Unusual Coordination Assemblies from Platinum(II) Thienyl and Bithienyl Complexes

Article abstract of DOI:10.1021/ic034690u

Dinuclear Pt₂Br₂(dppf)₂(μ-C _BH₄S₂) exchanges with isonicotinic acid to release free bithiophene and gives a molecular square [Pt₄(dppf) ₄(μ₂-O₂CC₅H₄N) ₄]⁴⁺4OTf^- which is an all-ring system with four Pt rings disposed at the corners of a larger macrocyclic ring. The related mononuclear complex PtBr(η¹(C2)-C₄H ₃S)(dppf) reacts with AgOTf (OTf = triflate) to give [Pt ₂(dppf)₂(μ₂,η¹(C),η ¹(S)-C₄H₃S)₂]²⁺2OTf ^- with an unusual six-membered ring formed by the fusion of two Pt-thienyl entities at the sulfur sites. All the complexes are structurally characterized by single-crystal X-ray crystallography.

Full text of DOI:10.1021/ic034690u

Inorg. Chem. 2003, 42, 7290−7296
Unusual Coordination Assemblies from Platinum(II) Thienyl and
Bithienyl Complexes
Peili Teo, L. L. Koh, and T. S. Andy Hor*
Department of Chemistry, National UniVersity of Singapore, 3 Science DriVe 3, Singapore 117543
Received June 18, 2003
Dinuclear Pt2Br2(dppf)2(µ-C H S ) exchanges with isonicotinic acid to release free bithiophene and gives a molecular
8
4 2
square [Pt4(dppf)4(µ2-O CC H N)4]4+4OTf- which is an “all-ring” system with four Pt rings disposed at the corners
2
5 4
of a larger macrocyclic ring. The related mononuclear complex PtBr(η1(C2)-C H S)(dppf) reacts with AgOTf (OTf
4
3
) triflate) to give [Pt2(dppf)2(µ2,η1(C),η1(S)-C H S)2]2+2OTf- with an unusual six-membered ring formed by the
4
3
fusion of two Pt−thienyl entities at the sulfur sites. All the complexes are structurally characterized by single-crystal
X-ray crystallography.
Introduction
In this paper, we illustrate the construction of molecular
entities with specific geometrical patterns, demonstrate that
the (bi)thienyl entity can be retained or replaced, depending
on conditions, and describe the unusual features of the
products thus obtained.
A key challenge facing the future of nanotechnology is
molecular manufacturing, a process that is designed to
synthesize advanced materials with targeted properties and
functions.1 Over the past decade, the use of metal coordina-
tion as a means to drive and preserve the formation of
discrete molecular ensembles has become a methodology of
emerging significance in supramolecular chemistry.1 The
metal polymers thus formed are often electroactive and
conducting, and very importantly, they are potential candi-
dates for a new generation of polymers that have both
classical (e.g., mechanical and processing advantages) and
contemporary (e.g., optical and semiconducting behaviors)
functions and strengths.2 Some recent uses of electroactive
spacers such as bipyridine and functional groups such as
ferrocene in metal-containing polymers are typical of such
examples.3-5 Our current interest in Pt(II)-thienyl and
-bithienyl chemistry is developed along a similar vein as
these complexes are generally redox-6 and electroactive.7,8
Results and Discussion
The PPh3 thienyl and bithienyl complexes have been
reported.6 Replacement of PPh3 by a flexible and functional
1,1′-bis(diphenylphosphino)ferrocene (dppf)9 in the syntheses
led to the isolation of the analogous dppf complexes, viz.
PtBr(C4H3S)(dppf), 1, and Pt2Br2(dppf)2(µ2-C8H4S2), 2, in
good yields (ca. 80%, 87%, respectively). The 31P NMR
spectrum of 2 shows two discrete resonances (δ 13.6, 12.7
ppm), corresponding to two phosphine centers opposite two
different ligands, viz. bithienyl and bromide. The significantly
lower π-acidity of bromide (compared to bithienyl) gives a
much higher (by ca. 50%) Pt-P coupling for the trans-
1
phosphine.10 This, together with the H NMR data of the
bithienyl group, pointed to a dinuclear complex with two
Pt(II)-chelating dppf entities bridged by a bithienyl group.
Crystallographic analysis of 2 confirmed this proposition with
terminal bromide completing a dinuclear core (Figure 2,
Table 1). As expected, the bithienyl bridge is C-coordinated
with free S sites. The Pt-P bond trans to bromide (2.232-
* To whom correspondence should be addressed. E-mail: andyhor@
nus.edu.sg.
(1) Jean, J. M. Supramolecular Chemistry, Concepts and PerspectiVes;
VCH: Weinheim, 1995.
(2) Heeger, A. J. Synth. Met. 2002, 125, 23.
(3) Biani, F. D.; Jackle, F.; Spiegler, M.; Wagner, M.; Zanello, P. Inorg.
Chem. 1997, 36, 2103.
(4) Wagner, M. Abstracts of Papers, 225th National Meeting of the
American Chemical Society, New Orleans, LA, Mar 23-27, 2003;
American Chemical Society: Washington, DC, 2003; INOR 334.
(5) Batten, S. R.; Jeffery, J. C.; Ward, M. D. Inorg. Chim. Acta 1999,
292, 231.
(6) Xie, Y.; Wu, B. M.; Xue, F.; Ng, S. C.; Mak, T. C. W.; Hor, T. S. A.
J. Organomet. Chem. 1997, 531, 175.
(8) Levi, M. D.; Gofer, Y.; Aurbach, D. Polym. AdV. Technol. 2002, 13,
697.
(9) Gan, K. S.; Hor, T. S. A. Ferrocene-Homogeneous Catalysis, Organic
Syntheses and Materials Science; Togni, A., Hayashi, T., Eds.; VCH:
Weinheim, 1995; Chapter 1, p 3.
(7) Heeger, A. J. Angew. Chem., Int. Ed. 2001, 40, 2591. Levi, M. D.;
Gofer, Y.; Aurbach, D. Polym. AdV. Technol. 2002, 13, 697.
(10) Colacot, T. J.; Qian, H.; Olivares, R. C.; Ortega, S. H. J. Organomet.
Chem. 2001, 637, 697.
7290 Inorganic Chemistry, Vol. 42, No. 22, 2003
10.1021/ic034690u CCC: $25.00 © 2003 American Chemical Society
Published on Web 09/27/2003

Pt(II) Thienyl and Bithienyl Complexes
understood as the absolute structure in solution, it neverthe-
less points to a possible source for Pt-bithienyl polymer or
cyclic frameworks upon bromide replacement with other
bidentate ligands. In principle, such anion exchange could
proceed in parallel but opposite (anti) orientation, taking into
consideration the role of anions, solvent, etc.12
To examine the potential for 2 in polymer synthesis, we
studied its exchange behavior with an incoming nucleophile.
An anionic, bifunctional, and heterocyclic ligand such as
isonicotinate (O2CC5H4N)13 (abbreviated as isonic) was
chosen. Complex 2 was found to be sluggish toward isonic
and acetate (OAc) (H+, Na+, or K+ form), even in the
presence of a strong base (KOH) or under reflux conditions.
However, with AgOAc, it reacts almost instantaneously to
give the expected diacetate product. Monosubstitution cannot
be achieved through stoichiometric control. Reaction of 2
with Ag+ salts (e.g., OTf- ) triflate) in CH3CN gives the
solvent complex [Pt2(dppf)2(µ2-C8H4S2)(MeCN)2]2+2OTf-,
3, which cannot be isolated as a solid. The mass spectro-
scopic analysis of 3 showed that 3 is dinuclear in solution.
Thus, 3 can be used in situ to generate other substitution
products. For example, with isonic (K+) in acetone, it initially
gave a yellow solid which, upon further addition of acetone
dropwise, swelled to a brown lump. Upon addition of large
excess of acetone, it turned into a pale brown gelatinous
precipitate, whose 31P NMR spectrum (acetone) showed,
unexpectedly, four resonances with respective Pt satellites.
This spectral pattern is inconsistent with the expected di-
isonic (O-coordinated) product, viz. [Pt2(isonic)2(dppf)2(µ2-
C8H4S2)], but supports an O,N-isonic bridged polymeric
product [Pt2(isonic)(dppf)2(µ2-C8H4S2)]nn+nOTf-. Unfortu-
nately, its limited solubility precludes further characterization.
Use of free isonicotinic acid (isonicH+) with 3 gave an
unexpected product 4, with no evidence of bithienyl presence,
but with successful introduction of the isonic group (νCOOasym
1647 and 1637 cm-1).14 31P NMR analysis at room temper-
ature (rt) (300 K) showed a major product with two mutually
coupled resonances (δ 9.1, 5.4 ppm), and a pair of much
weaker neighboring peaks with similar P-Pt couplings. At
213 K, the minor product disappeared leaving behind the
major species (9.9, 6.6 ppm) in a clean spectrum (Figure 3).
The original spectrum was restored when the temperature
returned to rt. The Pt-P couplings (3755 and 3489 Hz) are
significantly different from those of the starting bithienyl
complex (1976, 4192 Hz), and there is also a significant high-
field shift (9.1 and 5.4 vs 13.6 and 12.7 ppm in 2). These
point to the conservation of a molecular square framework
(see in a following paragraph) within the temperature range
213-300 K.
Figure 1. ORTEP drawing (50% probability ellipsoids) of the molecular
structure of PtBr(dppf)(C4H3S), 1. The hydrogen atoms and solvent
molecules are omitted for clarity.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 1 and 2
1
2
Pt(1)-Br(1)
2.4707(10)
2.333(2)
2.240(2)
2.4759(10)
2.345(2)
2.232(2)
2.042(7)
2.4760(11)
2.336(2)
2.234(2)
2.036(7)
84.0(2)
171.1(2)
102.81(8)
87.0(2)
168.75(6)
86.91(6)
170.7(3)
87.7(3)
Pt(1)-P(1)
Pt(1)-P(2)
Pt(1)-C(1)
2.048(10)
Pt(2)-Br(2)
Pt(2)-P(3)
Pt(2)-P(4)
Pt(2)-C(8)
C(1)-Pt(1)-P(2)
C(1)-Pt(1)-P(1)
P(2)-Pt(1)-P(1)
C(1)-Pt(1)-Br(1)
P(2)-Pt(1)-Br(1)
P(1)-Pt(1)-Br(1)
C(8)-Pt(2)-P(3)
C(8)-Pt(2)-P(4)
P(4)-Pt(2)-P(3)
C(8)-Pt(2)-Br(2)
P(4)-Pt(2)-Br(2)
P(3)-Pt(2)-Br(2)
88.6(3)
171.0(3)
100.36(8)
85.4(3)
85.63(6)
101.28(8)
86.3(3)
173.40(6)
84.90(6)
(2) Å) is significantly shorter than that opposite the bithiophene
(2.345(2) Å) group (Table 1). Similar spectroscopic and
crystallographic patterns were observed for 1, which is a
mononuclear Pt(II) square planar complex with terminal
bromide and thienyl and chelating dppf (Figure 1; Table 1).
Similarly, the thienyl is a C-donor with a free sulfur end,
which is known to be weakly basic.11 Unlike the PPh3
analogue, in which the phosphines are trans-oriented, both
1 and 2 adopt a cis configuration, which is geometrically
imposed by the chelating dppf.
These spectral features suggested that a new ligand
environment is present. This could be achieved if both
bromide and bithienyl are replaced by the N- and O-bonded
isonic groups. Subsequent single-crystal crystallographic
analysis proved this and revealed the formation of an unusual
The anti orientation of the two dppf ligands in 2 keeps
steric repulsion to its minimum. It also directs a similar anti
orientation for the bromides. Although this cannot be
(12) Fujita, M. Chem. Soc. ReV. 1998, 27, 417.
(11) Chen, B. L. Synthesis and characterization of thiophene derivatives
and their metal complexes. Ph.D. Thesis, National University of
Singapore, 1999.
(13) Song, R.; Kim, K. M.; Sohn, Y. S. Inorg. Chim. Acta 1999, 292, 238.
(14) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, 4th ed.; Wiley: New York, 1986.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7291

Teo et al.
Figure 2. ORTEP drawing (50% probability ellipsoids) of the molecular structure of Pt2Br2(dppf)2(µ2-C8H4S2), 2. The hydrogen atoms and solvent molecules
are omitted for clarity.
Figure 3. Variable temperature 31P NMR spectra of the product from the
reaction between 3 and isonicH+, giving 4, [Pt4(µ2-isonic)4(dppf)4]4+4OTf-.
macrocyclic structure, [Pt4(µ2-isonic)4(dppf)4]4+4OTf-, 4,
Figure 4. ORTEP drawing (50% probability ellipsoids) of the molecular
with four isonic groups bridging four metals through the
pyridyl N and carboxyl O donors (Figure 4, Table 2). The
coordination sphere at each Pt(II) center is completed by a
chelating dppf. Since the local geometry of each Pt(II) is
square planar, and they fuse through four bridging groups
in a system that has no terminal ligand, this effectively is a
macrocyclic molecular square assembled from four molecular
subsquares. Effectively, we therefore witness an “all-ring”
system with good C4 symmetry. The isonic coordination
mode is different from that observed by Sohn et al. who
reported an N-coordination (to Pt(II)) to give zwitterions.12
Rendina et al. reported isonicotic acids bridging platinum
phosphine groups through H-bonds15,16 to give dimeric
or macrocyclic compounds. Compound 4 is different, in
which the acid group is deprotonated. The carbonyl O atom
structure of [Pt4(µ2-isonic)4(dppf)4]4+4OTf-, 4. The hydrogen atoms and
solvent molecules are omitted for clarity.
Table 2. Selected Bond Distances (Å) and Angles (deg) of 4
bond length
bond angles
Pt(1)-N(1)
Pt(1)-O(3)
Pt(1)-P(1)
Pt(1)-P(2)
Pt(2)-O(1)
Pt(2)-N(2)
Pt(2)-P(3)
Pt(2)-P(4)
2.068(18)
2.093(15)
2.252(6)
2.287(5)
2.042(14)
2.062(19)
2.252(6)
2.263(6)
N(1)-Pt(1)-O(3)
N(1)-Pt(1)-P(1)
O(3)-Pt(1)-P(1)
N(1)-Pt(1)-P(2)
O(3)-Pt(1)-P(2)
P(1)-Pt(1)-P(2)
O(1)-Pt(2)-N(2)
O(1)-Pt(2)-P(3)
N(2)-Pt(2)-P(3)
O(1)-Pt(2)-P(4)
N(2)-Pt(2)-P(4)
P(3)-Pt(2)-P(4)
86.5(6)
91.1(5)
176.4(4)
172.1(5)
86.2(4)
96.1(2)
87.0(6)
170.9(5)
88.5(4)
84.0(4)
169.8(5)
101.1(2)
(CdO) is noncoordinating in the macrocyclic compound (4)
as compared to the bidentate carboxylate bridge formation
reported in other macrocyclic complexes.17 The quality of
the crystallographic data of 4 does not permit any meaningful
(15) Crisp, M. G.; Tiekink, E. R. T.; Rendina, L. M. Inorg. Chem. 2003,
42, 1057.
(16) Gianneschi, N. C.; Tiekink, E. R. T.; Rendina, L. M. J. Am. Chem.
Soc. 2000, 122, 8474.
7292 Inorganic Chemistry, Vol. 42, No. 22, 2003

Pt(II) Thienyl and Bithienyl Complexes
Scheme 1. Synthesis of [Pt4(µ2-isonic)4(dppf)4]4+4OTf-
4
structural discussion in detail, but the molecular structure is
without question. It also reveals some insight into the
formation pathway. The acidic isonicH+ helps to liberate
bithienyl in form of bithiophene which then facilitates the
ligand replacement (Scheme 1). The trans orientation of the
O,N functional groups of the incoming ligand and the square
planarity of the metal collectively help to assemble this
molecular square architecture. The chelating dppf thus
completes an “all-ring” formation. The side product observed
in solution at rt therefore likely arises from other molecular
geometries with the same stoichiometry and architecture. The
square is the self-assembled thermodynamic product as it
represents a good balance of entropy and geometry influ-
ences. The inequivalent phosphines with similar Pt-P
couplings can then be explained by their trans orientation
to two different but similarly hard ligands. In the crystal
packing diagram (Figure 5), the molecular squares stack on
top of each other, without any identifiable solvate trapped
within the molecular ring.
The reaction between 1 and AgOTf in MeCN proceeds
by a completely different pathway. It resulted in a yellow
air-stable solid which redissolves in CHCl3 to give an orange
solution and, within minutes, a white gel. Upon standing
overnight, orange crystals formed. Single-crystal crystal-
lographic analysis (5) showed another unusual and unex-
pected six-membered {Pt2C2S2} ring formed by the fusion
of two platinum-thienyl moieties through the S atoms. This
Figure 5. Molecular packing diagram of 4.
is the only example in our study that shows S-coordination
of a thiophene or thienyl group. This sulfur center in a
conjugated system is notoriously weakly basic.11,18,19 The
metal-coordination, e.g., η5, has precedent but is rare.20
σ-Coordination through sulfur from thiophenes to transition
metals is even less common.21,22 To our knowledge, this is
(18) Xie, Y.; Wu, B. M.; Xue, F.; Ng, S. C.; Mak, T. C. W.; Hor, T. S. A.;
Organometallics 1998, 17, 3988.
(19) Angelici, R. J. Coord. Chem. ReV. 1990, 105, 61.
(20) Veiros, L. F. J. Organomet. Chem. 2001, 632, 3.
(21) Draganjac, M.; Ruffing, C. J.; Rauchfuss, T. B. Organometallics 1985,
4, 1909.
(17) Bera, J. K.; Smucker, B. W.; Walton, R. A.; Dunbar, K. R. Chem.
Commun. 2001, 24, 2562.
Inorganic Chemistry, Vol. 42, No. 22, 2003 7293

Teo et al.
Scheme 2. Possible Synthetic Route to 5, [Pt2(dppf)2(µ2,η1(C),η1(S)-C4H3S)2]2+2OTf-
the first example of C,S-bidentate coordination of thienyl.
The facile formation of 5 can be explained by the generation
of [Pt(η1(C2)-C4H3S)(dppf)(MeCN)]+OTf- (Scheme 2). This
C-bonded thienyl complex could release the solvate (in the
evaporation process) and dimerize as a result of coordination
unsaturation of the metal. The proximity of the sulfur ensures
a rapid dimerization process, which compensates for the
solvent loss. It also explains our futile attempts to isolate
the intermediate MeCN complex. Effectively, the two halves
of the molecule are brought together by three fused rings
comprising a six-membered Pt2C2S2 metallo-ring sandwiched
by two five-membered heterocyclic rings (Figure 6). The
Pt-S bonds (av 2.398(3) Å) are typical of covalent Pt-S
interaction23-25 and comparable to those in other reported
Pt-S rings (cf. 2.332 (4) Å22 and 2.369(2), 2.351(2) Å23)
(Table 3).
The stability of the [Pt4(isonic)4] square and the [Pt2-
(thienyl)2] ring is being studied, together with the construc-
tion of other unusual molecular geometries from our
substrates. The thienyl and bithienyl systems have turned
out to be very fruitful, not only as precursors to bifunctional
coordination polymers but also in terms of the flexibility of
functional replacement and sulfur involvement. These are
unusual features that help pave our immediate path for new
directions in molecular assemblies.
Experimental Section
General Procedures. All reactions were performed under pure
dry nitrogen using standard Schlenk techniques. The products are
air-stable, and hence, recrystallizations were performed in air. All
solvents and reagents were of reagent grade obtained from
commercial sources and used without further purification. Pt-
Figure 6. (a) ORTEP drawing (50% probability ellipsoids) of the
molecular structure of 5, [Pt2(dppf)2(µ2,η1(C),η1(S)-C4H3S)2]2+2OTf-. The
hydrogen atoms and solvent molecules are omitted. (b) The central three-
ring region is expanded for clarity.
26
6
(PPh3)4 and PtBr(2-thienyl)(PPh3)2 were prepared according to
literature methods.
Table 3. Selected Bond Distances and Angles of 5
1
All H and 31P NMR spectra were recorded at ca. 300 K at
bond length
bond angle
operating frequencies of 299.96 and 121.49 MHz, respectively. 1H
and 31P chemical shifts are quoted in ppm downfield of Me4Si and
85% H3PO4, respectively. All IR spectra were recorded in the solid
state on a Bio-Rad FT-IR spectrometer using KBr disk. Elemental
analyses and Mass Spectrometry were performed by the Elemental
Analysis Laboratory and Mass Spectrometry Laboratory of our
department.
Pt(1)-C(5)
Pt(1)-P(2)
Pt(1)-P(1)
Pt(1)-S(1)
Pt(2)-C(1)
Pt(2)-P(3)
Pt(2)-S(2)
2.067(10)
2.277(3)
2.350(3)
2.396(3)
2.012(10)
2.343(3)
2.400(3)
C(5)-Pt(1)-P(2)
C(5)-Pt(1)-P(1)
P(2)-Pt(1)-P(1)
C(5)-Pt(1)-S(1)
P(2)-Pt(1)-S(1)
P(1)-Pt(1)-S(1)
C(1)-Pt(2)-P(4)
C(1)-Pt(2)-P(3)
P(4)-Pt(2)-P(3)
C(1)-Pt(2)-S(2)
P(4)-Pt(2)-S(2)
P(3)-Pt(2)-S(2)
85.6(3)
172.2(3)
101.19(9)
86.4(3)
172.01(9)
86.80(9)
85.4(3)
172.6(3)
101.56(10)
86.7(3)
171.93(9)
86.41(9)
(22) Amari, C.; Ianelli, S.; Pelizzi, C.; Predieri, G. Inorg. Chim. Acta 1993,
211, 89.
(23) Meiji, R.; Stufkens, D. J.; Vrieze, K.; Roosendaal, E.; Schenk, H. J.
Organomet. Chem. 1978, 155, 323.
(24) Jones, R.; Williams, D. J.; Wood, P. T.; Woollins, J. D. Polyhedron
1987, 6, 539.
(25) Albano, V. G.; Monari, M.; Orabona, I.; Panunzi, A.; Roviello, G.;
Ruffo, F. Organometallics 2003, 22, 1223.
Syntheses. Synthesis of Pt(dppf)(C4H3S)Br, 1. PtBr(C4H3S)-
(PPh3)2 (0.4414 g, 0.5 mmol) dissolved in CH2Cl2 (20 mL) to give
a colorless solution, upon which dppf (0.2772 g, 0.5 mmol) was
added. The resultant yellow solution was concentrated to ca. 3 mL
(26) Ugo, R. Inorg. Synth. 1968, 11, 105.
7294 Inorganic Chemistry, Vol. 42, No. 22, 2003

Pt(II) Thienyl and Bithienyl Complexes
Table 4. Crystallographic Data and Refinement Details for 1, 2, 4, and 5
1a
2
4
5
empirical formula
(C38H31BrFeSPt × 0.9) +
(C34H28Br2FePt ×
0.1) + CH2Cl2
223 (2)
997.08
monoclinic
C81H65Br2Cl15-
Fe2P4Pt2S2
C
165H129Cl3F12-
Fe4 N4O24P8Pt4S4
C84H68Cl18F6-
Fe2O6P4Pt2S4
T (K)
fw
cryst syst
space group
unit cell dimensions
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
223 (2)
223 (2)
4265.83
triclinic
P1
223 (2)
2679.48
triclinic
P1
2419.78
monoclinic
P21/c
P21/c
22.8672 (13)
9.4384 (5)
16.4891 (10)
90
104.6670 (10)
90
3442.9 (3)
4
1.924
17.9506 (10)
17.2014 (10)
29.4006 (17)
90
97.1910 (10)
90
9006.8 (9)
4
1.784
13.081 (3)
19.233 (4)
20.302 (4)
101.189 (4)
105.355 (4)
105.829 (4)
4539.3 (15)
1
1.560
3.614
2098
0.14 × 0.08 × 0.04
-15 e h e 15,
-22 e k e 22,
-24 e l e 24
0.2245, 0.3014
0.1064, 0.2490
2.734 and -2.047
14.0474 (9)
14.3402 (9)
26.0749 (17)
99.2230 (10)
100.7800 (10)
97.7680 (10)
5018.8 (6)
Z
D
2
calcd (mg/m3)
1.773
3.748
2624
0.40 × 0.28 × 0.16
-16 e h e 16,
-17 e k e 17,
-31 e l e 31
0.0968, 0.1548
0.0673, 0.1446
2.239 and -2.846
abs coeff (mm-1
F(000)
)
6.089
1941
4.904
4704
cryst size (mm3)
index ranges
0.36 × 0.10 × 0.08
-27 e h e 27,
-11 e k e 11,
-12 e l e 19
0.0623, 0.1301
0.0505, 0.1244
2.634 and -2.055
0.30 × 0.25 × 0.20
-21 e h e 20,
-20 e k e 20
-17 e l e34
0.0617, 0.1186
0.0438, 0.1111
1.493 and -0.793
R, wR2 (all data)
final R, wR2
largest diff peak
and hole (e Å-3
)
a Compound 1 ) 0.9[PtBr(2-thienyl)(dppf)] + 0.1[PtBr2(dppf)] + CH2Cl2.
in vacuo, and Et2O was added to precipitate a yellow solid. Upon
isolation, it was washed with Et2O and dried in vacuo. Recrystal-
lization from CH2Cl2/hexane gave yellow crystals (80%). 1H
NMR: δ ) 8.0, 7.9, 7.5, 7.3, 7.2(m), 6.6(d), 6.2(t), 4.7(t), 4.5(s),
condensed and spectroscopically analyzed. 31P NMR: δ ) 19.6-
(d), 8.6(d) ppm; 1JP-Pt ) 2068, 4396 Hz. ESI: m/z ) 831.5 (100%)
1
[3 - 2MeCN]2+. A sharp singlet at 10.7 ppm, JP-P ) 4433 Hz,
and some fine peaks are observed in the 31P NMR when the solid
product was isolated and redissolved in CDCl3. The identities of
the decomposed products are not known.
2
4.1(d), 3.7(t). 31P NMR: δ ) 13.6(d), 13.2(d) JP-P ) 15.26 Hz,
1JP-Pt ) 2006.58, 4135.22 Hz. ESI: m/z ) 832.1 (100%) [1 -
Br]+. Anal. Calcd for 90% C38H31P2SBrFePt + 10% C34H28P2Br2-
FePt: C, 49.50; H, 3.39; S, 3.16. Found: C, 49.05; H, 3.31; S,
2.78.
Synthesis of Pt2Br2(dppf)2(µ2-C8H4S2), 2. 5,5′-Dibromo-2,2′-
bithiophene (0.4051 g, 1.25 mmol) was added to a solution of Pt-
(PPh3)4 (3.1104 g, 2.5 mmol) in toluene. After 15 h of reflux, a
pale yellow precipitate was obtained. Et2O was added to complete
the precipitation. Filtration gave a solid which was washed with
Et2O and dried in a vacuum to give a pale yellow solid (90%).
This solid (0.2645 g; 0.15 mmol) was added to toluene (30 mL) to
give a yellow mixture, upon which dppf (0.1663 g, 0.3 mmol) was
added. The resultant mixture was refluxed overnight to give a bright
yellow mixture, upon which Et2O was added. The precipitate was
Synthesis of [Pt4(µ2-isonic)4(dppf)4]4+4OTf-, 4. AgOTf (0.0129
g, 0.05 mmol) was dissolved in MeCN (3 mL), and CHCl3 (15
mL) was added, followed by 2 (0.0456 g, 0.025 mmol). A clear
yellow solution with an off-white precipitate formed immediately.
The mixture was stirred for 45 min and filtered. IsonicH+ (0.0062
g, 0.05 mmol) was added to the filtrate, and the mixture stirred for
5 h. A white suspension in a yellow solution was obtained. The
mixture was filtered and the filtrate condensed to ca. 3 mL. Et2O
was added to precipitate the product. Careful recrystallization in
CHCl3/hexane gave yellow triclinic crystals (64%). 31P NMR (213
2
1
K): δ ) 9.9(d), 6.6(d); JP-P ) 15.26 Hz, JP-Pt ) 3755, 3489
1
Hz. H NMR (213 K): δ ) 8.5(s) (pyridyl H), 7.8, 7.5, 7.3, 7.0-
(m) (phenyl H), 4.6, 4.5, 4.4, 4.3(s) (Cp). IR/cm-1: ν(COO)asym
,
1647, 1637; ν(COO)sym, 1342. ESI: m/z ) 871.0 (100%) (molecular
ion, M4+). Anal. Calcd for C164H128P8O20N4F12S4Fe4Pt4‚2CHCl3‚
4H2O: C, 45.75; H, 3.19; N, 1.29; S, 2.94. Found: C, 45.72; H,
3.20; N, 0.78; S, 3.43. Some chloroform as appeared in the X-ray
crystals has been lost in the process of drying the samples for
elemental analysis.
filtered, washed with Et2O and dried in vacuo to give a bright yellow
2
solid product (87%). 31P NMR: δ ) 13.6 (d), 12.7 (d), JP-P
)
1
1
15.26 Hz, JP-Pt ) 1976, 4192 Hz. H NMR: δ ) 8.1, 7.5, 7.3,
7.1(m), 6.3 (d), 5.9 (d), 4.7(s), 4.4(s), 4.1(s), 3.7(s). FAB: m/z )
1823.0 (25%) (molecular ion, M+ peak), 1743.0 (25%) [2 - Br]+,
831 (40%) [2 - 2Br]2+. Compound 2 was recrystallized in CHCl3/
hexane to give orange crystals. Anal. Calcd for C76H60P4S2Br2Fe2-
Pt2‚2CHCl3: C, 45.43; H, 3.18; S, 3.10. Found: C, 45.96; H, 3.03;
S, 3.10. Some chloroform as appeared in the X-ray crystals has
been lost in the process of drying the samples for elemental analysis.
Synthesis of [Pt2(dppf)2(µ2-C8H4S2)(MeCN)2]2+ 2OTf-, 3.
AgOTf (0.0129 g, 0.05 mmol) was dissolved in MeCN (3 mL)
shielded from light followed by the addition of acetone (15 mL).
Complex 2 (0.0456 g 0.025 mmol) was added to the solution to
give a yellow suspension. The mixture was stirred until the solution
turned clear yellow with an off-white precipitate, which was
removed by filtration over a column of Celite. The filtrate was
When 3 was reacted with potassium isonicotinate, the solution
remained yellow after overnight stirring. A yellow precipitate was
obtained when Et2O was added to the condensed solution. The solid
dissolved in acetone (a few drops) to give a swollen brown lump,
and on addition of excess acetone, a yellow solution with pale brown
gelatinous precipitate was obtained. 31P of solid product in CD3-
COCD3: δ ) 23.5(t), 20.3(t), 7.5(t), 3.1(t); 2JP-P ) 15.25 Hz, 1JP-Pt
) 2109, 2091, 4209, 3649 Hz.
Synthesis of [Pt2(dppf)2(µ2,η1(C),η1(S)-C4H3S)2]2+2OTf-, 5.
AgOTf (0.0128 g, 0.05 mmol) was dissolved in MeCN (3 mL),
followed by addition of CHCl3 (15 mL). Complex 1 (0.0456 g,
Inorganic Chemistry, Vol. 42, No. 22, 2003 7295

Teo et al.
0.05 mmol) was added to give a clear yellow solution with an off-
white precipitate of AgBr. The mixture was stirred for 30 min and
filtered to give a clear yellow filtrate, which was condensed to ca.
3 mL, and Et2O added to give a yellow precipitate. This precipitate
was redissolved in CHCl3 to give an orange solution which, upon
standing, gave a white gel in the orange solution. Orange crystals
were obtained when this mixture was left to stand overnight. 31P-
NMR analysis of the gel mixture showed a sharp singlet at 9.1
one chosen for X-ray analysis was disordered at the thienyl ring.
The resulting best model showed that about 10% of the thienyl
group was replaced by Br; i.e., the crystal contained 90% compound
1 and 10% PtBr2(dppf) as impurity. The presence of residual PtBr2-
(dppf) was supported by a small singlet observed at 12.3 ppm in
the 31P NMR spectrum of 1. Compound 4 crystallized with four
triflate anions, four CHCl3 molecules, and four H2O molecules.
The CHCl3 molecules were severely disordered, and a model with
occupancy of 50:50 was resolved and included in the least squares
refinement cycles. The size of the square gives a free space of ca.
4-5 Å, which is big enough to accommodate a small solvent
molecule. However, the general background difference peaks are
high due to the poor data quality. There is only one peak of 1.4
e/Å3 inside the square. The other peaks inside the square are below
0.8 e/Å3. On the basis of these, we could not ascertain or identify
any solvent in the cavity, but it is probable that some fractional
solvent molecules are trapped within during crystallization. The
crystallographic data of 4 were poor due to the poor quality and
small size of the crystal. Despite numerous attempts, we could not
produce better crystals for reanalysis. Compound 5 crystallized with
six CHCl3 molecules, and two out of six of them were severely
disordered with occupancy of 50:50 and 70:30.
1
ppm, JP-Pt ) 3941 Hz and 2 small doublets at 11.4, 14.7 ppm,
2JP-P ) 15.26 Hz,1JP-Pt ) 3685, 4219 Hz. The identities of these
decomposed materials are unknown. The limited solubility of the
crystals did not allow further solution studies. Anal. Calcd for
C78H62P4S4O6F6Fe2Pt2‚CHCl3: C, 45.55; H, 3.05; S, 6.16. Found:
C, 45.07; H, 3.14; S, 3.79. Some chloroform as appeared in the
X-ray crystals has been lost in the process of drying the samples
for elemental analysis.
Crystal Structure Determinations. The diffraction experiments
were carried out on a Bruker SMART CCD diffractometer with a
Mo KR sealed tube at -50 °C. The program SMART27 was used
for collecting frames of data, indexing reflections, and determining
lattice parameters, SAINT26 for integration of the intensity of
reflections and scaling, SADABS28 for absorption correction, and
SHELXTL29 for space group and structure determination and least-
squares refinements on F2. The relevant crystallographic data and
refinement details are shown in Table 4. Compound 2 crystallized
with five molecules of CHCl3. Compound 1 crystallized with one
CH2Cl2 molecule. Good single crystals were difficult to obtain. The
Acknowledgment. We acknowledge the National Uni-
versity of Singapore for financial support and technical
assistance from our department. We are grateful to F. Zhao
for some supporting experiments.
(27) SMART and SAINT Software Reference Manuals, version 5.611; Bruker
Analytical X-ray Systems, Inc.: Madison, WI, 2000.
(28) Sheldrick, G. M. SADABS, software for empirical absorption correc-
tion; University of Go¨ttingen: Go¨ttingen, Germany, 2000.
(29) SHELXTL Reference Manual, version 5.1; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1997.
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
IC034690U
7296 Inorganic Chemistry, Vol. 42, No. 22, 2003