New organometallic palladium(II) complexes containing P∩N ligands - Synthesis, characterization and X-ray structure

Article abstract of DOI:10.1002/(sici)1099-0682(199811)1998:11<1811::aid-ejic1811>3.0.co;2-r

New neutral organometallic palladium(II) complexes, [PdPhI(PNMe₂)] (1), [PdPhI(PC=NMe)] (2), [PdPhI(PC=NEt)] (3), and [PdMeCl(PNMe₂)] (4), [PNMe₂ means N,N-dimethyl-2-(diphenylphosphanyl)aniline; PC=NMe means N-[2-(diphenylphosphanyl)benzylidene]-N-methylamine; PC=NEt means N-[2-(diphenylphosphanyl)benzylidene]-N-ethylamine} have been synthesized by oxidative addition of PhI to [Pd(dba)₂] in the presence of the P^∩N ligand (1-3), or by substitution reaction on [PdMeCl(COD)] with PNMe₂ (4). Cationic σ-organometallic species [PdR(PPh₃) (P^∩N)]⁺ are obtained upon treating complexes of the type [PdRX(P^∩N)] with PPh₃ and AgCF₃SO₃ and consist predominantly of the trans-P,P isomer in CDCl₃ solution, as shown by NMR spectroscopic studies. The cationic η³-allyl complex [Pd(η³-all)(PNMe₂)]PF₆ has also been prepared and characterized, both in solution and in the solid state. Compounds [PdPhI(PNMe₂)] (P2₁/n), [PdPhI(PC=NMe)] (P1?), [PdPhI(PC= NEt)] (P1?). and [Pd(η³-all)(PNMe₂)]PF₆ (P1?) have been authenticated by X-ray analysis.

Full text of DOI:10.1002/(sici)1099-0682(199811)1998:11<1811::aid-ejic1811>3.0.co;2-r

FULL PAPER
New Organometallic Palladium(II) Complexes Containing PʝN Ligands –
Synthesis, Characterization and X-ray Structure
Laura Crociania, Giuliano Bandolib[°], Alessandro Dolmellab, Marino Basato*c, and Benedetto Coraind[°°]
Istituto di Chimica e Tecnologia dei Materiali Avanzati, C. N. R.a,
C. so Stati Uniti, 4, I-35020 Padova, Italy
b
`
Dipartimento di Scienze Farmaceutiche, Universita di Padova ,
Via Marzolo 5, I-35131 Padova, Italy
Fax: (internat.) ϩ39 (0)49/8275345
E-mail: bandoli@pdfar3.dsfarm.unipd.it
c
`
Dipartimento di Chimica Inorganica, Metallorganica e Analitica, Universita di Padova ,
Via Marzolo 1, I-35131 Padova, Italy
Fax: (internat.)ϩ39 (0)49/8275223
E-mail: basato@chim02.unipd.it
Institut für Organische Chemie und Biochemied,
TU München, Lichtenbergstraße 4, D-85747 Garching, Germany
Received April 6, 1998
Keywords: Phosphanyl-amine / Phosphanyl-imine / Palladium / Organometallic complexes / Crystal structure
New neutral organometallic palladium(II) complexes,
[PdPhI(PNMe2)] (1), [PdPhI(PC=NMe)] (2), [PdPhI(PC=NEt)]
(3), and [PdMeCl(PNMe2)] (4), {PNMe2 means N,N-dimethyl-
2-(diphenylphosphanyl)aniline; PC=NMe means N-[2-(di-
obtained upon treating complexes of the type [PdRX(PʝN)]
with PPh3 and AgCF3SO3 and consist predominantly of the
trans-P,P isomer in CDCl3 solution, as shown by NMR
spectroscopic studies. The cationic η3-allyl complex [Pd(η3-
all)(PNMe2)]PF6 has also been prepared and characterized,
both in solution and in the solid state. Compounds
phenylphosphanyl)benzylidene]-N-methylamine;
PC=NEt
means N-[2-(diphenylphosphanyl)benzylidene]-N-ethylami-
ne} have been synthesized by oxidative addition of PhI to
[Pd(dba)2] in the presence of the PʝN ligand (1–3), or by
substitution reaction on [PdMeCl(COD)] with PNMe2 (4).
Cationic σ-organometallic species [PdR(PPh3)(PʝN)]+ are
¯
[PdPhI(PNMe2)] (P21/n), [PdPhI(PC=NMe)] (P1), [PdPhI(PC=
NEt)] (P1), and [Pd(η3-all)(PNMe2)]PF6 (P1) have been
¯
¯
authenticated by X-ray analysis
ene[7], and the telomerization of butadiene[8]), prompted us
to extend our investigations to this metal center[*].
Introduction
We have recently synthesized a number of nickel(II) com-
plexes featuring mixed soft-hard coordination spheres[1][2][3]
of the types {P2NCl2} and {P2NCl}. The ultimate aim of
this work was the evaluation of these species as potential
catalysts in the oligomerization of olefins (Shell Higher Ole-
fin Process, SHOP[4]). Although the catalytic results turned
out to be unsatisfactory, PʝN ligands of the type depicted
in Scheme 1 are expected to exhibit hemilabile behavior
when coordinated to a soft metal center such like pal-
ladium(II)[5]. This feature, coupled with the known ability
of palladium(II) complexes to promote catalytically a series
of important CϪC bond-forming reactions (such as the oli-
gomerization of olefins[6], copolymerization of CO/ethyl-
Scheme 1
The PʝN ligands employed in this work can be expected
to exhibit rather different coordinating behavior. While the
PNMe2 ligand clearly contains hard (N) and soft (P) donor
atoms and forms five-membered metal chelates[9], the imino
nitrogen in PCϭNR can be expected to possess appreciable
soft character (π-acceptor properties) and the ligands
clearly afford six-membered rings upon metal coordination.
In this context, it is remarkable that the coordinating ability
[°]
Corresponding author for crystallographic section.
[°°]
Humboldt Stipendiat Ϫ On leave of absence from Diparti-
mento di Chimica, Ingegneria Chimica e Materiali, Via Vetoio
Coppito Due, I-67010 LЈAquila, Italy, and from Centro di
Studio sulla Stabilita e Reattivita dei Composti di Coordina-
zione, CNR, c/o Dipartimento di Chimica Inorganica Metal-
[*] Preliminary catalytic results indicate that the new complexes re-
ported in this paper, [PdMe(PPh3)(PNMe2)]CF3SO3·C6H6, and
[Pd(η3-all)(PNMe2)]PF6, are efficient catalysts in the telomeri-
zation of butadiene with MeOH.
`
`
`
lorganica e Analitica, Universita di Padova, Via Marzolo 1, I-
35131 Padova, Italy.
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/1111Ϫ1811 $ 17.50ϩ.50/0
1811

L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain
FULL PAPER
of these imino ligands remains largely unexplored, with the [PdMeCl(COD)][18] (see Eq. 2) (COD ϭ 1,5 cyclooc-
exception of their behavior towards rhodium(I)[10] tadiene), similar to that employed with related PʝN li-
The importance of ligands based on a P,N set of donor gands[11]
.
.
atoms is well illustrated by other results obtained, e.g. by
Vrieze with 1-(dimethylamino)-8-(diphenylphosphanyl)-
r.t.
Ǟ
[PdMeCl(COD)] ϩ PNMe2 ᎏᎏᎏᎏᎏ
(2)
N2, C6H6, 24 h
naphthalene
phanyl)propane[11], and by Venanzi with 2-(2-pyridyl)-4,5-
dimethylphosphinine[12]
and
1-(dimethylamino)-3-(diphenylphos-
[PdMeCl(PNMe2)]·0.5 C6H4 ϩ COD
.
Some IR and NMR spectroscopic data of the complexes
[PdRX(PʝN)] and of the corresponding free ligands are re-
ported in Table 1.
Results and Discussion
The investigated PʝN ligands form neutral and cationic
η3-allyl and σ organometallic complexes, characterized as
(i) neutral complexes: [PdPhI(PNMe2)] (1), [PdPhI(PCϭ
NMe)] (2), [PdPhI(PCϭNEt)] (3), [PdMeCl(PNMe2)]·0.5
C6H6 (4), and (ii) cationic complexes: [PdMe(PPh3)-
(PNMe2)]CF3SO3 ·C6H6 (5), [PdPh(PPh3)(PNMe2)]CF3-
SO3 ·0.5 C6H6 (6), [PdPh(PPh3)(PCϭNMe)]CF3SO3 ·
0.5 C6H6 (7), [PdPh(PPh3)(PCϭNEt)]CF3SO3 ·0.5 C6H6
(8), [Pd(η3-all)(PNMe2)]PF6 (9), where PNMe2 means N,N-
dimethyl-2-(diphenylphosphanyl)aniline, PCϭNMe stands
for N-[2-(diphenylphosphanyl)benzylidene]-N-methylamine,
and PCϭNEt for N-[2-(diphenylphosphanyl)benzylidene]-
N-ethylamine.
While the phosphanylamine PNMe2 is well-known as a
ligand from the literature[9] and its reactivity with many me-
tal centers[1][2][3][[13], including palladium(II)[9], has been
widely investigated, only a few rhodium(I)[10], molyb-
denum(0)[14], and iridium(I)[15] complexes with PCϭNR
(R ϭ Me, Et) have been produced, and generally speaking,
the coordination chemistry of ligands of this type has yet
to be fully explored.
Direct evidence for the coordination modes of the ligands
PNMe2, PCϭNMe, PCϭNEt has been obtained from X-
ray analyses of complexes 1, 2, and 3 (see below). The coor-
dination of the PʝN ligands through both the P and N
atoms has also been deduced in solution on the basis of
NMR data, where the resonances of the 31P nucleus and of
the protons of the amino or imino alkyl groups are shifted
towards lower fields than the corresponding resonances of
the free ligand. NMR data also give useful information
about the composition of the reaction product mixtures in
CDCl3 solutions. In fact, both reactions 1 and 2 produce
only one isomer of complexes 2Ϫ4, while [PdPhI(PNMe2)]
(1) is obtained as a mixture of trans P,I and cis P,I isomers
in a 3:1 ratio (Table 1). IR data are less helpful in dis-
tinguishing the type of coordination; in fact, the typical Cϭ
N stretching bands (at 1637 cmϪ1) of the phosphanyl-im-
ines PCϭNMe and PCϭNEt in the spectra of 2 and 3 are
practically unchanged relative to those of the free ligands.
However, at the same time, coordination of the ligand
slightly affects the aromatic CϭC stretching values.
The available data are not helpful in unambiguously es-
tablishing the geometries of [PdPhI(PCϭNMe)] and
[PdPhI(PCϭNEt)], which are present as single isomers in
solution. As a matter of fact, upon crystallization, the trans-
P,I isomer is obtained. In contrast to these cases, the assign-
ment of the molecular structure as trans-P,Cl in solution is
possible for [PdMeCl(PNMe2)]·0.5 C6H6 by virtue of the
Synthesis and Characterization of the Neutral σ Organometallic
Complexes [PdRX(PʝN)]
Two routes have been followed for the synthesis of com-
plexes [PdPhI(PNMe2)] (1), [PdPhI(PCϭNMe)] (2),
[PdPhI(PCϭNEt)] (3), and [PdMeCl(PNMe2)]·0.5 C6H6
(4), depending on the type of organic group. The phenyl
complexes [PdPhI(PʝN)] were prepared by oxidative ad-
dition of iodobenzene to the palladium(0) complex
[Pd(dba)2][16] (dba ϭ dibenzylideneacetone) in the presence
3JPH coupling constant value[11]
.
Synthesis and Characterization of the Cationic Palladium(II)
Complexes
of the PʝN ligand (see Eq. 1)[17]
.
The cationic complexes of the type [PdR(PPh3)(PʝN)]ϩ
50°C, 45 minǞ
ʝ
[Pd(dba)2] ϩ PhI ϩ P N ᎏᎏᎏᎏᎏ
(1)
Ϫ
N2, THF
(with CF3SO3 as the counterion), [PdMe(PPh3)(PN-
Me2)]ϩ ·C6H6 (5), [PdPh(PPh3)(PNMe2)]ϩ ·0.5 C6H6 (6),
[PdPhI(PʝN)] ϩ 2 dba
[PdPh(PPh3)(PCϭNMe)]ϩ ·0.5
C6H6
(7),
[PdPh-
The complexes [PdPhI(PʝN)] were obtained as colored (PPh3)(PCϭNEt)]ϩ ·0.5 C6H6 (8), were synthesized by ad-
powders (yellow or pink-yellow) after filtration of the reac- ding an AgCF3SO3/PPh3 solution in Me2CO to a CH2Cl2
tion mixture through Celite to eliminate metallic Pd, con- solution of the corresponding neutral precursor
centration of the filtrate to dryness, and repeated washing [PdRX(PʝN)] at 0°C (see Eq. 3). Removal of the silver salt
with Et2O. No further recrystallization was necessary and by filtration and recrystallization of the product from
crystals suitable for X-ray analysis could be grown by slow CH2Cl2, C6H6, and Et2O afforded the pure products as
evaporation of the solvent from Me2CO/MeOH solutions.
white or off-white powders. Complexes 5؊8 are stable in
The methyl complex [PdMeCl(PNMe2)]·0.5C6H6 (4) was the solid state, but they tend to decompose slowly in solu-
prepared by a substitution reaction on the complex tion (over a period of days).
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Eur. J. Inorg. Chem. 1998, 1811Ϫ1820

New Organometallic Palladium(II) Complexes Containing PʝN Ligands
Table 1. Selected IR and NMR absorptions of complexes [PdRX(PʝN)] and of the corresponding free ligands
FULL PAPER
ν[a] (cmϪ1
)
δ[b] (ppm), J (Hz)
CϭC
CϭN
CH2
CH3
Harom
HCϭN
31P{1H}
Complex 1 1574
3.40 (s)[c], 3.66 (s)
6.63Ϫ6.72 (m),
6.88Ϫ6.99 (m),
7.22Ϫ7.89 (m)
6.50Ϫ7.50 (m)
6.38Ϫ6.68 (m),
7.04Ϫ7.68 (m)
6.80Ϫ6.97 (m),
7.13Ϫ7.48 (m),
7.89Ϫ8.05 (m)
6.40Ϫ6.68 (m),
6.99Ϫ7.70 (m)
6.75Ϫ6.95 (m),
7.13Ϫ7.56 (m),
7.91Ϫ8.03 (m)
24.3(s)[c],
37.3 (s)
PNMe2
1570
2.58 (s)
4.00 (s)
Ϫ16.2 (s)
23.6 (s)
Complex 2 1562
1637
1640
8.00 (bs)
PCϭNMe 1582
3.38 (d) 3JHH ϭ 1.8
8.85Ϫ8.95 (m) Ϫ14.0 (s)
4JPH ϭ 4.8
Complex 3 1561
PCϭNEt 1583
1637
1637
4.42 (q) 3JHH ϭ
7.3
1.22 (t) 3JHH ϭ 7.3
1.10 (t) 3JHH ϭ 4.4
8.00 (bs)
21.6 (s)
3.49 (qd) 4JHH ϭ
1.5, 3JHH ϭ 4.4
8.84Ϫ8.93 (m) Ϫ13.3 (s)
4JPH ϭ 4.8
Complex 4 1583
0.78 (d, PdϪCH3) 3JHP ϭ 2.9; 7.13Ϫ7.81 (m)
3.15 [s, N(CH3)2]
35.6 (s)
[a]
[b]
[c]
In KBr: CϭC refers to the aromatic CϭC stretching, while CϭN refers to the CϭN stretching. Ϫ
In CDCl3. Ϫ More abun-
dant isomer.
0°C, 45 min Ǟ
In the 31P{1H} spectrum of complex 6 (Figure 2), the AB
system (2JPP ϭ 372 Hz) is associated with the trans species,
while the AX system (2JPP ϭ 24 Hz) is associated with the
cis species.
[PdRX(PʝN)] ϩ AgCF3SO3 ϩ PPh3 ᎏᎏᎏᎏᎏ
(3)
CH2Cl2, Me2CO
[PdR(PPh3)(PʝN)]CF3SO3 ϩ AgX
The more stable allyl complex [Pd(η3-all)(PNMe2)]PF6
Figure 2. 31P{1H}-NMR spectrum of the mixture of isomers of
(9) was obtained as a cream-coloured powder following a
[19]
different synthetic procedure, employing [Pd(η3-all)Cl]2
,
complex 6
two equivalents of the ligand PNMe2, and a large excess of
KPF6 (see Eq. 4).
r.t.
[Pd(η3-all)Cl]2 ϩ PNMe2 ϩ 2 KPF6 ᎏᎏᎏᎏᎏ
(4)
Ǟ
CH2Cl2, 3 h
2 [Pd(η3-all)(PNMe3)]PF6 ϩ 2 KCl
All the cationic complexes have been characterized by
means of the usual physicochemical techniques. Molar con-
ductivity values of 152 ohmϪ1cm2molϪ1 (see Experimental
Section) confirm that they are uni-univalent electrolytes[20]
Ϫ
Ϫ
and the presence of the anions CF3SO3 and PF 6 is con-
firmed by very sharp, intense bands in their solid-state IR
spectra at 1265 cmϪ1 [ν(SϪO)] and 834 cmϪ1 [ν(PϪF)],
respectively[21]
.
In the case of complexes [PdR(PPh3)(PʝN)]ϩ, the pres-
ence of two nonequivalent 31P nuclei and the value of their
coupling constants[22] (Table 2) permits the assignment of
On the basis of these findings, and the values reported in
their molecular structures in CDCl3 solution. This is fortu- Table 2, it can be stated that the phosphanyl-imino com-
nate, since no crystal structure could be determined. Thus, plexes 7 and 8 exhibit only the trans configuration.
the 31P{1H} spectrum of [PdPh(PPh3)(PNMe2)]ϩ is very in-
The methyl σ organometallic cationic complex [PdMe-
1
formative and the complex is found to consist of a mixture (PPh3)(PNMe2)]ϩ (5) gives rise to an interesting H-NMR
of isomers (Figure 1), the trans isomer being prevalent spectrum, which indicates the presence of the two expected
(82%) (the terms cis and trans refer here to the mutual P po- isomers; while the cis species is stereochemically rigid at
sitions).
room temperature [the signal of the methyl group bound to
palladium(II) of this isomer appears as a doublet of dou-
blets at δ ϭ 0.67 with JHP ϭ 2.2 and 6.6 Hz] (Figure 3a),
Figure 1. The trans and cis isomers of complex 6
3
the trans species is stereochemically nonrigid. Broad signals
at δ ϭ 0.53 (Figure 3a) and δ ϭ 2.87 can be attributed to
the protons of the methyl group bound to palladium(II)
and of the methyl groups of the dimethylamino ligand,
respectively. This isomer is the prevalent species, as deduced
from integration of the signals. In the 31P{1H} spectrum,
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820
1813

L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain
Table 2. NMR absorptions of the palladium(II) cationic complexes
FULL PAPER
δ (ppm)[a], J (Hz)
CH
Complex CH2
CH3
Harom
31P{1H}
5
0.53 (bs, PdϪCH3 trans), 0.67 6.90Ϫ7.97 (m)
(dd, PdϪCH3 cis) 3JHP ϭ 2.2,
6.6; 2.87 [bs, N(CH3)2 trans];
3.25 [s, N(CH3)2 cis]
23.8 (d, cis) 2JPP ϭ 26,
40.1 (d, cis) 2JPP ϭ 26
6
7
2.76 (bs), 2.94 (s)
6.16Ϫ6.67 (m),
6.91Ϫ7.97 (m)
18.4 (d, trans) 2JPP ϭ 372,
24.4 (d, trans) 2JPP ϭ 372;
20.5 (d, cis) 2JPP ϭ 24,
27.7 (d, cis) 2JPP ϭ 24
2.87 (s)
6.30Ϫ6.49 (m),
6.65Ϫ6.79 (m),
6.88Ϫ8.05 (m)
6.32Ϫ6.53 (m),
6.69Ϫ6.80 (m),
7.00Ϫ7.92 (m)
6.40Ϫ6.68 (m),
6.99Ϫ7.70 (m)
8.21 (bs)
8.33 (bs)
20.1 (d, trans) 2JPP ϭ 376,
21.6 (d, trans) 2JPP ϭ 376
8
9
3.03 (q)
0.54 (t) 3JHH ϭ 7.3
3.45 (s)
17.8 (d, trans) 2JPP ϭ 389,
22.2 (d, trans) 2JPP ϭ 389
3JHH ϭ 7.3
2.90Ϫ3.80 (m, H3,,H3Ј)[b]
,
Ϫ141[c] (sept, JPF ϭ 708)
33.6 (s)
4.17 (dd, H1) 3JHP ϭ 9.5,
3JHH ϭ 13.9, 4.95 (dd, H1Ј)
3JHP ϭ 5.3, 3JHH ϭ 7.7,
5.80Ϫ6.15 (m, H2)
[a] In CDCl3. Ϫ [b] H1ЈH1C1C2H2C3H3ЈH3, where C1 is trans to P. Ϫ [c] In CD3CN.
Figure 3. (a) 1H-NMR signals of the methyl groups bound to palla- group bound to palladium(II) (Figure 3b) becomes a triplet
1
3
dium(II) of the mixture of isomers of complex 5 at 25°C; (b) H-
at δ ϭ 0.30 with JHP ϭ 6.5 Hz, this value being of the
NMR signals of the methyl groups bound to palladium(II) of the
same order as the corresponding value of 5 Hz observed in
the H-NMR spectrum of trans-[PdMeI(PPh3)2][23]
mixture of isomers of complex 5 at Ϫ20°C
1
.
We speculate that at low temperature (Ϫ20°C) the trans
species is undissociated. When the temperature is increased,
a fast dissociation process takes place so that the triplet,
arising from the coupling of the protons of the methyl
bound to palladium(II) with the two 31P nuclei, merges into
one very broad singlet. Considering the high trans effect of
the phosphane group and the stabilization of the PʝN li-
gand due to the chelate effect, we postulate that this dis-
sociation process involves the PPh3 ligand, leading to a T-
shaped intermediate (Figure 4).
Figure 4. Dissociation of the PPh3 group and formation of a T-
shaped intermediate in the case of trans-[PdMe(PPh3)(PNMe2)]ϩ
The complex [Pd(η3-all)(PNMe2)]PF6 is also stereochem-
ically nonrigid in CDCl3 as a consequence of a selective
syn-anti interchange of the allyl protons trans to the NMe2
group through the usual η3Ϫη1Ϫη3 interconversion process
(Scheme 2).
This fluxional phenomenon has been observed pre-
viously[24]. The PPh2 group weakens the trans PdϪCH2
bond, thus promoting the opening of the allyl ring and, by
only the cis isomer gives rise to well-defined, sharp signals rotation about the σ bonds, the interchange of the syn-anti
(2JPP ϭ 26 Hz).
Lowering of the temperature blocks the stereochemical
H3 and H3Ј protons.
The relevant signal is not discernible in the 1H-NMR
nonrigidity of the trans species and at Ϫ20°C the AB sys- spectrum owing to its partial overlap with that of the
tem of the stereoisomer eventually appears (δ ϭ 27.0 and N(CH3)2 group (Figure 5) and only a broad absorption can
2
δ ϭ 31.7 with JPP ϭ 375 Hz). The signal of the methyl be observed. On the contrary, the signals of the other three
1814
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820

New Organometallic Palladium(II) Complexes Containing PʝN Ligands
Scheme 2
FULL PAPER
protons (Figure 6) are well defined: the multiplet between
δ ϭ 5.80 and δ ϭ 6.15 is due to the central allyl proton H2,
while the two doublets of doublets at δ ϭ 4.95 (3JHH ϭ 7.7
Figure 6. Signals of protons H1, H1Ј, and H2 in the 1H-NMR spec-
trum of complex 9 in CDCl3
3
Hz and JHP ϭ 5.3 Hz) and at δ ϭ 4.17 (3JHH ϭ 13.9 Hz
3
and JHP ϭ 9.5 Hz) can be assigned to H1 (anti in relation
to H2) and H1Ј (syn in relation to H2), respectively, on the
basis of the magnitudes of the coupling constants[25]
.
Figure 5. Overlapping of the signals of the protons of the N(CH3)2
group and of the protons H3 and H3Ј in the 1H-NMR spectrum of
complex 9 in CDCl3
X-ray Structure
The unique portion of the unit cells is different in com-
pounds 1, 2, 3·3/2 H2O, and 9. In 1, the asymmetric unit
consists of a single molecule of the neutral complex
[PdPhI(PNMe2)] (Figure 7), while two molecules of
[PdPhI(PCϭNMe)] are present in 2 (Figure 8). In 3·3/2
H2O, the unique portion comprises two molecules of
[PdPhI(PCϭNEt)], along with three molecules of water
(Figure 9), and in 9 two molecules of the salt [Pd(η3-
C3H5)(PNMe2)]PF6 are likewise present (Figure 10). In 2,
3·3/2 H2O, and 9, the geometries shown by the two such
independent and chemically well-separated molecules are
practically superimposable (Figure 11), the differences be-
ing restricted to minor features only. This is also confirmed
by the fact that no bond distance differs by more than two
standard deviations in any of these molecule pairs. Hence,
in the present discussion, all geometrical parameters refer
to the mean values.
Figure 7. Molecular structure of 1. H atoms have been omitted for
clarity. Thermal ellipsoids are shown at the 40% probability level
In 1 and 9, the bidentate PʝN ligand coordinates to pal-
ladium(II) forming a five-membered chelate ring, which ad-
opts a somewhat envelope-like (Cs) conformation (pertinent
torsion angles in the range from Ϫ16.1° to ϩ16.1°). The
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820
1815

L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain
Figure 8. The asymmetric unit of 2. H atoms have been omitted for clarity. Thermal ellipsoids are shown at the 40% probability level
FULL PAPER
Figure 9. The asymmetric unit of 3·3/2 H2O. H atoms have been omitted for clarity. The C(9Ј) atom obscures N(1Ј).
Figure 10. The asymmetric unit of 9. H atoms have been omitted for clarity
1816
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820

New Organometallic Palladium(II) Complexes Containing PʝN Ligands
FULL PAPER
Figure 11. Superimposition of the two independent moieties of 2, roughly orthogonal to the mean coordination plane (di-
3·3/2 H2O, and 9. Weighted root mean square deviation of 0.02,
hedral angle of 82.1°).
˚
0.05, and 0.03 A, respectively, when fitting is performed on the
In 2 and 3·3/2 H2O, the PʝN ligand forms a six-mem-
bered chelate ring with the palladium(II) center. In this ar-
labelled atoms
˚
rangement, the Pd and N(1) atoms in 2 deviate by ϩ1.56 A
˚
and ϩ0.49 A from the mean plane defined by the eight
atoms P(1), C(1)Ϫ(7). The corresponding values in 3·3/2
˚
H2O are ϩ1.41 and ϩ0.32 A. The latter plane forms di-
hedral angles (“elbow angles”) of 55.8° and 53.9° with the
coordination plane in 2 and 3·3/2 H2O, respectively. In
turn, the Ph ligand forms a dihedral angle with the coordi-
nation plane of 72.0° (in 2) and of 75.3° (in 3·3/2 H2O).
The “bite” distances and angles match those found in 1 and
˚
˚
9 [2.95(1) A, 84.0(2)° in 2 and 3.00(1) A, 85.8(2)° in 3·3/
2 H2O].
The donor atoms deviate from the mean coordination
˚
˚
˚
plane by ±0.04 A in 1, ±0.07 A in 2, ±0.04 A in 3·3/2 H2O,
˚
and ±0.06 A in 9, with the palladium(II) correspondingly
out by 0.02, 0.02, 0.04, and 0.09 A. In all the complexes,
˚
the major departure from the ideal square-planar geometry
is manifested in the “bite” angle. From comparison of the
distances with reference values obtained from the Cam-
bridge Structural Database[26], the following comments can
II
˚
be made: (i) The Pd ϪI distance (mean 2.654 A) is consist-
˚
ent with both the reference value (2.639 A) derived from
164 observations and the sum of the covalent radii (1.33
ϩ 1.31 A)[27]; (ii) the PdIIϪP distance in the three neutral
˚
˚
complexes (mean 2.228 A), which is slightly shorter than
˚
that in the allyl cationic complex (2.260 A), is remarkably
II
˚
shorter than the Pd ϪPPh3 bond reference value (2.302 A)
encountered in 248 entries, and falls at the short end of a
II
˚
wide range (2.21Ϫ2.46 A); (iii) the Pd ϪCPh distance
˚
˚
(mean 2.015 A) matches the reference value (2.013 A) de-
rived from 34 observations, and (iv) the PdIIϪN distance in
1 (2.252 A) is considerably longer than the corresponding
distances in 2 and 3·3/2 H2O (mean 2.17 A), which may
˚
˚
be ascribed to the different environment of the nitrogen.
Accordingly, on going from a five- to a six-membered che-
late ring, the PdϪN(sp3)ϪC angle (113.6°) widens to the
mean value of 125.5° observed for PdϪN(sp2)ϭC.
The packing observed for the four complexes does not
show intermolecular contacts shorter than the sum of the
van der WaalsЈ radii, the shortest IϪH approach being 3.1
˚
A. The opportunity for hydrogen bonding seems to be re-
stricted to that between the water molecules of 3·3/2 H2O,
˚
which show OϪO separations of 2.8 A.
coordination sphere of 1 is completed by an iodide and a
phenyl ligand, whereas the remaining coordination posi-
tions in 9 are occupied by the η3-allyl ligand. In the latter
compound, the coordination plane can be defined by the
Conclusions
The phosphanyl-amine PNMe2 and the phosphanyl-im-
P,N donor atoms and by the terminal carbon atoms of the ines PCϭNMe and PCϭNEt are able to stabilize or-
˚
allyl group, the central carbon atom residing 0.50 A above ganometallic neutral and cationic palladium(II) complexes,
this plane. The mean plane defined by the eight atoms P(1), acting as chelating bidentate ligands via their P and N do-
C(1)Ϫ(6), N(1) forms dihedral angles of 5.4° and 5.1° with nor atoms, forming five- or six-membered rings with the
the mean coordination plane in 1 and 9, respectively. The metal center in the expected manner.
The neutral complexes [PdRX(PʝN)] are stable species,
˚
PϪN “bite” distance and the PϪPdϪN angle are 3.00(1) A
and 85.1(3)° in both complexes. The Ph ligand in 1 is both in solution and in the solid state. The phenyl com-
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820
1817

L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain
FULL PAPER
plexes [PdPhI(PʝN)] and [PdMeCl(PNMe2)] exist as the
trans-P,I isomer in the solid state, as indicated by X-ray
analysis, as well as trans-P,Cl isomer in solution, as deduced
under N2. After 15 min, a white solid began to precipitate. After
24 h, the pale-yellow mixture was filtered and the white solid was
collected, washed with C6H6 and Et2O, and dried in vacuo. The
filtrate was concentrated under a flow of N2 and upon addition of
Et2O a precipitate was formed. This was filtered off, washed with
Et2O and a small volume of THF, and dried in vacuo.
1
from the H-NMR spectrum in CDCl3.
The σ organometallic cationic complexes [PdR(PPh3)-
(PʝN)]ϩ can be obtained by the reaction of the neutral pre-
cursor with PPh3 and AgCF3SO3 and exist in solution
mainly as trans-P,P species. In particular, a fluxional be-
havior is observed for trans-[PdMe(PPh3)(PNMe2)]ϩ, prob-
ably due to the dissociation of a PPh3 molecule. The η3-
allyl complex [Pd(η3-all)(PNMe2)]PF6, obtained from the
dimer [Pd(η3-all)Cl]2 and a stoichiometric amount of
PNMe2 in the presence of excess KPF6, also exhibits
fluxional behavior in CDCl3 solution, owing to the selective
interchange of the protons of the CH2 group trans to the
phosphorus of the diphenylphosphanyl group.
Comparison of the crystal structure of [Pd(η3-
all)(PNMe2)]PF6 with those of the neutral complexes con-
taining the phosphanyl-imines PCϭNMe and PCϭNEt re-
veals moderate differences relating to the size of the chelate
ring in terms of bond lengths and the “bite” angle
PϪPdϪN.
Synthesis of 5Ϫ8 Ϫ General Procedure: To a solution of the neu-
tral complex [PdRX(PʝN)] (0.41 mmol) in 5 ml of CH2Cl2 at 0°C
under N2, a solution containing 0.108 g of PPh3 (0.41 mmol) and
0.106 g of AgCF3SO3 (0.41 mmol) in 3 ml of Me2CO was added
dropwise, resulting in immediate silver halide precipitation. After
45 min., the mixture was concentrated under a flow of N2 and
filtered, and the solvent was removed from the filtrate in vacuo.
The residue was redissolved in CH2Cl2 and upon addition of Et2O
a precipitate was deposited, which was separated from the solution
by decantation of the supernatant and redissolved in a small
amount of CH2Cl2. Addition of C6H6 and Et2O under vigorous
stirring caused the formation of a solid, which was filtered off,
washed with C6H6 and Et2O, and dried in vacuo.
Synthesis of 9: To a solution of 0.130 g of [Pd(η3-all)Cl]2 (0.36
mmol) in 10 ml of CH2Cl2 was added 0.265 g of KPF6 (1.44 mmol)
followed by 0.282 g of the ligand PNMe2 (0.40 mmol), and the
yellow mixture was stirred at room temperature. After 3 h, the col-
orless mixture was filtered and the filtrate was concentrated under
reduced pressure. Addition of Et2O caused the formation of a white
precipitate, which was filtered off, washed with Et2O, and dried in
vacuo. The solid was recrystallized from MeCN and Et2O and
dried in vacuo. Crystals suitable for X-ray analysis were grown
by slow evaporation of the solvent from CH2Cl2/EtOH/Et2O
solutions.
This work was partially supported by Progetto Strategico “Tec-
nologie Chimiche Innovative”, Consiglio Nazionale delle Ricerche.
Benedetto Corain is grateful to the Alexander von Humboldt Foun-
dation for supporting his activities at the TU München.
Experimental Section
[ PdPhI( PNMe ) ] (1): Yield 0.574 g (85%). Ϫ IR (KBr): ν ϭ
˜
2
3055 m cmϪ1, 1574 m, 1469 s, 1433 s, 743 vs, 691 s, 500 vs. Ϫ
General: All chemicals and solvents were of analytical grade and
were used as received unless otherwise stated. Anhydrous Et2O and
C6H6 were distilled from potassium/benzophenone under N2; anhy-
drous THF was freshly distilled from potassium/benzophenone un-
C
26H25INPPd (615.79): calcd. C 50.71, H 4.10, N 2.28; found C
49.03, H 4.03, N 2.02.
[ PdPhI( PCϭNMe) ] (2): Yield: 0.637 g (94%). Ϫ IR (KBr): ν˜ ϭ
3050 m cmϪ1, 1637 m (CϭN), 1562 m, 1478 m, 1434 s, 739 s, 688
s. Ϫ C26H23INPPd (613.79): calcd. C 50.88, H 3.78, N 2.28; found
C 50.73, H 4.01, N 2.13.
der N2. The complexes [Pd(dba)2][16], [PdMeCl(COD)][18], [Pd(η3-
[19]
all)Cl]2
and the ligands PNMe2[9], PCϭNR (R ϭ Me, Et)[10]
were synthesized according to literature procedures. Ϫ IR: Mattson
3030 Fourier transform spectrometer. Ϫ 1H and 31P{1H} NMR:
Bruker AC-200 (200 MHz for 1H and 80.9 MHz for 31P). Typical
NMR samples were prepared by dissolving the complexes (20 mg)
in 0.4 ml of the deuterated solvent. For 1H NMR, CDCl3 as sol-
vent, TMS as internal standard; for 31P{1H} NMR, CDCl3 as sol-
vent, 85% aqueous H3PO4 as external standard. Ϫ Conductivity
measurements: Amel conductimeter Model 131, ca. 10Ϫ3  solu-
tions in MeCN at 25°C. Ϫ Elemental analyses (C, H, N): Fisons
EA 1108 elemental analyzer.
[ PdPhI( PCϭNEt) ] (3): Yield: 0.421 g (61%). Ϫ IR (KBr): ν˜ ϭ
3043 m cmϪ1, 1637 m (CϭN), 1561 m, 1467 m, 1434 s, 727 vs, 691
vs. Ϫ C27H25INPPd (627.82): calcd. C 51.65, H 4.02, N 2.23; found
C 51.00, H 3.99, N 2.03.
[ PdMeCl( PNMe2) ] ·0.5 C6H6 (4): Yield: 0.074 g (78%). Ϫ IR
(KBr): ν ϭ 3049 w cmϪ1, 1583 w, 1480 s, 1436 s, 748 s, 694 s, 502
˜
s. Ϫ C21H23ClNPPd ·0.5 C6H6 (501.33): calcd. C 57.50, H 5.24, N
2.79; found C 55.32, H 5.15, N 2.69.
Synthesis of 1Ϫ3 Ϫ General Procedure: To a blood-red solution
of 0.633 g of [Pd(dba)2] (1.1 mmol) in 90 ml of dry THF at 50°C
under N2, a stoichiometric amount of the PʝN ligand and 520 µl
of PhI (4.4 mmol, d ϭ 1.73 g/ml) were added, and the mixture was
stirred under N2 at the same temperature. After 45 min, the yellow-
green mixture was concentrated under a flow of N2 and filtered
through Celite. The solvent was removed from the filtrate under
reduced pressure and the residue was washed several times with
Et2O until the washings were colorless. The residual solid was then
dried in vacuo. Crystals suitable for X-ray analysis were grown by
slow evaporation of the solvent from Me2CO/MeOH solutions
(Crystals of complex 3 from Me2CO/MeOH/H2O solutions).
[ PdMe( PPh3) ( PNMe2) ] CF3SO3 ·C6H6 (5): Yield: 0.252
(67%). Ϫ IR (KBr): ν˜ ϭ 3053 w cmϪ1, 1593 w, 1502 m, 1435 m,
1273 vs (SϪO), 693 s, 636 s. Ϫ ΛM (MeCN): 150 ohmϪ1cm2molϪ1
Ϫ C40H38F3NO3P2PdS·C6H6 (916.31): calcd. C 60.29, H 4.85, N
1.53, S 3.50; found C 60.93, H 5.56, N 1.63, S, 3.36.
g
.
[ PdPh( PPh3) ( PNMe2) ] CF3SO3 ·0.5 C6H6 (6): Yield: 0.362 g
(94%). Ϫ IR (KBr): ν ϭ 3056 m cmϪ1, 1564 m, 1473 m, 1437 s,
˜
1263 vs (SϪO), 691 s, 637 s. Ϫ ΛM (MeCN): 152 ohmϪ1cm2molϪ1
.
Ϫ C45H40F3NO3P2PdS·0.5 C6H6 (939.32): calcd. C 61.37, H 4.62,
N 1.48, S 3.41; found C 61.70, H 5.25, N 1.60, S 3.38.
[ PdPh( PPh3) ( PCϭNMe) ] CF3SO3 · 0.5 C6H6 (7): Yield: 0.361
g (94%). Ϫ IR (KBr): ν˜ ϭ 3052 m cmϪ1, 1641 m (CϭN), 1564
Synthesis of 4: To a solution of 0.508 g of [PdMeCl(COD)] (0.19
mmol) in 60 ml of dry C6H6 under N2, was added 0.058 g of the m, 1482 m, 1435 s, 1261 vs (SϪO), 693 s. Ϫ ΛM (MeCN): 152
phosphanyl-amine PNMe2 (0.19 mmol) and the mixture was stirred
1818
ohmϪ1cm2molϪ1. Ϫ C45H38F3NO3P2PdS·0.5 C6H6 (937.3): calcd.
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820

New Organometallic Palladium(II) Complexes Containing PʝN Ligands
FULL PAPER
Table 3. Crystal data and summary of data collection and refinement for [PdPhI(PNMe2)] (1), [PdPhI(PCϭNMe)] (2), [PdPhI(PCϭ
NEt)]·3/2 H2O (3·3/2 H2O), and [Pd(η3-C3H5)(PNMe2)]PF6 (9)
1
2
3·3/2 H2O
9
Empirical formula
Form. weight
Crystal system
Space group
C26H25INPPd
615.74
C26H23INPPd
613.72
C27H28INO1.5PPd
654.77
C23H25F6NP2Pd
597.78
monoclinic
P21/n
triclinic
triclinic
triclinic
P1
¯
¯
P1
P1
˚
a [A]
9.283(2)
16.645(4)
15.542(4)
90
94.06(2)
90
2395.5(10)
4
1.707
2.143
0.71073
2512
9.200(6)
16.067(10)
16.147(9)
92.86(5)
90.95(5)
96.27(5)
2369(3)
4
11.972(4)
15.356(5)
15.874(6)
105.03(3)
90.03(3)
96.63(3)
2798(2)
4
9.042(2)
10.980(3)
14.408(3)
72.11(2)
71.86(2)
65.75(2)
1212.6(5)
2
1.637
0.955
0.71073
2672
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
V [A3]
˚
Z
Dcalcd [Mg/m3]
1.721
2.167
0.71073
5059
0.0469, 0.1211
1.059
1.554
1.843
0.71073
6798
0.0727, 0.2012
1.105
µ [mmϪ1
]
˚
λ [A]
obsd. refl.
R1, Rw2[a]
GooF[b]
0.0404, 0.1016
1.063
0.0398, 0.0997
1.058
2
2
[a] R1 ϭ ΣʈFo͉ Ϫ ͉Fcʈ/Σ͉Fo͉; Rw2 ϭ [Σ[w(Fo Ϫ Fc2)2]/Σ[w(Fo2)2]]1/2. Ϫ [b] GooF ϭ [Σ[w(Fo Ϫ Fc2)2]/(Nobs Ϫ Npar)]1/2
.
Table 4. Selected bond lengths [A] and angles [°] for 1, 2[a], 3·3/2 H2O[a], and 9[a]
˚
1
2
3·3/2H2O
9
PdϪI(1)
2.655(1)
2.208(2)
2.252(5)
2.029(6)
2.664(2)
2.232(2)
2.169(6)
2.007(8)
2.671(2)
2.239(2)
2.172(6)
2.026(7)
2.628(1)
2.228(2)
2.176(8)
2.651(1)
PdϪP(1)
2.235(3)
2.166(8)
2.257(4)
2.17(1)
2.26(2)
2.15(2)
1.84(2)
1.47(2)
2.263(5)
2.17(1)
2.19(2)
2.14(2)
1.85(2)
1.50(2)
PdϪN(1)
PdϪC(9)
PdϪC(10)
2.007(8)
1.826(9)
2.026(7)
1.830(9)
P(1)ϪC(1)
1.819(6)
1.464(9)
1.835(7)
1.26(1)
175.6(1)
175.6(1)
94.6(2)
89.8(2)
84.2(2)
91.6(2)
1.828(7)
1.28(1)
175.4(1)
175.4(1)
94.1(2)
89.6(2)
83.8(2)
92.7(2)
N(1)ϪC(6)
N(1)ϪC(7)
1.29(1)
178.3(1)
94.0(2)
88.0(2)
86.2(2)
1.25(1)
178.9(1)
95.6(2)
87.3(3)
85.5(2)
I(1)ϪPdϪP(1)
I(1)ϪPdϪN(1)
I(1)ϪPdϪC(9)
P(1)ϪPdϪN(1)
P(1)ϪPdϪC(9)
P(1)ϪPdϪC(10)
P(1)ϪPdϪC(11)
N(1)ϪPdϪC(9)
N(1)ϪPdϪC(10)
N(1)ϪPdϪC(11)
PdϪP(1)ϪC(1)
PdϪN(1)ϪC(6)
PdϪN(1)ϪC(7)
177.7(1)
97.3(1)
90.2(2)
84.9(1)
87.7(2)
85.2(3)
85.1(3)
167.4(6)
137.1(9)
101.6(6)
167.4(6)
137.0(8)
102.0(6)
91.8(3)
91.6(3)
171.7(2)
174.9(3)
175.2(3)
175.9(3)
106.4(3)
123.3(7)
174.7(4)
107.3(3)
124.7(7)
136.5(9)
173.0(7)
100.8(5)
113.0(9)
136.7(9)
172.4(7)
100.8(5)
112.6(9)
103.4(2)
112.6(4)
105.7(3)
127.7(6)
105.7(2)
126.7(5)
[a] Since the asymmetric unit contains two independent molecules, two values are reported for each entry.
C 61.50, H 4.42, N 1.50, S 3.42; found C 60.74, H 4.59, N 1.32,
S 3.31.
ferred to a Siemens Nicolet R3m/V four-circle automated dif-
fractometer. Using graphite-monochromated Mo-Kα radiation, ac-
curate cell parameters were determined and diffraction intensities
(up to Θ 23°) were measured. Two standard reflections were meas-
ured after every 150 data points to check for crystal deterioration
and/or misalignment. No significant deterioration in intensity was
observed. Data were corrected for Lorentz, polarization and ab-
sorption (using ψ scans) effects.
[ PdPh( PPh3) ( PCϭNEt) ] CF3SO3 · 0.5 C6H6 (8): Yield: 0.316 g
(81%). Ϫ IR (KBr): ν˜ ϭ 3056 m cmϪ1, 1640 m (CϭN), 1563 m,
1501 m, 1436 s, 1263 vs (SϪO), 694 s, 636 s. Ϫ ΛM (MeCN): 156
ohmϪ1cm2molϪ1. Ϫ C46H40F3NO3P2PdS·0.5 C6H6 (951.33): calcd.
C 61.86, H 4.57, N 1.47, S 3.37; found C 61.25, H 4.86, N 1.37,
S 3.19.
The crystals of 3·3/2 H2O were found to be slightly sensitive to
X-rays (decay of up to 19% during data collection) and decom-
posed after prolonged irradiation. Consequently, the empirical ab-
sorption correction was not applied. No unusually high correlation
values were noted between any of the variables in the last cycle of
full-matrix least-squares refinements on F2 and the final difference
[ Pd( η3-all) ( PNMe2) ] PF6 (9): Yield: 0.200 g {93% based on
[Pd(η3-all)Cl]2}. Ϫ IR (KBr): ν˜ ϭ 3061 w cmϪ1, 1583 w, 1474 m,
1439 m, 834 vs (PϪF), 556 s. Ϫ ΛM (MeCN): 183 ohmϪ1cm2molϪ1
.
Ϫ C23H25F6NP2Pd (597.83): calcd. C 46.20, H 4.22, N 2.34; found
C 46.35, H 4.30, N 2.38.
X-ray Crystal Structure Determinations: The crystals were maps were essentially featureless. Programs used and the sources
mounted on glass fibres, coated with epoxy resin, and were trans-
of scattering factors are contained in the SHELXTL (PC version
1819
Eur. J. Inorg. Chem. 1998, 1811Ϫ1820

L. Crociani, G. Bandoli, A. Dolmella, M. Basato, B. Corain
FULL PAPER
[11]
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