Synthesis and characterization of diacetyl platinum(II) complexes with two primary and secondary amine ligands

Article abstract of DOI:10.1016/j.jorganchem.2012.05.043

[Pt(COMe)₂(bpy)] (2; bpy = 2,2′-bipyridine) and [Pt(COMe)₂{H(Me)dmg}] (5; H(Me)dmg = MeO-NC(Me)-C(Me)N-OH) were found to react with primary and secondary amines yielding diacetyl platinum(II) complexes with two monodendate amine ligands [Pt(COMe)₂(NH ₂R)₂] (R = Bn, 3a; CH₂CH₂Ph, 3b; Et, 3c; i-Pr, 3d; CH₂CHCH₂, 3e; Cy, 3f; Bn = benzyl, Cy = cyclohexyl) and [Pt(COMe)₂(NHR₂)₂] (R = Me, 6a; Et, 6b), respectively. The equilibrium of these ligand exchange reactions was investigated by NMR experiments and DFT calculations showing that complex 5 is the more preferable starting complex and a large excess of the amine has to be used. The sterically demanding diisopropylamine was found to react with 5 yielding a thermally highly unstable dinuclear bis(acetyl) bridged complex [{Pt(COMe){NH(i-Pr)₂}}₂(μ-COMe)₂] (7). Analogous reactions with ethylenediamine derivatives resulted in the formation of [Pt(COMe)₂(N^N)] (N^N = ethylenediamine, en, 8a; N,N′-dimethylethylenediamine, 8b; N,N-dimethylethylenediamine, 8c; N,N,N′,N′-tetramethylethylenediamine, TMEDA, 8d). All complexes were fully characterized by microanalysis/high-resolution ESI mass spectrometry, by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopies as well as by single-crystal X-ray diffraction measurements (3a/3d). Due to the high trans influence of the acetyl ligands, the Pt-N bonds were found to be relatively long (2.164(2)-2.182(3) ). The resulting weak coordination of the amines gave rise to a decomposition of complexes 3 under CO extrusion yielding carbonyl-methyl complexes.

Full text of DOI:10.1016/j.jorganchem.2012.05.043

Journal of Organometallic Chemistry 715 (2012) 93e101
Contents lists available at SciVerse ScienceDirect
Journal of Organometallic Chemistry
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Synthesis and characterization of diacetyl platinum(II) complexes with two
primary and secondary amine ligands
,
Tim Kluge a, Martin Bette a, Cornelia Vetter a, Jürgen Schmidt b, Dirk Steinborn a
*
a Institute of Chemistry e Inorganic Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 2, D-06120 Halle, Germany
b Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120 Halle, Germany
a r t i c l e i n f o
a b s t r a c t
[Pt(COMe)2(bpy)] (2; bpy ¼ 2,20-bipyridine) and [Pt(COMe)2{H(Me)dmg}] (5; H(Me)dmg ¼ MeOeN]C(Me)
eC(Me)]NeOH) were found to react with primary and secondary amines yielding diacetyl platinum(II)
complexes with two monodendate amine ligands [Pt(COMe)2(NH2R)2] (R ¼ Bn, 3a; CH2CH2Ph, 3b; Et, 3c; i-Pr,
3d; CH2CH]CH2, 3e; Cy, 3f; Bn ¼ benzyl, Cy ¼ cyclohexyl) and [Pt(COMe)2(NHR2)2] (R ¼ Me, 6a; Et, 6b),
respectively. The equilibrium of these ligand exchange reactions was investigated by NMR experiments and
DFT calculations showing that complex 5 is the more preferable starting complex and a large excess of the
amine has to be used. The sterically demanding diisopropylamine was found to react with 5 yielding
Article history:
Received 11 April 2012
Accepted 30 May 2012
Keywords:
Organoplatinum complexes
Acetyl ligands
Amine ligands
Ligand substitution
Quantum chemical calculations
a thermally highly unstable dinuclear bis(acetyl) bridged complex [{Pt(COMe){NH(i-Pr)2}}2(m-COMe)2] (7).
Analogous reactions with ethylenediamine derivatives resulted in the formation of [Pt(COMe)2(N^N)]
(N^N ¼ ethylenediamine, en, 8a; N,N0-dimethylethylenediamine, 8b; N,N-dimethylethylenediamine,
8c; N,N,N0,N0-tetramethylethylenediamine, TMEDA, 8d). All complexes were fully characterized by
microanalysis/high-resolution ESI mass spectrometry, by NMR (1H, 13C, 195Pt) and IR spectroscopies as
well as by single-crystal X-ray diffraction measurements (3a/3d). Due to the high trans influence of the
ꢀ
acetyl ligands, the PteN bonds were found to be relatively long (2.164(2)e2.182(3) A). The resulting
weak coordination of the amines gave rise to a decomposition of complexes 3 under CO extrusion
yielding carbonylemethyl complexes.
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
their tetranuclear solid-state structures, to platinum blue complexes
with central Pt/Pt (d8/d8) closed shell interactions [5]. The only
Dinuclear platina-
b
-diketones such as the parent complex 1
exception proved to be the reaction of 1 with hexamethyldisilazane
which resulted under deprotonation of OeH/O bridges and
cleavage of chloride to the formation of a coordination polymeric
diacetyl platinum(II) complex IV (Scheme 1, D) [6]. Due to its very
weak PteO bonds, complex IV undergoes readily ligand exchange
reactions with formation of [Pt(COMe)2L2] complexes, among them
the formation of type II complexes (Scheme 1, E) and of the diace-
tylbis(benzylamine) complex 3a (Scheme 1, F) [6].
(Scheme 1), which can be regarded as hydroxycarbene complexes
stabilized by intramolecular OeH/O hydrogen bonds, are easily
accessible from hexachloroplatinic acid and silylated alkynes [1].
Complex1 provedtobeaversatilestartingcomplex forthesyntheses
both of diacetyl platinum(II) and platinum(IV) complexes. Thus,
reactions with bidentate N^N donors such as 2,20-bipyridine led to
extraordinarily stable diacetylhydridoplatinum(IV) complexes I
(Scheme 1, reaction path A) [2] from which, with bases, under
cleavage of HCl diacetyl platinum(II) complexes II were obtained
Organyl platinum(II) complexes with bidentate amine ligands
are very well known, whereas those with two monodentate amine
ligands are rare; examples are [Pt(C6X5)2(NH2R)2] (R ¼ Ph, Bn;
(Scheme 1, B) [3]. In contrast to this, reactions of the platina-b-
diketone1 withmonodentate amines, irrespectivewhether primary,
secondary, or tertiary amines (such as NH2(n-Bu), NH(i-Pr)2, NEt3)
X ¼ F, Cl) [7] and [PtCl(L-
k
C5)(NH2Me)2] (HL ¼ 1,3-dimethyluracil)
[8]. Here, we report on a straightforward synthesis and character-
ization of diacetyl platinum(II) complexes with two monodentate
primary or secondary amine ligands (or, alternatively, with one
ethylenediamine derivative as ligand) via ligand substitution
starting from type II complexes. Furthermore, DFT calculations give
an insight into which factors affect the substitution of the bidentate
N^N ligand by two monodentate amines.
were used, resulted in the formation of platina-
b-diketonates of
platina- -diketones III (Scheme 1, C) [4], which resemble, due to
b
* Corresponding author. Tel.: þ49 345 55 25620; fax: þ49 345 55 27028.
E-mail address: dirk.steinborn@chemie.uni-halle.de (D. Steinborn).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2012.05.043

94
T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
aromatic amines (NH2Ph, NH2(p-Et-C6H4)) did not react at all with
[Pt(COMe)2(bpy)] (2), even not in the neat liquids.
The complexes 3aef were fully characterized by NMR (1H, 13C,
195Pt) and IR spectroscopy, by microanalysis and high-resolution
ESI mass spectrometry, respectively, as well as by single-crystal
X-ray diffraction analyses (3a/3d). The solids proved to be stable
at ꢀ40 ꢁC at least for several months but at room temperature for
few hours only. A thermoanalysis (TG) of complex 3a revealed that
the decomposition starts at 120 ꢁC yielding Pt (mass loss found
61.1%, calc. 60.6%). At room temperature, solutions of complexes
3aef in methylene chloride or THF decompose within 2e6 h with
the formation of platinum black.
In the case of complexes 3a, 3d and 3f, as intermediates
carbonylemethyl complexes, [Pt(COMe)Me(NH2R)(CO)] (R ¼ Bn,
4a; i-Pr, 4d; Cy, 4f; Scheme 2, B), were identified by NMR and IR
spectroscopy as well as by high-resolution ESI mass spectrometry.
Likely, complexes 4 were formed after cleavage of one amine ligand
by CO extrusion from an acetyl ligand. Although there is no
experimental proof, DFT calculations made clear that the configu-
ration (SP-4-3) given in Scheme 2 is the most stable one. Thus, for
the model complex [Pt(COMe)Me(NH2Me)(CO)] this configuration
Scheme 1. Reactivity of the platina-b-diketone 1 toward N,N donors and amines.
2. Results and discussion
2.1. Syntheses and characterization
showed a preference in the D
Gꢁ values (in CH2Cl2 as solvent) over
the other two configurations (SP-4-4/SP-4-2) by 4.9/5.5 kcal/mol
(see Supplemental material).
The diacetyl(2,20-bipyridine)platinum(II) complex 2 was found
to react in neat primary amines NH2R (R ¼ Bn, CH2CH2Ph, Et, i-Pr,
CH2CH]CH2, Cy) with substitution of the bidentate bipyridine
ligand by two amine ligands (Scheme 2, A). The resulting diace-
tylbis(amine) platinum(II) complexes 3aef could be isolated as
colorless powders in yields between 40 and 95%. The excess of the
amines as realized in the neat liquids is crucial for the success of
these substitution reactions: As exemplified with NH2R (R ¼ Bn, i-
Pr), in solution (such as chloroform or methylene chloride) even
with a 10-fold excess of the amine, no complexes 3a/3d could be
isolated. An equilibrium between 2 and 3a/3d could be detected 1H
NMR spectroscopically (see Paragraph 2.3). In contrast, secondary
and tertiary alkyl amines (NHEt2, NH(i-Pr)2, NHBu2, NEt3) and
The diacetyl platinum(II) complex [Pt(COMe)2{H(Me)dmg}] (5)
having coordinated instead of the 2,20-bipyridine ligand the weaker
coordinating diacetyldioxime mono methyl ether ligand, was found
to react in neat secondary amines NHR2 (R ¼ Me, Et) yielding the
complexes [Pt(COMe)2(NHR2)2] (6a/b) (Scheme 2, C). As shown in
reactions with benzyl and isopropyl amine, [Pt(COMe)2{H(Me)dmg}]
(5) also reacts with primary amines yielding complexes 3a and 3d,
respectively, even in methylene chloride and chloroform solutions
(Scheme 2, D). With the tertiary amine NEt3 only decomposition
under formation of platinum black was observed.
Complexes 6a/b were isolated as colorless powders in moderate
yields (70/45%). At room temperature, the solids decompose within
Scheme 2. Synthesis routes to acetyl platinum(II) complexes bearing amine and diamine ligands.

T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
95
2
10e60 min and solutions in chloroform and methylene chloride
within few minutes under formation of platinum black. The iden-
tities of the complexes 6a/b were confirmed by NMR (1H, 13C, 195Pt)
and IR spectroscopy and by microanalysis or high-resolution ESI
mass spectrometry, respectively.
(19.1e26.8 Hz) and JPt,C (351e397 Hz) coupling constants. Only
in the case of complex 8c bearing the unsymmetrically substituted
N,N-dimethylethylenediamine ligand, two sets of signals for the
acetyl ligands were found. The platinum chemical shifts dPt (ꢀ3272
to ꢀ3439) are in the range of typical diacetyl platinum(II)
complexes [6].
A special case is the reaction of complex 5 with neat diisopro-
pylamine, which resulted in the formation of the complex
NMR spectra of the thermally less stable dinuclear complex 7
were measured at ꢀ40 and ꢀ70 ꢁC in CD2Cl2. For the acetyl ligands,
both in the 1H and 13C NMR spectra two sets of signals were found
(Table 1). In accord with data given for an iridium complex [9],
likely, the carbonyl carbon atom signals at lower (253.4 ppm) and
higher (214.6 ppm) field had to be assigned to the bridging and the
terminal acetyl ligands, respectively. The presence of only one
signal in the 195Pt NMR spectra (dPt ꢀ3138 ppm), both at ꢀ40 and
at ꢀ70 ꢁC, gave proof of a symmetric structure of the complex.
At ꢀ70 ꢁC, in the 1H and 13C NMR spectra for the methyl groups of
the diisopropylamine ligand four sets of signals (dH ¼ 1.07/1.12/
1.37/1.83; dC ¼ 19.6/20.1/23.0/23.4) were found and for the two CH
groups two sets (dH ¼ 3.25, br, overlapping with NH; dC ¼ 47.2/47.4).
At ꢀ40ꢁC, signalbroadeningalongwithareductionofthenumber
of signals (see Experimental) exhibits a dynamic process. This could
be (with respect to the NMR time scale) a fast ligand exchange
(NH(i-Pr)2) reaction and/or an inversion of the six-membered
Pt2C2O2 ring. In other diacetyl-bridged metal complexes, rings of
this type have a boat conformation [9]. DFTcalculations on the model
[{Pt(COMe){NH(i-Pr)2}}2(m-COMe)2] (7) in 85% yield (Scheme 2, E).
Complex 7 proved to be highly temperature sensitive. At room
temperature, even the solid was found to decompose within 1 h
and CHCl3/CH2Cl2 solutions within 5 min. Analytical and NMR (1H,
13C, 195Pt) spectroscopical data exhibited that complex 7 is an
bis(acetyl) bridged dimer. NMR spectroscopically, complex 7 was
shown to react with 2,20-bipyridine and pyridine under bridge
cleavage to yield the well known mononuclear complexes 2 and
[Pt(COMe)2(py)2] [6], respectively. On the other hand, with DMSO
or D2O no reactions were observed.
Ethylenediamine (en) and its methylated derivatives (N,N0-di-
methylethylenediamine; N,N-dimethylethylenediamine; N,N,N0,N0-
tetramethylethylenediamine, TMEDA) were also found to react with
the precursor complex 5 (Scheme 2, F). By cleavage of the H(Me)dmg
ligand, complexes [Pt(COMe)2(N^N)] (8aed) were formed. They
were isolated as colorless products in moderate yields (30e90%) and
fully characterized by the established analytical and spectroscopical
methods. At room temperature, all complexes are stable in the solid
state. The diacetyleTMEDA complex 8d proved also to be stable in
chloroform solution, whereas the other complexes 8aec undergo
decomposition within a few hours. A solution of complex 2 with
ethylenediamine became immediately colorless (8a), with the
doubly methylated derivatives in several minutes (8bec) and with
TMEDA only after one day (8d), which indicates a reaction, but in all
cases no isolation was attempted.
complex [{Pt(COMe)(NHMe2)}2(m-COMe)2], in which the isopropyl
groups in complex 7 were replaced by methyl groups, showed that
the boat conformation is energetically favored by
D
Gꢁ ¼ 5.9 kcal/mol
over the planar conformation and by
D
Gꢁ ¼ 6.8 kcal/mol over the
chair conformation. Furthermore, the SP-4-4 configuration (as
depicted in Scheme 2) is energetically favored over the SP-4-3 isomer
by more than 40 kcal/mol. Thus, the latter one must not be taken into
account.
At room temperature, 1H and 195Pt NMR spectroscopically,
a decomposition of 7 into the coordination polymer [{Pt(COMe)2}n]
(IV) [6] and noncoordinated diisopropylamine was found, which is
an indication for the fast ligand exchange reaction discussed before.
In the IR spectrum of complex 7, two strong C]O bands
2.2. Spectroscopic characterization
Characteristic 1H, 13C and, 195Pt NMR spectroscopic data of the
mononuclear diacetyl platinum complexes with amine ligands
(3aef, 6a/b, 8aed) were compiled in Table 1. In order to accom-
modate the restricted thermal stability of complexes 6a/b, the NMR
spectra were measured at ꢀ40 ꢁC. The 1H and 13C NMR spectra of all
complexes confirmed their identities; all signals were found in the
expected shift range with correct intensities in the 1H NMR spectra.
As in other diacetyl platinum(II) complexes with trans standing
nitrogen ligands [3], the acetyl ligands showed characteristic 3JPt,H
(
nCO ¼ 1514,1608 cmꢀ1) were observed. The vibrationwith the lower
wavenumber (1514 cmꢀ1) is in accord with those of the bridging
acetyl ligands in platina-
b-diketonates of platina-b-diketones,
[Cl2Pt(
m
-COMe)2Pt{(COMe)2H}]ꢀ
(
nCO ¼ 1524e1534 cmꢀ1) [4] and in
the iridium complex [Ir2H2{PPh2(o-C6H4CO)}2{m-PPh2(o-C6H4CO)}2]
(
nCO ¼ 1504 cmꢀ1) [9]. The vibration at 1608 cmꢀ1 has to be assigned
to the terminal acetyl ligands.
The methylecarbonyl complexes, [Pt(COMe)Me(NH2R)(CO)]
(4a,d,f), being identified as intermediates of the decomposition of
complexes 3 (Scheme 2), showed chemical shifts characteristic for
the methyl ligand PteCH3 (dH ¼ 0.24e0.29; dC ¼ 3.4) and IR bands
characteristic for carbonyl ligands (nCO ¼ 2048e2061 cmꢀ1).
Furthermore, high-resolution ESI mass spectra (cationic mode) of
the corresponding complexes 3 showed, apart from the molecular
peaks of 3 ([M þ H]þ) and other peaks, also the molecular peaks of 4
([M0 þ H]þ) with the correct isotopic pattern. Likely, these findings
can be explained in terms of the restricted thermal stability of 3 and
the thermal load during the ESI measurements.
Table 1
Selected NMRa spectroscopic parameters of the complexes [Pt(COMe)2L2] (3aef, 6a/
b, 8aed) and [{Pt(COMe){NH(i-Pr)2}}2(m-COMe)2] (7) (d in ppm, J in Hz).
Amine ligand
dH (3JPt,H
COCH3
)
dC (2JPt,C
COCH3
)
dC (1JPt,C
)
dPt
CO
3a
3b
3c
3d
3e
3f
NH2Bn
NH2CH2CH2Ph
NH2Et
NH2(i-Pr)
NH2CH2CHCH2
NH2Cy
2.15 (22.0)
2.21 (19.1)
2.21 (23.2)
2.21 (23.0)
2.18 (22.7)
2.20
2.05 (25.0)
2.04 (20.7)
2.22 (22.4)
44.1 (372)
44.3 (356)
44.5
44.3 (367)
44.2 (362)
44.3 (351)
43.5
43.4
44.5
44.9 (351)
232.6
ꢀ3329
233.8 (1275) ꢀ3299
234.5
233.7
ꢀ3274
ꢀ3304
233.6 (1295) ꢀ3272
234.0
229.5
230.0
240.6
ꢀ3296
ꢀ3439
ꢀ3399
ꢀ3337
6ab NHMe2
6bb NHEt2
8a
8b
8c
H2NCH2CH2NH2
MeHNCH2CH2NHMe 2.31 (19.3)
Me2NCH2CH2NH2
2.3. On the equilibrium between complexes 2/5 and the amine
complexes 3/6/8/9
238.7 (1233) ꢀ3293
2.05 (25.7); 43.8 (397); 224.3;
ꢀ3347
2.19 (20.8)
2.10 (26.8)
1.90; 2.05
44.1 (363)
43.6 (393)
42.2; 43.7
234.3
The formation of the diacetylbis(amine) complexes 3 from the
8d
7c
Me2NCH2CH2NMe2
NH(i-Pr)2
228.5 (1283) ꢀ3430
diacetyl(2,20-bipyridine) complex
2 according to Scheme 2
214.6; 253.4 ꢀ3138
(pathway A) proved to be an equilibrium reaction. With the ben-
zylamine ligand, the equilibrium constant (2 þ 2NH2Bn # 3a þ bpy)
was estimated 1H NMR spectroscopically to be in the order of
a
If not otherwise noted, in CDCl3 at room temperature.
In CD2Cl2 at ꢀ40 ꢁC.
b
c
In CD2Cl2 at ꢀ70 ꢁC.

96
T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
Table 2
Table 3
(D
Gꢁ) and with
ꢀ
Selected bond lengths (in A) and angles (in deg) of the calculated equilibrium
structures 2* and 3a* (gas phase) in comparison with data obtained by X-ray
diffraction measurements of complexes 2a and 3a.
Standard Gibbs free energies (in kcal/mol) in the gas phase
consideration of CH2Cl2 as solvent (
D
Gꢁsolv) of the reactions according to Scheme 3.
Starting complex
2* (N^N ¼ bpy)
Gꢁ
5* (N^N ¼ H(Me)dmg)
2*
1.991
1.991
2.194
2.194
1.219
1.219
2
3a*
1.989
1.989
2.232
2.232
1.226
1.226
3a
2 L in [Pt(COMe)2L2]
D
D
Gꢁ
D
Gꢁ
D
Gꢁ
solv
solv
PteC
PteN
C]O
1.991(8)/1.986(8)
1.99(1)/2.011(9)
2.099(7)/2.119(7)
2.138(8)/2.116(7)
1.22(1)/1.21(1)
1.22(1)/1.23(1)
91.7(4)/88.2(4)
95.6(3)/96.7(3)
95.9(3)/97.8(3)
76.8(3)/77.0(3)
54.3(4)/73.9(3)
78.4(5)/84.3(6)
1.979(2)
2NH2Bn (3a*)
2.3
2.2
4.7
22.8
ꢀ3.0
ꢀ2.4
ꢀ1.3
0.8
4.7
4.1
8.7
2.3
2.2
4.7
0.6
0.0
4.6
20.9
ꢀ8.8
ꢀ7.6
ꢀ6.2
ꢀ3.8
2NH2Me (3g*)
2NHMe2 (6a*)
2NMe3 (9*)
2.164(2)
1.210(3)
25.0
ꢀ4.7
ꢀ3.5
ꢀ2.1
0.3
22.8
ꢀ2.9
ꢀ2.3
ꢀ1.3
0.8
en (8a*)
MeHNCH2CH2NHMe (8b*)
Me2NCH2CH2NH2 (8c*)
TMEDA (8d*)
CePteC
CePteN
90.6
98.1
91.8(1)
87.8(1)
97.7
97.7
74.7
47.9
47.9
84.1
84.0
93.9
32.4
32.4
NePteN
3
92.7(1)
53.9(1)
3
a
Fig. 1 along with selected structural parameters in the figure
caption. The asymmetric unit of complex 3d contains two
symmetry independent molecules with very similar structures.
One of them is shown in Fig. 2, selected distances and angles are
given in the figure caption.
Taken from Ref. [3].
magnitude of 10ꢀ3e10ꢀ4 L/mol, thus corresponding to a Gibbs free
energy G of about 4e6 kcal/mol. In accordance with that, synthesis
D
The platinum centers in the two complexes are square-planar
coordinated by two nitrogen and two carbon atoms (sum of
angles around Pt: 360.1ꢁ, 3a; 360.1/360.0ꢁ,2 3d) in mutual cis
position (configuration index: SP-4-2). The acetyl ligands include
an angle with the complex plane of 53.9ꢁ (3a) as well as 52.4/72.1ꢁ
and 74.2/75.3ꢁ, respectively (3d). They are oriented in a “transoid”
conformation, meaning that the oxygen atoms of the two acetyl
ligands are lying on different sides of the complex plane.
of 3a required a large excess of the amine as realized in neat NH2Bn.
To get further insight into ligand substitution reactions
according to Scheme 2, DFT calculations using the mPW1PW91
functional [10] and highly qualitative basis sets as well as an ECP for
Pt have been performed. The comparison of structural data of the
calculated complexes 2* and 3a*1 (representing structures in the
gas phase) with those obtained by X-ray diffraction measurements
of crystals of 2 and 3a exhibited a good agreement (Table 2).
Table 3 shows the calculated standard Gibbs free energies in the
ꢀ
While the C]O bond lengths (1.210(3)e1.224(5) A) are in
the range of other structurally characterized acetyl platinum(II)
gas phase (
D
Gꢁ) and in methylene chloride solution (
D
Gꢁsolv) for
ꢀ
ꢀ
complexes (median: 1.214 A; lower/upper quartile 1.193/1.228 A;
number of observations 29 [11]), the PteC bonds
reactions according to Scheme 3. Noteworthy, the
D
Gꢁ values are
n
¼
essentially the same, irrespective whether 2* (N^N ¼ bpy) or 5*
(N^N ¼ H(Me)dmg) is used as starting complex. Considering
solvent effects (CH2Cl2), in all cases, in full accord with the exper-
imental findings, the substitution of the H(Me)dmg ligand in
complex 5* proved to be thermodynamically more favorable than
that of the bpy ligand in complex 2* (DDGꢁsolv ca. 4.1 kcal/mol). In
ꢀ
ꢀ
(1.976(4)e1.985(4) A) are relatively short (median: 2.003 A; lower/
ꢀ
upper quartile 1.986/2.019 A; n ¼ 29 [11]). In accord with the high
trans influence of the acetyl ligands, the PteN bonds are relatively
ꢀ
long (2.164(2)e2.182(3) A). Thus, in platinum(II) complexes with
halido and phosphane ligand trans to a primary amine ligand, PteN
ꢀ
bond lengths of 2.041 A (median; lower/upper quartile 2.030/
the following, only the D
Gꢁsolv values will be discussed.
ꢀ
ꢀ
2.057 A; n ¼ 268, [11]) and 2.108 A (median; lower/upper quartile
ꢀ
Ligand exchange reactions according to Scheme 3 will be ther-
modynamically more feasibleintheorder tertiaryamine < secondary
amine < primary amine < diamine. Thus, for instance, starting from
complex 5*, the reactions with NMe3 and NHMe2 are strongly and
weakly endergonic, those with primary amines (NH2Bn, NH2Me) are
thermoneutral and those with diamines are exergonic. In good
agreement with the experiment (4e6 kcal/mol), for the reaction of 2*
2.095/2.121 A; n ¼ 50; [11]), respectively, were found. Organyl
ꢀ
ligands in trans position give rise to PteN bond lengths of 2.127 A
ꢀ
(median; lower/upper quartile 2.098/2.136 A; n ¼ 30, [11]).
In crystals of 3a intermolecular interactions were found (Fig. 3).
The phenyl rings of the benzylamine ligands are
p stacked as
indicated by the centroidecentroid distance of the phenyl rings
ꢀ
(3.724(2) A) and the angle between the centroidecentroid vector
with benzylamine
D
Gꢁ
¼ 4.7 kcal/mol was calculated. Obviously,
and the normal to the plane (10.3ꢁ) [12]. Furthermore, intermo0-0
solv
lecular NeH/O00 hydrogen bonds (N/O00 2.926(3) A; NeH/O
ꢀ
this endergonicity could be overcome in the experiments by a large
excess of the amine. Thus, starting from 2, in neat primary amines
(NH2Bn, NH2Me) and starting from 5 even in neat secondary amines
(NHMe2) the diacetylbis(amine) complexes could be prepared
(cf. Scheme 2). Furthermore, on the one hand, neither starting from 2
nor from 5, the tertiary amine NMe3 underwent a ligand substitution
reaction and all ethylenediamine derivatives were prone to ligand
exchange both with 2 and 5 as starting complex on the other.
153ꢁ) were observed [13]. In crystals of 3d, the molecules are
connected by a two-dimensional network of weak intermolecular
0
0
0
ꢀ
NeH/O hydrogen bonds (N/O 2.939(5)e3.190(5) A; NeH/O
134e177ꢁ). The two protons in the NH2 groups act as hydrogen
donors and the carbonyl oxygen atoms as hydrogen acceptors such
that bifurcated hydrogen bonds are formed.
2.5. Conclusion
2.4. Structural characterization
The present investigation shows that diacetylbis(amine)plati-
num(II) complexes bearing two monodendate and bidendate
primary and secondary amine ligands can be synthesized by ligand
exchange reactions according to Scheme 2. Due to the higher purity
[Pt(COMe)2(NH2Bn)2] (3a) and [Pt(COMe)2(NH2i-Pr)2] (3d) were
found to crystallize in the monoclinic crystal system in the space
group I2/a and P21/c, respectively. Molecules of 3a exhibit crystal-
lographically imposed C2 symmetry. Their structure is shown in
2
Here and in the following the values for the two symmetry independent
1
Here and in the following, calculated complexes are marked with a star.
molecules are given separated by a slash.

T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
97
Scheme 3. Equilibrium between the precursor complexes 2*/5* and amine complexes 3*, 6*, 8*, and 9*.
of the products and the easier accessibility of the starting
complexes, this method is superior to the synthesis route starting
from the coordination polymer IV (Scheme 1, F).
The formation of the dinuclear twofold acetyl-bridged complex 7
in the reaction of 5 with diisopropylamine is unique. As the Gibbs
free energies shown in Scheme 4 exhibit, the formation of the
(hypothetical) mononuclear complex [Pt(COMe)2L2] (L ¼ NH(i-Pr)2)
is energetically much more disfavored than that with L ¼ NHMe2
Both the experimental results and DFTcalculationsgave proof that
the starting complex with the diacetyldioxime mono methyl ether
ligand (5) is more prone to ligand substitution than that with the
bipyridine ligand (2), indicating a weaker coordination of the
H(Me)dmgligandthanthe bpyligand. Interestingly, calculation of the
dissociation process [Pt(COMe)2(N^N)] (2/5) / [Pt(COMe)2] þ N^N
made clear, that this is caused by solvent effects: Whereas the
dissociation energies for the two processes are nearly identical
(
DDGꢁ
¼ 9.3 kcal/mol; solvent: CH2Cl2), likely due to steric
solv
reasons (see above). On the other hand, in the case of diisopropyl-
amine, the formation of the dinuclear acetyl-bridged complex 7 is
strongly favored over the corresponding (hypothetical) complex
with L ¼ NHMe2 (DDGꢁ
¼ 18.3 kcal/mol).
solv
Summing up, complexes [Pt(COMe)2L2] (L ¼ amine), which are
easily accessible, have two substitutionally labile ligands at their
disposal and might be envisioned as suitable starting complexes for
synthesizing other diacetyl platinum complexes as has been shown
(
D
E ¼ 32.0/32.7 kcal/mol, 2/5), the Gibbs free energies in CH2Cl2 as
solventaresignificantlydifferent(
D
Gsolv ¼ 10.1/6.0kcal/mol,2/5).The
order NH2R > NHR2 [ NR3 for the readiness of the substitution
reactions might be primarily caused by an increasing sterical
hindrance in the complexes.
The weakness of the amine coordination (NHR2 > NH2R) will also
be obvious in a fast decomposition reaction, whereas for primary
amines an extrusion of CO from an acetyl ligand yielding
acetylecarbonylemethyl complexes could be proved. This is
preceded by the cleavage of one amine ligand which is favored in all
these complexes by the high trans influence of the acetyl ligand [14].
Fig. 2. Molecular structure of one of the two symmetry independent molecules of
[Pt(COMe)2(NH2i-Pr)2] (3d) (displacement ellipsoids at 30% probability). Selected
ꢀ
distances (A) and angles (deg); the values for the two symmetry independent mole-
cules are given separated by a slash: PteC1 1.985(4)/1.982(4), PteC3 1.976(4)/1.977(4),
PteN1 2.176(3)/2.174(3), PteN2 2.177(3)/2.182(3), N1eC5 1.476(6)/1.477(6), N2eC8
1.489(6)/1.471(6), C1eO1 1.224(5)/1.222(5), C3eO2 1.219(5)/1.224(5), C1ePteC3
89.1(2)/87.5(2), C1ePteN2 91.3(2)/93.8(2), N2ePteN1 88.3(1)/87.7(1), N1ePteC3
91.4(2)/91.0(2), PteN1eC5 117.3(3)/118.6(3), PteN2eC8 119.9(2)/121.1(3).
Fig. 1. Molecular structure of [Pt(COMe)2(NH2Bn)2] (3a). Ellipsoids are shown at the
ꢀ
30% probability level. Selected distances (A) and angles (deg): PteC1 1.979(2), PteN
2.164(2), C1eO 1.210(3), NeC3 1.459(4), C1ePteC10 91.8(1), C1ePteN 87.8(1), NePteN0
92.7(1), C3eNePt 115.2(2).

98
T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
3.2. Synthesis of [Pt(COMe)2(NH2R)] (3aef)
To [Pt(COMe)2(bpy)] (2) (150 mg, 0.3 mmol) the respective
primary amine NH2R (1 mL, ca. 10 mmol) was added with stirring.
The resulting red solutions became colorless within 10e20 min.
Further stirring for 1 h resulted in the precipitation of complexes
[Pt(COMe)2(NH2R)2] (R ¼ Bn, 3a; CH2CH2Ph, 3b; Cy, 3f). To
complete the precipitation and to precipitate the other complexes
(R ¼ Et, 3c; i-Pr, 3d; CH2CH]CH2 3e), respectively, diethyl ether
(3 mL) was added. Then, the solids were filtered off, washed with
cold (ꢀ10 ꢁC) diethyl ether (2 ꢂ 1 mL), and dried in vacuo. Analo-
gously, instead of complex 2, [Pt(COMe)2{H(Me)dmg}] (5) can be
used as starting material.
Fig. 3. Solid-state structure of [Pt(COMe)2(NH2Bn)2] (3a) showing the
and hydrogen bonds by dashed lines. H atoms have been omitted for clarity, except
those of the NH2 group.
pep stacking
3a (R ¼ Bn). Yield: 153 mg (90%). Found (Calc.): [C18H25N2O2Pt]
(495.46); C 43.79 (43.63), H 4.99 (4.88). HRMS (ESI) m/z calc. for
[C18H25N2O1294Pt þ H]þ 495.1537; found 495.1551 (in addition to
other signals). 1H NMR (200 MHz, CDCl3):
d
2.15 (s
þ
d,
3JPt,H ¼ 22.0 Hz, 6H, COCH3), 3.68 (s(br), 8H, NH2þCH2), 7.28e7.31
in reactions with tris- and tetrakis(pyrazolyl)borates yielding in
new diacetyl platinum(II) and platinum(IV) complexes with
hemilabile scorpionate ligands [15].
(m, 10H, C6H5). 13C NMR (50 MHz, CDCl3):
d
44.1 (s þ d,
2JPt,C ¼ 372 Hz, COCH3), 49.2 (s, CH2), 127.9 (s, p-CH), 128.1 (s, o-CH),
128.8 (s, m-CH), 139.2 (s þ d, 3JPt,C ¼ 19 Hz, i-C), 232.6 (s, CO). 195Pt
NMR (107 MHz, THF-d8):
d
ꢀ3329 (s). DTA: Tdec. ¼ 125 ꢁC, mass loss
3. Experimental section
at 200 ꢁC: 61.1% (calc. for residual Pt: 60.6%). IR:
n 3285 (m), 3225
(m), 3121 (m), 3026 (m), 2968 (m), 1547 (s), 1495 (m), 1455 (m),
1406 (m), 1359 (m), 1330 (m), 1208 (w), 1159 (m), 1147 (m), 1122 (s),
1099 (s), 1070 (w), 1025 (w), 995 (s), 929 (w), 749 (m), 695 (s), 610
3.1. General remarks
All reactions were performed in an argon atmosphere using
the standard Schlenk techniques. Solvents were dried (Et2O and
n-pentane over Na/benzophenone, CH2Cl2 over CaH2) and distilled
prior to use. NMR spectra were, unless otherwise specified, recorded
at 27 ꢁC on Varian Gemini 200, VXR 400 and Unity 500 NMR
spectrometers. Solvent signals (1H, 13C) were used as internal
(m), 595 (w), 530 (w), 491 (w), 441 (w), 354 (w) cmꢀ1
.
To estimate the equilibrium constant between complex 3a and
its starting complex 2, in an NMR tube a solution of 2 (8.9 mg,
0.02 mmol) and benzylamine (13.2
mL) in CD2Cl2 (0.9 mL) was
prepared and measured 1H NMR spectroscopically. Then, stepwise
references and H2PtCl6 (d(
195Pt) ¼ 0 ppm) as external reference. IR
a defined amount of benzylamine (6 times 4.4 mL) was added and
from the 1H NMR spectra the ratio of complexes 2:3a were
calculated.
spectra were recorded on a Bruker Tensor 27 spectrometer with
a Platinum ATR unit. The positive ion high-resolution ESI mass
spectra were measured at a Bruker Apex III Fourier transform ion
cyclotron resonance (FT-ICR) mass spectrometer (Bruker Daltonics,
Billerica, USA), which is equipped with an infinity cell, a 7.0 T
superconducting magnet (Bruker), an RF-only hexapole ion guide,
and an external electron spray ion source (Agilent, off axis spray,
voltages: endplate, ꢀ3.700 V; capillary, ꢀ4.200 V; capillary exit,
100 V; skimmer 1, 15.0 V; skimmer 2, 12.0 V). Nitrogen was used as
drying gas at 150 ꢁC. The sample solutions (in MeOH) were intro-
duced continuously via a syringe pump with a flow rate of
3b (R ¼ CH2CH2Ph). Yield: 170 mg (95%). Found (Calc.):
[C20H28N2O2Pt] (523.53); C 45.57 (45.88), H 5.29 (5.39). 1H NMR
3
(500 MHz, CDCl3):
d
2.21 (s þ d, JPt,H ¼ 19.1 Hz, 6H, COCH3), 2.75
(m, 4H, NH2CH2), 2.81 (m, 4H, CH2Ph), 3.45 (m(br), 4H, NH2),
7.09e7.30 (m, 10H, C6H5). 13C NMR (125 MHz, CDCl3):
d 38.3
2
(s, CH2Ph), 44.3 (s þ d, JPt,C ¼ 356 Hz, COCH3), 46.1 (s, NH2CH2),
126.7 (s, p-CH), 128.7 (s(br), o þ m-CH), 138.0 (s, i-C), 233.8 (s þ d,
1JPt,C ¼ 1275 Hz, CO). 195Pt NMR (107 MHz, CDCl3):
d
ꢀ3299 (s). IR:
n
3307 (m), 3259 (m), 3136 (m), 3062 (m), 3028 (m), 2960 (m), 2946
(m), 1610 (s), 1537 (s), 1454 (m), 1411 (m), 1337 (m), 1202 (w), 1155
(w),1123 (s), 1090 (m), 1039 (m),1008 (m), 941 (w), 912 (w), 749 (s),
120 m
L hꢀ1. The data were acquired with 512K data points and zero
filled to 2048K by averaging 32 scans. The data were evaluated
by the Bruker XMASS 7.0.8 software. Thermal gravimetric
analysis was performed on a Netzsch STA449 unit under argon
(heating rate 10 K/min). Microanalyses were performed by the
University of Halle microanalytical laboratory using CHNS-932
(LECO) elemental analyzer. The complex [Pt(COMe)2(bpy)] (2) was
prepared according to literature methods [3], whereas the synthesis
of [Pt(COMe)2{H(Me)dmg}] (5) is unpublished yet [16].
701 (s), 612 (m), 549 (w), 507 (m) cmꢀ1
.
3c (R ¼ Et). Yield: 57 mg (45%). Found (Calc.): [C8H20N2O2Pt]
(371.35); C 25.93 (25.88), H 5.21 (5.43). 1H NMR (200 MHz, CDCl3):
d
1.24 (t, 3JH,H ¼ 7.2 Hz, 6H, CH2CH3), 2.21 (s þ d, 3JPt,H ¼ 23.2 Hz, 6H,
COCH3), 2.73 (m, 4H, CH2), 3.46 (m(br), 4H, NH2). 13C NMR (50 MHz,
CDCl3):
d
18.1 (s, CH2CH3), 40.4 (s, CH2), 44.5 (s, COCH3), 234.5
ꢀ3274 (s). IR: 3276 (w), 3219
(s, CO). 195Pt NMR (86 MHz, CDCl3):
d
n
Scheme 4. Differences in the reactivity of 5 with dimethyl- and diisopropylamine and the corresponding Gibbs free energies (in kcal/mol) obtained by DFT calculations.

T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
99
(w), 3116 (w), 2974 (w), 2958 (w), 2883 (w), 1732 (m), 1554 (s), 1471
(w), 1446 (w), 1404 (m), 1329 (m), 1194 (m), 1117 (s), 1093 (m), 1057
(s), 922 (m), 881 (w), 812 (w), 609 (m), 596 (m), 349 (s) cmꢀ1
3.4. Synthesis of [Pt(COMe)2(NHR2)2] (6a/b) and [{Pt(COMe){NH(i-
Pr)2}}2( -COMe)2] (7)
m
.
3d (R ¼ i-Pr). Yield: 130 mg (95%). Found (Calc.): [C10H28N2O2Pt]
[Pt(COMe)2{H(Me)dmg}] (5) (150 mg, 0.4 mmol) and the
respective secondary amine NHR2 (1 mL) were stirred for 1 h
at ꢀ78 ꢁC (R ¼ Me) and 0 ꢁC (R ¼ Et), respectively, resulting in
a change of color (from red to colorless) and precipitation of a fine
white solid. Then, diethyl ether (3 mL) was added and, in the case of
NHEt2, the reaction mixture was immediately cooled down
to ꢀ78 ꢁC. The solid was filtered off at about ꢀ10 ꢁC, washed with
cooled (ꢀ78 ꢁC) diethyl ether (2 ꢂ 1 mL), and dried in vacuo. The
solid complexes 6 proved to be stable at ꢀ70 ꢁC over several weeks,
but decomposition occurred at temperatures above ꢀ20 ꢁC within
few days. Complex 7 was synthesized analogously by adding di-
isopropylamine (1 mL) to the starting complex 5 (150 mg, 0.4 mmol)
and stirred for 1 h at ꢀ78 ꢁC.
(399.15); C 29.86 (30.07), H 6.03 (6.06). 1H NMR (200 MHz, CDCl3):
d
3
1.24 (d, JH,H ¼ 6.2 Hz, 12H, NH2CH(CH3)2), 2.21 (s þ d,
3JPt,H ¼ 23.0 Hz, 6H, COCH3), 2.91 (m, 2H, NH2CH(CH3)2), 3.40 (d(br),
3JH,H ¼ 6.4 Hz, 4H, NH2CH(CH3)2). 13C NMR (50 MHz, CDCl3):
d 25.3
2
(s, NH2CH(CH3)2), 44.3 (s þ d, JPt,C ¼ 367 Hz, COCH3), 46.9
(s, NH2CH(CH3)2), 233.7 (s, CO). 195Pt NMR (107 MHz, CDCl3):
d
ꢀ3304 (s). IR:
2880 (w), 1564 (s), 1442 (w), 1384 (m), 1329 (m), 1214 (w), 1164 (w),
1104 (m), 928 (w), 819 (w), 775 (w), 608 (w), 549 (w) cmꢀ1
n 3285 (m), 3244 (s), 3159 (m), 2968 (m), 2926 (w),
.
3e (R ¼ CH2CH]CH2). Yield: 54 mg (40%). Found (Calc.):
[C10H20N2O2Pt] (395.15); C 30.02 (30.38), H 4.84 (5.10). 1H NMR
3
(500 MHz, CDCl3):
d
2.18 (s þ d, JPt,H ¼ 22.7 Hz, 6H, COCH3), 3.27
(m, 4H, NH2CH2), 3.67 (m(br), 4H, NH2), 5.15 (d(br), 3JH,H ¼ 10.2 Hz,
6a (R ¼ Me). Yield: 95 mg (70%). HRMS (ESI) m/z calc. for
2H, ]CH(Z)H), 5.22 (d(br), JH,H ¼ 17.2 Hz, 2H, ]CHH(E)), 6.03
[C8H20N2O2Pt þ H]þ 372.1259; found 372.1245 (in addition to other
3
(m, 2H, CH]CH2). 13C NMR (50 MHz, CDCl3):
d
44.2 (s þ d,
signals). 1H NMR (200 MHz, CD2Cl2, ꢀ40 ꢁC):
d
2.05 (s þ d,
2JPt,C ¼ 362 Hz, COCH3), 47.6 (s, NH2CH2), 117.4 (s, ]CH2), 136.0 (s,
3JPt,H ¼ 25.0 Hz, 6H, COCH3), 2.42 (d, 3JH,H ¼ 6.2 Hz, 12H, NH(CH3)2),
CH]CH2), 233.6 (s þ d, 1JPt,C ¼ 1295 Hz, CO). 195Pt NMR (107 MHz,
3.63 (m(br), 2H, NH). 13C NMR (50 MHz, CD2Cl2, ꢀ40 ꢁC):
d 41.3
2
CDCl3):
d
ꢀ3272 (s). IR:
n
3264 (w), 3218 (w), 3104 (w), 2976 (w),
(s þ d, JPt,C ¼ 149 Hz, NCH3), 43.5 (s, COCH3), 229.5 (s, CO). 195Pt
2903 (w), 2868 (w), 1648 (w), 1552 (s), 1456 (m), 1409 (m), 1331
(m), 1147 (w), 1118 (s), 1110 (s), 1025 (m), 994 (m), 924 (s), 694 (w),
NMR (107 MHz, CD2Cl2, ꢀ40 ꢁC):
d
ꢀ3439 (s). IR:
n 3228 (m), 2968
(w), 2901 (w), 1608 (s), 1572 (s), 1462 (m), 1402 (m), 1325 (m), 1211
(w), 1086 (s), 1020 (w), 901 (s), 590 (m), 530 (w), 443 (w), 361 (w),
609 (m), 602 (m), 529 (m), 411 (m), 352 (s) cmꢀ1
.
3f (R ¼ Cy). Yield: 156 mg (95%). Found (Calc.): [C16H32N2O2Pt]
(479.52); C 39.24 (40.08), H 6.61 (6.73). HRMS (ESI) m/z calc. for
[C16H33N2O1294Pt þ H]þ 479.2163; found 479.2174 (in addition to
341 (s) cmꢀ1
.
6b (R ¼ Et). Yield: 69 mg (45%). Found (Calc): C12H28N2O2Pt
(427.44); C 33.29 (33.72), H 6.37 (6.60). 1H NMR (500 MHz,
other signals). 1H NMR (200 MHz, CDCl3):
d
1.08 (m, 6H, C6H11), 1.23
CD2Cl2, ꢀ40 ꢁC):
d
1.32 (t, 3JH,H ¼ 7.0 Hz, 12H, CH2CH3), 2.04 (s þ d,
(m, 6H, C6H11), 1.61 (m, 4H, C6H11), 1.74 (m, 4H, C6H11), 2.20 (s, 6H,
3JPt,H ¼ 20.7 Hz, 6H, COCH3), 2.56 (m(br), 4H, CH2CH3), 2.79 (m(br),
COCH3), 2.46 (m, 2H, NH2CH), 3.34 (d(br), 3JH,H ¼ 6.0 Hz, 4H, NH2).
4H, CH2CH3), 3.33 (s(br), 2H, NH). 13C NMR (125 MHz,
13C NMR (50 MHz, CDCl3):
d
25.0 (s, C4 Cy), 25.3 (s, C3/5 Cy), 35.9
CD2Cl2, ꢀ40 ꢁC):
d 14.5 (s, CH2CH3), 43.4 (s, COCH3), 47.3 (s,
2
(s, C2/6 Cy), 44.3 (s þ d, JPt,C ¼ 351 Hz, COCH3), 54.1 (s, NH2CH),
CH2CH3), 230.0 (s, CO). 195Pt NMR (107 MHz, CD2Cl2, ꢀ40 ꢁC):
234.0 (s, CO). 195Pt NMR (107 MHz, CDCl3):
d
ꢀ3296 (s). IR:
n
3285
d
ꢀ3399 (s). IR:
n 3240 (m), 3167 (m), 2968 (m), 2898 (m), 1616 (s),
(m), 3109 (w), 2933 (m), 2854 (w), 1589 (w), 1545 (s), 1449 (w),
1401 (w), 1334 (m), 1232 (m), 1122 (m), 1100 (m), 1055 (m), 615 (m)
1562 (s), 1472 (m), 1377 (m), 1151 (m), 1107 (m), 1080 (s), 1055 (m),
1026 (m), 910 (m), 851 (w), 829 (w), 783 (w), 606 (w), 588 (w), 540
cmꢀ1
.
(w), 430 (w), 370 (m) cmꢀ1
.
7. Yield: 115 mg (85%). Found (Calc): C20H42N2O4Pt2 (764.71); C
3.3. On the decomposition of complexes 3a, 3d, and 3f in solution
30.99 (31.41), H 5.15 (5.54). 1H NMR (500 MHz, CD2Cl2, ꢀ70 ꢁC):
d
1.07 (s(br), 6H, CHCH3), 1.12 (s(br), 6H, CHCH3), 1.37 (s(br), 6H,
Solutions of the requisite complex [Pt(COMe)2(NH2R)2] (3a, 3d,
3f; 20 mg) in CDCl3 or THF-d8 (0.7 mL) were transferred in an NMR
tube and spectra were measured from the freshly prepared solu-
tions after 3 h. In addition to signals of the starting complex (3a, 3d,
3f, see below) and of non-identified decomposition products, those
of complexes [Pt(COMe)Me(CO)(NH2R)] (4a, 4d, 4f) were observed.
Then, the solvent was removed in vacuo and IR spectra were
recorded.
CHCH3), 1.83 (s(br), 6H, CHCH3), 1.90 (s, 6H, COCH3), 2.05 (s, 6H,
COCH3), 3.25 (s(br), 6H, CH
þ
NH). 1H NMR (500 MHz,
d 1.16 (s(br), 12H, CHCH3), 1.58 (s(br), 12H, CHCH3),
CD2Cl2, ꢀ40 ꢁC):
1.96 (s, 6H, COCH3), 2.07 (s, 6H, COCH3), 3.29 (s(br), 6H, CH þ NH).
1H NMR (500 MHz, CD2Cl2, 27 ꢁC after ca. 5 min): uncoordinated
3
amine (ca. 30%):
d
0.99 (d, JH,H ¼ 6.2 Hz, 12H, CH3), 2.87 (sept,
3JH,H ¼ 6.2 Hz, 2H, CH), complex 7 (ca. 70%): 1.26 (d, 3JH,H ¼ 6.0 Hz,
3
12H, CHCH3), 1.62 (d, JH,H ¼ 6.1 Hz, 12H, CHCH3), 2.05 (s, 6H,
4a (R ¼ Bn). HRMS (ESI) m/z calc. for [C11H16N1O1294Pt þ H]þ
COCH3), 2.13 (s, 6H, COCH3), 3.34 (m, 6H, CH þ NH), complex IV (ca.
388.0807; found 388.0802 (in addition to other signals). 1H NMR
30%): 2.38 (s, COCH3). 13C NMR (125 MHz, CD2Cl2, ꢀ70 ꢁC):
d 19.6
(500 MHz, THF-d8):
d
0.29 (s þ d, 2JPt,H ¼ 69.8 Hz, 3H, PtCH3), 2.20
(s, CHCH3), 20.1 (s, CHCH3), 23.0 (s, CHCH3), 23.4 (s, CHCH3), 42.2
(s, COCH3), 43.7 (s, COCH3), 47.2 (s, CH), 47.4 (s, CH), 214.6 (s, CO
terminal), 253.4 (s, CO bridged). 13C NMR (125 MHz,
3
(s þ d, JPt,H ¼ 18.9 Hz, 3H, COCH3), 3.96 (m, 2H, CH2), 4.24 (s(br),
2H, NH2), 7.14e7.35 (m, 5H, C6H5). 13C NMR (125 MHz, THF-d8):
d 3.4
(s þ d, 1JPt,C ¼ 708.7 Hz, PtCH3), 45.3 (s, COCH3), 51.6 (s, CH2), 128.3
(s, p-CH), 128.9 (s, o-CH), 129.3 (s, m-CH), 141.5 (s, i-C), 180.9 (s þ d,
1JPt,C ¼ 1125.5 Hz, PtCO), 214.0 (s, COCH3). 195Pt NMR (107 MHz,
CD2Cl2, ꢀ40 ꢁC):
d 22.0 (s(br), CHCH3), 42.6 (s, COCH3), 43.7
(s, COCH3), 47.7 (s, CH), 214.0 (s, CO terminal), 253.1 (s, CO bridged).
195Pt NMR (107 MHz, CD2Cl2, ꢀ70/ꢀ40 ꢁC):
d
ꢀ3138 (s). IR:
n 3209
THF-d8):
d
ꢀ3455 (s). IR:
n
(CO) 2052 (m) cmꢀ1
.
(w), 2974 (w), 2962 (w), 1608 (s), 1514 (s), 1460 (m), 1381 (m), 1331
(m), 1165 (m), 1130 (s), 1093 (s), 1045 (s), 984 (w), 941 (m), 808 (w),
4d (R ¼ i-Pr). 1H NMR (200 MHz, CDCl3):
d
0.24 (s þ d,
2JPt,H ¼ 67.7 Hz, 3H, PtCH3), 2.33 (s þ d, 3JPt,H ¼ 20.4 Hz, 3H, COCH3).
648 (m), 600 (m), 416 (m), 358 (s) cmꢀ1
.
13C NMR (50 MHz, CDCl3):
d
3.4 (s, PtCH3). IR:
n
(CO) 2061 (w) cmꢀ1
.
At ꢀ40 ꢁC, to a solution of complex 7 (35 mg, 0.05 mmol) in
CD2Cl2 (0.7 mL), bpy (0.18 mmol) or pyridine (ca. 0.5 mmol) was
added and 1H NMR spectra (ꢀ40 ꢁC) were recorded. Apart from
residual signals of bpy/py, the diacetyl platinum(II) complex 2a and
[Pt(COMe)2(py)2] [6], respectively, were identified. Performing
these reactions with DMSO and D2O, no reactions were observed.
4f (R ¼ Cy). HRMS (ESI) m/z calc. for [C10H19N1O1294Pt þ H]þ
380.1115; found 380.1122 (in addition to other signals). 1H NMR
(500 MHz, CDCl3):
d
0.28 (s þ d, 3JPt,H ¼ 66.8 Hz, 3H, PtCH3), 2.34 (s,
3H, COCH3). 195Pt NMR (107 MHz, THF-d8):
d
ꢀ3484 (s). IR:
n(CO)
2048 (s) cmꢀ1
.

100
T. Kluge et al. / Journal of Organometallic Chemistry 715 (2012) 93e101
Table 4
3.5. Synthesis of [Pt(COMe)2(N^N)] (8aed)
Crystal data, data collection, and refinement parameters of [Pt(COMe)2(NH2Bn)2]
(3a) and [Pt(COMe)2(NH2i-Pr)2] (3d).
[Pt(COMe)2{H(Me)dmg}] (5) (150 mg, 0.4 mmol) and the respec-
tive ethylenediamine derivative (0.5 mL) were stirred for about 1 h
at room temperature resulting in a colorless solution of [Pt(CO-
Me)2(N^N)] (N^N ¼ H2NCH2CH2NH2, en, 8a; MeHNCH2CH2NHMe,
8b; Me2NCH2CH2NH2, 8c; Me2NCH2CH2NMe2, TMEDA, 8d). Addition
of diethyl ether (1 mL) yielded a precipitation which was filtered off,
washed with diethyl ether (2 ꢂ 0.5 mL), and dried in vacuo.
3a
3d
Empirical formula
Formula weight
Crystal system/space
group
C
18H24N2O2Pt
C10H24N2O2Pt
399.40
Monoclinic/P21/c
495.48
Monoclinic/I2/a
Z
a/A
b/A
c/A
4
8
ꢀ
9.3628(2)
20.0751(2)
9.6263(1)
96.049(1)
1799.28(5)
1.829
11.6904(5)
13.7554(6)
19.7478(8)
116.154(3)
2850.4(2)
1.861
ꢀ
8a (N^N ¼ H2NCH2CH2NH2). Yield: 36 mg (30%). Found (Calc):
ꢀ
C6H14N2O2Pt (341.27); C 21.57 (21.12), H 4.21 (4.13). 1H NMR
ꢁ
ꢀ
b
/
3
(200 MHz, CDCl3):
d
2.22 (s þ d, JPt,H ¼ 22.4 Hz, 6H, COCH3), 2.79
3
V/A
(s(br), 4H, CH2), 3.87 (s(br), 4H, NH2). 13C NMR (100 MHz, CDCl3):
44.5 (s, COCH3), 45.5 (s, CH2), 240.6 (s, CO). 195Pt NMR (86 MHz,
CDCl3): 3242 (m), 3128 (w), 2949 (w), 2889 (w),
1579 (m), 1539 (s), 1404 (m), 1327 (m), 1111 (s), 1084 (s), 1045 (s),
981 (w), 927 (m), 866 (w), 758 (w), 607 (m), 592 (m), 559 (m) 347
Dcalc/g cmꢀ3
m
(Mo K
F(000)
Scan range
a
)/mmꢀ1
7.809
960
9.833
1536
d
d
ꢀ3337 (s). IR:
n
ꢁ
q/
3.53e28.28
ꢀ11 / 12,
ꢀ26 / 26,
ꢀ12 / 12
22,854
2.70e26.00
ꢀ14 / 14,
ꢀ16 / 16,
ꢀ22 / 24
18,342
5589 (Rint ¼ 0.0399)
5589/1/283
0.968
0.0215, 0.0496
0.0289, 0.0524
1.268 and ꢀ1.193
Reciprocal lattice
segments h, k, l
(s) cmꢀ1
.
Reflections collected
8b (N^N ¼ MeHNCH2CH2NHMe). Yield: 120 mg (90%). Found
(Calc): C8H18N2O2Pt (369.32); C 25.94 (26.02), H 4.61 (4.91). 1H
Reflections independent
Data/restrains/parameters
Goodness-of-fit on F [2]
2236 (Rint ¼ 0.0277)
2236/0/106
1.065
NMR (500 MHz, CDCl3):
d
2.31 (s þ d, 3JPt,H ¼ 19.3 Hz, 6H, COCH3),
2.40 (m, 2H, CHH), 2.54 (d(br), 3JH,H ¼ 6.0 Hz, 6H, NHCH3), 2.91 (m,
R1, wR2 [I > 2
R1, wR2 [all data]
s
(I)]
0.0153, 0.0380
0.0174, 0.0383
1.213 and ꢀ0.679
2H, CHH), 5.51 (s(br), 2H, NHCH3). 13C NMR (50 MHz, CDCl3):
d
40.1
(s, NHCH3), 44.9 (s þ d, 2JPt,C ¼ 351 Hz, COCH3), 53.8 (s, CH2), 238.7
Largest diff. peak and
ꢀꢀ3
hole/e A
(s þ d, 1JPt,C ¼ 1233 Hz, CO). 195Pt NMR (107 MHz, CDCl3):
d
ꢀ3293
(s). IR:
n 3250 (m), 3145 (w), 2932 (w), 2878 (w), 1587 (m), 1458
(m), 1406 (m), 1325 (m), 1151 (m), 1090 (s), 1003 (w), 920 (m), 895
were applied empirically using the PLATON program package [18]
(3a, Tmin/Tmax 0.49/1.00) or numerically (3d, Tmin/Tmax 0.19/0.50).
The structures were solved by direct methods using SHELXS-97 [19]
and refined using full-matrix least-square routines against F2 with
SHELXL-97 [20]. All non-hydrogen atoms were refined with
anisotropic displacement parameters and hydrogen atoms with
isotropic ones. H atoms were placed in calculated positions
according to the riding model.
(m), 785 (m), 602 (m), 492 (m), 372 (m) cmꢀ1
.
8c (N^N ¼ Me2NCH2CH2NH2). Yield: 105 mg (80%). Found
(Calc): C8H18N2O2Pt (369.32); C 25.86 (26.02), H 4.55 (4.91). 1H
NMR (500 MHz, CDCl3):
d
2.05 (s þ d, 3JPt,H ¼ 25.7 Hz, 3H, COCH3),
2.19 (s þ d, 3JPt,H ¼ 20.8 Hz, 3H, COCH3), 2.62 (s þ d, 3JPt,H ¼ 20.6 Hz,
8H, CH2N(CH3)2), 2.94 (m, 2H, CH2NH2), 3.57 (m, 2H, NH2). 13C NMR
2
(50 MHz, CDCl3):
d
41.3 (s, CH2NH2), 43.8 (s þ d, JPt,C ¼ 397 Hz,
2
COCH3), 44.1 (s þ d, JPt,C ¼ 363 Hz, COCH3), 49.4 (s, NCH3), 64.7
(s, CH2NCH3), 224.3 (s, CO), 234.3 (s, CO). 195Pt NMR (107 MHz,
3.7. Computational details
CDCl3):
1566 (s), 1448 (m), 1412 (m), 1325 (m), 1286 (w), 1059 (m), 983 (m),
912 (m), 860 (m), 839 (m), 592 (m), 420 (m), 341 (s) cmꢀ1
d
ꢀ3347 (s). IR:
n 3186 (w), 3147 (m), 2934 (m), 1603 (m),
DFT calculations were performed by the Gaussian09 program
package [21] using the functional mPW1PW91 [10]. The
6-311þþG** basis sets as implemented in Gaussian09 were
employed for main group elements. For platinum, the ECP by Hay
and Wadt [22] and concomitant basis set (LanL2DZ) were used. All
systems were fully optimized without any symmetry restrictions.
The resulting geometries were characterized as equilibrium struc-
tures by the analysis of the force constants of normal vibrations.
Solvent effects were considered according to Tomasi’s polarized
continuum model [23] as implemented in Gaussian 09.
.
8d (N^N ¼ Me2NCH2CH2NMe2). Yield: 85 mg (60%). Found
(Calc): C10H22N2O2Pt (397.37); C 30.99 (30.23), H 5.27 (5.58). 1H
NMR (200 MHz, CDCl3):
d
2.10 (s þ d, 3JPt,H ¼ 26.8 Hz, 6H, COCH3),
3
3
2.52 (s þ d, JPt,H ¼ 12.1 Hz, 4H, CH2), 2.61 (s þ d, JPt,H ¼ 22.2 Hz,
12H, NCH3). 13C NMR (100 MHz, CDCl3):
d
43.6 (s þ d, 2JPt,C ¼ 393 Hz,
COCH3), 49.2 (s þ d, 2JPt,C ¼ 10 Hz, CH3), 61.1 (s, CH2), 228.5 (s þ d,
1JPt,C ¼ 1283 Hz, CO). 195Pt NMR (86 MHz, CD2Cl2, ꢀ40 ꢁC):
ꢀ3430
d
(s). IR: n 3493 (w), 2996 (w), 2972 (w), 2896 (w), 1612 (m), 1585 (s),
1456 (m), 1323 (m), 1103 (m), 1082 (s), 1024 (m), 954 (m), 904 (w),
802 (s), 771 (m), 590 (m), 484 (w), 347 (s) cmꢀ1
.
Appendix A. Supplementary material
3.6. X-ray crystallography
CCDC 875056 (3a) and CCDC 875057 (3d) contain the supple-
mentary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
Crystals of [Pt(COMe)2(NH2i-Pr)2] (3d) suitable for X-ray
diffraction analysis were obtained by slow diffusion of diethyl ether
into a CH2Cl2 solution of 3d which contained a few drops of iso-
propyl amine to reduce the decomposition of the complex. Crystals
of [Pt(COMe)2(NH2Bn)2] (3a) were obtained from a methylene
chloride/diethyl ether (1:2) solution containing a thioglycoside
(per-benzylated 4-(pyridin-2-yl)thiazol-2-yl thioglucopyranoside)
for stabilization [17]. Data for X-ray diffraction analyses of 3a were
collected on a CCD Oxford Xcalibur S diffractometer at 130 K and of
Appendix B. Supplementary material
Supplementary data related to this article can be found online at
doi:10.1016/j.jorganchem.2012.05.043.
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ꢀ
(l
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