Ruthenium complexes supported by 2,6-bis(pyrazol-1-yl)pyridines

Article abstract of DOI:10.1016/S0020-1693(02)01173-8

The synthesis and characterization of a series of ruthenium(II) complexes containing the planar tridentate ligands 2,6-bis(pyrazol-1-yl)pyridine (BPP) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (Me₄BPP) are described. The reaction of BPP with RuCl₂(PPh₃)₃ yields both the cis (1a) and trans (1b) isomers of [RuCl(PPh₃)₂(BPP)]Cl. Complexes of the general formula trans-RuCl₂(L)(Me₄BPP) (L=PPh₃, 2; C₂H₄, 3a; CO, 3b; MeCN, 3c) are also reported, and were prepared from either RuCl₂(PPh₃)₃ and Me₄BPP (i.e. 2), Et₃N reductions of RuCl₃(Me₄BPP) in the presence of L (i.e. 2 and 3b,c), or from [RuCl₂(p-cymene)]₂, Me₄BPP and L (i.e. 3a). The neutral vinylidene complex cis-RuCl₂(=C=CHPh)(Me₄BPP) (4), was isolated from reactions of phenylacetylene with either 3a or mixtures of [RuCl₂(p-cymene)]₂ and Me₄BPP, while the cationic allenylidene complex [RuCl(PPh₃)(=C=C=CPh₂)(Me₄BPP)][BF ₄] (5), was prepared from 2, AgBF₄ and 1,1-diphenyl-2-propyn-1-ol. Complexes 1-5 were characterized by multinuclear NMR and IR spectroscopy.

Full text of DOI:10.1016/S0020-1693(02)01173-8

Inorganica Chimica Acta 343 (2003) 244ꢁ252
/
www.elsevier.com/locate/ica
Ruthenium complexes supported by 2,6-bis(pyrazol-1-yl)pyridines
Nicholas J. Beach, Gregory J. Spivak *
Department of Chemistry, Lakehead University, Thunder Bay, Ont., P7B 5E1 Canada
Received 21 May 2002; accepted 25 June 2002
Abstract
The synthesis and characterization of a series of ruthenium(II) complexes containing the planar tridentate ligands 2,6-bis(pyrazol-
1-yl)pyridine (BPP) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (Me4BPP) are described. The reaction of BPP with RuCl2(PPh3)3
yields both the cis (1a) and trans (1b) isomers of [RuCl(PPh3)2(BPP)]Cl. Complexes of the general formula trans-
RuCl2(L)(Me4BPP) (Lꢀ
and Me4BPP (i.e. 2), Et3N reductions of RuCl3(Me4BPP) in the presence of L (i.e. 2 and 3b,c), or from [RuCl2(p-cymene)]2, Me4BPP
and L (i.e. 3a). The neutral vinylidene complex cis-RuCl2(ꢀCꢀCHPh)(Me4BPP) (4), was isolated from reactions of phenylacetylene
with either 3a or mixtures of [RuCl2(p-cymene)]2 and Me4BPP, while the cationic allenylidene complex [RuCl(PPh3)(ꢀCꢀCꢀ
CPh2)(Me4BPP)][BF4] (5), was prepared from 2, AgBF4 and 1,1-diphenyl-2-propyn-1-ol. Complexes 1ꢁ5 were characterized by
/PPh3, 2; C2H4, 3a; CO, 3b; MeCN, 3c) are also reported, and were prepared from either RuCl2(PPh3)3
/
/
/
/
/
/
multinuclear NMR and IR spectroscopy.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Ruthenium; Vinylidene; Allenylidene; Tridentate nitrogen donor ligand
1. Introduction
phosphine oxides, and ortho-metallation reactions) dur-
ing catalysis, especially under thermal conditions.
Furthermore, organometallic complexes bearing nitro-
gen donor ligands often exhibit high reactivities [1].
Synthetic applications involving transition metals con-
taining tridentate nitrogen donor ligands have been well
developed in recent years; some of the more notable
classes include tris(pyrazolyl)borate ligands [2], 1,4,7-
triazacyclononane ligands [3], and 2,6-bis(imino)pyri-
dine [4], and the closely related 2,6-bis(oxazolinyl)pyr-
idine [5], ligands. As well, some of these polydentate
nitrogen donor ligands have found applications in the
area of enzyme mimicry [6].
Transition metal complexes containing the class of
planar tridentate nitrogen donor ligands 2,6-bis(pyrazol-
1-yl)pyridines (Structure I) [7] have proven to be useful
structural and redox mimics for analogous 2,2?:6?,2ƒ-
terpyridine complexes [8]. This ligand system is particu-
larly more attractive than the terpyridine system because
the steric and electronic properties can be readily and
systematically altered by varying the substituents on the
pyrazole rings. Several studies have shown that the
structural, spectroscopic, magneto- and electrochemical
properties of metal complexes bearing these ligands are
sensitive towards substituent effects [9]. There have been
Rational ligand design in organometallic chemistry
and catalysis generally has been directed by a desire to
enhance the reactivity, selectivity and/or thermal stabi-
lity of homogeneous transition metal-based catalysts. In
the wake of this desire, a multitude of new ligand
systems have emerged, many of which have proven to
exhibit exceptional properties with regard to catalysis.
Undeniably, phosphorus-based ligands (and, to a lesser
extent, the higher homologues) have played a crucial
role in developing early synthetic applications involving
transition metal catalysts; indeed, they have remained a
dominant co-ligand in organometallic chemistry. How-
ever, in recent years, there has been increased interest in
developing new classes of ligands bearing donor atoms
other than phosphorus, particularly nitrogen donor
ligands. This is partly in response to the susceptibility
of common phosphine ancillary ligands to undergo
degradation (e.g. Pꢁ
/
C bond cleavage, oxidation to
* Corresponding author. Tel.: ꢂ
7775
E-mail address: greg.spivak@lakeheadu.ca (G.J. Spivak).
/
1-807-343 8458; fax: ꢂ1-807-346
/
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 1 7 3 - 8

N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ
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245
several reports regarding the redox properties of ruthe-
nium complexes bearing this general class of ligand
[8,10,11]. We wished to screen the coordination and
organometallic chemistry of ruthenium complexes con-
taining this ligand, especially since its sterics can be
easily manipulated, and report the results herein.
idine) [13]. The overall C2v symmetry of 1a renders the
3- and 5-pyridyl hydrogens equivalent, as well as the 3
and 3ƒ, 4 and 4ƒ, and 5 and 5ƒ hydrogens of the
pyrazolyl rings. Thus, in addition to the two pyridyl
hydrogen signals (dꢀ
/
7.31 for 3,5-H and dꢀ
/
7.63 for 4-
8.26 for
H) and three pyrazolyl hydrogen signals (dꢀ
/
3,3ƒ-H, dꢀ
/
6.60 for 4,4ƒ-H and dꢀ8.71 for 5,5ƒ-H), the
/
1H NMR spectrum of 1a clearly shows a series of
overlapping multiplets corresponding to, and integrat-
ing well for, the six phenyl groups of the two PPh3
ligands (dꢀ
/
7.33ꢁ7.19).
/
Further examination of the filtrate from the synthesis
of 1a via 31P{1H} NMR spectroscopy reveals the
presence of the cis isomer, cis-[RuCl(PPh3)2(BPP)]Cl
(1b) (Scheme 1), as the main (ca. 80%) component, with
the balance consisting primarily of 1a (ca. 15%) and free
PPh3. Separating pure 1b from the mixture (i.e. via
fractional crystallization or chromatography) was fru-
strated by the very low solubility of each complex, even
in very polar solvents (i.e. DMSO). Similar structural
elements are common to both 1a and 1b, as evidenced by
2. Results and discussion
solution NMR studies. Thus, two pyridyl (dꢀ
/
8.33 and
2.1. Synthesis and characterization of cis- (1a) and
trans- (1b) [RuCl(PPh3)2(BPP)]Cl (1), and trans-
RuCl2(PPh3)(Me4BPP) (2)
8.05) and three pyrazolyl (dꢀ9.19, 8.25 and 6.76)
/
hydrogen signals are observed in the 1H NMR spectrum
of 1b, which shows that both halves of the mer-
tridentate molecule are magnetically equivalent. The
31P{1H} NMR spectrum of complex 1b is more diag-
nostic of its structure, and shows (in accord with the
absence of C2 symmetry) an AB doublet of doublets
When a 1:1 mixture of RuCl2(PPh3)3 and BPP are
boiled in CH2Cl2 for 3 h, the air-stable complex trans-
[RuCl(PPh3)2(BPP)]Cl (1a), deposits as a pale yellow
microcrystalline solid in fair (32%) isolated yield
(Scheme 1). The PMe3 analogue of 1a has been prepared
[11] by a much different route, while similar results were
observed [12] for the reaction between RuCl2(PPh3)3
and the structurally similar mer-tridentate ligand pybox
pattern centered at dꢀ
/
41.32 (2JPP
ꢀ28 Hz), consistent
/
with overall Cs symmetry of 1b (i.e. a perpendicular
mirror plane bisecting the BPP ligand through the
pyridyl nitrogen and para carbon) brought about by
the relative cis arrangement of the two PPh3 ligands.
Given the more sterically congested cis arrangement of
the PPh3 ligands in 1b (vs. the trans arrangement in 1a),
we considered the possibility that 1b is a kinetic product
in the reaction of BPP with RuCl2(PPh3)2, and that a
trans disposition of phosphine ligands (i.e. 1a) would be
more thermodynamically preferred. Heating (80 8C) a
DMSO solution of 1b initially leads to a smooth
increase in population of the trans isomer 1a, and a
concomitant decrease in 1b, as monitored by 31P{1H}
NMR spectroscopy. However, although 1b is comple-
tely consumed within 24 h, several new complexes, along
with free PPh3, accompany the formation of 1a during
this time, and they could not be confidently character-
[pyboxꢀ
/
2,6-bis(dihydrooxazolinyl)pyridine],
which
yielded trans-[RuCl(PPh3)2(pybox)]ꢂ. The structure of
1a is readily deduced via NMR spectroscopy. The
31P{1H} NMR spectrum of 1a shows only a singlet at
dꢀ24.50, which is consistent with two mutually trans
/
phosphine ligands about the ruthenium center. This
chemical shift is similar to that observed [12] for the
cation trans-[RuCl(PPh3)2(pybox)]ꢂ (dꢀ
/
22.0), as well
as for the cation trans-[RuCl(PPh3)2(terpy)]ꢂ (dꢀ
20.1), which also contains a planar mer-tridentate 2,6-
disubstituted pyridine ligand (terpyꢀ2,2?:6?,2ƒ-terpyr-
/
/
ized (the formation of ruthenium(II)ꢁ
/
BPPꢁPPh3 com-
/
plexes containing DMSO should not be ruled out under
these conditions, considering the polar nature and
coordinating ability of this solvent).
As part of this work, we wished to examine and
compare the steric effects of this ligand class, and this
prompted us to investigate reactions involving alkyl
substituted derivatives of 2,6-bis(pyrazol-1-yl)pyridine.
Indeed, substituents may be readily incorporated onto
Scheme 1.

246
N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ252
/
the pyrazole rings of the BPP framework [7]. Thus, when
a benzene solution containing RuCl2(PPh3)3 and the
1H NMR data. We, however, postulate a trans arrange-
ment. The 31P{1H} NMR spectrum of 2 shows a singlet
methyl substituted Me4BPP ligand [Me4BPPꢀ2,6-
/
at dꢀ49.51, which is consistent with only one PPh3
/
bis(3,5-dimethylpyrazol-1-yl)pyridine] in a 1:1 molar
ratio is refluxed for 48 h, a color change from brown
ligand coordinated to the ruthenium center. More
importantly, this chemical shift lies in a range observed
for several structurally similar ruthenium complexes of
to deep redꢁorange is observed, and the complex trans-
/
RuCl2(PPh3)(Me4BPP) (2), precipitates as an air-stable,
red microcrystalline solid (Scheme 2). Complex 2 was
found to be more soluble (vs. complexes 1), particularly
in halogenated solvents. Despite the lengthy reaction
time, the yield via this method (38%) was moderate at
best, therefore, alternative methods of preparing 2 were
investigated. Interestingly, performing the same reaction
in a higher boiling solvent (i.e. toluene) only produced
intractable residues that did not contain 2, based on
31P{1H} and 1H NMR spectroscopic analyses. However,
Et3N reductions of ethanol slurries containing
RuCl3(Me4BPP) [10,11] and PPh3 (1:1) at reflux tem-
peratures yielded 2 (Scheme 2) in much better isolated
yields (80% after recrystallization) and significantly
shorter reaction times (5 h). We attempted to extend
this latter procedure to include bulkier phosphines such
as PCy3 [i.e. trans-RuCl2(PCy3)(Me4BPP)], however,
under analogous conditions only insoluble black pow-
ders (presumably ruthenium metal) could be isolated.
There has been some discussion [11] regarding the
meridional steric crowding of 2,6-bis(pyrazol-1-yl) pyr-
idine ligands bearing substituents in the 3,3ƒ-positions of
the pyrazole rings. Perhaps the comparatively larger
PCy3 phosphine, coupled with the sterics of the Me4BPP
ligand, inhibit the formation of trans-RuCl2(P-
Cy3)(Me4BPP) under these conditions.
the general formula RuCl2(PR3)(EN?E) (EN?Eꢀmer-
/
tridentate 2,6-disubstituted pyridine ligand, where E is
either a nitrogen or phosphorus donor atom) in which
the chloride ligands are trans, including trans-
RuCl2[P(p-C6H4CH3)](terpy) (dꢀ
RuCl2(PPh3)(pybox) (dꢀ46.48) [14] and trans-
RuCl2(PPh3)(PNP) [PNPꢀ2,6-bis(diphenylphosphino-
methyl)pyridine] (dꢀ42.0) [15]. Furthermore, similarly
/41.6) [13], trans-
/
/
/
formulated complexes in which the chloride ligands are
cis display 31P resonances that are shifted substantially
upfield (Dd :
/
10ꢁ15 ppm) [13,14,16] compared with
/
those observed for trans geometries. Within the context
of this latter point, it seemed somewhat unusual that the
PPh3 ligand would preferentially occupy the more
sterically congested meridional plane containing the
Me4BPP ligand (vs. the apical positions), considering
the methyl substituents in the 3 and 3ƒ-positions [for
example [16], reactions of RuCl2(PPh3)3 with tridentate
2,6-bis(imino)pyridine ligands bearing bulky substitu-
ents exclusively yield products analogous to 2 but with
cis chlorides]. However, complex 2 does not isomerize to
the corresponding cis isomer after heating (80 8C) in
either C2D4Cl2 or polar CD3OD (60 8C) over 24 h (2 is
insoluble in toluene-d8, even at 110 8C). These results
contrast that observed [13] for the isomerization of
trans-RuCl2(PPh3)(terpy) to the cis isomer, which goes
to completion under similar conditions, despite lacking
any groups in the 6 and 6ƒ-positions of the terpy ligand.
A recent comparative X-ray crystallographic study [11]
between analogous ruthenium complexes containing
either 6,6ƒ-substituted terpy ligands or 3,3ƒ-substituted
BPP ligands (both ligands bearing the same substitu-
ents) has shown that the 6,6ƒ-substituted terpy complex
imparts a greater steric impact on the fourth position in
the meridional plane. Thus, a similar argument also may
be made for 2 and trans-RuCl2(PPh3)(terpy), where the
dramatic difference in isomerization rates may simply
rely on the fact that the terpy ligand greatly facilitates
ligand (e.g. phosphine) dissociation in the meridional
plane (vs. Me4BPP) due to a greater steric hindrance,
thus accelerating isomerization. This is supported [14]
by the fact that trans-RuCl2(PPh3)[(SS)-iPr-pybox]
1
The proposed structure of 2 is based on its H and
31P{1H} NMR spectra. In addition to two pyridyl
hydrogen signals (dꢀ
for 4-H), the 1H NMR spectrum of 2 shows one
pyrazolyl hydrogen (dꢀ6.05 for 4,4ƒ-H) and two
pyrazolyl methyl signals (dꢀ2.83 and 2.60 for 3,3ƒ-
/
7.04 for the 3,5-H and dꢀ
/
7.37
/
/
and 5,5ƒ-CH3). While this data is consistent with overall
C2v symmetry, considering the meridionally coordinat-
ing geometry of the Me4BPP ligand, the chloride ligands
conceivably could adopt a cis geometry and yield similar
{(SS)-iPr-pyboxꢀ
2,6-bis[4?-(S)-isopropyloxazolin-2?-
/
yl]pyridine}, which bears bulky isopropyl groups on the
4?-position of the oxazoline ring, quantitatively rear-
ranges to the cis isomer in refluxing acetone over 24 h,
whereas trans-RuCl2(PPh3)(pybox) (i.e. only hydrogens
at the 4?-positions) does not under the same conditions.
Scheme 2.

N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ
/252
247
2.2. Synthesis and characterization of trans-
RuCl2(L)(Me4BPP) (3) (LꢀC2H4, 3a; CO, 3b;
MeCN, 3c)
fluxed benzene mixtures of [RuCl2(p-cymene)]2 and
Me4BPP (1:2) (i.e. in the absence of any ligand L), but
were unsuccessful (i.e. only reactants were isolated after
work-up).
/
Extending this general procedure for the preparation
Several other trans-RuCl2(L)(Me4BPP) derivatives
also could be prepared, all of which are isostructural
with complex 2. Following a procedure reported by
Nishiyama et al. [17], a 1:2 mixture of [RuCl2(p-
cymene)]2 and Me4BPP refluxed under an ethylene
of 3a to include other ligands L (LꢀCO or MeCN)
/
proved difficult, yielding mixtures of products even with
slight modifications to the reaction conditions. How-
ever, using a similar approach (Scheme 4) for the
preparation of complex 2, stirring methanol suspensions
of RuCl3(Me4BPP) in the presence of excess Et3N and
atmosphere cleanly provides the orangeꢁbrown ethylene
/
complex trans-RuCl2(h2-C2H4)(Me4BPP) (3a), in mod-
erate yield (64%) after work-up (Scheme 3). Complex 3a
is stable in the solid state, even under reduced pressure
for weeks, and solutions of 3a show no decomposition
over 24 h when left exposed to atmospheric elements.
The C2v-symmetric structure of 3a is easily deduced via
NMR spectroscopy. The 1H NMR spectrum reveals
details indicating structural similarities with 2, in
particular the presence of a {trans-RuCl2(Me4BPP)}
fragment (i.e. two pyridyl hydrogen signals, one pyr-
azolyl hydrogen signal and two pyrazolyl methyl signals,
all of which are consistent with a plane of symmetry
bisecting the planar Me4BPP ligand through the para-
carbon and nitrogen of the 2,6-pyridine bridge). The
coordinated ethylene ligand of 3a appears as a sharp
reagent L (LꢀCO or MeCN), the complexes trans-
/
RuCl2(CO)(Me4BPP) (3b), or trans-RuCl2(NC-
Me)(Me4BPP) (3c), could be prepared in good to
excellent yields (78 and 90%, respectively). NMR
spectroscopic data clearly indicate that 3aꢁc are iso-
/
structural (see Section 4). Interestingly, the nCO stretch
in the IR spectrum of 3b appears at 1938 cmꢃ1, which is
slightly lower than that observed (nCO
for the structurally analogous
RuCl2(CO)(NN?N) {NN?Nꢀ2,6-[bis(dimethylami-
ꢀ
/
1948 cmꢃ1) [21]
mer,trans-
/
no)methyl]pyridine}. This would seem to suggest that
the Lewis basicity of the Me4BPP ligand is comparable
to the NN?N ligand, despite containing ‘softer’ pyrazolyl
donors (compared with ‘harder’ dimethylamino do-
nors). Perhaps the methyl groups in the 3,3ƒ and 5,5ƒ-
positions on the pyrazole rings of the Me4BPP ligand
influence its basicity. Indeed, electrochemical and spec-
singlet at dꢀ
other rutheniumꢁ
dentate nitrogen donor ligands) [16,18ꢁ
either the ethylene ligand in solution is fluxional (i.e.
freely rotating about the ruthenium centroidꢁethylene
/
3.11 (similar to that reported for several
ethylene complexes bearing mer-tri-
20] indicating
/
/
troscopic studies [10] performed on ruthenium(II)ꢁ
/
Me4BPP complexes containing b-diketonate ligands
suggest that the electron density of the ruthenium center
is strongly influenced by the electron donating nature of
the pyrazole substituents on the BPP framework.
/
axis at room temperature on the NMR time scale) or is
rigidly coplanar with either of the two mirror planes
present in the {trans-RuCl2(Me4BPP)} fragment of 3a.
X-ray crystallographic analysis of structurally related
trans-RuCl2(h2-C2H4)(pybox) [20], and cis-[RuCl(h2-
C2H4)2{2,6-bis[1-(2,6-
2.3. Vinylidene complexes containing Me4BPP: synthesis
and characterization of cis-[RuCl2(ꢀ
/
Cꢀ
/
?
dimethylphenylimino)ethyl]pyridine}][BAr4] [18] has re-
vealed that the C2H4 molecule coordinated trans to the
CHPh)(Me4BPP)] (4)
2,6-pyridine bridge lies parallel to the Nꢁ
/
Ruꢁ
/
N plane.
Substitution of the ethylene ligand in 3a was found to
occur quite readily (Scheme 5). Thus, refluxing a
benzene mixture of 3a in the presence of a slight (i.e.
1.2-fold) excess of phenylacetylene over 24 h cleanly
yields the air-stable dark brown vinylidene complex cis-
Considering the similarities between these mer-triden-
tate ligands and Me4BPP, a similar (preferred) confor-
mation of the ethylene ligand in 3a could be expected.
We attempted to isolate a coordinatively unsaturated
16-electron trans-RuCl2(Me4BPP) complex from re-
[RuCl2(ꢀ
/
CꢀCHPh)(Me4BPP)] (4), in moderate iso-
/
lated yield (67%). Performing similar reactions with tert-
Scheme 3.
Scheme 4.

248
N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ252
/
the order of several kcal molꢃ1) [24]. The far-infrared
spectrum of 4 shows two intense absorptions at 315 and
223 cmꢃ1, consistent with a relative cis arrangement of
chloride ligands about the ruthenium center [25]. Similar
spectroscopic results were observed for the structurally
similar and crystallographically characterized complex
cis-RuCl2(ꢀ
/
CꢀCHPh)(NN?N) [19] in which the chloride
/
ligands are cis disposed. Clearly, in the synthesis of 4
from 3a, the apical trans-chlorides rearrange to cis in
the product. One could argue that positioning the
vinylidene in the apical position minimizes any steric
interactions between the Cb substituents on the vinyli-
dene and the more congested meridional plane. Equally
arguable, electronics may also contribute to this re-
arrangement.
Scheme 5.
butylacetylene or trimethylsilylacetylene, in benzene or
toluene, led either to decomposition to unidentified
products or the quantitative isolation of 3a. Alterna-
tively, and more conveniently, 4 also may be prepared
(Scheme 5) in comparable yields (67%) directly from
[RuCl2(p-cymene)]2, Me4BPP and a comparatively large
excess of phenylacetylene (1:2:5, respectively) in reflux-
ing benzene over 24 h. The reaction proceeds at a much
slower rate via this method (i.e. several days are required
for completion) when only stoichiometric or even a
slight (1.2 M) excess amount of phenylacetylene is used.
Unfortunately, this alternate approach also failed for
bulkier alkynes (i.e. tert-butylacetylene); clearly, steric
demands of the larger alkynes and the coordinated
Me4BPP ligand must inhibit tautomerization by the
ruthenium center to the corresponding vinylidene in
these reactions. There are few precedents in the litera-
ture describing the isomerization of terminal alkynes to
the corresponding vinylidene by ruthenium(II) com-
plexes containing tridentate nitrogen donor ligands
[19,22], and even fewer examples in which the complex
does not bear a phosphine ligand.
2.4. Allenylidene complexes containing Me4BPP:
synthesis and characterization of [RuCl(PPh3)(ꢀ
/
Cꢀ
/
Cꢀ
/
CPh2)(Me4BPP)][BF4] (5)
Intrigued by the synthesis of the neutral vinylidene 4,
we tried to extend this general procedure to include
higher cumulenes, in particular allenylidenes, by using
propargyl alcohols as convenient precursors. The ma-
jority of reported allenylidene complexes are cationic
[26], and examples of neutral allenylidene complexes
remain comparatively rare. Unfortunately, despite mod-
ifying the conditions over several runs, reactions of 3a
with, for example, 1,1-diphenyl-2-propyn-1-ol, did not
produce the anticipated allenylidene RuCl2(ꢀ
/
Cꢀ
/
Cꢀ
/
CPh2)(Me4BPP) (i.e. the allenylidene analogue of 4),
nor did reactions of this alkyne with mixtures of
[RuCl2(p-cymene)]2 and Me4BPP. Presumably sterics
are responsible for the lack of reactivity in these
reactions. However, refluxing CH2Cl2 solutions of 2
and AgBF4 (1:1) in the presence of a slight excess of 1,1-
diphenyl-2-propyn-1-ol yields (76%) the deep, dark red
The structure of 4 is easily deduced via 1H and
13C{1H} NMR spectroscopy, and IR spectroscopy.
Along with signals attributed to the coordinated
Me4BPP ligand, the 13C{1H} NMR spectrum of 4
reveals resonances that clearly indicate tautomerization
of phenylacetylene has occurred, the most diagnostic of
cationic allenylidene complex [RuCl(PPh3)(ꢀ
/
Cꢀ
/
Cꢀ
/
CPh2)(Me4BPP)][BF4] (5), after work-up (Scheme 6).
As expected, the 31P{1H} NMR spectrum of 5 shows a
singlet resonance; more importantly, the chemical shift
which are Ca (dꢀ
/
356.1) and Cb (dꢀ111.3) of the
/
1
vinylidene ligand [23]. The H NMR spectrum of 4 at
room temperature is consistent with a mirror plane
bisecting the coordinated Me4BPP ligand through the
para-carbon and nitrogen of the 2,6-pyridine bridge,
and containing the cis-chloride ligands [i.e. one signal
(dꢀ/41.96) of this signal is consistent with that observed
for complexes reported in this, and other [13ꢁ
/15] work,
in which the PPh3 ligand is trans to the 2,6-pyridine
bridge of the Me4BPP ligand (vide supra). The 13C{1H}
each for the pyridyl 3,5-H (dꢀ
(dꢀ6.25), and pyrazolyl 3,3ƒ- and 5,5ƒ-methyl groups
(dꢀ2.76 and 2.73) are observed]. No changes were
observed when the spectrum was acquired at ꢃ80 8C.
/
7.60), pyrazolyl 4,4ƒ-H
/
/
/
Thus, the presence of this mirror plane would seem to
suggest that the vinylidene ligand rapidly rotates about
the Ruꢁ
above ꢃ
NMR spectroscopic studies of d6 rutheniumꢁ
complexes have revealed that the barrier to rotation
about the rutheniumꢁcarbon double bond is small, on
/
C bond on the NMR time scale at temperatures
80 8C (theoretical and variable temperature
vinylidene
/
/
/
Scheme 6.

N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ
/252
249
NMR spectrum of 5 clearly shows the presence of an
allenylidene ligand, with the typical downfield resonance
ately prior to use: CH2Cl2 (CaH2); C6H6, Et2O and
hexanes (sodium/benzophenone); MeCN, MeOH and
of Ca appearing as a doublet (2JPC
ꢀ
/
20 Hz) at dꢀ
/
EtOH (activated 4 A sieves). NMR solvents used in
solution structure elucidations were dried with appro-
˚
313.5; Cb and Cg of the allenylidene ligand appear as
singlets at dꢀ
/
212.2 and 157.7, respectively. The IR
spectrum of 5 supports the 13C{1H} NMR data and
shows a strong absorption for the allenylidene ligand at,
priate drying agents, vacuum distilled, freezeꢁ
thaw degassed three times, and stored in bulbs with
Teflon taps: CDCl3 (anhydrous CaCl2); CD3CN,
/
pumpꢁ
/
1922 cmꢃ1, a region characteristic of such
˚
CD3OD and DMSO-d6 (activated 4 A sieves); CD2Cl2
n(CꢀCꢀC)
ꢀ
/
ligands [26]. Complex 5 is frustratingly soluble, even in
solvents of low polarity (e.g. hexanes and Et2O), and
despite numerous attempts, including changing the
counteranion (e.g. PF6ꢃ), we were unable to grow X-
ray quality single crystals for a structure determination.
and C2D4Cl2 (CaH2); toluene-d8 (Na metal). NMR
spectra (1H, 13C and 31P) were obtained on a Varian
Unity INOVA 500 MHz spectrometer, with chemical
shifts (in ppm) referenced to residual protio solvent
peaks (1H and 13C) or external 85% H3PO4 (31P). IR
spectra were recorded using a Bruker IFS-66 FT IR
spectrophotometer as Nujol mulls between either NaCl
or polyethylene plates. Elemental analyses were per-
formed on a CEC 240XA analyzer by the Lakehead
University Center for Analytical Services. The ligands
[7] BPP and 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine
(Me4BPP), and the complexes RuCl2(PPh3)3 [28a],
3. Conclusions
Several key points emerge from this work. There
appears to be a subtle balance between steric and
electronic effects of the BPP ligands examined as part
of this work. Thus, halide dissociation occurs in reac-
tions of RuCl2(PPh3)3 with BPP (e.g. cationic dipho-
sphine 1a) presumably because of the increased electron
density at the metal center (brought about by the
coordination of BPP) which would subsequently weaken
the bond between the metal and the p-donor chloride
ligand. However, when the sterics of the BPP ligand are
increased (i.e. Me4BPP), phosphine dissociation prevails
(e.g. neutral monophosphine 2), despite the Me4BPP
ligand being a better Lewis base versus BPP. Although
we were unable to isolate the 16-electron complex
RuCl2(Me4BPP), the presence of a labile C2H4 ligand
in complex 3a makes it a convenient source for this
coordinatively unsaturated complex, which can serve as
[RuCl2(p-cymene)]2
[10b,11a] were prepared according to the methods cited
[28b]
and
RuCl3(Me4BPP)
previously.
4.1. Synthesis of cis- (1a) and trans- (1b)
[RuCl(PPh3)2(BPP)]Cl (1)
A brown CH2Cl2 (15 ml) solution of RuCl2(PPh3)3
(0.500 g, 0.521 mmol) and BPP (0.110 g, 0.521 mmol)
was refluxed for 3 h, during which time trans-
[RuCl(PPh3)2(BPP)]Cl (1a), deposited as a pale yellow
solid. The solid was collected using a glass filter frit and
washed with several volumes of Et2O (3ꢄ10 ml) before
/
a
precursor
for
the
synthesis
of
other
drying under reduced pressure. Yield: 0.153 g (32%).
Anal. Calc. for C44H39Cl2N5P2Ru: C, 58.21; H, 4.33; N,
RuCl2(L)(Me4BPP) complexes (e.g. the vinylidene com-
plex 4). The most intriguing results presented in this
work center around the ability of the {Ru(Me4BPP)}
fragment to isomerize terminal alkynes, including pro-
pargyl alcohols, to the corresponding vinylidenes (e.g. 4)
and allenylidenes (e.g. 5). Ruthenium(II)ꢁ
complexes containing tridentate nitrogen donor ligands
are known to be effective catalysts in a variety of
1
7.72. Found: C, 58.54; H, 4.26; N, 7.15%. H NMR
3
(499.9 MHz, DMSO-d6, 22 8C): 8.71 (d, 2H, JHH
ꢀ3
/
Hz, C5H of Pz), 8.25 (d, 2H, JHH
ꢀ
3 Hz, C3H of Pz),
/
3
ꢀ
8 Hz, C4H of Py), 7.31 (d, 2H,
/
3
7.63 (t, 1H, JHH
/cumulene
3JHH
ꢀ
/
8 Hz, C3H of Py), 7.33ꢁ
/
7.19 (m, 30H, Ph), 6.60
3 Hz, C4H of Pz). 31P{1H} NMR (202.3
(dd, 2H, 3JHH
ꢀ
/
MHz, DMSO-d6, 22 8C): 24.50 (s, PPh3). Removal of
the volatiles from the filtrate under reduced pressure
applications, particularly Cꢁ
/
C coupling reactions [27].
Thus, complexes 4 and 5 may exhibit novel reactivities
in this regard; studies in our group are currently
underway.
followed by several Et2O washes (3ꢄ
/
20 ml) yielded a
cis-
yellowꢁorange solid which contained
/
[RuCl(PPh3)2(BPP)]Cl (1b) (ca. 80%), along with small
quantities of 1a (ca. 15%) and free PPh3, as determined
by 31P{1H} NMR spectroscopy. Despite numerous
attempts and methods, complex 1b could not be isolated
4. Experimental
1
as a pure product. NMR data for 1b follows. H NMR
3
All experiments and manipulations were conducted
under an inert atmosphere of prepurified N2 using
standard Schlenk and syringe techniques. Bulk solvents
used in large-scale preparations were rigorously dried
and distilled from appropriate drying agents immedi-
(499.9 MHz, DMSO-d6, 22 8C): 9.19 (d, 2H, JHH
ꢀ3
/
Hz, C5H of Pz), 8.33 (t, 1H, JHH
ꢀ
8 Hz, C4H of Py),
/
3
3
8.25 (d, 2H, JHH
ꢀ
3 Hz, C3H of Pz), 8.05 (d, 2H,
/
3JHH
ꢀ
/
8 Hz, C3H of Py), 7.32ꢁ
/
7.19 (m, Ph), 6.76 (dd,
3 Hz, C4H of Pz). 31P{1H} NMR (202.3
3
2H, JHH
ꢀ
/

250
N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ
/252
2
43.85 (d, JPP
MHz, DMSO-d6, 22 8C): d(PA)ꢀ
/
ꢀ/28
out an orangeꢁ
glass frit and washed with Et2O (2ꢄ10 ml) before
/
brown solid. The solid was collected on a
2
38.78 (d, JPP
Hz, PPh3), d(PB)ꢀ
/
ꢀ
/
28 Hz, PPh3).
/
drying under reduced pressure. Yield: 0.0980 g (64%).
Anal. Calc. for C17H21Cl2N5Ru: C, 43.68; H, 4.54; N,
4.2. Synthesis of trans-RuCl2(PPh3)(Me4BPP) (2)
1
14.99. Found: C, 42.39; H, 4.21; N, 14.41%. H NMR
4.2.1. Method A
(499.9 MHz, CDCl3, 22 8C): 7.72 (t, 1H, 3JHH
ꢀ8.5 Hz,
/
3
A Schlenk tube containing RuCl2(PPh3)3 (0.200 g,
0.209 mmol) and Me4BPP (0.0559 g, 0.209 mmol) was
treated with C6H6 (15 ml), and the mixture was refluxed.
After 48 h, a red microcrystalline solid had deposited.
Once the mixture had cooled to room temperature (r.t.),
C4H of Py), 7.46 (d, 2H, JHH
ꢀ
8.5 Hz, C3,5H of Py),
/
6.33 (s, 2H, C4,4ƒH of Pz), 3.11 (s, 4H, C2H4), 2.84 (s,
6H, CH3 of Pz), 2.80 (s, 6H, CH3 of Pz). 13C{1H} (125.7
MHz, CDCl3, 22 8C): 157.2, 152.7 (s, C2,6 of Py and
C5,5ƒ of Pz), 143.2 (C4 of Py), 135.7 (C3,3ƒ of Pz), 113.8,
105.6 (s, C4,4ƒ of Pz and C3,5 of Py), 68.71 (s, C2H4),
the solid was filtered off, washed with Et2O (2ꢄ10 ml)
/
and dried under reduced pressure. Yield: 0.0711 g (38%).
Anal. Calc. for C33H32Cl2N5PRu: C, 56.49; H, 4.61; N,
15.33, 14.12 (s, 2ꢄCH3 of Pz).
/
1
9.98. Found: C, 55.20; H, 4.33; N, 9.30%. H NMR
4.4. Synthesis of trans-RuCl2(CO)(Me4BPP) (3b)
(499.9 MHz, CDCl3, 22 8C): 7.37 (t, 1H, 3JHH
ꢀ10 Hz,
/
C4H of Py), 7.30 (m, 6H, Ph), 7.21 (m, 3H, Ph), 7.10 (m,
A methanol (10 ml) suspension of RuCl3(Me4BPP)
(0.103 g, 0.217 mmol) was saturated with CO by passing
a slow stream of the gas through the mixture for 5 min.
Excess Et3N (0.5 ml) was added via syringe and the
mixture was allowed to stir under CO. After 30 min, the
flow of CO was stopped and the deep, dark brown
mixture was reduced to dryness under reduced pressure.
The dark brown solid that remained was extracted into
CH2Cl2 (25 ml) and filtered through Celite. The volatiles
were removed from the filtrate under reduced pressure
3
6H, Ph), 7.04 (d, 2H, JHH
ꢀ
10 Hz, C3,5H of Py), 6.05
/
(s, 2H, C4,4ƒH of Pz), 2.83 (s, 6H, CH3 of Pz), 2.60 (s,
6H, CH3 of Pz). 13C{1H} (125.7 MHz, CDCl3, 22 8C):
157.7, 153.0 (s, C2,6 of Py and C5,5ƒ of Pz), 142.8 (C4 of
Py), 133.7 (d, 1JPC
2JPC
128.3 (s, C4 of Ph in PPh3), 127.5 (d, 3JPC
Ph in PPh3), 113.4, 104.7 (s, C4,4ƒ of Pz and C3,5 of Py),
15.12, 14.43 (s, 2ꢄ
CH3 of Pz). 31P{1H} NMR (202.3
ꢀ
/
42 Hz, C1 of Ph in PPh3), 133.2 (d,
10 Hz, C2,6 of Ph in PPh3), 128.9 (C3,3ƒ of Pz),
9 Hz, C3,5 of
ꢀ
/
ꢀ
/
/
MHz, CDCl3, 22 8C): 49.51 (s, PPh3).
to yield an orangeꢁ
Et2O (2ꢄ20 ml) before drying under reduced pressure.
Yield: 0.0788 (78%). Anal. Calc. for
C16H17Cl2N5ORu: C, 41.12; H, 3.87; N, 14.99. Found:
C, 41.07; H, 5.59; N, 12.18%. IR (Nujol): n(CO) 1938
(s) cmꢃ1. H NMR (499.9 MHz, CDCl3, 22 8C): 8.32
/
brown solid, which was washed with
/
4.2.2. Method B
g
An ethanol (10 ml) slurry of RuCl3(Me4BPP) (0.200 g,
0.421 mmol) and PPh3 (0.110 g, 0.421 mmol) was treated
with excess Et3N (1 ml) via syringe. After 5 h at reflux,
ꢀ
/
1
3
3
the deep dark redꢁ
to r.t. before removing the volatiles under reduced
pressure. The dark redꢁorange solid that remained
/orange solution was allowed to cool
(t, 1H, JHH
ꢀ
/
8 Hz, C4H of Py), 7.85 (d, 2H, JHH
ꢀ8
/
Hz, C3,5H of Py), 6.25 (s, 2H, C4,4ƒH of Pz), 2.93 (s, 6H,
CH3 of Pz), 2.65 (s, 6H, CH3 of Pz). 13C{1H} (125.7
MHz, CDCl3, 22 8C): 205.1 (s, CO), 157.7, 149.7 (s,
/
was extracted into CH2Cl2 (25 ml) and filtered through
Celite. The volume of the filtrate was reduced to
approximately 10 ml under reduced pressure and excess
hexanes (30 ml) were carefully layered and allowed to
slowly diffuse into the CH2Cl2 solution. Over 24 h, red
crystals were obtained. The crystals were filtered off,
C
2,6 of Py and C5,5ƒ of Pz), 144.4 (C4 of Py), 142.5 (C3,3ƒ
of Pz), 112.5, 107.2 (s, C4,4ƒ of Pz and C3,5 of Py), 15.25,
15.11 (s, 2ꢄCH3 of Pz).
/
4.5. Synthesis of trans-RuCl2(NCMe)(Me4BPP) (3c)
washed well with Et2O (2ꢄ10 ml) and dried under
/
reduced pressure. Yield: 0.237 g (80%). The NMR data
were analogous to the product obtained by Method A,
above.
The complex RuCl3(Me4BPP) (0.100 g, 0.211 mmol)
was suspended in MeOH (10 ml). Excess MeCN (1 ml)
followed by excess Et3N (0.5 ml) were added via syringe
and the solution immediately turned deep, dark yellowꢁ
/
4.3. Synthesis of trans-RuCl2(h2-C2H4)(Me4BPP) (3a)
brown. The solution was stirred at r.t. for 30 min and
then the volatiles were removed under reduced pressure.
The dark brown residue was extracted into CH2Cl2 (15
ml) and filtered through Celite. The solvent was
removed from the filtrate and the remaining brown
The ligand Me4BPP (0.0872 g, 0.326 mmol) and
[RuCl2(p-cymene)]2 (0.100 g, 0.163 mmol) were dis-
solved in CH2Cl2 (15 ml). The solution was heated to
reflux while a slow, steady stream of ethylene was passed
through the mixture. After 6 h at reflux, the solution had
solid was washed with Et2O (2ꢄ10 ml) before drying
/
under reduced pressure. Yield: 0.0912 g (90%). Anal.
Calc. for C17H20Cl2N6Ru: C, 42.5; H, 4.20; N, 15.00.
turned orangeꢁ
/
brown. The flow of ethylene was
1
Found: C, 43.06; H, 6.75; N, 14.05%. H NMR (499.9
stopped and the mixture was allowed to cool to r.t.
Next, excess hexanes (40 ml) were added, precipitating
MHz, CDCl3, 22 8C): 7.69 (t, 1H, 3JHH
ꢀ
8 Hz, C4H of
/

N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ
/252
251
Py), 7.58 (d, 2H, 3JHH
ꢀ
/
8 Hz, C3,5H of Py), 6.22 (s, 2H,
red solution was obtained, along with a white precipi-
C4,4ƒH of Pz), 2.87 (s, 6H, CH3 of Pz), 2.77 (s, 6H, CH3
of Pz), 2.73 (s, 3H, CH3CN). 13C{1H} (125.7 MHz,
CDCl3, 22 8C): 155.7, 154.3 (s, C2,6 of Py and C5,5ƒ of
Pz), 143.6 (C4 of Py), 134.6 (C3,3ƒ of Pz), 125.8 (s,
CH3CN), 112.2, 105.5 (s, C4,4ƒ of Pz and C3,5 of Py),
tate. The mixture was allowed to cool to r.t. and then it
was filtered through Celite. The volatiles were removed
from the dark red filtrate under reduced pressure, and
the dark red solid that remained was washed with small
portions of Et2O (2ꢄ
pressure. Yield: 0.123
C48H42BClF4N5PRu: C, 61.12; H, 4.50; N, 7.43. Found:
C, 60.52; H, 5.25; N, 6.65%. IR (Nujol): n(CꢀCꢀC) 1922
(s) cmꢃ1. H NMR (499.9 MHz, CDCl3, 22 8C): 8.32
/5 ml) before drying under reduced
15.11, 14.02 (s, 2ꢄ/CH3 of Pz), 5.191 (s, CH3CN).
g
(76%). Anal. Calc. for
4.6. Synthesis of cis-[RuCl2(ꢀ
(4)
/
CꢀCHPh)(Me4BPP)]
/
ꢀ
/
1
3
3
(t, 1H, JHH
ꢀ
/
8 Hz, C4H of Py), 7.96 (d, 2H, JHH
ꢀ8
/
4.6.1. Method A
Hz, C3,5H of Py), 7.97ꢁ
7.01 (m, 25H, Ph), 6.17 (s, 2H,
/
Complex 3a (0.100 g, 0.214 mmol) in C6H6 (10 ml)
was treated with a slight (1.2 molar) excess of phenyla-
cetylene (29 ml, 0.257 mmol), and the mixture was
refluxed for 24 h. During this time, the color of the
solution gradually turned deep, dark brown. Next, the
solution was allowed to cool to r.t. and then the volatiles
were removed under reduced pressure. The remaining
C4,4ƒH of Pz), 2.83 (s, 6H, CH3 of Pz), 2.11 (s, 6H, CH3
of Pz). 13C{1H} (125.7 MHz, CDCl3, 22 8C): 313.5 (d,
2JPC
ꢀ
/
20 Hz, Ruꢀ
CPh2), 159.5, 146.5 (s, C2,6 of Py and C5,5ƒ of Pz),
157.7 (s, RuꢀCꢀCꢀ
CPh2), 145.6 (C4 of Py), 144.5 (s,
Ph), 144.3 (s, Ph), 143.7 (C3,3ƒ of Pz), 132.6 (d, 2JPC
10
Hz, C2,6 of Ph in PPh3), 131.0 (s, Ph), 129.3 (s, Ph), 128.5
(d, 3JPC 9.4 Hz, C3,5 of Ph in PPh3), 128.3 (s, C4 of Ph
in PPh3), 127.8 (s, Ph), 126.0 (s, Ph), 113.9, 108.6 (s, C4,4ƒ
/
C ꢀ
/
Cꢀ
/
CPh2), 212.2 (s, Ruꢀ
/
Cꢀ
/
C ꢀ
/
/
/
/
ꢀ
/
dark brown solid was washed with Et2O (2ꢄ
/10 ml) and
ꢀ
/
then dried under reduced pressure. Yield: 0.0777 g
(67%). Anal. Calc. for C23H23Cl2N5Ru: C, 51.01; H,
4.29; N, 12.94. Found: C, 50.95; H, 4.13; N, 12.33%. 1H
of Pz and C3,5 of Py), 15.77, 15.21 (s, 2ꢄ
CH3 of Pz).
/
31P{1H} NMR (202.3 MHz, CDCl3, 22 8C): 41.96 (s,
PPh3).
NMR (499.9 MHz, CDCl3, 22 8C): 8.12 (t, 1H, 3JHH
ꢀ
/
8 Hz, C4H of Py), 7.60 (d, 2H, JHH
ꢀ
8 Hz, C3,5H of
/
3
Py), 7.05 (m, 2H, Ph), 6.88 (m, 1H, Ph), 6.74 (m, 2H,
Ph), 6.25 (s, 2H, C4,4ƒH of Pz), 4.62 (s, 1H, Ruꢀ
Cꢀ
CHPh), 2.76 (s, 6H, CH3 of Pz), 2.73 (s, 6H, CH3 of Pz).
/
/
Acknowledgements
13C{1H} (125.7 MHz, CDCl3, 22 8C): 356.1 (s, Ruꢀ
/
C ꢀ
/
We gratefully acknowledge financial support from the
Lakehead University Senate Research Committee.
CHPh), 158.7, 150.5 (s, C2,6 of Py and C5,5ƒ of Pz), 144.0
(C4 of Py), 142.3 (C3,3ƒ of Pz), 141.4 (s, Ph), 129.0 (s, Ph),
128.6 (s, Ph), 125.2 (s, Ph), 113.6, 107.2 (s, C4,4ƒ of Pz
and C3,5 of Py), 111.3 (s, Ruꢀ
2ꢄCH3 of Pz).
/
Cꢀ/CHPh), 15.43, 14.50 (s,
References
/
[1] A. Togni, L.M. Venanzi, Angew. Chem., Int. Ed. Engl. 33 (1994)
497.
4.6.2. Method B
[2] (a) S. Trofimenko, Scorpionates: the Coordination Chemistry of
Polypyrazolylborate Ligands, Imperial College, London, 1999;
(b) S. Trofimenko, Chem. Rev. 93 (1993) 943.
A mixture of [RuCl2(p-cymene)]2 (0.100 g, 0.163
mmol) and Me4BPP (0.0872 g, 0.326 mmol) in C6H6
(15 ml) was treated with excess phenylacetylene (179 ml,
1.63 mmol) via syringe. After refluxing for 24 h, a deep,
dark brown mixture was obtained. The mixture was
allowed to cool to r.t. and then the volatiles were
stripped off under reduced pressure. The deep dark
[3] (a) K.P. Wainwright, Coord. Chem. Rev. (1997) 35;
(b) P. Chaudhuri, K. Wieghardt, Prog. Inorg. Chem. (1987) 329;
(c) L.F. Lindoy, The Chemistry of Macrocyclic Ligand Com-
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[4] Recent applications using 2,6-bis(imino)pyridine ligands: (a) S.S.
Ivanchev, G.A. Tolstikov, V.K. Badaev, N.I. Ivancheva, I.I.
Oleinik, M.I. Serushkin, L.V. Oleinik, Polym. Sci., Ser. A 43
(2001) 1189;
brown solid that remained was washed with Et2O (2ꢄ
/
10 ml) before drying under reduced pressure. Yield:
1
0.117 g (67%). The H NMR spectrum (CDCl3) of the
(b) Z. Ma, H. Wang, J.M. Qui, D.M. Xu, Y.L. Hu, Macromol.
Rapid Commun. 22 (2001) 1280;
product obtained by this method was identical to that
obtained by Method A, above.
(c) G.J.P Britovsek, V.C. Gibson, B.S. Kimberley, S. Mastroianni,
C. Redshaw, G.A. Solan, A.J.P. White, D.J. Williams, J. Chem.
Soc., Dalton Trans. (2001) 1639;
4.7. Synthesis of [RuCl(PPh3)(ꢀ
/
Cꢀ
/
Cꢀ
/
(d) B. Cetinkaya, E. Cetinkaya, M. Brookhart, P.S. White, J.
Mol. Catal. A 142 (1999) 101;
CPh2)(Me4BPP)][BF4] (5)
(e) S. De Matrin, G. Zassinovich, G. Mestroni, Inorg. Chim. Acta
174 (1990) 9.
Complex 2 (0.120 g, 0.171 mmol), AgBF4 (0.0333 g,
0.171 mmol) and 1,1-diphenyl-2-propyn-1-ol (0.0427 g,
0.205 mmol) were combined and dissolved in CH2Cl2
(10 ml). After refluxing the mixture for 24 h, a deep dark
[5] Recent applications using 2,6-bis(oxazolinyl)pyridine ligands: (a)
C. Provent, G. Bernardinelli, A.F. Williams, N. Vulliermet, Eur.
J. Inorg. Chem. (2001) 1963;
(b) S. Fukuzawa, H. Matsuzawa, K. Metoki, Synlett (2001) 709;

252
N.J. Beach, G.J. Spivak / Inorganica Chimica Acta 343 (2003) 244ꢁ252
/
(c) C.-X. Zhao, M.O. Duffey, S.J. Taylor, J.P. Morken, Org. Lett.
3 (2001) 1829;
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Takeuchi, J. Chem. Soc., Dalton Trans. (1991) 2801.
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(e) Y. Motoyama, O. Kurihara, K. Murata, K. Aoki, H.
Nishiyama, Organometallics 19 (2000) 1025.
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