Synthesis, structure, and reactivity study of iron(II) complexes with bulky bis(anilido)thioether ligation

Article abstract of DOI:10.1021/om201010a

The synthesis, molecular structure, and ligand substitution reactivity of iron(II) complexes bearing the bulky N,N′-dimesityl-2,2′- diamidophenyl sulfide ligand have been studied. The ligand H₂( ^mesNSN) (1) was synthesized by a Pd-me

Full text of DOI:10.1021/om201010a

Article
pubs.acs.org/Organometallics
Synthesis, Structure, and Reactivity Study of Iron(II) Complexes with
Bulky Bis(anilido)thioether Ligation
Jie Xiao and Liang Deng*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345
Lingling Road, Shanghai, People’s Republic of China 200032
S
* Supporting Information
ABSTRACT: The synthesis, molecular structure, and ligand substitution reactivity of iron(II) complexes bearing the bulky N,N′-
dimesityl-2,2′-diamidophenyl sulfide ligand have been studied. The ligand H2(mesNSN) (1) was synthesized by a Pd-mediated
Buchwald−Hartwig amination method. An amine elimination reaction between 1 and [Fe(NTMS2)2]2 afforded the high-spin
complex [(mesNSN)Fe(THF)] (2), displaying a distorted trigonal-monopyramidal geometry. Interaction of 2 with PMe3 and 2,5-
di-tert-butylimidazol-1-ylidene (IBut) gave the ligand substitution products [(mesNSN)Fe(PMe3)] (3) and [(mesNSN)Fe(IBut)]
(4), respectively. Both 3 and 4 are high spin and display molecular geometry similar to that of 2. The reaction of 2 with 3 equiv
of isocyanide gave the low-spin complexes [(mesNSN)Fe(CNR)3] (R = But (5), Ph-2,6-Me2 (6)). Recrystallization of 6 has led to
the isolation of the carbon−sulfur bond cleavage product [(mesNS)Fe(CNPh-2,6-Me2)3] (7). Quite unexpectedly, the interaction
of 2 with 3-hexyne and deuterated benzene could induce Fe−N(amido) bond cleavage, giving [(mesHNSN)2Fe(THF)] (8) and
[(mesHNSN)2Fe] (9), respectively. The formation of 7−9 suggests the lability of the [(mesNSN)Fe] fragment, which could suffer
from degradation in the presence of bulky strong field ligands.
pyridine,10 and o-phenylenediamido11 constitute the few
examples (Chart 1). The evident of this scarcity is quite
INTRODUCTION
■
Bulky amido anions are useful ligands for the construction of
iron complexes with unusual structural features, providing
unparalleled opportunities to explore the versatile chemical and
physical properties of the iron compounds.1 For example, the
bis(trimethylsilyl)amido anion [N(TMS)2]−, as the simplest
bulky amido ligand, could coordinate to an iron(II) center to
furnish the low-coordinate iron(II) compound [Fe(N-
(TMS)2)2]2, which is a very useful precursor for the preparation
of iron complexes.1,2 The more bulky anilido ligands
[NHC6H3-2,6-Ar2]− (Ar = Mes, Dipp) are able to stabilize
two-coordinated iron complexes [Fe(NHC6H3-2,6-Ar2)2] with
large quenching of first-order orbital angular momentum.3 The
trianionic ligands [N(o-C6H4NR)3]3−,4 [N(CH2CONAr)3]3‑,5
Chart 1. Representative Bulky Dianionic Amido Ligands in
Iron Complexes
[tpaAr]3− (tpa = tris(pyrrolylmethyl)amine),6a−c and [tpeMes 3−
]
(tpe = tris(pyrrolyl)ethane)6d,e could support trigonal-monop-
yramidal iron centers, offering unique platforms to study iron-
mediated small-molecule activation and carbon−hydrogen
bond hydroxylation. Recently, a category of hexadentate
amido ligands has been developed. Their application in iron
chemistry has resulted in the successful preparation of tri- and
hexanuclear iron complexes having unusual redox and magnetic
properties.7
We note that the bulky amido ligands applied in iron
chemistry are dominated by mono- and trianionic species,
whereas dianionic ligands are rare; 1,8-bis(silylamido)-
naphthalene,8 bis(enamido)pyridine,9 2,6-bis(anilido)-
surprising, as dianionic amido ligands are readily available and
their application in early-transition-metal chemistry has been
widely studied. In view of this status quo, we decide to set the
stage for a systematic study of iron chemistry under bulky
dianionic amido ligation. With respect to this goal, we report
herein the synthesis, structure, and reactivity study of iron(II)
complexes bearing bulky dianionic bis(anilido)thioether
ligation.
Received: October 21, 2011
Published: December 15, 2011
© 2011 American Chemical Society
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and Hidai13 and applied as tridentate ligands in zirconium and
ruthenium chemistry. Very recently, the parent ligand [NSN]2−
was used as a surrogate for the cyclopentadienyl anion in
tantalum chemistry.14
RESULTS AND DISCUSSION
■
Synthesis of the Ligand. The bulky ligand N,N′-
dimesityl-2,2′-diamidophenyl sulfide (H2(mesNSN), 1) was
prepared by a palladium-catalyzed coupling reaction between
2,2′-diamidophenyl sulfide and an excess amount of mesityl
bromide in 78% yield (Scheme 1). Compound 1 is a new
Four-Coordinated Complexes [(mesNSN)FeL] (L = THF,
PMe3, IBut). Treatment of H2(mesNSN) (1) with 1 equiv of
Fe(N(TMS)2)2 in THF, after workup, gave the yellow ferrous
complex [(mesNSN)Fe(THF)] (2) in 68% yield (Scheme 2).
Complex 2 is air- and moisture-sensitive and is soluble in low-
polarity organic solvents such as THF and Et2O. In d8-THF, its
1H NMR spectrum shows nine broad peaks in the range −38 to
+47 ppm, indicating unconstrained rotation of the mesityl and
THF moieties. A solution magnetic moment measurement by
the Evans method gave μeff = 4.4(2) μB. This value is in line
with the spin-only value for a quintet ground state.
Scheme 1. Preparation of the Ligand H2(mesNSN)
member of the bis(anilido)thioether ligand family. Similar
ligands with less sterically demanding substituents, including
H2(PrNSN),12 H2(BuNSN),12 H2(xyNSN),13 and H2(xyfNSN)13
(xy = 3,5-dimethylphenyl, xyf = 3,5-ditrifluoromethylphenyl)
(Chart 2), have been independently developed by Schrock12
The molecular structure of 2 in the solid state has been
established by a single-crystal X-ray diffraction study. As shown
in Figure 1, 2 displays pseudo-Cs symmetry, in which the iron
center is four-coordinated with one tridentate ligand
[MesNSN]2− and one THF molecule, forming a heavily
distorted trigonal monopyramidal geometry. Selected structural
parameters of 2 are compiled in Table 1. Important structural
features for 2 include (1) coplanarity of the iron center with the
N(1)−N(2)−O(1) plane, with the sum of the three angles
around Fe(1) being 354.5(2)°, (2) out-of-vertical alignment of
the S(1)−Fe(1) bond toward the N(1)−N(2)−O(1)−Fe(1)
plane having an S(1)−Fe(1)−O(1) angle of 135.2(1)°, (3) a
larger N(1)−Fe(1)−N(2) angle compared with those observed
in the five- and six-coordinated Zr, Ru, and Ta complexes,12,13
and (4) an Fe(1)−S(1) separation (2.480(1) Å) longer than
those observed in the high-spin ferrous complexes with
tris(thioether) ligation.15 These structural features point to a
weak Fe−S interaction, which is found quite commonly in the
other [(mesNSN)Fe] fragments (vide infra).
Chart 2. The Diamidophenyl Sulfide Ligand Family
Scheme 2. Preparation of the Iron(II) Complexes
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Figure 1. Molecular structures of [(mesNSN)Fe(THF)] (2, left), [(mesNSN)Fe(PMe3)] (3, middle), and [(mesNSN)Fe(IBut)] (4, right), showing
30% probability ellipsoids and partial atom-numbering schemes.
Table 1. Selected Bond Lengths (Å) and Angles (deg) of Compounds 2−4 and 6 from X-ray Diffraction Studies
c
a
b
complex
geom
TMP
α
β
γ
Fe−N(1)
Fe−N(2)
Fe−S
Fe−X
2
3
4
6
135.2(1)
124.7(1)
120.8(1)
136.4(2)
131.9(2)
122.3(1)
354.5(2)
357.3(2)
358.4(1)
1.951(4)
1.960(4)
1.995(2)
1.946(4)
1.967(4)
2.016(2)
2.113(2)
2.480(1)
2.489(1)
2.523(1)
2.262(1)
2.036(3)
2.431(1)
2.155(2)
TMP
TMP
octahedral
92.63(7)
2.033(2)
a
b
c
γ = ∠N1−Fe−N2 + ∠N1−Fe−X + ∠N2−Fe−X. X = O in 2, P in 3, and C in 4. TMP = trigonal monopyramidal.
Complex 2 can readily undergo ligand substitution reactions,
isocyanide-coordinated complexes are diamagnetic, and their
1H NMR spectra display resonances in the range 0−8 ppm. For
5, the 2:3 integral ratio of the methyl protons on the mesityl
moieties (1.95, 2.26, and 2.29 ppm) to those of the tert-butyl
groups (0.88 and 0.97 ppm) clearly demonstrates the presence
as the interaction of 2 with 1 equiv of trimethylphosphine or
2,5-di-tert-butylimidazol-1-ylidene (IBut)16 could result in
replacement of THF by the corresponding ligand, giving
[(mesNSN)Fe(PMe3)] (3) or [(mesNSN)Fe(IBut)] (4) in high
yield (Scheme 2). Complexes 3 and 4 have been characterized
1
of three ButNC ligands. Due to overlapping, the H NMR
1
spectrum of 6 is less informative in revealing its formulation,
but an X-ray single-crystal diffraction study has unequivocally
established its structure. As shown in Figure 2, 6 adopts a
by H NMR, elemental analyses, and X-ray diffraction studies.
1
The H NMR spectra in C6D6 show eight broad peaks in the
range −56 to +59 ppm for 3 and 11 peaks in the range −87 to
+53 ppm for 4, revealing free and restricted rotation of the
mesityl groups in 3 and 4, respectively. Consistent with the case
for 2, both 3 and 4 have magnetic moments around 4.5 μB,
indicative of their high-spin electronic configuration.
X-ray diffraction studies revealed that 3 and 4 have a
distorted-trigonal-monopyramidal geometry similar to that of 2
(Figure 1). For comparison, their selected bond distances and
angles within the trigonal monopyramid are compiled in Table
1. A close examination of these data shows that the S−Fe−X (X
= O, P, C) (α) and N(1)−Fe−N(2) (β) angles decrease in the
order 2 > 3 > 4, while their Fe−N and Fe−S distances increase
the other way around. These trends could be ascribed to the
increasing bulkiness of the ancillary ligand from THF to PMe3
and to IBut.
Reaction of [(mesNSN)Fe(THF)] with Isocyanides. The
reactivity of 2 with isocyanides differs from the aforementioned
ligand substitution reactions. Interaction of 2 with 3 equiv of
ButNC and 2,6-Me2-PhNC in THF afforded [(mesNSN)Fe-
(CNBut)3] (5) and [(mesNSN)Fe(CNPh-2,6-Me2)3] (6),
respectively, as red crystalline solids (Scheme 2). Complexes
Figure 2. Molecular structure of [(mesNSN)Fe(CNPh-2,6-Me2)3] (6),
showing 30% probability ellipsoids and a partial atom-numbering
scheme.
distorted-octahedral structure with the [mesNSN]2− ligand
binding to the iron center in a facial fashion. Its Fe−N(amido)
bond distances (2.033(2) and 2.113(2) Å) are slightly longer
than those of 2−4, but the Fe−S bond (2.262(1) Å) is
1
5 and 6 have been characterized by H and 13C NMR and
infrared spectroscopy, as well as elemental analyses. Both of the
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significantly shorter. The three isocyanide ligands are tightly
bonded to the iron center with average Fe−C(isocyanide)
distances around 1.801(1) Å, which are in line with those in
other low-spin iron(II) isocyanide compounds, such as
[Fe(CNBut)4(CN)2]17a and [Fe(CNPh-2,6-Me2)4Cl2].17b
Although 5 and 6 are isostructural, they exhibit distinct
stability in solution. Under an N2 atmosphere, the red solution
of 5 in THF could be stored for weeks without a noticeable
color change. However, a color change from red to greenish-
brown was observed when performing recrystallization of 6 in
THF, from which a small amount of green crystals of
[(mesNS)Fe(CNPh-2,6-Me2)3] (7) has been isolated. The
very low yield of 7 makes its full characterization difficult, but
its structure has been confirmed by an X-ray diffraction study.
As shown in Figure 3, 7 has a trigonal-bipyramidal geometry in
reminiscent of those in the ferric complex [(C6F5NS)2Fe]−.18
The observation of the N-mesityl-o-amidobenzenethiolato
ligand suggests a carbon−sulfur bond cleavage step in the
conversion of 6 to 7. Despite the fact that the reaction
mechanism is unclear, steric congestion between the bulky
mesityl and 2,6-dimethylphenyl groups as revealed by long Fe−
N(amido) separations in 6 (Table 1) might contribute to the
instability of 6.
Reactions of [(mesNSN)Fe(THF)] with 3-Hexyne and
C6D6. In addition to the aforementioned monodentate ligands,
we also examined the reactivity of 2 toward H2, Et3SiH,
PhCHCH2, and EtCCEt; no reaction was observed when
treating a THF solution of 2 with H2, Et3SiH, or PhCHCH2,
but a noticeable color change from yellow to brown took place
when treating the solution of 2 with 3 equiv of EtCCEt
(Scheme 2). Recrystallization of the brown solution afforded
the yellow solid [(mesHNSN)2Fe(THF)] (8) in 46% yield.
Complex 8 is paramagnetic, as indicated by broad resonances in
1
its H NMR spectrum. An X-ray diffraction study showed that
this bis(amido)iron complex has pseudo-C2 symmetry, in which
the iron center has a trigonal-bipyramidal geometry with long
Fe−S (2.558(1), 2.582(4) Å), Fe−N(amido) (1.991(2),
1.993(3) Å), and Fe−O(THF) (2.136(2) Å) separations
(Figure 4). Two appending amine side arms are dangling out
of the coordination sphere and have N−H···π interactions with
their neighboring mesityl rings (H···arene center distances
2.708 and 2.640 Å).19
The isolation of 8 rather than the alkyne-coordinated
complex (mesNSN)Fe(η2-EtCCEt) is quite unexpected. We
believe its formation might result from an alkyne-induced
degradation process, presumably via the intermediate
Figure 3. Molecular structure of [(mesNS)Fe(CNPh-2,6-Me2)3] (7),
showing 30% probability ellipsoids and a partial atom-numbering
scheme. Selected distances (Å) and angles (deg): Fe(1)−S(1) =
2.220(1), Fe(1)−N(1) = 1.884(2), Fe(1)−C(16) = 1.817(2), Fe(1)−
C(25) = 1.793(3), Fe(1)−C(34) = 1.843(3); C(25)−Fe(1)−C(16) =
94.8(1), N(1)−Fe(1)−C(16) = 141.1(1), N(1)−Fe(1)−C(25) =
123.6(1), N(1)−Fe(1)−S(1) = 85.47(6).
(
(
mesNSN)Fe(η2-EtCCEt), (mesNSN)Fe(η4-C4Et4), or
mesNSN)Fe(η6-C6Et6), rather than protonation by the
presence of a fortuitous proton. On the basis of this
assumption, the reaction of 2 with benzene was attempted.
Dissolution of 2 in C6D6 gave a red-brown solution which
shows a distinct 1H NMR spectrum in comparison to that of 2
in d8-THF. Recrystallization of the solution by vapor diffusion
yielded a small amount of yellow crystals, whose structure has
been characterized by XRD as [(mesHNSN)2Fe] (9). As
depicted in Figure 4, 9 displays Ci symmetry. Its ferrous ion
which the iron center is coordinated with one N-mesityl-o-
amidobenzenethiolato ligand and three isocyanide molecules.
The Fe−S and Fe−N bond distances in 7 are found to be
Figure 4. Molecular structures of [(mesHNSN)2Fe(THF)] (8, left) and [(mesHNSN)2Fe] (9, right), showing 30% probability ellipsoids and partial
atom-numbering schemes. Selected distances (Å) and angles (deg): for 8, Fe(1)−S(1) = 2.558(1), Fe(1)−S(1) = 2.526(3), Fe(1)−N(1) =
1.991(2), Fe(1)−N(3) = 1.993(3), Fe(1)−O(1) = 2.136(2), N(1)−Fe(1)−N(3) = 131.3(1), S(1)−Fe(1)−S(2) = 168.6(1), N(1)−Fe(1)−O(1) =
114.6(1), N(3)−Fe(1)−O(1) = 114.1(1); for 9: Fe(1)−S(1) = 2.480(1), Fe(1)−N(1) = 1.969(2), N(1)−Fe(1)−S(1) = 82.88(5), N(1)−Fe(1)−
S(1A) = 97.12(5).
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APEX CCD-based diffractometer equipped with an Oxford low-
temperature apparatus. Data were collected with scans of 0.3 s/frame
for 30 s. Cell parameters were retrieved with SMART software and
refined using SAINT software on all reflections. Data integration was
performed with SAINT, which corrects for Lorentz−polarization and
decay. Absorption corrections were applied using SADABS.21 Space
groups were assigned unambiguously by analysis of symmetry and
systematic absences determined by XPREP. All structures were solved
and refined using SHELXTL.22 Metal and first-coordination-sphere
atoms were located from direct-methods E maps; other non-hydrogen
atoms were found in alternating difference Fourier synthesis and least-
squares refinement cycles and during final cycles were refined
anisotropically. Hydrogen atoms were placed in calculated positions
employing a riding model. Final crystal parameters and agreement
factors are reported in Table S1.
sits on the inversion center and is bonding with two
monoanionic bidentate amido thioether ligands [mesHNSN]−
having Fe−N(amido) and Fe−S bond distances of 1.969(2)
and 2.480(1) Å, respectively. Similar to the case for 8, two
appending amine side arms were also observed in the molecular
structure of 9. These results, in addition to the isolation of 7,
suggest the instability of the [(mesNSN)Fe] fragment when
interacting with sterically demanding strong field ligands.
CONCLUSION
■
In this report, we have studied the synthesis, structure, and
ligand substitution reactivity of the iron(II) complex
[(mesNSN)Fe(THF)] (2) having bulky dianionic bis(anilido)-
thioether ligation. Complex 2 has a high-spin electronic
configuration and adopts a distorted-trigonal-monopyramidal
geometry. Depending on both the steric and electronic
properties of the ancillary ligands, the four-coordinated iron(II)
complex displays versatile reactivity when treated with different
ancillary ligands. The reaction of 2 with PMe3 and IBut resulted
in replacement of the THF ligand, giving [(mesNSN)Fe(PMe3)]
(3) and [(mesNSN)Fe(IBut)] (4), respectively, both of which
are high spin and have a distorted-trigonal-monopyramidal
geometry. When 2 was reacted with isocyanides, which are
sterically less demanding and strong field ligands, the low-spin
octahedral complexes [(mesNSN)Fe(CNBut)3] (5) and
[(mesNSN)Fe(CNPh-2,6-Me2)3] (6) were obtained. All these
iron(II) complexes have a [(fac-mesNSN)Fe] motif.
Preparation of N,N′-Dimesityl-2,2′-diamidophenyl Sulfide
(H2(mesNSN), 1). A 250 mL round-bottomed flask equipped with a
nitrogen inlet was charged with bis(2-aminophenyl) sulfide (1.30 g,
6.00 mmol), tris(dibenzylideneacetone)dipalladium (0.266 g, 0.29
mmol), rac-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (0.463 g, 0.74
mmol), sodium tert-butoxide (1.70 g, 17.7 mmol), toluene (80 mL),
and mesityl bromide (10.5 mL, 69.6 mmol). The reaction mixture was
refluxed at 110 °C under a nitrogen atmosphere for 48 h. After it was
cooled to room temperature, the mixture was quenched with saturated
NH4Cl aqueous solution and extracted with methylene chloride. The
extracts were combined, dried with anhydrous MgSO4, and
concentrated to dryness under reduced pressure to afford a brown
oil. This crude product was purified via flash column chromatography
(SiO2, 200−300 mesh, CH2Cl2/n-hexanes, 1/4, as eluent) to give a
1
pale pink solid (2.12 g, 78% yield). H NMR (300 MHz, CDCl3): δ
1.90 (s, 12H, o-CH3), 2.24 (s, 6H, p-CH3), 5.92 (s, 2H, NH), 6.08 (d,
J = 8.1 Hz, 2H, C6H4), 6.61 (t, J = 7.5 Hz, 2H, C6H4), 6.84 (s, 4H,
Me3C6H2), 6.98 (t, J = 7.5 Hz, 2H, C6H4), 7.38 (d, J = 7.8 Hz, 2H,
C6H4). 13C NMR (75 MHz, CDCl3): δ 17.7, 20.8, 111.7, 116.0, 117.8,
129.0, 129.4, 133.9, 134.8, 135.7, 136.1, 146.5. MALDI MS: calcd for
C30H32N2SNa+, m/z 475.2178; found, 475.2186.
In addition to ligand substitution/coordination, “non-
innocent” reactivity within the [(mesNSN)Fe] fragment has
been found in these iron(II) complexes. The observation of
conversions of [(mesNSN)Fe(CNPh-2,6-Me2)3] (6) to
[(mesNS)Fe(CNPh-2,6-Me2)3] (7) and of [(mesNSN)Fe-
(THF)] (2) to [(mesHNSN)2Fe(THF)] (8) and
[(mesHNSN)2Fe] (9) revealed the instability of the [(mesNSN)-
Fe] fragment, which could suffer from degradation in the
presence of bulky strong field ligands. With this understanding,
we are now modifying the bis(anilido) ligand, aiming to enforce
its bonding with the iron center.
Preparation of [(mesNSN)Fe(THF)] (2). To a solution of N,N′-
dimesityl-2,2′-diamidophenyl sulfide (1; 45.2 mg, 0.10 mmol) in THF
(15 mL) was added [Fe(NTMS2)2]2 (38 mg, 0.05 mmol) at room
temperature. The yellow solution was stirred overnight at room
temperature and then filtered. After removal of the solvent, the solid
residue was dissolved in diethyl ether (6 mL) and n-hexane (1 mL)
was added. Slow evaporation of Et2O afforded the product as a yellow
crystalline solid (39.3 mg, 68%). The 1H NMR spectrum of this
paramagnetic complex displayed nine characteristic peaks in the range
EXPERIMENTAL SECTION
■
1
−150 to +150 ppm in d8-THF. H NMR (400 MHz, d8-THF): δ
General Procedures. All experiments were performed under an
atmosphere of dry dinitrogen with the rigid exclusion of air and
moisture using standard Schlenk or cannula techniques or in a
glovebox. All organic solvents were freshly distilled from sodium
−38.35 (s, 4H, OC4H8), −5.43 (s, 4H, OC4H8), 2.45 (s, 2H, C6H4),
21.78 (s, 2H, C6H4), 24.82 (s, 6H, p-CH3), 28.53 (s, 2H, C6H4), 32.54
(s, 12H, o-CH3), 37.43 (s, 2H, C6H4), 46.92 (s, 4H, Me3C6H2).
Magnetic susceptibility (C6D6): μeff = 4.4(2) μB. Anal. Calcd for
C34H38FeN2OS: C, 70.58; H, 6.62; N, 4.84. Found: C, 69.90; H, 7.01;
N, 5.03.
2
benzophenone ketyl immediately prior to use. [Fe(NTMS2)2]2 and
2,5-di-tert-butylimidazol-1-ylidene (IBut)16 were prepared according to
literature methods. All chemicals were purchased from either Strem or
Preparation of [(mesNSN)Fe(PMe3)] (3). To a yellow solution of
2 (0.115 g, 0.20 mmol) in diethyl ether (15 mL) was added PMe3
(0.80 mL, 0.30 M in n-hexane, 0.24 mmol). After the mixture was
stirred overnight at room temperature, the color of the solution
changed to red. After filtration, the filtrate was concentrated to about 5
mL and n-hexane (1 mL) was added. Slow evaporation of Et2O
afforded the product as a red crystalline solid (60.6 mg, 52%). The 1H
NMR spectrum of this paramagnetic complex displayed eight
1
J&K Chemical Co. and used as received unless otherwise noted. H
and 13C NMR spectra were recorded on a Varian Mercury 300 or 400
MHz spectrometer. All chemical shifts were reported in δ units with
reference to the residual protons of the deuterated solvents for proton
chemical shifts and the 13C of deuterated solvents for carbon chemical
shifts. MALDI/DHB mass spectra were recorded with an IonSpec 4.7
T FTMS spectrometer. GC/MS was performed on a Shimadzu
GCMS-QP2010 Plus spectrometer. Elemental analysis was performed
by the Analytical Laboratory of the Shanghai Institute of Organic
Chemistry (CAS). Magnetic moments were measured at 23 °C by the
method originally described by Evans with stock and experimental
solutions containing a known amount of a (CH3)3SiOSi(CH3)3
standard.20 Infrared spectra were obtained from KBr pellets prepared
in the glovebox on a Perkin-Elmer 1600 Fourier transform
spectrometer.
1
characteristic peaks in the range −100 to +100 ppm. H NMR (400
MHz, C6D6): δ −56.01, −4.92, 38.46, 38.83, 40.28, 47.05, 57.32,
58.28. Magnetic susceptibility (C6D6): μeff = 4.5(1) μB. Anal. Calcd for
C33H39FeN2PS: C, 68.04; H, 6.75; N, 4.81. Found: C, 67.38; H, 6.95;
N, 4.72.
Preparation of [(mesNSN)Fe(IBut)] (4). In a long test tube, a
solution of 2,5-di-tert-butylimidazol-1-ylidene (IBut; 18.0 mg, 0.10
mmol) in n-hexane (4 mL) was carefully layered on a solution of 2
(57.8 mg, 0.10 mmol) in diethyl ether (5 mL). Slow diffusion over 4
days afforded the product as a yellow crystalline solid (30.9 mg, 45%).
X-ray Structure Determinations. The structures of the seven
compounds in Table S1 (Supporting Information) were determined.
Crystals were coated with Paratone-N oil and mounted on a Bruker
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1
The H NMR spectrum of this paramagnetic complex displayed 11
ASSOCIATED CONTENT
■
1
characteristic peaks in the range −100 to +100 ppm. H NMR (400
S
* Supporting Information
A table and CIF files giving X-ray crystallographic data. This
material is available free of charge via the Internet at http://
pubs.acs.org.
MHz, C6D6): δ −86.41, −36.43, −17.88, −15.40, −6.65, 24.15, 26.91,
32.45, 37.15, 38.22, 53.24. Magnetic susceptibility (C6D6): μeff
=
4.6(2) μB. Anal. Calcd for C41H50FeN4S: C, 71.70; H, 7.34; N, 8.16.
Found: C, 71.36; H, 7.34; N, 7.71.
Preparation of [(mesNSN)Fe(CNBut)3] (5). To a solution of 2
(57.8 mg, 0.10 mmol) in THF (10 mL) was added ButNC (1.0 mL,
0.30 M in n-hexane, 0.30 mmol). The reaction mixture was stirred
overnight at room temperature, providing a red solution. After
filtration and removal of the solvent, the red residue was dissolved in
diethyl ether (6 mL) and n-hexane (1 mL) was added. Slow
evaporation of Et2O afforded the product as a red crystalline solid
(49.1 mg, 65%). 1H NMR (400 MHz, C6D6): δ 0.88 (18H,
C(CH3)3NC), 0.96 (9H, C(CH3)3NC), 1.95 (6H, p-CH3), 2.26−
2.29 (12H, o-CH3), 6.22−6.28 (4H, Me3C6H2), 6.82−6.89 (6H,
C6H4), 7.71−7.73 (2H, C6H4). 13C NMR (100 MHz, C6D6): δ 19.81,
20.85, 22.00, 29.71, 30.27, 56.07, 56.28, 109.2, 115.5, 123.5, 128.9,
129.2, 129.5, 130.2, 132.4, 135.5, 138.7, 152.8, 161.8, 162.4, 165.0. IR
(KBr, cm−1): νCN 2170 (s), 2132 (s). Anal. Calcd for C45H57FeN5S:
C, 71.50; H, 7.60; N, 9.27. Found: C, 71.43; H, 7.74; N, 9.02.
Preparation of [(mesNSN)Fe(CNPh-2,6-Me2)3] (6). Method 1.
In a long test tube, a solution of 2,6-dimethylphenyl isocyanide
(CNPh-2,6-Me2) (39.3 mg, 0.30 mmol) in n-hexane (4 mL) was
layered on a solution of 2 (57.8 mg, 0.10 mmol) in diethyl ether (5
mL). Slow diffusion over 2 days afforded the product as a red
AUTHOR INFORMATION
■
Corresponding Author
*deng@sioc.ac.cn.
ACKNOWLEDGMENTS
■
This research was financially supported by the National Basic
Research Program of China (973 Program, No.
2011CB808705) and the National Natural Science Foundation
of China (Nos. 21002114 and 20872168).
REFERENCES
■
(1) (a) Lappert, M.; Power, P.; Protechenko, A.; Seeber, A. Metal
Amide Chemistry; Wiley: Chichester, U.K., 2009. (b) Power, P. J.
Organomet. Chem. 2004, 689, 3904−3919. (c) Power, P. Comments
Inorg. Chem. 1989, 8, 177−202.
(2) Andersen, R. A.; Faegri, K.; Green, J. C.; Haaland, A.; Lappert, M.
F.; Leung, W.-P. Inorg. Chem. 1988, 27, 1782−1786.
1
(3) (a) Merrill, W. A.; Stich, T. A.; Brynda, M.; Yeagle, G. J.;
Fettinger, J. C.; De Hont, R.; Reiff, W. M.; Schulz, C. E.; Britt, R. D.;
Power, P. P. J. Am. Chem. Soc. 2009, 131, 12693−12702. (b) Ni, C.;
Fettinger, J. C.; Long, G. J.; Power, P. P. Inorg. Chem. 2009, 48, 2443−
2448. (c) Ni, C.; Fettinger, J. C.; Long, G. J.; Brynda, M.; Power, P. P.
Chem. Commun. 2008, 6045−6047.
crystalline solid (36 mg, 40%). H NMR (400 MHz, C6D6): δ 1.97
(3H, Me3C6H2), 2.07−2.11 (18H, Me2C6H3NC), 2.16 (6H,
Me3C6H2), 2.23 (6H, Me3C6H2), 2.30 (3H, Me3C6H2), 6.31−6.39
(3H, Me2C6H3NC), 6.60−6.62 (4H, C6H4), 6.68−6.70 (3H,
Me2C6H3NC), 6.75−6.79 (4H, C6H4), 6.88−6.93 (2H, Me3C6H2),
6.99 (1H, Me2C6H3NC), 7.38−7.39 (1H, Me2C6H3NC), 7.55−7.57
(1H, Me2C6H3NC), 7.78−7.80 (2H, Me3C6H2). Due to the low
solubility of 6 in C6D6 and d8-THF, a satisfactory 13C NMR spectrum
was not obtained. IR (KBr, cm−1): νCN 2139 (s), 2092 (s). Anal.
Calcd for C57H57FeN5S: C, 76.07; H, 6.38; N, 7.78. Found: C, 75.25;
H, 6.22; N, 7.90.
Method 2. To a solution of 2 (57.8 mg, 0.10 mmol) in THF (10
mL) was added was added 2,6-dimethylphenyl isocyanide (39.3 mg,
0.30 mmol) at room temperature. The reaction mixture was stirred
overnight and then filtered. The filtrate was concentrated to ca. 4 mL.
Slow evaporation of THF afforded the product as a red crystalline
solid (19 mg, 21%). The composition of this material was identical
with that of the product from method A. Anal. Calcd for
C57H57FeN5S: C, 76.07; H, 6.38; N, 7.78. Found: C, 75.41; H, 6.98;
N, 6.95. A very small quantity of platelike green crystals was separated
from the bulk product and shown to be [(mesNS)Fe(CNPh-2,6-Me2)3]
(7) by an X-ray structure determination.
(4) (a) Paraskevopoulou, P.; Ai, L.; Wang, Q.; Pinnapareddy, D.;
Acharyya, R.; Dinda, R.; Das, P.; C
Sanakis, Y.; Choudhury, A.; Rath, N. P.; Stavropoulos, P. Inorg. Chem.
2010, 49, 108−122. (b) Celenligil-Cetin, R.; Paraskevopoulou, P.;
Dinda, R.; Staples, R. J.; Sinn, E.; Rath, N. P.; Stavropoulos, P. Inorg.
elenligil-Cetin, R.;
̧elenligil-Çetin, R.; Floros, G.;
̧
̧
Chem. 2008, 47, 1165−1172. (c)
Ç
̧
Paraskevopoulou, P.; Dinda, R.; Lalioti, N.; Sanakis, Y.; Rawashdeh,
A. M.; Staples, R. J.; Sinn, E.; Stavropoulos, P. Eur. J. Inorg. Chem.
2008, 673−677.
(5) (a) Ray, M.; Golombek, A. P.; Hendrich, M. P.; Yap, G. P. A.;
Liable-Sands, L. M.; Rheingold, A. L.; Borovik, A. S. Inorg. Chem. 1999,
38, 3110−3115. (b) Hammes, B. S.; Ramos-Maldonado, D.; Yap, G. P.
A.; Liable-Sands, L.; Rheingold, A. L.; Young, V. G. Jr.; Borovik, A. S.
Inorg. Chem. 1997, 36, 3210−3211. (c) Mukherjee, J.; Lucas, R. L.;
Zart, M. K.; Powell, D. R.; Day, V. W.; Borovik, A. S. Inorg. Chem.
2008, 47, 5780−5786. (d) Ray, M.; Golombek, A. P.; Hendrich, M. P.;
Young, V. G. Jr.; Borovik, A. S. J. Am. Chem. Soc. 1996, 118, 6084−
6085.
(6) (a) Harman, W. H.; Chang, C. J. J. Am. Chem. Soc. 2007, 129,
15128−15129. (b) Freedman, D. E.; Harman, W. H.; Harris, T. D.;
Long, G. J.; Chang, C. J.; Long, J. R. J. Am. Chem. Soc. 2010, 132,
1224−1225. (c) Harman, W. H.; Harris, T. D.; Freedman, D. E.; Fong,
H.; Chang, A.; Rinehart, J. D.; Ozarowski, A.; Sougrati, M. T.;
Grandjean, F.; Long, G. J.; Long, J. R.; Chang, C. J. J. Am. Chem. Soc.
2010, 132, 18115−18126. (d) Sazama, G. T.; Betley, T. A. Inorg.
Chem. 2010, 49, 2512−2524. (e) Sazama, G. T.; Betley, T. A.
Organometallics 2011, 30, 4315−4319.
Preparation of [(mesHNSN)2Fe(THF)] (8). To a solution of 2
(57.8 mg, 0.10 mmol) in diethyl ether (10 mL) was added 3-hexyne
(24.6 mg, 0.30 mmol, dried with CaH2) at room temperature. The
reaction mixture was stirred overnight, providing a brown solution.
After filtration, the filtrate was concentrated to about 5 mL and n-
hexane (1 mL) was added. Slow evaporation of Et2O afforded the
1
product as a yellow crystalline solid (24 mg, 46%). H NMR (400
MHz, C6D6): δ 1.36−1.39 (4H, OC4H8), 1.89−2.08 (36H, Me3C6H2),
3.52−3.57 (4H, OC4H8), 6.04−6.22 (6H, Me3C6H2), 6.50−6.83
(16H, C6H2), 7.47−7.49 (2H, Me3C6H2). Magnetic susceptibility
(C6D6): μeff = 4.8(2) μB. Anal. Calcd for C64H70FeN4OS2: C, 74.54; H,
6.84; N, 5.43. Found: C, 74.21; H, 6.94; N, 5.38.
(7) (a) Zhao, Q.; Betley, T. A. Angew. Chem., Int. Ed. 2011, 50, 709−
712. (b) Power, T. M.; Fout, A. R.; Zheng, S.-L.; Betley, T. A. J. Am.
Chem. Soc. 2011, 133, 3336−3338. (c) Zhao, Q.; Harris, T. D.; Betley,
T. A. J. Am. Chem. Soc. 2011, 133, 8293−8306. (d) Harris, T. D.;
Isolation of [(mesHNSN)2Fe] (9). Dissolution of 2 (11.5 mg, 0.02
mmol) in C6D6 (0.5 mL) gave a red-brown solution. Slow vapor
diffusion of n-hexane into the solution afforded a small amount of
yellow crystals, whose structure has been established as
[(mesHNSN)2Fe] (9) by a single-crystal X-ray diffraction study.
́ ́
Zhao, Q.; Hernandez Sanchez, R.; Betley, T. A. Chem. Commun. 2011,
50, 6837−6845. (e) Harris, T. D.; Betley, T. A. J. Am. Chem. Soc. 2011,
133, 13852−13855.
(8) Blake, A. J.; Gillbrand, N. L.; Moxey, G. J.; Kays, D. L. Inorg.
Chem. 2009, 48, 10837−10844.
433
dx.doi.org/10.1021/om201010a | Organometallics 2012, 31, 428−434

Organometallics
Article
(9) (a) Scott, J.; Gambarotta, S.; Korobkov, I.; Budzelaar, P. H. M. J.
Am. Chem. Soc. 2005, 127, 13019−13029. (b) Bouwkamp, M. W.;
Lobkovsky, E.; Chirik, P. J. Inorg. Chem. 2006, 45, 2−4.
(10) Weintrob, E. C.; Tofan, D.; Bercaw, J. E. Inorg. Chem. 2009, 48,
3808−3813.
(11) (a) Khusniyarov, M. M.; Weyhermuller, T.; Bill, E.; Wieghardt,
K. Angew. Chem., Int. Ed. 2008, 47, 1228−1231. (b) Khusniyarov, M.
M.; Bill, E.; Weyhermuller, T.; Bothe, E.; Harms, K.; Sundermeyer, J.;
Wieghardt, K. Chem. Eur. J. 2008, 14, 7608−7622. (c) Khusniyarov, M.
M.; Weyhermuller, T.; Bill, E.; Wieghardt, K. J. Am. Chem. Soc. 2009,
131, 1208−1221.
(12) Graf, D. D.; Schrock, R. R.; Davis, W. M.; Stumpf, R.
Organometallics 1999, 18, 842−852.
(13) Takemoto, S.; Kawamura, H.; Yamada, Y.; Okada, T.; Ono, A.;
Yoshikawa, E.; Mizobe, Y.; Hidai, M. Organometallics 2002, 21, 3897−
3904.
́
(14) Fandos, R.; Fernandez-Gallardo, J.; Otero, A.; Rodríguez, A.;
Ruiz, M. J. Organometallics 2011, 30, 1551−1557.
(15) (a) Popescu, C. V.; Mock, M. T.; Stoian, S. A.; Dougherty, W.
G.; Yap, G. P. A.; Riordan, C. G. Inorg. Chem. 2009, 48, 8317−8324.
(b) Mock, M. T.; Popescu, C. V.; Yap, G. P. A.; Dougherty, W. G.;
Riordan, C. G. Inorg. Chem. 2008, 47, 1889−1891.
(16) Viciu, M. S.; Navarro, O.; Germaneau, R. F.; Kelly, R. A. III;
Sommer, W.; Marion, N.; Stevens, E. D.; Cavallo, L.; Nolan, S. P.
Organometallics 2004, 23, 1629−1635.
(17) (a) Halbauer, K.; Donnecke, D.; Gorls, H.; Imhof, W. Z. Anorg.
Allg. Chem. 2006, 632, 1477−1482. (b) Perry, M. C.; Law, T. C.;
Wheeler, K. A. J. Chem. Cryst. 2010, 40, 482−485.
(18) Roy, N.; Sproules, S.; Bill, E.; Weyhermuller, T.; Wieghardt, K.
Inorg. Chem. 2008, 47, 10911−10920.
(19) Kumita, H.; Kato, T.; Jitsukawa, K.; Einaga, H.; Masuda, H.
Inorg. Chem. 2001, 40, 3936−3942.
(20) (a) Evans, D. F. J. Chem. Soc. 1959, 2003−2005. (b) Sur, S. K. J.
Magn. Reson. 1989, 82, 169−173.
(21) Sheldrick, G. M. SADABS: Program for Empirical Absorption
Correction of Area Detector Data; University of Gottingen, Gottingen,
̈
̈
Germany, 1996.
(22) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure
Determination Software Programs; Bruker Analytical X-ray Systems,
Inc., Madison, WI, 1997.
434
dx.doi.org/10.1021/om201010a | Organometallics 2012, 31, 428−434