Synthesis, reactivity, and structural transformation of mono- and binuclear carboranylamidinate-based 3d metal complexes and metallacarborane derivatives

Article abstract of DOI:10.1021/om2011358

A series of carboranylamidinate-based 3d metal complexes are reported. Treatments of 3d metal dichlorides (CoCl₂, NiCl₂(DME), CuCl₂) with the lithium salts of carboranylamidines (Cab ^NH) generate the mononuclear C,N-coordinated complexes [(RN=C(closo-1,2-C₂B₁₀H₁₀)(NHR)]₂M (1-6; M = Co, Ni, Cu; R = iPr, Cy) in moderate yields, respectively. These complexes have similar structures in the solid state, in which the metal atom is coordinated to two nitrogen atoms and bonded to two cage carbon atoms in a distorted-tetrahedral geometry. As a noninnocent ligand, Cab^NH can be modified to produce carboranylamidinate thiol (Cab^NSH) and nido derivatives Dcab^NH (9, 10), respectively. Reaction of cupric acetate with 1 equiv of Cab^NSH gave the binuclear complexes {[RN=C(closo-1,2-C₂B₁₀H₁₀)(NHR)]SCu} ₂ (R = iPr (7), Cy (8)) in 66 and 63% yields, respectively. The structure of 7 shows the formation of a Cu-Cu bond, and the geometry of the Cu₂S₂ core is planar. The zwitterionic nickel dicarbollide complexes (Dcab^N)Ni(PPh₃)Cl (11, 12) were prepared by reactions of the lithium salts of Dcab^NH (9, 10) with NiCl ₂(PPh₃)₂ in THF. All complexes were characterized by elemental analysis and IR and NMR spectroscopy. The structures of 1, 3-5, 7, and 9-11 were further confirmed by single-crystal X-ray diffraction.

Full text of DOI:10.1021/om2011358

Article
pubs.acs.org/Organometallics
Synthesis, Reactivity, and Structural Transformation of Mono- and
Binuclear Carboranylamidinate-Based 3d Metal Complexes and
Metallacarborane Derivatives
Zi-Jian Yao† and Guo-Xin Jin*,†,‡
†Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai
200433, People's Republic of China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People's Republic of China
S
* Supporting Information
ABSTRACT: A series of carboranylamidinate-based 3d metal
complexes are reported. Treatments of 3d metal dichlorides
(CoCl2, NiCl2(DME), CuCl2) with the lithium salts of
carboranylamidines (CabNH) generate the mononuclear
C,N-coordinated complexes [(RNC(closo-1,2-C2B10H10)-
(NHR)]2M (1−6; M  Co, Ni, Cu; R = iPr, Cy) in
moderate yields, respectively. These complexes have similar
structures in the solid state, in which the metal atom is
coordinated to two nitrogen atoms and bonded to two cage
carbon atoms in a distorted-tetrahedral geometry. As a
noninnocent ligand, CabNH can be modified to produce
carboranylamidinate thiol (CabNSH) and nido derivatives
DcabNH (9, 10), respectively. Reaction of cupric acetate with 1
equiv of CabNSH gave the binuclear complexes {[RNC(closo-1,2-C2B10H10)(NHR)]SCu}2 (R = iPr (7), Cy (8)) in 66 and
63% yields, respectively. The structure of 7 shows the formation of a Cu−Cu bond, and the geometry of the Cu2S2 core is planar.
The zwitterionic nickel dicarbollide complexes (DcabN)Ni(PPh3)Cl (11, 12) were prepared by reactions of the lithium salts of
DcabNH (9, 10) with NiCl2(PPh3)2 in THF. All complexes were characterized by elemental analysis and IR and NMR
spectroscopy. The structures of 1, 3−5, 7, and 9−11 were further confirmed by single-crystal X-ray diffraction.
were synthesized by Edelmann’s group recently.11 This unique
INTRODUCTION
■
Carborane derivatives have been widely used1 in the fields of
ligand could afford an unexpected C,N-chelating coordination
catalysis,2a−g polymers,2h nonlinear optical materials,2i and
mode, which is different from the normal N,N-coordination
BNCT (boron−neutron capture therapy) techniques,2j because
of their versatile properties and the exceptionally stable
mode of amidinate ligands. However, the reactivity of
carboranylamidinates has been rarely reported so far, although
carborane backbone.3 Recent reports on unusually stable
one Sn and two Cr carboranylamidinate complexes have been
structurally characterized.11 Moreover, in the search for new
types of ligand systems as alternatives to the ubiquitous
cyclopentadienyl (Cp) ligand for stabilization of the metal
center, the dicarbollyl moiety appears to be a suitable candidate
as a π-bonding group instead of the Cp.12 It is worthwhile to
investigate the synthesis and reactivity of dicarbollylamidinate.
Our previous work exhibited the versatile reactivity of
carboranylamidinates toward half-sandwich iridium and rho-
dium complexes.13 As an ongoing project, we are interested in
the effects of ligands and the nature of transition metals on the
formation, structure, and stability of metal carboranylamidinate
complexes. We herein report the synthesis and structure
characterization of 3d metal carboranylamidinate and dicarbol-
C,N-,4 C,P-,5 C,S-,6 N,P-,7 N,S-,8 P,P-9 and S,S-chelating10 o-
carboranyl metal complexes imply that the o-carboranyl ligand
backbone could largely stabilize metal intermediates in
organometallic reactions. Therefore, the study of carboranyl-
based transition-metal complexes with ligands containing
dissimilar donor atoms has been of considerable interest,
especially a ligand system containing one functional group
strongly bound to the metal center and another group that is
coordinatively labile.4c These types of metal complexes often
exhibit good catalytic activity in polymerization processes,
because the coordinatively labile group in such ligands may
dissociate from the metal center to produce a necessary vacancy
for substrate complexation during the homogeneous catalytic
cycle.
Carboranylamidinates, which combine the versatile charac-
teristics of both carboranes and amidinates into one system,
Received: November 16, 2011
Published: February 21, 2012
© 2012 American Chemical Society
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a
Scheme 1. Synthesis of C,N-Chelating Coordination Mode Complexes 1−6
a
Reaction conditions: (i) 1 equiv of n-BuLi, THF, −78 °C; (ii) 0.5 equiv of metal sources (CoCl2, NiCl2(DME), and CuCl2, respectively), THF,
room temperature.
lyamidinate complexes. On the basis of the systematic research
on 1,2-dicarba-closo-dodecarborane-1,2-dichalcogenolates,14 the
reactivity of carboranylamidinate thiol was also studied in the
present work. All complexes were fully characterized by
elemental analysis and IR and NMR spectroscopy.
highly soluble in THF and CH2Cl2 and slightly soluble in ether
and toluene.
All complexes were fully characterized by various spectro-
scopic techniques and elemental analysis. The IR spectra of
these complexes all display a typical strong and broad
characteristic B−H absorption at approximately 2565 cm−1,
and the absorption at approximately 3425 cm−1 is ascribed to
RESULTS AND DISCUSSION
1
N−H bond vibrations. The H and 13C NMR spectra of these
■
Recently, we have prepared a series of 18-electron and 16-
electron half-sandwich carboranylamidinate-based transition-
metal complexes of the type [Cp*MClCabC,N](18e) and
[Cp*MCabC,N′](16e) (M  Ir, Rh).13 We observed that
these complexes all show an unexpected C,N-chelating
coordination mode. Moreover, the 18-electron iridium complex
exhibited a good catalytic activity for norbornene polymer-
ization in the presence of cocatalyst (MAO). It is a natural
extension for us to do a stepwise study on the reactivity of
carboranylamidinate with 3d metals (Fe, Co, Ni, Cu), because
of the wide utilization of these metal complexes as catalysts in
organic synthesis15 such as cross-couplings,15a−c Diels−Alder
reactions,15d and cycloadditions,15e as well as polymerization
processes.15f
complexes were not informative because of the strong
paramagnetism of the metal ions. The 11B NMR spectrum of
nickel complex 3 exhibits signals at −3.4, −4.2, and −8.4 ppm
in a ratio of 1:1:8. The elemental analysis of these complexes
indicates that their structures are similar to each other.
To unambiguously elucidate their structures, single crystals
suitable for X-ray diffraction analyses were obtained by the slow
diffusion of hexane into their saturated CH2Cl2 solutions. The
crystallographic data of 1 and 3−5 are summarized in Table 1.
Figure 1 shows their molecular structures together with
selected bond lengths and angles. These complexes have
similar solid-state structures, in which the metal atom is bonded
to two cage carbon atoms and coordinated to two nitrogen
atoms of imine groups in a distorted-tetrahedral geometry. The
C−C bond distances of the carborane cage in these complexes
were found to increase on complexation. Complex 3 shows the
largest increase (1.702(4) Å), that is, 0.065 Å relative to the free
ligand (1.637(3) Å). The reason for the increase of the C−C
distances can be attributed to the formation of the carbon−
metal bond and the coordination interaction of the N atom.
The X-ray diffraction study of these complexes further reveals
the C,N-coordination mode of the carboranylamidinate ligand
with a nearly planar MNC3 (M  Co, Ni, Cu) ring. Similar to
the case for half-sandwich complexes,13 all of the structures
suggested that the imine group has a preferential coordination
ability because no amine-coordinated products were obtained
under the previous reaction conditions. Generally, in the
presence of methylaluminoxane (MAO), the labile imine group
may dissociate from the metal center to produce a necessary
vacancy for olefin insertion. Therefore, we tried to investigate
the catalytic activity of the nickel complexes for norbornene
polymerization on the basis of our previous work.17
Unfortunately, both of them exhibited poor catalytic activities.
The reason may be ascribed to the nonplanar geometry of the
metal center, which indicates that the d orbital of the metal was
occupied by a single electron. This also explains why the Ni2+
complex is paramagnetic. The dihedral angles between the two
M−C−N rings are 88.8° (1), 34.6° (3), 35.7° (4), and 57.7°
(5), respectively. For complex 3, the angles of C(2)−C(1)−
Ni(1) (108.7(18)°) and C(2)−C(1)−Ni(1) (108.2(18)°)
Reactivity of Carboranylamidinate with 3d Metals
(Co, Ni, Cu). Treatments of the carboranylamidine CabNH
(CabNH = RNC(closo-1,2-C2B10H11)(NHR), R = iPr, Cy)
with 1 equiv of n-BuLi in THF at −78 °C, followed by the
addition of 0.5 equiv of anhydrous CoCl2 at room temperature,
afforded mononuclear complexes 1 and 2 ([(RNC(closo-1,2-
C2B10H10)(NHR)]2Co, R = iPr (1), Cy (2)) as purple solids in
48% and 51% isolated yields, respectively (Scheme 1). It is
noteworthy that the yields were greatly decreased when
cobaltous chloride hexahydrate was used as the starting
material. Under the same reaction conditions, purple nickel
complexes 3 and 4 and blue copper complexes 5 and 6 were
obtained, in moderate isolated yields after column chromatog-
raphy on silica gel, respectively. Complexes 1−4 are very stable
in air for months, but copper complexes 5 and 6 are moderately
stable in air and show slow decomposition when they contact
with moisture. They are also very thermally stable, and no
decomposition is observed even after prolonged heating in
THF. The unusual thermal stability of these complexes is
related to the formation of a five-membered ring and the
advantageous properties of the bulky o-carborane unit,
including both its electronic and steric effects.16 Different
nickel salts such as NiCl2(PPh3)2, NiBr2(PPh3)2, and (Ph3P)-
Ni(Ph)Cl2 were used as starting materials, respectively.
However, the products (3 and 4) were all obtained in yields
more or less the same. These mononuclear complexes 1−6 are
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Figure 1. Molecular structures of 1 and 3−5 with thermal ellipsoids drawn at the 30% level. All hydrogen atoms are omitted for clarity. Selected
lengths (Å) and angles (deg) are as follows. 1: C(1)−C(2), 1.682(5); C(10)−C(11), 1.670(5); Co(1)−C(1), 2.041(3); Co(1)−C(10), 2.031(4);
Co(1)−N(1), 2.040(3); Co(1)−N(3), 2.072(3); C(1)−Co(1)−N(1), 85.4(13), N(1)−Co(1)−N(3), 127.8(12). 3: C(1)−C(2), 1.700(4); C(10)−
C(11), 1.702(4); Ni(1)−C(1), 1.902(3); Ni(1)−C(10), 1.903(3); Ni(1)−N(1), 1.947(2); Ni(1)−N(3), 1.951(2); C(1)−Ni(1)−N(1), 85.9(10),
N(1)−Ni(1)−N(3), 97.9(10). 4: C(1)−C(2), 1.691(5); C(16)−C(17), 1.671(6); Ni(1)−C(1), 1.905(4); Ni(1)−C(16), 1.904(4); Ni(1)−N(1),
1.967(4); Ni(1)−N(3), 1.959(3); C(1)−Ni(1)−N(1), 85.9(16), N(1)−Ni(1)−N(3), 98.6(16). 5: C(1)−C(2), 1.651(6); Cu(1)−C(1), 2.036(4);
Cu(1)−N(1), 2.010(4); C(1)−Cu(1)−N(1), 85.4(15); N(1)−Cu(1)−N(1A), 152.6(2); C(1)−Cu(1)−C(1A), 132.8(3).
within the two five-membered rings are almost the same as the
expected 108°. The Ni(1)−C bond lengths (1.902(3) and
1.903(3) Å) are similar to those observed in other crystallo-
graphically characterized nickel(II) complexes.17
CH3OH at room temperature afforded the sulfur-bridged
binuclear copper complexes {[RNC(closo-1,2-C2B10H10)-
(NHR)]SCu}2 (R  iPr (7), Cy (8)) in 66 and 63% yields,
respectively (Scheme 2). To our surprise, this reaction occurred
Reactivity of Carboranylamidinate Thiol. The synthesis
of multinuclear complexes containing metal−metal bonds has
attracted considerable attention over the past few decades, and
this great interest was stimulated by the numerous applications
of these complexes.18 On the basis of our systematic study, we
found that 1,2-dicarba-closo-dodecarborane-1,2-dichalcogeno-
lates were useful ligands in facilitating the formation of
multinuclear complexes containing metal−metal bonds. The
sulfur atom can readily be used as a good bridging or chelating
donor by an incoming low-oxidation-state metal fragment to
form multinuclear complexes,14b owing to their filled pz
orbitals. In view of another untouched C−H bond in the
carborane cage of carboranylamidinate, we then focused on the
stepwise modification of CabNH after successful preparation of
1−6. Therefore, the reactivity of carboranylamidinate thiol
CabNSH (CabNSH = RNC(closo-1,2-C2B10H10-SH)(NHR),
R  iPr, Cy) was studied as an extension of ligand variation.
The reaction of CabNSH with 1 equiv of cupric acetate in
Scheme 2. Synthesis of Binuclear Copper Complexes 7 and 8
very rapidly and the products precipitated from the solution in
5 min. The complexes are air and moisture stable. Their
solubility is poor: they are slightly soluble in DMSO and
CH2Cl2 and almost insoluble in toluene, THF, and CHCl3. The
1H NMR data do not offer any structural information on
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whether 7 is a monomeric or dimeric species. The molecular
structure of 7 was characterized by single-crystal X-ray analysis.
Figure 2 shows the molecular structure of 7 together with
selected bond lengths and angles. The structure is centrosym-
solvents made it impossible for us to get useful information
from the 11B NMR spectra.
Synthesis and Reactivity of Nido Derivatives. Upon
heating in neat methanol, CabNH underwent facile degradation
to selectively remove the boron atom and generate the new
nido ligands DcabNH (DcabNH = nido-7-[C(NHR)2]+(7,8-
C2B9H11)−, R = iPr (9), Cy (10)), respectively (Scheme 3).
The products were recrystallized in a CH2Cl2/hexane mixture
as colorless crystals in yields of 82% and 80%, respectively. This
type of ligand is often used in the synthesis of zwitterionic
metallacarboranes.22 The solubility of DcabNH is much less
than that of CabNH because of the destruction of a symmetric
structure. The characteristic asymmetric pattern in the 11B
NMR spectrum in the range of −7.3 to −36.3 ppm and the
presence of an absorption at approximately −3.3 ppm in the 1H
NMR spectrum both imply a B−H−B interaction on the C2B3
open face.23 Single-crystal X-ray diffraction analysis of DcabNH
ligands further supports the spectral data. The crystallographic
data of them are summarized in Table 1. As shown in Figure 3,
compound 9 is clearly a zwitterionic structure. Interestingly, the
C(1)−N(1) distance of 1.317(3) Å is almost the same as that
of the C(1)−N(2) bond, suggesting the charge is delocalized
over the N(1)−C(1)−N(2) unit. The structure of 10 is similar
to that of 9 (see the Supporting Information). The B−B and
C−B distances in 9 and 10 are normal and very comparable to
those in their parent compounds. The investigation of the
reactivity of DcabNH is desired due to the rich coordination
sites (a η5-C2B3 face and two N atoms) in this ligand.
Figure 2. Molecular structure of 7 with thermal ellipsoids drawn at the
30% level. Some hydrogen atoms are omitted for clarity. Selected
lengths (Å) and angles (deg) are as follows: C(1)−C(2), 1.755(4);
S(1)−C(2), 1.775(3); Cu(1)−N(1), 1.968(3); Cu(1)−S(1),
2.481(12); Cu(1)−Cu(1A), 2.549(11); N(1)−Cu(1)−S(1), 98.7(9);
S(1)−Cu(1)−S(1A), 114.5(3); Cu(1)−S(1)−Cu(1A), 65.4(3).
metric with the symmetry center located between the two
copper atoms. Thus, the planar four-membered ring of Cu2S2 is
a parallelogram, in which the lengths of the sides are 2.215(13)
and 2.481(12) Å, respectively. In the solid structure of 7,
Cu(II) was reduced to Cu(I), and each copper atom was ligated
by two sulfur bridges and a nitrogen donor. No doubt there is a
tendency for the Cu(I) centers to cluster together.19 The
intromolecular distance between the two Cu atoms is
2.549(11) Å, suggesting the formation of the metal−metal
bond. The Cu−N bond lengths (1.968(3) Å) are identical and
comparable to other similar complexes. The Cu···H(B(3))
distance of 2.23 Å is much shorter than that of complex 5 (3.0−
3.5 Å), which may indicate some weak interaction between the
two atoms. In addition to the typical strong characteristic B−H
absorption at approximately 2570 cm−1 in the IR spectrum of 7,
a new B−H band at lower frequency (∼2360 cm−1) is shown in
the spectrum, also indicating that a specific B−H···Cu
interaction and lower overall symmetry of the cage.20 Similar
splittings of the B−H absorption were observed in 8. Such
interaction would be further confirmed by the significantly
reduced JBH values in the 11B NMR spectrum;21 however, the
poor solubility of the binuclear copper complexes in organic
The reactions of the lithium salts of DcabNH with the
NiCl2(PPh3)2 in THF gave, after workup, the zwitterionic
nickel dicarbollide complexes (DcabN)Ni(PPh3)Cl ((DcabN)-
Ni(PPh3)Cl = nido-7-[C(NHR)2]+[(η5-7,8-C2B9H10)Ni(PPh3)-
Cl]−, R = iPr (11), 67%; Cy (12), 61%) rather than the N-
coordinated CGC-type complexes (Scheme 3). The reason can
possibly be ascribed to the steric effects of the isopropyl or
cyclohexyl group. To our knowledge, nido-carboranylamidinate-
based transition-metal complexes are unknown so far. These
complexes were obtained as purple red powders after
chromatographic purification column on silica gel. They are
highly soluble in THF and CH2Cl2 and slightly soluble in
1
CHCl3 and toluene. In the H NMR spectrum of 11, several
groups of signals in the range of δ 7.85−7.33 ppm for aromatic
protons of PPh3, a multiplet at 4.13−4.05 ppm for NCH
protons, and two doublets at 1.51 and 1.32 ppm for CH(CH3)2
protons were observed. The 1H NMR spectrum of 12 is similar
to that of 11 except for several groups of signals for Cy in the
range δ 1.93−0.90 ppm, instead of the signals of iPr in 11. The
incorporation of the phosphine ligand was verified by the 31P
NMR chemical shift, which appeared at δ 34.3 ppm for the
triphenylphosphine of 11.
Scheme 3. Synthesis and Reactivity of Dicarbollylamidinate Ligands
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Figure 3. Molecular structures of 9 and 11 with thermal ellipsoids drawn at the 30% level. All hydrogen atoms of 11 are omitted for clarity. Selected
lengths (Å) and angles (deg) are as follows. 9: C(7)−C(8), 1.563(3); C(1)−C(8), 1.479(3); N(1)−C(1), 1.317(3); N(2)−C(1), 1.313(3). 11:
C(7)−C(8), 1.628(4); Ni(1)−C(7), 2.250(3); Ni(1)−C(8), 2.105(3); Ni(1)−B(9), 2.154(3); Ni(1)−B(10), 2.089(4); Ni(1)−B(11), 2.086(3);
Ni(1)−P(1), 2.1764(11); Ni(1)−Cl(1), 2.2250(10); Ni−C2B3(centroid), 1.56; P(1)−Ni(1)−Cl(1), 91.5(4).
Single crystals suitable for X-ray diffraction analyses were
obtained by the slow diffusion of hexane into a saturated
solution of 11 in CH2Cl2. Complex 11 crystallized in the
monoclinic space group P21/c. The crystallographic data of 11
are summarized in Table 1. Figure 3 shows the molecular
structure of 11 together with selected bond lengths and angles.
In comparison with DcabNH 9 (1.563(3) Å), the C−C bond
length of the carborane cage in 11 (1.628(4) Å) was also found
to increase on complexation. The structure shows that the
nickel atom is η5 coordinated to the dicarbollide ligand, and the
geometry at the metal atom is that of a two-legged piano stool
with the nickel atom coordinated by the η5-C2B3, Cl, and P
atoms. The molecule is comprised of a nickel(II) phosphine
unit which is bonded to a C2B3 face of a dicarbollylamidinate
ligand. This is further confirmed by the IR spectrum of the
absorption at approximately 1095 cm−1, which is ascribed to the
C−P bond vibration. The Ni−P bond length of 2.176(11) Å is
within the range of known values for the bond,24 and the plane
of P(1)−Ni(1)−Cl(1) is almost perpendicular to the C2B3 face
(the dihedral angle is 89.9(65)°). The Ni−C(cage) bond
length (2.18 Å (av)) is longer than that of the Ni−B bond (2.11
Å (av)), which indicates that the nickel atom is closer to boron
atoms and is not centered over the ring. The Ni−
C2B3(certroid) distance of 1.56 Å is similar to reported
values.24a
the production of a zwitterionic metallacarborane complex
rather than a CGC-type complex indicated that steric effects
played an important role in this reaction. Further studies on the
synthesis of half-sandwich metallacarboranes incorporating
nido-carboranylamidinate ligands are currently underway in
our laboratory.
EXPERIMENTAL SECTION
■
General Data. All manipulations were performed under an
atmosphere of nitrogen using standard Schlenk techniques. CH2Cl2
was dried over CaH2, and THF, diethyl ether, hexane, and toluene
were dried over Na and then distilled under a nitrogen atmosphere
immediately prior to use. n-Butyllithium (1.6 M in n-hexane, Acros), o-
carborane, and other chemicals were used as commercial products
without further purification. CabNH and CabNSH were synthesized
according to the literature.11,13 1H NMR (400 MHz) and 31P NMR
(162 MHz) spectra were measured with a VAVCE DMX-400
spectrometer. 11B NMR (160 MHz) spectra were recorded with a
Bruker DMX-500 spectrometer. Elemental analysis was performed on
an Elementar vario EL III analyzer. IR (KBr) spectra were measured
with the Nicolet FT-IR spectrophotometer.
Synthesis of Mononuclear Metal Complexes 1−6. Complex
1. n-BuLi (1.6 M in n-hexane, 0.25 mL, 0.4 mmol) was added to
a solution of iPr-CabNH (108 mg, 0.4 mmol) in THF (10 mL)
at −78 °C; the mixture was stirred at −78 °C for 1 h and at
room temperature for another 2 h. Then anhydrous CoCl2 (26
mg, 0.2 mmol) was added as solid to the above mixture and
stirred for 8 h at room temperature. After removal of the
solvent under vacuum, the residue was purified by column
chromatography on silica gel. Elution with petroleum ether/
CH2Cl2 (1/1) gave 1 (58 mg, 48%) as purple solid. A suitable
single crystal of 1 was obtained by slow diffusion of n-hexane
into its concentrated dichloromethane solution. IR (KBr, disk):
ν 3430 (N−H), 2601, 2548 (B−H) cm−1. Anal. Calcd for
C18H50B20CoN4: C, 36.17; H, 8.43; N, 9.37. Found: C, 36.33;
H, 8.49; N, 9.56.
CONCLUSIONS
■
In summary, a series of novel carboranylamidinate-based metal
complexes were obtained through the reactions of 3d metal
compounds with carboranylamidinates and their derivatives.
Mononuclear complexes 1−6 all showed an unexpected C,N-
chelating coordination mode rather than a normal N,N-
chelating mode. Interestingly, a binuclear Cu(I) complex,
which is comprised of a Cu−Cu bond and two sulfur bridges,
was obtained through the reaction of cupric acetate with
carboranylamidinate thiol. We speculated that Cu(II) was
reduced by the lone pair electrons of sulfur. This further
confirmed that the sulfur atom can be used as a good bridging
or chelating donor owing to their filled pz orbitals. In addition,
Complex 2. A procedure analogous to that used to prepare 1 was
used, but starting from Cy-CabNH (140 mg, 0.4 mmol). Yield: 77 mg,
51%. IR (KBr, disk): ν 3423 (N−H), 2606, 2545 (B−H) cm−1. Anal.
Calcd for C30H66B20CoN4: C, 47.53; H, 8.78; N, 7.39; Found: C,
47.67; H, 8.80; N, 7.44.
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Complex 3. A procedure analogous to that used to prepare 1 was
used, but starting from NiCl2(DME) (44 mg, 0.2 mmol). Yield: 66 mg,
55%. 11B NMR (160 MHz, CDCl3, 25 °C): −3.4 (2B), −4.2 (2B),
−8.4 (16B) ppm. IR (KBr, disk): ν 3425 (N−H), 2611, 2536 (B−H)
cm−1. Anal. Calcd for C18H50B20NiN4: C, 36.18; H, 8.43; N, 9.38;
Found: C, 36.25; H, 8.44; N, 9.42.
Complex 4. A procedure analogous to that used to prepare 1 was
used, but starting from Cy-CabNH (140 mg, 0.4 mmol) and
NiCl2(DME) (44 mg, 0.2 mmol). Yield: 82 mg, 54%. IR (KBr,
disk): ν 3430 (N−H), 2610, 2530 (B−H) cm−1. Anal. Calcd for
C30H66B20NiN4: C, 47.55; H, 8.78; N, 7.39; Found: C, 47.68; H, 8.88;
N, 7.39.
Complex 5. A procedure analogous to that used to prepare 1 was
used, but starting from anhydrous CuCl2 (68 mg, 0.2 mmol). Yield: 43
mg, 36%. IR (KBr, disk): ν 3425 (N−H), 2611, 2536 (B−H) cm−1.
Anal. Calcd for C18H50B20CuN4: C, 35.89; H, 8.37; N, 9.30; Found: C,
35.86; H, 8.37; N, 9.44.
removal of the solvent under vacuum, the residue was purified
by column chromatography on silica gel. Elution with
petroleum ether/CH2Cl2 (2/1) gave 11 (165 mg, 67%) as a
purple-red solid. A suitable single crystal of 11 was obtained by
slow diffusion of n-hexane into its concentrated dichloro-
1
methane solution. H NMR (400 MHz, CD2Cl2, 25 °C): δ
7.85−7.80 (m, 6H, Ph), 7.53−7.33 (m, 9H, Ph), 4.13−4.05 (m,
2H, NCH), 1.51 (d, J = 8.0 Hz, 6H, CH(CH3)2), 1.32 (d, J =
8.0 Hz, 6H, CH(CH3)2) ppm. 11B NMR (160 MHz, CDCl3, 25
°C): −8.4 (3B), −16.3 (2B), −21.7 (1B), −25.5 (1B), −31.2
31
(1B), −36.3 (1B) ppm. P NMR (162 MHz, CD2Cl2, 25 °C):
δ 34.4 (s, PPh3) ppm. IR (KBr, disk): ν 3430 (N−H), 2601,
2548 (B−H), 1095 (C−P) cm−1. Anal. Calcd for
C27H41B9ClN2NiP: C, 52.64; H, 6.71; N, 4.55. Found: C,
52.66; H, 6.71; N, 4.56.
Complex 12. A procedure analogous to that used to prepare 11 was
used, but starting from Cy-DcabNH (136 mg, 0.4 mmol). Yield: 542
mg, 80%. 1H NMR (400 MHz, CD2Cl2, 25 °C): δ 7.84−7.79 (m, 6H,
Ph), 7.53−7.41 (m, 9H, Ph), 3.72−3.66 (m, 2H, NCH), 1.93−0.90
(m, 20H, CH(CH2)5) ppm. IR (KBr, disk): ν 3429 (N−H), 2615,
2536 (B−H), 1094 (C−P) cm−1. Anal. Calcd for C33H49B9ClN2NiP:
C, 56.93; H, 7.09; N, 4.02. Found: C, 56.86; H, 7.08; N, 4.11.
X-ray Crystallography. Diffraction data of were collected on a
Bruker Smart APEX CCD diffractometer with graphite-monochro-
mated Mo Kα radiation (λ = 0.710 73 Å). All the data were collected
at room temperature, and the structures were solved by direct methods
and subsequently refined on F2 by using full-matrix least-squares
techniques (SHELXL).25 SADABS26 absorption corrections were
applied to the data, all non-hydrogen atoms were refined anisotropi-
cally, and hydrogen atoms were located at calculated positions. All
calculations were performed using the Bruker program Smart. A
summary of the crystallographic data and selected experimental
information are given in Table 1.
Complex 6. A procedure analogous to that used to prepare 1 was
used, but starting from Cy-CabNH (140 mg, 0.4 mmol) and anhydrous
CuCl2 (68 mg, 0.2 mmol). Yield: 60 mg, 39%. IR (KBr, disk): ν 3430
(N−H), 2606, 2530 (B−H) cm−1. Anal. Calcd for C30H66B20CuN4: C,
47.25; H, 8.72; N, 7.35. Found: C, 47.38; H, 8.78; N, 7.39.
Synthesis of Carboranylamidinate Thiolate Binuclear Com-
plexes 7 and 8. Complex 7. iPr-CabNSH (156 mg, 0.5 mmol)
was dissolved in 20 mL of MeOH, to which was added
Cu(OAc)2·H2O (100 mg, 0.5 mmol). A yellow precipitate soon
appeared. The resulting solid was obtained by filtration after the
reaction mixture was stirred for another 2 h. The product was
washed with Et2O several times and dried under vacuum. Yield:
120 mg, 66%. A suitable single crystal of 7 was obtained by slow
diffusion of n-hexane into its concentrated dichloromethane
1
solution. H NMR (400 MHz, CD2Cl2, 25 °C): δ 3.97 (br s,
4H, NCH), 1.43−1.30 (m, 24H, CH(CH3)2) ppm. IR (KBr,
disk): ν 3430 (N−H), 2570 (B−H), 2360 (B−H···Cu) cm−1.
Anal. Calcd for C18H50B20Cu2N4S2: C, 29.61; H, 6.90; N, 7.67.
Found: C, 29.63; H, 6.91; N, 7.77.
Complex 8. A procedure analogous to that used to prepare 7 was
used, but starting from Cy-CabNSH (191 mg, 0.5 mmol). Yield: 140
mg, 63%. IR (KBr, disk): ν 3425 (N−H), 2610 (B−H), 2353 (B−
H···Cu) cm−1. Anal. Calcd for C30H66B20Cu2N4S2: C, 40.47; H, 7.47;
N, 6.29. Found: C, 40.52; H, 7.48; N, 6.36.
ASSOCIATED CONTENT
* Supporting Information
■
S
CIF files giving crystallographic data for 1, 3−5, 7, and 9−11.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Synthesis of Ligands 9 and 10. Ligand 9. iPr-CabNH (540
mg, 2 mmol) was dissolved in degassed MeOH (20 mL), and
the reaction mixture was stirred at 65 °C for 6 h. After removal
of the solvent under vacuum, the residue was purified by
column chromatography on silica gel. Elution with petroleum
ether/CH2Cl2 (1/3) gave 7 (425 mg, 82%) as a white solid. 1H
NMR (400 MHz, DMSO-d6, 25 °C): δ 3.80−3.73 (m, 1H,
NCH), 3.53−3.44 (m, 1H, NCH), 1.33 (d, J = 6.4 Hz, 6H,
CH(CH3)2), 1.29 (d, J = 6.4 Hz, 6H, CH(CH3)2) ppm. 11B
NMR (160 MHz, CDCl3, 25 °C): −7.3 (2B), −11.7 (3B),
−18.9 (2B), −31.7(1B), −36.3 (1B) ppm. IR (KBr, disk): ν
3379 (N−H), 2583, 2538 (B−H), 1622 (CN) cm−1. Anal.
Calcd for C9H27B9N2: C, 41.48; H, 10.44; N, 10.75. Found: C,
41.50; H, 10.44; N, 10.82.
AUTHOR INFORMATION
Corresponding Author
*Tel: (+86)-21-65643776. Fax: (+86)-21-65641740. E-mail:
gxjin@fudan.edu.cn.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Shanghai Science and
Technology Committee (Nos. 08DZ2270500, 08J1400103),
the Shanghai Leading Academic Discipline Project (No. B108),
and the National Basic Research Program of China (Nos.
2009CB825300 and 2010DFA41160).
Ligand 10. A procedure analogous to that used to prepare 9 was
used, but starting from Cy-CabNH (700 mg, 2 mmol). Yield: 542 mg,
1
80%. H NMR (400 MHz, DMSO-d6, 25 °C): δ 3.48−3.45 (m, 1H,
REFERENCES
■
NCH), 3.07−3.05 (m, 1H, NCH), 1.96−1.07 (m, 20H, CH(CH2)5)
ppm. IR (KBr, disk): ν 3429 (N−H), 2615, 2536 (B−H) cm−1. Anal.
Calcd for C15H35B9N2: C, 52.87; H, 10.35; N, 8.22. Found: C, 52.83;
H, 10.35; N, 8.40.
(1) (a) Bregadze, V. I. Chem. Rev. 1992, 92, 209−223.
(b) Hawthorne, M. F.; Zheng, Z.-P. Acc. Chem. Res. 1997, 30, 267−
276. (c) Valliant, J. F.; Guenther, K. J.; King, A. S.; Morel, P.; Schaffer,
P.; Sogbein, O. O.; Stephenson, K. Coord. Chem. Rev. 2002, 232, 173−
230. (d) Jin, G. -X. Coord. Chem. Rev. 2004, 248, 587−602.
(e) Chizhevsky, I. T. Coord. Chem. Rev. 2007, 251, 1590−1619.
(2) (a) Xie, Z. Acc. Chem. Res. 2003, 36, 1−9. (b) Qiu, Z.; Xie, Z. J.
Am. Chem. Soc. 2009, 131, 2084−2085. (c) Shen, H.; Xie, Z. J. Am.
Chem. Soc. 2010, 132, 11473−11480. (d) Deng, L.; Chan, H. -S.; Xie,
Z. J. Am. Chem. Soc. 2005, 127, 13774−13775. (e) Lee, J. D.; Lee, Y. J.;
Son, K. C.; Cheong, M.; Ko, J.; Kang, S. O. Organometallics 2007, 26,
Synthesis of Nickel Dicarbollide Complexes 11 and 12.
Complex 11. n-BuLi (1.6 M in n-hexane, 0.25 mL, 0.4 mmol)
was added to a solution of iPr-DcabNH (104 mg, 0.4 mmol) in
THF (10 mL) at −78 °C; the mixture was stirred at −78 °C for
1 h and at room temperature for another 2 h. Then
NiCl2(PPh3)2 (262 mg, 0.4 mmol) was added as a solid to
the above mixture, and this mixture was stirred for 8 h at room
temperature. The mixture turned dark red immediately. After
1773
dx.doi.org/10.1021/om2011358 | Organometallics 2012, 31, 1767−1774

Organometallics
Article
3374−3384. (f) Tutusaus, O.; Vinas, C.; Nunez, R.; Teixidor, F.;
(19) Mehrotra, P. K.; Hoffmann, R. Inorg. Chem. 1978, 17, 2187−
2189.
́
̃
̃
Demonceau, A.; Delfosse, S.; Noels, A. F.; Mata, I.; Molins, E. J. Am.
Chem. Soc. 2003, 125, 11830−11831. (g) Felekidis, A.; Goblet-
(20) (a) Crowther, D. J.; Borkowsky, S. L.; Swenson, D.; Meyer, T.
Y.; Jordan, R. F. Organometallics 1993, 12, 2897−2903. (b) Shelly, K.;
Finster, D. C.; Lee, Y. J.; Scheidt, W. R.; Reed, C. A. J. Am. Chem. Soc.
1985, 107, 5955−5959. (c) Shelly, K.; Reed, C. A. J. Am. Chem. Soc.
1986, 108, 3117−3118. (d) Gupta, G. P.; Lang, G.; Lee, Y. J.; Scheidt,
W. R.; Shelly, K.; Reed, C. A. Inorg. Chem. 1987, 26, 3022−3030.
(21) (a) Franken, A.; McGrath, T. D.; Stone, F. G. A. J. Am. Chem.
Soc. 2006, 128, 16169−16177. (b) McGrath, T. D.; Du, S.; Hodson, B.
E.; Lu, X.; Stone, F. G. A. Organometallics 2006, 25, 4444−4451.
(c) Hodson, B. E.; McGrath, T. D.; Stone, F. G. A. Organometallics
2005, 24, 3386−3394.
́
Stachow, M.; Liegeois, J. F.; Pirotte, B.; Delarge, J.; Demonceau, A.;
Fontaine, M.; Noel, A. F.; Chizhevsky, I. T.; Zinevich, T. V.; Bregadze,
V. I.; Dolgushin, F. M.; Yanovsky, A. I.; Struchkov, Y. T. J. Organomet.
Chem. 1997, 536−537, 405−412. (h) Brown, D. A.; Colquhoun, H.
M.; Daniels, A. J.; MacBride, J. A. H.; Stephenson, I. R.; Wade, K. J.
Mater. Chem. 1992, 2, 793−804. (i) Murphy, D. M.; Mingos, D. M. P.;
Haggitt, J. L.; Poell, H. R.; Westcott, S. A.; Marder, T. B.; Taylor, N. J.;
Kanis, D. R. J. Mater. Chem. 1993, 3, 139−148. (j) Hawthorne, M. F.;
Maderna, A. Chem. Rev. 1999, 99, 3421−3434.
(3) Spokoyny, A. M.; Machan, C. W.; Clingerman, D. J.; Rosen, M.
S.; Wiester, M. J.; Kennedy, R. D.; Stern, C. L.; Sarjeant, A. A.; Mirkin,
C. A. Nature Chem. 2011, 3, 590−596.
(22) (a) Hawthorne, M. F.; Francis, J. N. Inorg. Chem. 1971, 10,
594−597. (b) Hawthorne, M. F.; Kang, H. C.; Lee, S. S.; Knobler, C.
B. Inorg. Chem. 1991, 30, 2024−2031. (c) Llop, J.; Vinas, C.; Teixidor,
̃
(4) (a) Lee, J. D.; Kim, S. J.; Yoo, D.; Ko, J.; Cho, S.; Kong, S. O.
Organometallics 2000, 19, 1695−1703. (b) Wang, S.; Li, H.-W.; Xie, Z.
Organometallics 2004, 23, 3780−3787. (c) Wang, X.; Jin, G.-X.
Chem.Eur. J. 2005, 11, 5758−5764.
F.; Lluís, V.; Kivekas, R.; Sillanpaa, R. Organometallics 2001, 24, 4024−
̈
̈
̈
4030.
(23) Lee, Y.-J.; Lee, J.-D.; Jeong, H.-J.; Son, K.-C.; Ko, J.; Cheong,
M.; Kang, S. O. Organometallics 2005, 24, 3008−3019.
(24) (a) Park, J.-S.; Kim, D.-H.; Kim, S.-J.; Ko, J.; Kim, S. H.; Cho, S.;
Lee, C.-H.; Kang, S. O. Organometallics 2001, 20, 4483−4491. (b) Qiu,
Z.; Deng, L.; Chan, H.-S.; Xie, Z. Organometallics 2010, 29, 4541−
4547.
(5) Lee, T.; Lee, S. W.; Wang, H. G.; Ko, J. S.; Kang, O.
Organometallics 2001, 20, 741−748.
(6) Yao, Z.-J.; Jin, G.-X. Organometallics 2011, 30, 5365−5373.
(7) Lee, H.-S.; Bae, J.-Y.; Ko, J.; Kang, Y. S.; Kim, H. S.; Kim, S.-J.;
Chung, J.-H.; Kang, S. O. J. Organomet. Chem. 2000, 614−615, 83−91.
(25) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
(8) Teixidor, F.; Laromaine, A.; Kivekas, R.; Sillanpaa, R.; Vinas, C.;
̈
̈
̈
̃
Crystal Structures; Universitat Gottingen, Gottingen, Germany, 1997.
̈
̈
̈
Vespalec, R.; Horak
́
ova,
́
H. Dalton Trans. 2008, 345−354.
(26) Sheldrick, G. M. SADABS (2.01), Bruker/Siemens Area Detector
Absorption Correction Program; Bruker AXS, Madison, WI, 1998.
(9) Popescu, A.-R.; Laromaine, A.; Teixidor, F.; Sillanpaa, R.;
Kivekas, R.; Llambias, J. I.; Vinas, C. Chem.Eur. J. 2011, 17, 4429−
̈
̈
̈
̃
4443.
(10) (a) Jin, G.-X.; Wang, J.-Q.; Zhang, C.; Weng, L.-H.; Herberhold,
M. Angew. Chem., Int. Ed. 2005, 44, 259−262. (b) Wang, J.-Q.; Cai, S.;
Jin, G.-X.; Weng, L.-H.; Herberhold, M. Chem Eur. J. 2005, 11, 7342−
7350. (c) Liu, S.; Jin, G.-X. Dalton Trans. 2007, 949−954. (d) Cai, S.;
Jin, G.-X. Organometallics 2007, 26, 5442−5445. Bae, J.-Y.; Lee, Y.-J.;
Kim, S.-J.; Ko, J.; Cho, S.; Kang, S. O. Organometallics 2002, 21, 210−
219. (e) Lee, H. -S.; Bae, J.-Y.; Kim, D.-H.; Kim, H. S.; Kim, S.-J.; Cho,
S.; Ko, J.; Kang, S. O. Organometallics 2000, 19, 1514−1521. (f) Liu,
S.; Han, Y. -F.; Jin, G. -X. Chem. Soc. Rev. 2007, 36, 1543−1560.
(g) Xu, B.-H.; Peng, X.-Q.; Li, Y.-Z.; Yan, H. Chem. Eur. J. 2008, 14,
9347−9356. (h) Liu, G.; Hu, J.; Wen, J.; Dai, H.; Li, Y.; Yan, H. Inorg.
Chem. 2011, 50, 4187−4194. (i) Ye, H.; Xu, B.; Xie, M.; Li, Y.; Yan, H.
Dalton Trans. 2011, 40, 6541−6546. (j) Xu, Z.; Han, L.; Ji, C.; Zhang,
R.; Shen, X.; Yan, H. Dalton Trans. 2011, 40, 6992−6997.
(11) Drose, P.; Hrib, C. G.; Edelmann, F. T. J. Am. Chem. Soc. 2010,
̈
132, 15540−15541.
(12) Saxena, A. K.; Hosmane, N. S. Chem. Rev. 1993, 93, 1081−1124.
(13) Yao, Z.-J.; Su, G.; Jin, G.-X. Chem. Eur. J. 2011, 17, 13298−
13307.
(14) (a) Liu, S.; Han, Y.-F.; Jin, G.-X. Chem. Soc. Rev. 2007, 36,
1543−1560. (b) Meng, X.; Wang, F.; Jin, G.-X. Coord. Chem. Rev.
2010, 254, 1260−1272.
(15) For reviews see: (a) Cahiez, G.; Moyeux, A. Chem. Rev. 2010,
110, 1435−1462. (b) Rosen, B. M.; Quasdorf, W. F.; Wilson, D. A.;
Zhang, N.; Resmerita, A.-M.; Garg, N. K.; Percec, V. Chem. Rev. 2011,
111, 1780−1824. (c) Liu, C.; Zhang, H.; Shi, W.; Lei, A. Chem. Rev.
2011, 111, 1780−1824. (d) Reymond, S.; Cossy, J. Chem. Rev. 2008,
108, 5359−5406. (e) Meldel, M.; Tornoe, C. W. Chem. Rev. 2008, 108,
2952−3015. (f) Ouchi, M.; Terashima, T.; Sawamoto, M. Chem. Rev.
2009, 109, 4963−5050.
(16) Lee, Y.-J.; Lee, J.-D.; Kim, S.-J.; Keum, S.; Ko, J.; Suh, I.-H.;
Cheong, M.; Kang, S. O. Organometallics 2004, 23, 203−214.
(17) Wang, X.; Jin, G.-X. Organometallics 2004, 23, 6319−6322.
(18) (a) Crabtree, R. H. The Organometallic Chemistry of the
Transition Metals. 4th ed.; Wiley InterScience: New York, 2005.
(b) Gade, L. H. Angew. Chem., Int. Ed. 2000, 39, 2658−2678.
(c) Bosnich, B. Inorg. Chem. 1999, 38, 2554−2562. (d) Van den
Beuken, E. K.; Feringa, B. L. Tetrahedron 1998, 54, 12985−13011.
(e) Chifotides, H. T.; Dunbar, K. R. Acc. Chem. Res. 2005, 38, 146−
156.
1774
dx.doi.org/10.1021/om2011358 | Organometallics 2012, 31, 1767−1774