Functionalization of planar chiral fused arene ruthenium complexes: Synthesis, x-ray structures, and spectroscopic characterization of monodentate triarylphosphines

Article abstract of DOI:10.1021/om200897k

The efficient functionalization of planar chiral ruthenium naphthalene-and ruthenium indenyl-scaffolds is reported. Mild reaction conditions employing microwave heating have been developed for the derivatization of sensitive cationic naphthalene ruthenium complexes. In particular, a series of novel planar chiral monodentate phosphines and their gold(I) complexes have been synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Furthermore, the electronic properties of these phosphines (L) have been evaluated via the infrared CO stretching frequencies of the corresponding Ni(CO)₃(L) complexes, providing valuable insight for the design and application of these chiral ligands in asymmetric catalysis.

Full text of DOI:10.1021/om200897k

Article
pubs.acs.org/Organometallics
Functionalization of Planar Chiral Fused Arene Ruthenium
Complexes: Synthesis, X-ray Structures, and Spectroscopic
Characterization of Monodentate Triarylphosphines
Philipp Buchgraber, Audrey Mercier, Wee Chuan Yeo, Celine Besnard, and E. Peter Kundig*
́
̈
Department of Organic Chemistry, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland
S
* Supporting Information
ABSTRACT: The efficient functionalization of planar chiral ruthenium naphthaleneand ruthenium indenylscaffolds is
reported. Mild reaction conditions employing microwave heating have been developed for the derivatization of sensitive cationic
naphthalene ruthenium complexes. In particular, a series of novel planar chiral monodentate phosphines and their gold(I)
complexes have been synthesized and fully characterized by NMR spectroscopy and X-ray crystallography. Furthermore, the
electronic properties of these phosphines (L) have been evaluated via the infrared CO stretching frequencies of the
corresponding Ni(CO)3(L) complexes, providing valuable insight for the design and application of these chiral ligands in
asymmetric catalysis.
of valuable classes of compounds. Indeed, the resulting planar
chiral backbones are well suited for further derivatizations,
owing to the presence of a remaining bromide atom. Herein,
we present our synthetic efforts to functionalize the scaffolds
obtained after the hydrogenolysis reaction (Scheme 2). A
special emphasis is placed on the development of a new subset
of chiral phosphines, as well as on the evaluation of their
structural and electronic properties in view of further
applications in asymmetric catalysis.
INTRODUCTION
■
Tertiary phosphines are arguably the most important ancillary
ligands in transition-metal chemistry and catalysis. A variety of
derivatives have been designed and fine-tuned in terms of steric
and electronic properties to realize highly active and selective
catalytic reactions. While phosphines featuring elements of
central or axial chirality are among the most widely employed
chiral ligands,1 the inherent planar chirality of unsymmetrically
substituted metal arene complexes or metallocenes constitutes
another prominent motif for chiral phosphines. In particular,
ligands based on a chiral ferrocenyl core have found widespread
applications in asymmetric catalysis.2 A synergistic combination
of two elements of chirality (central and planar chiralities)
usually accounts for their notable success in promoting high
asymmetric induction.3 However, ferrocene ligands exhibiting
only planar chirality could also provide excellent enantiose-
lectivities in various transformations, demonstrating the
prominent role of this stereogenic element.2h,4 In addition to
the ubiquitous ferrocenyl chiral ligands, (arene)-
tricarbonylchromium complexes have also been explored, albeit
to a lesser extent, and proved to induce effective chiral
environments.5 In sharp contrast, the homologous ruthenium
sandwich scaffold has received scarce attention.6
RESULTS AND DISCUSSION
■
Synthesis. In analogy with chromium complex 1,9
cyclopentadienyl(indenyl)ruthenium and iron complexes 3a−
c and 4b are compatible with bromine/lithium exchange
conditions. As such, functionalization with various chlorodi-
phosphine derivatives as electrophiles allowed for an expedient
access to neutral planar chiral phosphines 5−8 (Scheme 3).10
Importantly, the use of nBuLi in diethyl ether was not
appropriate11 and clean reactions were only obtained after
treatment with 2 equiv of tBuLi at low temperature. The
sequential trapping of the resulting organolithium species with
different R2″PCl derivatives provided phosphines with diverse
electronic and steric properties in moderate to good yields.
Products 5−8 proved stable in their solid state but slowly
oxidized in solution.
We have recently succeeded in accessing planar chiral fused
arene chromium, ruthenium, and iron complexes in moderate
to high enantioselectivities through two complementary Pd-
catalyzed asymmetric transformations (Scheme 1).7,8 These
desymmetrization processes paved the way for the development
Received: September 27, 2011
Published: November 1, 2011
© 2011 American Chemical Society
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Scheme 1. Access to Planar Chiral Complexes via Pd-Catalyzed Desymmetrization Processes
the other hand, the great activating effect of the metal fragment
was ideally suited for the development of transition-metal-
catalyzed cross-coupling reactions. As demonstrated for the
hydrogenolysis reaction, the oxidative addition of the Pd(0)
species into the CAr−Br bond was significantly accelerated,
owing to the decrease of π-electron density. Therefore,
transition-metal-catalyzed C−P bond-forming reactions were
envisaged to realize the challenging sought-after transformation
under mild conditions.14 Palladium-,15 nickel-,16 and copper-
catalyzed17 C−P cross-coupling reactions are emerging in
importance for the preparation of phosphine ligands. However,
these transformations are significantly more challenging than
related carbon−heteroatom (C−O, C−N) cross-coupling
reactions. Aryl iodides as coupling partners, high temperatures
(100−110 °C), and long reaction times (several hours or days)
are generally required. In contrast to such harsh conditions, the
use of secondary phosphine−boranes allowed for the develop-
ment of ambient processes.15e,f However, the use of acetonitrile
as solvent and amine bases prevented their application to
ruthenium(II) arene complexes. To the best of our knowledge,
only two protocols (enabling an asymmetric C−P bond
Scheme 2. Synthetic Approach to Functionalized Planar
Chiral Complexes
In stark contrast, the high electrophilicity of the [RuCp]+
unit in complexes 2 precluded the use of strongly basic and
nucleophilic reagents such as tBuLi. Indeed, nucleophilic attack
onto the coordinated arene or reduction to [Ru(I)] via single-
electron transfer could occur under such conditions.12,13 On
Scheme 3. Neutral Indenylphosphines Prepared via Bromine/Lithium Exchange
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forming reaction) describe the use of unprotected secondary
phosphines at room temperature.15c,d Moreover, the use of
microwave heating has recently been introduced to circumvent
the long reaction times associated with this type of coupling.18
The latter precedents18 combined with the results obtained in
the microwave-promoted Suzuki−Miyaura cross-coupling of
complex 2b7b prompted us to implement a similar strategy for
the targeted C−P bond construction. Indeed, the use of
microwave heating appeared as an essential tool to streamline
the coupling of 2b with various boronic acids. The reaction
performed best in methanol using Pd(OAc)2/oTol3P as catalyst
and K3PO4 as base at 100 °C.19 Reaction times were
dramatically shortened, thereby reducing side reactions and
allowing for the isolation of the coupled products in moderate
to good yields (Scheme 4).
purification by flash chromatography to remove a small
unidentified impurity (δP +35 ppm, CD2Cl2), phosphine 10b
(R = Ph) could be isolated in 73% yield. Reaction in the
presence of bis(3,5-dimethylphenyl)phosphine21 as coupling
partner proceeded equally well and afforded phosphine 11b (R
= Xyl) in 77% yield. In sharp contrast, the use of the sterically
more demanding di-o-tolylphosphine22 resulted in partial
conversion under such conditions. Increasing both catalyst
loading (10 mol %) and reaction time (80 min) resulted only in
decomposition. With NiCl2(dppp) as catalyst, the starting
material remained unchanged. In contrast, when Pd(dba)2 was
used in combination with dppp as ligand at 140 °C, complete
consumption of the substrate could be achieved after 1 h, albeit
with substantial decomposition. As such, pure phosphine 12b
was isolated in variable yields (20−40%). Moreover, the C−P
cross-coupling of the less robust [Ru(η 5-Cp)(η 6-5-
bromonaphthalene)][PF6] (2a) under standard conditions
resulted in a messy mixture of products. Control experiments
disclosed that complex 2a was unstable in the presence of
diphenylphosphine (3% of decomplexation after 1 h at room
temperature). Therefore, reduction of the microwave irradi-
ation time to 5 min limited the decomposition process and
allowed for the isolation of phosphine 10a (R = Ph) in a
satisfactory yield of 45% (Scheme 6).
Scheme 4. Suzuki−Miyaura Cross-Coupling of 2b with
Representative Boronic Acids
Scheme 6. Pd-Catalyzed C−P Cross-Coupling of Complex
2a
Not unexpectedly, after reaction of 2b with Ph2PH in the
presence of Pd(dba)2/tBu3P and DABCO in DME at room
temperature for 4 h, only trace amounts of the desired product
could be identified by 31P NMR analysis of the crude mixture
(δP −13.3 ppm, CDCl3), along with many other signals.
Microwave irradiation (100 °C, 10 min) of a mixture
containing the air-stable borane adduct Ph2PH·(BH3), 2b,
Pd(OAc)2/tBu3P, and K2CO3 in DME gave significantly more
conversion into the corresponding phosphine. Interestingly, the
cross-coupled product was mainly deprotected under these
conditions. Other diphenylphosphine coupling partners, such
as Ph2PSiMe3, Ph2PK, and Ph2P(O)H, resulted in failure.
Pleasingly, the best set of conditions appeared with the use of
unprotected diphenylphosphine in conjunction with Pd(dba)2
and dppf as catalyst precursors and K3PO4 as base in CH2Cl2.
Optimal conditions were refined upon scale up (0.5 mmol),
leading to complete conversion of the starting material within
40 min of microwave heating at 105 °C and reducing side
product formation to a minimum (Scheme 5).20 After
Gold Complexes. With the purpose of evaluating the
performance of the synthesized phosphines as chiral ligands in
asymmetric catalysis, their coordination chemistry was first
explored. Reaction of phosphines 10b−12b with [AuCl·SMe2]
in CH2Cl2 gave the corresponding gold(I) complexes 13b−15b
in quantitative yields as yellow solids after precipitation in
pentane (Scheme 7).
Scheme 7. Synthesis of Gold(I) Complexes
Scheme 5. Pd-Catalyzed C−P Cross-Coupling of Complex
2b
Structural Analysis. Suitable crystals for X-ray diffraction
studies were obtained by slow diffusion of diethyl ether into
dichloromethane solutions at 4 °C. Crystallographic data for
[Ru(η5-Cp*)(η6-5,8-dibromonaphthalene)][PF6] (16b) and
phosphines (±)-11b and (±)-12b, as well as for gold
complexes (S)-13b and (±)-14b are summarized in Table 1.
Selected bond distances, bond angles, and torsion angles are
collected in Table 2. The ORTEP views of the complexes are
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Table 1. Crystallographic Data for Complexes 11b, 12b, (S)-13b, 14b, and 16b
11b
12b
(S)-13b
14b
16b
chem formula
mol wt
cryst syst
space group
a (Å)
C36H40PRu·PF6·CH2Cl2
C34H36PRu·PF6·0.5CH2Cl2
C32H32PRuAuCl·PF6
C36H40PRuAuCl·PF6
982.11
C20H21Br2Ru·PF6
667.3
834.65
monoclinic
P21/c
764.13
monoclinic
P21/c
926.03
orthorhombic
P212121
8.8175(3)
16.5684(9)
21.9915(9)
90
triclinic
orthorhombic
Pca21
P1
̅
12.430(2)
13.083(3)
24.751(5)
90
12.063(4)
29.793(9)
11.307(6)
90
9.7785(5)
14.0984(7)
14.8098(7)
67.035(4)
78.308(4)
74.928(4)
1803.41(17)
2
16.9376(9)
8.3480(4)
15.1736(11)
90
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
90.99(3)
90
112.60(2)
90
90
90
90
90
4024.4(14)
4
3752(3)
4
3212.8(2)
4
2145.5(2)
4
d (g/cm−3
)
1.378
1.352
1.914
1.809
2.066
T (K)
200
293
200
200
150
radiation type
μ (mm−1
min, Tmax
Mo Kα
5.271
)
0.65
0.63
4.701
0.45, 0.83
36 082
12 344
6746
4.587
0.396, 0.496
25 524
4626
T
0.860, 0.900
34 662
10 221
6559
0.71, 1.00
49 948
7316
0.18, 0.45
22 487
7409
no. of rflns measd
no. of indep rflns
no. of rflns obsd (I/σ > 2)
Rint
4770
6076
3734
0.033
550
0.052
534
0.038
0.058
424
0.036
271
no. of params
no. of restraints
refinement
389
216
270
0
0
0
full matrix on F2
R[F2 > 2σ(F2)]
Rw(F2)
0.038
0.045
0.020
0.0354
0.0822
1.13
0.018
0.060
0.110
0.034
0.018
S
1.03
1.04
1.07
1.25
Δρmin, Δρmax (e Å−3
)
−0.40, 0.50
−0.56, 0.56
−2.26, 2.15
−0.015(3)
−2.54, 1.00
−0.52, 0.54
−0.005(6)
Flack param
Table 2. Selected Distances (Å) and Angles (deg)
entry
11b
12b
13b
14b
Bond Lengths
1
2
3
4
5
6
7
8
9
10
Ru1−C3
Ru1−C4
Ru1−C5
Ru1−C6
Ru1−C7
Ru1−C12
P1−C11
P1−C13a
P1−C13b
Au1−P1
2.218(3)
2.219(4)
2.218(4)
2.229(5)
2.222(5)
2.273(4)
2.304(4)
1.839(4)
1.848(5)
1.838(5)
2.230(4)
2.217(4)
2.226(4)
2.201(4)
2.250(4)
2.295(4)
1.828(4)
1.814(4)
1.805(4)
2.2341(10)
2.215(6)
2.202(6)
2.228(6)
2.182(6)
2.254(6)
2.295(5)
1.811(6)
1.812(6)
1.808(5)
2.2308(14)
2.222(3)
2.221(3)
2.189(3)
2.257(3)
2.274(3)
1.832(4)
1.830(3)
1.833(3)
Bond Angles
11
12
13
14
15
16
C13b−P1−C13a
C13b−P1−C11
C13a−P1−C11
Au1−P1−C11
Au1−P1−C13a
Au1−P1−C13b
101.85(13)
102.67(14)
101.07(13)
103.6(2)
101.8(2)
102.3(2)
108.18(18)
104.91(18)
104.49(18)
113.58(13)
111.04(14)
113.99(14)
105.2(3)
105.0(2)
106.6(3)
113.12(18)
111.94(19)
114.27(19)
Dihedral Angles
17
18
19
20
21
22
C18a−C13a−P1−C11
C18b−C13b−P1−C11
C12−C11−P1−C13a
C12−C11−P1−C13b
C3−C12−C11−P1
108.41(3)
−166.42(2)
174.27(2)
69.32(2)
89.49(4)
96.14(3)
−135.66(3)
164.96(3)
51.25(3)
9.64(5)
94.95(5)
−150.94(5)
162.08(4)
50.75(5)
7.56(8)
−167.16(4)
177.13(4)
70.18(4)
−2.90(3)
−1.34(7)
Au1−P1−C11−C12
−73.90(3)
−74.46(5)
depicted in Figures 1−3. For clarity, the same enantiomer is
shown in Figures 2 and 3.
The crystal structure of [Ru(η 5-Cp*)(η 6-5,8-
dibromonaphthalene)][PF6] (16b) is a good starting point
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Distances and angles were restrained to ideal values. Restraints
were also applied to anisotropic displacement parameters.
Although this disorder affects the R values, the bonding
situation within the relevant cationic part of the complex is
unambiguous. The aryl substituents on phosphines 11b and
12b showed elongated anisotropic parameters, which are
compatible with a pendulum movement with center C13 and
axis C13−C16.25
Despite highly disordered Cp* rings, all Ru−CCp* (ranging
from 2.127(8) to 2.210(6) Å for 11b and 2.097(17) to
2.166(13) Å for 12b) and Ru−Cnapht distances (Table 2, entries
1−6) are routine and similar to those of the parent [(η 5-
Cp*)(η6-5,8-dibromonaphthalene)] (16b). The two structures
are essentially superimposable and differ only in the twist of the
aryl rings (Table 2, entries 17 and 18). The torsion angles
between the naphthalene ring system and the aryl rings are
174.27(2) and 69.32(2)° for 11b and 177.13(4) and 70.18(4)°
for 12b (Table 2, entries 19 and 20). The phosphorus atom is
slightly bent down toward the [RuCp*]+ moiety (11b,
−2.90(3)°; 12b, −1.34(7)°; Table 2, entry 21). The bond
lengths and angles around the phosphorus atom are routine for
an sp3-hybridized trivalent phosphorus (Table 2, entries 7−9
and 11−13) and compare well with those of the parent 1-
naphthyldiphenylphosphine (PPh2Np, not shown), devoid of
the [RuCp*]+ moiety (1.8284(17)−1.8387(17) Å, 101.85(7)−
104.12(7)°).17c Interestingly, the latter displayed a similar
arrangement of the aryl rings (torsion angles C12−C11−P1−
C13a/b = 178.5/75.8°), demonstrating the small influence of
the η6 coordination of the [RuCp*]+ moiety on the solid-state
structure.
The two gold(I) complexes 13b and 14b are almost
superimposable (Figure 3). The Ru−CCp* (ranging from
2.167(4) to 2.193(4) Å for 13b and 2.165(6) to 2.186(6) Å for
14b) and Ru−Cnapht distances (Table 2, entries 1−6) are in the
usual range observed for related complexes. The overall
orientation of the phosphorus atom is close to that of
phosphines 11b and 12b, as indicated by the similar dihedral
angles C12−C11−P1−C13a/b (164.96(3)/51.25(3)° for 13b;
162.08(4)/50.75(5)° for 14b; Table 2, entries 19 and 20). Such
Figure 1. ORTEP drawing of the molecular structure of [Ru(η 5-
Cp*)(η6-5,8-dibromonaphthalene)][PF6] (16b). Thermal ellipsoids
are set to 50% probability. Hydrogen atoms and PF6 anion are omitted
for clarity. Selected bond distances (Å) and dihedral angles (deg):
Ru−C1 = 2.255(5), Ru−C2 = 2.215(5), Ru−C3 = 2.226(5), Ru−C4
= 2.213(5), Ru−C5 = 2.225(5), Ru−C6 = 2.274(5), Ru−C11 =
2.189(5), Ru−C12 = 2.192(5), Ru−C13 = 2.177(5), Ru−C14 =
2.178(5), Ru−C15 = 2.175(4); C2−C1−C10−Br2 = −1.1(7), C5−
C6−C7−Br1 = +6.1(7).
for comparison (Figure 1). Ruthenium is bound in an η6
fashion to the less substituted ring with slightly elongated Ru−
C1 and Ru−C6 distances (2.255(5) and 2.274(5) Å,
respectively) compared to the Ru−C2 to Ru−C5 bonds
(2.215(5), 2.226(5), 2.213(5), 2.225(5) Å), which are all
routine for ruthenium(II) arene complexes.23 Such slippage
toward the less substituted side of the η6-arene complex is well-
known in the literature.24 Similarly, the Cp* is bound in an η5
fashion with relatively average Ru−C distances (2.175(4)−
2.192(5) Å).23a The two planes of the sandwich are almost
parallel (1.4°). The two arene rings of the naphthalene are
twisted, as indicated by the dihedral angles C2−C1−C10−Br2
(−1.1(7)°) and C5−C6−C7−Br1 (+6.1°(7)).
The structures of 11b and 12b are of low quality, due to a
strong disorder observed for the counterion, the Cp* ring, and
the solvent molecules (Figure 2). For both compounds, the
Cp* and the PF6 anion were modeled using two molecules.
Figure 2. ORTEP drawings of the molecular structures of 11b (left) and 12b (right). Thermal ellipsoids are set to 60% probability. Hydrogen atoms
and PF6 anion are omitted for clarity.
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Figure 3. ORTEP drawings of the molecular structures of (S)-13b (left) and 14b (right). Thermal ellipsoids are set to 60% probability. Hydrogen
atoms and PF6 anion are omitted for clarity.
arrangement implies that the coordinated [AuCl] moiety points
toward the [RuCp*]+ unit (Table 2, entry 22). However,
distortion of the tetrahedral coordination sphere of the
phosphorus is observed, as characterized by the bond angles
around the phosphorus varying from 104.49(18)° to
113.99(13)° for 13b and from 105.0(2)° to 114.27(19)° for
14b (Table 2, entries 11−16). Furthermore, the [RuCp*]+
moiety is bent away from the P1−Au1−C11 axis, which results
in dihedral angles C3−C12−C11−P1 of +9.64(5)° for 13b and
+7.56(8)° for 14b (Table 2, entry 21) and an increased angle
between the η6-arene and η5-Cp* planes (13b: 3.3°; 14b:
4.3°).
NMR Spectroscopic Studies. The NMR spectra of 10b−
15b deserve some comments. As already shown for the parent
[Ru(η5-Cp*)(η6-5,8-dibromonaphthalene)][PF6] (16b), selec-
tive coordination of the [RuCp*]+ fragment onto the less
substituted ring causes a high-field shift of the four-proton spin
system of ca. 2 ppm, whereas the singlet corresponding to the
two protons of the uncoordinated ring is only shifted by 0.3
ppm as compared to that of the free 1,4-dibromonaphthalene.26
Similarly, the 13C NMR chemical shifts (δC) of the π-
coordinated carbons are in the range 85.4−97.4 ppm, whereas
δC shifts for the free ligand are in the range 124.8−134.9
ppm.26 Such coordination chemical shifts (Δδ) to higher field
are typical for π complexes of Ru(II).27 Similar observations
apply to [Ru(η5-Cp*)(η6-5-bromonaphthalene)][PF6] (2b).
However, the situation becomes more complex for the
phosphine complexes 10b−12b. High-resolution28 HSQC
and HMBC experiments in combination with classical 1D
and 2D NMR experiments were essential to unambiguously
attribute all 13C signals (Table S1, Supporting Information).
Analogously, δC for the π-coordinated carbons are in the range
83.5−100.0 ppm, whereas the uncoordinated carbons have
typical aromatic carbon shifts (128.3−144.3 ppm). The aryl
rings on the phosphines are diastereotopic, and the symmetri-
cally substituted 10b (Ar = Ph) and 11b (Ar = Xyl) show local
C2 symmetry, indicating a free rotation along the P−C axis. The
groups of the Cp* unit feature a JC,P coupling of ca. 3 Hz. This
long-range JC,P coupling through a metal center has not been
reported and is not observed in the corresponding gold
complexes 13b and 14b. Coordination of gold(I) chloride
affects in particular the 13C chemical shifts and JC,P coupling
constants in the vicinity, whereas the π-coordinated carbons
remain unchanged. In contrast to the free phosphines 10b and
11b, which have well-correlated 13C NMR spectra, δC and JC,P
in the corresponding gold complexes 13b and 14b are random
(Table S2). Similar observations were made for [AuCl-
(PPh2Np)].30 1H and 31P NMR signals of gold complex 15b,
bearing the sterically more demanding o-tolyl substituents, are
broad, precluding a full assignment. As for the neutral
indenylphosphines, a similar analysis can be made (Table S3).31
Tolman Electronic Parameter (TEP). Evaluation of the
electronic properties of this series of novel phosphines
appeared essential for the design and application of these
motifs as chiral ligands in asymmetric catalysis. The importance
of quantifying steric and electronic effects of ligands has been
recognized in pioneering studies by Tolman on tertiary
phosphines32 and has had a crucial impact on homogeneous
catalysis. In particular, Tolman’s lasting achievement consists of
the introduction of the electronic parameter ν, known as the
Tolman electronic parameter (TEP). This tool has been used
to quantify the electron-donor ability of a wide range of
phosphorus ligands and, more recently, of NHCs.33 The TEP
corresponds to the frequency of the A1 carbonyl mode of a
Ni(CO)3L complex and represents a direct probe to gauge the
electronic characteristics of ligand L. Indeed, replacement of
one CO in the Ni(CO)4 complex by a tertiary phosphine
increases the electron density at the metal center, which
compensates by more π back-bonding into CO π* orbitals.
This synergistic phenomenon further strengthens the remaining
Ni−CO bonds and weakens the C−O bond, implying a
decrease of the CO stretching frequency by an amount
depending on the net donating ability of the phosphorus
ligand.34 However, the high toxicity of Ni(CO)4 fostered the
search for alternative methods.35 As such, a plethora of
analogous transition-metal carbonyl complexes were inves-
tigated (e.g. Rh, Cr, Mo, W, Ir),36 and considerable efforts were
invested to assess the donor properties by means of
J
C,P coupling constant pattern of the diastereotopic aryl rings in
10b and 11b correlates well with the data reported for Ph3P.29
JC,P coupling in the naphthyl part is somewhat disturbed by the
π-coordinated [RuCp*]+ moiety. Interestingly, the methyl
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computational methods.37 In addition to CO stretching
frequencies, 13C NMR chemical shifts of these metal carbonyl
complexes, as well as C−P and M−P coupling constants, were
notably studied for the same purpose. Despite the incon-
venience of handling Ni(CO)4, the simplicity and reliability of
the experimental measurement coupled with the large number
of reference values available prompted us to choose Tolman’s
original system for our study.
Ni(CO)3L complexes were prepared according to the
procedure of Tolman,38 except that Ni(CO)4 was conveniently
generated in situ by ligand exchange from Ni(cod)2 with
CO(g) in CH2Cl2. Upon disappearance of the slight yellow
color of Ni(cod)2, ensuring complete formation of Ni(CO)4, a
solution containing phosphine L was added and immediate
evolution of CO was observed (eq 1, Scheme 8). The
Table 3. ν CO(A1) Values for [Ni(CO)3L] Complexes
Measured in CH2Cl2
a
entry
ligand
complex
νCO(A1) (cm‑1)
1
2
3
4
5
6
7
8
5a
5b
5c
8b
6a
17
C1
C2
C3
C4
C5
C6
C7
C8
2066.7
2066.1
2067.3
2066.5
2060.3
2071.1
2073.3
2074.6
2068.9
2056.1
2066.6
2071.2
2076.3
[10b][PF6]
[10b][BArF]
Ph3P
b
9
Ni(CO)3(Ph3P)
b
10
tBu3P
Ni(CO)3(tBu3P)
b
11
oTol3P
Ni(CO)3(oTol3P)
Ni(CO)3(Ph2(EtO)P)
Ni(CO)3((EtO)3P)
b
12
Ph2(EtO)P
(EtO)3P
b
13
a
Corrected experimental values using [Ni(CO)3(Ph3P)] as reference
b
(lit., νCO(A1) 2068.9 cm−1; exptl, νCO(A1) 2069.5 cm−1). From ref
32.
complexes were not isolated but directly analyzed by means
of FT-IR spectroscopy. The recorded carbonyl stretching
frequencies of complexes C1−C8 were referenced to the
Tolman scale using Ni(CO)3(Ph3P) as reference (νCO(A1)
2068.9 cm−1).32 The corrected values are presented in Table 3
together with those of representative Ni(CO)3(R3P) complexes
to allow for a direct comparison. Figure 4 provides a clear
overview of the electron richness of the new planar chiral
phosphines. All these characteristic stretching frequencies in
hand allowed for a comparative study of the electronic
properties of the eight selected phosphines. In particular, we
were intrigued by the impact of the coordinated transition-
metal fragment on the electron-donating ability of the
complexes, since no data relative to this effect have been
reported yet.
From Table 3 and Figure 4, it appears that the phosphine
family covers a wide range of electronic properties, the carbonyl
stretches falling between 2060.3 and 2074.6 cm−1. The neutral
cyclopentadienyl(indenyl)ruthenium complexes 5a−c and iron
complex 8b are very similar in basicity and compare well with
triarylphosphines such as oTol3P (Table 3, compare entries 1−
4 and 11). The coordination of a neutral [RuCp] fragment
results in slightly more electron-donating ligands than the
parent PPh3 (Table 3, compare entries 1−4 and 9). Electronic
communication from the cyclopentadienyl ring to the
phosphorus atom is reflected by the distinct TEP values within
complexes 5a−c (Table 3, entries 1−3). Incorporation of
cyclohexyl substituents on the phosphorus generates the most
basic phosphine of the series (6a, Table 3, entry 5).
On the other hand, the strongly electron-withdrawing effect
of the [Cr(CO)3] entity significantly depletes electron density
from the phosphorus center (Table 3, entry 6). As such,
complex 17 and phosphinite Ph2(EtO)P are electronically
comparable (Table 3, compare entries 6 and 12). Of particular
interest is the effect of the [RuCp*]+ fragment in phosphine
10b+. The positive charge overrides completely the strong
electron-donating character of the [RuCp*] moiety, resulting in
the least electron-rich phosphine of the family (Table 3, entry
7). Furthermore, a strong counterion effect is observed for
10b+. Replacing the PF6 anion by the more lipophilic BArF
considerably decreases the electron density of the system
(Δ(TEP) = 1 cm−1; Table 3, compare entries 7 and 8).
The TEPs of the neutral indenyl complexes 5a−c and 8b
deserve some further comment. During the desymmetrization
studies of [Ru(η5-Cp*)(η5-4,7-dibromoindene)],7b,c the other-
wise efficient catalyst system afforded the hydrogenolysis
product in a moderate 68% ee. At first, it was surmised that
this effect might be of electronic origin caused by the increased
electron donation of the [RuCp*] fragment. To support this
hypothesis, the complex featuring an η5-C5Me4CF3 ligand was
evaluated. The latter possesses similar electronic properties of
Cp and the steric bulk of Cp*.39 An intermediate enantiomeric
excess of 78% was obtained, indicating that both electronic and
steric factors are operative. A similar conclusion could be drawn
from the TEP analysis of the corresponding diphenylphosphine
complexes 5a−c. On the basis of Tolman’s reasoning that only
inductive effects are responsible for the electronic properties,
TEP values for 5a,c should be identical. However, a a Δ(TEP)
value of 0.6 cm−1 was found experimentally. This indicates that
Scheme 8. Set of Phosphines Considered in the Study
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Figure 4. Comparison of Tolman electronic parameters.
chemical shifts (δ) are quoted in ppm relative to SiMe4 (residual
CHCl3, δH 7.26 ppm; CDCl3, δC 77.05 ppm; residual CHDCl2, δH
5.32 ppm; CD2Cl2, δC 53.9 ppm; residual C6HD5, δH 7.15 ppm; C6D6,
δC 128.0 ppm). 31P NMR chemical shifts are referenced to H3PO4 as
external standard. 19F NMR chemical shifts are referenced to CFCl3 as
external standard. Coupling constants J are quoted in Hz. Infrared
spectra were recorded on a Perkin−Elmer 1650 FT-IR spectrometer
using a diamond ATR Golden Gate sampling. Electron impact (EI)
HRMS mass spectra were obtained using a Finnigan MAT 95
instrument operating at 70 eV. Electrospray ionization (ESI) HRMS
analyses were measured on a VG Analytical 7070E instrument. Optical
rotations were measured at 20 °C on a Perkin-Elmer 241 polarimeter
using a quartz cell (l = 10 cm) with a Na high-pressure lamp (λ 589
Tolman’s simple assumption of purely additive inductive effects
on the net donor ability is not valid in such a sterically
demanding environment.40
CONCLUSION
■
In conclusion, we have reported efficient and useful trans-
formations of sensitive ruthenium complexes. The planar chiral
building blocks were transformed into valuable derivatives
either by metalation/electrophilic quenching sequences or by
Pd-catalyzed cross-coupling reactions. The latter took advant-
age of the strong activation of the system toward oxidative
addition. Particularly, we developed mild reaction conditions
that exploit the benefits of microwave heating to address the
challenging functionalization of cationic ruthenium complexes.
Of particular importance was the development and character-
ization of new planar chiral monodentate phosphines.
Evaluation of their structural features by X-ray crystallography
and their electronic properties through TEP values provided
valuable insight for further applications in asymmetric catalysis,
which will be the subject of further studies.
nm). Melting points were measured in open capillary tubes on a Buchi
̈
540 apparatus and are uncorrected. Elemental analyses were carried
out by H. Eder and K. L. Buchwalder from the University of Geneva.
X-ray structure determinations were performed using a STOE IPDS 2
image-plate diffractometer with graphite-monochromated Mo Kα
radiation (λ 0.710 69 Å). Specimens of suitable size and quality were
selected and mounted onto a nylon loop. The structures were solved
either by direct methods using sir 9245 (for 13b and 14b) and sir 9746
(for 16b) or by the charge-flipping method using superflip47 (for 11b
and 12b); all the structures could be solved by either method.
Subsequent refinement on F2 was realized using the CRYSTALS
software package48 (for 11b−14b) or with XTAL49 (for 16b). Details
about the refinement can be found in Table 1 as well as in the
Supporting Information.
EXPERIMENTAL SECTION
■
General Remarks. All reactions and manipulations were carried
out under an inert atmosphere of nitrogen using an inert gas/vacuum
double-manifold line and standard Schlenk techniques unless
otherwise stated. Solvents were dried by passing through activated
Al2O3 using a Solvtek purification system or by following standard
procedures.41 When required, the solvents were degassed by three
successive freeze−thaw−pump cycles. Commercially available chem-
icals were purchased from Fluka, Aldrich, Pressure Chemicals, and
Acros and used as received unless otherwise stated. The following
metal complexes and reagents were synthesized according to literature
procedures: (S)-1−4,7c [Ru(η5-Cp*)(η6-5,8-dibromonaphthalene)]-
[PF6] (16b),7c [Cr(CO)3(η 6-5-diphenylphosphinonaphthalene)]
(17),9 Pd(dba)2,42 AuCl·SMe2,43 bis(3,5-dimethylphenyl)phosphine,
and di-o-tolylphosphine.44
General Procedure for the Metalation/Electrophilic Trap-
ping Sequence. The monohalide complex was dissolved in diethyl
ether, and the resulting solution was cooled to −78 °C. tBuLi (2
equiv) was added dropwise. After the mixture was stirred for 30 min at
this temperature, R2PCl (2 equiv) was added. The resulting mixture
was stirred for 30 min and passed through a short pad of silica gel
under N2 (pentane/CH2Cl2 9/1). The crude product was purified by
column chromatography on silica gel. The enantiomeric purity of the
phosphine was determined by HPLC on chiral stationary phase.
[Ru(η5-Cp)(η5-4-(diphenylphosphino)indene)] (5a). Prepared ac-
cording to the general procedure from [Ru(η 5-Cp)(η5-4-bromoin-
dene)] (3a, 96% ee (S), 412 mg, 1.14 mmol), tBuLi (2.26 M, 1.01 mL,
2.28 mmol), and Ph2PCl (423 μL, 2.28 mmol) in diethyl ether (11
mL). A yellow solid was obtained after purification by flash
chromatography (pentane, then pentane/CH2Cl2 9/1) (440 mg,
83% yield, 96% ee (S)). Rf = 0.6 (pentane/CH2Cl2 9:1). Mp: 68−70
°C. [α]D = +849° (c = 0.33, CHCl3). 1H NMR (500 MHz, CD2Cl2): δ
7.46−7.32 (m, 11H), 6.72 (dd, J = 8.5, 6.7 Hz, 1H), 6.53 (t, J = 6.5 Hz,
1H), 5.24−5.20 (m, 2H), 4.57 (t, J = 2.4 Hz, 1H), 4.11 (s, 5H). 13C
NMR (125 MHz, CD2Cl2): δ 137.2 (d, J = 10.7 Hz), 136.5 (d, J = 10.6
Flash column chromatography was performed using silica gel 60
(32−63 mesh, Brunschwig) or neutral alumina (50−200 μm, Acros).
Analytical thin-layer chromatography (TLC) was performed on
precoated aluminum plates (silica gel 60 F254, Merck; aluminum
oxide, POLYGRAM ALOX N/UV254). Microwave reactions were
1
performed in a Biotage Initiator SW apparatus. H, 13C, 31P, and 19F
NMR spectra were recorded on 500, 400, and 300 MHz Bruker
Avance spectrometers in the solvent indicated. 1H and 13C NMR
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Hz), 135.6 (d, J = 13.8 Hz), 134.7 (d, J = 20.5 Hz), 134.1 (d, J = 19.7
Hz), 129.4, 129.0, 128.9 (d, J = 3.9 Hz), 128.8 (d, J = 6.9 Hz), 128.7
(d, J = 7.3 Hz), 128.4, 122.6 (d, J = 2.7 Hz), 95.5 (d, J = 26.0 Hz), 91.9
(d, J = 5.6 Hz), 73.2, 70.5, 66.3 (d, J = 11.5 Hz), 66.0 (d, J = 1.6 Hz).
31P NMR (162 MHz, CD2Cl2): δ −13.1. IR: 3053, 2962, 2921, 2851,
1738, 1584, 1474, 1432, 1331, 1300, 1260, 1178, 1100, 1026, 995, 855,
808, 773, 764, 741, 724, 692 cm−1. HRMS (ESI) for C26H22PRu [M +
H]+: calcd 467.0497, found 467.0468. Anal. Calcd for C26H21PRu
(465.49): C, 67.09; H, 4.55. Found: C, 65.84; H, 4.52.
NMR (162 MHz, CDCl3): δ −10.1. HRMS (ESI) for C26H34PRu [M
+ H]+: calcd 479.1436, found 479.1430.
[Ru(η5-Cp)(η5-4-(diethylphosphino)indene)] (7a). Prepared ac-
cording to the general procedure from [Ru(η 5-Cp)(η5-4-bromoin-
dene)] ((±)-3a, 150 mg, 0.42 mmol), tBuLi (1.95 M, 431 μL, 0.84
mmol), and Et2PCl (102 μL, 0.84 mmol) in diethyl ether (4.0 mL). A
yellow solid was obtained after purification by flash chromatography
(pentane, then pentane/CH2Cl2 1/1) (85 mg, 55% yield). Mp: 38−40
1
°C. H NMR (500 MHz, CD2Cl2): δ 7.37 (dd, J = 8.6, 0.7 Hz), 6.92
[Ru(η 5-Cp*)(η5-4-(diphenylphosphino)indene)] (5b). Prepared
according to the general procedure from [Ru(η 5-Cp*)(η 5-4-
bromoindene)] (3b, 67% ee (R), 368 mg, 0.85 mmol), tBuLi (2.4
M, 724 μL, 1.70 mmol), and Ph2PCl (315 μL, 1.70 mmol) in diethyl
ether (15 mL for solubility reasons). A yellow solid was obtained after
purification by flash chromatography (pentane, then pentane/CH2Cl2
9/1) (391 mg, 86% yield, 67% ee (R)). Rf = 0.3 (pentane/CH2Cl2
(td, J = 6.4, 0.9 Hz), 6.78 (dd, J = 8.6, 6.5 Hz), 5.45−5.44 (m, 1H),
5.23−5.22 (m, 1H), 4.64 (t, J = 2.5 Hz), 4.20 (s, 5H), 1.98−1.72 (m,
4H), 1.10−1.04 (m, 6H). 13C NMR (125 MHz, CD2Cl2): δ 136.4 (d, J
= 19.2 Hz), 127.6, 126.0 (d, J = 6.0 Hz), 122.7 (d, J = 3.4 Hz), 95.9 (d,
J = 21.8 Hz), 92.0 (d, J = 4.6 Hz), 73.2, 70.4, 66.1 (d, J = 9.6 Hz), 66.0
(d, overlap), 18.6 (d, J = 11.7 Hz), 18.1 (d, J = 11.2 Hz), 10.4 (d, J =
15.0 Hz), 10.1 (d, J = 12.2 Hz). 31P NMR (162 MHz, CDCl3): δ
−20.9. HRMS (ESI) for C18H22PRu [M + H]+: calcd 371.0497, found
371.0490.
1
9:1). Mp: 126−128 °C. [α]D = −791° (c = 0.50, CHCl3). H NMR
(500 MHz, CD2Cl2): δ 7.43−7.25 (m, 10H), 7.12 (dt, J = 8.6, 0.8 Hz,
1H), 6.71 (ddd, J = 8.6, 6.6, 0.9 Hz, 1H), 6.28 (ddd, J = 6.5, 5.6, 0.8
Hz, 1H), 4.75 (td, J = 2.9, 1.0 Hz, 1H), 4.72−4.70 (m, 1H), 4.36 (t, J
= 2.5 Hz, 1H), 1.70 (s, 15H). 13C NMR (125 MHz, CD2Cl2): δ 137.4
(d, J = 11.3 Hz), 136.8 (d, J = 11.8 Hz), 135.1 (d, J = 20.1 Hz), 134.5
(d, J = 12.7 Hz), 134.5 (d, J = 20.2 Hz), 129.2 (d, J = 18.1 Hz), 128.9
(d, J = 7.2 Hz), 126.5, 125.8, 120.8 (d, J = 0.9 Hz), 94.5 (d, J = 24.6
Hz), 91.8 (d, J = 6.1 Hz), 83.1, 77.3, 68.9 (d, J = 11.0 Hz), 68.7 (d, J =
2.1 Hz), 11.1 (d, J = 1.6 Hz). 31P NMR (162 MHz, CD2Cl2): δ −13.4.
IR: 3053, 2966, 2903, 1739, 1587, 1475, 1434, 1378, 1329, 1299, 1091,
1069, 1033, 1024, 814, 805, 765, 744, 721, 604 cm−1. HRMS (ESI) for
C31H32PRu [M + H]+: calcd 537.1281, found 537.1279. Anal. Calcd
for C31H31PRu (535.62): C, 69.51; H, 5.83. Found: C, 69.44; H, 6.07.
[Ru(η5-Cp*CF3)(η5-4-(diphenylphosphino)indene)] (5c). Prepared
according to the general procedure from [Ru(η 5-Cp*CF3)(η5-4-
bromoindene)] ((±)-3c, 46.7 mg, 0.96 mmol), tBuLi (2.28 M, 90
μL, 0.21 mmol), and Ph2PCl (26 μL, 0.15 mmol) in diethyl ether (2
mL). A yellow solid was obtained after purification by flash
chromatography (pentane, then pentane/CH2Cl2 5/1) (49 mg, 84%
yield). Mp: 105−106 °C. 1H NMR (500 MHz, CD2Cl2): δ 7.41−7.27
(m, 10H), 7.15 (dt, J = 8.5, <1 Hz, 1H), 6.77 (ddd, J = 8.7, 6.6, 0.8 Hz,
1H), 6.35 (ddd, J = 6.1, 5.4, 0.8 Hz, 1H), 5.01 (td, J = 2.7, 0.9 Hz, 1H),
[Fe(η5-Cp*)(η5-4-(diphenylphosphino)indene)] (8b).4b Prepared
according to the general procedure from [Fe(η 5-Cp*)(η 5-4-
bromoindene)] ((±)-4b, 70.4 mg, 0.18 mmol), tBuLi (1.96 M, 190
μL, 0.37 mmol), and Ph2PCl (50 μL, 0.28 mmol) in diethyl ether (2.0
mL). The reaction was quenched by the addition of brine. The
aqueous phase was extracted with diethyl ether, dried over Na2SO4,
and concentrated. A purple solid was obtained after purification by
flash chromatography (pentane, 1% Et3N) (61.7, 68% yield). Mp:
158−161 °C (lit. 159−161 °C). 1H NMR (500 MHz, C6D6): δ 7.62−
7.57 (m, 2H), 7.42−7.36 (m, 2H), 7.21 (d, J = 8.5 Hz, 1H), 7.18−7.08
(m, 3H), 7.10−6.90 (m, 3H), 6.77−6.71 (m, 1H), 6.68 (t, J = 5.8 Hz,
1H), 4.46 (d, J = 1.8 Hz, 1H), 4.15 (t, J < 1 Hz, 1H), 3.57 (t, J = 2.4
Hz, 1H), 1.70 (s, 15H). 13C NMR (125 MHz, C6D6): δ 137.2 (d, J =
13.7 Hz); 137.0 (d, J = 10.9 Hz), 137.0 (d, J = 12.0 Hz), 135.2 (d, J =
20.2 Hz), 134.4 (d, J = 20.1 Hz), 129.2, 128.8 (d, J = 7.3 Hz); 128.8,
128.8, 128.7 (d, J = 7.1 Hz), 127.4, 122.2, 91.2 (d, J = 23.6 Hz), 88.2
(d, J = 6.0 Hz), 78.1, 76.8, 66.7 (d, J = 10.4 Hz), 66.3 (d, J = 1.9 Hz),
10.4 (d, J = 2.5 Hz). 31P NMR (202 MHz, CD2Cl2): δ −12.0. IR:
3068, 3052, 2964, 2901, 2856, 1587, 1476, 1434, 1380, 1327, 1031,
910, 742, 696 cm−1. HRMS (ESI) for C31H31FeP [M, 56Fe]+: calcd
490.150, found 490.1517.
Representative Procedure for the Microwave-Assisted
Suzuki−Miyaura Cross-Coupling. The crystalline mixture of 2b
and over-reduced complex 18b (90% 2b (97% ee (S)) and 10% 18b,
323.3 mg, 0.50 mmol of 2b), Pd(OAc)2 (5.6 mg, 0.025 mmol, 5 mol
%), oTol3P (15.2 mg, 0.050 mmol, 10 mol %), PhB(OH)2 (a; 183 mg,
1.5 mmol), and K3PO4 (318 mg, 1.5 mmol) were placed in a 20 mL
microwave vial, which was then sealed and purged with N2. Degassed
methanol (12 mL) was added, and the mixture was sonicated for 2 min
before being subjected to microwave irradiation for 15 min at 100 °C
(prestirring 30 s; initial power ca. 180 W; after the temperature had
reached 100 °C, the temperature was maintained for 15 min with a
power of ca. 30 W). The mixture was filtered through Celite and
washed with CH2Cl2. After evaporation of the solvents, the residue was
dissolved in CH2Cl2 (40 mL), washed with saturated NaHCO3 (3 ×
30 mL) and then with water (2 × 40 mL), and dried over MgSO4. The
solvent was removed, and the residue was dissolved in acetone (10
mL). KPF6 (386 mg, 2.1 mmol) was added, and the mixture was
stirred at room temperature for 30 min. The solvent was removed, and
the crude product was passed through a short column of neutral
alumina. The enantiomeric purity of the coupled product was
determined by 1H NMR analysis with 1.7 equiv of [nBu4N][Δ-
TRISPHAT] using CDCl3 as solvent.
5
4.88−4.86 (m, 1H), 4.53 (t, J = 2.5 Hz, 1H), 1.94 (q, JH,F = 0.9 Hz,
3H), 1.68 (s, 3H), 1.65 (q, 5JH,F = 1.3 Hz, 3H), 1.56 (s, 3H). 13C NMR
(125 MHz, CD2Cl2): δ 136.9 (d, J = 11.0 Hz), 136.2 (d, J = 11.7 Hz),
134.9 (d, J = 20.2 Hz), 134.8 (d, J = 14.0 Hz), 134.5 (d, J = 20.3 Hz),
129.4, 129.2, 128.9 (d, J = 7.3 Hz), 128.9 (d, J = 7.3 Hz), 128.6 (q, J =
270 Hz), 127.1, 126.2, 122.2, 95.6 (d, J = 24.3 Hz), 92.8 (d, J = 6.0
3
Hz), 86.0, 85.7, 82.1 (q, JC,F = 1.4 Hz), 81.8 (q, 3JC,F = 1.4 Hz), 77.7,
2
76.2 (q, JC,F = 35.8 Hz), 69.8 (d, J = 11.0 Hz), 69.2 (d, J = 1.9 Hz),
11.7 (pent, JC,F ≈ JC,P ≈ 2 Hz), 10.5 (q, 4JC,F = 1.8 Hz), 10.4 (d, J = 2.7
Hz), 9.7 (d, J = 3 Hz). 31P NMR (202 MHz, CD2Cl2): δ −13.3. 19F
NMR (470 MHz, CD2Cl2): δ −53.2. IR: 2962, 2908, 2872, 1454,
1424, 1380, 1334, 1261, 1241, 1189, 1098, 1035, 1015, 743, 728, 693
cm−1. HRMS (ESI) for C31H29F3PRu [M + H, 102Ru]+: calcd
591.0996, found 591.1038.
[Ru(η5-Cp)(η5-4-(dicyclohexylphosphino)indene)] (6a). Prepared
according to the general procedure from [Ru(η 5-Cp)(η5-4-bromoin-
dene)] (3a, 96% ee (S), 54 mg, 0.15 mmol), tBuLi (1.89 M, 152 μL,
0.30 mmol), and Cy2PCl (66 μL, 0.30 mmol) in diethyl ether (1.5
mL). A yellow solid was obtained after purification by flash
chromatography (pentane, then pentane/CH2Cl2 1/1) (42 mg, 59%
yield, 96% ee (S)). Mp: 79−81 °C. [α]D = +872° (c = 0.2, CHCl3). 1H
NMR (400 MHz, CDCl3): δ 7.39 (d, J = 8.4 Hz, 1H), 6.92 (t, J = 6.0
Hz, 1H), 6.79 (dd, J = 8.4, 6.0 Hz, 1H), 5.48 (t, J = 2.4 Hz, 1H), 5.24
(t, J = 2.4 Hz, 1H), 4.64 (t, J = 2.4 Hz, 1H), 4.23 (s, 5H), 1.02−1.92
(m, 20H). 13C NMR (100 MHz, CDCl3): δ 132.5 (d, J = 1.6 Hz),
127.9, 127.7, 122.1, 98.3 (d, J = 26.4 Hz), 91.9 (d, J = 5.9 Hz), 72.9,
70.1, 68.9 (d, J = 14.0 Hz), 65.8 (d, J = 1.4 Hz), 33.7 (d, J = 12.8 Hz),
31.7 (d, J = 10.1 Hz), 31.1 (d, J = 14.7 Hz), 30.1 (d, J = 13.8 Hz), 29.7
(d, J = 15.6 Hz), 28.6 (d, J = 3.7 Hz), 27.8 (d, J = 12.9 Hz), 27.4 (d, J
= 6.4 Hz), 27.3 (d, J = 3.7 Hz), 27.2 (d, J = 3.7 Hz), 26.7, 26.5. 31P
[Ru(η5-Cp*)(η6-5-phenylnaphthalene)][PF6] (9ba). Purification
through neutral alumina (CH2Cl2, then CH2Cl2/acetone 2:1) and
crystallization from CH2Cl2/diethyl ether gave complex 9ba as orange
crystals (155 mg, 53% yield, 99% ee (S)). Mp: 213-214 °C. [α]D
=
1
+434° (c = 0.59, CHCl3). H NMR (400 MHz, CDCl3): δ 7.74−7.38
(m, 8H), 6.65 (d, J = 6.0 Hz, 1H), 6.41 (d, J = 6.0 Hz, 1H), 6.12 (t, J =
6.0 Hz, 1H), 6.00 (t, J = 6.0 Hz, 1H), 1.62 (s, 15H). 13C NMR (100
MHz, CDCl3): δ 139.8, 137.5, 131.1, 130.6, 129.7, 129.6, 129.3, 128.0,
97.9, 96.8, 94.6, 89.3, 88.6, 85.8, 83.4, 10.0. 31P NMR (162 MHz,
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1
CDCl3): δ −143.8 (sept, J = 713 Hz). IR: 2922, 1475, 1450, 1387,
1354, 1078, 1031, 868, 831, 792, 760, 738, 705, 695, 617 cm−1. HRMS
(ESI) for C26H27Ru [M − PF6]+: calcd 441.1150, found 441.1159.
Anal. Calcd for C26H27PF6Ru (585.53): C, 53.33; H, 4.65. Found: C,
53.10; H, 4.63.
(S)). Mp: 207−208 °C. [α]D = +474° (c = 0.63, CHCl3). H NMR
(400 MHz, CDCl3): δ 7.51−7.66 (m, 2H), 7.38 (d, 1H, J = 8.6 Hz),
6.67 (d, 1H, J = 15.7 Hz), 6.56−6.62 (m, 1H), 6.44−6.52 (m, 1H),
6.21 (dd, 1H, J = 15.7, 7.3 Hz), 5.98−6.11 (m, 2H), 2.22−2.34 (m,
1H), 1.63 (s, 15H), 1.14−1.91 (m, 10H). 13C NMR (100 MHz,
CDCl3): δ 144.4, 137.0, 131.1, 126.7, 126.5, 122.4, 97.3, 95.9, 94.4,
89.0, 88.6, 85.9, 81.9, 41.9, 33.1, 26.3, 26.2, 9.9. 31P NMR (162 MHz,
CDCl3): δ −143.8 (sept, J = 713 Hz). IR: 3097, 2923, 2851, 1641,
1612, 1475, 1449, 1388, 1074, 1030, 968, 872, 825, 741 cm−1. HRMS
(ESI) for C28H35Ru [M − PF6]+: calcd 473.1776, found 473.1749.
Representative Procedure for the Microwave-Assisted C−P
Cross-Coupling. The crystalline mixture of 2b and over-reduced
complex 18b (79% 2b (99% ee (S)) and 21% 18b, 363.2 mg, 0.50
mmol of 2b), Pd(dba)2 (8.6 mg, 0.015 mmol, 3 mol %), ddpf (8.3 mg,
0.015 mmol, 3 mol %), and K3PO4 (180 mg, 0.85 mmol) were placed
in a microwave vial, which was then sealed and purged with N2. Dry,
degassed CH2Cl2 (1.5 mL) was added, and the mixture was stirred for
a few minutes before diphenylphosphine (0.148 mL, 0.85 mmol) was
added. The mixture was sonicated for 2 min before being subjected to
microwave irradiation for 40 min at 105 °C (prestirring 30 s; initial
power ca. 75 W; after the temperature had reached 105 °C, the
temperature was maintained for 40 min with a power of ca. 20 W).
The crude product was purified by column chromatography on silica
[Ru(η 5-Cp*)(η 6-5-(p-methylphenyl)naphthalene)][PF6] (9bb).
Prepared according to the general procedure using the crystalline
mixture of complexes 2b and 18b (90% 2b (97% ee (S)) and 10%
18b, 65 mg, 0.10 mmol of 2b), Pd(OAc)2 (1.1 mg, 0.005 mmol),
oTol3P (3.04 mg, 0.010 mmol), p-MePhB(OH)2 (b; 40.8 mg, 0.3
mmol), and K3PO4 (63.7 mg, 0.3 mmol) in methanol (2 mL).
Purification through neutral alumina (CH2Cl2, then CH2Cl2/acetone
1/1) and crystallization from CH2Cl2/diethyl ether gave complex 9bb
as orange crystals (45 mg, 75% yield, 99% ee (S)). Mp: 194−195 °C.
1
[α]D = +452° (c = 0.1, CHCl3). H NMR (300 MHz, CDCl3): δ
7.73−7.64 (m, 1H), 7.61−7.55 (m, 2H), 7.33 (q, J = 8.1 Hz, 4H), 6.63
(d, J = 6.0 Hz, 1H), 6.42 (d, J = 6.2 Hz, 1H), 6.11 (t, J = 5.9 Hz, 1H),
5.98 (t, J = 6.0 Hz, 1H), 2.46 (s, 3H), 1.62 (s, 15H). 13C NMR (75
MHz, CDCl3): δ 139.5, 137.2, 135.6, 130.7, 129.4, 128.7, 127.6, 98.2,
97.0, 94.2, 89.3, 88.4, 85.8, 83.3, 21.5, 9.6. 31P NMR (162 MHz,
CDCl3): δ −143.8 (sept, J = 713 Hz). IR: 2919, 1615, 1509, 1474,
1387, 1074, 1031. 828, 739, 741, 674 cm−1. HRMS (ESI) for
C27H29Ru [M − PF6]+: calcd 455.1307, found 455.1307.
[Ru(η5-Cp*)(η6-5-(p-methoxyphenyl)naphthalene)][PF6] (9bc).
Prepared according to the general procedure using the crystalline
mixture of complexes 2b and 18b (90% 2b (97% ee (S)) and 10%
18b, 65 mg, 0.10 mmol of 2b), Pd(OAc)2 (1.1 mg, 0.005 mmol),
oTol3P (3.04 mg, 0.010 mmol), p-MeOPhB(OH)2 (c; 45.6 mg, 0.3
mmol), and K3PO4 (63.7 mg, 0.3 mmol) in methanol (2 mL).
Purification through neutral alumina (CH2Cl2, then CH2Cl2/acetone
1/1) gave complex 9bc as an orange solid (34 mg, 54% yield, 99% ee
gel. The enantiomeric purity of the phosphine was determined by H
1
NMR and 31P NMR (CDCl3) after coordination to a chiral palladium
template (2 equiv).50
[Ru(η 5-Cp*)(η 6-5-(diphenylphosphino)naphthalene)][PF6]
(10b). Purification through two successive flash chromatographies
(CH2Cl2, then CH2Cl2/acetone 5/1) afforded phosphine 10b as a
yellow solid (252 mg, 73% yield, 99% ee (S)). Mp: 107−109 °C. [α]D
1
= +485° (c = 0.62, CHCl3). H NMR (400 MHz, CDCl3): δ 7.21−
7.61 (m, 12H). 6.97−7.04 (m, 1H), 6.64 (d, J = 5.8 Hz, 1H), 5.54−
3
1
(S)). Mp: 196−197 °C. [α]D = +461° (c = 0.1, CHCl3). H NMR
6.61 (m, 1H), 6.11 (t, J = 5.8 Hz, 1H), 5.84 (t, J = 5.8 Hz, 1H), 1.74
(s, 15H). 13C NMR (100 MHz, CDCl3): δ 137.4 (d, J = 20.2 Hz),
135.7, 134.9 (d, J = 20.2 Hz), 134.4 (d, J = 20.2 Hz), 133.6 (d, J = 6.4
Hz), 133.2 (d, J = 8.3 Hz), 130.5, 130.3, 130.1, 129.7 (d, J = 8.3 Hz),
129.5 (d, J = 7.4 Hz), 129.2, 98.5 (d, J = 21.1 Hz), 97.0 (d, J = 2.8 Hz),
94.7, 89.1, 88.2, 86.3, 83.2 (d, J = 25.7 Hz), 10.0 (d, J = 1.8 Hz). 31P
NMR (162 MHz, CDCl3): δ −13.3, −144.1 (sept, J = 713 Hz). IR:
2913, 1474, 1435, 1387, 1340, 1074, 1029, 913, 830, 735, 696, 665
cm−1. HRMS (ESI) for C32H32PRu [M − PF6]+: calcd 549.1279,
found 549.1299. Anal. Calcd for C32H32P2F6Ru·0.5CH2Cl2 (736.07):
C, 53.03; H, 4.52. Found: C, 53.15; H, 4.21.
(300 MHz, CDCl3): δ 7.65 (dd, J = 8.5, 7.0 Hz, 1H), 7.57−7.46 (m,
2H), 7.33 (d, J = 8.6 Hz, 2H), 7.05 (d, J = 8.7 Hz, 2H), 6.57 (d, J = 5.9
Hz, 1H), 6.43 (d, J = 6.1 Hz, 1H), 6.05 (t, J = 5.8 Hz, 1H), 5.96 (t, J =
5.9 Hz, 1H), 3.87 (s, 3H), 1.58 (s, 15H). 13C NMR (75 MHz,
CDCl3): δ 160.2, 139.3, 130.6, 130.3, 129.3, 127.0, 114.7, 97.7, 96.6,
94.1, 89.0, 88.3, 85.5, 83.1, 55.5, 9.6. 31P NMR (162 MHz, CDCl3): δ
−143.8 (sept, J = 713 Hz). IR: 2921, 1607, 1508, 1472, 1387, 1248,
1179, 1028, 831, 742, 675 cm−1. HRMS (ESI) for C27H29ORu [M −
PF6]+: calcd 471.1256, found 471.1238.
[Ru(η 5-Cp*)(η 6-5-(1-naphthyl)naphthalene)][PF6] (9bd). Pre-
pared according to the general procedure using the crystalline mixture
of complexes 2b and 18b (90% 2b (97% ee (S)) and 10% 18b, 65 mg,
0.10 mmol of 2b), Pd(OAc)2 (1.1 mg, 0.005 mmol), oTol3P (3.04 mg,
0.010 mmol), 1-napthB(OH)2 (d; 51.6 mg, 0.3 mmol), and K3PO4
(63.7 mg, 0.3 mmol) in methanol (2 mL). Purification through neutral
alumina (CH2Cl2, then CH2Cl2/acetone 1/1) and crystallization from
CH2Cl2/diethyl ether gave complex 9bd as orange crystals (23 mg,
50% yield, 99% ee (S)). Mp: 230−233 °C. [α]D = +425° (c = 0.1,
[Ru(η5-Cp)(η6-5-(diphenylphosphino)naphthalene)][PF6] (10a).
Prepared according to the general procedure from (±)-2a (52 mg, 0.1
mmol), Pd(dba)2 (2.9 mg, 0.005 mmol), ddpf (2.8 mg, 0.005 mmol),
K3PO4 (31.8 mg, 0.15 mmol), and diphenylphosphine (26 μL, 0.15
mmol) in CH2Cl2 (1 mL). The microwave irradiation time was
reduced to 5 min. Purification through flash chromatography (CH2Cl2,
then CH2Cl2/acetone 6/1) afforded phosphine 10a as a yellow solid
(28 mg, 45% yield). Mp: 159−161 °C. 1H NMR (500 MHz, CD2Cl2):
δ 7.72 (d, J = 8.5 Hz, 1H), 7.47−7.54 (m, 6H), 7.38−7.43 (m, 3H),
7.26−7.33 (m, 4H), 6.96 (d, J = 6.0 Hz, 1H), 6.28 (t, J = 6.0 Hz, 1H),
6.15 (t, J = 5.7 Hz, 1H), 4.78 (s, 5H). 13C NMR (125 MHz, CD2Cl2):
δ 139.3 (d, J = 22.0 Hz), 137.6, 135.3 (d, J = 21.5 Hz), 134.0 (d, J =
8.3 Hz), 134.0 (d, J = 19.7 Hz), 133.1 (d, J = 8.8 Hz), 131.5, 131.1,
130.6, 130.1, 129.6 (d, J = 8.3 Hz), 129.5 (d, J = 7.3 Hz), 99.6 (d, J =
25.2 Hz), 97.5 (d, J = 3.7 Hz), 86.2, 85.8 (d, J = 1.8 Hz), 84.9, 82.2 (d,
J = 29.3 Hz), 80.2. 31P NMR (202 MHz, CD2Cl2): δ −16.5, −144.1
(sept, J = 711 Hz). IR: 3117, 1607, 1477, 1435, 1341, 1195, 824, 792,
748, 736, 697, 665 cm−1. HRMS (ESI) for C27H22PRu [M − PF6]+:
calcd 479.0502, found 479.0491. Anal. Calcd for
C27H22P2F6Ru·0.15CH2Cl2 (636.21): C, 51.26; H, 3.53. Found: C,
51.25; H, 3.32.
1
CHCl3). H NMR (300 MHz, CDCl3): δ 8.03 (d, J = 8.2 Hz, 1H),
7.97 (d, J = 8.2 Hz, 1H), 7.82−7.69 (m, 3H), 7.64 (t, J = 7.6 Hz, 1H),
7.53 (t, J = 7.5 Hz, 1H), 7.46 (d, J = 6.8 Hz, 1H), 7.34 (t, J = 7.7 Hz,
1H), 7.09 (d, J = 8.6 Hz, 1H), 6.76 (d, J = 6.0 Hz, 1H), 6.12 (t, J = 6.2
Hz, 1H), 5.72 (m, 2H), 1.67 (s, 15H). 13C NMR (75 MHz, CDCl3): δ
138.3, 134.8, 133.7, 132.1, 130.9, 130.5, 130.0, 128.9, 128.3, 127.2,
127.2, 126.7, 125.5, 125.3, 98.9, 96.0, 94.3, 89.0, 88.2, 85.5, 83.6, 9.8.
31P NMR (162 MHz, CDCl3): δ −143.8 (sept, J = 713 Hz). IR: 3087,
3042, 1666, 1405, 1333, 1245, 1098, 1026, 996, 809, 744, 724 cm−1
.
HRMS (ESI) for C30H29Ru [M − PF6]+: calcd 491.1307, found
491.1308.
[Ru(η 5-Cp*)(η 6-5-((E)-2-cyclohexylvinyl)naphthalene)][PF6]
(9be). Prepared according to the general procedure using the
crystalline mixture of complexes 2b and 18b (85% 2b (97% ee (S))
and 15% 18b, 338.1 mg, 0.50 mmol of 2b), Pd(OAc)2 (5.6 mg, 0.025
mmol), oTol3P (15.2 mg, 0.050 mmol), (E)-2-cyclohexylvinylboronic
acid (e; 231.0 mg, 1.5 mmol), and K3PO4 (318 mg, 1.5 mmol) in
methanol (12 mL). Purification through neutral alumina (CH2Cl2,
then CH2Cl2/acetone 2/1) and crystallization from CH2Cl2/diethyl
ether gave complex 9be as yellow crystals (225 mg, 73% yield, 99% ee
[Ru(η 5-Cp*)(η 6-5-(bis(3,5-dimethylphenyl)phosphino)-
naphthalene)][PF6] (11b). Prepared according to the general
procedure from (±)-2b (69.3 mg, 0.118 mmol), Pd(dba)2 (3.4 mg,
0.006 mmol, 5 mol %), ddpf (3.4 mg, 0.006 mmol, 5 mol %), K3PO4
(50.3 mg, 0.240 mmol), and bis(3,5-dimethylphenyl)phosphine (65.0
mg, 0.19 mmol) in CH2Cl2 (1.2 mL). Purification through flash
6312
dx.doi.org/10.1021/om200897k|Organometallics 2011, 30, 6303−6315

Organometallics
Article
chromatography (CH2Cl2, then CH2Cl2/acetone 20/1) and recrystal-
549.1279, found 549.1254. Anal. Calcd for C64H44PBF24Ru (1411.85):
C, 54.45; H, 3.14. Found: C, 54.74; H, 3.45.
lization from Et2O/CH2Cl2 at 4 °C afforded phosphine 11b as yellow
1
plates (69 mg, 77% yield). Mp: >240 °C dec. H NMR (500 MHz,
Representative Procedure for the Synthesis of Gold(I)
Complexes. AuCl·SMe2 (34.0 mg, 0.115 mmol) was added to a
solution of 10b (80.0 mg, 0.115 mmol, 99% ee (S)) in CH2Cl2 (1.0
mL) followed by CH2Cl2 (1.0 mL) at ambient temperature in the
dark. After 4 h (the initially intense yellow color almost vanished), the
reaction mixture was filtered over a pad of Celite, which was washed
with CH2Cl2, and the eluent was concentrated. This procedure was
repeated several times until the product became pale yellow and no
black precipitate was observed.
[AuCl((S)-10b)] ((S)-13b). A yellow solid was obtained after
precipitation in pentane (61.4 mg, quantitative). Yellow crystals
suitable for X-ray analysis were grown by slow diffusion of Et2O in a
CH2Cl2 solution of (S)-13 at 4 °C. Mp: 210 °C dec. [α]D = +305.6° (c
= 1.01, CH2Cl2). 1H NMR (500 MHz, CD2Cl2): δ 7.83 (d, J = 8.7 Hz,
1H), 7.72−7.67 (m, 1H), 7.67−7.55 (m, 6H), 7.50−7.40 (m, 4H),
7.27−7.21 (m, 2H), 6.53 (d, J = 6.0 Hz, 1H), 6.01 (td, J = 6.0, <1 Hz,
1H), 5.85−5.82 (m, 1H), 1.81 (s, 15H). 13C NMR (125 MHz,
CD2Cl2): δ 140.1 (d, J = 5.9 Hz), 135.4 (d, J = 14.4 Hz), 135.3 (d, J =
14.5 Hz), 134.7 (d, J = 2.4 Hz), 133.6 (d, J = 2.7 Hz), 133.6 (d, J = 2.6
Hz), 130.4 (d, J = 12.4 Hz), 130.2 (d, J = 12.4 Hz), 129.2 (d, J = 10.6
Hz), 126.4 (d, J = 19.5 Hz), 126.1 (d, J = 14.3 Hz), 125.7 (d, J = 22.8
Hz), 99.0 (d, J = 11.9 Hz), 96.2, 95.4 (d, J = 6.1 Hz), 89.0, 87.6, 86.3
(d, J < 1 Hz), 83.2 (d, J = 14.4 Hz), 10.7. 31P NMR (202 MHz,
CD2Cl2): δ +24.4, −144.3 (sept, J = 711 Hz). IR: 3062, 2912, 1611,
1473, 1438, 1387, 1268, 1100, 1028, 831, 729, 692 cm−1. HRMS (ESI)
for C32H32ClPRuAu [M − PF6, 35Cl, 102Ru, 197Au]+: calcd 781.0633,
found 781.0640. Anal. Calcd for C32H32AuClF6P2Ru·0.6CH2Cl2
(977.0): C, 40.08; H, 3.43. Found: C, 40.10; H, 3.30.
CD2Cl2): δ 7.51 (ddd, J = 8.7, 6.7, <1 Hz, 1H), 7.46 (br d, J = 8.7 Hz,
1H), 7.13 (br s, 1H), 7.10 (ddd, J = 6.7, 3.6, 1.2 Hz, 1H), 7.03 (br s,
1H), 6.96 (br d, J = 9.0 Hz, 1H), 6.89 (br d, J = 8.7 Hz, 1H), 6.65−
6.61 (m, 1H), 6.42 (d, J = 6.0 Hz, 1H), 5.95 (t, J = 5.8 Hz, 1H), 5.76
(td, J = 6.0, <1 Hz, 1H), 2.31 (s, 6H), 2.21 (s, 6H), 1.73 (s, 15H). 13
C
NMR (125 MHz, CD2Cl2): δ 139.3 (d, J = 8.4 Hz, 1C), 139.1 (d, J =
8.4 Hz), 138.4 (d, J = 20.7 Hz), 136.1 (d, J = 1.5 Hz), 133.6 (d, J = 6.2
Hz), 133.0 (d, J = 7.9 Hz), 132.7 (d, J = 21.2 Hz), 132.3, 132.1 (d, J =
20.9 Hz), 132.0, 130.7, 128.3, 98.8 (d, J = 20.6 Hz), 97.3 (d, J = 3.1
Hz), 94.7, 88.6 (d, J = 1.3 Hz), 87.0 (d, J = 1.5 Hz), 86.0 (d, J = 1.4
Hz), 83.6 (d, J = 26.0 Hz), 21.4, 21.3, 10.0 (d, J = 2.0 Hz). 31P NMR
(202 MHz, CD2Cl2): δ −13.2, −144.4 (sept, J = 711 Hz). IR: 3091,
2915, 2860, 1600, 1472, 1456, 1387, 1344, 1183, 1224, 1034, 874, 829,
791, 692 cm−1. HRMS (ESI) for C36H40PRu [M − PF6, 102Ru]+: calcd
605.1905, found 605.1878. Anal. Calcd for C36H40F6P2Ru·0.9CH2Cl2
(826.2): C, 53.65; H, 5.10. Found: C, 53.67; H, 5.06.
[Ru(η 5-Cp*)(η 6-5-(di-o-tolylphosphino)naphthalene)][PF6]
(12b). Prepared according to the general procedure using the
crystalline mixture of complexes 2b and 18b (85% 2b (97% ee (S))
and 15% 18b, 57.4 mg, 0.085 mmol of 2b), Pd(dba)2 (4.9 mg, 0.0085
mmol, 10 mol %), ddpf (3.5 mg, 0.0085 mmol, 10 mol %), K3PO4
(28.4 mg, 0.134 mmol), and di-o-tolylphosphine (32.8 mg, 0.138
mmol) in CH2Cl2 (1.2 mL). The reaction mixture was subjected to 1 h
of microwave irradiation at 140 °C. Purification through flash
chromatography (CH2Cl2, then CH2Cl2/acetone 20/1) and recrystal-
lization from Et2O/CH2Cl2 at 4 °C afforded phosphine 12b as yellow
plates (24.7 mg, 40% yield, 99% ee (S)). Mp: 142−144 °C. [α]D
=
+554° (c = 0.87, CHCl3). 1H NMR (500 MHz, CD2Cl2): δ 7.53−7.45
(m, 2H), 7.43−7.36 (m, 2H), 7.31−7.23 (m, 2H), 7.20−7.14 (m, 1H),
7.07−7.03 (m, 1H), 7.00−6.94 (m, 1H). 6.90−6.84 (m, 1H), 6.59−
6.54 (m, 1H), 6.48 (ddd, J = 6.2, 4.1, < 1 Hz, 1H), 6.41 (d, J = 6.0 Hz,
1H), 5.92 (td, J = 5.7, < 1 Hz, 1H), 5.74−5.69 (m, 1H), 2.66 (s, 3H),
2.42 (d, J = 1.3 Hz, 3H), 1.73 (s, 15H). 13C NMR (125 MHz,
CD2Cl2): δ 144.3 (d, J = 28.5 Hz), 142.9 (d, J = 28.2 Hz), 136.8 (d, J =
21.0 Hz), 136.3 (d, J = 3.5 Hz), 135.2, 134.0, 133.5 (d, J = 6.8 Hz),
131.2 (d, J = 5.5 Hz), 130.9 (d, J = 8.0 Hz), 130.9 (d, J = 5.9 Hz),
130.8, 130.8, 130.1, 128.4 (d, J = 1.4 Hz), 127.5 (d, J = 1.4 Hz), 126.7,
100.0 (d, J = 19.4 Hz), 96.9 (d, J = 2.7 Hz), 95.0, 88.7 (d, J < 1 Hz),
87.8 (d, J = 1.4 Hz), 85.7 (d, J < 1 Hz), 83.8 (d, J = 23.3 Hz), 21.9 (d, J
= 22.0 Hz), 21.0 (d, J = 22.9 Hz), 10.1 (d, J = 1.1 Hz). 31P NMR (202
MHz, CD2Cl2): δ −27.6, −144.1 (sept, J = 711 Hz). IR: 2965, 2916,
2860, 1470, 1454, 1384, 1033, 874, 830, 754 cm−1. HRMS (ESI) for
C34H36PRu [M − PF6, 102Ru]+: calcd 577.1564, found 577.1598. Anal.
Calcd for C34H36F6P2Ru·CH2Cl2 (806.6): C, 52.12; H, 4.75. Found: C,
52.25; H, 4.58.
[AuCl(11b)] (14b). Prepared according to the general procedure
from (±)-11b (30.7 mg, 0.041 mmol) and AuCl·SMe2 (13.3 mg, 0.045
mmol). A yellow solid was obtained after precipitation in pentane
(44.1 mg, quantitative). Yellow crystals suitable for X-ray analysis were
grown by slow diffusion of Et2O in a CH2Cl2 solution of 14 at 4 °C.
1
Mp: >215 °C dec. H NMR (500 MHz, CD2Cl2): δ 7.81 (d, J = 8.6
Hz, 1H) 7.64 (ddd, J = 8.5, 7.0, 1.3 Hz, 1H), 7.30 (br s, 1H), 7.24 (dd,
J = 11.8, 6.7 Hz, 1H), 7.23 (d, J = 6.5 Hz, 1H), 7.18 (br s, 1H), 7.17
(d, J = 14.8 Hz, 2H), 6.99 (d, J = 14.3 Hz, 2H), 6.53 (d, J = 5.8 Hz,
1H), 5.99 (t, J = 5.8 Hz, 1H), 5.81 (t, J = 6.0 Hz, 1H), 2.37 (s, 6H),
2.23 (s, 6H), 1.81 (s, 15H). 13C NMR (125 MHz, CD2Cl2): δ 140.5
(d, J = 13.0 Hz), 140.2 (d, J = 13.1 Hz), 140.0 (d, J = 6.0 Hz), 135.3
(d, J = 2.8 Hz), 135.3 (d, J = 2.5 Hz), 134.4 (d, J = 2.4 Hz), 132.8 (d, J
= 14.4 Hz), 132.5 (d, J = 14.5 Hz), 129.3 (d, J = 10.7 Hz), 126.9 (d, J
= 55.8 Hz), 125.9 (d, J = 19.6 Hz), 125.4 (d, J = 19.7 Hz), 99.3 (d, J =
11.7 Hz), 96.1, 95.2 (d, J = 6.0 Hz), 88.8, 87.5, 86.2, 83.3 (d, J = 14.0
Hz), 21.5, 21.4, 10.7. 31P NMR (202 MHz, CD2Cl2): δ +24.4, −144.3
(sept, J = 711 Hz). IR: 2953, 2916, 2860, 1601, 1470, 1448, 1386,
1345, 1129, 1036, 832, 786, 731, 686 cm−1. HRMS (ESI) for
C36H40ClPRuAu [M − PF6, 102Ru]+: calcd 837.1259, found 837.1271.
Anal. Calcd for C36H40AuClF6P2Ru·(CH2Cl2)0.5 (1024.6): C, 42.79;
H, 4.03. Found: C, 42.57; H, 3.58.
[Ru(η 5-Cp*)(η 6-5-(diphenylphosphino)naphthalene)][BArF]
(10b). (±)-[10b][PF6] (131.50 mg, 0.223 mmol) and NaBArF
(200.00 mg, 0.226 mmol) were charged in a Schlenk tube. Dry and
degassed CH2Cl2 (26 mL) was added, and the resulting cloudy yellow
solution was stirred for 15 min at room temperature. The solvent was
evaporated to dryness. The residue was redissolved in dry CH2Cl2 (6
mL), filtered, and washed (12 mL). The filtrate was concentrated to
[AuCl(12b)] (15b). Prepared according to the general procedure
from 12b (11.7 mg, 0.016 mmol mmol, 99% ee (S)) and AuCl·SMe2
(5.0 mg, 0.017 mmol). A yellow solid was obtained after precipitation
in pentane (19.0 mg, quant.). Mp: >200 °C dec. [α]D = +232° (c =
1
afford (±)-[10b][BArF] as a yellow solid (279 mg, 96% yield). H
1
NMR (500 MHz, CD2Cl2): δ 7.74 (s, 8H), 7.57 (s, 4H), 7.52−7.45
(m, 4H), 7.43−7.39 (m, 1H), 7.37−7.27 (m, 7H), 7.10 (ddd, J = 6.8,
3.5, 1.0 Hz, 1H), 6.68 (dd, J = 5.5, <1 Hz, 1H), 6.23 (d, J = 6.0 Hz,
0.95, CH2Cl2). H NMR (500 MHz, CD2Cl2): δ 7.89 (d, J = 8.7 Hz,
1H), 7.85−7.20 (m, 10H), 7.10−6.93 (m, 1H), 6.57 (d, 6.0 Hz, 1H),
6.04 (t, J = 5.9 Hz, 1H), 5.88 (d, J = 6.0 Hz, 1H), 3.10−2.50 (2 br s,
6H), 1.84 (s, 15H). 31P NMR (202 MHz, CD2Cl2): δ −3.1 (br),
−144.1 (sept, J = 711 Hz). IR: 2961, 2910, 1608, 1589, 1472, 1450,
1381, 1260, 1071, 1025, 830, 818, 806, 768, 747 cm−1. HRMS (ESI)
for C34H36ClPRuAu [M − PF6, 102Ru]+: calcd 809.0952, found
809.0850.
IR Spectroscopic Characterization of Phosphines. Ni(CO)3L
complexes were generated in situ from Ni(cod)2 and carbon monoxide
in CH2Cl2. The phosphine complexes were not isolated but directly
analyzed in solution by means of FT-IR spectroscopy. Caution!
Carbon monoxide is toxic; Ni(CO)4 is very toxic and highly volatile.
All transformations have to be carried out in a well-ventilated fume
1H), 5.78 (t, J = 5.8 Hz, 1H), 5.70 (t, J = 6.0 Hz, 1H), 1.70 (s, 15H).
1
13C NMR (125 MHz, CD2Cl2): δ 162.3 (q, JC,B = 49.9 Hz, CipsoBAr ),
F
F
138.3 (d, J = 20.8 Hz), 136.5 (d, J = 1.5 Hz), 135.3 (br s, CorthoBAr ),
135.1, 134.6 (d, J = 20.6 Hz), 133.8 (d, J = 6.8 Hz), 133.1 (d, J = 8.2
Hz), 131.1, 130.9, 130.6, 129.9 (d, J = 7.9 Hz), 129.7 (d, J = 8.0 Hz),
2
3
1
129.4 (qq, JC,F = 31.5, JC,B = 2.9 Hz, CCF3), 128.1, 125.1 (q, JC,F
=
F
272.4 Hz, CF3), 118.0 (br s, CparaBAr ), 99.0 (d, J = 20.6 Hz), 97.3 (d, J
= 3.1 Hz), 95.2, 88.3, 87.8 (d, J = 1.6 Hz), 85.7, 83.7 (d, J = 26.3 Hz),
10.2 (d, J = 1.9 Hz). 31P NMR (162 MHz, CD2Cl2): δ −13.1. IR:
2963, 1610, 1475, 1437, 1353, 1272, 1115, 1028, 886, 838, 744, 696,
712, 669, 681 cm−1. HRMS (ESI) for C32H32PRu [M − BArF]+: calcd
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Organometallics
Article
hood, including the generation of Ni(CO)4, preparation of IR samples,
and cleanup. The waste can be destroyed by oxidation with bromine.
Ni(cod)2 is air-sensitive and rapidly decomposes to black Ni(0). All
reactions were carried out with dry and degassed CH2Cl2. The IR cell
was purged with nitrogen before use.
Ni(CO)3L. Carbon monoxide was bubbled for 2−5 min through a
yellow solution of Ni(cod)2 (9.1−13.2 mg, 0.033−0.05 mmol) in
CH2Cl2 (1.0 mL) until the yellow color vanished.51 A stock solution of
the phosphine (ca. 0.1 M, 1.0 equiv) was added to the colorless clear
solution of Ni(CO)4, and the mixture was stirred for 5 min, followed
by bubbling nitrogen through the solution for 5 min.52 IR spectra
(2150−1850 cm−1) were measured in transmission mode in a NaCl
cuvette with a resolution of 1 cm−1. The recorded νCO(A1) values were
referenced to the Tolman scale using νCO(A1) of Ni(CO)3(PPh3) as a
reference (lit.32 2068.9 cm−1, exptl 2069.5 cm−1). The corrected values
for νCO(A1) are depicted in Table 3.
Spencer, J.; Steiner, I.; Togni, A. Organometallics 1996, 15, 1614−
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̈
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Commun. 2009, 5227−5229. (c) Mercier, A.; Urbaneja, X.; Yeo, W. C.;
Chaudhuri, P. D.; Cumming, G. R.; House, D.; Bernardinelli, G.;
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(9) Cumming, G. R.; Bernardinelli, G.; Kundig, E. P. Chem. Asian J.
̈
ASSOCIATED CONTENT
* Supporting Information
■
̈
S
2006, 1, 459−468.
(10) A similar sequence was previously reported for the synthesis of
Text giving additional details about the crystal structures of 11b
and 12b, tables and spectra giving NMR data, and CIF files
giving X-ray crystallographic data for complexes 11b−14b and
16b. This material is available free of charge via the Internet at
http://pubs.acs.org.
analogue iron complex 8b.4b
(11) The bromine/lithium exchange did not occur, as indicated by
the formation of Ph2(nBu)P (31P NMR (162 MHz, CD2Cl2): δ +16.5
ppm).
(12) (a) Robertson, D. R.; Stephenson, T. A. J. Organomet. Chem.
1977, 142, C31−C34. (b) Volkenau, N. A.; Bolesova, I. N.; Shulpina,
L. S.; Kitaigorodskii, A. N. J. Organomet. Chem. 1984, 267, 313−321.
(c) Older, C. M.; Stryker, J. M. J. Am. Chem. Soc. 2000, 122, 2784−
2797.
AUTHOR INFORMATION
Corresponding Author
*E-mail: peter.kundig@unige.ch.
■
(13) For addition of carbanions to cationic [Fe(η 5-Cp)(η6-
naphthalene)] complexes, see: (a) Nesmeyanov, A. N.; Solodovnikov,
S. P.; Vol’kenau, N. A.; Kotova, L. S.; Sinitsyna, N. A. J. Organomet.
ACKNOWLEDGMENTS
We thank the Swiss National Science Foundation and the
University of Geneva for financial support.
■
Chem. 1978, 148, C5−C8. (b) Kundig, E. P.; Jeger, P.; Bernardinelli,
̈
G. Angew. Chem., Int. Ed. 1995, 34, 2161−2163.
(14) For reviews on transition-metal-catalyzed C−P cross-coupling
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Synthesis 2010, 3037−3062. (b) Glueck, D. S. In C-X Bond Formation;
Vigalok, A., Ed.; Springer-Verlag: Berlin, 2010; Topics in Organo-
metallic Chemistry Vol. 31, p 65.
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