Reactivity of bis(3,5-dimethylpyrazol-1-yl)methyllithium with S or CS 2, followed by reaction with Fe3(CO)12 and Ar3SnCl or RX: Unexpected formation of (3,5-dimethylpyrazol-1-yl) dithioformate derivatives

Article abstract of DOI:10.1021/om300448a

Reaction of bis(3,5-dimethylpyrazol-1-yl)methyllithium with sulfur at -70 °C, followed by reaction with Fe₃(CO)₁₂ and triaryltin chlorides, yielded trinuclear butterfly cluster complexes. When the triaryltin chlorides were replaced by organic halides, unexpected (3,5-dimethylpyrazol-1- yl)dithioformate derivatives were obtained. In addition, treatment of bis(3,5-dimethylpyrazol-1-yl)methane with n-BuLi at 0 °C resulted in partial decomposition to yield a carbene intermediate and a 3,5-dimethylpyrazolate anion. The carbene intermediate readily dimerized, and reaction of the anion with carbon disulfide, and subsequently with Fe₃(CO)₁₂ and organic halides, also gave the dithioformate derivatives.

Full text of DOI:10.1021/om300448a

Article
pubs.acs.org/Organometallics
Reactivity of Bis(3,5-dimethylpyrazol-1-yl)methyllithium with S or
CS2, Followed by Reaction with Fe3(CO)12 and Ar3SnCl or RX:
Unexpected Formation of (3,5-Dimethylpyrazol-1-yl)dithioformate
Derivatives
Xia-Li Liu, Xiao-Yan Zhang, Hai-Bin Song, and Liang-Fu Tang*
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, People’s
Republic of China
S
* Supporting Information
ABSTRACT: Reaction of bis(3,5-dimethylpyrazol-1-yl)-
methyllithium with sulfur at −70 °C, followed by reaction
with Fe3(CO)12 and triaryltin chlorides, yielded trinuclear
butterfly cluster complexes. When the triaryltin chlorides were
replaced by organic halides, unexpected (3,5-dimethylpyrazol-
1-yl)dithioformate derivatives were obtained. In addition,
treatment of bis(3,5-dimethylpyrazol-1-yl)methane with n-BuLi at 0 °C resulted in partial decomposition to yield a carbene
intermediate and a 3,5-dimethylpyrazolate anion. The carbene intermediate readily dimerized, and reaction of the anion with
carbon disulfide, and subsequently with Fe3(CO)12 and organic halides, also gave the dithioformate derivatives.
chlorides (Ar3SnCl) or organic halides (RX). Markedly different
reaction patterns were observed.
INTRODUCTION
■
Bis(pyrazol-1-yl)methanes have been extensively used to
synthesize main group and transition metal complexes.1 To
increase the success of such reactions, the coordination behaviors
of this family of ligands can be readily adjusted by changing the
electronic and steric characteristics of the substituents on the
pyrazolyl rings. Recent investigations have shown that the
methylene bridge of bis(pyrazol-1-yl)methane (the pyrazolyl
groups are substituted at the 3- and 5-positions) can be
deprotonated by n-BuLi to form bis(pyrazol-1-yl)methide
anions.2 These anions have a wide spectrum of reactivity with
various electrophiles such as carbon dioxide,2a carbon disulfide,3
sulfur trioxide,4 isocyanates,5 isothiocyanates,5 aldehydes and
ketones,6 imines,7 carbodiimides,8 fulvenes,9 organosilyl chlor-
ides,10 and organotin chlorides11 to form versatile hetero-
scorpionate ligands, and this has driven the rapid development of
bis(pyrazol-1-yl)methane chemistry.1,12 Our previous investiga-
tions on bis(pyrazol-1-yl)methanes indicated that reaction of a
bis(3,5-dimethylpyrazol-1-yl)methide anion with sulfur afforded
a bis(3,5-dimethylpyrazol-1-yl)methylthiolate anion,13 which
was expected to act as a good donor for main group and
transition metal atoms because of the high affinity of sulfur for
metals. It is known that reactions of thiolate anions with
Fe3(CO)12 yield butterfly Fe/S cluster monoanions,14 and
subsequent reaction with electrophiles gives rise to the formation
of butterfly Fe/S cluster complexes. These complexes have
received extensive attention because of their novel structures and
reactivities15 and, recently, as biomimetic models for the active
sites of [FeFe]-hydrogenases.16 In this paper, we report the
related reactions of bis(3,5-dimethylpyrazol-1-yl)methyllithium
with S or CS2, followed by reaction with Fe3(CO)12 and triaryltin
RESULTS AND DISCUSSION
■
Reaction of Bis(3,5-dimethylpyrazol-1-yl)-
methyllithium with S, Followed by Reaction with
Fe3(CO)12 and Ar3SnCl or RX. Treatment of bis(3,5-
dimethylpyrazol-1-yl)methyllithium, prepared in situ by the
reaction of bis(3,5-dimethylpyrazol-1-yl)methane with n-BuLi at
−70 °C,2a with sulfur yielded the bis(3,5-dimethylpyrazol-1-
yl)methylthiolate anion.13 This anion reacted with Fe3(CO)12
and subsequently with Ar3SnCl to give Fe/Sn/S cluster
complexes 1 (Scheme 1). However, unexpected (3,5-dimethyl-
pyrazol-1-yl)dithioformate derivatives 2 were obtained when
Ar3SnCl was replaced by RX in these reactions. Complexes 2
could also be obtained by the reaction of lithium 3,5-
dimethylpyrazolate with CS2, followed by reaction with
Fe3(CO)12 and RX. Complexes 1a and 2 are air-stable in the
solid state, and even their solutions can be manipulated in air
without notable decomposition, whereas complex 1b is slightly
air-sensitive, especially in solution.
The molecular structures of 1a and 2b have been confirmed by
X-ray crystallography and are presented in Figures 1 and 2,
respectively. As shown in Figure 1, a novel trinuclear butterfly
cluster core is formed in 1a. The three-membered Fe(1)Fe(2)-
S(1) and five-membered Fe(2)S(1)C(7)N(1)N(2) rings
respectively serve as the two wings of the butterfly cluster core.
Bis(3,5-dimethylpyrazol-1-yl)methylthiolate coordinates to the
diiron hexacarbonyl unit through the sulfur atom, and only one
Received: May 22, 2012
Published: July 9, 2012
© 2012 American Chemical Society
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Scheme 1. Formation and Reactivity of Bis(3,5-
dimethylpyrazol-1-yl)methylthiolate
Figure 2. Molecular structure of 2b. The thermal ellipsoids are drawn at
the 30% probability level. Selected bond distances (Å) and angles (deg):
Fe(1)−Fe(2) = 2.6182(9), Fe(1)−S(2) = 2.1972(9), Fe(2)−S(1) =
2.2901(9), Fe(2)−S(2) = 2.2815(9), Fe(1)−C(7) = 2.002(3), C(7)−
S(1) = 1.794(3), C(7)−S(2) = 1.761(3), C(13)−S(1) = 1.835(3);
C(7)−S(1)−Fe(2) = 81.4(1), C(7)−S(2)−Fe(1) = 59.6(1), C(7)−
S(2)−Fe(2) = 82.4(1), Fe(1)−S(2)−Fe(2) = 71.52(3), N(1)−C(7)−
S(1) = 117.4(2), S(1)−C(7)−S(2) = 107.8(2), N(1)−C(7)−Fe(1) =
126.1(2), S(1)−C(7)−Fe(1) = 106.0(1), C(1)−Fe(1)−Fe(2) =
163.1(1), C(4)−Fe(2)−S(1) = 166.91(9), C(7)−Fe(1)−Fe(2) =
69.76(8).
distance (2.6182(9) Å) is slightly shorter than that in 1a
(2.6853(8) Å). The other geometric parameters, such as the Fe−
C, Fe−S, and C−S bond distances, are normal and similar to
those of the reported thioester derivatives of iron carbonyls.5a,18
The CS double bond (C(7)−S(2) 1.761 Å) is significantly
elongated compared with a normal CS double bond,19
evidently as a result of π-coordination to the iron atom,
weakening the double-bond character of the thiocarbonyl.
Complexes 1 and 2 were also characterized using IR and NMR
spectroscopy. Their IR spectra showed strong absorption bands
for their terminal carbonyls in the range 2075−1940 cm−1. Two
sets of 1H and 13C NMR signals corresponding to the pyrazolyl
rings were observed in 1, attributed to their locations in different
coordination environments (one coordinated, the other
uncoordinated). The NMR spectra of 2 were remarkably
different from those of 1. A notable feature is that the proton
signal of the methine in 1 disappeared in 2. The 13C NMR spectra
of 2 also indicate π-coordination of the thiocarbonyl. Remarkably
high shifts of the thiocarbonyl carbon atoms were observed in
these two complexes. In addition, the methylene protons of the
benzyl group were not equivalent in 2b, and an AB system was
observed at room temperature, possibly as a result of the nearby
chiral carbon atom (the C(7) atom shown in Figure 2).
Analogous observations have been made for (μ-CH3C(O)-
CH2SCHS)Fe2(CO)6.18a
Possible Pathway for the Formation of 2. It is known that
the reactions of thiolates with Fe3(CO)12 lead to the formation of
dinuclear [(μ-RS)(μ-CO)(Fe2(CO)6]− anions.14a Also, C−H
activation adjacent to a nitrogen atom by dinuclear iron carbonyl
derivatives has been observed.20 On the basis of these results and
other known facts, a plausible reaction pathway is depicted in
Scheme 2. First, reaction of bis(3,5-dimethylpyrazol-1-yl)-
methylthiolate with Fe3(CO)12 yields intermediate A. Then,
intramolecular C−H activation takes place to give intermediate
B, followed by a 1,2-elimination reaction, leading to formation of
Figure 1. Molecular structure of 1a. The thermal ellipsoids are drawn at
the 30% probability level. Selected bond distances (Å) and angles (deg):
Fe(1)−Fe(2) = 2.6853(8), Fe(1)−Sn(1) = 2.5843(7), Fe(1)−S(1) =
2.200(1), Fe(2)−S(1) = 2.227(1), Fe(2)−N(2) = 2.010(3), C(7)−
S(1) = 1.832(4); Sn(1)−Fe(1)−Fe(2) = 158.14(3), Fe(1)−S(1)−
Fe(2) = 74.29(4), S(1)−Fe(1)−Fe(2) = 52.99(3), C(7)−S(1)−Fe(2)
= 99.5(1), C(30)−Sn(1)−C(24) = 99.0(1), C(24)−Sn(1)−Fe(1) =
126.1(1), N(1)−C(7)−N(3) = 111.9(3), C(5)−Fe(2)−N(2) =
176.2(2).
pyrazolyl nitrogen atom takes part in the coordination to one
iron center. The Fe(1)−Sn(1) bond distance is 2.5843(7) Å,
falling within the range of values observed in iron−tin-supported
transition metal−tin complexes (2.41−2.77 Å).17 It is note-
worthy that some angles around the tin atom (such as the
C(24)−Sn(1)−C(30) angle of 99.0(1)o and the C(24)−Sn(1)−
Fe(1) angle of 126.1(1)o) significantly deviate from the
tetrahedral geometry of the sp3-hybridized tin atom, suggesting
a large steric repulsion in this complex, which suggests that the
second pyrazolyl ring is not coordinated to the Fe(1) or Sn(1)
atom. To decrease the steric repulsion, the uncoordinated
pyrazolyl group is distant from the Fe(1) and Sn(1) atoms.
Figure 2 shows that bis(3,5-dimethylpyrazol-1-yl)-
methylthiolate is absent in 2b. The bis(3,5-dimethylpyrazol-1-
yl)methyl moiety decomposed during the reaction, and the
unexpected (3,5-dimethylpyrazol-1-yl)dithioformate ligand was
formed. This ligand functions as a six-electron donor with both
sulfur atoms as well as the π-bond of CS bound in a side-on
manner to the diiron hexacarbonyl unit. The fundamental
molecular framework of 2b is similar to that in other diiron
hexacarbonyl complexes of dithioesters.18 The Fe−Fe bond
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Scheme 2. Possible Pathway for Formation of 2 through C−H Activation
intermediate C with a heteroatom-substituted carbene ligand.21
Scheme 3. Treatment of Bis(3,5-dimethylpyrazol-1-
The related heteroatom-substituted carbene diiron clusters have
been extensively investigated.21,22 The reaction of sulfur still in
the reaction system with the carbene carbon of C results in the
formation of one thiocarbonyl, which subsequently coordinates
to two iron atoms, in different ways, to produce intermediate D,
with the loss of one carbonyl. Finally, nucleophilic attack of the
sulfur atom in D at RX gives 2.
yl)methane with n-BuLi at 0 °C and Subsequent Related
Reactions
When Ar3SnCl is used as the electrophile instead of RX, the
nucleophilic iron anion of A attacks the tin atom, followed by the
displacement of one carbonyl by one pyrazolyl nitrogen atom to
give 1. Intermediate A is therefore consumed midway, and no
analog of 2 is obtained. The cause of the difference may be that
the C−H activation step inherently has a relatively high
activation energy and needs to be promoted by the external
addition of electrophiles. Moreover, the sulfur atom is a good
nucleophilic reagent for organic halides. However, the tin atom
prefers to bond with the iron atom in this reaction because of the
formation of the strong Fe−Sn bond,17 preventing the oxidative
addition of the C−H bond to the iron center.
Reaction of Bis(3,5-dimethylpyrazol-1-yl)-
methyllithium with CS2, Followed by Reaction with
Fe3(CO)12 and RX. The above-mentioned results inspired us
to exploit the related reactions of other sulfur-containing
functionalized bis(pyrazol-1-yl)methanes. With this goal, we
initiated our studies by testing the reactions of bis(pyrazol-1-
yl)dithioacetates, which have been prepared by the reaction of
bis(pyrazol-1-yl)methide anions with CS2.3 When we treated
bis(3,5-dimethylpyrazol-1-yl)methyllithium with CS2 at −70 °C,
and subsequently with Fe3(CO)12 and RX, as in the above-
mentioned reactions of bis(3,5-dimethylpyrazol-1-yl)-
methyllithium with sulfur, no identifiable product was obtained.
However, we serendipitously found that in the treatment of
bis(3,5-dimethylpyrazol-1-yl)methane with n-BuLi at 0 °C, and
subsequently with CS2, Fe3(CO)12, and RX, the dithioester
complexes 2 were again obtained along with 1,2-bis(3,5-
dimethylpyrazol-1-yl)ethene (3) (Scheme 3). The bis(3,5-
dimethylpyrazol-1-yl)methyl fragment decomposed during the
reaction.
Figure 3. Molecular structure of 3. The thermal ellipsoids are drawn at
the 30% probability level. The water molecules are omitted for clarity.
Selected bond distances (Å) and angles (deg): C(6)−C(6A) =
1.327(4), C(6)−N(2) = 1.409(3); C(6A)−C(6)−N(2) = 123.6(2),
C(4)−N(2)−C(6)−C(6A) = 180.0(2). Symmetry code: A = x, −y + 1/
2, z.
0.0063 Å. It is interesting that this molecule crystallizes with two
molecules of water and forms an infinite 2D network through
intermolecular O−H···O and O−H···N hydrogen bonds (Figure
4).
To ascertain whether the decomposition of the bis(3,5-
dimethylpyrazol-1-yl)methyl framework takes place before or
after addition of CS2, water instead of CS2 was added to a mixture
The molecular structure of 3 has been confirmed by X-ray
crystallography and is presented in Figure 3. This compound has
practically planar molecules. Two pyrazolyl planes are coplanar
with the double bond, with a mean deviation from the plane of
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philes. For example, when Ar3SnCl was used as the final
electrophile, novel trinuclear butterfly cluster complexes were
isolated. Similar reactions using RX instead of Ar3SnCl gave rise
to the formation of unexpected (3,5-dimethylpyrazol-1-yl)-
dithioformate derivatives. In addition, the decomposition of
the bis(3,5-dimethylpyrazol-1-yl)methyl anion at 0 °C generated
a carbene intermediate and a 3,5-dimethylpyrazolate anion. The
carbene intermediate readily dimerized, and the pyrazolate anion
underwent a series of reactions to yield the dithioformate
derivatives. Different pathways for the formation of the
dithioformate derivatives were proposed.
EXPERIMENTAL SECTION
■
General Considerations. All reactions were carried out under an
argon atmosphere. Solvents were dried and distilled prior to use
according to standard procedures. NMR spectra were recorded using a
Bruker 400 spectrometer using CDCl3 as the solvent unless otherwise
noted, and the chemical shifts were reported in ppm with respect to the
reference (internal SiMe4 for 1H and 13C NMR spectra, external SnMe4
for 119Sn NMR). IR spectra were recorded as KBr pellets using a Nicolet
380 spectrometer. Element analyses were carried out using an Elementar
Vairo EL analyzer.
Figure 4. Crystal packing diagram of 3·2H2O, emphasizing the
hydrogen-bonding interactions. Hydrogen bond distances (Å) and
angles (deg): O(1)−H···N(1) = 1.986/2.841, O(1)−H···O(1)a
=
1.868/2.729; O(1)−H···N(1) = 173.43, O(1)−H···O(1)a = 176.51.
Symmetry code: a = −x + 3/2, y, z − 1/2.
of a cooled (0 °C) solution of bis(3,5-dimethylpyrazol-1-
yl)methane in THF and n-BuLi in hexane (see Scheme 3).
After removing the volatile materials under reduced pressure, the
Reaction of Bis(3,5-dimethylpyrazol-1-yl)methyllithium
[(3,5-Me2Pz)2CHLi] with S, Followed by Reaction with
Fe3(CO)12 and Ar3SnCl. To a solution of bis(3,5-dimethylpyrazol-1-
yl)methane [CH2(3,5-Me2Pz)2] (0.20 g, 1 mmol) in THF (30 mL) was
added a hexane solution of n-BuLi (1.6 M, 0.63 mL, 1 mmol) at −70 °C,
and the mixture was stirred for 1 h at that temperature. Sulfur (32 mg, 1
mmol) was added to the mixture. The reaction mixture was stirred at
−70 °C for 1 h, allowed to reach room temperature slowly, and stirred
for 2 h. Then Fe3(CO)12 (0.50 g, 1 mmol) was added, and the reaction
mixture was continuously stirred for 2 h at room temperature. Ar3SnCl
(1 mmol) was added to the above-mentioned reaction mixture, and the
mixture was stirred overnight. The solvent was removed under reduced
pressure, and the residue was purified by column chromatography on
silica using CH2Cl2 as the eluent. The red eluate was concentrated to
dryness, and the residue was recrystallized from CH2Cl2/hexane to give
a red solid.
1
residue was monitored using H NMR spectroscopy, which
revealed the presence of three components, namely, bis(3,5-
dimethylpyrazol-1-yl)methane, 3, and 3,5-dimethylpyrazole in a
ratio of ca. 1:1.3:3.6. This result suggests that the bis(3,5-
dimethylpyrazol-1-yl)methide anion possibly partly decomposes
during its formation at 0 °C, although a solution of this anion can
be warmed to 0 °C from −70 °C without decomposition.5a,8c,9b
In addition, Scheme 1 has shown that the reaction of the 3,5-
dimethylpyrazolate anion with CS2, followed by reaction with
Fe3(CO)12 and RX, yielded 2. Combining the above-mentioned
results with other known facts, the possible pathway for the
formation of 2 during this reaction is depicted in Scheme 4; it is
Synthesis of 1a. This complex was obtained using Ph3SnCl as the
starting material. Yield: 25%. 1H NMR: δ 1.54 (s, 3H), 2.02 (s, 3H), 2.09
(s, 3H), 2.48 (s, 3H) (CH3), 5.80 (s, 2H, H4 of pyrazole), 6.00 (s, 1H,
CH), 7.30−7.44, 7.62−7.78 (m, m, 9H, 6H, C6H5). 13C NMR: δ 10.8,
11.3, 13.7, 16.7 (CH3), 72.7 (CH), 107.1, 111.2 (C4 of pyrazole), 128.3,
128.4, 137.1, 143.9 (C6H5), 138.3, 143.1, 150.6, 153.3 (C3 and C5 of
pyrazole), 211.5 (CO). 119Sn NMR: δ 19.7. IR (cm−1): νCO = 2057.4 (s),
2010.3 (vs), 1979.0 (vs), 1940.7 (vs). Anal. Found: C, 48.40; H, 3.41; N,
6.57. Calcd for C35H30Fe2N4O6SSn: C, 48.59; H, 3.50; N 6.48.
Synthesis of 1b. This complex was obtained using (p-tolyl)3SnCl as
the starting material. Yield: 11%. 1H NMR: δ 1.53 (s, 3H), 2.03 (s, 3H),
2.09 (s, 3H), 2.47 (s, 3H) (CH3), 2.34 (s, 9H, C6H4CH3), 5.80 (s, 2H,
H4 of pyrazole), 6.00 (s, 1H, CH), 7.17 (d, J = 7.6 Hz, 6H), 7.57 (d, J =
7.6 Hz, 6H) (C6H4). 13C NMR: δ 10.6, 11.1, 13.6, 16.6 (CH3), 21.4
(C6H4CH3), 72.8 (CH), 107.0, 111.1 (C4 of pyrazole), 128.8, 129.1,
136.6, 137.0 (C6H4), 137.8, 140.1, 150.4, 153.2 (C3 and C5 of pyrazole),
209.3 (CO). 119Sn NMR: δ 20.6. IR (cm−1): νCO = 2054.2 (vs), 2007.9
(vs), 1975.1 (vs), 1940.4 (vs). Anal. Found: C, 50.14; H, 4.35; N, 6.05.
Calcd for C38H36Fe2N4O6SSn: C, 50.31; H, 4.00; N 6.18.
Scheme 4. Possible Pathway for Formation of 2 through
Partial Decomposition of the Bis(3,5-dimethylpyrazol-1-
yl)methide Anion
markedly different from that shown in Scheme 2. First, the
bis(3,5-dimethylpyrazol-1-yl)methide anion decomposes to
form the 3,5-dimethylpyrazolate anion and (3,5-dimethylpyr-
azol-1-yl)carbene. The latter dimerizes to form 3. The former
reacts with CS2 to give the (3,5-dimethylpyrazol-1-yl)-
dithioformate anion, which subsequently reacts with
Fe3(CO)12 to yield intermediate D. Finally, as in Scheme 2,
nucleophilic attack of the sulfur atom in D at RX gives 2.
In summary, the related reactions of bis(3,5-dimethylpyrazol-
1-yl)methyllithium with S or CS2, followed by reaction with
Fe3(CO)12 and Ar3SnCl or RX, were investigated. It was found
that the final products depended significantly on the electro-
Reaction of (3,5-Me2Pz)2CHLi with S, Followed by Reaction
with Fe3(CO)12 and RX. These reactions were carried out as in the
aforementioned treatment with Ar3SnCl, using RX instead of Ar3SnCl.
The eluent was CH2Cl2/hexane (2:1 v/v).
Synthesis of 2a. This complex was obtained using CH3I as the
1
starting material. Yield: 20%. H NMR: δ 2.15 (s, 3H), 2.17 (s, 3H)
(CH3), 2.36 (s, 3H, SCH3), 5.84 (s, 2H, H4 of pyrazole). 13C NMR: δ
12.4, 13.5 (CH3), 30.9 (SCH3), 77.2 (CS2), 108.4 (C4 of pyrazole),
138.5, 148.4 (C3 and C5 of pyrazole), 206.4, 209.3, 216.3 (CO). IR
(cm−1): νCO 2075.0 (s), 2029.6 (vs), 2011.2 (vs), 1980.9 (s), 1958.7 (s).
Anal. Found: C, 33.30; H, 2.35; N, 6.18. Calcd for C13H10Fe2N2O6S2: C,
33.50; H, 2.16; N, 6.01.
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Synthesis of 2b. This complex was obtained using PhCH2Br as the
starting material. Yield: 28%. H NMR: δ 2.07 (s, 3H), 2.18 (s, 3H)
(CH3), 3.66 (d, J = 13.6 Hz, 1H), 3.89 (d, J = 13.6 Hz, 1H) (CH2), 5.58
(s, 2H, H4 of pyrazole), 6.76−6.84, 7.08−7.16 (m, m, 2H, 3H, C6H5).
13C NMR: δ 11.8, 13.4 (CH3), 54.5 (CH2), 78.0 (CS2), 108.5 (C4 of
methods and difference Fourier map using SHELXS of the SHELXTL
package and refined with SHELXL24 by full-matrix least-squares on F2.
All non-hydrogen atoms were refined anisotropically. A summary of the
fundamental crystal data for these compounds is given in Table 1.
1
pyrazole), 127.8, 128.3, 128.5, 133.9 (C6H5), 138.6, 148.1 (C3 and C5 of
pyrazole), 206.3, 209.2, 216.0 (CO). IR (cm−1): νCO 2070.1 (s), 2013.2
(vs), 1986.5 (sh), 1961.1 (s), 1942.4 (s). Anal. Found: C, 42.09; H, 2.49;
N, 5.14. Calcd for C19H14Fe2N2O6S2: C, 42.09; H, 2.60; N, 5.17.
Reaction of (3,5-Me2Pz)CS2Li with Fe3(CO)12 and Subsequent
Treatment with RX. To a solution of 3,5-dimethylpyrazole (96 mg, 1
mmol) in THF (30 mL) was added a hexane solution of n-BuLi (1.6 M,
0.63 mL, 1 mmol) at 0 °C, and the mixture was stirred for 1 h at that
temperature. CS2 (0.06 mL, 1 mmol) was added to the mixture, and then
the reaction mixture was continuously stirred at room temperature.
After 5 h, Fe3(CO)12 (0.50 g, 1 mmol) was added. The reaction mixture
was stirred for 12 h at room temperature. RX (CH3I or PhCH2Br, 1
mmol) was added to the reaction mixture, and the mixture was stirred
overnight. The solvent was removed under reduced pressure, and the
residue was purified by column chromatography on silica using CH2Cl2/
hexane (2:1 v/v) as the eluent. The red eluate was concentrated to
dryness; the residue was recrystallized from CH2Cl2/hexane to give a red
solid. Complexes 2a and 2b were obtained by this method in ca. 35% and
37% yields, respectively.
Table 1. Crystallographic Data for 1a, 2b, and 3
1a
2b
3.2H2O
formula
fw
C35H30Fe2N4O6SSn
865.08
C19H14Fe2N2O6S2
542.14
C12H20N4O2
252.32
cryst size,
mm
0.22 × 0.20 × 0.18
0.20 × 0.18 × 0.12 0.30 × 0.18 ×
0.10
cryst syst
space group
a, Å
triclinic
monoclinic
P21/n
orthorhombic
Pccn
P1
̅
9.7770(11)
12.0010(14)
15.9930(14)
71.639(11)
75.339(12)
88.962(14)
1719.1(3)
2
7.7591(16)
11.023(2)
25.811(5)
90
14.576(11)
20.042(15)
4.695(3)
90
b, Å
c, Å
α, deg
β, deg
γ, deg
V, Å3
Z
95.64(3)
90
90
90
2196.9(8)
4
1371.6(18)
4
λ, Å
0.71075
0.71075
1.639
0.71073
1.222
Treatment of CH2(3,5-Me2Pz)2 with n-BuLi at 0 °C and
Subsequent Reaction with CS2, Fe3(CO)12, and RX. To a solution
of CH2(3,5-Me2Pz)2 (0.20 g, 1 mmol) in THF (30 mL) was added a
hexane solution of n-BuLi (1.6 M, 0.63 mL, 1 mmol) at 0 °C, and the
mixture was stirred for 1 h at that temperature. CS2 (0.06 mL, 1 mmol)
was added to the mixture; then the reaction mixture was continuously
stirred for 1 h, allowed to reach room temperature slowly, and stirred for
2 h. Fe3(CO)12 (0.50 g, 1 mmol) was added, and the reaction mixture
was stirred for 2 h at room temperature. RX (CH3I or PhCH2Br, 1
mmol) was added to the reaction mixture, and the mixture was stirred
overnight. The solvent was removed under reduced pressure, and the
residual solid was purified by column chromatography on silica using
CH2Cl2/hexane (2:1 v/v) as the eluent to give 2a and 2b in ca. 22% and
21% yields, respectively. After complexes 2 were isolated, ethyl acetate
was used as the eluent to give compound 3, which was recrystallized
from hexane to yield a white solid.
calcd density, 1.671
Mg/m−3
F(000)
μ, mm−1
868
1096
544
1.666
1.549
0.086
no. of rflns
collcd/
unique
17626/8092 (0.0415) 14411/3870
(0.0375)
10434/1214
(0.0671)
(Rint)
no. of rflns
obsd with
(I ≥ 2σ(I))
6494
3324
1148
no. of params 446
282
93
R, Rw (I ≥
2σ(I))
0.0483, 0.0842
0.0380, 0.0884
0.0539, 0.1397
R, Rw (all
0.0647, 0.0922
0.0467, 0.0940
1.025
0.0588, 0.1441
1.146
data)
Spectroscopic Data for 3. Yield: ca. 10%. 1H NMR: δ 2.28 (s, 6H),
goodness-of- 1.034
fit on F2
2.33 (s, 6H) (CH3), 5.89 (s, 2H, H4 of pyrazole), 7.56 (s, 2H, CH). 13
C
NMR: δ 11.0, 13.7 (CH3), 106.6 (C4 of pyrazole), 114.8 (CH), 139.7,
149.7 (C3 and C5 of pyrazole). Anal. Found: C, 66.32; H, 7.25; N, 25.52.
Calcd for C12H16N4: C, 66.64; H, 7.46; N, 25.90.
largest diff
peak and
0.940, −1.308
0.381, −0.433
0.195, −0.175
hole, e Å−3
Reaction of CH2(3,5-Me2Pz)2 with n-BuLi at 0 °C and
Subsequent Reaction with H2O. To a solution of CH2(3,5-
Me2Pz)2 (0.20 g, 1 mmol) in THF (30 mL) was added a hexane
solution of n-BuLi (1.6 M, 0.63 mL, 1 mmol) at 0 °C, and the mixture
was stirred for 1 h at that temperature. To the mixture was added H2O
(18 μL, 1 mmol), and then the reaction mixture was continuously stirred
for 1 h, allowed to reach room temperature slowly, and stirred for 2 h.
The solvent was removed under reduced pressure, and the residue was
ASSOCIATED CONTENT
■
S
* Supporting Information
Crystallographic details for 1a, 2b, and 3 in CIF format. This
material is available free of charge via the Internet at http://pubs.
acs.org.
1
characterized using H NMR spectroscopy, which showed that the
AUTHOR INFORMATION
reaction mixture consisted of three components, namely, CH2(3,5-
Me2Pz)2, 3, and 3,5-dimethylpyrazole, in a ratio of ca. 1:1.3:3.6,
according to the integral of the 4-position hydrogen of the pyrazolyl ring.
When the reaction of CH2(3,5-Me2Pz)2 with n-BuLi was carried out
at −70 °C, stirred for 1 h at that temperature, and subsequently treated
with H2O as mentioned above, only CH2(3,5-Me2Pz)2 was recovered.
No 3,5-dimethylpyrazole and 3 were observed using 1H NMR
spectroscopy.
X-ray Structure Determinations of 1a, 2b, and 3. Red crystals of
1a and 2b suitable for X-ray analyses were grown by diffusion of hexane
into their CH2Cl2 solutions at −18 °C. White crystals of 3 suitable for X-
ray analyses were obtained by slow diffusion of hexane into its THF
solution at 4 °C. All intensity data were collected with a Rigaku Saturn
CCD diffractometer at −160(2) °C, using graphite-monochromated
Mo Kα radiation. Semiempirical absorption corrections were applied
using the CrystalClear program.23 The structures were solved by direct
■
Corresponding Author
*E-mail: lftang@nankai.edu.cn. Fax: 86-22-23502458.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is supported by the National Natural Science
Foundation of China (No. 20972075).
REFERENCES
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dx.doi.org/10.1021/om300448a | Organometallics 2012, 31, 5108−5113

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