Dialkyl- and diaryl-platinum(II) complexes with secondary phosphines: Preparation, structure and thermal reaction giving the metallopolymer

Article abstract of DOI:10.1016/j.jorganchem.2009.03.009

Alkyl and arylplatinum complexes with 1,5-cyclooctadiene ligand, [PtR₂(cod)] (R = Me, Ph, C₆H₄-p-CF₃, C₆F₅), react with secondary phosphines, PHR′₂ (R′ = i-Bu, t-Bu, Ph), to affo

Full text of DOI:10.1016/j.jorganchem.2009.03.009

Journal of Organometallic Chemistry 694 (2009) 2270–2278
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Dialkyl- and diaryl-platinum(II) complexes with secondary phosphines:
Preparation, structure and thermal reaction giving the metallopolymer
*
Masaki Kakeya, Makoto Tanabe, Yoshiyuki Nakamura, Kohtaro Osakada
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Alkyl and arylplatinum complexes with 1,5-cyclooctadiene ligand, [PtR2(cod)] (R = Me, Ph, C6H4-p-CF3,
C6F5), react with secondary phosphines, PHR02 (R0 = i-Bu, t-Bu, Ph), to afford the mononuclear platinum
complexes, cis-[PtR2(PHR02)2] (1a: R = Me, R0 = i-Bu; 1b: R = Me, R0 = t-Bu; 1c: R = Me, R0 = Ph; 2a: R = Ph,
R0 = i-Bu; 2b: R = Ph, R0 = t-Bu; 2c: R = R0 = Ph; 3a: R = C6H4-p-CF3, R0 = i-Bu; 3b: R = C6H4-p-CF3, R0 = t-
Bu; 3c: R = C6H4-p-CF3, R0 = Ph; 4a: R = C6F5, R0 = i-Bu; 4c: R = C6F5, R0 = Ph) in 81–98% yields. Molecular
structures of the complexes except for 1a, 1c and 2a were determined by X-ray crystallography. Complex
1b has a square-planar structure with Pt–C(methyl) bonds of 2.083(8) and 2.109(8) Å, while the Pt–
C(aryl) bonds of 2b–c, 3a–c, 4a and 4c (2.055(1)–2.073(8) Å) are shorter than them. Thermal decompo-
sition of 1b, 2a–c, and 3a–c releases methane, biphenyl or 4,40-bis(trifluoromethyl)biphenyl as the
organic products, which are characterized by NMR spectroscopy. The solid product of the thermal reac-
tions of 2b and 2c were characterized as the metallopolymers formulated as [Pt(PR02)2]n (5b: R0 = tBu; 5c:
R0 = Ph), based on the solid-state NMR and elemental analyses.
Received 28 January 2009
Received in revised form 4 March 2009
Accepted 6 March 2009
Available online 13 March 2009
Keywords:
Platinum
Secondary phosphine
Thermogravimetry
Metallopolymer
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
tend to undergo b-hydrogen elimination, giving alkenes, rather
than the reductive elimination of alkanes [13].
Tertiary phosphines have long been employed as the auxiliary
ligands of organotransition–metal complexes and of the transition
metal complexes which catalyze the synthetic organic reactions
[1–3]. Since the substituents on the phosphorus atom influence
the steric and electron-releasing (or -withdrawing) characters of
the tertiary phosphines [4], one could obtain the transition metal
complexes with desired chemical properties by choosing the phos-
phines suited as the auxiliary ligands. Dialkyl- and diaryl-com-
plexes of group 10 metals, Ni(II), Pd(II) and Pt(II), with tertiary
phosphines ligands, [MR2(PR03)2] (M = Ni, Pd, Pt; R = R0 = alkyl, aryl)
were well characterized owing to the rigid square-planar struc-
tures as well as to the presence of 31P and/or 195Pt nuclei which
render the NMR spectra of the complexes more informative [5–
9]. Dialkyl- and diaryl-platinum(II) complexes with tertiary phos-
phines prefer the cis-structure, although dialkylpalladium com-
plexes exist as the trans- or cis-structure [8,10]. The
diarylplatinum complexes undergo thermally induced reductive
elimination of the corresponding biaryls [11]. Recent studies on
the unsymmetrical diarylplatinum complexes, [Pt(Ar)(Ar0)(dppf)]
(DPPF = 1,10-bis(diphenylphosphino)ferrocene), revealed that the
thermodynamic and kinetic parameters for the reductive elimina-
tion of biaryl is influenced by the substituents of the aryl ligands
[12]. Dialkylplatinum complexes with tertiary phosphine ligands
Secondary phosphines, however, have attracted much less
attention than the tertiary phosphines as the auxiliary ligands of
the mononuclear organoplatinum complexes. The Pt complexes
with the secondary phosphine ligands have recently been reported
in relation to the mechanism of hydrophosphination catalyzed by
Pd complexes [14]. The secondary phosphines are often reported
to lose the P–H hydrogen, upon coordination to Pt to yield the
bridging phosphide (PR2) ligands [15]. The reaction of PHPh2 with
a Pt(0) complex affords the cyclic triplatinum complexes with
bridging diphenylphosphide ligands probably via oxidative addi-
tion of the phosphine ligand to the metal center [16]. Herein, we
report the synthesis and molecular structures of the mononuclear
platinum complexes with secondary phosphine ligands, cis-
[PtR2(PHR02)2] (R = Me, Ph, C6H4-p-CF3, C6F5; R0 = i-Bu, t-Bu, Ph),
as well as their thermal properties.
2. Results and discussion
The reactions of secondary phosphines, PHR02 (R0 = i-Bu, t-Bu,
Ph), with [PtR2(cod)] (R = Me, Ph, C6H4-p-CF3, C6F5) at room tem-
perature produced the mononuclear platinum complexes formu-
lated as cis-[PtR2(PHR02)2] (1a: R = Me, R0 = i-Bu; 1b: R = Me,
R0 = t-Bu; 1c: R = Me, R0 = Ph; 2a: R = Ph, R0 = i-Bu; 2b: R = Ph,
R0 = t-Bu; 2c: R = R0 = Ph; 3a: R = C6H4-p-CF3, R0 = i-Bu; 3b:
R = C6H4-p-CF3, R0 = t-Bu; 3c: R = C6H4-p-CF3, R0 = Ph; 4a: R = C6F5,
R0 = i-Bu; 4c: R = C6F5, R0 = Ph), as shown in Scheme 1.
* Corresponding author.
E-mail address: kosakada@res.titech.ac.jp (K. Osakada).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.03.009

M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
2271
R'2HP
R
2 PHR'2, toluene / hexane
r.t., - COD
R
R
Pt
Pt
R'2HP
R
1a:
1b:
1c:
2a:
2b:
2c:
3a:
3b:
3c:
4a:
4c:
R = Me,
R' = i-Bu
R' = t-Bu
R' = Ph
R = Me,
R = Me,
R = Ph,
R = Ph,
R = Ph,
R' = i-Bu
R' = t-Bu
R' = Ph
R = C6H4-p-CF3, R' = i-Bu
R = C6H4-p-CF3, R' = t-Bu
R = C6H4-p-CF3, R' = Ph
R = C6F5,
R = C6F5,
R' = i-Bu
R' = Ph
Scheme 1.
Table 1 summarizes the yields and analytical data of the com-
plexes. Complex 4c was prepared by Forniés et al. and character-
ized based on the spectroscopic data [17]. A reaction of PH(t-Bu)2
with [Pt(C6F5)2(cod)] did not give a phosphine-coordinated com-
plex partly due to the sterically bulky P-ligand and to unfavorable
dissociation of the cod owing to a small trans effect of the pentaflu-
orophenyl ligand. Most of the obtained compounds were fully
characterized by X-ray crystallography and NMR spectroscopy,
while 1a, 1c and 2a were characterized based on the NMR and ele-
mental analyses data.
Figs. 1–4 show the molecular structures of 1b, 2b–c, 3a–c, 4a
and 4c determined by X-ray crystallography. Major bond parame-
ters are summarized in Table 2. All these complexes are adopted to
square-planar structures around the Pt center, which are coordi-
nated to two secondary phosphine ligands at cis positions and to
two methyl or aryl ligands. Pt–C(methyl) bond distances of 1b
Fig. 1. ORTEP drawing of 1b with ellipsoids drawn at the 30% probability level.
Positions of P–H hydrogens are obtained by calculation. Other hydrogen atoms are
omitted in the drawing for simplicity.
are 2.083(8) and 2.109(8) Å, which are longer than Pt–C(aryl)
bonds of 2b–c, 3a–c, 4a and 4c (2.051(1)–2.077(8) Å) due to signif-
icant p-back donation from Pt to the ipso carbon of the aryl ligand.
The molecular structures are classified into three types summa-
rized in Scheme 2, based on conformation of the two secondary
phosphine ligands. Complexes 1b and 3a contain the two P–H
bonds, which are parallel to each other, and orientated toward in-
ner area of the P–Pt–P angle (i). The P–H bonds of 2b, 3b and 4c are
also orientated toward the inner area, although they are not paral-
lel (ii). On the other hand, complexes 2c, 3c and 4a have one P–H
bond orientated to the inner area of the P–Pt–P, and the other
Table 1
Yields, analytical results, IR data, and melting points of the complexes 1–4.
Complex
Yield (%)a
Anal. (%)b
C
IRc
m
(P–H)
m.p. (°C)
H
d
cis-[PtMe2{PH(i-Bu)2}2] (1a)
cis-[PtMe2{PH(t-Bu)2}2] (1b)
cis-[PtMe2(PHPh2)2] (1c)
89
94
87
89
95
81
91
85
96
95
98
41.69
(41.77)
8.29
(8.57)
2305
–
41.45
(41.77)
8.67
(8.57)
2311
2299
158
146
168
52.02
(52.26)
4.75
(4.72)
2330
cis-[PtPh2{PH(i-Bu)2}2] (2a)
cis-[PtPh2{PH(t-Bu)2}2] (2b)
cis-[PtPh2(PHPh2)2] (2c)
52.15
(52.41)
7.49
(7.54)
2345
2311
e
52.34
(52.41)
7.41
(7.54)
2307
–
60.00
(59.92)
4.33
(4.47)
2341
2328
176
126
160
178
191
241
cis-[Pt(C6H4-p-CF3)2{PH(i-Bu)2}2] (3a)
cis-[Pt(C6H4-p-CF3)2{PH(t-Bu)2}2] (3b)
cis-[Pt(C6H4-p-CF3)2(PHPh2)2] (3c)
cis-[Pt(C6F5)2{PH(i-Bu)2}2] (4a)
cis-[Pt(C6F5)2(PHPh2)2] (4c)f
46.23
(46.33)
6.03
(5.96)
2338
2307
2336
2363
2334
46.21
(46.33)
5.94
(5.96)
52.99
(53.22)
3.50
(3.53)
41.04
(40.93)
4.54
(4.66)
–
–
a
Isolated yield.
b
Calculated values are shown in parentheses.
c
cmꢀ1 in KBr disks.
d
Oil at room temperature.
Not observed.
Reported by Forniés et al. See Ref. [17].
e
f

2272
M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
Fig. 2. ORTEP drawings of (a) 2b and (b) 2c with ellipsoids drawn at the 30%
probability level. One of the two crystallographically independent molecules of 2b
is shown. All the P–H hydrogens of 2b and one of the P–H hydrogens of 2c were
located by calculation, although position of the remaining P–H hydrogen of 2c was
determined from D-map.
P–H bond to the outer area, and these molecules are classified into
unsymmetric structure (iii). The complexes with dialkylphosphine
ligands except for 4a belong to (i) or (ii), which the complexes with
diphenylphosphine ligands, 2c and 3c, prefer the unsymmetrical
structure in (iii) the crystalline state.
IR data of the complexes are listed in Table 1. The stretching
vibration of the P–H bonds of the secondary phosphine ligands
are observed at 2299–2363 cmꢀ1, which are at higher positions
than those of the free secondary phosphines (PH(i-Bu)2:
2284 cmꢀ1, PH(t-Bu)2: 2278 cmꢀ1, PHPh2: 2286 cmꢀ1). Complexes
1b, 2a and 2c show two peaks for the P–H stretching vibrations.
It may be ascribed to the presence of the conformational isomers
shown in Scheme 2, although the molecules in the single crystals
of each complex were characterized as a single conformational iso-
mer by X-ray crystallography. The shift of P–H stretching vibration
of PH(t-Bu)2 caused by its coordination to the Pt center of 1b, 2b
and 3b (21–33 cmꢀ1) is smaller than most of the change of the
peak positions of PH(i-Bu)2 (54–79 Hz) except 1a (21 Hz) and 2a
(27 Hz for one peak) and of free PHPh2 (42–55 Hz). The 1H and
13C{1H} NMR data of 1–4 are listed in Tables 3 and 4, respectively.
The two methyl ligands of 1a–1c show the 1H NMR signals at
d 1.04–1.46 and the 13C{1H} NMR signals at d ꢀ0.50 to 5.04.
These signals are splitted with reasonable coupling constants,
Fig. 3. ORTEP drawings of (a) 3a, (b) 3b and (c) 3c with ellipsoids drawn at the 30%
probability level. All the P–H hydrogens were located by calculation, and other
hydrogen atoms are omitted in the drawing for simplicity. One of the disordered
positions of the fluorine atoms is shown.
assigned based on the coupling patterns and peak positions. 1H
NMR peaks due to the P–H hydrogen of the complexes with the
dialkylphosphine ligands, 1a–b, 2a–b, 3a–b and 4a, are observed
at d 3.81–4.06, which are at higher magnetic field positions than
the free dialkylphosphines (PH(i-Bu)2: d 6.76 and PH(t-Bu)2: d
5.80). The P–H hydrogen resonances of diphenylphosphine com-
plexes, 1c, 2c, 3c and 4c, appear in the lower magnetic field region
(d 5.68–5.88) than free PHPh2 (d 5.19). JP–H values of the complexes
with PH(i-Bu)2 and PH(t-Bu)2 ligands (1a–b, 2a–b and 3a–b) (330–
350 Hz) are smaller than those of the PHPh2-coordinated com-
plexes 1c, 2c and 3c (360–380 Hz), although the pentafluorophenyl
complex with PH(i-Bu)2 ligands 4a shows a large JP–H value
(360 Hz).
1
2JPt–H = 69–71 Hz and JPt–C = 600–616 Hz. The 13C{1H} NMR peaks
19F{1H} and 31P{1H} NMR data of the complexes are listed in
Table 5. 31P{1H} NMR signals of the ligands, PH(i-Bu)2 (1a, 2a, 3a
and 4a), PH(t-Bu)2 (1b, 2b and 3b) and PHPh2 (1c, 2c, 3c and 4c),
are observed at d ꢀ30.2 to ꢀ23.0, d 49.7–59.2 and d –7.78–3.96,
due to ipso carbons of the aryl ligand of 2–4 were observed in
the range of d 145.1–167.6 with JPt–C = 825–850 Hz. The NMR spec-
tra of the arylplatinum complexes (2a–c, 3a–c, 4a and 4c) exhibit
the signals of aromatic hydrogens and carbons, and they are

M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
2273
R'
R'
R'
R'
R'
R'
P
H
P
P
P
P
H
H
H
R'
Pt
Pt
Pt
H
P
R'
R'
R'
R'
R'
H
(i)
(ii)
(iii)
Scheme 2.
above complexes, indicating a smaller trans influence of the C6F5
ligand than the methyl, phenyl, and p-(trifluoromethyl)phenyl li-
gands. The 19F{1H} NMR spectra of 4a and 4c show signals for
the fluorine atoms at ortho position with coupling constants of
3JPt–F = 318 and 330 Hz, respectively.
Complexes prepared in this study are expected to undergo ther-
mally induced coupling of the methyl and aryl ligands and/or hydro-
gen loss of the secondary phosphide ligands. Another possible
reaction, which may take place upon heating, is the coupling of the
methyl (or aryl) ligands with a P–H hydrogen. TG measurement of
1b, 2b, 3b and 4a was conducted in order to monitor weight loss of
the complexes during heating in the solid-state. Fig. 5 compares
the thermal weight change of these complexes monitored up to
450 °C. Complexes 1b, 2b and 3b start to decrease the weights at
150 °C, 135 °C, and 160 °C, respectively. The weight loss of 1b at
200 °C (6%) corresponds to that calculated by assuming evolution
of methane (see below) from the starting molecule. Complexes 2b
and 3b undergo initial decrease of the weight below 190 °C, and
the weight loss at that temperature (24% and 38%) corresponds to
those calculated assuming reductive elimination of biphenyl from
2b (24%) and of 4,40-bis(trifluoromethyl)biphenyl from 3b (37%),
respectively. Complex 4a is thermally more stable, and starts ther-
mal weight decrease above 180 °C. Weight loss at 270–330 °C
(65%) is larger than that obtained by assuming elimination of two
pentafluorophenyl ligands, and it can be ascribed to the decomposi-
tion including elimination of the phosphine ligands. Complexes 1b,
2b and 3b also show further thermal decomposition at 260–
330 °C. These results suggest that complexes 1b, 2b and 3b undergo
elimination of methane or reductive elimination of biaryls at the ini-
tial stage of thermolysis and that thermolysis of 4a with the more
stablePt–C bondsoccurs at muchhigher temperature, and accompa-
nies elimination of the phosphine ligands.
Fig. 4. ORTEP drawings of (a) 4a and (b) 4c with ellipsoids drawn at the 30%
probability level. All the P–H hydrogens were located by calculation, and other
hydrogen atoms are omitted in the drawing for simplicity.
respectively, which are at much lower magnetic field positions
than the signals of free secondary phosphines (PH(i-Bu)2: d
ꢀ83.5, PH(t-Bu)2: d 20.1, and PHPh2: d ꢀ39.7). The JPt–P values of
the complexes 1a–c, 2a–c and 3a–c are within the range, 1516–
1721 Hz, which is similar to those of already reported cis-dialkyl-
and diphenylplatinum complexes with tertiary phosphine ligands.
JPt–P values of 4a and 4c (2304 and 2175 Hz) are larger than the
Table 2
Selected bond lengths (Å) and bond angles (°) for 1b, 2b–c, 3a–c, 4a and 4c.
1b
2ba
2c
3a
3b
3c
4a
4c
Bond lengths (Å)
Pt–C1
Pt2–C29
Pt–C2, C7, C8b
Pt2–C35
Pt–P1
Pt2–P3
Pt–P2
Pt2–P4
2.083(8)
2.109(8)
2.306(2)
2.288(2)
2.065(7)
2.065(8)
2.072(7)
2.077(8)
2.319(2)
2.338(2)
2.343(2)
2.343(2)
2.065(7)
2.071(8)
2.288(2)
2.283(2)
2.054(3)
2.068(3)
2.296(1)
2.301(1)
2.070(6)
2.061(6)
2.340(2)
2.343(2)
2.051(3)
2.057(3)
2.300(1)
2.275(1)
2.067(4)
2.073(5)
2.276(1)
2.276(2)
2.070(3)
2.067(3)
2.277(1)
2.286(1)
Bond angles (°)
P1–Pt–P2
P3–Pt2–P4
92.33(7)
93.4(2)
82.2(3)
92.1(2)
90.67(8)
91.l3(7)
96.2(2)
94.7(2)
81.9(3)
82.0(3)
92.0(2)
92.2(2)
95.40(6)
89.2(2)
86.7(3)
88.8(2)
95.88(3)
88.3(1)
87.1(1)
88.7(1)
92.28(6)
93.5(2)
80.1(2)
94.5(2)
93.9(1)
90.2(1)
87.5(2)
88.6(1)
94.27(5)
89.2(2)
88.6(2)
88.3(1)
90.41(3)
90.7(1)
88.1(1)
90.8(1)
P2–Pt–C1
P4–Pt2–C29
C1–Pt–C2, C7, C8b
C29–Pt2–C35
P1–Pt–C2, C7, C8b
P3–Pt2–C35
a
Parameters of two crystallographically independent molecules are shown.
C2 for 1b; C7 for 2b, 2c, 4a and 4c; C8 for 3a–c.
b

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M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
Table 3
1H NMR spectroscopic data for 1–4.a
PtR
PH
PR02
H
3
3
1a
1b
1.04 (dd, CH3, 6H, JP–H = 7.2, 9.0 Hz, JPt–H = 69 Hz)
4.06(m, 2H, JP–H = 330 Hz, JP–H = 7.3 Hz)
1.91 (septet, CH, 4H), 1.63 (m, CH2, 8H)
3
0.94 (d, CH3, 12H, JH–H = 6.6 Hz)
3
0.87 (d, CH3, 12H, JH–H = 6.6 Hz)
3
3
1.23 (apparent triplet, CH3, 6H, JP–H = 6.4 Hz,
3.67 (brm, 2H, JP–H = 330 Hz, JP–H = 13 Hz)
1.29 (s, 9H, CH3)
2JPt–H = 70 Hz)
1.26 (s, 9H, CH3)
2
3
1c
2a
1.46 (dd, CH3, JP–H = 6.9, 9.9 Hz, JPt–H = 71 Hz)
5.82 (brm, 2H, JP–H = 360 Hz, JP–H = 10 Hz)
7.40 (m, 8H, ortho)
6.94 (m, 12H, para and meta)
3
3
7.70 (tt, 4H, ortho, JPt–H = 59 Hz, JH–H = 6.0 Hz)
7.18 (t, 4H, meta, JH–H = 6.0 Hz)
6.92 (t, 2H, para, JH–H = 6.0 Hz)
7.77 (t, 4H, ortho, JH–H = 6.3 Hz, JPt–H = 31 Hz)
7.08 (t, 4H, meta, JH–H = 7.8 Hz)
6.92 (t, 2H, para, JH–H = 6.9 Hz)
3.99 (m, 2H, JP–H = 330 Hz, JP–H = 6.3 Hz)
1.98 (m, 4H, CH), 1.47 (m, 4H, CH2) 1.29 (m, 4H, CH2)
3
3
0.97 (d, 6H, CH3, JH–H = 6.6 Hz)
3
3
0.83 (d, 6H, CH3, JH–H = 6.6 Hz)
3
3
3
2b
2c
3a
3.83 (m, 2H, JP–H = 330 Hz, JP–H = 19 Hz)
1.21 (s, 9H, CH3)
1.17 (s, 9H, CH3)
3
3
3
3
7.73 (t, 4H, ortho, JH–H = 6.3 Hz, JPt–H = 62 Hz)
7.08 (t, 4H, meta, JH–H = 6.0 Hz),
6.92 (m, 2H, para)
5.88 (m, 2H, PH, JP–H = 370 Hz)
7.27 (t, 8H, ortho, JH–H = 7.8 Hz)
3
6.92 (m, 12H, meta, para)
3
3
3
7.57 (tt, 4H, ortho, JH–H = 5.7 Hz, JPt–H = 23 Hz)
3.85 (m, 2H, PH, JP–H = 330 Hz, JP–H = 6.6 Hz)
1.84 (m, 4H, CH), 1.24 (m, 8H, CH2) 0.89 (d, 12H,
3
CH3, JH–H = 6.6 Hz)
3
3
7.40 (t, 4H, meta, JH–H = 6.9 Hz)
0.76 (d, 12H, CH3, JH–H = 6.6 Hz)
3
3
3
3b
3c
4a
7.54 (tt, 4H, ortho, JH–H = 6.0 Hz, JPt–H = 59 Hz)
3.81 (m, 2H, PH, JP–H = 350 Hz, JP–H = 18 Hz)
1.06 (s, 9H, CH3)
1.02 (s, 9H, CH3)
3
7.02 (d, 4H, meta, JH–H = 7.8 Hz)
3
7.54 (tt, 4H, ortho, JH–H = 6.9 Hz, JPt–H = 30 Hz)
7.02 (t, 4H, meta, JH–H = 7.2 Hz)
5.68 (br-m, 2H, PH, JP–H = 380 Hz, JP–H = 6.6 Hz)
7.11 (m, 8H, para)
6.91 (m, 12H, ortho, meta)
3
4.00 (m, 2H, PH, JP–H = 360 Hz, JP–H = 7.2 Hz)
1.89 (m, 4H, CH), 1.39 (m, 8H, CH2) 0.86 (d, 12H,
3
CH3, JH–H = 6.6 Hz)
3
0.74 (d, 12H, CH3, JH–H = 6.6 Hz)
4c
Ref. [17]
Ref. [17]
Ref. [17]
a
At 300 MHz in C6D6 at room temperature except for 1b. At 400 MHz in C6D6 at room temperature for 1b.
Table 4
13C{1H} NMR spectroscopic data for 1–4.a
PtR
PR02
H
2
2
2
2
1a 1.69 (dd, CH3, JPtrans–C = 9 Hz, JPcis–C = 10 Hz, JPt–C = 601 Hz)
31.3 (d, CH2, JP–C = 3 Hz, JPt–C = 15 Hz), 26.6 (apparent triplet, CH, JP–C = 9 Hz),
3
3
24.4 (apparent triplet, CH3, JP–C = 5 Hz), 23.6 (apparent triplet, CH3, JP–C = 3 Hz)
2
2
2
3
1b ꢀ0.50 (dd, CH3, JPtrans–C = 11 Hz, JPcis–C = 100 Hz, JPt–C = 600 Hz)
33.8 (m, CCH3), 32.1 (d, CCH3, JP–C = 4 Hz, JPt–C = 11 Hz)
2
2
2
1c 5.04 (dd, CH3, JPtrans–C = 8 Hz, JPcis–C = 101 Hz, JPt–C = 616 Hz)
134.1 (apparent triplet, ortho, JP–C = 5 Hz), 130.7 (m, ipso), 129.9 (s, para), 128.4
3
(apparent triplet, meta, JP–C = 5 Hz)
2
2
2a 161.3 (dd, ipso, JPtrans–C = 114 Hz, JPcis–C = 13 Hz, JPt–C = 840 Hz), 137.0 (t, meta,
30.2 (m, CH, 2JP–C = 31 Hz), 26.7 (t, CH2, JP–C = 8 Hz), 24.4 (t, CH3, 3JP–C = 5 Hz), 23.5
(t, CH3, JP–C = 5 Hz)
3JPt–C = 17 Hz), 127.8 (t, ortho, JPt–C = 2 Hz), 122.2 (t, para, JPt–C = 6 Hz)
2
4
3
2
2
2b 157.6 (dd, ipso, JPtrans–C = 110 Hz, JPcis–C = 12 Hz, JPt–C = 843 Hz), 138.7 (t, ortho,
34.6 (m, CCH3, JP–C = 20 Hz), 32.2 (s, CCH3)
2JPt–C = 18 Hz), 127.2 (t, para, JPt–C = 2 Hz), 121.7 (t, meta, JPt–C = 6 Hz)
4
3
2
2
2c 160.3 (dd, ipso, JPtrans–C = 113 Hz, JPcis–C = 13 Hz, JPt–C = 850 Hz), 128.5 (m, ortho
137.4 (t, meta, 3JPt–C = 15 Hz), 134.1 (apparent triplet, ortho, 2JP–C = 6 Hz), 130.2 (s,
para), 129.5 (s, ipso)
3
overlapped with C6D6), 122.6 (t, meta, JPt–C = 43 Hz)
2
2
3a 167.6 (m, ipso, JPtrans–C = 112 Hz, JPcis–C = 13 Hz, JPt–C = 840 Hz), 140.0 (brt, para),
30.2 (m, CH), 26.6 (apparent triplet, CH2, JP–C = 8 Hz), 24.3 (apparent triplet, CH3,
3
2
136.8 (t, meta, JPt–C = 36 Hz), 123.8 (m, ortho), 126.1 (quartet, CF3, JF–C = 271 Hz)
2JP–C = 5 Hz), 23.4 (apparent triplet, CH3, JP–C = 5 Hz)
2
3
3b 164.0 (dd, ipso, 2JPtrans–C = 108 Hz, 2JPcis–C = 12 Hz), 136.1 (brm, para), 125.3 (d, CF3, 34.6 (m, CCH3, JP–C = 10 Hz), 31.9 (s, CCH3, JP–C = 218 Hz, JPt–C = 422 Hz)
2
JF–C = 229 Hz), 123.1 (t, ortho, JPt–C = 67 Hz)
2
2
3c 166.0 (m, ipso, JPtrans–C = 112 Hz, JPcis–C = 11 Hz, JPt–C = 825 Hz), 137.0 (t, meta,
3JPt–C = 18 Hz), 129.3 (s, para), 125.3 (quartet, CF3, JF–C = 270 Hz), 123.9 (t, ortho,
2JP–C = 34 Hz)
137.8 (s, ipso), 133.8 (m, ortho), 130.6 (s, para), 128.7 (m, meta)
2
2
2
4a 146.9 (dd, ortho, JF–C = 229 Hz, JPt–C = 18 Hz), 137.9 (m, meta and para, JF–
31.4 (d, CH2, JP–C = 10 Hz, JPt–C = 34 Hz), 26.3 (apparent triplet, CH, JP–C = 9 Hz),
3
3
C = 248 Hz)
24.1 (apparent triplet, CH3, JP–C = 6 Hz), 23.1 (apparent triplet, CH3, JP–C = 2 Hz)
3
4c 148.3 (m, ortho), 145.1 (m, ipso), 139.7 (m, para), 136.3 (m, meta)
133.5 (m, ortho),131.2 (s, para), 128.7 (m, meta), 125.4 (apparent triplet, ipso, JP–
C = 38 Hz)
a
At 75 MHz in C6D6 at room temperature except for 1b. At 100 MHz in C6D6 at room temperature for 1b.
Heating complexes 1a–c in a pressure-resistant NMR tube at
150 °C for 18 h in C6D6/n-C11H24 (3:1) forms CH4 which is character-
ized by 1H NMR spectra of the reaction mixtures. Thermal reactions
of 2a–c and 3a–c in undecane at 180 °C (18 h) and 1H NMR measure-
ment of a part of the reaction mixture in CDCl3 showed formation of
biphenyl and 4,40-bis(trifluoromethyl)biphenyl, respectively. Prod-
ucts of thermolysis of 4a and 4c formed by TG measurement up to
330 °C, however, did not contain decafluorobiphenyl.
Pt-containing products of the thermal reactions of 2b and 2c
(200 °C for 18 h) are obtained as yellow solids after washing the

M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
2275
Table 5
31P{1H} and 19F{1H} NMR spectroscopic data for 1–4.
31P{1H}a
19F{1H}b
1a ꢀ23.0 (JPt–P = 1721 Hz)
1b 59.2 (JPt–P = 1705 Hz)
1c
3.96 (JPt–P = 1721 Hz)
2a ꢀ29.3 (JPt–P = 1624 Hz)
2b 51.0 (JPt–P = 1574 Hz)
2c
3a ꢀ30.2 (JPt–P = 1673 Hz) ꢀ61.9 (s, CF3)
3b 49.7 (JPt–P = 1630 Hz)
ꢀ61.9 (s, CF3)
3c
ꢀ1.47 (JPt–P = 1663 Hz) ꢀ59.9 (s, CF3)
0.75 (JPt–P = 1516 Hz)
3
4a ꢀ29.6 (JPt–P = 2304 Hz) ꢀ115.0 (apparent triplet, C6F5 ortho, JPt–F = 318 Hz,
4JP–F = 160 Hz), ꢀ158.6 (s, C6F5 para), ꢀ160.9
(s, C6F5 meta)
4c
ꢀ7.78 (JPt–P = 2175 Hz) Ref. [17]
a
At 121 MHz in C6D6 at room temperature.
At 376 MHz in C6D6 at room temperature.
b
product with hexane. The following data of the product indicate
formation of the Pt-containing polymers, 5b and 5c, as shown in
Scheme 3.
The IR spectra of 5b and 5c do not show a peak assignable to the
P–H bond stretching vibration. The results of elemental analysis
are consistent with the value calculated as the doubly phos-
phide-bridged platinum complexes. Fig. 6 shows the solid-state
CPMAS 31P{1H} NMR spectrum of 5b, which shows a single signal
at d 73.4 franked with 195Pt nucleus (JPt–P = 1770 Hz). The peak po-
sition as well as that of 5c (d 81.3, JPt–P = 2130 Hz) are shifted to
lower magnetic field positions compared with that of the mononu-
clear platinum complexes 2b (d 51.0) and 2c (d 0.75) in the solu-
tion. The JPt–P values change, depending on the bridging ligands.
Glueck reported that cationic Pt(II) complexes with doubly bridg-
Fig. 6. CPMAS 31P{1H} NMR spectrum of 5b. Signals marked with arrows are
assigned to 195Pt satellite signals. The satellites due to the 195Pt–31P–195Pt
isotopomer are not observed probably due to low intensity. Signals with asterisk
are due to the spinning side band that resulted from the spinning speed of 5 kHz.
PMes)2] and [{Pt(dppe)}2(
values, 805 and 744 Hz, respectively [19]. Leoni reported that a
neutral Pt(I) complex with doubly -P(t-Bu)2 ligands and a Pt–Pt
bond, [{PtL{PH(t-Bu)2}{ -P(t-Bu)2}2] (L = CO, PH(t-Bu)2) show JPt–P
value of 2431–2670 Hz, and Mastrorilli reported a neutral Pt(II)
complex without Pt–Pt bond [20], [{PtH2{PH(t-Bu)2}2{ -P(t-
l-PMeMes)(l-PMes)][BF4] showed JPt–P
l
l
l
ing phosphide ligands, [{Pt(dppe)}2(
Mes = 2,4,6-C6H2Me3) and [{Pt(dppe)}2(
l
-PRMes)2][BF4]2 (R = H, Me;
-PMeMes)( -PMes)][BF4]
Bu)2}2] shows JPt–P value of 1963 Hz [21]. Although JPt–P value of
5b are higher than those, which is closer to a neutral Pt(II) complex
without Pt–Pt bond than that of a Pt–Pt bond. Forniés reported that
l
l
showed JPt–P values in the range, 1632–1770 and 1898 Hz, respec-
tively [19]. On the other hand JPt–P value of neutral Pt(II) complexes
with bridging phosphinidene ligands (l-PMes), [{Pt(dppe)}2(l-
a
cationic trinuclear Pt(II) complex with
l-PPh2 ligands,
[Pt3(C6F5)3{PPh2(C6F5)}( -PPh2)3] shows JPt–P value in the range,
l
1964–2263 Hz. The JPt–P value of 5c is in the range of these values
[22]. The cyclic complex with the bridging phosphide group with-
out Pt(I)–Pt(II) bond, [Pt3H(l-PPh2)3(PEt3)3] (1960, 2239 Hz) show
large Pt–P coupling constants [16]. Thus, 5b and 5c are proposed to
have the multinuclear structure with the bridging phosphide li-
gands, as shown in Scheme 3, although the solid-state NMR data
did not provide useful information to determine the more detailed
structures.
3. Conclusion
We demonstrated the preparation and structure of the methyl-
and arylplatinum complexes having two secondary phosphine
ligands are the presence of conformational isomers of the ligands
in the crystal state. Thermal degradation of the complexes causes
elimination of methane or coupling of two aryl ligands depending
on the kind of the ligands. The thermal reaction of 2b and 2c yields
multinuclear complexes with bridged phosphide ligands as the
solid products.
Fig. 5. Thermogravimetric curves of (a) 1b, (b) 2b, (c) 3b and (d) 4a. Measurements
were performed under stream of nitrogen. Rate of the temperature was
10 °C minꢀ1 during the measurements.
a
4. Experimental
R'2
P
C11H24 / toluene
200 oC, 18 h
R'2HP
R'2HP
Ph
Ph
Pt
4.1. General remark
Pt
+ Ph Ph
P
R'2
n
All manipulations of the complexes were carried out using stan-
dard Schlenk techniques under an argon or nitrogen atmosphere.
Hexane and toluene were purified by passing through a solvent
purification system (Glass Contour). 1H, 13C{1H}, 19F{1H}, and
2b:
R' = t-Bu
5b:
R' = t-Bu
2c: R' = Ph
5c: R' = Ph
Scheme 3.

Table 6
Crystallographic data and details of refinement for 1b, 2b–c, 3a–c, 4a and 4c.
1b
2b
2c
3a
3b
3c
4a
4c
Formula
C18H44P2Pt
517.56
Orthorhombic
Pna21 (No. 33)
0.40 ꢂ 0.30 ꢂ 0.18
Colorless
14.086(5)
8.569(3)
18.696(7)
C56H85P2Pt
1272.36
Monoclinic
P21/n (No. 14)
0.12 ꢂ 0.10 ꢂ 0.10
Colorless
16.690(5)
21.020(6)
17.860(6)
C36H32P2Pt
721.65
Orthorhombic
Pnma (No. 62)
0.12 ꢂ 0.10 ꢂ 0.04
Colorless
19.714(2)
16.306(2)
9.303(1)
C30H46F6P2Pt
777.72
Monoclinic
P21/n (No. 14)
0.25 ꢂ 0.13 ꢂ 0.10
Colorless
14.625(3)
13.582(3)
17.408(4)
C30H46F6P2Pt
777.72
C38H30F6P2PtꢁC7H8
949.82
Monoclinic
P21/a (No. 14)
0.33 ꢂ 0.20 ꢂ 0.10
Colorless
14.098(2)
18.657(2)
15.242(2)
C28H38F10P2Pt
821.63
Monoclinic
P21/n (No. 14)
0.25 ꢂ 0.20 ꢂ 0.08
Colorless
10.105(2)
15.331(3)
21.242(5)
C36H22F10P2Pt
901.59
Orthorhombic
P212121 (No. 19)
0.20 ꢂ 0.15 ꢂ 0.10
Colorless
12.560(2)
14.681(3)
17.892(3)
Formula weight
Crystal system
Space group
Crystal size (mm)
Crystal color
a (Å)
Triclinic
ꢀ
P1 (No. 2)
0.23 ꢂ 0.21 ꢂ 0.15
Colorless
11.382(6)
11.649(6)
13.417(7)
86.42(2)
68.37(2)
88.32(2)
1650(2)
2
b (Å)
c (Å)
a
(°)
b (°)
112.970(4)
103.8770(9)
99.712(2)
100.785(1)
c
(°)
V (Å3)
2257(2)
4
1.523
1040
6.355
15672
5769(3)
4
1.465
2548
4.969
42278
2990.5(6)
4
1.603
1424
4.804
21932
3357(1)
4
1.539
1552
4.309
23631
3951(1)
4
1.596
1880
3.677
28854
3232.7(1)
4
1.688
1616
4.497
21267
3299(1)
4
1.815
1744
4.416
24354
Z
Dcalc (g cmꢀ3
F(000)
)
1.565
776
4.382
11396
l
(mmꢀ1
)
Number of reflections
measured
Number of unique
reflections
2627
13182
3531
7381
6882
9003
6930
7481
Rint
0.0440
2154
0.058
9935
0.056
2834
0.022
6236
0.034
5569
0.036
7659
0.037
5413
0.026
6282
Number of observed
reflections (I > 2
Number of variables
R1 (I > 2 (I))
wR2 (I > 2 (I))
Goodness-of-fit (GOF)
r(I))
204
651
341
450
404
471
414
462
r
0.0524
0.1361
1.090
0.0622
0.1547
1.002
0.0331
0.0777
1.157
0.0309
0.0810
0.997
0.0403
0.0996
1.009
0.326
0.0920
0.969
0.0379
0.0841
1.018
0.0203
0.0288
0.836
r

M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
2277
31P{1H} NMR spectra were recorded on Varian Mercury 300 and
JEOL EX-400 spectrometers. The peak positions of the 19F{1H}
and 31P{1H} NMR spectra were referenced to an external CF3COOH
(d ꢀ74.1) and to an external 85% H3PO4, respectively. Solid-state
CPMAS 31P{1H} NMR measurement was carried out at 161.7 MHz
(JPt–P = 1770 Hz). Anal. Calc. for C16H36P2Pt: C, 39.58; H, 7.47.
Found: C, 39.36; H, 7.88%. Data for 5c: solid-state CPMAS 31P{1H}
NMR (161 MHz, r.t.): d 81.3 (JPt–P = 2130 Hz). Anal. Calc. for
C24H20P2Pt: C, 50.98; H, 3.57. Found: C, 50.67; H, 3.70%.
on
a
JEOL ECA-400 spectrometer using spinning speed of
4.5. X-ray crystallography
5330 Hz. 31P chemical shift was referenced to (NH4)2HPO4 (d
1.60). [PtR2(cod)] (R = Me [18a], Ph [18b], C6H4-p-CF3 [18c], C6F5
[5b]) was prepared according to the reported procedure. A second-
ary phosphines, PHR02 (R0 = i-Bu, t-Bu, Ph), and n-undecane (n-
C11H24) are commercially available products from Strem Chemicals
and Wako Pure Chemical Industries. These employed in the re-
search were in the reagent grade and used as received without fur-
Crystals of 1b, 2b–c, 3a–c, 4a and 4c suitable for X-ray diffrac-
tion study were mounted in glass capillaries. All of data were col-
lected at ꢀ160 °C on a Rigaku Saturn CCD diffractometer equipped
with monochromated Mo K
a radiation (k = 0.71073 Å). Crystal
Structure, version 3.8 for Windows. A full-matrix least-squares
refinement was used for non-hydrogen atoms with anisotropic
thermal parameters. Hydrogen atoms except for the P–H hydro-
gens of all complexes were located by assuming the ideal geometry
and were included in the structure calculation without further
refinement of the parameters. There are few significant differences
in crystallographic data and details of refinement for complexes
1b, 2b–c, 3a–c, 4a and 4c as shown in Table 6. Three methyl car-
bons (C53–C59 atoms) of the PH(t-Bu)2 ligand of 2b were
disordered.
ther purification. IR absorption spectra were recorded on
a
Shimadzu FT/IR-8100 spectrometer. Elemental analysis was car-
ried out with a LECO CHNS-932 or Yanaco MT-5 CHN autorecorder.
Thermogravimetric analysis (TGA) experiments were conducted
using a Seiko Instruments Inc. TG/DTA 6200R. Dry samples were
weighted (10–20 mg) into a platinum pan and were heated at
10 °C minꢀ1 under a stream of N2.
4.2. Synthesis of cis-[PtMe2(PR2H)2] (1a: R = i-Bu, 1b: t-Bu, 1c: Ph)
5. Supplementary material
Secondary phosphines, PR2H (R = iBu: 0.10 mL, tBu: 0.12 mL, Ph:
0.12 mL; 0.66 mmol), were added to a n-hexane solution (3 mL) of
[PtMe2(cod)] (100 mg, 0.30 mmol) and the reaction mixture was
stirred for 3 h at room temperature. The solution of 1a was filtered
to remove by-products, the resultant filtrate was concentrated un-
der reduced pressure to obtain complex 1a as a colorless oil
(123 mg). The crude solids, which were precipitated from the reac-
tion mixture of 1b and 1c, were washed with hexane (3 mL ꢂ 3)
and dried in vacuo. Crystals of 1b suitable for X-ray crystallography
were obtained by recrystallization from toluene/n-hexane (1b,
1 mL/4 mL; 1c, 8 mL/1 mL) at room temperature (1b, 146 mg; 1c,
116 mg).
CCDC 718321, 718322, 718323, 718324, 718325, 718326,
718327 and 718328 contains the supplementary crystallographic
data for 1b, 2b, 2c, 3a, 3b, 3c, 4a and 4c. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment
This work was financially supported by a Grant-in-Aid for Sci-
entific Research on Priority Areas, from the Ministry of Education,
Culture, Sport, Science, and Technology of Japan.
4.3. Synthesis of cis-[PtR2(PR02H)2] (R = Ph, 2a: R0 = i-Bu, 2b: t-Bu, 2c:
Ph; R = C6H4-p-CF3, 3a: R0 = i-Bu, 3b: t-Bu, 3c: Ph; R = C6F5, 4a: R0 = i-
Bu, 4c: Ph)
References
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temperature. The crude solids, which were precipitated from the
reaction mixture of 2a, were washed with hexane (3 mL ꢂ 3) and
dried in vacuo. Crystal of 2a was obtained by recrystallization from
toluene/n-hexane (2a, 6 mL/1 mL) at room temperature to give a
colorless crystal (2a, 376 mg). Complexes 2b–c, 3a–c, 4a and 4c
were synthesized in a similar manner to 4.1. The crude solids,
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of 2b (1.0 g, 1.56 mmol) and of 2c (500 mg, 0.69 mmol) at 200 °C
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The mixture was filtered to collect the precipitates and the
obtained solid was washed with 10 mL of n-hexane and dried in
vacuo to yield yellow solid products (5b, 370 mg, 49%; 5c,
270 mg, 69%). The filtrate and washings of the reaction of 2c were
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for 5b: solid-state CPMAS 31P{1H} NMR (161 MHz, r.t.): d 73.4
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M. Kakeya et al. / Journal of Organometallic Chemistry 694 (2009) 2270–2278
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