Organoplatinum(IV) complexes with amide groups: Supramolecular structure as a function of ligand flexibility

Article abstract of DOI:10.1002/ejic.200900030

The oxidative addition of the benzyl bromide derivative 4-BrCH ₂C₆H₄(CH₂)_xC(=O) NH(CH₂)_y-4-C₆H₄-t Bu (A), x = y = 0; (B), x = 0, y = 1; (C), x = 1, y = 0; (

Full text of DOI:10.1002/ejic.200900030

FULL PAPER
DOI: 10.1002/ejic.200900030
Organoplatinum(IV) Complexes with Amide Groups: Supramolecular Structure
as a Function of Ligand Flexibility
Richard H. W. Au,[a] Michael C. Jennings,[a] and Richard J. Puddephatt*[a]
Keywords: Organometallic / Platinum / Amides / Self-assembly / Polymers
The oxidative addition of the benzyl bromide derivative 4-
BrCH2C6H4(CH2)xC(=O)NH(CH2)y-4-C6H4-tBu (A), x = y = 0;
(B), x = 0, y = 1; (C), x = 1, y = 0; (D), x = y = 1, to the
dimethylplatinum(II) complex [PtMe2(bu2bipy)] (1), bu2bipy
= 4,4Ј-di-tert-butyl-2,2Ј-bipyridine, gave the corresponding
amide-substituted benzylplatinum(IV) complexes of the for-
mula [PtBrMe2(4-CH2C6H4(CH2)xC(=O)NH(CH2)y-4-C6H4-
tBu)(bu2bipy)], bu2bipy = 4,4Ј-di-tert-butyl-2,2Ј-bipyridine,
2–5. In the solid state, the complexes 2–5 undergo self-as-
sembly to give the supramolecular polymers 2–4 or the di-
mers 5. Intermolecular N–H···Br-Pt hydrogen bonds are fa-
vored over the typical NH···O=C hydrogen bonds found in
organic amides. The carbonyl group may be hydrogen-
bonded to solvent or not involved in hydrogen bonding. The
structures are dependent on the size and flexibility of the
amide-substituted benzyl group. In solution, the complexes
3–5 exhibited an equilibrium between the neutral complexes
and the bromo-bridged, ionic binuclear complexes [(µ-
Br){PtBrMe2(4-CH2C6H4(CH2)xC(=O)NH(CH2)y-4-C6H4-tBu)-
(bu2bipy)}2]Br.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
NH group of a methylcarbamate unit forms a hydrogen
bond NH···ClPt to the Pt–Cl group of a neighboring mole-
cule, in preference to the alternative NH···O=C hydrogen
Introduction
Coordination complexes or organometallic compounds
which contain acid amide groups as substituents can give
interesting structures by self-assembly through hydrogen
bonding.[1–3] They can also act as selective hosts, either by
hydrogen bonding of the NH group to an anion or nucleo-
phile or by coordination of the carbonyl group to a cation
or electrophile.[1,4,5] In developing the field of supramolec-
ular organometallic chemistry, the use of hydrogen bonding
has found only limited use because many organometallic
compounds are incompatible with protic reagents.[1] How-
ever, there have been significant advances, and it is known
that the classic hydrogen bonding in amides through
NH···O=C interactions may be in competition with other
types such as M–X···H–N, where M = metal and X = Cl,
Br or I.[1,6] Alkyl and aryl complexes of platinum have much
promise in supramolecular chemistry, because the Pt–C σ-
bond is relatively unreactive towards protic reagents.[7–10]
The alkylplatinum(II) complexes do react with acids to give
alkanes but they are tolerant to alcohols and amines, while
the alkylplatinum(IV) complexes are typically inert towards
cleavage of the Pt–C bonds under mild conditions.[9] Plati-
num complexes may have biological activity, so hydrogen
bonding involving the functional groups present in proteins
and nucleic acids has broad relevance.[8a]
Two supramolecular polymers relevant to the present
work are shown in Scheme 1. In the neutral complex A, The
[a] Department of Chemistry, University of Western Ontario,
London, N6A 5B7, Canada
Scheme 1. Two supramolecular organoplatinum(IV) polymers (LL
= bu2bipy).
Fax: +1-519-661-3022
E-mail: pudd@uwo.ca
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Organoplatinum(IV) Complexes with Amide Groups
bond motif, and this leads to the formation of the supra-
The reagents 1–4 reacted easily with [PtMe2(bu2bipy)]
molecular polymer.[10a] In the binuclear bromo-bridged (5), to give the corresponding complexes [PtBrMe2(4-
complex B, the hydrogen bonding occurs by the common CH2C6H4(CH2)xC(=O)NH(CH2)y-4-C6H4-tBu)(bu2bipy)] (6),
complementary hydrogen bonding between carboxylic acid x = y = 0; (7), x = 0, y = 1; (8), x = 1, y = 0; (9), x = y =
groups and gives a different form of supramolecular poly- 1, as shown in Scheme 3. The length and flexibility of the
mer.[10d] The present work describes the syntheses and added alkyl group follow the series 6 Ͻ 7, 8 Ͻ 9, and the
structures of some related complexes containing acid amide solubility in organic solvents followed the same trend.
groups as substituents of a benzylplatinum(IV) unit, in
complexes of the type [PtBrMe2(4-CH2C6H4R)(bu2bipy)],
where bu2bipy = 4,4Ј-di-tert-butyl-2,2Ј-bipyridine, and fo-
cuses on the supramolecular structure as a function of the
size and flexibility of the amide-containing group R.
Results and Discussion
The strategy used to incorporate amide groups into plati-
num(IV) complexes was to use reagents which contain both
a bromobenzyl group and an acid amide group. The bro-
mobenzyl group is used to oxidatively add to a suitable di-
methylplatinum(II) complex,[11] and the amide group is then
available for self-assembly of the product benzylplati-
num(IV) complex. Many amides have low solubility in com-
mon organic solvents as a result of strong intermolecular
hydrogen bonding, and dissolution often requires a polar
aprotic solvent or a mixture of an alcohol and a chlorinated
solvent. These solvents are able to break the intermolecular
hydrogen bonds from the amide functionality.[12,13] The rea-
gents 1–4 (Scheme 2) were designed to contain both bulky
tert-butylphenyl groups and, in the cases of 2–4, one (2, 3)
or two (4) additional methylene groups to add flexibility.
The addition of bulky and flexible groups is often used to
increase solubility of macromolecules.[14] The reagents 1–4
were prepared by using known coupling procedures and
they were indeed found to have sufficient solubility in sol-
vents such as acetone or dichloromethane to allow easy ma-
nipulation and characterization (see experimental section).
To further enhance the solubility of the coordinated organo-
platinum(IV) complex, the ligand bu2bipy was used as the
supporting ligand in the reagent [PtMe2(bu2bipy)]; 5, in-
stead of the parent 2,2Ј-bipyridine.[15]
Scheme 3. Synthesis of platinum(IV) complexes 6–9.
The characterization of complex 6 in solution was
straightforward. The 1H NMR spectrum contained a single
2
methylplatinum resonance at δ = 1.46 ppm [s, JPt,H
=
69 Hz, 6 H] and a single PtCH2 resonance at δ = 2.87 ppm
[s, 2JPt,H = 96 Hz, 2 H]; as expected for the product of trans
oxidative addition.[10] None of the product of cis oxidative
addition was detected. Complex 6 has effective Cs sym-
metry, with the plane of symmetry containing the BrPt axis
and bisecting the PtMe2 and bu2bipy groups.
The structure of complex 6 was confirmed crystallo-
graphically and is shown in Figure 1. It is typical of the
structures of complexes 6–9.
The platinum(IV) center has the expected octahedral
stereochemistry, and the benzyl C6H4 group is π-stacked
with one of the pyridyl groups, while avoiding steric effects
of the bulky tert-butyl substituent. The amide group has the
expected anti conformation of the carbonyl and NH units.
Scheme 2. Bromomethyl amide reagents 1–4.
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R. H. W. Au, M. C. Jennings, R. J. Puddephatt
FULL PAPER
first of these. The molecular structure of the dichloroethane
solvate is similar and is not shown. Both solvates form sup-
ramolecular polymers through NH···BrPt hydrogen bond-
ing, as shown in Figure 4, but the detailed supramolecular
structures are different. In the solvate 7·H2O·0.5iPr2O,
neighboring molecules are rotated by 180° with respect to
each other and a zig-zag polymer is formed, similar to com-
plex 6. However, in the solvate 7·2C2H4Cl2, neighboring
molecules are related by a simple translation and so a more
linear polymer is formed (Figure 4). In the solvate
7·H2O·0.5iPr2O, the bromo ligand is hydrogen-bonded to
the water solvate as well as to the NH group of a neigh-
boring molecule. Also, the diisopropyl ether solvent, at 50%
occupancy, is hydrogen-bonded to the water solvate (Fig-
ure 4).
Figure 1. Molecular structure of complex 6. Selected bond lengths
[Å]: Pt–C(21) 2.050(6), Pt–C(22) 2.054(6), Pt–C(31) 2.066(6), Pt–
N(1) 2.167(4), Pt–N(12) 2.151(4), Pt–Br 2.5912(6).
The C6H4 units of the benzyl and tBuC6H4 units are twisted
by 24° and 10°, respectively out of the amide plane, al-
lowing conjugation to occur between these groups.
Complex
6
crystallizes as
a
methanol solvate
6·1.3MeOH. The methanol at full occupancy is hydrogen-
bonded to the carbonyl oxygen of the amide group [O(39)···
O(61) 2.783(6) Å]; as shown in Figure 2. The NH group
acts as a hydrogen-bond donor to the bromoplatinum
group of a neighboring molecule to form an intermolecular
N–H···Br–Pt structural motif, with N···Br 3.552(5) Å (Fig-
ure 2). The normal range for N–H···Br hydrogen bonding
interactions is N···Br 3.12–3.69 Å,[16] and the value for com-
plex 6 indicates that the hydrogen bond is relatively weak.
Propagation of the NH···Br interactions leads to formation
of the zig-zag supramolecular polymer shown in Figure 2.
Figure 3. Molecular structure of complex
7 in the solvate
8·H2O·0.5iPr2O. Selected bond lengths [Å]: Pt–C(1) 2.05(1), Pt–
C(2) 2.04(1), Pt–C(31) 2.11(1), Pt–N(11) 2.151(7), Pt–N(22)
2.158(7), Pt–Br = 2.572(2).
Figure 2. The supramolecular polymeric structure of complex
6·MeOH. The tert-butyl groups of bu2bipy are omitted for clarity.
Hydrogen bond lengths [Å]: N(40A)···Br 3.552(5), O(39)···O(61)
2.783(6). Symmetry transformations for neighboring molecules: x,
1/2 – y, –1/2 + z; x, 1/2 – y, 1/2 + z.
Figure 4. The supramolecular polymeric structures of complex 7.
Left, the solvate 7·H2O·0.5iPr2O with tBu and tBuC6H4 groups
omitted for clarity. H-bond lengths [Å]: O(61)···O(74) 2.98(2),
O(61)···Br 2.69(1), N(40A)···Br 3.384(7). Symmetry transforma-
tions for neighboring molecules: 3/2 – x, 1/2 + y, 1/2 – z; 3/2 – x,
–1/2 + y, 1/2 – z. Right, the solvate 7·2C2H4Cl2. The tert-butyl
groups of bu2bipy ligands are omitted for clarity. Hydrogen bond
length [Å]: N(40A)···Br 3.36(1). Symmetry transformations for
The molecular structure of complex 7 is shown in Fig-
ure 3. This complex has been crystallized as the solvates
7·H2O·0.5iPr2O and 7·2C2H4Cl2, and Figure 3 shows the neighboring molecules: x, y + 1, z; x, y – 1, z.
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Organoplatinum(IV) Complexes with Amide Groups
The structure of complex 8 is shown in Figure 5. The
main difference in molecular structure compared to com-
plexes 6 and 7 arises because the carbonyl group is not con-
jugated to the benzylic C6H4 group, and so is free to rotate.
Now the benzyl group π-stacks over the center of the
bu2bipy ligand, and the amide group lies roughly orthogo-
nal to the C6H4 group. The carbonyl oxygen atom O(40)
lies close to intramolecular aromatic C–H groups and forms
three weak C–H···O=C hydrogen bonds.[13] The amide NH
group is directed away from the bu2bipy ligand, and this
conformation of the amide group is favorable for intermo-
lecular hydrogen bond formation by the NH group, which
again occurs through NH···BrPt bond formation. The re-
sulting supramolecular structure is a polymer and neigh-
boring molecules are mirror images. The distance N···Br
3.311(9) Å is somewhat shorter than in complexes 6 and 7.
Figure 6. Molecular structure of complex 9, showing the two inde-
pendent molecules in the asymmetric unit. Selected bond lengths
[Å]: Pt(1)–Br(1) 2.558(5); Pt(2)–Br(2) 2.547(6).
planar C6H4NHCO atoms and that would lead to steric
repulsion between the ortho hydrogen atom and bromide in
a structure analogous to 9. The presence of the extra CH2
group in 9, although it is present only on the periphery,
allows the dimer formation.
Figure 5. The supramolecular polymeric structure of complex 8,
with tert-butyl groups of the bu2bipy ligands omitted for clarity.
Selected bond lengths [Å]: Pt–C(1) 2.04(1), Pt–C(2) 2.06(1), Pt–
C(31) 2.10(1), Pt–N(11) 2.167(8), Pt–N(22) 2.173(9), Pt–Br
2.505(2). Hydrogen bond length [Å]: N(41)···Br(A) 3.311(9). Sym-
metry transformations for neighboring molecules: x + 1, 1/2 + y,
1/2 – z; x + 1, –1/2 + y, 1/2 – z.
The complex 9 has the longest, most flexible alkyl chain.
Its structure is illustrated in Figure 6, and shows the pres-
ence of two independent, but similar, molecules in the unit
cell. The flexibility leads to minor, unresolved disorder and
the atoms are not as precisely located as in the other struc-
tures. Now neither C6H4 group is conjugated to the amide
and, in contrast to complex 8, the conformation has the
benzyl group π-stacked with just one pyridyl group and
with the carbonyl oxygen atom not forming intramolecular
CH···O=C hydrogen bonds.
Figure 7. Structure of the dimer of molecules containing Pt(2) in
complex 9. H-bond length [Å]: N(41B)···Br(2)Ј 3.45(3). Symmetry
transformation for neighboring molecules: –x, 1 – y, 2 – z. The
molecules containing Pt(1) form a similar dimer with N(41A)···
Br(1)Ј 3.44(3) Å, related by symmetry transformation 1 – x, 1 – y,
1 – z.
Each independent molecule [containing Pt(1) or Pt(2)]
forms a dimer with its equivalent molecule related by inver-
sion. The dimer of molecules containing Pt(2) is shown in
Figure 7. The dimers are held together by complementary
The way in which the dimers are arranged with respect
NH···BrPt hydrogen bonds with N···Br 3.45(3) Å. The way to each other is shown in Figure 8. The orientation of the
in which the conformation of the amide group adapts to carbonyl group with respect to a bu2bipy ligand is remarka-
form either a polymer or dimer can be seen by comparison bly similar in complexes 8 and 9, as seen by comparison of
of Figures 5 and 7. The dimer structure is not favoured for Figure 5 and Figure 8, but in complex 9 the interaction is
complex 8, probably because conjugation of the NHC6H4 intermolecular whereas in 8 it is intramolecular. The effect
group leads to a preferred conformation with roughly co- in 9 is to form a loose supramolecular polymer of dimers.
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R. H. W. Au, M. C. Jennings, R. J. Puddephatt
FULL PAPER
Figure 8. The loose polymer of dimers in the structure of complex
9, formed through weak CH···O=C hydrogen bonding with short-
est contact O(40A)···C(15B) 3.34 Å.
1
An unexpected feature in the H NMR spectra of com-
plexes 7–9, was the presence of two sets of resonances of un-
equal intensity, with each displaying the peaks expected for a
product of trans oxidative addition (effective Cs symmetry).
The ESI-MS of the solution of complex 8 in acetone con-
tained key peaks assigned to [PtMe2R(bu2bipy)(acetone)]+ at
m/z = 831 and to [{PtMe2(bu2bipy)R}2(µ-Br)]+ at m/z = 1625
(R = CH2-4-C6H4CH2CONH-4-C6H4-tBu). On this basis, it
is suggested that the second complex present in solution is
complex 11, which can be formed reversibly by dissociation
of bromide from complex 8 to give 10, followed by combina-
tion of 10 and 8 with loss of acetone as shown in Scheme 4.
There are precedents for formation of bridging halide com-
plexes on oxidative addition of alkyl halides to platinum(II),
but the binuclear complexes are not usually thermodynami-
cally stable unless the precursor is a bridged binuclear plati-
num(II) complex.[17] With mononuclear precursor complexes
such as 5 it is possible to form the µ-bromo complexes, such
as B in Scheme 1, but a bromide abstraction step is needed.
We suggest that the reversible bromide abstraction from com-
plex 8 is aided kinetically by formation of NH···BrPt hydro-
gen bonds in solution, and favoured thermodynamically by
hydrogen bonding of the dissociated bromide by the two NH
groups, as shown in 11, Scheme 4.[4] This chelation of the
bromide ion must overcome the unfavourable entropy effect
of forming the binuclear complex 11. Note that no binuclear
complex was detected in solutions of complex 6, which con-
tains the most rigid benzyl-amide group. In terms of Pear-
son’s Hard-Soft Acid-Base theory, the hydrogen-bond donor
is a hard acid whereas platinum is a soft acid. The ionization
should therefore be relatively less favourable for the softer
iodide compared to bromide. The iodide complexes 12–15
(Scheme 5) were prepared by halide exchange from the corre-
Scheme 4. The proposed equilibrium present in solutions of com-
plex 8 (S = acetone).
Scheme 5. The iodide complexes 12–15.
Conclusions
This study of the supramolecular chemistry of organo-
sponding bromoplatinum complexes 6–9. In solution, they all platinum(IV) complexes containing amide groups has es-
1
existed as a single form as determined by their H NMR tablished several principles. There is a general preference
spectra, in accord with expectation.
for NH···Br-Pt over NH···O=C hydrogen bonding, so the
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Organoplatinum(IV) Complexes with Amide Groups
2.34 mmol) was added, and the reaction mixture was stirred for
10 min. A solution of 4-tert-butylaniline (350 mg, 2.34 mmol) in
dry CH2Cl2 (5 mL) was then added dropwise to the mixture over
15 min. The reaction mixture was warmed to ambient temperature,
stirred for 1 h, and then diluted with EtOAc (25 mL) and washed
with 1  HCl (25 mL), saturated aqueous NaHCO3 (25 mL) and
brine (25 mL). The organic layer was dried with MgSO4, filtered,
and concentrated in vacuo. Recrystallization from EtOAc/heptane
gave a light brown crystalline solid in 45% yield (380 mg). 1H
NMR (CDCl3): δ = 1.28 (s, 9 H, tBu), 3.73 (s, 2 H, O=CCH2), 4.50
analogy to organic amides, in which NH···O=C bonding
dominates, is limited. The inorganic component plays a piv-
otal role. In most of the complexes studied, the hydrogen
bonding leads to formation of supramolecular polymers
but, in one case, a dimer is formed. The nature of the hydro-
gen bonding, and hence the supramolecular structure, de-
pends on the length and flexibility of the alkyl group con-
taining the amide functionality. When an aryl group is adja-
cent to either the carbonyl or the amine group, it tends to
lie very roughly coplanar with the amide group and this (s, 2 H, BrCH2), 6.98 (br. s, 1 H, NH), 7.32 (m, 6 H, C6H4), 7.42
(d, 3JH,H = 8 Hz, 2 H, C6H4) ppm. MS: m/z calcd. 359.0885; found
359.0880.
limits the hydrogen bonding. Introduction of a methylene
group between the aryl and amide units both increases the
length of the alkyl group and increases the flexibility. Both
features are important and only the complex with the long-
est and most flexible alkyl group forms a dimer by comple-
BrCH2-4-C6H4CH2CONHCH2-4-C6H4-tBu (4): This was prepared
similarly from 4-(bromomethyl)phenylacetic acid (540 mg,
2.34 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hy-
mentary hydrogen bonding. The involvement of solvent drochloride (EDC, 450 mg, 2.34 mmol) and 4-tert-butylbenzyl-
amine (380 mg, 2.34 mmol). A white solid was produced. Yield
molecules in the crystalline products is common; it may
simply be present to fill cavities in the lattice or it may play
a more significant role by taking part in hydrogen bonding.
Finally, the hydrogen bonding is shown to be important in
aiding bromide ligand dissociation.
1
25% (220 mg). H NMR (CDCl3): δ = 1.30 (s, 9 H, tBu), 3.61 (s,
3
2 H, O=CCH2), 4.39 (d, JH,H = 6 Hz, 2 H, NCH2), 4.48 (s, 2 H,
3
BrCH2), 5.65 (br. s, 1 H, NH), 7.13 (d, JH,H = 8 Hz, 2 H, C6H4),
3
3
7.27 (t, JH,H = 8 Hz, 2 H, C6H4), 7.33 (d, JH,H = 8 Hz, 2 H,
3
C6H4), 7.37 (d, JH,H = 8 Hz, 2 H, C6H4) ppm. MS: m/z calcd.
373.1041; found 373.1032.
Experimental Section
[PtBrMe2(bu2bipy)(CH2-4-C6H4CONH-4-C6H4-tBu)] (6): A mix-
ture of [PtMe2(bu2bipy)] (25.0 mg, 0.05 mmol) and compound 1
(17.5 mg, 0.05 mmol) in acetone (5 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 prod-
uct was isolated as a yellow solid, which was dried in vacuo. Yield
General: All reactions were performed under nitrogen using stan-
dard Schlenk techniques. [PtMe2(bu2bipy)] was prepared using the
literature method.[15] 1D and 2D H NMR spectra were recorded
1
with a Varian Mercury 400 NMR or a Varian Inova 400 NMR
spectrometer at room temperature unless specified otherwise. Mass
spectra were recorded with an Electrospray PE-Sciex API 365 spec-
trometer or a Micromass LCT spectrometer. Exact molecular
masses were determined by using a Finnigan MAT 8400 mass spec-
trometer.
1
95% (39.9 mg). H NMR (CDCl3): δ = 1.31 (s, 9 H, tBu), 1.41 (s,
2
2
18 H, bipy-bu), 1.46 (s, JPt,H = 69 Hz, 6 H, PtMe), 2.87 (s, JPt,H
3
4
= 96 Hz, 2 H, PtCH2), 6.43 (d, JH,H = 8, JPt,H = 18 Hz, 2 H,
3
3
C6H4), 7.12 (d, JH,H = 8 Hz, 2 H, C6H4), 7.36 (d, JH,H = 8 Hz, 2
H, C6H4), 7.44 (d, 3JH,H = 8 Hz, 2 H, C6H4), 7.49 (d, 3JH,H = 6 Hz,
2 H, bipy(H5, H5Ј)), 7.54 (s, 1 H, NH), 7.99 [s, 2 H, bipy(H3, H3Ј)],
BrCH2-4-C6H4CONH-4-C6H4-tBu (1): 4-(Bromomethyl)benzoyl
bromide (560 mg, 2.01 mmol) was dissolved in dry THF (6 mL),
and the solution was cooled to 0 °C. Triethylamine (150 mg,
1.46 mmol) and 4-tert-butylaniline (220 mg, 1.46 mmol) in dry
THF (6 mL) were added dropwise to the solution over 15 min. The
reaction mixture was warmed to ambient temperature and stirred
for 2 h. The product precipitated out from the solution as a white
solid and was filtered and washed with THF, 1  HCl, saturated
aqueous NaHCO3, H2O and heptane to give a 95% yield (480 mg).
1H NMR (CDCl3): δ = 1.32 (s, 9 H, tBu); 4.52 (s, 2 H, BrCH2);
8.53 [d, JH,H = 6, JPt,H = 19 Hz, 2 H, bipy(H6, H6Ј)] ppm.
C38H50BrN3OPt (839.83): calcd. C 54.35, H 6.00, N 5.00; found C
54.55, H 6.02, N 4.99.
3
3
[PtBrMe2(bu2bipy)(CH2-4-C6H4CONHCH2-4-C6H4-tBu)] (7): This
was prepared similarly from [PtMe2(bu2bipy)] (25.0 mg, 0.05 mmol)
and compound 2 (18.0 mg, 0.05 mmol). A yellow solid was pro-
duced. Yield 96% (41.0 mg). Two sets of resonance, (a) and (b),
1
were found in the spectrum. (a) H NMR (CD2Cl2): δ = 1.31 (s, 9
3
3
H, tBu), 1.39 (s, 18 H, bipy-bu), 1.35 (s, 6 H, 2JPt,H = 69 Hz, PtMe),
7.40 (d, JH,H = 8 Hz, 2 H, C6H4), 7.51 (d, JH,H = 8 Hz, 2 H,
2
3
3
2.80 (s, 2 H, JPt,H = 96 Hz, PtCH2), 4.44 (d, 2 H, JH,H = 6 Hz,
C6H4), 7.55 (d, JH,H = 8 Hz, 2 H, C6H4), 7.74 (br. s, 1 H, NH),
3
3
3
NCH2), 6.15 (t, 1 H, JH,H = 6 Hz, NH), 6.37 (d, 2 H, JH,H =
8 Hz, JPt,H = 15 Hz, C6H4), 7.02 (d, 2 H, JH,H = 8 Hz, C6H4),
7.84 (d, JH,H = 8 Hz, 2 H, C6H4) ppm. MS: m/z calcd: 345.0728;
4
3
found 345.0726.
3
3
7.22 (d, 2 H, JH,H = 8 Hz, C6H4), 7.37 (d, 2 H, JH,H = 8 Hz,
BrCH2-4-C6H4CONHCH2-4-C6H4-tBu (2): This was prepared
similarly from 4-(bromomethyl)benzoyl bromide (560 mg,
2.01 mmol), triethylamine (150 mg, 1.46 mmol) and 4-tert-butyl-
benzylamine (220 mg, 1.46 mmol). A white solid was produced.
Yield 97% (510 mg). 1H NMR (CDCl3): δ = 1.32 (s, 9 H, tBu),
C6H4), 7.46 [d, 2 H, JH,H = 6 Hz, bipy(H5, H5Ј)], 7.96 [s, 2 H,
3
4JH,H = 2 Hz, bipy(H3, H3Ј)], 8.49 [d, 2 H, JH,H = 6 Hz, JPt,H
=
3
3
19 Hz, bipy(H6, H6Ј)] (b) δ = 1.31 (s, 9 H, bu), 1.39 (s, 18 H, bipy-
2
2
bu), 1.43 (s, JPt,H = 69 Hz, 6 H, PtMe), 2.84 (s, JPt,H = 96 Hz, 2
H, PtCH2), 4.44 (d, JH,H = 6 Hz, 2 H, NCH2), 6.15 (t, JH,H
6 Hz, 1 H, NH), 6.38 (d, JH,H = 8, JPt,H = 15 Hz, 2 H, C6H4),
7.02 (d, JH,H = 8 Hz, 2 H, C6H4), 7.22 (d, JH,H = 8 Hz, 2 H,
3
3
=
3
4.49 (s, 2 H, BrCH2), 4.61 (d, JH,H = 5 Hz, 2 H, NCH2), 6.33 (br.
3
4
3
3
s, 1 H, NH), 7.29 (d, JH,H = 8 Hz, 2 H, C6H4), 7.39 (d, JH,H
=
3
3
8 Hz, 2 H, C6H4), 7.45 (d, 3JH,H = 8 Hz, 2 H, C6H4), 7.84 (d, 3JH,H
= 8 Hz, 2 H, C6H4) ppm. MS: m/z calcd: 359.0885, found 359.0880.
3
3
C6H4), 7.37 (d, JH,H = 8 Hz, 2 H, C6H4), 7.46 [d, JH,H = 6 Hz, 2
H, bipy(H5, H5Ј)], 7.97 [s, 2 H, bipy(H3, H3Ј)], 8.51 [d, JH,H = 6,
3
BrCH2-4-C6H4CH2CONH-4-C6H4-tBu (3): 4-(Bromomethyl)phen- 3JPt,H = 19 Hz, 2 H, bipy(H6, H6Ј)] ppm. C39H52BrN3OPt (853.85):
ylacetic acid (540 mg, 2.34 mmol) was dissolved in 1:1 DMF/
CH2Cl2 (6 mL), and the solution was cooled to 0 °C. 1-(3-Dimeth-
ylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC, 450 mg,
calcd. C 54.86, H 6.14, N 4.92; found C 54.58, H 6.40, N 5.05.
ESI-MS: m/z = 773 [PtMe2(bu2bipy)R]+, 831 [PtMe2(bu2bipy)-
((CH3)2CO)R]+, 876 [PtBrMe2(bu2bipy)R + Na]+, 1625 [{PtMe2-
Eur. J. Inorg. Chem. 2009, 1526–1534
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1531

R. H. W. Au, M. C. Jennings, R. J. Puddephatt
FULL PAPER
(bu2bipy)R}2(µ-Br)]+ where R = CH2-4-C6H4CONHCH2-4-C6H4-
tBu.
[PtIMe2(bu2bipy)(CH2-4-C6H4CONHCH2-4-C6H4-tBu)] (13): This
was prepared by the same synthetic procedures as 13, with complex
8
(91.0 mg, 0.11 mmol) and excess lithium iodide (44.0 mg,
[PtBrMe2(bu2bipy)(CH2-4-C6H4CH2CONH-4-C6H4-tBu)] (8): This
was prepared similarly from [PtMe2(bu2bipy)] (50.0 mg, 0.10 mmol)
and ligand 4 (36.0 mg, 0.10 mmol). A yellow solid was produced.
Yield 95% (81.1 mg). Two sets of resonance, (a) and (b), were found
in the spectrum. (a) 1H NMR (CD2Cl2): δ = 1.27 (s, 9 H, tBu),
0.33 mmol). A yellow solid was produced. Yield 87% (90.5 mg). 1H
NMR (CD2Cl2): δ = 1.31 [s, 9 H, tBu], 1.39 [s, 18 H, bipy-bu], 1.56
[s, 2JPt,H = 70 Hz, 6 H, PtMe], 2.87 [s, 2JPt,H = 94 Hz, 2 H, PtCH2],
3
3
4.44 [d, JH,H = 6 Hz, 2 H, NCH2], 6.15 [t, JH,H = 6 Hz, 1 H,
NH], 6.34 [d, JH,H = 8, JPt,H = 19 Hz, 2 H, C6H4], 7.01 [d, JH,H
3
4
3
2
1.39 (s, 18 H, bipy-bu), 1.34 (s, JPt,H = 68 Hz, 6 H, PtMe), 2.77
3
2
= 8 Hz, 2 H, C6H4], 7.22 [d, JH,H = 8 Hz, 2 H, C6H4], 7.37 [d,
(s, JPt,H = 94 Hz, 2 H, PtCH2), 3.31 (m, 2 H, O=CCH2), 6.31 (d,
3
4
3JH,H = 8 Hz, 2 H, C6H4], 7.45 [d, JH,H = 6 Hz, 2 H, bipy(H5,
3JH,H = 8, JPt,H = 18 Hz, 2 H, C6H4), 6.52 (m, 2 H, C6H4), 7.01
3
H5Ј)], 7.95 [s, 2 H, bipy(H3, H3Ј)], 8.55 [d, 3JH,H = 6, 3JPt,H = 19 Hz,
2 H, bipy(H6, H6Ј)] ppm. C39H52IN3OPt (900.85): calcd. C 52.00,
H 5.82, N 4.66; found C 52.38, H 5.75, N 4.37.
(br. s, 1 H, NH), 7.29 (m, 4 H, C6H4), 7.46 [d, JH,H = 6 Hz, 2 H,
bipy(H5, H5Ј)], 8.00 [s, 2 H, bipy(H3, H3Ј)], 8.52 [d, 3JH,H = 6, 3JPt,H
= 17 Hz, 2 H, bipy(H6, H6Ј)] ppm. (b) δ = 1.27 (s, 9 H, tBu), 1.39
2
(s, 18 H, bipy-bu), 1.43 (s,, JPt,H = 68 Hz 6 H, PtMe), 2.80 (s,
[PtIMe2(bu2bipy)(CH2-4-C6H4CH2CONH-4-C6H4-tBu)] (14): This
was prepared by the same synthetic procedures as 13, with complex
2JPt,H = 94 Hz, 2 H, PtCH2), 3.31 (m, 2 H, O=CCH2), 6.32 (d,
4
3
3JH,H = 8 Hz, JPt,H = 18 Hz, 2 H, C6H4), 6.52 (d, JH,H = 8 Hz, 2
H, C6H4), 7.01 (br. s, 1 H, NH), 7.29 (m, 4 H, C6H4), 7.46 [d, 3JH,H
= 6 Hz, 2 H, bipy(H5, H5Ј)], 8.00 [s, 2 H, bipy(H3, H3Ј)], 8.55 [d, 2
9
(91.0 mg, 0.11 mmol) and excess lithium iodide (44.0 mg,
0.33 mmol). A yellow solid was produced. Yield 86% (77.7 mg). 1H
NMR (CD2Cl2): δ = 1.27 (s, 9 H, tBu), 1.39 (s, 18 H, bipy-bu),
H, JH,H = 6 Hz, JPt,H = 17 Hz, bipy(H6, H6Ј)]. C39H52BrN3OPt
(853.85): calcd. C 54.86, H 6.14, N 4.92; found C 54.94, H 6.23, N
5.14. ESI-MS: m/z = 773 [PtMe2(bu2bipy)L]+, 831 [PtMe2(bu2-
3
3
2
2
1.56 (s, JPt,H = 70 Hz, 6 H, PtMe), 2.82 (s, JPt,H = 92 Hz, 2 H,
PtCH2), 3.30 (m, 2 H, O=CCH2), 6.27 (d, 3JH,H = 8, 4JPt,H = 20 Hz,
3
2 H, C6H4), 6.50 (d, JH,H = 8 Hz, 2 H, C6H4), 6.94 (br. s, 1 H,
bipy)((CH3)2CO)R]+, 876 [PtBrMe2(bu2bipy)L
+
Na]+, 1625
3
3
NH), 7.29 (m, JH,H = 8 Hz, 2 H, C6H4), 7.32 (m, JH,H = 8 Hz, 2
[{PtMe2(bu2bipy)R}2(µ-Br)]+ where R = CH2-4-C6H4CH2CONH-
H, C6H4), 7.46 [d, JH,H = 6 Hz, 2 H, bipy(H5, H5Ј)], 7.99 [s, 2 H,
3
4-C6H4C(CH3)3.
bipy(H3, H3Ј)], 8.60 [d, JH,H = 6, JPt,H = 19 Hz, 2 H, bipy(H6,
H6Ј)] ppm. C39H52IN3OPt (900.85): calcd. C 52.00, H 5.82, N 4.66;
found C 51.95, H 5.79, N 4.48.
3
3
[PtBrMe2(bu2bipy)(CH2-4-C6H4CH2CONHCH2-4-C6H4-tBu)] (9):
This was prepared similarly, from [PtMe2(bu2bipy)] (50.0 mg,
0.10 mmol) and ligand 5 (37.0 mg, 0.10 mmol). A yellow solid was
produced. Yield 92% (79.8 mg). A mixture of product was gener-
ated as discussed previously [i.e. platinum(IV) complex together
with either the acetone-solvated complex or the bromo-bridged di-
mer]. Two sets of resonance, (a) and (b), were found in the spec-
[PtIMe2(bu2bipy)(CH2-4-C6H4CH2CONHCH2-4-C6H4-tBu)] (15):
This was prepared by the same synthetic procedures as 13, with
complex 10 (92.0 mg, 0.10 mmol) and excess lithium iodide
(40.0 mg, 0.30 mmol). A yellow solid was produced. Yield 78%
(77.7 mg). 1H NMR (CD2Cl2): δ = 1.27 (s, 9 H, tBu), 1.42 (s, 18
1
2
trum. (a) H NMR (CD2Cl2): δ = 1.27 (s, 9 H, tBu), 1.33 (s, JPt,H
2
2
2
H, bipy-bu), 1.54 (s, JPt,H = 70 Hz, 6 H, PtMe), 2.80 (s, JPt,H
92 Hz, 2 H, PtCH2), 3.18 (m, 2 H, O=CCH2), 4.27 (d, JH,H
=
=
= 69 Hz, 6 H, PtMe), 1.41 (s, 18 H, bipy-bu), 2.74 (s, JPt,H
95 Hz, 2 H, PtCH2), 3.19 (m, 2 H, O=CCH2), 4.27 (d, JH,H
=
=
3
3
3
3
3
3
6 Hz, 2 H, NCH2), 5.55 (t, JH,H = 6 Hz, 1 H, NH), 6.22 (d, JH,H
6 Hz, 2 H, NCH2), 5.55 (t, JH,H = 6 Hz, 1 H, NH), 6.26 (d, JH,H
= 8, 4JPt,H = 19 Hz, 2 H, C6H4), 6.44 (d, 3JH,H = 8 Hz, 2 H, C6H4),
= 8, 4JPt,H = 17 Hz, 2 H, C6H4), 6.46 (d, 3JH,H = 8 Hz, 2 H, C6H4),
3
3
3
3
7.07 (d, JH,H = 8 Hz, 2 H, C6H4), 7.30 (d, JH,H = 8 Hz, 2 H,
7.07 (d, JH,H = 8 Hz, 2 H, C6H4), 7.30 (d, JH,H = 8 Hz, 2 H,
C6H4), 7.44 [d, JH,H = 6 Hz, 2 H, bipy(H5, H5Ј)], 7.98 [s, 2 H,
3
C6H4), 7.45 [d, JH,H = 6 Hz, 2 H, bipy(H5, H5Ј)], 7.99 [s, 2 H,
3
bipy(H3, H3Ј)], 8.57 [d, JH,H = 6, JPt,H = 19 Hz, 2 H, bipy(H6,
H6Ј)] ppm. C40H54IN3OPt (914.88): calcd. C 52.51, H 5.95, N 4.59;
found C 52.64, H 5.75, N 4.42.
3
3
bipy(H3, H3Ј)], 8.50 [d, JH,H = 6, JPt,H = 19 Hz, 2 H, bipy(H6,
3
3
H6Ј)] ppm. (b) δ = 1.27 (s, 9 H, tBu), 1.41 (s, JPt,H = 69 Hz, 6 H,
2
2
HPtMe), 1.41 (s, 18 H, bipy-bu), 2.77 (s, JPt,H = 95 Hz, 2 H,
PtCH2), 3.19 (m, 2 H, O=CCH2), 4.27 (d, JH,H = 6 Hz, 2 H,
3
X-ray Structure Determinations: A crystal suitable for X-ray analy-
sis was mounted on a glass fibre. Data were collected with a Non-
ius-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 re-
duction was carried out using the HKL2000 DENZO-SMN (Ot-
winowski & Minor, 1997). The absorption correction was applied
using HKL2000 DENZO-SMN (SCALEPACK). The SHELXTL/
PC V6.14 for Windows NT (G. M. Sheldrick, 2001) program pack-
age was used to solve the structure by direct methods. Subsequent
difference Fourier syntheses allowed the remaining atoms to be lo-
cated. All non-hydrogen atoms were refined with anisotropic ther-
mal parameters. The hydrogen atom positions were calculated geo-
metrically and were included as riding on their respective carbon,
nitrogen and oxygen atoms. Details of the data collection and re-
finement are given in Table 1.
3
3
NCH2), 5.55 (t, JH,H = 6 Hz, 1 H, NH), 6.27 (d, JH,H = 8 Hz,
4JPt,H = 17 Hz, 2 H, C6H4), 6.46 (d, 3JH,H = 8 Hz, 2 H, C6H4), 7.07
3
3
(d, JH,H = 8 Hz, 2 H, C6H4), 7.30 (d, JH,H = 8 Hz, 2 H, C6H4),
7.45 (d, JH,H = 6 Hz, 2 H, bipy(H5, H5Ј)), 8.00 (s, 2 H, bipy(H3,
3
H3Ј)), 8.52 [d, JH,H = 6 Hz, JPt,H = 19 Hz, 2 H, bipy(H6, H6Ј)].
C40H54BrN3OPt (867.88): calcd. C 55.36, H 6.27, N 4.84; found C
55.63, H 6.51, N 4.84. ESI-MS: m/z = 787 [PtMe2(bu2bipy)R]+, 846
[PtMe2(bu2bipy)((CH3)2CO)R]+, 890 [PtBrMe2(bu2bipy)R + Na]+,
where R = CH2-4-C6H4CH2CONH-4-C6H4-tBu.
3
3
[PtIMe2(bu2bipy)(CH2-4-C6H4CONH-4-C6H4-tBu)] (12): This was
prepared by the same synthetic procedures as 13, with complex 7
(93.0 mg, 0.11 mmol) and excess lithium iodide (44.0 mg,
0.33 mmol). A yellow solid was produced. Yield 80% (92.4 mg). 1H
NMR (CDCl3): δ = 1.31 (s, 9 H, tBu), 1.42 (s, 18 H, bipy-bu), 1.46
(s, 2JPt,H = 70 Hz, 6 H, PtMe), 2.90 (s, 2JPt,H = 94 Hz, 2 H, PtCH2),
3
4
3
6.40 (d, JH,H = 8, JPt,H = 19 Hz, 2 H, C6H4), 7.10 (d, JH,H
=
8 Hz, 2 H, C6H4), 7.36 (d, 3JH,H = 8 Hz, 2 H, C6H4), 7.43 (d, 3JH,H CCDC-715919 (for 6·1.3MeOH), -715920 (for 7·H2O·0.5iPr2O),
3
= 8 Hz, 2 H, C6H4), 7.48 [d, JH,H = 6 Hz, 2 H, bipy(H5, H5Ј)],
-715921 (for 7·2C2H4Cl2), -715922 (for 8), -715923 (for
7.53 (s, 1 H, NH), 7.98 [s, 2 H, bipy(H3, H3Ј)], 8.58 [d, JH,H = 6, 9·0.5CH2Cl2) contain the supplementary crystallographic data for
3
3JPt,H = 19 Hz, 2 H, bipy(H6, H6Ј)] ppm. C38H50IN3OPt (886.83): this paper. These data can be obtained free of charge from the
calcd. C 51.47, H 5.68, N 4.74; found C 51.71, H 5.55, N 4.59.
1532
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1526–1534

Organoplatinum(IV) Complexes with Amide Groups
Table 1. X-ray data and structure refinement.
6·1.3MeOH
7·H2O·0.5iPr2O
7·2C2H4Cl2
8
9·0.5CH2Cl2
Formula
Fw
Temperature [K]
λ [Å]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C39.50H56BrN3O2.50Pt2 C42H61BrN3O2.50Pt
C43H60BrCl4N3OPt
1051.74
150(2)
0.71073
orthorhombic
Pbca
24.5624(5)
10.2379(2)
35.9093(7)
90
90
90
9030.0(3)
8
1. 547
C39H52BrN3OPt
853.84
150(2)
0.71073
monoclinic
P21/c
11.3904(4)
13.7507(5)
23.4710(7)
90
96.118(2)
90
3655.2(2)
4
1.552
4.965
C40.50H55BrClN3OPt
910.32
150(2)
887.87
150(2)
922.94
150(2)
0.71073
monoclinic
P21/c
13.4236(5)
21.2226(7)
13.5954(3)
90
0.71073
monoclinic
P21/n
18.0300(4)
12.7859(3)
18.3151(5)
90
0.71073
triclinic
¯
P1
12.1947(9)
19.987(2)
21.137(1)
111.398(5)
99.947(5)
95.133(5)
4659.0(6)
4
94.287(2)
90
3862.3(2)
4
98.658(2)
90
3955.0(2)
4
γ [°]
V [Å3]
Z
dcalcd. [Mg/m3]
µ [mm–1]
F(000)
1.527
4.705
1.469
4.357
1.298
3.955
1828
4.264
4224
1788
1868
1712
R1, wR2
0.0429, 0.0945
0.0672, 0.1797
0.0821, 0.2288
0.0710, 0.1946
0.1166, 0.2940
Li, H. W. Hou, Inorg. Chim. Acta 2008, 361, 2203; c) D. R.
Turner, S. N. Pek, S. R. Batten, Chem. Asian J. 2007, 2, 1534;
d) F. G. Gatti, D. A. Leigh, S. A. Nepogodiev, A. M. Slawin,
S. J. Teat, J. K. Y. Wong, J. Am. Chem. Soc. 2001, 123, 5983.
a) N. L. S. Yue, M. C. Jennings, R. J. Puddephatt, Dalton
Trans. 2006, 3886; b) T. J. Burchell, D. J. Eisler, M. C. Jennings,
R. J. Puddephatt, Dalton Trans. 2005, 268; c) T. J. Burchell,
D. J. Eisler, M. C. Jennings, R. J. Puddephatt, Chem. Commun.
2003, 2228; d) Z. Qin, M. C. Jennings, R. J. Puddephatt, Chem.
Commun. 2001, 2676; e) Z. Qin, M. C. Jennings, R. J. Pudde-
phatt, Inorg. Chem. 2001, 40, 6220.
a) M. G. Fisher, P. A. Gale, M. E. Light, S. J. Loeb, Chem.
Commun. 2008, 5695; b) R. Custelcean, P. Remy, P. V.
Bonneson, D.-E. Jiang, B. A. Moyer, Angew. Chem. Int. Ed.
2008, 47, 1866.
a) N. L. S. Yue, M. C. Jennings, R. J. Puddephatt, Eur. J. Inorg.
Chem. 2007, 1690; b) N. L. S. Yue, D. J. Eisler, M. C. Jennings,
R. J. Puddephatt, Inorg. Chem. 2005, 44, 1125; c) N. L. S. Yue,
D. J. Eisler, M. C. Jennings, R. J. Puddephatt, Inorg. Chem.
2005, 43, 7671.
data_request/cif. Brief comments on unusual features are given be-
low.
[PtBrMe2(bu2bipy)(CH2-4-C6H4CONH-4-C6H4-tBu)]·1.3MeOH
(6·1.3MeOH): Crystals were grown by slow diffusion of hexane
into a solution of 7 in carbon tetrachloride and methanol. One
methanol molecule of solvation was well ordered, the other was
modeled isotropically at 0.3 occupancy with C–O constrained to
be 1.40 Å.
[3]
[PtBrMe2(bu2bipy)(CH2-4-C6H4CONHCH2-4-C6H4-tBu)]·H2O·
iPr2O (7·H2O·iPr2O): Crystals were grown from CH2Cl2/isopropyl
ether. There was evidence of unresolved disorder and soft con-
straints (SIMU and DELU) were used. The 0.5 occupancy isopro-
pyl ether was located on a symmetry site. Crystals of 7·2C2H4Cl2
were grown from CH2Cl2/hexane. The C–Cl bonds of solvate mole-
cules were restrained to be equal (1.75 Å).
[4]
[5]
[PtBrMe2(bu2bipy)(CH2-4-C6H4CH2CONH-4-C6H4-tBu)] (8):
Crystals were grown from CH2Cl2/hexane.
[6]
[PtBrMe2(bu2bipy)(CH2-4-C6H4CH2CONHCH2-4-C6H4-tBu)]·
0.5CH2Cl2 (9·0.5CH2Cl2): Crystals were grown from CH2Cl2/hex-
ane. The crystal diffracted weakly and showed evidence of twin-
ning. A single Twin Law was suggested by ROTAX, and confirmed
by improved refinement. The bond lengths in the CH2Cl2 molecule
were fixed. Some weak high angle data were discarded in the refine-
ment.
a) G. Aullon, D. Bellamy, L. Brammer, E. A. Bruton, A. G.
Orpen, Chem. Commun. 1998, 653; b) D. Braga, F. Grepioni,
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Chem. Soc. 2000, 122, 8474; b) M. Rashidi, M. C. Jennings,
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[7]
[8]
[9]
Acknowledgments
a) C. Vetter, C. Wagner, G. N. Kaluderovic, R. Paschke, D. Ste-
inborn, Inorg. Chim. Acta 2009, 362, 189; b) F. Zhang, M. C.
Jennings, R. J. Puddephatt, Chem. Commun. 2007, 1496.
We thank the Canadian Natural Sciences and Engineering Re-
search Council (NSERC) for financial support.
Recent articles on organoplatinum chemistry: a) A. J. Canty
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Received: January 12, 2009
Published Online: March 12, 2009
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