Transmetalation of arylpalladium and platinum complexes. Mechanism and factors to control the reaction

Article abstract of DOI:10.1016/j.jorganchem.2006.05.064

This article reviews recent studies on intra- and intermolecular transfer of the aryl ligand bonded to Pd(II) and Pt(II). Cationic arylpalladium complexes with bpy and THF ligands undergo intermolecular aryl group transfer to produce biaryl via a diarylpalladium intermediate. This reaction is applied to cyclization of cationic dinuclear arylpalladium complexes, affording the crown ether derivative with biphenylene units. Analogous arylplatinum complexes do not form diaryl complexes via transmetalation, while they react with CO and phenylallene to cause replacement of the coordinated solvent and insertion of the small molecules into the Pt-C bond, respectively. Conproportionation of PtCl₂(cod) and PtPh₂(cod) produces PtCl(Ph)(cod), which is induced by dissociation of a Cl ligand from the former complex. PtCl₂(cod) reacts also with diarylplatinum complexes with bpy and dppe. Disproportionation of PtPh(CH₂COMe)(cod) and conproportionation of PtPh₂(cod) and Pt(CH₂COMe)₂(cod) take place at 50 °C, but the rates of apparently reversible reactions differ from each other. Addition of OH^- to a solution of PtI(Ph)(cod) causes intermolecular phenyl ligand transfer to produce PtPh₂(cod). The dinuclear intermediate complex with bridging OH ligand is prepared from an independent route and fully characterized. The complex causes transmetalation of aryl group of aryl boronic acid.

Full text of DOI:10.1016/j.jorganchem.2006.05.064

Journal of Organometallic Chemistry 692 (2007) 326–342
www.elsevier.com/locate/jorganchem
Transmetalation of arylpalladium and platinum complexes.
Mechanism and factors to control the reaction
*
Yuji Suzaki, Takeyoshi Yagyu, Kohtaro Osakada
Chemical Resources Laboratory, Mail Box R1-03, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
Received 26 March 2006; received in revised form 12 May 2006; accepted 17 May 2006
Available online 1 September 2006
Abstract
This article reviews recent studies on intra- and intermolecular transfer of the aryl ligand bonded to Pd(II) and Pt(II). Cationic aryl-
palladium complexes with bpy and THF ligands undergo intermolecular aryl group transfer to produce biaryl via a diarylpalladium
intermediate. This reaction is applied to cyclization of cationic dinuclear arylpalladium complexes, affording the crown ether derivative
with biphenylene units. Analogous arylplatinum complexes do not form diaryl complexes via transmetalation, while they react with CO
and phenylallene to cause replacement of the coordinated solvent and insertion of the small molecules into the Pt–C bond, respectively.
Conproportionation of PtCl2(cod) and PtPh2(cod) produces PtCl(Ph)(cod), which is induced by dissociation of a Cl ligand from the for-
mer complex. PtCl2(cod) reacts also with diarylplatinum complexes with bpy and dppe. Disproportionation of PtPh(CH2COMe)(cod)
and conproportionation of PtPh2(cod) and Pt(CH2COMe)2(cod) take place at 50 ꢀC, but the rates of apparently reversible reactions dif-
fer from each other. Addition of OHꢀ to a solution of PtI(Ph)(cod) causes intermolecular phenyl ligand transfer to produce PtPh2(cod).
The dinuclear intermediate complex with bridging OH ligand is prepared from an independent route and fully characterized. The com-
plex causes transmetalation of aryl group of aryl boronic acid.
ꢁ 2006 Elsevier B.V. All rights reserved.
Keywords: Platinum; Palladium; Transmetalation; Boronic acid; OH ligand
1. Background
state containing one transition metal center, which renders
elucidation of the mechanism by kinetic measurement, etc.
relatively easy. This article focuses on recent studies of our
group on mechanism of transmetalation of aryl ligand
between Pt and Pd complexes.
We reported the reaction of NiAr(Br)(bpy) which
released Ar–Ar easily in DMF solution [2–4]. The reaction
is related to the mechanism of a Ni(0) complex-promoted
coupling of aryl bromide and polycondensation of aryl-
enedihalides (Eq. (1)) [5–13].
Transmetalation is one of the fundamental reactions of
organotransition metal complexes and involves transfer
of alkyl or aryl ligand from one metal to the other [1,2].
Detailed reaction mechanisms of transmetalation still
remain unclarified in many cases, although it is closely
related to a number of synthetic organic reactions cata-
lyzed by transition metal complexes. One of the difficulties
of the mechanistic studies of transmetalation lies in inter-
mediacy of dinuclear complexes in the reactions. Other fun-
damental reactions of organotransition metal complexes
such as oxidative addition, reductive elimination, b-hydro-
gen elimination, and insertion of small molecules into M–C
and M–H bonds involve the intermediate or transition
Ni(0) complex
2
Ar
X
Ar Ar
ð1Þ
X = halogen
Detailed kinetic studies on this reaction and the properties
of bpy-coordinated arylnickel complexes indicate the
mechanism shown in Scheme 1. In DMF, the aryl(bromo)-
nickel complex undergoes dissociation of the bromo ligand
*
Corresponding author. Fax: +81 45 924 5224.
E-mail address: kosakada@res.titech.ac.jp (K. Osakada).
0022-328X/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.064

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
327
biaryl is considered to proceed via cationic arylpalladium–
bpy complex which is converted into diarylpalladium com-
plex via the dinuclear intermediate complex with a bridging
aryl ligand as shown in Scheme 2. MeCN ligand of the cat-
ionic square-planar Pd complex is not liberated easily from
the metal center, while dissociation of labile THF ligand
from the cationic complex leads to the dinuclear species
with bridging aryl ligand. The produced PdAr2(bpy) under-
goes rapid reductive elimination of biaryl and is not iso-
lated from the reaction mixture (Scheme 2(ii)).
+
Ar
Ar
(bpy)Ni
(bpy)Ni
(bpy)Ni
Br-
DMF
Br
Ar
DMF
+
Ar
Ar
Br
Br
(bpy)Ni
(bpy)Ni
Br-
+
(bpy)Ni
2
DMF
Ar
Ar
Ar
Ar
Scheme 1.
Disproportionation of cationic monoaryl complex,
forming biaryl, is applied to dinuclear cationic palladium
complex whose metal centers are bridged by long tether
with expecting formation of macrocyclic compound via
intramolecular transmetalation. Scheme 3 displays outline
of this study. Reaction of AgBF4 with dipalladium com-
plexes with bpy, iodo, and bridging bisaryl ligands forms
the dicationic dinuclear Pd complex whose intramolecular
transmetalation and coupling of the ligand would form
macrocycle.
to form cationic arylnickel complex with the coordinated
solvent. The formed cationic complex undergoes facile dis-
proportionation to yield diarylnickel complex which under-
goes smooth reductive elimination of biaryl. Although this
mechanism was well supported by the above results, the
proposed cationic intermediate, [NiAr(bpy)(DMF)]+Brꢀ,
was not detected in the reaction mixture due to its rapid
transmetalation and successive reductive elimination.
Thus, we conducted studies on chemical properties of Pd
and Pt analogues of the arylnickel complexes with bpy li-
gand, which is described in the following section.
Preparation of dinuclear palladium complex with long
(CH2CH2O)n tether is easily accomplished according to
the reaction shown in Eq. (3) [15,16]. The NMR spectra
2 Pd(dba)2
+
+
2 bpy
2. Cationic arylpalladium and platinum complexes and their
relevance to transmetalation
I
O
X
O
I
(dba = dibenzylideneacetone)
PdAr(I)(bpy) (Ar = Ph, 3,5-Me2C6H3) are stable in
polar solvents such as DMF and do not undergo spontane-
ous disproportionation. The reaction of AgBF4 with these
complexes in acetone or THF produces biaryl as shown in
Eq. (2), while the reaction in MeCN results in isolation of
the cationic arylpalladium complex ½PdArðNCMeÞ-
ðbpyÞꢁþðBFꢀ4 Þ [14]. The reaction forming
(bpy)Pd
Pd(bpy)
O
X
O
I
I
benzene
ð3Þ
1a, 33%, X=
O
O
O
1b, 37%, X=
1c, 39%, X=
1d, 20%, X=
O
O
O
O
O
O
Ar
of the complexes are consistent with symmetrical dinuclear
complex having two Pd centers with the same coordination
environment. Carbonylation of 1b converts it into complex
+ 2 AgBF4
(bpy)Pd
Ar
Ar
2
ð2Þ
acetone
(or THF)
I
2+
+
Ar solvent
N
N
N
N
Ar
-
-
(i)
Pd
BF4
Pd
Pd
(BF4 )2
2
N
N
solvent
R
R
Ar = Ph, C H Me -3,5
solvent = acetone, THF
6
3
2
(R = H, Me)
2+
N
N
Pd
N
solvent
Ar
Ar
-
Pd
(BF4 )2
+
N
solvent
N
Pd
N
Ar
Ar
Ar
Ar
(ii)
Scheme 2.

328
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
2+
AgBF4
solvent
L
L
L
L
L
L
L
L
-
(i)
Pd
Pd
Pd
Pd
Pd
Pd
(BF4 )2
I
I
solvent solvent
(L^L = bidentate ligand)
2+
2+
L
L
L
L
L
L
+
solvent
solvent
-
-
(ii)
Pd
Pd
(BF4 )2
(BF4 )2
solvent solvent
L
L
L
(iii)
Pd
L
Scheme 3.
2 with two aroylpalladium centers via insertion of CO mol-
ecules into the two Pd–C bonds, as shown in Eq. (4). Com-
plex 2 also has a symmetrical structure with two equivalent
Pd centers.
sponding crown ethers, 3a (72%), 3b (>99%), and 3c
(>99%), respectively. Fig. 1 shows change of the reaction.
Rate of formation of the crown-type product is faster in
the mixed solvent than that in DMF. The reaction of equi-
molar AgBF4 with the Pd complex ([1b]:[AgBF4] = 1:2) in
acetone/CH2Cl2 forms the product 3b in lower yield
(80%). Thus, addition of excess Ag+ to the Pd complex is
helpful for the cyclization of the ligand smoothly. The reac-
tion of AgBF4 with dinuclear aroyl complex 2 yields the
crown ether having benzophenone group 4 (94%) and a
minor amount of carbonyl-free product 3b (6%) (Eq. (6)).
Presence of CO (1 atm) causes decrease of yields of both
the products and forms 4 and 3b in 2% and <1%, respec-
tively (Eq. (6)).
(bpy)Pd
Pd(bpy)
O
O
O
3
I
I
1b
ð4Þ
O
I
O
I
CO (1 atm)
CH2Cl2
O
O
O
3
(bpy)Pd
Pd(bpy)
2, 94%
Insertion of CO into the Pd–C bond of arylpalladium com-
plexes with the diimine ligands were reported by several
researchers including van Asselt et al. and Vicente et al.
[17–19].
O
I
O
I
O
O
O
3
(bpy)Pd
Pd(bpy)
Dinuclear palladium complexes, [(bpy)(I)Pd{C6H4-
2
(OCH2CH2)0.5n+0.5}]2O (n = 1 (1a),
3 (1b), 5 (1c)),
[(bpy)(I)Pd{C6H4O(CH2)6}]2 (1d), and [(bpy)(I)Pd{CO-
C6H4(OCH2CH2)2}]2O (2) are employed in the study of
the cyclization reactions involving intramolecular trans-
metalation. Reaction of AgBF4 with 1b ([1b]0 = 5 mM,
[1b]:[AgBF4] = 1:3) in acetone/CH2Cl2 (1:1) forms the
crown ether with 3,30-biphenylene group in the macrocycle
as shown in Eq. (5). Cyclization reactions of 1a, 1b, and
O
O
ð6Þ
O
O
AgBF4
+
O
O
acetone/CH2Cl2
3
O
O
O
under Ar
under CO
4, 94%
3b, 6%
<1%
2%
N
N
N
N
Pd
Pd
O
O
O
n
I
I
100
50
0
1a, n = 1
1b, n = 3
1c, n = 5
CH2Cl2/acetone
[1b]o = 5 mM
ð5Þ
O
O
O
AgBF4 (3 eq.)
acetone/CH2Cl2
DMF
[1b]o = 5 mM
n
3a, 72% (n = 1)
3b, >99% (n = 3)
3c, >99% (n = 5)
0
10
20
t
/h
1c take place smoothly even when the concentration of the
complexes are as high as 100 mM and afford the corre-
Fig. 1. Profile of the cyclization reaction of 1b (in CH2Cl2/acetone,
[1b]0 = 5 mM).

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
329
Scheme 4 illustrates the plausible mechanism to account
for the reactions of aryl and aroyl ligands bonded to dinu-
clear palladium complexes. Complex 2 reacts with AgBF4
to form a dicationic complex, ½fðbpyÞðLÞPdCOC6H4-
latter product is determined to be approximately 5000
based on polystyrene standards.
(bpy)Pd
Pd(bpy)
2þ
O
O
ðOCH2CH2Þ2g2Oꢁ ðBFꢀ4 Þ2 (A) (L = acetone, CO).
I
I
Decarbonylation of an aroyl ligand of A [20] produces
1d
2þ
½ðbpyÞðLÞPdfC6H4ðOCH2CH2Þ4OC6H4COPdðLÞðbpyÞgꢁ
ðBFꢀ4 Þ2 (B). Aryl ligand contained in B undergoes intramo-
lecular transfer from the Pd to the other, giving an interme-
diate with a cyclometalated aryl–aroyl ligand bonded to
Pd, and then reductive elimination of benzophenone-con-
taining crown ether 4 takes place. Coupling of two aroyl
ligands of intermediate A forming a double carbonylation
product does not take place at all. It is probably because
dissociation of labile acetone ligand from palladium leads
to facile decarbonylation, which occurs prior to intramo-
lecular transfer of the aroyl ligand. The result of the reac-
tion of AgBF4 under CO atmosphere with 2, giving 4
and 3b in much lower yields, suggests that the carbonyl
ligand bonded to the intermediate strongly prevents not
only decarbonylation but also transfer of the aroyl ligand.
The reaction of AgBF4 with dinuclear complex 1d with
polymethylene bridging group in low concentration
([1d]0 = 1.7 mM) also forms cyclic product 5 via intramo-
lecular transfer of the aryl group followed by intramolecu-
lar coupling of the ligand in 78% yield (Eq. (7)). The
reaction with higher concentration of the complex
([1d]0 = 34 mM) forms the cyclic product in low yield
(23%) due to concurrent formation of linear polymeric
products which are characterized by GPC analysis of the
reaction mixture. Averaged molecular weight (Mn) of the
O
O
ð7Þ
AgBF4
acetone/CH2Cl2
5, 78% ([1d]0 = 1.7 mM)
23% ([1d]0 = 34 mM)
Different results of the reaction of 1b (or 1c) and 1d
depending on the concentration can be explained as fol-
lows. Bridging oligoether chain of 1b and 1c coordinates
to Ag+ as a polydentate ligand and functions as a template
for the cyclization. Complex 1d, however, is not expected
to cyclize with help of such a template effect. Thus, the
dinuclear complex with a similar structure, but with a
polymethylene chain between the two aryl ligands, pro-
duces undesirable linear polymer products even in the pres-
ence of Ag+.
Pt analogues of the cationic arylpalladium complex,
½PdArðsolventÞðbpyÞꢁþðBFꢀ4 Þ, is prepared according to
Scheme 5 [21]. PtPh(I)(bpy), prepared from ligand substitu-
tion of PtPh(I)(cod) with bpy, reacts with AgBF4 in the sol-
vents such as acetone and MeCN to afford the
corresponding cationic complexes ½PtPhðsolventÞðbpyÞꢁþ
ðBFꢀ4 Þ (solvent = acetone (6-acetone), MeCN (6-MeCN)).
O
O
I
O
O
O
3
(bpy)Pd
Pd(bpy)
Pd(bpy)
I
2
AgBF4
acetone
2+
(BF4- )2
O
O
L
O
O
O
3
(bpy)Pd
(bpy)Pd
L
A
O
2+
2+
O
O
O
(bpy)Pd
(bpy)Pd
O
O
O
3
(BF4- )2
Pd(bpy)
Pd(bpy)
L
O
L
O
O
B
4
O
O
O
O
(BF4- )2
O
(bpy)Pd
O
O
O
3
L
L
(L = acetone or CO)
3b
Scheme 4.

330
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
Ph
I
Ph
I
(cod)Pt
(bpy)Pt
(i)
+ bpy
+ COD
(bpy)Pt
r. t., Et2O
+
- AgI
Ph
I
Ph
-
(ii)
+ AgBF4
(bpy)Pt
BF4
solvent, r. t.
solvent
6-acetone (solvent = acetone)
6-MeCN (solvent = MeCN)
Scheme 5.
½PtPhðNCMeÞðbpyÞꢁþðBF4ꢀÞ (6-MeCN) was isolated as an
analytþically pure complex, although ½PtPhðacetoneÞ-
ðbpyÞꢁ ðBFꢀ4 Þ (6-acetone) is hygroscopic in the solid state
and is characterized by NMR spectroscopy in the solution.
The 1H NMR spectrum of 6-MeCN in CD3CN shows
exchange of the coordinated solvent with deuterated one
but no other change for a month at 50 ꢀC. Complex
6-acetone in acetone-d6 solution does not undergo intermo-
lecular transfer of the aryl ligands, although ½PdPh-
ðacetoneÞðbpyÞꢁþðBF4ꢀÞ releases biaryl spontaneously in
solution (Eq. (2)).
Scheme 6 summarizes reactions of the cationic arylplat-
inum complexes having bpy ligand. ½PtPhðsolventÞðbpyÞꢁþ-
ðBFꢀ4 Þ (6-acetone, 6-MeCN) undergoes carþbonylation
under 1 atm of CO to afford ½PtPhðbpyÞðCOÞꢁ ðBFꢀ4 Þ (6-
CO) which is isolated from the reaction mixtures. The reac-
tion of CO with 6-MeCN requires 7 days for completion at
room temperature, while the complex with labile acetone
ligand, 6-acetone, reacts with CO more smoothly to pro-
duce the carbonyl complex within 3 h. Complex 6-acetone
reacts with phenylallene to cause insertion of a double
bond into the Pt–C bond to yield the p-allylplatinum com-
plex ½Ptfg3 ꢀ CH2CðPhÞCHðPhÞgðbpyÞꢁþðBFꢀ4 Þ (7-syn, 7-
anti). The product is composed of the isomers with phenyl
substituents at the syn and anti positions of the p-allylic
ligand (52:48). Recrystallization of the product yielded
single crystals of 7-syn which is characterized by X-ray
crystallography. Complex 6-MeCN undergoes oxidative
addition of MeI to afford cationic Pt(IV) complex for-
mulated as ½PtðIÞðMeÞðPhÞðNCMeÞðbpyÞꢁþðBF4ꢀÞ (8). The
crystal structure of one of the products contains Me and
iodo ligand at trans positions of the bpy ligand. Most of
octahedral Pt(IV) complexes formed via oxidative addi-
tion of alkyl halides to the Pt(II) complexes with chelating
N-ligand contain the alkyl and halo ligands at the apical
positions via formal trans addition [22]. Thus, complex 8
obtained from this reaction probably has the thermody-
namically stable structure formed via thermal isomeriza-
tion of the initial trans addition product.
Recently, Kubas and Peters independently reported that
the reaction of arene with the cationic methylplatinum(II)
complexes produced dinuclear platinum(II) complexes
whose metal centers were bridged by a formally dianionic,
bis-p-allylic ligand, as shown in Scheme 7 [23,24]. The
bridging biaryl ligand is liberated upon treatment of the
dinuclear complex with I2 or HCl. Combination of the che-
lating phosphine ligands and labile Et2O or THF ligand
enabled the C–C bond formation, although it may be under
+
Ph
-
(bpy)Pt
BF4
CO (1 atm)
solvent, r. t.
Ph
CO
6-CO
+
+
Ph
+
·
Ph
Ph
+
(bpy)Pt
-
-
-
(bpy)Pt
BF4
BF4
BF4
(bpy)Pt
Ph
Ph
solvent
solvent = acetone
MeI
6-acetone
6-MeCN
7-syn
7-anti
+
Ph
Me
-
bpy Pt
BF4
+ isomer of 8
solvent = MeCN
I
NCCH3
8
Scheme 6.

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
331
2+
Cy2
+
P
Cy2
P
+
Cy2
P
Cy2
P
Pt
Me
P
+
+
Pt
Pt
Pt
Cy2
P
OEt2
P
OEt2
P
Cy2
Cy2
Cy2
Ph2
P
Pt
Ph2
P
Pt
2+
Ph2
Ph
O
Me
P
Ph
Ph
Ph
Ph
Ph
Ph2
Si
Si
Pt
Si
P
Ph
Ph
Ph
O
P
P
P
Pt
Si
Ph2
Ph2
Ph2
P
Ph2
Scheme 7.
F
discussion whether the biphenyl formation is ascribed
to aryl ligand transfer between the Pt centers or to inter-
molecular reductive elimination of the two cationic
complexes. Cationic arylplatinum complexes with bpy
mentioned in this section do not undergo such C–C bond
formation. Other examples of intermolecular aryl ligand
transfer of the Pt complexes will be raised in the following
sections.
F
Me
(dmpe)Pt
2
125 oC
OCOCF3
Ar
OCOCF3
Ar
(dmpe)Pt
+
+(dmpe)Pt
(dmpe)Pt
Ar
OCOCF3
OCOCF3
25%
25%
50%
(Ar = C6H3F2-2,3)
ð9Þ
3. Transmetalation of neutral Pd and Pt complexes
promoted by the methylplatinum complex and intermolec-
ular transfer of the aryl ligand. Aryl ligand transfer be-
tween the Pt and Pd complexes was also reported. cis-
PtMe(C6H4Me-4)(L2) (L2 = cod, 2PMe2Ph) reacts with
cis-PdCl2(PMe2Ph)2 to form different products depending
on the kind of the auxiliary ligand at the Pt center (Scheme
8) [27]. PtMe(C6H4Me-4)(cod) having cod ligand reacts
with Pd complex to form PtCl(Me)(cod) via transfer of
the chloro ligand from Pd to Pt. Transfer of the aryl ligand
from Pt to Pd should take place at the same time, but the
corresponding arylpalladium product was not isolated
from the reaction mixture. The reaction of PtMe-
(C6H4Me-4)(PMe2Ph)2 causes transfer of the methyl ligand
from Pt to Pd and forms a mixture of PtCl(C6H4Me-4)-
(PMe2Ph)2 and PdCl(Me)(PMe2Ph)2.
Several neutral arylplatinum complexes were also
reported to undergo transfer of the aryl ligands between
the Pt centers. Eaborn found that conproportionation reac-
tion of PtR2(cod) (R = 2-thienyl) and PtCl2(cod) yielded
chloro(thienyl)platinum complex via transfer of the thienyl
ligand between the Pt centers, as shown in Eq. (8) [25].
Cl
Cl
S
S
S
ð8Þ
(cod)Pt
2 (cod)Pt
(cod)Pt
+
Cl
Peters reported the reaction of 1,2-difluorobenzene with
PtMe(OCOCF3)(dmpe) (dmpe = 1,2-bis(dimethylphosph-
ino)ethane), which forms a mixture of PtAr2(dmpe) (25%,
Ar = C6H3F2-2,3), PtAr(OCOCF3)(dmpe) (50%), and
Pt(OCOCF3)2(dmpe) (25%), as shown in Eq. (9) [26]. This
reaction involves the activation of a C–H bond of the arene
In this section, the reactions involving transfer of aryl
ligands between Pd and Pt complexes are described [28].
The cod ligand plays an important role in the aryl ligand
Me
Cl
C6H4Me-4
Cl
L2 = cod
25 oC, < 5min
(cod)Pt
+
(PhMe2P)2Pd
C6H4Me-4
not detected
(L2)Pt
cis
+
cis-PdCl2(PMe2Ph)2
Me
C6H4Me-4
PMe2Ph
Cl
PhMe2P
PhMe2P
Pd
Me
L2 = 2 PMe2Ph
25 oC, < 5min
Pt
+
Cl
PMe2Ph
Scheme 8.

332
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
Table 1
Conproportionation of PtPh2(cod) and Pt–cod (Eq. (10))a
Run
Pt–cod complex
X = Cl
Additive
Time (h)
PtX(Ph)(cod)b (%)
1
2
3
4
5
6
7
8
9
None
None
3
24
3
3
3
3
3
3
24
3
72
93
0
Et4NCl (0.50 mmol)
KCl (0.50 mmol)c
COD (0.10 mmol)
COD (0.50 mmol)
COD (1.0 mmol)
None
0
57
51
57
36
75
94
X = I
None
None
2þ
d
10
a
½PtðacetoneÞ2ðcodÞꢁ ðBFꢀ4 Þ2
Conditions: PtPh2(cod) (0.10 mmol), Pt–cod complex (0.10 mmol), solvent: CH2Cl2 (runs 1–9), acetone (run 10), room temperature.
Yield of the product are based on the Pt complex used (0.20 mmol).
An aqueous solution (0.1 mL) of [18]crown-6 was added.
½PtðacetoneÞ2ðcodÞꢁ ðBF4ꢀÞ2 was generated in situ from AgBF4 and PtCl2(cod). The reaction mixture was terminated by addition of KCl which
b
c
2þ
d
quenched the cationic complex to give the inactive neutral chloro complex.
transfer. At first, we conducted the reaction in order to elu-
cidate the mechanism of the reaction of thienylplatinum
complex shown in Eq. (8). A mixture of PtPh2(cod) and
PtX2(cod) (X = Cl, I) undergoes conproportionation, giv-
ing PtX(Ph)(cod) via intermolecular exchange of the phe-
nyl and chloro (or iodo) ligands, as shown in Eq. (10).
Table 1 summarizes results of the reactions under sev-
eral conditions. The conproportionation of PtPh2(cod) with
ascribed to less labile character of the iodo ligand than that
of the chloro ligand. Cationic halogeno-free Pt complex
2þ
½PtðacetoneÞ2ðcodÞꢁ ðBF4ꢀÞ2 undergoes more facile aryl li-
gand transfer of the phenyl ligand than PtX2(cod)
(X = Cl, I) (run 10).
Since
isolated
halo(phenyl)platinum
complexes
PtX(Ph)(cod) (X = Cl, I) are stable in solution and do
not undergo spontaneous disproportionation reaction that
would form a mixture of diphenyl and dihalo complexes, as
shown in Eq. (11). Thus, the conproportionation reaction
2+
Ph
Ph
X
X
acetone
acetone
-
(BF4 )2
(cod)Pt
+
(cod)Pt
or (cod)Pt
Ph
no reaction
(cod)Pt
(X = Cl, I)
ð11Þ
CH2Cl2
r. t., 24 h
X
Ph
(cod)Pt
X
Additive
(X = Cl, I)
2
CH2Cl2
r. t.
in Eq. (10) is irreversible at room temperature probably
due to unfavorable dissociation of the halo ligand from
the halo(phenyl)platinum complex. Another explanation
for these results may involve formally reversible reactions
in Eqs. (10) and (11) and much higher thermodynamic sta-
bility of PtX(Ph)(cod) than that of the mixture of the di-
phenyl and dihalo complexes.
Scheme 9 summarizes plausible mechanism of the above
reactions. Partial dissociation of a halogeno ligand from
the dihaloplatinum complex generates cationic intermedi-
ð10Þ
PtCl2(cod) is effectively inhibited by addition of Et4NCl
and KCl (runs 3 and 4), while addition of cod ligand to
the reaction mixture affects yield of the product to a limited
extent (runs 5–7). These results indicate that dissociation of
a halogeno ligand from the Pt–cod complex induces the
aryl group transfer between the Pt centers. Lower reactivity
of PtI2(cod) than that of PtCl2(cod) (runs 8 and 9) may be
+
X
X
X-
(i)
Pt
Pt
X
solvent
(X = Cl, I)
+
+
X-
Ph
X
X
Ph
X-
(ii)
Pt
+
Pt
+
Pt
Pt
Pt
solvent
Ph
+
Ph
X
Ph
X
solvent
Ph
X-
X-
(iii)
Pt
Pt
+
Pt
Scheme 9.

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
333
ate [PtX(solvent)(cod)]+Xꢀ (X = Cl, I) (i). The formed cat-
Cl
Cl
Ph
Ph
ionic complex reacts with diphenylplatinum complex to
produce intermediate dinuclear species that contains bridg-
ing phenyl ligand (ii). Activation of a Pt–Ph bond of the
bridging phenyl ligand yields neutral and cationic mon-
ophenyl complexes (iii), and the latter complex undergoes
ligation of the halo ligand to generate neutral
halo(phenyl)platinum complex. The dinuclear complexes
with a bridging aryl ligand between the two Pt (or Pd) cen-
ters were reported [29–33].
2
Pd
+
Pt
Ph
Cl
Cl
Cl
2
Pd
+
Pt
CH2Cl2
94%Pt
Ph
Ph
Pd
Cl
Cl
Pd
The reaction of PtPh2(dppe) (dppe = 1,2-bis(diph-
enylphosphino)ethane) with PtCl2(cod) forms a mixture
of PtPh2(cod) (38%), PtCl(Ph)(cod) (53%), and PtCl-
(Ph)(dppe) (72%) smoothly, as shown in Eq. (12).
9, 76%Pd
Scheme 10.
Ph
Ph
Cl
Cl
(cod)Pt
+
(dppe)Pt
CH2Cl2
Insertion of a C@C double bond of the cod ligand into
the Pd–Ph bond produces the 2-phenyl-5-cyclooctenyl
ligand bonded to Pd center. A similar reaction was
reported by Albeniz et al. who observed the reaction of
C6F5Li with PdCl2(cod) to form [Pd(l-Cl)(g1,g2-
C8H12C6F5)]2 via intermediate Pd complex with C6F5
ligand [34,35]. The mechanism of this reaction was revealed
based on isolation of an intermediate PdCl(C6F5)(cod) with
stable C6F5 ligand from the reaction mixture.
The reaction of PdCl2(cod) with PtPh2(dppe) also pro-
duces dinuclear complex 9 in 76% yield as shown in Eq.
(15). PtPh2(bpy) reacts with PdCl2(cod) to form the same
complex but in a low yield (6%) after the reaction for
20 h.
ð12Þ
Ph
Cl
Ph
Ph
+
Cl
+
(cod)Pt
(cod)Pt
(dppe)Pt
72%
Ph
38%
53%
Formation of PtCl(Ph)(dppe) indicates occurrence of aryl
ligand transfer between the Pt centers during the reaction.
On the other hand, PtCl2(dppe) and PtPh2(L2)
(L2 = dppe, cod) do not cause any intermolecular
exchange of the phenyl and chloro ligands, as shown in
Eq. (13).
Ph
Cl
Cl
no reaction
(dppe)Pt
+ L2Pt
ð13Þ
CH2Cl2
Ph
(L2 = dppe, cod)
Cl
Cl
Ph
2 (cod)Pd
+
(L2)Pt
Ph
Comparison of the reactions in Eqs. (12) and (13) indicates
that the phenyl ligand transfer between the Pt centers
highly depends on the kind of chelating ligand; dichloro-
platinum complex with cod ligand undergoes aryl ligand
transfer from aryl platinum complexes with other chelating
ligands.
The reaction of PtCl2(cod) with excess PdCl(Ph)(bpy) in
CH2Cl2 forms PtCl(Ph)(cod), as shown in Eq. (14). The
products of the reaction do not contain PtPh2(cod).
(L2 = dppe, bpy)
Ph
Pd
Ph
Pd
ð15Þ
Cl
Cl
Cl
Cl
(L2)Pt
+
CH2Cl2
r. t., 20 h
9 (76%Pd for L2 = dppe)
(6%Pd for L2 = bpy)
Low yield of the product is partly due to low solubility of
the PtPh2(bpy) in the solvent. PdCl(Ph)(bpy) also functions
as the source of phenyl ligand that is transferred to the Pd–
cod complex with chloro ligands, as shown in Eq. (16). Sol-
ubility of PdCl(Ph)(bpy) is also limited, but the heteroge-
neous reaction in CH2Cl2 forms the dinuclear complex 9
in 97% yield after 20 h at room temperature.
Ph
Cl
Cl
Cl
(cod)Pt
+
(bpy)Pd
ð14Þ
Ph
Cl
(cod)Pt
CH2Cl2, r. t., 5 d
66%
PdCl2(bpy) should also be formed although limited solubil-
ity of the complex prevents full characterization of the
complex contained in the reaction mixture.
Reaction of PdCl2(cod) and PtPh2(cod) in CH2Cl2 pro-
duces the dinuclear palladium complex 9 (76%) and
PtCl2(cod) (94%), as shown in Scheme 10. Formation of
9 by the reaction is explained by transfer of the phenyl
ligand from Pt to Pd, as described below. Transmetalation
of the Pd and Pt complexes forms PdCl(Ph)(cod) initially.
Cl
Cl
Ph
Cl
2
(cod)Pd
+
(bpy)Pd
Ph
Ph
Pd
ð16Þ
Cl
Pd
CH2Cl2
r. t.
Cl
9, 97%Pd

334
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
Table 2
Transmetalation between dichloro and diphenyl complexes of Pd and Pta
Phenyl complexes
PtPh2(cod)
PtPh2(dppe)
PtPh2(bpy)
Y
PdCl(Ph)(bpy)
PdCl2(cod)
PtCl2(cod)
PtCl2(dppe)
PdCl2(dppe)
PtCl2(bpy)
a
Y
Y
N
N
N
Y
Y
N
N
Y
Y
Y: Phenyl complex formed via transmetalation was observed spectroscopically; N: formation of phenyl complex via transmetalation was not
confirmed.
Dichloropalladium complexes with other chelating
Table 2 summarizes relative reactivities of the phenyl and
chloro complexes with various chelating auxiliary ligands.
Transmetalation of the diphenyl complexes with dichloro
complexes of Pd and Pt takes place smoothly when the di-
chloro complex contains cod ligand, while the dichloro
complexes with dppe and bpy ligand do not undergo trans-
metalation with diphenyl complexes. Kind of the auxiliary
ligands on the diphenyl complexes do not affect the reac-
tion results.
These observations suggest the plausibility of the mech-
anism shown in Scheme 11, which involves dissociation of
the chloro ligand of the dichloro complexes as the initiation
step of transmetalation. Cationic chloro complex forms
dinuclear complex with bridging phenyl ligand easily, and
cleavage of a metal–carbon bond of the bridging ligand
results in chloro(phenyl)platinum (or palladium) complex.
Among three chelating ligands, cod, bpy, and dppe, the
cod ligand is known to show higher p-acceptor ability than
bpy and lower r-donor ability than the other two ligands.
Table 3 compares 13C{1H} NMR data of the dimethylplat-
inum complexes with several chelating ligands [36–39].
Peak positions of the methyl ligand bonded to Pt are influ-
enced significantly by the chelating ligands used. The com-
plexes with cod and dppe ligands having strong p-acceptor
character exhibit the methyl carbon signals at the positions
lower than the complex with diimine ligand by more than
10 ppm. It indicates low electron density of the methyl
group of PtMe2(cod) due to the electronic character of
the ligand.
ligands such as PdCl2(dppe) and PdCl2(bpy) do not react
with the diphenyl complexes of Pt, as shown in Eqs.
(17)–(19).
Ph
Ph
Cl
Cl
(dppe)Pd
(dppe)Pd
(bpy)Pd
+ (cod)Pt
no reaction
2
2
2
ð17Þ
ð18Þ
ð19Þ
CH2Cl2
r. t., 20 h
Ph
Cl
+ (dppe)Pt
+ (cod)Pt
no reaction
Cl
Ph CH2Cl2
r. t., 20 h
Ph
Cl
Cl
no reaction
CH2Cl2
Ph
r. t., 14 h
+
Cl
M
Cl
Cl
(i)
M
Cl-
solvent
+
L
L
X
Cl
M
Cl-
+
m
(ii)
solvent
(M, m = Pt, Pd)
(X = Ph, Cl)
+
L
L
Cl
X
M
m
Cl-
L
L
Cl
X
M
+
m
Cl
Enhancement of the transmetalation by the cod ligand
may be explained as below. A large trans effect of the
cod ligand promotes dissociation of the chloro ligand
Scheme 11.
Table 3
13C{1H} NMR data of cis-PtMe2(ligand)
Ligand
cod
nbda
4.56
814.5
[37]
dppe
2 pyb
ArN = CH–CH = NArc
tmedad
Me peak positions (dc)
J(PtC)/Hz
Reference
4.7
2
1.0
610
[38]
ꢀ8.18
688.5
[37]
ꢀ14.2
793.5
[39]
ꢀ23.67
826.2
[37]
773
[36]
a
nbd = 2,5-norbornadiene.
py = pyridine.
Ar = C6H3Me2-2,6.
tmeda = N,N,N0,N0-tetramethylethylenediamine.
b
c
d

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
335
bonded at the trans position of the cod, which facilitates
Ph
I
(cod)Pt
- AgI
2
+
2 AgBF4
Ph
the transmetalation by the dissociation mechanism. At
the same time, facile association of the cationic intermedi-
ate with neutral diaryl complex via bridging coordination
of the aryl ligand should also be taken into consideration.
Electronically deficient Pt center of the cationic complex
with cod ligand is favorable for formation of the bridging
ligand. The latter factor seems to be more operative
because Tobe and Gosling studied the solvolysis of
[NEt4][PtCl3(L)] in methanol (Eq. (20)) and concluded that
+
-
(cod)Pt
2
BF4
acetone-d6
acetone-d6
2+
Ph
Ph
acetone-d6
acetone-d6
-
(cod)Pt
+ (cod)Pt
(BF4 )2
Scheme 12.
Cl
Cl
Pt
H
[NEt4]
+ MeOH
L
O
+
[NEt4][Cl]
L
Pt Cl
Me
Cl
Cl
Ph
Ph
(cod)Pt
I
- AgI
(cod)Pt
(L = C2H4, OSMe2, SMe2, AsEt3, P(OMe)3, PPh3, P(n-Bu)3, PEt3)
+
Ag2O
OAg
ð20Þ
+ CH3COCH3
- AgOH
the Cl ligand at trans position of olefin ligand is not disso-
ciated to a significant degree due to rapid ligation of Cl li-
gand to neutral Pt center [40]. So the concentration of the
cationic complexes [MCl(solvent)(cod)]+(Clꢀ) (M = Pt,
Pd) in solution is not higher than those of [MCl(sol-
vent)(L2)]+(Clꢀ) (L2 = dppe, bpy) in Scheme 11, and cod li-
gand of the dichloro complex enhances the transmetalation
by facile formation of the dinuclear intermediate with
bridging ligand.
Ph
(cod)Pt
CH2COMe
10
Scheme 13.
elimination of AgI. The AgOꢀ ligand formed by the reac-
tion is highly basic and activates a C–H bond of acetone
to form the acetonyl ligand. Thus, Ag2O exhibits dual roles
such as Pt–I bond activation and C–H bond activation of
the acetone. The reaction of acetone with a dichloroplati-
num complex in the presence of Ag2O was reported to form
PtCl(CH2COMe)(PEt3)2 [42]. Wimmer et al. [43] and Mint-
cheva et al. [44] independently reported activation of O–H
4. Transmetalation of acetonylplatinum complexes
Phenylplatinum complex with acetonyl ligand also
undergoes intermolecular transfer of the phenyl ligand.
The reaction of Ag2O with PtI(Ph)(cod) in acetone forms
a mixture of Pt(CH2COMe)(Ph)(cod) (10, 61%), PtPh2-
(cod) (20%), and Pt(CH2COMe)2(cod) (11, 19%), as shown
in Eq. (21) [41].
a
Ph
8.0
(cod)Pt
+
Ag2O
+
CH3COCH3
10
I
6.0
t
Ph
Ph
Ph
CH2COMe
CH2COMe
- AgI
(cod)Pt
+
(cod)Pt
20%
+ (cod)Pt
4.0
CH2COMe
10, 61%
11, 19%
2.0
0
PtPh2(cod)
ð21Þ
11
0
20
40
/ h
60
The produced complexes were characterized by X-ray crys-
tallography and comparison of the NMR data with
authentic complexes prepared independently. The yields
of the products suggests the initial formation of 10 and
its disproportionation to form PtPh2(cod) and 11. Cationic
phenylplatinum complex with acetone-d6 ligand,
½PtPhðacetone-d6ÞðcodÞꢁþðBFꢀ4 Þ, prepared in situ from the
reaction of AgBF4 and PtI(Ph)(cod) in acetone-d6 does
not cause disproportionation reaction at 50 ꢀC (Scheme
12). Thus, the cationic arylplatinum complex with coordi-
nated acetone and cod ligands is not the intermediate for
formation of the diphenyl complex.
t
8.0
b
6.0
4.0
10
t
PtPh2(cod)
2.0
0
11
0
20
40
/ h
60
t
Fig. 2. (a) Profile of disproportionation of 10 into 11 and PtPh2(cod) in
acetone-d6 at 50 ꢀC. (b) Profile of conproportionation of 11 and
PtPh2(cod) into 10 in acetone-d6 at 50 ꢀC.
Scheme 13 shows a plausible pathway for formation of
10. Ag2O abstracts iodo ligand of PtI(Ph)(cod) to cause

336
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
bond of the ligand (aqua ligand or silanolate ligand) by
Ag2O.
Heating of acetone-d6 solution of Pt(CH2COMe)(Ph)-
(cod) (10) at 50 ꢀC forms a mixture of PtPh2(cod) and
Pt(CH2COMe)2(cod) (11), as shown in Eq. (22). Fig. 2(a)
shows
PtPh2(cod) and 11 ([PtPh2(cod)]0, [11]0 = 4.0 · 10ꢀ2 M) in
C6D6 changes the ratio of the complexes as shown in
Fig. 3(b). After 50 h, the ratio between 10 and 11 becomes
80:10. The curves in these figures suggest that the dispro-
portionation occurs slower than the conproportionation
under similar conditions although the complexes are
apparently in equilibrium in the solutions. Schemes 14
and 15 show possible mechanisms of the ligand transfer be-
tween two Pt centers to account for the above results. Dis-
proportionation of 10 involves a dinuclear intermediate C
in which the two Pt centers are bridged by a phenyl and
j2-C–O-acetonyl ligand (Scheme 14). Cleavage of Pt–C
bonds of coordinated acetonyl and phenyl groups at shown
positions leads to PtPh2(cod) and an enolate isomer of 11.
The latter product is soon converted to thermodynamically
stable 11. Conproportionation of PtPh2(cod) and 11 also
proceeds via dinuclear intermediate with bridging phenyl
and j2-C–O-acetonyl ligand (Scheme 15). Bridging coordi-
nation of the ligand probably takes place via coordination
of the carbonyl oxygen to another Pt center, and direction
of bridging acetonyl ligand differ between the intermediates
of disproportionation C and conproportionation D. Differ-
ent structure of the dinuclear intermediates may render the
rates of these apparently reversible reactions different.
Dinuclear and multinuclear palladium complexes with
unsymmetrically bridged acetonyl ligands were reported,
as shown in Chart 1; [Pd{CH2C(O)Me}Cl]n and
[Pd2{CH2C(O)Me}{l-j2-C,O-CH2C(O)Me}(l-Cl)Cl(dmso)2]
contain unsymmetrically bridged acetonyl ligands [45].
Ph
Ph
CH2COMe
CH2COMe
Ph
(cod)Pt
+
(cod)Pt
2
(cod)Pt
acetone-d6
50 oC
CH2COMe
10
11
ð22Þ
change of 10 in acetone-d6 ([10]0 = 8.0 · 10ꢀ2 M) into a
mixture of PtPh2(cod) and 11, the ratio of the complex at-
tains to 75:13:12 after 70 h. The reaction rate does not
change by addition of Ag2O to the reaction mixture. Thus,
formation of 10 in the reaction in Scheme 13 is induced by
Ag2O, although the disproportionation of the complex is
not related to the added Ag2O. This reaction accompanies
exchange of the acetonyl ligand with the deuterated ace-
tone via protonation of the acetonyl ligand by the solvent.
An equimolar mixture of PtPh2(cod) and 11 in acetone-
d6 ([PtPh2(cod)]0 = [11]0 = 4.0 · 10ꢀ2 M) undergoes con-
proportionation and gives a mixture of 10, PtPh2(cod),
and 11 in 65:19:16 after the reaction for 46 h (Eq. (23)).
Ph
Ph
CH2COMe
CH2COMe
11
Ph
(cod)Pt
+
(cod)Pt
(cod)Pt
2
acetone-d6
50 o
CH2COMe
C
10
ð23Þ
Fig. 3 shows progress of the reactions in Eqs. (22) and (23)
in C6D6. Complex 10 ([10]0 = 8.0 · 10ꢀ2 M) in C6D6 is con-
verted into a mixture of 10, PtPh2(cod), and 11 in
10:11 = 90:5 after 70 h. An equimolar mixture of
5. Transmetalation of hydroxoplatinum complexes
Organoplatinum(II) hydroxo complexes have long been
studied and were reported to exhibit a nucleophilic charac-
ter [46,47] in a similar way to the more common alkoxo-
platinum(II) complexes [48–53]. The hydroxo platinum
complexes show a tendency to form dinuclear complex by
bridging of the OH ligand [54–60]. These dinuclear Pt com-
plexes are stabilized by highly basic OH ligand and flexible
Pt–OH–Pt bonding. Transmetalation involving mononu-
clear and dinuclear hydroxoplatinum complexes as the
intermediates is described in this section [61,62].
8.0
a
10
6.0
t
4.0
2.0
11
0
0
100
200
t
/ h
Me
O
8.0
b
Ph
Ph
(cod)Pt
(cod)Pt
Pt(cod)
O
2
6.0
4.0
t
10
CH2COMe
10
Me
C
2.0
0
11
60
Ph
CH2COMe
O
(cod)Pt
+
(cod)Pt
Me
Ph
0
20
40
/ h
t
Fig. 3. (a) Profile of disproportionation of 10 into 11 and PtPh2(cod) in
benzene-d6 at 50 ꢀC. (b) Profile of conproportionation of 11 and
PtPh2(cod) into 10 in benzene-d6 at 50 ꢀC.
11
Scheme 14.

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
337
Me
O
Ph
Ph
CH2COMe
CH2COMe
Ph
(cod)Pt
(cod)Pt
+ (cod)Pt
Pt(cod)
O
11
Me
D
Ph
Ph
O
(cod)Pt
10
+
CH2COMe
(cod)Pt
Me
10
Scheme 15.
X-ray diffraction, GPC, and MS measurement indicate for-
mation of [nBu4N]+[I]ꢀ (TBA+Iꢀ) and anionic Pt-contain-
Me
Pd
O
Me
O
Me2S
Cl
Pd
O
Me
O
Pd
Cl
Cl
ing oligomer, [Ptm(OH)n]ꢀ(nꢀ2m)
.
Cl
Pd
O
O
Pd
Cl
Pd
O
SMe2
Cl
In order to clarify structure of the intermediates, the fol-
lowing experiments were conducted. Reaction of AgBF4
with PtI(Ar)(cod) (Ar = Ph, C6H4Me-4, C6F5), followed
by addition of a small amount of H2O to the resultant
½PtArðTHFÞðcodÞꢁþðBF4ꢀÞ, yields the dinuclear Pt com-
plexes with a bridging hydroxo ligand, ½fPtArðcodÞg2-
ðl-OHÞꢁþðBF4ꢀÞ ðAr ¼ Ph ð12-BF4ꢀÞ, C6H4Me-4 ð13-BFꢀ4 Þ,
C6F5 ð14-BFꢀ4 ÞÞ (Scheme 16). The obtained complexes were
fully characterized by X-ray crystallography, NMR spec-
troscopy, and elemental analyses [63]. Table 4 summarizes
spectroscopic data of the complexes. The IR spectra con-
tain the stretching vibration of OH ligand at the character-
istic positions as the bridging ligand (3345–3432 cmꢀ1).
The 1H NMR peaks of OH hydrogen appear at 4.1–
4.6 ppm at ꢀ55 ꢀC in CDCl3, but the signals are not
observed at room temperature. The dinuclear complexes
with bridging hydroxo ligand, 12-BFꢀ4 and 13-BF4ꢀ react
with TBA+Xꢀ (Xꢀ = Iꢀ, OHꢀ) in a 2:1 molar ratio to yield
PtAr2(cod), as shown in Eq. (25).
O
n
Me
Me
Me
Chart 1.
The reaction of [nBu4N]+[OH]ꢀ (TBA+OHꢀ) with
PtI(Ph)(cod) in a 2:1 molar ratio forms PtPh2(cod), as
shown in Eq. (24).
Ph
2
(cod)Pt
+
TBA+OH-
I
0.20 mmol
0.10 mmol
Ph
+
Ph
[Ptm(OH)n]-(n-2m) + TBA+I-
(cod)Pt
THF
r. t.
0.083 mmol
ð24Þ
+
Since PtI(Ph)(cod) does not undergo spontaneous dispro-
portionation to form the diphenyl complex (Eq. (11)),
TBA+OHꢀ promotes the transmetalation of the phenyl-
platinum complex. Analyses of the products by wide-angle
TBA+X-
Ar Ar
Ar
Ar
-
(cod)Pt
Pt(cod) BF4
(cod)Pt
THF, r. t.
O
H
12-BF4- (Ar = Ph)
13-BF4- (Ar = C6H4Me-4)
14-BF4- (Ar = C6F5)
+ 2 AgBF4
+
BF4
Ar
Ar
I
- 2 AgI
-
ð25Þ
2 (cod)Pt
2
(cod)Pt
Ar
THF
THF
The results are summarized in Table 5. The reaction takes
place by addition of TBA+Iꢀ or TBA+OHꢀ, giving PtAr2(-
cod) (Ar = Ph, C6H4Me-4) via transfer of the aryl ligand,
while addition of TBAþPF6ꢀ to 12-BFꢀ4 does not cause
the aryl ligand transfer at all (run 3). Complex 14-BFꢀ4 hav-
ing stable Pt–C6F5 bond does not undergo transmetalation
even in the presence of TBA+OHꢀ (run 5). Scheme 17
shows the plausible reaction mechanism based on the
above results. TBA+OHꢀ reacts with PtI(Ph)(cod) to form
Pt(OH)(Ph)(cod) (15) and TBA+Iꢀ. Mononuclear phenyl-
+
Ar
+ H2O
- HBF4
-
(cod)Pt
Pt(cod) BF4
O
H
12-BF4- (59%Pt, Ar = Ph)
13-BF4- (64%Pt, Ar = C6H4Me-4)
14-BF4- (38%Pt, Ar = C6F5)
Scheme 16.

338
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
Table 4
IR and 1H NMR data of ½fPtArðcodÞg2ðl-OHÞꢁþðBFꢀÞ ðAr ¼ Phð12-BFꢀÞ; C6H4Me-4ð13-BFꢀÞ; C6F5ð14-BFꢀÞÞ
4
4
4
4
Complex
IR, m(OH)
dH (OH) (solvent, temperature)
12-BFꢀ4 ðAr ¼ PhÞ
3428 cmꢀ1 (CHCl3)
Not detected (KBr)
4.17 (CDCl3, ꢀ55 ꢀC)
Not detected (CDCl3 or C6D6, r.t.)
13-BFꢀ4 ðAr ¼ C6H4Me-4Þ
14-BFꢀ4 ðAr ¼ C6F5Þ
3432 cmꢀ1(CHCl3)
4.13 (CDCl3, ꢀ55 ꢀC)
Not detected (CDCl3 or C6D6, r.t.)
3345 cmꢀ1 (KBr)
4.61 (CDCl3, ꢀ55 ꢀC)
Not detected (CDCl3 or acetone-d6, r.t.)
Table 5
Reaction of tetrabutylammonium salt with the dinuclear Pt complexes
Run
Complex
TBA+Xꢀ
PtAr2(cod)
1
2
3
4
5
12-BFꢀ4 ðAr ¼ PhÞ
TBA+OHꢀ
TBA+Iꢀ
TBAþPFꢀ6
TBA+OHꢀ
TBA+OHꢀ
Quant (ꢂ50%Pt)
41%Pt
0%
13-BFꢀ4 ðAr ¼ C6H4Me-4Þ
14-BFꢀ4 ðAr ¼ C6F5Þ
48%Pt
0%
hydroxo complex 15 reacts further with PtI(Ph)(cod) to
form the dinuclear complex with a bridging hydroxo li-
gand, having iodo as the counter anion, [{PtPh(cod)}2(l-
OH)]+(Iꢀ) (12-Iꢀ). OHꢀ or Iꢀ in the solution coordinates
to a Pt center of the dinuclear complex to form the interme-
diate having a penta-coordinate Pt center. Phenyl ligand
transfer takes place from the penta-coordinated Pt center
to square-planar Pt center accompanied by cleavage of a
Pt–O bond. The last reaction step involves cleavage of
Pt–Ph bond of the penta-coordinative center, which is sim-
ilar to associative ligand substitution of the square planar
transition metal complexes, involving a trigonal-bipyrami-
dal intermediate. The isolated dinuclear complex 12-BFꢀ4 is
stable in the solution and does not cause the phenyl ligand
transfer because BFꢀ4 counter anion is much less basic than
OHꢀ and Iꢀ and does not form an intermediate complex
with penta-coordinate Pt center.
The initial mononuclear intermediate Pt(OH)(Ph)(cod)
(15) is prepared in situ from an independent reaction of
bpy with equimolar 12-BFꢀ4 in benzene-d6 or in toluene
(Scheme 18(i)). Complex Pt(CH2COMe)(Ph)(cod) (10) is
obtained from a similar reaction in acetone (Scheme
18(ii)). Isolation of 15 as crystals is not feasible due to its
spontaneous disproportionation, but its solution was
obtained by removing 16 which is insoluble in the aromatic
1
solvents by filtration. The H NMR and IR spectra of the
solution indicate the presence of non-bridging OH ligand,
showing the OH vibration (3677 and 3600 cmꢀ1) within
the normal range of non-bridging OH ligand (3600–
3690 cmꢀ1) [43,64–69]. They are at much higher wavenum-
ber than those of 12-BFꢀ4 , 13-BF4ꢀ, and 14-BF4ꢀ (3345–
1
3428 cmꢀ1) with bridging OH ligand. The H NMR spec-
trum of 15 exhibits the signal of OH hydrogen at
3.39 ppm at room temperature.
+ TBA+OH-
Ph
Ph
Ph
I
2
Pt
Pt
+
Pt
- TBA+I-
I
OH
15
+
Ph Ph
Pt
Pt
I-
O
H
12-I-
+ TBA+X-
X
Ph Ph
(X = OH, I)
+ TBA+I-
Pt
Pt
O
H
Ph
Ph
X
Pt
+
Pt
HO
Scheme 17.

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
339
+
Ph
C6D6
(or toluene)
Ph
N
N
-
(cod)Pt
+
Pt
BF4
OH
+
Ph Ph
15
(i)
(ii)
N
N
16, 50%Pt
(in toluene)
-
(cod)Pt
Pt(cod)
BF4
+
O
H
-
+
Ph
12-BF4
Ph
N
-
(cod)Pt
+
Pt
N
BF4
acetone
CH2COMe
10, 22%Pt
16, 47%Pt
Scheme 18.
The 13C{1H} NMR spectrum of complex 15 after pro-
longed measurement indicate formation of PtPh2(cod),
indicating gradual disproportionation reaction in the solu-
tion. Disproportionation of complex 15 shown in Eq. (26)
is responsible for formation of the diphenyl complex,
E having a penta-coordinate and square-planar Pt centers
causes phenyl ligand transfer between the Pt centers.
The reaction of BF3 Æ Et2O with 12-BFꢀ4 in toluene-d8 at
room temperature for 12 h, followed by treatment with
NH4Cl(aq), produces a mixture of PtCl2(cod) (54%), Ph–
Ph (76%), and benzene (22%), as shown in Eq. (27).
Ph
Ph
Ph Ph
76%
(0.038 mmol)
+
Ph H
2
(cod)Pt
(cod)Pt
+ Pt-cod complex
+
1) BF3Et2O, 12 h
2) NH4Cl(aq)
Ph Ph
toluene
r. t., 5 d
22%
(0.022 mmol)
-
OH
Ph
(cod)Pt
Pt(cod) BF4
O
H
15
29%
(0.011 mmol)
toluene-d8, r. t.
-
12-BF4
+
PtCl2(cod)
+
COD
(ca. 0.075 mmol)
in situ
54%
(0.05 mmol)
(0.054 mmol)
ð26Þ
ð27Þ
which is contrasted with the results that bþoth PtPh(X)(cod)
(X = Cl, I) and ½PtPhðacetone-d6ÞðcodÞꢁ ðBFꢀ4 Þ does not
undergo the disproportionation reaction (Eq. (11), Scheme
12). Scheme 19 displays the reaction mechanism for the
transmetalation reaction of 15. Dimerization of
Pt(OH)(Ph)(cod) (15) takes place via bridging coordination
of the hydroxo ligand. The neutral dinuclear intermediate
Scheme 20 shows a mechanism for the reaction proposed
based on the reports by Kubas and Peters [23,24]. The reac-
tion of BF3 Æ Et2O with 12-BFꢀ4 forms the cationic mononu-
clear platinum(II) complex [PtPh(OEt2)(cod)]+(BF3Xꢀ)
(X = F, OH) via abstraction of the OH ligand by BF3.
The formed mononuclear complex with a labile OEt2 li-
gand undergoes facile formation of dinuclear intermediate
F accompanied by C–C bond formation between the phe-
nyl ligand of two cationic Pt complex molecules. NH4Cl
promotes liberation of biphenyl and formation of
PtCl2(cod).
OH
Ph Ph
Ph
2
Pt
Pt
Pt
OH
O
H
15
E
Reaction of arylboronic acids with 12-BFꢀ4 in 1:2 molar
ratio leads to transfer of the aryl ligand from boron to plat-
inum, giving mononuclear diarylplatinum complexes, as
shown in Eq. (28) and the results are summarized in Table
6.
Ph
HO
Pt
+
Pt
Ph HO
Scheme 19.
+
+
Ph Ph
.
Ph
Pt
BF3 Et2O
-
Pt
Pt
BF4
2
BF3X-
OEt2
O
H
(X = F, OH)
12-BF4
2+
(BF3X-)2
Pt
Pt
Ph
F
NH4Cl
Cl
Pt
+
Ph-Ph
Cl
Scheme 20.

340
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
Table 6
a
Reaction of arylboronic acid with 12-BF4ꢀ
Run
Ar–B(OH)2
Solvent
PtAr(Ph)(cod)b (%)
1
2
3
4
5
6
7
a
(C6H2F3-2,4,6)B(OH)2
Toluene
36
83
38
66
Mixture
14 (64d)
2
Toluene/H2Oc
Toluene
PhB(OH)2
Toluene/H2Oc
THF
Toluene
Toluene/H2Oc
(C6H4OMe-4)B(OH)2
At room temperature, 1 h.
b
c
Yield based on Pt.
toluene/H2O = 100/1.
Yield of PtPh2(cod).
d
+
Ar
Ph Ph
Ph
Pt
Ph
OH
-
Pt
Ar
B(OH)2
(cod)Pt
Pt(cod)
BF4
Ar
B
+ 2
O
OH
O
H
OH
H
B(OH)2
-
12-BF4
ð28Þ
G
G'
Ph
Ar
- B(OH)3
r. t., 1 h
Chart 2.
2 (cod)Pt
(Ar = C H F -2,4,6, Ph, C H OMe-4)
(Ar = Ph)). ½PtPhðsolventÞðcodÞꢁþðBF4ꢀÞ is also produced
by the reaction, but it does not undergo further reaction
in the absence of water. Addition of water converts the
mononuclear cationic complex into 12-BFꢀ4 , similarly to
the reaction in Scheme 16.
6
4
6
2 3
The reaction of trifluorophenylboronic acid forms unsym-
metrical diaryl platinum complex Pt(C6H2F3-2,4,6)(Ph)-
(cod) as a major product (36%). A small amount (<1%)
of Pt(C6H2F3-2,4,6)2(cod) is also detected probably due
to disproportionation or other scrambling reaction. Addi-
tion of water to the reaction mixture increases the yield
of Pt(C6H2F3-2,4,6)(Ph)(cod) (83%) (run 2). The product
insoluble in toluene contains B(OH)3 indicating that substi-
tution of aryl group of the arylboronic acid with OH ligand
or OH group from water occurs during the reaction. The
reaction of phenylboronic acid shows the same tendency
(run 3–5). The reaction of 4-methoxyphenylboronic acid
produces PtPh2(cod) as a major product, indicating occur-
rence of intramolecular transfer of the phenyl ligand prior
to the transmetalation of the arylboronic acid (runs 6 and
7). Thus, not only transmetalation of arylboronic acid but
also intramolecular aryl ligand transfer takes place during
the reaction; ratio of the products depends on reactivity
of arylboronic acid toward the transmetalation.
Scheme 21 summarizes a pathway of the reaction of
ArB(OH)2 with 12-BFꢀ4 in the presence of H2O. The reac-
tion of H2O with 12-BFꢀ4 generates 15 and a cationic phe-
nylplatinum complex with aquo ligand (i). Complex 15 is
responsible for transmetalation. Activation of B–C bond
in reaction (28) may proceed via intermediate G (Chart
2) which is formed by coordination of the OH ligand to
the boron atom of arylboronic acid giving a four-coordi-
nate boron center. The intramolecular activation of the
B–C and Pt–O bonds of G forms a new Pt–Ar bond,
accompanied by the elimination of B(OH)3. An alternative
concerted mechanism, involving the intermediate G0 with a
four-membered ring, may also be possible for the simulta-
neous formation of Pt–C and B–O bonds of the products.
The coupling of ½PtPhðOH2ÞðcodÞꢁþðBF4ꢀÞ accompanied by
deprotonation may regenerate 12-BFꢀ4 (Scheme 15). Reac-
tion of H2O with ½PtPhðTHFÞðcodÞꢁþðBF4ꢀÞ was reported
to produce 12-BFꢀ4 [61].
Yields of the diaryl complex in the reaction of (C6H2F3-
2,4,6)B(OH)2 and of PhB(OH)2 without addition of H2O
do not exceed 50% (36% (Ar = C6H2F3-2,4,6), 38%
+
+
Ph
Ph
Ph
Ph
-
-
Pt
BF4
(i)
Pt
+
Pt
Pt
BF4
+ H2O
OH
O
OH2
H
-
12-BF4
15
Ph
Ar
Ph
Pt
+ B(OH)3
(ii)
Pt
Ar B(OH)2
+
OH
15
Scheme 21.

Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
341
6. Conclusion
20.7 (CH3), 27.0 (CH2), 31.3 (CH2), 82.1 (CH (trans to
O), J(PtC) = 218 Hz), 115.9 (CH (trans to C)), 129.2 (meta-
C6H4), 134.4 (para-C6H4), 134.7 (ortho-C6H4), 140.7 (ipso-
C6H4). IR (CHCl3): m(OH); 3432 cmꢀ1. Anal. Calc. for
C30H39BF4OPt2: C, 40.37; H, 4.40. Found: C, 40.11; H,
4.33%. Data fot 14-BFꢀ4 : 1H NMR (300 MHz, CDCl3,
r.t.): d 2.26–2.36 (8H, CH2), 2.45–2.58 (8H, CH2), 4.78
(m, 4H, CH (trans to O), J(PtH) = 68 Hz), 5.96 (m, 4H,
CH (trans to C), J(PtH) = ca. 30 Hz). 1H NMR
(400 MHz, CDCl3, ꢀ55 ꢀC): d 2.24–2.57 (16H, CH2), 4.61
(s, 1H, OH), 4.76 (m, 4H, CH (trans to O)), 5.87 (m, 4H,
CH (trans to C)). 13C{1H} NMR (100 MHz, CD2Cl2,
The arylpalladium and platinum complexes undergo
intermolecular or intramolecular aryl ligand transfer from
one metal to the other. The reaction is regulated by struc-
ture, auxiliary ligand, and the ligand that promotes the aryl
ligand transfer. Neutral square-planar complexes are able
to undergo the transmetalation when cod is selected as a
bidentate ligand of dihalogeno complex. Reaction proceeds
via initial dissociation of a halogeno ligand to form cat-
ionic complex. Actual role of the auxiliary ligand is to con-
trol the reactivity of the cationic mononuclear species
which undergoes facile formation of dinuclear intermediate
having bridging aryl ligand. Cationic complexes undergo
more facile aryl ligand transfer probably because of kinet-
ically favored formation of the dinuclear intermediates.
The OH ligand enhances the transmetalation between the
Pt complex. The role of OH ligand is to form stable dinu-
clear intermediate that is isolated in this study and to form
pentacoordinate metal center that releases aryl ligand in
the intramolecular transmetalation. The dinuclear
hydroxoplatinum complex is in equilibrium with the mono-
nuclear complex with OH ligand and activates C–B bond
of aryl boronic acid in the transmetalation.
r.t.):
d
28.3 (CH2), 32.3 (CH2), 87.5 (CH,
J(PtH) = 198 Hz), 117.0 (CH, J(PtC) = 54 Hz), 136.4–
148.1 (C6F5). 19F{1H} NMR (282 MHz, CDCl3, r.t.): d
ꢀ161.2 (m, 2F, meta-C6F5), ꢀ156.5 (m, 1F, para-C6F5),
ꢀ151.4 (BF4), ꢀ151.3 (BF4), ꢀ122.8 (m, 2F, ortho-C6F5,
J(PtF) = 251 Hz). IR (KBr disk): m(OH); 3345 cmꢀ1. Anal.
Calc. for C28H25BF14OPt2: C, 32.20; H, 2.41. Found: C,
31.81; H, 2.20%.
References
[1] K. Osakada, Transmetalation, in: H. Kurosawa, A. Yamamoto
(Eds.), Current Methods in Inorganic Chemistry, vol. 3, Elsevier
Science, 2003, pp. 233–291.
Acknowledgements
[2] K. Osakada, T. Yamamoto, Coord. Chem. Rev. 198 (2000) 379.
[3] T. Yamamoto, S. Wakabayashi, K. Osakada, J. Organomet. Chem.
428 (1992) 223.
[4] K. Osakada, R. Sato, T. Yamamoto, Organometallics 13 (1994) 4645.
[5] M.F. Semmelhack, P.M. Helquist, L.D. Jones, J. Am. Chem. Soc. 93
(1971) 5908.
This work was supported by a Grant-in-Aid for Scien-
tific Research from the Ministry of Education, Science,
Sports, and Culture, Japan ‘‘Dynamic Complexes
(16033220)’’. Y.S. and T.Y. acknowledge the scholarship
by Japan Society for the Promotion of Science.
[6] M.F. Semmelhack, P.M. Helquist, J.D. Gorzynski, J. Am. Chem.
Soc. 94 (1972) 9234.
[7] M. Zembayashi, K. Tamao, J. Yoshida, M. Kumada, Tetrahedron
Lett. (1977) 4089.
[8] K. Takagi, N. Hayama, S. Inokawa, Bull. Chem. Soc. Jpn. 53 (1980)
3691.
Appendix
Data of unpublished complexes are as follows: Data for
1a: 1H NMR (300 MHz, CDCl3, r.t.): d 3.85 (br, 4H, CH2),
4.07 (br, 4H, CH2), 6.47 (m, 2H, C6H4), 6.85–6.98 (6H,
C6H4), 7.28 (2H), 7.46 (2H), 7.57 (2H), 7.94–7.96 (4H),
8.04–8.06 (4H), 9.52 (2H). Anal. Calc. for C36H32I2-
N4O3Pd2: C, 41.76; H, 3.12; N, 5.41; I, 24.52. Found: C,
[9] M. Iyoda, M. Sakaitani, H. Otsuka, M. Oda, Chem. Lett. (1985) 127.
[10] T. Yamamoto, Prog. Polym. Sci. 17 (1992) 1153.
[11] T. Yamamoto, A. Morita, Y. Miyazaki, T. Maruyama, H. Wakay-
ama, Z.-H. Zhou, Y. Nakamura, T. Kanbara, S. Sasaki, K. Kubota,
Macromolecules 25 (1992) 1214.
[12] T. Yamamoto, T. Maruyama, Z.-H. Zhou, T. Ito, T. Fukuda, Y.
Yoneda, F. Begum, T. Ikeda, S. Sasaki, H. Takezoe, A. Fukuda, K.
Kubota, J. Am. Chem. Soc. 116 (1994) 4832.
1
41.74; H, 3.51; N, 5.13; I, 24.05%. Data fot 13-BFꢀ4 : H
[13] T. Yamamoto, Z.-H. Zhou, T. Kanbara, M. Shimura, K. Kizu, T.
Maruyama, Y. Nakamura, T. Fukuda, B.-L. Lee, N. Ooba, S.
Tomaru, T. Kurihara, T. Kaino, K. Kubota, S. Sasaki, J. Am.
Chem. Soc. 118 (1996) 10389.
[14] T. Yagyu, M. Hamada, K. Osakada, T. Yamamoto, Organometallics
20 (2001) 1087.
NMR (300 MHz, C6D6, r.t.): d 1.16–1.36 (8H, CH2),
1.62–1.68 (8H, CH2), 2.21 (s, 6H, CH3), 3.78 (m, 4H, CH
(trans to O), J(PtH) = 72 Hz), 5.49 (br, 4H, CH (trans to
C)), 6.96 (d, 4H, meta-C6H4, J(HH) = 8 Hz), 7.37 (d, 4H,
1
ortho-C6H4, J(HH) = 8 Hz). H NMR (300 MHz,CDCl3,
[15] Y. Suzaki, K. Osakada, Organometallics 22 (2003) 2193.
[16] Y. Suzaki, K. Osakada, unpublished results.
[17] R. van Asselt, E.E.C.G. Gielens, R.E. Rulke, K. Vrieze, C.J. Elsevier,
¨
J. Am. Chem. Soc. 116 (1994) 977.
[18] J. Vicente, J.A. Abad, A.D. Frankland, M.C.R. de Arellano, Chem.
Eur. J. 5 (1999) 3066.
[19] J. Vicente, J.A. Abad, W. Fo¨rtsch, P.G. Jones, A.K. Fischer,
Organometallics 20 (2001) 2704.
[20] M.A. Cinellu, S. Gladiali, G. Minghetti, J. Organomet. Chem. 363
(1989) 401.
[21] T. Yagyu, Y. Suzaki, K. Osakada, Organometallics 21 (2002) 2088.
[22] L.M. Rendina, R.J. Puddephatt, Chem. Rev. 97 (1997) 1735.
r.t.): d 1.96–2.11 (8H, CH2), 2.25–2.38 (8H, CH2), 2.31 (s,
6H, CH3), 4.24 (m, 4H, CH (trans to O), J(PtH) = 69 Hz),
5.23 (br, 4H, CH (trans to C)), 7.04 (d, 4H, meta-C6H4,
J(HH) = 8 Hz), 7.28 (d, 4H, ortho-C6H4, J(HH) = 8 Hz,
J(PtH) = ca. 36 Hz). 1H NMR (400 MHz, CDCl3,
ꢀ55 ꢀC): d 1.95–2.05 (8H, CH2), 2.22–2.34 (8H, CH2),
2.31 (s, 6H, CH3), 4.13 (s, 1H, OH), 4.28 (m, 4H, CH (trans
to O)), 4.95 (brs, 4H, CH (trans to C)), 7.06 (d, 4H, meta-
C6H4, J(HH) = 8 Hz), 7.35 (d, 4H, ortho-C6H4,
J(HH) = 8 Hz). 13C{1H} NMR (75.5 MHz, CDCl3, r.t.): d

342
Y. Suzaki et al. / Journal of Organometallic Chemistry 692 (2007) 326–342
[23] W.V. Konze, B.L. Scott, G.J. Kubas, J. Am. Chem. Soc. 124 (2002)
[44] N. Mintcheva, Y. Nishihara, M. Tanabe, K. Hirabayashi, A. Mori,
K. Osakada, Organometallics 20 (2001) 1243.
12550.
´
´
[24] J.C. Thomas, J.C. Peters, J. Am. Chem. Soc. 125 (2003) 8870.
[45] J. Vicente, A. Arcas, J.M. Fernandez-Hernandez, D. Bautista,
[25] C. Eaborn, K.J. Odell, A. Pidcock, J. Chem. Soc., Dalton Trans.
Organometallics 20 (2001) 2767.
(1978) 357.
[46] M.A. Bennett, G.B. Robertson, P.O. Whimp, T. Yoshida, J. Am.
Chem. Soc. 95 (1973) 3028.
[26] R.G. Peters, S. White, D.M. Roddick, Organometallics 17 (1998)
4493.
[47] T. Yoshida, T. Matsuda, T. Okano, T. Kitani, S. Otsuka, J. Am.
Chem. Soc. 101 (1979) 2027.
[27] J.K. Jawad, R.J. Puddephatt, M.A. Stalteri, Inorg. Chem. 21 (1982)
332.
[28] Y. Suzaki, K. Osakada, Bull. Chem. Soc. Jpn. 77 (2004) 139.
[29] R. Uson, J. Fornies, M. Tomas, J.M. Casas, R. Navarro, J. Chem.
Soc. Dalton Trans. (1989) 169.
[30] R. Uson, J. Fornies, M. Tomam, J.M. Casas, F.A. Cotton, L.R.
[48] H.E. Bryndza, W. Tam, Chem. Rev. 88 (1988) 1163.
[49] V.K. Jain, L. Jain, Coord. Chem. Rev. 249 (2005) 3075.
[50] M.A. Bennett, T. Yoshida, J. Am. Chem. Soc. 100 (1978) 1750.
[51] K. Osakada, Y.-J. Kim, A. Yamamoto, J. Organomet. Chem. 382
(1990) 303.
´
´
´
´
´
´
Falvello, X. Feng, J. Am. Chem. Soc. 115 (1993) 4145.
[52] K. Osakada, Y.-J. Kim, M. Tanaka, S. Ishiguro, A. Yamamoto,
Inorg. Chem. 30 (1991) 197.
´
´
´
[31] L.R. Falvello, J. Fornies, C. Fortuno, F. Duran, A. Martın,
˜
Organometallics 21 (2002) 2226.
[53] G.M. Kapteijn, A. Dervisi, D.M. Grove, H. Kooijman, M.T. Lakin,
A.L. Spek, G. van Koten, J. Am. Chem. Soc. 117 (1995) 10939.
[54] G.W. Bushnell, K.R. Dixon, R.G. Hunter, J.J. McFarland, Can. J.
Chem. 50 (1972) 3694.
[55] J.J. Li, P.R. Sharp, Inorg. Chem. 33 (1994) 183.
[56] J.J. Li, W. Li, P.R. Sharp, Inorg. Chem. 35 (1996) 604.
[57] J.J. Li, W. Li, A.J. James, T. Holbert, T.P. Sharp, P.R. Sharp, Inorg.
Chem. 38 (1999) 1563.
´
´
[32] A.C. Albeniz, P. Espinet, B. Martın-Ruiz, Chem. Eur. J. 7 (2001)
2481.
[33] A.C. Albe´niz, P. Espinet, O. Lo´pez-Cimas, B. Mart´ın-Ruiz, Chem.
Eur. J. 11 (2005) 242.
´
[34] A.C. Albeniz, P. Espinet, Y. Jeannin, M. Philoche-Levisalles, B.E.
Mann, J. Am. Chem. Soc. 112 (1990) 6594.
[35] G.R. Hoel, R.A. Stockland Jr., G.K. Anderson, F.T. Ladipo, J.
Braddock-Wilking, N.P. Rath, J.C. Mareque-Rivas, Organometallics
17 (1998) 1155.
[58] S. Kannan, A.J. James, P.R. Sharp, Polyhedron 19 (2000)
155.
[36] M.H. Chisholm, H.C. Clark, L.E. Manzer, J.B. Stothers, J.E.H.
Ward, J. Am. Chem. Soc. 97 (1975) 721.
[37] T.G. Appleton, J.R. Hall, M.A. Williams, J. Organomet. Chem. 303
(1986) 139.
[38] S. Hietkamp, D.J. Stufkens, K. Vrieze, J. Organomet. Chem. 169
(1979) 107.
[59] P.R. Sharp, J. Chem. Soc., Dalton Trans. (2000) 2647.
[60] B. Longato, G. Bandoli, A. Dolmella, Eur. J. Inorg. Chem. (2004)
1092.
[61] Y. Suzaki, K. Osakada, Organometallics 23 (2004) 5081.
[62] Y. Suzaki, K. Osakada, Organometallics, 25 (2006) 3251.
[63] Y. Suzaki, K. Osakada, unpublished results.
[64] T.G. Appleton, M.A. Bennett, Inorg. Chem. 17 (1978) 738.
[65] R. Ros, R.A. Michelin, R. Bataillard, R. Roulet, J. Organomet.
Chem. 161 (1978) 75.
[66] D.P. Arnold, M.A. Bennett, J. Organomet. Chem. 199 (1980) 119.
[67] M.A. Bennett, A. Rokicki, Inorg. Synth. 25 (1989) 100.
[68] M.A. Bennett, H. Jin, S. Li, L.M. Rendina, A.C. Willis, J. Am.
Chem. Soc. 177 (1995) 8335.
´ ˇ
[39] W. Kaim, A. Klein, S. Hasenzahl, H. Stoll, S. Zalis, J. Fiedler,
Organometallics 17 (1998) 237.
[40] R. Gosling, M.L. Tobe, Inorg. Chem. 22 (1983) 1235.
[41] Y. Suzaki, T. Yagyu, Y. Yamamura, A. Mori, K. Osakada,
Organometallics 21 (2002) 5254.
[42] M.A. Cairns, K.R. Dixon, M.A.R. Smith, J. Organomet. Chem. 135
(1977) 135, C33.
[43] S. Wimmer, P. Castan, F.L. Wimmer, N.P. Johnson, J. Chem. Soc.,
Dalton Trans. (1989) 403.
[69] A. Klein, K.-W. Klinkhammer, T. Scheiring, J. Organomet. Chem.
592 (1999) 128.