Structure of diiodine adducts of some di- and tri-tertiaryphosphines in the solid state and in solution

Article abstract of DOI:10.1039/a706277j

A series of ditertiaryphosphine-tetraiodine adducts R₂P(I₂)(CH₂)_nP(I₂)R ₂ (R = Ph, n = 1-4; R = PhCH₂ or o-CH₃C₆H₄, n = 2) and two tritertiaryphosphine-hexaiodine adducts, PhP(CH₂CH₂PPh₂)₂I₆ and CH₃C(CH₂-PPh₂)₃I₆ have been prepared and characterised by ³¹P-{H} solution NMR and Raman spectroscopy. In the case of Ph₂P(I₂)(CH₂)_nP(I ₂)Ph₂ (n = 2 or 4), ³¹P-{H} NMR magic angle spinning NMR spectroscopy has been used to investigate the nature of the compounds in the solid state. In agreement with our previous extensive studies on the monophosphine derivatives, R₃PI₂, the tetraiododiphosphine compounds Ph₂P(I₂)(CH₂)_nP(I ₂)Ph₂ (n = 2 or 4) isolated from diethyl ether contain molecular four-co-ordinate phosphorus centres onto which the diiodine is bound as a linear spoke, as indicated by their ^3IP-{H} NMR shifts obtained in CDCl₃ solution. Again, in agreement with our previous solution studies of the monophosphine derivatives R₃PI₂, the diphosphine-tetraiodine adducts completely ionise in CDCl₃ solution to produce the ionic compounds [R₂P(I)(CH₂)_nP(I)R₂]2I; the solution ³¹P-{H} NMR shifts are very similar to analogous solution shifts previously assigned to [R₃PI]I. The Raman band assignable to v(P-I) has been identified for the compounds and a further band at lower frequency has been observed and assigned to v(I-I). Although the solid-state NMR spectra of the triphosphine-hexaiodine adducts were not recorded, a band assignable, to v(I-I) was observed in the Raman spectrum, suggesting the molecular four-co-ordinate spoke structure also prevails for these hexaiodotritertiaryphosphine compounds in the solid state. From solution ³¹P-{H} NMR shifts these adducts also appear to ionise in CDCl₃ solution.

Full text of DOI:10.1039/a706277j

View Article Online / Journal Homepage / Table of Contents for this issue
Structure of diiodine adducts of some di- and tri-tertiaryphosphines
in the solid state and in solution
a
,a
,a
b
Neil Bricklebank, Stephen M. Godfrey,* Charles A. McAuliffe,* Paula Deplano,
b
a
Marie L. Mercuri and Joanne M. Sheffield
a
Department of Chemistry University of Manchester, Institute of Science and Technology,
PO Box 88, Manchester, UK M60 1QD
b
Dipartimento di Chimica Inorganische, University of Cagliari, Via Ospedale 72, 09124 Cagliari,
Italy
A series of ditertiaryphosphine–tetraiodine adducts R P(I )(CH ) P(I )R (R = Ph, n = 1–4; R = PhCH or
2
2
2
n
2
2
2
o-CH C H , n = 2) and two tritertiaryphosphine–hexaiodine adducts, PhP(CH CH PPh ) I and CH C(CH -
3
6
4
2
2
2
2
6
3
2
31
PPh ) I have been prepared and characterised by P-{H} solution NMR and Raman spectroscopy. In the case
2
3 6
31
of Ph P(I )(CH ) P(I )Ph (n = 2 or 4), P-{H} NMR magic angle spinning NMR spectroscopy has been used to
2
2
2
n
2
2
investigate the nature of the compounds in the solid state. In agreement with our previous extensive studies on
the monophosphine derivatives, R PI , the tetraiododiphosphine compounds Ph P(I )(CH ) P(I )Ph (n = 2 or 4)
3
2
2
2
2
n
2
2
isolated from diethyl ether contain molecular four-co-ordinate phosphorus centres onto which the diiodine is
31
bound as a linear spoke, as indicated by their P-{H} NMR shifts obtained in CDCl solution. Again, in agree-
3
ment with our previous solution studies of the monophosphine derivatives R PI , the diphosphine–tetraiodine
3
2
adducts completely ionise in CDCl solution to produce the ionic compounds [R P(I)(CH ) P(I)R ]2I; the
3
2
2
n
2
31
solution P-{H} NMR shifts are very similar to analogous solution shifts previously assigned to [R PI]I. The
3
Raman band assignable to ν(P᎐I) has been identified for the compounds and a further band at lower frequency
has been observed and assigned to ν(I᎐I). Although the solid-state NMR spectra of the triphosphine–hexaiodine
adducts were not recorded, a band assignable to ν(I᎐I) was observed in the Raman spectrum, suggesting the
molecular four-co-ordinate spoke structure also prevails for these hexaiodotritertiaryphosphine compounds in
31
the solid state. From solution P-{H} NMR shifts these adducts also appear to ionise in CDCl solution.
3
6
Reports concerning the reaction of di- or poly-tertiary-
phosphines with dihalogens are extremely scarce and, in the few
examples available, the products formed have not been well
characterised. The tetrachloro adduct of bis(dimethylphos-
or (CH ᎐CHCH ) Ph]. Additionally, we have also identified
2
᎐
2 2
some R PI2 compounds which, whilst being predominantly
molecular R P᎐I᎐I, also contain a small but significant propor-
tion of the ionic species, [R Pl]I, [R = (p-FC H ) Ph, (C H )-
Ph , (PhCH CH ) , (o-CH OC H )Ph or (CH CHCH )Ph ],
2 2 2 3 3 6 4 2 2 2 2
31 6
3
3
3
3
6
4
2
6
11
1
phino)ethane, Me P(Cl )CH CH P(Cl )Me and the tetra-
2
2
2
2
2
2
bromo and tetraiodo adducts of bis(diphenylphosphino)ethane,
again from solid-state MAS P-{H} NMR results. Consider-
ing the renewed interest in triorganophosphorus dihalogen
compounds, and the fact that virtually nothing is known
regarding the products formed from the reaction of diphos-
phine or polyphosphine compounds with dihalogens, we felt
that an investigation into the diiodine adducts of these species
was worthwhile. Specifically, we were interested to know if these
di- and poly-tertiaryphosphine–diiodine adducts adopted the
four-co-ordinate molecular spoke structure exhibited by the
2
Ph P(X )CH CH P(X )Ph (X = Br or I) have been reported.
2
2
2
2
2
2
No attempt was made to isolate or characterise the products
formed, which were assigned an ionic structure, [R P(X)CH -
2
2
2ϩ
Ϫ
CH P(X)R ] 2[X] (R = Me, X = Cl; R = Ph, X = Br or I) in
2
2
the solid state. Similarly, the dihalogen adducts of the polyden-
tate phosphine C(CH PPh ) have been prepared and character-
2
2 4
3
ised. It was concluded that these were also phosphonium salts
C{CH P(X)Ph } ] 4[X] (X = Cl, Br or I). The only inter-
4
ϩ
Ϫ
[
2 2 4
halogen adduct which has been reported is the BrCl adduct
of bis(dimethylphosphino)ethane which was postulated to be
majority of our monophosphine diiodine compounds, R P᎐I᎐I.
3
1
Additionally, we have already demonstrated the ability of R PI2
3
Me P(Cl, Br)CH CH P(Cl, Br)Me but again no characterisa-
compounds to oxidise crude metals at ambient temperatures to
2
2
2
2
tion of this product was reported. Clearly, the nature of di- and
poly-tertiaryphosphine dihalogen adducts is very poorly
understood.
produce, in some cases, unpredictable products, e.g. Aul -
3
9
(PMe ) . Here we report the characterisation of some diiodine
3
2
adducts of di- and tri-tertiary phosphines and we will describe
their utilisation as reagents for metal activation in due course. It
is thus likely that the reaction of these species with metal
powders will result in novel products (analogous to the reaction
of R PI with metal powders) which, considering the ubiquitous
Our interest in this area stems from our discovery that, when
prepared in diethyl ether monophosphine–diiodine adducts,
R PI , do not exhibit trigonal-bipyramidal geometry or an ionic
3
2
formulation, [R PI]I, but rather than a molecular charge-
3
3
2
transfer structure, R P᎐I᎐I, where the diiodine binds to the
use of diphosphine ligands in co-ordination chemistry, is clearly
of importance. We therefore report a comprehensive study of
di- and poly-phosphine–diiodine adducts isolated from diethyl
ether and have characterised these compounds by elemental
3
4–6
phosphorus centre as a linear ‘spoke’. Such an observation
was unexpected and contrasts with conventional wisdom
7,8
which, for example, from vibrational spectroscopic studies,
31
did not consider this structural modification. We have since
shown that this charge-transfer structure is the norm for almost
all compounds of stoichiometry R PI prepared in diethyl ether,
analysis, P-{H} NMR solution spectroscopy and solid-state
Raman spectroscopy. In the case of the compounds Ph -
2
31
P(I )(CH ) P(I )Ph (n = 2 or 4), the solid-state MAS P-{H}
3
2
2
2
n
2
2
although we have also isolated a few compounds which, as indi-
cated from solid-state magic angle spinning (MAS) P-{H}
NMR spectra are also reported. Previous workers have con-
cluded that di- and poly-phosphine dihalogen compounds are
ionic in both the solid state and in solution.
31
3
NMR results, adopt the ionic structure [R PI]I [R = (Me N)
3
3
2
3
J. Chem. Soc., Dalton Trans., 1998, Pages 2379–2382
2379

View Article Online
Table 1 Analytical and spectroscopic data for the di- and tri-tertiaryphosphine diiodine adducts
b
Ϫ1
Analysis (%)
Raman/cm
a
31
c
Compound
Colour
C
H
I
δ( P-{H})
ν(P᎐X)
ν(I᎐I)
dppmؒI4
dppeؒI4
dtpeؒI4
Yellow
Yellow
33.6 (33.6)
34.7 (34.4)
37.2 (37.4)
37.1 (37.4)
35.5 (35.2)
35.5 (35.7)
43.0 (43.2)
31.2 (31.5)
35.9 (35.5)
2.5 (2.5)
2.8 (2.7)
3.1 (3.3)
2.9 (3.3)
2.8 (2.8)
3.0 (3.0)
3.2 (2.9)
2.9 (2.5)
2.7 (2.8)
56.1 (56.9)
55.8 (56.1)
53.1 (52.8)
53.2 (52.8)
54.7 (55.2)
54.5 (54.0)e
44.5 (45.8)
56.1 (58.0)
54.7 (55.0)
48.0
59.9
48.4
59.9
54.7
58.0
54.3
56.0, 55.6
45.4
181
150
d
141
146
151
151
148
147
112
109
d
101
105
111
111
110
110
Mustard
Mustard
Mustard
Mustard
Mustard
Mustard
Mustard
db peؒI4
2
dpppؒI4
dppbؒI4
dpenؒI4
PhP(CH CH PPh ) ؒI
2
2
2
2
6
CH C(CH PPh ) ؒI
3
2
2 3
6
a
dppm = Bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphosphino)ethane, dtpe = 1,2-bis(di-o-tolylphosphino)ethane, dbzpe = 1,2-bis-
dibenzylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, dppb = 1,4-bis(diphenylphosphino)butane, dpen = N,NЈ-bis[(diphenyl-
(
b
c
phosphino)benzylidene]ethylenediamine. Required values given in parentheses. All shifts are recorded relative to 85% phosphoric acid standard.
d
e
Sample decomposed in the Raman beam. Found (calc.): N, 2.7 (2.5)%.
3
1
P-{H} NMR results in CDCl solution
X
P
X
X
P
X
3
R
R
R
R
31
(CH2)n
The P-{H} NMR spectra of all the compounds in CDCl3
solution, with the exception of PhP(CH CH PPh ؒI , exhibit a
)
2
2
2
2
6
single resonance, as expected, indicating that all the phosphorus
centres in the compound are equivalent, Table 1. The spectrum
of PhP(CH CH PPh ) ؒI contains two closely spaced peaks at
δ 56.0 and 55.6 in approximately 2:1 ratio. The peak at δ 56.0
results from the two terminal phosphorus atoms, whereas the
peak at δ 55.6 is due to the bridging phosphorus atom in PhP-
(
a)
2+
R
R
2
2
2
2
6
P
X
(CH2)n
P
X
2X–
R
R
(b)
(
CH PPh ) ؒI and these occur in a 2:1 ratio, as expected.
2 2 2 6
R
R
R
R
None of these compounds reported here has previously been
P
X
X
(CH2)n
P
X
X
31
the subject of a P-{H} NMR study. However, by comparison
with their monophosphorus analogues, which have similar P-
{H} NMR values in CDCl solution it seems likely that all
the compounds are ionic, [R P(I)(CH ) P(I)R ]2I in solution.
31
5,6
3
(c)
Ϫ
2
2
n
2
Confirmation of this was achieved by the addition of a further
or 3 mol equivalents of diiodine to the di- and tri-phosphine–
2
+
R
R
2
P
I
(CH2)n
(CH2)n
P
I
R
R
2I3–
diiodine adducts, respectively, which resulted in the formation
of the corresponding ionic tetraiodo adducts, analogous to the
monophosphine derivatives, [R PI]I . For example addition of
R
R
P
P
3
3
R
R
2
mol equivalents of diiodine to Ph PCH CH PPh ؒI yields
2 2 2 2 4
2ϩ Ϫ
(d)
[
Ph P(I)CH CH P(I)Ph ] 2I . In all cases addition of the
2 2 2 2 3
Fig. 1 Four possible structural modifications for the compounds
R P(I )(CH ) (I )PR ; (a) trigonal bipyramidal, (b) ionic, (c) molecular
extra 2 or 3 mol equivalents of diiodine to the di- and tri-
phosphine–diiodine adducts resulted in a pronounced darken-
ing of the solution and bands appearing at 294 and 366 nm in
2
2
2
n
2
2
charge transfer, (d) iodine-bridged dimer
Ϫ
9
31
the UV/VIS spectrum, diagnostic for the I3 ion. The P-{H}
Results and Discussions
Ϫ
NMR shifts for these ionic species containing the I3 ion are
identical to those of the parent compounds prior to the ad-
dition of extra diiodine, thus providing proof that the tetra-
iododiphosphorus and hexaiodotriphosphorus compounds are
The di- and tri-tertiaryphosphine–diiodine adducts were
synthesised by the reaction of 1 mol of the di- or tri-
phosphine species with either 2 or 3 mol of diiodine, respect-
ively, in diethyl ether suspension, equations (1) and (2) (r.t. =
ionic in CDCl solution.
3
Raman spectroscopic studies
Et
4
2
O, N
2
R P(CH ) PR ϩ 2I
R P(I )(CH ) P(I )R (1)
2 2 2 n 2 2
2
2
n
2
2
d, r.t.
Assignment of the bands in the low frequency Raman spectra
of the di- and tri-phosphine–diiodine compounds is more
difficult than for their monophosphine–diiodine analogues. In
each spectrum, Table 1, the dominant band appears at ca. 110
Et
2
O, N
2
CH C(CH PPh ) ϩ 3I
CH C(CH PPh ) ؒI (2)
3 2 2 3 6
3
2
2
3
2
4
d, r.t.
Ϫ1
cm , but several slightly weaker bands are also observed in the
Ϫ1
5,6
room temperature). Analytical and spectroscopic data for the
compounds are contained in Table 1.
140–185 cm region. The analogous R PI compounds
3 2
Ϫ1
exhibit ν(P᎐I) over a wide range (132–222 cm ), the more basic
tertiary phosphines exhibiting the highest ν(P᎐I), as expected.
By comparison with the diiodomonophosphine compounds,
4–6
Like their monophosphine analogues, there are four pos-
sible structures which these compounds could adopt: the five-
co-ordinate molecular species, Fig. 1(a), the ionic phosphonium
species, Fig. 1(b), the molecular four-co-ordinate charge-
transfer ‘spoke’ structure, Fig. 1(c), or a further example of an
ionic species where one iodine atom is shared between each pair
of phosphorus atoms, the charge being balanced by a triiodide
anion, Fig. 1(d). Analogous structural behaviour exhibited in
Fig. 1(d) has previously been observed in diiodine derivatives
Ϫ1
the band appearing between 140 and 185 cm for each com-
pound is assigned to ν(P᎐I). The band appearing at ca. 110
Ϫ1
cm in each of the di- and tri-phosphine adducts of diiodine is
tentatively assigned to ν(I᎐I), since bands appearing in this
12–14
region for other reported
compounds which contain weak
I᎐I bonds have also been assigned to ν(I᎐I). A list of the ν(P᎐I)
and ν(I᎐I) stretching frequencies for the di- and tri-phosphine–
diiodine compounds is given in Table 1. The structure of the
10
of cyclic compounds containing a nitrogen-donor atom.
2
380
J. Chem. Soc., Dalton Trans., 1998, Pages 2379–2382

View Article Online
3
1
Solid-state P-{H} MAS NMR spectra of Ph P(I )(CH ) -
2
2
2 n
3
1
Table 2 Solid-state MAS and solution P-{H} NMR data for mono-
P(I
2 2
)Ph (n = 2 or 4)
a
and di-phosphorus–diiodine adducts
In order to gain more information regarding the solid-state
structures of diphosphine–diiodine adducts, the solid-state P-
31
3
1
δ( P-{H})
{
H} MAS NMR spectra of Ph P(I )(CH ) P(I )Ph (n = 2 or 4)
2
2
2
n
2
2
b
c
Compound
Solid-state MAS Solution
Ref.
solution values,
were recorded and compared to the CDCl
3
31
Ph PI2
Ϫ17.8
Ϫ7.6
Ϫ5.6
25.7, 26.6, 27.3
6.9
44.8
61.9
80.0
25.4
8.8
5
5
5
6
6
6
6
6
Table 2. The solid-state P-{H} MAS NMR spectrum of
P(I )CH CH P(I )Ph is illustrated in Fig. 4. The solid-state
3
PhMe PI2
2
Ph2
2
2
2
2
2
3
Me PI2
values, δ Ϫ14.8 and Ϫ0.9 are markedly different from the solu-
tion values of δ 59.9 and 58.0 for dppeؒI and dppbؒI , respect-
ively. Moreover, the difference in these values, and the values
(
(
(
(
(
(
(
Me N) PI
2
3
2
4
4
CH ᎐CHCH ) PhPI
2
᎐
2
2
2
p-FC H ) PhPI
Ϫ22.2/42.8
10.3/52.1
19.9/89.7
Ϫ28.1/42.2
Ϫ27.7/42.2
Ϫ14.8
44.3
52.7
82.0
46.8
40.4
59.9
58.0
6
4
2
2
31
C H )PhPI
2
themselves, are similar to the solid-state P-{H} MAS NMR5
6
11
PhCH CH ) PI
and solution shifts for Ph PI of δ Ϫ17.8 and 44.8, respectively.
2
2
3
2
3
2
o-CH OC H )Ph PI
6
6
For this compound, single-crystal X-ray diffraction has
unequivocally shown that it is molecular Ph P᎐I᎐I in the solid
state, and we have shown that it may be considered as ionic,
3
6
4
2
2
CH ᎐CHCH )Ph PI
2
᎐
2
2
2
3
Ph P(I )(CH ) P(I )Ph
This work
This work
2
2
2
2
2
2
2
Ph P(I )(CH ) P(I )Ph
Ϫ0.88
2
2
2
4
2
15
[
Ph PI]I, in CDCl solution. However, a recent study of R PI2
3
3
3
a
b
All peaks recorded relative to 85% phosphoric acid standard. Peaks
assignable to both a molecular, R P᎐I᎐I and an ionic, [R PI]I form, see
31
compounds has concluded from P-{H} NMR and Raman
spectroscopy, that these charge-transfer complexes, R P᎐I᎐I
may also be considered as interaction of the strong nucleophilic
3
3
c
3
text and ref. 6. In CDCl3.
Ϫ
ϩ
I and the electrophilic I atom in R PI . These results, therefore,
3
overwhelmingly point to the diphosphorus–diiodine adducts as
having the molecular four-co-ordinate ‘spoke’ structure in the
solid state, Fig. 1(c), like Ph PI and the majority of R PI com-
PPh2 Ph2P
3
2
3
2
N
N
pounds. Additionally, unlike some R PI compounds studied,
3
2
the diphosphorus–diiodine adducts dppeؒI and dppbؒI are
4
4
Fig. 2 Schematic representation of the structure of the ditertiary-
exclusively four-co-ordinate molecular species in the solid state,
and no minor peak in the NMR spectrum of each is observed
which could be assigned to an ionic component.
phosphine
N,NЈ-bis[o-(diphenylphosphino)benzylidene]ethylene-
diamine (dpen)
Conclusion
In agreement with previous studies on R Pl compounds, the
3
2
di- and tri-phosphorus–diiodine adducts completely ionise in
3
1
CDCl , as shown from solution P-{H} NMR studies. The
3
Ϫ1
observation of a Raman band at ca. 110 cm for solid samples
of the compounds, tentatively assigned to ν(I᎐I), and more
31
importantly, the vastly different solid-state P-{H} MAS NMR
shift compared to the solution values for Ph P(I )CH CH -
2
2
2
2
P(I )Ph2 and Ph P(I )(CH ) P(I )Ph , strongly indicate that
2
2
2
2
4
2
2
these compounds are molecular four-co-ordinate species in the
solid state. This statement is further strengthened by the fact
31
that the solid-state P-{H} NMR shift for Ph PI is similar to
3
2
that of the Ph P(I )(CH ) P(I )Ph and Ph P(I )(CH ) P(I )Ph
2
2
2
2
2
2
2
2
2
4
2
2
adducts described here; Ph Pl has been shown to be a molecu-
3
2
lar four-co-ordinate species in the solid state by a single-crystal
X-ray diffraction study. Additionally, the CDCl solution
3
Fig.
3
Low frequency Raman spectrum of tetraiodo-N,NЈ-bis-
o-(diphenylphosphino)benzylidene]ethylenediamine (dpenؒI4)
31
P-{H} NMR shift of Ph PI , known to be ionic, [Ph PI]I, is
[
3
2
3
similar to the shifts of Ph P(I )(CH ) P(I )Ph and Ph P(I )-
2
2
2
2
2
2
2
2
(
CH ) P(I )Ph in CDCl solution, thus indicating, in agree-
2 4 2 2 3
1–3
ment with previous studies,
that ditertiaryphosphine di-
iodides ionise, [R P(I)(CH ) P(I)R ]2I, in CDCl solution.
2
2
n
2
3
Experimental
All the di- and tri-tertiaryphosphine–diiodine adducts
described are moisture sensitive. Therefore strictly anaerobic
and anhydrous conditions must be observed for their successful
synthesis. Any subsequent manipulation of the compounds was
performed in a Vacuum Atmospheres HE-493 glove-box. The
tritertiaryphosphines, bis(2-diphenylphosphinoethyl)phenyl-
phosphine and tris(diphenylphosphinomethyl)ethane were
obtained commercially (Aldrich) as was diiodine. All were used
as received. The ditertiaryphosphines were all synthesised by
the same method, the synthesis of bis(diphenylphosphino)-
ethane is typical. Small pieces of lithium metal (5.25 g, 0.75
mol) were added with stirring to a solution of triphenyl-
3
1
Fig. 4 Solid-state P-{H} MAS NMR spectrum of tetraiodo-1,2-
bis(diphenylphosphino)ethane (dppeؒI4)
ditertiaryphosphine
idene]ethylenediamine (dpen) is illustrated in Fig. 2. The low
N,NЈ-bis[o-(diphenylphosphino)benzyl-
3
phosphine (53.4 g, 0.2 mol) in tetrahydrofuran (THF) (300 cm )
frequency Raman spectra of its diiodine adduct (dpenؒI ) is
illustrated in Fig. 3.
in a 1 l three-necked flask equipped with a condenser. The
resultant mixture was then refluxed until a deep red solution
4
J. Chem. Soc., Dalton Trans., 1998, Pages 2379–2382
2381

View Article Online
formed and all of the lithium had been consumed. The result-
NMR spectra for the compounds Ph P(I )(CH ) P(I)Ph (n = 2
2 2 2 2
n
ant solution of lithium diphenylphosphide was cooled to 0 ЊC
or 4) were recorded on a Bruker ASL 500MHz high-resolution
multiprobe MAS solid-state spectrometer relative to concen-
trated phosphoric acid as standard.
and a solution of 1,2-dichloroethane (5.94 g, 0.06 mol) in THF
3
(
20 cm ) was added dropwise. After stirring for ca. 30 min a
change from red to straw coloured was observed. The mixture
was allowed to slowly warm to room temperature and sub-
sequently poured slowly into water (ca. 2 l). The organic layer
was separated and dried over sodium sulfate. The THF was
then removed and the resultant solid recrystallised from
toluene–methanol. Yield ca. 70%.
Acknowledgements
We thank Mr. P. J. Kobryn (University of Manchester) for
recording the Raman spectra and the EPSRC for a research
studentship (to J. M. S.).
Diethyl ether (BDH) was dried over sodium wire for ca. 1 d
and subsequently distilled over CaH in an inert atmosphere
2
References
(
N ). All the diiodine adducts of the di- or tri-tertiaryphosphine
2
1
B. M. Gladstein, V. G. Noskov and L. Z. Soborovskii, Zh. Obshch.
Khim., 1967, 37, 2513.
compounds were synthesised by the direct reaction of the di- or
tri-tertiaryphosphine with 2 or 3 mol equivalents of diiodine,
respectively. The synthesis of Ph P(I )CH CH P(I )Ph is typ-
2
3
4
S. P. Schmidt and D. W. Brooks, Tetrahedron Lett., 1987, 28, 767.
J. Ellermann and D. Schirmacher, Chem. Ber., 1969, 102, 289.
S. M. Godfrey, D. G. Kelly, A. G. Mackie, C. A. McAuliffe, R. G.
Pritchard and S. M. Watson, J. Chem. Soc., Chem. Commun., 1991,
1163.
2
2
2
2
2
2
ical: 1,2-bis(diphenylphosphino)ethane (dppe) (2.00 g, 5.02
3
mmol) was suspended in diethyl ether (ca. 100 cm ) in a rotaflo
tube and subsequently diiodine (2.55 g, 10.05 mmol) was
added. After ca. 4 d the resultant mustard coloured solid was
isolated by standard Schlenk techniques and dried in vacuo. The
reaction product was then transferred to pre-dried argon-filled
ampoules which were flame sealed. Elemental analyses (Table 1)
were performed by the analytical laboratory of this depart-
ment. Electronic spectra were recorded on a Shimadzu UV-
5
6
N. Bricklebank, S. M. Godfrey, A. G. Mackie, C. A. McAuliffe,
R. G. Pritchard and P. J. Kobryn, J. Chem. Soc., Dalton Trans., 1993,
1
01.
N. Bricklebank, S. M. Godfrey, H. P. Lane, C. A. McAuliffe, R. G.
Pritchard and J. M. Moreno, J. Chem. Soc., Dalton Trans., 1995,
2421.
7 J. Goubeau and R. Baumigartner, Z. Elektrochem., 1960, 64, 598.
8
9
F. W. Parrett, Spectrochim. Acta, Part A, 1969, 26, 1271.
S. M. Godfrey, N. Ho, C. A. McAuliffe and R. G. Pritchard, Angew.
Chem., Int. Ed. Engl., 1996, 35, 2343.
2
101PC spectrophotometer. Raman spectra were recorded by
the University of Manchester Raman service using a Coherent
Innova 90 5W argon-ion laser and SPEX 1403 double mono-
chromator (focal lengths 0.85 m) fitted with a BGCS micro-
scope sampling attachment. The radiation was detected using a
Hamamatsu R928 photomultiplier tube which was cooled to
Ϫ30 ЊC in a Products for Research Inc. TE 177 RF-005 cooler
housing. The data were processed on a SPEX DM1B data
1
1
0 H. Pritzkow, Acta Crystallogr., Sect. B, 1975, 31, 1505.
1 A. I. Popov and R. F. Svenson, J. Am. Chem. Soc., 1955, 77, 3724.
12 F. W. Parrett and N. J. Naylor, J. Inorg. Nucl. Chem., 1970, 32, 2458.
13 E. M. Nour, L. H. Chen and J. Lane, J. Phys. Chem., 1986, 90, 2481.
1
4 R. Poli, J. C. Gordon, R. K. Khanna and P. E. Fanwich, Inorg.
Chem., 1992, 31, 3165.
31
15 P. Deplano, S. M. Godfrey, F. Isaia, C. A. McAuliffe, M. L. Mercuri
and E. F. Trogu, Chem. Ber., 1997, 130, 299.
station. The P-{H} NMR spectra for all the compounds were
recorded as CDCl3 solutions on a Bruker AC200 high-
resolution multiprobe spectrometer relative to concentrated
31
phosphoric acid as standard. The P-{H} MAS solid-state
Received 27th August 1997; Paper 7/06277J
2
382
J. Chem. Soc., Dalton Trans., 1998, Pages 2379–2382