Functionalized homoleptic cis- and trans-C,N-ortho-chelated aminoaryl platinum(II) complexes

Article abstract of DOI:10.1021/om050144s

For the synthesis of corner building blocks with a 90° angle, to be used for the construction of larger structures, several homoleptic platinum(II) complexes [Pt(η²-C,N)₂] (10-14), as both cis- and trans-isomers, have been prepared s

Full text of DOI:10.1021/om050144s

2944
Organometallics 2005, 24, 2944-2958
Functionalized Homoleptic cis- and
trans-C,N-ortho-Chelated Aminoaryl Platinum(II)
Complexes
Catelijne H. M. Amijs,† Gerard P. M. van Klink,† Martin Lutz,‡
Anthony L. Spek,‡,§ and Gerard van Koten*,†
Department of Organic Chemistry and Catalysis, Debye Institute, and Department of Crystal
and Structural Chemistry, Bijvoet Center for Biomolecular Research, Utrecht University,
Padualaan 8, 3584 CH Utrecht, The Netherlands
Received March 1, 2005
For the synthesis of corner building blocks with a 90° angle, to be used for the construction
of larger structures, several homoleptic platinum(II) complexes [Pt(η2-C,N)2] (10-14), as
both cis- and trans-isomers, have been prepared starting from newly synthesized ortho-
lithiated (dimethylamino)methyl arene ligands. The aryl groups of these arylplatinum(II)
complexes contain additional substituents such as halides or methyl, naphthyl, or (di-
methylamino)methyl groups. With these functionalities on the aryl rings the cis/trans ratio
could be tuned. The presence of steric groups ortho to the metal center (methyl or naphthyl)
favors the formation of planar-chiral cis-isomers. The trans-isomers isomerize irreversibly
to the thermodynamically favored cis-isomers upon heating. The arylplatinum(II) complexes
were used in various substitution reactions. Addition of a stronger coordinating ligand
changes the denticity of the C,N-attached ligands. The halide functionalities were exploited
for chemoselective lithiation and subsequent transmetalation reactions in order to synthesize
the SnMe3-functionalized [Pt(C,N)2] complexes. A Suzuki-Miyaura C-C coupling reaction
on one of these complexes was also performed, resulting in the preparation of a mixed
trinuclear palladium/platinum complex (25). The crystal structure determinations of four
functionalized cis-[Pt(C,N)2] complexes, cis-12‚Et2O, cis-14‚xC6H6, 19, and 25‚xCH2Cl2, are
reported. With these structures it is shown that depending on the substituents, the degree
of planarity around the platinum center can be tuned.
Introduction
ligands. The advantage of such complexes is that they
have predefined structures, e.g., linear or angular in the
case of square-planar complexes, as well as high stabil-
ity as compared to coordination complexes. It should be
noted that especially the 90° angle is rarely observed
in entirely organic donor compounds. Examples of right-
angled structures are complexes A and B (Chart 1)
reported by Stang and co-workers.1 For our research,
we have chosen to use the homoleptic platinum(II)
complex [Pt(dmba)2] (dmba ) [C6H4(CH2NMe2)-2]-) (C,
X ) R ) H (1), Chart 1)2 as a corner building block with
a predefined 90° angle. The choice for this system is
motivated by the possibility to introduce donor func-
tionalities on both the two arene rings3 and the nitrogen
donor substituents.2,4 Our strategy has been to prepare
the organometallic precursor complexes [Pt(C,N)2] (C,N
) C,N-ortho-chelating ligand) and to functionalize these
in subsequent reactions. This reaction sequence starts
with the synthesis of various C,N-chelating ligands
Two important factors for a rational design of coor-
dination-based supramolecular entities are the sym-
metry and the shape of the assembly. These two factors
are determined solely by the type and properties of the
building blocks. For two-dimensional structures two
types of building blocks are required: (1) linear ditopic
units, which contain reactive sites with a 180° orienta-
tion relative to each other, and (2) angular ditopic units,
possessing reactive sites with other desirable angles.
Generally, building blocks consist of either an electron-
deficient metal center as an acceptor or an organic
ligand with Lewis-base functionalities (often pyridine)
as donor. Square-planar platinum(II) and palladium-
(II) centers with coordination angles of approximately
180° or 90° are frequently used as linear or corner
acceptor units, respectively. Only in a few cases have
organometallic complexes been used as donor building
blocks. In these cases, the metal center itself is not used
as an acceptor unit, but instead the metal center directs
the orientation of the donor units via the attached
(1) (a) Manna, J.; Whiteford, J. A.; Stang, P. J. J. Am. Chem. Soc.
1996, 118, 8731-8732. (b) Mu¨ller, C.; Whiteford, J. A.; Stang P. J. J.
Am. Chem. Soc. 1998, 120, 9827-9837. (c) Stang, P. J. Chem. Eur. J.
1998, 4, 19-27.
(2) Longoni, G.; Fantucci, P.; Chini, P.; Canziani, F. J. Organomet.
Chem. 1972, 39, 413-425.
(3) Rodr´ıguez, G.; Albrecht, M.; Schoenmaker, J.; Ford, A.; Lutz, M.;
Spek, A. L.; van Koten, G. J. Am. Chem. Soc. 2002, 124, 5127-5138.
(4) Jude, H.; Krause Bauer, J. A.; Connick, W. B. Inorg. Chem. 2002,
41, 2275-2281.
* Corresponding author. Phone: +31-30-2533120. Fax: +31-30-
2523615. E-mail: g.vankoten@chem.uu.nl.
† Debye Institute.
‡ Bijvoet Center for Biomolecular Research.
§ Corresponding author for crystallographic data. Phone: +31-30-
2532538. Fax: +31-30-2523940. E-mail: a.l.spek@chem.uu.nl.
10.1021/om050144s CCC: $30.25 © 2005 American Chemical Society
Publication on Web 05/06/2005

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2945
Chart 1. Organoplatinum Corner Complexes
Scheme 1. Ligand Synthesisa
having a halide substituent on the arene ring, which
allows further functionalization by C-C bond formation
reactions such as Suzuki-Miyaura reactions. In this
paper we describe the synthesis and characterization
of various types of [Pt(C,N)2] (C, X ) Br, I, R ) H, Me,
CH2NMe2) complexes and their use in subsequent
lithiation and transmetalation reactions. It was dem-
onstrated that C-C coupling reactions on these orga-
nometallic complexes without affecting the metal-
carbon bond are possible as well. We also describe the
synthesis of [Pt(C,N)2] complexes with planar chirality,
which is induced by introduction of steric bulk on the
aryl rings.
a
(i) HNMe2, Et2O, 2 h; (ii) n-BuLi, Et2O, -78 °C f RT, 1
h, C2H4I2.
Results and Discussion
procedure.10 Nucleophilic substitution of 2-4 with
HNMe2 yielded the benzylic amines 5, 6, and 7, respec-
tively.Thepreparationof1,4-diiodo-2,5-bis{(dimethylamino)-
methyl}benzene (8) was achieved via double lithiation
of 7 followed by quenching of the dilithio compound with
1,2-diiodoethane.
Lithiation of benzylamines 5-8 with 1 equiv of
n-BuLi in Et2O occurred in all cases at the desired ortho
C-halide position, without any trace of C-H activation.
Quenching of the respective reaction mixtures with S2-
Me2 and subsequent analysis of the ortho-MeS products
by 1H NMR and GC-MS spectroscopy showed a unique
chemoselectivity for lithiation at the C-I bond for both
5 and 6.
Ligands 5-8 and 1-bromo-2-{(dimethylamino)methyl}-
naphthalene (9)11 were used to synthesize the corre-
sponding [Pt(C,N)2] complexes by sequential chemose-
lective lithiation and transmetalation reactions. The
transmetalation reactions were performed by reacting
the in situ prepared lithium complexes with 0.5 equiv
of trans-[PtCl2(SMe2)2] (Scheme 2). Full conversion to
the respective homoleptic complexes 10-14 was ob-
tained within 3 h. The complexes were obtained as a
mixture of cis- and trans-isomers (see Table 1), except
for 11, for which only the formation of the cis-isomer
was observed. This is in accordance with results re-
ported by Longoni et al., who showed that upon reacting
the lithium complex [Li(dmba)] with trans-[PtCl2-
(SMe2)2], a mixture of cis- and trans-isomers of the
nonfunctionalized [Pt(dmba)2] (1) was obtained (Table
1, entry 1).2
Synthesis of [Pt(C,N)2] Complexes. The commonly
applied route for the synthesis of homo- and heteroleptic
bis-cyclometalated [M(C,N)2] complexes is the introduc-
tion of the metal center via a transmetalation reaction.
Previous reports showed that homoleptic compounds can
be prepared via reaction of an organolithium or Grig-
nard reagent with either a cis- or trans-[PtX2L2] salt (X
) Br, Cl, L ) cod, SEt2, SMe2),2,5 while the synthesis of
heteroleptic complexes involved reaction of a dinuclear,
halide-bridged, complex [MX(C,N)]2 (M ) Pt, Pd, X )
Br, Cl) with an organolithium,6 -mercury,7,8 or -zinc9
complex. Various new 2,5-bis{(dimethylamino)methyl}-
arene ligands (C,N), which are functionalized at the 1-
and 4-positions with halide substituents, were designed
for the synthesis of the platinum complexes (Scheme 1).
The choice of halide, bromide or iodide, ortho to the
potentially chelating (dimethylamino)methyl group, was
made in such way that regioselective metalation would
occur at that position. The second halide would thereby
be unaffected, as a C-I bond is more reactive than the
C-Br bond in both oxidative addition and halide-
lithium exchange reactions.
The various amine ligands were prepared starting
from their methyl analogues by benzylic bromination
(Scheme 1). The synthesis of the starting compounds
2-4 was carried out following a new, highly efficient
(5) Wehman-Ooyevaar, I. C. M.; Grove, D. M.; Kooijman, H.; van
der Sluis, P.; Spek, A. L.; van Koten, G. J. Am. Chem. Soc. 1992, 114,
9916-9924.
(6) Valk, J.-M. Maassarani, F.; van der Sluis, P.; Spek, A. L.;
Boersma, J.; van Koten, G. Organometallics 1994, 13, 2320-2329.
(7) Berger, A.; Djukic, J.-P.; Pfeffer, M. Organometallics 2003, 22,
5243-5260.
(8) van der Ploeg, A. F. M. J.; van Koten, G.; Vrieze, K. J.
Organomet. Chem. 1981, 222, 155-174.
(9) Valk, J.-M.; Boersma, J.; van Koten, G. Organometallics 1996,
15, 4366-4372.
A mechanism for the formation of homoleptic plati-
num complexes was proposed by von Zelewsky and co-
(10) Amijs, C. H. M.; van Klink, G. P. M.; van Koten, G. Green Chem.
2003, 5, 470-474.
(11) Gay, R. L.; Hauser, C. R. J. Am. Chem. Soc. 1967, 89, 2297-
2303.

2946 Organometallics, Vol. 24, No. 12, 2005
Scheme 2. Synthesis of cis- and trans-[Pt(C,N)2]a
Amijs et al.
a
(i) n-BuLi, Et2O, -78 °C, 10 min; (ii) 0.5 equiv [PtCl2L2] (L2 ) cod, 2(SMe2)), Et2O, -78 °C f RT, 3 h; (iii) toluene, ∆T, 3-16
h.
Table 1. Observed cis/trans Ratios When Using Either cis-[PtCl2(cod)] or trans-[PtCl2(SMe2)2] as Starting
Reagent
Pt complex
[Pt(C,N)2]
substituents
R, R′, Xb
ratio cis/transa
entry
[trans-PtCl2(SMe2)2]
[cis-PtCl2(cod)]
ref
1
2
3
4
5
6
7
1
H, H, H
75/25
85/15
100/0
40/60d
45/55d
85/15d
2
c
c
c
c
c
5
10
11
12
13
14
15e
H, H, Br
100/0
100/0
100/0
100/0
100/0
100/0
H, Me, Br
CH2NMe2, H, Br
CH2NMe2, H, I
naphthyl
H, H, He
a After analysis of the reaction mixtures by 1H NMR spectroscopy in CDCl3. b Substituents as depicted in Scheme 2. c This work. d C6D6
solutions. e C,N ) [C6H4(CH(Me)NMe2)-2-(R)]-.
Scheme 3. Mechanism for the Formation of
Homoleptic Platinum Complexes as Proposed by
von Zelewsky et al.12
This mechanism is based on the trans-effect of bound
ligands. According to this mechanism, in the first step
one lithiated C,N-ligand is bound to the metal center
by its nitrogen atom, causing liberation of a diethyl
sulfide molecule. The chelation is completed with the
formation of a metal-carbon bond and is followed by
elimination of one chloride anion. The strong trans-effect
of the bonded carbon atom directs the coordination of
the second nitrogen atom into the trans-position, and
formation of the second metal-carbon bond yields cis-
[Pt(C,N)2].
Although it is likely that the trans-effect does play
an important role in the reaction mechanism, the
present results show that other factors also affect the
cis/trans-preference during the formation of these
complexes. Most likely, the difference lies in the nature
of the used C,N-ligands. Whereas von Zelewsky used
rigid arylpyridine ligands, we and others used the more
flexible dmba-type ligands. We found that the presence
of substituents on the arene rings strongly influences
the cis/trans ratio. As compared to parent complex 1,
a slightly higher ratio was observed for the para-bromo-
substituted complex 10 (Table 1, entry 2). Interestingly,
workers (Scheme 3), who obtained only cis-isomers of
[Pt(C,N)2] even when starting from trans-[PtCl2(SEt2)2].12
(12) Jolliet, P.; Gianni, M.; von Zelewsky, A.; Bernardelli, G.;
Stoeckli-Evans, H. Inorg. Chem. 1996, 35, 4883-4888.

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2947
Scheme 4. Synthesis of 10 in a Two-Step
Procedurea
the presence of a meta substituent in addition to the
para halide group favors the formation of the trans-
isomers (entries 4 and 5). In contrast, substituents at
the ortho-positions favored the formation of cis-isomers
(entries 3 and 6), most likely due to steric hindrance.
Apparently, the steric interference between the ortho-
substituents and the Me2N groups in trans-11 and
trans-14 destabilizes the trans-complexes with respect
to the cis-complexes. This is in accordance with earlier
observations for complexes with substantial sterically
interacting ligands. Also in these cases, only cis-isomers
were formed.2,12,13 For example, the N,N-ethyl substit-
uents on the benzylamine group in the closely related
complex cis-[Pt(deba)2] (deba ) [C6H4(CH2NEt2)-2]-) are
sufficiently large to direct the reaction toward the
complete formation of only the cis-isomer using reaction
conditions similar to those applied for the synthesis of
1.2
a
(i) n-BuLi, Et2O, -78 °C, 10 min; (ii) [PtCl2(SEt2)2], Et2O,
-78 °C f RT, 3 h; (iii) Et2O, O °C f RT, 3 h.
Table 2. Selected Bond Lengths (Å), Bond Angles
(deg), and Torsion Angles (deg) for cis-12‚Et2O
Interatomic Distances
Pt-C(1)
Pt-N(1)
1.992(4)
2.202(3)
Pt-C(13)
Pt-N(3)
1.991(4)
2.202(4)
The formation of 10 and 12 was monitored by taking
samples of the reaction mixture at regular intervals. 1H
NMR spectra of these samples showed that the cis/trans
ratio did not change during the reaction.
Interatomic Angles and Torsion Angles
97.38(16) N(1)-Pt-N(3)
C(1)-Pt-C(13)
N(1)-Pt-C(1)
N(1)-Pt-C(13)
102.53(14)
80.95(16)
171.84(14)
80.25(14) N(3)-Pt-C(13)
When the transmetalation reactions were performed
with cis-[PtCl2(cod)], only cis-isomers were obtained
without any trace of trans-complexes, as was already
observed by Wehman-Ooyevaar et al., for the synthesis
of cis-[Pt{C6H4(CH(Me)NMe2)-2-(R)}2] (15, Table 1,
entry 7).5 In the mechanism, starting from a cis-
complex, in the first step one C,N-ligand is bound to the
metal center by its nitrogen atom, thereby replacing one
of the coordinated olefinic groupings of the initially η2-
bidentate-bonded cod ligand. Subsequently, the metal-
carbon bond is formed and the strong trans-effect of the
carbon atom directs the coordination of the second
nitrogen atom to the trans-position. This nitrogen atom
replaces the η1-monodentate-bonded cod ligand, result-
ing in the formation of cis-[Pt(C,N)2].
Separation of the cis- from the trans-isomers was
possible due to the considerable solubility differences.
The trans-complexes are generally more soluble in
various solvents such as benzene, toluene, and THF. A
convenient method for getting the pure cis-complex
involved washing of the reaction mixture with THF or
precipitation of the cis-product from a CH2Cl2/Et2O
mixture. Unfortunately, it was not possible to obtain
completely pure trans-isomers, as small amounts of the
cis-isomers remained present in the THF washing
layers.
The synthesis of homoleptic complexes via a two-step
procedure was also investigated. If successful, this
would create new opportunities for the synthesis of both
homo- and heteroleptic complexes and would provide
insight in the mechanism of the reaction. The first step
would result in the formation of [PtCl(C,N)L] (L )
coordinating ligand), which after isolation and purifica-
tion could be reacted in a second step with additional
bidentate C,N-lithium complexes to form either a ho-
moleptic [Pt(C,N)2] or heteroleptic [Pt(C′,N′)(C,N)] com-
plex. We tested this procedure for the synthesis of 10.
The in situ generated lithium complex 16 was reacted
with 0.95 equiv of [PtCl2(SEt2)2] (cis/trans ) 1:1) in Et2O
(Scheme 4). The conversion to the trans-complex 17 was
171.40(14) N(3)-Pt-C(1)
N(1)-Pt-C(1)-C(2) -15.4(3) N(3)-Pt-C(13)-C(14) -13.9(3)
C(1)-Pt-C(13)-C(18) -29.3(4) C(13)-Pt-C(1)-C(6) -30.6(3)
3
complete in 3 h. On the basis of the JPt-H coupling
constants, which are consistent with other trans-
complexes (3JPt-H ) 35 and 42 Hz for NMe2 and CH2N,
respectively, see Table 4),2 complex 17 was assigned to
be the trans-isomer with the anionic groups (aryl and
chloride) positioned trans to each other. NMR analysis
of the product showed the presence of 17 and a small
amount of cis-10 (5%), which could be removed by
column chromatography.14 In the second step, pure 17
was reacted with 16 in Et2O. This led to a complete
conversion of 17 to homoleptic 10 in a cis/trans ratio of
80:20. It is interesting to note that the cis/trans ratio is
in accordance with that found for the single-step pro-
cedure, thus showing that 17 is the intermediate in that
reaction.
It should be noted that the in situ prepared lithium
reagents contain either LiI (reaction of 5, 6, and 8 with
t-BuLi) or n-BuI (reaction with n-BuLi) in the reaction
mixtures. Workup of the reaction mixtures of 10, 11,
and 13 revealed that these bisaryl platinum(II) com-
plexes are prone to further reacting to platinum(IV)
derivatives; that is, under these conditions these plati-
num(II) compounds undergo oxidation by reaction with
electrophiles.15 For example, during the synthesis of cis-
10, in the presence of LiI, a rapid, subsequent conver-
sion of cis-10 to the PtIV compound trans,cis-[PtI2{C6H3-
Br-4-(CH2NMe2)-2}2] (18) was observed.16 In this com-
plex, the bidentate ligands are in their original position,
3
(14) In the 1H NMR spectra JPt-H couplings of 35 and 42 Hz were
observed for the NMe2 and CH2 groups, respectively. This is in line
with values found for the closely related trans-[PtCl(C,N)(DMSO)]
complexes (32-34 and 39-40 Hz, respectively). (a) Meijer, M. D.; de
Wolf, E.; Lutz, M.; Spek, A. L.; van Klink, G. P. M.; van Koten, G.
Organometallics 2001, 20, 4198-4206. (b) Kleij, A. W.; Klein Gebbink,
R. J. M.; Lutz, M.; Spek, A. L.; van Koten, G. J. Organomet. Chem.
2001, 621, 190-196.
(15) (a) van Beek, J. A. M.; van Koten, G.; Wehman-Ooyevaar, I. C.
M.; Smeets, W. J. J.; van der Sluis, P.; Spek, A. L. J. Chem. Soc., Dalton
Trans. 1991, 883-893. (b) Wehman, E.; van Koten, G.; Knaap, C. T.;
Ossor, H.; Pfeffer, M.; Spek, A. L. Inorg. Chem. 1988, 27, 4409-4417.
(13) Deuschel-Cornioley, C.; Stoeckli-Evans, H.; von Zelewsky, A.
J. Chem. Soc., Chem. Commun. 1990, 121-122.

2948 Organometallics, Vol. 24, No. 12, 2005
Amijs et al.
Table 3. Selected Bond Lengths (Å), Bond Angles (deg), and Torsion Angles (deg) for cis-14‚xC6H6
Interatomic Distances
Pt(1)-C(11)
Pt(1)-N(1)
2.008(3)
2.196(2)
Pt(1)-C(12)
Pt(1)-N(2)
2.002(3)
2.203(2)
Interatomic Angles and Torsion Angles
C(11)-Pt(1)-C(12)
100.82(11)
79.57(9)
169.45(9)
-22.18(18)
-41.7(2)
N(1)-Pt(1)-N(2)
101.53(8)
79.86(10)
170.49(9)
-20.6(2)
-40.9(2)
N(1)-Pt(1)-C(11)
N(2)-Pt(1)-C(12)
N(2)-Pt(1)-C(11)
N(1)-Pt(1)-C(12)
N(1)-Pt(1)-C(11)-C(21)
C(11)-Pt(1)-C(12)-C(92)
N(2)-Pt(1)-C(12)-C(22)
C(12)-Pt(1)-C(11)-C(91)
1
Table 4. Selected H, 13C, and 195Pt NMR Data for Complexes 10-14, 17, 19, 20, 24, and 25a
NMe2 (3JPt-H
)
CH2N (3JPt-H
)
Cipso (1JPt-C
)
Pt
complex
cis
2.80 (11)
2.37 (18), 2.94 (12)
1.98 (19), 2.23
1.96 (10), 2.22
1.93, 2.20e
trans
cis
trans
cis
trans
167.6e
cis
trans
10b
11b
12d
13d
14d
17
3.02 (43)
3.58 (18)
3.96 (40)
137.4 (1182)
138.9 (1215)
139.5e
-3388
-3470
-3384
-3391
-3440
-2872
3.28/4.48c,e
3.20 (13), 3.64
3.18 (17), 3.55
3.08/4.46c,e
2.59 (44), 2.29
2.58 (45), 2.28
2.44, 2.47e
3.33 (40), 3.76
3.31 (40), 3.67
3.03/ 4.69c,e
3.90 (42)
168.8e
-2865
-2880
-2827
-3700
140.9e
169.9e
143.9 (1133)
174.4e
2.98 (35)
133.3 (1077)
19b
20d
24b
25b
2.08e
2.73-3.88c,e
3.44, 3.51e
3.96e
155.7e,f
140.5e
139.2e
139.2e
-447g
-3412
-3386
-3382
2.06, 2.13e
2.85e
2.84e
3.94e
a Chemical shifts in ppm, coupling in hertz, singlet resonances unless stated otherwise, 25 °C. b In CDCl3 solutions. c AX pattern. d In
e 3
1
2
2
1
C6D6 solutions.
1744 Hz.
J
or JPt-C coupling not observed. f Double doublet, JP-C ) 98 Hz (trans), JP-C ) 15 Hz (cis). g Doublet, JPt-P
)
Pt-H
Scheme 5. Synthesis of Platinum(IV) Complex 18a
the reaction mixtures at regular intervals). All isomer-
ization reactions were irreversible.
The reaction mechanism for trans-cis isomerization
of the platinum group organometallic complexes has
been the subject of considerable debate. Five-coordinate
intermediates have been assumed to be involved in
isomerization reactions, either catalyzed by the solvent
or by addition of an extra ligand.18 For trans-cis
isomerization in the absence of free ligands a dissocia-
tive pathway through three-coordinate intermediates
and coordination of a solvent molecule has been pro-
posed.19 It was found that electron-donating para and
meta substituents in [PtX(C6H4R)(PEt3)2] (R ) OMe,
Me) enhanced the rate of isomerization.19a The relatively
fast isomerization of complexes 12 and 13 can be
ascribed to the presence of the potentially chelating
5-CH2NMe2 substituents. These groups can enhance the
thermal isomerization reaction both due to their electron-
donating properties and via intermolecular coordination
in an associative pathway.
Structural Aspects of [Pt(C,N)2] Complexes 10-
14. Solid-State Structures of cis-12 and cis-14‚
xC6H6. Slow distillation of Et2O to a saturated solution
of cis-12 in CH2Cl2 afforded single crystals of cis-12‚
Et2O, which were suitable for X-ray crystal structure
determination. The molecular structure is depicted in
Figure 1 (see Table 2 for relevant bond lengths, bond
angles, and torsion angles). The structure shows that
the metal center is bonded to two bidentate, C,N-bonded
amino aryl ligands in the cis-configuration and has a
slightly distorted square-planar geometry. The two
meta-amino substituents are not coordinated. The dis-
torted square-planar geometry is reflected by the acute
bite angles of the two C,N-ligands at the platinum
a
(i) CH2Cl2, 1 h.
while the new iodide ligands were placed trans to each
other, above and below the coordination plane.15a Inde-
pendent synthesis of 18 by adding 1 equiv of I2 to a
solution of cis-10 in CH2Cl2 afforded immediately a
bright orange-colored solid (Scheme 5). This solid, which
is insoluble in the greater part of the common solvents,
had the correct elemental analysis based on the pro-
posed composition for 18. 1H NMR analysis was carried
out on an in situ prepared solution of 18 in CDCl3 and
confirmed the proposed structure.17
Isomerization of trans-[Pt(C,N)2] Complexes. All
trans-complexes of 10 and 12-14 can be isomerized
quantitatively into the corresponding cis-isomers by
heating a solution of cis-trans mixture to reflux for
several hours in toluene. Geometrical isomerization by
heating solid trans-1 for 5 h at 150 °C, which resulted
in the quantitative formation of cis-1, has already been
reported.8 Complete isomerization of trans-12 and trans-
13 into the corresponding cis-isomers occurred within
a few hours, whereas full isomerization of trans-10 and
trans-14 needed 16 h of reaction time (all reactions were
1
monitored by H NMR analysis of samples taken from
(16) I- is in equilibrium with I2, which upon formation immediately
(18) (a) Favez, R.; Roulet, R.; Pinkerton, A. A.; Schwarzenbach, D.
Inorg. Chem. 1980, 19, 1356-1365. (b) van Eldik, R.; Palmer, D. A.;
Kelm, H.; Louw, W. J. Inorg. Chem. 1980, 19, 3551-3552.
(19) (a) Romeo, R.; Minniti, D.; Lanza, S. Inorg. Chem. 1979, 18,
2362-2368. (b) Price, J. H.; Birk, J. P.; Wayland, B. B. Inorg. Chem.
1978, 17, 2245-2250.
reacts with the platinum(II) complex (I3 + 2e- T 3I- (+0.53 V) and
-
I2 + 2e- T 2I- (+0.62 V).
(17) Since the isolated PtIV complex was insoluble in common organic
solvents, its 1H NMR spectrum was obtained from a CDCl3 solution of
the PtII complex to which a known amount of I2 had been added.

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2949
C-Pt and N-Pt bond lengths that are comparable to
those of cis-12 (Table 3). The mutual steric intramo-
lecular interference of the hydrogen atoms on C(81) and
C(82) (H(81)‚‚‚H(82) ) 3.33 Å) causes the ligands to
distort in a unilateral anti-twist fashion. As the crystal
is centrosymmetric, both ∆ and Λ enantiomers are
present in a 1:1 ratio (Figure 3). The torsion angles of
Figure 1. Displacement ellipsoid plot (50% probability
level) of the molecular structure of cis-12‚Et2O, with the
adopted labeling scheme. The Et2O solvent molecule has
been omitted for clarity.
Figure 3. PLUTON plot of the two enantiomers of racemic
cis-14‚xC6H6, Λ, left-handed helicity, and ∆, right-handed
helicity.
center, 80.25(14)° (N(1)-Pt-C(1)) and 80.95(16)° (N(3)-
Pt-C(13)). The two five-membered metallacycles are
puckered, which is shown by angles between the plati-
num coordination plane and the aryl plane of -15.4(3)°
and -13.9(3)° (N(1)-Pt-C(1)-C(2) and N(3)-Pt-C(13)-
C(14), respectively). The C-Pt and N-Pt bond lengths
fall in the range of other platinum(II) complexes with
chelate-bonded C,N-ligands (C-Pt: 2.000-2.025 Å,
N-Pt: 2.139-2.164 Å).13,14,20,21
Crystals of cis-14‚xC6H6 suitable for single X-ray
crystal structure determination were obtained from a
saturated solution of cis-14 in benzene/pentane (9:1).
The molecular structure of cis-14 (Figure 2) reveals a
platinum(II) center that is ligated by two bidentate C,N-
bonded amino naphthyl ligands in a cis-fashion, with
the platinum coordination plane with the aryl plane are
considerably larger than for cis-12, -41.7(2)° and -40.9-
(2)° for C(11)-Pt-C(12)-C(92) and C(12)-Pt-C(11)-
C(91), respectively. Similar values for these torsion
angles were found for related planar chiral palladium-
(II) and platinum(II) complexes (38.3-44.5°).12,22 The
C-Pt-N bite angles (79.57(9)° and 79.86(10)° for N(1)-
Pt-C(11) and N(2)-Pt-C(12), respectively) are similar
to those of cis-12 and are in the range of angles found
for related homo- and heteroleptic [M(η2-C,N)] (M ) Pt,
Pd) complexes (78.5-80.9°).13,22,23
NMR Analysis of Complexes 10-14. Complexes 11
and 14 showed two singlet signals for the dimethyl-
amino protons and an AX pattern for the benzylic
protons for cis-11, cis-14, and trans-14 (Table 4). The
Figure 2. Displacement ellipsoid plot (50% probability level) of the molecular structure of cis-14‚xC6H6, with the adopted
labeling scheme. Disordered solvent molecules are not shown. The inset shows a side view of cis-14‚xC6H6.

2950 Organometallics, Vol. 24, No. 12, 2005
Amijs et al.
Scheme 6. Reaction of cis-10 with dpppa
resonances of trans-14 have distinct downfield shifts
with respect to those of cis-14. The presence of AX
patterns indicates that under these conditions there is
no apparent molecular symmetry plane containing the
benzylic carbon and nitrogen centers. This arises from
the asymmetric environment that is created by the
presence of steric bulk, which prevents a twist of the
arene rings with respect to each other and thus induces
planar chirality. The asymmetric environment was
already observed for 14 in solid state. Both cis- and
trans-isomers have a C2 symmetry in solution. Variable-
temperature 1H NMR experiments of 11 and cis-14 from
-95 to +95 °C in toluene-d8 did not reveal changes in
the spectra. Interconversion of the two diastereoisomers,
∆ and Λ, is not observed on the NMR time scale.
a
(i) dppp, CH2Cl2, RT, 5 min.
case a partial ligand displacement, i.e., substitution of
the chelating amine groups, should result in the forma-
tion of monodentate η1-C-bonded aminoaryl ligands with
a dangling CH2NMe2 base functionality. Reaction of cis-
10 with 1 equiv of the bidentate 1,3-(diphenylphosphi-
no)propane (dppp) ligand in CH2Cl2 resulted in the rapid
conversion to cis-[Pt(η1-C6H3(CH2NMe2)-2-Br-4)2(η2-
dppp)] (19), which contains a chelate-bonded dppp
ligand (Scheme 6). The results of 1H and 31P NMR
analysis of a solution of 19 excluded the possibility that
the dppp ligand was either η1-P monodentate or µ2-η2-
P,P′ bridge bonded. To study whether the dppp ligand
could induce trans-to-cis isomerization, the synthesis of
19 was attempted starting from a cis/trans-10 isomeric
mixture. Mixing of 1 equiv of dppp with 1 equiv of a 1:1
molar mixture of pure cis-10 and trans-10 isomers in
CDCl3 at room temperature for 7 days did not result in
complete conversion to 19. Although the cis/trans ratio
was increased to 3:1 (75% of cis-complex 19, 25% of
trans-complex [Pt(η1-C,N)(η2-C,N)(η1-dppp)]), indicating
that 50% trans-to-cis isomerization was achieved, the
presence of dppp did not enhance the isomerization
reaction to a great extent.
Structural Aspects of [Pt(η1-C,N)2(η2-dppp)] (19).
Solid-State Structure. Single crystals of 19 were
obtained by cooling a saturated solution of 19 in CH2-
Cl2 at 4 °C. A molecular plot of the molecular structure
is depicted in Figure 4, while Table 5 shows a selection
of bond lengths, bond angles, and torsion angles. The
structure has an exact, crystallographic C2 symmetry.
The molecular structure shows a square-planar plati-
num(II) complex, which possesses two monodentate η1-
C-bonded C,N-ligands in cis-configuration and an η2-
P,P′-bidentate-bonded dppp ligand. The C,N-aryl planes
are oriented perpendicular to the coordination plane of
the platinum center, which contrasts with the almost
coplanar situation in, for example, cis-12. The Pt-C(1)
bond is slightly elongated from 1.992(4) Å in cis-12 to
2.065(4) Å in 19. The noncoordinating ortho-amino
groups are directed away from the metal center, in an
E-conformation.27 Only the E-stereoisomer is present in
the crystal, whereas a mixture of E- and Z-conformers
is present in solution. The P(1)-Pt-P(1)i bite angle
(89.69(6)°) has a lower value than the P-Pt-P bite
angles observed in related complexes (94.63-97.02(8)°),
Singlet signals for the methyl protons and benzylic
protons of the coordinated methylene amino substitu-
ents of the cis- and trans-isomers of 10, 12, and 13 were
observed. Similar downfield shifts of the signals for the
trans-compounds with respect to the corresponding cis-
isomers were observed (∆δ(H) ) 0.13-0.64 ppm, Table
3
4). The benzylic protons showed the JPt-H coupling
constants of 18 (cis) and 40 (trans) Hz, while the methyl
signals displayed coupling constants of 11 and 44 Hz
for the cis- and trans-isomers, respectively. These dif-
ferences point to a different Pt-N bond strength, as a
result of the different trans-ligands, either aryl (cis) or
amine (trans). In the trans-complexes, the trans-influ-
ence is weaker, giving rise to larger platinum couplings.2
The cis-complexes have C2v symmetry, whereas the
trans-complexes exert a C2h symmetry.
Variable-temperature 1H NMR experiments were
carried out to study the dynamic aspects of the cis-
isomers. Low-temperature 1H NMR spectra were re-
corded in CD2Cl2. Lowering the temperature resulted
in broadening of the proton resonances of the CH2NMe2
groups coordinated to the platinum center. For com-
plexes cis-12 and cis-13, the NMe2 and CH2N singlet
signals decoalesced into two broad singlets at -93 °C
(∆Gq ) 35 kJ‚mol-1).24 The decoalescence of these
resonances for cis-10 was not observed at temperatures
down to -110 °C. This indicates that for cis-12 and cis-
13 at low temperatures the interconversion process
between the two diastereoisomers ∆ and Λ is sufficiently
slow. In contrast, this process is not observed for cis-10
at low temperatures. This is probably caused by the
absence of meta-substituents, whose steric interference
can hamper twisting of the arene rings.
Ligand Displacement. Previous reports have shown
that the hard donor amine ligands in cyclometalated
aminoaryl platinum complexes can be replaced by
phosphine ligands, as the soft platinum center favors
coordination to the softer phosphine ligands.3,25,26 In our
(20) Meijer, M. D.; Kleij, A. W.; Williams, B. S.; Ellis, D. D.; Lutz,
M.; Spek, A. L.; van Klink, G. P. M.; van Koten, G. Organometallics
2002, 21, 264-271.
(21) Amijs, C. H. M.; Berger, A.; van Klink, G. P. M.; Lutz, M.; Spek,
A. L.; van Koten, G. Manuscript in preparation.
(22) Valk, J.-M. Ph.D. Thesis, Utrecht University, The Netherlands,
1993.
(25) Zucca, A.; Stoccoro, S.; Cinellu, M. A.; Minghetti, G.; Manassero,
M.; Sansoni, M. Eur. J. Inorg. Chem. 2002, 3336-3346.
(26) (a) Albrecht, M.; Dani, P.; Lutz, M.; Spek, A. L.; van Koten, G.
J. Am. Chem. Soc. 2000, 122, 11822-11833. (b) van Koten, G.; Timmer,
K.; Noltes, J. G.; Spek, A. L. J. Chem. Soc., Chem. Commun. 1978,
250-252.
(23) (a) Janecki, T.; Jeffreys, J. A. D.; Pauson, P. L.; Pietrzykowski,
A. Organometallics 1987, 6, 1553-1560. (b) Fuchita, Y.; Yoshinaga,
K.; Hanaki, T.; Kawano, H.; Kinoshita-Nagaoka, J. J. Organomet.
Chem. 1999, 580, 273-281.
(24) Calculated with formula ∆Gq
)
RTc ln{(x2)kbTc)/hπ(∆ν)}
from: Drago, R. S. Physical Methods in Inorganic Chemistry; Reinhold
(27) Baumga¨rtner, R.; Schmidtberg, G.; Brune, H.-A. J. Organomet.
Chem. 1988, 345, 221-232.
Publishing Corporation: New York, 1965.

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2951
Figure 4. Displacement ellipsoid plot (50% probability level) of the molecular structure of 19, with the adopted labeling
scheme. Disordered solvent molecules have been omitted for clarity. Symmetry operation i: 1-x, y, 0.5-z. The inset shows
a view along the 2-fold axis of 19 with the E-conformation.
Table 5. Selected Bond Lengths (Å), Bond Angles
(deg), and Torsion Angles (deg) for 19
to +50 °C in CD2Cl2). Apparently, the presence of the
ortho-CH2NMe2 substituents does not cause enough
steric interference for the rotation or wagging process
to become slow on the NMR time scale.
Interatomic Distances
Pt(1)-C(1)
P(1)-C(10)
P(1)-C(22)
2.065(4)
1.829(5)
1.833(5)
Pt(1)-P(1)
P(1)-C(16)
2.2998(11)
1.828(5)
Functionalization of [Pt(C,N)2] Complexes. As
mentioned above, the [Pt(C,N)2] complexes were design-
ed as such that they would allow further functionaliza-
tion, for example by displacement of the chelate-bonded
amine ligands by addition of a stronger coordinating
phosphine ligand (vide supra). Furthermore, the halide
groups at the aryl rings can be used for substitution
reactions, via either lithiation or metal-catalyzed C-C
bond formation reactions. These kinds of nucleophilic
substitution reactions are rarely performed on organo-
metallic complexes, and only a few examples have been
reported.30,31 We have performed two types of function-
alization reactions with the cis-isomers of 10 and 12,
i.e., lithiation and subsequent transmetalation reactions
and C-C coupling reactions.
Lithiation and Transmetalation Reactions. Lithi-
ation of the bromide substituents of cis-10 and cis-12,
respectively, was carried out by reaction with either n-
or t-BuLi, followed by quenching the in situ prepared
4,4′-bis(lithio-aryl) platinum complex with [SnBrMe3].
Double lithiation and subsequent transmetalation of cis-
12 was possible by adding 4 equiv of n-BuLi to a solution
of cis-12 in THF at 0 °C (Scheme 7).32 The bisstannane
product 20 was purified by column chromatography.
Interatomic Angles and Torsion Angles
C(1)-Pt(1)-C(1)i
89.7(2)
P(1)-Pt(1)-P(1)i
89.69(6)
P(1)-Pt(1)-C(1)
90.34(12) P(1)-Pt(1)-C(1)i
179.00(13)
P(1)-Pt(1)-C(1)-C(2) 85.8(3)
C(1)i-Pt(1)-C(1)-C(2) -95.2(4)
while the Pt-P distance (2.2998(11) Å) lies within the
range found for these complexes (2.271-2.305 Å).28
1
Structure in Solution. The H NMR spectrum of
19 in CD2Cl2 reveals an AX pattern for the benzylic
protons with platinum couplings. This shows that 19
lacks a symmetry plane containing the benzylic carbon
atoms. 31P and 195Pt NMR analysis showed that the cis-
1
configuration is retained. The coupling constant JPt-P
is 1721 Hz, which is in accordance with values found
for related cis-complexes (1669-1748 Hz).29 The pres-
ence of one sharp phosphor signal at -4.46 ppm points
to one single complex in solution, i.e., a complex with
an intramolecularly coordinated dppp ligand. The NMR
spectra did not reveal the presence of the two E- and
Z-conformers. Most likely, this indicates that the barrier
for rotation of the aryl rings about the Pt-Cipso axis is
very low, and therefore fast interchange between the
two conformers on the NMR time scale occurs. The
alternate possibility, i.e., a high rotation barrier for the
E-Z interconversion process, can be excluded because
this would lead to two resonance patterns, one for the
E- and one for the Z-conformer, whereas one resonance
pattern is observed over a wide temperature range (-85
(30) Lithiation reactions: (a) Ref 3. (b) Clark, A. M.; Richard, C. E.
F.; Roper, W. R.; Wright, L. J. Organometallics 1998, 17, 4535-4537.
(c) Clark, A. M.; Richard, C. E. F.; Roper, W. R.; Wright, L. J.
Organometallics 1999, 18, 2813-2820. (d) Slagt, M. Q.; Klein Gebbink,
R. J. M.; Lutz, M.; Spek, A. L.; van Koten, G. J. Chem. Soc., Dalton
Trans. 2002, 2591-2592.
(31) C-C coupling reactions: (a) Lau, M.-K.; Zhang, Q.-F.; Chim,
J. L C.; Wong, W.-T.; Leung, W.-H. Chem. Commun. 2001, 1478-1479.
(b) Fraysse, S.; Coudret, C.; Launay, J.-P. J. Am. Chem. Soc. 2003,
125, 5880-5888. (c) Chodorowski-Kimmes, S.; Beley, M.; Collin, J.-P.;
Sauvage, J.-P. Tetrahedron Lett. 1996, 37, 2963-2966.
(28) (a) Thomas, J. C.; Peters, J. C. J. Am. Chem. Soc. 2003, 125,
8870-8888. (b) Bruce, M. I.; Costuas, K.; Halet, J.-F.; Hall, B. C.; Low,
P. J.; Nicholson, B. K.; Skelton, B. W.; White, A. H. J. Chem. Soc.,
Dalton Trans. 2002, 383-398.
(29) Braterman, P. S.; Cross, R. J.; Young, G. B. J. Chem. Soc.,
Dalton Trans. 1977, 1892-1897.

2952 Organometallics, Vol. 24, No. 12, 2005
Scheme 7. Lithiation and Transmetalation Reaction with cis-12a
Amijs et al.
a
(i) n-BuLi, THF, 0 °C, 15 min; (ii) [SnBrMe3], THF, 0 °C f RT, 1 h.
Selective double lithiation of cis-10 at the bromide
position could not be achieved. Using either n-BuLi or
t-BuLi in THF at low temperatures (< -80 °C, 15 min
to 1 h) did not result in the required lithiation. Each
time, unchanged cis-10 was recovered after the lithia-
tion reaction and it could even be reused after purifica-
tion. At higher temperatures in THF (> -30 °C, 5 min
to 1 h), mixtures of products were obtained from the
reaction of cis-10 with n-BuLi and subsequent quench-
ing with [SnBrMe3]. Next to some nonreacted cis-10,
some transmetalated complexes and significant amounts
of n-butyl-functionalized complexes were obtained. As
each complex can react at the 4- and 4′-bromide posi-
tions, a variety of products can be expected to form, for
example, [Pt(C,N-4-{SnMe3})(C,N-4-{n-Bu})], [Pt(C,N-
4-{SnMe3})2], [Pt(C,N-4-Br)(C,N-4-{n-Bu})], etc. Separa-
tion of these complexes was not possible. The ratios of
these products were dependent on the applied reaction
conditions; higher temperatures or longer reaction times
resulted in higher conversions to transmetalated and
n-butyl-functionalized complexes. The n-butyl-function-
alized complexes are formed in a cross-coupling reaction
of the lithiated complex and in situ generated 1-bromobu-
tane.30a Activation of the bromide position of cis-10 was
also attempted by reaction with [i-PrMgCl] according
to recently reported procedures by Knochel et al.33
Surprisingly, upon using 8 equiv of [i-PrMgCl] in THF
at temperatures from 0 to 40 °C (3 h), no reaction was
observed.
used, because of its usefulness for further metalation
reactions. The SCS-pincer ligand (SCS ) [C6H3(CH2-
SR)2-2,6]-, R ) Ph, Bu, etc.) is well known to easily
undergo cyclopalladation. Moreover, its cationic pal-
ladium complexes have a versatile coordination chem-
istry with Lewis bases.34 The cis-[Pt(C,N)2] complexes
functionalized with SCS-Pd pincers could therefore be
used as multimetallic building blocks in coordination
chemistry for the construction of supramolecular as-
semblies.
The reagent for the C-C coupling reaction, the
pinacol-protected boronic acid of the SCS-pincer, was
prepared starting from 3,5-bis(bromomethyl)bromoben-
zene (21, Scheme 8). Nucleophilic displacement of the
benzylic bromides in 21, employing t-BuSNa in ethan-
olic solution, yielded 22 in high yield.34a Compound 22
was reacted in a one-pot synthesis with 2 equiv of t-BuLi
in Et2O at -78 °C and B(OMe)3, and pinacol to form
23. This compound is well soluble in organic solvents
and contrary to most boronic acids (RB(OH)2) insoluble
in water. The pinacol-protected boronic acid 23 was
reacted with cis-10 under Suzuki coupling reaction
conditions at 70 °C, without affecting the C-Pt bonds
in the complex. The reaction was complete within 3 h.
It is noteworthy that no decomposition of cis-10 was
observed and that conversion to the cis-complex 24 was
quantitative. Purification by column chromatography
afforded 24 in moderate yield as an air- and moisture-
stable, white solid.
The fact that full lithiation of cis-10 appeared to be
impossible is in contrast to the results obtained with
cis-12 and the previously reported terdentate N,C,N-
chelating aminoaryl PtII complexes [PtX{C6H2I-4-(CH2-
NMe2)2-2,6}] (X ) Br, I). The latter complexes smoothly
lithiated at the iodo position para to the platinum
center, by reaction with 2 equiv of t-BuLi in THF at
-100 °C.3,26 The potentially chelating amino groups in
cis-12 stabilize the formed lithium species, which pre-
vents further reaction with the n-bromobutane present
in the reaction mixture.
C-C Coupling and Palladation Reactions. The
presence of the halide functionalities should, next to
lithiation, also enable the attachment of new groups via
metal-catalyzed C-C coupling reactions. To test this
possibility, a Suzuki-Miyaura coupling reaction be-
tween cis-10 and a boronic acid was performed. For this
reaction, a para-functionalized SCS-pincer ligand was
The commonly applied method for cyclopalladation of
SCS-pincer ligands is by reaction with [Pd(NCMe)4]-
(BF4)2.34 Indeed, complex 24 could be cyclopalladated
twice by reaction with [Pd(NCMe)4](BF4)2 in the pres-
ence of NEt3, following the method reported by Swager
and co-workers.35 The in situ formed dicationic bisac-
etonitrile complex, which contains two noncoordinating
[BF4]- counteranions, was reacted with NaCl to form
the neutral cis-complex 25. This air- and moisture-stable
complex was purified by slow distillation of Et2O to a
saturated solution of 25 in CH2Cl2.
Full conversion to the bis-SCS-functionalized complex
24 and its cyclopalladated derivative 25 was confirmed
by MALDI-TOF mass analysis. The positive MALDI-
TOF spectrum of 24 showed a signal corresponding to
[M + H]+ (m/z ) 1024.9), while the spectrum of 25
showed a signal corresponding to [M - Cl]+ (m/z )
1270.7).
(32) Four equivalents of n-BuLi were used to enhance solubility of
the lithiated complex, see: Kronenburg, C. M. P.; Rijnberg, E.;
Jastrzebski, J. T. B. H.; Kooijman, H.; Spek, A. L.; van Koten, G. Eur.
J. Org. Chem. 2004, 153-159.
(33) Knochel, P.; Dohle, W.; Gommermann, N.; Kneisel, F. F.; Kopp,
F.; Korn, T.; Sapountzis, I.; Anh Vu, V. Angew. Chem., Int. Ed. 2003,
42, 4302-4320.
(34) (a) Hall, J. R.; Loeb, S. J.; Shimizu, G. K. H.; Yap, G. P. A.
Angew. Chem., Int. Ed. 1998, 37, 121-123. (b) van Manen, H.-J.;
Nakashima, K.; Shinkai, S.; Kooijman, H.; Spek, A. L.; van Veggel, F.
C. J. M.; Reinhoudt, D. N. Eur. J. Inorg. Chem. 2000, 2533-2540.
(35) Gime´nez, R.; Swager, T. M. J. Mol. Catal. A 2001, 166, 265-
273.

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2953
Scheme 8. Synthesis of SCS-Functionalized Corner Complexes 24 and 25 via Suzuki-Miyaura Couplinga
a
(i) t-BuSNa, EtOH, ∆T; (ii) 2 equiv t-BuLi, Et2O, -78 °C, 10 min, B(OMe)3, -78 °C f RT, 16 h; (iii) pinacol, HOAc, 1 h; (iv)
thf/dme/H2O (1:1:1), [PdCl2(dppf)], Na2CO3, 70 °C, 3 h; (v) 2 equiv [Pd(NCMe)4](BF4)2, NEt3, MeCN, ∆T, 2 h; (vi) NaCl (aq), 1 h.
Figure 5. Displacement ellipsoid plot (50% probability level) of the molecular structure of 25‚xCH2Cl2, with the adopted
labeling scheme. Solvent molecules have been omitted for clarity.
Table 6. Selected Bond Lengths (Å), Bond Angles (deg), and Torsion Angles (deg) for 25‚xCH2Cl2
Pt(1)-C(11), Pt(1)-C(21)
Pd(1)-Cl(1), Pd(2)-Cl(2)
Pd(1)-S(1), Pd(1)-S(2)
N(1)-Pt(1)-C(11)
1.999(4), 1.985(4)
2.4064(12), 2.4213(11)
2.3071(14), 2.3076(13)
80.54(15)
98.31(17)
178.58(15), 175.83(13)
Pt(1)-N(1), Pt(1)-N(2)
Pd(1)-C(113), Pd(2)-C(213)
Pd(2)-S(3), Pd(2)-S(4)
N(2)-Pt(1)-C(21)
2.218(3), 2.208(3)
1.979(4), 1.976(4)
2.3181(12), 2.2959(13)
80.38(15)
101.50(13)
170.91(5), 169.63(4)
C(11)-Pt(1)-C(21)
N(1)-Pt(1)-N(2)
Cl(1)-Pd(1)-C(113),
S(1)-Pd(1)-S(2),
Cl(2)-Pd(2)-C(213)
S(3)-Pd(2)-S(4)
S(1)-Pd(1)-C(113),
85.48(14), 85.48(14)
109.9(2), 109.53(19)
31.8(4), 25.3(4)
9.9(5), 6.0(4)
S(3)-Pd(2)-C(213),
85.25(14), 84.80(14)
107.26(18), 107.07(17)
14.3(3), 13.5(3)
S(2)-Pd(1)-C(113)
S(4)-Pd(2)-C(213)
Pd(1)-S(1)-C(117),
Pd(2)-S(3)-C(217),
Pd(1)-S(2)-C(122)
Pd(2)-S(4)-C(222)
C(21)-Pt(1)-C(11)-C(16),
C(11)-Pt(1)-C(21)-C(26)
S(1)-Pd(1)-C(113)-C(112),
S(2)-Pd(1)-C(113)-C(114)
C(15)-C(14)-C(110)-C(115)
N(1)-Pt(1)-C(11)-C(12),
N(2)-Pt(1)-C(21)-C(22)
S(3)-Pd(2)-C(213)-C(212),
S(4)-Pd(2)-C(213)-C(214)
C(25)-C(24)-C(210)-C(215)
-8.6(4), -11.7(4)
-18.9(7)
-34.8(8)
Structural aspects of 24 and 25. Solid-State
Structure of 25. Single crystals of 25‚xCH2Cl2 were
obtained by cooling a solution of 25 in CH2Cl2/Et2O (10:
1) at -30 °C. A plot of its molecular structure is depicted
in Figure 5, while Table 6 shows a selection of bond
lengths, bond angles, and torsion angles. In the crystal
two diastereoisomers (SS,SS and RR,RR) are present
(Figure 6). The molecular structure of 25‚xCH2Cl2
reveals a platinum(II) center that is ligated by two
bidentate C,N-bonded amino aryl ligands in a cis-
fashion. Each aryl group is substituted at the para-
position with a diorganosulfide aryl moiety, which is

2954 Organometallics, Vol. 24, No. 12, 2005
Amijs et al.
CH2S signals occurred at -10 °C. The singlet signal
resonance of the tert-butyl groups of 25 splits in two
singlet signals with a coalescence point of -30 °C.
Although large differences for the SCS-pincer units of
25 were observed at low temperatures, no significant
changes were observed for the dimethylbenzyl amino
groups. Lowering the temperature to -60 °C did not
result in decoalescence of the singlet peaks of the
benzylic protons of 24 and 25, as was also observed for
the parent complex cis-10.
Conclusions
Figure 6. PLUTON plot of the two diastereoisomers of
25‚xCH2Cl2.
We have synthesized a series of new homoleptic C,N-
ortho-chelated aminoaryl platinum(II) complexes as cis-
and trans-isomers in one- or two-step reactions. The cis/
trans ratio is dependent on the functionalities on the
aryl ring, such as halide, methyl, naphthyl, and (di-
methylamino)methyl groups. Sterically demanding
groups at the ortho-position favor the formation of cis-
complexes, which in that case contain a planar-chiral
metal center. The trans-complexes could be irreversibly
isomerized to the thermodynamically more stable cis-
isomers. The complexes could be further functionalized
by (1) ligand displacement, (2) lithiation of the halide
groups, followed by a transmetalation reaction with
[SnClMe3], and (3) C-C Suzuki-Miyaura coupling
reactions, affecting neither the conformation nor the
nature of the complexes. By the latter method a bis-
SCS-pincer functionalized complex was prepared, which
could be cyclopalladated twice in an additional reaction.
This yielded an unusual neutral mixed trinuclear bis-
palladium/platinum corner complex, which has potential
applications in the synthesis of larger (self-assembled)
molecular architectures. Addition of other functional-
ities is of course also possible via either lithiation or
C-C coupling reactions. The halide-functionalized com-
plexes are thus excellent precursors for the synthesis
of various organometallic complexes as, for example,
molecular squares.38
cyclopalladated at the position between the CH2S(t-Bu)
groups. This affords square-planar PdII centers with a
ligand environment that comprises a tridentate SCS
coordination by the organic moiety and a chloride trans
to the metal-bonded aromatic carbon atom. The Pt-C
and Pt-N bonds fall in the range observed for cis-12
and cis-14, and the angles and torsion angles of the
organoplatinum moiety fall in the range observed for
cis-12. Figure 6 clearly shows that the structure is
nearly flat. The palladium atoms adopt slightly distorted
square-planar geometries with angles and distances
that are similar to related tert-butylsulfido SCS-PdII
complexes.36 The four butyl groups are oriented anti
with respect to the square planes, in axial positions,
with Pd-S-C(t-Bu) angles of 107.07(17)-109.9(2)°,
similar to reported SCS(t-Bu)-PdII complexes (107.5(4)-
113.5(9)°).36 The torsion angles between the C,N-aryl
and SCS-aryl rings of -34.8(8)° and -18.9(7)° (C(15)-
C(14)-C(110)-C(115) and C(25)-C(24)-C(210)-C(215),
respectively) fall in the range normally observed for
biphenyl compounds.
Structure in Solution. The 1H NMR spectra of
complexes 24 and 25 in CDCl3 showed the same signals
for the dimethylbenzyl amino groups as cis-10. The
singlet signals of the CH2S and S(t-Bu) groups of 25 are
shifted downfield with respect to the free ligand 24, ∆δ-
(H) ) 0.41 and 0.24 ppm for CH2S and S(t-Bu), respec-
tively. The resonance of the diastereotopic CH2S protons
of 25 is somewhat broadened due to fluxional behavior.
This behavior is attributed to the pyramidal inversion
of the sulfur atoms and/or to the inversion of the ring
puckering, leading to a multiplicity of isomers with axial
and/or equatorial positions for each SBu group in a
single molecule.37 These two combined processes give
rise to a dynamic equilibrium between two conforma-
tional isomers that make the benzylic protons non-
equivalent. At lower temperatures (down to -60 °C) no
significant changes were observed for 24. For complex
25, the coupling of the two diastereotopic CH2S protons
resulted in splitting of the signal into two AB patterns,
3.76/4.65 (2JH-H ) 17 Hz) and 4.05/4.37 (2JH-H ) 16 Hz)
ppm at low temperatures (down to -60 °C). This points
to the presence of two isomers; that is, the t-Bu groups
are in axial or equatorial positions with respect to the
palladium coordination plane.37 The coalescence of the
Experimental Section
General Comments. 4-Bromo-2-bromomethyl-1-iodoben-
zene (2),10 5-bromo-1-bromomethyl-2-iodo-3-methylbenzene
(3),10 1,4-dibromo-2,5-bis(bromomethyl)benzene (4),10 1-bromo-
2-dimethylaminomethylnaphthalene (9),11 and 3,5-bis(bro-
momethyl)bromobenzene (21)10 were synthesized according to
literature procedures. All solvents and other reagents were
obtained from commercial sources and were used without
further purification unless stated otherwise. Reactions involv-
ing organolithium and -magnesium derivatives were carried
out under an inert atmosphere of dry, oxygen-free nitrogen
using standard Schlenk techniques. Et2O and THF were
distilled from Na/benzophenone prior to use. The 1H, 13C, 31P,
and 195Pt NMR spectra were recorded at 300, 75.5, 81, and
64.3 MHz, respectively, at 25 °C. Chemical shifts are reported
in ppm. 195Pt NMR spectra were referenced to external K2-
PtCl4 (δ ) -1630). MALDI-TOF mass spectra were acquired
using a Applied Biosystems Voyager System 6347, with
dithranol as matrix. Elemental analyses were obtained from
Kolbe, Mikroanalytisches Laboratorium (Mu¨lheim a.d. Ruhr,
Germany).
(36) (a) Errington, J.; McDonald, W. S.; Shaw, B. L. J. Chem. Soc.,
Dalton Trans. 1980, 2312-2314. (b) Loeb, S. J.; Shimizu, G. K. H.;
Wisner, J. A. Organometallics 1998, 17, 2324-2327. (c) Nakai, H.; Ogo,
S.; Watanabe, Y. Organometallics 2002, 21, 1674-1678.
(37) Dupont, J.; Beydoun, N.; Pfeffer, M. J. Chem. Soc., Dalton
Trans. 1989, 1715-1720.
Crystal Structure Determinations. X-ray intensities
were measured on a Nonius KappaCCD diffractometer with
(38) Wu¨rthner, F.; You, C.-C.; Saha-Mo¨ller, C. R. Chem. Soc. Rev.
2004, 33, 133-146, and the references therein.

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2955
Table 7. Crystallographic Detailsa
cis-12‚Et2O
cis-14‚xC6H6
19
25‚xCH2Cl2
formula
C24H36Br2N4Pt‚C4H10
O
C26H28N2Pt +
disordered solvent
563.59 [*]
0.21 × 0.21 × 0.21
yellow
monoclinic
P21/c (no. 14)
9.9208(1)
11.6735(1)
21.8509(2)
90
99.9722(5)
90
2492.33(4)
4
1.502 [*]
5.642 [*]
analytical
0.33-0.48
37 241/5674
266/0
0.0208/0.0451
0.0297/0.0474
1.049
C45H48Br2N2P2Pt
C50H70Cl2N2Pd2PtS4‚
2CH2Cl2 + disordered solvent
1475.96 [*]
0.42 × 0.09 × 0.06
yellow
fw
809.60
1033.70
cryst size [mm3]
cryst color
cryst syst
space group
a [Å]
0.48 × 0.12 × 0.12
colorless
monoclinic
P21/c (no. 14)
11.2540(1)
13.4683(1)
20.6529(2)
90
0.42 × 0.18 × 0.06
colorless
monoclinic
P2/c (no. 13)
10.0910(10)
9.3702(7)
23.476(3)
90
triclinic
P1h (no. 2)
11.0727(1)
17.2827(2)
18.1957(2)
86.1892(7)
79.8100(8)
82.8972(4)
3397.27(6)
2
b [Å]
c [Å]
R [deg]
â [deg]
100.3196(4)
90
3079.77(5)
4
1.746
7.177
analytical
0.21-0.56
35 139/7012
333/37
0.0304/0.0684
0.0364/0.0705
1.133
111.232(7)
90
2069.1(4)
2
1.659
5.433
analytical
0.32-0.70
30 763/4772
239/0
0.0322/0.0881
0.0339/0.0891
1.095
γ [deg]
V [Å3]
Z
Dcalc [g/cm3]
1.443 [*]
µ [mm-1
]
2.967 [*]
abs corr
multiscan
abs corr range
measd/unique reflns
params/restraints
R1/wR2 [I>2σ(I)]
R1/wR2 [all reflns]
S
0.66-0.84
65 488/15 545
620/0
0.0391/0.1047
0.0489/0.1104
1.072
a Derived parameters do not contain the contribution of the disordered solvent.
3
rotating anode and graphite monochromator (λ ) 0.71073 Å)
at a temperature of 150(2) K. The structures were solved with
automated Patterson methods39 (cis-12‚Et2O, cis-14‚xC6H6,
25‚xCH2Cl2) or direct methods40 (19) and refined with SHELXL-
9741 against F2 of all reflections. Non-hydrogen atoms were
refined with anisotropic displacement parameters. Hydrogen
atoms were refined as rigid groups. Structure calculations and
checking for higher symmetry were performed with the PLA-
TON package.42
(s, 1H, ArH-3), 7.64 (d, 1H, JH-H ) 10 Hz, ArH-6). 13C{1H}
NMR (CDCl3): δ 45.8 (NCH3), 67.8 (CH2N), 98.4 (ArC-1), 122.9
(ArC-4), 131.9, 133.3, 140.8, 143.6 (ArC-2). Anal. Calcd for
C9H11NBrI: C, 31.79; H, 3.26; N, 4.12. Found: C, 31.97; H,
3.32; N, 4.20.
5-Bromo-1-(dimethylamino)methyl-2-iodo-3-methyl-
benzene (6). Compound 3 (1.36 g, 3.49 mmol) was dissolved
in Et2O (40 mL) and treated with dimethylamine (4 mL, 56
mmol, 16 equiv) at room temperature. After 2 h the salts were
removed by filtration and the reaction mixture was concen-
trated in vacuo. The resulting oil was purified by protonating
with excess of HCl (4 M), extraction with water, addition of
excess NaOH, and extraction with Et2O. Yield of 6: 0.62 g (1.75
The crystals of cis-14‚xC6H6 contain large voids (374.6 Å3/
unit cell) filled with severely disordered benzene solvent
molecules. Their contribution to the structure factors was
secured by back Fourier transformation with the SQUEEZE
procedure of PLATON,42 resulting in 94 electrons/unit cell.
The crystals of 19 appeared to be nonmerohedrally twinned
with a 2-fold rotation about hkl ) (001) as twin operation. The
HKLF5 twin refinement43 resulted in a twin fraction of 0.3666-
(11).
The crystals of 25‚xCH2Cl2 contain ordered CH2Cl2 mol-
ecules and additionally large voids (678.4 Å3/unit cell) filled
with severely disordered CH2Cl2 solvent molecules. The con-
tribution of the latter to the structure factors was secured by
back Fourier transformation with the SQUEEZE procedure
of PLATON,42 resulting in 178 electrons/unit cell.
1
mmol, 50%). H NMR (CDCl3): δ 2.30 (s, 6H, NCH3), 2.44 (s,
3H, ArCH3), 3.44 (s, 2H, CH2N), 7.28 (s, 1H, ArH-5), 7.36 (s,
1H, ArH-3). 13C{1H} NMR (CDCl3): δ 29.4 (ArCH3), 45.7
(NCH3), 68.7 (CH2N), 105.7 (ArC-4), 122.2 (ArC-1), 130.1,
131.0, 153.8, 144.1. Anal. Calcd for C10H13NBrI: C, 33.93; H,
3.70; N, 3.96. Found: C, 34.02; H, 3.82; N, 3.80.
1,4-Dibromo-2,5-bis{(dimethylamino)methyl}ben-
zene (7). To a solution of 4 (5.6 g, 13.2 mmol) in Et2O (130
mL) was added dimethylamine (15 mL, 216 mmol, 16 equiv)
at room temperature. The suspension was stirred for 2 h, after
which the salts were removed by filtration. The reaction
mixture was washed with brine (40 mL, 2×). Evaporating the
solvent in vacuo yielded 4.0 g of 7 as a white solid (11.4 mmol,
Further details about the crystal structure determinations
are given in Table 7.
1
87%). H NMR (CDCl3): δ 2.31 (s, 12H, NCH3), 3.49 (s, 4H,
4-Bromo-2-(dimethylamino)methyl-1-iodobenzene (5).
To a solution of 2 (17.1 g, 45.5 mmol) was added dimethyl-
amine (60 mL, 865 mmol, 19 equiv) in Et2O (250 mL) at room
temperature. After 2 h the salts were removed by filtration
and the reaction mixture was concentrated in vacuo. The
resulting oil was purified by flash distillation, yielding 13.4 g
of 5 (39.3 mmol, 86%). 1H NMR (CDCl3): δ 2.29 (s, 6H, NCH3),
CH2N), 7.64 (s, 2H, ArH-3,6). 13C{1H} NMR (CDCl3): δ 45.7
(NCH3), 62.7 (CH2N), 123.5 (ArC-1,4), 134.6 (ArC-3,6), 138.7
(ArC-2,5). Anal. Calcd for C12H18N2Br2: C, 41.17; H, 5.18; N,
8.00. Found: C, 41.08; H, 5.03; N, 7.88.
1,4-Diiodo-2,5-bis{(dimethylamino)methyl}benzene (8).
Compound 7 (1.9 g, 5.5 mmol) was dissolved in Et2O (40 mL),
and to this solution was added n-BuLi (7.8 mL, 1.6 M in
hexane, 12.5 mmol, 2.3 equiv) at -78 °C. The reaction mixture
was stirred for 15 min at this temperature, after which the
suspension was allowed to reach room temperature and stirred
for 45 min. The reaction mixture was quenched with a solution
of 1,2-diiodoethane (3.2 g, 11.5 mmol, 2.1 equiv) in Et2O (30
mL) and stirred for 15 min. The mixture was acidified with a
2 M solution of HCl (20 mL), and the aqueous layer was
separated from the organic layer and washed with Et2O (40
mL). The aqueous layer was made basic with KOH pellets until
the amino compound precipitated from solution. Extracting
3
3.40 (s, 2H, CH2N), 7.07 (d, 1H, JH-H ) 10 Hz, ArH-5), 7.55
(39) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla C. The
DIRDIF99 program system, Technical Report of the Crystallography
Laboratory; University of Nijmegen: The Netherlands, 1999.
(40) Sheldrick, G. M. SHELXS-97, Program for crystal structure
solution; University of Go¨ttingen: Germany, 1997.
(41) Sheldrick, G. M. SHELXL-97, Program for crystal structure
refinement; University of Go¨ttingen: Germany, 1997.
(42) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7-13.
(43) Herbst-Irmer, R.; Sheldrick, G. M. Acta Crystallogr. 1998, B54,
443-449.

2956 Organometallics, Vol. 24, No. 12, 2005
Amijs et al.
with Et2O and removal of the solvent yielded 2.14 g of 8 as an
washing the solid with Et2O (5 mL) and pentane (5 mL, 2×)
yielded 0.20 g (0.27 mmol, 48%) of 12 as a mixture of the cis-
(cis-12) and trans-isomers (trans-12). Ratio cis/trans ) 60:40.
The cis-complex was isolated by precipitation from a CH2Cl2/
Et2O mixture. Crystals of the cis-complex (colorless needles)
were obtained by slow distillation of Et2O in a saturated
solution of cis-12 in CH2Cl2/EtOH (90:10) for 2 days at room
1
off-white powder (4.8 mmol, 88%). H NMR (CDCl3): δ 2.32
(s, 12H, NCH3), 3.42 (s, 4H, CH2N), 7.86 (s, 2H, ArH-3,6). 13C-
{1H} NMR (CDCl3): δ 45.6 (NCH3), 67.1 (CH2N), 100.3 (ArC-
1,4), 140.5 (ArC-3,6), 141.9 (ArC-2,5). Anal. Calcd for C12H18N2I2:
C, 32.46; H, 4.09; N, 6.31. Found: C, 32.58; H, 4.15; N, 6.39.
cis-[Pt(C6H3Br-4{CH2NMe2}-2)2] (cis-10) and trans-[Pt-
(C6H3Br-4{CH2NMe2}-2)2] (trans-10). To a solution of 5 (1.4
g, 4.12 mmol) in Et2O (30 mL) was added n-BuLi (4.16 mmol,
1.6 M in hexane, 2.6 mL, 1 equiv) at -78 °C. The reaction
mixture was stirred for 5 min, after which a suspension of
trans-[PtCl2(SMe2)2] (0.80 g, 2.06 mmol, 0.5 equiv) in Et2O (10
mL) was added. The off-white suspension was allowed to warm
to room temperature and stirred for 2 h. The precipitate was
isolated by centrifugation, dissolved in CH2Cl2, and filtered
over Celite. The solvent was removed in vacuo. The remaining
white solid (ratio cis/trans ) 85:15) was washed with THF
(10 mL) and precipitated from refluxing THF to give 0.56 g
(0.90 mmol, 44%) of the cis-complex cis-10 as a white solid.
The THF mother liquor was evaporated in vacuo to yield a
mixture of trans-10 and cis-10 as a white solid (cis/trans )
3
temperature. cis-12: 1H NMR (C6D6): δ 1.98 (s, JPt-H ) 19
Hz, 12H, CH2NCH3-2), 2.23 (s, 12H, CH2NCH3-5), 3.20 (s,
3JPt-H ) 13 Hz, 4H, CH2NCH3-2), 3.64 (s, 4H, CH2NCH3-5),
4
3
7.28 (s, JPt-H ) 16 Hz, 2H, ArH-3), 7.90 (s, JPt-H ) 64 Hz,
2H, ArH-6). 13C{1H} NMR (C6D6): δ 45.5 (CH2NCH3-2), 49.2
(CH2NCH3-5) 64.0 (CH2NCH3-2), 72.4 (CH2NCH3-5), 119.5
(ArC-4), 125.4 (ArC-3), 135.5 (ArC-5), 139.5 (ArCipso), 142.2
(ArC-6), 148.5 (ArC-2). 195Pt{1H} NMR (CDCl3): δ -3384.6.
Anal. Calcd for C24H36N4Br2Pt: C, 39.19; H, 4.93; N, 7.62.
Found: C, 39.25; H, 4.93; N, 7.51. trans-12: 1H NMR (C6D6):
δ 2.29 (s, 12H, CH2NCH3-5), 2.59 (s, 3JPt-H ) 44 Hz, 12H, CH2-
3
NCH3-2), 3.33 (s, JPt-H ) 40 Hz, 4H, CH2NCH3-2), 3.76 (s,
4H, CH2NCH3-5), 7.37 (s, 4JPt-H ) 28 Hz, 2H, ArH-3), 7.85 (s,
3JPt-H ) 25 Hz, 2H, ArH-6). 13C{1H} NMR (C6D6): δ 45.7
(CH2NCH3-2), 53.2 (CH2NCH3-5) 64.2 (CH2NCH3-2), 78.9 (CH2-
NCH3-5), 119.2 (ArC-4), 125.2 (ArC-3), 134.3 (ArC-5), 137.9
(ArC-6), 150.5 (ArC-2), 168.8 (ArCipso). 195Pt{1H} NMR (CDCl3):
δ -2865.4.
3
25:75). cis-10: 1H NMR (CDCl3): δ 2.80 (s, JPt-H ) 11 Hz,
12H, NCH3), 3.85 (s, 3JPt-H ) 18 Hz, 4H, CH2N), 7.11 (d, 3JH-H
3
unresolved, 2H, ArH-5), 7.12 (s, 2H, ArH-3), 7.25 (d, JH-H
)
12 Hz JPt-H ) 18 Hz, 2H, ArH-6). 13C{1H} NMR (CDCl3): δ
50.3 (NCH3), 73.1 (2JPt-C ) 55 Hz, CH2N), 116.5 (ArC-4), 124.3
(3JPt-C ) 45 Hz, ArC-3), 128.9 (3JPt-C ) 91 Hz, ArC-5), 137.4
(1JPt-C) 1182 Hz, Cipso), 140.2 (2JPt-C ) 116 Hz, ArC-6), 149.6
(ArC-2). 195Pt{1H} NMR (CDCl3): δ -3387.9. Anal. Calcd for
C18H22N2PtBr2: C, 34.80; H, 3.57; N, 4.51. Found: C, 34.71;
H, 3.61; N, 4.50. trans-10: 1H NMR (CDCl3): δ 3.02 (s, 3JPt-H
3
cis-[Pt(C6H2I-4{CH2NMe2}2-2,5)2] (cis-13) and trans-[Pt-
(C6H2I-4{CH2NMe2}2-2,5)2] (trans-13). The synthesis of cis-
13 and trans-13 is similar to the synthesis of cis-12 and trans-
12, but starts from 8 (0.5 g, 1.1 mmol) in Et2O (30 mL) with
n-BuLi (0.7 mL, 1.6 M in hexane, 1.1 mmol, 1 equiv) and trans-
[PtCl2(SMe2)2] (0.22 g, 0.6 mmol, 0.5 equiv). The reaction
mixture was concentrated in vacuo, dissolved in CH2Cl2, and
filtered over Celite. After removal of the solvent in vacuo and
washing with hexane (5 mL), an off-white powder was ob-
tained. The cis/trans ratio was 47:53. Yield of 13: 0.43 g (0.5
3
) 43 Hz, 12H, NCH3), 3.96 (s, JPt-H ) 40 Hz, 4H, CH2N),
3
7.22 (d, JH-H ) 8 Hz, 2H, ArH-5), 7.28 (s, 2H, ArH-3), 7.37
(d, 3JH-H ) 8 Hz, 3JPt-H unresolved, 2H, ArH-6). 13C{1H} NMR
(CDCl3): δ 53.8 (NCH3), 79.5 (CH2N), 116.4 (ArC-4), 124.0
(3JPt-C ) 45 Hz, ArC-6), 128.0 (3JPt-C ) 37 Hz, ArC-3,5), 136.5
(3JPt-C ) 43 Hz, ArC-3,5), 151.5 (ArC-2), 167.6 (ArCipso). 195Pt-
{1H} NMR (CDCl3): δ -2871.5.
3
mmol, 46%). cis-13: 1H NMR (C6D6): δ 1.96 (s, JPt-H ) 10
Hz, 12H, CH2NCH3-2), 2.22 (s, 12H, CH2NCH3-5), 3.18 (s,
3JPt-H ) 17 Hz, 4H, CH2NCH3-2), 3.55 (s, 4H, CH2NCH3-5),
3
7.57 (s, 2H, ArH-3), 7.84 (s, JPt-H ) 63 Hz, 2H, ArH-6). 13C-
cis-[Pt(C6H3{CH2NMe2}-2-Br-4-Me-6)2] (11). To a solution
of 6 (0.62 g, 1.75 mmol) in Et2O (15 mL) at -78 °C was added
n-BuLi (1.6 M in hexane, 1.1 mL, 1.76 mmol, 1 equiv). The
resulting yellow suspension was stirred for 10 min at this
temperature, after which neat trans-[PtCl2(SMe2)2] (0.32 g,
0.81 mmol, 0.46 equiv) was added. The reaction mixture was
warmed to room temperature and stirred for 3 h. The solvent
was removed in vacuo. The mixture was dissolved in CH2Cl2
and filtered over Celite. After removal of the solvent by
evaporation, the solid was washed with Et2O (5 mL) and
pentane (5 mL, 2×), yielding 0.4 g of the cis-isomer of 11 as
an off-white solid (0.62 mmol, 77%). 1H NMR (CDCl3): δ 1.99
{1H} NMR (C6D6): δ 45.6 (CH2NCH3-2), 49.4 (CH2NCH3-5)
68.4 (CH2NCH3-2), 72.3 (CH2NCH3-5), 94.6 (ArC-4), 132.1
(ArC-3), 138.6 (ArC-5), 140.9 (ArCipso), 142.2 (ArC-6), 149.3
(ArC-2). 195Pt{1H} NMR (C6D6): δ -3390.7. Anal. Calcd for
C24H36N4I2Pt: C, 34.75; H, 4.37; N, 6.75. Found: C, 34.63; H,
4.31; N, 6.79. trans-13: 1H NMR (C6D6): δ 2.28 (s, 12H, CH2-
3
NCH3-5), 2.58 (s, JPt-H ) 45 Hz, 12H, CH2NCH3-2), 3.31 (s,
3JPt-H ) 40 Hz, 4H, CH2NCH3-2), 3.67 (s, 4H, CH2NCH3-5),
3
7.64 (s, 2H, ArH-3), 7.79 (s, JPt-H ) 25 Hz, 2H, ArH-6). 13C-
{1H} NMR (C6D6): δ 45.7 (CH2NCH3-2), 53.2 (CH2NCH3-5)
68.9 (CH2NCH3-2), 78.5 (CH2NCH3-5), 94.3 (ArC-4), 131.8
(ArC-3), 137.1 (ArC-5), 137.7 (ArC-6), 151.1 (ArC-2), 169.9
(ArCipso). 195Pt{1H} NMR (C6D6): δ -2880.1.
3
(s, 6H, ArCH3), 2.37 (s, JPt-H ) 18 Hz, 6H, NCH3), 2.94 (s,
2
3JPt-H ) 12 Hz, 6H, NCH3), 3.28/4.48 (AX, JH-H ) 12 Hz,
3JPt-H unresolved, 4H, CH2N), 6.87 (s, 4JPt-H ) 24 Hz, 2H, ArH-
cis-[Pt(C10H6{CH2NMe2}-2)2] (cis-14) and trans-[Pt-
(C10H6{CH2NMe2}-2)2] (trans-14). To a solution of 9 (0.27 g,
1.02 mmol) in Et2O (40 mL) was added n-BuLi (1.6 M in
hexane, 0.64 mL, 1.02 mmol, 1.0 equiv) at -78 °C. After 30
min at this temperature, trans-[PtCl2(SMe2)2] (180 mg, 0.46
mmol, 0.45 equiv) was added. The mixture was stirred for 15
min at -78 °C and slowly warmed to room temperature. The
reaction was complete after 2 h. The solvents were evaporated
in vacuo. The remaining solid was dissolved in CH2Cl2 and
filtered over Celite. Subsequent evaporation of the solvent and
washing the remaining yellow solid with pentane (5 mL, 3×)
yielded 14 as a mixture of cis- and trans-isomers. Ratio cis/
trans ) 85:15. Yield of 14: 0.21 g (0.38 mmol, 82%). The cis-
isomer was obtained pure by crystallization from a saturated
solution of 14 in benzene/pentane (9:1). cis-14: 1H NMR
(C6D6): δ 1.93 (s, 3JPt-H unresolved, 6H, NCH3), 2.20 (s, 3JPt-H
3), 6.92 (s, 2H, ArH-5). 13C{1H} NMR (C6D6): δ 26.5 (3JPt-C
)
81 Hz, ArCH3), 47.8 (NCH3), 50.8 (NCH3), 73.9 (2JPt-C ) 57
Hz, CH2N), 115.7 (ArC-4), 122.0 (3JPt-C ) 42 Hz, ArC-3), 128.8
(3JPt-C ) 65 Hz, ArC-5), 138.9 (1JPt-C ) 1215 Hz, ArCipso), 148.0
(ArC-6), 148.7 (ArC-2). 195Pt{1H} NMR (CDCl3): δ -3470.3.
Anal. Calcd for C20H26N2PtBr2: C, 36.99; H, 4.04; N, 4.31.
Found: C, 36.91; H, 3.94; N, 4.25.
cis-[Pt(C6H2Br-4-{CH2NMe2}2-2,5)2] (cis-12) and trans-
[Pt(C6H2Br-4{CH2NMe2}2-2,5)2] (trans-12). To a suspension
of 7 (0.39 g, 1.12 mmol) in Et2O (20 mL) was added n-BuLi
(1.12 mmol, 1.6 M in hexane, 0.7 mL, 1 equiv) at -78 °C. The
green suspension was stirred for 15 min at this temperature,
after which trans-[PtCl2(SMe2)2] (0.22 g, 0.56 mmol, 0.5 equiv)
in Et2O (10 mL) was added. The reaction mixture was stirred
for 15 min at -78 °C, warmed to room temperature (30 min),
and stirred for an additional 3 h. All solvents were then
evaporated, and the yellow solid was dissolved in CH2Cl2 and
filtered over Celite. Evaporation of the solvent in vacuo and
2
3
unresolved, 6H, NCH3), 3.08/4.46 (AX, JH-H ) 12 Hz, JPt-H
unresolved, 4H, CH2N), 6.69 (t, 3JH-H ) 8 Hz, 2H, NaphH-7),
6.97 (t, JH-H ) 8 Hz, 2H, NaphH-6), 7.26 (d, JH-H ) 8 Hz,
3
3

ortho-Chelated Aminoaryl Pt(II) Complexes
Organometallics, Vol. 24, No. 12, 2005 2957
2H, NaphH), 7.66 (d, 3JH-H ) 8 Hz, 4H, NaphH), 8.20 (d, 3JH-H
) 8 Hz, 2H, NaphH-8). 13C{1H} NMR (C6D6): δ 47.5 and 50.1
(NCH3), 75.0 (2JPt-C ) 60 Hz, CH2N), 121.1 (3JPt-C ) 47 Hz),
123.4, 123.7, 124.8, 129.3, 133.3 (3JPt-C ) 54 Hz), 135.4 (3JPt-C
) 92 Hz), 141.6, 142.9, 143.9 (1JPt-C ) 1133 Hz, Cipso). 195Pt-
{1H} NMR (C6D6): δ -3439.9. Anal. Calcd for C26H28N2Pt: C,
55.41; H, 5.01; N, 4.97. Found: C, 55.28; H, 4.96; N, 4.89. trans-
14: 1H NMR (C6D6,): δ 2.44 (s, 6H, NCH3), 2.47 (s, 6H, NCH3),
3.03/4.69 (AX, JH-H ) 13 Hz, 4H, CH2N), 7.43 (t, JH-H ) 6
Hz, 2H, NaphH), 7.74 (d, 3JH-H ) 8 Hz, 2H, NaphH). 13C{1H}
NMR (C6D6): δ 51.5 (NCH3), 56.0 (NCH3), 80.5 (CH2N), 121.1
(3JPt-C ) 47 Hz), 123.5, 123.6, 124.5, 132.2, 133.9, 141.2, 144.6,
174.4 (Cipso). One aromatic signal remained unresolved due to
overlap with solvent signals. 195Pt{1H} NMR (C6D6): δ -2826.6.
General Procedure for Isomerization Reactions. A
mixture of the cis- and trans-isomers of 10, 12, 13, or 14 (0.6
mmol) was dissolved in toluene (40 mL) and refluxed for
several hours. The conversion of trans-12 and trans-13 was
complete within 3-5 h, whereas the conversion of trans-10
and trans-14 was only complete in 16 h (determined by 1H
NMR spectroscopy). After full isomerization the reaction
mixtures were allowed to cool to room temperature, after which
the solvent was removed in vacuo. The solid residues were
washed with Et2O (5 mL, 2×). Yield of cis-10: 83%, cis-12:
53%, cis-13: 77%, cis-14: 79%.
after which the solvent was evaporated. The white product was
purified by precipitation from a CH2Cl2/pentane mixture. Yield
of 19: 64.1 mg (62 µmol, 61%). Crystals (colorless needles) were
obtained by cooling a saturated solution of 19 in CH2Cl2 at 4
1
°C. H NMR (CDCl3): δ 2.00 (m, 2H, P(CH2)3P) 2.08 (s, 12H,
NCH3), 2.41 (m, 2H, P(CH2)3P), 2.56 (m, 2H, P(CH2)3P), 2.73/
2
3
3.88 (AX, JH-H ) 14 Hz, 4H, CH2N), 6.58 (d, JH-H ) 6 Hz,
2H, ArH), 6.86 (m, 4H, PPh), 6.99 (s, 2H, ArH-3), 7.12 (m, 6H,
PPh), 7.28 (m, 2H, ArH), 7.44 (m, 6H, PPh), 7.86 (m, 4H, PPh).
13C{1H} NMR (CDCl3): δ 14.3, 31.8, and 22.8 (P(CH2)3P), 45.9
(NCH3), 65.7 (3JPt-H ) 70 Hz, CH2N), 116.7 (ArC-4), 127.2
(3JPt-C ) 66 Hz, ArC-3), 127.9, 128.6, 129.2 (3JPt-C ) 49 Hz,
ArC-5), 129.7, 130.8 131.8, 134.0, 139.5 (2JPt-C ) 32 Hz, ArC-
6), 147.0 (ArC-2), 155.7 (dd, 2JP-C ) 98 Hz (trans), 2JP-C ) 15
Hz (cis), Cipso). 31P NMR (CDCl3): δ -4.46 (1JPt-P ) 1723 Hz).
195Pt{1H} NMR (CDCl3): δ -4479.4 (d, 1JPt-P ) 1744 Hz). Anal.
Calcd for C45H48N2P2Br2Pt: C, 52.29; H, 4.68; N, 2.71. Found:
C, 52.34; H, 4.61; N, 2.67.
2
3
cis-[Pt{C6H2(SnMe3)-4-(CH2NMe2)2-2,5}2] (20). A solution
of cis-12 (67 mg, 0.09 mmol) in THF (15 mL) was cooled to
-35 °C, after which n-BuLi (0.36 mmol, 0.53 M in hexane, 0.7
mL, 4.0 equiv) was added. After 15 min at this temperature,
the reaction mixture was quenched with [SnBrMe3] (0.4 mmol,
0.50 M in THF, 0.8 mL, 4.4 equiv). The mixture was stirred
for 1 h at room temperature and extracted with a CH2Cl2/brine
mixture. A white solid was obtained after evaporation of the
solvents, which was purified using column chromatography
over silica (CH2Cl2/NEt3 ) 97:3). Yield of 20: 53 mg (0.06
mmol, 67%). 1H NMR (C6D6): δ 0.45 (s, 2JSn-H ) 53 Hz, 18H,
SnCH3), 2.06 (s, 2JSn-H unresolved, 12H, CH2NCH3-5), 2.13 (s,
12H, CH2NCH3-2), 3.44 (s, 2JSn-H ) unresolved, 4H, CH2NCH3-
5), 3.51 (s, 4H, CH2NCH3-2), 7.53 (s, 3JSn-H ) 56 Hz, 2H, ArH-
3), 7.82 (s, 3JPt-H ) 20 Hz, 4JSn-H ) 62 Hz, 2H, ArH-6). 13C{1H}
NMR (C6D6): δ -7.2 (1JSn-C ) 338 and 353 Hz, SnCH3), 45.3
(CH2NCH3-2), 49.5 (CH2NCH3-5), 67.0 (CH2NCH3-2), 73.6
(CH2NCH3-5), 129.5, 133.7, 140.5, 142.3, 142.8, 146.9. 195Pt-
{1H} NMR (CDCl3): δ -3412.1. Anal. Calcd for C30H54N4-
PtSn2: C, 39.89; H, 6.03; N, 6.20. Found: C, 39.83; H, 5.95;
N, 6.16.
trans-[PtCl(C6H3Br-4-{CH2NMe2}-2)(SEt2)] (17). The syn-
thesis of 17 is similar to the synthesis of 10, starting from 5
(1.28 g, 3.8 mmol) in Et2O (40 mL) with n-BuLi (2.3 mL, 1.6
M in hexane, 3.7 mmol, 0.98 equiv) and [PtCl2(SEt2)2] (1.62 g,
3.63 mmol, 0.97 equiv). The reaction mixture was concentrated
in vacuo, dissolved in CH2Cl2, and filtered over Celite. After
removal of the solvent in vacuo and washing with pentane (5
mL, 3×), 17 was obtained as an off-white powder, with 5% of
cis-10 as impurity. The complexes were separated by column
chromatography over silica (CH2Cl2/pentane ) 90:10, Rf(17)
) 0.57, Rf(cis-10) ) 0.73). Yield of 17: 1.47 g (2.75 mmol, 76%).
1H NMR (CDCl3): δ 1.38 (m, 6H, SCH2CH3), 2.86 (m, 2H,
SCH2CH3), 2.98 (s, 3JPt-H ) 34.8 Hz, 6H, NCH3), 3.27 (m, 2H,
SCH2CH3), 3.90 (s, 3JPt-H ) 41.7 Hz, 2H, CH2N), 7.09 (d, 2JH-H
2
) 8 Hz, 1H, ArH-5), 7.16 (s, 1H, ArH-3), 7.26 (d, JH-H ) 8
3,5-Bis(tert-butylsulfidomethyl)bromobenzene (22). So-
dium (1.14 g, 49.6 mmol) was dissolved in EtOH (150 mL),
and t-BuSH (5.5 mL, 48.8 mmol, 0.98 equiv) was added. This
mixture was heated to reflux for 30 min, after which 21 (8.35
g, 24.35 mmol, 0.50 equiv) was added. The reaction was heated
to reflux for 16 h. The white suspension was concentrated,
extracted with pentane, washed with brine, dried over MgSO4,
and evaporated in vacuo. Yield of 22 as an off-white solid: 7.79
g (21.6 mmol, 89%). 1H NMR (CDCl3): δ 1.33 (s, 18H, CCH3),
3.68 (s, 4H, CH2S), 7.25 (s, 1H, ArH-4), 7.35 (s, 2H, ArH-2,6).
13C{1H} NMR (CDCl3): δ 31.0 (CCH3), 32.9 (CH2S), 43.2
(CCH3), 122.4 (ArC-1), 128.4 (ArC-4), 130.5 (ArC-2,6), 141.1
(ArC-3,5). Anal. Calcd for C16H25BrS2: C, 53.17; H, 6.97; S,
17.74. Found: C, 53.25; H, 6.89; S, 17.65.
Hz, 3JPt-H ) 60 Hz 1H, ArH-6). 13C{1H} NMR (CDCl3): δ 13.3
(SCH2CH3), 31.9 (SCH2CH3), 52.4 (NCH3), 74.5 (2JPt-C ) 51
Hz, CH2N), 117.3 (ArC-4), 124.6 (3JPt-C ) 37 Hz, ArC-3),
128.3 (3JPt-C ) 62 Hz, ArC-5), 133.3 (1JPt-C ) 1077 Hz, ArCipso),
133.5 (2JPt-C ) 68 Hz, ArC-6), 149.6 (ArC-2). 195Pt{1H}
NMR (CDCl3): δ -3699.8. Anal. Calcd for C13H21BrClN-
PtS: C, 29.25; H, 3.97; N, 2.62. Found: C, 29.23; H, 3.89; N,
2.49.
Reaction of 17 with 16 to Yield 10. To a solution of 5
(0.25 g, 0.74 mmol) in Et2O (20 mL) was added n-BuLi (1.6 M
in hexane, 0.45 mL, 0.72 mmol, 1.0 equiv) at -78 °C. After 5
min, solid 17 (0.36 g, 0.67 mmol, 0.9 equiv) was added and
the mixture was allowed to warm to room temperature and
stirred for 3 h. After standard workup, 0.25 g of 10 (0.40 mmol,
60%) was obtained in a cis/trans ratio of 80:20, after analysis
by NMR spectroscopy.
3,5-Bis(tert-butylsulfidomethyl)pinacolboraneben-
zene (23). To a solution of 22 (4.16 g, 11.5 mmol) in Et2O (100
mL) was added t-BuLi (16 mL, 24 mmol, 2.1 equiv, 1.5 M in
hexane) at -78 °C. The reaction mixture was stirred at this
temperature for 20 min, after which B(OMe)3 (2.0 mL, 17.5
mmol, 1.5 equiv) was added dropwise. The mixture was slowly
warmed to room temperature overnight. Pinacol (1.43 g, 12.1
mmol, 1.1 equiv) was added, followed by HOAc (0.7 mL, 12.1
mmol, 1.1 equiv) after 10 min. The reaction mixture was
stirred for 1 h and filtered, and the solvents were evaporated
in vacuo. The product was washed with MeOH (10 mL, 2×)
and evaporated to dryness, after which 23 was obtained as a
[PtI2(C6H3Br-4-{CH2NMe2}-2)2] (18). Complex cis-10
(33 mg, 0.054 mmol) was dissolved in CH2Cl2 (1 mL). To
this I2 (4.0 mL, 0.014 M in toluene, 0.056 mmol, 1.0 equiv)
was added dropwise. A dark red-orange precipitate was
formed immediately. After 1 h stirring, the precipitate was
isolated, washed with Et2O (5 mL, 2×), and dried in vacuo.
1
Yield of 18: 45 mg (0.051 mmol, 94%). H NMR (CDCl3): δ
3
3
2.78 (s, JPt-H ) 10 Hz, 12H, NCH3), 4.04 (s, JPt-H ) 11 Hz,
4H, CH2N), 7.07-7.23 (m, 6H, ArH). Anal. Calcd for C18H22-
Br2I2N2Pt: C, 24.71; H, 2.53; N, 3.20. Found: C, 24.86; H, 2.47;
N, 3.12.
1
white solid. Yield: 3.31 g (8.1 mmol, 70%). H NMR (CDCl3):
cis-[Pt(η1-C6H3Br-4-{CH2NMe2}-2)2(η2-dppp)] (19). To a
solution of cis-10 (63.6 mg, 102 µmol) in CH2Cl2 (6 mL) was
added dppp (42.2 mg, 102 µmol, 1.0 equiv) at room tempera-
ture. The solution was stirred for 4 h at room temperature,
δ 1.33 (s, 12H, OCCH3), 1.35 (s, 18H, SCCH3), 3.74 (s, 4H,
CH2S), 7.46 (s, 1H, ArH-4), 7.62 (s, 2H, ArH-2,6). 13C{1H} NMR
(CDCl3): δ 25.0 (OCCH3), 31.0 (SCCH3), 33.3 (CH2S), 43.0
(SCCH3), 83.9 (OCCH3), 132.8, 134.0, 138.0. Anal. Calcd for

2958 Organometallics, Vol. 24, No. 12, 2005
Amijs et al.
C22H37BO2S2: C, 64.69; H, 9.13; S, 15.70. Found: C, 64.70; H,
8.92; S, 15.51.
temperature, and filtered over Celite. The mixture was diluted
with CH2Cl2 (50 mL) and stirred with brine (20 mL) for 1 h.
The organic layer was collected, dried over MgSO4, and
evaporated to dryness. A concentrated solution of the remain-
ing solid in CH2Cl2 was prepared. Slow distillation of Et2O into
this mixture afforded pure 25 as light yellow crystals or a
powder. Crystals suitable for X-ray structure determination
were obatined by cooling a saturated solution of 25 in a
mixture of CH2Cl2/Et2O (10:1) at -30 °C. Yield: 102 mg
(0.078mmol, 56%). 1H NMR (CDCl3): δ 1.61 (s, 36H, CCH3)3),
2.84 (s, 12H, NCH3), 3.94 (s, 4H, CH2N), 4.21 (s, 8H, CH2S),
7.18 (m, 8H, ArH), 7.52 (d, 3JH-H ) 7 Hz, 2H, ArH-6). 13C{1H}
NMR (CDCl3): δ 30.8 (CCH3), 42.8 (CCH3), 50.3 (NCH3), 52.1
(CH2S), 73.8 (CH2N), 119.6, 119.7, 124.2, 134.5, 138.6, 139.2
(Cipso, Pt), 148.3, 150.3, 157.1 (Cipso, Pd). 195Pt{1H} NMR
(CDCl3): δ -3381.4. Anal. Calcd for C50H70N2S4Cl2PtPd2: C,
45.98; H, 5.40; N, 2.14; S, 9.82. Found: C, 46.08; H, 3.84; N,
2.03; S, 9.74.
cis-[Pt(dmba-4-SCS{t-Bu})2] (24). Complex cis-10 (280
mg, 0.45 mmol), 23 (391 mg, 0.96 mmol, 2.1 equiv), [PdCl2-
dppf] (21 mg, 0.029 mmol, 6%), and Na2CO3 (266 mg, 2.51
mmol, 5.6 equiv) were introduced in a Schlenk flask, which
was evacuated for 30 min. To this, a degassed mixture of DME
(10 mL), THF (10 mL), and H2O (10 mL) was added. The
reaction mixture was stirred at 70 °C until the reaction was
complete ((3 h). The reaction mixture was cooled to room
temperature, extracted with CH2Cl2 (50 mL), dried over
MgSO4, and evaporated to dryness. The product was purified
by column chromatography (basic alumina, CH2Cl2, Rf ) 1.0)
and subsequently washed with hexane and Et2O (5 mL, 3×).
Complex 24 was isolated as a white solid. Yield: 0.36 g (0.35
mmol, 78%). 1H NMR (CDCl3): δ 1.37 (s, 36H, CCH3), 2.84 (s,
12H, NCH3), 3.80 (s, 8H, CH2S), 3.95 (s, 4H, CH2N), 7.25 (m,
3
6H, ArH), 7.46 (s, 4H, ArH-8,12), 7.55 (d, JH-H ) 9 Hz, 2H,
ArH-6). 13C{1H} NMR (CDCl3): δ 31.1 (CCH3), 33.6 (CH2S),
43.0 (CCH3), 50.3 (NCH3), 73.8 (CH2N), 120.0, 124.7, 125.9,
127.6, 134.8, 138.6, 139.0, 139.2 (Cipso), 142.6, 148.0. 195Pt{1H}
NMR (CDCl3): δ -3385.8. Anal. Calcd for C50H72N2S4Pt: C,
58.62; H, 7.08; N, 2.73; S, 12.52. Found: C, 58.47; H, 7.19; N,
2.78; S, 12.46.
Acknowledgment. M.L. and A.L.S. kindly acknowl-
edge the Netherlands Organization for Scientific Re-
search (NWO) for financial support.
Supporting Information Available: CIF files for the
X-ray structural data of complexes cis-12‚Et2O, cis-14‚xC6H6,
19, and 25‚xCH2Cl2. This material is free of charge via the
Internet at http://pubs.acs.org.
cis-[Pt(dmba-4-{PdCl(SCS{t-Bu})})2] (25). To a solution
of 24 (145 mg, 0.14 mmol) in degassed MeCN (30 mL) was
added [Pd(NCMe)4](BF4)2 (125 mg, 0.28 mmol, 2.0 equiv). After
10 min NEt3 (39 µL, 0.28 mmol, 2.0 equiv) was added. The
reaction mixture was heated at reflux for 2 h, cooled to room
OM050144S