Dinuclear Pt(II) and Pd(I) complexes with bridging PPh2 ligands from the reaction of PPh2H with zero-valent complexes of these metals

Article abstract of DOI:10.1246/bcsj.78.1288

Reactions of PPh₂H with [M(PCy₃)₂] (M = Pt, Pd) produce the dinuclear complexes with bridging PPh₂ ligands of these metals, [{Pt(H)(PCy₃)}₂(μ-PPh₂) ₂] and [{Pd-(PCy

Full text of DOI:10.1246/bcsj.78.1288

1288 Short Articles
Bull. Chem. Soc. Jpn., 78, 1288–1290 (2005)
Dinuclear Pt(II) and Pd(I)
Complexes with Bridging PPh2
Ligands from the Reaction
of PPh2H with Zero-Valent
Complexes of These Metals
Makoto Tanabe, Masumi Itazaki, Osamu Kitami,
ꢀ
Yasushi Nishihara, and Kohtaro Osakada
Fig. 1. ORTEP drawing of 1 at 30% ellipsoidal level. The
molecule has a C2 symmetry center at the midpoint of
two Pt centers. Atoms with asterisks are crystallographi-
cally equivalent to those having the same number without
Chemical Resources Laboratory (Mail Box R1-3),
Tokyo Institute of Technology, 4259 Nagatsuta,
Midori-ku, Yokohama 226-8503
ꢁ
ꢀ
asterisks. Selected distances (A) and angles ( ): Pt–P1
ꢀ
3.6499(2), P2 P2 2.945(2), Pt–H1 1.89(5), P1–Pt–P2
ꢀ
2.282(1), Pt–P2 2.322(1), Pt–P2 2.369(1), Pt Pt
ꢂꢂꢂ
ꢂꢂꢂ
Received February 23, 2005; E-mail: kosakada@res.titech.ac.jp
ꢀ
168.18(4), P1–Pt–P2 107.49(4), P2–Pt–P2 77.79(4),
ꢀ
P1–Pt–H1 75(1), P2–Pt–H1 99(1), Pt–P2–Pt 102.21(4).
ꢀ
ꢀ
Reactions of PPh2H with [M(PCy3)2] (M ¼ Pt, Pd)
produce the dinuclear complexes with bridging PPh2 ligands
of these metals, [{Pt(H)(PCy3)}2(ꢀ-PPh2)2] and [{Pd-
(PCy3)}2(ꢀ-PPh2)2], respectively.
ꢀ
to the hydrido ligand (2.369(1) A) is longer than that trans
ꢀ
to PCy3 ligand (2.322(1) A) due to a larger trans influence
of H atom than of PCy3.
Ph
60 0C
Cy3P Pt Ph
PCy3
2
)
2 Pt(PCy3 2
Phosphides (PR2) have been employed commonly as the
useful bridging ligands1 in forming the diplatinum2–5 and di-
palladium6–9 complexes, as well as heterobimetallic10–13 com-
plexes having group 10 metals. Flexible coordination of the
bridging phosphido ligands enables one to bind the two metals
with and without metal–metal bonds. Leoni and co-workers
obtained the phosphido-bridged dinuclear Pt(II) and Pd(I)
complexes from the reaction of [M(ꢁ3-C3H5)(ꢁ5-C5H5)]
(M ¼ Pt, Pd) with secondary bulky phosphine ligands.14,15 Re-
cently, we prepared dinuclear and trinuclear complexes with
bridging phosphido ligands from the reaction of PPh2H with
[Pt(PEt3)3].16 An initial product of the reaction is the dinuclear
Pt complex with bridging PPh2 ligands, [{Pt(H)(PEt3)}2(ꢀ-
PPh2)2], although it is readily converted into cyclic or linear
trinuclear Pt complexes under the reaction conditions. Similar
dinuclear complexes having bulky ligands would be kinetically
stabilized due to steric protection of the metal center. In this
paper, we report the reaction of PPh2H with Pt(0) and Pd(0)
complexes having PCy3 ligands to afford stable dinuclear com-
plexes of these metals.
toluene, 1 h
Ph2
ð1Þ
+ 2 PPh2H
r. t., 20 h
P
H
PCy3
H
Pt
Pt
Cy3P
P
Ph2
1
1
The hydrido signal of 1 in the H NMR spectrum appears
at ꢂ ꢃ7:57, accompanied by coupling with three phosphorus
nuclei (J(HP) ¼ 14, ꢃ23, 161 Hz) and one Pt nucleus
(J(HPt) ¼ 1042 Hz). The IR spectrum also shows the peak
due to Pt–H stretching at a characteristic position (2031
cmꢃ1). The 31P{1H} NMR spectrum of 1 contains two signals
at ꢂ 42.7 and ꢃ93:4 with a large J(PP) value (265 Hz). They
are assigned to PCy3 and bridging PPh2 ligands, respectively.
Appearance of a single signal due to the bridging PPh2 ligands
indicates anti structure of the complex in solution. No forma-
tion of syn isomer is noted in the NMR spectra. The coupling
pattern is consistent with the spectrum simulated by assuming
an AA0MM0XX0 spin system.17 Two 195Pt satellite signals
(J(PPt) ¼ 1330, 1730 Hz) are observed for the signals of
bridging PPh2 ligands. These J(PPt) values are attributed to
the Pt nucleus involved in the linear PPh2–Pt–H group and that
in the linear PPh2–Pt–PCy3 group. The 31P{1H} NMR signal
of PCy3 ligand shows a large J(PPt) coupling constant (2340
Hz).
[Pt(PCy3)2] is prepared in situ by heating a toluene solution
ꢁ
of cis-[Pt(Ph)2(PCy3)2] at 60 C and is reacted directly with
PPh2H in solution at room temperature. anti-[{Pt(H)(PCy3)}2-
(ꢀ-PPh2)2] (1) is formed as the product, as shown in Eq. 1.
Figure 1 displays the molecular structure of 1, which has
two Pt centers bridged by two PPh2 ligands. Table 1 summa-
rizes the crystallographic data of the obtained dinuclear Pt(II)
and Pd(I) complexes. Each Pt center is bonded to a hydrido
and a PCy3 ligand in a distorted square planar coordination.
Two hydrido ligands in the molecule are situated at the
The reaction of PPh2H with [Pd(PCy3)2] forms the phos-
phido-bridged dinuclear Pd(I) complex, [{Pd(PCy3)}2(ꢀ-
PPh2)2] (2), as a dark red solid in 67% yield (Eq. 2). The mole-
ꢀ
cule of 2 contains a Pd–Pd bond (2.5755(7) A) and a linear
opposite sides of the Pt Pt alignment, similarly to anti-
[{Pt(H)(PEt3)}2(ꢀ-PtBu2)2].16 The length of Pt–P bond trans
alignment of two non-bridging P and two Pd atoms (Fig. 2).
The Pd–P–Pd angle of the Pd2P2 core (67.58(5)ꢁ) is much
ꢂꢂꢂ
Published on the web July 1, 2005; DOI 10.1246/bcsj.78.1288

Bull. Chem. Soc. Jpn., 78, No. 7 (2005)
Table 1. Crystallographic Data for 1 and 2
Ó 2005 The Chemical Society of Japan 1289
1
C60H88P4Pt2 + toluene
1429.60
2
C60H86P4Pd2
1144.04
Formula
Formula weight
Color
Crystal size/mm3
Crystal system
Space group
yellow
0:14 ꢄ 0:06 ꢄ 0:04
red
0:32 ꢄ 0:25 ꢄ 0:20
monoclinic
P21=a (No. 14)
10.603(7)
triclinic
ꢁ
P1 (No. 2)
ꢀ
a/A
10.258(2)
10.731(2)
14.801(3)
87.018(5)
81.025(5)
72.603(4)
1535.6
1
ꢀ
b/A
17.101(12)
15.647(11)
ꢀ
c/A
ꢃ/deg
ꢄ/deg
ꢅ/deg
92.334(11)
ꢀ 3
V/A
Z
2834.9
2
1.340
1196
7.84
Dcalcd/g cmꢃ3
1.546
722
46.76
Fð000Þ
ꢀ/cmꢃ1
No. of reflns total
No. of reflns obsd (>3ꢆ)
No. of variables
R1 (I > 3ꢆðIÞ)
wR2
11565
9067
386
0.035
0.050
0.988
19964
7683
341
0.062
0.058
0.964
GOF
intermediate mononuclear complexes formulated as [M(H)-
(PPh2)(PCy3)n] (M ¼ Pd, Pt; n ¼ 1 or 2). Dimerization of
[Pt(H)(PPh2)(PCy3)n] yields complex 1, while formation of 2
requires elimination of hydrogen atoms during the dimeriza-
tion of the above Pd-containing intermediates. Leoni also
proposed a similar pathway for formation of the dipalladium
complex, [{Pd(PtBu2H)}2(ꢀ-PtBu2)2] in the reaction of the
secondary phosphine with the starting Pd(II) complex,
[M(ꢁ3-C3H5)(ꢁ5-C5H5)].15
We report preparation of the phosphido-bridged dinuclear
Pt(II) and Pd(I) complexes from the reaction of PPh2H with
the zero-valent complexes of these metals having PCy3 ligands.
Fig. 2. ORTEP drawing of 2 at 30% ellipsoidal level. The
molecule has a C2 symmetry center at the midpoint of
two Pt centers. Atoms with asterisks are crystallographi-
cally equivalent to those having the same number without
Experimental
General. All manipulations of the complexes were carried out
using standard Schlenk techniques under an argon or a nitrogen
atmosphere. Hexane and toluene were distilled from sodium
benzophenone ketyl and stored under nitrogen. 1H, 13C{1H},
and 31P{1H} NMR spectra were recorded on Varian Mercury
300 spectrometers. Peak position of the 31P{1H} NMR spectrum
was referenced to an external 85% H3PO4. [Pt(PCy3)2] was
prepared by an improved version of the previous method.18
[Pt(Ph)2(PCy3)2] and [Pd(PCy3)2] were prepared from the reac-
tion of [Pt(Ph)2(cod)] or [Pd(Me)2(tmeda)] (tmeda = N,N,N0,N0-
tetramethylethylenediamine) with PCy3.19 Diphenylphosphine
was obtained from commercial suppliers and was distilled before
using. IR absorption spectra were recorded with a Shimadzu
FT/IR-8100 spectrometer. Elemental analyses were carried out
with a Yanaco MT-5 CHN autocorder.
ꢁ
ꢀ
ꢀ
asterisks. Selected distances (A) and angles ( ): Pd–Pd
ꢀ
2.321(2), P1–Pd–P2 124.85(6), P2–Pd–P2 112.42(6),
2.5755(7), Pd–P1 2.291(2), Pd–P2 2.310(2), Pd–P2
ꢀ
Pd–P2–Pd 67.58(5).
ꢀ
smaller than the Pt–P–Pt angle of diplatinum complex 1
(102.21(4)ꢁ). The 31P{1H} NMR spectrum of 2 shows the
bridging phosphorus signal at ꢂ 174.6, which is in a much
lower magnetic field than that of 1 (ꢂ ꢃ93:4).
Ph2
P
r. t., 2 h
2 Pd(PCy3)2
+ 2 PPh2H
Cy3P Pd Pd PCy3
ð2Þ
toluene
P
Ph2
Preparation of anti-[{Pt(H)(PCy3)}2(ꢀ-PPh2)2] (1). A tol-
uene (3 cm3) solution of cis-[Pt(Ph)2(PCy3)2] (211 mg, 0.23
2
ꢁ
mmol) was heated at 60 C for 1 h to produce [Pt(PCy3)2] by re-
ductive elimination of biphenyl. Diphenylphosphine (0.044 cm3,
0.26 mmol) was added to the resulting mixture, which was stirred
Reactions (1) and (2) both involve initial oxidative addition
of PPh2H to the zero-valent complexes of these metals to form

1290 M. Tanabe et al.
Bull. Chem. Soc. Jpn., 78, No. 7 (2005)
at room temperature for 20 h. The solvent was removed under re-
duced pressure. The residual material was washed with 2 cm3 of
hexane twice and dried in vacuo to give 1 as yellow powder
(88%). Elemental analysis. Calcd for C60H88P4Pt2: C, 54.45; H,
6.70%; Found: C, 52.31; H, 6.49%. 1H NMR (300 MHz, CD2Cl2,
25 ꢁC): ꢂ ꢃ7:57 (ddd, 2H, PtH, J(HP) ¼ 14, ꢃ23, 161 Hz,
J(HPt) ¼ 1042 Hz), 1.06 (t, 12H, C6H11, J(HH) ¼ 12 Hz), 1.16
(t, 6H, C6H11, J(HH) ¼ 12 Hz), 1.48 (t, 12H, C6H11, J(HH) ¼
12 Hz), 1.65 (t, 24H, C6H11, J(HH) ¼ 12 Hz), 1.79 (t, 12H,
C6H11, J(HH) ¼ 11 Hz), 7.03 (m, 12H, C6H5-meta and para),
7.52 (br, 8H, C6H5-ortho). 13C{1H} NMR (75 MHz, CD2Cl2, 25
ꢁC): ꢂ 26.9 (s, PCHCH2CH2CH2), 27.6 (d, PCHCH2CH2,
J(CP) ¼ 10:3 Hz), 30.5 (apparent triplet, PCHCH2, J(CPt) ¼
12:1 Hz), 36.1 (m, PCH, J(CP) ¼ 23:5 Hz), 126.8 (m, C6H5-meta,
J(CP) ¼ 8:7 Hz), 128.5 (s, C6H5-para), 136.0 (m, C6H5-ortho,
J(CP) ¼ 11:0 Hz), 142.7 (m, C6H5-ipso, J(CP) ¼ 28:4 Hz).
31P{1H} NMR (121 MHz, CD2Cl2, 25 ꢁC): ꢂ ꢃ93:4 (PPh2,
2J(PP) ¼ ꢃ14, ꢃ80, 265 Hz, 1J(PPt) ¼ 1330, 1730 Hz), 42.7
refinement of the parameters. Crystallographic data for the struc-
tural analyses have been deposited with the Cambridge Crystallo-
graphic Data Centre, CCDC Nos. 264269 and 264270 for 1 and 2,
respectively. Copies of this information may be obtained free of
charge from the Director, CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (Fax: +44-1223-336-033; e-mail: deposit@ccdc.
cam.ac.uk or http://www.ccdc.cam.ac.uk).
This work was supported by Grants-in-Aid for Scientific
Research from the Ministry of Education, Culture, Sports,
Science and Technology, Japan.
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ꢂ 0.99 (t, 6H, C6H11, J(HH) ¼ 12 Hz), 1.11 (q, 12H, C6H11,
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´
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5:1 Hz), 31.1 (s, PCHCH2CH2), 35.6 (apparent quintet, PCH,
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ꢁ
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