Perfluoroalkyl Cobaloximes: Preparation Using Hypervalent Iodine Reagents, Molecular Structures, Thermal and Photochemical Reactivity

Article abstract of DOI:10.1021/acs.organomet.7b00892

Treatment of cobaloximes(II), [Co(Hdmg)₂(L)₂] (Hdmg = dimethylglyoximate, L = neutral ligand), with perfluoroalkyl iodane reagents leads to the formation of perfluoroalkyl cobaloximes(III), [CoR_F(Hdmg)₂(L)] (R_F = CF₃, C₂F₅, n-C₃F₇, CF₂CF₂Ph; L = Py, NH₃, MeNH₂, PhNH₂, MeOH). The synthetic protocol can be significantly simplified to a one-pot procedure starting from cobalt(II) acetate-tetrahydrate. The products have been fully characterized by NMR, IR, and UV/vis spectroscopy as well as single-crystal X-ray diffraction, and the thermal and photochemical reactivity has been studied. According to the Co-L distances in the crystal, the trans influence of the R_F^- ligands can be rated as C₂F₅^- ≈ n-C₃F₇^- < CF₂CF₂Ph^- ≈ CF₃^- < CH₃^-. The thermal decomposition of the complexes is different from that of nonfluorinated analogues, probably including perfluoroalkylation of an Hdmg^- ligand as the initial step. In the CF₃ complexes, the Co-C bond is very resistant against photolysis, but the ligand L is readily exchanged by MeOH upon exposure to blue light. In the complexes with longer R_F chains, the Co-C bond is more readily cleaved, and the product distribution depends strongly on the presence of O₂. Thus, the alkane R_FH is the main product under exclusion of O₂, while a fluorinated methyl ester and HF are formed in a methanol solution exposed to air.

Full text of DOI:10.1021/acs.organomet.7b00892

Article
Cite This: Organometallics XXXX, XXX, XXX−XXX
Perfluoroalkyl Cobaloximes: Preparation Using Hypervalent Iodine
Reagents, Molecular Structures, Thermal and Photochemical
Reactivity
Phil Liebing,*,† Florian Oehler,‡ Mona Wagner,† Pascal F. Tripet,† and Antonio Togni†
†Swiss Federal Institute of Technology, ETH Zurich, Department of Chemistry and Applied Biosciences, Vladimir-Prelog-Weg 2,
8093 Zurich, Switzerland
‡Martin-Luther-Universitat Halle-Wittenberg, Institut fur Chemie, Kurt-Mothes-Str. 2, 06120 Halle (Saale), Germany
̈
̈
S
* Supporting Information
ABSTRACT: Treatment of cobaloximes(II), [Co(Hdmg)2-
(L)2] (Hdmg = dimethylglyoximate, L = neutral ligand), with
perfluoroalkyl iodane reagents leads to the formation of
perfluoroalkyl cobaloximes(III), [CoRF(Hdmg)2(L)] (RF
=
CF3, C2F5, n-C3F7, CF2CF2Ph; L = Py, NH3, MeNH2, PhNH2,
MeOH). The synthetic protocol can be significantly simplified
to a one-pot procedure starting from cobalt(II) acetate−
tetrahydrate. The products have been fully characterized by
NMR, IR, and UV/vis spectroscopy as well as single-crystal X-
ray diffraction, and the thermal and photochemical reactivity
has been studied. According to the Co−L distances in the
−
crystal, the trans influence of the RF ligands can be rated as
C2F5 ≈ n-C3F7 < CF2CF2Ph− ≈ CF3 < CH3 . The thermal decomposition of the complexes is different from that of
nonfluorinated analogues, probably including perfluoroalkylation of an Hdmg− ligand as the initial step. In the CF3 complexes,
the Co−C bond is very resistant against photolysis, but the ligand L is readily exchanged by MeOH upon exposure to blue light.
In the complexes with longer RF chains, the Co−C bond is more readily cleaved, and the product distribution depends strongly
on the presence of O2. Thus, the alkane RFH is the main product under exclusion of O2, while a fluorinated methyl ester and HF
are formed in a methanol solution exposed to air.
−
−
−
−
Chart 1. Molecular Structures of Cobaloximes(II) (a) and
Alkyl Cobaloximes(III) (b) (L = Neutral Ligand, R = Alkyl)
INTRODUCTION
■
Since their discovery in the 1960s,1 bis(diorganyldioximato)
cobalt(III) complexes (“cobaloximes”; Chart 1) such as
[CoR(Hdmg)2(L)] (Hdmg = dimethylglyoximate; R = e.g.,
CN, Alkyl; L = neutral ligand), which are structurally closely
related to the corresponding cobalt(II) complexes [Co-
(Hdmg)2(L)2], have been in the focus of numerous research
groups. The organometallic cobalt(III) complexes are not only
useful models for cobalamines, biologically important com-
pounds of the vitamin B12 family,2 but are also of interest as
homogeneous catalysts for various radical reactions.3 An
important feature of cobaloximes is the versatile reactivity of
the Co−C bond. Thus, this bond is resistant against hydrolysis
under physiological conditions, but is readily cleaved homolyti-
cally to afford alkyl radicals under mild conditions, e.g., by
visible-light photolysis. The reactivity of the Co−C bond can be
tuned widely by varying the axial ligands R and L, while the
Co(Hdmg)2 scaffold is comparatively inert.3
−
ligands RF , and corresponding extensive reactivity studies.
[CoCF3(Hdmg)2(Py)], the first cobaloxime comprising a
perfluoroalkyl ligand, was briefly mentioned in the literature
as early as 1966.1 This compound was structurally characterized
by Toscano et al. in 1989, revealing that the Co−C bond in this
complex is remarkably shortened as compared to the CH3
analogue [CoCH3(Hdmg)2(Py)].8 The preparation and crystal
9,10
structures of a few related complexes with RF = e.g., i-C3F7
and C2F4H,11 have been reported in the early 1990s, and the
reactivity of the CF3 complexes has been investigated in detail.
For instance, a weaker trans effect of the CF3 ligand as
Due to a continuously rising demand for selective late-stage
perfluoroalkylation methods for organic molecules, there is a
remarkable research interest in perfluorinated organometal
compounds.4−7 This includes the development of protocols for
the efficient synthesis of metal complexes with perfluoroalkyl
−
Received: December 14, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00892
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Article
compared to the CH3− ligand,12 and a facile cleavage of the C−
F bonds by aqueous bases13 have been reported. Very recently,
related cobalamines with RF chains up to n-C8F17 have been
postulated as catalytically active species in the electrochemical
perfluoroalkylation of arenes.14
Perfluoroalkyl cobaloximes have been predominantly pre-
pared following the “classical” route,3 including the reaction of
a nucleophilic CoI species with a perfluoroalkyl halide RFX (X =
Br or I; Scheme 1a).8,9,11−13 Similar conditions have been used
CF2CF2X moieties (X = e.g., OAr, SAr, pyrazolyl) have been
reported from our laboratory.21 All of these reagents have been
successfully employed for the perfluoroalkylation of various C,
O, N, and P nucleophiles, where reagents like 1a−e show
different reactivities. On the one hand, coordination to a Lewis-
acidic metal or protonation enhances electrophilic reactivity as
RF equivalents.18 On the other hand, perfluoroalkyl iodanes
+
often show radical reactions, which are initiated by transition
metal catalysis or by one-electron reduction of the
reagent.18−20,22 Notwithstanding this possibility to vary the
reactivity of the iodane reagents by metal catalysts, reactions
with metal compounds themselves have been investigated to a
much lesser extent thus far. The only documented example of
transformations of metal complexes with perfluoroalkyl iodanes
is the trifluoromethylation of a binuclear PdII complex
employing reagent 1a or 1b. In this case, a two-electron
oxidation of a Pd atom under formation of a PdIV-CF3 species
takes place. However, mechanistically, this reaction goes
Scheme 1. Synthetic Routes to Perfluoroalkyl
Cobaloximes(III) from Cobaloximes(II), Using a
Nucleophilic Co(I) Intermediate (a) or an RF Radical Source
Such as RFI (b)
beyond a simple CF3 transfer, as it involves a binuclear PdIII
+
intermediate.4,23,24
To gain a deeper insight into reactions of perfluoroalkyl
iodane reagents such as 1a−e with different metal complexes,
we have been looking for novel model reactions, where the
reagent shows clean radical reactivity. A detailed knowledge
about such reactions forms a valuable basis for the development
of new metal-catalyzed perfluoroalkylations with iodane
reagents. This knowledge includes similarities and differences
between acid- and alcohol-type reagents, the behavior of
different perfluoroalkyl groups, and the tuning of the reactivity
by the ligands around the metal center. In the course of our
research, we were particularly interested in complexes of cheap
3d metals with simple and readily accessible ligand systems,
which are attractive for potential commercial applications. In
two recent contributions, it has been shown that complexes of
cobalt are suitable for radical perfluoroalkylations of arenes,
based on photolytic homolysis of a Co−RF bond.14,25
In this work, we investigated the reactivity of the reagents
toward cobaloximes(II), [Co(Hdmg)2(L)2], that can be
expected to enable radical reactivity of the iodane reagents
according to reaction (b) in Scheme 1. Complexes like
[Co(Hdmg)2(H2O)2] (2) are very easily accessible from a
CoII salt and dimethylglyoxime, and their redox potential is
widely tunable by the axial ligands attached to Co.3,26 For
instance, the pyridine complex [Co(Hdmg)2(Py)2] (3) is more
readily oxidized than the dihydrate 2, while [Co-
(Hdmg)2(PPh3)2] is comparatively stable against oxidation.27,28
Herein, we report a unique model reaction for the one-electron
oxidative perfluoroalkylation of a metal center. This study led
us to a straightforward synthetic protocol for perfluoroalkyl
cobaloximes(III) and the full characterization (1H, 13C, 19F, and
for the derivatization of related cobalamines.15 However, this
reaction bears various disadvantages, including the handling of a
highly reactive and air-sensitive CoI intermediate, and harmful
gases such as CF3Br or CF3I. The CoI compound is most
frequently accessed by reduction of a CoII or CoIII precursor
with NaBH4, which can undergo side reactions with the RF
moiety to reveal defluorination products such as CHF2
complexes.8,16 [CoCF3(Hdmg)2(Py)] was also obtained
directly by reaction of a CoII complex with CF3I,1 which acts
formally as a source of CF3 radicals in this reaction (Scheme
1b). This synthetic strategy is also less attractive due to the use
of light-sensitive, hazardous CF3I gas and the difficulty to
separate the byproduct [CoI(Hdmg)2(Py)].3,16 Therefore, a
facile, widely applicable synthetic protocol including a cheap
and easy to handle perfluoroalkyl source is still lacking.
Hypervalent iodine reagents for electrophilic perfluoroalky-
lation are readily accessible, shelf-stable crystalline solids, and
their versatility has been widely demonstrated since the first
report from our laboratory in 2006.17,18 The first developed and
most popular members of this reagent class are 1-(trifluoro-
methyl)-1,2-benziodoxol-3(1H)-one (1a; “Togni’s reagent I” or
“acid reagent”) and trifluoromethyl-1,3-dihydro-3,3-dimethyl-
1,2-benziodoxole (1b; “Togni’s reagent II” or “alcohol reagent”;
cf. Scheme 2). During the past 5 years, the library of iodane
reagents has continuously been growing and includes now
compounds with perfluorinated groups other than CF3, e.g., the
C2F5 analogue of the acid reagent (1c),19 as well as the
corresponding n-C3F7 homologue (1d).20 In 2016, a large
variety of acid and alcohol reagents with functionalized
Scheme 2. Reaction of Cobaloximes(II) with the Perfluoroalkyl Iodanes 1a−e
B
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59Co NMR spectroscopy, IR and UV/vis spectroscopy, single-
crystal X-ray structure analysis, as well as thermal and
photochemical reactivity studies) of the literature-known
[CoCF3(Hdmg)2(Py)] (4) and nine novel [CoRF(Hdmg)2(L)]
complexes (5−13). The influence of both L and RF on the
properties of the compounds is discussed.
lucky to find that similar reactions of 3 with acid reagents
delivering RF groups larger than CF3 (1c−e; RF = C2F5, n-C3F7,
CF2CF2Ph) lead to the corresponding perfluoroalkyl
cobaloximes(III) (9, 12, 13) in significantly better CoIII-RF/
RF-H ratios than observed for RF = CF3.
The reaction between the CoII precursor complex and the
iodanes also depends strongly on the nature of ligand L. This is
easily explained by the fact that the ligands around Co define
the redox potential of the complex.27,28 Thus, the strongly
reducing [Co(Hdmg)2(Py)2] (3) is readily oxidized by, e.g., 1a,
while [Co(Hdmg)2(PPh3)2] is inert against oxidation and
consequently CHF3 and CF3I are observed as the main reaction
products (cf. Table S1 in the SI). Other suitable precursor
complexes with L = NH3, MeNH2, and PhNH2, which reveal
the corresponding CoIII-CF3 complexes 5−7 in a straightfor-
ward manner corresponding to Scheme 2, have been generated
in situ from the dihydrate 2. Within the series of nitrogen
ligands, the highest 19F NMR yields of the target CoIII-CF3
complexes are reached with Py and PhNH2, while the yields are
somewhat lower in the case of NH3 and MeNH2 (cf. Table S1
in the SI). Consequently, the yield seems not to be determined
exclusively by the redox potential of the CoII complex, as, e.g.,
the NH3 complex (E(CoII/CoIII) = −0.65 V vs SCE in H2O) is
a stronger reducing agent than the Py complex (E(CoII/CoIII)
= −0.22 V vs SCE in H2O).27 The reduction potential of
reagent 1a has been reported to be −0.68 V (vs SCE) in MeCN
solution.29
RESULTS AND DISCUSSION
■
Reaction Screening. In an initial set of experiments, we
explored the reactivity of the trifluoromethyl iodanes 1a and 1b
toward [Co(Hdmg)2(Py)2] (3) under variation of solvent and
stoichiometry of the starting materials. The product distribu-
tion can easily be estimated by 19F NMR spectroscopy (cf.
Table S1 in the SI). The target complex [CoCF3(Hdmg)2-
(Py)2] (4) shows a signal at −31.8 ppm, which can simply be
assigned as it is slightly broadened due to the quadrupolar
moment of the 59Co nucleus. When equimolar amounts of 1a
and 3 are used, a considerable amount of unreacted reagent 1a
remains, but the latter is completely consumed when 2 equiv of
3 are employed (Figure 1a,b). The need for 2 mol of cobalt(II)
The reaction of the less reducing [Co(Hdmg)2(H2O)2] (2;
E(CoII/ CoIII) = +0.31 V vs SCE in H2O28) with 1a proceeds
to completion after a longer reaction time. However, the
product turned out to be the MeOH complex [CoCF3-
(Hdmg)2(MeOH)] (8) instead of the expected H2O complex.
This can possibly be attributed to expulsion of the
comparatively weak H2O ligand in 2 by the solvent MeOH
prior to reaction with 1a, together with a lower redox potential
of the corresponding MeOH complex. For L = NH3 and
PhNH2, the [Co(Hdmg)2(L)2](o-IC6H4COO) byproducts
have been identified by single-crystal X-ray diffraction after
isolation from the reaction mixture, while a corresponding
complex salt was not isolable in the case of L = MeNH2 and
H2O/MeOH.
Figure 1. 19F NMR spectra of the reaction solution of [Co-
(Hdmg)2(Py)2] (3) after 15 h at r.t., using different iodane reagents
and molar ratios of reagent/cobalt(II) complex (Co = target CoIII-CF3
complex 4, H = CHF3, I = CF3I).
Preparation and Properties. The [CoRF(Hdmg)2(L)]-
type complexes with nitrogen ligands, L = Py, NH3, MeNH2,
and PhNH2 (4−7 and 9−13), have been isolated in 31−67%
yield from reactions of the appropriate acid reagent (1a, 1c−e)
on a 3 mmol scale with a slight excess (2.05 equiv) of the
corresponding CoII precursor in methanol (cf. Figures S1−S4
in the SI). The products can easily be separated from the
specific ortho-iodobenzoate salt (14−16) or decomposition
products thereof, by exploiting the different solubility in water,
ethyl acetate, or acetone. Even though the potential iodide
source CF3I was observed in the reaction mixtures in the case
of reagent 1a (cf. Figure 1), the appropriate iodido complex
[CoI(Hdmg)2(L)] was not detected in the isolated products.
The MeOH complex 8 could be isolated in only 14% yield,
which is due to the need for several purification steps (the
hypothetical byproduct [Co(Hdmg)2(MeOH)2](o-IC6H4-
COO) is unstable; see below). It is worth mentioning that
the perfluoroalkyl cobaloximes have been obtained in
comparable yields from a one-pot reaction directly from
cobalt(II) acetate−tetrahydrate, H2dmg, ligand L, and the
appropriate iodane reagent, this representing a further
complex per mol of iodane reagent arises from the formation of
an ortho-iodobenzoate salt [Co(Hdmg)2(Py)2](o-IC6H4COO)
together with the target CoIII-CF3 complex 4 (cf. right reaction
in Scheme 2). The mentioned byproduct has been identified by
single-crystal X-ray diffraction after crystallization from the
reaction mixture. Fluoroform, CHF3, has been identified as the
major side product, which appears in the 19F NMR spectrum as
a sharp signal at −79.5 ppm in methanol. The formation of the
latter depends strongly on the solvent, where methanol was
found to be the best choice (best CoIII-CF3/CHF3 ratio).
Another minor side product was identified as CF3I (δF = −10.7
ppm in methanol). Use of excess 3 in the attempt to suppress
side reactions does not lead to a significant shift of the product
spectrum in favor of the target complex 4 (cf. Table S1 in the
SI). Replacing the acid reagent 1a by the corresponding alcohol
reagent 1b leads to the Co-CF3 complex 4 as well, but the
reaction does not proceed to completion even after a prolonged
reaction time (Figure 1c). Moreover, the undefined byproducts
are difficult to separate from the reaction mixture. Con-
sequently, acid reagents like 1a are clearly preferable for
preparative purposes. With this knowledge in hand, we were
C
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b
Table 1. 19F and 59Co NMR Data of Compounds 4−13
tremendous simplification of the synthetic procedure (Scheme
3).
comp.
δ(19F)/ppm
|1JC,F|/Hz
δ(59Co)/ppm
w1/2(59Co)/kHz
4
5
−32.7
−35.1
−34.3
−31.3
−28.5
−99.0
−104.0
−103.2
−95.7
379
376
379
380
378
3828
3856
3839
3856
4350
4040
4044
4034
4168
4146
3.42
3.89
3.42
3.89
6.83
5.03
3.70
3.13
5.79
6.74
Scheme 3. One-Pot Synthesis of Compounds 4−13 from
Cobalt(II) Acetate−Tetrahydrate
6
7
8
a
a
9
320
a
10
11
12
13
a
a
314
a
a
a
−87.7
b
328
a
α-CF2 signal. 4, 9, 12, and 13 measured in CDCl3, all other
compounds in CD3OD.
of the acidic OH moieties of the Hdmg− ligands are not
observable due to fast H/D exchange with the solvent, while
the NH moieties of NH3, MeNH2, and PhNH2 appear as
broadened singlets in methanol-D4 solution (cf. Figures S5 and
S8 in the SI). In the 13C NMR spectra, the signals of all CF2
and CF3 moieties are not visible due to quadrupolar coupling
with the 59Co nucleus and additional coupling with the 19F
nuclei (cf. Figures S6 and S9 in the SI). However, the 13C
satellites in the 19F NMR spectra are usually clearly resolved (cf.
Figures S7 and S10 in the SI). In the case of the CF3 complexes
4−8, the 19F NMR signals appear in a range between −28.5 and
−35.1 ppm. The |1JC,F| values are in a narrow range of 376−380
Hz, which is large as compared to the values observed in other
CF3 compounds (e.g., CHF3: |1JC,F| = 272 Hz; CF3Cl: |1JC,F| =
299 Hz; CF3I: |1JC,F| = 344 Hz).30 The 59Co NMR shifts of 4−7
are in a range of 3828−4350 ppm, which is significantly
downfield-shifted as compared to related non-fluorinated
With the attempt to prepare authentic samples of the
byproducts [Co(Hdmg)2(L)2](o-IC6H4COO), we treated a
mixture of cobalt(II) ortho-iodobenzoate−dihydrate, H2dmg,
and ligand L in ethanol with air (Scheme 4). The results were
Scheme 4. Targeted Preparation of the ortho-Iodobenzoate
Salts 14−16
n
n
cobaloximes like [CoR(Hdmg)2(Py)] (R = Me, Et, Pr, Bu;
δCo = 3640−3680 ppm).31 The line widths of the signals are in
the lower kilohertz range and, as expected, increase with
increasing size of the RF group (e.g., within the series of the
pyridine complexes 4, 9, 12, and 13; cf. Figure S11 in the SI).
The signal of the MeOH complex 8 is unexpectedly broad at
6.83 kHz in CD3OD solution (cf. 4−7: w1/2 = 3.42−3.89 kHz).
This may be due to a higher asymmetry of the electronic
environment around the Co nucleus, or symmetry reduction by
hydrogen bonding between coordinated and solvent meth-
anol.32 Surprisingly, the 59Co NMR signals have not been
found in the case of the very symmetric cationic complexes
[Co(Hdmg)2(L)2]+ in 14−16, which may be due to symmetry
reduction by contact ion pairing.33
Compounds 4−13 have been additionally characterized by
IR and UV/vis spectroscopy. The IR spectra (cf. Figure S12 in
the SI) display characteristic strong bands of the Co(Hdmg)2
scaffold around 1565 cm−1 (νCN), 1240 cm−1 (νN−O), and 510
cm−1 (νCo−N), which are very similar to those observed in
related methyl cobaloximes [CoCH3(Hdmg)(L)].34 In the CF3
complexes 4−8, a strong band at ca. 1030 cm−1 can most likely
be assigned to a νC−F vibration. In the C2F5 complexes 9−11,
strong bands appear at approximately 1160, 1200, and 1300
cm−1 (each νC−F), and at 905 cm−1 (νC−C). Similar νC−F and
νC−C bands have been reported for [CoCF3(CO)4]35 and
[Co(C2F5)(CO)4],36 respectively. The UV/vis spectra of 4−13
are very similar, displaying a strong band at approximately 250
cm−1, which can be assigned to π transitions within the Hdmg−
ligands (Figure 2).37 Further unassigned shoulders of medium
intensity are present between 300 and 350 cm−1. In the visible
surprisingly different depending on the employed ligand L, and
the desired target products have only been obtained in the case
of [Co(Hdmg)2(NH3)2](o-IC6H4COO) (15) and [Co-
(Hdmg)2(PhNH2)2](o-IC6H4COO) (16). The reaction using
pyridine as a ligand led, even with excess of the latter, to the
ortho-iodobenzoic acid adduct [Co(Hdmg)2(Py)2][H(o-
IC6H4COO)2] (14·o-IC6H4COOH). In the case of methyl-
amine, only (o-IC6H4COO)(MeNH3) and H2dmg could be
isolated. When Co(o-IC6H4COO)2 and H2dmg were treated
with air in the absence of any ligand L, ortho-iodobenzoic acid
could be isolated as the only defined product from the reaction
mixture.
The perfluoroalkyl cobaloximes 4−13 are yellow to orange
solids, which are stable against air and moisture. The solubility
in methanol decreases with increasing size of the RF group,
while the solubility in nonpolar solvents like chloroform and
diethyl ether increases in the same direction (e.g., going from 4
to 9 to 12). Characteristic NMR parameters of 4−13 are
summarized in Table 1. In all compounds, the 1H NMR signals
D
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the Co−C bond in [Co(i-C4F7)(Hdmg)2(Py)] is even longer
due to the steric bulk of the i-C3F7 residue (Co−C 208.4(4)
pm).9 Inspection of the Co−N(Py) bond lengths in 4,8 9, 12,
and 13 allows a comparison of the trans influence of the
−
different RF ligands. The Co−Py separation in 13 (203.9(2)
pm) is virtually equal to that in 4 (204.3(3) pm),8 indicating a
very similar trans influence of the CF3− and CF2CF2Ph− ligand.
−
−
The trans influence of C2F5 and n-C3F7 seems to be weaker,
as the corresponding Co−N(Py) bonds are slightly shorter in 9
(201.3(3) pm) and 12 (201.9(3) pm), respectively. Nonethe-
−
less, all the mentioned RF ligands are considerably stronger
trans ligands than, e.g., pyridine. Thus, the Co−N(Py)
separations observed in the [Co(Hdmg)2(Py)2]+ complex
cation in 14·o-IC6H4COOH are much shorter at 195.7(2)
pm. On the other hand, all RF groups exert a weaker trans
−
influence than alkyl ligands like CH3 . For instance, the Co−
N(Py) bond length in [CoCH3(Hdmg)2(Py)] has been
observed at 206.9(3) pm.39 This is also confirmed by the
Co−O(MeOH) separation of 200.4(1) pm in 8, which is
considerably shorter than in an earlier reported alkyl
cobaloxime comprising a MeOH ligand (Co−O 208.19(5)
pm).40 As shown by previous work, cobaloximes with the i-
C3F7 ligand display a larger steric contribution to the trans
influence than corresponding i-C3H7 derivatives.10 The steric
bulk of the i-C3F7 ligand leads to bending of the Co(Hdmg)2
scaffold toward the trans ligand, which can be quantified by the
angle between the two dmg planes (≡ α), and by the
displacement of the Co atom from the plane defined by the
four dmg N atoms (≡ δ). Negative values of α and δ indicate a
bending of the two Hdmg ligands toward the L ligand (e.g.,
[Co(i-C3F7)(Hdmg)2(Py)]: α = −10.3°, δ = −7.5 pm), while
positive values mean bending away from the L ligand (e.g.,
[Co(i-C3H7)(Hdmg)2(Py)]: α = +4.0°, δ = +2.0 pm).10 For
complexes 4−13, α values from −0.6(2)° to −5.3(4)° and δ
values from −0.2(4) to −6.6(4) pm have been observed (Table
3). Consequently, a relatively small, but mostly significant,
steric trans influence of the RF ligand can be inferred. The
magnitude of this contribution is similar for the different RF
groups. This can be expected since all of these groups comprise
a CF2 moiety bonded to the Co atom. The C−F bonds in 4−8
cover a range of 131.4(8)−136.3(2) pm, which fits the
reference value of a C−F single bond of 134 pm.41 However,
the C−F bonds within the α-CF2 moiety in 9−13 are
Figure 2. UV/vis spectra of complexes 4−8 in methanol solution.
wavelength range of the spectrum, only a very weak absorption
around 435 nm has been observed. This is almost identical to
the visible-light absorption in related nonfluorinated complexes
(e.g., maximum at 441 nm for [CoCH3(Hdmg)2(Py)] in
methanol),37 where it has been assigned to a CT(Co→C)
transition.37,38 The spectra of the pyridine complexes 9, 12, and
13 are virtually identical to that of 5, and therefore the
absorbance properties are not significantly influenced by
−
substitutions within the RF ligand (cf. Figure S41 in the SI).
Crystal Structures. All new perfluoroalkyl complexes 5−13
and the ortho-iodobenzoate salts 14−16 have been charac-
terized by single-crystal X-ray diffraction. The crystal structure
of 4 has already been determined by Toscano et al. in 1989.8 In
the crystalline state, all cobaloximes 4−13 exist as monomeric
molecules with an octahedral environment of the Co atom
(Figure 3). Characteristic bond lengths are summarized in
Table 2. In the CF3 complexes 4−8, the Co−C distance ranges
from 193.0(2) pm in 8 to 195.3(4) pm 5. This finding meets
the expectation that the Co−C bond is significantly influenced
by the ligand L trans to CF3, and is particularly short in the case
of weak trans ligand MeOH in 8. In 9−13 comprising longer RF
chains, the Co−C bond is significantly longer at 197.2(4)−
200.0(2) pm. These values are comparable with that observed
in [Co(C2F4H)(Hdmg)2(Py)] (Co−C 199.8(6) pm),11 while
Figure 3. Molecular structures of 5−13 in the crystal (H atoms attached to C atoms omitted for clarity).
E
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Table 2. Selected Interatomic Distances (pm) in 4−13
compound
Co−C
194.9(4)
Co−L
204.3(3)
C−F
48
131.4(8)−133.8(6)
a
5
195.3(4)
201.4(3)
−
6
194.4(2)
202.8(2)
134.7(2)−136.3(2)
135.5(3)−136.1(3)
134.3(2)−135.4(2)
7
193.2(2)
209.0(2)
8
193.0(2)
200.4(1)
b
9
199.9(4)
201.3(3)
138.1(5)
b
10
11
12
13
197.2(4)−198.5(5)
197.7(2)
199.5(4)−200.6(3)
203.5(2)
136.2(5)−143.3(5)
b
136.6(2), 138.6(2)
137.1(5), 142.8(6)
137.5(2), 138.2(2)
b
199.9(5)
201.9(3)
b
200.0(2)
203.9(2)
a
b
Values not reliable due to CF3 disorder. α-CF2 moiety.
a
Table 3. Selected Parameters of the Coordination Octahedron around the Co Atom in 4−13
compound
C−Co−L/deg
177.4(2)
α/deg
δ/pm
48
−0.6(2)
−2.3(1)
−1.2(1)
−2.8(1)
−3.6(1)
−3.7(1)
−0.2(4)
−2.9(4)
−1.4(2)
−3.3(2)
−3.8(2)
−3.4(4)
5
179.7(1)
6
176.57(7)
179.0(1)
7
8
177.51(7)
175.1(1)
9
10
11
12
13
175.3(2)−176.1(2)
179.75(7)
174.1(2)
−3.7(1) to −5.3(1)
−3.2(1)
−2.1(1)
−4.1(5) to −6.6(1)
−3.9(2)
−2.7(4)
174.74(6)
−2.3(1)
−2.2(2)
Negative values of α and δ indicate bending of the Co(hdmg)2 scaffold towards L.10
a
significantly longer at 136.2(5)−143.3(5) pm, and conse-
quently, these C−F bonds can be expected to be more reactive.
The observed values agree with those reported for other CoIII
complexes with RF− ligands, e.g., [CoCp(X)(C2F5)(PR3)] (X =
F, CF3; C−F(α) 136.7(2)−139.6(6) pm).42
Thermal Decomposition Studies. Compounds 4−13
have been investigated by thermogravimetric and differential
thermo analysis (TG/DTA), and some volatile thermolysis
products have been identified by mass spectrometry.
Complexes 4−7 and 9−13 were found to decompose under
an inert atmosphere of nitrogen at 231−256 °C (Table 4).
While the crystal structures of the pyridine complexes 4,8 9,
12, and 13 do not feature any specific intermolecular
interactions, the molecules are aggregated to supramolecular
assemblies by hydrogen bonding in all other cases. For instance,
in 7, dimers by N−H···O connections between MeNH2 N-H
moieties and Hdmg O atoms were observed (Figure 4). Similar
a
Table 4. Thermogravimetric Analysis of Compounds 4−13
Tdec/°C
Tend/°C
mass loss/%
calcd/%
4
5
6
7
8
250
256
251
245
170
237
246
246
236
249
231
619
631
653
671
207
638
651
648
660
622
678
61
59
59
58
9
60
53
55
61
9 (−MeOH)
64 (total)
68
64
63
56
71
66
9
10
11
12
13
64
59
60
67
68
a
Total mass loss between Tdec and Tend given; calcd for release of RF,
L, C4H6, and 2 NO.
Figure 4. Supramolecular dimer of [Co(CF3)(Hdmg)2(MeNH2)] (6)
in the crystal formed by N−H···O hydrogen bonds, and further
aggregation thereof through N−H···F interactions. N···O 289.2(2)
pm, N···F 321.6(2) pm.
Therefore, the decomposition temperatures are similar as those
reported for [CoCH3(Hdmg)2(Py)] (Tdec = 246−250 °C), and
higher than for complexes with longer alkyl moieties, e.g.,
[Co(C2H5)(Hdmg)2(Py)] (Tdec = 196−208 °C).43 Just like for
the non-fluorinated analogues, both axial ligands L and RF are
released in this range, as indicated by two exothermic processes
detected by DTA (cf. Figures S30−S39 in the SI). The RF
ligand seems to be released at first, as it was detected by MS
prior to the L ligand (e.g., CF3, m/z = 69 and Py, m/z = 79 for
dimers exist in 8 and 11 (cf. Figures S20 and S24 in the SI),
while the NH3 complex 5 exhibits a polymeric chain structure
(cf. Figure S14 in the SI). In cases where not all N-H donors
are involved in N−H···O bonding (5, 6, and 11), the structures
are further aggregated by N−H···F interactions.
F
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4). While, in the case of the alkyl cobaloximes, alkanes are
usually formed,1,43 the corresponding perfluoroalkanes have not
been detected. We surmise that decomposition is initiated by
transfer of the RF group to the Hdmg− ligand, followed by
release of a perfluoroalkylated fragment of the latter. This
hypothesis is supported by the finding that decomposition of
the Hdmg ligands begins simultaneously with RF release, and is
not completed until ca. 650 °C. In contrast, the Co(Hdmg)2
scaffold shows a sharp decomposition around 290 °C in the
case of the alkyl complexes.43 For 4−13, butadiene (m/z = 54),
MeCN (m/z = 41), and N2O (m/z = 44) were identified by
MS among several decomposition products of the Hdmg−
ligands. The overall mass loss between 230 and ca. 650 °C
corresponds to liberation of L, RF, and fragments of the
Co(Hdmg)2 scaffold with a molar mass of approximately 115
g/mol. Table 4 displays the calculated mass loss for the release
of 1 equiv of butadiene and 2 equiv of NO, which agrees
relatively well with the experimental values. However, the
detection of MeCN indicates that there is more than one
relevant decomposition pathway of the Co(Hdmg)2 core.
Moreover, detection of N2O instead of NO indicates
contribution of the N2 atmosphere to the decomposition
processes. The release pathway of the RF group remains elusive,
since only the RF group itself, but no perfluoroalkylated
molecule, could be detected by mass spectrometry. The MeOH
complex 8 behaves differently than the other compounds,
showing clean MeOH release already at 170 °C. Further
degradation was similar as for the other complexes.
leads to increasing side reactions, including formation of free
fluoride (Figure 5; cf. Figures S45−S48 in the SI).
Photolysis Experiments. Not only the thermal decom-
position, but also the photochemical reactivity of 4−13 is
different from that of related non-fluorinated alkyl cobaloximes.
The photolysis can easily be monitored by 19F NMR
spectroscopy (cf. Figures S45−S51 in the SI), while UV/vis
spectroscopy is less suited due to the similarity of the spectra
before and after irradiation (cf. Figures S42−S44 in the SI).
While alkyl cobaloximes tend to homolytic Co−C bond
cleavage mediated by visible light,1,44,45 the trifluoromethyl
analogues 4−8 show no significant decomposition upon
exposure to blue light in the solid state and even in chloroform
solution. The results are very different when irradiation is
carried out in methanol solution. In the case of 4−7, a fast
exchange of the nitrogen ligand to solvent methanol takes
place, thus providing complex 8 in each case (Scheme 5a). The
ligand exchange runs toward an equilibrium with 50−70% of 8
depending on the leaving ligand L, and prolonged irradiation
Figure 5. Degradation of complexes 4−7 upon irradiation (a),
concentration of MeOH complex 8 vs irradiation time (b).
However, only very small amounts of CHF3 have been
detected upon prolonged irradation, demonstrating a high
resistance of the Co−C bond against photolysis. Under
ambient conditions, the ligand exchange is slow, and only
minor amounts of 8 (<5 mol %) have been detected in
methanol solutions of 4−7 upon standing under “normal”
artificial light for several days. Consequently, the photolysis
behavior is entirely different than reported for complexes with
−
CH3 ligands, where Co-C homolysis is strongly favored in
protic media.45 The ligand exchange in 4−7 is presumably
induced by photolytic cleavage of the Co−L bond, leading to a
reactive [CoCF3(Hdmg)2] intermediate with a penta-coordi-
nated Co atom. A similar dissociation is documented for non-
fluorinated cobaloximes to occur in the dark, leading to
binuclear [CoR(Hdmg)2]2 species in noncoordinating sol-
vents.3
−
Scheme 5. Photoinduced Ligand Exchange in the CF3
−
Complexes 4−7 (a), Defluorination of RF Ligands at the
Example of the Pyridine Complexes 9, 12, and 13 (b)
For 9−13 comprising perfluoroalkyl chains longer than CF3,
the results depend even more on the photolysis conditions than
described for 4−7. In chloroform solution, no reaction is
observed when irradiation is performed under an inert
atmosphere of argon (Figure 6a), while gradual undefined
decomposition takes place in the presence of air (Figure 6b). In
the latter case, a slight line broadening of the 19F NMR signals
indicates the formation of paramagnetic CoII species. We
surmise that photolytically formed RF radicals are readily
quenched by O2, which prevents recombination of CoII/RF
radical pairs. A similar mediation of photolysis by oxygen has
been reported for non-fluorinated complexes.44 In methanol,
G
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intermediate. This perfluoroalcohol is unstable and decomposes
readily under HF elimination to an acyl fluoride RF′-COF.46
The latter is known to react readily with alcohols47 and can
therefore be expected to be transformed immediately by
MeOH to the observed product RF′-COOMe. In the case of
13, the final reaction step was slow enough to detect the acyl
fluoride intermediate by 19F NMR spectroscopy (PhCF2COF,
δF = 15.4 ppm in MeOH; cf. Figure S51 in the SI).
The formation of an RF radical as the initial photolysis
product of 4−13 has further been corroborated by a radical
trapping experiment. Thus, performing irradiation in the
presence of excess 2,2,6,6-tetramethylpiperidyl-N-oxide
(TEMPO) as a radical scavenger leads to formation of the
corresponding TEMPO-RF adduct, which is easily identified by
its 19F NMR shift.48 Thereby, the amount of this product
formed within a defined irradiation time is a qualitative measure
of how readily the Co−C bond is cleaved. Thus, only a minor
amount of TEMPO-CF3 (δF = −55.3 ppm in CHCl3) was
observed from 4 after 60 min in chloroform under exclusion of
air (cf. Figure S53 in the SI), while TEMPO-C2F5 (δF = −83.8
(CF2) and −84.4 (CF3) ppm in CHCl3) is formed from 9 in
high yield under the same conditions (cf. Figure S54 in the SI).
Figure 6. 19F NMR spectra of 9 after 60 min of irradiation under
various conditions (Co = starting complex, Co′ = tentative MeOH
complex, E = CF3COOMe, H = CF3CF2H).
CONCLUSIONS
■
9−13 seem to undergo a similar ligand exchange as described
for 4−7, but the corresponding MeOH complexes are
obviously less stable and we did not succeed in isolating any
from the reaction mixtures. Moreover, significant evolution of
the corresponding alkane RFH was observed, when irradiation
was carried out under anaerobic conditions (Figure 6c). This
results most likely from hydrogen abstraction by RF radicals,
giving evidence for a more facile Co−C homolysis as compared
to the CF3 complexes 4−8. For related non-fluorinated
cobaloximes, it has been found that this decomposition
pathway is favored in protic media like alcohols.45 When
photolysis is performed in methanol-D4, the corresponding
deutero-alkane RFD was obtained, thus demonstrating that the
hydrogen atom is not abstracted intramolecularly from a dmg
methyl group (cf. Figure S52 in the SI). The photolysis of 9−
13 in methanol led to entirely different products when the same
is carried out in the presence of air. In this case, a perfluorinated
methyl ester and 2 equiv of free fluoride have been detected as
the main products, while only minor amounts of the alkane
RFH were obtained (Figure 6d, and Scheme 5b; cf. Figures
S49−S51 in the SI). Reference experiments in wet methanol
under exclusion of oxygen and in dry methanol under
treatment with dry air revealed conclusively that the ester
formation is mediated by O2 and not by H2O. A plausible
mechanism is outlined in Scheme 6. This reaction is most likely
initiated by oxidation of an RF radical with O2 to RF-O·,
followed by hydrogen abstraction to give an RF-OH
The oxidative perfluoroalkylation of cobaloximes(II) by
hypervalent iodanes is both a unique model reaction for radical
perfluoroalkylation of metal complexes and a convenient
preparation method for perfluoroalkyl cobaloximes(III). This
reaction is particularly valuable for the synthesis of complexes
with RF− ligands larger than CF3 , which have been obtained in
−
−
significantly higher yields than those containing CF3 . More-
over, this method opens a pathway to complexes which are
additionally functionalized within the RF residue, as shown by
complex 13 bearing a CF2CF2Ph group. A radical mechanism is
supported by the formation of the alkane RFH as the major side
product, which arises from hydrogen abstraction of RF radicals
from the solvent or any other ligand. Since it is well-understood
that the trifluoromethyl acid reagent 1a is activated by
coordination to a Lewis-acidic metal center,18 we assume that
the same plays also a key role in the reaction with
cobaloximes(II). Such a pre-organization of the reactants
facilitates an electron transfer from the CoII center to the
iodane, resulting in the formation of a perfluoroalkyl radical
(Scheme 7a). The latter is expected to react readily with
another equiv of the CoII precursor to afford the target CoIII-RF
complex (Scheme 7b). While the velocity of the first step
Scheme 7. Postulated Key Steps in the Reaction between
Cobaloximes(II) and Perfluoroalkyl Iodanes: Cobalt-
Mediated Formation of an RF Radical (a), Oxidation of a
CoII Complex by the Latter (b)
Scheme 6. Assumed Mechanism of Photolytic α-
Defluorination in 9−13
H
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51
well as Co(o-IC6H4-COO)2(H2O)2 were prepared following
literature procedures. Commercially available dry acetonitrile for the
preparation of 1a−e, and all other materials were used as received.
Unless otherwise noted, the purity of all new compounds reported in
this work has been assessed by elemental analyses (C, H, N).
defines the overall reaction rate (i.e., the consumption of iodane
reagent), the rate of the second step determines the observed
CoIII-RF/RF-H ratio (due to increasing side reactions of the RF
radical with decreasing reaction rate). It can be expected that
primarily the first step is influenced by the ligand L, as it
determines the redox potential of the CoII precursor. However,
the second step seems to also depend on L to some extent,
since different CoIII-RF/RF-H ratios have been observed for L =
Py, NH3, MeNH2, and PhNH2 (cf. Table S1 in the SI). The
CoIII-RF/RF-H ratio might be further improved by the use of a
bidentate L ligand, which supports pre-organization of two
cobalt centers. The suggested mechanistic model also agrees
with the higher yields achieved for 9−13 as compared to 4−8.
The corresponding RF radicals are less reactive than CF3
radicals, and therefore, side reactions such as hydrogen
abstraction are of less importance. Theoretical and exper-
imental studies on the reactive intermediates will be the subject
of future research.
NMR Spectroscopy. All NMR spectra were measured at ambient
temperature (298(2) K). 1H, 13C, and 19F NMR spectra were recorded
on a Bruker Avance III HD Nanobay 300 spectrometer (1H: 300.13
MHz; 13C: 75.47 MHz; 19F: 282.40 MHz). Where necessary, COSY
and HSQC experiments have been carried out for unambiguous
assignment of the 1H and 13C signals. 1H NMR shifts are referenced to
1
the residual H signal of the deuterated solvent (CHCl3: δH = 7.260
ppm; CD2HOD: δH = 3.310 ppm), 13C NMR shifts to the deuterated
solvent itself (CDCl3: δC = 77.16 ppm; CD3OD: δC = 49.00 ppm). 19
F
NMR shifts are referenced to neat CFCl3 (δC = 0.00 ppm). 59Co NMR
spectra were acquired with a Bruker DPX-400 machine (1H: 401.65
MHz; 59Co: 95.30 MHz), and the shifts are referenced to 1.0 mol/L
K3[Co(CN)6] in D2O (δCo = 0 ppm). Unless otherwise noted, the 13C,
19F, and 59Co NMR spectra were measured H-decoupled.
1
Single-Crystal X-ray Diffraction. Single-crystal X-ray data for the
compounds reported in this work were collected on a Bruker Smart
Apex II diffractometer52 equipped with an Apex II CCD detector,
using graphite-monochromated Mo−Kα radiation, at T = 100(2) K.
Absorption correction of the intensity data was carried out with the
multi-scan method.53 The structures were solved by intrinsic phasing
methods (SHELXT-2014/554) and refined by full matrix least-squares
methods on F2 (SHELXL-2014/755), using Olex 1.2.56 For
compounds 9 and 12, the Flack parameter was determined using
[(I+) − (I−)]/[(I+) + (I−)] quotients.57
Miscellaneous Characterization Methods. IR spectra were
recorded with a Thermo Fischer Scientific Nicolet 6700 FT-IR
spectrometer equipped with a PIKE technologies GladiATR unit.
Band intensities are given as strong (s), medium (m), weak (w), or
shoulder (sh). Elemental analyses were performed with a LECO
TruSpec Micro apparatus. UV/vis spectra were recorded on a
PerkinElmer Lambda 750 UV/vis/NIR spectrometer using 10 mm
quartz cuvettes. For comparison purposes, the strongest band
maximum around 250 nm was set to an absorption value of 1.00.
GC/MS analyses were carried out with an Agilent Technologies
7890A GC/5975C VL MSD system.
Thermal Analyses. Simultaneous thermal analyses (TG/DTA)
were carried out on a Netzsch STA 449C thermobalance. Therefore,
3−5 mg samples were heated from r.t. to 1000 °C with a constant
heating rate of 10 K/min, using Al2O3 crucibles and a gas flow of 40
mL/min nitrogen as an inert atmosphere. For identification of
thermolysis products by MS, see the SI.
Photolysis Experiments. An NMR tube containing 0.5 mL of an
approximately 25 mmol/L solution of the appropriate complex 4−13
in CHCl3, MeOH, or CD3OD was placed into a photoreactor
equipped with blue LEDs (λmax ≈ 445 nm, w1/2 ≈ 20 nm, total output
power 275 W; cf. Figures S40 and S41 in the SI). The sample
temperature was maintained below 40 °C by air cooling. Degradation
of the samples was monitored by 19F NMR spectroscopy. For CHCl3
and MeOH samples, an external C6D6 sample was used for Field Lock
and Shim. For details on modifications of the photolysis conditions, a
radical trapping experiment with TEMPO, and characterization of
photolysis products by MS, see the SI.
The properties of the perfluoroalkylated cobaloximes(III) are
not only very different from those of the non-fluorinated
analogues, but there is also a significant difference between
trifluoromethyl complexes and those with longer RF chains.
−
The Co−C bond strength rises from CH3− going to higher RF
−
going to CF3 , as shown by the crystal structure analyses and
confirmed by the photochemical decomposition studies. The
latter demonstrated that not the Co−C bond, but the Co−L
bond in 4−13 is most readily cleaved upon excitation with
visible light. Among the trifluoromethyl complexes 4−8, the
MeOH complex 8 is of particular stability, which may be traced
back to a stabilization of weak trans ligands by the
trifluoromethyl ligand. To understand why the ligand exchange
in the CF3 complexes is enabled by photoexcitation,
investigation of the electronic structure of the complexes by
means of theoretical studies is necessary. On the other hand,
the MeOH ligand in 8 is readily liberated thermally. For the
complexes with longer RF groups (9−13), the Co−C bond is
more readily cleaved upon photoexcitation, while thermal
cleavage was observed at similar temperatures as for 4−8. In the
course of our ongoing investigations, we will carry out
computational studies on different [CoRF(Hdmg)2(L)] sys-
tems, to gain a more detailed insight into the observed
reactivity of these systems. Moreover, we will evaluate the
suitability of the complexes for new (photochemical)
perfluoroalkylations. Particularly in the case of the very stable
CF3 complexes, L ligands exerting a strong trans influence can
be useful to increase the reactivity of the Co−C bond. For
instance, a MeCN ligand trans to CF3 can enable radical
trifluoromethylation of arenes, as it has been shown in a very
recent contribution.25 In future research, the here reported
photochemical and thermal Co−L cleavage reactions can be
useful tools for the synthesis of hitherto inaccessible complexes
with the desired reactivity profile.
Preparation of 1-(2-Phenyl-1,1,2,2-tetrafluoroethyl)-1,2-
benziodoxol-3(1H)-one (1e). Me3SiCF2CF2Ph. PhCF2CF2Br was
prepared following a literature protocol.58 5.00 g (19.5 mmol) thereof
was, according to a published procedure,21 dissolved in THF (60 mL),
and Me3SiCl (7.4 mL, 58.4 mmol) was added at −78 °C. A solution of
iPrMgCl·LiCl in THF (1.3 mol/L, 18.0 mL, 23.3 mmol) was added
dropwise, and subsequently stirred at −78 °C for 1 h. The brownish
mixture was allowed to warm to r.t., and n-pentane (120 mL) and
water (120 mL) were added. The organic phase was separated, and the
water phase was extracted with n-pentane (120 mL) and then
discarded. The combined organic phases were washed with water (2 ×
150 mL), dried over Na2SO4, and filtered. The clear filtrate was
evaporated to dryness on a rotary evaporator at 40 °C and ≥50 mbar,
EXPERIMENTAL SECTION
■
General. All procedures including air- or moisture-sensitive
substances were carried out under an inert atmosphere of argon
using standard Schlenk techniques. Iodane reagents 1a,49 1b,50 1c,19
and 1d20 were prepared by published procedures. All operations with
CoII compounds were performed under rigorous exclusion of oxygen,
and the workup of the CoIII products was carried out in air. Methanol,
ethanol, THF, acetone, pyridine, and aniline used in the reactions were
freshly distilled under argon prior to use. Aqueous solutions of
ammonia and methylamine were freed from oxygen by freeze-
pumping. [Co(Hdmg)2(H2O)2] (2) and [Co(Hdmg)2(Py)2] (3)26 as
I
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revealing almost pure (according to 1H NMR spectrum)
Me3SiCF2CF2Ph as pale yellowish oil. The product was stored at
1370w, 1241s, 1230s, 1154w, 1092m, 1059s, 1032s, 1019sh, 1000sh,
977m, 956w, 882m, 765s, 740m, 710m, 700s, 650w, 641m, 583w, 511s,
457m, 427s cm−1.
1
−20 °C. Yield: 4.6 g (94%). H NMR (CDCl3): 0.30 (s, 9H; SiCH3),
7.45 (m, 1H; p-CH Ph), 7.47 (m, 2H; m-CH Ph), 7.55 (m, 2H; o-CH
[CoCF3(Hdmg)2(NH3)] (5). Oxygen-free aqueous ammonia solution
(0.71 mL, 25 wt %, 9.5 mmol) was added to a suspension of complex 2
(2.05 g, 6.3 mmol) in methanol (30 mL), resulting in formation of a
dark precipitate. After stirring at r.t. for 30 min, the suspension was
cooled to 0 °C and reagent 1a (0.95 g, 3.0 mmol) was added. The
deep red-brown mixture changed to yellow-brown within 10 min. After
1 h at 0 °C, stirring was continued at r.t. for 3 h. The suspension was
then filtered, the residue was rinsed with methanol (10 mL), and the
collected methanol solutions were evaporated to dryness on a rotary
evaporator at 40 °C. The residue was extracted with ethyl acetate (60
mL), and filtered, and the residue (which contained the ortho-
iodobenzoate salt 15 as the major component) was rinsed with further
ethyl acetate (2 × 10 mL). The collected filtrates were evaporated to
dryness, and the residue was washed with diethyl ether (2 × 20 mL)
and dried in vacuo. Yield: 0.45 g (40%). Bright yellow, crystalline solid,
soluble in methanol, acetone, ethyl acetate, and water, insoluble in
chloroform and diethyl ether. Dec. 256 °C. Anal. Calcd for
C9H17CoF3N5O4 (M = 375.19 g mol−1): C 28.81, H 4.57, N
18.67%; Found: C 28.68, H 4.72, N 18.38%. 1H NMR (CD3OD): 2.26
1
Ph) ppm. 13C NMR (CDCl3): −1.8 (s; SiCH3), 119.3 (t, JC,F = 246
Hz; CF2Ph), 122.5 (t, 1JC,F = 270 Hz; CF2Si), 127.0 (t, 3JC,F = 6.6 Hz;
2
o-CH Ph), 128.2 (s; m-CH Ph), 130.7 (s; p-CH Ph), 131.4 (t, JC,F
=
25.7 Hz; i-C Ph) ppm. 19F NMR (CDCl3): −107.1 (s+d, JF,C = 245
Hz, 2F; PhCF2), −125.2 (s+d+d, JF,C = 271 Hz, JF,Si = 31 Hz, 2F;
Me3SiCF2) ppm.
1
1
2
Reagent 1e. Following a published procedure,21 1-chloro-1,2-
benziodoxol-3(1H)-one (895 mg, 3.2 mmol) and dry potassium
fluoride (870 mg, 15.0 mmol) were suspended in acetonitrile (8 mL),
and the mixture was vigorously stirred at 65 °C for 4 h. The resulting
thick white suspension was filtered, and the residue was rinsed with
further acetonitrile (2 mL). The filtrate was cooled to 0 °C, and
solutions of crude Me3SiCF2CF2Ph (250 mg, 1.0 mmol) in acetonitrile
(2.5 mL), and tetrabutylammonium difluorotriphenylsilicate (27 mg,
0.05 mmol) in acetonitrile (1.5 mL) were added simultaneously within
30 min. The mixture was stirred for 1 h at 0 °C, and stirring was
continued at r.t. overnight. Celite (approximately 1 g) was added, and
the suspension was then evaporated to dryness in vacuo. The product
was isolated by automated flash column chromatography, using an n-
hexane/ethyl acetate gradient, and stored at −20 °C. Yield: 218 mg
(53%). Colorless crystals, soluble in acetonitrile, chloroform and
methanol, poorly soluble in alkanes. Anal. Calcd for C15H9F4IO2 (M =
(s, 12H; CH3 dmg), 2.52 (s br, 3H; NH3) ppm; OH not observed. 13
C
NMR (CD3OD): 12.2 (s; CH3 dmg), 153.4 (s; CNO) ppm; CF3
not observed. 19F NMR (CD3OD): −35.1 (s+d, 1JF,C = 376 Hz) ppm.
59Co NMR (CD3OD): 3856 (s, w1/2 = 3.89 kHz) ppm. IR: 3356w,
3294w, 3215m, 3154m, 2926w, 1637m, 1569s, 1440m, 1371m, 1278m,
1240s, 1193sh, 1061s, 1013s, 1000sh, 976s, 876m, 815w, 770sh, 741s,
710m, 595w, 584w, 510s, 437m, 429m, 416s, 406m cm−1. Single
crystals of 5 suitable for X-ray structure analysis were obtained by slow
evaporation of a methanol solution at r.t. Recrystallization from wet
ethyl acetate afforded crystals of a hydrate 5·H2O.
1
424.13 g mol−1): C 42.48, H 2.14%; Found: C 42.52, H 2.21%. H
NMR (CDCl3): 0.30 (s, 9H; CH3), 7.53−7.79 (6 × m, 8H; 3-;4-;5-CH
and o-;m-;p-CH Ph), 8.46 (m, 1H; 6-CH) ppm. 13C NMR (CDCl3):
114.7 (s; C-I), 126.9 (t, 3JC,F = 6.3 Hz; o-CH Ph), 128.2 (t, 4JC,F = 5.7
Hz; 3-CH), 129.2 (s; m-CH Ph), 131.6 (s; 4-CH), 132.6 (s; p-CH Ph),
132.8 (s; C-CO), 134.0 (s; 6-CH), 135.1 (s; 5-CH), 166.0 (s; C
1
O) ppm. 19F NMR (CDCl3): −83.6 (s+d, JF,C = 335 Hz, 2F; ICF2),
[CoCF3(Hdmg)2(MeNH2)] (6). Oxygen-free aqueous MeNH2 sol-
ution (0.81 mL, 40 wt %, 9.5 mmol) was added dropwise to a
suspension of complex 2 (2.05 g, 6.3 mmol) in methanol (30 mL),
resulting in a color change to deep red-brown and formation of a
crystalline precipitate. After stirring at r.t. for 30 min, the suspension
was cooled to 0 °C and reagent 1a (0.95 g, 3.0 mmol) was added. The
mixture changed to yellow-orange within 10 min. After 1 h at 0 °C,
stirring was continued at r.t. for 1 h. The solution was then freed from
a minor amount of pink precipitate (tentatively CoF2) by filtration, the
residue was rinsed with methanol (5 mL), and the collected filtrates
were evaporated to dryness on a rotary evaporator at 40 °C. The deep
orange, oily residue solidified immediately to yellow sheets upon
cooling to r.t. The crude product was thoroughly extracted with ice
water (20 mL), then filtered off and washed with further ice water (2 ×
10 mL). Extraction was repeated with diethyl ether* (50 mL), then
filtered off, washed with further diethyl ether (2 × 20 mL), and dried
in vacuo. (*The combined diethyl ether washings contained H2dmg as
the major component.) Yield: 0.36 g (31%). Bright yellow,
microcrystalline plates, soluble in methanol, acetone, and ethyl acetate,
poorly soluble in water and insoluble in chloroform and diethyl ether.
Dec. 251 °C. Anal. Calcd for C10H19CoF3N5O4 (M = 389.22 g mol−1):
1
−104.4 (s+d, JF,C = 250 Hz, 2F; PhCF2) ppm.
19F NMR Reaction Screening. The appropriate CoII complex 2 or
3 (0.5−2.0 mmol) was suspended in methanol (10 mL), and the
corresponding ligand L (1.57 equiv relating to CoII complex) was
added. After stirring for 1 h at r.t., the mixture was cooled to 0 °C and
reagent 1a or 1b (0.5 mmol) was added as a solid. The mixture was
stirred for 1 h at 0 °C and for 15 h at r.t. Subsequently, any precipitate
was allowed to settle down, and a 0.5 mL sample of the solution was
subjected to 19F NMR spectroscopy, using an external C6D6 sample
for Field Lock and Shim. The product contribution observed for
different reaction conditions are listed in Table S1 in the SI.
Preparation of Cobalt Complexes 4−16. [CoCF3(Hdmg)2(Py)]
(4). Reagent 1a (0.95 g, 3.0 mmol) was added to a suspension of
complex 3 (2.82 g, 6.3 mmol) in methanol (30 mL) at 0 °C and then
stirred for 1 h. Stirring was continued for 3 h at r.t., and the resulting
thick yellow-brown suspension was subsequently evaporated to
dryness on a rotary evaporator at 40 °C. The residue was extracted
with chloroform (30 mL), and filtered, and the residue was rinsed with
further chloroform (10 mL). The combined filtrates were evaporated
to dryness, and the orange-brown residue was extracted with ethyl
acetate (60 mL). The suspension was filtered, and the residue (which
contained the ortho-iodobenzoate salt 14 as the major component)
was rinsed with further ethyl acetate (2 × 10 mL). The collected
filtrates were evaporated to dryness, and the residue was washed with
−20 °C cold methanol (2 × 5 mL) and dried in vacuo. Yield: 0.43 g
(33%). Yellow, microcrystalline solid, soluble in methanol, acetone,
chloroform, and ethyl acetate, poorly soluble in water and diethyl
ether. Dec. 250 °C. Anal. Calcd for C14H19CoF3N5O4 (M = 437.26 g
mol−1): C 38.46, H 4.38, N 16.02%; Found: C 38.17, H 4.59, N
1
C 30.86, H 4.92, N 17.99%; Found: C 30.92, H 4.99, N 17.81%. H
NMR (CD3OD): 1.89 (t, 3JH,H = 6.5 Hz, 3H; CH3NH2) 2.27 (s, 12H;
CH3 dmg), 3.08 (s br, 2H; NH2) ppm; OH not observed. 13C NMR
(CD3OD): 12.2 (s; CH3 dmg), 28.3 (s; CH3NH2), 153.4 (s; CNO)
ppm; CF3 not observed. 19F NMR (CD3OD): −34.3 (s+d, 1JF,C = 379
Hz) ppm. 59Co NMR (CD3OD): 3839 (s, w1/2 = 3.42 kHz) ppm. IR:
3290w, 3235w, 3159m, 3011w, 2992w, 2956w, 2926w, 2899w, 1608w,
1570s, 1470w, 1460w, 1434w, 1421w, 1364m, 1238s, 1195sh, 1157w,
1093m, 1040s, 1029s, 1014s, 975s, 880s, 794m, 732s, 709s, 629s,
584m, 510s, 431s, 418m, 406m cm−1. Single-crystals of 6 suitable for
X-ray structure analysis were obtained by slow evaporation of a
methanol solution at r.t.
1
15.84%. H NMR (CDCl3): 2.19 (s, 12H; CH3 dmg), 7.34 (m, 2H;
3,5-CH Py), 7.77 (m, 1H; 4-CH Py), 8.52 (m, 2H; 2,6-CH Py) ppm;
OH not observed. 13C NMR (CDCl3): 12.4 (s; CH3 dmg), 125.7 (s;
3,5-CH Py), 138.6 (s; 4-CH Py), 150.0 (s; 2,6-CH Py), 151.5 (s; C
[CoCF3(Hdmg)2(PhNH2)] (7). Aniline (0.86 mL, 9.45 mmol) was
added to a suspension of complex 2 (2.05 g, 6.3 mmol) in methanol
(30 mL), resulting in formation of a microcrystalline precipitate. The
mixture is stirred for 1 h at r.t., followed by addition of reagent 1a
(0.95 g, 3.0 mmol) at 0 °C. The mixture was allowed to warm to r.t.
NO) ppm; CF3 not observed. 19F NMR (CDCl3): −31.8 (s+d, 1JF,C
=
379 Hz) ppm. 59Co NMR (CDCl3): 3828 (s, w1/2 = 3.42 kHz) ppm.
59Co NMR (CD3OD): 3931 (s, w1/2 = 2.28 kHz) ppm. IR: 3124w,
3059w, 2962w, 2921w, 1609w, 1562m, 1495w, 1450m, 1428sh,
J
DOI: 10.1021/acs.organomet.7b00892
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
within 1 h, and stirring was continued overnight. The dark amorphous
matter was filtered off, and rinsed with methanol (2 × 10 mL), and the
combined methanol solutions were reduced to dryness on a rotary
evaporator at 40 °C. The remaining dark oil was treated with water
(50 mL) and vigorously stirred overnight. During this time, the dark
material has completely dissolved and a microcrystalline yellow solid
remained. The latter was filtered off, extracted with acetone (40 mL),
and filtered. The orange-brown residue (which contained the ortho-
iodobenzoate salt 16 as the major component) was rinsed with further
acetone (10 mL), and the combined filtrates were evaporated almost
to dryness. Addition of water (20 mL) led to crystallization of the
product as a hydrate 7·H2O, which was filtered off, and washed with
water (2 × 15 mL) and diethyl ether (2 × 20 mL). The crystal water
was released upon drying in vacuo. Yield: 0.83 g (61%). Yellow,
microcrystalline solid, soluble in methanol, acetone, ethyl acetate, and
chloroform, poorly soluble in water and diethyl ether. Dec. 245 °C.
Anal. Calcd for C15H21CoF3N5O4 (M = 451.29 g mol−1): C 39.92, H
4.69, N 15.52%; Found*: C 40.88, H 5.19, N 15.00%. (*The relatively
large differences can be traced back to minor contamination of the
Py), 138.6 (s; 4-CH Py), 149.8 (s; 2,6-CH Py), 152.3 (s; CNO)
1
ppm; CF2, CF3 not observed. 19F NMR (CDCl3): −81.3 (s+d, JF,C
=
289 Hz, 3F; CF3), −99.0 (s+d br, 1JF,C = 320 Hz, 2F; CF2) ppm. 59Co
NMR (CDCl3): 4040 (s, w1/2 = 5.03 kHz) ppm. 59Co NMR
(CD3OD): 4156 (s, w1/2 = 2.94 kHz) ppm. IR: 3098w, 2919w, 1612w,
1563s, 1500w, 1456m, 1374m, 1302s, 1272w, 1238s, 1202s, 1158s,
1126w, 1091m, 1077m, 1039s, 1021s, 1002m, 973s, 955sh, 933w,
905s, 884sh, 870m, 817m, 760s, 736sh, 729s, 694s, 649w, 641m, 615m,
581w, 533w, 513s, 472w, 462s, 442w, 425m cm−1. Single-crystals of 9
suitable for X-ray structure analysis were obtained by slow evaporation
of a methanol solution at r.t.
[Co(C2F5)(Hdmg)2(NH3)] (10). The compound was prepared as
described for 5, from reagent 1c (366 mg, 1.0 mmol), complex 2 (683
mg, 2.1 mmol), and aqueous ammonia solution (0.24 mL, 25 wt %, 3.2
mmol) in methanol (20 mL). Yield: 251 mg (59%). Bright yellow
solid, soluble in methanol, acetone, and ethyl acetate, moderately
soluble in water and chloroform, poorly soluble in diethyl ether. Dec.
246 °C. Anal. Calcd for C10H17CoF5N5O4 (M = 425.20 g mol−1): C
1
28.25, H 4.03, N 16.47%; Found: C 28.19, H 4.06, N 16.22%. H
1
product by trifluoromethylanilines (see 19F NMR data).) H NMR
NMR (CD3OD): 2.27 (s, 12H; CH3 dmg), 2.50 (s br, 3H; NH3) ppm;
OH not observed. 13C NMR (CD3OD): 12.3 (s; CH3 dmg), 154.1 (s;
CNO) ppm; CF2, CF3 not observed. 19F NMR (CD3OD): −82.7 (s
+d, 1JF,C = 288 Hz, 3F; CF3), −104.0 (s br, 2F; CF2) ppm. 59Co NMR
(CD3OD): 4044 (s, w1/2 = 3.70 kHz) ppm. IR: 3361w, 3309m, 3256w,
3166m, 1566s, 1441m, 1372m, 1300s, 1267w, 1237s, 1192s, 1159s,
1091s, 1040s, 1023s, 1003m, 978s, 938sh, 905s, 874sh, 748m, 727s,
612m, 597w, 587w, 513s, 429s, 414m cm−1. Single-crystals of 10·H2O
suitable for X-ray structure analysis were obtained by slow evaporation
of a wet methanol solution at r.t.
(CD3OD): 2.06 (s, 12H; CH3 dmg), 5.62 (s br, 2H; PhNH2), 6.66 (m,
2H; o-CH Ph), 7.09 (m, 1H; p-CH Ph), 7.18 (m, 2H; m-CH Ph) ppm;
OH not observed. 13C NMR (CD3OD): 12.0 (s; CH3 dmg), 122.2 (s;
o-CH Ph), 125.6 (s; p-CH Ph), 129.4 (s; m-CH Ph), 140.9 (s; C-NH2
Ph), 153.5 (s; CNO) ppm; CF3 not observed. 19F NMR (CD3OD):
−31.3 (s+d, 1JF,C = 380 Hz) ppm; minor side signals at −62.4 (s, 0.7%
of overall intensity; p-CF3-aniline) and −64.3 (s, 0.4% of overall
intensity; m-CF3-aniline) ppm, assigned by comparison with authentic
samples. 59Co NMR (CD3OD): 3856 (s, w1/2 = 3.89 kHz) ppm. IR:
3328w, 3277w, 3149w, 3046w, 1602m, 1587w, 1567s, 1494m, 1472w,
1435m, 1373sh, 1365m, 1314w, 1238s, 1181sh, 1152w, 1091m, 1047s,
1026s, 1012m, 979m, 903w, 907m, 876s, 829sh, 807m, 760s, 712m,
694s, 631m, 607m, 555m, 533s, 510s, 483sh, 435s, 405m cm−1. Single-
crystals of 7·H2O suitable for X-ray structure analysis were obtained by
addition of excessive water to a concentrated methanol solution.
[CoCF3(Hdmg)2(MeOH)] (8). Reagent 1a (0.95 g, 3.0 mmol) was
added to a suspension of complex 2 (2.05 g, 6.3 mmol) in methanol
(30 mL) at r.t, and the mixture was stirred overnight. The deep red-
brown solution was filtered and reduced to dryness on a rotary
evaporator at 40 °C. The dark residue was thoroughly washed with
water (30 mL), chloroform (30 mL), and diethyl ether (30 mL). The
residue was extracted with methanol (20 mL), and filtered, and the
clear orange filtrate was reduced almost to dryness. Orange crystals
have formed upon cooling to r.t., which were collected by filtration,
washed with 5 °C cold methanol (5 mL), and dried in vacuo. Yield:
0.16 g (14%). Orange prisms, soluble in methanol, poorly soluble in
water, acetone, ethyl acetate, diethyl ether, and chloroform. Dec. 170
°C. Anal. cald. for C10H18CoF3N4O5, M = 390.20 g mol−1: C 30.78, H
4.65, N 14.36%. Found: C 30.70, H 4.57, N 14.43%. 1H NMR
(CD3OD): 2.31 (s, 12H; CH3 dmg), 3.35 (s, 3H; CH3OH) ppm; OH
dmg, MeOH not observed. 13C NMR (CD3OD): 12.2 (s; CH3 dmg),
154.4 (s; CNO) ppm; CH3OH, CF3 not observed. 19F NMR
[Co(C2F5)(Hdmg)2(MeNH2)] (11). The compound was prepared as
described for 6, from reagent 1c (366 mg, 1.0 mmol), complex 2 (683
mg, 2.1 mmol), and aqueous methylamine solution (0.27 mL, 40 wt %,
3.2 mmol) in methanol (20 mL). Yield: 180 mg (41%). Pale yellow
solid, soluble in methanol, acetone, ethyl acetate, and chloroform,
poorly soluble in water and diethyl ether. Dec. 236 °C. Anal. Calcd for
C11H19CoF5N5O4 (M = 439.22 g mol−1): C 30.08, H 4.36, N 15.94%;
Found: C 30.08, H 4.44, N 15.95%. 1H NMR (CD3OD): 1.83 (t, 3JH,H
= 6.5 Hz, 3H; CH3NH2) 2.28 (s, 12H; CH3 dmg), 3.05 (s br, 2H;
NH2) ppm; OH not observed. 13C NMR (CD3OD): 12.3 (s; CH3
dmg), 28.1 (s; CH3NH2), 154.2 (s; CNO) ppm; CF2, CF3 not
observed. 19F NMR (CD3OD): −82.7 (s+d, 1JF,C = 288 Hz, 3F; CF3),
1
−103.2 (s br, JF,C = 314 Hz, 2F; CF2) ppm. 59Co NMR (CD3OD):
4034 (s, w1/2 = 3.13 kHz) ppm. IR: 3309m, 3235m, 3160m, 3012w,
2990w, 2953w, 2923w, 2898w, 2812w, 1604w, 1565s, 1469w, 1458w,
1436w, 1419w, 1377m, 1368sh, 1301sh, 1296s, 1267w, 1238s, 1209s,
1199sh, 1165s, 1157sh, 1127w, 1094s, 1067sh, 1053s, 1021m, 1006s,
976m, 932w, 904s, 878sh, 800sh, 746m, 727s, 690sh, 641m, 616m,
587m, 514s, 473sh, 448m, 433w, 425s cm−1. Single-crystals of 11
suitable for X-ray structure analysis were obtained by slow evaporation
of a methanol solution at r.t.
[Co(n-C3F7)(Hdmg)2(Py)] (12). The compound was prepared as
described for 4, from reagent 1d (416 mg, 1.0 mmol) and complex 3
(940 mg, 2.1 mmol) in methanol (20 mL). Yield: 274 mg (51%).
Yellow, microcrystalline solid, soluble in acetone, ethyl acetate, and
chloroform, moderately soluble in methanol and diethyl ether, poorly
soluble in water. Dec. 249 °C. Anal. Calcd for C16H19CoF7N5O4 (M =
537.28 g mol−1): C 35.77, H 3.56, N 13.03%; Found: C 35.72, H 3.64,
N 12.78%. 1H NMR (CDCl3): 2.20 (s, 12H; CH3 dmg), 7.32 (m, 2H;
3,5-CH Py), 7.75 (m, 1H; 4-CH Py), 8.50 (m, 2H; 2,6-CH Py) ppm;
OH not observed. 13C NMR (CDCl3): 12.5 (s; CH3 dmg), 125.6 (s;
3,5-CH Py), 138.6 (s; 4-CH Py), 149.7 (s; 2,6-CH Py), 152.4 (s; C
NO) ppm; CF2, CF3 not observed. 19F NMR (CDCl3): −79.2 (t+dt,
1
(CD3OD): −28.5 (s+d, JF,C = 378 Hz) ppm. 59Co NMR (CD3OD):
4350 (s, w1/2 = 6.83 kHz) ppm. IR: 3016m, 2984m, 2927w, 2842w,
2778m, 2582w, 2548m, 1588sh, 1562s, 1501w, 1472m, 1448m,
1429m, 1380m, 1370w, 1317w, 1236s, 1140w, 1083s, 1043s, 1013s,
976m, 936sh, 868m, 843w, 792w, 738s, 718m, 605m, 576w, 536m,
526m, 510s, 483m, 475sh, 448m, 431w, 413m cm−1. Single crystals of
8 suitable for X-ray structure analysis were obtained by slow
evaporation of a methanol solution at r.t.
[Co(C2F5)(Hdmg)2(Py)] (9). The compound was prepared as
described for 4, from reagent 1c (366 mg, 1.0 mmol) and complex
3 (940 mg, 2.1 mmol) in methanol (20 mL). Yield: 326 mg (67%).
Yellow, microcrystalline solid, soluble in methanol, acetone, chloro-
form, and ethyl acetate, poorly soluble in water and diethyl ether. Dec.
246 °C. Anal. Calcd for C15H19CoF5N5O4 (M = 487.27 g mol−1): C
1
3JF,F = 12.5 Hz, JF,C = 291 Hz, 3F; CF3), −95.7 (s br, 2F; α-CF2),
1
−122.7 (m+dm, JF,C = 261 Hz, 2F; β-CF2) ppm. 59Co NMR
(CDCl3): 4168 (s, w1/2 = 5.79 kHz) ppm. IR: 3058w, 1611w, 1564s,
1501w, 1456m, 1374m, 1313s, 1237s, 1218s, 1180s, 1170sh, 1162sh,
1091sh, 1086s, 1080sh, 1036sh, 1025s, 1019m, 1002sh, 976m, 952w,
804s, 761m, 753m, 720s, 698s, 666s, 650w, 641m, 581w, 569w, 532w,
513s, 470m, 455s, 428m, 404s cm−1. Single-crystals of 12 suitable for
1
36.97, H 3.93, N 14.37%; Found: C 37.20, H 4.06, N 14.15%. H
NMR (CDCl3): 2.19 (s, 12H; CH3 dmg), 7.33 (m, 2H; 3,5-CH Py),
7.75 (m, 1H; 4-CH Py), 8.50 (m, 2H; 2,6-CH Py) ppm; OH not
observed. 13C NMR (CDCl3): 12.5 (s; CH3 dmg), 125.6 (s; 3,5-CH
K
DOI: 10.1021/acs.organomet.7b00892
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
X-ray structure analysis were obtained by slow evaporation of a
methanol solution at r.t.
min, leading to immediate precipitation of a voluminous yellow solid.
The latter was filtered off, washed with ethanol (10 mL), and dried in
vacuo. Yield: 0.88 g (78%). Bright yellow, microcrystalline solid,
soluble in methanol, ethanol, and water, poorly soluble in acetone,
chloroform, diethyl ether, and ethyl acetate. Anal. Calcd for
C15H26CoIN6O7 (M = 588.24 g mol−1): C 30.63, H 4.46, N
14.29%; Found: C 30.42, H 4.49, N 14.23%. 1H NMR (CD3OD): 2.42
(s, 12H; CH3 dmg), 6.97 (m, 1H; 4-CH anion), 7.31 (m, 1H; 5-CH
anion), 7.36 (m, 1H; 6-CH anion), 7.79 (m, 1H; 3-CH anion) ppm;
NH3, OH dmg, H2O not observed. 13C NMR (CD3OD): 12.9 (s; CH3
dmg), 92.6 (s; C-I), 128.4 (s; 6-CH anion), 128.7 (s; 5-CH anion),
129.9 (s; 4-CH anion), 140.3 (s; 3-CH anion), 155.5 (s; CNO)
ppm; C-COO, C-COO of anion not observed. 59Co NMR (CD3OD):
no signal observed. IR: 3485w, 3142s, 3048s, 3008m, 2922m, 2670w,
1608sh, 1570s, 1552m, 1456w, 1419m, 1372s, 1346s, 1239sh, 1232s,
1190sh, 1151w, 1091s, 1039w, 1010s, 997m, 978s, 913m, 876m, 825m,
805m, 762s, 739s, 719sh, 677s, 638s, 510s, 483m, 460m, 442s, 433m
cm−1. Single-crystals of 15·H2O suitable for X-ray structure analysis
were obtained by slow evaporation of a methanol solution at r.t.
[Co(Hdmg)2(PhNH2)2](o-IC6H4COO) (16). Co(o-IC6H4COO)2-
(H2O)2 (1.18 g, 2.0 mmol) was suspended in ethanol (95%, 25
mL), and freshly distilled aniline (0.68 mL, 7.5 mmol) was added at r.t.
After 10 min of stirring, dimethylglyoxime (0.46 g, 4.0 mmol) was
added, resulting in a color change from pink to orange-brown. A slight
flow of air was bubbled through the mixture for 1 h. The resulting clear
solution was reduced to approximately 15 mL, and diethyl ether (30
mL) was added, upon which a yellow precipitate has formed. The
latter was filtered off, washed with diethyl ether (2 × 10 mL), and
dried in vacuo. Yield: 0.78 g (56%). Yellow-orange solid, soluble in
methanol, ethanol, and water, poorly soluble in acetone, ethyl acetate,
diethyl ether, and chloroform. Anal. Calcd for C27H32CoIN6O6 (M =
722.42 g mol−1): C 44.89, H 4.46, N 11.63%; Found: C 44.66, H 4.55,
[Co(CF2CF2Ph)(Hdmg)2(Py)] (13). The compound was prepared as
described for 4, from reagent 1e (212 mg, 0.50 mmol) and complex 3
(470 mg, 1.05 mmol) in methanol (10 mL). Yield: 156 mg (57%).
Yellow, microcrystalline solid, soluble in acetone, ethyl acetate, and
chloroform, moderately soluble in methanol, poorly soluble in diethyl
ether and water. Dec. 231 °C. Anal. Calcd for C21H24CoF4N5O4 (M =
545.38 g mol−1): C 46.25, H 4.44, N 12.84%; Found: C 46.44, H 4.52,
N 12.56%. 1H NMR (CDCl3): 2.18 (s, 12H; CH3 dmg), 7.30 (m, 2H;
3,5-CH Py), 7.32 (m, 2H; m-CH Ph), 7.33 (m, 1H; p-CH Ph), 7.45
(m, 2H; o-CH Ph), 7.74 (m, 1H; 4-CH Py), 8.58 (m, 2H; 2,6-CH Py)
ppm; OH not observed. 13C NMR (CDCl3): 12.4 (s; CH3 dmg), 125.5
3
(s; m-CH Ph), 127.2 (t, JC,F = 6.6 Hz; o-CH Ph), 127.6 (s; 3,5-CH
Py), 129.8 (s; p-CH Ph), 133.5 (t, 2JC,F = 6.8 Hz; i-C Ph), 138.3 (s; 4-
CH Py), 149.8 (s; 2,6-CH Py), 152.1 (s; CNO) ppm; CF2 not
observed. 19F NMR (CDCl3): −87.7 (s+d, 1JF,C = 328 Hz, 2F; α-CF2),
1
−106.8 (s+d, JF,C = 260 Hz, 2F; β-CF2) ppm. 59Co NMR (CDCl3):
4146 (s, w1/2 = 6.74 kHz) ppm. IR: 3116w, 3071w, 3049w, 3004w,
1605w, 1564s, 1495m, 1455sh, 1449m, 1371w, 1320w, 1266m, 1239s,
1192m, 1169w, 1157w, 1148w, 1128m, 1117w, 1089s, 1073sh, 1061s,
1030s, 1019s, 1012m, 994sh, 978m, 954w, 925w, 882m, 808s, 765m,
753s, 740sh, 703s, 697m, 670s, 649w, 633s, 621sh, 595w, 580w, 558w,
537w, 514s, 485m, 468w, 453m, 421s, 408m cm−1. Single-crystals of
13 suitable for X-ray structure analysis were obtained by slow
evaporation of a methanol solution at r.t.
One-Pot Preparation of Perfluoroalkyl Cobaloximes. To a mixture
of Co(OAc)2·4 H2O (1.57 g, 6.3 mmol), H2dmg (1.46 g, 12.6 mmol),
and methanol (30 mL), the appropriate nitrogen ligand (16.5 mmol)
was added at r.t. After stirring for 1 h, the mixture was cooled to 0 °C
and the corresponding acid reagent 1a or 1c (3.0 mmol) was added.
Stirring was continued for 1 h at 0 °C and 3 h at r.t., followed by
workup as described above. [CoCF3(Hdmg)2(Py)] (4), Yield: 0.67 g
(51%). [CoCF3(Hdmg)2(NH3)] (5), Yield: 0.37 g (33%).
[CoCF3(Hdmg)2(MeNH2)] (6), Yield: 0.34 g (29%). [Co(C2F5)-
(Hdmg)2(Py)] (9) was obtained accordingly on a 1.0 mmol scale,
Yield: 287 mg (59%).
1
N 11.43%. H NMR (CD3OD): 2.12 (s, 12H; CH3 dmg), 6.66 (m,
4H; o-CH PhNH2), 6.96 (m, 1H; 4-CH anion), 7.18 (m, 4H; m-CH
PhNH2), 7.20 (m, 2H; p-CH PhNH2), 7.31 (m, 1H; 5-CH anion),
7.35 (m, 1H; 6-CH anion), 7.78 (m, 1H; 3-CH anion) ppm; NH2, OH
not observed. 13C NMR (CD3OD): 12.7 (s; CH3 dmg), 92.5 (s; C-I),
123.5 (s; o-CH PhNH2), 127.3 (s; p-CH PhNH2), 128.4 (s; 6-CH
anion), 128.7 (s; 5-CH anion), 129.8 (s; m-CH PhNH2), 129.9 (s; 4-
CH anion), 139.4 (s; C-N PhNH2), 140.3 (s; 3-CH anion), 155.9 (s;
CNO) ppm; C-COO, C-COO of anion not observed. 59Co NMR
(CD3OD): no signal observed. IR: 3236w, 3184w, 3042w, 3018w,
2919w, 2519w, 2462w, 2359w, 1609sh, 1601m, 1578s, 1550s, 1492s,
1476m, 1446w, 1430w, 1356s, 1334sh, 1311w, 1267m, 1232s, 1213m,
1205sh, 1193m, 1175w, 1158w, 1086s, 1076m, 1043w, 1027w, 1011m,
1004sh, 975s, 957sh, 908w, 885w, 829m, 812m, 768sh, 763m, 749s,
733sh, 702sh, 697s, 682s, 641m, 623w, 603w, 579m, 565s, 509s, 489w,
462m, 448s, 439s, 417m, 411m cm−1. Single crystals of 16·2MeOH
suitable for X-ray structure analysis were obtained from a methanol/
diethyl ether solution (v:v ca. 1:2) at −20 °C.
[Co(Hdmg)2(Py)2][H(o-IC6H4COO)2] (14·o-IC6H4COOH). Co(o-IC6-
H4COO)2(H2O)2 (1.18 g, 2.0 mmol) was suspended in ethanol (95%,
25 mL), and pyridine (0.96 mL, 12.0 mmol) was added at r.t. To the
resulting bright pink suspension, dimethylglyoxime (0.46 g, 4.0 mmol)
was added, leading to a sharp color change to yellow-brown.
Subsequently, a slight flow of air was bubbled through the reaction
mixture for 30 min. The voluminous yellow precipitate was filtered off,
washed with ethanol (10 mL), and dried in vacuo. Yield: 0.80 g (43%).
Yellow, microcrystalline solid, soluble in methanol, ethanol, and
chloroform, poorly soluble in water, acetone, diethyl ether, and ethyl
acetate. Anal. Calcd for C32H33CoI2N6O8 (M = 942.39 g mol−1): C
1
40.78, H 3.53, N 8.92%; Found: C 40.85, H 3.65, N 8.92%. H NMR
(CD3OD): 2.34 (s, 12H; CH3 dmg), 7.08 (m, 2H; 4-CH anion), 7.38
(m, 2H; 5-CH anion), 7.47 (m, 4H; 3,5-CH Py), 7.58 (m, 2H; 6-CH
anion), 7.90 (m, 2H; 3-CH anion), 7.95 (m, 2H; 4-CH Py), 8.33 (m,
4H; 2,6-CH Py) ppm; OH dmg, OH anion not observed. 13C NMR
(CD3OD): 13.3 (s; CH3 dmg), 93.4 (s; C-I), 127.9 (s; 3,5-CH Py),
128.9 (s; 5-CH anion), 130.0 (s; 6-CH anion), 131.7 (s; 4-CH anion),
141.3 (s; 3-CH anion), 141.8 (s; 4-CH Py), 152.4 (s; 2,6-CH Py),
157.8 (s; CNO) ppm. 59Co NMR (CD3OD): no signal observed.
IR: 3124w, 3114w, 3075w, 3051 w, 3031w, 1702m, 1653w, 1606m,
1579w, 1558m, 1492w, 1450m, 1428w, 1368w, 1255sh, 1238s, 1228sh,
1158w, 1091s, 1068s, 1034m, 1012s, 983m, 957m, 886m, 868m, 825m,
799m, 778s, 740s, 720sh, 698s, 664s, 653s, 643m, 634s, 543s, 538s,
514s, 474m, 459sh, 441s, 425s, 411sh cm−1. Single-crystals of 14·o-
IC6H4COOH suitable for X-ray structure analysis were obtained by
slow evaporation of the mother liquor at r.t.
Attempted Preparation of [Co(Hdmg)2(MeNH2)2](o-IC6H4COO).
Co(o-IC6H4COO)2(H2O)2 (1.18 g, 2.0 mmol) was suspended in
ethanol (95%, 25 mL), and aqueous methylamine solution (0.54 mL,
40 wt %, 6.3 mmol) was added at r.t. After 5 min of stirring,
dimethylglyoxime (0.46 g, 4.0 mmol) was added to the greenish
suspension, resulting in a color change to intense orange-brown. A
slight flow of air was bubbled through the solution for 30 min. The
mixture was subsequently filtered, and diethyl ether (30 mL) was
added. A colorless crystalline precipitate has formed upon storing the
solution at −20 °C overnight, which was identified as (o-IC6H4COO)-
(MeNH3). Yield: 0.37 g (1.33 mmol). Anal. Calcd for C8H10INO2 (M
= 279.07 g mol−1): C 34.43, H 3.61, N 5.02%; Found: C 34.41, H
+
3.64, N 5.00%. 1H NMR (CD3OD): 2.52 (s, 3H; CH3NH3 ), 7.00 (m,
1H; 4-CH anion), 7.34 (m, 1H; 5-CH anion), 7.37 (m, 1H; 6-CH
[Co(Hdmg)2(NH3)2](o-IC6H4COO) (15)·H2O. Co(o-IC6H4COO)2-
(H2O)2 (1.18 g, 2.0 mmol) was suspended in ethanol (95%, 25
mL), and aqueous ammonia solution (0.56 mL, 25 wt %, 7.5 mmol)
was added at r.t., resulting in complete dissolution of the cobalt salt
with red-brown color. After addition of dimethylglyoxime (0.46 g, 4.0
mmol), a slight flow of air was bubbled through the solution for 30
anion), 7.81 (m, 1H; 3-CH anion) ppm. 13C NMR (CD3OD): 25.4 (s;
+
CH3NH3 ), 92.5 (s; C-I), 128.3 (s; 6-CH), 128.8 (s; 5-CH), 130.1 (s;
4-CH), 140.3 (s; 3-CH), 148.6 (s; C-COO), 177.3 (s; COO) ppm.
After isolation of the crystals by filtration in the cold, the mother liquor
was reduced to approx. 20 mL. Addition of water (50 mL) afforded a
precipitate of 0.11 g (0.95 mmol) of H2dmg.
L
DOI: 10.1021/acs.organomet.7b00892
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Attempted Preparation of [Co(Hdmg)2(L)2](o-IC6H4COO) (L =
H2O or MeOH). Dimethylglyoxime (0.46 g, 4.0 mmol) and Co(o-
IC6H4COO)2(H2O)2 (1.18 g, 2.0 mmol) were dissolved in methanol
(25 mL), and a slight flow of air was bubbled through the brown
solution for 2 h at r.t. Slow evaporation of the solvent afforded a
crystalline precipitate of ortho-iodobenzoic acid besides undefined dark
decomposition products.
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ASSOCIATED CONTENT
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AUTHOR INFORMATION
Corresponding Author
*E-mail: liebing@inorg.chem.ethz.ch.
ORCID
Phil Liebing: 0000-0002-4660-1691
Antonio Togni: 0000-0003-3868-1799
Notes
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ACKNOWLEDGMENTS
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This work is supported by a research scholarship of the German
Research Foundation (DFG), project number 320225637.
http://gepris.dfg.de/gepris/projekt/320225637. General finan-
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