Coordination chemistry of cis,cis and trans,trans 1,1′-[1,2- phenylenebis(methylene)]bis(2,2,3,4,4-pentamethylphosphetane)

Article abstract of DOI:10.1039/b924982f

The cis,cis (5) and trans,trans (9) forms of the bidentate ligand 1,1′-[1,2-phenylenebis(methylene)]bis(2,2,3,4,4-pentamethylphosphetane) have been prepared from common precursors using two separate synthetic routes. The cis,cis isomer is attained selecti

Full text of DOI:10.1039/b924982f

View Article Online / Journal Homepage / Table of Contents for this issue
PAPER
www.rsc.org/dalton | Dalton Transactions
Coordination chemistry of cis,cis and trans,trans
1,1¢-[1,2-phenylenebis(methylene)]bis(2,2,3,4,4-pentamethylphosphetane)†
Dennis Coleman, Peter G. Edwards,* Benson M. Kariuki and Paul D. Newman
Received 27th November 2009, Accepted 19th February 2010
First published as an Advance Article on the web 11th March 2010
DOI: 10.1039/b924982f
The cis,cis (5) and trans,trans (9) forms of the bidentate ligand 1,1¢-[1,2-phenylenebis(methylene)]bis-
(2,2,3,4,4-pentamethylphosphetane) have been prepared from common precursors using two separate
synthetic routes. The cis,cis isomer is attained selectively through the direct reaction of two mol
equivalents of 2,2,3,4,4-pentamethylphosphetane with a,a¢-dibromo-o-xylene in acetone. Protection of
the 2,2,3,4,4-pentamethylphosphetane with BH3 and conversion to the lithium phosphido-borane prior
to adding the a,a¢-dihalo-o-xylene leads to the isolation of the trans,trans isomer of 1,1¢-[1,2-
phenylenebis(methylene)]bis(2,2,3,4,4-pentamethylphosphetane). Both isomers have been fully
characterised by spectroscopic and, in the case of the all-cis isomer, single-crystal X-ray methods. The
two isomers have been coordinated to Mo(0) to give complexes of the type cis-Mo(CO)4(L). The solid
state structures of cis-Mo(CO)4(5), 10, and cis-Mo(CO)4(9), 12, have been determined by single-crystal
X-ray methods and reveal significant differences between the two forms, most notably in the chelate bite
angle which is 100.68(18)◦ in 10 compared to 88.12(2)◦ in 12. Ligand 5 has also been coordinated to
Pd(II) and Pd(0) and the structure of the complex Pd(5)Cl2 (11) determined by single-crystal methods.
The solid-state structure of Pd(5)Cl2 reveals a significant tetrahedral distortion from the normal square
planar geometry.
The success of chiral diphospholanes in asymmetric catalysis
paved the way for the exploration of other phosphacycles and
The 4-membered phosphetanes belong to a homologous series of
recent work by Marinetti has shown bidentate phosphetanes
Introduction
to be useful ligands in asymmetric catalysis.5 Although gener-
ally inferior to the related phospholane systems, complexes of
bidentate phosphetanes show unusual properties under certain
catalytic conditions that has prompted further investigation of this
ligand class.6 However, although these 4-membered heterocycles
remain a fascination, a cautionary note that may restrict their
potential in catalysis is provided by Glueck who demonstrated
that coordinated phosphetanes can be susceptible to ring-opening
under relatively mild conditions.7
Our combined interest in phosphacycles and the coordination
chemistry of bidentate phosphorus donors with an ortho-xylyl
backbone led us to explore the synthesis and subsequent com-
plexation chemistry of systems of the general type o-C6H4(cyc-
C3P)2 where cyc-C3P represents a phosphetane ring. Surpris-
ingly, very little coordination chemistry has been reported for
the Me2CC(Me)CMe2 bridged phosphetane (abbreviated as cyc-
C3Me5P for our purposes) originally reported by McBride and,
to our knowledge, there are no examples of bidentate ligands
containing such donors. This apparent neglect invoked our interest
and the current paper presents the results of investigations of new
bidentate phosphetanes.
saturated heterocyclic compounds containing a single phosphorus
atom. Examples of a wide variety of these compounds are
known in the chemical literature from three membered phos-
phiranes through to the larger ring phospholanes (5-membered
ring), phosphinanes (6-membered), phosphepanes (7-membered)
and phosphocanes (8-membered). The first synthesis of a C3P
ring was reported by Kosolapoff and Struck who produced a
phosphetane in poor yield via the Michaelis Arbuzov coupling
of triethylphosphite with 1,3-dibromopropane.1 The first general
method for the formation of phosphetanes came from the AlCl3
catalysed addition of PCl3 to an electron-rich olefin in what is
now known as the McBride synthesis.2 However, this route is
inherently limited and has been largely superseded by a more
general methodology utilising di-lithiumphosphide reagents and
1,3-di-electrophiles, most notably cyclic sulfates.3
Phosphetanes have a folded structure with the fold angle (made
by the in◦tersection of the C–C–C and C–P–C planes) being
between 0 and 30◦.4 The direction of the fold is usually dictated
by the steric size of the substituents at the phosphorus and the
C3 carbon of the ring; phosphetanes substituted at the 1- and 3-
positions can produce cis and/or trans isomers. P–C bond lengths
˚
are in the range of 1.79-1.96 A for monocyclic phosphetanes (P–C
˚
for classical acyclic phosphines is 1.84 A) and the internal C–P–C
angle is usually compressed to 76-86◦.
Results and discussion
Ligand synthesis
School of Chemistry, Cardiff University, Cardiff, UK CF10 3AT. E-mail:
edwardspg@cardiff.ac.uk; Fax: 029 20874030; Tel: 029 20874083
The synthetic procedure for the preparation of the desired o-
C6H4(CH2-cyc-C3Me5P)2 is shown in Scheme 1. The precursor
† CCDC reference numbers 756177–756180. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b924982f
3842 | Dalton Trans., 2010, 39, 3842–3850
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
Scheme 1 Synthesis of ligands 5 and 9 and the metal complexes 10-12.
compound for the synthesis of the phosphetane, and ulti-
mately the bidentate ligand, is the 1-chloro-2,2,3,4,4-pentamethyl-
phosphetane-1-oxide originally reported by McBride.2 Minor
modification of the reported procedure gave 1 in increased yield
and higher purity than that reported (see experimental). It was
found that samples of 1 were unstable when left in air as
a consequence of slow hydrolysis of the P–Cl bond and the
compound was best stored in a dry nitrogen or argon atmosphere.
heterocycle, to our knowledge no examples of a bidentate ligand
containing this heterocycle have been reported. Part of our interest
in this phosphetane stems from the fact that it can be considered
as a ‘tied-back’ di-tert-butylphosphine derivative and, although
it is not expected to share the electronic or steric properties
of the acyclic form, we wished to explore the relationship
between the phosphetane and the acyclic species. As alluded
above, for historical and other reasons our backbone of choice
was the 1,2-ortho-xylyl bridge. Thus, 1,2-bis-cis,cis-(2,2,3,4,4-
pentamethylphosphetanemethyl)benzene, 5, was prepared using
a reaction scheme analogous to that described by Moulton and
Shaw (Scheme 1).9 The initially formed phosphonium dihydro-
1
1
The 31P{ H}, 1H and 13C{ H} NMR spectra of 1 were found to be
1
consistent with those previously reported.8 The 31P{ H} NMR
spectrum consists of a singlet at dP 82.9 ppm indicative of a
1
single isomer of 1. The H NMR spectrum shows a doublet at
dH 0.92 ppm (3JH–H = 7.1 Hz), which is assigned to the protons of
the methyl group at the 3 position of the ring, and two doublets at
dH 1.31 ppm, (3JH–P = 11.0 Hz) and dH 1.38 (3JH–P = 9.3 Hz) ppm
for the 12 hydrogens of the methyl groups at the 2 and 4 positions
of the ring. The unique hydrogen on the C3 carbon was seen as
a multiplet at dH = 1.78 ppm. LiAlH4 reduction of 1 gave the
phosphetane 2 as a volatile liquid in 80% yield. The compound
has an unpleasant odour typical of secondary phosphines and,
as observed previously, was isolated as a 9 : 1 mixture of trans:cis
isomers.
bromide (3) gave a 31P{ H} NMR spectrum that consisted of
1
three singlets of relative intensity 16 : 4 : 1 at dP 49.7, 39.5 and
36.0 ppm reflecting the presence of at least three species as might be
anticipated considering the starting phosphetane (2) is a mixture of
two isomers. The nature of the phosphonium salt 3 was confirmed
by 31P NMR spectroscopy where the coupling to the P–H proton
gave the familiar doublet of multiplets pattern of a R3PH+ group
1
with a large JP–H coupling constant of 467 Hz. Analysis of the
reaction mixture after isolation of 3 showed a major resonance at
1
dP 92.2 ppm in the 31P{ H} NMR spectrum that is assigned to the
Although 2 was one of the first phosphetanes to be readily
accessed in gram quantities and is a simple example of a bulky C3P
R4P+ type phosphonium salt 4 which is a typical by-product of
this synthetic route.9
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3842–3850 | 3843
©

View Article Online
Reaction of the hydrobromide salt 3 with a base (sodium
bicarbonate) led to the corresponding 16 : 4 : 1 isomeric mixture of
phosphines in modest yield (38%). Subsequent recrystallisation of
this mixture from hot methanol gave a single isomer as colourless
needles. As the exact structure of this single isomer was not known,
a single-crystal X-ray structure determination was performed to
elucidate the configuration (Fig. 1). The ligand adopts the all-
cis configuration as confirmed in Fig. 1; this is not unexpected
as electrophilic addition via a SN2 mechanism to the major
trans-phosphetane 2 should give the cis,cis isomer as the major
product. All metric data compare with those for the reported
2,2,3,4,4-pentamethylphosphetanes10 with the mean torsion angle
of 21.25◦ for the ring being within the range expected (0-30◦) for a
phosphetane.11 The mean C–P–C angle◦of 77.9(2)◦ lies towards the
lower end of the known range of 76-86 for related compounds.11
No inversion of configuration of the phosphetane rings was
observed for 5 after prolonged periods at elevated temperature
(110 ◦C, 48 h) which is consistent with the observations of Cremer
et al.,12 who found the related 1,2,2,3,4,4-hexamethylphosphetane
to be configurationally stable. However, the 1-phenyl and 1-tert-
butyl analogues did invert under similar conditions.12
In order to isolate the trans,trans form of the bidentate ligand
(9), it was necessary to protect the secondary phosphetane as the
borane adduct to enable the generation of a nucleophilic lone
pair orientated trans to the C3 methyl (provided no inversion
occurred during formation of the borane adduct and/or sub-
sequent generation of the phosphido species) as highlighted in
Scheme 1. Aside from this desired stereocontrol, the use of BH3
as a protecting agent should help to suppress formation of the
familiar, unwanted cyclic monophosphonium species 4. Reaction
of 2,2,3,4,4-pentamethylphosphetane, 2, with an excess of borane-
THF adduct afforded 6 as a colourless low-melting solid in near
1
quantitative yield. The 31P{ H} NMR spectrum of 6 consisted
1
of two four line resonances at dP 58.0 and 55.7 ppm with JP–B
values of 29.8 and 32.8 Hz, respectively; the same 9 : 1 ratio of
isomers (cis:trans) was observed indicating that no isomerism had
1
taken place during the formation of the BH3 adduct.‡ The 11B{ H}
1
NMR spectrum was concordant with the 31P{ H} NMR spectrum
in that two doublets were observed in a 9 : 1 ratio at dB -44.6 and
1
-43.8 ppm. The H NMR spectrum of the cis isomer could be
assigned (see experimental) and showed characteristic doublets
for the protons of the C3 methyl group at dH 0.92 ppm (3JH–H
=
7.3 Hz) and the methyl groups at the 2 and 4 position of the ring
at dH 1.32 ppm (3JH–P = 11.6 Hz). The final ring proton at C3
was observed as a quartet with a chemical shift of dH 2.60 ppm
(3JH–H = 7.3 Hz). The P–H proton was observed as a doublet of
2
four lines at dH 5.17 ppm (1JH–P = 331.9 Hz, JH–B = 6.2 Hz).
Partial NMR spectroscopic data for the minor trans isomer of
6 is given in the experimental section. Upon deprotonation with
n-BuLi at low temperature, the two four line patterns of 6 are
seen to shift to lower field with the protected lithium phosphides
7 being observed at dP 23.9 ppm (1JP–B 29.8 Hz, cis isomer) and
1
dP 30.1 ppm (1JP–B 29.8 Hz, trans isomer) in the 31P{ H} NMR
1
spectrum. Two doublets were observed in the 11B{ H} NMR
spectrum with chemical shifts of dB -37.3 ppm (cis isomer) and
dB -35.8 ppm (trans isomer). Again the 9 : 1 ratio of cis:trans
isomers is maintained upon deprotonation suggesting that the
configurational integrity of the species is maintained during de-
protonation as indicated in the scheme. Addition of 0.5 equivalents
of a,a¢-dichloro-o-xylene gave, after work-up, 1,2-bis-trans,trans-
(2,2,3,4,4-pentamethylphosphetanemethyl)benzene diborane, 8,
Fig. 1 Crystal structure of 5. Thermal ellipsoids are drawn at 50%
˚
probability, hydrogens are omitted for clarity. Selected bond lengths (A)
and angles(◦) for 5: P1-C7 1.864(4), P1-C8 1.882(5), P1-C10 1.887(4),
P2-C16 1.862(4), P2-C17 1.899(5), P2-C19 1.888(5), C8-P1-C10 78.18(19),
Cl7-P2-C19 77.5(2).
1
1
The 31P{ H} NMR spectrum consists of a singlet with a
in 89% yield (Scheme 1). The 31P{ H} NMR spectrum of 8
chemical shift of dP 29.3 ppm as expected for two chemically
revealed a broad resonance with a chemical shift of dP 66.4 ppm.
As expected, alkylation of the 2◦-phosphetane-borane adduct to
form the 3◦ phosphetane-borane adduct produced a downfield
shift of 8.4 ppm. It was not obvious how many isomers were
and magnetically equivalent phosphorus atoms. This position lies
1
upfield of the 31P{ H} signals for the two other isomers (observed
in solution before recrystallisation from MeOH) which are seen at
dP 42.5 and 60.0 ppm; this accords with the observation of Cremer
where cis forms of 1,3-disubstituted phosphetanes have chemical
1
present from the 31P{ H} NMR spectrum but it seems likely
that an isomeric mixture was present as, upon deprotection,
an isomeric mixture of phosphines was obtained (see below).
1
shifts 20 to 30 ppm upfield of the trans forms. The H NMR
1
spectrum showed the basic pattern of resonances now familiar
to the pentamethylphosphetane unit8 with the methyl protons
The 11B{ H} NMR spectrum consisted of a broad resonance
1
at dB -43.0 ppm. The H NMR spectrum was also found to be
adjoining the 3 position of the ring giving a doublet at dH
=
consistent with the proposed structure of 8 (see experimental).
Deprotection of 8 gave the free phosphine 9 as a 16 : 4 : 1 mixture
of isomers. However, the distribution of products was different to
that previously observed in the reaction with unprotected 2. As
anticipated from the chemistry outlined in Scheme 1, the reaction
0.84 ppm (3JH–H = 7.1 Hz) and the twelve protons of the methyl
groups at the 2 and 4 positions of the ring being seen as two
doublets at dH 1.20 and dH 1.24 ppm. The methine proton at
the 3 position of the ring was observed as the familiar quartet
with a chemical shift of dH 2.26 ppm (3JH–H = 7.1 Hz). The xylyl
CH2 groups are observed as a broadened singlet in the 1H NMR
‡ No isomerisation has occurred but the CIP priority of the groups
attached to the P-atom has changed such that cis-6 derives from trans-
2 upon formation of the BH3 adduct.
spectrum at 3.07 ppm and as a doublet at 32.5 ppm (1JC–P
=
1
27.7 Hz) in the 13C{ H} NMR spectrum.
3844 | Dalton Trans., 2010, 39, 3842–3850
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
the related cis-Mo(CO)4{o-C6H4(CH2PtBu2)}2 system a P–Mo–P
angle of 94.16◦ is observed.14 Acute P-M-P angles in bidentate
systems with ortho-xylyl backbones push the xylyl ring into an
orthogonal orientation with respect to the P2ML2 plane as is
evident in Fig. 3. In this orientation, the phenyl ring is in close
proximity to one of the carbonyl donors (labelled C4-O4 in
Fig. 3) resulting in the Mo-C4-O4 bond angle being compressed to
168.7(2)◦ compared to 177.53(19)◦ for the equivalent angle in 10.
The close contact is further highlighted by the distance between
the centroid of the aromatic ring and the midpoint of the C4-O4
of 7 with o-C6H4(CH2Cl)2 produced, after deprotection, the
bidentate ligand with phosphetane rings in the trans configuration
as the major product. This predominant trans-isomer, 9, has
a chemical shift of dP 42.6 ppm, ~13 ppm downfield of that
observed for the cis form, 5. This observation is consistent
with previous work.8 9 was purified by recrystallisation from
hot methanol to give fine colourless needles of a single isomer.
Unfortunately, the crystals were not suitable for determination
1
of the solid-state structure by X-ray diffraction. The 31P{ H}
NMR spectrum of 9 consists of a single peak at dP 42.6 ppm
highlighting the chemical equivalence of the two phosphorus
atoms. The 1H NMR spectrum has the familiar pattern of peaks
seen for the compounds previously described. The only significant
˚
˚
bond which is 3.011 A in 12 and 4.139 A in 10. Surprisingly, the
larger bite angle in 10 does not lead to significant compression of
the C1-Mo1-C3 angle with the observed value of 83.35(9)◦ being
very similar to the equivalent angle in 12 {84.13(11)◦}. It is not
easy to rationalise why the cis form of the ligand adopts, at least
in the solid-state, a large P–Mo–P bite angle while the trans form
has a small P–Mo–P angle. Unsurprisingly, there is little difference
in the geometric features of the phosphetane rings with the mean
fold angle being 20.20◦ in 10 and 17.3◦ in 12. One difference
between the two Mo(0) structures is in the relative ‘puckering’ of
the four-membered rings (Fig. 4). In 12, the C21-C23 hinge of
the C3P envelope is on the Mo side of the P-C22 vector so that
each C22 carbon approaches its nearest xylyl CH2 carbon at an
1
difference between the H NMR spectra of the two isomers of
1,2-bis(2,2,3,4,4-pentamethylphosphetanemethyl)benzene is that
the C3-H resonance is shifted 0.45 ppm downfield (dH 2.71 ppm,
3JH–H = 7.3 Hz) in the trans- form relative to the cis isomer, again
in accordance with previous observations.8
Molybdenum(0) complexes
Addition of either 5 or 9 to cis-Mo(CO)4(C5H11N)2 gave buff
coloured solids which could be recrystallised from CHCl3–
MeOH to give colourless crystals of cis-Mo(CO)4(5), 10, and cis-
Mo(CO)4(9), 12. The solid state structures of both 10 and 12 are
shown in Fig. 2 and 3. There are a number of significant differences
in the solid state structures of the two complexes, most notably in
the values of the P–Mo–P “bite” angles which are 100.682(18)◦
in 10 and 88.12(2)◦ in 12. Ortho-xylyl backbones are known to
be flexible with reported bite angles ranging from ~87 to ~115◦
depending, to a large degree, on the steric demands of the other
substituents on the P-donors.13 Wider P-M-P angles are often seen
with bulky groups on the phosphorus donors and are associated
with the xylyl backbone adopting a flattened arrangement with
regard to the P2ML2 plane with the CH2 carbons of the chelate
backbone tending towards coplanarity with the P2ML2 plane. In
˚
average distance of 3.286 A, whereas in 10 it is more distant at an
˚
average 3.803 A as the hinge lies towards the backbone rather than
the metal (Fig. 4). This may have as much to do with the desire
of the C22-methyl to minimise unfavourable contacts within the
phosphetane ring as it does with undesirable contacts with the
o-xylyl backbone.
Fig.
3
Crystal structure of 12. Thermal ellipsoids are drawn at
50% probability, hydrogens are omitted for clarity. Selected bond
lengths (A) and angles (◦) for 12: P1-Mo1 2.5588(7), P2-Mo1
˚
2.5599(6), Mo1-C1 1.968(3), Mo1-C2 2.021(3), Mo1-C3 1.988(3),
Mo1-C4 2.055(3), P2-Mo1-P1 88.12(2), C1-Mo1-P1 91.69(8), C2-Mo1-P1
94.15(8), C3-Mo1-P1 175.79(7), C4-Mo1-P1 94.16(8), C1-Mo1-P2
173.44(10), C2-Mo1-P2 97.88(8), C3-Mo1-P2 95.99(7), C4-Mo1-P2
90.61(7), C13-P1-C15 77.12(12), C21-P2-C23 77.71(12).
Fig. 2 Crystal structure of 10. Thermal ellipsoids are drawn at 50% prob-
ability, hydrogens are omitted for clarity. Selected bond lengths (A) and
The mean bond lengths (Mo–C) for the carbonyl ligands
˚
˚
trans to the phosphine ligand are 1.991(2) A for 10 and
angles (◦) for 10: P1-Mo1 2.5427(5), P2-Mo1 2.5451(6), Mo1-C1 1.993(2),
Mo1-C2 2.028(2), Mo1-C3 1.988(2), Mo1-C4 2.038(2), P2-Mo1-P1
100.682(18), C1-Mo1-P1 88.07(6), C2-Mo1-P1 88.07(7), C3-Mo1-P1
171.42(6), C4-Mo1-P1 86.81(6), C1-Mo1-P2 170.98(7), C2-Mo1-P2
86.59(7), C3-Mo1-P2 87.89(6), C4-Mo1-P2 87.82(6), C13-P1-C15
77.82(10), C21-P2-C23 77.80(9).
˚
1.978(3) A for 12 and are, as expected, marginally shorter
than those of the carbonyl ligands cis to the phosphine which
˚
˚
average 2.033(2) A in 10 and 2.038(3) A in 12. The mean P–
˚
Mo bond length in 10 is 2.544(1) A compared to 2.559(1) in
12 although both are significantly shorter than the value of
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3842–3850 | 3845
©

View Article Online
7.65 ppm regions; this is consistent with that observed by previous
workers on related systems.15
The Pd(5)Cl2 complex was synthesised via displacement of
the dba ligand in complex Pd(5)(dba) by chloride using anhy-
drous HCl in diethyl ether in the presence of an oxidant (1,4-
p-benzoquinone). The desired complex precipitated from the
reaction mixture as a yellow solid. Crystals of Pd(5)Cl2 were
grown by vapour diffusion of diethyl ether into a concentrated
THF solution of the complex to give Pd(5)Cl2 as a crop of yellow
to orange coloured crystals. A small amount of red crystals were
also isolated, and subsequently found to be the THF solvate. The
solid state structure was determined via X-ray diffraction, and
is shown in Fig. 5. The most striking feature of the structure
is the deviation from the expected square-planar geometry. The
extent of this distortion is emphasised by the extent to which
the two chloride ligands are twisted out of the P1-Pd1-P2 plane;
the angle between this plane and the Cl2 ◊ ◊ ◊ Cl1 vector is 22.5◦.
Similar, albeit smaller, distortions have been observed previously
in Pd(II) complexes containing bulky ligands.17 The origin of such a
distortion is not clear as the phosphetane units are relatively slight
in steric terms and not anticipated to lead to such a digression
from square planar geometry and it may be that the demands
of the xylyl backbone are responsible for the distortion as has
been suggested for related species in solution.20 The most stable
conformation of the ligand has been suggested to be the C2
symmetric “scorpionate” arrangement, similar to that observed
in the solid state structures of 10 and 12 where the o-xylene moiety
“hangs” below the x-y coordination plane.13f
Fig. 4 Orientation of the phosphetane substituents in complex 10 (top)
and 12 (bottom).
t
14
˚
2.658(1) A for the cis-Mo(CO)4{o-C6H4(CH2P Bu2)}2 complex.
The related cis-Mo(CO)3(C3H6PPh)3 which contains monodentate
15
˚
1-phenylphosphetane has Mo–P bond lengths of 2.501(1) A.
The 31P{ H} spectra of 10 and 12 consist of singlets at dP 69.9
1
and 84.1 ppm showing typical coordination shifts. The 1H and 13
C
NMR spectra of both complexes are largely unremarkable. Ions
for the M+ fragment and the M+ fragment after the loss of one
CO were observed in the APCI mas spectra at m/z 598 (M+) and
m/z 570 (M+ -CO). The infra-red spectrum of 10 recorded as a
KBr disc showed three bands in the carbonyl region at nCO = 1848,
1915 and 2014 cm-1, the first of which has an obvious shoulder.
The infrared spectrum of 12 is closely analogous to that of 10
although four bands were clearly evident in the carbonyl region at
nCO = 1857, 1877, 1912 and 2016 cm-1.
Palladium(0/II) complexes
Fig. 5 Crystal structure of 11. Thermal ellipsoids are drawn at 50%
probability, hyd◦rogens are omitted for clarity. Selected bond lengths
The zerovalent palladium complex Pd(5)(dba) was isolated as an
˚
(A) and angles( ) for 11: P1-Pd1 2.2474(7), P2-Pd1 2.2650(7), Pd1-Cl1
orange solid in 76% yield from the reaction of 1 mol equivalent of
2.3781(7), Pd1-Cl2 2.3628(7), P2-Pd1-P1 92.36(2), Cl1-Pd1-P1 165.17(3),
Cl2-Pd1-P1 93.79(3), Cl1-Pd1-Cl2 89.37(2), Cl1-Pd1-P2 86.67(2),
Cl2-Pd1-P2 170.03(2), C1-P1-C6 79.64(12), C9-P2-C14 78.85(13).
1
5 with Pd(dba)2 in THF. The 31P{ H} NMR spectrum recorded
at RT consisted of two broad resonances at dP 58.3 and 64.4 ppm
reflecting inequivalence between the two P-donors and the absence
of any C2 axis or plane of symmetry in the complex. This is
not surprising, as dba may bind in a number of different ways
at a metal centre, usually through only one of the two alkene
functions.16 The dynamic behaviour of coordinated dba is well
known and systems such as (R2PCH2CH2PR2)Pd(dba) have been
˚
The mean P–Pd bond length of 2.256(7) A is somewhat shorter
than that observed for the Pd–P(phosphetane) bond in the singly
ring-opened complex of Glueck where a value of 2.3791(10) was
observed,7 however, this latter complex has a P–Pd–P bite angle
of 99.77◦ appreciably larger than that observed here {92.36(2)◦}.
The relatively acute bite angle in Pd(5)Cl2 is accommodated by
the xylene ring adopting the so-called scorpionate conformation
(Cs) with the xylyl CH2 groups out of the P–Pd–P plane. The
1
examined in detail.15 Observation of the 31P{ H} NMR spectra
at low temperature (248 K) revealed the presence of a host of
species in solution as indicated by a complex pattern of peaks.15
1
The H NMR spectrum of Pd(5)(dba) at this low temperature
˚
revealed resonances from the hydrogens of both coordinated and
uncoordinated alkene groups of the dba ligand in the dH 5.03 and
Pd–Cl bond lengths average 2.370(7) A and are unremarkable. In
common with 10 and 12 the mean C–P–C angle of 79.25(13)◦ and
3846 | Dalton Trans., 2010, 39, 3842–3850
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
C–C–C angle of 100.8(2)◦ for the phosphetane ring remain largely
reaction mixture over 3 h. The addition was performed cautiously
at first due to the exothermic nature of the reaction. After addition
of the methanol, the reaction was stirred at 0 ◦C for a further 0.5 h,
ice-cold water (200 ml) added to the cooled reaction mixture and
the organic layer isolated via cannula. After drying over Na2SO4,
the solution was filtered and the solvent removed under reduced
pressure to yield the product as fine off-white crystals that were
unchanged from that of the free ligand 5. The room temperature
1
31P{ H} NMR spectrum consisted of a singlet with a chemical
shift of dP 84.0 ppm indicating that the two-phosphine donors are
in a time-averaged chemically equivalent environment suggesting
flexibility in the xylyl backbone as observed with related systems.13
The 1H NMR spectrum showed the usual pattern of peaks for the
2,2,3,4,4-pentamethylphosphetane functionality.
1
dried carefully under vacuum. Yield = 21.6 g (82%). 31P{ H} NMR
2
1
The monoligand ethylene complex [Pd(5)(h -C2H4)] was syn-
(CDCl3, 121.65 MHz): d 82.9 (s) ppm. H NMR (CDCl3, 300
5
3
thesised via the reaction of 5 with [(h -C5H5)(h -C3H5)Pd] in
MHz): 0.92 (3H, d, 3JH–H = 7.1 Hz), 1.31 (6H, d, 3JH–P = 11.0 Hz),
cold (-40 ◦C) diethyl ether under an atmosphere of ethylene. The
1.38 (6H, d, JH–P = 9.3 Hz), 1.78 (1H, m) ppm. 13C{ H} NMR
3
1
1
2
31P{ H} NMR spectrum of [Pd(5)(h -C2H4)] when recorded at
room temperature consisted of a single broad resonance at dP
54.8 ppm. The broadening was presumably due in part to the
Cs ↔ C2 chelate ring interconversion and also to the propeller
like rotation of the C2H4 ligand around the metal-ethylene s-
bond. At low temperature (258 K) the broad resonance in the
(CDCl3, 75.56 MHz): 7.31 (d, JC–P = 30.2 Hz), 18.23 (d, JC–P =
4.1 Hz) 25.96 (d, JC–P = 6.8 Hz), 42.29 (d, JC–P = 1.8 Hz), 56.87
(d, JC–P = 56.0 Hz) ppm. MS (APCI): m/z 159.1 (M, -Cl).
2,2,3,4,4-Pentamethylphosphetane, 2. To a cooled slurry of
LiAlH4 (0.11 g, 2.83 mmol) in Et2O (20 ml) at 0 ◦C was added
slowly a solution of 1-chloro 2,2,3,4,4 pentamethylphosphetane-
1-oxide (0.5 g, 2.57 mmol) in Et2O (20 ml). The solution was
stirred for a further 1 h at 0 ◦C before allowing to warm to room
temperature and stirring for a further 24 h. Water (1 ml) was
added to the cooled (0 ◦C) reaction mixture cautiously via cannula
fo◦llowed by 15% NaOH solution (4 ml) and the solution stirred at
0 C for a further 0.5 h. The Et2O layer was isolated, dried over
anhydrous Na2SO4, filtered and the Et2O removed by distillation to
yield the 2,2,3,4,4 pentamethylphosphetane as a malodorous clear
liquid. Yield = 0.28 g (80%). Spectroscopic analysis revealed a 9 : 1
1
31P{ H} spectrum resolved into two doublets (2JP–P = 23.8 Hz)
consistent with the observations for the Pd(II) systems above and
likely reflecting the presence of the asymmetric form of the o-xylyl
backbone. The 1H NMR spectrum consisted of the usual pattern
of resonances for the diphosphetane ligand and a broadened
2
resonance for the h -ethylene ligand which was invariant over the
studied temperature range suggesting rapid alkene rotation at all
recorded temperatures.
Experimental
1
mixture of trans:cis isomers. For trans 2: 31P{ H} NMR (CDCl3,
121.65 MHz): d 17.0 (s) ppm. 1H NMR (CDCl3, 300 MHz): 0.79
(3H, d, 3JH–H = 7.0 Hz), 1.22 (12H, d, 3JH–P = 7.9 Hz), 2.68 (1H,
Methods and materials
All compounds were prepared using standard Schlenk techniques
under an atmosphere of dinitrogen or argon. 31P (referenced to
H3PO4 at dP = 0) and 11B (referenced to Et2O.BF3 at dB = 0)
NMR data were collected on a Jeol Eclipse 300 MHz spectrometer
and 1H and 13C data on a Bruker 400 MHz DPX Avance.
Mass spectra (ES and APCI) were obtained on a VG Fisons
Platform II mass spectrometer. Tetrahydrofuran, Diethyl ether
and hexane were dried over sodium benzophenone, toluene over
sodium and methanol and acetonitrile over calcium hydride.
Water used during the work-up of all compounds was carefully
deoxygenated by several cycles of heating at reflux and cooling
to room temperature under a nitrogen purge. Deuterated solvents
31
q, 3JH–H = 7.0 Hz), 3.78 (1H, d, 1JH–P = 176.1 Hz) ppm. 1H{ P}
NMR (CDCl3, 300 MHz): 0.79 (3H, d, 3JH–H = 7.0 Hz), 1.23 (12H,
3
1
s), 2.68 (1H, q JH–H = 7.1 Hz), 3.78 (s br) ppm. 13C{ H} NMR
(CDCl3, 75.56 MHz): 10.24 (s), 23.16 (d, JC–P = 25.4 Hz), 27.58
(d, JC–P = 11.5 Hz), 33.18 (s), 56.64 (d, JC–P = 5.9 Hz) ppm. Partial
data for cis-2: 31P{ H} NMR (CDCl3, 121.65 MHz): d 14.7 (s)
1
ppm. 1H NMR (CDCl3, 300 MHz): 0.87 (3H, d, 3JH–H = 7.2 Hz),
1
31
1.18 (12H, d, br) ppm. H{ P} (CDCl3, 300 MHz): 1.21 ppm
(12H, s) ppm.
1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-penta-
methylphosphetane), 5. An acetone solution (70 ml) of a,a¢-
dibromo-o-xylene (4.10 g, 16 mmols) was added to a stirred
solution of 2,2,3,4,4-pentamethylphosphetane (4.47 g, 31 mmols)
in acetone (25 ml) and the solution allowed to stir for 16 h
after which time an aqueous solution of sat. sodium bicarbonate
(100 ml) was added and the mixture stirred vigorously for 1 h.
The organic layer was removed via cannula, dried over anhydrous
Na2SO4 and subsequently filtered. The solvent was removed under
reduced pressure to yield the desired compound 5 as a white solid.
The crude product was then recrystallised from hot methanol to
give a mixture of the cis,cis and trans,trans isomers in a ratio of
9 : 1. Yield = 2.30 g (38%). The following data is for the major
˚
were used as purchased after drying over 3 A molecular sieves
(CDCl3 and d3-acetonitrile) or sodium (C6D6) and freeze-thaw
degassing before use. Unless stated otherwise, all other chemicals
5
3
were used as purchased. [(h -cyclopentadiene)(h -allyl)Pd(II)] and
[Pd(h -allyl)Cl]2 were prepared as detailed in the literature.17d
3
Syntheses
1-chloro-2,2,3,4,4-pentamethylphosphetane-1-oxide, 1. Adap-
ted from the method of McBride.2 To a cooled (0 ◦C) suspension
of PCl3 (18.4 g, 0.134 mols) and AlCl3 (22.33 g, 0.168 mols) in
dichloromethane (250 ml) was added slowly over the course of 1 h a
solution of 2,4,4 trimethylpent-2-ene in DCM (50 ml). During the
addition of the alkene the amount of suspended AlCl3 decreased
noticeably until the solution became clear and yellow in colour.
The reaction was stirred for 24 h whereupon the solution darkened
to a deep orange. Methanol (110 ml) was added to the cooled (0 ◦C)
1
all-cis isomer. 31P{ H} NMR (CDCl3, 121.65 MHz): d 29.3 (s)
ppm. 1H NMR (CDCl3, 300 MHz): 0.84 (6H, d, 3JH–H = 7.1 Hz),
3
3
1.20 (12H, d, JH–P = 18.0 Hz), 1.24 (12H, d, JH–P = 5.3 Hz),
3
2.26 (2H, q, JH–H = 7.1 Hz), 3.07 (4H, s br), 7.05 (2H, m),
7.19 (2H, m) ppm. 13C{ H} NMR (CDCl3, 75.56 MHz): 8.49 (d,
1
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3842–3850 | 3847
©

View Article Online
JC–P = 11.5 Hz), 20.35 (s), 26.58 (d, JC–P = 6.9 Hz), 31.53 (d, JC–P
=
sphetane) trihydroboron, 8 (0.40 g, 0.97 mmol) in DCM (40 ml)
◦
4.6 Hz), 32.50 (d, JC–P = 27.7 Hz), 50.48 (s), 126.06 (s), 129.79 (d,
JC–P = 6.9 Hz), 137.60 (d, JP–C = 11.5 Hz) ppm. MS (APCI): m/z
391.2 (M + H+).
at 0 C was added tetrafluoroboric acid dimethyl ether complex
◦
(10 eq, 9.70 mmol). The solution was stirred at 0 C for 30 min
and then allowed to warm to room temperature. After stirring for
6 h at room temperature, saturated sodium bicarbonate solution
(80 ml) was added and the solution stirred rapidly for 16 h. Stirring
was arrested and the two phases allowed to separate. The organic
phase was isolated and the aqueous phase washed with one portion
of DCM (30 ml). The combined organic phases were dried over
MgSO4 and subsequently filtered. Removal of the solvent under
reduced pressure gave the desired compound as a white solid.
2,2,3,4,4-pentamethylphosphetane trihydroboron, 6. To a solu-
tion of 2,2,3,4,4-pentamethylphosphetane (0.28 g, 1.95 mmol) in
THF (20 ml) was added a solution of borane:THF adduct (1M,
1.5 eq, 2.93 mmol). The solution was stirred for 2.5 h and the
solvent removed under vacuum to yield the product as a low-
melting white solid. Yield = 0.30 g (99%). The product was a 9 : 1
1
mixture of trans:cis isomers. For trans 6: 31P{ H} NMR (CDCl3,
1
Yield = 0.32 g (86%). 31P{ H} NMR (CDCl3, 121.65 MHz): d
1
1
121.65 MHz): d 58.0 (m, JP–B = 29.8 Hz) ppm. 11B{ H} NMR
42.6 (s) ppm. 1H NMR (CDCl3, 300 MHz): 0.81 (6H, d, 3JH–H
=
=
1
1
(CDCl3, 96.42 MHz): -44.6 (d, JB–P = 29.8 Hz) ppm. H NMR
3
3
9.7 Hz), 1.14 (12H, d, JH–P = 7.3 Hz), 1.24 (12H, d, JH–P
3
(CDCl3, 300 MHz): 0.92 (3H. d, JH–H = 7.3 Hz), 1.32 (12H, d,
18.5 Hz), 2.71 (2H, q, 3JH–H = 7.3 Hz), 3.34 (4H, s br), 7.06 (2H,
3JH–P = 11.6 Hz), 2.60 (1H, q, JH–H = 7.3 Hz), 5.17 (1H. dm,
3
1
m), 7.16 (2H, m) ppm. 13C{ H} NMR (CDCl3, 100 MHz) 9.80 (s),
1JH–P = 331.9 Hz, JH–B = 6.2 Hz) ppm. 13C{ H} NMR (CDCl3,
2
1
25.62 (d, JC–P = 28.0 Hz), 26.73 (s), 27.64 (d, JC–P = 30.0 Hz), 29.50
(s), 53.15 (d, JC–P = 3.0 Hz), 126.31 (s), 130.47 (d, JC–P = 7.9 Hz),
139.75 (s) ppm. MS (APCI): m/z 391.2 (M + H+).
100 MHz) 9.14 (s) 18.76 (d) 32.77 (d) 53.77 (d) ppm. Partial data
for cis-6: 31P{ H} NMR (CDCl3, 121.65 MHz): d 55.7 (m, 1JP–B
=
1
32.8 Hz) ppm. 11B{ H} NMR (CDCl3, 96.42 MHz): -43.8 (d,
1
1JB–P = 32.8 Hz) ppm. H NMR (CDCl3, 300 MHz): 0.97 (3H,
1
d, 3JH–H = 7.3 Hz), 1.27 (12H, d, 3JH–P = 14.1 Hz) ppm. 13C{ H}
1
{1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-penta-
methylphosphetane)}(tetracarbonyl)molybdenum(0), 10.
A so-
NMR (CDCl3, 100 MHz): 23.97 (s) 29.92 (d) 31.67 (d) 51.73 (d)
ppm. MS (APCI): m/z 158.9 (M, + H+).
lution of 1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-
pentamethylphosphetane) (0.21 g, 0.53 mmol) in DCM (15 ml)
was added to cis-[Mo(CO)4(C5H11N)2] (0.20 g, 0.53 mmol) to
give an orange coloured suspension. Upon heating under reflux
for 15 mins the suspended material dissolved to give a yellow
solution which was allowed to cool to room temperature before
the solvent was removed in vacuo to leave a buff coloured solid
which was recrystallised from a chloroform–methanol solution.
1,1¢-[1,2-phenylenebis(methylene)]bis-trans,trans-(2,2,3,4,4-pen-
tamethylphosphetane) trihydroboron, 8. To
a solution of
2,2,3,4,4-pentamethylphosphetane trihydroboron (0.31 g,
1.95 mmol) in THF (25 ml) at -78 ◦C was added sec-BuLi
(2.10 mmol). The resultant bright yellow solution was stirred for
2 h at -78 ◦C and then a further 0.5 h at room temperature to give
1-lithio-2,2,3,4,4-pentamethylphosphetanide trihydroboron. The
deprotonation was monitored by either 31P{H} or 11B{H} NMR
1
Yield = 0.16 g (52%). 31P{ H} NMR (CDCl3, 121.65 MHz): d
69.9 (s) ppm. 1H NMR (CDCl3, 300 MHz): 0.86 (6H, d, 3JH–H
=
=
1
spectroscopy [31P{ H} NMR, 121.65 MHz, trans isomer: d 23.9
3
3
6.7 Hz), 1.34 (12H, d, JH–P = 17.5 Hz), 1.49 (12H, d, JH–P
1
(m, 1JP–B 29.8 Hz); cis isomer: 30.1 (m, 1JP–B 29.8 Hz) ppm. 11B{ H}
9.7 Hz), 2.49 (2H, q, 3JH–H = 6.1 Hz), 3.39 (4H, d, 2JH–P = 5.7 Hz),
1
1
7.12 (2H, m), 7.31 (2H, m) ppm. 13C{ H} NMR (CDCl3, 75.56
NMR, 96.42 MHz, trans isomer: -37.3 (d, JB–P 29.8 Hz); cis
isomer: -35.8 (d, 1JB–P 29.8 Hz) ppm]. The solution was re-cooled
MHz): 7.78 (s), 21.91 (s), 30.90 (s), 33.68 (s), 41.05 (d, JC–P
=
◦
to -78 C and a THF solution (10 ml) of a,a¢-dichloro-o-xylene
27.7 Hz), 49.12 (s), 126.64 (s), 131.77 (s), 135.37 (s) ppm. MS
(APCI): m/z 598 (M+), 570 (M+ -CO). IR (KBr): nCO 1847, 1914,
2013 cm-1. Anal Calc. for C28H40MoO4P2 (598.48): C, 56.19; H,
6.75. Found: C, 56.0; H, 6.7%.
(0.17 g, 0.97 mmol) was added slowly thereto. The solution was
◦
stirred at -78 C for 1 h, before being allowed to warm to room
temperature and subsequently being left to stir for a further 18 h.
During this time the solution became cloudy as LiCl precipitated.
The solvent was removed under vacuum and dichloromethane
(30 ml) and water (30 ml) added to give a two-phase system.
The organic phase was isolated, dried over Na2SO4, filtered and
the solvent removed under reduced pressure to yield the product
1,1¢-[1,2-phenylenebis(methylene)]bis-trans,trans-(2,2,3,4,4-pen-
tamethylphosphetane)(tetracarbonyl)molybdenum(0),
12. The
compound was synthesised by an identical procedure to that
described for 10 (see above) except that 1,1¢-[1,2-phenylenebis-
(methylene)]bis-trans,trans-(2,2,3,4,4-pentamethylphosphetane)
(0.9 g, 2.2 mmol) and 0.89 g (2.2 mmol) of cis-[Mo(CO)4(C5H11N)2]
1
as a white solid. Yield = 0.36 g (89%). 31P{ H} NMR (CDCl3,
1
121.65 MHz): d 66.4 (m, br) ppm. 11B{ H} NMR (CDCl3, 96.42
MHz) -43.0 (d, br) ppm. 1H NMR (CDCl3, 300 MHz): 0.91 (6H,
1
were used. Yield = 0.78 g (59%). 31P{ H} NMR (CDCl3, 121.65
3
3
d, JH–H = 7.3 Hz), 1.35 (24H, d, JH–P = 9.9 Hz), 2.56 (2H, q,
1
MHz): d 84.1 (s) ppm. H NMR (CDCl3, 300 MHz): 0.86 (6H,
3JH–H = 7.3 Hz), 3.51 (4H, d, JH–P = 11.9 Hz), 7.15-7.36 (4H,
2
d, 3JH–H = 7.1 Hz), 1.28 (12H, d, 3JH–P = 11.4 Hz), 1.39 (12H, d,
m) ppm. 13C{ H} NMR (CDCl3, 75.56 MHz): 9.00 (d, JC–P
=
1
3JH–P = 18.2 Hz), 2.74 (2H, q, 3JH–H = 7.0 Hz), 3.40 (4H, d, 2JH–P
=
9.2 Hz), 20.98 (d, JC–P = 3.5 Hz), 25.50 (d, JC–P = 21.9 Hz), 26.48
1
7.7 Hz), 7.16 (2H, m), 7.25 (2H, m) ppm. 13C{ H} NMR (CDCl3,
75.56 MHz): 9.49 (s), 25.39 (d, JC–P = 5.2 Hz), 26.94 (s), 30.89
(s), 36.30 (d, JC–P = 28.9 Hz), 38.70 (d, JC–P = 16.2 Hz), 53.13 (s),
127.40 (s), 130.78 (s), 137.71 (s) ppm. MS (APCI): m/z 598 (M+),
570 (M+ -CO). IR (KBr): nCO 1857, 1877, 1912, 2016 cm-1. Anal
Calc. for C28H40MoO4P2 (598.48): C, 56.19; H, 6.75. Found: C,
55.8; H, 6.8%.
(d, JC–P = 3.5 Hz), 34.74 (d, JC–P = 38.1 Hz), 52.22 (d, JC–P
=
10.4 Hz), 126.97 (s), 129.49 (s), 130.75 (s) ppm. MS (APCI): m/z
419.1 (M+H+).
1,1¢-[1,2-phenylenebis(methylene)]bis-trans,trans-(2,2,3,4,4-pen-
tamethylphosphetane), 9. To a stirred solution of 1,1¢-[1,2-phe-
nylenebis(methylene)]bis-trans,trans-(2,2,3,4,4-pentamethylpho-
3848 | Dalton Trans., 2010, 39, 3842–3850
This journal is
The Royal Society of Chemistry 2010
©

View Article Online
it gradually darkened to a red colour. An anhydrous diethyl ether
solution of HCl (0.28 mmols) was then added via syringe to the
solution and an instant colour change to yellow was observed.
At this point the stirring was stopped and over a period of 2.5 h
a yellow precipitate formed. The supernatant was removed via
cannula filtration and the solid dried under vacuum. X-ray quality
crystals were obtained via the slow vapour diffusion of diethyl
ether into a concentrated solution of the complex in DCM.
{1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-pentame-
thylphosphetane)}(trans,trans-dibenzylideneacetone)palladium(0)].
To solid [Pd2(dba)3] (0.28 g, 0.30 mmols) was added, a solution
of
1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-pen-
tamethylphosphetane) (0.190 g, 0.48 mmols) in THF (20 ml). The
solution was stirred for 2 h whereupon a gradual colour change
from deep violet to red/orange was observed. The solvent was
removed under reduced pressure and the remaining red solid was
extracted with hexane (3 ¥ 30 ml). The resultant hexane solution
was reduced in volume under reduced pressure until an orange
solid precipitated. The orange complex was isolated by filtration,
washed with cold (-15 ◦C) diethyl ether (3 ¥ 5 ml) and dried at the
1
1
31P{ H} NMR (CDCl3, 121.65 MHz): d 84.0 (s) ppm. H NMR
3
(CDCl3, 300 MHz): 0.96 (6H, d, JH–H = 7.3 Hz), 1.45 (12H, d,
3JH–P = 14.9 Hz), 1.66 (12H, d, 3JH–P = 20.4 Hz), 3.03 (2H, q, br),
3.55 (2H, d, 2JH–P = 4.2 Hz), 3.59 (d, 2H), 7.25 (m), 7.29 (m) ppm.
(Found: C, 49.97; H 6.89%. Calc. For complex: C, 50.76; H, 7.10;
Cl, 12.48; P, 10.90%). MS (APCI): m/z 531.8 (M, -Cl). Anal Calc.
for C25H41Cl4P2Pd (652.73): C, 46.00; H, 6.34. Found: C, 45.5; H,
6.1%.
1
pump. Yield = 0.27 g (76%). 31P{ H} NMR (C6D6, 121.65 MHz,
298 K): d 58.3 (s,br), 64.4 (s, br) ppm. 1H NMR (C6D6, 300 MHz)
3
0.62 (6H, d, JH–H = 7.2 Hz), 0.98 (24H, m, br), 2.15 (2H, q,
3JH–H = 6.4 Hz), 2.91 (4H, d, 2JH–P = 7.9 Hz), 5.29 (2H, br), 7.25
1
(12H, m) ppm. 13C{ H} (C6D6, 75.45 MHz): 1.14 (s) 8.77 (m)
20.99 (m) 28.88 (d) 29.29 (d) 31.40 (d) 37.50 (m) 49.08 (s) 50.521
[{1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-penta-
1
(s) 125.521 (s) 128.790 (s) 135.188 (s) ppm. 31P{ H} NMR (C7D8,
methylphosphetane)}(g2-ethene)palladium(0)].
A
solution of
121.65 MHz, 248 K): 52.8-57.1 (m) 66.87-69.84 (m) ppm. 1H
NMR (C7D8, 300 MHz, 248 K): 0.67 (6H, d, br), 0.84-0.94 (12H,
1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-pentame-
thylphosphetane) in diethyl ◦ether (20 ml) was added
3
5
=
m, br), 2.57 (4H, d, br), 5.03 (2H, m, br, C C coordinated), 7.65
gradually to a cooled (-40 C) solution of [(h -allyl)(h -
cyclopentadiene)palladium(II)] (0.12 g, 0.54 mmols) in Et2O
(15 ml) under an atmosphere of ethene to give an orange solution.
A small portion of the solution was removed and the solvent
=
(2H, d, J = 15.4 Hz, C C free) ppm. MS (ES): m/z 496 (M,
-DBA). Anal Calc. for C41H54OP2Pd (731.29): C, 67.33; H, 7.46.
Found: C, 68.0; H, 7.3%.
1
removed in vacuo to give an orange coloured solid. 31P{ H} NMR
1
1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-pentame-
thylphosphetane)dichloropalladium(II)]·CH2Cl2, 11. A solution
of [{1,1¢-[1,2-phenylenebis(methylene)]bis-cis,cis-(2,2,3,4,4-pen-
tamethylphosphetane)}(dba)Palladium(0)] (0.1 g, 0.14 mmol) in
diethyl ether (8 ml) was added to 1,4-p-benzoquinone (0.01 g,
0.14 mmols). The solution was stirred for 1 h during which time
(d6-acetone, 298 K, 121.65 MHz): d 54.8 (br) ppm. 31P{ H}
NMR (d6-acetone, 258 K, 121.65 MHz): d 53.5 (dd, J 23.8 Hz,
J 190.6 Hz) ppm. 1H NMR (d6-acetone, 300 MHz): 0.89 (6H, d,
3JH–H = 6.4 Hz), 1.19 (12H. d, br), 1.44 (12H, d, br), 2.39-2.61
(2H, q, br), 3.36 (4H, d, br), 6.91 (2H, m), 7.18 (2H, m) ppm.
1
13C{ H} NMR (d6-acetone, 75.56 MHz): 7.42 (d) 20.64 (m) 31.16
Table 1 Details of X-ray crystallographic data collection for ligand 5 and the complexes
5
10
12
11
Empirical formula
Formula weight
Crystal system
Space group
C24H40P2
390.50
Triclinic
¯
P1
C28H40MoO4P2
598.48
Monoclinic
C28H40MoO4P2
598.48
Monoclinic
C25H41Cl4P2Pd
652.73
Triclinic
¯
P1
P21/n
C2/c
˚
a/A
6.0343(3)
13.2316(8)
15.4746(10)
83.084(3)
79.072(3)
87.465(3)
1204.02(12)
2
1.077
428
0.15 ¥ 0.04 ¥ 0.04
3.92 to 25.32
12.5960(2)
17.2901(3)
13.8362(2)
37.8437(7)
8.7185(2)
18.4939(4)
8.7866(1)
10.8661(2)
15.9424(3)
109.6672(8)
93.1967(8)
95.8861(10)
1419.13(3)
2
1.525
670
0.30 ¥ 0.28 ¥ 0.25
2.98 to 27.51
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
105.5887(7)
109.0023(10)
3
˚
U/A
2902.49(8)
4
1.370
1248
0.20 ¥ 0.06 ¥ 0.06
3.05 to 27.49
5769.4(2)
8
1.378
2496
0.22 ¥ 0.20 ¥ 0.18
3.22 to 27.45
Z
Dc/Mg m-3
F(000)
Crystal size/mm
q range/◦
Index ranges
-7 ≤ h ≤ 7, -15 ≤ k ≤ 15, -16 ≤ h ≤ 16, -22 ≤ k ≤ 22, -48 ≤ h ≤ 48, -11 ≤ k ≤ 11, -11 ≤ h ≤ 11, -14 ≤ k ≤ 14,
-18 ≤ l ≤ 18
-17 ≤ l ≤ 17
-23 ≤ l ≤ 23
-20 ≤ l ≤ 20
Reflections collected
Independent reflections
Rint
13420
39770
26788
26820
4369
0.1640
6638
0.0761
6561
0.0891
6456
0.0572
Data/restraints/parameters
Goodness of fit on F2
Final R1, wR2 [I > 2s(I)]
(all data)
4369/30/245
1.030
0.0900, 0.2117
0.1273, 0.2368
6638/0/326
1.024
0.0324, 0.0707
0.0432, 0.0748
0.537 and -0.567
6561/0/326
1.020
0.0399, 0.0836
0.0644, 0.0915
0.661, -0.964
6456/0/309
1.007
0.0348, 0.0741
0.0458, 0.0785
0.661, -0.964
-3
˚
Largest difference peak and hole/e A 1.293 and -0.568
This journal is
The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 3842–3850 | 3849
©

View Article Online
(d) 48.99 (d) 125.95 (s) 129.61 (s) 137.89 (s) ppm. Unfortunately
satisfactory elemental analytical data could not be obtained on
this compound.
Acknowledgements
We are grateful to Dr G. Eastham and colleagues in Lucite
International PLC for support (DC).
Crystallography
Notes and references
Data collection was carried out on a Bruker-Nonius Kappa
CCD diffractometer using graphite monochromated Mo-Ka
radiation (l(Mo-Ka) = 0.71073 A). The instrument was equipped
1 G. M. Kosolapoff and R. F. Struck, J. Chem. Soc., 1957, 3739.
2 E. Jungermann, J. J. McBride, R. Clutter and A. Mais, J. Org. Chem.,
1962, 27, 606.
˚
with an Oxford Cryosystems cooling apparatus. Data collection
(see Table 1 for details) and cell refinement were carried out
using COLLECT18 and HKL SCALEPACK.19 Data reduction
was applied using HKL DENZO and SCALEPACK.26 The
structures were solved using direct methods (Sir92)20 and refined
with SHELX-97.21 Absorption corrections were performed using
SORTAV.22 All non-hydrogen atoms were refined anisotropically,
while the hydrogen atoms were inserted in idealised positions with
Uiso set at 1.2 or 1.5 times the Ueq of the parent atom. In the final
cycles of refinement, a weighting scheme that gave a relatively
flat analysis of variance was introduced and refinement continued
until convergence was reached. The data for compound 5 were very
weak due to the small size of the crystal, noting that the material
contains no heavy metals. This necessitated the use of restraints in
the refinement and is reflected in the Rint and final residual values.
3 A. Marinetti, V. Kruger and F. X. Buzin, Tetrahedron Lett., 1997, 38,
2947.
4 C. Moret and L. M. Trefonas, J. Am. Chem. Soc., 1969, 91, 2255.
5 A. Marinetti, S. Jus, J.-P. Gennet and L. Ricard, Tetrahedron, 2000, 56,
95.
6 A. Marinetti, S. Jus, J.-P. Geneˆt and L. Ricard, J. Organomet. Chem.,
2001, 624, 162.
7 T. J. Brunker, J. R. Moncarz, D. S. Glueck, L. N. Zakharov, J. A. Golen
and A. L. Rheingold, Organometallics, 2004, 23, 2228.
8 (a) S. E. Cremer and R. J. Chorvat, J. Org. Chem., 1967, 32, 4066;
(b) J. R. Corfield, R. K. Oram, D. J. H. Smith and S. Trippet, J. Chem.
Soc., Perkin Trans. 1, 1972, 713; (c) G. A. Gray and S. E. Cremer, J. Org.
Chem., 1972, 37, 3458.
9 C. J. Moulton and B. L. Shaw, J. Chem. Soc., Chem. Commun., 1976,
365.
10 (a) M. Haque, J. Chem. Soc. (B), 1970, 934; (b) M. Haque, J. Chem.
Soc. (B), 1970, 938.
11 A. Marinetti and D. Carmichael, Chem. Rev., 2002, 102, 201.
12 S. H. Cremer, R. J. Chorvat, C. H. Chang and D. W. Davis, Tetrahedron
Lett., 1968, 9, 5799.
13 (a) N. Carr, B. J. Dunne, L. Mole, A. G. Orpen and J. L. Spencer,
J. Chem. Soc., Dalton Trans., 1991, 863; (b) A. Leone, S. Gischig and
G. Consiglio, J. Organomet. Chem., 2006, 691, 4816; (c) M. D. Brown,
W. Levason, G. Reid and R. Watts, Polyhedron, 2005, 24, 75; (d) C.
Jimenez-Rodriguez, P. J. Pogorzelec, G. R. Eastham, A. M. Z. Slawin
and D. J. Cole-Hamilton, Dalton Trans., 2007, 4160; (e) A. Leone, S.
Gischig, C. J. Elsevier and G. Consiglio, J. Organomet. Chem., 2007,
692, 2056; (f) M. Camalli, F. Caruso, S. Chaloupka, E. M. Leber, H.
Rimml and L. M. Venanzi, Helv. Chim. Acta, 1990, 73, 2263.
14 D. Coleman, PhD thesis, Cardiff University, 2004.
15 D. C. R. Hockless, Y. B. Kang, M. A. McDonald, M. Pabel, A. C.
Willis and S. B. Wild, Organometallics, 1996, 15, 1301.
16 S. M. Reid, J. T. Mague and M. J. Fink, J. Organomet. Chem., 2000,
616, 10.
17 (a) V. V. Dunina, L. G. Kuz’mina, M. Y. Rubina, Y. K. Grishin, Y. A.
Veits and E. I. Kazakova, Tetrahedron: Asymmetry, 1999, 10, 1483;
(b) R. Schmid, J. Foricher, M. Gereghetti and P. Schonholzer, Helv.
Chim. Acta, 1991, 74, 370; (c) H. Jendralla, Ch. H. Li and E. Paulus,
Tetrahedron: Asymmetry, 1994, 5, 1297; (d) T. Yatsuno, T. Yoshida and
S. Otsuka, Inorg. Synth., 1990, 28, 343.
Conclusions
In conclusion, two isomers, namely the cis,cis and trans,trans
forms, of the bidentate ligand 1,1¢-[1,2-phenylenebis-
(methylene)]bis(2,2,3,4,4-pentamethylphosphetane) have been
prepared from common precursors using two separate synthetic
routes. The all-cis isomer is attained through the direct reaction
of two mol equivalents of 2,2,3,4,4-pentamethylphosphetane
with a,a¢-dibromo-o-xylene and the all-trans form after prior
protection of the phosphetane with BH3 and subsequent
conversion to the lithium phosphide before adding the dibromide.
Both isomers have been coordinated to Mo(0) to give complexes
of the type cis-Mo(CO)4(L) where L is the diphosphetane ligand.
The solid state structures of the two forms reveal some significant
differences most notably in the chelate bite angle which is
100.68(18)◦ for the all-cis complex compared to 88.12(2)◦ for the
trans analogue. It is not known what the overriding influence is on
these disparate values but the four-membered rings are puckered
in opposite directions in each of the complexes which may have
some bearing on the resultant P–Mo–P angle. The all-cis ligand
has also been coordinated to Pd(II) and Pd(0) and the structure of
the complex Pd(5)Cl2 determined by single-crystal methods. The
solid-state structure of Pd(5)Cl2 reveals a significant tetrahedral
distortion.
18 COLLECT, B. V. Nonius, 1998, Delft, The Netherlands.
19 Z. Otwinowski and W. Minor, Methods Enzymol., 1997, 276, 307.
20 A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi, J. Appl.
Crystallogr., 1993, 26, 343.
21 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Go¨ttingen, Germany, 1997; G. M. Sheldrick,
SHELXS-97, Program for solution of crystal structures, University of
Go¨ttingen, Germany, 1997.
22 R. H. Blessing, Acta Crystallogr., Sect. A: Found. Crystallogr., 1995,
51, 33.
3850 | Dalton Trans., 2010, 39, 3842–3850
This journal is
The Royal Society of Chemistry 2010
©