Cyclopalladated compounds derived from [C,N,O] terdentate ligands: Synthesis, characterization and reactivity

Article abstract of DOI:10.1016/S0277-5387(01)00970-6

Treatment of the Schiff base ligands 2-ClC₆H₄C(H)=NCH₂(C₄ H₇O) (a) and 3,4-(MeO)₂C₆H₃C(H)=NCH₂(C ₄H₇O) (b) with palladium(II) acetate in toluene or glacial acetic acid gave the dinuclear cyclometallated complexes [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}(μ-OAc)]₂ (1a) and [Pd{3,4-(MeO)₂C₆H₂C(H)=NCH₂(C ₄H₇O)}(μ-OAc)]₂ (1b) with the ligand bonded to the palladium atom through the imine nitrogen and the C6 carbon atom. The ¹H and ¹³C-{¹H} NMR spectra of the complexes show the occurrence in solution of three pairs of enantiomers. The acetato-bridged cyclometallated complex [Pd{3,4-(MeO)₂C₆H₂C(H)=NCH₂(C ₄H₇O)}(μ-OAc)]₂ (1c) was prepared from the enantiopure ligand (R)-3,4-(MeO)₂C₆H₃(H)= NCH₂(C₄H₇O) (c). The NMR spectra of 1c showed the existence of only two diastereomers in the solution. The reaction of 1a and 1b with aqueous sodium chloride gave the chloro-bridged complexes [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}(μ-Cl)]₂ (2a) and [Pd{3,4-(MeO)₂C₆H₂C(H)=NCH₂(C ₄H₇O)}(μ-Cl)]₂ (2b) after a metathesis reaction. The reaction of 2a with PPh₃ in acetone gave the mononuclear cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}(Cl)(PPh₃)] (3a) in a bridge-splitting reaction. Treatment of 3a with silver triflate gave the cyclometallated complex [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}(PPh₃)][CF₃SO₃] (4a) in which the palladium atom is bonded to four different atoms C, N, O and P. When complex 2a was reacted with silver triflate in acetone complex [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}((CH₃)₂CO)][CF₃SO ₃] (5a) was obtained with the ligand as [C,N,O] coordinated. The reaction of complexes 2a and 2b with the diphosphine dppp in a complex-phosphine 1:1 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)](Cl)}₂(μ-Ph₂P(CH₂) ₃PPh₂)] (8a) and [{Pd[3,4-(MeO)₂C₆H₂C(H)=NCH₂(C ₄H₇O)](Cl)}₂(μ-Ph₂P(CH ₂)₃PPh₂)] (5b) with the diphosphine bridging the two palladium atoms. Reaction of complexes 2a and 2b with the phosphines dppp and cis-dppe in a 1:2 molar ratio gave the mononuclear complexes [Pd{2-ClC₆H₃C(H)=NCH₂(C₄H ₇O)}{Ph₂P(CH₂)₃Ph₂-P, P}][ClO₄] (6a), [Pd{3,4-(MeO)₂C₆H₂C(H)=NCH₂(C ₄H₇O)}{Ph₂P(CH₂)₃Ph ₂P,P}][ClO₄] (3b) and [Pd{2-ClC₆H₂C(H)=NCH₂(C₄H ₇O)}(cis-Ph₂PCH=CHPh₂-P,P)][Cl] (4b). The treatment of 2a with the triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio, followed by treatment with sodium perchlorate gave [Pd{3,4-(MeO)₂ClC₆H₃C(H)=NCH₂(C ₄H₇O)}{(PPh₂CH₂CH₂) ₂PPh-P,P,P}][ClO₄] (7a) in which the palladium atom is bonded to the triphosphine through the three phosphorus atoms and to the Schiff base ligand through one carbon atom and the imine nitrogen.

Full text of DOI:10.1016/S0277-5387(01)00970-6

Polyhedron 21 (2002) 39–48
www.elsevier.com/locate/poly
Cyclopalladated compounds derived from [C,N,O] terdentate
ligands: synthesis, characterization and reactivity
Alberto Ferna´ndez a,*, Esther Pereira a, Jesu´s J. Ferna´ndez a, Margarita Lo´pez-Torres a,
Antonio Sua´rez a, Roberto Mosteiro a, Jose´ M. Vila b,*
a Departamento de Qu´ımica Fundamental, Uni6ersidad de La Corun˜a, E-15071 La Corun˜a, Spain
b Departamento de Qu´ımica Inorga´nica, Uni6ersidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain
Received 1 June 2001; accepted 1 October 2001
Abstract
Treatment of the Schiff base ligands 2-ClC6H4C(H)ꢀNCH2(C4H7O) (a) and 3,4-(MeO)2C6H3C(H)ꢀNCH2(C4H7O) (b) with
palladium(II) acetate in toluene or glacial acetic acid gave the dinuclear cyclometallated complexes [Pd{2-ClC6H3C-
(H)ꢀNCH2(C4H7O)}(m-OAc)]2 (1a) and [Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}(m-OAc)]2 (1b) with the ligand bonded to the
1
palladium atom through the imine nitrogen and the C6 carbon atom. The H and 13C–{1H} NMR spectra of the complexes show
the occurrence in solution of three pairs of enantiomers. The acetato-bridged cyclometallated complex [Pd{3,4-
(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}(m-OAc)]2 (1c) was prepared from the enantiopure ligand (R)-3,4-(MeO)2C6H3(H)ꢀ
NCH2(C4H7O) (c). The NMR spectra of 1c showed the existence of only two diastereomers in the solution. The reaction of 1a
and 1b with aqueous sodium chloride gave the chloro-bridged complexes [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(m-Cl)]2 (2a) and
[Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}(m-Cl)]2 (2b) after a metathesis reaction. The reaction of 2a with PPh3 in acetone gave
the mononuclear cyclometallated complex [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(Cl)(PPh3)] (3a) in a bridge-splitting reaction.
Treatment of 3a with silver triflate gave the cyclometallated complex [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(PPh3)][CF3SO3] (4a) in
which the palladium atom is bonded to four different atoms C, N, O and P. When complex 2a was reacted with silver triflate in
acetone complex [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}((CH3)2CO)][CF3SO3] (5a) was obtained with the ligand as [C,N,O] coordi-
nated. The reaction of complexes 2a and 2b with the diphosphine dppp in a complex–phosphine 1:1 molar ratio gave the dinuclear
cyclometallated complexes [{Pd[2-ClC6H3C(H)ꢀNCH2(C4H7O)](Cl)}2(m-Ph2P(CH2)3PPh2)] (8a) and [{Pd[3,4-(MeO)2C6H2C-
(H)ꢀNCH2(C4H7O)](Cl)}2(m-Ph2P(CH2)3PPh2)] (5b) with the diphosphine bridging the two palladium atoms. Reaction of
complexes 2a and 2b with the phosphines dppp and cis-dppe in a 1:2 molar ratio gave the mononuclear complexes [Pd{2-
ClC6H3C(H)ꢀNCH2(C4H7O)}{Ph2P(CH2)3Ph2-P,P}][ClO4] (6a), [Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}{Ph2P(CH2)3Ph2–
P,P}][ClO4] (3b) and [Pd{2-ClC6H2C(H)ꢀNCH2(C4H7O)}(cis-Ph2PCHꢀCHPh2–P,P)][Cl] (4b). The treatment of 2a with the
triphosphine bis(2-diphenylphosphinoethyl)phenylphosphine in 1:2 molar ratio, followed by treatment with sodium perchlorate
gave [Pd{3,4-(MeO)2ClC6H3C(H)ꢀNCH2(C4H7O)}{(PPh2CH2CH2)2PPh-P,P,P}][ClO4] (7a) in which the palladium atom is
bonded to the triphosphine through the three phosphorus atoms and to the Schiff base ligand through one carbon atom and the
imine nitrogen. © 2002 Elsevier Science Ltd. All rights reserved.
Keywords: C–H activation; Cyclometallation; Phosphorus ligands; Schiff bases; Palladium
1. Introduction
[1–5]. They present numerous applications in organic
and organometallic synthesis [6], in insertion reactions
[7], in optical resolution [8], in the determination of the
enantiomeric excess [9], in the synthesis of new metal
mesogenic compounds [10], biologically active com-
pounds [11,12], in catalytic materials [13], in the build-
ing of new self assembly supramolecular species [14],
and to promote unusual coordination environments
[15].
The study of cyclometallated compounds has at-
tracted much attention over the last three decades
* Corresponding authors. Fax: +34-981-595-012 (J.M.V.); 34-981-
167-065 (A.F.).
E-mail addresses: qiluaafl@udc.es (J.M. Vila), qideport@usc.es (A.
Ferna´ndez).
0277-5387/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0277-5387(01)00970-6

40
A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
Our interest in cyclometallated complexes has been,
trophotometers. NMR spectra were obtained as CDCl3
solutions and referenced to SiMe4 (1H, 13C–{1H}) or
85% H3PO4 (31P–{1H}) and were recorded on a Bruker
AC-2005 spectrometer. All chemical shifts were re-
ported downfield from standards. The FAB mass spec-
tra were recorded using a Quatro mass spectrometer
with a Cs ion gun; 3-nitrobenzyl alcohol was used as
the matrix. Conductivity measurements were made on a
CRISON GLP 32 conductivimeter using 10−3 mol
dm−3 solutions in dry acetonitrile.
in part, focused on the study of compounds derived
from potentially [C,N,X] (X=O, S, N) terdentate lig-
ands, such as semicarbazones [16,17], thiosemicarba-
zones [18,19] or Schiff bases [20–23] which react with
palladium(II) and platinum(II) or palladium(0) to give
cyclometallated complexes with two fused rings at the
metal. In spite of the large number of [C,N,N] deriva-
tives reported [24], relatively few [C,N,O] derivatives
are known [25].
Semicarbazones are known to react readily with
M2[PdCl4] (M=Li, K) to give mononuclear cy-
clometallated complexes; however, complexes derived
from thiosemicarbazones show tetranuclear structures.
In the present paper we report the synthesis of new
cyclometallated compounds derived from the poten-
tially terdentate Schiff bases 2-ClC6H4C(H)ꢀNCH2-
(C4H7O) (a) and 3,4-(MeO)2C6H3C(H)ꢀNCH2(C4H7O)
(b). We have found that direct reaction with Pd(II) or
Pd(0) salts did not yield the expected complex with the
ligand in a [C,N,O] terdentate fashion. Thus, in an
The syntheses of 2-ClC6H4C(H)ꢀNCH2(C4H7O) (a)
and 3,4-(MeO)2C6H3C(H)ꢀNCH2(C4H7O) (b) were per-
formed by heating chloroform solutions of the appro-
priate quantities of tetrahydrofurfurylamine and
2-chlorobenzaldehyde or 3,4-dimethoxybenzaldehyde,
respectively, in a Dean–Stark apparatus under reflux.
Schiff base ligand (R)-3,4-(MeO)2C6H3C(H)ꢀNCH2-
(C4H7O) (c) was prepared similarly using enantiopure
(R)-tetrahydrofufurylamine. IR (wmax/cm−1
) (CꢀN)
1640s (a), 1645s (b, c). 13C–{1H} NMR for ligand a:
(50.28 MHz, CDCl3): l 158.9 (CꢀN); l 135.0 (C1); l
129.6 (C6); l 131.1 (C2); l 126.8 (C5); l 128.3, 131.4
(C3, C4); l 78.3 (C8); l 68.1 (C11); l 65.8 (C7); l 29.2,
25.7 (C9, C10). 13C–{1H} NMR for ligand b, c: l 161.9
(CꢀN); l 151.3, 149.2 (C3, C4); l 129.4 (C1); l 123.1
(C6); l 110.3, 108.8 (C2, C5); l 78.5 (C8); l 68.1 (C11);
l 65.7 (C7); l 29.3, 25.6 (C9, C10); l 55.8 (OCH3).
oxidative addition reaction, treatment of
a with
[Pd2(dba)3], in benzene under reflux, gave an untreat-
able mixture which was not further investigated, and
reaction of a or b with palladium(II) acetate, in glacial
acetic acid, only yielded the dimeric acetato-bridged
complexes 1a and 1b with the corresponding ligand as
[C,N] bidentate. However, the vacant site produced in
the coordination sphere of the palladium atom, upon
reaction of the cyclometallated halogen-bridged dimer
complexes with a Ag(I) salt, promotes formation of the
Pd–O bond. The reactivity of the cyclometallated com-
plexes with mono-, di- and triphosphines is reported,
and we also describe a new type of stereoisomerism
arising from the folded open-book disposition of the
cyclometallated ligands in the acetato-bridged dimers
1a and 1b.
2.2. Syntheses
2.2.1. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(v-OAc)]2
(1a)
A pressure tube containing 2-ClC6H4C(H)ꢀNCH2-
(C4H7O) (a) (150 mg, 0.67 mmol), palladium(II) acetate
(150 mg, 0.67 mmol) and 25 cm3 of dry toluene was
sealed under argon. The resulting mixture was heated at
60 °C for 3 h. After cooling to room temperature (r.t.)
the orange precipitate formed was filtered off and dis-
solved in chloroform. The red solution obtained was
filtered through Celite to remove the black palladium
formed. The solvent was removed under vacuum to
give an orange solid which was chromatographed on a
column packed with silica gel. Elution with
dichloromethane–methanol (1%) afforded the final
product after concentration. Yield 44%. Anal. Found:
C, 43.2; H, 4.2; N, 3.6. Calc. for C28H32N2O6Cl2Pd2: C,
2. Experimental
Safety note: Caution: perchlorate salts of metal com-
plexes with organic ligands are potentially explosive.
Only small amounts of these materials should be pre-
pared and handled with great caution.
2.1. General procedures
43.3; H, 4.1; N, 3.6%. IR: w(CꢀN), 1610s cm−1
was(COO), 1560s cm−1; ws(COO), 1410s cm−1 13C–
;
.
Solvents were purified by standard methods [26].
Chemicals were reagent grade. The phosphines PPh3,
{1H} NMR: (50.28 MHz, CDCl3): l 171.6, 171.7
(CꢀN); l 156.9, 156.7 (C6); l 143.2, 143.0 (C1); l 131.0
(C2); l 124.6, 124.7 (C5); l 130.1, 130.2, 130.3, 130.4
(C3, C4); l 76.6 (C8); l 68.5 (C11); l 63.6, 61.6 (C7); l
29.1, 28.4, 25.9, 25.5 (C9, C10); l 173.0 (CH3COO); l
24.4 (CH3COO). FAB MS: m/z=776 [M]+; 717 [M−
AcO]+.
cis-Ph2PCHꢀCHPPh2
(cis-dppe),
Ph2P(CH2)3PPh2
(dppp) and (Ph2PCH2CH2)2PPh (triphos) were pur-
chased from Aldrich-Chemie. Microanalyses were car-
ried out using a Carlo–Erba elemental analyzer, model
1108. IR spectra were recorded as Nujol mulls or KBr
discs on a Perkin–Elmer 1330 and on a Mattson spec-
Complexes 1b and 1c were prepared similarly.

A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
41
2.2.2. [Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2-
(C4H7O)}(v-OAc)]2 (1b)
Yield 56%. Anal. Found: C, 46.2; H, 5.2; N, 3.3.
Found: C, 57.1; H, 4.9; N, 2.3. Calc. for
C30H28NOCl2PdP: C, 57.5; H, 4.5; N, 2.2%. IR:
w(CꢀN), 1620m cm−1 13C–{1H} NMR: (50.28 MHz,
.
Calc. for C32H42N2O10Pd2: C, 46.4; H, 5.1; N, 3.4%. IR:
CDCl3): l 175.0 (d, CꢀN, JPC=4.2 Hz); l 160.0 (C6);
l 145.0 (C1); l 131.3 (C2); l 124.8 (C5); l 131.0, 131.9
(C3, C4); l 77.5 (C8); l 67.9 (C11); l 65.6 (C7); l 28.8,
25.8 (C9, C10). P-phenyl: l 135.4 (d, Co, JPC=12.1
Hz); l 128.0 (d, Cm, JPC=11.3 Hz); l 130.8 (d, Cp,
JPC=2.8 Hz); l 130.7 (d, Ci, JPC=42.5 Hz). FAB
MS: m/z=627 [M]+; 590 [M−Cl]+.
w(CꢀN), 1608m cm−1
;
was(COO), 1570s cm−1
;
ws(COO), 1415s cm−1 13C–{1H} NMR: (50.28 MHz,
.
CDCl3): l 173.8, 173.7, 172.5, 172.4 (CꢀN); l 149.3,
149.0 (C6); l 149.4, 146.0 (C3, C4); l 137.8, 137.4 (C1);
l 114.1, 109.9 (C2, C5); l 76.9 (C8); l 68.3, 67.8 (C11);
l 62.7, 60.1 (C7); l 29.1, 28.6, 25.8, 25.4 (C9, C10); l
181.1, 180.0 (CH3COO); l 24.4, 24.3 (CH3COO); l
56.2, 55.7 (OCH3).
2.2.7. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}-
(PPh3)][CF3SO3] (4a)
2.2.3. (R)-[Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2-
(C4H7O)}(v-OAc)]2 (1c)
Yield 65%. Anal. Found: C, 45.7; H, 5.4; N, 3.2.
A suspension of 3a (24.0 mg, 0.020 mmol) in acetone
(15 cm3) was treated with silver trifluoromethanesul-
fonate (5.2 mg, 0.020 mmol) and stirred for 24 h. The
resulting solution was filtered through Celite to elimi-
nate the AgCl precipitate and the solvent removed to
give a yellow solid, which was recrystallized from chlo-
roform–hexane. Yield 60%. Anal. Found: C, 50.1; H,
3.7; N, 2.1. Calc. for C31H28NO4F3ClSPdP: C, 50.3; H,
Calc. for C32H42N2O10Pd2: C, 46.4; H, 5.1; N, 3.4%. IR:
w(CꢀN), 1608m cm−1
;
was(COO), 1570s cm−1
;
ws(COO), 1415s cm−1 13C–{1H} NMR: (50.28 MHz,
.
CDCl3): l 173.8, 172.4 (CꢀN); l 149.3 (C6); l 149.4,
146.0 (C3, C4); l 137.8, 137.4 (C1); l 114.1, 109.9 (C2,
C5); l 76.9 (C8); l 68.3, 67.8 (C11); l 62.7, 60.1 (C7);
l 29.1, 28.6, 25.8, 25.4 (C9, C10); l 181.1, 180.0
(CH3COO); l 24.4, 24.3 (CH3COO); l 56.2, 55.7
(OCH3).
3.8; N, 1.9%. IR: w(CꢀN), 1620m cm−1 13C–{1H}
.
NMR: (50.28 MHz, CDCl3): l 173.6 (d, CꢀN, JPC=
3.5 Hz); l 151.3 (C6); l 145.5 (C1); l 127.7 (C2); l
126.3 (C5); l 128.7 (C3, C4); l 81.9 (C8); l 69.7 (C11);
l 61.7 (C7); l 28.4 (C9, C10). P-phenyl: l 134.9 (d, Co,
JPC=12.1 Hz); l 129.0 (d, Cm, JPC=10.6 Hz); l
131.8 (d, Cp, JPC=2.8 Hz); l 132.4 (d, Ci, JPC=48.2
Hz). FAB MS: m/z=592 [M−CF3SO3]+. Specific mo-
lar conductivity, \m=156.4 ohm−1 cm2 mol−1 (in
acetonitrile).
2.2.4. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(v-Cl)]2 (2a)
An aqueous solution of NaCl (ca. 10−2 M) was
added dropwise to a solution of 1a (200.0 mg, 0.257
mmol) in 10 cm3 of acetone. The resulting mixture was
stirred for 6 h. The yellow precipitate formed was
filtered off, washed with water and dried under vac-
uum. Yield 86%. Anal. Found: C, 39.9; H, 3.3; N, 3.7.
Calc. for C24H26N2O2Cl4Pd2: C, 39.5; H, 3.6, N, 3.8%.
2.2.8. [{Pd[2-ClC6H3C(H)ꢀNCH2(C4H7O)](Cl)}2-
(v-Ph2P(CH2)3PPh2)] (8a)
IR: w(CꢀN), 1615s cm−1
.
13C–{1H} NMR: (50.28
Ph2P(CH2)3PPh2 (dppp) (17.0 mg, 0.041 mmol) was
added to a suspension of 2a (30.0 mg, 0.041 mmol) in
acetone (15 cm3). The mixture was stirred for 12 h and
the precipitate formed filtered off and dried under
vacuum to give a white solid which was recrystallized
from chloroform–hexane. Yield 51%. Anal. Found: C,
49.1; H, 4.3; N, 2.3. Calc. for C51H52N2O2Cl4-
Pd2P2.CHCl3: C, 49.5; H, 4.2; N, 2.2%. IR: w(CꢀN),
MHz, CDCl3): l 174.4 (CꢀN); l 155.2 (C6); l 143.3
(C1); l 131.1 (C2); l 125.4 (C5); l 131.3, 131.7 (C3,
C4); l 76.7 (C8); l 68.2 (C11); l 63.7 (C7); l 28.9, 25.8
(C9, C10). FAB MS: m/z=765 [M+Cl]+; 693 [M−
+
Cl]
.
Complex 2b was prepared similarly as a yellow solid.
2.2.5. [Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2-
(C4H7O)}(v-Cl)]2 (2b)
Yield 91%. Anal. Found: C, 43.4; H, 4.3; N, 3.7.
Calc. for C28H36N2O6Cl2Pd2: C, 43.1; H, 4.6, N, 3.6%.
IR: w(CꢀN), 1610m cm−1. FAB MS: m/z=780 [M]+;
745 [M−Cl]+.
1623m cm−1
.
Compound 5b was prepared similarly as a white
solid.
2.2.9. [{Pd[3,4-(MeO)2C6H2C(H)ꢀNCH2-
(C4H7O)](Cl)}2(v-Ph2P(CH2)3PPh2)] (5b)
Yield 55%. Anal. Found: C, 55.1; H, 5.0; N, 2.3.
2.2.6. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(Cl)(PPh3)]
(3a)
Calc. for C55H62N2O6Cl2Pd2P2: C, 55.4; H, 5.2; N,
2.3%. IR: w(CꢀN), 1615m cm−1
.
PPh3 (22.0 mg, 0.082 mmol) was added to a suspen-
sion of 2a (30.0 mg, 0.041 mmol) in acetone (15 cm3).
The mixture was stirred for 12 h and the white precipi-
tate formed filtered off, dried under vacuum and recrys-
tallized from chloroform–hexane. Yield 74%. Anal.
2.2.10. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}-
(Ph2P(CH2)3Ph2–P,P)][ClO4] (6a)
Ph2P(CH2)3Ph2 (dppp) (34.0 mg, 0.082 mmol) was
added to a suspension of 2a (30.0 mg, 0.041 mmol) in

42
A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
acetone (20 cm3). The mixture was stirred for 1 h, after
which an excess of sodium perchlorate was added. The
complex was then precipitated out by addition of water,
filtered off and dried in vacuo. Recrystallization from
chloroform–hexane gave the final compound as a white
solid. Yield 85%. Anal. Found: C, 55.1; H, 4.2; N, 3.0.
Calc. for C39H39N2O5Cl2P2Pd: C, 54.8; H, 4.6; N, 3.3%.
IR: w(CꢀN), 1617m cm−1. Specific molar conductivity,
\m=113.5 ohm−1 cm2 mol−1 (in acetonitrile).
Complex 3b was synthesized similarly as a yellow
solid.
Calc. for C16H19NO5F3ClSPd: C, 35.8; H, 3.6; N, 2.6%.
IR: w(CꢀN), 1608m cm−1 13C–{1H} NMR: (50.28
.
MHz, CDCl3): l 174.1 (CꢀN); l 151.3 (C6); l 143.3
(C1); l 131.4 (C2); l 126.1 (C5); l 132.0, 129.8 (C3,
C4); l 79.6 (C8); l 70.1 (C11); l 62.4 (C7); l 28.5, 25.6
(C9, C10); l 31.2, 29.7 (CH3CꢀO). Specific molar con-
ductivity, \m=240.2 ohm−1 cm2 mol−1 (in
acetonitrile).
3. Results and discussion
2.2.11. [Pd{3,4-(MeO)2C6H3C(H)ꢀNCH2(C4H7O)}-
(Ph2P(CH2)3Ph2–P,P)][ClO4] (3b)
Yield 85%. Anal. Found: C, 56.1; H, 5.0; N, 1.9.
Calc. for C41H44NO7ClPdP2: C, 56.8; H, 5.1; N, 1.6%.
IR: w(CꢀN), 1615m cm−1. Specific molar conductivity,
\m=140.3 ohm−1 cm2 mol−1 (in acetonitrile).
For the convenience of the reader the compounds
and reactions are shown in Scheme 1. The compounds
described in this paper were characterized by elemental
analysis (C, H, N) and by IR spectroscopy (data in
1
Section 2) and by H, 31P–{1H} (see Table 1) and, in
part, 13C–{1H} NMR spectroscopy and FAB mass
spectrometry (Section 2).
2.2.12. [Pd{3,4-(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}-
(cis-Ph2PCHꢀCHPh2–P,P)][Cl] (4b)
Reaction of the Schiff base ligands 2-ClC6H4C(H)ꢀ
NCH2(C4H7O) (a) and 3,4-(MeO)2C6H3C(H)ꢀNCH2-
(C4H7O) (b) with palladium(II) acetate in toluene gave
the dinuclear cyclometallated complexes [Pd{2-
cis-Ph2PCHꢀCHPh2 (cis-dppe) (30.0 mg, 0.074
mmol) was added to a suspension of 2b (29.0 mg, 0.037
mmol) in acetone (20 cm3). The mixture was stirred for
1 h. The complex was then precipitated out by addition
of water, filtered off and dried in vacuo. Recrystalliza-
tion from chloroform–hexane gave the final compound
as a white solid. Yield 62%. Anal. Found: C, 48.8; H,
4.5; N, 2.0. Calc. for C40H40NO3ClP2Pd·2CHCl3: C,
49.2; H, 4.1; N, 1.4%. IR: w(CꢀN), 1606m cm−1. Spe-
cific molar conductivity, \m=90.3 ohm−1 cm2 mol−1
(in acetonitrile).
ClC6H3C(H)ꢀNCH2(C4H7O)}(m-OAc)]2
(1a)
and
[Pd{3,4 - (MeO)2C6H2C(H)ꢀNCH2(C4H7O)}(m - OAc)]2
(1b), respectively, which were fully characterized. The
IR spectra of 1a and 1b showed the w(CꢀN) stretch at
1610 and 1608 cm−1, respectively, shifted to lower
wavenumbers (as compared to the free ligand) due to
N-coordination of the imine [27,28]. The IR spectra
also showed strong bands assigned to the symmetric
and asymmetric w(COO) vibrations, in agreement with
those expected for bridging acetate ligands [29] (see
Section 2). The resonance corresponding to the HCꢀN
Complex 7a was synthesized as a yellow solid using a
similar procedure to the one described for complex 6a.
1
proton in the H NMR spectra was shifted to lower
2.2.13. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}-
{(PPh2CH2CH2)2PPh–P,P,P}][ClO4] (7a)
Yield 95%. Anal. Found: C, 52.0; H, 4.5; N, 1.5.
frequency consequent upon coordination of the imine
group to the palladium atom 6ia the lone pair of the
nitrogen atom [30]. The assignment of the aromatic
proton resonances unequivocally showed that metalla-
tion had taken place at the C6 carbon atom for both
compounds (see Table 1).
Calc. for C46H46NO5Cl2P3Pd·CHCl3: C, 52.1; H, 4.4; N,
1.3%. IR: w(CꢀN), 1615m cm−1 13C–{1H} NMR:
.
(50.28 MHz, CDCl3): l 168.8 (d, CꢀN, JPC=5.0); l
139.6 (C1); l 135.4 (C2); l 124.5 (C5); l 77.7 (C8); l
67.9 (C11); l 63.1 (C7); l 28.8, 25.8 (C9, C10). FAB
MS: m/z=862.2 [M−ClO4]+. Specific molar conduc-
tivity, \m=146.3 ohm−1 cm2 mol−1 (in acetonitrile).
1
A noticeable feature of the H NMR spectra of 1a
and 1b is the number of signals for the HCꢀN and
aromatic protons. Four singlets for the HCꢀN protons
were assigned in each case. For complex 1a a multiplet
was assigned to the H3, H4 and H5 resonances, whereas
for complex 1b two singlets were assigned to each one
of the H2 and H5 protons. We reasoned that the
splitting could be caused by the presence of the syn and
anti conformations, as acetato-bridged dimers exist in a
folded arrangement which gives rise to two isomers: the
anti isomer with C2 symmetry and the syn isomer with
Cs symmetry (see Fig. 1). By far, the anti disposition is
the most frequent [31].
2.2.14. [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}-
((CH3)2CO)][CF3SO3] (5a)
A suspension of 2a (30.0 mg, 0.041 mmol) in acetone
(8 cm3) was treated with silver trifluoromethanesul-
fonate (22.0 mg, 0.082 mmol) and stirred for 24 h. The
resulting solution was filtered through Celite to elimi-
nate the AgCl precipitate and the solvent removed to
give a hygroscopic yellow solid which was recrystallized
from dichloromethane–hexane and stored under nitro-
gen. Yield 65%. Anal. Found: C, 36.1; H, 3.3; N, 2.1.
If both isomers were present two resonances would
be expected for the HCꢀN protons and three for the

A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
43
acetate MeCOO protons (one for the anti isomer and
two for the syn separated by approximately 0.2 ppm
[32]). However in the H NMR spectra of 1a and 1b
cyclometallated unit of the acetate dimer. Thus, four
signals could be assigned to the HCꢀN protons in the
1H NMR spectra of the complexes, two resonances for
the aromatic protons and two for the acetate methyl
protons. The intensities of the signals for V and VI are
the same as those for the I–IV enantiomers. Due to
their similar solubility we were not able to separate the
three pairs of enantiomers. Surprisingly, none of the
other derivatives of ligands a and b showed splitting of
the NMR signals. We attribute these findings to the
folded structure of the acetato-bridged complex which
brings close together the cyclometallated units. The
asymmetric C8 carbon atom of one unit is situated
close to the neighboring cyclometallated ligand, thus
experiencing a different chemical environment in each
diastereomer. Since the folded structure brings the
HCꢀN proton close to the C8 carbon, the chemical
differences between the diastereoisomers are most evi-
dent in the HCꢀN resonances.
1
only two resonances, separated by approximately 0.02
ppm, were assignable to the acetate methyl groups.
Therefore, we believe that the number of signals
found may be due to the presence of several
diastereoisomers in solution.
Because the syntheses of ligands a and b were per-
formed by heating a chloroform solution of (R,S)-te-
trahydrofurfurylamine with 2-chlorobenzaldehyde or
3,4-dimethoxybenzaldehyde, as appropriate, the ligands
would in fact be equimolar mixtures of both enan-
tiomers and the cyclopalladated compounds 1a and 1b
would yield a mixture of three pairs of enantiomers (see
Fig. 2).
The NMR spectra of each pair of enantiomers are
identical, but obviously different from those of their
correspondent diastereoisomers. One set of signals is
expected for enantiomers I and II, and another set for
enantiomers III and IV; however, V and VI should give
two groups of resonances for the protons of each
In order to confirm this we synthesized the enantiop-
ure ligand c by reaction of (R)-tetrahydrofufurylamine
with 3,4-dimethoxybenzaldehyde. The 1H NMR spectra
Scheme 1. (i) Pd(AcO)2 (toluene or acetic acid); (ii) NaCl (acetone/water); (iii) PPh3 (acetone); (iv) AgCF3SO3 (acetone); (v) dppp, NaClO4 or
cis-dppe (acetone, 1:2 molar ratio); (vi) triphos (acetone 1:2 molar ratio); (vii) dppp (acetone, 1:1 molar ratio).

44
A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
Table 1
31P and 1H NMR
Compound
31P
Aromatic
Others
a
8.03[d, 1H, H6, 5.86 a]
7.3[m, 3H, H3, H4, H5]
8.71[s, 1H, Hi]
4.21[m, 1H, H8]
3.65[m, 4H, H7, H11
]
1.8[m, 4H, H9, H10
]
1a b
6.9[m, 6H, H3, H4, H5]
7.76, 7.73, 7.69, 7.64 [s, 2H, Hi]
4.30[m, 2H, H8]
3.75[m, 4H, H11
4.04[m, 2H, H7]
3.30[m, 2H, H7]
]
1.9[m, 8H, H9, H10
8.21[s, 2H, Hi]
]
2a
7.23[m, 2H, H3]
6.97[m, 4H, H4, H5]
4.41[m, 2H, H8]
3.46[m, 2H, H7]
3.85[m, 6H, H7, H11
1.93[m, 8H, H9, H10
]
]
3a
43.0s
6.82[d, 1H, H3, 7.3 a]
6.43[t, 1H, H4, 7.3 a]
6.25[dd, 1H, H5, 6.4 d]
8.62[d, 1H, Hi, 8.3 d]
4.60[m, 2H, H7, H8]
3.40[m, 1H, H7]
3.87[m, 2H, H11
]
1.90[m, 4H, H9, H10
]
4a
39.60s
6.93[dd, 1H, H3, 7.8 a, 0.98 c]
6.51[t, 1H, H4, 7.8 a]
8.62[d, 2H, Hi, 7.8 d]
4.40[m, 1H, H8]
6.23[m, 1H, H5, 5.9 d]
4.05, 3.90, 3.72 [m, 3H, H7, H11
3.36[m, 1H, H7]
]
]
2.3–1.7 [m, 4H, H9, H10
8.07[s, 1H, Hi]
]
5a e
6.98, 6.92 [m, 3H, H3, H4, H5]
4.40[m, 1H, H8]
4.05, 3.90, 3.80 [m, 3H, H7, H11
3.49[m, 1H, H7]
2.0 [m, 4H, H9, H10
]
6a
25.2d, −2.9d, 58.2 f
6.86[d, 1H, H3, 7.4 a]
6.40m[s, 1H, H4, H5]
8.74[d, 1H, Hi, 7.0 d]
4.50[m, 1H, H8]
3.7[m, 4H, H7, H11
]
1.90[m, 4H, H9, H10
8.37[s, 1H, Hi]
]
7a
8a
89.3t, 45.4d, 27.1 f
33.3s
6.91[d, 1H, H3, 7.8 a]
6.36[dd, 1H, H4, 7.8 a, 0.98 c]
5.76[t, 1H, H5, 7.8 d]
6.80[d, 1H, H3, 7.8 a]
6.46[t, 1H, H4, 7.8 a]
6.22[dd, 1H, H5, 5.9 d]
3.48, 3.24 [m, 5H, H8, H7, H11
]
8.52[d, 1H, Hi, 7.8 d]
4.47[m, 2H, H7, H8]
3.52[m, 1H, H7]
3.87[m, 2H, H11
]
2.10–1.70[m, 4H, H9, H10
8.10[s, 1H, Hi]
]
b, c
7.34[d, 1H, H2, 1.9 c]
7.06[dd, 1H, H5, 8.3 a]
7.76[d, 1H, H6]
4.20[m, 1H, H8]
3.65, 3.55 [m, 4H, H7, H11
]
1.9[m, 8H, H9, H10
3.83, 3.79[s, 6H, OMe]
]
1bb
2b
6.71, 6.69, 6.55, 6.53[s, 4H, H2, H5]
6.80, 6.89[2, 4H, H2, H5]
7.43, 7.42, 7.33, 7.29[s, 2H, Hi]
4.29[m, 2H, H8]
1.9[m, 8H, H9, H10
]
3.86, 3.79[s, 12H, OMe]
7.75[s, 2H, Hi]
4.38[m, 2H, H8]
3.46[m, 2H, H7]
3.80[m, 6H, H7, H11
1.92[m, 8H, H9, H10
]
]
3.92, 3.81[s, 12H, OMe]
3b
4b
27.0d, −2.0d, 56.0 f
7.0[s, 1H, H2]
8.24[d, 1H, Hi, 7.3d]
6.08[dd, 1H, H5, 6.3, 8.8 d]
1.9[m, 8H, H9, H10
]
3.81, 2.91 g [s, 6H, OMe]
8.32[d, 1H, Hi, 6.8 d]
4.30[m, 1H, H8]
63.5d, 51.0d, 10.2 f
7.13[s, 1H, H2]
6.36[dd, 1H, H5, 6.3, 8.7 d]
3.77, 2.12 g [s, 6H, OMe]
1.9[m, 8H, H9, H10
]

A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
45
Table 1 (Continued)
Compound
31P
33.2s
Aromatic
Others
5b
6.90[s, 1H, H2]
8.03[d, 1H, Hi, 7.8 d]
4.2[br, 1H, H8]
5.86[d, 1H, H5, 6.3 d]
1.9[m, 8H, H9, H10
]
3.78, 2.87 g [s, 6H, OMe]
7.44 7.30[s, 2H, Hi]
4.29[m, 2H, H8]
1c
6.71, 6.69, 6.55, 6.53[s, 4H, H2, H5]
1.9[m, 8H, H9, H10
]
3.87, 3.80[s, 12H, OMe]
31P NMR: in CDCl3 unless otherwise stated. Measured at 80.9 MHz (ca. 920 °C); chemical shifts (l) in ppm (90.1) to high frequency of
85% H3PO4. 1H NMR: in CDCl3. Measured at 200 MHz (ca. 920 °C); chemical shifts (l) in ppm (90.01) to high frequency of SiMe4.
Coupling constants in Hz. s, singlet; d, doublet; dd, doublet of doublets; t, triplet; m, multiplet; br, broad.
a 3JHH.
b l(CHacetate)=2.14, 2.11[s, 6H] (compound 1a); 2.14, 2.13[s, 6H] (compound 1b).
c 4JHH.
d JPH.
e l [(CH2)2CO]=2.5 br, ppm.
f JPP.
g C4–(OMe).
as compared to the free ligands. The FAB mass spectra
showed the peaks which were assigned to the [M]+ and
[M−Cl]+ fragments; a similar fragmentation of cy-
clometallated chloro-bridged complexes has been re-
ported [33].
of c was identical to the one recorded for b. The
cyclometallated acetato-bridged complex 1c was pre-
pared following an analogous procedure to that used
1
for 1b. The H NMR spectrum of 1c showed only two
resonances for the HCꢀN proton at l 7.44 and 7.30,
indicating the presence of only two distinct
diastereoisomers in solution (I and III).
Reaction of 2a with PPh3 in acetone gave the
mononuclear
cyclometallated
complex
[Pd{2-
The 13C–{1H} spectra of the complexes showed the
signals assigned to the C6, CꢀN, and C1 resonances
shifted to higher frequency confirming that metallation
had occurred [20]. The signals exhibited the splitting
due to the mixture of diastereoisomers (see Section 2).
Four signals were observed for the CꢀN carbon atom
due to the three pairs of enantiomers present in solu-
tion, as opposed to only two signals for the CꢀN
carbon in the spectrum of complex 1c.
ClC6H3C(H)ꢀNCH2(C4H7O)}(Cl)(PPh3)], 3a, in a typi-
1
cal bridge-splitting reaction. In the H NMR spectra
the HCꢀN and H5 resonances showed coupling to the
phosphorus nucleus [l 8.62 (JPH=8.3 Hz) and l 6.25
(JPH=6.4 Hz), respectively]; in the 31P–{1H} spec-
trum the resonance of the coordinated phosphine was a
singlet at l 43.0; these findings are in agreement with a
phosphorus trans to nitrogen arrangement [34–37]. The
FAB mass spectrum showed peaks centered at 627 and
590 amu for the [M]+ and [M−Cl]+ fragments,
respectively.
The mass FAB spectrum of 1a showed a cluster of
peaks, centered at 776 and 717 amu which correspond
to [M]+ and [M−AcO]+, respectively. The isotopic
pattern is in good agreement with the expected dinu-
clear structure.
Treatment of 3a with silver triflate gave the complex
[Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(PPh3)][CF3SO3]
(4a) after the removal of the AgCl precipitate formed.
1
The most noteworthy differences in the H NMR spec-
The reaction of 1a and 1b with aqueous sodium
chloride gave the chloro-bridged complexes [Pd{2-
ClC6H3C(H)ꢀNCH2(C4H7O)}(m-Cl)]2 (2a) and [Pd{3,4-
(MeO)2C6H2C(H)ꢀNCH2(C4H7O)}(m-Cl)]2 (2b), respec-
tively, which were fully characterized (see Table 1 and
Section 2). The IR spectra showed the absence of the
w(COO) bands. The 1H NMR spectra of 2a and 2b
showed the HCꢀN resonance at l 8.21 and l 7.75,
respectively. The aromatic proton resonances of 2a
were at l 7.23 (H3) and l 6.97 (H4, H5), as multiplets,
whereas two singlets were observed for the H2, H5
resonances at l 6.80 and 6.89, respectively, for com-
pound 2b. In the 13C–{1H} spectra the CꢀN, C1 and
C6 carbon resonances were shifted to higher frequency
trum of 4a as compared to 3a, were in the THF proton
resonances, although overlapping of these resonances
made an exact assignment difficult, especially in the
Fig. 1.

46
A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
Fig. 2.
splitting pattern shown by the H7, H8, and H11 protons.
Furthermore, the 13C–{1H} spectrum of 4a showed the
signal assigned to C8 at l 81.9, downfield shifted
consequent upon Pd–O bond formation (cf. l 78.6, a,
and l 77.5, 3a). Compound 4a is a 1:1 electrolyte, as
shown by molar conductivity measurements. The FAB-
mass spectrum showed a set of peaks centered at 592
amu for the [M−CF3SO3]+ fragment.
Pd–O bond formation could also be achieved by
reacting 2a with silver triflate in acetone which gave the
complex [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}((CH3)2-
CO)][CF3SO3] (5a) after AgCl removal. The IR spectra
supports the presence of the [CF3SO3]− anion, which
contains the characteristic stretching bands of the free
anion [38], approximately 1274, 1251, 1170 and 1031
cm−1. The 1H NMR spectrum showed the HCꢀN
resonance at l 8.07 and the signals corresponding to
the H2, H3 protons and H4 as multiplets at l 6.98 and
6.92, respectively. The splitting pattern and chemical
shift resonances for the THF ring are clearly different
from those observed in the spectrum of 2a. In the
13C–{1H} spectrum of 4a the C8 resonance appeared at
l 79.6, downfield shifted upon Pd–O bond formation.
Molar conductivity measurements were in agreement
with the ionic nature of the complex.
The 31P–{1H} NMR spectra only showed a singlet
resonance in accordance with the centrosymmetric na-
ture of this dinuclear complexes.
1
In the H NMR spectra of complex 5b, the C(4)–
OCH3 resonance was shifted towards lower frequency
by approximately 0.8 ppm, as compared complex 2b,
due to the shielding effects of the phosphine phenyl
ring, in agreement with a N–Pd–P trans geometry
[16,21,39]. This arrangement was confirmed by the cou-
pling of the HCꢀN and H5 proton resonances to the
phosphorus nucleus.
Reaction of complexes 2a and 2b with the diphosphi-
nes Ph2P(CH2)3Ph2, dppp, and Ph2PCHꢀCHPh2, cis-
dppe, in a 1:2 molar ratio gave the mononuclear
complexes [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}{Ph2P-
(CH2)3Ph2–P,P}][ClO4] (6a), [Pd{2-(MeO)2C6H3C(H)ꢀ
NCH2(C4H7O)}{Ph2P(CH2)3Ph2–P,P}][ClO4]
(3b)
and [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}(cis-Ph2PCHꢀ
CHPh2–P,P)][Cl] (4b) as air-stable solids which were
fully characterized (see Table 1 and Section 2).
The 31P–{1H} NMR spectra showed two doublets
for the two unequivalent phosphorus nuclei. The reso-
nance at lower frequency was assigned to the phospho-
rus nucleus trans to the phenyl carbon atom in
accordance with the higher trans influence of the latter
with respect to the CꢀN nitrogen atom [40]. The HCꢀN
resonance was only coupled to the 31P nucleus trans to
nitrogen. This was confirmed by selective decoupling
experiments on the 31P atoms. The H5 resonance
showed coupling to both phosphorus atoms. Measure-
ments of the specific molar conductivity have shown the
complexes to be 1:1 electrolytes.
Treatment of complexes 2a and 2b with
Ph2P(CH2)3PPh2, dppp, in a complex/phosphine 1:1
molar ratio gave the dinuclear cyclometallated com-
plexes
[{Pd[2-ClC6H3C(H)ꢀNCH2(C4H7O)](Cl)}2(m-
Ph2P(CH2)3PPh2)] (8a) and [{Pd[3,4-(MeO)2C6H2C(H)ꢀ
NCH2(C4H7O)](Cl)}2(m-Ph2P(CH2)3PPh2)] (5b) which
were fully characterized (see Section 2 and Table 1).

A. Ferna´ndez et al. / Polyhedron 21 (2002) 39–48
47
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Reaction of 2a with the triphosphine bis(2-
diphenylphosphinoethyl)phenylphosphine in 1:2 molar
ratio, followed by treatment with sodium perchlorate
gave [Pd{2-ClC6H3C(H)ꢀNCH2(C4H7O)}{(PPh2CH2-
CH2)2PPh–P,P,P}][ClO4] (7a). The phosphorus reso-
nances in the 31P–{1H} NMR spectrum were downfield
shifted from their values in the free phosphine suggest-
ing coordination of the three phosphorus atoms to the
metal centre. A triplet resonance at l 89.3 was assigned
to the central 31P nucleus, trans to the phenyl carbon
atom, and a doublet at l 45.4 was assigned to the two
equivalent mutually trans phosphorus nuclei. The latter
signal appeared at lower frequency in accordance with
the high trans influence of the phosphine ligand [11].
The resonance of the proton in the ortho position to the
metallated carbon appeared as a triplet showing cou-
pling to the central 31P atom [J(PH) 7.8 Hz]; no cou-
pling was observed to the terminal phosphorus nuclei.
These data are in accordance with a disposition in
which the metallated ring is nearly perpendicular to the
plane defined by the three phosphorus atoms; these
observations were confirmed by selective decoupling
experiments. The shift of the w(CꢀN) stretching vibra-
tion to lower wavenumbers [27,28] as well as the upfield
1
shift of the HCꢀN proton resonance in the H NMR
spectra [30] indicates the existence of palladium–nitro-
gen interaction in solution. These results strongly agree
with those previously obtained by us in related penta-
coordinated palladium(II) species, and hence we pro-
pose a similar disposition of the triphos ligand in this
case [15]. The CꢀN signal in the 13C–{1H} spectrum at
l 168.8 coupled to the central phosphorus (JPC=5.0
Hz) was also indicative of Pd–N interaction.
Molar conductivity measurements have shown that
complex 7a is a 1:1 electrolyte. The FAB mass spectrum
showed a set of peaks centered at 862 amu assigned to
the [M−ClO4]+ fragment.
[24] J.M. Vila, M.T. Pereira, A. Sua´rez, J.J. Ferna´ndez, J.M. Or-
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Acknowledgements
We thank the Ministerio de Educacio´n y Cultura
(Proyecto PB98-0638-C02-01/02), the Xunta de Galicia
(Proyecto PGIDT99PXI20907B) and the Universidad
de la Corun˜a for financial support.
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