Rhenium carbonyl compounds with (diphenyl)phosphinoalkynes and a sterically hindered phosphinoalkyne

Article abstract of DOI:10.1016/j.jorganchem.2008.05.026

The synthesis and characterization of two series of rhenium carbonyl complexes with P-coordinated phosphinoalkynes are reported. The anionic fac-[ReBr₂(CO)₃(Ph₂PC{triple bond, long}CR)]^- and neutral fac-[ReBr(CO)₃(Ph₂PC{triple bond, long}CR)₂] (R = Ph, Tol, ^tBu) complexes have been prepared and the crystal structures of fac-[ReBr₂(CO)₃(Ph₂PC{triple bond, long}CTol)]^- and fac-[ReBr(CO)₃(Ph₂PC{triple bond, long}C^tBu)₂] have been determined by X-ray crystallography, evidencing the presence of the uncoordinated alkyne in all these compounds. The phosphinoalkyne (o-Tol)₂PC{triple bond, long}CPh with bulky groups linked to the phosphorus atom was prepared in order to avoid the coordination of two phosphinoalkynes in cis-position around the rhenium metal. As a result, surprisingly the complex fac-[ReBr(CO)₃{(o-Tol)₂PC{triple bond, long}CPh}₂] was obtained. The crystal structure of this compound was determined confirming the cis-coordination of two bulky phosphinoalkynes in an octahedral rhenium atom. The electronic properties of the uncoordinated alkyne in these new rhenium complexes was analyzed, based on ¹³C NMR data and was compared with reported data on iron complexes. The results obtained indicate that the electronic characteristics of uncoordinated alkynes are similar in both families of complexes. Thus, the different reactivity observed between rhenium and iron complexes is related to the different nature of metallic fragments rather than to electronic features of uncoordinated alkynes.

Full text of DOI:10.1016/j.jorganchem.2008.05.026

Journal of Organometallic Chemistry 693 (2008) 2775–2783
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Rhenium carbonyl compounds with (diphenyl)phosphinoalkynes
and a sterically hindered phosphinoalkyne
Cristian Ledesma a, Angel Alvarez-Larena b, Joan Suades a,
*
a Departament de Química, Edifici C, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
b Servei de Difracció de Raigs X, Edifici C, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 April 2008
Received in revised form 15 May 2008
Accepted 15 May 2008
Available online 24 May 2008
The synthesis and characterization of two series of rhenium carbonyl complexes with P-coordinated
phosphinoalkynes are reported. The anionic fac-[ReBr2(CO)3(Ph2PC„CR)]ꢀ and neutral fac-
t
[ReBr(CO)3(Ph2PC„CR)2] (R = Ph, Tol, Bu) complexes have been prepared and the crystal structures of
fac-[ReBr2(CO)3(Ph2PC„CTol)]ꢀ and fac-[ReBr(CO)3(Ph2PC„CtBu)2] have been determined by X-ray crys-
tallography, evidencing the presence of the uncoordinated alkyne in all these compounds. The phos-
phinoalkyne (o-Tol)2PC„CPh with bulky groups linked to the phosphorus atom was prepared in order
to avoid the coordination of two phosphinoalkynes in cis-position around the rhenium metal. As a result,
surprisingly the complex fac-[ReBr(CO)3{(o-Tol)2PC„CPh}2] was obtained. The crystal structure of this
compound was determined confirming the cis-coordination of two bulky phosphinoalkynes in an octahe-
dral rhenium atom. The electronic properties of the uncoordinated alkyne in these new rhenium com-
plexes was analyzed, based on 13C NMR data and was compared with reported data on iron
complexes. The results obtained indicate that the electronic characteristics of uncoordinated alkynes
are similar in both families of complexes. Thus, the different reactivity observed between rhenium and
iron complexes is related to the different nature of metallic fragments rather than to electronic features
of uncoordinated alkynes.
Keywords:
Rhenium
Tricarbonyl
Phosphinoalkyne
fac-Triaquatricarbonylrhenium(1+)
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
Although no further studies have shown if it could be per-
formed with other metals, this reaction has recently attracted
Alkynyl phosphines Ph2PC„CR are attracting ligands that have
been extensively studied because of their versatile behaviour,
resulting from their ability to react via the phosphine and the al-
kyne functions. The first studies in the 1980s were focused on their
capacity to support polynuclear metal clusters by means of phos-
phido and alkynyl fragments, which were formed after P–C bond
cleavage [1]. However, further studies with a broad range of metal
complexes have revealed other interesting abilities of these ligands
such as the preparation of metal complexes with uncoordinated al-
kynes [2–4], intramolecular coupling of the alkynyl moieties [5–7],
insertion of the triple bond in M–H or M–C bonds [8,9], preparation
of heterometallic compounds [6,10–12], or the development of
new materials [13]. These ligands can also lead to the formation
of metallacycles by means of a reaction between the alkyne and
another ligand linked to metal [9,14,15]. We reported some years
ago that cationic P-coordinated iron complexes [(C5H5)Fe-
(CO)2(Ph2PC„CR)]+ can lead to the formation of metallacycles in
mild conditions, giving good yields by the reaction pathway shown
in Scheme 1 [15].
our attention again in the course of our work with rhenium
carbonyl complexes [16]. The chemistry of the cation [Re(CO)3-
(H2O)3]+ and its homologous technetium-99m complex has be-
come a relevant topic in radiopharmaceutical chemistry [17] after
the publication of simple methods that allow the preparation of
[
99mTc(CO)3(H2O)3]+ starting from [99mTcO4]ꢀ [18]. One of the goals
of this field is the search for new stable coordination sets that
could be prepared in water medium starting from [99mTc(CO)3-
(H2O)3]+. The most common approach to this objective has been
the replacement of the labile water molecules by other ligands
with heteroatoms as oxygen [19], nitrogen [20], phosphorus [21],
sulphur [22] or mixed donor atoms [23]. However, there are few
examples of substitution reactions of the water molecules by an
organometallic fragment. The most relevant studies have been
done with cyclopentadienyl [24], and as far as we know no studies
have been reported with metallacycles.
Therefore, the main objective of the present work is to prepare
new P-coordinated phosphinoalkynes with the fragment fac-
{Re(CO)3}+. These compounds will be the starting material to study
the viability of a reaction similar to Scheme 1 with rhenium
carbonyls, which could lead to the formation of stable metallacy-
cles in water medium. The preparation of P-coordinated
* Corresponding author. Tel.: +34 935812893; fax + 34 935813101.
E-mail address: Joan.Suades@uab.es (J. Suades).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.05.026

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C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
Ph
P
Ph
Ph
Ph
Ph
Fe
Ph
P
C
C
R
+ OH
- CO
O
P
C
C
R
C
H
Fe
Fe
CO
CO
CO
OH
CO
C
R
Scheme 1.
phosphinoalkynes can also supply interesting information about
the electronic properties of the metal fragment. In a previous paper
we reported a relationship between the 13C NMR chemical shift of
acetylenic carbons and the donor properties of the phosphine
group [3], thus the alkyne can act as a sensor of electronic interac-
were obtained by recrystallization in dichloromethane/toluene
which yielded crystals of complexes 1–3 contaminated with small
quantities of [NEt4]Br. The crystal structure of complex 2 was
determined by X-ray diffraction methods (Fig. 1), confirming the
proposed structure for these complexes. The 13C NMR spectra of
complexes 1–3 also supply relevant information in agreement with
the proposed structure since in all cases two doublets can be ob-
served in the 70–120 ppm region assigned to the two acetylenic
carbons. The shift observed respect to the free ligands and the in-
crease in the JP–C coupling constants is characteristic of P-coordi-
nated phosphinoalkynes [3,4,7,11,12].
tion between phosphorus and metal. Therefore, the analysis of 13
C
NMR data in P-coordinated rhenium carbonyl phosphinoalkynes
will allow us to compare the electronic properties of fac-{Re(CO)3}+
with other previously reported metals fragments.
2. Results and discussion
Once the formation of P-coordinated phosphinoalkyne com-
plexes was corroborated, the next goal was to study the possible
reaction between the coordinated phosphinoalkyne and a water
molecule linked to the rhenium atom. This was studied by means
of the reaction between [NEt4]2[ReBr3(CO)3] with the phos-
phinoalkyne in water/ethanol medium (Scheme 3). Under these
conditions, Re–Br bonds are hydrolysed [27]. This reaction was
t
2.1. Complexes with Ph2PC„CR (R = Ph, Tol, Bu)
In order to prepare P-coordinated complexes with the fragment
{Re(CO)3}+ the anion [ReBr3(CO)3]2ꢀ was chosen as starting prod-
uct. This complex is commonly used in the preparation of com-
plexes with the fragment {Re(CO)3}+ because bromide ligands are
easily substituted by other ligands and using this approach [Re-
Br2(CO)3(L)]ꢀ complexes (L = monodentate phosphine) have been
reported [21]. The P-coordinated rhenium carbonyl complexes
1–3 (Scheme 2) were prepared by simple addition at room temper-
ature of the phosphinoalkyne to the rhenium precursor in dichlo-
romethane solution in stoichiometric ratio. This reaction was
monitored by IR in the m(CO) region and was performed at different
temperatures (room temperature and reflux), phosphine/metal ra-
tios (values of 1 or 2) and reaction times. In all cases the observed
IR spectra were nearly identical, in agreement with the formation
monitored by IR in the m
(CO) region and by 31P NMR spectroscopy
and no significant differences was observed if certain reaction con-
ditions such as temperature, reaction time and phosphine excess
were modified. In all cases a main compound was formed, which
displayed a sole signal in the 31P NMR spectra between ꢀ24/
ꢀ27 ppm with the characteristic shift to low field respect to free li-
gands (ꢀ32/ꢀ34 ppm) after coordination of the phosphorus atom
O1
C1
O2
to the metal. The IR spectra in the m(CO) region also is consistent
C2
with this hypothesis since in all cases an intense signal is observed
around 2175 cmꢀ1
,
assigned to the uncoordinated alkyne
P
C12
[4,7,11,12] and three bands characteristic of the fac-{Re(CO)3}+
fragment [23a,25]. Unfortunately, all attempts to isolate complexes
1–3 in solid state led to compounds contaminated with [NEt4]Br,
which is formed in the substitution reaction of bromide by the
phosphine (Scheme 2). The isolation of pure complexes 1–3 has
been attempted by treatment and recrystallization with a wide
range of solvents, as well as the use of Reverse Phase Sep-Pack car-
tridges, however in all cases the complexes obtained were contam-
inated by tetraethylammonium bromide. This situation has been
previously described in the literature of rhenium carbonyl com-
plexes prepared from [NEt4]2[ReBr3(CO)3] [26]. The best results
C11
Re
C3
O3
Br1
Br2
Fig. 1. ORTEP drawing of the anionic fragment fac-[ReBr2(CO)3(Ph2PC„CTol)]ꢀ (2)
with thermal ellipsoids at the 30% probability level, including the atom numbering
of selected atoms. All hydrogen atoms have been omitted for clarity.
Ph
Ph
P
C
C
R
+ Ph2PCCR
Br
Br
[NEt4]2[ReBr3(CO)3]
[NEt4]
+
[NEt4]Br
Re
CO
CO
OC
t
R = Ph(1), Tol(2), Bu(3)
Scheme 2.

C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
2777
Ph
Ph
R
C
C
P
CO
CO
R
Br
+ Ph2PCCR
+ H2O
C
Re
CO
n-2
[ReBr (CO)3(H2O)n]
3-n
C
2
[ReBr3(CO)3]
P
Ph
Ph
t
R = Ph(4), Tol(5), Bu(6)
Scheme 3.
of the same compound in all cases, and the reaction conditions
essentially affect the yields of the reaction.
Complexes 4–6 could be isolated by simple addition of water to
the reaction medium because the polar medium promotes the pre-
cipitation of these compounds. In this case, pure complexes could
be isolated in high yield because tetraethylammonium bromide is
soluble in ethanol/water medium. The IR spectra of complexes 4–6
are very similar and the m(CO) bands are shifted to higher frequen-
P2
cies in comparison with those of complexes 1–3. This shift is con-
sistent with the expected change between an anionic carbonyl and
a neutral carbonyl complex. The signal of the uncoordinated alkyne
is observed in a position nearly identical to that of complexes 1–3
but the intensity of this signal visibly increases. This could be re-
lated to an increase in the triple bond dipole moment [3]. The
31P NMR spectra show a sole signal in a position similar to those
of complexes 1–3 but slightly shifted to low field (ꢀ22/
ꢀ24 ppm). These results are consistent with the coordination of
phosphorus atom and the existence of free alkyne in complexes
4–6. This hypothesis is also supported by the 13C NMR spectra that
show the signals of the alpha acetylenic carbons with JP–C cou-
plings higher than 100 Hz, typical values of P-coordinated phos-
phinoalkynes [3,7,11,12]. These spectra also provided the first
evidence of the presence of two phosphinoalkynes coordinated to
rhenium in complexes 4–6. The signals of alpha acetylenic carbons
O3a
C3a
C132
C232
O1
C231
P1
C131
C1
Re
Br3a
C2
O2
Fig. 2. ORTEP drawing of fac-[ReBr(CO)3(Ph2PC„CtBu)2] (6) with thermal ellipsoids
at the 30% probability level, including the atom numbering of selected atoms. All
hydrogen atoms have been omitted for clarity.
1
3
appear as double doublets (5: JP–C = 102.2 Hz, JP–C = 7.2 Hz) and
the signals of beta acetylenic carbons as the A part of a second or-
der AXX0 system [28]. This split suggest the existence of two phos-
ratio value is equal to 1. On the contrary, the reaction with [Re-
Br3(CO)3]2ꢀ led to the substitution of only one bromide by
phosphorus for phosphine/metal ratios between 1 and 2. Conse-
quently, the reaction with [ReBr3(CO)3]2ꢀ favours the formation
of a complex with a phosphine bonded to metal and the reaction
with the hydrolyzed complex has a tendency to form the complex
with two phosphines linked to metal. The trend to form complexes
4–6 in water medium is reflected by the evolution of the anionic
complexes 1–3 in a medium with water. Thus, complexes 1–3 were
dissolved in ethanol and water was added to the solution in iden-
phorus atoms linked to the metal,
a supposition that was
corroborated by the MS-ESI of complexes 4–6 that show in all cases
a main signal of cation [Re(CO)3(H2O)(Ph2PC„CR)2]+. The crystal
structure of complex 6 was determined by X-ray diffraction meth-
ods (Fig. 2) and it confirms the presence of the two P-coordinated
phosphinoalkynes bonded to the fac-{Re(CO)3}+ fragment. The
coordination set around the metal is completed by a bromide
ligand. Hence, the formation and subsequent precipitation of com-
plexes 4–6 can be understood from the perspective that the
reaction between the phosphinoalkyne and the hydrolyzed rhe-
nium complex [ReBr3ꢀn(CO)3(H2O)n]2ꢀn is visibly different from
the reaction with [ReBr3(CO)3]2ꢀ. In the reaction with the hydro-
lyzed complex we observed that complexes with two phos-
phinoalkynes linked to the metal are formed as the main
compound in all experiments, even when the phosphine/metal
tical conditions to the preparation of complexes 4–6. The IR and 31
NMR spectroscopy evidence the fast, nearly quantitative formation
of neutral complexes 4–6 as shown in Scheme 4.
Since the formation of the metallacycles shown in Scheme 1 is
more favourable in basic medium, the hydrolysis of complexes
1–3 in presence of bases was studied by means of IR and 31P
NMR spectroscopy. Experiments using the weak base 2,6-lutidine
P
Ph
Ph
R
Ph
Ph
C
C
P
P
C
C
R
CO
CO
R
Br
P
EtOH / H2O
Br
Br
C
Re
CO
C
Re
CO
CO
Ph
OC
Ph
4, 5, 6
1, 2, 3
Scheme 4.

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C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
in acetonitrile/water medium were performed at different reaction
times and temperatures. In all studied cases the evolution was sim-
ilar. Initially, the IR spectrum shows changes in the position of
complexes 1–3. The IR spectrum of this complex in the m(CO) re-
gion is nearly identical to that of complexes 1–3 and the 31P
NMR spectra are also very similar (7, ꢀ21.7 ppm; 1, ꢀ23.9 ppm),
although the free phosphines show resonances at more dissimilar
positions as was stated in the previous paragraph. The forma-
tion of an anionic complex similar to 1–3 with the phosphine
(o-Tol)2PC„CPh confirms that the higher steric hinderance around
the phosphorus atom is compatible with the coordination to the
fragment {ReBr2(CO)3}ꢀ leading to complex 7.
m
(CO) bands but
m
(C„C) band remains practically unaltered. After
-OH)3] is
some time, a white precipitate of [NEt4][Re2(CO)6(
l
formed [29] and the 31P NMR of filtrate shows the characteristic
signal of the free phosphinoalkyne ligand. Similar results were
found using strong bases as NaOH. These results can be related
with the initial substitution of bromide by other ligands present
in the reaction medium but the absence of a metallacycle in this
step is revealed by the unaltered signal of the uncoordinated al-
kyne. Subsequent evolution to the formation of the binuclear com-
The reaction between the phosphine (o-Tol)2PC„CPh and [NE-
t4]2[ReBr3(CO)3] was performed in water/ethanol, in a similar way
to the preparation of complexes 4–6, with the aim of preparing a
complex with a sole phosphinoalkyne bonded to the {Re(CO)3-
plex [Re2(CO)6(l
-OH)3]ꢀ and free phosphinoalkyne evidence that
in the studied reaction conditions this reaction way is more favor-
(H2O)}+ fragment. Unexpectedly, the IR spectrum in the
m(CO)
able than other possibilities as the metallacycle formation.
region of the resulting solution was analogous to that of complexes
4–6, even with a phosphine/rhenium molar ratio of 1. Complex 8
was isolated from this solution and was characterized by IR, ESI-
MS, 1H, 13C, 31P NMR spectroscopy, and elemental analysis. All data
agree with a structure identical to that found for complexes 4–6
with two phosphinoalkyne ligands linked to the {ReBr(CO)3} frag-
ment. The most relevant difference was observed in the 31P NMR
spectrum. The position of the resonance was similar to those of
complexes 4–6 (ꢀ23.4 ppm) but the signal was displayed as a more
broad band for complex 8 at room temperature. The shape of this
signal evolves with temperature and at higher temperatures
(50 °C) a sharp signal is observed. Low-temperature 31P NMR spec-
troscopic measurements were performed in order to determine if
this phenomenon could be associated with the presence of an equi-
librium process (Fig. 3). Although at first sight the spectrum at low
temperatures resembles an AB system, the asymmetric appearance
and the different separation between the two peaks at high field
(260 Hz) and low field (289 Hz) rules out this possibility. An alter-
native possibility to explain the splitting of this signal could be the
presence of different conformers in solution. An EXSY 31P–31P NMR
experiment showed correlations between all signals in agreement
with this hypothesis. This different behaviour observed in complex
8 with respect to 4–6 could be associated with the presence of the
o-tolyl groups in 8 that hinder the rotation around the metal–phos-
phorus bond leading to different conformers, which can be de-
tected by 31P NMR at low temperatures. The ESI-MS of 8 shows a
main signal assigned to the cation [Re(CO)3{(o-Tol)2 PC„CPh}2]+,
evidencing the presence of two phosphines linked to the metal
atom.
2.2. Complexes with X2PC„CPh (X = o-Tol)
Since the reactivity of the hydrolyzed rhenium complex with
phosphinoalkynes Ph2PC„CR showed a propensity to form com-
plexes with two phosphines coordinated to rhenium, we decided
to study the same reaction with a sterically hindered phos-
phinoalkyne by substitution of phenyl groups with bulkier o-tolyl
groups. The aim was to study if the use of this more sterically hin-
dered phosphine could led to a different reactivity since this sce-
nario might favour the formation of a complex with a sole
phosphine linked to the fac-{Re(CO)3}+ fragment. The synthesis of
(o-Tol)2PC„CPh has been reported [30] but it has been only used
in phosphinoalkyne cyclization reactions and, as far as we know,
no coordination studies have been reported. Thus, the phosphine
(o-Tol)2PC„CPh was synthesized by the same procedure employed
for phosphines Ph2PC„CR, but using (o-Tol)2PCl instead of Ph2PCl.
This phosphine (o-Tol)2PC„CPh was crystallized in ethanol and
was obtained in good yield after crystallization (60 %). The IR spec-
trum of this phosphine shows the characteristic m(C„C) band at
2160 cmꢀ1. The position of the two acetylenic carbons in the 13C
NMR spectrum (84.8 and 107.8 ppm) is very similar to that found
for Ph2PC„CPh (85.2 and 107.6 ppm), showing that the electronic
properties of the two acetylenic fragments should be comparable.
However, the differences around the phosphorus atom are re-
vealed by the 31P NMR spectrum that displays
a signal at
ꢀ46.5 ppm, nearly 14 ppm shifted highfield with respect to
Ph2PC„CR phosphines. This change in behaviour can be related
to a higher distortion around the phosphorus atom [31].
The reaction between phosphine (o-Tol)2PC„CPh and the anion
[ReBr3(CO)3]2ꢀ led to the formation of the respective P-coordinated
complex [ReBr2(CO)3(L)]ꢀ (7, L = (o-Tol)2PC„CPh), analogous to
It should be emphasized that complex 7 evolves in ethanol/
water medium to complex 8 in an identical manner to that found
with complexes 1–3 (Scheme 5). This result shows that the trend
to form complexes with two phosphinoalkynes linked to the metal
Fig. 3. Low-temperature 31P NMR spectra for complex 8.

C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
2779
P
C
C
Ph
X
(X=o-Tol)
X
2
[ReBr3(CO)3]
EtOH, H2O
2
[ReBr3(CO)3]
CH2Cl2
EtOH, H2O
[ReBr(CO)3(X2PCCPh)2]
[ReBr2(CO)3(X2PCCPh)]
(8)
(7)
Scheme 5.
Table 1
Selected bond distances (Å) for complexes 2, 6 and 8
2
6
8
Re–P
2.4849 (19)
2.4855 (15)/Re–P1
2.4856 (15)/Re–P2
2.5132 (12)/Re–P1
2.5252 (11)/Re–P2
C22
Re–Br
C21
2.6454 (9)/Re–Br1
2.6244 (16)/Re–Br3A
2.618 (7)/Re–Br3B
2.6423 (5)
P2
2.6227 (11)/Re–Br2
O3
Re–C
C11
P1
1.908 (9)/Re–C1
1.890 (8)/Re–C2
1.910 (9)/Re–C3
1.937 (6)/Re–C1
1.955 (7)/Re–C2
1.895 (11)/Re–C3A
1.945 (9)/Re–C3B
1.945 (5)/Re–C1
1.928 (5)/Re–C2
1.917 (5)/Re–C3
C3
Re
C1
C12
O1
C–O
Br
C2
1.099(10) (1)/C1–O1
1.153 (9)/C2–O2
1.142(11) (1)/C3–O3
1.151 (6)/C1–O1
1.136 (7)/C2–O2
1.158 (19)/C3A–O3A
1.144 (10)/C3B–O3B
1.135 (6)/C1–O1
1.149 (5)/C2–O2
1.123 (5)/C3–O3
O2
C„C
1.217(11) (1)/C11–C12
1.189 (7)/C131–C132
1.181 (7)/C231–C231
1.200 (6)/C11–C12
1.179 (6)/C21–C22
Fig. 4. ORTEP drawing of fac-[ReBr(CO)3{(o-Tol)2PC„Ph}2] (8) with thermal
ellipsoids at the 30% probability level, including the atom numbering of selected
atoms. All hydrogen atoms have been omitted for clarity.
Br(CO)3P2] [21,32,33]. When comparing these parameters
between complexes 6 and 8, we can see that the substitution of
the phenyl groups by the o-tolyl groups implies that Re–P bonds
are somewhat lengthier and some angle bonds that contain phos-
phorus are slightly more opened, changes that should be attributed
to higher steric hindrance of o-tolyl groups. It must be born in
mind that, as far as we know, only one structure of an octahedral
transition metal complex with two bis(o-tolyl)phosphine groups
in cis-position has been reported [34], and in this case the ligand
is a tripodal phosphine.
in ethanol/water media is retained although the phosphine is ste-
rically hindered. Finally, the crystal structure of complex 8 was
determined by X-ray diffraction methods (Fig. 4) and it confirmed
the presence of the two P-coordinated phosphinoalkynes bonded
to the fac-{Re(CO)3}+ fragment.
2.3. Crystal structures of complexes 2, 6 and 8
Selected bond distances and angles for complexes 2, 6 and 8 are,
respectively, displayed in Tables 1 and 2. Rhenium metal atom pre-
sents a slightly distorted octahedral arrangement for the three
complexes. The structure of the coordination set around rhenium
metal for complex 2 is very similar to the few previously reported
complexes [21] that contain a phosphine ligand linked to the anio-
nic fragment fac-{ReBr2(CO)3}ꢀ. Complexes with two phoshine li-
gands linked to the neutral fragment fac-{ReBr(CO)3} have been
reported but it should be emphasized that the two phosphines in
cis-position have never contained bulky groups as in complex 8.
With monodentate phosphines, the reported complexes contain
two triarylphosphines [21b,32], alkyldiarylphosphines [33] or
1,3,5-triaza-7-phosphaadamantane [21a]. Another option is the
presence of a sole bidentate bis(diphenylphosphine) ligand occu-
pying the two cis-positions [33]. The geometric parameters around
rhenium metal for complex 6 are very similar to those of previ-
ously reported complexes with the coordination set fac-[Re-
The structure of fac-{Re(CO)3} fragment in the three complexes
(2, 6, 8) does not differ significantly and it is also similar to previ-
ously reported rhenium carbonyl complexes [21,32,33]. The C„C
bond distance is also similar for the three complexes and resem-
bles reported values for other P-coordinated phosphinoalkyne me-
tal complexes [3,4,7,11,12]. This result implies that no relevant
structural differences are observed if the phosphinoalkyne is coor-
dinated to the anionic fragment {ReBr2(CO)3}ꢀ or to the neutral
fragment {ReBr(CO)3}. However, a remarkable difference is ob-
served on comparing the relative positions of the two alkyne frag-
ments between complexes 6 and 8. In complex 8 the two alkyne
fragments are positioned in the same direction, so they are close
each other, whereas in complex 6 they are placed in opposite direc-
tions and as a result they are far away. This difference is probably a
consequence of the steric hindrance between the bulky o-tolyl
fragments. Although in the present work no significant chemical
differences have been observed between complexes 6 and 8, this

2780
C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
Table 3 displays the 13C NMR chemical shifts of the acetylenic
atoms for complexes 1–6, their respective free phosphinoalkynes
and the values of a series of cationic [3] and anionic [36] iron com-
plexes for comparison purposes. The P-coordination of a phos-
phinoalkyne to a metal involves an increase in the C„C triple
bond polarization and the 13C resonances of acetylenic carbon
atoms C1 and C2 are shifted upfield and downfield, respectively,
with regard to that of the corresponding free phosphinoalkyne.
Table 3 shows that dC2 ꢀ dC1 values for the anionic complexes (1,
2, 3) are nearly six ppm lower than the values for neutral com-
plexes (4, 5, 6). The same tendency was previously observed when
comparing anionic and cationic iron complexes [3] (see Table 3)
and is explained by the higher charge on phosphorus atom in the
cationic complexes that induces the polarization of the triple bond.
On comparing the metal complexes for the three phosphinoalkynes
studied (Ph2PC„CR; R = Ph, Tol, tBu), it can be seen that in all cases
the triple bond polarization increases following the same pattern
as it is shown in Scheme 6.
Table 2
Selected bond angles (deg) for complexes 2, 6 and 8
2
6
8
P–Re–C
91.4 (3)/P–Re–C1
87.0 (2)/P–Re–C2
176.6 (3)/P–Re–C3
174.8 (2)/P1–Re–C1
88.7 (2)/P1–Re–C2
93.8 (4)/P1– Re–C3A
87.6 (2)/P2–Re–C1
174.0 (2)/P2–Re–C2
89.7 (3)/P2–Re–C3A
175.3 (1)/P1–Re–C1
90.3 (1)/P1–Re–C2
91.3 (1)/P1–Re–C3
87.6 (1)/P2–Re–C1
168.5 (1)/P2–Re–C2
84.9 (1)/P2–Re–C3
P–Re–Br
94.51 (5)/P–Re–Br1
87.85 (5)/P–Re–Br2
89.90 (5)/P1–Re–Br3A
90.54 (5)/P2–Re–Br3A
91.57 (3)/P1–Re–Br
96.28 (3)/P2–Re–Br
P–Re–P
94.22 (5)/P1–Re–P2
96.24 (4)/P1–Re–P2
Br–Re–Br
88.08 (4)/Br1–Re–Br2
C–Re–C
89.6 (4)/C1–Re–C2
89.7 (4)/C2–Re–C3
89.4 (4)/C1–Re–C3
90.0 (2)/C1–Re–C2
84.8 (4)/C2–Re–C3A
91.1 (4)/C1–Re–C3A
86.3 (2)/C1–Re–C2
85.6 (2)/C2–Re–C3
91.7 (2)/C1–Re–C3
(Fp = Fe(CO)2Cp). The values of dC2 ꢀ dC1 for the neutral com-
plexes (4, 5, 6) are only 4.0–4.6 ppm lower than those obtained
for the cationic iron complexes [FpPh2PC„CR]+, that means that
the alkyne polarization is not very different between these rhe-
nium and iron compounds. In addition, when complexes 4, 5, 6
are in solution in a medium that contains water, the Re–Br bond
is probably hydrolyzed to form cationic complexes like [Re(H2O)-
(CO)3(Ph2PC„CR)2]+ where the polarization of the C„C bond
should be even higher than in the neutral complexes 4, 5, 6. Con-
sequently, the different chemical behaviour observed between iron
and rhenium complexes, namely the iron compounds quickly
evolve to form metallacycles while, to date rhenium compounds
do not, cannot be attributed to different electron properties of
the alkyne fragment.
C–Re–Br
89.9 (3)/C1–Re–Br1
177.7 (2)/C1–Re–Br2
178.4 (2)/C2–Re–Br1
92.4 (2)/C2–Re–Br2
88.8 (3)/C3–Re–Br1
91.5 (3)/C3–Re–Br2
85.2 (2)/C1–Re–Br3A
94.8 (2)/C2–Re–Br3A
176.2 (4)/C3A–Re–Br3A
85.4 (1)/C1–Re–Br
92.9 (1)/C2–Re–Br
176.8 (1)/C3–Re–Br
P–C„C
171.8(8)/P–C11–C12
172.8 (6)/P1–C131–C132
174.1 (6)/P2–C231–C232
175.8(4)/P1–C11–C12
175.9(4)/P2–C21–C22
feature could lead to design in future attracting strategies to ap-
proach alkyne groups in P-coordinated phosphinoalkyne metal
complexes.
3. Conclusions
2.4. 13C NMR spectra of acetylenic carbon atoms
We have examined the reactivity of phosphinoalkynes
Ph2PC„CR (R = Ph, Tol, Bu) with the rhenium carbonyl precursor
t
As previously mentioned, the analysis of 13C NMR resonances of
acetylenic carbon in phosphinoalkynes and their P-coordinated
metal complexes is a useful tool to compare the electronic proper-
ties of metal fragments linked to phosphinoalkynes. The chemical
shift differences (dC2 ꢀ dC1) of acetylenic carbons for different
compounds can be related to the triple bond polarization [35],
fac-[ReBr3(CO)3]2ꢀ and the anionic P-coordinated complexes fac-
[ReBr2(CO)3(Ph2PC„CR)]ꢀ (1, 2, 3) were formed in all cases. These
complexes evolve in an ethanol/water medium to form neutral
fac-[ReBr(CO)3(Ph2PC„CR)2] (4, 5,6) complexes. The same com-
plexes were obtained by direct reaction between the carbonyl pre-
cursor fac-[ReBr3(CO)3]2ꢀ and the respective phosphinoalkyne in
ethanol/water medium, independently of whether the metal/phos-
phine ratio used was one or two. This singular behaviour can be
related with a higher tendency of the hydrolyzed complex to form
compounds with two phosphorus atoms linked to the metal. The
same behaviour has been observed even with the phos-
phinoalkyne (o-Tol)2PC„CPh, which contains two bulky o-tolyl
groups linked to the phosphorus atom. Complex 8 contains two
cis coordinated (o-Tol)2PC„CPh ligands, and the bulky groups do
not modify substantially the reactivity towards rhenium com-
plexes with respect to Ph2PC„CPh ligands. To date, the most sig-
nificant differences were found in: (1) the different orientation of
alkyne fragments in crystal structure of 8 with respect to 6; (2) the
31P NMR spectra of 8 at low temperature that show the presence of
different conformers, probably as a result of hindered rotation by
bulky groups.
Table 3
13C NMR chemical shift (d, ppm) for the acetylenic atoms in phosphinoalkynes and P-
coordinated phosphinoalkynes
Compound
C1
C2
C2–C1
Ph2PC1„C2Ph
85.2
83.2
80.0
87.0
80.3
107.6
108.3
111.1
107.1
115.7
22.4
25.1
31.1
20.1
35.4
[ReBr2(CO)3Ph2PC1„C2Ph]ꢀ (1)
[ReBr(CO)3(Ph2PC1„C2Ph)2] (4)
[Fe3(CO)9(CCH3)(Ph2PC1„C2Ph)]ꢀa
[CpFe(CO)2Ph2PC1„C2Ph]+b
Ph2PC1„C2Tol
84.3
82.3
79.2
86.1
80.0
107.9
108.7
111.7
107.4
116.5
23.6
26.4
32.5
21.3
36.5
[ReBr2(CO)3Ph2PC1„C2Tol]ꢀ (2)
[ReBr(CO)3(Ph2PC1„C2Tol)2] (5)
[Fe3(CO)9(CCH3)(Ph2PC1„C2Tol)]ꢀa
[CpFe(CO)2Ph2PC1„C2Tol]+b
The analysis of 13C NMR resonances of acetylenic carbons show
that alkyne polarization for neutral complexes (4, 5, 6) is only
slightly lower than the values previously reported for P-coordi-
nated cationic iron complexes, so the electronic properties of al-
kynes should be comparable for both kind of complexes.
However, up to now no reaction that could yield a metallacycle
similar to those reported for iron complexes has been observed.
Ph2PC1„C2-tBu
73.7
72.3
69.7
75.7
70.9
118.2
119.3
122.1
117.7
127.9
44.5
47.0
52.4
42.0
57.0
[NEt4][ReBr2(CO)3Ph2PC1„C2-tBu]ꢀ (3)
[ReBr(CO)3(Ph2PC1„C2-tBu)2] (6)
[Fe3(CO)9(CCH3)(Ph2PC1„C2-tBu)]ꢀa
[CpFe(CO)2Ph2PC1„C2-tBu]+b
a
Ref. [36].
b
Ref. [3].

C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
2781
[Fe3(CO)9(CCH3)(Ph2PC≡CR)] - < [ReBr2(CO)3Ph2PC≡CR] - < [ReBr(CO)3(Ph2PC≡CR) 2] < [FpPh2PC≡CR] +
Scheme 6.
3
ppm): 2.37 (s; CH3), 7.27 (d, JH–H = 8.1 Hz; H meta position tolyl
4. Experimental
3
group), 7.61 (d, JH–H = 8.1 Hz; H ortho position tolyl group),
7.30–8.20 (m; Har). 31P{1H} NMR ((CD3)2CO, d in ppm): ꢀ24.3 (s).
4.1. Synthesis
13C{1H} NMR ((CD3)2CO, d in ppm): 20.4 (s, CH3), 82.3 (d, JC–P
=
1
2
85.0 Hz; „C–P), 108.7 (d, JC–P = 12.8 Hz; „C–Car), 118.5 (d,
J = 2.9 Hz; Car), 127.2–133.8 (m; Car), 140.0 (s; Car), 191.5–193.6
(m; CO).
All reactions were performed under nitrogen by standard
Schlenk tube techniques. Infrared spectra were recorded with a
Perkin–Elmer 2000 FT spectrometer. The NMR spectra were re-
corded by the Servei de Ressonància Magnètica Nuclear de la Univer-
4.1.2.3. Complex 3. IR (CH2Cl2, cmꢀ1): 2167 (s, C„C), 2173 (s, C„C),
2020 (vs, C„O), 1919 (vs, C„O), 1884 (vs, C„O). 1H NMR
((CD3)2CO, d in ppm): 1.41 (s; CH3), 7.36–8.15 (m; Har). 31P{1H}
NMR ((CD3)2CO, d in ppm): ꢀ26.4 (s). 13C{1H} NMR ((CD3)2CO, d
sitat Autònoma de Barcelona on
a Bruker AVANCE DPX-250
instrument. Microanalyses were performed by the Servei de Micro-
anàlisi de l’Institut d’Investigacions Químiques i Ambientals de Barce-
lona (IIQAB). Mass spectra were obtained on an Esquire 3000 with
electrospray ionization and an ion trap Bruker Daltonics by Servei
d’Anàlisi Química del Departament de Química de la Universitat Autò-
noma de Barcelona. Crystal structure determinations were per-
1
in ppm): 29.5 (s; C–(CH3)3), 29.7 (s; CH3), 72.3 (d, JC–P = 88.3 Hz;
2
„C–P), 119.3 (d, JC–P = 11.7 Hz; „C–C), 127.6–139.7 (m; Car),
191.5–193.6 (m; CO).
formed by Servei de Difracció de Raigs
Autònoma de Barcelona.
X de la Universitat
4.1.2.4. Complex 7. IR (CH2Cl2, cmꢀ1): 2177 (s, C„C), 2021 (vs,
C„O), 1919 (vs, C„O), 1884 (vs, C„O). 1H NMR (CD2Cl2, d in
ppm): 2.16 (s; CH3), 7.10–8.60 (m; Har). 31P{1H} NMR (CD2Cl2, d
in ppm): ꢀ21.7 (s). 13C NMR spectrum could not be obtained
because solubility was too low.
The complex [NEt4]2[ReBr3(CO)3] [27a] and the acetylenic phos-
t
phines Ph2PC„CR {R = p-tolyl, Ph and Bu} [37] were prepared by
published procedures.
4.1.1. Synthesis of (o-tolyl)2PC„CPh
4.1.3. Synthesis of [ReBr(CO)3(Ph2PC„CR)2] {R = p-tolyl (4), Ph (5), tBu
(6)}
The phosphine (o-tolyl)2PC„CPh was prepared by using a sim-
ilar procedure to that reported for Ph2PC„CR [37]. To a solution of
phenylacetylene (0.45 mL, 4 mmol) in diethyl ether (20 mL) main-
tained at ꢀ78 °C was dropwise added under stirring a solution of
butyllithium (2.5 mL, 1.6 M in hexane; 4 mmol) in diethyl ether
(20 mL). The solution was stirred for 30 min; then (o-tolyl)2PCl
(1 g, 3.9 mmol) in solution in 20 mL of diethyl ether was dropwise
added keeping the temperature at ꢀ78 °C. This mixture was slowly
raised to room temperature and the solution was stirred for addi-
tional 1 h. After filtration to remove LiCl, the solution was evapo-
rated to dryness. Crystallization in absolute ethanol gave 0.76 g
of product as white solid. Yield: 63%. IR (CH2Cl2, cmꢀ1): 2159 (s,
C„C). 1H NMR ((CD3)2CO, 25 °C, d in ppm): 2.50 (s; CH3), 7.20–
7.70 (m; Har). 31P{1H} NMR ((CD3)2CO, d in ppm): ꢀ46.5 (s).
13C{1H} NMR ((CD3)2CO, d in ppm): 19.9 (s, CH3), 20.2 (s, CH3),
To a solution of [NEt4]2[ReBr3(CO)3] (50 mg, 0.07 mmol) in
EtOH/H2O (4 mL:3 mL) was added a solution of the acetylenic
phosphines (0.18 mmol) in EtOH (10 mL). The reaction mixture
was heated to reflux and water (9 mL) was slowly added during
90 min (1 mL/10 min). After addition was complete, reflux was
continued for additional 90 min. A white precipitated was formed,
which was filtered, washed with 2 ꢁ 5 mL of a cold 50% water:
EtOH mixture and recrystallized in toluene/hexane.
4.1.3.1. Complex 4. Yield: 73%. Anal. Calc. for C43H30O3BrP2Re: C,
55.97; H, 3.28. Found: C, 55.93; H, 3.14%. IR (CH2Cl2 cmꢀ1): 2177
(s, C„C), 2040 (vs, C„O), 1964 (vs, C„O), 1909 (vs, C„O). 1H
3
NMR (CDCl3, d in ppm): 2.43 (s; CH3), 7.26 (d, JH–H = 8.1 Hz; H
3
1
2
meta position tolyl group), 7.50 (d, JH–H = 8.1 Hz; H ortho position
84.8 (d, JC–P = 7.9 Hz; „C–P), 107.8 (d, JC–P = 4.5 Hz; „C–Car),
tolyl group), 7.42–7.72 (m; Har). 31P{1H} NMR (CDCl3, d in ppm):
ꢀ21.9 (s). 13C{1H} NMR (CDCl3, d in ppm): 21.4 (s; CH3), 79.2 (dd,
1
122.4 (s; Car–C„), 125.7–133.2 (m; Car), 141.4 (d, JC–P = 7.2 Hz;
Car–P). ESI/MS (positive mode, m/z): 315.1 [MH+].
3
1JC–P = 103.7 Hz, JC–P = 7.2 Hz; „C–P), 111.7 (AXX0, three lines are
2
observed, JC–P + 4JC–P=13.4; „C–Car), 117.9 (d, J = 2.1 Hz; Car),
4.1.2. Synthesis of [NEt4][ReBr2(CO)3(X2PC„CR)] {(X = R = Ph, 1),
(X = Ph, R = p-tolyl, 2), (X = Ph, R = tBu, 3), (X = o-tolyl, R = Ph, 7)}
A solution of the acetylenic phosphines (0.14 mmol) in CH2Cl2
(20 mL) was added to a solution of [NEt4]2[ReBr3(CO)3] (0.1 g,
0.13 mmol) in CH2Cl2 (70 mL) and stirred for 3 h at room temper-
ature for complexes 1–3. This reaction must be performed under
reflux for 7. Next, the reaction mixture was concentrated by evap-
oration to a few milliliters and toluene was added. The complexes
crystallize contaminated with NEt4Br.
127.0–134.4 (m; Car), 140.2 (s; Car), 187.2–189.0 (m; CO). ESI/MS
(positive mode, m/z): 889.3 [MꢀBr+H2O]+.
4.1.3.2. Complex 5. Yield: 80%. Anal. Calc. for C45H34O3BrP2Re: C,
56.85; H, 3.60. Found: C, 56.84; H, 3.53%. IR (CH2Cl2, cmꢀ1): 2179
(s, C„C), 2040 (vs, C„O), 1966 (vs, C„O), 1909 (vs, C„O). 1H
NMR (CDCl3, d in ppm): 7.10–7.90 (m; Har). 31P{1H} NMR (CDCl3,
d in ppm): ꢀ21.5 (s). 13C{1H} NMR (CDCl3, d in ppm): 80.0 (dd,
3
1JC–P = 102.2 Hz, JC–P = 7.0 Hz; „C–P), 111.1 (AXX0, three lines are
2
observed, JC–P + 4JC–P = 13.8 Hz; „C–Car), 120.9 (s; Car), 127.0–
4.1.2.1. Complex 1. IR (CH2Cl2, cmꢀ1): 2178 (s, C„C), 2021 (vs,
C„O), 1920 (vs, C„O), 1884 (vs, C„O). 1H NMR ((CD3)2CO, d in
134.0 (m; Car), 187.1–190.0 (m; CO). ESI/MS (positive mode, m/z):
861.2 [MꢀBr+H2O]+.
ppm): 7.40–8.25 (m; Har). 31P{1H} NMR ((CD3)2CO, d in ppm):
ꢀ23.9 (s). 13C{1H} NMR ((CD3)2CO, d in ppm): 83.2 (d, JC–P
=
1
2
4.1.3.3. Complex 6. Yield: 82%. Anal. Calc. for C39H38O3BrP2Re: C,
53.06; H, 4.34. Found: C, 53.11; H, 4.41%. IR (CH2Cl2, cmꢀ1): 2211
(s, C„C), 2171 (s, C„C), 2039 (vs, C„O), 1962 (vs, C„O), 1908
(vs, C„O). 1H NMR (CDCl3, d in ppm): 1.47 (s; CH3), 7.26-7.77
(m; Har). 31P{1H} NMR (CDCl3, d in ppm): ꢀ23.8 (s). 13C{1H} NMR
83.8 Hz; „C–P), 108.3 (d, JC–P = 12.4 Hz, „C–Car,), 121.5 (d,
J = 2.7 Hz; Car), 127.2- 133.7 (m; Car), 191.5–193.6 (m; CO).
4.1.2.2. Complex 2. IR (CH2Cl2, cmꢀ1): 2175 (s, C„C), 2021 (vs,
C„O), 1921 (vs, C„O), 1885 (vs, C„O). 1H NMR ((CD3)2CO, d in

2782
C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
Table 4
Crystal data and structure refinement details
2
6
8 ꢂ C7H8
Formula
C32H37Br2NO3PRe
860.62
296(2)
C39H38BrO3P2Re
882.74
296(2)
Monoclinic
P 21/c
10.4976(6)
9.7402(6)
36.753(2)
90
90.474(1)
90
3757.8(4)
4
1.560
4.42
C54H46BrO3P2Re
1070.96
296(2)
Formula weight
Temperature (K)
Crystal system
Space group
a (Å)
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
10.1649(6)
10.5660(6)
16.7362(10)
94.542(1)
90.217(1).
106.493(1)
1717.5(2)
13.1572(7)
14.4084(8)
14.8729(8)
109.139(1)
115.375(1)
90.212(1)
2372.1(2)
2
1.499
3.51
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
2
Dcalc (Mg cmꢀ3
)
1.664
5.94
840
0.47 ꢁ 0.26 ꢁ 0.06
2.02–29.07
11596/7918 (0.0441)
7918/34/358
0.962
Absorption coefficient (mmꢀ1
F(000)
)
1744
1068
Crystal size (mm3)
h Range for data collection
0.54 ꢁ 0.46 ꢁ 0.05
1.11–29.07
25547/9225 (0.0604)
9225/26/449
1.023
0.40 ꢁ 0.16 ꢁ 0.10
1.63–29.03
16631/11105 (0.0207)
11105/18/504
1.036
Number of reflections collected/unique (Rint
)
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0609, wR2 = 0.1501
R1 = 0.0751, wR2 = 0.1564
2.31 and ꢀ1.50
R1 = 0.0495, wR2 = 0.0794
R1 = 0.0891, wR2 = 0.0903
0.88 and ꢀ0.69
R1 = 0.0399, wR2 = 0.0966
R1 = 0.0505, wR2 = 0.1024
0.96 and ꢀ0.49
Largest difference in peak and hole (e Åꢀ3
)
(CDCl3, d in ppm): 28.7 (s; C–(CH3)3), 30.4 (s; CH3), 69.7 (dd, 1JC–P
=
corresponding site occupation factors were refined. Geometric re-
straints were applied. These five split atoms were refined with iso-
tropic displacement parameters, U, and the rest of non-hydrogen
atoms in the structure, with anisotropic Uij. Hydrogen atoms were
placed in calculated positions with isotropic displacement param-
eters fixed at 1.5 (methyl H atoms) or 1.2 (the rest) times the Ueq of
the corresponding carbon atoms.
3
105.4 Hz, JC–P = 7.0 Hz; „C–P), 122.1 (AXX0, three lines are ob-
2
served, JC–P + 4JC–P = 12.4 Hz; „C–Car), 127.2–134.6 (m; Car),
187.1–189.8 (m; CO). ESI/MS (positive mode, m/z): 803.3 [MꢀBr]+.
4.1.4. Synthesis of [ReBr(CO)3{(o-tolyl)2PC„CPh}2] ꢂ C7H8 (8)
To a solution of [NEt4]2[ReBr3(CO)3] (0.1 g, 0.13 mmol) in EtOH/
H2O (6 mL:4 mL) was added
a
solution of (o-tolyl)2PC„CPh
In 6, the Br and the opposite CO show positional disorder. In
Fig. 2, only the main component of disorder (70%) is shown. Non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were placed in calculated positions
with isotropic displacement parameters fixed at 1.5 (methyl H
atoms) or 1.2 (benzenic H atoms) times the Ueq of the correspond-
ing carbon atoms.
(0.14 mmol) in EtOH (10 mL). The reaction mixture was heated
to reflux and water (20 mL) was slowly added during 100 min
(2 mL/min). After addition was complete, reflux was continued
for additional 80 min. A white precipitated was formed, which
was filtered, washed with 2 ꢁ 5 mL of a cold 50% water:EtOH mix-
ture and recrystallized in toluene/hexane.
Yield: 56%. Anal. Calc. for C54H46O3BrP2Re: C, 60.56; H, 4.33.
Found: C, 60.70; H, 4.28%. IR (CH2Cl2, cmꢀ1): 2177 (s, C„C), 2038
(vs, C„O), 1958 (vs, C„O), 1913 (vs, C„O). 1H NMR (CDCl3, d
in ppm): 2.08 (s; CH3), 2.16 (s; CH3), 7.00-7.30 (m; Har), 8.35 (dd,
In 8, the crystal structure is a 1:1 complex:toluene solvate. The
solvent molecule is highly disordered. Two constrained benzene
rings and four positions for methyl C atom, partially overlapped,
were considered and refined with isotropic displacement parame-
ters. H atoms were not included in this model of disordered sol-
vent. For the complex, non-hydrogen atoms were refined with
anisotropic displacement parameters and hydrogen atoms were
placed in calculated positions with isotropic displacement param-
eters fixed at 1.5 (methyl H atoms) or 1.2 (benzenic H atoms) times
the Ueq of the corresponding carbon atoms.
4
4JP–H = 14.4 Hz, JH–H = 7.4 Hz; H ortho position tolyl group), 8.45
4
4
(dd, JP–H = 14.4 Hz, JH–H = 7.4 Hz; H ortho position tolyl group).
31P{1H} NMR (CDCl3, d in ppm): ꢀ23.4 (s). 13C{1H} NMR (CDCl3, d
in ppm): 21.5 (s; CH3), 21.8 (s; CH3), 82.3 (d, 1JC–P = 88.6 Hz; „C–P),
2
109.4 (d, JC–P = 11.4 Hz; „C–Car), 121.2 (s; Car), 124.8–137.3 (m;
Car), 141.2 (d, J = 10.4 Hz; Car), 187.1–189.3 (m; CO). ESI/MS (posi-
tive mode, m/z): 899.1 [MꢀBr]+.
4.2. X-ray crystallography
5. Supplementary material
Table 4 reports crystal data and structure refinement details for
complexes 2, 6 and 8. Colorless crystals of these compounds were
obtained by slow evaporation from dichloromethane/toluene solu-
tions at room temperature under nitrogen atmosphere. Diffraction
data were collected using a SMART Apex CCD area detector diffrac-
CCDC 686111, 686112, and 686113 contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
tometer with Mo K
a radiation. Data reduction was carried out
using the SAINT program [38] and absorption corrections were ap-
plied (SADABS [39]). Structures were solved by direct methods and
refined by full-matrix least-squares methods on F2 for all reflec-
tions (SHELXTL [40]).
Acknowledgements
This research was supported by the Dirección General de Investi-
gación, Ministerio de Ciencia y Tecnología (Project CTQ2007-63913).
We thank Dr. J. Real and Dr. T. Parella for helpful discussions about
NMR data.
In 2, the cation, [NEt4]+, is disordered. Two positions for every
methylene and for one methyl groups were considered and the

C. Ledesma et al. / Journal of Organometallic Chemistry 693 (2008) 2775–2783
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