity, whereas the torsion angle C(21)-
P(2)-P(1)-C(11) is 68.6°, indicative of a completely
(30) J ime´nez-Tenorio, M. A.; J ime´nez-Tenorio, M.; Puerta, M. C.;
Valerga, P. J . Chem. Soc., Dalton Trans. 1998, 3601.
(31) J ime´nez-Tenorio, M. A.; J ime´nez-Tenorio, M.; Puerta, M. C.;
Valerga, P. Organometallics 2000, 19, 1333.

Half-Sandwich RuIV Alkynyl Hydrido Complexes
Organometallics, Vol. 22, No. 10, 2003 2013
drated product.5,32 Compound 3i also dehydrates spon-
taneously in the solid state to give the allenylidene
complex 5i. The spectral properties of these vinylvi-
nylidene and allenylidene complexes are consistent with
their formulation and compare well with our data for
other related [Cp*RudCdCHC(R)dCH2(P2)][BPh4] and
[Cp*RudCdCdCR2(P2)][BPh4] systems (P2 ) dippe,3,6
(PEt3)24,5). The observed pattern of dehydration of the
hydroxyvinylidene complexes follows in general the
pathways reported in previous works4-6 and do not
require further comment.
Con clu sion s
The reaction of the 16-electron complex [Cp*Ru(PMei-
Pr2)2][BAr′4] with 1-alkynes or 3-hydroxyalkynes leads
to the corresponding alkynyl hydrido or hydroxyalkynyl
hydrido complexes. These complexes have four-legged
piano-stool structures, as shown by X-ray structure
analysis, and display a fluxional behavior in solution
which has been explained in terms of two mechanistic
proposals: (a) hindered rotation around the Ru-PMei-
Pr2 bond and (b) rapid equilibration between transoid
and cisoid steroisomers. Dynamic NMR line shape
analysis revealed a very small energy difference be-
tween the two stereoisomers in equilibrium (less than
1 kcal mol-1) and an activation energy of 11 kcal mol-1
at 298 K for the process. Proposals a and b both
satisfactorily explain the observed dynamic behavior,
and neither of them can be disregarded in principle.
However, the failure to observe such behavior in other
related compounds which give rise to rotamers seems
to be more consistent with the equilibrium between
cisoid and transoid stereoisomers (proposal b). In any
case, further evidence is necessary to prove this unam-
biguously. Isomerization to vinylidene tautomers takes
place smoothly in most cases, both in solution and in
the solid state. Hydroxyvinylidene complexes undergo
further dehydration reactions, leading to either vinylvi-
nylidene complexes or allenylidene complexes, depend-
ing on the substituents present on the hydroxyvi-
nylidene ligand.
F igu r e 6. ORTEP drawing (30% thermal ellipsoids) of the
cation of [Cp*RudCdCHSiMe3(PMeiPr2)2][BAr′4] in com-
plex 3c. Hydrogen atoms have been omitted. Selected bond
lengths (Å) and angles (deg) with estimated standard
deviations in parentheses: Ru-C(1), 2.345(3); Ru-C(2),
2.366(3); Ru-C(3), 2.294(3); Ru-C(4), 2.259(3); Ru-C(5),
2.289(3); Ru-P(1), 2.3701(8); Ru-P(2), 2.3621(9); Ru-
C(31), 1.850(3); C(31)-C(32), 1.289(5); C(32)-Si, 1.876(5);
Si-C(33), 1.856(9); Si-C(34), 1.797(8); Si-C(35), 1.842(6);
P(1)-Ru-P(2), 96.08(3); P(1)-Ru-C(31), 87.75(9); P(2)-
Ru-C(31), 93.5(1); Ru-C(31)-C(32), 171.6(3); C(31)-
C(32)-Si, 136.3(3).
staggered conformation of the methyl substituents in
the PMeiPr2 ligands. The relative orientation of the
substituents of the PMeiPr2 groups in the solid state
makes the phosphorus atoms nonequivalent, unless we
assume fast spinning aroung the Ru-P bonds. However,
as has been already mentioned above, no decoalescence
was observed in the low-temperature 31P{1H} NMR
spectrum of 3c or in the 31P{1H} NMR spectra of any
other vinylidene or hydroxyvinylidene complex 3b-j.
Although this observation seems to support the idea
that the fluxional behavior exhibited by compounds
2a -j might be attributable to a transoid/cisoid equilib-
rium rather than to an equilibrium between phosphine
rotamers, it must be noted that the angles C(31)-Ru-
P(1) and C(31)-Ru-P(2) in 3c are ca. 10° greater than
the corresponding angles in complexes 2a ,i. Therefore,
a less hindered rotation around the Ru-P bond is
expected for 3c, meaning a lower barrier to rotation and,
hence, a lower coalescence temperature.
Ack n ow led gm en t. We thank the Ministerio de
Ciencia y Tecnologia (DGICYT, Project BQU2001-4046)
and the Ministerio de Asuntos Exteriores of Spain
(Accion Integrada HU2001-0020) for financial support
and J ohnson Matthey plc for generous loans of ruthe-
nium trichloride.
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
structural data, including data collection parameters, posi-
tional and thermal parameters, and bond distances and angles
for complexes 2a ,i and 3c. This material is available free of
charge via the Internet at http://pubs.acs.org.
All hydroxyvinylidene complexes, with the only ex-
ception of 3d , undergo dehydration leading to either
vinylvinylidene complexes (4e,g,j) or allenylidene com-
plexes (5f,h ,i) (Scheme 7). The dehydration is ac-
complished by stirring a dichloromethane solution of the
corresponding hydroxyvinylidene complex at room tem-
perature for 8-10 h. In case of allenylidene complexes,
after 12 h of stirring, the solution was passed through
a column of acidic alumina, affording the pure dehy-
OM020940N
(32) (a) Martin, M.; Werner, H. J . Chem. Soc., Dalton Trans. 1996,
2275. (b) Werner, H.; Rappert, T.; Wiedemann, R.; Wolf, J .; Mahr, N.
Organometallics 1994, 13, 2721. (c) Werner, H.; Lass, R. W.; Gevert,
O.; Wolf, J . Organometallics 1997, 166, 4077.