Synthesis and characterization of a novel heteroditopic macrocyclic system - Monometallic nickel(II) and uranyl complexes and their corresponding heterobimetallic carbonylrhodium(I) complexes

Article abstract of DOI:10.1002/ejic.200500703

A novel heteroditopic macrocyclic ligand system for selective coordination of two different transition metal ions has been obtained in the form of monometallic salen complexes of Ni^II (LNi, 1) and uranyl (LUO ₂, 2). The system is cha

Full text of DOI:10.1002/ejic.200500703

FULL PAPER
DOI: 10.1002/ejic.200500703
Synthesis and Characterization of a Novel Heteroditopic Macrocyclic System –
Monometallic Nickel(II) and Uranyl Complexes and Their Corresponding
Heterobimetallic Carbonylrhodium( ) Complexes
I
Mauro Bassetti,*[a] Andrea Calenne,[a] Lucilla Mastrofrancesco,[a] Michela Salamone,[a]
Gabriele Bocelli,*[b] Andrea Cantoni,[b] and Amos Musatti[b]
Keywords: Heterometallic complexes / Ligand design / Macrocyclic ligands / Metallacycles / Schiff bases
A novel heteroditopic macrocyclic ligand system for selective
coordination of two different transition metal ions has been
obtained in the form of monometallic salen complexes of NiII
(LNi, 1) and uranyl (LUO2, 2). The system is characterized by
the presence of a dianionic, tetradentate salen donor system
(N2O2) derived from cis-1,2-diaminocyclohexane and of a
neutral, tridentate 2,6-bis(alkylthiomethyl)pyridine group
(NS2). The two binding sites are connected by two oxyethyl
chains. The synthetic procedure involves the coupling of the
disodium salt of 2,6-bis(mercaptomethyl)pyridine with two
equivalents of 3-(2-bromoethoxy)-2-(2-propenyloxy)benzal-
dehyde. Removal of the protecting allyl groups from the reac-
tion product (I) by palladium catalysis yields the ligand syn-
uranyl acetate salts, respectively, in the presence of barium bis-
(trifluoroacetate), have been fully characterized by spectro-
scopic techniques in solution and by X-ray diffraction analy-
ses in the solid state. Both complexes react readily at room
temperature with [Rh(CO)2Cl]2 in methanol to form the bime-
tallic cationic carbonyl complexes [LNiIIRh(CO)]PF6 (3) and
[LUO2Rh(CO)]PF6 (4) upon addition of NH4PF6. Two con-
formers of complex 3 are observed in solution by IR and NMR
spectroscopy, in a 5:1 ratio in [D2]dichloromethane, which ex-
hibit a fluxional behavior and are shown to interconvert
above room temperature in [D3]acetonitrile. The carbon-
ylrhodium group in the bimetallic systems reacts further with
methyl iodide in dichloromethane solution to form oxidative-
thon 2,6-bis[2-(3-formyl-2-hydroxyphenyl)oxyethyl]thiometh- addition products.
ylpyridine (II). The monometallic macrocyclic complexes 1
and 2, obtained by metal-templated synthesis from cis-1,2-
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
diaminocyclohexane, ligson II, and the corresponding NiII or Germany, 2006)
are a significant advantage in this respect,[7] the introduc-
Introduction
tion of different binding sites implies more elaborate syn-
thetic approaches than those used in the preparation of sys-
tems with higher symmetry.[5c,7a,7b,7e,8] Various types of het-
erobimetallic macrocyclic systems have been reported.[1,5c,9]
We have planned the synthesis of a heterobifunctional
macrocyclic structure bearing different donor sites. The
choice of the binding units has fallen on systems widely
used in catalysis and in coordination chemistry, namely the
dianionic tetradentate (N2O2) salen-type ligand and the
neutral tridentate (NS2) 2,6-bis(alkylthiomethyl)pyridine
system. The classic salen [N,NЈ-ethylenebis(salicylideneami-
nato)] metal complexes and related derivatives[5a–5c,10] are
nowadays finding significant applications, most notably in
host–guest chemistry,[1a,8,11] in asymmetric synthesis,[12] and
in supramolecular and polymer catalysis.[13] The tridentate,
neutral NS2 ligands form complexes with different transi-
tion-metal ions[14] and have been used in the preparation of
homo- and heterobimetallic macrocyclic structures, includ-
ing those containing rhodium().[15] Square planar rhodi-
um() complexes are of special interest in homogeneous ca-
talysis with regard to oxidative addition and carbonylation
processes.[16]
Compartmental ligands characterized by at least two dif-
ferent binding sites are interesting synthetic targets in the
field of macrocyclic chemistry[1] as heterobimetallic macro-
cyclic complexes can be derived from such structures and
used as appropriate models in heterogeneous or homogen-
eous catalysis, in which cooperative effects may arise from
the vicinity of two metal centers.[2] Most dinucleating
macrocycles available to date contain either one ligand type
incorporated into a crown ether ring,[1a,1c,3,4] or the same
donor set replicated within the macrocycle,[1a,3,5] which lim-
its, but does not exclude, selectivity toward coordination of
different transition-metal ions.[6] Although heteroditopic
macrocyclic frames containing nonequivalent ring cavities
[a] CNR, Istituto di Metodologie Chimiche, Sezione Meccanismi
di Reazione, and Dipartimento di Chimica, Università La Sapi-
enza,
00185 Roma, Italy
E-mail: mauro.bassetti@uniroma1.it
[b] CNR, Istituto dei Materiali per l’Elettronica ed il Magnetismo,
Parco Area delle Scienze 37a, 43010 Fontanini (Parma), Italy
E-mail: bocelli@unipr.it
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author
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The combination of a hard and a soft metal center has (Scheme 1). Following the preparation of monometallic
driven the design and synthesis of binucleating systems.[17] macrocyclic complexes of NiII and UO2, derived from II
In the case of metal carbonyl complexes, the proximity of and
cis-1,2-diaminocyclohexane, the reaction with
the two metal atoms may activate a carbon monoxide group [Rh(CO)2Cl]2 afforded bimetallic NiII/RhI and UO2/RhI spe-
by interaction of the electrophilic metal center with the oxy- cies (Scheme 2). The nickel and uranyl ions were selected for
gen of CO.[18] In this context, we have selected a carbon- the preparation of the bimetallic carbonylrhodium() com-
ylrhodium() group for coordination to the bis(mercapto- plexes due to their different electronic and coordinative
methyl)pyridine ligand and a uranyl or a nickel() metal properties − uranyl is oxophilic whereas nickel() is not.
center for the salen binding unit. The electrophilic character
of the uranyl system has been well documented, especially
its ability to coordinate organic carbonyl groups, such as
that of urea, in its planar fifth coordination site,[19] or to
act as an electrophilic catalyst for Michael additions[13a] and
acyl-transfer reactions.[20] Detection of an intramolecular
interaction of the (NS2)Rh–CO group with crown-ether-
complexed alkaline metal ions has been attempted.[15b]
The synthesis of the precursor for the metal-templated ring-
closure involves the coupling of the disodium salt of 2,6-bi-
s(mercaptomethyl)pyridine[21]
with
3-(2-bromoethoxy)-
2-(2-propenyloxy)benzaldehyde,[22] in tetrahydrofuran, to
give the allyl protected bis-formyl compound I (yield Ͼ
50%, Scheme 1). The allyl groups of I are then removed
by palladium catalysis, following a method described in the
literature,[20] to give ligand II (yield Ͼ 60%), which contains
the NS2 donor set, the oxyethyl spacers, and the formyl-2-
hydroxyaryl sub-units. Compounds I and II were purified
by column chromatography and characterized by 1H NMR,
13C NMR, and FT-IR spectroscopy, ESI mass spectrome-
try, and elemental analysis. The chemical shifts of the hy-
drogen atoms of the aryl rings in compound II were iden-
tified by a NOESY experiment, which shows correlations
between the OCH2 triplet at δ = 4.17 ppm and the doublet
of doublets at δ = 6.93 ppm, due to the aryl 4-H ortho to
the oxyethyl chain, as well as between the formyl H atoms
at δ = 10.08 ppm and the doublet of doublets at δ =
7.20 ppm, due to the aryl 6-H.
Results and Discussion
Synthesis of Monometallic Macrocyclic Complexes
The synthetic strategy followed for the preparation of the
target structure was directed by the fact that salen N2O2
type complexes form monometallic macrocyclic systems
when a precursor molecular chain appropriately function-
alized at both ends undergoes a metal-templated Schiff-base
ring-closure reaction in the presence of a diamine partner
and the chosen metal ion.[4b] In order to ensure the further
coordination within the ring of a second metal ion, an NS2
The synthesis of the macrocyclic structures was per-
donor set was incorporated into the molecular chain. formed by treatment of ligson II with cis-1,2-diaminocyclo-
Therefore the synthesis of the ligand synthon II, which hexane, in the presence of Ba(CF3SO3)2 as template, fol-
bears two terminal formyl-2-hydroxyaryl groups, was devised lowed by transmetalation in situ with the desired metal ace-
Scheme 1. Synthesis of the macrocyclic dialdehyde precursors I and II.
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Scheme 2. Template synthesis of monometallic nickel() (1) and uranyl (2) macrocyclic complexes and subsequent formation of heterobi-
metallic nickel()–rhodium() (3) and uranylrhodium() (4) complexes.
tate M(OAc)2 (M = Ni, UO2; Scheme 2). Due to the poor ric azamacrocyclic ligands.[7e] However, in the present case,
solubility of II, which is a sticky red oil, in alcoholic sol- the yields of complexes 1 and 2 were only slightly lower
vents, the compound was added to the reaction mixture as upon performing the reactions in the absence of the barium
a solution in methanol/tetrahydrofuran. The cyclization salt. This fact, along with the relatively low yields of the
process involving the dialdehyde, the diamine, and the metal macrocyclization reactions, may be due to the lower binding
ion entails the formation of a metal–salen structure and af- ability of the hybrid thioether chain of ligand II toward the
fords the desired monometallic macrocyclic complexes 1 barium ion with respect to a polyether chain.
and 2. Both complexes were isolated from their respective
reaction mixtures as pure products by column chromatog- NMR, and 13C NMR spectroscopy (see Experimental Sec-
raphy with yields of around 30%. tion), ESI mass spectrometry, elemental analysis, and sin-
Complexes 1 and 2 were characterized by FT-IR, 1H
The presence of Ba2+ as a template cation has been found gle-crystal X-ray diffraction analyses. In the 1H NMR spec-
to be beneficial in cyclization reactions involving a diamine trum of complex 1 ([D2]dichloromethane), the hydrogens of
and a precursor containing two formyl-2-hydroxyaryl sub- the pyridine ring (py) appear as one triplet at δ = 7.65 ppm
units linked by a polyether chain, affording the correspond- (4-H) and one doublet at δ = 7.26 ppm (3,5-H), while the
ing uranyl macrocyclic complexes with yields in the range arene protons appear as two close doublets at δ = 6.79 and
35–50% by transmetalation.[19,23] The same template has 6.75 ppm, due to 4,6-H, and one apparent triplet at δ =
also been used successfully in the preparation of dissymmet- 6.45 ppm, due to 5-H, thus confirming the presence of the
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A Novel Heteroditopic Macrocyclic System
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salen and of the pyridine moieties in the expected ratio. The method from solutions of dichloromethane layered with
protons of the linking chains are also clearly identifiable. heptane and kept at room temperature for several days. Se-
The fluxional character of the cyclohexane ring (cy) is indi- lected bond angles and distances are reported in Tables 1
cated by the broad shape of the corresponding signals. One and 2 for complexes 1 and 2, respectively.
significant spectral feature is the presence of the imine
Table 1. Selected bond lengths [Å] and angles [°] for the macrocyclic
nickel() complex 1.
CH=N protons, resulting from the coupling of the original
aldehyde with the amine groups, at δ = 7.37 ppm in complex
Ni1–O4
1.877(4)
1.874(5)
1.888(5)
1.854(4)
1.295(7)
1.288(8)
1.501(8)
1.506(8)
1.281(9)
94.4(2)
C26–O29
C27–O28
O29–C30
C30–C31
C31–S32
S32–C33
C40–S41
S41–C42
C43–O44
C12–N13–C14 122.63(5)
Ni1–N13–C14 111.2(4)
Ni1–N20–C19 111.0(4)
Ni1–N20–C21 124.97(5)
Ni1–O28–C27 128.2(4)
1.359(8)
1.319(8)
1.452(7)
1.483(10)
1.825(7)
1.787(9)
1.867(7)
1.802(7)
1.456(10)
1. In the case of the uranyl complex 2, the same protons
appear at higher frequency, δ = 9.31 ppm, thereby indicat-
ing the stronger electron-withdrawing character of the ura-
nyl group with respect to nickel(). The 7-H protons of the
cyclohexyl ring appear at δ = 3.45 and 4.66 ppm in com-
plexes 1 and 2, respectively.
Ni1–N13
Ni1–N20
Ni1–O28
O4–C6
C12–N13
N13–C14
C19–N20
N20–C21
N20–Ni1–O28
N13–Ni1–O28
In the 13C NMR spectra, the imine carbon atoms are
observed at δ = 159.2 and 167.2 ppm for 1 and 2, respec-
tively, while the infrared frequencies of the CH=N double
bonds are virtually unaffected by the metal ion (1616 cm–1
in dichloromethane). The electropositive uranyl center af-
177.0(2)
N13–Ni1–N20 86.5(2)
O4–Ni1–O28
O4–Ni1–N20
O4–Ni1–N13
Ni1–O4–C6
85.6(2)
176.8(2)
93.7(2)
126.2(4)
126.0(5)
1
fects the rest of the molecule as well, since the H NMR
C31–S32–C33
C40–S41–C42
98.6(3)
103.3(3)
chemical shifts of the methylene hydrogens of pyCH2S
and –SCH2CH2O– change from δ = 3.83 and 2.92 ppm in
the nickel complex 1 to δ = 4.57–4.49 and 3.13 ppm, respec-
tively, in complex 2. The pyCH2S hydrogen atoms exhibit
Ni1–N13–C12
Table 2. Selected bond lengths [Å] and angles [°] for the macrocyclic
uranyl complex 2.
1
AB patterns in the H NMR spectra, characterized by ∆ν
= 7.1 Hz (1, CDCl3) and 24 Hz (2, [D2]dichloromethane),
due to their diastereotopic character,[15] while the same hy-
drogens of complex 1 appear equivalent in [D2]dichloro-
methane. In a NOESY spectrum of complex 1 in CDCl3,
the absorption at δ = 6.47 ppm exhibits a cross-peak with
the imine proton at δ = 7.04 ppm and is therefore assigned
to the 6-H protons, while the peaks at δ = 6.71 ppm, due to
4-H, correlate with the OCH2 signal at δ = 4.08 ppm.
Symmetric macrocyclic ligands containing two tetraden-
tate salen coordination sites formed from trans-1,2-diami-
nocyclohexane, and the corresponding mono- and dinuclear
nickel() complexes, have been reported.[24] With trans-1,2-
diaminocyclohexane as the Schiff base counterpart, dissym-
metric macrocyclic structures incorporating one nickel()
salen unit, which acts as an intramolecular redox catalyst,
and a 1,4-bis(chloromethylarene) function have been pre-
pared by a multistep synthesis.[25] A macrocyclic compound
characterized by the presence of a salen–uranyl moiety op-
posite a pyridine group and linked by oxyethyl chains has
been reported.[23] With 1,2-phenylenediamine or cis-1,2-di-
aminocyclohexane, symmetric, dinuclear salophen or salen
UO2 macrocyclic complexes have been described,[26] as well
as macrocyclic ligands containing 2,6-bis(alkylthiomethyl)
U1–O2
U1–O3
U1–O4
U1–O5
U1–N13
U1–N20
U1–O28
O4–C6
O2–U1–O3
O2–U1–O28
O3–U1–O28
O2–U1–O4
O3–U1–O4
O28–U1–O4
O2–U1–O5
O3–U1–O5
O28–U1–O5
O4–U1–O5
O2–U1–N13
O3–U1–N13
O28–U1–N13
O4–U1–N13
1.572(16)
1.806(13)
2.226(8)
2.499(7)
2.546(13)
2.569(9)
2.193(8)
1.293(14)
178.4(6)
92.8(6)
87.9(6)
91.1(5)
89.0(5)
151.3(4)
89.5(5)
92.1(4)
80.5(4)
71.1(4)
93.1(7)
85.4(5)
136.4(3)
71.6(4)
C12–N13
N20–C21
C27–O28
C31–S32
S32–C33
C40–S41
S41–C42
1.278(21)
1.278(17)
1.325(15)
1.806(19)
1.789(16)
1.771(23)
1.834(22)
O5–U1–N13
O2–U1–N20
O3–U1–N20
O28–U1–N20
O4–U1–N20
O5–U1–N20
N13–U1–N20
C6–O4–U1
C12–N13–U1
C14–N13–U1
C21–N20–U1
C19–N20–U1
C31–S32–C33
C42–S41–C40
142.7(4)
86.1(3)
92.8(3)
71.6(3)
137.1(4)
151.4(3)
65.8(3)
134.8(8)
127.8(10)
112.5(10)
127.4(9)
117.2(7)
101.9(8)
98.0(11)
Geometry of Complex 1
The nickel atom in the N2O2 ligand set shows a slightly
pyridine subunits and the corresponding [Rh(CO)][PF6] di- deformed square-planar conformation (Figure 1) in which
nuclear complexes.[15d] However, complexes 1 and 2 are the the bond angles around the metal range from 85.6(4)° for
first macrocyclic structures in which a metal–salen unit is O(4)–Ni(1)–O(28) to 93.7(5)° for O(4)–Ni(1)–N(13); the
faced by an uncomplexed tridentate donor set that is suitable maximum out-of-plane deformation of the five atoms of the
for further coordination of a second transition metal ion.
coordination moiety is 0.06(1) Å. The average Ni–O and
Ni–N(13) bond lengths [1.865 and 1.8481 Å, respectively]
compare well with the values observed in other monomeric
nickel macrocyclic[24] or open complexes[27] formed from
trans-1,2-diaminocyclohexane. The complex as a whole lies
X-ray Crystal Structure of Macrocyclic Nickel(II) (1) and
Uranyl (2) Complexes
Single crystals of compounds 1 and 2 suitable for X-ray approximately on a plane, with the exception of the cyclo-
diffraction analysis were obtained by the “liquid diffusion” hexane and pyridine rings, which are almost orthogonal to
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M. Bassetti, G. Bocelli et al.
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the mean plane of the macrocycle and in a relative transoid the pentagonal planar base. When compared to the S-
fashion. In fact, the dihedral angles formed by the mean shaped conformation of the nickel complex 1, complex 2
C(6)–C(11), C(22)–C(27), C(34)–N(39) (py) and C(14)– can be regarded as lying approximately on a plane including
C(19) (cy) ring planes with that of the coordinative moiety the pyridine and cyclohexyl rings. Since the two phenyl
are 7.7(2)°, 2.9(3)°, 82.3(2)°, and 114.5(2)°, respectively. rings C(6)–C(11) and C(22)–C(27) of the salen moiety form
While the chain from O(29) to C(33) is planar and forms a a dihedral angle of 47.5(5)° with respect to each other, this
dihedral angle of 4.4(2)° with the coordinative mean plane, part of the complex assumes, as a whole, a butterfly orienta-
the C(42) and C(43) carbon atoms lie 1.02(2) and 1.25(2) Å, tion. These two rings are tilted by 28.2(4)° and 19.7(4)°,
respectively, out of the plane formed by the three remaining respectively, with respect to the mean plane formed by the
atoms of the chain. The water molecule is not coordinated five atoms coordinated by uranium. This conformation,
to nickel [O(1W)···Ni = 3.99(5) Å] but is hydrogen bonded which is due to the relatively large ionic radius of uranium
within the cavity through the oxygen of one ethylene chain pushing apart the phenyl rings, is typical of uranyl–salen
[H(1W)···O(29) = 1.94(5) Å] and one of the methylene hy- complexes and is similar to that observed in other mono-
drogens of the opposite one [O(1W)···H(43) = 2.47(5) Å]. meric macrocyclic uranyl systems[19,28] formed from cis-1,2-
Other short contacts are an intramolecular H(1W)···O(28) diaminocyclohexane. The C(14)–N(13) distance of the cy-
contact [2.52(2) Å] and an intermolecular H(12)–O(1W)i clohexyl axial bond is 1.588 Å, while the C(19)–N(20) dis-
(i = 1 – x, y – 1/2, 3/2 – z) contact [2.49(2) Å]. The C(14)– tance of the equatorial bond is 1.464 Å. In the crystals the
N(13) distance of the cyclohexyl equatorial bond is 1.501 Å, molecules are connected by intra- [H(18a)····N(13) =
while the C(19)–N(20) distance of the axial bond is 2.53(3); O(5)····N(39) = 2.76(2); O(5)····H(40) = 2.90(1) Å],
1.506(7) Å. The molecules are connected in the crystal by and intermolecular [H(21A)···O(3)i (i = 1/2 – x, 1/2 – y, –z)
van der Waals contacts. We have not been able to find other = 2.33(1); H(30B)···O(5)ii (ii = –x, –y, –z) = 2.58(1); H(40B)
crystal structures of salen–nickel complexes obtained from ···O(3)iii (iii = 1/2 – x, –1/2 – y, –z) = 2.49(1) Å] van der
cis-1,2-diaminocyclohexane in the literature. The conforma- Waals contacts involving, in particular, the water molecule.
tion of the bis(alkylthiomethyl)pyridine ligand set in com- The uncomplexed bis(thiomethyl)pyridine group of the ura-
plex 1 is characterized by the presence of the sulfur atoms nyl complex 2 has one exocyclic and one endocyclic sulfur
oriented outwards with exocyclic lone pairs, with C–S–C atom and is characterized by C–S–C bond angles of
bond angles of 98.6(3)° and 103.3(3)°. The C–S bond 101.9(8)° and 98.0(9)°, respectively, and C–S bond lengths
lengths lie between 1.825 and 1.867 Å, in the usual range in the range 1.77–1.81 Å.
observed in macrocyclic structures including this uncom-
plexed ligand.[15d]
Figure 1. Molecular structure and atom-labelling scheme for the
macrocyclic nickel() complex 1.
Geometry of Complex 2
The uranyl moiety in complex 2 exhibits a pentagonal-
bipyramidal coordination (Figure 2). Two imine nitrogen
atoms [N(20), N(13)], two phenoxy oxygen atoms [O(4),
O(28)], and one oxygen from a molecule of water (O5) form
the pentagonal base, which is almost planar, while the two
Figure 2. Molecular structure and atom-labelling scheme for the
macrocyclic uranyl complex 2.
uranyl oxygen atoms occupy the apex positions, with out-
of-plane deviations of 1.57 and 1.81 Å, respectively. The
aromatic rings are planar and the cyclohexane ring adopts
the typical chair conformation. This coordinative arrange-
ment compares well with that found for a similar complex
Synthesis of Bimetallic NiII–RhI (3) and UO2–RhI (4)
Macrocyclic Complexes
containing a coordinated molecule of urea in place of the
A suspension of the monometallic macrocyclic nickel
water molecule.[19] The pyridine ring is oriented in such a complex 1 in methanol was treated with a methanolic solu-
way as to form a dihedral angle of 20.7(4)° with respect to tion of [RhCl(CO)2]2 (Scheme 2). The mixing of the two
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A Novel Heteroditopic Macrocyclic System
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compounds yielded a clear amber solution which, when an- the presence of the two isomeric species observed in [D2]-
alyzed after about 10 min, showed an intense IR band at dichloromethane. When the temperature is raised, intercon-
2009 cm–1 and the disappearance of the absorption bands version of these isomers occurs with a coalescence tempera-
(2088 and 2014 cm–1) of the dicarbonylchlororhodium di- ture of 44 °C, at which both the chain methylene groups
mer. Addition of a methanolic solution of NH4PF6 caused appear as single, broad peaks at δ = 3.50 and 4.55 ppm,
the formation of an orange precipitate, which corresponds respectively, while the multiplet of the pyCH2S– protons is
to the expected macrocyclic bimetallic NiII–RhI complex 3 only slightly affected by this temperature change. The ob-
(yield 70%). The monometallic uranyl complex 2 reacts served isomers may arise from the relative position of the
with the dicarbonylchlororhodium dimer in a similar man- metal ions with respect to the mean ligand plane – either
ner (yield 47%). Therefore, the macrocyclic metal–salen opposite or on the same side – and interconvert by confor-
structure connected by a relatively short oxyethyl chain mational changes of the oxyethylene chains, in analogy with
does not hinder the coordinative ability of the NS2 ligand what is observed for the symmetric bimetallic RhCO+
set. Both complexes 3 and 4 exhibit good solubility in or- macrocyclic complex incorporating two 2,6-bis(alkylthi-
ganic solvents, especially in dichloromethane. This is due, omethyl)pyridine groups.[15c] Detailed variable-temperature
presumably, to the presence of the cyclohexane ring, as a NMR studies involving fluxional processes related to inver-
cyclohexyl group is known to increase the solubility of sion at sulfur[30] and/or conformational equilibria in the
macrocyclic salen complexes with respect to analogous sal- macrocyclic frame have been described for mono- and bi-
ophen derivatives.[19]
metallic carbonylrhodium macrocyclic complexes.[15]
The bimetallic complexes were characterized by FT-IR,
1H NMR, and 13C NMR spectroscopy (3), FAB mass spec-
trometry, and elemental analyses. Complexation of the cat-
ionic carbonylrhodium group to the tridentate NS2 ligand
system is indicated by the presence of a strong split absorp-
tion at 2026–2017 cm–1 for complex 3 and of a band at
2020 cm–1 for complex 4, both in dichloromethane. The 13
C
NMR chemical shifts of the methylene carbons of pyCH2S–
and –SCH2CH2O– move from δ = 37.7 and 30.0 ppm in the
monometallic nickel complex 1 to δ = 47.0 and 37.3 ppm,
respectively, in the bimetallic nickel–rhodium complex 3.
The 13C NMR spectrum obtained overnight from a [D2]-
dichloromethane solution of the bimetallic uranylrhodium
complex 4 is identical to that of the monometallic uranyl
complex 2, which suggests solvolysis of the (RhCO)+ frag-
ment. In analogy, decomposition by loss of CO was ob-
served when monitoring a dichloromethane solution of
complex 4 by IR spectroscopy over several hours.
In complex 3, in addition to the two CO stretching bands
1
in the IR spectrum, broad and split peaks appear in the H
NMR spectrum, indicating the existence of two isomers in
an approximately 5:1 ratio in [D2]dichloromethane. Split
peaks are also observed in the 13C NMR spectrum. In [D3]-
acetonitrile solution, the three methylene groups of py–
CH2SCH2CH2O– are well separated in the region δ = 5.2–
3.0 ppm (Figure 3). At room temperature, the multiplet due
1
Figure 3. H NMR spectra of the heterobimetallic NiII–RhI com-
plex 3 in [D3]acetonitrile at different temperatures, displaying the
methylene groups of the pyCH2SCH2CH2O moiety.
The CO stretching band of the complex [Rh(L)(CO)]-
to the pyCH2S– methylene groups is better resolved than PF6, in which L is the “open” NS2 ligand 2,6-bis(benzylthi-
the broad signals of the –SCH2CH2O– methylene chain, omethyl)pyridine, is observed at 2019 cm–1 in dichlorometh-
thus indicating rapid conformational equilibria along the ane.[29] A comparison with the macrocyclic systems re-
carbon chain spacers and greater flexibility of the macro- ported here shows that the carbonylrhodium group is not
cyclic structure at these sites. The pyCH2S– protons display perturbed by the adjacent metal centers. It is worth men-
a distorted AB system (δHa = 4.80, δHb = 4.73 ppm; ∆ν = tioning that during the synthesis of the bimetallic com-
22 Hz), corresponding to the coordination of the NS2 do- plexes the intermediate chloride species shows a carbonyl
nor set to the metal ion in a stable configuration. This band at 2009 cm–1 for the nickel–rhodium complex 3 and
pattern agrees well with that observed for the open complex 2015 cm–1 for the uranylrhodium complex 4, in methanol,
[Rh(L)(CO)]PF6 [L = 2,6-bis(benzylthiomethyl)pyridine] in indicating a small effect of the salen–metal ion on the car-
[D2]dichloromethane at –65 °C,[29b] and for the macrocyclic bonylrhodium group. The dinuclear [2+2] symmetric car-
Rh(CO)+ complexes in which a 2,6-bis(thiomethyl)pyridine bonylrhodium macrocyclic complexes incorporating two
subunit is linked by a polyether chain.[15c] In addition, the 2,6-bis(alkylthiomethyl)pyridine sub-units linked by (CH2)n
doubled absorptions of the –SCH2CH2O– groups confirm chains (n = 5–10) exhibit CO stretching values in the range
Eur. J. Inorg. Chem. 2006, 914–925
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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919

M. Bassetti, G. Bocelli et al.
FULL PAPER
1991–2009 cm–1 (KBr).[15d] The values of 2013 and 1676 cm–1. Due to the smaller absorptivity of the acyl moi-
2012 cm–1 observed in the solid state (KBr) for the heterobi- ety with respect to the parent terminal RhI and RhIII com-
metallic complexes 3 and 4, respectively, indicate a larger plexes, it can be deduced that the acyl product is more
triple-bond character than in the homobimetallic systems. abundant than both the substrate and the methylrhodi-
This suggests reduced electron density on rhodium, and um() intermediate. The presence of the acyl derivative
hence reduced back-donation from rhodium to carbonyl, from the bimetallic UO2/RhI complex suggests an easier mi-
rather than an intramolecular CO···M contact in the het- gratory-insertion reaction than in the corresponding nickel
erobimetallic complex, which would have lowered the car- complex. It appears that the IR frequencies of the carbonyl
bonyl stretching frequency.
group in the [Rh(CO)(Me)I]+ moiety are affected by the
We have recently described that the monometallic com- different environments in the two heterobimetallic com-
plex [Rh(L)(CO)]PF6 reacts with MeI to give an intermedi- plexes and in the open system.
ate methylrhodium() iodide species [Rh(L)(CO)(Me)I]+
and an isolable acylrhodium() complex [Rh(L)(COMe)I]-
PF6 as the result of consecutive oxidative addition/mi-
Conclusions
gratory insertion reactions.[29a] This was the first report of
the organometallic reactivity of a carbonylrhodium com-
The synthesis of a novel macrocyclic ligand system con-
plex of the neutral tridentate 2,6-bis(substituted thiomethyl) taining a neutral, tridentate NS2 donor set and a tetraden-
pyridine system. The product of oxidative addition is ob- tate, dianionic N2O2 unity has been described, in particular
served as a relatively stable intermediate that accumulates the isolation and structural characterization of the corre-
in solution and exhibits a strong infrared band at 2106 cm–1 sponding monometallic salen complexes of NiII and of UO2
(acetonitrile). We therefore tested the reactivity of both obtained from cis-1,2-diaminocyclohexane. These are the
complexes 3 and 4 toward methyl iodide (3.5 ) in solution first examples of macrocycles in which a different uncoordi-
in dichloromethane (Scheme 3). In the case of the nickel– nated ligand set (NS2) faces the salen–metal group. Both
rhodium complex 3, the reaction solution, when stirred for monometallic compounds react with [RhCl(CO)2]2 to yield
5 h at 40 °C, gave an abundant red precipitate, which, ana- heterobimetallic, cationic complexes characterized by the
lyzed in [D3]acetonitrile, exhibits a strong carbonyl band at presence of the [(NS2)RhCO]+ fragment. This synthetic
2128 cm–1 due to the methylrhodium species, thus indicat- method allows the sequential and selective coordination of
ing the conversion of complex 3 into the product of oxidat- two different metal ions onto a dissymmetric ligand frame
ive addition of methyl iodide. In the case of the macrocyclic using conventional procedures. The uranyl group enhances
uranylrhodium complex 4, the solution was stirred for 6 h the lability of the CO ligand with respect to nickel(). In
at room temperature in order to minimize the spontaneous fact, the UO2–RhI complex decomposes slowly by loss of
loss of CO. After removal of excess MeI and solvent, the CO and solvolysis of the Rh(CO)+ fragment. The NiII–RhI
spectrum showed the presence of starting material complex, which is more stable, exists in solution as two con-
(2001 cm–1),
the
oxidative-addition
intermediate formational isomers. The [Rh–CO]+ fragment of both bime-
(2116 cm–1), and the migratory-insertion product at tallic complexes undergoes oxidative addition of MeI.
Scheme 3. Reactions of complexes 3 or 4 with methyl iodide.
920
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 914–925

A Novel Heteroditopic Macrocyclic System
FULL PAPER
(OCH2CH=CH2), 67.98 (OCH2), 38.01 (pyCH2S), 30.41
Experimental Section
(OCH CH S) ppm. FT-IR (dichloromethane): ν
= 1687 cm–1
˜
max
2
2
(C=O). ESI (acetonitrile): m/z = 580.7 [M + 1]+, 602.4 [M + Na]+,
618.8 [M + K]+. C31H33NO6S2·H2O (597.74): calcd. C 62.29, H
5.90, N 2.34, S 10.73; found C 62.62, H 5.64, N 2.64, S 10.82.
General Methods: Reactions involving air- and moisture-sensitive
compounds were carried out under nitrogen using standard
Schlenk line techniques. Tetrahydrofuran was distilled from Na/K
alloy, acetonitrile from phosphorus pentoxide, and methanol from
magnesium turnings. 1H, 13C, and 2-D NOESY NMR spectra were
obtained with a Bruker AM-300 spectrometer. Chemical shifts are
2,6-Bis{[2-(3-formyl-2-hydroxyphenyl)oxyethyl]thiomethyl}pyridine
(II): Formic acid (0.28 mL, 7.5 mmol), triethylamine (freshly dis-
tilled from over sodium; 1.0 mL, 7.5 mmol), triphenylphosphane
(49 mg, 0.19 mmol), palladium acetate (10 mg, 0.046 mmol), and
compound I were dissolved in 11 mL of ethanol/water/tetra-
hydrofuran (5:1:5). The yellow solution was kept under reflux for
2 h, then the solvents were removed in vacuo. The residue was ex-
tracted with water (50 mL) and chloroform (3×50 mL). The com-
bined extracts were washed with water (3×50 mL) and dried with
sodium sulfate. Evaporation in vacuo gave 667 mg of crude product
as a sticky, red oil. Purification of this material was carried out by
column chromatography using a mixture of petroleum ether and
acetone (2:1, v/v) to afford pure II in 60% yield. Compound II
appears as the most intense spot in a TLC analysis from hexane/
acetone (1:1) with Rf = 0.56. When the reaction was performed
under more dilute conditions, the deallylation process was slower
and incomplete. On the other hand, longer reaction times produced
decomposition of the expected product. 1H NMR (CDCl3): δ =
11.14 (s, 2 H, OH), 10.08 (s, 2 H, CHO), 7.71 (t, J = 7.7 Hz, 1 H,
1
reported in ppm relative to tetramethylsilane with (for H NMR)
chloroform (δ = 7.24 ppm) or dichloromethane (δ = 5.32 ppm) or
(for 13C NMR) CDCl3 (δ = 77.0 ppm), [D2]dichloromethane (δ =
53.1 ppm) or [D3]acetonitrile (δ = 118.2 ppm) as internal standards.
IR spectra were recorded for KBr pellets or in 0.1-mm CaF2 solu-
tion cells with a FT-IR Nicolet 510 instrument using the Omnic 4
software. ESI mass spectra were recorded with a Fisons Instru-
ments VG-Platform Benchtop LC-MS (positive ions). FAB mass
spectra were obtained with m-nitrobenzyl alcohol as matrix on a
VG-Quattro Instrument of the University of Tor Vergata, Roma.
Elemental analyses were performed by the Servizio di Microanalisi
of the Department of Chemistry, Università La Sapienza, Roma.
The compounds 3-(2-bromoethoxy)-2-(2-propenyloxy)benzalde-
hyde[22] and 2,6-bis(mercaptomethyl)pyridine[21,29a] were prepared
according to literature procedures. Commercial [RhCl(CO)2]2 was
purified by sublimation before use. Silica gel 60 was used for pre-
parative column chromatography, unless stated otherwise. Other
chemicals were used as supplied commercially.
3
4
py 4-H), 7.41 (d, J = 8.0 Hz, 2 H, py 3,5-H), 7.20 (dd, J = 7.7, J
3
4
= 1.5 Hz, 2 H, Ar 6-H), 6.93 (dd, J = 7.8, J = 1.3 Hz, 2 H, Ar 4
H), 6.82 (pseudo-t, J = 7.9 Hz, 2 H, Ar 5-H), 4.17 (t, J = 6.2 Hz,
4 H, OCH2CH2S), 4.01 (s, 4 H, pyCH2S), 2.76 (t, J = 6.1 Hz, 4 H,
OCH2CH2S) ppm. 13C NMR (CDCl3): δ = 194.50 (CHO), 157.93
(py C-2), 151.56 (Ar C-3), 146.99 (Ar C-2), 137.99 (py C-4), 132.08
(Ar C-1), 128.53 (Ar C-5), 123.31, 122.21, 119.22 (py C-3 and Ar
C-4, C-6), 69.99 (OCH2), 37.39 (SCH2py), 29.14 (OCH2CH2S)
ppm. FT-IR (tetrahydrofuran): ν
= 1658 cm–1 (C=O). ESI
˜
max
(acetonitrile): m/z = 500.4 [M + 1]+ , 522.3 [M + Na]+ .
C
25H25NO6S2·H2O (517.62): calcd. C 58.01, H 5.26, N 2.71, S
12.39; found C 58.56, H 5.60, N 2.45, S 11.15.
2,6-Bis{[2-[3-formyl-2-(propenyloxy)phenyl]oxyethyl]thiomethyl}pyr-
idine (I): Sodium hydride (80% dispersion in mineral oil; 438 mg,
14.6 mmol) was introduced into a 250-mL, three necked flask and
washed three times with dry hexane under nitrogen. Tetra-
hydrofuran (50 mL) and a tetrahydrofuran solution of 2,6-bis(mer-
Nickel(II) Complex 1: Separate solutions of cis-1,2-diaminocyclo-
hexane (0.115 mL, 0.96 mmol) in 70 mL of methanol and dialde-
hyde II (475 mg, 0.95 mmol) in 70 mL of methanol/tetrahydrofuran
were added simultaneously, within 1 h, to a refluxing solution of
Ba(CF3SO3)2 (430 mg, 0.99 mmol) in 250 mL of dry methanol. The
captomethyl)pyridine (1.24 g, 7.3 mmol) were introduced by can- solution of II was prepared by dissolving compound II in 10 mL
nula, and the mixture was stirred for 15 min. 3-(2-Bromoethoxy)-
2-(2-propenyloxy)benzaldehyde (4.13 g, 14.5 mmol) was added
dropwise to the resulting solution. After 12 h at reflux, the reaction
mixture was poured into water and chloroform, and extracted with
chloroform (3×50 mL). The combined organic layers were washed
with 0.5  NaOH (3×30 mL), twice with water, then dried with
sodium sulfate. After filtration, evaporation of the solvent under
vacuum afforded 3.9 g of crude product, which appeared in a TLC
analysis (silica/chloroform) as the most intense spot with a reten-
tion factor of 0.11–012, preceded and followed by weaker spots.
Purification by column chromatography with chloroform as eluent
gave pure I as a yellow, sticky oil in 54% yield. 1H NMR (CDCl3):
of tetrahydrofuran, followed by addition of methanol up to the
desired volume. After 30 min, Ni(CH3COO)2·4H2O (249 mg,
1.0 mmol) was added. The solution turned brown and was kept at
reflux for 50 min, then cooled to room temperature. The solvent
was removed under vacuum, and the residue was extracted with
dichloromethane. The organic solution was washed with saturated
aqueous solutions of sodium sulfate (3×100 mL), sodium hydrogen
carbonate (1×100 mL), and sodium chloride (1×100 mL), then
dried with sodium sulfate. After filtration and removal of the sol-
vent under vacuum, the crude product was separated into two
equal portions, each of which was purified by column chromatog-
raphy over alumina deactivated with 3% of water. Initial elution
δ = 10.38 (s, 2 H, CHO), 7.60 (t, J = 7.7 Hz, 1 H, py 4-H), 7.38 with dichloromethane separated two yellow bands of a material
(pseudo-t, J = 4.7 Hz, 2 H, aryl 5-H), 7.23 (d, J = 7.7 Hz, 2 H, py which was not identified. Continued elution with dichloromethane/
3,5-H), 7.05 (pseudo-d, J = 4.7 Hz, 4 H, aryl 4,6-H), 6.08–5.94 (m, methanol (at first 150:1, then 100:1) moved a long, brown band,
2 H, =CH), 5.34–5.18 (m, 4 H, =CH2), 4.65–4.62 (m, 4 H, OCH2),
4.11 (t, J = 6.7 Hz, 4 H, OCH2CH2S), 3.85 (s, 4 H, pyCH2S), 2.92
(t, J = 6.5 Hz, 4 H, OCH2CH2S) ppm. 13C NMR (CDCl3): δ =
190.17 (CHO), 158.06 (py C-2), 151.72, 151.20 (Ar C-2, C-3),
which left the product as a red-brown solid (93 mg from the first
portion of crude material and 90 mg from the second; combined
yield 30%). 1H NMR ([D2]dichloromethane): δ = 7.65 (t, J = 8 Hz,
1 H, py 4-H), 7.37 (s, 2 H, CH=N); 7.26 (d, J = 8 Hz, 2 H, py 3,5-
3
4
3
137.49 (py C-4), 133.03 (CH=), 130.06 (Ar C-1), 123.94, 121.24, H), 6.79 (dd, J = 8.2, J = 1.5 Hz, 2 H, Ar 4-H), 6.75 (dd, J =
119.15, 118.82 (py C-3 and Ar C-4, C-5, C-6), 119.34 (=CH2), 75.07 7.6, 4J = 1.5 Hz, 2 H, Ar 6-H), 6.45 (pseudo-t, J = 7.8 Hz, 2 H, Ar
Eur. J. Inorg. Chem. 2006, 914–925
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
921

M. Bassetti, G. Bocelli et al.
FULL PAPER
5-H), 4.05 (t, J = 7.8 Hz, 4 H, –CH2OAr), 3.83 (s, 4 H, pyCH2S),
NiII–RhI Complex 3: In a Schlenk tube, 52.1 mg (0.082 mmol) of
3.45 (br. s, 2 H, cy 7-H), 2.92 (d, J = 7.9 Hz, 4 H, –CH2CH2S), the macrocyclic nickel complex 1 was suspended in 3 mL of dry
2.29 (br. m, 2 H, cy 8-H), 1.93 (s, 2 H, H2O), 1.69 (br. m, 2 H, cy
8-H), 1.41 (m, 4 H, cy 9-H) ppm. H NMR (CDCl3): δ = 7.61 (t,
methanol and stirred under argon at room temperature. [RhCl(CO)
(16 mg, 0.041 mmol) dissolved in 2 mL of methanol was then
1
]
2 2
J = 7.5 Hz, 1 H, py 4-H); 7.25 (d, J = 8 Hz, 2 H, py 3,5-H), 7.04
(s, 2 H, ArCHN), 6.71 (d, J = 7.4 Hz, 2 H, Ar 4-H), 6.47 (d, J =
7.6 Hz, 2 H, Ar 6-H), 6.30 (pseudo-t, J = 7.7 Hz, 2 H, Ar 5-H),
4.08 (m, 4 H, –CH2OAr), 3.84 and 3.81 (AB system: ∆ν = 7.1 Hz,
4 H, pyCH2S), 3.56 (br. s, 2 H, cy 7-H), 2.89 (m, 4 H, SCH2CH2O),
2.32 (s, 2 H, H2O), 2.21 (br. m, 2 H, cy 8-Ha), 1.60 (br. m, 2 H, cy
8-Hb), 1.35 (br. m, 4 H, cy 9-H) ppm. 13C NMR (CDCl3): δ =
added with a cannula from another Schlenk tube into the suspen-
sion of 3 to afford a clear, amber solution. An infrared analysis of
the solution after 10 min showed the presence of an intense peak
at 2009 cm–1, and the absence of the 2088 and 2014 cm–1 bands
of the dicarbonylchlororhodium dimer. Addition of a methanolic
solution (2 mL) of NH4PF6 (85 mg) caused the formation of an
orange solid, and the mixture was stirred for a few minutes. The
159.2 (CH=N), 158.6 (py C-2), 155.9, 149.1 (Ar C-2, C-3), 137.6 solid was then allowed to deposit and the solvent was decanted off.
(py C-4), 125.4, 121.4, 120.8, 117.1, 113.5 (py C-3 and Ar C-1, C-
4, C-5, C-6), 67.6 (CH2OAr), 67.4 (br. s, cy C-7), 37.7 (pyCH2S),
30.0 (CH2S), 27.32 (C-8), 20.9 (C-9) ppm. ESI (acetonitrile): clus-
ters centered at m/z = 635 [1 + H+], 657 [1 + Na+]. FT-IR (KBr):
The precipitate was washed twice with cold methanol and vacuum-
dried to leave 42 mg of an orange powder. Addition of 0.5 mL of
pentane to the reaction solution caused the precipitation of an ad-
ditional 10 mg of solid. Both materials were characterized by in-
ν
max
= 1614 cm–1 (vs, C=N), 1572, (py) 1543, 1470, 1446 (vs, Ar), tense infrared absorptions near 2020 cm–1 in dichloromethane solu-
˜
1322, 1229 (s),1085, 1002, 864, 739 (s). Analytically pure material tion. Overall yield 70%. The compound is moderately air-sensitive,
was obtained by precipitation upon addition of pentane to a solu-
tion in dichloromethane. C31H33N3NiO4S2·H2O (652.45): calcd. C
57.07, H 5.41, N 6.44; found C 57.38, H 4.64, N 6.15.
as indicated by the slow decay of intensity of the carbonyl infrared
band upon standing in air. 1H NMR ([D2]dichloromethane): δ =
7.98 (t, J = 7 Hz, 4-H py) and 7.86 (m due to the minor isomer, 1
H, py 4-H), 7.59 (d, J = 8 Hz, 2 H, py 3,5-H), 7.31 and 7.38 (2×s
due to the minor isomer, 2 H, CH=N), 6.83 (d, J = 7 Hz, 2 H, Ar
4-H), 6.68 (br. s, 2 H, Ar 6-H), 6.40 (br. s, 2 H, Ar 5-H), 4.72–4.50
(br. m, 8 H, pyCH2S and –CH2OAr), 3.47 and 3.68 (2×m, due to
the minor isomer, 4 H, CH2S; 5:1 ratio), 3.22 (br. s, 2 H, cy C-7),
2.24, 1.76, 1.39 (br. m, 8 H, cy 8,9-H) ppm. 13C NMR ([D3]acetoni-
trile, peaks of the major isomer): δ = 161.8 (ArCHN), 161.4 (py C-
2), 154.9, 147.8 (Ar C-2, C-3), 140.2 (py C-4), 127.5, 122.1, 121.9,
119.0, 115.3 (py C-3 and Ar C-1, C-4, C-5, C-6), 69.7 (br. s, cy C-
7), 68.4 (–CH2OAr), 47.0 (pyCH2S), 37.3 (–CH2S), 27.8 (C-8), 21.4
Uranyl Complex 2: Separate solutions of cis-1,2-diaminocyclohex-
ane (0.068 mL, 0.576 mmol) in 50 mL of methanol and dialdehyde
II (288 mg, 0.576 mmol) in 50 mL of methanol/tetrahydrofuran
were added simultaneously, within 1 h, to a refluxing solution of
Ba(CF3SO3)2 (251 mg, 0.576 mmol) in 200 mL of dry methanol.
The solution of II was prepared by dissolving compound II in 5 mL
of tetrahydrofuran, followed by addition of methanol up to the
desired volume. After 30 min, UO2(CH3COO)2·2H2O (244 mg,
0.576 mmol) was added. The solution was kept at reflux for 30 min,
then cooled to room temperature. The solvent was removed under
vacuum, and the residue was extracted with dichloromethane. The
organic solution was washed with saturated aqueous solutions of
sodium sulfate (3 × 100 mL), sodium hydrogen carbonate
(1×100 mL), and sodium chloride (1×100 mL), then dried with
sodium sulfate. After filtration and removal of the solvent under
vacuum, the crude product was purified by column chromatog-
raphy. Elution was first performed using dichloromethane, which
slowly separated a yellow band. Subsequent elution with dichloro-
methane/methanol (500:1) separated out a second yellow band
from the top of the column. Neither of these materials was the
expected product and they were not identified. A red band was
eluted with dichloromethane/methanol (100:1), and collected as a
red powder after removal of solvent. Pure uranyl macrocycle 2 was
obtained by precipitation with hexane from a concentrated dichlo-
(C-9) ppm. FT-IR (dichloromethane): ν
2026, 2017 cm–1 (vs,
˜
max
CO), 1618 (s, C=N), 1606 (w, py), 1545, 1470, 1446. FT-IR (KBr):
ν
= 2013 cm–1 (CO), 1618 (C=N), 1544, 1444, 1321, 1230, 840,
˜
max
741, 558. FAB: clusters centered at m/z =765.3 [3 + H+] and 737 [3
·
+ H+ – CO]. C32H33F6N3NiO5PRhS2 3H2O (964.36): calcd. C
39.85, H 4.08, N 4.36; found C 39.54, H 3.52, N 4.40.
UO2–RhI Complex 4: The monometallic uranyl complex 2
(60.6 mg, 0.070 mmol) was suspended in 9 mL of methanol in a
Schlenk tube and stirred at room temperature. A yellow solution
of [RhCl(CO)2]2 (13.6 mg, 0.035 mmol) in 4 mL of methanol was
then added with a cannula and the suspension changed into a clear
red-orange solution. After 20 min, the infrared analysis of the solu-
tion showed an intense absorption at 2015 cm–1 and the absence of
the bands due to the starting rhodium dimer. A methanolic solu-
tion (3 mL) of NH4PF6 (155 mg) was added to the reaction flask,
causing the immediate formation of a red-brown powder. After stir-
ring for a few minutes the precipitate was allowed to settle, then
the solution was decanted off. The solid was washed twice with
cold methanol and vacuum-dried to give 17 mg of a brown-red
powder. A second crop precipitated out of the mother solution
upon standing under argon for a few hours (15 mg). Both crops
were characterized by an intense infrared absorption at 2015 cm–1
in dichloromethane. Yield: 42%. As in the case of complex 3, this
1
romethane solution (140 mg, 29% yield). H NMR ([D2]dichloro-
methane): δ = 9.31 (s, 2 H, CH=N), 7.79 (t, J = 7.6 Hz, 1 H, py 4-
3
H), 7.49 (d, J = 7.6 Hz, 2 H, py 3,5-H), 7.24 and 7.22 (two dd, J
4
= 6.5, J = 1.4 Hz, 2 H + 2 H, Ar 4-H and 6-H), 6.70 (pseudo-t,
J = 7.8 Hz, 2 H, Ar 5-H), 4.66 (br. m, 2 H, cy 7-H), 4.57 and 4.49
(AB system, ∆ν = 24 Hz, 4 H, pyCH2S), 4.48 (t, J = 5.1 Hz, 4 H,
–CH2OAr), 3.13 (t, J = 5.1 Hz, 4 H, –CH2S), 2.44 (m, 2 H, cy 8-H),
1.99 (m, 2 H, cy 8-H), 1.75 (m, 4 H, cy 9-H) ppm. 13C NMR ([D2]-
dichloromethane): δ = 167.2 (CH=N), 159.4 (py C-2), 157.5, 149.7
(Ar C-2, C-3), 138.48 (py C-4), 126.0, 123.3, 122.1, 116.8, 116.0 (py
C-3 and Ar C-1, C-4, C-5, C-6), 71.14 (cy C-7), 69.76 (–CH2OAr),
38.32 (pyCH2S), 31.58 (CH2S), 27.36 (C-8), 21.42 (C-9) ppm. ESI
(methanol): positive, cluster centered at m/z = 847 [2 + H+]. FT-
material is moderately air sensitive. FT-IR (dichloromethane): ν
˜
max
= 2020 cm–1 (s, CO), 1616 (vs, C=N), 1556, 1453; (KBr): ν
=
˜
max
2011 cm–1 (CO), 1614 (C=N), 1553, 1450, 1400, 1306, 1230, 1085,
997, 890 (UO2), 844, 745, 558. FAB: clusters centered at m/z =
976.7 [4+] and 949 [4+ – CO]. C32H33F6N3O7PRhS2U (1121.7):
calcd. C 34.27, H 2.97, N 3.75; found C 34.32, H 3.67, N 3.32.
IR (KBr): νmax = 1612 cm–1 (vs, C=N), 1594 (py), 1522, 1466, 1451,
˜
1309, 1246, 1223, 1086, 898 (s, UO2), 738. FT-IR (dichlorometh-
ane): νmax = 1616 cm–1 (vs, C=N), 1597, 1575 (py), 1555, 1456 (vs).
Crystal Structure Determination of the Macrocyclic Nickel Complex
1: The data were collected on a Philips PW1100 diffractometer
using Mo-Kα radiation (λ = 0.71069 Å), controlled by a local pro-
˜
C31H33N3O6S2U·2H2O (881.80): calcd. C 42.22, H 4.23, N 4.77;
found C 42.77, H 4.16, N 4.62.
922
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 914–925

A Novel Heteroditopic Macrocyclic System
FULL PAPER
gram.[31] The preliminary cell parameters were obtained from least-
squares plots of the (θ,χ,φ) angular values of 25 reflections (θ range
= 7.3–12.7°) accurately centered on the diffractometer. The inten-
sity of one standard reflection, recorded for every 100, showed a
decomposition of about 29%. The recorded data (θ range = 3–
27°) were corrected for this decay, for polarization, and for Lorentz
effects. The absorption correction was performed with the method
of Walker and Stuart,[32] using a program written by Gluzinski.[33]
The low quality of the employed crystal resulted in the low number
of observed reflections. The structure was solved by direct methods
with SIR97,[34] and refined full-matrix anisotropic least-squares
methods with SHELX97.[35] Most of the H atoms were found in a
difference Fourier map, and the remainder were put in their theo-
retical positions, refined by a few cycles with isotropic thermal pa-
rameters, and then blocked in the refined positions. The ORTEP
drawings were produced with the ORTEP-3 program.[36]
CCDC-253882 (for 1) and -253883 (for 2) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/data_request/cif.
Supporting Information (see footnote on the first page of this arti-
cle): 1H NMR, 13C NMR, and FT-IR spectra of complexes 1–4.
FT-IR spectra of the products of oxidative addition of methyl io-
dide to complexes 3 and 4.
Acknowledgments
We wish to thank Prof. Frank van Veggel for discussions during
the early stages of this project, Dr. Valeria van Axel Castelli for
many helpful suggestions throughout the work, and Dr. Giovanna
Mancini for the 2D NMR measurements. Partial funding from
MIUR (projects COFIN1999 “Effetti cooperativi in sistemi orga-
nometallici polifunzionali” and COFIN2003 “Effetti cooperativi in
nuovi sistemi metallo-ciclopentadienilici polifunzionali”) is grate-
fully acknowledged.
Crystal Structure Determination of the Macrocyclic Uranyl Complex
2: The data were collected on a Bruker AXS Smart CCD dif-
fractometer with Mo-Kα radiation (λ = 0.71069 Å) (θ range = 3–
29°). Auto-indexing was performed with an algorithm operating on
difference vectors derived from the input reflections. During the
data collection the specimen decomposed by about 23%. Data re-
duction, absorption, and decomposition corrections, structure
solution and refinement were all performed with the programs con-
tained in SHELXTL-NT V5.1.[37] The small dimensions of the em-
ployed crystal and its low quality resulted in a small number of
observed reflections. All the non-hydrogen atoms were refined an-
isotropically. While most of the hydrogen atoms were found in a
difference Fourier map, the remainder ones were put in their geo-
metrical positions, refined by a few cycles with isotropic thermal
parameters, and then blocked in the refined positions. The hydro-
gen atoms of the water molecule were not localized. Experimental
crystallographic information for both complexes 1 and 2 are re-
ported in Table 3.
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Table 3. Selected crystallographic details for complexes 1 and 2.
1
2
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Formula
C31H33N3NiO4S2·H2O C31H33N3O6S2U·H2O
652.45
amber
prism
Formula weight
Crystal color
Crystal shape
Size [mm]
Crystal system
Space group
a [Å]
863.79
red
prism
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0.29×0.34×0.39
monoclinic
P21/c
15.866(3)
11.983(4)
16.505(2)
106.98(4)
3001.17
8.25
293(2)
4
–20/19, 0/15, 0/21
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C2/c
23.788(2)
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21.737(2)
112.24(3)
6390.91
49.91
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8
–30/14, –15/16, –28/28
19496
b [Å]
c [Å]
β [°]
Cell volume [Å3]
µcalcd. [cm–1]
Temperature [K]
Z
h, k, l ranges
No. collected
reflns.
No. indep. reflns.
Rint
No. reflns. obsd.
[I Ͼ 2σ(I)]
Final R factor
Final Rw factor
GOF
6261
0.08
1828
6843
0.14
2730
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Eur. J. Inorg. Chem. 2006, 914–925
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
923

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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 914–925

A Novel Heteroditopic Macrocyclic System
FULL PAPER
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Received: August 4, 2005
Published Online: January 9, 2006
Eur. J. Inorg. Chem. 2006, 914–925
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
925