Syntheses, structures and solution behaviour of cyclotriphosphato complexes of Pd(II), Pt(II) and Pt(IV)

Article abstract of DOI:10.1039/b301223a

The cyclotriphosphate ion (P₃O₉^3-) as a PPN [PPN = (Ph₃P)₂N⁺] salt reacted in CH₂Cl₂ at room temperature with the cationic solvated complexes of Pd(II) and Pt(II), [M(phosphine)₂(Me₂CO)₂]²⁺ [M = Pd, Pt; phosphine = PPh₃, PMePh₂, 1/2 Ph₂P(CH₂)₂PPh₂ (dppe), 1/2 Ph₂P(CH₂)₄PPh₂ (dppb)], to give the anionic P₃O₉ complexes (PPN)-[Pd(P₃O₉)(PPh₃)₂] (1), (PPN)[Pd(P₃O₉)(PMePh₂)₂] (2), (PPN)[Pt(P₃O₉)(PPh₃)₂] (3), (PPN)[Pt(P₃O₉)(PMePh₂)₂] (4), (PPN)[Pt(P₃O₉)(dppe)] (5) and (PPN)[Pt(P₃O₉)(dppb)] (6). Crystallographic studies revealed that the P₃O₉ ligand in complexes 1-4 and 6 adopts a normal chair conformation and behaves as a pseudo-tridentate ligand with two normal M-O bonds and an additional weak M ··· O interaction. In 1 and 3, the terminal P₃O₉ oxygen atom weakly bound to the metal centre forms relatively strong intramolecular CH ··· O hydrogen bonds with the phosphine ligands. In contrast, the P₃O₉ ligand in 5 is bidentate and takes a pseudo-boat conformation. Complexes 1-6 are fluxional in solution and exhibit only one singlet due to the P₃O₉ ligand in the ³¹P-{¹H} NMR spectra at room temperature; the signals of complexes 4-6 split into two at -40 to -70°C. The activation parameters for the fluxional behaviour of 6 were determined by the line shape analysis of the variable temperature ³¹P-{¹H} NMR spectra. The Pt(IV) complex (PPN)₂[PtMe₃(P₃O₉)] (7) was also synthesised and structurally characterised.

Full text of DOI:10.1039/b301223a

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Syntheses, structures and solution behaviour of cyclotriphosphato
complexes of Pd(II), Pt(II) and Pt(IV)
Sou Kamimura,a Shigeki Kuwata,b Masakazu Iwasakic and Youichi Ishii*d
a Institute of Industrial Science, The University of Tokyo, Komaba, Meguro-ku,
Tokyo 153-8505, Japan
b Department of Applied Chemistry, Graduate School of Science and Engineering,
Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
c Department of Applied Chemistry, Faculty of Engineering, Saitama Institute of Technology,
Okabe, Saitama 369-0293, Japan
d Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University,
Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan
Received 30th January 2003, Accepted 14th May 2003
First published as an Advance Article on the web 28th May 2003
The cyclotriphosphate ion (P3O93Ϫ) as a PPN [PPN = (Ph3P)2Nϩ] salt reacted in CH2Cl2 at room temperature with
the cationic solvated complexes of Pd() and Pt(), [M(phosphine)2(Me2CO)2]2ϩ [M = Pd, Pt; phosphine = PPh3,
PMePh2, 1/2 Ph2P(CH2)2PPh2 (dppe), 1/2 Ph2P(CH2)4PPh2 (dppb)], to give the anionic P3O9 complexes (PPN)-
[Pd(P3O9)(PPh3)2] (1), (PPN)[Pd(P3O9)(PMePh2)2] (2), (PPN)[Pt(P3O9)(PPh3)2] (3), (PPN)[Pt(P3O9)(PMePh2)2] (4),
(PPN)[Pt(P3O9)(dppe)] (5) and (PPN)[Pt(P3O9)(dppb)] (6). Crystallographic studies revealed that the P3O9 ligand in
complexes 1–4 and 6 adopts a normal chair conformation and behaves as a pseudo-tridentate ligand with two normal
M–O bonds and an additional weak M ؒ ؒ ؒ O interaction. In 1 and 3, the terminal P3O9 oxygen atom weakly bound
to the metal centre forms relatively strong intramolecular CH ؒ ؒ ؒ O hydrogen bonds with the phosphine ligands. In
contrast, the P3O9 ligand in 5 is bidentate and takes a pseudo-boat conformation. Complexes 1–6 are fluxional in
solution and exhibit only one singlet due to the P3O9 ligand in the 31P–{1H} NMR spectra at room temperature;
the signals of complexes 4–6 split into two at Ϫ40 to Ϫ70 ЊC. The activation parameters for the fluxional behaviour
of 6 were determined by the line shape analysis of the variable temperature 31P–{1H} NMR spectra. The Pt()
complex (PPN)2[PtMe3(P3O9)] (7) was also synthesised and structurally characterised.
behaviour in solution. In some complexes, relatively strong
Introduction
intramolecular CH ؒ ؒ ؒ O hydrogen bonds are observed
Considerable interest has been focussed on how the properties
between the P3O9 and ancillary phosphine ligands.
and reactivities of late transition metal complexes are modified
on moving from the commonly used P- or N-donor ancillary
Experimental
ligand sets to the O-donor sets.1–3 This originally stemmed from
the intention of providing a correlation between atomic level
structures and functions of the metal species on oxide surfaces
in heterogeneous catalysts. More recently, silsesquioxane-2
and polyoxometalate-supported3 complexes of late transition
metals have been found to show unique reactivities and catalytic
activities; therefore O-donor ligands, particularly polyoxoanion
ligands, have received increasing attention for their possibility
of producing new types of catalytic materials. Among such poly-
oxoanion ligands, we took note of cyclophosphates (PnO3n)nϪ.
These anions comprise n corner-sharing PO4 tetrahedra and
have terminal P–O groups in a regular cyclic arrangement,4
which is suitable for the model of the oxo surfaces in the
heterogeneous oxide-supported catalysts. Inorganic salts of
cyclophosphates have already been well-characterised for n = 3,
4, 5, 6, 8, 10 and 12, but their organometallic derivatives have
not been investigated extensively. With respect to cyclotriphos-
phate (P3O93Ϫ), Klemperer has synthesised several organo-
metallic complexes in his pioneering work.5 For example, the
anionic iridium complex with a κ3-P3O9 ligand [Ir(P3O9)(cod)]2Ϫ
(cod = 1,5-cyclooctadiene) has been reported to undergo
unusual oxygenation with O2 to form an oxametallabutane
complex, where the flexidentate nature of the P3O9 ligand
plays an important role in controlling the reaction course.5e,6
However, examples of molecular complexes with this ligand
have been limited to those of Group 4 (Hf7b), 7 (Mn,5a,b Re 5a,b),
8 (Fe,7a Ru 5f,g,8) and 9 (Rh,5b Ir5c–e) metals, and their synthetic
methods with high generality still remain to be developed. In
this article, we report the syntheses and structures of new P3O9
complexes of palladium and platinum, as well as their dynamic
General methods
All manipulations were carried out under a dry nitrogen
atmosphere by using standard Schlenk tube techniques.
Solvents were dried by usual methods and distilled before use.
[PdCl2(PPh3)2],9 [PdCl2(PMePh2)2],9 [PtCl2(PPh3)2],10 [PtCl2-
(PMePh2)2],10 [PtCl2(dppe)]11 [dppe
=
Ph2P(CH2)2PPh2],
[PtCl2(dppb)]11 [dppb = Ph2P(CH2)4PPh2], [PtMe3I]4 and
(PPN)3(P3O9)ؒH2O5d [PPN = (PPh3)2Nϩ] were prepared accord-
ing to the literature methods. Other reagents were commercially
obtained and used without further purification. 1H and
31P–{1H} NMR spectra were recorded on a JEOL JNM-
EX-270 (1H, 270 MHz; 31P, 109 MHz), JEOL JNM-LA-400
(1H, 400 MHz; 31P, 162 MHz) or JEOL JNM-GSX-400 (1H,
400 MHz) spectrometer, whilst IR spectra were recorded on
a JASCO FT/IR-410 spectrometer. Elemental analyses were
performed with a Perkin-Elmer 2400 series II CHN analyzer.
The rates of intramolecular ligand exchange were estimated
by using the computer program DNMR5,13 and the calcu-
lated 31P–{1H} NMR spectra were visually compared to the
experimental spectra.
12
Preparations
(PPN)[Pd(P3O9)(PPh3)2]ؒ2.5CH2Cl2 (1ؒ2.5CH2Cl2). AgPF6
(55.9 mg, 0.22 mmol) and [PdCl2(PPh3)2] (77.4 mg, 0.11 mmol)
were dissolved in acetone (3.0 cm3) and stirred overnight
at room temperature. After the precipitate was filtered off, the
filtrate was evaporated to dryness in vacuo. To the residual solid
were added (PPN)3(P3O9)ؒH2O (203 mg, 0.11 mmol) and
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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CH2Cl2 (4.0 cm3), and the mixture was stirred overnight at
room temperature. The black precipitate that formed was
filtered off, and the filtrate was evaporated under reduced
pressure. The residue was extracted with MeOH and evapor-
ated to dryness. The resultant solid was washed repeatedly with
acetone and recrystallised from CH2Cl2–Et2O to give yellow
crystals of 1ؒ2.5CH2Cl2. The X-ray diffraction study of this salt
clearly showed that it contains 2.5 molecules of CH2Cl2 per
complex anion. However, since the crystals are efflorescent,
thoroughly dried samples were found to possess the empirical
formula 1ؒ1.7CH2Cl2. The yield after drying in vacuo was 21.2
mg (0.014 mmol, 13%). νmax/cmϪ1 (KBr): 1292s, 1267s, 1130m,
1117s, 1101m, 1070m, 998m, 981m, 957m. 31P–{1H} NMR
(CDCl3, 20 ЊC): δ 33.2 (s, PPh3), 21.1 (s, PPN), Ϫ15.9 (s, P3O9).
1H NMR (CDCl3, 20 ЊC): δ 7.17–7.73 (m, PPN and PPh3).
Found: C, 57.06; H, 4.32; N, 0.89; C73.7H63.4Cl3.4NO9P7Pd
requires C, 57.08; H, 4.12; N, 0.90%.
(PPh4)[Pt(P3O9)(dppe)]ؒMeCNؒ0.5CH2Cl2 (5ЈؒMeCNؒ0.5CH2-
Cl2), which was used for X-ray analysis, was obtained by anion
metathesis of 5 with PPh4Cl and recrystallisation by slow
diffusion of hexane into a MeCN/CH2Cl2 (1/3 v/v) solution of
the PPh4 salt.
(PPN)[Pt(P3O9)(dppb)]ؒMeCNؒ0.5CH2Cl2
(6ؒMeCNؒ
0.5CH2Cl2). This compound was prepared from [PtCl2(dppb)]
and (PPN)3(P3O9)ؒH2O in a manner similar to that described
for 2ؒMeCN except that pure samples were obtained by
addition of Et2O to a MeCN/CH2Cl2 (2/1 v/v) solution. Color-
less crystals, 42% yield. νmax/cmϪ1 (KBr): 1296s, 1269s, 1129m,
1117s, 1104m, 1069m, 997m, 983s, 957m. 31P–{1H} NMR
(CD2Cl2, 20 ЊC): δ 20.8 (s, PPN), 1.95 [s, 1J(PtP) 3995 Hz, dppb],
1
Ϫ17.3 (s, P3O9). H NMR (CD2Cl2, 21 ЊC): δ 7.33–7.74 (50 H,
m, Ph of PPN and dppb), 2.46, 2.07 (4 H each, br, CH2 of
dppb). Found: C, 54.27; H, 4.35; N, 1.98; C66.5H62ClN2O9P7Pt
requires C, 53.95; H, 4.22; N, 1.89%.
(PPN)[Pd(P3O9)(PMePh2)2]ؒMeCN (2ؒMeCN). [PdCl2(PMe-
Ph2)2] (172 mg, 0.30 mmol) was treated with AgPF6 (151 mg,
0.60 mmol) in acetone (3.0 cm3) and then allowed to react with
(PPN)3(P3O9)ؒH2O (552 mg, 0.30 mmol) in CH2Cl2 (3.0 cm3) as
described above. The black precipitate was filtered off, and the
filtrate was evaporated under reduced pressure. Recrystallis-
ation of the resulting yellow solid from MeCN–Et2O gave
(PPN)2[PtMe3(P3O9)] (7). A mixture of [PtMe3I]4 (51.5 mg,
0.035 mmol) and (PPN)3(P3O9)ؒH2O (261 mg, 0.14 mmol) in
CH2Cl2 (3.0 cm3) was stirred overnight at room temperature.
Then the reaction mixture was filtered, and the filtrate was
evaporated to dryness in vacuo. The residual solid was washed
with acetone and recrystallised from CH2Cl2–Et2O to give
colorless crystals of 7 (151 mg, 0.097 mmol, 70%). νmax/cmϪ1
(KBr): 1327m, 1297s, 1272s, 1116s, 996m, 983m, 954m.
31P–{1H} NMR (CDCl3, 17 ЊC): δ 21.1 (s, PPN), Ϫ9.3 [s, 2J(PtP)
yellow crystals of 2ؒMeCN (263 mg, 0.20 mmol, 67%). νmax
/
cmϪ1 (KBr): 1295s, 1265s, 1135m, 1117s, 1104s, 1073m, 997s,
980s, 959m, 902m, 890m. 31P–{1H} NMR (CDCl3, 22 ЊC):
1
δ 24.8 (s, PMePh2), 21.1 (s, PPN), Ϫ15.8 (s, P3O9). H NMR
1
63 Hz, P3O9]. H NMR (CDCl3, 17 ЊC): δ 7.44–7.69 (60 H, m,
(CDCl3, 22 ЊC): δ 7.19–7.67 (50 H, m, PPN and PMePh2), 2.04
[6 H, d, 2J(PH) 12.0 Hz, PMePh2]. Found: C, 57.81; H, 4.52; N,
1.91; C64H59N2O9P7Pd requires C, 58.08; H, 4.49; N, 2.12%.
2
PPN), 1.02 [9 H, s, J(PtH) 79 Hz, Me]. Found: C, 58.29; H,
4.52; N, 1.86; C75H69N2O9P7Pt requires C, 57.96; H, 4.47; N,
1.80%.
(PPN)[Pt(P3O9)(PPh3)2]ؒ2C2H4Cl2 (3ؒ2C2H4Cl2). This com-
pound was prepared from [PtCl2(PPh3)2] and (PPN)3(P3O9)ؒ
H2O in a manner analogous to that described for 1ؒ2.5CH2Cl2
except that 1,2-dichloroethane was used as the solvent for
recrystallisation. Colorless crystals, 69% yield. νmax/cmϪ1 (KBr):
1297s, 1270s, 1130m, 1116s, 1102s, 1067m, 998s, 987s, 957m.
31P–{1H} NMR (CDCl3, 18 ЊC): δ 21.1 (s, PPN), 4.9 [s, 1J(PtP)
Crystallography
For 3ؒ2.5CH2Cl2, diffraction data were collected at Ϫ170 ЊC on
a Rigaku RAXIS RAPID imaging plate area detector with
graphite monochromatised Mo-Kα radiation (λ = 0.71069 Å)
to a maximum 2θ value of 54.9Њ. For the other compounds,
data were collected at room temperature on a Rigaku AFC7R
four-circle automated diffractometer with graphite mono-
chromatised Mo-Kα radiation using the ω–2θ scan technique
to a maximum 2θ value of 50Њ (for 1ؒ2.5CH2Cl2) or 55Њ (except
for 1ؒ2.5CH2Cl2). Details of the crystals and data collection
parameters are summarised in Table 1.
1
4256 Hz, PPh3], Ϫ16.8 (s, P3O9). H NMR (CDCl3, 18 ЊC):
δ 7.17–7.73 (m, PPN and PPh3). Found: C, 53.65; H, 4.23;
N, 0.76; C76H68Cl4NO9P7Pt requires C, 53.92; H, 4.05; N,
0.83%. Crystals of 3ؒ2.5CH2Cl2 suitable for X-ray analysis were
obtained by further recrystallisation from CH2Cl2–Et2O.
The structure solution and refinements were carried out by
using teXsan14 and CrystalStructure15 crystallographic soft-
ware packages. The positions of non-hydrogen atoms were
determined by Patterson methods (DIRDIF PATTY16) or
direct methods (SIR9217) and expanded using Fourier
techniques (DIRDIF-9418 or -9919). For 1ؒ2.5CH2Cl2 and
3ؒ2.5CH2Cl2, the carbon atoms of the solvating CH2Cl2
molecules were refined isotropically. In each case one of the
CH2Cl2 molecules was found to be located on the centre of
symmetry; the carbon atom for this CH2Cl2 molecule was
refined with a 50% occupancy. For 5ЈؒMeCNؒ0.5CH2Cl2 and
6ؒMeCNؒ0.5CH2Cl2, the CH2Cl2 molecules were found to be
located near the centre of symmetry. For the CH2Cl2 molecule
in 5ЈؒMeCNؒ0.5CH2Cl2, the chlorine atoms were refined aniso-
tropically with a 50% occupancy, whilst the carbon atoms were
included in the refinement with fixed isotropic parameters with
a 50% occupancy. The disordered carbon and chlorine atoms of
the CH2Cl2 molecule in 6ؒMeCNؒ0.5CH2Cl2 were treated with
fixed isotropic parameters with a 50% occupancy. All the other
non-hydrogen atoms were refined by full-matrix least-squares
techniques with anisotropic thermal parameters. Hydrogen
atoms except for those of the disordered CH2Cl2 molecules in
3ؒ2.5CH2Cl2 and 6ؒMeCNؒ0.5CH2Cl2 were placed at calculated
positions (dC–H = 0.95 Å) and included in the final stages of
refinements with fixed parameters.
(PPN)[Pt(P3O9)(PMePh2)2]ؒMeCN (4ؒMeCN). This com-
pound was prepared from [PtCl2(PMePh2)2] and (PPN)3(P3O9)ؒ
H2O in a manner similar to that described for 2ؒMeCN.
Colorless crystals, 57% yield. νmax/cmϪ1 (KBr): 1296s, 1271s,
1255s, 1134m, 1116s, 1105s, 1070m, 984s, 961m, 903m, 894m.
31P–{1H} NMR (CDCl3, 18 ЊC): δ 21.0 (s, PPN), Ϫ5.4 [s, 1J(PtP)
1
4156 Hz, PMePh2], Ϫ16.4 (s, P3O9). H NMR (CDCl3, 18 ЊC):
2
δ 7.19–7.68 (50 H, m, PPN and PMePh2), 1.96 [6H, d, J(PH)
11.7 Hz, PMePh2]. Found: C, 54.39; H, 4.39; N, 1.79;
C64H59N2O9P7Pt requires C, 54.44; H, 4.21; N, 1.98%.
(PPN)[Pt(P3O9)(dppe)]ؒ0.5MeCNؒ0.5CH2Cl2 (5ؒ0.5MeCNؒ
0.5CH2Cl2). This compound was prepared from [PtCl2(dppe)]
and (PPN)3(P3O9)ؒH2O in a manner similar to that described
for 2ؒMeCN except that pure samples were obtained by
addition of Et2O to a MeCN/CH2Cl2 (3/2 v/v) solution.
Colorless crystals, 52% yield. νmax/cmϪ1 (KBr): 1310s, 1293s,
1266s, 1132m, 1116s, 1105m, 1069m, 997m, 987m, 962m.
1
31P–{1H} NMR (CD2Cl2, 18 ЊC): δ 31.3 [s, J(PtP) 4063 Hz,
dppe], 20.8 (s, PPN), Ϫ16.4 (s, P3O9). 1H NMR (CD2Cl2, 24 ЊC):
δ 7.46–8.06 (50 H, m, Ph of PPN and dppe), 2.33 [4 H, br d,
2J(PH) 17.6 Hz, CH2 of dppe]. Found: C, 53.58; H, 4.10;
N, 1.24; C63.5H56.5ClN1.5O9P7Pt requires C, 53.26; H, 3.98;
N, 1.47%. The corresponding tetraphenylphosphonium salt
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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CCDC reference numbers 202873–202879.
See http://www.rsc.org/suppdata/dt/b3/b301223a/ for crystal-
lographic data in CIF or other electronic format.
Results and discussion
Syntheses and structures of (PPN)[Pd(P3O9)(PPh3)2] (1) and
(PPN)[Pd(P3O9)(PMePh2)2] (2)
Our initial attempts to synthesise Pd() P3O9 complexes with
diene ligands resulted in the formation of products unstable at
room temperature, although the Rh() and Ir() analogues have
been known for some time.5b–e In contrast, use of phosphines
as the ancillary ligands produced much more stable P3O9
3Ϫ
complexes of palladium. Thus, the P3O9 as a PPN salt
smoothly reacted with the cationic solvated palladium complex
[Pd(Me2CO)2(PPh3)2](PF6)2 20 in CH2Cl2 at room temperature to
form the anionic complex (PPN)[Pd(P3O9)(PPh3)2] (1), which
was isolated as air-stable yellow crystals (Scheme 1). The struc-
ture of 1ؒ2.5CH2Cl2 was established by X-ray crystallography
[Fig. 1(a)]. Selected bond lengths and angles are given in Table 2.
Scheme 1
The palladium atom is coordinated by the two phosphine
ligands and two oxygen atoms of the P3O9 ligand with a square-
planar geometry [Pd–O(1) = 2.089(4), Pd–O(2) = 2.078(4),
Pd–P(4) = 2.258(2), Pd–P(5) = 2.267(2) Å] and has an additional
weak interaction with another oxygen atom [O(3)] of the P3O9
ligand [Pd ؒ ؒ ؒ O(3) = 2.902(5) Å]. This Pd ؒ ؒ ؒ O(3) distance is
considerably longer than the corresponding Rh–O [2.343(5) Å]
and Ir–O [2.70(2) Å] distances in [NBun ] [Rh(P3O9)(nbd)]
4 2
(nbd = 2,5-norbornadiene)5b and [NBun ] [Ir(P3O9)(cod)],5c but
4 2
is comparable to those of Pd ؒ ؒ ؒ O weak interactions found
in Pd() complexes such as [Pd(C6H4CH2NMe2-C2,N)Cl-
{P[C6H3(OMe)2]3}] [Pd ؒ ؒ ؒ O = 2.920(8) Å].21 With this inter-
action, the coordination structure around the palladium centre
may be regarded as a highly distorted square pyramid. Due to
this coordination mode of the tripodal P3O9 ligand, the P(3)–
O(3) bond [1.480(4) Å] is shorter than the other coordinating
P–O units [P(1)–O(1) = 1.509(4), P(2)–O(2) = 1.502(4) Å]
but is slightly longer than the non-coordinating equatorial
P–Oterminal bonds [1.455(4)–1.460(5) Å].
The O(3) atom is also located very close to two ortho CH
groups of the PPh3 ligands [O(3) ؒ ؒ ؒ C(2)
=
3.185(9),
O(3) ؒ ؒ ؒ H(1)
O(3) ؒ ؒ ؒ C(20)
=
=
2.25 Å, O(3) ؒ ؒ ؒ H(1)–C(2)
3.216(9), O(3) ؒ ؒ ؒ H(16)
=
167.3Њ;
=
2.34 Å,
O(3) ؒ ؒ ؒ H(16)–C(20) = 154.0Њ; the C–H bond distances are
normalised to 0.95 Å], and these contacts are regarded as
intramolecular CH ؒ ؒ ؒ O hydrogen bonds.22 With this type of
interaction, the C ؒ ؒ ؒ O (D) and H ؒ ؒ ؒ O (d ) contacts usually
fall in the range of 3.0 < D < 4.0 Å and 2.0 < d < 3.0 Å,
respectively. In 1, the estimated O ؒ ؒ ؒ H distances are signifi-
cantly short (2.3 Å) and the O ؒ ؒ ؒ H–C angles are close to
linearity (>150Њ). These metrical features indicate that the
O(3) atom forms relatively strong intramolecular CH ؒ ؒ ؒ O
hydrogen bonds. Some of the oxygen atoms in the P3O9 ligand
also have short non-bonding contacts with CH groups in the
PPN cation and solvating CH2Cl2 molecules. For example, the
O(2) and O(3) atoms lie close to the C(39)–H(32) and C(71)–
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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Table 2 Selected bond distances (Å) and angles (Њ) in complexes 1–6
2ؒMeCNa
3ؒ2.5CH2Cl2
4ؒMeCNb
5ЈؒMeCNؒ0.5CH2Cl2
6ؒMeCNؒ0.5CH2Cl2
a
b
b
b
1ؒ2.5CH2Cl2
M–O(1)
M–O(2)
M–O(3)
M–P(4)
2.089(4)
2.078(4)
2.902(5)
2.258(2)
2.267(2)
1.509(4)
1.455(4)
1.502(4)
1.458(4)
1.480(4)
1.460(5)
2.081(2)
2.107(2)
2.838(2)
2.229(1)
2.2397(8)
1.509(2)
1.459(2)
1.508(2)
1.456(2)
1.473(2)
1.461(2)
2.076(2)
2.091(2)
3.030(2)
2.236(1)
2.232(1)
1.513(2)
1.468(2)
1.522(2)
1.462(2)
1.476(2)
1.467(2)
2.082(2)
2.100(2)
3.032(4)
2.217(1)
2.221(1)
1.511(3)
1.457(3)
1.506(3)
1.457(3)
1.472(3)
1.463(3)
2.093(3)
2.090(3)
4.131(6)
2.217(1)
2.208(1)
1.506(3)
1.456(3)
1.508(3)
1.453(3)
1.413(4)
1.439(4)
2.084(3)
2.101(4)
3.030(4)
2.216(1)
2.222(1)
1.512(4)
1.465(4)
1.515(4)
1.457(4)
1.471(4)
1.465(4)
M–P(5)
P(1)–O(1)
P(1)–O(4)
P(2)–O(2)
P(2)–O(6)
P(3)–O(3)
P(3)–O(8)
P(4)–M–P(5)
P(4)–M–O(1)
P(4)–M–O(2)
P(5)–M–O(1)
P(5)–M–O(2)
O(1)–M–O(2)
97.84(7)
176.3(1)
88.5(1)
84.1(1)
170.4(1)
89.1(2)
98.38(3)
174.77(6)
83.37(6)
86.25(6)
166.56(6)
92.69(7)
98.38(3)
171.34(6)
84.59(6)
88.65(7)
176.43(6)
88.22(9)
99.69(4)
173.12(8)
83.50(7)
86.24(7)
169.74(7)
91.26(10)
86.52(4)
177.78(8)
92.27(8)
91.66(7)
178.68(9)
89.57(10)
93.74(5)
171.0(1)
87.2(1)
90.1(1)
177.7(1)
88.7(1)
a M = Pd. b M = Pt.
O(6) ؒ ؒ ؒ H(62)–C(73) = 171.7Њ]. We consider that the strong
tendency of the P3O9 ligand to form CH ؒ ؒ ؒ O hydrogen bonds
has a crucial effect on controlling the conformation of its
complexes at least in the solid state.
The 31P–{1H} NMR spectrum of 1 at ambient temperature
displays only one phosphorus resonance for the P3O9 ligand at
δ Ϫ15.9 in spite of its local Cs structure in the solid state.
The equivalence of the phosphorus atoms is accounted for by
a rapid intramolecular ligand exchange process involving the
hapticity change and pseudo-rotation of the P3O9 ligand
(Scheme 2). However, the 31P–{1H} NMR spectrum shows
essentially no line broadening on cooling to Ϫ60 ЊC. This
fluxional behaviour is similar to that observed for the above-
mentioned anionic iridium complex [Ir(P3O9)(cod)]2Ϫ 5c
.
Scheme 2
It is expected that use of more electron-donating ancillary
ligands disfavors the coordination of the third oxygen atom and
decelerates the ligand exchange process. Since the dynamic
behaviour of metal complexes involving the hapticity change
of flexidentate ligands has been attracting intense research
activity,22–24 we have synthesised the PMePh2 analogue of 1.
The reaction of the cationic solvated complex [Pd(Me2CO)2-
(PMePh2)2](PF6)2 with (PPN)3(P3O9) in CH2Cl2 at room
temperature gave (PPN)[Pd(P3O9)(PMePh2)2] (2) in good yield.
The structure of 2ؒMeCN has been confirmed by X-ray crystal-
lography [Fig. 1(b)]. Selected bond distances and angles are
given in Table 2.
Fig. 1 The molecular structures of the anionic parts of 1ؒ2.5CH2Cl2
(a) and 2ؒMeCN (b). Solvating molecules are omitted for clarity.
H(59) groups of the PPN cation, respectively [O(2) ؒ ؒ ؒ C(39) =
3.376(8), O(2) ؒ ؒ ؒ H(32) = 2.44 Å, O(2) ؒ ؒ ؒ H(32)–C(39) =
169.1Њ; O(3) ؒ ؒ ؒ C(71) = 3.273(9), O(3) ؒ ؒ ؒ H(59) = 2.41 Å,
O(3) ؒ ؒ ؒ H(59)–C(71)
= 151.4Њ], whilst the O(6) atom
approaches the C(73)–H(62) of one of the solvated CH2Cl2
molecules [O(6) ؒ ؒ ؒ C(73) = 3.20(1), O(6) ؒ ؒ ؒ H(62) = 2.26 Å,
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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The coordination structure around the palladium atom in 2 is
similar to that of 1 [Pd–O(1) = 2.081(2), Pd–O(2) = 2.107(2),
Pd–P(4) = 2.229(1), Pd–P(5) = 2.2397(8) Å], and the palladium
centre has a weak interaction with the third oxygen atom [O(3)]
of the P3O9 ligand [Pd ؒ ؒ ؒ O(3) = 2.838(2) Å]. Again, the O(3)
atom forms intramolecular CH ؒ ؒ ؒ O hydrogen bonds with
one methyl and one phenyl group of the PMePh2 ligands
[O(3) ؒ ؒ ؒ C(13) = 3.239(4), O(3) ؒ ؒ ؒ C(15) = 3.425(4) Å],
although the O ؒ ؒ ؒ C non-bonding separations are somewhat
longer than those found in 1. The 31P–{1H} NMR spectrum of
2 at ambient temperature also exhibits only one phosphorus
resonance attributable to the P3O9 ligand at δ Ϫ15.8, and
unfortunately no temperature dependence is observed.
Syntheses and structures of (PPN)[Pt(P3O9)(PPh3)2] (3) and
(PPN)[Pt(P3O9)(PMePh2)2] (4)
It is known that the rate of ligand substitution is often faster for
Pd() than for Pt().24 So we changed the central metal from
palladium to platinum in order to gain further insights into the
intramolecular ligand exchange process in the P3O9 complexes.
The platinum complexes (PPN)[Pt(P3O9)(PPh3)2] (3) and
(PPN)[Pt(P3O9)(PMePh2)2] (4) were synthesised by the reaction
of (PPN)3(P3O9) with the cationic solvated complexes
[Pt(Me2CO)2(PPh3)2](PF6)2 and [Pt(Me2CO)2(PMePh2)2](PF6)2,
respectively, and were isolated as stable colorless crystals
(Scheme 1). The structures of 3 and 4 have been established by
X-ray diffraction study as depicted in Fig. 2, and selected bond
distances and angles are summarised in Table 2.
The crystals of 3ؒ2.5CH2Cl2 and 4ؒMeCN are isomorphic
with those of the palladium complexes 1ؒ2.5CH2Cl2 and
2ؒMeCN, respectively. In both 3 and 4, the platinum centre
is coordinated by P2O2 donor atoms with a square-planar
geometry and has an additional weak interaction with the third
oxygen atom [O(3)] in the P3O9 ligand, where the Pt ؒ ؒ ؒ O(3)
separation [3.030(2) Å for 3, 3.032(4) Å for 4] is slightly longer
than the corresponding Pd ؒ ؒ ؒ O distance in 1 and 2. The O(3)
atom is also engaged in intramolecular CH ؒ ؒ ؒ O hydrogen
bonds with phosphine CH groups. In particular, the
O(3) ؒ ؒ ؒ H(1)–C(2) and O(3) ؒ ؒ ؒ H(16)–C(20) interactions
in 3 may be regarded as relatively strong CH ؒ ؒ ؒ O hydrogen
bonds [O(3) ؒ ؒ ؒ C(2) = 3.201(4), O(3) ؒ ؒ ؒ H(1) = 2.32 Å,
O(3) ؒ ؒ ؒ H(1)–C(2)
= 154.8Њ; O(3) ؒ ؒ ؒ C(20) = 3.211(4),
O(3) ؒ ؒ ؒ H(16) = 2.28 Å, O(3) ؒ ؒ ؒ H(16)–C(20) = 167.2Њ].
The 31P–{1H} NMR spectra of 3 and 4 at room temperature
are similar to those of 1 and 2, showing one signal attributable
to the P3O9 ligand at δ Ϫ16.8 and Ϫ16.4, respectively. The signal
of 3 is broadened at Ϫ60 ЊC in CDCl3, although we could not
observe complete coalescence. In contrast, the P3O9 signal of 4
in CD2Cl2 coalesces at Ϫ70 ЊC and splits into two broad signals
at Ϫ90 ЊC [δ Ϫ14.1 (2 P), Ϫ24.1 (1 P)]. These observations
clearly indicate that the intramolecular ligand exchange process
is slower for the platinum complexes 3 and 4 than for their
palladium analogues.
Fig. 2 The molecular structures of the anionic parts of 3ؒ2.5CH2Cl2
(a) and 4ؒMeCN (b). Solvating molecules are omitted for clarity.
salt 5ЈؒMeCNؒ0.5CH2Cl2 derived from 5, whilst recrystallis-
ation of 6 directly gave crystals suitable for diffraction study.
Selected bond lengths and angles are given in Table 2, and
ORTEP26 drawings for the anions are in Fig. 3.
Syntheses and structures of (PPN)[Pt(P3O9)(dppe)] (5) and
(PPN)[Pt(P3O9)(dppb)] (6)
In 5Ј, the conformation of the P3O9 ligand is deformed from
a chair form to a pseudo-boat, where the P(1)–O(9)–P(3)–O(7)–
P(2) part of the six-membered ring is almost planar. This type
of structure has not been found previously in crystallo-
graphically characterised P3O9 complexes, but we assume that
the pseudo-boat conformation of the P3O9 ligand reflects the
conformational flexibility of the P3O3 ring. This deformation is
considered to be the result of steric congestion between the
dppe and P3O9 ligands. Consequently, the O(3) atom moves
away from the platinum centre; the large Pt ؒ ؒ ؒ O(3) separation
[4.131(6) Å] precludes any bonding interaction between these
atoms. Thus the platinum centre takes a normal square-planar
coordination structure. It would also be interesting to point out
that the P(3)–O(3) distance in 5Ј [1.413(4) Å] is noticeably
shorter than those in complexes 1–4.
We have further turned our attention to P3O9 complexes of
platinum with a chelate phosphine ligand, because the chelate
ring size and the bridge structure of the ancillary diphosphine
ligand have been documented to possess profound effects on
the dynamic behaviour of TpiPr2 (TpiPr2 = hydrotris-3,5-diiso-
propylpyrazolylborato) complexes of rhodium [TpiPr2Rh-
(diphosphine)] (vide infra).25 (PPN)[Pt(P3O9)(dppe)] (5) and
(PPN)[Pt(P3O9)(dppb)] (6) were synthesised from the cationic
solvated complexes [Pt(Me2CO)2(dppe)](OTf )2 and [Pt(Me2-
CO)2(dppb)](OTf )2, respectively, by the reaction with
(PPN)3(P3O9) in CH2Cl2 at room temperature (Scheme 1). The
structure of [Pt(P3O9)(dppe)]Ϫ ion has been determined by the
X-ray crystallographic study of the tetraphenylphosphonium
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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Scheme 3
opened arrangement. Obviously this conformation enables the
O(3) atom of the P3O9 ligand to approach the platinum centre.
A similar folded chelate structure of dppb has also been found
in [PdCl2(dppb)].27
In the 31P–{1H} NMR spectrum of 6 in CD2Cl2 at room
temperature, the signal of the P3O9 ligand appears again as one
singlet at δ Ϫ17.3, but this signal coalesces at Ϫ40 ЊC and is split
2
into a set of one doublet [δ Ϫ14.6, 2 P, J(PP) 26 Hz] and one
2
triplet [δ Ϫ23.6, 1 P, J(PP) 26 Hz] at Ϫ95 ЊC, which is in full
agreement with the solid state structure.
Akita and co-workers have revealed that the (CH2)n bridge
in the diphosphine ligands in related square-planar hydrotris-
(pyrazolyl)borato complexes [TpiPr2Rh(diphosphine)] is folded
toward the apical position.25 They have concluded that the
steric repulsion between the folded (CH2)n bridge and the
pendant pyrazole ring disfavors the penta-coordinate structure
of the rhodium centre and consequently retards intramolecular
ligand exchange processes. In contrast, the sterically less
demanding P3O9 ligand can interact with the platinum centre
irrespective of the steric effect of the (CH2)4 bridge in the dppb
ligand in 6 [Fig. 3(b)]. Nevertheless, judging from the tem-
perature dependence of the 31P–{1H} NMR spectra, the intra-
molecular ligand exchange process of 6 is much slower than
that of 3 and 4. We have concluded that this is a consequence
of the slow pseudo-rotation process of the penta-coordinate
intermediate. As shown in Scheme 4, simple pseudo-rotation of
Fig. 3 The molecular structures of the anionic parts of 5ЈؒMeCNؒ
0.5CH2Cl2 (a) and 6ؒMeCNؒ0.5CH2Cl2 (b) and (c) (side view to show
the arrangement of phenyl groups). Solvating molecules, all hydrogen
atoms and phenyl carbon atoms in (b) are omitted for clarity.
In the 31P–{1H} NMR spectrum of 5 in CD2Cl2, one singlet
resonance (δ Ϫ16.4) is observed for the P3O9 ligand at room
temperature, but this signal coalesces at Ϫ50 ЊC and is further
changed into two broad signals [δ Ϫ13.0 (2 P), Ϫ24.3 (1 P)] at
Ϫ90 ЊC. The higher coalescence temperature of 5 than those of
3 and 4 is accounted for by the pseudo-boat conformation
of the P3O9 ligand in 5, where the large Pt ؒ ؒ ؒ O(3) separation
substantiates the difficulty in forming the penta-coordinate Pt
centre (Scheme 3). Such steric deceleration is considered to be
typical of a dynamic process by an associative mechanism.25
In contrast to 5Ј, 6 takes a coordination structure similar to
those of 1–4. Thus, the platinum atom resides at the centre of
the P2O2 donor atoms with a square-planar geometry and in
addition is weakly coordinated by the third oxygen atom [O(3)]
of the P3O9 ligand. The Pt ؒ ؒ ؒ O(3) distance of 3.030(4) Å is
comparable to those in 3 and 4. The (CH2)4 bridge of the dppb
ligand is folded upward from the PtO2P2 coordination plane,
and in compensation for this, the two Ph groups take a widely
Scheme 4
the square-pyramidal intermediate leads to the sterically
unsuitable relative arrangement of the folded (CH2)4 bridge and
the apical coordination site (B). To complete the exchange
process, it is necessary to invert the dppb chelate ring during the
C), which we assume to be unfavorable
for the sterically congested penta-coordinate state of 6.
The exchange rates for 6 at different temperatures were
determined by comparing the computer-simulated 31P–{1H}
NMR spectra with the experimental data (Fig. 4). An Eyring
plot of the temperature dependence of the rate constants
pseudo-rotation (A
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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Table 3 Selected bond distances (Å) and angles (Њ) in complex 7
Pt–O(1)
Pt–O(3)
Pt–C(2)
P(1)–O(1)
P(3)–O(3)
2.191(8)
2.223(7)
2.002(10)
1.492(9)
1.478(7)
Pt–O(2)
Pt–C(1)
Pt–C(3)
P(2)–O(2)
2.197(6)
2.05(1)
2.00(1)
1.510(6)
O(1)–Pt–O(2)
O(2)–Pt–O(3)
89.0(2)
88.3(2)
O(1)–Pt–O(3)
88.8(3)
Fig. 6 The molecular structure of the anionic part of 7. All hydrogen
atoms are omitted for clarity.
cation [O(8) ؒ ؒ ؒ C(66) = 3.14(1), O(8) ؒ ؒ ؒ H(61) = 2.27 Å,
O(8) ؒ ؒ ؒ H(61)–C(66) = 150.4Њ], and this contact may be
regarded as a relatively strong CH ؒ ؒ ؒ O hydrogen bond.
Acknowledgements
This work was supported by a Grant-in-aid for Scientific
Research from the Ministry of Education, Science, Sports and
Culture, Japan.
References
1 P. R. Sharp, J. Chem. Soc., Dalton Trans., 2000, 2647.
2 F. J. Feher and T. A. Budzichowski, Polyhedron, 1995, 14, 3239;
R. Murugavel, A. Voigt, M. G. Walawalkar and H. W. Roesky,
Chem. Rev., 1996, 96, 2205; E. A. Quadrelli, J. E. Davies, B. F. G.
Johnson and N. Feeder, Chem. Commun., 2000, 1031; B. Marciniec
and H. Maciejewski, Coord. Chem. Rev., 2001, 223, 301.
3 H. Weiner and R. G. Finke, J. Am. Chem. Soc., 1999, 121, 9831;
H. Weiner, Y. Hayashi and R. G. Finke, Inorg. Chem., 1999, 38, 2579.
4 A. Durif, Crystal Chemistry of Condensed Phosphates, Plenum Press,
New York, 1995.
Fig. 4 Experimental (left) and computed (right) 31P–{1H} NMR
spectra of 6.
5 (a) C. J. Besecker and W. G. Klemperer, J. Organomet. Chem., 1981,
205, C31; (b) C. J. Besecker, V. W. Day and W. G. Klemperer,
Organometallics, 1985, 4, 564; (c) V. W. Day, W. G. Klemperer and
D. J. Main, Inorg. Chem., 1990, 29, 2345; (d ) W. G. Klemperer
and D. J. Main, Inorg. Chem., 1990, 29, 2355; (e) V. W. Day,
W. G. Klemperer, S. P. Lockledge and D. J. Main, J. Am. Chem. Soc.,
1990, 112, 2031; ( f ) V. W. Day, T. A. Eberspacher, W. G. Klemperer,
R. P. Planalp, P. W. Schiller, A. Yagasaki and B. Zhong, Inorg.
Chem., 1993, 32, 1629; (g) W. G. Klemperer and B. Zhong, Inorg.
Chem., 1993, 32, 5821.
6 V. W. Day, T. A. Eberspacher, W. G. Klemperer and B. Zhong, J. Am.
Chem. Soc., 1994, 116, 3119.
7 (a) K.-N. Han, D. Whang, H.-J. Lee, Y. Do and K. Kim, Inorg.
Chem., 1993, 32, 2597; (b) S. Ryu, D. Whang, J. Kim, W. Yeo and
K. Kim, J. Chem. Soc., Dalton Trans., 1993, 205.
Fig. 5 Eyring plot of the temperature dependence of the rate
constants (k) for the intramolecular ligand exchange in 6.
(Fig. 5) gives the activation parameters ∆H‡ = 45 1 kJ molϪ1
,
∆S‡ = 10 6 J molϪ1 KϪ1 and ∆G‡ = 42 2 kJ molϪ1 ( Ϫ40 ЊC).
The relatively small but positive ∆S‡ value is compatible with
the above-mentioned intramolecular associative mechanism
where the pseudo-rotation–chelate inversion is the rate-
determining process (Scheme 4).
8 D. Attanasio, F. Bachechi and L. Suber, J. Chem. Soc., Dalton
Trans., 1993, 2373.
9 J. M. Jenkins and B. L. Shaw, J. Chem. Soc. A, 1966, 770.
10 J. A. Rahn, L. Baltusis and J. H. Nelson, Inorg. Chem., 1990, 29,
750.
Synthesis and structure of (PPN)2[PtMe3(P3O9)] (7)
11 M. Hacket and G. Whitesides, J. Am. Chem. Soc., 1988, 110,
Finally, the synthesis and structure of the Pt() P3O9 complex
(PPN)2[PtMe3(P3O9)] (7) was investigated. This complex was
prepared by the reaction of [PtMe3I]4 with (PPN)3(P3O9) in
CH2Cl2 at room temperature and isolated as stable colorless
crystals. Both 31P–{1H} and 1H NMR spectra exhibit one
singlet for the P3O9 ligand [δ Ϫ9.3, J(PtP) 63 Hz] and the
Me groups (δ 1.02), respectively, indicating a C3v molecular
symmetry for this anion.
1449.
12 J. C. Baldwin and W. C. Kaska, Inorg. Chem., 1975, 14, 2020.
13 D. S. Stephenson and G. Binsch, Program QCPE365; Quantum
Chemistry Program Exchange, Indiana University, Bloomington,
1978.
14 teXsan, Crystal Structure Analysis Package, Molecular Structure
Corporation, Houston, TX, 1985 & 1999.
2
15 CrystalStructure 3.00, Crystal Structure Analysis Package, Rigaku
and Rigaku/MSC, Tokyo, Japan, 2000–2002.
The molecular structure of 7 has been unambiguously
determined by X-ray diffraction study (Fig. 6 and Table 3). The
platinum centre adopts a typical octahedral geometry, where
the Pt–O distances [2.20 Å (mean)] are slightly longer
than those found in complexes 3–6. Similar κ3-coordination
of the P3O9 ligand has been commonly found in d6-metal
complexes.5a,b,f,7a,8 The O(8) atom in the P3O9 ligand in 7 is
located in the vicinity of the C(66)–H(61) group of a PPN
16 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
S. Garsia-Granda, R. O. Gould, J. M. M. Smits and C. Smykalla,
The DIRDIF program system, Technical Report of the Crystallo-
graphy Laboratory, University of Nijmegen, The Netherlands,
1992.
17 A. Altomare, G. Cascarano, C. Giacovazzo, A Guagliardi, M. Burla,
G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994, 27, 435.
18 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
R. de Gelder, R. Israel and J. M. M. Smits, The DIRDIF-94
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
2672

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program system, Technical Report of the Crystallography
Laboratory, University of Nijmegen, The Netherlands, 1994.
19 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
R. de Gelder, R. Israel and J. M. M. Smits, The DIRDIF-99
program system, Technical Report of the Crystallography
Laboratory, University of Nijmegen, The Netherlands, 1999.
20 F. R. Hartley, S. G. Murray and A. Wilkinson, Inorg. Chem., 1989,
28, 549.
23 T. Rüther, M. C. Done, K. J. Cavell, E. J. Peacock, B. W. Skelton and
A. H. White, Organometallics, 2001, 20, 5522.
24 J. A. Casares, P. Espinet, J. M. Martínez-Ilarduya and Y.-S. Lin,
Organometallics, 1997, 16, 770.
25 K. Ohta, M. Hashimoto, Y. Takahashi, S. Hikichi, M. Akita and
Y. Moro-oka, Organometallics, 1999, 18, 3234; M. Akita,
M. Hashimoto, S. Hikichi and Y. Moro-oka, Organometallics, 2000,
19, 3744.
21 J.-F. Ma, Y. Kojima and Y. Yamamoto, J. Organomet. Chem., 2000,
616, 149.
26 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National
Laboratory, Oak Ridge, TN, USA, 1976.
22 G. R. Desiraju and T. Steiner, The Weak Hydrogen Bond in
Structural Chemistry and Biology, Oxford University Press, New
York, 2001.
27 V. D. Makhaev, Z. M. Dzhabieva, S. V. Konovalikhin,
O. A. D’yachenko and G. P. Belov, Russ. J. Coord. Chem., 1996, 22,
563.
D a l t o n T r a n s . , 2 0 0 3 , 2 6 6 6 – 2 6 7 3
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