Binding two C2 units to an electron-rich transition-metal center: The interplay of alkyne(alkynyl), bisalkynyl(hydrido), alkynyl(vinylidene), alkynyl(allene), alkynyl(olefin), and alkynyl(enyne) rhodium complexes

Article abstract of DOI:10.1021/om049389f

The preparation of rhodium compounds having two different C₂ units coordinated to the metal center from two rhodium complexes was investigated. The possible interconversion of isomeric alkyne(alkynyl), bisalkynyl-(hydrido) and alkynyl(vinyliden

Full text of DOI:10.1021/om049389f

Organometallics 2004, 23, 5713-5728
5713
Binding Two C2 Units to an Electron-Rich
Transition-Metal Center: The Interplay of
Alkyne(alkynyl), Bisalkynyl(hydrido),
Alkynyl(vinylidene), Alkynyl(allene), Alkynyl(olefin), and
Alkynyl(enyne) Rhodium Complexes†
Martin Scha¨fer, Justin Wolf, and Helmut Werner*
Institut fu¨r Anorganische Chemie der Universita¨t Wu¨rzburg, Am Hubland,
D-97074 Wu¨rzburg, Germany
Received August 6, 2004
A series of alkynyl(vinylidene)rhodium(I) complexes of the general composition trans-[Rh-
(CtCR)(dCdCHR)(PiPr3)2] (R ) H, Me, tBu, and Ph) were prepared from either [Rh(η3-
C3H5)(PiPr3)2] (1) or [Rh(η3-CH2Ph)(PiPr3)2] (18) and 2 equiv of RCtCH as the precursors.
In some cases, the four-coordinate alkynyl(alkyne)rhodium(I) compounds trans-[Rh(CtCR)-
(RCtCH)(PiPr3)2] and/or the five-coordinate bis(alkynyl)hydridorhodium(III) complexes
[RhH(CtCR)2(PiPr3)2] were isolated as intermediates. In the presence of pyridine, the
octahedral compounds [RhH(CtCR)2(py)(PiPr3)2] were obtained. Upon warming, they
eliminate one molecule of RCtCH and afford trans-[Rh(CtCR)(py)(PiPr3)2]. The reaction
of 18 with an equimolar amount of terminal alkyne under an atmosphere of C2H4 gave the
alkynyl(ethene) complexes trans-[Rh(CtCR)(C2H4)(PiPr3)2] (21-23), which react with pyr-
idine, CO, and PhCtCR by displacement of the olefinic ligand. Treatment of 22 (R ) tBu)
and 23 (R ) Ph) with methylpropiolate gave the rhodium vinylidenes trans-[Rh(CtCR)-
(dCdCHCO2Me)(PiPr3)2]. The related complex trans-[Rh(CtCPh)(dCdCH2)(PiPr3)2] was
prepared by two routes using trans-[Rh(CtCPh)(C2H4)(PiPr3)2] or trans-[Rh(CtCH)(C2H4)-
(PiPr3)2] as the precursor. The reaction of 1 or 18 and excess MeCtCH leads, under different
conditions, either to four-coordinate trans-[Rh(CtCMe)(η2-CH2dCdCH2)(PiPr3)2] or to five-
coordinate [Rh(CtCMe)2{C(CH3)dCH2}(PiPr3)2]. The latter rearranges at room temperature
to yield the enyne complex trans-[Rh(CtCMe){η2-MeCtCC(Me)dCH2}(PiPr3)2] by intramo-
lecular C-C coupling. Treatment of 1 with excess PhCtCH gave a mixture of trans-[Rh-
(CtCPh)(η2-PhCtCCHdCHPh)(PiPr3)2] (43), trans-[Rh(CtCPh){η2-PhCtCC(Ph)dCH2}-
(PiPr3)2] (45), PhCtCCHdCHPh (44), and PhCtCC(Ph)dCH2 (46). With catalytic amounts
of 1 and excess phenylacetylene, the 1,4- and 1,3-disubstituted butenynes 44 and 46 were
formed in the ratio of 70:30, probably via trans-[Rh(CtCPh)(PhCtCH)(PiPr3)2] and [RhH-
(CtCPh)2(PiPr3)2] as intermediates.
Introduction
CO2H, and C6H5CO2H to give the monomeric rhodium-
(I) compounds [Rh(κ2-O2CR)(PiPr3)2] in virtually quan-
titative yields. The reactivity of these chelate compounds,
in particular toward H2, O2, CO, olefins, and terminal
alkynes, has been the subject of two previous publica-
tions.4,5
In the search for monomeric, highly reactive bis-
(triisopropylphosphine)rhodium(I) complexes of the gen-
eral composition [RhX(PiPr3)2], we reported the prepa-
ration of the η3-allyl and η3-benzyl derivatives [Rh(η3-
C3H4R)(PiPr3)2] and [Rh(η3-CH2C6H4R)(PiPr3)2], which
were obtained upon treatment of the dimeric chloro
In continuation of these studies, we discuss in this
paper the synthetic potential of the two complexes [Rh-
(η3-C3H5)(PiPr3)2] and [Rh(η3-CH2C6H5)(PiPr3)2] as start-
ing materials for the preparation of a series of rhodium
compounds having two different C2 units coordinated
to the metal center. Moreover, we illustrate the possible
interconversion of isomeric alkyne(alkynyl), bisalkynyl-
(hydrido), and alkynyl(vinylidene) rhodium derivatives
compound [RhCl(PiPr3)2]2 with Grignard reagents.2
1
Due to the lability of the allyl- and benzyl-rhodium
bond, the respective complexes react not only with H2
and CO2,3 but also with acids such as CH3CO2H, CF3-
† Dedicated to Professor Helmut Fischer on the occasion of his 60th
birthday, with our best wishes and congratulations for his scientific
achievements.
(1) (a) Preparation in situ: Busetto, C.; D’Alfonso, A.; Maspero, F.;
Perego, G.; Zazzetta, A. J. Chem. Soc., Dalton Trans. 1977, 1828-
1834. (b) Isolation: Werner, H.; Wolf, J.; Ho¨hn, A. J. Organomet. Chem.
1985, 287, 395-407. (c) Molecular structure: Binger, P.; Haas, J.;
Glaser, G.; Goddard, R.; Kru¨ger, K. Chem. Ber. 1994, 127, 1927-1929.
(2) Werner, H.; Scha¨fer, M.; Nu¨rnberg, O.; Wolf, J. Chem. Ber. 1994,
127, 27-38.
(3) Wolf, J.; Nu¨rnberg, O.; Scha¨fer, M.; Werner, H. Z. Anorg. Allg.
Chem. 1994, 620, 1157-1162.
(4) Scha¨fer, M.; Wolf, J.; Werner, H. J. Organomet. Chem. 1994,
476, 85-91.
(5) Scha¨fer, M.; Wolf, J.; Werner, H. J. Organomet. Chem. 1995,
485, 85-100.
10.1021/om049389f CCC: $27.50 © 2004 American Chemical Society
Publication on Web 10/29/2004

5714 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
Scheme 1a
Scheme 2a
a L ) PiPr3.
and describe the ability of the η3-allyl complex [Rh(η3-
C3H5)(PiPr3)2] to afford, by dimerization of two terminal
alkyne molecules, isomeric substituted enynes. Part of
this work has already been communicated.6
a L ) PiPr3.
complexes 5-7 (Scheme 2). These reactions are consid-
erably slower than the reaction of 1 with phenylacety-
lene and take 6-10 h at room temperature (R ) H, Me)
or 5 h at 40 °C (R ) tBu). Since, in contrast to the chloro-
(vinylidene) compounds trans-[RhCl(dCdCHR)(PiPr3)2],7
the alkynyl analogues 5-7 slowly decompose in solution,
the yield is rather low and for 5 amounts only to ca.
30%. However, the yield of 5 can be increased to about
80% if instead of 1 the dihydrido complex 12, in the
presence of NaOH/NEt3, is used as the starting mate-
rial. For compounds 6 and 7, the yield could also be
considerably improved if a mixture of pentane or hexane
and NEt3 is used as the solvent. The alkynyl(vinylidene)
complexes 5-7 are blue, moderately air-sensitive solids,
which in the absence of solvents are quite stable and
under argon can be stored for weeks without decomposi-
tion. Typical spectroscopic features are the high-field
resonance for the vinylidene proton in the 1H NMR
spectra at δ -0.13 (for 5), 0.40 (for 6), and -0.21 (for 7)
and the low-field signals for carbon atoms of the Rhd
CdC unit in the 13C NMR spectra at around δ 307-
309 (R-C) and δ 92-121 (â-C), both of which are split
into doublets of triplets. The 1J(Rh,C) and 2J(Rh,C)
coupling constants for these signals are somewhat
smaller than those of the chloro(vinylidene) counter-
parts trans-[RhCl(dCdCHR)(PiPr3)2], pointing to a
weakening of the RhdC bond as a consequence of the
strong trans influence of the alkynyl ligand.
Results and Discussion
Preparation of Isomeric Alkynyl(vinylidene),
Alkynyl(alkyne), and Bis(alkynyl)hydrido Rhodi-
um Complexes. The reaction of the η3-allyl compound
1 with 2 equiv of phenylacetylene in pentane proceeds
slowly at room temperature and after 4 h affords the
alkynyl(vinylidene) complex 2 in 78% yield (Scheme 1).
If the reaction of 1 with phenylacetylene is carried out
at -40 °C, the alkynyl(alkyne)rhodium(I) derivative 3
can be isolated. It is possibly formed via the oxidative
addition product [RhH(CtCPh)(η3-C3H5)(PiPr3)2] and
the rearranged isomer trans-[Rh(CtCPh)(C3H6)(PiPr3)2]
containing a weakly bound propene ligand as short-lived
intermediates. Compound 3 is a yellow air-sensitive
solid, the composition of which has been substantiated
by elemental analysis and spectroscopic means. The IR
spectrum of 3 displays two bands at 2080 and 1848
cm-1, being assigned to the ν(CtC) stretching modes
1
of the alkynyl and the alkyne ligands. The H NMR
spectrum of 3 shows (in toluene-d8 at -40 °C) for the
alkyne tCH proton a resonance at δ 4.42 ppm, which
1
is split into a doublet due to H-103Rh coupling. Apart
from this signal, the 1H NMR spectrum displays a high-
field resonance at δ -29.42, indicating that in solution
there is an equilibrium between compound 3 and the
bis(alkynyl)hydridorhodium(III) isomer 4. In agreement
with this observation, the 31P NMR spectrum shows (in
toluene-d8 at -40 °C) two doublets at δ 38.8 (for 3) and
52.9 (for 4) in the approximate ratio of 60:40. After
increasing the temperature to 25 °C, the ratio changes
to ca. 40:60. This change is reversible. Attempts to
enrich the mixture in compound 4 failed, since at 25 °C
or above the rhodium(III) isomer rearranges quantita-
tively to the vinylidene complex 2. We note that this
complex has already been prepared from [RhH(CtCPh)-
(κ2-O2CMe)(PiPr3)2] and phenylacetylene in the presence
of excess NaOH and a mixture of pentane and NEt3 as
the solvent.5
If the starting material 1 reacts with 2 equiv of RCt
CH in the presence of excess pyridine, instead of the
four-coordinate rhodium(I) vinylidenes 5-7 the six-
coordinate rhodium(III) complexes 8-11 are isolated in
good to excellent yields. By taking the detection of the
hydridometal derivative 4 (see Scheme 1) into consid-
eration, we assume that not only compound 2 but also
the analogous vinylidene complexes 5-7 are formed via
five-coordinate bis(alkynyl)hydridorhodium(III) species
as intermediates. The pyridine adducts 8-11 are white,
practically air-stable solids, for which correct elemental
1
analyses have been obtained. The H NMR spectra of
8-11 display, besides the hydride resonance at δ -18
to -19 and the signals for the alkynyl and pyridine
The starting material 1 reacts not only with PhCt
CH but also with acetylene, propyne, and tert-butyl-
acetylene to give the corresponding alkynyl(vinylidene)
(7) (a) Werner, H.; Garcia Alonso, F. J.; Otto, H.; Wolf, J. Z.
Naturforsch. 1988, 43b, 722-726. (b) Werner, H.; Brekau, U. Z.
Naturforsch. 1989, 44b, 1438-1446.
(6) Scha¨fer, M.; Wolf, J.; Werner, H. J. Chem. Soc., Chem. Commun.
1991, 1341-1343.

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5715
Scheme 3a
a L ) PiPr3.
Scheme 4a
protons, only one set of signals for the methyl protons
of the PCH(CH3)2 groups, indicating that both the
alkynyl units and the phosphine ligands are stereo-
chemically equivalent and thus trans disposed.
The bis(alkynyl)hydridorhodium(III) complexes 8-11
can also be prepared by treatment of a solution of the
vinylidene compounds 2 and 5-7 in pentane with a
large excess of pyridine. By using this route, the bis-
(propiolate)hydridorhodium(III) derivative 14 has like-
wise been obtained (Scheme 3). Since the 1H NMR
spectra of both 8 and 14 show in C6D6 not only the
signals for the pyridine-containing rhodium(III) com-
plexes but also those for the vinylidene compounds 5
and 13, we conclude that in these cases an equilibrium
between the six- and the four-coordinate species exists.
Attempts to abstract the pyridine ligand also from 9-11
and to regenerate the metal vinylidenes 2, 6, and 7 led
to the elimination of the corresponding terminal alkyne
and gave the alkynyl(pyridine)rhodium(I) complexes
15-17 in about 50% yield. As expected, these square-
planar compounds smoothly react with Broensted acids
by oxidative addition, as is illustrated by the formation
of 11 from 17 and phenylacetylene in pentane at room
temperature.
For the preparation of the alkynyl(vinylidene) com-
plexes 2, 6, and 7, the related η3-benzyl complex 18 can
also be used instead of the η3-allyl compound 1 as the
starting material. As was shown by earlier work from
our group,2 the reaction of 18 with carboxylic acids is
much faster than that of 1 with the same substrates
and affords the substitution products [Rh(κ2-O2CR)-
(PiPr3)2] nearly quantitatively. In agreement with this
result, compound 18 reacts with phenylacetylene in
pentane even at -30 °C to give as the primary product
the alkynyl(alkyne) complex 3 (Scheme 4). Compared
with the reaction of 1 with PhCtCH, the yield of 3 could
be improved from 27% to 54% with 18 as the starting
material. Under the same conditions, also the formerly
undetected propynerhodium(I) derivative 19 is gener-
ated from 18 and propyne. Since 19 is rather labile, the
product isolated from the reaction mixture contained
besides the propyne complex 19 (ca. 90%) small amounts
of the vinylidene isomer 6 (ca. 10%), which at room
temperature is formed from 18 and MeCtCH in high
yield. Diagnostic for 19 are the two ν(CtC) stretching
modes for the alkynyl and the alkyne ligand at 2100
and 1895 cm-1 in the IR spectrum and the doublet
resonance at δ 38.5 in the 31P NMR spectrum, the
respective 31P-103Rh coupling constant being almost
identical to that of 3.
a L ) PiPr3.
The reaction of 18 with tert-butylacetylene, which
proceeds only at room temperature, affords instead of
the alkynyl(alkyne)rhodium(I) complex trans-[Rh(Ct
CtBu)(HCtCtBu)(PiPr3)2] the hydridorhodium(III) iso-
mer [RhH(CtCtBu)2(PiPr3)2] (20). In contrast to 4, the
analogue 20 is quite stable (for a short period of time
even in air) and has been characterized by a correct
elemental analysis. Since some of the typical NMR data
of 20 are similar to those of [RhH(CtCCiPr2OH)2-
(PiPr3)2], which has been characterized by an X-ray
crystal structure analysis,8 we assume that the struc-
ture of 20 corresponds to a square pyramid with the
hydrido ligand in the apical position and both the
alkynyl and the phosphine units trans-disposed. Com-
pound 20 rearranges in a 1:1 mixture of pentane/NEt3
at 40 °C completely to give the alkynyl(vinylidene)
isomer 7.
Synthesis and Reactivity of Four-Coordinate
Alkynyl(ethene) Rhodium(I) Complexes. To find
out whether complexes of the general composition trans-
[Rh(CtCR)(CH2dCHR′)(PiPr3)2], which for R′ ) CH3
were supposed to be formed in the reaction of 1 with
RCtCH as intermediates, can be prepared using 18 as
the starting material, the reactivity of the η3-benzyl
compound toward terminal alkynes in the presence of
excess ethene has been investigated. Stirring a solution
of 18 in neat NEt3 under an ethene atmosphere leads,
after addition of a solution of propyne in pentane, to a
gradual change of color from orange to orange-brown
and gives the alkynyl(ethene) complex 21 in 52%
(8) Werner, H.; Wiedemann, R.; Mahr, N.; Steinert, P.; Wolf, J.
Chem. Eur. J. 1996, 5, 561-569.

5716 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
Scheme 5a
Scheme 6a
a L ) PiPr3.
isolated yield (Scheme 5). In a similar way the Rh(Ct
CtBu) and Rh(CtCPh) counterparts 22 and 23 are also
accessible. For both 21 and 23 an alternative route has
already been described using [RhH(CtCMe)(κ2-O2CMe)-
(PiPr3)2] or [RhH2(κ2-O2CMe)(PiPr3)2] as the precursors.5
The formerly unknown tert-butyl-substituted alkynyl
complex 22 is thermally remarkably stable and readily
soluble in common organic solvents without decomposi-
tion. Diagnostic for the coordinated ethene in 22 is the
a L ) PiPr3.
of 26, 27, or 28 in benzene is stirred under an ethene
atmosphere, the precursors 23 and 24 are regenerated.
Similarly to 3, the 1H NMR spectra of 26 and 27 display
two signals for the protons of the diastereotopic methyl
groups of the P-bonded isopropyl fragments, indicating
that the rotation of the alkyne ligand, lying perpen-
dicular to the coordination plane, around the Rh-(η2-
PhCtCMe) axis is considerably hindered.
In contrast to the reactions of 21-24 with pyridine
and internal alkynes, the corresponding reactions of 21,
23, and 24 with CO are irreversible and afford in
pentane at room temperature the square-planar rhodi-
um(I) complexes 29-31 in nearly quantitative yield. The
Rh(CtCPh) derivative 31 is known and has recently
been prepared from trans-[Rh(CH2Ph)(CO)(PiPr3)2] and
phenylacetylene.5 The alkynyl(carbonyl) compounds are
pale yellow, practically air-stable solids, the composition
of which has been confirmed by elemental analysis and
spectroscopic techniques. We note that by comparing the
chemical shift of the alkynyl 13C carbon resonances for
the two pairs of complexes 25/29 and 17/31 there is only
a small difference, which is surprising insofar as the
σ-donor/π-acceptor capabilities of pyridine on one hand
and CO on the other differ significantly.
If the ethynyl(ethene)rhodium(I) compound 24 is
treated with acidic substrates, the ethynyl ligand is
readily converted to a vinylidene unit. Thus, the reaction
of 24 with [pyH]BF4 in acetone/diethyl ether affords the
cationic complex 32 (Scheme 7), which is also accessible
upon treatment of 1 with [pyH]BF4 in the presence of
acetylene.9 Moreover, compound 24 reacts with the
weak acid cyclopentadiene in benzene at room temper-
ature to give the cyclopentadienyl complex 33 in 85%
yield. This half-sandwich-type compound was previously
prepared from trans-[RhCl(HCtCH)(PiPr3)2] and NaC5H5
in THF.10 The formation of 33 from 24 as the precursor
possibly proceeds via the η2-cyclopentadienerhodium-
(I) intermediate trans-[Rh(CtCH)(η2-C5H6)(PiPr3)2],
which after elimination of one phosphine ligand and
proton transfer from the coordinated diolefin to the
metal and subsequently to the â-carbon atom of the
1
signal at δ 3.03 in the H NMR spectrum (observed as
a doublet of triplets due to 1H-103Rh and 1H-31P
couplings) and the resonance at δ 51.9 in the 13C NMR
spectrum, which is also split into a doublet of triplets.
Regarding the mechanism of formation of 21-23 from
18 as the starting material, we assume that in the initial
step an intermediate A containing a σ-bonded benzyl
ligand is generated, which reacts with the alkyne by
protolytic cleavage of the Rh-CH2Ph bond and elimina-
tion of toluene to give the required product. In this
respect, it is worth mentioning that we have illustrated
by variable-temperature NMR measurements the highly
fluxional behavior of compound 18 in solution.2 At room
temperature, besides a very fast metallotropic shift a
somewhat slower η3-η1-η3 rearrangement occurs which
involves the 14-electron species [Rh(η1-CH2Ph)(PiPr3)2]
as an intermediate. This intermediate probably reacts
with ethene instantaneously to give the 16-electron
compound A, which upon treatment with RCtCH
affords the product. We note that we failed to prepare
the ethynyl complex trans-[Rh(CtCH)(C2H4)(PiPr3)2]
(24) from 18 and acetylene. However, similarly to 23
this compound is accessible from [RhH2(κ2-O2CMe)-
(PiPr3)2] and HCtCH at low temperature.5
Due to the strong trans influence of the alkynyl
ligand, the metal-ethene bond in 21-24 is rather labile,
and thus the olefinic ligand can be easily displaced by
various Lewis bases (see Scheme 6). If the reactions of
22 and 24 with an equimolar amount of pyridine are
monitored by NMR spectroscopy, an equilibrium be-
tween the starting material and the substitution prod-
uct 16 or 25 is observed, which in the presence of an
excess of pyridine or by removing the ethene under
reduced pressure can be shifted to the product side.
Under these conditions, the yield of isolated 16 and 25
is, respectively, 63% and 84%.
The reactions of 23 and 24 with the internal alkynes
PhCtCMe and PhCtCPh also lead to an equilibrium,
which after removal of the olefin is completely shifted
to the side of the alkyne complexes 26-28. These are
isolated as orange solids in 88-92% yield. If a solution
(9) Nu¨rnberg, O.; Werner, H. J. Organomet. Chem. 1993, 460, 163-
175.
(10) Werner, H.; Wolf, J.; Garcia Alonso, F. J.; Ziegler, M. L.;
Serhadli, O. J. Organomet. Chem. 1987, 336, 397-411.

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5717
Scheme 7a
intermediates B and D. Similarly to 3 (see Scheme 1),
these intermediates are converted via an intramolecular
oxidative addition to the hydridorhodium(III) isomer C,
which then rearranges to the product. To explain the
stereoselective formation of 36 instead of the isomer
trans-[Rh(CtCH)(dCdCHPh)(PiPr3)2], we point to the
fact that for the related six-coordinate alkynyl(hydrido)
complexes [RhH(CtCR)(η2-O2CMe)(PiPr3)2] the rate of
conversion to the isomeric rhodium(I) vinylidenes trans-
[Rh(κ1-O2CMe)(dCdCHR)(PiPr3)2] increases in the or-
der R ) alkyl < aryl < H ≈ CO2Me.5 The question
whether the formation of 36 compared with that of the
isomer trans-[Rh(CtCH)(dCdCHPh)(PiPr3)2] is not
only kinetically but also thermodynamically favored
cannot be answered as yet.
a L ) PiPr3.
The properties of the “mixed substituted” alkynyl-
(vinylidene)rhodium(I) compounds 34-36 are quite
similar to those of the “nonmixed” counterparts 2 and
5-7 (see Schemes 1 and 2). The deeply colored micro-
crystalline solids, for which correct elemental analyses
were obtained, are only slightly air-sensitive and soluble
in most common organic solvents. The 13C NMR spectra
display in the low-field region two signals at around δ
300-310 (RhdCdC) and δ 92-109 (RhdCdC) for the
vinylidene carbon atoms and also two resonances at
around δ 135-145 (Rh-CtC) and δ 108-125 (Rh-Ct
C) for the alkynyl carbon atoms. The 13C-103Rh coupling
constants for the signals of the respective R-C atoms
lie between 36 and 53 Hz and those for the â-C atoms
between 9 and 14 Hz.
Scheme 8a
Analogously to 2, 5-7, and 13, the “mixed substi-
tuted” complexes 35 and 36 also react with pyridine by
proton transfer from the vinylidene ligand to the metal
and formation of the bis(alkynyl)hydridorhodium(III)
compounds 37 and 38 (Scheme 10). In benzene solution,
the six-coordinate complexes partially rearrange to the
four-coordinate starting materials and free pyridine; at
equilibrium the ratios 37:35 and 38:36 are approxi-
mately 2:1.
a L ) PiPr3.
ethynyl ligand yields the product. With regard to this
proposal it should be mentioned that the reaction of
alkynyl complexes with electrophiles is one of the
standard methods to generate a vinylidene unit at a
transition-metal center.11
The alkynyl(ethene) complexes also react with ter-
minal alkynes by substitution of the olefinic ligand. By
using this route, it is possible to prepare not only the
parent Rh(CtCH)(dCdCH2) derivative 5 (see Scheme
8) but also alkynyl(vinylidene)rhodium compounds trans-
[Rh(CtCR)(dCdCHR′)(PiPr3)2] with two different sub-
stituents R and R′, which are not accessible directly
from 1 or 18 as the starting material. As exemplified
with methyl propiolate as the substrate, the correspond-
ing complexes 34 and 35 with R ) tBu or Ph and R′ )
CO2Me have been obtained from 23 and 24, in a 1:1
mixture of pentane and NEt3 as the solvent, in 67-76%
yield. Regarding this methodology, an interesting facet
is that the related Rh(CtCPh)(dCdCH2) compound 36
can be prepared from either 23 or 24 as the precursor.
A proposed mechanism for these reactions is shown in
Scheme 9. By taking the formation of 26-28 from 23
and 24 into account (see Scheme 6), we assume that the
initial step in the synthesis of 36 is the displacement of
ethene by acetylene or phenylacetylene to give the
Allene, Vinyl, and Enynyl Rhodium Complexes
from Terminal Alkynes as Substrates. A surprising
result was obtained when we treated the starting
materials 1 and 18 with an excess of propyne in pentane
at -50 °C. After the reaction mixture was warmed to
room temperature, instead of the alkynyl(alkyne) com-
pound 6 (which is dark green) a yellow microcrystalline
solid was isolated, which turned out to be the isomeric
alkynyl(allene) complex 39 (Scheme 11). Although there
are some similarities in the spectroscopic data of the
two isomers 6 and 39 (e.g., the 31P NMR spectra are
nearly identical), the IR spectrum of 39 shows an
intense absorption at 1740 cm-1, being assigned to the
ν(CdCdC) stretching mode of coordinated allene. The
13C NMR spectrum of 39 displays three resonances for
the C3H4 carbon atoms at δ 182.4 (dCd), 94.2 (dCH2
uncoordinated), and 17.2 (dCH2 coordinated), which are
all split into doublets of triplets due to 13C-103Rh and
13C-31P couplings. The inequivalence of the terminal
1
CH2 units is also confirmed by the H NMR spectrum
(11) Reviews: (a) Bruce, M. I.; Swincer, A. G. Adv. Organomet.
Chem. 1983, 22, 59-128. (b) Antonova, A. B.; Ioganson, A. A. Russ.
Chem. Rev. 1989, 58, 693-710. (c) Werner, H. Angew. Chem. 1990,
102, 1109-1121; Angew. Chem., Int. Ed. Engl. 1990, 29, 1077-1089.
(d) Bruce, M. I. Chem. Rev. 1991, 91, 197-257. (e) Puerta, M. C.;
Valerga, P. Coord. Chem. Rev. 1999, 193-195, 977-1025.
of 39, in which one signal at relatively high field (δ 2.48)
for the two protons of the metal-bonded CH2 group and
two signals at lower field (δ 5.45 and 5.25) for the exo-
and endo-protons of the uncoordinated CH2 group

5718 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
Scheme 9a
a L ) PiPr3.
Scheme 10a
derivatives trans-[RhCl(η2-CH2dCdCHR)(AsiPr3)2] (R
) H, Me, tBu).16 With MeCtCD as the substrate, the
bisdeuterated compound trans-[RhCl(η2-CH2dCdCD2)-
(AsiPr3)2] was obtained.16 We note that in contrast to
trans-[RhCl(η2-CH2dCdCH2)(AsiPr3)2], which reacts
quite slowly with CO, the reaction of 39 with carbon
monoxide in benzene at room temperature proceeds in
a few seconds and affords allene and the alkynyl-
(carbonyl) complex 30 in quantitative yield.
a L ) PiPr3.
With regard to the mechanism of formation of 39, we
have considered two different routes (see Scheme 12).
After it was shown that the starting material 18 reacts
with a slight excess of propyne to generate 19 (see
Scheme 4), we assume that this alkynyl(alkyne) complex
is formed in the initial stage of the reaction as an
intermediate. Following path a it could rearrange via
the zwitterionic species E and the hydrido compound F
to give 39. Alternatively, on path b 19 can be converted
by intramolecular oxidative addition to G, which reacts
with another molecule of propyne by insertion into the
Rh-H bond to afford the alkynyl(vinyl) intermediate H.
This intermediate could undergo a â-hydride shift to
yield isomer I, which subsequently forms via reductive
elimination the isolated product 39. Although a tung-
sten17 as well as some iron-group compounds,18-20
containing a C3 fragment similar to that postulated in
transient F, are known, we nevertheless consider path
b as more likely since only in the presence of an excess
of propyne is the alkynyl(allene) complex 39 formed.
By changing the conditions, the reaction of the labile
intermediate 19 with MeCtCH can follow a route that
does not lead to 39. If a slow stream of propyne is passed
through either a solution of 1 in pentane/NEt3 (1:1) at
-20 °C or a solution of 19, generated from 18 and
propyne in pentane at -40 °C, the color changes from
orange-yellow to red and, after recrystallization of the
crude product from pentane or acetone, the bisalkynyl-
Scheme 11a
a L ) PiPr3.
appear. These data are in good agreement with those
for other allene-transition-metal compounds.12,13
There is some precedent for the metal-initiated rear-
rangement of an alkyne into the isomeric allene. For
example, Richards et al. described the formation of [Re-
Cl(η2-CH2dCdCHPh)(diphos)2] from [ReCl(N2)(diphos)2]
(diphos ) Ph2PCH2CH2PPh2) and PhCtCMe,14 and we
reported the conversion of trans-[IrCl(MeCtCMe)-
(PiPr3)2] to the methylallene isomer trans-[IrCl(η2-CH2d
CdCHMe)(PiPr3)2].15 With respect to rhodium as the
metal center, it was shown that the ethene complex
trans-[RhCl(C2H4)(AsiPr3)2] reacts with propyne and
internal alkynes MeCtCR to give the isomeric allene
(16) Werner, H.; Schwab, P.; Mahr, N.; Wolf, J. Chem. Ber. 1992,
125, 2641-2650.
(17) McMullen, A. K.; Selegue, J. P.; Wang, J.-G. Organometallics
1991, 10, 3421-3423.
(18) Gotzig, H.; Otto, H.; Werner, H. J. Organomet. Chem. 1985,
287, 247-254.
(12) Otsuka, S.; Nakamura, A. Adv. Organomet. Chem. 1976, 14,
245-283, and references therein.
(13) Pu, J.; Peng, T.-S.; Gladysz, J. A. Organometallics 1992, 11,
3232-3241.
(14) Hughes, D. L.; Pombeiro, A. J. L.; Pickett, C. J.; Richards, R.
L. J. Chem. Soc., Chem. Commun. 1984, 992-993.
(15) Werner, H.; Ho¨hn, A. J. Organomet. Chem. 1984, 272, 105-
113.
(19) (a) Jia, G.; Rheingold, A. L.; Meek, D. W. Organometallics 1989,
8, 1378-1380. (b) Jia, G.; Meek, D. W. Organometallics 1991, 10,
1444-1450.
(20) (a) Field, L. D.; George, A. V.; Hambley, T. W. Inorg. Chem.
1990, 29, 4565-4569. (b) Hills, A.; Hughes, D. L.; Jimenez-Tenorio,
M.; Leigh, G. J.; McGeary, C. A.; Rowley, A. T.; Bravo, M.; McKenna,
C. E.; McKenna, M.-C. J. Chem. Soc., Chem. Commun. 1991, 522-
524.

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5719
Scheme 12a
a [M] ) Rh(C2Me)(PiPr3)2.
Scheme 13a
Mechanistically, it is conceivable that the formation of
40 proceeds via the bis(alkynyl)hydrido intermediate I
(see Scheme 12), which instead of eliminating propyne
could lose, under different conditions, allene and gener-
ate the five-coordinate [RhH(CtCMe)2(PiPr3)2], which
reacts with MeCtCH by insertion into the Rh-H bond
to produce the bis(alkynyl)vinyl complex 40.
Compound 40 is significantly more labile than the
analogous iridium complex [Ir(CtCMe)2{C(CH3)dCH2}-
(PiPr3)2]. If a solution of 40 is stirred in benzene at room
temperature for 24 h, an intramolecular C-C coupling
takes place and the isomer 41 is formed in virtually
quantitative yield. In agreement with the stereochem-
istry of the vinyl unit in the precursor, the enyne ligand
contains a carbon-carbon double bond with a nonsub-
stituted dCH2 moiety. This is confirmed by the 1H NMR
spectrum of 41, which displays two multiplets at δ 5.91
and 5.27 for the nonequivalent methylene protons. The
13C NMR spectrum of 41 shows two singlets for the
carbon atoms of the olefinic CdC bond at δ 133.6 (d
CMe-) and 117.4 (dCH2, assignment substantiated by
DEPT measurements) and two doublet of triplets for the
carbon atoms of the alkyne CtC bond at δ 89.3 and
77.9. The resonances for the alkynyl 13C atoms are also
split into a doublet of triplets and appear at δ 117.1 and
105.8, respectively. Compound 41 reacts with CO in
C6D6 at room temperature nearly instantaneously and
affords the alkynyl(carbonyl) complex 30 and the sub-
stituted enyne 42.
In contrast to [η3-C3H5)Ir(PiPr3)2], which upon treat-
ment with phenylacetylene gives [Ir(CtCPh)3(PiPr3)2],24
the reaction of 1 with excess phenylacetylene yields a
mixture of products (Scheme 14). The major organome-
tallic components are the enyne complex 45 (the phenyl-
substituted analogue of 41) and the isomer 43, the ratio
of these two compounds being approximately 2:3. Be-
sides 43 and 45, somewhat larger amounts of the free
enynes 44 and 46 were formed. If the reaction mixture
obtained from 1 and PhCtCH was worked up by column
chromatography, an orange fraction eluted from which
43 and 44 could be isolated by fractional crystallization
from pentane. The identity of 43 was furthermore
a L ) PiPr3.
(vinyl)rhodium(III) complex 40 could be isolated (Scheme
13). As far as the structure of 40 is concerned, the most
characteristic feature consists of the position of the
methyl group at the R-carbon atom of the vinyl ligand.
If one assumes that the insertion of a terminal alkyne
RCtCH into a metal-hydride bond occurs via a four-
center transition state, it is to be expected that mainly
for steric reasons the group R should be linked to the
â-carbon atom of the vinyl ligand.12 There is, however,
precedence for the regioselectivity observed in the
formation of 40, as the insertion of CF3CtCH into the
M-H bond of the niobium and tantalum hydrides [(η5-
C5H5)2MH(CO)]21 and of HCtCCO2Me into the Os-H
bond of [OsHCl(CO)(PMetBu2)2]22 affords vinylmetal
derivatives having the substituent R in the R-position.
Moreover, the iridium counterpart of 40 is known and
has been prepared from [IrH5(PiPr3)2] and propyne.23
(21) Amaudrut, J.; Leblanc, J.-C.; Moise, C.; Sala-Pala, J. J. Orga-
nomet. Chem. 1985, 295, 167-174.
(22) Werner, H.; Meyer, U.; Peters, K.; von Schnering, H. G. Chem.
Ber. 1989, 122, 2097-2107.
(23) Werner, H.; Ho¨hn, A.; Schulz, M. J. Chem. Soc., Dalton Trans.
1991, 777-781.
(24) Schulz, M.; Werner, H. J. Organomet. Chem. 1994, 470, 243-
247.

5720 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
Scheme 14a
a L ) PiPr3.
Scheme 15a
a L ) PiPr3.
Scheme 16
confirmed by the independent preparation of the com-
plex (yield 78%) from the corresponding ethene deriva-
tive 23 and the 1,4-disubstituted butenyne PhCHd
CHCtCPh (see Scheme 15). Typical spectroscopic
features of 43 are the two ν(CtC) stretching modes in
the IR spectrum for the alkynyl and enyne ligand at
2080 and 1885 cm-1 and the two doublet resonances in
the 1H NMR spectrum for the vinylic protons at δ 7.41
and 7.11. Owing to the relatively large 3J(H,H) coupling
constant of 15.7 Hz, there is no doubt that these protons
are trans-disposed to each other. The mixture of 43 and
45 (of which we could not isolate the latter in analyti-
cally pure form) reacts with CO to give the carbonyl
complex 31 and both 44 and 46. The two isomeric
regard to the observed ratio of the 1,4- and the 1,3-
disubstituted isomers, we note that by using the Wilkin-
son catalyst [RhCl(PPh3)3] and PhCtCH as the sub-
strate also both butenynes 44 and 46 are generated, the
ratio being 65:35.25 In contrast, the dimerization of
phenylacetylene with [RhCl(PMe3)2]2 as the catalyst
leads exclusively to isomer 46.26
The proposed mechanistic scheme for the catalytic
reaction of 1 with PhCtCH is shown in Scheme 17.
Taking into account that upon treatment of 1 with 2
equiv of phenylacetylene at room temperature the
alkynyl(alkyne) complex 3 is formed (see Scheme 1), we
assume that this compound is also generated under
catalytic conditions. In solution, complex 3 is in equi-
librium with the bis(alkynyl)hydrido isomer 4, which
can react with another molecule of PhCtCH by inser-
tion to give either intermediate M or N. Subsequent
intramolecular C-C coupling would lead to the enyne
1
enynes have been identified by comparison of their H
NMR spectra with reference data.25
The dimerization of phenylacetylene to the butenynes
44 and 46 could also be achieved with catalytic amounts
of the starting material 1. With 0.11 mmol of the
catalyst and a 100-fold excess of PhCtCH in 9 mL of
hexane, after 4 h at 40 °C ca. 50% of the alkyne was
consumed and a mixture of 44 and 46 in the molar ratio
of 70:30 was obtained (Scheme 16). Quite remarkably,
an increase of the time of the reaction did not lead to a
significant increase of the yield of the dimers. With
(25) Ohshita, J.; Furumori, K.; Matsuguchi, A.; Ishikawa, M. J. Org.
Chem. 1990, 55, 3277-3280.
(26) Boese, W. T.; Goldman, A. S. Organometallics 1991, 10, 782-
786.

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5721
Scheme 17a
a [Rh] ) Rh(C2Ph)(PiPr3)2.
complexes 43 and 45, from which in the presence of a
large excess of the alkyne the coupling product is
displaced and compound 3 regenerated. Since not only
the substituent R of the terminal alkyne but also the
steric bulk around the metal center determine whether
the insertion of the alkyne into the metal-hydride bond
affords a vinylmetal species such as M or N,27,28 it is
not unexpected that with the bis(trimethylphosphine)
complex [RhCl(PMe3)2]2 as the catalyst the dimerization
of PhCtCH yields only 46 while with the bis(triisopro-
pylphosphine) derivative 1 both isomers 44 and 46 are
formed. The substitution of the enyne in 43 and 45 by
phenylacetylene is probably reversible, and thus with
decreasing concentration of PhCtCH the rate of dimer-
ization also decreases.
followed by a â-H shift from metal to carbon by either
a monomolecular or a bimolecular mechanism.30 De-
pending on the substituent R of the alkyne and the
reaction conditions, it is possible to isolate intermediate
alkynyl(alkyne)rhodium(I) and bis(alkynyl)hydridorho-
dium(III) complexes which finally rearrange to the most
stable alkynyl(vinylidene) isomers. The reaction of the
η3-benzyl complex 18 with an equimolar amount of RCt
CH under an ethene atmosphere affords the alkynyl-
(ethene) compounds trans-[Rh(CtCR)(C2H4)(PiPr3)2],
which are rather labile. The olefinic ligand is easily
displaced not only by pyridine, CO, and internal alkynes
PhCtCR but also by acetylene and methylpropiolate.
This process thus opens a preparative route to com-
plexes trans-[Rh(CtCR)(dCdCHR′)(PiPr3)2] having dif-
ferent substituents at the â-carbon atoms of the alkynyl
and the vinylidene units. A noteworthy result is that
the “mixed-substituted” compound trans-[Rh(CtCPh)-
(dCdCH2)(PiPr3)2] can be prepared either from trans-
[Rh(CtCPh)(C2H4)(PiPr3)2] and acetylene or from trans-
Conclusions
The present investigation has shown that from rho-
dium(I) precursors containing a labile or an easy-to-
labilize ligand such as η3-benzyl or η3-allyl, treatment
with 2 equiv of terminal alkynes affords four-coordinate
complexes of the general composition trans-[Rh(CtCR)-
(dCdCHR)(PiPr3)2] in high yields. The conversion of a
coordinated alkyne RCtCH to the isomeric vinylidene
:CdCHR occurs, in the coordination sphere of rhodium-
(I),29 stepwise via intramolecular oxidative addition
(29) Wakatsuki, Y.; Koga, N.; Werner, H.; Morokuma, K. J. Am.
Chem. Soc. 1997, 119, 360-366.
(30) For recent theoretical work on the acetylene to vinylidene
isomerization see inter alia: (a) Wakatsuki, Y.; Koga, N.; Yamazaki,
H.; Morokuma, K. J. Am. Chem. Soc. 1994, 116, 8105-8111. (b)
Stegmann, R.; Frenking, G. Organometallics 1998, 17, 2089-2095. (c)
Oliva´n, M.; Clot, E.; Eisenstein, O.; Caulton, K. G. Organometallics
1998, 17, 3091-3100. (d) Pere´z-Carreno, E.; Paoli, P.; Ienco, A.; Mealli,
C. Eur. J. Inorg. Chem. 1999, 1315-1324. (e) Cadierno, V.; Gamasa,
M. P.; Gimeno, J.; Pere´z-Carreno, E.; Garc´ıa-Granda, S. Organome-
tallics 1999, 18, 2821-2832. (f) Garc´ıa-Yebra, C.; Lo´pez-Mardomingo,
C.; Fajardo, M.; Antinolo, A.; Otero, A.; Rodr´ıguez, A.; Vallat, A.; Lucas,
D.; Mugnier, Y.; Carbo´, J. J.; Lledo´s, A.; Bo, C. Organometallics 2000,
19, 1749-1765. (g) De Angelis, F.; Sgamellotti, A.; Re, N. Organome-
tallics 2002, 21, 2715-2723.
(27) Thorn, D. L.; Hoffmann, R. J. Am. Chem. Soc. 1978, 100, 2079-
2090.
(28) (a) Huggins, J. M.; Bergman, R. G. J. Am. Chem. Soc. 1981,
103, 3002-3011. (b) Clark, H. C.; Ferguson, G.; Goel, A. B.; Janzen,
E. G.; Ruegger, H.; Siew, P. Y.; Wong, C. S. J. Am. Chem. Soc. 1986,
108, 6961-6972.

5722 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
with phenylacetylene (149 µL, 1.36 mmol). The solution was
slowly warmed to room temperature, stirred for 1 h, and then
worked up as described for method a: yield 334 mg (79%). The
product was characterized by comparison of the 1H and 31P
NMR data with those of an authentic sample.5
[Rh(CtCH)(C2H4)(PiPr3)2] and phenylacetylene as the
precursors.
The reactions of the starting materials 1 and 18 with
terminal alkynes do not lead necessarily to the alkynyl-
(vinylidene) complexes trans-[Rh(CtCR)(dCdCHR)-
(PiPr3)2]. Depending on the reaction conditions, from 1
or 18 and excess MeCtCH either the four-coordinate
allenerhodium(I) compound trans-[Rh(CtCMe)(η2-CH2d
CdCH2)(PiPr3)2] or the five-coordinate vinylrhodium-
(III) complex [Rh(CtCMe)2{C(CH3)dCH2}(PiPr3)2] can
be isolated. We assume that in both cases the alkynyl-
(alkyne) derivative trans-[Rh(CtCMe)(MeCtCH)(PiPr3)2]
is generated as an intermediate. The bis(alkynyl)vinyl-
rhodium(III) complex [Rh(CtCMe)2{C(CH3)dCH2}-
(PiPr3)2] rearranges already at room temperature to the
enynerhodium(I) isomer trans-[Rh(CtCMe){η2-MeCt
CC(Me)dCH2}(PiPr3)2] by intramolecular C-C coupling.
With excess phenylacetylene, the reaction of 1 affords
not only the analogous butenyne complex trans-[Rh(Ct
CPh){η2-PhCtCC(Ph)dCH2}(PiPr3)2] (45) but also the
stereoisomer trans-[Rh(CtCPh){η2-PhCtCCHdCHPh}-
(PiPr3)2] (43). Under similar conditions, with catalytic
amounts of compound 1, a dimerization of PhCtCH can
be performed leading to a mixture of the two disubsti-
tuted butenynes PhCtCCHdCHPh and PhCtCC(Ph)d
CH2 in a 70:30 ratio. Also in this case, the key interme-
diate seems to be the alkynyl(alkyne) complex trans-
[Rh(CtCPh)(PhCtCH)(PiPr3)2] (3), which in the absence
of exess PhCtCH could be isolated and fully character-
ized. Some preliminary results indicate that with the
vinylidene compounds trans-[Rh(CtCPh)(dCdCHPh)-
(PiPr3)2] and trans-[Rh(κ1-O2CCF3)(dCdCHPh)(PiPr3)2]
as catalysts, also a dimerization of phenylacetylene
takes place, but the mechanistic scheme for these
processes remains to be elucidated by further experi-
ments.
Preparation of trans-[Rh(CtCPh)(HCtCPh)(PiPr3)2]
(3). Method a: A solution of 1 (302 mg, 0.65 mmol) in pentane
(30 mL) was treated dropwise under stirring during 30 min
with a 0.1 M solution of phenylacetylene in pentane (13 mL,
1.30 mmol) at room temperature. The solution was concen-
trated in vacuo to ca. 2 mL and then stored at -78 °C for 12
h. A yellow microcrystalline solid precipitated, which was
separated from the mother liquor, washed three times with
small amounts of pentane (0 °C), and dried: yield 109 mg
(27%). Method b: A solution of 18 (204 mg, 0.40 mmol) in
pentane (10 mL) was treated at -30 °C with phenylacetylene
(87 µL, 0.80 mmol) and stirred for 3 min. The solvent was
evaporated in vacuo, the residue was dissolved in pentane (5
mL), and the solution was stored at -78 °C for 12 h to give
yellow crystals: yield 131 mg (54%); mp 96 °C dec. Anal. Calcd
for C34H53P2Rh: C, 65.18; H, 8.53. Found: C, 65.39; H, 8.53.
1
IR (KBr): ν(CtC) 2080, ν(η2-CtC) 1850 cm-1. H NMR (400
MHz, C6D5CD3, -40 °C): δ 8.13 (br m, 2 H, ortho-H of HCt
CC6H5), 7.50 (br m, 2 H, ortho-H of RhCtCC6H5), 7.01-6.83
(br m, 6 H, meta- and para-H of C6H5), 4.42 [d, J(Rh,H) ) 2.2
Hz, 1 H, HCtCPh], 2.32 (m, 6 H, PCHCH3), 1.27, 1.06 (both
m, 18 H each, PCHCH3). 31P NMR (36.2 MHz, C6D5CD3, -40
°C): δ 38.8 [d, J(Rh,P) ) 124.5 Hz].
Generation of [RhH(CtCPh)2(PiPr3)2] (4). A solution of
3 (31 mg, 0.05 mmol) in toluene-d8 (0.5 mL) was stirred for 15
1
min at -40 °C. The H and 31P NMR spectra revealed that a
mixture of 3 and 4 in the approximate ratio of 3:2 was formed.
After the temperature had been increased to 25 °C, the ratio
of 3 to 4 changed to 2:3. By further increasing the temperature
to ca. 40 °C, a fast rearrangement of 4 to the vinylidene
complex 2 occurred. Data for 4: 1H NMR (400 MHz, C6D5CD3,
-40 °C): δ 7.50 (br m, ortho-H of RhCtCC6H5), 7.01-6.83 (br
m, meta- and para-H of C6H5), 2.74 (m, 6 H, PCHCH3), 1.25
[dvt, N ) 14.0, J(H,H) ) 7.0 Hz, 36 H, PCHCH3], -29.42 [dt,
J(Rh,H) ) 50.4, J(P,H) ) 12.9 Hz, 1 H, RhH]. 31P NMR (36.2
MHz, C6D5CD3, -40 °C): δ 52.9 [d, dd in off-resonance, J(Rh,P)
) 99.6 Hz].
Experimental Section
Preparation of Compound 2 from 3 as the Precursor.
A solution of 3 (81 mg, 0.13 mmol) in benzene (2 mL) was
stirred for 3 h at room temperature. The solvent was evapo-
rated in vacuo and the residue recrystallized from pentane at
-78 °C to give blue crystals of 2: yield 72 mg (89%).
All reactions were carried out under an atmosphere of argon
by Schlenk techniques. The starting materials 1,2 12,5 13,5 18,2
and 245 were prepared as described in the literature. The
alkynes were commercial products from Aldrich and Messer
Griesheim. NMR spectra were recorded on JEOL FX 90 Q,
Bruker AC 200, and Bruker AMX 400 instruments at room
temperature, if not otherwise stated. IR spectra were recorded
on a Perkin-Elmer 1420 infrared spectrometer and mass
spectra on a Varian MAT CH 7 instrument. Melting points
were measured by DTA. Abbreviations used: s, singlet; d,
doublet; t, triplet; q, quartet; m, multiplet; br, broadened sig-
Preparation of trans-[Rh(CtCH)(dCdCH2)(PiPr3)2]
(5). Method a: A slow stream of acetylene was passed for 30 s
through a solution of 1 (132 mg, 0.28 mmol) in pentane (5 mL)
at room temperature. While the solution was stirred for 10 h
at ca. 20 °C, a smooth change of color from yellow to brownish
green occurred and a dark violet solid precipitated. The solvent
was evaporated, the oily residue was dissolved in pentane (2
mL), and the solution was chromatographed at -30 °C on
Al2O3 (basic, activity grade V, height of column 5 cm). With
pentane a blue fraction was eluted from which after removal
of the solvent and recrystallization from pentane at -78 °C a
blue microcrystalline solid was isolated: yield 43 mg (32%).
Method b: A solution of 12 (171 mg, 0.35 mmol) in a 1:1
mixture of pentane and NEt3 (8 mL) was treated with NaOH
(140 mg, 3.50 mmol) at room temperature. After the mixture
was cooled to -30 °C, a slow stream of acetylene was passed
through the solution until a change of color from pale yellow
to deep orange occurred. The reaction mixture was concen-
trated to ca. 4 mL in vacuo and then slowly warmed to room
temperature. This led to a change of color from deep orange
to blue. The solvent was evaporated in vacuo, the residue was
extracted with pentane (30 mL), and the extract was filtered.
After the filtrate was concentrated to ca. 3 mL in vacuo, it
was stored for 6 h at -78 °C. A blue microcrystalline solid
3
nal. The term vt indicates a virtual triplet, and N ) J(P,H)
5
1
3
+ J(P,H) or J(P,C) + J(P,C).
Preparation of trans-[Rh(CtCPh)(dCdCHPh)(PiPr3)2]
(2). Method a: A solution of 1 (244 mg, 0.53 mmol) in pentane
(8 mL) was treated with phenylacetylene (115 µL, 1.06 mmol)
and stirred for 4 h at room temperature. A smooth change of
color from yellow to dark blue-green occurred. The solvent was
evaporated, the residue was extracted with pentane (30 mL),
and the extract was concentrated in vacuo until the first
crystals precipitated. After the solution was stored at -78 °C
for 12 h, a blue microcrystalline solid was formed. It was
separated from the mother liquor, washed twice with small
amounts of pentane (0 °C), and dried: yield 236 mg (72%).
The yield could be improved to ca. 85%, if instead of pentane
a 1:1 mixture of pentane and NEt3 was used as the solvent.
Method b: A solution of 18 (348 mg, 0.68 mmol) in a 1:1
mixture of pentane and NEt3 (10 mL) was treated at -30 °C

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5723
precipitated, which was separated from the mother liquor,
washed twice with small amounts of pentane (0 °C), and
dried: yield 130 mg (78%); mp 85 °C dec. Anal. Calcd for
C22H45P2Rh: C, 55.70; H, 9.56. Found: C, 55.63; H, 9.80. MS
(70 eV): m/z 474 (M+). IR (hexane): ν(tCH) 3290, ν(CtC)
1940, ν(CdC) 1620 cm-1. 1H NMR (90 MHz, C6D6): δ 3.22 [dt,
J(Rh,H) ) 1.3, J(P,H) ) 0.5 Hz, 1 H, tCH], 2.89 (m, 6 H,
PCHCH3), 1.37 [dvt, N ) 13.4, J(H,H) ) 7.0 Hz, 36 H,
PCHCH3], -0.13 [t, J(P,H) ) 3.4 Hz, 2 H, dCH2]. 13C NMR
(50.3 MHz, C6D6): δ 309.0 [dt, J(Rh,C) ) 50.0, J(P,C) ) 15.3
Hz, RhdC], 121.7 [dt, J(Rh,C) ) 36.6, J(P,C) ) 18.3 Hz, RhCt
C], 118.8 [d, J(Rh,C) ) 9.2 Hz, RhCtC], 92.4 [dt, J(Rh,C) )
14.1, J(P,C) ) 7.0 Hz, dCH2], 25.1 (vt, N ) 20.9 Hz, PCHCH3),
20.6 (s, PCHCH3). 31P NMR (36.2 MHz, C6D6): δ 45.6 [d,
J(Rh,P) ) 137.0 Hz].
Preparation of [RhH(CtCH)2(py)(PiPr3)2] (8). Method
a: A solution of 1 (67 mg, 0.14 mmol) in pentane (5 mL) was
treated with pyridine (0.1 mL, 1.20 mmol) at room tempera-
ture. After a slow stream of acetylene was passed through the
solution for 30 s, the reaction mixture was stirred for 1 h. The
solvent was evaporated, the residue was extracted with
pentane (30 mL), and the extract was brought to dryness in
vacuo. A white microcrystalline solid precipitated, which was
separated from the mother liquor, washed three times with
small amounts of pentane (2 mL each), and dried: yield 40
mg (52%). Method b: A solution of 5 (74 mg, 0.16 mmol) in
pentane (5 mL) was treated with pyridine (0.1 mL, 1.20 mmol)
and stirred for 3 h at room temperature. The reaction mixture
was then worked up as described for method a: yield 78 mg
(90%); mp 90 °C dec. Anal. Calcd for C27H50NP2Rh: C, 58.58;
H, 9.10; N, 2.53. Found: C, 58.13; H, 9.61; N, 2.29. IR (KBr):
Preparation of trans-[Rh(CtCMe)(dCdCHMe)(PiPr3)2]
(6). Method a: A solution of 1 (235 mg, 0.51 mmol) in a 1:1
mixture of pentane and NEt3 (6 mL) was cooled to -20 °C,
and a slow stream of propyne was passed through the solution
for 20 s. After the reaction mixture was warmed to room
temperature, it was stirred for 6 h, which led to a change of
color from yellow to green. The solution was then worked up
as described for 5, method b, to give dark green crystals: yield
100 mg (39%). Method b: A solution of 18 (112 mg, 0.22 mmol)
in NEt3 (3 mL) was treated at -20 °C with a 0.15 M solution
of propyne in hexane (3 mL, 0.45 mmol). After the reaction
mixture was warmed to room temperature, it was stirred for
4 h and then worked up as described for method a: yield 68
mg (62%); mp 65 °C dec. Anal. Calcd for C24H49P2Rh: C, 57.36;
H, 9.83. Found: C, 57.30; H, 10.03. IR (KBr): ν(CtC) 2125,
1
ν(tCH) 3290, ν(RhH) 2190, ν(CtC) 1940 cm-1. H NMR (90
MHz, C6D6): δ 10.03 (br m, 2 H, ortho-H of C5H5N), 6.90-
6.60 (br m, 3 H, meta- and para-H of C5H5N), 3.06 (m, 6 H,
PCHCH3), 2.25 [dt, J(Rh,H) ) 1.7, J(P,H) ) 1.7 Hz, 2 H, t
CH], 1.25 [dvt, N ) 13.0, J(H,H) ) 6.2 Hz, 36 H, PCHCH3],
-18.10 [dt, J(Rh,H) ) 16.0, J(P,H) ) 14.0 Hz, 1 H, RhH]. 31
P
NMR (36.2 MHz, C6D6): δ 40.1 [d, dd in off-resonance, J(Rh,P)
) 98.2 Hz].
Preparation of [RhH(CtCMe)2(py)(PiPr3)2] (9). This
compound was prepared analogously as described for 8, using
either (method a) 1 (98 mg, 0.21 mmol), pyridine (0.5 mL, 6.0
mmol), and propyne or (method b) 6 (67 mg, 0.13 mmol) and
pyridine (0.5 mL, 6.0 mmol) as starting materials. For method
b, the reaction mixture was stirred for 20 min at 40 °C. A white
microcrystalline solid was obtained: yield for method a 107
mg (87%) and for method b 68 mg (88%); mp 104 °C dec. Anal.
Calcd for C29H54NP2Rh: C, 59.89; H, 9.36; N, 2.41. Found: C,
59.73; H, 9.51; N, 2.23. IR (KBr): ν(RhH) 2195, ν(CtC) 2100
1
ν(CdC) 1670 cm-1. H NMR (90 MHz, C6D6): δ 2.74 (m, 6 H,
PCHCH3), 2.18 [t, J(P,H) ) 2.0 Hz, 3 H, tCCH3], 1.79 [ddt,
J(Rh,H) ) 0.5, J(P,H) ) 2.6, J(H,H) ) 7.5 Hz, 3 H, dCHCH3],
1.39 [dvt, N ) 13.3, J(H,H) ) 7.1 Hz, 36 H, PCHCH3], 0.40
[tq, J(P,H) ) 3.3, J(H,H) ) 7.5 Hz, 1 H, dCHCH3]. 13C NMR
(50.3 MHz, C6D6): δ 307.6 [dt, J(Rh,C) ) 46.1, J(P,C) ) 15.8
Hz, RhdC], 129.8 [d, J(Rh,C) ) 10.0 Hz, RhCtC], 111.1 [dt,
J(Rh,C) ) 38.0, J(P,C) ) 18.8 Hz, RhCtC], 102.0 [dt, J(Rh,C)
) 12.7, J(P,C) ) 6.0 Hz, dCHCH3], 25.2 (vt, N ) 20.0 Hz,
PCHCH3), 20.6 (s, PCHCH3), 7.2 (s, tCCH3), -2.0 [d, J(Rh,C)
) 2.0 Hz, dCHCH3]. 31P NMR (36.2 MHz, C6D6): δ 46.5 [d,
J(Rh,P) ) 138.5 Hz].
1
cm-1. H NMR (90 MHz, C6D6): δ 9.84 (br m, 2 H, ortho-H of
C5H5N), 6.92-6.60 (br m, 3 H, meta- and para-H of C5H5N),
2.84 (m, 6 H, PCHCH3), 2.14 [t, J(P,H) ) 1.5 Hz, 6 H, tCCH3],
1.30 [dvt, N ) 13.0, J(H,H) ) 7.0 Hz, 36 H, PCHCH3], -18.74
[dt, J(Rh,H) ) 15.1, J(P,H) ) 15.1 Hz, 1 H, RhH]. 31P NMR
(36.2 MHz, C6D6): δ 41.8 [d, dd in off-resonance, J(Rh,P) )
101.1 Hz].
Preparation of [RhH(CtCtBu)2(py)(PiPr3)2] (10). Method
a: A solution of 1 (95 mg, 0.20 mmol) in pentane (5 mL) was
treated first with pyridine (0.5 mL, 6.0 mmol) and second with
tert-butylacetylene (53 µL, 0.41 mmol) at room temperature.
After the reaction mixture was stirred for 6 h at 40 °C, it was
cooled to room temperature and the solvent was evaporated
in vacuo. The residue was dissolved with acetone (3 mL), and
the solution was stored for 12 h at -20 °C. A white micro-
crystalline solid precipitated, which was separated from the
mother liquor, washed twice with acetone (1 mL each,
-20 °C), and dried: yield 83 mg (61%). Method b: A solution
of 7 (142 mg, 0.24 mmol) in pentane (8 mL) was treated with
pyridine (0.5 mL, 6.0 mmol) and stirred for 30 min at 40 °C.
The reaction mixture was then worked up as described for
method a: yield 155 mg (96%); mp 109 °C dec. Anal. Calcd for
C35H66NP2Rh: C, 63.14; H, 9.99; N, 2.10. Found: C, 63.33; H,
10.10; N, 2.07. IR (KBr): ν(RhH) 2150, ν(CtC) 2100 cm-1. 1H
NMR (90 MHz, C6D6): δ 10.21 (br m, 2 H, ortho-H of C5H5N),
6.93 (br m, 1 H, para-H of C5H5N), 6.71 (br m, 2 H, meta-H of
C5H5N), 3.02 (m, 6 H, PCHCH3), 1.42 (s, 18 H, C(CH3)3), 1.26
[dvt, N ) 12.9, J(H,H) ) 7.1 Hz, 36 H, PCHCH3], -18.84 [dt,
J(Rh,H) ) 17.1, J(P,H) ) 15.1 Hz, 1 H, RhH]. 31P NMR
(36.2 MHz, C6D6): δ 42.2 [d, dd in off-resonance, J(Rh,P) )
101.1 Hz].
Preparation of trans-[Rh(CtCtBu)(dCdCHtBu)(P-
iPr3)2] (7). Method a: A solution of 1 (146 mg, 0.31 mmol) in
a 1:1 mixture of pentane and NEt3 (4 mL) was treated with
tert-butylacetylene (77 µL, 0.62 mmol) and stirred for 5 h at
40 °C. A smooth change of color from yellow to green occurred.
After the solution was cooled to room temperature, the solvent
was evaporated, the oily residue was extracted with pentane
(20 mL), and the extract was brought to dryness in vacuo. After
recrystallization of the residue from acetone (2 mL) at -78
°C, a dark green microcrystalline solid was obtained: yield
119 mg (65%). Method b: A solution of 18 (182 mg, 0.54 mmol)
in a 1:1 mixture of pentane and NEt3 (6 mL) was treated with
tert-butylacetylene (133 µL, 1.08 mmol) and stirred for 4 h at
40 °C. It was then worked up as described for method a: yield
262 mg (82%); mp 119 °C dec. Anal. Calcd for C30H61P2Rh: C,
61.42; H, 10.48. Found: C, 60.94; H, 10.78. IR (hexane):
ν(CtC) 2125, ν(CdC) 1660, 1630 cm-1 1H NMR (400 MHz,
.
C6D6): δ 2.91 (m, 6 H, PCHCH3), 1.39 [dvt, N ) 13.2, J(H,H)
) 7.0 Hz, 36 H, PCHCH3], 1.26 [s, 9 H, tCC(CH3)3], 1.04 [s, 9
H, dCHC(CH3)3], -0.21 [dt, J(Rh,H) ) 0.8, J(P,H) ) 3.7 Hz,
1 H, dCH(CH3)3]. 13C NMR (100.6 MHz, C6D6): δ 307.0 [dt,
J(Rh,C) ) 48.6, J(P,C) ) 15.8 Hz, RhdC], 144.5 [dt, J(Rh,C)
) 9.2, J(P,C) ) 1.7 Hz, RhCtC], 121.2 [dt, J(Rh,C) ) 12.3,
J(P,C) ) 5.4 Hz, dCHtBu], 109.3 [dt, J(Rh,C) ) 37.0, J(P,C)
) 19.2 Hz, RhCtC], 32.4, 32.3 [both t, J(P,C) ) 1.2 Hz, CCH3],
29.7 (s, CCH3), 25.0 [t, J(P,C) ) 1.6 Hz, CCH3], 25.2 [dvt, N )
19.9, J(Rh,C) ) 1.2 Hz, PCHCH3], 20.7 (s, PCHCH3). 31P NMR
(162.0 MHz, C6D6): δ 45.8 [d, J(Rh,P) ) 137.9 Hz].
Preparation of [RhH(CtCPh)2(py)(PiPr3)2] (11). Method
a: A solution of 1 (131 mg, 0.28 mmol) in pentane (10 mL) was
treated first with pyridine (0.5 mL, 6.0 mmol) and second with
phenylacetylene (62 µL, 0.56 mmol). After the reaction mixture
was stirred for 1 h at room temperature, the solvent was
evaporated in vacuo and the white residue was washed three

5724 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
times with pentane (2 mL each, 0 °C) and dried: yield 159
mg (86%). Method b: A solution of 2 (120 mg, 0.19 mmol) in
pentane (5 mL) was treated with pyridine (0.5 mL, 6.0 mmol)
and stirred for 1 h at room temperature. The reaction mixture
was then worked up as described for method a: yield 120 mg
(89%); mp 65 °C dec. Anal. Calcd for C35H58NP2Rh: C, 66.37;
H, 8.28; N, 1.98. Found: C, 66.24; H, 8.46; N, 1.96. IR (KBr):
ν(RhH) 2177, ν(CtC) 2080 cm-1. 1H NMR (90 MHz, C6D6): δ
10.02 (br m, 2 H, ortho-H of C5H5N), 7.70-6.70 (br m, 13 H,
meta- and para-H of C5H5N and C6H5), 2.95 (m, 6 H, PCHCH3),
1.25 [dvt, N ) 13.3, J(H,H) ) 6.6 Hz, 36 H, PCHCH3], -18.00
[dt, J(Rh,H) ) 15.0, J(P,H) ) 15.0 Hz, 1 H, RhH]. 31P NMR
(36.2 MHz, C6D6): δ 41.3 [d, dd in off-resonance, J(Rh,P) )
98.5 Hz].
Preparation of [RhH(CtCCO2Me)2(py)(PiPr3)2] (14).
This compound was prepared analogously as described for 11,
method b, using 13 (136 mg, 0.23 mmol) and pyridine (0.5 mL,
6.0 mmol) as starting materials. The time for the reaction was
20 min. A white microcrystalline solid was obtained: yield 105
mg (68%); mp 116 °C dec. Anal. Calcd for C31H54NO4P2Rh: C,
55.60; H, 8.14; N, 2.09. Found: C, 56.31; H, 8.37; N, 2.03. IR
(KBr): ν(RhH) 2180, ν(CtC) 2080, ν(CdO) 1670 cm-1. 1H NMR
(90 MHz, C6D6): δ 9.72 (br m, 2 H, ortho-H of C5H5N), 6.68
(br m, 3 H, meta- and para-H of C5H5N), 3.41 (s, 6 H, CO2Me),
2.95 (m, 6 H, PCHCH3), 1.25 [dvt, N ) 13.2, J(H,H) ) 6.6 Hz,
36 H, PCHCH3], -17.57 [dt, J(Rh,H) ) 16.0, J(P,H) ) 13.0
Hz, 1 H, RhH]. 31P NMR (36.2 MHz, C6D6): δ 41.9 [d, dd in
off-resonance, J(Rh,P) ) 93.8 Hz].
Preparation of trans-[Rh(CtCMe)(py)(PiPr3)2] (15). A
solution of 9 (116 mg, 0.20 mmol) in benzene (1.0 mL) was
stirred for 3 days at 50 °C. The color gradually changed from
yellow to orange-brown. The solvent was evaporated in vacuo,
the residue was extracted with pentane (30 mL), and the
extract was concentrated in vacuo until a precipitate began
to be formed. After the solution was stored for 12 h at -78 °C,
an orange microcrystalline solid was formed, which was
identified by comparison of the 1H and 31P NMR data with
those of an authentic sample:10 yield 67 mg (62%).
Preparation of trans-[Rh(CtCtBu)(py)(PiPr3)2] (16).
A solution of 10 (112 mg, 0.17 mmol) in benzene (1 mL) was
stirred for 2 days at 80 °C. A smooth change of color from
yellow to orange-brown occurred. The solvent was evaporated
in vacuo, the residue was extracted with pentane (30 mL), and
the extract was brought to dryness in vacuo. After recrystal-
lization of the oily residue from pentane at -78 °C, an orange
microcrystalline solid was obtained: 51 mg (52%); mp 146 °C
dec. Anal. Calcd for C29H56NP2Rh: C, 59.68; H, 9.67; N, 2.40.
Found: C, 60.02; H, 9.69; N, 2.48. IR (hexane): ν(CtC) 2080
cm-1. 1H NMR (200 MHz, C6D6): δ 8.84 (br m, 2 H, ortho-H of
C5H5N), 6.64 (br m, 1 H, para-H of C5H5N), 6.24 (br m, 2 H,
meta-H of C5H5N), 2.31 (m, 6 H, PCHCH3), 1.43 (s, 9 H,
C(CH3)3), 1.39 [dvt, N ) 12.6, J(H,H) ) 6.8 Hz, 36 H,
PCHCH3]. 31P NMR (81.0 MHz, C6D6): δ 41.1 [d, J(Rh,P) )
151.1 Hz].
residue was obtained, which owing to the 31P NMR spectrum
consisted of a mixture of 6 (ca. 10%) and 19 (ca. 90%). Attempts
to separate the mixture by fractional crystallization remained
unsuccessful. Data for 19: IR (hexane): ν(CtC) 2100, ν(η2-
CtC) 1895 cm-1 31P NMR (36.2 MHz, C6D6): δ 38.5 [d,
.
J(Rh,P) ) 126.0 Hz].
Preparation of [RhH(CtCtBu)2(PiPr3)2] (20). A solution
of 18 (372 mg, 0.72 mmol) in pentane (10 mL) was treated
with tert-butylacetylene (178 µL, 1.45 mmol) and stirred for
15 min at room temperature. After the solution was stored
for 12 h at -78 °C, orange-brown crystals precipitated, which
were separated from the mother liquor, washed twice with
pentane (2 mL each, 0 °C), and dried: yield 229 mg (54%);
mp 40 °C dec. Anal. Calcd for C30H61P2Rh: C, 61.42; H, 10.48.
Found: C, 61.31; H, 10.47. IR (hexane): ν(RhH) 2120, ν(CtC)
2080 cm-1 1H NMR (400 MHz, C6D6): δ 2.97 (m, 6 H,
.
PCHCH3), 1.31 [dvt, N ) 13.9, J(H,H) ) 6.8 Hz, 36 H,
PCHCH3], 1.30 (s, C(CH3)3), -30.45 [dt, J(Rh,H) ) 49.6, J(P,H)
) 13.6 Hz, 1 H, RhH]. 13C NMR (100.6 MHz, C6D6): δ 124.5
[dt, J(Rh,C) ) 8.7, J(P,C) ) 1.2 Hz, RhCtC], 103.9 [dt, J(Rh,C)
) 37.1, J(P,C) ) 15.5 Hz, RhCtC], 32.6 (s, CCH3), 29.8 (s,
CCH3), 24.7 (vt, N ) 22.6 Hz, PCHCH3), 20.3 (s, PCHCH3).
31P NMR (162.0 MHz, C6D6): δ 53.6 [d, dd in off-resonance,
J(Rh,P) ) 100.8 Hz].
Preparation of Compound 7 from 20 as the Precursor.
A solution of 20 (98 mg, 0.17 mmol) in a 1:1 mixture of pentane
and NEt3 (3 mL) was stirred for 4 h at 40 °C. The reaction
was worked up as described for the preparation of 7: yield 87
mg (89%).
Preparation of trans-[Rh(CtCMe)(C2H4)(PiPr3)2] (21).
A solution of 18 (169 mg, 0.33 mmol) in NEt3 (4.0 mL) was
treated under an ethene atmosphere (0.2 bar) at -78 °C with
a 0.12 M solution of propyne in pentane (2.8 mL, 0.33 mmol).
The solution was slowly warmed to 0 °C and stirred for 5 min.
A gradual change of color from orange to orange-brown
occurred. The solvent was evaporated in vacuo, the residue
was extracted with pentane (30 mL), and the extract was
brought to dryness in vacuo. After recrystallization of the
residue from acetone at -78 °C an orange microcrystalline
solid was obtained, which was identified by comparison of the
1H and 31P NMR data with those of an authentic sample:5 yield
51 mg (52%).
Preparation of trans-[Rh(CtCtBu)(C2H4)(PiPr3)2] (22).
A solution of 18 (216 mg, 0.42 mmol) in pentane (15 mL) was
treated under an ethene atmosphere at -30 °C with tert-
butylacetylene (52 µL, 0.42 mmol). After the solution was
warmed to room temperature, it was stirred for 15 min. The
solvent was evaporated in vacuo, the residue was dissolved in
acetone (8 mL), and the solution was stored for 20 h at -30
°C. An orange microcrystalline solid precipitated, which was
separated from the mother liquor, washed three times with
acetone (3 mL each, -20 °C), and dried: yield 183 mg (82%);
mp 118 °C dec. Anal. Calcd for C26H55P2Rh: C, 58.64; H, 10.59.
Found: C, 58.75; H, 10.41. IR (hexane): ν(CtC) 2070, ν(Cd
C) 1505 cm-1. 1H NMR (90 MHz, C6D6): δ 3.03 [dt, J(Rh,H) )
1.5, J(P,H) ) 3.4 Hz, 4 H, C2H4], 2.45 (m, 6 H, PCHCH3), 1.31
[dvt, N ) 12.6, J(H,H) ) 6.8 Hz, 36 H, PCHCH3], 1.30 (s,
C(CH3)3). 13C NMR (22.5 MHz, C6D6): δ 108.6 [dt, J(Rh,C) )
47.6, J(P,C) ) 21.2 Hz, RhCtC], 51.9 [dt, J(Rh,C) ) 10.3,
J(P,C) ) 1.8 Hz, C2H4], 32.1 (s, CCH3), 29.7 (s, CCH3), 23.1
[dvt, N ) 17.6, J(Rh,C) ) 1.5 Hz, PCHCH3], 20.7 (s, PCHCH3);
signal of RhCtC not exactly located. 31P NMR (36.2 MHz,
C6D6): δ 39.3 [d, J(Rh,P) ) 129.0 Hz].
Preparation of trans-[Rh(CtCPh)(py)(PiPr3)2] (17).
This compound was prepared analogously as described for 15,
using 11 (141 mg, 0.20 mmol) as the starting material. A
yellow microcrystalline solid was obtained, which was identi-
fied by comparison of the 1H and 31P NMR data with those of
an authentic sample:10 yield 66 mg (54%).
Reaction of Compound 17 with Phenylacetylene. A
solution of 17 (78 mg, 0.11 mmol) in pentane (5 mL) was
treated with phenylacetylene (14 µL, 0.13 mmol) and stirred
for 30 min at room temperature. The solvent was evaporated
in vacuo, and the remaining white solid was identified by NMR
spectroscopy as 11: yield 74 mg (81%).
Generation of trans-[Rh(CtCMe)(HCtCMe)(PiPr3)2]
(19). A slow stream of propyne was passed through a solution
of 18 (136 mg, 0.27 mmol) in pentane (5 mL) for 10 s at -30
°C. The solution was warmed to -10 °C and stirred for 10 min.
After the solvent was evaporated in vacuo, a brownish oily
Preparation of trans-[Rh(CtCPh)(C2H4)(PiPr3)2] (23).
A solution of 18 (154 mg, 0.30 mmol) in pentane (15.0 mL)
was treated under an ethene atmosphere with a solution of
phenylacetylene (32 µL, 0.30 mmol) in pentane (5 mL) at -15
°C. The solution was slowly warmed to 0 °C and stirred for 5
min. The solvent was evaporated in vacuo, the residue was
washed three times with pentane (2 mL each, 0 °C), and dried.

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5725
1
The orange solid was identified by comparison of the H and
31P NMR data with those of an authentic sample:5 yield 119
mg (72%).
Preparation of trans-[Rh(CtCPh)(PhCtCPh)(PiPr3)2]
(28). A solution of 23 (61 mg, 0.11 mmol) in hexane (5 mL)
was treated with PhCtCPh (20 mg, 0.11 mmol) and stirred
for 30 min at room temperature. The solvent and the olefin
were evaporated in vacuo, and the oily residue was layered
with a small amount of pentane to initiate crystallization. After
the mixture was stored for 6 h at 0 °C, an orange microcrys-
talline solid was formed, which was separated from the mother
liquid, washed three times with pentane (1 mL each, 0 °C),
and dried: yield 69 mg (89%); mp 136 °C dec. Anal. Calcd for
C40H57P2Rh: C, 68.37; H, 8.18. Found: C, 68.62; H, 8.18. IR
Preparation of Compound 16 from 22 as the Precur-
sor. A solution of 22 (79 mg, 0.15 mmol) in pentane (5 mL)
was treated with pyridine (0.1 mL, 1.24 mmol) and stirred for
10 min at room temperature. The reaction was worked up as
described for the preparation of 16: yield 54 mg (63%).
Preparation of trans-[Rh(CtCH)(py)(PiPr3)2] (25). A
solution of 24 (72 mg, 0.15 mmol) in pentane (5 mL) was
treated with pyridine (0.1 mL, 1.24 mmol) and stirred for 10
min at room temperature. The solvent and the olefin were
evaporated in vacuo, and the orange residue was washed three
times with pentane (1 mL each, 0 °C) and dried: yield 67 mg
(84%); mp 96 °C dec. Anal. Calcd for C25H48NP2Rh: C, 56.92;
H, 9.17; N, 2.66. Found: C, 56.59; H, 9.06; N, 2.53. IR
1
(hexane): ν(CtC) 2070, ν(η2-CtC) 1895 cm-1. H NMR (400
MHz, C6D6): δ 8.17, 7.51 (both m, 6 H, ortho-H of C6H5), 7.22,
7.17 (both m, 6 H, meta-H of C6H5), 7.05, 6.95 (both m, 3 H,
para-H of C6H5), 2.35 (m, 6 H, PCHCH3), 1.24 [dvt, N ) 13.1,
J(H,H) ) 6.9 Hz, 36 H, PCHCH3]. 13C NMR (100.6 MHz,
C6D6): δ 131.4, 130.9, 129.8, 129.5, 128.5, 128.1, 126.7, 124.8
(all s, C6H5), 126.8 [dt, J(Rh,C) ) 13.4, J(P,C) ) 1.9 Hz, RhCt
C], 124.3 [dt, J(Rh,C) ) 48.1, J(P,C) ) 20.9 Hz, RhCtC], 91.6
[dt, J(Rh,C) ) 10.5, J(P,C) ) 2.3 Hz, PhCtCPh], 25.2 (vt,
N ) 18.0 Hz, PCHCH3), 20.9 (s, PCHCH3). 31P NMR (162.0
MHz, C6D6): δ 38.7 [d, J(Rh,P) ) 122.8 Hz].
(benzene): ν(tCH) 3280, ν(CtC) 1920 cm-1 1H NMR (200
.
MHz, C6D6): δ 8.81 (br m, 2 H, ortho-H of C5H5N), 6.64 (br m,
1 H, para-H of C5H5N), 6.25 (br m, 2 H, meta-H of C5H5N),
2.42 [dt, J(Rh,H) ) 2.3, J(P,H) ) 2.1 Hz, 1 H, tCH], 2.35 (m,
6 H, PCHCH3), 1.39 [dvt, N ) 12.6, J(H,H) ) 6.9 Hz, 36 H,
PCHCH3]. 13C NMR (50.3 MHz, C6D6): δ 155.8 (s, ortho-C of
C5H5N), 133.7 (s, para-C of C5H5N), 122.7 (s, meta-C of C5H5N),
113.6 [dt, J(Rh,C) ) 46.5, J(P,C) ) 22.5 Hz, RhCtC], 100.5
[dt, J(Rh,C) ) 14.5, J(P,C) ) 3.0 Hz, RhCtC], 24.9 [dvt, N )
16.4, J(Rh,C) ) 2.3 Hz, PCHCH3], 20.9 (s, PCHCH3). 31P NMR
(81.0 MHz, C6D6): δ 40.3 [d, J(Rh,P) ) 150.9 Hz].
Preparation of trans-[Rh(CtCH)(CO)(PiPr3)2] (29). A
slow stream of CO was passed for 30 s through a solution of
24 (67 mg, 0.14 mmol) in pentane (5 mL) at room temperature.
A rapid change of color from orange to pale yellow occurred.
The solvent and the olefin were evaporated in vacuo, and the
pale yellow microcrystalline residue was washed three times
with pentane (1 mL each, 0 °C) and dried: yield 65 mg (97%);
mp 126 °C dec. Anal. Calcd for C21H43OP2Rh: C, 52.94; H, 9.10.
Found: C, 53.38; H, 9.62. IR (hexane): ν(tCH) 3280, ν(CtC)
Preparation of trans-[Rh(CtCH)(PhCtCMe)(PiPr3)2]
(26). A solution of 24 (67 mg, 0.14 mmol) in hexane (5 mL)
was treated with PhCtCMe (18 µL, 0.14 mmol) and stirred
for 30 min at room temperature. The solvent and the olefin
were evaporated in vacuo, and the orange microcrystalline
residue was washed three times with pentane (1 mL each,
0 °C) and dried: yield 69 mg (88%); mp 90 °C dec. Anal. Calcd
for C29H51P2Rh: C, 61.70; H, 9.10. Found: C, 61.70; H, 9.09.
1
and ν(CO) 1975, 1930 cm-1. H NMR (90 MHz, C6D6): δ 2.57
(m, 6 H, PCHCH3), 2.55 [dt, J(Rh,H) ) 1.6, J(P,H) ) 2.3 Hz,
1 H, tCH], 1.32 [dvt, N ) 13.7, J(H,H) ) 7.0 Hz, 36 H,
PCHCH3]. 13C NMR (22.5 MHz, C6D6): δ 196.0 [dt, J(Rh,C) )
58.6, J(P,C) ) 13.7 Hz, RhCO], 116.7 [dt, J(Rh,C) ) 41.0,
J(P,C) ) 21.5 Hz, RhCtC], 104.7 [dt, J(Rh,C) ) 11.7, J(P,C)
) 2.9 Hz, RhCtC], 26.2 (vt, N ) 21.5 Hz, PCHCH3), 20.6 (s,
PCHCH3). 31P NMR (36.2 MHz, C6D6): δ 52.9 [d, J(Rh,P) )
127.5 Hz].
IR (KBr): ν(tCH) 3280, ν(η2-CtC) 1958, ν(CtC) 1925 cm-1
.
1H NMR (400 MHz, C6D6): δ 7.94 (m, 2 H, ortho-H of C6H5),
7.15 (m, 2 H, meta-H of C6H5), 6.98 (m, 1 H, para-H of C6H5),
2.96 [dt, J(Rh,H) ) 1.8, J(P,H) ) 1.7 Hz, 1 H, tCH], 2.42 (m,
6 H, PCHCH3), 2.30 (s, 3 H, tCCH3), 1.33, 1.25 [both dvt,
N ) 13.2, J(H,H) ) 6.8 Hz, 18 H each, PCHCH3]. 13C NMR
(100.6 MHz, C6D6): δ 131.6, 131.2, 127.8, 125.9 (all s, C6H5),
115.5 [dt, J(Rh,C) ) 47.8, J(P,C) ) 20.2 Hz, RhCtC], 109.3
[dt, J(Rh,C) ) 13.8, J(P,C) ) 1.7 Hz, RhCtC], 86.7 [dt, J(Rh,C)
) 9.1, J(P,C) ) 2.5 Hz, PhCtCMe], 76.0 [dt, J(Rh,C) ) 10.4,
J(P,C) ) 1.5 Hz, PhCtCMe], 25.0 [dvt, N ) 17.6, J(Rh,C) )
1.1 Hz, PCHCH3], 21.2, 20.5 (both s, PCHCH3), 13.9 [d, J(Rh,C)
) 1.2 Hz, tCCH3]. 31P NMR (162.0 MHz, C6D6): δ 39.6 [d,
J(Rh,P) ) 126.2 Hz].
Preparation of trans-[Rh(CtCMe)(CO)(PiPr3)2] (30).
This compound was prepared analogously as described for 29,
using 21 (51 mg, 0.10 mmol) and CO as starting materials. A
pale yellow microcrystalline solid was obtained: yield 42 mg
(82%). Anal. Calcd for C22H45OP2Rh: C, 53.88; H, 9.25.
1
Found: C, 53.76; H, 9.16. IR (hexane): ν(CO) 1945 cm-1. H
NMR (90 MHz, C6D6): δ 2.42 (m, 6 H, PCHCH3), 1.93 [t, J(P,H)
) 2.6 Hz, 3 H, tCCH3], 1.33 [dvt, N ) 14.0, J(H,H) ) 7.0 Hz,
36 H, PCHCH3]. 31P NMR (36.2 MHz, C6D6): δ 50.0 [d, J(Rh,P)
) 126.0 Hz].
Preparation of trans-[Rh(CtCPh)(CO)(PiPr3)2] (31).
This compound was prepared analogously as described for 29,
using 23 (55 mg, 0.10 mmol) and CO as starting materials.
The pale yellow microcrystalline product was characterized by
comparison of the NMR data with those of an authentic
sample:5 yield 51 mg (93%).
Preparation of trans-[Rh(dCdCH2)(py)(PiPr3)2]BF4
(32). A solution of 24 (96 mg, 0.20 mmol) in diethyl ether (5
mL) was treated at 0 °C with a solution of [pyH]BF4 (33 mg,
0.20 mmol) in acetone (5 mL). The solution was slowly warmed
to room temperature, which led to a change of color from
orange to violet. After the solution was stirred for 15 min, it
was concentrated in vacuo to ca. 2 mL and hexane (15 mL)
was added. A violet microcrystalline solid precipitated, which
was characterized by comparison of the 1H and 31P NMR data
with those of an authentic sample:9 yield 112 mg (91%).
Preparation of [(η5-C5H5)Rh(dCdCH2)(PiPr3)] (33). A
solution of 24 (52 mg, 0.11 mmol) in benzene (5 mL) was
treated with freshly distilled cyclopentadiene (9 µL, 0.11 mmol)
and stirred for 2 h at room temperature. The solvent was
evaporated in vacuo, and the residue was recrystallized from
Preparation of trans-[Rh(CtCPh)(MeCtCPh)(PiPr3)2]
(27). A solution of 23 (83 mg, 0.15 mmol) in benzene (5 mL)
was treated with PhCtCMe (19 µL, 0.15 mmol) and stirred
for 30 min at room temperature. After the reaction was worked
up as described for 26, an orange microcrystalline solid was
obtained: yield 89 mg (92%); mp 96 °C dec. Anal. Calcd for
C35H55P2Rh: C, 65.62; H, 8.65. Found: C, 66.04; H, 8.77. IR
(hexane): ν(CtC) 2090, ν(η2-CtC) 1965 cm-1. H NMR (400
1
MHz, C6D6): δ 7.98, 7.48 (both m, 2 H each, ortho-H of C6H5),
7.17, 7.15 (both m, 2 H each, meta-H of C6H5), 7.00, 6.94 (both
m, 1 H each, para-H of C6H5), 2.35 (m, 6 H, PCHCH3), 2.32 (s,
3 H, tCCH3), 1.33, 1.22 [both dvt, N ) 13.2, J(H,H) ) 6.8 Hz,
18 H each, PCHCH3]. 13C NMR (100.6 MHz, C6D6): δ 131.7,
131.2, 129.9, 129.8, 128.5, 127.9, 126.0, 124.5 (all s, C6H5),
125.6 [dt, J(Rh,C) ) 13.5, J(P,C) ) 1.0 Hz, RhCtC], 125.4
[dt, J(Rh,C) ) 47.9, J(P,C) ) 20.7 Hz, RhCtC], 87.5 [dt,
J(Rh,C) ) 8.7, J(P,C) ) 2.3 Hz, PhCtCMe], 76.9 [dt, J(Rh,C)
) 10.4, J(P,C) ) 1.0 Hz, PhCtCMe], 24.9 (vt, N ) 17.7 Hz,
PCHCH3), 21.1, 20.3 (both s, PCHCH3), 13.8 (s, tCCH3). 31P
NMR (162.0 MHz, C6D6): δ 40.2 [d, J(Rh,P) ) 126.2 Hz].

5726 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
pentane to give an orange microcrystalline solid. This was
characterized by comparison of the 1H and 13C NMR data with
those of an authentic sample:10 yield 33 mg (85%).
Preparation of Compound 5 from 24 as the Precursor.
A slow stream of acetylene was passed for 10 s at -10 °C
through a solution of 24 (127 mg, 0.27 mmol) in a 1:1 mixture
of pentane and NEt3 (4 mL). After the solution was warmed
to room temperature, it was stirred for 5 min and then worked
up as described for 5: yield 99 mg (78%).
61.09; H, 8.97. Found: C, 61.02; H, 9.27. IR (KBr): ν(CtC)
1
2080, ν(CdC) 1620, 1580 cm-1. H NMR (90 MHz, C6D6): δ
7.42 (m, 2 H, ortho-H of C6H5), 7.25-6.97 (br m, 3 H, para-
and meta-H of C6H5), 2.83 (m, 6 H, PCHCH3), 1.37 [dvt, N )
13.5, J(H,H) ) 7.1 Hz, 36 H, PCHCH3], -0.03 [dt, J(Rh,H) )
0.7, J(P,H) ) 3.4 Hz, 2 H, dCH2]. 13C NMR (100.6 MHz,
C6D6): δ 309.2 [dt, J(Rh,C) ) 48.1, J(P,C) ) 15.8 Hz, RhdC],
134.4 [d, J(Rh,C) ) 9.4 Hz, RhCtC], 130.2, 129.4, 128.3, 125.1
(all s, C6H5), 92.4 [dt, J(Rh,C) ) 14.0, J(P,C) ) 5.3 Hz, dCH2],
25.2 (vt, N ) 20.2 Hz, PCHCH3), 20.5 (s, PCHCH3); signal for
RhCtC not exactly located. 31P NMR (36.2 MHz, C6D6): δ 47.1
[d, J(Rh,P) ) 136.3 Hz].
Preparation of trans-[Rh(CtCtBu)(dCdCHCO2Me)-
(PiPr3)2] (34). A solution of 22 (158 mg, 0.30 mmol) in a 1:1
mixture of pentane and NEt3 (6 mL) was treated at -78 °C
with HCtCCO2Me (26 µL, 0.30 mmol). After the solution was
warmed to room temperature, it was stirred for 30 min, which
led to a change of color from orange to dark green. The solvent
was evaporated in vacuo, the residue was extracted with
pentane (30 mL), and the extract was concentrated to ca. 10
mL in vacuo. After the solution was stored for 6 h at -78 °C,
blue-green crystals precipitated, which were separated from
the mother liquor, washed twice with pentane (2 mL each, 0
°C), and dried: yield 117 mg (67%); mp 76 °C dec. Anal. Calcd
for C28H55O2P2Rh: C, 57.14; H, 9.42. Found: C, 56.81; H, 9.36.
Preparation of [RhH(CtCH)(CtPh)(py)(PiPr3)2] (37).
A solution of 36 (129 mg, 0.24 mmol) in pentane (4 mL) was
treated with pyridine (0.5 mL, 6.0 mmol) and stirred for 20
min at room temperature. A change of color from blue to pale
yellow occurred. The solvent was evaporated in vacuo, and the
white residue was washed three times with pentane (1 mL
each, 0 °C) and dried: yield 105 mg (72%); mp 106 °C dec.
Anal. Calcd for C33H54NP2Rh: C, 62.95; H, 8.64; N, 2.22.
Found: C, 62.89; H, 9.13; N, 2.37. IR (KBr): ν(tCH) 3280,
1
ν(RhH) 2180, ν(CtCPh) 2095, ν(CtCH) 1945 cm-1. H NMR
IR (benzene): ν(CtC) 2105, ν(CdO) 1680, ν(CdC) 1585 cm-1
.
(90 MHz, C6D6): δ 9.90 (br m, 2 H, ortho-H of C5H5N), 7.63-
6.65 (br m, 8 H, meta- and para-H of C5H5N and C6H5), 3.03
(m, 6 H, PCHCH3), 2.34 [dt, J(Rh,H) ) 1.6, J(P,H) ) 1.6 Hz,
1 H, tCH], 1.26, 1.24 [both dvt, N ) 13.4, J(H,H) ) 6.8 Hz,
18 H each, PCHCH3], -17.94 [dt, J(Rh,H) ) 16.5, J(P,H) )
14.2 Hz, 1 H, RhH]. 31P NMR (36.2 MHz, C6D6): δ 41.6 [d, dd
in off-resonance, J(Rh,P) ) 98.2 Hz].
1H NMR (400 MHz, C6D6): δ 3.47 (s, 3 H, CO2Me), 2.77 (m, 6
H, PCHCH3), 1.32 [dvt, N ) 13.7, J(H,H) ) 7.2 Hz, 36 H,
PCHCH3], 1.28 [t, J(P,H) ) 3.1 Hz, 1 H, dCHCO2CH3], 1.19
(s, 9 H, CCH3). 13C NMR (100.6 MHz, C6D6): δ 299.3 [dt,
J(Rh,C) ) 52.9, J(P,C) ) 14.6 Hz, RhdC], 158.0 [t, J(P,C) )
2.0 Hz, CO2Me], 145.1 [dt, J(Rh,C) ) 9.0, J(P,C) ) 1.8 Hz,
RhCtC], 108.6 [dt, J(Rh,C) ) 12.7, J(P,C) ) 4.7 Hz, dCHCO2-
Me], 108.5 [dt, J(Rh,C) ) 36.6, J(P,C) ) 19.3 Hz, RhCtC],
50.3 (s, CO2CH3), 32.1 (s, CCH3), 29.6 (s, CCH3), 25.4 (vt, N )
21.3 Hz, PCHCH3), 20.5 (s, PCHCH3). 31P NMR (81.0 MHz,
C6D6): δ 48.5 [d, J(Rh,P) ) 135.2 Hz].
Preparation of [RhH(CtCPh)(CtCCO2Me)(py)(PiPr3)2]
(38). A solution of 35 (86 mg, 0.14 mmol) in diethyl ether (5
mL) was treated with pyridine (0.5 mL, 6.0 mmol) and stirred
for 20 min at room temperature. A change of color from blue
to pale yellow occurred. The reaction mixture was worked up
as described for 37 to give a white microcrystalline solid: yield
64 mg (65%); mp 116 °C dec. Anal. Calcd for C35H56NO2P2Rh:
C, 61.13; H, 8.21; N, 2.04. Found: C, 61.56; H, 7.91; N, 2.02.
Preparation of trans-[Rh(CtCPh)(dCdCHCO2Me)-
(PiPr3)2] (35). A solution of 23 (96 mg, 0.17 mmol) in a 1:1
mixture of pentane and NEt3 (4 mL) was treated at -78 °C
with HCtCCO2Me (15 µL, 0.17 mmol). After the solution was
warmed to room temperature, it was stirred for 1 h and then
worked up as described for 34. A blue microcrystalline solid
was obtained: yield 80 mg (76%); mp 104 °C dec. Anal. Calcd
for C30H51O2P2Rh: C, 59.21; H, 8.45. Found: C, 59.38; H, 8.84.
IR (KBr): ν(RhH) 2180, ν(CtC) 2070 (br), ν(CdO) 1670 cm-1
.
1H NMR (90 MHz, C6D6): δ 9.96 (br m, 2 H, ortho-H of C5H5N),
7.56-6.51 (br m, 8 H, meta- and para-H of C5H5N and C6H5),
3.48 (s, 3 H, CO2CH3), 2.90 (m, 6 H, PCHCH3), 1.20 [dvt, N )
13.2, J(H,H) ) 7.0 Hz, 36 H, PCHCH3], -17.66 [dt, J(Rh,H)
) 16.5, J(P,H) ) 13.7 Hz, 1 H, RhH]. 31P NMR (36.2 MHz,
C6D6): δ 42.0 [d, dd in off-resonance, J(Rh,P) ) 95.3 Hz].
IR (benzene): ν(CtC) 2080, ν(CdO) 1685, ν(CdC) 1585 cm-1
.
1H NMR (400 MHz, C6D6): δ 7.34 (m, 2 H, ortho-H of C6H5),
7.08 (m, 1 H, para-H of C6H5), 6.90 (m, 2 H, meta-H of C6H5),
3.48 (s, 3 H, CO2Me), 2.73 (m, 6 H, PCHCH3), 1.40 [t, J(P,H)
) 3.1 Hz, 1 H, dCHCO2CH3], 1.33 [dvt, N ) 13.8, J(H,H) )
7.1 Hz, 36 H, PCHCH3]. 13C NMR (100.6 MHz, C6D6): δ 300.7
[dt, J(Rh,C) ) 53.1, J(P,C) ) 14.7 Hz, RhdC], 157.8 (br s, CO2-
Me), 136.1 [d, J(Rh,C) ) 9.4 Hz, RhCtC], 130.2, 128.7, 128.4,
125.6 (all s, C6H5), 125.4 [dt, J(Rh,C) ) 36.8, J(P,C) ) 18.9
Hz, RhCtC], 109.0 [dt, J(Rh,C) ) 13.0, J(P,C) ) 5.0 Hz, d
CHCO2Me], 50.4 (s, CO2CH3), 25.7 (vt, N ) 21.5 Hz, PCHCH3),
20.4 (s, PCHCH3). 31P NMR (162.0 MHz, C6D6): δ 48.4 [d,
J(Rh,P) ) 133.6 Hz].
Preparation of trans-[Rh(CtCMe)(η2-CH2dCdCH2)-
(PiPr3)2] (39). Method a: To a solid sample of 1 (70 mg, 0.15
mmol), stored in a Schlenk tube at -50 °C, an excess of
propyne (ca. 1 mL, ca. 17 mmol)) was condensed. An orange
suspension was obtained to which pentane (2 mL, -50 °C) was
added. After the reaction mixture was stirred for 5 min at -50
°C, it was slowly warmed to room temperature. The solvent
was evaporated in vacuo and the residue was recrystallized
from pentane (3 mL) at -78 °C to give a yellow microcrystal-
line solid: yield 60 mg (79%). Method b: The same procedure
was applied as described for a using 18 (78 mg, 0.15 mmol) as
starting material: yield 63 mg (83%); mp 68 °C dec. Anal.
Calcd for C24H49P2Rh: C, 57.36; H, 9.83. Found: C, 57.67; H,
9.95. IR (KBr): ν(CtC) 2100, ν(CdCdC) 1740 cm-1. 1H NMR
Preparation of trans-[Rh(CtCPh)(dCdCH2)(PiPr3)2]
(36). Method a: A slow stream of acetylene was passed for 30
s through a solution of 23 (151 mg, 0.27 mmol) in a 1:1 mixture
of pentane and NEt3 (10 mL) at room temperature. The
reaction was stirred for 10 min, which led to a change of color
from orange to dark violet. The solvent was evaporated in
vacuo, the residue was dissolved in pentane (30 mL), and the
solution was stored for 12 h at -78 °C. A dark violet solid
precipitated, which was separated from the mother liquor,
washed twice with pentane (1 mL each, 0 °C), and dried: yield
117 mg (78%). Method b: A solution of 24 (138 mg, 0.29 mmol)
in a 1:1 mixture of pentane and NEt3 (8 mL) was treated at
-15 °C with phenylacetylene (31 µL, 0.29 mmol). After the
solution was warmed to room temperature, it was stirred for
10 min and then worked up as described for method a: yield
130 mg (81%); mp 89 °C dec. Anal. Calcd for C28H49P2Rh: C,
1
(400 MHz, C6D6): δ 5.45, 5.25 [both m, in H{31P} both ddt,
J(Rh,H) ) 1.0, 2J(H,H) ) 2.7, 4J(H,H) ) 3.5 Hz, 1 H each,
dCH2 uncoordinated], 2.48 [dtt, J(Rh,H) ) 1.7, J(P,H) ) 5.0,
4J(H,H) ) 3.5 Hz, 2 H, dCH2 coordinated], 2.44 (m, 6 H,
PCHCH3), 2.00 [t, J(P,H) ) 2.1 Hz, 3 H, tCCH3], 1.35 [dvt,
N ) 13.0, J(H,H) ) 6.9 Hz, 36 H, PCHCH3]. 13C NMR (100.6
MHz, C6D6): δ 182.4 [dt, J(Rh,C) ) 16.1, J(P,C) ) 4.5 Hz,
dCd], 117.2 [dt, J(Rh,C) ) 12.7, J(P,C) ) 2.1 Hz, RhCtC],
108.5 [dt, J(Rh,C) ) 45.8, J(P,C) ) 21.0 Hz, RhCtC], 94.2
[dt, J(Rh,C) ) 2.4, J(P,C) ) 2.4 Hz, dCH2 uncoordinated], 24.5
[dvt, N ) 18.8, J(Rh,C) ) 1.1 Hz, PCHCH3], 20.8 (s, PCHCH3),
17.2 [dt, J(Rh,C) ) 8.1, J(P,C) ) 1.9 Hz, dCH2 coordinated],

Alkynyl(vinylidene)rhodium(I) Complexes
Organometallics, Vol. 23, No. 24, 2004 5727
6.8 [dt, J(Rh,C) ) 1.0, J(P,C) ) 1.0 Hz, tCCH3]. 31P NMR
(162.0 MHz, C6D6): δ 38.5 [d, J(Rh,P) ) 126.6 Hz].
Reaction of Compound 39 with CO. A slow stream of
Hz, 1 H, one H of dCH2 trans to CH3], 1.77 [dd, 4J(H,H) )
4
6
1.5, J(H,H) ) 1.0 Hz, 3 H, dCCH3], 1.57 [dd, J(H,H) ) 0.6,
6J(H,H) ) 0.4 Hz, 3 H, CtCCH3].
Reaction of Compound 1 with Excess Phenylacety-
lene. A solution of 1 (87 mg, 0.19 mmol) in pentane (10 mL)
was treated with phenylacetylene (1.0 mL, 9.11 mmol) and
stirred for 1 h at room temperature. A change of color from
yellow to orange-red occurred. The solvent and unreacted
phenylacetylene were evaporated in vacuo, and the remaining
orange oil was characterized by IR and NMR spectroscopy.
Owing to the relative intensities of the signals in the 1H NMR
spectrum (in C6D6), the product contained 43 (ca. 15%), 44 (ca.
50%), 45 (ca. 10%), 46 (ca. 20%), and traces of some unknown
substances. Compounds 44 and 46 were identified by com-
parison of the NMR data with those in the literature.25 After
the orange oil was dissolved in hexane (2 mL) and the solution
chromatographed on Al2O3 (basic, activity grade III, height of
column 5 cm), an orange fraction was eluted, from which 43
(41 mg) and 44 (25 mg) were isolated by fractional crystal-
lization from pentane. Data for 45: IR (hexane): ν(CtC) 2080,
CO was passed for 10 s through a solution of 39 (50 mg, 0.10
mmol) in C6D6 (0.5 mL) at room temperature. The 1H and 31
P
NMR spectra revealed that besides allene the carbonyl complex
30 was formed: yield virtually quantitative.
Preparation of trans-[Rh(CtCMe)2{C(CH3)dCH2}(P-
iPr3)2] (40). Method a: A slow stream of propyne was passed
for 1 min through a solution of 1 (228 mg, 0.49 mmol) in a 1:1
mixture of pentane and NEt3 (6 mL) at -20 °C. After the
solution was warmed to room temperature, it was stirred for
10 h, which led to a smooth change of color from orange-yellow
to red. The solvent was evaporated in vacuo, the residue was
dissolved in pentane (10 mL), and the solution was concen-
trated to ca. 2 mL in vacuo. After the solution was stored for
48 h at -78 °C, a red microcrystalline solid precipitated, which
was separated from the mother liquor, washed twice with
pentane (2 mL each, -20 °C), and dried: yield 104 mg (39%).
Method b: A slow stream of propyne was passed for 15 s
through a solution of 18 (143 mg, 0.28 mmol) in pentane (5
mL) at -40 °C. After the solution was warmed to -20 °C, it
was stirred for 10 min and then the solvent was evaporated
in vacuo. The oily residue was dissolved in pentane (5 mL),
and a stream of propyne was passed through the solution for
1 min at room temperature. The solution was stirred for 5 min,
and the solvent was removed. The oily residue was dissolved
in a 4:1 mixture of benzene/hexane (2 mL), and the solution
was chromatographed on Al2O3 (basic, activity grade IV, height
of column 7 cm). With benzene/hexane (4:1) a red fraction was
eluted, which was brought to dryness in vacuo. After recrys-
tallization of the residue from acetone at -78 °C, a red
microcrystalline solid was obtained: yield 81 mg (54%); mp
74 °C dec. Anal. Calcd for C37H53P2Rh: C, 59.77; H, 9.84.
Found: C, 59.48; H, 9.93. IR (KBr): ν(CtC) 2105, ν(CdC) 1575
ν(η2-CtC) 1860 cm-1
J(Rh,P) ) 121.6 Hz].
.
31P NMR (36.2 MHz, C6D6): δ 39.2 [d,
Preparation of trans-[Rh(CtCPh){η2-(E)-PhCtCCHd
CHPh}(PiPr3)2] (43). A solution of 23 (133 mg, 0.24 mmol)
in diethyl ether (5 mL) was treated with a solution of 44 (49
mg, 0.24 mmol) in diethyl ether (3 mL) and stirred for 30 min
at room temperature. The solvent was evaporated in vacuo,
the residue was extracted with pentane (25 mL), and the
extract was brought to dryness in vacuo. The remaining orange
solid was washed twice with pentane (2 mL each, 0 °C) and
dried: yield 136 mg (78%); mp 108 °C dec. Anal. Calcd for
C42H59P2Rh: C, 69.22; H, 8.43. Found: C, 69.08; H, 8.43. IR
1
(hexane): ν(CtC) 2080, ν(η2-CtC) 1885 cm-1. H NMR (400
MHz, C6D6): δ 8.12, 7.50, 7.46 (all m, 6 H, ortho-H of C6H5),
7.41 [d, J(H,H) ) 15.7 Hz, 1 H, CHdCHPh], 7.23, 7.16, 7.14
(all m, 6 H, meta-H of C6H5), 7.11 [d, J(H,H) ) 15.7 Hz, 1 H,
CHdCHPh], 7.05, 7.04, 6.95 (all m, 3 H, para-H of C6H5), 2.40
(m, 6 H, PCHCH3), 1.34, 1.24 [both dvt, N ) 13.5, J(H,H) )
6.8 Hz, 18 H each, PCHCH3]. 13C NMR (100.6 MHz, C6D6): δ
138.2 (s, CHdCH-Cipso), 135.6 (br s, CHdCHPh), 131.5 [d,
J(Rh,C) ) 0.7 Hz, ortho-C of RCtCC6H5], 131.3 [d, J(Rh,C) )
1.1 Hz, η2-CtC-Cipso], 129.8 [t, J(P,C) ) 0.8 Hz, ortho-C of
RhCtCC6H5], 129.5 [dt, J(Rh,C) ) 1.0, J(P,C) ) 1.3 Hz, RhCt
C-Cipso], 129.2, 128.5, 128.1, 127.7, 126.9, 126.3, 124.8 (all s,
C6H5), 126.8 [dt, J(Rh,C) ) 12.5, J(P,C) ) 1.8 Hz, RhCtC],
124.8 [dt, J(Rh,C) ) 48.2, J(P,C) ) 20.5 Hz, RhCtC], 117.3
(br s, CHdCHPh), 96.7 [dt, J(Rh,C) ) 11.4, J(P,C) ) 2.9 Hz,
RCtCPh], 90.2 [dt, J(Rh,C) ) 9.5, J(P,C) ) 1.8 Hz, RCtCPh],
24.9 (vt, N ) 18.0 Hz, PCHCH3], 21.1, 20.4 (both s, PCHCH3).
31P NMR (36.2 MHz, C6D6): δ 38.8 [d, J(Rh,P) ) 123.1 Hz].
Reaction of the Mixture of Compounds 43 and 45 with
CO. This reaction was carried out under the same conditions
as described for the reaction of 39 with CO. The color changed
from orange to pale yellow. The 1H NMR spectrum confirmed
the formation of the carbonyl complex 31 and of the isomeric
butenynes 44 and 46. The latter were identified by comparison
of their NMR data with those reported in the literature.25
Catalytic Dimerization of Phenylacetylene. A solution
of 1 (52 mg, 0.11 mmol) in hexane (9 mL) was treated with
phenylacetylene (1.2 mL, 11.0 mmol) and 1 mL of benzene (as
reference for GC) and stirred at 40 °C. After 4 h, GC
measurements revealed that ca. 50% of the alkyne had been
reacted. Besides small amounts of a brownish solid (possibly
an oligomer or polymer of PhCtCH) a red solution was formed,
which, after it was cooled to room temperature, was brought
to dryness in vacuo. Owing to the 1H NMR spectrum, the oily
residue consisted of a mixture of 44 and 46 in the ratio of
70:30.
cm-1 1H NMR (90 MHz, C6D6): δ 5.54 [m, in 1H{31P} br d,
.
J(Rh,H) ) 2.4 Hz, 1 H, one H of dCH2 trans to CH3], 4.31 [m,
1
in H{31P} br d, J(Rh,H) ) 4.3 Hz, 1 H, one H of dCH2 cis to
CH3], 2.98 (m, 6 H, PCHCH3), 2.30 (m, 3 H, RhCCH3), 2.06
[dt, J(Rh,H) ) 0.6, J(P,H) ) 1.7 Hz, 6 H, tCCH3], 1.40 [dvt,
N ) 13.0, J(H,H) ) 7.1 Hz, 36 H, PCHCH3]. 31P NMR (81.0
MHz, C6D6): δ 30.2 [d, J(Rh,P) ) 104.6 Hz].
Preparation of trans-[Rh(CtCMe){η2-MeCtCC(Me)d
CH2}(PiPr3)2] (41). A solution of 40 (81 mg, 0.15 mmol) in
benzene (1 mL) was stirred for 20 min at room temperature.
A change of color from deep red to orange occurred. The solvent
was evaporated in vacuo, and the remaining orange oil was
dried in vacuo: yield 80 mg (98%). IR (hexane): ν(CtC) 2090,
1
ν(η2-CtC) 1930 cm-1. H NMR (90 MHz, C6D6): δ 5.91 (m, 1
H, one H of dCH2), 5.27 (m, 1 H, one H of dCH2), 2.35 (m, 6
H, PCHCH3), 2.20 (br s, 3 H, η2-RCtCCH3), 2.07 [dt, J(Rh,H)
) 0.6, J(P,H) ) 1.8 Hz, 3 H, RhCtCCH3], 2.00 (m, 3 H, CH2d
CCH3), 1.38, 1.33 [both dvt, N ) 13.1, J(H,H) ) 7.1 Hz, 18 H
each, PCHCH3]. 13C NMR (100.6 MHz, C6D6): δ 133.6 (s,
C(CH3)dCH2), 117.4 (s, C(CH3)dCH2), 117.1 [dt, J(Rh,C) )
13.3, J(P,C) ) 2.9 Hz, RhCtC], 105.8 [dt, J(Rh,C) ) 46.7,
J(P,C) ) 21.2 Hz, RhCtC], 89.3 [dt, J(Rh,C) ) 9.1, J(P,C) )
2.9 Hz, one C of CtC], 77.9 [dt, J(Rh,C) ) 10.5, J(P,C) ) 1.5
Hz, one C of CtC], 25.2 [dvt, N ) 17.5, J(Rh,C) ) 1.2 Hz,
PCHCH3], 24.0 (s, C(CH3)dCH2), 21.0, 20.4 (both s, PCHCH3),
13.7 [d, J(Rh,C) ) 1.2 Hz, η2-RCtCCH3], 7.1 [dt, J(Rh,C) )
0.9, J(P,C) ) 0.9 Hz, RhCtCCH3]. 31P NMR (36.2 MHz,
C6D6): δ 40.1 [d, J(Rh,P) ) 130.4 Hz].
Reaction of Compound 41 with CO. A slow stream of
CO was passed for 10 s through a solution of 41 (49 mg, 0.09
mmol) in C6D6 (0.5 mL) at room temperature. The 1H and 31
P
NMR spectra revealed that besides the carbonyl complex 30
the enyne 42 was formed: yield virtually quantitative. Data
2
for 42: 1H NMR (90 MHz, C6D6): δ 5.29 [dqq, J(H,H) ) 1.6,
To isolate the main component 44, the procedure was as
follows: The oily residue was dissolved in benzene (3 mL) and
the solution was chromatographed on Al2O3 (neutral, activity
6
4J(H,H) ) 1.0, J(H,H) ) 0.6 Hz, 1 H, one H of dCH2 cis to
2
4
6
CH3], 5.01 [dqq, J(H,H) ) 1.6, J(H,H) ) 1.5, J(H,H) ) 0.4

5728 Organometallics, Vol. 23, No. 24, 2004
Scha¨fer et al.
grade I, 15 × 5 cm columns). With hexane, a pale brown
fraction was eluted containing butenyne 46 as the major
species. Subsequent elution with dichloromethane gave a
yellow fraction, from which the solvent was evaporated in
vacuo. The residue was extracted with hexane (45 mL), the
extract was brought to dryness in vacuo, and the residue (276
mg) was recrystallized from pentane at 0 °C. A pale yellow
solid was obtained, which by comparison of the NMR data was
identified as 44.25 Yield: 171 mg (ca. 30%, based on PhCt
CH).
Acknowledgment. We thank the Deutsche For-
schungsgemeinschaft (Grant SFB 347) and the Fonds
der Chemischen Industrie for financial support. More-
over, we gratefully acknowledge support by Mrs. R.
Schedl and Mr. C. P. Kneis (elemental analysis and DTA
measurements), Mrs. M.-L. Scha¨fer and Dr. W. Buchner
(NMR spectra), and Dr. G. Lange and Mr. F. Dadrich
(mass spectra).
OM049389F