Reactivity of [Re(η2-H2)(CO)2P3]+ cations with alkynes: Preparation of vinylidene and propadienylidene complexes

Article abstract of DOI:10.1016/S0022-328X(00)00020-6

Treatment of [Re(η²-H₂)(CO)₂P₃]⁺ cations with phenylacetylene leads to the displacement of H₂ and the formation of vinylidene [Re{C=C(H)Ph}(CO)₂P₃]⁺ (1-3) [

Full text of DOI:10.1016/S0022-328X(00)00020-6

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Journal of Organometallic Chemistry 609 (2000) 10–20
Reactivity of [Re(h2-H2)(CO)2P3]+ cations with alkynes:
preparation of vinylidene and propadienylidene complexes
Gabriele Albertin *, Stefano Antoniutti, Emilio Bordignon, Davide Bresolin
Dipartimento di Chimica, Uni6ersita` Ca’ Foscari di Venezia, Dorsoduro 2137, I-30123 Venice, Italy
Received 22 November 1999; received in revised form 29 December 1999
Abstract
Treatment of [Re(h2-H2)(CO)2P3]+ cations with phenylacetylene leads to the displacement of H2 and the formation of
vinylidene [Re{CꢀC(H)Ph}(CO)2P3]+ (1–3) [P=P(OEt)3, PPh(OEt)2 or PPh2OEt] derivatives. Infrared and NMR data support
equilibrium in solution [Re(CO)2P3]++PhCꢁCH ? [Re{ꢀCꢀC(H)Ph}(CO)2P3]+ involving the unsaturated complex, free alkyne
and vinylidene derivative. 1,4-Diethynylbenzene also tautomerises to the Re(I) centre, affording the [Re{ꢀCꢀC(H)(1,4-
C6H4CꢁCH)}(CO)2P3]BF4 [P=P(OEt)3 or PPh(OEt)2] vinylidene derivatives. Vinylidene complexes 1–3 are deprotonated easily
by NEt3 to give acetylides Re(CꢁCR)(CO)2P3 (4–6) (R=Ph or 1,4-C6H4CꢁCH), which may in turn be reprotonated with
HBF4·Et2O to reform vinylidenes 1–3. Acetylide complexes 4–6 were also prepared by reacting unsaturated cations [Re(CO)2P3]+
with lithium acetylide. Binuclear complexes {Re(CO)2P3}2(m-1,4-CꢁCC6H4CꢁC) (7, 8) [P=PPh(OEt)2 or PPh2OEt] were obtained
by sequential treatment of [Re(CO)2P3]+ cations, first with 1,4-HCꢁCC6H4CꢁCH and then with an excess of NEt3. Propadienyli-
dene complexes [Re(ꢀCꢀCꢀCPh2)(CO)2P3]BF4 (9, 10) [P=PPh(OEt)2 or PPh2OEt] were prepared by allowing [Re(h2-
H2)(CO)2P3]+ cations or unsaturated species [Re(CO)2P3]+ to react with HCꢁCC(Ph2)OH at room temperature. The
characterisation of all new complexes by IR and 1H-, 31P{1H}- and 13C{1H}-NMR spectra is also discussed. © 2000 Elsevier
Science S.A. All rights reserved.
Keywords: Rhenium; Hydride; Vinylidene; Acetylide; Propadienylidene
creased greatly in the past few years [8]. Acetylides and
binuclear complexes with linear carbon chains Cn (n=
2–5) as bridging ligands are among the most interesting
results [9] in the organometallic chemistry of rhenium,
as well as the use of Re complexes in metal-assisted
catalytic reactions such as alkyne metathesis [10],
epoxydation of olefins [11] and alkane dehydrogenation
[12]. However, the chemistry of metalꢂcarbon single
and multiple bonds of rhenium is mainly based on the
cyclopentadienyl ligand [5a,8,9,13], and only recently
[3a,14] have vinylidene and other carbene complexes
bonded to a Re fragment not containing the Cp ligand
been reported.
1. Introduction
Transition metal complexes containing a P-conju-
gated unsaturated chain continue to attract interest
from both fundamental and applied viewpoints. Some
of these complexes have potentially useful material
properties [1], while others are probably intermediate in
the coupling of alkynes to give enynes or butatrienes
[2], in synthesis of unsaturated carbene complexes [3]
and in other CꢂC coupling reactions [4]. Several studies
have been reported on vinylidene complexes [5,6]
MꢀCꢀCR2, which constitute the simplest of these sys-
tems, but the next highest member, propadienylidene, is
also receiving increased attention, and numerous metal
complexes have been prepared recently [7]. These com-
plexes, however, do not include rhenium as the central
metal, although its organometallic chemistry has in-
In a previous paper [15] we described the synthesis of
[Re(h2-H2)(CO)5−nPn]+ (n=2, 3 or 4; P=phosphites)
and of the related unsaturated complexes [Re(CO)5−n
-
Pn]+, which turned out to be good precursors for some
reactions. As an extension of our studies on the chem-
istry of acetylide and vinylidene complexes [16], we
have now begun systematic investigation of the
* Corresponding author. Tel.: +39-041-2578555.
E-mail address: albertin@unive.it (G. Albertin).
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(00)00020-6

G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
11
reactivity of these h2-H2 rhenium complexes with termi-
nal alkynes, which allowed new vinylidene and the first
example of propadienylidene complexes of rhenium to
be prepared. Results are reported here.
2.2.1. [Re{ꢀCꢀC(H)Ph}(CO)2P3]BF4 (1a–3a)
[P=P(OEt)3 (1a), PPh(OEt)2 (2a) or PPh2OEt (3a)]
To a solution of the acetylide complex Re(CꢁCPh)-
(CO)2P3 (0.1 mmol) in 5 cm3 of diethylether cooled to
−80°C was added a slight excess of HBF4·Et2O (0.11
mmol, 16 ml) and the reaction mixture, brought to
room temperature (r.t.), was stirred for 3 h. A red–or-
ange solid separated out slowly, which was filtered and
dried under vacuum; yield ]80%.
2. Experimental
2.1. General considerations and physical measurements
Anal. Calc. for C28H51BF4O11P3Re (1a): C, 36.18; H,
5.53. Found: C, 36.02; H, 5.58%. LM=84.8 S cm2
All synthetic work was carried out under an appro-
priate atmosphere (argon or H2) using standard
Schlenk techniques or a vacuum atmosphere dry-box.
Once isolated, the complexes turned out to be quite
air-stable and were stored at −20°C. All solvents used
were dried over appropriate drying agents, degassed on
a vacuum line, and distilled into vacuum-tight storage
flasks. Phosphines PPh(OEt)2 and PPh2OEt were pre-
pared by the method of Rabinowitz and Pellon [17];
triethylphosphite was an Aldrich product, purified by
distillation under nitrogen. Alkynes RCꢁCH (R=Ph,
mol−1
.
Anal. Calc. for C40H51BF4O8P3Re (2a): C, 46.84; H,
5.01. Found: C, 46.63; H, 5.08%. LM=85.5 S cm2
mol−1
.
Anal. Calc. for C52H51BF4O5P3Re (3a): C, 55.67; H,
4.58. Found: C, 55.81; H, 4.64%. LM=85.9 S cm2
mol−1
.
The complexes may also be prepared by treating
ReH(CO)2P3 (0.1 mmol) with HBF4·Et2O (0.11 mmol,
16 ml) in CH2Cl2 (5 cm3) and then with an excess of
PhCꢁCH (0.3 mmol, 26 ml). Removal of the solvent
under reduced pressure and treatment with ethanol (2
cm3) gives a red solid or a red oil which, however, turns
out to be a mixture also containing the unsaturated
[Re(CO)2P3]BF4 compound.
But,
4-MeC6H4,
COOMe
or
COOEt)
and
HCꢁCC(OH)RR% (R=Ph; R%=Ph, H or CH3) were
Aldrich products, used without further purification.
Lithium phenylacetylide Li+PhCꢁC− was prepared by
reacting a slight excess of phenylacetylene (40 mmol,
4.4 cm3) with lithium (35 mmol, 0.24 g) in 10 cm3 of
tetrahydrofuran (THF). 1,4-Diethynylbenzene was pre-
pared following the method reported previously [18].
The related lithium acetylide Li+[1,4-HCꢁCC6H4CꢁC]−
was prepared by reacting 1,4-diethynylbenzene (16
mmol, 2 g) with lithium (15 mmol, 0.104 g) in 30 cm3 of
THF. The reaction mixture was refluxed until all the
lithium had dissolved (about 8 h), and was then kept
under argon. Other reagents were purchased from com-
mercial sources in the highest available purity and used
as received. Infrared spectra were recorded on Digilab
Bio-Rad FTS-40 or Nicolet Magna 750 FT-IR spec-
trophotometers. NMR spectra (1H, 13C, 31P) were ob-
tained on a Bruker AC200 spectrometer at tempera-
tures between −90 and +30°C, unless otherwise
2.2.2. [Re{ꢀCꢀC(H)(1,4-C6H4CꢁCH)}(CO)2P3]BF4
(1c–2c) [P=P(OEt)3 (1c) or PPh(OEt)2 (2c)]
A slight excess of HBF4·Et2O (0.11 mmol, 16 ml) was
added to a solution of the acetylide complex Re(1,4-
CꢁCC6H4CꢁCH)(CO)2P3 in
5
cm3 of diethylether
cooled to −80°C. The reaction mixture was brought to
r.t. and stirred vigorously until a dark-green solid sepa-
rated out, which was filtered and dried under vacuum;
yield ]40%.
Anal. Calc. for C30H51BF4O11P3Re (1c): C, 37.78; H,
5.39. Found: C, 37.62; H, 5.47%. LM=85.3 S cm2
mol−1
.
Anal. Calc. for C42H51BF4O8P3Re (2c): C, 48.05; H,
4.90. Found: C, 48.19; H, 4.95%. LM=84.5 S cm2
mol−1
.
1
stated. H and 13C{1H} spectra are referred to internal
tetramethylsilane; 31P{1H} chemical shifts are reported
with respect to 85% H3PO4, with downfield shifts con-
sidered positive. The SWAN-MR software package [19]
was used to treat NMR data. The conductivity of 10−3
mol dm−3 solutions of the complexes in MeNO2 at
25°C was measured with a radiometer CDM 83
instrument.
2.2.3. Re(CꢁCPh)(CO)2P3 (4a–6a) [P=P(OEt)3 (4a),
PPh(OEt)2 (5a) or PPh2OEt (6a)]
The complexes may be prepared following two differ-
ent methods.
1. A slight excess of CF3SO3H (0.66 mmol, 58 ml) was
added to a solution of ReH(CO)3P2 (0.6 mmol) in
10 cm3 of CH2Cl2 cooled to −80°C. The reaction
mixture was brought to r.t., stirred for 1 h, and an
excess of Li[PhCꢁC] added (0.75 mmol, 0.31 cm3 of
a 2.44 mol dm−3 solution in THF). After 3 h of
stirring, the solvent was removed under reduced
pressure, giving an oil which was treated with etha-
nol (2 cm3). The resulting solution was stirred vigor-
2.2. Synthesis of complexes
Hydrides ReH(CO)2P3 and unsaturated complexes
[Re(CO)2P3]BPh4 [P=P(OEt)3, PPh(OEt)2 or PPh2OEt]
were prepared according to the reported method [15].

12
G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
ously until a pale-yellow solid separated out, which
giving an oil which was triturated with ethanol (3 cm3)
until an orange solid separated out, which was filtered
and dried under vacuum; yield ]65%. Compound 4c
did not solidify, but was found to be pure by NMR and
analysis.
Anal. Calc. for C30H50O11P3Re (4c): C, 41.62; H,
5.82. Found: C, 41.48; H, 5.90%.
Anal. Calc. for C42H50O8P3Re (5c): C, 52.44; H, 5.24.
Found: C, 52.58; H, 5.19%.
was filtered and dried under vacuum. In the case of
4a, an oil was obtained, which was chromato-
graphed onto a silica gel column (length 50 cm,
diameter 4 cm) using a mixture of light petroleum
(b.p. 40–60°C), benzene and diethylether (ratio
10:1:1) as eluent. The first fraction eluted (60 cm3)
was evaporated to dryness, giving an oily product
which was pure by NMR and elemental analysis.
2. A slight excess of HBF4·Et2O (0.11 mmol, 16 ml of a
54% solution in diethylether) was added to a solu-
tion of ReH(CO)3P2 (0.1 mmol) in 3 cm3 of CH2Cl2
cooled to −80°C. The reaction mixture was
brought to r.t., stirred for 1 h, and an excess of
PhCꢁCH (0.3 mmol, 26 ml) added. After 3–4 h of
stirring, an excess of NEt3 (0.3 mmol, 42 ml) was
added and stirring was continued for 3 h. The
solvent was removed under reduced pressure, giving
an oil from which the acetylide complex was ex-
tracted with three 2 cm3-portions of benzene. The
solvent was evaporated to dryness and the resulting
oil triturated with 2 cm3 of ethanol until a pale-yel-
low solid separated out, which was filtered and dried
under vacuum. This method also provided com-
pound 4a as an oil, which was purified by chro-
matography. The yield with each of the two
methods was about 80%.
Anal. Calc. for C54H50O5P3Re (6c): C, 61.30; H, 4.76.
Found: C, 61.18; H, 4.69%.
2.2.6. [{Re(CO)2P3}2(v-1,4-CꢁCC6H4CꢁC)] (7c–8c)
[P=PPh(OEt)2 (7c) or PPh2OEt (8c)]
A slight excess of HBF4·Et2O (0.22 mmol, 32 ml) was
added to a solution of the appropriate hydride Re-
H(CO)2P3 (0.2 mmol) in 3 cm3 of CH2Cl2 cooled to
−80°C and the reaction mixture was stirred for 1 h. A
solution of 1,4-diethynylbenzene (0.1 mmol, 12.6 mg) in
2 cm3 of CH2Cl2 was added and, after 4 h of stirring,
an excess of NEt3 (0.6 mmol, 85 ml) was further added.
Stirring of the reaction mixture was continued for
about 3 h, and the solvent was then removed under
reduced pressure, giving an oil which was chro-
matographed onto a silica gel column (50×4 cm) using
a mixture of light petroleum, benzene and diethylether
(ratio 8:1:1) as eluent. The first fraction eluted (100
cm3) was evaporated to dryness, giving a red–brown oil
which was triturated with ethanol (3 cm3) until an
orange solid separated out, which was filtered and dried
under vacuum; yield ]60%.
Anal. Calc. for C28H50O11P3Re (4a): C, 39.95; H,
5.99. Found: C, 40.11; H, 5.85%.
Anal. Calc. for C40H50O8P3Re (5a): C, 51.22; H, 5.37.
Found: C, 51.08; H, 5.40%.
Anal. Calc. for C52H50O5P3Re (6a): C, 60.40; H, 4.87.
Found: C, 60.22; H, 4.95%.
Anal. Calc. for C74H94O16P6Re2 (7c): C, 49.44; H,
5.27. Found: C, 49.52; H, 5.35%.
Anal. Calc. for C98H94O10P6Re2 (8c): C, 59.15; H,
4.76. Found: C, 59.32; H, 4.79%.
2.2.4. Re(CꢁCBut)(CO)2[PPh(OEt)2]3 (5b)
This complex was prepared like the related phenyl-
acetylide 5a following method (2) and obtaining the
compound as an oil; yield ]70%.
Anal. Calc. for C38H54O8P3Re: C, 49.72; H, 5.93.
Found: C, 49.88; H, 5.99%.
2.2.7. [Re(ꢀCꢀCꢀCPh2)(CO)2P3]BF4 (9–10)
[P=PPh(OEt)2 (9) or PPh2OEt (10)]
To a solution of ReH(CO)2P3 (0.1 mmol) in 3 cm3 of
CH2Cl2 cooled to −80°C was added a slight excess of
HBF4·Et2O (0.11 mmol, 16 ml) and the reaction mix-
ture, brought to r.t., was stirred for about 1 h. An
excess of HCꢁCC(Ph2)OH (0.3 mmol, 62 mg) in 2 cm3
of CH2Cl2 was added, and stirring was continued for
about 3 h. The solvent was removed under reduced
pressure, giving a red–brown oil which was triturated
with ethanol (3 cm3) until a purple solid separated out.
Cooling of the mixture to 0°C favoured separation of
the solid, which was filtered, washed three times with
hexane (3 cm3), and crystallised from CH2Cl2 (1 cm3)
and ethanol (3 cm3); yield ]60%.
2.2.5. Re(1,4-CꢁCC6H4CꢁCH)(CO)2P3 (4c–6c)
[P=P(OEt)3 (4c), PPh(OEt)2 (5c) or PPh2OEt (6c)]
A solution of ReH(CO)2P3 (0.1 mmol) in 3 cm3 of
CH2Cl2 cooled to −80°C was treated with a slight
excess of HBF4·Et2O (0.11 mmol, 16 ml of a 54%
solution) and the reaction mixture, brought to r.t., was
stirred for 1 h. An excess of 1,4-diethynylbenzene (0.3
mmol, 37.8 mg) in 2 cm3 of CH2Cl2 was added and,
after 3 h of stirring, an excess of NEt3 (0.3 mmol, 42 ml)
was further added. After 1 h the solvent was removed
under reduced pressure, giving a red–brown solid
which was chromatographed onto a silica gel column
(50×4 cm) using a mixture of light petroleum, di-
ethylether and benzene (ratio 8:1:1) as eluent. The first
fraction eluted (100 cm3) was evaporated to dryness,
Anal Calc. for C47H55BF4O8P3Re (9): C, 50.68; H,
4.98. Found: C, 50.56; H, 5.07%. LM=86.2 S cm2
mol−1
.
Anal Calc. for C59H55BF4O5P3Re (10): C, 58.57; H,
4.58. Found: C, 58.79; H, 4.46%. LM=85.1 S cm2
mol−1
.

G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
13
3. Results and discussion
showed equilibrium Eq. (1), forming free alkyne and
[Re(CO)2P3]+ cations. Only the addition of a large
excess of PhCꢁCH made the concentration of
[Re(CO)2P3]+ negligible.
3.1. Vinylidene complexes
Dissociation of a vinylidene complex to give free
alkyne and an unsaturated complex, as observed in our
case, is rather unexpected, since the previously reported
vinylidene complexes 2–6 are very stable and the
ꢀCꢀC(H)R ligand may undergo several reactions but
not displacement by other ligands. Only recently has
the dissociation of a terminal alkyne from a monosub-
stituted vinylidene complex been reported [16a,b,c] for
[M(CꢁCR){ꢀCꢀC(H)R}P4]+ (M=Fe, Ru), containing
phosphite as ancillary ligands. It therefore seems that
these phosphite molecules, acting as ancillary ligands,
make vinylidene species ꢀCꢀC(H)Ph rather labile in
complexes 1–3, the dissociation of which gives the free
alkyne PhCꢁCH, as in Eq. (1).
Diagnostic for the presence of the vinylidene ligand
in complexes 1–3 and of the existence of equilibrium
(Eq. (1)) in solution are the IR and NMR data reported
in Table 1. The IR spectra of [Re{ꢀCꢀC(H)Ph}-
(CO)2P3]BF4 (1–3) derivatives show two w(CO) bands
at 2056–1958 cm−1, due to two carbonyl ligands in a
mutually cis position. Furthermore, in the 1660–1630
cm−1 region, the characteristic couple of medium-in-
tensity w(CꢀC) bands of the vinylidene ligand is present,
in agreement with the proposed formulation.
The reactions of rhenium dicarbonyl complexes with
phenylacetylene are summarised in Scheme 1.
Sequential treatment of hydride ReH(CO)2P3, first
with HBF4·Et2O and then with phenylacetylide, affords
the vinylidene [Re{ꢀCꢀC(H)Ph}(CO)2P3]+ (1–3)
cations, as shown in Scheme 1. The reactions proceed
via the intermediacy of the [Re(h2-H2)(CO)2P3]+
cation, which undergoes displacement of the h2-H2
ligand by PhCꢁCH. The latter molecule probably forms
P-adducts and tautomerises to the vinylidene ligand via
a 1,2-hydrogen shift, which is the mechanism followed
generally by d6 metal systems [5,6,20,21]. Unfortu-
nately, in our case, no P-acetylide complex was de-
tected by variable-temperature NMR studies, which
showed the presence of the vinylidene complex and
PhCꢁCH species only.
Alternatively, vinylidene derivatives 1–3 are also
formed by treating the unsaturated complex cations [15]
[Re(CO)2P3]+ with phenylacetylide according to Eq.
(1):
[Re(CO)2P3]++PhCꢁCH ?
[Re{ꢀCꢀC(H)Ph}(CO)2P3]+
(1)
1−3
Instead, the IR spectra of samples 1–3 prepared by
reacting [Re(CO)2P3]+ with PhCꢁCH showed invari-
ably not only the w(CO) and w(CꢀC) absorptions but
also two other w(CO) bands, due to unsaturated
[Re(CO)2P3]+ compounds present in the samples, in
agreement with Eq. (1). The establishment of this equi-
librium is supported strongly by the NMR data which,
in the 31P{1H} spectra, show two sets of AB2 multiplets,
one due to the [Re{ꢀCꢀC(H)Ph}(CO)2P3]+ vinylidene
complex and the other to the [Re(CO)2P3]+ precursor.
The addition of a free alkyne decreases the intensity of
the [Re(CO)2P3]+ signals and increases that of the
multiplet attributed to the vinylidene, which turns out
to be predominant with a fivefold excess of PhCꢁCH.
The 13C{1H}-NMR spectra confirm this equilibrium
and indicate unambiguously the presence of the vinyli-
dene ligand in 1–3, showing the characteristic highly
deshielded ReꢀC carbene carbon resonance at 345–317
ppm, which appears as a doublet of triplets (or a triplet
of doublets) due to coupling with AB2-type phosphorus
nuclei. The spectra also show the signal of the vinyl
ꢀC(H)Ph carbon resonance at 119–116 ppm. The reso-
nances of the carbonyl carbon atoms appear at 200–
187 ppm as only one triplet of doublets, in agreement
with the equivalence of the two CO ligands. On the
basis of the spectroscopic data, we therefore propose a
fac–cis geometry in solution, as shown in Scheme 1 for
our vinylidene complexes 1–3.
Owing to equilibrium Eq. (1), attempts to isolate
vinylidene complexes 1–3 in pure form failed, because a
crude product also containing the [Re(CO)2P3]+ start-
ing materials was always obtained. However, analyti-
cally pure samples of compounds [Re{ꢀCꢀC(H)Ph}-
(CO)2P3]BF4 (1–3) may be yielded by the protonation
with HBF4 of the acetylide Re(CꢁCPh)(CO)2P3 (vide
infra). Dissolving these samples of 1–3 in CH2Cl2
Scheme 1.

14
G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
Table 1
Infrared and NMR spectroscopic data for rhenium compounds
a
b,c
Compound
IR
1H-NMR
Spin system 31P{1H}-NMR b,d 13C{1H}-NMR b,e
w (cm−1) Assign
l
Assign
l (J Hz)
l (J Hz)
Assign
Ca
1a
1c
2a
[Re{ꢀCꢀC(H)Ph}
2056 m wCO
(CO)2{P(OEt)3}3]BF4 1965 s
4.56 m
4.10 m
1.37 m
ꢀC(H)
CH2
CH3
AB2
A2B
A2B
lA=106.8
lB=105.8
317.8 td
J
CP=JCP=13
193.8 td
CP=JCP=18
1660 m wCꢀC
1632 m
J
AB=55.5
CO
J
117.8 m, br
62.3 m
16.1 t
317.0 m, br
187.4 m
117.8 m, br
77.9 s
68.7 s
63.3 m
16.2 t, br
344.9 dt
Cb
CH2
CH3
Ca
CO
Cb
Cg
Cd
CH2
CH3
Ca
[Re{ꢀCꢀC(H)
(1,4-C6H4CꢁCH)}
3261 m wCH
2046 m wCꢁC
4.55 m
4.10 m
1.38 m
ꢀC(H)
CH2
CH3
lA=111.9
lB=105.8
JAB=35
(CO)2{P(OEt)3}3]BF4 1969 s
wCO
1643 m wCꢀC
[Re{ꢀCꢀC(H)Ph}
(CO)2{PPh(OEt)2}3]
BF4
2040 s
1958 s
wCO
4.00–3.70 m
1.35 t
1.33 t
CH2
CH3
lA=121.4
lB=127.6
JAB=27
J
J
CP=39
CP=11
1654 m wCꢀC
1630 m
1.31 t
189.8 td
CP=JCP=11
CO
J
117. 5 br
64.3 t
Cb
CH2
63.9 d
16.0 m
343.4 m
199.7 td
CH3
Ca
CO
2c
3a
4a
[Re{ꢀCꢀC(H)
(1,4-C6H4CꢁCH)}
(CO)2{PPh(OEt)2}3]
BF4
2051 m wCꢁC
3.89 m
2.59 s
1.34 t
1.30 t
1.21 t
CH2
ꢁCH
CH3
AB2
AB2
A2B
lA=128.1
lB=122.2
1959 s
wCO
1640 m wCꢀC
J
AB=38
J
J
CP=12
CP=7
116.4 m, br
84.6 s
66.5 s
63.0 m
16.1 m
344.9 dt
Cb
Cg
Cd
CH2
CH3
Ca
[Re{ꢀCꢀC(H)Ph}
(CO)2(PPh2OEt)3]BF4 1972 s
2035 s
wCO
4.22 m
3.48 m
1.04 t
0.92 t
ꢀC(H)
CH2
CH3
lA=104.6
lB=99.4
JAB=33
J
J
CP=10
CP=35
1656 m wCꢀC
1637 m
192.1 td
CP=JCP=10
119.2 td
CP=1
CO
J
Cb
J
65.0 t
15.8 t
194.0 dt
CH2CH3
CO
Re(CꢁCPh)(CO)2
[P(OEt)3]3
2088 m wCꢁC
4.15 m
1.28 t
CH2
CH3
lA=117.7
lB=115.9
1966 s
1889 s
wCO
J
J
CP=10
CP=80
J
AB=46.1
193.5 td
CP=JCP=12
114.76 td
CP=JCP=3.5
105.9 td
CP=JCP=20
J
Cb
J
Ca
J
61.3 br
16.5 m
CH3CH2
4c
Re(1,4-CꢁCC6H4Cꢁ
CH)(CO)2[P(OEt)3]3
3264 m wCH
2082 m wCꢁC
2013 m wCꢁCH 2.80 s
4.30–4.00 m
2.86 s
CH2
ꢁCH
AB2
A2B
lA=122.6
lB=118.6
JAB=28
lA=118.4
lB=116.8
1966 s
1914 s
1894 s
wCO
1.22 t
CH3
J
AB=46

G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
15
Table 1 (Continued)
a
b,c
Compound
IR
1H-NMR
Spin system 31P{1H}-NMR b,d 13C{1H}-NMR b,e
w (cm−1
)
Assign
l
Assign
l (J Hz)
l (J Hz)
Assign
CO
5a Re(CꢁCPh)(CO)2
2086 m
1970 s
1885 s
wCꢁC
wCO
4.40–3.80 m CH2
1.36 t
1.39 t
AB2
lA=130.7
lB=130.4
195.6 td
[PPh(OEt)2]3
CH3
J
CP=JCP=10
J
AB=34.0
194.6 dt
J
J
CP=12
CP=57
115.13 td
CP=JCP=3
111.3 td
CP=JCP=18
Cb
J
Ca
J
62.62 t
62.26 t
16.5 m
CH2
CH3
f
5b Re(ButCꢁC)(CO)2
2046 m
1968 s
1867 s
wCꢁC
wCO
4.30–3.60 m CH2
AB2
AB2
lA=135.4 f
lB=132.4
[PPh(OEt)2]3
1.20 s
1.17 t
1.14 t
CH3 But
CH3 phos
J
AB=17
5c Re(1,4-CꢁCC6H4Cꢁ
3280 m
wCH
wCꢁC
wCꢁCH 1.33 t
wCO
4.20–3.60 m CH2
lA=134.8
lB=131.9
JAB=19
195.4 td
CO
Cb
CH)(CO)2[PPh(OEt)2]3 2078 s
3.15 s
ꢁCH
CH3
J
CP=JCP=12
2006 m
1903 s
113.9 dt
1.31 t
J
J
CP=17
CP=2
107.1 dt
Ca
J
J
CP=36
CP=16
Cg
84.8 s
Cd
77.2 s
CH2
62.24 t
61.37 d
16.4 m
197.6 dt
CH3
CO
6a Re(CꢁCPh)(CO)2
2083 m
1944 s
1873 s
wCꢁC
wCO
3.76 m
3.39 qi
1.17 t
0.99 t
CH2
CH3
AB2
lA=101.7
lB=99.0
(PPh2OEt)3
J
J
CP=9.5
CP=45
J
AB=30
197.0 dt
J
J
CP=8
CP=20
118.7 td
CP=JCP=2
117.06 td
CP=JCP=16
Cb
Ca
J
J
63.1 d
CH2
63.3 t
16.20 m
197.3 m
123.3 td
CH3
CO
Ca
6c Re(1,4-CꢁCC6H4Cꢁ
3269 w
wCH
wCꢁC
wCꢁCH 3.11 s
wCO
3.80–3.20 m CH2
AB2
AB2
lA=105.4
lB=101.8
CH)(CO)2(PPh2OEt)3 2082 m
3.18 s
ꢁCH
1999 m
1938 m
1892 s
J
AB=18
J
CP=JCP=16
1.14 t
1.07 t
0.99 t
0.95 t
CH3
lA=101.8
lB=99.4
JAB=30
113.4 dt
J
J
CP=33
CP=16
1859 m
118.8 br
118.5 br
84.80 s
84.68 s
77.53 s
77.16 s
63.3 t
Cb
Cg
Cd
CH2
62.8 t
62.9 t
CH3
16.3 t
16.2 t
16.0 t

16
G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
Table 1 (Continued)
a
b,c
Compound
IR
1H-NMR
Spin system 31P{1H}-NMR b,d 13C{1H}-NMR b,e
w (cm−1) Assign
l
Assign
CH2
l (J Hz)
l (J Hz)
Assign
CO
7c {Re(CO)2[PPh(OEt)2]3}2 2087 m wCꢁC
4.15 m
3.87 m
1.33 t
1.31 t
AB2
lA=134.7
lB=131.9
195.5 td
(m-1,4-CꢁCC6H4CꢁC)
1964 s
1908 s
wCO
JCP=JCP=11
CH3
J
AB=18
114.2 dt
Cb
J
J
CP=18
CP=2
99.2 dt
Ca
J
J
CP=35
CP=16
62.2 br
16.4 m
197.3 m
118.9 br
112.7 m
63.3 m
62.9 m
16.1 m
298.0 dt
CH2
CH3
CO
Cb
Ca
CH2
8c [Re(CO)2(PPh2OEt)3]2
(m-1,4-CꢁCC6H4CꢁC)
2077 m wCꢁC
1945 m wCO
1896 s
3.70–3.20 m
1.10 t
1.03 t
CH2
CH3
AB2
AB2
A2B
lA=105.3
lB=102.5
J
AB=18
1875 m
0.95 t
lA=102.1
lB=99.6
J
AB=30
CH3
Ca
9
[Re(ꢀCꢀCꢀCPh2)(CO)2 2014 m wCꢀCꢀC 3.80 m
CH2
CH3
lA=129.3
lB=125.2
{PPh(OEt)2}3]BF4
1927 s
wCO
1.26 t
1.22 t
JCP=21
CP=10
J
AB=27
J
204.3 td
CP=JCP=10
CO
J
202.5 br
163.2 s
63.6 t
Cb
Cg
CH2
63.1 d
16.1 m
298.9 dt
CH3
Ca
10 [Re(ꢀCꢀCꢀCPh2)(CO)2 2011 m wCꢀCꢀC 3.33 m
CH2
CH3
A2B
lA=103.6
lB=98.3
(PPh2OEt)3]BF4
1922 s
wCO
0.95 t
0.92 t
JCP=20
CP=10
J
AB=26
J
199.2 br
191.8 dt
Cb
CO
J
J
CP=20
CP=10
160.2 s
65.1 m
15.9 t
Cg
CH2
CH3
a In KBr pellets.
b In CD2Cl2 at 25°C.
c Phenyl proton resonances are omitted.
d Positive shift downfield from 85% H3PO4.
e Phenyl carbon resonances are omitted.
f In C6D6.
The proton NMR spectra of 1–3 are also consistent
with the presence of the vinylidene ligand, showing the
characteristic ꢀC(H)Ph signal as a multiplet at 4.56–
4.22 ppm. In addition to the resonances of the phos-
phite and BPh−4 anion, the spectra also show the signals
of free PhCꢁCH, in agreement with the dissociation of
the terminal alkyne from the vinylidene complexes, as
in Eq. (1).
H2)(CO)3P2]+, [Re(h2-H2)(CO)P4]+, etc., were also re-
acted with phenylacetylide, but no formation of
vinylidene or P-acetylide complexes was ever observed.
This unreactivity led us to attempt to prepare vinyli-
dene complexes by protonation of the related acetylide
Re(PhCꢁC)(CO)3P2 and Re(PhCꢁC)(CO)P4 derivatives,
containing a carbonyl–phosphite ratio different from
2:3. Although the reaction with HBF4·Et2O proceeded
easily at low temperature, no evidence of the formation
of ꢀCꢀC(H)Ph or P-alkyne complexes was detected by
NMR. The reaction mixture, in fact, only showed the
Unsaturated complexes or dihydrogen derivatives
containing a carbonyl–phosphite ratio different from
2:3, i.e. of the type [Re(CO)3P2]+, [Re(CO)P4]+, [Re(h2-

G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
17
presence of unsaturated [Re(CO)3P2]+, [Re(CO)P4]+
species and the free PhCꢁCH. It seems, therefore, that
the stoichiometry of rhenium precursors is important in
determining the stability of vinylidene complexes; in
particular, only the dicarbonyl Re(CO)2P3 fragment
allows vinylidene complexes 1–3 to be obtained.
Instead, varying the steric and electronic properties
of the phosphite ligands in the series from P(OEt)3 to
PPh(OEt)2 or PPh2OEt does not seem to influence the
stability of rhenium vinylidene derivatives, all the
[Re{ꢀCꢀC(H)Ph}(CO)2P3]+ (1–3) being insoluble in
the solid state and giving Eq. (1) in solution.
one w(CO) band in the IR and an AB2-type multiplet in
the 31P{1H}-NMR.
3.2. Acetylide complexes
Vinylidene complexes [Re{ꢀCꢀC(H)R}(CO)2P3]+ (1–
3) react with base (NEt3) to give acetylide derivatives
Re(CꢁCR)(CO)2P3 (4–6), which were isolated in good
yield and characterised. Alternatively, acetylides 4–6
may be prepared by reacting unsaturated [Re(CO)2P3]+
complexes with lithium acetylide in THF, as shown in
Scheme 3.
The results obtained with phenyl acetylide prompted
us to extend investigations to other terminal alkynes
RCꢁCH (R=4-MeC6H4, But, COOMe or COOEt),
The new rhenium acetylide complexes are pale-yellow
solids stable in air and in solution of polar and non-po-
lar organic solvents, in which they behave as non-elec-
trolytes [22]. The analytical and spectroscopic data
(Table 1) support their formulation. In particular, the
IR spectra show a medium-intensity band at 2082–2050
cm−1 due to w(CꢁC) of the acetylide ligand, and two
strong absorptions between 1970 and 1859 cm−1 at-
tributed to the two carbonyl ligands in a mutually cis
position. The 13C{1H}-NMR spectra are consistent
with the presence of the acetylide ligand, showing the
Ca and Cb carbon signals as doublets of triplets, or
including
bis(alkyne)
1,4-diethynylbenzene
1,4-
HCꢁCC6H4CꢁCH. In these cases too, treatment of
dihydrogen cations [Re(h2-H2)(CO)2P3]+ with an excess
of terminal alkynes afforded vinylidene complexes ac-
cording to Scheme 2.
However, equilibrium (2) is shifted substantially to
the left side, and only in the presence of a large excess
of alkyne was the vinylidene [Re{ꢀCꢀC(H)R}(CO)2P3]+
species detected by NMR spectroscopy. This result
prevented the preparation of solid samples of vinylidene
complexes with a substituent different from phenyl (i.e.
R=4-MeC6H4, But, etc.). Instead, in the case of the
bis(alkyne), equilibrium (3) is shifted far enough to the
right to allow vinylidene [Re{ꢀCꢀC(H)(1,4-C6H4Cꢁ
CH)}(CO)2P3]+ (1c, 2c) to be isolated as BF4 salts in
the solid state. The IR and NMR data (Table 1)
support the proposed formulation for 1c and 2c, but
also show that the unsaturated complex [Re(CO)2P3]+
is always present in the resulting solid. In fact, analyti-
cally pure samples of 1c and 2c were prepared, like the
related 1–3, by treatment of acetylide Re(1,4-
CꢁCC6H4CꢁCH)(CO)2P3 with HBF4. The spectroscopic
data of vinylidene 1c and 2c also suggest a mer–trans
geometry of the type shown in Scheme 2, revealing only
2
triplets of doublets, the former with JCP of 16–36 Hz
3
at 123–106 ppm, and the latter with JCP of 3–4 Hz at
119–113 ppm, due to coupling with two equivalent
phosphorus nuclei, unlike the third. The spectra also
show two doublets of triplets at 198–194 ppm at-
tributed to the carbonyl carbon atoms of two inequiva-
lent CO ligands. On the basis of these data and of the
31P{1H}-NMR spectra, which appear as AB2 or A2B
multiplets, a mer–cis geometry of the type shown in
Scheme 3 is proposed for the acetylide derivatives.
Complexes Re(1,4-CꢁCC6H4CꢁCH)(CO)2P3 (4c, 5c,
6c) show some differences in their IR and NMR spectra
(Table 1) and deserve brief discussion. The IR spectrum
of PPh(OEt)2 derivative 5c shows the characteristic
bands of the CꢁCC6H4CꢁCH ligand, including w(CꢁC)
Scheme 2. R=4-MeC6H4, But, COOMe or COOEt; P=P(OEt)3 (1) or PPh(OEt)2 (2).
Scheme 3. R=Ph (a), But (b) or 1,4-C6H4CꢁCH (c); P=P(OEt)3 (4), PPh(OEt)2 (5) or PPh2OEt (6).

18
G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
Fig. 1.
Scheme 4. P=PPh(OEt)2 (7) or PPh2OEt (8).
at 2078, w(CH) at 3288 and w(CꢁCH) at 2006 cm−1
,
with an excess of NEt3 afforded binuclear {Re(CO)2-
P3}2(m-1,4-CꢁCC6H4CꢁC) complexes (7, 8) (Scheme 4),
which were isolated as yellow–orange solids and
characterised.
but only one w(CO) band, suggesting the presence of
two trans carbonyl ligands. The 31P{1H}-NMR spec-
trum is an AB2 multiplet, whereas the 13C{1H} spec-
trum unambiguously shows the Ca and Cb acetylide
carbon atoms as doublets of triplets at 113.9 and 107.1
ppm. On the basis of these data, a mer–trans geometry
of the type shown in Fig. 1 is proposed for acetylide
complex 5c.
The complexes are air-stable and non-electrolytic,
and their formulation is confirmed by analytical and
spectroscopic data (Table 1). In particular, the appear-
ance of only one w(CꢁC) band in the IR spectra and the
absence of any w(CꢁCH) absorption indicate a binu-
clear species. This is further confirmed by comparison
of their 13C{1H}-NMR spectra with those of mononu-
clear 4c, 5c, 6c, which only show the presence of only
the signals of Ca and Cb acetylide carbon atoms for
binuclear species 7, 8. However, comparison between
these spectra shows some significant differences, sug-
gesting here again the existence of several isomers.
Complex [Re(CO)2{PPh(OEt)2}3]2(m-1,4-CꢁCC6H4-
CꢁC) (7) shows two strong w(CO) IR bands at 1964 and
1908 cm−1, attributed to two carbonyl ligands in a
mutually cis position and only one AB2 multiplet in the
31P{1H}-NMR spectrum. Furthermore, besides the sig-
nals of the Ca and Cb acetylide ligands, only one triplet
of doublets at 195.5 ppm is present in the 13C{1H}
spectra, attributed to two magnetically equivalent car-
bonyl carbon atoms. On this basis, a fac–cis geometry
of the type shown in Fig. 2 is proposed for the complex.
On the contrary, the IR spectra of related complexes
Re(1,4-CꢁCC6H4CꢁCH)(CO)2P3 (4c, 6c) show three
bands in the w(CO) region, indicating the presence of
more than one compound. The 31P{1H}-NMR spectra
support this hypothesis, showing two well-separated
AB2 or A2B multiplets which may be simulated with the
parameters reported in Table 1. These data are inter-
preted on the basis of two isomers, with the two CO
ligands in a mutually cis position in one case, and trans
in the other. The 13C{1H}-NMR spectra confirm the
presence of the two isomers of the type shown in Fig. 1,
with two sets of signals for the Ca and Cb acetylide
carbon atoms, consisting of one triplet of doublets and
one doublet of triplets for the Ca and two broad signals
for the Cb. Two singlets for the Cg and two for the Cd
are also visible, together with two sets of partially
overlapping carbonyl carbon atoms, in agreement with
the proposed formulation. However, it may be noted
that the IR spectra of compounds 4c, 6c only reveal one
w(CꢁC) band, probably due to the small difference in
the values of w(CꢁC) between the two isomers, which
makes the bands practically coincide. Support for this
hypothesis is given by comparison of the w(CꢁC) values
of our acetylides 4–6 (Table 1), which shows how these
values are only very slightly influenced by the nature of
the phosphite ligands, with changes within 3–6 cm−1
,
in agreement with the presence of two w(CꢁC) bands
overlapping the two isomers.
The preparation of acetylide complexes 4c, 5c, 6c
with 1,4-diethynylbenzene prompted us to extend the
study to the synthesis of binuclear complexes contain-
ing the ReCꢁCC6H4CꢁCRe unit. Treatment of
[Re(CO)2P3]+ cations first with the alkyne and then
Fig. 2.

G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
19
Scheme 5. P=PPh(OEt)2 (9) or PPh2OEt (10).
Instead, the IR spectrum of complex {Re(CO)2-
(PPh2OEt)3}2(m-1,4-CꢁCC6H4CꢁC) (8) shows three
w(CO) bands at 1945, 1896 and 1875 cm−1. In the
temperature range between +30 and −90°C, the re-
lated 31P{1H}-NMR spectrum displays two AB2 multi-
plets which may be interpreted, as in the case of
mononuclear complexes 4c, 6c, as indicating two iso-
mers with fac–cis and mer–trans arrangement of car-
bonyl and phosphite ligands around the rhenium atom.
Since the complex is binuclear, four isomers should be
expected of the type shown in Fig. 2, the two mer–
trans/fac–cis isomers being equivalent. The 13C{1H}-
NMR spectra fit this hypothesis, showing two partly
overlapping sets of both carbonyl carbon signals and
acetylide carbon atoms (both Ca and Cb) resonances.
acted with [Re(h2-H2)(CO)2P3]+ or [Re(CO)2P3]+ and,
although the reaction proceeded with colour changes of
the solution, no stable propadienylidene complexes
were isolated.
Complexes 9, 10 are dark-blue solids and stable in air
and in solution of polar organic solvents, in which they
behave as 1:1 electrolytes [22]. Their analytical and
spectroscopic data (Table 1) support their formulation
and suggest a mer–trans geometry in solution (Scheme
5). In particular, the IR spectra show only one strong
w(CO) band at 1927 (9) and 1922 cm−1 (10) due to two
carbonyl ligands in a mutually trans position. The
spectra also have one medium-intensity band at 2014
(9) and 2011 cm−1 (10), attributed to the w(CꢀCꢀC) of
the propadienylidene ligand. However, diagnostic for
the presence of the ꢀCaꢀCbꢀCgPh2 ligand are the
13C{1H}-NMR spectra, which show one doublet of
triplets at 298.0 (9) and 298.9 ppm (10), due to the Ca
carbon atom of the propadienylidene ligand. Further-
more, at 202.5–199.2 and 163.2–160.2 ppm there are
also the signals of the Cb and Cg carbon atoms, respec-
tively, of the CaꢀCbꢀCgPh2 ligand, whereas at 204.3–
191.8 ppm the carbonyl carbon resonances appear as a
triplet of doublets or a doublet of triplets, due to
coupling with the phosphorus nuclei of the phosphite.
Finally, in the temperature range +30 to −80°C, the
31P{1H}-NMR spectra show an AB2 or A2B multiplet,
in agreement with a mer–trans geometry for the first
propadienylidene complexes of rhenium.
3.3. Propadienylidene complexes
Dihydrogen derivatives [Re(h2-H2)(CO)2P3]+, pre-
pared in situ by the protonation of ReH(CO)2P3, re-
acted at r.t. with 1,1-diphenyl-2-propyn-1-ol to give
propadienylidene complexes [Re(ꢀCꢀCꢀCPh2)(CO)2-
P3]BF4 (9, 10), which were isolated as dark-blue solids
and characterised (Scheme 5).
Propadienylidene species 9, 10 may also be obtained
by reacting the unsaturated [Re(CO)2P3]+ cations with
1,1-diphenyl-2-propyn-1-ol. The reaction probably pro-
ceeds through tautomerisation of the terminal alkyne
HCꢁCC(Ph2)OH on the rhenium centre to give the
vinylidene
intermediate
[Re{ꢀCꢀC(H)C(Ph2)OH}-
(CO)2P3]+ which, by elimination of H2O, affords final
complexes 9, 10. Although in this case too equilibrium
probably involves the formation of the vinylidene inter-
mediate, the final propadienylidene complex is stable
with respect to dissociation of the ligands, and only
after 24 h does its solution show decomposition.
Acknowledgements
The financial support of MURST — Programmi di
Ricerca Scientifica di Rilevante Interesse Nazionale,
Cofinanziamento 1998–1999 — is gratefully acknowl-
edged. We thank Daniela Baldan for technical
assistance.
As observed in the synthesis of monosubstituted vi-
nylidene complexes 1–3, only the Re(CO)2P3 fragment
with a carbonyl:phosphite ratio of 2:3 allows propadi-
enylidene complexes to be prepared. The reactions of
other h2-H2 derivatives such as [Re(h2-H2)(CO)3P2]+
and [Re(h2-H2)(CO)P4]+ with HCꢁCC(Ph2)OH do not
afford any propadienylidene complexes, unsaturated
cations [Re(CO)3P2]+ or [Re(CO)P4]+ being the only
isolated products. It may also be noted that other
propargylic alcohols, such as HCꢁCC(H2)OH,
HCꢁCC(H)(Ph)OH and HCꢁC(CH3)(Ph)OH, were re-
References
[1] (a) I.R. Whittall, A.M. McDonagh, M.G. Humphrey, M.
Samoc, Adv. Organomet. Chem. 42 (1998) 291. (b) S.R. Marder,
in: D.W. Bruce, D. O’Hare (Eds.), Inorganic Materials, Wiley,
Chichester, 1992. (c) M. Altmann, U.H.S. Bunz, Angew. Chem.
Int. Ed. Engl. 34 (1995) 569. (d) N.J. Lang, Angew. Chem. Int.
Ed. Engl. 33 (1994) 547. (e) V. Grosshenny, A. Harriman, R.

20
G. Albertin et al. / Journal of Organometallic Chemistry 609 (2000) 10–20
Ziessel, Angew. Chem. Int. Ed. Engl. 34 (1995) 1100. (f) T.
N. Lugan, R. Mathieu, R.L. Ostrander, B.E. Owens-Waltermire,
A.L. Rheingold, Organometallics 13 (1994) 843. (c) C.P. Casey,
Y. Ha, D.R. Powell, J. Organomet. Chem. 472 (1994) 185. (d)
W. Weng, T. Bartik, M. Brady, B. Bartik, J.A. Ramsden, A.M.
Arif, J.A. Gladysz, J. Am. Chem. Soc. 117 (1995) 11922. (e) T.
Bartik, W. Weng, J.A. Ramsden, S. Szafert, S.B. Falloon, A.M.
Arif, J.A. Gladysz, J. Am. Chem. Soc. 120 (1998) 11071. (f) N.E.
Kolobova, A.B. Antonova, O.M. Khitrova, M.Y. Antipin, Y.T.
Struchkov, J. Organomet. Chem. 137 (1977) 69.
Marder, H. Fyfe, M. Mlekuz, G. Stringer, N. Taylor, in: R.
Laine (Ed.), Inorganic and Organometallic Polymers with Spe-
cial Properties, NATO ASI 206, Kluwer, Dordrecht, 1992. (g)
N.J. Long, Angew. Chem. Int. Ed. Engl. 34 (1995) 21.
[2] (a) C.S. Yi, N. Liu, A.L. Rheingold, L.M. Liable-Sands,
Organometallics 16 (1997) 3910. (b) C. Bianchini, P. Innocenti,
M. Peruzzini, A. Romerosa, F. Zanobini, P. Frediani,
Organometallics 15 (1996) 272. (c) H. Matsuzaka, Y. Takagi, Y.
Ishii, M. Nishio, M. Hidai, Organometallics 14 (1995) 2153. (d)
J.F. Corrigan, N.J. Taylor, A.J. Carty, Organometallics 13
(1994) 3778. (e) M. Scha¨fer, N. Mahr, J. Wolf, H. Werner,
Angew. Chem. Int. Ed. Engl. 32 (1993) 1315. (f) D.L. Hughes,
M. Jime´nez-Tenorio, G.J. Leigh, A.T. Rowley, J. Chem. Soc.
Dalton Trans. (1993) 3151. (g) L.D. Field, A.V. George, G.R.
Purches, I.H.M. Slip, Organometallics 11 (1992) 3019.
[3] (a) C. Bianchini, A. Marchi, L. Marvelli, M. Peruzzini, A.
Romerosa, R. Rossi, Organometallics 15 (1996) 3804. (b) D.
Pilette, K. Ouzzine, H. Le Bozec, P.H. Dixneuf, C.E.F. Richard,
W.R. Roper, Organometallics 11 (1992) 809.
[4] (a) C. Bruneau, P.H. Dixneuf, Acc. Chem. Res. 32 (1999) 311.
(b) M.A. Esteruelas, A.V. Go´mez, A.M. Lo´pez, J. Modrego, E.
On˜ate, Organometallics 16 (1997) 5826. (c) C. Slugovc, P. Wiede,
K. Mereiter, R. Schmid, K. Kirchner, Organometallics 16 (1997)
2768. (d) H.M. Lee, J. Yao, G. Jia, Organometallics 16 (1997)
3927. (e) V. Cadierno, M.P. Gamasa, J. Gimeno, M.C. Lo´pez-
Gonza´lez, J. Borge, J. Garc´ıa-Granda, Organometallics 16
(1997) 4453. (f) B.M. Trost, J.A. Flygare, J. Am. Chem. Soc. 114
(1992) 5476. (g) A.K. McMullen, J.P. Selegue, J.G. Wang,
Organometallics 10 (1991) 3421. (h) Y. Wakatsuki, H. Ya-
mazaki, N. Kumegawa, T. Satoh, J.Y. Satoh, J. Am. Chem. Soc.
113 (1991) 9604.
[10] (a) W.A. Herrmann, W. Wagner, U.N. Flessner, U. Volkhardt,
H. Komber, Angew. Chem. Int. Ed. Engl. 30 (1991) 1636. (b) R.
Toreky, R.R. Schrock, W.M. Davis, J. Am. Chem. Soc. 114
(1992) 3367.
[11] W.A. Herrmann, R.W. Fischer, D.W. Marz, Angew. Chem. Int.
Ed. Engl. 30 (1991) 1638.
[12] M.L. Loza, S.R. De Gala, R.H. Crabtree, Inorg. Chem. 33
(1994) 5073 and references therein.
[13] (a) C.P. Casey, R.S. Carin˜o, R.K. Hayashi, K.D. Schladetzky, J.
Am. Chem. Soc. 118 (1996) 1617. (b) M. Leeaphon, A.L. On-
dracek, R.J. Thomas, P.E. Fanwick, R.A. Walton, J. Am. Chem.
Soc. 117 (1995) 9715. (c) L.L. Padolik, J.C. Gallucci, A. Wojci-
cki, J. Am. Chem. Soc. 115 (1993) 9986.
[14] A.J.L. Pombeiro, S.S.P.R. Almeida, M.F.C.G. Silva, J.C. Jef-
frey, R.L. Richards, J. Chem. Soc. Dalton Trans. (1989) 2381.
[15] G. Albertin, S. Antoniutti, S. Garcia-Fonta´n, R. Carballo, F.
Padoan, J. Chem. Soc. Dalton Trans. (1998) 2071.
[16] (a) G. Albertin, S. Antoniutti, E. Bordignon, M. Granzotto, J.
Organomet. Chem. 585 (1999) 83. (b) G. Albertin, S. Antoniutti,
E. Bordignon, F. Cazzaro, S. Ianelli, G. Pelizzi, Organometallics
14 (1995) 4114. (c) G. Albertin, S. Antoniutti, E. Bordignon, E.
Del Ministro, S. Ianelli, G. Pelizzi, J. Chem. Soc. Dalton Trans.
(1995) 1783. (d) G. Albertin, S. Antoniutti, E. Bordignon, J.
Chem. Soc. Dalton Trans. (1995) 719. (e) G. Albertin, S. Anto-
niutti, E. Del Ministro, E. Bordignon, J. Chem. Soc. Dalton
Trans. (1992) 3203. (f) G. Albertin, P. Amendola, S. Antoniutti,
S. Ianelli, G. Pelizzi, E. Bordignon, Organometallics 10 (1991)
2876.
[17] R. Rabinowitz, G. Pellon, J. Org. Chem. 26 (1961) 4623.
[18] A.S. Hay, J. Org. Chem. 25 (1960) 637.
[19] G. Balacco, J. Chem. Inf. Comput. Sci. 34 (1994) 1235.
[20] (a) J. Silvestre, R. Hoffmann, Helv. Chim. Acta 68 (1985) 1461.
(b) Y. Wakatsuki, N. Koga, H. Yamazaki, K. Morokuma, J.
Am. Chem. Soc. 116 (1994) 8105.
[21] (a) M.D. Fryzuk, L. Huang, N.T. McManus, P. Paglia, S.J.
Rettig, G.S. White, Organometallics 11 (1992) 2979. (b) J.R.
Lumphrey, J.P. Selegue, J. Am. Chem. Soc. 114 (1992) 5518. (c)
C. Bianchini, M. Peruzzini, A. Vacca, F. Zanobini,
Organometallics 10 (1991) 3697.
[5] (a) M.I. Bruce, Chem. Rev. 91 (1991) 197. (b) M.I. Bruce, B.C.
Hall, N.N. Zaitseva, B.W. Skelton, A.H. White, J. Chem. Soc.
Dalton Trans. (1998) 1793.
[6] (a) D. Touchard, P. Haquette, S. Guesmi, L. Le Pichon, A.
Daridor, L. Toupet, P.H. Dixneuf, Organometallics 16 (1997)
3640. (b) I. de los Rios, M. Jimenez-Tenorio, M.C. Puerta, P.
Valerga, J. Am. Chem. Soc. 119 (1997) 6529. (c) Y. Kawata, M.
Sato, Organometallics 16 (1997) 1093. (d) B. Buriez, I.D. Burns,
A.F. Hill, A.J.P. White, D.J. Williams, J.D.E.T. Wilton-Ely,
Organometallics 18 (1999) 1504.
[7] M.I. Bruce, Chem. Rev. 98 (1998) 2797.
[8] (a) K.A. Conner, R.A. Walton, in: G. Wilkinson, R.D. Gillard,
J.A. McCleverty (Eds.), Comprehensive Coordination Chem-
istry, vol. 4, Pergamon, Oxford, 1987. (b) C.P. Casey, Science
259 (1993) 1552.
[9] (a) D.R. Senn, A. Wong, A.T. Patton, M. Marsi, C.E. Strouse,
J.A. Gladysz, J. Am. Chem. Soc. 110 (1988) 6096. (b) M.R.
Terry, L.A. Mercando, C. Kelley, G.L. Geoffroy, P. Nombell,
[22] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
.