Palladium (II) compounds containing mono- and bidentate primary ferrocenylamines. a study of the cyclopalladation of: [ (η5-C5H5)Fe{ (η5-C5H4)- (CH2)n-NH2}] (with n=1 or 2)

Article abstract of DOI:10.1016/S0277-5387(98)00276-9

The reactions of palladium (II) salts with the primary ferrocenylamines: [ (η⁵-C₅H₅)Fe{ (η⁵-C₅H₄)- (CH₂)_n-NH₂}] [with n=1 (1a) or 2 (1b)] are reported These substrates react with Na₂ [PdCl₄] in methanol at room temperature giving: [Pd{ (η⁵-C₅H₅)Fe [ (η⁵-C₅H₄)- (CH₂)_n-NH₂]}₂Cl₂] [with n=1 (2a) or 2 (2b)] with the ferrocenylamine acting as a monodentate N-donor ligand Howeverwhen compounds 1 are treated with Pd (CH₃COO)₂ in toluenefollowed by the addition of LiBr and the subsequent treatment of the solids formed with triphenylphosphinethe cyclopalladated complexes: [Pd{ (η⁵-C₅H₅)Fe [ (η⁵-C₅H₃)- (CH₂)_n-NH₂]}Br (PPh₃)] [with n=1 (3a) or 2 (3b)] were obtained NMR studies reveal that compounds 3 contain a five- (in 3a) or a six- (in 3b) membered metallacycle fused with the ferrocenyl unit

Full text of DOI:10.1016/S0277-5387(98)00276-9

\
Polyhedron 07 "0888# 024Ð032
PERGAMON
Palladium"II# compounds containing mono! and bidentate
primary ferrocenylamines[ a study of the cyclopalladation of]
ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł "with nꢀ0 or 1#
Ramon Bosque\ Concepcion Lopezꢂ
ꢁ
ꢁ
ꢁ
Departament de Quꢀ(mica Inorganica\ Facultat de Quꢀ(mica\ Universitat de Barcelona\ Martꢀ( Franques 0!00\ 97917 Barcelona\ Spain
Á
Á
Received 02 May 0887^ accepted 09 July 0887
Abstract
The reactions of palladium"II# salts with the primary ferrocenylamines] ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł ðwith nꢀ0 "0a# or
1 "0b#Ł are reported[ These substrates react with Na1ðPdCl3Ł in methanol at room temperature giving] ðPd""h4!C4H4#Feð"h4!C4H3#!
"CH1#n!NH1Ł#1Cl1Ł ðwith nꢀ0 "1a# or 1 "1b#Ł with the ferrocenylamine acting as a monodentate N!donor ligand[ However\ when
compounds 0 are treated with Pd"CH2COO#1 in toluene\ followed by the addition of LiBr and the subsequent treatment of the solids
formed with triphenylphosphine\ the cyclopalladated complexes] ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#n!NH1Ł#Br"PPh2#Ł ðwith nꢀ0 "2a#
or 1 "2b#Ł were obtained[ NMR studies reveal that compounds 2 contain a _ve! "in 2a# or a six! "in 2b# membered metallacycle fused
with the ferrocenyl unit[ Þ 0888 Elsevier Science Ltd[ All rights reserved[
Keywords] Cyclopalladation^ Palladacycles^ Ferrocenylamines^ Metallation
1
0[ Introduction
containing a s"PdÐCsp \ferrocene# bond described so far ð04Ð
25Ł and the prochiral nature of ferrocene derivatives ð26Ð
28Ł\ the number of articles dealing with cyclopalladated
One of the areas of organometallic chemistry that has
seen great advances during the last years is the area
involving cyclopalladated derivatives ð0Ð3Ł[ A wide var!
1
compounds containing a s"PdÐCsp \ferrocene# bond and fer!
rocenylamines are very scarce ð21Ð25Ł[ As far as we know\
only palladacycles derived from ð"h4!C4H4#Fe""h4!C4H3#!
C"R#H!N"CH2#1#Ł "with RꢀH\ CH2 or CF2# ðFig[ 0"D#Ł
ð21Ð25Ł have been prepared and characterized[ However\
cyclopalladated complexes derived from primary or sec!
ondary ferrocenylamines have not been reported[
Therefore\ we decided to study the reaction of the
primary ferrocenylamines] ð"h4!C4H4#Fe""h4!C4H3#!
"CH1#n!NH1#Ł ðwith nꢀ0 "0a# or 1 "0b#Ł ðFig[ 0"E#Ł vs
palladium"II# salts[
1
iety of palladacycles containing] s"PdÐCsp \aryl#\ s"PdÐ
2
1
Csp #\ or s"PdÐCsp \ferrocene# bonds have been described in
the literature[ Present interest in these compounds stems
for their multiple applications in several _elds[ For
instance\ it is well known that palladacycles are used
as precursors in the syntheses of new organic and:or
organometallic compounds ð4\5Ł and in the manufacture
dyestu} materials ð6Ł[ Some cyclopalladated compounds
have been also used in homogeneous catalysis ð7\8Ł[ In
addition\ metallomesogens ð09Ł and antitumoral drugs
ð00Ð02Ł containing cyclopalladated units have also been
described[ Optically active palladacycles derived from
amines "i[e[ substituted benzyl! or naphthyl!amines "Fig[
0"A#Ð"C## applied as auxiliar reagents for determining
enantiomeric excesses and even for resolving of racemic
mixtures of chiral phosphines arsines or amines have also
been reported ð03Ł[
1[ Results and discussion
1[0[ The ligands
The ferrocenylamines] ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!
NH1#Ł ðwith nꢀ0 "0a# or 1 "0b#Ł were prepared from N\N!
dimethylaminomethylferrocene following the sequences
of reactions described in the literature ð39Ð33Ł\ which are
summarized in Scheme 0[ In both synthetic methods\
the _rst step is to prepare the quaternary salt] ³"h4!
C4H4#Fe""h4!C4H3#!CH1!N"CH2#2#×I ³39\ 30×[ In
In spite of the range of cyclopalladated compounds
ꢂ Corresponding author[ Tel[] ¦23!8239!10163^ Fax] ¦23!8239!
6614^ E!mail] clopezÝkripto[qui[ub[es
9166!4276:88:, ! see front matter Þ 0888 Elsevier Science Ltd[ All rights reserved[
PII] S9166!4276 "87#99165!8

025
R[ Bosque\ C[ Lopez : Polyhedron 07 "0888# 024Ð032
ꢀ
Fig[ 0[ Schematic view of the primary and secondary amines used in cyclopalladation reactions "AÐC#\ derivatives of N\N!dimethylaminomethyl!
ferrocene "D# and the ferrocenylamines under study[
Scheme 0[ i# CH2I\ in methanol[ ii# NaN2\ in H1O[ iii# LiðAlH3Ł\ diethylether[ iv# NaCN\ in H1O[
order to isolate ligand 0a\ this salt was _rst transformed
into its azide derivative\ which was later reduced to the
corresponding ferrocenylamine ³31×[ For ligand 0b\
the quaternary salt was converted into the nitrile] ³"h4!
C4H4#Fe""h4!C4H3#!CH1!CN#× ³30\ 32× and its sub!
sequent reduction with LiðAlH3Ł in anhydrous diethy!
lether ³32\ 33× produced the desired ligand[ The two
ferrocenylamines were puri_ed by vacuum distillation\
which produced brownish oils[
1[1[ Palladium"II# compounds
In order to study whether palladium"II# salts could
1
induce the activation of the s"Csp \ferroceneÐH# bond in the

R[ Bosque\ C[ Lopez : Polyhedron 07 "0888# 024Ð032
026
ꢀ
ferrocenylamines 0a and 0b\ several strategies were used[
The _rst one involved the reaction of the ligands with
Na1ðPdCl3Ł "in a 0]0 molar ratio# in methanol at room
temperature[ In both synthetic methods\ pale ochre solids
formed when the solution mixed[ Characterization data
of these solids were as expected for the coordination
compounds] trans!ðPd""h4!C4H4#Feð"h4!C4H3#!"CH1#n!
NH1Ł#1Cl1Ł ðwith nꢀ0 "1a# or 1 "1b#Ł ðScheme 1\ equation
"A#×[ Compounds 1 were obtained in higher yields "61
and 57)# when the reaction was carried out using a
Pd]ligand molar ratio equal to 0]1[
compound was not detected by NMR[ This _nding di}ers
from the results obtained in the reaction of primary and
secondary benzylamines such as] C5H4!C"R#"R?#!
NH"Rý# "with RꢀR?ꢀPh and RýꢀH or Me^ RꢀH and
R?ꢀRýꢀMe or RꢀH\ R?ꢀMe and RýꢀCHMe1# or
the naphthylamine] C09H6!CH"Me#!NH"CHMe1# which
undergo orthopalladation of the aryl rings under ident!
ical experimental conditions "ligand]Na1ðPdCl3Ł in a 1]0
molar ratio in methanol at room temperature# ³34Ð
36×[
Although it is widely accepted that] "a# cyclo!
palladation of N!donor ligands proceeds in two steps] the
coordination of the nitrogen to the palladium followed by
Various reaction periods were used " from 0 h to 0 day#\
but evidence of the formation of any other palladium"II#
Scheme 1[ i# Na1ðPdCl3Ł\ methanol\ room temperature 2 h[ ii# Pd"AcO#1 in toluene\ 2 h[ iii# LiBr in ethanol at room temperature[ iv# PPh2 in benzene[
v# SiO1*column chromatography\ for ligand 0b\ small amounts "³4)# of compound ðPd""h4!C4H4#Feðh4!C4H2#!"CH1#1!NH1Ł#Br"PPh2#1Ł "3b# were
also isolated after the elution with a CHCl2 ] CH2OH "099 ] 4# mixture[

027
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ꢀ
the electrophilic attack to the s"CÐH# bond ð37Ð40Ł and
"b# ferrocene derivatives are more prone to undergo elec!
trophilic attacks than benzene ð12\14Ł^ the reaction of
ligands 0 with Na1ðPdCl3Ł does not produce the cyclo!
palladated compounds in contrast with the results
obtained for N!benzylamines with bulky substituents
ð34Ð36Ł[ Thus\ the reactivity of ligands 0 is more alike to
that of the less hindered benzylamines] R!C5H3!CH"R?#!
NH1 "with R?ꢀH or CH2# ð41Ð47Ł which do undergo the
activation of the ortho s"CÐH# bond in the presence of
Na1ðPdCl3Ł[
centration of the solution in a rotary evaporator followed
by an SiO1 column chromatography allowed us to isolate
di}erent sorts of palladium"II# compounds[ When the
reaction was carried out using ð"h4!C4H4#Fe""h4!C4H3#!
CH1!NH1#Ł "0a#\ elution with CHCl2 produced a yellow
band which contained ðPdBr1"PPh2#1Ł[ A second coloured
fraction was eluted with mixture CHCl2]CH2OH "099]0#[
Concentration to dryness of the solution in a rotary evap!
orator enabled the isolation of the cyclopalladated com!
pound] ðPd""h4!C4H4#Feð"h4!C4H2#!CH1!NH1Ł#Br"PPh2#Ł
"2a# in a 27) yield ðScheme 1\ equation "B#Ł[
In view of these results\ we decided to test whether the
general procedure described for the cyclopalladation of
most N!donor ferrocenyl ligands ð04Ð25Ł could also be
extended to the ferrocenylamines 0[ This method\ which
consists of the reaction of equimolar amounts of the
ligand ðhereinafter referred to as "HÐCÐN#Ł\ Na1ðPdCl3Ł
and Na"CH2COO#=2H1O in methanol at room tempera!
ture\ produces the di!m!chloro!bridged cyclopalladated
complexes] ðPd"CÐN#"m!Cl#Ł1[ However\ when the reac!
tion was carried out using the ferrocenylamines "0a or
0b# as starting materials and di}erent reaction periods
" from 2 to 13 h#\ only the coordination compounds]
trans ! ðPd""h4 ! C4H4#Feð"h4 ! C4H3# ! "CH1#n ! NH1Ł#1Cl1Ł
ðwith nꢀ0 "1a# or 1 "1b#Ł were formed in low yield "ca[
27)#[ Small amounts of starting materials were present
in the _ltrate but no evidence of the formation of any
other palladium"II# compound was detected by NMR
spectroscopy[
These _ndings di}er from the results obtained for the
tertiary amines] ð"h4!C4H4#Fe""h4!C4H3#!CH"R#!NMe1#Ł
ðwhere RꢀH "0c#\ CH2 "0d# or CF2 "0e#Ł for which cyclo!
palladation of the ferrocenyl fragment occurs\ giving]
ðPd""h4!C4H4#Feð"h4!C4H2#!CH"R#!NMe1Ł#"m!Cl#Ł1 in a
fairly good yield "79) for 0c\ 55) for 0d and 71) for
0e# ð21Ð23\25Ł[ In addition\ for amines 0c and 0d the
formation of] trans!ðPd""h4!C4H4#Feð"h4!C4H3#!CH"R#!
NMe1Ł#1Cl1Ł ðwith RꢀH "1c#\ Me "0d#Ł\ which are for!
mally analogous to compounds 1a and 1b\ could only be
formed when the reaction was carried out in the absence
of sodium acetate ð48Ł[
Similar results were obtained when the reaction was
carried out using the ferrocenylamine 0b[ Complex]
ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#1!NH1Ł#Br"PPh2#Ł "2b#
was isolated from the second band\ but in this case the
yield was even lower[ Unlike the results obtained for
ligand 0a\ an increase in the polarity of the eluant
"CHCl2]CH2OHꢀ099]4# allowed us to collect a narrow
additional band[ The concentration of this solution to
dryness in a rotary evaporator yielded a small amount
"³4)# of a pale orange solid[ Proton and 20P!NMR
studies of this material were consistent with those
expected for complex ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#1!
NH1Ł#Br"PPh2#1Ł "3b#\ in which the ferrocenylamine acts
as a monoanionic C!donor ligand[ Compound 3b arises
from 2b by cleavage of the PdÐN bond and the incor!
poration of a second phosphine into the coordination
sphere of the palladium[
The yields of the syntheses of compounds 2 are slightly
lower than those reported for primary and secondary
organic amines\ particularly for substituted benzylamines
"which fall in the range] 33Ð89)# ð34Ð36\41Ð45Ł[ In order
to try to improve the yields of these reactions\ di}erent
strategies were used[ For instance\ reaction times were
increased up to two days\ but no signi_cant di}erences
were found[ In order to test whether the yield of syntheses
could be increased thermically\ the reaction was carried
out in re~uxing toluene for 0 h[ However\ under these
conditions\ the starting materials decomposed and a mir!
ror of metallic palladium became visible[ Consequently\
the low yield of the reactions shown in Scheme 1ðequation
"B#Ł could be attributed to several factors\ among which
the instability of the ferrocenylamines and:or their highly
reductive nature may be important[ Electrochemical
studies have demonstrated that compounds 0 are more
prone to oxidize than ferrocene ðthe half!wave potentials
"referred to ferrocene# are −9[914 and −9[920 V for 0a
and 0b\ respectivelyŁ ð59Ł[ The instability of these two
ligands has been ascribed to this property since their
reductive character may be responsible for the formation
of metallic palladium in the course of the cyclo!
palladation process[ A similar argument has been used
to explain why cyclopalladation of the ferrocenylimines]
Recently\ some authors have reported that the acti!
vation of the s"CÐH# bonds in benzylamines] C5H4!CH1!
i
NHR "with RꢀH\ Me\ Pr\ CHEt1 or Ph#\ a!methyl!
benzylamines\ 1!phenylaniline or a!methylbenzylamine
can be achieved in fairly good yields " from 39 to 89)#\
using palladium"II# acetate as metallating agent and tolu!
ene as solvent ð41Ð45Ł[ On this basis\ we decided to test
whether this procedure could be extended to the fer!
rocenylamines
ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł
ðwith nꢀ0 "0a# or 1 "0b#Ł[ When ligands 0 were treated
with Pd"CH2COO#1 in toluene at room temperature for
08 h\ a deep brown solid formed[ Further reaction of
this material with LiBr in ethanol at room temperature
produced a highly insoluble brown solid\ which reacted
with PPh2 in benzene to give a redÐbrown solution[ Con!
ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#n!NꢀCHRŁ#Ł
"with
nꢀ0 or 1 and Rꢀaryl or ferrocenyl groups# also occurs
at low yield ð12Ð20Ł\ though these ferrocenylimines are a

R[ Bosque\ C[ Lopez : Polyhedron 07 "0888# 024Ð032
028
ꢀ
bit more resistant to oxidation than the amines "the half!
wave potentials for the imines with nꢀ0 and 1 range from
−9[979 to −9[919 V and from −9[919 to −9[939 V\
respectively ð59Ł#[ As far as we know compounds 2 are the
_rst examples of _ve " for 2a# and six! " for 2b# membered
palladacycles derived from primary ferrocenylamines[
group represents a bidentate ferrocenylimine\ oxime or
azineŁ which do not react with large excesses of PPh2 ð04Ð
25Ł[ This suggests that in compounds 2 the PdÐN bond
is more labile than in the palladacycles derived from
ferrocenylimines\ azines\ oximes or hydrazones[ These
results are consistent with previous studies on the reac!
tivity of cyclopalladated and cycloplatinated complexes\
which showed that\ depending on the nature of the met!
allacycle and the basicity of the nitrogen\ the PdÐN bond
can be cleaved ð51\52Ł[ In particular\ for palladacycles
derived from organic imines\ an increase in the basicity
enhances the reactivity of the PdÐN bond[ This argument
can also be used to explain the higher lability of the PdÐ
N bond in 2 and in their analogues] ðPd""h4!C4H4#Feð"h4!
C4H2#!C"R#ꢀN!R?Ł#Cl"PPh2#Ł "with RꢀH\ Me or Ph
and R?ꢀphenyl or benzyl groups#\ since imine nitrogen
is less basic than amine nitrogen[
1
The ortho!s"Csp \phenylÐH# bonds of benzylamines C5H3!
C"R#H!NH1 "RꢀH or Me# can be activated using an
alternative pathway ð46\ 47Ł which consists of "a# the
reaction of the coordination compounds] trans!
ðPd"C5H3!CH"R#!NH1#X1Ł "with XꢀCl or I# with sil!
ver"I# salts to give] ðPd"C5H3!CH"R#!NH1#"solvent#1Ł1¦
and "b# the subsequent electrophilic attack of the coor!
dinated palladium to the s"CÐH# bond^ however\ when
compounds 1 were treated with AgClO3 at room tem!
perature\ the formation of a metallic mirror was detected[
This can also be explained by the highly reductive nature
of the ferrocenylamines mentioned above[
The di}erence in the products obtained in the reactions
of 0 with Na1ðPdCl3Ł or Pd"CH2COO#1 can be interpreted
as due to the higher electrophilic character of the pal!
ladium"II# in the coordination complexes trans!ðPd""h4!
1[1[ Characterization
The compounds prepared for this study are pale!ochre
" for 1#\ reddish " for 2# or orange " for 3b# solids at room
temperature[ Compounds 2 are highly soluble in most
common solvents and practically insoluble in alkanes or
diethylether[ Elemental analyses of all the complexes are
consistent with the proposed formulae "see Section 2#[
The most relevant feature of the infrared spectra of 1 and
2 is the presence of a band in the range 2299Ð2049 cm−0
due to the stretching of the NÐH bond[ The IR spectra
of compounds 2 showed a band at ca[ 806 cm−0 which is
according to Rosenblum|s criteria ð53Ł\ characteristic of
0\1!disubstituted ferrocene derivatives[ This band was
not observed in the infrared spectra of the coordination
complexes 1[ Proton!NMR spectroscopic data for com!
pounds under study are summarized in Table 0[ The
resonances due to the ferrocenyl fragment appeared as
one singlet and two triplets of relative intensities 4]1]1 for
the free ligands 0 and compounds 1 and as four singlets
of relative intensities 4]0]0]0 for complexes 2 and 3\ which
C4H4#Feð"h4!C4H3#!"CH1#n!NH1Ł#1"CH2COO#1Ł
"with
nꢀ0 or 1# formed in the _rst step of the cyclopalladation
reaction\ which may ease the activation of the
1
s"Csp \ferroceneÐH# bond[
Finally\ it is worth noting that compounds 1 and 2 are
more stable than the free ligands\ since no signi_cant
variation in their colours or their NMR spectra was
detected after several weeks of storage[ This _nding is
consistent with the results obtained for related coor!
dination complexes such as] trans!ðPd""h4!C4H4#Feð"h4!
C4H3#!CH1N!"CH1#1!NMe1Ł#1Cl1Ł or trans!ðPd""h4!
C4H4#Feð"h4!C4H3#!CH1N!NMe1Ł#1Cl1Ł ð50Ł[ For these
complexes\ electrochemical studies\ based on cyclic vol!
tammetry\ revealed that the binding of the palladium to
the N!donor ligand causes an increase in the half!wave
potential\ so reducing the propensity of the Fe"II# to
oxidize ð59Ł[
1
In order to check the stability of the PdÐN bond in the
cyclopalladated complexes 2 an excess of PPh2 was added
to their CDCl2 solutions[ These experiments were per!
formed in an NMR!tube and studied by 20P!NMR spec!
troscopy[ When the experiment was carried out using
complexes 2a and 2b\ the spectrum showed a singlet "at
18[1 and 16[4 ppm\ respectively#[ It is worth noting that
the position and multiplicity of these signals were con!
sistent with the values expected for compounds ðPd""h4!
C4H4#Feð"h4!C4H2#!"CH1#n!NH1Ł#Br"PPh2#1Ł ðnꢀ0 "3a#
or 1 "3b#Ł in which the amine acts as a monodentate
anionic ligand bound to the palladium through the ortho!
C atom of the ferrocenyl fragment[ Compounds 3 arise
from the opening of the metallacycle and the coor!
dination of a second phosphine to the palladium"II#[ This
_nding di}ers from previous studies on _ve!membered
palladacycles ðPd"CÐN#Cl"PPh2#Ł ðwhere the "CÐN#
contain a s"PdÐCsp \ferrocene# bond[ The high_eld shift of
the signal due to the H2 proton in 2 is consistent with
the results reported for palladacycles with the general
formula] ðPd"CÐN#Cl"PPh2#Ł ðwhere the "CÐN# groups
represent a metallated ferrocenylimine\ oxime\ hydra!
zone\ azine or a tertiary ferrocenylamineŁ[ It has been
interpreted in terms of the ring current of the phenyl rings
of the PPh2 ligand in a cis!arrangement to the metallated
carbon atom ð12Ð20Ł[ For complex 2a the two protons of
the !NH1 group were diastereotopic and appeared as two
singlets in the region] 3[4Ð4[2 ppm\ but the 0H!NMR
spectra of 3\ which arose from a ring!opening process
involving the cleavage of the PdÐN bond\ showed broad
singlets in the area 4[0Ð4[4 ppm[
Phosphorus!20 NMR spectra of 2 showed a singlet at
27[8 ppm " for 2a# and at 25[4 ppm " for 2b#[ The position
of these signals were consistent with the values reported

039
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ꢀ
Table 0
Selected 0H!NMR data "in ppm# for the ferrocenylamines] ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł and for their palladium"II# com!
pounds 1\ 2 and 3 and 20P!NMR data "in ppm# for compounds] ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#n!NH1Ł#Br"PPh2#Ł ðwith nꢀ0 "2a#
and nꢀ1 "2b#Ł and ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#n!NH1Ł#Br"PPh2#1Ł ðwith nꢀ0 "3a# and nꢀ1 "3b#Ł[ Numbering of the atoms refers
to the schemes shown below
Proton!NMR
20P!NMR
others
C4H4
H1
H2
H3
H4
!CH1ÐN!a
!CH1!b
!NH1
d
20P
0a
0b
1a
1b
2a
3[99
3[09
3[03
3[09
2[81
3[09
3[04
3[19
3[21
−
3[95
3[98
3[90
3[97
2[18
3[95
3[98
3[90
3[97
3[07
3[09
3[04
3[19
3[21
3[16
2[45
2[59
2[59
2[54
2[61
3[99e
2[77
3[09e
2[29
2[39
−
1[59
−
1[57
−
3[61c
−
−
−
−
d
d
d
4[19
3[59
4[17
3[34f
4[15c
4[39c
6[29Ð6[79\ m "Ph#
27[8
25[4
2b
3[02
−
2[27
3[95
3[39
2[09
1[69
−
6[14Ð6[64\ m "Ph#
3a
3b
3[95
3[06
−
−
3[93
3[90
3[19
3[98
3[31
3[25
6[19Ð6[64\ m "Ph#
6[18Ð6[74\ m "Ph#
18[1
16[4
1[49
a The signal due to the protons of the !CH1ÐN moiety appears as a singlet in compounds 0a and 1a\ as a doublet of doublets in 2a\
as a triplet in 0b\ 1b and 3b and as two multiplets in 2b "centered at the values given#[
b The signal due to the protons of the !CH1! group in complex 2b appears as two multiplets[
c Broad signal[
d Not observed[
e Partially overlapped by the signals due to the protons of the C4H4 ring and the resonance of H3[
f Partially overlapped by the signals due to the resonance of H4[
for related _ve! and six!membered cyclopalladated com!
ðPd""C5H3!1!"C5H3#!NH1#Br"PPh2#Ł "4b#[ These two
compounds contain metallated primary amines and a
_ve! "in 4a# or a six! "in 4b# membered palladacycle[
Since the remaining ligands bound to the palladium in
compounds 2a\ 2b\ 4a and 4b are identical\ the di}erences
detected in the position of the signal observed in the 20P!
NMR spectra can be\ as a _rst approach\ indicative of
the e}ect of the chelate ligand in compounds ðPd"CÐ
N#Br"PPh2#Ł upon the phosphine group[ Such an e}ect
can be monitored through the coordination shift Dd of
the phosphine ligand]
1
plexes containing a s"PdÐCsp \aryl# bond or a s"PdÐ
1
Csp \ferrocene# bond in which the imine nitrogen and the
phosphine ligand are in a trans!arrangement ð12Ð20Ł[ For
compounds 3\ the spectrum showed a singlet in the range
16Ð29 ppm\ in good agreement with the results reported
for ðPd""h4!C4H4#Feð"h4!C4H2#!CH1!NMe1Ł#Cl"PPh2#1Ł
ð18Ł[
Quite recently\ Albert et al[ ð45Ł have described the
syntheses and NMR spectra of the cyclopalladated com!
plexes] ðPd"C5H3!CH"Me#!NH1#Br"PPh2#Ł "4a# and

R[ Bosque\ C[ Lopez : Polyhedron 07 "0888# 024Ð032
030
ꢀ
Ddꢁd"complex#−d"free PPh2#
2[0[ Materials and synthesis
Since d" free PPh2# is a constant value "−5[91 ppm in
CDCl2# the low_eld shift of the signal due to the PPh2 in
the complex is directly associated with an increase in the
coordination shift[ Comparison of the position of this
signal for compounds 2a "27[8 ppm#\ 2b "25[4 ppm#\ 4a
"30[6 ppm ð45Ł# and 4b "24[8 ppm ð45Ł#\ permit the chel!
ating ligands to be listed according to a decreasing order
of the coordination shifts Dd]
N\N!Dimethylaminomethylferrocene was obtained
from commercial sources and used as received[ The
amines] ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł ðwith
nꢀ0 "0a# or 1 "0b#Ł were prepared using the three!step
sequences previously described ð39Ð33Ł[ The synthesis of
0a requires the use and manipulation of large amounts of
highly hazardous materials "NaN2 and ð"h4!C4H4#Fe""h4!
C4H3#!CH1!N2#Ł# which may explode[ To prepare 0b\
KCN is needed[ Consequently the two ferrocenylamines
must be prepared with maximum caution[ The fer!
rocenylamines were puri_ed by vacuum distillation
before their use[ Due to the instability of the amines 0a
and 0b\ all the preparations described below require the
use of freshly prepared and puri_ed samples of these
ligands[ The preparations of compounds 2 require ben!
zene which should be handled with care[
4b³2b³2a³4a
This variation can be ascribed to two major e}ects] "a#
the di}erent basicity of the nitrogen in a trans!arrange!
ment to the PPh2 and:or "b# the electronic e}ects due to
distinct ring!current density in the metallated rings "C4H2
in 2a\ 2b or a phenyl in 4a or 4b#[ These two e}ects
regulate the abilities of the chelated ligands to donate
electrons[
2[0[0[ Preparation of trans!ðPd""h4!C4H4#Feð"h4!
C4H3#!"CH1#n!NH1Ł#1Cl1Ł ðwith nꢁ0 "1a# or 1
"1b#Ł
1[2[ Conclusions
To a solution containing 9[499 mmol of the cor!
responding ferrocenylamine " freshly prepared and pur!
i_ed# and 29 ml of methanol\ the stoichiometric amount
of Na1ðPdCl3Ł was added[ The resulting mixture was pro!
tected from the light with aluminium foil and stirred at
room temperature "ca[ 19>C# for 2 h[ The pale ochre
solids formed were collected by _ltration\ washed with
methanol "2 portions of ca[ 4 ml# and air!dried[ "Yields]
61 and 57) for 1a and 1b\ respectively[# Characterization
data for 1a] Anal[ ")# calcd for C11H15N1Cl1Fe1Pd
" found#] C\ 32[38 "32[4#^ H\ 3[17 "3[2# and N\ 3[15 "3[19#[
IR] n"NÐH#ꢀ2125 and 2155 cm−0[ 1b] Anal[ ")# calcd
for C13H29N1Cl1Fe1Pd " found#] C\ 34[24 "34[1#^ H\ 3[65
"3[7# and N\ 3[39 "3[3#[ IR] n"NÐH#ꢀ2139 and
The results reported in this paper show that the reac!
tion of the ferrocenylamines] ð"h4!C4H4#Fe""h4!C4H3#!
CH1N!"CH1#n!NH1#Ł "0# with palladium"II# salts pro!
duces "depending on the experimental conditions and on
the nature of the initial palladium complex# di}erent sorts
of compounds] trans!ðPd""h4!C4H4#Feð"h4!C4H3#!"CH1#n!
NH1Ł#1Cl1Ł "1# or ðPd""h4!C4H4#Feð"h4!C4H2#!"CH1#n!
NH1Ł#Br"PPh2#Ł "2#\ which di}er in the mode of coor!
dination of the amine ðwhich acts as an N!donor mon!
odentate in 1 or as a monoanionic "CÐN#− bidentate
group in 2Ł[ It is worth noting that compounds 2 are
the _rst examples of palladacycles derived from primary
ferrocenylamines containing a _ve ðfor "2a#Ł or a six!
membered ðfor "2b#Ł ring[ In addition\ the reaction of
compounds 2 with PPh2 in CDCl2 produces] ðPd""h4!
C4H4#Feð"h4!C4H2#!"CH1#n!NH1Ł#Br"PPh2#1Ł ðwith nꢀ0
"3a# or 1 "3b#Ł where the ferrocenyl amines act as a
monoanionic C!donor ligand[
2157 cm−0
[
2[0[1[ Preparation of ðPd""h4!C4H4#Feð"h4!C4H2#!
"CH1#n!NH1Ł#Br"PPh2#Ł ðwith nꢁ0 "2a# or 1
"2b#Ł
A suspension containing 9[499 mmol of Pd"CH2
COO#1\ 9[499 mmol of the corresponding fer!
2[ Experimental
rocenylamine
ð"h4!C4H4#Fe""h4!C4H3#!"CH1#n!NH1#Ł
ðwith nꢀ0 "0a# or 1 "0b#Ł and 49 ml of toluene was stirred
at room temperature for 07 h[ The resulting suspension
was concentrated to dryness in a rotary evaporator[ The
dark brown residue was suspended in 29 ml of ethanol
and treated with 9[499 mmol of LiBr[ The reaction mix!
ture was stirred at room temperature for 34 min[ Then
the undissolved materials were removed by _ltration and
discarded[ The brownÐred _ltrate was concentrated to
dryness in a rotary evaporator[ The residue formed was
dissolved in the minimum amount of benzene ca[ 49 ml
and treated with 9[4 mmol of triphenylphosphine[ The
resulting mixture was stirred at room temperature for 0 h
Elemental analyses "C\ H and N# were carried out at
the Serveis Cienti_co!Tecnics "Universitat de Barcelona#
Á
and at the Institut de Qu(mica Bio!Organica "C[S[I[C[#\
ꢁ
ꢁ
Barcelona[ Infrared spectra were recorded with a Nicolet
419!FTIR spectrophotometer using KBr pellets[ Proton!
NMR spectra were recorded with a Varian Gemini!
199 MHz instrument using CDCl2 "88[8)# as solvent and
Si"CH2#3 as internal standard[ Phosphorus!NMR spectra
were obtained with a Bruker!149DXR instrument using
CDCl2 as solvent and P"OCH2#2 as internal reference "d
20Pꢀ039[06 ppm#[

031
R[ Bosque\ C[ Lopez : Polyhedron 07 "0888# 024Ð032
ꢀ
Alvarez!Valdes A\ Martin A\ Raithby PR\ Masaguer JR\ Alonso
C[ Inorg[ Chem[ 0885^24]4070[
ð02Ł Navarro!Ranninger C\ Lopez!Solera I\ Masaguer JR\ Alonso C[
ꢁ
ꢁ
and then concentrated to dryness on a rotary evaporator[
The gummy materials formed were dissolved in the mini!
mum amount of chloroform and passed through a SiO1!
column "149×09 mm#[ After elution with CHCl2 a yellow
band which containing ðPdBr1"PPh2#1Ł could be collected[
The cyclopalladated complexes 2a and 2b were isolated
after elution with a CHCl2]CH2OH "099]0# mixture[ Con!
centration to dryness of the eluted solutions in a rotary
evaporator produced red solids\ which were collected and
air!dried[ "Yields] 27 and 23)\ respectively[# Charac!
terization data for 2a] Anal[ ")# calcd for C18H16N!
BrFePPd " found#] C\ 41[5 "41[7#^ H\ 3[09 "3[04# and N\
1[00 "1[9#[ IR] n"NÐH#ꢀ2104 and 2059 cm−0[ 2b] Anal[
")# calcd for C29H18NBrFePPd " found#] C\ 42[13 "42[3#^
H\ 3[20 "3[24# and N\ 1[96 "0[84#[ IR] n"NÐH#ꢀ2086 and
Appl[ Organomet[ Chem[ 0882^6]46[
ð03Ł Wild SB[ Coord[ Chem[ Rev[ 0886^055]180 and references therein[
ð04Ł Knox GR\ Pauson PL\ Willison D[ J[ Organomet[ Chem[
0882^349]066[
ð05Ł Butler IR[ Organometallics 0881^00]63[
ð06Ł Nonoyama M[ Inorg[ Nucl[ Chem[ Lett[ 0857^03]226[
ð07Ł Nonoyama M[ Inorg[ Nucl[ Chem[ Lett[ 0865^01]698[
ð08Ł Lopez C\ Bosque R\ Solans X\ Font!Bard(a M[ J[ Organomet[
ꢁ
ꢁ
Chem[ 0886^428]88[
ð19Ł Lopez C\ Granell J[ J[ Organomet[ Chem[ 0887^444]100[
ꢁ
ð10Ł Wu YJ\ Huo SQ\ Zhu Y[ J[ Organomet[ Chem[ 0884^374]050[
ð11Ł Huo SQ\ Wu YJ\ Du CX\ Zhu Y\ Yuan HZ\ Mao XA[ J[ Organ!
omet[ Chem[ 0883^372]028[
ð12Ł Lopez C\ Sales J\ Zquiak R\ Solans X[ J[ Chem[ Soc[\ Dalton
ꢁ
Trans[ 0881^1210[
2045 cm−0
[
ð13Ł Lopez C\ Bosque R\ Solans X\ Font!Bard(a M[ J[ Organomet[
ꢁ
ꢁ
Chem[ 0886^428]88[
ð14Ł Bosque R\ Lopez C\ Sales J\ Solans X\ Font!Bard(a M[ J[ Chem[
ꢁ
ꢁ
2[0[2[ Preparation of ðPd""h4!C4H4#Feð"h4!C4H2#!
"CH1#n!NH1Ł#Br"PPh2#1Ł ðwith nꢁ0 "3a# or 1
"3b#Ł
These compounds were prepared in an NMR tube
and characterized by NMR spectroscopy[ They were
Soc[\ Dalton Trans[ 0883^624[
ð15Ł Bosque R\ Font!Bard(a M\ Lopez C\ Sales J\ Silver J\ Solans X[ J[
ꢁ
ꢁ
Chem[ Soc[\ Dalton Trans[ 0883^636[
ð16Ł Bosque R\ Lopez C\ Sales J\ Solans X[ J[ Organomet[ Chem[
ꢁ
0883^372]50[
ð17Ł Lopez C\ Bosque R\ Solans X\ Font!Bard(a M[ J[ Organomet[
ꢁ
ꢁ
synthesised
as
follows]
triphenylphosphine
Chem[ 0886^424]88[
"3[9×09−1 mmol# was added to a solution containing
3[9×09−1 mmol of the corresponding complex 2 and
9[6 ml of CDCl2[ The resulting mixture was shaken vig!
orously for 4 min giving a pale orange solution[ Complex
3b could also be isolated as a by!product "³4)# in the
preparation of 2b and its NMR data were identical to
those obtained when its preparation was carried out in
an NMR tube[
ð18Ł Lopez C\ Bosque R\ Font!Bard(a M\ Solans X\ Silver J\ Fern G[
ꢁ
ꢁ
J[ Chem[ Soc[\ Dalton Trans[ 0884^3942[
ð29Ł Bosque R\ Lopez C\ Sales J[ J[ Organomet[ Chem[ 0884^387]036[
ꢁ
ð20Ł Lopez C\ Bosque R\ Solans X\ Font!Bard(a M[ J[ Chem[ Soc[
ꢁ
ꢁ
Dalton Trans[ 0883\ 2928[
ð21Ł Gaunt JG\ Shaw BL[ J[ Organomet[ Chem[ 0864^091]400[
ð22Ł Kotz JC\ Getty EE\ Lin L[ Organometallics 0874^3]509[
ð23Ł Lopez C\ Bosque R\ Solans X\ Font!Bardꢁ(a M[ Tetrahedron]
ꢁ
Asymm[ 0885^6]1416[
ð24Ł Lopez C\ Bosque R\ Sainz D\ Solans X\ Font!Bard(a M[ Organ!
ꢁ
ꢁ
ometallics 0886^05]2150[
ð25Ł Sokolov VI\ Trotiskaya LL\ Rozhkova TI[ Gazz[ Chim[ Ital[
0876^006]414[
Acknowledgements
ð26Ł Togni A[ Ferrocenes[ In] Hayashi\ editor[ Homogeneous catalysis\
organic synthesis\ materials sciences[ Weinheim\ Germany] VCH\
0884[
ð27Ł Sokolov VI[ Chirality and optical activity in organometallic com!
pounds[ New York] Gordon and Beach\ 0889[
ð28Ł Gmelin[ Handbuch der Anorganische Chemie\ Eisen Organische
Verbindunge\ Ferrocen\ Teil A0ÐA09[ Heidelberg\ Germany]
Springer\ 0863[
We are indebted to the Ministerio de Educacion and
ꢁ
to the Generalitat de Catalunya for _nancial support
"Grants No[ PB85!9053 and 0886!SRG!99063#[
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032
ꢀ
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