C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- And trimerization of terminal alkynes

Article abstract of DOI:10.1039/b415541f

The synthesis of a series of four-coordinate enynylrrhodium(I) complexes was reported. Their reactions with acidic substrates to give either enynes and/or butatrienes were investigated. Different routes to prepare enynerrhodium(I) compounds by intramolecular C-C coupling were also studied. A new mechanistic pathway for the trimerization of a terminal alkyne that selectively leads to a hexadienyne derivative was presented.

Full text of DOI:10.1039/b415541f

View Article Online / Journal Homepage / Table of Contents for this issue
F U L L P A P E R
C–C coupling reactions in the coordination sphere of rhodium(I) and
rhodium(III): New routes for the di- and trimerization of terminal
alkynes†
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 7th October 2004, Accepted 11th February 2005
First published as an Advance Article on the web 10th March 2005
= =
The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C≡CR)( C CHR)(PiPr3)2] 2, 5, 6 react with CO by
1
=
migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{g -(Z)-C( CHR)C≡CR}-
(CO)(PiPr3)2] (Z)-7–9, of which (Z)-7 (R = Ph) and (Z)-8 (R = tBu) rearrange upon heating or UV irradiation to the
1
1
=
(E) isomers. Similarly, trans-[Rh{g -C( CH2)C≡CPh}(CO)(PiPr3)2] 12 and trans-[Rh{g -(Z)-
=
C( CHCO2Me)C≡CR}(CO)(PiPr3)2] (Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding
1
=
“non-substituted” derivative trans-[Rh{g -C( CH2)C≡CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl
1
= = =
isomer trans-[Rh(g -CH C C CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex
ꢀ
=
trans-[Rh(C≡CCH CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R CO2H
ꢀ
=
(R = CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC≡CCH CHR or a mixture of the butenyne and the
isomeric butatriene, the ratio of which depends on both R and Rꢀ. Treatment of 2 (R = Ph) with HCl at −40 ◦C
=
affords five-coordinate [RhCl(C≡CPh){(Z)-CH CHPh}(PiPr3)2] 23, which at room temperature reacts by C–C
2
=
coupling to give trans-[RhCl{g -(Z)-PhC≡CCH CHPh}(PiPr3)2] (Z)-21. The related compound
2
=
= =
trans-[RhCl(g -HC≡CCH CH2)(PiPr3)2] 27, prepared from trans-[Rh(C≡CH)( C CH2)(PiPr3)2] 17 and HCl,
= =
=
rearranges to the vinylvinylidene isomer trans-[RhCl( C CHCH CH2)(PiPr3)2] 28. While stepwise reaction of 2
with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes
1
2
=
trans-[Rh(j -O2CCF3)(g -PhC≡CCH CHPh)(PiPr3)2] (Z)-30 and (E)-30, from 2 and CH3CO2H the acetato
2
=
derivative [Rh(j -O2CCH3)(PiPr3)2] 33 and (Z)-PhC≡CCH CHPh are obtained. From 6 (R = CO2Me) and HCl or
2
=
=
HC≡CCO2Me the chelate complexes [RhX(C≡CCO2Me){j (C,O)-CH CHC(OMe) O}(PiPr3)2] 34 (X = Cl) and
35 (X = C≡CCO2Me) have been prepared. In contrast to the reactions of [Rh(j2-O2CCH3)(C≡CE)-
=
(CH CHE)(PiPr3)2] 37 (E = CO2Me) with chloride sources which give, via intramolecular C–C coupling, four-
2
=
coordinate trans-[RhCl{g -(E)-EC≡CCH CHE}(PiPr3)2] (E)-36, treatment of 37 with HC≡CE affords, via insertion
of the alkyne into the rhodium–vinyl bond, six-coordinate [Rh(j2-O2CCH3)(C≡CE){g -(E,E)-
1
2
=
=
=
C( CHE)CH CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{g -(E,E)-EC≡CC( CHE)-
=
CH CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne
=
=
(E,E)-EC≡CC( CHE)CH CHE 40.
Introduction
The catalytic dimerization of terminal alkynes has been inten-
sively studied in recent years.1 With electron-rich transition-
metal compounds as catalysts, it is generally assumed that
the C–C bond-forming reaction occurs either by alkynyl–
vinyl or alkynyl–vinylidene coupling.2 Although it has been
observed that occasionally the dimerization of RC≡CH can
3–7
= = =
lead to butatriene derivatives (E)/(Z)-RCH C C CHR, in
most cases a mixture of 1,3- and 1,4-disubstituted butenynes,
8
=
=
RC≡CC(R) CH2 and (E)/(Z)-RC≡CCH CHR, is formed.
In the context of our investigations on the chemistry of
vinylidenerhodium(I) complexes,9 we found that the chloro
= =
derivatives trans-[RhCl( C CHR)(PiPr3)2] react with organo-
Scheme 1 (L = PiPr3).
lithium compounds or Grignard reagents to give the substitution
ꢀ
ꢀ
= =
products trans-[Rh(R )( C CHR)(PiPr3)2] (R = alkyl, aryl,
vinyl, alkynyl) in high yields.10 An alternative route to obtain the
termediates 3 and 4, the first of which could be isolated in
analytically pure form.
complexes with Rꢀ = C≡CR consists of the reaction of the g -
3
3
allyl compound [Rh(g -C3H5)(PiPr3)2] 1 with terminal alkynes
The present work is an extension of our studies on the
rhodium-assisted coupling of an alkyl, aryl or vinyl group
with a vinylidene ligand.10 We report the synthesis of a series
of four-coordinate enynylrhodium(I) complexes, their reactions
with acidic substrates to give either enynes and/or butatrienes,
different routes to prepare enynerhodium(I) compounds by
intramolecular C–C coupling, and a new mechanistic pathway
for the trimerization of a terminal alkyne that does not lead to a
in the molar ratio of 1 : 2 in pentane or pentane/NEt3 as the
solvent.11 As illustrated with phenylacetylene as the substrate
(see Scheme 1), the alkynyl(vinylidene) complex 2 is formed
via the alkynerhodium(I) and alkynyl(hydrido)rhodium(III) in-
† Dedicated to Professor Wolfgang Kla¨ui, with the best of good wishes,
on the occasion of his 60th birthday.
1 4 6 8
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

View Article Online
=
benzene but selectively to a hexadienyne derivative. Part of the
results have already been communicated.12,13
as the resonance for the vinyl CH proton appears at d 6.91 and
5.44 and is thus shifted by more than 1.1 ppm to higher fields.
The 13C NMR spectra of (Z)-7, (Z)-8 and (E)-7, (E)-8 display
four signals for the carbon atoms of the C4 enynyl unit in the
range of d 85 to 160 and there are only minor differences in the
chemical shifts between the (Z) and the (E) isomers.
Results and discussion
CO-induced coupling of alkynyl and vinylidene units
An alternative method to obtain (E)-7 consists of the reaction
of the hydrido compound 10 with the diyne PhC≡CC≡CPh
affording the product in 75% yield (see Scheme 2). We note that
there is precedent for the preparation of enynyl transition-metal
complexes from hydrido–metal precursors and diynes which in
all cases led to the formation of the corresponding (E) isomers.15
In the presence of CO, the alkynyl(vinylidene) complexes 11,
13 and 14, having different substituents at the b-carbon atoms
of the alkynyl and the vinylidene ligands, behave analogously
to their more symmetrical counterparts 2, 5 and 6. Under
similar conditions as applied for the preparation of (Z)-7–
9, the enynylrhodium(I) compounds 12 and (Z)-15, (Z)-16
were formed in high yields (Scheme 3). Since the reactions
of 13 and 14 with CO afford exclusively the complexes with
the CO2Me group linked to b-carbon atom of the vinylic
moiety, we assume that the mechanism of formation of (Z)-
15, (Z)-16 is best described as the CO-induced migration of
the alkynyl ligand to the a-carbon atom of the vinylidene unit.
If the rearrangement proceeded via an intermediate hexa-
coordinate [RhH(C≡CR)(C≡CCO2Me)(CO)(PiPr3)2] species,
presumably a mixture of (Z)-15 or (Z)-16 and the corresponding
The alkynyl(vinylidene) complexes 2, 5 and 6, prepared from
1 and two equivalents of RC≡CH,11,14 are highly reactive
toward carbon monoxide. Passing a slow stream of CO through
a solution of 2, 5 or 6 in pentane at −40 ◦C leads to a
change of colour from blue-green to yellow and, after low-
temperature crystallization from pentane, gave yellow crystalline
solids of composition (Z)-7–9 in about 80% yield (Scheme 2).
The IR spectra of the moderately air-sensitive products show
two characteristic bands at, respectively, 1930–1955 cm−1 and
2155–2160 cm−1, which are assigned to the CO and C≡C
1
stretching frequencies. Since in the H NMR spectra of (Z)-7–
=
9 the chemical shift of the signal of the vinylic CH proton,
which appears as a doublet-of-triplets due to 1H–103Rh and
1H–31P couplings, is quite similar to that found for the enyl
ꢀ
=
complexes trans-[Rh(CR CHR )(CO)(PiPr3)2] (R = Me, Ph, p-
Tol, CH CH2; R = tBu, Ph),10 we assume that the (Z) isomers,
ꢀ
=
having the substituents R and C≡CR in a trans orientation
=
at the C C bond, are exclusively formed. The stereochemical
course of the reaction is noteworthy insofar as Wakatsuki
et al. reported the exclusive formation of the thermodynami-
cally favoured (E) isomer of the enynylruthenium compound
=
isomer trans-[Rh{C( CHR)C≡CCO2Me}(CO)(PiPr3)2] would
=
[RuCl{C( CHtBu)C≡CtBu}(CO)(PPh3)2] after stepwise treat-
be formed. The importance of steric factors probably explains
why not only for (Z)-7–9 but also in the case of (Z)-15 and (Z)-
16 the attack of the alkynyl residue takes place exclusively at that
side of the molecule which is opposite to the CO2Me group.
3
= =
ment of [RuCl2( C CHtBu)(PPh3)2] with LiC≡CtBu and CO.
Scheme 3 (L = PiPr3).
Treatment of the “non-substituted” alkynyl(vinylidene) com-
plex 17 with CO led to a remarkable rearrangement of the
carbon-bonded ligands. As expected, in the initial step the enynyl
compound 18 is formed and isolated as a yellow microcrystalline
solid in 84% yield (Scheme 4). Typical spectroscopic features of
Scheme 2 (L = PiPr3).
The proposed stereochemistry of the four-coordinate rhodium
complexes obtained from the starting materials 2, 5, 6 and CO
has been confirmed by an X-ray crystal structure analysis of
(Z)-9.12 The most important result is that the enynyl unit lies
perpendicular to the coordination plane around rhodium and
that there is no additional interaction between the triple bond
or the ester unit and the metal centre.
In benzene solution, the tBu-substituted complex (Z)-8 is
slightly labile and, after stirring the solution for 6 h at 40 ◦C,
rearranges nearly quantitatively to the isomer (E)-8. This
compound, being a yellow solid similar to (Z)-8, is equally
formed by UV-irradiation of a solution of the (Z) isomer in
benzene for 2 h at 15 ◦C. In this case the yield is 74%. While the
photochemical route can also be applied for the isomerization of
(Z)-7 to (E)-7, attempts to generate the isomer (E)-9 from (Z)-9
failed. Regarding the 1H NMR spectra of (E)-7 and (E)-8, there
is a characteristic difference to those of the (Z) isomers insofar
18 are the signals for the three protons of the enynyl ligand in
1
=
the H NMR spectrum which appear for the CH2 protons at
d 6.66 and 5.52 as doublets-of-doublets-of-triplets and for the
≡CH proton at d 3.41 as a singlet.
When a solution of 18 in toluene-d8 was slowly warmed
to room temperature, NMR spectra indicated the formation
of a new compound of proposed formulation 19. The ratio
of 18 : 19 is about 65 : 35, which does not change after
the solution has been stirred for 2 h. The 1H NMR spec-
trum of 19 displays the three resonances for the butatrienyl
=
protons at d 7.93 (RhCH) and d 5.45 and 5.23 ( CH2),
all of them are split into doublets-of-doublets-of-doublets-
of-triplets. Similar chemical shifts (as well as 1H–1H and
1H–31P coupling constants) were found for the octahedral
= = =
iridium complex [IrCl(OTf)(CH C C CHMe)(CO)(PPh3)2]
(Tf = triflate), which was prepared by Stang et al. from
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 6 9

View Article Online
Scheme 4 (L = PiPr3).
16
=
trans-[IrCl(CO)(PPh3)2] and HC≡CC(OTf) CHMe. In con-
trast to 18, the 1H and 13C NMR spectra of 19 illustrate
that the two triisopropylphosphine ligands are equivalent, thus
indicating that the rotation of the C4 ligand around the Ir–C axis
is fast on the NMR timescale.
When we attempted to enrich the mixture of 18 and 19 in
the butatrienyl complex 19 by UV irradiation, we observed
that under the chosen conditions (C6D6, 15 ◦C) both com-
pounds are labile and rearrange to a third isomer assumed
to be the substituted alkynyl complex 20. In addition, some
unidentified decomposition products were formed which could
not be separated from 20 by fractional crystallization or column
chromatography. The 1H NMR spectrum of 20 shows for
the protons of the vinyl group three doublets-of-doublets-
of-triplets with chemical shifts that are similar to those of
Scheme 5 (L = PiPr3).
The reaction of (E)-8 with both acetic acid (in benzene)
and trifluoroacetic acid (in benzene or acetone) always leads
= = =
to a mixture of the butatrienes (E)/(Z)-tBuCH C C CHtBu
=
and the butenyne (Z)-tBuC≡CCH CHtBu, with either the
former or the latter as the dominating products. The isomer
(Z)-8 reacts with CF3CO2H in benzene or acetone to give
mainly a mixture of (E)- and (Z)-tBuCH C C CHtBu,
whereas with CH3CO2H in benzene besides the butatrienes
= = =
= = =
(E)/(Z)-tBuCH C C CHtBu (ca. 40%) also the butenyne
=
the CH CH2 protons of the vinylvinylidene compound trans-
=
(E)-tBuC≡CCH CHtBu (ca. 60%) is formed (Scheme 6). In
17
= =
=
[RhCl( C CHCH CH2)(PiPr3)2]. When we attempted to
elucidate the mechanism of formation of 20 by monitoring the
isomerization reaction in an NMR tube, we were unable to detect
any intermediate. The most plausible path to give 20 appears to
be a 1,3-shift of the enynyl ligand of 18 along the C–C≡CH axis,
followed by the migration of the alkynyl proton to the c-carbon
atom. If instead of 18 the butatrienyl derivative 19 would be the
precursor, the generation of a short-lived five-coordinate hydri-
all cases, the organic products were known and identified by
comparison of the NMR data with those reported in the
literature.5,7,20–25
= = = =
dorhodium(I) compound [RhH( C C C CH2)(CO)(PiPr3)2]
is conceivable which via a 1,3-hydride shift from the metal to the
c-carbon atom of the cumulated C4 unit would give the product.
It should be mentioned that while we succeeded in preparing an
iridium(I) complex with an Ir C C C CR2 chain,18 we failed
= = = =
to generate the rhodium(I) counterpart.
Acid-induced formation of butenynes and butatrienes
The cleavage of the enynyl–metal bond in (E)-7 by acetic acid in
benzene affords, besides the carboxylato complex trans-[Rh(j1-
O2CCH3)(CO)(PiPr3)2],19 exclusively the expected butenyne (Z)-
=
PhC≡CCH CHPh (Scheme 5). If the reaction of (E)-7 is
carried out with CF3CO2H instead of acetic acid and in
acetone instead of benzene as solvent, besides trans-[Rh(j1-
O2CCF3)(CO)(PiPr3)2]19 surprisingly a mixture of (E)/(Z)-
= = =
=
PhCH C C CHPh (ca. 95%) and (Z)-PhC≡CCH CHPh
(ca. 5%) is formed. The ratio of the (E) and (Z) isomers of
1,4-diphenylbutatriene is 9 : 1.
In contrast to (E)-7, the corresponding (Z) isomer is inert
toward CH3CO2H. If (Z)-7 is treated with CF3CO2H, the
composition of the organic products, obtained by cleavage of
the enynyl–rhodium bond, depends on the solvent used. While
in benzene at 40 ◦C as well as in acetone at room temperature the
dominating products are the 1,4-diphenylbutatrienes (E)/(Z)-
Scheme 6 (L = PiPr3).
To summarize the results about the reactivity of the enynyl
complexes (E)/(Z)-7 and (E)/(Z)-8 toward CH3CO2H and
CF3CO2H, the first conclusion is that independent of the
strength of the acid and the type of the solvent the (E)-
isomers (E)-7 and (E)-8 afford (either as the major or the minor
= = =
PhCH C C CHPh, the minor product formed in benzene is
=
(E)-PhC≡CCH CHPh but in acetone it is the (Z) isomer.
1 4 7 0
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
+
= =
product) the corresponding (Z)-butenyne and the (Z)-isomers
(Z)-7 and (Z)-8 afford the corresponding (E)-butenyne. This is
in agreement with work in the literature.26 Mechanistically we
assume that the formation of the butenynes proceeds via a hexa-
coordinate intermediate A (see Scheme 7, shown for the (Z)-
enynyl complexes as the precursors), which is generated from
the four-coordinate starting material by oxidative addition of
the acid HX at the metal centre. Reductive elimination from A
the hydridoiridium(III) cations [IrH(Cl)( C CHR)(PiPr3)2]
which rearrange to the carbyne–metal isomers [IrCl(≡CCH2R)-
(PiPr3)2]+,29 prompted us to investigate also the reactivity of
the rhodium vinylidenes 2, 6 and 17 toward Brønsted acids.
Treating a solution of 2 in benzene with an equimolar amount
of HCl at room temperature leads to a smooth change of colour
from blue-green to orange and, as indicated by the 31P NMR
spectrum, affords a mixture of the alkyne complex (Z)-21 and the
chlororhodium(I) compound 22 (Scheme 9). After evaporation
of the solvent and extraction of the residue with pentane, the
major product (Z)-21 was isolated as an orange-red solid in
49% yield.
=
would give (E)-RC≡CCH CHR and trans-[RhX(CO)(PiPr3)2].
To explain the formation of the butatrienes, it is conceivable that
in solution intermediate A is in equilibrium with intermediate B
(see the generation of 19 from 18, shown in Scheme 4), which
analogously to A reacts by reductive elimination to produce the
cumulene.
Scheme 7 ([Rh] = Rh(CO)(PiPr3)2).
However, since the reductive elimination of intermediate B can
only lead to the (E)-isomer of the corresponding butatriene and
since at least for the reactions of (Z)-7 with CF3CO2H in benzene
and of (Z)-8 with CF3CO2H in acetone the (Z)-configured
butatriene is the dominant isomer, a second mechanism shown
in Scheme 8 has also to be taken into consideration. We assume
that in particular for the stronger acid CF3CO2H the attack of
the proton can not only occur at the metal centre but also at the
C≡C triple bond.27 The generated cationic butatriene complex
C could subsequently react with the carboxylate anion to give
Scheme 9 (L = PiPr3).
However, if the reaction of 2 with HCl was carried out in
diethyl ether at −40 ◦C, instead of the alkynerhodium(I) complex
(Z)-21 the five-coordinate alkynyl(vinyl)rhodium(III) compound
23 was generated. It was isolated as a red, only moderately air-
sensitive solid that is quite labile and rearranges in benzene at
room temperature to give the isomer (Z)-21 in nearly quantita-
tive yield. In contrast to the 1H NMR spectrum of (Z)-21, which
= = =
trans-[RhX(CO)(PiPr3)2] and (Z)-RCH C C CHR. We note
that the molecular structure of (Z)-9 reveals,12 that the proton
attack at the C≡C triple bond is favoured from the side opposite
to the metal, which could explain why compounds (Z)-7 and
(Z)-8, in the presence of CF3CO2H, predominantly afford the
(Z)- and not the (E)-configured butatriene. Moreover, if we take
results obtained for cleavage reactions of vinyl transition-metal
compounds into account,28 we can not completely exclude that
in the enynyl complexes 7 and 8 or in intermediates such as A
or B an acid-induced isomerization of the metal-bound C4 unit
occurs. However, under the reaction conditions (ratio of starting
material to acid = 1 : 1) this possibility is less likely.
displays the signals for the protons of the vinyl group at d 6.75
1
=
=
(CH CHPh) and 6.45 (CH CHPh), the H NMR spectrum
of 23 shows the resonances for the vinyl protons at d 8.09
=
=
(CH CHPh) and 5.76 (CH CHPh), respectively. Both spectra
display two doublets-of-virtual triplets for the methyl protons
of the isopropyl units thus indicating that the phosphine ligands
are trans-disposed. Although for 23 a trigonal-bipyramidal
structure can not be excluded, we assume that in analogy to
=
five-coordinate [Rh(C≡CMe)2{C(Me) CH2}(PiPr3)2] a square-
pyramidal configuration is preferred.14
Regarding the mechanism of formation of the alkynyl(vinyl)
complex, the initial step probably consists of an attack of the
proton at the metal centre of 2 to give the six-coordinate inter-
= =
mediate [RhH(Cl)(C≡CPh)( C CHPh)(PiPr3)2], which reacts
by migratory insertion of the vinylidene ligand into the Rh–
H bond to produce 23. The observed (Z)-selectivity would
be in agreement with the stereochemistry found for (Z)-7 (see
Scheme 2). The subsequent C–C coupling reaction of 23 to give
(Z)-21 obviously has a low energy of activation since it proceeds
also in the absence of solvent and, under these conditions, is
completed at 60 ◦C in ca. 90 min. To explain the formation
of 22 as a by-product in the reaction of 2 with HCl at room
temperature, it is likely that at room temperature the supposed
Scheme 8 ([Rh] = Rh(CO)(PiPr3)2).
Acid-induced C–C coupling reactions
= =
The observation, that the vinylidene complexes trans-[IrCl( C
= =
intermediate [RhH(Cl)(C≡CPh)( C CHPh)(PiPr3)2] can elim-
CHR)(PiPr3)2] (R = H, Me, Ph) react with HBF4 to give initially
inate phenylacetylene and thus gives the four-coordinate species.
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 7 1

View Article Online
We finally note that treatment of (Z)-21 with CO rapidly leads
to a displacement of the enyne ligand and gives the carbonyl
=
complex 24 and (Z)-PhC≡CCH CHPh.
Under UV-irradiation, compound (Z)-21 is also labile and
rearranges (benzene, 15 ◦C, 30 min) quantitatively to the (E)-
isomer (see Scheme 9). An alternative route to prepare (E)-21
consists of the reaction of the dimeric rhodium(I) complex 25
=
with (E)-PhC≡CCH CHPh that affords the product in almost
quantitative yield. Typical spectroscopic features of (E)-21 are
1
=
the CH CHPh proton resonance in the H NMR spectrum,
=
which appears at lower field than the signal for the CH CHPh
proton, and the size of the corresponding J(H,H) coupling
3
constant that is significantly smaller than for (Z)-21. Similarly
to (Z)-7 and (E)-7, the 13C NMR spectra of (Z)-21 and (E)-21
reveal only minor differences in the chemical shifts and coupling
constants for the resonances of the carbon atoms of the C4 unit.
The “non-substituted” alkynyl(vinylidene) complex 17 reacts
with HCl under the same conditions as applied for the prepara-
tion of 23 to afford the alkynyl(vinyl)rhodium(III) compound 26
in virtually quantitative yield (Scheme 10). The isolated orange
solid is only slightly air-sensitive and readily soluble in most
organic solvents. Diagnostic for the presence of the vinyl ligand
1
are the three resonances in the H NMR spectrum at d 7.29
=
(RhCH), 5.47 and 4.50 (both CH2) which appear as doublets-
1
1
of-doublets-of-doublets-of triplets due to H–1H (twice), H–
103Rh and 1H–31P couplings.
Scheme 11 (L = PiPr3).
vinylic proton in aposition and a multiplet (doublet-of-doublets
31
=
after P-decoupling) at d 6.60 for the CH CHPh proton in b
position. For isomer B, the corresponding resonances appear
at d 7.60 as a doublet-of-doublets-of-triplets and at d 6.32 as a
multiplet (doublet-of-doublets after 31P-decoupling). Since the
=
signal at lower field for the CH CHPh proton shows a relatively
large 2J(Rh,H) coupling constant, we assume that, similarly to
26, the structure of B corresponds to a square-pyramid.
If a solution of (Z)-29 in toluene-d8, containing both isomers
A and B, is irradiated at low temperature, a quantitative
isomerization to (E)-29 occurs. After evaporation of the solvent
in vacuo, the product was isolated as a light yellow, slightly air-
sensitive solid in 94% yield. The 1H and 31P NMR spectra of (E)-
29 reveal that only one isomer is formed, probably containing
the carboxylate as a chelating ligand. Diagnostic for the trans-
Scheme 10 (L = PiPr3).
=
Similarly to compound 23, the five-coordinate complex 26 is
exceedingly labile and rearranges in benzene at room tempera-
ture to give the rhodium vinylidene 28 in 89% yield. However,
if a solution of 26 in toluene-d8 is slowly warmed from −60 ◦C
to −20 ◦C, the formation of intermediate 27 could be detected.
After increasing the temperature, it reacts to form isomer 28.
Both 27 and 28 had already been described in the literature
and were prepared from 25 and vinylacetylene.17 The stepwise
conversion of 26 to 27 and fin◦ally to 28 also occurs in a KBr
disposition of rhodium and the phenyl group at the C C double
bond in (E)-29 is the size of the 1H–1H coupling constant for the
signals of the vinylic protons which is larger by 3 Hz compared
to isomer A of (Z)-29.
In the solid state, both compounds (Z)-29 and (E)-29 are
relatively stable and rearrange very slowly at room temperature
(in 5 to 7 days) to the enyne complexes (Z)-30 and (E)-30.
However, in solution the (Z)-isomer (Z)-29 is significantly more
labile and reacts in benzene at 25 ◦C in 4 h quantitatively to
(Z)-30. Under the same conditions, the rearrangement of (E)-
29 to (E)-30 is much slower and is only completed after 10 h.
Isomer (E)-30 is also accessible either by UV-irradiation of (Z)-
◦
matrix between −40 C and 0 C and can easily be monitored
by IR spectroscopy.
The starting material 2 reacts not only with HCl but also
with CF3CO2H in diethyl ether at −40 ◦C to generate the
alkynyl(vinyl) complex (Z)-29 (Scheme 11). This product is a
yellow, practically air-stable solid for which a correct elemental
analysis has been obtained. The IR-spectrum of (Z)-29 shows
for the asymmetric OCO-stretching mode of the CF3CO2 unit
a characteristic absorption at 1640 cm−1 indicating that the
carboxylate is coordinated to rhodium in a chelating fashion.30
In contrast to the IR spectrum, the 1H NMR spectrum of (Z)-
29 reveals that in solution two isomeric forms A and B exist, one
of which contains the carboxylate as a monodentate ligand. In
toluene-d8 at 233 K, the ratio of A : B is approximately 1 :
1. Typical features for the hexa-coordinate isomer A in the
1H NMR spectrum are a doublet-of-triplets at d 7.79 for the
30 in benzene or upon treatment of the chelate complex 31 with
1
(E)-PhC≡CCH CHPh (see Scheme 11). The H and 13C NMR
=
data for the enyne ligands in (Z)-30 and (E)-30 are very similar
to those of the chloro compounds (Z)-21 and (E)-21 and thus
deserve no forther comment.
The reactions of the alkynyl(vinylidene) complexes 2 and
17 with acetic acid in benzene at room temperature proceed
differently. While the “non-substituted” derivative 17 affords by
protolytic cleavage of the Rh–C≡CH bond the four-coordinate
rhodium vinylidene 32, the phenyl-substituted compound 2
gives, under the same conditions, the chelate complex 33 and the
=
(Z)-configurated enyne (Z)-PhC≡CCH CHPh (Scheme 12).
We assume that in the initial step an oxidative addition of the
1 4 7 2
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
for the corresponding carbon atom (d 204.7 and 218.2) is
observed at rather low field which is in agreement with data
reported for the related iridium compound [IrH(Cl){j2(C,O)-
33
=
=
CH CHC(OMe) O}(PiPr3)2]. We note that a variety of
transition-metal complexes of general composition [M{j2(C,O)-
ꢀ
=
=
CR CHC(R ) O}(L)n] are known and have been prepared
either from low-valent transition-metal precursors and Michael
ꢀ
33,34
=
systems RCH CHC(O)R by C–H activation
or from hy-
dridometal compounds and RC≡CC(O)Rꢀ by insertion of the
activated alkyne into the M–H bond.32,35
The alkynyl(vinyl)rhodium(III) derivatives 34 and 35 are
relatively inert and in benzene at 50 ◦C react rather slowly. While
in the case of 35 only decomposition occurs, the reaction of 34
leads to a mixture of products with the alkyne complex (Z)-36
as the dominating species (see Scheme 13). Attempts to separate
the by-products (which could not be identified) by fractional
crystallization or column chromatography failed. Typical spec-
troscopic features of (Z)-36 are the m(C≡C) absorption in the IR
spectrum at 1860 cm−1 and the resonances for the vinylic protons
1
in the H NMR spectrum at d 6.52 and 5.77, respectively. The
size of the 3J(H,H) coupling constant of these signals (11.8 Hz)
indicates that the vinylic protons are cis-disposed.
Scheme 12 (L = PiPr3).
In contrast to 34 and 35, the acetatorhodium(III) compound
37, being previously prepared either from 6 or [RhH(C≡CCO2-
Me)(j2-O2CMe)(PiPr3)2] as the precursor,31 is more labile. It not
acid to the metal centre of 2 occurs followed by rearrangement
of intermediate D to isomer E. In contrast to (Z)-29, this hexa-
coordinate species is very labile at room temperature and gen-
erates via intramolecular C–C coupling and elimination of the
only reacts with CO to give trans-[Rh(j1-O2CMe)(CO)(PiPr3)2]
13
=
and (E)-EC≡CCH CHE (E = CO2Me), but also affords, in
the presence of chloride ions, the four-coordinate alkyne com-
plex (E)-36 via intramolecular C–C coupling. By using MgCl2
as the chloride source and diethyl ether as the solvent, the yield
of (E)-36, isolated as a red air-stable solid, is 72%. We assume
that in the initial step of the reactions shown in Scheme 14
a displacement of the acetato ligand by chloride occurs and
enyne the acetate complex 33. We note that the four-coordinate
1
= =
compound trans-[Rh(j -O2CMe)( C CHPh)(PiPr3)2], previ-
ously prepared from [RhH(C≡CPh)(j2-O2CMe)(PiPr3)2]31 but
not isolated in the reaction of 2 with acetic acid, also reacts with
=
phenylacetylene to give 33 and (Z)-PhC≡CCH CHPh.
The reaction of the CO2Me-substituted alkynyl(vinylidene)-
rhodium(I) compound 6 with HCl in diethyl ether at low
temperature leads to the formation of complex 34, in which the
substituted vinyl unit acts as a chelating ligand (Scheme 13). In
contrast to the products obtained from 2 or 17 and HCl (which
are orange or red), compound 34 is a white solid, the colour
being typical for hexa-coordinate rhodium(III) derivatives.
=
that the intermediate [RhCl(C≡CE)(CH CHE)(PiPr3)2] (E =
CO2Me), analogously to compounds 23 and 26 (see Schemes 9
and 10), rapidly rearranges to the coupling product.
Scheme 14 (L = PiPr3, E = CO2Me).
Quite surprisingly, the hexa-coordinate alkynyl(vinyl) com-
plex 37 reacts, even at room temperature, also with methyl
propiolate. In contrast to the reaction with CO,13 a white
solid analyzing as 38 is formed instead of the butenyne (E)-
=
EC≡CCH CHE (E = CO2Me). As the X-ray crystal structure
analysis of 38 revealed,13 the metal centre is octahedrally coordi-
nated with the two phosphines in trans position. Noteworthy is
the unsymmetrical coordination of the acetato ligand (distances
˚
Rh–O = 2.151(5) and 2.260(6) A), which is probably due to
the different trans influence of the alkynyl and the butadienyl
group. It is also worth mentioning, that the C4 unit has the
thermodynamically more favoured (E) configuration at both
=
C C double bonds. In agreement with the structure found in
the crystal, the 13C NMR spectrum of 38 displays for the carbon
atoms of the butadienyl ligand four resonances at d 163.6, 148.0,
126.9 and 118.3, which were assigned on the basis of the splitting
patterns and DEPT measurements. Regarding the mechanism
of formation of 38, we assume that initially by partial opening
of the acetate–metal bond one molecule of methyl propiolate is
added to the rhodium centre to generate intermediate F. This
step is followed by a rearrangement of the coordinated terminal
alkyne to the isomeric vinylidene to afford G (Scheme 15).
Subsequent migration of the vinyl unit to the a-carbon atom of
the vinylidene and chelation of the acetate ligand would finally
Scheme 13 (L = PiPr3; E = CO2Me).
Under similar conditions, the starting material 6 also re-
acts with HC≡CCO2Me in neat NEt3 as solvent to af-
ford the rhodium(III) complex 35 with the fragment cis-
Rh(C≡CCO2Me)2 as a molecular building block. Diagnostic for
=
=
the presence of a five-membered MCH CHC(OMe) O chelate
=
ring in both 34 and 35 is the position of the C O stretching
mode in the IR spectrum,32 which appears at 1580 cm−1. In
the H and 13C NMR spectra of 34 and 35, the resonance for
1
the RhCH proton (d 10.14 and 10.45) as well as the signal
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 7 3

View Article Online
yield the product. It should be mentioned that upon treatment
Similarly to the butenyne complex (Z)-21 (see Scheme 9),
compound 39 reacts with CO in benzene readily at room tem-
perature. A rapid ligand substitution occurs which is indicated
by an instantaneous change of colour from deep-red to light
yellow. Equimolar amounts of both the carbonylrhodium(I)
derivative 24 and the hexadienyne 40 are formed in virtually
quantitative yield. The composition of 40 has been substan-
=
= =
of trans-[Rh(CH CH2)( C CHPh)(PiPr3)2] with CO a similar
migratory insertion occurs to give a carbonylrhodium(I) com-
10
=
=
plex with r-bonded C( CHPh)CH CH2 as a ligand.
1
tiated by GC/MS and H NMR spectroscopy. We note that,
in contrast to the reaction of [Ni(CO)2(PPh3)2] with methyl
propiolate,36 in the stepwise rhodium-assisted trimerization of
HC≡CCO2Me no cyclic C6H3(C≡CCO2Me)3 isomer can be
detected. As far as we know, only in the oligomerization of ferro-
cenylethyne, catalyzed by [Ni(CO)2(PPh3)2], a branched trimer
5
5
=
=
(E,E)-FcC≡C–C( CHFc)CH CHFc [Fc = (g -C5H4)Fe(g -
C5H5)], structurally related to 40, is formed apart from the
corresponding butenyne and benzene derivatives.37
Conclusion
The results reported in this paper illustrate that the coupling of
the two carbon-bonded ligands in four-coordinate alkynyl(vinyl-
idene)rhodium(I) complexes can be achieved by two dif-
= =
ferent routes. While treatment of trans-[Rh(C≡CR)( C
CHRꢀ)(PiPr3)2] with CO yields the butenynylrhodium(I) deri-
1
ꢀ
=
vatives trans-[Rh{g -(Z)-C( CHR )C≡CR}(CO)(PiPr3)2] by
migratory insertion of the vinylidene unit into the alkynyl–
metal bond, the same starting materials react with HCl, at low
temperature, to give five-coordinate alkynyl(vinyl)rhodium(III)
compounds which rearrange upon warming to give the alkyne
Scheme 15 (L = PiPr3, E = CO2Me).
In the absence of a further substrate, compound 38 is
thermally stable and even on heating to 60 ◦C does not react
by C–C coupling. However, the coupling of the alkynyl and
butadienyl ligands at rhodium can be achieved if a solution of
38 in diethyl ether is treated with an excess of MgCl2·6H2O and
Na2CO3 and then stirred for 4 h at 40◦C. From the crude reaction
product, a deep-red air-stable solid analyzing as 39 has been
isolated in 79% yield (Scheme 16). Owing to the X-ray crystal
structure analysis of 39,13 the metal centre is coordinated in a
distorted square-planar fashion with the phosphorus, chlorine,
rhodium atoms and the alkyne carbon atom carrying the CO2Me
group lying in the same plane. The second alkyne carbon atom is
located significantly above this plane. However, despite the un-
symmetrical coordination of the RC≡CRꢀ moiety to the metal
centre, the two Rh–C distances are nearly identical. The
butadienyl substituent at the C≡C bond still has the (E,E) con-
figuration which illustrates that during the C–C coupling process
no (E)/(Z) isomerization takes place. In the 1H NMR spectrum
of 39, the resonances of the protons of the C4 substituent are
observed at d 9.10 (doublet), 8.00 (singlet) and 7.40 (doublet)
and are thus shifted to lower field, compared to precursor 38.
2
ꢀ
=
complexes trans-[RhCl{g -(Z)-RC≡CCH CHR }(PiPr3)2].The
= =
reactions of trans-[Rh(C≡CPh)( C CHPh)(PiPr3)2] with car-
boxylic acids RꢀCO2H (Rꢀ CF3, CH3) proceed similarly and
=
afford either the four-coordinate butenynerhodium(I) complex
1
2
=
trans-[Rh(j -O2CCF3){g -(Z)-PhC≡CCH CHPh}(PiPr3)2] or
[Rh(j2-O2CCH3)(PiPr3)2] and free butenyne (Z)-PhC≡C-
=
CH CHPh. An interesting aspect of the reactivity of the
1
=
compounds trans-[Rh{g -(Z)-C( CHR)C≡CR}(CO)(PiPr3)2]
1
=
and trans-[Rh{g -(E)-C( CHR)C≡CR}(CO)(PiPr3)2] (R =
Ph, tBu) is that upon treatment with carboxylic acids RꢀCO2H
=
either the butenyne (Z)/(E)-RC≡CCH CHR or a mixture of
the butenyne and the isomeric butatriene is formed, the ratio
depending on both R and Rꢀ. Another noteworthy result of
this work is that the hexa-coordinate alkynyl(vinyl) complex
2
=
[Rh(j -O2CCH3)(C≡CE)(CH CHE)(PiPr3)2] (E = CO2Me)
reacts with HC≡CE by insertion of the alkyne into the vinyl–
rhodium bond to give the butadienyl–metal derivative [Rh(j2-
1
=
=
O2CMe)(C≡CE){g -(E,E)-C( CHE)CH CHE}(PiPr3)2],
which in the presence of MgCl2 undergoes an intramolecular
2
C–C coupling to yield four-coordinate trans-[RhCl{g -(E,E)-
=
=
EC≡CC( CHE)CH CHE}(PiPr3)2]. The reaction of this
compound with CO generates the formerly unknown branched
=
=
trisubstituted hexadienyne (E,E)-EC≡CC( CHE)CH CHE,
formally built up by three alkyne molecules HC≡CE.
Experimental
All experiments were carried out under an atmosphere of argon
by Schlenk techniques. The starting materials 2, 5, 6,14 10,38 11,
13, 14, 17,14 2539 and 3140 were prepared as described in the
literature. NMR spectra were recorded at room temperature (if
not otherwise stated) on Jeol FX 90 Q, Bruker AC 200 and
Bruker AMX 400 instruments. IR spectra were recorded on a
IFS 25 FT-IR infrared spectrometer, and mass spectra on a
Finnigan 90 MAT instrument. Melting points were measured
by differential thermal analysis (DTA) with a Thermoanalyzer
Du Pont 900. Abbreviations used: s, singlet; d, doublet; t, triplet;
q, quartet; vt, virtual triplet; m, multiplet; br, broadened signal;
3
5
coupling constants J and N in Hz; N = J(PH) + J(PH) or
4
Scheme 16 (L = PiPr3, E = CO2Me).
2J(PC) + J(PC).
1 4 7 4
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
Preparations
grade V, height of column 5 cm). With hexane/toluene (5 : 1)
an orange fraction was eluted which was brought to dryness
in vacuo. The residue was recrystallized from pentane to give
orange, air-stable crystals: yield 47 mg (59%).
1
=
trans-[Rh{g -(Z)-C( CHPh)C≡CPh}(CO)(PiPr3)2] (Z)-7.
A slow stream of CO was passed through a solution of 2
(123 mg, 0.20 mmol) in pentane (10 cm3) at −40 ◦C. A smooth
change of colour from blue-green to yellow occurred. After the
solution was stirred for 5 min, it was concentrated in vacuo
to ca. 2 cm3 and then stored at −78 ◦C for 5 days. A pale
yellow solid precipitated, which was separated from the mother
liquor, washed twice with 0.5 cm3 portions of pentane (−20 ◦C)
Method b. A solution of 10 (141 mg, 0.32 mmol) in benzene
(5 cm3) was treated with PhC≡CC≡CPh (38 mg, 0.19 mmol) and
stirred for 4 h at room temperature. The solvent was evaporated
in vacuo, and the residue was extracted with pentane (25 cm3).
The extract was brought to dryness in vacuo, the remaining
orange residue was washed three times with 2 cm3 portions of
pentane and dried: yield 155 mg (75%); mp 108 ◦C (Found:
C, 64.42; H, 8.45. C35H53OP2Rh requires C, 64.21; H, 8.16%).
IR (hexane): (C≡C) 2120, (CO) 1945 cm−1. NMR (C6D6): dH
(200 MHz) 8.12, 7.57 (2 H each, both m, ortho-H of C6H5),
7.28, 7.12, 7.03 (2 H each, all m, meta- and para-H of C6H5),
◦
and dried: yield 100 mg (78%); mp 138 C (decomp.) (Found:
C, 64.35; H, 8.62. C35H53OP2Rh requires C, 64.21; H, 8.16%).
IR (hexane): (C≡C) 2155, (CO) 1945 cm−1. NMR (C6D6): dH
(90 MHz) 8.61, 7.53 (2 H each, both m, ortho-H of C6H5), 8.02
=
[1 H, dt, J(Rh,H) = 2.4, J(P,H) = 2.3 Hz, CHPh], 7.31 − 6.93
(6 H, br m, meta- and para-H of C6H5), 2.37 (6 H, m, PCHCH3),
1.33 [18 H, dvt, N = 13.9, J(H,H) = 7.1 Hz, PCHCH3], 1.08 [18
H, dvt, N = 13.2, J(H,H) = 7.0 Hz, PCHCH3]; dC (100.6 MHz)
195.8 [dt, J(Rh,C) = 55.8, J(P,C) = 15.5 Hz, RhCO], 159.7 [dt,
=
6.91 [1 H, dt, J(Rh,H) = 1.8, J(P,H) = 1.8 Hz, CHPh], 2.38
(6 H, m, PCHCH3), 1.31 [18 H, dvt, N = 13.3, J(H,H) =
6.8 Hz, PCHCH3], 1.27 [18 H, dvt, N = 13.5, J(H,H) = 6.8 Hz,
PCHCH3]; dC (100.6 MHz) 196.5 [dt, J(Rh,C) = 57.2, J(P,C) =
14.8 Hz, RhCO], 152.1 [dt, J(Rh,C) = 26.9, J(P,C) = 14.3 Hz,
=
J(Rh,C) = 28.4, J(P,C) = 14.2 Hz, RhC C], 146.4 [t, J(P,C) =
=
4.3 Hz, CHPh], 143.8 [d, J(Rh,C) = 1.9 Hz, ipso-C of CHPh],
=
=
RhC C], 144.4 [t, J(P,C) = 5.0 Hz, CHPh], 141.1 [br d,
J(Rh,C) = 2.4 Hz, ipso-C of CHPh], 130.8, 128.7, 128.6, 128.5,
127.4, 126.7, 125.6 (all s, C6H5), 106.0 (s, C≡CPh), 98.0 (s,
C≡CPh), 26.2 (vt, N = 19.6 Hz, PCHCH3), 20.5, 20.4 (both s,
PCHCH3); dP (162.0 MHz) 45.1 [d, J(Rh,P) = 140.7 Hz].
131.1, 129.3, 128.5, 127.8, 127.5, 126.5, 125.9 (all s, C6H5), 102.6
[t, J(P,C) = 1.9 Hz, C≡CPh], 97.5 (s, C≡CPh), 26.4 (vt, N =
20.3 Hz, PCHCH3), 20.8, 19.8 (both s, PCHCH3); dP (36.2 MHz)
43.1 [d, J(Rh,P) = 139.2 Hz].
1
=
trans-[Rh{g -(Z)-C( CHtBu)C≡CtBu}(CO)(PiPr3)2] (Z)-8.
1
=
trans-[Rh{g -(E)-C( CHtBu)C≡CtBu}(CO)(PiPr3)2] (E)-8.
This compound was prepared as described for (Z)-7, from 5
(120 mg, 0.20 mmol) and CO in diethyl ether (5 cm3). Yellow
microcrystalline solid: yield 102 mg (81%); mp 94 ◦C (decomp.)
(Found: C, 60.54; H, 10.26. C31H61OP2Rh requires C, 60.58;
H, 10.00%). IR (KBr): (C≡C) 2160, (CO) 1930 cm−1. NMR
(C6D6): dH (400 MHz) 6.81 [1 H, dt, J(Rh,H) = 2.3, J(P,H) =
Method a. Analogously as described for (E)-7, method a),
from (Z)-8 (60 mg, 0.10 mmol) in C6D6 (0.5 cm3); time of
irradiation 2 h. Yellow microcrystalline solid: yield 45 mg (74%).
Method b. A solution of (Z)-8 (60 mg, 0.10 mmol) in benzene
(2 cm3) was stirred for 6 h at 40 ◦C. After the solution was cooled
to room temperature, the solvent was evaporated in vacuo. The
residue was dissolved in pentane (1 cm3) and the solution was
stored for 12 h at −78 ◦C. Yellow air-stable crystals precipitated,
which were separated from the mother liquor, washed twice with
0.5 cm3 portions of pentane (−20 ◦C) and dried; yield 52 mg
(86%); mp 88 ◦C (Found: C, 60.24; H, 10.20. C31H61OP2Rh
requires C, 60.58; H, 10.00%). IR (KBr): (C≡C) 2175, (CO)
1930 cm−1. NMR (C6D6): dH (400 MHz) 5.44 [1 H, dt, J(Rh,H) =
=
2.2 Hz, CHtBu], 2.46 (6 H, m, PCHCH3), 1.33 [18 H, dvt,
N = 13.1, J(H,H) = 7.0 Hz, PCHCH3], 1.32 [18 H, dvt, N =
13.4, J(H,H) = 7.1 Hz, PCHCH3], 1.29, 1.28 (9 H each, both s,
CCH3); dC (50.3 MHz) 196.2 [dt, J(Rh,C) = 55.6, J(P,C) =
=
16.5 Hz, RhCO], 155.2 [t, J(P,C) = 4.5 Hz, CHtBu], 143.2 [dt,
=
=
J(Rh,C) 27.4, J(P,C) = 13.7 Hz, RhC C], 100.6 (s, C≡CtBu),
90.2 [td, J(P,C) = 1.8, J(Rh,C) = 1.3 Hz, C≡CtBu], 34.3 [td,
=
J(P,C) = 1.3, J(Rh,C) = 1.0 Hz, CHCCH3], 32.0 (s, ≡CCCH3),
=
31.2 [t, J(P,C) = 1.8 Hz, CHCCH3], 28.8 (s, ≡CCCH3), 26.4
=
1.9, J(P,H) = 1.9 Hz, CHtBu], 2.44 (6 H, m, PCHCH3), 1.36
[dvt, N = 18.9, J(Rh,C) = 1.0 Hz, PCHCH3], 20.9, 20.3 (both s,
=
(9 H, s, CHCCH3), 1.33 [18 H, dvt, N = 13.5, J(H,H) =
PCHCH3); dP (162.0 MHz) 40.8 [d, J(Rh,P) = 143.7 Hz].
7.1 Hz, PCHCH3], 1.31 [18 H, dvt, N = 12.8, J(H,H) = 7.1 Hz,
PCHCH3], 1.28 (9 H, s, ≡CCCH3); dC (100.6 MHz) 196.4 [dt,
J(Rh,C) = 56.4, J(P,C) = 15.1 Hz, RhCO], 150.7 [t, J(P,C) =
1
=
trans-[Rh{g -(Z)-C( CHCO2Me)C≡CCO2Me}(CO)(PiPr3)2]
(Z)-9. This compound was prepared as described for (Z)-7,
from 6 (98 mg, 0.17 mmol) and CO in pentane (10 cm3).
=
5.0 Hz, CHtBu], 145.9 [dt, J(Rh,C) = 26.2, J(P,C) = 13.9 Hz,
◦
=
RhC C], 112.3 (s, C≡CtBu), 85.6 [td, J(P,C) = 1.9, J(Rh,C) =
Light yellow, air-stable crystals: yield 84 mg (82%); mp 85 C
1.0 Hz, C≡CtBu], 36.1 [dt, J(Rh,C) = 1.1, J(P,C) = 1.0 Hz,
(decomp.) (Found: C, 52.46; H, 7.91. C27H49O5P2Rh requires C,
52.43; H, 7.98%). IR (hexane): (C≡C) 2155, (CO) 1955 cm−1.
NMR (C6D6): dH (200 MHz) 7.21 [1 H, td, J(P,H) = 2.7,
=
=
CHCCH3], 31.4 (s, ≡CCCH3), 30.7 [t, J(P,C) = 1.2 Hz,
CHCCH3], 29.2 (s, ≡CCCH3), 25.8 [dvt, N = 19.5, J(Rh,C) =
1.4 Hz, PCHCH3], 20.8, 20.4 (both s, PCHCH3); dP (162.0 MHz)
44.5 [d, J(Rh,P) = 145.9 Hz].
=
=
J(Rh,H) = 2.6 Hz, CHCO2Me], 3.51 (3 H, s, CHCO2CH3),
3.34 (3 H, s, ≡CCO2CH3), 2.23 (6 H, m, PCHCH3), 1.35 [18 H,
dvt, N = 14.0, J(H,H) = 7.1 Hz, PCHCH3], 1.13 [18 H, dvt,
N = 13.3, J(H,H) = 7.0 Hz, PCHCH3]; dC (50.3 MHz) 196.3 [dt,
J(Rh,C) = 57.8, J(P,C) = 15.6 Hz, RhCO], 186.6 [dt, J(Rh,C) =
1
=
trans-[Rh{g -C( CH2)C≡CPh}(CO)(PiPr3)2] 12. This com-
pound was prepared as described for (Z)-7, from 11 (97 mg,
0.18 mmol) and CO in pentane (5 cm3). Pale yellow, air-stable
crystals: yield 84 mg (82%); mp 93 ◦C (decomp.) (Found: C,
60.54; H, 8.49. C29H49OP2Rh requires C, 60.20; H, 8.54%).
MS (70 eV): m/z 578 (M+). IR (hexane): (C≡C) 2150, (CO)
1940 cm−1. NMR (C6D6): dH (400 MHz) 7.53 (2 H, m, ortho-H
of C6H5), 7.09 (2 H, m, meta-H of C6H5), 6.97 (1 H, m, para-H
of C6H5), 6.69 [1 H, ddt, J(H,H) = 4.9, J(Rh,H) = 2.8, J(P,H) =
=
27.8, J(P,C) = 13.9 Hz, RhC C], 169.7 [dt, J(Rh,C) = 1.9,
=
J(P,C) = 1.4 Hz, CHCO2CH3], 155.6 (s, ≡CCO2CH3), 135.1
=
[td, J(P,C) = 3.9, J(Rh,C) = 1.9 Hz, CHCO2CH3], 100.4 (s,
C≡CCO2CH3), 96.6 [t, J(P,C) = 1.6 Hz, C≡CCO2CH3], 51.5 (s,
=
C≡CCO2CH3), 50.7 (br s, CHCO2CH3), 26.4 [dvt, N = 20.4,
J(Rh,C) = 1.4 Hz, PCHCH3], 20.5, 19.5 (both s, PCHCH3); dP
(162.0 MHz) 44.1 [d, J(Rh,P) = 136.3 Hz].
=
2.6 Hz, one H of CH2 trans to Rh], 5.57 [1 H, dtd, J(H,H) =
1
=
=
trans-[Rh{g -(E)-C( CHPh)C≡CPh}(CO)(PiPr3 )2 ] (E)-7.
4.9, J(P,H) = 2.1, J(Rh,H) = 1.5 Hz, one H of CH2 cis to Rh],
Method a. A solution of (Z)-7 (80 mg, 0.12 mmol) in C6D6
(0.5 cm3) was irradiated at 15 ◦C with a UV lamp (Osram 500 W,
water filter, k = 300 nm) for 5 h. A change of colour from light
yellow to orange-brown occurred. After the solvent was evapo-
rated in vacuo, the oily residue was dissolved in hexane (1 cm3)
and the solution was chromatographed on Al2O3 (basic, activity
2.42 (6 H, m, PCHCH3), 1.33 [18 H, dvt, N = 13.1, J(H,H) =
6.8 Hz, PCHCH3], 1.30 [18 H, dvt, N = 13.3, J(H,H) = 6.9 Hz,
PCHCH3]; dC (100.6 MHz) 196.7 [dt, J(Rh,C) = 56.7, J(P,C) =
14.7 Hz, RhCO], 159.9 [dt, J(Rh,C) = 27.6, J(P,C) = 14.6 Hz,
=
=
RhC C], 130.3 [t, J(P,C) = 4.8 Hz, CH2], 131.0, 128.5, 127.5,
126.4 (all s, C6H5), 100.8 [t, J(P,C) = 1.8 Hz, C≡CPh], 95.8
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 7 5

View Article Online
=
(s, C≡CPh), 26.1 (vt, N = 20.0 Hz, PCHCH3), 20.6, 20.3 (both s,
PCHCH3); dP (162.0 MHz) 46.5 [d, J(Rh,P) = 140.4 Hz].
1.2 Hz, one H of CH2], 5.23 [1 H, ddtd, J(H,H) = 10.5 and
=
5.2, J(P,H) = 2.1, J(Rh,H) = 1.5 Hz, one H of CH2], 2.24
(6 H, m, PCHCH3), 1.22 [36 H, dvt, N = 13.8, J(H,H) =
7.0 Hz, PCHCH3]; dC (100.6 MHz) 196.9 [dt, J(Rh,C) = 58.1,
J(P,C) = 13.8 Hz, RhCO], 185.9 [td, J(P,C) = 3.9, J(Rh,C) =
1
=
trans-[Rh{g -(Z )-C( CHCO2Me)C≡CPh}(CO)(PiPr3 )2 ]
(Z)-15. This compound was prepared as described for (Z)-7,
from 13 (192 mg, 0.33 mmol) and CO in pentane (10 cm3) at
−40 ◦C. Yellow air-stable crystals: yield 159 mg (75%); mp
126 ◦C (Found: C, 58.78; H, 8.21. C31H51O3P2Rh requires C,
58.49; H, 8.07%). IR (KBr): (C≡C) 2150, (CO) 1935 cm−1.
NMR (C6D6): dH (400 MHz) 7.43 (2 H, m, ortho-H of C6H5),
=
= =
1.9 Hz, RhCH C], 162.6 [t, J(P,C) = 4.8 Hz, RhCH C C],
154.3 [dt, J(Rh,C) = 27.7, J(P,C) = 17.2 Hz, RhCH], 84.8 [t,
=
J(P,C) = 3.3 Hz, CH2], 25.8 [vt, N = 20.7 Hz, PCHCH3], 20.2
(s, PCHCH3); dP (162.0 MHz) 50.3 [d, J(Rh,P) = 136.6 Hz].
=
7.35 [1 H, dt, J(Rh,H) = 2.4, J(P,H) = 2.4 Hz, CHCO2Me],
=
Generation of trans-[Rh(C≡CCH CH2)(CO)(PiPr3)2] 20.
7.06 (2 H, m, meta-H of C6H5), 6.97 (1 H, m, para-H of C6H5),
3.59 (3 H, s, CO2CH3), 2.31 (6 H, m, PCHCH3), 1.38 [18 H, dvt,
N = 13.8, J(H,H) = 7.1 Hz, PCHCH3], 1.20 [18 H, dvt, N =
13.2, J(H,H) = 7.0 Hz, PCHCH3]; dC (100.6 MHz) 196.9 [dt,
J(Rh,C) = 56.7, J(P,C) = 15.6 Hz, RhCO], 191.6 [dt, J(Rh,C) =
A solution containing a mixture of 18◦and 19 (51 mg, 0.10 mmol)
in C6D6 (0.5 cm3) was irradiated at 15 C with a UV lamp (Osram
500 W, water filter, k > 300 nm) for 45 min. The NMR spectra
indicate that besides some unidentified by-products compound
20 was formed as the dominant species: yield ca. 70%. Data for
20: NMR (C6D6): dH (400 MHz) 6.08 [1 H, ddt, J(H,H) = 17.3
=
28.4, J(P,C) = 14.0 Hz, RhC C], 170.4 [dt, J(Rh,C) = 1.4,
J(P,C) = 1.4 Hz, CO2CH3], 134.0 [td, J(P,C) = 3.7, J(Rh,C) =
=
and 10.7, J(P,H) = 1.9 Hz, CH CH2], 5.35 [1 H, ddt, J(H,H) =
=
1.0 Hz, CHCO2CH3], 131.3, 128.6, 127.5, 126.3 (all s, C6H5),
=
17.3 and 3.0, J(P,H) = 1.0 Hz, one H of CH2], 4.99 [1 H,
106.3 (s, C≡CPh), 99.4 [t, J(P,C) = 1.6 Hz, C≡CPh], 50.5 (s,
CO2CH3), 26.4 [dvt, N = 20.0, J(Rh,C) = 1.3 Hz, PCHCH3],
20.7, 19.7 (both s, PCHCH3); dP (162.0 MHz) 43.9 [d, J(Rh,P) =
140.0 Hz].
=
ddt, J(H,H) = 10.7 and 3.0, J(P,H) = 0.7 Hz, one H of CH2],
2.46 (6 H, m, PCHCH3), 1.31 [36 H, dvt, N = 13.8, J(H,H) =
7.1 Hz, PCHCH3]; dC (100.6 MHz) 196.5 [dt, J(Rh,C) = 58.4,
J(P,C) = 13.6 Hz, RhCO], 126.3 [dt, J(Rh,C) = 41.3, J(P,C) =
=
22.7 Hz, RhC≡C], 121.9 (br s, CH CH2), 119.3 [dt, J(Rh,C) =
1
=
trans-[Rh{g -(Z )-C( CHCO2Me)C≡CtBu}(CO)(PiPr3 )2]
12.6, J(P,C) = 3.2 Hz, RhC≡C], 117.8 [t, J(P,C) = 2.6 Hz,
(Z )-16. This compound was prepared as described for (Z)-7,
from 14 (117 mg, 0.22 mmol) and CO in pentane (10 cm3) at
−40 ◦C. Yellow air-stable crystals: yield 104 mg (85%); mp
121 ◦C (Found: C, 56.58; H, 9.11. C29H55O3P2Rh requires C,
56.49; H, 8.99%). IR (hexane): (CO) 1940 cm−1. NMR (C6D6):
dH (400 MHz) 7.25 [1 H, dt, J(Rh,H) = 2.4, J(P,H) = 2.4 Hz,
=
CH2], 26.3 [vt, N = 22.3 Hz, PCHCH3], 20.5 (s, PCHCH3); dP
(162.0 MHz) 54.0 [d, J(Rh,P) = 127.5 Hz].
Reaction of (E)-7 with carboxylic acids.
Method a. A solution of (E)-7 (39 mg, 0.06 mmol) in C6D6
(0.5 cm3) was treated with acetic acid (0.0034 cm3, 0.06 mmol)
and stirred for 10 min at room temperature. The NMR spectra
revealed that besides trans-[Rh(j1-O2CCH3)(CO)(PiPr3)2]19 the
=
CHCO2Me], 3.56 (3 H, s, CO2CH3), 2.31 (6 H, m, PCHCH3),
1.40 [18 H, dvt, N = 13.8, J(H,H) = 7.1 Hz, PCHCH3], 1.23
(9 H, s, CCH3), 1.22 [18 H, dvt, N = 13.1, J(H,H) = 7.0 Hz,
PCHCH3]; dC (100.6 MHz) 197.0 [dt, J(Rh,C) = 56.2, J(P,C) =
15.8 Hz, RhCO], 194.1 [dt, J(Rh,C) = 28.7, J(P,C) = 14.3 Hz,
=
butenyne (Z)-PhC≡CCH CHPh was exclusively formed. It
was characterized by comparison of the NMR data with those
reported in the literature.5,20
=
RhC C], 170.5 [dt, J(Rh,C) = 1.4, J(P,C) = 1.4 Hz, CO2CH3],
Method b. A solution of (E)-7 (39 mg, 0.06 mmol) in acetone-
d6 (0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 10 min at room temperature. The NMR spectra
=
133.6 [td, J(P,C) = 3.8, J(Rh,C) = 1.0 Hz, CHCO2CH3],
113.6 (s, C≡CtBu), 89.4 [t, J(P,C) = 1.6 Hz, C≡CtBu], 50.3 (s,
CO2CH3), 31.3 (s, CCH3), 29.0 (s, CCH3), 26.4 [dvt, N = 19.9,
J(Rh,C) = 1.4 Hz, PCHCH3], 20.8, 19.8 (both s, PCHCH3); dP
(162.0 MHz) 43.9 [d, J(Rh,P) = 141.6 Hz].
revealed that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19
a
= = =
mixture of (E)/(Z)-PhCH C C CHPh (ca. 95%, ratio of
=
(E)/(Z) = 9 : 1) and (Z)-PhC≡CCH CHPh (ca. 5%) was
1
=
formed. The isomeric butatrienes were characterized by com-
parison of the NMR data with those reported in the literature.7
trans-[Rh{g -C( CH2)C≡CH}(CO)(PiPr3)2] 18. This com-
pound was prepared as described for (Z)-7, from 17 (80 mg,
0.17 mmol) and CO in pentane (4 cm3) at −78 ◦C. Yellow,
moderately air-stable crystals: yield 71 mg (84%); mp 90 ◦C
(decomp.) (Found: C, 55.35; H, 9.28. C23H45OP2Rh requires
C, 54.98; H, 9.03%). IR (KBr): m(≡CH) 3305, m(C≡C) 2055,
(CO) 1935 cm−1. NMR (toluene-d8, −20 ◦C): dH (400 MHz)
6.66 [1 H, ddt, J(H,H) = 5.0, J(Rh,H) = 2.8, J(P,H) = 2.1 Hz,
Reaction of (Z)-7 with CF3CO2H.
Method a. A solution of (Z)-7 (39 mg, 0.06 mmol) in C6D6
(0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 30 min at 40 ◦C. The NMR spectra revealed
that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19 a mixture of
= = =
(E)/(Z)-PhCH C C CHPh (ca. 90%, ratio of (E)/(Z) = 1 : 4)
=
one H of CH2 trans to Rh], 5.52 [1 H, ddt, J(H,H) = 5.0,
=
and (E)-PhC≡CCH CHPh (ca. 10%) was formed. The organic
=
J(Rh,H) = 2.2, J(P,H) = 2.1 Hz, one H of CH2 cis to Rh],
products were characterized by comparison of the NMR data
with those reported in the literature.5,20,21
3.41 (s, C≡CH), 2.24 (6 H, m, PCHCH3), 1.31 [18 H, dvt,
N = 13.3, J(H,H) = 7.0 Hz, PCHCH3], 1.28 [18 H, dvt, N =
13.8, J(H,H) = 7.2 Hz, PCHCH3]; dC (100.6 MHz) 196.6 [dt,
J(Rh,C) = 56.3, J(P,C) = 14.8 Hz, RhCO], 159.7 [dt, J(Rh,C) =
Method b. A solution of (Z)-7 (39 mg, 0.06 mmol) in acetone-
d6 (0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 20 min at room temperature. The NMR spectra
=
27.6, J(P,C) = 15.0 Hz, RhC C], 132.2 [t, J(P,C) = 4.7 Hz,
revealed that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19
a
=
CH2], 94.6 [t, J(P,C) = 1.8 Hz, C≡CH], 82.2 (s, C≡CH), 26.1
= = =
mixture of (E)/(Z)-PhCH C C CHPh (ca. 95%, ratio of
[vt, N = 20.0 Hz, PCHCH3], 20.6, 20.4 (both s, PCHCH3); dP
(162.0 MHz) 46.9 [d, J(Rh,P) = 139.8 Hz]. Note: The NMR
spectra measured at room temperature display also some signals
assigned to 19.
=
(E)/(Z) = 45 : 55) and (Z)-PhC≡CCH CHPh (ca. 5%) was
formed. The organic products were characterized by comparison
of the NMR data with those reported in the literature.5,7,20,21
1
Reaction of (E)-8 with carboxylic acids.
= = =
Isomerization of 18 to trans-[Rh(g -CH C C CH2)(CO)-
(PiPr3)2] 19. A solution of 18, generated from 17 (51 mg,
0.11 mmol) and CO in toluene-d8 (0.5 cm3) at −78 ◦C, was slowly
warmed to room temperature. The NMR spectra indicate that a
mixture of 18 and 19 in the ratio 65 : 35 is formed. Data for 19:
NMR (toluene-d8): dH (400 MHz) 7.93 [1 H, ddtd, J(Rh,H) =
3.8, J(P,H) = 4.2, J(H,H) = 10.5 and 10.7 Hz, RhCH], 5.45
[1 H, dddt, J(H,H) = 10.7 and 5.2, J(P,H) = 1.9, J(Rh,H) =
Method a. A solution of (E)-8 (37 mg, 0.06 mmol) in
C6D6 (0.5 cm3) was treated with acetic acid (0.0034 cm3,
0.06 mmol) and stirred for 2 h at 40 ◦C. The NMR spectra
revealed that besides trans-[Rh(j1-O2CCH3)(CO)(PiPr3)2]19
a
= = =
mixture of (E)/(Z)-tBuCH C C CHtBu (ca. 65%, ratio of
=
(E)/(Z) = 15 : 85) and (Z)-tBuC≡CCH CHtBu (ca. 35%)
was formed. The butenyne5,22,23 and the isomeric butatrienes24,25
1 4 7 6
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
=
were characterized by comparison of the NMR data with those
reported in the literature.
Method b. A solution of (E)-8 (37 mg, 0.06 mmol) in C6D6
(0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 5 min at room temperature. The NMR spectra
dd, J(H,H) = 12.4, J(P,H) = 1.5 Hz, CH CHPh], 6.45 [1 H, d,
=
J(H,H) = 12.4 Hz, CH CHPh], 2.37 (6 H, m, PCHCH3), 1.31
[18 H, dvt, N = 13.3, J(H,H) = 6.8 Hz, PCHCH3], 1.17 [18 H,
dvt, N = 12.6, J(H,H) = 7.0 Hz, PCHCH3]; dC (100.6 MHz)
=
137.7 (s, ipso-C of C6H5), 133.7 (s, CH CHPh), 130.7, 129.6,
revealed that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19
a
129.4, 128.5, 127.6, 127.4, 126.9 (all s, C6H5), 119.5 [d, J(Rh,C) =
= = =
=
mixture of (E)/(Z)-tBuCH C C CHtBu (ca. 20%, ratio of
1.9 Hz, CH CHPh], 91.7 [dt, J(Rh,C) = 17.1, J(P,C) = 3.0 Hz,
=
(E)/(Z) = 7 : 3) and (Z)-tBuC≡CCH CHtBu (ca. 80%) was
PhC≡C], 78.5 [d, J(Rh,C) = 12.8 Hz, PhC≡C], 23.3 (vt, N =
17.3 Hz, PCHCH3), 20.8, 19.9 (both s, PCHCH3); dP (36.2 MHz)
32.0 [d, J(Rh,P) = 118.7 Hz].
formed. The butenyne5,22,23 and the isomeric butatrienes24,25 were
characterized by comparison of the NMR data with those
reported in the literature.
2
=
trans-[RhCl{g -(E)-PhC≡CCH CHPh}(PiPr3)2] (E)-21.
Method c. A solution of (E)-8 (37 mg, 0.06 mmol) in acetone-
d6 (0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 5 min at room temperature. The NMR spectra
Method a. A solution of (Z)-21 (77 mg, 0.12 mmol) in
benzene (2 cm3) was irradiated with a UV lamp (Osram 500 W,
water filter, k > 300 nm) at 17 ◦C. The 31P NMR spectrum
revealed that after 30 min a quantitative isomerization had taken
place. The solvent was evaporated in vacuo and the residue was
recrystallized from pentane at −78 ◦C to give an orange-red
microcrystalline solid: yield 62 mg (87%).
revealed that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19
a
= = =
mixture of (E)/(Z)-tBuCH C C CHtBu (ca. 65%, ratio of
=
(E)/(Z) = 85 : 15) and (Z)-tBuC≡CCH CHtBu (ca. 35%)
was formed. The butenyne5,22,23 and the isomeric butatrienes24,25
were characterized by comparison of the NMR data with those
reported in the literature.
Method b. A solution of 25 (73 mg, 0.08 mmol) in diethyl
3
=
ether (4 cm ) was treated with (E)-PhC≡CCH CHPh (32.5 mg,
Reaction of (Z)-8 with carboxylic acids.
0.16 mmol) and stirred for 5 min at room temperature. A quick
change of colour from deep violet to orange-red occurred. The
solution was worked-up as ◦described for a). Orange-red solid:
yield 94 mg (89%); mp 147 C (decomp.) (Found: C, 61.35; H,
8.59. C34H54ClP2Rh requires C, 61.58; H, 8.21%). IR (KBr):
(C≡C) 1830 cm−1. NMR (C6D6): dH (90 MHz) 8.15, 7.47 (2 H
Method a. A solution of (Z)-8 (37 mg, 0.06 mmol) in C6D6
(0.5 cm3) was treated with acetic acid (0.0034 cm3, 0.06 mmol)
and stirred for 2 h at 40 ◦C. The NMR spectra revealed
that besides trans-[Rh(j1-O2CCH3)(CO)(PiPr3)2]19 a mixture of
= = =
(E)/(Z)-tBuCH C C CHtBu (ca. 40%, ratio of (E)/(Z) =
=
=
4 : 1) and (E)-tBuC≡CCH CHtBu (ca. 60%) was formed. The
each, m, ortho-H of C6H5), 7.54 [1 H, d, J(H,H)
15.6 Hz,
butenyne5,22,23 and the isomeric butatrienes24 were characterized
by comparison of the NMR data with those reported in the
literature.
CH CHPh], 7.21 − 7.04 (6 H, br m, meta- and para-H of C6H5),
=
=
6.99 [1 H, dd, J(H,H) = 15.6, J(Rh,H) = 1.7 Hz, CH CHPh],
2.32 (6 H, m, PCHCH3), 1.28 [18 H, dvt, N = 13.4, J(H,H) =
6.8 Hz, PCHCH3], 1.22 [18 H, dvt, N = 13.2, J(H,H) = 6.7 Hz,
PCHCH3]; dC (100.6 MHz) 138.3 (s, ipso-C of C6H5), 135.2
Method b. A solution of (Z)-8 (37 mg, 0.06 mmol) in C6D6
(0.5 cm3) was treated with CF3CO2H (0.0047 cm3, 0.06 mmol)
and stirred for 5 min at room temperature. The NMR spectra
=
(s, CH CHPh), 131.0, 130.8, 129.2, 128.1, 127.7, 126.8, 126.3
revealed that besides trans-[Rh(j1-O2CCF3)(CO)(PiPr3)2]19
a
(all s, C6H5), 117.1 (s, CH CHPh), 89.5 [dt, J(Rh,C) = 17.2,
=
= = =
mixture of (E)/(Z)-tBuCH C C CHtBu (ca. 75%, ratio of
J(P,C) = 3.7 Hz, PhC≡C], 82.4 [dt, J(Rh,C) = 16.1, J(P,C) =
2.1 Hz, PhC≡C], 24.1 (vt, N = 17.6 Hz, PCHCH3), 20.9, 20.4
(both s, PCHCH3); dP (162.0 MHz) 33.4 [d, J(Rh,P) = 116.0 Hz].
=
(E)/(Z) = 55 : 45) and (E)-tBuC≡CCH CHtBu (ca. 25%)
was formed. The butenyne5,22,23 and the isomeric butatrienes24
were characterized by comparison of the NMR data with those
reported in the literature.
=
[RhCl(C≡CPh){(Z)-CH CHPh}(PiPr3)2] 23.
A
slow
stream of gaseous HCl was passed over the so◦lution of 2
(140 mg, 0.22 mmol) in diethyl ether (5 cm3) at −40 C. As soon
as the colour of the solution changed from blue-green to bright
red, the volatiles were evaporated in vacuo. The remaining ◦red
solid was washed twice with 2 cm3 portions of pentane (−20 C)
and dried; yield 130 mg (88%); converting temperature to
(Z)-21 65 ◦C (Found: C, 61.90; H, 7.89. C34H54ClP2Rh requires
C, 61.58; H, 8.21%). IR (KBr): (C≡C) 2075 cm−1. NMR
(toluene-d8, 233 K): dH (400 MHz) 8.19, 7.47 (2 H each, both m,
Method c. A suspension of (Z)-8 (37 mg, 0.06 mmol) in ace-
tone-d6 (0.5 cm3) was treated with CF3CO2H (0.0047 cm3,
0.06 mmol) and stirred for 2 h at room temperature. The
NMR spectra revealed that besides trans-[Rh(j1-O2CCF3)-
(CO)(PiPr3)2]19 a mixture of (E)/(Z)-tBuCH C C CHtBu
= = =
=
(> 95%, ratio of (E)/(Z) = 3 : 7) and (E)-tBuC≡CCH CHtBu
(< 5%) was formed. The butenyne5,22,23 and the isomeric
butatrienes24 were characterized by comparison of the NMR
data with those reported in the literature.
1
31
ortho-H of C6H5), 8.09 [1 H, m, dd in H{ P}, J(H,H) = 4.8,
2
=
=
J(Rh,H) = 4.6 Hz, CH CHPh], 7.19 − 6.93 (6 H, br m, meta-
1 31
trans-[RhCl{g -(Z)-PhC≡CCH CHPh}(PiPr3)2] (Z)-21.
Method a. A solution of 2 (102 mg, 0.16 mmol) in benzene
(2 cm3) was treated dropwise with a 0.35 M solution of HCl
in benzene (0.46 cm3, 0.16 mmol), and the mixture was stirred
for 3 h at room temperature. The 31P NMR spectrum indicated
that besides some decomposition products a mixture of (Z)-
and para-H of C6H5), 5.76 [1 H, m, dd in H{ P}, J(Rh,H) =
=
4.8, J(H,H) = 4.8 Hz, CH CHPh], 2.95 (6 H, m, PCHCH3),
1.13 [18 H, dvt, N = 13.5, J(H,H) = 7.1 Hz, PCHCH3], 1.09 [18
H, dvt, N = 13.6, J(H,H) = 7.0 Hz, PCHCH3]; dP (36.2 MHz)
30.5 [d, J(Rh,P) = 98.2 Hz].
= =
21 (ca. 70%) and trans-[RhCl( C CHPh)(PiPr3)2] 22 (ca. 15–
Reaction of (Z)-21 with CO. A slow stream of CO was
20%) was generated. The solvent was evaporated in vacuo and
the residue was extracted with pentane (30 cm3). The extract
was concentrated to ca. 3 cm3 in vacuo and then stored for 12 h
at −78 ◦C. An orange-red microcrystalline solid precipitated,
which was separated from the mother liquor, washed twice with
small amounts of pentane (−20 ◦C) and dried: yield 53 mg
(49%).
passed through a solution of (Z)-21 (66 mg, 0.10 mmol) in
C6D6 (0.5 cm3) for 30 s at room temperature. The H and 31P
1
NMR spectra revealed that besides trans-[RhCl(CO)(PiPr3)2]41
=
(E)-PhC≡CCH CHPh was exclusively formed. It was charac-
terized by comparison of the NMR data with those reported in
the literature.5,20
=
Method b. A solution of 23 (90 mg, 0.14 mmol) in benzene
(2 cm3) was stirred for 3 h at room temperature and then worked-
up as described for a). Orange-red crystals: yield 77 mg (85%);
mp 119 ◦C (decomp.) (Found: C, 61.25; H, 8.31. C34H54ClP2Rh
requires C, 61.58; H, 8.21%). IR (KBr): (C≡C) 1850 cm−1. NMR
(C6D6): dH (90 MHz) 8.04, 7.51 (2 H each, m, ortho-H of C6H5),
7.20 − 6.84 (6 H, br m, meta- and para-H of C6H5), 6.75 [1 H,
[RhCl(C≡CH)(CH CH2)(PiPr3)2] 26. This compound was
prepared as described for 23, from 17 (67 mg, 0.14 mmol) and
HCl in diethyl ether (10 cm3) at −40 ◦C. Orange-yellow micro-
crystalline solid: yield 66 mg (91%); converting temperature to 27
62 ◦C (Found: C, 51.64; H, 8.88. C22H46ClP2Rh requires C, 51.72;
H, 8.68%). IR (KBr): (≡CH) 3285, (C≡C) 1960 cm−1. NMR
(toluene-d8, 243 K): dH (90 MHz) 7.29 [1 H, ddtd, J(H,H) = 13.1
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 7 7

View Article Online
1
2
=
and 4.8, J(P,H) = 1.8, J(Rh,H) = 1.6 Hz, RhCH], 5.47 [1 H,
ddtd, J(H,H) = 13.1, J(Rh,H) = 2.4, J(P,H) = 2.3, J(H,H) =
trans-[Rh(j -O2CCF3){g -(Z)-PhC≡CCH CHPh}(PiPr3)2]
(Z)-30.
=
2.2 Hz, one H of CH2 cis to Rh], 4.50 [1 H, dddt, J(Rh,H) =
Method a. A solution of 2 (107 mg, 0.17 mmol) in
benzene (2 cm3) was treated with CF3CO2H (0.0134 cm3,
0.17 mmol) and stirred for 5 h at room temperature. The 31P
NMR spectrum indicated that besides some decomposition
=
4.8, J(H,H) = 4.8 and 2.2, J(P,H) = 2.1 Hz, one H of CH2
trans to Rh], 3.05 (6 H, m, PCHCH3), 2.35 [1 H, dt, J(Rh,H) =
2.6, J(P,H) = 1.5 Hz, C≡CH], 1.21, 1.19 [18 H each, both dvt,
N = 13.8, J(H,H) = 6.8 Hz, PCHCH3]; dP (36.2 MHz) 27.2 [d,
J(Rh,P) = 99.6 Hz].
products a mixture of (Z)-30 (ca. 85%) and trans-[Rh(j1-
31
= =
O2CCF3)( C CHPh)(PiPr3)2] (ca. 5%) was formed. The sol-
vent was evaporated in vacuo and the residue was extracted with
pentane (30 cm3). The extract was concentrated to ca. 3 cm3
in vacuo and then stored for 12 h at −78 ◦C. An orange-red
microcrystalline solid precipitated, which was separated from
the mother liquor, washed twice with small amounts of pentane
(−20 ◦C) and dried: yield 85 mg (67%).
=
Generation of trans-[RhCl(HC≡CCH CH2)(PiPr3)2] 27.
A
solution of 26 (48 mg, 0.09 mmol) in toluene-d8 (0.5 cm3) was
slowly warmed from −60 ◦C to −20 ◦C. The 31P NMR spectrum
indicated that the starting material was converted to isomer 27:
dP (36.2 MHz) 33.3 [d, J(Rh,P) = 117.2 Hz]. The conversion of 26
to 27 also occurred in a KBr matrix by warming from −40 ◦C
to 0 ◦C; in this case the generated isomer was identified by
comparison of the IR data with those reported in the literature.17
Method b. A solution of (Z)-29 (113 mg, 0.15 mmol) in
benzene (2 cm3) was stirred for 4 h at room temperature and
then worked-up as described for a). Orange-red crystals: yield
98 mg (87%); mp 104 ◦C (decomp.) (Found: C, 58.48; H,
7.50. C36H54F3O2P2Rh requires C, 58.38; H, 7.35%). IR (KBr):
(C≡C) 1860, m(OCOas) 1680 cm−1. NMR (C6D6): dH (90 MHz)
8.37, 7.46 (2 H each, m, ortho-H of C6H5), 7.21 − 6.92 (6 H,
br m, meta- and para-H of C6H5), 6.65 [1 H, dd, J(H,H) =
= =
=
Conversion of 26 to trans-[RhCl( C CHCH CH2)(PiPr3)2]
28. A solution of 26 (77 mg, 0.15 mmol) in benzene (2 cm3)
was stirred for 20 min at room temperature. The solvent was
evaporated in vacuo and the residue recrystallized from pentane
at −78 ◦C to give a dark green microcrystalline solid: yield 67 mg
(89%). The product was characterized by comparison of the 1H
and 13C NMR data with those reported in the literature.17
=
12.4, J(Rh,H) = 1.4 Hz, CH CHPh], 6.45 [1 H, d, J(H,H) =
=
12.4 Hz, CH CHPh], 1.96 (6 H, m, PCHCH3), 1.29 [18 H, dvt,
N = 13.5, J(H,H) = 6.9 Hz, PCHCH3], 1.00 [18 H, dvt, N =
12.7, J(H,H) = 6.9 Hz, PCHCH3]; dC (100.6 MHz) 160.4 [q,
J(F,C) = 35.1 Hz, CF3CO2], 137.4 (s, ipso-C of C6H5), 134.1
[Rh(j1(2)-O2CCF3)(C≡CPh){(Z)-CH CHPh}(PiPr3)2] (Z)-
=
29. A solution of 2 (163 mg, 0.26 mmol) in diethyl ether (5 cm3)
was treated dropwise with a 0.4 M solution of CF3CO2H in
diethyl ether (0.7 cm3) at −40 ◦C. A change of colour from blue-
green to yellow occurred. The solvent was evaporated in vacuo,
the remaining light yellow solid was washed twice with 2 cm3
portions of pentane (−20 ◦C) and dried; yield 141 mg (73%);
converting temperature to (Z)-29 75 ◦C (Found: C, 58.32; H,
7.56. C36H54F3O2P2Rh requires C, 58.38; H, 7.35%). IR (KBr):
(C≡C) 2105, (OCOas) 1640 cm−1. The NMR spectra (toluene-d8,
233 K) revealed that in solution a mixture of two isomers A and B
(see Scheme 11) in the ratio of ca. 1 : 1 are present: dH (400 MHz)
8.27, 7.73, 7.56, 7.45 (2 H each, all m, ortho-H of C6H5), 7.79
=
(s, CH CHPh), 131.0, 129.9, 129.6, 128.6, 127.9, 127.8, 127.6
=
(all s, C6H5), 118.3 (s, CH CHPh], 116.9 [q, J(F,C) = 292.8 Hz,
CF3CO2], 87.8 [dt, J(Rh,C) = 17.8, J(P,C) = 2.3 Hz, PhC≡C],
72.4 [d, J(Rh,C) = 13.4 Hz, PhC≡C], 23.0 (vt, N = 16.8 Hz,
PCHCH3), 20.6, 19.3 (both s, PCHCH3); dP (36.2 MHz) 30.0 [d,
J(Rh,P) = 121.6 Hz].
1
2
=
trans-[Rh(j -O2CCF3){g -(E)-PhC≡CCH CHPh}(PiPr3)2]
(E)-30.
Method a. A solution of (E)-29 (97 mg, 0.13 mmol) in benzene
(2 cm3) was stirred for 10 h at room temperature. A change of
colour from yellow to orange-red occurred. The solvent was
evaporated in vacuo and the residue was recrystallized from
pentane at −78 ◦C. Orange-red microcrystalline solid: yield
85 mg (88%).
=
[1 H, dt, J(H,H) = 10.5, J(P,H) = 3.7 Hz, CH CHPh of isomer
A], 7.60 [1 H, ddt, J(H,H) = 7.5, J(Rh,H) = 5.2, J(P,H) =
=
1.7 Hz, CH CHPh of isomer B], 7.26 − 6.94 (12 H, br m, meta-
Method b. A solution of (Z)-30 (73 mg, 0.10 mmol) in benzene
1
31
and para-H of C6H5), 6.60 [1 H, m, dd in H{ P}, J(H,H) =
(1 cm3) was irradiated with a UV lamp (Osram 500 W, water
=
10.5, J(Rh,H) = 1.6 Hz, CH CHPh of isomer A], 6.32 [1 H, m,
◦
filter, k > 300 nm) at 17 C. The 31P NMR spectrum revealed
1
31
=
dd in H{ P}, J(H,H) = 7.5, J(Rh,H) = 2.3 Hz, CH CHPh of
isomer B], 2.53, 2.47 (6 H each, both m, PCHCH3), 1.25 [18 H,
dvt, N = 13.7, J(H,H) = 7.1 Hz, PCHCH3], 1.19 [18 H, dvt,
N = 13.6, J(H,H) = 7.2 Hz, PCHCH3], 1.03 [18 H, dvt, N =
13.2, J(H,H) = 7.1 Hz, PCHCH3], 0.96 [18 H, dvt, N = 13.2,
J(H,H) = 7.2 Hz, PCHCH3]; dP (36.2 MHz) 27.3, 26.8 [both d,
J(Rh,P) = 96.7 Hz].
that after 1 h a quantitative isomerization had taken place. The
solution was worked-up as described for a). Orange-red solid:
yield 98 mg (87%).
Method c. A solution of 31 (69 mg, 0.13 mmol) in diethyl
3
=
ether (4 cm ) was treated with (E)-PhC≡CCH CHPh (26.2 mg,
0.13 mmol) and stirred for 3 min at room temperature. The
solution was worked-up as described for a). Orange-red solid:
yield 85 mg (89%); mp 98 ◦C (decomp.) (Found: C, 58.60; H,
7.39. C36H54F3O2P2Rh requires C, 58.38; H, 7.35%). IR (KBr):
(C≡C) 1840, m(OCOas) 1690 cm−1. NMR (C6D6): dH (400 MHz)
8.35, 7.50 (2 H each, m, ortho-H of C6H5), 7.79 [1 H, d, J(H,H) =
2
=
[Rh(j -O2CCF3)(C≡CPh){(E)-CH CHPh}(PiPr3)2] (E)-29.
A solution of (Z)-29 (63 mg, 0.09 mmol) in toluene-d8 (1 cm3)
was irradiated at −78 ◦C with a UV lamp (Osram 500 W, water
filter, k > 300 nm). The 31P NMR spectrum revealed that after 6 h
a quantitative isomerization had taken place. After the solution
was warmed to −20 ◦C, the solvent was evaporated in vacuo,
the remaining light yellow solid was washed twice with 2 cm3
portions of pentane (−20 ◦C) and dried; yield 58 mg (94%);
converting temperature to (E)-30 89 ◦C (Found: C, 57.83; H,
6.99. C36H54F3O2P2Rh requires C, 58.38; H, 7.35%). IR (KBr):
(C≡C) 2100, (OCOas) 1630 cm−1. NMR: dH (400 MHz, CD2Cl2,
295 K) 7.97 [1 H, ddt, J(H,H) = 13.4, J(Rh,H) = 2.6, J(P,H) =
=
15.7 Hz, CH CHPh], 7.23 − 7.04 (6 H, br m, meta- and
para-H of C6H5), 6.93 [1 H, dd, J(H,H) = 15.7, J(Rh,H) =
=
1.5 Hz, CH CHPh], 1.96 (6 H, m, PCHCH3), 1.22 [18 H, dvt,
N = 13.4, J(H,H) = 6.8 Hz, PCHCH3], 1.10 [18 H, dvt, N =
13.2, J(H,H) = 6.8 Hz, PCHCH3]; dC (100.6 MHz) 160.4 [q,
J(F,C) = 35.2 Hz, CF3CO2], 137.8 (s, ipso-C of C6H5), 136.3
=
(s, CH CHPh), 130.9, 130.1, 129.3, 128.3, 128.0, 127.3, 126.4
(all s, C6H5), 117.0 [q, J(F,C) = 292.8 Hz, CF3CO2], 115.9
=
(s, CH CHPh], 84.7 [dt, J(Rh,C) = 18.2, J(P,C) = 3.3 Hz,
=
2.6 Hz, CH CHPh], 7.24, 7.13, 7.09 (10 H, all m, C6H5), 6.52
PhC≡C], 77.4 [dt, J(Rh,C) = 16.4, J(P,C) = 2.2 Hz, PhC≡C],
23.6 (vt, N = 17.0 Hz, PCHCH3), 20.4, 19.8 (both s, PCHCH3);
dP (162.0 MHz) 33.4 [d, J(Rh,P) = 116.0 Hz].
[1 H, dtd, J(H,H) = 13.4, J(P,H) = 2.1, J(Rh,H) = 1.9 Hz,
=
CH CHPh], 2.75 (6 H, m, PCHCH3), 1.38 [18 H, dvt, N =
13.8, J(H,H) = 7.0 Hz, PCHCH3], 1.31 [18 H, dvt, N = 13.6,
J(H,H) = 7.0 Hz, PCHCH3]; dP (36.2 MHz, toluene-d8, 223 K)
25.9 [d, J(Rh,P) = 98.2 Hz].
1
= =
trans-[Rh(j -O2CCH3)( C CH2)(PiPr3)2] 32. A solution
of 17 (81 mg, 0.17 mmol) in benzene (1 cm3) was treated
1 4 7 8
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
with acetic acid (0.01 cm3, 0.17 mmol) and stirred for 1 h at
room temperature. The solvent was evaporated in vacuo and
the residue was extracted with pentane (20 cm3). The extract
was concentrated to ca. 5 cm3 in vacuo and the solution was
stored for 12 h at −78 ◦C. Violet crystals precipitated which
were identified by comparison of the IR and NMR data with
those of an authentic sample:31 60 mg (69%).
J(P,C) = 2.0 Hz, O–Rh–C≡C], 52.9, 51.0, 50.9 (all s, CO2CH3),
25.0 (vt, N = 21.5 Hz, PCHCH3), 20.6, 20.2 (both s, PCHCH3);
dP (36.2 MHz) 31.5 [d, J(Rh,P) = 86.5 Hz].
2
=
trans-[RhCl{g -(Z)-MeO2CC≡CCH CHCO2Me}(PiPr3)2]
(Z)-36. A solution of 34 (70 mg, 0.11 mmol) in benzene
(1 cm3) was stirred for 36 h at 50 ◦C. A change of colour from
yellow to red occurred. After the solvent was evaporated in
vacuo, an oily red residue was obtained. The 1H and 31P NMR
spectra indicate that a mixture of products was formed with
(Z)-36 as the main component (ca. 75%). Attempts to separate
(Z)-36 from the by-products either by fractional crystallization
Reaction of 2 with acetic acid. A solution of 2 (75 mg,
0.12 mmol) in toluene-d8 (1 cm3) was treated with acetic acid
(0.007 cm3, 0.12 mmol) and stirred for 2 h at room temperature.
1
The H and 31P NMR spectra revealed that a mixture of 3340
=
or chromatographic techniques failed. Data for (Z)-36: IR
and (Z)-PhC≡CCH CHPh was formed. If the reaction was
−1
monitored by 31P NMR spectroscopy, an intermediate could be
detected [dP (36.2 MHz) 26.6 (d, J(Rh,P) = 98.2 Hz)] which
was tentatively assigned as [Rh(j2-O2CCH3)(C≡CPh){(Z)-
=
(C6H6): (C≡C) 1860, (C O) 1715, 1690 cm . NMR (C6D6):
dH (200 MHz) 6.52 [1 H, dd, J(H,H) = 11.8, J(Rh,H) =
=
1.3 Hz, CH CHCO2Me], 5.77 [1 H, d, J(H,H) = 11.8 Hz,
=
=
CHCO2Me], 3.53, 3.41 (3 H each, both s, CO2CH3), 2.48
CH CHPh}(PiPr3)2] E (see Scheme 12).
(6 H, m, PCHCH3), 1.30 [18 H, dvt, N = 13.3, J(H,H) =
7.0 Hz, PCHCH3], 1.23 [18 H, dvt, N = 13.6, J(H,H) = 7.1 Hz,
PCHCH3]; dP (81.0 MHz) 34.3 [d, J(Rh,P) = 111.9 Hz].
trans-[RhCl{g -(E)-MeO2CC≡CCH CHCO2Me}(PiPr3)2]
2
=
=
[RhCl(C≡CCO2Me){j (C,O)-CH CHC(OMe) O}(PiPr3)2]
34. A slow stream of HCl was passed under stirring through
a solution of 6 (183 mg, 0.31 mmol) in diethyl ether (4 cm3) at
−78 ◦C. A change of colour from blue-green to yellow occurred
and a white solid precipitated. After removal of excess HCl in
vacuo, the precipitate was separated from the mother liquor,
washed twice with 2 cm3 portions of pentane (−20 ◦C) and
dried. The mother liquor was brought to dryness in vacuo, the
residue was washed with small amounts of pentane (−20 ◦C)
and, after it was dried, combined with the white precipitate:
yield 175 mg (91%); mp 101 ◦C (decomp.) (Found: C, 49.88;
H, 7.97. C26H50ClO4P2Rh requires C, 49.81; H, 8.04%). IR
2
=
(E)-36.
Method a. A solution of 37 (104 mg, 0.16 mmol) in benzene
(2 cm3) was chromatographed on Al2O3 (neutral, activity
grade V, height of column 15 cm). With benzene as the eluant,
the colour of the mobile phase changed from yellow to red. The
red fraction was brought to dryness in vacuo. After the residue
was recrystallized from pentane at −78 ◦C, a red microcrystalline
solid was obtained: yield 53 mg (53%).
(CH2Cl2): (C≡C) 2110, (C Ouncoord) 1680, (C Ocoord) 1580 cm−1.
NMR (C6D6): dH (400 MHz) 10.14 [1 H, ddt, J(H,H) = 7.3,
J(Rh,H) = 1.8, J(P,H) = 1.7 Hz, RhCH], 5.91 [1 H, dtd,
=
=
Method b. A solution of 37 (97 mg, 0.15 mmol) in diethyl
ether (5 cm3) was treated with an excess of both MgCl2·6H2O
(ca. 250 mg) and Na2CO3 (ca. 250 mg) and stirred for 2 h at
◦
=
J(H,H) = 7.3, J(P,H) = 1.7, J(Rh,H) = 1.5 Hz, RhCH CH],
40 C. A change of colour from yellow to red occurred. After
3.46, 3.43 (3 H each, both s, OCH3), 2.63 (6 H, m, PCHCH3),
1.44, 1.13 [18 H each, both dvt, N = 13.0, J(H,H) = 6.8 Hz,
PCHCH3]; dC (100.6 MHz) 204.7 [dt, J(Rh,C) = 26.0, J(P,C) =
the solution was cooled to room temperature, the solvent was
evaporated in vacuo and the residue was extracted with pentane
(20 cm3). The extract was brought to dryness in vacuo and the
residue was recrystallized from pentane at −78 ◦C to give a red
microcrystalline solid: yield 66 mg (72%); mp 125 ◦C (decomp.)
=
7.8 Hz, RhCH], 178.9 [d, J(Rh,C) = 3.0 Hz, CHCO2Me],
153.6 [dt, J(Rh,C) = 2.0, J(P,C) = 2.0 Hz, ≡CCO2Me], 121.0
=
[td, J(P,C) = 2.5, J(Rh,C) = 2.1 Hz, RhCH CH], 103.8
(Found: C, 50.04; H, 8.08. C26H50ClO4P2Rh requires C, 49.81;
−1
=
[dt, J(Rh,C) = 53.2, J(P,C) = 17.2 Hz, RhC≡C], 102.4 [dt,
J(Rh,C) = 9.1, J(P,C) = 2.8 Hz, RhC≡C], 53.0, 51.0 (both s,
CO2CH3), 23.9 (vt, N = 20.4 Hz, PCHCH3), 20.6, 20.0 (both s,
PCHCH3); dP (162.0 MHz) 27.0 [d, J(Rh,P) = 89.9 Hz].
H, 8.04%). IR (KBr): (C≡C) 1830, (C O) 1705, 1675 cm .
NMR (C6D6): dH (400 MHz) 7.51 [1 H, dd, J(H,H) = 15.3,
=
J(Rh,H) = 1.7 Hz, CH CHCO2Me], 7.13 [1 H, d, J(H,H) =
=
15.3 Hz, CHCO2Me], 3.49, 3.39 (3 H each, both s, CO2CH3),
2.30 (6 H, m, PCHCH3), 1.25 [18 H, dvt, N = 13.6, J(H,H) =
2
=
=
[Rh(C≡CCO2Me)2{j (C,O)-CH CHC(OMe) O}(PiPr3)2]
35. A solution of 6 (107 mg, 0.18 mmol) in NEt3 (4 cm3) was
treated with HC≡CCO2Me (0.0017 cm3, 0.19 mmol) at −78 ◦C
and, while it was stirred, in 1 h warmed to room temperature.
A change of colour from blue-green to yellow occurred. The
solvent was evaporated in vacuo, the residue was dissolved
in benzene (1 cm3) and the solution was chromatographed
on Al2O3 (neutral, activity grade V, height of column 5 cm).
With benzene a pale yellow fraction was eluted, which was
brought to dryness in vacuo. The remaining off-white solid
was washed twice with 2 cm3 portions of pentane (−20 ◦C)
and dried: yield 78 mg (64%) (Found: C, 53.47; H, 7.74.
C30H53O6P2Rh requires C, 53.41; H, 7.92%). IR (CH2Cl2):
6.9 Hz, PCHCH3], 1.19 [18 H, dvt, N = 13.3, J(H,H) =
=
6.8 Hz, PCHCH3]; dC (100.6 MHz) 166.8 (s, CHCO2Me), 156.6
=
(br s, ≡CCO2Me), 130.9 (s, CHCO2Me), 126.8 [d, J(Rh,C) =
=
1.0 Hz, CH CHCO2Me], 95.0 [dt, J(Rh,C) = 17.2, J(P,C) =
2.9 Hz, C≡C], 89.9 [dt, J(Rh,C) = 18.1, J(P,C) = 4.1 Hz, C≡C],
51.5, 51.4 (both s, CO2CH3), 23.8 (vt, N = 18.5 Hz, PCHCH3),
20.4, 20.0 (both s, PCHCH3); dP (162.0 MHz) 35.4 [d, J(Rh,P) =
110.8 Hz].
2
1
=
[Rh(j -O2CCH3)(C≡CCO2Me){g -(E,E)-C( CHCO2Me)-
=
CH CHCO2Me}(PiPr3)2] 38. A solution of 37 (98 mg,
0.15 mmol) in benzene (1 cm3) was treated with HC≡CCO2Me
(0.0013 cm3, 0.15 mmol) and stirred for 1 h at room temperature.
The solvent was evaporated in vacuo and the residue was
extracted with hexane/diethyl ether (1 : 1, 15 cm3). The extract
was brought to dryness in vacuo and the residue recrystallized
from pentane at −78 ◦C. The precipitated white solid was
washed with 2 cm3 portions of pentane (−20 ◦C) and dried: yield
84 mg (76%); mp 110 ◦C (decomp.) (Found: C, 52.15; H, 7.79.
(C≡C) 2105, 2085, (C Ouncoord) 1670, (C Ocoord) 1580 cm−1.
=
=
1
31
NMR (C6D6): dH (400 MHz) 10.45 [1 H, m, dd in H{ P},
J(H,H) = 8.9, J(Rh,H) = 1.8 Hz, RhCH], 6.26 [1 H, m, d
1
31
=
in H{ P}, J(H,H) = 8.9 Hz, RhCH CH], 3.45, 3.43, 3.36
(3 H each, all s, OCH3), 2.56 (6 H, m, PCHCH3), 1.36 [18 H,
dvt, N = 13.8, J(H,H) = 7.0 Hz, PCHCH3], 1.22 [18 H,
dvt, N = 13.4, J(H,H) = 6.9 Hz, PCHCH3]; dC (100.6 MHz)
218.2 [dt, J(Rh,C) = 20.9, J(P,C) = 8.6 Hz, RhCH], 180.8 [d,
C32H57O8P2Rh requires C, 52.32; H, 7.82%). IR (C6H6): (C≡C)
−1
=
2100, (C O) 1710, 1685 cm . NMR (C6D6): dH (400 MHz)
=
=
8.36 [1 H, d, J(H,H) = 15.8 Hz, CH CHCO2Me], 6.72 [1 H,
1 31
J(Rh,C) = 1.9 Hz, CHCO2Me], 154.3 (br s, ≡CCO2Me),
=
153.4 [d, J(Rh,C) = 1.8 Hz, ≡CCO2Me], 124.6 [dt, J(Rh,C) =
m, d in H{ P}, J(Rh,H) = 2.4 Hz, RhC CHCO2Me], 6.34
=
=
33.7, J(P,C) = 16.8 Hz, C–Rh–C≡C], 123.0 (br s, RhCH CH),
[1 H, d, J(H,H) = 15.8 Hz, CH CHCO2Me], 3.44, 3.38, 3.37
106.9 [d, J(Rh,C) = 5.0 Hz, C–Rh–C≡C], 103.8 [dt, J(Rh,C) =
53.2, J(P,C) = 17.2 Hz, O–Rh–C≡C], 99.5 [dt, J(Rh,C) = 10.9,
(3 H each, all s, OCH3), 2.67 (6 H, m, PCHCH3), 1.68 (3 H, s,
CH3CO2Rh), 1.40 [18 H, dvt, N = 14.0, J(H,H) = 7.1 Hz,
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 7 9

View Article Online
PCHCH3], 1.12 [18 H, dvt, N = 13.1, J(H,H) = 6.8 Hz,
PCHCH3]; dC (100.6 MHz) 184.3 [dt, J(Rh,C) = 1.2, J(P,C) =
3 Y. Wakatsuki, H. Yamazaki, H. Kumegawa, T. Satoh and J. Y. Satoh,
J. Am. Chem. Soc., 1991, 113, 9604.
4 H. J. Heeres, J. Nijhoff, J. H. Teuben and R. D. Rogers,
Organometallics, 1993, 12, 2609.
5 C. S. Yi and N. Liu, Organometallics, 1996, 15, 3968.
6 T. Ohmura, S. Yorozuya, Y. Yamamoto and N. Miyaura,
Organometallics, 2000, 19, 365.
7 M. A. Esteruelas, J. Herrero, A. M. Lopez and M. Olivan,
Organometallics, 2001, 20, 3202.
8 Some leading references: L. Dahlenburg, K.-M. Frosin, S. Kerstan
and D. Werner, J. Organomet. Chem., 1991, 407, 115; C. Bianchini, P.
Frediani, D. Masi, M. Peruzzini and F. Zanobini, Organometallics,
1994, 13, 4616; T. Rappert and A. Yamamoto, Organometallics,
1994, 13, 4984; C. Slugovc, K. Mereiter, E. Zobetz, R. Schmid
and K. Kirchner, Organometallics, 1996, 15, 5275; C. S. Yi, N. Liu,
A. L. Rheingold and L. M. Liable-Sands, Organometallics, 1997,
16, 3910; B. M. Trost, M. T. Sorum, C. Chan, A. E. Harms and
G. Ru¨ther, J. Am. Chem. Soc., 1997, 119, 698; C. S. Yi and N. Liu,
Organometallics, 1998, 17, 3158; W. Baratta, W. A. Herrmann, P.
Rigo and J. Schwarz, J. Organomet. Chem., 2000, 593, 489; M. A.
Jimenez Tenorio, M. Jimenez Tenorio, M. C. Puerta and P. Valerga,
Organometallics, 2000, 19, 1333; S. Pavlik, C. Gemel, C. Slugovc, K.
Mereiter, R. Schmid and K. Kirchner, J. Organomet. Chem., 2001,
617, 301.
=
1.2 Hz, RhO2CCH3], 167.0 (s, CH CHCO2Me), 163.9 [dt,
=
J(Rh,C) = 3.5, J(P,C) = 1.0 Hz, RhC CHCO2Me], 163.6 [dt,
=
J(Rh,C) = 30.6, J(P,C) = 7.8 Hz, RhC CHCO2Me], 153.7 [br
d, J(Rh,C) = 1.4 Hz, ≡CCO2Me], 153.4 [d, J(Rh,C) = 1.8 Hz,
=
≡CCO2Me], 148.0 (br s, CH CHCO2Me), 126.9 [br t, J(P,C) =
=
=
2.5 Hz, RhC CHCO2Me], 118.3 (s, CH CHCO2Me), 111.8
[dt, J(Rh,C) = 51.4, J(P,C) = 16.8 Hz, RhC≡C], 100.5 [dt,
J(Rh,C) = 10.1, J(P,C) = 2.0 Hz, RhC≡C], 51.2, 51.1, 50.6
(all s, CO2CH3), 24.8 (s, RhO2CCH3), 24.1 (vt, N = 20.0 Hz,
PCHCH3), 20.1, 19.7 (both s, PCHCH3); dP (162.0 MHz) 26.3
[d, J(Rh,P) = 93.2 Hz].
2
=
=
trans-[RhCl{g -(E,E )-MeO2CC≡CC( CHCO2Me)CH
CHCO2Me}(PiPr3)2] 39. A solution of 38 (125 mg, 0.17 mmol)
in diethyl ether (10 cm3) was treated with an excess of both
MgCl2·6H2O (ca. 250 mg) and Na2CO3 (ca. 250 mg) and
stirred for 4 h at 40 ◦C. A change of colour from yellow to
cherry-red occurred. After the solution was cooled to room
temperature, the solvent was evaporated in vacuo and residue
was extracted with pentane (30 cm3). The extract was brought
to dryness in vacuo and the residue was recrystallized from
pentane at −78 ◦C to give a deep-red microcrystalline solid:
yield 96 mg (79%); mp 128 ◦C (decomp.) (Found: C, 51.15;
9 H. Werner, Nachr. Chem. Tech. Lab., 1992, 40, 435; H. Werner,
J. Organomet. Chem., 1994, 475, 45.
10 R. Wiedemann, P. Steinert, M. Scha¨fer and H. Werner, J. Am. Chem.
Soc., 1993, 115, 9864; H. Werner, R. Wiedemann, P. Steinert and J.
Wolf, Chem. Eur. J., 1997, 3, 127.
H, 7.87. C30H54ClO6P2Rh requires C, 50.68; H, 7.65%). IR
11 M. Scha¨fer, J. Wolf and H. Werner, J. Chem. Soc., Chem. Commun.,
1991, 1341.
−1
=
(hexane): (C≡C) 1845, (C O) 1725, 1715, 1700 cm . NMR
(C6D6): dH (400 MHz) 9.11 [1 H, d, J(H,H) = 16.0 Hz,
12 M. Scha¨fer, N. Mahr, J. Wolf and H. Werner, Angew. Chem., Int. Ed.
=
=
Engl., 1993, 32, 1315.
CH CHCO2Me], 8.00 (1 H, s, C≡CC CHCO2Me), 7.40
13 H. Werner, M. Scha¨fer, J. Wolf, K. Peters and H. G. von Schnering,
Angew. Chem., Int. Ed. Engl., 1995, 34, 191.
=
[br d, J(H,H) = 16.0 Hz, CH CHCO2Me], 3.49, 3.37, 3.35
(3 H each, all s, OCH3), 2.35 (6 H, m, PCHCH3), 1.28 [18
H, dvt, N = 13.8, J(H,H) = 7.0 Hz, PCHCH3], 1.11 [18 H,
dvt, N = 13.1, J(H,H) = 6.7 Hz, PCHCH3]; dC (100.6 MHz)
14 M. Scha¨fer, J. Wolf and H. Werner, Organometallics, 2004, 23, 5713.
15 A. Dobson, D. S. Moore, S. D. Robinson, M. B. Hursthouse and
L. New, J. Organomet. Chem., 1979, 177, C8; A. F. Hill and R. P.
Melling, J. Organomet. Chem., 1990, 396, C22; G. Jia and D. W.
Meek, Organometallics, 1991, 10, 1444; N. W. Alcock, A. F. Hill and
R. P. Melling, Organometallics, 1991, 10, 3898; M. C. J. Harris and
A. F. Hill, Organometallics, 1991, 10, 3903; S. A. MacLaughlin, S.
Doherty, N. J. Taylor and A. J. Carty, Organometallics, 1992, 11,
4315.
=
166.7, 166.5 (both s, CHCO2Me), 158.8 (br s, ≡CCO2Me],
=
=
138.6 (s, C≡CC CH), 137.0 (s, C≡CCCH CH), 130.7 (s,
=
=
C≡CC CHCO2Me), 128.0 (s, CH CHCO2Me), 93.1 [dt,
J(Rh,C) = 17.9, J(P,C) = 2.6 Hz, C≡CCO2Me], 88.2 [br
d, J(Rh,C) = 16.5 Hz, C≡CCO2Me], 51.7, 51.5, 51.3 (all s,
CO2CH3), 23.5 (vt, N = 18.4 Hz, PCHCH3), 20.6, 19.6 (both s,
PCHCH3); dP (162.0 MHz) 33.6 [d, J(Rh,P) = 110.6 Hz].
16 P. J. Stang, V. Dixit, M. D. Schiavelli and P. Drees, J. Am. Chem. Soc.,
1987, 109, 1150.
17 T. Rappert, O. Nu¨rnberg, N. Mahr, J. Wolf and H. Werner,
Organometallics, 1992, 11, 4156.
Reaction of 39 with CO. A slow stream of CO was passed
through a solution of 39 (59 mg, 0.08 mmol) in C6D6 (0.5 cm3)
for 15 s at room temperature. A quick change of colour
18 K. Ilg and H. Werner, Angew. Chem., Int. Ed., 2000, 39, 1632; K. Ilg
and H. Werner, Chem. Eur. J., 2002, 8, 2812; H. Werner, K. Ilg, R.
Lass and J. Wolf, J. Organomet. Chem., 2002, 661, 137.
1
from red to yellow occurred. The H and 31P NMR spectra
19 M. Sch
85.
a¨fer, J. Wolf and H. Werner, J. Organomet. Chem., 1994, 476,
revealed that besides 2441 an equimolar amount of (E,E)-
=
=
MeO2CC≡CC( CHCO2Me)CH CHCO2Me 40 was formed.
20 J. Ohshita, K. Furumori, A. Matsuguchi and M. Ishikawa, J. Org.
Data for 40: NMR (C6D6): dH (200 MHz) 8.78 [1 H, d,
Chem., 1990, 55, 3277.
=
J(H,H) = 15.9 Hz, CH CHCO2Me], 6.66 [d, J(H,H) = 15.9 Hz,
21 A. M. Echavarren, J. Lo´pez, A. Santos and J. Montoya, J. Organomet.
Chem., 1991, 414, 393.
=
=
CH CHCO2Me], 5.95 (1 H, s, C≡CC CHCO2Me), 3.28, 3.20,
22 W. Neugebauer, G. A. P. Geiger, A. J. Klos, J. J. Stezowski and P. von
Rague´ Schleyer, Chem. Ber., 1985, 118, 1504.
3.15 (3 H each, all s, OCH3).
23 W. T. Boese and A. S. Goldman, Organometallics, 1991, 10, 782.
24 H. Yamazaki, J. Chem. Soc., Chem. Commun., 1976, 841.
25 H. Kleijn, M. Tigchelaar, R. J. Bullee, C. J. Elsevier, J. Meijer and P.
Vermeer, J. Organomet. Chem., 1982, 240, 329.
26 J. Schwartz, D. W. Hart and J. L. Holden, J. Am. Chem. Soc., 1972,
94, 9269; B. L. Booth and A. D. Lloyd, J. Organomet. Chem., 1972,
35, 195; A. A. H. van der Zeijden, H. W. Bosch and H. Berke,
Organometallics, 1992, 11, 563.
27 For the protonation of alkynes see: G. Modena and U. Tonellato,
Adv. Phys. Org. Chem., 1971, 9, 185; Z. Rappoport, in Reactive
Intermediates, ed. R. A. Abramovitch, Plenum Press, New York,
1983, vol. 3, pp. 427–615.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (SFB 347) and
the Fonds der Chemischen Industrie for financial support. We
are also most grateful to Mrs R. Schedl and Mr C. P. Kneis
(DTA measurements and elemental analyses), Dr G. Lange
and Mr F. Dadrich (mass spectra) and Dr W. Buchner and
Mrs M.-L. Scha¨fer (NMR spectra). Moreover, we acknowledge
support by BASF AG and Degussa AG for chemicals.
28 D. W. Hart and J. Schwartz, J. Organomet. Chem., 1975, 87, C11; J. M.
Huggins and R. G. Bergman, J. Am. Chem. Soc., 1981, 103, 3002;
H. Werner, J. Wolf, U. Schubert and K. Ackermann, J. Organomet.
Chem., 1986, 317, 327; M. I. Bruce, A. Catlow, M. G. Humphrey,
G. A. Koutsantonis, M. R. Snow and E. R. T. Tiekink, J. Organomet.
Chem., 1988, 338, 59; M. I. Bruce, A. Catlow, M. P. Cifuentes,
M. R. Snow and E. R. T. Tiekink, J. Organomet. Chem., 1990, 397,
187.
References
1 J. M. Winter, in The Chemistry of the Metal-Carbon Bond, ed.
F. R. Hartley and S. Patai, Wiley, New York, 1985, vol. 3, p. 259;
N. E. Schore, in Comprehensive Organic Synthesis, ed. B. M. Trost,
Pergamon Press, New York, 1991, vol. 5, p. 1129; B. M. Trost, Angew.
Chem., Int. Ed. Engl., 1995, 34, 259.
2 Y. Wakatsuki and H. Yamazaki, J. Organomet. Chem., 1995, 500,
349; C. Bruneau and P. H. Dixneuf, Acc. Chem. Res., 1999, 32, 311;
C. Slugovc and K. Kirchner, Coord. Chem. Rev., 1999, 185, 109.
29 A. Ho¨hn and H. Werner, Angew. Chem., Int. Ed. Engl., 1986, 25,
737.
1 4 8 0
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1

View Article Online
30 S. D. Robinson and M. F. Uttley, J. Chem. Soc., Dalton Trans., 1973,
1912; G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980, 33,
227.
M. R. Snow and E. R. T. Tiekink, J. Organomet. Chem., 1988, 338,
59; H. Werner, U. Meyer, K. Peters and H. G. von Schnering, Chem.
Ber., 1989, 122, 2097; M. I. Bruce, A. Catlow, M. P. Cifuentes, M. R.
Snow and E. R. T. Tiekink, J. Organomet. Chem., 1990, 397, 187.
36 L. S. Meriwether, M. F. Leto, E. C. Colthup and G. W. Kennerly,
J. Org. Chem., 1962, 27, 3930.
31 M. Scha¨fer, J. Wolf and H. Werner, J. Organomet. Chem., 1995, 485,
85.
32 H. Werner, R. Weinand and H. Otto, J. Organomet. Chem., 1986, 307,
49; G. Jia, D. W. Meek and J. C. Gallucci, Organometallics, 1990, 9,
2549.
37 C. U. Pittman Jr. and L. R. Smith, J. Organomet. Chem., 1975, 90,
203.
33 H. Werner, T. Dirnberger and M. Schulz, Angew. Chem., Int. Ed.
38 T. Yoshida, T. Okano, Y. Ueda and S. Otsuka, J. Am. Chem. Soc.,
1981, 103, 3411.
Engl., 1988, 27, 948.
34 S. Komiya, T. Ito, M. Cowie, A. Yamamoto and J. A. Ibers, J. Am.
Chem. Soc., 1976, 98, 3874; T. Ito, H. Tosaka, S. Yoshida, K. Mita
and A. Yamamoto, Organometallics, 1986, 5, 735; T. Dirnberger and
H. Werner, Chem. Ber., 1992, 125, 2007.
35 B. L. Booth and A. D. Lloyd, J. Organomet. Chem., 1972, 35, 195;
M. I. Bruce, A. Catlow, M. G. Humphrey, G. A. Koutsantonis,
39 H. Werner, J. Wolf and A. Ho¨hn, J. Organomet. Chem., 1985, 287,
395.
40 H. Werner, M. Scha¨fer, O. Nu¨rnberg and J. Wolf, Chem. Ber., 1994,
127, 27.
41 C. Busetto, A. D’Alfonso, F. Maspero, G. Perego and A. Zazzetta,
J. Chem. Soc., Dalton Trans., 1977, 1828.
D a l t o n T r a n s . , 2 0 0 5 , 1 4 6 8 – 1 4 8 1
1 4 8 1