Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne Dimerization

Article abstract of DOI:10.1021/acs.organomet.0c00361

Several mononuclear ruthenium complexes containing bulky diphosphines have been easily prepared from acetate ruthenium precursors. The cyclohexyl complex [Ru(n 2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bis(dicyclohexylphosphino)ferrocene) is synthesized from [R

Full text of DOI:10.1021/acs.organomet.0c00361

pubs.acs.org/Organometallics
Article
Bulky Diphosphine Acetate Ruthenium Complexes: Synthesis and
Catalytic Activity in Ketone Transfer Hydrogenation and Alkyne
Dimerization
Maurizio Ballico, Daniele Zuccaccia, Rosario Figliolia,* and Walter Baratta*
Cite This: https://dx.doi.org/10.1021/acs.organomet.0c00361
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Several mononuclear ruthenium complexes containing bulky
diphosphines have been easily prepared from acetate ruthenium precursors. The
cyclohexyl complex [Ru(η2-OAc)2(DCyPF)] (1-cy; DCyPF = 1,1′-bis-
(dicyclohexylphosphino)ferrocene) is synthesized from [Ru(η2-OAc)2(PPh3)2]
and DCyPF in toluene at reflux, whereas the ethylenediamine (en) derivatives
trans-[Ru(η1-OAc)2(PP)(en)] (PP = 1,1′-bis(diisopropylphosphino)ferrocene
(DiPPF) (2), DCyPF (3)) have been obtained in a one-pot reaction from
[Ru(η2-OAc)2(PPh3)2], PP, and en in n-heptane. Treatment of the isopropyl-
phosphine complex [Ru(η2-OAc)2(DiPPF)] (1-ip) with 2-(aminomethyl)pyridine
(ampy) in methanol affords the isolation of a mixture of the cationic [Ru(η2-
OAc)(DiPPF)(ampy)]OAc (5a) and cis-[Ru(η1-OAc)2(DiPPF)(ampy)] (5b) (4/
1 molar ratio), via trans-[Ru(η1-OAc)2(DiPPF)(ampy)] (4) characterized at low
temperature. The analogous cyclohexyl compound trans-[Ru(η1-OAc)2(DCyPF)-
(ampy)] (6), synthesized from [Ru(η2-OAc)2(PPh3)2], DCyPF and ampy in heptane, slowly converts into [Ru(η2-
OAc)(DCyPF)(ampy)]OAc (7) at RT. The monocarbonyl derivatives [Ru(η1-OAc)(η2-OAc)(PP)(CO)] (PP = 1,3-
bis(cyclohexylphosphino)propane (DCyPP) (8), (R)-1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldicyclohexylphosphine
(Josiphoscy) (9)) are obtained from [Ru(η1-OAc)(η2-OAc)(PPh3)2(CO)] and the suitable diphosphine. Treatment of [Ru(η1-
OAc)(η2-OAc)(DiPPF)(CO)] (10) with phenylacetylene and in the presence of pyridine leads to the alkynyl complex [Ru(η2-
OAc)(CCPh)(DiPPF)(CO)] (11), characterized by X-ray diffraction analysis. Protonation of 10 with 2 equiv of TFA at RT gives
[Ru(η1-OCOCF3)(η2-OCOCF3)(DiPPF)(CO)] (12). The dicarbonyl trans,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (13) is obtained by
reaction of 1-ip with CO (1 atm) in CH2Cl2, whereas the isomer cis,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (14) can be prepared from
carbonylation of 10. When 13 is heated in the solid state, 10 is formed by decarbonylation. These complexes promote the transfer
hydrogenation of acetophenone in 2-propanol (S/C = 1000−2000) with NaOiPr (2 mol %), affording a TOF value of up to 81000
h−1 for complex 9 at 30 °C. Complex 10 catalyzes the head-to-head dimerization of terminal alkynes to 1,4-enynes in toluene at
reflux with high stereoselectivity for the kinetic Z isomer.
[RuCl2(CHPh)(PCy3)(L)] (L = PCy3, N-heterocyclic
INTRODUCTION
■
carbene)5 for the olefin metathesis.6 On the other hand,
Ruthenium phosphine complexes still attract a great deal of
[Ru(η2-OAc)2(PP)]7 and trans-[RuCl2(PP)(1,2-diamine)]8
attention due to their extensive reactivity and their broad
(PP = BINAP)9 were developed by Noyori for the asymmetric
application as homogeneous catalysts1 with particular regard to
HY of the CC and CO bonds (Figure 1).10
hydrogenation (HY) and metathesis reactions. The stereo-
The use of a single diphosphine ligand, which binds more
electronic properties of the phosphines play a crucial role in
tightly in comparison to two monophosphines, results in a
dictating the final stability, reactivity, and catalytic activity of
more robust catalyst, imposing a cis-RuP2 arrangement and a
the complexes, containing additional (spectator/actor)
restricted ring conformation, the latter being crucial for
ligands.2 Seminal works on the isolation and reactivity of
stereoselective catalysis. In contrast to aryldiphosphines (i.e.,
coordinatively unsaturated ruthenium complexes with bulky
alkylphosphines have been provided by Caulton in the 1990s.3
Conversely, we reported 16- and 14-electron ruthenium
Received: May 23, 2020
complexes displaying the arylphosphine PPh2(2,6-Me2C6H3),
showing a δ-agostic interaction, and affording C−H activation
reactions.4 With regard to the catalytic applications of
phosphine ruthenium complexes, pioneering works have
been carried out by Grubbs on the 16-electron species
https://dx.doi.org/10.1021/acs.organomet.0c00361
© XXXX American Chemical Society
Organometallics XXXX, XXX, XXX−XXX
A

Organometallics
pubs.acs.org/Organometallics
Article
complexes were found to catalyze the HY of the olefinic,7b,23
carbonyl,24 and carboxylic compounds,25 alcohol dehydrogen-
ation,26 and TH.27 In addition, a higher activity in the TH has
been observed for acetate vs chloride pincer complexes
[RuX(CNN)(dppb)] (X = Cl, OAc).28 Ruthenium carbox-
ylates were described to promote C−H bond activation and
functionalization reactions, assisted by RCO2 ,29 including the
−
formation of vinylidene compounds.30 Finally, ruthenium
carboxylates have been used as suitable starting products for
the synthesis of carbene catalysts, via imidazolium salt
deprotonation, for TH and Oppenauer-type oxidation
reactions.27a,31
We report herein the straightforward synthesis of ruthenium
complexes containing electron-rich and bulky diphosphines,
starting from acetate precursors, and their reactivity with
carbon monoxide and bidentate nitrogen ligands. The catalytic
Figure 1. Ruthenium phosphine catalysts for metathesis and
hydrogenation reactions.
BINAP), bulky electron-rich alkyldiphosphines have been
sparingly employed in asymmetric HY: namely, [RuX2(PP)-
(DMF)m] (X = Cl, Br; PP = TangPhos;11 X = Br, PP = i-Pr-
BPE12), [RuCl2(PP)(NN)] (PP = MeO-BIBOP,13 BICP14).9
9,15
In addition, the dimers [RuCl(μ-Cl)(DCyPB)(CO)]2
and
[RuX(μ-X)(CO)(DiPPF)]2 (X = Cl, Br),9,16 prepared from
(η3-allyl)ruthenium(II) precursors, were found to be active in
the HY and TH of carbonyl compounds.17 Interestingly, the
system [RuHCl(CO)(PPh3)3]/DiPPF has been found to
catalyze C−C coupling reactions via alcohol dehydrogenation,
the alkyldiphosphines being more efficient than the aryl species
(DPPF, BINAP).9,18 During the past decade we developed the
efficient TH catalysts cis-[RuCl2(ampy)(PP)],19 which are
complementary to the Noyori HY catalysts and in which the
ampy9 ligand produces a strong acceleration effect in the TH
with 2-propanol (Figure 2).
activity of these complexes for the transfer hydrogenation of
acetophenone and alkyne dimerization is described.
RESULTS AND DISCUSSION
■
Synthesis of Diacetate Ruthenium Complexes with
Bulky Diphosphine and NN Ligands. Following the
procedure described for the synthesis of the isopropyl
derivative [Ru(η2-OAc)2(DiPPF)] (1-ip),21 treatment of the
acetate ruthenium precursor [Ru(η2-OAc)2(PPh3)2] with 1
equiv of the cyclohexyldiphosphine DCyPF9 in toluene at
reflux for 2 h affords the thermally stable complex [Ru(η2-
OAc)2(DCyPF)] (1-cy), isolated in 49% yield, showing a
singlet at δ 64.1 in the 31P{1H} NMR spectrum (eq 1). The
reaction of [Ru(η2-OAc)2(PPh3)2] with the isopropyl
diphosphine DiPPF (1 equiv) in n-heptane at reflux (2 h)
and addition of the nitrogen ligand en9 at RT (2 h) results in
the formation of the derivative trans-[Ru(η1-OAc)2(DiPPF)-
(en)] (2) in 52% yield, through a one-pot reaction (Scheme
1).
Figure 2. Ruthenium phosphine catalysts for TH and N-alkylation
reactions.
More recently, we described the monocarbonyl complexes
[RuX(CO)(PP)(ampy)]X20 (X = Cl, OAc) and the acetate
[Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)],21 which are efficient
catalysts in the TH and in the N-alkylation of amines with
alcohols (via borrowing hydrogen), respectively (Figure 2).
The presence of a CO ligand increases stability, retarding the
catalyst deactivation that may occur through substrate
decarbonylation.4c,22 It is worth pointing out that carboxylates
are not innocent ligands and can play a pivotal role in catalysis
(i.e., proton acceptors for H2 splitting), as well as in the
preparative scope, stabilizing monomeric species by switching
from mono- to bidentate mode. Thus, ruthenium carboxylate
Control 31P{1H} NMR experiments show that 2 is easily
formed by reaction of the intermediate 1-ip21 with en at RT.
Complex 2 shows a 31P{1H} NMR singlet at δ 44.9 in CDCl3,
shifted significantly upfield in comparison to 1-ip (δ 67.6),
1
whereas in the H NMR spectrum the two broad signals at δ
5.99 and 2.97 are for the NH2 and the methylene groups of the
Scheme 1. Synthesis of the trans Acetate Ruthenium Complexes 2 and 3 with en
B
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Scheme 2. Synthesis of Ruthenium trans, cis, and Cationic Acetate Complexes 4−7
en ligand, respectively. The low-field proton chemical shift is
consistent with the presence of a NH···OC hydrogen bond
interaction involving the four NH protons and the two acetate
ligands.28,32 In addition, in the 13C{1H} NMR spectrum the
doublet of doublets at δ 183.6 (3J(C,P) = 1.9 and 0.8 Hz) and
the singlet at δ 43.5 have been attributed to the acetate CO
group and the CH2N group, respectively. The cyclohexyl
derivative 3 was isolated in 64% yield from [Ru(η2-
OAc)2(PPh3)2], DCyPF, and en, following the procedure for
2 (Scheme 1). The 31P{1H} NMR spectrum of 3 in CD2Cl2
displays a singlet at δ 38.0, shifted upfield in comparison to 1-
cy (Δδ 26.1). The NCH2 protons appear as a singlet at δ 2.92
reaction of 1-ip with ampy (1 equiv) in toluene-d8 at RT gives
4 as the main species, which at 50 °C leads to the starting
products 1-ip with concomitant formation of 5a/b, according
to the equilibrium of Scheme 2 (Figure S17 in the Supporting
Information). Attempts to isolate 4 from [Ru(η2-
OAc)2(PPh3)2], DiPPF in cyclohexane, and ampy in methyl
ethyl ketone (MEK) at RT (4 h) failed, resulting in the
formation of 4 as the main product in the presence of 1-ip and
5a/b in a 3/0.5/1/0.1 molar ratio, respectively. The synthesis
of the DiPPF ampy complex as a mixture of 5a and 5b (4/1
molar ratio) was attained in 77% yield by treatment of 1-ip
with ampy (1 equiv) in methanol at RT (2 h) (Method A in
the Experimental Section). Alternatively, 5a/b (65% yield)
were prepared from [Ru(η2-OAc)2(PPh3)2], DiPPF, and ampy
in cyclohexane/MEK (4 h), via 4 and solubilization in MeOH
(Method B). The 31P{1H} NMR spectrum of 5a/b in
CD3OD/CD2Cl2 (1/10 in volume) reveals two doublets at δ
62.9 and 51.2 (2J(P,P) = 27.5 Hz) for the cationic complex 5a
and two doublets at δ 65.5 and 45.4 (2J(P,P) = 24.7 Hz) for
the cis isomer 5b. The doublets at δ 9.07 (3J(H,H) = 5.6 Hz)
1
in the H NMR spectrum, while the four NH2 protons give a
broad singlet at δ 6.09, a value close to that observed for 2.
Reaction of 1-ip with ampy (1 equiv) in CD2Cl2 at −60 °C
leads to the formation of the kinetic complex trans-[Ru(η1-
OAc)2(DiPPF)(ampy)] (4) (Scheme 2).
The 31P{1H} NMR spectrum of 4 at low temperature
2
displays two doublets at δ 45.2 and 43.4 with J(P,P) = 29.2
1
Hz. In the H NMR spectrum the two signals at δ 8.80 and
1
and 8.73 (3J(H,H) = 4.7 Hz) in the H NMR spectrum were
4.86 are for the NH2 protons, indicating that one NH
undergoes a strong N−H···OC hydrogen bond interaction
with the acetate, whereas the singlets at δ 1.78 and 1.42 are for
two nonequivalent Me groups in the acetate. This has also
been confirmed by the 13C{1H} NMR spectrum with two
different acetate carbonyl resonances at δ 182.5 and 181.0.
When the temperature is raised to 0 °C, the 31P{1H} NMR
measurements of 4 show coalescence of the two doublets into
a singlet at δ 45.0 (Figure S12 in the Supporting Information),
while the 1H NMR resonances of the NH2 and methyl acetate
groups appear as broad peaks at δ 3.41 and 1.62, respectively
(Figure S13 in the Supporting Information). At RT in CD2Cl2
complex 4 equilibrates with the precursor 1-ip and ampy, as
inferred from NMR measurements, with concomitant and
complete isomerization to the cationic [Ru(η2-OAc)(DiPPF)-
(ampy)]OAc (5a) and cis-[Ru(η1-OAc)2(DiPPF)(ampy)]
(5b) species in about a 5/1 molar ratio in 1 day (Scheme 2
and Figure S14 in the Supporting Information). Addition of
CD3OD to a solution of 4 in CD2Cl2 caused the rapid
conversion to 5a and 5b in a 4/1 molar ratio at RT. The
attributable to the ortho pyridine signals of 5b and 5a,
respectively. Control 1H NMR experiments show that addition
of NaOAc (1.0−3.5 equiv) to 5a/b in CD3OD at RT results in
an increase of the peak at δ 1.92, attributed to free acetate of
5a, indicating that in 5a one acetate is bidentate, while the
second acetate acts as a counterion (Figures S23 and S24 in
the Supporting Information), as observed for [Ru(η2-OAc)-
(PPh3)(NN)(CO)]OAc (NN = en, ampy).20a
Conversely, the derivative trans-[Ru(η1-OAc)2(DCyPF)-
(ampy)] (6) has been prepared from [Ru(η2-OAc)2(PPh3)2],
DCyPF, and ampy in heptane and isolated in 65% yield
(Scheme 2). Complex 6 displays in the 31P{1H} NMR
spectrum at RT two doublets at δ 39.2 and 37.0 with
2J(P,P) = 28.9 Hz. The methylene protons of the ampy ligand
1
appear in the H NMR spectrum as a broad signal at δ 4.11,
whereas the NH2 resonances are at δ 7.25 and 4.36. These
results are consistent with the presence of one NH···OC
hydrogen bond interaction, in line with the behavior of 4 at
−60 °C. In addition, the 13C{1H} NMR spectrum shows two
C
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
chemically nonequivalent acetate ligands with signals at δ
180.3 and 176.4 for COMe and at δ 25.4 and 24.5 for the
methyl groups. The trans derivative 6 is more stable than the
analogous species 4 and in CDCl3 slowly partially converts at
RT (24 h) into the cationic complex [Ru(η2-OAc)(DCyPF)-
(ampy)]OAc (7) with a 6/7 molar ratio of 3/2 (Scheme 2 and
Figure S29 in the Supporting Information). Complex 7 shows
two doublets at δP 45.3 and 40.0 (2J(P,P) = 31.0 Hz) and
signals at δH 8.61 and 1.94 for the ortho pyridine and the free
acetate protons, consistent with the formation of the cationic
species (Figure S30 in the Supporting Information). A
comparison of the reactivity of the cyclohexyl- vs isopropyldi-
phosphine derivatives [Ru(η1-OAc)2(PP)(NN)] (NN = en,
ampy) shows that the trans complexes form promptly from the
acetate diphosphine precursor and NN even at low temper-
ature. While the trans derivatives with en are thermally stable,
the trans ampy complexes at RT equilibrate with the starting
ruthenium acetate [Ru(η2-OAc)2(PP)] and afford the
thermodynamically more stable cationic and cis ampy
complexes. This process is favored for the iPr vs the Cy
phosphine derivative and involves the dissociation of acetate,
due to the strong trans influence exerted by the iPr
phosphine.33 In addition, the acetate ligand facilitates the
isomerization at the Ru center through a rapid interchange
between η1 and η2 coordination modes, as well as OAc
displacement involving a hydrogen bond interaction with OH
protic (alcohol) solvents34 or an NH amine function, as
observed for [Ru(acac)(dppb)(ampy)]OAc.27b
the CO stretching absorbance in the IR spectrum is at
relatively low wavenumber (1932 cm−1), in agreement with the
presence of an electron-rich diphosphine.33,35
Complex 9 has been isolated in 45% yield, as a mixture of
two stereoisomers, by the reaction of [Ru(η1-OAc)(η2-
9
OAc)(PPh3)2(CO)] with the chiral Josiphoscy in toluene at
90 °C for 24 h (Scheme 3). The 31P{1H} NMR spectrum of 9
in CD2Cl2 displays two broad peaks at δ 71.0 and 39.7, in
addition to a second species at δ 77.2 and 46.4. Accordingly,
1
the H NMR spectrum shows broad signals in the aliphatic
region with distinguishable methyl acetate singlets at δ 2.00
and 1.87, overlapped with the cyclohexyl methylene protons.
The 13C{1H} NMR signals of the carbonyl group are in the
range of δ 206.0−205.1, whereas the methyl acetate signals
appear at δ 24.7 and 24.1. Finally, the IR νCO band of 9 is at
1948 cm−1, in line with the values for monocarbonyl
ruthenium diphosphine complexes.20a
The compound [Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)]
(10), obtained previously from 1-ip via H2CO decarbon-
ylation,21 has been prepared by reaction of the commercially
available dicarbonyl precursor [RuCl2(CO)2]n with DiPPF and
sodium acetate (10 equiv) in toluene at reflux in 1 day and was
isolated in 53% yield (eq 2, Method A in the Experimental
Section). Complex 10 cleanly reacts with phenylacetylene (1
equiv) in the presence of pyridine as a base in toluene at 50 °C,
affording the alkynyl derivative [Ru(η2-OAc)(CCPh)-
(DiPPF)(CO)] (11), isolated in 65% yield, by elimination of
acetic acid (Scheme 4).
The molecular structure of 11 was confirmed by an X-ray
single-crystal diffraction experiment carried out at 170 K, an
ORTEP drawing of 11 is displayed in Figure 3.
Synthesis of Monocarbonyl Ruthenium Acetate
Complexes Bearing Bulky Diphosphines. Monocarbonyl
acetate complexes containing bulky (chiral) diphosphines (PP)
can be easily obtained from [Ru(η1-OAc)(η2-OAc)-
(PPh3)2(CO)] by displacement of PPh3 with PP, according
to the procedure reported in the literature.20a Thus, treatment
of the precursor [Ru(η1-OAc)(η2-OAc)(PPh3)2(CO)] with an
excess of DCyPP9 in cyclohexane at 90 °C for 6 h leads to
[Ru(η1-OAc)(η2-OAc)(DCyPP)(CO)] (8), isolated in 70%
yield (Scheme 3).
The ruthenium center of 11 is in a pseudo-octahedral
environment with a Ru−C1 bond length of 2.040 Å, in
agreement with a ruthenium(II) alkynyl complex36 and
significantly longer in comparison to that observed in a related
vinylidene derivative,37 while the C1−C2 length is 1.199 Å, in
the range of a typical CC triple bond. The Ru−C1−C2
angle of 172.3° is almost linear, whereas the O2−Ru−O3 angle
(59.51°) is similar to that observed for ruthenium η2 acetate
complexes.38 The 31P{1H} NMR spectrum of 11 in CD2Cl2
displays two doublets at δ 70.0 and 30.4 with a significantly
small 2J(P,P) value of 15.9 Hz. Cα and Cβ of the alkynyl appear
in the 13C{1H} NMR spectrum as a doublet of doublets at δ
105.0 (2J(C,P) = 23.9 and 2.0 Hz) and a doublet at δ 129.1
(2J(C,P) = 2.2 Hz), respectively. Furthermore, the doublet of
doublets at δ 207.4 (2J(C,P) = 20.9 and 11.8 Hz) is for the
CO, while the triplet at δ 186.7 (2J(C,P) = 2.3 Hz) is for the
carbonyl acetate. In the IR spectrum, the νCO band is at 1923
cm−1, whereas the CC group gives a stretching band at 2098
cm−1. Protonation of 10 with 2 equiv of trifluoroacetic acid
(TFA) in diethyl ether at RT, followed by addition of CaCO3
to eliminate HOAc, affords [Ru(η1-OCOCF3)(η2-OCOCF3)-
(DiPPF)(CO)] (12) in 70% yield, showing a broad singlet at
δP 62.3 in CD2Cl2 (Scheme 4). The 13C{1H} NMR resonance
of the CO ligand of 12 appears as a triplet at δ 203.6 with a
2J(C,P) value of 18.7 Hz, and the trifluoroacetate carbonyl
groups give two signals at δ 166.7 and 164.8, whereas the
19F{1H} NMR spectrum shows two singlets at δ −70.2 and
−70.3 for the CF3 groups. Finally, the IR νCO band of 12 is at
1932 cm−1, while the asymmetrical νOCO bands of the
trifluoroacetate ligands are at 1607 and 1558 cm−1. Control
NMR experiments carried out by adding 1 equiv of TFA to 10
display the formation of the mixed carboxylate complex
Scheme 3. Synthesis of the Monocarbonyl Acetate
Ruthenium Complexes 8 and 9
1
The 31P{1H} and H NMR spectra of 8 in CD2Cl2 at RT
display broad peaks at δP 42.0 and δH 1.90 (acetate),
suggesting a fluxional behavior involving the acetate ligands,
as observed for [Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)]21 (10).
Conversely, the 13C{1H} NMR spectrum of 8 presents two
singlets at δ 25.2 and 24.4 for the methyl acetate moieties and
a triplet at δ 204.0 (2J(C,P) = 17.2 Hz) for Ru−CO, whereas
D
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Scheme 4. Synthesis of the Alkynyl (11) and Trifluoroacetate (12) Ruthenium Complexes
Figure 3. ORTEP style plot of compound 11 in the solid state. Ellipsoids are drawn at the 50% probability level. H atoms are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ru−P1 2.4658(7), Ru−P2 2.3018(6), Ru−O2 2.2013(17), Ru−O3 2.1936(17), Ru−C1 2.040(2),
Ru−C9 1.816(3),C1−C2 1.199(3), P1−Ru−P2 100.28(2), O2−Ru−O3 59.51(6), C1−Ru−P1 172.56(7).
Scheme 5. Synthesis of the Ruthenium Complex Dicarbonyl Isomers 13 and 14 and the Monocarbonyl 10
[Ru(η1-OAc)(η1-OCOCF3)(DiPPF)(CO)], characterized by
two broad singlets in the 31P{1H} NMR spectrum at δ 67.8
and 59.9 in CD2Cl2 (Scheme 4 and Figures S44 and S45 in the
Supporting Information). Upon addition of a second
equivalent of TFA, the two peaks disappear, leading to a
singlet at δ 62.3, indicating the quantitative formation of 12 by
protonation of the remaining acetate with TFA.
Synthesis and Reactivity of DiPPF Dicarbonyl
Ruthenium Diacetate Complexes. The precursor 1-ip
cleanly reacts with CO (1 atm) in dichloromethane at RT in
30 min, affording the dicarbonyl complex trans,cis-[Ru(η1-
OAc)2(DiPPF)(CO)2] (13) in 98% yield (Scheme 5).
The 31P{1H} NMR spectrum of 13 in CDCl3 displays a
sharp singlet at δ 26.5, whereas the 13C{1H} NMR signal of the
E
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
two cis CO ligands appears as a doublet of doublets at δ 195.9
(2J(C,P) = 105.0 and 21.5 Hz) and the acetate carbonyl group
as a triplet at δ 177.0 with J(C,P) = 1.9 Hz. The presence of
Table 1. Catalytic TH of Acetophenone (0.1 M) with
Ruthenium Complexes (S/C = 1000) and NaOiPr (2 mol
%) in 2-Propanol at 82 °C
3
the strong and sharp IR stretching bands at 2058 and 1964
cm−1 is in agreement with a cis coordination of the two
carbonyl ligands.39 Heating of complex 13 in the solid state at
120 °C under reduced pressure for 16 h leads selectively to 10
in 93% yield, which represents an alternative synthetic pathway
for 10, via decarbonylation and a rearrangement from a mer to
fac geometry of the Ru(PP)(CO) core (Scheme 5 and Method
B in the Experimental Section). Carbonylation of 10 (CO, 1
atm) in CH2Cl2 at RT (24 h) leads to cis,cis-[Ru(η1-
OAc)2(DiPPF)(CO)2] (14) in 92% yield (Scheme 5). The
31P{1H} NMR spectrum in CD2Cl2 of 14 shows two doublets
a
b
additive
conversion
(%)
TOF
(h−1
entry catalyst
(10 equiv)
time
)
1
2
3
4
5
6
1-ip
1-ip
1-ip
1-ip
5a/b
6
4.5 h
4 h
1 h
2 h
2 h
96
94
73
91
60
99
98
1400
1700
1600
1200
550
3000
38000
58000
81000
30000
8000
10000
25000
30000
450
en
bipy
ampy
1 h
7
9
1.5 min
1 min
5 min
10 min
2 h
2 h
1 h
3 h
3 h
c
8
9
9
9
96
99
d
e
2
at δ 50.8 and 32.2 with a J(P,P) value of 20.5 Hz. The
10
11
12
13
14
15
16
17
9
ampy
98
85
13C{1H} NMR triplet at δ 201.5 (2J(C,P) = 14.0 Hz) and the
doublet of doublets at δ 193.4 (2J(C,P) = 115.2 and 13.0 Hz)
are for the apical and equatorial CO groups, respectively, in
agreement with a cis arrangement of the two nonequivalent
CO ligands. The methyl acetate groups of 14 give two distinct
singlets at δ 2.00 and 1.93 in the 1H NMR spectrum, while the
resonances of the COMe groups appears at δC 176.1 and 175.8,
with 3J(C,P) = 2.7 and 2.0 Hz, respectively, consistent with the
formation of a complex with two cis OAc ligands, thus
excluding the formation of a cationic acetate species of the type
5a. Finally, the cis CO ligands show two strong stretching
bands in the IR spectrum at 2048 and 1992 cm−1. Control
NMR experiments show that 14 in CD2Cl2 at RT undergoes a
slow decarbonylation, affording 10 (26% conversion in 40 h)
by displacement of the weakly coordinated CO trans to P
atom. Thermal CO dissociation has been reported for
dicarbonyl ruthenium(II) complexes containing cyclometa-
lated and bulky alkyl diphosphines: namely, [Ru{(2-CH2-6-
MeC6H3)PPh2}(en)(CO)2]Cl,40 [RuCl2(dtbpe)(CO)],9,41
and [RuCl(μ-Cl)(DCyPB)(CO)]2.15a
10
10
10
10
10
13
14
e
92
ampy
BnNH2
BnNH2
92
90
f
80
5 h
3 h
82
91
300
10000
a
b
Conversions have been determined by GC analyses. Turnover
frequency (moles of ketone converted to alcohol per mole of catalyst
per hour) calculated at 50% conversion. Temperature 60 °C. S/C =
c
d
e
f
2000. Temperature 30 °C. Without NaOiPr.
5a/b affords poor activity (60% conversion in 2 h, entry 5).
Complex 6 bearing the DCyPF and ampy ligands exhibits
moderate performances with complete conversion of the
substrate in 1 h (TOF of 3000 h−1, entry 6).
Moving to monocarbonyl species, we see that complex 9
displays high catalytic activity imparted by the bulky and basic
Josiphoscy diphosphine. Interestingly, 9 (S/C = 1000−2000)
gives a quantitative conversion of acetophenone in a few
minutes at 82 °C (TOF 38000 h−1) and the rate increases by
lowering the reaction temperature to 30 °C, achieving a
remarkably high rate with a TOF of 81000 h−1 (entries 7−9),
possibly due to the facile acetate displacement promoted by
the alkyl PCy2CH moiety exerting a strong trans influence, but
with very poor enantiomeric excess (ee = 15%). Addition of
ampy to 9 at 82 °C leads to a slightly lower activity (TOF
30000 h−1, entry 10). The isopropyl derivative 10 displays a
lower reaction rate with respect to the Cy complex 9, with a
better performance at 30 °C with respect to 82 °C with TOF
values of 10000 and 8000 h−1, respectively (entries 12 and 11).
This behavior can be ascribed to the low stability of the
resulting 16-electron dihydride species [RuH2(PP)(CO)]
involved in the TH. Addition of ampy and benzylamine to
10 at 82 °C results in an increase in rate (TOF 25000 and
30000 h−1, respectively), even though the reduction requires
1−3 h to be completed (entries 13 and 14). Furthermore, in
the absence of NaOiPr, complex 10 and benzylamine give only
80% conversion in 3 h with a significantly low reaction rate
(TOF 450 h−1, entry 15).
TH of Acetophenone Catalyzed by Bulky Diphos-
phine Ruthenium Complexes. The ruthenium acetate
complexes with bulky diphosphines have been investigated in
the TH of the model substrate acetophenone with 2-propanol
in the presence of 2 mol % of NaOiPr at S/C = 1000−2000
(eq 3). The in situ addition of NN ligands to the ruthenium
complexes has been investigated to verify the NH acceleration
effect on the TH.8,32,42
The acetate precursor 1-ip (S/C = 1000) affords complete
reduction of acetophenone in 2-propanol at reflux within 4.5 h,
with a low rate (TOF = 1400 h−1) (Table 1, entry 1).
Addition of NN bidentate ligands (10 equiv) to 1-ip has
been proven to have a moderate effect on the catalysis. While
with en the TOF value is 1700 h−1 (entry 2), addition of bipy
or ampy leads to 73−91% conversion with TOF values of 1600
and 1200 h−1, respectively (entries 3 and 4). These data are
similar to those obtained with the Noyori-type aryldiphosphine
catalyst trans-[RuCl2(dppb)(en)], under identical TH con-
ditions (TOF = 1000 h−1).19d This is an unexpected result,
since the addition of ampy to ruthenium precursors containing
aryldiphosphine,19d cyclometalated phosphine,4b or carbene43
ligands resulted in an increase of activity of up to 2 orders of
magnitude.19a Employment of the isolated ampy derivatives
With regard to the dicarbonyl complexes, the trans,cis
species 13 shows very poor activity with 82% conversion of
acetophenone in 5 h (TOF of 300 h−1, entry 16). In contrast,
the cis,cis isomer 14 is more active, leading to 91% conversion
in 3 h with a TOF value of 10000 h−1 (entry 17). This can be
ascribed to the easy decarbonylation of 14, affording 10 in situ
under mild reaction conditions, due to the presence of the
basic phosphine trans to CO.
F
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
These results indicate that, for ruthenium complexes
containing basic alkyldiphosphines, the addition of amines
leads to a poor NH acceleration effect in TH, on account of
the high trans influence of the phosphines, resulting in a weak
Ru−N bond. Thus, for these complexes a better performance
is attained at low temperature, at which catalyst deactivation is
retarded.
With regard to the mechanism of the TH, it is likely that the
complex [Ru(η1-OAc)(η2-OAc)(PP)(CO)] reacts with the
strong base NaOiPr, affording the dihydride species
[RuH2(PP)(CO)] via an alkoxide β-H-elimination reaction.
Coordination of the acetophenone to the vacant site leads to
the formation of an alkoxide/hydride ruthenium species which
is protonated by 2-propanol, affording the dihydride complex
via β-H elimination and closing the cycle (inner-sphere
mechanism). Conversely, previous studies on complex 10
show that in the presence of a weak bases (NEt3) and 2-
propanol the corresponding monohydride acetate complex is
formed.21
Head-to-Head Dimerization of Terminal Alkynes
Catalyzed by Complex 10. Several transition-metal
complexes have been described to efficiently catalyze alkyne
dimerization. This represents a practical and atom-economical
way to prepare conjugated enyne products, which are relevant
intermediates for synthetic applications. However, mixtures of
different regioisomeric (head-to-head and head-to-tail prod-
ucts) and stereoisomeric Z/E enynes are usually obtained. In
addition to the studies carried out on gold and copper catalysts
in the past decade,44 great attention has been focused on group
8 metal catalysts, displaying bulky ligands that can enhance the
stereoisomeric control by limiting the substrate access to the
metal center.45 Interestingly, the ruthenium derivative 10,
containing the isopropyldiphosphine DiPPF, has been proven
to catalyze the dimerization of terminal alkynes, leading
selectively to the corresponding head-to-head 1,4-(Z/E)-
enynes (eq 4).46 Thus, phenylacetylene is dimerized to 1,4-
indicating a higher catalytic activity for the trifluoroacetate vs
acetate species. By employment of 10 with pyridine (80 equiv)
as a base, the reaction proceeds more quickly, achieving 96%
conversion of phenylacetylene in 6 h (entry 3). Conversely,
using potassium carbonate (40 equiv) as a suspension in
toluene, only 70% conversion has been observed in 6 h (entry
4). With a lower amount of N-methylcyclohexylamine, which is
more basic than pyridine, a partial conversion is attained (75%
conversion, entry 5). Complex 10 (S/C 100) in the presence
of pyridine (80 equiv) catalyzes the dimerization of 3-phenyl-
1-propyne with the same regiochemistry, leading to 1,6-
diphenyl-2-hexen-4-yne in 95% yield in 6 h with a Z/E ratio of
85/15 (entry 6). In contrast, no conversion of 1-hexyne at 60
°C has been attained.
According to mechanistic studies on ruthenium-catalyzed
terminal alkyne dimerization to enynes, the proposed pathways
entail the formation of alkynyl vinylidene M(CCR)(C
CHR) as well as alkynyl alkyne M(CCR)(η2-HCCR)
species, followed by the (migratory) insertion into the σ Ru−C
bond.47 For the head-to-head C−C coupling the control of
selectivity strongly depends on the orientation of both
fragments. Control NMR experiments show that 10 cleanly
reacts with phenylacetylene (30 equiv) in toluene at 110 °C,
affording the (Z)-enyne product and the alkynyl complex 11 as
the only detected intermediate, in accordance with eq 4 and
Scheme 4 (Figures S56 and S57 in the Supporting
Information). Thus, it is likely that the alkyne dimerization
catalyzed by 10 entails the formation of the alkynyl species
[Ru(η2-OAc)(CCR)(DiPPF)(CO)], which reacts with a
second 1-alkyne molecule, giving the alkynyl alkyne species
[Ru(η1-OAc)(CCR)(η2-HCCR)(DiPPF)(CO)]. On ac-
count of the steric hindrance of the bulky diphosphine, the R
alkyne groups will be oriented away from the metal center,
resulting in the head-to-head C−C coupling and formation of
the kinetic (Z)-enyne product.
CONCLUDING REMARKS
■
In summary, we have reported the straightforward preparation
of a class of ruthenium complexes with bulky diphosphines (PP
= DiPPF, DCyPF, DCyPP, Josiphoscy) prepared by acetate
ruthenium precursors. The high trans influence exerted by the
basic diphosphines allows easy displacement of the nitrogen
and CO ligands trans to the P atoms. The acetate ligand plays
an active role, stabilizing mononuclear complex species by
rapid switching between the mono- and bidentate modes,
favoring hydrogen bonding interactions with the solvents and
the substrates, and fostering a substitution reaction on the
metal by protonation. These complexes catalyze the transfer
hydrogenation of acetophenone, reaching a TOF of up to
81000 h−1 at 30 °C for [Ru(η1-OAc)(η2-OAc)(Josiphoscy)-
(CO)]. No significant NH acceleration effect has been
diphenyl-1-buten-3-yne (85% yield in 20 h) using 10 (S/C
100) at 110 °C, with high stereoselectivity for the kinetic Z
product (Z/E = 95/5) (entry 1, Table 2).
The effect of acidic and basic additives on the catalytic
activity of 10 was investigated, showing a variation in the
reaction rate while the regio- and stereoselectivity are
preserved. Addition of TFA (10 equiv) as strong organic
acid to 10, which leads to the in situ formation of 12, affords
99% conversion in the same reaction time (entry 2, Table 2),
Table 2. Catalytic Head-to-Head Dimerization of Terminal Alkynes (1 M) with Complex 10 (S/C = 100) in Toluene at 110 °C
a
a
entry
substrate
additive (equiv)
time (h)
product
conversion (%)
Z/E ratio
1
2
3
4
5
6
PhCCH
PhCCH
PhCCH
PhCCH
PhCCH
BnCCH
20
20
6
6
6
PhCCCHCHPh
PhCCCHCHPh
PhCCCHCHPh
PhCCCHCHPh
PhCCCHCHPh
BnCCCHCHBn
85
99
96
70
75
95
95/5
95/5
95/5
95/5
95/5
85/15
TFA (10)
pyridine (80)
K2CO3 (40)
CyNHCH3 (30)
pyridine (80)
6
a
1
Conversions have been determined by H NMR analyses.
G
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
refluxed for 2 h, until a suspension containing [Ru(η2-
OAc)2(DCyPF)] (1-cy) was formed (as verified by NMR). En (9
μL, 0.135 mmol, 1.02 equiv) was added to the mixture, which was
stirred at room temperature for 2 h, affording a yellow solution. When
the solution was cooled in an ice bath, a precipitate was formed. The
solid was filtered, washed with cold n-heptane (2 × 1 mL), and then
dried under reduced pressure. Yield: 72 mg (64%). Anal. Calcd for
C40H66FeN2O4P2Ru (857.84): C, 56.01; H, 7.75; N, 3.27. Found: C,
observed by addition of amine ligands to the dialkylphosphine
derivatives, on account of the strong P trans influence, resulting
in facile amine displacement. The derivative [Ru(η1-OAc)(η2-
OAc)(DiPPF)(CO)] is found to catalyze the selective
dimerization of PhCCH to the kinetic (Z)-enyne product
via an alkynyl ruthenium species. Further studies on the
development of new ruthenium complexes with bulky
diphosphines and their application in C−X (X = H, C, N)
bond forming reactions are underway.
1
56.10; H, 7.70; N, 3.20. H NMR (200.1 MHz, CD2Cl2, 20 °C): δ
6.09 (s, 4H; NH2), 4.32 (m, 4H; C5H4), 4.25 (pseudo t, J(H,H) = 1.7
Hz, 4H; C5H4), 2.92 (s, 4H; CH2N), 2.34−2.12 (br m, 8H; CH2 of
Cy), 2.01−1.84 (br m, 4H; CH of Cy), 1.83−1.56 (br m, 9H; CH2 of
Cy), 1.69 (s, 6H; CH3CO2), 1.55−1.10 (br m, 22H; CH2 of Cy).
13C{1H} NMR (50.3 MHz, CD2Cl2, 20 °C): δ 183.4 (t; 3J(C,P) = 2.0
Hz; OCOCH3), 79.6 (pseudo t, J(C,P) = 16.3 Hz, ipso-C5H4), 75.0
(pseudo t, J(C,P) = 3.0 Hz; C5H4), 70.3 (pseudo t, 3J(C,P) = 2.4 Hz;
EXPERIMENTAL SECTION
■
All reactions were carried out under an argon atmosphere using
standard Schlenk techniques. The solvents were carefully dried by
standard methods and distilled under argon before use.
The ruthenium complexes [Ru(η2-OAc)2(PPh3)2],23c [Ru(η2-
OAc)2(DiPPF)] (1-ip),21 [Ru(η1-OAc)(η2-OAc)(PPh3)2(CO)],48
1
C5H4), 43.8 (s; CH2N), 39.8 (t, J(C,P) = 8.7 Hz; PCH), 29.8 (d,
2J(C,P) = 7.9 Hz; CH2 of Cy), 28.4 (t, 3J(C,P) = 4.6 Hz; CH2 of Cy),
26.9 (s; CH2 of Cy), 26.1 (s; OCOCH3). 31P{1H} NMR (81.0 MHz,
CD2Cl2, 20 °C): δ 38.0 (s).
[Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)] (10),21 and [RuCl2(CO)2]n
49
were prepared according to literature procedures, whereas all other
chemicals were purchased from Aldrich and Strem and used without
further purification. NMR measurements were recorded on Bruker
AC 200 and Avance III HD NMR 400 spectrometers. Chemical shifts
NMR Evidence of trans-[Ru(η1-OAc)2(DiPPF)(ampy)] (4). The
trans isomer 4 (kinetic product) was characterized by NMR analysis
of the in situ reaction between 1-ip (25 mg 0.039 mmol) and ampy
(4.1 μL, 0.040 mmol, 1.02 equiv) in 0.5 mL of CD2Cl2 at -60 °C. 1H
1
(ppm) are relative to TMS for H and 13C{1H}, whereas H3PO4 was
used for 31P{1H}. Infrared measurements were obtained with a Bruker
Vector 22 FTIR spectrometer. Elemental analyses (C, H, N) were
carried out with a Carlo Erba 1106 analyzer, whereas GC analyses
were performed with a Varian CP-3380 gas chromatograph equipped
with a 25 m length MEGADEX-ETTBDMS-β chiral column with
hydrogen (5 psi) as the carrier gas and a flame ionization detector
(FID).
3
NMR (200.1 MHz, CD2Cl2, −60 °C): δ 9.01 (d, J(H,H) = 5.5 Hz,
1H; o-C5H4N), 8.80 (br s, 1H; NH2), 7.69 (t, 3J(H,H) = 7.7 Hz, 1H;
p-C5H4N), 7.33 (d, 3J(H,H) = 7.7 Hz, 1H; m-C5H4N), 7.20 (t,
3J(H,H) = 6.7 Hz, 1H; m-C5H4N), 4.86 (br s, 1H; NH2) 4.55−3.80
(br m, 8H; C5H4), 4.16 (s, 2H; CH2N), 2.95−2.30 (br m, 4H;
CH(CH3)2), 1.78 (s, 3H; CH3CO2), 1.67−1.10 (br m, 15H;
CH(CH3)2), 1.42 (br s, 3H; CH3CO2), 0.88 (m, 3H; CH(CH3)2),
0.77 (m, 3H; CH(CH3)2), 0.57 (m, 3H; CH(CH3)2). 13C{1H} NMR
(50.3 MHz, CD2Cl2, −60 °C): δ 182.5 (s; OCOCH3), 181.0 (s;
OCOCH3), 164.8 (s; NCCH2), 154.5 (s; C(6) of Py), 135.8 (s; C(4)
of Py), 122.0 (s; C(3) of Py), 119.7 (s; C(5) of Py), 84.8 (d, 1J(C,P)
= 34.8 Hz, 3J(C,P) = 3.1 Hz; ipso-C5H4), 83.8 (d, 1J(C,P) = 30.8 Hz;
ipso-C5H4), 73.1 (s; C5H4), 71.0 (s; C5H4), 70.0 (s; C5H4), 67.3 (s;
C5H4), 50.8 (s; CH2N), 31.3 (d, 1J(C,P) = 17.9 Hz; CH(CH3)2), 29.8
Synthesis of [Ru(η2-OAc)2(DCyPF)] (1-cy). [Ru(η2-
OAc)2(PPh3)2] (100 mg, 0.134 mmol) and DCyPF (81.6 mg,
0.141 mmol, 1.05 equiv) were suspended in toluene (0.75 mL), and
the mixture was refluxed for 1 h. The obtained red solution was
concentrated to almost 1 mL, with evaporation of the solvent under
reduced pressure, and the product was precipitated by addition of n-
pentane (10 mL). The solid was filtered, washed with n-pentane (2 ×
3 mL), and dried under reduced pressure. Yield: 49.2 mg (46%). Anal.
Calcd for C38H58FeO4P2Ru (797.74): C, 57.21; H, 7.33. Found: C,
57.30; H, 7.40. 1H NMR (200.1 MHz, CD2Cl2, 20 °C): δ 4.28 (br t,
1
1
(d, J(C,P) = 14.3 Hz; CH(CH3)2), 27.5 (d, J(C,P) = 18.7 Hz;
CH(CH3)2), 25.2 (s; OCOCH3), 24.8 (d, 1J(C,P) = 17.2 Hz;
CH(CH3)2), 23.5 (s; CH(CH3)2), 20.2 (br s; CH(CH3)2), 20.0 (s;
CH(CH3)2), 19.1 (s; CH(CH3)2), 18.3 (s; CH(CH3)2), 17.8 (br s;
CH(CH3)2), 17.6 (s; CH(CH3)2), 16.6 (s; CH(CH3)2). 31P{1H}
3
3J(H,H) = 1.4 Hz, 4H; C5H4), 4.19 (br t, J(H,H) = 1.7 Hz, 4H;
C5H4), 2.23 (br s, 4H; PCH of Cy), 2.04−1.56 (br m, 20H; CH2 of
Cy), 1.85 (s, 6H; CH3CO2), 1.52−1.01 (br m, 20H; CH2 of Cy).
31P{1H} NMR (81.0 MHz, CD2Cl2, 20 °C): δ 64.1 (s).
2
NMR (81.0 MHz, CD2Cl2, −60 °C): δ 45.2 (d, J(P,P) = 29.2 Hz),
43.5 (d, 2J(P,P) = 29.2 Hz). 1H NMR (200.1 MHz, CD2Cl2, 0 °C): δ
Synthesis of trans-[Ru(η1-OAc)2(DiPPF)(en)] (2). [Ru(η2-
OAc)2(PPh3)2] (139 mg, 0.187 mmol) and DiPPF (82 mg, 0.196
mmol, 1.05 equiv) were suspended in n-heptane (2.0 mL) and
refluxed for 2 h, leading to an orange suspension of [Ru(η2-
OAc)2(DiPPF)] (1-ip) (verified by NMR). En (12.5 μL, 0.187 mmol,
1.0 equiv) was added, and the mixture was stirred for 2 h at RT,
affording a yellow precipitate. The complex was filtered, washed with
cold n-pentane (2 × 1 mL), and dried under reduced pressure. Yield:
67.8 mg (52%). Anal. Calcd for C28H50FeN2O4P2Ru (697.58): C,
48.21; H, 7.22; N, 4.02. Found: C, 48.20; H, 7.20; N, 3.96. 1H NMR
(200.1 MHz, CDCl3, 20 °C): δ 5.99 (br s, 4H; NH2), 4.42 (br s, 4H;
C5H4), 4.27 (pseudo t, J(H,H) = 1.7 Hz, 4H; C5H4), 2.97 (br s, 4H;
CH2N), 2.54 (hept, 3J(H,H) = 7.0 Hz, 4H; CH(CH3)2), 1.72 (s, 6H;
3
3
9.13 (d, J(H,H) = 7.8 Hz, 1H; o-C5H4N), 7.69 (t, J(H,H) = 14.5
Hz, 1H; p-C5H4N), 7.33 (d, 3J(H,H) = 15.3 Hz, 1H; m-C5H4N), 7.19
(t, 3J(H,H) = 13.0 Hz, 1H; m-C5H4N), 4.47 (s, 2H; C5H4), 4.35 (br t,
3J(H,H) = 11.1 Hz, 2H; CH2N), 4.28 (s, 2H; C5H4), 4.21 (s, 2H;
C5H4), 4.15 (s, 2H; C5H4), 3.41 (br s, 2H; NH2), 2.83−2.51 (br m,
3
4H; CH(CH3)2), 1.62 (s, 6H; CH3CO2), 1.38 (dd, J(P,H) = 27.5
3
3
Hz, J(H,H) = 15.0 Hz, 6H; CH(CH3)2), 1.16 (dd, J(P,H) = 21.1
3
Hz, J(H,H) = 13.6, 18H; CH(CH3)2). 31P{1H} NMR (81.0 MHz,
CD2Cl2, 0 °C): δ 45.0 (br s).
Synthesis of the Cationic [Ru(η2-OAc)(DiPPF)(ampy)]OAc
(5a) and cis-[Ru(η1-OAc)2(DiPPF)(ampy)] (5b) Derivatives.
Method A. 1-ip (50 mg, 0.0784 mmol) and ampy (6.0 μL, 0.0827
mmol, 1.05 equiv) were dissolved in MeOH (2 mL), and the mixture
was stirred for 1 h at RT. The solvent was evaporated under reduced
pressure from the resulting orange solution, and the residue was
dissolved in CH2Cl2 (0.5 mL). Addition of cold n-pentane (2 mL)
afforded a yellow-orange precipitate that was filtered, washed with n-
pentane (3 × 2 mL), and dried under reduced pressure. Yield: 45 mg
(77%).
3
3
CH3CO2), 1.26 (dd, J(P,H) = 12.1 Hz, J(H,H) = 7.0 Hz, 12H;
3
3
CH(CH3)2), 1.15 (dd, J(P,H) = 12.2 Hz, J(H,H) = 7.1 Hz, 12H;
CH(CH3)2). 13C{1H} NMR (50.3 MHz, CDCl3, 20 °C): δ 183.6 (dd,
3J(C,P) = 1.9 Hz, 3J(C,P) = 0.8 Hz; OCOCH3), 79.4 (pseudo-t,
J(C,P) = 17.4 Hz, ipso-C5H4), 74.3 (pseudo t, J(C,P) = 3.1 Hz;
C5H4), 69.9 (pseudo t, J(C,P) = 2.2 Hz; C5H4), 43.5 (s; CH2), 27.8
(pseudo t, J(C,P) = 9.5 Hz; CH(CH3)2), 26.1 (s; OCOCH3), 19.8 (s;
CH(CH3)2), 19.7 (s; CH(CH3)2). 31P{1H} NMR (81.0 MHz, CDCl3,
20 °C): δ 44.9 (s).
Method B. [Ru(η2-OAc)2(PPh3)2] (2.0 g, 2.690 mmol) and DiPPF
(1.181 g, 2.823 mmol, 1.05 equiv) were suspended in cyclohexane (14
mL), and the mixture was refluxed for 2 h. The resulting orange
suspension consists of 1-ip, as verified by NMR analysis. A solution of
ampy (278 μL, 2.697 mmol, 1.0 equiv) in MEK (2 mL) was added to
the mixture, which was stirred at room temperature for 4 h, affording
Synthesis of trans-[Ru(η1-OAc)2(DCyPF)(en)] (3). [Ru(η2-
OAc)2(PPh3)2] (98 mg, 0.132 mmol) and DCyPF (80 mg, 0.138
mmol, 1.05 equiv) were suspended in n-heptane (1.5 mL) and
H
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
a yellow precipitate containing 4 as the main species (4/1-ip/5a/5b =
3/0.5/1/0.1). The mixture was evaporated under reduced pressure,
and the residue was dissolved in MeOH (10 mL) and stirred at RT
for 1 h. The solvent was evaporated under reduced pressure from the
resulting orange solution, and the residue was dissolved in CH2Cl2 (2
mL). Addition of cold n-pentane (10 mL) afforded a yellow-orange
precipitate that was filtered, washed with n-pentane (3 × 10 mL), and
dried under reduced pressure. The product consists of a 4/1 molar
mixture of the cationic [Ru(η2-OAc)(DiPPF)(ampy)]OAc (5a) and
cis-[Ru(η1-OAc)2(DiPPF)(ampy)] (5b) derivatives. Yield: 1.31 g
(65%). Anal. Calcd for C32H50FeN2O4P2Ru (745.62): C, 51.55; H,
OCOCH3 major), 21.8 (m; CH(CH3)2 minor), 20.9 (d, 2J(C,P) = 4.6
Hz; CH(CH3)2 major), 20.3 (d, 2J(C,P) = 2.9 Hz; CH(CH3)2 major),
2
20.2 (s; OCOCH3 major), 20.1 (d, J(C,P) = 2.0 Hz; CH(CH3)2
major), 19.8 (d, 2J(C,P) = 3.7 Hz; CH(CH3)2 major), 19.6 (d,
2J(C,P) = 3.7 Hz; CH(CH3)2 major), 19.4 (br s; CH(CH3)2 major),
2
18.6 (d, J(C,P) = 1.2 Hz; CH(CH3)2 major). 31P{1H} NMR (81.0
MHz, CD2Cl2/CD3OD, 20 °C): δ 65.5 (d, 2J(P,P) = 24.7 Hz; minor
isomer), 62.9 (d, 2J(P,P) = 27.5 Hz; major isomer), 51.2 (d, 2J(P,P) =
2
27.5 Hz; major), 45.4 (d, J(P,P) = 24.7 Hz; minor).
Synthesis of trans-[Ru(η1-OAc)2(DCyPF)(ampy)] (6). [Ru(η2-
OAc)2(PPh3)2] (98 mg, 0.132 mmol) and DCyPF (80 mg, 0.138
mmol, 1.05 equiv) were suspended in n-heptane (1.5 mL). The
mixture was refluxed for 2 h, leading to 1-cy as inferred by NMR
analysis. Ampy (14 μL, 0.136 mmol 1.03 equiv) was added to the
solution, rapidly affording a yellow precipitate. The solid was filtered,
washed with cold n-heptane (3 × 2 mL), and then dried under
reduced pressure. Yield: 78 mg (65%). Anal. Calcd for
C44H66FeN2O4P2Ru (905.88): C, 58.34; H, 7.34; N, 3.09. Found:
C, 58.40; H, 7.26; N, 3.01. 1H NMR (200.1 MHz, CDCl3, 20 °C): δ
9.02 (d, 3J(H,H) = 2.0 Hz, 1H; o-C5H4N), 7.62 (t, 3J(H,H) = 7.1 Hz,
1H; p-C5H4N), 7.25 (br s, 1H; NH2), 7.16 (pseudo t, J(H,H) = 6.7
Hz, 2H; m-C5H4N), 4.43 (br s, 2H; C5H4), 4.36 (br s, 3H; C5H4 and
NH2), 4.16 (br s, 4H; C5H4), 4.11 (m, 2H; CH2N), 2.39 (s, 4H; PCH
of Cy), 2.27−0.91 (m, 46H; CH3CO2 and CH2 of Cy). 13C{1H}
NMR (50.3 MHz, CDCl3, 20 °C): δ 180.3 (s; OCOCH3), 176.4 (s;
OCOCH3), 163.1 (s; NCCH2), 150.3 (s; C(6) of Py), 137.1 (s; C(4)
of Py), 123.0 (s; C(3) of Py), 120.9 (s; C(5) of Py), 95.0−93.2 (m;
ipso-C5H4), 88.9 (m; ipso-C5H4), 73.5−71.2 (m; C5H4), 73.5−71.2
(m; C5H4), 69.5 (m; C5H4), 68.7 (m; C5H4), 68.2 (d, J(C,P) = 3.0
Hz; C5H4), 52.6 (s; CH2N), 32.6−32.2 (m; PCH (Cy)), 32.1−26.4
(m; CH2 (Cy)), 25.4 (s; OCOCH3), 24.5 (s; OCOCH3). 31P{1H}
NMR (81.0 MHz, CDCl3, 20 °C): δ 39.2 (d, 2J(P,P) = 28.9 Hz), 37.0
1
6.76; N, 3.76. Found: C, 51.60; H, 6.85; N, 3.80. H NMR (400.1
MHz, CD3OD, 25 °C): δ 9.17 (d, 3J(H,H) = 5.5 Hz, 0.2H; o-C5H4N
3
minor isomer), 8.86 (d, J(H,H) = 5.6 Hz, 0.8H; o-C5H4N major
3
4
isomer), 8.06 (td, J(H,H) = 7.8 Hz, J(H,H) = 1.4 Hz, 0.8H; p-
3
C5H4N major), 7.82 (t, J(H,H) = 7.7 Hz, 0.2H; p-C5H4N minor),
7.72 (d, 3J(H,H) = 7.8 Hz, 0.8H; m-C5H4N major), 7.63 (t, J(H,H)
3
3
= 6.5 Hz, 0.8H; m-C5H4N major), 7.51 (d, J(H,H) = 7.7 Hz, 0.2H;
m-C5H4N minor), 7.37 (t, 3J(H,H) = 6.2 Hz, 0.2H; m-C5H4N minor),
4.86−4.26 (m, 8H; C5H4 major + minor), 4.59 (br s, 0.8H; CH2N
major), 4.53 (s, 0.2H; CH2N minor), 4.34 (s, 0.8H; CH2N major),
4.30 (s, 0.2H; CH2N minor). 2.83−2.65 (m, 2H; CH(CH3)2 major +
minor), 2.60−2.48 (m, 2H; CH(CH3)2 major + minor), 2.01 (s,
0.6H; CH3CO2 minor), 1.92 (s, 3.6H; CH3CO2 major + minor), 1.76
(s, 2.4H; CH3CO2 major), 1.63−1.44 (m, 6H; CH(CH3)2 major +
minor), 1.43−1.28 (m, 9H; CH(CH3)2 major + minor), 1.23 (dd,
3J(P,H) = 12.6 Hz, 3J(H,H) = 7.1 Hz, 2.4H; CH(CH3)2 major),
3
1.08−0.99 (m, 0.6H; CH(CH3)2 minor), 0.86 (dd, J(P,H) = 12.9
Hz, 3J(H,H) = 7.1 Hz, 2.4H; CH(CH3)2 major), 0.66 (dd, 3J(P,H) =
12.2 Hz, 3J(H,H) = 7.2 Hz, 2.4H; CH(CH3)2 major), 0.09 (dd,
3
3J(P,H) = 14.8 Hz, J(H,H) = 7.7 Hz, 0.6H; CH(CH3)2 minor).
2
31P{1H} NMR (162.0 MHz, CD3OD, 25 °C): δ 65.1 (d, J(P,P) =
2
(d, J(P,P) = 28.9 Hz).
25.4 Hz; minor), 62.8 (d, 2J(P,P) = 27.2 Hz; major), 50.8 (d, 2J(P,P)
Synthesis of [Ru(η1-OAc)(η2-OAc)(DCyPP)(CO)] (8). [Ru(η1-
OAc)(η2-OAc)(PPh3)2(CO)] (200 mg, 0.259 mmol) and DCyPP
(226 mg, 0.518 mmol, 2.0 equiv) were suspended in cyclohexane (3.5
mL) and heated at 90 °C for 6 h. The obtained solution was cooled to
4 °C overnight, affording a precipitate that was filtered, washed with
cold n-pentane (3 × 1 mL), and dried under reduced pressure. Yield:
124 mg (70%). Anal. Calcd for C32H56O5P2Ru (683.81): C, 56.21; H,
8.25. Found: C, 56.28; H, 8.24. IR (Nujol): 1932 (s) cm−1 (νCO).
1H NMR (200.1 MHz, CD2Cl2, 25 °C): δ 2.51−2.31 (m, 2H; PCH of
Cy), 2.31−2.10 (m, 6H; PCH of Cy and PCH2), 2.00 (br s, 2H;
PCH2CH2), 1.95−1.83 (m, 6H; CH2 of Cy), 1.90 (br s, 6H;
CH3CO2), 1.83−1.73 (m, 6H; CH2 of Cy), 1.69 (br d, J(H,H) = 12.4
Hz, 2H; CH2 of Cy), 1.61−1.08 (m, 26H; CH2 of Cy). 13C{1H}
2
= 27.2 Hz; major), 44.5 (d, J(P,P) = 25.4 Hz; minor).
1H NMR (200.1 MHz, CD2Cl2/CD3OD, 20 °C): δ 9.07 (d,
3J(H,H) = 5.6 Hz, 0.2H; o-C5H4N minor isomer), 8.73 (d, 3J(H,H) =
3
4.7 Hz, 0.8H; o-C5H4N major isomer), 7.92 (t, J(H,H) = 7.7 Hz,
3
0.8H; p-C5H4N major), 7.71 (t, J(H,H) = 9.0 Hz, 0.2H, p-C5H4N
3
minor), 7.59 (d, J(H,H) = 7.8 Hz, 0.8H; m-C5H4N major), 7.48 (t,
3J(H,H) = 6.2 Hz, 0.8H; m-C5H4N major), 7.22 (m, 0.4H; m-C5H4N
minor), 4.55 (br s, 0.8H; CH2N major), 4.46−4.07 (m, 8H; C5H4
major + minor), 4.34 (s, 0.8H; CH2N major), 4.19 (s, 0.2H; CH2N
minor), 3.88 (s, 0.2H; CH2N minor), 2.76−2.32 (br m, 4H;
CH(CH3)2 major + minor), 1.97 (s, 0.6H; CH3CO2 minor), 1.88
(s, 3.6H; CH3CO2 major + minor), 1.71 (s, 2.4H; CH3CO2 major),
3
3
2
1.48 (dq, J(P,H) = 15.0 Hz, J(H,H) = 7.0 Hz, 6H; CH(CH3)2
major + minor), 1.39−0.99 (br m, 12H; CH(CH3)2 major + minor),
NMR (100.6 MHz, CD2Cl2, 25 °C): δ 204.0 (t, J(C,P) = 17.2 Hz;
3
CO), 182.9 (d, J(C,P) = 16.0 Hz; OCOCH3), 182.5−181.6 (m;
3
3
1
0.67 (dq, J(P,H) = 15.8 Hz, J(H,H) = 7.1 Hz, 6H; CH(CH3)2
OCOCH3), 34.9−34.4 (m; PCH(Cy)), 33.6 (br dd, J(C,P) = 20.2
major + minor). 3C{1H} NMR (50.3 MHz, CD2Cl2/CD3OD, 20 °C):
δ 188.7 (s; OCOCH3 minor isomer), 188.1 (d, J(C,P) = 2.0 Hz;
3
Hz, J(C,P) = 5.5 Hz; PCH(Cy)), 29.6 (s; CH2 of Cy), 29.2 (d,
3
J(C,P) = 6.6 Hz; CH2 of Cy), 28.9 (d, J(C,P) = 8.1 Hz; CH2 of Cy),
28.7 (d, J(C,P) = 7.3 Hz; CH2 of Cy), 28.4 (d, J(C,P) = 11.7 Hz; CH2
of Cy), 28.0 (pseudo-t, J(C,P) = 5.9 Hz; CH2 of Cy), 27.5 (d, J(C,P)
= 8.1 Hz; CH2 of Cy), 26.9 (s; CH2 of Cy), 26.5 (s; CH2 of Cy), 25.2
(s; OCOCH3), 24.4 (s; OCOCH3), 19.3 (s; PCH2CH2), 16.6 (d,
1J(C,P) = 31.5 Hz; PCH2). 31P{1H} NMR (162.0 MHz, CD2Cl2, 25
°C): δ 42.0 (br s).
OCOCH3 major isomer), 186.2 (s; OCOCH3 minor), 179.1 (d,
3
3J(C,P) = 1.1 Hz; OCOCH3 major), 162.1 (d, J(C,P) = 1.1 Hz;
NCCH2 major), 150.5 (br s; C(6) of Py major), 149.1 (s; C(6) of Py
minor), 138.4 (s; C(4) of Py major), 137.1 (s; C(4) of Py minor),
124.7 (d, 3J(C,P) = 2.3 Hz; C(3) of Py major), 123.2 (s; C(3) of Py
3
minor), 122.5 (s; C(5) of Py minor), 121.5 (d, J(C,P) = 1.4 Hz;
1
Synthesis of [Ru(η1-OAc)(η2-OAc)(Josiphoscy)(CO)] (9). [Ru-
(η1-OAc)(η2-OAc)(PPh3)2(CO)] (200 mg, 0.259 mmol) and
Josiphoscy (157 mg, 0.259 mmol) were suspended in toluene (2
mL), and the mixture was heated at 90 °C for 24 h. The resulting
solution was cooled to room temperature and concentrated to almost
1 mL, by removal of the solvent under reduced pressure. Addition of
cold n-pentane (4 °C, 1 mL) afforded an orange precipitate that was
filtered, washed with cold n-pentane (2 × 2 mL), and dried under
reduced pressure. Yield: 100 mg (45%). Anal. Calcd for
C41H62FeO5P2Ru (853.80): C, 57.68; H, 7.32. Found: C, 57.73; H,
C(5) of Py major), 84.3 (d, J(C,P) = 35 Hz; ipso-C5H4 major), 82.6
(d, 1J(C,P) = 39 Hz; ipso-C5H4 major), 75.0 (br s; C5H4 minor), 74.1
(m; C5H4 minor), 73.9 (m; C5H4 minor), 73.5 (d, 2J(C,P) = 3.8 Hz;
C5H4 major), 73.4 (d, 2J(C,P) = 3.4 Hz; C5H4 major), 73.2 (d,
2
2J(C,P) = 3.6 Hz; C5H4 minor), 72.6 (d, J(C,P) = 1.3 Hz; C5H4
minor), 72.2 (d, J(C,P) = 5.8 Hz; C5H4 major), 72.0 (d, J(C,P) = 2.0
Hz; C5H4 major), 71.7 (d, J(C,P) = 2.5 Hz; C5H4 major), 71.6 (br s;
C5H4 major), 70.0 (d; J(C,P) = 3.6 Hz; C5H4 major), 69.8 (d; J(C,P)
= 3.9 Hz; C5H4 major), 52.6 (d; 3J(C,P) = 2.8 Hz CH2N major), 30.6
(d, 1J(C,P) = 28.6 Hz; CH(CH3)2 major), 30.3 (d, 1J(C,P) = 24.7 Hz;
CH(CH3)2 major), 29.8 (d, J(C,P) = 22.0 Hz; CH(CH3)2 major),
1
7.38. IR (Nujol): 1948 (s) cm−1 (νCO). H NMR (400.1 MHz,
1
29.1 (d, J(C,P) = 21.6 Hz; CH(CH3)2 major), 24.5 (s; OCOCH3
CD2Cl2, 20 °C): δ 4.70 (br s; C5H3), 4.58 (br s; C5H3), 4.45 (m;
major), 24.4 (d, 1J(C,P) = 1.5 Hz; CH(CH3)2 minor), 24.2 (s;
C5H3), 4.42 (br s; C5H3), 4.39 (br s; C5H3), 4.27 (s; C5H5), 4.25 (s;
I
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
2
C5H5), 3.37 (pseudo-p; CHCH3), 2.82 (d, 3J(P,H) = 10.7 Hz; CH of
Cy), 2.71 (m; CH of Cy), 2.60−2.13 (m; CH2 of Cy), 2.00 (br s;
CH3CO2), 1.87 (br s; CH3CO2), 2.12−1.54 (m; CHCH3 + CH2 of
Cy), 1.48−1.09 (m; CHCH3 + CH2 of Cy). 13C{1H} NMR (100.6
MHz, CD2Cl2, 20 °C): δ 206.0−205.1 (m; CO), 187.0 (br s;
OCOCH3), 176.0−175.8 (m; OCOCH3), 170.4−169.9 (m;
= 2.7 Hz; CH(CH3)2), 19.2 (d, J(C,P) = 4.7 Hz; CH(CH3)2), 19.0
(s; CH(CH3)2). 31P{1H} NMR (81.0 MHz, CD2Cl2, 20 °C): δ 70.0
2
2
(d, J(P,P) = 15.9 Hz), 30.4 (d, J(P,P) = 15.9 Hz).
Synthesis of [Ru(η1-OCOCF3)(η1-OCOCF3)(DiPPF)(CO)] (12).
Complex 10 (130 mg, 0.195 mmol) was suspended in diethyl ether (3
mL). TFA (32 μL, 0.418 mmol, 2.14 equiv) was added, and the
mixture was stirred for 30 min at room temperature, affording a dark
yellow solution; then CaCO3 (80 mg, 0.799 mmol, 4.10 equiv) was
added and this mixture was stirred for 2 h at room temperature. The
mixture was filtered, and the solvent was removed from the filtrate by
evaporation under reduced pressure, affording the product as a yellow
powder. Yield: 106 mg (70%). Anal. Calcd for C27H36F6FeO5P2Ru
(773.43): C, 41.93; H, 4.69. Found: C, 42.01; H, 4.74. IR (Nujol):
1932 (vs) (νCO); 1607 (s), 1558 (s) cm−1 (νCO). 1H NMR (400.1
MHz, CD2Cl2, 25 °C): δ 4.90 (br s, 2H; C5H4), 4.61 (s, 2H; C5H4),
4.52 (s, 2H; C5H4), 4.44 (s, 2H; C5H4), 3.40−2.35 (br m, 2H;
CH(CH3)2), 2.59 (br s, 2H; CH(CH3)2), 1.62 (br s, 6H;
1
OCOCH3), 93,4 (m; ipso-C5H3), 91.8 (d, J(C,P) = 14.8 Hz; ipso-
C5H3), 74.3 (s; C5H5), 71.7 (s; C5H5), 70.3 (s; C5H5), 69.7 (s; C5H5),
69.3 (s; C5H5), 69.0 (d, J(C,P) = 7.1 Hz; C5H3), 68.8 (d, J(C,P) = 5.2
Hz; C5H3), 67.8 (d, J(C,P) = 5.8 Hz; C5H3), 44.6 (d, 1J(C,P) = 30.9
Hz; CHCH3), 39.6 (d, 1J(C,P) = 23.6 Hz; CHCH3), 35.2 (d, 1J(C,P)
1
= 19.2 Hz; PCH(Cy)), 33.4 (d, J(C,P) = 24.7 Hz; PCH(Cy)), 30.8
(s; CH2 of Cy), 29.7 (s; CH2 of Cy), 29.4 (d, J(C,P) = 6.1 Hz; CH2 of
Cy), 28.6 (d, J(C,P) = 7.4 Hz; CH2 of Cy), 28.4 (d, J(C,P) = 14.0 Hz;
CH2 of Cy), 28.0 (d, J(C,P) = 10.0 Hz; CH2 of Cy), 27.6 (d, J(C,P) =
11.4 Hz; CH2 of Cy), 27.3 (d, J(C,P) = 8.5 Hz; CH2 of Cy), 27.1 (d,
J(C,P) = 15.0 Hz; CH2 of Cy), 26.4 (d, J(C,P) = 8.5 Hz; CH2 of Cy),
26.2 (br s; CH2 of Cy), 24.7 (s; OCOCH3), 24.1 (s; OCOCH3), 15.9
(d, 2J(C,P) = 3.4 Hz; CHCH3), 14.9 (d, 2J(C,P) = 6.5 Hz; CHCH3),
3
3
CH(CH3)2), 1.42 (dd, J(P,H) = 15.3 Hz, J(H,H) = 6.9 Hz, 6H;
3
CH(CH3)2), 1.28 (br s, 6H; CH(CH3)2), 0.94 (dd, J(P,H) = 11.6
Hz, 3J(H,H) = 6.3 Hz, 6H; CH(CH3)2). 13C{1H} NMR (100.6 MHz,
2
13.8 (d, J(C,P) = 6.1 Hz; CHCH3). 31P{1H} NMR (162.0 MHz,
2
CD2Cl2, 25 °C): δ 203.6 (t, J(C,P) = 18.7 Hz, CO), 166.7 (m;
OCOCF3), 164.8 (m; OCOCF3), 115.6 (q, JCF = 287.1 Hz; CF3),
CD2Cl2, 20 °C): δ 77.2 (br s; minor species), 71.0 (br s; major
species), 46.4 (br s; minor species), 39.7 (br s; major species).
Synthesis of [Ru(η1-OAc)(η2-OAc)(DiPPF)(CO)]21 (10). Meth-
od A. [RuCl2(CO)2]n (131 mg, 0.574 mmol) and DiPPF (264 mg,
0.631 mmol, 1.1 equiv) were suspended in toluene (5 mL) and
refluxed for 2.5 h. Sodium acetate (236 mg, 2,88 mmol) was added to
the yellow suspension, and the mixture was refluxed for 24 h. The
resulting solution was cooled to room temperature, and diethyl ether
(5 mL) was added, affording a yellow precipitate. The solid was
filtered, washed with diethyl ether (2 × 1 mL), and dried under
reduced pressure. Yield: 203 mg (53%).
1
79.4 (m; ipso-C5H4), 78.8 (m; ipso-C5H4), 74.9 (br s; C5H4), 72.1 (br
s; C5H4), 70.4 (t, J(C,P) = 2.5 Hz; C5H4), 26.7 (d, 1J(C,P) = 25.9 Hz;
CH(CH3)2), 26.0−25.3 (br m; CH(CH3)2), 20.8 (br s; CH(CH3)2),
19.0 (s; CH(CH3)2), 17.9 (br s; CH(CH3)2). 31P{1H} NMR (162.0
MHz, CD2Cl2, 25 °C): δ 62.3 (s). 19F{1H} NMR (376.6 MHz,
CD2Cl2, 25 °C): δ −70.2 (s), −70.3 (s).
NMR Evidence of [Ru(OAc)(OCOCF3)(DiPPF)(CO)]. Addition of
1 equiv of TFA (1.2 μL; 0.0157 mmol) to 10 (10.4 mg, 0.0157 mmol)
in 0.5 mL of CD2Cl2 at RT afforded quantitatively the mixed
carboxylate complex as inferred from NMR analysis. 1H NMR (200.1
MHz, CD2Cl2, 20 °C): δ 5.04−4.68 (m, 2H; C5H4), 4.52 (m, 2H;
C5H4), 4.44 (br s, 2H; C5H4), 4.34 (s, 2H; C5H4), 3.07−2.71 (br m,
1H; CH(CH3)2), 2.70−2.25 (br m, 2H; CH(CH3)2), 2.42 (hept,
3J(H,H) = 7.1 Hz, 1H; CH(CH3)2), 1.87 (s, 3H; OCOCH3), 1.81−
1.52 (m, 6H; CH(CH3)2), 1.50−1.15 (m, 12H; CH(CH3)2), 1.12−
0.81 (m, 6H; CH(CH3)2). 31P{1H} NMR (81.0 MHz, CD2Cl2, 20
°C): δ 67.8 (br s), 59.9 (br s).
Method B. trans,cis-[Ru(η1-OAc)2(CO)2(DiPPF)] (13; 197 mg,
0.284 mmol) was heated at 120 °C under reduced pressure for 16 h,
affording 10. Yield: 176 mg (93%).
Synthesis of [Ru(η2-OAc)(CCPh)(DiPPF)(CO)] (11). Complex
10 (100 mg, 0.150 mmol) was suspended in toluene (3 mL), and
phenylacetylene (18.4 mg, 0.180 mmol, 1.2 equiv) and pyridine (24.2
μL, 0.30 mmol, 2 equiv) were added. The resulting solution was
stirred at 50 °C for 30 min and cooled at 4 °C overnight, affording a
precipitate that was filtered, washed with cold n-pentane (3 × 2 mL),
and dried under reduced pressure. Yield: 69 mg (65%). Anal. Calcd
for C33H44FeO3P2Ru (707.52): C, 56.02; H, 6.27. Found: C, 55.97;
H, 6.24. IR (Nujol): 2098 (s) (νCC); 1923 (vs) (νCO); 1592 (s),
1532 cm−1 (νCO). 1H NMR (200.1 MHz, CD2Cl2, 20 °C): δ 7.37−
7.02 (m, 5H; aromatic protons), 4.70 (dd, 3J(H,H) = 2.2 Hz, 3J(P,H)
= 1.1 Hz, 1H; C5H4), 4.62 (dd, 3J(H,H) = 2.3 Hz, 3J(P,H) = 1.2 Hz,
1H; C5H4), 4.47 (m, 2H; C5H4), 4.41 (m, 2H; C5H4), 4.36 (m, 2H;
Synthesis of trans,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (13). Com-
plex 1-ip (60 mg, 0.094 mmol) was dissolved in CH2Cl2 (3 mL) and
vigorously stirred under a CO atmosphere (1 atm) for 30 min at room
temperature. The solvent was evaporated under reduced pressure,
leading to the product as a yellow powder. Yield: 63.9 mg (98%).
Anal. Calcd forC28H42FeO6P2Ru (693.50): C, 48.49; H, 6.10. Found:
C, 48.40; H, 6.20. IR (Nujol): 2058 (vs), 1964 (vs) (νCO); 1625 (s),
1598 (w) cm−1 (νCO). H NMR (200.1 MHz, CDCl3, 20 °C): δ
1
3
4.69 (br s, 4H; C5H4), 4.48 (br s, 4H; C5H4), 2.57 (hept, J(H,H) =
3
C5H4), 2.94 (hept, J(H,H) = 7.1 Hz, 1H; CH(CH3)2), 2.85−2.64
5.9 Hz, 4H; CH(CH3)2), 1.93 (s, 6H; CH3CO2), 1.29 (dd, 3J(P,H) =
(m, 1H; CH(CH3)2), 2.42 (hept, 3J(H,H) = 7.1 Hz, 2H; CH(CH3)2),
1.92 (s, 3H; OCOCH3), 1.59 (dd, 3J(P,H) = 16.2 Hz, 3J(H,H) = 7.1
Hz, 3H; CH(CH3)2), 1.48 (dd, 3J(H,H) = 7.1 Hz, 3J(P,H) = 3.0 Hz,
3H; CH(CH3)2), 1.45−1.18 (several m, 15H; CH(CH3)2), 0.92 (dd,
3
3
13.2 Hz, J(H,H) = 7.1 Hz, 12H; CH(CH3)2), 1.14 (dd, J(P,H) =
13.3 Hz, J(H,H) = 7.1 Hz, 12H; CH(CH3)2). 13C{1H} NMR (50.3
3
2
2
MHz, CDCl3, 20 °C): δ 195.9 (dd, J(C,P) = 105.0 Hz, J(C,P) =
21.5 Hz; CO), 177.0 (t, 3J(C,P) = 1.9 Hz; OCOCH3), 74.9 (t,
2J(C,P) = 3.6 Hz; C5H4), 74.0 (d, 1J(C,P) = 20.1 Hz; ipso-C5H4), 73.6
3
3J(P,H) = 13.5 Hz, J(H,H) = 7.1 Hz, 3H; CH(CH3)2). 13C{1H}
2
NMR (50.3 MHz, CD2Cl2, 20 °C): δ 207.4 (dd, J(C,P) = 20.9 Hz,
1
2
(d, J(C,P) = 20.1 Hz; ipso-C5H4), 71.4 (t, J(C,P) = 2.8 Hz; C5H4),
26.8 (d, 1J(C,P) = 11.0 Hz; CH(CH3)2), 26.6 (d, 1J(C,P) = 10.8 Hz;
CH(CH3)2), 23.2 (s; OCOCH3), 19.7 (s; CH(CH3)2), 18.8 (s;
CH(CH3)2). 31P{1H} NMR (81.0 MHz, CDCl3, 20 °C): δ 26.5 (s).
Synthesis of cis,cis-[Ru(η1-OAc)2(DiPPF)(CO)2] (14). Complex
10 (100 mg, 0.150 mmol) was dissolved in CH2Cl2 (3 mL), and
vigorously stirred under a CO atmosphere (1 atm) for 24 h at room
temperature. The solvent was evaporated under reduced pressure,
giving the product as a yellow powder. Yield: 96 mg (92%). Anal.
Calcd for C28H42FeO6P2Ru (693.50): C, 48.49; H, 6.10. Found: C,
48.50; H, 6.12. IR (Nujol): 2048 (vs), 1992 (vs) (νCO); 1629 (vs)
2
2J(C,P) = 11.8 Hz; CO), 186.7 (t, J(C,P) = 2.3 Hz; OCOCH3),
2
138.7 (s; ipso-C6H5), 131.3 (d, J(C,P) = 0.8 Hz; o-C6H5), 129.1 (d,
2J(C,P) = 2.2 Hz; CCPh), 128.1 (s; m-C6H5), 124.9 (s; p-C6H5),
105.0 (dd, 2J(C,P) = 23.9 Hz, 2J(C,P) = 2.0 Hz; CCPh), 83.1 (dd,
1J(C,P) = 40.5 Hz, 3J(C,P) = 5.5 Hz; ipso-C5H4), 78.9 (dd, 1J(C,P) =
3
33.5 Hz, J(C,P) = 1.1 Hz; ipso-C5H4), 74.4 (d, J(C,P) = 3.6 Hz;
C5H4), 73.6 (d, J(C,P) = 5.0 Hz; C5H4), 73.1 (d, J(C,P) = 14.2 Hz;
C5H4), 72.9 (d, J(C,P) = 11.9 Hz; C5H4), 71.6 (d, J(C,P) = 4.9 Hz;
C5H4), 71.2 (d, J(C,P) = 6.0 Hz; C5H4), 70.4 (d, J(C,P) = 4.3 Hz;
1
C5H4), 69.9 (d, J(C,P) = 4.9 Hz; C5H4), 28.9 (d, J(C,P) = 2.9 Hz;
CH(CH3)2), 28.3 (d, 1J(C,P) = 11.2 Hz; CH(CH3)2), 27.5 (d,
1J(C,P) = 26.2 Hz; CH(CH3)2), 26.5 (d, 1J(C,P) = 15.3 Hz;
CH(CH3)2), 24.9 (t, 4J(C,P) = 1.4 Hz; OCOCH3), 20.9 (s;
CH(CH3)2), 20.0 (pseudo-t, J(C,P) = 2.2 Hz; CH(CH3)2), 19.9 (s;
CH(CH3)2), 19.7 (d, 2J(C,P) = 1.8 Hz; CH(CH3)2), 19.3 (d, 2J(C,P)
cm−1 (νCO). H NMR (200.1 MHz, CD2Cl2, 20 °C): δ 4.60 (dt,
1
3J(H,H) = 5.0 Hz, 4J(H,H) = 1.5 Hz, 4H; C5H4), 4.53−4.46 (m, 4H;
C5H4), 3.02 (hept, J(H,H) = 6.8 Hz, 1H; CH(CH3)2), 2.86−2.19 (m,
3H; CH(CH3)2), 2.00 (s, 3H; CH3CO2), 1.93 (s, 3H; CH3CO2),
1.75−0.80 (m, 24H; CH(CH3)2). 13C{1H} NMR (50.3 MHz,
J
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
2
CD2Cl2, 20 °C): δ 201.5 (t, J(C,P) = 14.0 Hz; CO), 193.4 (dd,
2J(C,P) = 115.2 Hz, 2J(C,P) = 13.0 Hz; CO), 176.1 (t, 3J(C,P) = 2.7
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.organomet.0c00361.
■
sı
3
Hz; OCOCH3), 175.8 (d, J(C,P) = 2.0 Hz; OCOCH3), 78.1 (d,
1J(C,P) = 41.6 Hz; ipso-C5H4), 78.0 (d, J(C,P) = 41.5 Hz; ipso-
1
C5H4), 75.6 (d, J(C,P) = 5.3 Hz; C5H4), 75.4 (d, J(C,P) = 5.1 Hz;
C5H4), 73.6 (d, J(C,P) = 8.5 Hz; C5H4), 72.4 (d, J(C,P) = 6.3 Hz;
C5H4), 71.8 (d, J(C,P) = 5.2 Hz; C5H4), 71.4 (d, J(C,P) = 4.8 Hz;
C5H4), 71.3 (d, J(C,P) = 5.4 Hz; C5H4), 69.9 (d, J(C,P) = 3.4 Hz;
NMR spectra of the isolated complexes, catalytic results
of the TH reactions, and crystallographic details of
complex 11 (PDF)
1
1
C5H4), 29.5 (d, J(C,P) = 30.0 Hz; CH(CH3)2), 27.3 (d, J(C,P) =
1
Accession Codes
25.7 Hz; CH(CH3)2), 25.8 (d, J(C,P) = 21.6 Hz; CH(CH3)2), 25.3
1
(d, J(C,P) = 17.6 Hz; CH(CH3)2), 24.4 (s; OCOCH3), 22.8 (d,
CCDC 1989777 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
2J(C,P) = 4.5 Hz; CH(CH3)2), 20.3 (s; OCOCH3), 20.0 (d, J(C,P)
2
= 3.8 Hz; CH(CH3)2), 19.8 (br s; CH(CH3)2), 19.6 (br s;
CH(CH3)2), 19.5 (br s; CH(CH3)2), 19.4 (d, 2J(C,P) = 4.0 Hz;
CH(CH3)2), 19.1 (d, 2J(C,P) = 3.5 Hz; CH(CH3)2), 18.2 (br s;
CH(CH3)2). 31P{1H} NMR (81.0 MHz. CD2Cl2, 20 °C): δ 50.8 (d,
2J(P,P) = 20.5 Hz), 32.2 (d, J(P,P) = 20.5 Hz).
2
Procedure for TH of Acetophenone with Ruthenium
Catalysts. The ruthenium catalyst solution used for TH was
prepared by dissolving the ruthenium complex (2.0 μmol) in 2 mL
of 2-propanol. The catalyst solution (1 mL, 1.0 μmol) and a 0.1 M
solution of NaOiPr (200 μL, 20 μmol) in 2-propanol were added to
the acetophenone solution (117 μL, 1.0 mmol) in 2-propanol (final
volume 10 mL), and the resulting mixture was kept at the defined
temperature (30, 60, or 82 °C). The reaction mixture was sampled by
removing an aliquot (0.5 mL), which was quenched by addition of
diethyl ether (1/1 v/v), filtered over a short silica pad, and submitted
to GC analysis. The addition of the base was considered as the start
time of the reaction. The S/C molar ratio was 1000/1, whereas the
base concentration was 2 mol % with respect to the substrate (0.1 M).
The same procedure was followed for TH at S/C = 2000, using the
appropriate amount of catalyst.
Procedure for TH of Acetophenone with In Situ Prepared
Ruthenium Catalysts. The catalyst solutions were prepared by
adding 2-propanol (2 mL) to the Ru complexes 1-ip, 9, and 10 (2
μmol) and the corresponding nitrogen ligand (ampy, en, bipy, or
benzylamine; 20 μmol, 10 equiv). The mixtures were stirred for 30
min at reflux. The solutions of the in situ formed catalyst were used in
the TH reactions as described above.
AUTHOR INFORMATION
Corresponding Authors
■
̀
Rosario Figliolia − Dipartimento DI4A, Universita di Udine, I-
33100 Udine, Italy; orcid.org/0000-0003-2103-6080;
Email: rosario.figliolia@uniud.it
Walter Baratta − Dipartimento DI4A, Universita di Udine, I-
33100 Udine, Italy; orcid.org/0000-0002-2648-1848;
̀
Email: walter.baratta@uniud.it
Authors
̀
Maurizio Ballico − Dipartimento DI4A, Universita di Udine, I-
33100 Udine, Italy; orcid.org/0000-0001-6588-8037
Daniele Zuccaccia − Dipartimento DI4A, Universita di Udine,
I-33100 Udine, Italy; orcid.org/0000-0001-7765-1715
̀
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.organomet.0c00361
Notes
The authors declare no competing financial interest.
Procedure for Dimerization of Terminal Alkynes with
Complex 10. The catalyst 10 (5.4 mg, 7.6 μmol) was added to
phenylacetylene (83 μL, 0.76 mmol) and pyridine (49 μL, 0.61
mmol), dissolved in toluene (final volume 0.76 mL), and the solution
was stirred at reflux for 24 h. The S/C molar ratio was 100/1, whereas
the base concentration was 80 mol % with respect to the substrate
(1.0 M). The reaction mixture was sampled by removing an aliquot
(0.1 mL), which was quenched by addition of n-pentane (1.0 mL)
and filtered over a short silica pad and the solvent removed under
reduced pressure. The residue was dissolved in CDCl3 and submitted
to 1H and 13C{1H} NMR analysis. The same procedure was followed
for the reactions without pyridine or with different additives, namely
K2CO3, N-methylcyclohexylamine (40 and 30 mol %), and TFA (10
mol %), and for the substrate 3-phenyl-1-propyne.
ACKNOWLEDGMENTS
This work was supported by the Ministero dell’Universita e
della Ricerca (MIUR), PRIN 2015 program no.
20154X9ATP_005, and Johnson Matthey (Cambridge) for
providing a grant for R.F. The authors thank Dr. Massimiliano
■
̀
̀
Curcio of the Universita di Bologna for assistance and crystal
data interpretation, Mr. Pierluigi Polese for the elemental
analyses, Dr. Paolo Martinuzzi for NMR assistance, and Dr.
Antonio Zanotti-Gerosa of JM for helpful discussions.
REFERENCES
■
(1) Murahashi, S.-I. Ruthenium in organic synthesis; Wiley-VCH:
Weinheim, Germany, 2004; p 383.
(2) Tolman, C. A. Steric Effects of Phosphorus Ligands in
Organometallic Chemistry and Homogeneous Catalysis. Chem. Rev.
1977, 77, 313−348.
(3) (a) Marchenko, A. V.; Huffman, J. C.; Valerga, P.; Tenorio, M.
J.; Puerta, M. C.; Caulton, K. G. Effect of Lewis Acidity on the
Synthesis of RuHCl(CO)(phosphine)2: Subtle Influence of Steric and
Electronic Effects among PiPr3, PiPr2(3,5-(CF3)2C6H3), and PiPr2Me.
Inorg. Chem. 2001, 40, 6444−6450. (b) Huang, D. J.; Streib, W. E.;
Bollinger, J. C.; Caulton, K. G.; Winter, R. F.; Scheiring, T. 14-
electron four-coordinate Ru(II) carbyl complexes and their five-
coordinate precursors: Synthesis, double agostic interactions, and
Single-Crystal X-ray Crystallographic Structure Determina-
tion of Compound 11. Single-crystal data of complex 11 were
obtained by slow cooling of a concentrated solution of the species in
toluene. Crystal data were collected at 170 K on an Oxford Diffraction
Excalibur diffractometer using graphite-monochromated Mo Kα
radiation and an Eos CCD detector (λ = 0.71073 Å). The structure
was solved by direct methods with the aid of successive difference
Fourier maps and was refined against all data using SHELXL-201450
in conjunction with SHELXLE51 and refined by full-matrix least
2
2
squares minimizing ∑w(Fo − Fc )2 with the SHELXL-2014
weighting scheme.50 Direct methods determined the positions of all
the atoms. All programs were used within the Olex suite.52 All non-
hydrogen atoms were refined anisotropically. Structural illustrations
were drawn with ORTEP-3 for Windows.53 The CCDC deposition
number of the X-ray crystal structure of complex 11 is 1989777. For
additional details of the collection and refinement of data, see the
Supporting Information.
́
reactivity. J. Am. Chem. Soc. 1999, 121, 8087−8097. (c) Olivan, M.;
Clot, E.; Eisenstein, O.; Caulton, K. G. Hydride Is Not a Spectator
Ligand in the Formation of Hydrido Vinylidene from Terminal
Alkyne and Ruthenium and Osmium Hydrides: Mechanistic Differ-
K
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
ences. Organometallics 1998, 17, 3091−3100. (d) Huang, D. J.; Streib,
W. E.; Eisenstein, O.; Caulton, K. G. [Ru(Ph)(CO)(PtBu2Me)2]+: A
unique 14-electron RuII complex with two agostic interactions. Angew.
Chem., Int. Ed. Engl. 1997, 36, 2004−2006.
Homogeneous Hydrogenation; Wiley-VCH: Weinheim, 2007; Vols. 1−
3, p 1568.
(11) Wang, C.-J.; Tao, H.; Zhang, X. Highly enantioselective Ru-
catalyzed hydrogenation of β-keto esters using electron-donating
bis(trialkylphosphine) ligand-TangPhos. Tetrahedron Lett. 2006, 47,
1901−1903.
(12) Burk, M. J.; Harper, T. G. P.; Kalberg, C. S. Highly
Enantioselective Hydrogenation of. beta-Keto Esters under Mild
Conditions. J. Am. Chem. Soc. 1995, 117, 4423−4424.
(13) Rodriguez, S.; Qu, B.; Fandrick, K. R.; Buono, F.; Haddad, N.;
Xu, Y. B.; Herbage, M. A.; Zeng, X. Z.; Ma, S. L.; Grinberg, N.; Lee,
H.; Han, Z. X. S.; Yee, N. K.; Senanayake, C. H. Amine-Tunable
Ruthenium Catalysts for Asymmetric Reduction of Ketones. Adv.
Synth. Catal. 2014, 356, 301−307.
(14) Cao, P.; Zhang, X. Ru-BICP-Catalyzed Asymmetric Hydro-
genation of Aromatic Ketones. J. Org. Chem. 1999, 64, 2127−2129.
(15) (a) Drouin, S. D.; Monfette, S.; Amoroso, D.; Yap, G. P. A.;
Fogg, D. E. Simultaneous Observation of Doubly and Triply Chloride
Bridged Isomers of an Electron-Rich Ruthenium Dimer: Role of
Dimer Geometry in Determining Reactivity. Organometallics 2005, 24,
4721−4728. (b) Drouin, S. D.; Amoroso, D.; Yap, G. P. A.; Fogg, D.
E. Multifunctional Ruthenium Catalysts: A Novel Borohydride-
Stabilized Polyhydride Complex Containing the Basic, Chelating
Diphosphine 1,4-Bis(dicyclohexylphosphino)butane and Its Applica-
tion to Hydrogenation and Murai Catalysis. Organometallics 2002, 21,
1042−1049.
(4) (a) Baratta, W.; Mealli, C.; Herdtweck, E.; Ienco, A.; Mason, S.
A.; Rigo, P. Nonclassical vs Classical Metal···H3C-C Interactions:
Accurate Characterization of a 14-Electron Ruthenium(II) System by
Neutron Diffraction, Database Analysis, Solution Dynamics, and DFT
Studies. J. Am. Chem. Soc. 2004, 126, 5549−5562. (c) Baratta, W.; Del
Zotto, A.; Esposito, G.; Sechi, A.; Toniutti, M.; Zangrando, E.; Rigo,
P. RuCl2[(2,6-Me2C6H3)PPh2]2: A New Precursor for Cyclo-
metalated Ruthenium(II) Complexes. Organometallics 2004, 23,
6264−6272. (d) Baratta, W.; Herdtweck, E.; Rigo, P.
[RuCl2{PPh2(2,6-Me2C6H3)}2]: A Neutral 14-Electron Ruthenium-
(II) Complex with Two Agostic Interactions. Angew. Chem., Int. Ed.
1999, 38, 1629−1631. (b) Baratta, W.; Da Ros, P.; Del Zotto, A.;
Sechi, A.; Zangrando, E.; Rigo, P. Cyclometalated Ruthenium(II)
Complexes as Highly Active Transfer Hydrogenation Catalysts.
Angew. Chem. 2004, 116, 3668−3672.
(5) (a) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Synthesis and
Activity of a New Generation of Ruthenium-Based Olefin Metathesis
Catalysts Coordinated with 1,3-Dimesityl-4,5-dihydroimidazol-2-
ylidene Ligands. Org. Lett. 1999, 1, 953−956. (b) Schwab, P.;
France, M. B.; Ziller, J. W.; Grubbs, R. H. A Series of Well-Defined
Metathesis Catalysts-Synthesis of [RuCl2(=CHR’)(PR3)2] and Its
Reactions. Angew. Chem., Int. Ed. Engl. 1995, 34, 2039−2041.
(6) Grubbs, R. H.; Wenzel, A. G.; O’Leary, D. J.; Khosravi, E.
Handbook of metathesis, 2nd ed.; Wiley-VCH: Weinheim, 2015; Vols.
1−3, p 1630.
(7) (a) Kitamura, M.; Tokunaga, M.; Noyori, R. Practical synthesis
of BINAP-ruthenium(II) dicarboxylate complexes. J. Org. Chem.
1992, 57, 4053−4054. (b) Ohta, T.; Takaya, H.; Noyori, R.
Bis(diarylphosphino)-1,1 binaphthyl (BINAP)-ruthenium(II) dicar-
boxylate complexes: new, highly efficient catalysts for asymmetric
hydrogenations. Inorg. Chem. 1988, 27, 566−569. (c) Noyori, R.;
Ohkuma, T.; Kitamura, M.; Takaya, H.; Sayo, N.; Kumobayashi, H.;
Akutagawa, S. Asymmetric hydrogenation of beta-keto carboxylic
esters. A practical, purely chemical access to beta-hydroxy esters in
high enantiomeric purity. J. Am. Chem. Soc. 1987, 109, 5856−5858.
(8) Doucet, H.; Ohkuma, T.; Murata, K.; Yokozawa, T.; Kozawa,
M.; Katayama, E.; England, A. F.; Ikariya, T.; Noyori, R. trans-
[RuCl2 (phosphane)2 (1,2-diamine)] and Chiral trans-
[RuCl2(diphosphane)(1,2-diamine)]: Shelf-Stable Precatalysts for
the Rapid, Productive, and Stereoselective Hydrogenation of Ketones.
Angew. Chem., Int. Ed. 1998, 37, 1703−1707.
(9) Abbreviations: BICP = 2,2′-bis(diphenylphosphino)-1,1′-dicy-
clopentane; BINAP = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl;
BPE = 1,2-bis[(2R,5R)-2,5-diisopropylphospholano]ethane; DCyPB
= 1,4-bis(dicyclohexylphosphino)butane; DCyPF = 1,1′-bis(dicyclo-
hexylphosphino)ferrocene; DCyPP = 1,3-bis(cyclohexylphosphino)
propane; DiPPF = 1,1′-bis(diisopropylphosphino)ferrocene; dppb =
1,4-bis(diphenylphosphino)butane; DPPF = 1,1′-bis(diphenylphos-
phino)ferrocene; dtbpe = 1,2-bis(di-tert-butylphosphino)ethane; i-Pr-
BPE = 1,2-bis[(2,5-diisopropylphospholano]ethane; Josiphoscy = (R)-
1-[(S)-2-(dicyclohexylphosphino)ferrocenyl]ethyldicyclohexylphos-
phine; MeO-BIBOP = (2R,2′R,3R,3′R)-3,3′-di-tert-butyl-4,4′-dime-
thoxy-2,2′,3,3′-tetrahydro-2,2′-bibenzo[d][1,3]oxaphosphole; Tang-
Phos = (1S,1S′,2R,2R′)-1,1′-di-tert-butyl(2,2′)diphospholane; ampy
= 2-(aminomethyl)pyridine; en = ethylenediamine.
(16) Cadierno, V.; Crochet, P.; Diez, J.; Garcia-Garrido, S. E.;
Gimeno, J. An Easy Entry to Dimers [{RuX(μ-X)(CO)(P∧P)}2] (X =
Cl, Br; P∧P = 1,1‘-Bis(diphenylphosphino)ferrocene, 1,1‘-Bis-
(diisopropylphosphino)ferrocene) from η3-Allylruthenium(II) Deriv-
atives [RuX(η3-2-C3H4R)(CO)(P∧P)] (R = H, Me): Efficient
Catalyst Precursors in Transfer Hydrogenation of Ketones. Organo-
metallics 2003, 22, 5226−5234.
(17) (a) Wang, D.; Astruc, D. The Golden Age of Transfer
Hydrogenation. Chem. Rev. 2015, 115, 6621−6686. (b) Foubelo, F.;
́
Najera, C.; Yus, M. Catalytic Asymmetric Transfer Hydrogenation of
Ketones: Recent Advances. Tetrahedron: Asymmetry 2015, 26, 769−
790. (c) Ito, J.-i.; Nishiyama, H. Recent Topics of Transfer
Hydrogenation. Tetrahedron Lett. 2014, 55, 3133−3146. (d) Morris,
R. H. Asymmetric Hydrogenation, Transfer Hydrogenation and
Hydrosilylation of Ketones Catalyzed by Iron Complexes. Chem. Soc.
Rev. 2009, 38, 2282−2291. (e) Baratta, W.; Rigo, P. 1-(Pyridin-2-
yl)methanamine-Based Ruthenium Catalysts for Fast Transfer
Hydrogenation of Carbonyl Compounds in 2-Propanol. Eur. J.
Inorg. Chem. 2008, 2008, 4041−4053.
(18) (a) Shi, J.; Hu, B.; Chen, X.; Shang, S.; Deng, D.; Sun, Y.; Shi,
W.; Yang, X.; Chen, D. Synthesis, Reactivity, and Catalytic Transfer
Hydrogenation Activity of Ruthenium Complexes Bearing NNN
Tridentate Ligands: Influence of the Secondary Coordination Sphere.
ACS Omega 2017, 2, 3406−3416. (b) Zbieg, J. R.; McInturff, E. L.;
Krische, M. J. Allenamide Hydro-Hydroxyalkylation: 1,2-Amino
Alcohols via Ruthenium-Catalyzed Carbonyl anti-Aminoallylation.
Org. Lett. 2010, 12, 2514−2516.
(19) (a) Chelucci, G.; Baldino, S.; Baratta, W. Ruthenium and
Osmium Complexes Containing 2-(aminomethyl)pyridine (Ampy)-
based Ligands in Catalysis. Coord. Chem. Rev. 2015, 300, 29−85.
(b) Putignano, E.; Bossi, G.; Rigo, P.; Baratta, W. MCl2(ampy)(dppf)
(M = Ru, Os): Multitasking Catalysts for Carbonyl Compound/
Alcohol Interconversion Reactions. Organometallics 2012, 31, 1133−
1142. (c) Baratta, W.; Chelucci, G.; Herdtweck, E.; Magnolia, S.;
Siega, K.; Rigo, P. Highly Diastereoselective Formation of Ruthenium
Complexes for Efficient Catalytic Asymmetric Transfer Hydro-
genation. Angew. Chem., Int. Ed. 2007, 46, 7651−7654. (d) Baratta,
W.; Herdtweck, E.; Siega, K.; Toniutti, M.; Rigo, P. 2-
(Aminomethyl)pyridine-Phosphine Ruthenium(II) Complexes:
Novel Highly Active Transfer Hydrogenation Catalysts. Organo-
metallics 2005, 24, 1660−1669.
(10) (a) Xie, X.; Lu, B.; Li, W.; Zhang, Z. Coordination Determined
Chemo- and Enantioselectivities in Asymmetric Hydrogenation of
Multi-Functionalized Ketones. Coord. Chem. Rev. 2018, 355, 39−53.
(b) Yoshimura, M.; Tanaka, S.; Kitamura, M. Recent Topics in
Catalytic Asymmetric Hydrogenation of ketones. Tetrahedron Lett.
2014, 55, 3635−3640. (c) Shang, G.; Li, W.; Zhang, X. Transition
Metal-Catalyzed Homogeneous Asymmetric Hydrogenation. In
Catalytic Asymmetric Synthesis, 3rd ed.; Ojima, I., Ed.; Wiley:
Hoboken, NJ, 2010; Vol. 1, pp 343−436. (d) The Handbook of
(20) (a) Giboulot, S.; Comuzzi, C.; Del Zotto, A.; Figliolia, R.;
Lippe, G.; Lovison, D.; Strazzolini, P.; Susmel, S.; Zangrando, E.;
L
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Zuccaccia, D.; Baldino, S.; Ballico, M.; Baratta, W. Preparation of
monocarbonyl ruthenium complexes bearing bidentate nitrogen and
phosphine ligands and their catalytic activity in carbonyl compound
reduction. Dalton Transactions 2019, 48, 12560−12576. (b) Zhang,
S.; Baldino, S.; Baratta, W. Synthesis of [RuX(CO)(dppp)(NN)]Cl
(X = H, Cl; NN = en, ampy) Complexes and Their Use as Catalysts
for Transfer Hydrogenation. Organometallics 2013, 32, 5299−5304.
(21) Figliolia, R.; Baldino, S.; Nedden, H. G.; Zanotti-Gerosa, A.;
Baratta, W. Mild N-Alkylation of Amines with Alcohols Catalyzed by
the Acetate Ru(OAc)2(CO)(DiPPF) Complex. Chem. - Eur. J. 2017,
23, 14416−14419.
(22) (a) Omura, S.; Fukuyama, T.; Murakami, Y.; Okamoto, H.;
Ryu, I. Hydroruthenation Triggered Catalytic Conversion of
Dialdehydes and Keto Aldehydes to Lactones. Chem. Commun.
2009, 6741−6743. (b) Bolton, P. D.; Grellier, M.; Vautravers, N.;
Vendier, L.; Sabo-Etienne, S. Access to Ruthenium(0) Carbonyl
Complexes via Dehydrogenation of a Tricyclopentylphosphine Ligand
and Decarbonylation of Alcohols. Organometallics 2008, 27, 5088−
5093. (c) Miecznikowski, J. R.; Crabtree, R. H. Hydrogen Transfer
Reduction of Aldehydes with Alkali-Metal Carbonates and Iridium
NHC Complexes. Organometallics 2004, 23, 629−631. (d) Coalter
III, J. N.; Huffman, J. C.; Caulton, K. G. Cleavage of H-C(sp2) and
C(sp2)-X Bonds (X = Alkyl, Aryl, OR, NR2): Facile Decarbonylation,
Isonitrile Abstraction, or Dehydrogenation of Aldehydes, Esters,
Amides, Amines, and Imines by [RuHCl(PiPr3)2]2. Organometallics
2000, 19, 3569−3578. (e) Beck, C. M.; Rathmill, S. E.; Park, Y. J.;
Chen, J.; Crabtree, R. H.; Liable-Sands, L. M.; Rheingold, A. L.
Aldehyde Decarbonylation Catalysis under Mild Conditions. Organo-
metallics 1999, 18, 5311−5317.
(23) (a) Salvi, L.; Salvini, A.; Micoli, F.; Bianchini, C.; Oberhauser,
W. Mononuclear ruthenium complexes containing two different
phosphines in trans position: II. Catalytic hydrogenation of C=C and
C=O bonds. J. Organomet. Chem. 2007, 692, 1442−1450. (b) Skapski,
A. C.; Stephens, F. A. X-Ray crystal structure of acetatohydridotris-
(triphenylphosphine)ruthenium(II): a hydrogenation catalyst with a
strained octahedral co-ordination. J. Chem. Soc., Dalton Trans. 1974,
390−395. (c) Mitchell, R. W.; Spencer, A.; Wilkinson, G.
Carboxylato-triphenylphosphine complexes of ruthenium, cationic
triphenylphosphine complexes derived from them, and their
behaviour as homogeneous hydrogenation catalysts for alkenes. J.
Chem. Soc., Dalton Trans. 1973, 846−854.
P. Pincer CNN Ruthenium(II) Complexes with Oxygen-Containing
Ligands (O2CR, OAr, OR, OSiR3, O3SCF3): Synthesis, Structure, and
Catalytic Activity in Fast Transfer Hydrogenation. Organometallics
2009, 28, 4421−4430.
(29) (a) Arockiam, P. B.; Bruneau, C.; Dixneuf, P. H. Ruthenium-
(II)-Catalyzed C-H Bond Activation and Functionalization. Chem.
Rev. 2012, 112, 5879−5918. (b) Ackermann, L. Carboxylate-Assisted
Transition-Metal-Catalyzed C-H Bond Functionalizations: Mecha-
nism and Scope. Chem. Rev. 2011, 111, 1315−1345.
(30) (a) Lynam, J. M.; Welby, C. E.; Whitwood, A. C. Exploitation
of a Chemically Non-innocent Acetate Ligand in the Synthesis and
Reactivity of Ruthenium Vinylidene Complexes. Organometallics
2009, 28, 1320−1328. (b) Johnson, D. G.; Lynam, J. M.; Slattery,
J. M.; Welby, C. E. Insights into the intramolecular acetate-mediated
formation of ruthenium vinylidene complexes: a ligand-assisted
proton shuttle (LAPS) mechanism. Dalton Transactions 2010, 39,
10432−10441.
̈
̈
(31) (a) Witt, J.; Pothig, A.; Kuhn, F. E.; Baratta, W. Abnormal N-
Heterocyclic Carbene-Phosphine Ruthenium(II) Complexes as Active
Catalysts for Transfer Hydrogenation. Organometallics 2013, 32,
4042−4045. (b) Bitzer, M. J.; Pothig, A.; Jandl, C.; Kuhn, F. E.;
Baratta, W. Ru-Ag and Ru-Au dicarbene complexes from an abnormal
carbene ruthenium system. Dalton Transactions 2015, 44, 11686−
11689. (c) Bitzer, M. J.; Ku
Miyaura/transfer hydrogenation reaction catalyzed by a Pd-Ru
̈
hn, F. E.; Baratta, W. Tandem Suzuki-
complex bearing an anionic dicarbene. J. Catal. 2016, 338, 222−
̈
226. (d) Pardatscher, L.; Hofmann, B. J.; Fischer, P. J.; Holzl, S. M.;
Reich, R. M.; Kuhn, F. E.; Baratta, W. Highly Efficient Abnormal
̈
NHC Ruthenium Catalyst for Oppenauer-Type Oxidation and
Transfer Hydrogenation Reactions. ACS Catal. 2019, 9, 11302−
11306.
(32) Baratta, W.; Baldino, S.; Calhorda, M. J.; Costa, P. J.; Esposito,
G.; Herdtweck, E.; Magnolia, S.; Mealli, C.; Messaoudi, A.; Mason, S.
A.; Veiros, L. F. CNN Pincer Ruthenium Catalysts for Hydrogenation
and Transfer Hydrogenation of Ketones: Experimental and Computa-
tional Studies. Chem. - Eur. J. 2014, 20, 13603−13617.
(33) Angelici, R. J. Basicities of Transition Metal Complexes from
Studies of Their Heats of Protonation: A Guide to Complex
Reactivity. Acc. Chem. Res. 1995, 28, 51−60.
(34) (a) Meot-Ner, M. The Ionic Hydrogen Bond. Chem. Rev. 2005,
105, 213−284. (b) Meot-Ner, M.; Elmore, D. E.; Scheiner, S. Ionic
Hydrogen Bond Effects on the Acidities, Basicities, Solvation, Solvent
Bridging, and Self-Assembly of Carboxylic Groups. J. Am. Chem. Soc.
1999, 121, 7625−7635.
(24) Dupau, P.; Bonomo, L.; Kermorvan, L. Angew. Chem., Int. Ed.
2013, 52, 11347−11350.
(25) Naruto, M.; Saito, S. Cationic mononuclear ruthenium
carboxylates as catalyst prototypes for self-induced hydrogenation of
carboxylic acids. Nat. Commun. 2015, 6, 9.
́
(35) (a) Berstler, J.; Lopez, A.; Menard, D.; Dougherty, W. G.;
Kassel, W. S.; Hansen, A.; Daryaei, A.; Ashitey, P.; Shaw, M. J.; Fey,
N.; Nataro, C. Synthesis and spectroelectrochemistry of transition
metal carbonyls with 1,1′-bis(phosphino)metallocene ligands. J.
Organomet. Chem. 2012, 712, 37−45. (b) Fey, N.; Harvey, J. N.;
Lloyd-Jones, G. C.; Murray, P.; Orpen, A. G.; Osborne, R.; Purdie, M.
Computational Descriptors for Chelating P,P- and P,N-Donor
Ligands. Organometallics 2008, 27, 1372−1383. (c) Beckett, M. A.;
Brassington, D. S.; Coles, S. J.; Gelbrich, T.; Light, M. E.; Hursthouse,
M. B. A crystallographic and spectroscopic investigation of the
stereochemistry of [MBr(CO)3L2] (M = Mn, Re) complexes: crystal
and molecular structures of [MBr(CO)3L2] {M = Mn, L = P(C6H4Cl-
4)3, 1/2dppe, 1/2dppf; M = Re, L = P(C6H4OMe-4)3, 1/2dppf}. J.
Organomet. Chem. 2003, 688, 174−180. (d) Hor, T. S. A.; Phang, L.-
T. Substituted metal carbonyls XI. 1,1′-Bis(diphenylphosphino)-
ferrocene  a bridging, chelating and unidentate ligand in the
synthesis of M2(CO)10(μ-P-P), M(CO)4(η2-P-P) and M(CO)5(η1-P-
P) (where M = Cr, Mo, W and P-P = Fe(C5H4PPh2)2). J. Organomet.
Chem. 1989, 373, 319−324.
(26) (a) van Buijtenen, J.; Meuldijk, J.; Vekemans, J. A. J. M.;
Hulshof, L. A.; Kooijman, H.; Spek, A. L. Dinuclear Ruthenium
Complexes Bearing Dicarboxylate and Phosphine Ligands. Accept-
orless Catalytic Dehydrogenation of 1-Phenylethanol. Organometallics
2006, 25, 873−881. (b) Creswell, C. J.; Dobson, A.; Moore, D. S.;
Robinson, S. D. Complexes of the Platinum Metals. 17. Molecular
Dynamics of the Species [M(O2CR)2(CO)(PPh3)2] (M = Ruthe-
nium, R = Methyl, Trifluoromethyl, Pentafluoroethyl, Pentafluor-
ophenyl; M = Osmium, R = Methyl, Trifluoromethyl). Inorg. Chem.
1979, 18, 2055−2059. (c) Dobson, A.; Robinson, S. D. Complexes of
the Platinum Metals. 7. Homogeneous Ruthenium and Osmium
Catalysts for the Dehydrogenation of Primary and Secondary
Alcohols. Inorg. Chem. 1977, 16, 137−142.
(27) (a) Hey, D. A.; Fischer, P. J.; Baratta, W.; Kuhn, F. E.
̈
Ru(O2CCF3)2(PPh3)2 and ruthenium phosphine complexes bearing
fluoroacetate ligands: synthesis, characterization and catalytic activity.
Dalton Transactions 2019, 48, 4625−4635. (b) Hey, D. A.; Sauer, M.
J.; Fischer, P. J.; Esslinger, E.-M. H. J.; Ku
̈
hn, F. E.; Baratta, W.
(36) (a) Wong, C.-Y.; Che, C.-M.; Chan, M. C. W.; Han, J.; Leung,
K.-H.; Phillips, D. L.; Wong, K.-Y.; Zhu, N. Probing Ruthenium-
Acetylide Bonding Interactions: Synthesis, Electrochemistry, and
Spectroscopic Studies of Acetylide-Ruthenium Complexes Supported
by Tetradentate Macrocyclic Amine and Diphosphine Ligands. J. Am.
Chem. Soc. 2005, 127, 13997−14007. (b) Manna, J.; John, K. D.;
Acetate Acetylacetonate Ampy Ruthenium(II) Complexes as Efficient
Catalysts for Ketone Transfer Hydrogenation. ChemCatChem 2020,
12, 3537.
(28) Baratta, W.; Ballico, M.; Del Zotto, A.; Herdtweck, E.;
Magnolia, S.; Peloso, R.; Siega, K.; Toniutti, M.; Zangrando, E.; Rigo,
M
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX

Organometallics
pubs.acs.org/Organometallics
Article
Hopkins, M. D.; Stone, F. G. A.; West, R. The Bonding of Metal-
Alkynyl Complexes. Adv. Organomet. Chem. 1995, 38, 79−154.
(37) (a) Albertin, G.; Autoniutti, S.; Bordignon, E.; Cazzaro, F.;
Ianelli, S.; Pelizzi, G. Preparation, Structure, and Reactivity of New
Bis(acetylide) and Acetylide-Vinylidene Ruthenium(II) Complexes
Stabilized by Phosphite Ligands. Organometallics 1995, 14, 4114−
4125. (b) Werner, H.; Stark, A.; Schulz, M.; Wolf, J. Vinylidene
transition-metal complexes. XIX. Preparation of vinylideneruthenium
complexes promoted by hemilabile chelating phosphine ligands.
Organometallics 1992, 11, 1126−1130.
(53) Farrugia, L. ORTEP-3 for Windows - a version of ORTEP-III
with a Graphical User Interface (GUI). J. Appl. Crystallogr. 1997, 30,
565−567.
(38) Welby, C. E.; Eschemann, T. O.; Unsworth, C. A.; Smith, E. J.;
Thatcher, R. J.; Whitwood, A. C.; Lynam, J. M. Ruthenium Acetate
Complexes as Versatile Probes of Metal-Ligand Interactions: Insight
into the Ligand Effects of Vinylidene, Carbene, Carbonyl, Nitrosyl
and Isocyanide. Eur. J. Inorg. Chem. 2012, 2012, 1493−1506.
(39) (a) Nakamoto, K. Infrared and Raman spectra of inorganic and
coordination compounds. Part A: Theory and Applications in Inorganic
Chemistry, 6th ed.; Wiley: Hoboken, NJ, 2009. (b) Nakanishi, K.;
Solomon, P. H. Infrared absorption spectroscopy, practical, 2nd ed.;
Holden-Day: Sydney, 1977.
(40) Giboulot, S.; Baldino, S.; Ballico, M.; Nedden, H. G.;
Zuccaccia, D.; Baratta, W. Cyclometalated Dicarbonyl Ruthenium
Catalysts for Transfer Hydrogenation and Hydrogenation of Carbonyl
Compounds. Organometallics 2018, 37, 2136−2146.
(41) Goicoechea, J. M.; Mahon, M. F.; Whittlesey, M. K.; Kumar, P.
G. A.; Pregosin, P. S. Mononuclear and dinuclear complexes with a
[Ru(tBu2PCH2CH2PtBu2)(CO)] core. Dalton Transactions 2005,
588−597.
(42) Haack, K.-J.; Hashiguchi, S.; Fujii, A.; Ikariya, T.; Noyori, R.
The Catalyst Precursor, Catalyst, and Intermediate in the RuII-
Promoted Asymmetric Hydrogen Transfer between Alcohols and
Ketones. Angew. Chem., Int. Ed. Engl. 1997, 36, 285−288.
(43) Baratta, W.; Schutz, J.; Herdtweck, E.; Herrmann, W. A.; Rigo,
̈
P. Fast transfer hydrogenation using a highly active orthometalated
heterocyclic carbene ruthenium catalyst. J. Organomet. Chem. 2005,
690, 5570−5575.
(44) Temkin, O. N. “Golden Age” of Homogeneous Catalysis
Chemistry of Alkynes: Dimerization and Oligomerization of Alkynes.
Kinet. Catal. 2019, 60, 689−732.
(45) García-Garrido, S. E. Catalytic Dimerization of Alkynes. In
Modern Alkyne Chemistry 2014, 299−334.
(46) Trost, B. M.; Toste, F. D.; Pinkerton, A. B. Non-Metathesis
Ruthenium-Catalyzed C-C Bond Formation. Chem. Rev. 2001, 101,
2067−2096.
(47) (a) Wakatsuki, Y.; Yamazaki, H. Some organometallic
chemistry of ruthenium(II). J. Organomet. Chem. 1995, 500, 349−
362. (b) Wakatsuki, Y.; Koga, N.; Yamazaki, H.; Morokuma, K.
Acetylene π-Coordination, Slippage to α-Coordination, and 1, 2-
Hydrogen Migration Taking Place on a Transition Metal. The Case of
a Ru(II) Complex As Studied by Experiment and ab Initio Molecular
Orbital Simulations. J. Am. Chem. Soc. 1994, 116, 8105−8111.
(48) Spencer, A.; Wilkinson, G. Reactions of μ3-oxo-Triruthenium
Carboxylates with π-acid Ligands. J. Chem. Soc., Dalton Trans. 1974,
786−792.
(49) Anderson, P. A.; Deacon, G. B.; Haarmann, K. H.; Keene, F. R.;
Meyer, T. J.; Reitsma, D. A.; Skelton, B. W.; Strouse, G. F.; Thomas,
N. C.; Treadway, J. A.; White, A. H. Designed Synthesis of
Mononuclear Tris(heteroleptic) Ruthenium Complexes Containing
Bidentate Polypyridyl Ligands. Inorg. Chem. 1995, 34, 6145−6157.
(50) (a) Sheldrick, G. Crystal structure refinement with SHELXL.
Acta Crystallogr., Sect. C: Struct. Chem. 2015, C71, 3−8. (b) Sheldrick,
G. SHELXT - Integrated space-group and crystal-structure determi-
nation. Acta Crystallogr., Sect. A: Found. Adv. 2015, A71, 3−8.
(51) Hubschle, C. B.; Sheldrick, G. M.; Dittrich, B. ShelXle: a Qt
graphical user interface for SHELXL. J. Appl. Crystallogr. 2011, 44,
1281−1284.
(52) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A.
K.; Puschmann, H. OLEX2: a complete structure solution, refinement
and analysis program. J. Appl. Crystallogr. 2009, 42, 339−341.
N
https://dx.doi.org/10.1021/acs.organomet.0c00361
Organometallics XXXX, XXX, XXX−XXX