Bulky 1,1′-bisphosphanoferrocenes and their coordination behaviour towards Cu(i)

Article abstract of DOI:10.1039/d0dt00941e

Two bulky mesityl substituted dppf-analogues Fe(C₅H₄PMes₂)₂ (Mes = 2,4,6-Me₃C₆H₂, 1) and Fe(C₅H₄PMes₂)(C₅H₄PPh₂) (Mes = 2,4,6-Me₃C₆H₂, Ph = C₆H₅, 3) have been prepared and their properties as donor ligands have been explored using heteronuclear NMR spectroscopy and in particular via¹J_P-Se coupling, cyclic voltammetry and DFT calculations. Based on the results obtained, a series of mono- and dinuclear Cu(i) complexes have been prepared with these new diphosphane ligands using Br^-, I^-, and BF₄^- as counter anions. For the very bulky ligand 1 rare and unprecedented double bridging complexation modes have been observed containing two non-planar Cu₂Br₂ units, while for the other dinuclear complexes planar Cu₂Br₂ units have been found. The Cu(i) complexes of 1 and 3 were then used as catalysts for CO₂-fixation reaction with terminal alkynes, and complexes with ligand 3 were found to be more efficient than those with 1. DFT calculations performed on compounds 1, 3 and their Cu(i) complexes were able to verify the trend of these catalytic reactions.

Full text of DOI:10.1039/d0dt00941e

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DOI: 10.1039/D0DT00941E
ARTICLE
Bulky 1,1'-bisphosphanoferrocenes and their coordination
behaviour towards Cu(I)
Subhayan Dey,† Daniel Buzsáki,‡ Clemens Bruhn,† Zsolt Kelemen*‡ and Rudolf Pietschnig*†
Received 00th January 20xx,
Accepted 00th January 20xx
Two bulky mesityl substituted dppf-analogs Fe(C5H4PMes2)2 (Mes
Fe(C5H4PMes2)(C5H4PPh2) (Mes = 2,4,6-Me3C6H2, Ph = C6H5, 3) have been prepared and their properties as
donor ligands have been explored using heteronuclear NMR spectroscopy and in particular via the JP-Se
=
2,4,6-Me3C6H2, 1) and
DOI: 10.1039/x0xx00000x
1
coupling, cyclic voltammetry and DFT calculations. Based on these results, a series of mono and dinuclear Cu(I)
-
complexes have been prepared with these new diphosphane ligands using Br-, I-, BF4 as counter anions. For
the very bulky ligand 1 rare and unprecedented double bridging complexation modes have been observed
containing two non-planar Cu2Br2 units, while for the other dinuclear complexes planar Cu2Br2 units have been
found. The Cu(I) complexes of 1 and 3 were then used as catalysts for CO2-fixation reaction with terminal
alkyne, where complexes with ligand 3 were found more efficient than those with 1. DFT calculations
performed on compounds 1, 3 and their Cu(I) complexes were able to verify the trend of these catalytic
reactions.
dominated by 1,1′-bis(diphenylphosphano)ferrocene (dppf, D, Figure
Introduction
1) for many decades.15, 16, 24 However, in 2007, it has been reported
that 1,1′-bis(di-tert-butylphosphano)ferrocene (dtbpf, E, Figure 1) is
superior to dppf for the Pd-catalyzed α-arylation of ketones and
certain Pd-catalyzed Suzuki coupling reactions.41, 42 Moreover, in the
recent past, several reports have theoretically proven the fact that
with the increase of the steric bulk on phosphorus, the donating
ability and βn increase, and as a result increases the catalytic
activity.43, 44 In this context, two obvious questions arise: 1) What is
the maximum attainable steric before the complexation of 1,1′-
bisphosphanoferrocene compromises? 2) How much steric bulk can
be used without harming the catalytic activity of the resulting
complexes? Since the steric situation will differ from one metal to the
other, we have explored a catalytic process and addressed the
previous questions with the help of two novel sterically congested
1,1′-diphosphanoferrocene ligands, namely 1,1′-bis(dimesityl-
phosphano)ferrocene and 1-(dimesitylphosphano)-1′-(diphenyl-
phosphano)ferrocene. The complete syntheses of these ligands,
their electrochemical properties and donating abilities will be
investigated herein, as well as a first insight into their potential in
catalysis.
Being an extremely useful and unique building block, ferrocene
remains a center of attraction for several decades now. Apart from
the fact that it is important for synthesizing organometallic
6-8
polymers,1-5
discovery,9,
preparing redox-tunable substances,4,
drug
and fabrication of other functional materials,11-14
10
ferrocene has played a vital role in homogenous catalysis.15, 16 When
the diphosphane ligand-systems emerged from their mono-
phosphane counterparts, ferrocene provided them with an
unprecedented backbone,17-19 which helped to stabilize variety of
20
metal centers by attaining flexible geometries.15,
This special
arrangement has further been appreciated, when it emerged that
the bite angles (βn, A, Figure 1) of such ligands, which have an
apparent positive effect on the efficiency of catalysts,21, 22 can be
manipulated by changing the substituents on phosphorus.23
Systematic investigations further revealed that the alteration of
substituents on phosphorus can be achieved by simple and modular
24
synthetic approaches.23,
The aforementioned qualities made
ferrocene-based diphosphane ligands remarkably successful for
16
homogenous catalysis.15, The quest for new ligands, with ideal
steric demand and optimum donating ability, is still relevant to
PR2
PR2
PR2
PR2
PR'2
date.25-30
n
M
Fe
Fe
Fe
PR'2
Although many different 1,1'-symmetrically and unsymmetrically
B
A
C
substituted bisphosphanoferrocenes have been reported in the past
23, 25, 31-40
(B and C, Figure 1),19,
the catalytic discussions were
PPh2
PPh2
PtBu2
PtBu2
PMes2
PR2
Fe
Fe
Fe
D
E
F,
R = Mes, Ph
† Institut für Chemie und CINSaT, University of Kassel, Heinrich Plett-Straße 40, 34132
Kassel, Germany
Department of Inorganic and Analytical Chemistry, Budapest University of
Technology and Economics, and MTA-BME Computation Driven Chemistry Research
Group, Szent Gellért tér 4, 1111 Budapest, Hungary.
Electronic Supplementary Information (ESI) available: NMR spectra, crystal
structures of 4 and 6, crystal refinement data, CV and Details of DFT calculations.
See DOI: 10.1039/x0xx00000x
Fig 1. Bite angle (βn, A),21, 22 previously (B-E),23 and herein reported (F) achiral
1,1'-bisphosphanoferrocene ligands. Known symmetrically substituted dppf
analogs (B): R = Me,17 Et,34 iPr,31, 45 Cy,19 tBu,32 o-tolyl,33, 46 o-MeO-C6H4,34 p-
MeO-C6H4,47 p-PhO-C6H4,46 p-CF3-C6H4,48 3,5-CF3-C6H3,33 2-furyl,33 5-Me-2-
furyl,37 o-iPr-C6H4,34 1-Nap,46 2-Nap,46 C6F5.34 Known 1,1'-unsymmetrically
‡
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substituted dppf analogs (C): R = Ph, R' = tBu;35, 36 R = Ph, R' = iPr;25 R = Ph, R' =
Cy;25 R = Ph, R'= p-MeO-C6H4;38 R = Ph, R'= 5-Me-2-furyl;37 R = Ph, R'= Cl;39 R =
Ph, R'= OPh;40 R = Ph, R'= OMen;39 R = Ph, R'= p-Me-Ph;38 R = p-Me-Ph, R'= p-
CF3-Ph.38
The synthesis of our mesityl-substituted bisphosphano ligand 1 was
carried out by two complementary pathways. The VfiierwstArtpicalethOwnlianye
DOI: 10.1039/D0DT00941E
involves PCl2-substituted ferrocene 2, which was synthesized by a
known method,56, 57 and subsequently reacted with four equivalents
of MesLi·LiBr·OEt2 (Scheme 3a). On the other hand, the second
pathway (Scheme 3b) uses tmeda-stabilized dilithioferrocene, which
was reacted with two equivalents of Mes2PX (X = Cl, Br). Although
both the pathways can produce 1 in an acceptable purity, the first
pathway (Scheme 3a) gives slightly higher yield than the second
(Scheme 3b).
Owing to the current interest in using CO2 as sustainable feedstock
in catalytic transformations, we set out to investigate the catalytic
formation of propiolic acid derivatives from CO2 and terminal
alkynes. The first report of such catalytic CO2-fixation reaction was
published by the Inoue group in 1994, where CuI was used as catalyst
(Scheme 1a).49 Although insertion of CO2 into alkynylcopper was
successful, high temperature and a large excess of base were needed
4MesLi LiBr
PCl2
1) 2 nBuLi, tmeda
OEt2
50
for the execution of this reaction.49, Recently, Rath et. al. has
a)
Fe
Fe
2) 2 ClP(NEt2)2
3) 4 HCl
reported the similar carboxylation reactions with Cu-complexes of
dtbpf, where ambient temperature have been used for high yielding
transformations (Scheme 1b).51 Considering the fact that copper is
an affordable late transition metal and potentially active for the
reaction of our interest,50, 52, 53 we first decided to synthesize the CuX
(X = Br, I, (MeCN)nBF4) complexes of our ligands. The structural
properties of these complexes and their catalytic behaviour have
further been studied in this report. Finally, to take an insight into the
energetic scenario of complexation and the related catalysis, we
have used density functional theory (DFT), which further helped us
to verify the experimentally obtained results.
PCl2
2
PMes2
PMes2
Fe
1
Li
Li
b)
c)
Fe
2/3 tmeda
PMes2
2 Mes2PX
(X = Cl, Br)
Br
PMes2
PPh2
1) nBuLi
1) nBuLi
Fe
Fe
Fe
2) Mes2PX
Br
2) Ph2PCl
Br
(X = Cl, Br)
CO2, 1atm
4
3
4 mol% CuI
2 equiv. R'Br
6 equiv. K2CO3
DMA, 100 oC, 4h
Scheme 3. Syntheses of mesityl-substituted bisphosphano ligands 1 and 3.
a)
R
R
COOR'
The unsymmetrically substituted bisphosphano ligand
3 was
1) CO2, 1atm
3 mol% dtbpf CuI
1.5 equiv. Cs2CO3
2) HCl
synthesized by following a simple and modular approach (Scheme
3c). At first, compound 4 was synthesized by selective monolithiation
of 1,1'-dibromoferrocene,58 and subsequent in situ reaction with
Mes2PX. When compound 4 was further monolithiated and in situ
reacted with Ph2PCl, compound 3 was obtained in an overall yield of
33%, starting from 1,1’-dibromoferrocene.
R
R
COOH
b)
DMF, rt, 24h
Scheme 1. Cu-catalyzed carboxylation of terminal alkynes.50
Result and Discussion
PR2
P[Se]R2
P[Se]R'2
4 eq. Sered
Fe
Fe
Syntheses and Complexation
PR'2
5
6
, R = R' = Mes
, R = Mes, R' = Ph
A
few 1,1'-substituted ferrocenyl compounds, with two
1
3
, R = R' = Mes
, R = Mes, R' = Ph
dimesitylphosphanyl groups were previously synthesized by reacting
modified dilithoferrocene with Mes2PCl as reagents (G, H, I, Scheme
Scheme 4. Syntheses of diselenide derivatives of 5 and 6.
55
2).54,
However, their properties as bidentate ligands in metal
complexation and homogenous catalysis have not been explored in
detail, except for a few instances of silver-mediated nucleophilic
fluorination.55
In order to explore the donating abilities of our ligands, the
selenophosphorane derivatives of 1 and 3 were synthesized by
1
adapting a reported procedure (Scheme 4), and their JP-Se values
were compared with selenides of other phosphane ligands.59, 60 Since
compounds 5 and 6 are not soluble in common NMR solvents like
CDCl3 and C6D6, our comparison became restricted to data available
for toluene solutions. To this end we recorded 31P and 77Se NMR
spectra of Ph3P[Se] and dppf[Se]2 in toluene as benchmark for this
comparison as well, since the underlying phosphanes Ph3P and dppf
are extremely popular and useful ligand in many synthetic
PMes2
PMes2
PMes2
1) 2 nBuLi, tmeda
2) 2 Mes2PCl
Ac2O
a)
Fe
Fe
Fe
-AcNMe2
-AcOH
PMes2
NMe2
NMe2
Me
Me
G
H
tBu
tBu
tBu
16, 61-77
1
applications.15,
The JP-Se for compound 5 (723 Hz) is
PMes2
PMes2
1) 2 nBuLi, tmeda
2) 2 Mes2PCl
1) 2 MeLi
2) FeCl2
b)
2
Fe
Fe
significantly lower than the corresponding values for Ph3P[Se] (732
Hz in CDCl3;78 758 Hz in toluene-d8, see Figure S61 in SI file), and
dppf[Se]2 (737 Hz in CDCl3;59, 79 761 Hz in toluene-d8, see Figure S59
in SI file), which indicates that the lone pairs of phosphorus centres
in 1 have a lower s character, and therefore, higher donating ability
than Ph3P and dppf. A similar trend could also be noticed for the 77Se
NMR chemical shifts, where the resonance of compound 5 at -82
tBu
I
Scheme 2. Syntheses of substituted 1,1′-bis(dimesitylphosphano)-
ferrocenes.54, 55
2 | J. Name., 2012, 00, 1-3
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ppm is deshielded by ca. δ 200 ppm and 220 ppm, compared to 6 (321.8(3)°), while the PSePh2 unit shows only 315.2(2)°. Consistent
View Article Online
Ph3P[Se] and dppf[Se]2, respectively (see Figures S21, S62 and S60 in with these findings the P-Se bond lengths are slightly longer in the
DOI: 10.1039/D0DT00941E
SI file), which is in fact closer to values observed for the selenides of sterically more demanding PSeMes2 units (5: 2.1216(6) Å, 6:
push pull substituted phosphane.60
2.1246(14) Å) than in the PSePh2 unit (6: 2.0971(13) Å). These
structural features indicate more pronounced dative P-Se
a
In line with the lower symmetry in compound 6, two different values
interaction for the PPh2 than for the PMes2 unit in agreement with
the NMR data outlined above, where the sterically less hindered
1
for JP-Se have been observed: 723 Hz for Mes2P[Se] and 763 Hz for
1
Ph2P[Se], which are coherent with the corresponding values of 5 and
dppf[Se]2, respectively. The 77Se NMR spectra of compound 6 shows
a set of two doublets, for the Se atoms at the two different
phosphorus centres at -78 ppm (PSeMes2) and -299 ppm (PSePh2),
which are consistent with the values observed for 5 and dppf[Se]2
(see Figures S21, S25 and S60 in SI file). It should be noted that
phosphane unit entails larger JP-Se coupling values and stronger
shielding of the 77Se resonance in the corresponding
selenophosphorane. The solid-state structures of 4 and 6 have been
included in the SI file (Figures S65 and S66).
1
although the JP-Se values for dtbpf[Se]2,80 dippf[Se]2 (dippf = 1,1'-
bis(di-iso-propylphosphano)ferrocene),81 dchpf[Se]2 (dchpf = 1,1'-
bis(dicyclohexylphosphano)ferrocene),82 dchpdppf[Se]2 [dchpdppf =
1-(dicyclohexylphosphano)-1′-(diphenylphosphano)ferrocene],25
dippdppf[Se]2 [dippdppf = 1-(diisopropylphosphano)-1′-(diphenyl-
phosphano)ferrocene],25 dppdtbpf[Se]2 [dppdtbpf = 1-(diphenyl-
phosphano)-1′-(di-tert-butylphosphano)ferrocene]25 are reported in
the literature, they were measured in CDCl3 and therefore, could not
be considered for this comparison.
Se1
P1
Fe1
C5
C6
C1
C3
P1
C2
C23
Se1
C21
C18
C15
C20
C19
C15
C14
C16
C19
C16
C18
C22
C17
C13
C11
C12
C17
C5
C3
C4
P1 C1
C2
Fig 3. Ortep plots of the molecular structures of 5 in the solid state with
ellipsoids drawn at the 50% probability level. Labels for some selected C
atoms, solvent molecules and H atoms are omitted for clarity. Selected bond
lengths [Å] and angles [°]: P(1)-C(1) 1.798(2), P(1)-Se(1) 2.1216(6), P(1)-C(6)
1.847(2), C(15)-C(20) 1.411(3), C(20)-C(23) 1.507(3), C(1)-C(5) 1.440(3), C(1)-
Fe(1) 2.051(2), C(1)-P(1)-Se(1) 109.11(7), C(1)-P(1)-C(6) 102.94(10), C(1)-P(1)-
C(15) 112.25(10), C(1)-P(1)-C(15) 112.25(10), C(6)-P(1)-Se(1) 122.09(7), C(15)-
P(1)-Se(1) 106.20(7).
Fe1
P2
C6
C34
C29
C33
C30
To explore the overall electronic effect of replacing phenyl with
mesityl units in this molecular scaffold, the redox properties of the
metallocene unit have been investigated using cyclic voltammetry
(CV). The results, obtained by CV investigation, were further clarified
by DFT calculations using ω-B97XD/6-311+G** level of theory (more
details in SI file) as the oxidation of P(III) substituted ferrocenes may
involve iron or phosphorus centred redox events.83-89 Oxidation of
compounds 1 and 3 occur at 0.13 V and 0.16 V (see Figures S69 and
S70 in SI file), respectively, which are slightly shifted to lower
potential in comparison to that of dppf (E° = 0.18 V). Investigating the
Kohn-Sham molecular orbitals of 1, 3 and the parent dppf, it could be
established that the lone pairs of the phosphorus atoms have
significant contribution to the HOMO (Figure 4; Figures S71 and S72
in SI file). In agreement with the increased bond angles around the
phosphorus in case of PMes2 units, the energy of this lone pair
increases, thus it has more contribution to the HOMOs as well. It was
in full agreement with the slightly shifted oxidation potential of 1 and
3. The calculated spin density distribution of the corresponding
cations of 1 and 3 are extensively localised at the iron center (Figure
S73 in SI), thus the iron centred redox process is reversible for
compound 3 (Figure S70 in SI file) and quasi-reversible for compound
1 (Figure S69 in SI file). Moreover, for both complexes, several follow
up oxidation processes can be found at higher anodic potentials,
which are likely to involve PR2 moieties, in agreement with the
significant contribution of the phosphorus lone pairs to the HOMO of
C31
C32
Fig 2. Ortep plots of the molecular structures of 3 in the solid state with
ellipsoids drawn at the 50% probability level. Labels for some selected C
atoms, solvent molecules and H atoms are omitted for clarity. Selected bond
lengths [Å] and angles [°]: C(1)-C(2) 1.428(5), C(1)-P(1) 1.816(3), C(11)-P(1)
1.850(3), C(11)-C(16) 1.418(5), C(15)-C(16) 1.391(5), C(14)-C(15) 1.382(5),
C(16)-C(19) 1.504(5), C(6)-P(2) 1.823(3), C(29)-P(2) 1.835(4), C(29)-C(34)
1.394(5), C(33)-C(34) 1.384(5), C(32)-C(33) 1.372(6), C(5)-C(1)-P(1) 122.7(3),
C(1)-P(1)-C(11) 108.70(15), P(1)-C(11)-C(16) 127.6(2), C(6)-P(2)-C(29)
101.70(15).
Suitable single crystals for X-ray analyses were obtained for
compounds 3-6. While Figure 2 and 3 show the molecular structures
of 3 and 5 respectively, their refinement data have been listed in
Table S1 (SI file). The molecular structure of 3 in the solid state shows
a sum of angles of 311.98(15)° at the phosphorus atom of the PMes2
unit which is larger than the respective value for the PPh2 unit in the
same molecule (303.37(16)°), indicating increased steric interaction
in the former.
Similar trends are found for
5 and 6 which are the
selenophosphorane derivates of 1 and 3. The sum of the C-P-C angles
in 5 carrying two PSeMes2 units is 319.5(1)° which is almost identical
to the corresponding value of the PSeMes2 unit in mixed substituted
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J. Name., 2013, 00, 1-3 | 3
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the corresponding dicationic species. These follow up oxidations are The previous findings classify 1 and 3 as electron rich lVigieawnAdrtiscylesOtenmlines
non-reversible and show small anodic shifts during reduction. To with increased steric congestion along with iDnOcrI:e1a0s.e10d3p9-/cDh0aDrTa0c0te9r41oEf
further characterize our ligands NBO calculations were performed, the phosphorus lone pair for the PMes2 unit. To explore their ligand
which reveal that changing the two phenyls to two mesityl groups, properties towards d-block metals and possible effects on catalytic
the p-character of the phosphorus lone pairs increased from 53% for systems Cu(I) complexes have been chosen, owing to their proclivity
dppf to 55-56% for 1 and 3 (Table S4 in SI file). Recently it was shown to adopt small coordination numbers for which steric effects should
that the electronic effects of phosphorus containing bidentate be less decisive. Using a common synthetic methodology CuX-
ligands can be described by calculating the CO-stretching frequencies complexes 7-12 (X = Br, I, (MeCN)nBF4, Chart 1) were synthesized
of corresponding L2PdCO complexes (analogously to the from ligands 1 and 3. Among them, the solid state structures could
experimental Tolman parameter).43 This method (more details in SI only be obtained for complex 10 and 12, which are depicted in
file) has further been used to show that the electron donating ability Figures 5 and 6, respectively. Although no suitable single crystals for
increases from dppf to 1 and 3 in an order of dppf < 3 < 1 (Table S4 X-ray analysis could be isolated for complexes 7-9, their formation
in SI file).
was indicated by the upfield shifts of 31P signals (from δ -33.5 for 1 to
δ -26.8 for 7, δ -25.0 for 8 and δ -27.8 for 9; see Figures S8, S28, S31
and S34 in SI file). Moreover, the broad lines in their 1H and 31P NMRs
(see Figures S26-S34 in SI file) are suggesting a fast exchange of Cu+
ions in the solution. On the other hand, the formation of complex 11
could be confirmed by the shifts and multiplicities of its 31P signals
[from δ -35.1 (s), -17.2 (s) for 3 to δ -30.1 (brm), -20.2 (d) for 11, see
Figures S17 and S45 in SI file], which suggest a coupling between two
non-equivalent phosphorus atoms. It is needless to say that the
evidence of similar P-P coupling could also be noticed for complexes
10 and 12 (see Figures S42 and S48 in SI file).
PMes2
CuX
PMes2
PR2
CuX
a)
Fe
Fe
toluene : thf :
MeCN = 5 : 5 : 1
reflux
PR2
dppf
ε = -7.90 eV
7
8
9
, R = Mes, X = Br
, R = Mes, X = I
, R = Mes, X = BF4
1
3
, R = Mes
, R = Ph
10
11
12
, R = Ph, X = Br
, R = Ph, X = I
, R = Ph, X = (MeCN)2BF4
Br
Fe
PMes2
Mes2
P
Cu
Br
Br
14
CuBr
b)
P
Cu
Mes2
Fe
toluene : thf :
MeCN = 5 : 5 : 1
reflux
Br
Fe
4
Br
Br
Br
Mes2
Mes2
P
Cu
P
Cu
1
Fe
Fe
ε = -7.37 eV
Br
P
Cu
P
Cu
Mes2
Mes2
Br
13
Scheme 5. CuX-complexes (X = Br, I, (MeCN)nBF4) of 1, 3 and 4.
The X-ray crystal structure of 10 and 12 revealed that the copper
atoms are bonded to two phosphorus units with bite angles
116.53(6)° and 114.65(3)°, respectively (see Figures 5 and 6). As the
mesityl group is bulkier than phenyl, the Cu-P bond in P(Mes)2 side
[2.2651(15) Å for 10 and 2.3302(8) Å for 12] is slightly longer (1 pm
for 10 and 9 pm for 12) than the similar bond in PPh2 side [2.2540(15)
Å for 10 and 2.2437(8) Å for 12], which introduces lower symmetry
in complexes 10-12 for what a certain hemilability may be
anticipated. To the best of our knowledge, there are only two
complexes reported in the literature in which the ligands show a
larger bite angle than 10 and both of them are based on dtbpf.20, 51,
3
ε = -7.43 eV
Fig. 4. The Kohn-Sham HOMOs of dppf, 1 and 3 (Structures were optimized at
ω-B97XD/6-311+G** level of theory). Hydrogen atoms are omitted for clarity.
90
For comparison, a few related complexes, ordered by increasing
4 | J. Name., 2012, 00, 1-3
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91.98(12), P(1)-Cu(1)-N(1) 115.34(8), P(1)-Cu(1)-N(2) 118.70(9), F(1)-B(1)-F(2)
bite angles (in parentheses) are listed in the following: [Cu2(μ-
View Article Online
91
SCN)2(κ2-P,P-dppf)2]
(112.13(4)°),20,
[Cu2(μ2-SCN)2(κ2-P,P-
108.9(3), F(1)-B(1)-F(4) 112.5(4), F(2)-B(1)-F(3) 110.3(4).
DOI: 10.1039/D0DT00941E
dppdtbpf)2] (112.82(3)°),90 [Cu2(μ-CN)2(κ2-P,P-dppf)2] (115.85(3)°),92
[Cu(κ2-P,P-dppdtbpf)(CH3CN)2]PF6 (116.36(8)°),90 [Cu2(µ-NO3-O)2(κ2-
P,P-dppf)2] (117.8(1)°),93 [CuI(dtbpf)] (120.070(19))°.51
Upon recrystallization of complex 7, crystals of complex 13 formed
(see Scheme 5), along with micro-crystalline and powdery by-
products. The X-ray crystal-structure of complex 13 shows a
combination of ‘double-bridge’ and ‘quasi-closed bridge’ modes of
coordination,15 where two molecules of ligand 1 are connected via
two diamond shaped (Cu2Br2) units (Figure 7). In order to avoid the
formation of complex 13, several steps have been taken, such as,
changing the condition of crystallization and reaction of 1 with sub-
stoichiometric amounts of CuBr (1: CuBr = 1: 0.8, 1: 0.7 and 1: 0.5).
However, all these experiments resulted in complex 13 as the only
crystalline product and 13 can be prepared in straightforward
manner using the proper stoichiometry of metal to ligand.
C39
C36
C35
C40
C34
C37
C32
C10
C9
C33
C6
C7
C8
C23
P2
C38
Fe1
Cu1
C1
Br1
P1
C17
C11
Br2
C12
C16
C13
C14
P1
Cu2
P2
Cu1
Br1
C15
C6
Fig 5. Ortep plots of the molecular structures of 10 in the solid state with
ellipsoids drawn at the 50% probability level. Labels for some selected C
atoms, solvent molecules and H atoms are omitted for clarity. The refinement
data for this structure can be found in table S2 (SI file). Selected bond lengths
[Å] and angles [°]: C(1)-P(1) 1.816(5), C(11)-P(1) 1.827(5), Cu(1)-P(1)
2.2540(15), Cu(1)-Br(1) 2.3428(9), Cu(1)-P(2) 2.2651(15), C(23)-P(2) 1.843(5),
C(6)-P(2) 1.820(6), C(6)-P(2)-C(23) 103.7(2), C(23)-P(2)-C(32) 104.0(2), C(23)-
P(2)-Cu(1) 120.25(17), C(32)-P(2)-Cu(1) 112.91(17), C(6)-P(2)-Cu(1)
104.52(17), C(6)-P(2)-C(32) 111.0(2), C(1)-P(1)-Cu(1) 115.88(17), C(1)-P(1)-
C(11) 103.4(2), C(1)-P(1)-C(17) 102.4(2), C(11)-P(1)-Cu(1) 116.86(17), C(11)-
P(1)-C(17) 102.4(2), P(1)-Cu(1)-Br(1) 113.81(5), P(2)-Cu(1)-Br(1) 128.24(5),
P(1)-Cu(1)-P(2) 116.53(6).
Fe1
Fe1
C1
Br1
Cu1
Cu2
P2
C11
P1
C20
Br2
C19
C18
C6
C20
C11
Br2
P2
Br1
P1
C1
Fe1
C17
P1
C31
Fe1
C27
C24
C21
C28
C22
C30
Br1
Br2
C26
C25
Cu1
C1
C6
F2
N1
C41
C42
C23
P2
N2
F1
C32
B1
C29
F4
F3
Fig 7. Ortep plot of the molecular structure of 13 in the solid state with
ellipsoids drawn at the 50% probability level. Labels for some selected C
atoms, solvent molecules and H atoms are omitted for clarity. When the
figure at the top is showing the [Cu2Br2] bridges, the figure at the bottom is
showing the side view of the molecule. The plane of symmetry, passing
through the four Br atoms, made this molecule achiral. The refinement data
for this structure can be found in table S2, SI file. Selected bond lengths [Å]
and angles [°]: C(1)-P(1) 1.804(6), C(11)-P(1) 1.831(6), Cu(1)-P(1) 2.2095(16),
Cu(2)-P(2) 2.2059(15), Cu(1)-Br(1) 2.3949(10), Cu(1)-Cu(2) 2.9295(11), C(1)-
P(1)-C(11) 102.7(3), C(1)-P(1)-C(20) 110.4(3), C(1)-P(1)-Cu(1) 110.21(19),
Cu(1)-P(1)-C(11) 121.37(19), Cu(1)-P(1)-C(20) 103.6(2), C(20)-P(1)-C(11)
108.5(3), P(1)-Cu(1)-Br(1) 131.98(5), P(1)-Cu(1)-Br(2) 124.84(5), Br(1)-Cu(1)-
Br(2) 102.34(4), Cu(1)-Br(1)-Cu(2) 74.46(3), Cu(2)-Cu(1)-Br(1) 53.57(3).
Fig 6. Ortep plots of the molecular structures of 12 in the solid state with
ellipsoids drawn at the 50% probability level. When 50% split layer of
acetonitrile has been shown, labels for some selected C atoms, other solvent
molecules and H atoms are omitted for clarity. The refinement data for this
structure can be found in table S2 (SI file). Selected bond lengths [Å] and
angles [°]: C(1)-P(1) 1.803(3), C(11)-P(1) 1.829(3), Cu(1)-P(1) 2.2437(8), Cu(1)-
P(2) 2.3302(8), C(6)-P(2) 1.818(3), C(23)-P(2) 1.853(3), Cu(1)-N(1) 2.018(3),
C(6)-P(2)-Cu(1) 103.33(10), C(6)-P(2)-C(23) 103.77(13), C(32)-P(2)-C(23)
104.36(13), C(6)-P(2)-C(32) 112.34(13), C(32)-P(2)-Cu(1) 103.22(9), C(1)-P(1)-
Cu(1) 113.69(10), C(1)-P(1)-C(11) 102.41(13), C(1)-P(1)-C(17) 103.13(14),
C(17)-P(1)-Cu(1) 117.22(10), P(1)-Cu(1)-P(2) 114.65(3), N(1)-Cu(1)-N(2)
This journal is © The Royal Society of Chemistry 20xx
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The complexation via the formation of Cu2X2 (X = Cl, Br, I) bridges is catalytic reaction was further carried out with dppf·Cu(MeCN)2BF4
View Article Online
92-96
common for dppf,51,
and some sterically encumbered dppf (Entry 10, Table 1) as a catalyst, where 33% yiDeOldI:h1a0v.1e0b39e/eDn0oDbTt0a0in94e1dE,
However, apart from this rare bonding motif, the which was slightly higher than free Cu(MeCN)4BF4, but significantly
97-99
analogs.90,
classical chelating coordination mode of single metal centre is also lower than 9 and 12 (Entries 6 and 9, Table 1). For the sake of
90, 100
known for them.25,
For the [Mes2P]-substituted ferrocene completeness, it should be mentioned that CuCl and its respective
ligands, the formation of Cu2X2 bridges seems to be favoured as non- complexes were not included into this comparison as they showed
chelating ligand 4 similarly results in this motif to complex 14, which much lower catalytic conversion (ca. 5-10%) at otherwise identical
was synthesized by reacting 4 with one equivalent of CuBr. X-ray conditions with no significant difference between complexes and
crystallographic analysis revealed that this complex shows a similar free salt.
bonding motif as 13, where two molecules of 4 are bridged by one
planar Cu2Br2 unit (Figure 8). The distances between the Cu atoms in
the Cu2Br2 moieties of complex 13 and 14 are ca. 2.93 and 3.07 Å,
respectively. These values are significantly lower, compared to the
Table 1. Survey of catalytic activity in the formation of phenylpropiolic acid
from phenylacetylene using 3 mol% of the respective catalysts (cf. table S3
further details and variations).
similar Cu-Cu distances of other halogen-bridged complexes,
Entry
Catalyst
Product
yield
58
reported in the literature.92, 94-96
1
2
CuI
CuBr
41
3
Cu(MeCN)4(BF4)
29
4
7
62
Br2
5
8
69
C29
Cu2
6
9
59
7
10
88
P2
C48
Cu1
C20
P1
C1
8
9
11
12
86
76
Br3
10
dppf·Cu(MeCN)2(BF4)
33
C6
Br1
Fig 8. Ortep plot of the molecular structure of 14 in the solid state with
ellipsoids drawn at the 50% probability level. Labels for some selected C
atoms, solvent molecules and H atoms are omitted for clarity. While the
refinement data for this structure is listed in Table S2 (SI file) the side view of
this molecule is shown in Figure S67 (SI file). The refinement data for this
structure can be found in table S2, SI file. Selected bond lengths [Å] and angles
[°]: C(1)-P(1) 1.815(6), C(20)-P(1) 1.842(6), Cu(1)-P(1) 2.2044(15), Cu(1)-Br(2)
2.4592(9), Br(1)-C(6) 1.886(6), C(1)-P(1)-Cu(1) 111.33(18), C(1)-P(1)-C(20)
102.1(3), C(1)-P(1)-Cu(1) 111.33(18), Cu(1)-P(1)-C(20) 121.7(2), P(1)-Cu(1)-
Br(2) 130.81(5), P(1)-Cu(1)-Br(3) 127.82(5), Cu(1)-Br(2)-Cu(2) 78.64(3).
Catalysis
Complexes 7-12 were then used to explore their catalytic activity in
the CO2-fixation of terminal alkynes as outlined in the introduction.
In this investigation, the carboxylation of phenylacetylene was
selected as a model reaction to study the influence of various ligands
on catalysis compared with CuI, CuBr and Cu(MeCN)4BF4.
Fig 9. Catalytic efficiency for the carboxylation reaction from Ph-C≡CH to Ph-
C≡C-COOH. The blue, orange and grey bars show the yields resulting from free
copper salts, corresponding Cu(I) complexes with ligand 1 and 3, respectively.
As the yields listed here are the averages of two consecutive catalytic
reactions, error bars of 5% are shown for all yields.
As shown in Figure 9, complexes 7-12 exhibited higher catalytic
activity compared to the free copper salts. The maximum increase of
such catalytic activity can be seen for the Cu(MeCN)nBF4 analogs,
where the yield increased from 29% for Cu(MeCN)4BF4, to 59% and
76% for complexes 9 and 12 respectively (Entries 3, 6, and 9, Table 1;
Figure 9). However, the catalytic advantage of such complexes over
the simple Cu halide decreases as the size of the halide increases
[CuBr salts: 41% for CuBr, to 62% for 7, and 88% for 10 (Entries 2, 4
and 7, Table 1; Figure 9); CuI salts: 58% for CuI to 69% for 8 and 86%
for 11 (Entries 1, 5 and 8, Table 1; Figure 9)]. In order to draw a fair
comparison between dppf and our ligands (i.e. 1 and 3), similar
In general, the catalytic activity of complexes of phosphane ligands is
raised by increasing the steric bulk of the substituents on
51
phosphorus.21, An opposite trend is being noticed in our case,
where complexes 10-12 produce higher yields than 7-9 (Table S3, SI
file) which may be attributed to the complexation mode observed for
ferrocene based ligands where all phosphorus donor sites are mesityl
substituted. Complexes 13 and 14 are the only examples for these
ligands where structural information is available and show this
feature consistently. Since the conversion of 7 to 13 involves the
transfer of CuBr units, it can be speculated that in complexes 7-9 the
metal is more loosely bound, due to the high steric bulk of ligand 1.
6 | J. Name., 2012, 00, 1-3
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The lower complex stability of Cu(I) with 1 (in comparison to 3) was Br).105 It should be noted that all the chemical manipulations,
View Article Online
involving Mes2PX as a reagent, require caDreOfuI:l10c.a10lc3u9l/aDti0oDnTs00o9f4i1tEs
formula weights. This is because, the H NMR spectra of Mes2PX,
further corroborated by the 7+310+1 ligand-exchange reaction,
which is slightly exothermic (-4.4 kcal/mol at the ω-B97X-D/6-
311+G**//ω-B97X-D/6-31G* level of theory, Figure S74 in SI file). To
test this hypothesis experimentally, the organic washings of the
catalytic reactions were collected, dried under high vacuum, and
analyzed by 31P NMR, which revealed that complexes 7-9 dissociate
to give free ligand 1 during catalysis (Figures S55 and S56 in SI file),
whereas for complexes 10-12 the Cu-P bonds remain intact (Figures
S57 and S58 in SI file). It should be highlighted that we have further
investigated computationally the CO2 insertion step in the catalytic
system, which is usually the rate limiting step.101, 102 The calculated
reaction barriers are somewhat lower (by 1.2 kcal/mol at the ω-
B97X-D/6-311+G**//ω-B97X-D/6-31G* level of theory) in case of the
complexes with 3 in comparison to those of 1, which can be also an
explanation for the lower activity of its complexes (see Table S5 in
the SI file).
1
obtained from different preparation attempts, have shown different
proportional ratios of Mes2PCl and Mes2PBr (e.g. 48:52 and 53:47).
Due to minor side reactions, such as, unwanted dilithiation and
subsequent in situ hydrolysis, compounds 3 and 4 contain an
impurity, where only dimesitylphosphano group is present on
ferrocene. We could not remove this compound from the targeted
species and, therefore, used species 3 and 4, contaminated with ca.
1-4% of dimesitylphosphanoferrocene for the next chemical
transformations (see Figure S9, S12 and S13 in SI file).
NMR spectra were measured with Varian 500VNMRS and Varian MR-
400 spectrometers at 22 °C. Chemical shifts (δ in ppm) were
expressed with respect to the following standards, set as 0 ppm:
SiMe4 (for 1H and 13C), aqueous H3PO4 (for 31P), BF3·OEt2 (in CDCl3 for
11B) and CFCl3 (for 19F). The peaks, resulting from the residual non-
deuterated NMR solvents, were locked as indicated in the
literature.106 In addition to the standard notation of the signal
multiplicity (s = singlet, d = doublet, m = multiplet, dd = doublet of
doublet etc.), pst, brs, brd and brm were used to abbreviate pseudo-
triplet, broad singlet, broad doublet and broad multiplet,
respectively in order. The amount of residual solvents (if present)
was verified by NMR analysis and the expected values for elemental
analyses were calculated accordingly. When the NMRs of
compounds 1 and 3-6 were measured in toluene-d8 and thf-d8,
those for the corresponding complexes (7-12, 14) were only
measured either in thf-d8 or CD3CN. This is because, the complexes
could not be dissolved in toluene-d8 by any means. Due to the reason
of lower solubility even in the donating solvents (like thf-d8 or
CD3CN), the 13C NMRs of some complexes are relatively poor and as
a result, signals for the ipso-carbons could not be seen after
substantially high number of scans. On the other hand, the
diphosphano ferrocene ligands were insoluble in CD3CN and
therefore, the NMRs in the corresponding solvent could not be
measured.
Conclusion
In summary, the tetra- and dimesityl analogs of dppf, 1 and 3, have
been synthesized and their ligand properties were explored. The
phosphorus lone pairs of tetramesityl substituted 1 show lower s
character, and therefore, higher donating ability than those in Ph3P
and dppf as indicated by spectroscopic, structural, electrochemical
and computational means. In line with these experimental findings
the lone pair at phosphorus makes a significant contribution to the
HOMO in 1 and 3, which explains the cathodic shift of the oxidation
potentials with increasing mesityl substitution. For a series of Cu(I)
complexes of these ligands a variety of structural motifs has been
found, ranging from the rare double bridging mode over dimeric
bridging to isolated Cu-centers. With unsymmetrical ligand 3 stable
complexes were formed with isolated Cu(I) centers, while the
sterically more challenged tetramesityl substituted 1 is prone to
dimeric bridging with increased separation of the phosphorus atoms
and its adjacent mesityl substituents. As a consequence of its
hemilabile nature, the Cu(I) complexes of 3 showed improved
catalytic activity in the addition of CO2 to terminal alkynes as
compared with the respective complexes of 1 which in turn
performed superior to the respective dppf complexes. The potential
of these ligands for complexation of other metals and the catalytic
activity of these complexes will be explored in the near future.
Infrared spectra measured from the neat substances of 9 and 12
were obtained by a Bruker Alpha Platinum ATR spectrometer, where
opus 6.5 (by Bruker Optics) was used for analysing the data. Strong,
medium strong and week peaks for these species have been denoted
as s, m and w, respectively. For the sake of comparison, Infrared
spectra of Cu(MeCN)4BF4 and dppf·Cu(MeCN)2BF4 were also
measured under identical conditions for comparison and have been
depicted in SI file (Figure S75). When Electrospray ionisation (ESI) and
Atmospheric pressure chemical ionization (APCI) mass spectra were
measured with a Finnigan LCQ Deca (ThermoQuest, San Jose, USA)
instrument using samples dissolved in HPLC-quality thf, MALDI was
measured with an UltraFlex ToF / ToF (Bruker Daltonics, Bremen, D)
instrument, where an N2 laser with 337 nm wavelength and 3 ns
pulse duration was used. The matrix used for MALDI measurements
was DCTB (2-[(2E)-3-(4-tert-butylphenyl)-2-methylprop-2-enylidene]
malononitrile). Elemental analyses were performed without the
presence of any external oxidizer (like V2O5) in an EA 3000 Elemental
Analyzer (EuroVector). X-ray diffraction experiments were
performed using either a STOE IPDS II [using Mo-Kα source (λ =
0.71073 Å)] or a STOE StadiVari [using either Mo-GENIX source (λ =
0.71073 Å), or Cu-GENIX source (λ = 1.54186 Å)] diffractometer.
Structures were solved using dual space method (SHELXT) and were
refined with SHELXL-2018.107 All non-hydrogen atoms were refined
anisotropically, whereas hydrogen atoms were placed on adjacent
Experimental Section
All manipulations were performed under Argon atmosphere unless
mentioned otherwise. Prior to use, the glasswares were dried in
drying oven under 120 °C. Solvents were distilled over drying agents,
prescribed in CRC Handbook of chemistry and subsequently stored
under Argon atmosphere over 4 Å molecular sieves. Solvents for
column chromatography and aqueous workups were used from
bottle (analytical grade supplied by VWR and Alfa-Aesar) without
further purification. NMR solvents (purchased from Deutero) were
degassed via a few cycles of freeze, pump and thaw, and finally
stored over 3 Å molecular sieves under Argon atmosphere.
Reagents and chemicals were purchased from commercial suppliers
(Sigma-Aldrich, ABCR, Alfa-Aesar) and used as received. Fc'(PCl2)2,
MesLi·LiBr·OEt2 and dppf·Cu(MeCN)2BF4 were synthesized by
57, 103, 104
following the procedure, reported in the literature.56,
Mes2PX (X = Cl/Br, 48%/52%; Figures S1 and S2 in SI file) was
synthesized by following the procedure, reported for Xyl2PX (X = Cl,
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Journal Name
atoms using a riding model. Further programs used in the structure dibromoferrocene (0.687 g, 2.00 mmol). After the VgierwadArutiaclle Oconllioner
analyses were Mercury and Platon.108-110
change from pale yellow to bright orange, thDeOsoI:l1u0t.i1o0n39w/Das0DstTi0rr0e9d41aEt
-84 °C for another 30 mins. Another solution of Mes2PX (X = Cl/Br,
48%/52%, FW = 327.914 g/mol, 0.679 g, 2.07 mmol) in thf (20 mL)
was slowly added to the previous cold solution over 5 mins. After
warming up to the ambient temperature, the reaction mixture was
stirred for overnight. All the volatiles were removed under high
vacuum (10-3 mbar) and the product was extracted with hexanes (50
mL). The volume of the filtrate was reduced to ca. 10mL and the
almost pure compound was obtained as yellow crystals upon
refrigeration at -78 °C. This product had an impurity of
dimesitylphosphanoferrocene (ca. 5%) which could be reduced to ca.
2-3% upon further crystallization in hexanes at -10 °C and the final
product was obtained as bright orange crystals (53%). 1H NMR (C6D6):
δ 2.08 (s, 6H, p-CH3 of Mes), 2.37 (s, 12H, o-CH3 of Mes), 3.85 (pst,
2H, β-H of CpBr), 4.19 (pst, 2H, α-H of CpBr), 4.23 (pst, 2H, β-H of
CpPMes2), 4.32 (m, 2H, α-H of Cp PMes2), 6.71 (d, 4H, m-H of Mes, J = 3
Hz). 13C{1H} NMR (C6D6): δ 20.89 (s, p-CH3 of Mes), 23.51 (d, o-CH3 of
Mes, J = 15 Hz), 69.04 (s, β-C of CpBr), 71.59 (s, α-C of CpBr), 74.20 (d,
β-C of CpPMes2, J = 4 Hz), 77.23 (d, α-C of CpPMes2, J = 18 Hz), 78.09 (s,
ipso-C of CpBr), 81.55 (d, ipso-C of CpPMes2, J = 13 Hz), 130.57 (d, m-
Aryl C of Mes, J = 3 Hz), 132.47 (d, o-Aryl C of Mes, J = 21 Hz), 137.81(s,
p-Aryl C of Mes), 142.57 (d, ipso-Aryl C of Mes, J = 14 Hz). 31P{1H} NMR
(C6D6): δ -35.5. MS (APCI-DIP): m/z (%) 533 (100) [M]+. HRMS (APCI-
DIP; m/z): [M]+ calc for C28H30BrFeP, 533.06179; found 533.069069.
Anal. Calcd. for C28H30BrFeP: C, 63.07; H, 5.67. Found: C, 63.32; H,
5.75.
All cyclic voltammetry measurements were carried out in an MBraun
acrylic glovebox GB2202-C-VAC under Argon atmosphere. Samples
were measured as a solution (0.1 M) in dry and deoxygenated CH2Cl2,
where anhydrous [Bu4N][PF6] was used as conducting salt at a
concentration of 0.1 M. The three-electrode cell consisted of a
platinum working electrode, a silver counter electrode and a silver
pseudo reference electrode. The potential was driven on
a
WaveDriver 20 Bipotentiostat from Pine Research Instrument and
the electrochemical data was recorded via AfterMath (Ver. 1.5.9807,
Pine Instrument). All the redox processes were refenced using half
wave potentials of (C5Me5)2Fe as standard, which was added to the
analyzed solution. Its corresponding value was then subtracted from
the recorded potentials to convert them to the Fc/Fc+ scale following
established procedures,111 and finally evaluated with AfterMath and
Excel.
Fc'(PMes2)2 (1). A solution of Fc'(PCl2)2 (0.388 g, 1.00 mmol) in thf (10
mL) was added dropwise to a cold (-84 °C) and stirred suspension of
MesLi·LiBr·OEt2 (1.145 g, 3.99 mmol) in hexanes (100 mL). The
reaction mixture was slowly warmed to rt over 3-4 hrs and stirred for
18 hrs at rt. After all the volatiles were removed under vacuum (10-3
mbar), the resulting compound was extracted in toluene (60 mL) and
tested with 7Li NMR. A small peak at δ 7.33 ppm in 7Li NMR indicated
the presence of soluble LiCl in the crude, which was further
evacuated to dryness and extracted with toluene (30 mL). The
volume of thus obtained toluene solution was reduced to c.a. 5 mL
and finally precipitated on cold (-20 °C) and vigorously stirred mixture
of Et2O and pentane (40 mL, 1:1). The supernatant solution was
carefully decanted and the precipitate was dried under high vacuum
(10-3 mbar), resulting in compound 1 as a pale yellow amorphous
solid (70%). NOTE This compound have also been synthesized (with
a yield of 66%) by the reaction of FcLi2·(tmeda)2/3 (1 mmol) and
Mes2PX (X = Cl/Br, 48%/52%, FW = 327.914 g/mol, 0.669 g, 2.04
mmol) in thf at -84 °C, with a subsequent workup as mentioned
n
Fc'(PMes2)(PPh2) (3). BuLi (2.5 M in hexanes, 0.15 mL, 0.38 mmol)
was added dropwise to a cold (0 °C) thf (20 mL) solution of
Fc'(PMes2)Br (0.200 g, 0.38 mmol). After the gradual color change
from orange to bright red, the solution was stirred at 0 °C for 30 mins.
Another solution of Ph2PCl (72 μL, 0.086 g, 0.40 mmol) in hexanes (10
mL) was slowly added to the previous cold solution over 5 mins. After
warming up to the ambient temperature, the reaction mixture was
stirred overnight. All the volatiles were removed under high vacuum
(10-3 mbar) and the product was extracted with hexanes (20 mL). The
volume of the filtrate was reduced to ca. 5 mL and the almost pure
compound was obtained as yellow crystals (62%) upon refrigeration
1
above. H NMR (toluene-d8): δ 2.08 (s, 12H, p-CH3 of Mes), 2.31 (s,
24H, o-CH3 of Mes), 4.20 (m, 4H, β-H of Cp), 4.25 (m, 4H, α-H of Cp),
6.66 (brs, 8H, m-H of Mes). 1H NMR (thf-d8): δ 2.17 (s, 24H, o-CH3 of
Mes), 2.18 (s, 12H, p-CH3 of Mes), 4.19 (m, 4H, β-H of Cp), 4.22 (m,
4H, α-H of Cp), 6.74 (brs, 8H, m-H of Mes). 13C{1H} NMR (toluene-d8):
δ 21.28 (s, p-CH3 of Mes), 23.47 (d, o-CH3 of Mes, J = 15 Hz), 72.50 (d,
β-C of Cp, J = 4 Hz), 76.00 (d, α-C of Cp, J = 19 Hz), 80.14 (d, ipso-C of
Cp, J = 13 Hz), 127.34 (s, p-Aryl C of Mes), 130.48 (d, m-Aryl C of Mes,
J = 3 Hz), 132.65 (d, ipso-Aryl C of Mes, J = 21 Hz), 142.53 (d, o-Aryl C
of Mes, J = 15 Hz). 13C{1H} NMR (thf-d8): δ 20.72 (s, p-CH3 of Mes),
23.29 (d, o-CH3 of Mes, J = 15 Hz), 72.68 (d, β-C of Cp, J = 4 Hz), 76.24
(d, α-C of Cp, J = 18 Hz), 80.27 (d, ipso-C of Cp, J = 13 Hz), 130.52 (d,
p-Aryl C of Mes, J = 4 Hz), 132.82 (d, ipso-Aryl C of Mes, J = 20 Hz),
137.95 (s, m-Aryl C of Mes), 142.75 (d, o-Aryl C of Mes, J = 15 Hz).
31P{1H} NMR (toluene-d8): δ -35.1. 31P{1H} NMR (thf-d8): δ -33.5. MS
(APCI-DIP): m/z (%) 722 (100) [M]+. HRMS (APCI-DIP; m/z): [M]+ calc
for C46H52FeP2, 722.28937; found 722.28882. Anal. Calcd. for
C46H52FeP2: C, 76.45; H, 7.25. Found: C 75.23; H, 7.16. Probably due
to the presence of a little amount of LiCl, the CHN values for this
compound differ significantly than expected. As these values could
not be improved after several attempts, the purity of the species was
further clarified by mass spectrometry (see Figure S68 in SI file).
at
-78
°C.
This
product
had
an
impurity
of
dimesitylphosphanoferrocene (ca. 3-4%) which could not be reduced
upon further crystallization. H NMR (toluene-d8): δ 2.08 (s, 6H, p-
1
CH3 of Mes), 2.30 (s, 12H, o-CH3 of Mes), 4.04 (m, 2H, β-H of CpPPh2),
4.10 (pst, 2H, α-H of CpPPh2), 4.17 (m, 2H, β-H of CpMes), 4.21 (pst, 2H,
α-H of CpMes), 6.66 (brd, 4H, m-H of Mes, J = 3 Hz), 7.01-7.02 (m, 6H,
m and p-H of Ph), 7.38 (m, 4H, o-H of Ph). 1H NMR (thf-d8): δ 2.16 (s,
12H, o-CH3 of Mes), 2.19 (s, 6H, p-CH3 of Mes), 4.01 (m, 2H, β-H of
CpPPh2), 4.14 (m, 2H, α-H of CpPPh2), 4.18 (m, 2H, β-H of CpMes), 4.26
(pst, 2H, α-H of CpMes), 6.74 (brd, 4H, m-H of Mes, J = 3 Hz), 7.23-7.29
(m, 10H, o, m and p-H of Ph). 13C{1H} NMR (toluene-d8): δ 20.87 (s,
p-CH3 of Mes), 23.47 (d, o-CH3 of Mes, J = 15 Hz), 72.27 (d, β-C of
CpPPh2, J = 3 Hz), 72.80 (d, β-C of Cp PMes2, J = 4 Hz), 74.28 (d, α-C of
CpPPh2, J = 15 Hz), 75.86 (d, α-C of CpPMes2, J = 18 Hz), 77.34 (d, ipso-C
of CpPPh2, J = 10 Hz), 80.57 (d, ipso-C of CpPMes2, J = 13 Hz), 128.34 (d,
m-Aryl C of Ph, J = 7 Hz), 128.57 (s, p-Aryl C of Ph), 130.49 (d, m-Aryl
C of Mes, J = 3 Hz), 132.61 (d, o-Aryl C of Mes, J = 21 Hz), 133.92 (d,
o-Aryl C of Ph, J = 21 Hz), 140.05 (d, ipso-Aryl C of Ph, J = 15 Hz),
142.54 (d, ipso-Aryl C of Mes, J = 15 Hz). 13C{1H} NMR (thf-d8): δ 20.90
(s, p-CH3 of Mes), 23.48 (d, o-CH3 of Mes, J = 15 Hz), 72.68 (dd, β-C of
CpPPh2, J = 4, 1 Hz), 73.11 (d, β-C of Cp PMes2, J = 4 Hz), 74.63 (d, α-C of
CpPPh2, J = 15 Hz), 76.28 (d, α-C of CpPMes2, J = 18 Hz), 77.71 (d, ipso-C
of CpPPh2, J = 10 Hz), 80.81 (d, ipso-C of CpPMes2, J = 13 Hz), 128.78 (d,
Fc'(PMes2)Br (4). nBuLi (2.5 M in hexanes, 0.84 mL, 2.10 mmol) was
added dropwise to a cold (-84 °C) and stirred thf (20 mL) solution of
8 | J. Name., 2012, 00, 1-3
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m-Aryl C of Ph, J = 7 Hz), 129.09 (s, p-Aryl C of Ph), 130.70 (d, m-Aryl shown in the following: MS (ESI): m/z (%) 787 [M+1V]+ie.wHARrtMicleSO(nElSinIe;
C of Mes, J = 3 Hz), 132.95 (d, o-Aryl C of Mes, J = 21 Hz), 134.27 (d, m/z): [M]+ calc for C46H52CuFeP2, 785.21897;DfOouI:n1d0.1708359./2D108D4T20.0941E
o-Aryl C of Ph, J = 20 Hz), 138.11 (s, p-Aryl C of Mes), 140.43 (d, ipso-
Fc'(PMes2)2.CuBr (7). Yield: 63%. 1H NMR (thf-d8): δ 2.00-2.50 (brs,
36H, o- and p-CH3 of Mes), 4.24 (brs overlapped with another brs, 8H,
α- and β-H of Cp), 6.79 (brs, 8H, m-H of Mes). 13C{1H} NMR (thf-d8):
δ 20.88 (brs, p-CH3 of Mes), 73.12 (brs, α- and β-H of Cp), 78.46 (brs,
ipso-C of Cp), 126.01 (s, p-Aryl C of Mes), 128.88 (s, m-Aryl C of Mes),
129.64 (s, o-Aryl C of Mes), 131.52 (brs, ipso-Aryl C of Mes). 31P{1H}
NMR (thf-d8): δ -26.8. Anal. Calcd. for C46H52BrCuFeP2: C, 63.79; H,
Aryl C of Ph, J = 11 Hz), 142.91 (d, ipso-Aryl C of Mes, J = 15 Hz). 31P{1H}
NMR (toluene-d8): δ -34.8 (PMes2), -17.0 (PPh2). 31P{1H} NMR (thf-
d8): δ -35.1 (PMes2), -17.2 (PPh2). MS (APCI-DIP): m/z (%) 639 [M+1]+.
HRMS (APCI-DIP; m/z): [M+1]+ calc for C40H40FeP2, 639.19547; found
639.20281. Anal. Calcd. for C40H40FeP2: C, 75.24; H, 6.31. Found: C,
74.92; H, 6.45.
Diselenide derivatives of 1 and 3. A suspension of red Se (0.120 g, 6.05. Found: C, 63.72; H, 5.88.
1.52 mmol) and 1 (0.170 g, 0.24 mmol) or 3 (0.153 g, 0.24 mmol) in
1
Fc'(PMes2)2.CuI (8). Yield: 58%. H NMR (thf-d8): δ 2.00-2.50 (brs,
36H, o- and p-CH3 of Mes), 4.27 (brs overlapped with another brs, 8H,
α- and β-H of Cp), 6.83 (brs, 8H, m-H of Mes). 13C{1H} NMR (thf-d8):
δ 20.87 (brs, p-CH3 of Mes), 72.72 (brs, α- and β-H of Cp), 126.01 (s,
p-Aryl C of Mes), 128.88 (s, m-Aryl C of Mes), 129.64 (s, o-Aryl C of
Mes), 131.52 (brs, ipso-Aryl C of Mes). 31P{1H} NMR (thf-d8): δ -25.0.
Anal. Calcd. for C46H52CuFeIP2: C, 60.50; H, 5.74. Found: C, 60.72; H,
5.35.
thf (20 mL) was stirred for 1 hr at r.t. All the volatiles were removed
under high vacuum (10-3 mbar) and the product was extracted with
hot toluene. Analytically pure compound was crystallized from the
hot toluene solution by slow cooling up to ambient temperature.
NOTE If all the residual Se is not removed by single filtration attempt,
the procedure of filtration must be repeated for multiple times
before crystallization.
Fc'(PSeMes2)2 (5). Yield: 67%. 1H NMR (toluene-d8): δ 1.99 (s, 12H, p-
CH3 of Mes), 2.38 (brs, 24H, o-CH3 of Mes), 4.79 (m, 4H, Cp), 4.90 (brs,
4H, Cp), 6.52 (m, 8H, m-H of Mes). 13C{1H} NMR (toluene-d8): δ 24.43
(d, o-CH3 of Mes, J = 6 Hz), 75.72 (d, β-C of Cp, J = 9 Hz), 78.25 (brs,
α-C of Cp), 82.45 (d, ipso-C of Cp, J = 78 Hz), 125.63 (s, p-Aryl C of
Mes), 132.15 (d, o-Aryl C of Mes, J = 11 Hz), 139.72 (d, m-Aryl C of
Mes, J = 2 Hz), 140.49 (brm, ipso-Aryl C of Mes). 31P{1H} NMR
(toluene-d8): δ 14.7 (1JP,Se = 723 Hz). 77Se{1H} NMR (toluene-d8): δ -
82.6 (PSeMes2, 1JP,Se = 723 Hz). MS (MALDI): m/z (%) 880 (100) [M]+.
Anal. Calcd. for C46H52FeP2Se2: C, 62.74; H, 5.95. Found: C, 62.89; H,
5.90.
1
Fc'(PMes2)2.Cu(BF4) (9). Yield: 69%. H NMR (CD3CN): δ 2.00-2.50
(brs, 36H, o- and p-CH3 of Mes), 4.24 (brs, 4H, β-H of Cp), 4.45 (brs,
4H, α -H of Cp), 6.91 (brs, 8H, m-H of Mes). 13C{1H} NMR (CD3CN): δ
20.82 (s, p-CH3 of Mes), 24.98 (brs, o-CH3 of Mes), 73.47 (brs, α- and
β-H of Cp), 78.70 (t, ipso-H of Cp, J = 17 Hz), 126.21 (s, p-Aryl C of
Mes), 129.18 (s, m-Aryl C of Mes), 129.87 (s, o-Aryl C of Mes), 131.89
(brs, ipso-Aryl C of Mes). 31P{1H} NMR (CD3CN): δ -27.8. 11B{1H} NMR
(CD3CN): δ -1.2. 19F{1H} NMR (CD3CN): δ -151.9. IR (ATR) ν: 1024 (m),
1159 (m), 1444 (m), 1466 (m), 1602 (w), 2918 (w). Anal. Calcd. for
C46H52BCuF4FeP2: C, 63.28; H, 6.00. Found: C, 63.25; H, 6.01.
1
Copper complexes of 3. A suspension of 3 (0.128 g, 0.20 mmol), CuX
(0.2 mmol), toluene (10 mL), thf (10 mL) and CH3CN (2 mL) was
refluxed for 24 hrs. After removal of all insoluble materials by
filtration, the volume of the filtrate was reduced to ca. 15 mL and
analytically pure crystalline or semi-crystalline materials were
obtained by slow evaporation under inert atmosphere at ambient
temperature. For all the compounds, mentioned under this section,
the mass spectrometric measurements gave similar data, where
corresponding peak for Fc'(PMes2)(PPh2)Cu+ has arrived as molecular
ion peak. One example is shown in the following: MS (ESI): m/z (%)
701 [M]+. HRMS (ESI; m/z): [M]+ calc for C40H40CuFeP2, 701.12507;
found 701.12452.
Fc'(PSeMes2)(PSePh2) (6). Yield: 65%. H NMR (toluene-d8): δ 1.99
(s, 6H, p-CH3 of Mes), 2.35 (brs, 12H, o-CH3 of Mes), 4.42 (brs, 2H, β-
H of CpPPh2), 4.69 (brs, 2H, α-H of CpPPh2), 4.73 (brs, 2H, α-H of CpMes),
4.76 (brs, 2H, β-H of CpMes), 6.49 (brd, 4H, m-H of Mes, J = 4 Hz), 6.92-
6.94 (m, 6H, m and p-H of Ph), 7.70 (m, 4H, o-H of Ph). 13C{1H} NMR
(toluene-d8): δ 20.69 (d, p-CH3 of Mes, J = 2 Hz), 24.32 (d, o-CH3 of
Mes, J = 6 Hz), 74.94 (d, β-C of CpPPh2, J = 12 Hz), 75.38 (d, α-C of Cp
PPh2, J = 9 Hz), 75.99 (d, ipso-C of CpPPh2, J = 86 Hz), 76.12 (d, β-C of
CpPMes2, J = 10 Hz), 78.05 (brd, α-C of Cp PMes2, J = 13 Hz), 82.82 (d,
ipso-C of CpPMes2, J = 78 Hz), 128.27 (d, p-Aryl C of Ph, J = 3 Hz), 131.10
(d, m-Aryl C of Ph, J = 3 Hz), 132.08 (d, o-Aryl C of Ph, J = 11 Hz), 132.38
(d, o-Aryl C of Mes, J = 11 Hz), 134.34 (d, ipso-Aryl C of Ph, J = 78 Hz),
139.62 (d, m-Aryl C of Mes, J = 3 Hz), 140.39 (brd, ipso-Aryl C of Mes).
31P{1H} NMR (toluene-d8): δ 14.8 (PMes2, 1JP,Se = 723 Hz), 30.8 (PPh2,
1
Fc'(PMes2)(PPh2).CuBr (10). Yield: 71%. H NMR (thf-d8): δ 2.22 (s,
1JP,Se = 763 Hz). 77Se{1H} NMR (toluene-d8): δ -298.8 (PSePh2, 1JP,Se
=
6H, p-CH3 of Mes), 2.32 (s, 12H, o-CH3 of Mes), 4.14 (s, 2H, β-H of
CpPPh2), 4.27 (pst, 2H, β-H of CpPMes2), 4.42 (s, 4H, α-H of CpPPh2), 4.49
(brs, 4H, α-H of Cp PMes2), 6.82 (brm, 4H, m-H of Mes), 7.38 (m, 6H, m
and p-H of Ph), 7.92 (m, 4H, o-H of Ph). 13C{1H} NMR (thf-d8): δ 20.67
(s, p-CH3 of Mes), 30.46 (s, o-CH3 of Mes), 72.69 (s, β-C of CpPPh2,
PMes2), 74.48 (s, α-C of CpPPh2), 77.41 (s, α-C of CpPMes2), 129.12 (d, p-
Aryl C of Ph, J = 10 Hz), 130.67 (s, m-Aryl C of Ph), 131.63 (s, m-Aryl C
of Mes), 134.95 (d, p-Aryl C of Mes, J = 15 Hz), 139.66 (s, o-Aryl C of
Ph), 142.92 (s, o-Aryl C of Mes). 31P{1H} NMR (thf-d8): δ -31.5 (d,
PMes2, J = 135 Hz), -19.3 (d, PPh2, J = 135 Hz). Anal. Calcd. for
C40H40BrCuFeP2: C, 61.44; H, 5.16. Found: C, 61.04; H, 5.15.
763 Hz), -77.5 (PSeMes2, 1JP,Se = 723 Hz). MS (ESI): m/z (%) 797 (100)
[M+1]+. HRMS (ESI; m/z): [M+1]+ calc for C40H40FeP2Se2, 799.02851;
found 799.03579. Anal. Calcd. for C40H40FeP2Se2: C, 60.32; H, 5.06.
Found: C, 60.44; H, 5.17.
Copper complexes of 1. A suspension of 1 (0.144 g, 0.20 mmol), CuX
(0.20 mmol), toluene (10 mL), thf (10 mL) and CH3CN (2 mL) was
refluxed for 24 hrs. After removal of all insoluble materials by
filtration, the volume of the filtrate was reduced to ca. 15 mL and
analytically pure crystalline or semi-crystalline materials were
obtained by slow introduction of dry pentane while kept in a double
arm H-tube at ambient temperature. For all the compounds,
mentioned under this section, the mass spectrometric
measurements gave similar data, where corresponding peak for
Fc'(PMes2)2Cu+ has arrived as molecular ion peak. One example is
Fc'(PMes2)(PPh2).CuI (11). Yield: 74%. 1H NMR (thf-d8): δ 2.22 (s, 6H,
p-CH3 of Mes), 2.29 (s, 12H, o-CH3 of Mes), 4.12 (pst, 2H, β-H of
CpPPh2), 4.26 (pst, 2H, β-H of CpPMes2), 4.42 (s, 4H, α-H of CpPPh2), 4.52
(brs, 4H, α-H of Cp PMes2), 6.82 (d, 4H, m-H of Mes, J = 3 Hz), 7.39 (m,
6H, m and p-H of Ph), 7.92 (m, 4H, o-H of Ph). 13C{1H} NMR (thf-d8):
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J. Name., 2013, 00, 1-3 | 9
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δ 20.85 (s, p-CH3 of Mes), 24.75 (dd, o-CH3 of Mes, J = 9 and 1 Hz), (s, β-C of CpBr), 72.48 (s, α-C of CpBr), 76.10 (d, β-C of CpPMes2, J = 7
View Article Online
72.91 (m, β-C of CpPPh2, PMes2), 74.82 (d, α-C of CpPPh2, J = 10 Hz), 77.59 Hz), 77.96 (d, ipso-C of CpPMes2, J = 41 Hz), 78.41 (s, ipso-C of CpBr),
DOI: 10.1039/D0DT00941E
(m, α-C of CpPMes2), 129.28 (d, p-Aryl C of Ph, J = 10 Hz), 130.88 (m, 79.09 (brd, α-C of CpPMes2), 128.79 (d, ipso-Aryl C of Mes, J = 36 Hz),
m-Aryl C of Ph), 131.83 (d, m-Aryl C of Mes, J = 6 Hz), 135.20 (d, p- 131.74 (d, p-Aryl C of Mes, J = 7 Hz), 139.97 (s, m-Aryl C of Mes),
Aryl C of Mes, J = 15 Hz), 139.86 (s, o-Aryl C of Ph), 142.94 (d, o-Aryl 142.11 (d, o-Aryl C of Mes, J = 11 Hz). 31P{1H} NMR (thf-d8): δ -26.5.
C of Mes, J = 11 Hz). 31P{1H} NMR (thf-d8): δ -30.1 (brm, PMes2), - MS (MALDI and APCI): m/z (%) 532 (100) [M]+ for starting ligand
20.2 (d, PPh2, J = 98 Hz). Anal. Calcd. for C40H40CuFeIP2: C, 57.95; H, Fc'(PMes2)Br and no peak for its corresponding CuBr complex 14
4.86. Found: C, 57.66; H, 4.90.
could be found. Anal. Calcd. for C56H60Br4Cu2Fe2P2: C, 49.70; H, 4.47.
Found: C, 49.99; H, 4.43.
Fc'(PMes2)(PPh2).Cu(MeCN)2(BF4) (12). Yield: 77%. 1H NMR (thf-d8):
δ 2.08 (s, 6H, CH3 of MeCN) 2.23 (s, 6H, p-CH3 of Mes), 2.30 (s, 12H, Catalytic reaction. A mixture of Ph‒C≡C‒H (0.204 g, 0.22 mL, 2 mmol,
o-CH3 of Mes), 4.11 (m, 2H, β-H of CpPPh2), 4.32 (pst, 2H, β-H of 1 equiv.), respective catalyst (mole% with respect to Cu, mentioned
CpPMes2), 4.54 (pst, 4H, α-H of CpPPh2), 4.63 (pst, 4H, α-H of Cp PMes2), in Table S3, SI file), dry DMF (10 mL), and Cs2CO3 (0.978 g, 3 mmol,
6.90 (, 4H, m-H of Mes), 7.48 (m, 6H, m and p-H of Ph), 7.68 (m, 4H, 1.5 equiv.) was degassed by three consecutive cycles of freeze (at -
o-H of Ph). 13C{1H} NMR (thf-d8): δ 1.16 (s, CH3CN), 20.84 (s, p-CH3 of 98 °C, MeOH and liquid N2), pump and thaw. A balloon, filled with
Mes), 24.45 (dd, o-CH3 of Mes, J = 11 and 1 Hz), 73.27 (d, β-C of CpPPh2 dry CO2, was placed on it and the resulting reaction mixture was
, J = 5 Hz), 73.61 (d, β-C of CpPMes2 , J = 6 Hz), 74.62 (d, α-C of CpPPh2, J stirred for 36 h at rt, followed by quenching with water (20 mL). The
= 9 Hz), 75.25 (d, ipso-C of CpPPh2, J = 47 Hz), 77.71 (d, α-C of CpPMes2
,
organic layer then was separated by washing with DCM (3 × 20 mL)
J = 14 Hz), 78.94 (d, ipso-C of CpPMes2, J = 39 Hz), 119.76 (s, CH3CN), and the combined DCM phases were stored for further investigation.
126.06 (dd, ipso-C of Ph, J = 28 and 3 Hz), 130.08 (d, p-Aryl C of Ph, J The aqueous layer was acidified with conc. HCl (up to pH 1) and
= 10 Hz), 131.57 (d, m-Aryl C of Ph, J = 2 Hz), 132.02 (d, p-Aryl C of extracted with EtOAc (3 × 20 mL). The resulting EtOAc phases were
Mes, J = 7 Hz), 133.34 (d, ipso-C of Mes, J = 31 Hz), 134.70 (d, o-Aryl combined and the residual DMF was removed by washing with water
C of Ph, J = 16 Hz), 140.61 (d, m-Aryl C of Mes, J 2 = Hz), 142.94 (d, o- (2 × 30 mL) and brine (30 mL), followed by drying upon anhydrous
Aryl C of Mes, J = 11 Hz). 31P{1H} NMR (thf-d8): δ -33.5 (d, PMes2, J = Na2SO4. Volatiles were removed under rotatory evaporator and the
119 Hz), -11.8 (d, PPh2, J = 119 Hz). 11B{1H} NMR (thf-d8): δ -0.9. resulting colourless oil was subjected under controlled vacuum (5 ×
19F{1H} NMR (thf-d8): δ -153.2. IR (ATR) ν: 1025 (s), 1034 (s), 1053 (s), 10-2 mbar), until colourless crystals arrive (see Figure S54 in SI file).
1093 (m), 1436 (m), 1600 (w), 2228 (w), 2922 (w). Anal. Calcd. for The previously collected DCM phase was then washed with water (2
C44H46BCuF4FeN2P2: C, 60.67; H, 5.32; N, 3.22. Found: C, 60.45; H, × 30 mL) and brine (30 mL), dried under rotatory evaporator and
5.34; N, 2.96.
finally subjected under high vacuum (10-3 mbar) for overnight at 40
°C. Thus-obtained yellow solids were then characterized with 31P
NMR, which revealed them as the remnants of catalysts.
[Fc'(PMes2)2.(CuBr)2]2 (13). A suspension of 1 (0.144 g, 0.20 mmol),
CuBr (0.057 g, 0.40 mmol), toluene (10 mL), thf (15 mL) and CH3CN
(5 mL) was refluxed for 48 hrs. After removal of all insoluble materials
by filtration, the volume of the filtrate was reduced to ca. 20 mL and
crystalline substance along with semi-crystalline materials were
obtained by slow introduction of dry pentane while kept in a double
arm H-tube at ambient temperature. After several washing with a
mixture of dry toluene and pentane (1:1), followed by removal of all
volatiles under high vacuum (10-3 mbar) compound 13 was obtained
in a Yield of 56%. 1H NMR (CD3CN): δ 2.00-2.50 (brs overlapped with
another brs, 72H, o- and p-CH3 of Mes), 4.25 (brs, 8H, α-H of Cp), 4.60
(brs, 8H, β-H of Cp), 6.88 (brs, 16H, m-H of Mes). 31P{1H} NMR (thf-
d8): δ -26.9. 31P{1H} NMR (CD3CN): δ -27.5. MS (MALDI): m/z (%) 850
[M]+ for [Fc'(PMes2)2.Cu2]2+, 786 [M]+ for [Fc'(PMes2)2.Cu]+. Anal.
Calcd. for C46H52BrCuFeP2: C, 54.72; H, 5.19. Found: C, 54.59; H, 5.06.
Note: Compound 13 is highly insoluble in commonly available
organic solvents (including thf-d8 and CD3CN). After a prolonged
NMR experiment only 1H (with a low S/N ratio and unresolved broad
signals near to the baseline) and 31P{1H} NMR (with a satisfactory S/N
ratio) could be obtained, which revealed the absence of any starting
ligand (1) in the resulting mixture.
Acknowledgement
The authors would like to thank the funding programs LOEWE and
MASH for financial support. Zsolt Kelemen is grateful for the general
support of Hungarian Academy of Science under the Premium
Postdoctoral Research Program 2019.
Associated Content
The NMR spectra of all reported compounds, detail of the
computational studies and X-ray crystallography can be found in the
supporting information file, which is available free of charge on the
ACS Publication website.
The CCDC deposition with number 1980151-1980158 contain the
supplementary crystallographic data for compounds 3-6, 10, 12-14,
published in this paper, which can be obtained free of charge via
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre at 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
[Fc'(PMes2)Br.CuBr]2 (14). A suspension of 4 (0.107 g, 0.20 mmol),
CuBr (0.029 g, 0.20 mmol), toluene (10 mL), thf (10 mL) and CH3CN
(2 mL) was refluxed for 24 hrs. After removal of all insoluble materials
by filtration, the volume of the filtrate was reduced to ca. 15 mL and
analytically pure crystalline materials (72%) were obtained by slow
References
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D. E. Herbert, U. F. Mayer and I. Manners, Angew. Chem., Int. Ed.,
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evaporation under inert atmosphere. H NMR (thf-d8): δ 2.22 (brs,
2.
3.
V. Bellas and M. Rehahn, Angew. Chem., Int. Ed., 2007, 46, 5082.
A. Alkan, L. Thomi, T. Gleede and F. R. Wurm, Polym. Chem., 2015,
6, 3617.
12H, p-CH3 of Mes), 2.29 (brs, 12H, o-CH3 of Mes), 4.19 (pst, 2H, β-H
of CpPMes2), 4.32 (pst, 2H, β-H of CpBr), 4.51 (s, 2H, α-H of CpBr), 4.77
(s, 2H, α -H of CpPMes2), 6.83 (d, 8H, m-H of Mes, J = 5 Hz). 13C {1H}
NMR (thf-d8): 20.87(s, p-CH3 of Mes), 24.77 (s, o-CH3 of Mes), 70.76
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DOI: 10.1039/D0DT00941E
Table of contents entry
Bulky dppf analogs are reported for which the donor properties and coordination behavior
has been explored and tested in a catalytic model reaction.