{CoII/III5} horseshoe and {NiII4} lacunary cubane coordination clusters: The isobutyrate/N-butyldiethanolamine reaction system

Article abstract of DOI:10.1039/c6ra19232g

The polynuclear coordination compounds [Co^II₃Co^III₂ (Hbda)₂(bda)₂(ib)₆]·2MeCN (1) and [Ni^II₄ (Hbda)₃(ib)₅(MeCN)] (2) (H₂bda = N-butyldiethanolamine, ib = isobutyrate) are prepared under aerobic conditions using an identical synthetic protocol that solely differs in the employed transition metal (Co^IIvs. Ni^II). Whereas compound 1 displays a mixed-valent, pentanuclear, horseshoe-shaped structure with alternating Co(ii) and Co(iii) ions, compound 2 presents a tetrahedrally-shaped Ni(ii) structural motif where four nickel centers are bridged by three O atoms to afford a lacunary Ni₄O₃ cubane, a motif hitherto only observed as a substructure of higher-nuclearity coordination clusters and polyoxometalates. Both compounds are thermally surprisingly stable (>130 °C). 1 exhibits weak antiferromagnetic exchange interactions; 2 shows a ferromagnetic coupled triangle of three Ni centers interacting antiferromagnetically with a single Ni apex.

Full text of DOI:10.1039/c6ra19232g

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{CoI5I/III} horseshoe and {NiI4I} lacunary cubane
coordination clusters: the isobutyrate/N-
butyldiethanolamine reaction system†
Cite this: RSC Adv., 2016, 6, 100664
Sebastian Schmitz,a Kirill Yu. Monakhov,a Jan van Leusen,a Natalya V. Izarova,b
ab
Volkmar Heßab and Paul Kogerler
*
¨
The polynuclear coordination compounds [CoI3ICo2III(Hbda)2(bda)2(ib)6]$2MeCN (1) and [Ni4II(Hbda)3
(ib)5(MeCN)] (2) (H2bda
¼
N-butyldiethanolamine, ib
¼
isobutyrate) are prepared under aerobic
conditions using an identical synthetic protocol that solely differs in the employed transition metal (CoII
vs. NiII). Whereas compound 1 displays a mixed-valent, pentanuclear, horseshoe-shaped structure with
alternating Co(II) and Co(III) ions, compound 2 presents a tetrahedrally-shaped Ni(II) structural motif
where four nickel centers are bridged by three O atoms to afford a lacunary Ni4O3 cubane, a motif
Received 29th July 2016
Accepted 17th October 2016
hitherto only observed as
polyoxometalates. Both compounds are thermally surprisingly stable (>130 ꢀC).
a
substructure of higher-nuclearity coordination clusters and
exhibits weak
1
DOI: 10.1039/c6ra19232g
antiferromagnetic exchange interactions; 2 shows a ferromagnetic coupled triangle of three Ni centers
www.rsc.org/advances
interacting antiferromagnetically with a single Ni apex.
MnII in the mixed-valent {Mn MnI7I} coordination cluster on
III
12
Introduction
Au(111)6) at the molecule–surface interface or by external elec-
tromagnetic elds.
Polynuclear transition metal coordination compounds are an
attractive, large playground for comparative experimental and
computational studies1 of their bulk-to-surface structure–
magnetism relations, in particular in the area of molecular
conductivity and spintronics2 and quantum computing.3 When
we aim to explore the charge transport characteristics of
discrete coordination complexes (where studies in the literature
thus far predominantly focus on single-molecule magnets4) via
magnetic (e.g. X-ray magnetic circular dichroism) or scanning
probe microscopy experiments,5 important molecular charac-
teristics for their deposition on a substrate are: low-nuclearity,
charge neutrality, moderate solubility and structural stability
in organic solvents, thermal stability and sublimability.
Furthermore, even paramagnetic coordination clusters with no
magnetic anisotropy-induced slow magnetization relaxation or
hysteresis (as opposed to SMMs) generate considerable interest
if they can be deposited as intact, single molecules, as they can
undergo substantial changes in their molecular magnetic
anisotropy upon redox processes (see, e.g., reduction of MnIII to
We here report a simple reaction system that results in
thermally stable, low-nuclearity, charge-neutral coordination
clusters [CoI3ICo2III(Hbda)2(bda)2(ib)6]$2MeCN (1) or [Ni4II(Hbda)3
(ib)5(MeCN)] (2) which fall into the archetypal horseshoe-7 and
cubane8-type structure families, from which numerous chemi-
cally9 and magnetically functionalized derivatives can then be
generated. 1 and 2 were obtained under aerobic conditions in
the reactions of M(ib)2 (M ¼ Co and Ni) and N-butyldiethanol-
amine in acetonitrile (MeCN) and were characterized by
elemental analysis, IR spectroscopy, electrospray ionization
mass spectrometry (ESI-MS), thermogravimetric analysis (TGA),
X-ray photoelectron spectroscopy (XPS) and single-crystal X-ray
diffraction, and by ac and dc susceptibility measurements
that were reproduced using CONDON 2.0.10
Results and discussion
Synthetic procedures and stability
The isobutyrate precursors11 M(ib)2 (see ESI† for IR spectra)
were freshly prepared by heating M(OOCMe)2$4H2O (M ¼ Co,
Institut fur Anorganische Chemie, RWTH Aachen University, Landoltweg 1, 52074 Ni) in an excess of isobutyric acid at 150 ꢀC until all organic acid
a
¨
was evaporated.12 The facile reactions of the thus-obtained
Aachen, Germany. E-mail: paul.koegerler@ac.rwth-aachen.de
b
¨
¨
Julich-Aachen Research Alliance (JARA-FIT) and Peter Grunberg Institute (PGI-6),
M(ib)2 powders with H2bda in a 1 : 1 ratio in MeCN under
reux conditions (Scheme 1) in the presence of air oxygen afforded
the dark-green pentanuclear mixed-valent {CoI3ICo2III} complex (1)
and the light-green homovalent tetranuclear {NiI4I} complex (2),
which were isolated in yields of 49% and 22%, respectively. TGA of
¨
¨
Forschungszentrum Julich, 52425 Julich, Germany
† Electronic supplementary information (ESI) available: Crystal data and structure
renement details, IR, ESI-MS, TGA and XPS data. CCDC 1487791 and 1487792.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c6ra19232g
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environments, while Co3 ion is ligated by six O atoms. All Co
atoms are very close to a common plane (Fig. 1b).
˚
Co/Co distances range from 2.963(1) to 3.032(1) A. The
II
II
˚
distance between the equal Co 1 and Co 5 centers is 7.509(1) A
II
˚
and their distance to Co 3 ranges from 5.275(1) A (Co1/Co3) to
ꢀ
˚
5.257(1) A (Co5/Co3). The Co1–Co2–Co3 angle is 122.99(3) ,
Co3–Co4–Co5: 123.00(3)ꢀ. One monodentate m1-ibꢁ ligand
coordinates to each Co1 and Co5. These two ibꢁ ligands are
assumed to be deprotonated, because of their short C–O bond
Scheme 1 Synthesis of pentanuclear compound 1 and tetranuclear
compound 2.
˚
˚
lengths of 1.256(7) A (C1B1–O2B1) and 1.247(8) A (C1B6–O2B6).
The terminal monodentate ibꢁ ligands form strong H bonds
with the monoprotonated Hbdaꢁ ligands with O/O distances
compound 1 conrms that the solvent-free [CoI3ICo2III(Hbda)2
(bda)2(ib)6] complex retains its integrity up to 140 ꢀC against
degradation under a nitrogen atmosphere or air (Fig. S8 and S9†).
Compound 2 is thermally stable up to 130 ꢀC (Fig. S10 and S11†).
of 2.513(6)–2.526(6) A. The m2-O of the Hbdaꢁ is assumed to be
˚
protonated, given the BVS values of ꢁ1.18 and ꢁ1.21 (C–O bond
˚
lengths of 1.425(7) and 1.442(10) A) as compared to the depro-
ꢁ
˚
˚
tonated arms of Hbda : 1.400(7) A and 1.404(7) A (BVS: ꢁ2.00
and ꢁ2.03). Co1, CoIII2 and Co3 as well as Co3, CoIII4 and Co5
are bridged by a m2,h1:h2 ibꢁ ligand. In addition, Co1 and Co2 as
well as Co4 and Co5 are linked by Hbdaꢁ and bda2ꢁ ligands
through the bridging ethanolate groups. The CoIII ion (Co2 and
Co4) is connected with Co3 by a m2,h1:h1-ibꢁ ligand and an
ethanolate group of bda2ꢁ. The distance between the two CoIII
X-ray crystal structure analysis
ꢀ
Complex 1 crystallizes in the triclinic space group P1. Its
molecular structure (Fig. 1) reveals a horseshoe-shaped metal
core with Co atoms alternating in their formal oxidation states
of +II and +III, established by bond valence sum analysis
[Sbv(CoII) ¼ 1.74–2.07 and Sbv(CoIII) ¼ 2.91 and 2.94], reecting
partial oxidation of Co(II) by air oxygen throughout the
synthesis. XPS analysis also conrms the mixed-valent Co(II/III)
formulation of compound 1 (Fig. S12†). The Co ions are ligated
by four N-butyldiethanolamine and six isobutyrate groups. Co1,
Co2, Co4 and Co5 adopt pseudo-octahedral NO5 coordination
ꢀ
˚
ions is 5.783(1) A (Co2–Co3–Co4: 145.80(3) ).
We note that in 2015 Lazzarini et al.13 described a bent
mixed-valent {Co3IICo2III} complex with the CoII–CoII–CoII angle
of 138.98(1)ꢀ that was obtained in 8% yield by reacting a [Co2
(H2O)(piv)4(Hpiv)4] precursor (Hpiv ¼ pivalic acid) with a Schiff-
base ligand and triethylamine in MeCN. Contrary to compound
1 bearing two different types of ligands (carboxylate and ami-
noalcohol) and a metal core with alternating Co(II) and Co(III)
centers, the pentanuclear {CoI3ICo2III} core in the reported
complex consists of three inner cobalt(II) atoms and two
terminal cobalt(III) atoms and is supported by six m-carboxylate
ligands, two Schiff-base ligands, two m3-OH groups and four
terminal water molecules that complete the octahedral coordi-
nation of some Co(II) centers.
Complex 2 crystallizes in the orthorhombic space group
P212121. Its molecular structure consists of four octahedrally
coordinated NiII ions, three partially deprotonated Hbdaꢁ
ligands, three bidentate and two monodentate ibꢁ ligands and
one terminally coordinated MeCN molecule (Fig. 2). The nickel
atoms form a distorted tetrahedron with the non-bonding Ni/
˚
Ni distances ranging from 2.9953(9) to 3.851(1) A. The apex
˚
(Ni1) is 2.042 A above the Ni2/Ni3/Ni4 triangle. Ni1 is sur-
rounded by six O atoms: (i) three of these belong to the biden-
tate m2,h1:h1-ibꢁ ligands (Ni1–Oib: 2.018(4)–2.046(4) A); (ii) the
˚
other three are the m4-O atoms of the Hbdaꢁ ligands (Ni1–OHbda
:
˚
2.096(4)–2.131(4) A). Ni2 and Ni3 reside in NO5 environments
from two m4-O atoms of Hbdaꢁ (Ni2-m4Hbda-O: 2.057(4)–2.091(4)
ꢁ
˚
˚
A and Ni3-m4Hbda-O: 2.063(4)–2.105(4) A), one m2-O of Hbda
˚
(Ni2–O1N2: 2.123(4), Ni3–O1N3: 2.138(3) A), one N atom of
Hbdaꢁ (Ni2–N2: 2.149(5), Ni3–N3 2.165(5) A), and the O atoms
˚
Fig.
1
(a) Molecular structure of [CoI3ICo2III(Hbda)2(bda)2(ib)6] in 1
˚
of the bidentate (Ni2–O2B1: 2.044(4), Ni3–O2B2: 2.013(4) A) and
monodentate (Ni2–O1B5: 2.075(4), Ni3–O1B4: 2.068(4) A) ib
ligands. The N2O4 environment of Ni4 is characterized by Ni4–
MeCN: 2.122(5), Ni4–NHbda: 2.137(5), Ni4-m4Hbda-O: 2.054(4)–
2.062(4), Ni4-m2Hbda-O: 2.103(4) and Ni4–Oib: 2.014(4) A.
emphasizing the horseshoe-type structure and Co atom numbering.
(b) Perspective showing the common plane (transparent blue) spanned
by the five Co centers in 1, with terminal butyl/isopropyl residues not
shown. Color code: Co(II), violet; Co(III), dark yellow; C(bda), grey; C(ib),
green; N, blue; O, red. Hydrogen atoms are omitted for clarity.
ꢁ
˚
N
˚
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Another interesting feature of 2 is the weakly coordinated,
labile MeCN molecule that can be regarded as a potential
substrate docking position for catalytic conversions.19 To probe
the accessibility of this Ni4 site, we stirred compound 2 in
MeOH at room temperature for several minutes. The micro-
crystalline product was ltered off and dried in air. EA indicates
the composition [Ni4(Hbda)3(ib)5]$MeOH$2H2O, thus suggest-
ing that the MeCN molecule was readily replaced by MeOH or
one of the two water solvent molecules (calcd/found: C, 44.34/
44.28; H, 8.02/7.86 and N, 3.45/3.68%). Also, analysis of
freshly prepared 2 that was washed with small amounts of
MeCN and dried in air was performed several times. The results
of these analyses show the following ranges: C, 43.2–43.7; H,
7.44–7.73; N, 2.93–2.98%. The low amount of C and N is
indicative of de-coordination of the terminal MeCN molecule
under the used mild conditions (air and moisture). Thus, the
obtained C/H/N values indicate the formula [Ni4(Hbda)3(ib)5]$
3H2O [calcd: C, 43.86; H, 7.95; N, 3.49%]. This de-coordination
is furthermore revealed by the absence of a CN band (n(CN) of
free MeCN: 2254 cmꢁ1) in the IR spectrum of compound 2. The
retention of the {Ni4} core is indicated by nearly identical IR
ngerprints of compound 2 and its MeOH-treated derivative
(Fig. S2 and S3†) as well as the obtained ESI-MS data (Fig. S7 and
Table S3†).
Magnetism and magnetochemical modeling
Fig. 2 (a) Molecular structure of [Ni4(Hbda)3(ib)5(MeCN)] in 2 with Ni
atom numbering. (b) The Ni4O3 core structure with the isosceles Ni3
triangle base, highlighted in transparent blue, with m4-O sites of the
lacunary cubane shown as red spheres. Butyl and isopropyl residues
are not shown. Color code: Ni, green spheres; C, dark grey; N, blue; O,
red. The terminal MeCN molecule is shown in ball-and-stick repre-
sentation. Hydrogen atoms are omitted for clarity.
For the analysis of the paramagnetic susceptibility caused by
the three Co(II) centers of compound 1, we note that the octa-
hedrally coordinated low-spin Co(III) centers signicantly
contribute
via
their
temperature-independent
para-
magnetism.20 We assume cTIP ¼ +0.4 ꢂ 10ꢁ3 cm3 molꢁ1 (ref.
20b) in total for both centers in 1, thus obtaining cmT ¼ 8.69
cm3 K molꢁ1 at 290 K instead of 8.80 cm3 K molꢁ1. The corre-
sponding net data for three Co(II) centers are shown in Fig. 3.
The value of 8.69 cm3 K molꢁ1 is in the range 6.94–9.78 cm3 K
In 2007 Biswas et al.14 reported an octadecanuclear {Ni16Na2}
coordination cluster composed of four [Ni4(Hmda)3(OOCMe)5
(OOCH)0.5] fragments (H2mda ¼ N-methyldiethanolamine),
interconnected via two sodium cations and two formate anions.
The central Ni4O3 core (i.e. a lacunary Ni4O4 cubane core) in
each of these fragments is isostructural to that in the isolated
compound 2. In 2005 Salameh et al.15 prepared a cationic
[Ni9L8(OH)6(NH3)4(H2O)8]4+ coordination cluster (HL ¼ 7,8-
dihydro-1,2,4-triazolo[4,3-a]pyrimidin-7-one), which comprises
two {Ni4} fragments linked by six L ligands through a ninth
Ni(II) ion. In 1977 Strouse et al.16 and in 2003 Murrie et al.17
reported the compound (NMe4)10[Ni8(cit)6(OH)2(H2O)2] (H4cit ¼
citric acid), differing only in crystal packing and the number of
lattice water molecules. This compound is a dimer of two {Ni4}
fragments that are bridged by two m3-O atoms of two cit ligands.
In addition, the Ni4O3 coordination has been observed in the
chemistry of polyoxometalates,18 where it was found to coordi-
nate to polyoxotungstates to form {XW9Ni4} building units,
which are obtained by using e.g. nickel nitrate or nickel acetate
and Na10[A-a-XW9O34]$nH2O as precursors (X ¼ Si, P). To the
best of our knowledge, compound 2 represents the rst example
of a metal complex featuring a discrete, organic ligand-
supported Ni4O3 core whose molecular ions are detectable in
the ESI-MS spectrum in MeOH (see ESI†).
Fig. 3 Temperature dependence of cmT at 1.0 T of compound 1; inset:
molar magnetization Mm vs. B at 2.0 K: experimental data for three
Co(II) centers (open circles), least-squares fit (red solid lines).
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molꢁ1 that is expected for three non-interacting high-spin Co(II)
centers.20a With decreasing temperature, cmT is almost
constant down to ca. 150 K, and subsequently decreases to 3.97
cm3 K molꢁ1 at 2.0 K. The latter is caused by the split of the 4F
ground term of the free ion by the ligand eld into a 4T1g ground
4
4
term (and excited T2g, A2g terms) which is potentially further
split due to the distorted octahedral geometry of the ligands.
Irrespective of a symmetry-decreasing distortion, spin–orbit
4
coupling causes a split of the T1g ground term in addition to
mixing of excited states and ground state, which is reected by
a temperature dependence of cmT due to thermal (de)pop-
ulation of the resulting states. Additionally, antiferromagnetic
exchange interactions may be present. The molar magnetiza-
tion reaches 5.2 NAmB at 5.0 T and 2.0 K, well below a saturation
value of ca. 11–12 NAmB extrapolated from the cmT value at
ambient temperature. The magnetization does not, however,
saturate as revealed by the small but distinct slope of Mm vs. B at
this eld. The magnetization behavior may be thus determined
by antiferromagnetic exchange interactions and/or single-ion
effects. Due to the structure of compound 1, a chain of alter-
nating Co(II) and Co(III) centers and extended –O–Co(III)–O–
Fig. 4 Temperature dependence of cmT at 0.1 T of compound 2;
inset: molar magnetization Mm vs. B at 2.0 K: experimental data (open
circles), least-squares fit (red solid lines).
exchange pathways between the Co(II) centers, we expect negli- to the spin-only nature of the Ni(II) centers, the magnetization
gible or very weak exchange interactions. curve at 2.0 K indicates a saturation step at about 4.5–5.0NA mB,
Using the “full model” Hamiltonian implemented in CON- therefore indicating a total ground state S ¼ 2 derived from
DON 2.0,10 the magnetic data of compound 1 was modeled Mm,step ¼ gSSNA mB, and gS > 2 for Ni(II).
assuming the three Co(II) centers to be identical, and in a C4v-
The magnetic data of compound 2 is reproduced by
symmetric ligand eld. Potential exchange interactions are employing the spin-only option of CONDON 2.0.10 Assuming
accounted for by a mean-eld approach. Treating the standard approximately isotropic Ni(II) centers, we restrict the number of
Racah parameters B ¼ 1115 cmꢁ1 and C ¼ 4366 cmꢁ1 and the independent exchange interaction pathways to two to avoid
one-electron spin–orbit coupling parameter z3d ¼ 533 cmꢁ1 as over-parameterization. The parameters describing the interac-
constants,21 we use the full basis of 120 states. The least-squares tion of the three Ni(II) centers forming an almost equilateral
2
ꢁ
t of goodness SQ ¼ 1.6% yields the ligand eld parameters B0
triangle of side length 3.8 A are denoted as J2, while the
4
4
¼ (ꢁ5060 ꢃ 2130) cmꢁ1, B0 ¼ (12 247 ꢃ 2598) cmꢁ1, B4
¼
remaining three shorter pathways exhibiting Ni–Ni distances of
(29 985 ꢃ 1088) cmꢁ1 (in Wybourne notation) and zJ0 # ꢁ0.1 ca. 3.0 A are characterized by J1. The least-squares t of good-
cmꢁ1 (ꢁ2zJ0 notation; Fig. 3). The mean-eld parameter zJ0 ness SQ ¼ 1.1% yields J1 ¼ (ꢁ1.6 ꢃ 0.1) cmꢁ1, J2 ¼ (+0.7 ꢃ 0.2)
reveals very small antiferromagnetic exchange interactions. The cmꢁ1 and geff ¼ 2.21 ꢃ 0.02 (ꢁ2J notation). The corresponding
ligand eld parameters describe a ligand eld of distorted calculated data are depicted as solid lines in Fig. 4. The calcu-
octahedral symmetry which splits, along with the spin–orbit lated ground state is also characterized by S ¼ 2. Introduction of
ꢁ
4
coupling, the T1g ground term into six Kramers doublets. The additional exchange pathways does not signicantly enhance
rst excited states are at ca. 190 cmꢁ1, 350 cmꢁ1, and 610 cmꢁ1 the goodness-of-t. The compound may thus be described as
above the ground state while the remaining two doublets are at three centers with effective S ¼ 1 forming a ferromagnetic
ca. 3900 cmꢁ1 and 4000 cmꢁ1
.
coupled triangle that is opposed to a single spin-1 center which
The magnetic data of compound 2 are shown in Fig. 4 as cmT antiferromagnetically interacts with the triangle.
vs. T and Mm vs. B plots. At 290 K, the cmT value of 4.86 cm3 K
molꢁ1 lies within the range 3.92–6.13 cm3 K molꢁ1 expected for
four non-interacting high-spin Ni(II) centers.20a Upon tempera-
Conclusions
ture decrease, cmT slightly increases to a maximum of 4.93 cm3 We showcased that the aerobic one-pot reaction of simple
K molꢁ1 at 200 K, subsequently decreases to 4.45 cm3 K molꢁ1 at M(ib)2 precursors (M ¼ Co and Ni) with N-butyldiethanolamine
25 K, and falls off to a minimum of 3.64 cm3 K molꢁ1 at 2.6 K. results in starkly different polynuclear compounds with prop-
3
Since the ground term of octahedral Ni(II) centers is A2g, such erties (charge neutrality, relatively high thermal stability, char-
compounds exhibit nearly spin-only paramagnetism, i.e. 2 may acteristic geometries) that render these species amenable for
be described as system of effective spin-1 centers. The shape of surface deposition: a mixed-valent Co(II/III) complex (1) with
the cmT vs. T curve is thus essentially due to weak exchange negligible antiferromagnetic interactions due to an alternating
interactions of approximately same magnitude. The low- CoII–CoIII–CoII–CoIII–CoII sequence, and a Ni(II) complex (2)
temperature data (T < 30 K) may, however, also be signi- with both ferromagnetic and antiferromagnetic nearest-
cantly inuenced by effects of zero-eld splitting which occurs neighbor coupling. The lacunary cubane structure of 2 was
for Ni(II) centers in case of ligand eld symmetry distortion. Due hitherto not known as discrete motif; 1 represents an entirely
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different CoII/III valence pattern compared to the only other (sh), 859 (w), 832 (m), 779 (w), 675 (w), 616 (w), 580 (w), 448 (w).
known {Co5II/III} horseshoe cluster.13 The ligand environments at MS (MeOH, ESI): m/z: 1006.201 (C37H78N3Ni4O13+, 100%; [Ni4
certain metal sites are in principle conducive to facile metath- (Hbda)2(bda)1(ib)3(MeOH)]+–ib–Hib–MeCN + MeOH); 974.265
esis, an important aspect for a potential catalytic functionality (C36H74N3Ni4O12+, 72%; [Ni4(Hbda)2(bda)1(ib)3]+–MeOH); 886.212
that we plan to explore in the future.
(C32H66N3Ni4O10+, 38%; [Ni4(Hbda)1(bda)2(ib)2]+–Hib); 798.160
(C28H58N3Ni4O8 , 28%; [Ni4(bda)3(ib)1]+–Hib).
+
Experimental
Materials and methods
X-ray crystallography
Single-crystal diffraction data for compounds 1 and 2 were
collected on an Agilent Technologies SuperNova diffractometer
Compounds 1 and 2 were synthesized under aerobic conditions.
All starting materials were from commercial sources and used
as received. Solvents were used without further purication.
The IR spectra of compounds 1 and 2 were recorded on a Nicolet
Avatar 360 FTIR spectrometer (KBr pellets, n ¼ 4000–400 cmꢁ1).
TG/DT analyses of compounds 1 and 2 were performed under
N2 ow and a heating rate of 5 K minꢁ1 in the temperature
range 25–800 ꢀC on a Mettler Toledo TGA/SDTA 851e instru-
ment. The ESI-MS spectra of compounds 1 and 2 in the positive
ion mode was recorded on a 4000 QTRAP mass spectrometer
system, using the LC/LC-MS method with direct infusion.
˚
with MoKa radiation (l ¼ 0.71073 A) at 120 K. The crystals were
mounted in a Hampton cryoloop with Paratone-N oil to prevent
solvent loss. Absorption corrections were applied numerically
based on multifaceted crystal model using CrysAlis soware.22
The SHELXTL soware package23 was used to solve and rene
the structure. The structures were solved by direct methods and
rened by full-matrix least-squares method against |F|2 with
anisotropic thermal parameters for all atoms besides hydro-
gens. The hydrogen atoms of the OH groups of Hbdaꢁ and
bda2ꢁ ligands as well as CH3 groups of co-crystallized solvent
molecules in compound 1 were not located. Also in the both
structures (1 and 2) disorder of the butyl moiety of one of the (H)
bdaꢁ and CH(CH3)2 groups of several ibꢁ ligands precluded
a possibility for calculation of some geometrical positions of
hydrogen atoms, therefore we decided to not include these
hydrogens in the model for 1 and any hydrogens into the model
for 2 (the nal formulae in the CIFs for the both compounds
contain all hydrogen atoms for overall consistency). The relative
site occupancy factors for the disordered positions of carbon
atoms were rened using combination of PART and EADP
instructions. DELU restrictions had to be applied to some
carbon atoms of the disordered Hbdaꢁ ligands in compound 2.
Additional crystallographic data are summarized Table S1 in
the ESI.†
Synthesis of [Co3IICo2III(Hbda)2(bda)2(ib)6]$2MeCN (1)
A 10 mL MeCN solution of freshly prepared Co(ib)2 (0.233 g; 1.0
mmol) and N-butyldiethanolamine (0.170 mL; 1.0 mmol) were
stirred under reux for 1 h to give a clear violet solution. The
MeCN solution was ltered off and the ltrate was kept in
a capped vial at room temperature. The color of solution
became dark green with time. Aer two days the dark-green
block-shaped single crystals suitable for single-crystal X-ray
diffraction analysis were obtained. Yield: 0.143 g (49% based
on Co). Elemental analysis, calcd for C56Co5H112N4O20
(1456.17 g molꢁ1; no solvent): Co, 20.24; C, 46.19; H, 7.75; N,
3.85%. Found: Co, 20.6; C, 46.13; H, 7.80; N, 3.63%. IR (KBr
pellet), nmax/cmꢁ1: 3434 (m, br), 2960 (s), 2930 (sh), 2868 (sh),
1614 (s), 1577 (vs), 1537 (sh), 1469 (s), 1414 (s), 1371 (m), 1357
(sh), 1296 (m), 1169 (w), 1092 (s), 1029 (sh), 1015 (sh), 984 (w),
917 (m), 827 (w), 767 (w), 641 (w), 584 (w), 546 (w), 522 (w), 496
Magnetic susceptibility measurements
Magnetic susceptibility data of compounds 1 and 2 were
recorded using a Quantum Design MPMS-5XL SQUID magne-
tometer. The polycrystalline samples were immobilized into
PTFE capsules. The data were acquired as a function of the eld
(0.1–5.0 T) and temperature (2.0–290.0 K) and were corrected for
diamagnetic contributions from the sample holder and the
compounds (cdia ¼ ꢁ7.28 ꢂ 10ꢁ4 cm3 molꢁ1 (1), ꢁ5.96 ꢂ 10ꢁ4
cm3 molꢁ1 (2)).
(w). MS (MeOH, ESI): m/z: 1280.355 (C48Co5H97N4O16+, 100%;
+
[Co5(Hbda)1(bda)3(ib)4]+–ib–Hib); 1368.407 (C52Co5H105N4O18
82%; [Co5(Hbda)2(bda)2(ib)5]+–ib); 1192.303 (C44Co5H89N4O14
27%; [Co5(bda)4(ib)3]+–ib–2Hib); 757.193 (C28Co3H56N2O10
23%; [Co3(Hbda)2(ib)3]+–3ib–2bda).
,
,
,
+
+
Synthesis of [Ni4(Hbda)3(ib)5(MeCN)] (2)
A 10 mL MeCN of freshly prepared Ni(ib)2 (0.233 g; 1.0 mmol)
and N-butyldiethanolamine (0.170 mL; 1.0 mmol) were stirred
under reux for 1 h to give a clear green solution. The MeCN
solution was ltered off and the ltrate was kept in a capped vial
at room temperature. The light-green block-shaped single
crystals suitable for single-crystal X-ray diffraction analysis were
obtained aer one week. Yield: 0.065 g (22% based on Ni).
Acknowledgements
This work was supported by an ERC Starting Grant (MOL-
SPINTRON, 308051). We thank Dr Iurie L. Malaestean (Institute
of Chemistry, Academy of Sciences of Moldova) for helpful
discussions.
Elemental analysis, calcd for C46H92N4Ni4O16 (1192.01 g molꢁ1
;
:
no solvent): see discussion above. IR (KBr pellet), nmax/cmꢁ1
Notes and references
3423 (s, br), 2964 (s), 2930 (sh), 2876 (sh), 1620 (s), 1587 (sh),
1557 (vs), 1474 (s), 1427 (s), 1373 (m), 1360 (sh), 1287 (m), 1169
(w), 1142 (w), 1095 (w), 1067 (m), 1026 (sh), 980 (w), 905 (m), 891
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