Synthesis of binuclear platinum complexes containing the ligands 8-naphthyridine, 2-aminopyridine, and 7-azaindolate. An experimental study of the steric hindrance of the bulky pentafluorophenyl ligands in the synthesis of binuclear complexes

Article abstract of DOI:10.1021/ic8006475

The bidentate N-donor ligands 2-aminopyridine (2-ampy), 7-azaindolate (aza) and 1,8-naphthyridine (napy) have been used to study the steric effect of pentafluorophenyl groups in the synthesis of binuclear platinum(II) complexes. The 2-ampy and aza ligands

Full text of DOI:10.1021/ic8006475

Inorg. Chem. 2008, 47, 8767-8775
Synthesis of Binuclear Platinum Complexes Containing the Ligands
8-Naphthyridine, 2-Aminopyridine, and 7-Azaindolate. An Experimental
Study of the Steric Hindrance of the Bulky Pentafluorophenyl Ligands
in the Synthesis of Binuclear Complexes
Jose´ M. Casas,† Beatriz E. Diosdado,† Juan Fornie´s,*,† Antonio Mart´ın,† Angel J. Rueda,†
and A. Guy Orpen‡
Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n, UniVersidad
de Zaragoza-C.S.I.C., E-50009 Zaragoza, Spain, and School of Chemistry, UniVersity of Bristol,
Bristol, U. K. BS8 1TS, U.K.
Received April 10, 2008
The bidentate N-donor ligands 2-aminopyridine (2-ampy), 7-azaindolate (aza) and 1,8-naphthyridine (napy) have
been used to study the steric effect of pentafluorophenyl groups in the synthesis of binuclear platinum(II) complexes.
The 2-ampy and aza ligands bridge two “Pt(C6F5)2” fragments with Pt · · · Pt distances of 4.1 and 3.4 Å, respectively
(complexes 1 and 3). Under the same reaction conditions the napy ligand shows chelating behavior and makes the
mononuclear complex (A) highly reactive because of its strained coordination. One of the Pt-N bonds of the
chelating complex is broken on reaction with HX {X ) Cl (4), Br (5)} because of protonation while the anion X-
occupies a created vacant site. The resulting mononuclear complex eliminates C6F5H when refluxed, and a binuclear
complex (6) with two napy ligands bridging two “Pt(C6F5)Cl” fragments is obtained. The reaction of A with HPPh2
affords a mononuclear complex (7) analogous to complexes 5 and 6, but reflux gives a binuclear complex (8) with
the two napy ligands terminally bound and the PPh2 groups bridging the “Pt(C6F5)napy” moieties. The reaction of
A with HCt CPh gives a binuclear complex; moreover, the final product does not depend on the ratio of complex
A to HCt CPh. Complexes 1, 4, 6, 9 have been structurally characterized by X-ray diffraction.
Introduction
to face” (Chart 1c), the platinum coordination planes are
parallel or nearly parallel.9-14
The ability of bidentate ligands to facilitate the synthesis
of bi- and polynuclear complexes is well-known.10,11,15-18
Nevertheless, some bidentate ligands with a flexible con-
nection between their donor atoms, such as dppm, en, tmeda,
Binuclear platinum(II) complexes containing two identical
bridging ligands can adopt three extreme structure types (see
Chart 1). In one of them (Chart 1a) the two platinum square
planar environments may be in the same plane1-3 or bent
(Chart 1b),4-8 while in the other type, usually known as “face
(6) Janka, M.; Anderson, G. K.; Rath, N. P. Organometallics 2000, 19,
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* To whom correspondence should be addressed. E-mail: juan.fornies@
unizar.es.
(7) Freeman, W. A.; Nicholls, L. J.; Liu, C. F. Inorg. Chem. 1978, 17,
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Kopacka, H. A. R.; Bruggeller, P. Inorg. Chim. Acta 1999, 290, 167.
(9) Blake, A. J.; Reid, G.; Schroder, M. Acta Crystallogr., Sect. C: Cryst.
Struct. Commun. 1991, 47, 64.
†
Universidad de Zaragoza-C.S.I.C.
University of Bristol.
‡
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10.1021/ic8006475 CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 19, 2008 8767
Published on Web 09/04/2008

Casas et al.
Chart 1
prefer to act as chelate ligands when they react with metal
complexes if the metal center has two labile ligands in
suitable positions.19-25
In other cases di- or polydentate ligands prefer to act as
bridging ligands rather than chelating [napy, hpp (1,3,4,6,7,8-
hexahidro-2H-pyramido-1,2-a-pyramidinate), tbo (1,3,6-tri-
azabicyclo-3,3,0-oct-4-ene)].26-28 However, formation of
binuclear complexes using typical binucleating ligands can
be precluded by the steric hindrance of the ancillary ligands
bonded to the metal center. So, in spite of the well-known
ability of the 1,8-naphthyridine to act as a bridging
ligand28-32 we have not been able to prepare the binuclear
[Pt2(µ-napy)2(C6F5)4] but obtained instead the mononuclear
and very reactive complex cis-[Pt(C6F5)2(napy)] (A)33 be-
cause this complex contains a strained four-membered ring
with a small bite angle [N-Pt-N 62.3(3)°]. On the other
hand, some examples in which the presence of sterically
demanding coligands causes the formation of higher nucle-
arity complexes are also known.34
The formation of the mononuclear complex cis-[Pt-
(C6F5)2(napy)] (A) instead of the binuclear one seems to be
due to the position of the bulky pentafluorophenyl rings with
respect to the platinum coordination planes (perpendicular
or nearly perpendicular), which if bridged by the N donor
atoms of the 1,8-naphthyridine ligand should adopt an
approximately face to face disposition with the platinum
coordination planes nearly parallel, thus producing congestion
of the C6F5 groups.
Chart 2
In this paper we report a careful study of the effects of
sterically bulky ligands on the formation of diplatinum(II)
complexes. With this aim we have synthesized and structur-
ally characterized several binuclear complexes, two of them
containing the “Pt(C6F5)2” moiety as in A but with more
flexible bridging ligands such as 2-aminopyridine or 7-aza-
indole (see Chart 2).
In addition we have also prepared two binuclear platinum
complexes with 1,8-naphthyridine as bridging ligands but
with only one C6F5 group per platinum atom to avoid the
steric congestion that precluded the formation of the binuclear
complex. Other reactions with cis-[Pt(C6F5)2(napy)] have also
been studied.
(15) Fornie´s, J.; Garcia, A.; Gil, B.; Lalinde, E.; Moreno, M. T. Dalton
Trans. 2004, 22, 3854–3863.
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A.; Ienco, A.; Mealli, C. Organometallics 2004, 23, 471–481.
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Trans. 2003, 11, 2313–2317.
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(20) Colquhoun, H. M.; Stoddart, J. F.; Williams, D. J. Chem. Commun.
1981, 851.
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Bercaw, J. E. Inorg. Chim. Acta 1998, 270, 467.
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C: Cryst. Struct. Commun. 1991, 47, 1819.
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Commun. 2003, 23, 2882.
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L. M.; Fackler, J. P., Jr Inorg. Chem. 2007, 46, 11165.
(28) Maekawa, M.; Munakata, M.; Kuroda-Sowa, T.; Suenaga, Y.; Yama-
moto, M. Inorg. Chim. Acta 1998, 271, 129.
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Scand. 1999, 53, 230.
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2736.
Experimental Section
General Methods. C, H, and N analyses were carried out with
a Perkin-Elmer 240B microanalyzer. IR spectra were recorded over
the 4000-200 cm-1 range on a Perkin-Elmer 883 spectrophotometer
using Nujol mulls between polyethylene sheets. 1H, and 19F NMR
spectra at room temperature were recorded on a Bru¨ker ARX-300
or a Unity-300 spectrometer in CDCl3 or acetone-d6 solutions. 1H,
19F NMR spectra at low and variable temperature were recorded
in acetone-d6 or DMSO-d6 solutions on a Bru¨ker ARX-300
spectrometer. Positive and negative ion FAB mass spectra were
recorded on a VG-Autospec spectrometer operating at about 30
kV, using the standard cesium ion FAB gun and 3-nitrobenzyl
alcohol as matrix. [NBu4]2[Pt2(µ-Cl)2(C6F5)4],2 cis-[Pt(C6F5)2(thf)2]35
cis-[Pt(C6F5)2(napy)] (A)33 and 1,8-naphthyridine (napy)36 were
prepared as described elsewhere. The 2-aminopyridine (ampy),
7-azaindol (azaH) and phenylacetilene were used as purchased from
Aldrich; diphenylphosphine was purchased from Fluka.
[Pt2(µ-ampy)2(C6F5)4] (1). To a solution of cis-[Pt(C6F5)2(thf)2]
(0.200 g, 0.297 mmol) in CH2Cl2 (10 mL) was added the equimolar
amount of ampy ligand (0.028 g, 0.297 mmol). The solution was
immediately evaporated to dryness. The yellow residue was treated
with n-hexane, filtered off, and washed with CHCl3 and n-hexane
and air-dried (92% Yield). Anal. Found (Calcd for C34H12F20N4Pt2):
C, 32.65 (32.76); H, 1.10 (0.97); N, 4.24 (4.49).
(32) Griffith, W. P.; Yuen Koh, T.; White, A. J. P.; Williams, D. J.
Polyhedron 1995, 14, 2019.
(33) Casas, J. M.; Diosdado, B. E.; Falvello, L. R.; Fornie´s, J.; Mart´ın, A.;
Rueda, A. J. J. Chem. Soc., Dalton Trans. 2004, 2733–2740.
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4, 1912.
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8768 Inorganic Chemistry, Vol. 47, No. 19, 2008

Synthesis of Binuclear Platinum Complexes
FAB- MS: m/z 1247 [Pt2(µ-ampy)2(C6F5)4]-. IR (cm-1): C6F5
X-sensitive mode,37 812, 801 s; others, 1623 m, 1619 w, 1465 vs,
1060 vs, 956 vs; ampy: ν(N-H) 3332 m, others, 1584 m, 1504 s,
771 sw. 1H NMR room temperature (acetone-d6): δ ampy: 8.21 (d,
1H, -NH2), 8.05 aprox. (d + t overlapped, 2H), 7.89 (d, 1H, -NH2),
7.65 (d, 1H), 7.03 (t, 1H). 19F NMR room temperature (acetone-
d6): δ -118.60 [m, 4F, o-F,3J(195Pt, F) ) 445 Hz], -119.70 (m,
4F, o-F), -162.77 (t, 2F, p-F), -162.88 (t, 2F, p-F), -165.19 (m,
2F, m-F), -165.30 (d, 2F, m-F), -165.37 (t, 2F, m-F), -165.44
(d, 2F, m-F).1H NMR 223 K (acetone-d6): δ ampy: 8.50 (d, 2H),
8.10 (m, 4H), 7.96(d, 2H), 7.70(d, 2H), 7.04(t, 2H). 19F NMR 223
K (acetone-d6): -117.53 [d, 2F, o-F, 3J(195Pt, F) ) 443 Hz],
-118.98 [d, 2F, o-F, 3J(195Pt, F) ) 365 Hz], -119.37 (d, 2F, o-F),
-120.12 [d, 2F, o-F, 3J(195Pt, F) ) 470 Hz], -162.31 (t, 2F, p-F),
-162.41 (t, 2F, p-F), -164.36 (m, 2F, m-F), -164.96 (m, 6F, m-F).
[NBu4][Pt(C6F5)2Cl(Haza)] (2). To a solution of [NBu4]2[Pt2(µ-
Cl)2(C6F5)4] (0.500 g, 0.031 mmol) in CH2Cl2 (30 mL) were added
0.073 g (0.062 mmol) of 7-azaindol (1:2 molar ratio). The solution
was stirred at room temperature for 30 min and then evaporated to
dryness. A mixture of 2 mL of iPrOH and 30 mL of H2O was added
to the residue, and after 15 min of stirring a white solid was
obtained, filtered off, and air-dried (65% Yield). Anal. Found (Calcd
for C33H42F12N3ClPt): C, 44.61 (44.43); H, 4.71 (4.57); N, 4.16
(4.54).
IR (cm-1): C6F5 X-sensitive mode,37 815 s, 803 s; others, 1501
vs, 1058 vs, 958 vs; napyH: ν(N-H) 3634 s m, others, 1634 s,
1
1618 s, 1548 s, 825 s, 784 s; ν(Pt-Cl) 341 m; H2O 3460 m. H
NMR room temperature (acetone-d6): δ 10.1 [dd, 1H, o-H, 3J(o-H,
m-H) ) 5.6 Hz], 9.6 [dd, 1H, o-H, 3J(o-H, m-H) ) 5.2 Hz, 3J(195Pt,
3
o-H) ) 29.7 Hz], 8.6 [dd, 1H, m-H, J(m-H, p-H) ) 8.3 Hz], 8.1
3
3
[dd, 1H, m-H, J(m-H, p-H) ) 8.4 Hz], 9.7 [dd, 1H, p-H, J(p-H,
o-H) ) 1.7 Hz], 9.3 [dd, 1H, p-H, J(p-H, o-H) ) 1.6 Hz]. 19F
3
NMR (acetone-d6): δ -117.4 [d, 2F, o-F, J(195Pt,F) ) 488 Hz],
3
-119.0 [d, 2F, o-F, J(195Pt,F) ) 493 Hz], -165.9 (m, 2F, m-F),
3
-167.6 (m, 2F, m-F), -165.7 (t, 1F, p-F), -165.8 (t, 1F, p-F).
cis-[Pt(C6F5)2Br(napyH)] · H2O (5). To a solution of cis-
[Pt(C6F5)2(napy)] (A) (0.200 g, 0.303 mmol) in CH2Cl2 (30 mL)
were added 0.85 mL of a solution of HBr (aq.) in MeOH (0.354
M, 0.303 mmol). The solution was stirred at room temperature for
15 min and then evaporated to dryness. Twenty milliliters of CHCl3
were added to the residue, and the resulting yellow solid was filtered
off, washed with 5 mL of CHCl3 and n-hexane, and finally air-
dried(71% Yield). Anal. Found (Calcd for C20H9BrF10N2OPt): C,
31.84 (31.69); H, 1.32 (1.19); N, 3.84 (3.69).
IR (cm-1): C6F5 X-sensitive mode,37 813 s, 803 s; others, 1501
vs, 1058 vs, 959 vs; napyH: ν(N-H) 3629 s m, others, 1632 s,
1
1607 s, 1546 s, 827 s, 783 s, 636 s; H2O 3469 m. H NMR room
temperature (acetone-d6): δ 10.2 [dd, 1H, o-H, 3J(o-H, m-H) ) 5.5
Hz], 9.7 [dd, 1H, o-H, 3J(o-H, m-H) ) 5.1 Hz], 8.7 [dd, 1H, m-H,
IR (cm-1): C6F5 X-sensitive mode,37 807 s, 796 s; others, 1501
vs, 1056 vs, 959 vs; azaH: ν(N-H): 3421 m, others:1598 m, 546 w,
3
3J(m-H, p-H) ) 8.1 Hz], 8.2 [dd, 1H, m-H, J(m-H, p-H) ) 8.4
3
Hz], 9.8 [dd, 1H, p-H, J(p-H, o-H) ) 1.5 Hz], 9.3 [dd, 1H, p-H,
496 w, 445 w; ν(Pt-Cl): 292 w; NBu4+: 888 m. H NMR room
1
3J(p-H, o-H) ) 1.5 Hz]. 19F NMR (acetone-d6): δ -116.6 [d, 2F,
o-F, 3J(195Pt, F) ) 484 Hz], -118.9 [d, 2F, o-F, 3J(195Pt, F) ) 487
Hz], -165.6 (m, 2F, m-F), -167.7 (m, 2F, m-F), -164.6 (t, 1F,
p-F), -165.9 (t, 1F, p-F).
temperature (CDCl3): δ aza: 8.4 (d, 1H, H1), 6.9 (dd, 1H, H2), 7.9
(d, 1H, H3), 6.5 (d, 1H, H4), 7.3 (m, 1H, H5), 10.3 (s, 1H, H6);
NBu4: 0.95 (t, 12H, -CH3), 1.38 (sext., 8H, R-CH2), 1.61 (m, 8H,
ꢀ-CH2), 3.12 (m, 8H, γ-CH2). 19F NMR (CDCl3): δ -118.5 [d,
2F, o-F, 3J(195Pt, F) ) 487 Hz], -120.2 [d, 2F, o-F, 3J(195Pt, F) )
527 Hz], -166.4 (m, 2F, m-F), -167.1 (m, 2F, m-F), -165.4 (t,
1F, p-F), -166.4 (t, 1F, p-F).
[PtCl(C6F5)(µ-napy)2PtCl(C6F5)] (6). A suspension of cis-
[Pt(C6F5)2Cl(napyH)] (4) (0.200 g, 0.288 mmol) in CH2Cl2 (30 mL)
was refluxed for 90 min and then evaporated to dryness. Twenty
milliliters of CHCl3 were added to the residue. The resulting yellow
solid was filtered off, washed with 5 mL of CHCl3 and n-hexane,
and, finally air-dried (62% Yield). Anal. Found (Calcd for
C28H12Cl2F10N4Pt2): C, 31.83 (31.86); H, 0.89 (1.15); N, 5.31 (5.31).
IR (cm-1): C6F5 X-sensitive mode,37 804 s; others, 1500 vs, 1056
[NBu4]2[Pt2(µ-aza)2(C6F5)4] (3). To a solution of [NBu4][Pt-
(C6F5)2Cl(azaH)] (2) (0.400 g, 0.432 mmol) in CH2Cl2 (20 mL)
were added 0.54 mL of a solution of NBu4OH in methanol (0.8
M, 0.432 mmol). The solution was stirred for 15 min, and after
that, the solution was evaporated to dryness. Twenty milliliters of
iPrOH were added to the residue precipitating a white solid that
1
vs, 963 vs; ν(Pt-Cl) 340 m; napy: 847 s, 837 s, 791 s, 667 s. H
3
NMR room temperature (acetone-d6): δ 10.4 [d, 2H, o-H, J(o-H,
i
was filtered off, washed with 5 mL of PrOH and n-hexane, and,
m-H) ) 5.1 Hz], 9.6 [d, 2H, o-H, 3J(o-H, m-H) ) 5.6 Hz], 8.1 [dd,
2H, m-H, 3J(m-H, p-H) ) 8.0 Hz], 7.5 [dd, 2H, m-H, 3J(m-H, p-H)
) 8.0 Hz], 8.9 (d, 2H, p-H), 8.7 (d, 2H, p-H). 19F NMR room
temperature (acetone-d6): δ the signals for the ortho-fluor atoms
cannot be appreciated over the noise level -166.9 (very broad
signal, 4F, m-F), -164.4 (t, 2F, p-F).19F NMR (acetone-d6, -80
°C): δ -109.2 [d, 2F, o-F, 3J(195Pt, F) ) 118 Hz], -121.7 [d, 2F,
o-F, 3J(195Pt, F) ) 245 Hz], -165.6 (m, 2F, m-F), -166.5 (m, 2F,
m-F), -163.3 (t, 2F, p-F).
finally air-dried (80% Yield). Anal. Found (Calcd for
C70H82F20N6Pt2): C, 47.42 (47.30); H, 4.81 (4.65); N, 4.92 (4.72).
IR (cm-1): C6F5 X-sensitive mode,37 809 s, 796 s; others, 1501
+
vs, 1056 vs, 957 vs; azaH: 1598 m, 580 w, 468 w, 446 w; NBu4
:
1
888 m. H NMR room temperature (CDCl3): δ aza: 8.4 (d, 2H,
H1), 6.9 (dd, 2H, H2), 7.9 (d, 2H, H3), 6.5 (d, 1H, H4), 7.3 (m,
1H, H5); NBu4: 0.95 (t, 12H, -CH3), 1.38 (sext., 8H, R-CH2), 1.61
(m, 8H, ꢀ-CH2), 3.12 (m, 8H, γ-CH2). 19F NMR (CDCl3): δ -118.5
[d, 4F, o-F, 3J(195Pt, F) ) 494 Hz], -120.3 [d, 4F, o-F, 3J(195Pt, F)
) 537 Hz], -166.4 (m, 4F, m-F), -167.1 (m, 4F, m-F), -165.4
(t, 2F, p-F), -166.4 (t, 2F, p-F).
cis-[Pt(C6F5)2(HPPh2)(napy)] (7). To a suspension of cis-
[Pt(C6F5)2(napy)] (A) (0.200 g, 0.303 mmol) in CH2Cl2 (30 mL)
under nitrogen atmosphere were added 52 µL (0.303 mmoles) of
HPPh2. The solution was stirred for 15 min at room temperature
and then evaporated to dryness. Thirty milliliters of n-hexane were
added to the residue yielding a solid which was filtered off, washed
with n-hexane, and finally air-dried(71% Yield). Anal. Found (Calcd
for C32H17F10N2PPt): C, 45.63 (45.45); H, 2.15 (2.04); N, 3.36
(3.15).
cis-[Pt(C6F5)2Cl(napyH)] ·H2O (4). To a CH2Cl2 (30 mL)
solution of cis-[Pt(C6F5)2(napy)] (A) (0.200 g, 0.303 mmol were
added 0.65 mL of a solution of HCl (aq.) in MeOH (0.464 M, 0.303
mmol). The solution was stirred at room temperature for 15 min,
and the precipitation of a yellow solid was observed. This solid
was filtered off, washed with 5 mL of CH2Cl2, and air-dried (76%
Yield). Anal. Found (Calcd for C20H9ClF10N2OPt): C, 33.44 (33.67);
H, 0.96 (1.27); N, 3.84 (3.92).
IR (cm-1): C6F5 X-sensitive mode,37 803 vs, 782 s, others, 958
vs; HPPh2: 2377 s, 1239 m, 1191 m, 703 m; napy: 834 m,, 632 w.
1H NMR room temperature (acetone-d6): δ 9.3 [d, 1H, o-H], 9.2
3
(37) Uso´n, R.; Fornie´s, J. AdV. Organomet. Chem. 1988, 28, 188.
[s, 1H, o-H], 7.6 [m, 1H, m-H, J(m-H, p-H) ) 7.6 Hz], 7.7 [m,
Inorganic Chemistry, Vol. 47, No. 19, 2008 8769

Casas et al.
Table 1. Crystal Data and Structure Refinement For [Pt2(µ-ampy)2(C6F5)4]·2CH2Cl2 (1·2CH2Cl2), cis-[Pt(C6F5)2Cl(napyH)]·H2O (4·H2O),
[Pt2(C6F5)2Cl2(napy)2]·0.375CH2Cl2 (6·0.375CH2Cl2), and [Pt2(C6F5)3(Ct CPh)(napy)2]·2.5Me2CO (9·2.5Me2CO)
complex
1·2CH2Cl2
4·H2O
6·0.75CH2Cl2
9·2.5Me2CO
empirical formula
C34H12F20N4Pt2
C20H7ClF10N2Pt
C56H12Cl4F20N4Pt2
C47H17F15N4Pt2
·2CH2Cl2
·H2O
·0.375CH2Cl2
·2.5Me2CO
unit cell dimensions
a (Å)
b (Å)
10.326(2)
11.2017(13)
18.241(2)
13.035(4)
13.677(4)
12.292(4)
9.4640(10)
35.601(4)
20.671(4)
12.442(2)
25.214(4)
16.797(2)
c (Å)
R (deg)
97.550(11)
94.610(6)
100.28(2)
2046.2(5), 2
0.71073
200(1)
90
108.16(3)
90
2082.3(11), 4
0.71073
293(1)
graphite monochromated
Mo KR
monoclinic
P21/c
90
90
ꢀ (deg)
93.550(10)
90
6951.3(17), 8
0.71073
293(1)
graphite monochromated
Mo KR
111.116(7)
90
4915.8(11), 4
0.71073
173(1)
graphite monochromated
Mo KR
γ (deg)
V (Å3), Z
wavelength (Å)
temp (K)
radiation
graphite monochromated
Mo KR
cryst syst
space group
triclinic
monoclinic
P21/c
monoclinic
P21/c
j
P1
cryst dimens (mm)
0.45 × 0.30 × 0.25
0.50 × 0.25 × 0.25
0.32 × 0.19 × 0.13
0.55 × 0.40 × 0.40
abs coeff (mm-1
)
7.218
6.973
8.331
5.787
transmissn factors
abs cor
1.000-0.379
516 azimuthal scan data
0.439-0.360
432 azimuthal scan data
0.865-0.420
432 azimuthal scan data
0.512-0.228
10141 symmetry equivalent
reflections
diffractometer
Siemens P4
Siemens P3m
Enraf Nonius CAD4
Siemens SMART
2θ range for
data collect.(deg)
no. of rflns collected
no. of indep rflns
refinement method
4.04-25.00
3.28-50.00
4.12-49.96
3.06-52.08
7600
3853
13030
23535
7172 [R(int) ) 0.0197]
full-matrix least-squares on
F2
3667 [R(int) ) 0.0320]
12191 [R(int) ) 0.0935]
full-matrix least-squares on
F2
8531 [R(int) ) 0.0383]
full-matrix least-squares on
F2
full-matrix least-squares on
F2
goodness-of-fit on F2
1.039
1.041
1.006
1.710
final R indices (I > 2σ(I))a
R1 ) 0.0462,
wR2 ) 0.1390
R1 ) 0.0554,
wR2 ) 0.1514
R1 ) 0.0291
wR2 ) 0.0695
R1 ) 0.0399
wR2 ) 0.0755
2
R1 ) 0.0780
wR2 ) 0.1654
R1 ) 0.2236
wR2 ) 0.2258
R1 ) 0.0336
wR2 ) 0.0966
R1 ) 0.0391
wR2 ) 0.1014
R indices (all data)
a R1 ) ∑||Fo| - |Fc||)/∑|Fo|; wR2 ) [∑w(Fo - Fc )2/∑w(Fc )2]0.5
2
2
3
1H, m-H, J(m-H, p-H) ) 7.6 Hz], 8.4 [d, 1H, p-H], 8.5 [d, 1H,
of n-hexane yielding a solid that was filtered off, washed with
n-hexane and, finally air-dried(82% Yield). Anal. Found (Calcd for
p-H]. 19F NMR room temperature (acetone-d6): δ -116.7 [d, 2F,
o-F, 3J(195Pt, Fo)) 446 Hz], -117.3 [d, 2F, o-F, 3J(195Pt, Fo)) 355
Hz], -164.5(t, 1F, p-F), -163.2 (t, 1F, p-F), -164.9 (m, 2F, m-F),
-166.1 (m, 2F, m-F).31P-{1H} NMR room temperature (acetone-
C42H17F15N4Pt2): C, 40.15 (40.27); H, 1.10 (1.37); N, 4.36 (4.47).
37
IR (cm-1): C6F5 X-sensitive mode,
811 m, 802 m, 792 m;
others, 1501 s, 1058 s, 965 s, 956 s; napy: 839 m, 634 w; CCPh:
2020 w, 1990 m, 751 m. 1H NMR room temperature (acetone-d6):
δ 10.3 [br, 1H], 9.6 [d, 1H], 9.9 [dd, 1H], 8.9 [dd, 3H], 8.0 [br,
1H], 8.7 [dd, 1H], 7.6 [dd, 1H], 7.2 [dd, 3H], 9.2 [br, 1H], 8.9 [dd,
1H], 7.8 [dd, 4H]. 19F NMR (acetone-d6): δ -113.0 [d, 2F, o-F],
-116.2 [d, 2F, o-F], -119.8 [d, 2F, o-F], -164.6 (m, 2F, m-F),
-166.0 (m, 2F, m-F), -167.4 (m, 2F, m-F), -163.7 (t, 1F, p-F),
-165.1 (t, 1F, p-F), -166.0 (t, 1F, p-F).
d6): δ -8, 43 [1J(195Pt, P) ) 2469 Hz, J(Fo(trans), P) ) 211 Hz,
4
4J(Fo(cis), P) ) 74 Hz].
[Pt(C6F5)(napy)(µ-PPh2)2Pt(C6F5)(napy)] (8). A suspension of
cis-[Pt(C6F5)2(HPPh2)(napy)] (7) (0.100 g, 0.120 mmol) in toluene
(20 mL) was refluxed for 3 h, and gradually the suspension turned
into an orange solution. This was evaporated to dryness, and the
i
residue was treated with 5 mL of PrOH, yielding a solid which
was filtered off, washed with n-hexane, and finally air-dried (57%
Yield). Anal. Found (Calcd for C52H32F10N4P2Pt2): C, 46.30 (46.09);
H, 2.41 (2.38); N, 3.75 (4.13).
X-ray Structure Determinations. Crystal data and other details
of the structure analyses are presented in Table 1. Suitable crystals
were obtained by slow diffusion of n-hexane into CH2Cl2 or Me2CO
solutions of the complexes 1, 4, 6, and 9. Crystals were mounted
at the end of a glass fiber. The structures were solved by Patterson
and Fourier methods. All refinements were carried out using the
program SHELXL-93 or SHELXL-97.38,39 All non-hydrogen atoms
were assigned anisotropic displacement parameters and refined
without positional constraints except as noted below. For 1, 6, and
9, all hydrogen atoms were constrained to idealized geometries and
assigned isotropic displacement parameters 1.2 times the Uiso value
of their attached carbon atoms (1.5 times for methyl hydrogen
atoms). For 4, all hydrogen atoms, except for those in water
molecules, were located in the Fourier maps and refined with a
common displacement parameter. For 1, one CH2Cl2 moiety was
IR (cm-1): C6F5 X-sensitive mode,37 802 s, others, 965 s; PPh2:
777 m, 699 m, 510 m, 469 m; napy: 832 m. 1H NMR room
3
temperature (acetone-d6): δ 9.3 [d, 1H, o-H, J(o-H, m-H) ) 5.0
3
Hz], 9.1 [d, 1H, o-H, J(o-H, m-H) ) 4.7 Hz], 7.7 [m, 1H, m-H,
3
3J(m-H, p-H) ) 8.1 Hz], 7.6 [m, 1H, m-H, J(m-H, p-H) ) 8.2
3
Hz], 8.5 [d, 1H, p-H, J(p-H, o-H) ) 1.6 Hz], 8.4 [d, 1H, p-H,
3J(p-H, o-H) ) 1.6 Hz]. 19F NMR room temperature (acetone-d6):
δ -114.2 [d, 2F, o-F, 3J(195Pt, Fo)) 446 Hz], -114.3 [d, 2F, o-F,
3J(195Pt, Fo) ) 355 Hz], -168.6 (t, 2F, p-F), -166.8 (m, 4F, m-F).
31P-{1H} NMR room temperature (acetone-d6): δ -137, 64 [2J(PA,
PA′) ) 174 Hz, 1J(195Pt, PA) ) 2671 Hz, 1J(195Pt, PA′) ) 1823 Hz].
[Pt(C6F5)2(µ-napy)(µ-Ct CPh)Pt(C6F5)(napy)] (9). To a solu-
tion of [Pt(C6F5)2(napy)] (A) (0.300 g, 0.455 mmol) in CH2Cl2 (30
mL) under nitrogen atmosphere were added 46.5 µL (0.277 mmol)
of HCt CPh. The solution was stirred at room temperature for 2 h
and then evaporated to dryness. To the residue were added 30 mL
(38) Sheldrick, G. M. SHELXL-97, Fortran program for crystal structure
refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(39) Sheldrick G. M., SHELXL-93, program for crystal structure deter-
mination; University of Go¨ttingen: Go¨ttingen, Germany, 1993.
8770 Inorganic Chemistry, Vol. 47, No. 19, 2008

Synthesis of Binuclear Platinum Complexes
Table 2. Selected Bond Distances (Å) and Angles (deg) for
[Pt2(µ-ampy)2(C6F5)4]·2CH2Cl2 (1·2CH2Cl2)
which two “Pt(C6F5)2” moieties are bridged by two ampy
ligands. The more important structural observation is that
the two square planar platinum environments form a dihedral
angle of 79.9(3)°, so that the disposition of the coordination
planes does not cause the C6F5 groups to clash as would
occur if the coordination planes were forced by the bridging
ligand to be approximately parallel (as would presumably
occur for napy). The complex exhibits a HT configuration
and the long Pt · · · Pt distance [4.077(1)Å] precludes any
intermetallic interaction. Within each platinum environment
the Pt-N(amine) distances are slightly longer than those for
Pt-N (pyridine) indicating that the latter are slightly stronger
bonds (see Experimental Section). The angles formed by each
C6F5 ring and its respective platinum coordination planes
are 58.3(3)° (C(1)), 84.9(3)° (C(7)), 86.8(4)° (C(13)), and
85.0(3)° (C(19)).
Pt(1)-C(7)
Pt(1)-N(1)
Pt(2)-C(19)
Pt(2)-N(3)
N(1)-C(29)
N(2)-C(29)
N(3)-C(30)
2.009(8)
2.102(6)
2.014(9)
2.096(7)
1.352(10)
1.434(11)
1.371(11)
Pt(1)-N(4)
Pt(2)-C(13)
Pt(2)-N(2)
Pt(1)-C(1)
N(1)-C(25)
N(3)-C(34)
N(4)-C(34)
2.177(7)
2.017(9)
2.169(8)
2.018(8)
1.367(11)
1.326(11)
1.402(11)
C(7)-Pt(1)-C(1)
C(1)-Pt(1)-N(1)
C(1)-Pt(1)-N(4)
C(19)-Pt(2)-C(13)
C(13)-Pt(2)-N(3)
C(13)-Pt(2)-N(2)
C(29)-N(1)-Pt(1)
C(34)-N(3)-Pt(2)
C(34)-N(4)-Pt(1)
N(3)-C(34)-N(4)
91.5(3)
177.3(3)
88.7(3)
89.3(4)
176.3(3)
89.0(3)
122.2(5)
125.1(6)
113.6(5)
117.3(8)
C(7)-Pt(1)-N(1)
C(7)-Pt(1)-N(4)
N(1)-Pt(1)-N(4)
C(19)-Pt(2)-N(3)
C(19)-Pt(2)-N(2)
N(3)-Pt(2)-N(2)
C(29)-N(2)-Pt(2)
C(30)-N(3)-Pt(2)
N(1)-C(29)-N(2)
88.2(3)
177.6(3)
91.8(3)
90.3(3)
176.3(3)
91.5(3)
113.4(6)
116.0(6)
116.5(7)
Complex 1 is one of the few examples which contains
neutral ampy ligands acting as bridges.40,41 Noteworthy are
the marked out of plane binding modes of the two metal
ions from the aminopyridine planes. Relevant spectroscopic
data for complex 1 are given in the Experimental Section.
The synthesis of the binuclear anionic complex [NBu4]2-
[Pt2(µ-aza)2(C6F5)4] (3) containing two azaindolate bridging
ligands has been carried out in a two step process. The
reaction of the binuclear [NBu4]2[Pt2(µ-Cl)2(C6F5)4] with
azaindol (Haza) in CH2Cl2 (molar ratio 1:2) gives the
mononuclear [NBu4][Pt(C6F5)2Cl(Haza)] (2), which is fully
found to be disordered over two sets of positions and their
occupancies fixed to 0.5. The anisotropic parameters for the chlorine
and carbon atoms of these disordered molecules were constrained
to be the same. The C-Cl distances in the CH2Cl2 molecules were
restrained to chemically reasonable values. For 6, three very diffuse
molecules of CH2Cl2 were found in the density maps. They were
refined isotropically and with common sets of isotropic displacement
parameters for all the atoms in each molecule. Again, the C-Cl
distances were restrained to sensible values. Full-matrix least-
squares refinement of these models against F2 converged to final
residual indices given in Table 1.
1
characterized by its IR, H, and 19F NMR spectra (see
Results and Discussion
Experimental Section).
Synthesis of [(C6F5)2Pt(µ-N-N)2Pt(C6F5)2]n- (N-N )
2-aminopyridine, n ) 0; 7-azaindolate, n ) 2). Reaction
of cis-[Pt(C6F5)2(thf)2] with 2-aminopyridine (ampy) in
CH2Cl2 (molar ratio 1:1) allows the isolation of complex
[Pt2(µ-ampy)2(C6F5)4] (1) in high yield. Its binuclear nature
is suggested by the FAB+ mass spectrum (m/z: 1247).
The molecular structure of complex 1 has been established
by an X-ray diffraction study. Important crystallographic data
and data collection parameters are summarized in Table 1.
Selected bond distances and angles are given in Table 2.
The molecular structure along with the atom labeling
scheme is given in Figure 1. 1 is a binuclear compound in
Deprotonation of the 7-azaindole in [NBu4][Pt(C6F5)2-
Cl(Haza)] (2) (in CH2Cl2) with NBu4OH in MeOH solution
results in the deprotonation of the coordinated 7-azaindole,
the displacement of the chloro ligand, and the formation of
the binuclear complex [NBu4]2[Pt2(µ-aza)2(C6F5)4] (3). Its IR
spectrum shows, as expected, no signal corresponding to
ν(N-H) and two strong absorptions, at 807 and 796 cm-1,
indicating cis- disposition of the pentafluorophenyl groups.
However, these data are compatible with complex 3 being
either mono- or binuclear (i.e., HH or HT configuration).
NMR data for complex 3 are given in Experimental Section.
The final confirmation of the binuclear nature of 3 was
obtained by an X-ray diffraction study. Unfortunately we
have not been able to obtain crystals of sufficient quality as
to carry out a complete X-ray structure analysis. Neverthe-
less, from the data available, the molecular skeleton can be
established and shows that the anion of 3 is binuclear with
the aza- ligands bridging the two metal atoms in an HT
disposition. Figure 2 shows a schematic representation of
the skeleton of the anion. As can be seen the orientation of
the platinum coordination planes does not result in steric
clashing of the C6F5 ligands, thus allowing formation of this
binuclear complex.
Considering that the reaction between cis-[Pt(C6F5)2(thf)2]
and napy does not produce the binuclear complex but the
(40) Charland, J. P.; Beauchamp, A. L. J. Crystallogr. Spectrosc. Res. 1985,
15, 581.
Figure 1. Molecular structure of the complex [Pt2(µ-ampy)2(C6F5)4] (1)
(50% probability ellipsoid level).
(41) Darensbourg, D. J.; Frost, B. J.; Larkins, D. L. Inorg. Chem. 2001,
40, 1993.
Inorganic Chemistry, Vol. 47, No. 19, 2008 8771

Casas et al.
Figure 3. Molecular structure of the complex cis-[Pt(C6F5)2Cl(napyH)]
(4) (50% probability ellipsoid level).
Figure 2. Schematic representation of the anion [Pt2(µ-aza)2(C6F5)4]2- (3).
Table 3. Selected Bond Distances (Å) and Angles (deg) for
cis-[Pt(C6F5)2Cl(napyH)]·H2O (4·H2O)
Pt-C(7)
Pt-C(1)
1.996(6)
1.994(6)
Pt-Cl
2.378(2)
2.099(5)
mononuclear A, due, in all likelihood, to the bulkiness of
the C6F5 groups, we have attempted to prepare binuclear
platinum complexes containing the 1,8 napy ligand as a
bridge by using other smaller ligands bonded to platinum.
One of the simplest complexes with small ancillary ligands
would result from the reaction between PtCl2 and 1,8 napy,
which in appropriate molar ratios could produce the binuclear
derivative. Unfortunately, the reaction between PtCl2 and 1,8
napy is very slow. Refluxing the mixture in 1,2 dichloroet-
hane for 12 h gives a yellow solid which is rather insoluble
in all common solvents. The C, H, and N analyses agree
with the values expected for [PtCl2(napy)]x. However, its very
low solubility does not allow study of its NMR spectrum
nor production of crystals for an X-ray crystal study. Its
binuclear character is suggested by the FAB+ mass spectrum
that show peaks corresponding to the [Pt2Cl3(napy)2]+
fragment (m/z ) 757).
Pt-N(1)
C(1)-Pt-C(7)
C(1)-Pt-Cl
88.7(2)
92.0(2)
C(7)-Pt-N(1)
N(1)-C(20)-N(2)
90.3(2)
117.7(5)
acidic character and exchange processes involving the H2O
present. The 19F NMR spectrum shows signals due to two
inequivalent C6F5 groups (see Experimental Section).
An X-ray diffraction study of complex 4 has also been
carried out (Figure 3, Table 3). The Pt-C, Pt-N, and Pt-Cl
distances are in the range found for other platinum(II)
complexes.33,42-44 The position of all the hydrogen atoms
of the complex were determined from the electron density
maps and freely refined. It was also found that the hydrogen
atom bonded to the nitrogen establishes a hydrogen bond
with a water molecule, which explains the formation of a
persistent hydrate complex, observed in the IR and 1H NMR.
Formation of 4 demonstrates the high reactivity of the
strained four-membered chelate ring in A. The bromo
derivative 5 can be formed by a similar reaction (see
Experimental Section).
Complex 4 is moderately stable at room temperature both
in solid state and in solution. However, when a suspension
of 4 in CH2Cl2 is refluxed for 90 min, a yellow solid
[PtCl(C6F5)(µ-napy)2PtCl(C6F5)] (6) is obtained (see Scheme
1). All the available structural data are in agreement with
this formulation. The FAB+ mass spectrum shows a peak
corresponding to [Pt2Cl2(C6F5)2(napy)2]+. The IR spectrum
shows only one absorption at 804 cm-1 due to the X-sensitive
mode of the C6F5 groups (suggesting only one C6F5 group
per Pt atom), and the ν(Pt-Cl) appears at 340 cm-1. The
1H NMR spectrum shows six signals assigned to the 1,8-
naphthyridine protons indicating the inequivalence of the
pyridine rings. One of the ortho-protons shows platinum
satellites [9.6 ppm, d, 3JPt-H) 52.9 Hz] while the other, which
Usually substitution of one C6F5 group bonded to a
platinum center can be readily achieved by reacting the
pentafluorophenyl platinum complex with HX (X ) Cl, Br)
solutions, in a process which produces breaking of the
Pt-C6F5 bond, and formation of HC6F5 and a Pt-X bond.2
However, the reaction between A in CH2Cl2 and HCl in
MeOH/H2O (1:1 molar ratio) rather leads to protonation of
the napy ligand and formation of cis-[Pt(C6F5)2Cl(napyH)]·
H2O as a yellow solid. Spectroscopic data are in agreement
with this formula. An IR absorption around 3630 cm-1 is
due to the ν(N-H) vibration and the ν(Pt-Cl) is observed
at 341 cm-1, and two absorptions due to the X-sensitive mode
of the C6F5 groups (see Experimental Section) are observed
at 815 (s) and 803(s) cm-1. A broad absorption at around
3460 cm-1 is due to the presence of H2O which can not be
eliminated.
(42) Ara, I.; Casas, J. M.; Fornie´s, J.; Rueda, A. J. Inorg. Chem. 1996, 35,
1
The H and 19F NMR spectra in acetone-d6 are also in
7345.
agreement with the proposed formula (see Experimental
Section). The signal due to the hydrogen atom bonded to
the nitrogen atom cannot be detected, probably because its
(43) Casas, J. M.; Fornie´s, J.; Mart´ın, A. J. Chem. Soc., Dalton Trans.
1997, 1559–1563.
(44) Casas, J. M.; Fornie´s, J.; Mart´ın, A.; Rueda, A. J. Organometallics
2002, 21, 4560–4563.
8772 Inorganic Chemistry, Vol. 47, No. 19, 2008

Synthesis of Binuclear Platinum Complexes
Scheme 1
Scheme 2
Table 4. Selected Bond Distances (Å) and Angles (deg) for
[Pt2(C6F5)2Cl2(napy)2]·0.375CH2Cl2 (6·0.375CH2Cl2)
Pt(1)-Pt(2)
Pt(1)-C(1)
Pt(1)-Cl(1)
Pt(1)-N(1)
Pt(1)-N(3)
Pt(3)-Pt(4)
Pt(3)-C(29)
Pt(3)-Cl(3)
Pt(3)-N(5)
Pt(3)-N(7)
2.997(2)
2.02(3)
2.262(8)
2.12(2)
2.03(2)
3.050(2)
1.98(3)
2.298(9)
2.08(3)
2.09(2)
Pt(2)-C(7)
Pt(2)-N(2)
Pt(2)-N(4)
Pt(2)-Cl(2)
1.97(3)
2.02(2)
2.13(2)
2.302(7)
Pt(4)-C(35)
Pt(4)-N(6)
Pt(4)-N(8)
Pt(4)-Cl(4)
1.99(3)
2.11(2)
2.04(3)
2.282(8)
appears at higher frequencies, does not clearly show platinum
satellites. The 19F NMR spectrum at low temperature shows
signals due to one type of C6F5 groups with hindered rotation
around the Pt-C bond (see Experimental Section).
C(1)-Pt(1)-Pt(2)
N(3)-Pt(1)-N(1)
C(1)-Pt(1)-Cl(1)
N(1)-Pt(1)-Cl(1)
N(1)-Pt(1)-Pt(2)
N(3)-Pt(1)-Pt(2)
Cl(1)-Pt(1)-Pt(2)
C(29)-Pt(3)-Pt(2)
N(5)-Pt(3)-N(7)
C(29)-Pt(3)-Cl(3)
N(7)-Pt(3)-Cl(3)
N(5)-Pt(3)-Pt(4)
N(7)-Pt(3)-Pt(4)
Cl(3)-Pt(3)-Pt(4)
119(1)
89.4(9)
88(1)
92.0(7)
74.2(6)
81.3(5)
100.4(2)
99.8(9)
89(1)
N(2)-Pt(2)-N(4)
N(4)-Pt(2)-Cl(2)
C(7)-Pt(2)-Cl(2)
C(7)-Pt(2)-Pt(1)
N(2)-Pt(2)-Pt(1)
N(4)-Pt(2)-Pt(1)
Cl(2)-Pt(2)-Pt(1)
N(6)-Pt(4)-N(8)
N(6)-Pt(4)-Cl(4)
C(35)-Pt(4)-Cl(4)
C(35)-Pt(4)-Pt(3)
N(6)-Pt(4)-Pt(3)
N(8)-Pt(4)-Pt(3)
Cl(4)-Pt(4)-Pt(3)
89.5(9)
92.0(6)
88.7(8)
118.8(9)
83.3(7)
74.0(7)
97.6(2)
94(1)
90.0(9)
87.7(8)
118(1)
74.4(8)
77.5(9)
109.2(3)
All these structural data are consistent with the proposed
formula for 6 [Pt2(C6F5)2Cl2(napy)2] with a symmetrical
structure. Two possible structures might account for the
spectroscopic data (see Scheme 2a,b). The X-ray structure
of 6 (see Figure 4) shows that the complex is binuclear with
bridging napy ligand and face to face platinum coordination
planes. Two essentially identical molecules are found in the
asymmetric unit, and we will focus on one, since structural
parameters are very similar for both (Table 4). The Pt-C,
Pt-N, and Pt-Cl distances are in the range found in other
Pt complexes containing ligands of this type,33,42-44 and the
angles around the platinum atoms for mutually cis ligands are
between 87.7(8)° and 94(1)°. The pentafluorophenyl groups and
hence the chloro ligands are arranged in such a way that they
93(1)
91.4(8)
77.0(9)
79.7(9)
112.7(2)
avoid steric clashes between the C6F5 ligands. This arrangement
also produces a closer packing of the ligands that viciates the
movement of the C6F5 rings which would make the Fo of each
group equivalent and the Fm as well.
Each platinum center is bonded to two N-atoms, one from
each napy ligand, but the Pt-N distances are slightly
different [Pt(1)-N(3) ) 2.03(2) Å; Pt(1)-N(1) ) 2.12(2)
Å; Pt(2)-N(2) ) 2.02(2) Å; Pt(2)-N(4) ) 2.13(2) Å] in
agreement with the higher trans-influence of the C6F5 ligand.
Each napy ligand is essentially planar and is oriented almost
perpendicular to one of the platinum coordination planes
(dihedral angles: plane Pt(1)-plane napy N(3,4) ) 87.7(4)°;
plane Pt(2)-plane napy N(1,2) ) 85.6(4)°] but rotated with
respect to the other platinum plane [dihedral angles: plane
Pt(1)-plane napy N(1,2) ) 62.7(5)°; plane Pt(2)-plane napy
N(3,4) ) 64,1(4)°]. It is notable that the two Pt-N bonds
of each ligand are not in the plane of their respective napy
plane; these “mis-directed” Pt-N bonds allow reduction of
interligand steric interactions. The platinum coordination
planes are not completely parallel (dihedral angle ) 35.9(5)°)
while the Pt(1)-Pt(2) distance is 2.997(2) Å. This is a short
intermetallic distance for a compound that does not require
the presence of a Pt-Pt bond. Notably the Pt · · ·Pt distance
Figure 4. Molecular structure of the complex [Pt2(C6F5)2Cl2(napy)2] (6)
(50% probability ellipsoid level).
Inorganic Chemistry, Vol. 47, No. 19, 2008 8773

Casas et al.
in complex 1 is 4.077(1) Å, and long distances have also
been observed in other complexes of this general type.
Although the shortest Pt · · · Pt distance found in a binuclear
Pt(II) complex bridged by two identical bidentate ligands in
a face to face disposition is 2.789(1) Å (in [Pt2(C4-
H6NO)2(bipy)2](ClO4)2), 10 more typical Pt · · ·Pt separations
are around 3.0 Å for ligands with N-, or O- donor atoms45-47
or even longer (3.2-4.0 Å) for ligands with P donor
atoms.5,12,48 This short Pt · · · Pt distance is presumably
enforced by the proximity of the nitrogen atoms in the
skeleton of the napy ligand which requires proximity of the
platinum centers to which they are bonded. The formation
of “mis-directed” Pt-N bonds allows a longer Pt · · · Pt
distance, but even in this situation the metal centers are very
close. In all likelihood, the whole structure is a compromise
between the formation of a binuclear complex, which is
presumably thermodynamically favored, and the necessity
of avoiding the steric repulsions between the metal atoms
and the C6F5 groups.
With the aim of investigating further the reactivity of
complex A toward other reagents ZH to produce elimination
of C6F5H and incorporation of the nucleophile Z- to the
platinum coordination environment, we have studied the
reaction between cis-[Pt(C6F5)2(napy)] (A) and PPh2H at
room temperature in a 1:1 molar ratio. This results in the
formation of cis-[Pt(C6F5)2(HPPh2)(napy)] (7) (Scheme 1),
a complex which contains PPh2H and monodentate napy as
ligands. The structure of 7 can be inferred from the
spectroscopic data.
The FAB+ mass spectrum shows a peak corresponding
to the cation cis-[Pt(C6F5)2(HPPh2)(napy)]+ (m/z ) 845). The
IR spectrum of this complex shows an absorption at 2377
cm-1 corresponding to the ν(H-P) vibration of HPPh2 and
other absorptions due to the same ligand at 520, 475, and
427 cm -1. The 1H NMR data are given in the Experimental
Section. At 6.3 ppm there is a doublet due to the hydrogen
atom bonded to the phosphorus [1J(31P,H) ) 378 Hz], which
also shows platinum satellites [2J(195Pt,H) ) 35 Hz]. The
19F NMR spectrum shows signals corresponding to two
chemically inequivalent C6F5 groups. The 31P NMR spectrum
shows a signal at -8.4 ppm with platinum satellites
[1J(195Pt,31P) ) 2469 Hz].
Figure 5. Molecular structure of the complex [Pt2(C6F5)3(Ct CPh)(napy)2]
(9) (50% probability ellipsoid level).
of a central singlet at -137.7 ppm with no 195Pt centers (spin
system A2), eight signals (as two doublets of doublets) due
to the AA′ part of the AA′X spin system from the isotopomer
2
1
with one 195Pt center. The parameters J(PA, PA′), J(195Pt,
PA), and 1J(195Pt, PA′) can be extracted from this subspectrum.
Finally, the isotopomer with two 195Pt centers, for which only
1
two signals appear, are separated by N ) J(195Pt, PA′) +
1J(195Pt, PA).49-51 The chemical shift of the P atoms appear
at high field as it should be expected for a 32 valence electron
skeleton, that is, the two PPh2 are supporting two Pt atoms
not joined by a Pt-Pt bond. In agreement with this, the value
of the coupling between the two P atoms (174 Hz) is in the
range usually found for the phosphido groups in a “Pt(µ-
PPh2)2Pt” fragment.52-54 The assignment of the two values
(see Experimental Section) can be carried out unambiguously
by comparison with other analogous complexes.55
Complexes A, 6, and 8 are noteworthy examples of the
structural differences induced by the type of ligands in
complexes of similar stoichiometry [Pt(C6F5)Z(napy)]x (Z )
C6F5, x ) 1, A; Z ) Cl, x ) 2, 6; Z ) PPh2, x ) 2, 8).
Finally, cis-[Pt(C6F5)2(napy)] (A) reacts with HCCPh either
in 1:1 or 2:1 molar ratio to produce, under mild conditions,
[Pt2(C6F5)3(Ct CPh)(napy)2] (9). The structure of 9 has been
established by single crystal X-ray diffraction (see Figure
5). Relevant crystallographic details are summarized in Table
1 while selected bond distances and angles are listed in Table
5. Complex 9 is binuclear and each platinum center displays
square planar coordination environments, with one napy and
an acetylide acting as bridging ligands. One of the platinum
centers is coordinated to two C6F5 groups in cis positions,
one N atom of the bridging napy ligand, and η2 to the Ct C
Deprotonation of the PPh2H does not take place at room
temperature, but when a toluene solution of 7 is refluxed,
deprotonation of the phosphine and concomitant elimination
of C6F5H takes place, thus resulting in the formation of
[Pt2(C6F5)2(PPh2)2(napy)2] (8) (Scheme 1).
All the spectroscopic data (see Experimental Section) are
in agreement with the proposed structure (Scheme 1) for 8
with bridging PPh2 and terminal monodentate napy ligands.
The 31P {1H} NMR spectrum is the result of the super-
imposition of the spectra of the three isotopomers. It consists
(49) Garrou, P. E. Chem. ReV. 1985, 85, 171.
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45, 4850.
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Organometallics 2002, 21, 2226.
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Organometallics 2003, 22, 2723.
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2416.
(47) Oskui, B.; Mintert, M.; Sheldrick, W. S. Inorg. Chim. Acta 1999, 287,
72–81.
(48) Wing-Wah Yam, V.; Yu, K.-L.; Man-Chung Wong, K.; Cheung, K.-
K. Organometallics 2001, 20, 721.
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8774 Inorganic Chemistry, Vol. 47, No. 19, 2008

Synthesis of Binuclear Platinum Complexes
Table 5. Selected Bond Distances (Å) and Angles (deg) for
[Pt2(C6F5)3(Ct CPh)(napy)2]·2.5Me2CO (9·2.5Me2CO)
of the phenyl ring. The napy resonances are difficult to assign
because of the inequivalence of the two napy ligands. Six
well defined signals corresponding to a bridging napy are
observed besides other six poorly resolved signals whose
chemical shift suggests that this ligand is terminal. The 19F
NMR spectrum indicates the existence of three chemically
inequivalent C6F5 groups.
Pt(1)-C(1)
Pt(1)-C(35)
Pt(1)-N(1)
Pt(1)-N(3)
Pt(1)-Pt(2)
C(35)-C(36)
2.005(6)
1.939(5)
2.146(5)
2.085(4)
3.065(5)
1.225(8)
Pt(2)-C(13)
Pt(2)-C(7)
Pt(2)-N(2)
Pt(2)-C(35)
Pt(2)-C(36)
2.010(6)
2.012(6)
2.115(5)
2.230(5)
2.305(5)
C(35)-Pt(1)-C(1)
C(35)-Pt(1)-N(1)
C(1)-Pt(1)-N(3)
N(3)-Pt(1)-N(1)
C(35)-Pt(1)-Pt(2)
N(1)-Pt(1)-Pt(2)
N(3)-Pt(1)-Pt(2)
C(1)-Pt(1)-Pt(2)
C(13)-Pt(2)-Pt(1)
C(7)-Pt(2)-Pt(1)
C(35)-C(36)-C(37)
88.1(2)
91.2(2)
89.8(2)
91.8(2)
45.8(2)
77.3(1)
128.5(1)
107.2(2)
95.3(2)
126.6(2)
164.2(6)
C(13)-Pt(2)-C(7)
C(7)-Pt(2)-N(2)
C(13)-Pt(2)-C(35)
N(2)-Pt(2)-C(35)
C(13)-Pt(2)-C(36)
N(2)-Pt(2)-C(36)
C(35)-Pt(2)-C(36)
C(35)-Pt(2)-Pt(1)
C(36)-Pt(2)-Pt(1)
N(2)-Pt(2)-Pt(1)
88.6(2)
90.7(2)
95.3(2)
84.4(2)
93.4(2)
88.4(2)
31.3(2)
38.6(1)
69.8(1)
81.9(1)
Conclusions
Attempts to synthesize binuclear complexes with two
bridging “cis-Pt(C6F5)2” fragments have succeeded with the
2-ampy and the 7-aza bidentate ligands. The first one
apparently works because of the high flexibility between the
two N-donor atoms of the ligands and the second because,
although the donor atoms are in rigid positions, they have a
large bite angle. The distances between the platinum centers
in the binuclear complexes are 4.1 and 3.4 Å for 2-ampy
and 7-aza, respectively, in agreement with the structural
characteristics of these ligands.
The rigid napy ligand, with a more restricted bite angle,
gives a mononuclear complex with the “Pt(C6F5)2” fragment
having the bidentate ligand in a strained chelating form. Our
hypothesis that the steric requirement of the C6F5 groups is
the cause of the formation of a mononuclear complex with
the napy ligand instead of the binuclear alternatives was
confirmed because the substitution of one pentafluorophenyl
group for a chloro ligand in each platinum ion and the
decrease in spatial requirements led to formation of a
binuclear complex with a short Pt · · · Pt distance of 2.98 Å
and a bridging 1,8-naphthyridine ligand.
The substitution of one C6F5 anion by the more bulky PPh2
group (also potentially a bridging ligand) in complex A
affords a binuclear complex of type 1a (see Chart 1) with
monodentate napy ligands.
Use of the less bulky bridging ligand -Ct CPh produces
substitution of one pentafluorophenyl group, independent of
the Pt/napy ratio (1:1 or 2:1), affording an asymmetrical
binuclear complex with two different bridging ligands: the
acetylide in a σ-π coordination and one of the two napy
ligands.
of the acetylide ligand, while the other is bonded to one C6F5
group, the acetylide ligand (σ-bound) and one of the N atoms
of the bridging napy and to the N atom of the other,
monodentate, napy ligand. The dihedral angle between the
metal coordination planes is 81.4(3)°; the Pt(1) · · · Pt(2)
distance is 3.065(1) Å, which seems to indicate that there is
no intermetallic bond. Both napy ligands are planar. The
Pt-N distances for the bridging napy are almost equal within
experimental error (Table 5). The Pt(2)-N(2) vector lies
almost in the napy plane but the Pt(1)-N(1) deviates
significantly from this plane by 13.4(2)°. The Pt(1)-
N(1)-N(2)-Pt(2) torsion angle is 13.3(3)°. This is the result
of mis-directed bonding between the napy ligands and the
Pt centers imposed by the coordination of the rest of the
ligand and the steric strain. The Ct C distance 1.228(8) Å
is in agreement with the η2-interaction56,57 as is the
C(35)-C(36)-C(37) angle [164.2(6)°]. Finally, the η2-
Pt(2)-Ct CPh interaction is slightly asymmetric [Pt(2)-C(35)
) 2.230(5) Å and Pt(2)-C(36) ) 2.305(5) Å].
The overall process involves substitution of a C6F5 group
on one platinum by the action of the HCt CPh while the
other remains; bridging by the acetylide group of one of the
substrates and the napy of the other leads to formation of
the binuclear entity. Finally, the tendency of the Pt(II)
substrates to four coordination leads to cleavage of one Pt-N
bond of the napy ligand (which as we have seen before is
strained when acting as a chelating ligand) and results in a
monodentate napy ligand.
Acknowledgment. This work has been supported by the
Spanish Ministerio de Educacio´n y Ciencia (Spain) y Fondos
FEDER (Projects CTQ2005-08606-C02-01) and the Gobi-
erno de Arago´n (Grupo de Excelencia: Qu´ımica Inorga´nica
y de los Compuestos Organometa´licos).
The spectroscopic data of 9 are in agreement with this
stoichiometry. Thus, the infrared spectrum shows an absorp-
tion at 839 cm-1 corresponding to the napy ligand. The
acetylide ligand gives two absorptions at 1990 cm-1 [ν(Ct C)]
Supporting Information Available: Further details of the
structure determinations of 1·2CH2Cl2, 4·H2O, 6·0.375CH2Cl2, and
9·2.5Me2CO including atomic coordinates, bond distances and
angles, and thermal parameters. This material is available free of
charge via the Internet at http://pubs.acs.org.
and 751 cm-1. The H NMR spectrum shows two signals
1
[7.8 ppm (3H) and 7.3 ppm (2H)] for the hydrogen atoms
(56) Fornie´s, J.; Go´mez-Saso, M. A.; Lalinde, E.; Mart´ınez, F.; Moreno,
M. T. Organometallics 1992, 11, 2873.
(57) Carpenter, P.; Lukehart, C. M. Inorg. Chim. Acta 1991, 190, 7.
IC8006475
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