Synthesis, characterization and reactivity of carbohydrate platinum(iv) complexes with thioglycoside ligands

Article abstract of DOI:10.1039/b927058b

Reactions of fac-[PtMe₃(4,4′-R₂bpy)(Me ₂CO)][BF₄] (R = H, 1a; ^tBu, 1b) and fac-[PtMe₃(OAc-κ²O,O′)(Me₂CO)] (2), respectively, with thioglycosides containing thioethyl (ch-SEt) and thioimidate (ch-STaz, Taz = thiazoline-2-yl) anomeric groups led to the formation of the carbohydrate platinum(iv) complexes fac-[PtMe₃(4,4′-R ₂bpy)(ch*)][BF₄] (ch* = ch-SEt, 8-14; ch-STaz, 15-23) and fac-[PtMe₃(OAc-κ²O,O′)(ch*)] (ch* = ch-SEt, 24-28; ch-STaz = 29-35), respectively. NMR (¹H, ¹³C, ¹⁹⁵Pt) spectroscopic investigations and a single-crystal X-ray diffraction analysis of 19 (ch-STaz = 2-thiazolinyl 2,3,4,6-tetra-O-benzoyl-1-thio-β-d-galactopyranose) revealed the S coordination of the ch-SEt glycosides and the N coordination of the ch-STaz glycosides. Furthermore, X-ray structure analyses of the two decomposition products fac-[PtMe₃(bpy)(STazH-κS)][BF₄] (21a) and 1,6-anhydro-2,3,4-tri-O-benzoyl-β-d-glucopyranose (23a), where a cleavage of the anomeric C-S bond had occurred in both cases, gave rise to the assumption that this decomposition was mediated due to coordination of the thioglycosides to the high electrophilic platinum(iv) atom, in non-strictly dried solutions. Reactions of fac-[PtMe₃(Me₂CO)₃][BF ₄] (3) with ch-SEt as well as with ch-SPT and ch-Sbpy thioglycosides (PT = 4-(pyridine-2-yl)-thiazole-2-yl; bpy = 2,2′-bipyridine-6-yl), having N,S and N,N heteroaryl anomeric groups, respectively, led to the formation of platinum(iv) complexes of the type fac-[PtMe₃(ch*)][BF ₄] (ch* = ch-SEt, 36-40, ch-SPT 42-44, ch-Sbpy 45, 46). The thioglycosides were found to be coordinated in a tridentate κS, κ²O,O′, κS,κN,κO and κS,κ²N,N′ coordination mode, respectively. Analogous reactions with ch-STaz ligands succeeded for 2-thiazolinyl 2,3,4-tri-O-benzyl-6-O-(2,2′-bipyridine-6-yl)-1-thio-β-d- glucopyranoside (5h) resulting in fac-[PtMe₃(ch-STaz)][BF ₄] (41, ch-STaz = 5h), having a κ³N,N′, N′′coordinated thioglycoside ligand.

Full text of DOI:10.1039/b927058b

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PAPER
www.rsc.org/dalton | Dalton Transactions
Synthesis, characterization and reactivity of carbohydrate platinum(IV)
complexes with thioglycoside ligands†
a
b
c
b
d
Cornelia Vetter, Papapida Pornsuriyasak, J u¨ rgen Schmidt, Nigam P. Rath, Tobias R u¨ ffer,
b
a
Alexei V. Demchenko* and Dirk Steinborn*
Received 23rd December 2009, Accepted 16th April 2010
First published as an Advance Article on the web 1st June 2010
DOI: 10.1039/b927058b
t
Reactions of fac-[PtMe
3
(4,4¢-R
2
bpy)(Me
2
CO)][BF
4
] (R = H, 1a; Bu, 1b) and fac-[PtMe
3
-
2
(
OAc-k O,O¢)(Me
2
CO)] (2), respectively, with thioglycosides containing thioethyl (ch-SEt) and
thioimidate (ch-STaz, Taz = thiazoline-2-yl) anomeric groups led to the formation of the carbohydrate
platinum(IV) complexes fac-[PtMe
3
(4,4¢-R
2
bpy)(ch*)][BF
4
] (ch* = ch-SEt, 8–14; ch-STaz, 15–23) and
2
1 13
fac-[PtMe
3
(OAc-k O,O¢)(ch*)] (ch* = ch-SEt, 24–28; ch-STaz = 29–35), respectively. NMR ( H, C,
1
95
Pt) spectroscopic investigations and a single-crystal X-ray diffraction analysis of 19 (ch-STaz =
2
-thiazolinyl 2,3,4,6-tetra-O-benzoyl-1-thio-b-D-galactopyranose) revealed the S coordination of the
ch-SEt glycosides and the N coordination of the ch-STaz glycosides. Furthermore, X-ray structure
analyses of the two decomposition products fac-[PtMe (bpy)(STazH-kS)][BF ] (21a) and
,6-anhydro-2,3,4-tri-O-benzoyl-b-D-glucopyranose (23a), where a cleavage of the anomeric C–S bond
3
4
1
had occurred in both cases, gave rise to the assumption that this decomposition was mediated due to
coordination of the thioglycosides to the high electrophilic platinum(IV) atom, in non-strictly dried
solutions. Reactions of fac-[PtMe
3
(Me
2
CO)
3
][BF ] (3) with ch-SEt as well as with ch-SPT and ch-Sbpy
4
thioglycosides (PT = 4-(pyridine-2-yl)-thiazole-2-yl; bpy = 2,2¢-bipyridine-6-yl), having N,S and N,N
heteroaryl anomeric groups, respectively, led to the formation of platinum(IV) complexes of the type
fac-[PtMe
3
(ch*)][BF
4
] (ch* = ch-SEt, 36–40, ch-SPT 42–44, ch-Sbpy 45, 46). The thioglycosides were
2
2
found to be coordinated in a tridentate kS,k O,O¢, kS,kN,kO and kS,k N,N¢ coordination mode,
respectively. Analogous reactions with ch-STaz ligands succeeded for 2-thiazolinyl
2
,3,4-tri-O-benzyl-6-O-(2,2¢-bipyridine-6-yl)-1-thio-b-D-glucopyranoside (5h) resulting in
3
fac-[PtMe
3
(ch-STaz)][BF
4
] (41, ch-STaz = 5h), having a k N,N¢,N¢¢coordinated thioglycoside ligand.
1
. Introduction
to possess significant bioactivity. It was found that 5-thio-b-D-
glucopyranose, where the ring oxygen is replaced by sulfur, can
Carbohydrates are one of the most important classes of
biomolecules. Attached to lipids, proteins and nucleobases they
exert versatile functions in living organisms, ranging from
immune defence and cell growth to inflammation and ma-
lignant transformations. Carbohydrate-based pharmaceuticals
have been proven to be promising therapeutics for neurode-
generative diseases, because they can easily pass the blood
4
cause temporary diabetes and sterility in rats. Moreover, this
carbohydrate class, having a ring sulfur atom, exhibit cancerostatic
5
6
properties and act as enzyme inhibitors. Up to now, it has
also been shown that thioglycosides and carbohydrates with
mercapto groups instead of hydroxyl groups are enzyme inhibitors
and thereby possess antiproliferative and anti-inflammatory
1,2
7
properties. Metal-coordination of carbohydrates also plays a
3
brain barrier. Thiofunctionalized carbohydrates were proved
significant role in biosyntheses, including metal transportation
8,9
and storage or the regulation of metalloenzymes. Furthermore,
metal–carbohydrate complexes have been investigated as potent
a
Institut f u¨ r Chemie – Anorganische Chemie, Martin-Luther-Universit a¨ t
10
Halle-Wittenberg, D-06120, Halle, Kurt-Mothes-Straße 2, Germany.
E-mail: dirk.steinborn@chemie.uni-halle.de; Fax: +49345 5527028;
Tel: +49345 5525620
radiopharmaca and cancerostatica, where platinum compounds
11
are of considerable interest. From a coordination chemistry
perspective the syntheses of carbohydrate platinum(IV) complexes,
particularly with non-functionalized carbohydrate ligands, rep-
resent a notable challenge, due to their weak donor ability and
b
Department of Chemistry and Biochemistry, University of Missouri-
St. Louis, 63121, Missouri, One University Boulevard, USA. E-mail:
demchenkoa@umsl.edu; Tel: +1314 5167995
c
12
Leibniz-Institut f u¨ r Pflanzenbiochemie, D-06120, Halle, Weinberg 3,
their propensity to act as reducing agents. On the other hand,
Germany
platinum(IV) complexes are kinetically inert due to the low-
d
Institut f u¨ r Chemie – Technische Universit a¨ t Chemnitz, D-09111, Chemnitz,
6
spin d electron configuration, so substitution reactions are not
Straße der Nationen 62, Germany
favored. However, numerous platinum(IV) complexes with neutral
carbohydrate ligands have been synthesized using trimethylplat-
†
Electronic supplementary information (ESI) available: Experimental
t
data for fac-[PtMe
3
2
I(4,4¢- Bu bpy)]. Spectroscopic data for complexes
1
–46. Energies and Cartesian coordinates calculated for equilibrium
inum(IV) precursor complexes such as fac-[PtMe
3
(Me
2
CO)
3
][BF ].
4
structures 2 and 2¢. CCDC reference numbers 758897–758899. For ESI
Complexes of this type have proven especially useful in this respect
because the high donor capability of the methyl ligands stabilizes
and crystallographic data in CIF or other electronic format see DOI:
1
0.1039/b927058b
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1
the platinum(IV) oxidation state. Furthermore, the leaving ligands
acetone) are only weakly coordinated and their substitution is
additionally facilitated by the high trans effect of the methyl
ligands. Herein we present the synthesis, characterization and
reactivity of various types of trimethylplatinum(IV) complexes with
thioglycoside ligands.
ligand is cleaved off and the acetato ligand remains to be k O
(
coordinated or three in the case of complete cleavage of the acetato
ligand.
13
The analogous reaction of fac-[(PtMe
3
I)
4
] with Ag[BF ] led to
fac-[PtMe (Me CO) ][BF ] (3; Scheme 1), which possesses three
4
3
2
3
4
13
substitution-labile acetone ligands. It should be noted that
all complexes described here were synthesized in situ and used
directly for reactions with thioglycosides which are summarized
in Scheme 1. Four different classes of thioglycosides have been
investigated, namely those with SEt anomeric groups ch-SEt
2
. Results and discussion
2
.1. Starting complexes and ligands
(
4a–f) and those having N,S or N,N heterocyclic anomeric groups:
For the synthesis of trimethylplatinum(IV) complexes with thiogly-
coside ligands, starting complexes having up to three substitution-
labile ligands were used. Complexes with one substitution-
ch-STaz (5a–h; Taz = thiazoline-2-yl), ch-SPT (6a–c; PT =
4
-(pyridine-2-yl)-thiazole-2-yl) and ch-Sbpy (7a,b; bpy = 2,2¢-
bipyridine-6-yl).
labile acetone ligand, fac-[PtMe
3
(Me
2
CO)(bpy)][BF
] (1b; Scheme 1), were pre-
4
] (1a) and
t
fac-[PtMe
3
(Me
2
CO)(4,4¢- Bu
2
bpy)][BF
4
2.2. Cationic platinum(IV) complexes with monodentately
coordinated thioglycoside ligands
pared by the reaction of fac-[PtMe
3
I(bpy)] and fac-[PtMe
3
I(4,4¢-
t
14
Bu
2
bpy)], respectively, with Ag[BF
4
]. The reaction of the
Syntheses and X-ray diffraction analysis. Complexes 1a and 1b
reacted in acetone with stoichiometric amounts of thioglycosides
of type 4 and 5 (Scheme 1) yielding ionic complexes of the type
tetranuclear heterocubane complex fac-[(PtMe
resulted in the formation of fac-[PtMe (OAc)(Me
acetato ligand can be bidentately or monodentately coordinated
3
I)
4
] with AgOAc
3
2
CO) ] (2). The
n
t
2
fac-[PtMe (4,4¢-R bpy)(ch-SEt-kS)][BF ] (R = H: 8–11; R = Bu:
3
2
4
(
OAc-k O,O¢, n = 1; OAc-kO, n = 2). DFT calculations showed
1
3, 14) and fac-[PtMe
3
(4,4¢-R
2
bpy)(ch-STaz-kN)][BF
4
] (R = H:
that the free energy at 298 K of the reaction
t
1
7–23; R = Bu: 15, 16), respectively (Scheme 2, Table 1). The
fac-[PtMe (OAc-kO)(Me CO)
fac-[PtMe (OAc-k O,O¢)(Me CO)] + Me
amounts to be -44 kJ mol in the gas phase and -61 kJ mol
3
2
2
] ꢀ
complexes were isolated as moderately air-stable yellow and white
powders, respectively, in yields of 45–94%. All complexes were
2
3
2
2
CO
1
13
195
-
1
-1
characterized by H, C and Pt NMR spectroscopy as well as
by IR spectroscopy, high resolution ESI mass spectrometry and in
the case of 19 also by X-ray diffraction analysis.
in acetone. This gives proof that the acetato ligand is bidentately
bound. Nevertheless, both complexes have at their disposal up
to three substitution-labile coordination sites, namely one when
the acetone ligand is cleaved off and the acetato ligand is still
coordinated in a chelating binding fashion, two when the acetone
Scheme
2
Syntheses of carbohydrate platinum(IV) complexes
fac-[PtMe
3
(4,4¢-R
2
bpy)(ch*)][BF
4
]
(ch*
=
ch-SEt,
R
=
H
8–11,
t
t
R = Bu 13, 14; ch-STaz, R = H 17–23, R = Bu 15, 16).
Small colorless needles of fac-[PtMe
3
(bpy)(ch-STaz)][BF
4
] (19;
ch-STaz = 5c) were formed in an acetone solution layered with
tetrahydrofuran and diethyl ether. Complex 19 crystallized in the
chiral space group P4
symmetry independent fac-[PtMe
1
2 2. The asymmetric unit consists of two
1
+
3
(bpy)(ch-STaz)] (ch-STaz =
-
5c) cations, and two [BF
4
] anions, wherein one exhibits a disorder.
In Fig. 1, only one of the cations is illustrated, whereas the
other one exhibits a similar structure. Selected bond lengths and
angles are given in the figure caption. In complex 19 the platinum
atom [PtC
3
3
N ] is octahedrally coordinated by three methyl ligands
in facial arrangement, a bipyridine ligand and the thiazoline-2-
yl ring, which is coordinated via the nitrogen atom. The angle
between the thiazoline-2-yl ring and the equatorial [PtC
is nearly perpendicular (86.5/89.8 ‡). The Pt–N bond length
2
N ] plane
2
◦
˚
(
2.16(1)/2.17(2) A) belongs to the longest bonds known for Pt(IV)–
Scheme 1 Platinum(IV) precursor complexes and b-D-thioglycosides used
)=C complexes (median: 2.139 A, lower/upper quartile:
˚
a
b
N(CH
2
as ligands. b-D-Galactose: OR at C4 in axial position. Abbrevi-
ations: ch-STaz: Taz = thiazoline-2-yl; ch-SPT: PT = 4-(pyridine-2-yl)-
c
thiazole-2yl; ch-Sbpy: bpy = 2,2¢-bipyridine-6-yl. pic: 2-picoline-2-yl.
‡ The values of the two symmetry independent molecules are given
separated by a slash.
d
bpy-H: 2,2¢-bipyridine-6-yl.
6
328 | Dalton Trans., 2010, 39, 6327–6338
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1
13
195
Table 1 H and C NMR spectroscopic data (d in ppm, J in Hz) of the methyl ligands and Pt chemical shifts of the complexes fac-
t
[
PtMe
3
(bpy)(ch*)][BF
4
] (8–12; 17–23) and fac-[PtMe
3
2 4
(4,4¢- Bu bpy)(ch*)][BF ] (13–16)
1
2
d
H
d
C
J
Pt,C
J
Pt,H
Complex
ch*
trans ch*
trans Nbpy
trans ch*
trans Nbpy
trans ch*
trans Nbpy
trans ch*
trans Nbpy
d
Pt
ch-SEt
4a
8
9
0.66
0.65
0.71
0.64
0.68
0.66
0.59
1.09
1.09/1.11
1.16
1.14/1.16
1.18/1.19
1.03/1.10
1.04
5.8
5.1
5.4
5.1
5.2
5.8
5.8
-5.0/-5.1
-5.1/-5.4
-4.5/-4.7
-5.1/-5.2
-4.6/-4.7
-5.2/-5.3
-5.0/-5.2
662.0
652.0
660.0
649.5
648.4
647.1
658.3
657.0./658.3
662.0/654.5
657.3/662.8
663.2/662.0
662.2/661.5
659.4/664.6
655.8/662.0
72.0
71.6
72.3
71.0
71.1
72.6
72.2
67.8
69.3/67.8
67.5
66.9/66.9
67.4/67.4
66.4/67.1
68.2
-2772
-2529
-2447
-2446
-2469
-2769
-2435
4b
10
11
12
13
14
4c
4d
4e
4a
4c
ch-STaz
5c
15
16
17
18
19
20
21
22
23
0.53
0.32
0.45
0.38
0.39
0.45
0.42
0.42
0.37
1.13
-5.4
-6.1
-5.5
-5.7
-5.7
-5.7
-5.5
-5.6
-5.7
-3.3
678.2
676.6
673.1
672.4
674.4
674.3
673.8
677.5
678.5
675.7
71.4
72.5
72.2
72.2
72.2
72.2
72.2
72.2
72.2
68.1
-2716
-2452
-2730
-2683
-2710
-2695
-2704
-2444
-2445
5g
0.83/1.02
1.13/1.17
0.93/1.08
0.93/1.08
1.21/1.23
1.18/1.19
1.19
-3.2/-4.7
-3.2/-4.2
-3.6
667.0/684.4
677.0/677.8
676.2
678.2/676.9
679.4/679.3
680.6/680.7
679.4/679.8
679.4/675.6
67.6/66.9
68.5/67.2
67.2/67.2
67.2/68.1
67.2/68.1
67.2/68.1
68.1
5a
5b
5c
-3.6/-4.2
-3.7/-4.0
-4.0/-4.1
-3.7/-4.1
-3.6/-4.2
5d
5e
5f
5g
0.93/1.06
67.2/67.2
1
5
˚
complex 11, where the carbon atom of the methylene group was
shifted upfield by 1.9 ppm. For complex 12, wherein thioglycoside
2
.049/2.163 A, n = 36; n – number of observations ), likely
13,16
due to the high trans influence of the methyl ligands.
STaz ring exhibits a distorted half-chair conformation, while
the pyranose ring assumes a distorted chair conformation.
complex hydrogen bond network of moderate to weak inter- and
intramolecular hydrogen bonds of the types C–H ◊ ◊ ◊ O, C–H ◊ ◊ ◊ F
and C–H ◊ ◊ ◊ S, respectively, is found in crystals of 19.
The
4e, having an additional N-donor site (picoline-2-yl), was used,
17
the coordination mode could not be unambiguously assigned. On
A
1
13
the one hand, the picoline-2-yl resonances in the H and C NMR
spectra are shifted downfield up to 0.2 and 2.4 ppm, respectively,
which indicated an N coordination. Conversely, the broadening
and increase of the shift differences for the signals of the CH
2
1
NMR spectroscopic characterization of the complexes 8–23.
group of the SEt moiety in the H NMR spectrum, as well as the
1
13
1
The H and C NMR spectra of complexes 8–23 showed
unambiguously the coordination of the thioglycosides. Due to
the coordination of the chiral carbohydrates to the platinum atom
JPt,C coupling constant of the methyl ligand in trans position to
the thioglycoside ligand of 648.4 Hz, indicated an S coordination.
In the case of complexes 15–23 the kN coordination of the
STaz moiety has been proven unambiguously by the X-ray
the complexes exhibited C symmetry. Thus, a double signal set
1
1
13
for the two halves of the bipyridine ligand, as along with the
methyl ligands in trans position to the bipyridine ligand could be
observed (Table 1). However, the chemical shifts of the methyl
ligands were still very similar, leading to coincidence of signals for
some compounds (Table 1). Coordination of the carbohydrates in
complexes 8–23 led to a partial broadening of the signals of the
carbohydrate protons and carbon atoms at room temperature,
which has been proven to be characteristic for carbohydrate
structure analysis of complex 19. Comparison of H and
C
NMR data of complex 19 with those of the other complexes
clearly demonstrated that the complexes 15–18 and 20–23 also
possess bound kN coordinated ligands. Without the structural
information on complex 19 it would be impossible to derive the
coordination mode solely based on the NMR data. The signals
for the NCH
0.98 ppm and 0.57 ppm, respectively). On the other hand, the
carbon atom resonances of the SCH groups were strongly shifted
upfield (up to 3.4 ppm), whereas the carbon atom resonances of
the NCH groups were only marginally shifted (up to 0.4 ppm).
2
and H1 protons showed the greatest CIS’s (up to
13
coordination also in other carbohydrate platinum(IV) complexes.
2
A general shift of the resonances of the carbohydrate protons to
higher field was observed for the complexes 8–23. Furthermore,
the shift differences of the signals for the two protons belonging
to the CH groups of the SEt and STaz moieties were significantly
increased due to the coordination to the platinum atom. On the
2
1
13
The H and C NMR signals of the methyl ligands trans to the
thioglycoside ligands of type 4 were found in the range of 0.59–0.71
and 5.1–5.8 ppm, respectively. The requisite signals in complexes
15–23 with carbohydrate ligands of type 5 were found upfield
shifted, with the shifts ranging from 0.32–0.53 ppm and -5.4 to
2
other hand, only marginal coordination-induced shifts (CIS ≤
1
.6 ppm) for the resonances of the pyranose ring carbon atoms
1
could be found.
-6.1 ppm, respectively. It had been shown, that the JPt,C coupling
In the case of complexes 8–11, 13 and 14 the S coordination of
constants in complexes of this type can be regarded to be a measure
16
1
the SEt group gave rise to upfield shifts of the CH
of the SEt group up to 0.32 ppm and of the H1 protons up to
.11 ppm. Interestingly, the coordination-induced shifts both of
2
proton signals
for the trans influence. The comparison of the JPt,C couplings
constants of the methyl ligands trans to the carbohydrate ligands
in complexes 8–14 (647.1–662.0 Hz) with those in complexes
15–23 (672.4–678.5 Hz) indicated a higher trans influence of the
thioglycosides with the SEt group than that of the respective
0
the carbon atom resonances of the Et group and of the anomeric
C atom resonances were small (≤ 1.0 ppm) with the exception of
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with the formation of well-shaped crystals, which were suitable
for X-ray diffraction analysis. The compound 21a crystallized in
the space group P2
1
/c. The asymmetric unit consists of a fac-
+
[
PtMe (bpy)(STazH-kS)] cation and a disordered tetrafluorobo-
3
rate anion. The molecular structure of the cation of 21a is shown
in Fig. 2. Selected bond lengths and angles are given in the figure
caption. The primary donor set [PtC
3
2
N S] of the octahedrally
coordinated platinum atom is built up by three methyl ligands
in facial arrangement, the bipyridine ligand and the thiazolidine-
2-thione (STazH) ligand, which is coordinated via the exocyclic
sulfur atom to the platinum atom. The five membered heterocycle
possesses a distorted half chair conformation along the C12–C13
17
bond, based on the torsion angle concept. Compared to the
20
C=S bond in the free ligand (1.671–1.680 A ) no significant
˚
coordination-induced lengthening can be observed. Thus, the
˚
C11–S bond (1.683(4) A) in complex 21a exhibits double bond
character. In accordance with the high trans influence of the
˚
methyl ligands, the Pt1–S1 bond length (2.4818(9) A) belongs to
the longest ones known, as compared with thioketone platinum(IV)
˚
˚
complexes (median: 2.372 A, lower/upper quartile: 2.312/2.474 A;
15
n = 9, ). The interplanar angle between the STazH ligand and the
Fig. 1 Molecular structure of one of the two crystallographically
independent cations of fac-[PtMe (bpy)(ch-STaz-kN)][BF ] (19, ch-S-
◦
equatorial [PtC
2
N
2
] plane is 75.7 . As shown in Fig. 3, cation–
3
4
anion interactions in crystals of 21a are related to hydrogen
bond interactions of the type N3–H ◊ ◊ ◊ F2 (N3 ◊ ◊ ◊ F2 2.854(4) A).
Furthermore, molecules of 21a are packed like a “staircase” in
Taz = 5c). Hydrogen atoms are omitted for clarity. The ellipsoids
˚
are drawn at the 30% probability level. Selected bond lengths (in A˚ )
◦
a
and angles (in ) : Pt–C1 2.14(2)/2.03(1), Pt–C2 1.98(1)/2.07(2),
Pt–C3 2.02(2)/2.05(2), Pt–N3 2.16(1)/2.17(2), N3–C4 1.30(2)/1.33(2),
C4–S2 1.73(2)/1.67(2), C1ch–S2 1.85(2)/1.82(2), C1ch–C2ch 1.55(2)/
infinite columns (Fig. 3). The distances between the bpy ligands
◦
˚
(3.79/3.81 A) together with the displacement§ angle of 26.2 and
◦
1
1
.64(2), C2ch–C3ch 1.51(2)/1.56(2), C3ch–C4ch 1.44(2)/1.54(2), C4ch–C5ch
.43(2)/1.70(2), C5ch–O1 1.41(2)/1.51(2), C1ch–O1 1.42(2)/1.42(2),
25.1 , respectively, indicated a weak stabilization through p–p
21
and/or s–p (C–H ◊ ◊ ◊ p) interactions.
C1–Pt1–C2 88.8(6)/84.5(8), C2–Pt1–N3 179.5(6)/174.0(8), C3–Pt1–N2
1
1
75.3(6)/177.2(6), C4–S2–C1ch 104.6(8)/101.8(9), C1ch–O1–C5ch 111(1)/
17(1), O1–C1ch–C2ch 111(2)/111(2), C1ch–C2ch–C3ch 104(1)/107(1),
a
C2ch–C3ch–C4ch 113(2)/117(2), C4ch–C5ch–O1 116(1)/104(1). The values
of the two symmetry independent molecules are given separated by a
slash.
STaz functionalized glycosides. Comparison with data given in
the literature revealed that SEt carbohydrates in 8–14 possess a
similar trans influence like in analogous platinum(IV) complexes
having thionucleobase ligands fac-[PtMe
3
(bpy)L][BF
4
] (L = SCy,
4
2
4
1
18
1-MeSCy, s Ura, s s Ura; JPt,C: 642.1–651.5 Hz). The respective
values in the complexes 15–23 were also found in accordance
with those observed for trimethyl platinum(IV) complexes having
N-bound ligands like 2-(methylthio)-2-thiazoline and pyrrazole in
1
19 195
trans position ( JPt,C: 675.4, 682.3 Hz).
Pt chemical shifts for
Fig.
2
Molecular structure of the cation of fac-[PtMe
3
(bpy)-
complexes 8–23 (Table 1) were found to be in the same range as for
(
STazH-kS)][BF
4
] (21a). The ellipsoids are drawn at the 30% probability
16,18
other trimethyl(bipyridine)platinum(IV) complexes.
complexes 8–14 (-2435 to -2772 ppm) and 15–23 (-2444 to
2730 ppm) no distinct shift differences were found. Thus,
Between
◦
level. Selected bond lengths (in A˚ ) and angles (in ): Pt–C15 2.050(3),
Pt–C16 2.048(3), Pt–C14 2.046(3), Pt–N1 2.155(2), Pt–N2 2.163(3),
Pt–S1 2.4818(9), C11–S1 1.683(4), N1–Pt–N2 76.4(1), C15–Pt–C16
85.5(2), C14–Pt–N2 90.0(1), S1–Pt–C14 172.12(9), C15–Pt–N1 173.9(1),
C11–S1–Pt 117.0(1).
-
differences in the donor strength of the carbohydrate ligands seems
to be too small to be clearly reflected in the dPt values.
On the decomposition of the carbohydrate platinum(IV) com-
plexes. Under strictly dehydrated conditions solutions of the
complexes 8–23 were stable over weeks. Within two to three
months only a slow decomposition with formation of platinum
black took place, as indicated by NMR spectroscopy. In contrast,
solutions in acetone, which were not strictly dehydrated, were
Most likely, complex 21a is a product of the hydrolysis of 21,
which was induced by traces of water in the reaction mixture,
followed by an isomerization (Scheme 3(a)). The cleavage of
the glycosidic bond in 21 gave proof for the platinum mediated
activation of the glycosidic bond due to coordination to the
found to be less stable. Thus, a solution of fac-[PtMe
3
(bpy)(ch-
§
The displacement, measured by the angle between the ring normal and
STaz-kN)][BF
4
] (21, ch-STaz = 5e) was found to decompose
the centroid–centroid vector, is a measure for the ring–ring overlap.
6
330 | Dalton Trans., 2010, 39, 6327–6338
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Fig. 3 Solid state structure of fac-[PtMe
3
(bpy)(STazH-kS)][BF ] (21a)
4
showing the packing of the cations by p–p stacking (---) and the hydrogen
bonds ( ◊ ◊ ◊ ) between cations and anions. Hydrogen atoms are omitted for
clarity. Only one of the two disordered positions of the fluorine atoms are
shown.
Fig. 4 Molecular structure of one of the two symmetry independent
molecules of 1,6-anhydro-2,3,4-tri-O-benzoyl-b-D-glucopyranose (23a).
Hydrogen atoms are omitted for clarity. Ellipsoids are drawn at the 30%
◦
a
probability level. Selected bond lengths (in A˚ ) and angles (in ) : O1–C5
.425(5)/1.433(1), O1–C1 1.423(4)/1.417(5), O2–C1 1.417(4)/1.417(4),
O2–C6 1.436(5)/1.439(4), C5–C6 1.533(5)/1.516(4), C1–C2 1.541(6)/
.507(7), C2–C3 1.513(6)/1.505(6), C3–C4 1.559(6)/1.554(6),
C4–C5 1.523(6)/1.507(5), O1–C5–C6 102.2(3)/101.7(2), O2–C6–C5
1
1
1
1
03.5(3)/104.0(3), C1–O2–C6 107.1(3)/106.1(3), O1–C1–O2 106.1(3)/
06.2(3), C1–O1–C5 102.2(3)/101.2(2), C2–C3–C4 113.4(4)/112.7(4),
O1–C5–C4 108.7(3)/109.2(2), C5–C4–C3 111.7(3)/111.0(3), C3–C2–C1
a
1
12.2(3)/113.2(3), C2–C1–O1 109.3(3)/110.5(3). The values of the two
symmetry independent molecules are given separated by a slash.
Scheme 3 Possible mechanisms for the decomposition of 21 to 21a (a)
and 23 to 23a (b).
2.3. Neutral platinum(IV) complexes with monodentately
coordinated thioglycoside ligands
electrophilic cationic Pt(IV) center. Another indication for this is
the product of hydrolysis, obtained in the reaction of complex 1a
with 2-thiazolinyl 2,3,4-tri-O-benzoyl-1-thio-b-D-glucopyranose
Synthesis and NMR spectroscopic characterization. The reac-
2
tion of fac-[PtMe
3
(OAc-k O,O¢)(Me
2
CO)] (2) with carbohydrate
ligands of type 4 and 5 (Scheme 1) led to the formation of the
(
5g). Crystals of a decomposition product (1,6-anhydro-2,3,4-
2
complexes fac-[PtMe
3
(OAc-k O,O¢)(ch*)] (ch* = ch-SEt 24–28;
tri-O-benzoyl-b-D-glucopyranose, 23a) were obtained from the
acetone mother liquor. X-Ray diffraction analysis revealed that
ch-STaz 29–35) (Scheme 4, Table 2). The yellow, white and beige
powders, respectively, are moderately air stable and were isolated
in yields of 35–89%. The identities of the complexes 24–35 were
confirmed by H, C and Pt NMR spectroscopy as well as by
IR spectroscopy and high resolution ESI mass spectrometry.
23a crystallizes in the space group P1. The unit cell consists of two
symmetry independent, but structurally very similar, molecules.
The molecular structure of one molecule is depicted in Fig. 4.
Selected bond lengths and angles are given in the figure caption.
The pyranose ring possesses a distorted chair conformation on
O1 and C3, while the five membered ring exhibits an envelope
1
13
195
17
conformation on O1. The anhydro moiety was most likely formed
due to an intramolecular nucleophilic attack of the oxygen atom
O6 belonging to the unprotected hydroxyl group at C6, whereas
the glycosidic bond was activated by platinum coordination, as
discussed above (Scheme 3(b)).
Scheme
fac-[PtMe
4
Syntheses of carbohydrate platinum(IV) complexes
2
3
(OAc-k O,O¢)(ch*)] (ch* = ch-SEt, 24–28; ch-STaz, 29–35).
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-1
2
Table 2 Selected NMR and IR spectroscopic data (d in ppm, J in Hz, n in cm ) of the complexes fac-[PtMe (OAc-k O,O¢)(ch*)] (24–35)
3
a
a
2
a
Complex
ch*
d
H
d
C
J
Pt,H
d
Pt
n
sym. (CO2
)
n
asym. (CO2
)
DnCO2
ch-SEt
4a
2
2
2
2
2
4
5
6
7
8
1.08
1.07
1.10
0.96
1.15
-11.2
-11.7
-11.4
-11.3
-10.3
77.2
78.0
77.2
75.1
76.4
-2175
-2174
-2173
-2149
-2444
1411
1411
1409
1404
1402
1535
1560
1550
1571
1568
124
149
141
167
166
4b
4c
4d
b
4e
ch-STaz
5a
2
3
3
3
3
3
3
9
0
1
2
3
4
5
1.00c
0.91
0.87
1.17
1.07
1.08
0.91
-11.7
-11.1
-11.3
-11.3
-11.4
-11.3
-11.5
77.8
77.2
73.0
74.4
75.6
76.4
76.4
-1910
-1921
-1918
-1907
-1904
-1911
-1916
1534
c
5b
1411
1409
1418
5c
1535
1552
1533
126
134
5d
5e
5f
1411
5g
1531
a
b
◦
c
◦
Chemical shifts and coupling constants refer to the methyl ligands. At -80 C: 0.98/0.92 ppm. At -50 C: 0.72/0.78 ppm (74.4/70.4 Hz).
1
1
In the H NMR spectra, the signals of the PtMe
3
protons
H1 (0.34–0.50 ppm). The shift differences in H NMR spectra
of the two methylene proton resonances of the SCH (up to
0.21 ppm) and NCH (up to 0.30 ppm) were increased in complexes
exhibited broad mean signals at 0.87–1.17 ppm flanked by
platinum satellites (singlet plus doublet). The requisite signals in
the C NMR spectra for 24–35 were found as broad mean singlets.
2
2
1
3
24–28. Furthermore, upfield shifts ranging from 2.5–3.2 ppm
were observed in the C NMR spectra for the signals of the
2
13
The chemical shifts (d
H
1
/d
C
) and coupling constants ( JPt,H) are
◦
assembled in Table 2. H NMR measurements at -50 C of the
selected samples 28 and 30 showed that the expected split into three
separate signals becomes apparent, although a broadening of the
signals can be still observed. In the case of trimethylplatinum(IV)
complexes with non-functionalized carbohydrate ligands at lower
carbon atoms of the SCH
N coordination of the STaz groups, because the complexes fac-
[PtMe (bpy)(ch-STaz-kN)][BF ] (15–23), where this coordination
mode could be unambiguously proved, showed analogous fea-
2
groups (except 35). This indicated an
3
4
1
95
tures. Pt NMR chemical shifts of all these complexes between
-1910 and -2444 ppm (Table 2) are in the expected range for
13
temperatures, three separated sharp signals were observed. As
discussed in the previous section, some H and C NMR signals
1
13
13,16
trimethylplatinum(IV) complexes.
of the carbohydrate ligands in the complexes 24–35 are also
High resolution ESI mass spectrometry. High resolution ESI
mass spectrometric measurements were performed for complexes
broadened. In contrast to the previously discussed fac-[PtMe
bpy)(ch-SEt-kS)][BF ] (8–11, 13, 14) complexes, only marginal
CIS’s up to 0.12 ppm could be observed for the signals of the
3
(4,4¢-
R
2
4
2
4–35, which showed in all cases the existence of the molecu-
+
lar cation fac-[PtMe
a–5g), exhibiting an isotopic envelope characteristic for monoca-
tions containing one platinum atom [natural isotopic composition:
3
(ch*)] -OAc (ch* = ch-SEt, 4a–4e; ch-STaz;
1
CH groups of the SEt moieties in the H NMR spectra of the
2
5
complexes 24–27, having ch-SEt ligands. The chemical shifts for
the signals of H1 of the carbohydrate backbones were shifted
up to 0.10 ppm. The corresponding CIS’s for the carbon atoms
1
90
192
194
195
196
Pt (0.01%), Pt (0.79%), Pt (32.9%), Pt (33.8%), Pt
1
98
(
25.3%) and Pt (7.2%)]. The observed isotopic patterns of
1
3
of the SEt groups and C1 resonances in the C NMR spectra
amount up to 1.3 ppm and 1.7 ppm, respectively. For complex
the molecular cations were in very good agreement with the
calculated values. In Fig. 5, the full scan mass spectrum and the
2
8, where the ch-SEt ligand 4e possesses at C6 an additional
+
+
expanded spectrum of fac-[PtMe (ch-SEt)] (complex [28 - OAc] ;
3
◦
N-donor-site (picoline-2-yl), NOE experiments at -80 C were
performed to examine whether the nitrogen atom is involved in
the coordination to platinum. Irradiation into the resonance for
H6 of the picoline-2-yl group led to an increase of intensity for one
ch-SEt = 4e) is shown as an example. Furthermore, other peaks
could be detected, which were assigned to be dinuclear complexes
+
+
fac-[(PtMe
3
)
2
(OAc)(4e)] at 1124.3432 m/z, fac-[PtMe
3
(4e) ] at
2
+
1
410.5450 m/z and fac-[(PtMe
3
)
2
(OAc)(4e)
2
] at 1708.5787 m/z.
signal of the PtMe moiety, stating the spatial surrounding. Thus, a
3
According to the NMR spectra, in which the presence of such
species can be clearly excluded, these species are formed during
the ionization process and/or result from thermal decomposition
during the ESI experiment.
coordination of the nitrogen atom of picoline-2-yl to the platinum
atom is likely. In accordance with this, signals of the picoline-2-yl
1
13
groups were shifted downfield in H and C NMR spectra up to
1
95
0
.24 and 2.1 ppm, respectively. Furthermore, the Pt chemical
shift of complex 28 was found to be about 270 ppm highfield
shifted compared to those of complexes 24–27 (-2444 ppm versus
IR spectroscopy. IR spectra were recorded to examine the
coordination mode of the acetato ligand. The separation (DnCO2
)
-
2149 to -2175 ppm, Table 2). However, a fast exchange between
between the symmetric and asymmetric stretching band is a
N and S coordination in solution could not be definitely ruled out,
as indicated by the resonance downfield shift of 0.8 ppm for the
suitable tool to distinguish between the different coordination
22
modes. Typical DnCO2 values for a monodentate coordination are
1 22
-
CH
2
carbon atom signal of the SEt moiety.
in general much higher (215–565 cm
) than those observed in
2
-1
22
The complexes with type 5 ligands fac-[PtMe
3
(OAc-k O,O¢)(ch-
ionic acetates (164–171 cm in MOAc, M = alkaline metal ). On
STaz)] (29–35) showed remarkable upfield shifts for the signals of
332 | Dalton Trans., 2010, 39, 6327–6338
the other hand, a chelating coordination mode gives rise to Dn
CO
2
6
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of either nasym or nsym is in the same range as that observed in
complexes 24–28, 31 and 32. Hence, the analogous coordination
mode is likely.
2.4. Cationic platinum(IV) complexes with tridentately
coordinated thioglycoside ligands
Syntheses and NMR spectroscopic investigations. Complex
fac-[PtMe
ligands of type 4 to give mononuclear complexes fac-[PtMe
SEt)][BF ] (36–40) in good yields of 62–87% (Scheme 5, Table 3),
3
(Me
2
CO)
3
][BF
4
] (3) reacted in anhydrous acetone with
3
(ch-
4
where the carbohydrate ligands could coordinate in a tridentate
binding fashion. The colorless and beige powders are highly
(
36–38) and moderately (39, 40) air and moisture sensitive,
respectively. All complexes were fully characterized by NMR
1
13
195
(
H, C, Pt) spectroscopy, IR spectroscopy and high resolution
mass spectroscopy.
+
Fig. 5 (a) Positive ESI-mass spectrum of fac-[PtMe
3
(ch-SEt)] (complex
+
[
28 - OAc] ; ch-SEt = 4e). (b) Isotopic pattern of the molecular ion
+
fac-[PtMe
3
(4e)] at 825.2871 m/z showing the expected intensity due to
the isotopic composition given by horizontal bars.
values, which are similar or significantly lower (65–175 cm-1 22
)
in comparison to those for ionic compounds. The stretching
frequencies for the asymmetric and symmetric vibrational bands
and the differences of those frequencies (DnCO ) for the complexes
2
2
2
4–35 are given in Table 2. For the fac-[PtMe
SEt)] complexes 24–28, DnCO amounts to 124–167 cm , indicating
3
(OAc-k O,O¢)(ch-
-
1
2
a chelating coordination mode of the acetato ligand. In the case
2
of the fac-[PtMe
3
(OAc-k O,O¢)(ch-STaz)] complexes 29–35, the
assignment of the carboxyl stretching bands is often difficult
because of the overlap with the absorption bands of the STaz
moiety. Only for complexes 31 and 32 have both the symmetric and
asymmetric vibrational bands been assigned unambiguously. The
separation by 126 (31) and 134 cm (32), respectively, indicated
a chelating coordination mode of the acetato ligand. As shown
in Table 2, in the other complexes (29, 30, 33–35) the position
Scheme
5
Syntheses of carbohydrate platinum(IV) complexes
fac-[PtMe (ch*)][BF ] (ch* = ch-SEt, 36–40; ch-STaz, 41; ch-SPT,
3
4
42–44; ch-Sbpy, 45, 46). Npic = picoline-2-yl.
-
1
1
In the H NMR spectra of 36–38 the methyl ligands possessed
broad mean signals in a range of 1.18–1.28 ppm flanked by
1
13
195
3 4
Table 3 H and C NMR spectroscopic data (d in ppm, J in Hz) of the methyl ligands and Pt chemical shifts of the complexes fac-[PtMe (ch*)][BF ]
(
36–46)
2
Complex
ch*
d
H
d
C
J
Pt,H
d
Pt
ch-SEt
4a
36
37
38
39
40
1.28
1.26
1.18
1.06/1.12
0.89/1.26/1.65
-11.2
73.9
74.0
75.9
69.8/72.8
72.9/69.3/71.1
-2673
-2442
-2610
-2068
-2679
a
4c
-11.7
a
4d
-11.3
-5.4/-8.6
4.5/-1.3/-3.8
4e
4f
ch-STaz
5h
4
1
0.81/1.31/1.75
0.2/-4.9/-8.1
73.0/71.4/70.5
-2377
ch-SPT
6a
4
4
4
2
3
4
1.47
1.32
1.41
-5.8
-5.9
-5.7
br
br
br
-2154
-2158
-2151
6b
6c
ch-Sbpy
7a
7b
b
b
45
46
1.45
1.33
-3.4
-3.5
70.5
br
-2123
-2120
a
◦
b
◦
At -50 C: 0.94/1.07/1.33 ppm (76.9/80.6/79.3 Hz). At -80 C: 0.94/1.27/1.31 ppm (79.2/65.9/68.4 Hz).
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platinum satellites. Chemical shifts and coupling constants are
◦
given in Table 3. Measurements at -50 C using complex 38 as
an example, showed the expected split into three separate, sharp
signals, revealing the non-equivalence of the methyl ligands. For
complexes 39 and 40 having protecting groups at C6 with addi-
1
tional N-donor sites (picoline-2-yl, bipyridine-6-yl), the H NMR
spectra showed two slightly broadened (39) and three separate
sharp signals (40) for the methyl ligands, respectively, flanked by
platinum satellites (Table 3). For the signals of the carbohydrate
protons in the complexes 36–40, a broadening of all signals was
found for 36–38. For complexes 39 and 40 only partial broadening
was observed. The respective signals for the carbon atoms are
partially broadened in all complexes 36–40. Coordination-induced
shifts (Dd
H
/Dd ) for the methylene group resonances of the SEt
C
moiety (0.16–0.52/0.5–3.2 ppm) and H1 (0.17–0.43/1.3–3.1 ppm)
gave evidence that the sulfur atom is coordinated to the platinum
atom. The two remaining coordination sites of the platinum atom
in 36–38 are, most likely, occupied by any of the following: ring,
ether or ester oxygen donor atoms of the carbohydrates. Thus,
2
an kS,k O,O¢ coordination mode of the carbohydrate ligands in
complexes 36–38 can be assumed. In complexes 39 and 40, the
coordination of the picoline-2-yl and bipyridine-6-yl moiety could
be clearly seen by a significant downfield shift of the appropriate
+
Fig. 6 Isotopic pattern of the cation fac-[PtMe
3
(5h)] of complex 41
at 945.2684 m/z, showing the expected intensity due to the isotopic
1
13
composition given by horizontal bars.
signals in H and C NMR spectra up to 0.67 and 5.8 ppm,
2
respectively. This corresponds to an kS,kN,kO (39) and kS,k N,N¢
be caused by the presence of traces of hydrochloric acid. The
(
40) coordination mode of the carbohydrate ligands.
1
13
195
identities of the complexes were confirmed by H, C and Pt
NMRspectroscopy, IRspectroscopy and high resolution ESImass
spectrometry.
The methyl ligands gave broad mean signals in the H NMR
spectra at 1.32–1.47 ppm, flanked by platinum satellites (Table 3).
Surprisingly, reactions of fac-[PtMe (Me CO) ][BF ] (3) with
3
2
3
4
ligands of type 5 led to no isolable products. After adding a
solution of 3 in acetone to the thioglycoside, in contrast to the
1
1
common reactions, white precipitates were formed. H NMR
spectra of the reaction mixtures showed a multitude of products in
the carbohydrate area, including the a-hemiacetal. This indicated
that a cleavage of the C1–S bonds had occurred in a similar fashion
to the decomposition reactions shown in Scheme 3.
1
◦
H NMR experiments performed at -80 C with complex 45 as
an example showed the expected split into three separate signals
due to the non-equivalence of the methyl ligands. The SPT and
Sbpy moieties were unambiguously found to be coordinated to
the platinum atom. This was verified by remarkable downfield
shifts of the related signals of the protons and carbon atoms up to
To succeed in the formation of fac-[PtMe
3
(ch-STaz)][BF ]
4
complexes, carbohydrate 5h having a stabilizing bipyridine-6-yl
moiety at C6 (as in 4f) was selected. In the reaction of fac-
1
13
1
.0 ppm ( H NMR) and 5.1 ppm ( C NMR). The carbohydrate
proton resonances are shifted up to 0.41 ppm and are partially
[
PtMe
3
(Me
2
CO)
3
][BF
4
] (3) with 5h the complex fac-[PtMe (ch-
3
STaz)][BF
4
] (41; ch-STaz = 5h) was isolated as a moderately air
1
3
1 13
broadened, whereas the C NMR spectra of compounds 45 and
6 only showed a significant shift of 2.4 (45) and 2.9 (46) ppm for
the signals of C1. Also, a broadening of the resonances of C1 and
C2 (42–46) and C4 (44) can be observed. This indicates that the
exocyclic sulfur of the SPT and Sbpy moieties might be the third
donor atom coordinated to the platinum atom.
stable, yellow powder in a yield of 60%. H and C NMR spectra
showed unambiguously the coordination of the bipyridine-6-yl
moiety with chemical shift differences of the bipyridine resonances
shifted downfield up to 0.92 ppm and 7.1 ppm, respectively.
Furthermore, remarkable CIS’s of the signals of H1 and C1, which
4
1
13
amount to 0.23 ( H NMR) and 4.9 ppm ( C NMR), respectively,
are observed. The identity of 41 was also confirmed by high resolu-
tion mass spectrometry (Fig. 6). The isotopic pattern of the molec-
ular cation is in a very good agreement with the calculated values.
Obviously, carbohydrates possessing chelating donor groups are
The ESI mass spectra for complexes 42–46 showed the pres-
+
ence of a mononuclear cation fac-[PtMe
3
(ch*)] (ch* = ch-SPT,
4
2–44; ch-Sbpy, 45, 46) containing one platinum atom. The full
scan mass spectrum of 43, depicted in Fig. 7, shows no other
platinum-containing cations. The isotopic pattern of the fac-
the key to yield stable fac-[PtMe
the carbohydrate classes ch-SPT (type 6, Scheme 1) and ch-Sbpy
type 7, Scheme 1), havingachelatinggroupinthe aglyconemoiety,
were included in the subsequent investigations. Reactions of fac-
PtMe (Me CO) ][BF ] (3) with ligands of type 6 and 7 led to the
3
(ch*)][BF ] complexes. Therefore,
4
+
[
PtMe
3
(ch-SPT)] (ch-SPT = 6b) cation at 1012.1890 m/z is in
very good agreement with the calculated values.
(
[
3
2
3
4
3
. Conclusion
formation of complexes 42–46, which were isolated as yellow and
beige powders, respectively, in yields of 54–75% (Scheme 5). These
complexes are stable in anhydrous acetone solutions over a few
weeks, without any evidence of decomposition. In chloroform,
however, decomposition was observed within 4 days, which might
Platinum(IV) complexes with thioglycoside ligands of the types
fac-[PtMe (4,4¢-R bpy)(ch*)][BF
] (ch* = ch-SEt, 8–14; ch-STaz,
15–23), fac-[PtMe
(OAc-k O,O¢)(ch*)] (ch* = ch-SEt, 24–28; ch-
STaz, 29–35) and fac-[PtMe (ch*)][BF
] (ch* = ch-SEt, 36–40;
3
2
4
2
3
3
4
6
334 | Dalton Trans., 2010, 39, 6327–6338
This journal is © The Royal Society of Chemistry 2010

View Article Online
these findings, we succeeded to get stable complexes of the type fac-
[
PtMe
3
(ch-STaz)][BF ] with a derivative having additional strong
4
donor sites in form of a 2,2¢-bipyridine-6-yl protecting group at
C6 of the carbohydrate moiety (41).
For the first time the investigations presented in this study give
a deeper insight into the coordination chemistry of thioglycosides
to platinum(IV) being a coordination center in a relatively high
oxidation number. It has been shown that these ligands can be
coordinated not only monodentately through a relatively strong
donor site (kS or kN) but also facial tridentately using donor sets
2
consisting of one stronger and two weaker donor sites (kS,k O,O¢;
O = oxygen atom from the carbohydrate backbone), two stronger
and one weaker donor sites (kS,kN,kO) or three stronger donor
2
3
sites (kS,k N,N¢ or k N,N¢,N¢¢). Furthermore, coordination of
thioglycosides to the highly electrophilic platinum center may
give rise to platinum-assisted cleavage of glycosidic C–S bonds,
which creates a basis to a deeper understanding of stereocontrolled
+
Fig. 7 (a) Positive ESI-mass spectrum of the cation fac-[PtMe
complex 43. (b) Isotopic pattern of the molecular ion fac-[PtMe
3
(6b)] of
+
(6b)]
14
3
chemical glycosylations, mediated by metal coordination.
at 1012.1890 m/z showing the expected intensity due to the isotopic
composition given by horizontal bars.
4
. Experimental
4
.1. General considerations
ch-STaz, 41; ch-SPT, 42–44; ch-Sbpy, 45, 46), with the thioglyco-
sides coordinated in a mono- (8–35) and tridentate (36–46) binding
fashion have been synthesized. Despite the kinetic inertness
General considerations. Syntheses were performed, in general,
under strictly dehydrated conditions in an argon atmosphere using
standard Schlenk techniques. As precipitates, the carbohydrate
platinum complexes are stable for a few hours (2–4 h) even in
open air, whereas a strictly anhydrous environment was required
for handling their solutions in acetone. Acetone and pentane
were dried over phosphorus pentoxide followed by 4 A molecular
sieves and LiAlH , respectively. Diethyl ether was dried over Na-
benzophenone. All solvents were distilled prior to use. NMR
spectra were obtained with Varian UNITY 500, Gemini 2000 and
Bruker 800 spectrometers using solvent signals ( H and C NMR
spectroscopy) as internal references and Na
0
Mattson FT IR spectrometer, using KBr pellets. The positive ion
high resolution ESI mass spectra were obtained from a Bruker
Apex III Fourier transform ion cyclotron resonance (FT-ICR)
mass spectrometer (Bruker Daltonics, Billerica, USA) equipped
with an Infinity cell, a 7.0 Tesla superconducting magnet (Bruker),
a RF-only hexapole ion guide and an external electron spray ion
source (Agilent, off axis spray, voltages: endplate, -3.700 V; capil-
6
of platinum(IV) complexes due to their low spin d electron
configuration, it could be shown that in trimethylplatinum(IV)
complexes weakly coordinating ligands like acetone could be
smoothly substituted by thioglycosides. These ligand exchange
reactions are further supported by the high trans effect of the
methyl ligands. Furthermore, platinum mediated decomposition
of thioglycosides in complexes 21 and 23 involving the cleavage
of the C–S glycosidic bonds, yielded the corresponding products
˚
4
1
13
21a and 23a (Scheme 3). This result is in accordance with
1
95
2
[PtCl
6
] (d( Pt) =
common glycosylation procedures, wherein the glycosidic bond
of the glycosyl donor is activated in the first step by adding an
ppm) as external reference. IR spectra were recorded on a Galaxy
2
electrophilic promoter, such as MeOTf or NIS/TfOH.
As expected from the coordination chemistry perspective,
complexes of platinum(IV) in which the thioglycoside ligands
have three coordination sites at their disposal (i.e. using fac-
[
PtMe
3
(Me
2
CO)
3
][BF ] (3) as starting complex) proved to be
4
more air and moisture sensitive than the cationic complexes
with bipyridine and the neutral complexes with acetato ligands.
Thus, complexes with thioglycoside ligands having only the SEt
group as strong donor site could be prepared and characterized
lary, -4.200 V; capillary exit, 100 V; skimmer 1, 15.0 V; skimmer 2,
◦
6
.0 V). Nitrogen was used as drying gas at 150 C. The sample solu-
tions were introduced continuously via a syringe pump with a flow
rate of 120 ml h . The data were acquired with 512 k data points
and zero filled to 2048 k by averaging 64 scans. fac-[(PtMe
and fac-[PtMe
methods. All other materials were purchased from commercial
sources. Synthesis of fac-[PtMe
data as well as the NMR and IR spectroscopic data of the carbo-
hydrate platinum complexes 1–46 are available as ESI.† Selected
spectroscopic data of complexes 1–46 are given in Table 1–3.
(
36–38), whereas it was not possible with complexes having
-
1
only the STaz group as the strongest donor site. In the latter
cases, a partial cleavage of the glycosidic bonds instead of
the anticipated complex formation took place. These cleavage
reactions are promoted by the STaz coordination to Pt, as
discussed before being a further example for the cleavage of
14,25
3
I)
4
]
20
3
I(bpy)] were prepared according to literature
t
3
I(4,4¢- Bu
2
bpy)] and its analytical
2
glycosidic bonds by electrophilic promoters. However, it can’t
be strictly ruled out that these reactions are also influenced
by traces of water and/or Ag[BF]
4
(present in the reaction
mixtures despite using strictly anaerobic conditions and from
General method for the synthesis of the complexes fac-
23,24
the in situ synthesis of complex 3, respectively).
Analogous
[PtMe
3
(4,4¢-R
2
bpy)(ch*)][BF
4
](ch* = ch-SEt, R = H: 8–12; R =
t
t
platinum-mediated reactions, such as cleavage and formation of
isopropylidene protecting groups and Schiff bases, were frequently
observed in carbohydrate trimethylplatinum(IV) complexes, with
Bu: 13, 14; ch-STaz, R = H: 17–23, R = Bu: 15, 16).
A suspension of fac-[PtMe
3
I(bpy)] (70.0 mg, 0.14 mmol) or
t
fac-[PtMe
3
I(4,4¢- Bu
2
bpy)] (88.9 mg, 0.14 mmol) and Ag[BF ]
4
12,13
non-functionalized carbohydrate ligands.
In full accord with
(26.5 mg, 0.14 mmol) in acetone (10 ml) was stirred for 30 min
This journal is © The Royal Society of Chemistry 2010
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under the absence of light. Precipitated AgI was removed by filtra-
(23.0 mg, 0.14 mmol) in acetone (10 ml) was stirred for 12 h under
tion and the clear, colorless solution of fac-[PtMe
3
(Me
2
CO)(4,4¢-
the absence of light. Precipitated AgI was removed by filtration
t
2
R
2
bpy)][BF
4
] (R = H, 1a; R = Bu, 1b) was added to the respective
and the clear, colorless solution of fac-[PtMe
3
(OAc-k O,O¢)(Me
2
-
b-D-thiopyranoside (0.14 mmol). After 5 h the volume of the
solution was reduced in vacuo to 3 ml and pentane (10 ml) was
added. The precipitated solid was filtered, washed with pentane
CO)] (2) was directly added to the respective b-D-thiopyranoside
(0.14 mmol). After 5 h the volume of the solution was reduced in
vacuo to 3 ml and pentane (6 ml) was added. The precipitated solid
(
2 ¥ 2 ml) and dried in vacuo.
fac-[PtMe (bpy)(ch-SEt)][BF
m/z (ESI) 788.2192 ([PtMe
was filtered, washed with pentane (2 ¥ 2 ml) and dried in vacuo.
2
3
4
] (8, ch-SEt = 4a). (88 mg, 72%);
fac-[PtMe
3
(OAc-k O,O¢)(ch-SEt)] (24, ch-SEt = 4a). (55 mg,
+
2
+
3
(bpy)(4a)] . C29
H
41
N
2
O
9
PtS requires
57%); m/z (ESI) 632.1498 ([PtMe
PtS requires 632.1493).
fac-[PtMe
(OAc-k O,O¢)(ch-SEt)] (25, ch-SEt = 4b). (62 mg,
70%); m/z (ESI) 632.1498 [PtMe (OAc-k O,O¢)(4b)] -OAc
PtS requires 632.1493).
fac-[PtMe
3
(OAc-k O,O¢)(4a)] -OAc.
7
88.2181).
C
30
H
40
N
3
O
9
2
2
fac-[PtMe
3
(bpy)(ch-SEt)][BF
4
] (9, ch-SEt = 4b). (115 mg, 73%);
PtS requires
3
+
2
+
m/z (ESI) 788.2193 ([PtMe
7
3
(bpy)(4b)] . C29
H
41
N
2
O
9
3
.
88.2181).
C
30
H
40
N
3
O
9
2
2
fac-[PtMe
3
(bpy)(ch-SEt)][BF
4
] (10, ch-SEt = 4c). (102 mg, 65%);
PtS requires
3
(OAc-k O,O¢)(ch-SEt)] (26, ch-SEt = 4c). (64 mg,
+
+
m/z (ESI) 1036.2805 ([PtMe
3
(bpy)(4c)] . C49
H
49
N
2
O
9
54%); m/z (ESI) 880.2108 ([PtMe
3
(OAc-kO,O¢)(4c)] -OAc
.
1
036.2807).
fac-[PtMe
8%); m/z (ESI) 980.3623 ([PtMe
C
30
H
40
N
3
O
9
PtS
2
requires 880.2119).
2
3
(bpy)(ch-SEt)][BF
4
] (11, ch-SEt = 4d). (107 mg,
(bpy)(4d)] . C49 PtS
fac-[PtMe
3
(OAc-k O,O¢)(ch-SEt)] (27, ch-SEt = 4d). (64 mg,
2 +
3 49 5
+
7
3
H
49
N
2
O
9
54%); m/z 824.2939 ([PtMe (OAc-k O,O¢)(4d)] -OAc. C39H O PtS
requires 980.3636).
fac-[PtMe (bpy)(ch-SEt)][BF
m/z (ESI) 981.3586 ([PtMe
requires 824.2948).
2
3
4
] (12, ch-SEt = 4e). (90 mg, 68%);
fac-[PtMe
3
(OAc-k O,O¢)(ch-SEt)] (28, ch-SEt = 4e). (75 mg,
+
2
+
3
(bpy)(4e)] . C48
H
56
N
3
O
5
PtS requires
58%); m/z (ESI) 825.2871 ([PtMe
PtS requires 825.2901).
3
(OAc-k O,O¢)(4e)] -OAc.
9
81.3588).
fac-[PtMe
C
38
H
48NO
5
t
2
3
(4,4¢- Bu
2
bpy)(ch-SEt)][BF
4
] (13, ch-SEt = 4a).
fac-[PtMe
89%); m/z (ESI) 689.1172 ([PtMe
PtS requires 689.1166).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (30, ch-STaz = 5b). (120 mg,
86%); m/z (ESI) 937.1753 ([PtMe (OAc-k O,O¢)(5b)] -OAc
PtS requires 937.1792).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (31, ch-STaz = 5c). (86 mg,
68%); m/z (ESI) 937.1789 ([PtMe (OAc-k O,O¢)(4e)] -OAc
PtS requires 937.1792).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (32, ch-STaz = 5d). (102 mg,
80%); m/z (ESI) 881.2630 ([PtMe (OAc-k O,O¢)(5d)] -OAc
PtS requires 881.2622).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (33, ch-STaz = 5e). (30 mg,
35%); m/z (ESI) 577.1368 [PtMe (OAc-k O,O¢)(5e)] -OAc
PtS requires 577.1370).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (34, ch-STaz = 5f ). (67 mg,
60%); m/z (ESI) 737.1525 ([PtMe (OAc-k O,O¢)(5f)] -OAc
PtS requires 737.1530).
fac-[PtMe
(OAc-k O,O¢)(ch-STaz)] (35, ch-STaz = 5g). (44 mg,
35%); m/z (ESI) 833.1553 ([PtMe (OAc-k O,O¢)(5g)] -OAc
3
(OAc-k O,O¢)(ch-STaz)] (29, ch-STaz = 5a). (93 mg,
t
+
2
+
(
82 mg, 65%); m/z (ESI) 900.3437 ([PtMe
3
(4,4¢- Bu
2
bpy)(4a)] .
3
(OAc-k O,O¢)(5a)] -OAc
.
C
37
H
57
N
2
O
9
PtS requires 900.3432).
C
20
H
32NO
9
2
t
2
fac-[PtMe
3
(4,4¢- Bu
2
bpy)(ch-SEt)][BF
4
]
(14, ch-SEt = 4c).
3
t
+
2
+
(
72 mg, 54%); m/z (ESI) 1148.4030 ([PtMe
3
(4,4¢- Bu
2
bpy)(6c)] .
3
.
C
37
H
57
N
2
O
9
PtS requires 1148.4058).
C
40
H
40NO
9
2
t
2
fac-[PtMe
3
(4,4¢- Bu
2
bpy)(ch-STaz)][BF
4
] (15, ch-STaz = 5c).
3
t
+
2
+
(
82 mg, 45%); m/z (ESI) 1205.3743 ([PtMe
3
(5c)(4,4¢- Bu
2
bpy] .
3
.
C
58
H
64
N
3
O
9
PtS
2
requires 1205.3732).
C
16
H
32NO
5
2
t
2
fac-[PtMe
3
(4,4¢- Bu
2
bpy)(ch-STaz)][BF
4
] (16, ch-STaz = 5g).
3
t
+
2
+
(
108 mg, 76%); m/z (ESI) 1101.3480 ([PtMe
3
(4,4¢- Bu
2
bpy)(5g)] .
3
.
C
58
H
64
N
3
O
9
PtS
2
requires 1101.3470).
C
40
H
48NO
5
2
2
fac-[PtMe
3
(bpy)(ch-STaz)][BF
4
] (17, ch-STaz = 5a). (130 mg,
3
+
2
+
8
5%); m/z (ESI) 845.1841 ([PtMe
requires 845.1854).
fac-[PtMe (bpy)(ch-STaz)][BF
3
(bpy)(5a)] . C30
H
40
N
3
O
9
PtS
2
3
.
C
16
H
32NO
5
2
2
3
4
] (18, ch-STaz = 5b). (76 mg,
3
+
2
+
6
4%); m/z (ESI) 1093.2478 ([PtMe
requires 1083.2480).
fac-[PtMe (bpy)(ch-STaz)][BF
3
(bpy)(5b)] . C50
H
48
N
3
O
9
PtS
2
3
.
C
25
H
36NO
8
2
2
3
4
] (19, ch-STaz = 5c). (115 mg,
3
+
2
+
7
3%); m/z (ESI) 1093.2479 ([PtMe
requires 1093.2480).
fac-[PtMe (bpy)(ch-STaz)][BF
3
(bpy)(5c)] . C50
H
48
N
3
O
9
PtS
2
3
.
C
33
H
36NO
8
PtS requires 833.1530).
2
3
4
] (20, ch-STaz = 5d). (72 mg,
+
7
2%); m/z (ESI) 1037.3305 ([PtMe
requires 1037.3309).
fac-[PtMe (bpy)(ch-STaz)][BF
3
(bpy)(5d)] . C50
H
48
N
3
O
9
PtS
2
General method for the synthesis of the complexes [PtMe
3
(ch*)]-
] (ch* = ch-SEt, 36–40; ch-STaz, 41, ch-SPT, 42–44, ch-Sbpy,
I) ] (70.0 mg, 0.04 mmol)
] (26.5 mg, 0.14 mmol) in acetone (10 ml) was stirred
[BF
4
3
4
] (21, ch-STaz = 5e). (91 mg,
45, 46). A suspension of fac-[(PtMe
and Ag[BF
3
4
+
8
3%); m/z (ESI) 733.2074 ([PtMe
requires 733.2057).
fac-[PtMe (bpy)(ch-STaz)][BF
112 mg, 94%); m/z (ESI-MS) 893.2203 ([PtMe
3
(bpy)(5e)] . C26
H
40
N
3
O
5
PtS
2
4
for 30 min under the absence of light. Precipitated AgI was
removed by filtration and the clear, colorless solution of fac-
3
4
]
(22, ch-STaz
=
5f ).
(bpy)(5f)] .
+
(
3
[PtMe
3
(Me
2
CO)
3
][BF ] (3) was directly added to the respective
4
C
35
H
44
N
3
O
8
PtS
2
requires 893.2218).
b-D-thiopyranoside (0.14 mmol). After 5 h the volume of the
solution was reduced in vacuo to 3 ml and pentane (10 ml) was
added. The precipitated solid was filtered, washed with pentane
(2 ¥ 2 ml) and dried in vacuo.
fac-[PtMe
3
(bpy)(ch-STaz)][BF
4
] (23, ch-STaz = 5g). (91 mg,
+
8
3%); m/z 989.2243 (ESI) ([PtMe
3
(bpy)(5g)] . C43
H
44
N
3
O
8
PtS
2
requires 989.2218).
fac-[PtMe
(ESI) 632.1492 [PtMe
fac-[PtMe (ch-SEt)][BF
(ESI) 880.2115 ([PtMe
3
(ch-SEt)][BF
4
] (36, ch-SEt = 4a). (42 mg, 87%); m/z
+
General method for the synthesis of the complexes [PtMe
3
(OAc-
j O,O¢)(ch*)] (ch* = ch-SEt, 24–28; ch-STaz, 29–35).
suspension of fac-[(PtMe I) ] (50.0 mg, 0.04 mmol) and AgOAc
3
(4a)] . C19
H
33
O PtS requires 632.1493).
9
2
A
3
4
] (37, ch-SEt = 4c). (40 mg, 62%); m/z
+
3
4
3
(4c)] . C39
H
41
9
O PtS requires 880.2119).
6
336 | Dalton Trans., 2010, 39, 6327–6338
This journal is © The Royal Society of Chemistry 2010

View Article Online
Table 4 Crystal data, data collection and refinement parameters of fac-[PtMe
kS)][BF ] (21a) and 1,6-anhydro-2,3,4-tri-O-benzoyl-b-D-glucopyranose (23a)
3
(bpy)(ch-STaz-kN)][BF
4
3
] (19, ch-STaz = 5c), fac-[PtMe (bpy)(STazH-
4
1
9
21a
23a
Formula
FW
C
50
H
48BF
4
N
3
O
9
PtS
2
C
16
H
22BF
4
N
3
PtS
2
27 22 8
C H O
474.45
Triclinic
P1
9.6936(8)
11.011(1)
11.449(1)
66.414(4)
89.999(4)
89.894(4)
1119.9(2)
2
1.407
100(2)
0.104
1.94–26.44
496
-11 ≤ h ≤ 12
-13 ≤ k ≤ 13
-14 ≤ l ≤ 14
28835
1180.94
Tetragonal
P4
22.1611(9)
22.1611(9)
43.735(2)
602.39
Monoclinic
P2 /c
13.2216(5)
12.6149(5)
12.8474(5)
Crystal system
Space group
a/A˚
b/A˚
c/A˚
1
2
1
2
1
◦
a/
◦
b/
115.776(2)
◦
g /
V/A˚
3
21479(2)
16
1.461
100(2)
6.194
4.47–61.49
9472
1929.6(1)
4
2.074
100(2)
7.532
1.71–36.00
1160
-21 ≤ h ≤ 21
-19 ≤ k ≤ 20
-21 ≤ l ≤ 21
56461
Z
D
calc./g cm-
3
T/K
-1
m/mm
◦
q/
F(000)
Index ranges
-23 ≤ h ≤ 20
-
25 ≤ k ≤ 25
49 ≤ l ≤ 47
-
Reflns collected
Reflns obs [I > 2s(I)]
Reflns independent
66857
4582
7098
6186
16385 (Rint = 0.1328)
16385/1332/1103
0.617
0.0481/0.0785
0.1755/0.0966
1.009 and -0.519
-0.044(9)
9070 (Rint = 0.0643)
8089 (Rint = 0.0699)
8089/3/604
1.003
0.0602/0.1447
0.0810/0.1593
0.358 and -0.350
0.4(10)
Data/restraints/parameters
9070/1/257
2
GOF(F )
1.034
R
R
1
, wR
, wR
2
(I > 2s)
(all data)
0.0347/0.0757
0.0529/0.0828
1.958 and -1.058
1
2
Largest diff. peak and hole/e A˚
Flack parameter
-3
fac-[PtMe
ESI) 824.2948 ([PtMe
fac-[PtMe (ch-SEt)][BF
ESI) 825.2903 ([PtMe
fac-[PtMe (ch-SEt)][BF
ESI) 888.2940 ([PtMe
fac-[PtMe (ch-STaz)][BF
3
(ch-SEt)][BF
4
] (38, ch-SEt = 4d). (53 mg, 70%); m/z
(19) and acetone/ether/pentane solutions (1 : 1 : 1) (21a, 23a),
respectively. Intensity data were collected on a Oxford Gemini S
+
(
(
(
3
(4d)] . C39
H
49
O
5
PtS requires 824.2948).
˚
3
4
] (39, ch-SEt = 4e). (92 mg, 72%); m/z
diffractometer with Cu-Ka radiation (l = 1.54184 A, graphite
+
3
(4e)] . C38
H
48NO
5
PtS requires 825.2901).
monochromator) at 100(2) K (19) and on a Bruker Apex II
˚
3
4
] (40, ch-SEt = 4f ). (118 mg, 85%); m/z
Kappa diffractometer with Mo-Ka radiation (l = 0.71073 A,
+
3
(4f)] . C43
H
48
N
3
O
5
PtS
2
requires 888.3010).
graphite monochromator) at 100(2) K (21a, 23a). A summary of
the crystallographic data, the data collection parameters and the
refinement parameters is given in Table 4. Numerical (21a) and
multiscan (23a) absorption corrections were applied (Tmin/Tmax
0.18/0.55, 21a; Tmin/Tmax 0.97/0.98, 23a). The structures were
3
4
] (41, ch-STaz = 5h). (87 mg, 60%);
+
m/z (ESI) 945.2684 ([PtMe
3
(5h)] . C43
H
48
N
3
O
5
PtS
2
requires
9
45.2683).
fac-[PtMe
3
(ch-SPT)][BF
4
] (42, ch-SPT = 6a). (77 mg, 65%);
+
26
m/z (ESI) 764.1262 ([PtMe
3
(6a)] . C25
H
33
N
2
O
9
PtS
2
requires
solved by direct methods with SHELXS-97 and refined using
2
26
7
64.1275).
full matrix least square routines against F with SHELXL-97.
fac-[PtMe
m/z (ESI) 1012.1890 ([PtMe
012.1901).
3
(ch-SPT)][BF
4
] (43, ch-SPT = 6b). (83 mg, 54%);
Non-hydrogen atoms were refined with anisotropic displacement
parameters. The hydrogen atom attached to nitrogen in 21a
was found in the difference Fourier map and refined freely. All
other hydrogen atoms were positioned geometrically and refined
with isotropic displacement parameters according to the “riding
model”. Although measured at 100 K with Cu-Ka radiation the
small sized needle-like crystals (0.3 ¥ 0.03 ¥ 0.03 mm) of complex
19 showed only a weak reflectivity resulting in a limited quality
+
3
(6b)] . C45
H
41
N
2
O
9
PtS requires
2
1
fac-[PtMe
3
(ch-SPT)][BF
4
] (44, ch-SPT = 6c). (98 mg, 67%);
+
m/z (ESI) 956.2702 ([PtMe
56.2731).
3
(6c)] . C45
H
49
N
2
O
5
PtS
2
requires
9
fac-[PtMe
3
(ch-Sbpy)][BF
4
] (45, ch-Sbpy = 7a). (89 mg, 75%);
+
m/z (ESI) 758.1679 ([PtMe
3
(7a)] . C27
H
35
N
2
9
O PtS requires
7
58.1711).
fac-[PtMe
of the structure solution. The required fixing of disordered groups
-
3
(ch-Sbpy)][BF
4
] (46, ch-Sbpy = 7b). (101 mg, 66%);
(phenyl rings and [BF
4
] anions) for the refinement of 19, led to
+
m/z (ESI) 1006.2331 ([PtMe
3
(7b)] . C47
H
43
N
2
O
9
PtS requires
the comparatively high number of restraints. The fluoroatom F4
of the tetrafluoroborate anion in complex 21a was found to be
disordered over two equally occupied positions.
1006.2337).
4
.2. X-Ray crystallography†
Single crystals of fac-[PtMe
3
(bpy)(ch-STaz-kN)][BF
] (21a) and 1,6-anhydro-
,3,4-tri-O-benzoyl-glucopyranose (23a) for X-ray diffraction
4
] (ch-STaz =
4
.3. Computational details
5
c, 19), fac-[PtMe
3
(bpy)(STazH-kS)][BF
4
2
DFT calculations of compounds were carried out by the Gaussian
03 program package using the hybrid functional B3LYP. The
27
28
measurements were obtained from acetone/ether/THF (1 : 1 : 1)
This journal is © The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 6327–6338 | 6337

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6
-311G(d,p) basis sets as implemented in Gaussian 03 were
Angew. Chem., Int. Ed. Engl., 1997, 36, 2686; (c) H. Junicke, C. Bruhn,
R. Kluge, A. S. Serianni and D. Steinborn, J. Am. Chem. Soc., 1999,
employed for main group atoms. The valence shell of platinum
has been approximated by a split valence basis set too; for its
core orbitals an effective core potential in combination with
consideration of relativistic effects has been used. The appro-
priateness of the functional in combination with the basis sets and
effective core potential used for reliable interpretation of structural
and energetic aspects of related platinum complexes has been
demonstrated. All systems were fully optimized without any sym-
metry restrictions. The resulting geometries were characterized as
equilibrium structures by the analysis of the force constants of
normal vibrations. Solvent effects were considered according to
1
21, 6232; (d) H. Junicke, R. Kluge and D. Steinborn, J. Inorg. Biochem.,
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2
14 P. Pornsuriyasak, C. Vetter, S. Kaeothip, M. Kovermann, J. Balbach,
29
D. Steinborn and A. V. Demchenko, Chem. Commun., 2009, 6379.
5 Cambridge Structural Database (CSD) Version 5.30 2008, University
Chemical Laboratory, Cambridge (England).
1
1
6 (a) T. G. Appleton, H. C. Clark and L. E. Manzer, Coord. Chem. Rev.,
1973, 10, 335; (b) C. Vetter, C. Wagner, J. Schmidt and D. Steinborn,
Inorg. Chim. Acta, 2006, 359, 4326.
30
1
1
7 R. Bucourt, Top. Stereochem., 1974, 8, 159.
8 (a) C. Vetter, C. Wagner, G. N. Kaluąerovi c´ , R. Paschke and D.
Steinborn, Inorg. Chim. Acta, 2009, 362, 189; (b) C. Vetter, G. N.
Kaluąerovi c´ , R. Paschke and D. Steinborn, Inorg. Chim. Acta, 2010,
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31
the polarized continuum model as implemented in Gaussian 03.
1
2
9 (a) C. Vetter, diploma thesis, Martin-Luther-Universit a¨ t Halle-
Wittenberg, Halle 2005; (b) R. Lindner, G. N. Kaluąerovi c´ , R. Paschke,
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1983, 77, L89; (b) H. T. Flakus, A. Miros and P. G. Jones, Spectrochim.
Acta, Part A, 2002, 58, 225; (c) R. S. Corr eˆ a, S. A. Santana, R. Salloum,
R. M. Silva and A. C. Doriguetto, Acta Crystallogr., Sect. C: Cryst.
Struct. Commun., 2006, 62, o115.
Acknowledgements
Financial support from the National Science Foundation (award
CHE-0547566 to AVD), the National Institute of General Medical
Sciences (award GM077170 to AVD), and gifts of chemicals by
Merck (Darmstadt) is gratefully acknowledged. Special thanks
to Prof. J. Balbach and Dipl.-Phys. M. Kovermann (Martin-
Luther-Universit a¨ t Halle-Wittenberg) for the NMR spectroscopic
measurements on the 800 MHz spectrometer.
2
1 C. Janiak, J. Chem. Soc., Dalton Trans., 2000, 3885.
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338 | Dalton Trans., 2010, 39, 6327–6338
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