Synthesis of bis(2,6-dinitroaryl)palladium(II) and mono(2,6-dinitroaryl) platinum(II) complexes. A new example of the transphobia effect and of transmetalation from Pt to Hg

Article abstract of DOI:10.1021/om701077y

The reaction of [Pd(κ²-Ar)(O,O-acac)] (κ ²-Ar = κ²-C,O-C₆(NO₂) ₂-2,6-(OMe); 1) with 1 equiv of RNC gives [Pd(κ²-Ar) (O,O-acac)(CNR)] [R = Xy (2a), ^tBu (2b)] and with 4

Full text of DOI:10.1021/om701077y

1582
Organometallics 2008, 27, 1582–1590
Synthesis of Bis(2,6-dinitroaryl)palladium(II) and
Mono(2,6-dinitroaryl)platinum(II) Complexes. A New Example of
the Transphobia Effect and of Transmetalation from Pt to Hg
José Vicente,*,† Aurelia Arcas,† María-Dolores Gálvez-López, and
Francisco Juliá-Hernández
Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química,
UniVersidad de Murcia, Aptdo. 4021, E-30071 Murcia, Spain
Delia Bautista‡
SAI, UniVersidad de Murcia, Aptdo. 4021, E-30071 Murcia, Spain
Peter G. Jones§
Institut für Anorganische and Analytische Chemie, Technische UniVersität Braunschweig, Postfach 3329,
38023 Braunschweig, Germany
ReceiVed October 25, 2007
The reaction of [Pd(κ2-Ar)(O,O-acac)] (κ2-Ar ) κ2-C,O-C6(NO2)2-2,6-(OMe); 1) with 1 equiv of RNC
t
gives [Pd(κ2-Ar)(O,O-acac)(CNR)] [R ) Xy (2a), Bu (2b)] and with 4 equiv of XyNC, trans-[Pd(κ1-
Ar)2(CNXy)2] (κ1-Ar ) κ1-C-C6(NO2)2-2,6-(OMe); 3). This complex has also been obtained (1) by reacting
Tl(acac) with 1 equiv of trans-[Pd(κ1-Ar)Cl(CNXy)2] (4), obtained in turn by reacting trans-(NMe4)2[Pd(κ1-
Ar)Cl(µ-Cl)]2 (5) with 4 equiv of XyNC or (2) by reacting [Pd(κ1-Ar)(C-acac)(phen)] (6) with 4 equiv
of XyNC. cis-[Pt(κ2-Ar)(κ1-Ar)(PPh3)] (7) reacts (1) with Hg(OAc)2 (1:1) to afford a mixture of
[Hg(Ar)(OAc)], cis-[{Pt(κ1-Ar)(PPh3)}2(µ-OH)(µ-OAc)] (8), and trans-[{Pt(κ1-Ar)(PPh3)}2(µ-OH)2] (9)
or (2) with HgCl2 (1:1) to give trans-[{Pt(κ1-Ar)(PPh3)}2(µ-Cl)2] (10), which reacts with an excess of
Ag(OAc) to give 8. The reaction of 10 with excess of KOH, or with Tl(acac) (1:1) gives 9. Reaction of
palladium complex 5 with 2 equiv of Hg(OAc)2 affords trans-[Pd(κ2-Ar)(µ-OAc)]2 (11). The crystal
structures of 2a, 2b, 3, 5, 8, 9, and 11 have been determined.
C6H3R-2-R′-5 (R ) R′ ) CH(OMe)2, CH(SCH2CH2S),10 CHO,
Introduction
CO2H, R ) CHO, R′ ) CO2H11) through transmetalation reactions
We have reported the synthesis of monoaryl palladium com-
plexes [Pd](Ar) (Ar ) C6H3Me-2,NO2-6,1 C6(NO2)2-2,6-(OMe)3-
3,4,5,2 C6H4NO2-2,3 C6H4(NO2)3-2,4,6,4C6H(CHO)-2-(OMe)3-3,4,
5,5,6 C6HR-6-(OMe)3-2,3,4 (R ) CHO,5–7 CH2OEt,8 C(O)NHBut),9
using the corresponding mercurial [HgAr2] or [Hg(Ar)Cl]. Except
for Ar ) C6H4NO2-2,3 no diaryl complexes were obtained even
when their syntheses were attempted by using an excess of mercu-
rial.1,10,11 Monoaryl palladium complexes are also the result of the
reaction between other aryl mercurials and Pd(II) complexes,12–14
* Corresponding author.
† To whom correspondence regarding the synthesis of complexes should
be addressed. E-mail: jvs1@um.es (J.V.); aurelia@um.es (A.A.).
‡ To whom correspondence regarding the X-ray diffraction studies of
complexes 2a, 2b, 3, 5, and 11 should be addressed. E-mail: dbc@um.es.
§ To whom correspondence regarding the X-ray diffraction studies of
complexes 8 and 9 should be addressed. E-mail: p.jones@tu-bs.de.
(1) Vicente, J.; Arcas, A.; Borrachero, M. V.; Hursthouse, M. B. J. Chem.
Soc., Dalton Trans. 1987, 1655.
(10) Vicente, J.; Abad, J. A.; Hernández-Mata, F. S.; Rink, B.; Jones,
P. G.; Ramírez de Arellano, M. C. Organometallics 2004, 23, 1292.
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Arellano, M. C. Organometallics 1997, 16, 5269.
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Cross, R. J.; Wardle, R. J. Chem. Soc. A 1970, 840.
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Arellano, M. C. Organometallics 1998, 17, 5374.
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Chem. 1981, 222, 155. Anderson, G. K. Organometallics 1983, 2, 665.
Constable, E. C.; Leese, T. A. J. Organomet. Chem. 1987, 335, 293.
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Gladiali, S.; Manassero, M.; Sansoni, M. Organometallics 2005, 24, 53.
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Altaba, M.; Aguiló, M. J. Chem. Soc., Dalton Trans. 1988, 141.
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Chem. Commun. 1991, 137. Vicente, J.; Abad, J. A.; Gil-Rubio, J.; Jones,
P. G.; Bembenek, E. Organometallics 1993, 12, 4151.
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Martinez-Viviente, E.; Jones, P. G. Organometallics 2000, 19, 5597.
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Ramírez de Arellano, M. C. Organometallics 1996, 15, 24.
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Arellano, M. C.; Jones, P. G. Organometallics 1997, 16, 4557.
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10.1021/om701077y CCC: $40.75
2008 American Chemical Society
Publication on Web 03/11/2008

Preparation of trans-[Pd(κ1-Ar)2(CNXy)2]
Organometallics, Vol. 27, No. 7, 2008 1583
except in one case.14 In contrast, [Pt](Ar)2 (Ar ) C6H4NO2-2,15
C6(NO2)2-2,6-(OMe)3-3,4,5)6 is always the product of the trans-
metalation reaction and all attempts to obtain [Pt](Ar) by reacting
[HgAr2] with (Me4N)2[Pt2Cl6] or K2[PtCl4] in a 1:1 molar ratio
were unsuccessful. Instead, [Pt](Ar)2 and the starting platinum
complex were isolated.15,16 However, complexes [Pt](Ar) (Ar )
Ph, 2-arylazoaryl, C6H3NH2-2-NO2-5)12,17,18 and [Pt](Ar)2 (Ar )
Ph)17 have been prepared by using organomercurials. These data
suggest that transmetalation reactions with aryl mercurials can only
monoarylate palladium complexes, except in a few cases, and
mono- or diarylate platinum complexes, depending on the nature
of the aryl ligand. The synthetic challenge of preparing [Pd](Ar)2
and [Pt](Ar) when Ar ) C6(NO2)2-2,6-(OMe)3-3,4,5, for which
all attempts with the corresponding mercurial were unsuccessful,
is the object of the present article. We have successfully used
mercurials to prepare nitrophenyl complexes of other metals such
as Au19 and Rh.20
Suzuki, Stille, and other catalytic reactions) or the insertion of
dioxygen into a C-Pd bond have been reported.25 We have
also shown that the resistance to being trans (transphobia) of
C-donor/C-donor ligands pairs is greater than that for C-donor/
P-donor ligands. The concept of transphobia is being used
successfully by other authors mainly to discuss geometrical
preferences in Pd(II) complexes.28
With respect to the synthesis of [Pt](Ar) (Ar ) C6(NO2)2-
2,6-(OMe)3-3,4,5) complexes, we report attempts based on
oxidative addition reactions of IAr toward Pt(0) and Pt(II) to
Hg(II) transmetalation reactions. We are not aware of a Pt to
Hg Ar-transmetalation, i.e., [Pt(II)]R + [Hg]X f [Hg(II)]R +
[Pt(II)]X for R ) aryl, but one example for R ) Ct CR′ has
been reported.29 Previous attempts to prepare [Pt](Ar) complexes
by reacting [Hg(Ar)2] with Pt(0) complexes led to complexes
with Pt-Hg bonds.30
The most general method for the synthesis of [Pd](Ar)2 is
the use of the corresponding Li or Mg derivative but we ruled
out this method because of the presence of nitro groups in the
aryl ligand. In fact, LiC6H4NO2-2 is very unstable21 and has
only been used to prepare a family of complexes cis-
[Pt(Ar)(C6H4NO2-2)L2] (L ) PPh3, R ) C6H4R′-x where x )
2, 4, R′ ) OMe, Me, CF3, NO2; L2 ) cod, x ) 4, R′ ) OMe,
Me), a synthesis that functions only at very low temperatures.22
We report here the preparation of [Pd](Ar)2 complexes from a
[Pd](Ar) complex by a new method that we have discovered in
an experiment designed to study the consequences of forcing
two carbon donor ligands to be coordinated mutually trans. We
have shown that when a pair of C-donor/P-donor or C-donor/
C-donor ligands in a Pd(II) complex is forced to be trans, the
resulting species tends to be unstable, and some transformation
(transphobia23–25 effect) is expected to prevent the attainment
of such an arrangement. For example, a C-P25,26 or C-S27
coupling process (or the C-C coupling in the well-known
Experimental Section
The reactions were carried out without precautions to exclude
light or atmospheric oxygen or moisture. The IR (Nujol/polyeth-
ylene), C, H, and N analyses, and melting point determinations
were carried out as described elsewhere.31 NMR spectra were
recorded in a Varian Unity 300, Bruker AC 200, or Avance 300 or
400 spectrometer at room temperature. Chemical shifts were referred
to TMS (1H, 13C{1H}) or H3PO4 (31P). The NMR probe temperature
was calibrated with use of ethylene glycol 1H NMR standard
methods. The ligands κ1-C-C6(NO2)2-2,6-(OMe)3 and κ2-C,O-
C6(NO2)2-2,6-(OMe)3 are represented by κ1-Ar and κ2-Ar. When
the coordination mode of this aryl ligand is not known, it is
formulated simply as Ar. Complexes [Pd(κ2-Ar)(O,O-acac)] (1),
(NMe4)2[Pd(κ1-Ar)Cl(µ-Cl)]2 (5),2 [Pd(κ1-Ar)(C-acac)(phen)] (6),
and cis-[Pt(κ2-Ar)(κ1-Ar)(PPh3)]23 (7) were prepared as reported
previously. Single crystals of 5 · 0.5Me2CO were obtained by slow
diffusion of Et2O into a Me2CO solution of 5.
Synthesis of [Pd(K1-Ar)(acac)(CNXy)] (2a). XyNC (7.5 mg,
0.06 mmol) was added to a solution of [Pd(κ2-Ar)(O,O-acac)] (26.5
mg, 0.06 mmol) (1) in Me2CO (6 mL). After 45 min, the resulting
solution was concentrated (1 mL) and addition of n-pentane (4 mL)
gave a suspension that was filtered off and air-dried to give complex
2a as a pale yellow solid. Yield: 29.1 mg, 86%. Mp: 162.5–163.7
(15) Vicente, J.; Chicote, M. T.; Martin, J.; Jones, P. G.; Fittschen, C.;
Sheldrick, G. M. J. Chem. Soc., Dalton Trans. 1986, 2215.
(16) Vicente, J.; Arcas, A.; Gálvez-López, M. D.; Jones, P. G. Orga-
nometallics 2004, 23, 3521.
(17) Segnitz, A.; Kelly, E.; Taylor, S. H.; Maitlis, P. M. J. Organomet.
Chem. 1977, 124, 113.
1
°C. IR (cm-1): ν (CN) 2202; ν (CO) 1566. H NMR (400 MHz,
2
(18) Anderson, G. K.; Cross, R. J. J. Chem. Soc., Dalton Trans. 1979,
1246. Anderson, G. K.; Cross, R. J. J. Chem. Soc., Dalton Trans. 1980,
712. Vicente, J.; Abad, J. A.; Teruel, F.; Garci, J. J. Organomet. Chem.
1988, 345, 233.
CDCl3): δ 7.22 (t, 1 H, p-H, JHH ) 7.62 Hz), 7.09 (d, 2 H, m-H,
2JHH ) 7.53 Hz), 5.40 (s, 1 H, CH), 3.99 (s, 6 H, OMe), 3.90 (s,
3 H, OMe), 2.38 (s, 6 H, Me Xy), 1.99 (s, 3 H, Me acac), 1.95 (s,
3 H, Me acac). Anal. Calcd for C23H25N3O9Pd · C2H5O0.5: C, 47.44;
H, 4.78; N, 6.64. Found: C, 47.51; H, 4.78; N, 6.64. Single crystals
(19) Vicente, J.; Arcas, A.; Chicote, M. T. J. Organomet. Chem. 1983,
252, 257. Vicente, J.; Chicote, M. T.; Arcas, A.; Artigao, M. Inorg. Chim.
Acta 1982, 65, L251. Vicente, J.; Arcas, A.; Jones, P. G.; Lautner, J.
J. Chem. Soc., Dalton Trans. 1990, 451. Vicente, J.; Bermúdez, M. D.;
Chicote, M. T.; Sánchez-Santano, M. J. J. Organomet. Chem. 1990, 381,
285. Vicente, J.; Chicote, M. T.; González-Herrero, P.; Grünwald, C.; Jones,
P. G. Organometallics 1997, 16, 3381.
(28) Lohner, P.; Pfeffer, M.; Fischer, J. J. Organomet. Chem. 2000, 607,
12. Crespo, M.; Granell, J.; Solans, X.; Fontbardia, M. J. Organomet. Chem.
2003, 681, 143. Fernandez, S.; Navarro, R.; Urriolabeitia, E. P. J.
Organomet. Chem. 2000, 602, 151. Albert, J.; Cadena, J. M.; Delgado, S.;
Granell, J. J. Organomet. Chem. 2000, 603, 235. Marshall, W. J.; Grushin,
V. V. Organometallics 2003, 22, 555. Jalil, M. A.; Fujinami, S.; Nishikawa,
H. J. Chem. Soc., Dalton Trans. 2001, 1091. Carbayo, A.; Cuevas, J. Y.;
Garcia Herbosa, G.; Garcia Granda, S.; Miguel, D. Eur. J. Inorg. Chem.
2001, 2361. Fernandez, A.; Vazquez Garcia, D.; Fernandez, J. J.; López
Torres, M.; Suarez, A.; Castro Juiz, S.; Vila, J. M. Eur. J. Inorg. Chem.
2002, 2389. Fernandez-Rivas, C.; Cardenas, D. J.; Martin-Matute, B.;
Monge, A.; Gutierrez-Puebla, E.; Echavarren, A. M. Organometallics 2001,
20, 2998. Bartolome, C.; Espinet, P.; Vicente, L.; Villafañe, F.; Charmant,
J. P. H.; Orpen, A. G. Organometallics 2002, 21, 3536. Amatore, C.;
Bahsoun, A. A.; Jutand, A.; Meyer, G.; Ntepe, A. N.; Ricard, L. J. Am.
Chem. Soc. 2003, 125, 4212. Ng, J. K. P.; Chen, S.; Li, Y.; Tan, G. K.;
Koh, L. L.; Leung, P. H. Inorg. Chem. 2007, 46, 5100. Casas, J. M.; Fornies,
J.; Fuertes, S.; Martin, A.; Sicilia, V. Organometallics 2007, 26, 1674.
(29) Cross, R. J.; Gemmill, J. J. Chem. Soc., Dalton Trans. 1984, 199.
(30) Vicente, J.; Arcas, A.; Gálvez-López, M. D.; Jones, P. G. Orga-
nometallics 2004, 23, 3528.
(20) Vicente, J.; Martin, J.; Chicote, M. T.; Solans, X.; Miravitlles, C.
J. Chem. Soc., Chem. Commun 1985, 1004. Vicente, J.; Martin, J.; Solans,
X.; Font-Altaba, M. Organometallics 1989, 8, 357. Vicente, J.; Abad, J. A.;
Lahoz, F. J.; Plou, F. J. J. Chem. Soc., Dalton Trans. 1990, 1459.
(21) Parham, W. E.; Piccirilli, R. M. J. Org. Chem. 1976, 41, 1268.
Buck, P.; Koebrich, G. Chem. Ber. 1970, 103, 1412.
(22) Stapp, B.; Schmidtberg, G.; Brune, H. A. Z. Naturforsch., B 1986,
41b, 541.
(23) Vicente, J.; Arcas, A.; Gálvez-López, M. D.; Jones, P. G. Orga-
nometallics 2006, 25, 4247.
(24) Vicente, J.; Arcas, A.; Bautista, D.; Jones, P. G. Organometallics
1997, 16, 2127. Vicente, J.; Abad, J. A.; Hernández-Mata, F. S.; Jones,
P. G. J. Am. Chem. Soc. 2002, 124, 3848. Vicente, J.; Abad, J. A.; Martínez-
Viviente, E.; Jones, P. G. Organometallics 2002, 21, 4454.
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M. C. Chem. Eur. J. 1999, 5, 3066.
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Organometallics 2006, 25, 4404.

1584 Organometallics, Vol. 27, No. 7, 2008
Vicente et al.
of 2a · 0.5Et2O were obtained by slow diffusion of n-pentane into
an Me2CO/Et2O solution of 2a.
3.34. Found: C, 41.83; H, 3.40; N, 3.42. Single crystals of 8 were
obtained by slow diffusion of n-hexane into a CH2Cl2 solution
of 8.
t
Synthesis of [Pd(K1-Ar)(acac)(CNtBu)] (2b). BuNC (8.9 µL,
Synthesis of trans-[{Pt(K1-Ar)(PPh3)}2(µ-OH)2] (9). Method
a. KOH (85%, 15 mg, 0.23 mmol) was added to a stirred suspension
of 10 (38 mg, 0.03 mmol) in thf (10 mL). The mixture was stirred
for 24 h, the solvent was evaporated to dryness, and CH2Cl2 (5
mL) was added. The resulting suspension was filtered and the
filtrated was concentrated to 1 mL. Addition of Et2O (15 mL) gave
a suspension that was filtered off, washed with Et2O, and air-dried
to give complex 9 as a pale yellow solid.Yield: 30 mg, 82%.
Method b. Tl(acac) (20 mg, 0.07 mmol) was added to a
suspension of 10 (50 mg, 0.03 mmol) in Me2CO/H2O (3/0.5 mL).
The mixture was stirred for 24 h, then the suspension was
concentrated and extracted with CH2Cl2 (2 × 5 mL). The resulting
solution was stirred with Celite for 12 h. The suspension was filtered
and the filtrate was concentrated (1 mL). Addition of Et2O (1 mL)
gave a suspension that was filtered off, washed with Et2O, and air-
dried. Yield: 23 mg, 48%. Mp: 284 °C dec. IR (cm-1): ν (OH)
3602. 1H NMR (400.9 MHz, CD2Cl2, 25 °C): δ 7.80–7.29 (m, 30
0.08 mmol) was added to a solution of 1 (35.6 mg, 0.08 mmol) in
Me2CO (5 mL). After 50 min, the resulting solution was concen-
trated (1 mL) and addition of n-pentane (4 mL) gave a suspension
that was filtered off and air-dried to give complex 2b as a pale
yellow solid. Yield: 29.7 mg, 71%. Mp: 153–154 °C. IR (cm-1):
1
ν (CN) 2218; ν (CO) 1580. H NMR (400 MHz, CDCl3, 25 °C):
δ 5.35 (s, 1 H, CH), 3.99 (s, 6 H, OMe), 3.90 (s, 3 H, OMe), 1.97
(s, 3 H, Me), 1.91 (s, 3 H, Me), 149 (s, 9 H, tBu). Anal. Calcd for
C19H25N3O9Pd: C, 41.80; H, 4.58; N, 7.70. Found: C, 41.43; H,
4.80; N, 7.67. Single crystals of 2b were obtained by slow diffusion
of n-pentane into a Et2O solution of 2b.
Synthesis of trans-[Pd(K1-Ar)2(CNXy)2] (3). XyNC (39.5 mg,
0.30 mmol) was added to a solution of 1 (34.8 mg, 0.075 mmol)
in Me2CO (6 mL). After 1 h of stirring the solution was concentrated
(3 mL) and the resulting solid was filtered off and washed with
Et2O to give 3 as a colorless solid. Concentration of the filtrate
afforded a second crop of 3. Yield: 27.2 mg, 82%. Mp: 260–261
1
°C dec. IR (cm-1): ν (CN) 2204. H NMR (300 MHz, CDCl3): δ
3
H, PPh3), 3.66 (s, 18 H, OMe), -0.71(d, 2 H, OH, JPH ) 3 Hz).
2
2
7.19 (t, 2 H, p-H, JHH ) 7.5 Hz), 7.05 (d, 4 H, m-H, JHH ) 7.5
Hz), 3.96 (s, 12 H, OMe), 3.89 (s, 6 H, OMe), 2.30 (s, 12 H, Me).
Anal. Calcd for C36H36N6O14Pd: C, 48.96; H, 4.11; N, 9.52. Found:
C, 48.61; H, 4.15; N, 9.56. Single crystals of 3 were obtained by
slow diffusion of n-pentane into a CHCl3 solution of 3.
1H NMR (300.1 MHz, CDCl3, 25 °C): δ 7.78–7.35 (m, 30 H, PPh3),
3.651 (s, 6 H, OMe), 3.645 (s, 12 H, OMe), -0.75 (d, 2 H, OH,
3JPH ) 3 Hz). 31P{1H} NMR (162.29 MHz, CD2Cl2, 25 °C): δ
4.29 (s, PPh3, 1JPtP ) 4168 Hz). 31P{1H} NMR (121 MHz, CDCl3,
25 °C): δ 5.15 (s, PPh3, 1JPtP ) 4152 Hz). 13C{1H} NMR (100.81
MHz, CD2Cl2, 25 °C): δ 148.64 (s, Cq Ar), 146.82 (s, Cq Ar), 143.16
Synthesis of trans-[Pd(K1-Ar)Cl(CNXy)2] (4). XyNC (98.5 mg,
0.75 mmol) was added to a suspension of 5 (191 mg, 0.19 mmol)
in CH2Cl2 (7 mL). After 1 h of stirring, the reaction mixture was
filtered through anhydrous MgSO4. The filtrate was concentrated
(2 mL) and n-pentane was added (1 mL). The suspension was
filtered and the filtrate was concentrated (ca. 2 mL) to give a solid
that was filtered off, washed with n-pentane, and air-dried to give
11 as a colorless solid. Yield: 137.9 mg, 55%. Mp: 150–151 °C.
IR (cm-1): ν (CN) 2203; ν (PdCl) 314. 1H RMN (400 MHz,
2
(s, Cq Ar), 134.70 (d, o-C PPh3, JPC ) 11 Hz), 131.56 (s, p-C
3
PPh3), 128.93 (d, m-C PPh3, JPC ) 11 Hz), 128.69 (d, i-C PPh3,
1JPC ) 65 Hz), 115.31 (d, Cq Ar, 2JPC ) 10 Hz), 62.48 (s, m-OMe),
61.49 (s, p-OMe). Anal. Calcd for C54H50N4O16P2Pt2: C, 44.33; H,
3.44; N, 3.83. Found: C, 44.06; H, 3.24; N, 3.83. Single crystals
of 9 · 1.28CDCl3 · 0.72CH2Cl2 were obtained by slow diffusion of
n-hexane into a CDCl3 + CH2Cl2 solution of 9.
Synthesis of trans-[Pt(K1-Ar)(PPh3)(µ-Cl)]2 (10). HgCl2 (110
mg, 0.41 mmol) was added to a solution of 7 (357 mg, 0.37 mmol)
in CH2Cl2 (5 mL) and the resulting suspension was stirred for 24 h.
The suspension was filtered and the solid was washed with CH2Cl2
(5 mL). The filtrate was concentrated (3 mL) and Et2O (10 mL)
was added. The resulting suspension was filtered and the solid was
washed with Et2O and air-dried to give 10 as a pale yellow solid.
Yield: 262 mg, 95%. Mp: 308 °C dec. IR (cm-1): ν (PtCl) 290,
2
CDCl3): δ 7.25 (t, 2 H, p-H, JHH ) 7.7 Hz), 7.10 (d, 4 H, m-H,
2JHH ) 7.6 Hz), 3.99 (s, 6 H, OMe), 3.91 (s, 3 H, OMe), 2.37 (s,
12 H, Me). Anal. Calcd for C27H27N4ClO7Pd: C, 48.99; H, 4.11;
N, 8.47. Found: C, 48.97; H, 4.31; N, 8.51. Single crystals of 4
were obtained by slow diffusion of n-pentane into a CDCl3 solution
of 4.
Synthesis of ArI (6). A solution of [Hg(Ar)2] (204 mg, 0.29
mmol) and I2 (213 mg, 0.84 mmol) in dimethylformamide (10 mL)
was heated for 1 h. When the solution was cooled, a 1 M aqueous
solution of NaBr (50 mL) was added and the resulting suspension
was filtered. The solid was washed with water and air-dried to give
1
272. H NMR (400 MHz, CDCl3): δ 8.11–6.91 (m, 30 H, PPh3),
3.68 (s, 18 H, OMe). 31P{1H} NMR (162.29 MHz, CDCl3): δ 8.33
1
(s, PPh3, JPtP ) 4473 Hz). Anal. Calcd for C54H48Cl2N4O14P2Pt2:
1
C, 43.24; H, 3.23; N, 3.75. Found: C, 43.05; H, 3.20; N, 3.80.
Crystals apparently suitable for an X-ray crystallographic study were
obtained for 10 by slow diffusion of n-hexane into a CDCl3 solution
of 10.
6 as a colorless solid. Yield: 191 mg, 87%. Mp: 175–177 °C. H
NMR (200 MHz, CDCl3): δ 4.03 (s, 6 H, OMe), 3.99 (s, 3 H,
OMe). Anal. Calcd for C9H9IN2O7: C, 28.14; H, 2.36; N, 7.29.
Found: C, 28.54; H, 2.28; N, 7.31.
Synthesis of trans-[Pd(K2-Ar)(µ-OAc)]2 (11). Hg(OAc)2 (63.3
mg, 0.20 mmol) was added to a suspension of (NMe4)2[Pd(κ1-
Ar)Cl(µ-Cl)]2 (5) (101.1 mg, 0.10 mmol) in Me2CO (6 mL). The
resulting suspension was stirred for 30 min and then concentrated
(2 mL) and filtered. The solid was treated with CH2Cl2 (5 mL), the
mixture was filtered through Celite, Et2O (10 mL) was added to
the filtrate, and the suspension was filtered to give 11 as a red solid.
Yield: 28 mg, 34%. Mp: 210–211 °C. IR (cm-1): ν (CO) 1548,
1530. 1H NMR (400 MHz, CDCl3): δ 4.13 (s, 6 H, p-OMe), 3.96,
3.89 (two s, 6 H, m-OMe), 2.08 (s, 6 H, Me). Anal. Calcd for
C44H48N8O36Pd2: C, 31.24; H, 2.84; N, 6.63. Found: C, 31.26; H,
2.86; N, 6.63. Single crystals of 11 were obtained by slow diffusion
of n-hexane vapor into a CH2Cl2 solution of 11.
Synthesis of cis-[{Pt(K1-Ar)(PPh3)}2(µ-OH)(µ-OAc)] · 2CH2Cl2
(8). Ag(OAc) (20 mg, 0.12 mmol) was added to a solution of 10
(42 mg, 0.03 mmol) in CH2Cl2 (5 mL). After 48 h of stirring, the
suspension was filtered, the filtrate was concentrated (2 mL), and
AcOH (1 µL) was added. A crystalline solid was obtained by slow
diffusion of n-hexane (20 mL) into the resulting solution. The solid
was isolated by filtration, washed with n-hexane, and air-dried to
give 8 as a yellow solid. Yield: 28 mg, 61%. Mp: 170–174 °C. IR
(cm-1): ν (OH) 3605. 1H NMR (400.9 MHz, CDCl3): δ 7.73–7.31
(m, 30 H, PPh3), 3.74 (s, 6 H, OMe), 3.70 (s, 12 H, OMe), 1.78
1
(br, 1 H, OH), 0.69 (s, 3 H, AcO). H NMR (400 MHz, CDCl3,
-30 °C): δ 7.95–7.89 (m, 8 H, PPh3), 7.51–7.47 (m, 14 H, PPh3),
7.07–7.00 (m, 8 H, PPh3), 3.75 (s, 6 H, OMe), 3.71 (s, 12 H, OMe),
3
1.93 (t, 1 H, OH, JPH ) 2.4 Hz), 0.68 (s, 3 H, AcO). 31P{1H}
X-ray Structure Determinations. For clarity, solvent contents
are omitted here, but are defined in Tables 1 and 2. Compounds
2a, 2b, 3, 5, and 11 were measured on a Bruker Smart APEX
diffractometer. Data were collected with use of monochromated
1
NMR (81.01 MHz, CDCl3): δ 4.6 (s, PPh3, JPtP ) 4292 Hz).
31P{1H} NMR (162.29 MHz, CDCl3): δ 4.08 (s, PPh3, 1JPtP ) 4292
Hz). Anal. Calcd for C58H56Cl4N4O17P2Pt2: C, 41.59; H, 3.37; N,

Preparation of trans-[Pd(κ1-Ar)2(CNXy)2]
Organometallics, Vol. 27, No. 7, 2008 1585
Table 1. Crystallographic Data for Complexes 2a, 2b, 3, and 5
2a · 0.5Et2O
2b
3
5 · 0.5Me2CO
formula
Mr
C25H30N3O9.5Pd
630.92
C19H25N3O9Pd
545.82
C36H36N6O14Pd
883.11
C
27.5H45Cl4N6O14.5Pd2
1046.30
cryst habit
cryst size (mm3)
cryst syst
space group
cell constants
a, Å
colorless block
0.20 × 0.16 × 0.08
triclinic
colorless prism
0.24 × 0.12 × 0.08
monoclinic
colorless needle
0.13 × 0.09 × 0.07
monoclinic
orange lath
0.17 × 0.12 × 0.07
triclinic
¯
¯
P1
P21/n
P21/c
P1
10.0026(5)
10.5211(5)
14.3597(7)
107.407(2)
103.434(2
91.700(2)
1394.50(12)
2
16.322(2)
8.2938(11)
18.474(2)
90
112.011(2)
90
21.1560(9)
11.2128(5)
16.2406(7)
90
92.797(2)
90
14.6377(6)
16.8923(7)
18.0811(7)
73.573(2)
88.311(2)
71.063(2)
4046.6(3)
4
b, Å
c, Å
R, deg
ꢁ, deg
γ, deg
V (Å3)
2318.5(5)
4
3848.0(3)
4
Z
λ (Å)
0.71073
1.503
0.72
646
100(2)
56
16229
6240
0.945, 0.869
0.0232
40/377
0.0775
0.0296
1.05
0.71073
1.56
0.853
1112
100(2)
56
24490
5320
0.935, 0.821
0.0406
6/296
0.0726
0.0306
1.05
0.71073
1.52
0.558
1808
100(2)
56
41574
7865
0.962, 0.931
0.0511
0/524
0.0844
0.0368
1.07
0.71073
1.72
1.222
2112
100(2)
56
F(calcd) (Mg m-3
)
µ (mm-1
F(000)
T (K)
)
2θmax (deg)
no. of reflns measd
no. of indep reflns
transmissions
Rint
47676
18222
0.919, 0.819
0.0299
26/1007
0.1006
0.0424
1.02
no. rest/params
Rw(F2, all reflns)
R(F, > 4σ(F))
S
max ∆F (e Å-3
)
0.97
0.82
0.64
1.22
Table 2. Crystallographic Data for Complexes 8, 9, and 11
8 · 2CH2Cl2
9 · 1.28CDCl3 · 0.72CH2Cl2
11
formula
Mr
C58H56Cl4N4O17P2Pt2
1674.99
C56H52.7Cl5.3N4O16P2Pt2
1677.04
C22H24N4O18Pd2
845.25
cryst habit
pale yellow prism
0.28 × 0.22 × 0.10
triclinic
yellow, irregular
0.19 × 0.18 × 0.08
triclinic
red needle
cryst size (mm3)
cryst syst
space group
cell constants
a, Å
0.30 × 0.05 × 0.03
triclinic
¯
¯
¯
P1
P1
P1
13.2770(8)
13.5786(8)
18.7001(11)
98.449(4)
91.862(4)
107.581(4)
3168.4(3)
2
14.1641(8)
14.3015(8)
18.3803(12)
68.708(4)
74.876(4)
63.103(4)
3072.8(3)
2
10.2492(5)
11.6858(6)
14.5201(8)
66.848(2)
72.464(2)
64.161(2)
1421.30(13)
2
b, Å
c, Å
R, deg
ꢁ, deg
γ, deg
V (Å3)
Z
λ (Å)
0.71073
1.76
4.701
1644
133(2)
60
64157
18469
0.746, 0.528
0.0333
176/800
0.0639
0.0259
0.99
0.71073
1.81
4.90
1641
133(2)
60
0.71073
1.98
1.358
840
100(2)
56
F(calcd) (Mg m-3
)
µ (mm-1
F(000)
T (K)
)
2θmax (deg)
no. of reflns measd
no. of indep reflns
transmissions
Rint
64443
17889
15553
5744
0.535, 0.746
0.0341
774/799
0.0808
0.0294
0.99
0.960, 0.686
0.0355
0/423
0.0756
0.0362
1.09
no. rest/params
Rw(F2, all reflns)
R(F, > 4σ(F))
S
max ∆F (e Å-3
)
1.57
1.47
0.666
Mo KR radiation in ω scan mode. Data for compounds 8 and 9
were measured on a Bruker SMART 1000 diffractometer, using
monochromated Mo KR radiation in ω and ꢀ scan modes.
Absorption corrections were based on the multiscan method
(program SADABS). All were refined anisotropically on F.2
Restraints to local aromatic ring symmetry or light atom displace-
ment factor components were applied in some cases. The ordered
methyl groups were refined by using rigid groups, and the other
hydrogens were refined by using a riding mode. Special features:
2a, the ether of solvation is disordered over an inversion center;
2b, one of the nitro groups is disordered over two positions, ca.
60:40%; 5, NMe4 cations are disordered over two positions; 8, one
dichloromethane is disordered over two positions; the OH hydrogen
was refined freely; and 9, the solvent content was interpreted as
overlapping CDCl3 and CH2Cl2; the OH hydrogens were refined
freely, but with an O-H distance restraint.

1586 Organometallics, Vol. 27, No. 7, 2008
Vicente et al.
Scheme 1
Scheme 2
Results and Discussion
[Pd(κ2-Ar)(O,O-acac)] (1) reacts with 1 equiv of isocyanides
to give the adducts [Pd(κ1-Ar)(O,O-acac)(CNR)] [R ) Xy (2a),
tBu (2b); Scheme 1]. We have reported reactions of 1 with other
neutral ligands to give adducts [Pd(κ1-Ar)(O,O-acac)L] [L )
PPh3, py, tht, bis(diphenylphosphino)methanemonoxide (dpp-
mo)] and [Pd(κ2-Ar)(O,O-acac)(phen).2 When 1 was reacted
with 4 equiv of XyNC in acetone, several fast changes of color
were observed (to orange via colorless, green, and yellow) and
after 5 min a colorless solid begin to precipitate. After 1 h of
stirring, concentration of the solution precipitated trans-[Pd(κ1-
Ar)2(CNXy)2] (3) in 82% yield as a colorless solid. In the orange
a mixture in which, at least, a product of stoichiometry
“Pd(acac)2(CNXy)5” (X) was obtained (see above). Formation
of 3 containing four C-donor ligands suggests that T(Ar/C-acac)
in the intermediate complex A is greater than T(Ar/Ar) or
T(CNXy/CNXy) in 3. The formation of 3 as a stable complex
in spite of the four C-Pd bonds must be attributed to the strong
Ar-M bonds. 1H NMR spectra of complex 3 at 20, 30, 40, 50,
and 60 °C in CDCl3 during 45 min show no decomposition or
isomerization process. Its platinum homologue, trans-[Pt(κ1-
Ar)2(CNXy)2], is obtained by heating the cis isomer at 150 °C.
The greater stability of the trans isomer was rationalized in the
case of the Pt complex on steric grounds.23 The low yield of 3
in the 1:2 reaction suggests that formation of X is a fast process
consuming part of the XyNC required for the synthesis of 3.
A Proposal for the Reaction Pathway of Formation of
3 from 1. It is reasonable to assume that the first step in this
process is formation of complex 2a, which in turn reacts with
XyNC to give the desired complex A (Scheme 2). We assume
this complex to be trans because, with exclusively C-donor
ligands, this seems the geometry with the lower steric hindrance
between Ar and acac ligands. Formation of 3 requires an
intermolecular transmetalation reaction that could occur through
a dinuclear complex such as B. The replacement of the acac
ligand could be favored by the strong T(Ar/C-acac) and the trans
geometry of A. Complexes with bridging aryl ligands have been
postulated as intermediates in the formation of diaryl from
monoaryl complexes.32 A few palladium complexes containing
bridging aryl ligands have been isolated.33 Cleavage of the
1
filtrate, a complex mixture of products was detected by H
NMR, among which 3 was identified. An X-ray crystallographic
study of a few crystals obtained from this filtrate was carried
out. Although a complete crystallographic analysis was not
possible because of poor data quality, the presence of a
palladium atom in a square-planar environment with two cis
XyNC ligands was shown with certainty. The other two
coordination positions were occupied by a complex chelate
ligand apparently resulting from the insertion of XyNC into
Pd-C(acac) bonds in which three isocyanides and two acac
ligands were involved. When this reaction was carried out in
CH2Cl2, the same fast changes of color were observed, although
the green persisted longer (∼2 min), but complex 3 was also
isolated. When 1 was reacted with 2 equiv of XyNC, the yield
of 3 decreased (19%) and 2a also was obtained. Addition of 4
t
equiv of BuNC to an acetone solution of 1 also led to several
rapid color changes (to pale yellow via orange and yellow) but
only a complex mixture of products was isolated.
The above reactions were designed with the purpose of
obtaining a complex with four carbon donor ligands [Pd(κ1-
Ar)(C-acac)(XyNC)2] (A; Scheme 2). We hypothesize that the
great C/C transphobia, T(C/C), should destabilize the complex,
favoring an isocyanide insertion into the Pd-Cacac bond or
inducing some C-C coupling process (see Introduction).
However, instead, a new transphobia effect was observed in
the 1:4 reaction: a disproportionation reaction leading to 3 and
(32) Sokolov, V. I.; Reutov, O. A. Coord. Chem. ReV. 1978, 27, 89.
Suzaki, Y.; Yagyu, T.; Osakada, K. J. Organomet. Chem. 2007, 692, 326.
(33) Albeniz, A. C.; Espinet, P.; Lopez-Cimas, O.; Martin-Ruiz, B.
Chem. Eur. J. 2004, 11, 242. Albeniz, A. C.; Espinet, P.; Martinruiz, B.
Chem. Eur. J. 2001, 7, 2481. Usón, R.; Forniés, J.; Tomás, M.; Casas, J. M.;
Navarro, R. J. Chem. Soc., Dalton Trans. 1989, 169.

Preparation of trans-[Pd(κ1-Ar)2(CNXy)2]
Organometallics, Vol. 27, No. 7, 2008 1587
Scheme 3
weakest Ar-Pd bond, i.e., that trans to the acac ligand, and
coordination of the replaced acac ligand would give 3 and a
highly reactive species trans-[Pd(C-acac)2(CNXy)2] (because
of the strong T(C-acac/C-acac)), which would insert XyNC to
give, among other products, complex “Pd(acac)2(CNXy)5” (X).
We have studied the reaction between [Pd(acac)2] and XyNC
under different reaction conditions but we have not yet isolated
any pure compound from the mixtures of complexes that we
obtain. We have reported that isocyanides insert into the C-Pd
bond of acetonyl complexes giving ꢁ-ketoenamino derivatives.34
A similar insertion followed by tautomerization could have
occurred in the synthesis of X.
the isolation of an impure sample of [Pt(κ1-Ar)I(bpy)] in low
yield (13%). Therefore, this route to monoaryl derivatives was
discarded.
Transmetalation Reactions. The room temperature reaction
of cis-[Pt(κ2-Ar)(κ1-Ar)(PPh3)] (7) with Hg(OAc)2 (1:1) in
CH2Cl2 gives a mixture of [Hg(Ar)(OAc)] and the dinuclear
platinum(II) complexes cis-[{Pt(κ1-Ar)(PPh3)}2(µ-OH)(µ-OAc)]
(8) and trans-[Pt(κ1-Ar)PPh3(µ-OH)]2 (9; Scheme 3). It is
reasonable to assume that the transmetalation reaction took place
through the dinuclear complex B, containing two bridging
acetato ligands, that complex 8 is the result of a partial
hydrolysis of B, and that 9 is the product of the hydrolysis of
8. The mixture of 8, 9, and [Hg(Ar)(OAc)] could not be
separated and all attempts to prevent any hydrolysis failed. The
only [Pt](Ar)(µ-OAc) complexes reported, the cycloplatinated
derivatives [Pt(C^E)(µ-OAc)]2 (E ) N, P, As), seem to be stable
toward moisture.36,37 The main difference between these
complexes and B is that the latter has a much more crowded
environment around Pt and this could be the reason for its high
reactivity toward moisture. This would also explain the facile
hydrolysis of complex 8.
To support this proposal we have attempted the synthesis of
A by two other routes. Thus, (1) we have prepared trans-[Pd(κ1-
Ar)Cl(CNXy)2] (4) from trans-(Me4N)2[Pd(κ1-Ar)Cl(µ-Cl)]2 (5)
and excess of XyNC, and reacted it with 1 equiv of Tl(acac)
and (2) we have reacted cis-[Pd(κ1-Ar)(C-acac)(phen)] (6) with
4 equiv of XyNC. In agreement with the above proposed
mechanism, both reactions led to the isolation of complex 3
instead of A. The low stability of this intermediate contrasts
with that of the related complexes 4 and 6 in which, for all
trans pairs of groups, T < T(Ar/C-acac).
Synthesis of Monoaryl Pt Complexes: Oxidative Addi-
tion Reactions. To prepare [Pt](Ar) complexes by an oxidative
addition reaction, we synthesized IC6(NO2)2-2,6-(OMe)3-3,4,5
(6) by reacting [HgAr2] with I2, following the method reported
by Deacon.35 However, 6 did not react at room temperature
with 1 equiv of [Pt2(dba)3] · dba in toluene under nitrogen and
decomposition was observed upon refluxing. Addition of 2,2′-
bipyridine to the reaction mixture at room temperature allowed
The above reverse transmetalation reaction was unexpected,
as we have reported that [Hg(O2CR)2] (R ) Me, CF3, C6F5)
reacts with 1 equiv of cis-Me4N[Pt(κ2-Ar)(κ1-Ar)Cl] or 0.5 equiv
of cis-[Pt(κ2-Ar)(κ1-Ar)L] (L ) H2O, PhCN) to give Pt-Hg
(36) Duff, J. M.; Mann, B. E.; Shaw, B. L.; Turtle, B. J. Chem. Soc.,
Dalton Trans. 1974, 139. Cockburn, B. N.; Howe, D. V.; Keating, T.;
Johnson, B. F. G.; Lewis, J. J. Chem. Soc., Dalton Trans. 1973, 404. Buey,
J.; Diez, L.; Espinet, P.; Kitzerow, H.-S.; Miguel, J. A. Chem. Mater. 1996,
8, 2375. Navarro-Ranniger, C.; Lopez-Solera, I.; Perez, J. M.; Rodriguez,
J.; Garcia-Ruano, J. L.; Raithby, P. R.; Masaguer, J. R.; Alonso, C. J. Med.
Chem. 1993, 36, 3795. Navarro-Ranninger, C.; Lopez-Solera, I.; Alvarez-
Valdes, A.; Rodriguez-Ramos, J. H.; Masaguer, J. R.; Garcia-Ruano, J. L.;
Solans, X. Organometallics 1993, 12, 4104.
(34) Vicente, J.; Arcas, A.; Fernández-Hernández, J. M.; Bautista, D.;
Jones, P. G. Organometallics 2005, 24, 2516.
(37) Navarro-Ranninger, C.; López-Solera, I.; González, V. M.; Pérez,
J. M.; Alvarez-Valdés, A.; Martín, A.; Raithby, P.; Masaguer, J. R.; Alonso,
C. Inorg. Chem. 1996, 35, 5181.
(35) Deacon, G. B.; Farquharson, G. J.; Miller, J. M. Aust. J. Chem.
1977, 30, 1013.

1588 Organometallics, Vol. 27, No. 7, 2008
Vicente et al.
Scheme 4
Figure 1. Ellipsoid representation of complex 2a (50% probability).
Selected bond lengths (Å) and angles (deg): Pd(1)–C(6) ) 1.925(2),
Pd(1)–C(11) ) 2.000(2), Pd(1)–O(1) ) 2.0130(14), Pd(1)–O(2) )
2.0456(15), O(1)–C(1) ) 1.280(3), O(2)–C(3) ) 1.275(3), O(3)–N(2)
) 1.208(3), O(4)–N(2) ) 1.218(2), O(5)–N(3) ) 1.227(2),
O(6)–N(3) ) 1.223(3), N(1)–C(6) ) 1.145(3), N(1)–C(21) )
1.405(3), N(2)–C(16) ) 1.475(3), N(3)–C(12) ) 1.477(3),
C(6)–Pd(1)–C(11) ) 88.56(8), C(11)–Pd(1)–O(1) ) 87.58(7),
C(6)–Pd(1)–O(2) ) 91.23(7), O(1)–Pd(1)–O(2) ) 92.67(6).
complexes Me4N[Hg(µ-OAc)2{Pt(κ1-Ar)2Cl}], [Hg(µ-OAc)2-
{Pt(κ2-Ar)2}2], [Hg{Pt(κ2-Ar)2(O2CR)}2], or cis-Me4N[Pt(κ2-
Ar)(κ1-Ar)(O2CCF3)].30 It is possible that some adduct similar
to these Pt-Hg complexes is an intermediate (for example, C
in Scheme 4). As the presence of PPh3 in the intermediate C is
the only difference with respect to the stable Me4N[Hg(µ-
OAc)2{Pt(κ1-Ar)2Cl}], it is possible that this ligand is respon-
sible for the cleavage of the Pt–Hg bond in C and the formation
of a complex with a bridging aryl group (D) finally affording
complex B and [Hg(Ar)(OAc)].
This unexpected result opened a route for the synthesis of
the desired [Pt](Ar) complexes that we had attempted previously,
but without success (see Introduction). However, given the
difficulties we encountered in isolating 8 and 9, we attempted
the reaction of 7 with 1 equiv of HgCl2 giving [Pt(κ1-Ar)(µ-
Cl)PPh3]2 (10), the homologue of complex B. This complex
can be easily precipitated from the reaction mixture by addition
of Et2O while the byproduct, [Hg(Ar)Cl], remains soluble. The
addition of an excess of Ag(OAc) to a CH2Cl2 solution of 10
gave 8, which must be recrystallized in the presence of acetic
acid to avoid formation of traces of 9. We have unsuccessfully
attempted to prepare the intermediate B by reacting 8 with a
large excess of HOAc; a complex mixture of products resulted.
The reaction of 10 with excess KOH in thf or with 2 equiv of
Tl(acac) in a mixture of Me2CO and water (6:1) gave 9 in 82%
or 48% yields, respectively.
Figure 2. Ellipsoid representation of complex 2b (50% probability).
Selected bond lengths (Å) and angles (deg): Pd(1)–C(6) ) 1.927(2),
Pd(1)–C(11) ) 2.002(2), Pd(1)–O(1) ) 2.0098(16), Pd(1)–O(2) )
2.0519(16), N(1)–C(6) ) 1.143(3), N(1)–C(7) ) 1.474(3), O(1)–C(1)
) 1.280(3), O(2)–C(3) ) 1.271(3), N(3)–O(4) ) 1.222(3), N(3)–O(3)
) 1.229(3), N(3)–C(12) ) 1.477(3), N(2)–O(6′) 1.126(6), N(2)–O(5)
) 1.185(4), N(2)–O(6) ) 1.279(4), N(2)–O(5′) ) 1.301(6),
N(2)–C(16) ) 1.482(3), O(7)–C(15) ) 1.373(2), O(7)–C(19) )
1.443(3), O(8)–C(14) ) 1.363(3), O(8)–C(18) ) 1.444(3),
O(9)–C(13) ) 1.360(3), O(9)–C(17) ) 1.449(3), C(6)–Pd(1)–C(11)
) 86.68(9), C(11)–Pd(1)–O(1) ) 88.02(8), C(6)–Pd(1)–O(2) )
92.92(8), O(1)–Pd(1)–O(2) ) 92.36(6).
The reaction of palladium complex 5 with 2 equiv of
Hg(OAc)2 does not proceed via transmetalation or formation
of a Pd-Hg compound but simply with a ligand substitution
of chloro by acetato to give the dinuclear complex [Pd(κ2-Ar)(µ-
O2CMe)]2 (11; Scheme 3).
dinuclear complexes with two single-atom bridges,38 while in
8 the two coordination planes subtend an angle of 44.3°. A
search of the Cambridge Structural Database reveals two
platinum complexes containing both carboxylate and OH
bridging ligands, [Pt2(µ-carboxylate)(µ-OH)(NH3)4]2+ (carboxy-
late ) acetate,39,40 glycolate40) and the angles between the
coordination planes are 75.5° and 73.0°, respectively. Probably,
8 adopts a wider interplanar angle because of the steric hindrance
of the large phosphine and aryl ligands.
Crystal Structures. Crystals apparently suitable for an X-ray
crystallographic study were obtained for 10. However, although
a complete crystallographic analysis was not possible because
the rings with the nitro and methoxy groups were badly
disordered, the position of the ligands was established with
certainty to be that indicated in Scheme 3.
Bond distances at palladium in complexes are consistent with
the trans influence scale. Thus, we observe (1) similar Pd-O(1)
Complete crystallographic analysis was carried out for
complexes 2a (Figure 1), 2b (Figure 2), 3 (Figure 3), 5 (Figure
4), 8 (Figure 5), 9 (Figure 6), and 11 (Figure 7). Solvent contents
are given in Tables 1 and 2. All structures reveal a metal in a
distorted square-planar coordination. In the dinuclear complexes
5 and 9, the coordination planes are almost coplanar (angle
between coordination planes: 1.8°, 2.9° (5) and 0° by symmetry
(9)) as has been found and theoretically predicted for most
(38) Aullon, G.; Ujaque, G.; Lledos, A.; Alvarez, S. Chem. Eur. J. 1999,
5, 1391. Aullon, G.; Ujaque, G.; Lledos, A.; Alvarez, S.; Alemany, P. Inorg.
Chem. 1998, 37, 804.
(39) Appleton, T. G.; Mathieson, M.; Byriel, K. A.; Kennard, C. H. L.
Z. Kristallogr. New Cryst. Struct. 1998, 213, 247.
(40) Sakai, K.; Takeshita, M.; Tanaka, Y.; Ue, T.; Yanagisawa, M.;
Kosaka, M.; Tsubomura, T.; Ato, M.; Nakano, T. J. Am. Chem. Soc. 1998,
120, 11353.

Preparation of trans-[Pd(κ1-Ar)2(CNXy)2]
Organometallics, Vol. 27, No. 7, 2008 1589
Figure 5. Ellipsoid representation of complex 8 (50% probability).
Selected bond lengths (Å) and angles (deg): Pt(1)–C(11) 1.984(3),
Pt(1)–O(3) 2.063(2), Pt(1)–O(1) 2.1162(19), Pt(1)–P(1) 2.2192(7),
Pt(2)–C(51) 1.985(3), Pt(2)–O(3) 2.069(2), Pt(2)–O(2) 2.0890(19),
Pt(2)–P(2) 2.2069(7), N(11)–O(12) 1.211(3), N(11)–O(11) 1.212(3),
N(11)–C(12) 1.468(4), N(12)–O(17) 1.215(3), N(12)–O(16) 1.225(3),
N(12)–C(16) 1.467(4), N(51)–O(51) 1.193, N(51)–O(52) 1.205(3),
N(51)–C(52) 1.478(4), N(52)–O(56) 1.226(3), N(52)–O(57) 1.231(3),
N(52)–C(56), 1.472(4), O(1)–C(1) 1.271(3), O(2)–C(1) 1.254(3),
C(11)–Pt(1)–O(3)89.84(10),O(3)–Pt(1)–O(1)90.20(8),C(11)–Pt(1)–P(1)
94.06(8), O(1)–Pt(1)–P(1) 85.84(6), C(51)–Pt(2)–O(3) 89.35(10),
O(3)–Pt(2)–O(2) 87.98(9), C(51)–Pt(2)–P(2) 92.47(8), O(2)–Pt(2)–
P(2) 90.09(6).
Figure 3. Ellipsoid representation of complex 3 (50% probability).
Selected bond lengths (Å) and angles (deg): Pd(1)–C(11) 1.965(3),
Pd(1)–C(1) 1.966(3), Pd(1)–C(21) 2.069(3), Pd(1)–C(31) 2.071(3),
O(1)–N(3) 1.219(3), O(2)–N(3) 1.207(3), O(3)–N(4) 1.220(3),
O(4)–N(4) 1.224(3), O(5)–C(23) 1.367(3), O(5)–C(27) 1.440(4),
O(6)–C(24) 1.370(3), O(6)–C(28) 1.432(4), O(7)–C(25) 1.369(3),
O(7)–C(29) 1.445(4), O(8)–N(5) 1.215(3), O(9)–N(5) 1.215(3),
O(10)–N(6) 1.218(3), O(11)–N(6) 1.219(3), O(12)–C(33) 1.371(3),
O(12)–C(37) 1.433(4), O(13)–C(34) 1.368(3), O(13)–C(38) 1.444(3),
O(14)–C(35) 1.371(3), O(14)–C(39) 1.446(3), N(1)–C(1) 1.149(3),
N(1)–C(2) 1.405(3), N(2)–C(11) 1.151(3), N(2)–C(12) 1.404(3),
N(3)–C(26) 1.479(3), N(4)–C(22) 1.474(3), N(5)–C(32) 1.472(3),
N(6)–C(36)1.477(3),C(11)–Pd(1)–C(21)89.37(10),C(1)–Pd(1)–C(21)
89.97(10), C(11)–Pd(1)–C(31) 90.89(10), C(1)–Pd(1)–C(31)
89.73(10),
Figure 6. Ellipsoid representation of complex 9 (50% probability).
Selected bond lengths (Å) and angles (deg): Pt(1)–C(11) 1.983(3),
Pt(1)–O(1) 2.067(3), Pt(1)–O(1)#1 2.087(3), Pt(1)–P(1) 2.2085(9),
Pt(1)–Pt(1)#1 3.2228(4), O(1)–Pt(1)#1 2.087(3), N(11)–O(11)
1.184(4), N(11)–O(12) 1.199(5), N(12)–O(16) 1.179(5), N(12)–O(17)
1.232(5), Pt(2)–C(11′) 1.994(3), Pt(2)–O(2)#2 2.081(3), Pt(2)–O(2)
2.095(3), Pt(2)–P(2) 2.2137(9), Pt(2)–Pt(2)#2 3.2161(3), O(2)–Pt(2)#2
2.081(3),N(11′)–O(11′)1.213(4),N(11′)–O(12′)1.230(4),N(12′)–O(16′)
1.194(4), N(12′)–O(17′) 1.219(5), C(11)–Pt(1)–O(1) 94.07(12),
O(1)–Pt(1)–O(1)#1 78.24(11), C(11)–Pt(1)–P(1) 92.69(10), O(1)#1–
Pt(1)–P(1)95.07(8),O(1)–Pt(1)–Pt(1)#139.35(8),O(1)#1–Pt(1)–Pt(1)#1
38.90(7), P(1)–Pt(1)–Pt(1)#1 133.94(2), C(11′)–Pt(2)–O(2)#2
92.43(11), C(11′)–Pt(2)–O(2) 171.70(11), O(2)#2–Pt(2)–O(2)
79.27(11), C(11′)–Pt(2)–P(2) 93.42(9), O(2)#2–Pt(2)–P(2) 173.94(7),
O(2)–Pt(2)–P(2) 94.89(7), C(11′)–Pt(2)–Pt(2)#2 132.23(9), O(2)#2–
Pt(2)–Pt(2)#239.80(7),O(2)–Pt(2)–Pt(2)#239.47(7),P(2)–Pt(2)–Pt(2)#
134.34(2).
Figure 4. Ellipsoid representation of one of the two independient
anionic complexes [Pd2(κ1-Ar)2Cl2(µ-Cl)2]2– (5a) (50% probability).
Selected bond lengths (Å) and angles (deg) for the two independient
complexes 5a and 5b. 5a: Pd(1)–C(1) 1.979(3), Pd(1)–Cl(1)
2.2931(8), Pd(1)–Cl(2) 2.3199(8), Pd(1)–Cl(3) 2.4323(8), Pd(2)–C(11)
1.981(3), Pd(2)–Cl(4) 2.2943(8), Pd(2)–Cl(3) 2.3464(8), Pd(2)–Cl(2)
2.4230(8), C(1)–Pd(1)–Cl(1) 89.58(8), C(1)–Pd(1)–Cl(2) 90.94(8),
Cl(1)–Pd(1)–Cl(3)92.97(3),Cl(2)–Pd(1)–Cl(3)86.50(3),C(11)–Pd(2)–
Cl(4) 89.28(9), C(11)–Pd(2)–Cl(3) 92.53(9), Cl(4)–Pd(2)–Cl(2)
92.09(3), Cl(3)–Pd(2)–Cl(2) 86.13(3). 5b: Pd(1)–C(1) 1.970(3),
Pd(1)–Cl(1) 2.3113(8), Pd(1)–Cl(2) 2.3222(8), Pd(1)–Cl(3) 2.4262(8),
Pd(2)–C(11) 1.972(3), Pd(2)–Cl(4) 2.3055(8), Pd(2)–Cl(3) 2.3395(8),
Pd(2)–Cl(2) 2.4089(9), C(1)–Pd(1)–Cl(1) 91.09(9), C(1)–Pd(1)–Cl(2)
87.99(9), Cl(1)–Pd(1)–Cl(3) 93.50(3), Cl(2)–Pd(1)–Cl(3) 87.45(3),
C(11)–Pd(2)–Cl(4)90.59(9),C(11)–Pd(2)–Cl(3)89.75(9),Cl(4)–Pd(2)–Cl(2)
92.18(3), Cl(3)–Pd(2)–Cl(2) 87.46(3).
distance trans to the aryl group (9 2.087(3) Å) longer than that
trans to PPh3 (9 2.067(3) Å), (4) the Pd-O bonds trans to aryl
(11 2.086(2) Å) longer than those trans to oxygen atoms (11
2.005(2)–2.019(2) Å), (5) Pd-CNXy bond distances trans to
isocyanide [3 1.965(3) and 1.966(3) Å] longer than those trans
to O [2a 1.925(2) Å], and (6) Pd-Ar bond distances trans to
oxygen [2a 2.0002(2) Å, 2b 2.002(2) Å] shorter than trans to
Ar [3 2.069(3), 2.071(3) Å]. In addition, the Pd-Cl bond
t
distances trans to XyNC and BuNC [2a 2.0130(14) Å, 2b
2.0098(16) Å], (2) Pd-O bond distances trans to Ar [2a
2.0456(15) Å, 2b 2.0519(16) Å] longer than those trans to
isocyanide [2a 2.0130(14) Å, 2b 2.0098(16) Å], (3) Pt-O bond

1590 Organometallics, Vol. 27, No. 7, 2008
Vicente et al.
The crystal structure of 11 consists of dinuclear molecules
that adopt an anti geometry, with the acetate bridges conferring
an open-book shape upon the molecule. The planes of coordina-
tion around the Pd centers are stacked with a relatively short
Pd-Pd distance of 2.8227(4) Å, which is shorter than that
expected for the Pd-Pd covalent bond (3.00 Å) and lies in the
range found in some other [Pd]2(µ-OAc)2 complexes (2.821–2.936
Å).37,41
Spectroscopic Properties. The NMR spectra of all complexes
are in agreement with the proposed structures. Thus, at room
temperature, the 1H NMR spectra of complexes show the
expected two (2:1) or three (1:1:1) methyl singlets per κ1-Ar or
κ2-Ar groups, respectively, except in 10, which fortuitously
shows only one resonance corresponding to 18 protons. In
complex 8, the Me protons of the acetato ligand (0.68 ppm)
are shielded with respect to those in complex 11 (2.08 ppm),
certainly because of the proximity of aryl groups of PPh3 (see
Figure 5).
Figure 7. Ellipsoid representation of complex 11 (50% probability).
Selected bond lengths (Å) and angles (deg): Pd(1)–C(11) 1.955(3),
Pd(1)–O(4) 2.005(2), Pd(1)–O(5) 2.019(2), Pd(1)–O(1) 2.086(2),
Pd(1)–Pd(2) 2.8227(4), Pd(2)–C(21) 1.958(4), Pd(2)–O(12) 2.006(2),
Pd(2)–O(2) 2.008(2), Pd(2)–O(3) 2.086(2), N(1)–O(6) 1.206(4),
N(1)–O(5) 1.294(4), N(1)–C(12) 1.432(4), N(2)–O(10) 1.222(4),
N(2)–O(11) 1.226(4), N(2)–C(16) 1.471(4), N(3)–O(13) 1.214(4),
N(3)–O(12) 1.284(4), N(3)–C(22) 1.432(4), N(4)–O(18) 1.222(3),
N(4)–O(17) 1.221(4), N(4)–C(26) 1.485(4), O(1)–C(1) 1.253(4),
O(2)–C(1)1.274(4),O(3)–C(3)1.258(4),O(4)–C(3)1.272(4),C(11)–Pd(1)–
O(4) 97.03(12), C(11)–Pd(1)–O(5) 81.29(12), O(4)–Pd(1)–O(1)
89.08(10), O(5)–Pd(1)–O(1) 92.60(9), C(21)–Pd(2)–O(12) 81.28(12),
C(21)–Pd(2)–O(2)97.64(12),O(12)–Pd(2)–O(3)91.37(10),O(2)–Pd(2)–
O(3) 89.77(10)
The IR spectra of 8 and 9 show a weak band at 3605 and
3602 cm-1, respectively, assignable to ν(OH). In 10, bands
at 290 and 272 cm-1 are assigned to ν(PdCl)trans
and
P
to
ν(PdCl)trans Ar, respectively, in agreement with its crystal
to
structure. The chloro complex 4 shows a band assignable to
ν(PdCl) at 314 cm-1
.
Conclusions
We report a rare example of disproportionation when [Pd(κ2-
Ar)(O,O-acac)] is reacted with 4 equivalents of XyNC, yielding
trans-[Pd(κ1-Ar)2(CNXy)2]. We attribute this to a new transpho-
bia effect associated with formation of the intermediate [Pd(Ar)(C-
acac)(XyNC)2], the instability of which arises from the strong
T(aryl/C-acac). We have attempted to prepare this intermediate
by two other routes, confirming its instability and observing
instead the formation of trans-[Pd(κ1-Ar)2(CNXy)2]. This
complex is the first [Pd](Ar)2 with Ar ) C6(NO2)2-2,6-(OMe)3;
we had previously attempted to prepare this compound, unsuc-
cessfully, by a transmetalation using [HgAr2]. A rare example
of Pt-to-Hg transmetalation has allowed us to prepare a family
of [Pt](Ar)s, by reacting cis-[Pt(κ2-Ar)(κ1-Ar)(PPh3)] with
Hg(OAc)2 or HgCl2. Such monoaryl platinum complexes could
not be prepared by an Hg-to-Pt transmetalation.
distances in 5 follow the expected order: Pd-Cl bridging trans
to Ar (2.4323(8), 2.4230(8), 2.4262(8), 2.4089(9) Å) > bridging
trans to Cl (2.3199(8), 2.3464(8), 2.3222(8), 2.3395(8) Å) >
terminal trans to Cl (2.2931(8), 2.2943(8), 2.3113(8), 2.3055(8)
Å).
In 5, two crystallographically independent, but very similar,
units are present. One of them (5a) is represented in Figure 4.
The anion dimer is not far from approximate inversion symmetry
with four chloro ligands, two bridging and two terminal, and
two mutually trans κ1-Ar groups.
The structure of 8 consists of a dimer formed by carboxylato
and OH ligands bridging two PtAr(PPh3) units. The bridging
acetato and hydroxo ligands are trans to Ar and PPh3,
respectively. The Pt-OH (2.063(2), 2.069(2) Å) and Pt-C
(1.984(3), 1.985(3) Å) bond lengths are similar but the Pt(1)-P
(2.2192(7) Å) and Pt(1)-O(1) (2.1162(19) Å) bond distances
are significantly greater than Pt(2)-P (2.2069(7) Å) and
Pt(1)–O(2) (2.0890(19) Å) in spite of being both trans to OH
and Ar ligand. The acetato ligand occupies a strangely asym-
metric position, with C(1)–O(1) 1.271(2) Å > C(1)–O(2)
1.254(3) Å and O1 · · · Pt2 3.22 Å > O2 · · · Pt1 3.53 Å, and
C(1)–O(1)–Pt(1) 127.6(2)° > C(1)–O(2)–Pt(2) 122.3(2)°. There
is no obvious reason for this; in particular, there are no especially
short nonbonded interactions involving these atoms (indeed,
even the OH group forms no H bonds, presumably for steric
reasons).
In the crystals of 9, two crystallographically independent, but
very similar molecules are present, one of which is represented
in Figure 5. Both molecules display inversion symmetry. There
is a slight difference in the Pt · · · Pt distances (3.2228(4) and
3.2161(3) Å), which are intermediate between the expected
values for a van der Waals interaction (3.44 Å) and a covalent
bond (3.00 Å), but are bound to be short in view of the bridging
OH groups. Again, the OH groups do not participate in hydrogen
bonds.
Acknowledgment. We thank the Dirección General de
Investigación/FEDER for financial support (Grant CTQ2004-
05396). M.D.G.-L. and F. J.-H thank Fundación Séneca and
Universidad de Murcia, respectively, for grants.
Supporting Information Available: Crystallographic data in
CIF format for 2a, 2b, 3, 5, 8, 9, and 11. This material is available
free of charge via the Internet at http://pubs.acs.org.
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