Reductive Carbonylation of [NiCl2(dippf)] (dippf = 1,1′-Bis(diisopropylphosphino)ferrocene) with Fe(CO)5 and (Spectro)electrochemistry of the Resulting [Ni(CO)2(dippf)]

Article abstract of DOI:10.1021/acs.organomet.8b00881

[Ni(CO)₂(dippf)] [1] (dippf = 1,1′-bis(diisopropylphosphino)ferrocene) was synthesized from [NiCl₂(dippf)] and [Fe(CO)₅] at elevated temperature/pressure using microwave (MW) heating. [1] showed two oxidation waves in the cyclic voltammogram, and UV-vis-NIR spectroelectrochemistry (SEC) and IR SEC at -30 °C as well as computation support by means of DFT were used to determine the location and electron configuration after both oxidation events. The monocation [1]⁺ showed a strong NIR absorption in the UV-vis-NIR spectrum that was a IVCT [Ni^I → Fe^II] and inverse IVCT (iIVCT) [Fe^II → Ni^I], and the IR SEC spectrum of [1]⁺ showed multiple bands associated with two similar configurations, one where the spin is delocalized over both metal atoms and a second configuration where the spin is Ni localized. The second oxidation to [1]²⁺ occurred at the Ni atom and resulted in the formation of a Fe → Ni dative bond.

Full text of DOI:10.1021/acs.organomet.8b00881

Article
pubs.acs.org/Organometallics
Cite This: Organometallics XXXX, XXX, XXX−XXX
Reductive Carbonylation of [NiCl2(dippf)] (dippf = 1,1′-
Bis(diisopropylphosphino)ferrocene) with Fe(CO)5 and
(Spectro)electrochemistry of the Resulting [Ni(CO)2(dippf)]
̈
Florian Dottinger and Mark R. Ringenberg*
Institut fur Anorganische Chemie, Universitat Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart, Germany
̈
̈
S
* Supporting Information
ABSTRACT: [NiCl2 (dippf)] [1] (dippf = 1,1′-bis-
(diisopropylphosphino)ferrocene) was synthesized from
[NiCl2(dippf)] and [Fe(CO)5] at elevated temperature/pressure
using microwave (MW) heating. [1] showed two oxidation waves in
the cyclic voltammogram, and UV−vis−NIR spectroelectrochemis-
try (SEC) and IR SEC at −30 °C as well as computation support by
means of DFT were used to determine the location and electron
configuration after both oxidation events. The monocation [1]+
showed a strong NIR absorption in the UV−vis−NIR spectrum that
was a IVCT [NiI → FeII] and inverse IVCT (iIVCT) [FeII → NiI],
and the IR SEC spectrum of [1]+ showed multiple bands associated
with two similar configurations, one where the spin is delocalized
over both metal atoms and a second configuration where the spin is
Ni localized. The second oxidation to [1]2+ occurred at the Ni atom and resulted in the formation of a Fe → Ni dative bond.
Chart 1. Noninnocent κ3 and (Inverse) Intervalence Charge
Transfer (iIVCT) of Ferrocene-Based Ligands
INTRODUCTION
■
Many metalloenzymes contain hetero- and homo-bi(poly)-
metallic clusters in their active sites, which in turn inspires
bi(poly)metallic catalysts.1 The burden of creating homo- and
hetero-bimetallic complexes is facilitated by using ferrocene-
based ligands with the form Fe(C5H4−D)2, where D = donor
atom such as a P atom in 1,1′-bis(diisopropylphosphino)-
ferrocene (dippf).2−4 A metallocene in the ligand backbone
can enhance catalysis through cooperative affects and/or
flexible binding modes. This property can be beneficial in
advancing catalysis of “less common” oxidation states (NiI/III
)
that are thought to play a role in some catalytic cycles.5−10
Ferrocene-based ligands most often behave as a simple bis-
chelate; however, many interesting exceptions have been
reported,2,11−13 including κ3-D,Fe,D-chelate where there is a
Fe → TM (transition metal) interaction. This types of ligands
can also behave noninnocently14 by distributing electron spin/
density from the central metal atom on the iron atom (Chart
1). The noninnocent behavior of these ligands is increased
through the formation of a dative bond from the Fe → TM
(Chart 1), and such interactions have been reported for
carbonyl complexes of ruthenium, iron, manganese, and
cobalt.11−13,15−18 The iron atom in the ferrocene moiety can
also provide electrons through a low-energy charge transfer,
including inverse charge transfer (iIVCT), to an electron hole
found on a transition metal center (Chart 1).11−13
(Scheme 1).19 Dicarbonylnickel phosphine complexes can also
be formed by reduction of [NiBr2(PR3)2] R = Ph, or Cy with
Na-sand under a CO atmosphere; however, this method can
result in additional side reactions to occur, such as P−C bond
cleavage.20 Most methods for forming L2Ni0(CO)2 rely on the
use of toxic, i.e., [Ni(CO)4], or harsh conditions that require
specialized and cautious handling. Herein, we report the
synthesis of [Ni(CO)2(dippf)] ([1]) in THF from
[NiCl2(dippf)] with less hazardous [Fe(CO)5], which provides
both the CO ligands and acts as the reductant (Scheme 2).
RESULTS AND DISCUSSION
■
Synthesis of [1] was performed in a sealed tube microwave
(MW) reactor where the reaction occurred rapidly (90 s)
when a temperature of 130 °C was registered. The reaction
Lang et al. reported that [Ni(CO)4] reacts with dppf (dppf
= 1,1′-bis(diphenylphosphino)ferrocene) to form a mixture of
[{Ni(CO)3}2(μ-dppf)] and [Ni(CO)2(dppf)], and the latter
can be generated by heating the former to release [Ni(CO)4]
Received: December 6, 2018
© XXXX American Chemical Society
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Kohn−Sham orbitals for [1] are depicted in Figure 2. The
HOMO resides over both metal ions but is dominated by an
Scheme 1. [Ni(CO)4] Reactions with Phosphine Ligands
Scheme 2. Synthesis of [1] Using [Fe(CO)5] as Reductant
and CO Source
Figure 2. Energies of frontier orbitals from [1] determined by DFT
calculations at TPSS/def2-TZVP/J level of theory.
orbital on the Fe atom. The HOMO−1 is nearly degenerate in
energy to the HOMO, and it resides on the ferrocene moiety.
The HOMO−2 is in phase MO located over both metal ions
and the HOMO−4 is the out-of-phase MO, suggesting a
degree of M−M communication. The dFe−Ni = 4.267 Å found
in the molecular structure of [1] is outside the range for a Fe
→ Ni bond; e.g., ([Ni(Fe(C5H4S)2)(PMePh2)]) was reported
with a Fe−Ni distance 2.886(1) Å21 and [NiCl(ArF)(dippf)]
showed dFe−Ni = 3.498 Å, which is at the limits of a Fe−Ni
interaction.22,23 The HOMO−3 is located on the Ni(CO)2
moiety. The LUMO for [1] is located at the ferrocene with
some mixing from the dicarbonylnickel moiety. The UV−vis−
NIR spectrum of [1] showed an absorption band at λmax/nm
[cm−1] (ϵ/M−1 cm−1) [1] = 440 [22727] (251). This band
was described using TD-DFT (time dependence density
functional theory) and was a combination of MLCT from
the Ni and/or Fe to the Cp or CO ligands, see Figure S8 for a
depiction of the orbital transitions.
progress could be monitored by observing the change in color
from green to yellow. The iron species were removed by
filtration through a plug of neutral alumina, and after removal
of the solvent the resulting yellow solid was [1]. [1] was
crystallized from EtOH to yield X-ray quality crystals. The
molecular structure of [1] is shown in Figure 1. Complex [1]
The location and electron configuration of both oxidation
events of [1] was further probed by (spectro)electrochemical
methods. The cyclic voltammogram (CV) of [1] in 0.1 M
Bu4NB(ArF)4/CH2Cl2 (B(ArF)4 = Tetrakis(3,5-bis-
(trifluoromethyl)phenyl)borate) (Figure 3) showed a rever-
sible oxidation event at E1/2 ([1]0/+) = −0.200 V vs [Fe(η5-
C5H5) ([FcH]0/+) (the internal standard for all potentials
reported herein), and a second quasireversible oxidation at E1/2
([1]+/2+) = 0.340 V. A comproportionation constant, i.e., [1]2+
Figure 1. Molecular structure of [1] determined by X-ray diffraction.
Ellipsoids shown at 50% probability. Hydrogen atoms were omitted
for clarity.
crystallized in P121/C1 (Table S1), the molecular structure
(Figure 1) showed dFe−Ni = 4.243 Å with P−Ni−P of 108.9°,
and the η5-C5H4-ligands are staggered with a torsion angle P1−
C2−C2′−P1′ = 26.72°. The molecular structure showed
tetrahedral geometry at the Ni atom, and the η5-C5H4 ligands
are not bent or distorted.
Starting from the molecule structure of [1], a geometry-
optimized model was generated using DFT calculations (see
Supporting Information of coordinate tables). The frontier
Figure 3. CV of 1 mM [1] in 0.1 M Bu4NPF6 (red) or Bu4NB(ArF)4
in CH2Cl2 at 50 mV s−1.
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Figure 4. UV−vis−NIR and IR SEC spectra for [1]0/+ in 0.1 M Bu4NB(ArF)4/CH2Cl2 at −30 °C.
Table 1. CT Bands from UV−Vis−NIR SEC of [1]
complex
charge transfer
λmax
νmax (calc.)
ν1/2
ϵmax
Hab
[1]
MLCT
420
22.779 (23.610)
7.607 (8.303)
9.665 (9.196)
21.978 (22.070)
17.393 (19.490)
25.451 (24.386)
0.255
0.520
0.420
2.248
1.568
2.873
[1]+
iIVCT FeII → NiI
IVCT NiI → FeII
MMLCT
1.654
2.038
430
483
455
575
390
[1]2+
FeII → NiII
(C5H4)2FeII → NiII
1915 cm−1 shifted to higher energy bands at and νCO[1]+ =
2064, 2046, 2035, 2023 cm−1 (Figure 4). The role of the
electrolyte is clearly seen when the IR SEC was performed in
0.1 Bu4NPF6/CH2Cl2 (Figures S6 and S7) where mixtures of
all three redox states were observed in the spectra, although a
similar spectral response was also observed. The ΔνCO[1] =
80/106 cm−1 for [1]0/+ is larger than expected if the oxidation
occurred at the ferrocene moiety.25−27 The first oxidation
event was assigned to Ni0/I oxidation on the basis of the IR
SEC spectrum; however, four CO bands from νCO[1]+ are too
numerous for a single dicarbonylnickel product.
Kc
+ [1] F 2[1]+, Kc ([1]) = 10ΔE/59 mV = 109.15, was determined
from the ΔE and is consistent with a stable mixed-valence state
for the monocation. Changing the electrolyte to Bu4NPF6
caused the second redox wave to cathodically shift, and the ΔE
was smaller E1/2 ([1]0/+) = −0.200 V and E1/2 ([1]+/2+) =
0.040 V, Kc ([1]) = 104.06 (Figure 3). The strong influence on
Kc has been described in detail elsewhere24 and is likely due to
ion pairing with the monocation [1]+.
The location of the oxidation, i.e., Ni or Fe based, is not
evident based on the HOMO found during the DFT
calculation; e.g., [1]+ could have an electron configuration of
[NiIFeII] or [Ni0FeIII] and [1]2+ could be either [NiIFeIII] or
[NiIIFeII]. Further oxidations were not observed within the
potential window provided by the solvent/electrolyte. In order
to assign the electron configuration of the both metal atoms
after oxidation, both redox events were studied by means of
UV−vis−NIR/IR spectroelectrochemistry (SEC); however,
both SEC experiments were performed at low temperature
(−30 °C) due to nonisosbestic behavior at room temperature.
Additionally, attempts to chemically oxidize [1] with [FcH]-
B(ArF)4 at −30 in Et2O, THF, or CH2Cl2 resulted in loss of
the of the CO signals.
Open shell calculations on [1]+ revealed a distorted trigonal
bipyramidal molecular geometry with a dFe−Ni[1]+ = 3.873 Å,
and the spin density was distributed nearly equally over both
Fe and Ni sites (Mulliken spin Ni: 0.43, Fe: 0.39). A DFT
potential energy surface scan was performed in which the
d
Fe−Ni was scanned from 2.6−5 Å. The energy surface is shown
in Figure 5 and shows the lowest energy configuration with
dFe−Ni[1]+ = 3.873 Å, and second configuration was found at
+4 kcal mol−1 above the global minimum energy with
dFe−Ni[1]+ = 4.511 Å, and the spin was not as evenly
The oxidation event [1]0/+ was monitored by UV−vis−NIR
SEC at −30 °C in 0.1 Bu4NB(ArF)4/CH2Cl2 due to the large
separation of the two oxidation events. Oxidation resulted in
the band at λmax/nm [cm−1] [1] = 439 [22 779] to be replaced
by new bands at at λmax/nm [cm−1] (ϵ/M−1 cm−1) [1]+ = 468
[21 367] (1596), 709 [13 175] (162) 1276 [7836] (640)
(Figure 4 and Table 1), see Figure S4 for spectrum fitting. The
large NIR band was also observed for other metal−carbonyls
containing ferrocene-based ligands,11−13 although the NIR
band for [1]+ was more intense and broader than those
previously described.
The infrared SEC spectrum at −30 °C in 0.1 Bu4NB(ArF)4/
CH2Cl2 of [1]0/+ showed the two bands for νCO[1] = 1983,
Figure 5. Potential energy surface scan for [1]+ along Fe−Ni axis with
spin density shown in light blue.
C
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distributed, locating more at the Ni site (Mulliken spin Ni:
0.46, Fe: 0.22) (Figure 5). The appearance of multiple bands
in the IR SEC spectrum of [1]+ is conjectured to be a result of
the weak Fe−Ni interaction, which allows for two close energy
configurations to be observed, one where the electron spin is
distributed almost equally over both metal atoms that results in
a smaller ΔνCO[1]+ = 80 cm−1,11,12 and one where the spin
density is primary located at the Ni atom ΔνCO[1]+ = 106
cm−1.25−27
The UV−vis−NIR spectrum of the lower energy geometry
of open-shell [1]+ was described using TD-DFT calculations.
The near IR transition at 7836 cm−1 was described as a
combination of two different intervalence charge transfer
(IVCT) bands, one at 7607 cm−1 and another at 9665 cm−1
(Figure S4). The higher energy band at 9665 cm−1 was a
classic IVCT from a low to high valent metal ion (NiI → FeII),
while the lower energy band at 7607 cm−1 was an inverse
intervalence charge transfer (iIVCT), i.e., from a high to low
valent metal ion (FeII → NiI) (Scheme 3). TD-DFT
The iIVCT is possible because of the different ligation, i.e., η5-
C5H4 donating for iron and π-accepting CO for the Ni.
Performing a Hush analysis on these two bands show Hab
=
430 cm−1 (iIVCT) and Hab = 483 cm−1 (IVCT), where dFe−Ni
= 4.227 Å (calc), are consistent with a valence localized
system.28−30
The UV−vis−NIR SEC spectrum at −30 °C (Figure 6) in
0.1 Bu4NB(ArF)4/CH2Cl2 for [1]+/2+ caused a decrease in NIR
band and two new absorption bands to appear at λmax/nm
[cm−1] (ϵ/M−1 cm−1) [1]2+ = 575 [17393] (1568) and 390
[25451] (2873) (Figure 6 and Table 1). The band at 575 nm
is typical for a Fe → TM interaction.23,31 These two bands
were described using TD-DFT and the lower energy band was
a MMCT and the higher energy band was an ICVT from Fe →
Ni, see Figure S11 for a depiction of the transitions. The IR
SEC spectrum at −30 °C for [1]+/2+ (Figure 6) showed the
bands from [1]+ converged into two bands νCO[1]2+ = 2108,
and 2077 cm−1 (Figure 6). The two bands were consistent
with a trigonal-bipyramidal configuration with the two CO-
bands equatorially coordinated.32−34
The closed-shell DFT calculations for the dication [1]2+
showed a short dFe−Ni[1]2+ = 2.973 (calc.) Å, and the intrinsic
bonding orbital (IBO)35 shows the dative bond from the Fe to
the Ni atom (Figure 7). A DFT potential energy surface scan
Scheme 3. NiI → FeII iIVCT and FeII → NiI IVCT Exchange
Energy (Hab) Determined from Analysis of NIR Band
calculations were also performed on the higher energy
geometry of [1]+, and showed similar iIVCT (6610 cm−1)
and IVCT (13507 cm−1), see Figure S10 for depiction of
transitions. These data on both geometries showed similar
transitions in the UV−vis−NIR spectrum; however, the lower
energy geometry fits closer the spectrum in Figure 4, as the
higher energy IVCT band at 13507 cm−1 was not observed.
Figure 7. Intrinsic bond orbital (IBO)35 generated from closed shell
calculations of [1]2+ showing Fe → Ni bonding orbital. Potential
energy surface scan for [1]2+ along Fe−Ni axis S = 0 (blue) S = 1
(red).
Figure 6. UV−vis−NIR and IR SEC spectra for [1]+/2+ in 0.1 M Bu4NB(ArF)4/CH2Cl2 at −30 °C.
D
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Supporting Information. Spectroelectrochemistry was performed
using a optically transparent thin-layered electrode (OTTLE) cooled
using a liquid nitrogen cryostat previously described.37 X-ray
diffraction data were collected using a Bruker Kappa Apex2duo
diffractometer. The structures were solved using Patterson method
and refined by full-matrix least-squares techniques on F2 using the
OLEX2 program.38 The absorption corrections were done by
multiscan technique. All non-hydrogen atoms were anisotropically
refined. Hydrogen atoms were included in the refinement process as
per the riding model.
Density functional theory (DFT) calculations were performed
using the solid-state structures of [1], and the closed-shell structure of
[1]2+ was determined by removing 2e− from the structure of [1]. A
computational analysis was performed by means of restricted Kohn−
Sham density functional theory (DFT) using TPSS39 functional in
combination with the D3 dispersion correction40 with the def2-
TZVP41,42 and Weigend J auxiliary basis set.41,42 Geometry
optimizations were realized with the ORCA program package with
TightSCF convergence (1.0 × 10−7 au).43 Solvation in CH2Cl2 was
modeled using the CPCM solvation model.44 Open-shell calculations
on the structure [1]+ and [1]2+ were determined by subtracting 1e− or
2e−, respectively, and calculations were performed by means of
unrestricted Kohn−Sham DFT using the same basis set, functionals,
and solvent models as the closed-shell structures.
1,1′-Bis(diisopropylphosphino)ferrocene was purchased from
ABCR and used without further purification. THF was distilled
from sodium-benzophenone and stored over 3 Å molecular sieves.
NaB(ArF)4 was synthesized according to literature procedure.45
1,1′-Bis(diisopropylphosphino)ferrocenenickeldichloride was made
according to modified reported procedure46 by heating an equal
molar [Ni(H2O)6]Cl2 (568 mg, 2.39 mmol) and dippf (999 mg, 2.39
mmol) solution in 2-propanol:methanol 2:1 (75 mL), and cooling the
solution to −30 °C yielded green microcrystals that were collected by
filtration and dried at reduced pressure. Yield 79%. The substance was
used in the next step without further purification.
was performed in which the dFe−Ni was scanned from 2.6−5 Å.
Scanning along the Fe−Ni axis showed the energy minimum at
dFe−Ni = 2.973 Å, increasing the distance caused an increase in
the energy. Elongation of the Fe−Ni distance did not afford a
reasonable minimum structure with a singlet ground state. A
proposed intersystem crossing to a triplet state was observed at
4 Å. A PES scan of the triplet state showed two energy minima
that were both higher in energy than the singlet state. These
minima were found at dFe−Ni = 3.8 and 4.6 Å, which
corresponded to a delocalized triplet state with spin density
over both Fe and Ni atoms (dFe−Ni = 3.8, Mulliken spin Ni:
0.71, Fe: 1.18) and (dFe−Ni = 4.6, Mulliken spin Ni: 0.58, Fe:
1.24) (Figure 7). The result of this intersystem crossing is that
the Fe−Ni bond energy is about 15 kcal mol−1, which falls at
the lower energy range for “typical” Fe-TM bonds that have a
range of 22−24 kcal mol−1.23 This behavior was also observed
in a nickel complex containing a ferrocene-based ligand, e.g.,
[{Fe(C5H4NIm)2}Ni(NCMe)2]2+ Im = imidazole,36 which
had a BDE(Fe−Ni) = 11.3 kcal mol−1.
CONCLUSIONS
■
The complex [Ni(CO)2(dippf)] [1] was synthesized by
reduction of [NiCl2(dippf)] and transfer of CO ligands from
less toxic and readily available [Fe(CO)5] at elevated
temperature under MW heating. DFT calculations on [1]
showed the HOMO to be delocalized over both metal atoms,
which complicated the assignment of the two oxidation events
observed in the CV. UV−vis−NIR SEC spectrum of [1]+
showed a large NIR absorption, which was described according
to TD-DFT as a IVCT [NiI → FeII] and inverse IVCT
(iIVCT) [FeII → NiI] or hole transfer. The IR SEC spectrum
of [1]+ shows four bands, which was ascribed to two similar
configurations, one which contains a Fe → Ni dative bond
where the spin is delocalized over both metal atoms, and a
second configuration where the spin is primarily Ni localized;
therefore, [FeIINiI] was assigned as the electron configuration
of [1]+. The second oxidation to [1]2+ results in the formation
of a Fe → Ni dative bond, which was found during DFT
calculations and was further supported by UV−vis−NIR/IR
SEC. Attempts to calculate the BDE(Fe−Ni) of [1]2+ were
complicated by an intersystem crossing from a singlet state to a
triplet state, resulting in BDE(Fe−Ni) = 15 kcal mol−1. The
ferrocene-based phosphine ligands can be used to help support
the higher oxidation states (NiI and NiII) of metal atoms
through the formation of a Fe interaction and by providing
electrons through low energy charge transfer from the Fe to
the Ni atom.
1,1′-Bis(diisopropylphosphino)ferrocenedicarbonylnickel
[1]. A 30 mL MW reaction tube was charged with [NiCl2(dippf)]
(480 mg, 0.70 mmol), [Fe(CO)5] (411 mg, 2.10 mmol) and THF
(10 mL). The reaction solution was purged with N2 for 5 min. The
reaction tube was placed in the MW, and it was heated to 130 °C for
3 min until the color turned from green to yellow (90 s). The
resulting reaction solution was cooled to room temperature, and the
solution was passed quickly through as small plug of neutral alumina.
The THF was removed at reduced pressure, and the resulting sticky
yellow solid was crystallized from hot ethanol, yield = 75%. 1H NMR
(CD2Cl2) δ 5.32 (s, CH2Cl2) 4.27 (4H, s), 4.23 (4H, s), 2.14 (4H,
m), 1.25−1.70 (24H, m). 31P{1H} NMR (CD2Cl2) δ 41.38 (s) ppm.
CH: elemental analysis calcd. (%) for C24H36FeNiO2P2(CH2Cl2)0.25
C 52.55, H, 6.64. Found: C 52.77, H 6.62.
:
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.8b00881.
EXPERIMENTAL SECTION
■
Microwave (MW) reactions were carried out in a 30 mL glass tube
with a maximum volume of 10 mL in Monowave 400 microwave
Fitted UV−vis−NIR and IR spectrum of [1]+, TD-DFT,
EDDM, crystallographic tables, and coordinates deter-
mined by DFT (PDF)
1
synthesis reactor by Anton Paar. H and 31P{1H} NMR spectra were
1
obtained on a Bruker AC 250 spectrometer. H NMR spectra were
referenced versus residual solvent peak and 31P{1H} NMR spectra
were referenced against an external standard H3PO4. IR spectra were
obtained using a Nicolet 6700 FT-IR instrument. UV−vis−NIR
absorption spectra were recorded on J&M TIDAS spectrophotometer.
Cyclic voltammetry was carried out in 0.1 M Bu4NB(ArF)4/CH2Cl2
solutions using a three-electrode configuration (glassy carbon
working, Pt wire counter electrodes, and Ag reference) and were
performed using a Metrohm Autolab potentiostat. The ferrocene/
ferrocenium ([FcH]0/+) couple served as internal reference to all
potentials reported herein. Tetrabutylammonium tetrakis[3,5-bis-
(trifluoromethyl)phenyl]borate synthesis can be found in the
XYZ files (ZIP)
Accession Codes
CCDC 1874489 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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(15) Kluwer, A. M.; Krafft, M. J.; Hartenbach, I.; de Bruin, B.; Kaim,
W. Hydroformylation of 1-Octene Mediated by the Cobalt Complex
[CoH(dchpf)(CO)2]. Top. Catal. 2016, 59, 1787−1792.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: mark.ringenberg@iac.uni-stuttgart.de. Phone: +49
(0)711 685-64196. Fax: +49 (0)711 685-64165.
(16) Krafft, M. J.; Bubrin, M.; Paretzki, A.; Lissner, F.; Fiedler, J.;
́
̌
Zalis, S.; Kaim, W. Identifying Intermediates of Sequential Electron
and Hydrogen Loss from a Dicarbonylcobalt Hydride Complex.
Angew. Chem., Int. Ed. 2013, 52, 6781−6784.
ORCID
Mark R. Ringenberg: 0000-0001-7585-5757
Notes
The authors declare no competing financial interest.
(17) Krafft, M. J.; Lissner, F.; Fiedler, J.; Kaim, W. Cobalt Carbonyl
Hydrides with 1,1’-Diphosphinylferrocene Ligands - Structural and
Electrochemical Diversity. Z. Anorg. Allg. Chem. 2017, 643, 1971−
1977.
(18) Sixt, T.; Sieger, M.; Krafft, M. J.; Bubrin, D.; Fiedler, J.; Kaim,
W. Ambi-Valence Taken Literally: Ruthenium vs Iron Oxidation in
(1,1’-Diphosphinoferrocene)ruthenium(II) Hydride and Chloride
Complexes as Deduced from Spectroelectrochemistry of the
Heterodimetallic ”Mixed-Valent” Intermediates. Organometallics
2010, 29, 5511−5516.
ACKNOWLEDGMENTS
■
The authors thank Prof. Wolfgang Kaim for support and
continued advice. Dr. Wolfgang Frey is thanked for advice and
crystallographic measurements. M.R.R. gratefully acknowl-
̈
edges support by the state of Baden-Wurttemberg through
bwHPC and the German Research Foundation (DFG)
through grant no. INST 40/467-1 FUGG for access to the
̈
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