Polymetalated aromatic compounds. 1. Synthesis of mono-, Di-, and tripalladated mesitylene derivatives

Article abstract of DOI:10.1021/om0105472

The reaction of 1,3,5-triidomesitylene (C₆Me₃I₃) with a mixture of [Pd(dba)₂] and PR₃ leads to the mononuclear complexes trans-[Pd(C₆Me₃I₂)I(PR₃)₂ ] (R = Ph (1), R₃ = Me₂Ph (2)) or the dinuclear complex [{trans-PdI(PMe₂Ph)₂}₂(μ₂- C₆Me₃I)] (3), depending on the nature of the phosphine, the temperature, and the molar ratio of the reagents. All attempts to prepare trinuclear complexes, using this method of synthesis, were unsuccessful. However, addition of C₆Me₃I₃ to a mixture of [Pd(dba)₂] and L₂ gives at room temperature [(PdIL₂)₃(μ₃-C₆Me₃)] (L₂ = 2,2′-bipyridine (bpy) (4), 4,4′-di-tert-butyl-2,2′-bipiridine (tbbpy) (5)), even if substoichiometric amounts of Pd were used. Complex 5 does not react with PPh₃ or PMe₂Ph, but it does react with PMe₃ to give [trans-{PdI(PMe₃)₂}₃(μ₃- C₆Me₃)] (6). The crystal structures of 1, 2, and 5 have been determined by X-ray diffraction studies.

Full text of DOI:10.1021/om0105472

Organometallics 2001, 20, 4695-4699
4695
P olym eta la ted Ar om a tic Com p ou n d s. 1. Syn th esis of
Mon o-, Di-, a n d Tr ip a lla d a ted Mesitylen e Der iva tives
J ose´ Vicente*,† and Mykhaylo Lyakhovych
Grupo de Quı´mica Organometa´lica, Departamento de Quı´mica Inorga´nica,
Facultad de Quı´mica, Universidad de Murcia, Apartado 4021, Murcia 30071, Spain
Delia Bautista‡
SACE, Universidad de Murcia, Apartado 4021, Murcia 30071, Spain
Peter G. J ones§
Institut fu¨r Anorganische und Analytische Chemie, Technische Universita¨t Braunschweig,
Postfach 3329, 38023 Braunschweig, Germany
Received J une 22, 2001
The reaction of 1,3,5-triiodomesitylene (C6Me3I3) with a mixture of [Pd(dba)2] and PR3
leads to the mononuclear complexes trans-[Pd(C6Me3I2)I(PR3)2] (R ) Ph (1), R3 ) Me2Ph
(2)) or the dinuclear complex [{trans-PdI(PMe2Ph)2}2(µ2-C6Me3I)] (3), depending on the nature
of the phosphine, the temperature, and the molar ratio of the reagents. All attempts to
prepare trinuclear complexes, using this method of synthesis, were unsuccessful. However,
addition of C6Me3I3 to a mixture of [Pd(dba)2] and L2 gives at room temperature [(PdIL2)3-
(µ3-C6Me3)] (L2 ) 2,2′-bipyridine (bpy) (4), 4,4′-di-tert-butyl-2,2′-bipiridine (tbbpy) (5)), even
if substoichiometric amounts of Pd were used. Complex 5 does not react with PPh3 or PMe2-
Ph, but it does react with PMe3 to give [trans-{PdI(PMe3)2}3(µ3-C6Me3)] (6). The crystal
structures of 1, 2, and 5 have been determined by X-ray diffraction studies.
In tr od u ction
pounds include Sn(IV),1,3,18-21 Li,1,3,22-26 Mg,3 Al,27,28 and
Ge derivatives.29,30 Many Hg(II) derivatives were pre-
pared by metalation, but in a few cases transmetalation
reactions using the corresponding Sn(IV)1 or Li3 deriva-
tives were used. Most Sn(IV) compounds were synthe-
sized by reacting NaSnMe3 with the corresponding
halobenzene, but 1,3,5-C6H3(SnMe3)3 has also been
prepared from the corresponding Li derivative.3,21
The synthesis and applications of polymetalated
derivatives of benzene (C6R6-nMn, n ) 3-6) are well-
documented. However, most of these compounds involve
only a few representative elements and many remain
poorly characterized, especially from a structural view-
point. The element best studied is Hg(II), of which
compounds with three to six metal atoms have been
reported.1-17 Other members of this family of com-
(13) Formanek, H.; Formanek, S. Eur. J . Biochem. 1970, 17, 78.
(14) Alvey, F. B.; J arboe, C. H. J . Med. Chem. 1968, 11, 1269.
(15) Malaiyandi, M.; Sawatzky, H.; Wright, G. F. Can. J . Chem.
1961, 39, 1827.
(16) Poethke, W.; Fuerst, W. Arch. Pharm. (Weinheim, Ger.) 1961,
294, 524; Chem. Abstr. 1962, 56, 1469f.
(17) Deacon, G. B.; O’Donoghue, M. F. J . Organomet. Chem. 1980,
194, C60.
(18) Corsico, E. F.; Rossi, R. A. Synlett 2000, 230.
(19) Corsico, E. F.; Rossi, R. A. Synlett 2000, 227.
(20) Schultz, G.; Hargittai, I.; Rot, N.; Bickelhaupt, F. Struct. Chem.
1998, 9, 209.
(21) Gibson, S. E.; Saladin, S. A.; Sur, S. Chem. Commun. 2000,
2011.
(22) Theologitis, M.; Screttas, G. C.; Raptis, S. G.; Papadopoulos,
M. G. Int. J . Quantum Chem. 1999, 72, 177.
(23) Adamson, G. A.; Rees, C. W. J . Chem. Soc., Perkin Trans. 1
1996, 1535.
† Corresponding author regarding the synthesis of complexes. E-
mail: jvs@um.es. Web: http://www.scc.um.es/gi/gqo/.
‡ Corresponding author regarding the X-ray diffraction studies of
complexes 1 and 2. E-mail: dbc@um.es.
§ Corresponding author regarding the X-ray diffraction studies of
complex 5. E-mail: jones@xray36.anchem.nat.tu-bs.de.
(1) Rot, N.; De Kanter, F. J . J .; Bickelhaupt, F.; Smeets, W. J . J .;
Spek, A. L. J . Organomet. Chem 2000, 593-594, 369.
(2) Layeghi, H.; Tyrra, W.; Naumann, D. Z. Anorg. Allg. Chem. 1998,
624, 1601.
(3) Rot, N.; Bickelhaupt, F. Organometallics 1997, 16, 5027.
(4) Rothmaier, M.; Schaller, U.; Morfb, W. E.; Pretsch, E. Anal.
Chim. Acta 1996, 327, 17.
(5) Popov, V. I.; Lib, M.; Haas, A. Ukr. Khim. Zh. 1990, 56, 1115.
Chem. Abstr. 1991, 114, 185701.
(6) Khomutov, A. R.; Khurs, E. N.; Khomutov, R. M. Bioorg. Khim.
1988, 14, 385.
(24) Baran, J . R., J r.; Hendrickson, C.; Laude, D. A., J r.; Lagow, R.
J . J . Org. Chem. 1992, 57, 3759.
(25) Howells, R. D.; Gilman, H. Tetrahedron Lett. 1974, 1319.
(26) Buck, P.; Ko¨brich, G. Chem. Ber. 1970, 103, 1420.
(27) Troyanov, S. I.; Rybakov, V. B. Metalloorg. Khim. 1988, 1, 1061;
Chem. Abstr. 1990, 112, 77414.
(28) Troyanov, S. I.; Tafeenko, V. A. Zh. Obshch. Khim. 1990, 60,
2416; Chem. Abstr. 1991, 114, 247441.
(29) Yamakawa, T.; Kagechika, H.; Kawachi, E.; Hashimoto, Y.;
Shudo, K. J . Med. Chem. 1990, 33, 1430.
(7) Khomutov, R. M.; Khomutov, A. R. Izv. Akad. Nauk SSSR, Ser.
Khim. 1985, 2649; Chem. Abstr. 1986, 105, 209076.
(8) Deacon, G. B.; Farquharson, G. J . Aust. J . Chem. 1977, 30, 1701.
(9) Yagupol’skii, L. M.; Popov, V. I.; Kondratenko, N. V. Zh. Org.
Khim. 1976, 12, 916. Chem. Abstr. 1976, 85, 46115.
(10) Deacon, G. B.; Farquharson, G. J . Aust. J . Chem. 1976, 29, 627.
(11) Deacon, G. B.; Farquharson, G. J . J . Organomet. Chem. 1974,
67, C1.
(12) Friedman, H. A.; Koelle, G. B. Org. Prep. Proced. Int. 1973, 5,
251.
(30) Weissensteiner, W.; Schuster, I. I.; Blount, J . F.; Mislow, K. J .
Am. Chem. Soc. 1986, 108, 6664.
10.1021/om0105472 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 10/03/2001

4696 Organometallics, Vol. 20, No. 22, 2001
Vicente et al.
Syn th esis of tr a n s-[P d (C6Me3I2)I(P P h 3)2] (1). [Pd(dba)2]
(288 mg, 0.5 mmol), PPh3 (262 mg, 1 mmol), and C6Me3I3 (250
mg, 0.5 mmol) were mixed under nitrogen in degassed toluene
(25 mL) and allowed to react at room temperature for 14 h.
Workup was then continued in air. The solvent was evaporated
to dryness and the residue extracted with CH2Cl2 (20 mL). The
extract was filtered over Celite, the resulting solution concen-
trated to about 5 mL, and Et2O (30 mL) added. The resulting
solid was separated by filtration, washed with Et2O, and
recrystallized from CH2Cl2/Et2O, to give 1 as a pale yellow
solid. Yield: 460 mg (82%). Mp: 249 °C dec. 1H NMR (200
MHz, CDCl3): δ 7.56-7.14 (m, 30 H, PPh3), 2.55 (s, 3 H, Me),
2.46 (s, 6 H, Me). 13C{1H} NMR (50 MHz, CDCl3): δ 159.91 (s,
Lithium derivatives were obtained by reacting organo-
lithium compounds with halobenzenes.
Surprisingly, there are only two polymetalated de-
rivatives of benzene with transition metals, namely
those of formula 1,3,5-C6H3[M]3, where [M] ) Mn(CO)5,
Fe(η5-Cp)(CO)2. They were prepared in two steps involv-
ing the reaction of Na[M] with 1,3,5-C6H3(COCl)3 and
subsequent decarbonylation of the resulting triacyl
complexes 1,3,5-C6H3[C(O)M]3.31
The interest in these polymetallic compounds has
manifested itself in the publication of one review on
permetalated aromatic compounds,32 some patents,33-36
and many theoretical22,37-44 or biological studies.13,29,45-48
Some of them have been used as arene ligands, in [(η6-
1,3,5-C6H3[M]3)Cr(CO)3], [M] being Fe(η5-Cp)(CO)249 or
SnMe3,21 or in [(η6-C6H5)Ti(η6-µ4-1,3,5-C6H3(AlI2)3){Ti3-
(µ2-I)6}].27,28 We believe that these polymetalated de-
rivatives of benzene also have potential applications in
the synthesis of metallodendrimers.
In this paper, we report some attempts to prepare the
compounds 1,3,5-C6Me3[M]3, where [M] ) PdL2I and L
) PPh3, PMe2Ph, PMe3 or L2 ) 2,2′-bipyridine (bpy),
4,4′-di-tert-butyl-2,2′-bipyridine (tbbpy). The successful
synthesis of some of the desired compounds, using
oxidative addition reactions, is not as direct and simple
as we initially expected.
2
2C2, Ar), 141.45 (t, C-Pd, J PC ) 4 Hz), 138,22 (s, C4-Me,
2
4
Ar), 134.71 (“t”, ortho C’s PPh3, J PC + J PC ) 6 Hz), 131.46
1
3
(“t”, ipso C’s PPh3, J PC + J PC ) 23 Hz), 130.13 (s, para C’s
3
PPh3), 127.57 (“t”, meta C’s PPh3, J PC + 5J PC ) 5 Hz), 104.05
(s, C-I), 37.24 (s, Me), 34.88 (s, Me). 31P{1H} NMR (121 MHz,
CDCl3): δ 22.01 (s). Anal. Calcd for C45H39I3P2Pd: C, 47.88;
H, 3.48. Found: C, 47.66; H, 3.44.
Syn th esis of tr a n s-[P d (C6Me3I2)I(P Me2P h )2] (2). [Pd-
(dba)2] (288 mg, 0.5 mmol), PMe2Ph (138 mg (142 µL), 1 mmol),
and C6Me3I3 (250 mg, 0.5 mmol) were mixed under nitrogen
in degassed toluene (25 mL) and allowed to react at room
temperature for 6 h. Workup was then continued in air. The
solvent was evaporated to dryness and the residue extracted
with CH2Cl2 (20 mL). The extract was filtered over Celite, the
resulting solution concentrated to about 5 mL and an Et2O/
pentane mixture (15 mL/15 mL) added. The resulting solid was
separated by filtration, washed with Et2O, and recrystallized
from CH2Cl2/pentane, to give 2 as a beige solid. Yield: 270
mg (61%). Mp: 162 °C dec. 1H NMR (200 MHz, CDCl3): δ
Exp er im en ta l Section
Melting points were determined on a Reichert apparatus
and are uncorrected. Infrared spectra were recorded in the
range 4000-200 cm-1 on a Perkin-Elmer 16FC FT-IR spec-
trometer with Nujol mulls between polyethylene sheets. 1H,
31P, and 13C NMR spectra were carried out with a Varian Unity
300 or a Bruker 200 instrument. Chemical shifts are refer-
enced to TMS (1H and 13C{1H}) or to H3PO4 (31P).
7.34-7.26 (m, 10 H, Ph), 2.75 (s, 3 H, Me), 2.47 (s, 6 H, Me),
2
1.67 (“t”, 12H, J PH
+
4J PH ) 3 Hz, PMe2Ph). 31P{1H} NMR
(121 MHz, CDCl3): δ -10.77 (s). Anal. Calcd for C25H31I3P2-
Pd: C, 34.10; H, 3.48. Found: C, 34.37; H 3.46.
Syn th esis of [{tr a n s-P d I(P Me2P h )2}2(µ2-C6Me3I)] (3).
[Pd(dba)2] (432 mg, 0.75 mmol), PMe2Ph (207 mg (214 µL), 1.5
mmol), and C6Me3I3 (125 mg, 0.25 mmol) were mixed under
nitrogen in degassed toluene (25 mL), and the reaction mixture
was refluxed under a slow stream of nitrogen for 2 h. From
this point the workup was carried out in air. The solvent was
evaporated to dryness and the residue extracted with CH2Cl2
(20 mL). The extract was filtered over Celite, the resulting
solution concentrated to about 5 mL, and an Et2O/pentane
mixture (15 mL/15 mL) added. The resulting solid was
separated by filtration, washed with Et2O, and recrystallized
from CH2Cl2/pentane to give 3 as a beige solid. Yield: 210 mg
“Pd(dba)2”50,51 and 1,3,5-C6Me3I3 were prepared as de-
52
scribed previously.
(31) Hunter, A. D.; Szigety, A. B. Organometallics 1989, 8, 2670.
(32) Winteer, C. H.; Seneviratine Kapilan, N.; Bretschneider, H.
Comments Inorg. Chem. 1996, 19, 1.
(33) Nakajima, K.; Sonoda, N.; Tanaka, K.; Yamabe, T. (Matsushita
Electric Ind. Co. Ltd., J apan) J pn. Patent J P 06122769; Chem. Abstr.
1994, 121, 301657.
(34) Chamberlain, L. R.; Defriend, P. A. (Shell International Re-
search Maatschappij BV, The Netherlands) Eur. Patent EP 475495;
Chem. Abstr. 1992, 117, 8752.
(35) Teranaka, O.; Kakutani, T.; Tabata, H.; Teraoka, T. (J apan
Elastomer Co., Ltd., J apan) Eur. Patent EP 46668; Chem. Abstr. 1982,
96, 200828.
(36) Massachusetts Institute of Technology. Brit. Patent GB 1444174;
Chem. Abstr. 1977, 86, 106764.
(37) Raptis, S. G.; Papadopoulos, M. G.; Sadlej, A. J . Phys. Chem.
Chem. Phys. 2000, 2, 3393.
(38) Belanzoni, P.; Sgamellotti, A.; Re, N.; Floriani, C. Inorg. Chem.
2000, 39, 1147.
(39) Papadopoulos, M. G.; Raptis, S. G.; Demetropoulos, I. N.;
Nasiou, S. M. Theor. Chem. Acta 1998, 99, 124.
(40) Belanzoni, P.; Fantacci, S.; Re, N.; Rosi, M.; Sgamellotti, A.;
Floriani, C. Inorg. Chem. 1997, 36, 2018.
(41) Smith, B. J . Chem. Phys. Lett. 1993, 207, 403.
(42) Glukhovtsev, M. N.; Simkin, B. Y.; Minkin, V. I. Zh. Org. Khim.
1991, 27, 432; Chem. Abstr. 1991, 115, 92329.
(43) Xie, Y.; Schaefer, H. F., III. Chem. Phys. Lett. 1991, 179, 563.
(44) Glukhovtsev, M. N.; Simkin, B. Y.; Minkin, V. I. Metalloorg.
Khim. 1990, 3, 1289; Chem. Abstr. 1991, 114, 122460.
(45) Pepe, F. A. J . Biophys. Biochem. Cytol. 1961, 11, 515; Chem.
Abstr. 1962, 56, 10763g.
(46) Pepe, F. A.; Finck, H. J . Biophys. Biochem. Cytol. 1961, 11, 521;
Chem. Abstr. 1962, 56, 10763h.
(47) Pepe, F. A.; Finck, H.; Holtzer, H. J . Biophys. Biochem. Cytol.
1961, 11, 533; Chem. Abstr. 1962, 56, 10763i.
1
(51%). Mp: 179 °C dec. H NMR (200 MHz, CDCl3): δ 7.74-
7.65 (m, 8 H, PMe2Ph), 7.33-7.26 (m, 12 H, PMe2Ph), 2.74 (s,
6 H, Me), 2.36 (s, 3 H, Me), 1.54 (“t”, 12H, 2J PH + 4J PH ) 3 Hz,
2
PMe2Ph), 1.29 (“t”, 12H, J PH
+
4J PH ) 3 Hz, PMe2Ph). 31P-
{1H} NMR (121 MHz, CDCl3): δ -12.28 (s). Anal. Calcd for
41H53I3P4Pd2: C, 39.98; H, 4.23. Found: C, 39.90; H 4.62.
C
Syn th esis of [{P d I(bp y)}3(µ3-C6Me3)] (4). Pd(dba)2 (432
mg, 0.75 mmol), bpy (120 mg, 0.75 mmol), and C6Me3I3 (125
mg 0.25 mmol) were mixed under nitrogen in degassed toluene
(25 mL) and allowed to react at room temperature for 10 h.
The precipitation of a dark yellow solid was observed. The
solvent was evaporated to dryness and the residue extracted
with DMF. The extract was filtered over Celite, the resulting
solution concentrated to about 20 mL, and Et2O (50 mL) added.
The resulting solid was separated by filtration, washed with
Et2O, and recrystallized from DMF/Et2O to give 4 as a
brownish yellow solid. Yield: 140 mg (44%). Mp: 238 °C dec.
IR (Nujol): ν(CN, bpy) 1596 cm-1. Because of insufficient
(48) Keil, R. Pharmazie 1959, 14, 76.
(51) Heck, R. F. Palladium Reagents in Organic Synthesis; Academic
Press: New York, 1985.
(52) Merkushev, E. B.; Simakhina, N. D.; Koveshnikova, G. M.
Synthesis 1980, 486.
(49) Hunter, A. D. Organometallics 1989, 8, 1118.
(50) Takahashi, Y.; Ito, S.; Sakai, S.; Ishii, Y. J . Chem. Soc., Chem.
Commun. 1970, 1065.

Polymetalated Aromatic Compounds
Organometallics, Vol. 20, No. 22, 2001 4697
Ta ble 1. Cr ysta l Da ta for Com p lexes 1, 2, a n d 5
1
2‚CDCl3
5‚3CH2Cl2‚Et2O
formula
Mr
C
25H31I3P2Pd
C46H39DCl3I3P2Pd
1248.16
C70H97Cl6I3N6OPd3
1951.14
880.54
cryst size (mm)
cryst syst
space group
cell constants
a (Å)
0.54 × 0.48 × 0.48
orthorhombic
P212121
0.39 × 0.38 × 0.32
0.40 × 0.25 × 0.15
monoclinic
monoclinic
P21/c
P21/n
11.5674(5)
12.4874(6)
19.2819(9)
90
2785.2(2), 4
0.710 73
2.100
17.593(2)
11.9216(6)
21.5095(12)
100.457(5)
4436.5(5), 4
0.710 73
18.9252(14)
22.7739(16)
18.9973(14)
103.442(3)
7963.5(10), 4
0.710 73
b (Å)
c (Å)
â (deg)
V (Å3), Z
λ (Å)
F(calcd) (Mg m-3
F(000)
)
1.867
2404
1.627
3864
1664
T (K)
173
4.118
173
2.791
133
2.077
µ (mm-1
)
transmissions
θ range (deg)
limiting indices
0.969-0.516
3.20-24.99
-13 e h e 13
-14 e k e 0
-22 e l e 0
0.789-0.749
3.20-25.00
-20 e h e 0
-14 e k e 1
-25 e l e 25
0.802-0.605
1.37-28.28
-25 e h e 25
-30 e k e 30
-25 e l e 25
no. of rflns
measd
indep
5262
4887
8885
7795
176 960
19 781
Rint
abs cor
refinement method
0.0152
ψ-scans
0.0222
0.0356
multiscan
ψ-scans
full-matrix least squares on F2
no. of data/restraints/params
4886/24/287
1.126
0.0221
0.0579
0.591
7792/419/496
1.011
0.0252
0.0629
0.766
19 781/821/843
1.096
0.0350
0.1026
1.331
S (F2)
R1a
wR2b
largest diff peak (e Å-3
)
a
b
2
R1 ) ∑||Fo| - |Fc||/∑|Fo| for reflections with I > 2σ(I). wR2 ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]0.5 for all reflections; w-1 ) σ2(F2) + (aP)2
+ bP, where P ) (2Fc + Fo2)/3 and a and b are constants set by the program.
2
solubility, NMR spectra of complex 4 could not be measured.
Anal. Calcd for C39H33I3N6Pd3: C, 36.44; H, 2.59, N, 6.54.
Found: C, 36.43; H, 2.86, N, 7.05.
diffractometer (1 and 2, Siemens P4 with LT2 low-temperature
attachment; 5, Bruker SMART 1000 CCD with LT3 low-
temperature attachment), as summarized in Table 1. The
structures were solved by the heavy-atom method and refined
anisotropically on F2 (program SHELX-93 or SHELX-97, G.
M. Sheldrick, University of Go¨ttingen). Hydrogen atoms were
included using a riding model or rigid methyl groups.
Special features of the refinement are as follows. For
compound 2, the absolute structure parameter53 is -0.05(2).
Compound 5 crystallizes with three molecules of dichlo-
romethane and one of diethyl ether, which display slightly high
U values but are otherwise well ordered. The tert-butyl groups
at C17 and C27 are disordered over two positions.
Syn th esis of [{P d I(tbbp y)}3(µ3-C6Me3)] (5). Pd(dba)2 (432
mg, 0.75 mmol), tbbpy (200 mg, 0.75 mmol), and C6Me3I3 (125
mg 0.25 mmol) were mixed under nitrogen in degassed toluene
(25 mL) and allowed to react at room temperature for 14 h.
Workup was then continued in air. The solvent was evaporated
to dryness and the residue extracted with CH2Cl2 (20 mL). The
extract was filtered over Celite, the resulting solution concen-
trated to about 5 mL, and an Et2O/pentane mixture (15 mL/
15 mL) added. The resulting solid was separated by filtration,
washed with Et2O, and recrystallized from CH2Cl2/pentane to
give 5 as a yellow solid. Yield: 335 mg (83%). Mp: 218 °C dec.
3
1H NMR (300 MHz, CDCl3): δ 9.48 (d, 2H, J HH ) 6 Hz, CH,
Resu lts a n d Discu ssion
tbbpy), 9.34 (d, 1H, 3J HH ) 6 Hz, CH, tbbpy), 8.03 (d, 2H, 3J HH
) 6 Hz, CH, tbbpy), 7.93-7.88 (m, 7H, tbbpy), 7.60 (dd, 1H,
3J HH ) 6 Hz, 4J HH ) 1.8 Hz, tbbpy), 7.45-7.36 (m, 5H, tbbpy),
3.20 (s, 3 H, ArMe), 3.17 (s, 6 H, ArMe), 1.404, 1.401, 1.387
(54H, t-Bu). Anal. Calcd for C63H81I3N6Pd3: C, 46.64; H, 5.03,
N, 5.18. Found: C, 46.62; H, 5.06, N, 5.24.
The reaction of 1,3,5-triiodomesitylene (C6Me3I3) with
a mixture of [Pd(dba)2] ([Pd2(dba)3]‚dba) and PPh3 (1:
1:2 molar ratio) in toluene at room temperature gave
trans-[Pd(C6Me3I2)I(PPh3)2] (1) in high yield (Scheme
1). The same compound was obtained when the reagents
were reacted in the molar ratio 1:2:4 or even 1:3:6. When
the reaction of C6Me3I3 with a mixture of [Pd(dba)2] and
PPh3 (1:3:6 molar ratio) was carried out in boiling
toluene for 3 h, complex 1 was obtained in low yield
(41%) and decomposition also occurred. Refluxing a
mixture of C6Me3I3, [Pd(dba)2], and PPh3 (1:3:6 molar
ratio) in toluene for 6 h led to decomposition to Pd metal
and an unresolved mixture of compounds. The use of
the more basic and less sterically demanding phosphine
PMe2Ph allowed the preparation of mono- and dinuclear
complexes. Thus, trans-[Pd(C6Me3I2)I(PMe2Ph)2] (2) was
obtained by reacting at room temperature, in a 1:1:2
Syn th esis of [tr a n s-{P d I(P Me3)2}3(µ3-C6Me3)] (6). Com-
plex 5 (105 mg, 0.065 mmol) and PMe3 (0.585 mL of a 1 M
solution in toluene, 0.585 mmol) were mixed under nitrogen
in degassed dichloromethane (20 mL) and allowed to react at
room temperature for 12 h. The precipitation of a white solid
was observed. The solvents and excess PMe3 were evaporated
under reduced pressure to give a slightly gray residue, which
was transferred to the filter funnel and washed thoroughly
with acetone to give analytically pure 6 as a slightly gray solid.
Yield: 75 mg (90%). Mp: 235 °C dec. 1H NMR (200 MHz,
2
4
CDCl3): 2.66 (s, 9H, Me), 1.41 (“t”, 54H, J PH + J PH ) 3 Hz,
PMe3). 31P{1H} NMR (121 MHz, CDCl3): δ -21.57 (s). Anal.
Calcd for C27H63I3P6Pd3: C, 25.46; H, 4.99. Found: C, 25.78;
H, 4.96.
X-r a y Str u ctu r e Deter m in a tion s. The crystals were
mounted in inert oil on a glass fiber and transferred to the
(53) Flack, H. D. Acta Crystallogr., Sect. A 1983, 39, 876.

4698 Organometallics, Vol. 20, No. 22, 2001
Vicente et al.
Sch em e 1
F igu r e 1. Thermal ellipsoid plot (50% probability level)
of 1. Selected bond lengths (Å) and angles (deg): Pd-C(1)
) 2.044(3), Pd-P(1) ) 2.3409(9), Pd-P(2) ) 2.3429(9), Pd-
I(1) ) 2.7000(4); C(1)-Pd-P(1) ) 88.82(9), C(1)-Pd-P(2)
) 88.58(9), P(1)-Pd-I(1) ) 92.20(2), P(2)-Pd-I(1) )
91.24(2).
The access to the trinuclear complexes 4 and 5,
containing nitrogen donor ligands, encouraged us to
synthesize trinuclear complexes containing phosphine
donor ligands by employing ligand exchange reactions.
Although attempts to replace tbbpy in 5 by PPh3 or
PMe2Ph resulted in decomposition to Pd metal, the use
of PMe3 was successful; the desired trinuclear complex
[trans-{PdI(PMe3)2}3(µ3-C6Me3)] (6) was obtained when
5 was stirred at room temperature for 12 h with an
excess of PMe3 in dichloromethane.
Str u ctu r e of Com p lexes. The NMR data agree with
the structures proposed in Scheme 1 for complexes 1-6.
Of particular interest are those of complex 5 (its
homologue 4 is insufficiently soluble in organic sol-
vents). Two 2:1 singlets in the 1H NMR spectrum,
corresponding to mesitylene methyls, indicate that the
structure found in the solid state (see Scheme 1 and
Figure 3) is maintained in solution and that the PdI-
(tbbpy) moieties do not rotate around the Pd-C bond.
The expected four singlets from the tbbpy methyls
appear as three very close signals.
In the solid state, complexes 1 and 2 each show a
palladium atom in a square-planar coordination envi-
ronment consisting of two trans phosphine ligands, an
iodo ligand, and the aryl ligand C6Me3I2 (Figures 1 and
2). The mean deviation of the atoms Pd, P(1), P(2), I(1),
and C(1) from the best plane is 0.1146 Å in complex 1
and 0.0722 Å in complex 2. As expected, Pd-C bond
distances (2.044(3) (1), 2.048(5) (2) Å) are not signifi-
cantly different. However, the Pd-I bond distance in 1
(2.7000(4) Å) is significantly longer than that in 2
(2.6882(5) Å), probably because of the greater steric
requirement of PPh3 as compared to that of PMe2Ph.
The Pd-P distances in 1 (2.3409(9), 2.3429(9) Å) are
longer than those in complex 2 (2.316(2), 2.328(2) Å).
Both are in the ranges found in other trans-[PdX2L2]
(L ) PPh3 (2.340-2.326 Å),54-57 PMe2Ph (2.333-2.317
Å)58-60) complexes.
molar ratio, a mixture of C6Me3I3, [Pd(dba)2], and PMe2-
Ph, whereas using a 1:2:4 molar ratio of these reagents
in refluxing toluene, the dinuclear complex [{trans-PdI-
(PMe2Ph)2}2(µ2-C6Me3I)] (3) was obtained. Complex 3
was also isolated instead of the desired trinuclear
species using 1:3:6 and 1:4:8 molar ratios. More severe
conditions were examined. Thus, the reaction of C6-
Me3I3, [Pd(dba)2], and PMe2Ph in a 1:3:6 molar ratio and
long reaction time at room temperature (72 h) led to a
drastic decrease of the yield of 3 (<10%), and when the
reaction was carried out in refluxing toluene more than
3 h or in a Carius tube at 150 °C, decomposition to Pd
occurred and an intractable mixture was obtained. We
attempted to prepare the trinuclear complex using the
less bulky phosphine PMe3, but the reaction of 1,3,5-
triiodomesitylene with a mixture of [Pd(dba)2] and PMe3
(1:3:6 molar ratio) in toluene at room temperature
resulted only in the formation of Pd metal and an
unresolved mixture of compounds.
In contrast to the above results, addition of C6Me3I3
to a mixture of [Pd(dba)2] and 2,2′-bipyridine (bpy) or
4,4′-di-tert-butyl-2,2′-bipyridine (tbbpy) in toluene gave
at room temperature [(PdIL2)3(µ3-C6Me3)] (L2 ) bpy (4),
tbbpy (5)), even if substoichiometric amounts of Pd were
used. Thus, with 1:2:2 or 1:3:3 molar ratios and L2 )
tbbpy, only the formation of 5 was observed, and with
1:1:1 molar ratios and L2 ) tbbpy, a mixture of com-
plexes was obtained containing mainly 5. Therefore, it
seems that the substituent [M] ) [PdIL2], when L2 )
bpy, tbbpy, activates the C6Me3I2[M] or C6Me3I[M]2
rings for the next oxidative addition reactions, whereas
the contrary occurs when L ) PR3.
(54) Vicente, J .; Abad, J . A.; Frankland, A. D.; Ram´ırez de Arellano,
M. C. Chem. Eur. J . 1999, 5, 3066.
(55) Flemming, J . P.; Pilon, M. C.; Borbulevitch, O. Y.; Antipin, M.
Y.; Grushin, V. V. Inorg. Chim. Acta 1998, 280, 87.

Polymetalated Aromatic Compounds
Organometallics, Vol. 20, No. 22, 2001 4699
F igu r e 3. Thermal ellipsoid plot (30% probability level)
of 5. Hydrogen atoms and solvent atoms are omitted for
clarity. Selected bond lengths (Å) and angles (deg): Pd-
(1)-C(1) ) 2.001(4), Pd(1)-N(11) ) 2.072(3), Pd(1)-N(21)
) 2.146(3), Pd(1)-I(1) ) 2.5886(4), Pd(2)-C(3) ) 1.989-
(4), Pd(2)-N(31) ) 2.111(3), Pd(2)-N(41) ) 2.163(3), Pd-
(2)-I(2) ) 2.5846(4), Pd(3)-C(5) ) 2.009(4), Pd(3)-N(51)
) 2.081(3), Pd(3)-N(61) ) 2.148(3), Pd(3)-I(3) ) 2.5791-
(4); C(1)-Pd(1)-N(11) ) 93.31(14), N(11)-Pd(1)-N(21) )
78.47(13), C(1)-Pd(1)-I(1) ) 88.77(10), N(21)-Pd(1)-I(1)
) 99.45(9), C(3)-Pd(2)-N(31) ) 91.93(13), N(31)-Pd(2)-
N(41) ) 77.74(12), C(3)-Pd(2)-I(2) ) 92.17(10), N(41)-
Pd(2)-I(2) ) 100.29(8), C(5)-Pd(3)-N(51) ) 94.13(13),
N(51)-Pd(3)-N(61) ) 77.54(12), C(5)-Pd(3)-I(3) ) 89.02-
(10), N(61)-Pd(3)-I(3) ) 99.46(8).
F igu r e 2. Thermal ellipsoid plot (50% probability level)
of 2. Selected bond lengths (Å) and angles (deg): Pd-P(2)
) 2.316(2), Pd-P(1) ) 2.328(2), Pd-I(2) ) 2.6882(5); C(1)-
Pd-P(2) ) 90.03(14), C(1)-Pd-P(1) ) 88.99(14), P(2)-Pd-
I(2) ) 90.34(4), P(1)-Pd-I(2) ) 90.88(4).
In complex 5 (Figure 3), three palladium atoms are
bonded to the mesitylene ring. Each shows a square-
planar coordination, but the extent of distortion is very
different. Pd(1) and its four immediate neighbors are
coplanar with a mean deviation of only 0.016 Å. At Pd-
(3) the distortion is greater (mean deviation 0.09 Å),
with N(51) lying 0.33 Å out of the plane of the other
four atoms (mean deviation 0.001 Å). The greatest
distortion is observed at Pd(2), with a mean deviation
of 0.17 Å; N(41) lies 0.74 Å out of the plane of the other
four atoms (mean deviation 0.05 Å). The nine carbon
atoms of the mesityl ring are coplanar, with a mean
deviation of only 0.025 Å, but the palladium substitu-
ents lie out of this plane by 0.24, -0.83, and -0.26 Å
for Pd(1), Pd(2), and Pd(3), respectively. They are
arranged with the Pd-I vectors all approximately
perpendicular to the mesityl plane, whereby I(1) lies on
one side of the plane I(2) and I(3) are on the other side.
Scheme 1 shows a simple representation of this ar-
rangement. The Pd-C bond distances (2.001(4), 1.989-
(4), 2.009(4) Å) are shorter than those in 1 (2.044(3) Å)
or 2 (2.048(5) Å) because of the order of trans influence
I > tbbpy. Similarly, the order of trans influence aryl
> tbbpy is manifested in the much shorter Pd-I bond
lengths in 5 (2.5886(4), 2.5846(4), 2.5791(4) Å) as
compared to those in complex 1 (2.7000(4) Å) or 2
(2.6882(5) Å). Finally, the order of trans influence aryl
> I is shown in the longer Pd-N(21) (2.146(3) Å), Pd-
N(41) (2.163(3) Å), and Pd-N(61) (2.148(3) Å) bonds
compared to Pd-N(11) (2.072(3) Å), Pd-N(31) (2.111-
(3) Å), and Pd-N(51) (2.081(3) Å).
Ack n ow led gm en t. We thank the Direccio´n General
de Investigacio´n Cient´ıfica y Te´cnica (PB97-1047), IN-
TAS (97-166), and the Fonds der Chemischen Industrie
for financial support. M.L. is grateful to Fundacion
Seneca (Comunidad Autonoma de la Region de Murcia,
Spain), for a Grant.
(56) Veya, P.; Floriani, C.; Chiesivilla, A.; Rizzoli, C. Organometallics
1993, 12, 4899.
(57) Vicente, J .; Abad, J . A.; Rink, B.; Herna´ndez, F.-S.; Ram´ırez
de Arellano, M. C. Organometallics 1997, 16, 5269.
(58) Crociani, B.; Sala, M.; Polo, A.; Bombieri, G. Organometallics
1986, 5, 1369.
(59) Ozawa, F.; Sugawara, M.; Hasebe, K.; Hayashi, T. Inorg. Chim.
Acta 1999, 296, 19.
(60) Benetollo, F.; Bombieri, G.; Dibianca, F.; Crociani, B. Inorg.
Chim. Acta 1991, 188, 51.
Su p p or tin g In for m a tion Ava ila ble: Listings of both
refined and calculated atomic coordinates, all anisotropic
thermal parameters, and all bond lengths and angles for
compounds 1, 2, and 5. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM0105472