Attempts to prepare palladium(II) complexes with the O,C,O pincer aryl ligand C6(NO2)2-2,6-(OMe)3-3,4,5 a

Article abstract of DOI:10.1021/om980633a

The complex [HgR₂] (R = C₆(NO₂)₂-2,6-(OMe)₃-3,4,5-C ¹ (2)), obtained by thermal decomposition of [Hg(O₂CR)₂] (1), reacts with Q₂[Pd₂Cl₄

Full text of DOI:10.1021/om980633a

5374
Organometallics 1998, 17, 5374-5383
Attem p ts To P r ep a r e P a lla d iu m (II) Com p lexes w ith th e
O,C,O P in cer Ar yl Liga n d C6(NO2)2-2,6-(OMe)3-3,4,5†
J ose´ Vicente,*,‡ Aurelia Arcas, Miguel-Angel Blasco, J ose´ Lozano, and
M. Carmen Ram´ırez de Arellano
Grupo de Quı´mica Organometa´lica,§ Departamento de Quı´mica Inorga´nica, Facultad de
Quı´mica, Universidad de Murcia, Apartado 4021, Murcia, 30071 Spain
Received J uly 27, 1998
The complex [HgR2] (R ) C6(NO2)2-2,6-(OMe)3-3,4,5-C1 (2)), obtained by thermal decom-
position of [Hg(O2CR)2] (1), reacts with Q2[Pd2Cl4(µ-Cl)2] to give [Hg(R)Cl] (3) and Q2[Pd-
(R)Cl(µ-Cl)]2 (Q ) (PhCH2)Ph3P (4a ), Me4N (4b)), which react (i) with Tl(acac) (1:2, acac )
acetylacetonate) to give Q[Pd(R)Cl(O,O-acac)] (Q ) (PhCH2)Ph3P (5a ), Me4N (5b)) or (ii)
with AgClO4 (1:2) to give [Pd(κ3-R)Cl] (κ3-R ) κ3-C6(NO2)2-2,6-(OMe)3-3,4,5-C1,O,O′ (6)), which
can also be obtained by reacting 5a with HBF4. Complex 6 reacts with p-toluidine (1:1, L)
to give [Pd(R)(µ-Cl)L]2 (7). Complex 5b decomposes in a mixture of acetone/water to give
[Pd(κ2-R)(O,O-acac)] (κ2-R ) κ2-C6(NO2)2-2,6-(OMe)3-3,4,5-C1,O (8)), which reacts (i) with
neutral monodentate ligands to give [Pd(R)(O,O-acac)L] (L ) PPh3 (9), pyridine (py) (10),
tetrahydrothiophene (11)), (ii) with bis(diphenylphosphino)methane (dppm) to give a complex
that readily oxidizes to give [Pd(R)(O,O-acac)(dppmO)] (dppmO ) monoxide of bis-
(diphenylphosphino)methane (12)), (iii) with 1,10-phenanthroline (phen) to give [Pd(R)(C-
acac)(phen)] (13), and (iv) with protonated ligands (HL)ClO4 to give 10 (L ) py) or
cis-[Pd(R)(H2O)2(PPh3)]‚H2O (L ) PPh3 (14)). Trifluoromethanesulfonic acid (HOSO2CF3)
reacts with 9 and PPh3 or with 13 to give trans-[Pd(R)(OSO2CF3)(PPh3)2] (15) or [Pd(R)(OSO2-
CF3)(phen)] (16), respectively. The X-ray crystal structures of 7‚2CH2Cl2, 8, 10, and 14‚
H2O have been determined.
In tr od u ction
ligands, as well as bimetallic complexes10,12 and, in
general, complexes with interesting properties.13-19
Other complexes with X,C,X pincer ligands20 (X ) N,21,22
P,23-42 S43-47) have also been reported, and some have
Complexes with the well-known pincer ligand 2,6-bis-
[(dimethylamino)methyl]phenyl have been shown to be
synthetically useful catalysts.1-4 This and related
ligands have been used to prepare complexes with
(12) Steenwinkel, P.; J astrzebski, J .; Deelman, B. J .; Grove, D. M.;
Kooijman, H.; Veldman, N.; Smeets, W. J . J .; Spek, A. L.; van Koten,
G. Organometallics 1997, 16, 5486.
(13) Toyota, S.; Futawaka, T.; Ikeda, H.; Oki, M. J . Chem. Soc.,
Chem. Commun. 1995, 2499.
unusual metal oxidation states (e.g. stable Ni(III)
7-10
complexes),5,6 with arenonium
or bridging11 aryl
† Dedicated to Professor Helmut Werner on the occasion of his 65th
birthday.
(14) Abbenhuis, H. C. L.; Feiken, N.; Grove, D. M.; J astrzebski, J .;
Kooijman, H.; Vandersluis, P.; Smeets, W. J . J .; Spek, A. L.; van Koten,
G. J . Am. Chem. Soc. 1992, 114, 9773.
‡ E-mail: jvs@fcu.um.es.
§ WWW: http://www.scc.um.es/gi/gqo/.
(1) van de Kuil, L. A.; Luitjes, H.; Grove, D. M.; Zwikker, J . W.; van
der Linden, J . G. M.; Roelofsen, A. M.; J enneskens, L. W.; Drenth, W.;
van Koten, G. Organometallics 1994, 13, 468.
(2) Knapen, J . W. J .; van der Made, A. W.; de Wilde, J . C.; van
Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; van Koten, G. Nature
1994, 372, 659.
(15) Maassarani, F.; Davidson, M. F.; Wehman-Ooyevaar, I. C. M.;
Grove, D. M.; van Koten, M. A.; Smeets, W. J . J .; Spek, A. L.; van
Koten, G. Inorg. Chim. Acta 1995, 235, 327.
(16) Sutter, J . P.; Grove, D. M.; Beley, M.; Collin, J . P.; Veldman,
N.; Spek, A. L.; Sauvage, J . P.; van Koten, G. Angew. Chem., Int. Ed.
Engl. 1994, 33, 1282.
(3) Grove, D. M.; van Koten, G.; Verschuuren, A. H. M. J . Mol. Catal.
1988, 45, 169.
(17) Carre´, F.; Chuit, C.; Corriu, R. J . P.; Mehdi, A.; Reye´, C. Angew.
Chem., Int. Ed. Engl. 1994, 33, 1097.
(4) van de Kuil, L. A.; Grove, D. M.; Gossage, R. A.; Zwikker, J . W.;
J enneskens, L. W.; Drenth, W.; van Koten, G. Organometallics 1997,
16, 4985.
(5) Grove, D. M.; van Koten, G.; Zoet, R.; Murall, N. W.; Welch, A.
J . J . Am. Chem. Soc. 1983, 105, 1379.
(6) Grove, D. M.; van Koten, G.; Mul, P.; van der Zeijden, A. A. H.;
Terheijden, J .; Zoutberg, M. C.; Stam, C. H. Organometallics 1986, 5,
322.
(18) van de Kuil, L. A.; Veldhuizen, Y. S. J .; Grove, D. M.; Zwikker,
J . W.; J enneskens, L. W.; Drenth, W.; Smeets, W. J . J .; Spek, A. L.;
van Koten, G. J . Organomet. Chem. 1995, 488, 191.
(19) Kapteijn, G. M.; Wehman-Ooyevaar, I. C. M.; Grove, D. M.;
Smeets, W. J . J .; Spek, A. L.; van Koten, G. Angew. Chem., Int. Ed.
Engl. 1993, 32, 72.
(20) Steenwinkel, P.; Gossage, R. A.; van Koten, G. Chem. Eur. J .
1998, 4, 759.
(7) Steenwinkel, P.; J ames, S. L.; Grove, D. M.; Kooijman, H.; Spek,
A. L.; van Koten, G. Organometallics 1997, 16, 513.
(8) Terheiden, J .; van Koten, G.; Vinke, I. C.; Spek, A. L. J . Am.
Chem. Soc. 1985, 107, 2891.
(9) Grove, D. M.; van Koten, G.; Louwen, J . N.; Noltes, J . G.; Spek,
A. L.; Ubbels, H. J . C. J . Am. Chem. Soc. 1982, 104, 6609.
(10) Lagunas, M.-C.; Gossage, R. A.; Spek, A. L.; van Koten, G.
Organometallics 1997, 17, 7731.
(21) Stark, M. A.; Richards, C. J . Tetrahedron Lett. 1997, 38, 5881.
(22) Denmark, S. E.; Stavenger, R. A.; Faucher, A. M.; Edwards, J .
P. J . Org. Chem. 1997, 62, 3375.
(23) Moulton, C. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1976,
1020.
(24) J ouaiti, A.; Geoffroy, M.; Terron, G.; Bernardinelli, G. J . Chem.
Soc., Chem. Commun. 1992, 155.
(25) Kaska, W. C.; Nemeh, S.; Shirazi, A.; Potuznik, S. Organome-
tallics 1988, 7, 13.
(11) Abbenhuis, H. C. L.; Rietveld, M. H. P.; Haarman, H. F.;
Hogerheide, M. P.; Spek, A. L.; van Koten, G. Organometallics 1994,
13, 3259.
(26) Gorla, F.; Togni, A.; Venanzi, L. M.; Albinati, A.; Lianza, F.
Organometallics 1994, 13, 1607.
10.1021/om980633a CCC: $15.00 © 1998 American Chemical Society
Publication on Web 11/06/1998

Pd(II) Complexes with an O,C,O Pincer Ligand
Organometallics, Vol. 17, No. 24, 1998 5375
been used as catalysts.21,22,26,27,31,48-52 The only com-
plexes containing O,C,O pincer ligands have been
described while this paper was in preparation. These
are tin(IV) complexes containing the ligand C6H2[P(O)-
(OEt)2]2-1,3-t-Bu-4.53 We report here the first palladium
complex containing an O,C,O pincer ligand ([Pd{C6-
(NO2)2-2,6-(OMe)3-3,4,5}Cl]) as well as other complexes
with the same ligand acting as a mono- and dicoordi-
nated group. Among these derivatives there are com-
plexes showing interesting intra- and intermolecular
hydrogen bonds as well as complexes with the weakly
coordinating ligand CF3SO3 and, as far as we are aware,
the first organometallic diaquapalladium(II) complex.
rhodium,74-76 using the corresponding mercury deriva-
tives as transmetalating agents. This is the method
most frequently employed in the preparation of nitroaryl
complexes. Other methods using organolithium or tin
derivatives,77 oxidative-addition reactions,78-80 arylhy-
drazonium salts,81 or direct metalation of arenes82-84
have more limited applicability. Recently, even the
nitration of aryl complexes has been reported.85,86 Our
interest in the synthesis of nitroaryl complexes is based
on the great stability of these complexes (allowing, for
example, the synthesis of carbonyl arylpalladium(II)
complexes70) and on the study of the structural proper-
ties and the coordination ability of the nitro group. We
have shown, for example, that the -I rather than -M
effect is observable in most nitroaryl complexes, accord-
ing to their structures.57,58,64,66-76 We have studied
complexes containing 2-nitro- and 2,4,6-trinitroaryl
ligands and shown that, while for the former case the
aryl ligand can be mono- or dicoordinated, for the latter
the ligand68-70 can only be monocoordinated. We de-
signed this last type of ligand to see if it can be
dicoordinated or act as a pincer. We assumed that the
4-NO2 group could be responsible for the decrease of the
2,6-dinitro groups in coordinating one or both O atoms.
For that we designed the ligand C6(NO2)2-2,6-(OMe)3-
3,4,5, which, according to the electron-releasing capacity
of the three OMe groups, could help the coordination of
We have synthesized a large family of nitroaryl
complexes of gold,54-65 palladium,66-71 platinum,72,73 and
(27) Gupta, M.; Hagen, C.; Flesher, R. J .; Kaska, W. C.; J ensen, C.
M. Chem. Commun. 1996, 2083.
(28) J ouaiti, A.; Geoffroy, M.; Terron, G.; Bernardinelli, G. J . Am.
Chem. Soc. 1995, 117, 2251.
(29) Rybtchinski, B.; Vigalok, A.; Ben-David, Y.; Milstein, D. J . Am.
Chem. Soc. 1996, 118, 12406.
(30) Dani, P.; Karlen, T.; Gossage, R. A.; Smeets, W. J . J .; Spek, A.
L.; van Koten, G. J . Am. Chem. Soc. 1997, 119, 11317.
(31) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein, D. J . Am.
Chem. Soc. 1997, 119, 11687.
(32) J ouaiti, A.; Geoffroy, M.; Collin, J . P. Inorg. Chim. Acta 1996,
245, 69.
(33) Kennedy, A. R.; Cross, R. J .; Muir, K. W. Inorg. Chim. Acta
1995, 231, 195.
(34) Kennedy, A. R.; Cross, R. J .; Muir, K. W. Inorg. Chim. Acta
1995, 231, 207.
(35) van der Boom, M. E.; Liou, S. Y.; Ben-David, Y.; Vigalok, A.;
Milstein, D. Angew. Chem., Int. Ed. Engl. 1997, 36, 625.
(36) Weisman, A.; Gozin, M.; Kraatz, H. B.; Milstein, D. Inorg. Chem.
1996, 35, 1792.
(37) Cross, R. J .; Kennedy, A. R.; Manojlovic-Muir, L.; Muir, K. W.
J . Organomet. Chem. 1995, 493, 243.
(38) J ia, G. C.; Lee, H. M.; Williams, L. D. J . Organomet. Chem.
1997, 534, 173.
(39) van der Boom, M. E.; Kraatz, H. B.; Bendavid, Y.; Milstein, D.
Chem. Commun. 1996, 2167.
(40) Rybtchinski, B.; Bendavid, Y.; Milstein, D. Organometallics
1997, 16, 3786.
(41) Lee, H. M.; Yao, J . Z.; J ia, G. C. Organometallics 1997, 16, 3927.
(42) Vigalok, A.; Ben-David, Y.; Milstein, D. Organometallics 1996,
15, 1839.
(43) Giesbretch, G. R.; Hanan, G. S.; Kickham, J . E.; Loeb, S. J .
Inorg. Chem. 1992, 31, 3286.
(61) Vicente, J .; Bermu´dez, M. D.; Escribano, J . Organometallics
1991, 10, 3380.
(62) Vicente, J .; Bermu´dez, M. D.; Carrio´n, F. J .; J ones, P. G. J .
Organomet. Chem. 1996, 508, 53.
(63) Vicente, J .; Bermu´dez, M. D.; Carrio´n, F. J .; J ones, P. G. Chem.
Ber. 1996, 129, 1301.
(64) Vicente, J .; Bermu´dez, M. D.; Carrio´n, F. J .; J ones, P. G. Chem.
Ber. 1996, 129, 1395.
(65) Vicente, J .; Chicote, M. T.; Gonza´lez-Herrero, P.; Gru¨nwald, C.;
J ones, P. G. Organometallics 1997, 16, 3381.
(66) Vicente, J .; Arcas, A.; Borrachero, M. V.; Hursthouse, M. B. J .
Chem. Soc., Dalton Trans. 1987, 1655.
(67) Vicente, J .; Chicote, M. T.; Martin, J .; Artigao, M.; Solans, X.;
Font-Altaba, M.; Aguilo´, M. J . Chem. Soc., Dalton Trans. 1988, 141.
(68) Vicente, J .; Arcas, A.; Borrachero, M. V.; Molı´ns, E.; Miravitlles,
C. J . Organomet. Chem. 1989, 359, 127.
(44) Lucena, N.; Casabo, J .; Escriche, L.; Sanchezcastello, G.;
Teixidor, F.; Kivekas, R.; Sillanpaa, R. Polyhedron 1996, 15, 3009.
(45) Dupont, J .; Pfeffer, M. J . Chem. Soc., Dalton Trans. 1990, 3193.
(46) Huck, W. T. S.; van Veggel, F. C. J . M.; Kropman, B. L.; Blank,
D. H. A.; Keim, E. G.; Reinhoudt, D. N. J . Am. Chem. Soc. 1995, 117,
8293.
(47) Loeb, S. J .; Shimizu, G. K. H.; Wisner, J . A. Organometallics
1998, 17, 2324.
(48) Xu, W. W.; Rosini, G. P.; Gupta, M.; J ensen, C. M.; Kaska, W.
C.; Krogh-J espersen, K.; Goldman, A. S. Chem. Commun. 1997, 2273.
(49) Longmire, J . M.; Zhang, X. M. Tetrahedron Lett. 1997, 38, 1725.
(50) Gupta, M.; Kaska, W. C.; J ensen, C. M. Chem. Commun. 1997,
461.
(51) Lee, D. W.; Kaska, W. C.; J ensen, C. M. Organometallics 1998,
17, 1.
(52) Gupta, M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; J ensen, C.
M. J . Am. Chem. Soc. 1997, 119, 840.
(53) Mehring, M.; Schurmann, M.; J urkschat, K. Organometallics
1998, 17, 1227.
(54) Vicente, J .; Chicote, M. T.; Arcas, A.; Artigao, M. Inorg. Chim.
Acta 1982, 65, L251.
(69) Vicente, J .; Arcas, A.; Borrachero, M. V.; de Goicoechea, M. L.;
Lanfranchi, M.; Tiripicchio, A. Inorg. Chim. Acta 1990, 177, 247.
(70) Vicente, J .; Arcas, A.; Borrachero, M. V.; Tiripicchio, A.;
Tiripicchio-Camellini, M. Organometallics 1991, 10, 3873.
(71) Vicente, J .; Arcas, A.; Borrachero, M. V.; Molı´ns, E.; Miravitlles,
C. J . Organomet. Chem. 1992, 441, 487.
(72) Vicente, J .; Chicote, M. T.; Martin, J .; J ones, P. G.; Fittschen,
C.; Sheldrick, G. M. J . Chem. Soc., Dalton Trans. 1986, 2215.
(73) Vicente, J .; Chicote, M. T.; Martin, J .; J ones, P. G.; Fittschen,
C. J . Chem. Soc., Dalton Trans. 1987, 881.
(74) Vicente, J .; Martin, J .; Chicote, M. T.; Solans, X.; Miravitlles,
C. J . Chem. Soc., Chem. Commun. 1985, 1004.
(75) Vicente, J .; Martin, J .; Solans, X.; Font-Altaba, M. Organome-
tallics 1989, 8, 357.
(76) Vicente, J .; Abad, J . A.; Lahoz, F. J .; Plou, F. J . J . Chem. Soc.,
Dalton Trans. 1990, 1459.
(77) Brune, H. A.; Stapp, B.; Schmidtberg, G. J . Organomet. Chem.
1986, 307, 129.
(78) Fitton, P.; Rick, E. A. J . Organomet. Chem. 1971, 28, 287.
(79) Beck, W.; Schorpp, K.; Stetter, K. H. Z. Naturforsch., B 1971,
26, 684.
(55) Vicente, J .; Chicote, M. T.; Arcas, A.; Artigao, M.; J ime´nez, R.
J . Organomet. Chem. 1983, 247, 123.
(56) Vicente, J .; Arcas, A.; Chicote, M. T. J . Organomet. Chem. 1983,
252, 257.
(57) Vicente, J .; Arcas, A.; Mora, M.; Solans, X.; Font-Altaba, M. J .
Organomet. Chem. 1986, 309, 369.
(58) Vicente, J .; Arcas, A.; J ones, P. G.; Lautner, J . J . Chem. Soc.,
Dalton Trans. 1990, 451.
(80) Vicente, J .; Abad, J . A.; Sa´nchez, J . A. J . Organomet. Chem.
1988, 352, 257.
(81) Braunstein, P.; Clark, R. J . H. Inorg. Chem. 1974, 13, 2241.
(82) Shibaeva, R. P.; Rozenberg, L. P.; Lobkovskaya, R. M.; Shilov,
A. E.; Shul’pin, G. B. J . Organomet. Chem. 1981, 220, 271.
(83) de Graaf, P. W. J .; Boersma, J .; van der Kerk, G. J . M. J .
Organomet. Chem. 1976, 105, 399.
(84) Shilov, A. E.; Shulpin, G. B. Chem. Rev. 1997, 97, 2879.
(85) Clark, G. R.; Headford, C. E. L.; Roper, W. R.; Wright, L. J .;
Yap, V. P. D. Inorg. Chim. Acta 1994, 220, 261.
(59) Vicente, J .; Bermu´dez, M. D.; Chicote, M. T.; Sa´nchez-Santano,
M. J . J . Organomet. Chem. 1990, 381, 285.
(60) Vicente, J .; Bermu´dez, M. D.; Escribano, J .; Carrillo, M. P.;
J ones, P. G. J . Chem. Soc., Dalton Trans. 1990, 3083.
(86) Clark, G. R.; Rickard, C. E. F.; Roper, W. R.; Wright, L. J .; Yap,
V. P. D. Inorg. Chim. Acta 1996, 251, 65.

5376 Organometallics, Vol. 17, No. 24, 1998
Vicente et al.
62.7 (s, m- MeO), 145.5 (s, p-C), 147.1 (s, Hg-C), 148.8 (s, o-C),
152.4 (s, m-C). Anal. Calcd for C18H18HgN4O14: C, 30.24; H,
2.54; N, 7.84. Found: C, 30.50; H, 2.84; N, 7.72.
Ch a r t 1
Syn th esis of [Hg(R)Cl] (3) a n d [P P h 3(CH2P h )]2[P d (R)-
Cl(µ-Cl)]2 (4a ). A suspension of 2 (2.30 g, 3.22 mmol) and
[PPh3(CH2Ph)]2[Pd2Cl4(µ-Cl)2] (1.82 g, 1.60 mmol) in acetone
(150 mL) was refluxed for 40 min, and the resulting suspension
was filtered hot. The solution was used to prepare 3 (solution
A). The orange solid was an acetone solvate (by IR) of 4a (1.9
g). The resulting solution was concentrated (40 mL) to give a
solid that was washed with diethyl ether to get a second crop
of 4a (474 mg). Yield: 2.37 g, 87% (assuming the formula 4a ‚
2Me2CO like that of the related complex with R ) C6H3(NO2)-
2,4,6).68 Mp: 215-220 °C. The insolubility of 4a in organic
solvents prevented NMR studies. An unsolvated sample was
obtained by heating the solid (70 °C) over 24 h. IR (cm-1):
ν(PdCl) 330, 285, 258. Anal. Calcd for C68H62Cl4N4O14P2Pd2:
C, 51.83; H, 3.97; N, 3.56. Found: C, 51.53; H, 3.95; N, 3.50.
one or both O atoms of the 2,6-dinitro groups (see Chart
1). In this paper we show that our expectations were
fulfilled.
Exp er im en ta l Section
Unless otherwise stated, all reactions were carried out under
normal laboratory conditions. The conductivity measurements
were made using ∼5 × 10-4 mol L-1 solutions in acetone.
3,4,5-Trimethoxybenzoic acid was purchased from Fluka. The
complexes [Pd2Cl4(µ-Cl)2]2- 68 and Tl(acac)87 were prepared as
reported. The notation used to designate the different modes
of coordination of the aryl groups can be seen in Chart 1.
Unless otherwise stated, NMR spectra were recorded on a
Varian Unity 300. Chemical shifts are referenced to TMS (1H
and 13C{1H}) and H3PO4 (31P{1H}).
Syn th esis of 1,2,3-Tr in itr o-4,5,6-tr im eth oxyben zen e
a n d Mer cu r y(II) 2,6-Din itr o-3,4,5-tr im eth oxyben zoa te
(1). 3,4,5-Trimethoxybenzoic acid was added (20 g, 94.25
mmol) in small portions to a well-stirred mixture of concen-
trated sulfuric (96%, 160 mL) and nitric (60%, 48 mL) acids
in a flask placed in a ice-salt bath, at such a rate that the
temperature remained at around 10 °C. After 3-4 h without
stirring, the mixture was poured into 500 g of crushed ice. The
resulting precipitate was filtered after 12 h and washed with
cold water to give 8.12 g of a mixture of 2,6-dinitro-3,4,5-
trimethoxybenzoic acid and 1,2,3-trimethoxy-4,5,6-trinitroben-
zene that was washed with boiling water (100 mL). The
insoluble product was identified as 1,2,3-trimethoxy-4,5,6-
trinitrobenzene. Yield: 1.8 g, 6.3%. Mp: 153 °C. 1H NMR
(CDCl3): δ 4.08 (s, 3H, MeO), 4.07 (s, 6H, MeO). 13C{1H} NMR
(CDCl3): δ 61.99 (MeO-5), 63.20 (MeO-4,6), 129.67 (CNO2-2),
135.18 (CNO2-1,3), 148.0 (COMe-4,6), 151.67 (COMe-5). MS:
m/z (%) 303 (M+, 39), 168 (43), 140 (100), 92 (81), 75 (64), 46
(54). Anal. Calcd for C9H9N3O9: C, 35.65; H, 2.99; N, 13.86.
Found: C, 35.91; H, 2.98; N, 13.61.
Solution A was concentrated, and addition of hexane
precipitated a solid which was filtered, washed with hexane,
and air-dried to give 3 as a off-white solid. Yield: 1.06 g, 67%.
Mp: 166-171 °C. 1H NMR (d6-acetone): δ 4.10 (s, 6H, MeO),
4.00 (s, 3H, MeO). 13C{1H} NMR (d6-acetone): δ 61.72 (s,
p-MeO), 62.86 (s, m-MeO), 138.43 (s, Hg-C), 143.34 (s, p-C),
149.28 (s, o-C), 153.07 (s, m-C). Anal. Calcd for C9H9-
ClHgN2O7: C, 21.92; H, 1.84; N, 5.68. Found: C, 22.04; H,
1.66; N, 5.70.
Syn th esis of (NMe4)2[P d (R)Cl(µ-Cl)]2 (4b). (NMe4)2[Pd2-
Cl4(µ-Cl)2] (136 mg, 0.24 mmol) was added to a solution of 2
(306 mg, 0.43 mmol) in acetone (8 mL) solid. After it was
stirred for 50 min at room temperature, the solution was
concentrated and the suspension filtered. The resulting
precipitate was washed with diethyl ether and air-dried to give
4b as an orange solid. Yield: 205 mg, 94%. Mp: 226-230
°C. The insolubility of 4b in any solvent prevented NMR
studies. IR (cm-1): ν(PdCl) 335, 293, 263. Anal. Calcd for
C
26H42Cl4N6O14Pd2: C, 30.70; H, 4.16; N, 8.26. Found: C,
30.69; H, 4.05; N, 8.26.
Syn th esis of Q[P d (R)Cl(O,O-a ca c)] (Q ) P P h 3(CH2P h )
(5a ), NMe4 (5b)). Tl(acac) (2:1) was added to a suspension of
4a (1.90 g, 1.21 mmol) or 4b (380 mg, 0.37 mmol) in acetone.
After 25 min the resulting suspension was filtered through
Celite, the resulting solution was concentrated (5 mL), and
diethyl ether was added to precipitate 5a or 5b as a yellow
solid.
5a : yield 1.605 g, 78%. Mp: 172-178 °C. ΛM ) 93 Ω-1 cm2
mol-1 1H NMR (CDCl3): δ 1.55 (s, 3H, Me), 1.80 (s, 3H, Me),
.
3.75 (s, 3H, MeO), 3.87 (s, 6H, MeO), 5.00 (s, 1H, CH), 5.06 (s,
To the resulting solution was added mercuric acetate (3.33
g, 10.45 mmol) in small portions. The resulting precipitate
was collected by filtration, washed with water, and dried in
vacuo to give 1 as a yellow solid. Yield: 4.4 g, 12.4% (over
the calculated amount of 2,6-dinitro-3,4,5-trimethoxybenzoic
acid present in the solution). 1H NMR (d6-acetone): δ 4.04 (s,
2H, CH2), 6.97-7.76 [m, 22H, Ph]. 13C{1H} NMR (CDCl3): δ
1
26.1 (s, Me), 27.1 (s, Me), 30.5 (d, CH2, J P-C ) 47.9 Hz), 60.9
(s, p-MeO), 61.9 (s, m-MeO), 99.7 (s, CH), 117.7 (d, Cipso-P,
1J P-C ) 85.8 Hz), 128.8 (s, o-C of PhCH2), 130.2 (d, o-C of PhP,
3
2J P-C ) 12.48 Hz), 134.3 (d, m-C of PhP, J P-C ) 9.71 Hz),
135.0 (s, p-C of CH2Ph), 185.0 (s, CO), 186.1 (s, CO). Anal.
12H, MeO), 4.09 (s, 6H, MeO). Anal. Calcd for C20H18
-
Calcd for
C39H38ClN2O9PPd: C, 55.01; H, 4.50; N, 3.29.
HgN4O18: C, 29.92; H, 2.26; N, 6.98. Found: C, 29.58; H, 2.13;
N, 6.99.
Found: C, 54.79; H, 4.37; N, 3.28.
5b: yield 305 mg, 71%. Mp: 212-214 °C. ΛM ) 121 Ω-1
Syn th esis of [HgR2] (2). Compound 1 (4 g, 4.98 mmol)
was heated to 180 °C using a glycerin bath. This temperature
was maintained until the resulting liquid solidified. After the
mixture was cooled, dichloromethane (30 mL) was added and
the suspension centrifuged. The decanted yellow dichlo-
romethane solution was purified by passing it through a
column of silica gel (8 cm high, 2 cm diameter). The pale
yellow solution was concentrated (10 mL) and n-hexane added
to precipitate 2 as an off-white solid, which was filtered off,
washed with hexane, and air-dried. Yield: 1.99 g, 56%. Mp:
250-252 °C. 1H NMR (d6-acetone): δ 4.09 (s, 12H, MeO), 4.01
(s, 6H, MeO). 13C{1H} NMR (d6-acetone): δ 61.7 (s, p-MeO),
cm2 mol-1 1H NMR (d6-acetone): δ 1.73 (s, 3H, Me), 1.76 (s,
.
3H, Me), 3.43 (s, 12H, NMe4), 3.87 (s, 3H, p-MeO), 3.91 (s, 6H,
m-MeO), 5.18 (s, 1H, CH). 13C{1H} NMR (d6-acetone): δ 26.2
1
(s, Me), 27.2 (s, Me), 56.1 (t, NMe4, J C-N ) 4 Hz), 61.3 (s,
MeO), 62.3 (s, MeO), 99.6 (s, CH), 128.2, 143.0, 146.3 (s,
quaternary aryl carbons), 185.2 (s, CO), 186.7 (s, CO). Anal.
Calcd for C18H28ClN3O9Pd: C, 37.78; H, 4.93; N, 7.34.
Found: C, 37.86; H, 4.83; N, 7.20.
Syn th esis of [P d (K3-R)Cl] (6). Meth od a . AgClO4 (18.4
mg, 0.09 mmol) was added to a suspension of 4a (70 mg, 0.04
mmol) in acetone (15 mL). After it was stirred for a few
minutes, the suspension was filtered through Celite and the
resulting solution was evaporated to dryness. Addition of
(87) Vicente, J .; Chicote, M. T. Inorg. Synth. 1998, 32, 172.

Pd(II) Complexes with an O,C,O Pincer Ligand
Organometallics, Vol. 17, No. 24, 1998 5377
dichloromethane (1 mL) gave first a solution, and immediately
6 precipitated as an intense orange solid. Yield: 20.7 mg, 58%.
Meth od b. A solution (0.24 mL) of HBF4 (1.75 mmol) in
diethyl ether (54%) was added to a solution of 5a (1.50 g, 1.77
mmol) in dichloromethane (4 mL). The resulting precipitate
was filtered to give 6. Yield: 0.50 g, 71%. Mp: 259-261 °C.
IR (cm-1): ν(PdCl) 293. 1H NMR (CDCl3): δ 3.87 (s, 3H,
p-MeO), 4.08 (s, 6H, m-MeO). Anal. Calcd for C9H9ClN2O7-
Pd: C, 27.09; H, 2.27; N, 7.02. Found: C, 27.08; H, 2.31; N,
6.75.
186.02 (CO), 186.32 (CO). Anal. Calcd for C18H24N2O9PdS:
C, 39.25; H, 4.39; N, 5.09, S, 5.82. Found: C, 39.13; H, 4.42;
N, 5.04; S, 5.50.
Syn th esis of [P d (R)(O,O-a ca c)(d p p m O)] (d p p m O ) bis-
(d ip h en ylp h osp h in o)m eth a n e Mon oxid e) (12). Bis(diphe-
nylphosphino)methane (66.5 mg, 0.17 mmol) was added to a
solution of 8 (80 mg, 0.17 mmol) in dichloromethane (3 mL).
The solution was filtered, the resulting solution concentrated
(2 mL), and n-hexane added to precipitate 12 as a pale yellow
solid. Yield: 105.1 mg, 72%. Mp: 177-179 °C. 1H NMR
(CDCl3): δ 1.84 (s, 3H, Me), 1.94 (s, 3H, Me), 3.38 (d, 2H, CH2,
2J H-P ) 9 Hz), 3.68 (s, 3H, MeO), 3.78 (s, 6H, MeO), 5.34 (s,
1H, CH), 7.16-7.69 (m, 20H, Ph), 31P{1H} NMR (CDCl3): δ
-28.31 (d, 2J P-P ) 32 Hz), 22.81 (d, PdO, 2J P-P ) 32 Hz). Anal.
Syn th esis of [P d (R)(µ-Cl)(H2NC6H4Me-4)]2 (7). Solid
p-toluidine (16.3 mg, 0.15 mmol) was added to a suspension
of 6 (60.8 mg, 0.15 mmol) in dichloromethane (6 mL). The
solution was concentrated (2 mL) and n-pentane added to
precipitate 7 as a yellow solid. Yield: 53.5 mg, 70%. Mp:
Calcd for
C39H38N2O10P2Pd: C, 54.27; H, 4.44; N, 3.25.
183-185 °C. IR: ν(Pd-Cl) 320, 278 cm-1 1H NMR (CDCl3):
.
Found: C, 54.27; H, 4.35; N, 3.34.
3
δ 2.22 (s, 3H, Me), 3.81 (d, 3H, MeO, J HH ) 1.5 Hz, see
Discussion), 3.83 (s, 3H, MeO), 3.94 (s, 3H, MeO), 4.94-4.96
(br, 1H, NH2), 5.08 (s, 1H, NH2), 6.76-6.97 (m, 4H, p-
toluidine). Anal. Calcd for C32H36Cl2N6O14Pd2: C, 37.97; H,
3.58; N, 8.30. Found: C, 38.03; H, 3.48; N, 8.02. Single
crystals of 7‚2CH2Cl2 were obtained by slow diffusion of
hexane into a solution of 7 in dichloromethane.
Syn th esis of [P d (K2-R)(O,O-a ca c)] (8). Water (15 mL)
was added to a solution of 5b (305 mg, 0,53 mmol) in acetone
(5 mL). The resulting precipitate was filtered and air-dried
to give 8 as an intensely orange solid. Yield: 200 mg, 82%.
Mp: 168 °C dec. 1H NMR (CDCl3): δ 2.04 (s, 3H, Me), 2.06
(s, 3H, Me), 3.88 (s, 3H, p-MeO), 4.04, 4.12 (two s, 3H, m-MeO),
5.45 (s, 1H, CH). Anal. Calcd for C14H16N2O9Pd: C, 36.34; H,
3.49; N, 6.05. Found: C, 36.27; H, 3.46; N, 6.04. Single
crystals of 8 were obtained by slow diffusion of n-pentane into
a solution of 8 in acetone.
Syn th esis of [P d (R)(O,O-a ca c)(P P h 3)] (9). PPh3 (57.2
mg, 0.22 mmol) was added to a solution of 8 (100 mg, 0.22
mmol) in dichloromethane (7 mL). The resulting solution was
concentrated (2 mL) and n-pentane added to give 9 as a yellow
solid. Yield: 131 mg, 83%. Mp: 223-224 °C. 1H NMR
(CDCl3): δ 1.56 (s, 3H, Me), 1.97 (s, 3H, Me), 3.76 (s, 3H, MeO),
3.77 (s, 6H, MeO), 5.33 (s, 1H, CH), 7.31-7.56 (m, 15H, PPh3).
31P{1H} NMR (CDCl3): δ 27.39 (s). Anal. Calcd for C32H31N2O9-
PPd: C, 53.02; H, 4.31; N, 3.86. Found: C, 53.25; H, 4.26; N,
3.85.
Syn th esis of [P d (R)(O,O-a ca c)(p y)] (10). Meth od a .
Two drops of pyridine were added to a suspension of 8 (50 mg,
0.11 mmol) in dichloromethane (4 mL). The solution was
concentrated (2 mL) and diethyl ether added to give 10 as an
off-white solid. Yield: 33.8 mg, 58%. Mp: 194-197 °C. 1H
NMR (CDCl3): δ 1.908 (s, 3H, Me), 1.914 (s, 3H, Me), 3.87 (s,
3H, MeO), 3.96 (s, 6H, MeO), 5.33 (s, 1H, CH), 7.26-7.33 (m,
2H, m-py), 7.76-7.82 (m, 1H, p-py), 8.54-8.57 (m, 2H, o-py).
Anal. Calcd for C19H21N3O9Pd: C, 42.12; H, 3.91; N, 7.76.
Found: C, 42.26; H, 3.80; N, 7.82.
Meth od b. A saturated solution of pyridinium perchlorate
(24 mg, 0.13 mmol) in water was added to a suspension of 8
(50.2 mg, 0.11 mmol) in acetone (1 mL). After the mixture
was stirred for 4 h at room temperature, a solid precipitated,
which was filtered and washed with water and then methanol
to give 10. Yield: 44.3 mg, 76%. Single crystals of 10 were
obtained by slow diffusion of a solution of 8 in acetone into a
solution of pyridinium perchlorate in water.
Syn th esis of [P d (R)(O,O-a ca c)(th t)] (11). A drop of
tetrahydrothiophene was added to a solution of 8 (100 mg, 0.22
mmol) in dichloromethane. The resulting solution was con-
centrated (2 mL). Addition of diethyl ether gave yellow
crystals of complex 11. Yield: 88.7 mg, 75%. Mp: 172-174
°C. 1H NMR (CDCl3): δ 1.897 (s, 3H, Me), 1.901 (s, 3H, Me),
2.5-3.6 (m, br, 8H, tht), 3.89 (s, 3H, MeO), 3.99 (s, 6H, MeO),
5.29 (s, 1H, CH). 13C{1H} NMR (CDCl3): δ 26.37 (Me), 27.28
(Me), 30.00 (CH2), 36.57 (CH2), 61.10 (MeO), 62.16 (MeO),
100.29 (CH), 127.69, 143.50, 147.10, 147.56 (arylic carbons),
Syn th esis of [P d (R)(C-a ca c)(p h en )] (13). 1,10-Phenan-
throline (43 mg, 0.22 mmol) was added to a solution of 8 (100
mg, 0.22 mmol) in dichloromethane (3 mL). The solution was
concentrated (2 mL) and diethyl ether added to precipitate 13
1
as a yellow solid. Yield: 114 mg, 82%. Mp: 205-206 °C. H
NMR (CDCl3): δ 2.13 (s, 6H, Me), 4.02 (s, 3H, MeO), 4.10 (s,
6H, MeO), 5.29 (s, 1H, CH), 7.63-9.77 (m, 8H, phen). Anal.
Calcd for C26H24N4O9Pd: C, 48.57; H, 3.76; N, 8.71. Found:
C, 48.50; H, 3.76; N, 8.41.
Syn th esis of cis-[P d (R)(H2O)2(P P h 3)]ClO4‚H2O (14).
Solid (HPPh3)ClO4 (79 mg, 0.22 mmol) was added to a solution
of 8 (100 mg, 0.22 mmol) in dichloromethane (3 mL). The
solution was concentrated (2 mL) and n-pentane added to
precipitate 14 as a yellow solid. Yield: 140.5 mg, 85%. Mp:
140-143 °C. ΛM ) 101 Ω-1 cm2 mol-1 (acetone). 1H NMR
(CDCl3): δ 2.8-3.4 (br, 4H, H2O), 3.77 (s, 3H, MeO), 3.79 (s,
6H, MeO), 7.39-7.53 (m, 15H, PPh3). 31P{1H} NMR (CDCl3):
δ 27.55 (s). Anal. Calcd for C27H30ClN2O14PPd: C, 41.61; H,
3.88; N, 3.59. Found: C, 41.55; H, 3.88; N, 3.59. Single
crystals of 14 were obtained by slow diffusion of n-pentane
into a solution of 14 in chloroform.
Syn th esis of [P d (R)(OSO2CF 3)(P P h 3)2] (15). PPh3 (62
mg, 0.24 mmol) and trifluoromethanesulfonic acid (3 drops)
were added to a solution of 9 (81 mg, 0.11 mmol) in dichlo-
romethane. After the mixture was stirred for 2 days at room
temperature, it was concentrated (2 mL) and diethyl ether
added to precipitate 15 as a yellow solid. Yield: 94 mg, 81%.
Mp: 190 °C dec. 1H NMR (CDCl3): δ 3.56 (s, 6H, MeO), 3.61
(s, 3H, MeO), 7.26-7.93 (m, 30H, PPh3). 31P{1H} NMR
(CDCl3): δ 19.09 (s). Anal. Calcd for C46H39F3N2O10SP2Pd:
C, 53.27; H, 3.79; N, 2.70; S, 3.09. Found: C, 53.29; H, 3.84;
N, 2.85; S, 2.94.
Syn th esis of [P d (R)(OSO2CF 3)(p h en )] (16). Three drops
of trifluoromethanesulfonic acid were added to a solution of
13 (90 mg, 0.14 mmol) in dichloromethane (3 mL). After it
was stirred for 30 min, the solution was concentrated (2 mL)
and addition of diethyl ether gave 16 as yellow crystals.
Yield: 89.5 mg, 91%. Mp: 210 °C dec. 1H NMR (d6-acetone):
δ 4.00 (s, 3H, MeO), 4.06 (s, 6H, MeO), 7.96-9.04 (m, 8H,
phen). Anal. Calcd for C22H17F3N4O10PdS: C, 38.14; H, 2.47;
N, 8.09; S, 4.63. Found: C, 37.57; H, 2.43; N, 7.95; S, 4.55.
X-r a y Str u ctu r e Deter m in a tion s. Crystals of 7‚2CH2Cl2,
8, 10, and 14‚H2O were mounted in inert oil on a glass fiber
and transferred to the diffractometer (Siemens P4 with LT2
low-temperature attachment) as summarized in Table 1. The
structure of 10 was solved by direct methods and the others
by the heavy-atom method and refined anisotropically on F2
(program SHELXL-97 (10), SHELXL-93 (7‚2CH2Cl2, 8, and
14‚H2O)).88,89 For compound 10 unit cell parameters were
determined from a least-squares fit of 72 accurately centered
(88) Sheldrick, G. M. SHELXL 93; University of Go¨ttingen: Go¨t-
tingen, Germany.
(89) Sheldrick, G. M. SHELXL 97; University of Go¨ttingen: Go¨t-
tingen, Germany.

5378 Organometallics, Vol. 17, No. 24, 1998
Ta ble 1. Cr ysta l Da ta for Com p ou n d s 7‚2CH2Cl2, 8, 10, a n d 14‚H2O
Vicente et al.
7‚2CH2Cl2
8
10
14‚H2O
mol formula
mol wt
source
C
34H40Cl6N6O14Pd2
C14H16N2O9Pd
462.69
CH2Cl2/n-pentane
liquid diffusion
tablet
yellow
triclinic
7.8605(8)
10.2155(12)
11.0542(10)
C19H21N3O9Pd
541.79
acetone/water
liquid diffusion
prism
pale yellow
monoclinic
8.878(2)
C27H30ClN2O14PPd
779.35
CH2ClCH2Cl/n-pentane
liquid diffusion
lath
yellow
monoclinic
33.526(5)
1182.22
CH2Cl2/n-hexane
liquid diffusion
prism
descripn
color
cryst syst
a, Å
b, Å
c, Å
yellow
monoclinic
13.056(2)
9.6249(10)
18.651(2)
72.720(8)
94.684(8)
78.806(8)
2335.8(5)
2
16.194(3)
14.837(3)
9.162(2)
23.422(4)
R, deg
â, deg
79.387(8)
92.57(2)
119.125(14)
γ, deg
V, Å3
823.83(15)
2
2131.0(8)
4
6284.8(18)
8
Z
radiation
λ, Å
Mo KR
Mo KR
0.710 73
173(2)
graphite
P1h
Mo KR
0.710 73
173(2)
graphite
P21/n
Mo KR
0.710 73
173(2)
graphite
C2/c
0.710 73
173(2)
T, K
monochr
space group
cryst size, mm
µ, mm-1
abs cor
graphite
P21/n
0.58 × 0.42 × 0.36
0.42 × 0.28 × 0.12
0.73 × 0.20 × 0.16
0.60 × 0.24 × 0.12
1.180
1.181
ψ scans
0.963
0.765
ω
6.2-50.0
(h,-k,(l
4014
2877
0.013
0.928
0.798
ψ scans
0.798
0.707
ψ scans
0.944
0.669
ψ scans
0.767
0.694
max transmissn, %
min transmissn, %
scan method
2θ range, deg
hkl limits
no. of rflns measd
no. of indep rflns
Rint
ω
ω
ω
6.1-50.0
-h,(k,(l
8299
6.0-50.0
+h,(k,(l
6317
6.1-50.0
(h,-k,(l
10 320
5515
4107
0.016
0.0214
0.0560
3102
0.028
0.0248
0.0695
0.046
0.0462
0.1198
R1a
0.0218
0.0529
wR2b
R1 ) Σ||Fo| - |Fc||/Σ|Fo| for reflections with I > 2σ(I). wR2 ) [Σ[w(Fo - Fc2)2]/Σ[w(Fo2)2]]0.5 for all reflections; w-1 ) σ2(F2) + (aP)2
a
b
2
+ bP, where P ) (2Fc + Fo2)/3 and a and b are constants set by the program.
2
reflections (12.8 < 2θ < 25.0°). Hydrogen atoms were included
using a riding model or as rigid methyl groups. Maximum
∆/σ ) 0.002; maximum ∆F ) 0.68 e Å-3. Unit cell parameters
of 14‚H2O were determined from a least-squares fit of 62
accurately centered reflections (6.4 < 2θ < 24.7°). The
perchlorate anion is disordered over two sites (50% occupancy).
A large peak near an inversion center was interpreted as half
a disordered water molecule. A second large peak, about 2.1
Å from the one mentioned above, was tentatively identified
as a half-occupied water molecule. Solvent hydrogen atoms
were not considered. The hydrogen atoms of the coordinated
water molecules were located in a difference Fourier synthesis
and refined with restrained O-H bond lengths. Other hydro-
gen atoms were included as rigid methyls or riding. Maximum
∆/σ ) 0.002; maximum ∆F ) 0.89 e Å-3. Unit cell parameters
of 8 were determined from a least-squares fit of 65 accurately
centered reflections (9.3 < 2θ < 25.0°). The methyl groups
corresponding to C(8) and C(9) are disordered over two sites
(50% occupancy). Hydrogen atoms were included using a
riding model or as rigid nondisordered methyl groups. Maxi-
trimethoxybenzoic acid to a mixture of sulfuric and
nitric acid at around 10 °C gives a mixture of 1,2,3-
trimethoxy-4,5,6-trinitrobenzene and 1,2-dinitro-3,4,5-
trimethoxybenzoic acid. The reaction of this acid with
mercuric acetate in water leads to the precipitation of
the corresponding mercuric benzoate 1 (see Scheme 1).
Decarboxylation of 1 occurs when it is heated at 180 °C
to give bis(2,6-dinitro-3,4,5-trimethoxyphenyl)mercury
(2). Kharash first reported this method for the synthe-
sis of arylmercury compounds, preparing 2,4,6-trinitro-
phenyl derivatives.91 Other authors have also employed
it to prepare polyfluorophenyl,92-96 polychlorophenyl,97
and pentabromophenyl98 derivatives.
Syn th eses of (2,6-Din itr o-3,4,5-tr im eth oxyp h en -
yl)p a lla d iu m Com p lexes. When a 2:1 mixture of 2
and Q2[PdCl2(µ-Cl)]2 is refluxed in acetone, a trans-
metalation occurs, giving a mixture of [Hg(R)Cl] (3) and
Q2[Pd(R)Cl(µ-Cl)]2 (Q ) PPh3(CH2Ph) (4a )) (see Chart
1 and Scheme 2) that can easily be resolved due to the
low solubility of 4a in organic solvents. When (NMe4)2-
[PdCl2(µ-Cl)]2 is reacted with 2, the reaction occurs at
room temperature, giving the insoluble complex (NMe4)2-
[Pd(R)Cl(µ-Cl)]2 (4b ) and the mercurial 3. A slight
mum ∆/σ ) 0.001; maximum ∆F ) 0.40 e Å-3
. Unit cell
parameters of 7 were determined from a least-squares fit of
62 accurately centered reflections (8.8 < 2θ < 25.2°). Hydro-
gen atoms were included using a riding model. Maximum ∆/σ
) 0.001; maximum ∆F ) 0.36 e Å-3. The programs use the
neutral atom scattering factors ∆f ′ and ∆f ′′ and absorption
coefficients from ref 90.90
(91) Kharash, M. S. J . Am. Chem. Soc. 1921, 43, 2238.
(92) Connett, J . E.; Davies, A. G.; Deacon, G. B.; Green, J . H. S. J .
Chem. Soc. C 1966, 106.
(93) Buxton, M. W.; Mobbs, R. H.; Wotton, D. E. M. J . Fluorine
Chem. 1971, 1, 179.
(94) Sartori, P.; Adelt, H. J . Fluorine Chem. 1973, 3, 275.
(95) Sartori, P.; Frohm, H. J . Chem. Ber. 1974, 107, 1195.
(96) Deacon, G. B.; Felder, P. W. Aust. J . Chem. 1970, 23, 1359.
(97) Deacon, G. B.; Felder, P. W. J . Chem. Soc. C 1967, 2313.
(98) Deacon, G. B.; Farquharson, G. J .; Miller, J . M. Aust. J . Chem.
1977, 30, 1013.
Resu lts a n d Discu ssion
Syn t h esis of Bis(2,6-d in it r o-3,4,5-t r im et h oxy-
p h en yl)m er cu r y (2). Slow addition of solid 3,4,5-
(90) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C, Tables
6.1.1.4 (pp 500-502), 4.2.6.8 (pp 219-222), and 4.2.4.2 (pp 193-199).

Pd(II) Complexes with an O,C,O Pincer Ligand
Organometallics, Vol. 17, No. 24, 1998 5379
Sch em e 1
Sch em e 3
Sch em e 2
aware of the previous synthesis of anionic [Pd(R)X(O,O-
acac)]- complexes.
The complex [Pd(κ3-R)Cl] (6), containing an O,C,O
pincer ligand, can be prepared by reacting 4a with
AgClO4 (1:2) or 5a with HBF4 (1:1). Complex 6 is the
first palladium complex containing an O,C,O pincer
ligand. As far as we are aware, the only complexes
containing an O,C,O pincer ligand are some recently
reported tin derivatives containing the aryl ligand
C6H2[P(O)(OEt)2]2-1,3-tBu-5.53 Complex 6 is soluble in
acetone but only slightly soluble in chlorinated solvents.
These solutions decompose to palladium metal when
diethyl ether or hydrocarbon solvents are added. At-
tempts to dissolve 6 in diethyl ether also lead to
decomposition. Complex 6 reacts with p-toluidine to
give the dinuclear complex [Pd(R)(µ-Cl)L]2 (L ) p-
toluidine (7)) instead of the desired [Pd(κ2-R)Cl(L)]. It
is probable that coordination of one nitro group causes
repulsions between the uncoordinated nitro group and
the other ligand cis to the aryl group. This problem does
not seem to occur in the complex [Pd(κ2-R)(O,O-acac)]
(8). This complex is precipitated upon the addition of
water to a concentrated solution of 5b in acetone.
Probably, the lower spatial requirement of the oxygen
donor atom of the acac ligand in 8 compared with that
of chloro or p-toluidine ligands is the reason for this
different result.
Complex 8 reacts with PPh3, pyridine (py), tetrahy-
drothiophene (tht), or bis(diphenylphosphino)methane
(1:1) to give the adducts [Pd(R)(O,O-acac)(L)] (L ) PPh3
(9), py (10), tht (11), bis(diphenylphosphino)methane
monoxide (dppmO) (12)) and with 1,10-phenanthroline
to give [Pd(R)(C-acac)(phen)] (13) (see Scheme 3). The
reaction between 8 and PPh3 gives 9 even when a 1:2
molar ratio is used. Attempts to prepare complexes
with the pincer ligand κ3-R or κ2-R from complexes 8-10
proved unsuccessful. Thus, the synthesis of [Pd(κ3-R)-
(PPh3)]+ or [Pd(κ2-R)X(PPh3)]+ (X ) OClO3 or OSO2CF3)
was attempted via two different routes. The first was
excess of 2 (about 0.5-1%) over the stoichiometric
amount is recommended to avoid contamination of 4a
or 4b with the corresponding [PdCl2(µ-Cl)]22- salt. We
have previously reported this synthetic method in the
preparation of related nitroaryl palladium complexes.66,68
The reaction of 4a or 4b with Tl(acac) gives Q[Pd(R)-
Cl(O,O-acac)] (Q ) (PhCH2)Ph3P (5a ), Me4N (5b)) (see
Scheme 2). This result contrasts with that obtained in
the reaction between (NMe4)2[Pd(Ar)Cl(µ-Cl)]2 (Ar )
C6H3Me-6, NO2-2) and Tl(acac), which gives the neutral
complex [Pd(κ2-Ar)(O,O-acac)].71 However, we have
been able to obtain the related neutral complex with
the ligand κ2-R (8) from 5b (see below). We are not

5380 Organometallics, Vol. 17, No. 24, 1998
Vicente et al.
F igu r e 1. ORTEP plot of 7 with the labeling scheme (50%
probability level).
F igu r e 2. ORTEP plot of 8 with the labeling scheme (50%
probability level).
the reaction between 8 and (HPPh3)ClO4. Working
under anaerobic conditions, we could only isolate an oil.
The complex cis-[Pd(R)(H2O)2(PPh3)]ClO4‚H2O (14) was
obtained when working in the air. The second attempt
was the reaction between 9 and triflic acid (HOSO2CF3).
When this acid was added to a solution of 9 in dichlo-
romethane, a change of color was observed from yellow
to orange. From this mixture we could only obtain an
oil. Addition of PPh3 (PPh3:Pd ) 1:1) gave trans-
[Pd(R)(OSO2CF3)(PPh3)2] (15). The difficulty of prepar-
ing [Pd(κ3-R)(PPh3)]+ can be related with the transpho-
bia between the aryl and the PPh3 ligands.99 The
unsuccessful synthesis of [Pd(κ2-R)(OSO2CF3)(PPh3)]
could be due to the repulsion between the PPh3 and the
uncoordinated nitro group.
The reaction between 8 and (Hpy)ClO4 or between 10
and HClO4, designed to prepare [Pd(κ3-R)(py)]+, gave
instead complex 10 or 8, respectively. The equilibrium
8 + (Hpy)ClO4 a 10 + HClO4 can explain these results.
Finally, an attempt to prepare [Pd(κ2-R)(phen)]CF3SO3,
by reacting 13 and triflic acid, gave instead [Pd(R)(OSO2-
CF3)(phen)] (16).
F igu r e 3. ORTEP plot of 10 with the labeling scheme
(50% probability level).
Complexes 6 and 8 have an intense orange color
which clearly distinguish them from all the other
complexes containing the monocoordinated R group,
which are yellow or pale orange. It is clear that
coordination of one or the two nitro groups is responsible
for the color of complexes 6 and 8. According to this,
the yellow solutions obtained when complex 6 is dis-
solved in acetone or when an stream of CO is passed
through an orange dichloromethane solution of 6, could
contain in the first case [Pd(R)Cl(acetone)2], or [Pd(R)-
Cl(CO)2] or [Pd(R)(µ-Cl)(CO)]2 in the latter. However,
from these solutions only complex 6 could be isolated.
The change of color from yellow to orange when triflic
acid is added to a solution of 9 in dichloromethane could
be indicative of the formation of [Pd(κ3-R)(PPh3)]CF3-
SO3 or [Pd(κ2-R)(OSO2CF3)(PPh3)].
F igu r e 4. ORTEP plot of 14 with the labeling scheme
(50% probability level). Hydrogen atoms are omited for
clarity.
coordination. Complex 7 crystallizes with two molecules
of dichloromethane and 14 with one molecule of water.
The structure of 7 consists of a chain polymer formed
through alternate chloro bridges and intermolecular
NH‚‚‚OMe hydrogen bonds [N(1)-H(2)‚‚‚O(7C), 2.42 Å;
N(1)‚‚‚O(7C), 3.29 Å; N(1)-H(1)-O(3), 152°] (Figure 5).
Additionally, the other hydrogen atom of the amine
group establishes an intramolecular hydrogen bond with
one oxygen atom of a nitro group (N(1)-H(1)‚‚‚O(3), 2.30
Str u ctu r e of Com p lexes. The crystal structures of
complexes 7, 8, 10, and 14 have been determined
(Figures 1-4 and Tables 2-5). In all of them, the
palladium atom shows slightly distorted square planar
(99) Vicente, J .; Arcas, A.; Bautista, D.; J ones, P. G. Organometallics
1997, 16, 2127.

Pd(II) Complexes with an O,C,O Pincer Ligand
Organometallics, Vol. 17, No. 24, 1998 5381
2.94 Å; O(2)-H(03)-O(9A), 156°; O(2)-H(04)‚‚‚O(7B),
2.23 Å; O(2)‚‚‚O(7B), 2.91 Å; O(2)-H(04)-O(7B), 167°)
(Figure 6). Additionally, the other water molecule and
one oxygen atom of the perchlorate anion are hydrogen-
bonded (because of disorder of the perchlorate anion the
O(10A) and O(13′A) atoms are considered: O(1)-
H(02)‚‚‚O(10A), 2.21 Å; O(1)‚‚‚O(10A), 2.78 Å; O(1)-
H(02)-O(10A), 140°; O(1)-H(02)‚‚‚O(13′A), 2.08 Å;
O(1)‚‚‚O(13′A), 2.71 Å; O(1)-H(02)-O(13′A), 150°). As
far as we are aware, only one crystal structure of a
diaquapalladium complex, [Pd(OH2)2{Ph2P(CH2)3-
PPh2}](CF3SO3)2, has been reported.100 However, in this
complex each cation and its corresponding two anions
are intramolecularly hydrogen-bonded instead of form-
ing a polymer like in 14. Recently, chiral diaqua
complexes [Pd(binap)(H2O)2]2+ have been shown to
catalyze asymmetric addition of enol silyl ethers to
imines and aldehydes.101,102 Complex 14 is the first
organometallic diaquapalladium(II) complex.
In complex 8, the molecules are stacked, forming
dimers in which the vector formed by the metal atom
of one molecule and the center of the aryl ligand of the
other molecule has a length of 3.59 Å and forms an angle
of 87.2° with the C(1)-C(6) plane (Figure 7).
F igu r e 5. Hydrogen bond interactions in 7.
The Pd-C bond distances are all significantly differ-
ent. The order is 1.967(2) (8) < 1.986(2) (7) < 2.002(3)
(10) < 2.035(2) (14) Å. However, given that in 8 and
10 the aryl ligand has the same ligand in a trans
position (O-acac), probably the order of trans influence
that these data suggest is O-acac ≈ µ-Cl < H2O. The
greater Pd-X bond distance trans to the aryl group
(Pd-XAr) compared to that of the other ligand (Pd-XL)
shows that the aryl group has a greater trans influence
than the amine ligand in 7 (Pd-ClAr, 2.4222(6) Å; Pd-
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Com p lex 7‚2CH2Cl2
Pd-C(1)
Pd-N(1)
1.986(2)
2.076(2)
Pd-Cl(1)
Pd-Cl(1A)
2.3179(6)
2.4222(6)
C(1)-Pd-N(1)
N(1)-Pd-Cl(1A)
Pd-Cl(1)-Pd(A)
87.34(8)
96.74(5)
94.33(2)
C(1)-Pd-Cl(1)
Cl(1)-Pd-Cl(1A)
90.25(6)
85.67(2)
Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Com p lex 8
ClNH R, 2.3179(6) Å), than the O-NO group in 8 (Pd-
2
O
Ar, 2.030(2) Å; Pd-OONOAr, 1.969(2) Å), than py in 10
Pd-C(1)
Pd-O(1)
Pd-O(3)
Pd-O(2)
1.967(2)
1.969(2)
2.014(2)
2.030(2)
O(2)-C(13)
O(3)-N(1)
O(4)-N(1)
O(5)-N(2)
1.278(3)
1.290(3)
1.209(3)
1.218(3)
(Pd-OAr, 2.0408(18) Å; Pd-Opy, 1.9990(18) Å), and than
PPh3 in 14 (Pd-OAr, 2.142(4) Å; Pd-OPPh , 2.124(4) Å).
3
In complexes 7, 10, and 14, the plane formed by the
six carbon atoms of the aryl ligand (C6 plane) is almost
perpendicular to the coordination plane (Pd and the four
atoms coordinated to it) (7, 81.7°; 10, 75.4°; 14, 82.5°),
while in 8 both are almost coplanar (1.2°) due to the
chelating nature of the aryl ligand. This is also the
reason for the almost coplanarity of the C6 plane and
the CN(1)O2 plane (6.5°). The other nitro group in 8
and those of complexes 7, 10, and 14 are rotated with
respect to its own C6 plane by an angle in the range
41.9-81.0°. The coordination of the N(1)O2 group in 8
has two other structural consequences: (i) the lengthen-
ing of the N(1)-O(Pd) bond distance (1.290(3) Å) in 8
with respect to the other three N-O bonds (N(1)-O(4),
1.209(3) Å; N(2)-O(5), 1.218(3) Å; N(2)-O(6), 1.222(3)
Å), which are in the range observed in complexes 7, 10,
and 14 (1.208(3)-1.230(5) Å) and (ii) the shortening of
the C(2)-N(1) bond distance (1.439(3) Å) with respect
to the C(6)-N(2) bond length (1.485(3) Å). This is
O(1)-C(11)
1.286(3)
94.72(8)
81.36(8)
O(6)-N(2)
1.222(3)
92.83(7)
91.04(7)
C(1)-Pd-O(1)
C(1)-Pd-O(3)
O(1)-Pd-O(2)
O(3)-Pd-O(2)
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Com p lex 10
Pd-O(1)
Pd-N(1)
1.9990(18)
2.021(2)
Pd-C(1)
Pd-O(2)
2.002(3)
2.0408(18)
O(1)-Pd-C(1)
O(1)-Pd-O(2)
88.97(8)
93.27(7)
C(1)-Pd-N(1)
N(1)-Pd-O(2)
91.41(9)
86.35(8)
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) in Com p lex 14‚H2O
Pd-C(1)
Pd-O(2)
2.035(2)
2.142(4)
Pd-O(1)
Pd-P
2.124(4)
2.228(2)
C(1)-Pd-O(2)
C(1)-Pd-P
92.4(2)
90.41(10)
O(1)-Pd-O(2)
O(1)-Pd-P
83.5(2)
93.7(2)
Å; N(1)-O(3), 2.99 Å; N(1)-H(1)-O(3), 137°). Surpris-
ingly, the N(1)-O(3) and N(1)-O(4) bond distances are
almost identical (1.221(3), 1.223(3) Å). In complex 14,
a chain polymer is also formed although only through
intermoleculecular OH‚‚‚OMe hydrogen bonds. The
polymerization is achieved via hydrogen bonds connect-
ing each water molecule trans to the phosphine ligand
with two methoxy groups each from two neighbor
molecules (O(2)-H(03)‚‚‚O(9A), 2.29 Å; O(2)‚‚‚O(9A),
similar to C-N bond distances in complexes
7
(1.465(3), 1.479(3) Å) and 10 (1.477(3), 1.482(4) Å), while
(100) Stang, P. J .; Cao, D. H.; Poulter, G. T.; Arif, A. M. Organo-
metallics 1995, 14, 1110.
(101) Hagiwara, E.; Fujii, A.; Sodeoka, M. J . Am. Chem. Soc. 1998,
120, 2474.
(102) Sodeoka, M.; Ohrai, K.; Shibasaki, M. J . Org. Chem. 1995,
60, 2648.

5382 Organometallics, Vol. 17, No. 24, 1998
Vicente et al.
F igu r e 6. Hydrogen bond interactions in 14.
intermolecular NH‚‚‚OMe hydrogen bonds (see Figure
5) are responsible for the observation of three reso-
nances due MeO groups. One of these is a doublet with
3J HH ) 1.5 Hz because of the coupling through the
hydrogen bond between the methyl and NH protons.
The NH protons of the amine are not isochronous
because of this interaction and, probably too, because
of the intermolecular NH‚‚‚ONO hydrogen bond.
According to the assignment of ν(PdCl) in related
nitrophenylpalladium complexes,66,68-70 the band at 330
(4a ), 335 (4b) cm-1 can be assigned to ν(PdCl), corre-
sponding to a terminal chloro ligand, and the bands at
258 (4a ), 263 (4b) and 285 (4a ), 293 (4b) cm-1 to ν(PdCl)
modes due to bridging chloro ligands. These two bands
move to higher frequency (298, 320 cm-1) in complex 7,
probably because it is neutral instead of anionic, and
this increases the π-donor ability of the chloro ligand.
In complex 6, the weak band at 293 cm-1 can be
assigned to ν(PdCl). Similar values have been assigned
in trans-[PdClR(PPh3)2] (R ) C6H3Me-2,NO2-6) (300
F igu r e 7. Packing diagram of 8.
those in 14 (1.435(5), 1.441(5) Å) are similar to C(2)-
N(1) in 8, probably due to the cationic nature of 14. As
we have previously shown, these data suggest that the
nitro group exerts an -I rather than -M effect in these
metalated aryl rings.57,58,64,66-76 In fact, the presence
in the aryl groups of electron-releasing and -withdraw-
ing groups do not affect significantly the C-C bond
distances (range 1.379(3)-1.410(3) Å; in 14 the C-C
bond distances have been fixed at 1.39 Å). Additionally,
not only is the angle between the C6 and CNO2 planes
not appropiate for pπ(C) f pπ(N) bonding but also the
C-C(NO2)-C angle is g120° when it would be expected
to be <120° if the C-N bond were of some multiple
character. The -I effect exerted by the nitro group is
responsible for C-C(NO2)-C angles >120° according to
the isovalent hybridization model proposed by Bent.103
cm-1 66
and [PPh3(CH2Ph)][PdRCl2(CO)] (R ) C6H3Me-
)
2, NO2-6) (285 cm-1).70
All complexes show a very strong band at around 1520
cm-1 corresponding to νasym(NO2). Additionally, in all
complexes except 6, a band at around 1350 cm-1 is
assignable to νsym(NO2). According to the lowering of
ν
sym(NO2) observed in cyclometalated o-nitrophenyl
complexes, we assign the strong band observed at 1200
cm-1 in complexes 6 and 8 to νsym(NO2) of the coordi-
nated nitro groups.
Con clu sion s
Sp ectr oscop ic P r op er ties. 1H NMR spectroscopy
can be used to determine the mode of coordination of
the aryl group in solutions of complexes 1-16. As
expected, complex 8 shows three different MeO groups,
while the others, except 7, show two 2:1 singlets
according to the structures proposed. In complex 7, the
We have prepared one complex with the pincer ligand
κ3-C6(NO2)2-2,6-(OMe)3-3,4,5-C1,O,O′, another one with
the chelating ligand κ2-C6(NO2)2-2,6-(OMe)3-3,4,5-C1,O,
and a series of neutral, anionic, and cationic complexes
with the monocoordinated ligand C6(NO2)2-2,6-(OMe)3-
3,4,5-C1 using the corresponding mercury derivative as
transmetalating agent. However, some attempts to
prepare other complexes with the pincer and κ2-chelat-
(103) Bent, H. A. Chem. Rev. 1961, 61, 275.

Pd(II) Complexes with an O,C,O Pincer Ligand
Organometallics, Vol. 17, No. 24, 1998 5383
ing ligands failed, probably because even poor donor
ligands compete with the very weak Pd-O bonds. The
presence of the three methoxy groups in the aryl ligand
seems to be crucial to success in the synthesis of
complexes with the pincer and κ2-chelating ligands, as
previous attempts to prepare 2,4,6-trinitrophenyl com-
plexes with such types of coordination failed. The
presence of the nitro and methoxy substituents in the
aryl ligand allows the formation of interesting chain
polymers through hydrogen bonds.
Ack n ow led gm en t. We thank the DGES for finan-
cial support and the Ministerio de Educacio´n y Cultura
(Spain) for the award of a contract to M.C.R.A.
Su p p or tin g In for m a tion Ava ila ble: Tables giving crys-
tal data and structure refinement details, positional and
thermal parameters, and bond distances and angles for
7‚2CH2Cl2, 8, 10, and 14‚H2O (21 pages). Ordering informa-
tion is given on any current masthead page.
OM980633A