Synthesis of amidate-hanging platinum mononuclear complexes by base hydrolysis of nitrile complexes

Article abstract of DOI:10.1016/j.ica.2006.12.036

The "amidate-hanging" Pt mononuclear complexes, which can easily bind a second metal ion with the non-coordinated oxygen atoms in the amidate moieties, have been synthesized and characterized by ¹H NMR, MS, IR spectroscopy, and single crystal X

Full text of DOI:10.1016/j.ica.2006.12.036

Inorganica Chimica Acta 360 (2007) 2623–2630
www.elsevier.com/locate/ica
Synthesis of amidate-hanging platinum mononuclear complexes by
base hydrolysis of nitrile complexes
1
2
*
ˆ
Kazuhiro Uemura , Kana Yamasaki, Koichi Fukui , Kazuko Matsumoto
Department of Chemistry, School of Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo 169-8555, Japan
Received 29 October 2006; received in revised form 23 December 2006; accepted 28 December 2006
Available online 9 January 2007
Abstract
The ‘‘amidate-hanging’’ Pt mononuclear complexes, which can easily bind a second metal ion with the non-coordinated oxygen atoms
1
in the amidate moieties, have been synthesized and characterized by H NMR, MS, IR spectroscopy, and single crystal X-ray analysis.
Five new complexes with various amidate ligands and co-ligands, cis-[Pt(PVM)2(en)] Æ 4H2O (1, PVM = pivaloamidate, en = ethylenedi-
t
amine), cis-[Pt(PVM)2(NH2CH3)2] Æ H2O (2), cis-[Pt(PVM)2(NH2 Bu)2] (3), cis-[Pt(TCM)2(NH3)2] (4, TCM = trichloroacetamidate), and
cis-[Pt(BZM)2(NH3)2] (5, BZM = benzamidate), were successfully synthesized by direct base hydrolysis of the corresponding Pt nitrile
complexes, cis-[Pt(NCR)2(Am)2]2+ (P1, P2, P3, and P5) (NCR = nitrile, Am = amine). These nitrile complexes were obtained by intro-
ducing nitriles into the Pt aqua complexes, cis-[Pt(OH2)2(Am)2](ClO4)2, whereas introduction of trichloronitrile into [Pt(OH2)2(NH3)2]-
(ClO4)2 induced more facilitated water nucleophilic attack to afford [Pt(TCM)(NH(C@OH)CCl3)(NH3)2](ClO4) (P4). The base
treatments of the precursor complexes (P1–5) lead to produce ‘‘amidate-hanging’’ Pt mononuclear complexes (1–5) without geometry
isomerization. The 195Pt chemical shifts for 1–5 exhibit subtle differences of the Pt electron densities among them.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Platinum complexes; Amidate; Nitrile; Base hydrolysis; Crystal structures
1. Introduction
(Amid = amidate, Am = amine) have been synthesized
and characterized up to date [4–10]. Such hetero-nuclear
complexes have been expected for the unique oxidation
states and redox properties due to the metal–metal interac-
tion. For example, our previously reported hetero-nuclear
The occupied dz2 orbital in the d8 transition metal ion
with square-planar coordination geometry can act as a
donor to another metal ion (M) to form a dative Pt(d8) ! M
bond, where the Pt dz2 orbital is stabilized by overlap with
the dz2 orbital on M [1–3]. By utilizing such dative bonds,
a large number of amidate-bridged Pt–M dinuclear and
Pt–M–Pt trinuclear complexes of the formula [(Am)2Pt-
M(Amid)2]n+ and [(Am)2Pt(Amid)2M(Amid)2Pt(Am)2]m+
1-D
chain
({[PtRh(PVM)2(NH3)2Cl2.5]2[Pt2(PVM)2-
(NH3)4]2(PF6)6 Æ 2MeOH Æ 2H2O}n), which comprises ami-
date-bridged Pt–Rh and Pt–Pt dinuclear complexes, showed
the unprecedented phenomena that an unpaired electron
hops among Rh atoms through the linear Pt units [11,12].
In order for rational synthesis of Pt and hetero-metal
multinuclear linear complexes, ‘‘amidate-hanging’’ Pt
mononuclear complexes [Pt(Amid)2(Am)2] are suitable
starting materials, since they can easily bind a second metal
ion with the non-coordinated oxygen atoms in the amidate
moieties (Scheme 1) [7,13]. Such complexes were prepared
by utilizing the direct base hydrolysis of the corresponding
cis Pt nitrile complexes [14–20]. In the procedure, no geom-
etry isomerization took place during the hydrolysis,
*
Corresponding author. Present address: 3-9-12-105, Daizawa, Seta-
gaya-ku, Tokyo 155-0032, Japan. Tel./fax: +81 3 3413 5352.
E-mail address: kmatsu@yf6.so-net.ne.jp (K. Matsumoto).
Present address: Environmental Science and Engineering, Graduate
1
School of Science and Engineering, Yamaguchi University, Tokiwadai 2-
16-1, Ube-shi, Yamaguchi 755-8611, Japan.
2
Present address: Graduate School of Life Science and Systems
Engineering, Kyushu Institute of Technology, Hibikino 2-4, Wakama-
tsu-ku, Kitakyushu 808-0196, Japan.
0020-1693/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.12.036

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K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
CAUTION: The following preparations use AgClO4,
which is potentially explosive.
2.2. Synthesis of cis-[Pt(PVM)2(en)] Æ 4H2O (1)
An aqueous solution (40 mL) of cis-[Pt(en)I2] (9.7 mmol,
4.94 g), which was prepared according to the reported pro-
cedure [21], was stirred with 2 equiv. of AgClO4 Æ H2O
(19.4 mmol, 4.37 g) for 20 h in the dark, and AgI was then
removed by filtration. The yellow filtrate was stirred with
2 equiv. of pivalonitrile (19.4 mmol, 2.12 mL) for 1 day.
The resulting white powder, cis-[Pt(NCCMe3)2(en)](ClO4)2
(P1), was recrystallized by diffusing 2.0 equiv. NaOH solid
to the aqueous (10 mL) solution, to obtain white powder
(1). Yield 33%. Elemental Anal. Calc. for C12H36N4O6Pt:
C, 27.32; H, 6.88; N, 10.62. Found: C, 27.97; H, 5.91; N,
10.71%.
Scheme 1.
although the isomerization is known to occur at high tem-
perature. The final amidate-hanging complex is readily
obtainable in a pure form without further procedure to
remove large excess of free amide ligand released during
the reaction. In the early studies [14–20], those direct
hydrolysis reaction on Pt complexes have been thoroughly
investigated, however, systematic synthetic reports of the
‘‘amidate-hanging’’ Pt mononuclear complexes were only
a few. Herein we report a systematic synthetic method
for novel five ‘‘amidate-hanging’’ Pt mononuclear com-
plexes, cis-[Pt(PVM)2(en)] Æ 4H2O (1), cis-[Pt(PVM)2(NH2
2.3. Synthesis of cis-[Pt(PVM)2(NH2CH3)2] Æ H2O (2)
cis-[Pt(NH2CH3)2Cl2] was obtained according to the
procedure for analogous compounds [16]. An aqueous
solution (50 mL) of cis-[Pt(NH2CH3)2Cl2] (13.0 mmol,
4.26 g) was stirred with 2 equiv. of AgClO4 Æ H2O
(26.0 mmol, 5.86 g) for 19 h in the dark, and AgCl was then
removed by filtration. The colorless filtrate was stirred with
2 equiv. of pivalonitrile (26.0 mmol, 2.84 mL) for 2 days.
The resulting white powder, cis-[Pt(NCCMe3)2(NH2CH3)2]
(ClO4)2 (P2), was recrystallized by diffusing 2.0 equiv.
NaOH to the aqueous (20 mL) solution, to obtain white
powder (2). Yield 52%. Elemental Anal. Calc. for
C12H32N4O3Pt: C, 30.31; H, 6.78; N, 11.78. Found: C,
30.52; H, 6.17; N, 11.71%.
t
CH3)2] Æ H2O (2), cis-[Pt(PVM)2(NH2 Bu)2] (3), cis-[Pt-
(TCM)2(NH3)2] (4), and cis-[Pt(BZM)2(NH3)2] (5) (Scheme
2), which could be useful for the synthesis of Pt and hetero-
metal multinuclear chain complexes. Discussion on the
crystal packing of the compounds related to 1–5 and the
results of the 195Pt NMR spectroscopy of 1–5 are also
included.
2. Experimental
2.1. Materials
t
2.4. Synthesis of cis-[Pt(PVM)2(NH2 Bu)2] (3)
Pivalonitrile and trichloroacetonitrile were obtained
An aqueous solution (4 mL) of K2PtCl4 (1.0 mmol,
0.42 g) was stirred with 4 equiv. of KI (4.0 mmol, 0.66 g)
for 15 min at 40 °C, and then 2 equiv. 30 w% NH2 Bu
(2.0 mmol, 0.49 g) was added. After stirring for 20 min at
from Tokyo Kasei Industrial Co. AgClO4 Æ H2O, NH2CH3,
and NH2 Bu were obtained from Kanto Chemical
Co. NaOH and benzonitrile were obtained from Wako
Co. K2PtCl4 was obtained from Tanaka Kikinzoku Co.
t
t
Scheme 2.

K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
2625
40°C, yellow powder was obtained. An aqueous solution
(4 mL) of the yellow powder (0.60 g) was stirred with
AgClO4 Æ H2O (2.0 mmol, 0.45 g) for 20 h in the dark,
and AgCl was then removed by filtration. The colorless
filtrate was stirred with pivalonitrile (2.0 mmol, 0.22 mL)
for 3 h. The resulting white powder, cis-[Pt(NCCMe3)2-
applied by using SADABS [23]. All the structures were solved
by the direct method with the subsequent difference Fou-
rier syntheses and the refinement with the SHELXTL (version
5.1) software package [24]. The crystal data and the details
of the structure determinations are summarized in Table 1.
For all compounds, the non-hydrogen atoms were refined
anisotropically and all hydrogen atoms were placed in the
ideal positions. In 1, highly disordered H2O molecules
(O5–12), C1–3, C11, C13, and C18 atoms were refined iso-
tropically. In 40, N2 and C3 atoms were refined isotropi-
cally. In P5, benzene rings (C2–7 and C9–14) were
isotropically refined under rigid condition. In 5, C9 atom
was refined isotropically.
t
(NH2 Bu)2](ClO4)2 (P3), was recrystallized by diffusing
2.0 equiv. NaOH to the aqueous (2 mL) solution, to obtain
white powder (3). Yield 15%. Elemental Anal. Calc. for
C18H42N4O2Pt: C, 39.92; H, 7.82; N, 10.34. Found: C,
39.86; H, 7.81; N, 10.18%. For single crystal X-ray analy-
t
sis, cis-[Pt(PVM)2(NH2 Bu)2] Æ MeOH (30) was obtained
by the recrystallization in MeOH solution.
2.5. Synthesis of cis-[Pt(TCM)2(NH3)2] (4)
3. Results and discussion
An aqueous solution (16 mL) of cis-[Pt(NH3)2Cl2]
(4.0 mmol, 1.20 g) was stirred with 2 equiv. of
AgClO4 Æ H2O (8.0 mmol, 1.80 g) for 18 h in the dark,
and AgCl was then removed by filtration. The colorless fil-
trate was dried up and dissolved in 4.5 mL MeOH, and
stirred with 2 equiv. of trichloroacetonitrile (8.0 mmol,
0.92 mL) for 14 h. The resulting white suspension was dried
up to obtain the white product, [Pt(TCM)(NH(C@OH)-
CCl3)(NH3)2](ClO4) (P4). The product was recrystallized
by diffusing 2.0 equiv. NaOH to the aqueous (4 mL) solu-
tion of P4, to obtain white powder (4). Yield 55%. Elemen-
tal Anal. Calc. for C4H8Cl6N4O2Pt: C, 8.70; H, 1.46; N,
10.15. Found: C, 8.78; H, 1.57; N, 9.81%. For single crystal
X-ray analysis, cis-[Pt(TCM)2(NH3)2] Æ MeOH (40) was
obtained by the recrystallization in MeOH solution.
3.1. Synthesis, products, and 195Pt NMR
Compounds 1–5 were obtained by direct base hydrolysis
of the corresponding nitrile complexes as shown in Scheme
3. As mentioned in Section 2, the aqueous solutions of [Pt(O-
t
H2)2(Am)2](ClO4)2 (Am = NH3, NH2CH3, NH2 Bu,
(Am)2 = en) were obtained by the removal of halogen ions
from cis-[PtX2(Am)2] (X = Clꢀ, Iꢀ) with silver salts. Nitriles
were successfully introduced into [Pt(OH2)2(Am)2](ClO4)2 in
H2O to obtain white powders, cis-[Pt(NCCMe3)2(en)]-
(ClO4)2 (P1), cis-[Pt(NCCMe3)2(NH2CH3)2](ClO4)2 (P2),
t
cis-[Pt(NCCMe3)2(NH2 Bu)2](ClO4)2 (P3), and cis-
[Pt(NCPh)2(NH3)2](ClO4)2 (P5) as the precursor complexes
for 1, 2, 3, and 5, respectively. On the other hand, the reaction
of [Pt(OH2)2(NH3)2](ClO4)2 and 2 equiv. trichloroacetonit-
rile in H2O lead to the dinuclear complex,
[Pt2(TCM)2(NH3)4](ClO4)2, since the N„C moiety in tri-
chloroacetonitrile more easily undergoes water nucleophilic
attack than other nitriles [25]. In MeOH, this dimerization
did not occur, and the mononuclear complex with mixed-
ligands, [Pt(TCM)(NH(C@OH)CCl3)(NH3)2](ClO4) (P4),
was obtained as white powder.
2.6. Synthesis of cis-[Pt(BZM)2(NH3)2] (5)
An aqueous solution (8 mL) of cis-[Pt(NH3)2Cl2]
(4.0 mmol, 1.20 g) was stirred with 2 equiv. of
AgClO4 Æ H2O (8.0 mmol, 1.80 g) for 30 h in the dark,
and AgCl was then removed by filtration. The colorless fil-
trate was stirred with 2 equiv. of benzonitrile (8.0 mmol,
0.82 mL) for 1 day. The resulting white powder, cis-
[Pt(NCPh)2(NH3)2](ClO4)2 (P5), was recrystallized by dif-
fusing 2.0 equiv. NaOH to the aqueous (20 mL) solution,
to obtain white powder (5). Yield 49%. Elemental Anal.
Calc. for C14H18N4O2Pt: C, 35.82; H, 3.87; N, 11.94.
Found: C, 34.79; H, 3.85; N, 11.42%.
All of the compounds P1–5 were treated by base-hydro-
lysis to give the bisamidate cis-[Pt(HNCOR)2(Am)2] (1:
R = tBu, (Am)2 = en; 2: R = tBu, Am = NH2CH3; 3:
R = tBu, Am = NH2 Bu; 4: R = CCl3, Am = NH3; 5: R
t
1
= Ph, Am = NH3), which were characterized by MS, H
NMR, and IR spectroscopy.3 The IR spectra of 1–5 lack
the CN stretching bands and show clearly the presence of
amide-I bands; 1591 and 1556 (1), 1625 and 1545 (2),
1552 (3), 1662 (4), and 1597 cmꢀ1 (5).
2.7. X-ray structure determination
Subtle differences were observed in the 195Pt NMR data,
showing the differences of the Pt electron densities between
1–5. The 195Pt NMR chemical shifts obtained in MeOD by
using an aqueous solution of K2[PtCl6] as an external ref-
erence are ꢀ2692 (1), ꢀ2593 (2), ꢀ2599 (3), ꢀ2512 (4),
and ꢀ2473 ppm (5) (Fig. 1), which are in the expected
range for Pt(2+) complexes [25,26]. The 195Pt NMR signals
Measurements were carried out on a Bruker SMART
APEX CCD diffractometor equipped with a normal focus
Mo-target X-ray tube (k = 0.71073 A) operated at
2000 W power (50 kV, 40 mA) and a CCD two-dimen-
sional detector. A total of 1315 frames were collected with
a scan width of 0.3° in x with an exposure time of 20 (1), 20
(3), 20 (P4), 15 (4), 45 (P5), and 35 (5) s/frame. The frames
were integrated with the SAINT software package with a nar-
row frame algorithm [22]. Absorption correction was
˚
MS, 1H NMR, and IR spectra are shown in supplementary material.
3

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K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
Table 1
t
Crystal data and structure refinement of [Pt(PVM)2(en)] Æ 4H2O (1), [Pt(PVM)2(NH2 Bu)2] Æ MeOH (30), [Pt(TCM)(NH(C@OH)CCl3)(NH3)2](ClO4) (P4),
[Pt(TCM)2(NH3)2] Æ MeOH (40), [Pt(NCPh)2(NH3)2](ClO4)2 (P5), and [Pt(BZM)2(NH3)2] (5)
Compound
1
30
P4
40
P5
5
Chemical formula
Formula weight
Crystal system
C24H56N8O12Pt2
1038.95
triclinic
C19H46N4O3Pt
573.69
monoclinic
P21/n
C4H8Cl7N4O6Pt
651.38
monoclinic
P21/n
C5H11Cl6N4O3Pt
582.97
monoclinic
P21/n
C14H16Cl2N4O8Pt
C14H18N4O2Pt
469.41
monoclinic
P21/c
634.30
monoclinic
C2
ꢀ
Space group
P1
Temperature (K)
Unit cell dimensions
120
120
120
120
120
120
˚
a (A)
12.359(5)
13.270(6)
13.980(6)
111.819(7)
99.763(8)
106.139(7)
1946.6(14)
2
11.080(3)
17.501(5)
13.248(4)
90
98.935(5)
90
2537.8(12)
4
1.502
6.1429(12)
35.252(7)
8.1764(16)
90
94.941(3)
90
1764.0(6)
4
2.453
15.234(7)
6.411(3)
17.018(7)
90
92.441(8)
90
1660.6(13)
4
2.332
25.016(6)
8.2083(18)
9.620(2)
90
92.670(4)
90
1973.1(7)
4
2.135
15.933(10)
5.854(4)
16.827(10)
90
94.528(12)
90
1564.7(17)
4
1.993
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dc (g cmꢀ1
l (MoKa) (mmꢀ1
F(000)
)
1.773
7.239
1016
)
5.552
1160
9.041
1220
9.420
1092
7.433
1216
8.977
896
h Range (°)
1.65–27.56
1.103
0.1150, 0.3010
0.1458, 0.3215
1.94–27.57
1.023
0.0416, 0.1005
0.0526, 0.1069
1.16–27.52
1.041
0.0590, 0.1491
0.0779, 0.1608
1.83–27.64
1.020
0.0984, 0.2188
0.1188, 0.2359
1.63–27.51
1.100
0.0462, 0.1191
0.0579, 0.1389
1.28–27.58
1.063
0.0711, 0.1719
0.0967, 0.1959
Goodness-of-fit on F2
R1,a wR2 [I > 2d(I)]
b
R1,a wR2 (all data)
b
P
P
a
R = iFoj ꢀ jFci/ jFoj.
ꢂ
h
i.h
io
1=2
ꢀ
ꢁ
ꢀ
ꢁ
P
P
2
2
b
Rw
¼
w
F 2o ꢀ F 2c
wF 2o
.
Scheme 3.
Fig. 1. 195Pt chemical shifts of 1–5 in MeOH.
were broad, probably due to the coupling of the 195Pt
nuclear spin with the 14N nuclear spins around it [26].
Whereas relatively small variation (<100 ppm) of the
195Pt NMR chemical shift was observed between cis-
[Pt(PVM)2(NH3)2]Æ2H2O, 4, and 5, the change of the chem-
ical shift by substitution of the amine ligands was signifi-
cantly large between cis-[Pt(PVM)2(NH3)2] Æ 2H2O [13]
and 1–3. More electron-donating substitution of R from
H to CH3, and Bu in NH2R induced marked upfield shift
of the platinum signal. The signal in compound 1 was
t

K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
2627
150 ppm more upfield shifted than that in cis-
[Pt(PVM)2(NH3)2] Æ 2H2O. There is no clear suggestion
relating these observations to chemical shift theory, but
the tendency is similar to those observed in cis-
[PtCl2(Am)2] series; cis-[PtCl2(NH3)2] (ꢀ2097 ppm), cis-
[PtCl2(NH2Me)2]
(ꢀ2188 ppm),
cis-[PtCl2(NH2iPr)2]
(ꢀ2224 ppm), cis-[PtCl2(en)] (ꢀ2345 ppm) [27].
3.2. Crystal structures
The single crystals suitable for X-ray analysis, cis-
t
[Pt(PVM)2(en)] Æ 4H2O (1), cis-[Pt(PVM)2(NH2 Bu)2] Æ
MeOH (30), [Pt(TCM)(NH(C@OH)CCl3)(NH3)2](ClO4)
(P4), cis-[Pt(TCM)2(NH3)2] Æ MeOH (40), cis-[Pt(NCPh)2
(NH3)2](ClO4)2 (P5), and cis-[Pt(BZM)2(NH3)2] (5), were
successfully obtained during the above synthesis or by the
recrystallization in MeOH. Selected bond distances found
in 1, 30, P4, 40, P5, and 5 are listed in Table 2. The details
of the molecular structures and the crystal packings will be
shown.
Fig. 2. (a) Crystal structure of [Pt(PVM)2(en)] Æ 4H2O (1). Hydrogen
atoms and water molecules are omitted for clarity. (b) Crystal structure of
1. Four molecules of the mononuclear complex are stabilized by
intermolecular hydrogen bonds to form one-dimensional tetrametallic
units.
3.3. Crystal structures of cis-[Pt(PVM)2(en)] Æ 4H2O (1)
˚
Fig. 2a shows the crystal structure of compound 1.
Compound 1 has two individual mononuclear complexes
in the unit cell. The square-planar coordination geometry
around the Pt atom consists of two cis N atoms of ethy-
lenediamine and two cis N atoms of PVM ligands. The
sum of the four N–Pt–N angles is 360.0° and 360.1°, which
is indicative of their co-planarity. As shown in Table 2, the
C(3)@O(1) (1.28(3) A) and C(8)@O(2) (1.24(4) A) bond
lengths are in agreement with a double-bond character
and sp2 hybridized the C and O atoms. On the other hand,
where Pt–Pt distance is a relatively short (3.95 A). Those
dimeric units are stabilized with four hydrogen bonds
between ethylenediamine and amidate moieties to afford
tetrameric units (Fig. 2b). The tetrameric units are aligned
in a quasi one-dimensional chain without significant inter-
action among them.
˚
˚
3.4. Crystal structures of cis-
t
[Pt(PVM)2(NH2 Bu)2] Æ MeOH (30)
˚
˚
the C(3)–N(3) (1.31(4) A) and C(8)–N(4) (1.30(3) A) are
shorter than expected, indicating a partial double-bond
character. The bond distances and angles are essentially
the same as reported for cis-[Pt(NH3)2(PVM)2] Æ 2H2O
[13]. The crystal is solvated and contains four highly disor-
dered water molecules.
Fig. 3 shows the crystal structure of 30. The Pt atom of 30
is cis coordinated to two NH2 Bu and two PVM ligands
with the Pt–N bond distances similar to 1 (Table 2). The
amidate planes inclines by 39° and 62° with respect to the
Pt coordination plane. Both t-butyl moieties in the NH2 Bu
ligands are located in the upper side of the coordination
plane, whereas those in the PVM ligands are located in
the opposite side. One amidate moiety in the PVM ligand
t
t
An interesting feature of the crystal packing is that two
complex molecules stack in a face-to-face fashion with dou-
ble intermolecular NH (en)–O (amide) hydrogen bonds,
t
is hydrogen bonded to the NH2 Bu ligands (O(amide)
Table 2
0
0
˚
Selected bond distances (A) for 1, 3 , P4, 4 , P5, and 5
Compound
1a
30
P4
40
P5
5
Pt(1)–N(1)
Pt(1)–N(2)
Pt(1)–N(3)
Pt(1)–N(4)
C@O (amide)
2.06(2)
2.01(2)
2.00(2)
1.97(2)
1.28(3)
1.24(4)
1.31(4)
1.30(3)
2.080(4)
2.079(5)
2.009(4)
2.004(5)
1.254(6)
1.260(6)
1.311(7)
1.323(7)
2.056(10)
2.031(10)
2.011(10)
2.039(9)
1.240(14)
1.326(14)
1.291(15)
1.252(14)
2.053(11)
2.030(11)
2.014(12)
1.997(13)
1.212(17)
1.235(17)
1.299(17)
1.316(18)
2.132(13)
2.038(7)
1.881(12)
1.975(8)
2.087(11)
2.072(11)
2.027(11)
2.023(11)
1.287(17)
1.267(16)
1.338(17)
1.316(16)
N–C (amide)
1.160(16)b
1.139(12)b
a
Compound 1 contains two crystallographically independent mononuclear complexes, and other distances are Pt(2)–N(5) = 2.00(2), Pt(2)–
˚
N(6) = 2.07(3), Pt(2)–N(7) = 1.99(2), Pt(2)–N(8) = 2.00(2), C@O (amidate) = 1.27(3) and 1.30(3), and N–C (amidate) = 1.32(4) and 1.32(3) A.
b
N„C distance.

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K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
Fig. 4. (a) Crystal structure of [Pt(TCM)(NH(C@OH)CCl3)(NH3)2]-
(ClO4) (P4). Hydrogen atoms are omitted for clarity. (b) Crystal packing
of P4. Platinum mononuclear complexes are stacked along the c-axis to
afford one-dimensional dipole array attributed to amidate–amidate
hydrogen bonds.
t
Fig. 3. (a) Crystal structure of [Pt(PVM)2(NH2 Bu)2] Æ MeOH (30).
Hydrogen atoms are omitted for clarity. (b) Two mononuclear 30 are
dimerized with four intermolecular hydrogen bonds.
(Fig. 4b). These amidate–amidate hydrogen bonds afford
one-dimensional dipole arrays along the c-axis, forming
dipole columns. The dipole columns are aligned to create
sheets (A and B), in which all dipole arrays are directed
to the same direction. The sheets A and B are juxtaposed
t
˚
–N(NH2 Bu) = 2.87, 2.88 A) in the neighboring molecule,
and another is hydrogen bonded to a MeOH molecule
(O(amide)–O(MeOH) = 2.72 A). Since PVM ligands have
both hydrogen-donor and -acceptor sites, congested hydro-
gen bonding network is formed in this case, and the Pt
mononuclear complexes are dimerized as shown in Fig. 3b.
˚
ꢀ
with the repetition, –A–C–B–B–C–A–, including ClO4
anions (C), and thus the dipole moments are cancelled out.
Fig. 5 shows the crystal structure of 40. The Pt atom of 40 is
also cis coordinated to four N-donor ligands. The C(1)–O(1)
˚
˚
(1.212(17) A) and C(3)–O(2) (1.235(17) A) bond lengths are
in agreement with a double-bond character and sp2 hybrid-
ized C and O atoms. Thus, X-ray analysis also reveals that
base hydrolysis of P4 is completed without the geometry
isomerization. Both amidate planes are perpendicular to
the Pt coordination plane, and the carbonyl moieties are
hydrogen bonded to the neighboring NH3 ligands to form
the one-dimensional column along the b-axis. The columns
are aligned in parallel, and methanol molecules fill the cavi-
ties among the columns as guest molecules.
3.5. Crystal structures of
[Pt(TCM)(NH(C@OH)CCl3)(NH3)2](ClO4) (P4) and
cis-[Pt(TCM)2(NH3)2] Æ MeOH (40)
Fig. 4 shows the crystal structure of P4. The Pt atom of
P4 is also cis coordinated to four N-donor ligands with
similar distances to 1 and 30 (Table 2). Most remarkable
feature of P4 is that it comprises the mixed-ligands,
NH(C@O)CCl3 and NH(C@OH)CCl3. The X-ray analysis
surely exhibits a significant difference among the C@O dis-
tances; C(1)@O(1) = 1.240(14) and C(3)–O(2) = 1.326(14)
ꢀ
˚
3.6. Crystal structures of cis-[Pt(NCPh)2(NH3)2](ClO4)2
(P5) and cis-[Pt(BZM)2(NH3)2] (5)
A. Considering the electronic charge balance to ClO4
anion in the P4 crystal, a H+ ion must exist around the
O(2) atom, although the position was not determined by
X-ray analysis. The Pt mononuclear complexes are stacked
along the c-axis, where amidate–amidate hydrogen bonds
Fig. 6 shows the crystal structures of P5 and 5. In both
P5 and 5, the Pt atom is also cis coordinated to four N-
donor ligands. In P5, the benzonitrile ligands are almost
˚
are effectively formed; N(amidate)–O(amidate) = 2.83 A

K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
2629
Fig. 6. (a) Crystal structure of [Pt(NCPh)2(NH3)2](ClO4)2 (P5). Hydrogen
ꢀ
atoms and ClO4 molecules are omitted for clarity. (b) Crystal structure of
[Pt(BZM)2(NH3)2] (5). Hydrogen atoms are omitted for clarity.
Fig. 5. (a) Crystal structure of [Pt(TCM)2(NH3)2] Æ MeOH (40). Hydrogen
atoms and MeOH molecules are omitted for clarity. (b) Crystal packing of
40. Platinum mononuclear complexes are stacked along the b-axis, where
cavities fulfilled with MeOH molecules are formed.
Pt mononuclear complexes is maintained during the con-
version. The 195Pt NMR measurement showed subtle dif-
ference of the Pt electronic densities between 1–5. Using
amidate-hanging Pt mononuclear complexes described
here, attempts to prepare new hetero-metal chain com-
plexes composed of Pt–M and Pt–M–Pt, are currently in
progress.
linear (N(3)–C(1)–C(2) = 179.9(16)° and N(4)–C(8)–
C(9) = 178.9(16)°) and are bound to the Pt atom through
the electron lone pair on the nitrogen atom with the coor-
dination angles Pt(1)–N(3)–C(1) = 171.7(12)° and Pt(1)–
N(4)–C(8) = 174.1(17)°. Such slightly bent M–N–C moie-
ties are also observed in other metal nitrile complexes
and are attributed to a partial sp2 character of the donor
nitrogen atom [16]. The Pt–N bond lengths are in good
agreement with those in other Pt nitrile complexes.
Acknowledgements
This work was supported by the Iketani Science and
Technology Foundation, Grants-in-Aid for Scientific Re-
search (Young Scientist (B) No. 17750058), and the
21COE program ‘‘Practical Nano-Chemistry’’ from
MEXT, Japan.
Compound 5 is obtained by the base hydrolysis of P5.
ꢀ
No ClO4 anion and water molecule is incorporated in
Appendix A. Supplementary material
the crystal lattice, showing completion of the base hydroly-
˚
sis. As shown in Table 2, the C(1)@O(1) (1.287(17) A) and
˚
CCDC 624151, 624152, 624153, 624154, 624155 and
624156 contain the supplementary crystallographic data
for 1, 30, P4, 40, P5 and 5. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/conts/retriev-
ing.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.ica.2006.
12.036.
C(8)@O(2) (1.267(16) A) bond lengths are in agreement
with a double-bond character and sp2 hybridized C and
O atoms. Amidate planes tilt to both the Pt coordination
planes (28.1° and 33.3°) and benzene rings (29.3° and
26.5°).
In summary, the present work established the synthesis
of five ‘‘amidate-hanging’’ Pt mononuclear complexes,
which were synthesized by conversion of the Pt-bound
nitrile into amidate. As confirmed by X-ray diffraction
analysis, the cis geometry of the PtN4 coordination in the

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K. Uemura et al. / Inorganica Chimica Acta 360 (2007) 2623–2630
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