Supramolecular organoplatinum(IV) chemistry: A nanotube structure supported by hydrogen bonds

Article abstract of DOI:10.1039/b900855a

The oxidative addition of 4-BrCH₂C₆H ₄-C(=O)NH-t-Bu to [PtMe₂(bu₂bipy)], bu ₂bipy = 4,4′-di-tert-butyl-2,2′-bipyridine, gave [PtBrMe₂(CH₂C₆H₄-C(=

Full text of DOI:10.1039/b900855a

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Supramolecular organoplatinum(IV) chemistry: a nanotube structure
supported by hydrogen bonds†
Richard H. W. Au, Michael C. Jennings and Richard J. Puddephatt*
Received 15th January 2009, Accepted 12th February 2009
First published as an Advance Article on the web 5th March 2009
DOI: 10.1039/b900855a
The oxidative addition of 4-BrCH2C6H4-C(=O)NH-t-Bu to [PtMe2(bu2bipy)], bu2bipy = 4,4¢-di-tert-
butyl-2,2¢-bipyridine, gave [PtBrMe2(CH2C6H4-C(=O)NH-t-Bu)(bu2bipy)], which reacted with AgX
and a bridging ligand LL to give binuclear complexes [{PtMe2(CH2C6H4-C(=O)NH-t-Bu)-
(bu2bipy)}2(m-LL)]X2, LL = 1,4-pyrazine or 4,4¢-bipyridine, X = BF4 or PF6. The complexes all take
=
part in hydrogen bonding through either NH ◊ ◊ ◊ O C, NH ◊ ◊ ◊ FB or NH ◊ ◊ ◊ FP interactions and, in the
case with LL = 4,4¢-bipyridine, X = PF6, a supramolecular structure containing tubes is formed.
hollow tube supramolecular structure, of a type potentially useful
for selective absorption of small molecules.1
Introduction
The synthesis of supramolecular polymers and network materials
is a topical and challenging field of research, with potential
applications in functional materials for sensors or molecular
machines, or in catalysis.1 The synthesis of supramolecular
organometallic polymers and network materials is particularly
challenging because many metal–carbon bonds are reactive to-
wards the functional groups commonly used in supramolecular
self-assembly and because the organometallic complexes often
contain several functional groups, so making it difficult to
predict or to engineer the supramolecular structure.2 However,
despite these challenges, the synthesis of hybrid organic-inorganic
macrocycles, oligomers or polymers with organometallic units in
the backbone structure, together with functional groups to allow
planned self-assembly, is a rapidly developing field of research.
We have previously shown that organoplatinum(IV) complexes
are useful for assembling hydrogen bonding groups, and that the
subsequent self-assembly can give polymers, including a double-
stranded polymer and a polyrotaxane.3 The chemistry is possible
because the alkylplatinum(IV) bond is stable to air and to protic
reagents, and because the oxidative addition reaction used to
introduce the primary functional groups occurs selectively and
under mild conditions.4
Results and discussion
Amide groups often form strong intermolecular hydrogen bonds
and this typically leads to low solubility in many organic
solvents. The reagent N-t-butyl-4-bromomethylbenzamide,8 4-
=
BrCH2C6H4C( O)NH-t-Bu, 1, was found to be most suitable
among several reagents tested that contain both a bromomethyl
group for use in oxidative addition to platinum(II) and an
amide group for hydrogen bonding. In particular, the presence
of the t-butyl group was needed to give adequate solubility in
organic solvents that were compatible with the organoplatinum
complex co-reagent. There is a necessary compromise involved
here, because the enhanced solubility of 1 compared to reagents
with smaller alkyl substituents arises because the bulky t-butyl
group blocks the formation of strong intermolecular hydrogen
bonds. It is also expected to prevent very strong hydrogen bonding
in the product complexes, and this is a potential disadvantage.
The oxidative addition of the Br–CH2 bond of
1 to
[PtMe2(bu2bipy)], 2,9 bu2bipy = 4,4¢-di-t-butyl-2,2¢-bipyridine, oc-
=
curred easily to give the complex [PtBrMe2(CH2C6H4C( O)NH-
t-Bu)], 3, as shown in eqn (1).
Organic amides have proved to be a useful functional group in
self-assembly through hydrogen bonding, with relevance to folding
and self-assembly of proteins in biology, and oligoamides have
been designed to give supramolecular structures such as single or
double helices.5 Catenanes, rotaxanes and knots, prepared by tem-
plate synthesis, have been constructed to incorporate hydrogen-
bonding amide functionalities.6 Self assembly of cyclic peptides
via amide-amide hydrogen bonding can give supramolecular
structures, most notably protein nanotubes.7 This paper reports
the synthesis of an organoplatinum(IV) complex containing an
amide group, and its further functionalisation to create building
blocks for self-assembly. Most interesting is the formation of a
(1)
The structure of complex 3 was readily deduced from its
1H NMR spectrum, which contained a single methylplatinum
resonance at d = 1.46, with coupling constant 2J(PtH) = 69 Hz,
and a single Pt–CH2 resonance at d = 2.82, with 2J(PtH) =
96 Hz. The data show that the complex 3 is formed selectively
by trans oxidative addition. None of the product of cis oxidative
Department of Chemistry, University of Western Ontario, London, Canada
N6A 5B7. E-mail: pudd@uwo.ca; Fax: +1 519 661 3022; Tel: +1 519 661
2111
† CCDC reference numbers [CCDC NUMBER(S)]. For crystallographic
data in CIF or other electronic format see DOI: 10.1039/b900855a
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3519–3525 | 3519
©

View Article Online
addition, which would give a more complex NMR spectrum,3,4,10
was observed. The structure of complex 3 is shown in Fig. 1.
Fig. 1 The structure of complex 3, with the t-butyl groups of the Bu2bipy
ligands omitted for clarity. Selected bond distances: Pt–Me = 2.02(1),
2.05(1); Pt–CH2 = 2.10(1); Pt–N = 2.14(1), 2.16(1); Pt–Br = 2.583(1)
˚
˚
A. H-bond distance: N ◊ ◊ ◊ O = 3.36(1) A. Symmetry transformations of
nearest neighbours: x, y, z; x, - -y, -12 + z; x, -21 - y, + z.
1
2
1
2
Scheme 1 Reagents: (i) AgX + pyrazine; (ii) AgX = 4,4¢-bipyridine. X =
The structure (Fig. 1) confirms that 3 is formed by trans
oxidative addition, and the benzyl group is p-stacked with one
BF4 or PF6.
of the pyridyl groups. The amide groups are oriented as expected
methanol solvate molecules for each binuclear complex, and they
and the two tetrafluoroborate anions are involved in hydrogen
bonding. Each NH proton is hydrogen bonded to a tetrafluo-
roborate anion, which is also hydrogen bonded to a methanol
molecule so giving NH ◊ ◊ ◊ F–B–F ◊ ◊ ◊ HOMe groupings (Fig. 2).
The carbonyl groups are hydrogen bonded to the other methanol
1–3,5–7
=
for formation of intermolecular NH ◊ ◊ ◊ O C hydrogen bonds,
˚
but the distance O(39) ◊ ◊ ◊ N(40A) = 3.36(1) A is longer than the
˚
usual range of 2.5–3.2 A in organic amides, indicating a weaker
than normal hydrogen bond.11 The very weak hydrogen bonding is
attributed to the presence of the bulky t-butyl substituents which
prevent closer approach.
=
molecules to give C O ◊ ◊ ◊ HOMe units. The hydrogen bonding
Four binuclear organoplatinum(IV) complexes were prepared
by reaction of the bromoplatinum complex 3 with a silver salt,
AgBF4 or AgPF6, in the presence of a bridging ligand, pyrazine
or 4,4¢-bipyridyl, as shown in Scheme 1. The silver salt abstracts
the bromide group from complex 3 and the bridging ligand acts
as a template to assemble the two organoplatinum(IV) units. The
product complexes 4 and 5 each contain two amide groups, and so
have the potential to self-assemble to form polymers or network
materials.
distances N(40) ◊ ◊ ◊ F(64) = 2.920(8); N(40) ◊ ◊ ◊ O(62) = 2.83(1);
˚
=
O(39) ◊ ◊ ◊ O(81) = 2.782(8) A are all shorter than the NH ◊ ◊ ◊ O C
distance in complex 3, and indicate strong hydrogen bonding.11
Thus, it seems that the hydrogen bonding to tetrafluoroborate
anions and methanol molecules is stronger than the potential
amide ◊ ◊ ◊ amide hydrogen bonding, and so complex 4a forms
only the binuclear structure shown in Fig. 2, with no long range
supramolecular structure.
The structure of complex 5a is shown in Fig. 3. The complex
crystallized as a tetrahydrofuran solvate, but the THF molecules
were not involved in hydrogen bonding and are not illustrated in
Fig. 3. The structure is similar to that of 4a (Fig. 2), but with a
bridging 4,4¢-bipyridine ligand in 5a. There is a centre of symmetry
at the centre of the 4,4¢-bipyridine ligand. The benzyl groups and
the platinum(IV) centres are oriented with respect to the Bu2bipy
ligands in a similar way as in complex 4a. The NH groups in 5a
are involved in hydrogen bonding to the tetrafluoroborate anions,
but the carbonyl groups are not involved in hydrogen bonding.
Hence, there is no long range supramolecular structure based on
the amide hydrogen bonds.
1
The H NMR spectra of the complexes showed that the stere-
ochemistry at platinum(IV) was unchanged during the reactions
1
to give 4 and 5. For example, the H NMR spectrum of 4b gave
a single methylplatinum resonance at d = 1.44, with coupling
constant 2J(PtH) = 60 Hz, and a single resonance for the PtCH2
2
protons at d = 3.06, with coupling constant J(PtH) = 92 Hz.
A single resonance for the pyrazine protons was observed at d =
8.65.
The structure of complex 4a is shown in Fig. 2. The structure
of the dicationic diplatinum(IV) complex is as predicted from
the NMR data. Each benzyl group is p-stacked with a pyridyl
group of the adjacent bu2bipy ligand, as in the parent complex
3. There is a centre of symmetry at the centre of the pyrazine
ligand, so the two platinum(IV) units are oriented anti to each
other with respect to the bridging pyrazine group. There are four
The hexafluorophosphate salts 4b and 5b crystallized with
difficulty. However, crystals, which had the composition de-
=
termined crystallographically as [{PtMe2(CH2C6H4C( O)NH-t-
Bu)}2(m-4,4¢-bipy)]3Cl[PF6]5·2CH2Cl2, 5b¢, were finally obtained
3520 | Dalton Trans., 2009, 3519–3525
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
Fig.
2 The structure of binuclear pyrazine bridged complex
4a·4MeOH. Selected bond distances: Pt–C(1) = 2.059(7); Pt–C(2) =
2.063(7); Pt–C(31) = 2.094(6); Pt–N(11) = 2.140(5); Pt–N(22) = 2.155(5);
˚
Pt–N(51) = 2.186(5) A. Hydrogen bond distances: N(40) ◊ ◊ ◊ F(64) =
Fig. 3 The structure of binuclear 4,4¢-bipyridine bridged complex
5a·2THF. Selected bond distances: Pt–C(1) = 2.049(5); Pt–C(2) =
2.075(5); Pt–C(31) = 2.097(5); Pt–N(11) = 2.150(4); Pt–N(22) = 2.164(4);
˚
2.920(8); N(40) ◊ ◊ ◊ O(62) = 2.83(1); O(39) ◊ ◊ ◊ O(81) = 2.782(8) A.
˚
Pt–N(51) = 2.169(5) A. Hydrogen bond distance: N(40) ◊ ◊ ◊ F(84) =
from a solution of 5b. The partial replacement of hexafluo-
rophosphate by chloride is presumed to occur by reaction with
dichloromethane solvent. The anions not involved in hydrogen
bonding showed disorder but, although the accuracy of the
structure is not high, the overall structure of 5b¢ is reliably
determined and is illustrated in Figs. 4 and 5. There are two
independent binuclear dications in complex 5b¢. In one of them,
containing Pt(A), there is a centre of symmetry and so the
two platinum(IV) units are exactly anti to one another with
respect to the 4,4¢-bipyridine ligand, as in complex 5a (Fig. 3).
However, the second dication, containing Pt(B) and Pt(C), has no
crystallographically imposed symmetry and the two platinum(IV)
centres are in a staggered syn conformation with respect to the
bridging 4,4¢-bipyridine ligand, with an average torsion angle of
56◦ between equivalent methyl or Bu2bipy substituents (Fig. 4).
However, the more significant difference between 5b¢ and 5a is
that only half of the anions (PF6 ) are involved in hydrogen
bonding to the NH groups of the amide units, and so there is a
long range supramolecular structure arising from weak NH ◊ ◊ ◊ F–
P–F ◊ ◊ ◊ HN hydrogen bonds with bridging PF6 ions. The two
non-equivalent binuclear dications give rise to two non-equivalent
supramolecular polymer chains, one containing Pt(A) centres and
the other containing Pt(B) and Pt(C) centres, as illustrated in
Fig. 4. Both of these polymer chains propagate in a zig-zag fashion
along the c axis.
˚
3.125(6) A.
The most interesting feature of the structure of 5b¢ is the
arrangement of the polymer chains into tubes, as illustrated in
Fig. 5 and 6. One of these tubes is constructed by supramolecular
assembly of twelve polymer chains, four containing Pt(A) chains
and eight containing Pt(B)Pt(C) chains. The hexafluorophosphate
anions involved in hydrogen bonding are embedded in the chains
(Fig. 4 and 5), while the free anions and resolved solvent CH2Cl2
molecules (not shown) are in the spaces in the lattice between the
tubes. The inside of each tubes is lined with non-polar t-butyl
groups (Fig. 6). The inner and outer diameters of the tube are
˚
˚
~ 16 A and ~ 42 A, respectively, estimated with all t-butyl and
hydrogen atoms included. Analysis of the structure indicated that
about half of the lattice space was vacant and, consistent with
this surprising result, the crystal density for 5b¢ was calculated
to be only 0.834 g cm-3, compared to a more typical value
of 1.475 g cm-3 for complex 5a. Analysis using the program
SQUEEZE, with all solvent molecules omitted, indicated 56%
void space and enough electron density (6933 e) to account for 142
CH2Cl2 molecules per unit cell in contrast to the 8 molecules that
were located. The calculated density was then 1.26 g cm-3. None
of the solvent molecules inside the tubes could be located, and
they are probably in a mobile, liquid-like state in those areas. The
structure is robust although there are no strong secondary binding
-
-
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3519–3525 | 3521
©

View Article Online
Fig. 4 The two independent supramolecular polymeric chains of binu-
clear complexes in 5b¢, with t-butyl groups omitted for clarity. Hydrogen
bond distances: N(40A) ◊ ◊ ◊ F(92) = 3.22(2); N(40B) ◊ ◊ ◊ F(75) = 3.12(2);
˚
N(40C) ◊ ◊ ◊ F(74) = 3.03(2) A.
interactions between the twelve polymer chains from which the
tubes are constructed. The circular tube structure, Fig. 6, has a
natural strength and is not easily collapsed. The polar groups,
including volatile dichloromethane molecules, held in the regions
between the tubes, are evidently more tightly bound than the
solvent molecules within each tube.
Conclusions
The aim of this work was to develop the supramolecular chem-
istry of platinum(IV)3,4 by incorporating alkyl groups containing
amide units for hydrogen bonding. The major experimental
problem was that the complexes proved to have only very limited
solubility when smaller amide groups were used, and so the alkyl
=
group CH2C6H4C( O)NH-t-Bu was used to give complexes that
were sufficiently soluble to be crystallized and to be characterized
by NMR spectroscopy. The bulky t-butyl group interferes with
hydrogen bonding using the adjacent NH group as H-bond donor.
Intermolecular amide-amide hydrogen bonding was observed in
Fig. 5 Views of the hollow tube structure of complex 5b¢. The t-butyl
groups are omitted for clarity; above, side view; below, top view.
=
the complex [PtBrMe2(CH2C6H4C( O)NH-t-Bu)], 3, eqn (1), but
it was very weak (Fig. 1). Clearly, the presence of the t-butyl group
has both an advantage (solubility) and disadvantage (limited
hydrogen bonding).
In the binuclear complexes 4 and 5 (Scheme 1), amide–amide
hydrogen bonding was not observed and the NH group always
formed a hydrogen bond to a tetrafluoroborate or hexafluorophos-
phate anion, presumably controlled by relative steric effects. The
amide carbonyl group either formed a hydrogen bond to solvent
3522 | Dalton Trans., 2009, 3519–3525
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
acetone/pentane. NMR in CD2Cl2: d (1H) = 1.35 [s, 9H, t-Bu];
1.42 [s, 18H, bipy-Bu]; 1.44 [s, 6H, 2J(PtH) = 69 Hz, PtMe]; 2.82
2
[s, 2H, J(PtH) = 96 Hz, PtCH2]; 5.68 [s, 1H, NH]; 6.34 [d, 2H,
4
3J(HH) = 8 Hz, J(PtH) = 19 Hz, C6H4, H2, H6]; 6.94 [d, 2H,
3
3J(HH) = 8 Hz, C6H4, H3, H5]; 7.47 [dd, 2H, J(HH) = 6 Hz,
4
4J(HH) = 2 Hz, bipy, H5]; 7.97 [d, 2H, J(HH) = 2 Hz, bipy,
3
3
H3]; 8.52 [d, 2H, J(HH) = 6 Hz, J(PtH) = 19 Hz, bipy, H6].
Anal. calcd for C32H46BrN3OPt: C 50.33, H 6.07, N 5.50. Found:
C 49.94, H 5.76, N 5.42%.
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)}2(l-
pyrazine)][BF4]2, 4a
A solution of AgBF4 (21.1 mg, 0.1085 mmol) in acetone (5 mL)
was added dropwise to complex 3 (84.5 mg, 0.1085 mmol) in
acetone (15 mL) and allowed to stir for 1 h. AgBr precipitated and
the mixture was filtered through Celite into a solution of pyrazine
(4.3 mg, 0.05425 mmol). After 12 h of stirring at room temperature,
the solvent was evaporated and the product was recrystallized from
CH2Cl2/pentane to give a pale yellow solid. Yield: 92% (80.8 mg).
NMR in CD2Cl2: d (1H) = 1.37 [s, 18H, t-Bu]; 1.43 [s, 36H, bipy-
Bu]; 1.44 [s, 12H, 2J(PtH) = 64 Hz, PtMe]; 3.06 [s, 4H, 2J(PtH) =
Fig. 6 A space-filling view of four adjacent tubes, and the area between
them, in the structure of complex 5b¢.
3
96 Hz, PtCH2]; 5.86 [s, 2H, NH]; 6.40 [d, 4H, J(HH) = 8 Hz,
3
4J(PtH) = 17 Hz, C6H4, H2, H6]; 7.03 [d, 4H, J(HH) = 8 Hz,
C6H4, H3, H5]; 7.68 [dd, 4H, 3J(HH) = 6 Hz, 4J(HH) = 2 Hz, bipy,
H5]; 7.97 [d, 2H, 4J(HH) = 2 Hz, bipy, H3]; 8.59 [d, 4H, 3J(HH) =
6 Hz, 3J(PtH) = 19 Hz, bipy, H6]; 8.65 [s, 4H, m-pyz]. Anal. calcd.
for C68H96B2F8N8O2Pt2: C 50.38, H 5.97, N 6.91. Found: C 50.25,
H 6.20, N 7.16%.
(4a) or was not involved in hydrogen bonding (5a, 5b¢). The most
interesting structure was the nanotube structure, assembled from
twelve parallel supramolecular polymer chains, established for
complex 5b¢. The structure could not have been predicted, but it
does indicate the continued promise of interesting new structures
in supramolecular organometallic chemistry.1–3
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)}2(l-pyz)][PF6]2, 4b
Experimental
This was prepared similarly from complex
3 (84.5 mg,
1H NMR spectra (1D and COSY to aid assignments) were
recorded using a Varian Mercury 400 or a Varian Inova 400
NMR spectrometer. Exact molecular masses were determined
by using a Finnigan MAT 8400 mass spectrometer. Reactions
involving air-sensitive reagents were performed under a nitrogen
atmosphere using standard Schlenk techniques. Solvents were
HPLC grade or freshly dried, distilled and degassed prior to
0.1085 mmol), AgPF6 (27.4 mg, 0.1085 mmol) and pyrazine
(4.3 mg, 0.05425 mmol). A pale yellow solid was produced. Yield:
90% (84.8 mg). NMR in CD2Cl2: d (1H) = 1.35 [s, 18H, t-Bu];
1.43 [s, 36H, bipy-Bu]; 1.44 [s, 12H, 2J(PtH) = 60 Hz, PtMe]; 3.06
2
[s, 4H, J(PtH) = 92 Hz, PtCH2]; 5.76 [s, 2H, NH]; 6.40 [d, 4H,
4
3J(HH) = 8 Hz, J(PtH) = 17 Hz, C6H4, H2, H6]; 7.02 [d, 4H,
3
3J(HH) = 8 Hz, C6H4, H3, H5]; 7.67 [dd, 4H, J(HH) = 6 Hz,
=
4J(HH) = 2 Hz, bipy, H5]; 8.03 [d, 2H, 4J(HH) = 2 Hz, bipy, H3];
8.56 [d, 4H, 3J(HH) = 6 Hz, 3J(PtH) = 19 Hz, bipy, H6]; 8.65 [s,
4H, m-pyz]. Anal. calcd for C68H96F12N8O2P2Pt2: C 47.00, H 5.57,
N 6.45. Found: C 46.90, H 5.28, N 6.72%.
use when necessary. The compounds 4-BrCH2C6H4C( O)NH-t-
Bu, 1, and [PtMe2(bu2bipy)], 2, were prepared using the literature
methods.8,9 Elemental analyses were performed by Guelph Chem-
ical Laboratories LTD.
BrCH2–4-C6H4CONH-t-Bu, 18
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)}2(l-4,4¢-
NMR in CDCl3: d (1H) = 1.47 [s, 9H, t-Bu]; 4.50 [s, 2H, BrCH2];
5.92 [s, broad, 1H, NH]; 7.44 [d, 2H, 3J(HH) = 8 Hz, C6H4, H2,
H6)]; 7.69 [d, 2H, 3J(HH) = 8 Hz, C6H4, H3, H5]. MS: m/z calcd:
269.0415, found: 269.0418.
bipy)][BF4]2, 5a
This was prepared similarly from complex 3 (7.8 mg, 0.10 mmol),
AgBF4 (19.5 mg, 0.10 mmol) and 4,4¢-bipyridyl (7.8 mg,
0.050 mmol). A pale yellow solid was produced. Yield: 90% (76.4
mg). NMR in CD2Cl2: d (1H) = 1.36 [s, 18H, t-Bu]; 1.39 [s, 36H,
bipy-Bu]; 1.41 [s, 12H, 2J(PtH) = 66 Hz, PtMe]; 2.95 [s, 4H,
2J(PtH) = 93 Hz, PtCH2]; 5.76 [s, 2H, NH]; 6.35 [d, 4H, 3J(HH) =
8 Hz, 4J(PtH) = 17 Hz, C6H4, H2, H6]; 6.98 [d, 4H, 3J(HH) = 8 Hz,
C6H4, H3, H5]; 7.57 [d, 4H, 3J(HH) = 6 Hz, m-bipy, H3, H5]; 7.63
[dd, 4H, 3J(HH) = 6 Hz, 4J(HH) = 2 Hz, bipy, H5]; 7.96 [d, 2H,
4J(HH) = 2 Hz, bipy, H3]; 8.16 [d, 4H, 3J(HH) = 6 Hz, 3J(PtH) =
19 Hz, bipy, H6]; 8.58 [d, 4H, 3J(HH) = 6 Hz, 3J(PtH) = 18 Hz,
[PtBrMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)], 3
A mixture of [PtMe2(Bu2bipy)] (50.0 mg, 0.10 mmol) and com-
pound 1 (27.0 mg, 0.10 mmol) in acetone (10 mL) was stirred
for 5 h. at room temperature. The solvent was evaporated under
vacuum and the resulting solid was washed with water and then
pentane. The product was isolated as a yellow solid, which was
dried in vacuo. Yield: 94% (71.8 mg). It was recrystallized from
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3519–3525 | 3523
©

View Article Online
Table 1 Crystal data and structure refinement
3
4a·4MeOH
5a·2THF
5b¢·CH2Cl2
Formula
FW
T/K
C32H46BrN3OPt
763.72
150(2)
Monoclinic
P21/c
20.9830(8)
14.4635(5)
10.5574(5)
90
92.691(2)
90
3200.5(2)
4
1.585
C72H112B2F8- N6O6Pt2
1749.50
150(2)
Monoclinic
P21/n
16.9121(9)
11.2195(6)
21.758(1)
90
96.689(2)
90
4124.7(4)
2
1.409
C82H116B2F8N8O4Pt2
1841.63
150(2)
Monoclinic
P21/n
13.2476(3)
15.2782(4)
20.4940(4)
90
90.757(2)
90
4147.6(2)
2
1.475
C222H300ClF30N24O6P5Pt6
5331.70
150(2)
Crystal system
Space group
Tetragonal
¯
P4n2
˚
a/A
50.993(2)
50.993(2)
16.8394(5)
90
90
90
4378.7(2)
4
0.809
1.978
10712
0.0953, 0.121
˚
b/A
˚
c/A
a/◦
b/◦
g /◦
3
˚
V/A
Z
D
calcd/Mg m-3
m/mm-1
F(000)
R1, wR2
5.660
1520
0.062, 0.163
3.456
1772
0.046, 0.120
3.439
1868
0.038, 0.092
m-bipy, H2, H6]. Anal. calcd for C74H100B2F8N8O2Pt2: C 52.36, H
5.94, N 6.60. Found: C 51.96, H 5.94, N 6.17%.
and refinement are given in Table 1. Brief comments on unusual
features are given below.
[PtBrMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)], 3
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)}2(l-4,4¢-
Crystals were grown by slow diffusion of pentane into an acetone
solution.
bipy)][PF6]2, 5b
This was prepared similarly from complex 3 (7.8 mg, 0.10 mmol),
AgPF6 (25.3 mg, 0.10 mmol) and 4,4¢-bipyridyl (7.8 mg,
0.050 mmol). A pale yellow solid was produced. Yield: 88%
(79.8 mg). NMR in CD2Cl2: d (1H) = 1.36 [s, 18H, t-Bu]; 1.39 [s,
36H, bipy-Bu], 1.41 [s, 12H, 2J(PtH) = 68 Hz, PtMe]; 2.96 [s, 4H,
2J(PtH) = 94 Hz, PtCH2]; 5.71 [s, 2H, NH]; 6.36 [d, 4H, 3J(HH) =
8 Hz, 4J(PtH) = 17 Hz, C6H4, H2, H6]; 6.98 [d, 4H, 3J(HH) = 8 Hz,
C6H4, H3, H5]; 7.50 [d, 4H, 3J(HH) = 6 Hz, m-bipy, H3, H5]; 7.62
[dd, 4H, 3J(HH) = 6 Hz, 4J(HH) = 2 Hz, bipy, H5]; 7.97 [d, 2H,
4J(HH) = 2 Hz, bipy, H3]; 8.12 [d, 4H, 3J(HH) = 6 Hz, 3J(PtH) =
18 Hz, bipy, H6]; 8.54 [d, 4H, 3J(HH) = 6 Hz, 3J(PtH) = 16 Hz,
m-bipy, H2, H6]. Anal. calcd for C74H100F12N8O2P2Pt2: C 49.00, H
5.56, N 6.18. Found: C 49.28, H 5.66, N 6.28%.
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(Bu2bipy)}2(l-
pyrazine)][BF4]2·4MeOH, 4a·4MeOH
Crystals were grown by slow evaporation of a solution of 4a in
CH2Cl2–MeOH.
[{PtMe2(CH2-4-C6H4CONH-t-Bu)(bu2bipy)}2(l-4,4¢-
bipy)][BF4]2·2THF, 5a·2THF
Crystals were grown from a solution of 5a in THF by slow diffusion
of pentane. One of the tert-butyl groups showed some disorder and
was modelled at 50/50 occupancy.
=
[{PtMe2(CH2C6H4C( O)NH-t-Bu)}2(l-4,4¢-
bipy)]3Cl[PF6]5·CH2Cl2, 5b¢
X-Ray structure determinations
Crystals were grown by slow diffusion of hexane into a solution
of 5b in CH2Cl2. The structure is of limited accuracy and all
carbon atoms were treated isotropically, with heavier atoms treated
anisotropically. Several constraints and restraints were applied
to allow for unresolved disorder. One dichloromethane solvate
molecule was located. Treatment with SQUEEZE indicated 56%
void space. No solvent molecules were located in that area, but
SQUEEZE indicated the presence of disordered solvent. The
calculated density was 1.26 g cm-3 including all electron density,
0.834 g cm-3 including just the ordered CH2Cl2, and 0.809 g cm-3
excluding all solvent.
A crystal was mounted on a glass fibre. Data were collected using
a Nonius-Kappa CCD diffractometer using COLLECT (Nonius,
B.V. 1997–2002) software. The unit cell parameters were calculated
and refined from the full data set. Crystal cell refinement and
data reduction was carried out using the HKL2000 DENZO-
SMN (Otwinowski & Minor, 1997). The absorption correction
was applied using HKL2000 DENZO-SMN (SCALEPACK).
The SHELXTL/PC V6.14 for Windows NT (Sheldrick, G.M.,
2001) program package was used to solve the structure by direct
methods. Subsequent difference Fourier syntheses allowed the
remaining atoms to be located. All non-hydrogen atoms were
refined with anisotropic thermal parameters. The hydrogen atom
positions were calculated geometrically and were included as
riding on their respective carbon, nitrogen and oxygen atoms. All
thermal ellipsoid diagrams are shown at 35% probability except
for 5b¢, which is modelled at 20%. Details of the data collection
Acknowledgements
We thank the NSERC of Canada for financial support of this
work.
3524 | Dalton Trans., 2009, 3519–3525
This journal is
The Royal Society of Chemistry 2009
©

View Article Online
252, 1668; M. Rashidi and B. Momemi, J. Organomet. Chem., 1999,
574, 286; D. Song, W. L. Jia and S. Wang, Organometallics, 2004,
23, 1194; R. P. Hughes, R. B. Laritchev, L. N. Zakharov and A. L.
Rheingold, Organometallics, 2005, 24, 4845; A. J. Canty, R. P. Watson,
S. S. Karpiniec, T. Rodemann, M. G. Gardiner and R. C. Jones,
Organometallics, 2008, 27, 3203; P. K. Monaghan and R. J. Puddephatt,
Dalton Trans., 1988, 595.
5 C. Dolain, V. Maurizot and I. Huc, Angew. Chem., Int. Ed., 2003, 42,
2738; J. T. Ernst, J. Becerril, H. S. Park, H. Yin and A. D. Hamilton,
Angew. Chem., Int. Ed., 2003, 42, 535.
6 F. G. Gatti, D. A. Leigh, S. A. Nepogodiev, A. M. Z. Slawin, S. J. Teat
and J. K. Y. Wong, J. Am. Chem. Soc., 2001, 123, 5983.
7 J. D. Hartgerink, T. D. Clark and M. R. Ghadiri, Chem.–Eur. J., 1998,
4, 1367.
8 K. L. Reddy, Tet. Lett., 2003, 44, 1453; R. W. Hartmann, M. Reichert
and S. Go¨hring, Eur. J. Med. Chem., 1994, 29, 807.
Notes and references
1 J. M. Lehn, Supramolecular Chemistry: Concepts and Perspectives,
Wiley-VCH, Weinheim, 1995; J. W. Steed, and J. L. Atwood,
Supramolecular Chemistsry, VCH, New York, 2000; A. Y. Robin and
K. M. Fromm, Coord. Chem. Rev., 2006, 250, 2127; R. Hoogenboom
and U. S. Schubert, Chem. Soc. Rev., 2006, 35, 622; I. G. Georgiev and
L. R. MacGillivray, Chem. Soc. Rev., 2007, 36, 1239; A. J. Wilson,
Soft Matter, 2007, 3, 409; C. L. Chen, B. S. Kang and C. Y. Su,
Aust. J. Chem., 2006, 59, 3; B. Wang, A. P. Cote, H. Furukawa, M.
O’Keeffe and O. M. Yaghi, Nature, 2008, 453, 207.
2 D. Braga and F. Grepioni, Coord. Chem. Rev., 1999, 183, 19; J. C.
Mareque Rivas and L. Brammer, Coord. Chem. Rev., 1999, 183,
43; I. Haiduc, and F. T. Edelmann, Supramolecular Organometal-
lic Chemistry, Wiley-VCH, Weinheim, 1999; A. Laguna, Modern
Supramolecular Gold Chemistry, Wiley-VCH, Weinheim, 2008.
3 C. S. A. Fraser, H. A. Jenkins, M. C. Jennings and R. J. Puddephatt,
Organometallics, 2000, 19, 1635; C. S. A. Fraser, M. C. Jennings and
R. J. Puddephatt, Chem. Commun., 2001, 1310; C. S. A. Fraser, M. C.
Jennings and R. J. Puddephatt, Chem. Commun., 2002, 1224; C. S. A.
Fraser, D. J. Eisler and R. J. Puddephatt, Polyhedron, 2005, 25, 266.
4 Comprehensive Organometallic Chemistry III, ed. A. J. Canty, Elsevier,
Amsterdam, vol. 8, 2007(a) A. Capape, M. Crespo, J. Granell, M. Font-
Bardia and X. Solans, Dalton Trans., 2007, 2030; E. Hager, A. H. S.
Clayton, M. M. Mogorosi and J. R. Moss, Coord. Chem. Rev., 2008,
9 J. D. Scott and R. J. Puddephatt, Organometallics, 1983, 2, 1643; S.
Achar, J. D. Scott, J. J. Vittal and R. J. Puddephatt, Organometallics,
1993, 12, 4592.
10 M. C. Janzen, H. A. Jenkins, M. C. Jennings, L. M. Rendina and R. J.
Puddephatt, Organometallics, 2002, 21, 1257; L. M. Rendina and R. J.
Puddephatt, Chem. Rev., 1997, 97, 1735.
11 G. R. Desiraju and T. Steiner, The Weak Hydrogen Bond, Oxford
Science Publication, Oxford, 1999; G. A. Jeffrey, An Introduction to
Hydrogen Bonding, Oxford University Press, Oxford, 1997.
This journal is
The Royal Society of Chemistry 2009
Dalton Trans., 2009, 3519–3525 | 3525
©