Lanthanide(III) 4,6-dimethylpyrimidine-2-thionate complexes as efficient catalysts for isocyanate cyclodimerization

Article abstract of DOI:10.1021/om100671s

Protonolysis reactions of [(Me₃Si)₂N] ₃Ln(μ-Cl)Li(THF)₃ (Ln = Pr, Nd, Sm, Eu) with 3 equiv of 4,6-dimethylpyrimidine-2-thiol (dmpymtH) gave rise to the four Ln(III) pyrimidine-2-thionate complexes Li[Ln(dmpymt)₄] (Ln = Pr (1), Nd (2), Sm (3), Eu (4)). Compounds 1-4 were characterized by elemental analysis, IR and ¹H NMR spectroscopy, and single-crystal X-ray diffraction. X-ray diffraction analysis shows that the structures of 1-4 are similar and each eight-coordinate Ln(III) ion is chelated by four dmpymt ligands. Complexes 1-4 display excellent catalytic performance in the cyclodimerization of isocyanates to produce substituted ureas via elimination of CO, which represents the first example of lanthanide thiolates exhibiting a high catalytic activity and a high selectivity in the cyclodimerization of isocyanates. The effects of the solvents, temperatures, catalyst loadings, and rare-earth metals on the catalytic activities of the complexes were examined.

Full text of DOI:10.1021/om100671s

208 Organometallics 2011, 30, 208–214
DOI: 10.1021/om100671s
Lanthanide(III) 4,6-Dimethylpyrimidine-2-thionate Complexes as
Efficient Catalysts for Isocyanate Cyclodimerization
Hong-Xi Li,†,‡ Mei-Ling Cheng,†,§ He-Ming Wang,† Xiao-Juan Yang,† Zhi-Gang Ren,† and
Jian-Ping Lang*,†,‡
†College of Chemistry, Chemical Engineering and Materials Science, Suzhou University, Suzhou 215123,
People’s Republic of China, ‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute
of Organic Chemistry, Chinese Academy of Sciences, Shanghai 210032, People’s Republic of China, and
§School of Chemistry and Chemical Engineering, Changzhou University, Changzhou 213164, People’s
Republic of China
Received July 10, 2010
Protonolysis reactions of [(Me3Si)2N]3Ln( μ-Cl)Li(THF)3 (Ln = Pr, Nd, Sm, Eu) with 3 equiv of
4,6-dimethylpyrimidine-2-thiol (dmpymtH) gave rise to the four Ln(III) pyrimidine-2-thionate
complexes Li[Ln(dmpymt)4] (Ln = Pr (1), Nd (2), Sm (3), Eu (4)). Compounds 1-4 were
characterized by elemental analysis, IR and 1H NMR spectroscopy, and single-crystal X-ray
diffraction. X-ray diffraction analysis shows that the structures of 1-4 are similar and each eight-
coordinate Ln(III) ion is chelated by four dmpymt ligands. Complexes 1-4 display excellent catalytic
performance in the cyclodimerization of isocyanates to produce substituted ureas via elimination of
CO, which represents the first example of lanthanide thiolates exhibiting a high catalytic activity and
a high selectivity in the cyclodimerization of isocyanates. The effects of the solvents, temperatures,
catalyst loadings, and rare-earth metals on the catalytic activities of the complexes were examined.
Introduction
of these complexes with alkane- or arenethiolates5,6 have
been synthesized. Among them, the tendency for thiolates to
serve as bridging ligands and for the lanthanide ions to
maximize coordination numbers generally leads to the for-
mation of oligomeric or polymeric lanthanide thiolate com-
plexes unless the lanthanide ion is coordinated by strong
donor molecules or very bulky thiolate ligands. Nitrogen-
donor-containing thiolates such as pyridine-2-thione have
attracted much attention, because these ligands could chelate
Ln(II)/Ln(III) metal atoms via both sulfur and nitrogen
atoms to stabilize them.7,8 Another kind of N,S-donor
ligand, pyrimidine-2-thione and its derivatives, has been
In the past decades, the synthesis of lanthanide thiolate
complexes has attracted much attention due to their inter-
esting structures,1 luminescence properties,2 and potential
applications in catalytic processes3 and the preparation of
organic or organolanthanide complexes.4 So far, a number
*To whom correspondence should be addressed. Fax and tel: int. code
þ86 512 65880089. E-mail: jplang@suda.edu.cn.
ꢀ
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pubs.acs.org/Organometallics
Published on Web 12/15/2010
2010 American Chemical Society

Article
Organometallics, Vol. 30, No. 2, 2011 209
applied extensively to synthesizing main-group and transition-
metal complexes, in which pyrimidine-2-thionate works
as a monodentate ligand by coordination through the S
atom, as an N,S chelating ligand, or as a bridging ligand
through the S atom and one or two N atoms.9-12 However,
only one paper has reported the synthesis of lanthanide
pyrimidine-2-thionate complexes.13 Weak coordination of
the soft base sulfur at a hard acidic Ln center may cause
the resulting lanthanide thiolate complexes to possess high
catalytic activity for the intramolecular alkene hydroami-
nation reaction,3d olefin polymerization,3a,b and homo- and
copolymerization of 2,2-dimethyltrimethylene carbonate
(DTC) and ε-caprolactone.3c,14 In 2002, phenyl isocyanate
(PhNCO) was reported to be inserted stoichiometri-
cally into the Ln-S bond of [(C5H4CH3)2Nd( μ-SPh)-
(THF)]2 to give the corresponding insertion product
[(C5H4CH3)2Nd( μ,η2-O(SPh)NPh]2.4 Isocyanates could un-
dergo cyclodimerization, cyclotrimerization, and polymeri-
zation reactions, catalyzed by the lanthanocene com-
plexes (MeC5H4)2LnNiPr2(THF) (Ln = Y, Er, Yb)15 and
(C5H5)2LnCl/n-BuLi16 or lanthanide amides {(CH2SiMe2)-
Scheme 1. Formation of Li[Ln(dmpymt)4] from Reactions of
[(Me3Si)2N]3Ln( μ-Cl)Li(THF)3 (Ln = Nd, Sm, Eu) with
dmpymtH
[(2,6-iPr2C6H3)N]2}LnN(SiMe3)2(THF) (Ln = Yb, Y,
Dy, Sm, Nd) and {(Me2Si)[(2,6-R1 -4-R2-C6H2)N]2}LnN-
2
(SiMe3)2(THF) (R1 = iPr, R2 = H, Ln = Yb, Y, Eu, Sm,
Nd; R1 = R2 = H, Ln = Yb, Sm).17 However, a systematic
study of the catalytic transformation of the isocyanates to
isocyanurates with lanthanide thiolates as catalysts has been
far less explored. Recently, we have been interested in study-
ing the synthesis and catalytic properties of lanthanide
thiolate complexes.14 In a continuing effort to make new
lanthanide thiolate complexes, we chose the (bis(trimeth-
ylsilyl)amino)lanthanide(III) chloride complexes ([(Me3-
Si)2N]3Ln( μ-Cl)Li(THF)3 (Ln = Pr, Nd, Sm, Eu)) as start-
ing materials to react with a pyrimidine-2-thione derivative,
4,6-dimethylpyrimidine-2-thiol (dmpymtH). The four anio-
nic mononuclear Ln(III) complexes Li[Ln(dmpymt)4] (1, Ln =
Pr; 2, Ln = Nd; 3, Ln = Sm; 4, Ln = Eu) were isolated; they
displayed high catalytic activity and selectivity in the cyclo-
dimerization of isocyanates. Herein we report their synthe-
sis, characterization, and catalytic activity.
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Results and Discussion
Synthesis. As shown in Scheme 1, reactions of [(Me3Si)2-
N]3Pr( μ-Cl)Li(THF)3 with dmpymtH in a 1:3 molar ratio
afforded a large amount of slightly yellow precipitate. After
filtration, the precipitate was further dissolved in MeCN and
filtered again. The filtrate was allowed to stand at -18 °C for
2 days, forming colorless crystals of Li[Pr(dmpymt)4] (1) in
67% yield. The analogous reaction of the precursor and
dmpymtH in 1:1 or 1:2 molar ratio did not give rise to the
corresponding 1:1 or 1:2 product. Compound 1 was the only
product isolated in a crystalline form regardless of the
precursor/dmpymtH molar ratios. However, the change of
the precursor to dmpymtH molar ratio from 1:3 to 1:4 only
slightly increased the yield of 1. The reason for it may be due
to the formation of other unidentified materials containing
Pr/dmpymt/Cl complexes. Similar reactions of [(Me3Si)2-
N]3Ln( μ-Cl)Li(THF)3 (Ln = Nd, Sm, Eu) with 3 equiv of
dmpymtH in THF resulted in the formation of Li[Nd-
(dmpymt)4] (2) in 73% yield, Li[Sm(dmpymt)4] (3) in 63%
yield, and Li[Eu(dmpymt)4] (4) in 71% yield, respectively
(Scheme 1).
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G. M.; de; Casagrande, G. A.; Vazquez-Lopez, E. M. Inorg. Chem.
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Commun. 2003, 6, 1297. (f ) Fernandez-Galan, R.; Manzano, B. R.; Otero,
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Compounds 1-4 were air and moisture sensitive and were
soluble in MeCN, slightly soluble in THF, and insoluble in
toluene and n-hexane. Elemental analyses of 1-4 were
consistent with the formulas. In the IR spectra of 1-4, the
strong absorption at 1200-1300 cm-1 could be assigned to
(14) (a) Li, H. X.; Ren, Z. G.; Zhang, Y.; Zhang, W. H.; Lang, J. P.;
Shen, Q. J. Am. Chem. Soc. 2005, 127, 1122. (b) Li, H. X.; Cheng, M. L.;
Ren, Z. G.; Zhang, W. H.; Lang, J. P.; Shen, Q. Inorg. Chem. 2006, 45, 1885.
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Z. G.; Zhang, Y.; Lang, J. P. Eur. J. Inorg. Chem. 2007, 1889.
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3711.
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lics 2001, 20, 5700.

210 Organometallics, Vol. 30, No. 2, 2011
Li et al.
Scheme 2. Catalytic Cyclodimerization of Isocyanates
Table 2. Influence of the Conditions on the Cyclodimerization of
Phenyl Isocyanate
entry cat. (mol %)a temp (°C) time (h)
solvent
yield (%)b
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
2
3
20
20
20
20
20
40
60
20
20
12
12
12
12
12
12
12
12
12
n-hexane
CH2Cl2
toluene
THF
MeCN
MeCN
MeCN
MeCN
MeCN
NR
NR
NR
14
66
90
99
85
98
Figure 1. Perspective view of the anion of 1 with a labeling
scheme and 30% thermal ellipsoids. All hydrogen atoms are
omitted for charity. Symmetry codes: (A) -x, -y, z; (B) -y,
x, -z; (C) y, -x, -z.
a
˚
Table 1. Selected Bond Lengths (A) and Angles (deg) for 1, 3, and 4
a The catalyst is complex 1, and the catalyst loading is given in mole
Ln = Pr (1)
Ln = Sm (3)
Ln = Eu (4)
percent (mol %). b Isolated yield.
Ln(1)-N(2)
Ln(1)-S(1)
2.654(4)
2.9071(11)
2.605(5)
2.8611(13)
2.598(5)
2.8494(13)
close to the corresponding distance found in [Pr(bipy)-
(S2CNEt2)3]18 (2.905(5) A; bipy = 2,2 -bipyridine) but long-
er than that observed in [(DME)3Pr(SC6F5)2]2[Hg2(SC6F5)6]
6b
0
N(2A)-Ln(1)-N(2)
N(2)-Ln(1)-N(2B)
S(1)-Ln(1)-S(1A)
S(1)-Ln(1)-S(1B)
N(2A)-Ln(1)-S(1)
N(2)-Ln(1)-S(1)
N(2B)-Ln(1)-S(1)
N(2)-Ln(1)-S(1B)
165.15(15)
90.957(19)
82.49(5)
124.43(3)
138.67(8)
56.18(8)
164.64(18)
91.02(3)
81.36(5)
125.11(3)
138.36(10)
57.00(10)
84.09(10)
84.28(10)
164.64(19)
91.02(3)
81.27(5)
125.16(3)
138.32(10)
57.05(10)
84.07(10)
84.29(10)
˚
˚
˚
(2.8619(8) A). The mean Pr-N bond distance (2.654(4) A)
is comparable to that observed in [Pr(bipy)(S2CNEt2)3]
18
˚
(2.659(5) A). In 3, the mean Sm-S bond distance of
84.53(8)
84.31(8)
˚
2.8611(13) A is close to those of [Sm(SC5H4N)2(HMPA)3]I
˚
(2.870(3) A; SC5H4N = 2-thiopyridyl; HMPA = hexameth-
a Symmetry codes: (A) -x, -y, z, (B) -y, x, -z, and (C) y, -x, -z for
ylphosphoric amide)7b and [Sm(TpMe,Me)2SC5H4N]
1; (A) -x þ 1, -y, z, (B) -y þ /2, x - 1/2, -z, and (C) y þ /2, -x þ /2,
1
1
1
(2.862(4) A; TpMe,Me = tris(3,5-dimethylpyrazolyl)borate)7c
˚
3
1
3
-z þ /2 for 3; (A) -x þ 1, -y, z, (B) -y þ /2, x - 1/2, -z þ /2, and (C) y
˚
1
1
3
and between those of [(py)4Sm(SC6F5)3] (2.836(3) A, py =
þ /2, -x þ /2, -z þ /2 for 4.
pyridine)6e and [(DMSO)2Sm(C5H4NOS)3] (2.894(3) A;
˚
1
DMSO = dimethyl sulfoxide; C5H4NOS = 1-hydroxy-
2(1H)-pyridinethionato).8b The average Sm-N bond distance
the ν(C-S) vibration of dmpymt ligands. The H NMR
spectra of 1-3 in DMSO-d6 showed two singlets at δ 1.653
and 3.511 ppm (1), δ 1.741 and 3.584 ppm (2), δ 2.218 and
2.282 ppm (3), which were assignable to the six protons of the
two methyl groups of the dmpymt ligand. The singlet at
δ 8.510 (1), 7.834 (2), and 6.483 ppm (3) was ascribed to the
one proton of the heterocycle of the dmpymt ligand. The
identities of 1, 3, and 4 were finally confirmed by X-ray
crystallography.
(2.605(4) A) is slightly longer than those in [Sm(TpMe,Me)2-
˚
7c
[Sm(TpMe,Me)2SC6H4-Me-4]
˚
SC5H4N] (2.523(9) A),
7b
˚
(2.531(6) A), and [Sm(SC5H4N)2(HMPA)3]I (2.542(7) A).
In 4, the mean Eu-S bond length (2.8494(13) A) is shorter
than that of [(PEt4){Eu(SC5H4N)4}] (2.87(1) A), while the
mean Eu-N bond length (2.598(5) A) is consistent with that
of [(PEt4){Eu(SC5H4N)4}] (2.52(1) A).
˚
˚
˚
˚
7d
˚
Catalytic Activities of 1-4. To explore the reactivity of
1-4 toward isocyanates, complex 1 was mixed with phenyl
isocyanate in a 1:100 molar ratio and stirred at room
temperature for 12 h. The reaction mixture was hydrolyzed
by water and extracted with diethyl ether. After removal of
all the volatile species of the extract in vacuo, the residue was
re-extracted with hot toluene/THF and filtered off. The
filtrate was allowed to stand at -18 °C for several days,
forming colorless crystals of 1,3-diphenylurea (5) in 66%
yield. The formation of 5 is assumed to proceed through
elimination of CO from the phenyl isocyanate cyclodimer-
ization product (Scheme 2).17b To our knowledge, it repre-
sents the first example of employing lanthanide thiolate
complexes to catalyze the cyclodimerization of isocyanates.
Crystal Structures of Li[Ln(dmpymt)4] (Ln = Pr (1), Sm
(3), Eu (4)). In the tetragonal space group I4, the asymmetric
units for 1, 3, 4 contain one-fourth of a [Ln(dmpymt)4]-
anion, one-fourth of a Liþ, and half of a MeCN solvent
molecule. As the structures of the [Ln(dmpymt)4]- anions in
1, 3, and 4 are essentially identical, only the perspective view
of the anion of 1 is shown in Figure 1. The pertinent bond
distances and angles for 1, 3, and 4 are compared in Table 1.
In the structures of the anions of 1, 3, and 4, the Pr, Sm, or Eu
atom is coordinated by four S and four N atoms from four
η2-dmpymt ligands to form a distorted-dodecahedral coor-
dination geometry. The four dmpymt anions chelate to each
Ln ion in a bidentate chelating S,N mode. The average Ln-S
˚
(2.9071(11) (1), 2.8611(13) (3), 2.8494(13) A (4)) and Ln-N
˚
(2.654(4) (1), 2.605(5) (3), 2.598(5) A (4)) bond distances
decrease along with the ionic radius in the order Pr > Sm >
˚
(18) Bower, J. F.; Cotton, S. A.; Fawcett, J.; Hughes, R. S.; Russell,
D. R. Polyhedron 2003, 22, 347.
Eu. In 1, the average Pr-S bond distance of 2.9071(11) A is

Article
Organometallics, Vol. 30, No. 2, 2011 211
Table 3. Data for the Cyclodimerization of Different Isocyanatesd
a Catalyst loading: 1 mol %. b Isolated yields by running the reaction in MeCN. c [(Me3Si)2N]3Ln( μ-Cl)Li(THF)3 (Ln = Pr (10), Nd (20), Sm (30), Eu
(40)). d Conditions: isocyanate to catalyst ratio 100:1; solvent MeCN; T = 60 °C; time 12 h.
Complex 1 was employed to optimize the reaction condi-
tions of cyclodimerization of phenyl isocyanate. Five differ-
ent solvents (CH2Cl2, toluene, THF, n-hexane, and MeCN)
were used to evaluate their influence on the catalytic perfor-
mance of 1. As shown in Table 2, a strong solvent depen-
dence of the cyclodimerization was observed. 1 did not work
in n-hexane, toluene, or CH2Cl2, but it showed low activity in
THF. Almost complete conversion of the phenyl isocyanate
into 1,3-diphenylurea (1 mol % catalyst) was achieved within
12 h at 60 °C in MeCN (Table 2, entry 7). The catalytic
activity of 1 in MeCN was enhanced as the reaction tem-
perature was increased. A 66% yield of 1,3-diphenylurea
could be obtained in the presence of 1 mol % catalyst in
MeCN in 12 h at room temperature (Table 2, entry 5), while
the temperature was raised to 40 or 60 °C, and the yields can
be raised to 90% and 99%, respectively (Table 2, entries 6
and 7). The catalyst to phenyl isocyanate molar ratio may
also affect the catalytic activity. The product yield was
gradually increased from 66% to 85% to 98% when the
catalyst loading was changed from 1 mol % to 2 mol % and
3 mol % in the presence of MeCN at 20 °C (Table 2, entries 5,
8, and 9). Thus, the following optimized conditions were
determined: isocyanate:cat. = 100:1 (molar ratio); solvent
MeCN; T = 60 °C; time 12 h.
With these optimized conditions, the catalytic perfor-
mances of the other lanthanide thiolates were also investi-
gated. Complexes 2-4 also exhibited good to excellent
catalytic activity for the cyclodimerization of phenyl isocya-
nate (Table 3, entries 1-4). In all cases, the 1,3-diphenylurea
was the only product, indicating the high selectivity of these
catalysts. For comparison, the catalytic activity of the pre-
cursor complexes [(Me3Si)2N]3Ln( μ-Cl)Li(THF)3 (Ln = Pr

212 Organometallics, Vol. 30, No. 2, 2011
Li et al.
Scheme 3. Proposed Catalytic Mechanism for the
Cyclodimerization of Isocyanates
Figure 2. View of the molecular structure of 10.
In summary, the present work demonstrates that the
protonolysis reaction of lanthanide amide complexes with
dmpymtH readily produces the four lanthanide pyrimidine-
2-thionate complexes 1-4. Complexes 1-4 exhibit a high
catalytic activity and a high selectivity for the cyclodimeriza-
tion of aryl isocyanates, producing the corresponding sub-
stituted ureas, which represents a useful approach to the
synthesis of ureas under mild reaction conditions. It is
anticipated that other pyrimidine-2-thiols may be applied to
afford other lanthanide thiolate complexes to yield pre-
viously unknown species with better catalytic activities.
Studies on these respects are under way in our laboratory.
(10), Nd (20), Sm (30), Eu (40)) was studied (Table 3, entries
21-24). However, 10-40 exhibited good to high catalytic
activity for the cyclotrimerization of phenyl isocyanate,
which was observed in the case of [(Me3Si)2N]3Yb( μ-Cl)Li-
(THF)3.17a Therefore, the catalytic activities of 1-4 are
completely different from those of lanthanide amides, sug-
gesting ligand binding at the lanthanide center makes an
great impact on the selectivity of the catalysts.
Experimental Section
Complexes 1-4 showed a similar catalytic activity for the
cyclodimerization of other alkyl or aryl isocyanates such as
cyclohexyl isocyanate, benzyl isocyanate, 4-isopropylphenyl
isocyanate, and allyl isocyanate (Table 3, entries 5-20).
The corresponding products were identified as 1,3-dicyclo-
hexylurea (6), 1,3-dibenzylurea (7), 1,3-bis(4-isopropylphe-
nyl)urea (8), and 1,3-diallylurea (9). In comparison to that
for the cyclodimerization of aryl isocyanates, 1-4 exhibited
lower catalytic activity for the cyclodimerization of alkyl
isocyanates. It is noted that other byproducts such as trimer-
ization products or polymerization products were observed
in the cases of alkyl isocyanates, indicating that 1-4 exhib-
ited not only a high catalytic activity but also a high
selectivity for the cyclodimerization of aryl isocyanates.
The structures of products 5, 6, and 8 were determined for
the clear identification of their identities.
The catalytic reaction mechanism for the above reactions
is proposed as follows (Scheme 3). First, insertion of an
isocyanate into the Ln-S bond of the catalyst may lead to
the formation of the six-membered intermediate II. Second,
the intermediate II may combine with the another isocyanate
to give the eight-membered intermediate III. Third, the
intermediate III may eliminate the cyclodimerization prod-
uct that subsequently loses 1 equiv of carbon monoxide
(CO), producing the urea and thus furnishing the catalytic
cycle. To confirm the proposed mechanism, we carried out
the reaction of 2 with 4 equiv of PhNCO in MeCN. Intrigu-
ingly, it did not produce the expected insertion species “Nd-
[OC(dmpymy)NPh]4” but gave rise to 5. When phenyl
isocyanate was added to the mixture containing [(Me3Si)2-
N]3Sm( μ-Cl)Li(THF)3 and 3 equiv of dmpymtH in THF,
a standard workup produced colorless crystals of phe-
nylthiocarbamic acid S-4,6-dimethylpyrimidin-2-yl ester
(10) (Figure 2). These results showed that the intermediate
II should be formed but is protonated by (Me3Si)2NH
released in the reaction.
All manipulations were carried out under argon using stan-
dard Schlenk techniques. Solvents were dried by distillation
from sodium/benzophenone (tetrahydrofuran, toluene, hexane)
or P2O5 (MeCN or CH2Cl2) under argon prior to use. LiN-
(SiMe3)219 and [(Me3Si)2N]3Ln( μ-Cl)Li(THF)320 were prepared
according to the literature methods. The dmpymtH ligand and
phenyl isocyanate, cyclohexyl isocyanate, benzyl isocyanate,
4-isopropylphenyl isocyanate, and allyl isocyanate were pur-
chased from Aldrich. 1H NMR spectra were recorded at ambi-
ent temperature on a Varian UNITYplus-300 spectrometer.
1H NMR chemical shifts were referenced to the solvent signal
in DMSO-d6 or CDCl3. Elemental analyses for C, H, and N were
performed on a Carlo-Erbo CHNO-S microanalyzer. The IR
spectra (KBr disk) were recorded on a Nicolet Magna-IR550
FT-IR spectrometer (4000-400 cm-1). The uncorrected melting
points were measured on a Mel-Temp II apparatus.
Synthesis of Li[Pr(dmpymt)4] (1). To a solution of dmpymtH
(0.346 g, 2.471 mmol) in THF (30 mL) was added a solution of
[(Me3Si)2N]3Pr( μ-Cl)Li(THF)3 (0.670 g, 0.818 mmol) in THF
(10 mL). The reaction mixture was stirred overnight. The
solution turned light yellow with a large amount of light yellow
precipitate. After filtration, the resulting precipitate was dis-
solved in 30 mL of MeCN. Colorless crystals of 1 were isolated
by cooling the solution to -18 °C for 2 days. After filtration, the
crystals were dried under vacuum. Yield: 0.381 g (67% based on
Pr), Anal. Calcd for C24H28N8PrS4: C, 41.32; H, 4.04; N, 16.06;
S, 18.38. Found: C, 41.53; H, 4.34; N, 16.24; S, 18.45. IR (KBr
disk): 3046 (m), 2960 (m), 2923 (m), 1631 (w), 1573 (s), 1535 (s),
1432 (m), 1384 (s), 1341 (s), 1254 (s), 1029 (w), 987 (w), 955 (w),
886 (m), 758 (w), 554 (w) cm-1. 1H NMR (300 MHz, DMSO-d6,
ppm): δ 8.510 (s, 4H, -CH), 3.511 (s, 12H, -CH3), 1.653
(s, 12H, -CH3). 13C NMR (DMSO-d6, ppm): δ 170.6, 163.0,
130.6, 80.5, 67.6, 25.7.
(19) Ghotra, J. S.; Hursthouse, M. B.; Welch, A. J. J. Chem. Soc.,
Chem. Commun. 1973, 669.
(20) Zhou, S. L.; Wang, S. W.; Yang, G. S.; Liu, X. Y.; Sheng, E. H.;
Zhang, K. H.; Cheng, L.; Huang, Z. X. Polyhedron 2003, 22, 1019.

Article
Organometallics, Vol. 30, No. 2, 2011 213
Table 4. Crystallographic Data and Refinement Results for 1, 3, 4, and 10
1
3
4
10
empirical formula
formula mass (g mol-1
cryst syst
C
704.67
tetragonal
I4
0.60 ꢀ 0.50 ꢀ 0.45
10.8874(15)
10.8874(15)
13.790(3)
24H28N8S4PrLi
C24H28N8S4LiSm
714.12
tetragonal
I4
0.38 ꢀ 0.34 ꢀ 0.20
10.8871(15)
10.8871(15)
13.748(3)
C24H28EuN8S4Li
715.73
tetragonal
I4
0.30 ꢀ 0.30 ꢀ 0.20
10.8407(15)
10.8407(15)
13.720(3)
C13H13N3OS
259.32
triclinic
)
space group
cryst dimens (mm3)
P1
0.20 ꢀ 0.29 ꢀ 0.30
10.070(2)
10.085(2)
14.158(3)
103.00(3)
93.27(3)
113.14(3)
1271.2(4)
4
1.355
544
0.246
6.09-54.91
10 508
5569 (Rint = 0.0403)
3674 (I > 2.00σ(I ))
329
0.9299-0.9525
0.0709
0.1602
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
3
˚
V (A )
Z
1634.6(5)
2
1.432
708
1.772
7.49-50.70
7909
1500 (Rint = 0.0283)
1496 (I > 2.00σ(I ))
99
0.358-0.456
0.0223
0.0623
1.072
0.609, -0.511
P
1614.6(4)
2
1.469
714
2.103
7.52-50.69
7887
1492 (Rint = 0.0339)
1490 (I > 2.00σ(I ))
97
1612.4(4)
2
1.474
716
2.230
6.88-54.98
7967
1492 (Rint = 0.0347)
1490 (I > 2.00σ(I ))
97
0.554-0.663
0.0222
0.0646
1.141
0.641, -0.278
Dcalcd (g cm-3
F(000)
)
μ (mm-1
)
2θ range for data collcn (deg)
total no. of rflns
no. of unique rflns
no. of obsd rflns
no. of variables
transmission factor
Ra
0.501-0.678
0.0231
0.0673
b
Rw
GOFc
residual peaks (e A
1.146
0.504, -0.322
P
1.019
0.651, -0.345
-3
˚
)
P
P
P
a R = ||Fo| - |Fc||/ |Fo|. b Rw = { w(|Fo| - |Fc|)2/ w|Fo|2}}1/2
.
c GOF = { w(|Fo| - |Fc|)2/(M - N)}1/2, where M is the number of reflections
and N is the number of parameters.
Synthesis of Li[Nd(dmpymt)4] (2). A similar reaction of
dmpymtH (0.318 g, 2.271 mmol) with [(Me3Si)2N]3Nd( μ-Cl)Li-
(THF)3 (0.633 g, 0.718 mmol) in THF followed by a workup
similar to that used in the isolation of 1 afforded colorless
crystals of 2. Yield: 0.371 g (73% based on Nd). Anal. Calcd
for C24H28LiN8NdS4: C, 40.72; H, 3.99; N, 15.83; S, 18.12.
Found: C, 40.48; H, 3.55; N, 16.11, S, 17.98. IR (KBr disk): 3055
(m), 2963 (m), 2920 (m), 1627 (w), 1576 (s), 1535 (s), 1428 (m)
1385 (m), 1386 (s), 1343 (s), 1254 (s), 1027 (w), 987 (w), 958 (w),
888 (m), 767 (w) cm-1. 1H NMR (300 MHz, DMSO-d6, ppm): δ
7.834 (s, 4H, -CH), 3.584 (s, 12H, -CH3), 1.741 (s, 12H, -CH3).
13C NMR (DMSO-d6, ppm): δ 179.4, 167.7, 147.0, 134.8, 66.9,
25.1.
Synthesis of Li[Sm(dmpymt)4] (3). A similar reaction of dmpy-
mtH (0.292 g, 2.086 mmol) with [(Me3Si)2N]3Sm( μ-Cl)Li-
(THF)3 (0.613 g, 0.689 mmol) in THF followed by a workup
similar to that used in the isolation of 1 afforded colorless
crystals of 3. Yield: 0.310 g (63% based on Sm). Anal. Calcd
for C24H28LiN8S4Sm: C, 40.37; H, 3.95; N, 15.69; S, 17.96.
Found: C, 40.75; H, 3.89; N, 15.52; S, 17.67. IR (KBr disk): 3055
(m), 2963 (m), 2920 (m), 1627 (w), 1576 (s), 1535 (s), 1428 (m),
1386 (s), 1343 (s), 1254 (s), 1027 (w), 987 (w), 958 (w), 888 (m),
767 (w) cm-1. 1H NMR (300 MHz, DMSO-d6, ppm): δ 6.483 (s,
4H, -CH), 2.282-2.218 (d, 24H, -CH3). 13C NMR (DMSO-
d6, ppm): δ 190.0, 164.9, 112.9, 112.0, 23.8, 23.2.
Synthesis of Li[Eu(dmpymt)4] (4). A similar reaction of
dmpymtH (0.387 g, 2.764 mmol) with [(Me3Si)2N]3Eu( μ-Cl)Li-
(THF)3 (0.808 g, 0.908 mmol) in THF followed by a workup
similar to that used in the isolation of 1 afforded colorless
crystals of 4. Yield: 0.461 g (71% based on Eu). Anal. Calcd
for C24H28LiN8EuS4: C, 40.28; H, 3.94; N, 15.66; S, 17.92.
Found: C, 40.56; H, 3.67; N, 15.35; S, 17.75. IR (KBr disk): 3058
(m), 2967 (m), 2931 (m), 1634 (w), 1578 (s), 1539 (s), 1428 (m),
1385 (m), 1343 (s), 1256 (s), 1025 (w), 989 (w), 957 (w), 887 (m),
761 (w) cm-1. Satisfactory 1H NMR and 13C NMR spectra of 4
were not obtained.
2.0 mmol). The resulting mixture was stirred at room tempera-
ture for 12 h. After the reaction was complete, the reaction
mixture was hydrolyzed by water (1 mL), extracted with diethyl
ether (3 ꢀ 10 mL), dried over anhydrous MgSO4, and filtered.
The solvent was removed under reduced pressure. The final
products were further purified by recrystallization from THF
and toluene. Compound 521 was isolated colorless crystals. Mp:
234.5-235.3 °C (lit.21 mp 234-235 °C). 1H NMR (CDCl3, ppm): δ
7.363-7.330 (m, 8H, aromatic CH), 7.157-7.1380 (m, 2H, aro-
matic CH), 6.509 (s, 2H, NH); 13C NMR (CDCl3, ppm) δ 148.7,
134.1, 131.5, 128.2, 127.3. HRMS (EI) m/z: calcd. for C13H12N2O
212.0950; Found: 212.0951.
Compound 6:22 white solid. Mp: 231.6-232.4 °C (lit.22 mp
1
229-230 °C). H NMR (CDCl3, ppm): δ 4.076-4.045 (d, 2H,
NH), 3.501-3.488 (m, 2H, CH), 2.012-1.922 (m, 4H, CH2),
1.719-1.612 (m, 8H, CH2), 1.410-1.295 (m, 4H, CH2),
1.160-1.036 (m, 4H, CH2). 13C NMR (CDCl3, ppm): δ 156.9,
49.4, 35.7, 25.8, 25.2. HRMS (EI): m/z calcd for C13H24N2O
224.1889, found 224.1889.
Compound 7:22 white solid. Mp: 167.9-168.6 °C (lit.22 mp
169-170 °C). 1H NMR (CDCl3, ppm): δ 7.319-7.227 (m, 10H,
aromatic CH), 4.870 (s, 2H, NH), 4.338 (s, 4H, CH2). 13C NMR
(CDCl3, ppm): δ 158.8, 139.3, 128.9, 127.6, 127.5, 44.8. HRMS
(EI): m/z calcd for C15H16N2O 240.1263, found 240.1263.
Compound 8:23 white solid. Mp: 237.5-238.6 °C (lit.23 mp
238.4 °C). 1H NMR (CDCl3, ppm): δ 7.266-7.262 (d, 2H,
aromatic CH), 7.245-7.239 (d, 2H, aromatic CH), 7.171-7.167
(d, 2H, aromatic CH), 7.145-7.139 (d, 2H, aromatic CH), 6.774
(s, 2H, NH), 2.938-2.822 (m, 2H, CH), 1.233-1.210 (d, 12H,
CH3). 13C NMR (CDCl3, ppm): δ 154.1, 145.3, 135.7, 127.4, 121.9,
33.8, 24.2. HRMS (EI): m/z calcd for C19H24N2O 296.1889, found
296.1888.
(21) Franz, R. A.; Applegath, F.; Morriss, F. V.; Baiocchi, F.; Bolze,
C. J. Org. Chem. 1961, 26, 3311.
(22) (a) Franz, R. A.; Morriss, F. V.; Baiocchi, F. J. Org. Chem. 1961,
26, 3306. (b) Emma, A.; Lacopo, D.; Rita, F.; Claudio, M. Synthesis 2007,
3497.
(23) Takumi, M.; Masatoshi, M.; Toshiyuki, I.; Takatoshi, I.;
Yoshio, I. Synthesis 2006, 2825.
General Procedure for the Synthesis of Substituted Ureas
Catalyzed by Li[Ln(dmpymt)4] (5 as an Example). A 30 mL
Schlenk tube under dried argon was charged with 1 (0.014 g,
0.020 mmol), MeCN (10 mL), and phenyl isocyanate (0.2387 g,

214 Organometallics, Vol. 30, No. 2, 2011
Li et al.
Compound 9:22 white solid. Mp: 91.4-92.8 °C (lit.22 mp 96.8-
97.5 °C). 1H NMR (CDCl3, ppm): δ 5.926-5.815 (m, 2H),
5.328-5.089 (m, 4H), 4.611 (s, 2H, NH), 3.825-3.799 (m, 4H).
13C NMR (CDCl3, ppm): δ 153.2, 137.3, 115.1, 44.9, 34.4. HRMS
(EI): m/z calcd for C7H12N2O 140.0960, found 140.0965.
1, 3, and 4, the solvent-accessible void occupies a volume of
3
192.3, 179.0, and 181.5 A , respectively, and may be filled with
˚
highly disordered MeCN solvents. Since disorder models did
not give satisfactory results, the solvent contribution to the
scattering factors have been taken into account with PLA-
TON/SQUEEZE.26 A total of 20 (1), 18 (3), and 10 (4) electrons
were found in each unit cell, corresponding to 0.45 MeCN (1),
0.40 MeCN (3), and 0.22 MeCN (4) molecules per cell. While
relevant, the crystal data reported in this paper do not include
the contribution of the disordered solvent molecules. All non-
hydrogen atoms were refined anisotropically. All non-hydrogen
atoms were placed in geometrically idealized positions (C-H =
Synthesis of S-4,6-Dimethylpyrimidin-2-yl Ester 10. To a solu-
tion of dmpymtH (0.2208 g, 1.577 mmol) in MeCN (10 mL) was
added a solution of [(Me3Si)2N]3Pr( μ-Cl)Li(THF)3 (0.4621 g,
0.525 mmol) in THF (20 mL). The reaction mixture was stirred
overnight. The solution turned light yellow with a large amount
of light yellow precipitate. At ambient temperature, a solution of
PhNCO (0.1916 g, 1.610 mmol) in MeCN (10 mL) was added to
the mixture and the suspension gradually. The resulting mixture
was stirred for 12 h, and then the solution was concentrated to
dryness in vacuo. The resulting solid was extracted with toluene
(20 mL) and then filtered. The filtrate was kept at -18 °C for 2
days, and colorless crystals of 10 were formed. Yield: 1.80 g
(59%). Anal. Calcd for C13H13N3OS: C, 60.21; H, 5.05; N,
16.20; S, 12.37. Found: C, 60.07; H, 4.97; N, 16.33; S, 12.65. IR
(KBr disk): 3454 (s), 1710 (s), 1652 (m), 1594 (w), 1491 (m), 1414
(s), 1220 (w), 1073 (w), 1028 (w), 754 (m), 689 (m), 590 (m), 506
(w) cm-1. 1H NMR (400 MHz, ppm, C6D6): 7.791 (s, 2H, -Ph),
7.312 (s, 2H, -Ph), 7.042 (s, 1H, -Ph), 6.921 (s, 1H, -CH), 6.03
(s, 1H, -NH), 2.364 (s, 6H, -CH3).
˚
˚
0.98 A for methyl groups, C-H = 0.99 A for methylene groups,
˚
or C-H = 0.95 A for phenyl groups) and constrained to ride on
their parent atoms with Uiso(H) = 1.2[Ueq(C)], or Uiso(H) =
1.5[Ueq(C)] for methyl groups. All the calculations were per-
formed on a Dell workstation using the CrystalStructure crys-
tallographic software package (Rigaku and MSC, Version 3.60,
2004). A summary of the important crystallographic informa-
tion for 1, 3, 4, and 10 is given in Table 4.
Acknowledgment. This work was supported by the
National Nature Science Foundation of China (Nos.
20871088, 20871038, and 90922018), the Nature Science
Key Basic Research of Jiangsu Province for Higher
Education (09KJA150002), the NSF of the Education
Committee of Jiangsu Province (No. 07KJD150182), the
State Key Laboratory of Organometallic Chemistry
of Shanghai Institute of Organic Chemistry (08-25), the
Qin-Lan Project of Jiangsu Province, and the SooChow
Scholar Program and Program for Innovative Research
Team of Suzhou University. We highly appreciate the
careful comments and suggestions of the reviewers and
the editor.
X-ray Crystallography. All measurements were made on a
Rigaku Mercury CCD X-ray diffractometer (3 kV, sealed tube)
by using graphite-monochromated Mo KR radiation (λ =
˚
0.710 73 A). Single crystals of 1, 3, 4, and 10 were obtained
directly from the above preparations. Single crystals of 1, 3, and
4 were mounted on a glass capillary and cooled in a liquid
nitrogen stream at 193 K, while that of 10 was placed at the top
of a glass fiber at 293 K. Diffraction data were collected in a ω
mode with a detector to crystal distance of 35 mm. The collected
data were reduced by using the program CrystalClear (Rigaku
and MSC, Version 1.3, 2001), and an absorption correction
(multiscan) was applied. The reflection data were also corrected
for Lorentz and polarization effects.
The crystal structures of 1, 3, 4, and 10 were solved by direct
Supporting Information Available: CIF files giving crystal-
lographic data for 1, 3, 4, and 10 and figures and tables giving
crystallographic data and a view of the molecular structure for 8
and the 1H NMR and 13C NMR spectra of 1-3 and dmpymtH.
This material is available free of charge via the Internet at http://
pubs.acs.org.
methods24 and refined by full-matrix least squares on F2.25 For
(24) Sheldrick, G. M. SHELXS-97: Program for the Solution of
€
€
Crystal Structure; University of Gottingen, Gottingen, Germany, 1997.
(25) Beurskens, P. T.; Admiral, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. PATTY:
The DIRDIF Program System; Technical Report of the Crystallography
Laboratory, University of Nijmegen, Nijmegen, The Netherlands, 1992.
(26) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.