Synthesis, structural characterization, and photophysical properties of palladium and platinum(II) complexes containing 7,8-benzoquinolinate and various phosphine ligands

Article abstract of DOI:10.1021/ic048272g

A series of mononuclear cyclometalated benzo[h]quinolinate platinum and palladiurn(II) complexes with phosphine ligands, namely, [M(bzq)CIL] (L = PPh₂H, Pt 1, Pd 2; PPh₂C=CPh, Pt 3, Pd 4), [Pt(bzq)(PPh₂H)(PPh₂C=

Full text of DOI:10.1021/ic048272g

Inorg. Chem. 2005, 44, 2443−2453
Synthesis, Structural Characterization, and Photophysical Properties of
Palladium and Platinum(II) Complexes Containing 7,8-Benzoquinolinate
and Various Phosphine Ligands
Alvaro D´ıez,† Juan Fornie´s,*,‡ Ana Garc´ıa,† Elena Lalinde,*,† and M. Teresa Moreno†
Departamento de Qu´ımica-Grupo de S´ıntesis Qu´ımica de La Rioja, UA-CSIC, UniVersidad de La
Rioja, 26006, Logron˜o, Spain, and Departamento de Qu´ımica Inorga´nica, Instituto de Ciencia de
Materiales de Arago´n, UniVersidad de Zaragoza-Consejo Superior de InVestigaciones Cient´ıficas,
50009 Zaragoza, Spain
Received December 9, 2004
A series of mononuclear cyclometalated benzo[h]quinolinate platinum and palladium(II) complexes with phosphine
ligands, namely, [M(bzq)ClL] (L PPh2H, Pt 1, Pd 2; PPh2C CPh, Pt 3, Pd 4), [Pt(bzq)(PPh2H)(PPh2C CPh)]ClO4
5, [Pt(bzq)(PPh2C(Ph) C(H)PPh2)]ClO4 6, and [Pt(bzq)(C CPh)(PPh2C CPh)] (7a, 7b), were synthesized. The
X-ray crystal structures of 1, 6 CH3COCH3 CH3COCH3 have been determined. In 1, the
1/2CH3(CH2)4CH3, and 7b
metalated carbon atom and the P atom are mutually cis, whereas in 7b they are trans located. For complex 6, C
and N are crystallographically indistinguishable. Reaction of [Pt(bzq)( -Cl)]2 with PPh2H and excess of NEt3 leads
to the phosphide-bridge platinum dimer [Pt(bzq)( -PPh2)]2 8 (X-ray). Moderate π−π intermolecular interactions
and no evident Pt Pt interactions are found in 1, 7b, and in 8. All of the complexes exhibit absorption bands at
)
t
t
d
t
t
‚
‚
‚
µ
µ
−
high energy due to the intraligand transitions (1IL π f π*) and absorptions at lower energy which are attributed
to MLCT (5d) π f π* (CΛN) transition. Platinum complexes show strong luminescence in both solid state and
frozen solutions. The influence of the coligands on the photophysics of the platinum complexes has been examined
by absorption and emission spectroscopy.
Introduction
palladium analogue, the Pt(II) complexes benefit from having
higher energy, metal-centered (MC) or ligand-field excited
states that do not serve in deactivation pathways from
intraligand and MLCT emissive states. The strong spin-
orbit coupling of the heavy Pt atom allows for efficient
mixing of the 1MLCT with the 3MLCT and 3ππ excited states
thus leading to high efficiency and long luminescent lifetimes
of the emissive states that are very attractive in materials
science.13-36
The chemistry of Pt(II) and Pd(II) complexes containing
cyclometalated ligands has attracted great interest in recent
years due to their applications in different areas.1-9 In
particular, a significant research effort has focused on the
study of platinum complexes mainly due to the potential
antitumor activity9-12 of some of these complexes and their
interesting photophysical properties. Compared with the
* Corresponding authors. E-mail: elena.lalinde@dq.unirioja.es (E.L.);
forniesj@posta.unizar.es (J.F.).
(10) Ranatunge-Bandarage, P. R. R.; Duffy, N. N.; Johnson, S. J.; Simpson,
J. Organometallics 1994, 13, 511.
(11) Navarro-Ranninger, C.; Lo´pez Solera, I.; Gonza´lez, V. M.; Pe´rez, J.
M.; Alvarez-Valdes, A.; Mart´ın, A.; Raithby, P. R.; Masaguer, J. R.;
Alonso, C. Inorg. Chem. 1996, 35, 5181.
(12) Headford, C. E.; Mason, R.; Ranatunge-Bandarage, P. R. R.; Robinson,
B. H.; Simpson, J. J. Chem. Soc., Chem. Commun. 1990, 601.
(13) Chan, C. W.; Cheng, L. K.; Che, C. M. Coord. Chem. ReV. 1994,
132, 87.
(14) Craig, C. A.; Garces, F. O.; Watts, R. J.; Palmans, R.; Frank, A. J.
Coord. Chem. ReV. 1990, 97, 193.
† Universidad de La Rioja, UA-CSIC.
‡ Universidad de Zaragoza-CSIC.
(1) Espinet, P.; Esteruelas, M. A.; Oro, L. A.; Serrano, J. L.; Sola, E.
Coord. Chem. ReV. 1992, 117, 215.
(2) Omae, I. Coord. Chem. ReV. 1988, 83, 137.
(3) Omae, I. Applications of Organometallic Compounds; Wiley:
Chichester, U.K., 1998.
(4) Ryabov, A. D. Chem. ReV. 1990, 90, 403.
(5) Newkome, G. R.; Puckett, W. E.; Gupta, V. K.; Kiefer, G. E. Chem.
ReV. 1986, 86, 451.
(6) Wild, S. B. Coord. Chem. ReV. 1997, 166, 291.
(7) Spencer, J.; Pfeffer, M. AdV. Organomet. Chem. 1998, 6, 103.
(8) Dupont, J.; Pfeffer, M.; Spencer, J. Eur. J. Inorg. Chem. 2001, 1917.
(9) Hambley, T. Coord. Chem. ReV. 1997, 166, 118.
(15) Brooks, J.; Babayan, Y.; Lamansky, S.; Djuorovich, P. I.; Tsyba, I.;
Bau, R.; Thompson, M. E. Inorg. Chem. 2002, 41, 3055.
(16) Ferna´ndez, S.; Fornie´s, J.; Gil, B.; Go´mez, J.; Lalinde, E. J. Chem.
Soc., Dalton Trans. 2003, 822.
10.1021/ic048272g CCC: $30.25
Published on Web 02/24/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 7, 2005 2443

D´ıez et al.
In addition, the open square-planar geometry of these d8
molecules allows axial nucleophilic attack or intermolecular
Pt‚‚‚Pt stacking, facilitating other deactivating pathways in
these complexes.13,19,20,22,23,27 Furthermore, the influence of
the noncovalent π-π ligand contacts on the photolumines-
cence of these species has many precedents.20-24 It has been
shown that the nature of the ancillary ligands can have a
strong effect on the lowest emitting excited state. In fact,
the lowest energy excited state in these types of complexes
phine ligands, PPh2H and/or PPh2CtCPh. In addition, the
formation of the phosphido-bridged Pt(II) dimer [Pt(bzq)-
(µ-PPh2)]2 is presented. Through ligand modification, the
variations in photophysical properties (electronic absorption
and luminescence) have been analyzed.
Experimental Section
General Procedures. All reactions were carried out under argon
atmosphere, and solvents were dried by standard procedures and
distilled before use. Proton, 13C{1H}, and 31P NMR spectra were
recorded on a Bruker ARX-300 spectrometer with chemical shifts
externally referenced to SiMe4 and 85% H3PO4, working at 300.1
MHz for 1H, at 121.5 MHz for 31P, and at 100.6 MHz for 13C{1H}.
Infrared spectra were recorded with a Perkin-Elmer FT-IR 1000
spectrometer as Nujol mulls between polyethylene sheets, and C,
H, and N analyses were carried out with a Carlo Erba EA1110
CHNS-O microanalyzer. Mass spectra were obtained on a HP-
5989B mass spectrometer (ES technique), and conductivities were
measured in acetone solutions (ca. 5 × 10-4 mol-1) with a Crison
GLP 31 conductimeter. UV-visible spectra were obtained on a
Hewlet Packard 8453 spectrometer. Emission and excitation spectra
were obtained on a Perkin-Elmer luminescence spectrometer LS
50B and on a Jobin-Yvon Horiba Fluorolog 3-11 Tau-3 spectro-
fluorimeter, in which the lifetime measurements were performed
operating in the phosphorimeter mode. The precursors [Pt(bzq)(µ-
3
has been attributed to ligand-centered LC metal-to-ligand
3
3
charge-transfer MLCT, excimeric (ππ*) metal-metal-to-
ligand charge-transfer 3MMLCT (or [dσ* f π*]), and
LL’CT.
Despite considerable advances in this area, few systems
containing phosphine fragments have been studied.29-32,37-39
Recently, we have described the synthesis and properties of
heteroleptic bis(alkynyl)(benzoquinolinate)platinate(II) com-
plexes,16 whose emissions were proposed to arise from mixed
[πCtCR/Pt d/π(bzq) f π*bzq] transitions on the basis of
TD-DFT calculations. On heteroleptic phosphine CΛNPtLX
derivatives, the modification of charge, the electron-donating
or -withdrawing character of the L or X ligand, and solubility
can serve to tune the photophysical properties.
In this paper, we describe the synthesis and characteriza-
tion of heteroleptic platinum and palladium(II) “M(CΛN)”
(CΛN ) 7,8-benzoquinolinate) complexes bearing the phos-
Cl)]2,40 [Pd(bzq)(µ-Cl)]2 (bzqH ) benzo[h]quinoline), and the
41
ligand PPh2CtCPh42 were prepared according to reported proce-
dures. PPh2H and HCtCPh were used as received.
Synthesis of [Pt(bzq)Cl(PPh2H)] (1). PPh2H (84.7 µL, 0.489
mmol) was added to a yellow suspension of [Pt(bzq)(µ-Cl)]2 (0.200
g, 0.245 mmol) in CH2Cl2 (20 mL) and stirred for 1 h. Evaporation
of the solution to a small volume (2 mL) afforded a yellow solid.
Yield: 0.220 g (76%). This was identified by NMR spectroscopy
as 1 with small traces of the other isomer [1H NMR δ 9.23, 8.72
(H2, H9, bzq)]. Crystallization from CHCl3/hexane at -20 °C gave
pure 1 as a microcrystalline yellow solid. Yield: 0.16 g (55%).
Anal. Calcd for C25ClH19NPPt: C, 50.47; H, 3.22; N, 2.35.
Found: C, 49.94; H, 3.06; N, 2.35. MS ES(+): m/z 560 [M -
(17) Jolliet, P.; Gionini, M.; von Zelewsky, A.; Bernardinelly, G.; Stoeckli-
Evans, H. Inorg. Chem. 1996, 35, 4883.
(18) Zheng, G. Y.; Rillema, D. P.; DePriest, J.; Woods, C. Inorg. Chem.
1998, 37, 3588.
(19) Lai, S. W.; Lam, H. W.; Lu, W.; Cheung, K. K.; Che, C. M.
Organometallics 2002, 21, 226.
(20) Lu, W.; Chan, C. W.; Zhu, N.; Che, C. M.; Li, C.; Hui, Z. J. Am.
Chem. Soc. 2004, 126, 7639.
(21) Lu, W.; Chan, M. C. W.; Cheung, K. K.; Che, C. M. Organometallics
2001, 20, 2477.
(22) Lu, W.; Mi, B. X.; Chan, M. C. W.; Hui, Z.; Zhu, N.; Lee, S. T.;
Che, C. M. Chem. Commun. 2002, 206.
(23) Lai, S. W.; Chan, M. C. W.; Cheung, T. C.; Peng, S. M.; Che, C. M.
Inorg. Chem. 1999, 38, 4046.
(24) Lai, S. W.; Chan, M. C. W.; Cheung, K. K.; Che, C. M. Organo-
metallics 1999, 18, 3327.
(25) Song, D.; Wu, Q.; Hook, A.; Kozin, I.; Wang, S. Organometallics
2001, 20, 4683.
(26) Newman, C. P.; Cave, G. W. V.; Wong, M. W.; Errinton, W.; Alcock,
N. W.; Rourke, J. P. J. Chem. Soc., Dalton Trans. 2001, 2678.
(27) Zheng, G. Y.; Rillema, D. P. Inorg. Chem. 1998, 37, 1392.
(28) Jude, H.; Bauer, J. A. K.; Connick, W. B. Inorg. Chem. 2002, 41,
2275.
(29) Cheung, T. C.; Cheung, K. K.; Peng, S. M.; Che, C. M. J. Chem.
Soc., Dalton Trans. 1996, 1645.
(30) DePriest, J.; Zheng, G. Y.; Goswami, N.; Eichhorn, D. M.; Woods,
C.; Rillema, D. P. Inorg. Chem. 2000, 39, 1955.
(31) DePriest, J.; Zheng, G. Y.; Woods, C.; Rillema, D. P.; Mikirova, N.
A.; Zandler, M. E. Inorg. Chim. Acta 1997, 264, 287.
(32) Shi, J. C.; Chao, H. Y.; Fu, W. F.; Peng, S. M.; Che, C. M. J. Chem.
Soc., Dalton Trans. 2000, 3128.
(33) Yam, V. W. W.; Tang, R. P. L.; Wong, K. M. C.; Lu, X. X.; Cheung,
K. K.; Zhu, N. Chem.sEur. J. 2002, 8, 4066.
(34) Neve, F.; Crispini, A.; Campagna, S. Inorg. Chem. 1997, 36, 6150.
(35) Yip, J. H. K.; Suwarno; Vital, J. J. Inorg. Chem. 2000, 39, 3537.
(36) Che, C. M.; Fu, W. F.; Lai, S. W.; Hou, Y. J.; Liu, Y. L. Chem.
Commun. 2003, 118.
1
Cl]+ 100%. IR (cm-1): ν(P-H) 2364 (m); ν(Pt-Cl) 292 (m). H
3
NMR (δ, CDCl3): 9.87 (m, JPt-H ) 26 Hz, H2, bzq), 8.35 (d,
JH-H ) 7.8 Hz, H9, bzq), 7.93 (m, 4H, Ph/bzq), 7.77 (d, JH-H
)
8.7 Hz, bzq), 7.63 (m, 4H, Ph/bzq), 7.44 (m, 6H, Ph/bzq), 7.31
1
2
(m, 1H, Ph/bzq), 6.81 (d, JP-H ) 414 Hz, JPt-H ) 41.3 Hz, 1H,
PPh2H; only one of the signals is seen, the other is overlapped with
the aromatic signals. 31P{1H} NMR (δ, CDCl3): -1.51 (s, JPt-P
1
) 4149 Hz). 31P NMR (δ, CDCl3): -1.28 (d, JP-H ) 414 Hz,
1
1JPt-P ) 4150 Hz). 13C{1H} NMR (δ, CDCl3): 154.8 (s, C10 bzq),
147.8 (s, JPt-C ) 28.3 Hz, C2 bzq), 141.9 (s, JPt-C ) 22.0 Hz,
C13/14 bzq), 138.5 (s, C3/4 (CH) bzq), 138.4 (s, C13/14 bzq), 134.5
(d, 2JC-P ) 11.2 Hz, 3JPt-C ) 31.6 Hz, Cortho PPh2), 134.2 (s, JPt-C
2
2
) 35 Hz, C11/12), 131.5 (d, JC-P ) 9.6 Hz, JPt-C ) 94.9 Hz, C9
3
2
bzq), 131.3 (d, 4JC-P ) 2.5 Hz, Cpara PPh2), 129.7 (d, 4JC-P ) 3.1
Hz, C7 bzq), 129.4 (s, CH bzq), 128.8 (d, JC-P ) 12.5 Hz, Cmeta
3
PPh2), 126.7 (d, JC-P ) 2.0 Hz, 2JPt-C ) 26.4 Hz, C11/12 bzq), 126.3
1
2
(d, JP-C ) 62.3 Hz, JPt-C ) 27.2 Hz, Cipso, PPh2), 123.4 (s, CH
bzq), 122.6 (s, CH bzq), 121.2 (d, JC-P ) 3.8 Hz, JC-Pt ) 25.8
4
3
Hz, C8 bzq).
(37) Minghetti, G.; Doppiu, A.; Stoccoro, S.; Zucca, A.; Cinellu, M. A.;
Manassero, M.; Sansoni, M. Eur. J. Inorg. Chem. 2002, 431.
(38) Meijer, M. D.; Kleij, A. W.; Williams, B. S.; Ellis, D.; Lutz, M.; Spek,
A. L.; van Klink, G. P. M.; van Koten, G. Organometallics 2002, 21,
264.
(39) Sa´nchez, G.; Garc´ıa, J.; Meseguer, D.; Serrano, J. L.; Garc´ıa, L.; Pe´rez,
J.; Lo´pez, G. J. Chem. Soc., Dalton Trans. 2003, 4709.
(40) Pregosin, P. S.; Wombacher, F.; Albinati, A.; Lianza, F. J. Organomet.
Chem. 1991, 418, 249.
(41) Hartwell, G. E.; Lawrence, R. W.; Smas, M. J. J. Chem. Soc., Chem.
Commun. 1970, 912.
(42) Carty, A. J.; Hota, N. K.; Ng, T. W.; Patel, H. A.; O’Connor, T. J.
Can. J. Chem. 1971, 49, 2706.
2444 Inorganic Chemistry, Vol. 44, No. 7, 2005

Palladium and Platinum(II) Complexes
Synthesis of [Pd(bzq)Cl(PPh2H)] (2). PPh2H (216 µL, 1.25
mmol) was added to a pale yellow solution of [Pd(bzq)(µ-Cl)]2
(0.401 g, 0.626 mmol) in CH2Cl2 (20 mL) at 0 °C. The dark-yellow
solution obtained was filtered through Celite and evaporated to
dryness. Treatment of the residue with n-hexane (5 mL) afforded
a pale yellow solid (0.585 g, 92% yield), which contains (NMR
spectroscopy) 2 and traces of other isomer (1H NMR δ 9.91, 9.22,
8.73 bzq). Recrystallization from CHCl3/hexane gave 2 as unique
product. Yield: 0.42 g (66%). Anal. Calcd for C25ClH19NPd: C,
59.31; H, 3.78; N, 2.77. Found: C, 59.31; H, 3.72; N, 2.64. MS
ES(+): m/z 470 [M - Cl]+, 100%. IR (cm-1): ν(P-H) 2341 (m);
ν(Pd-Cl) 278 (m). 1H NMR (δ, CDCl3): 9.66 (s br, H2, bzq), 8.32
(d, 1JH-H ) 7.6 Hz, H9, bzq), 7.95 (m, 4H, Ph/bzq), 7.77 (d, 1JH-H
) 8.6 Hz, bzq), 7.62 (m, 3H, Ph/bzq), 7.43 (m, 7H, Ph/bzq), 7.26
acetone (10 mL), NaClO4‚H2O (0.118 g, 0.841 mmol) and PPh2Ct
CPh (0.096 g, 0.336 mmol) were added. After 1 h of stirring at
room temperature, the solvent was evaporated to dryness and the
residue was treated with CH2Cl2 (20 mL) and filtered through Celite.
The resulting pale yellow solution was removed in vacuo, and the
residue was treated with Et2O (5 mL) to give a yellow solid. The
spectroscopic data indicate the presence mainly of complex 5,
although contaminated with other products [δ 48.7, 45.41 (due to
6a) and other unknown signals]. All attempts to obtain pure 5 from
this solid were unsuccessful since 5 evolves in solution, even at
low temperature, to the mixture of species 6a + 6b. Yield: 0.246
g (83%). ΛM (acetone 5 × 10-4 M): 123 Ω-1 cm2 mol-1. MS
ES(+): m/z 846 [M - ClO4]+, 100%. IR (cm-1): ν(P-H) 2352
(w); ν(CtC) 2172 (s); ν(ClO4-) 1084 (m, br), 624 (s). H NMR
1
1
(m, 1H, bzq, overlapped P-H), 6.62 (d, JP-H ) 376 Hz, PPh2H).
(δ, CDCl3): 8.7 (br), 8.58 (d, JH-H ) 7.7 Hz), 8.48 (d, JH-H ) 7.6
1
3
Only one of the signals (at δ 6.00) for PPh2H doublet can be
Hz), 7.92-7.33 (m, bzq/Ph), 6.12 (dd, JP-H ) 411 Hz, JP-H
)
)
observed; the other is overlapped with the signal at δ 7.26. 31P{1H}
19.5 Hz, PPh2H). 31P{1H} NMR (δ, CDCl3): 6.29 (s, br, 1JP-Pt
NMR (δ, CDCl3): 20.21 (s). 31P NMR (δ, CDCl3): 20.2 (JP-H
)
1792 Hz, PPh2CtCPh trans to C), -5.08 (s, br, 1JP-Pt ) 3798 Hz,
1
376 Hz).
PPh2H trans to N). 31P NMR (δ, CDCl3): 6.46 (s, JP-Pt ) 1784
Hz, PPh2CtCPh trans to C), -4.90 (d, JP-H ) 415 Hz).
Synthesis of [Pt(bzq)Cl(PPh2CtCPh)] (3). A yellow suspen-
sion of [Pt(bzq)(µ-Cl)]2 (0.400 g, 0.489 mmol) in CH2Cl2 (20 mL)
was treated with PPh2CtCPh (0.280 g, 0.979 mmol), and the
resulting orange solution was stirred for 30 min at room temperature.
Evaporation to dryness and treatment of the oily residue with EtOH
gave 3 as a yellow solid. Yield: 0.528 g (78%). Anal. Calcd for
C33ClH23NPPt: C, 57.02; H, 3.33; N, 2.01. Found: C, 56.98; H,
3.30; N, 2.25. MS ES(+): m/z 659 [M - Cl]+, 100%. IR (cm-1):
Synthesis of [Pt(bzq)(PPh2C(Ph)dC(H)PPh2)]ClO4 (6a, 6b).
To a suspension of [Pt(bzq)Cl(PPh2H)] 1 (0.100 g, 0.168 mmol)
in acetone (10 mL), NaClO4‚H2O (0.070 g, 0.504 mmol) and
PPh2CtCPh (0.048 g, 0.168 mmol) were added. The solution was
stirred at room temperature for 3 days, and then, volatiles were
removed in vacuo. The resultant residue was treated with CH2Cl2
(20 mL), filtered through Celite, evaporated to dryness, and treated
with Et2O to give a yellow solid. This was identified by NMR
spectroscopy as a mixture of isomers 6a and 6b (48:52). All
attempts to separate these isomers by repeated crystallizations were
unsuccessful. Yield: 0.121 g (89%). Anal. Calcd for C45ClH34-
NO4P2Pt: C, 57.18; H, 3.62; N, 1.48. Found: C, 57.01; H, 3.97;
N 1.36. ΛM: 127.8 Ω-1 cm2 mol-1. MS ES(+): m/z 845 [M -
ClO4]+, 100%. IR (cm-1): ν(CdC) 1574 (m); ν(ClO4-) 1086 (m,
1
ν(CtC) 2181 (m); ν(Pt-Cl) 296, 286 (w). H NMR (δ, CDCl3):
9.99 (m, H2, bzq), 8.32 (d, JH-H ) 7.4 Hz, H9, bzq), 7.99 (m, 4H,
2
Ph/bzq), 7.76 (dd, JH-H ) 8.5, 3.5 Hz, 1H, bzq), 7.64-7.34 (m,
16H, Ph/bzq). 31P{1H} NMR (δ, CDCl3): -5.06 (s, 1JPt-P ) 4408
2
Hz). 13C{1H} NMR (δ, CDCl3): 155.0 (d, JP-C ) 2.4 Hz, C10,
bzq), 148.4 (s, 2JPt-C ) 27.9 Hz, C2, bzq), 141.8 (s, 2JPt-C ) 24.9
Hz, C13/14, bzq), 140.4 (d, JP-C ) 9.0 Hz, C11/12, bzq), 138.4 (s,
2
1
C3/4, bzq), 133.8 (d, JC-P ) 12.6 Hz, Cortho, PPh2), 133.7, 133.6
br). H NMR (δ, CD3COCD3): 9.11 (st, H2, bzq), 8.87 (st, H2,
4
(bzq), 132.3 (d, Cortho, CtCPh), 131.0 (d, JC-P ) 2.4 Hz, Cpara
,
bzq), 8.80 (d, JH-H ) 8.1 Hz, H9, bzq), 8.75 (d, JH-H ) 8.1 Hz,
H9, bzq), 8.23 (m), 7.96 (m), 7.71 (m), 7.58 (m), 7.40 (m), 7.25
(m, bzq/Ph), 6.80 (d, 3JP-H ) 38.5 Hz), 6.77 (d, 3JP-H ) 38.4 Hz).
PPh2), 130.3 (d, JP-C ) 68 Hz, 2JPt-C ) 30 Hz, Cipso, PPh2), 130.1
(s, Cpara, CtCPh), 129.5 (d, JC-P ) 2.6 Hz, C9, bzq), 129.4 (s,
3
1
bzq), 128.4 (d, JC-P ) 11.7 Hz, Cmeta, PPh2), 128.2 (s, Cmeta
,
31P{1H} NMR (δ, CD3COCD3): 6a, 49.35 (s, br, JPt-P ) 3787
4
3
1
CtCPh), 126.7 (d, JC-P ) 2.4 Hz, JPt-C ) 26 Hz, C12, bzq),
Hz, PPH2C(Ph), P trans to N), 46.28 (s, br, JP-Pt ) 1859 Hz,
123.2 (s), 122.3 (s), 121.2 (s), 121.1 (bzq, Cipso CtCPh), 107.4 (d,
PPh2C(Ph), P trans to C) (molar ratio 6a/6b 48:52); 6b, 65.03 (s,
br, 1JPt-P ) 1886 Hz, PPh2C(Ph), P trans to C), 33.31 (s, br, 1JPt-P
) 3732 Hz, C(H)PPh2, P trans to N). 31P NMR (δ, CD3COCD3):
1
2JC-P ) 17.0 Hz, Câ, PPh2CRtCâPh), 80.2 (d, JC-P ) 113 Hz,
CR, PPh2CRtCâPh).
1
3
6a, 49.4 (d, JPt-P ) 3799 Hz, JP-H ) 50.5 Hz, P trans to N),
Synthesis of [Pd(bzq)Cl(PPh2C≡CPh)] (4). A pale-yellow
suspension of [Pd(bzq)(µ-Cl)]2 (0.250 g, 0.392 mmol) in CH2Cl2
(25 mL) was treated with PPh2CtCPh (0.223 g, 0.784 mmol), and
the mixture was stirred for 2 h at room temperature. The resulting
solution was filtered through Celite, and the solvent was evaporated
to 2 mL to give 4 as a pale yellow solid, which was recrystallized
from CH2Cl2/EtOH. Yield: 0.350 g (74%). Anal. Calcd for
C33ClH23NPPd: C, 65.37; H, 3.82; N, 2.31. Found: C, 65.33; H,
3.73; N, 2.44. MS ES(+): m/z 570 [M - Cl]+, 100%. IR (cm-1):
1
46.32 (s, JPt-P ) 1874 Hz, PPh2C(Ph), P trans to C); 6b, 65.03
1
3
(d, JPt-P ) 1873 Hz, JP-H ) 48.8 Hz, P trans to C), 33.36 (s,
1JP-Pt ) 3739 Hz, PPh2C(Ph), P trans to N).
Synthesis of [Pt(bzq)(CtCPh)(PPh2CtCPh)] (7a, 7b). A
yellow solution of [Pt(bzq)Cl(PPh2CtCPh)] 3 (0.100 g, 0.144
mmol) in CHCl3 (20 mL) was treated with HCtCPh (47.4 µL,
0.432 mmol), CuI (0.005 g, 0.026 mmol), and NEt3 (1 mL) and
stirred for 30 min at room temperature. The orange-red solution
1
i
ν(CtC) 2175 (s); ν(Pd-Cl) 301 (s). H NMR (δ, CDCl3): 9.76
obtained was evaporated and treated with PrOH to give 7a as an
(d, JH-H ) 4.7 Hz, H2, bzq), 8.28 (d, JH-H ) 7.8 Hz, H9, bzq),
8.01 (m, 4H, Ph/bzq), 7.73 (d, JH-H ) 8.6 Hz, 1H, bzq), 7.62-
7.21 (m, 16H, Ph/bzq). 31P{1H} NMR (δ, CDCl3): 13.76. 13C{1H}
orange solid. Starting from the same products and the same molar
ratios but stirring for 10 days at room temperature, a mixture of 7a
and 7b (50:50) was obtained. Crystals of 7b were separated by
crystallization of the mixture in acetone/hexane at -30 °C.
Data for 7a. Yield: 0.102 g (94%). Anal. Calcd for C41H28NPPt:
C, 64.73; H, 3.71; N, 1.84. Found: C, 64.60; H, 4.50; N, 2.03. MS
ES(+): m/z 659.5 [M - CtCPh]+, 100%. IR (cm-1): ν(CtC)
2
NMR (δ, CDCl3): 154.3 (d, JP-C ) 2.9 Hz, C10, bzq), 154.2 (s,
C2, bzq), 149.4 (s, bzq), 142.6 (d, JP-C ) 2.2 Hz, bzq), 137.7 (s,
2
bzq), 134.6-121.2 (bzq/Ph), 108.4 (d, JC-P ) 14.0 Hz, Câ,
1
PPh2CRtCâPh), 81.5 (d, JC-P ) 97 Hz, CR, PPh2CRtCâPh).
1
3
Reaction of [Pt(bzq)Cl(PPh2H)] (1) with PPh2CtCPh. For-
mation of [Pt(bzq)(PPh2H)(PPh2CtCPh)]ClO4 (5). To a yellow
suspension of [Pt(bzq)Cl(PPh2H)] 1 (0.200 g, 0.336 mmol) in
2175 (s), 2104 (m). H NMR (δ, CDCl3): 10.23 (t, JPt-H ) 30
Hz, JH-H ≈ 3.9 Hz, H2), 8.34 (d, JH-H ) 7.6 Hz, H9), 8.02 (m,
bzq/Ph), 7.77 (d, JH-H ) 8.6 Hz, bzq), 7.57-7.00 (bzq, Ph). 31P{1H}
Inorganic Chemistry, Vol. 44, No. 7, 2005 2445

D´ıez et al.
Table 1. Crystallographic Data for 1, 6‚CH3COCH3‚1/2CH3(CH2)4CH3, 7b‚CH3COCH3, and 8
1
6‚CH3COCH3‚1/2CH3(CH2)4CH3
7b‚CH3COCH3
8
empirical formula
Fw
C25H19ClNPPt
594.92
C51H47ClNO5P2Pt
1046.38
C44H34NOPPt
818.78
C50H36N2P2Pt2
1116.93
T (K)
293(2)
173(1)
173(1)
293(2)
cryst syst, space group
a (Å)
b (Å)
c (Å)
monoclinic, P21/n
12.5956(3)
10.0448(2)
17.7985(3)
90
110.4890(10)
90
2109.42(7)
4
monoclinic, P21/n
15.5499(2)
14.5206(2)
20.9079(4)
90
110.6080(10)
90
4418.79(12)
4
triclinic, P1h
8.7368(2)
13.2354(3)
16.5095(5)
72.1340(10)
84.2960(10)
75.8270(10)
1761.10(8)
2
triclinic, P1h
8.9636(2)
10.7454(2)
17.8301(3)
103.6040(10)
103.9800(10)
100.4650(10)
951.87(4)
1
R (deg)
â (deg)
γ (deg)
vol (Å3)
Z
D
calcd (Mg/m3)
1.873
6.866
1.573
3.358
1.544
4.064
1.948
7.465
abs coeff (mm-1
)
F(000)
1144
2100
812
536
θ range for data collection (deg)
no. of data/restraints/params
goodness-of-fit on F2a
3.17-27.88
5020/0/266
0.893
R1 ) 0.0296
wR2 ) 0.0617
R1 ) 0.0494
wR2 ) 0.0669
1.664 and -1.047
3.42-26.02
8686/0/553
1.006
R1 ) 0.0450
wR2 ) 0.0821
R1 ) 0.0850
wR2 ) 0.0928
1.476 and -0.652
1.78-27.90
8365/0/435
1.045
R1 ) 0.0351
wR2 ) 0.0754
R1 ) 0.0467
wR2 ) 0.0793
1.958 and -1.681
2.40-27.91
4513/0/253
1.040
R1 ) 0.0207
wR2 ) 0.0471
R1 ) 0.0228
wR2 ) 0.0480
0.864 and -1.116
final R indices [I > 2σ(I)]a
R indices (all data)a
largest diff peak and hole (e Å-3
)
2
2
2
2
2
a R1 ) ∑(|Fo| - |Fc|)/|Fo|; wR2 ) [∑w(Fo - Fc )2/∑wFo ]1/2; goodness-of-fit ) ∑w(Fo - Fc )2/(Nobs - Nparam)]; w ) [σ2(Fo) + (g1P)2 + g2P]-1; P
2
2
) [max(Fo ; 0) + 2Fc ]/3.
1
NMR (δ, CDCl3): -8.0 (s, JPt-P ) 4127 Hz). 13C{1H} NMR (δ,
CD3COCD3): 161.6 (d, 2JP-C ) 6.8 Hz, C10, bzq), 157.1 (s br, C2,
bzq), 151.1 (s, bzq), 144.4 (s, bzq), 139.0 (s, bzq), 135.4-121.0
(bzq/Ph/CR CtCPh), 107.7 (s, Câ, CtCPh), 107.2 (d, 2JC-P ) 16.7
correction at this point for complex 8. For the rest of complexes,
the absorption correction was performed using SORTAV.44 All the
structures were solved by Patterson and Fourier methods using the
DIRDIF92 program45 and refined by full-matrix least squares on
F2 with SHELXL-97.46 All non-hydrogen atoms were assigned
anisotropic displacement parameters, and all hydrogen atoms were
constrained to idealized geometries fixing isotropic displacement
parameters of 1.2 times the Uiso value of their attached carbon for
the phenyl and CH2 hydrogens and 1.5 for the methyl groups. To
establish the identities of the C and N atoms of the 7,8-
benzoquinoline ligand, each structure (except 8) was refined in three
different ways (with the identities of the C and N in one position,
with the element types reversed, and with 50/50 hybrid scattering
factor at each of the affected atomics sites). Examination of the
∆MSDA values for bonds involving these atoms revealed the
correct assignments47,48 (Supporting Information). For complexes
1, 6, and 7b, some residual peaks higher than 1 e Å-3 were observed
close to their respective platinum atoms but with no chemical
meaning.
1
Hz, Câ, PPh2CR≡CâPh), 80.7 (d, JC-P ) 109 Hz, CR, PPh2CR≡
CâPh).
Data for 7b. Signals obtained from the mixture 7a + 7b. 31P{1H}
NMR (δ, CDCl3): 3.75 (s, JPt-P ) 1788 Hz). 1H NMR (δ,
1
CDCl3): 9.47, 9.23, 9.05, 8.74 (bzq). The rest of signals overlap
with those of 7a.
Synthesis of [Pt(bzq)(µ-PPh2)]2 (8). Method a. To a yellow
suspension of [Pt(bzq)(µ-Cl)]2 (0.100 g, 0.122 mmol) in acetone
(15 mL), PPh2H (42.0 µL, 0.245 mmol) and NEt3 (1 mL) were
added. After 30 min of stirring at room temperature, the yellow
solid was filtered and washed with acetone (4 × 2 mL) and
identified as 8. Yield: 0.118 g (86%).
Method b. To a yellow suspension of [Pt(bzq)Cl(PPh2H)] 1
(0.254 g, 0.426 mmol) in a mixture 1:1 of CH2Cl2/acetone (20 mL)
was added K2CO3 (0.088 g, 0.640 mmol). After 5 h of stirring at
room temperature, the yellow solid formed was recovered by
filtration, washed with distilled water, and dried under reduced
pressure (0.236 g, 96% yield). Anal. Calcd for C50H36N2P2Pt2‚
2H2O: C, 52.08; H, 3.50; N, 2.43. Found: C, 51.92; H, 2.93; N,
2.80. Its insolubility in all common solvent precluded its spectro-
scopic characterization.
Results and Discussion
Synthesis and Characterization. The synthesis of the
platinum and palladium complexes is shown in Scheme 1.
Bridge cleavage of [M(bzq)(µ-Cl)]2 (M ) Pt, Pd; bzqH )
benzoquinoline ligand) with 2 equiv of PPh2H or PPh2CtCPh
in CH2Cl2 affords the neutral mononuclear yellow complexes
X-ray Crystallography. Crystal data and other details of the
structure analyses are presented in Table 1. Yellow (1, 6, 7b)
crystals were obtained by slow diffusion of n-hexane into acetone
(6, 7 at -30 °C) or chloroform (1 at room temperature) solution of
the complexes, while yellow crystals of 8 were obtained by slow
reaction of complex 1 with NEt3 in a CH2Cl2 solution at room
temperature. For complex 6, one molecule of acetone and half a
molecule of n-hexane was found in the asymmetric unit, and for
complex 7b, one molecule of acetone was found in the asymmetric
unit. X-ray intensity data were collected with a NONIUS κCCD
area-detector diffractometer using graphite-monochromated Mo KR
radiation. Images were processed using the DENZO and
SCALEPACK suite of programs,43 carrying out the absorption
(43) Otwinowski, Z.; Minor, W. In Methods in Enzymology; Carter, C. V.,
Jr., Sweet, R. M., Eds.; Academic Press: New York, 1997; Vol. 276A,
p 307.
(44) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(45) Beursken, P. T.; Beursken, G.; Bosman, W. P.; de Gelder, R.; Garc´ıa-
Granda, S.; Gould, R. O.; Smith, J. M. M.; Smykalla, C. The
DIRDIF92 Program System; Technical Report of the Crystallography
Laboratory; University of Nijmegen: Nijmegen, The Netherlands,
1992.
(46) Sheldrick, G. M. SHELX-97, a Program for the Refinement of Crystal
Structures; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(47) Hirshfeld, F. L. Acta Crystallogr., Sect. A 1976, 32, 239.
(48) Displacement parameter analysis was done using the program
PLATON: Speck, A. L. Acta Crystallogr., Sect. A 1990, 46, C34.
2446 Inorganic Chemistry, Vol. 44, No. 7, 2005

Palladium and Platinum(II) Complexes
Scheme 1
Chart 1
[M(bzq)Cl(L)] (L ) PPh2H, M ) Pt 1, Pd 2; L ) PPh2Ct
CPh, M ) Pt 3, Pd 4). Their spectroscopic data and the
structural analysis of complex 1 (see below) confirm the
formation of the isomers with the nitrogen and the P atoms
in trans position. The preferential formation of this isomer
is in agreement with the so-called transphobia effect49,50 and
the antisymbiotic effect,51 which show the tendency to locate
2
the softer ligands (Csp and P) in cis position. Infrared spectra
show the characteristic absorption of the phosphine ligands,
ν(P-H) vibration (2364 cm-1 1, 2341 cm-1 2) and a weak
absorption in the expected range for the P-coordinated
alkynylphosphine (2181 cm-1 3, 2175 cm-1 4). The 31P{1H}
NMR spectra of 1-4 contain one sharp singlet, with 195Pt
satellites in 1 and 3. In accordance with the isomer shown
In complex 1, the value of 3JPt-H2 (26 Hz) is similar to those
observed in related Pt(II) complexes.15-17 In addition,
complexes 1 and 2 display the P-H resonance as a doublet,
with Pt satellites in the case of 1, in the expected region (δ
6.81 1, 6.62 2). The 13C{1H} NMR spectra of 1, 3, and 4
show the expected resonances for the bzq ligand in addition
to those of PPh2H or PPh2CtCPh ligands. Some of the
signals are tentatively assigned on the basis of the 195Pt-
13C (1, 3) and 31P-13C coupling constants and according to
the signals observed in related Pt(II) complexes15-17(see
Experimental Section). In complexes 3 and 4, the CR and
Câ acetylenic carbons appear (δ CR/Câ 80.2/107.4 3, 81.5/
108.4 4) as doublets, with coupling constants JP-C of 113
and 17 Hz (3), 97 and 14 Hz (4), respectively. Although
both signals are upfield-shifted with regard to those of the
free PPh2CtCPh (δ CR /Câ 86.5/109.4), the chemical shift
difference [∆δ(Câ - CR) 27.2 3, 26.9 4], which has been
previously related to the triple-bond polarization,52,53 is
slightly higher than in PPh2CtCPh.
1
in Scheme 1, the high value of the JPt-P (4149 Hz 1, 4408
Hz 3) is consistent with the trans disposition of the phosphine
ligands with the N atom, and it is in agreement with the
lower trans influence of nitrogen in relation to orthometalated
carbon. Similar values have been reported in related com-
plexes with bzq and phosphine ligands.30,40 As expected, the
proton coupled 31P NMR spectra of 1 and 2 exhibit a doublet
due to phosphorus-hydrogen coupling (1JP-H is 414 Hz 1,
376 Hz 2) with 195Pt satellites. The proton NMR spectra (see
Chart 1 for labeling) exhibit two characteristic15-17 low-field
signals in the range 9.99-9.66 (ppm) and 8.35-8.28 (ppm)
due to the H2 and H9 protons of the bzq ligand, respectively.
(49) Vicente, J.; Abad, J. A.; Mart´ınez-Viviente, E.; Jones, P. G. Organo-
metallics 2002, 21, 4454.
(50) Vicente, J.; Arcas, J. A.; Farkland, A. D.; Ram´ırez de Arellano, M.
C. Chem.sEur. J. 1999, 5, 3066.
We also decided to examine the preparation of a platinum
complex containing the bzq ligand and two different
(51) Pearson, R. G. Inorg. Chem. 1973, 2, 163.
Inorganic Chemistry, Vol. 44, No. 7, 2005 2447

D´ıez et al.
Scheme 2
coordinated phosphorus ligands, PPh2H and PPh2CtCPh.
This kind of system could be of interest, taking into account
the precedents on P-H activation bond by addition of a
secondary phosphine to a coordinated alkynylphosphine.54,55
Treatment of [Pt(bzq)Cl(PPh2CtCPh)] 3 with 1 equiv of
PPh2H in CH2Cl2 immediately resulted in the exchange of
phosphine ligands yielding complex [Pt(bzq)Cl(PPh2H)] 1.
When the reaction was carried out in the presence of NaClO4,
an equimolar mixture of 1 and of the isomers 6a and 6b
was obtained, and in the presence of a stoichiometric amount
of AgClO4, a mixture of species (which includes in this case
the complex 5) was also obtained. As an alternative route,
we used [Pt(bzq)Cl(PPh2H)] 1 as precursor (Scheme 1). Thus,
treatment of 1 with PPh2CtCPh in the presence of an excess
of NaClO4 gave a pale yellow solid identified as [Pt(bzq)-
(PPh2H)(PPh2CtCPh)](ClO4) 5, contaminated with small
amounts of 6a and small amounts of other unknown species.
Attempts to purify 5 by recrystallization in several solvents
were unsuccessful, since this complex 5 evolves in solution,
even at low temperature, to the asymmetric diphosphine
complex [Pt(bzq)(PPh2C(Ph)dC(H)PPh2)]ClO4 6. In fact, the
synthetic strategy for making complex 6 involves the
prolongated reaction of 1 with PPh2CtCPh at room tem-
perature in the presence of NaClO4 (excess) for 3 days.
Complex 6 was obtained as a pale yellow solid in high yield
(90%) and identified by NMR spectroscopy as an equi-
molecular mixture of isomers 6a and 6b of the cis-
1,2-diphosphinoalk-1-ene complex [Pt(bzq)(PPh2C(Ph)d
C(H)PPh2)]ClO4 6. Formally, 6 is generated by addition of
a P-H bond to the coordinated PPh2CtCPh ligand and has
been confirmed by an X-ray diffraction study.
Both complexes (5 and 6) behave as 1:1 electrolytes,56
and 6 shows the molecular peak [M - ClO4]+ as the parent
peak. Their spectroscopic data are very different. The most
remarkable fact is the absence of the ν(P-H) and ν(CtC)
absorptions in the IR spectrum of 6, which are in the expected
range in complex 5 (2352 and 2172 cm-1). In 6, a medium
band at ca. 1574 cm-1 was in the expected range for the
ν(CdC) stretch from the diphosphine-alkene. The presence
of the chelated diphosphine is clearly inferred from the
31P{1H} NMR spectra. Thus, complex 5 shows two broad
singlets at δ 6.29 and -5.08 flanked by platinum satellites.
The low-frequency signal (δ -5.08), which exhibits a large
195Pt-P coupling constant of 3798 Hz and splits into a
doublet due to P-H coupling (415 Hz) under off conditions,
is attributed to the phosphorus atom of the PPh2H ligand
trans to N. The signal at δ 6.29 assigned to the PPh2CtCPh
ligand shows smaller 1JPt-P coupling (1792 Hz) in accordance
with the higher trans influence of the metalated carbon.
However, the 31P{1H} NMR spectrum (CD3COCD3) of 6
exhibits two pairs of broad singlet signals with platinum
satellites in the low-field region indicating the presence of a
mixture of two isomers (6a and 6b) in a ca. molar ratio of
48:52, which cannot be separated by crystallization proce-
dures. A similar mixture of isomers is observed even in
microcrystalline samples obtained from slow crystallization
of acetone/n-hexane at low temperature. The assignment of
each signal, shown in Scheme 2, was made on the basis of
their coupling constants, their intensity ratio, and the analysis
of their 31P NMR spectrum, which shows that the signals at
δ 65.03 and 49.35 split into doublet resonances by P-H
coupling (3JP-H ∼ 50 Hz) being therefore attributed to
phosphorus atoms trans to the vinylic proton in each isomer.
The proton spectra of 5 and 6 are also different. Whereas
complex 5 shows a doublet of doublets centered at δ 6.12
(1JP-H 411 Hz, JP-H 19.5 Hz) due to the P-H proton, the
3
1H NMR spectrum of 6 indicates the presence of both
isomers 6a and 6b (∼1:1), exhibiting two doublet resonances
of similar intensity at δ 6.80 and 6.77 (3JP-H 38.5, 38.4 Hz)
assigned to each vinyl proton on each isomer.
Alkynyl complexes are often obtained by a CuI-catalyzed
chloride-to-alkyne metathesis.22,57-59 With the aim of incor-
porating acetylide units to modulate the luminescent proper-
ties, we have examined the reaction of [Pt(bzq)Cl(PPh2Ct
CPh)] 3 with a mixture of HCtCPh, NEt3, and CuI in CHCl3
at room temperature (see Experimental Section). With a short
time of reaction (30 min), the reaction takes place initially
with retention of the geometry of the precursors affording
the alkynyl derivative [Pt(bzq)(CtCPh)(PPh2CtCPh)] 7a
(P trans to N). However, monitoring of the reaction for longer
time indicates the slow isomerization of 7a to 7b yielding a
final mixture of ca.1:1 molar ratio after 10 days of stirring.
The identity of 7a has been confirmed by satisfactory
analyses, H, 31P{1H}, and 13C{1H} NMR spectroscopies,
1
IR, and ES(+) MS, and for isomer 7b, X-ray crystallography
(see below) on a suitable crystal obtained from the mixture
7a + 7b dissolved in CH3COCH3 and layered with hexane
at -30 °C. The IR spectrum of 7a confirms the presence of
P-coordinated PPh2CtCPh [ν(CtC) 2175 cm-1] and ter-
(52) Carty, A. J. Pure Appl. Chem. 1982, 54, 113.
(53) Louattani, E.; Lledo´s, A.; Suades, J.; Alvarez-Larena, A.; Piniella, J.
F. Organometallics 1995, 14, 1053.
(54) Carty, A. J.; Johnson, D. K.; Jacobson, S. E. J. Am. Chem. Soc. 1979,
101, 5612.
(55) Johnson, D. K.; Rukachaisirikul, T.; Sun, Y.; Taylor, N. J.; Canty, A.
J.; Carty, A. J. Inorg. Chem. 1993, 32, 5544.
(56) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.
(57) Janka, M.; Anderson, G. K.; Rath, N. P. Organometallics 2004, 23,
4382.
(58) D’Amato, R.; Fratoddi, I.; Cappotto, A.; Altamura, P.; Delfini, M.;
Bianchetti, C.; Bolasco, A.; Polzonetti, G.; Russo, M. V. Organo-
metallics 2004, 23, 2860.
(59) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N. Synthesis
1980, 627.
2448 Inorganic Chemistry, Vol. 44, No. 7, 2005

Palladium and Platinum(II) Complexes
Table 2. Selected Bond [Å] and Angles (deg) for [Pt(bzq)Cl(PPh2H)] 1
Table 5. Selected Bond [Å] and Angles (deg) for [Pt(bzq)(µ-PPh2)]2 8
Pt(1)-N(1)
Pt(1)-C(1)
2.090(4)
2.014(5)
Pt(1)-P(1)
Pt(1)-Cl(1)
2.2097(12)
2.3869(12)
Pt(1)-N(1)
Pt(1)-C(1)
Pt‚‚‚Pt
2.091(3)
2.092(3)
3.601
Pt(1)-P(1a)
Pt(1)-P(1)
2.2982(8)
2.3108(8)
N(1)-Pt(1)-C(1)
N(1)-Pt(1)-P(1)
C(1)-Pt(1)-Cl(1)
N(1)-Pt(1)-Cl(1)
C(1)-Pt(1)-P(1)
82.33(19)
P(1)-Pt(1)-Cl(1)
C(14)-P(1)-C(20)
C(14)-P(1)-H(1)
C(20)-P(1)-H(1)
89.37(5)
106.6(2)
101(2)
177.56(11)
174.33(15)
92.15(12)
96.11(15)
N(1)-Pt(1)-C(1)
N(1)-Pt(1)-P(1)
C(1)-Pt(1)-P(1a)
Pt(1a)-P(1)-Pt(1)
80.01(12)
C(1)-Pt(1)-P(1)
N(1)-Pt(1)-P(1a)
P(1a)-Pt(1)-P(1)
173.85(8)
175.27(8)
77.25(3)
101.13(9)
102.07(9)
102.75(3)
100(2)
a Symmetry transformations used to generate equivalent atoms are #1
-x, -y + 2, -z.
Table 3. Selected Bond [Å] and Angles (deg) for
[Pt(bzq)(PPh2C(Ph)dC(H)PPh2]ClO4‚CH3COCH3‚1/2CH3(CH2)4CH3
a
6‚CH3COCH3‚1/2CH3(CH2)4CH3
Pt(1)-N(1a)
Pt(1)-C(43a)
P(2)-C(2)
2.099(5)
2.084(5)
1.816(6)
1.818(6)
Pt(1)-P(1)
Pt(1)-P(2)
C(1)-C(2)
C(2)-H(2)
2.2598(15)
2.2672(15)
1.338(7)
0.9300
P(1)-C(1)
N(1a)-Pt(1)-C(43a)
N(1a)-Pt(1)-P(2)
C(43a)-Pt(1)-P(1)
P(2)-C(2)-C(1)
P(2)-C(2)-C(1)
P(1)-C(1)-C(3)
C(2)-C(1)-P(1)
C(2)-C(1)-C(3)
80.01(19)
P(1)-Pt(1)-P(2)
Pt(1)-P(2)-C(2)
Pt(1)-P(1)-C(1)
P(1)-C(1)-C(2)
C(2)-C(1)-P(1)
P(2)-C(2)-H(2)
H(2)-C(2)-C(1)
85.18(5)
107.99(19)
110.03(18)
116.2(4)
116.2(4)
119.8
98.74(13)
96.17(14)
120.4(4)
120.4(4)
120.5(4)
116.2(4)
123.0(5)
119.8
a Symmetry transformations used to generate equivalent atoms are #1
-x, -y, -z; #2 x - 1/2, -y + 1/2, z - 1/2; #3 x + 1/2, -y + 1/2, z + 1/2;
#4 -x + 3/2, y + 1/2, -z + 1/2; #5 -x + 3/2, y - 1/2, -z + 1/2.
Table 4. Selected Bond [Å] and Angles (deg) for
[Pt(bzq)(CtCPh)(PPh2CtCPh)]‚CH3COCH3 7b‚CH3COCH3
Pt(1)-C(1)
Pt(1)-C(31)
P(2)-N(1)
1.965(4)
2.061(4)
2.111(3)
Pt(1)-P(1)
C(1)-C(2)
2.3162(10)
1.203(6)
C(1)-Pt(1)-C(31)
C(1)-Pt(1)-N(1)
C(31)-Pt(1)-N(1)
90.34(15)
169.27(14)
79.88(14)
C(1)-Pt(1)-P(1)
C(31)-Pt(1)-P(1)
N(1)-Pt(1)-P(1)
86.11(11)
173.86(11)
104.01(9)
minal CtCPh [ν(CtC) 2104 cm-1] ligands, respectively.
The most remarkable difference between the isomers 7a and
7b is seen in the 31P{1H} NMR spectra. A singlet at δ -8.0
is due to 7a (1JPt-P 4127 Hz), whereas the singlet at δ 3.75
(1JPt-P 1788 Hz), observed in the mixture of both species in
solution, is attributed to 7b.
The dinuclear phosphido-bridge complex [Pt(bzq)(µ-
PPh2)]2 8 is obtained in a single step by treatment of
[Pt(bzq)(µ-Cl)]2 with 2 equiv of PPh2H in the presence of
excess of NEt3 or alternatively, as is shown in Scheme 1,
by treatment of [Pt(bzq)Cl(PPh2H)] 1 in CH2Cl2 with excess
of K2CO3 as deprotonating agent (see Experimental Section).
Its extreme insolubility precluded its spectroscopic charac-
terization. However, the molecular structure of 8 could be
determined by X-ray diffraction (see below) on crystals
obtained as described in the Experimental Section.
X-ray Crystal Structures. Molecular structures of 1, 6,
7b, and 8 were confirmed by X-ray diffraction. Selected bond
distances and angles are shown in Tables 2-5, and the
perspective drawing of the complexes are depicted in Figures
1-4. The structural analyses of 1 confirms the relative cis
position of the metalated carbon atom and the P atom of the
PPh2H ligand. The preference for this cis arrangement (C,
P), which has been previously observed in other mononuclear
cyclometalated phosphine platinum complexes,38,50 is prob-
ably associated with the destabilization inherent to isomers
Figure 1. (a) Molecular structure of [Pt(bzq)Cl(PPh2H)] 1. Ellipsoids are
drawn at the 50% probability. (b) Packing diagram for 1.
placing ligands with high trans influence in mutually trans
position. In fact, the driving force behind the isomerization
of 7a to 7b can be rationalized on the same basis. Initial
alkynyl-chloride exchange on 3 produces 7a as the kinetic
product but, due to the fact that the CtCPh group displays
a higher trans influence than the PPh2CtCPh ligand, this
isomer 7a evolves slowly, in this case, to a final equimolar
mixture of 7a and 7b.
As is observed in Figure 2, in complex 7b the P atom of
the PPh2CtCPh ligand is now located trans to the metalated
carbon atom. In complex 6 (Figure 3), which confirms the
formation of the new diphosphine-alkene ligand, the C and
N are found to be crystallographically indistinguishable (see
Experimental Section and Supporting Information). Both
atoms randomly occupy the same site through the crystal
lattice giving rise to averaged Pt-C and Pt-N bond lengths.
The binuclear complex 8 is stabilized by a double phosphide
bridge (Figure 4) and crystallizes as the more symmetrical
antiisomer as observed previously for other µ-phosphide
dimers.60-65
(60) Falvello, L. R.; Fornie´s, J.; Go´mez, J.; Lalinde, E.; Mart´ın, A.; Moreno,
M. T.; Sacrista´n, J. Chem.sEur. J. 1999, 5, 474.
Inorganic Chemistry, Vol. 44, No. 7, 2005 2449

D´ıez et al.
Figure 2. (a) Molecular structure of [Pt(bzq)(CtCPh)(PPh2CtCPh)] 7b.
Ellipsoids are drawn at the 50% probability. (b) Packing diagram for 7b.
Figure 4. (a) View of the molecular structure [Pt(bzq)(µ-PPh2)]2 8. (b)
Packing lattice for 8.
Pt-C metalated/Pt-N bond distances in 1 and 7b [2.014(5)/
2.090(4) Å 1; 2.061(4)/2.111(3) Å 7b] are found to vary in
accordance with the trans influence of the two ligands
occupying the other two sites. For complex 6, in which the
C and N atoms are crystallographically indistinguishable
[2.084(5)/2.099(5) Å 6], and for the binuclear bis(µ-phos-
phido) platinum complex 8 [2.092(3)/2.091(3) Å], these
distances are identical within experimental error. By com-
parison, the Pt-C and Pt-N bond distances of the homo-
leptic derivative cis-[Pt(bzq)2] are 1.999(12), 1.976(9)
Å/2.153(8), 2.149(9) Å.17
In 8, the central Pt2P2 core is almost planar, exhibiting
angles at the Pt center [P(1)-Pt(1)-P(1a) 77.25(3)°] and at
the phosphorus atom [Pt(1)-P(1)-Pt(1a) 102.75(3)°] com-
parable to those found in other phosphide-bridge platinum(II)
dimers without metal-metal bonds60-65 (Pt‚‚‚Pt 3.601 Å).
It is noteworthy that the Pt-P bonds trans to Pt-C bond
are longer than Pt-P bonds trans to a Pt-N bond [Pt(1)-
P(1) 2.3162(10) Å 7b vs Pt(1)-P(1) 2.2097(12) Å 1], which
could be attributed, again, to the greater trans influence of
an anionic carbon center over that of a neutral iminic nitrogen
atom.
Figure 3. Molecular structure of the cation in [Pt(bzq)(PPh2C(Ph)d
C(H)PPh2)]ClO4 6. Ellipsoids are drawn at the 50% probability.
In all complexes, the platinum environments are ap-
proximately square planar with the “Pt(C∧N)” moieties
essentially planar and bond parameters comparable to those
observed in related complexes. The narrow NPtC bite angle
[range 79.88(4)-82.33(19)°] is comparable to those found
in other orthoplatinated complexes.15-17,30,31,37,38,66-68 The
(61) Kourkine, I. V.; Chapman, M. B.; Glueck, D. S.; Eichele, K.;
Wasylishen, R. E.; Yap, G. P. A.; Liable-Sands, L. M.; Rheingold,
A. L. Inorg. Chem. 1996, 35, 1478.
(62) Bleeke, J. R.; Rhode, A. M.; Robinson, K. D. Organometallics 1995,
14, 1674.
(63) Brown, M. P.; Buckett, J.; Harding, M. M.; Lynden-Bell, R. M.; Mays,
M. J.; Woulfe, K. W. J. Chem. Soc., Dalton Trans. 1991, 3097.
(64) Leoni, P.; Manetti, S.; Pasquali, M. Inorg. Chem. 1995, 34, 749.
(65) Fornie´s, J.; Fortun˜o, C.; Navarro, R.; Mart´ınez, F.; Welch, A. J. J.
Organomet. Chem. 1990, 394, 643.
In the molecular packing of complex 1 (Figure 1b), the
molecules pack as head-to-tail dimers along the x axes related
by a center of inversion, with the pyridinic and the metalated
rings of both bzq ligands almost eclipsed. However, the
interplanar separation (3.85 Å) is long, implying an almost
2450 Inorganic Chemistry, Vol. 44, No. 7, 2005

Palladium and Platinum(II) Complexes
Table 6. Absorption Data (5 × 10-5 M Solutions) for Complexes 1-4, 6, and 7a
compd
absorption/nm (103 ꢀ/M-1 cm-1
)
1
220 sh (16.4), 240 (63.0), 255 sh (54.1), 305 (27.7), 322 sh (18.5), 395 (4.9), 410 (5.6) (CH2Cl2)
226 (41.2), 255 sh (37.6), 300 (12.8), 319 sh (7.9), 395 (2.13), 405 (2.1) (acetonitrile)
212 (14), 319 sh (2.5), 326 (6.6), 338 sh (4.3), 390 (2.0), 402 (2.4) (acetone)
2
241 (65.3), 278 sh (31.2), 290 (35.8), 310 sh (19.1), 347 (4.8), 362 (5.8), 382 (7.1) (CH2Cl2)
215 sh (47.6), 229 (52.3), 239 sh (44.4), 277 sh (16.4), 289 (18.9), 310 sh (10.2), 345 (4.2), 362 (4.1), 385 (3.6) (acetonitrile)
211 (13.4), 326 (2.9), 345 (2.0), 365 (2.4), 382 (2.7) (acetone)
3
220 sh (15.4), 242 (63.8), 267 (56.3), 306 (30.2), 400 (4.9), 414 (5.3) (CH2Cl2)
218 sh (43.7), 234 (55.7), 257 sh (42.9), 303 (16.2), 400 (2.8) (acetonitrile)
211 (12.7), 326 (6.5), 342 sh (3.9), 375 (1.7), 401 (2.2), 414 (2.3) (acetone)
4
241 (67.3), 274 sh (58.3), 290 sh (42.2), 312 sh (23.2), 345 (7.7), 367 (7.7), 385 (7.8) (CH2Cl2)
234 (58.0), 268 sh (34.4), 290 sh (21.1), 314 sh (9.7), 344 (3.8), 364 (3.2), 383 (3.2) (acetonitrile)
211 (11.5), 319 (2.0), 327 (4.7), 345 (3.2), 365 (2.7), 387 (2.7) (acetone)
6
258 (60.1), 287 (41.1), 298 (39.0), 343 (4.34), 382 (4.34), 403 (4.7) (CH2Cl2)
327 (8.3), 341 sh (4.9), 380 (4.2), 396 (4.5) (acetone)
198 (58.0), 213 (67.3), 253 (63.1), 283 (40.3), 293 (37.9), 340 (4.1), 380 (4.1), 400 (4.1) (acetonitrile)
220 sh (15.8), 242 (63.1), 270 (56.3), 306 sh (30.5), 347 sh (17.7), 380 sh (5.1), 425 (5.0) (CH2Cl2)
212 (68.1), 240 (70.4), 265 (62.3), 310 (33.6), 333 (25.0), 346 (21.5), 380 (7.7), 420 (4.7) (acetonitrile)
211 (12.6), 319 (5.4), 333 (13.8), 347 sh (11.8), 380 (3.8), 420 (2.7) (acetone)
7a
negligible π-π interaction.20-24 In complex 7b, the mol-
ecules are also packed in dimers along the x axes through
π‚‚‚π interactions between the aromatic benzoquinolate rings,
which are parallel and displaced ca. 4 Å (defined as the
distance between the centers of the pyridinic and cyclo-
metalated rings of related bzq ligands) (Figure 2b). In this
complex, there is a close interaction between the piridinic
and central fused rings (3.56 Å) but a large Pt‚‚‚Pt separation
of 7.233 Å. The crystal packing of the dimeric complex 8 is
shown in Figure 4b. The presence of two bzq ligands in each
molecule facilitates the existence of π‚‚‚π stacking interac-
tions between different molecules of adjacent columns
running along the x axes, yielding layers. In this case, the
bzq ligands of the adjacent molecules of different columns
are also parallel and slightly displaced (3.60 Å, defined as
above). The pyridinic and the central rings are almost
eclipsed but with a very weak intermolecular π-stacking
(∼3.75 Å).
(CH2Cl2, range 380-425 nm, ꢀ (4.2-7.8) × 103 M-1 cm-1)
which are tentatively assigned as metal-to-ligand charge-
transfer transitions from the dπ filled metal orbitals to a
vacant π*(CΛN) orbital (MLCT) [(d) π f π*(CΛN)] in
agreement with previous assignments in analogous platinum
and palladium(II) complexes based on cyclometalated CΛN
aromatic rings,14,17,22,27,30,31,68,69 These low-energy bands do
not exhibit a remarkable solvatochromism (Table 6 and see
Figure 5 for complex 6) but are significantly red-shifted in
the platinum complexes in relation to those in the analogous
palladium systems (382 nm 2 vs 410 nm 1; 385 nm 4 vs
414 nm 3), which is indicative of their metal-to-ligand
charge-transfer character.25,34,70 For 6, the low-energy absorp-
tions are slightly blue-shifted probably due to its cationic
nature, which will tend to decrease the energy of the dπ(Pt)
orbitals, consequently raising the energy of the transition.
The absorption profile of complex 7a in the low-energy
region shows a continuum from 345 to 425 nm (CH2Cl2)-
420 (acetonitrile or acetone) with a tail to 450 nm. This result
could be due to an overlapping of the MLCT transition with
some metal-perturbed intraligand ππ*(CtCR) character or
even with some contribution of ligand-to-ligand charge-
transfer from the acetylide ligand to bzq ligand (LL’CT).
Emission Spectra. The palladium complexes 2 and 4 are
not luminescent. All platinum complexes, except 8 at room
temperature, which emits very weakly, and 7a, are intensively
emissive in both the solid state and in CH2Cl2 glass. None
of the compounds emits in solution at 298 K, most likely
because of nonradiative deactivation by facile solvent/
complex interaction in fluid state at room temperature. The
results of the measurements in solid (298, 77 K) and glass
are summarized in Table 7. Representative emission spectra
are shown in Figures 6, 7, and 8. As can be observed in
Optical Properties. Absorption Spectra. The UV-vis
absorption data of complexes 1-7 are summarized in Table
6. All complexes show several high-energy intense absorp-
tions in the range 211-347 nm (CH2Cl2, ꢀ > 104 M-1 cm-1)
that are assigned to metal-perturbed ligand-centered transi-
tions (1IL π f π*) of the bzq ligand and/or coligands.27,30,31
They also exhibit two less intense transitions at lower energy
(66) Hoogervost, J. W.; Elsevier, C. J.; Lutz, M.; Spek, A. Organometallics
2001, 20, 4437.
(67) McAdam, C. J.; Blackie, E. J.; Morgan, J. L.; Mole, S. A.; Robinson,
B. H.; Simpson, J. J. Chem. Soc., Dalton Trans. 2001, 2362.
(68) Ghedini, M.; Pucci, D.; Crispini, A.; Barberio, G. Organometallics
1999, 18, 2116.
(69) Balashev, K. P.; Puzyk, M. V.; Kotlyar, V. S.; Kulikova, M. V. Coord.
Chem. ReV. 1997, 159, 109.
(70) Pe´rez, S.; Lo´pez, C.; Caubet, A.; Bosque, R.; Solans, X.; Bard´ıa, M.
F.; Roig, A.; Molins, E. Organometallics 2004, 23, 224 and references
therein.
Figure 5. Normalized UV-vis absorption spectra of 6 in several solvents
at 298 K.
Inorganic Chemistry, Vol. 44, No. 7, 2005 2451

D´ıez et al.
Figure 7. Normalized emission spectra of 3 in solid state at 77 K (-,
excited at 330 nm; - - -, excited at 360 nm; ‚‚‚, excited at 400 nm; ‚-‚,
excited at 450 nm).
Figure 6. Normalized emission spectra of 1 in solid state at 298 K (-,
ex 400), at 77 K (- - -, λex 400), and in CH2Cl2 glass at 77 K (‚‚‚, λex 390).
λ
Figure 6, complex 1 displays in solid state a slightly
structured and high-energy broad band (489 sh, 508 nm max)
with a tail to lower energies and a second structured, low-
energy band with a maximum at 634 and 693 nm. A similar
pattern is observed for complex 3 in solid state. For both
complexes, the decays of the high-energy band measured at
each vibronic peak maximum are in the range of micro-
seconds (14 µs for 1 and 10 µs for 3) indicative of metal
complex phosphorescence. The low-energy band displays a
longer lifetime (110 µs 1, 142 µs 3). Upon cooling at 77 K,
the emission profile of 1 became intensified and clearly
structured with maxima shifted to lower energies (506, 544
nm). For complex 3 (see Figure 7), excitation at 450 nm
resulted in a structured emission with a maximum starting
at 520 nm, while by exciting at higher energies (330-400
nm), a structured emission with a high-energy component
located at 497 nm was observed suggesting the presence of
different emitting states. Interestingly, the low and long life
energy bands observed in the solid state are not seen in frozen
CH2Cl2 glasses, suggesting that they could be due to
excimeric species resulting from the aromatic stacking
between the bzq rings. In these complexes, the high-energy
emission is tentatively assigned to mixed ligand-centered
(3LC) and metal-to-ligand charge-transfer (3MLCT) transi-
tions.27,30,31 As shown in Figure 8, the cationic complex 6
Figure 8. Normalized emission spectra of 6 in solid state at 298 K (-,
λ
ex 390), at 77 K (- - -, λex 390), and in CH2Cl2 glass at 77 K (‚‚‚, λex 360).
shows, in solid state, a structured emission profile, which is
red-shifted at 77 K (see Table 7) and has a vibronic spacing
(1356 cm-1, 298 K; 1419 cm-1, 77 K) related to the skeletal
stretching of the bzq ligand, suggesting its implication in
the excited emissive state. This cationic complex has an
exceptionally long lifetime of 189 µs in solid state at room
temperature. Similar long lifetimes have been observed in
other cationic and neutral platinum complexes containing the
Table 7. Photophysical Data for Platinum Complexes in Solid State and in CH2Cl2 Solutions
compd
λemmax/nm
τ/µs
[Pt(bzq)Cl(PPh2H)] 1
solid (298 K)
solid (77 K)
489, 508 (max) (tail to 600), 634, 693 (λex 340-480)
14 (508)
110 (634)
506, 544, 595 (sh) (tail to 700) (λex 340-480)
CH2Cl2 5 × 10-4 M (77 K) 474 (sh), 506 (tail to 650) (λex 390)
[Pt(bzq)Cl(PPh2CtCPh)] 3
KBr (298 K)
solid (298 K)
510, 620 (sh) (tail to 690) (λex 340-480)
494 (sh), 520 (max) (tail to 600), 629 (λex 360-460)
10 (520)
142 (629)
solid (77 K)
497, 520 (max), 560, 605 (sh), 626 (sh), 650 (sh) (λex 330-400)
520, 560, 605, 626, 650 (λex 450)
474 (sh), 497, 535, 577 (sh), 627 (sh) (tail to 700) (λex 340-460)
470, 479, 502, 548 (sh) (tail to 650) (λex 390)
486, 501, 522, 562 (tail to 650) (λex 320-390)
502, 540 (tail to 650) (λex 450)
CH2Cl2 10-3 M (77 K)
[Pt(bzq)(PPh2C(Ph)C(H)PPh2)]ClO4 6 crystalline solid (298 K)
189 (470, 502)
solid (77 K)
CH2Cl2 5 × 10-4 M (77 K) 480, 513, 560 (tail to 650) (λex 340-440)
[Pt(bzq)(CtCPh)(PPh2CtCPh)] 7a
[Pt(bzq)(µ-PPh2)]2 8
solid (298, 77 K)
CH2Cl2 (77 K)
KBr (298 K)
no emissive
474 (sh), 494, 527, 567 (tail to 650) (λex 340-440)
615 (w) (λex 400-490)
602 (λex 360-480)
11
solid (77 K)
2452 Inorganic Chemistry, Vol. 44, No. 7, 2005

Palladium and Platinum(II) Complexes
bridge platinum complex 8 displays a long-lived (11 µs) very
weak emission at room temperature in the solid state (KBr)
centered at ca. 615 nm, which is enhanced and slightly blue-
shifted (602 nm) at 77 K (see Figure 9). These emissions
appear clearly red-shifted compared with the mononuclear
precursor 1 and are tentatively assigned to a mixture of
3MLCT excited states with some 3(ππ*) excimeric character
due to the weak π-π interactions between the bzq rings.
This assignment is in agreement with the packing observed
in solid state dominated by extensive intermolecular π-π
interactions.
Acknowledgment. We thank the Ministerio de Ciencia
y Tecnolog´ıa (Project No. BQU2002-03997-C02-01, 02 and
a grant for A. Garc´ıa).
Figure 9. Normalized emission spectra of 8 in solid state at 77 K (λex
Supporting Information Available: Crystallographic data in
CIF format; PLATON plots and refine structure studies of 1, 6,
and 7b in three different ways (model 1, with the identities of C
and N as presented in this article; model 2, with the elements types
reversed; model 3, with a 50/50 hybrid scattering factor at each of
the affected atomic sites), pdf file. This material is available free
of charge via the Internet at http://pubs.acs.org.
460).
bzq ligand15,18,30,31 and have been attributed to a higher
conjugation within the π system, stabilizing the energy of
3
3
the LC excited state and thus increasing the LC character
of the emissive state. Complex 7a is only emissive in CH2Cl2
glass at 77 K, displaying a structured band at a similar energy
to its precursor complex 3. Finally, the dinuclear phosphide-
IC048272G
Inorganic Chemistry, Vol. 44, No. 7, 2005 2453