The use of 1,2-dipiperidinoacetylene for the preparation of monometallic diaminoacetylene and homo- or heterobimetallic diaminodicarbene ruthenium(ii) complexes

Article abstract of DOI:10.1039/c1dt10606f

The reaction of the ynediamine 1,2-dipiperidinoacetylene (1) with [(η²-COE)Cr(CO)₅], [(THF)W(CO)₅] and [RuCl₂(η⁶-cymene)]₂ afforded homobimetallic complexes 2a, 2b and 3, in which the diaminoacetylene 1 acts as a bis(aminocarbene) ligand by bridging two complex fragments Cr(CO)₅ (in 2a), W(CO)₅ (in 2b) and RuCl₂(η⁶- cymene) (in 3). The reaction of 1 with [RuCl₂(PPh₃) ₃] gave trans-[(1)RuCl(PPh₃)₂]Cl, [4]Cl, in which the alkyne 1 coordinates as a 4-electron donor ligand. The cation 4 represents a rare example of a square-planar Ru(ii) complex with a low-spin ground state (S = 0), and its stability can be ascribed to the strong alkyne-metal π-interaction as confirmed by DFT calculations. Treatment with one or two equivalents of NaBPh₄ in acetonitrile gave [4]BPh ₄ and the dicationic [(1)Ru(PPh₃)₂(CH ₃CN)₂](BPh₄)₂, [5](BPh ₄)₂. [4]Cl can be used for the preparation of heterobimetallic Ru-Pd bis(aminocarbene) complexes by reaction with [(MeCN) ₂PdCl₂], resulting in the formation of bimetallic 6 and tetrametallic 7.

Full text of DOI:10.1039/c1dt10606f

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PAPER
The use of 1,2-dipiperidinoacetylene for the preparation of monometallic
diaminoacetylene and homo- or heterobimetallic diaminodicarbene
ruthenium(II) complexes†
Alex R. Petrov, Thomas Bannenberg, Constantin G. Daniliuc, Peter G. Jones and Matthias Tamm*
Received 8th April 2011, Accepted 21st June 2011
DOI: 10.1039/c1dt10606f
2
The reaction of the ynediamine 1,2-dipiperidinoacetylene (1) with [(h -COE)Cr(CO)5], [(THF)W(CO)5]
6
and [RuCl2(h -cymene)]2 afforded homobimetallic complexes 2a, 2b and 3, in which the
diaminoacetylene 1 acts as a bis(aminocarbene) ligand by bridging two complex fragments Cr(CO)5 (in
6
2a), W(CO)5 (in 2b) and RuCl2(h -cymene) (in 3). The reaction of 1 with [RuCl2(PPh3)3] gave
trans-[(1)RuCl(PPh3)2]Cl, [4]Cl, in which the alkyne 1 coordinates as a 4-electron donor ligand. The
cation 4 represents a rare example of a square-planar Ru(II) complex with a low-spin ground state (S =
0), and its stability can be ascribed to the strong alkyne-metal p-interaction as confirmed by DFT
calculations. Treatment with one or two equivalents of NaBPh4 in acetonitrile gave [4]BPh4 and the
dicationic [(1)Ru(PPh3)2(CH3CN)2](BPh4)2, [5](BPh4)2. [4]Cl can be used for the preparation of
heterobimetallic Ru-Pd bis(aminocarbene) complexes by reaction with [(MeCN)2PdCl2], resulting in
the formation of bimetallic 6 and tetrametallic 7.
Introduction
The majority of transition metal diaminoacetylene complexes of
2
the type [(h -R2NC CNR2)M] have been prepared by template
methods that involve the formation of the C–C triple bond at the
metal atom by coupling of adjacent isocyanide and/or aminocar-
byne ligands.1–4 In the resulting early transition metal complexes
(M = Nb, Mo, W, Re), the diaminoacetylene ligand was shown to
act usually as a four-electron donor with substantial contributions
of “dicarbenoid” mesomeric structures such as B–D (Scheme 1).
Naturally, these diaminodicarbene characteristics become even
more pronounced in bimetallic complexes, as indicated by the
resonance forms E–G, and the first bis(aminocarbene) complexes
of this type were also obtained by indirect methods through
reductive C–C coupling of cationic Fischer carbyne complexes
such as [Et2NC M(CO)5]BF4 (M = Cr, W).5
Scheme 1 Selected mesomeric structures for monometallic diaminoacety-
lene (A–D) and bimetallic (E–G) diaminodicarbene complexes.
diaminoacetylene.6 On rare occasions, bimetallic metal complexes
have also been reported, and the CO substitution reaction between
5
[(h -C5H5)M(CO)3]2 (M = Mo, W) and Et2NC CNEt2 af-
5
1
1
In contrast, free diaminoacetylenes (ynediamines) have been
only rarely employed for metal complexation, and to the best of
our knowledge, the reaction of Fe(CO)5 with Me2NC CNMe2 to
forded [{(h -C5H5)M(CO)2}2(m-h :h -Et2NC CNEt2)], in which
the presence of a metal–metal bond allows a formal description
of these complexes as 1,2-dimetalacyclobuta-2,4-dienes and thus
as dimeric carbyne complexes.7 Finally, it should be noted that
a ditungsten dicarbene complex was isolated in low yield as
a side product from the reaction of [(CO)5W C(Ph)H] with
Me2NC CNMe2 by substitution of the alkylidene moiety,8 and
the resulting complex, in which the alkyne ligand is bridging two
W(CO)5 units, is closely related to those obtained by reductive
dimerization of cationic Fischer carbyne complexes (vide supra).5
Evidently, the coordination chemistry of diaminoacetylenes is
comparatively poorly developed, which can be ascribed to the high
reactivity of these electron-rich compounds and to the lack of reli-
able and adaptable synthetic protocols,9 although the preparation
2
afford [(h -Me2NC CNMe2)Fe(CO)3] via a ferracyclobutenone
complex represents the only example of the formation of a
mononuclear metal complex by coordination of an authentic
Institut fu¨r Anorganische und Analytische Chemie, Technische Universita¨t
Braunschweig, Hagenring 30, D-38106, Braunschweig, Germany. E-mail:
m.tamm@tu-bs.de; Fax: (+49) 531-391-5387; Tel: (+49) 531-391-5309
† Electronic supplementary information (ESI) available: Details of the elec-
tronic structure calculations and presentations of all calculated structures
together with Cartesian coordinates of their atomic positions are provided.
CCDC reference numbers 819865–819872. For ESI and crystallographic
data in CIF or other electronic format see DOI: 10.1039/c1dt10606f
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10503–10512 | 10503
©

◦
˚
Table 1 Selected bond lengths (A) and angles ( ) for the diaminoalkyne
moiety in complexes 2–7
C1–C2
C1–N1
C2–N2
C1–C2–N2
C2–C1–N1
1a
1b
2a
2b
3c
1.206(2)
1.221
1.468(2)
1.484(3)
1.508(4)
1.399(2)
1.404(2)
1.357(2)
1.351
1.315(2)
1.306(3)
1.307(2)
1.301(2)
1.298(2)
1.359(2)
1.352
1.318(2)
1.315(3)
—
1.303(2)
1.303(2)
177.87(14)
177.8
117.28(13)
116.7(2)
115.88(16)
146.27(15)
148.11(15)
173.92(14)
177.4
116.90(13)
117.4(2)
—
147.23(15)
146.56(16)
4d
4e
4f
1.388
1.405
1.316
1.328
1.312
1.322
148.4
148.8
148.4
148.1
1.405
1.318
1.313
146.3
147.5
5
6
7
1.427(3)
1.463(9)
1.485(4)
1.299(3)
1.330(7)
1.311(4)
1.309(3)
1.273(9)
1.297(4)
144.3(2)
123.8(5)
121.9(3)
139.7(2)
117.6(5)
116.6(3)
Fig.
rameters drawn at 50% probability. Selected bond lengths (A)
and angles (◦) in 2a (M
Cr)/2b (M W): M1–C1
2.167(2)/2.316(2), M2–C2 2.208(2)/2.277(2), M1–Ctrans 1.856(2)/1.985(3),
øM1–Ccis 1.906(2)/2.039(3), M2–Ctrans 1.856(2)/1.987(3), øM2–Ccis
1.907(2)/2.040(3), C1–C2 1.468(2)/1.484(3), C1–N1 1.315(2)/1.306(3),
C2–N2 1.318(2)/1.315(3); C1–M1–Ctrans 174.9(1)/173.0(1), C1–M1–Ccis
87.4(1)–96.3(1)/84.7(1)–100.8(1), C2–M2–Ctrans 173.8(1)/175.2(1), C2–
M2–Ccis 85.3(1)–100.4(1)/87.8(1)–96.4(1), C1–C2–N2 117.3(1)/116.7(2),
C2–C1–N1 116.9(1)/117.4(2), N1–C1–C2–N2 93.2(2)/93.8(3).
1 ORTEP diagram of 2a with thermal displacement pa-
˚
a Experimental values taken from ref. 12 for 1,2-di(4-
methylpiperidino)acetylene. b Calculated values at the MP2/cc-pVTZ level
of theory. c Centrosymmetric structure. d In [4]Cl. e In [4]BPh4. f Values for
the M06-L (top), BP86 (middle) and B3LYP (bottom) functionals.
=
=
of the first ynediamine, 1,2-di-(diethylamino)acetylene, from 1,1-
dichloro-2-fluoroethylene was reported as long ago as 1964 by
Viehe and Reinstein.10 Stimulated by our interest in the chemistry
of diaminocyclopropenylidenes,11 we have recently published a
novel and simple synthetic methodology that relies on a Fritsch–
Buttenberg–Wiechell (FBW) rearrangement upon monolithiation
of 2,2-dibromo-1,1-ethenediamines and allows for the preparation
of aromatic and aliphatic ynediamines with a variable substitution
in high yield.12,13 Moreover, we were able to establish the first X-
ray crystal structures of diaminoacetylenes, which show almost
perpendicular orientations of the NC3 planes. With these alkynes
at hand, we present here the first reports of their coordination
chemistry, with particular emphasis on the ability of these ligands
to act either as chelating or bridging ligands in mono- or bimetallic
transition metal complexes, respectively.
Results and Discussion
Scheme 2 Synthesis of diaminodicarbene complexes.
Preparation of homobimetallic diaminodicarbene complexes
˚
agreement with the values of 2.167(1) and 2.208(2) A determined
1,2-Dipiperidinoacetylene (1) was the alkyne of choice for
for 2a. Likewise, the two aminocarbene moieties are oriented in an
almost perpendicular fashion as indicated by an N1–C1–C2–N2
torsion angle of 93.2(2)◦ and by an angle of 95.7◦ between the Cr1–
C1–N1–C2 and Cr2–C2–N2–C1 planes. This orientation rules
out any p-conjugation between the two adjacent aminocarbene
the present study,12 and its reaction with two equivalents of
2
the Cr(CO)5 transfer reagent [(h -COE)Cr(CO)5] (COE = cis-
cyclooctene)14 afforded the chromium complex [(1){Cr(CO)5}2]
(2a), which could be isolated as a yellow, crystalline solid in
89% yield after redissolution and filtration through alumina
(Scheme 2). The 13C NMR spectrum of 2a (in C6D6) exhibits
three low-field resonances at 216.9, 221.9 and 249.3 ppm, which
can be assigned to the cis-CO, trans-CO and Cr C–N carbon
atoms, respectively, indicating that a bis(aminocarbene) complex
has formed.15 The molecular structure was additionally established
by X-ray diffraction analysis (Fig. 1, Table 1), confirming that the
alkyne bridges two Cr(CO)5 moieties in a dicarbenoid fashion.
The structural parameters are very similar to those reported
for the analogous diethylamino-substituted dicarbene complex,
which had been prepared by reduction of the carbyne complex
[Et2NC M(CO)5]BF4.5 For the latter complex, which displays
crystallographic C2-symmetry, a comparatively long Cr–Ccarbene
˚
fragments, and the C1–C2 distance of 1.468(2) A complies with
the presence of a C(sp2)–C(sp2) single bond.16 For comparison,
the molecular structure of the isomorphous tungsten complex 2b
was also established by X-ray diffraction analysis (see ESI for
experimental details†); its structural parameters (Fig. 1, Table 1)
are in good agreement with those reported for the analogous
ditungsten complex containing Me2NC CNMe2 as a bridging
bis(aminocarbene) ligand.5
6
The alkyne 1 was also reacted with bimetallic [RuCl2(h -
cymene)]2,17 since this compound has been successfully employed
for the preparation of numerous ruthenium half-sandwich com-
plexes containing N-heterocyclic carbenes.18 A few brick-red
crystals of the dicarbene complex 3 were isolated from benzene
solution, allowing the determination of its X-ray crystal structure
˚
bond length of 2.190(7) A had been reported, which is in good
10504 | Dalton Trans., 2011, 40, 10503–10512
This journal is
The Royal Society of Chemistry 2011
©

(Fig. 2). Unfortunately, we were unable to obtain 3 in sufficient
quantity and purity for conclusive analytical and spectroscopic
characterization, which could be attributed to the high lability of
the cymene moiety in 3 and further agglomeration reactions as
reported for similar systems.19 Nevertheless, the structure of 3 is
discussed herein, since it provides evidence for the ability of the
alkyne ligand 1 to bridge two Ru atoms, in contrast to the coordi-
nation to one Ru atom in a chelating fashion as observed below. In
the solid state, complex 3 exhibits crystallographic C2-symmetry
presumably formed in the course of this reaction, e.g. by stepwise
ligand substitution and rearrangement. Elemental analysis of the
purple solid revealed that the isolated complex has the composition
[(1)RuCl2(PPh3)2]·THF; the solvent can be removed by extensive
drying in vacuo. The resulting material is highly soluble in
CH2Cl2 and MeCN, only marginally soluble in CHCl3 and
insoluble in ethers (THF, Et2O) and hydrocarbons, implying an
ionic nature. Recrystallization from chloroform solution afforded
single crystals, and X-ray diffraction analysis revealed that the
complex [(1)RuCl(PPh3)2]Cl·3CHCl3 has formed, which is indeed
composed of the cation [(1)RuCl(PPh3)2]+ (4) and a solvated
chloride counterion [Cl(CHCl3)3]- with Cl ◊ ◊ ◊ H distances of 2.33–
6
with two structurally identical [RuCl2(h -cymene)] units. Similar
to complexes 2, the orientation of the two aminocarbene moieties
is close to orthogonality as indicated by an interplanar angle of
83.0◦ together with a N–C1–C1¢–N1¢ torsion angle of 81.2(3)◦
˚
2.44 A. The molecular structure of the cation 4 (Fig. 2) is
˚
(Table 1). The Ru–C1 distance is 2.097(2) A, which falls in the
best described as pseudo-square-planar with an almost perfectly
2
range observed for related mono- and bimetallic complexes with
carbenes coordinated to the cymene-RuCl2 complex fragment.18
perpendicular arrangement of the h -bound diaminoacetylene
ligand with regard to the P1–Ru–P2 axis. The Cl–Ru–P angles
are 88.00(1)◦ and 87.43(1)◦, indicating that the phosphine ligands
are slightly tilted towards the chlorine atom (Fig. 3).
Fig. 2 ORTEP diagram of 3 in 3·C6H6 with thermal displacement pa-
Fig. 3 ORTEP diagram of 4 in [4]Cl·3CHCl3 with thermal displacement
rameters drawn at 50% probability. Primes indicate symmetry-equivalent
˚
parameters drawn at 50% probability. Selected bond lengths (A)
◦
˚
atoms. Selected bond lengths (A) and angles ( ):Ru–C1 2.097(2), Ru–Cl1
2.417(1), Ru–Cl2 2.414(1), Ru–Ccymene 2.172(2)–2.283(2), C1–C2 1.508(4),
C1–N1 1.307(2); C1–Ru–Cl1 88.3(1), C1–Ru–Cl2 87.5(1), Cl1–Ru–Cl2
87.5(1), C1–C2–N 115.9(2), N–C1–C1¢-N¢ 81.2(3).
and angles (◦) in [4]Cl/[4](BPh4): Ru–C1 1.9188(15)/1.9265(16)
Ru–C2 1.9215(15)/1.9174(16), Ru–Cl 2.3840(4)/2.3856(4), Ru–P1
2.3836(4)/2.3839(4), Ru–P2 2.3890(4)/2.3959(4), C1–C2 1.399(2)/
1.404(2), C1–N1 1.301(2)/1.298(2), C2–N2 1.303(2)/1.303(2);
P1–Ru–P2 175.42(1)/174.48(1), P1–Ru–Cl 88.0(1)/86.25(1), P2–Ru–
Cl 87.43(1)/89.29(1), C1–C2–N2 146.3(2)/148.1(2), C2–C1–N1
147.2(2)/146.6(2).
Preparation of monometallic diaminoacetylene complexes
2
Although ruthenium h -alkyne complexes represent important in-
termediates in numerous organic transformations and are involved
in alkyne/vinylideneand alkyne/allenylidene interconversions,20,21
they have only been isolated in a limited number of cases.22 Aiming
The most important structural feature is the observation
˚
of a long C1–C2 bond of 1.399(2) A, which is significantly
longer than usually observed in alkyne complexes25 and is also
among the longest reported for diaminoacetylene complexes;1–4,6
2
at the synthesis of a ruthenium complex containing a h -bound di-
2
aminoacetylene ligand, the reactivity of 1 towards [RuCl2(PPh3)3]
was investigated, since this complex and also related Grubbs-
type complexes readily undergo phosphine exchange reactions.23,24
Hence, addition of 1 to a suspension of this complex in THF
at low temperature (-20 ◦C) led to an immediate formation of
a deep-green solution. Upon warming to ambient temperature,
the colour of the reaction mixture gradually turned maroon, and
a purple, microcrystalline solid precipitated (Scheme 3). These
colour changes indicate that various intermediate species are
for instance, the corresponding C–C bond length in [(h -
6
˚
Me2NC CNMe2)Fe(CO)3] was reported to be 1.375(4) A. This
C–C bond elongation is associated with short N–Calkyne and Ru–C
˚
bond lengths of 1.301(2)/1.303(2) A and 1.9188(15)/1.9215(15)
˚
A, respectively, which strongly suggests the presence of a four-
electron alkyne ligand with ligand-to-metal s- and p-donation and
with extensive p-electron delocalization as described in Scheme 1
by the resonance structures B–D.25 Accordingly, the cation 4 can
reliably be regarded as a 16-electron complex.
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Dalton Trans., 2011, 40, 10503–10512 | 10505
©

Scheme 3 Synthesis of monometallic diaminoacetylene and heterobimetallic diaminodicarbene complexes; for compounds 6 and 7, the drawings refer
to the stereoisomers depicted in Fig. 6 and 7.
1
The H NMR spectrum shows two multiplets for the a-CH2-
groups, in agreement with the expected restricted rotation of the
piperidyl groups around the N–Calkyne axis, which is also confirmed
by the observation of two sets of 13C NMR resonances each for
the a- and b-CH2 carbon atoms. Upon coordination, a very
large low-field shift is observed for the C C resonance from
74.8 ppm in the free alkyne 112 to 203.1 ppm in [4]Cl. The latter
resonance appears as a triplet because of coupling with the two
phosphorus nuclei (2JCP = 8.5 Hz). It should be noted that the
position and the shape of all NMR resonances are fully consistent
with the presence of a diamagnetic species with a stable low-
spin configuration, e.g. the 31P NMR resonance at +31.6 ppm
is sharp (Dn1/2 = 3.1 Hz) and shows no temperature dependence.
In contrast, the NMR data of the recently reported pincer complex
[(PNP)RuCl] [PNP = N(CH2CH2PtBu2)2], which represents an
unprecedented example of a square-planar Ru(II) complex with
a low-spin (LS) ground state (S = 0),26 suggested the presence
of an energetically low-lying intermediate-spin (IS) excited state
(S = 1).27 For the latter complex, the stability of the electronic LS
configuration was attributed to a combination of steric bulk and
the strong nitrogen-to-metal p-donation from the chelating amido
ligand. Accordingly, the high stability of the diamagnetic square-
planar arrangement in 4 can also be explained by the effective p-
interaction between the metal and the four-electron alkyne ligand
(vide supra).
(B3LYP), -27.4 (BP86) and -22.6 kcal mol-1 (M06-L), respectively.
In agreement with the spectroscopic results, this gap is much
larger than calculated for the pincer complex [(PNP)RuCl] [PNP =
N(CH2CH2PtBu2)2] (vide supra), for which the small separation of
DES-T = +2.3 (B3LYP) and -2.0 kcal mol-1 (BP86), derived at the
same level of theory, did not allow a reliable theoretical assignment
of the electronic ground state.27 Together with the experimental
data, however, these calculations are in agreement with a singlet
ground state for this complex, whereas related square-planar
pincer complexes of the type [RuX{N(SiMe2CH2PtBu)2}] (X =
F, Cl, OTf) exhibit triplet (IS) ground-state configurations.28 As
already deduced from the structural characteristics of 4 (vide
supra), the exceedingly strong stabilization of its diamagnetic
ground state arises from an efficient ligand-to-metal p-donation,
which increases the energy of the lowest unoccupied molecular
orbital (LUMO) in comparison with the above-mentioned pincer
complexes, which contain more weakly p-donating amido-units.
Accordingly, the LUMO represents the antibonding alkyne-metal
p*-combination involving the p^ alkyne orbital and the dxy metal
orbital (with the square around the Ru atom being defined as
the xy plane),25,29 whereas the highest occupied molecular orbital
2
(HOMO) exhibits the expected pronounced metal dz character
(Fig. 4).26,27
These assumptions are supported by a series of DFT cal-
culations, whereby the geometry of the cation 4 was freely
optimized in the singlet (S = 0) and triplet state (S = 1) employing
different functionals (B3LYP, BP86 and M06-L). In all cases, the
calculated structures of the singlet state are in good agreement
with those determined by X-ray diffraction analysis (Table 1, see
also Supplementary Information), whereas longer metal–ligand
distances are derived for the triplet state structures. The calculated
energy gap between the singlet and triplet states is of the same
order of magnitude for all three functionals with DES-T = -22.1
Fig. 4 Contour plots of the HOMO (left) and LUMO (right) in the cation
4 (singlet state); CH and CH2 groups were partially omitted for clarity.
10506 | Dalton Trans., 2011, 40, 10503–10512
This journal is
The Royal Society of Chemistry 2011
©

The chloride counterion in [4]Cl can be easily exchanged,
and treatment with one equivalent of NaBPh4 in acetonitrile
resulted in the formation of [4]BPh4 (Scheme 3). The spectroscopic
data of the cation 4 in the BPh4-salt are virtually identical
with those in the chloride congener, and an X-ray diffraction
analysis confirmed the presence of a square-planar cation 4
with almost identical structural features (see caption of Fig. 3,
Table 1). The same reaction with two equivalents of NaBPh4
allows the additional removal of the coordinated chloride ion to
afford a crystalline amber-colored solid, which was identified as
[(1)RuCl(PPh3)2(CH3CN)2](BPh4)2, [5](BPh4)2, by elemental and
X-ray diffraction analysis (Scheme 3). The molecular structure of
the dication 5 is shown in Fig. 5, revealing that two acetonitrile
ligands are bound to the Ru atom in a cis-fashion and are coplanar
with the alkyne ligand. Since the P–Ru–N and the N–Ru–N angles
are all close to 90◦, the coordination sphere around the Ru atom
is probably best described as pseudo-octahedral, with the alkyne
ligand formally occupying two coordination sites. The structural
parameters of the coordinated diaminoacetylene ligand are again
completely consistent with the alkyne acting as a four-electron
donor ligand and thus comply with an 18-electron count for 5; the
complexes, since the addition of other metal cations could lead to
a bridging dicarbene ligand with reincorporation of the chloride
counterion into the coordination sphere. Therefore, the reaction
of [4]Cl with [(MeCN)2PdCl2] was investigated (Scheme 3). Opti-
mization of the reaction conditions indicated that 1.5 equivalents
of the palladium(II) reagent were required to obtain an authentic
reaction product, and the reaction in CH2Cl2 resulted in immediate
precipitation of [PdCl2(PPh3)2], which serves as a triphenyl phos-
phine scavenger.30 Filtration and recrystallization of the reaction
product from acetonitrile afforded orange needles in 70% yield. X-
ray diffraction analysis revealed that a heterobimetallic complex 6
had indeed formed, in which a ruthenium and a palladium atom
are bridged by a chloro ligand and by the alkyne 1 acting as
a bis(aminocarbene) ligand (Fig. 6). The Pd atom resides in a
square-planar environment composed of the carbene ligand, one
bridging and two terminal chlorine atoms, whereas the Ru atom
is coordinated in an octahedral fashion by the carbene and only
one PPh3 ligand, a bridging and a terminal chlorine atom and
1
two cis-coordinated CH3CN ligands. The H NMR spectrum is
rather complicated, in particular in the aliphatic region because
of the low symmetry of the complex, but unambiguously confirms
the presence of only one PPh3 ligand per Ru atom; however, the
low solubility of 6 did not allow to obtain a conclusive 13C NMR
spectrum. The 31P NMR resonance is found at +49.5 ppm, which
is downfield from the signals observed for the cations 4 and 5.
˚
C1–C2 bond length of 1.427(3) A in the dication 5 is even longer
than those established for the monocations in [4]Cl and [4]BPh4
(Table 1). As expected, similar NMR data are recorded for 5, and
the resonances for the metal-bound carbon and phosphorus atoms
are observed at 210.7 (2JPC = 8.4 Hz) and +35.8 ppm, respectively,
slightly downfield from the resonances of 4.
Fig. 6 ORTEP diagram of 6 in 6·7CH3CN with thermal displacement
˚
parameters drawn at 30% probability. Selected bond lengths (A) and
Fig. 5 ORTEP diagram of 5 in [5](BPh4)2·0.5CH3CN with thermal
angles (◦): Ru–C1 2.041(6), Ru–Cl1 2.478(1), Ru–Cl2 2.418(2), Ru–N3
2.020(6), Ru–N4 2.108(5), Pd–C2 1.983(6), Pd–Cl1 2.314(2), Pd–Cl3
2.377(2), Pd–Cl4 2.315(2), C1–C2 1.463(9), C1–N1 1.330(7), C2–N2
1.273(9); P–Ru–Cl1 174.9(1), P–Ru–Cl2 86.9(1), N3–Ru–N4 85.6(2),
C1–Ru–P 97.0(2), C1–Ru–Cl1 86.2(2), C1–Ru–Cl2 92.9(2); Cl1–Pd–Cl3
92.3(1), Cl1–Pd–Cl4 174.9(1), Cl3–Pd–Cl4 91.6(1), C2–Pd–Cl1 86.3(2),
C2–Pd–Cl4 90.0(2), C1–C2–N2 123.8(5), C2–C1–N1 117.6(5).
displacement parameters drawn at 50% probability. Selected bond lengths
◦
˚
(A) and angles ( ):Ru–C1 1.959(2), Ru–C2 1.922(2), Ru–N3 2.159(2),
Ru–N4 2.120(2), Ru–P1 2.4059(6), Ru–P2 2.4291(6), C1–C2 1.427(3),
C1–N1 1.299(3), C2–N2 1.309(3); P1–Ru–P2 173.2(1), N3–Ru–N4 83.7(1),
P1–Ru–N3 85.3(1), P1–Ru–N4 91.3(1), P2–Ru–N3 87.9(1), P2–Ru–N4
88.8(1), C1–C2–N2 144.3(2), C2–C1–N1 139.7(2), N1–C1–C2–N2 17.7(6).
Preparation of heterobimetallic diaminodicarbene complexes
The formation of complex 6 can be rationalized by the assump-
tion that chloride exchange in an acetonitrile solution of [4]Cl
delivers sufficient quantities of the dication 5, which undergoes
PdCl2 insertion with concomitant chloride coordination and
phosphine dissociation. The low solubility of [PdCl2(PPh3)2]29 and
The ability of the alkyne 1 to act as a chelating diaminoacetylene
ligand towards a single metal or as a bridging diaminodicarbene
ligand towards two metals suggested that complex [4]Cl might
serve as a starting material for the preparation of heterobimetallic
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10503–10512 | 10507
©

also the inability of the bimetallic system to accommodate two
PPh3 ligands for steric reasons might provide the driving force
for the latter process. Recrystallization of 6 from CH2Cl2 afforded
orange crystals of different shape, which were identified as the
tetranuclear complex 7 by an X-ray diffraction study (Scheme 3,
Fig. 7). 7 can be regarded as a dimer of 6, and its formation
involves dissociation of one CH3CN ligand in 6 and association
of the resulting coordinatively unsaturated complex fragments via
the two bridging chlorine atoms Cl2 and Cl2¢. It should be noted
that the asymmetric unit of 7·4CH2Cl2 contains one molecule with
inversion symmetry (in the centre of the four-membered Ru2Cl2
ring) and one molecule on a general position, but with approximate
more strongly coordinating ligands such as trialkyl phosphines
and N-heterocyclic carbenes and might therefore allow delivery
of the ruthenium dicarbene complex in a more controlled
fashion.
Conclusions
The present paper shows that ynediamines such as 1 can be
used for the preparation of homobimetallic or monometallic
diaminoacetylene complexes; in both systems, the alkyne ligand
acts as a 4-electron donor either by bridging two metals
as a bis(aminocarbene) ligand or by coordination to a single
transition metal as a 2s,2p-electron donor. The latter behaviour
was exemplified by isolation of the cationic pseudo-square-
planar Ru(II) complex trans-[(1)RuCl(PPh3)2]+ (4), which ex-
hibits an unusual, very stable low-spin singlet ground state
as a consequence of strong alkyne-to-metal p-donation. The
monometallic complex 4 can be used for the preparation of
heterobimetallic bis(aminocarbene) complexes, indicating that a
controlled conversion between monometallic diaminoacetylene
and bimetallic dicarbene complexes is possible. In that respect,
the diaminoacetylene 1 might be regarded as a diaminodicarbene
source and consequently as a conjoined bifunctional analogue
of well-established alkyl-aminocarbenes such as iPr2N(tBu)C: or
their cyclic (CAAC) congeners.33
˚
inversion symmetry (r.m.s. deviation 0.20 A). The orientation of
the ligands and the overall structural parameters in both molecules
are very similar, and only those of the centrosymmetric molecule
are discussed here (Fig. 7). The Ru–C and Pd–C distances in 7
˚
[2.010(3), 1.951(3) A] differ only slightly from those in 6 [2.041(6),
˚
1.983(6) A]; they fall in the range observed for other ruthenium(II)-
and palladium(II)-aminocarbene complexes.31,32
Experimental
General procedures
All manipulations, unless otherwise stated, were performed under
inert gas atmosphere (Ar), using Schlenk and glovebox techniques.
All solvents were purified by standard methods and degassed prior
to use. 1H, 13C{ H} and 31P{ H} NMR spectroscopic studies were
carried out on Bruker DPX200, AV300 and Bruker DRX400
devices and were referenced to internal SiMe4 (1H, 13C) and to
external H3PO4 (31P). Splitting patterns are indicated as s (singlet),
d (doublet), t (triplet), m (multiplet) and pst (pseudotriplet).
Elemental analyses were performed by combustion analysis on
a Vario Micro Cube device with WLD and IR detectors. FTIR
spectra were recorded using a Bruker Vertex 70 spectrometer
equipped with a diamond ATR cell. The starting materials were
prepared according to published procedures: [RuCl2(PPh3)3],22a
[(h -cymene)RuCl2]2,17 [(THF)W(CO)5],34 [(h -COE)Cr(CO)5],14
[(MeCN)2PdCl2],35 1,2-dipiperidinoacetylene (1),12 or purchased
and used as delivered: (-)-p-mentha-1,5-diene (TCI Europe),
[W(CO)6] (Acros).
1
1
Fig. 7 ORTEP diagram of 7 in 7·4CH2Cl2 with thermal displacement
parameters drawn at 50% probability. The asymmetric unit contains 1.5
molecules of 7, but only the structure of the centrosymmetric molecule
is shown. The phenyl groups of the PPh3 ligands were omitted for
◦
˚
clarity. Selected bond lengths (A) and angles ( ):Ru–C1 2.010(3), Ru–P
2.313(1), Ru–Cl1 2.446(1), Ru–Cl2 2.470(1), Ru–Cl2¢ 2.453(1), Ru–N3
1.995(3), Pd–C2 1.951(3), Pd–Cl1 2.332(1), Pd–Cl3 2.377(1), Pd–Cl4
2.305(1), C1–C2 1.485(4), C1–N1 1.311(4), C2–N2 1.297(4); C1–C2–N2
121.9(3), C2–C1–N1 116.6(3), C1–Ru–P 101.8(1), C1–Ru–Cl1 88.1(1),
C1–Ru–Cl2¢ 92.7(1), C1–Ru–Cl2 172.0(1), C1–Ru–N3 91.1(1); C2–Pd–Cl1
85.0(1), C2–Pd–Cl3 179.3(1), C2–Pd–Cl4 87.8(1), Cl1–Pd–Cl3 94.3(1),
Cl3–Pd–Cl4 92.9(1).
6
2
The formation of the Ru–Pd complexes 6 and 7 from [4]Cl
shows that this complex can serve as a starting material for the
preparation of heterobimetallic diaminocarbene complexes. Orig-
inally, we anticipated that this reaction might formally proceed via
a dicarbene intermediate of the type [{Ru} C(NR2)-(R2N)C:]
with {Ru} = RuCl2(PPh3)2, followed by coordination of a bridig-
ing PdCl2 moiety; however, phosphine dissociation and ligand
scrambling was observed. Although we cannot provide evidence
for the intermediate occurrence of such a dicarbene species at this
time, the isolation of the cationic complex [(OC)4Fe C(NMe2)-
(Me2N)CH]+ by Filippou might serve as an example of the
trapping of a similar dicarbene complex by protonation.6 In
future work, phosphine dissociation could be avoided by use of
Synthesis and characterization of 2a
A solution of 1 (240 mg, 1.12 equiv.) in toluene (5 mL) was added
2
to a solution of [(h -COE)Cr(CO)5] (600 mg, 2.0 mmol) in 20 mL
of the same solvent. The reaction mixture gradually turned deep
yellow. After stirring for another 0.5 h, the volume was decreased
by half and hexane (10 mL) was added, whereupon a yellow
crystalline solid formed. It was isolated by filtration, washed twice
with hexane (10 mL) and dried in vacuo. Further purification was
achieved by filtration of its CH2Cl2 solution through a short Al2O3-
pad(Super I)andsubsequent solvent removal. Yield: 89% (510 mg)
1
of a bright yellow microcrystalline solid. H NMR (200.1 MHz,
10508 | Dalton Trans., 2011, 40, 10503–10512
This journal is
The Royal Society of Chemistry 2011
©

1
2H, a-HCHB), 7.41–7.60 (m, 3 ¥ 5H, Ph) ppm. 13C{ H} NMR
C6D6, 300 K): d = 1.4–2.0 (m, 6H), 3.6 (m, 2H), 3.8, 4.8 (2 ¥d, 2 ¥
2
1H, JHH = 12 Hz, 2¥a-CH2) ppm. 13C NMR (50.1 MHz, C6D6,
(100.6 MHz, CH2Cl2, 300 K): d = 23.1 (g -CH2), 25.7, 25.8 (2¥b-
CH2), 25.9 (THF), 57.4, 59.0 (2¥a-CH2), 68.1 (THF), 129.0 (pst,
3JCP = 5.0 Hz, m-Ph), 131.3 (s, p-Ph), 132.3 (pst, 1JCP = 22 Hz, ipso-
Ph), 134.5 (pst, 2JCP = 5.8 Hz, o-Ph), 203.1 (t, 2JCP = 8.5 Hz, Ru C)
300 K): d = 23.4 (g -CH2), 26.7, 26.8 (2¥b-CH2), 57.6, 59.5 (2¥a-
CH2), 216.9 (cis-CO), 221.9 (trans-CO), 249.3 (Cr C–N) ppm.
Anal. calc’d for C22H20Cr2N2O10 (576.41): C 45.84, H 3.49, N 4.86;
found C 45.45, H 3.56, N 4.91. IR: n 2957w, 2060 m, 2045 m, 1986
m, 1877 s, 1528 m, 1502 m, 1444 m, 1279 m, 1265 m, 1225 m, 1091
m, 1022 m, 861 m, 645 s cm-1.
ppm. 31P{ H} NMR (81.1 MHz, CH2Cl2, 300 K): d = +31.6 ppm.
1
Anal. calc’d for [4]Cl·THF, C52H58Cl2N2OP2Ru (960.97): C 64.99,
H 6.08, N 2.92; found: C 64.69, H 6.43, N 2.85.
Synthesis of 2b
Synthesis and characterization of [4]BPh4·THF
A suspension of [W(CO)6] (362 mg, 1.03 mmol) in THF (80 mL)
was irradiated with UV light for 60 min under a slow flow of inert
gas, affording a deep yellow solution. The reagent was transferred
to a Schlenk flask, and the solution was concentrated in vacuo to
half of the original volume and cooled to -20 ◦C. Upon addition
of 1, the reaction mixture gradually turned deep orange. After
overnight stirring, the solvent was completely evaporated, and the
residue was additionally dried for 3 h (2 ¥ 10-2 mbar) at ambient
temperature. Crystalline material was obtained upon storing a
THF solution at 5 ◦C.
To a solution of [4]Cl·THF (385 mg, 0.40 mmol) in MeCN (20 mL),
solid NaBPh4 (144 mg, 0.42 mmol, 1.05 equiv.) was added, and
the resulting brown suspension was stirred vigorously for 30 min.
The solid was filtered off, and all volatiles were evaporated. THF
(10 mL) was added to the remaining brown foamy solid, and the
solution was stored at -30 ◦C, affording a crystalline material. It
was collected by decantation, washed with ether (3 ¥ 5 mL) and
dried in vacuo. Yield: 64% (321 mg) of a lustrous sand-colored solid
of the composition [4]BPh4·THF. The complex is highly soluble
in polar solvents. Single crystals suitable for X-ray diffraction
analysis were obtained upon storing a concentrated THF solution
◦
Synthesis and characterization of 3
1
at 5 C. H NMR (300.1 MHz, CD3CN, 300 K): d = 1.17 (br s,
2H, g -CH2), 1.45 (br s, 4H, 2¥b-CH2), 1.81 (m, 4H, THF), 2.74,
3.95 (2 ¥ m, 2 ¥ 2H, a-C(H)H), 3.65 (m, 4H, THF), 6.84 (t,
A solution of 1 (130 mg, 0.68 mmol, 1.1 equiv.) in THF (3 mL)
◦
6
was added dropwise at -20 C to a stirred suspension of [(h -
cymene)RuCl2]2 (380 mg, 0.62 mmol) in THF (10 mL), affording
a deep orange reaction mixture. The clear reaction mixture was
stirred for 30 min and subsequently concentrated in vacuo to ca.
2 mL. Upon addition of benzene (5 mL), slow precipitation of
a deep red solid was observed. Precipitation was completed by
dropwise addition of hexane (3 mL). The precipitate was isolated
by filtration and dried in vacuo for 2 h (2 ¥ 10-2 mbar), affording
160 mg of a brown amorphous solid. NMR spectroscopic data in
C6D6 indicate the presence of a very complex reaction mixture. All
attempts to isolate an analytically pure compound failed. Several
crystals of the composition 3·C6H6, suitable for X-ray diffraction
analysis, were obtained by storing concentrated C6H6 solutions at
5 ◦C.
3
3JHH = 7.2 Hz, 4H, p-PhB), 6.99 (t, JHH = 7.2 Hz, 8H, m-PhB),
7.25–7.33 (m, 8H, o-PhB),7.39–7.50 (m, 18H, m-/p-PhP) 7.61–
1
7.71 (m, 12H, o-PhP) ppm. 13C{ H} NMR (75.5 MHz, CD3CN,
300 K): d = 23.5 (g -CH2), 26.1, 26.8 (2 ¥b-CH2), 26.2 (THF),
58.9, 59.3 (2 ¥a-CH2), 68.3 (THF), 122.7 (s, p-PhB), 126.6 (m,
3J(13C-11B) = 2.7 Hz, m-PhB), 129.3 (pst, |3JCP + 5JCP¢| = 5.0 Hz,
3
m-PhP), 131.3 (s, p-PhP), 132.2 (pst, |1JCP + JCP¢| = 22.5 Hz,
4
ipso-PhP), 135.0 (pst, |2JCP + JCP¢| = 5.6 Hz, o-PhP), 136.7 (m,
2J(13C-11B) = 1.3 Hz, o-PhB), 164.8 (m, 1J(13C-11B) = 50 Hz, 1J(13C-
2
10B) = 16.7 Hz, ipso-PhB), 199.7 (t, JCP = 8.4 Hz, Ru C) ppm.
1
31P{ H} NMR (81.0 MHz, CD3CN, 300 K): d = +32.1 ppm. Anal.
calc¢d for [4]BPh4·THF, C76H78BClN2OP2Ru (1244.76): C 73.33,
H 6.32, N 2.25; found: C 72.52, H 6.40, N 2.45.
Synthesis and characterization of [4]Cl·THF
Synthesis and characterization of [5](BPh4)2
A suspension of [RuCl2(PPh3)3] (1.92 g, 2.00 mmol) in THF
(50 mL) was cooled to 0 ◦C, and a solution of 1 (404 mmol,
2.10 mmol) in THF (5 mL) was added, whereupon a brilliant
deep-green solution formed. After 15 min of vigorous stirring,
the reaction mixture was brought to ambient temperature without
stirring. The solution gradually turned maroon, and a purple,
amorphous solid precipitated. The solid was isolated by filtration,
washed with THF (3 ¥ 5 mL) and dried in vacuo (1 mbar,
60 min). Yield: 71% (1.36 g). NMR spectroscopy and elemental
analysis reveal the presence of one THF molecule per formula unit.
Extended drying at higher temperatures (>60 ◦C) led to an unsol-
vated material. Crystallization from hot CHCl3 (100 mg/6 mL)
resulted in the formation of the CHCl3 solvate [4]Cl·3CHCl3) as
a brown, crystalline solid. [4]Cl·THF is highly soluble in CH2Cl2
and MeCN, marginally soluble in CHCl3 and insoluble in ethers
Solid NaBPh4 (320 mg, 0.96 mmol, 2.2 equiv) was added to a
solution of [4]Cl·THF (420 mg, 0.44 mmol) in MeCN (20 mL), and
the resulting brown suspension was stirred vigorously for 30 min.
The solid was filtered off, and all volatiles were removed in vacuo.
The remaining green-brown foamy solid was triturated with THF
(8 mL), whereupon a sand-colored, microcrystalline solid formed.
It was collected by decantation, washed with THF (2 ¥ 4 mL)
and dried in vacuo. Yield: 69% (470 mg). Complex [5](BPh4)2 is
highly soluble in polar solvents (CH2Cl2, MeCN, acetone). Single
crystals suitable for X-ray diffraction analysis were obtained upon
storing a concentrated MeCN solution at ambient temperature.
1H NMR (400.0 MHz, CD3CN, 300 K): d = 1.17 (m, 2H, g -CH2),
2
1.51, 1.60 (2 ¥ m, 2 ¥ 2H, 2 ¥b-CH2), 2.74, 3.93 (2 ¥ t, JHH
=
3
6.0 Hz, 2 ¥ 2H, a-C(H)H), 6.82 (t, JHH = 7.2 Hz, 4H, p-Ph-B),
3
6.79 (t, JHH = 7.2 Hz, 8H, m-Ph-B), 7.25–7.30 (m, 8H, o-Ph-
1
1
(THF, Et2O) and hydrocarbons. H NMR (400.1 MHz, CH2Cl2,
300 K): d = 1.24 (m, 4H, b/g -CH2), 1.46 (m, 2H, b-CH2), 1.82
(m, 4H, THF), 2.95 (m, 2H, a-CH2), 3.69 (m, 4H, THF), 4.00 (m,
B), 7.40–7.52 (m, 15H, Ph3P) ppm. 13C{ H} NMR (100.6 MHz,
CD3CN, 300 K): d = 1.7 (CH3CN), 23.4 (g -CH2), 26.3 (b-CH2),
60.1, 60.3 (2 ¥a-CH2), 79.2 (CHCl3), 122.8 (s, p-Ph-B), 126.6 (m,
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 10503–10512 | 10509
©

Table 2 Crystallographic data
2a
2b
3·C6H6
[4]Cl·3 CHCl3 [4](BPh4)·3 THF 5·0.5 MeCN 6·7 MeCN
C48H62-
7·4 CH2Cl2
Empirical
formula
C22H20Cr2N2O10 C22H20W2N2O10 C38H54Ru2N2Cl4 C51H53RuN2- C84H94RuN2P2- C100.99H97.49
-
C68H84Ru2Pd2-
P2Cl11
ClBO3
14.3816(2)
26.5861(2)
18.6904(2)
90
97.387(2)
90
7086.97(14)
4
1388.88
RuN4.49P2B2 RuPdN11PCl4 N6P2Cl16
˚
a/A
9.4757(8)
9.6051(6)
15.9506(14)
103.107(6)
94.293(6)
118.080(8)
1219.32(17)
2
9.5233(4)
9.7656(4)
15.9927(6)
102.934(4)
94.073(4)
118.147(4)
1250.88(9)
2
17.3697(6)
9.7250(2)
22.3104(6)
90
95.454(2)
90
3751.62(18)
4
882.77
14.3361(2)
23.2191(2)
17.3423(2)
90
107.837(2)
90
5495.27(11)
4
1246.91
11.6660(2)
26.9068(6)
26.0151(6)
90
97.058(2)
90
9.5899(8)
15.9641(18)
17.390(2)
80.429(9)
76.303(8)
86.480(8)
2550.0(5)
2
17.1006(4)
18.8239(4)
21.0090(6)
94.226(2)
110.213(2)
98.865(2)
6211.5(3)
3
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
˚
V (A3)
8104.1(3)
4
Z
Formula weight 576.40
840.10
1558.76
P21/n
1173.33
P1
2029.49
P1
¯
¯
¯
¯
Space group
P1
P1
C2/c
P21/n
P21/c
T/K
100(2)
0.71073
1.570
110(2)
0.71073
2.230
100(2)
0.71073
1.563
100(2)
1.54184
1.507
100(2)
1.54184
1.302
100(2)
1.54184
1.278
100(2)
1.54184
1.528
173(2)
0.71073
1.628
˚
l/A
Dc/g cm-3
m/mm-1
0.950
36726
9.246
48699
1.120
64425
8.070
90022
2.958
84768
2.333
7.827
1.382
Reflections
collected
93253
27607
196062
Independent
reflections
6041
7185
4458
11424
14703
16852
9682
25393
Rint = 0.0596
Rint = 0.0418
0.824
Rint = 0.0637
0.785
Rint = 0.0279 Rint = 0.0352
1.045
Rint = 0.0925 Rint = 0.0593 Rint = 0.0513
0.886
Goodness of fit 0.924
1.088
1.027
0.892
on F2
R(Fo),
0.0257
0.0166
0.0227
0.0236
0.0601
0.0306
0.0846
0.0397
0.0894
0.0570
0.1557
0.0314
0.0702
[I > 2s(I)]
Rw(Fo2)
0.0613
0.367/-0.298
0.0236
0.626/-0.622
0.0429
0.609/-0.416
-3
˚
Dr/e A
0.377/-0.673 0.503/-0.685
0.504/-0.957 1.712/-0.892 1.423/-1.313
3J(13C-11B) = 2.7 Hz, m-Ph-B), 130.2 (pst, |3JCP + 5JCP¢| = 5.0 Hz,
Isolation of 7
3
m-Ph-P), 132.1 (s, p-Ph-P), 132.2 (pst, |1JCP + JCP¢| = 22.5 Hz,
Red–orange crystals of the solvate 7·4CH2Cl2 were obtained
by storing a concentrated CH2Cl2 solution of 6 at ambient
temperature for two days. The crystalline material was carefully
dried in vacuo and used for combustion analysis. Single crystals
suitable for X-ray diffraction analysis were obtained upon storing
a concentrated CH2Cl2 solution at 5 ◦C. Because of the very low
solubility of 7 in deuterated organic solvents, we were unable
to collect sufficient NMR spectroscopic data. Anal. calc’d for
7¥4CH2Cl2, C64H76Cl8N6P2Pd2Ru2 (1689.91): C 45.49, H 4.53, N
4.97; found: C 45.32, H 4.37, N 5.32.
4
ipso-Ph-P), 134.4 (pst, |2JCP + JCP¢| = 5.6 Hz, o-Ph-P), 136.8
2
1
(m, J(13C-11B) = 1.3 Hz, o-Ph-B), 164.9 (m, J(13C-11B) = 50 Hz,
1J(13C-10B) = 16.7 Hz, ipso-Ph-B), 210.7 (t, 2JCP = 8.4 Hz, Ru C)
ppm. 31P{ H} NMR (81.1 MHz, CD3CN, 300 K): d = +35.8 ppm.
1
Anal. calc’d for [5](BPh4)2·CHCl3, C101H97B2Cl3N4P2Ru (1657.91):
C 73.17, H 5.90, N 3.38; found: C 72.82, H 5.97, N 3.39.
Synthesis and characterization of 6
Solid [(MeCN)2PdCl2] (142 mg, 0.545 mmol, 1.54 equiv.) was
added to a stirred solution of [4]Cl·THF (342 mg, 0.356 mmol)
in CH2Cl2 (13 mL), which soon led to precipitation of bright
yellow [PdCl2(PPh3)2]. The reaction mixture was stirred for an
additional hour and then, to complete the precipitation, stirred at
0 ◦C for 30 min. The precipitate was removed by filtration, and the
filtrate was concentrated in vacuo to ca. 2◦mL, and MeCN (10 mL)
was added. Storing this solution at -30 C for two days resulted
in the crystallization of an orange microcrystalline solid. This was
separated by filtration, washed with cold MeCN (2 ¥ 2 mL) and
dried in vacuo. Yield: 70% (231 mg). Single crystals suitable for X-
ray diffraction analysi◦s were obtained by storing a concentrated
Single-crystal X-ray structure determination
Crystals were mounted on glass fibres in perfluorinated oil.
Diffraction data for complexes 2a, 2b, 3 and 7 were collected
with an Oxford Diffraction Xcalibur diffractometer using Mo-
˚
Ka radiation (l = 0.71073 A) and for complexes [4]Cl, [4]BPh4,
[5](BPh4)2 and 6 with an Oxford Diffraction Nova diffractometer
˚
using Cu-Ka radiation (l = 1.54184 A). The structures were solved
with SHELXS-9736 by direct methods and refined on F2 with
SHELX-97.37 Hydrogen atoms were included using rigid idealised
methyl groups or a riding model. ORTEP-III for Windows38
was used for all molecular plots. Special features and problems:
Crystals of compound 3 diffracted weakly. Several structures were
negatively affected by the presence of substantial amounts of
incorporated solvent. For structures [4]BPh4 and 6, the program
SQUEEZE (A. L. Spek, University of Utrecht, Netherlands)
was used to remove the effects of severely disordered solvent.
Acetonitrile hydrogens proved difficult to locate, and their slow
convergence indicated probable rotational disorder. In some cases,
these H atoms were excluded from the refinement (for details,
1
MeCN solution at 5 C. H NMR (400.1 MHz, CD2Cl2): d =
1.25–1.85 (m, 12H, b-/g -CH2), 1.97 (s, 12H, free MeCN), 2.37 (s,
3H, coord. MeCN), 2.68 (d, 2JHH = 13 Hz, HC(H)N), 3.23 (m, 3H,
CH2), 3.88 (d, J = 12 Hz, CH2), 4.03 (t, JHH = 12 Hz, CH2), 4.23 (d,
JHH = 12 Hz, CH2), 5.71 (d, 2JHH = 13 Hz, HC(H)N), 7.31–7.47 (m,
1
10H, m-/p-PhP), 7.56–7.66 (m, 6H, o-PhP) ppm. 31P{ H} NMR
(81.1 MHz, CD2Cl2): d = +49.5 ppm. Anal. calc’d for 6 ¥ 3 MeCN,
C36H44Cl4N5PPdRu (927.06): C 46.64, H 4.78, N 7.55; found: C
47.19, H 4.87, N 7.95.
10510 | Dalton Trans., 2011, 40, 10503–10512
This journal is
The Royal Society of Chemistry 2011
©

see the ESI†). For structure 5, two rings of the anion displayed
alternative orientations; only one was consistent with the solvent
site and was therefore assigned the same occupation factor as the
solvent.
CCDC 819865–819872 (in the same order as Table 2) 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.
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10512 | Dalton Trans., 2011, 40, 10503–10512
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The Royal Society of Chemistry 2011
©