Concise syntheses of tridentate PNE ligands and their coordination chemistry with palladium(ii): A solution- and solid-state study

Article abstract of DOI:10.1039/b605995c

A straightforward methodology for the high-yielding synthesis of the di-functionalised phosphines {Ph₂P(CH₂)₂NC ₄H₈E, E = NMe (1), O (2), S (3)} via base-catalysed Michael addition is described. Reaction of the functionalised tertiary phosphines 1-3 with PdCl₂(MeCN)₂ affords complexes in which the ligands are bound in a tridentate fashion, namely [PdCl(κ ³-PNE)]Cl (6a, 8) as the predominant products. A κ²- PN coordination mode was also identified crystallographically for ligand 1 following its reaction with PdCl₂(MeCN)₂, which afforded [PdCl₂(1-κ²-PN)] (6b) in ca. 5% yield. Conductivity studies of solutions of 6a are consistent with an ionic formulation, however the poor solubility of 7 and 8 precluded their study in a similar fashion. Analysis of bulk samples of [PdCl₂(1)] (6) and [PdCl₂(3)] (8) by ¹⁵N and ³¹P NMR spectroscopy in the solid state as consistent with exclusive tridentate binding of the PNE ligands. An X-ray crystallographic study has probed the coordination of 1 in the unusual salt [PdCl(1-κ³-PNN)]₂[Mg(SO₄) ₂(OH₂)₄] (10) prepared by treating a methanolic solution of 6 with excess MgSO₄. No data could be obtained to support the transformation of 6a into 6b on addition of excess chloride. In contrast, 6a reacts regioselectively with the water-soluble phosphine Cy ₂PCH₂CH₂NMe₃Cl to afford the cis-diphosphine complex cis-[PdCl(Cy₂PCH₂CH ₂NMe₃Cl)(1-κ²-PN)]Cl₂ (9). Reaction of 1 with PdCl(Me)(COD) results in the formation of the κ²-PN dichloride complex [PdCl(Me)(1-κ²-PN)] (11). Attempts to prepare [Pd(Me)(MeCN)(1-κ²-PN)][PF ₆] (12) through reaction of 11 with NaPF₆ in MeCN led to decomposition. Treatment of PdMe₂(TMEDA) with 1 at low temperature initially affords [PdMe₂(1-κ²-NN)], which isomerises to afford [PdMe₂(1-κ²-PN)] (13); at temperatures greater than 10 °C complex 13 decomposes rapidly. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b605995c

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www.rsc.org/dalton | Dalton Transactions
Concise syntheses of tridentate PNE ligands and their coordination chemistry
with palladium(II) : a solution- and solid-state study†
Carly E. Anderson, David C. Apperley, Andrei S. Batsanov, Philip W. Dyer* and Judith A. K. Howard
Received 27th April 2006, Accepted 8th June 2006
First published as an Advance Article on the web 20th June 2006
DOI: 10.1039/b605995c
A straightforward methodology for the high-yielding synthesis of the di-functionalised phosphines
{Ph2P(CH2)2NC4H8E, E = NMe (1), O (2), S (3)} via base-catalysed Michael addition is described.
Reaction of the functionalised tertiary phosphines 1–3 with PdCl2(MeCN)2 affords complexes in which
the ligands are bound in a tridentate fashion, namely [PdCl(j3-PNE)]Cl (6a, 8) as the predominant
products. A j2-PN coordination mode was also identified crystallographically for ligand 1 following its
reaction with PdCl2(MeCN)2, which afforded [PdCl2(1-j2-PN)] (6b) in ca. 5% yield. Conductivity
studies of solutions of 6a are consistent with an ionic formulation, however the poor solubility of 7 and
8 precluded their study in a similar fashion. Analysis of bulk samples of [PdCl2(1)] (6) and [PdCl2(3)] (8)
by 15N and 31P NMR spectroscopy in the solid state as consistent with exclusive tridentate binding of
the PNE ligands. An X-ray crystallographic study has probed the coordination of 1 in the unusual salt
[PdCl(1-j3-PNN)]2[Mg(SO4)2(OH2)4] (10) prepared by treating a methanolic solution of 6 with excess
MgSO4. No data could be obtained to support the transformation of 6a into 6b on addition of excess
chloride. In contrast, 6a reacts regioselectively with the water-soluble phosphine Cy2PCH2CH2NMe3Cl
to afford the cis-diphosphine complex cis-[PdCl(Cy2PCH2CH2NMe3Cl)(1-j2-PN)]Cl2 (9). Reaction of 1
with PdCl(Me)(COD) results in the formation of the j2-PN dichloride complex [PdCl(Me)(1-j2-PN)]
(11). Attempts to prepare [Pd(Me)(MeCN)(1-j2-PN)][PF6] (12) through reaction of 11 with NaPF6 in
MeCN led to decomposition. Treatment of PdMe2(TMEDA) with 1 at low temperature initially affords
[PdMe2(1-j2-NN)], which isomerises to afford [PdMe2(1-j2-PN)] (13); at temperatures greater than
10 ◦C complex 13 decomposes rapidly.
of the various donor fragments is essential. One means of achieving
Introduction
this is to design metal scaffolds such as L that feature a third, pen-
The entropic effects associated with the coordination of mul-
dant labile donor moiety E (potentially providing reversible coor-
tidentate ligands have been long known to direct a metal’s
coordination number, stoichiometry, stereochemistry and hence
reactivity.1 The potentialof such systems has been further extended
dinative unsaturation at M), e.g. A vs. B, in addition to the essential
mixed-donor chelate (e.g. a j2-PN unit) that provides electronic
control at the metal centre. However, to gain maximum benefit
from such ligands, it is crucial that the nature of the j3-tridentate
binding mode of the scaffold remains the same following each cycle
of dissociation–reassociation, thereby avoiding the complication
of isomerisation within the metal’s coordination sphere. To ensure
such control, geometric constraints can be imposed upon the
system through the inclusion of ‘double chelate linkages’, such as
those provided by piperazine (E = NH) for example, forcing merid-
ional coordination B over the alternative facial geometry C.11–17 In-
deed, open-chain and macrocyclic tetraaza ligands that contain a
piperazino moiety are known to show enhanced stability to demet-
allation, as a result of their rigid and pre-defined coordination.18,19
Here we report both the preparation of PNE ligands of type
L and their coordination behaviour with a variety of Pd(II)
fragments.
by the development of so-called ‘hybrid’ ligands. These combine
electronically (and often sterically) disparate binding sites within
a single scaffold,2 and offer significant control over reactions
occurring at the metal centre to which they are bound.3–6 Indeed,
‘hybrid’ ligand complexes have been exploited to considerable
effect in a wide variety of homogeneously-catalysed processes,
where their potential to provide a donor moiety that may
dissociate/recoordinate in a reversible manner is advantageous.7–10
To further maximise the utility of ‘hybrid’ ligand frameworks,
engendering high levels of control over the coordination behaviour
Results and discussion
Department of Chemistry, Durham University, South Road, Durham, UK
DH1 3LE. E-mail: p.w.dyer@durham.ac.uk; Fax: +44 (0)191 384 4737;
Tel: +44 (0)191 334 2150
Ligand syntheses
The acid- or base-catalysed Michael addition of an amine
across a vinyl phosphine provides a concise methodology for
† Electronic supplementary information (ESI) available: Structure of 10.
See DOI: 10.1039/b605995c
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Scheme 1 Reagents and conditions: (i) HNC4H8E, cat. NaNH2, THF, reflux, 24 h. (ii) HCl(g), Et2O, RT.
the preparation of a diverse range of potentially chelating PN
ligands.20,21 Here, this approach has been extended to afford access
to potentially tridentate scaffolds that comprise a PN-chelating
core bearing a third donor site tethered through a double ethylene
bridge.
The desired ligands were synthesised using an extension to
Davies’ method for the preparation of 2-diphenylphosphino-
ethylamines.22 Reaction of diphenylvinylphosphine with an
equimolar quantity of the appropriate heterocyclic secondary
amine in the presence of a catalytic quantity of NaNH2 in THF
afforded the PNE derivatives 1–3 (E = NMe, O,23 S, respectively)
in near-quantitative isolated yields (ca. 95%) (Scheme 1). Each
compound presents a single, characteristic resonance by 31P
NMR spectroscopy (Table 1). This approach is advantageous
since it provides direct access to the desired P(III) phosphine-
derived ligands, rather than necessitating initial preparation of
the phosphine oxide followed by reduction.21
broadened at room temperature), its hydrochloride was prepared
through treatment of 4 with excess gaseous HCl. Salt 5 was isolated
as a colourless solid, which was recrystallised from CHCl3–
1
1
Et2O. The combination of H and H–1H COSY NMR spectra
(ambient temperature) readily established the structure of 5, with
4
a characteristic methyl resonance appearing at d 1.05 (d, JPH
=
6.4 Hz) ppm. Unambiguous confirmation of the regiochemistry
of 5 was obtained from its X-ray structural analysis (vide infra).
The formation of 4 is believed to result from initial base-
catalysed isomerisation of the allyl- to the methylvinyl-phosphine,
which then undergoes addition of the piperazino moiety, in
accordance with comparable observations in the literature.25,26 The
coordination chemistry of 4 is entirely analogous to that of 1 and
hence will be discussed elsewhere.27
Coordination of 1–3 with ‘PdCl2’
The coordination chemistry of compounds 1–3 has been probed
with Pd(II) and is summarised in Scheme 2. Compounds 1–3
react readily with 1 eq. PdCl2(MeCN)2 in CH2Cl2 with the rapid
formation of a yellow precipitate in each case. Analysis of the
resulting complexes 6–8 (>65% yield) confirms that they have
empirical formulae that correspond to [PdCl2(1–3)], each giving
rise to [M–Cl]+ ions by mass spectrometry with m/z = 455.0,
441.9 and 457.9, respectively. For each complex a significant
high frequency coordination chemical shift (d ≈ +70 ppm) was
observed upon coordination of 1–3, according to 31P NMR
spectroscopy (Table 1), indicative of P–Pd binding. The three
complexes are poorly soluble in common solvents, with limited
solubility only being achieved in polar media such as DMSO,
water or MeOH. This behaviour is suggestive of tridentate j3-PNE
coordination of ligands 1–3, following chloride ion dissociation,
and the resultant formation of a salt.
The room temperature 1H NMR spectrum of 1 exhibits extreme
line broadening for all methylene resonances (no appreciable line-
sharpening was observed on warming the sample to 323 K), as a
result of conformational changes and inversion at nitrogen within
the heterocyclic ring system.24 At 223 K (CDCl3) the spectrum is
somewhat simplified, but is clearly non-first-order comprising a
complex set of five resonances assigned to the CH2 protons and a
singlet for the N–CH3 group (in addition to phenyl resonances).
The complexity of these spectra is enhanced by the asymmetric
substitution of the piperazino moiety.19
1
The ambient temperature H NMR spectra for both the mor-
pholine and thiomorpholine derivatives, 2 and 3 respectively, are
significantly less broadened than that of 1, reflecting the differing
geometric constraints imposed by each of the heteroatoms N, O
and S. Again, neither spectrum is first-order; both compounds 2
and 3 present four sets of methylene resonances in addition to the
expected phenyl signals.
Coordination of 1 with ‘PdCl2’. In solution (D2O),‡ 6 presented
a static structure according to 1H, 13C and 31P NMR spectroscopy.
In contrast to unbound 1, the proton resonance for the N–Me
moiety of 6 shows coupling to phosphorus (4JPH ≈ 5 Hz), in
agreement with tridentate binding, 6a (Scheme 2, Fig. 1). A
combination of ROESY, 1H–31P HMQC and 1H–1H COSY spectra
were used to aid spectral assignment. The protons of the P-to-N
ethylene linkage appear as two non-first order resonances at d 3.12
(Ha) and 3.37 (Hb) ppm, both coupling to phosphorus. The eight
protons of the piperazino ring appear as four multiplet resonances
1
The 13C{ H} NMR spectra for compounds 1–3 are as expected
and unremarkable, each showing four sharp methylene carbon
1
resonances. Although H–13C correlation spectra were acquired,
they did not assist in the assignment of the 1H NMR spectra.
With a view to extending this Michael addition-based syn-
thetic methodology to the preparation of compounds with a
longer, potentially 1,3-PN-chelating scaffold, the reaction of
allyldiphenylphosphine with N-methylpiperazine was undertaken
using identical reaction conditions to those used above. How-
ever, rather than the desired 1,3-product, the methyl-branched
compound 4 was obtained quantitatively (according to 31P NMR
spectroscopy). To facilitate purification and structural analysis
‡ Although complexes 6–8 are all poorly soluble, complex 6 is markedly
more soluble in water, compared with 7 and 8, which exhibit a greater
solubility in DMSO compared to water.
1
of 4 (the aliphatic region of its H NMR spectrum is severely
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Scheme 2 Reagents and conditions: (i) [PdCl2(MeCN)2], CH2Cl2, RT, 12 h. (ii) Cy2PC2H4NMe3Cl, D2O, RT, 0.5 h. (iii) MgSO4, MeOH, RT, 12 h.
(iv) [PdCl(Me)(COD)], CH2Cl2, RT, 18 h. (v) NaPF6, MeCN, CH2Cl2, RT, 7 d. (vi) [PdMe2(TMEDA)], CH2Cl2, RT, 0.75 h.
consistent with 6 being a 1 : 1 electrolyte and hence, with j3-PNN
binding of 1, it adopts form 6a.
Surprisingly, addition of excess magnesium sulfate to a suspen-
sion of 6a in MeOH resulted in the complete dissolution of the
palladium complex to yield a yellow solution, which after filtration
and slow evaporation of the solvent, gave yellow crystals of the new
complex [PdCl(1-j3-PNN)]2[Mg(SO4)2(H2O)4] (10) (vide infra) in
89% yield, presumably via loss of MgCl2. As would be expected
from the ionic structures of 6a and 10, the NMR spectroscopic
data (d4-MeOH) of their cations are identical; the aqua ligands
of the anion of 10 could not be detected due to rapid exchange
on the NMR timescale. Crystals of 10 were found to decompose
rapidly out of the mother liquor to leave a weakly-coloured
amorphous material of indeterminate composition. Consequently,
the homogeneity of the sample of 10 could not be completely
verified. However, the unit cells of several crystals were determined
and were found to be identical. In direct support of the structure
of 10, conductimetry studies performed in MeOH solution (KM
=
360 X cm2 mol−1) are consistent with 10 being a 1 : 2 electrolyte
(with a monocationic metal centre). Attempts were made to
characterise the anion of 10 by IR and Raman spectroscopies,
however none of the expected bands for an O-sulfato ligand
could be detected in the region 600–1200 cm−1.28 Despite repeated
attempts, mass spectrometry (ES−) was unable to identify the
[Mg(SO4)2(H2O)4]2− anion intact, although the [HSO4]− ion was
observed on each attempt. In contrast, the [PdCl(1-j3-PNN)]+
cation of 10 was readily observed by ES+ analysis.
31
Fig. 1 1H (A) and 1H{ P} (B) NMR spectra of 6a in D2O (400.1 MHz).
at d 3.05 (Hf), 3.19 (Hd), 3.95 (He), and 4.07 (Hc) ppm, none of
1
which exhibit coupling to phosphorus. The 13C{ H} spectrum of
In the absence of MgSO4, prolonged standing (days) of freshly
prepared solutions of 6 in MeOH afford small quantities of pale
yellow crystals of complex 6b (∼5% yield) in which 1 is bound
in a bidentate j2-PN fashion (vide infra). Surprisingly, crystals
of 6b proved insoluble in both chloroform and dichloromethane,
while their dissolution in polar solvents such as methanol, and
6a was readily assigned, consisting of five non-phenyl resonances
as expected.
Confirmation of the ionic nature of complex 6 in solution was
obtained from conductivity studies. In MeOH (5 × 10−3 mol dm−3)
a molar conductance KM = 68 X cm2 mol−1 was obtained. This is
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1
subsequent analysis by H and 31P NMR spectroscopies, merely
of 6, a different strategy was sought for probing the lability
of the N–Me donor moiety. Reaction of a D2O solution of
6a with a stoichiometric quantity of the water-soluble phos-
phine Cy2PCH2CH2NMe3Cl30 led to the clean formation of the
gave spectra consistent with 6a. Consequently, it proved impossible
to characterise 6b in solution spectroscopically. Disappointingly,
6b could not be isolated in sufficient quantity for analysis by solid-
state NMR spectroscopy, in order to probe the binding mode of 1
by 15N NMR spectroscopy in the bulk sample (vide infra). Analysis
of 6b by ES+ mass spectrometry gave rise to the same [PdCl(1-j3-
PNN)]+ ion as was observed for 6a.
1
diphosphine complex 9 according to 31P{ H} NMR spectroscopy
(Scheme 2, Table 1). The j2-PN coordination of 1 and the cis-
P–P geometry are highlighted by the small magnitude of the 2JPP
coupling constant (12.0 Hz) and are consistent with 9 being the
thermodynamic product of this reaction (with P trans to N).31
Although the above observations (and those made by solid
state NMR spectroscopy, vide infra) suggest that 6a is the major
product from the reaction of 1 with [PdCl2(MeCN)2], the origins
of 6b (isolated in low yield) remain obscure. Further study of the
behaviour of 6b was precluded by its insolubility in solvents other
than methanol (in which it rapidly converts into 6a). However,
there is a notable preference for the formation of 6a as evidenced
by the reaction between [PdCl2(MeCN)2] and 2 eq. of 1 in
CH2Cl2. This affords complex 6a and unreacted 1 rather than
the corresponding bis(phosphine) complex.
A number of attempts were made to abstract a chloride ion from
both 6 and 10 using NaPF6, NaBPh4 and AgBF4. Irrespective of
the solvent (MeOH, CH3CN) or the stoichiometry (1 : 1 or 1 :
2) reactions with the silver salt led to decomposition signified by
the precipitation of ‘palladium black’, while no reaction at all was
observed with the sodium salts.
Since both the j3-PNN (6a) and j2-PN (6b) forms of 6 have been
isolated, it raises the question of whether these two binding modes
of ligand 1 may interconvert in solution. Such behaviour would
be consistent with that observed for related aminophosphine P–N
chelates and the premise of so-called ‘hemilability’.2,29
In order to explore this possibility both D2O and d4-MeOH
solutions of 6a were treated with increasing amounts of chloride
ions in the form of NaCl (0.035–3.50 M, 1–100 eq.). The resulting
solutions were monitored by 1H and 31P{ H} NMR spectroscopies.
1
At chloride ion concentrations below 1.4 M no change in composi-
tion was detected spectroscopically, irrespective of the solvent. At
higher Cl− loadings the formation of an insoluble yellow powder
became apparent, with complete precipitation of the palladium
complex occurring on addition of ca. 100 equivalents of NaCl.
The 31P{ H} NMR spectrum of the yellow precipitate, redissolved
1
in fresh D2O, was identical to that for 6a. These observations reflect
the inferior solubility of 6 compared with NaCl, the precipitation
of the complex occurring as a result of ‘salting-out’.
To try and circumvent the problem of precipitation, an alterna-
tive approach was adopted. A biphasic experiment was undertaken
in which a yellow solution of 6 in D2O was suspended above
initially colourless CDCl3. Addition of concentrations of NaCl ≥
1.4 M (≥ 40 eq.) resulted in the complete loss of colour in the
aqueous phase and the yellow colouration of the lower organic
phase. However, analysis of the CDCl3 phase (in the presence of
Coordination of 2 and 3 with ‘PdCl2’. Confirmation of the
coordination mode of the morpholine (2) and thiomorpholine
(3) ligands with PdCl2 was hampered by the poor solubility of
the complexes 7 and 8, which are only very sparingly soluble in
MeOH, H2O and DMSO.‡ The bulk composition of both 7 and 8
was probed by solid-state NMR spectroscopy (vide infra).
In solution (d6-DMSO), both complexes 7 and 8 present a single
1
the upper aqueous phase, but with no mixing) by 1H and 31P{ H}
1
slightly broadened resonance by 31P{ H} NMR spectroscopy (m1
2
NMR spectroscopies only gave rise to spectra consistent with 6a.
Notably, removal of the aqueous phase led to complete precipita-
tion of 6 and loss of colour from the CDCl3 layer (consistent with
the previously observed insolubility of 6b). Identical results were
obtained when nBu4NCl was used in the place of NaCl.
∼ 25 Hz) at d +50.4 and +49.8 ppm (300 K), respectively,
comparable to the shifts recorded for 6a (Table 1). No changes
were observed on warming. Similarly, the 1H NMR spectra (300
K) of 7 and 8 are broadened which, combined with their non-first-
order nature, hindered structural assignment.
Since the above experiments did not establish the chloride
ion-dependent interconversion of the j3-PNN and j2-PN forms
As was the case for 6, complexes 7 and 8 are not amenable to
anion exchange. Reactions with AgBF4 in either MeOH or MeCN
Table 1 31P NMR spectroscopic data of compounds 1–5 and complexes 6–8 and 10–14
1
Compound
d31P{ H)a
Ph2PC2H4N(C2H4)2NMe
Ph2PC2H4N(C2H4)2O
Ph2PC2H4N(C2H4)2S
1
−19.1b,c
2
−18.2b
3
−18.3b
Ph2PCH2CH(Me)N(C2H4)2NMe
Ph2PCH2CH(Me)N(C2H4)2NMe·HCl
[PdCl(1-j3-PNN)]Cl
4
−18.6
5
−17.3
6a
7
+45.7d; +46.5d
[PdCl(2-j3-PNN)]Cl
+50.4 (m = 24 Hz)f
1
2
[PdCl(3-j3-PNN)]Cl
8
9
+49.8 (m = 27 Hz)f
1
2
[PdCl(1-j2-PN)(Cy2PCH2CH2NMe3Cl)]Cl
+54.8 (2JPP = 12.0 Hz)g
+44.1 (2JPP = 12.0 Hz)g
[PdCl(1-j3-PNN)]2[Mg(SO4)2(H2O)4]
[PdCl(Me)(1-j2-PN)]
10
11
13a
13b
+46.5e
+45.7h
+16.5h
+43.8
[PdMe2(1-j2-NN)]
[PdMe2(1-j2-PN)]
a 121.4 MHz, CDCl3, RT. b 202.3 MHz, CDCl3, RT. c 223 K. d D2O. e d4-MeOH. f d6-DMSO. g 81.0 MHz, CDCl3, RT. h d8-toluene.
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solution led to rapid decomposition of the starting complexes with
concomitant formation of ‘palladium black’. No reactions were
evident using either NaPF6 or NaBPh4.
the onset of decomposition is rapid with concomitant precipitation
of Pd(0) and loss of a signal by 31P NMR spectroscopy. This process
is accompanied by the formation of ethane, demonstrated by the
1
appearance of a singlet resonance at d 0.83 ppm by H NMR
spectroscopy. These data are consistent with 13b decomposing
in an exactly analogous manner to that established previously
for certain cis-[PdMe2L2] complexes, namely via thermally in-
duced elimination of ethane following reductive elimination.34
Collectively, these observations are in agreement with the initial
formation of a j2-NN dimethyl complex 13a, which isomerises
slowly to the j2-PN complex 13b (Scheme 3), possibly as a result
of the greater stability of the P–N chelate over that of the strained
N–N binding of the doubly-chelating piperazino moiety.
Coordination of 1 with ‘PdCl(Me)’ and ‘PdMe2’
Compound 1 reacts cleanly with 1 eq. of [PdCl(Me)(COD)]
to afford the air/moisture sensitive organometallic complex
[PdCl(Me)(1-j2-PN)] (11) as a single regioisomer according to
1
31P{ H} NMR spectrosocopy, d +45.7 (s) ppm (Scheme 2). To-
gether, the solubility and conductivity data (KM = < 5 X cm2 mol−1)
for 11 in CH2Cl2, are consistent with a bidentate coordination
of 1. Confirmation of this binding mode was obtained by 1H
NMR spectroscopy: upon saturation of the Pd–Me resonance at
d 0.51 ppm, a single NOE response (positive) was observed for the
resonance at d 7.64 ppm due to the ortho-phenyl protons, in the
NOE difference spectrum of 11. These data also substantiate the
trans-P–Cl geometry expected on thermodynamic grounds for 11.3
The absence of phosphorus coupling to the NMe proton resonance
is again consistent with j2-PN ligation of 1.
The preference for bi- rather than tri-dentate coordination of
1 with the PdCl(Me) fragment (cf. 6a) is readily explained. The
strong trans-influence of the methyl ligand (cf. Cl− in 6a) causes
an elongation of the trans Pd–N bond of 11, which forces the piper-
azino moiety away from the palladium centre. This, combined with
the geometric constraints imposed by the 6-membered piperazino
ring fragment, prevents close approach of the NMe donor unit to
the palladium centre, favouring j2-PN coordination of 1.32
Attempts to abstract the chloride ion from 11 through reaction
with a variety of salts of weakly-coordinating anions {i.e. AgBF4,
Scheme 3 Proposed isomerisation of 13a to 13b.
Molecular structures
The molecular structures of 1 and 5 are shown in Fig. 2, with
relevant geometric parameters listed in Table 2. The piperazino
moiety adopts the expected chair conformation in both the
neutral and protonated systems, with equatorial orientation of
the substituents at both nitrogen atoms in each case. In agreement
with the spectroscopic and analytical data, protonation of 4 occurs
uniquely at the sterically less hindered N(4) atom. The cation
and anion of 5 are linked by a strong N(4)–H. . .Cl hydrogen
33
nBu4NPF6, NaPF6, and NaB[3,5-(CF3)2-C6H3]4 } to afford com-
plexes 12 proved unproductive. All reactions undertaken in CH2Cl2
resulted in rapid decomposition, signified by precipitation of ‘pal-
ladium black’. This behaviour has been tentatively attributed to a
lack of intramolecular cation stabilisation by 1, as a consequence
of the electronic constraints imposed by the methyl ligand that
prevents j3-PNN binding (vide supra). With a view to trying to
‘trap’ the cation generated following halide loss, identical reactions
were performed in the coordinating solvent MeCN (Scheme 2).
However, in these cases no reactions at all were observed with the
[PF6]− salts, while use of NaB[3,5-(CF3)2C6H3]4 and AgBF4 led to
decomposition and the formation of Pd(0).
˚
bond (N. . .Cl 3.002(4) A) into an ionic pair. In the solid state
the N(1)C(7)C(8)P chains of both 1 and 5 adopt a gauche
conformation, with convergent P and N(1) lone pairs.
In order to probe this decomposition pathway further and to
assess whether it would be possible to prepare complexes of 1
in which the two nitrogen atoms of the piperazino ring bind in
preference to the P–N chelate, the reaction of 1 with the strongly
trans-influencing cis-PdMe2 fragment was undertaken.34,35
Treatment of [PdMe2(TMEDA)] with 1 eq. 1 at low temperature
led to the rapid formation of a new cis-dimethyl complex
[PdMe2(1-j2-NN)] (13a), stable at 253 K, which exhibits two
1
methyl resonances by 1H and 13C{ H} NMR spectroscopy and a
1
single resonance at d +16.5(s) ppm in its 31P{ H} NMR spectrum.
As the temperature of the sample was slowly increased, a new
resonance at d +43.8 (s) ppm gradually started to appear (>253
K), which continued to grow in intensity at the expense of the
1
resonance for 13a, according to 31P{ H} NMR spectroscopy. This
second signal has been assigned to the j2-PN cis-dimethyl complex
[PdMe2(1-j2-PN)] (13b) (c.f. 31P NMR: d +55.0 and +44.9 ppm for
[PdMe2(DPPE)]36 and 11, respectively). At temperatures >283 K
Fig. 2 Molecular structures of 1 (50% thermal ellipsoids) and 5 (30%
thermal ellipsoids).
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◦
a
˚
Table 2 Selected bond distances (A) and angles ( ) for compounds 1, 5 and complexes 6b, 10 and 14
1
5
6b
10
14
Pd–P
Pd–N(1)
Pd–N(4)
Pd–Cl(1)
—
—
—
—
—
—
—
—
2.2024(6)
2.118(2)
—
2.2243(5)
2.033(1)
2.143(1)
—
2.2897(5)
1.810(2)
1.832(2)
1.497(2)
1.486(2)
1.472(2)
106.6(1)
110.8(1)
110.4(1)
47.4(2)
—
2.041(2)
2.066(2)
2.3107(7)
2.3055(6)
—
2.3903(6)
2.3056(5)
1.807(2)
1.823(2)
1.501(2)
1.457(3)
1.457(3)
107.9(1)
107.9(1)
109.6(1)
54.2(2)
Pd–Cl(2)
—
—
P–C(Ph)b
P–C(8)
1.839(3)
1.859(3)
1.460(4)
1.460(4)
1.465(4)
100.7(2)
111.5(3)
110.2(3)
42.5(3)
1.835(5)
1.851(6)
1.464(7)
1.492(6)
1.473(6)
101.7(3)
112.2(4)
112.4(4)
54.4(6)
—
N(1)–Cb
1.488(2)
1.492(2)
1.478(3)
—
109.1(2)
110.0(1)
—
N(4)–C(3,5)b
N(4)–C(9)
C–P–Cb,c
C–N(1)–Cb,c
C–N(4)–Cb,c
N(1)–C(7)–C(8)–P
a In parentheses: e.s.d.s for individual values, r for averages. b Average. c Individual e.s.d.s in parentheses (r is meaningless due to systematic differences
between the angles).
In complex 6b (Fig. 3) the piperazino ring retains a chair confor-
mation and the equatorial orientation of the methyl substituent,
whereas the Ph2PCH2CH2 moiety is pushed into an axial position
upon coordination to Pd. The pendent N(4) atom has the lone pair
in a syn-orientation with respect to the Pd atom. The latter has a
distorted square-planar coordination; the Cl(1) and Cl(2) atoms
˚
deviate by 0.21 and −0.12 A from the P–Pd–N(1) plane, which
forms a 5.8◦ angle with the PdCl2 plane. The Pd–Cl(1) bond is
˚
0.085 A longer than Pd–Cl(2), consistent with the stronger trans-
influence of the P atom.
The asymmetric unit of 10 contains one [PdCl2(1-j3-PNN)]+
cation (Fig. 3), three water molecules of crystallisation and half
of the [Mg(SO4)2(H2O)4]2− dianion (Fig. 4) with monodentate
O-sulfato ligands and trans octahedral coordination geometry
about the magnesium atom, which lies at a crystallographic
inversion centre. Whereas such anions exist in the minerals
leonite,37 K2Mg(SO4)2·4H2O, and bloedite38 (alias astrakhanite39),
Na2Mg(SO4)2·4H2O, they have not been previously observed in
man-made solids. Indeed, the Cambridge Structural Database40
Fig. 4 An anion and water molecules of crystallisation in structure 10
(showing 50% thermal ellipsoids). Symmetry operations: (i) 1 − x, 1 − y,
1 − z; (ii) x, 1/2 − y, 1/2 + z; (iii) 1 − x, −y, 1 − z; (iv) 1 − x, 1/2 +
◦
˚
y, 1/2 − z; (v) x, y + 1, z. Selected bond distances (A) and angles ( ):
Mg–O(1) 2.048(1), Mg–O(5) 2.100(1), Mg–O(6) 2.052(1), S–O(1) 1.473(1),
other S–O (av.) 1.473(4); O(1)–Mg–O(5) 90.17(5), O(1)–Mg–O(6) 90.16(5),
O(5)–Mg–O(6) 92.02(5), Mg–O(1)–S 137.64(8).
Fig. 3 Molecular structures (showing 50% thermal ellipsoids) of 6b, the
cation of 10, and 14 (primed atoms are generated by the mirror plane).
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lists only one structure with magnesium–sulfate coordination of
any kind, namely cis-Mg(SO4)(H2O){OC(NH2)2}4.41
PtN2 and PtCl2 planes.32 In 14 the NH group forms an awkwardly
bifurcated, and rather weak, hydrogen bond with both Cl(1) and
Cl(2) atoms of a molecule related via the a glide plane: N. . .Cl
The anion and water molecules of 10 are linked by hydrogen
bonds into 2D layers, parallel to the (1 0 0) plane. The cations,
which take no part in hydrogen bonding, form parallel (hydropho-
bic) layers, which alternate with the hydrophilic anion layers (see
ESI†). In the cation, 1 binds in a tridentate fashion, as suggested by
its solution-state behaviour, the piperazino ring having switched
from a chair to a boat conformation, binding to the metal via
both nitrogen atoms. As in 6b, the fourfold coordination sphere of
palladium is not quite planar, the Cl and N(4) atoms deviate from
◦
˚
distances 3.311(2) and 4.186(2) A, N–H–Cl angles 124(3) and
171(3)◦, respectively.
Solid-state NMR spectroscopic studies
In order to probe the nature of the ligand coordination mode
in a bulk sample of 6 (1-j2-PN, 1-j3-PNN or a mixture), a
combination of solid-state 31P, 13C and natural abundance 15N
NMR spectroscopic studies were undertaken.42 Both the 31P and
15N NMR spectral data (Table 3) are consistent with a single
coordination mode of 1, with two distinct nitrogen environments
being observed (d −342.7 and −331.2 ppm), as expected. Both the
31P and 13C NMR data are entirely analogous to those obtained
in solution for complexes 6a and 10 (Table 1). Comparable 31P
and 15N NMR data, d +55.1 and −329.9 ppm, respectively,
were obtained for the thiomorpholine-based complex 8, again
consistent with a single coordination environment in the solid
state.
To provide a comparable, readily accessible reference for a
palladium-bound N-Me moiety, a sample of the previously
unknown Cs-symmetric complex cis-[PdCl2(N-methylpiperazine-
j2-NN)] (14) was prepared and fully characterised in the solid
state (vide supra) and in solution. Its natural abundance 15N NMR
spectrum showed two resonances at −362.5 and −350.2 ppm,
which have been assigned to the palladium-bound N–H and
N–Me units, respectively, with the aid of a dipolar dephasing
experiment.
˚
the P–Pd–N(1) plane by 0.17 and −0.24 A, respectively. The Pd–
˚
N(4) bond is 0.11 A longer than Pd–N(1), through the combined
effect of the P-donor trans-influence and the strain of the chelating
system. The P–Pd–N(1) ‘bite’ angle in 10 [87.35(4)◦] is comparable
to that in 6b [86.27(4)◦], while the N(1)–Pd–N(4) angle of 72.29(6)◦
is almost identical to the angle of 72.16(8)◦ found in 14 (vide infra),
but much smaller than the corresponding angle Cl(1)–Pd–N(1)
in 6b [94.02(4)◦]. The geometric constraints imposed by j3-PNN
coordination of 1 in complex 10 result in significant deviation
from the ideal linear P–Pd–N(4) arrangement, imposing an angle
of 158.57(4)◦.
The PdNC2P metallacycles in both 6b and 10 adopt a twist-
conformation; the C(7) and C(8) atoms are displaced to opposite
˚
sides of the PdN(1)P plane, by −0.34 and 0.40 A in 6b and −0.20
˚
and 0.46 A in 10. The N(1)–C(7)–C(8)–P torsion (Table 2) is
broadly similar to that in uncoordinated 1 and 5, hence the P. . .N
˚
˚
distances are also similar, viz. 2.958(3) A in 1 and 3.044(5) A in 5,
˚
˚
against 2.955(2) A in 6b and 2.943(2) A in 10. Upon coordination
to palladium the P–C bonds contract and the C–P–C angles widen,
in comparison with the free ligand 1. In contrast, the N–C bonds
lengthen on coordination, and the C–N–C angles either decrease
or remain the same (Table 2).
The resonance for the central palladium-bound N-atom of
ligands 1 and 3 can readily be assigned from comparison of the 15
N
NMR data from complexes 6 and 8, appearing at ca. d −330 ppm.
The second 15N NMR resonance observed for 6 (d−342.7 ppm)
has been assigned to a palladium-coordinated N–Me fragment
by comparison with the similar chemical shift observed for the
metal-bound N–Me from 14 (d −350.2 ppm). Together these data
are consistent with j3-PNN coordination of 1 in complex 6 in the
The molecule of 14 (Fig. 3) lies on a crystallographic mirror
plane that passes through the Pd, both Cl and both N atoms.
Thus, the metal coordination in 14 is rigorously planar, whereas its
related, symmetrical analogue [PtCl2(N,N-dimethylpiperazine-j2-
NN)] shows a small (ca. 3◦) pseudo-tetrahedral twist between the
Table 3 Selected solid-state 31P, 15N and 13C NMR spectral data for complexes 6–8 and 14a
1
Complex
Nucleus
d (Dm /Hz)
Assignment
2
6
31Pb
55.1(1.5)
−331.2(25)
−342.7(20)
32.9
Ph2P
CH2N(CH2CH2)2
NMe
15Nc
13Cd
PCH2
45.0
NMee
47.9
49.4
CH2
CH2
56.1
CH2
PCH2CH2N
Ph2P
63.8
7
31Pb
15Nc
31Pb
15Nc
15Nc
55.8, 53.5, 51.9, 48.6g
−290.4, −312.8, −332.3, −338.9
CH2N(CH2CH2)2
Ph2P
CH2N(CH2CH2)2
NMe
8
51.1 (2.0)
−329.9 (20)
−350.2 (33)
−362.5 (51)
60.2
14
NH
13Cd
CH2
f
51.5
NMee
a Ambient probe temperature. b 121.4 MHz. c 30.4 MHz. d 75.4 MHz. e Confirmed by dipolar dephasing with a 40.00 ls delay. f Resonances coincident.
g Overlapping resonances.
4140 | Dalton Trans., 2006, 4134–4145
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solid state. Consequently, a similar j3-PNS binding for ligand 3
with the PdCl2 fragment has been assigned to 8.
(Apollo) was purged with dry nitrogen. Deuterated solvents were
stored and handled under nitrogen.
In contrast, the 31P and 15N NMR spectra for the morpholine-
derived complex 7 each consisted of four resonances (Table 3).
The composition of 7 is clearly more complicated in the solid
state, despite its analytical data being consistent with the empirical
formula [PdCl2(2)] (vide supra). From the 31P NMR data it is clear
that the phosphine component of 2 is bound to palladium in each
case, however. The different behaviour observed for 7 compared
with that for complexes 6 and 8 is likely to be due to the presence of
the harder O-donor moiety, favouring j2-PN and intermolecular
ligation rather than j3-PNO binding to the soft palladium centre.
A similar bidentate coordination has been proposed previously for
ligand 2 in the rhodium complex [RhCl(CO)(2-j2-PN)].23
Palladium dichloride was used on loan from Johnson Matthey.
N-Methylpiperazine, morpholine, thiomorpholine, vinyl Grig-
nard, and NaNH2 were purchased from Aldrich and used as
received. Ph2PCl (Aldrich) was distilled under vacuum prior to
use. Allyl Grignard was prepared from allyl chloride (Aldrich)
in Et2O using standard conditions.43 The starting materials
[PdCl2(MeCN)2],44 [PdCl(Me)(COD)],45 [PdMe2(TMEDA)],34,35
NaB[3,5-(CF3)2-C6H3]4,33 and Cy2PC2H4NMe3Cl30 were prepared
according to literature procedures or slight modifications thereof.
Routine solution phase NMR spectra were collected on a Varian
Unity 300, Varian Mercury 400 or Varian Inova 500 at ambient
probe temperatures (∼290 K). Variable temperature and NOE
spectra were collected on a Bruker AMX400. Chemical shifts
were referenced to residual protio impurities in the deuterated
solvent (1H), 13C shift of the solvent (13C), or to external aqueous
85% H3PO4 (31P). Solvent proton shifts (ppm): CDCl3 (s), 7.27
(s); d4-MeOH (s), 3.31; d6-DMSO (sept.), 2.50; d8-toluene (sept.),
2.36; D2O (s), 4.79. Solvent carbon shifts (ppm): CDCl3, 77.2 (t);
Conclusions
The Michael addition of piperazine, morpholine and thiomor-
pholine with diphenylvinylphosphine provides easy access to
potentially tridentate PNE (E = N, O, S) donor ligands 1–
3 in near-quantitative yields. Similar reactions undertaken with
allyldiphenylphosphine gave rise to the methyl-branched ethane
derivative rather than the 1,3-P–N compound, as a result of base-
catalysed isomerisation of the allyl phosphine.
Ligands 1 and 3 favour meridional, j3-PNE coordination to the
PdCl2 fragment, affording complexes 6a and 8, respectively, follow-
ing chloride ion displacement, both in solution and the solid state.
However, it is apparent that the N–Me donor moiety of 1 is labile
since it can be displaced by the phosphine Cy2PCH2CH2NMe3Cl.
In contrast to the situation with 1 and 3, the precise mode of
binding of the PNO ligand 2 is less clear-cut, something attributed
to weak O–Pd ligation.
It is clear that ligands 1–3 can adopt a variety of different
coordination modes in response to the nature of the metal
fragment to which they are bound. This is highlighted by the
bidentate binding of 1 with both the PdCl(Me) and PdMe2
fragments affording complexes 11 and 13, respectively. Here, the
presence of the strongly trans-influencing methyl group precludes
tridentate binding of 1 as a consequence of elongation of the Pd–
N bond of the middle N-atom. Such ‘responsive’ behaviour may
prove beneficial in catalytic applications, where the electronic and
steric demands of the metal centre are constantly changing.
An exploration of the coordination chemistry of phosphines
1–3 with a range of metal-containing fragments is on-going. The
utility of such systems in a number of catalytic applications is
being investigated actively.
1
d4-MeOH, 49.0; d6-DMSO, 39.5; d8-toluene (sept.), 21.4. In H
NMR spectra, 31P coupled resonances were verified by running
31
1H { P} experiments. 13C NMR spectra were assigned with the
aid of DEPT 90, DEPT 135 and 1H–13C correlation experiments.
Chemical shifts are reported in ppm and coupling constants in Hz.
Solid-state NMR spectra were obtained on a Varian UNITY
Inova 300 MHz spectrometer (5.0 mm probe) at ambient probe
temperature; acquisition parameters are collected in Table 4.
Chemical shifts were referenced to tetramethylsilane (13C) by
setting the high-frequency signal from adamantane to 38.4 ppm;
to nitromethane (15N) by setting the nitrate signal from solid
ammonium nitrate to −5.1 ppm; and to H3PO4 (31P) by setting
the signal from CaHPO4·2H2O (Brushite) to 1.4 ppm.
Mass spectra were recorded either in Durham (ES: Micromass
Autospec; MALDI ToF: Applied Biosystems Voyager-DE STR)
or by the EPSRC National Mass Spectrometry Service at the
University of Wales, Swansea, (ES: Waters ZQ-4000) and are
reported in (m/z). The isotope distributions for all parent ion
peaks for metal complexes were verified via comparison with a
theoretical isotope pattern. Elemental analyses were performed
by The Analytical Services Department of the Chemistry De-
partment, Durham University. Infrared spectra were collected on
a Perkin Elmer 1600 spectrophotometer using KBr discs or a
Golden◦Gate ATR cell. Conductimetry measurements were made
at 22.5 C using 5 × 10−3 mol dm−3 solutions with a Jenway 4310
dip-in probe.
Table 4 Selected solid-state NMR acquisition parameters for complexes
6–8 and 14
Experimental
General considerations
Complex Nucleus Recycle/s Contact time/ms
Spin rate/kHz
31P
15N
13C
31P
15N
31P
15N
15N
13C
3.0
3.0
3.0
20.0
10.0
10.0
5.0
5.00
10.00
1.00
5.73
5.00
4.62
8.00
5.09
8.00
5.06
5.08
5.04
All operations were conducted under an atmosphere of dry
nitrogen using standard Schlenk and cannula techniques, or in a
Saffron Scientific nitrogen-filled glove box, unless stated otherwise.
All NMR-scale reactions were conducted using NMR tubes fitted
with J. Young tap valves. Bulk solvents were purified using an
Innovative Technologies SPS facility and degassed prior to use.
CDCl3 and d8-toluene were distilled from P2O5. Anhydrous d4-
MeOH and d6-DMSO (Apollo) were used as received. D2O
6
7
3.00
20.00
10.00
5.00
20.00
1.00
8
14
5.0
5.0
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Preparations
2.40 (m, 2H, PC2H4), 3.58 (m, 4H, NC2H4O), 7.23 (m, 6H, m-
1
/p-PhH), 7.34 (m, 4H, o-PhH); 13C{ H} (125.7 MHz, CDCl3) d
Synthesis of diphenylvinylphosphine. A solution of chlorodi-
phenylphosphine (7.35 cm3, 4.01 × 10−2 mol) in THF (50 cm3)
was allowed to cool to −78 ◦C and a solution of vinyl magnesium
chloride (30 cm3, 1.6 mol dm−3 solution in THF) added dropwise
with stirring over the course of 0.5 h. The resulting mixture
was allowed to stir at −78 ◦C for a further 0.5 h before being
allowed to warm slowly to room temperature and stirred for a
further 16 h. The THF was then removed in vacuo, replaced with
hexane and the resulting solution filtered via a glass frit. The
hexane was removed in vacuo to afford diphenylvinylphosphine
as a colourless oil following vacuum distillation (5.53 g, 65%).
ppm: 24.5 (d, 1JPC = 12.0 Hz, PCH2), 52.3 (s, NCH2CH2O), 54.5
(d, 2JPC = 23.0 Hz, PCH2CH2N), 65.8 (s, CH2O), 127. 4 (d, 3JPC
=
7.0 Hz, m-PhC), 127.6 (s, p-PhC), 131.7 (d, 2JPC = 19.0 Hz, o-PhC),
1
137.3 (d, 1JPC = 13.0 Hz, i-PhC); 31P{ H} (202.3 MHz, CDCl3) d
ppm: −18.2 (s); MS (ES+) m/z: 300.0 (MH+).
If a clean 31P NMR spectrum of 2 was obtained, it was used
without further purification.
Synthesis of 1-(2-diphenylphosphino-ethyl)-4-methyl-thiomor-
pholine, 3. A slight modification of the procedure used for the
preparation of 1 was employed, with diphenylvinylphosphine
(1.51 g, 7.10 × 10−3 mol) in THF (50 cm3), thiomorpholine
(0.7 cm3, 7.10 × 10−3 mol) and a catalytic quantity of NaNH2
(1.0 cm3 of a suspension in toluene), yield 2.15 g, 96%. 1H
NMR: (499.8 MHz, CDCl3) d ppm: 2.16 (m, 2H, PC2H4N),
2.42 (m, 2H, PC2H4N), 2.51 (m, 4H, NC2H4S), 2.59 (m, 4H,
1H NMR (499.8 MHz, CDCl3) d ppm: 5.49 (m, 1H, CH2 CH–
=
=
=
P), 5.77 (m, 1H, CH2 CH–P), 6.50 (m, 1H, CH2 CH–P), 7.16
(m, 6H, m-/p-PhH), 7.28 (m, 4H, o-PhH); 13C{ H} (100.6 MHz,
1
CDCl3) d ppm: 128.6 (d, 3JCP = 7.0 Hz, m-PhC), 128.8 (s, p-PhC),
1
2
=
129.6 (d, JCP = 24.0 Hz, CH2 CH), 133.3 (d, JPC = 19.0 Hz,
2
1
1
NC2H4S), 7.21 (m, 6H, m-/p-PhH), 7.33 (m, 4H, o-PhH); 13C{ H}
=
o-PhC), 136.9 (d, JPC = 14.0 Hz, CH2 CH), 137.7 (d, JPC
=
9.5 Hz, i-PhC); 31P{ H} (162.0 MHz, CDCl3) d ppm: −10.7 (s);
1
(125.7 MHz, CDCl3) d ppm: 24.7 (d, 1JPC = 13.0 Hz, PCH2), 25.6
(s, PCH2CH2N), 27.2 (s, NCH2CH2S), 54.0 (s, NCH2CH2S), 55.2
(d, 2JPC = 22.5 Hz, NCH2CH2S), 127.8 (d, 3JPC = 7.0 Hz, m-PhC),
MS (ES+) m/z: 213.1 (MH+).
Due to the oily nature/air sensitivity of this product, satisfactory
CHN analysis could not be obtained. Since the product gave sat-
isfactory NMR spectra, it was used without further purification.
128.0 (s, p-PhC), 132.0 (d, 2JPC = 19.0 Hz, o-PhC), 137.7 (d, 1JPC
=
1
12.5 Hz, i-PhC); 31P{ H} (202.3 MHz, CDCl3) d ppm: −18.3 (s);
MS (ES+) m/z: 316.1 (MH+).
Synthesis of 1-(2-diphenylphosphino-ethyl)-4-methyl-piperazine,
1. To a solution of diphenylvinylphosphine (1.40 g, 6.60 × 10−3
mol) in THF (50 cm3) was added N-methylpiperazine (0.80 cm3,
7.26 × 10−3 mol) and a catalytic quantity of NaNH2 (1.0 cm3 of
a suspension in toluene) under a flow of nitrogen. The resulting
mixture was heated at reflux for 24 h, before being allowed to cool
to room temperature and the NaNH2 quenched by addition of
NH4Cl (20 cm3, aq, 10%, degassed). The solution was extracted
with CH2Cl2 (3 × 30 cm3), the organic fractions combined and
dried over MgSO4. The drying agent was removed by filtration via
a glass frit and, following removal of the CH2Cl2 under vacuum,
1 was obtained as a viscous yellow-orange oil (yield 1.94 g, 94%),
which on prolonged standing (weeks) affords very pale yellow
crystals suitable for X-ray diffraction studies, 1.50 g, 73%, (calc.:
C14H25N2P C, 73.04; H, 8.08; N, 8.97. Found: C, 73.00; H, 7.88;
N, 8.74. 1H NMR: (499.8 MHz, 223 K, CDCl3) d ppm: 2.07
(m, 4H, NC2H4N), 2.23 (m, 5H, NC2H4N and CH3N), 2.41 (m,
2H, NC2H4N), 2.72 (m, 2H, PC2H4), 2.82 (m, 2H, PC2H4), 7.24
If a clean 31P NMR spectrum of 3 was obtained, it was used
without further purification.
Synthesis of allyldiphenylphosphine. This was prepared in
an analogous fashion to that used for the preparation of
vinyldiphenylphosphine from diphenylchlorophosphine (3.7 cm3,
2.02 × 10−2 mol) in THF (50 cm3) and allyl magnesium chloride
(30 cm3, 0.8 mol dm−3 solution in THF). Following purification
by vacuum transfer, allyldiphenylphosphine was isolated as a
colourless oil, yield 2.94 g, 64% (calc.: C15H15P C, 73.62; H, 6.70.
Found: C, 73.35; H, 6.72). 1H NMR: (499.8 MHz, CDCl3) d ppm:
3
3.00 (dd, 1JHH = 1.0 Hz, JHH = 7.5 Hz, 2H, CH2), 5.12 (m, 2H,
PCH2), 5.93 (m, 1H, CH), 7.42 (m, 6H, m-/p-PhH), 7.56 (m, 4H,
1
3
o-PhH); 13C{ H} (125.7 MHz, CDCl3) d ppm: 34.1 (d, JPC
=
1
14.0 Hz, CH2), 117.8 (d, JPC = 14.0 Hz, Ph2PCH2), 128.7 (d,
3JPC = 7.0 Hz, m-PhC), 129.0 (s, p-PhC), 133.2 (d, 2JPC 18.0 Hz,
2
1
o-PhC), 133.5 (d, JPC = 9.0 Hz, CH), 138.5 (d, JPC = 15.0 Hz,
i-PhC); 31P{ H} (202.3 MHz, CDCl3) d ppm: −14.7 (s); MS (ES+)
1
(m, 6H, m-/p-PhH), 7.36 (m, 4H, o-PhH); 13C{ H} (125.7 MHz,
1
m/z: 227.2 (MH+).
223 K, CDCl3) d ppm: 24.9 (d, 1JPC = 12.0 Hz, Ph2PCH2), 45.1 (s,
CH3N), 52.0 (s, MeN(CH2CH2)2), 54.1 (s, MeN(CH2CH2)2), 54.3
(s, Ph2PCH2CH2N), 127.5 (d, 3JPC = 7.0 Hz, m-PhC), 127.7 (s, p-
PhC), 131.8 (d, 2JPC = 19.0 Hz, o-PhC), 137.6 (d, 1JPC = 13.0 Hz,
Reaction of allyldiphenylphosphine with N-methyl piperazine;
syntheses of 4 and 5. Using analogous conditions to those
employed for the preparation of 1, allyldiphenylphosphine (1.51 g,
6.68 × 10−3 mol) was reacted with N-methylpiperazine (3.0 cm3,
2.70 × 10−2 mol) in the presence of NaNH2 (1.0 cm3 of a
suspension in toluene). Following heating at reflux for 24 h,
4 was isolated as a viscous pale brown oil (yield 1.96, 90%).
1H NMR: (499.7 MHz, CDCl3, 223 K) d ppm: 1.10 (d,
4JPH = 6.0 Hz, 3H, CH2CH(CH3)N), 1.97 (m, 2H, N(C4H8)N),
2.11 (m, 1H, N(C4H8)N), 2.26 (s, 3H, N(C4H8)NCH3), 2.36
(m, 1H, N(C4H8)N), 2.45 (m, 2H, N(C4H8)N), 2.55 (over-
lapping m, 3H, N(C4H8)N and Ph2PCH2CH), 2.72 (m, 2H,
Ph2PCH2CH), 7.25–7.42 (m, 8H, o-/m-PhH), 7.45 (m, 2H, p-
1
i-PhC); 31P{ H} (202.3 MHz, CDCl3) d ppm: −19.1 (s); MS (ES+)
m/z: 313.2 (MH+).
If a clean 31P NMR spectrum of 1 was obtained, it was used
without further purification.
Synthesis of 1-(2-diphenylphosphino-ethyl)-4-methyl-morpho-
line, 2. An analogous procedure to that used for the preparation
of 1 was employed, with diphenylvinylphosphine (2.00 g, 9.44 ×
10−3 mol) in THF (50 cm3), morpholine (0.9 cm3, 10.38 × 10−3
mol) and a catalytic quantity of NaNH2 (1.0 cm3 of a suspension
in toluene), yield 2.68 g, 95%. H NMR: (499.8 MHz, CDCl3) d
ppm: 2.18 (m, 2H, PC2H4), 2.34 (br, m1 = 13.9 Hz, 4H, NC2H4O),
1
1
3
PhH); 13C{ H} (100.6 MHz, CDCl3) d ppm: 14.6 (d, JCP
=
7.5 Hz, CH2CH(CH3)N), 31.8 (d, 1JCP = 13.0 Hz, Ph2PCH2CH),
2
4142 | Dalton Trans., 2006, 4134–4145
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44.9 (s, N(C4H8)NCH3), 46.5 (s, N(CH2CH2)2NCH3), 54.1 (s,
N(CH2CH2)2NCH3), 55.8 (d, 2JCP = 16.0 Hz, Ph2PCH2CH), 127.2
(d, 3JCP = 7.0 Hz, m-PhC), 127.3 (d, 3JCP = 7.0 Hz, m-PhC), 127.4
NMR(d6-DMSO): the spectrum was so broad that assignment was
1
impossible; limited solubility precluded acquisition of 13C{ H}
1
NMR spectral data; 31P{ H} NMR (121.4 MHz, d6-DMSO) d
2
(s, p-PhC), 127.5 (s, p-PhC), 131.8 (d, JCP = 15.0 Hz, o-PhC),
ppm: +50.4 (m1 = 24 Hz); MS (ES+) m/z: 441.9 (M–Cl+).
2
2
1
131.8 (d, JCP = 15.0 Hz, o-PhC), 138.1 (d, JCP = 14.0 Hz, i-
Synthesis of [PdCl2(3)], 8. An analogous procedure to that
used for the preparation of 6 was adopted, involving reaction of
PdCl2(MeCN)2 (0.16 g, 6.34 × 10−4 mol) with 3 (0.20 g, 6.34 ×
10−4 mol) in CH2Cl2 (20 cm3). This lead to the isolation of 8 as
a yellow powder (0.25 g, 80%) (calc.: C18H22NSPPdCl2 C, 43.87;
PhC), 138.4 (d, JCP = 14.0 Hz, i-PhC); 31P{ H} (121.4 MHz,
CDCl3) d ppm: −18.6 (s); MS (ES+) m/z: 327.2 (MH+).
1
1
Bubbling gaseous HCl through an ethereal solution of 4
(0.85 g, 2.60 × 10−3 mol) resulted in the immediate precipitation
of the mono-hydrochloride salt 5 as a white solid, which was
isolated in near-quantitative yield (0.93 g, 98%). Crystals of X-
ray quality were grown from CHCl3/Et2O. (Calc.: C20H28N2PCl
C, 66.19; H, 7.79; N, 7.72. Found: C, 66.36; H, 7.76; N,
1
H, 4.51; N, 2.84. Found: C, 43.93; H, 4.62; N, 2.82). H NMR
(299.9 MHz, d6-DMSO) d ppm: 2.80–3.45 (m, 8H, CH2), 3.82
(m, 2H, CH2), 4.34 (m, 2H, CH2), 7.51 (m, 6H, m-/p-PhH), 7.89
(m, 4H, o-PhH); the low solubility of 8 precluded the acquisition
of 13C NMR spectra; 31P NMR (121.4 MHz, d6-DMSO) d ppm:
1
4
7.92). H NMR (499.7 MHz, CDCl3) d ppm: 1.05 (d, JPH
=
6.4 Hz, 3H, CH2CH(CH3)NCH3), 1.90 (m, 1H, N(C4H8)N),
2.10–2.35 (m, 2H, N(C4H8)N), 2.45–2.85 (m, 6H, N(C4H8)N,
Ph2PCH2CH), 2.95–3.34 (m, 5H, N(C4H8)N, CH3N(C4H8)N, and
Ph2PCH2CH), 7.18–7.32 (m, 8H, o-/m-PhH), 7.41 (s, p-PhH),
+49.8 (m1 = 27 Hz); MS (ES+) m/z: 457.9 (M–Cl+).
2
Synthesis of [PdCl(Cy2PC2H4NMe3)(1-j2-PN)]Cl2, 9. A solu-
tion (D2O) of 6 (0.018 g, 3.68 × 10−5 mol) was treated under
12.27 (br s, m1 = 37.5 Hz, 1H, NH+); H (499.7 MHz, CDCl3,
N2 with Cy2PC2H4NMe3Cl (0.012 g, 3.68 × 10−5 mol). 31P{ H}
1
1
2
223 K) d ppm: 1.08 (s, 3H, CH2CH(CH3)N), 1.86–2.09 (m, 2H,
NMR (81.0 MHz, D2O) d ppm: +54.8 (d, 2JPP = 12.0 Hz), +44.1
Ph2PCH2CH and N(C4H8)N), 2.32–2.88 (m, 8H, Ph2PCH2CH,
N(C4H8)N, N(C4H8)NCH3, and Ph2PCH2CH), 3.07 (m, 3H,
N(C4H8)N), 3.34 (m, 1H, N(C4H8)N), 7.26–7.41 (m, 8H, o-/m-
(d, 2JPP = 12.0 Hz).
Synthesis of [PdCl2(1-j3-PNN)]2[Mg(SO4)2(H2O)4], 10. Un-
der air, complex 6 (0.10 g, 2.08 × 10−4 mol) was treated with
MgSO4 (1.01 g, 8.352 × 10−3 mol) in methanol (10 cm3) and the
resulting mixture allowed to stir at room temperature for 36 h. The
excess unreacted MgSO4 and MgCl2 by-product were removed by
filtration and the solvent removed in vacuo to afford 10 as a vivid
yellow powder (yield 0.22 g, 89%). Crystals of X-ray quality were
grown by slow evaporation of a dilute methanolic solution of the
product under air (CHN analyses proved unreliable as a result of
desolvation and decomposition). For spectroscopic assignments
see Fig. 2. 1H NMR (299.9 MHz, CD3OD) d ppm: 2.67 (d,
4JPH = 5.0 Hz, 3H, CH3N), 2.95 (m, 4H, MeNCH2CH2), 3.08
(m, 4H, MeNCH2CH2), 3.83 (m, 2H, Ph2PCH2CH2), 3.96 (m, 2H,
Ph2PCH2CH2N), 7.58 (m, 4H, m-PhH), 7.60 (m, 6H, p-PhH), 7.96
(m, 4H, o-PhH) {NB. the resonance due to the solvent obscures
PhH), 7.50 (s, p-PhH), 11.72 (br s, m1 = 33.3 Hz, 1H, NH+);
2
1
3
13C{ H} (100.6 MHz, CDCl3) d ppm: 14.4 (d, JPC = 8.0 Hz,
CH2CH(CH3)N), 31.9 (s, Ph2PCH2CH), 42.7 (s, N(C4H8)NCH3),
46.3 (s, N(CH2CH2)2NCH3), 52.0 (s, N(CH2CH2)2NCH3), 56.9 (s,
Ph2PCH2CH), 127.4 (d, 3JPC = 7.5 Hz, m-PhC), 127.6 (d, 3JPC
=
7.5 Hz, m-PhC), 127.7 (s, p-PhC), 127.9 (s, p-PhC), 131.5 (d, 2JPC
=
2
19.5 Hz, o-PhC), 132.1 (d, JPC = 19.5 Hz, o-PhC), 137.5 (br s,
i-PhC); 31P{ H} (121.4 MHz, CDCl3) d ppm: −17.3 (s); MS (ES+,
1
MeOH) m/z: 343.4 [M–Cl + Me]+.
Synthesis of [PdCl2(1)], 6. To a Schlenk flask charged with
PdCl2(MeCN)2 (0.11 g, 4.24 × 10−4 mol) was added 1 (0.13 g,
4.26 × 10−4 mol) and CH2Cl2 (20 cm3). The mixture was stirred at
room temperature for 12 h, which resulted in the formation of a
fine yellow solid. The precipitate was isolated by cannula filtration,
washed repeatedly with hexane and diethyl ether and dried in vacuo
to afford 6 as a bright yellow powder (yield 0.14 g, 68%). (calc.:
C19H25N2PPdCl2 C, 46.59; H, 5.16; N, 5.72. Found: C, 46.17; H,
5.15; N, 5.82). For spectroscopic assignments see Fig. 2. 1H NMR
(400.1 MHz, D2O) d ppm: 2.78 (d, 4JPH = 5.1 Hz, 3H, Hg), 3.05 (m,
2H, Hf), 3.12 (m, 2H, Ha), 3.19 (m, 2H, Hd), 3.37 (m, 2H, Hb), 3.95
(m, 2H, He), 4.07 (m, 2H, Hc), 7.58 (m, 4H, m-PhH), 7.64 (m, 2H,
1
a 2H multiplet}; 13C{ H} (100.6 MHz, CD3OD) d ppm: 34.4 (d,
2
1JPC = 12.0 Hz, Ph2PCH2), 44.9 (d, JPC = 2.5 Hz, CH3N), 56.5
2
(s, MeN(C2H4)2), 57.0 (s, MeN(C2H4)2), 57.5 (d, JPC = 4.0 Hz,
Ph2PCH2CH2), 126.5 (d, 1JPC = 53.0 Hz, i-PhC), 129.4 (d, 3JPC
=
=
12.0 Hz, m-PhC), 132.6 (d, 4JPC = 2.5 Hz, p-PhC), 133.2 (d, 2JPC
1
11.5Hz, o-PhC); 31P{ H} (121.4 MHz, CD3OD) d ppm: +46.5;MS
(ES+, MeOH) m/z: 455.0 (M–Cl+); MS (ES−, MeOH) m/z: 97.0
([HSO4]−); KM (MeOH, 5 × 10−3 mol, 22.5 ◦C: 360 X cm2 mol−1).
1
p-PhH), 7.96 (m, 4H, o-(PhH); 13C{ H} 100.6 MHz, D2O) d ppm:
Synthesis of [PdCl(Me)(2-j2-PN)], 11. To a Schlenk flask
charged with PdClMe(COD) (8.40 × 10−2 g, 3.20 × 10−4 mol)
was added 1 (0.100 g, 3.20 × 10−4 mol) in CH2Cl2 (10 cm3).
The resulting mixture was allowed to stir at room temperature
for 18 h with all light excluded from the Schlenk flask. The
solvent was then removed under vacuum, the product extracted
with hexane and dried thoroughly in vacuo to afford a yellow
powder (yield 0.11 g, 76%). 1H NMR (499.8 MHz, CDCl3, 223 K)
d ppm: 0.51 (s, 3H, PdCH3), 2.21 (s, 3H, CH3N(C4H8)N), 2.38–
2.66 (m, 6H, MeN(C4H8)N, Ph2PCH2CH2 and MeN(C4H8)N),
2.73–2.93 (m, 4H, MeN(C4H8)N and Ph2PCH2CH2N), 4.12 (m,
2H, MeN(C4H8)N), 7.41–7.56 (m, 6H, m-PhH and p-PhH), 7.64
35.0 (d, 1JPC = 32.0 Hz, Ph2PCH2), 45.9 (s, CH3N), 57.0 (s, CH2),
1
57.6 (s, CH2), 58.0 (s, Ph2PCH2CH2), 126.0 (d, JPC = 52.5 Hz,
i-PhC), 130.3 (d, 3JPC = 11.5 Hz, m-PhC), 133.8 (d, 4JPC = 7.0 Hz,
2
1
p-PhC), 134.0 (d, JPC = 12.0 Hz, o-PhC); 31P{ H} (121.4 MHz,
D2O) d ppm: +45.7 (s); 31P{ H} (121.4 MHz, CD3OD) d ppm:
1
+46.5 (s); MS (MALDI ToF, Dithranol matrix) m/z: 455.0 (M–
Cl+); KM (MeOH, 5 × 10−3 mol, 22.5 ◦C: 68 X cm2 mol−1).
Synthesis of [PdCl2(2)], 7. An analogous procedure to that
used for the preparation of 6 was adopted, involving reaction of
PdCl2(MeCN)2 (0.17 g, 6.68 × 10−4 mol) with 2 (0.20 g, 6.68 ×
10−4 mol) in CH2Cl2 (20 cm3). This lead to the isolation of 7 as
a dull yellow powder (yield 0.21 g, 67%) (calc.: C18H22NOPPdCl2
C, 45.35; H, 4.66; N, 2.94. Found: C, 45.18; H, 4.57; N, 2.78). 1H
1
(m, 4H, o-PhH); 13C{ H} (125.7 MHz, CDCl3) d ppm: 30.8
1
(d, JPC = 27.5 Hz, Ph2PCH2CH2), 46.5 (s, CH3N(CH2CH2)2),
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49.3 (s, MeN(CH2CH2)2N), 50.6 (s, PCH2CH2N), 53.9 (s,
MeN(CH2CH2)2N), 129.3 (d, 3JPC = 11.0 Hz, m-PhC), 129.9 (s, i-
On gradual warming isomerisation to the j2-PN derivative was
complete on attaining 10 ◦C, at which temperature the onset of
rapid decomposition started to become apparent.
1
PhC), 131.6 (s, p-PhC), 133.6 (d, 2JPC = 12.5 Hz, o-PhC); 31P{ H}
(202.3 MHz, CDCl3) d ppm: +45.7 (s); MS (ES+) m/z: 433.0 [M–
Cl]+; MS (EI) m/z: 433.0 [M–Cl]+; 454.3 [M–CH3]+.
1
[PdMe2(1-j2-PN)], 13b. 31P{ H} (202.3 MHz, d8-toluene, 283
K): d ppm: +43.8 (s, [PdMe2(1-j2-PN)]).
Synthesis of [PdCl2(N-methylpiperazine-j2-NN)]2, 14. Ini-
tially, K2PdCl4 was prepared by treating an aqueous suspension
of PdCl2 (0.32 g, 1.80 × 10−3 mol) with KCl (0.27 g, 3.62 × 10−3
mol) in water (ca. 10 cm3) under air. The resulting orange-brown
solution was filtered and neat N-methylpiperazine (0.20 cm3,
1.80 × 10−3 mol) added dropwise, under air, which resulted in
the immediate precipitation of an orange solid. Complex 14 was
isolated by filtration and subsequent washing with ice-cold water
(2 × 1 cm3), EtOH (2 × 10 cm3), MeOH (2 × 10 cm3), Et2O
(3 × 10 cm3) and dried in vacuo, as an orange solid in 94% (0.47
g) yield. Crystals of X-ray quality were grown from a solution
containing a small sample 14 in a minimum of water by cooling
at 5 ◦C for 18 h (calc.: C5H12Cl2N2Pd C, 21.64; H, 4.37; N, 10.10.
Found: C, 21.33; H, 4.37; N, 9.82). 1H NMR (400.1 MHz, D2O)
d ppm: 2.49 (s, 3H, CH3N), 2.55 (pseudo-d, JHH = 7.6 Hz, 4H,
Synthesis of [PdMe2(1)], 13. To a Schlenk flask charged with
PdMe2(TMEDA) (0.15 g, 5.95 × 10−4 mol) in toluene (10 cm3) was
added a toluene solution of 1 (0.19 g, 5.95 × 10−4 mol, 10 cm3).
◦
The resulting mixture was stirred at −20 C with light excluded
from the reaction vessel for 45 min by which time analysis by 31
P
NMR spectroscopy showed the formation of the initial j2-NN
product. The solvent was then removed under vacuum affording
the product as a yellow-orange solid, which was stored at −30 ◦C to
preserve the j2-NN coordination of the ligand (0.20 g, 74%). NMR
analysis was undertaken by addition of d8-toluene to a sample of
13 held at −196 ◦C in the absence of light. The frozen solution
was transferred to the pre-cooled (−90 ◦C) probe of the NMR
spectrometer and gradually warmed to ambient temperature in
10 ◦C increments.
1
CH2), 3.80 (d, pseudo-d, JHH = 7.6 Hz, 4H, CH2); 13C{ H} NMR
(100.6 MHz, d6-DMSO) d ppm: 46.0 (CH3), 50.0 (HN(CH2)2),
54.8 (MeN(CH2)2); MS (ES+, MeCN/DMSO) m/z: 283.2 [M–
Cl + MeCN]+, 316.2 [M–Cl + DMSO]+
[PdMe2(1-j2-NN)], 13a. 1H NMR (499.8 MHz, d8-toluene,
253 K) d ppm: 0.55 (s, 3H, PdCH3), 1.05 (s, 3H, PdCH3),
2.15 (m, 4H, MeN(C4H8)N), 2.21–2.28 (m, 5H, Ph2PC2H4N
and CH3N(C4H8)N), 2.62 (m, 4H, MeN(C4H8)N), 2.90 (m, 2H,
Ph2PC2H4N), 7.22–7.27 (m, 8H, o-/m-PhH), 7.79 (m, 2H, p-PhH);
X-Ray crystallography
1
13C{ H} (125.7 MHz, d8-toluene, 223 K) d ppm: −2.3 (s, PdCH3),
The X-ray single crystal data were collected on Bruker 3-circle
diffractometers equipped with CCD area detectors SMART 1 K
(5 and 10) and SMART 6 K (1, 6b, 14). Graphite monochromated
15.4 (s, PdCH3), 26.6 (s, PCH2CH2), 51.4 (s, CH3N(CH2CH2)2N),
58.2 (s, MeN(CH2CH2)2N), 60.5 MeN(CH2CH2)2N), 63.8 (s,
PCH2CH2N), 133.4 (s, m-PhC), 133.6 (s, p-PhC), 134.4 (s, o-
˚
Mo Ka radiation (k = 0.71073 A) was used. The crystals were
1
PhC), 138.6 (s, i-PhC); 31P{ H} (202.3 MHz, d8-toluene, 223 K)
cooled using Cryostream (Oxford Cryostreams) open-flow N2
cryostats. Crystal data and other experimental details are given
in Table 5. Semi-empirical absorption corrections46 (based on
d ppm: +16.5 (s); due to the thermal sensitivity of the complex,
satisfactory MS and CHN data could not be obtained.
Table 5 Data collection and refinement parameters for compounds 1, 5 and complexes 6b, 10 and 14
1
5
6b
10
14
CCDC dep. No.
Empirical formula
Formula weight
T/K
605821
C19H25N2P
312.38
120
Monoclinic
P21/c (#14)
7.183(1)
7.348(1)
33.014(6)
90
90.10(1)
90
1742.4(6)
4
1.191
0.16
605822
C20H28N2PCl
362.86
120
Orthorhombic
Fdd2 (#43)
20.016(2)
68.506(9)
5.9460(7)
90
605823
C19H25Cl2N2PPd
489.68
120
605824
605825
C5H12Cl2N2Pd
277.47
120
Orthorhombic
Pnma (#62)
11.055(1)
8.1413(3)
9.399(1)
90
[C19H25ClN2PPd]2[H8MgO12S2]·6H2O
1305.05
120
Crystal system
Space group (No.)
Triclinic
P-1 (#2)
7.938(1)
9.597(1)
13.675(1)
75.08(1)
80.52(1)
88.71(1)
992.7(2)
2
Monoclinic
P21/c (#14)
16.925(2)
8.657(1)
18.077(2)
90
92.94(1)
90
2645.3(5)
2
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
V/A
Z
90
90
90
90
˚
8153.3(17)
16
1.182
0.27
16540
845.94(14)
4
2.179
2.75
11409
1316
qcalc/ g cm−3
l(Mo Ka), mm−1
Reflections: collected
unique
1.638
1.29
16957
5768
1.638
1.00
30538
7011
16022
4000
3952
with I > 2r(I)
3059
8.2
200
7.5, 20.1
3234
5.2
225
7.1, 16.4
4813
4.7
228
2.7, 6.1
6194
3.4
355
2.5, 5.7
1233
2.2
81
1.9, 4.8
Rint (%)
Refined variables
R1 and wR2 (%)a
ꢀ
ꢀ
ꢀ
ꢀ
2
a R1 = ꢀFc| − |Foꢀ/ |Fo| for reflections with I > 2r(I), wR2 = [ w(Fo − Fc2)2/ w(Fo2)2]1/2 for all data.
4144 | Dalton Trans., 2006, 4134–4145
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Laue equivalents) were performed for 5, 10 and 14. Crystals of
1 grow as pseudo-merohedral twins with the approximate twin
law of (−1 0 0/0 −1 0/0 0 1). The structures were solved by direct
methods and refined by full-matrix least squares against F2 of all
data using SHELXTL software.47 All non-hydrogen atoms were
refined in anisotropic approximation. All H atoms in 14 and those
H atoms hydrogen-bonding in 5 (NH+) and 10 (H2O) were refined
in isotropic approximation. Methyl groups were refined as rigid
bodies, other H atoms were included as ‘riding’ on C atoms.
CCDC reference numbers 605821–605825.
16 A. J. Amoroso, S. S. M. Cheng, D. J. E. Spencer, J. P. Danks, M. W.
Glenny, A. J. Blake, P. A. Cooke, C. Wilson and M. Schro¨der, Chem.
Commun., 2003, 2020.
17 M. L. Clarke, A. M. Z. Slawin and J. D. Woollins, Polyhedron, 2003,
22, 19.
18 M. Boiocchi, M. Bonizzoni, L. Fabbrizzi, F. Foti, M. Licchelli, A.
Taglietti and M. Zema, Dalton Trans., 2004, 653.
19 J. A. Aguilar, E. Garcia-Espan˜a, J. A. Guerrero, J. M. Llinares, J. A.
Ram´ıerez, C. Soriano, S. V. Luis, A. Bianchi, L. Ferrini and V. Fusi,
J. Chem. Soc., Dalton Trans., 1996, 239.
20 M. S. Rahman, J. W. Steed and K. K. Hii, Synthesis, 2000, 1320.
21 M. Oliana, F. King, P. N. Horton, M. B. Hursthouse and K. K. Hii,
J. Org. Chem., 2006, 71, 2472.
22 M. Bassett, D. L. Davies, J. Neild, L. J. S. Prouse and D. R. Russell,
Polyhedron, 1991, 10, 501.
23 A very brief report of the use of 2 as a ligand for Rh(I) has appeared,
although to the best of our knowledge its synthesis has not been
described: B. A. Boyce, A. Carroy, J.-M. Lehn and D. Parker, J. Chem.
Soc., Chem. Commun., 1984, 1546.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b605995c
Acknowledgements
The EPSRC and Durham University (CEA); the Nuffield Foun-
dation and The Royal Society (PWD) are acknowledged for
financial support. Dr A. M. Kenwright, Mrs C. F. Heffernan
and Mr I. H. McKeag are gratefully thanked for their assistance
with the acquisition and interpretation of solution-phase NMR
spectroscopy. The EPSRC Solid State NMR service (DCA and
Mr F. Markwell) is acknowledged for the acquisition of solid-state
NMR spectra data and the EPSRC National Mass Spectrometry
Service at the University of Wales, Swansea, for FAB mass
spectrometric data. Johnson Matthey is thanked for the loan of
palladium salts.
24 R. A. Spragg, J. Chem. Soc. B, 1968, 1128.
25 D. Cavalla, W. B. Cruse and S. Warren, J. Chem. Soc., Perkin Trans. 1,
1987, 1883.
26 D. J. Collins, S.-A. Mollard, N. Rose and J. M. Swan, Aust. J. Chem.,
1974, 27, 2365.
27 C. E. Anderson, A. S. Batsanov, P. W. Dyer and J. A. K. Howard,
manuscript in preparation.
28 G. Tamasi and R. Cini, Dalton Trans., 2003, 2928.
29 A. Habtemariam, B. Watchman, B. S. Potter, R. Palmer, S. Parsons,
A. Parkin and P. J. Sadler, J. Chem. Soc., Dalton Trans., 2001,
1306.
30 B. Mohr, D. M. Lynn and R. H. Grubbs, Organometallics, 1996, 15,
4317.
31 P. S. Pregosin and R. W. Kunz, in 31P and 13C NMR of Transition Metal
Complexes, ed. P. Diehl, E. Fluck and R. Kosfeld, Springer-Verlag,
Berlin, 1979.
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