Synthesis, characterization, and optical properties of pentafluorophenyl complexes with a Pt-Cd bond

Article abstract of DOI:10.1021/om049719w

Novel bimetallic neutral [(C₆F₅) ₄PtCd(cyclen)] and [(C₆F₅) ₂(C≡CPh)₂PtCd(cyclen)] (1, 2) and cationic [(C ₆F₅)₂(bzq)PtCd(cyclen)](ClO₄) (3) pentafluorophenylplatinum(II)-cadmium-(II) derivatives have been prepared by treatment of the adequate anionic starting precursors [Pt(C₆F ₅)₂X₂]^n- (n = 2, X = C ₆F₅, C≡CPh; n = 1, X₂ = bzq) with Cd(ClO₄)₂ and cyclen. X-ray diffraction studies on complexes 1, 2, and 3 show that they are stabilized by a short Pt→Cd donor acceptor bond and, additionally, in complex 2 the Cd center is also coordinated to the C_α of one of the two alkynyl groups. In contrast, treatment of the binuclear compound [NBu₄]₂-[Pt ₂(μ-Cl)₂(C₆F₅)₄] with [Cd(cyclen)(MeOH)₂](ClO₄)₂ afforded the tetranuclear derivative [Pt(C₆F₅)₂Cl(μ-Cl) Cd(cyclen)]₂ (4) (X-ray), in which Pt and Cd atoms are connected by a μ₃-Cl bridging ligand, and the binuclear cadmium complex [Cd ₂(μ-Cl)₂(cyclen)₂](ClO₄) ₂ (5) (X-ray), in which two "Cd(cyclen)" fragments are bridged by two chlorine atoms. The photoluminescent properties of complexes 1-3 have also been examined and compared with those of their corresponding anionic parent compounds [NBu₄]₂[Pt(C₆F ₅)₄], [PMePh₃]₂[Pt(C ₆F₅)₂(C≡CPh)₂], and [NBu ₄][Pt(C₆F₅)₂(bzq)] (6).

Full text of DOI:10.1021/om049719w

Organometallics 2004, 23, 3963-3975
3963
Syn th esis, Ch a r a cter iza tion , a n d Op tica l P r op er ties of
P en ta flu or op h en yl Com p lexes w ith a P t-Cd Bon d
J uan Fornie´s,* Susana Iba´n˜ez, and Antonio Mart´ın
Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,
Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain
Bele´n Gil, Elena Lalinde,* and M. Teresa Moreno
Departamento de Qu´ımica, Grupo de Sı´ntesis Quı´mica de La Rioja, UA, CSIC,
Universidad de La Rioja, 26006, Logron˜o, Spain
Received April 19, 2004
Novel bimetallic neutral [(C6F5)4PtCd(cyclen)] and [(C6F5)2(CtCPh)2PtCd(cyclen)] (1, 2)
and cationic [(C6F5)2(bzq)PtCd(cyclen)](ClO4) (3) pentafluorophenylplatinum(II)-cadmium-
(II) derivatives have been prepared by treatment of the adequate anionic starting precursors
[Pt(C6F5)2X2]n- (n ) 2, X ) C6F5, CtCPh; n ) 1, X2 ) bzq) with Cd(ClO4)2 and cyclen. X-ray
diffraction studies on complexes 1, 2, and 3 show that they are stabilized by a short PtfCd
donor acceptor bond and, additionally, in complex 2 the Cd center is also coordinated to the
CR of one of the two alkynyl groups. In contrast, treatment of the binuclear compound [NBu4]2-
[Pt2(µ-Cl)2(C6F5)4] with [Cd(cyclen)(MeOH)2](ClO4)2 afforded the tetranuclear derivative [Pt-
(C6F5)2Cl(µ-Cl)Cd(cyclen)]2 (4) (X-ray), in which Pt and Cd atoms are connected by a µ3-Cl
bridging ligand, and the binuclear cadmium complex [Cd2(µ-Cl)2(cyclen)2](ClO4)2 (5) (X-ray),
in which two “Cd(cyclen)” fragments are bridged by two chlorine atoms. The photoluminescent
properties of complexes 1-3 have also been examined and compared with those of their
corresponding anionic parent compounds [NBu4]2[Pt(C6F5)4], [PMePh3]2[Pt(C6F5)2(CtCPh)2],
and [NBu4][Pt(C6F5)2(bzq)] (6).
Ch a r t 1
In tr od u ction
Although several heteropolymetallic systems involv-
ing Pt(II) and Cd(II) have been reported,1 in most of
them the metal centers are connected by bridging
ligands and, as far as we know, Pt(II)-Cd(II) interac-
tions have been structurally characterized only in a few
cases. Our recent interest in heteropolynuclear alkynyl
complexes2 based on Pt‚‚‚M and M‚‚‚acetylenic interac-
tions led us to the isolation of two of them: [NBu4]2-
[{Pt(µ-κCRCR-CtCPh)4}2(CdCl)2]3 and [{Pt4Cd6(CtCPh)4-
(µ-CtCPh)12(µ3-OH)4],4 which have been prepared by
the reaction of [NBu4]2[Pt(CtCPh)4] with CdCl2 or Cd-
(ClO4)2‚6H2O, respectively. Both complexes are lumi-
nescent and display weak Pt-Cd bonding interactions
(2.960(1) and 2.857(1) Å) and Cd-acetylide bonds, the
latter probably being the driving force for the formation
of these complexes. The other complexes {[(phpy)2PtCd-
(cyclen)](ClO4)2 and [(bpy)Me2PtCd(cyclen)](ClO4)2 (Hph-
py ) 2-phenylpyridine, bpy ) 2,2′-bipyridine, cyclen )
1,4,7,10-tetraazacyclododecane, see Chart 1)} have been
prepared by Ito et al.5 by reacting the corresponding
platinum precursors with [Cd(cyclen)(MeOH)2](ClO4)2,
the PtfCd bonds being very short (2.639(1) and
2.610(1) Å, respectively) and totally unsupported by any
kind of bridging interaction between the two metal
centers.
(1) (a) Pettinari, C.; Marchetti, F.; Cingolani, A.; Troyanov, S. I.;
Drozdov, A. J . Chem. Soc., Dalton Trans. 1998, 3335. (b) Li, Z.; Zheng,
W.; Liu, H.; Mok, K. F.; Hor, T. S. A. Inorg. Chem. 2003, 42, 8481. (c)
Capdevila, M.; Carrasco, Y.; Clegg, W.; Coxall, R. A.; Gonza´lez-Duarte,
P.; Lledo´s, A.; Ram´ırez, J . A. J . Chem. Soc., Dalton Trans. 1999, 3103.
(d) Li, Z.; Loh, Z.-H.; Audi Fong, S.-W.; Yan, Y.-K.; Henderson, W.;
Mok, K. F.; Andy Hor, T. S. J . Chem. Soc., Dalton Trans. 2000, 1027.
(2) (a) Chartmant, J . P. H.; Fornie´s, J .; Go´mez, J .; Lalinde, E.;
Merino, R. I.; Moreno, M. T.; Orpen, A. G. Organometallics 2003, 22,
652. (b) Ara, I.; Berenguer, J . R.; Eguiza´bal, E.; Fornie´s, J .; Go´mez,
J .; Lalinde, E. J . Organomet. Chem. 2003, 670, 221. (c) Berenguer, J .
R.; Fornie´s, J .; Go´mez, J .; Lalinde, E.; Moreno, M. T. Organometallics
2001, 20, 4847. (d) Ara, I.; Fornie´s, J .; Go´mez, J .; Lalinde, E.; Moreno,
M. T. Organometallics 2000, 19, 3137. (e) Chartmant, J . P. H.; Fornie´s,
J .; Go´mez, J .; Lalinde, E. Merino, R. I.; Moreno, M. T. Orpen, G. A.
Organometallics 1999, 18, 3353. (f) Ara, I.; Berenguer, J . R.; Fornie´s,
J .; Go´mez, J .; Lalinde, E.; Merino, R. I. Inorg. Chem. 1997, 36, 6461.
(3) Charmant, J . P. H.; Falvello, L. R.; Fornie´s, J .; Go´mez, J .;
Lalinde, E.; Moreno, M. T.; Orpen, A. G.; Rueda, A. Chem. Commun.
1999, 2045.
In the course of our current research on penta-
halophenyl platinate complexes with PtfM (M )
(4) Fornie´s, J .; Go´mez, J .; Lalinde, E.; Moreno, M. T. Inorg. Chem.
2001, 40, 5415.
(5) Yamaguchi, T.; Yamazaki, F.; Ito, T. J . Am. Chem. Soc. 1999,
121, 7405
10.1021/om049719w CCC: $27.50 © 2004 American Chemical Society
Publication on Web 07/08/2004

3964 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
Ag(I), Tl(II), Pb(II), Sn(II)) donor-acceptor bonds6 we
have prepared complexes with structures similar to the
ones displayed by Ito’s complexes, although in our case,
the pentafluorophenyl groups are specially oriented so
as to form o-F‚‚‚M secondary interactions, which had
been considered as an additional factor for stabilizing
the PtfM donor-acceptor bonds.6
We thought it would be interesting to explore the
reactions of the pentahalophenyl platinate(II) anionic
complexes with a simple cadmium salt (Cd(ClO4)2) and
with “Cd(cyclen)2+” in order to see how important the
negative charge of the anionic complex and the presence
of the C6X5 ligand is in the formation of the complexes.
We are now reporting the results of these reactions,
which allow the preparation of novel bimetallic neutral
[(C6F5)4PtCd(cyclen)] and [(C6F5)2(CtCPh)2PtCd(cyclen)]
(1, 2) and cationic [(C6F5)2(bzq)PtCd(cyclen)](ClO4) (3)
(bzq ) 7, 8-benzoquinolinate, see Chart 1) systems
containing Pt-Cd bonding interactions and also a
tetranuclear Pt2Cd2 (4) derivative in which Pt and Cd
atoms are connected by a µ3-Cl bridging ligand.
One important property of some mixed-metal systems
containing closed-shell metal‚‚‚metal contacts, including
d8-d8 and d8-d10 metal complexes or aggregates, is that
they are often intensely luminescent, making them
attractive with respect to potential applications.7 In fact,
the nature and the role of metallophilic bonding interac-
tions in the photophysical properties of this type of
system are currently an area of intense research.2,8 In
an effort to provide further insight into the importance
of the d8‚‚‚M bonding interactions in the nature of the
excited-state origin of these complexes, the optical
properties of complexes 1-3 have also been examined.
F igu r e 1. Structure of the complex [(C6F5)4PtCd(cyclen)]
(1).
sized and characterized in our group,9 and which
contains bridging pentafluorophenyl groups. This seems
to indicate that, at least partially, the naked Cd(II)
center acts as a dearylating agent toward the platinum
in [Pt(C6F5)4]2-
.
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
Neu t r a l [(C6F 5)4P t Cd (cyclen )] (1) a n d [(C6F 5)2-
(CtCP h )2P tCd (cyclen )] (2). The reactions of several
Pt complexes toward “Cd(cyclen)2+”, which has proved
to be so useful for preparing complexes containing
unsupported PtfCd bonds,5 result in the formation of
Pt-Cd derivatives. Thus, when [NBu4]2[Pt(C6F5)4] is
added to a solution of [Cd(cyclen)(MeOH)2](ClO4)2 in
MeOH prepared “in situ” (see Experimental Section and
Scheme 1i), in 1:1 molar ratio, the precipitation of a
white solid is observed upon stirring at room temper-
ature for a few minutes. This white solid is separated
by filtration and identified as [(C6F5)4PtCd(cyclen)] (1).
A single-crystal X-ray diffraction study of 1 has been
carried out, and its structure is shown in Figure 1.
Crystallographic data are given in Table 1, and selected
interatomic distances and angles appear in Table 2. 1
Resu lts a n d Discu ssion
Rea ction of [NBu 4]2[P t(C6F 5)4] w ith Cd (ClO4)2.
The reaction of the perhaloaryl anionic complex [NBu4]2-
[Pt(C6F5)4] toward the simple cadmium salt Cd(ClO4)2
in dichloromethane and in 1:1 or 1:2 molar ratio has
been investigated. In all cases unreacted platinum
starting material is recovered, along with a solid that
is a mixture of compounds which we have not been able
to separate but whose 19F NMR spectrum indicates the
presence of [Pt2(µ-C6F5)2(C6F5)4]2-, previously synthe-
is
a dinuclear complex formed by the moieties
“Pt(C6F5)4” and “Cd(cyclen)” bonded through a Pt-Cd
bond. The environment of the platinum atom is square
planar. The Pt-C distances are the usual ones for this
kind of complex.10 The platinum atom lies in the center
of the square in such a way that it separates slightly
(0.136(1) Å) from the best plane formed by the four Cipso
atoms toward the Cd atom. The geometry of the
“Cd(cyclen)” fragment is similar to that found in other
complexes containing it.5
(6) Fornie´s, J .; Mart´ın, A. In Metal Clusters in Chemistry; Braun-
stein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-VCH: Weinheim, 1999;
Vol. 1, pp 417-443.
(7) For some reviews see: (a) Gliemann, G.; Yersin, H. Struct.
Bonding 1985, 62, 87. (b) Rhoundhill, D. M.; Gray, H. B.; Che. C. M.
Acc. Chem. Res. 1989, 22, 55. (c) Forward, J . M.; Fackler, J . P., J r.;
Assefa, Z. In Optoelectronic Properties of Inorganic Compounds;
Plenum: New York, 1999; p 195. (d) Fung, E. Y.; Olmstead, M. M.;
Vickery, J . C.; Balch, A. L. Coord. Chem. Rev. 1998, 171, 151. (e) Gade,
L. H. Angew. Chem., Int. Ed. Engl. 1997, 36, 1171; 2001, 40, 3573. (f)
Pyykko¨, P. Chem. Rev. 1997, 97, 597.
The platinum and cadmium atoms are linked by a
bond that is unsupported by any covalent bridging
ligand. The Pt-Cd distance is 2.775(1) Å, which is
(9) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R.; Llusar, R. Organometallics 1988, 7, 2279.
(8) For some recent examples see: (a) Coker, N. L.; Bauer, J . A. K.;
Elder, R. C. J . Am. Chem. Soc. 2004, 126, 12. (b) Stender, M.;
Olmstead, M. M.; Balch, A. L.; Rios, D.; Attar, S. Dalton Trans. 2003,
4282. (c) J alilehvand, F.; Eriksson, L.; Glaser, J .; Maliarik, M.; Mink,
J .; Sandstro¨m, M.; To´th, I.; To´th, J . Chem. Eur. J . 2001, 7, 2167. (d)
Cariati, E.; Bu, X.; Ford, P. C. Chem. Mater. 2000, 12, 3385. (e)
Ferna´ndez, E. J .; Lo´pez de Luzuriaga, J . M.; Monge, M.; Olmos, M.
E.; Pe´rez, J .; Laguna, A. J . Am. Chem. Soc. 2002, 124, 5942. (f)
Catalano, V. J .; Bennett, B. L.; Kar, H. M.; Noll, B. C. J . Am. Chem.
Soc. 1999, 121, 10235. (g) Rawashdeh-Omary, M. A.; Omary, M. A.;
Patterson, H. H.; Fackler, J . P., J r. J . Am. Chem. Soc. 2001, 123, 11237.
(h) Lee, Y. A.; McGarrah, J . E.; Lachicotte, R. J .; Eisenberg, R. J . Am.
Chem. Soc. 2002, 124, 10662. (i) Omari, M. A.; Webb, T. R.; Assefa, Z.;
Shankle, G. E.; Patterson, H. H. Inorg. Chem. 1998, 37, 1380. (j) Yam,
W. W. V.; Hui, C. K.; Yu, S. Y.; Zhu, N. Inorg. Chem. 2004, 43, 812.
(10) See for example: (a) 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. (b) Bellamy, D.; Connely, N. G.; Lewis, G. R.; Orpen, A. G. Cryst.
Eng. Commun. 2002, 4, 68. (c) Casas, J . M.; Fornie´s, J .; Mart´ınez, F.;
Rueda, A. J .; Toma´s, M.; Welch, A. J . Inorg. Chem. 1999, 38, 1529. (d)
Uso´n, R.; Fornie´s, J .; Toma´s, M.; Ara, I. J . Chem. Soc., Dalton Trans.
1989, 1011. (e) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Mart´ınez, F.; Casas,
J . M.; Fortun˜o, C. Inorg. Chim. Acta 1995, 235, 51. (f) Uso´n, R.; Fornie´s,
J .; Toma´s, M.; Ara, I.; Casas, J . M.; Mart´ın, A. J . Chem. Soc., Dalton
Trans. 1991, 2253. (g) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B.;
Fortun˜o, C.; Welch, A. J .; Smith, D. E. J . Chem. Soc., Dalton Trans.
1993, 275. (h) Casas, J . M.; Fornie´s, J .; Mart´ın, A. J . Chem. Soc., Dalton
Trans. 1997, 1559. (i) Casas, J . M.; Fornie´s, J .; Mart´ın, A.; Welch, A.
J . Inorg. Chem. 1996, 35, 6009.

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3965
Sch em e 1
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for Com p lexes [(C6F 5)4P tCd (cyclen )]‚2Me2CO (1‚2Me2CO),
[(C6F 5)2P t(CtCP h )2Cd (cyclen )]‚2Me2CO (2‚2Me2CO), [(C6F 5)2(bzq)P tCd (cyclen )](ClO4)‚0.5MeOH (3‚0.5MeOH),
[P t(C6F 5)2Cl2Cd (cyclen )]2‚2Me2CO (4‚2Me2CO), a n d [Cd 2(µ-Cl)2(cyclen )2](ClO4)2 (5)
1‚2Me2CO
2‚2Me2CO
3‚0.5MeOH
4‚2Me2CO
5
formula
C
32H20CdF20N4Pt
C
36H30CdF10N4Pt
C
33H24CdClF10N5O4-
C
40H40Cd2Cl4F20
-
C
16H40Cd2Cl4N8O8
‚2Me2CO
‚2Me2CO
Pt‚0.5MeOH
N8Pt2‚2Me2CO
a [Å]
b [Å]
c [Å]
23.837(2)
9.9630(8)
17.4955(15)
90
16.5340(1)
19.2220(1)
27.5390(2)
90
12.7984(18)
17.239(3)
7.132(3)
9.7955(14)
12.1984(18)
12.6514(18)
79.633(3)
81.820(3)
74.375(3)
1425.0(4), 1
2.197
12.5374(10)
15.2365(13)
15.5517(13)
90
90
90
2970.8(4), 4
1.876
173(1)
R [deg]
â [deg]
γ [deg]
V [Å3], Z
90
96.821(2)
90
4125.5(6), 4
2.035
90
90
90.239(3)
90
3779.8(10), 4
1.939
8752.35(9), 8
1.719
173(1)
F
calc [g cm-3
T [K]
]
173(1)
293(1)
100(1)
cryst syst
space group
monoclinic
C2/c
orthorhombic
Pbca
monoclinic
P21/n
triclinic
P1h
orthorrombic
Pnma
dimensions [mm]
0.40 × 0.35 × 0.20
0.30 × 0.10 × 0.10
0.12 × 0.10 × 0.08
0.05 × 0.05 × 0.02
0.20 × 0.15 × 0.02
µ [mm-1
abs corr
]
4.034
3.761
4.425
5.929
1.844
3219 symmetry
equivalent reflns
1.72-24.87
semiempirical from
equivalents
2.12-27.89
142 986
4477 symmetry
equivalent reflns
1.68-25.10
19 921
3132 symmetry
equivalent reflns
1.64-25.04
7828
1696 symmetry
equivalent reflns
2.09-24.87
6071
θ range [deg]
no. of reflns collected 11 337
no. of indep reflns
3580 (R(int) )
0.0423)
10438 (R(int) )
0.0573)
6721 (R(int) )
0.0870)
4958 (Rint
0.0302)
)
2685 (Rint )
0.0755)
final R indices
[I > 2σ(I)][a]
R1 ) 0.0340,
R1 ) 0.0371,
R1 ) 0.0516,
R1 ) 0.0440,
R1 ) 0.0433,
wR2 ) 0.0888
R1 ) 0.0391,
wR2 ) 0.0982
1.029
wR2 ) 0.0912
R1 ) 0.0522,
wR2 ) 0.0982
1.075
wR2 ) 0.1027
R1 ) 0.1384,
wR2 ) 0.1163
1.037
wR2 ) 0.1114
R1 ) 0.0532,
wR2 ) 0.1171
1.001
wR2 ) 0.0885
R1 ) 0.0655,
wR2 ) 0.0945
0.903
R indices (all data)
goodness-of-fit
on F2 b
largest diff peak/
1.17/-1.53
1.07/-0.93
1.03/-0.77
1.53/-1.46
0.80/-0.78
hole [e Å-3
]
wR2 ) [∑w(Fo - Fc2)2/∑wFo
]
0.5; R1 ) ∑||Fo| - |Fc||/∑|Fo|. Goodness-of-fit ) [∑w(Fo - Fc2)2/(Nobs - Nparam)]0.5
.
a
2
4
b
2
longer than the distance found in [(phpy)2PtCd(cyclen)]-
(ClO4)2 (2.639(1) Å) and [(bpy)Me2PtCd(cyclen)](ClO4)2
(2.610(1) Å)5 although shorter than the Pt‚‚‚Cd interac-
tions described in [NBu4]2[{Pt(µ-CtCPh)4}2(CdCl)2]3
and [{Pt4Cd6(CtCPh)4(µ-CtCPh)12(µ3-OH)4].4 The Pt-
Cd bond is perpendicular to the best square planar
environment of the Pt atom.
It is also important to mention that, although most
of these pentafluorophenyl platinate (PtfM) complexes
display short o-F‚‚‚M interactions (for instance in [NBu4]-

3966 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
room temperature and the 19F NMR spectrum of this
solution is recorded, no signals due to the mononuclear
starting material are observed, and the only signal that
appears in the ortho F region of the spectrum is
displaced from that observed in the spectrum of pure
1. This displacement occurs toward the chemical shift
observed for the signal of pure [NBu4]2[Pt(C6F5)4]. When
a second fraction of [NBu4]2[Pt(C6F5)4] is added to the
solution mixture, the displacement of the o-F signal is
even greater.
Attempts to prepare the analogous dinuclear com-
plexes using [NBu4]2[Pd(C6F5)4] or [NBu4]2[Pt(C6Cl5)4]
as donor precursors have not been successful. In the case
of the palladium complex, only mixtures of the starting
materials and unidentified decomposition products were
recovered. In the case of the pentachlorophenyl deriva-
tive, no reaction took place and the unaltered platinum
precursor was recovered. It seems reasonable to assume
that the bulkier C6Cl5 ligands do not allow the Cd center
close enough to the platinum center to establish the
Pt-Cd bond.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [(C6F 5)4P tCd (cyclen )]‚2Me2CO
(1‚2Me2CO)a
Pt-C(7)
Cd-N(1)
Pt-Cd
2.060(6)
2.380(5)
2.775(1)
Pt-C(1)
Cd-N(2)
2.069(6)
2.399(4)
C(7)-Pt-C(7′)
C(7′)-Pt-C(1)
C(7)-Pt-Cd
N(1)-Cd-N(1′)
N(1′)-Cd-N(2)
N(1)-Cd-Pt
172.2(3)
90.5(2)
93.89(14)
117.7(2)
74.98(16)
121.16(12)
C(7)-Pt-C(1)
C(1)-Pt-C(1′)
C(1)-Pt-Cd
N(1)-Cd-N(2)
N(2)-Cd-N(2′)
N(2)-Cd-Pt
89.0(2)
172.7(3)
93.64(14)
74.40(16)
118.6(2)
120.69(12)
a
The symmetry transformation used to generate equivalent
primed atoms is 1-x, y, 1/2-z.
[(C6F5)4PtAg(SC4H8)] (A)10f the four o-F‚‚‚Ag contacts
range from 2.704(10) to 2.738(9) Å) and could contrib-
ute to the stability of the PtfM complex, in 1 all the
o-F‚‚‚Cd distances are longer that 3 Å, indicating that
such contacts are not present. An additional indication
of the lower interest of the Cd center to establish these
contacts is that the pentafluorophenyl rings are forming
dihedral angles with the platinum coordination plane
of 52.2° (C(1)) and 55.3° (C(7)), while the corresponding
angles in [NBu4][(C6F5)4PtAg(SC4H8)] (A) are 77.6°,
74.1°, 62.6°, and 62.0°, these latter values being obvi-
ously more adequate for forming o-F‚‚‚M contacts.
Considering that in 1 the Pt-Cd distance is longer
than the Pt-Ag one (2.641(1) Å in A; the metallic radii
for Cd and Ag are similar, 1.49 and 1.45 Å, respectively)
and than the Pt-Cd distances in [(phpy)2PtCd(cyclen)]-
(ClO4)2 and [(bpy)Me2PtCd(cyclen)](ClO4)2, it is clear
that the Pt-Cd bond in 1 is weaker than in other cases.
This weakness could well be a consequence of the steric
repulsion between the o-F atoms of the C6F5 rings and
the donor atoms of the cyclen. Such repulsion should
be much lower (if any) in the silver derivative [NBu4]-
[(C6F5)4PtAg(SC4H8)] (A), while in Ito’s complexes the
planarity of the whole environment of the platinum
center should favor the closing up of the acid and basic
centers.
A similar neutral platinum-cadmium complex [(C6F5)2-
(CtCPh)2PtCd(cyclen)] (2) is prepared using the dian-
ionic bis(phenylethynyl)bis(pentafluorophenyl)platinate-
(II), [PMePh3]2[Pt(C6F5)2(CtCPh)2],13 as starting ma-
terial (Scheme 1ii). In this case, treatment of [PMePh3]2-
[Pt(C6F5)2(CtCPh)2] with 1 equiv of cyclen and CdClO4
in methanol produces the precipitation of the complex
[(C6F5)2(CtCPh)2PtCd(cyclen)] (2) as a very pale yellow
microcrystalline solid in moderate yield (30%). Partial
evaporation of the solvent from the filtrate gives a
second fraction of complex (14%). The observation of two
ν(CtC) absorptions (2097, 2080 cm-1) at a position
similar to those observed in [PMePh3]2[Pt(C6F5)2-
(CtCPh)2] (2095, 2082 cm-1 13
suggests that the inter-
)
action of the Cd center with the acetylenic fragments
1
is probably weak. Additionally the IR and H NMR spec-
tra confirm the presence of cyclen and CtCPh ligands.
Conductivity measurements in acetone solution (3.3 Ω-1
cm2 mol-1) indicate its behavior as a neutral compound.
Crystals suitable for a single-crystal X-ray diffraction
study (Figure 2) were obtained by slow evaporation of
an acetone solution of complex 2. Under these condi-
tions, the complex crystallizes as 2‚2Me2CO. Selected
crystallographic data and atomic distances and angles
are listed in Tables 1 and 3, respectively. As can be
The IR spectrum of 1 shows bands corresponding to
the cyclen and pentafluorophenyl ligands. The latter
cause the presence of a sharp, strong band at 773 cm-1
,
assignable to the X-sensitive mode of the C6F5 group,
1
which is typical for a “Pt(C6F5)4” moiety. The H NMR
(HDA) contains three signals due to the cyclen ligand.
One is a broad band assignable to the four NH protons;
the other two are complex multiplets, which integrate
for 8 H each. The equivalence of the four pentafluo-
rophenyl groups is observed in the 19F NMR spectrum
(HDA). However, only three signals appear, both at
room or low temperature, each one corresponding to the
different types of fluorine atoms (ortho, meta, and para),
typical of an AA′MM′X spin system.11 The value of the
conductivity of an acetone solution of complex 1 (42 Ω-1
cm2 mol-1) indicates that it is a poor conductor in
solution, and this could be indicating that the Pt-Cd
bond exists even in a donor solvent such as acetone. In
fact, suitable crystals for the X-ray structure determi-
nation of 1 were grown from acetone solutions.
observed in Figure 2, the compound is also formed by
2-
the expected units “Pt(C6F5)2(CtCPh)2
”
and
“Cd(cyclen)2+” connected through a Pt-Cd donor-
acceptor bond. The Pt-Cd distance is only slightly
shorter (2.764(1) Å) than the distance in 1 (2.775(1) Å).
The most remarkable difference is the fact that in 2,
and probably due to the presence of the alkynyl entities,
the Pt-Cd vector is perceptibly displaced from the
normal to the platinum coordination plane (34.58(9)°)
and located above the Pt-C(1)tC(2) alkynyl fragment.
(11) For recent 19F NMR studies on pentafluorophenyl complexes
see: Casares, J . A.; Espinet, P.; Mart´ın-Alvarez, J . M.; Santos, V. Inorg.
Chem. 2004, 43, 189. See also ref 12.
(12) (a) Alonso, M, A.; Casares, J . A.; Espinet, P.; Mart´ınez-Ilarduya,
J . M.; Pe´rez-Briso, C. Eur. J . Inorg. Chem. 1998, 1745, and references
therein. (b) Casares, J . A.; Espinet, P.; Mart´ınez de Ilarduya, J . M.;
Lin, Y.-S. Organometallics 1997, 16, 770.
(13) Espinet. P.; Fornie´s, J .; Mart´ınez, F.; Sote´s, M.; Lalinde, E.;
Moreno, M. T.; Ruiz, A.; Welch, A. J . J . Organomet. Chem. 1991, 403,
253.
The existence of a AA′MM′X spin system for the C6F5
groups in the 19F NMR spectrum of 1 seems to be due
to a very fast dissociation equilibrium between 1 and
the mononuclear starting material. If a small amount
of [NBu4]2[Pt(C6F5)4] is added to a HDA solution of 1 at

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3967
F igu r e 2. Structure of the complex [(C6F5)2Pt(CtCPh)2Cd-
(cyclen)] (2). For the sake of clarity, only the cyclen atoms
of one of the components of the disorder (see Experimental
Section) are shown.
F igu r e 3. Variable-temperature 19F NMR spectra (ortho-
fluorine region) of [(C6F5)2Pt(CtCPh)2Cd(cyclen)] (2).
displays only one set of C6F5-fluorine signals [2o-F:
3(1-p-F, 2m-F)], thus confirming that both C6F5 rings
are equivalent and indicating the effective equivalence
of the o-F atom and the m-F as well. However, as can
be seen in Figure 3, which shows the ortho-fluorine
region at different temperatures, in acetone-d6, the
pattern observed at 190 K is that expected for a rigid
molecule. The presence of four ortho-fluorine resonances
indicates the existence of two different C6F5 rings with
their halves nonequivalent, thus confirming that the
possible exchange of the “Pt(cyclen)” unit between both
alkynyl ligands is slow on the NMR time scale and that
the rotation of the C6F5 groups around the Pt-Cipso bond
is also hindered. Increasing the monitoring tempera-
tures resulted in a clear broadening of the o-fluorine
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [(C6F 5)2P t(CtCP h )2Cd (cyclen )]‚2Me2CO
(2‚2Me2CO)
Pt-C(1)
2.011(5)
2.062(5)
2.332(9)
2.065(5)
2.289(6)
Pt-C(9)
Pt-Cd
Cd-N(3a)
Cd-N(4a)
2.015(5)
2.764(1)
2.359(5)
2.420(7)
Pt-C(17)
Cd-N(1a)
Pt-C(23)
Cd-N(2a)
C(1)-Pt-C(9)
C(1)-Pt-C(23)
C(9)-Pt-C(17)
C(23)-Pt-C(17)
C(2)-C(1)-Pt
92.50(18) C(1)-Pt-Cd
88.23(19) C(9)-Pt-Cd
89.69(19) C(23)-Pt-Cd
60.53(12)
75.17(12)
109.94(14)
117.52(15)
173.9(4)
89.9(2)
C(17)-Pt-Cd
C(10)-C(9)-Pt
174.1(4)
C(1)-C(2)-C(3) 178.4(5)
C(9)-C(10)-C(11) 177.5(5)
As a consequence, the Cd center is in a more compli-
cated environment formed by the four nitrogen atoms
of the cyclen ligand, the Pt atom, and the CR carbon of
one of the two alkynyl groups. The very acute Cd-Pt-
C(1) bond angle (60.53(12)°) and, particularly, the Cd-
C(1) carbon length (2.493 Å), which is comparable to
those observed in the anions [{Pt(µ-η1-CtCPh)4}2-
resonances. The two central signals [-116.0, d, J F-F
)
30 Hz; -116.3 d, J F-F ) 26 Hz] coalesce at about 208 K
and finally collapse to only one, centered at -116.2 at
220 K, while the external ones [-115.5, d, J F-F ) 30
Hz; -117.5, d, J F-F ) 26 Hz] coalesce at about 228 K
and average to one, centered at -116.7 at 240 K. The
∆Gq for both pairs of signals at their coalescence
temperature are similar (central ∆Gq ≈ 41.20 kJ /mol;
external ∆Gq ≈ 41.1 kJ /mol), suggesting that they are
involved in the same dynamic process. The external
resonances, which are seen as doublets with ortho-
meta-fluorine coupling constants of 30 and 26 Hz, are
tentatively assigned to endo ortho-fluorine atoms of
different C6F5 rings, and therefore the central signals
are attributed to the corresponding two exo-fluorine
atoms. The observed equilibration of both C6F5 groups
(average of endo with endo and exo with exo fluorine
atoms of each ring) at 240 K can be explained by
assuming a fast exchange of the Cd(cyclen) fragment
between both alkynyl ligands on the NMR time scale.
Above 245 K, the two ortho-fluorine resonances broaden
again, coalesce near 260 K, and finally collapse to only
one, centered at -117.2 at 270 K, requiring the consid-
eration of an additional dynamic process. As for complex
1, free rotation of the rings along the Pt-Cipso(C6F5)
bond or a fast and facile dissociation of the Cd(cyclen)
unit or a combination of both processes could adequately
explain such changes. However in this case, at 240 K,
the addition of a small amount of [PMePh3]2[Pt(C6F5)2-
(CtCPh)2] gives rise to a 19F NMR spectrum containing
separate signals of 2 and the starting material, thus
indicating that in 2 dissociation of the Cd(cyclen) unit
does not occur or it is very slow on the NMR time scale.
(CdCl)2]2-
and
[{Pt(µ-η2-CtCPh)4}(CdCl2)2]2-
(2.403(11)-2.657(12) Å),3 indicate that the C(1)tC(2)-
Ph fragment is acting as a µ-η1 alkynyl bridging ligand.
The structural details for the alkynyl fragments are
unexceptional for this type of ligand.2 The remaining
Cd-acetylenic carbon (Cd-C(2) 2.98 Å, Cd-C(9) 2.97
Å) and the shortest Cd-fluorine-ortho (Cd-F(24) 3.299
Å) distances are very long, excluding other bonding
interactions. The dihedral angle of the C6F5 ring con-
taining the F(24) atom with the platinum coordination
plane is slightly larger (71.14(18)°) than the angle
formed for the C6F5 ring trans to the µ-η1-CtCPh ligand
(65.04(20)°), and both are clearly more perpendicular
to the Pt plane than those seen in 1. It seems also clear
that the location of the “Cd(cyclen)2+” moiety toward the
acetylide ligands prevents the repulsion of the ortho-
fluorine atoms of the C6F5 group and the “Cd(cyclen)2+
”
moiety. A view along the a axis of the crystal lattice
reveals the existence of square channels formed for the
pentafluorophenyl rings in which the acetone molecules
are placed (see Figure 1S in the Supporting Informa-
tion). Although no contact between these solvent mol-
ecules and any of the fluorine atoms is observed, their
presence plays an important role in the luminescence
of this complex (see below).
Fluxional behavior of complex 2 in solution is evident
by 19F NMR spectroscopy. At room temperature, it

3968 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [(C6F 5)2(bzq)P tCd (cyclen )](ClO4)‚0.5MeOH
(3‚0.5MeOH)
Pt-C(7)
Pt-N(1)
Cd-N(3)
Pt-C(1)
Cd-N(4)
1.985(14)
2.065(10)
2.337(10)
2.011(11)
2.334(13)
Pt-C(23)
Pt-Cd
Cd-N(2)
Cd-N(5)
1.986(12)
2.688(1)
2.348(12)
2.361(13)
C(7)-Pt-C(23)
C(23)-Pt-C(1)
C(23)-Pt-N(1)
C(7)-Pt-Cd
173.6(5)
93.3(5)
81.3(5)
104.5(5)
105.7(4)
78.2(5)
C(7)-Pt-C(1)
C(7)-Pt-N(1)
C(1)-Pt-N(1)
C(23)-Pt-Cd
N(1)-Pt-Cd
N(4)-Cd-N(2)
N(4)-Cd-N(5)
N(2)-Cd-N(5)
N(3)-Cd-Pt
90.2(5)
94.8(5)
173.3(5)
79.7(3)
77.5(3)
123.9(5)
75.8(5)
75.0(6)
124.1(3)
115.6(4)
C(1)-Pt-Cd
N(4)-Cd-N(3)
N(3)-Cd-N(2)
N(3)-Cd-N(5)
N(4)-Cd-Pt
76.4(5)
119.7(5)
123.8(3)
111.9(3)
F igu r e 4. Structure of the cation of the complex [(C6F5)2-
(bzq)PtCd(cyclen)](ClO4) (3).
N(2)-Cd-Pt
N(5)-Cd-Pt
However, on raising the temperature (to 300 K), the
signals due to [PMePh3]2[Pt(C6F5)2(CtCPh)2] disappear
on the baseline and the only signal observed in the
ortho-fluorine region appears broader, suggesting a
possible fast equilibrium between 2 and [PMePh3]2-
[Pt(C6F5)2(CtCPh)2] at high temperature.
Pt-Cd distance is 2.688(1) Å, slightly shorter than those
observed in 1 and 2, but still longer that those found in
[(phpy)2PtCd(cyclen)](ClO4)2 (2.639(1) Å) and [(bpy)Me2-
PtCd(cyclen)](ClO4)2 (2.610(1) Å).5 The geometry of the
“Cd(cyclen)” fragment is as in complexes 1 and 2. The
Pt atom and the four atoms coordinated to it in its
square planar environment lie basically on the same
plane. The 7,8-benzoquinolate ligand is also essentially
planar, forming a dihedral angle of 10.2(3)° with the Pt
square plane in such a way that it moves away from
the Cd. The angle formed by the Pt-Cd line with the
perpendicular to the best Pt coordination square plane
takes an intermediate value (17.6(2)°) to that of the
same angles in the neutral complexes 1 (0°) and 2
(34.58(9)°). This line leans away from the perpendicular
toward the planar 7,8-benzoquinolate ligand in such a
way that the Cd atom moves away from the pentafluo-
rophenyl groups. As a concomitant result, the C6F5
planes form angles with the Pt coordination square
plane of 70.6(4)° (C(1)) and 78.6(4)° (C(7)) (cf. 52.2° (C(1))
and 55.3° (C(7)) in 1); that is, they are more perpen-
dicular to the Pt plane than for complex 1. The shortest
Cd-F distance is 2.966(9) Å, established with F(10);
although this separation is shorter than the sum of van
der Waals radii (3.10-3.20 Å),14 it is still too long to be
considered as an o-F‚‚‚Cd contact.
Comparison of the crystal structures of 1, 2, and 3
seems to indicate that there is a steric repulsion
between the pentafluorophenyl groups attached to the
platinum and the bulky cyclen ligand coordinated to the
cadmium. For 1, the presence of four C6F5 ligands
around the platinum causes the Pt-Cd distance to be
longer, while in 2 and 3 the Cd fragment can approach
the Pt center better due to the presence of linear alkynyl
fragments or the planar 7,8-benzoquinolate ligand mov-
ing away from the C6F5 groups. It is also interesting to
mention that in 2 the interaction between “Cd(cyclen)”
and one acetylide ligand could also favor the angle
between the perpendicular to the Pt coordination plane
and the Pt-Cd bond being greater than in 3.
Syn th esis of [(C6F5)2(bzq)P tCd(cyclen )](ClO4) (3).
We have also studied the reaction of the cationic
fragment “Cd(cyclen)2+” toward the monoanionic com-
plex [Pt(C6F5)2(bzq)]- (bzq ) 7,8-benzoquinolinate, see
Chart 1), which contains two pentafluorophenyl rings
mutually cis and a bidentate anionic ligand bzq (Scheme
1iii). The latter ligand is planar, and thus, in principle,
there is less steric hindrance for the cadmium atom to
approach the Pt center to establish an intermetallic
bond. The required precursor [NBu4][Pt(C6F5)2(bzq)] (6)
was prepared from [NBu4][Pt(C6F5)3(7,8-benzoquino-
line)] by thermal-induced deprotonation of the bzqH
ligand in CH2Cl2 at reflux temperature (3 h) (see
Experimental Section for details) and fully characterized
by elemental analysis and IR and NMR (1H, 19F)
spectroscopy. The NMR data unambiguously reveal the
presence of the bzq ligand and the unequivalence of both
C6F5 rings.
Treatment of 6 with a MeOH solution of [Cd(cyclen)-
(MeOH)2](ClO4)2, prepared in situ, in 1:1 molar ratio,
gives the binuclear cationic complex [(C6F5)2(bzq)PtCd-
(cyclen)](ClO4) (3) as a yellow solid. Its IR spectrum
shows, in the X-sensitive region, in addition to the two
expected typical sharp absorptions due to the presence
of the two mutually cis pentafluorophenyl rings, signals
due to bzq and cyclen ligands. In the 19F NMR spectrum,
the inequivalence of the two pentafluorophenyl groups
is confirmed, each C6F5 forming a AA′MM′X spin
system. Conductivity measurements in acetone solu-
tions of complex 3 confirm its behavior as a 1:1 electro-
lyte (see Experimental Section). This would indicate
that the Pt-Cd bond persists even in a donor solvent
such as acetone. 19F NMR studies similar to the ones
described for 1 have been carried out with similar
results, indicating that a dissociative equilibrium is
taking place in solution.
Rea ction of [NBu 4]2[P t2(µ-Cl)2(C6F 5)4] w ith [Cd -
(cyclen )(MeOH)2](ClO4)2. With the aim of preparing
a trinuclear complex15 in which the binuclear [Pt2(µ-
Cl)2(C6F5)4]2- moiety could act as a bidentate chelating
ligand and two Pt-Cd bonds would be present, we
performed the reaction of [NBu4]2[Pt2(µ-Cl)2(C6F5)4] with
The crystal structure of the cation of 3 is shown in
Figure 4. Crystallographic data are given in Table 1,
and selected interatomic distances and angles appear
in Table 4. The dinuclear cation 3 can be described as
the union of the moieties “Pt(C6F5)2(bzq)” and “Cd-
(cyclen)” through a Pt-Cd donor-acceptor bond. The
(14) Bondi, A. J . Phys. Chem. 1964, 68, 441.

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3969
Sch em e 2
F igu r e 5. Structure of the complex [Pt(C6F5)2Cl2Cd-
(cyclen)]2 (4). For the sake of clarity, only the cyclen atoms
of the major component of the disorder (see Experimental
Section) are shown.
(Pt-Cl(2) ) 2.386(2) Å, Pt-Cl(1) ) 2.400(2) Å), the two
Cd-Cl distances are perceptibly different: Cd-Cl(1) )
2.840(2) Å, Cd-Cl(1′) ) 2.655(2) Å. The first one is
somewhat long, but there are some reported examples
of similar long Cd-Cl distances in complexes in which
the Cl atoms are bridging three metal atoms.16 It is
noteworthy that the bridging Pt-Cl(1) distance is
slightly shorter than the terminal Pt-Cl(2) length.
Finally, the Pt square coordination planes are not
perpendicular to the “Cd2Cl2” cycle (which is perfectly
planar) but forms a dihedral angle of 101.9(1)°.
The solid-state structure found in the crystal cannot
account for the 19F NMR spectrum of 4, in which only
signals due to one type of C6F5 group are observed.
Should the structure in solution be the same as that in
the solid state, two types of pentafluorophenyl groups
should be observed in the 19F NMR spectrum. One
possible explanation that could combine both experi-
mental observations would be the existence of dynamic
processes in solution, faster than the NMR time scale,
and which would involve the rupture and formation of
Cd-Cl bonds (see Scheme 2).
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [P t(C6F 5)2Cl2Cd (cyclen )]2‚2Me2CO
(4‚2Me2CO)a
Pt-C(7)
Pt-Cl(1)
Cd-N(1)
Cd-Cl(1)
Pt-Cl(2)
1.982(8)
2.400(2)
2.417(9)
2.840(2)
2.386(2)
Pt-C(1)
Cd-N(2)
Cd-N(4)
Cd-Cl(1′)
Cd-N(3)
1.991(8)
2.319(9)
2.420(9)
2.655(2)
2.323(9)
C(7)-Pt-C(1)
C(1)-Pt-Cl(2)
C(1)-Pt-Cl(1)
N(2)-Cd-N(3)
N(3)-Cd-N(1)
N(3)-Cd-N(4)
N(2)-Cd-Cl(1′)
N(1)-Cd-Cl(1′)
N(2)-Cd-Cl(1)
N(1)-Cd-Cl(1)
Cl(1′)-Cd-Cl(1)
Pt-Cl(1)-Cd
87.3(3)
178.5(2)
91.5(2)
79.3(4)
118.6(4)
74.4(4)
94.8(3)
84.5(3)
155.2(2)
129.1(3)
85.57(6)
92.73(7)
C(7)-Pt-Cl(2)
C(7)-Pt-Cl(1)
Cl(2)-Pt-Cl(1)
N(2)-Cd-N(1)
N(2)-Cd-N(4)
N(1)-Cd-N(4)
N(3)-Cd-Cl(1′)
N(4)-Cd-Cl(1′)
N(3)-Cd-Cl(1)
N(4)-Cd-Cl(1)
Pt-Cl(1)-Cd′
Cd′-Cl(1)-Cd
92.6(2)
178.7(2)
88.61(7)
75.4(4)
119.2(4)
71.2(3)
153.1(3)
129.6(3)
89.1(3)
77.6(3)
106.93(7)
94.43(6)
a
The symmetry transformation used to generate equivalent
primed atoms is -x, -y, -z. For the sake of clarity, only the cyclen
atoms of the major component of the disorder (see Experimental
Section) are included.
The different behavior of the acidic [Cd(cyclen)]2+
moiety toward [NBu4]2[Pt(C6F5)4] or [NBu4]2[Pt2(µ-Cl)2-
(C6F5)4] is noteworthy. Thus, when the main basic
center present in the platinum complex is the metal
itself, the reaction leads to the formation of 1, a complex
with a donor-acceptor Pt-Cd bond. On the other hand,
when there are other basic centers, such as the chlorine
atoms, they compete with each other with the result,
in this case, that the formation of Cd-Cl bonds is
preferred. Moreover, the reaction of formation of 4
implies the existence of processes of asymmetric break-
ing of the bridging system in the dinuclear starting
material [NBu4]2[Pt2(µ-Cl)2(C6F5)4]. The relatively low
yield in the preparation of 4 (29%) indicates that there
have to be other products formed in this reaction. So
far, we have been able to identify and characterize only
one of these products, [Cd2(µ-Cl)2(cyclen)2](ClO4)2 (5), of
which suitable crystals for an X-ray structure determi-
nation were obtained during one of the attempts to
crystallize 4. Later, we were able to design a convenient
synthetic procedure to prepare 5 starting from [Cd-
(cyclen)(MeOH)2](ClO4)2 and (NBu4)Cl (see Experimen-
tal Section). The structure of the cation of 5 is shown
[Cd(cyclen)(MeOH)2](ClO4)2 in 1:1 molar ratio (Scheme
1iv). When the dinuclear platinum complex was added
to a MeOH solution of [Cd(cyclen)(MeOH)2](ClO4)2, a
white suspension appeared due to the insolubility of the
Pt complex in methanol. This suspension was stirred
for 1 h, and then the white solid was filtered off and
vacuum-dried. The stoichiometry of this material was
not clear. The elemental analysis did not coincide with
that calculated for the expected [(C6F5)4(µ-Cl)2Pt2Cd-
(cyclen)] formula (see Experimental Section).
A single-crystal X-ray study allowed us to determine
the solid-state structure of this complex, [Pt(C6F5)2Cl2-
Cd(cyclen)]2 (4). The structure is shown in Figure 5.
Crystallographic data are given in Table 1, and selected
interatomic distances and angles appear in Table 5. 4
is a tetranuclear compound without Pt-Cd bonds and
with two chlorine atoms acting as a µ3 ligand, bridging
two Cd and one Pt center. The platinum atoms lie in
the center of square planar environments formed by two
pentafluorophenyl ligands and two chlorine atoms in a
cis disposition. One of the chlorine atoms acts as a
terminal ligand, while the other is bridging the plati-
num atom with the two cadmium atoms present in the
complex. The Cd atoms are six coordinated and have a
cyclen ligand coordinated in the usual way. The long
Pt-Cd distances (3.805(1) Å for Cd and 4.065(1) Å for
Cd′) exclude any kind of intermetallic interaction.
Whereas the two Pt-Cl distances are very similar
(15) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Casas, J . M.; Cotton, F. A.;
Falvello, L. R. Inorg. Chem. 1987, 26, 3482.
(16) (a) Kubiak, M.; Glowiak, T.; Kozlowski, H. Acta Crystallogr.,
Sect. C 1989, 39, 1637. (b) Fawcett, T. G.; Ou, C. C.; Potenza, J . A.;
Schugar, H. J . J . Am. Chem. Soc. 1978, 100, 2058. (c) Corradi, A. B.;
Cramarossa, M. R.; Pellacani, G. C.; Battaglia, L. P.; Giusti, J . Gazz.
Chem. Ital. 1994, 124, 481.

3970 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
Ta ble 7. Absor p tion for Com p lexes (∼5 × 10-5
M
solu tion s)
compound
absorption/nm (103 ꢀ/M-1 cm-1
)
[NBu4]2[Pt(C6F5)4]
215(15.0), 326(3.2) acetone
236(48.77), 290sh(12.7) CH2Cl2
211(10.5), 327(7.2), 390sh(2.2)
acetone
[(C6F5)4PtCd(cyclen)] (1)
239(14.7), 297(8.8), 345(6.8) CH2Cl2
329(11.8) acetone
[PMePh3]2[Pt(C6F5)2-
(CtCPh)2]
232(42.8), 275(22.6), 290(21.8),
310(19.2), 325(12.4) CH2Cl2
327(1.5) acetone
230(25.6), 267(28.6), 280sh(25.3),
325(26.2), 349sh(10.7) CH2Cl2
[(C6F5)2(CtCPh)2PtCd-
(cyclen)] (2)
F igu r e 6. Structure of the cation of complex [Cd2(µ-Cl)2-
(cyclen)2](ClO4)2 (5). For the sake of clarity, only the cyclen
atoms of one of the components of the disorder (see
Experimental Section) are shown.
[NBu4][Pt(C6F5)2(bzq)] (6) 215(21), 328(13.4), 344(12.0),
393(8.4), 422sh(5.8) acetone
243(66.4), 260(58.4), 315(27.5),
345(20.1), 380(12.1), 425(6.9) CH2Cl2
[(C6F5)2(bzq)PtCd(cyclen]- 220(27.0), 328(12.8), 393(6.8)
Ta ble 6. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for [Cd 2(µ-Cl)2(cyclen )2](ClO4)2 (5)a
[ClO4] (3)
acetone
Cd(1)-N(2)
Cd(2)-N(4)
Cd(1)-Cl(1)
2.365(11)
2.388(14)
2.6177(19)
Cd(1)-N(1)
Cd(2)-N(3)
Cd(2)-Cl(1)
2.394(12)
2.418(15)
2.6012(19)
225(9.5), 242(14.3), 280(8.2),
325(5.2), 375(3.3), 410(2.7) CH2Cl2
presence of the cadmium atom, apart from those at 239
and 297 nm related to those observed for [NBu4]2[Pt-
(C6F5)4] at 236 and 290 nm. These high-energy bands
with a coefficient of extinction on the order of 104 M-1
cm-1 are as expected for predominantly ligand-centered
(C6F5) transitions (1LC).19 The absorption spectrum of
the precursor compound [NBu4][Pt(C6F5)2(bzq)] (6) in
CH2Cl2 contains high-energy bands (243-380 nm) due
to ligand-centered transitions (1LC, πfπ* bzq, C6F5)
with metal perturbation and a low-energy band at 425
nm (λ ) 422 nm in acetone) which, in accordance with
similar assignments,20 can be tentatively attributed to
a spin-allowed metal to ligand (1MLCT Pt(d)fπ*bzq*)
transition. For the binuclear cationic complex [(C6F5)2-
(bzq)PtCd(cyclen)](ClO4) (3), the low-energy band ob-
served in 6 at 425 nm in CH2Cl2 is blue-shifted to 410
nm and in acetone is overlapped with the high-energy
bands. This fact is consistent with the formation of the
Pt-Cd donorfacceptor bond, which produces an in-
crease in the electrophilicity of the Pt metal center,
resulting in a blue-shift for the MLCT absorption.
Comparison of the absorption spectrum of complex 2
with the spectrum of [PMePh3]2[Pt(C6F5)2(CtCPh)2] is
less illustrative in relation to the Pt-Cd bonding
interaction. In acetone solution, the band observed with
a peak maximum at 329 nm (ꢀ ) 11 790 M-1 cm-1) is
only slightly blue-shifted in the binuclear complex
[(C6F5)2(CtCPh)2PtCd(cyclen)] (2) (327 nm), although
the extinction coefficient is smaller (1520 M-1 cm-1). In
N(2)-Cd(1)-N(1)
75.2(3)
N(2)-Cd(1)-Cl(1′)
N(2)-Cd(1)-Cl(1)
N(1)-Cd(1)-Cl(1)
Cl(1′)-Cd(1)-Cl(1)
N(4)-Cd(2)-Cl(1′)
N(4)-Cd(2)-Cl(1)
N(3)-Cd(2)-Cl(1)
87.6(3)
155.2(3)
126.6(3)
80.82(9)
93.6(3)
131.1(3)
153.3(3)
93.04(6)
N(1)-Cd(1)-Cl(1′) 91.3(3)
N(2′)-Cd(1)-Cl(1) 87.6(3)
N(1′)-Cd(1)-Cl(1) 91.3(3)
N(4)-Cd(2)-N(3)
73.9(4)
N(3)-Cd(2)-Cl(1′) 88.2(3)
N(4′)-Cd(2)-Cl(1) 93.6(3)
Cl(1′)-Cd(2)-Cl(1) 81.44(9) Cd(2)-Cl(1)-Cd(1)
a
For the sake of clarity, only the cyclen atoms of one of the
components of the disorder (see Experimental Section) are in-
cluded.
in Figure 6. Crystallographic data are given in Table 1,
and selected interatomic distances and angles appear
in Table 6. 5 is a dinuclear complex in which the two
“Cd(cyclen)” fragments are bridged by two chlorine
atoms. The most remarkable feature of this structure
is the high value of the dihedral angle formed by the
two planes defined by one Cd atom and the two bridging
Cl. This angle takes a value of 34.4(1)° and is the
broadest of those reported for “Cd(µ-Cl)2Cd” systems
with no other bridging ligand linking the metal atoms.17
Absor p tion a n d Em ission Sp ectr oscop ic Resu lts
for Com p lexes 1-3. Whereas photochemistry and
photophysics of discrete d8‚‚‚d,8 d10‚‚‚d10 binuclear sys-
tems have been extensively studied,7,8a,b,d,h,i relatively
little attention has been paid to mixed metal d8‚‚‚d10
compounds. Most of these studies have been reported
for systems containing closed-shell d10 monovalent
coinage (Cu, Ag, Au) ions,2b,d,e,8j,18 and surprisingly very
few spectroscopic investigations have been carried out
for related d10 divalent metal ions. We have previously
suggested that Pt‚‚‚Cd(II) interactions play an impor-
tant role in interpreting the luminescence properties of
tetranuclear dianionic [{Pt(µ-κCRCR-CtCPh)4}2(CdX)2]2-
clusters.3,4 To gain further insights into the involvement
of metal‚‚‚metal bonding interactions in the excited-
state properties of these complexes, the optical proper-
ties of 1-3 and those of their precursors have been
investigated (Tables 7 and 8).
(18) (a) Balch, A. L.; Catalano, V. J .; Olmstead, M. M. Inorg. Chem.
1990, 29, 585. (b) Balch, A. L.; Catalano, V. J . Inorg. Chem. 1991, 30,
1302. (c) Yip, H. K.; Che, C. M.; Peng, S. M. J . Chem. Soc., Chem.
Commun. 1991, 1626. (d) Yip, H. K.; Lin, H. M.; Cheung, K. K.; Che,
C. M.; Wang, Y. Inorg. Chem. 1994, 33, 1644. (e) Yip, H. K.; Lin, H.
M.; Wang, Y.; Che, C. M. J . Chem. Soc., Dalton Trans. 1993, 2939. (f)
Yip, H. K.; Lin, H. M.; Wang, Y.; Che, C. M. Inorg. Chem. 1993, 32,
3402. (g) Pettijohn, C. N.; J ochnowitz, E. B.; Chuong, B.; Nagle, J . K.;
Vogler, A. Coord. Chem. Rev. 1998, 171, 85. (h) Xia, B. H.; Zhang, H.
X.; Che, C. M.; Leung, K. H.; Phillips, D. L.; Zhu, N.; Zhou, Z. Y. J .
Am. Chem. Soc. 2003, 125, 10362, and references therein.
(19) The absorption spectrum of BrC6F5 shows similar energy bands
at 227 (11.3), 245 (15.6), 263 (16.6), and 285 (54.80) nm. The cyclen
ligand also shows high-energy bands at 229 (6.78), 263 (2.98), and 269
(3.10) nm (ꢀ × 103 M-1 cm-1).
The absorption spectrum of 1 shows, in CH2Cl2, a low-
energy absorption at 345 nm, which is related to the
(17) See for example: (a) Zompa, L. J .; D´ıaz, H.; Margulis, T. N.
Inorg. Chim. Acta 1995, 232, 131. (b) Braunstein, P.; Douce, L.; Knorr,
M.; Strampfer, M.; Lanfranchi, M.; Tiripicchio, A. J . Chem. Soc., Dalton
Trans. 1992, 331. (c) Corradi, A. B.; Cramarossa, M. R.; Saladini, M.
Inorg. Chim. Acta 1997, 257, 19. (d) Allred, R. A.; MacAlexander, L.
H.; Arif, A. M.; Berreau, L. M. Inorg. Chem. 2002, 41, 6790.
(20) (a) Balashev, K. P.; Puzyk, M. V.; Kotlyar, V. S.; Kulikova, M.
V. Coord. Chem. Rev. 1997, 15, 109. (b) Lai, S. W.; Lam, H. W.; Cheung,
K. K.; Che, C. M. Organometallics 2002, 21, 226. (c) Williams, J . A.
G.; Beeby, A.; Davie, E. S.; Weinstein, J . A.; Wilson, C. Inorg. Chem.
2003, 42, 8609. (d) J ude, H.; Krause, J . A.; Connick, W. B. Inorg. Chem.
2004, 43, 725.

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3971
Ta ble 8. P h otop h ysica l Da ta for Com p lexes in Solid , KBr , a n d 10-3 M Solu tion s
compound
(T/K)
λ
exc/nm
λ
em/nm
φ
τ
[NBu4]2[Pt(C6F5)4]
solid (77)
323
311
423, 440
432
no emissive
444max, 487, 570 (λex340)
466max, 545(λex360)
473, 546max(λex370)
451
444max, 464, 475, 489,
515
CH2Cl2 (77)a
solid (298, 77)
CH2Cl2 (77)b
[(C6F5)4PtCd(cyclen)] (1)
320max, 342(λem466)
320, 370max (λem525)
[PMePh3]2[Pt(C6F5)2(CtCPh)2]
solid (298)
solid (77)
337, 362, 382, 392, 433
313, 341
957.8 ns
(74%, ø2 1.10)
CH2Cl2 (77)
acetone (77)
solid (298)
solid (77)
313, 324, 333
321, 335
333, 339, 356, 408
312, 340, 357, 407
326, 352, 400
430max, 452, 471
437max, 459, 477
451max, 468, 490c
446max, 469, 481, 492c
445max, 479, 491, 517,
549c
[(C6F5)2(CtCPh)2PtCd(cyclen)]
(2‚2Me2CO)
342.1 ns
(58%, ø2 0.37)
CH2Cl2 (77)
acetone (77)
KBr (298)
solid (298)
solid (77)
315, 348
445max, 476, 510c)
524, 590sh
[NBu4][Pt(C6F5)2(bzq)] (6)
334, 366, 392, 439, 480sh
344, 356, 391, 425sh, 432
334, 350, 394, 441, 478sh
380, 426max
16.5 µs
518
514, 550, 595sh
486
acetone (298)a
acetone (77)
CH2Cl2 (298)
CH2Cl2 (77)
KBr (298)
0.0019d
365, 427
488, 526, 567, 611she
no emissive
328, 340, 389, 423
356, 393, 407, 432, 479
336, 392, 425
333, 396, 425
380br, 432max
330, 358, 400
490, 525, 568
488, 519, 560sh
490, 518, 560sh
484, 518, 560sh
481
[(C6F5)2(bzq)PtCd(cyclen)[ClO4]
(3)
7.9 µs
solid (298)
solid (77)
acetone (298)
acetone (77)
0.0285d
483, 517, 560sh
a
b
d
Weak emission. Saturated solution. c With tail to 600 nm. Measured using dcm-pyram in MeOH as a standard. e With tail to 750
nm.
While the [NBu4]2[Pt(C6F5)4] precursor exhibited a
feeble luminescence structured band with maxima at
423 and 440 nm in the solid state at low temperature
(77 K), probably due to an intraligand metal-perturbed
3(ππ*) transition on the C6F5 rings (see Table 8 and
Figure 2S in the Supporting Information), complex 1 is
not emissive in the solid state. The absence of photo-
luminescence for 1 is not clear at this moment, but due
to the formation of a PtfCd donor-acceptor bond in
this complex, the Cd2+ behaves as a luminescence
quencher only in the solid state. Both derivatives are
nonemissive in fluid or frozen acetone solution. In frozen
CH2Cl2 solution, the precursor [NBu4]2[Pt(C6F5)4] also
exhibits a weak emission at ca. 432 nm. The solubility
of complex 1 in CH2Cl2 is very low. However, a frozen
saturated CH2Cl2 solution displays a more complex
F igu r e 7. UV-visible spectra of [(C6F5)2Pt(CtCPh)2Cd-
(cyclen)] (2) (s) and [PMePh3]2[Pt(C6F5)2(CtCPh)2] (- - -)
in CH2Cl2 solution (5 × 10-5 M).
behavior. Figure 8 shows the emission spectra, which
are dependent on the excitation energy, thus indicating
the existence of several emissive states. The low-energy
emission (545 nm), which is absent in the precursor, is
tentatively attributed to a transition related to the
formation of the Pt-Cd bond.
The emission spectra of the precursor [PMePh3]2[Pt-
(C6F5)2(CtCPh)2] in the solid state (at room tempera-
ture and 77 K and in frozen solutions (see Table 8)) show
a structured band (444-430 nm) with progressional
spacing suggestive of a combination of a vibrational
mode of CtC and Ph rings. With reference to earlier
work on platinum(II)-alkynyl systems,2e,8j,21,22 the ori-
gin of the luminescence is assigned as derived from
metal-perturbed triplet alkynyl intraligand states (πfπ*
CtCPh) mixed with some degree of metal-to-ligand (dπ-
(Pt)fπ*CtCPh) charge transfer character.
CH2Cl2 solution (5 × 10-5 M) this band becomes
resolved into three intense absorptions at 230, 267, and
325 nm with a small shoulder at 349 nm for 2, while
the precursor [PMePh3]2[Pt(C6F5)2(CtCPh)2] exhibits in
CH2Cl2 a high-energy band at 232 and a broad absorp-
tion profile with several maxima in the range 275-325
nm and a long tail to 360 nm (see Figure 7). Assignment
is difficult because overlapping of π-π* (1IL, C6F5,
CtCPh) with bands due to PMePh3+ is to be expected.
The low-energy absorptions, which lie out of the range
found in PMePh3Br (<275 nm) and that are not ob-
served in the homoleptic [NBu4]2[Pt(C6F5)4] (236, 290
sh), can be tentatively ascribed, in both complexes, to
an admixture of πfπ*(CtCPh) IL/dπ(Pt)-π*(CtCPh)
MLCT. In fact, similar absorptions were found in the
homoleptic derivative (NBu4)2[Pt(CtCPh)4]21 (335, 347
nm).
(21) Benito, J .; Berenguer, J . R.; Fornie´s, J .; Gil, B.; Go´mez, J .;
Lalinde, E. Dalton Trans. 2003, 4331.
(22) Ferna´ndez, S.; Fornie´s, J .; Gil, B.; Go´mez, J .; Lalinde, E. Dalton
Trans. 2003, 822.

3972 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
F igu r e 8. Excitation and emission spectra of [(C6F5)4PtCd-
(cyclen)] (1) in CH2Cl2 solution (77 K). Excitation: (.._.._.._
)
F igu r e 10. Emission spectra of [NBu4][Pt(C6F5)2(bzq)] (6)
in the solid state at 298 K (- - - ) and at 77 K (s).
λem 525; (._._._) λem 466. Emission: (s) λex 340; (- - - ) λex 360;
(‚‚‚) λex 370.
F igu r e 9. Emission spectra of [(C6F5)2Pt(CtCPh)2Cd-
(cyclen)] (2) in the solid state at 298 K (- - -) and at 77 K
(s).
F igu r e 11. Emission spectra of [(C6F5)2(bzq)PtCd(cyclen)]-
(ClO4) (3) in the solid state at 298 K (- - - ) and at 77 K
(s).
Curiously, when the microcrystalline solid of [(C6F5)2-
(CtCPh)2PtCd(cyclen)] 2 is inside the methanolic solu-
tion in which it is precipitated, it also displays at room
temperature a visible blue luminescence upon exciting
with 365 nm by means of a hand-held, dual-wavelength
mercury UV lamp, but this luminescence is lost when
the solid is dried. Emission is, however, detected for this
solid at 77 K at ca. 446 nm with a rich vibronic structure
(see Table 8). Crystallization of 2 from acetone/hexane
causes the incorporation of acetone in the lattice (see
Figure 1S in the Supporting Information) with again a
visible blue luminescence for the solid at room temper-
ature, the intensity of which is enhanced by lowering
the temperature. Figure 9 shows the luminescence
emission of this solid (2‚2Me2CO) at room temperature
and at 77 K. The structured emission observed at 77 K
(446 nm) with vibrational spacing of 1100, 1632, and
2097 cm-1 is again suggestive of the involvement of
alkynyl ligands in the optical transition. At 298 K, the
emission max is slightly red-shifted (451 nm) relative
to that observed for the precursor [PMePh3]2[Pt(C6F5)2-
(CtCPh)2] (444 nm) with a lifetime of 342.1 ns, shorter
than that measured for [PMePh3]2[Pt(C6F5)2(CtCPh)2]
(957.8 ns) and indicative of the forbidden nature of the
transition responsible for the radiative decay of the
excited state. In fluid acetone or CH2Cl2 solutions, no
emission is detected, but again intense structured
features are observed upon cooling to 77 K. The emission
maxima at 77 K (445 nm) are identical in both solvents,
suggesting that the IL(π-π*CtCPh) is more evident
3
in the excited state of this complex at low temperature.
Like many cyclometalated platinum complexes, [NBu4]-
[Pt(C6F5)2(bzq)] (6) and the binuclear cationic [(C6F5)2-
(bzq)PtCd(cyclen)](ClO4) (3) are emitters in both solu-
tion and in the solid state (see Table 8 and also Figures
10 and 11). While the room-temperature solid-state
emission of 6 is relatively diffused, the 77 K emission
is slightly blue-shifted and highly structured with
CdC and CdN vibration modes of the bzq ligand (Figure
10). Similar structured, but blue-shifted, emissions are
observed in frozen acetone or CH2Cl2 (10-5-10-3 M)
solutions. In the solid state, the intrinsic lifetime (16.5
µs), the emission, and the small hypochromic shift (298
K 518 nm; 77 K, 514 nm (max), 550, 595 (sh)) are similar
to those reported for [NBu4][PtCl2(bzq)] (298 K, 524 nm;
77 K, 514 (max), 554, 597 (sh))23c and [NBu4][Pt(bzq)-
(CtCR)2] (508-533 nm).22 With reference to earlier
work20,22,23 and the absence of any major solvatochromic
3
shift we assign the emission as mixed IL/3MLCT.
(23) (a) Brooks, J .; Babayan, Y.; Lamansky, S.; Djurovich, P. I.;
Tsyba, I.; Bau, R.; Thompson, M. E. Inorg. Chem. 2002, 41, 3055. (b)
J olliet, P.; Gianini, M.; von Zelewsky, A.; Bernardinelly, G.; Stoeckli-
Evans, H. Inorg. Chem. 1996, 35, 4883. (c) Lai, S. W.; Chan, M. C. W.;
Cheung, K. K.; Peng, S. M.; Che, C. M. Organometallics 1999, 18, 3991.

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3973
In contrast to complex 6, the emission spectrum of 3
is also vibrationally resolved even in the solid state at
room temperature with peak maxima at 490 and 518
(560 sh), which are slightly blue-shifted at 77 K (see
Figure 11). In fluid acetone solution, the emission is
weak and unstructured with a maximum at 481 nm but
again becomes highly structured in frozen solution (483,
517, 560 sh). On the basis of these observations, the
only typical structured emission bands associated with
3
mixed MLCT(dπ(Pt)fπ*CtCPh)/3IL(πfπ*CtCPh), and
similar to those seen in the precursor, are observed. For
complex 3, the formation of the Pt-Cd bond clearly
accounts for the substantial blue-shift in the observed
emission in relation to that of the precursor 6 (solid 490
nm in 3 at 298 K vs 518 nm in 6). The presence of the
PtfCd acceptor bond probably stabilizes the HOMO,
increasing the corresponding LUMO-HOMO energy
gap and, hence, increasing the MLCT energy transition.
It is remarkable that in both complexes 2 and 3 the
formation of the PtfCd bond causes a significant
decrease in the lifetime of the emission.
3
3
emission is also assigned as MLCT transitions with -
LC character. The substantial blue-shift (∼1205 cm-1
)
of the emission observed in the solid state for 3 in
relation to that observed in the mononuclear precursor
(77 K, 484 nm in 3 vs 514 nm in 6) is consistent with
the presence of the PtfCd donor-acceptor bond and
in agreement with some degree of charge transfer for
the transition. In this binuclear complex, the Cd2+ ion
drains electron density from the platinum atom, making
the transfer of charge away from the metal a more
energetic process. The PtfCd bond seems to have also
a marked effect on both the lifetime of the emission (7.9
µs in 3 vs 16.5 µs in 6) and the luminescent efficiency
(0.0285 in 3 vs 0.0019 in 6; Kr ) 3.6 × 103 s-1 for 3, Kr
) 0.115 × 103 s-1 for 6).
Exp er im en ta l Section
Gen er a l Com m en ts. Literature methods were used to
prepare the starting materials [NBu4]2[Pt(C6F5)4],24 [NBu4]2-
[Pd(C6F5)4],24 [NBu4]2[Pt(C6Cl5)4],24 [PMePh3]2[Pt(C6F5)2-
(CtCPh)2],13 [NBu4][Pt(C6F5)3(bzq)],10i and [NBu4]2[Pt2(µ-Cl)2-
(C6F5)4].24,25 Cyclen (1,4,7,10-tetraazacyclododecane) was
commercially purchased (Aldrich) and used as delivered. C,
H, and N analyses and mass, IR, and NMR spectra were
performed as described elsewhere. Molar conductances were
carried out on a Philips PW9509 conductimeter in acetone and
dichloromethane solutions (5 × 10-4 M). The optical absorption
spectra were recorded using a Hewlett-Packard 8453 (solution)
spectrophotometer in the visible and near-UV ranges. Lumi-
nescence and excitation spectra were recorded using a Pekin-
Elmer LS 50B luminescence spectrometer with an R928 type
red sensitive photomultiplier and standard calibrated 1000 W
xenon lamp (excitation). Emission lifetime measurements were
performed in the frequency domain with a Fluorolog-3 model
FL3-11 with F1-1029 lifetime emission PMT assembly, using
a 450 W Xe lamp. The solution emission quantum yields were
measured by the Demas and Crosby method,26 using dcm-
pyram [4-(dicyanomethylene)-2-methyl-6-(4-dimethyl-ami-
nostyryl)-4H-pyram] in degassed MeOH as the standard.
Sa fety Note: Perchlorate salts of metal complexes with
organic ligands are potentially explosive. Only small amounts
of material should be prepared, and these should be handled
with great caution.
Con clu sion s
Three novel binuclear Pt-Cd derivatives, 1-3, sta-
bilized by a short PtfCd donor acceptor bond have been
synthesized. In the complex [(C6F5)4PtCd(cyclen)] (1),
the Pt-Cd distance is longer (2.775(1) Å) than those
found in 2 and 3, suggesting that the presence of bulky
C6F5 ligands hinder the closing up of the basic Pt center
to the acidic Cd metal. In fact, substitution of two C6F5
groups for a planar benzoquinolate ligand in complex 3
allows a better approach of the Cd center to the Pt
center (Pt-Cd 2.688(1) Å), although one would expect
lower basic behavior of the monoanionic [Pt(C6F5)2(bzq)]-
fragment than of the dianionic one. On the other hand,
in the complex [(C6F5)2Pt(CtCPh)2Cd(cyclen)] (2) one
of the phenylethynyl ligands of the dianionic entity [cis-
Pt(C6F5)2(CtCPh)2]2- clearly competes with the plati-
num center to interact with the “[Cd(cyclen)]2+” moiety
in such a way that in this complex the Cd center moves
away from the normal to the platinum coordination
plane, being bonded not only to Pt but also to the CR
atom of the acetylenic fragment. Finally, the use of the
dinuclear substrate [NBu4]2[Pt2(µ-Cl)2(C6F5)4] as a build-
ing precursor causes the asymmetric breaking of the
bridging system and the final formation of the dimer
[Pt(C6F5)2Cl(µ-Cl)Cd(cyclen)]2 (4) containing Cd-Cl
bonds.
The optical properties of complexes 1-3 have also
been described. However, the very different electronic
nature of the platinum fragment used makes it, at the
moment, very difficult to establish a clear relationship
between the donor-acceptor PtfCd bond and the
electronic excited states. Thus, it is somewhat surprising
that the visible blue luminescence observed in the
precursor [PMePh3]2[Pt(C6F5)2(CtCPh)2] is clearly lost
for the unsolvated Pt-Cd complex 2, suggesting that
[Cd(cyclen)]2+ acts a quencher. In the solid state at room
temperature, the luminescence of this complex shows
an interesting solvent dependence, which seems to be
related to the existence of channels in the lattice.
However, at low temperature (solid and frozen solution)
Syn th esis of [Cd (cyclen )(MeOH)2](ClO4)2. Cyclen (0.025
g, 0.146 mmol) was added to a MeOH (6 mL) solution of Cd-
(ClO4)2‚6H2O (0.068 g, 0.22 mmol). The initial suspension,
which became a transparent solution after a few minutes, was
refluxed for 1 h. The solution of the complex [Cd(cyclen)-
(MeOH)2](ClO4)2 formed was allowed to reach room tempera-
ture and used in situ.
Syn th esis of [(C6F 5)4P tCd (cyclen )] (1). [NBu4]2[Pt(C6F5)4]
(0.20 g, 0.146 mmol) was added to a MeOH (10 mL) solution
of [Cd(cyclen)(MeOH)2](ClO4)2 (0.146 mmol) prepared in situ.
After a few minutes, the initial suspension became a transpar-
ent solution, from which a white solid precipitated after ∼20
min of stirring. The suspension was stirred for 40 min more,
and then the white solid was filtered off. This solid was washed
with CHCl3 (2 × 3 mL) and n-hexane (5 mL) and vacuum-
dried (1, 56% yield). Anal. Calcd (%) for C32H20F20N4CdPt: C
33.45, H 1.76, N 4.87. Found: C 33.38, H 1.76, N 4.83. IR
(Nujol): ν 773 cm-1 (s; C6F5, X-sensitive vibr.).27 ΛM ) 42
(acetone) Ω-1 cm2 mol-1 1H NMR (HDA, rt): 3.24 (br, 4H,
.
N-H), 3.07 (m, 8H), 2.91 ppm (m, 8H). 19F NMR (HDA, rt):
-109.0 (d, 8F, o-F, J Pt-F ) 526.9 Hz), -162.3 ppm (m, 12F,
(24) Uso´n, R.; Fornie´s, J .; Mart´ınez, F.; Toma´s, M. J . Chem. Soc.,
Dalton Trans. 1980, 888.
(25) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Fandos, R. J . Organomet.
Chem. 1984, 263, 253.
(26) Demas, J . N. G.; Crosby, A. J . Phys. Chem. 1971, 75, 991.
(27) Maslowsky, E., J r. In Vibrational Spectra of Organometallic
Compounds; Wiley: New York, 1977; p 437.

3974 Organometallics, Vol. 23, No. 16, 2004
Fornie´s et al.
(m, 8H, CH2). 19F NMR (HDA, rt): -112.3 (d, 2F, o-F, J Pt-F
407.0 Hz), -115.1 (br, 2F), -162.5 (m, 1F, p-F), -163.3 (m,
2F, m-F), -163.7 ppm (m, 1F, p-F), -165.0 (m, 2F, m-F).
m-F + p-F). Crystals suitable for X-ray diffraction analysis
were obtained by slow diffusion of a layer of n-hexane (20 mL)
into a solution of 25 mg of 1 in 5 mL of Me2CO at 4 °C.
R ea ct ion of [NBu 4]2[P t (C6Cl5)4] w it h [Cd (cyclen )-
(MeOH)2](ClO4)2. [NBu4]2[Pt(C6Cl5)4] (0.25 g, 0.146 mmol) was
added to a MeOH (10 mL) solution of [Cd(cyclen)(MeOH)2]-
(ClO4)2 (0.146 mmol) prepared in situ. After 1 h of stirring the
solution was evaporated to dryness. Treatment of the resulting
)
Syn th esis of [P t(C6F 5)2Cl2Cd (cyclen )]2 (4). [NBu4]2[Pt2-
(µ-Cl)2(C6F5)4] (0.23 g, 0.146 mmol) was added to a MeOH (10
mL) solution of [Cd(cyclen)(MeOH)2](ClO4)2 (0.146 mmol)
prepared in situ. The resulting white suspension was stirred
for 1 h, and then the white solid was filtered off. This solid
was washed with CHCl3 (2 × 3 mL) and n-hexane (5 mL) and
vacuum-dried (4, 29% yield). Anal. Calcd (%) for C40H40F20N4-
Cl4Cd2Pt2: C 27.13, H 2.26, N 6.33. Found: C 27.28, H 2.23,
N 6.27. IR (Nujol): ν 810, 799 cm-1 (s; C6F5, X-sensitive vibr.).27
1H NMR (HDA, rt): 3.50 (br, 4H, N-H), 3.16 (m, 8H), 2.90
i
white residue with PrOH (30 mL) produced a solid that was
filtered and identified as the starting material [NBu4]2[Pt(C6-
Cl5)4].
Rea ction of [NBu 4]2[P d (C6F 5)4] w ith [Cd (cyclen )(Me-
OH)2](ClO4)2. [NBu4]2[Pd(C6F5)4] (0.18 g, 0.146 mmol) was
added to a MeOH (10 mL) solution of [Cd(cyclen)(MeOH)2]-
(ClO4)2 (0.146 mmol) prepared in situ. After 1 h of stirring at
room temperature the solution was evaporated to dryness.
ppm (m, 8H). 19F NMR (HDA, rt): -115.2 (d, 8F, o-F, J Pt-F
)
528.2 Hz), -162.1 ppm (m, 4F, p-F), -163.0 ppm (m, 8F, m-F).
Crystals suitable for X-ray diffraction analysis were obtained
by slow diffusion of a layer of n-hexane (20 mL) into a solution
of 25 mg of 4 in 5 mL of Me2CO at 4 °C.
i
Treatment of the resulting white residue with PrOH (30 mL)
produced a solid that was filtered and identified mostly as the
starting material [NBu4]2[Pd(C6F5)4], along with some small
fractions of decomposition products, which we were not able
to identify.
Syn th esis of [Cd 2(µ-Cl)2(cyclen )2](ClO4)2 (5). (NBu4)Cl
(0.08 g, 0.290 mmol) was added to a MeOH (10 mL) solution
of [Cd(cyclen)(MeOH)2](ClO4)2 (0.290 mmol) prepared in situ,
and the precipitation of a white solid is observed almost
immediately. This white solid was filtered off and vacuum-
dried (5, 52% yield). Anal. Calcd (%) for C16H40Cl4N8O8Cd2: C
Syn th esis of [(C6F 5)2(CtCP h )2P tCd (cyclen )] (2). To a
white suspension of [PMePh3]2[Pt(C6F5)2(CtCPh)2] (0.25 g,
0.194 mmol) in MeOH (60 mL) were added cyclen (0.033 g,
0.194 mmol) and CdClO4‚6H2O (0.081 g, 0.194 mmol) to give
a pale yellow solution. Immediately a very pale yellow solid
started forming. After 15 min of stirring, the pale yellow solid
was filtered (0.076 g). By evaporation to a small volume of the
solvent (∼10 mL) a second fraction was obtained (0.034 g) (44%
yield). Anal. Calcd (%) for C36H30F10N4CdPt: C 42.55, H 2.98,
N 5.51. Found: C 42.34, H 2.74, N 5.33; IR (Nujol): ν 2097
(vs), 2080 (sh) cm-1 (CtC); 766, 758 cm-1 (s; C6F5, X-sensitive
vibr.).27 ΛM ) 3.3 (acetone) Ω-1 cm2 mol-1. 1H NMR (HDA, rt):
aromatics: 7.29 (m, 4H), 7.19 (m, 6H); cyclen ligand: 3.13 (br,
4H, N-H), 2.95 (m, 8H), 2.86 ppm (m, 8H). 19F NMR (HDA,
rt): -116.0 (d, 4F, o-F, J Pt-F ) 348.1 Hz), -166.5 ppm (m, 6F,
p-F + m-F); at 190 K: -115.5 (d, 1F, o-F, J o-F-m-F ) 30 Hz,
1
22.88, H 4.77, N 13.25. Found: C 23.33, H 5.32, N 13.50. H
NMR (DMSO, rt): 2.62 (br, 4H, N-H), 2.49 (m, 16H).
X-r a y Str u ctu r e Deter m in a tion s. Crystal data and other
details of the structure analyses are presented in Table 1.
Crystals were mounted at the end of a quartz fiber. The
radiation used in all cases was graphite-monochromated Mo
KR (λ ) 0.71073 Å).
For 1‚2Me2CO, 3‚0.5MeOH, 4‚2Me2CO, and 5, hemispheres
of X-ray intensity data were collected on a Bruker SMART
APEX diffractometer. An absorption correction was applied on
the basis of 3219, 4477, 3132, and 1696 symmetry equivalent
reflection intensities, respectively. For 2‚2Me2CO, X-ray in-
tensity data were collected with a NONIUS κCCD area-
detector diffractometer. Images were processed using the
DENZO and SCALEPACK suite of programs.28 The absorption
correction was performed using SORTAV.29
The structures, except 2‚2Me2CO, were solved by Patterson
and Fourier methods using the program SHELXS-97.30 The
structure of 2‚2Me2CO was solved using the DIRDIF9231
program. The structures were refined by full-matrix least
squares on F2 with SHELXL-97. All non-hydrogen atoms were
assigned anisotropic displacement parameters and refined
without positional constraints except as noted below. All
hydrogen atoms were constrained to idealized geometries and
assigned isotropic displacement parameters equal to 1.2 times
the Uiso values of their attached parent atoms (1.5 times that
for the methyl hydrogen atoms). In the structure of 2‚2Me2-
CO, two molecules of the crystallization solvent were found
in the asymmetric unit. One of the acetone molecules was
found to be disordered, and to model this molecule, the
O(100)-C(90) distance was constrained to 1.2(0.01) Å, while
the methyl carbon atoms (C(92), C(91)) were constrained to a
distance of 1.50(0.01) of the carbonyl carbon atom C(90). In
the structure of 3‚0.5MeOH, a molecule of MeOH, one of the
solvent molecules used for the preparation of the complex, was
found and refined with partial occupancy of 0.5. The OH
hydrogen atom of the methanol moiety was not added to the
model. In the structures of 2‚2Me2CO, 4‚2Me2CO, and 5, the
J Pt-F ) 422 Hz), -116.0 (d, 1F, o-F, J o-F-m-F ) 30 Hz, J Pt-F
≈
315 Hz), -116.3 (d, 1F, o-F, J o-F-m-F ) 26 Hz, J Pt-F ≈ 315
Hz), -117.5 (d, 1F, o-F, J o-F-m-F ) 26 Hz, J Pt-F ) 420 Hz),
-165.86, -165.97, -166.0 ppm (2p-F + 4m-F). Crystals
suitable for X-ray diffraction analysis were obtained by slow
evaporation of a saturated solution of 2 in Me2CO at 20°C.
Syn th esis of [NBu 4][P t(C6F 5)2(bzq)] (6). A 1,2-dichloro-
ethane (20 mL) solution of [NBu4][Pt(C6F5)3(bzq)] was refluxed
for 3 h. After this time, the solution is allowed to reach room
temperature and was evaporated to dryness and the orange
i
residue treated with PrOH (10 mL) and filtered off, washed
with n-hexane (5 mL), and vacuum-dried (63% yield). Anal.
Calcd (%) for C51H36F10NPt: C 51.80, H 4.64, N 2.94. Found:
C 51.14, H 4.07, N 2.83. IR (Nujol): ν 766, 796 cm-1 (s; C6F5,
X-sensitive vibr.).27 1H NMR (HDA, rt): 7,8-benzoquinolinate
ligand: 7.80 (m, 6H), 8.50 (d, 1H), 8.67 (d, 1H J Pt-H ) 33.6
+
Hz); NBu4 1.00 (t, 12H, CH3), 1.45 (q, 8H, γ-CH2), 1.77 (m,
8H, â-CH2), 3.45 (m, 8H, R-CH2). 19F NMR (HDA, rt): -112.1
(d, 2F, o-F, J Pt-F ) 360.6 Hz), -112.4 (d, 2F, o-F, J Pt-F ) 651.0
Hz), -163.6 (m, 2F, m-F), -166.2 (m, 2F, m-F), -164.5 ppm
(m, 1F, p-F), -167.2 (m, 1F, p-F).
Syn th esis of [(C6F5)2(bzq)P tCd(cyclen )](ClO4) (3). [NBu4]-
[Pt(C6F5)2(bzq)] (0.083 g, 0.087 mmol) was added to a MeOH
(8 mL) solution of [Cd(cyclen)(MeOH)2](ClO4)2 (0.087 mmol)
prepared in situ. After a few minutes, a yellow solid precipi-
tated from the yellow solution. The resulting suspension was
stirred for 1 h, and then the yellow solid was filtered off. This
solid was washed with n-hexane (5 mL) and vacuum-dried (3,
50% yield). Anal. Calcd (%) for C33H28F10N5O4ClCdPt: C 36.28,
H 2.56, N 6.41. Found: C 36.11, H 2.39, N 6.39. IR (Nujol): ν
776, 801 cm-1 (s; C6F5, X-sensitive vibr.).27 ΛM ) 81 (acetone)
(28) Otwinowski Z.; Minor, W. Methods Enzymol. A: Macromol.
Crystallogr. 1997, 276, 307.
(29) Blessing, R. H. Acta Crystallogr., Sect. A 1995, 51, 33.
(30) Sheldrick, G. M. SHELX-97, a program for the refinement of
crystal structures; University of Go¨ttingen, Germany, 1997.
(31) Beursken. P. T.; Beursken, G.; Bosman, W. P.; de Gelser, R.;
Garc´ıa Granda, S.; Gould, R. O.; Smith J . M. M.; Smykalla, C. The
DIRDIF92 program system, Technical Report of the Crystallography
Laboratory; 1992.
Ω-1 cm2 mol-1 1H NMR (HDA, rt): 7,8-benzoquinolinate
.
ligand: 7.83 (m, 6H), 8.80 (d, 1H), 8.95 (d, 1H J Pt-H ) 23.7
Hz); cyclen ligand: 2.26 (br, 4H, NH), 2.42 (m, 8H, CH2), 2.57

Pentafluorophenyl Complexes with a Pt-Cd Bond
Organometallics, Vol. 23, No. 16, 2004 3975
cyclen ring was found to be disordered over two positions. The
disordered sets of atoms were refined with partial occupancy
of 0.70/0.30 for 2‚2Me2CO, 0.75/0.25 for 4‚2Me2CO, and 0.50/
0.50 for 5. For 2‚2Me2CO, common sets of thermal anisotropic
parameters were used for the nitrogen atoms and for the
carbon atoms of the minor component of the disorder. For
4‚2Me2CO, C-C and C-N distances were constrained to
sensible values and common sets of thermal anisotropic
parameters were used for the nitrogen atoms of both compo-
nents and the carbon atoms of the minor component of the
disorder. For 5, the C-C and C-N distances were restrained
to be equal. Full-matrix least-squares refinement of these
models against F2 converged to final residual indices given in
Table 1.
FEDER (Project BQU2002-03997-C02-01, 02), the
Diputacio´n General de Arago´n (Grupos Consolidados),
and the Comunidad de La Rioja (ACPI-2002/08). S.I. and
B.G. thank the Ministerio de Ciencia y Tecnolog´ıa and
the CSIC, respectively, for a grant.
Su p p or tin g In for m a tion Ava ila ble: Listings of atomic
coordinates, bond distances and angles, and thermal param-
eters for 1‚2Me2CO, 2‚2Me2CO, 3‚0.5MeOH, 4‚2Me2CO, and
5. Extended structure of [(C6F5)2Pt(CtCPh)2Cd(cyclen)]‚2CH3-
COCH3 (2‚2CH3COCH3) (Figure 1S) and excitation and emis-
sion spectra of [NBu4]2[Pt(C6F5)4] in the solid state at 77 K
(Figure 2S). This material is available free of charge via the
Internet at http://pubs.acs.org.
Ack n ow led gm en t. Financial support has been ob-
tained from the Ministerio de Ciencia y Tecnolog´ıa and
OM049719W