A tetramethylplatinum(IV) complex with 1,1'-bis(diphenylphosphanyl)- ferrocene ligands: Reaction with trifluoroacetic acid

Article abstract of DOI:10.1002/ejic.200900454

A new tetramethylplatinum(IV) complex [PtMe₄(dppf)] [2; dppf = 1,1′-bis(diphenylphosphanyl)ferrocene], as the first platinum(IV) complex to contain a chelating dppf ligand, was prepared by the reaction of the known dimeric tetramethylplatinum(I

Full text of DOI:10.1002/ejic.200900454

FULL PAPER
DOI: 10.1002/ejic.200900454
A Tetramethylplatinum(IV) Complex with 1,1Ј-Bis(diphenylphosphanyl)-
ferrocene Ligands: Reaction with Trifluoroacetic Acid
Hamid R. Shahsavari,[a] Mehdi Rashidi,*[a] S. Masoud Nabavizadeh,[a]
Sepideh Habibzadeh,[a] and Frank W. Heinemann[b]
Keywords: Platinum / Metallocenes / P ligands / Conformation analysis
A new tetramethylplatinum(IV) complex [PtMe4(dppf)] [2;
dppf = 1,1Ј-bis(diphenylphosphanyl)ferrocene], as the first
platinum(IV) complex to contain a chelating dppf ligand, was
prepared by the reaction of the known dimeric tetrameth-
ylplatinum(IV) complex cis,cis-[Me4Pt(µ-SMe2)2PtMe4] (1)
with the biphosphane ligand dppf (2 equiv.) at room tem-
perature by replacement of the SMe2 ligands with the P ligat-
ing atoms of dppf. The single-crystal X-ray structure of com-
plex 2 revealed that the dppf chelating ligand is arranged
close to the “synperiplanar–eclipsed” conformation, with a
Cp(centroid)···Fe···Cp(centroid) twist angle of 17.6° and a
dppf bite angle, P1–Pt1–P2, of 95.77(3)°. This is in contrast to
the usually preferred “synclinal–staggered” conformation, in
which the Cp(centroid)···Fe···Cp(centroid) twist angle is close
to 36° as found in PtII complexes with chelating dppf ligands,
like for example [PtMe2(dppf)] exhibiting a dppf bite angle
close to 100°. When complex 2 was treated with the strong
acid CF3COOH (1 equiv.) first evolution of methane was ob-
served, followed by a C–C coupling reaction to give ethane
and the methylplatinum(II) complex [PtMe(OCOCF3)(dppf)]
(3). The reaction of complex 2 with the nucleophile HgCl2
(1 equiv.) similarly gave MeHgCl, ethane, and the methyl-
platinum(II) complex [PtMeCl(dppf)] (11). The structure of
complex 3 was also determined by X-ray crystallography.
The geometry around the platinum center is best described
as distorted square-planar and the dppf is arranged in the
usually preferred “synclinal–staggered” conformation.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Although several platinum(II) complexes containing the
biphosphane ligand dppf [dppf = 1,1Ј-bis(diphenylphos-
phanyl)ferrocene] have been reported,[5,6] the related plati-
num(IV) complexes are not common. We recently reported
a binuclear PtIV complex with dppf as a spacer ligand and
characterized its structure by using multinuclear studies,[6]
but there are no reports for a PtIV complex bearing a che-
lating dppf ligand.[5] The P–M–P bite angle of dppf has
been shown to be important in carbon–carbon coupling
reactions, and it seems to be influenced by several fac-
tors.[5b]
Reductive elimination involving C–C bond formation is
of fundamental importance in homogeneous catalysis by d6
and d8 transition-metal complexes.[7] The mechanistic evi-
dence obtained for the processes involving PtIV complexes
supported that either prior dissociation of a ligand or for-
mation of a cationic five-coordinated intermediate are re-
sponsible for the C–C coupling.[4,8]
In this study, a new tetramethylplatinum(IV) complex
[PtMe4(dppf)] (2) was synthesized and characterized by
multinuclear NMR studies and its single-crystal structure
was determined by X-ray crystallography. The reaction of
the complex with CF3COOH was also investigated. Our re-
sults indicate that the steric demand imposed by dppf has
an interesting effect on the related chemistry, and especially
on C–C bond formation.
Introduction
Ever since the serendipitous synthesis of the binuclear
tetramethylplatinum(IV) complex cis,cis-[Me4Pt(µ-SMe2)2-
PtMe4] by the reaction of cis-[PtCl2(SMe2)2] with a mixture
of MeLi/MeI,[1] several related tetramethylplatinum(IV)
complexes have been prepared by displacement of the labile
SMe2 ligands in this useful synthon with several phospho-
rus and nitrogen donor ligands, and some of their reactions
have been studied.[2] In these complexes, two Me groups are
forced into the trans position to each other, and as a result
of the high trans influence of the Me ligand, the Pt–Me
bonds become rather weak, as suggested by a comparatively
low Pt–C coupling constant;[3] interesting reactions and
properties are thus observed.[2] The only reported X-ray
crystal structures having a Pt(Me)4 moiety are [(dppe)-
PtMe4] [dppe = Ph2P(CH2)2PPh2] and [(dppbz)PtMe4]
[dppbz = o-PPh2(C6H4)PPh2], in which the Pt–Me bond
lengths vary only slightly with respect to the trans ligand.[4]
[a] Department of Chemistry, Faculty of Sciences, Shiraz Univer-
sity,
Shiraz 71454, Iran
Fax: +98-711-2286008
E-mail: rashidi@chem.susc.ac.ir
[b] Department of Chemistry and Pharmacy, Inorganic Chemistry,
Friedrich-Alexander-Universitaet Erlangen-Nuernberg,
Egerlandstrasse 1, 91058 Erlangen, Germany
3814
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A Pt(IV) Complex with 1,1Ј-Bis(diphenylphosphanyl)ferrocene Ligands
trans methyl groups is attributed to the high trans influence
of the methyl group trans to a Pt–C bond being cleaved.[2,3]
Subsequently, intermediate A1 very rapidly undergoes re-
ductive elimination of ethane, through intermediate A2, to
yield PtII complex 3. We attribute the latter reductive elimi-
nation of the C–C bond (forming ethane) to a large steric
demand imposed by dppf on the square base of the square
pyramidal intermediate A1.
Results and Discussion
The routes to prepare complexes 2, 3, and 5 from starting
complexes 1 and 4 are indicated in Scheme 1; the suggested
intermediates are shown by letters A–C.
Syntheses and Reactions
It is interesting to note that, in contrast to the above
routes observed for the reaction of 2 with CF3COOH
(Scheme 2), when either of the analogous tetramethylplati-
num(IV) complexes [PtMe4(dppm)] [6; dppm = bis(diphen-
ylphosphanyl)methane = Ph2PCH2PPh2] or [PtMe4(bpy)]
The reaction of the known dimeric tetramethylplati-
num(IV) complex cis,cis-[Me4Pt(µ-SMe2)2PtMe4] (1) with
the biphosphane ligand dppf (2 equiv.) at room temperature
gave in good yield the monomeric tetramethylplatinum(IV)
complex [PtMe4(dppf)] (2) by replacement of the SMe2 li-
gands with the P ligating atoms of dppf. Complex 2 was
very rapidly treated with the strong acid CF3COOH
(1 equiv.) to give methane, ethane, and the methylplati-
num(II) complex [PtMe(OCOCF3)(dppf)] (3). We suggest
that in this reaction, the initial protonation of the Pt–C
bond of one of the mutually trans methyl groups proceeds
through an SE2 (open) mechanism to give CH4 and the very
[7; bpy
= 2,2Ј-bipyridine] is similarly treated with
CF3COOH (1 equiv.), only methane is formed along with
the corresponding fac-trimethylplatinum(IV) complexes
[PtMe3(OCOCF3)(dppm)] (8)[2e] or [PtMe3(OCOCF3)(bpy)]
(9), respectively. This indicates that after initial protonation
of Pt–C by an SE2 mechanism to give CH4 and the related
intermediates, either [PtMe3(dppm)]+(OCOCF3)– or
unstable cationic five-coordinate intermediate [PtMe3- [PtMe3(bpy)]+(OCOCF3)–, respectively, rather than re-
(dppf)]+(OCOCF3)– (A1). The high reactivity of mutually ductive elimination of the C–C bond to give ethane, is
Scheme 1.
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M. Rashidi et al.
FULL PAPER
–
formed first and then the counteranion OCOCF3 is at- Characterization of the Complexes
tached to the metallic center to form stable PtIV complexes
8 and 9.
The complexes were fully characterized by their spectro-
scopic data, which are listed in the Experimental section.
The molecular and crystal structures of complexes 2 and 3
were further determined by single-crystal X-ray structure
determination.
In the 31P NMR spectrum of the complex 2 a singlet is
observed at δ = –17.6 ppm accompanied by platinum satel-
lites with 1JPt,P = 1119 Hz. This coupling is more than 16%
greater than the corresponding value of 1JPt,P = 936 Hz ob-
served for dppm complex 6. This discrepancy can be attrib-
uted to a rather large strain existing in the PCPPt ring of
dppm in forming chelate complexes with the metallic center.
In the 1H NMR spectrum of 2, the two equivalent Me
groups trans to P atoms appeared as a triplet at δ =
0.46 ppm with 3JP,H = 6.0 Hz and 2JPt,H = 59.4 Hz. The two
equivalent Me groups trans to each other appeared as a
3
triplet at δ = 0.00 ppm with JP,H = 6.0 Hz, but with a sig-
2
nificantly smaller JPt,H value of 44.0 Hz as a result of the
high trans influence of the Me group as compared to that
of the chelating P atoms. The α and β protons of dppf each
appeared as a broad singlet at δ = 4.24 ppm and δ = 4.14,
respectively.
In the 31P NMR spectrum of complex 3 shown in Fig-
ure 1; the P atom trans to the CF3COO ligand appeared at
1
δ = 12.8 ppm with JPt,P = 4773 Hz, whereas the P atom
trans to the Me group is observed at δ = 32.4 ppm with a
much smaller 1JPt,P value of 1995 Hz as a result of the trans
influence of the Me ligand being far greater than that of
the CF3COO ligand. It is interesting to note that probably
due to a rather large PP bite angle of dppf, which is found
to be 101.848(18)° (vide infra), the two inequivalent P
atoms of dppf in this complex are coupled to each other
through the Pt atom and so each signal appears as a doub-
Scheme 2.
A similar behavior is also observed when in the above
reactions, HgCl2 is used instead of CF3COOH as the nu-
cleophile. Thus, as described in Scheme 2, complex 6 was
treated with HgCl2 to give methane and the PtIV product
complex [PtMe3Cl(dppm)] (10), whereas a similar reaction
using dppf analog
[PtMeCl(dppf)] (11).
2
let with JP,P = 13 Hz. This kind of P,P coupling between
the two inequivalent P atoms in a cis (or chelate) platinum
complex is usually not observed. In the 195Pt NMR spec-
trum of complex 3, a doublet of doublets at δ = –2773 ppm
2
gave methane, ethane, and
1
Nolan, et al.[9] prepared the complex [PtMe2(dppf)] (5)
by reaction of [PtMe2(cod)] (cod = η4-1,5-cyclooctadiene)
with dppf. We, however, successfully made complex 5 by
reaction of cis,cis-[Me2Pt(µ-SMe2)PtMe2] (4) with dppf
(2 equiv.) in high yields. Although the reaction of complex
5 with HBF4 is reported to lead to decomposition,[10] we
found that the use of a stoichiometric equivalent of
CF3COOH, with CF3COO– having a much higher coordi-
with JPt,P values of 4774 and 1990 Hz, close to the values
obtained from the 31P NMR spectrum, is observed.
–
nating ability than that of BF4 , complex 3 could success-
fully be prepared in good yield (see Scheme 1).
It is known that MeI oxidatively adds to the dimethyl-
platinum(II) complex through the pentacoordinate interme-
diate [PtMe3(dppm)]+I– to give the PtIV product [PtMe3I-
(dppm)].[11] In contrast, we found that in a similar reac-
tion, MeI failed to react with the dppf analogous complex
5 (see Scheme 1). This observation confirms the suggested
large steric demand imposed by dppf (vide supra), pre-
venting the formation of the corresponding intermediate
[PtMe3(dppf)]+I– (C).
Figure 1. 31P NMR spectrum of complex [PtMe(OCOCF3)(dppf)]
(3). The trace impurity is shown by *.
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A Pt(IV) Complex with 1,1Ј-Bis(diphenylphosphanyl)ferrocene Ligands
1
In the H NMR spectrum of complex 9 the two equiva- trans to P is 2.102Ϯ0.004 Å, whereas for those trans to Me
lent Me ligands trans to the N atoms appear as a singlet at is 2.153Ϯ0.004 Å). The dppf bite angle, P1–Pt1–P2, which
2
δ = 1.27 ppm with JPt,H = 67.6 Hz. The Me ligand trans is 95.77(3)°, can be compared with the PP bite angle for the
to the O atom appeared as a singlet at δ = 0.48 ppm with a dppa [bis(diphenylphosphanyl)amine] ligand in the complex
2
larger JPt,H value of 77.7 Hz as a result of the lower trans [PtMe3I(η2-dppa)], in which the corresponding angle P1–
influence of the O donor atom as compared to that of the Pt1–P2 68.93(5)° is much smaller than the ideal angle of
N chelating atoms. Consistently, the structure of complex 9 90°.[12]
was confirmed by its 13C NMR spectrum. Thus, the two
Table 1. Selected bond lengths [Å] and angles [°] for complex
equivalent C atoms of the Me ligands trans to the N atoms
[PtMe4(dppf)] (2).
1
appear as a singlet at δ = –4.0 ppm with JPt,C = 670 Hz,
Pt1–C37
Pt1–C35
Pt1–C38
2.098(3)
2.106(3)
2.153(3)
Pt1–C36
Pt1–P1
Pt1–P2
C38–Pt1–P1
C36–Pt1–P1
C37–Pt1–P2
C35–Pt1–P2
C38–Pt1–P2
C36–Pt1–P2
P1–Pt1–P2
2.154(3)
2.3658(7)
2.3726(7)
92.34(8)
89.41(8)
90.53(8)
170.92(8)
91.75(8)
98.90(8)
95.77(3)
whereas the C atom of the Me ligand trans to O appeared
as a singlet at δ = –13.9 ppm with a larger value of JPt,C
735 Hz. The remaining signals appeared at expected chemi-
cal shifts.
1
=
C37–Pt1–C35
C37–Pt1–C38
C35–Pt1–C38
C37–Pt1–C36
C35–Pt1–C36
C38–Pt1–C36
C37–Pt1–P1
C35–Pt1–P1
81.86(12)
90.06(11)
83.37(11)
87.04(11)
85.69(11)
168.98(11)
173.19(8)
92.09(9)
The molecular and crystal structure of complex 2 was
determined by X-ray crystallography and is shown in Fig-
ure 2, with selected bond parameters listed in Table 1. The
geometry around the platinum center is somewhat distorted
from octahedral. Thus, as compared to the ideal angle of
90°, the dppf bite angle, P1–Pt1–P2, is increased to
95.77(3)°, whereas the angle formed by the Me ligands trans
to P, C37–Pt1–C35, is reduced to 81.86(12)°. The angle
formed by the two trans Me ligands with the platinum cen-
ter, C38–Pt1–C36, is 168.98(11)°, and these Me ligands lean
towards the Me ligands trans to P; one of the angles formed
by two of the different Me ligands and the platinum center,
C35–Pt1–C38, is 83.37(11)°, and the other C–Pt–C angles
are also more or less smaller than 90°. This indicates that
the axial Me ligands are significantly under pressure by the
steric demands of the Ph groups on the phosphorus ligating
atoms. Besides, although Goldberg et al. have reported that
for the complex [PtMe4(dppe)], the Pt–Me bond lengths
vary only slightly with respect to the trans ligands (average
for Pt–C bond trans to P is 2.11Ϯ0.01 Å, and for those
trans to Me is 2.13Ϯ0.02 Å) for complex 2, we found that
the difference is rather significant (average for Pt–C bond
The dppf ligand is arranged close to the “synperiplanar–
eclipsed” conformation,[5a] as defined by the Cp(centroid)···
Fe···Cp(centroid) twist angle of 17.6° [the angle was deter-
mined as the torsion angle C1···Cp(centroid)1···
Cp(centroid)2···C6]. This is in contrast to the usually pre-
ferred “synclinal–staggered” conformation found in PtII
complexes with chelating dppf ligands, like for example
[PtMe2(dppf)],[9] [PtMeCl(dppf)],[10] 3 (see below), and
[PtMe(dppf)(ppy-κ1C)] (ppy = deprotonated 2-phenylpyr-
idyl)[6] as defined by a Cp(centroid)···Fe···Cp(centroid) twist
angle close to 36°.[5a]
The molecular and crystal structure of complex 3 was
also determined by X-ray crystallography and is shown in
Figure 3, with selected bond parameters listed in Table 2.
The geometry is best described as distorted square-planar
and the bond angles around the Pt center range from 83 to
101°. The different trans influences implemented by the
strong σ-donor Me ligand and the trifluoroacetate
Figure 2. Molecular structure of complex [PtMe4(dppf)] (2; 50%
probability ellipsoids, H atoms omitted for clarity).
Figure 3. Molecular structure of complex [PtMe(OCOCF3)(dppf)]
(3; 50% probability ellipsoids, H atoms omitted for clarity).
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M. Rashidi et al.
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(CF3COO–) ligand is reflected by the bond length of the tions involving several tetramethylplatinum(IV) complexes
trans Pt–P bonds; the distance of the Pt1–P1 bond trans with other nitrogen or phosphorus bidentate ligands. For
to the trifluoroacetate ligand is 2.1995(5) Å, whereas the example, when complex [PtMe4(dppm)] (6) or [PtMe4(bpy)]
distance of the Pt1–P2 bond trans to the Me ligand is (7) was treated with CF3COOH, only methane was formed
2.3266(5) Å. The dppf bite angle, P1–Pt1–P2, amounts to along with the corresponding fac-trimethylplatinum(IV)
101.85(2)° and is close to those obtained for the PtII com- complex [PtMe3(OCOCF3)(dppm)] (8)[2e] or [PtMe3(OC-
plexes with dppf as a chelating ligand, for example 5,[9] with OCF3)(bpy)] (9), respectively. Similarly, reaction of complex
a corresponding bite angle of 100.77(3)°, but is significantly
6
with HgCl2 gave only MeHgCl along with
different from that obtained for complex 2, which is [PtMe3Cl(dppm)] (10).
95.77(3)°. The dppf ligand is arranged in the usually pre-
ferred “synclinal–staggered” conformation,[5a] as defined by
the Cp(centroid)···Fe···Cp(centroid) twist angle of 32.0° [the
angle has been determined as the torsion angle
C1···Cp(centroid)1···Cp(centroid)2···C6].
Experimental Section
General: 1H and 13C NMR spectra were recorded with a Bruker
Avance DPX 250 MHz spectrometer, and 19F, 31P, and 195Pt NMR
spectra were recorded with a Bruker Avance DRX 500 MHz spec-
trometer. Microanalyses were performed with a Thermo Finnigan
Flash EA-1112 CHNSO rapid elemental analyzer. 1,1Ј-Bis(diphen-
ylphosphanyl)ferrocene was purchased from Aldrich. The known
precursor complexes cis,cis-[Me2Pt(µ-SMe2)2PtMe2] (4),[13] cis,cis-
[Me4Pt(µ-SMe2)2PtMe4] (1),[1] [PtMe4(dppm)] (6),[1] and
[PtMe4(bpy)] (7)[1] were prepared according to literature methods.
The stock solution of CF3CO2H was prepared by adding
CF3CO2H (920 µL) to dichloromethane (10 mL).
Table 2. Selected bond lengths [Å] and angles [°] for complex
[PtMe(OCOCF3)(dppf)] (3).
Pt1–C35
Pt1–O1
C35–Pt1–O1
C35–Pt1–P1
O1–Pt1–P1
2.104(2)
2.108(2)
83.54(7)
85.57(6)
168.31(4)
Pt1–P1
Pt1–P2
C35–Pt1–P2
O1–Pt1–P2
P1–Pt1–P2
2.1995(5)
2.3266(5)
172.34(6)
89.20(4)
101.85(2)
Conclusions
[PtMe4(dppf)] (2): To
a solution of complex 1 (200 mg,
0.315 mmol), in acetone (30 mL) was added dppf (350 mg,
0.630 mmol, 2 equiv.), and the solution was stirred for 1 h. A yellow
solid precipitated, which was separated and dried under vacuum.
Yield: 450 mg, 82%; m.p. 177–180 °C (decomp.). C38H40FeP2Pt
(809.58): calcd. C 56.4, H 5.0; found C 56.1, H 4.8. 1H NMR
The tetramethylplatinum(IV) complex [PtMe4(dppf)] (2)
synthesized in the present study is the first PtIV complex
with a chelating dppf ligand reported so far. The dppf bite
angle amounts to 95.77(3)°, which is significantly smaller
than that of related PtII complex 5,[9] with a corresponding
bite angle of 100.77(3)°. This probably caused the dppf li-
2
3
(250 MHz, CDCl3, TMS): δ = 0.00 (t, JPt,H = 44.0 Hz, JP,H
=
2
6.0 Hz, Me ligands trans to Me, 6 H), δ = 0.46 (t, JPt,H = 59.4 Ht,
gand to arrange close to the “synperiplanar–eclipsed” con- 3JP,H = 6.0 Hz, 6 H, Me ligands trans to P), 4.14 (br. s, 4 H, β,βЈ
formation,[5a] as defined by the Cp(centroid)···Fe···
Cp protons), 4.24 (br. s, 4 H, α, αЈ Cp protons), 7.04–7.40 (aromatic
protons) ppm. 31P NMR (202 MHz, CDCl3, 85% H3PO4): δ =
Cp(centroid) twist angle of 17.6°, and this is in contrast to
1
–17.6 (s, JPt,P = 1119 Hz, 2 P) ppm.
the usually preferred “synclinal–staggered” conformation
found in PtII complexes with chelating dppf ligands, like for
[PtMe(OCOCF3)(dppf)] (3): To a solution of complex 2 (100 mg,
0.124 mmol) in dichloromethane (30 mL) was added the stock solu-
example [PtMe2(dppf)],[9] [PtMeCl(dppf)],[10] and [PtMe(O-
COCF3)(dppf)] (3; reported in the present communication),
as defined by a Cp(centroid)···Fe···Cp(centroid) twist angle
of close to 36°.[5a]
tion of CF3CO2H (100 µL, 0.124 mmol), and the solution was
stirred for 1 h. A bright-yellow solution was formed, then the sol-
vent was removed under reduced pressure, and the residue was trit-
urated with n-hexane (2ϫ3 mL). The product as a bright yellow
solid was dried under vacuum. Yield: 87 mg, 76%; m.p. 255–258 °C
(decomp.). C37H31F3FeO2P2Pt (877.50): calcd. C 50.6, H 3.6; found
Thus, it can be seen that the two Me ligands situated in
trans to each other are actually under significant steric pres-
sure imposed by the Ph groups of the dppf ligand. We be-
lieve that this steric effect is responsible for the fact that
PtIV complexes with dppf as chelating ligand cannot be
formed easily, with complex 2 being an exception. We have
confirmed this by the observation that the related PtII com-
plex 5[9] failed to react with MeI to give the expected PtIV
complex [PtMe3I(dppf)]. Consistently, we have found that
when complex 2 was treated with either of the electrophiles
H+ (using CF3COOH) or HgCl+ (using HgCl2), methane
or MeHgCl, respectively, was formed first and the steric
pressure expected to be imposed by the Ph groups of the
dppf ligand on the two trans ligands of the resulting PtIV
intermediate forced its two cis Me ligands to rapidly un-
dergo reductive elimination of ethane by a C–C coupling
1
C 50.1, H 3.4. H NMR (250 MHz, CDCl3, TMS): δ = 0.50 (dd,
3
2JPt,H = 48.6 Hz, JP,H = 7.2, 3.0 Hz, 3 H, Me ligand), 3.70 (br. m,
3JP,H = 1.8 Hz, 2 H, α Cp protons), 4.14 (br. m, 2 H, β Cp protons),
3
4.45 (br. m, 2 H, βЈ Cp protons), 4.70 (br. m, JP,H = 1.8 Hz, 2
H, αЈ Cp protons), 7.26–7.85 (aromatic protons) ppm. 19F NMR
(470 MHz, CDCl3, CFCl3): δ = –74.9 (s, 3 F) ppm. 31P NMR
2
1
(202 MHz, CDCl3, 85% H3PO4): δ = 12.8 (d, JP,P = 13 Hz, JPt,P
2
1
= 4773 Hz, 1 P, P trans to O), 32.4 (d, JP,P = 13 Hz, JPt,P
=
1995 Hz, 1 P, P trans to Me) ppm. 195Pt NMR (107 MHz, CDCl3,
1
aqueous Na2PtCl4): δ = –2773.0 (dd, JPt,P = 4774, 1990 Hz, 1 Pt)
ppm.
1
The reaction was followed by H NMR spectroscopy in an NMR
tube. To a small sample of complex 2 (10 mg, 0.012 mmol) dis-
solved in CD2Cl2 in a sealed NMR tube was added the stock solu-
reaction. The latter has not been observed in similar reac- tion of CF3CO2H (10 µL, 0.012 mmol). The 1H NMR spectrum
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A Pt(IV) Complex with 1,1Ј-Bis(diphenylphosphanyl)ferrocene Ligands
was recorded after a few minutes and the observation of two singlet
signals at δ = 0.17 and 0.81 ppm confirmed the formation of meth-
ane and ethane, respectively.
[PtMeCl(dppf)] (11): To a solution of complex 2 (100 mg,
0.124 mmol) in dichloromethane (30 mL) was added HgCl2 (34 mg,
0.124 mmol), and the solution was stirred for 1 h. A bright-yellow
solution was formed, then the solvent was removed under reduced
pressure, and the residue was triturated with n-hexane (2ϫ3 mL).
The product as a dark-yellow solid was dried under vacuum and
identified as the known complex [PtMeCl(dppf)] by its NMR spec-
troscopic data.[10]
This complex was also synthesized similarly by the reaction of com-
plex 5 (100 mg, 0.128 mmol) with the stock solution of CF3CO2H
(110 µL, 0.128 mmol).
[PtMe2(dppf)] (5): To a solution of complex 4 (200 mg, 0.348 mmol)
in ethyl ether (30 mL) was added dppf (386 mg, 0.696 mmol,
2 equiv.), and the solution was stirred for 1 h. A light-yellow solid
precipitated, which was separated and dried under vacuum. Yield:
463 mg, 79%; m.p. 266–270 °C (decomp.). C36H34FeP2Pt (779.55):
calcd. C 55.5, H 4.4; found C 55.1, H 4.4. 1H NMR (250 MHz,
Attempted Reaction of MeI with Complex [PtMe2(dppf)] (5): To a
solution of [PtMe2(dppf)] (10 mg, 0.013 mmol) in dichloromethane
(5 mL) was added an excess amount of MeI (3 mL), and the solu-
tion was stirred for 1 h. No reaction was detected, as confirmed by
1H NMR spectroscopic investigation.
2
3
CDCl3, TMS): δ = 0.11 (t, JPt,H = 68.8 Hz, JP,H = 6.4 Hz, 6 H,
Me ligands), 3.87 (br. s, 4 H, β,βЈ Cp protons), 4.05 (br. s, 4 H,
α,αЈ Cp protons), 7.00–7.48 (aromatic protons) ppm. 31P NMR
X-ray Crystal-Structure Determination: Single crystals of
[PtMe4(dppf)] (2) and [PtMe(OCOCF3)(dppf)] (3) were grown from
a concentrated dichloromethane solution by slow diffusion of
1
(202 MHz, CDCl3, 85% H3PO4): δ = 24.8 (s, JPt,P = 1903 Hz, 2
P) ppm. 195Pt NMR (107 MHz, CDCl3, aqueous Na2PtCl4): δ = n-hexane.
For
2,
a
yellowish
block
approximately
1
–3004 (t, JPt,P = 1905 Hz, 1 Pt) ppm.
0.13ϫ0.11ϫ0.10 mm3 in size and in the case of 3 a yellow prism
approximately 0.25ϫ0.19ϫ0.09 mm3 in size was coated with pro-
tective perfluoro polyalkylether oil and mounted on a glass fiber.
Data were collected at 150 K for 2 and 200 K for 3 with a Bruker-
Nonius KappaCCD diffractometer using Mo-Kα radiation (λ =
0.71073 Å, graphite monochromator). The data were corrected for
Lorentz and polarization effects, a semiempirical absorption cor-
rection based on multiple scans was carried out using SADABS.[14]
The structures were solved by direct methods and refined using
full-matrix least-squares procedures on F2 with SHELXTL NT
6.12 software.[15] All non-hydrogen atoms were refined with aniso-
tropic displacement parameters. Hydrogen atoms were placed in
positions of optimized geometry, their isotropic displacement pa-
rameters were tied to those of their corresponding carrier atoms by
a factor of 1.2 or 1.5. Crystal data, data collection, and structure
refinement details are listed in Table 3.
[PtMe3(OCOCF3)(bipy)] (9): To a solution of complex 7 (100 mg,
0.243 mmol) in dichloromethane (30 mL) was added the stock solu-
tion of CF3CO2H (200 µL, 0.243 mmol), and the solution was
stirred for 1 h. A colorless solution was formed, then the solvent
was removed under reduced pressure, and the residue was triturated
with n-hexane (2ϫ3 mL). The product as a white solid was dried
under vacuum. Yield: 93 mg, 73%; m.p. 230–233 °C (decomp.).
C15H17F3N2O2Pt (509.40): calcd. C 35.4, H 3.4, N 5.5; found C
35.1, H 3.4, N 5.3. 1H NMR (250 MHz, CDCl3, TMS): δ = 0.48
2
2
(s, JPt,H = 77.7 Hz, Me ligand trans to O, 3 H), 1.27 (s, JPt,H
=
3
67.6 Hz, 6 H, 2 Me ligands trans to N), 7.65 (m, JH5,H6 = 5.6 Hz,
3
2 H5 of bipy), 8.09 (m, JH4,H3 = 8.0 Hz, 2 H4 of bipy), 8.19 (d,
3JH3,H4 = 8.0 Hz, 2 H3 of bipy), 8.99 (d, JPt,H6 = 11.2 Hz, JH6,H5
= 5.6 Hz, 2 H6 of bipy) ppm. 13C NMR (69 MHz, CDCl3, TMS):
δ = –13.9 (s, 1JPt,C = 735 Hz, C trans to O, 1 C atom of Me ligand),
3
3
1
–4.0 (s, JPt,C = 670 Hz, C trans to N, 2 C atoms of Me ligands),
122.8 (s, JPt,C3 = 8 Hz, 2 C3 of bipy), 126.5 (s, JPt,C5 = 13 Hz, 2
C5 of bipy), 139.0 (s, 2 C4 of bipy), 147.2 (s, JPt,C6 = 15 Hz, 2 C6
CCDC-731082 (for 2) and -731083 (for 3) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
3
1
2
of bipy), 155.3 (s, 2 C2 of bipy) ppm.
Table 3. Crystal data, data collection, and structure refinement details for 2 and 3.
Complex 2
Complex 3
Formula
Formula weight
C38H40FeP2Pt
809.58
C37H31F3FeO2P2Pt
877.50
Crystal system
Space group
monoclinic
C2/c
triclinic
P1
¯
a [Å]
b [Å]
c [Å]
α [°]
16.6052(8)
14.1992(14)
26.448(2)
90
93.532(5)
90
6224.1(8)
8
1.728
9.4727(6)
12.6990(4)
15.2806(6)
109.977(3)
91.668(5)
106.728(3)
1637.8(2)
2
β [°]
γ [°]
vol. [Å3]
Z
Dcalcd. [Mgm–3]
Abs. coeff. [mm–1]
F(000)
1.779
4.857
860
5.086
3216
No. of collected reflection
No. of independent reflections
No. of observed reflections, [IϾ2σ(I)]
Tmin, Tmax
56282
7414[R(int) = 0.0498]
6106
0.510, 0.600
0.547, –0.524
0.926
70738
8286[R(int) = 0.0327]
7460
0.366, 0.650
0.457, –0.601
1.097
Largest diff. peak, hole [eÅ–3]
Goof (F2)
R1, wR2 [IϾ2σ(I)]
R1, wR2 (all data)
0.0233, 0.0436
0.0376, 0.0470
0.0160, 0.0346
0.0222, 0.0362
Eur. J. Inorg. Chem. 2009, 3814–3820
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3819

M. Rashidi et al.
FULL PAPER
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47, 5441.
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We thank the Iran National Science Foundation (Grant No. 86033/
13) and the Shiraz University Research Council for financial sup-
port. The generous loan of platinum metal salts by Johnson Mat-
they PLC is also gratefully appreciated.
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Received: May 19, 2009
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olecules, Wiley, England, 2008, part I.
Published Online: July 22, 2009
3820
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© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 3814–3820