Dinuclear platinum(II) complex bridged by an acetylacetonate(3-) anion

Article abstract of DOI:10.1016/S0022-328X(97)00432-4

[Pt(acac)₂] reacted with twice the molar amount of PPh₃ in hot MeOH to afford the first metal complex with an acetylacetonate trianion, [Pt₂(μ-acac(3-))(PPh₃)₄](acac), as a major product via [Pt(acac)(PPh₃)₂](acac). The η³:C, O-bridging structure of the trianion was deduced by ¹H, ¹³C, ³¹P and ¹⁹⁵Pt NMR spectra. This reaction system also afforded a minor product of an acetylacetonate dianion complex, [Pt(η³-acac(2-))(PPh₃)₂]; while [Pd(acac)₂] gave only [Pd(η³-acac(2-))(PPh₃)₂] in the same reaction conditions.

Full text of DOI:10.1016/S0022-328X(97)00432-4

Ž
.
Journal of Organometallic Chemistry 551 1998 117–123
ž /
ž
/
Dinuclear platinum II complex bridged by an acetylacetonate 3y
1
anion
b
c
d
Seichi Okeya a,), Yoshiaki Kusuyama , Kiyoshi Isobe , Yukio Nakamura ,
d,2
Shinichi Kawaguchi
a
Department of AdÕanced Material Science and Chemistry, Faculty of Systems Engineering, Wakayama UniÕersity, Wakayama 640, Japan
b
Faculty of Education, Wakayama UniÕersity, Wakayama 640, Japan
Department of Material Science, Faculty of Science, Osaka City UniÕersity, Sumiyoshi, Osaka 558, Japan
c
d
Department of Chemistry, Faculty of Science, Osaka City UniÕersity, Sumiyoshi, Osaka 558, Japan
Received 12 May 1997; received in revised form 20 June 1997
Abstract
w
Ž
. x
Pt acac
reacted with twice the molar amount of PPh3 in hot MeOH to afford the first metal complex with an acetylacetonate
2Ž
Ž
..Ž
. xŽ
.
w
Ž
.Ž
. xŽ
.
3
w
trianion, Pt2 m-acac 3y PPh3 4 acac , as a major product via Pt acac PPh3
acac . The h :C, O-bridging structure of the trianion
2
was deduced by H, 13C, 31P and 195Pt NMR spectra. This reaction system also afforded a minor product of an acetylacetonate dianion
complex, Pt h -acac 2y PPh3 ; while Pd acac
Elsevier Science S.A.
1
3
3
w
Ž
Ž
..Ž
. x
w
Ž
. x
w
Ž
Ž
..Ž . x
gave only Pd h -acac 2y PPh3 in the same reaction conditions. q 1998
2
2
2
Ž .
Keywords: Dinuclear platinum II ; acetylacetonate trianion; metal complex
1. Introduction
have reported the following four bonding modes for the
dianion of acac 2y or its derivatives.
Ž
.
Ž
.
Acetylacetone abbr. acacH and its derivatives have
been used as useful chelating reagents, forming O,OX-
chelate as the monoanion with almost all metal ions.
Besides this normal chelating mode, they exhibit many
other bonding modes to metal ions as the neutral
w
x
molecule, the monoanion and the dianion 1–3 . The
chemistry of Pd II and Pt II complexes with these
ligands has been especially studied extensively. We
Ž .
Ž .
)
Corresponding author.
1 Dedicated to Professor Peter M. Maitlis on the occasion of his
65th birthday.
1
3
3
Ž . 3Ž
ClC6 H4
.
w
Ž
Ž
..Ä Ž
i h C –C -coordination: Pt h -acac 2y P p-
2 Deceased, 8 September 1990.
.
342
x
w
Ž
.2 x
was prepared by the reaction of Pt acac
0022-328Xr98r$19.00 q 1998 Elsevier Science S.A. All rights reserved.

(
)
118
S. Okeya et al.rJournal of Organometallic Chemistry 551 1998 117–123
Ž
.
with tris p-chlorophenyl phosphine in chloroform at
w x Ž .
2.2. Measurements
room temperature 4 . A similar Pd II complex,
3
w
Ž
Ž
..Ž
.x
Pd h -acac 2y bpy was derived from the reaction
Infrared spectra were obtained with a Perkin Elmer
1725-X infrared spectrophotometer. NMR spectra were
recorded on JEOL EX-90, GX-400, LA-400 and GX-500
spectrometers. Chemical shifts are described in ppm
3
w
Ž
Ž
.Ž ..x2
Ž
of Pd m-Cl h -acac 1y with bipyridine, forming
1
w
.Ž
.x
PdCl h -CH2COCHCOCH bpy , followed by the
Ž
.
w x 3
reaction with T1 acac 5 . Bipyridine ligand in this
complex was easily displaced by diphosphine ligands
such as bis diphenylphosphino ethane dppe and cis-
Ž
.
downfield positive to the internal reference of TMS
Ž
.
Ž
.
1
13
Ž
.
Ž
for H and C and external ones of 85% H3PO4 for
Ž
.
w x
bis diphenylphosphino ethylene 6 . The X-ray structure
31
195
.
Ž
.
P and aqueous solution of K2 PtCl4 for
Pt . A
determination of this type of h3-allylic complex was
Ž
.
vapour-pressure osmometer Knauer; Berlin, Germany
was used for molecular weight determination.
p e rfo rm e d
Pt CH COR COCH COR PPh3
b y
K e m m itt e t a l. o n
.
w
Ä
.
Ž
.
Ž
4
Ž
.
2 x w x
Ž
RsOMe 7 ; Me
w x
w
Ä
Ž
.
Ž
.
4
x Ž
8
and Pd CH COOMe COCH COOMe L2 Ls
.
w x
PPh3, AsPh3, 1r2 bpy 9 . These crystal structures
[
(
)(
(
) ](
)
2.3. Preparation of Pt acac PPh3
acac 1a,
[ ( )( ) ](
)( 2
)
[
) ](
)
Ž
.
suggest that the bonding mode of the triketonate 2y
Pt acac PPh3 PF6 1b, Pd acac PPh3
acac
ligands is rather close to an h2-metallacycrobutane-3-
2
2
[
(
)(
) ](
)
1c and Pd acac PPh3
ClO4 1d
2
one type.
X
3
3
Ž .
Ž
Ž
.
ii h :O,O -bridging: the h -acac 2y ligand in
3
w
Ž
..Ž
.
x
Ž
.
w
Ž
.
2 x
Ž
.
Pd h -acac 2y PP PPsdppe, etc. reacted with
A suspension of Pt acac
and twice molar quantity of PPh3 269 mg in a small
quantity of MeOH 1 ml was stirred vigorously with a
spatula at 608C for several minutes to afford a clear pale
yellow solution of Pt acac PPh3
tempts to isolate the complex as solid have been unsuc-
cessful, but its yield in solution checked by NMR was
Ž . Ž
quantitative. dH CD3OH : 7.49, 7.31 complex, f30H,
198 mg, 0.503 mmol
Ž
.
a n o th e r m e ta l c o m p o u n d s u c h a s
1
3
3
w
Ž
.Ž
.
x
Ž
.
Ž
w
Ž
.
Ž
Ž
.
Pd dppe H2O ClO
to give PP Pd C –C -h -
2
.
4x2
.
w x
X
Ž
.
Ž
.
acac 2y -O,O Pd PP ClO4 7 .
Ž
.
Ž 2
.
w
Ž
.Ž
.
x
Ž
.
iii C, O-chelation: bis trifluoroacetylacetonato -
acac 1a. Any at-
2
Ž .
w
Ž
. x
platinum II , Pt tfac , reacted with two equivalents of
2
Ž
.
PPh3, P p-ClC6 H4 and AsPh3 in diethyl ether or
3
w
Ž
Ž
.
chloroform at room temperature to afford Pt tfac 2y -
X
X
.
x w x w
Ž
Ž
.
.
.
x
Ž
.
Ž
.
Ž
C, O L2 10 . Pd tfac 2- -C, O LL L,L s2PPh3,
Ph ; 5.67 s, 1H, chelating acac; CH ; 5.16 s, 1H,
X
y
y
. Ž . Ž
acac ; CH ; 2.05 br, 6H, acac ; CH3 , 1.51 s, 6H,
bpy; LsPPh3, L spy etc. was also prepared, and the
y
w
Ž
Ž
.
.Ž .Ž
. Ž . Ž
chelating acac; CH3 . dc CD3OH : 193.7 br, acac ;
structure of Pd tfac 2y -C, O PPh3 2,6-dimethyl-
.
x
w
x
. Ž Ž .
CO ; 186.8 virtual triplet abbr. vt , chelating acac;
3 2
pyridine was determined by X-ray diffraction 11 .
3
Ž
.
Ž .
<
Ž . Ž . Ž .
CO, J cis P–C q J trans P-C s2 Hz, J Pt–C s
2
4
<
The existence of the acac 2y analogue with Pt II was
w x
.
Ž
Ž
<
Ž
.
Ž
.<
reported 4 .
20 Hz ; 135.7 vt, PPh3; o-C, J P–C q J P–C s10
X
3
4
1
Ž .
1Ž
.
.
.
Ž
<
<
Ž
.
.
iv h C :O,O -bridging: the above-mentioned
Hz, J Pt–C s17 Hz ; 133.1 vt, PPh3; p-C, J P–C
3
1
6
w
Ž
Ž
..Ž
.
x
Ž
.
Ž
Ž
.
.
<
<
.
Ž
Ž
PdCl h -acac 1y bpy abbr. YH still has an enol
q J P–C s2 Hz ; 129.7 vt, PPh3; m-C, J P–C
2
5
.
Ž
Ž
.
proton and reacts with the other metal compounds such
q J P–C s12 Hz ; 127.3 m, PPh3; ipso-C, J Pt–
X
3
1
Ž
.
1Ž
.
.
.
Ž
Ž
as Pd acac to afford the complex with h C :O,O -
C s29 Hz ; 102.9 s, chelating acac; CH, J Pt–C s
2
y
y
Ž
.
w
x
w
Ž
. x w x
.
Ž
.
Ž
.
bridging acac 2y ligand, PdY2 and Pd acac Y 12 .
Thus, we have seen several kinds of complexes with the
dianion of acac or its derivatives. However, the complex
with their trianion has not been reported to the best of
our knowledge. We report here the preparation and
66 Hz ; 102.4 s, acac ; CH ; 28.2 br, acac ; CH3 ;
4
4
Ž
<
Ž
.
Ž
26.4 vt, chelating acac; CH3, J cis P–C q J trans
3
.
<
Ž
.
.
Ž
.
Ž
P–C s8 Hz, J Pt–C s28 Hz . dp CD3OH : 7.6 s,
1
Ž
.
.
J Pt–P s3867 Hz . CD3OH was used as a solvent to
prevent the complication caused by H–D scrambling
between CD3OD and the complexes.
Ž
.
spectroscopic characterization of the first acac 3y
Ž
trianion complex.
On addition of an equimolar amount of KPF6 97
.
mg , NaClO4 or p-toluenesulfonic acid to the hot MeOH
solution containing 1a white precipitates of
w
Ž
.Ž
.
x
Ž
Ž . .
XsPF6 1b , ClO4 , OTs were
Pt acac PPh3
X
2
2. Experimental
formed immediately. Precipitates were filtered and re-
crystallized from the mixture of CH2Cl2 and n-C5H12
to deposit colourless plates, which were filtered and
2.1. Starting materials
Ž
.
air-dried. The yield of 1b was 355 mg, 72% Pt-base .
A quarter molecule of CH2Cl2 per complex molecule
was involved in the crystal. Anal. Found: C, 50.38; H,
3.85. Calcd. as C41.25H27.5O2 P3F6Cl0.5Pt: C, 50.30; H,
3.84%. Molecular weight in CH2Cl2: 883 calcd. 902 .
nmax KBr ; 3059w, 1563vs, 1529vs, 1482m, 1437vs,
w
Ž
.2 x
The starting bischelate complexes, Pt acac and
w
Ž
. x
2
Pd acac , were prepared according to the previously
w
x
reported method 13,14 . Commercially supplied triph-
enylphosphine, methyldiphenylphosphine, potassium
hexafluorophosphate and sodium perchlorate were used
without further purification.
Ž
.
Ž
.
1368s, 1313vw, 1281w, 1188w, 1163vw, 1101s, 1028w,

(
)
S. Okeya et al.rJournal of Organometallic Chemistry 551 1998 117–123
119
3
Ž
.
[ (
(
))(
) ]
2
1000w, 941w, 840vs PF6 , 748s, 711s, 693vs, 620w,
2.4. Preparation of Pt h -acac 2y PPh3 3a and
558vs, 531vs, 521s, 514s, 501s cmy1. dH CDCl3 :
3
Ž
.
[
(
(
))(
) ]
Pd h -acac 2y PPh3 3b
2
4
Ž
.
Ž
Ž
7.3–7.4 br, f30H, Ph ; 5.58 s, 1H, acac; CH, J Pt–
4
Complex 3a was isolated by the method reported
.
.
Ž
Ž
.
.
3
H s5 Hz ; 1.50 s, 6H, acac; CH3, J Pt–H s3 Hz .
w x
3
previously 4 in a 55% yield and characterized. dC
Ž
.
Ž
<
Ž .
J cis P–C q
dC CDCl3 : 185.1 vt, acac; CO,
4
Ž
.
Ž
.
Ž
.
Ž
.
2
CD2Cl2 : 203.0 d, C , J P–C s4 Hz, J Pt–C s45
Ž
.
<
<
Ž
Ž
.
.
Ž
J trans P-C s2 Hz, J Pt–C s22 Hz ; 134.2 vt,
2
.
Ž
2
3
Hz ; 178.8 t, C ,
4
Ž
.
.
<
Ž
.
PPh3; o–C, J P–C q J P–C s11 Hz, J Pt–C s
Ž
.
.
Ž
Ž
22 Hz, 132.0 s, PPh3; p-C , 128.6 vt, PPh3; m-C,
3
5
<
Ž
.
Ž
.
<
J P–C q J P–C s11 Hz , 125.7 m, PPh3; ipso–
4
.
Ž
Ž
.
<
Ž
<
Ž
C , 102.4 s, acac; CH , 26.3 vt, acac; CH3, J cis
3
4
.
.
Ž
.
.
.
P–C q J trans P–C s8 Hz, J Pt–C s27 Hz .
1
3
2
Ž
.
Ž
.
Ž
J P–C and J P–C for the ipso-carbon, and J P–P
values in complexes 1a and 1b are calculated as 66,
w
x
Ž
.
-5, and around 30 Hz, respectively 15 . dP CDCl3 :
8.2 s, PPh3 J Pt–P s3851 Hz ; y143.9 heptet, PF6,
1
Ž . Ž . . Ž
J P–C s5 Hz, J Pt–P s163 Hz ; 134.4 d, PPh3;
Ž
Ž
.
.
Ž
1
Ž . Ž . .
o-C, J P–C s10 Hz, J Pt–C s22 Hz ; 130.7 and
Ž
.
.
J F–P s712 Hz .
Ž . Ž Ž .
130.6 s, PPh3; p-C ; 128.4 d, PPh3; m-C, J P–C s10
3
w
Ž
.
2 x
Ž
.
75 mg, 0.25 mmol and
A suspension of Pd acac
. Ž Ž . Ž .
Hz ; 73.3 dd, C , J P–C s6 and 53 Hz, J Pt–C s
1
Ž
.
two equivalents of PPh3 134 mg in a small quantity of
.
Ž
Ž
.
Ž
.
Ž
.
246 Hz ; 47.2 dd, C , J P–C s6 and 57 Hz, J Pt–C
MeOH 1 ml was stirred vigorously with a spatula to
.Ž
2
5
. Ž . Ž . Ž Ž
s233 Hz ; 31.0 s, C . dP CD2Cl2 : 20.1 AB, J P–
1 1
w
Ž
.
x
Ž
.
acac 1c
afford a yellow solution of Pd acac PPh3
2
.
Ž
.
.
Ž
Ž
.
P s9 Hz, J Pt–P s3210 Hz ; 19.4 AB, J Pt–P s
quantitatively. Complex 1c could not be isolated as
2896 Hz . 31 P NMR revealed that a small quantity of
.
Ž
.
Ž
.
Ž
solid. dH CD3OH : 7.4 br, f30H, Ph ; 2.08, br, 1H,
y
w
Ž
Ž
Ž
.
.Ž
.
x
4 was contaminated.
1
.
Ž
.
Pt acac 2 y -C,O PPh3
acac ; CH3 ; 1.53 s, 6H, chelating acac; CH3 .
Ž 2
.
Ž
.
2
y
.
Ž
Ž
.
Ž
.
Ž
dP CD2Cl2 : 33.6 d, J P–P s14 Hz, J Pt–P s
dC CD3OH : 193.2 br, acac ; CO ; 187.5 s, chelating
1
.
Ž
Ž
.
.
.
Ž
.
Ž
Ž
.
.
2043 Hz ; 13.6 d, J Pt–P s4081 Hz . Other spectral
acac; CO ; 135.4 br, PPh3; o-C ; 132.9 s, PPh3; p-C ;
w x
data were essentially the same as reported values 17 .
Ž
Ž
.
129.8 br, PPh3; m-C ; 102.1 s, chelating acac; CH ;
y
y
Ž
.
Ž
.
.
.
Ž
.
Ž
The MeOH solution 2 ml containing 1c 0.35 mmol
101.0 s, acac ; CH ; 27.8 br, acac ; CH3 ; 26,3 br,
Ž
.
was kept at room temperature. This solution was al-
lowed to evaporate spontaneously for 3 days and it gave
yellow plates of 3b, which were filtered and washed
with Et2O. The crude products were recrystallized from
the mixture of CH2Cl2 and n-C5H12. The yield was
105 mg, 37% Pd-base . One molecule of CH2Cl2 per
complex molecule were involved. Anal. Found: C,
61.97; H, 4.71. Calcd. as C42 H38O2 P2Cl2 Pd: C,
chelating acac; CH3 . dp CD3OH : 34.5 br. The broad-
ening of the NMR signals 1H, 13C, P is caused by
the fractional motion of the acac interconversion be-
tween the inner and outer spheres through the five-coor-
31
Ž
.
w
x
dinated complex 16 . On addition of an equimolar
Ž
.
Ž
.
amount of NaClO4 32 mg , KPF6 or p-toluenesulfonic
acid to the hot MeOH solution containing 1c yellow
w
Ž
.Ž
.
x
Ž
Ž
.
precipitates of Pd acac PPh3 X XsClO4 1d , PF6,
2
Ž
.
Ž
.
61.97;H, 4.71%. M.p.: 105– 1108C dec. . IR: nmax in
Nujol ; 1600m, 1540vs, 1483s, 1435vs, 1357s, 1334s,
OTs were formed immediately. The crude products
.
were recrystallized from the mixture of CH2Cl2 and
Ž
.
1158s, 1102s, 1098s, 1030m, 1019m, 1000m, 756s,
n-C5H12. The yield of 1d was 158 mg, 75% Pd-base .
One-third of CH2Cl2 molecule per complex molecule
was involved in the crystal. Anal. Found: C, 57.85; H,
4.53. Calcd. as C41.33H37.66O6 P2Cl1.66 Pd: C, 57.87; H,
740vs, 702vs, 697vs, 535s, 520vs, 511s cmy1. dH
Ž
.
Ž
.
Ž
CDCl3 : 8–7.2 f30H, complex, Ph ; 4.46 1H, t, br,
Ž
.
.
Ž
acac; CH, J P–H s4 Hz ; 3.04 2H, t, br, acac; CH2 ,
Ž . . Ž .
J P–H s6 Hz ; 1.25 3H, s, sl. br, acac; CH3 . dC
4 2
Ž
.
4.43%. nmax in nujol ; 1560vs, 1530vs, 1440vs, 1315w,
Ž . Ž Ž . . Ž
CDCl3 : 201.2 d, C , J P–C s4 Hz ; 173.8 t, C ,
Ž
.
1294m, 1189w, 1160w, 1095vs ClO4 , 1024m, 1000m,
940w, 850w, 810w, 760m, 745s, 712s, 697vs, 629s,
560s, 534vs, 520s, 516s, 500m, 465w cmy1. dH
Ž
.
.
.
Ž
Ž
J P–C s4 Hz ; 133.9 and 133.8 d, PPh3; o-C, J P–
.
Ž
.
Ž
C s13 Hz ; 130.3 and 130.1 s, PPh3; p-C ; 128.3 d,
3
Ž . . Ž Ž .
PPh3; m-C, J P–C s11 Hz ; 79.5 dd, C , J P–C s4
1
1
Ž
.
Ž
.
Ž
CDCl3 : 7.4 br, f30H, PPh3 ; 5.45 s, 1H, acac;
Ž . . Ž Ž .
and 40 Hz, J H–C s151 Hz ; 55.0 d, C , J P–C s
1 1
5
.
Ž
.
Ž
.
Ž
CH ; 1.53 s, 6H, acac; CH3 . dC CDCl3 : 186.2 vt,
3
3
Ž . . Ž Ž .
46 Hz, J H–C s152 Hz ; 31.0 s, C , J H–C s127
2
<
Ž
.
Ž
.
<
.
acac; CO, J cis P–C q J trans P–C s4 Hz ; 134.2
2
4
.
Ž
.
Ž
Ž
.
.
Ž .
Ž
Ž
Ž
Ž
<
Ž
Ž
.
.
.
Ž
.
<
.
Hz . dP CDCl3 : 31.8 d. J P–P s29 Hz ; 23.6 d .
vt, PPh3; o-C, J P–C q J P–C s11 Hz ; 132.1
4
6
<
Ž
.
.
<
.
.
vt, PPh3; p-C, J P–C q J P–C s3 Hz ; 128.9
[
(
(
(
))(
) ](
)
2.5. Preparation of Pt2 m-acac 3y PPh3
acac
3
5
4
<
.
.
Ž
Ž
<
vt, PPh3; m-C, J P–C q J P–C s11 Hz ; 126.0
(
)
[
(
)) (
) ](
) (
)
5a and Pt2 m-acac 3y PPh3
PF6 5b
4
Ž
.
Ž
m, PPh3; ipso-C ; 100.7 s, acac; CH ; 26.3 vt, acac;
4
1
4
<
Ž
Ž
.
<
.
.
Ž
.
Ž
.
Ž
.
CH33, J cis P–C q J trans P–C s10 Hz . J P–C
Pt acac
744 mg, 1.89 mmol and twice molar
amounts of PPh3 1000 mg were dissolved in hot
MeOH 5 ml and sealed in a glass tube. After heating
at 608C for 6 h, the glass tube was maintained at room
2
2
Ž
.
Ž
.
Ž
Ž
.
and J P–C for ipso-C PPh3 , and J P–P values in
this complex are calculated as 57, -5, and around 30
Ž
.
w
x
Ž
.
Hz 15 . dP CDCl3 : 35.2, s.

(
)
120
S. Okeya et al.rJournal of Organometallic Chemistry 551 1998 117–123
1
Ž
.
Fig. 1. H NMR spectrum 400 Hz, CD2Cl2 except for Ph signals and a proposed conformation of complex 5b.
temperature overnight. To the resulting pale yellow
solution was added Et2O 15 ml and the mixture was
and they were filtered and washed with Et2O. Recrystal-
lization from the mixture of CH2Cl2 and n-C5H12 was
repeated twice to afford white fine needles of 5b, which
were filtered and dried in vacuo. The yield was 703 mg,
56% Pt-base . Anal. Found: C, 54.34; H, 3.99. Calcd.
as C77 H65O2 P5F6 Pt2: C, 55.00; H, 3.90%. M.p.: 221–
Ž
.
kept at y58C in a refrigerator. The obtained white
Ž
precipitates were filtered and washed with Et2O yield
.
Ž
.
676 mg . Et2O and n-C5H12 were added to the filtrate,
then the solution was kept in the refrigerator to deposit
white precipitates, which were filtered and washed with
Ž
.
Ž
2288C dec. . Molecular weight in CH2Cl2: 1310 calcd.
Ž
.
.
Ž
.
Et2O yield 459 mg . These crude products were recrys-
tallized twice from the mixture of CH2Cl2 and n-C5H12
to give white-maple micro-crystals of 5a. They were
filtered, washed with Et2O and dried in vacuo. The
1681 . IR spectrum KBr disc was essentially similar to
that of complex 5a except for the additional absorption
y
y
band at 840vs PF6 and lack of 1573 acac cmy1
.
Ž
.
Ž
.
Following assigned 1H nuclei has an alphabetical scheme
as shown in Fig. 1. dH CD2Cl2 : 7.0–7.3 complex,
Ž
.
Ž
.
.
Ž
yield was 759 mg, 44% Pt-base . Two molecules of
CH2Cl2 per complex molecule are involved. Anal.
Found: C, 55.91; H, 4.24. Calcd. as C84 H76O4 P4Cl4 Pt2:
C, 55.90; H, 4.24%. M.p.: 150–1608C dec. . IR: nmax
KBr ; 3052w, 1636s, 1587m, 1573m, 1479vs, 1435vs,
3
2
c
.
.
Ž
Ž
Ž
Ž
.
.
60H, Ph ; 3.28 d, 1H, H , J P–H s11 Hz, J Pt–H
2
3
e
Ž
s66 Hz ; 2.86 dd, 1H, H , Jgem s8 Hz, J P–H s13
2
b
Ž
.
Ž
.
.
Ž
.
a
Hz, J Pt–H s98 Hz ; 1.88 dt, 1H, H , Jgem s6 Hz,
3
3
Ž
.
Ž . . Ž
J P–H s2 and 6 Hz ; 1.53 dd, 1H, H , Jgem s6 Hz,
2
Ž . Ž . . Ž
J P–H s11 Hz, J Pt–H s60 Hz ; 1.01 complex,
4
1412s, 1312w, 1251w, 1186w, 1160w, 1120w, 1097s,
1073w, 1027w, 999m, 946w, 881w, 861w, 745s, 694vs,
1H, Hd, Jgem s8 Hz . dC CD2Cl2 : 207.1 d, C ,
.
Ž
.
Ž
1
3
2
2
551s, 541s, 526vs, 514vs, 500s cmy1. H and 31 P NMR
J P–C s5 Hz, J Pt–C s56 Hz ; 176.7 dd, C ,
2
Ž
.
Ž
.
.
Ž
1
Ž . Ž . .
J P–C s2 and 5 Hz, J Pt–C s9 and 95 Hz ; 137–
2
3
spectra were almost the same as those of 5b except for
the signals assigned to acacy; CH3 dH : 2.54 br and
125 complex, Ph ; 68.4 dd, C , J P–C s6 and 45
Ž
.
Ž
.
Ž
Ž
.
1
3
2
Ž
.
Ž
.
Ž
Ž . Ž . . Ž
Hz, J Pt–C s172 Hz, J Pt–C s14 Hz ; 52.4 com-
1 2
1 5
CH dH : 5.2 very br . dPt CDCl3 : y2600 dd, Pt ,
1
Ž
.
.
Ž
Ž
Ž . . Ž Ž .
plex, C , J Pt–C s159 Hz ; 38.0 dd, C , J P–C s
1
J P–Pt s2216 and 4181 Hz ; y3450 ddd, Pt , J P–
.
.
Ž . . Ž .
3 and 67 Hz, J Pt–C s414 Hz . dP CD2Cl2 : 32.3
C
Pt s24,3384 and 3470 Hz .
Ž
Ž
.
Ž
.
dd, P , J P–P s1 and 16 Hz, J Pt–P s26 and
A
.
Ž
Ž
.
2214 Hz ; 17.6 AB, P , J P–P s1 and 11 Hz,
B
Ž
.
.
Ž
Ž
.
J Pt–P s7 and 3468 Hz ; 17.1 AB, P , J P–C s11
D
Ž
.
.
Ž
Ž
.
Hz, J Pt–P s3379 Hz ; 8.7 d, P , J P–P s16 Hz,
Ž
.
.
.
Ž
Ž
J Pt–P s9 and 4180 Hz ; y144.1 heptet, PF6, J F–
.
P s711 Hz .
[ (
) ]
2.6. Reaction of Pt acac 2 with two equiÕalents of
PMePh2
Ž
.
Ž
w
Ž
.
2 x Ž .
143 mg, 0.364 mmol
Addition of KPF6 150 mg to the MeOH solution 4
The mixture of Pt acac
and two equivalents of PMePh2 146 mg in a small
.
Ž
.
Ž
.
ml of 5a 1.49 mmol led to form white precipitates,

(
)
S. Okeya et al.rJournal of Organometallic Chemistry 551 1998 117–123
121
Ž
.
quantity of CD3OD 2 ml was kept at 608C for 6 h.
The 31 P NMR spectrum showed the formation of
3
w
Ž
Ž
..Ž
.
2 x
Ä
Ž
Pt h -acac 2y PMePh2
dP CH3OH, locked by
2
.
Ž
Ž
.
Ž
.
ext. D2O :0.2 AB, J P–P s11 Hz, J Pt–P s2986
Ž
Ž
.
.4
Hz; y0.8 AB, J Pt–P s3370 Hz and a small quan-
w
Ž
Ž
..Ž
.
x
Ž
.
C
tity of Pt2 m-acac 3 y PMePh2
acac , which
4
Ž
Ž
.
could not be isolated as solid. dP: 15.9 dd, P , J P–P
Ž
.
Ž
s2 and 16 Hz, J Pt–P s31 and 2288 Hz; y0.8 dd,
A
Ž
.
Ž
.
.
P , J P–P s3 and 12 Hz, J Pt–P s3471 Hz ; y3.3
B
Ž
Ž
.
Ž
.
.
Ž
d, P , J P–P s12 Hz, J Pt–P s3244 Hz ; y8.3 d,
D
Ž
.
Ž
.
.
P , J P–P s16 Hz, J Pt–P s8 and 3963 Hz .
3. Results and discussion
The novel acac trianion bridging dinuclear complex,
w
Ž
Ž
..Ž
.
x
Ž
.
Pt2 m-acac 3y PPh3 acac 5a, is formed by the
4
w
Ž
.
x
Fig. 2. Main signals of the 31 P NMR spectrum 24 MHz, CD2Cl2 of
reaction of Pt acac with PPh3 in hot MeOH through
2
Ž
.
the intermediates of the acac O,OX-chelate monoanion
31
complex 5b and a network of the P– 31 P and 195Pt– 31 P coupling
w
Ž
.Ž
.
x
Ž
.
constants.
complex, Pt acac PPh3
acac 1a, and the acac dien-
2
w
Ž
Ž
.
dienolate dianion complex, Pt acac 2 y -
X .Ž
.
2 x
O,O PPh3
2. Complex 5a was isolated from the
31
195
reaction system and was recrystallized repeatedly to get
pure micro-crystals. The acac anion in the outer sphere
of 5a was easily exchanged with PF6y by treating with
and a network of P–31 P and Pt– 31 P coupling con-
stants are shown in Fig. 2. The chemical shifts and
coupling constants of the signals assigned to C1, C2 and
13
31
C3 for C NMR, PA and PB for P NMR and Pt1 for
w
Ž
Ž
..Ž
.
x
Ž
.
KPF6 to give Pt2 m-acac 3 y PPh3 PF6 5b.
4
195
1
3
Ž
.
Ž .
Pt NMR are similar to those of h -acac 2y com-
The H NMR spectrum d 1.0;3.5 in CD2Cl2 and a
w
x
proposed structure of 5b are shown in Fig. 1, in which
plexes 4,17 , and those of the other signals assigned to
1
13
Ž
.
five kinds of H signals of acac 3y are clearly sepa-
C4 and C5 for C NMR, PC and PD for 31 P NMR and
rated. Signal assignments are mainly based on the cou-
Pt2 for 195Pt NMR are similar to those of C, O-chelated
1
1
pling correlation analyzed by H–1H decoupling and
tfac 2y complex 10 . The J H–C values of C and
C3 are 154 and 152 Hz, showing the sp2 character of
them. On the other hand, that of C5 is 136 Hz, showing
its sp3 character. Unfortunately, suitable crystals of 5
for X-ray experiment could not be obtained yet.
1
Ž
.
w
x
Ž
.
1
Ä31
4
P NMR measurements. The six-membered chelate
H
ring including Pt2 is not planar, and only one conforma-
Ž
.
tional isomer seems to exist exclusively see Fig. 1 .
The 13C, 31 P and 195Pt NMR spectra strongly suggest
3
Ž
.
the h :C, O-bridging structure of the acac 3y ligand.
We have elucidated the formation of 5a as shown in
Scheme 1 based on isolation of the intermediates and
The main signal part of the 31 P NMR spectrum of 5b
Scheme 1.

(
)
122
S. Okeya et al.rJournal of Organometallic Chemistry 551 1998 117–123
1
the monitoring of the reaction steps by H, 13C and 31 P
w
Ž
.2 x
NMR spectroscopies. The reaction of Pt acac with
two equivalents of PPh3 gave an intermediate of 1a
with the acac O,OX-chelate monoanion at the beginning.
Although complex 1a could not be isolated as a solid,
when the reaction mixture was treated with KPF6, the
crystals of 1b were isolated in a good yield. The
isolated complex 1b was subjected to further reaction
under the same reaction conditions: in hot MeOH at
608C. It did not give the acac trianion complex. This
means that the acac anion in the outer sphere of 1a
plays an important role to form the trianion of acac by a
proton abstraction from the coordinated acac ligand.
This is supported by the fact that the acac anion in the
outer sphere acts as a good proton acceptor because of
Ž
.
its strong basicity pKa of acacH is 8.80 , and that the
w
Ž
.
x
Ž
.
w
x
Ž
.
acac anions in Pd acac L2 acac and PdL4 acac
2
Ž
.
Lsamines abstract even the proton from chloroform
Scheme 2.
w
x
18,19 . To form the trianion of acac in 5a, two protons
of the chelating monoanion of acac in 1a must be
abstracted, but complex 1a has only one acac counter-
anion as a proton abstractor. Therefore, a stepwise
proton abstraction from 1a to 5a probably takes place,
and another intermediate that has a dianion of acac
might exist in the reaction. Although the intermediate
was not detected in the reaction in MeOH, it was found
with a diendienolate dianion of acac, 2, by means of the
31 P NMR spectroscopy in the sample prepared as fol-
lows: after quick evaporation of a fresh MeOH solution
of complex 1a in vacuo, the resulting pale yellow oil
was redissolved in C6 D6. Within 6 min after dissolu-
place of PPh3, the 31 P signals of Pt h -acac 2y
..Ž 2 x ..
3
w
Ž
Ž
.
w
Ž
Ž
P M e P h 2
a n d
P t 2 m -a c a c 3 y
-
Ž
.
x
Ž
.
PMePh2 acac were also observed. In this case, the
4
3
Ž
.
h -acac 3y bridged dimer complex 5 is a minor
product.
w
Ž
.
x
The reaction of Pd acac
with two equivalents of
3
w
Ž2
Ž
Ž
..Ž
.
2 x
PPh3 in MeOH gave Pd h -acac 2y PPh3
3b
w
Ž
.Ž
.
x
.
exclusively via Pd acac PPh3
acac 1c. It was
2
formed through the corresponding path A in Scheme 1.
Ž .
Ž
.
The Pd II analogue with acac 3y could not be de-
tected by NMR even for the reaction using refluxing
condition in MeOH.
Ä
Ž Ž
tion, the sample showed an AB quartet dP: 10.3 J P–
.
Ž
.
.
Ž Ž
.
P s27 Hz, J Pt–P s3848 Hz ; 5.9 J Pt–P s3859
.
4
Hz . This signal diminished and the signals due to 5a
appeared, by addition of MeOH to the sample. Without
addition of MeOH, complex 2 changed gradually to 3a
contaminated with 4 that was isolated and characterized.
The solvent is an important factor to select the reaction
path A or B, and the MeOH solvent lead to form the
cationic complex 5a. Although further experiments are
needed to establish the formation mechanism of 2 and
5a, we propose a possible mechanism in Scheme 2, that
is, an acetylacetonate 1y counter anion in complex 1a
abstracts a methyl proton from the chelating acac ligand
to afford the intermediate 2; in the next stage the
counter acac anion in another 1a abstracts a methyl
Acknowledgements
We wish to thank Professors Takakazu Yamamoto
and Kotaro Osakada at Tokyo Institute of Technology,
and Kazumi Hata of JEOL for NMR measurements. We
express appreciation to Mr. Takuya Matoba and Ms.
Reiko Moriguchi for their experimental assistance. S.O.
is grateful to the Ministry of Education, Science and
Culture for Grant-in-Aid for Scientific Research No.
08454210.
Ž
.
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Ž
.
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, expelling
w
Ž
.Ž
.
2 xq
w x
Ž
.
1
w x
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Ž
.
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Ž
.
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5
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.
Ž
.
4
Ž
. x
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Ž
.
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6
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.
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.
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x
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Ž
.
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