Flexible syntheses of tripodal phosphine ligands 1,1,2- tris(diarylphosphino)ethane and their ruthenium η5-C 5Me5 complexes

Article abstract of DOI:10.1021/om3005959

A series of four tripodal polyphosphine ligands (PAr₂) ₂CHCH₂PAr₂ (1a-d) were synthesized and coordinated to ruthenium to produce the complexes [Ru(η⁵-C ₅Me₅)((PAr₂)₂CHCH ₂PAr₂)]PF₆ (2a-d) (Ar = phenyl (a), p-tolyl (b), o-tolyl (c), m-xylyl (d)). The 1,1,2-tris(diarylphosphino)ethane compounds were generated in a novel trisubstitution reaction of diarylphosphorylacetaldehyde diethyl acetal, a useful synthetic precursor that was used previously for the synthesis of phosphonium dimers. The tridentate ligands were subsequently combined with the ruthenium(II) precursor Ru(η⁵-C₅Me₅)(1,5-COD)Cl, in order to probe the coordination geometry of 1a-d. The resulting complexes 2a-d displayed piano-stool type structures where the phosphine ligands were coordinated in a fac geometry. Despite the large steric bulk of the ligands, as well as the ring strain caused by the formation of a four-membered ring and two five-membered rings with the ruthenium center, complexes 2a-d were quite stable. The ruthenium salts were air and moisture stable and did not react with CO, H₂, or NaBH₄, even at elevated temperatures.

Full text of DOI:10.1021/om3005959

Article
pubs.acs.org/Organometallics
Flexible Syntheses of Tripodal Phosphine Ligands 1,1,2-
Tris(diarylphosphino)ethane and Their Ruthenium η5‑C5Me5
Complexes
Peter E. Sues, Alan J. Lough, and Robert H. Morris*
Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
S
* Supporting Information
ABSTRACT: A series of four tripodal polyphosphine ligands
(PAr2)2CHCH2PAr2 (1a−d) were synthesized and coordi-
nated to ruthenium to produce the complexes [Ru(η5-
C5Me5)((PAr2)2CHCH2PAr2)]PF6 (2a−d) (Ar = phenyl
(a), p-tolyl (b), o-tolyl (c), m-xylyl (d)). The 1,1,2-
tris(diarylphosphino)ethane compounds were generated in a
novel trisubstitution reaction of diarylphosphorylacetaldehyde
diethyl acetal, a useful synthetic precursor that was used
previously for the synthesis of phosphonium dimers. The
tridentate ligands were subsequently combined with the
ruthenium(II) precursor Ru(η5-C5Me5)(1,5-COD)Cl, in
order to probe the coordination geometry of 1a−d. The
resulting complexes 2a−d displayed piano-stool type structures where the phosphine ligands were coordinated in a fac geometry.
Despite the large steric bulk of the ligands, as well as the ring strain caused by the formation of a four-membered ring and two
five-membered rings with the ruthenium center, complexes 2a−d were quite stable. The ruthenium salts were air and moisture
stable and did not react with CO, H2, or NaBH4, even at elevated temperatures.
phosphorus ligands exhibit a strong trans influence, which
helps labilize ligands during catalysis, aiding in fast turnovers of
the catalytic cycle.20−24 Another benefit of phosphorus ligands
in general is that the electronic and steric parameters of the
phosphorus donors can easily be varied, the effects of which can
be quantified using Tolman cone angles and electronic
parameters.25 This is an attractive feature for catalytic systems,
as it allows for the systematic development of more active
catalysts utilizing rational catalyst design.
INTRODUCTION
■
Tripodal, multidentate phosphine ligands exhibit rich and
diverse coordination chemistry, and as such they have found an
integral place in inorganic and organometallic chemistry (see
Scheme 1 for some examples).1−5 These chelating ligands
Scheme 1. Selection of Tripodal Tridentate Phosphine
Ligands26,27
One tridentate phosphine donor of note is 1,1,1-tris-
(diphenylphosphinomethyl)ethane (TRIPHOS), a commonly
used ligand which forms three six-membered rings with a metal
center and binds in a fac geometry (see Scheme 1).28−31 This
ligand has been employed to generate various ruthenium- and
rhodium-based catalysts for the hydrogenation of al-
kenes,7,32−37 alkynes,5−7,34 ketones,6,34,38−40 esters,41−44 and
several other substrates of interest.34,39,45−51 A related ligand,
1,1,2-tris(diphenylphosphino)ethane (1a), was developed by
Bookham et al. and Schmidbaur et al. in the late 1980s.52,53
Like TRIPHOS, this ligand is a tripodal phosphine donor with
an aliphatic backbone, but unlike TRIPHOS, 1a would form
two five-membered rings and one four-membered ring with a
metal center when bound in a fac geometry. Although neither
research group prepared metal complexes of 1a, Bookham et al.
did propose several different binding modes that 1a could
provide a very controlled and stable coordination environment
around transition-metal centers, often occupying three cis sites
or a fac geometry in octahedral complexes. Such stability and
predictable coordination geometry are often important for
homogeneous catalytic processes and in some cases provide
enhanced catalytic activity over analogous monodentate or
bidentate phosphorus-containing systems.5−19 In addition,
Received: June 28, 2012
© XXXX American Chemical Society
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Scheme 2. Synthesis of Ligands 1a−d Starting from Diarylphosphines
Scheme 3. Proposed Mechanism for the Formation of Ligands 1a−d
adopt, including a fac arrangement of the ligand. They
hypothesized that, although 1a could feasibly coordinate to a
single metal center, the resulting complex would have a
considerable amount of strain. Despite the similarities to
TRIPHOS, no other research on this unique ligand has been
reported.
In this paper we report the general synthesis of 1,1,2-
tris(diarylphosphino)ethane ligands, 1a−d, as well as their
characterization. We have previously outlined the syntheses of
diarylphosphorylacetaldehyde diethyl acetals as convenient
precursors for the production of phosphonium dimers,54 and
herein we describe their use in the synthesis of 1a−d.
Furthermore, we report the first transition-metal complexes
bearing these types of ligands, ruthenium η5-C5Me5 (Cp*)
complexes 2a−d, and explore their coordination geometry.
With respect to nomenclature, throughout this paper,
compounds will be named according to their aryl substitution
pattern: a for phenyl, b for p-tolyl, c for o-tolyl, and d for m-
xylyl.
purchase from commercial sources, and difficult to purify if
synthesized from vinyl chlorides and diarylphosphines.52,53
The 31P{1H} NMR spectra of compounds 1a−d all show
characteristic peaks in the negative chemical shift region. The
two equivalent phosphorus nuclei produce a doublet in the
range between −27.6 and −3.8 ppm and are coupled to the
remaining inequivalent phosphorus nucleus, which displays a
triplet between −19.8 and −45.6 ppm. The 1H NMR spectra of
compounds 1a−d also exhibit several diagnostic peaks. The
proton α to the two equivalent phosphorus centers resonates as
a doublet of triplets between 3.3 and 3.0 ppm, while the
protons α to the lone phosphorus center exhibit a multiplet
between 2.3 and 2.0 ppm.
This general synthetic route for the production of 1,1,2-
tris(diarylphosphino)ethane compounds operates regardless of
the aryl groups on the phosphoryl moiety of the starting
material, but the reaction gave the cleanest products and
highest yields with bis(o-tolylphosphoryl)acetaldehyde diethyl
acetal. The latter acetal was used almost exclusively to
synthesize 1a−d, not only because it gave the highest yields
and cleanest products but also because its synthesis was facile,
and the bis(o-tolyl)phosphine oxide byproduct was easily
recovered and recrystallized (up to 70% recovery).
The mechanism of formation for compounds 1a−d is at this
time poorly understood but is believed to operate in a fashion
similar to the trisubstitution reaction that we described
previously which yields 1,1,2-tris(diarylphosphoryl)ethane
compounds.55 We propose that a deprotonated species in
solution abstracts a proton from the carbon α to the
phosphoryl functionality to produce a carbanion that is
stabilized by the adjoining PO group. Subsequently, in an
E1cb fashion, an ethoxide is eliminated with concomitant
carbon−carbon double bond formation. After nucleophilic
attack by a diarylphosphide in solution and another E1cb
elimination reaction, a 1,2-bis(diarylphosphino)ethylene spe-
cies could be produced. Protonated diarylphosphines in
solution could then react with the disubstituted intermediate
and hydrophosphinate the double bond, thus generating a
mixed phosphine−phosphine oxide product. In the last step,
RESULTS AND DISCUSSION
■
Synthesis and Characterization of Triphosphine
Ligands 1a−d. Compounds 1a−d were generated in a novel
trisubstitution reaction of a phosphoryl-substituted protected
aldehyde. Three equivalents of diarylphosphine were deproto-
nated with KH and then combined directly with 1 equiv of
diarylphosphorylacetaldehyde diethyl acetal to yield triphos-
phine ligands 1a−d as white solids in moderate yields (44−
58%). In this reaction the diarylphosphoryl and ethoxide
groups of the diarylphosphorylacetaldehyde diethyl acetal
precursor have been replaced by diarylphosphino functionalities
(see Scheme 2). Compound 1a has previously been prepared
via an alternative synthetic route employing 1,1-bis-
(diphenylphosphino)ethylene52,53 but was never fully charac-
terized. This method is less convenient than our new method
for the synthesis of 1,1,2-tris(diarylphosphino)ethane com-
pounds because the starting material used in our case is air
stable. The starting material used by Schmidbaur et al. as well as
Bookham et al., on the other hand, is air sensitive, expensive to
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Scheme 4. Synthesis of Ruthenium Complexes 2a−d using Ligands 1a−d
Figure 1. ORTEP3 representations (thermal ellipsoids at 50% probability) and atom numbering for (a) 2a (the counterion, and most hydrogens are
omitted for clarity), (b) 2b (the solvent, counterion, and most hydrogens are omitted for clarity), (c) 2c (the solvent, counterion, and most
hydrogens are omitted for clarity), and (d) 2d (the counterion and most hydrogens are omitted for clarity).
another 1 equiv of diarylphosphide in solution could displace
the phosphoryl group (a better leaving group than a
diarylphosphine) in an SN2 reaction and generate the observed
triphosphine product (summarized in Scheme 3).
excess of deprotonated diarylphosphine in an endeavor to
replace the ethoxides with phosphino functionalities. Unfortu-
nately, every effort resulted in recovery of the monosubstituted
starting material with no incorporation of the phosphine
functionalities. The phosphine oxide appears to be crucial in
initiating the trisubstitution process.
Efforts were made to isolate some of the possible
intermediates in the hypothetical mechanism, with special
emphasis placed on isolating or trapping the 1,2-bis-
(diarylphosphino)ethylene species, but these attempts met
with little success. Despite adding only 1 equiv of deprotonated
phosphine at a time at −78 °C and then warming to room
temperature, thus strictly controlling the stoichiometry of the
reaction, the only products isolated were the trisubstituted
ligand, diarylphosphine oxide, and the starting materials.
Furthermore, the addition of silane in order to trap either of
the proposed unsaturated intermediates was not successful, and
the only products observed were the 1,1,2-tris-
(diarylphosphino)ethane species, the reactants, and some
undetermined decomposition products. As in our related
phosphine oxide paper,54 several attempts were made to
generate structures similar to the polyfunctional phosphines by
first installing a different functional group (phosphino or
amino) in place of the diarylphosphoryl moiety in the
diarylphosphorylacetaldehyde diethyl acetal precursor. The
differently substituted products were then subjected to an
Variable-temperature NMR studies of the reaction mixture
were able to provide a little more insight into the mechanism of
formation for these tripodal ligands. We were able to
completely freeze the reaction at −40 °C, and in a 31P{1H}
NMR spectrum of the reaction mixture we were able to observe
several species in solution. Diphenylphosphide, diarylphosphor-
ylacetaldehyde diethyl acetal, deprotonated diarylphosphine
oxide, and the trisubstituted product could all be readily
identified in solution, but an unidentified phosphorus-
containing compound that displayed a singlet at −0.40 ppm
1
in the 31P{1H} NMR was also present. In addition, a H NMR
spectrum of the reaction mixture displayed a peak between 6.4
and 6.3 ppm that corresponds to a vinylic proton. As the
solution was warmed to −30 °C, the reaction began to proceed
and was monitored via 31P{1H} NMR. The diphenylphosphide,
diarylphosphorylacetaldehyde diethyl acetal, and the inter-
mediate at −0.40 ppm all diminished in intensity with a
corresponding increase in intensity for the tripodal ligand and
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deprotonated diarylphosphine oxide. However, when all of the
diarylphosphorylacetaldehyde diethyl acetal starting material
had disappeared, there were still residual amounts of the species
at −0.40 ppm and diphenylphosphide. These two species, upon
sitting, further decreased in intensity and disappeared, while the
trisubstituted product and deprotonated diarylphosphine oxide
grew in intensity. We believe that the species at −0.40 ppm is
the (2-ethoxyvinyl)phosphine oxide intermediate that we had
postulated in the mechanism, which, upon reaction with
diphenylphosphide, releases deprotonated diarylphosphine
oxide.
membered rings with a metal center (although it is important
to note that this may not be the case with other metal
complexes generated from ruthenium precursors containing
only monodentate ligands).52 This ring strain is reflected in the
P−Ru−P angles, all of which are compressed below the optimal
octahedral angles of 90°. For the two P−Ru−P angles that
represent the five-membered rings, P(1)−Ru(1)−P(2) and
P(1)−Ru(1)−P(3), the values lie between 78.13(9) and
83.75(9)°, while the angle that represents the four-membered
ring, P(2)−Ru(1)−P(3), is considerably smaller and more
constrained, between 68.01(6) and 69.59(6)°. In addition, the
P(1)−C(2)−C(1) bond angle has been compressed upon
coordination to the metal center, between 106(2) and
108.6(6)°, which is smaller than the optimal 109.5° angle for
a perfect tetrahedron. For comparison, the complex [Ru-
(indenyl)(TRIPHOS)]PF6 has P−Ru−P angles that are
between 86 and 89°.57 With respect to bond lengths, 1a,b,d
have typical Ru−P bond lengths, around 2.30 and 2.31 Å,
except for one longer Ru−P bond around 3.33 Å (Ru(1)−P(2)
for 2a,d, Ru(1)−P(3) for 2b).33,38,58 For 2c, however, all the
Ru−P bond lengths are elongated: 2.356(2), 2.331(2), and
2.381(3) Å for Ru(1)−P(1), Ru(1)−P(2), and Ru(1)−P(3),
respectively. This is most likely due to the increased bulk of the
o-tolyl substituents (for further notable bond lengths and
angles, see Table 1). Another feature of note is the stacking of
Synthesis and Characterization of Ruthenium Com-
plexes 2a−d. In order to probe the binding mode of
compounds 1a−d, the tripodal polyphosphine ligands were
bound to ruthenium and the resulting complexes were
characterized. One equivalent of 1a−d was dissolved in
dichloromethane and added to a solution of Ru(Cp*)(COD)
Cl in dichloromethane. After heating overnight, the solvent was
removed and the residue was dried to remove residual 1,5-
cyclooctadiene. 31P{1H} NMR spectra of the crude residues
revealed that multiple ruthenium complexes had formed, many
with pendant phosphorus functionalities. This indicated that
the tridentate ligands were not capable of displacing the
chloride ligand from ruthenium and, therefore, an abstracting
agent was necessary. To remove the chloride, the crude
residues were dissolved in acetone and an excess of NaPF6 was
added (see Scheme 4). After workup, air-stable pale yellow
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
2a−d
−
powders of 2a−d as PF6 salts were isolated in moderate to
exceptional yields (44−93%). The poor yields of 2b,d, 45% and
44%, respectively, can be attributed to their higher solubility in
organic solvents, because their conversions were nearly
quantitative as determined by NMR.
2a
2b·2CH2Cl2 2c·0.5CH2Cl2
Bond Lengths (Å)
2d
Ru(1)−P(1)
Ru(1)−P(2)
Ru(1)−P(3)
P(1)−C(2)
P(2)−C(1)
P(3)−C(1)
C(1)−C(2)
2.309(5)
2.333(6)
2.307(6)
1.87(2)
1.86(2)
1.84(2)
1.56(4)
2.316(2)
2.310(2)
2.336(2)
1.871(6)
1.861(6)
1.867(6)
1.539(9)
2.356(2)
2.331(2)
2.381(3)
1.857(9)
1.861(9)
1.877(9)
1.53(1)
2.303(2)
2.313(2)
2.357(2)
1.871(9)
1.852(9)
1.884(6)
1.54(1)
The 31P{1H} NMR spectra of compounds 2a,b,d all show
characteristic peaks significantly downfield from those of the
free ligand forms. The two equivalent phosphorus nuclei
display a doublet around 30 ppm and are coupled to the
remaining inequivalent phosphorus nucleus, which displays a
triplet around 60 ppm. The 31P{1H} NMR spectrum of 1c, on
the other hand, displays a triplet around 54 ppm, similar to the
other complexes, but the doublet for the two equivalent
phosphorus nuclei is split into four sets of doublets between 32
and 36 ppm. This arises from different orientations of the
methyl groups about the phosphorus centers, which give rise to
several rotamers in solution that do not interconvert because
the binding of the phosphine donors to the ruthenium center
locks the conformation of the methyl groups. This type of
behavior has been seen previously with bulky o-tolyl
substituents,54,55 which are known to have barriers of rotation
about the carbon−phosphorus bond.56 The 1H NMR spectra of
compounds 2a−d also exhibit several diagnostic peaks. The
proton α to the two equivalent phosphorus centers displays a
unique multiplet between 5.7 and 5.3 ppm, as do the protons α
to the lone phosphorus center, between 3.7 and 3.0 ppm.
In addition to NMR experiments, compounds 2a−d were
characterized in the solid state utilizing single-crystal X-ray
diffraction (see Figure 1). The ruthenium complexes display a
distorted-piano-stool geometry with a Cp* ligand occupying
half of the coordination sphere and the more sterically
demanding tripodal phosphine ligands occupying the other
three coordination sites. These crystal structures support the
predictions made by Bookham et al. that ligands 1a−d can
occupy a fac geometry despite the considerable amount of
strain involved in forming a four-membered ring and two five-
Bond Angles (deg)
P(1)−Ru(1)−P(2)
P(1)−Ru(1)−P(3)
P(2)−Ru(1)−P(3)
P(2)−C(1)−P(3)
P(1)−C(1)−C(2)
79.0(2)
81.79(3)
79.67(3)
68.59(6)
89.2(3)
81.84(9)
78.13(9)
69.36(9)
91.7(4)
83.75(9)
77.82(9)
68.01(6)
88.7(3)
80.8(2)
69.4(2)
90.9(9)
106(2)
107.4(4)
108.6(6)
106.6(5)
the aryl groups of the phosphine donors that is evident in the
solid-state structures. The aryl rings align themselves parallel to
each other, and for 2c the methyl substituents are oriented in
opposite directions to minimize unfavorable steric interactions.
Preliminary reactivity studies performed on ruthenium
complexes 2a−d have led to the interesting finding that they
are quite stable and are inert to ligand substitution reactions.
−
The PF6 salts are completely air and moisture stable and do
not react with either CO or H2 gas, even at elevated
temperatures. Furthermore, it was thought that reactions with
NaBH4 would yield ruthenium hydride complexes with
phosphorus−borane adducts, but this was not the case. Not
even 2c, which exhibited elongated Ru−P bonds in the crystal
structure, showed any reactivity; instead, the starting materials
were recovered unchanged. The Cp* ligand and the bulky
tripodal phosphine ligand shroud the ruthenium center and
prevent associative substitution reactions. Moreover, the Ru−P
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Kappa APEX DUO diffractometer with Mo Kα radiation (λ = 0.710 73
Å). The CCD data were integrated and scaled using the Denzo-SMN
package. The structures were solved and refined using SHELXTL
V6.1. Refinement was by full-matrix least squares on F2 using all data.
Synthesis of (C6H5)2PCH2CH(P(C6H5)2)2 (1a). Diphenylphos-
phine (0.500 g, 2.69 mmol) was dissolved in 2 mL of THF and added
to a suspension of KH (0.108 g, 2.69 mmol) in 5 mL of THF. Gas
evolved, and the solution turned bright red. After 30 min the gas
evolution ceased; then bis(o-tolyl)phosphineoxoacetaldehyde diethyl
acetal (0.310 g, 0.895 mmol) in 3 mL of THF was added. The solution
slowly turned yellow-orange in color and became cloudy. The solution
was left overnight. An excess of degassed 48% HBF4 (aq) (0.24 mL)
was added, and the solution turned colorless with a white precipitate.
The solvent was removed under reduced pressure, and the white
residue was redissolved in THF. An excess of Na2CO3 (approximately
0.100 g) was added and gas evolved. The solution was stirred
overnight and then filtered. The solvent was removed under reduced
pressure. The residue was washed with approximately 5 mL of
hexanes. Methanol was added to the colorless residue, and a white
precipitate formed. The precipitate was filtered to give a white solid.
bonds do not readily dissociate to open up a vacant
coordination site.
CONCLUSION
■
The 1,1,2-tris(diarylphosphino)ethane compounds 1a−d were
generated in an unprecedented trisubstitution reaction of
diarylphosphorylacetaldehyde diethyl acetal, a synthetic route
which was found to be a general method for producing new
tripodal phosphine ligands. Although the mechanism of this
process is currently unknown, it is suspected that the products
are generated through a series of E1cb reactions and
unsaturated intermediates, followed by a final substitution
reaction, all of which depend on the presence of the crucial
phosphoryl functionality. In order to test the predictions made
by Bookham et al. that ligands 1a−d can occupy a fac geometry
despite the considerable amount of strain involved, the
tridentate ligands were combined with a suitable ruthenium(II)
precursor to produce the complexes [Ru(Cp*)(L)]PF6.52 The
crystal structures of the ruthenium complexes revealed
distorted-piano-stool type structures where the phosphine
ligands are fac tripodal ligands. At the moment, however, this
coordination geometry is limited to the complexes we have
generated and the ruthenium precursor we have employed;
further studies utilizing ruthenium starting materials with only
monodentate ligands are needed. Despite the large steric bulk
of the ligands, as well as the ring strain caused by the formation
of a four-membered ring and two five-membered rings with the
ruthenium center, complexes 2a−d were quite stable with
respect to ligand exchange reactions. Further studies on these
interesting ruthenium systems are currently underway.
1
Yield: 49.5% (0.258 g). H NMR (400 MHz, CD2Cl2): δ 7.31−7.09
(m, 27H, Ar H), 6.93−6.88 (m, 3H, Ar H), 3.00 (dt, 1H, CH, J = 10.9,
7.4 Hz), and 2.09−2.00 (m, 2H, CH2) ppm. 31P{1H} NMR (161
MHz, CD2Cl2): δ −3.82 (d, J = 24.8 Hz) and −19.77 (t, J = 24.8 Hz)
ppm. 13C{1H} NMR (100 MHz, CD2Cl2): δ 138.60 (d, P−C, J = 16.6
Hz), 136.99 (t, C−P, J = 5.1 Hz), 136.52 (t, C−P, J = 5.2 Hz), 134.57
(td, Ar CH, J = 10.8, 1.5 Hz), 133.87 (td, Ar CH, J = 10.7, 1.3 Hz),
133.09 (d, Ar CH, J = 19.0 Hz), 129.02 (s, Ar CH), 128.78 (s, Ar CH),
128.68 (s, Ar CH), 128.50 (d, Ar CH, J = 6.5 Hz), 128.38−128.24 (m,
Ar CH), 29.81 (dt, CH2, J = 17.5, 10.2 Hz), and 28.94 (td, CH, J =
29.7, 11.3 Hz) ppm. Anal. Calcd for [C38H35P3]0.5[C4H10O]: C,
76.81; H, 6.60. Found: C, 77.14; H, 6.34. MS (DART; m/z+): 583.2
[C38H36P3]+.
Synthesis of (p-C7H7)2PCH2CH(P(p-C7H7)2)2 (1b). Similar to the
synthesis of 1a; see the Supporting Information.
Synthesis of (o-C7H7)2PCH2CH(P(o-C7H7)2)2 (1c). Similar to the
synthesis of 1a; see the Supporting Information.
EXPERIMENTAL SECTION
■
General Considerations. All procedures and manipulations were
performed under an argon or nitrogen atmosphere using standard
Schlenk line and glovebox techniques unless stated otherwise. All
solvents were degassed and dried using standard procedures prior to
all manipulations and reactions unless stated otherwise. Acetone was
dried and distilled over P2O5 under an argon atmosphere. THF,
pentane, hexanes, and diethyl ether were dried and distilled over
sodium and benzophenone under an argon atmosphere. All alcohols
were dried and distilled over activated magnesium (magnesium
turnings and a crystal of iodine) under an argon atmosphere.
Dichloromethane was dried and distilled over CaH2 under an argon
atmosphere. The synthesis of bis(o-tolyl)phosphineoxoacetaldehyde
diethyl acetal was described previously. Deuterated solvents were
purchased from Cambridge Isotope Laboratories or Sigma Aldrich,
degassed, and dried over activated molecular sieves prior to use. All
other reagents were purchased from commercial sources and utilized
without further purification. The ESI-MS data were collected on an
AB/Sciex QStar mass spectrometer with an ESI source, the EI-MS data
were collected on a Waters GC ToF mass spectrometer with an EI/CI
source, and the DART-MS data were collected on a JEOL AccuTOF-
DART mass spectrometer with a DART-ion source (no solvent is
required). NMR spectra were recorded at ambient temperature and
pressure using a Varian Gemini 400 MHz spectrometer (400 MHz for
1H, 100 MHz for 13C, 376 MHz for 19F, and 161 MHz for 31P) unless
stated otherwise. The 1H and 13C NMR spectra were measured
relative to partially deuterated solvent peaks but are reported relative
to tetramethylsilane (TMS). All 31P chemical shifts were measured
relative to 85% phosphoric acid as an external reference. The elemental
analyses were performed at the Department of Chemistry, University
of Toronto, on a Perkin-Elmer 2400 CHN elemental analyzer. Some
complexes gave inconsistent carbon analyses but acceptable hydrogen
and nitrogen contents; we attribute this to a combustion problem
caused by the hexafluorophosphate counterion.59 Single-crystal X-ray
diffraction data were collected using a Nonius Kappa-CCD or Bruker
Synthesis of (m-C8H9)2PCH2CH(P(m-C8H9)2)2 (1d). Similar to
the synthesis of 1a; see the Supporting Information.
Synthesis of [RuCp*(1a)]PF6 (2a). 1a (0.111 g, 0.190 mmol) and
RuCp*(COD)Cl (0.072 g, 0.190 mmol) were dissolved in dichloro-
methane (6 mL). The red-orange solution was stirred at 36 °C
overnight. The solution turned darker red-orange. The solvent was
removed under reduced pressure, and the residue was dissolved in
acetone (6 mL). An excess of NaPF6 (approximately 0.100 g) was
added, and the solution was stirred overnight. The solution turned
yellow-orange with a white precipitate. The solvent was removed
under reduced pressure, and the yellow-orange residue was dissolved
in dichloromethane. This solution was filtered, and the solvent was
removed under reduced pressure. Methanol (5 mL) was added to the
residue, and the slurry was stirred for 15 min. The yellow solid was
isolated and washed with ether (5 mL). Yield: 93.4% (0.145 g).
Crystals suitable for X-ray diffraction studies were grown from a
1
dichloromethane solution by diffusion of pentane vapor. H NMR
(400 MHz, CD2Cl2): δ 7.33−7.21 (m, 14H, Ar H), 7.16 (t, 2H, Ar H,
J = 7.4 Hz), 7.10 (t, 2H, J = 7.3 Hz), 7.00 (t, 8H, Ar H, J = 7.5 Hz),
6.75−6.67 (m, 4H, Ar H), 5.74−5.57 (m, 1H, CH), 3.38−3.19 (m,
2H, CH2), and 2.08 (s, 15H, Cp* CH3) ppm. 31P{1H} NMR (161
MHz, CD2Cl2) δ: 60.82 (t, J = 30.6 Hz) and 30.81 (d, J = 30.6 Hz)
ppm. 13C{1H} NMR (100 MHz, CD2Cl2) δ: 134.69−133.88 (m, Cp*
C), 132.77 (s, Ar CH), 132.66 (s, Ar CH), 132.06 (t, Ar CH, J = 5.9
Hz), 131.52−130.86 (m, Ar CH), 130.61 (s, Ar CH), 130.25 (s, Ar
CH), 129.99 (d, C−P, J = 2.4 Hz), 129.58 (t, C−P, J = 5.1 Hz), 128.28
(t, Ar CH, J = 5.4 Hz), 128.09 (s, Ar CH), 127.99 (s, Ar CH), 95.39
(d, CH, J = 1.5 Hz), 30.87 (d, CH2, J = 30.9 Hz), and 12.22 (s, Cp*
CH3) ppm. Anal. Calcd for [C48H48P3Ru][PF6]0.66[CH2Cl2]: C,
57.28; H, 4.87. Found: C, 57.37; H, 4.97. MS (ESI+, dichloromethane;
m/z+): 819.2 [C48H48P3Ru]+.
Synthesis of [RuCp*(1b)]PF6 (2b). Similar to the synthesis of 2a;
see the Supporting Information.
E
dx.doi.org/10.1021/om3005959 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Synthesis of [RuCp*(1c)]PF6 (2c). Similar to the synthesis of 2a;
see the Supporting Information.
Synthesis of [RuCp*(1d)]PF6 (2d). Similar to the synthesis of 2a;
see the Supporting Information.
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ASSOCIATED CONTENT
* Supporting Information
■
(27) Bontemps, S.; Bouhadir, G.; Dyer, P. W.; Miqueu, K.; Bourissou,
D. Inorg. Chem. 2007, 46, 5149−5151.
S
Text, a table, and CIF files giving an extended experimental
section and crystallographic data for 2a−d. This material is
available free of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: rmorris@chem.utoronto.ca.
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
We thank NSERC Canada for a Discovery grant to R.H.M.
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