Synthesis, Reactivity, and Coordination of Semihomologous dppf Congeners Bearing Primary Phosphine and Primary Phosphine Oxide Groups

Article abstract of DOI:10.1021/acs.organomet.0c00767

This contribution reports the synthesis of two phosphinoferrocene ligands desymmetrized by an inserted methylene spacer, viz., a bis-phosphine combining primary and tertiary phosphine moieties in its structure, Ph2PfcCH2PH2 (2), and a structurally unique, stable phosphine-primary phosphine oxide Ph2PfcCH2P(O)H2 (7; fc = ferrocene-1,1′-diyl). Compounds 2 and 7, together with 1,1′-bis(diphenylphosphino)ferrocene (dppf), the bis-tertiary phosphine Ph2PfcCH2PPh2, and the adduct Ph2P(BH3)fcCH2PH2 (6), were studied as ligands in Ru(II) complexes bearing auxiliary ν6-arene ligands and both free ligands and the isolated complexes were structurally authenticated, using spectroscopic methods and X-ray crystallography, and further investigated by cyclic voltammetry. The results suggest that distinct donor moieties in the unsymmetric ligands differentiate the otherwise identical coordinated metal centers and that the phosphine moiety in phosphine-phosphine oxide ligand 7 is preferably coordinated to Ru(II), before the phosphine oxide group, which must tautomerize into the hydroxyphosphine form prior to coordination.

Full text of DOI:10.1021/acs.organomet.0c00767

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Article
Synthesis, Reactivity, and Coordination of Semihomologous dppf
Congeners Bearing Primary Phosphine and Primary Phosphine
Oxide Groups
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Filip Horky, Ivana Císarova, and Petr Stepnicka*
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ABSTRACT: This contribution reports the synthesis of two phosphino-
ferrocene ligands desymmetrized by an inserted methylene spacer, viz., a
bis-phosphine combining primary and tertiary phosphine moieties in its
structure, Ph2PfcCH2PH2 (2), and a structurally unique, stable phosphine-
primary phosphine oxide Ph2PfcCH2P(O)H2 (7; fc = ferrocene-1,1′-diyl).
Compounds 2 and 7, together with 1,1′-bis(diphenylphosphino)ferrocene
(dppf), the bis-tertiary phosphine Ph2PfcCH2PPh2, and the adduct
Ph2P(BH3)fcCH2PH2 (6), were studied as ligands in Ru(II) complexes
bearing auxiliary η6-arene ligands and both free ligands and the isolated
complexes were structurally authenticated, using spectroscopic methods
and X-ray crystallography, and further investigated by cyclic voltammetry.
The results suggest that distinct donor moieties in the unsymmetric ligands differentiate the otherwise identical coordinated metal
centers and that the phosphine moiety in phosphine-phosphine oxide ligand 7 is preferably coordinated to Ru(II), before the
phosphine oxide group, which must tautomerize into the hydroxyphosphine form prior to coordination.
family of functional phosphinoferrocene ligands and organo-
metallic synthetic building blocks,5 or inserting a spacer into
the cyclopentadienyl-phosphorus bonds. The latter approach
has so far resulted in the preparation of symmetrical
homologous ligands A6 and B,7 their analogs with chiral
phospholane substituents8 and rigid phenylene spacers,9 and
C-chiral bis-phosphines C10 (Chart 1).11
INTRODUCTION
1,1′-Bis(diphenylphosphino)ferrocene (Chart 1), commonly
abbreviated as dppf and first reported in 1965,1 has become an
■
Chart 1
In our research, we desymmetrized the parent dppf structure
by introducing a spacer group into one of the equivalent
C(ferrocene)−P bonds and synthesized semihomologous dppf
congener 1.12 The current data on 1 and related compounds13
have shown that such a structural modification differentiates
the two coordination sites (both sterically and electronically)
and increases the structural flexibility of these ligands, thereby
altering their coordination behavior with respect to the more
rigid dppf.
Inspired by the structure of the simple, air-stable primary
phosphine FcCH2PH2 (Fc = ferrocenyl),14 we decided to
synthesize and study a novel ferrocene bis-phosphine, 2 (Chart
1), containing tertiary and primary phosphine moieties and the
flexible methylene linker. Compound 2 is a homologue of
indispensable ligand for coordination chemistry and catalysis.2
Its enormous practical success has prompted the search for
purpose-tailored dppf analogs. To date, several dppf derivatives
have been reported with varied substituents at the phosphorus
atoms,3 among which 1,1′-bis(di-tert-butylphosphino)-
ferrocene has attracted particular attention for its favorable
catalytic properties.4
Received: December 4, 2020
Published: January 22, 2021
In contrast, other approaches toward dppf modification that
only partly retain the parent structure have been studied less
often. These approaches include replacing one phosphine
moiety by another group, which provides access to a vast
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a
Ph2PfcPH2 (fc = ferrocene-1,1′-diyl), which has been used as
an intermediate in the synthesis of chiral phosphines for
catalytic C−C bond hydrogenation15 and is an isomer of the
somewhat overlooked, planar-chiral 1-(diphenylphosphino)-2-
(phosphinomethyl)ferrocene.16
Scheme 2. Synthesis of Phosphine Oxides 6−9
Furthermore, building upon our recent discovery that the
ferrrocenymethyl group can stabilize even the hitherto elusive
primary phosphine oxides,17 we also describe the synthesis of
compound 7 (Chart 1) as the first primary phosphine oxide
functionalized by an additional phosphine moiety.
The coordination preferences of the newly prepared ligands
are probed through reactions with RuII precursors with
aromatic π-ligands and compared with those of dppf and 1.
The complexes are further studied by cyclic voltammetry and
catalytically evaluated in Ru-catalyzed double bond isomer-
ization using anethole as a model substrate and in Ru-mediated
cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol into 2,3-dime-
thylfuran.
a
Legend: dabco = 1,4-bicyclo[2.2.2]octane
FcCH2P(O)H2,17 compounds 6 and 7 reacted with acetone at
slightly elevated temperature (40 °C; the reaction proceeds
even at room temperature but only slowly), providing the
corresponding addition products 8 and 9 in good yields.
Phosphine oxides 6−9 were stable under ambient conditions
(we noted, however, that compounds 8 and 9 slowly and partly
regenerated 6 and 7, respectively, in a dichloromethane
solution17,22).
RESULTS AND DISCUSSION
■
Synthesis of the Ligands. Bis-phosphine 2 was obtained
by manipulating the hydroxyl group in borane-protected
phosphinoalcohol 313d (Scheme 1). Specifically, the alcohol
a
31P NMR spectra of 2 and 5 displayed diagnostic triplets of
Scheme 1. Synthesis and Arylation of Bis-phosphine 2
triplets (1JPH = 194 Hz, JPH = 4−5 Hz) due to the primary
phosphine moieties at δP ≈ −126 (Figure 1). The signal of the
2
a
Legend: dabco = 1,4-bicyclo[2.2.2]octane, [Pd] = Pd(OAc)2.
was converted into phosphonic acid ester 4 via a reaction with
triethyl phosphite/ZnI2,18 and the ester was reduced with
19
Li[AlH4]/ClSiMe3 to give semiprotected bis-phosphine 5.
Subsequent deprotection with 1,4-diazabicyclo[2.2.2]octane
(dabco)20 in THF produced target compound 2 in
approximately 60% yield over the three steps after a final
crystallization.
Compound 2 was isolated as an air-stable and thermally
robust, crystalline solid (mp 114 °C) with a characteristic yet
only faint smell of phosphane. It did not react with acetone (at
40 °C; see below) but could be arylated21 with iodobenzene in
the presence of palladium(II) acetate (5 mol %) and an amine
additive, giving known12 bis-tertiary phosphine 1 in 78% yield
(Scheme 1). Similar results were found when using
[Pd2(dba)3] as the catalyst (dba = dibenzylideneacetone).
To synthesize a ferrocene-based, hybrid phosphine-primary
phosphine oxide ligand, we further oxidized P-protected
intermediate 5 with aqueous hydrogen peroxide at 0 °C
(Scheme 2). The oxidation proceeded rapidly and selectively,
producing phosphine oxide 6 in 84% yield. Upon treatment
with dabco, this compound was converted into phosphine
oxide 7 in a virtually quantitative yield (95%). Similarly to
Figure 1. 31P NMR spectra of 2 and 7. Spectra are shown with
identical scaling at both axes.
PPh2 group was observed as a singlet at δP −16.2 for 2 and as a
broad multiplet at δP 16.4 for BH3-adduct 5. Correspondingly,
the PH2 groups gave rise to doublets of multiplets at δH ≈ 2.8
in the 1H NMR spectra, whereas the signals of the CH2 linker
were observed as doublets of triplets at δH ≈ 2.3. The presence
of the PH2 moieties was further manifested as intense bands in
the ≈2300−2360 cm−1 range of IR spectra, attributable to P−
H stretching modes.
Oxidation of the PH2 group in 6 and 7 shifted the 31P NMR
1
signal downfield (δP ≈ 9) and increased the JPH coupling
constant (≈ 470 Hz; see Figure 1). The signal of the P(O)H2
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hydrogens also shifted (δH ≈ 6.8), reflecting the stronger
electron-withdrawing nature of the phosphinyl moiety. Even
so, replacing one PH hydrogen with the 2-hydroxyprop-2-yl
moiety in 8 and 9 was clearly indicated in the NMR spectra:
The 31P NMR spectra displayed doublets of multiplets with a
Synthesis of Ru(II) Complexes. The coordination
behavior of compounds 1, 2, 6, and 7 was evaluated through
reactions with Ru(II) precursors bearing auxiliary π-ligands.
The prototypical ligand dppf was also included in these studies
for comparison purposes. Initially, we focused on (η6-
mes)Ru(II) complexes featuring the ligands in a P,P′-bridging
mode. The reactions of [{(η6-mes)RuCl(μ-Cl)}2] (mes =
mesitylene) with dppf, 1, and 2 proceeded cleanly, producing
respective diruthenium complexes 10, 11, and 12 as the sole
products (Scheme 3).
1
large JPH coupling constant (≈ 455 Hz), whereas the PH
1
signals were observed at δH ≈ 2.3 in the H NMR spectrum,
split into a more complicated pattern (ddd for 8 and dt for 9)
due to the diastereotopic nature of the CH2 hydrogens
attached to the stereogenic phosphorus atom. For the same
reason, two separate signals were found for the chemically
equivalent methyl groups. No signals attributable to hydrox-
yphosphine tautomers were observed in the NMR spectra of
phosphine oxides 6−9.
a
Scheme 3. Synthesis of (η6-mes)Ru(II) Complexes 10−15
The crystal structures of 2 and 9 are shown in Figure 2 (for
additional diagrams and parameters, see the Supporting
a
mes = mesitylene.
When using hybrid ligand 7, the reaction was accompanied
by tautomerization of the primary phosphine oxide moiety,
leading to phosphine-hydroxyphosphine complex 13. Upon
reducing the amount of the Ru precursor by half, the analogous
reaction selectively produced phosphine complex 14 featuring
uncoordinated phosphine oxide moiety. Conversely, the
reaction of [(η6-mes)RuCl2]2 with ligand 6, whose tertiary
phosphine group was unavailable for coordination, led to
hydroxyphosphine complex 15 (Scheme 3).
Generally, complexes 10−15 were relatively poorly soluble
and exerted structural dynamics which complicated their
characterization by NMR spectroscopy. The coordination of
the PPh2 moiety led to a rather uniform downfield shift of the
31P NMR signal by 37−38 ppm (≈42 ppm for CH2PPh2 in 1),
whereas the coordination of the PH2 group in 2 or
tautomerization/coordination of the P(O)H2 groups in 6
and 7 resulted in a considerably larger shift of approximately
107 ppm (the tautomerization was further indicated by
changes in the non-decoupled 31P NMR spectra, wherein the
triplets due to P−H interactions in the P(O)H2 groups were
replaced by doublets of the PH(OH) fragments).
Figure 2. Molecular structures of 2 and 9. Selected distances and
angles (in Å and deg): for 2: P1−C1 1.806(2), P1−C12 1.844(2),
P1−C18 1.844(2), P2−C11 1.853(2), C6−C11−P2 114.9(1); for 9:
P1−C1 1.812(3), P1−C12 1.838(3), P1−C18 1.836(3), P2−O1
1.486(3), P2−C11 1.803(3), C6−C11−P2 111.8(2), C11−P2−O1
114.4(2). Parameters pertaining to the disordered CH2P(O) arm are
given for the more populated orientation.
Information). Both compounds comprised regular ferrocene
units with similar Fe−C distances (2.035(2)−2.055(2) Å for
2; 2.028(3)−2.056(3) Å for 9) and negligible tilting (4.86(9)
and 2.1(2)°, respectively). The cyclopentadienyls in 2 adopted
an approximate 1,2′-conformation23 with the torsion angle
C1−Cg1−Cg2−C6 (hencefort denoted as τ; Cg1 and Cg2 are
the centroids of the cyclopentadienyl rings C(1−5) and C(6−
10), respectively) of −81.8(1)°. A similar, though more
compact, arrangement was identified in 9 (τ = 69.7(2)°). In
the crystal, the molecules of 9 assembled into infinite chains
through O−H···OP hydrogen bonds (O1···O2 = 2.645(4)
Å; see the Supporting Information).
The molecular structures of 10·THF·2CH2Cl2 and 12·
2CHCl3 determined by X-ray crystallography (Figure 3) were
generally similar to that of [(L∧L){(η6-arene)RuCl2}2] (L∧L =
dppf and fc(CH2PPh2)2)24 and [(η6-p-cymene)-
RuCl2(FcCH2PH2-κP)].25 The complex molecule in the
structure of 10·THF·2CH2Cl2 was situated on the crystallo-
graphic inversion center, which rendered the ferrocene
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Figure 4. Molecular structure of complex 15. Selected distances (in
Å): Ru−P2 2.2815(8), Ru−Cl1 2.416(2) (dominant position), Ru−
Cl2 2.4052(9), Ru−C(arene) 2.193(3)−2.275(3), P2−O 1.637(3),
P1−B 1.924(4), Fe1−C(1−10) 2.025(3)−2.045(3).
Scheme 4. Synthesis of Complex 16
Figure 3. Views of the complex molecules in the structures of 10·
THF·2CH2Cl2 and 12·2CHCl3. Selected distances (in Å): for 10·
THF·2CH2Cl2: Ru1−P1 2.3598(5), Ru1−Cl1 2.4082(5), Ru1−Cl2
2.4113(5), Ru1−C(arene) 2.198(2)−2.270(2), Fe1−C(1−5)
2.039(2)−2.064(2); for 12: Ru1−P1 2.3620(7), Ru1−Cl1
2.4160(7), Ru1−Cl2 2.4122(8), Ru1−C(arene) 2.205(3)−2.271(3),
Ru2−P2 2.2770(7), Ru2−Cl3 2.4097(9), Ru2−Cl4 2.4027(9), Ru2−
C(arene) 2.176(3)−2.263(3), Fe1−C(1−10) 2.025(3)−2.053(3).
raphy. Practically identical mixtures were obtained in the
reaction of stoichiometric amounts of 1 or 2 with [(η6-
mes)RuCl(MeCN-κN)2][PF6] in dichloromethane (for the
synthesis of the Ru-precursor, see the Supporting Informa-
tion). Reactions with ligand 7 were also unsuccessful, albeit
mainly due to extensive decomposition of the ligand in the
reaction mixtures (compound 7 seems to decompose in the
−
presence of the PF6 anion).
The crystal structure of 16·CH2Cl2 (Figure 5) was
cyclopentadienyls exactly parallel and brought their phosphine
substituents and the ligated ruthenium fragments into anti
positions. Ferrocene cyclopentadienyls in unsymmetric com-
plex 12·2CHCl3 were mutually rotated by τ = 90.5(2)° and
tilted by 4.4(2)°. In both complexes, the ruthenium atoms
adopted the usual “piano stool” geometry, wherein the basal
planes (Cl2P) were oriented parallel to the π-coordinated arene
ring (interplanar angles: 2.89(7)° for 10 and 1.6(1)° (Ru1)
and 2.6(1)° (Ru2) for 12). Notably, the Ru−PPh2 bonds
(≈2.36 Å) were significantly elongated with respect to the Ru−
PH2 bond in 12 (≈2.28 Å), most likely for steric reasons.
The structure of 15 (Figure 4) corroborated that the
phosphine oxide moiety underwent tautomerization upon
coordination. The P−H and P−OH bonds of the Ru-bound
PH(OH) unit, located between the bulky (η6-mes)Ru and
ferrocene fragments, alternated in their positions, thereby
resulting in positional disorder. The length of the Ru−P bond
in 15 was very similar to the Ru−PH2 bond distance in
complex 12, and the geometry of the fcPPh2·BH3 fragment
matched that of dppf·2BH3.26
unexceptional in view of the data reported for [(η6-arene)-
24a,b
RuCl(dppf-κ2P,P′)][PF6], where arene = C6Me6
and p-
cymene.28 The complex cation had a three-legged piano stool
structure symmetrically capped with the η6-benzene ring
(Ru1−C(41−46) = 2.251(3)−2.310(3) Å). The Ru−Cl and
Ru−P distances were similar to those determined for 10·
Next, we focused on cationic (η6-mes)Ru(II) complexes
accommodating the studied ferrocene phosphines as chelating
donors. The reaction24a,b of [{(η6-mes)RuCl(μ-Cl)}2] with
dppf in the presence of Na[PF6] produced [(η6-mes)RuCl-
(dppf-κ2P,P′)][PF6] (16) in 89% yield (Scheme 4). Attempts
to similarly prepare complexes with ligands 1 and 2 only led to
equilibrium mixtures containing the respective compounds
[(η6-mes)RuCl(L∧L)][PF6], based on 31P NMR analysis,27
which could not be separated by crystallization or chromatog-
Figure 5. View of the complex cation in the structure of 16·CH2Cl2.
Selected distances and angles (in Å and deg): Ru−P1 2.3636(9), Ru−
P2 2.3619(9), Ru−Cl 2.4030(8), P1−Ru−P2 95.10(3), Cl−Ru−P1/
2 81.21(3)/88.64(3), Fe−C(1−10) 2.024(3)−2.062(3); the angle
subtended by the C(41−46) and the {P1,P2,Cl} basal plane is
3.9(1)°.
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2CH2Cl2·THF and did not differ much even from each other.
Nevertheless, an asymmetry arose around the Ru atom, most
likely resulting from the dissimilar steric demands of the Ru-
bound ligands, with the largest interligand angle associated
with the chelating dppf ligand. Because of chelate coordination,
the ferrocene cyclopentadienyls were practically eclipsed (τ =
6.0(2)°) and, additionally, exerted negligible tilting (2.1(2)°).
To eliminate the problem with compound isolation, we
replaced the (η6-mes)Ru(II) moiety by the iso-π-electronic
fragment (η5-C5H5)Ru(II) toward synthesizing charge-neutral
compounds analogous to the known dppf complex [(η5-
C5H5)RuCl(dppf-κ2P,P′)] (17).29 Indeed, a modified method
for preparing 17 based on thermally assisted replacement of
triphenylphosphine ligands in [(η5-C5H5)RuCl(PPh3)2] em-
ploying bis-phosphine 1 produced the corresponding chelate
complex [(η5-C5H5)RuCl(1-κ2P,P′)] (18), which was isolated
as a rusty brown, air-stable solid in a 82% yield (Scheme 5).
Scheme 5. Synthesis of (η5-C5H5)Ru(II) Complexes 18 and
19
Figure 6. Views of the complex molecules in the structures of 18·
2CHCl3 and 19·CH2Cl2. Selected distances and angles (in Å and
deg): for 18: Ru−P1 2.311(1), Ru−P2 2.296(1), Ru−Cl 2.4473(9),
P1−Ru−P2 101.66(4), Cl−Ru1−P1/2 89.28(2)/85.53(2), Ru−
C(41−45) 2.187(5)−2.218(4), Fe−C(1−10) 2.040(3)−2.057(5);
for 19: Ru−P1 2.2858(8), Ru1−P2 2.2698(5), Ru−Cl 2.4439(6),
P1−Ru−P2 96.19(6), Cl−Ru1−P1/2 89.28(2)/85.53(2), Ru−
C(41−45) 2.179(2)−2.225(2), Fe−(C1−10) 2.046(2)−2.074(2).
Regrettably, repeated attempts to similarly prepare complex
[(η5-C5H5)RuCl(2-κ2P,P′)] (19) were unsuccessful. The
reactions of bis-phosphine 2 with [(η5-C5H5)RuCl(PPh3)2]
or, alternatively, [(η5-C5H5)RuCl(cod)] (cod = η2:η2-cyclo-
octa-1,5-diene) afforded mixtures in which complex 19 was
detected as the main product30 but could not be isolated in
pure form. Even more complicated reaction mixtures were
obtained when sequentially adding 2 and (Bu4N)Cl as a
chloride source (1 equiv of each) to [(η5-C5H5)Ru(MeCN-
κN)3][PF6] in dichloromethane. Analogous reactions with 7
were hampered by the decomposition of the ligand in the
reaction mixtures at elevated temperatures or in the presence
18 and 5.6(1)° in 19, and the rings appeared rotated from an
ideal eclipsed conformation by −37.8(3)° in 18 and by
20.6(1)° in 19.
Electrochemistry. The electrochemical behavior of the
phosphine ligands and their neutral (η6-mes)Ru(II) complexes
that form a more complete series was investigated by cyclic
voltammetry at a glassy carbon disc electrode in dichloro-
methane containing Bu4N[PF6] as the supporting electrolyte,
with particular focus on the anodic region where the oxidation
of the metal centers was expected.
−
of PF6 .
The formation of complexes 18 and 19 was clearly indicated
by 31P NMR spectra showing a pair of doublets due to
interacting nonequivalent Ru-bound phosphorus atoms. In
addition, H and 13C NMR spectra of isolated complex 18
In line with previous reports,32 dppf underwent an oxidation
at 0.18 V versus ferrocene/ferrocenium reference (Figure 7).
This redox process, attributable to the ferrocene/ferrocenium
couple, was followed by chemical reactions that made it
quasireversible within the usual time scale of cyclic
voltammetry: Relatively faster scanning rendered the oxidation
virtually reversible, whereas slower scan rates or scanning
toward more positive potentials made it practically irreversible
(additional ill-defined oxidative waves due to newly formed
species could be observed at higher potentials; see Figure 7).
The redox response33 of semihomologous bis-phosphine 1 was
practically identical except that the redox wave was shifted to
less positive potentials (E = 0.08 V) because the influence of
one of the electron-withdrawing phosphine moieties was
lessened by the nonconjugated methylene spacer (σp for PPh2
is 0.19).34
1
displayed eight resonances for the diastereotopic ferrocene CH
groups (the Ru atom in 18 becomes a stereogenic center).
Although we could not isolate pure bulk samples of 19, we
serendipitously obtained a few single crystals of this compound
(as solvate 19·CH2Cl2) and were thus able to structurally
authenticate both 18 and 19 by X-ray diffraction analysis
(Figure 6).
Complexes 18 and 19 adopted the typical piano stool
structures similar to those of 16 and 17 (the Ru−C distances
in 18 and 19 were slightly shorter than in arene complex 16,
presumably strengthened by a stronger interaction with the
anionic cyclopentadienyl ligand). In both compounds, the Ru−
P bond involving the ferrocene-bound PPh2 group was longer
than the Ru−P bond with the CH2PR2 (R = H and Ph)
moiety. Both homologated ligands 1 and 2 forced wider bite
angles than did dppf in 17 (95.01(4)°).31 The dihedral angles
between the ferrocene cyclopentadienyl rings were 2.4(2)° in
For bis-phosphine 2, the ferrocene-centered oxidation was
essentially reversible at a 0.10 V s−1 scan rate and occurred at E
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Figure 7. Cyclic voltammograms of dppf and 1. The voltammograms recorded at a scan rate of 0.10 V s−1 are shown in red, and those at 0.010 V
−1 are shown in blue. The ratio of the anodic peak currents determined at 0.10 and 0.010 V s−1 scan rates, ipa(0.10)/ipa(0.010), was 2.9 for both
s
compounds (the theoretical value is 10 ≈ 3.16).
Figure 8. (left) Cyclic voltammograms of 2. The voltammograms recorded in dichloromethane at a scan rate 0.10 V s−1 are shown in red, and those
recorded at 0.010 V s−1 are shown in blue. (right) Cyclic voltammograms of 6 (blue) and 7 (red). The second scan is shown as a dashed line.
= 0.08 V, thus reflecting the presence of the methylene linker
that minimizes the influence of the attached moiety (PPh2 vs
PH2; Figure 7). At more positive potentials, an additional
redox event was observed, consisting of two closely spaced,
irreversible oxidations that convoluted into a composite wave
peaking at E ≈ 0.70 V and associated with a counter wave at
approximately 0.43 V (peak potentials at 0.10 V s−1 are given).
The cyclic voltammogram of phosphine oxide 7 also displayed
two redox changes in the anodic region (Figure 8). Initially,
the compound underwent a reversible oxidation presumably
located at the ferrocene core. The redox wave occurred at
more positive potentials (E = 0.17 V) with respect to that of 2,
in line with the electron-withdrawing nature of the CH2P(O)-
H2 moiety. The second oxidation at E = 0.59 V was also
reversible but affected the preceding redox step during reverse
scan. Finally, adduct 6 showed a single reversible oxidation in
the accessible potential range (Figure 7). The position of the
wave (E = 0.32 V) suggested further electron density removal
from the ferrocene core associated with P → B donation. In its
anodic branch, the redox wave was preceded by a prepeak,
which disappeared (or decreased in intensity) upon repeated
scanning and was explained by adsorption phenomena.
Overall, the initial oxidation of the studied phosphine
ligands can be ascribed to oxidation of the ferrocene unit, as
expected because the HOMO orbital of dppf is prevalently
localized at the ferrocene core.35 In some cases, the
reversibility of the ferrocene/ferrocenium redox transition is
affected by follow-up reactions in which the electro-generated
product is converted into other species (typically redox-active)
and can be linked to electron density relocations within the
conjugated ferrocene−phosphine system.36 The subsequent
oxidative steps are difficult to explain because they are often of
a composite nature and can be affected by chemical processes
coupled with the preceding redox step.
Complex 10, combining redox sites of two types (i.e., the
ferrocene unit and two equivalent (η6-arene)Ru(II) frag-
ments), underwent two successive oxidations.37 The first
reversible oxidation, which occurred at E = 0.16 V due to the
ferrocene ligand, was followed by an irreversible oxidation at
0.75 V (peak potential at 0.10 V s−1 is given), corresponding to
a simultaneous one-electron irreversible oxidation of the two
chemically equivalent Ru(II) centers. Similar behavior was
reported for the analogous (η6-arene)Ru(II) complexes
featuring dppf and A as the bridging ligands24a,b and was
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also observed for 11−13 (Figure 9). The ferrocene units in 11,
12, and 13 were oxidized reversibly at E = 0.06, 0.11, and 0.11
dirutenium complex). The results outlined in Table 1 indicate
the superior performance of the (η6-mes)Ru(II) complexes,
which can be related to their easier catalytic activation,
presumably by removal of the Ru-bound chloride ligand that
provides a vacant coordination at Ru. Among the arene
complexes, the compound with tertiary phosphine ligands
performed better than “hydroxyphosphine” complex 13, and
the most active dppf-based catalyst (10) also showed the
highest selectivity to (E)-alkene.
The other testing reaction was the cycloisomerization of
(Z)-3-methylpent-2-en-4-yn-1-ol (22) into 2,3-dimethylfuran
(23; Table 2).42 In these experiments, the Ru catalyst (0.3 mol
Table 2. Ru-Catalyzed Cyclization of Enynol 22
catalyst
yield of 23 (%)
catalyst
yield of 23 (%)
10
11
12
76
81
80
13
17
18
78
0
0
Figure 9. Cyclic voltammograms of 12 (red) and 15 (blue) as
recorded in dichloromethane at scan rate 0.10 V s−1. The second scan
is shown by dashed line.
a
Neat substrate 22 and Ru-catalysts (0.3 mol %) were reacted at
room temperature (23−25 °C) in the air for 18 h. The yield was
1
V, respectively, whereas the two nonequivalent Ru(II) centers,
distinguished by the asymmetric bis-phosphine ligands, were
oxidized in two closely separated irreversible redox steps in the
0.70−0.87 V range. Similar to the respective free ligand, the
first oxidation of complex 15 was shifted to 0.27 V, reflecting
the presence of the BH3 unit (see above), followed by an
additional one-electron irreversible oxidation of the RuII center
at 0.77 V (peak potential determined at 0.10 V s−1). Complex
14 could not be analyzed due to its instability in the presence
determined by H NMR spectroscopy.
%) was added directly to the neat substrate, and the reaction
was allowed to proceed in the air for 18 h. To our delight,
arene complexes 10−13 were catalytically active, even at room
temperature, without requiring a high temperature to initiate
the cyclization reaction, in contrast to other Ru catalysts.42,43
However, the product yields achieved with 10−13 varied only
slightly. The (η5-C5H5)Ru(II) complexes, 17 and 18, showed
no appreciable activity.
−
of the PF6 anion.
Catalytic Testing. Considering the wide applications of
ruthenium compounds in transition metal catalysis,38 we
evaluated the diruthenium(II) complexes, choosing two
reactions that manipulate unsaturated C−C bonds and
focusing on the possible influence of the different P-donor
moieties. The first series of experiments was performed using a
model catalytic double bond isomerization of estragole (20) to
anethole (21; see Table 1),39 in which the beneficial effect of
the P−OH moiety has been recently established.40 The
reaction was performed in water41 using potassium carbonate
as a base in the presence of 1 mol % Ru (i.e., 0.5 mol %
CONCLUSION
■
The findings of this study further demonstrate that the
“homologation” approach is a viable route toward new
unsymmetric ligands with modified steric and electronic
properties. Newly prepared bis-phosphine 2, combining
primary and tertiary phosphine moieties in its structure, and
phosphine-phosphine oxide 7, which is the first phosphine
ligand bearing an additional primary phosphine oxide moiety,
are remarkably stable and hence suitable for further synthesis
(this was already exemplified by the 2 → 1 conversion
reported herein) and for other applications (e.g., catalytic).
Moreover, both structural and electrochemical data indicate
that the two different donor moieties available in these ligands
differentiate the coordinated metal fragments, which can
further affect catalytic applications of these ligands.
a
Table 1. Ru-Catalyzed Isomerization of Estragole in Water
EXPERIMENTAL SECTION
catalyst
conversion (%)
E/Z
■
Materials and Methods. All syntheses were performed in argon
or nitrogen atmosphere using standard Schlenk techniques and oven-
dried glassware. Compounds 3,13d [(η5-C5H5)RuCl(PPh3)2],44 [(η5-
C5H5)Ru(MeCN-κN)3][PF6],45 and [(η5-C5H5)RuCl(cod)]46 (cod =
η2:η2-cycloocta-1,5-diene) were prepared according to literature
procedures. Other chemicals were purchased from commercial
suppliers (Sigma-Aldrich or Alfa-Aesar) and used as received.
Anhydrous dichloromethane, tetrahydrofuran and methanol used for
syntheses were prepared using a PureSolv MD5 solvent purification
system (Innovative Technology). Acetonitrile and toluene were dried
over anhydrous potassium carbonate and sodium metal, respectively,
10
11
12
13
17
18
97
85
68
25
<5
<5
90/10
78/22
76/24
70/30
a
Reaction conditions: 1 mol % [Ru], K2CO3 (6 mol %), and estragole
(2.0 mmol) were reacted in 1 mL of water at 80 °C for 6 h. The
conversion was determined by H NMR spectroscopy.
1
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and distilled prior to use. Solvents used for crystallizations and for
chromatography (reagent-grade; Lach-Ner, Czech Republic) were
utilized without additional purification.
cooling on ice. The resulting mixture was stirred for 10 min before
adding a solution of ester 4 (3.20 g, 6.0 mmol in 100 mL of THF).
After completing the addition, the cooling bath was removed, and the
reaction mixture was stirred at room temperature overnight. Then, the
reaction flask was cooled in an ice bath, and methanol (200 mL) was
cautiously added to terminate the reaction. The resulting mixture was
evaporated under vacuum, leaving an orange residue, which was taken
up with hexane (300 mL), filtered, and evaporated. The residue was
redissolved in chloroform, filtered, and evaporated to give pure
phosphine 5 as an orange oil. Yield: 2.53 g (98%).
NMR spectra were recorded at 25 °C on a Varian Unity Inova 400
1
spectrometer operating at 400, 101, and 162 MHz for H, 13C, and
31P, respectively. Chemical shifts (δ in ppm) are given relative to
internal tetramethylsilane (1H and 13C) and to external 85% aqueous
H3PO4 (31P). FTIR spectra were acquired with a Thermo Nicolet
6700 instrument over the 400−4000 cm−1 range. Electrospray
ionization (ESI) mass spectra were recorded on a Compact QTOF-
MS spectrometer (Bruker Daltonics). Elemental analyses were
conducted using a PE 2400 Series II CHNS/O Elemental Analyzer
(PerkinElmer). The amount of residual solvent(s) was verified by
NMR analysis.
1H NMR (400 MHz, CDCl3): δ 0.8−1.7 (br m, 3H, BH3), 2.27
3
2
1
(td, JHH = 7.5 Hz, JPH = 4.6 Hz, 2H, CH2), 2.78 (dm, JPH = 194.0
Hz, 2H, PH2), 3.99 (vt, J′ = 1.8 Hz, 2H, fc), 4.08 (vt, J′ = 1.8 Hz, 2H,
fc), 4.35 (vq, J′ = 2.0 Hz, 2H, fc), 4.48−4.50 (m, 2H, fc), 7.38−7.49
(m, 6H, PPh2), 7.55−7.62 (m, 4H, PPh2). 13C{1H} NMR (101 MHz,
CDCl3): δ 13.86 (d, JPC = 9 Hz, CH2), 68.85 (d, JPC = 69 Hz, Cipso of
fc), 69.26 (s, CH of fc), 69.60 (d, JPC = 3 Hz, CH of fc), 72.64 (d, JPC
= 8 Hz, CH of fc), 73.58 (d, JPC = 10 Hz, CH of fc), 90.84 (d, JPC = 3
Electrochemical measurements were recorded using a mAUTO-
LAB III multipurpose apparatus (Eco Chemie, Netherlands) at room
temperature and a standard three-electrode cell equipped with a glassy
carbon disc (2 mm diameter) working electrode, a platinum sheet
auxiliary electrode, and a double-junction Ag/AgCl (3 M KCl)
reference electrode. The compounds were dissolved in anhydrous
dichloromethane to give a solution containing 1 mM analyte and 0.1
M Bu4N[PF6] (Fluka, puriss grade for electrochemistry) as the
supporting electrolyte. The solutions were deaerated with argon
before the measurements and then kept under an argon blanket.
Decamethylferrocene (Alfa-Aesar) was added as an internal standard
for the final scans, and the redox potentials were converted into the
ferrocene/ferrocenium scale by subtracting 0.548 V.47
Hz, Cipso of fc), 128.40 (d, JPC = 10 Hz, CH of PPh2), 130.86 (d, JPC
=
1
2 Hz, CH of PPh2), 131.38 (d, JPC = 59 Hz, Cipso of PPh2), 132.64
(d, JPC = 10 Hz, CH of PPh2). 31P{1H} NMR (162 MHz, CDCl3): δ
−125.9 (s, PH2), 16.4 (br d, J = 74 Hz, PPh2BH3). 31P NMR (162
1
2
MHz, CDCl3): δ −125.9 (tt, JPH = 194 Hz, JPH = 5 Hz, PH2), 16.4
(br m, PPh2BH3). IR (Nujol) νmax: 3078 m, 3056 m, 2366 s, 2336 s,
2293 w, 1981 w, 1792 w, 1749 w, 1734 w, 1717 w, 1697 w, 1684 w,
1670 w, 1653w, 1647 w, 1636 w, 1584 w, 1576 w, 1559 w, 1540 w,
1521 w, 1507 w, 1457 s, 1435 s, 1418 w, 1313 m, 1198 w, 1182 m,
1174 m, 1134 m, 1109 s, 1059 s, 1027 s, 998 w, 928 m, 896 w, 830 s,
759 m, 741 s, 701 s, 669 m, 637 s, 622 m, 610 m, 531 m, 496 s, 466 s,
439 m, 419 w cm−1. ESI-MS (m/z): 429 ([M − H]+). Anal. Calcd for
C23H22FeP2 (430.0): C, 64.24; H, 5.86. Found: C, 64.25; H, 5.67.
Synthesis of 1-(Diphenylphosphino)-1′-(phosphino-
methyl)ferrocene (2). A reaction flask was charged with adduct 5
(2.58 g, 6.0 mmol) and 1,4-diazabicyclo[2.2.2]octane (1.35 g, 12.0
mmol). Dry tetrahydrofuran (50 mL) was introduced under argon,
and the resulting solution was stirred at 45 °C overnight. Subsequent
evaporation produced an orange residue, which was purified by
chromatography over silica gel, eluting with diethyl ether−hexane
(1:1). A single broad orange band was collected and evaporated,
affording 2 as an orange solid. The compound was further crystallized
from hot heptane. Yield: 1.80 g (72%), orange crystalline solid. Mp
114 °C (heptane).
Synthesis of 1-(Diphenylphosphino)-1′-[(diethoxy-
phosphinyl)methyl]ferrocene−borane (1:1) (4). A reaction
flask equipped with a large stirring bar was charged with alcohol 3
(4.14 g, 10.0 mmol), zinc(II) iodide (3.50 g, 11.0 mmol), and triethyl
phosphite (17 mL, 100 mol) under argon (the content of the reaction
flask gently warmed upon mixing). The resulting mixture was stirred
at room temperature overnight and then diluted with chloroform (180
mL) and 3 M aqueous hydrochloric acid (80 mL). The organic layer
was separated, washed with brine (200 mL), dried over anhydrous
magnesium sulfate, and evaporated under reduced pressure. The oily
residue was kept under oil pump vacuum (3 × 10−3 Torr at 50 °C) to
remove the excess of triethyl phosphite and subsequently purified by
column chromatography (silica gel, ethyl acetate). A second orange
band was collected, which afforded ester 4 after evaporation. Yield:
4.48 g (84%), orange oil. The compound may be contaminated with
up to 10% of diethyl phosphite. However, this impurity does not
hamper the subsequent reduction, after which it can be easily
removed during the crystallization step.
1H NMR (400 MHz, CDCl3): δ 2.34 (td, 3JHH = 7.3 Hz, 2JPH = 4.7
Hz, 2H, CH2), 2.82 (dm, 1JPH = 194.2 Hz, 2H, PH2), 4.00 (vt, J′ = 1.8
Hz, 2H, fc), 4.03 (vt, J′ = 1.7 Hz, 2H, fc), 4.04 (vq, J′ = 1.8 Hz, 2H,
fc), 4.34 (vt, J′ = 1.7 Hz, 2H, fc), 7.28−7.40 (m, 10H, PPh2). 13C{1H}
1H NMR (400 MHz, CDCl3): δ 0.8−1.7 (br m, 3H, BH3), 1.25 (t,
2
3JHH = 7.1 Hz, 6H, Me), 2.59 (d, JPH = 19.7 Hz, 2H, CH2P), 3.96
1
NMR (101 MHz, CDCl3): δ 14.07 (d, JPC = 9 Hz, CH2), 68.61 (s,
CH of fc), 68.77 (d, JPC = 2 Hz, CH of fc), 71.62 (d, JPC = 4 Hz, CH
of fc), 73.62 (d, JPC = 15 Hz, CH of fc), 75.79 (d, JPC = 5 Hz, Cipso of
fc), 89.89 (d, JPC = 3 Hz, Cipso of fc), 128.10 (d, JPC = 7 Hz, CH of
PPh2), 128.48 (s, CH of PPh2), 133.49 (d, JPC = 19 Hz, CH of PPh2),
(qd, J = 7.1, 0.9 Hz, 4H, CH2O), 4.02 (vt, J′ = 2.0 Hz, 2H, fc), 4.25 (d
vt, J′ = 1.0, 1.1 Hz, 2H, fc), 4.32 (vq, J′ = 2.0 Hz, 2H, fc), 4.48 (d vt, J′
= 1.1, 0.7 Hz, 2H, fc), 7.38−7.50 (m, 6H, PPh2), 7.55−7.61 (m, 4H,
3
PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ 16.43 (d, JPC = 6 Hz,
1
139.07 (d, JPC = 19 Hz, Cipso of PPh2). 31P{1H} NMR (162 MHz,
Me), 27.33 (d, 1JPC = 139 Hz, CH2P), 61.93 (d, 2JPC = 7 Hz, CH2O),
CDCl3): δ −126.7 (s, PH2), −16.2 (s, PPh2). 31P NMR (162 MHz,
69.22 (d, JPC = 68 Hz, Cipso of fc), 69.78 (s, CH of fc), 71.22 (d,JPC
=
1
2
CDCl3): δ −126.7 (tt, JPH = 194 Hz, JPH = 4 Hz, PH2), −16.2 (m,
PPh2). IR (Nujol) νmax: 3097 w, 3083 w, 3069 w, 3054 w, 3041 w,
3030 w, 3015 w, 2726 w, 2359 w, 2303 s, 2296 s, 1974 w, 1901 w,
1829 w, 1767 w, 1733 w, 1679 m, 1646 m, 1584 s, 1569 w, 1775 s,
1433 s, 1414 w, 1395 w, 1381 m, 1325 w, 1312 m, 1305 m, 1279 w,
1236 m, 1210 w, 1193 m, 1163 s, 1124 m, 1091 m, 1078 w, 1036 s,
1026 s, 998 m, 977 w, 936 w, 924 w, 916 w, 863 w, 856 m, 827 s, 812
s, 749 s, 699 s, 668 w, 661 w cm−1. ESI-HRMS: calcd for
C23H23FeOP2 ([M + H + O]+), 433.0568. Found, 433.0565. Anal.
Calcd for C23H22FeP2 (416.2): C, 66.37; H, 5.33. Found: C, 66.40; H,
5.27.
S y n t h e s i s o f 1 - ( D i p h e n y l p h o s p h i n o ) - 1 ′ -
[(diphenylphosphino)methyl]ferrocene (1). An oven-dried
Schlenk flask was charged (in this order) with phosphine 2 (205
mg, 0.5 mmol), iodobenzene (204 mg, 1.0 mmol), N,N-
diisopropylethylamine (162 mg, 1.25 mmol), and palladium(II)
acetate (5.6 mg, 25 μmol) under argon. Dry acetonitrile (5 mL) was
4 Hz, CH of fc), 72.81 (d, JPC = 7 Hz, CH of fc), 73.73 (d, JPC = 10
Hz, CH of fc), 79.77 (d,JPC = 3 Hz, Cipso of fc), 128.44 (d, JPC = 10
Hz, CH of PPh2), 130.92 (d, JPC = 3 Hz, CH of PPh2), 131.53 (s, Cipso
of PPh2), 132.62 (d, JPC = 10 Hz, CH of PPh2). 31P{1H} NMR (162
MHz, CDCl3): δ 16.4 (br s, PPh2BH3), 25.3 (s, PO(OEt)2). IR
(Nujol) νmax: 3075 w, 3056 w, 2724 w, 2349 s, 2344 s, 2255 m, 1701
m, 1588 w, 1572 w, 1483 w, 1438 s, 1415 w, 1311 w, 1251 s, 1237 m,
1217 m, 1205 w, 1182 m, 1174 m, 1130 m, 1110 s, 1059 s, 1029 s,
959 s, 928 m, 896 w, 865 m, 841 m, 823 m, 814 m, 800 m, 784 m, 764
m, 744 s, 670 s, 669 w, 639 s, 624 s, 610 s, 531 m, 495 s, 476 s, 467 m,
439 m cm−1. ESI-HRMS (m/z): calcd for C27H32BFeO3P2 ([M −
H]+), 533.1269. Found, 533.1262. Anal. Calcd for C27H33BFeO3P2
(534.2): C, 60.71; H, 6.23. Found: C, 60.58; H, 6.07.
Synthesis of 1-(Diphenylphosphino)-1′-(phosphino-
methyl)ferrocene−borane (1:1) (5). Neat trimethyl-chlorosilane
(3.8 mL, 30 mmol) was slowly introduced to a suspension of
Li[AlH4] (1.14 g, 30 mmol) in dry THF (150 mL) while stirring and
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introduced, and the reaction mixture was stirred at 80 °C overnight.
Then, the mixture was cooled to room temperature and evaporated
under vacuum with chromatographic silica gel. The crude,
preadsorbed product was transferred onto the top of a chromato-
graphic column and eluted with a diethyl ether−hexane mixture (1:1).
A single orange band was collected and evaporated, leaving phosphine
1 as orange oil, which solidifies when stored in a fridge. Yield: 220 mg
(78%).
J
PC = 7 Hz, CH of PPh2), 128.75 (s, CH of PPh2), 133.51 (d, JPC = 20
1
Hz, CH of PPh2), 138.75 (d, JPC = 9 Hz, Cipso of PPh2). 31P{1H}
NMR (162 MHz, CDCl3): δ −16.8 (s, PPh2), 9.3 (s, P(O)H2). 31P
NMR (162 MHz, CDCl3): δ −16.8 (s, PPh2·BH3), 9.3 (tt, 1JPH = 469
2
Hz, JPH = 16 Hz, P(O)H2). IR (Nujol) νmax: 3089 w, 3073 m, 3051
m, 2669 w, 2347 m, 2324 m, 1719 w, 1583 w, 1568 w, 1435 s, 1239 w,
1214 s, 1201 s, 1115 m, 1096 m, 1028 s, 1018 m, 998 w, 975 w, 914
w, 847 w, 834 m, 818 m, 752 s, 729 m, 700 s, 632 w, 489 s, 455 w, 437
w cm−1. ESI-MS (m/z): 455 ([M + Na]+), 887 ([2 M + Na]+). Anal.
Calcd for C23H22FeOP2·0.1CH2Cl2 (440.7): C, 62.96; H, 5.08.
Found: C, 62.93; H, 5.04.
Synthesis of 1-(Diphenylphosphino)-1′-{[(2-hydroxyprop-2-
yl)phosphinyl]methyl}ferrocene−borane (1:1) (8). A solution of
phosphine 6 (223 mg, 0.50 mmol) in reagent-grade acetone (5 mL)
was heated at 40 °C under argon overnight. The resulting mixture was
evaporated, and the crude product was purified by chromatography
over silica gel with a dichloromethane−methanol mixture (10:1) as
the eluent. Subsequent evaporation produced 8 as an orange powder.
Yield: 218 mg (87%).
1H NMR (400 MHz, CDCl3): δ 2.86 (s, 2H, CH2), 3.84 (vt, J′ =
1.8 Hz, 2H, fc), 3.89 (vt, J′ = 1.8 Hz, 2H, fc), 4.01 (vq, J′ = 1.9 Hz,
2H, fc), 4.32 (vt, J′ = 1.8 Hz, 2H, fc), 7.24−7.37 (m, 20H, PPh2).
31P{1H} NMR (162 MHz, CDCl3): δ −16.2 (s, PPh2), −11.4 (s,
CH2PPh2). The data match those in the literature.12a
Synthesis of 1-(Diphenylphosphino)-1′-(phosphinyl-
methyl)ferrocene−borane (1:1) (6). In air, phosphine 5 (0.70 g,
3.0 mmol) was dissolved in a mixture of methanol (20 mL) and
dichloromethane (30 mL), and the reaction flask, equipped with
stirring bar, was cooled in an ice bath. Hydrogen peroxide solution (3
mL of 30% aqueous solution, 58 mmol) was added over 5 min while
stirring, and the resulting mixture was stirred and cooled for another 5
min. Then, the excess of hydrogen peroxide was destroyed by slowly
adding saturated aqueous sodium thiosulfate (30 mL). Caution!Rapid
addition can result in overheating of the reaction mixture and
decomposition! The mixture was transferred to a separatory funnel
and diluted with dichloromethane (20 mL) and brine (30 mL). The
organic phase was separated, and the aqueous residue was extracted
with dichloromethane (20 mL). The combined organic layers were
dried over magnesium sulfate, filtered, and evaporated under vacuum.
The crude product was purified by flash chromatography over silica
gel eluting with a dichloromethane−methanol mixture (10:1).
Evaporation of the first orange band afforded phosphine oxide 6 as
a yellow solid. Yield: 613 g (84%).
1H NMR (400 MHz, CDCl3): δ 0.8−1.7 (br s, 3H, BH3), 1.35 (d,
3JPH = 14.7 Hz, 3H, Me), 1.37 (d, 3JPH = 14.9 Hz, 3H, Me), 2.65−2.82
(m, 2H, CH2), 3.79 (br s, 1H, OH), 4.03 (d vt, J′ = 1.3, 2.6 Hz, 1H,
fc), 4.05 (d vt, J′ = 1.4, 2.5 Hz, 1H, fc), 4.25−4.28 (m, 2H, fc), 4.33−
4.36 (m, 2H, fc), 4.52−4.54 (m, 2H, fc), 6.33 (ddd, 1JPH = 454.9 Hz,
J
HH = 5.1, 1.9 Hz, 1H, PH), 7.38−7.50 (m, 6H, PPh2), 7.54−7.62 (m,
4H, PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ 23.85 (d, JPC = 8
2
2
1
Hz, Me), 24.59 (d, JPC = 9 Hz, Me), 25.65 (d, JPC = 56 Hz, CH2),
69.11 (s, C−OH), 69.84 (d, JPC = 9 Hz, Cipso of fc), 69.91 (s, CH of
fc), 70.06 (s, CH of fc), 70.91 (d, JPC = 3 Hz, CH of fc), 71.21 (d, JPC
= 3 Hz, CH of fc), 72.80 (d, JPC = 7 Hz, CH of fc), 72.88 (d, JPC = 7
Hz, CH of fc), 73.70 (d, JPC = 9 Hz, CH of fc), 74.10 (d, JPC = 10 Hz,
CH of fc), 79.91 (d, JPC = 4 Hz, Cipso of fc), 128.49 (d, JPC = 10 Hz,
CH of PPh2), 128.50 (d, JPC = 10 Hz, CH of PPh2), 130.98 (d, JPC = 2
Hz, CH of PPh2), 131.02 (d, 1JPC = 59 Hz, Cipso of PPh2), 131.05 (d,
1H NMR (400 MHz, CDCl3): δ 0.8−1.7 (br m, 3H, BH3), 2.78
(dt, 2JPH = 16.0 Hz, 3JHH = 4.6 Hz, 2H, CH2), 4.09 (t, J′ = 1.9 Hz, 2H,
fc), 4.19 (dt, J′ = 0.9, 1.9 Hz, 2H, fc), 4.38 (q, J′ = 1.8 Hz, 2H, fc),
4.56 (dt, J′ = 1.1, 1.9 Hz, 2H, fc), 6.79 (dt, 1JPH = 470.0 Hz, 3JHH = 4.6
Hz, 2H, P(O)H2), 7.40−7.52 (m, 6H, PPh2), 7.56−7.62 (m, 4H,
PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ 28.20 (d, 1JPC = 62 Hz,
CH2), 69.72 (d, JPC = 68 Hz, Cipso of fc), 70.25 (s, CH of fc), 70.84
(d, JPC = 4 Hz, CH of fc), 72.74 (d, JPC = 8 Hz, CH of fc), 73.98 (d,
JPC = 2 Hz, CH of PPh2), 131.13 (d, JPC = 59 Hz, Cipso of PPh2),
1
132.60 (d, JPC = 9 Hz, CH of PPh2), 132.62 (d, JPC = 9 Hz, CH of
PPh2). 31P{1H} NMR (162 MHz, CDCl3): δ 16.3 (br s, PPh2BH3),
46.0 (s, P(O)H). 31P NMR (162 MHz, CDCl3): δ 16.3 (br m,
PPh2BH3), 46.0 (dm, 1JPH = 455 Hz, P(O)H). IR (Nujol) νmax: 3177
br m, 2332 m, 1629 w, 1309 w, 1202 s, 1172 m, 1157 w, 1135 m,
1109 m, 1059 m, 1029 m, 998 w, 974 w, 942 m, 929 m, 836 m, 819 m,
804 m, 764 m, 739 s, 702 s, 638 m, 608 m, 531 w, 499 m, 471 m, 442
w cm−1. ESI-MS (m/z): 527 ([M + Na]+), 1031 ([2 M + Na]+). Anal.
Calcd for C26H31BFeO2P2·0.25CH2Cl2 (525.4): C, 60.01; H, 6.04.
Found: C, 59.84; H, 5.95.
Synthesis of 1-(Diphenylphosphino)-1′-{[(2-hydroxyprop-2-
yl)phosphinyl]methyl}ferrocene (9). Phosphine 7 (173 mg, 0.40
mmol) was dissolved in reagent-grade acetone (5 mL), and the
solution was stirred at 40 °C under argon overnight. The mixture was
cooled to room temperature and evaporated under vacuum, leaving a
crude product, which was purified over silica gel using a dichloro-
methane−methanol mixture (10:1) as the eluent. Evaporation of the
second orange band afforded 9 as an orange solid. Yield: 155 mg
(79%). Crystals suitable for structure determination were obtained by
recrystallization from ethyl acetate/hexane.
J
PC = 9 Hz, CH of fc), 128.54 (d, JPC = 10 Hz, CH of PPh2), 130.97
(d, 1JPC = 60 Hz, Cipso of PPh2), 131.12 (d, JPC = 2 Hz, CH of PPh2),
132.62 (d, JPC = 10 Hz, CH of PPh2); the signal due to Cipso of fc is
obscured by the solvent resonance. 31P{1H} NMR (162 MHz,
CDCl3): δ 8.5 (s, P(O)H2), 16.2 (br m, PPh2). 31P NMR (162 MHz,
CDCl3): δ 8.5 (tt, 1JPH = 470 Hz, 2JPH = 16 Hz, P(O)H2), 16.2 (br m,
PPh2). IR (DRIFTS) νmax: 3074 m, 2383 s, 2344 s, 2247 w, 1587 w,
1485 m, 1466 m, 1434 s, 1387 w, 1363 w, 1363 w, 1311 w, 1250 w,
1220 s, 1201 s, 1182 s, 1172 s, 1129 m, 1109 s, 1060 s, 1025 s, 999 m,
924 w, 911 w, 870 w, 861 w, 837 s, 822 w, 810 w, 779 w, 762 w, 743 s,
700 s, 639 m, 624 s, 612 m, 531 m, 511 m, 496 s, 473 s, 441 w cm−1
.
ESI-MS (m/z): 469 ([M + Na]+), 915 ([2 M + Na]+). Anal. Calcd for
C23H25BFeOP2 (446.0): C, 61.93; H, 5.65. Found: C, 61.74; H, 5.61.
Synthesis of 1-(Diphenylphosphino)-1′-(phosphinyl-
methyl)ferrocene (7). Compound 6 (89.2 mg, 0.20 mmol), 1,4-
diazabicyclo[2.2.2]octane (26.9, 0.24 mmol), and tetrahydrofuran (5
mL) were mixed in a reaction flask under argon, and the mixture was
stirred at 50 °C overnight. Subsequent evaporation afforded an orange
residue, which was purified by chromatography over silica gel, eluting
with a dichloromethane−methanol mixture (10:1). The first orange
band was collected and evaporated to give phosphine 7 as orange oil,
which gradually solidified. Yield: 82 mg (95%). Mp 107 °C
(amorphous sample).
1H NMR (400 MHz, CDCl3): δ 1.34 (d, 3JPH = 12.9 Hz, 3H, Me),
1.38 (d, 3JPH = 13.0 Hz, 3H, Me), 2.72 (d, 3JHH = 3.5 Hz, 1H, CH2),
3
3
2.75 (d, JHH = 3.5 Hz, 1H, CH2), 3.25 (d, JPH = 3.8 Hz, 1H, OH),
4.04−4.08 (m, 4H, fc), 4.15 (vd, J′ = 1.4 Hz, 1H, fc), 4.20 (vd, J′ =
1
1.3 Hz, 1H, fc), 4.37 (vt, J′ = 1.8 Hz, 2H, fc), 6.35 (dt, JPH = 454.1
Hz, JHH = 3.5 Hz, 1H, PH), 7.30−7.39 (m, 10H, PPh2). 13C{1H}
3
2
NMR (101 MHz, CDCl3): δ 23.87 (d, JPH = 7 Hz, Me), 24.75 (d,
2JPH = 8 Hz, Me), 26.26 (d, 1JPH = 53 Hz, CH2), 69.40 (s, CH of fc),
69.69 (s, CH of fc), 70.08 (br s, CH of fc), 70.47 (br s, CH of fc),
71.89 (br s, 2CH of fc), 73.90 (d, JPC = 11 Hz, CH of fc), 74.04 (d,
JPC = 11 Hz, CH of fc), 78.87 (br s, Cipso of fc), 128.22 (s, CH of
PPh2), 128.65 (s, CH of PPh2), 133.57 (d, JPH = 17 Hz, CH of PPh2),
138.91 (s, Cipso of PPh2). Signals due to C−OH and Cipso fc were not
observed, presumably due to overlaps. 31P{1H} NMR (162 MHz,
CDCl3): δ −16.8 (s, PPh2), 45.9 (s, P(O)H). 31P NMR (162 MHz,
2
3
1H NMR (400 MHz, CDCl3): δ 2.78 (dt, JPH = 16.2 Hz, JHH
=
4.7 Hz, 2H, CH2), 4.08−4.11 (m, 6H, fc), 4.40 (vt, J′ = 1.8 Hz, 2H,
1
3
fc), 6.77 (dt, JPH = 469.3 Hz, JHH = 4.7 Hz, 2H, P(O)H2), 7.31−
7.40 (m, 10H, PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ 28.24 (d,
1JPC = 62 Hz, CH2), 69.04 (d, JPC = 84 Hz, Cipso of fc), 69.74 (s, CH
of fc), 70.03 (d, JPC = 4 Hz, CH of fc), 71.79 (d, JPC = 4 Hz, CH of
fc), 73.99 (d, JPC = 15 Hz, CH of fc), 75.91 (s, Cipso of fc), 128.25 (d,
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CDCl3): δ 16.8 (s, PPh2), 45.9 (d of septets, 1JPH = 454 Hz, 2JPH = 13
Hz, P(O)H). IR (Nujol) νmax: 3146 br s, 3066 m, 2326 s, 2170 w,
2066 w, 1435 s, 1210 w, 1192 m, 1119 s, 1097 m, 1030 m, 999 w, 975
m, 925 w, 908 m, 846 m, 804 s, 751 s, 743 s, 699 s, 568 w, 527 w, 503
s, 484 m, 462 w cm−1. ESI-MS (m/z): 529 ([M + O + Na]+), 1003
([2 M + Na]+). Anal. Calcd for C26H28FeO2P2·0.2CH2Cl2 (507.3): C,
62.03; H, 5.64. Found: C, 62.01; H, 5.41.
Synthesis of [μ-1κP:2κP′-1,1′-Bis(diphenylphosphino)-
ferrocene]bis[dichloro(η6-mesitylene)ruthenium(II)] (10).
[{(η6-Mesitylene)RuCl(μ-Cl)}2] (58 mg, 0.10 mmol) and dppf (55
mg, 0.10 mmol) were dissolved in dichloromethane (40 mL) under
argon, and the solution was stirred overnight. Subsequent evaporation
afforded analytically pure complex 10 as a red solid in quantitative
yield. Crystals suitable for structure determination were grown from a
dichloromethane/hexane mixture. The yield of crystalline material
was 58 mg (50%).
Hz, Me), 19.26 (d, 1JPC = 19 Hz, CH2), 70.40 (s, CH of fc), 70.97 (s,
CH of fc), 71.05 (s, CH of fc), 76.38 (d, JPC = 25 Hz, Cipso of fc),
82.06 (d, JPC = 5 Hz, CH of C6H3), 85.98 (d, JPC = 6 Hz, CH of fc),
86.57 (d, JPC = 4 Hz, CH of C6H3), 103.02 (br s, Cipso of C6H3),
104.48 (d, JPC = 2 Hz, Cipso of C6H3), 127.27 (d, JPC = 10 Hz, CH of
PPh2), 129.91 (d, JPC = 2 Hz, CH of PPh2), 133.95 (br s, CH of
PPh2). The signals due to Cipso of fc and PPh2 were not observed.
31P{1H} NMR (162 MHz, CDCl3): δ −19.4 (s, PH2), 20.8 (s, PPh2).
31P NMR (162 MHz, CDCl3): δ −19.4 (t, 1JPH = 361 Hz, PH2), 20.8
(s, PPh2). IR (Nujol) νmax: 1933 w, 1526 m, 1298 m, 1192 w, 1161 m,
1085 m, 1031 s, 930 m, 884 s, 837 m, 814 w, 760 s, 749 m, 698 s, 543
m, 524 m, 490 m, 469 m, 444 w, 426 w cm−1. ESI-MS (m/z): 669
([(M − RuCl2(mes) − 2Cl + OMe]+). Anal. Calcd for
C41H46Cl4FeP2Ru2·0.25CHCl3 (1030.4): C, 48.08; H, 4.52. Found:
C, 48.49; H, 4.44.
Synthesis of {μ-1κP:2κP′-1-(Diphenylphosphino)-1′-
[(hydroxyphosphino)methyl]ferrocene}bis[dichloro(η6-
mesitylene)ruthenium(II)] (13). Ligand 7 (43 mg, 0.10 mmol) and
[{(η6-mesitylene)RuCl(μ-Cl)}2] (58 mg, 0.10 mmol) were dissolved
in dichloromethane (10 mL), and the resulting mixture was stirred
overnight. Subsequent evaporation afforded pure complex 13 as a red
solid in an essentially quantitative yield (102 mg).
1H NMR (400 MHz, CDCl3): δ 1.87 (s, 18H, Me), 4.10 (very br s,
8H, CH of fc), 4.40 (s, 6H, C6H3), 7.27−7.37 (m, 12H, PPh2), 7.63−
7.72 (m, 8H, PPh2). 31P{1H} NMR (162 MHz, CDCl3): δ 20.7 (s).
IR (Nujol) νmax: 3567 br m, 3053 s, 1992 w, 1586 w, 1570 w, 1559 w,
1540 m, 1528 m, 1507 w, 1482 m, 1265 m, 1190 m, 1092 m, 1073 m,
1026 s, 879 w, 839 s, 751 s, 728 m, 698 s, 669 w, 623 w, 570 w, 542 s,
523 s, 487 m, 471 s, 445 m cm−1. ESI-MS (m/z): 811 ([M −
(mes)RuCl2 − Cl)]+). Anal. Calcd for C52H52Cl4FeRu2P2·1.5CH2Cl2
(1266.1): C, 50.75; H, 4.38. Found: C, 50.86; H, 4.29.
1H NMR (400 MHz, CDCl3): δ 1.94 (s, 9H, Me), 2.08 (d, JPC
=
0.8 Hz, 9H, Me), 3.22−3.50 (m, 2H, CH2), 3.41 (br s, 1H, fc), 3.69
(br s, 1H, fc), 4.00 (br s, 2H, fc), 4.45−4.55 (m, 7H, 3H of C6H3 and
1
3
4H of fc), 4.88 (s, 3H, C6H3), 6.80 (dt, JPH = 377.9 Hz, JHH = 5.4
Hz, 1H, PH), 7.34−7.42 (m, 6H, PPh2), 7.74−7.87 (m, 4H, PPh2).
13C{1H} NMR (101 MHz, CDCl3): δ 18.26 (s, Me), 18.73 (s, Me),
30.35 (br s, CH2), 70.29 (s, CH of fc), 70.91 (s, CH of fc), 71.26 (s,
CH of fc), 71.62 (s, CH of fc), 72.89 (s, Cipso of fc), 82.20 (s, Cipso of
fc), 82.77 (s, CH of C6H3), 86.55 (s, CH of C6H3), 103.05 (s, Cipso of
C6H3), 105.85 (s, Cipso of C6H3), 127.15 (d, JPC = 16 Hz, CH of
PPh2), 127.38 (d, JPC = 10 Hz, CH of PPh2), 129.94 (d, JPC = 9.0 Hz,
Synthesis of {μ-1κP:2κP′-1-(Diphenylphosphino)-1′-
[(diphenylphosphino)methyl]ferrocene}bis[dichloro(η6-
mesitylene)ruthenium(II)] (11). [{(η6-Mesitylene)RuCl(μ-Cl)}2]
(41 mg, 0.070 mmol) and phosphine 1 (40 mg, 0.070 mmol) were
dissolved in dichloromethane (20 mL) under argon, and the mixture
was stirred overnight. Subsequent evaporation produced a red solid,
which was redissolved in dichloromethane (3 mL), precipitated with
pentane, and isolated by suction. Yield of 11:64 mg (68%), red solid.
1H NMR (400 MHz, CDCl3): δ 1.84 (s, 9H, Me), 1.89 (s, 9H,
Me), 3.02 (br s, 2H, fc), 3.34 (br s, 2H, fc), 3.54 (br d, 2JPH = 7.1 Hz,
2H, CH2), 4.33 (br vq, J′ = 1.2 Hz, 2H, fc), 4.42 (br s, 2H, fc), 4.44
(s, 3H, C6H3), 4.65 (s, 3H, C6H3), 7.24−7.36 (m, 10H, PPh2), 7.38−
7.44 (m, 2H, PPh2), 7.60−7.68 (m, 4H, PPh2), 7.68−7.76 (m, 4H,
PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ 18.23 (s, Me), 18.36 (s,
Me), 26.89 (d, 1JPC = 24 Hz, CH2), 71.41 (s, CH of fc), 71.86 (s, CH
of fc), 72.01 (d, JPC = 8 Hz, CH of fc), 75.27 (br s, CH of fc), 82.24
(d, JPC = 8.5 Hz, Cipso of fc), 86.17 (d, JPC = 4 Hz, CH of C6H3), 87.20
(d, JPC = 3 Hz, CH of C6H3), 100.90 (d, JPC = 3 Hz, Cipso of C6H3),
102.86 (d, JPC = 2 Hz, Cipso of C6H3), 126.96 (d, JPC = 10 Hz, CH of
PPh2), 127.73 (d, JPC = 9 Hz, CH of PPh2), 129.69 (br s, CH of
PPh2), 130.46 (d, JPC = 2 Hz, CH of PPh2), 130.73 (d, JPC = 42 Hz,
1
CH of PPh2), 133.97 (br d, JPH = 112 Hz, Cipso of PPh2). 31P{1H}
NMR (162 MHz, CDCl3): δ 20.7 (s, PPh2), 117.1 (br s, P(OH)H).
31P NMR (162 MHz, CDCl3): δ 20.7 (s, PPh2), 117.1 (d, 1JPH = 378
Hz, P(OH)H). IR (Nujol) νmax: 1524 m, 1094 m, 1031 m, 931 w, 878
s, 836 w, 748 m, 699 m, 543 m, 523 m, 487 m, 471 m, 434 w cm−1.
ESI-MS (m/z): 945 ([M − HCl − Cl]+), 1237 ([M + RuCl2(mes) −
HCl − Cl]+). Anal. Calcd for C41H46Cl4FeOP2Ru2 (1016.5): C,
48.44; H, 4.56. Found: C, 48.16; H, 4.58.
Synthesis of {1-(Diphenylphosphino-κP)-1′-[(phosphinyl)-
methyl]ferrocene}[dichloro(η6-mesitylene)ruthenium(II)] (14).
Phosphine 7 (95 mg, 0.22 mmol) and [{(η6-mesitylene)RuCl(μ-
Cl)}2] (64 mg, 0.11 mmol) were dissolved in dichloromethane (15
mL). The resulting mixture was stirred overnight and then
evaporated, leaving complex 14 as an orange powdery solid in a
quantitate yield.
C
ipso of PPh2), 133.88 (d, JPC = 9 Hz, CH of PPh2), 134.25 (br d, JPC
= 6 Hz, CH of PPh2). The signals due to Cipso of fc and PPh2 were not
observed, presumably due to overlaps. 31P{1H} NMR (162 MHz,
CDCl3): δ 21.8 (s, PPh2), 30.4 (s, CH2PPh2). IR (Nujol) νmax: 2726
w, 1992 w, 1541 w, 1507 w, 1299 m, 1096 m, 1030 m, 922 w, 841 s,
746 m, 698 m, 669 w, 558 m, 537 w, 497 m cm−1. ESI-MSI (m/z):
789 ([M − (mes)RuCl2 − HCl − Cl]+). Anal. Calcd for
C54H54Cl4FeRu2P2·0.5CH2Cl2 (1195.2): C, 53.76; H, 4.64. Found:
C, 53.73; H, 4.55.
1H NMR (400 MHz, CDCl3): δ 1.91 (br s, 9H, Me), 2.96 (br d,
2JPH = 16.0 Hz, 2H, CH2), 3.58 (br s, 2H, fc), 3.86 (br s, 2H, fc), 4.44
(br s, 2H, fc), 4.54 (br s, 5H, 3H of C6H3 and 2H of fc), 6.79 (dt, 1JPH
3
= 470 Hz, JPH = 4.5 Hz, 2H, P(O)H2), 7.35−7.45 (m, 6H, PPh2),
7.78−7.85 (m, 4H, PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ
1
18.23 (s, Me), 28.04 (d, JPC = 62 Hz, CH2), 70.73 (s, CH of fc),
70.83 (br s, 2 × CH of fc), 71.70 (s, CH of fc), 77.22 (s, CH of fc),
86.98 (s, CH of C6H3), 102.56 (s, Cipso of C6H3), 127.05 (d, JPC = 10
Hz, CH of PPh2), 130.01 (d, JPC = 2 Hz, CH of PPh2), 133.88 (br s,
CH of PPh2). The signals due to Cipso of fc and PPh2 were not
observed. 31P{1H} NMR (162 MHz, CDCl3): δ 9.4 (s, P(O)H2), 21.1
(br s, PPh2). 31P NMR (162 MHz, CDCl3): δ 9.4 (tt, 1JPH = 470 Hz,
2JPH = 16 Hz, P(O)H2), 21.1 (br s, PPh2). IR (Nujol) νmax: 1541 w,
1250 w, 1221 w, 1193 w, 1027 s, 835 w, 822 w, 762 w, 746 w, 697 w,
545 m, 523 w, 483 w, 474 w, 458 w, 444 w, 420 w cm−1. ESI-MS (m/
z): 685 ([M − 2Cl + OMe]+), 1369 ([2M − HCl−3Cl + 2OMe]+).
Anal. Calcd for C32H34Cl2FeOP2Ru·0.2CH2Cl2 (741.4): C, 52.17; H,
4.68. Found: C, 52.30; H, 4.64.
Synthesis of [μ-1κP:2κP′-1-(Diphenylphosphino)-1′-
(phosphinomethyl)ferrocene]bis[dichloro(η6-mesitylene)-
ruthenium(II)] (12). [{(η6-Mesitylene)RuCl(μ-Cl)}2] (32 mg, 0.10
mmol) and phosphine 2 (58 mg, 0.10 mmol) were dissolved in dry
dichloromethane (40 mL), and the resulting solution was stirred
overnight. The reaction mixture was evaporated, and the residue was
crystallized from chloroform/hexane. The resulting crystals were
isolated by suction and dried under vacuum. Yield: 64 mg (64%), red
crystals.
1H NMR (400 MHz, CDCl3): δ 1.93 (s, 9H, Me), 2.17 (d, JPH
=
1.0 Hz, 9H, Me), 3.12 (br s, 2H, CH2), 3.52 (br s, 2H, fc), 3.89 (br s,
2H, fc), 4.46 (br s, 2H, fc), 4.50 (br s, 3H of C6H3 and 2H of fc), 4.60
Synthesis of {1-(Diphenylphosphino)-1′-[(hydroxy-
phosphino-κP)methyl]ferrocene}[dichloro(η6-mesitylene)-
ruthenium(II)]−borane (1:1) (15). Complex 6 (67 mg, 0.15 mmol)
and [{(η6-mesitylene)RuCl(μ-Cl)}2] (44 mg, 0.075 mmol) were
1
3
(dt, JPH = 361.5 Hz, JPH = 6.6 Hz, 2H, PH2), 4.98 (s, 3H, C6H3),
7.32−7.43 (m, 6H, PPh2), 7.77−7.85 (m, 4H, PPh2). 13C{1H} NMR
(101 MHz, CDCl3): δ 18.24 (d, JPC = 1 Hz, Me), 19.00 (d, JPC = 1
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dissolved in dichloromethane (10 mL), and the resulting solution was
stirred overnight. Subsequent evaporation left complex 15 as a red-
orange powder in quantitative yield. Crystals used for structure
determination were obtained from chloroform/hexane.
phosphine)ruthenium(II) (80 mg, 0.11 mmol) and dppf (61 mg, 0.11
mmol) were mixed in toluene (20 mL) under argon, and the mixture
was heated at reflux for 24 h. After cooling, the solvent was evaporated
under vacuum, and the residue was triturated with diethyl ether (50
mL). The remaining solid was filtered off, washed with diethyl ether
(50 mL), and dried under vacuum to produce complex 17 as an
orange solid. Yield: 61 mg (73%).
1H NMR (400 MHz, CDCl3): δ 0.8−1.7 (br s, 3H, BH3), 2.05 (d,
J
PH = 1.2 Hz, 9H, Me), 2.95−3.04 (m, 1H, CH2), 3.27−3.34 (m, 1H,
CH2), 4.10 (d vt, J = 1.3, 2.4 Hz, 1H, fc), 4.19 (d vt, J = 1.3, 2.4 Hz,
1H, fc), 4.30−4.32 (m, 3H, fc), 4.40−4.42 (m, 1H, fc), 4.52−4.54 (m,
1H NMR (400 MHz, CDCl3): δ 4.02 (v td, J′ = 1.3 Hz, 2H, fc),
4.11 (s, 5H, C5H5), 4.24 (br s, 2H, fc), 4.32 (br s, 2H, fc), 5.19 (br s,
2H, fc), 7.27−7.44 (m, 16H, PPh2), 7.76−7.83 (m, 4H, PPh2).
31P{1H} NMR (162 MHz, CDCl3): δ 45.7 (s). The data match those
1
3
2H, fc), 4.79 (s, 3H, C6H3), 6.77 (dtd, JPH = 375.3 Hz, JHH = 5.5,
1.4 Hz, 1H, PH), 7.39−7.66 (m, 10H, PPh2). 13C{1H} NMR (101
1
MHz, CDCl3): δ 18.71 (d, JPC = 1 Hz, Me), 29.53 (d, JPC = 38 Hz,
CH2), 69.58 (d, JPC = 68 Hz, Cipso of fc), 69.75 (s, CH of fc), 70.34 (s,
CH of fc), 71.27 (d, JPC = 2 H, CH of fc), 71.88 (d, JPC = 2 H, CH of
fc), 73.00 (d, JPC = 8 H, CH of fc), 73.21(d, JPC = 7 H, CH of fc),
73.90 (s, CH of fc), 74.00 (d, JPC = 2 H, CH of fc), 81.09 (d, JPC = 3
Hz, Cipso of fc), 82.53 (d, JPC = 5 Hz, CH of C6H3), 106.19 (d, JPC = 2
Hz, Cipso of C6H3), 128.50 (d, JPC = 2 Hz, CH of PPh2), 128.61 (d,
in the original report.29
Synthesis of {1-(Diphenylphosphino)-1′-[(diphenyl-
p h o s p h i n o ) m e t h y l ] f e r r o c e n e - κ 2 P , P ′ } c h l o r o ( η 5 -
cyclopentadienyl)ruthenium(II) (18). Analogously to the previous
synthesis, chloro(cyclopentadienyl)bis(triphenylphosphine)-
ruthenium(II) (72.5 mg, 0.10 mmol) and 1 (59 mg, 0.10 mmol)
were mixed in anhydrous toluene (8 mL), and the mixture was heated
under gentle reflux (in an oil bath) for 6 h. The clear reaction mixture
was cooled, diluted with hexane (12 mL), and filtered through a
PTFE syringe filter (0.45 μm pore size). The filtrate was evaporated,
and the residue was redissolved in chloroform (2.5 mL) and
crystallized by layering with hexane (5 mL). The crystals, which
separated during several days, were filtered off, washed with pentane,
and dried under vacuum. Yield of 18·1.8CHCl3: 81 mg (82%),
orange-brown crystalline solid.
JPC = 2 Hz, CH of PPh2), 130.72 (d, JPC = 60 Hz, Cipso of PPh2),
1
131.00 (d, JPC = 2 Hz, CH of PPh2), 131.09 (d, 1JPC = 60 Hz, Cipso of
PPh2), 131.33 (d, JPC = 2 Hz, CH of PPh2), 132.44 (d, JPC = 9 Hz,
CH of PPh2), 132.74 (d, JPC = 9 Hz, CH of PPh2). 31P{1H} NMR
(162 MHz, CDCl3): δ 16.3 (br s, PPh2BH3), 115.3 (s, P(OH)H). 31
NMR (162 MHz, CDCl3): δ 16.3 (br s, PPh2BH3), 115.3 (ddd, 1JPH
P
=
375 Hz, 2JPH = 18, 8 Hz, P(OH)H). IR (nujol) νmax: 3180 br m, 3079
m, 3053 m, 2914 w, 2379 m, 2341 m, 2326 m, 1572 w, 1528 m, 1483
w, 1455 w, 1436 m, 1399 w, 1383 w, 1371 m, 1311 w, 1298 w, 1266
w, 1240 w, 1185 w, 1173 s, 1127 m, 1108 s, 1053 s, 1030 s, 999 m,
986 m, 961 m, 923 s, 872 s, 840 m, 829 m, 806 w, 753 m, 737 s, 700 s,
638 m, 624 m, 530 m, 500 s, 477 m, 442 m, 404 m cm−1. ESI-MS (m/
z): 958 ([M + RuCl2(mes) − HCl − Cl]+). Anal. Calcd for
C32H37BCl2FeOP2Ru (738.2): C, 52.06; H, 5.05. Found: C, 51.82; H,
4.99.
1H NMR (400 MHz, CDCl3): δ 3.11 (br m, 1H, fc), 3.37 (ddd, J =
15.5, 13.8, 1.2 Hz, 1H, CH2), 3.94−3.96 (m, 1H, fc), 3.95 (s, 5H,
C5H5), 3.91−4.00 (m, 1H, fc), 4.12−4.13 (m, 3H, fc), 4.22−4.24 (m,
1H, fc), 4.34 (dd, J = 16.0, 7.5 Hz, 1H, CH2), 5.51−5.52 (m, 1H, fc),
7.12−7.92 (m, 20H, PPh2). 13C{1H} NMR (101 MHz, CDCl3): δ
26.53 (d, 1JPC = 20 Hz, CH2), 67.84 (s, CH of fc), 68.38 (s, CH of fc),
69.45 (s, CH of fc), 69.78 (d, JPC = 4 Hz, CH of fc), 70.39 (d, JPC = 3
Hz, CH of fc), 71.51 (d, JPC = 10 Hz, CH of fc), 72.66 (d, JPC = 7 Hz,
CH of fc), 76.43 (d, JPC = 16 Hz, CH of fc), 81.33 (t, JPC = 2 Hz,
C5H5), 82.12 (s, Cipso of fc), 84.43 (d, JPC = 35 Hz, Cipso of fc), 127.38
(d, JPC = 9 Hz, CH of PPh2), 127.56 (d, JPC = 9 Hz, 2CH of PPh2),
128.12 (s, 2CH of PPh2), 128.21 (s, CH of PPh2), 128.55 (s, CH of
PPh2), 129.96 (br d, JPC = 7 Hz, CH of PPh2), 130.25 (br s, CH of
PPh2), 132.05 (d, JPC = 9 Hz, CH of PPh2), 134.04 (d, JPC = 11 Hz,
CH of PPh2), 134.97 (d, JPC = 12 Hz, CH of PPh2), 135.94 (br d, JPC
= 37 Hz, Cipso of PPh2), 140.63 (d, JPC = 44 Hz, Cipso of PPh2), 143.21
(dd, JPC = 38, 4 Hz, Cipso of PPh2), 141.15 (br d, JPC = 40 Hz, Cipso of
Synthesis of [1,1′-Bis(diphenylphosphino)ferrocene-κ2P,P′]-
[chloro(η6-mesitylene)ruthenium(II)] hexafluorophosphate
(16). dppf (55 mg, 0.10 mmol), [{(η6-mesitylene)RuCl(μ-Cl)}2]
(29 mg, 0.05 mmol), and sodium hexafluorophosphate (84 mg, 0.5
mmol) were mixed in methanol and dichloromethane (10 mL each)
under argon, and the suspension was stirred overnight and then
evaporated. The solid residue was extracted with dichloromethane (15
mL), and the extract was filtered (PTFE syringe filter, 45 μm pore
size). The filtrate was evaporated, and the crude solid was further
purified by chromatography over a short silica gel column, eluting
with a dichloromethane−methanol mixture (10:1). Finally, the
product was dissolved in dichloromethane (approximately 5 mL)
and precipitated with cold pentane (ca. 40 mL). Separated solid was
isolated by suction and dried under vacuum. Yield of 16: 85 mg
(89%), orange powdery solid. Crystals suitable for structure
determination were obtained by liquid-phase diffusion of hexane
into a dichloromethane solution of the complex.
2
PPh2). 31P{1H} NMR (162 MHz, CDCl3): δ 33.7 (d, JPP = 34 Hz,
PPh2), 34.6 (d, 2JPP = 35 Hz, PPh2). IR (DRIFTS) νmax: 3078 m, 3053
m, 3002 w, 2879 w, 1586 w, 1480 m, 1432 s, 1411 m, 1309 w, 1222 w,
1186 w, 1165 m, 1094 s, 1070 m, 1046 w, 1031 s, 1000 m, 920 w, 860
w, 827 s, 806 m, 794 m, 743 s, 696 s, 662 m, 629 w, 618 w, 602 w, 542
s, 523 s, 513 s, 494 s, 479 s, 462 s, 444 s, 427 s cm−1. ESI-MS (m/z):
735 ([M − Cl]+). Anal. Calcd for C40H35ClFeRuP2·1.8CHCl3
(984.9): C, 50.97; H, 3.77. Found: C, 50.82; H, 3.82.
1H NMR (400 MHz, CDCl3): δ 1.74 (s, 9H, Me), 4.00−4.01 (m,
2H, fc), 4.09−4.11 (m, 2H, fc), 4.31−4.33 (m, 2H, fc), 4.85 (s, 3H,
C6H3), 5.10−5.11 (m, 2H, fc), 7.40−7.50 (m, 6H, PPh2), 7.52−7.60
(m, 4H, PPh2), 7.64−7.72 (m, 6H, PPh2), 7.86−7.94 (m, 4H, PPh2).
13C{1H} NMR (101 MHz, CDCl3): δ 19.38 (s, Me), 68.74 (t, JPC = 3
Catalytic Estragole to Anethole Isomerization. A Schlenk
tube was charged with the catalyst (0.010 mmol, 1.0 mol % of [Ru]),
potassium carbonate (8.0 mg, 0.060 mmol), and estragole (296 mg,
2.0 mmol) and flushed with nitrogen. Degassed deionized water was
introduced (1 mL), and the flask was stoppered and transferred into
an oil bath maintained at 80 °C. After heating for 6 h, the reaction
mixture was cooled to room temperature and diluted with diethyl
ether (15 mL) and brine (15 mL). The organic layer was separated,
and the aqueous residue was extracted with ether (15 mL). The
combined organic layers were dried over MgSO4 and evaporated. The
Hz, CH of fc), 73.82 (t, JPC = 3 Hz, CH of fc), 74.77 (t, JPC = 2 Hz,
CH of fc), 79.17 (t, JPC = 5 Hz, CH of fc), 84.38 (t, 1JPC = 28 Hz, Cipso
of fc), 92.65 (t, JPC = 3 Hz, CH of C6H3), 114.28 (t, JPC = 2 Hz, Cipso
of C6H3), 128.20 (t, JPC = 5 Hz, CH of PPh2), 128.25 (t, JPC = 5 Hz,
CH of PPh2), 130.48 (t, JPC = 24 Hz, Cipso of PPh2), 130.84 (s, CH of
PPh2), 132.47 (s, CH of PPh2), 132.91 (t, JPC = 4 Hz, CH of PPh2),
135.83 (t, JPC = 6 Hz, CH of PPh2), 137.81 (t, 1JPC = 24 Hz, Cipso of
PPh2). 31P{1H} NMR (162 MHz, CDCl3): δ −143.9 (hept, 1JPF = 713
Hz, PF6), 35.6 (s, PPh2). IR (Nujol) νmax: 1541 w, 1298 m, 1090 m,
1035 m, 842 v s, 743 m, 703 s, 631 w, 558 s, 546 w, 517 s, 508 m, 479
m, 440 w cm−1. ESI-MS (m/z): 811 ([M − PF6]+). Anal. Calcd for
C43H40ClF6FeRuP3 (956.1): C, 54.02; H, 4.22. Found: C, 54.08; H,
4.32.
1
conversion and (E/Z) ratios were determined by H NMR.
(E)-1-(4-Methoxyphenyl)prop-1-ene. 1H NMR (400 MHz,
3
CDCl3): δ 1.86 (d, JHH = 7.2 Hz, 3H, Me), 3.82 (s, 3H, OMe),
3
6.06−6.14 (m, 1H, CHCH), 6.34 (d, JHH = 11.6 Hz, 1H, CHCH)
6.84 (d, 3JHH = 8.4 Hz, 2H, C6H4), 7.27 (d, 3JHH = 8.4 Hz, 2H, C6H4).
(Z)-1-(4-Methoxyphenyl)prop-1-ene. 1H NMR (400 MHz,
Synthesis of [1,1′-Bis(diphenylphosphino)ferrocene κ2P,P′]-
chloro(η5-cyclopentadienyl)ruthenium(II) (17). The procedure
was adopted from ref 29. Chloro(cyclopentadienyl)bis(triphenyl-
3
CDCl3): δ 1.88 (d, JHH = 7.2 Hz, 3H, Me), 3.77 (s, 3H, OMe),
3
5.66−5.71 (m, 1H, CHCH), 6.36 (d, JHH = 11.6 Hz, 1H, CHCH),
437
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Organometallics 2021, 40, 427−441

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pubs.acs.org/Organometallics
Article
6.87 (d, 3JHH = 8.4 Hz, 2H, C6H4), 7.23 (d, 3JHH = 8.4 Hz, 2H, C6H4).
The spectroscopic data are in accordance with the literature.48
Catalytic Cycloisomerization of (Z)-3-Methylpent-2-en-4-
yn-1-ol into 2,3-Dimethylfuran. A vial was charged with a stirring
bar, catalyst (4.5 μmol, 0.3 mmol % [Ru]), (Z)-3-methylpent-2-en-4-
yn-1-ol (90%; 288 mg, 3.0 mmol), and anisole (324 mg, 3.0 mmol) as
an inert standard and sealed. The mixture was stirred 18 h at room
temperature under ambient atmosphere and then analyzed by 1H
NMR. The (E)-isomer of the starting enynol remains unchanged in
the reaction mixture.
Republic; orcid.org/0000-0002-5966-0578;
Email: petr.stepnicka@natur.cuni.cz
Authors
́
Filip Horky − Department of Inorganic Chemistry, Faculty of
Science, Charles University, 128 40 Prague, Czech Republic
̌
́
Ivana Císarova − Department of Inorganic Chemistry, Faculty
of Science, Charles University, 128 40 Prague, Czech
Republic
1
2,3-Dimethylfuran. H NMR (400 MHz, CDCl3): δ 1.94 (br s,
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00767
3H, Me), 2.19 (br s, 3H, Me), 6.15 (d, 3JHH = 1.8 Hz, 1H, CH), 7.20
3
(d, JHH = 1.8 Hz, 1H, CH). 13C{1H} NMR (101 MHz, CDCl3): δ
9.82 (Me), 11.27 (Me), 112.78 (CH), 113.74 (Cipso), 139.56 (CH),
Notes
147.36 (Cipso). The NMR data match those in the literature.49
The authors declare no competing financial interest.
X-ray Crystallography. Diffraction data ( h
k l, θmax = 27.5°)
were collected with a Bruker Apex II CCD (2, 9, and 18) or a Bruker
D8 VENTURE Kappa Duo diffractometer with a PHOTON detector
(all other compounds), both equipped with a Cryostream Cooler
(Oxford Cryosystems), using Mo Kα radiation (λ = 0.71073 Å). The
structures were solved using direct methods (SHELXT-201450 or
SIR-97)51 and then refined by full-matrix least-squares routine based
on F2 (SHELXL-2014).52 Non-hydrogen atoms were refined with
anisotropic displacement parameters. The PH hydrogens were
identified on the difference electron density maps and refined as
riding atoms with Uiso(H) set to 1.2Ueq(P). Hydrogens residing on
carbon atoms were included in their theoretical positions and refined
similarly. The phosphorus atom P2 in the structure of 9 is disordered
over two positions and was modeled accordingly. In the structure of
15, the H and OH groups bonding to phosphorus atom P2 alternated
in their positions with practically equal occupancies (the compound is
thus racemic), which also affected one of the Ru-bound chlorine
atoms. The positions of the disordered hydrogen atoms were based
not only on the difference Fourier maps but also on their
surroundings and crystal packing (mainly hydrogen bonding
interactions). Finally, the solvent molecules in the structure of 10·
THF·2CH2Cl2 were extensively disordered and could not be
satisfactorily included in the structure model. Hence, their
contribution to the overall scattering was numerically eliminated
using PLATON SQUEEZE.53 Relevant crystallographic data and
refinement parameters are presented in Table S1.
ACKNOWLEDGMENTS
■
This work was supported by the Grant Agency of Charles
University (project no. 920119) and by the Charles University
Research Centre program (project UNCE/SCI/014).
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Petr Stepnicka − Department of Inorganic Chemistry, Faculty
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