Cyclic tetramers of a five-membered palladacycle based on a head-to-tail-linked isocyanate dimer and their reactivity in cyclotrimerization of isocyanates

Article abstract of DOI:10.1039/c5dt00534e

Reactions of [Pd(styrene)(PR₃)₂], generated from trans-[PdEt₂(PR₃)₂] and styrene, with 2 equiv. of benzyl isocyanate in THF at room-temperature afforded unusual cyclic Pd-tetramers of five-membered rings consisting of organic isocyanate dimers and palladium, [Pd(PR₃){-C(O)N(R)C(O)N(R)-}]₄ (PR₃ = PMe₃, 1; PR₃ = PMe₂Ph, 2). Additionally, a cyclic trimer, (RNCO)₃, 3 (R = benzyl) was produced as a catalytic product. Treatment of the cyclic tetramer (1) with 4 equiv. of chelated phosphine, such as (1,2-bis(diethylphosphino)ethane) (DEPE) or (1,2-bis(dimethylphosphino)ethane) (DMPE), readily caused conversion to a metallacyclic cis-form, [Pd{N(R)C(O)N(R)C(O)}(P ～ P)] (P ～ P = DEPE, 4; P ～ P = DMPE, 5) in quantitative yields. In contrast, reactions of Pd(0)-PR₃ with 2 equiv. of Ar-NCO (Ar = Ph, p-tolyl, p-ClC₆H₄) afforded metallacyclic complexes having a dimeric isocyanato moiety, cis-[Pd{C(O)N(Ar)-C(O)N(Ar)}(PR₃)₂] (PR₃ = PMe₃ Ar = C₆H₅, 6; p-MeC₆H₄, 7; p-Cl-C₆H₄, 8; PR₃ = PMe₂Ph, Ar = p-Cl-C₆H₄, 9). Treatment of the palladacyclic complex (8) with an equimolar amount of chelated phosphine such as DEPE readily caused conversion to a palladacyclic cis-form, [Pd{N(Ar)C(O)N(Ar)C(O)}(DEPE)], 10 in quantitative yield. The catalytic cyclotrimerization of benzyl isocyanate to [Pd(styrene)(PMe₃)₂] was achieved by varying the molar ratio of R-NCO (R = benzyl). In addition, catalytic cyclotrimerization was performed from the five-membered palladacyclic complexes or the Pd(0)-PR₃ complex with excess Ar-NCO. This journal is

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Journal Name
RSCPublishing
ARTICLE
Cyclic tetramers of five-membered palladacycle based
on head-to-tail-linked isocyanate dimer and their
reactivity in cyclotrimerization of isocyanates
Cite this: DOI: 10.1039/x0xx00000x
Seon Gye Lee,a Keun-Young Choi,a Yong-Joo Kim,*a SuJin Parkb and Soon W. Leeb
Received 00th January 2012,
Accepted 00th January 2012
DOI: 10.1039/x0xx00000x
Reactions of [Pd(styrene)(PR3)2], generated from trans-[PdEt2(PR3)2] and styrene, with 2 equiv. of
benzyl isocyanate in THF at room-temperature afforded unusual cyclic Pd-tetramers of five-membered
rings consisting of organic isocyanate dimers and palladium, [Pd(PR3){-C(O)N(R)C(O)N(R)-}]4 (PR3 =
PMe3, 1; PR3 = PMe2Ph, 2). Additionally, a cyclic trimer, (RNCO)3, 3 (R = benzyl) was produced as a
catalytic product. Treatment of the cyclic tetramer (1) with 4 equiv. of chelated phosphine, such as (1,2-
bis(diethylphosphino)ethane) (DEPE) or (1,2-bis(dimethylphosphino)ethane) (DMPE), readily caused
conversion to a metallacyclic cis-form, [Pd{N(R)C(O)N(R)C(O)}(P~P)] (P~P = DEPE, 4; P~P = DMPE,
5) in quantitative yields. In contrast, reactions of Pd(0)-PR3 with 2 equiv. of Ar-NCO (Ar = Ph, p-Tolyl,
p-ClC6H4) afforded metallacyclic complexes having a dimeric isocyanato moiety, cis-[Pd{C(O)N(Ar)-
C(O)N(Ar)}(PR3)2] (PR3 = PMe3 Ar = C6H5, 6; p-MeC6H4, 7; p-Cl-C6H4, 8; PR3 = PMe2Ph, Ar = p-Cl-
C6H4, 9). Treatment of the palladacyclic complex (8) with an equimolar amount of chelated phosphine
www.rsc.org/
such
as
DEPE
readily
caused
conversion
to
a
palladacyclic
cis-form,
[Pd{N(Ar)C(O)N(Ar)C(O)}(DEPE)], 10 in quantitative yield. The catalytic cyclotrimerization of benzyl
isocyanate to [Pd(styrene)(PMe3)2] was achieved by varying the molar ratio of R-NCO (R = benzyl). In
addition, catalytic cyclotrimerization was performed from the five-membered palladacyclic complexes or
the Pd(0)-PR3 complex with excess Ar-NCO.
These results strongly indicate that the product formed depends on
the attacking isocyanate or supporting ligand. The reactivities of
Introduction
metallacyclic isocyanato complexes of Ni(II) and Pd(II) with olefins
and CO, and their thermal behaviors in the presence of other organic
isocyanates,
Organic isocyanates have attracted much attention because of their
wide range of applications such as the formation of metallacycles or
organic heterocycles, coupling with organic unsaturated compounds,
and catalytic polymerization.1-19 The cyclotrimerization of
isocyanates to isocyanurate is important, because these products are
of commercial significance, and are used in industry, e.g., in
polymeric processes.20 Some catalytic studies using main group21-24
or rare-earth metal complexes25-28 to produce cyclotrimers of
isocyanates have been reported recently. In particular, several
research groups have shown that organic isocyanates react with
zerovalent group 10 metal complexes (sometimes in the presence of
organic unsaturated compounds)13,14b,17,18 to give metallacycles,
have also been reported.13,14 Although several
transition-metal-catalyzed cyclotrimerization systems for organic
isocyanates are known, a few studies of the structural and chemical
characterization of the metallacyclic intermediates of alkyl or aryl
isocyanates in such reactions have been reported. In particular,
studies of the cyclotrimerization of aliphatic isocyanates are scarce
compared to those of aryl isocyanates and their intermediates.
Among them, Misono and coworkers et. al.12 reported Ni-catalyzed
cyclotrimerization or polymerization of alkyl isocyanates. Paul and
coworkers et. al.14b reported the mechanistic cyclotrimerization of
Ar–NCO in the presence of diimine-based Pd(0) catalysts.
isocyanate
cyclotrimers,
or
organic
heterocycles.
We recently observed that certain organic isothiocyanates
undergo cycloaddition to Pd(II) and Pd(0) complexes to afford
heterocyclic complexes or organic heterocycles.29 The aim of this
study was to extend the scope of such reactions by investigating the
reactivities of the Pd(0) complexes with organic isocyanates. We
treated, bis(phosphine)palladium(0) complexes with alkyl or aryl
isocyanates. Two significant results were observed: (i) the formation
of unexpected cyclic tetramers of a five-membered ring consisting of
an alkyl isocyanate dimer and Pd, and (ii) the cyclotrimerization of
the isocyanates to isocyanurates.
______________________________________________
a Department of Chemistry, Kangnung-Wonju National University,
Gangneung 210-702, Republic of Korea. E-mail: yjkim@ kangnung.ac.kr
Tel: + 82 + 33-640-2308; fax: + 82 + 33-640-2264
b Department of Chemistry, Sungkyunkwan University, Suwon 440-746,
Republic of Korea
† Electronic Supplementary Information (ESI) available: CCDC. 1037603
- 1037605. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c000000x/.
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of the two ketone oxygen atoms (O2) coordinates with the Pd in the
adjacent asymmetric unit, and this type of coordination ultimately
Results and discussion
The room-temperature reactions of 2 equiv. of benzyl isocyanate
with [Pd(styrene)(PR3)2], generated from trans-[PdEt2(PR3)2] and
(A)
styrene,
gave
the
cyclic
tetramers,
[Pd(PR3){C(O)N(R′)C(O)N(R′)}]4, (PR3 = PMe3, PMe2Ph; R′ =
benzyl), 1 and 2 in 51 and 40 % yields, respectively (Scheme 1). The
cyclic isocyanurate 3 was also isolated in 48–56% yield by
extracting the reaction products with excess diethyl ether. The yields
for compounds 1–3 were all calculated on the basis of R–NCO.
Complexes 1 and 2 are white solids and are slightly soluble in
common organic solvents. Single crystals of 1 were obtained from
dichloromethane/diethyl ether, and its molecular structure was
determined by X-ray diffraction. Compound 3 was identified using
IR and NMR spectroscopies and GC-MS.
L
R
N
O
O
N
Pd
O
R
L
(B)
N
N
N
Pd
R
R
R
R
O
L
Ph
Et
L
L
R-NCO
O
Pd
L2Pd
Pd
(2 equiv.)
Ph
Et
N
N
R
O
Pd
N
R
O
O
L
(R = benzyl) L = PMe3, 1
L = PMe2Ph, 2
+
R
R
O
N
O
N
N
O
R
3
Scheme 1
Fig. 1. (a) Molecular structure of complex 1·2(CH2Cl2) (30%
probability displacement ellipsoids). The lattice dichloromethane
molecules are omitted for clarity. Labeled atoms (A, B, C) are
related to unlabeled ones by a crystallographic four-fold rotation–
inversion axis. (b) Corresponding molecular structure without benzyl
fragments.
The IR spectra of the complexes display characteristic CO stretching
bands at 1653 and 1582 cm−1. In the 1H NMR spectrum of 1, the four
methylene protons (CH2Ph) on the two benzyl groups in the
[Pd(PR3){C(O)N(R′)C(O)N(R′)}] unit are magnetically inequivalent,
and appear at 6.72, 4.71, 3.96, and 2.80 ppm with separate geminal
couplings. One pair of low-field signals (6.72 and 4.71 ppm; JHH
=
creates a cyclic tetrameric structure. The four Pd atoms are not
coplanar; two of them lie above and the other two lie below the
molecular plane. For simplicity, the structure without the four benzyl
groups is shown in Fig. 1b.
16.8 Hz) may arise from the methylene protons in the exo N-benzyl
substituents between two ketone groups. Another pair of high-field
signals (3.96 and 2.80 ppm; JHH = 15.6 Hz) is assigned to
methylene protons in the endo benzyl group near the Pd center.
We investigated the chemical properties of complex 1 by
performing ligand replacement with chelating phosphines. When an
equimolar amount of 1,2-bis(diethylphosphino)ethane (DEPE) was
added to a dichloromethane suspension of 1, a mixture of a Pd(II)
chelate, [Pd(DEPE){–N(R)C(O)N(R)C(O)–}] (R = benzyl) (4), as
the major product, starting material, and an unidentified compound
was obtained. However, when excess DEPE (4 equiv.) was added,
the reaction mixture rapidly turned to a colorless solution. We finally
isolated a pure complex [Pd(DEPE){–N(R)C(O)N(R)C(O)–}] (R =
benzyl) (4) in 94% yield, and it was characterized using
spectroscopy and X-ray diffraction (Scheme 2). The corresponding
reaction with excess 1,2-bis(dimethylphosphino)ethane (DMPE) also
Complex
2
shows a pattern similar to that of complex
1. The
1H–1H COSY spectrum of
1
clearly illustrates correlation
signals for the low-field (6.72 and 4.71 ppm) and high-field
(3.96 and 2.80 ppm) pairs, and this confirms the diastereotopic
benzylic proton splittings.30,31 It should be mentioned that the
signal at 6.72 ppm appears as a double doublet (J = 16.8 Hz).
At present, it is difficult to assign these doublets because the
correlation between the hydrogen in question and the PMe3
ligand is not evident. A singlet in the 31P{1H} NMR spectrum
clearly demonstrates the magnetic equivalence of all four PMe3
ligands for complex
structure (Fig. 1a). Elemental analysis and MS (ESI-TOF) data
for and further support the proposed tetrameric structures.
The molecular structure of complex 1·2(CH2Cl2) is presented in
1, which is consistent with the molecular
afforded
a
metallacyclic Pd(II) complex, [Pd(DMPE){–
1
2
N(R)C(O)N(R)C(O)–}] (R = benzyl) (5), in 40% yield. The singlet
in the 31P{1H} NMR spectrum of complex 1 clearly changes to two
doublets as a result of the two inequivalent phosphorus atoms in
complexes 4 and 5. The molecular structure of 4 is shown in Fig. 2,
Fig. 1. It comprises an asymmetric unit, namely a five-membered
palladacycle, consisting of a Pd atom and an isocyanate dimer. One
2 | J. Name., 2012, 00, 1-3
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and is one of two crystallographically independent molecules. The the
expected
metallacyclic
complexes
cis-[Pd(PR3)2{–
Pd(II) atom is a member of a pentagonal palladacycle, the same as in N(Ar)C(O)N(Ar)C(O)–}] (PR3 = PMe3, PMe2Ph; 6–9 in Scheme 3)
the asymmetric unit in complex 1. The structures of complexes 1 and in moderate to good yields; the complexes were characterized using
4 strongly indicate that each of the four units in complex 1 reacts spectroscopic and elemental analyses. The room-temperature 31P{1H}
with 4 equiv. of each of the chelating bis(phosphine) ligands to form NMR spectra of the metallacyclic complexes 6–8 exhibit two
1
complex 4.
singlets without P-P coupling. However, the PMe3 region in the H-
NMR spectra of the complexes has two doublets, because of the
magnetic inequivalence of the two phosphorus atoms.
R
N
When the temperatures of the NMR samples of complexes 6–8
are lowered to −20 °C, the 31P-NMR spectra display two doublets as
expected, because of the two inequivalent phosphorus atoms. These
results indicate that the metallacyclic complexes containing the more
basic PMe3 ligand are more flexible than the metallacyclic complex
9, containing the PMe2Ph ligand. We also examined phosphine-
ligand exchange with a chelating phosphine (eq. 2 in Scheme 3), and
the Pd(II) chelate complex 10 was obtained in quantitative yield.
O
R
P
P
P ~ P
Pd
1
N
( 4 equiv.)
O
DEPE, 4
DMPE, 5
Scheme 2
Fig. 3. ORTEP diagram of complex 10·CH2Cl2, with displacement
ellipsoids for atoms show a 40% probability level.
Fig. 2. ORTEP diagram of complex 4, which is one of two
chemically equivalent, crystallographically independent molecules
showing the atom-labeling scheme and 50% probability thermal
ellipsoids.
Table 1. Selected bond lengths (Å) and bond angles (º)
1
4
10
Although we could not isolate the five-membered palladacyclic
intermediate cis-[Pd(PR3)2{–N(R)C(O)N(R)C(O)–}] (Scheme 1),
complex 1 could be formed in three steps: (1) the formation of a
palladacyclic intermediate, (2) dissociation of one phosphine, and (3)
ketone oxygen coordination to the Pd atom in the adjacent
asymmetric unit. Several attempts to isolate five-membered
palladacyclic complexes using various alkyl isocyanates, e. g., ethyl
and isopropyl isocyanate, failed. We then tried to prepare such
complexes using aryl isocyanates. The reactions of [Pd(styrene)L2]
with 2 equiv. of ArNCO (Ar = Ph, p-tolyl, p-chlorophenyl) afforded
Distances
Pd1–C4
Pd1–N2
Pd1–O2A
O1–C4
O2–C12
N2–C12
N1–C12
1.951(3)
2.058(2)
2.123(2)
1.219(3)
1.251(3)
1.317(3)
1.408(3)
Pd1–C1
Pd1–N2
Pd1–P2
Pd1–P1
O1–C1
O2–C2
N1–C1
N1–C2
N2–C2
2.042(4)
2.060(3)
2.246(1)
2.349(1)
1.225(5)
1.229(5)
1.365(5)
1.435(5)
1.327(5)
Pd1–C1
Pd1–N2
Pd1–P1
Pd1–P2
O1–C1
O2–C2
N1–C1
N1–C2
N2–C2
2.032(3)
2.056(2)
2.246(7)
2.354 (7)
1.220(3)
1.230(3)
1.400(3)
1.416(3)
1.340(3)
Angles
C4–Pd1–N2
81.67(9)
C1–Pd1–N2 80.2(2)
C1–Pd1–N2 80.55(10)
C4–Pd1–O2A 177.49(10) N2–Pd1–P2
172.5(1)
176.6(1)
85.28(5)
120.0(3)
121.6(4)
120.7(4)
127.9(4)
118.9(4)
113.2(3)
C1–Pd1–P1
N2–Pd1–P1
N2–Pd1–P2
P1–Pd1–P2
C1–N1–C2
C1–N1–C3
O2–C2–N2
O2–C2–N1
N2–C2–N1
91.97(8)
172.1(6)
101.65(6)
85.63(3)
120.0(2)
120.4(2)
127.7(2)
119.2(2)
113.1(2)
N2–Pd1–P1
172.51(6)
C1–Pd1–P1
P2–Pd1–P1
C1–N1–C2
C1–N1–C3
O1–C1–N1
O2–C2–N2
O2–C2–N1
N2–C2–N1
O2#1–Pd1–P1 90.44(6)
C12–O2–Pd1B 135.9(2)
C12–N2–C13 119.6(2)
C12–N2–Pd1 113.4(2)
C4–N1–C12 119.6(2)
O1–C4–Pd1
129.4(2)
Symmetry transformations used to generate equivalent atoms: A = y
+ 1, −x + 1, −z + 2; B = −y + 1, x − 1, −z + 2; C = −x + 1, −y, z.
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The molecular structure of complex 10 is shown in Fig. 3; the Pd
atom is coordinated to a chelating phosphine (DEPE) and an
isocyanate dimer. Selected bond lengths and angles are listed in
Table 1. The Pd-N bond lengths of the dimeric isocyanate rings for 1,
4, and 10 in Table 1, are slightly longer than the known value
(1.996(3) Å)14a of (o-phenanthrolene)[{C(O)N(Ar)-C(O)N(Ar)}].
The Pd-C bond lengths are longer (for 4 and 10) or shorter (for 1)
than that of the complex (1.963(4) Å). These results indicate strong
or weak trans influences due to the trans-positioned phosphorous or
oxygen atoms coordinated to the Pd center.
We investigated the catalytic cyclotrimerization of the isocyanate
in Scheme 1 by systematically varying the molar ratio of R–NCO (R
= benzyl) to [Pd(styrene)(PMe3)2]. Fig. 4 shows a plot of the yields
for complex 1 and the cyclic trimer (benzyl isocyanurate) as a
function of the number of molar equivalents of isocyanate. The
yields were determined based on NMR integration of the benzylic
protons in the final isolated mixture of complex 1 and the cyclic
trimer. As the amount of R–NCO increases from 1 to 3 equiv., the
amount of tetramer 1 decreases significantly, whereas the amount of
the cyclic trimer increases. However, for more than 3 equiv. of R–
NCO, both of the yields increase slightly; i.e., the cyclic trimer is the
sole product in this range. The use of 3 equiv. of R–NCO is therefore
suitable for the catalytic cyclotrimerization of organic isocyanates.
In addition, this result indicates that an increase in the amount of
benzyl isocyanate facilitates catalytic cyclotrimerization.
Paul and coworkers14b proposed Pd-catalyzed cyclotrimerization
of Ar–NCO and their mechanisms involving metallacyclic or
zwitterionic pathways.32 Our results in this study can be similarly
explained by the two pathway. The first is π-coordination of excess
R-NCO (R = benzyl or aryl) with Pd(styrene)L2 to give the Pd(0)
intermediate, Pd(R-NCO)L2, and then subsequent addition of R-
NCO affords a five-membered palladacycle. Finally, the seven-
membered palladacycle by cycloaddition of R-NCO causes the
cyclotrimerization of R-NCO including the Pd(0) intermediate via
reductive elimination. The second pathway involves the formation of
a zwitterionic intermediate, [Pd+{C(O)N-R}L2], followed by the
nucleophilic attack of the incoming R-NCO to afford a zwitterionic
Pd complex having a linearly dimeric isocyanate moiety or a five-
membered palladacycle. Then, a nucleophilic attack of R-NCO
affords a linearly zwitterionic trimer of R-NCO or a seven-
membered palladacycle, and finally causes cyclotrimerization via
reductive elimination. As shown in Scheme 4, the higher catalytic
yields of the cyclic trimer using the Pd(0) complex rather than the
metallacyclic complex suggests a tentative zwitterionic pathway,
which is considered one of the active oligomerization processes.
During our experiments using Pd(0) compounds, the reactions of
Scheme 1 and 4 liberated styrenes, which prohibited further
characterization of possible species. Presently, we cannot provide a
detailed explanation for the reaction mechanism.
Fig. 4 Plots of yields of complex 1 and cyclic trimer as a function of
R–NCO concentration; the y-axis shows the relative percentage
yields, and the x-axis shows molar equivalents of isocyanate.
We examined the possibility that complex 1 is an intermediate in the
isocyanate cyclotrimerization. When complex 1 was treated with
excess benzyl isocyanate (4 equiv.), no organic product was
observed. This result strongly indicates that complex 1 is not a
genuine intermediate in the isocyanate cyclotrimerization. We
performed the reactions with excess Ar–NCO (Ar = p-MeC6H4 or p-
ClC6H4; Scheme 4a and 4b) to investigate whether the cyclic trimers
of aryl isocyanates are formed from five-membered metallacyclic
complexes or Pd(0)-PR3 complexes.
When a reaction mixture containing compound 7 or 9 was
treated with 6 equiv. of Ar–NCO in dichloromethane at room
temperature for 2 h, a cyclic trimer (Ar–NCO)3 was formed in 39%
or 43% yield, respectively and some starting material was recovered
(Scheme 4a). In contrast, the corresponding reactions of the Pd(0)-
PR3 complexes, [PdL2(styrene)], with excess Ar–NCO afforded
cyclic trimers (75% or 90% yield, respectively) and the metallacyclic
complexes (Scheme 4b). The above results show that Pd(0)-PR3
complexes give higher yields than their corresponding metallacyclic
complexes.
Conclusions
In summary, we observed the formation of novel tetrameric
Pd(II) complexes linked by five-membered metallacycles based
on an organic (alkyl) isocyanate dimer, and the simultaneous
cyclotrimerization of the isocyanate. The reactions of aryl
isocyanates with the Pd(0)-PR3 complexes, [PdL2(styrene)],
afforded single five-membered palladacycles. In addition, the
single palladacycles and Pd(0)-PR3 complexes catalytically
cyclotrimerized aryl isocyanates. In particular, it is generally
known that the cyclic trimerization of aliphatic isocyanates is
more difficult to achieve than that of aromatic isocyanates. The
reason may be explained by considering the unstable catalytic
intermediate (metallacyclic or zwitterionic complexes) during
the catalytic cyclotrimerzation of aliphatic isocyanate,
compared with than that of aryl isocyanate. However, we have
demonstrated the cyclic trimerization using alkyl isocyanate
with a unique alkyl moiety such as the benzyl group. This is a
rare example of cyclic trimerization of alkyl isocyanate
mediated by a Pd catalyst.
4 | J. Name., 2012, 00, 1-3
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Synthesis of 4 and 5.
Experimental
General information. All manipulations of air-sensitive
DEPE (24 ꢀL, 0.10 mmol) was added to a CH2Cl2 (4 mL)
solution containing 1 (0.090 g, 0.05 mmol) at room temperature. The
initial white suspension slowly turned to a homogeneous colorless
solution. After stirring for 2 h at room temperature, the solvent was
completely removed under vacuum, and then the resulting residue
washed with hexane (2 mL × 3) to obtain the crude solids.
Recrystallization from CH2Cl2/n-hexane afforded white crystals of
[Pd(DEPE){C(O)N(R)-C(O)N(R)}], (R = benzyl) (4, 0.109 g, 94%).
IR (KBr/cm–1): 1636, 1589 (CO). Anal. Calc. for C26H38N2O2P2Pd
compounds were performed under N2 or Ar by Schlenk-line
techniques. Solvents were distilled from Na–benzophenone. The
analytical laboratories at Basic Science Institute of Korea and at
Kangnung-Wonju National University carried out elemental
analyses. IR spectra were recorded on a Perkin Elmer BX
spectrophotometer. NMR (1H, 13C{1H}, and 31P{1H}) spectra were
obtained in CDCl3 on a JEOL Lamda 300, ECA 600 MHz
spectrometer. Chemical shifts were referenced to internal Me4Si and
to external 85% H3PO4. X-ray reflection data were obtained at either
the Korea Basic Science Institute (Seoul Center) and the Cooperative
Center for Research Facilities at Sungkyunkwan University.
Complexes trans-[PdEt2L2] (L = PMe3 and PMe2Ph) were prepared
by the literature method.33
(578.96): C, 53.94; H, 6.61; N, 4.84. Found: C, 53.91; H, 6.69; N,
1
4.81. H NMR:
0.85-0.96 (m, 6H, P(CH2CH3)2), 1.08–1.27 (m,
10H, P(CH2CH3)2), 1.59–1.58 (m, 6H, P(CH2CH3)2), 2.10–2.26 (m,
2H, P(CH2CH3)2), 4.73 (s), 4.88 (d, J = 2.4 Hz, 2H, CH2), 7.10–7.18
(m, 2H, Ar), 7.22–7.32 (m, 6H, Ar), 7.41–7.44 (m, 2H, Ar). 13C{1H}
NMR: 9.40 (d, JP–C = 24 Hz, P(CH2CH3)2), 17.9 (d, JP–C = 16 Hz,
Synthesis of 1, 2 and 3.
P(CH2CH3)2), 18.0 (d, JP–C = 30 Hz, P(CH2CH3)2), 22.5 (dd, JP–C
=
15, 27 Hz, PCH2), 23.2 (dd, JP–C = 13, 24 Hz, PCH2), 45.0 (s), 54.4
(s), 125.9, 126.2, 126.4, 128.1, 128.3, 128.4, 140.6, 143.9, 167.0
(CO), 188.9 (dd, JP-C = 13, 148 Hz, CO). 31P{1H} NMR: 36.5 (d, J
= 29 Hz), 58.4 (d, J = 29 Hz).
Styrene (302 ꢀL, 2.63 mmol) and tetrahydrofuran (THF, 4 mL)
were added sequentially to a Schlenk flask containing trans-
[PdEt2(PMe3)2] (0.417 g, 1.32 mmol) at 0 °C. The mixture was
heated at 55 °C for 30 min to give a pale yellow solution. Benzyl
Isocyanate (325 ꢀL, 2.63 mmol) was added to the mixture at room
temperature, and then the yellow solution turned into a yellow
suspension. After stirring for 2 h at room temperature, the volatiles
were completely removed under vacuum, and then the remaining
residue was washed with n-hexane (2 mL × 3) to obtain yellow
solids. The crude solids under ice bath were extracted with excess
CH2Cl2 (1 ml x 3) to afford white solids of 1. The extracts were
evaporated under vacuum, and then the remaining residues were
extracted with THF ( 2 ml x 3) to afford again white solids of 1. The
collected white solids were recrystallized from CH2Cl2/n-hexane to
afford pure product of 1(0.302 g, 51%). The final extracts were
evaporated to afford crude organic products which were extracted
again with excess diethyl ether to give white solids of 3 (0.170 g,
48%). Complex 1: IR (KBr/cm–1): 1653, 1589 (CO). Anal. Calc. for
C76H92N8O8P4Pd4 (1795.17): C, 50.85; H, 5.17; N, 6.24. Found: C,
[Pd(DMPE){C(O)N(R)-C(O)N(R)}], (R = benzyl) (5, 61%) was
analogously prepared. IR (KBr/cm–1): 1638, 1579 (CO). Anal. Calc.
for C22H30N2O2P2Pd (522.85): C, 50.54; H, 5.78; N, 5.36. Found: C,
50.03; H, 5.65; N, 4.97. 1H NMR:
0.83 (d, 6H, J = 8.1 Hz,
P(CH3)2), 1.49–1.72 (m, 10H, P(CH3)2), 4.71 (s), 4.91 (s), 7.12–7.43
(m, 10H, Ar). 13C{1H} NMR:
11.3 (d, JP–C = 17 Hz, P(CH3)2),
12.8 (d, JP–C = 30 Hz, P(CH3)2), 26.5 (dd, JP–C = 15, 31 Hz, PCH2),
23.2 (dd, JP–C = 12, 29 Hz, PCH2), 45.0 (s), 53.8 (s), 66.0, 126.1,
126.3, 126.7, 128.0, 128.2, 128.4, 140.5, 143.6, 166.8 (CO), 188.4
(dd, JP-C = 13, 155 Hz, CO). 31P{1H} NMR: 9.05 (d, J = 26 Hz),
29.6 (d, J = 29 Hz).
Synthesis of cis-[Pd{C(O)N(Ar)-C(O)N(Ar)}(PR3)2] (Ar = C6H5,
p-MeC6H4, p-Cl-C6H4), 6-9.
1
50.71; H, 5.20; N, 6.16. H NMR ( 300 MHz in CDCl3): 0.84 (d,
Styrene (229 ꢀL, 2.0 mmol) and tetrahydrofuran (THF, 3 mL)
were added sequentially to a Schlenk flask containing trans-
[PdEt2(PMe3)2] (0.317 g, 1.0 mmol) at 0 °C. The mixture was heated
at 55 °C for 30 min to give a pale yellow solution. Phenyl isocyanate
(218 ꢀL, 2.0 mmol) was added to the mixture at room temperature,
and then the yellow solution turned into a white suspension. After
stirring for 2 h at room temperature, the solvent was completely
removed under vacuum, and then the resulting residue washed with
hexane (2 mL × 3) to obtain the crude solids. Recrystallization from
36H, J = 11 Hz, P(CH3)3), 2.80 (d, 4H, J = 15.6 Hz, CH2), 3.96 (d,
4H, J = 15.6 Hz, CH2), 4.71 (br d, 4H, J = 16.2 Hz, CH2), 6.72 (dd,
4H, J = 16.8 Hz, CH2), 6.98–7.48 (m, 40H, Ph). 13C{1H} NMR (75
MHz):
13.3 (d, JP–C = 30 Hz, P(CH3)3), 46.2 (s, CH2), 125.7,
126.0, 126.1, 126.6, 128.1, 128.3, 140.0, 142.3, 165.0 (C=O). Other
CO signal was not detected due to weak intensity. 31P{1H} NMR
(120 MHz): –4.36 (s). TOF-MS(ES+): calcd for [M+H]+: 1793.2206;
found: 1793.2110.
Complex 2 was analogously prepared. 2 (40 %): IR (KBr/cm–1):
1654, 1589 (CO). Anal. Calc. for C96H100N8O8P4Pd4 (2043.45): C,
56.43; H, 4.93; N, 5.48. Found: C, 56.17; H, 5.02; N, 5.68. 1H NMR:
0.65 (d, 12H, J = 10 Hz, P(CH3)2Ph), 1.49 (d, 12H, J = 9.9 Hz,
P(CH3)2Ph), 2.56 (d, 4H, J = 15.9 Hz, CH2), 3.83 (d, 4H, J = 15.9
Hz, CH2), 4.76 (br d, 4H, J = 15.9 Hz, CH2), 6.46 (dd, 4H, J = 8.4,
16.5 Hz, CH2), 6.91–7.29 (m, 60H, Ph). 13C{1H} NMR: 11.6 (s,
P(CH3)2Ph), 11.8 (s, P(CH3)2Ph), 12.1 (s, P(CH3)2Ph), 12.4 (s,
P(CH3)2Ph), 43.8 (s, CH2), 49.2 (s, CH2), 126.1, 126.2, 126.7, 128.0,
128.3, 128.5, 129.1, 130.7, 135.7, 136.3, 140.2, 142.0, 165.3 (C=O),
172.3 (d, JC-P = 7.4 Hz, CO). 31P{1H} NMR: 1.92 (s). TOF-MS(ES+)
: calcd for [M+H]+ : 2041.2831; found: 2041.2408.
CH2Cl2/n-hexane
afforded
white
crystals
of
cis-
[Pd(PMe3)2{C(O)N(Ph)-C(O)N(Ph)}] (6, 0.459 g, 92%). IR
(KBr/cm–1): 1655, 1602 (CO). Anal. Calc. for C20H28N2O2P2Pd
(496.82): C, 48.35; H, 5.68; N, 5.64. Found: C, 48.57; H, 5.72; N,
5.58. 1H NMR: 0.93 (d, 9H, J = 7.3 Hz, P(CH3)3), 1.57 (d, 9H,
J = 9.9 Hz, P(CH3)3), 6.96–7.01 (m, 2H, Ar), 7.17–7.38 (m, 8H, Ar).
13C{1H} NMR: 15.3 (d, JP–C = 19 Hz, P(CH3)3), 16.6 (d, JP–C = 30
Hz, P(CH3)3), 123.0, 126.5, 127.2, 127.8, 128.1, 138.6, 138.9, 151.7,
163.1 (CO), 183.5 (d, JC-P = 159 Hz, CO). 31P{1H} NMR (240
MHz at –20℃): –27.7 (d, JP-C = 26 Hz), –6.10 (d, JP-C = 30 Hz).
Complexes
7-9
were
analogously
prepared.
Cis-
[Pd(PMe3)2{C(O)N(Ar)-C(O)N(Ar)}] (Ar = p-MeC6H4) (7, 92%).
IR (KBr/cm–1): 1655, 1618 (CO). Anal. Calc. for C22H32N2O2P2Pd
(524.87): C, 50.34; H, 6.15; N, 5.33. Found: C, 50.39; H, 6.15; N,
5.36. 1H NMR: 0.94 (d, 9H, J = 7.4 Hz, P(CH3)3), 1.56 (d, 9H,
J = 9.8 Hz, P(CH3)3), 2.27 (s, 3H, CH3), 2.29 (s, 3H, CH3), 6.98–
7.26 (m, 8H, Ar). 13C{1H} NMR: 15.4 (d, JP–C = 19 Hz, P(CH3)3),
Compound 3 was isolated in 48-56 % yield. Compound 3: IR
(KBr/cm–1): 1688 (CO). Anal. Calc. for C24H21N3O3 (399.44): C,
1
72.16; H, 5.3; N, 10.52. Found: C, 72.24; H, 5.39; N, 10.12. H
NMR:
5.03 (s, 6H, CH2), 7.28–7.34 (m, 6H, Ph), 7.43–7.46 (m,
9H, Ph). 13C{1H} NMR: 46.3 (s, CH2), 128.2, 128.6, 129.1, 135.7,
149.1 (s, CO). MS (m/e): 399 (M+).
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

Dalton Transactions
Page 6 of 9
VJieowuArrtnicalelONnlainme e
ARTICLE
DOI: 10.1039/C5DT00534E
16.7 (d, JP–C = 30 Hz, P(CH3)3), 20.9 (s, CH3), 21.1 (s, CH3), 126.9, and then the resulting residue washed with hexane (2 mL × 3) to
127.0, 128.3, 128.9, 132.4, 136.1, 136.4, 149.1, 163.4 (CO), 183.7 obtain the crude solids. The crude solids were extracted with excess
(d, JC-P = 159 Hz, CO). 31P{1H} NMR (240 MHz at –20℃): –27.7
diethyl ether to afford white residues. The collected extracts were
evaporated under vacuum to give crude organic products. The
remaining residues were recrystallized from THF/n-hexane to afford
the complex 7 (0.092 g, 71 %). The organic products were purified
by chromatography over celite, eluting with ethyl acetate/hexane
(1:3).
(d, JP-C = 26 Hz), –6.43 (d, JP-C = 23 Hz).
Cis-[Pd(PMe3)2{C(O)N(Ar)-C(O)N(Ar)}] (Ar = p-ClC6H4) (8,
97 %). IR (KBr/cm–1): 1660, 1613 (CO). Anal. Calc. for
C20H26N2O2P2Cl2Pd (565.76): C, 42.46; H, 4.63; N, 4.95. Found: C,
42.78; H, 4.73; N, 4.50. 1H NMR:
0.99 (d, 9H, J = 7.8 Hz,
1.58 (d, 9H, J = 9.3 Hz, P(CH3)3), 7.16–7.32 (m, 8H,
Compound 11 was obtained as white solids (39 %). IR (KBr/cm–
1): 1706 (CO). Anal. Calc. for C24H21N3O3 (399.44): C, 72.16; H,
5.30; N, 10.52. Found: C, 71.53; H, 5.37; N, 10.41. 1H NMR: 2.38
(s, 9H, CH3), 7.04–7.29 (m, 12H, Ph). 13C{1H} NMR: 21.4 (s, CH3),
128.2, 131.4,139.5, 149.1 (CO). MS (m/e): 399 (M+).
P(CH3)3),
Ar). 13C{1H} NMR: 15.4 (d, JP–C = 19 Hz, P(CH3)3), 16.6 (d, JP–C
= 31 Hz, P(CH3)3), 127.9, 128.2, 128.3, 128.4, 123.0, 132.3, 137.1,
150.2, 162.9 (CO), 183.5 (d, JC-P = 160 Hz, CO). 31P{1H} NMR (240
MHz at –20℃): –27.9 (d, JP-C = 26 Hz), –5.47 (d, JP-C = 26 Hz).
Cis-[Pd(PMe2Ph)2{C(O)N(Ar)-C(O)N(Ar)}] (Ar = p-ClC6H4) (9,
85 %). IR (KBr/cm–1): 1664, 1615 (CO). Anal. Calc. for
C30H30N2O2P2Cl2Pd (618.94): C, 52.23; H, 4.38; N, 4.06. Found: C,
Analogous reaction of complex 9 of with p-chlorophenyl
isocyanate afforded a mixture of compound 12 (43 %) and complex
9 (87 %). Compound 12: IR (KBr/cm–1): 1709 (CO). Anal. Calc. for
C21H12N3O3Cl3 (460.71): C, 54.75; H, 2.63; N, 9.12. Found: C,
52.51; H, 4.57; N, 3.98. 1H NMR:
0.68 (d, 2H, J = 8 Hz,
54.50; H, 2.51; N, 8.98. 1H NMR:
7.10–7.61 (m, 12H, Ph).
129.9, 131.9,135.8, 148.3 (CO). MS (m/e): 459
P(CH3)2Ph), 1.58 (d, 6H, J = 10 Hz, P(CH3)2Ph), 7.11–7.37 (m, 18H,
Ar). 13C{1H} NMR: 12.8 (d, JP–C = 18 Hz, P(CH3)2Ph), 14.4 (d,
JP–C = 31 Hz, P(CH3)2Ph), 128.0, 128.5, 128.6, 128.8, 129.0, 130.1,
130.2, 130.5, 130.6, 130.8, 132.6, 135.6, 135.7, 136.2, 137.5, 150.1,
163.2 (CO), 181.8 (CO). 31P{1H} NMR : -19.04 (d, J = 40 Hz), 3.05
(d, J = 42 Hz).
13C{1H} NMR:
(M+).
Table 2. Crystallographic data for complexes
1
,
4
, and 10.
4
10
1
Synthesis of 10
C78H96C14
N8O8P4Pd4
C26H38N2
O2P2Pd
C25H34Cl4
N2O2P2Pd
Empirical formula
DEPE (71 ꢀL, 0.30 mmol) was added to a CH2Cl2 (3 mL)
solution containing 8 (0.149 g, 0.30 mmol) at room temperature.
After stirring the reaction mixture for 2 h at room temperature, the
solvent was completely removed under vacuum, and then the
resulting residue washed with hexane (2 mL × 3) to obtain the crude
solids. Recrystallization from CH2Cl2/diethyl ether afforded white
crystals of [Pd(DEPE){C(O)N(Ar)-C(O)N(Ar)}], (Ar = p-ClC6H4)
(10, 0.170 g, 91%). IR (KBr/cm–1): 1654, 1608 (CO). Anal. Calc. for
C24H32N2O2P2Cl2Pd (619.80): C, 46.51; H, 5.20; N, 4.52. Found: C,
Formula weight
Temperature, K
Crystal system
Space group
a, Å
1964.91
200(2)
578.92
200(2)
704.68
200(2)
monoclinic
P21/n
tetragonal
ꢀ
I4
monoclinic
P21/n
15.1307(6)
15.1307(6)
19.1938(15)
90
19.3654(8)
14.0152(6)
21.2584(9)
90
13.1299(9)
11.2538(8)
20.6433(14)
90
b, Å
c, Å
α, (º)
46.35; H, 5.22; N, 4.02.
1H NMR:
0.86-1.3 (m, 15H,
β, (º)
90
21.2584(9)
90
99.048(2)
90
P(CH2CH3)2), 1.61–1.88 (m, 8H, P(CH2CH3)2), 2.16–2.27 (m, 1H,
P(CH2CH3)2), 2.28 (s), 7.00–7.16 (m, 8H, Ar). 13C{1H} NMR:
9.51 (d, JP–C = 14 Hz, P(CH2CH3)2), 17.0 (d, JP–C = 17 Hz,
P(CH2CH3)2), 18.1 (d, JP–C = 29 Hz, P(CH2CH3)2), 21.2 (d, JP–C = 14
Hz, PCH2), 22.7 (s), 25.8 (s), 127.2, 127.3, 128.7, 128.9, 132.7,
135.8, 136.1, 136.3, 164.6, 174.2 (CO). 31P{1H} NMR: 38.8 (d, J =
29 Hz), 58.2 (d, J = 31 Hz).
γ, (º)
V, Å3
90
4394.2(4)
2
110.422(1)
8
3012.3(4)
4
Z
dcal, g cm–3
ꢀ, mm–1
F(000)
1.485
1.422
1.554
1.054
0.830
1.103
1992
2400
1432
Tmax
0.8664
0.6371
1.90–28.30
0.9676
0.8132
2.04–28.29
0.8790
0.7404
1.99–28.30
Tmin
Monitoring for tetranuclear Pd(II) complex and
cyclotrimerization of the isocyanate
q range (º)
No. of reflns collected
16059
38568
21550
In a typical run, benzyl isocyanate (one equiv.) was added to a
THF (3 ml) solution containing Pd(styrene)(PMe3)2 (0.145g, 0.46
mmol) at room temperature and the reaction mixture was stirred for
2 h. The product ratio of cyclic trimer (benzyl isocyanate) and the
tetranuclear complexes was confirmed from 1H-NMR intergration of
benzylic regions (CH2Ph) between the complex, 1 and cyclic trimer
of the isocyanate, 3.
No. ofreflnsindependent
5359
13151
7352
No. of reflns
4433
8462
5087
with I > 2σ(I)
No. of parameters
240
595
325
Analogous reactions with 2, 3, 4, 6, and 8 equiv. of the
isocyanate were carried out.
Max., in ꢀ
Min., in ꢀ
ρ
ρ
(e Å–3)
(e Å–3)
0.551
−0.622
1.792
−1.128
0.794
−1.142
Absolute structure
parameter
Reactions of metallacyclic Pd(II) complexes with excess aryl
isocyanate
-0.03(2)
1.080
1.078
1.002
GOF on F2
Ra
wR2b
0.0213
0.0472
0.0483
0.1272
0.0314
0.0647
p-Tolyl isocyanate (185 ꢀl, 1.47 mmol) was added to a CH2Cl2
(3 mL) solution containing 7 (0.128 g, 0.24 mmol) at room
temperature. After stirring the reaction mixture for 2 h at room
temperature, the solvent was completely removed under vacuum,
aR = ∑[|Fo| − |Fc|]/∑|Fo|], bwR2 = {∑[w(Fo2 − Fc )2]/∑[w(Fo )2]}1/2
2
2
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 7 of 9
Journal Name
Dalton Transactions
View ArticAle ROnTliInCeLE
DOI: 10.1039/C5DT00534E
Reactions of Pd0-PR3 with excess aryl isocyanate
6
7
G. P. Mitchell and T. D. Tilly, J. Am. Chem. Soc., 1997, 119, 11236.
O. Blacque, H. Brunner, M. M. Kubicki, J.-C. Leblanc, W. Meier, C.
Moise, Y. Mugnier, A. Sadorge, J. Wachter and M. Zabel, J. Organomet.
Chem., 2001, 634, 47.
Styrene (60 ꢀL, 0.53 mmol) and tetrahydrofuran (THF, 3 mL)
were added sequentially to a Schlenk flask containing trans-
[PdEt2(PMe2Ph)2] (0.116 g, 0.263 mmol) at 0 °C. The mixture was
heated at 55 °C for 30 min to give a pale yellow solution. p-
Chlorophenyl isocyanate (202 ꢀL, 1.58 mmol) was added to the
mixture at room temperature. After stirring for 2 h at room
temperature, the volatiles were completely removed under vacuum,
and then the remaining residue was washed with n-hexane (2 mL ×
3) to obtain pale yellow solids. The crude solids were extracted with
excess diethyl ether to afford white residues. The collected extracts
were evaporated under vacuum to give crude organic products. The
remaining residues were recrystallized from THF/n-hexane to afford
the complex 9 (0.085 g, 52%). The organic products were purified
by chromatography over celite, eluting with ethyl acetate/hexane
(1:3). The collected organic products recrystallized from CH2Cl2/n-
hexane at room temperature to afford white crystals of 12 (0.145 g,
90%).
8
9
Y. Li, H. Matsumura, M. Yamanaka and T. Takahashi, Tetrahedron
2004, 60, 1393.
,
T. Kondo, M. Nomura, Y. Ura, K. Wada and T. Mitsudo,
Tetrahedron Lett., 2006, 47, 7107.
10 R. B. Moerno, Ph. D. Thesis, Chapter 1, Univ. College London,
2010.
11 T. E. Patten and B. M. Novak, Macromolecules,1996, 29, 5882.
12 T. Kashiwagi, M. Hidai, Y. Uchida and A. Misono, J. Poly. Sci. Part
C, Poly. Lett., 1970,
8, 173.
13 Ni: (a) H. Hoberg and J. Korff, J. Organomet. Chem., 1978, 150
,
C20; (b) H. Hoberg, B. W. Oster, C. Krüger and Y. H. Tsay, J.
Organomet. Chem., 1983, 252, 365; (c) H, Hoberg, K. Sümmermann
and A. Milchereit, J. Organomet. Chem., 1985, 288, 237; (d) H.
Hoberg, K. Sümmermann and A. Milchereit, Angew. Chem., Int.Ed.
Analogous reaction of Pd(styrene)(PMe3)2 of with p-tolyl
isocyanate afforded a mixture of compound 11 (75%) and complex 7
(33%).
Engl., 1985, 24, 325; (e) H. Hoberg and E. Hernandez, J. Chem. Soc.,
Chem. Commun., 1986, 544. (f) H. Hoberg and E. Hernandez, J.
Organomet. Chem., 1986, 311, 307; (g) E. Hernandez and H.
Hoberg, J. Organomet. Chem., 1987, 328, 403; (h) H. Hoberg, K.
Sümmermann, E. Hernandez, C. Ruppin and D. Guhl, J. Organomet.
Chem., 1988, 344, C35; (i) H. Hoberg, J. Organomet. Chem., 1988,
358, 507; (j) H. Hoberg and D. Guhl, D. J. Organomet. Chem., 1990,
384, C43.
Crystallography.
Single crystals of 1, 4, and 10 for X-ray crystallography were
grown from CH2Cl2/ n-hexane at −35 °C. All X-ray data were
collected at 200(2) K with the use of a Bruker Smart diffractometer
equipped with a Mo X-ray tube. Collected data were corrected for
absorption with SADABS based upon the Laue symmetry by using
equivalent reflections.34 All calculations were carried out with
SHELXTL programs.35 All structures were solved by direct
methods. Unless otherwise stated, all non-hydrogen atoms were
refined anisotropically. All hydrogen atoms were generated in ideal
positions and refined in a riding mode.
14 Pd: (a) F. Paul, J. Fischer, P. Ochsenbein and J. A. Osborn, Angew.
Chem., Int.Ed. Engl. 1993, 32,1638; (b) F. Paul, S. Moulin, O.
Piechaczyk, P. Le Floch and J. A. Osborn, J. Am. Chem. Soc., 2007,
129, 7294; (c) F. Paul, J. Fischer, P. Ochsenbein and J. A. Osborn, C.
R. Chimie, 2002,
5
, 267; (d) F. Paul, Coord. Chem. Rev., 2000, 203
,
Details of crystal data, intensity collection, and refinement
details are given in Table 2.
269; (e) S. Moulin, O. Pellerin, L. Toupet and F. Paul, C. R. Chimie
2014, 17, 521.
,
15 (a) C. Larksarp and H. Alper, J. Am. Chem. Soc., 1997, 119, 3709; (b)
H. –B. Zhou and H. Alper, J. Org. Chem., 2003, 68, 3439.
Acknowledgements
16 K. D. Schleicher and T. F. Jamison, Org. Lett., 2007, 9, 875.
This work was supported by the Basic Science Research
Program through the National Research Foundation of Korea (NRF)
funded by the Ministry of Education, Science and Technology
(Grant No. 2012R1A1B3001569).
17 S. Hasegawa, K. Itoh and Y. Ishii, Inorg. Chem., 1974, 13, 2675.
18 W. Beck, W. Rieber, S. Canini, F. Porta and G. La Monica, J. C. S.
Dalton, 1973, 298.
19 G. R. Owen, R. Vilar, A. J. P. White and D. J. Williams,
Organometallics, 2003, 22, 4511.
20 Z. Wirpsza, Polyurethanes: Chemistry, Technologyand Application
;
Notes and references
Ellis Horwood: London, 1993.
21 Main group metals: A. Hermán-Gómez, T. D. Bradley, A. R.
Kennedy, Z. Livingstone, S. D. Robertson and E. Hevia, Chem.
Commum., 2013, 49, 8659.
1
2
3
See review: (a) P. Braunstein and D. Nobel, Chem. Rev., 1989, 89
,
1927; (b) S. Cenini and G. Monica, Inorg. Chim. Acta, 1976, 18, 279.
C. P. Casey, R. A. Widenhoefer, and R. K. Hayashi, Organometallics
1995, 34, 1138.
,
22 (a) Q. Liu, Z. Guo, H. Han, H. Tong and X. Wei, Polyhedron, 2015,
85, 15; (b) Z. Guo, S. Wang, H. Tong, J. Chao and X. Wei, Inorg.
Chem. Commun., 2013, 33, 68.
(a) A. E. Guiducci, C. L. Boyd and P. Mountford, Organometallics
,
2006, 25, 1167; (b) S. C. Dunn, N. Hazari, A. R. Cowley, J. C. Green
and P. Mountford, Organometallics, 2006, 25, 1755.
23 (a) S. R. Foley, G. P. A. Yap and D. S. Richeson, Organometallics
,
1999, 18, 4700; (b) S. R. Foley, Y. Zhou, G. P. A. Yap and D. S.
Richeson, Inorg. Chem., 2000, 39, 924.
4
5
H. Wang, H.-S. Chan, J. Okuda and Z. Xie, Organometallics, 2005, 24,
3118.
24 B. Srinvias, C.-C. Chang, C.-H. Chen, M. Y. Chang, I.-T. Chen, Y.
Wan and G.-H. Lee, Dalton Trans., 1997, 957.
(a) J. A. Tunge, C. J. Czerwinski, D. A. Gately, and J. R. Noton,
Organometallics, 2001, 20, 254; (b) D. A. Gately, J. R. Norton and P. A.
Goodson, J. Am. Chem. Soc., 1995, 117, 986.
25 Rare earth metals: Y. Sun, Z. Zhang, X. Wang, X. Li, L. Weng and X.
Zhou, Organometallics, 2009, 28, 6320.
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 7

Dalton Transactions
Page 8 of 9
ARTICLE
VJieowuArrtnicalelONnlainme e
DOI: 10.1039/C5DT00534E
26 X. Zhu, J. Fan, Y. Wu, S. Wang, L. Zhang, G. Yang, Y. Wei, C. Yin,
H. Zhu, S. Wu and H. Zhang, Organometallics, 2009, 28, 3882.
27 W. Yi, J. Zhang, L. Hong, Z. Chen and X. Zhou, Organometallics
2011, 30, 5809.
,
28 H.-M. Wang, H.-X. Li, X.-Y. Yu, Z.-G. Ren and J.-P. Lang,
Tetrahedron, 2011, 67, 1530.
29 (a) Y.-J. Kim, J.-T. Han, S. Kang, W. S. Han and S. W. Lee, Dalton
Trans., 2003, 3357; (b) Y.-J. Kim, X. Chang, J.-T. Han, M. S. Lim and
S. W. Lee, Dalton Trans., 2004, 3699; (c) Y.-J. Kim, H.-T. Jeon, K.-Y.
Lee and S. W. Lee, J. Organomet. Chem., 2010, 695, 2258.
30 K. Matsumoto, T. Uchida, H. Lida, N. Hayashi and R. A. Bulman,
Heterocl. Commun., 2007, 13, 263.
31 D. R. Brown, J. McKena and J. M. McKennam, J. Chem. Soc. (B), 1967,
1195
32 (a) J.-S. Tang and J. G. Verkade, Angew. Chem., Int. Ed. Engl., 1993,
32, 896; (b) J.-S. Tang and J. G. Verkade, J. Org. Chem., 1994, 59, 4931.
33 (a) F. Ozawa, T. Ito and A. Yamamoto, J. Am. Chem. Soc., 1980, 102,
6457; (b) Y.-J. Kim, K. Osakada, A. Takenaka and A. Yamamoto, J.
Am. Chem. Soc., 1990, 112, 1096.
34 G. M. Sheldrick, SADABS, Program for Absorption Correction,
University of Göttingen,
35 Bruker, SHELXTL, Structure Determination Software Programs, Bruker
Analytical X-ray Instruments Inc., Madison, Wisconsin, USA, 1997.
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

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Table of contents
Cyclic tetramers of five-membered palladacycle based on head-to-tail-
linked isocyanate dimer and their reactivity in cyclotrimerization of
isocyanates
Seon Gye Lee, Keun-Young Choi, Yong-Joo Kim,* SuJin Park and Soon W. Lee
Cyclic tetramers of five-membered palladacycle involving isocyanate dimer were prepared, and the catalytic
cyclotrimerization from palladium zero-compound or single palladacycle with organic isocyanates was performed.