Tetranuclear platinum phosphido complexes with different structures

Article abstract of DOI:10.1021/ic051248y

The addition of [NBu₄]Br or [NBu₄][BH₄] to solutions of [Pt₄(μ-PPh₂)₄(C ₆F₅)₄(CO)₂] (3) yields the complexes [NBu₄]₂-[Pt₄(μ-PPh₂) ₄(μ-X)₂(C₆F₅)₄] (X = Br, 4; H, 5) in which the two CO groups have been replaced by two anionic, bridging X ligands. The total valence electron counts are 64 and 60, respectively; thus, complex 4 does not require Pt-Pt bonds, while two metal-metal bonds are present in 5, as their NMR spectra confirm. Also, the NMR spectra indicate a nonsymmetrical Pt(μ-PPh₂) ₂Pt(μ-PPh₂)(μ-X)Pt(μ-PPh₂)(μ-X) Pt disposition for 4 and 5. Treatment of 5 with HX (X = Cl, Br) yields the complexes [NBu₄]₂[Pt₄(μ-PPh ₂)⁴(μ-H)₂(C₆F₅) ₃X] (X = Cl, 6; Br, 7). These complexes react with [Ag(OClO ₃)PPh₃] with displacement of the halide and formation of [NBu₄][Pt₄(μ-PPh₂)₄(μ-H) ₂(C₆F₅)₃-PPh₃] (8). Complexes 6-8 maintain the same basic skeleton as 5, with two Pt-Pt bonds. Complex 4 is, however, an isomer of the symmetric [NBu₄] ₂[{(C₆F₅)₂Pt(μ-PPh ₂)₂Pt(μ-Br)}₂] (9), which has been prepared by a metathetical process from the well-known [NBu₄] ₂[{(C₆F₅)₂Pt(μ-PPh ₂)₂Pt(μ-Cl)}₂] (1). The comparison of the X-ray structures of 4 and 9 confirms the different disposition of the bridging ligands, and their main structural differences seem to be related to the size of Br^- and its position in the skeleton.

Full text of DOI:10.1021/ic051248y

Inorg. Chem. 2005, 44, 9534−9541
Tetranuclear Platinum Phosphido Complexes with Different Structures†
Juan Fornie´s,* Consuelo Fortun˜o, Reyes Gil, and Antonio Mart´ın
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, UniVersidad
de Zaragoza, CSIC, E-50009 Zaragoza, Spain
Received July 26, 2005
The addition of [NBu4]Br or [NBu4][BH4] to solutions of [Pt4(
[Pt4( -PPh2)4( -X)2(C6F5)4] (X Br, 4; H, 5) in which the two CO groups have been replaced by two anionic,
bridging X ligands. The total valence electron counts are 64 and 60, respectively; thus, complex 4 does not require
Pt Pt bonds, while two metal metal bonds are present in 5, as their NMR spectra confirm. Also, the NMR spectra
indicate a nonsymmetrical “Pt( -PPh2)2Pt( -PPh2)( -X)Pt( -PPh2)( -X)Pt” disposition for 4 and 5. Treatment of 5
with HX (X Cl, Br) yields the complexes [NBu4]2[Pt4( -PPh2)4( -H)2(C6F5)3X] (X Cl, 6; Br, 7). These complexes
react with [Ag(OClO3)PPh3] with displacement of the halide and formation of [NBu4][Pt4( -PPh2)4( -H)2(C6F5)3-
PPh3] (8). Complexes 6 8 maintain the same basic skeleton as 5, with two Pt Pt bonds. Complex 4 is, however,
an isomer of the symmetric [NBu4]2[ (C6F5)2Pt( -PPh2)2Pt( -Br) 2] (9), which has been prepared by a metathetical
process from the well-known [NBu4]2[ (C6F5)2Pt( -PPh2)2Pt( -Cl) 2] (1). The comparison of the X-ray structures of
µ-PPh2)4(C6F5)4(CO)2] (3) yields the complexes [NBu4]2-
µ
µ
)
−
−
µ
µ
µ
µ
µ
)
µ
µ
)
µ
µ
−
−
{
µ
µ
}
{
µ
µ
}
4 and 9 confirms the different disposition of the bridging ligands, and their main structural differences seem to be
related to the size of Br- and its position in the skeleton.
Introduction
thought that the flexibility and stability of the M-P bonds
allowed the polynuclear complexes to be maintained, several
transformations14-17 and peculiar coordination modes18-25 of
The known ability of the phosphido ligands to form
polynuclear metal complexes in which the metal centers are
supported by these bridging ligands has produced a very rich
and interesting chemistry.1-13 Although it was originally
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* To whom correspondence should be addressed. E-mail:
juan.fornies@unizar.es.
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Organometallics 2003, 22, 5011-5019.
† Polynuclear Homo- or Heterometallic Palladium(II)-Platinum(II) Pen-
tafluorophenyl Complexes Containing Bridging Diphenylphosphido Ligands.
18. Part 17: Ara, I.; Chaouche, N.; Fornie´s, J.; Fortun˜o, C.; Kribii, A.;
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9534 Inorganic Chemistry, Vol. 44, No. 25, 2005
10.1021/ic051248y CCC: $30.25
© 2005 American Chemical Society
Published on Web 11/12/2005

Tetranuclear Platinum Phosphido Complexes
Scheme 1
the phosphido ligands have been described, making this field
more attractive.
(Scheme 1). The total valence electron counts are 64 and
60, respectively; thus, complex 4 does not require Pt-Pt
bonds, while two metal-metal bonds have to be present in
the tetranuclear 5, as is depicted in Scheme 1. The three-
center two-electron interaction (3c-2e) in a “PtHPt” unit
may also be described as a protonated metal-metal bond.27,28
Earlier we studied the reaction of the tetranuclear complex
[NBu4]2[{(C6F5)2Pt(µ-PPh2)2Pt(µ-Cl)}2] (1), with L (PPh3,
CO) in a 1:2 molar ratio, which results in the bridge cleavage
of the Pt(µ-Cl)2Pt moiety, producing the dinuclear anionic
derivative [(C6F5)2Pt(µ-PPh2)2PtClL]-. However, the elimi-
nation of the terminal chloride with AgClO4 surprisingly
results in very different complexes because when L ) PPh3,
the dinuclear derivative [(C6F5)2Pt(µ-PPh2)2PtPPh3] (2), with
a 30 valence electron count and hence a Pt-Pt bond, is
obtained.26 When L ) CO, the tetranuclear cluster [Pt4(µ-
PPh2)4(C6F5)4(CO)2] (3; 60 valence electron count), with two
Pt-Pt bonds and two terminal CO ligands, is obtained
(Scheme 1).15
In this paper, we study the reaction of complex 3, which
contains two labile CO ligands with H- and Br-. These
ligands displace CO and, although both can act as terminal
or bridging ligands, hydride is exclusively a two-electron
donor while bromide can potentially provide a higher number
of electrons. This fact is clearly reflected in the nature of
the resulting complexes, the reactivity of which is also
studied.
The most significant data in the IR spectra of these
tetranuclear derivatives are the presence of an absorption to
ca. 880 cm-1 due to the counterion [NBu4]+ along with the
absence of absorptions due to the CO ligands. It is well-
known that the ν(Pt-Hterminal) stretching mode is usually
observed in the range 1970-2250 cm-1, while for the
bridging hydride, such absorptions (ca. 1600 cm-1) are
usually weak and often difficult to assign.9,29-33 In complex
5, we have not been able to locate any absorption either in
the terminal region or in the bridging region.
1
The H NMR spectra of 4 and 5 show signals due to the
hydrogen atoms of the phenyl groups along with those due
to the counterion [NBu4]+. Their relative intensities are in
agreement with the proposed dianionic nature of the com-
plexes. In 5, two signals due to hydride ligands are observed.
(27) Zhuravel, M. A.; Moncarz, J. R.; Glueck, D. S.; Lam, K.-C.; Rheingold,
A. L. Organometallics 2000, 19, 3447-3454.
(28) van Leeuwen, P. W. N. M.; Roobeek, C. F.; Frijns, J. H. G.; Orpen,
A. G. Organometallics 1990, 9, 1211-1222.
Results and Discussion
(29) Leoni, P.; Pasquali, M.; Fortunelli, A.; Germano, G.; Albinati, A. J.
Am. Chem. Soc. 1998, 120, 9564-9573.
The addition of [NBu4]Br or [NBu4][BH4] to solutions of
3 (2:1 molar ratio) yields the dianionic complexes [NBu4]2-
[Pt4(µ-PPh2)4(µ-X)2(C6F5)4] (X ) Br, 4; H, 5) in which the
two CO groups have been replaced by two bridging X ligands
(30) Leoni, P.; Manetti, S.; Pasquali, M. Inorg. Chem. 1995, 34, 749-
752.
(31) Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Mart´ın, A.; Orpen, A. G.
Organometallics 2001, 20, 850-859.
(32) Ara, I.; Falvello, L. R.; Fornie´s, J.; Lalinde, E.; Mart´ın, A.; Mart´ınez,
F.; Moreno, M. T. Organometallics 1997, 16, 5392-5405.
(33) Kaesz, H. D.; Saillant, R. B. Chem. ReV. 1972, 72, 231-281.
(26) Falvello, L. R.; Fornie´s, J.; Fortun˜o, C.; Mart´ınez, F. Inorg. Chem.
1994, 33, 6242-6246.
Inorganic Chemistry, Vol. 44, No. 25, 2005 9535

Fornie´s et al.
without a metal-metal bond.1,5,39 Nevertheless, the signals
due to P3 and P4 atoms in 5 are observed at lower field, 96.0
and 95.4 ppm, respectively. These values are in the range
found in our complexes with short Pt-Pt distances in the
“Pt(µ-PPh2)Pt” and “Pt(µ-PPh2)(µ-H)Pt” fragments.15,18,31,41
The P1 and P2 signals are broad, as we have usually found
in all of our complexes with the “(C6F5)2Pt(µ-PPh2)2Pt”
fragment, probably because of the poorly resolved couplings
with the F atoms of the C6F5 groups.19 In both complexes,
the P2 signal appears as a doublet of doublets (306 and 167
Hz, 4; 249 and 122 Hz, 5) due to the coupling with P3 and
P1 (see Table l) and the P3 signal as a doublet. It is
noteworthy that the splitting of the P1 and P4 signals is
different for 4 and 5. In complex 4, P1 appears as a doublet
(coupled with P2, 167 Hz) and P4 is a singlet. In complex 5,
P1 appears as a doublet of doublets (122 and ca. 43 Hz) and
P4 as a doublet (43 Hz). The coupling between P1 and P4
observed in the hydrido derivative 5 (60 valence electron
count) but not in the bromo derivative 4 (64 valence electron
count) is in agreement12,18 with the existence or not of a
metal-metal bond between Pt2 and Pt3 in 5 or 4, respectively.
All of the signals show platinum satellites from which
1J(Pt,P) values can be extracted (see Table 1). The platinum
satellites in the P2 signal appear overlapped (separated by
ca. 1640 Hz, 4, and ca. 1745 Hz, 5); thus, the two coupling
values with Pt1 or with Pt2 have to be very similar in both
complexes. The P3 atom is bridging two Pt centers not
bonded to the C6F5 groups, and hence the P3 signal is sharp
in both cases. It is noteworthy that in complex 5 this signal
shows closed platinum satellites (143 Hz) assignable to the
coupling with Pt4, and this coupling is not observed in
complex 4, as expected. For our unsaturated complexes with
short intermetallic distances, for which metal-metal bonds
are proposed, we have observed that the coupling between
Pt and P atoms in a Pt-M-P system [“Pt(µ-PPh2)2M-
P”,15,18,26 “Pt(µ-PPh2)M-P”,12,18,31 and “Pt(µ-PPh2)(µ-H)Pt-
P”31,42 fragments) can be measured, while this Pt-P coupling
cannot be observed for saturated complexes with longer
Pt‚‚‚M distances. The values of these 2J(Pt,P) couplings are
in agreement with the assignment of the 143-Hz splitting in
Figure 1. Atom-numbering scheme for NMR discussion purposes.
The signal due to H1 (see Figure 1 for atom numbering)
appears at -4.0 ppm as a broad triplet (57 Hz), indicating
the same coupling value between H1 and the two P atoms in
trans positions, P1 and P.4 The signal due to H2 is a doublet
[2J(P3,H2) ) 54 Hz] centered at -6.6 ppm. Both signals are
flanked by platinum satellites from which 1J(Pt2,H1) ≈
1
1J(Pt3,H1) ≈ 408 Hz and J(Pt,H2) ) 450 and 504 Hz can
be measured. The 2J(Ptrans to H,H) values for the hydride ligand
2
are an indication of the bonding mode. Usually the J(Ptran
-
s
to H,H) values for the hydride ligand are ca. 55-80 Hz for
bridged hydrides, while this coupling is much larger for
terminal hydrides.9,30,31,34-36 Moreover, although there are
some exceptions,37 usually platinum hydride complexes,
bridging hydrides display 1J(Pt,H) values in the range 300-
600 Hz, while the terminal hydrides give signals with
1J(Pt,H) values in the range 800-1400 Hz.9,30,31,34-36 All of
these data are in good agreement with the proposed structure.
The 19F NMR spectrum (a deuterioacetone solution) of 4
shows in the o-F atom region four signals with platinum
satellites in a 2:2:2:2 intensity ratio. Some signals appear
3
overlapped, and all of the values of J(Pt,F) cannot be
measured unambiguously. In the high-field region (m- and
p-F atoms), four signals for the m-F atoms (a 2:2:2:2 intensity
ratio) and four signals for the p-F atoms (a 1:1:1:1 intensity
ratio) are observed. This pattern is in full agreement with
the inequivalence of the four C6F5 groups in 4. The spectrum
of 5 in a deuterioacetone solution shows, in the o-F region,
a pattern that is analogous to 4, while in the m- and p-F
atoms region, the signals appear overlapped (see the Ex-
perimental Section).
The 31P NMR spectra of 4 and 5 in a deuterioacetone
solution show four signals, and the different values of the
chemical shifts of the four inequivalent P atoms are
conclusive in establishing their structural disposition. All data
are given in Table 1. The signals due to P1 and P2 (see Figure
1 for atom numbering) appear at high field (from -126.8 to
-142.0 ppm), as is expected for P atoms of the PPh2 groups
in the “(C6F5)2Pt(µ-PPh2)2Pt” fragment without a metal-
metal bond.13,26,38-40 For complex 4, the signals due to P3
and P4 atoms appear at -32.0 and -47.9 ppm, respectively,
in the range observed for all of our derivatives that display
the bridged system “M(µ-PPh2)(µ-X)M” (X ) Cl, Br, I, OH)
2
5 to J(Pt4,P3). Although attempts to obtain a crystal of 5
suitable for X-ray study have been unsuccessful, the 60
valence electron count for a tetranuclear complex along with
the 31P NMR data [δ(P3), δ(P4), 3J(P1,P4), and 2J(Pt4,P3)] and
the comparison with the trinuclear [{(C6F5)(PPh3)Pt(µ-
PPh2)(µ-H)}2Pt]31,42 are in agreement with those of the
proposed structure with two Pt-Pt bonds in 5. All of these
observations point out that, because of the small size of the
hydrido ligand, the Pt-Pt-Pt angles in 5 are smaller than
180°, as in [{(C6F5)(PPh3)Pt(µ-PPh2)(µ-H)}2Pt], 146.84(1)°.31
Treatment of complex 5 with a methanol solution of HX
(X ) Cl, Br) in a 1:1 molar ratio yields the complexes
[NBu4]2[Pt4(µ-PPh2)4(µ-H)2(C6F5)3X] (X ) Cl, 6; Br, 7) as
yellow solids (Scheme 1). The process that gives 6 or 7
(34) Powell, J.; Fuchs, E.; Sawyer, J. F. Organometallics 1990, 9, 387-
393.
(35) Venanzi, L. M. Coord. Chem. ReV. 1982, 43, 251-274.
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A. L.; Zakharov, L. N. Dalton Trans. 2004, 2720-2727.
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M. Inorg. Chem. 2001, 40, 3055-3060.
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Organomet. Chem. 1990, 394, 643-658.
(39) Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Toma´s, M. J. Chem. Soc., Dalton
Trans. 1995, 3777-3784.
(41) Alonso, E.; Fornie´s, J.; Fortun˜o, C.; Mart´ın, A.; Orpen, A. G. Chem.
Commun. 1996, 231-232.
(42) Ara, I.; Chaouche, N.; Fornie´s, J.; Fortun˜o, C.; Kribii, A.; Tsipis, A.
C.; Tsipis, C. A. Inorg. Chim. Acta 2005, 358, 1377-1385.
(40) Alonso, E.; Casas, J. M.; Fornie´s, J.; Fortun˜o, C.; Mart´ın, A.; Orpen,
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5582.
9536 Inorganic Chemistry, Vol. 44, No. 25, 2005

Tetranuclear Platinum Phosphido Complexes
Table 1. 1H and 31P{1H} NMR Data for Complexes 4-8 (J/Hz)
4
5
6
7
8a
δ(H1)
-4.0 (t)
-6.6 (d)
57
54
408
-4.4 (t)
-6.1 (d)
63
42
520
-4.3(t)
-6.2(d)
60
45
b
-3.7(t)
-5.9(d)
61
40
530
δ(H2)
J(P1 or 4,H1)
J(P3,H2)
J(Pt2 or 3,H1)
J(Pt3 or 4,H2)
450
388
b
480
504
582
b
480
δ(P1)
-131.7 (d)
-142.0(dd)
-32.0(d)
-47.9 (s)
167
-126.8 (dd)
-136.6 (dd)
96.0 (d)
95.4 (d)
122
43
249
1974
2610
-114.2 (dd)
-124.1 (dd)
93.8 (d)
93.1 (d)
115
40
259
1924
2478
-115.5(br d)
-125.6(dd)
93.7(d)
97.6(d)
105
-123.1(dd)
-135.6(dd)
96.6(d)
104.8(dd)
126
41
262
1920
2520
δ(P2)
δ(P3)
δ(P4)
J(P1,P2)
J(P1,P4)
J(P2,P3)
J(Pt1 or 2,P1)
41
255
306
1965
2882
≈1640
1779
3234
2116
3248
2000
2500
b
1675
2950
3162
3162
134
J(Pt1,2,P2)
≈1745
≈1800
≈1615
J(Pt2 or 3,P3)
1611
1680
1649
3114
2021
3044
143
2970
3170
3170
134
2988
1869
3139
128
J(Pt3 or 4,P4)
J(Pt4,P3)
a J(Pt2,P4) ) 46, δ(P5Ph3) ) 20.2, J(P4,P5) ) 299, J(Pt4,P5) ) 2688, J(Pt3,P5) ) 54. b See text.
consists of the breaking of one Pt-C6F5 bond and the
elimination of C6F5H with the formation of a Pt-X bond.
This straightforward process has been largely used in our
pentafluorophenyl derivatives, and it has been suggested that
it takes place through an oxidative addition of HX to an
anionic metal center followed by reductive elimination of
C6F5H.43,44 We have obtained crystals of 7 for X-ray studies.
Unfortunately, the crystal decomposed before the data
collection could be completed, but the incomplete set of data
confirms the connectivity depicted in Scheme 1. The terminal
halide ligand is expected to be easily displaced by neutral
ligands. In fact, treatment of the bromo derivative 7 with
[Ag(OClO3)PPh3] results in the formation of [NBu4][Pt4(µ-
PPh2)4(µ-H)2(C6F5)3PPh3] (8; Scheme 1).
signals are observed for the o-F atoms (a 2:2:2 intensity
ratio), three signals (a 1:1:1 intensity ratio) are observed for
the p-F atoms, and the signals due to the m-F atoms appear
overlapped. The 31P{1H} NMR spectra of 6-8 show the four
signals due to the four inequivalent P atoms of phosphido
ligands. The values of the chemical shifts as well as the
corresponding coupling constants (see Table 1) are similar
to those observed for complex 5. For complex 7, the signal
due to the P2 atom shows overlapped platinum satellites,
which unambiguously preclude calculation of the 1J(Pt,1,2P2)
values. The spectrum of complex 8 shows a doublet (299
Hz) centered at 20.2 ppm due to the P atom of the PPh3
ligand, P5, and the P4 signals appears as a doublet of doublets
(299 and 41 Hz), while the P4 signal in 5-7 is a doublet.
This value of J(P4,P5) ) 299 Hz observed in complex 8 is
in full agreement with the trans arrangement of both atoms,
as is depicted in Scheme 1. Moreover, in complex 8, the P4
and P5 signals show very closed platinum satellites because
1
The H NMR spectra of 6-8 (a CDCl3 solution) show
signals due to the hydrogen atoms of the phenyl groups along
with those due to the counterion [NBu4]+. Their relative
intensities are in agreement with the proposed dianionic (6
and 7) or monoanionic (8) nature of the complexes.
Moreover, the expected signals in the hydride region are
observed. Their relevant data are given in Table 1. For
2
of the coupling with Pt2 and Pt3, respectively, J(Pt2,P4) )
2
46 Hz and J(Pt3,P5) ) 54 Hz.
Thus, although we have not been able to carry out a full
X-ray study of some of these hydrido derivatives with a 60
valence electron count, their structures have been clearly
established from their NMR data. The values of δ(P3) and
3J(P1,P4) in all hydride derivatives 5-8 as well as the
1
complex 7, the J(Pt,H) values cannot be calculated unam-
biguously because of overlapped platinum satellites, but the
patterns of the signals are like those in 5, 6, and 8. The 19F
NMR spectra of 6 and 7 show, for the o-F atoms, two signals
(a 4:2 intensity ratio) with platinum satellites. The pattern
of the most intense signal is characteristic of two different
overlapped signals. In the high-field region, two broad signals
(a 4:2 intensity ratio) due to m-F atoms and three signals (a
1:1:1 intensity ratio) due to p-F atoms are observed. These
spectra unambiguously indicate the inequivalence of the three
C6F5 groups. In the spectrum of 8, three well-separated
2
observed value of J(Pt2,P4) in 8 are in agreement with the
presence of a Pt2-Pt3 bond. The values of δ(P4) and 2J(Pt4,P3)
2
in 5-8 as well as J(Pt3,P5) in 8 are in agreement with the
presence of a Pt3-Pt4 bond.
The synthesis of the asymmetric complex 4 is worthy of
comment. Complex 3 was synthesized (Scheme 1) by the
addition of CO to the symmetric tetranuclear [NBu4]2[{-
(C6F5)2Pt(µ-PPh2)2Pt(µ-Cl)}2] and the elimination of the Cl-
groups, through the intermediate [(C6F5)2Pt(µ-PPh2)2PtClCO]-.
The whole process was formally the result of the substitution
of two bridging chloro ligands by two terminal CO groups.
(43) Fornie´s, J.; Mart´ın, A.; Mart´ın, L. F.; Menjo´n, B.; Kalamarides, H.
A.; Rhodes, L. F.; Day, C. S.; Day, V. W. Chem.sEur. J. 2002, 8,
4925-4934.
(44) Uso´n, R.; Fornie´s, J.; Toma´s, M.; Fandos, R. J. Organomet. Chem.
1984, 263, 253-260.
Inorganic Chemistry, Vol. 44, No. 25, 2005 9537

Fornie´s et al.
Table 2. Crystal Data and Structure Refinement for 4‚CH2Cl2 and 9‚1.4CH2Cl2
4‚CH2Cl2
9‚1.4CH2Cl2
empirical formula
formula weight
T/K
C104H112F20N2Br2P4Pt4‚CH2Cl2
2918.94
150(1)
C104H112F20N2Br2P4Pt4‚1.4CH2Cl2
2952.91
150(1)
λ/Å
0.71073
triclinic
P1h
0.71073
monoclinic
P21/m
12.334(3)
22.413(2)
19.9737(15)
90
97.706(11)
90
5471.6(14)
2
cryst syst
space group
a/Å
11.1142(9)
20.549(3)
25.464(3)
106.30(2)
99.595(13)
101.547(14)
5313.0(10)
2
b/Å
c/Å
R/deg
â/deg
γ/deg
V/Å3
Z
Dc/(g cm-3
)
1.825
6.194
1.792
6.034
µ
Mo KR/mm-1
diffractometer
θ range/deg
data collected
Enraf Nonius CAD4
2.0-25.0
19671
Enraf Nonius CAD4
2.0-25.0
2403
independent data (Rint
)
18615 (0.0278)
18528/8/1264
1.069
0.0393
0.0988
10366 (0.0788)
9876/30/601
1.053
0.0715
0.1783
iata/restraints/parameters
GOF on F 2 a
final R1 (I > 2σ(I))b
final wR2 (all data)c
2
2
2
2
2
a GOF ) [∑w(Fo - Fc )2/(Nobs - Nparam)]0.5
.
b R1 ) ∑(|Fo| - |Fc|)/∑|Fo|. c wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]0.5
.
It is noteworthy that in this process the tetranuclear starting
material shows one “Pt(µ-X)2Pt” and two “Pt(µ-PPh2)2Pt”
fragments while complex 3 shows one “Pt(µ-PPh2)2Pt” and
two “Pt(µ-PPh2)Pt” fragments. Complex 4 is formally the
result of the reverse process: the substitution of two terminal
CO ligands in 3 by two Br- groups, which act as bridging
ligands. Howewer, 4 shows one “Pt(µ-PPh2)2Pt” and two “Pt-
(µ-PPh2)(µ-X)Pt” fragments, unlike the tetranuclear chloro
derivative 1 (Scheme 1); i.e., the halide bridging ligands are
in different structural positions in complex 1 (a very
symmetric structure) and in complex 4. Both complexes (64
valence electron count) do not require any Pt-Pt bond. To
compare the two types of symmetric and asymmetric
structures, we have prepared the isomer of 4, i.e., the
symmetric bromo derivative [NBu4]2[{(C6F5)2Pt(µ-PPh2)2Pt-
(µ-Br)}2] (9), by a metathetical process from the well-known
[NBu4]2[{(C6F5)2Pt(µ-PPh2)2Pt(µ-Cl)}2].38 All data of 9 are
given in the Experimental Section, and they are analogous
to those of the starting chloro derivative.38 The study of the
solid-state structure of both isomers, 4 and 9, has been carried
out by X-ray studies.
Crystal Structures of [NBu4]2[{(C6F5)2Pt(µ-PPh2)2Pt-
(µ-Br)}2]‚1.4CH2Cl2 (9‚1.4CH2Cl2) and [NBu4]2[Pt4(µ-
PPh2)4(µ-Br)2(C6F5)4]‚CH2Cl2 (4‚CH2Cl2). Crystal data and
refinement parameters are given in Table 2. Structures of
the complex ions of 9 and 4 together with the atom-labeling
scheme are shown in Figures 2 and 3, respectively. Selected
bond distances and angles are listed in Tables 3 and 4. The
anions in both 9 and 4 are tetrametallic complexes in which
the Pt atoms are bridged by diphenylphosphide and bromine
ligands and the pentafluorophenyl groups are the terminal
ligands. Nevertheless, while in 9 the anion is symmetric, in
4 it has a nonsymmetric arrangement. The Pt atoms lie in a
crystallographic mirror plane in 9, and this symmetry
operator generates half of the molecule. The structure can
be regarded as two “(C6F5)2Pt(µ-PPh2)2Pt” subunits held
Figure 2. Two views of the molecular structure of the anion of complex
9‚1.4CH2Cl2.
together by two Br atoms. The Pt atoms lie in the center of
a square-planar environment. The intermetallic distances
clearly indicate that there is not any metal-metal bond in
the complex, in accordance with the overall electron count
of 64. The Pt(2)-Pt(3) distance, 3.682(1) Å, is longer than
the other two [Pt(1)-Pt(2) ) 3.564(1) Å and Pt(3)-Pt(4)
) 3.542(1) Å] probably because of the fact that the bridging
bromine ligand is bulkier than the P atom of the diphosphido
ligands, as reflected in the Pt-Br and Pt-P bond distances
(see Table 3). Because of the long intermetallic separation,
the Pt-P-Pt angles are quite broad [Pt(1)-P(1)-Pt(2) )
103.5(1)° and Pt(3)-P(2)-Pt(4) ) 102.2(2)°] and the inner
P-Pt-P ones quite narrow (around 76°; see Table 3), as
9538 Inorganic Chemistry, Vol. 44, No. 25, 2005

Tetranuclear Platinum Phosphido Complexes
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 4‚CH2Cl2
Pt(1)-C(7)
Pt(1)-Br(1)
Pt(2)-Br(2)
Pt(3)-P(4)
Pt(4)-C(19)
Pt(4)-P(4)
Pt(1)-C(1)
Pt(2)-P(1)
1.983(9)
2.539(1)
2.546(1)
2.316(2)
2.060(8)
2.302(2)
2.075(8)
2.239(2)
Pt(2)-Br(1)
Pt(3)-P(2)
Pt(4)-C(13)
Pt(1)-P(1)
Pt(2)-P(2)
Pt(3)-P(3)
Pt(3)-Br(2)
Pt(4)-P(3)
2.583(1)
2.325(2)
2.063(8)
2.297(2)
2.247(2)
2.264(2)
2.606(1)
2.295(2)
C(7)-Pt(1)-C(1)
C(1)-Pt(1)-P(1)
C(1)-Pt(1)-Br(1)
P(1)-Pt(2)-P(2)
P(2)-Pt(2)-Br(2)
P(2)-Pt(2)-Br(1)
P(1)-Pt(2)-Pt(3)
Br(2)-Pt(2)-Pt(3)
P(3)-Pt(3)-P(4)
P(4)-Pt(3)-P(2)
P(4)-Pt(3)-Br(2)
C(19)-Pt(4)-C(13)
C(13)-Pt(4)-P(3)
C(13)-Pt(4)-P(4)
Pt(1)-Br(1)-Pt(2)
Pt(2)-P(1)-Pt(1)
Pt(3)-P(3)-Pt(4)
90.0(3)
175.8(3)
95.6(3)
C(7)-Pt(1)-P(1)
C(7)-Pt(1)-Br(1)
P(1)-Pt(1)-Br(1)
P(1)-Pt(2)-Br(2)
P(1)-Pt(2)-Br(1)
Br(2)-Pt(2)-Br(1)
P(2)-Pt(2)-Pt(3)
Br(1)-Pt(2)-Pt(3)
P(3)-Pt(3)-P(2)
P(3)-Pt(3)-Br(2)
P(2)-Pt(3)-Br(2)
C(19)-Pt(4)-P(3)
C(19)-Pt(4)-P(4)
P(3)-Pt(4)-P(4)
Pt(2)-Br(2)-Pt(3)
Pt(2)-P(2)-Pt(3)
Pt(4)-P(4)-Pt(3)
94.1(2)
174.2(2)
80.35(6)
172.34(6)
80.48(6)
91.92(3)
46.65(6)
122.98(3)
106.72(7)
167.58(6)
80.25(6)
97.4(2)
172.7(2)
76.47(7)
76.68(3)
88.69(7)
101.23(8)
104.31(8)
83.03(6)
169.09(6)
131.55(6)
52.50(2)
76.81(7)
173.03(7)
97.42(6)
89.0(3)
173.3(2)
97.2(2)
84.59(3)
98.93(8)
103.02(8)
[Pt(3) and Pt(4)], whereas Pt(1)-Pt(2) and Pt(2)-Pt(3) are
bridged by a phosphide group and a bromine group each.
The intermetallic distances range from 3.197(1) to 3.569(1)
Å, which again excludes any Pt-Pt bonds, as is expected
for a valence electron count of 64. The replacement of the
CO groups in the starting material (valence electron count
of 60) with bromine ligands in 4 increases the overall number
of electrons by 4. Each Pt atom lies in the center of a square-
planar environment, with that of Pt(3) being the most
distorted one (see Table 4). Nevertheless, as can be seen in
Figure 3b, the anion complex of 4 is not planar, mainly
because of the µ-Br bridging groups. The dihedral angles
between the best planes around the Pt atoms are thus Pt-
(1)-Pt(2) ) 36.9°, Pt(2)-Pt(3) ) 61.6°, and Pt(3)-Pt(4)
) 19.9°. The larger the value of the dihedral angle, the
shorter the Pt-Pt distance: Pt(1)-Pt(2) ) 3.447(1) Å, Pt-
(2)-Pt(3) ) 3.197(1) Å, and Pt(3)-Pt(4) ) 3.569(1) Å. As
was previously observed in other phosphido-bridging plati-
num complexes, there is a relationship between the inter-
metallic distance and the Pt-P-Pt angle.5,13,15,18,19,31,40 Thus,
the shorter Pt(2)-Pt(3) distance is accompanied by the
narrowest angle [Pt(2)-P(2)-Pt(3) ) 88.7(1)°], whereas the
longer Pt(3)-Pt(4) distance is observed with the broadest
angles [Pt(3)-P(3)-Pt(4) ) 103.0(1)° and Pt(3)-P(4)-Pt-
(4) ) 101.2(2)°]. Like the Pt(1)-Pt(2) distance, the Pt(1)-
P(1)-Pt(2) angle has an intermediate value of 98.9(1)°.
Nevertheless, the Pt-P, Pt-Br, and Pt-C distances are very
similar in the two isomers 9 and 4, as can be seen in Tables
3 and 4.
Figure 3. Two views of the molecular structure of the anion of complex
4‚CH2Cl2.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
a
9‚1.4CH2Cl2
Pt(1)-C(1)
Pt(2)-Br
Pt(4)-C(7)
Pt(1)-P(1)
2.138(13)
2.554(2)
2.081(16)
2.289(4)
Pt(3)-P(2)
Pt(4)-P(2)
Pt(2)-P(1)
Pt(3)-Br
2.255(4)
2.296(4)
2.250(4)
2.540(2)
C(1′)-Pt(1)-C(1)
C(1)-Pt(1)-P(1)
P(1)-Pt(2)-P(1′)
P(1)-Pt(2)-Br
P(2)-Pt(3)-P(2′)
P(2)-Pt(3)-Br′
C(7′)-Pt(4)-C(7)
C(7)-Pt(4)-P(2′)
Pt(3)-Br-Pt(2)
Pt(3)-P(2)-Pt(4)
87.8(7)
98.2(3)
C(1)-Pt(1)-P(1′)
P(1′)-Pt(1)-P(1)
P(1)-Pt(2)-Br′
Br′-Pt(2)-Br
173.8(3)
75.68(18)
175.97(10)
84.79(7)
98.11(11)
85.38(7)
95.5(5)
77.23(19)
98.97(10)
78.4(2)
176.44(11)
92.2(9)
171.8(5)
92.56(5)
102.22(16)
P(2)-Pt(3)-Br
Br-Pt(3)-Br′
C(7)-Pt(4)-P(2)
P(2)-Pt(4)-P(2′)
Pt(2)-P(1)-Pt(1)
76.7(2)
103.49(14)
a The symmetry transformation used to generate equivalent primed atoms
is x, 0.5 - y, z.
was previously observed in other phosphido-bridging plati-
num complexes.5,13,15,18,19,31,40 Each Pt atom and the atoms
bonded to it lie essentially in the same plane. The environ-
ments of the Pt atoms bridged by the diphenylphosphido
ligands are almost coplanar [the dihedral angle between the
best Pt(1) and Pt(2) least-squares planes is 2.8°, and that
between the best Pt(3) and Pt(4) least-squares planes is 8.5°].
The whole anion is bent at the Br atoms (see Figure 2b),
with the dihedral angle between the best least-squares Pt(2)
and Pt(3) planes being 24.8°. The Pt-P, Pt-Br, and Pt-C
distances are in the range commonly found for these kinds
of complexes.5,13,15,18,19,31,40
To compare the reactivity of both types of isomers of [Pt4-
(µ-PPh2)4(µ-X)2(C6F5)4]2- (X ) halogen) stoichiometry
(symmetric 9 and asymmetric 4), we have studied the
reactions of the asymmetric 4 with [Ag(OClO3)PPh3] and
with AgClO4 (a 1:2 molar ratio). In the first case, the bromo
ligands are eliminated as AgBr, and after workup of the
mixture, the resulting red solid is identified (IR and NMR
spectroscopy) as the dinuclear [(C6F5)2Pt(µ-PPh2)2PtPPh3]
In 4, however, there are two kinds of phosphido ligands;
P(3) and P(4) are simultaneously bridging the same Pt atoms
Inorganic Chemistry, Vol. 44, No. 25, 2005 9539

Fornie´s et al.
mmol) in CH2Cl2 (25 mL) was added [NBu4]Br (0.143 g, 0.446
mmol). After 12 h of stirring at room temperature, the solution
was evaporated to dryness. iPrOH (5 mL) was added to the residue,
and the resulting suspension was stirred for 1 h. The yellow solid
was then filtered off, washed with n-hexane, and finally air-dried
(0.449 g, 71% yield). Anal. Calcd for C104H112F20N2Br2P4Pt4: C,
(2), with a 30 valence electron count (Scheme 1). The
reaction of 4 with AgClO4 renders the tetranuclear [Pt4(µ-
PPh2)4(C6F5)4] (10), with a 62 valence electron count
(Scheme 1). Earlier we reported that the symmetric complex
1 reacts with [Ag(OClO3)PPh3], yielding the dinuclear 2, and
when the elimination of the Cl ligands is achieved with
AgClO4, the tetranuclear cluster 10 is obtained.18,26 Moreover,
the addition of PPh3 to 10 does not yield the dinuclear
derivative 2, but rather the tetranuclear complex [Pt4(µ-
PPh2)4(C6F5)4PPh3] is formed.19
Thus, the elimination of the halo ligands as AgX from
the two types of isomers yields the same derivatives. All of
these results indicate that transformation between the “Pt-
(µ-PPh2)2Pt”, “Pt(µ-PPh2)(µ-X)Pt”, and “Pt(µ-PPh2)Pt” frag-
ment types can be carried out easily. This fact can be
understood if the possibility of the PPh2 groups to act as a
bridging ligand between three metal centers is con-
sidered.18-20,25,41,45,46 Moreover, it is noteworthy that the
nuclearity and structure of the phosphido derivatives are more
dependent on the ancillary ligands than the structural
arrangement of the phosphido groups in the starting materials.
1
44.03; H, 3.95; N, 0.98. Found: C, 44.04; H, 3.76; N, 1.33. H
NMR (room temperature, acetone-d6): δ from 7.8 to 6.6 (40 H,
C6H5), 3.4 (m, 16 H, CH2), 1.8 (m, 16 H, CH2), 1.4 (m, 16 H,
CH2), 0.95 (t, 24 H, CH3). 19F NMR (room temperature, acetone-
d6): δ -114.9 [2 o-F, 3J(195Pt,F) ) 262 Hz], -115.4 [2 o-F, 3J(195
-
Pt,F) cannot be measured], -116.3 [2 o-F, J(195Pt,F) cannot be
measured], -116.7 [2 o-F, 3J(195Pt,F) ) 523 Hz], -167.5 (2 m-F),
-167.6 (2 m-F), -168.0 (2 m-F), -168.3 (2 m-F), -169.0 (1 p-F),
-169.2 (1 p-F), -169.5 (1 p-F), -169.9 (1 p-F).
3
Preparation of [NBu4]2[Pt4(µ-PPh2)4(C6F5)4(µ-H)2] (5). To an
orange solution of 3 (0.500 g, 0.223 mmol) in CH2Cl2 (25 mL)
was added [NBu4][BH4] (0.172 g, 0.668 mmol). The solution was
stirred at room temperature for 12 h and then evaporated to dryness.
The residue was treated with CHCl3 (5 mL), and after a few minutes
of stirring, a yellow precipitate appears. It was filtered off, washed
with n-hexane, and finally air-dried (0.400 g, 67% yield). Anal.
Calcd for C104H114F20N2P4Pt4: C, 46.67; H, 4.26; N, 1.04. Found:
1
C, 46.26; H, 4.26; N, 1.05. H NMR (room temperature, acetone-
Concluding Remarks
d6): δ from 7.7 to 6.6 (40 H, C6H5), 3.4 (m, 16 H, CH2), 1.8 (m,
16 H, CH2), 1.4 (m, 16 H, CH2), 0.95 (t, 24 H, CH3). 19F NMR
The tetranuclear derivatives described in this paper show
typical square-planar metal environments with a bent ar-
rangement of the molecular skeleton. The bending of the
skeleton is strongly dependent on the bridging ligands (PPh2
or Br).
The total valence electron count of 64 or 60 for the
tetranuclear complexes implies the absence or presence of
metal-metal bonds.
It is interesting to point out that the elimination of two
bridging halides (4e- each) and coordination of two CO
ligands is a stoichiometrically reversible process, but the
starting and final resulting complexes are not the same but
rather isomers; i.e., complex 1 can be transformed into 3,
but the addition of Br- to 3 yields a complex of stoichiometry
similar to that of 1 (9) but with a different structure.
The main structural differences in both isomers 9 and 4
seem to be related to the size of the Br- and its position in
the skeleton.
3
(room temperature, acetone-d6): δ -112.7 [2 o-F, J(195Pt,F) )
3
365 Hz], -113.1 [2 o-F, J(195Pt,F) cannot be measured], -113.4
3
3
[2 o-F, J(195Pt,F) ) 467 Hz], -113.6 [2 o-F, J(195Pt,F) ) 349
Hz], -166.4 (7 m- + p-F), -167.2 (1 p-F), -167.4 (1 p-F), -167.9
(3 m- + p-F).
Preparation of [NBu4]2[Pt4(µ-PPh2)4(C6F5)3(µ-H)2X] [X ) Cl,
6; Br, 7]. To a yellow solution of 5 (0.200 g, 0.075 mmol) in CH2-
Cl2 (20 mL) kept at 0 °C was added HCl (6) or HBr (7) (0.075
mmol, MeOH/H2O solutions). After 1 h of stirring at 0 °C, the
i
solution was evaporated to dryness. To the residue was added -
PrOH (10 mL), and the resulting solid was filtered off, washed
with n-hexane, and finally air-dried (yield: 0.141 g, 74% (6); 0.171
g, 88% (7)).
6. Anal. Calcd for C98H114F15N2ClP4Pt4: C, 46.26; H, 4.52; N,
1.10. Found: C, 45.87; H, 4.90; N, 1.09. IR (cm-1): ν(Pt-Cl) 271.
1H NMR (room temperature, CDCl3): δ from 8.0 to 6.6 (40 H,
C6H5), 2.9 (m, 16 H, CH2), 1.3 (m, 16 H, CH2), 1.2 (m, 16 H,
CH2), 0.8 (t, 24 H, CH3). 19F NMR (room temperature, CDCl3): δ
3
3
-115.8 [4 o-F, J(195Pt,F) ≈ 385 Hz], -117.3 [2 o-F, J(195Pt,F)
) 437 Hz], -165.8 (1 p-F), -166.3 (4 m-F), -166.7 (2 m-F)
-167.5 (1 p-F), -167.7 (1 p-F).
Experimental Section
7. Anal. Calcd for C98H114F15N2BrP4Pt4: C, 45.46; H, 4.44; N,
1.08. Found: C, 44.98; H, 4.79; N, 1.12. 1H NMR (room
temperature, CDCl3): δ from 8.0 to 6.6 (40 H, C6H5), 2.9 (m, 16
H, CH2), 1.3 (m, 16 H, CH2), 1.2 (m, 16 H, CH2), 0.8 (t, 24 H,
CH3). 19F NMR (room temperature, CDCl3): δ -115.7 [4 o-F,
3J(195Pt,F) ≈ 344 Hz], -116.8 [2o-F, 3J(195Pt,F) ) 433 Hz], -165.7
(1 p-F), -166.3 (4 m-F) -166.6 (2 m-F), -167.3 (1 p-F), -167.5
(1 p-F).
General Comments. Literature methods were used to prepare
the starting materials [Pt4(µ-PPh2)4(C6F5)4(CO)2],15 [NBu4]2[{-
(C6F5)2Pt(µ-PPh2)2Pt(µ-Cl)}2],38 and [Ag(OClO3)PPh3].47 C, H, and
N analysis and IR and NMR spectra were performed as described
1
elsewhere.5 Relevant H and 31P NMR data are given in Table 1.
Safety Note! Perchlorate salts of metal complexes with organic
ligands are potentially explosiVe. Only small amounts of materials
should be prepared, and these should be handled with great caution.
Preparation of [NBu4]2[Pt4(µ-PPh2)4(C6F5)4(µ-Br)2] (4). To an
orange solution of [Pt4(µ-PPh2)4(C6F5)4(CO)2] (3; 0.500 g, 0.223
Preparation of [NBu4][Pt4(µ-PPh2)4(C6F5)3(µ-H)2PPh3] (8). To
a yellow solution of 7 (0.300 g, 0.116 mmol) in CH2Cl2 (15 mL)
was added [Ag(OClO3)PPh3] (0.054 g, 0.116 mmol). After 30 min
of stirring in the darkness, the resulting suspension was filtered
through Celite in order to eliminate the AgBr formed. The solution
(45) Eichhofer, A.; Fenske, D.; Holstein, W. Angew. Chem., Int. Ed. Engl.
1993, 32, 242-245.
(46) Corrigan, J. F.; Doherty, S.; Taylor, N. J. J. Am. Chem. Soc. 1992,
114, 7557-7558.
i
was then concentrated until approximately 1 mL and PrOH (10
mL) was added, causing the formation of a solid, which was filtered
off, washed with n-hexane, and finally air-dried (0.208 g, 71%
(47) Cotton, F. A.; Falvello, L. R.; Uso´n, R.; Fornie´s, J.; Toma´s, M.; Casas,
J. M.; Ara, I. Inorg. Chem. 1987, 26, 1366-1370.
9540 Inorganic Chemistry, Vol. 44, No. 25, 2005

Tetranuclear Platinum Phosphido Complexes
yield). Anal. Calcd for C100H93F15NP5Pt4: C, 47.49; H, 3.71; N,
0.55. Found: C, 47.80; H, 4.17; N, 0.81. 1H NMR (room
temperature, CDCl3): δ from 7.7 to 6.6 (55 H, C6H5), 3.0 (m, 8 H,
The structures were solved by Patterson and Fourier methods
and refined using the program SHELXL-97.49 All non-hydrogen
atoms were assigned anisotropic displacement parameters. All
hydrogen atoms were placed at calculated positions and constrained
to ride on their parent atoms with a constrained isotropic displace-
ment parameter. For 4‚CH2Cl2, two methyl groups of one of the
[NBu4]+ cations are disordered over two sets of positions and were
refined with occupancies 0.3/0.7 [C(92)/C(92′)] and 0.5/0.5 [C(96)/
C(96′)], and their distances to the methylene carbon bonded to them
were constrained to idealized values. One molecule of a CH2Cl2
solvent is present in the structure, showing a disorder of the Cl
atoms over two positions (0.65/0.35 occupancy) and sharing the
same C atom. For the disordered CH2Cl2, the C-Cl distances were
constrained to idealized geometries and all of the atoms were refined
with a common anisotropic thermal parameter. For 9, severe
disorder was encountered for the C atoms of the [NBu4]+ cations,
especially for the one containing the atom N(2). The possibility of
a lower symmetry P21 space group was investigated but discarded
on the basis of the least-squares refinement results. Because of the
symmetry, the four Pt atoms, both N atoms, and two of the butyl
branches of each [NBu4]+ lie in a mirror plane. C(39), which is a
γ-C atom of one butyl group in the N(1) [NBu4]+ cation and should
lie in this plane, is in fact disordered over two positions with partial
occupancy 0.25/0.25. The C atoms of the butyl branch C(49)/C(52),
belonging to the N(2) [NBu4]+ cation and which should also lie in
the mirror plane, are also disordered over two positions with partial
occupancy 0.25/0.25. Finally, in this same [NBu4]+ cation, C(57)
and C(58) are disordered over two positions with partial occupancy
0.5/0.5. For the disordered C atoms, a common isotropic thermal
parameter was used for each pair of congeners. Except for one butyl
branch of the N(1) [NBu4]+ cation, the N-C and C-C distances
of the cations were restrained to idealized values. Also, the C-Cl
distances were restrained for the CH2Cl2 solvent molecule, in which
the atoms were assigned a partial occupancy of 0.7. No attempts
were made to include the hydrogen attached to the C atoms of the
cations and solvent moieties. Full-matrix least-squares refinement
on F 2 of these models converged to final residual indices given in
Table 2.
CH2), 1.5 (m, 8 H, CH2), 1.3 (m, 8 H, CH2), 0.9 (t, 12 H, CH3).
3
19F NMR (room temperature, CDCl3): δ -114.9 [2 o-F, J(195
-
Pt,F) ) 326 Hz], -115.4 [2 o-F, 3J(195Pt,F) ) 328 Hz], -117.3 [2
o-F, 3J(195Pt,F) ) 376 Hz], -165.3 (1 p-F), -166.4 (6 m-F), -167.6
(1 p-F), -167.7 (1 p-F).
Preparation of [NBu4]2[{(C6F5)2Pt(µ-PPh2)2Pt(µ-Br)}2] (9). To
a yellow solution of 1 (0.151 g, 0.055 mmol) in Me2CO (20 mL)
was added AgClO4 (0.034 g, 0.110 mmol). After 30 min of stirring
in the darkness, the resulting suspension is filtered through Celite
in order to eliminate the AgCl formed. To the resulting solution
was added [NBu4]Br (0.035 g, 0.110 mmol), and after 10 min of
stirring, the solution was concentrated until approximately 1 mL
i
and PrOH (10 mL) was added, causing the formation of a solid,
which was filtered off, washed with n-hexane, and finally dried in
air (0.072 g, 46% yield). Anal. Calcd for C104H112F20N2Br2P4Pt4:
C, 44.03; H, 3.95; N, 0.98. Found: C, 43.97; H, 3.99; N, 1.18. IR
(cm-1): C6F5 X-sensitive mode,48 780, 773. 1H NMR (room
temperature, acetone-d6): δ 7.7 (m, 16 o-H, C6H5), 7.1 (m, 24 m-
+ p-H, C6H5), 3.4 (m, 16 H, CH2), 1.8 (m, 16 H, CH2), 1.4 (m, 16
H, CH2), 1.0 (t, 24 H, CH3). 19F NMR (room temperature, acetone-
3
d6): δ -110.8 [8 o-F, J(195Pt,F) ) 300 Hz], -161.2 (8 m-F),
-161.6 (4 p-F). 31P NMR (room temperature, acetone-d6): δ
-138.6 [1J(195Pt,P) ) 2626 and 1926 Hz].
Reaction of 4 with AgClO4. To a yellow solution of 4 (0.100
g, 0.035 mmol) in CH2Cl2 (20 mL) was added AgClO4 (0.145 g,
0.070 mmol). After 10 min of stirring at room temperature, the
resulting suspension was filtered through Celite in order to eliminate
the AgBr formed. The solution was then evaporated to dryness.
To the residue was added OEt2 (25 mL), and the insoluble [NBu4]-
[ClO4] was filtered off. The solution was again evaporated to
dryness, and the residue was treated with n-hexane (20 mL), filtered
off, and finally air-dried. This solid was identified for its spectro-
scopic data18 as 10 (0. 035 g, 46% yield).
Reaction of 4 with [Ag(OClO3)(PPh3)]. To a yellow solution
of 4 (0.100 g, 0.035 mmol) in CH2Cl2 (20 mL) was added [Ag-
(OClO3)(PPh3)] (0.033 g, 0.070 mmol), and immediately the
solution turned red. After 15 min of stirring at room temperature,
the resulting suspension was filtered through Celite in order to
eliminate the AgBr formed. The solution was then evaporated to
dryness. To the residue was added OEt2 (25 mL), and the insoluble
[NBu4][ClO4] was filtered off. The solution was again evaporated
to dryness, and the red residue was treated with n-hexane (20 mL),
filtered off, and finally dried in air. This solid was identified for
its spectroscopic data26 as 2 (0.031 g, 32% yield).
Acknowledgment. We thank the Ministerio de Ciencia
y Tecnolog´ıa and Fondos FEDER (Project BQU2002-03997-
C02-02) and DGA (Grupo Consolidado) for financial sup-
port.
Supporting Information Available: Further details of the
structure determinations of 4‚CH2Cl2 and 9‚1.4CH2Cl2 including
atomic coordinates, bond distances and angles, and thermal
parameters (CIF). This material is available free of charge via the
Internet at http://pubs.acs.org.
X-ray Structure Determinations of 4‚CH2Cl2 and 9‚1.4CH2Cl2.
Crystal data and other details of the structure analyses are presented
in Table 2. Crystals suitable for X-ray diffraction studies were
obtained by slow diffusion of n-hexane into solutions of 0.020 g
of the complexes in 3 mL of CH2Cl2. Absorption corrections were
applied for all structures based on azimuthal scan data.
IC051248Y
(48) Maslowsky, E., Jr. Vibrational Spectra of Organometallic Compounds;
(49) Sheldrick, G. M. SHELXL-97; University of Go¨ttingen: Go¨ttingen,
Wiley: New York, 1977.
Germany, 1997.
Inorganic Chemistry, Vol. 44, No. 25, 2005 9541