Synthesis and characterization of [Rh(PP)(PP)]X complexes (PP = DPPE or DPPP, X = Cl? or BF4-). Phosphine exchange and reactivity in transfer hydrogenation conditions

Article abstract of DOI:10.1016/j.jorganchem.2019.02.009

The synthesis of heteroleptic monomeric cationic Rh(I) bis-diphosphine complex [Rh(dppe)(dppp)]Cl (dppe = 1,2-bis-(diphenylphosphino)ethane and dppp = 1,3-bis-(diphenylphosphino)propane) was achieved by reaction between the neutral dimeric complex [Rh

Full text of DOI:10.1016/j.jorganchem.2019.02.009

Journal of Organometallic Chemistry 885 (2019) 59e64
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and characterization of [Rh(PP)(PP)]X complexes
(PP ¼ DPPE or DPPP, X ¼ Clꢀ or BF-4). Phosphine exchange and
reactivity in transfer hydrogenation conditions
, b,
Alberto Mannu a *, Gina Vlahopoulou a, Christoph Kubis a, Hans-Joachim Drexler a
a
€
Leibniz-Institut für Katalyse e.V. an der Universitat Rostock (LIKAT Rostock), Albert-Einstein-Straße 29a, 18059, Rostock, Germany
b Department of Chemistry, Materials and Chemical Engineering “G. Natta”, Politecnico di Milano, Piazza L. da Vinci 32, 20133, Milano, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of heteroleptic monomeric cationic Rh(I) bis-diphosphine complex [Rh(dppe)(dppp)]Cl
(dppe ¼ 1,2-bis-(diphenylphosphino)ethane and dppp ¼ 1,3-bis-(diphenylphosphino)propane) was ach-
ieved by reaction between the neutral dimeric complex [Rh2(dppe)2(m2-Cl)2] and the dppp ligand. The
corresponding complex [Rh(dppe)(dppp)]BF4 was instead obtained from reaction between
[Rh(dppe)(nbd)]BF4 (nbd ¼ bicyclo-[2.2.1]-hepta-2,5-diene) and the dppp ligand. Previous protocols had
extended to the synthesis of the analogous homoleptic complexes containing two dppe or two dppp
ligands. The structural analysis of such complexes conducted in the solid state by single-crystal x-ray
crystallography and in solution by 31P and 1H NMR revealed a distorted square planar geometry where
the anion and the cation are not bonded each other. Nevertheless, important differences in reactivity can
be found if same complexes with different anions are compared, as in the case of the phosphine ex-
change reaction between [Rh(dppp)2]X (X ¼ Clꢀ, BF4ꢀ) and the dppe ligand or in the case of the
employment of such complexes as catalytic precursors for the transfer hydrogenation reaction from 2-
propanol to acetophenone.
Received 7 January 2019
Received in revised form
4 February 2019
Accepted 5 February 2019
Available online 7 February 2019
Keywords:
Rhodium
Diphosphine
X-ray
Kinetics
Transfer Hydrogenation
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
have been employed as catalytic precursors in the hydrogenation of
CeC double bonds [1c,4], for the decarbonylation of aldehydes
Monomeric cationic bis-diphosphine Rh(I) complexes of the
type [Rh(PP)2]þ containing two dppp (1,3-bis-(diphenylphos-
phino)-propane) ligands or two dppe (1,2-bis-(diphenylphos-
phino)-ethane) ligands are known since more than 40 years. They
can be easily prepared by reaction of a suitable Rh precursor and an
excess of the selected diphosphine [1].
Early studies on such Rh(I) complexes revealed that they are
able to activate small molecules as CO, H2, O2 or HCl [2], sometimes
in a reversible way [3].
On this basis several catalytic applications have been
developed. [Rh(PP)2]X complexes (PP ¼ dppm, dppe, dppp,
dppb, and diop; X ¼ Clꢀ, BF4ꢀ) (dppm ¼ bis(diphenylphosphino)
methane, dppb ¼ 1,4-bis(diphenylphosphino)-butane), (diop ¼ O-
Isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane)
(PP ¼ dppp, X ¼ Clꢀ, BF4ꢀ) [5], in the synthesis of
b-amino esters
(PP ¼ dppe, X ¼ Cl) [6], in the intramolecular [4 þ 2] cycloaddition
reaction (PP ¼ dppe, X ¼ SbF6) [7], and for the Pauson-Khand
transformation [8]. Some more recent applications of the com-
plex [Rh(dppp)2]Cl as catalytic precursor include the decarbon-
ylation of aldehydes in gas-phase with a supported catalyst [9] or
with catalytically active ionic liquids [10], and the hydrogenation of
the CO2 [11].
Single-crystal x-ray crystallography studies on many monomeric
cationic Rh(I) diphosphine complexes [Rh(Ph2P(CH2)nPPh2)2]þ
revealed a distorted square-planar tetracoordinated structure where
the cation and the anion are independent each other [7,11,12]. The
coordination mode detected in the solid state not always is consis-
tent with the one observed in solution. In fact such complexes are
considered as ionic couple [Rh(PP)2]þXꢀ (Xꢀ ¼ Clꢀ, BF4ꢀ, PF6ꢀ, SbF6ꢀ)
for n ¼ 2 and 3, while coordination of the anion (pentacoordinated
geometry), has been proposed as in the case of n ¼ 1 and 4 [1c,13].
Many structure-reactivity studies have been reported in order to
clarify the influences of the anion and of the tetrahedral distortion
€
* Corresponding author. Leibniz-Institut für Katalyse e.V. an der Universitat
Rostock (LIKAT Rostock), Albert-Einstein-Straße 29a, 18059, Rostock, Germany.
E-mail address: alberto.mannu@polimi.it (A. Mannu).
https://doi.org/10.1016/j.jorganchem.2019.02.009
0022-328X/© 2019 Elsevier B.V. All rights reserved.

60
A. Mannu et al. / Journal of Organometallic Chemistry 885 (2019) 59e64
on the reactivity.
When
2
equivalents of dppp ligand were added to
In this regard James and Mahajan related the reactivity of
[Rh(PPh2(CH2)nPPh2)2]BF4 complexes toward CO, O2, H2 and HCl to
the length of the alkylic chain [1c]. More recently DuBois and co-
workers discussed the reactivity of [Rh(PP)2][CF3SO3] (PP ¼ dppe,
dmpe, depe, depp, depx) (dmpe ¼ 1,2-bis(dimethylphosphino)
ethane; depe ¼ 1,2-bis-(diethylphosphino)ethane; depp ¼ 1,3-bis-
(diethylphosphino)propane; depx ¼ 1,2-bis((diethylphosphanyl)
methyl-benzene)) with H2 in terms of electronic and steric effects,
relating the rate of the oxidative addition of H2 to [Rh(depx)2]
[CF3SO3] and to [Rh(depe)2][CF3SO3] to the bite angle of the
diphosphine [14]. The relation between bite angle and the rate of
oxidative addition of H2 to [Rh(PP)2]þ complexes was recently
reviewed by Mansel, and the following trend was reported: com-
plexes containing ligands as dcpe (1,2-bis(dicyclohexylphosphino)
ethane) and dppe do not form any hydride, the ones containing
ligands as depe, dppp, or dmpe form an equilibrium mixture of
hydrides, and finally complexes where PP ¼ depp or depx are able
to quantitatively form hydrides [15]. Also Leitner and co-workers
tried to relate the geometry of the cation [Rh(dppe)2]þ with the
values of chemical shift observed in 103Rh NMR experiments [16].
The usual model describing the reactivity of monomeric
cationic Rh(I) diphosphine complexes is based on a first oxidative
addition of a generic AB agent to the tetracoordinated [Rh(PP)2]þ
complex to give an hexacoordinate Rh(III) derivative of the type
[Rh(PP)2(A)(B)]þ. The differences in reactivity between complexes
containing different diphosphines are often justified by the
different steric influence of the ligands. Dissociation of the
diphosphine or an involvement of the anion has not been consid-
ered as important issue so far.
[Rh2(dppe)2(m2-Cl)2] the heteroleptic complex [Rh(dppp)(dppe)]Cl
(II) was formed accompanied by a small amount (3%) of [Rh(dppe)2]
Cl (III) and free dppp. The formation of III suggests a substitution of
the coordinated dppp in complex II by free dppe.
Complexes IV, V and VI, analogous to I, II and III but containing
BFꢀ4 instead of Clꢀ, were synthesized in quantitative yields by
adding one equivalent of PP (dppe, dppp) to the precursor
[Rh(PP)(nbd)]BF4.
Single yellow crystals suitable for X-ray analysis were obtained
by layering a CH2Cl2 solution with THF for complexes I, II, III (Fig. 1),
and VI (Fig. 2).
The distances between the Rh and the phosphorus atoms are
comparable for all the complexes considered and lay between 2.28
and 2.33 Å. The dihedral angle enclosed by the planes PeRheP and
PeRheP is close to 0 indicating a tetrahedral geometry for com-
plexes I, II and III, while a slightly tetrahedral distortion of 4.19ꢁ can
be observed in complex VI. Coordination of the anion has not been
observed in all the structure studied, as the average distance be-
tween the Rh atom and the anion is in all the cases bigger than 4 Å
(Table 1). A complete comparison of the main coordination char-
acteristics of complexes I, II, II and VI with the similar ones pre-
viously published can be found in the Supporting Information.
31P NMR analysis of complexes I, III, IV and VI shows in all cases
a sharp doublet, resulting from the 31Pe103Rh coupling, while
complexes II and V present a more complex pattern in according to
a second order spectrum with a spin system of the type MAA'XXꢀ.
The 31P NMR for the heteroleptic complexes II and V is in agree-
ment with the in situ observation of [Rh(dppe)(dppp)][BArF4] by
Weller and co-workers generated in a mixture with other products
With the aim to extend the current knowledge on the reactivity
of [Rh(PP)(PP)]X complexes (PP ¼ dppp or dppe and X ¼ Clꢀ or BF4ꢀ)
we report in this work our findings of the lability of the Rh-
diphosphine bonds and on a possible influence of the anion on
the behavior of such complexes. The synthesis and the character-
ization of the heteroleptic complexes [Rh(dppe)(dppp)]Cl and
[Rh(dppe)(dppp)]BF4 is herein reported for the first time. In addi-
tion, an explorative study of such complexes as catalytic precursors
for the transfer hydrogenation reaction is presented.
when complex [Rh(L)H(
s
,
h
2-PPh2BH2PPh2BH3)][BArF4] (L ¼ dppp)
was treated with an excess of dppe [21].
In Table 2 a comparison between the characteristic signals in 31
NMR for the complexes I-VI is reported.
P
Comparing the 31P NMR (CH2Cl2 at room temperature) data of
complexes which differ only by the nature of the anion (entries 1 vs
4, 2 vs 5 and 3 vs 6) we cannot observe any influence of it to the
structure of the cation (no variation in chemical shift or in the
coupling constants value are observed), suggesting the presence of
a cationic tetracoordinate Rh(I) complex.
2. Results and discussion
Nevertheless, Pignolet and co-workers conducted some variable
temperature 31P NMR analyses on [Rh(PP)2]BF4 complexes
(PP ¼ dppe, dppp, dppb) and proposed the formation of penta-
coordinate complexes (dppp), dimers or small clusters in solution
(dppb) [13]. Pentacoordination of Rh or formation of polynuclear
complexes was not observed even in the solid state by single-
crystal x-ray crystallography, as reported above (Fig. 1).
Concerning the characterization of complexes I-VI in solution,
we were able to exclude the formation of arene-bridged species
[22] from 1H NMR experiments and we did not detect in any case
the release of diphosphine in CH2Cl2 solutions, as well as any signal
related with oxidative addition processes.
Chlorine containing complexes I-III were synthesized exploiting
the known in situ monomerization of [Rh2(PP)2(m2-Cl)2] (PP ¼ dppp
or dppe, Scheme 1), already proposed in the presence of the ligands
dppp [17], dppe [18], dppb [19], MeO-BIPHEP (BIPHEP ¼ 2,20-bis-
(diphenylphosphanyl)-1,10-biphenyl) [16] and DPEPhos (DPE-
Phos ¼ Bis-[2-(diphenylphosphino)phenyl]ether) [20].
Adding 2 equivalents of PP (PP ¼ dppp, dppe) to a THF solution
of [Rh2(PP)2(m2-Cl)2], the corresponding homoleptic [Rh(PP)2]Cl
complexes containing the ligands dppp (I) or dppe (III) were ob-
tained in quantitative yields (Scheme 1).
Although complexes I-VI can be described as tetracoordinated
cations in CH2Cl2 solution at room temperature, ion pair influence
on their reactivity cannot be discarded. This specific aspect was
investigated by Pregosin and coworkers in the case of [Rh(cod)(-
Biphemp)]X complexes (Biphemp ¼ 2,20-Dimethyl-6,60-bis(diphe-
nylphosphino)biphenyl, X ¼ BFꢀ4 , PF6ꢀ, CF3SO3ꢀ) by meaning of PGSE
diffusion and 1He19F HOESY NMR experiments [23].
In order to gain more knowledge about the possible influence of
the anion (Clꢀ or BFꢀ4 ) on the behavior of complexes I-VI we con-
ducted some reactivity studies.
During the optimization of the synthesis of complex III we
observed that dppe displaces irreversibly dppp from complex
[Rh(dppp)2]Cl, while on the contrary the complex [Rh(dppe)2]Cl
Scheme 1. Synthetic strategy for the synthesis of [Rh(P1P1)2]Cl and [Rh(P1P1)(P2P2)]Cl
complexes.

A. Mannu et al. / Journal of Organometallic Chemistry 885 (2019) 59e64
61
Fig. 1. Molecular structure of complexes I (left), II (middle), III (right). ORTEP, 30% probability ellipsoids. Hydrogen atoms are omitted for clarity.
Table 2
Relevant 31P NMR data for complexes I-VI.
Entry
Complex
31P NMR1
(d)
1
1
2
3
4
5
6
I [Rh(dppp)2]Cl
II [Rh(dppe)(dppp)]Cl
III [Rh(dppe)2]Cl
IV [Rh(dppp)2]BF4
V [Rh(dppe)(dppp)]BF4
VI [Rh(dppe)2]BF4
7.77 (d, JP-Rh ¼ 131 Hz) ppm
56.3 (dppe) ppm; 10.1 ppm (dppp) ppm
1
57.49 (d, JP-Rh ¼ 133 Hz) ppm
1
7.44 (d, JP-Rh ¼ 131.6 Hz) ppm
56.3 (dppe) ppm; 10.1 (dppp) ppm
1
57.45 (d, JP-Rh ¼ 133 Hz) ppm
Table 3
Characteristic data from the 31P NMR of the considered phosphino-selenides.
Complex
d
(ppm)
J (31Pe77
)
Se
Solvent
Se2(dppe)
Se2(dppp)
30.6
33.0
736
730
CD2Cl2
CD2Cl2
A direct proof of the negligible effect of the electronic parame-
ters on the differences between dppe-Rh and dppp-Rh bonds is
represented by the measure of the
s-donor ability. In fact, the
J31Pe77Se calculated from the 31P NMR spectra of the corresponding
phosphino-selenides is representative of the electronic effect of the
phosphorus ion pair on the PPeRh bond [24]. Complexes
[Se2(dppe)] and [Se2(dppp)] were synthesized by reaction of the
suitable phosphine and selenium powder, following a known pro-
tocol [25]. The results revealed by 31P NMR spectroscopy are re-
ported in Table 3.
According to Table 3 the values of the coupling constants for
Se2(dppe) and Se2(dppp) are very similar, suggesting, as expected,
that the different behavior of [Rh(dppe)2]Cl with respect to
Fig. 2. Molecular structure of complex VI. ORTEP, 30% probability ellipsoids. Hydrogen
atoms are omitted for clarity.
[Rh(dppp)2]Cl is not related to the
diphosphine.
s-donor ability of the
does not react in the presence of free dppp. The reason of this
specific reactivity should be exclusively related to the higher ther-
modynamic stability of the fragment Rh(dppe) (5 member ring)
with respect to Rh(dppp) 6 member ring. Nevertheless, as substi-
tution of the diphosphine in complexes [Rh(PP)2]X is not common,
we conducted some additional studies on the matter.
In order to clarify the reaction sequence involved in this phos-
phine exchange process and investigate a possible influence of the
anion, a 31P NMR monitoring of the reaction between complexes I
or IV (I containing Clꢀ and IV containing BFꢀ4 ) in the presence of 2
equivalents of dppe in CD2Cl2 was conducted (Fig. 3).
Table 1
Relevant distances and angles for complexes I, II, III and VI.
Complex
Anion
RheP [Å]
RheP [Å]
PeRheP [ꢁ]
PeRheP/PeRhePa[ꢁ]
I
II
III
VI
Clꢀ
Clꢀ
Clꢀ
BFꢀ4
2.3319(5) 2.3354(5)
2.3064(14) 2.3102(15)
2.2857(6) 2.2931(9)
2.2867 2.3085(12)
4.430(1)
4.4842(3)
5.401(3)
e
88.56(2)
85.53(2)
82.58(2)
82.71(4) 83.32(4)
0.00(2)
0.00(8)
0.00(5)
4.19(8)

62
A. Mannu et al. / Journal of Organometallic Chemistry 885 (2019) 59e64
Fig. 3. Plots of the variation of the concentrations of I, II and III (left) and of IV, V and VI (right) for the reaction [Rh(dppp)2]X þ 2 dppe (X ¼ Clꢀ or BF4ꢀ) [26].
The reactivity of complexes [Rh(dppp)2]Cl (I) and [Rh(dppp)2]BF4
have shown some tendency to generate dihydrides in the presence
of molecular hydrogen [1c,2,3,30]. Even more important this pro-
cess is reversible in the presence of a suitable substrate, which lead
to the employment of these complex as catalytic precursors for the
hydrogenation reaction. Concerning the exploiting of 2-propanol as
hydrogen donor for the reduction of ketones, only few examples of
Rh(I) complexes have been reported so far, mainly focused on the
utilization of amino-phosphino ligands [31].
With the aim to extend this reactivity to different hydride donor
than molecular hydrogen, and to explore a possible influence of the
anion on the catalytic behavior, we tested the complexes I, II III, IV,
V, and VI, as catalytic precursors for the Transfer Hydrogenation
(TH) from 2-propanol to the model substrate acetophenone
(Scheme 3).
(IV) toward dppe resulted highly different: complex I reacts with
dppe ligand releasing free dppp with a kinetic profile compatible
with a consecutive two step reaction (Fig. 2, left side). The starting
material was consumed after 3 h (black line), when the concentra-
tion of [Rh(dppe)(dppp)Cl] reached its maximum (Scheme 2).
On the other side, complex IV reacts very slowly in the presence
of free dppe and after 20 h only 42% of the intermediate complex V
was observed [27], with no detectable amount of complex VI (Fig. 2,
right side). From the analysis of the kinetic data reported in Fig. 3 is
possible to notice that exchanging Clꢀ with BF4ꢀ the rate of the Rh-
dppp/dppe exchange process drops down for [Rh(dppp)2]þ and for
the intermediate species [Rh(dppe)(dppp)]þ. From the NMR spectra
acquired during the 31P NRM monitoring process, no visible signal
of anion coordination was shown.
In order to shed light on the mechanism of the reaction, the
concentration-time data for the reaction [Rh(dppp)2]Cl þ 2 dppe
were analyzed by a kinetic modeling based on the set of ordinary
differential equations (ODEs) which were derived from the depic-
ted reaction sequence (Scheme 2). We used an algorithm written in
Matlab® for a simultaneous procedure for the numerical integra-
tion of the ODEs and a respective regression fitting [28].
The following conditions were employed for all the catalytic
runs: 0.02 mmol of [Rh] and 0.1 mmol of tBuOK were dissolved in
i
25 mL of PrOH and heated at 80 ꢁC. After 30 min 4 mmol of ace-
tophenone were added and the reaction stirred at 80 ꢁC for 24 h
(Table 4).
As reported in Table 4 the compexes tested as catalytic pre-
cursors for the transfer hydrogenation reaction between the ace-
tophenone and 2-propanol show significant differences of
conversions, from very low (entry 6) to very high (entry 1). The
catalytic precursor I, containing two dppp, resulted much more
active than the others (entries 1 and 4), confirming the trend re-
ported in the case of the hydrogenation of olefins [4]. The presence
of dppe instead of dppp seems to slow down the catalytic activity of
the system (entries 2e3 and 5e6), while the heteroleptic com-
plexes II and V show activities close to the ones containing two
dppe (entries 2, 5 vs entries 3, 6).
The theoretical model obtained, based on the mechanism re-
ported in Scheme 2, does not fit with the experimental data showed
in Fig. 3, suggesting a different stoichiometry of the real reaction
mechanism [29]. Combining this information with the evidence of
an influence of the anion we can propose the in situ formation of
ionic couples as previous suggested by Pregosin and coworkers for
other Rh-diphosphine systems [23].
Exchanging of the anion Clꢀ with BFꢀ4 results in an important
reduction of the activity for all the complexes considered (entries 1,
2, 3 versus 4, 5, and 6), indicating a detrimental effect of the BFꢀ4 on
3. Catalytic application
Cationic monomeric Rh(I) complexes containing diphosphines
Scheme 2. Hypothesis of mechanism for the reaction between complex I (or IV) and 2 equivalents of dppe.

A. Mannu et al. / Journal of Organometallic Chemistry 885 (2019) 59e64
63
Scheme 3. Transfer hydrogenation from 2-propanol to acetophenone.
Table 4
Cambridge, CB21EZ, UK (fax: int. code þ (1223) 336e033; e-mail:
Catalysts screening for the transfer hydrogenation from 2-propanol to the
acetophenone.
deposit@ccdc.cam.ac.uk.
Entry
[Rh]
Conversion
5.1. General synthesis of [Se2(PP)]
1
2
3
4
5
6
I [Rh(dppp)2]Cl
II [Rh(dppe)(dppp)]Cl
III [Rh(dppe)2]Cl
IV [Rh(dppp)2]BF4
V [Rh(dppe)(dppp)]BF4
VI [Rh(dppe)2]BF4
92.4%
58.7%
49.4%
77.6%
36.0%
3.6%
A variation of a previous reported methodology was employed
[18]. 0.004 mmol of the diphosphine were dissolved in CH2Cl2 and
0.4 mmol of elemental selenium were added. The resulting mixture
was stirred overnight at room temperature. The crude product was
filtered on a pad of celite and the solvent removed under vacuum to
give the corresponding phosphino-selenide in quantitative yields.
the catalytic outcome.
5.2. General synthesis of [Rh(PP)2]Cl
4. Conclusions
Route 1: To a solution of 0.01 mmol of [Rh2(PP)2(m2-Cl)2] in 2 mL
of THF, 0.02 mmol of diphosphine were added. After few minutes a
yellow precipitate was formed. After stirring the mixture for
additional 2 h, the solvent was removed by syringe. The residue was
washed 2 times with THF and finally dried under vacuum.
Route 2: To a solution of 0.12 mmol of [Rh(cod)(m2-Cl)]2 in 2 mL
of THF, 0.54 mmol of diphosphine were added. After few minutes a
yellow precipitate was formed. After stirring the mixture for
additional 2 h, the solvent was removed by syringe. The residue was
washed 2 times with THF and finally dried under vacuum.
The synthesis and the characterization of six [Rh(PP)(PP)]X
complexes were reported, including for the first time the two
heteroleptic derivatives [Rh(dppe)(dppp)]X (X ¼ Clꢀ or BF4ꢀ). The
molecular structures of complexes I, II, III and IV were also
described. Phosphine exchange reaction between [Rh(dppp)2]X
and dppe suggests an important influence of the anion on the
reactivity of such complexes. All the complexes herein described
were tested as catalytic precursors for the Transfer Hydrogenation
reaction from 2-propanol to the acetophenone, resulting all active
for such transformation and showing a poisoning effect of the BF4ꢀ
anion. The results reported suggest that the influence of the anion
on the reactivity of such ionic organometallic complexes, including
their behavior as catalysts, can not be neglected.
5.3. General synthesis of [Rh(PP)2]BF4
To a solution of 0.07 mmol of [Rh(PP)(nbd)]BF4 in 1 mL of MeOH,
0.08 mmol of diphosphine were added. The resulting solution was
stirred overnight. The crude product was treated as reported below.
5. Experimental section
All manipulations were carried out under argon using standard
Schlenk techniques. THF and 2-propanol were distilled from so-
dium, MeOH was distilled from magnesium, and CH2Cl2 was
distilled from CaH2. Subsequent removal of traces of oxygen from
the deuterated solvents was carried out through the application of
three freeze-thaw cycles. The rhodium precursors [Rh(cod)(m2-Cl)]2
(98%) was purchased by STREM. The phosphine DPPE was pur-
chased from STREM and employed as received. DPPP was pur-
chased by Sigma Aldrich (98%) and recrystallized from MeOH.
[Rh2(dppe)2(m2-Cl)2], [Rh(dppe)(nbd)]BF4, [Rh(dppp)(nbd)]BF4,
[Se2(dppe)], and [Se2(dppp)] were prepared according to the
bibliography.
5.3.1. [Rh(dppe)2]Cl: yellow powder, 95% of yield
1H NMR (300 MHz, CDCl3, 25 ꢁC):
d
¼ 1.98e2.15 (m, 4H),
7.05e7.19 (m,16H), 7.25e7.36 (m, 4H) ppm. 31P{1H} NMR (300 MHz,
CDCl3, 25 ꢁC):
d
¼ 57.49 (d, JP-Rh ¼ 133 Hz) ppm. MS (HR-ESI(þ)): m/
z 672.3 [(M e P(Ph)3(CH2)2 þ HCN þ HCl]þ, 595.0 [(M e
P(Ph)4(CH2)2 þ HCN þ HCl]þ.
5.3.2. [Rh(dppp)2]Cl: yellow powder, 93% of yield
1H NMR (300 MHz, CD2Cl2, 25 ꢁC):
d
¼ 1.64e1.89 (m, 4H),
2.08e2.24 (m, 8H), 6.91e7.17 (m, 30H), 7.18e7.30 (m, 10H) ppm. 31
P
{1H} NMR (300 MHz, CD2Cl2, 25 ꢁC):
d
¼ 7.77 (d, JP-Rh ¼ 131 Hz)
ppm. MS (HR-ESI(þ)): m/z 927.1 [M]þ.
NMR: 1H NMR and 31P NMR spectra were obtained on a Bruker
AV-300 or AV-400 spectrometer at 297e298 K and were referenced
internally to the deuterated solvent. For 31P{1H} NMR spectra, 85%
H3PO4 was used as external standard. Data processing was per-
formed by Topspin software (3.5 version) (Bruker). All the NMR
spectra have been recorded at 297 K (24 ꢁC) unless otherwise
indicated.
5.3.3. [Rh(dppe)2]BF4: yellow powder, 95% of yield
1H NMR (300 MHz, CD2Cl2, 25 ꢁC):
¼ 1.94e2.13 (m, 4H),
d
7.06e7.22 (m, 16H), 7.23e7.36 (m, 4H) ppm. 31P{1H} NMR
(300 MHz, CD2Cl2, 25 ꢁC):
d
¼ 57.45 (d, JP-Rh ¼ 133 Hz) ppm. MS (HR-
ESI(þ)): m/z 899.0 [M]þ.
Crystallographic data (excluding structure factors) for the
structures reported in this paper were deposited at the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC- 873599 for I*THF, CCDC- 873597 for II, CCDC- 873596 for
III*i-PrOH and CCDC- 873598 for VI. Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
5.3.4. [Rh(dppp)2]BF4: yellow powder, 95% of yield
1H NMR (300 MHz, CD2Cl2, 25 ꢁC):
¼ 1.67e1.89 (m, 4H),
2.09e2.25 (m, 8H), 6.98e7.17 (m, 30H), 7.18e7.28 (m, 10H) ppm. 31
d
P
{1H} NMR (300 MHz, CH2Cl2, 25 ꢁC):
d
¼ 7.44 (d, JP-Rh ¼ 131.6 Hz)
ppm. MS (HR-ESI(þ)): m/z 927.1 [M]þ.

64
A. Mannu et al. / Journal of Organometallic Chemistry 885 (2019) 59e64
[7] S.I. Lee, S.Y. Park, J.H. Park, Y.K. Chung, J.W. Han, Bull. Korean Chem. Soc. 28
5.4. Synthesis of [Rh(dppe)(dppp)]Cl
(2007) 1919e1920.
[8] a) T. Shibata, N. Toshida, K. Takagi, J. Org. Chem. 67 (2002) 7446e7450;
b) T. Shibata, N. Toshida, K. Takagi, Org. Lett. 4 (2002) 1619e1621.
[9] P. Malcho, E.J. Garcia-Suarez, U.V. Mentzel, C. Engelbrekt, A. Riisager, Dalton
Trans. 43 (2014) 17230e17235.
[10] P. Malcho, E.J. Garcia-Suarez, A. Riisager, RSC Adv. 4 (2014) 58151e58155.
[11] J.T. Bays, N. Priyadershani, M.S. Jeletic, E.B. Hulley, D.L. Miller, J.C. Linehan,
W.J. Shaw, ACS Catal. 4 (2014) 3663e3670.
[12] a) C. Pettinari, F. Marchetti, R. Pettinari, A. Pizzabiocca, A. Drozdov,
S.I. troyanov, V. Vertlib, J. Organomet. Chem. 688 (2003) 216e226;
b) R.R. Burch, J.C. Calabrese, J. Am. Chem. Soc. 108 (1986) 5359e5360;
c) R. Dorta, L. Shimon, D. Milstein, J. Organomet. Chem. 689 (2004) 751e758;
d) J. van der Broeke, M. Lutz, H. Kooijman, A.L. Spek, B.-J. Deelman, G. van
Koten, Organometallics 20 (2001) 2114e2117;
0.05 mmol of DPPP were added to a solution containing
0.1 mmol of [Rh2(DPPE)2(m2-Cl)2] in 3 mL of THF and the resulting
mixture was stirred for 4 h. A yellow solid starts to precipitate from
the reaction medium after 10 min. The solvent was removed by
syringe and the residue washed with THF 2 times and then dried
under vacuum to give yellow powder in 90% of yield.
1H NMR (300 MHz, CD2Cl2, 25 ꢁC):
2.13e2.32 (m, 4H), 7.09e7.47 (m, 20H) ppm. 31P{1H} NMR (300 MHz,
CH2Cl2, 25 ꢁC):
d
¼ 1.85e2.04 (m, 6H),
d
¼ 56.3 (pdd, JP-Rh ¼ 225.8 Hz, JP-P ¼ 132.2 Hz, 2 P,
dppe) 10.1 ppm (pdd, JP-Rh ¼ 226.0 Hz, JP-P ¼ 128.7 Hz, 2 P, dppp)
e) R.J. Bowen, E.M. Coyanis, M. Layh, R. Meijboom, C.B. Poole, Acta Crystallogr.
Select. E: Struct. Rep. Online 62 (2006) m101em102.
[13] M.P. Anderson, L.H. Pignolet, Inorg. Chem. 20 (1981) 4101e4107.
[14] a) D.L. DuBois, D.M. Blake, A. Miedaner, C.J. Curtis, M.R. DuBois, J.A. Franz,
J.C. Linehan, Organometallics 25 (2006) 4414e4419;
ppm. MS (HR-ESI(þ)): m/z 897.1 [(M e Ph þ Cl þ CN)]þ.
5.5. Synthesis of [Rh(dppe)(dppp)]BF4
b) D.E. Berning, A. Miedaner, C.J. Curtis, B.C. Noll, M.C. Rakowski DuBois,
D.L. DuBois, Organometallics 20 (2001) 1832e1839.
[15] S.M. Mansel, Dalton Trans. 46 (2017) 15157e15174.
0.1 mmol of DPPP were added to a solution containing 0.1 mmol
of [Rh(DPPE)(nbd)]BF4 in 3 mL of MeOH and the resulting mixture
was stirred overnight. Then the solvent was removed under vac-
uum and the residue washed 3 times with THF to give a yellow
powder in 95% of yield.
[16] W. Leitner, M. Buhl, R. Fornika, C. Six, W. Baumann, E. Dinjus, M. Kessler,
C. Kruger, A. Rufinska, Organometallics 18 (1999) 1196e1206.
€
[17] A. Mannu, M. Ferro, S. Moller, D. Heller, J. Chem. Res. 42 (2018) 402e404.
[18] A. Mannu, H.-J. Drexler, R. Thede, M. Ferro, W. Baumann, J. Rüger, D. Heller,
J. Organomet. Chem. 871 (2018) 178e184.
1H NMR (300 MHz, CD2Cl2, 25 ꢁC):
d
¼ 1.76e1.95 (m, 6H),
2.08e2.22 (m, 4H), 6.91e7.42 (m, 20H) ppm. 31P{1H} NMR
(300 MHz, CH2Cl2, 25 ꢁC):
[19] S.M. Jackson, C.E. Hughes, S. Monfette, L. Rosenberg, Inorg. Chim. Acta 359
(2006) 2966e2972.
€
[20] U. Gellrich, A. Meißner, A. Steffani, M. Kahny, H.-J. Drexler, D. Heller,
d
¼ 56.3 (pdd, JP-Rh ¼ 225.5 Hz, JP-
D.A. Plattner, B. Breit, J. Am. Chem. Soc. 136 (2014) 1097e1104.
[21] M.A. Huertos, A.S. Weller, Chem. Sci. 4 (2013) 1881e1888.
[22] a) I. Thiel, M. Horstmann, P. Jungk, S. Keller, F. Fischer, H.-J. Drexler, D. Heller,
M. Hapke, Chem. Eur J. 23 (2017) 17048e17057;
¼ 131.9 Hz, 2 P, dppe) 10.1 ppm (pdd JP-
¼ 226 Hz, JP-
P
P
Rh
¼ 128,8 Hz, 2P, dppp) ppm. MS (HR-ESI(þ)): m/z 913,1 [M]þ.
€
b) A. Konig, C. Fischer, E. Alberico, C. Selle, H.-J. Drexler, W. Baumann,
Acknowledgements
D. Heller, Eur. J. Inorg. Chem. (2017) 2040e2047.
[23] P.G.A. Kumar, P.S. Pregosin, T.M. Schmid, G. Consiglio, Magn. Reson. Chem. 42
(2004) 795e800.
The Authors thank Prof. Detlef Heller for the kindly help and
support and Dr. Wolfgang Baumann for the very useful advice
about the interpretation of the NMR data.
[24] (The
s-character of the lone pair of the phosphorous atom increases in the
presence of electron-withdrawing groups and reduces with bulky sub-
stituents, which widen the intervalence angles. For more details): a)
U. Beckmann, D. Süslüyan, P.C. Kunz, Phosphorus, Sulfur, Silicon Relat. Elem.
186 (10) (2011) 2061e2070;
b) R.P. Pinnell, C.A. Megerle, S.L. Manatt, P.A. Kroon, J. Am. Chem. Soc. 95
(1973) 977e978.
Appendix A. Supplementary data
[25] R. Aznar, A. Grabulosa, A. Mannu, G. Muller, D. Sainz, V. Moreno, M. Font-
Bardia, T. Calvet, J. Lorenzo, Organometallics 32 (2013) 2344e2362.
[26] Conditions: 0.01 Mmol of [Rh(dppp)2]X (X ¼ Cl, BF4) Were Mixed with 0.02
Mmol of Dppe in 0.7 mL of CD2Cl2.
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jorganchem.2019.02.009.
[27] All the species involved in the reaction are soluble in CD2Cl2. More Details can
be found in the Supporting Informations.
References
[28] An implicit Runge-Kutta-Radau scheme was used for the integration of or-
dinary differential equations and an advanced Gauß-Newton code was used
for the optimization.
[29] More details, including the kinetic plot and equations are reported in the
Supporting Information.
[30] D. Sinuo, H.B. Kagan, J. Organomet. Chem. 114 (1976) 325e337.
[31] a) M. Aydemir, Y.S. Ocak, K. Rafikova, N. Kystaubayeva, C. Kayan, A. Zazybin,
F. Ok, A. Baysal, H. Temel, Appl. Organomet. Chem. 28 (2014) 396e404;
b) M. Aydemir, N. Meric, C. Kayan, F. Ok, A. Baysal, Inorg. Chim. Acta 398
(2013) 1e10;
[1] a) J. Chatt, B.L. Shaw, J. Chem. Soc. A (1966) 1437e1442;
b) D.A. Slack, M.C. Baird, J. Organomet. Chem. 142 (1977) C69eC72;
c) B.R. James, D. Mahajan, Can. J. Chem. 57 (2) (1979) 180e187;
d) M. Rosales, A. Gonzalez, B. Gonzalez, C. Moratinos, H. Perez, J. Urdaneta,
R.A. Sanchez-Delgado, J. Organomet. Chem. 690 (2005) 3095e3098.
[2] B.R. James, D. Mahajan, Can. J. Chem. 58 (10) (1980) 996e1004.
[3] A.D. Wilson, A.J.M. Miller, D.L. DuBois, J.A. Labinger, J.E. Bercaw, Inorg. Chem.
49 (2010) 3918e3926.
[4] L. Montalvo, A. Bolanos, A. Cabrera, J. Mex. Chem. Soc. 5 (2007) 8e14.
[5] a) D. Horton, T. Usui, Carbohydr. Res. 216 (1992) 51e59;
b) M. Murakami, H. Amii, K. Shigeto, Y. Ito, J. Am. Chem. Soc. 118 (35) (1996)
8285e8290.
c) Kayan, N. Meric, M. Aydemir, A. Baysal, D. Elma, B. Ak, E. Sahin, N. Gürbüz,
€
I. Ozdemir, Polyhedron 42 (2012) 142e148;
d) M. Aydemir, A. Baysal, N. Meric, C. Kayan, B. Gümgüm, S. Ozkar, E. Sahin,
€
[6] T. Muraoka, S. Kamiya, I. Matsuda, K. Itoh, Chem. Commun. (2002)
1284e1285.
J. Organomet. Chem. 696 (2011) 2584e2588.