Platinum(II) chloride complexes of linear alkyl-bridged 2,2′-bipyridine/catechol ligands

Article abstract of DOI:10.1002/(SICI)1521-3749(199908)625:8<1343::AID-ZAAC1343>3.0.CO;2-H

Platinum(II) chloride can selectively be coordinated to the 2,2′-bipyridine moiety of the alkyl bridged sequential catechol/2,2′-bipyridine ligand 1 a-H₂ and of the related ligands 1a/b-Me₂ and 2. Reaction of (1b-Me₂)PtCl₂ with BBr₃ produces the platinum(II) complex (1b-H₂)PtCl₂ while ether cleavage of the uncoordinated ligand 1b-Me₂ fails. Under basic conditions (1a-H₂)PtCl₂ forms polymeric/ oligomeric species [(1a)Pt]_n besides traces of the dinuclear complex [(1a)Pt]₂.

Full text of DOI:10.1002/(SICI)1521-3749(199908)625:8<1343::AID-ZAAC1343>3.0.CO;2-H

Platinum(II) Chloride Complexes of Linear Alkyl-bridged
2,2'-Bipyridine/Catechol Ligands
Markus Albrecht* a, Cyrill Riethera, and Roland FroÈhlichb
a Karlsruhe, Institut fuÈr Organische Chemie der UniversitaÈt
b MuÈnster, Organisch-Chemisches Institut der UniversitaÈt
Received February 5th, 1999.
Abstract. Platinum(II) chloride can selectively be coordi-
nated to the 2,2'-bipyridine moiety of the alkyl bridged se-
quential catechol/2,2'-bipyridine ligand 1 a-H2 and of the re-
lated ligands 1 a/b-Me2 and 2. Reaction of (1 b-Me2)PtCl2
with BBr3 produces the platinum(II) complex (1 b-H2)PtCl2
while ether cleavage of the uncoordinated ligand 1 b-Me2
fails. Under basic conditions (1 a-H2)PtCl2 forms polymeric/
oligomeric species [(1 a)Pt]n besides traces of the dinuclear
complex [(1 a)Pt]2.
Keywords: 2,2'-Bipyridine; Catechol; Platinum; Sequential li-
gands
Platin(II)-chlorid-Komplexe von linearen alkylverbruckten
È
Bipyridin/Brenzkatechin-Liganden
InhaltsuÈbersicht. Platin(II)-chlorid kann selektiv an die 2,2'-
Bipyridineinheit des sequentiellen alkylverbruÈckten Brenz-
katechin/2,2'-Bipyridin-Liganden 1 a-H2 und der analogen
Derivate 1 a/b-Me2 und 2 binden. Die Reaktion von (1 b-
Me2)PtCl2 mit BBr3 fuÈhrt zu dem Platin(II)-Komplex (1 b-
H2)PtCl2, waÈhrend die Etherspaltung bei dem freien Ligan-
den 1 b-Me2 fehlschlaÈgt. Bei der Reaktion von (1 a-H2)PtCl2
mit Base werden neben Spuren des zweikernigen Komplexes
[(1 a)Pt]2 polymere bzw. oligomere Spezies [(1 a)Pt]n erhal-
ten.
Introduction
Just recently linear sequential ligands with two or
more different binding sites for metal cations became
important building-blocks in metallo-supramolecular
chemistry [1±5]. Using such ligands it is possible to de-
sign supramolecular functional devices which allow to
investigate into energy transfer processes [2] or elec-
trochemical switches [3]. In the self-assembly of heli-
cates or helicate-type complexes the orientation of the
sequential ligands can be controlled by the choice of
appropriate metals or combinations of metals [4, 5].
We introduced alkyl-bridged 2,2'-bipyridine/cate-
chol ligands 1-H2 which can bind iron(II) ions using
the bipyridine moieties to form tris(bipyridine)iron(II)
complexes which possess uncoordinated catechol units
as substituents. On the other hand, the same ligands
in the presence of titanium(IV) ions and potassium
carbonate form a tris(catecholato)titanium(IV) com-
plex with ªfreeº bipyridine units [6].
Fig. 1 Selective binding of FeII-ions to the 2,2'-bipyridine-
and of TiIV-ions to the catecholate-binding site of 1 a-H2.
Results and Discussion
Ligand Syntheses
The ligands 1-H2 and 1-Me2 were prepared as de-
scribed before [6]. The derivative 2 was synthesized as
depicted in Scheme 1 starting from 4-t-butylcatechol 3
(s. Scheme 1).
In a mannich-type reaction 3 is transformed into
the N-morpholino derivative 4 [7]. The catechol unit
is protected as the benzophenone ketale by reaction
of 4 with dichlorodiphenyl methane to obtain 5 [8].
Phenylchloroformate reacts with 5 and substitutes the
morpholino substituent by chloride and the benzyl
chloride 6 is isolated [9]. Ligand 2 is formed upon
reaction with in situ lithiated 5,5'-dimethyl-2,2'-bi-
In this paper we discuss the coordination behavior
of the ligands 1-H2 and 1-Me2 towards the plati-
num(II) chloride and the X-ray structure of [(2)PtCl2]
is presented.
* Priv.-Doz. Dr. Markus Albrecht,
Institut fuÈr Organische Chemie der UniversitaÈt,
Richard-WillstaÈtter-Allee,
D-76131 Karlsruhe,
Fax: Int. Code + (7 21)69 85 29,
E-mail: albrecht@ochhades.chemie.uni-karlsruhe.de
Z. Anorg. Allg. Chem. 1999, 625, 1343±1348 Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999 0044±2313/99/6251343±1348 $ 17.50+.50/0 1343

M. Albrecht, C. Riether, R. FroÈhlich
Table 1 Preparation of platinum(II) chloride complexes
Platinum(II) complex
R =
Yield
[(1 a-Me2)PtCl2]
[(1 a-H2)PtCl2]
[(1 b-Me2)PtCl2]
[(2)PtCl2]
2-(2,3-dimethoxyphenyl)ethyl
2-(2,3-dihydroxyphenyl)ethyl
6-(2,3-dimethoxyphenyl)hexyl
2-(5-tbutyl-2,3-((diphenyl-
80%
100%
72%
68%
methylene)dioxy)phenyl)ethyl
free catechol unit [(1 b-H2)PtCl2]. This ether cleavage
reaction only proceeds if the platinum complex is
used. If similar reaction conditions are applied to the
free ligand 1 b-Me2, the BBr3 attacks the bipyridine
unit leading to an unspecific decomposition of the mo-
lecule. Thus the PtCl2-moiety acts as a protecting
group for the 2,2'-bipyridine unit of 1 b.
Scheme 1
pyridine [6]. All our attempts (e. g.: H+/H2O [10]; H2/
Pd±C [11]; (HOCH2)2/H+ [12]) to cleave the ketale
moiety of 2 failed. However, the protected ligand 2
was used for comparison studies.
Scheme 2
All PtCl2 complexes give characteristic 1H and
13C NMR spectra and can be characterized by mass
spectrometry. Molar peaks are detected at m/z = 599
([(1 a-Me2)PtCl2]; EI), 573 ([(1 a-H2)PtCl2H]+, FAB(+)),
656 ([(1 b-Me2)PtCl2H]+, FAB(+)), 593 ([(1 b-H2) ´
PtCl2H]+, FAB(+)), and 792 ([(2)PtCl2H]+, FAB(+)).
(1 b-H2)PtCl2 is not obtained in analytically pure form
because of a partial exchange of chloro by bromo substi-
tuents at platinum during BBr3 deprotection.
Preparation of Coordination Compounds
The PtCl2 complexes are synthesized by reaction of
the 2,2'-bipyridine derivatives 1 and 2 with potassium
tetrachloroplatinate(II) in 1 M hydrochloric acid [13].
The complexes [(1 a-Me2)PtCl2], [(1 a-H2)PtCl2], [(1 b-
Me2)PtCl2], and [(2)PtCl2] are obtained as yellow so-
lids which precipitate and are isolated by filtration
and recrystallized from acetone/diethyl ether. The co-
ordination compounds are isolated in good to excel-
lent yields (Table 1).
X-ray Structural Analysis of [(2)PtCl2]
The PtCl2 complex [(1 b-Me2)PtCl2] by reaction
with BBr3 and workup with hydrochloric acid can be
transformed into the corresponding derivative with a
The complexes [(1)PtCl2] crystallize from acetone/
diethyl ether in the form of yellow plates. Due to the
two dimensional character of the crystals we were not
1344
Z. Anorg. Allg. Chem. 1999, 625, 1343±1348

Platinum(II) Chloride Complexes
(Table 2) are in accordance with those observed for
related (bipyridine)platinum(II) chloride complexes
[14]. The plane of the aromatic moiety of the pro-
tected t-butylcatechol substituent which is attached to
the Pt-complex unit via an ethylene spacer is twisted
by 53.1° compared to the plane of the square planar
complex unit.
In the unit cell two of the molecules [(2)PtCl2] are
oriented anti-parallel to each other with an Pt±Pt se-
Ê
paration of 3.92 A. Due to the sterically hindered side
chain this distance is large compared to the one ob-
Ê
served for [(bpy)PtCl2] (dPt±Pt = 3.40 A) [14]. The
chloro substituents of one of the molecules [(2)PtCl2]
in the solid state are located on top of the plane of
the bipyridine unit of the second complex which is
reasonable because of electrostatic interactions.
Attempts to Synthesize [(1 a)Pt]2
(2,2'-Bipyridine)(catecholato)platinum(II) derivatives
are prepared by reaction of (2,2' bipyri-
dine)platinum(II) chloride with catechol in the pre-
sence of base [15]. Reaction of [(1 a-H2)PtCl2] with
methanolic KOH in acetone leads to the precipitation
of a purple solid material which is insoluble in com-
mon solvents. In propylene carbonate it can be partly
dissolved at elevated temperatures. However, UV-
spectroscopy of the solution indicates that decomposi-
tion of the (catecholato)(bipyridine)platinum complex
takes place upon dissolution.
Fig. 2 Molecular structure of [(2)PtCl2] in the solid state
and representation of the corresponding unit cell.
Table 2 Selected bond lengths and angles of [(2)PtCl2]
Ê
Distance A
Angle °
Pt±Cl1
Pt±Cl2
Pt±N1
Pt±N2
Pt ´ ´ ´ Pt
2.298(3)
2.291(3)
2.002(8)
2.019(8)
3.92
Cl1±Pt±Cl2
N1±Pt±N2
Cl1±Pt±N1
Cl2±Pt±N2
89.25(10)
79.9(4)
95.6(3)
95.2(3)
able to obtain an X-ray structural analysis of one of
the derivatives [(1)PtCl2]. The derivative [(2)PtCl2] on
the other hand led to crystals which were suitable to
determine an X-ray structure.
[(2)PtCl2] ´ 0.5 H2O crystallizes in the triclinic space
group P 1 (Z = 2) with the cell constants a = 8.273(1),
Ê
b = 9.485(3), c = 21.467(4) A, a = 101.51(2), b =
90.86(2), c = 100.05(2)°. The structure was refined to
R = 0.045. The crystal contains half a molecule of
water per asymmetric unit.
The central part of [(2)PtCl2] is the square planar
(2,2'-bipyridine)platinum(II) chloride moiety. The an-
gles and bond length which are found for [(2)PtCl2]
Scheme 3
Z. Anorg. Allg. Chem. 1999, 625, 1343±1348
1345

M. Albrecht, C. Riether, R. FroÈhlich
10.0 mmol) are heated to 170 °C for 20 minutes. The ob-
tained derivative 5 is recrystallized from methanol. Yield:
2.79 g (65%).
For the insoluble material an elemental analysis is ob-
tained which is consistent with the composition
ª[(1 a)Pt]2 ´ 8 H2Oº and FAB(+) mass spectrometry
shows the presence of the dinuclear species [(1 a)Pt]2
(HRMS: calcd. 998.1720, found 998.1514). However,
the insolubility of the material indicates that only
traces of the dinuclear complex are formed while
mainly oligomers or polymers are produced during
the reaction. Attempts to optimize the reaction condi-
tions (high temperatures, high dilution conditions) did
not lead to isolable quantities of the pure dinuclear
complex [(1 a)Pt]2.
M. p. 166±167 °C ± 1H NMR (CDCl3): d = 7.62 (m, 4 H), 7.40±7.34 (m,
6 H), 6.88 (d, J = 1.9 Hz, 1 H), 6.83 (d, J = 1.9 Hz, 1 H), 3.72 (t, J = 4.5 Hz,
4 H), 3.61 (s, 2 H), 2.50 (t, J = 4.5 Hz, 4 H), 1.29 (s, 9 H). ± 13C NMR
(CDCl3): d = 146.7 (C), 145.0 (C), 143.8 (C), 140.7 (C), 129.0 (CH), 128.2
(CH), 126.4 (CH), 119.8 (CH), 117.6 (C), 116.3 (C), 105.3 (CH), 67.1
(CH2), 57.0 (CH2), 53.3 (CH2), 34.6 (C), 31.7 (CH3).
± IR (KBr):
m = 2967, 2851, 1485, 1450, 1295, 1119, 1070, 760 cm±1. ± MS (EI, 70 eV):
m/z = 429 (34%) [M]+, 344 (100%), 287 (15%), 262 (51%). ± High resolu-
tion MS calcd. for C28H31NO3: 429.2304; found: 429.2293. ± Calcd. for
C
28H31NO3 ´ 1/2 CH3OH: C 76.82; H 7.47, N 3.14; found: C 76.84, H 7.23,
N 3.51.
5-tButyl-1,2-[(diphenylmethylene)dioxy]-3-(chloromethyl)-
benzene (6). Compound 5 (215 mg, 0.50 mmol) is dissolved
in phenyl chloroformate (118 mg, 0.75 mmol) and heated for
20 h to 120 °C. The mixture is dissolved in hexane and fil-
tered over silica gel to obtain after removal of the solvent 6
as a white solid. Yield: 160 mg (85%).
The isolation of mixtures of oligomeric as well as
dimeric species shows, that here not a selective self-as-
sembly process but unspecific complex formation
takes place. Unfortunately the ligand 1 a does not al-
low to control the assembly of the complexes by addi-
tion of e. g. appropriate templates as was recently
done to obtain defined metalla-cryptates instead of
complex mixtures of coordination compounds [16].
M. p. 97 °C ± 1H NMR (CDCl3): d = 7.62 (m, 4 H), 7.39 (m, 6 H), 6.92 (d,
J = 1.8 Hz, 1 H), 6.84 (d, J = 1.8 Hz, 1 H), 4.66 (s, 2 H), 1.28 (s, 9 H). ±
13C NMR (CDCl3): d = 147.1 (C), 145.6 (C), 143.2 (C), 140.3 (C), 129.1
(CH), 128.2 (CH), 126.4 (CH), 118.7 (CH), 117.5 (C), 117.2 (C), 106.8
(CH), 40.9 (CH2), 34.7 (C), 31.5 (CH3). ± IR (KBr): m = 2965, 2868, 1486,
1451, 1430, 1267, 1063 cm±1. ± MS (EI, 70 eV): m/z = 380/378 (21/100%)
[M]+, 365/363 (26/81%), 343 (17%), 303/301 (49/15%), 165 (37%). ± High
resolution MS calcd. for C24H23ClO2: 378.1387; found: 378.1401. ± Calcd.
for C24H23ClO2: C 76.08; H 6.12; found: C 75.87, H 6.27.
Conclusions
Platinum(II) chloride complexes [(1-H2)PtCl2], [(1-
Me2)PtCl2], and [(2)PtCl2] can be prepared by stan-
dard methods. In [(1-H2)PtCl2] the platinum(II) chlor-
ide selectively binds to the 2,2'-bipyridine units while
an uncoordinated catecholate moiety still is present.
Complexes of this type are ideal precursors for the
formation of large polymetallic arrays using the cate-
chol sites for further binding to other metal centers.
Reaction of [(1 a-H2)PtCl2] with base does not pro-
duce significant amounts of the desired dinuclear pla-
tinum complex [(1 a)Pt]2. However, this dinuclear spe-
cies can be characterized by mass spectrometry as one
component of the formed mixture of oligomers or
polymers.
5-(2-{5-tButyl-2,3-[(diphenylmethylene)dioxy]phenyl}ethyl)-
5'-methyl-2,2'-bipyridine (2). 1.6 M n BuLi in hexane (1.3 ml,
2.08 mmol) at 0 °C is added to a solution of diisopropyl
amine (0.3 ml, 2.30 mmol) in 5 ml of dry THF. The mixture
is cooled to ±78 °C and 5,5'-dimethyl-2,2'-bipyridine (382 mg,
2.07 mmol) in 10 ml of THF is added. At 0 °C this mixture is
transferred to a solution of 6 (786 mg, 2.07 mmol) in 40 ml
of THF. After 65 h at room temperature the solvent is re-
moved and the residue is dissolved in dichloromethane,
washed with water and dried (MgSO4). 2 is obtained by col-
umn chromatography (hexane/ethyl acetate/Et3N 20 : 1 : 2) as
a yellow solid. Yield: 221 mg (21%).
M. p. 64±65 °C ± 1H NMR (CDCl3): d = 8.50 (m, 1 H), 8.46 (m, 1 H), 8.23
(m, 2 H), 7.62±7.55 (m, 6 H), 7.33 (m, 6 H), 6.82 (d, J = 1.7 Hz, 1 H), 6.56
(d, J = 1.7 Hz, 1 H), 3.01 (m, 4 H), 2.39 (s, 3 H), 1.22 (s, 9 H). ± 13C NMR
(CDCl3): d = 154.2 (C), 153.8 (C), 149.6 (CH), 149.4 (CH), 146.7 (C),
142.9 (C), 140.7 (C), 137.4 (CH), 136.9 (CH), 136.8 (C), 133.1 (C), 129.0
(CH), 128.2 (CH), 126.3 (CH), 120.9 (C), 120.4 (CH), 120.3 (CH), 119.1
(CH), 116.2 (C), 104.5 (CH), 34.6 (C), 33.0 (CH2), 31.8 (CH2), 31.6
(CH3), 18.4 (CH3). ± IR (KBr): m = 2962, 1488, 1467, 1450, 1206, 1065,
1021, 834, 700 cm±1. ± MS (EI, 70 eV): m/z = 526 (100%) [M]+, 511
(32%), 449 (13%), 343 (34%), 184 (14). ± High resolution MS calcd. for
The X-ray structure of [(2)PtCl2] shows that
the square-planar (2,2'-bipyridine)dichloroplatinum
units staple in the solid state and lead to columns with
Ê
Pt±Pt separations of 3.92 and 5.21 A.
Experimental Part
C
36H34N2O2: 526.2620; found: 526.2634. ± Calcd. for C36H34N2O2:
General
C 82.10; H 6.51, N 5.32; found: C 81.95, H 6.49, N 4.69.
IR: Bruker IFS 88. ± EI (70 eV) or FAB(+) MS/HRMS:
Finnigan MAT 90; matrix for FAB(+): 3-nitrobenzoic acid
(3-NBA). ± UV/Vis: Perkin Elmer UV-Vis Lambda 2. ±
1H NMR and 13C NMR (BB/DEPT): Bruker DRX 500 or
AM 400; internal standard: CHCl3, HD2CC(=O)CD3, or
HD2CS(=O)CD3.
General Procedure for the Preparation
of (2,2'-Bipyridine)platinum(II) Chloride Complexes
Equimolar amounts of the 2,2'-bipyridine ligand and of po-
tassium tetrachloroplatinate in a mixture of 10 M HCl and
ethanol (10 : 1) are heated to reflux. The yellow precipitate is
collected, washed with a small amount of water and recrys-
tallized from acetone/diethyl ether.
5-tButyl-3-(morpholinomethyl)benzene-1,2-diol (4). Com-
pound 4 was prepared in 84% yield according to a literature
procedure [7].
[(1 a-Me2)PtCl2]
5-tButyl-1,2-[(diphenylmethylene)dioxy]-3-(N-morpholinome-
Yield: 23 mg (80%). ± 1H NMR (dmso-d6): d = 9.24 (br, 1 H), 9.21 (br,
thyl)benzene (5). The catechol derivative
4
(2.65 g,
10.0 mmol) and dichlorodiphenyl methane (1.92 ml,
1 H), 8.38 (m, 2 H), 8.19 (m, 2 H), 6.96 (m, 1 H), 6.89 (m, 1 H), 6.78 (m,
1346
Z. Anorg. Allg. Chem. 1999, 625, 1343±1348

Platinum(II) Chloride Complexes
±1
Ê
1 H), 3.77 (s, 3 H), 3.71 (s, 3 H), 3.32 (s, 3 H), 3.02 (t, J = 7.7 Hz, 2 H), 2.91
(t, J = 7.7 Hz, 2 H). ± 13C NMR (dmso-d6): d = 154.6 (C), 154.1 (C), 152.4
(C), 147.9 (CH), 147.6 (CH), 146.6 (C), 141.3 (C), 140.7 (CH), 140.2
(CH), 137.9 (C), 133.3 (C), 123.8 (CH), 123.4 (CH), 123.3 (CH), 121.6
(CH), 111.3 (CH), 60.1 (CH3), 55.6 (CH3), 33.0 (CH2), 30.2 (CH2), 18.3
(CH3). ± IR (KBr): m = 3051, 2939, 2838, 1584, 1479, 1271, 1080, 1013, 829,
754 cm±1. ± UV/Vis (methanol): k = 198, 261, 276, 318, 331 nm. ± MS (EI,
70 eV): m/z = 600 (0.2%) [M]+, 334 (100%). ± High resolution MS calcd.
lected (± h, ± k, ± l), [(sin h)/k] = 0.59 A , 5702 independent
and 3146 observed reflections [I ³ 2r(I)], 401 refined para-
meters, R = 0.045, wR2 = 0.085, max. residual electron density
0.99 (±0.70) e A , hydrogens calculated and refined as riding
±3
Ê
atoms, hydrogens of the water molecule could not be located.
Data set was collected with an Enraf Nonius CAD4 dif-
fractometer on a rotating anode generator. Programs used:
data reduction MolEN, structure solution SHELXS-86,
structure refinement SHELXL-93, graphics SCHAKAL-92.
Crystallographic data (excluding structure factors) for the
structures reported in this paper have been deposited with
the Cambridge Crystallographic Data Centre as supplemen-
tary publication no. CCDC-102662. Copies of the data can
be obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: int.
code + 44(12 23)3 36-0 33, e-mail: deposit@ccdc.cam.ac.uk].
for
C
21H22Cl2N2O2Pt: 599.0707; found: 599.0674.
±
Calcd. for
C
21H22Cl2N2O2Pt: C 42.01, H 3.69, N 4.67; found: C 41.86, H 3.69, N 4.70.
[(1 a-H2)PtCl2]
Yield: 574 mg (quant.). M.p. 209±212 °C (dec.). ± 1H NMR (acetone-d6):
d = 9.49 (m, 1 H), 9.43 (m, 1 H), 8.37 (br, OH), 8.23 (m, 2 H), 8.17 (m,
1 H), 8.12 (m, 1 H), 7.34 (br, OH), 6.73 (m, 1 H), 6.65±6.57 (m, 2 H), 3.15
(m, 2 H), 3.03 (m, 2 H), 2.55 (s, 3 H). ± 13C NMR (acetone-d6): d = 156.5
(C), 156.2 (C), 150.2 (CH), 150.0 (CH), 146.2 (C), 144.9 (C), 143.5 (C),
141.8 (CH), 141.3 (CH), 139.6 (C), 128.4 (C), 124.3 (CH), 124.2 (CH),
122.7 (CH), 120.8 (CH), 115.1 (CH), 34.3 (CH2), 32.5 (CH2), 19.4 (CH3).
± IR (KBr): m = 3372, 2924, 1609, 1595, 1477, 1282, 1250, 827, 781, 725,
717 cm±1. ± UV/Vis (methanol): k(e) = 198 (96800), 261 (36900), 275
(40000), 319 (19000), 332 nm (25900). ± MS (FAB(+), 3-NBA): m/z = 573
[M + H]+, 536 [M±Cl]+. ± Calcd. for C19H18Cl2N2O2Pt: C 39.87, H 3.17,
N 4.89; found: C 39.53, H 3.26, N 4.89.
[(1 b-H2)PtCl2]
At 0 °C a 1 M solution of BBr3 in CH2Cl2 (0.2 ml) is added
to [(1 b-Me2)PtCl2] (17.1 mg, 0.026 mmol) in 5 ml of CH2Cl2.
The mixture is allowed to warm to room temperature and is
stirred for 15 hours. Methanol (2 ml) is added and solvent is
removed in vacuo. The residue is refluxed in 2 N HCl. The
product is isolated by filtration and recrystallized from
acetone/diethyl ether. [(1 b-H2)PtCl2] can not be obtained
in analytically pure form due to the presence of traces of
[(1 b-H2)PtClBr].
[(1 b-Me2)PtCl2]
Yield: 47 mg (72%). M. p. 185±188 °C. ± 1H NMR (acetone-d6): d = 9.53 (d,
J = 1.8 Hz, 1 H), 9.48 (br s, 1 H), 8.33 (d, J = 8.3 Hz, 1 H) 8.32 (d,
J = 8.2 Hz, 1 H), 8.24 (dd, J = 8.3, 1.8 Hz, 1 H), 8.21 (dd, J = 8.2, 1.1 Hz,
1 H), 6.94 (t, J = 7.9 Hz, 1 H), 6.84 (dd, J = 7.9, 1.5 Hz, 1 H), 6.76 (dd,
J = 7.9, 1.5 Hz, 1 H), 3.82 (s, 3 H), 3.76 (s, 3 H), 2.86 (m, 2 H), 2.61 (m,
2 H), 2.56 (s, 3 H), 1.73 (m, 2 H), 1.57 (m, 2 H), 1.49±1.43 (m, 4 H). ±
13C NMR (acetone-d6): d = 153.8 (C), 152.9 (C), 149.6 (CH), 149.2 (CH),
148.2 (C), 144.2 (C), 143.4 (C), 141.1 (CH), 140.5 (CH), 139.0 (C), 136.9
(C), 124.4 (CH), 123.8 (CH), 123.7 (CH), 122.7 (CH), 111.3 (CH), 60.6
(CH3), 56.0 (CH3), 33.4 (CH2), 31.5 (CH2), 31.3 (CH2), 30.7 (CH2), 18.7
(CH3), two CH2-signals are hidden under the solvent peak. ± IR (KBr):
m = 3055, 2923, 2855, 1609, 1582, 1481, 1429, 1262, 1226, 1082, 1058, 1020,
836, 797, 765 cm±1. ± UV/Vis (methanol): k = 198, 260, 275, 318, 331 nm. ±
MS (FAB(+), 3-NBA): m/z = 656 [M + H]+, 621 [M ± Cl]+. ± High resolu-
tion MS calcd. for C25H30Cl2N2O2Pt: 655.1333; found: 655.1392. ± Calcd.
for C25H30Cl2N2O2Pt: C 45.75, H 4.61, N 4.27; found: C 46.05, H 4.79,
N 4.54.
Yield: 12.8 mg (~ 78%). ± 1H NMR (acetone-d6): d = 9.74 (d, J = 1.8 Hz,
1 H), 9.69 (dd, J = 1.3, 0.6 Hz, 1 H), 8.32 (d, J = 8.3 Hz, 1 H), 8.31 (d,
J = 8.2 Hz, 1 H), 8.27 (s, OH), 8.23±8.18 (m, 2 H), 7.11 (s, OH), 6.68 (dd,
J = 7.3, 2.0 Hz, 1 H), 6.59 (dd, J = 7.6, 2.0 Hz, 1 H), 6.57 (dd, J = 7.6,
7.3 Hz, 1 H), 2.85 (m, 2 H), 2.61 (m, 2 H), 2.54 (s, 3 H), 1.73 (m, 2 H), 1.62
(m, 2 H), 1.44 (m, 4 H). ± 13C NMR (acetone-d6): d = 155.8 (C), 155.6 (C),
150.7 (CH), 150.4 (CH), 145.4 (C), 144.1 (C), 143.5 (C), 141.1 (CH), 140.5
(CH), 139.0 (CH), 130.1 (C), 124.4 (CH), 124.0 (CH), 121.9 (CH), 119.9
(CH), 113.8 (CH), 33.4 (CH2), 31.2 (CH2), 30.6 (CH2), 30.5 (CH2), 18.7
(CH3), two CH2-signals are hidden under the solvent peak.
± MS
(FAB(+), 3-NBA): m/z = 593 [M ± Cl]+.
[(2)PtCl2]
Attempt to Synthesize [(1 a)2Pt2]
Yield: 27 mg (68%). M. p. 238 °C. ± 1H NMR (dmso-d6): d = 9.26 (br s,
1 H), 9.25 (d, J = 1.6 Hz, 1 H), 8.33 (d, J = 8.3 Hz, 1 H), 8.29 (d, J = 8.3 Hz,
1 H), 8.21 (d, J = 8.3 Hz, 1 H), 8.06 (dd, J = 8.3, 1.8 Hz, 1 H), 7.44 (d,
J = 7.5 Hz, 4 H), 7.35 (t, J = 7.5 Hz, 4 H), 7.26 (t, J = 7.5 Hz, 2 H), 6.87 (d,
J = 1.7 Hz, 1 H), 6.74 (d, J = 1.7 Hz, 1 H), 3.11 (t, J = 7.2 Hz, 2 H), 2.99 (t,
J = 7.2 Hz, 2 H), 1.20 (s, 9 H), CH3-signal is hidden under solvent peak. ±
13C NMR (dmso-d6): d = 154.6 (C), 154.2 (C), 147.9 (CH), 147.8 (CH),
145.9 (C), 145.2 (C), 142.4 (C), 140.8 (C), 140.7 (CH), 140.2 (CH), 140.1
(C), 138.0 (C), 129.0 (CH), 128.4 (CH), 125.6 (CH), 123.3 (CH), 123.0
(CH), 120.0 (C), 119.1 (CH), 115.5 (C), 104.5 (CH), 34.5 (C), 32.5 (CH2),
31.4 (CH3), 29.9 (CH2), 18.3 (CH3). ± IR (KBr): m = 3047, 2962, 2867,
1644, 1609, 1488, 1477, 1450, 1430, 1206, 1020, 754, 704, 642 cm±1. ± UV/
Vis (methanol): k = 193, 262, 278, 318, 332 nm. ± MS (FAB(+), 3-NBA):
A 1 M solution of KOH in methanol (1.1 ml) is added to
10 ml of acetone and the mixture is heated to reflux. A solu-
tion of [(1 a-H2)PtCl2] (31.7 mg, 0.055 mmol) in 120 ml of
acetone is added slowly. After the addition is complete, the
mixture is heated for another 15 h. A purple precipitate is
formed, which is collected and successively washed with
water, methanol and acetone and dried in vacuo. Yield:
ª25.6 mg (81%).º
IR (KBr): m = 3051, 2924, 2512, 1794, 1476, 1267, 877, 830, 713 cm±1. ± MS
(FAB(+), 3-NBA): m/z = 998 [M]+. ± High resolution MS calcd. for
m/z = 792 [M + H]+, 756 [M ± Cl]+.
± Calcd. for C36H34Cl2N2O2Pt ´
C
38H32N4O4Pt2: 998.1720; found: 998.1514. ± Calcd. for C38H32N4O4Pt2 ´
0.5 H2O: C 53.94, H 4.40, N 3.49; found: C 53.71, H 4.20, N 3.10.
8 H2O: C 39.93, H 4.23, N 4.90; found: C 39.75, H 3.90, N 5.08.
X-ray Structural Analysis of [(2)PtCl2] ´ 0.5 H2O
Financial support by the Fonds der Chemischen Industrie
and the Deutsche Forschungsgemeinschaft is gratefully ac-
knowledged.
X-ray quality crystals of [(2)PtCl2] ´ 0.5 H2O were obtained by
slow diffusion of diethyl ether into a solution of [(2)PtCl2] in
wet acetone. Formula C36H34N2O2Cl2Pt ´ 1/2 H2O, M = 801.65,
yellow crystal, 0.1 ´ 0.1 ´ 0.03 mm, a = 8.273(1), b = 9.485(3),
Literatur
Ê
Ê
c = 21.467(4) A, a = 101.51(2), b = 90.86(2), c = 100.05(2)°,
3
V = 1632.1(6) A , qcalc = 1.640 g ´ cm±3, F(000) = 794 e, l =
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Ê
k = 0.71073 A, T = 293 K, x/2 h scans, 6134 reflections col-
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