“This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorg. Chem. 2014,
53, 11675-11681, copyright © American Chemical Society after peer review and technical editing by the publisher. To
access the final edited and published work see DOI: 10.1021/ic501883z. This article may be used for non-commercial
purposes in accordance with the ACS guidelines published at http://pubs.acs.org/page/policy/articlesonrequest/index.html].”

1

Synthesis and Structural Features of Co(II) and
Co(III) Complexes Supported by Aminotrisphenolate Ligand Scaffolds
Carmen Martín,† Christopher J. Whiteoak,† Eddy Martin,† Eduardo C. Escudero-Adán,† José
Ramón Galán-Mascarós,†,§ Arjan W. Kleij*,†,§

†

Institute of Chemical Research of Catalonia (ICIQ), Av. Països Catalans 16, 43007 Tarragona,
Spain.

§Catalan Institute of Research and Advanced Studies (ICREA), Pg. Lluís Companys 23, 08010
Barcelona, Spain.

2

ABSTRACT: Co(II) complexes of amino-trisphenolate ((ArO)3N3-) ligands can be prepared
straightforwardly in high yield. X-ray analysis reveals these complexes to comprise of two
different hemi-spheres, one containing an anionic Co((ArO)3N) and the other a cationic
(ArO)3NH+ unit which are associated through hydrogen bonding. These Co(II) complexes can be
easily converted into their Co(III) analogues in air in the presence of suitable bases such as
dimethylaminopyridine (DMAP) and 2,2´-bipyridine (bipy), and the structural features and
magnetic properties of these latter compounds are also reported.

3

 INTRODUCTION
The use of amino-trisphenolate ligands (abbreviated as (ArOH)3N ligands) in inorganic and
catalysis related research is an active area of science with an ever increasing impact in several
communities.1 These (ArO)3N-chelating ligands combine a potentially multi-dentate coordination
ability with relative ease for variation of the ligand through synthetic modulation. As such,
complexes of these ligands have recently been the basis of several new catalyst systems for a
variety of applications involving high-valent metals including Ti(IV),2a-b V(V),2c Mo(VI),2d
Zr/Hf(IV),2e U(IV),2f Fe(III),2g-i and Al(III).2j-l Recently, the first examples of Co(II)(ArO)3N
complexes which contain bulky ortho-groups attached to the ligand framework have been
reported,3 as a prelude to activation of small molecules such as dioxygen. In addition to the use of
these (ArO)3N-chelating ligands, there are many examples of other tripodal (hybrid) ligands
systems that have been shown to incorporate Co(II) ions,4 having in most cases a N4-chelating
character such as in amino-trispyridyl (TPA) ligands. However, (reactivity) studies involving the
formation of Co(III) complexes of these aforementioned ligands are limited4f,h-i and to the best of
our knowledge Co(III)(ArO)3N species have thus far not been crystallographically characterized.
The chemistry of Co(III)-salen complexes has been well-developed over the years and shown to
be of eminent use in catalytic operations focusing on kinetic resolution of (rac)-epoxides5 and their
copolymerization with carbon dioxide (CO2) forming useful polycarbonates,6 with further reports
also detailing other types of catalysis with these complexes.7 Mechanistic studies have revealed
that in these copolymerization reactions a bimetallic transition state8 is operative activating two
substrate molecules leading to a more efficient conversion and improved reactivity and/or
selectivity behavior. We recently found that (ArO)3N based complexes of Fe(III)2g and Al(III)2k
have the ability to form hexa-coordinated structures with two cis-positioned coordination sites for

4

incoming substrates. This effect of an external ligand or substrate on the overall conformation and
fluxionality of amino-trisphenolate complexes has been reported before for Ti(IV) based systems;9
Zonta et al. reported in this respect an interesting Ti(IV) peroxo complex9b that after coordination
of a solvent molecule changes its coordination geometry and enables oxygen-transfer catalysis.
Further to this, the Fe(III) family of complexes was also shown to efficiently catalyze the
formation of poly(cyclohexene)carbonate similar to the aforementioned Co(III)-salen
complexes.10 As a result we hypothesized that two available cis-coordination sites on a Co(III)
center could be highly useful for the formation of organic carbonates from epoxides and CO2 and
therefore started to combine our interest in (ArO)3N ligands and the highly successful application
of Co(III) chemistry to mediate these epoxide/CO2 couplings. Herein we report the first synthesis
and full structural characterization of Co(III)(ArO)3N complexes.

5

Scheme 1. Synthesis of Co(II) and Co(III) complexes 4-9 from amino-triphenol ligand precursors
1-3. Note that the protonated (ArO)3NH+ ligand in complexes 4 and 5 forms an ion pair with the
Co(II) complex.

6

Figure 1. X-ray molecular structure for compound 5. Selected bond lengths (Å) and angles (º):
Co(1)-O(1) = 1.897(8), Co(1)-O(2) = 1.904(8), Co(1)-O(3) = 1.899(8), Co(1)-N(1) = 2.052(10);
O(1)-Co(1)-N(1) = 98.9(3), O(3)-Co(1)-N(1) = 98.5(3), O(2)-Co(1)-O(3) = 117.9(4).

 RESULTS AND DISCUSSION
To access Co-centered (ArO)3N complexes we followed a lead from Lehtonen11 who prepared
a Mo(VI)(ArO)3N complex directly from the corresponding amino-triphenol ligand and
MoO2(acac)2. Thus, direct treatment of known ligands 1-312 with Co(OAc)2·4H2O was probed and
furnished Co(II) complexes 4 and 5 in good yields as blue solids.13 Compounds 4 and 5 are airstable both in solution and solid phases (vide infra); both complexes crystallize conveniently from
MeOH (4-5) and DCM (5) and their X-ray molecular structures were determined (Figure 1 and
Supporting Information, Figure S39). The structure reported for compound 5 comprises of an

7

anionic part viz. Co((ArO)3N) and a cationic (ArO)3NH+ fragment; the latter is associated to the
Co(II) complex via hydrogen bonding.11 As a result, the two different hemispheres give rise to a
capsular system in which the metal center sits in a mono-pyramidal coordination geometry as was
also observed by Meyer and co-workers for their comparable Co(II)(ArO)3N complexes.3 The
observed structural parameters support that the Co center is tetra-coordinated and is slightly
displaced from the O3-plane of the ligand towards the nitrogen center N1. The overall features for
the anionic part of 5 closely relate to those reported for other mono-pyramidal coordination
geometries reported for Co(II) complexes based on other tetra-dentate ligand systems.4a,c,f,g
The synthetic approach towards Co(II) complexes 4 and 5 does not allow for the introduction of
other cations as the aminotrisphenolate ligand (ArOH)3N itself acts as a proton scavenger. The
cation (ArOH)3NH+ could also not be simply exchanged by addition of a NBu4Cl or alike in
separate experiments. Therefore we probed another route towards these Co(II)(ArO)3N complexes
by first deprotonation of the (ArOH)3N ligand using NaH followed by transmetalation of in situ
formed (ArONa)3N with Co(OAc)2 in THF. The product of this reaction, complex 6a (79% yield,
Scheme 1 and Figure 2), was isolated as a binuclear Co(II) complex that incorporates two (ArO)3N
ligands, three Na cations, a bridging hydroxo ligand and six THF ligands. These results
demonstrate that other cations may also be associated to the anionically charged Co(II)(ArO) 3N
complex. The presence of a hydroxo ligand (OH) can be explained by the presence of some NaOH
prior, during and/or after the reaction as a result of the presence of adventitious water. We thus
performed an alternative synthesis using anhydrous CoCl2 as transmetalating agent, and the
addition of bis-triphenylphosphineiminium chloride (PPN-Cl) provoked a cation exchange
affording complex 6b (45%). X-ray analysis of this latter complex (Figure 3) disclosed the
presence of an anionic Co(II) fragment reminiscent of complexes 4 and 5 though with an solvent

8

molecule occupying the apical position and having a non-coordinating cation associated (PPN+).
This result shows that, at least when isolation of the Co(II) complexes is concerned, a coordinating
cation is not a prerequisite.

9

N2A

O10A

O6A
O12A

Na2A

O13A

O2A
Co1A

Figure 2. X-ray molecular structure for binuclear complex 6a. Selected bond lengths (Å) and
angles (º): Co(1A)-O(1A) = 2.0008(14), Co(1A)-O(2A) = 1.9942(14), Co(1A)-O(3A) =
1.9929(15), Co(1A)-N(1A) = 2.1180(19), Co(1A)-O(7A) = 2.1056(18), Na(1A)-O(7A) =
2.4847(17), Na(2A)-O(7A) = 2.6512(19), Na(3A)-O(7A) = 2.4335(18); O(1A)-Co(1A)-O(2A) =
123.25(7), O(1A)-Co(1A)-O(3A) = 119.00(6), O(2A)-Co(1A)-O(3A) = 117.50(7), N(1A)Co(1A)-O(7A) = 175.74(6), Co(1A)-O(7A)-Na(1A) = 47.68(4), N(1A)-Co(1A)-O(1A) =
92.03(6), Na(1A)-O(7A)-Na(2A) = 109.44(7), Na(1A)-O(7A)-Na(3A) = 145.96(8).

10

Figure 3. X-ray molecular structure for complex 6b together with a partial numbering scheme.
Selected bond lengths (Å) and angles (º): Co(1)-O(1) = 1.953(2), Co(1)-O(2) = 1.950(2), Co(1)O(3) = 1.949(2), Co(1)-N(1) = 2.147(3), Co(1)-O(4) = 2.204(6); O(1)-Co(1)-O(3) = 114.54(9),
O(2)-Co(1)-O(3) = 120.64(9), O(1)-Co(1)-O(2) = 123.92(10), N(1)-Co(1)-O(4) = 87.37(15), N(1)Co(1)-O(1) = 94.00(9); N(1)-Co(1)-O(3) = 92.89(9).

The Co(II) complexes 4 and 5 probably gain stability by steric protection exerted by the cationic
unit (ArO)3NH+ that is associated to the Co(II) complex through an ionic as well as three H-bond
interactions. Further evidence for this hypothesis was gained from comparative stability studies of
complexes 4 and 5, and 6b. Interestingly, while complexes 4 and 5 seem to be stable both in the
solid as well as solution phase for at least 24 h, complex 6b shows clear signs of decomposition in

11

the solid and solution state within 24 h after exposure to air (see Supporting Information, Figures
S50-51). Thus, it seems that the presence of an interacting, coordinating cation may help to
stabilize the Co(II) oxidation state of these kinds of complexes. Cyclic voltammetry studies that
involved complex 6b also clearly showed that oxidation is significantly more feasible for this
complex as compared to complex 5 (Epox is 0.27 V and 0.650.70 V, respectively; see Supporting
Information).
We decided to deprotonate compound 5 to explore the opportunity to introduce other ligands.
When a solution of compound 5 in CH2Cl2 (blue) was treated in air14 with an excess of 4dimethylaminopyridine (DMAP) a drastic color change to dark violet was noted indicating a
change in the oxidation state of the Co center and/or coordination geometry; after removal of the
solvent the purple residue was re-crystallized from CH2Cl2/hexane to afford complex 7 in good
yield (83%). X-ray analysis revealed the presence of a Co-complex having two DMAP ligands
incorporated in the coordination sphere in complex 7 (Figure 4). The DMAP ligands occupy an
equatorial and axial position of the roughly octahedral geometry around the Co center. The
structure clearly demonstrates the flexibility of the (ArO)3N ligand to accommodate the formation
of a hexa-coordinated complex potentially useful in catalytic conversions.5,6

12

Figure 4. X-ray molecular structure for complex 7. Selected bond lengths (Å) and angles (º):
Co(1)-O(1) = 1.9231(13), Co(1)-O(2) = 1.8985(14), Co(1)-O(3) = 1.9079(13), Co(1)-N(1) =
2.0174(16), Co(1)-N(2) = 2.0350(17), Co(1)-N4) = 1.9783(16); O(1)-Co(1)-O(3) = 172.92(6),
N(2)-Co(1)-O(2) = 172.95(6), N(1)-Co(1)-N(4) = 176.23(6).

1

H NMR studies were then first performed using 5 and 7 (Supporting Information; Figures S2

and S5-8) to study their solution behavior. As expected, for 5 paramagnetically shifted resonances
are found in the region 48 to 36 ppm and no significant changes were noted upon lowering the
temperature. However, for complex 7 we found that the temperature had a dramatic effect on the
resolution of the 1H NMR spectrum (Figure S6). At ambient conditions (25ºC) clearly
paramagnetically induced 1H NMR shifts were noted, but upon lowering the temperature to

13

between 30 and 40ºC a fully resolved 1H NMR spectrum was obtained, indicative of the sole
presence of a diamagnetic complex. The 1H NMR spectrum at 40ºC displays two down-field
shifts for the DMAP-ortho hydrogens in line with the presence of two DMAP ligands in the
coordination sphere of complex 7 (cf., Figure 4). We hypothesized that at higher temperatures the
coordination of the DMAP ligands is fluxional leading to a paramagnetic, five-coordinate Co(III)
complex with a trigonal pyramidal (tbp) geometry. In order to challenge this hypothesis, we
prepared complex 8 as a control compound (Scheme 1); this complex bears more sterically
demanding tBu groups in the ortho-positions of the phenolate donors and is likely not able to allow
for hexa-coordination at the Co center. However, isolation of the Co(II) complex of ligand 3 was
not feasible, and therefore we attempted the direct synthesis of 8 through combination of 3,
Co(OAc)2·4H2O and excess DMAP. An indicative color change to dark purple was noted and,
fortunately, complex 8 could be conveniently isolated by re-crystallization from CH2Cl2/CH3CN
(73% yield). Crystallographic analysis showed this complex to be penta-coordinated, comprising
of one DMAP ligand occupying one axial position of a tbp coordination geometry around the Co
ion (Figure S40). Further to this, to block a potential dynamic behavior between penta- and hexacoordinated geometry, complex 5 was treated with a bidentate ligand (2,2´-bipyridine: 2,2´-bipy):
the presence of this ligand should give rise to a structure reminiscent of complex 7 and be
conformationally stable such that under ambient conditions a diamagnetic compound should
prevail. Complex 9 (Scheme 1) was isolated as a brown crystalline compound (23% yield; see
Supporting Information for details) and its molecular structure was determined by X-ray
diffraction (Figure S41). Complex 8 clearly displays 1H NMR characteristics of a paramagnetic
species at ambient and lower temperature (40ºC; Figure S9), whereas the bipy-complex 9 gives
rise to a well-resolved and defined 1H NMR spectrum under ambient conditions (Figure S10).

14

Interestingly, the presence of a bipy-ortho-H resonance located at  = 10.35 indicates hydrogenbonding to a phenolateO and may thus help to further stabilize this complex.
The oxidation processes for both cobalt (II) complexes (4 and 5) investigated by cyclic
voltammetry are observed at relative high potential (Epox = 1.05 and around 0.7 V, respectively,
vs. Ag/AgCl) which supports a high stability of theses complexes against oxidation (Supporting
Information; Figures S42-44). In the case of complex 4 a single quasi-reversible wave is observed
whereas complex 5 exhibits an irreversible oxidation process as a likely result of the oxidation of
the (ArMeO)3N ligand. The cyclic voltammogram (CV) for this complex showed a broad wave
between 0.65–0.75 V vs. Ag/AgCl due to overlapping oxidation processes that involve the
CoII/CoIII redox couple within the (ArMeO)3N ligand, and the (ArMeO)3NH+ cationic unit. The CV
obtained for cobalt (III) complex 7 displays, under these conditions, a reversible reduction process
at E1/2 = 0.09 V vs. Ag/AgCl attributed to the CoIII/CoII couple (Figure S47) and cobalt (III)
compounds 8 and 9 give rise to similar quasi-reversible CVs for the CoIII/CoII couple at E1/2 = 0.13
and 0.05 V respectively vs. Ag/AgCl (Figures S48-49). From these data it seems that the DMAP
ligands in complex 7 are effective in the stabilization of the Co III oxidation state, whereas
(ArMeO)3NH+ cation in complexes 4 and 5 is able to protect the CoII from low-potential oxidation.
Finally, we performed magnetic susceptibility measurements in polycrystalline samples of 4, 5
and 7-9 (Figure 5). The mT products at room temperature are 2.25, 2.79, –0.11, 1.28 and –0.26
emu K mol–1, respectively. These values correspond to a S = 3/2 with strong spin-orbit coupling,
as expected for high spin Co(II) in 4 and 5; a diamagnetic S = 0, from the octahedral low spin
Co(III) in 7 and 9; and a S = 1, from the two unpaired electrons expected in a Co(III) center with
tbp coordination in 8.15 These are in good agreement with the NMR data. The temperature
dependence of the magnetization is dominated by the zero-field splitting of the single ions.

15

From the room temperature values, mT decreases as temperature is decreased for the
paramagnetic complexes 4, 5 and 8. In the case of 4, mT remains constant at 2.25 emu K mol–1
down to 60 K, when it drops fast down to 1.0 emu K mol–1 at 2 K. In the case of 5, mT decreases
slowly from 2.79 down to 2.30 emu K mol–1 at 50 K, and then it drops fast down to 1.5 emu K
mol–1 at 2 K. This behavior in 4 and 5 is typical of high spin trigonal pyramidal Co(II) complexes,
with strong spin orbit coupling, analogous to that reported by Meyer for related Co(II) species.3 In
the case of 8, mT remains essentially constant down to 80 K, and then it also drops sharply
reaching 0.10 emu K mol–1 at 2 K, due to the zero-field splitting of the triplet ground state.
Complexes 7 and 9 are diamagnetic at room temperature. As the temperature is decreased, mT
shows a linear behavior, approaching positive values. This must be due to the presence of
paramagnetic impurities that represent less than 3% of the complexes.

Figure 5. Temperature dependence of the mT product for complexes 4, 5 and 7-9.

16

 CONCLUSION
In summary, we here present an easy route towards Co(III)(ArO)3N complexes and their full
characterization using a variety of analytical techniques. The straightforward dependence of the
coordination geometry around the Co ion on the ligand substitution in these complexes allows for
penta- and/or hexacoordinated metal centers. In the hexacoordinated Co(III) complexes 7 and 9
the presence of two cis-positioned N-donor ligands suggests that these complexes may be of value
in catalytic transformations such as the co-polymerization of epoxides and CO2. However, this
may be true only when suitable ligands or substrates are involved that can facilitate the oxidation
of the Co(II) complex. The catalytic CO2/epoxide coupling reactions are currently under
investigation.

 EXPERIMENTAL SECTION
General Considerations. All reagents were purchased from commercial suppliers and used as
received. All solvents were of reagent grade and use without any further purification. The ligands
H3LH, H3LMe, H3LtBu (compounds 1-3) were prepared according to literature methods.12,16
Elemental Analysis was performed by the Unidád de Análisis Elemental at the Universidad de
Santiago de Compostela (Spain). Mass spectrometric analyses and X-ray diffraction studies were
carried out by the Research Support Group at the ICIQ. FT-IR measurements were performed on
a Bruker Optics FTIR Alpha spectrometer equipped with a DTGS detector, KBr beam-splitter at
4 cm-1 resolution. UV-Vis measurements were carried out on a Shimadzu UV-2401PC
spectrophotometer equipped with a photomultiplier detector, double beam optics, and D2 and W
light sources. NMR spectra were recorded on a Bruker AV-400 or AV-500 spectrometer and
referenced to the residual NMR solvent signals.

17

Synthesis of [(ArHO)3NCo][(ArHOH)3NH]+, complex (4): To a solution of the ligand tris(2hydroxybenzyl)amine (ArHOH)3N 1 (201.0 mg, 0.6 mmol, 2 equiv.) in methanol (10 mL) was
added a solution of Co(OAc)2·4H2O (77.0 mg, 0.3 mmol, 1 equiv.) in methanol (10 mL). The
mixture was stirred at r.t. and after 1 h a crystalline blue solid precipitated. The blue complex was
filtrated, washed with methanol and dried. Yield: 145.7 mg (0.19 mmol, 62 %). The crystalline
complex 4 thus obtained from the reaction described above was suitable for X-ray crystallographic
analysis. 1H NMR (CDCl3, 400 MHz, RT): paramagnetic spectrum, = 32.46, 16.35, 10.00, 6.52,
4.73, 1.33, -8.98, -12.89, -43.30; MALDI(+)–MS (dctb): m/z = 336.2 [(ArHOH)3NH]+ (calcd.
336.2), MALDI()–MS (dctb): m/z = 391 [(ArHO)3NCo] (calcd. 391). Anal. calcd. for
C42H40CoN2O6·MeOH: C 67.98, H 5.84, N 3.69; found: C 68.03, H 5.62, N 3.86. IR (cm-1): 1593,
1478, 1456, 1265, 1248, 879, 751, 731, 596, 568, 479; UV/Vis (CH2Cl2, 0.2 mM, 25 ºC, ε = L·mol1

·cm-1): 338 nm (155), 572 nm (230), 606 nm (260), 624 nm (225).
Synthesis of [(ArMeO)3NCo][(ArMeOH)3NH]+, complex (5): To a solution of the ligand

tris(2-hydroxy-4,6-dimethylbenzyl)amine (ArMeOH)3N 2 (419.0 mg, 1.0 mmol, 2 equiv.) in
methanol (15 mL) was added a solution of Co(OAc)2·4H2O (124.0 mg, 0.5 mmol, 1 equiv.) in
methanol (15 mL). The mixture was stirred at r.t. and after 1 h a blue solid precipitated. The blue
complex was filtrated, washed with methanol and dried. Yield: 375.5 mg (0.4 mmol, 84 %).
Crystals suitable for X-ray crystallographic analysis were obtained by diffusing hexane into a
solution of 1 in dichloromethane. The sample for microanalysis was crystallized from MeOH. 1H
NMR (CD2Cl2, 500 MHz, RT): paramagnetic spectrum,  = 35.65, 27.11, 25.14, 9.30, 6.15, 3.46,
1.78, 1.53, 0.88, -7.80, -11.10, -48.45; MALDI(+)–MS (dctb): m/z = 420.5 [(ArMeOH)3NH]+
(calcd. 420.3), MALDI()–MS (dctb): m/z = 475.1 [(ArMeO)3NCo] (calcd. 475.2). Anal. calcd.
for C54H64CoN2O6∙1.5MeOH: C 70.61, H 7.47, N 2.97; found: C 70.59, H 7.52, N 2.95. IR (cm-1):

18

2916, 2856, 1494, 1474, 1436, 1254, 1208, 1161, 860, 800, 615, 473 (m); UV/Vis (CH2Cl2, 0.2
mM, 25 ºC, ε = L.mol-1.cm-1): 346 nm (225), 570 nm (230), 604 nm (245), 624 nm (205).
Synthesis of [(ArMeO)3NCo]2(OH)(Na)3(thf)6, complex (6a): A suspension of sodium hydride
(64.0 mg, 2.7 mmol, 3.5 equiv.) in 15 mL of tetrahydrofurane was added dropwise into a Schlenk
flask containing a solution of tris(2-hydroxy-4,6-dimethylbenzyl)amine (ArMeOH)3N ligand
(314.0 mg, 0.75 mmol, 1 equiv.) in 15 mL of tetrahydrofurane. The mixture was stirred at r.t. for
2 h and then it was added into a Schelenk flask containing Co(OAc)2.4H2O (186.0 mg, 0.75 mmol,
1 equiv.). After 12 h stirring at r.t. the solution was filtered through celite and complexes were
obtained as crystalline solids at r.t. by concentration of the solution. Yield: 305.0 mg (0.29 mmol,
79 %). 1H NMR (CDCl3, 400 MHz, RT): paramagnetic spectrum,  = 36.10, 30.11, 22.65, 6.39,
3.69, 1.96, 1.77, 1.12, 0.34. MALDI()–HRMS (dctb): m/z = 1013.2902 [MNa] (calcd.
1013.2938), Anal. calcd. for C54H61Co2N2Na3O7·(thf)2: C 63.05, H 6.57, N 2.37; found: C 62.55,
H 7.03, N 2.28. IR (cm-1): 2962, 2907, 1259, 1086, 1016, 796; UV/Vis (CH2Cl2, 0.4 mM, 25 ºC, ε
= L·mol-1·cm-1): 398 nm (4940), 490 nm (3200), 698 (695), 1032 (475).
Synthesis of [(ArMeO)3NCo][PPN]+, complex (6b): A suspension of sodium hydride (53.0
mg, 2.2 mmol, 3 equiv.) in 10 mL of tetrahydrofuran was added drop-wise into a Schlenk flask
containing a solution of tris(2-hydroxy-4,6-dimethylbenzyl)amine (ArMeOH)3N ligand (300.0 mg,
0.72 mmol, 1 equiv.) in 10 mL of tetrahydrofuran. The mixture was stirred at room temperature
for 2 h. After this time, 0.95 equiv. of anhydrous CoCl2 (88.0 mg, 0.68 mmol) in 10 mL of
acetonitrile was added. The reaction mixture was stirred at r.t. for 18 h and then it was filtered
through a path of Celite. The solution obtained was added into a Schlenk flask containing 1 equiv.
of bis(triphenylphosphine)iminium chloride, PPN-Cl, (0.7 mmol, 402 mg) to exchange the cation.
After 6 h, the mixture was filtered through a path of Celite. The complex was obtained as a

19

crystalline solid suitable for X-ray crystallographic analysis by concentration of the solution and
by addition of hexane (v/v = 1:1). Yield: 335.0 mg (0.14 mmol, 45 %). 1H NMR (CD2Cl2, 400
MHz, RT): paramagnetic spectrum,  = 37.82, 28.56, 27.89, 7.51, 7.36, 3.55, 1.89, 1.70, -7.79, 11.26, -48.80; MALDI(+)–MS (dctb): m/z = 538.3 [PPN]+ (calcd. 538.2), MALDI()–MS (dctb):
m/z

=

475.1563

[(ArMeO)3NCo]

(calcd.

475.1559).

Anal.

calcd.

for

C63H60CoN2O3P2∙thf·½CH3CN·2H2O: C 71.91, H 6.84, N 2.95; found: C 71.65, H 6.69, N 2.84.
The presence of both solvents (thf and CH3CN) and their 2:1 ratio is supported by 1H NMR of the
dried isolated complex, see Supporting Information. IR (cm-1): 3056, 2962, 2913, 2859, 1608,
1588, 1480, 1469, 1435, 1358, 1308, 1244, 1183, 1161, 1113, 1060, 1027, 997, 904, 860, 801,
749, 721, 690, 605, 549, 532, 495,423; UV/Vis (CH2Cl2, 0.2 mM, 25 ºC, ε = L·mol-1·cm-1): 348
nm (725), 580 nm (330), 605 nm (335), 622 nm (325).
Synthesis of (ArMeO)3NCo(DMAP)2, complex (7): A solution of 4-dimethylaminopyridine
(DMAP) in 10 mL of dichloromethane (102.5 mg, 0.84 mmol, 2.5 equiv.) was added to a round
bottom flask containing a blue solution of complex 5 (300.0 mg, 0.34 mmol, 1 equiv.) in
dichloromethane (10 mL). The mixture was stirred in the presence of air at r.t. for 8 h. Then the
solvent was removed to give a purple residue. The resulting compound was recrystallized from a
mixture of dichloromethane/hexane (1:1 v/v) to give purple crystals. Yield: 200.0 mg (0.28 mmol,
83 %). Synthesis in an inert atmosphere (either N2 or argon) under similar conditions yields 17 %
of the Co(III) complex 7. 1H NMR (CD2Cl2, 500 MHz, RT): paramagnetic spectrum,  = 54.94,
48.74, 41.09, 25.42, 8.24, 6.51, 3.00, 1.71, 1.26, -10.61, -53.61; 1H NMR (CD2Cl2, 500 MHz, 233
K): diamagnetic spectrum,  = 8.53 (d, 3J = 6.0 Hz, 2H, CHpyr), 8.13 (d, 3J = 6.0 Hz, 2H, CHpyr),
6.61 (d, 3J = 6.0 Hz, 2H, CHpyr), 6.54 (s, 2H, CHAr), 6.52 (s, 2H, CHAr), 6.38 (d, 3J = 6.0 Hz, 2H,
CHpyr), 6.12 (s, 1H, CHAr), 5.84 (s, 1H, CHAr), 4.13 (d, 2J = 12.0 Hz, 2H, ArCH2N), 3.08 (s, 6H,

20

NCH3), 3.01 (s br, 2H, ArCH2N), 2.94 (s, 6H, NCH3), 2.86 (d, 2J = 12.0 Hz, 2H, ArCH2N), 2.11
(s, 6H, ArCH3), 2.02 (s, 6H, ArCH3), 1.68 (s, 3H, ArCH3), 1.53 (s, 3H, ArCH3); 13C1H NMR
(CD2Cl2, 126 MHz, 233 K):  = 160.5 (Cq), 159.5 (Cq), 154.3 (Cq), 154.1 (Cq), 150.5 (CHpyr),
150.1 (CHpyr), 130.6 (CHAr), 130.0 (Cq), 129.8 (Cq), 129.1 (CHAr), 128.7 (Cq), 127.4 (CHAr), 126.9
(CHAr), 123.3 (Cq), 121.1 (Cq), 120.4 (Cq), 107.0 (CHpyr), 105.2 (CHpyr), 66.0 (ArCH2N), 61.2
(ArCH2N), 39.4 (NCH3), 39.3 (NCH3), 20.6 (ArCH3), 20.3 (ArCH3), 17.8 (ArCH3), 17.1 (ArCH3);
ESI(+)–MS (CH3CN): m/z = 720.2 [M+H]+ (calcd. 720.3), 598.2 [MDMAP+H]+ (calcd. 598.2),
476.1 [M2DMAP+H]+ (calcd. 476.2); Anal. calcd. for C41H50CoN5O3∙2H2O: C 65.15, H 7.20, N
9.27; found: C 64.90, H 7.02, N 9.13. IR (cm-1): 2983, 2904, 2852, 1614, 1530, 1469, 1440, 1383,
1271, 1219, 1009, 949, 806, 736, 499, 428 (m); UV/Vis (CH2Cl2, 0.2 mM, 25 ºC, ε = L·mol-1·cm1

): 330 nm (7560), 532 nm (5650), 894 nm (510).
Synthesis of (ArtBuO)3NCo(DMAP), complex (8): To a Schlenk flask containing a pink

solution of Co(OAc)2·H2O (223.0 mg, 0.9 mmol, 1 equiv) in MeOH (10 mL) was added a colorless
solution of tris(2-hydroxy-4,6-di-tert-buthylbenzyl)amine (ArtBuOH)3N ligand (600.0 mg, 0.9
mmol, 1 equiv.) in tetrahydrofuran (15 mL). The reaction was then stirred at r.t. for 2 h. After this
a solution of dimethylaminpyridine (DMAP) in 10 mL of tetrahydrofuran (244.0 mg, 2 mmol, 2.5
equiv.) was added to the flask. This mixture was further stirred open to the air at r.t. overnight.
Finally, the solvent was removed to obtain a purple residue. The resulting cobalt complex was
purified by recrystallization using a mixture of dichloromethane/acetonitrile in a proportion 1:1 to
yield purple crystals. Yield: 550.0 mg (0.65 mmol, 73 %). 1H NMR (CD2Cl2, 500 MHz, RT):
paramagnetic spectrum,  = 49.50, 26.60, 4.98, 2.76, 1.58, 1.42, 1.31, 0.96, 9.12, 45.25;
MALDI(+)–MS (dctb): m/z = 849.9 [M]+ (calcd. 849.5), 727.7 [MDMAP]+. (calcd. 727.4; cf.
Figure S32), 672.7 [MDMAPtBu+H]+ (calcd. 672.4; cf. Figure S32); Anal. calcd. for

21

C52H76CoN3O3·½H2O: C 72.70, H 9.03, N 4.89; found: C 72.66, H 9.31, N 4.98. IR (cm-1): 2951,
2903, 2865, 1620, 1536, 1458, 1443, 1412, 1383, 1361, 1263, 1220, 1171, 1022, 874, 834, 808,
624, 548, 536, 469 (m); UV/Vis (CH2Cl2, 0.2 mM, 25 ºC, ε = L·mol-1·cm-1): 334 nm (9425), 536
nm (7550), 926 nm (795).
Synthesis of (ArMeO)3NCo(bipy), complex (9): A solution of 2,2’-bipyridine (bipy) in 10 mL
of dichloromethane (183.0 mg, 1.17 mmol, 5.3 equiv.) was added to a round bottom flask
containing a blue solution of complex 5 (200.0 mg, 0.22 mmol, 1 equiv.) in dichloromethane (15
mL). The mixture was stirred at r.t. open to the air. After 3 days, the solvent was removed to obtain
a brown residue which was dissolved in acetone to obtain a brown solution and a blue precipitate
(complex 5). The solution was filtered to separate the starting material from the desired product.
Then, the solvent was removed and the resulting compound was purified by trituration with diethyl
ether and recrystallized from acetone to give brown crystals at room temperature. Yield: 33.0 mg
(0.05 mmol, 23 %). 1H NMR (CD2Cl2, 500 MHz, RT): diamagnetic spectrum,  = 10.34 (d, 3J =
5.0 Hz, 1H, CHpyr), 8.20 (t, 3J = 6.0 Hz, 1H, CHpyr), 8.07 (d, 3J = 7.0 Hz, 1H, CHpyr), 7.86 (t, 3J =
6.0 Hz, 1H, CHpyr), 7.82 (d, 3J = 7.0 Hz, 1H, CHpyr), 7.61(t, 3J = 6.0 Hz, 1H, CHpyr), 6.80 (s, 1H,
CHAr), 6.76 (d, 3J = 5.0 Hz, 1H, CHpyr), 6.72 – 6.67 (m, 3H, 2CHAr and 1 CHpyr), 6.66 (s, 1H,
CHAr), 6.41 (s, 2H, CHAr), 3.82 (d, 2J = 10.0 Hz, 2H, ArCH2N), 3.49 (s br, 2H, ArCH2N), 3.24 (d,
2

J = 13.0 Hz, 2H, ArCH2N), 2.44 (s, 3H, ArCH3), 2.13 (s, 3H, ArCH3), 2.08 (s, 6H, ArCH3), 1.40

(s, 6H, ArCH3); 13C1H NMR (CD2Cl2, 126 MHz, RT):  = 160.8 (Cq), 158.3 (Cq), 157.5 (Cq),
156.6 (Cq), 152.1 (CHpyr), 151.5 (CHpyr), 139.0 (CHpyr), 138.2 (CHpyr), 131.8 (Cq), 131.5 (CHAr),
130.1 (Cq), 130.0 (CHAr), 127.5 (Cq), 126.8 (CHAr), 123.7 (Cq), 123.5 (Cq), 123.1 (CHpyr), 122.2
(CHpyr), 120.5 (CHpyr), 120.4 (CHpyr), 64.9 (ArCH2N), 61.8 (ArCH2N), 20.4 (ArCH3), 20.2
(ArCH3), 19.1 (ArCH3), 16.2 (ArCH3); MALDI(+)–MS (dctb): m/z = 631.4 [M]+. (calcd. 631.2);

22

Anal. calcd. for C37H38CoN3O3∙2H2O: C 66.56, H 6.34, N 6.29; found: C 66.04, H 5.91, N 6.43.
IR (cm-1): 2973, 2906, 2856, 1605, 1470, 1443, 1310, 1267, 1157, 1033, 854, 804, 766, 730, 607,
556, 500, 408 (m); UV/Vis (CH2Cl2, 0.2 mM, 25 ºC, ε = L·mol-1·cm-1): 356 nm (4307), 468 nm
(2140).
X-ray diffraction studies. The measured crystals were stable under atmospheric conditions;
nevertheless they were treated under inert conditions immersed in perfluoropolyether as protecting
oil for manipulation. Data Collection: measurements were made on a Bruker-Nonius
diffractometer equipped with an APPEX II 4K CCD area detector, a FR591 rotating anode with
MoKa radiation, Montel mirrors and a Kryoflex low temperature device (T = 173ºC). Full-sphere
data collection was used with  and φ scans. Programs used: Data collection Apex2 V2011.3
(Bruker-Nonius 2008), data reduction Saint+Version 7.60A (Bruker AXS 2008) and absorption
correction SADABS V. 2008–1 (2008). Structure Solution: SHELXTL Version 6.10 (Sheldrick,
2000) was used.17 Structure Refinement: SHELXTL-97-UNIX VERSION.
Crystallographic data for complex 5. C62H76CoN2O7, Mr = 1020.17, monoclinic, Cc, a =
14.3608(6) Å, b = 24.8788(13) Å, c = 16.2469(7) Å, = = 90º, β = 90.053(2)°, V = 5804.7(5)
Å3, Z = 4, ρ = 1.167 mg·M−3, μ = 0.347 mm−1, λ = 0.71073 Å, T = 100(2) K, F(000) = 2180, crystal
size = 0.15 × 0.13 × 0.10 mm, θ(min) = 1.637°, θ(max) = 27.50°, 21502 reflections collected,
12701 reflections unique (Rint = 0.0399), GoF = 1.027, R1 = 0.0867 and wR2 = 0.2267 [I > 2σ(I)],
R1 = 0.1290 and wR2 = 0.2629 (all indices), Flack parameter: x = 0.51(4), min/max residual density
= −0.369/1.214 [e·Å−3]. Completeness to θ(27.50°) = 99.8%. The structure is disordered over two
positions (70:30 occupancy ratio) and is a MeOH/toluene solvate.
Crystallographic data for complex 6a. C78H109Co2N2Na3O13, Mr = 1469.50, monoclinic, Pn,
a = 13.7435(14) Å, b = 26.138(3) Å, c = 21.020(2) Å, = = 90º, β = 90.337(2)°, V = 7550.9(13)

23

Å3, Z = 2, ρ = 1.293 mg·M−3, μ = 0.519 mm−1, λ = 0.71073 Å, T = 100(2) K, F(000) = 3128, crystal
size = 0.13 × 0.10 × 0.10 mm, θ(min) = 0.779°, θ(max) = 35.34°, 320726 reflections collected,
48572 reflections unique (Rint = 0.0385), GoF = 1.017, R1 = 0.0370 and wR2 = 0.0916 [I > 2σ(I)],
R1 = 0.0460 and wR2 = 0.0972 (all indices), Flack parameter: x = 0.393(6), min/max residual
density = −0.455/0.720 [e·Å−3]. Completeness to θ(35.34°) = 95.3%. The structure is a THF
solvate and it contains two distinct complexes in the unit cell.
Crystallographic data for complex 6b. C73H79CoN3O5P2, Mr = 1199.26, monoclinic, P2(1), a
= 14.1572(11) Å, b = 13.5823(12) Å, c = 17.1867(17) Å, = = 90º, β = 107.672(3)°, V =
3148.8(5) Å3, Z = 2, ρ = 1.265 mg·M−3, μ = 0.377 mm−1, λ = 0.71073 Å, T = 100(2) K, F(000) =
1270, crystal size = 0.20 × 0.10 × 0.03 mm, θ(min) = 1.51°, θ(max) = 30.55°, 24268 reflections
collected, 14719 reflections unique (Rint = 0.0265), GoF = 1.026, R1 = 0.0425 and wR2 = 0.0943 [I
> 2σ(I)], R1 = 0.0549 and wR2 = 0.1005 (all indices), Flack parameter: x = 0.015(6), min/max
residual density = −0. 558/0.529 [e·Å−3]. Completeness to θ(30.55°) = 96.7%. The structure has a
disorder in the coordinated THF molecule and co-crystallized CH3CN, and the absolute
configuration was determined.
Crystallographic data for complex 7. C42H52Cl2CoN5O3, Mr = 804.71, triclinic, P-1, a =
11.4464(6) Å, b = 12.3420(6) Å, c = 15.9066(7) Å, = 108.305(2)º, β = 99.116(2)º, =
104.538(2)º, V = 1995.11(17) Å3, Z = 2, ρ = 1.340 mg·M−3, μ = 0.609 mm−1, λ = 0.71073 Å, T =
100(2) K, F(000) = 848, crystal size = 0.15 × 0.08 × 0.04 mm, θ(min) = 1.902°, θ(max) = 28.30°,
9576 reflections collected, 9576 reflections unique, GoF = 1.039, R1 = 0.0431 and wR2 = 0.0999
[I > 2σ(I)], R1 = 0.0586 and wR2 = 0.1072 (all indices), Flack parameter: x = 0.393(6), min/max
residual density = −0.471/0.394 [e·Å−3]. Completeness to θ(28.30°) = 96.4%. For this structure the

24

program TWINABS was used18 since the two types of monocrystals had formed. The structure
contains a disordered, modeled DCM molecule.
Cyclic voltammetry. Cyclic voltammetry measurements were carried out with a Princeton
Applied Research PARSTAT 2273 electrochemical analyzer. A three-component system
consisting of a glassy carbon working electrode, a platinum wire auxiliary electrode and Ag-AgCl
(sat. NaCl) reference electrode was used. All experiments were done under argon atmosphere at
r.t. and in dichlorometane solutions with 0.2 M tetrabuthylammonium hexafluorophosphate
(NBu4PF6) as the supporting electrolyte.
Magnetic data. Magnetic susceptibility measurements with polycrystalline samples of
complexes 4-8 were carried out in a Quantum Design MPMS-XL-7 SQUID magnetometer using
a field of 1000 Oe in the 2-300 K temperature range. Pascal’s constants were used to estimate the
diamagnetic corrections for the compounds.

 ASSOCIATED CONTENT
Supporting Information. X-ray crystallographic data in CIF format, further experimental
details and spectroscopic data of key compounds. This material is free of charge via the Internet
at http://pubs.acs.org.

 AUTHOR INFORMATION
Corresponding Author
* E-mail: akleij@iciq.es. Phone: +34 – 977920247. Fax: +34 - 977920823.
Notes

25

The authors declare no competing financial interest.

 ACKNOWLEDGMENT
We thank ICIQ, ICREA, the Spanish Ministerio de Economía y Competitividad (MINECO)
through project CTQ-2011-27385 and support through Severo Ochoa Excellence Accreditation
2014-2018 (SEV-2013-0319), and the European Union through project ERC Stg grant
CHEMCOMP for support. CM gratefully thanks the Marie Curie COFUND Action from the
European Commission for co-financing a postdoctoral fellowship. Dr. Noemí Cabello, Sofía Arnal
and Vanessa Martínez are thanked for the MS analyses.

 REFERENCES

(1) Licini, G.; Mba, M.; Zonta, C. Dalton Trans. 2009, 5265-5277.
(2) (a) Kim, Y.; Jnaneshwara, G. K.; Verkade, J. G. Inorg. Chem. 2003, 42, 1437-1447. (b) Mba,
M.; Prins, L. J.; Licini, G. Org. Lett. 2007, 9, 21-24. (c) Mba, M.; Pontini, M.; Lovat, S.; Zonta,
C.; Bernardelli, G.; Kundig, P. E.; Licini, G. Inorg. Chem. 2008, 47, 8616-8618. (d) Romano, F.;
Linden, A.; Mba, M.; Zonta, C.; Licini, G. Adv. Synth. Catal. 2010, 352, 2937-2942. (e) Chmura,
A. J.; Davidson, M. G.; Frankis, C. J.; Jones, M. D.; Lunn, M. D. Chem. Commun. 2008, 12931295. (f) Lam, O. P.; Anthon, C.; Meyer, K. Dalton Trans. 2009, 9677-9691. (g) Whiteoak, C. J.;
Gjoka, B.; Martin, E.; Martínez Belmonte, M.; Zonta, C.; Licini, G.; Kleij, A. W. Inorg. Chem.
2012, 51, 10639-10649; (h) Whiteoak, C. J.; Martin, E.; Martínez Belmonte, M.; Benet-Buchholz,
J.; Kleij, A. W. Adv. Synth. Catal. 2012, 354, 469-476; (i) Whiteoak, C. J.; Martin, E.; Escudero-

26

Adán, E. C.; Kleij, A. W. Adv. Synth. Catal. 2013, 355, 2233-2239; (j) Whiteoak, C. J.; Kielland,
N.; Laserna, V.; Escudero-Adán, E. C.; Martin, E.; Kleij, A. W. J. Am. Chem. Soc. 2013, 135,
1228-1231; (k) Whiteoak, C. J.; Kielland, N.; Laserna,V.; Castro-Gómez, F.; Martin, E.; EscuderoAdán, E. C.; Bo, C.; Kleij, A. W. Chem. Eur. J. 2014, 20, 2264-2275. (l) Su, W.; Kim, Y.; Ellern,
A.; Guzei, I. A.; Verkade, J. G. J. Am. Chem. Soc. 2006, 128, 13727-13735.
(3) Käß, M.; Hohenberger, J.; Adelhardt, M.; Zolnhofer, E. M.; Mossin, S.; Heinemann, F. W.;
Sutter, J.; Meyer, K. Inorg. Chem. 2014, 53, 2460-2470.
(4) (a) Ray, M.; Hammes, B. S.; Yap, G. P. A.; Rheingold, A. L.; Borovik, A. S. Inorg. Chem.
1998, 37, 1527-1532. (b) Stähler, R.; Bensch, W. Eur. J. Inorg. Chem. 2001, 3073-3078. (c) Searls,
C. E.; Kleespies, S. T.; Eppright, M. L.; Schwartz, S. C.; Yap, G. P. A.; Scarrow, R. C. Inorg.
Chem. 2010, 49, 11261-11263. (d) Suh, M. P; Lee, J.; Han, M. Y.; Yoon, T. S. Inorg. Chem. 1997,
36, 5651-5654. (e) El-Shafai, N. M.; Ibrahim, M. M.; Kamel, G. E.; El-Baradie, H. Y. J. Mater.
Environ. Sci. 2012, 3, 1101-1108. (f) Lucas, R. L.; Zart, M. K.; Murkerjee, J.; Sorrell, T. N.;
Powell, D. R.; Borovik, A. S. J. Am. Chem. Soc. 2006, 128, 15476-15489. (g) Jones, M. B.;
MacBeth, C. E. Inorg. Chem. 2007, 46, 8117-8119. (h) Hu, X.; Castro-Rodriguez, I.; Meyer, K. J.
Am. Chem. Soc. 2004, 126, 13464-13475. (i) Hu, X.; Meyer, K. J. Am. Chem. Soc. 2004, 126,
16322-16323.
(5) (a) Tokunaga, M.; Larrow, J. F.; Kakiuchi, F.; Jacobsen, E. N. Science, 1997, 277, 936-938.
(b) Jacobsen, E. N. Acc. Chem. Res. 2000, 33, 421-431. (c) Zheng, X.; Jones, C. W.; Weck, M. J.
Am. Chem. Soc. 2007, 129, 1105-1112. (d) Wezenberg, S. J.; Kleij, A. W. Adv. Synth. Catal. 2010,
352, 85-91. (e) Holbach, M.; Weck, M. J. Org. Chem. 2006, 71, 1825-1836.

27

(6) (a) Nakano, K.; Hashimoto, S.; Nakamura, M.; Kamada, T.; Nozaki, K. Angew. Chem. Int.
Ed. 2011, 50, 4868-4871. (b) Lu, X.-B.; Shi, L.; Wang, Y.-M.; Zhang, R.; Zhang, Y.-J.; Peng, X.J.; Zhang, Z.-C.; Li, B. J. Am. Chem. Soc. 2006, 128, 1664-1674. (c) Wu, G.-P.; Wei, S.-H.; Ren,
W.-M.; Lu, X.-B.; Xu, T.-Q.; Darensbourg, D. J. J. Am. Chem. Soc. 2011, 133, 15191-15199. (d)
Cohen, C. T.; Chu, T.; Coates, G. W. J. Am. Chem. Soc. 2005, 127, 10869-10878.
(7) (a) Hirahata, W.; Thomas, R. M.; Lobkovsky E. B.; Coates, G. W. J. Am. Chem. Soc. 2008,
130, 17658-17659. (b) Park, J.; Lang, K.; Abboud, K. A.; Hong, S. J. Am. Chem. Soc. 2008, 130,
16484-16485.
(8) Nielsen, L. P. C.; Stevenson, C. P.; Blackmond, D. G.; Jacobsen, E. N. J. Am. Chem. Soc.
2004, 126, 1360-1362.
(9) (a) Fortner, K. C.; Bigi, J. P.; Brown, S. N. Inorg. Chem. 2005, 44, 2803-2814. (b) Zonta, C.;
Licini, G. Chem. Eur. J. 2013, 19, 9438-9441.
(10) Taherimehr, M.; Al-Amsyar, S. M.; Whiteoak, C. J.; Kleij, A. W.; Pescarmona, P. P. Green
Chem. 2013, 15, 3082-3090.
(11) Lehtonen, A.; Kessler, V. G Inorg. Chem. Commun. 2004, 7, 691-693.
(12) (a) Prins, L. J.; Blázquez, M. M.; Kolarović, A.; Licini, G. Tetrahedron Lett. 2006, 47,
2735-2738. (b) Chandrasekaran, A.; Day, R. O.; Holmes, R. R. J. Am. Chem. Soc. 2000, 122, 10661072.
(13) The corresponding Co(II) complex from ligand 3 could not be isolated probably due to
steric restrictions; upon isolation only the starting materials were recovered.

28

(14) Note that the synthesis, using the same time frame, under nitrogen or argon afforded in both
cases a 17% of 7, whereas its synthesis in a glove box gave only 8% isolated yield. This indicates
that oxygen may be actively involved promoting the formation of complex 7 being one of the
oxidizing sources.
(15) Jaynes, B. S.; Ren, T.; Liu, S.; Lippard, S. J. J. Am. Chem. Soc. 1992, 114, 9670-9671.
(16) Kol, M.; Shamis, M.; Goldberg, I.; Goldschmidt, Z.; Alfi, S., Hayut-Salant, E. Inorg.
Chem. Comm. 2001, 4, 177-179.
(17) Sheldrick, G. M. SHELXTL Crystallographic System, version 6.10, Bruker AXS, Inc.,
Madison, Wisconsin, 2000.
(18) TWINABS Version 2008/4 Bruker AXS, see: Blessing, H. Acta Cryst. 1995, A51, 33-38.

29

For Table of Contents only:

Co(II) and Co(III) complexes comprising amino-trisphenolate ligands have been prepared and
fully characterized. X-ray analyses, variable temperature NMR measurements and SQUID
magnetization studies were conducted to support the oxidation states of the obtained complexes.
One of the isolated Co(III) derivatives shows fluxional ligand coordination behavior in solution
allowing for penta- and hexa-coordinated species to be identified in the high and low-temperature
regimes, respectively.

30