A structural and spectroscopic study of tris-aryl substituted R 3PI2 adducts

Article abstract of DOI:10.1016/j.poly.2011.12.023

A series of Ar₃PI₂ adducts [Ar = (o-OCH ₃C₆H₄), (m-OCH₃C₆H ₄), (p-OCH₃C₆H₄), (o-SCH ₃C₆H₄), (p-SCH₃C₆H ₄), (m-FC₆H₄), (p-FC₆H₄), (p-ClC₆H₄)] have been synthesized via the 1:1 reactions of Ar₃P with di-iodine. The ³¹P{¹H} NMR spectra of a series of Ar₃PI₂ adducts has been examined to resolve previous inconsistent reports. Ar₃PI₂ adducts do not ionize to [Ar₃PI]I in CDCl₃, and in many cases the molecular Ar₃PI₂ "spoke" adduct is stable in solution, with the degree of stability being highly dependent on the nature of the aryl group. The structures of the majority of these adducts have been established by X-ray diffraction studies. Whilst P-I and I-I bond lengths are primarily influenced by electronic effects, steric and crystal packing effects may also have an influence, as shown by the different polymorphs of (p-FC ₆H₄)₃PI₂, where a change in the conformation of the aryl groups in one of the molecules results in a lengthening of the P-I bond and shortening of the I-I bond.

Full text of DOI:10.1016/j.poly.2011.12.023

Polyhedron 35 (2012) 31–46
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A structural and spectroscopic study of tris-aryl substituted R3PI2 adducts
1
⇑
Nicholas A. Barnes , Stephen M. Godfrey , Rana Z. Khan, Amber Pierce, Robin G. Pritchard
School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of Ar3PI2 adducts [Ar = (o-OCH3C6H4), (m-OCH3C6H4), (p-OCH3C6H4), (o-SCH3C6H4), (p-SCH3C6H4),
(m-FC6H4), (p-FC6H4), (p-ClC6H4)] have been synthesized via the 1:1 reactions of Ar3P with di–iodine. The
31P{1H} NMR spectra of a series of Ar3PI2 adducts has been examined to resolve previous inconsistent
reports. Ar3PI2 adducts do not ionize to [Ar3PI]I in CDCl3, and in many cases the molecular Ar3PI2 ‘‘spoke’’
adduct is stable in solution, with the degree of stability being highly dependent on the nature of the aryl
group. The structures of the majority of these adducts have been established by X-ray diffraction studies.
Whilst P–I and I–I bond lengths are primarily influenced by electronic effects, steric and crystal packing
effects may also have an influence, as shown by the different polymorphs of (p-FC6H4)3PI2, where a
change in the conformation of the aryl groups in one of the molecules results in a lengthening of the
P–I bond and shortening of the I–I bond.
Received 8 September 2011
Accepted 20 December 2011
Available online 10 January 2012
Keywords:
Phosphines
Charge transfer adducts
Iodine
Ligand conformation
Crystal packing
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
latter type of CT complex should feature shorter P–X bonds and
long X–X bonds/soft–soft interactions.
Molecules of formula R3PX2 (X = F, Cl, Br, I) have been known for
many years, and are formed when tertiary phosphines are com-
bined with a stoichiometric ratio of the appropriate halogen. The
solid-state structures of R3PX2 adducts are surprisingly diverse,
and encompass three main structural types (Fig. 1), (i) molecular
five-coordinate trigonal bipyramidal species, (ii) ionic halo-phos-
phonium salts, and (iii) charge-transfer (CT) ‘‘spoke’’ adducts,
R3P–X–X, which feature a linear P–X–X angle. This linear arrange-
ment is consistent with a CT interaction between the HOMO orbital
of the phosphorus donor atom and the r⁄ LUMO orbital on the I2
acceptor. The structure favoured by a particular adduct is depen-
dent on the identity of the halogen and the R groups, and also
the solvent of preparation and/or recrystallisation [1].
The trigonal bipyramidal structure is favoured when X = F and is
also observed for a number of R3PCl2 adducts with electron with-
drawing R groups. In contrast, the majority of R3PCl2 and R3PBr2
adducts are ionic, [R3PX]X, whilst the CT ‘‘spoke’’ structure,
R3PX–X, is most commonly observed when X = I. The interpretation
of a particular structure as ionic or CT is often not straightforward
as halo-phosphonium halides often exhibit strong cation–anion
interactions between the P–X bound halogen atom and the halide
anion [2–16], especially when X = I. The ‘‘spoke’’ compounds may
be considered either as CT adducts with R3P as the donor and X2
as the acceptor, (10–I–2) CT systems, or alternatively as systems
featuring [R3PX]+ as the acceptor and XÀ as the donor [17]. This
Only four structures of ionic [R3PBr]Br salts have been reported,
where R = iPr3 [5], Et3 [6], Ph3 [4], and Bu2 Pr [7]. The BrÁ Á ÁBr dis-
tances between the cation and anion in these structures vary be-
tween 3.12 and 3.42 Å, these distances being considerably
shorter than the sum of the van der Waals radii for two bromine
atoms (3.9 Å), but considerably longer than the Br–Br distances
of 2.705(3)/2.717(1) Å observed for the CT complex Me2SBr2
[18,19]. This suggests that R3PBr2 adducts may be regarded either
as ionic, or as CT adducts of the [R3PBr]+ (acceptor)/BrÀ (donor)
type.
t
i
The situation for R3PI2 adducts has been the subject of some
controversy as I–I distances in reported structures of R3PI2 adducts
vary considerably, between 3.021(1) Å for (Mecarb)iPr2PI2 [Me-
carb = 1-(2-Me-1,2-C2B10H10)] [11], and 3.6389(14) Å for [(nPr2N)3
PI]I [14]. The length of the IÁ Á ÁI interaction in these systems is
clearly highly sensitive to the nature of the R groups bound to
the phosphorus atom. Adducts such as (Mecarb)iPr2PI2 [11], (o-
CH3C6H4)3PI2, d(I–I): 3.0727(4) Å [12], and Ph3PI2, d(I–I):
3.161(2) Å [3], feature relatively short I–I interactions, and are in-
tensely coloured yellow or orange materials. On the basis of these
observations a (10–I–2) CT assignment is appropriate for these
compounds. R3PI2 adducts of tri-alkyl or tris-(alkylamino) substi-
tuted phosphines are usually pale yellow or cream solids, and often
feature long I–I distances, i.e. [tBu3PI]I, d(I–I): 3.326(1) Å [2], and
[iPr3PI]I, d(I–I): 3.383(1)/3.372(1) Å [10]. These I–I distances are
still well within the sum of the van der Waals radii for two iodine
atoms (3.96 Å) [20], and these adducts can either be regarded as
ionic (with significant soft–soft, cation–anion interactions), or as
CT adducts of the [R3PI]+ (acceptor)/IÀ (donor) type. The propensity
⇑
Corresponding author. Tel.: +44 0 161 306 4516; fax: +44 0 161 306 4559.
E-mail address: nick_barnes28@hotmail.com (N.A. Barnes).
Deceased.
1
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.12.023

32
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
packing also play a significant role. The structures of the series of
tolyl-substituted adducts, o-, m- and p-(CH3C6H4)3PI2 show that
the o-substituted adduct displays a significantly longer P–I bond,
and significantly shorter I–I bond [2.5523(12) and 3.0727(4) Å,
respectively] than either the m- or p-substituted analogues
[2.472(4)–2.477(4)/3.1807(6)–3.1807(13), respectively] [12,16].
This reflects the cone angles of the tolyl-phosphine groups in these
three adducts; 192.2° for (o-CH3C6H4)3PI2, compared to 154.5° for
(m-CH3C6H4)3PI2 and 145.0° for (p-CH3C6H4)3PI2 [16]. The particu-
larly large cone angle in (o-CH3C6H4)3PI2 is due to the phosphine
adopting a sterically demanding exo3 conformation, (where an
exo substituent is defined as a group pointing towards the apex
of a pyramid consisting of the three para hydrogens as the base
and the atom bound to phosphorus as the apex) [22].
Fig. 1. Main structural types observed for R3PX2 adducts; (a) trigonal bipyramidal,
(b) ionic halo-phosphonium, (c) charge-transfer molecular ‘‘spoke’’ adduct.
These observations suggest that it is the large steric bulk of the
exo3 (o-CH3C6H4)3P group which is responsible for the lengthening
of the P–I bond and concomittant shortening of the I–I bond. The
exo3 conformation appears to be preferred over the less sterically
demanding exo2 conformation, since the exo3 conformation allows
two (o-CH3C6H4)3PI2 molecules to pack back-to-back as a dimer
pair (Fig. 2a), whereby a number of concerted multiple embraces
between the tolyl rings are set up. The dimer pair in (o-
CH3C6H4)3PI2 are linked by six edge-to-face (EF) embraces between
the rings (Fig. 2b). This (EF)6 aryl embrace has been shown by
Dance and co-workers to be one of the most commonly observed
ring embracing motifs in structures containing Ph3P and [Ph4P]+
groups [23–26]. In the structure of (o-CH3C6H4)3PI2 the embracing
pairs are further linked by hydrogen bonding between the iodine
and protons on the tolyl ring.
The conformation adopted by the Ar3P groups in Ar3PI2 adducts
has an impact on the steric properties, which may change signifi-
cantly with a change in orientation of the aryl rings, particularly
when the rings are substituted. These changes in the steric profile
in turn has an effect on the magnitude of the P–I and I–I bond
lengths.
We have therefore widened our studies on Ar3PI2 adducts in or-
der to establish how the substitution of different groups in differ-
ent positions on the aryl rings affects both the steric and electronic
properties of the Ar3P fragment, and what influence these changes
have on the magnitude of the P–I and I–I bond lengths.
2. Results and discussion
2.1. Synthesis of R3PI2 adducts and Raman spectroscopic data
The series of tris-aryl substituted R3PI2 adducts were synthe-
sized via the reaction of the appropriate phosphine with one equiv-
alent of iodine in dry diethyl ether as shown in Scheme 1.
The adducts formed are typically orange-yellow in colour
(except for 4 which is red, and 7 which is olive-green), and were
treated as moisture sensitive. All of the compounds have been
characterized by elemental analysis, multinuclear NMR spectros-
copy, Raman spectroscopy and in most cases by single-crystal
X-ray diffraction (except for 1 and 4 which exhibit poor solubility
in a range of common solvents). Elemental analytical results
confirmed the formation of a 1:1 adduct in all cases.
Fig. 2. (a) Dimer pairs formed by (EF)6 embrace between two back-to-back
molecules of (o-CH3C6H4)3PI2. (b) Formation of six edge-to-face tolyl ring embraces.
The deep red colour exhibited by (o-SCH3C6H4)3PI2 (4), is unu-
sual, and was initially suggestive of the formation of an [I3]À con-
taining salt. However, the bulk solid of 4 analyses to a 1:1 R3P:I2
stoichiometry, but the poor solubility prevented us from obtaining
crystals. The Raman spectrum of 4 also shows a significant differ-
ence to that of the other adducts. The spectra of 1–3 and 7–8 all
show peaks between 130 and 160 cmÀ1 (5 and 6 fluoresce and
for R3PI2 compounds to display soft–soft IÁ Á ÁI contacts is illustrated
by the fact that [N(CH2CH2NiBu)3PI]I is the only structure of an
R3PI2 adduct to feature no IÁ Á ÁI contact below the sum of the van
der Waals radii for two iodine atoms, the closest approach being
7.18 Å [21].
While the electronic properties of the R groups are an important
influencing factor in the magnitude of the P–I and I–I bond lengths
in R3PI2 adducts, other factors such as steric effects and crystal
decompose in the laser beam), which have been assigned as
m(P–
I) stretches in previous studies of R3PI2 compounds [8,27–29].

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
33
Scheme 1. Reactions of Ar3P with I2.
Table 1
31P{1H} NMR spectroscopic data for Ar3P, Ar3PI2, [Ar3PI]+, [Ar3POH]+/[{Ar3PO}2H]+, and [Ar3PH]+ species, (chemical shifts given in ppm, coupling constants in Hz).
a
Ar3P system
dP R3P
dP R3PI2 spoke
dP [R3PI]+
dP [R3POH]+/[{R3PO}2H]+
dP [R3PH]+ (1JPH
)
Ph3P
(o-CH3C6H4)3P
(m-CH3C6H4)3P
(p-CH3C6H4)3P
(o-OCH3C6H4)3P (1)
(m-OCH3C6H4)3P (2)
(p-OCH3C6H4)3P (3)
(o-SCH3C6H4)3P (4)
(p-SCH3C6H4)3P (5)
(m-FC6H4)3P (6)
(p-FC6H4)3P (7)
(p-ClC6H4)3P (8)
À7.7
À37.2
À10.2
À7.3
À23.4
À21.5
À13.1
À11.1
À34.6
À18.5
À12.7
À31.4
À16.3
À29.8
À20.2
À14.1
+12.0
À8.6
+6.0
+44.7
+48.6
+48.2
+47.3
+56.5
+47.8
+50.9
+40.7
+47.9
+40.6
+39.8
+35.0
À5.1 (514)
À10.9 (504)
À5.6 (518)
À5.0 (513)
À17.9 (551)
À5.6 (525)
À8.6 (531)
À12.9 (548)
À3.8 (515)
N/A
+4.6
À39.2
À2.6
À15.8
+5.5
À9.5
+5.7
N/A
+5.9
À14.7
À4.2
À5.1
À30.6
À8.3
À5.6
À8.4
N/A
N/A
À7.8
a
Data for [R3PI]+ cationic species from reported [R3PI][I3] salts [37].
The spectrum of 4 also displays a peak within this region (at
160 cmÀ1), but this peak is much more intense than the
(P–I)
bands in the spectra of the other adducts. This may be suggestive
that in the case of 4 this band is due to (I–I), not (P–I).
The m1 Raman active (I–I) mode for free I2 is observed at
180 cmÀ1 [30], and has been observed to fall to lower frequencies
upon formation of donor complexes D–I–I (D = donor atom) [31–
at much lower frequencies, i.e. À17.8 ppm for the CT form of Ph3PI2
[27].
m
Subsequently, Deplano et al. studied the reaction between Ph3P
and varying ratios of I2 using 31P{1H} NMR spectroscopy. They
showed that dP was highly dependent on the ratio of Ph3P:I2, with
continuous shifting of dP as the ratio of I2 is increased [17]. Initially,
dP shifts to lower frequency, from À7.7 ppm (Ph3P) to À23.4 ppm
when a 1:1 ratio is present. This value is consistent with that ob-
tained for the spoke form in solid-state 31P{1H} NMR spectroscopic
studies (À17.8 ppm), and shows that the CT spoke form is present
in solution, as well as in the solid-state. Addition of excess iodine
resulted in continuous shifts to higher frequency, up to a maxi-
mum of +12.0 ppm when the I2:Ph3P ratio exceeded 2:1. This sug-
gests that the correct shift for the [Ph3PI]+ cation is +12.0 ppm, not
+44.8 ppm as initially reported [3]. It therefore seems likely that
the shifts previously reported for the ionized forms of Ar3PI2 ad-
ducts (between +40 and +50 ppm), are incorrect, and arise from
hydrolysis of the cation to form either [Ar3POH]+ or [{Ar3PO}2H]+
species, which have been shown to be the major hydrolysis prod-
ucts obtained when R3PI2 compounds are exposed to water or
moist air [10]. We have observed that the CT spoke form of (o-
CH3C6H4)3PI2 is also stable in CDCl3 solution, as the 31P{1H} NMR
spectrum of this adduct shows a broad signal at À21.5 ppm [12].
In view of the conflicting data regarding the behaviour of R3PI2
adducts in solution we have carefully monitored the 31P{1H} NMR
spectra of 1–8 over a period of several weeks, and re-examined the
data for Ph3PI2 and (o/m/p-CH3C6H4)3PI2 adducts for comparative
purposes. In all cases the aryl phosphine was dissolved (or sus-
pended) in CDCl3 and one equivalent of iodine added. The reactions
were performed (a) in the dry box using CDCl3 dried over molecu-
lar sieves, and (b) in air using standard-grade CDCl3, in order to
determine which resonances are due to hydrolysis products. The
different species observed for each system and their shifts are sum-
marised in Table 1, along with data for [R3PI]+ cationic species from
[R3PI][I3] salts [37].
m
m
33]. This lowering of the m1(I–I) mode is consistent with donation
of electron density from the donor non-bonding orbital into the
LUMO di-iodine r⁄ antibonding orbital. Deplano et al. have corre-
lated m1(I–I) Raman data with I–I bond lengths for many donor:I2
adducts [32,34]. Where the I–I bond order is higher than 0.6, (rel-
ative to a bond order of 1.0 corresponding to that of free di-iodine
at 2.715(6) Å) [35], then the adduct is classified as being of the D–
I–I type (10–I–2) CT system, where the I–I bond is typically be-
tween 2.8 and 3.0 Å. m1(I–I) bands for this type of adduct are com-
monly observed between 150 and 180 cmÀ1, and the data for 4
suggests that this adduct may be of this type, which would be con-
sistent with the deep red colour of the compound. This would be
extremely unusual for a D–I2 complex where the donor is phospho-
rus, as the I–I bond order in these adducts is typically less than 0.4,
with I–I bonds over 3.01 Å. An alternative assignment of the struc-
ture of 4 (based on Raman m(I–I) data), could be a perturbed inter-
calated R3PÁ Á ÁI–IÁ Á ÁPR3 structure, as observed in the structure of
(Mecarb)Ph2PÁ Á ÁI–IÁ Á ÁPPh2(Mecarb) [36]. However, this is ruled
out as the microanalytical data suggests that the R3P:I2 ratio of 4
is 1:1.
2.2. 31P{1H} NMR spectroscopic studies
Conflicting data has previously been reported regarding the
31P{1H} NMR spectra of R3PI2 adducts. It was initially reported that
all R3PI2 adducts ionized to [R3PI]I in CDCl3 solution, irrespective of
whether the solid-state structure of the adduct was CT or ionic
[3,27]. The reported chemical shifts are highly dependent on the
nature of R, but when R is an aryl group the resonances assigned
to [Ar3PI]+ species have been reported to lie between +40 and
+50 ppm [3,8,27]. However, in the solid-state, MAS 31P{1H} NMR
studies showed that shifts for R3PI–I ‘‘spoke’’ adducts are observed
The 31P{1H} NMR spectra of the 1:1 mixtures of the aryl phos-
phine and I2 performed in anhydrous conditions initially display
a broad peak in the region À10 to À35 ppm. These peaks are usu-
ally shifted to lower frequencies from that of the starting phos-
phine, except for (o-CH3C6H4)3PI2 and (o-OCH3C6H4)3PI2 1, where

34
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
I2
I1
C14
C13
C12
O1
C4
C2
C3
P1
C1
C8
C15
C10
O2
C5
C7
C16
C6
C9
C21
C20
C11
C17
C19
C18
O3
Fig. 3. ORTEP representation of the molecular structure of (m-OCH3C6H4)3PI2 (2). Thermal ellipsoids are shown at the 30% probability level. Selected bond lengths [Å] and
angles [°]: P(1)–I(1): 2.454(2), I(1)–I(2): 3.2123(7), P(1)–C(1): 1.790(7), P(1)–C(8): 1.802(7), P(1)–C(15): 1.793(7), P(1)–I(1)–I(2): 177.42(5), I(1)–P(1)–C(1): 111.2(2), I(1)–
P(1)–C(8): 107.3(3), I(1)–P(1)–C(15): 112.0(3), C(1)–P(1)–C(8): 108.4(3), C(1)–P(1)–C(15): 107.8(3), C(8)–P(1)–C(15): 110.3(3).
I2
I1
C13
C14
O2
C11
C8
C16
C15
P1
C17
C12
C10
C9
C2
C1
C18
C7
O3
C3
C20
C6
C19
C4
C21
O1
C5
Fig. 4. ORTEP representation of the molecular structure of (p-OCH3C6H4)3PI2 (3). Thermal ellipsoids are shown at the 30% probability level. Selected bond lengths [Å] and angles
[°]: P(1)–I(1): 2.448(4), I(1)–I(2): 3.2575(15), P(1)–C(1): 1.66(3), P(1)–C(8): 1.802(16), P(1)–C(15): 1.757(18), P(1)–I(1)–I(2): 170.75(12), I(1)–P(1)–C(1): 115.4(7), I(1)–P(1)–
C(8): 106.6(5), I(1)–P(1)–C(15): 107.5(6), C(1)–P(1)–C(8): 108.0(8), C(1)–P(1)–C(15): 108.5(9), C(8)–P(1)–C(15): 110.8(8).
the shift is slightly to higher frequency. For the other o-substituted
adduct, (o-SCH3C6H4)3PI2 4, the shift to lower frequency is very
small. These broad peaks are often located at similar chemical
shifts to those of the free phosphine, and may have been mistaken
in the past for unreacted starting material. When the same samples
are made up in air (with no attempt to exclude moisture), two
peaks are typically seen in each spectrum. The peak for the spoke
adduct is again observed, along with a second peak found between

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
35
I2
I1
C9
C10
C11
S2
C8
C16
P1
C1
C2
C6
C5
C12
C14
C15
C13
C17
C18
C3
C4
C7
S1
C20
C19
S3
C21
Fig. 5. ORTEP representation of the molecular structure of (p-SCH3C6H4)3PI2 (5). Thermal ellipsoids are shown at the 30% probability level. Selected bond lengths [Å] and angles
[°]: P(1)–I(1): 2.468(2), I(1)–I(2): 3.1946(8), P(1)–C(1): 1.783(7), P(1)–C(8): 1.795(7), P(1)–C(15): 1.783(7), P(1)–I(1)–I(2): 173.55(5), I(1)–P(1)–C(1): 110.5(2), I(1)–P(1)–C(8):
107.5(3), I(1)–P(1)–C(15): 111.2(2), C(1)–P(1)–C(8): 110.6(3), C(1)–P(1)–C(15): 109.9(4), C(8)–P(1)–C(15): 107.1(3).
Table 2
Comparison of P–I and I–I bond lengths, and P–I–I angles in reported R3PI2 structures.
Compound
P–I (Å)
I–I (Å)
P–I–I (°)
Ref.
i
a
(Mecarb) Pr2PI2
2.5978(14)
2.5523(12)
2.507(3)
2.461(3)
2.488(2)
2.476(4)
2.475(4)
2.485(3)
2.481(4)
2.479(3)
2.472(5)
2.468(2)
2.460(3)
2.454(2)
2.448(4)
2.461(2)
3.021(1)
177.49(3)
174.32(3)
177.76(7)
173.07(7)
178.86(6)
177.58(10)
174.10(10)
170.02(8)
178.23(6)
173.82(8)
178.75(9)
173.55(5)
171.91(8)
177.42(5)
170.75(12)
177.6(1)
[11]
[12]
This paper
(o-CH3C6H4)3PI2
3.0727(4)
3.0807(12)
3.1529(11)
3.1332(9)
3.1347(13)
3.1500(14)
3.1463(11)
3.161(2)
3.1815(13)
3.1809(17)
3.1946(8)
3.1985(11)
3.2123(7)
3.2575(15)
3.326(1)
(p-FC6H4)3PI2, 7bb
(p-ClC6H4)3PI2, 8
(m-FC6H4)3PI2, 6c
This paper
This paper
(o–PhC6H4)Ph2PI2
Ph3PI2
[15]
[3]
[16]
[16]
This paper
This paper
This paper
This paper
[2]
(m-CH3C6H4)3PI2
(p-CH3C6H4)3PI2
(p-SCH3C6H4)3PI2, 5
(p-FC6H4)3PI2, 7ad
(m-OCH3C6H4)3PI2, 2
(p-OCH3C6H4)3PI2, 3
tBu3PI2
[2,4,6-(MeO)3C6H2]3PI2
2.482(1)
2.409(2)/2.420(2)
2.410(2)
2.4303(17)
2.4730(8)
2.427(3)–2.448(5)e
2.455(4)
3.3394(5)
3.383(1)/3.372(1)
3.408(2)
3.5170(6)
3.6168(4)
3.6378(14)
3.6389(14)
7.18f
174.52(5)
174.11(6)/179.06(5)
177.01(6)
167.97(4)
171.97(2)
175.08(8)
161.12(9)
N/A
[9]
[10]
[8]
[14]
[14]
[13]
[14]
[21]
iPr3PI2
Me2PhPI2
[(C4H8N)3PI]I
[(Et2N)3PI]I
[{(Me2N)3PI}I]6CH3CN
[(nPr2N)3PI]I
[N(CH2CH2NiBu)3PI]I
2.5814(8)
a
b
c
d
e
f
(Mecarb) = 1-(2-Me-1,2-closo-C2B10H10).
Triclinic form (orange) of (p-FC6H4)3PI2 with two independent molecules in the asymmetric unit.
Two independent molecules in the asymmetric unit.
Monoclinic form (olive-green) of (p-FC6H4)3PI2.
Value for P–I in cation interacting with an IÀ is 2.427(3) Å.
Closest IÁ Á ÁI contact in the structure, no linear P–IÁ Á ÁI motif observed.
À20 and 0 ppm, (with the exception of 6, 7 and 8 which show very
broad peaks assigned to the spoke adducts, and a second promi-
nent peak around +40 to +45 ppm, assigned to hydrolysis products,
see below). We have shown that dP for [Ar3PI]+ cations in [Ar3PI][I3]
salts is typically observed between +10 and À10 ppm [37], and it
was therefore assumed that the species observed between À20
and 0 ppm in the above reactions were due to ionization of the
Ar3PI2 spoke adducts to [Ar3PI][I]. However, when the 31P NMR
spectra are recorded proton coupled the resonances in this region
all appear as doublets with couplings in the range 500–560 Hz.

36
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
Couplings of this magnitude are consistent with 1J(PH) coupling for
[R3PH]+ cationic species. Previous literature data for [R3PH]+ is
sparse, however data for [Ph3PH][HBr2] (dP: À4.6 ppm, 1J(PH) =
532 Hz) [38], [{o-CH3C6H4}3PH][HB(C6F5)3] (dP: À12.1 ppm,
1J(PH) = 485 Hz in CD2Cl2) [39] and [{p-CH3C6H4}3PH][HBr2] (dP:
À4.2 ppm, 1J(PH) = 529 Hz in CD2Cl2) [38], are consistent in all
three cases with the second species observed in the 31P NMR spec-
tra of Ph3PI2, (o-CH3C6H4)3PI2 and (p-CH3C6H4)3PI2, see Table 1. It
would therefore appear that [Ar3PI]+ cationic species are not ob-
served in the 31P{1H} NMR spectra of Ar3PI2 compounds, either in
anhydrous conditions, or in samples prepared in air. This certainly
It would appear that steric arguments are less important when
ring substitution is in the m- or p-positions, where any variations
in the P–I and I–I bond lengths are due to changes in the electronic
properties of the aryl groups. The adduct displaying the shortest P–
I bond of the three compounds, (p-OCH3C6H4)3PI2 3, displays the
longest I–I bond, which is consistent with electronic arguments
whereby a more electron-donating R group will result in a short-
ened P–I bond and lengthened I–I bond. The bond length data for
2, 3 and 5 suggests that the order of electron-donating ability of
the three phosphines towards iodine is (p-OCH3C6H4)3P > (m-
OCH3C6H4)3P > (p-SCH3C6H4)3P, although the differences are fairly
small between the three, (see Table 2). The I–I bonds in 2 and 3
are among the longest seen for aryl-substituted R3PI2 adducts,
but are still noticeably shorter than those of tri-alkyl R3PI2 adducts
[2,10], and {2,4,6-(MeO)3C6H2}3PI2 [9], where the I–I bond is
3.3394(5) Å. This adduct displays a unusually long P–I bond of
2.482(1) Å for such an electron rich phosphine, and is significantly
longer than the P–I bond in either 2 or 3. This suggests that the
long P–I bond in {2,4,6-(MeO)3C6H2}3PI2 is due to a steric affect
arising from the presence of methoxy groups in both o-positions
on each the rings. This double substitution greatly increases the
steric bulk, as illustrated by the very large crystallographic cone
angle of 211.6°, significantly larger than 2 or 3.
We have previously shown that the crystal packing of Ph3PI2
and the (o/m/p-CH3C6H4)3PI2 series of adducts are dominated by
edge-to-face (EF) embraces between phenyl or tolyl rings, and
weak, non-classical, hydrogen bonding between the iodine spoke
and C–H proton atoms on the aryl rings [15,16]. The conformations
preferred by the aryl rings in these structures appear to be those
which facilitate the aryl embraces, which often results in an a spe-
cific conformation being favoured for a particular aryl group. This
has been illustrated by a comparison of Ar3PI–I spoke adducts with
linear [(Ar3P)AuX] gold(I) complexes with the same aryl group,
where the same conformations are often observed between the
two systems [15,16]. Where differences are observed between
the two systems it is often a consequence of the enhanced ability
of the P–IÁ Á ÁI iodide atom to participate in hydrogen bonding com-
pared to the metal bound halide in the gold(I) complexes. These
differences in hydrogen bonding can also result in different poly-
morphs being observed for these systems [16].
i
contrasts with analogous tri-alkyl phosphine systems such as Pr3-
PI2, which has been shown to exhibit an ionic structure in solution
[10].
The 31P{1H} NMR spectra of the Ar3PI2 adducts were examined
over time, with those prepared in air showing a peak in the region
+35 to +50 ppm becoming the predominant species, and are as-
signed as [Ar3POH]+/[{Ar3PO}2H]+ hydrolysis species [10]. Peaks
in this region only appear over many days for the samples prepared
in anhydrous conditions, again except for 6, 7 and 8 which appear
to be much more sensitive to moisture and show exclusively
hydrolysed species after several hours. In the cases of the bulky
o-substituted compounds the molecular spoke resonance persists
even in moist solution for many days, with the two new peaks only
appearing gradually over several weeks.
It therefore seems that hydrolysis of the Ar3PI2 adducts occurs
fairly rapidly with initial formation of HI, resulting in [Ar3PH]+ spe-
cies, followed by a slower hydrolysis to [Ar3POH]+/[{Ar3PO}2H]+. In
many cases the shift of [Ar3PH]+ is very close to that of the starting
phosphine, which may have resulted in previous incorrect assign-
ments of these peaks if the 31P NMR spectrum is recorded with
proton decoupling. The colour of all of the solutions darkens con-
siderably over time, suggesting that the counter anion is [I3]À,
not [I]À, although mixtures with the same cationic species may
be formed, as du Mont and co-workers have crystallised both [iPr3-
i
POH]I and [{iPr3PO}2H][I3] from the hydrolysis of Pr3PI2 [10].
2.3. Structural studies of Ar3PI2 adducts
2.3.1. Structures of anisyl- and thioanisyl-substituted Ar3PI2 adducts
Crystals of the di-iodide adducts (m-OCH3C6H4)3PI2 2, (p-
OCH3C6H4)3PI2 3, and the related thioanisyl-substituted adduct
(p-SCH3C6H4)3PI2 5, were obtained by layering dichloromethane
solutions of each with diethyl ether. Unfortunately, suitable crys-
tals of the o-analogues of both series (compounds 1 and 4) could
not be obtained due to the poor solubility of these adducts in a
range of common solvents. The molecular structures of 2, 3 and
5 are shown in Figs. 3–5, along with selected bond lengths and
angles.
The structures of all three adducts show the expected CT
‘‘spoke’’ motif, with P–I–I angles typically close to linear, e.g. be-
tween 170.76(12)° for 3, and 177.42(5)° for 2. The P–I and I–I bond
lengths for all three adducts fall within the range observed for
other Ar3PI2 compounds (see Table 2). The P–I bond lengths are
all somewhat shorter than the P–I bond in Ph3PI2, [2.454(2) Å for
2, 2.448(4) Å for 3, and 2.468(2) Å for 5], whilst the I–I distances
show an elongation in comparison to Ph3PI2, [3.2123(7) Å for 2,
3.2575(15) Å for 3, and 3.1946(8) Å for 5]. A comparison of the
crystallographic cone angles of the phosphine fragments in the
three adducts shows that there is little difference in size between
the three, with crystallographic cone angles [40,41] of 148.8° for
2, 152.5° for 3, and 147.0° for 5. All three adducts show shorter
P–I bonds and longer I–I bonds than Ph3PI2, as expected for more
electron donating phosphines, but there are only relatively small
variations in the P–I and I–I bond lengths between the three
adducts.
Whilst
a number of conformational studies of tri-phenyl
[15,23,42–44] and tri-tolyl phosphine systems [16,45–48] have
been undertaken, systems involving other substituted tri-aryl
phosphine systems have been less comprehensively examined
[46], although some reports have appeared concerning anisyl/thio-
anisyl systems [49,50], fluoro/trifluoromethyl substituted aryl
compounds [51], and those containing bulky aryl groups on the
aryl rings [52,53]. The conformations of the aryl rings in the struc-
tures of 2, 3 and 5 have been assigned by an examination of the I–
P–Cipso–Cortho torsion angles, as shown in Table 3, along with cone
angle data for comparison.
The conformation of the aryl rings in (m-OCH3C6H4)3PI2 2,
shows that all three rings are twisted in the same direction (stag-
gered propeller conformation) with I–P–C(ipso)–C(ortho) torsions
falling in a narrow range between À44° and À54°. However, in
one of the rings the methoxy group points upwards towards the
P–I bond, (exo group), whilst in the other two rings the methoxy
groups point away (endo groups), so 2 can be termed as having
an exo1 conformation using the notation of Howell et al. [22].
The structure of 2 is the first reported structure containing a (m-
OCH3C6H4)3P group, thus no previous conformational data is
known for this phosphine.
Molecules of 2 pack side-to-side in an infinite chain of slightly
offset parallel pairs, which stack down the c axis Fig. 6, with a
PÁ Á ÁP separation between adjacent molecules of 7.144 Å. The pres-
ence of the OCH3 group in the m-position clearly prevents the

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
37
Table 3
Torsion angles, cone angles and conformations of Ar3PI2 adducts.
Compound
I–P–C–C torsions (°)
Conformation
Cone angle (°)
(m-OCH3C6H4)3PI2, (2)
(p-OCH3C6H4)3PI2, (3)
(p-SCH3C6H4)3PI2, (5)
(m-FC6H4)3PI2, (6)a
À44.4(6) exo, À54.4(6) endo, À51.9(6) endo
À50.4(16), À53.1(14), À36.7(16)
63.6(7), 47.3(6), 47.6(7)
45.7(12) exo, 55.6(12) exo, 54.6(11) exo/endo
45.8(12) exo, 58.3(13) exo/endo, 43.9(13) exo
41.6(10), 53.4(10), 47.4(11)
À42.2(10), À52.3(9), À60.2(10)
À54.4(9), À52.3(10), À16.8(12)
72.9(9), 26.7(8), 28.8(9)
exo1
148.8
152.5
147.0
154.6/151.6
152.3/151.7
145.7
145.5
149.3
Staggered propeller
Staggered propeller
exo3/exo2
exo3/exo2
(p-FC6H4)3PI2, (7a)b
(p-FC6H4)3PI2, (7b)c
Staggered propeller
Staggered propeller
Staggered, one parallel ring
Staggered, one orthogonal ring
(p-ClC6H4)3PI2, (8)
145.0
a
b
c
Two independent molecules in the asymmetric unit.
Monoclinic form (olive-green) of (p-FC6H4)3PI2.
Triclinic form (orange) of (p-FC6H4)3PI2 with two independent molecules in the asymmetric unit.
slightly upwards. These differences in the ring conformations and
orientation of the ECH3 (E = O, S) groups result in slight differences
in the crystal packing.
Molecules of 3 form anti-parallel pairs which then link into
chains that propagate down the c axis, see Fig. 7. Pairs of molecules
are linked by a single offset face-to-face (OFF) embrace [54] be-
tween anisyl rings, with a PÁ Á ÁP separation of 6.944 Å between
the pair of molecules. The propagation of the chains are reinforced
by weak C–HÁ Á ÁO hydrogen bonds from aryl C–H protons to meth-
oxy oxygen atoms of neighbouring pairs, and PÁ Á ÁP separations be-
tween pairs down the chain are 7.210 Å. Each chain is linked to
neighbouring chains via a short C–HÁ Á ÁI non-classical hydrogen
bond from the terminal iodine atom, I(2), to an aryl C–H on a
neighbouring chain, [I(2)Á Á ÁH(20): 3.00 Å]. Each I(2) atom also par-
ticipates in two other hydrogen bonds to C–H atoms of neighbour-
ing chains, see Table S1.
In the packing of 5 individual molecules pair in an anti-parallel,
side-to-side fashion via two edge-to-face (EF)2 embraces. In con-
trast to 2 and 3 there are no short IÁ Á ÁH hydrogen bonds to the ter-
minal iodine atom. However, there is
a
much closer PÁ Á ÁP
separation (6.038 Å) between embracing molecules than observed
for 3. This closer PÁ Á ÁP distance may be a consequence of the pres-
ence of two (EF) aryl embraces rather than one (OFF) embrace in
the case of 3. These pairs stack diagonally down the cell parallel
to the b axis, and further embrace with neighbouring pairs via an
(OFF) interaction between thioanisyl rings, with a PÁ Á ÁP separation
of 7.088 Å between pairs. The packing is yet further extended as
these stacks are linked by (OFF) embraces between thioanisyl rings
in a back-to-back fashion down the a cell direction, with much
longer PÁ Á ÁP separations (9.076 Å). Finally, weak C–HÁ Á ÁH–C con-
tacts are observed between SCH3 groups of molecules (also along
the a cell direction). The network that is built up by these interac-
tions is shown in Fig. 8.
Fig. 6. Packing of (m-OCH3C6H4)3PI2 (2) looking down the
aggregation of offset-parallel pairs packing in a side-to-side fashion.
c axis, showing
back-to-back association of molecules, which instead pack side-to-
side with methoxy C–H protons pointing towards anisyl rings of
the neighbouring molecules. The I–PÁ Á ÁP–I torsion angle between
adjacent molecules is 2.9°, and chains of these pairs then build
up in a zig-zag fashion (also showing methoxy C–H to ring con-
tacts), with each pair the mirror image of the pairs either side.
The terminal iodine atom participates in three non-classical hydro-
gen bonds to ring protons on anisyl rings, see Table S1 in supple-
mentary material.
The structures of (p-OCH3C6H4)3PI2 (3) and (p-SCH3C6H4)3PI2 (5)
both exhibit slightly staggered propeller conformations. In 3 the I–
P–C(ipso)–C(ortho) torsion angles are À50.4(16)°, À53.1(14)°, and
À36.7(16)°, and the OCH3 groups on all three rings are oriented
such that they point downwards with respect to the P–I–I portion
of the molecule. In 5 the I–P–C(ipso)–C(ortho) torsion angles are
63.6(7)°, 47.3(6)°, and 47.6(7)°, with one ring somewhat flatter
than the other two. In contrast to 3 only two of the SCH3 groups
are orientated so that they are pointing downwards relative to
the P–I–I spoke, whereas in the flatter ring the SCH3 is pointing
2.3.2. Structures of halo-substituted Ar3PI2 adducts
The crystal structures of the halo-substituted aryl adducts (m-
FC6H4)3PI2 6, (p-FC6H4)3PI2 7, and (p-ClC6H4)3PI2 8 were obtained
via re-crystallization from dichloromethane solutions layered with
diethyl ether. In the case of 7 a mixture of olive-green and orange
crystals were formed. These were shown to be two different poly-
morphs (see below), the olive-green crystals being the monoclinic
form 7a, and the orange crystals the triclinic form 7b. The molec-
ular structures of 6, 7a, 7b and 8 are shown in Figs. 9–12 below,
along with selected bond lengths and angles. Both 6 and 7b contain
two independent molecules in the asymmetric unit. The conforma-
tions of 6, 7a, 7b and 8 have been assigned by an examination of
the I–P–Cipso–Cortho torsion angles, as shown in Table 3, along with
cone angle data.
The P–I and I–I bond lengths in the structure of 6 are 2.475(4)/
2.474(4) Å (P–I), and 3.1347(13)/3.1500(14) Å (I–I). These values

38
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
Fig. 7. Crystal packing of (p-OCH3C6H4)3PI2 (3) looking down the a axis, showing chains of anti-parallel molecules, and chains linked by weak C–HÁ Á ÁI non-classical hydrogen
bonds.
ports on ruthenium complexes containing the (m-FC6H4)3P ligand
also show partial occupancy of some of the m-fluorine atoms
[55], in some cases on all three rings on each ligand. This results
in all four possible conformations (exo0–exo3) being observed,
and no particular conformation seems to be preferred for the (m-
FC6H4)3P ligand.
The two different polymorphs of (p-FC6H4)3PI2, 7, show notice-
able variations in their P–I and I–I bond lengths. For this adduct we
can compare three independent (p-FC6H4)3PI2 molecules, the
monoclinic form 7a, and the two molecules of the triclinic form
7b. A comparison of P–I and I–I bond lengths again shows a rela-
tionship between the two bond lengths, however there are consid-
erable variations within the different independent molecules in the
same structure.
For example, in 7a the (p-FC6H4)3PI2 molecule has a P–I bond of
2.460(3) Å and an I–I bond of 3.1985(11) Å. These values are essen-
tially the same as those in 3 suggesting that replacement of an
SCH3 group by a fluorine atom in the p-position on the ring has
had essentially no impact on the P–I and I–I bond lengths, despite
the different electronic properties. In contrast, in 7b the molecule
Fig. 8. Crystal packing of (p-SCH3C6H4)3PI2 (5) looking down the c axis, showing the
based on P(1) has a P–I bond of 2.461(3) Å and an I–I bond of
formation of a network via propagation of anti-parallel pairs via a combination of
3.1529(11) Å, whereas the second molecule has a P–I bond of
2.507(3) Å and a I–I bond of 3.0807(12) Å. Therefore, while the
(OFF) and (EF)2 embraces, and weak C–HÁ Á ÁH–C contacts.
P–I bond in 7a and one of the molecules in 7b are essentially iden-
are fairly similar to those of Ph3PI2 [3], suggesting that the change
in electronic properties upon substitution of a fluorine atom in the
m-position has little effect on the P–I–I CT system. The structure of
6 shows disorder in that in each of the independent molecules
there are two partially occupied sites for the m-fluorine atoms on
one of the (m-FC6H4) rings, viz atoms F(3) 0.65(2) occupancy/
F(3b) 0.35(2) occupancy, and F(5) 0.56(3) occupancy/F(5b)
0.44(3) occupancy. This partial occupancy results in two slightly
different cone angles being calculated, one where all three fluorine
atoms are pointing upwards (exo3 conformation), or alternatively
when one fluorine atom points down (exo2 conformation). For
the molecule based on P(1) the cone angle is 154.6° (exo3) or
151.6° (exo2), whilst for molecule P(2) the differences are smaller,
152.3° (exo3) versus 151.7° (exo2), and in each case the exo3 confor-
mation results in a slightly larger cone angle. The exo2/exo3 confor-
mation observed for 6 contrasts with the exo1 conformations
observed for (m-CH3C6H4)3PI2 and (m-OCH3C6H4)3PI2. Recent re-
tical, the I–I bonds vary considerably between the two, and the sec-
ond molecule in 7b has a significantly longer P–I bond and shorter
I–I bond than the other two.
These differences in bond lengths may be due to a different ori-
entation of the (p-FC6H4) rings in each of the three (p-FC6H4)3PI2
molecules. The I–P–C(ipso)–C(ortho) torsion angles have been mea-
sured, (see Table 3), and in all three cases the rings do not adopt
the ideal C3 symmetric ‘‘propeller’’ conformation for a tri-aryl
phosphine system, but are staggered to varying degrees, as ob-
served for the other p-substituted Ar3PI2 adducts 3 and 5. In the
second molecule of 7b one of the rings is twisted so that it is much
more parallel with respect to the P–I bond, with a I–P–C–C torsion
angle of À16.8(12)°, compared to torsions of À54.4(9)° and
À52.3(10)° for the other two rings. This appears to result in steric
hindrance around the P–I bond with a resulting elongation of this
bond and a concomitant shortening of the I–I bond. A comparison
of cone angles shows that this molecule exhibits a slightly larger

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
39
F4
C22
C23
C24
C11
I1
F3
C10
C21
C20
C12
C7
C15
C14
C13
C16
C17
C19
C31
C36
C9
F2
P1
C26
F5
C8
P2
C25
F3b
C18
C32
C35
C33
C34
C27
I3
I4
C1
F6
I2
C6
C5
C28
C29
C2
C3
C30
C4
F1
F5b
Fig. 9. ORTEP representation of the molecular structure of (m-FC6H4)3PI2 (6). Thermal ellipsoids are shown at the 30% probability level, with hydrogen atoms omitted for clarity.
Atoms F(3)/F(3b) and F(5)/F(5b) are partially occupied. Selected bond lengths [Å] and angles [°]: P(1)–I(1): 2.476(4), I(1)–I(2): 3.1347(13), P(2)–I(3): 2.475(4), I(3)–I(4):
3.1500(14), P(1)–C(1): 1.814(14), P(1)–C(7): 1.799(14), P(1)–C(13): 1.795(15), P(2)–C(19): 1.788(14), P(2)–C(25): 1.812(14), P(2)–C(31): 1.772(14), C(3)–F(1): 1.33(2), C(9)–
F(2): 1.332(17), C(15)–F(3): 1.38(2), C(18)–F(3b): 1.42(3), C(21)–F(4): 1.338(18), C(27)–F(5): 1.34(3), C(29)–F(5b): 1.30(3), C(33)–F(6): 1.373(16), P(1)–I(1)–I(2): 177.58(10),
P(2)–I(3)–I(4): 174.10(10), I(1)–P(1)–C(1): 109.4(5), I(1)–P(1)–C(7): 108.1(5), I(1)–P(1)–C(13): 109.7(5), I(3)–P(2)–C(19): 112.2(4), I(3)–P(2)–C(25): 106.6(5), I(3)–P(2)–C(31):
109.8(5), C(1)–P(1)–C(7): 110.0(7), C(1)–P(1)–C(13): 107.3(6), C(7)–P(1)–C(13): 112.3(6), C(19)–P(2)–C(25): 111.7(6), C(19)–P(2)–C(31): 106.5(6), C(25)–P(2)–C(31):
110.2(6).
F3
C16
C15
C17
C14
C18
C13
I1
I2
C12
P1
C11
C7
C6
C10
F2
C1
C2
C5
C8
C4
C9
F1
C3
Fig. 10. ORTEP representation of the molecular structure of (p-FC6H4)3PI2 (monoclinic form) (7a). Thermal ellipsoids are shown at the 30% probability level. Selected bond
lengths [Å] and angles [°]: P(1)–I(1): 2.460(3), I(1)–I(2): 3.1985(11), P(1)–C(1): 1.805(11), P(1)–C(7): 1.794(12), P(1)–C(13): 1.789(12), C(4)–F(1): 1.332(14), C(10)–F(2):
1.349(15), C(16)–F(3): 1.364(15), P(1)–I(1)–I(2): 171.91(8), I(1)–P(1)–C(1): 109.9(4), I(1)–P(1)–C(7): 113.3(4), I(1)–P(1)–C(13): 108.6(4), C(1)–P(1)–C(7): 110.3(5), C(1)–P(1)–
C(13): 105.4(5), C(7)–P(1)–C(13): 109.2(5).
cone angle (149.3°) than the other molecule of 7b (145.5°) and that
of 7a (145.7°). The cone angles are all somewhat smaller than those
of (m-FC6H4)3PI2 6.
independent molecules of 7, but is close in magnitude to the value
observed for one of the molecules of 6. The cone angle of 8 is
145.0°, which is very similar to the values observed for 7.
The chloro-substituted analogue (p-ClC6H4)3PI2, 8, displays a P–
I bond of 2.488(2) Å, again similar to that of Ph3PI2 [3], whereas the
I–I bond is somewhat shorter, at 3.1332(9) Å. The conformation of
the aryl rings is different to both 7a and either molecule in 7b, with
one of the rings twisted so that it is orthogonal to the P–I bond,
with an I–P–C–C torsion angle of 72.9(9)°. As a consequence the
other two rings are more upright, which may result in a lengthen-
ing of the P–I bond. The I–I bond is shorter than in two of the three
The crystal packing of 6, 7a, 7b and 8 have also been examined.
In the structure of 6 each of the crystallographically independent
molecules, based on atoms P(1) and P(2), stack in the b cell direc-
tion, see Fig. 13. The stack of P(1) molecules is staggered with a
long PÁ Á ÁP separation of 7.874 Å, and is linked by distant (OFF) em-
braces, and a short F(3)Á Á ÁH(18) contact of 2.60 Å (sum of the van
der Waals radii of hydrogen and fluorine is 2.67 Å). The stack of
P(2) molecules is also staggered and linked in a similar fashion,

40
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
I2
F3
C16
C15
C17
F6
C14
I1
C18
C12
C33
C13
C34
C35
C6
C5
C1
C32
P1
C7
C36
C2
C31
P2
C4
C3
C8
F1
C30
C11
C29
C20
C21
C19
C25
F4
C10
F2
C28
C24
F5
C9
C22
I3
C23
C26
C27
I4
Fig. 11. ORTEP representation of the molecular structure of (p-FC6H4)3PI2 (triclinic form) (7b). Thermal ellipsoids are shown at the 30% probability level, with hydrogen atoms
omitted for clarity. Selected bond lengths [Å] and angles [°]: P(1)–I(1): 2.461(3), I(1)–I(2): 3.1529(11), P(2)–I(3): 2.507(3), I(3)–I(4): 3.0807(12), P(1)–C(1): 1.793(11), P(1)–
C(7): 1.794(11), P(1)–C(13): 1.785(11), P(2)–C(19): 1.801(11), P(2)–C(25): 1.798(12), P(2)–C(31): 1.792(11), C(4)–F(1): 1.361(13), C(10)–F(2): 1.368(14), C(16)–F(3):
1.340(14), C(22)–F(4): 1.359(15), C(28)–F(5): 1.372(14), C(34)–F(6): 1.346(15), P(1)–I(1)–I(2): 173.07(7), P(2)–I(3)–I(4): 177.76(7), I(1)–P(1)–C(1): 112.9(4), I(1)–P(1)–C(7):
110.1(4), I(1)–P(1)–C(13): 106.4(4), I(3)–P(2)–C(19): 107.2(4), I(3)–P(2)–C(25): 107.5(4), I(3)–P(2)–C(31): 113.4(4), C(1)–P(1)–C(7): 109.2(5), C(1)–P(1)–C(13): 107.7(5),
C(7)–P(1)–C(13): 110.5(5), C(19)–P(2)–C(25): 110.3(5), C(19)–P(2)–C(31): 110.5(5), C(25)–P(2)–C(31): 108.1(5).
Cl3
C17
Cl2
C16
C9
C10
C15
C8
C18
P1
C14
C13
C7
C11
C12
I1
I2
C1
C2
C3
C6
C4
C5
Cl1
Fig. 12. ORTEP representation of the molecular structure of (p-ClC6H4)3PI2 (8). Thermal ellipsoids are shown at the 30% probability level. Selected bond lengths [Å] and angles
[°]: P(1)–I(1): 2.488(2), I(1)–I(2): 3.1332(9), P(1)–C(1): 1.797(10), P(1)–C(7): 1.805(9), P(1)–C(13): 1.796(11), C(4)–Cl(1): 1.731(10), C(10)–Cl(2): 1.737(9), C(16)–Cl(3):
1.741(11), P(1)–I(1)–I(2): 178.86(6), I(1)–P(1)–C(1): 110.0(3), I(1)–P(1)–C(7): 112.5(3), I(1)–P(1)–C(13): 110.4(3), C(1)–P(1)–C(7): 108.7(4), C(1)–P(1)–C(13): 106.2(4), C(7)–
P(1)–C(13): 108.9(4).
but has an even longer PÁ Á ÁP separation of 8.006 Å, although the
paired molecules are liked by two short FÁ Á ÁH contacts,
F(4)Á Á ÁH(24): 2.58 Å, and F(4)Á Á ÁH(36): 2.63 Å. The closest PÁ Á ÁP
separation between molecules in the entire structure is however
between the stacks, i.e. between a P(1) molecule and a P(2) mole-
cule, where the separation is 6.715 Å. These molecules are

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
41
Fig. 13. Crystal packing of (m-FC6H4)3PI2 (6) looking down the b axis, showing alternating stacks based on P(1) molecules and P(2) molecules, linked by short FÁ Á ÁH contacts,
and weak IÁ Á ÁH contacts.
orientated anti-parallel to each other, and display three FÁ Á ÁH con-
tacts between P(1) and P(2) molecules, viz. F(1)Á Á ÁH(23): 2.47 Å,
F(5)Á Á ÁH(8): 2.32 Å and F(6)Á Á ÁH(14): 2.45 Å. The terminal iodine
atoms of both molecules also show weak IÁ Á ÁH hydrogen bonds, Ta-
ble S1.
The extended structures of the two polymorphs of 7 show much
closer PÁ Á ÁP separations than seen for 6. The monoclinic form of 7a
shows anti-parallel pairs of molecules stacking in the a direction,
with a PÁ Á ÁP separation of 6.044 Å and two (EF) interactions be-
tween pairing molecules. These pairs form a chain, as shown in
Fig. 14, with each pair linked to the next by a short F(2)Á Á ÁF(2) con-
tact of 2.867(14) Å, shorter than twice the van der Waals radii of
fluorine (2.94 Å). This chain of pairing molecules is linked to an
adjacent chain by a non-classical hydrogen bond of 3.15 Å from
the terminal iodine atom I(2) to a H(6) proton on the next chain.
In the second chain the PÁ Á ÁP separation between anti-parallel pairs
is slightly longer, (6.259 Å).
The packing of the triclinic form 7b is very similar to that of 7a,
see Fig. 15. Anti-parallel pairs of P(1) molecules stack in the a
direction, as do anti-parallel pairs of P(2) molecules. Whilst the
PÁ Á ÁP separation of the pairs of P(1) molecules is of a similar mag-
nitude (5.996 Å) to 7a, the separation between pairs of P(2) mole-
cules is significantly shorter (5.844 Å). This closer approach may be
linked to the different conformation observed for the P(2) molecule
(with one ring much more parallel to the P–I bond). The main dif-
ference to the packing of 7a is that pairs of molecules are linked
into a chain by FÁ Á ÁH contacts, rather than FÁ Á ÁF contacts. Each pair
of P(1) molecules is linked to the next by an F(2)Á Á ÁH(5) contact of
2.53 Å, whilst each pair of P(2) molecules is linked to the next by
two FÁ Á ÁH contacts, F(4)Á Á ÁH(35): 2.52 Å, and F(5)Á Á ÁH(24): 2.50 Å,
(all shorter than the sum of the van der Waals radii of hydrogen
and fluorine at 2.67 Å). Additionally, the two sets of chains are
linked to each both by IÁ Á ÁH contacts (see Table S1), and also by
two further short FÁ Á ÁH contacts, F(1)Á Á ÁH(27): 2.52 Å and
Fig. 14. Crystal packing of the monoclinic form of (p-FC6H4)3PI2 (7a) looking down the a axis, showing chains of anti-parallel pairs of molecules.

42
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
Fig. 15. Crystal packing of the triclinic form of (p-FC6H4)3PI2 (7b) looking down the a axis, showing chains of anti-parallel pairs of molecules. The chain of stacks of P(1)
molecules is at the top, and P(2) molecules at the bottom.
F(5)Á Á ÁH(3): 2.62 Å. The large number of FÁ Á ÁH contacts in the struc-
ture of 7b clearly contrasts with 7a where the only short FÁ Á ÁH con-
tact (2.51 Å) is between stacking molecules down the a axis. The
competition between the linking of stacks either by FÁ Á ÁH contacts
or FÁ Á ÁF contacts may have resulted in the formation of different
polymorphs.
The packing of 8 again shows a number of similarities to the
polymorphs of 7 as molecules pair in an anti-parallel fashion
(PÁ Á ÁP separation of 6.311 Å) and stack in the b cell direction, see
Fig. 16. These stacks are linked by short C–HÁ Á ÁCl–C contacts be-
tween the p-chlorophenyl rings, Cl(1)Á Á ÁH(11): 2.75 Å and
Cl(1)Á Á ÁH(11): 2.83 Å, (compared to the sum of the van der Waals
radii of chlorine and hydrogen, 2.95 Å). Weak IÁ Á ÁH hydrogen bond-
ing between the stacks is also observed, see Table S1.
back-to-back fashion [16]. Prediction of a conformation for the
m-substituted adducts 2 and 6 is much less reliable than for o-
substituted analogues, (which have an exo3 conformation). Whilst
(m-OCH3C6H4)3PI2 2 exhibits an exo1 conformation, as also ob-
served previously for (m-CH3C6H4)3PI2 [16], (m-FC6H4)3PI2 6 exhib-
its disorder of the fluorine atoms, which results in either an exo2 or
exo3 conformation being observed. The p-substituted derivatives 3,
5, 7a, 7b and 8 all exhibit staggered propeller conformations, with
distortions from an ideal propeller being most noticeable for 7b
(where one ring is much more parallel to the P–I bond than the
others), and 8 (which features one ring more orthogonal to the
P–I bond than the other two).
A consistent feature of the packing of these Ar3PI2 adducts is
formation of close packed pairs of Ar3PI2 molecules, with PÁ Á ÁP sep-
arations between neighbouring molecules ranging between
5.844 Å (for 7b), and 7.144 (for 2), see Table S2 in supplementary
data. All the p-substituted derivatives feature molecules packing
in an anti parallel, side-to-side fashion, whilst the m-substituted
adducts show some variation, e.g. in 2 molecules pack parallel
and side-to-side, whereas in 6 molecules pack offset and back-to-
back. Of all the structures studied here molecules of (p-FC6H4)3PI2
7 are able to pack the closest, with PÁ Á ÁP separations between 5.844
and 6.259 Å. The shortest of these is between two P(2) molecules in
the triclinic polymorph 7b. This is the molecule which has one par-
allel ring, and it appears that a conformation with a parallel ring
2.3.3. Comparison of conformations and crystal packing features of
Ar3PI2 adducts
This study of the crystal packing of the Ar3PI2 adducts 2, 3, 5, 6,
7a, 7b and 8 has shown that substitution of the aryl rings in differ-
ent positions can result in changes in the preferred conformation of
the aryl rings. All the Ar3PI2 structures display conformations
where all three rings are twisted in the same direction (based on
a propeller conformation), but substitution in the m- or p-positions
on the aryl rings results in disruption of the (EF)6 embrace ob-
served for (o-CH3C6H4)3PI2, where molecules are able to pack in a
Fig. 16. Crystal packing of (p-ClC6H4)3PI2 (8) looking down the b axis, showing stacks of paired molecules linked by ClÁ Á ÁH and IÁ Á ÁH contacts.

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
43
Table 4
Crystallographic parameters for compounds 2, 3, 5, 6, 7a, 7b and 8.
(m-OCH3C6H4)3PI2, 2
21H21I2O3P
605.98
Yellow, prism
monoclinic
P21/c (No. 14)
0.15 Â 0.17 Â 0.17
(p-OCH3C6H4)3PI2, 3
Empirical formula
Formula weight
Colour, habit
Crystal system
Space group
Crystal size (mmÀ3
C
C21H21I2O3P
605.98
Yellow, prism
triclinic
ꢀ
P1 (No. 2)
)
0.12 Â 0.15 Â 0.17 mmÀ3
Unit cell dimensions
a (Å)
b (Å)
c (Å)
12.1082(5)
13.8366(7)
13.9951(7)
10.1803(4)
10.7454(6)
11.4234(7)
80.074(3)
67.751(3)
84.443(4)
1138.59(11)
150(2)
a
(°)
b (°)
106.386(3)
c
(°)
Volume (ÅÀ3
)
2249.45(19)
100(2)
T (K)
Z
4
2
Dcalc (mg/m3)
k (Å)
1.790
0.71073
2.885
1.768
0.71073
2.850
l
(Mo K
a
) (mmÀ1
)
F(000)
1168
584
h range (°)
No. of reflections
Rint
2.94–27.50
31409 (5152 unique)
0.083
2.93–25.50
3938 (3938 unique)
0.124
R1/wR2
0.0532/0.1118
0.0870/0.1292
1.639 and À1.365
1.077
0.0889/0.2051
0.1656/0.2473
3.643 and –1.555
1.172
R1/wR2 (all data)
Largest diff. peak and hole (eÅÀ3
Goodness-of-fit
)
(p-SCH3C6H4)3PI2, 5
(m-FC6H4)3PI2, 6
Empirical formula
Formula weight
Colour, habit
Crystal system
Space group
Crystal size (mmÀ3
C
21H21I2S3P
C18H12I2F3P
569.95
yellow, plate
monoclinic
P21/n (No. 14)
0.12 Â 0.15 Â 0.17
654.33
yellow, rod
triclinic
P1 (No. 2)
ꢀ
)
0.14 Â 0.08 Â 0.08
Unit cell dimensions
a (Å)
b (Å)
c (Å)
10.5524(2)
10.5565(2)
12.0515(3)
71.361(1)
67.644(1)
82.370(1)
1176.37(4)
293(2)
18.5533(6)
10.1852(3)
19.8241(9)
a
(°)
b (°)
91.0760(10)
c
(°)
Volume (ÅÀ3
)
3745.5(2)
100(2)
T (K)
Z
2
8
Dcalc (mg/m3)
k (Å)
1.847
0.71073
3.013
2.022
0.71073
3.468
l
(Mo K
a
) (mmÀ1
)
F(000)
632
2144
h range (°)
No. of reflections
Rint
2.93–27.50
22702 (5387 unique)
0.071
3.04–25.50
20052 (6631 unique)
0.088
R1/wR2
0.0547/0.1227
0.0847/0.1415
1.837 and –1.906
1.048
0.0762/0.1622
0.1261/0.2007
2.062 and –1.395
1.179
R1/wR2 (all data)
Largest diff. peak and hole (eÅÀ3
Goodness-of-fit
)
(p-FC6H4)3PI2, 7a
(p-FC6H4)3PI2, 7b
Empirical formula
Formula weight
Colour, habit
Crystal system
Space group
Crystal size (mmÀ3
C
21H12I2F3P
C18H12I2F3P
570.05
orange, needle
570.05
olive green, prism
monoclinic
P21/c (No. 14)
0.17 Â 0.17 Â 0.19
triclinic
ꢀ
P1 (No. 2)
)
0.08 Â 0.08 Â 0.20
Unit cell dimensions
a (Å)
b (Å)
c (Å)
9.8484(3)
9.6638(3)
20.1127(6)
9.4690(1)
11.6950(2)
18.4350(3)
79.733
a
(°)
b (°)
94.279(2)
86.213(1)
68.624(1)
1870.61(5)
150(2)
c
(°)
Volume (ÅÀ3
)
1908.85(10)
150(2)
T (K)
(continued on next page)

44
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
Table 4 (continued)
(p-FC6H4)3PI2, 7a
(p-FC6H4)3PI2, 7b
Z
4
4
Dcalc (mg/m3)
k (Å)
1.984
0.7107
3.403
2.024
0.71073
3.472
l
(Mo K
a
) (mmÀ1
)
F(000)
1072
1072
h range (°)
No. of reflections
Rint
3.01–25.50
3495 (3495 unique)
0.092
3.07–25.50
6914 (6914 unique)
0.048
R1/wR2
0.0752/0.1974
0.1107/0.2426
4.438 and À2.125
1.094
0.0697/0.1774
0.0954/0.2045
2.968 and À1.388
1.104
R1/wR2 (all data)
Largest diff. peak and hole (eÅÀ3
Goodness-of-fit
)
(p-ClC6H4)3PI2, 8
Empirical formula
Formula weight
Colour, habit
C21H12I2Cl3P
619.30
Yellow, rod
Monoclinic
P21/n (No. 14)
0.10 Â 0.10 Â 0.16
Crystal system
Space group
Crystal size (mmÀ3
)
Unit cell dimensions
a (Å)
b (Å)
c (Å)
b (°)
10.8892(4)
12.4480(5)
14.8186(7)
91.135(2)
2008.25(14)
100(2)
Volume (ÅÀ3
)
T (K)
Z
4
Dcalc (mg/m3)
k (Å)
2.049
0.71073
3.609
l
(Mo K
a
) (mmÀ1
)
F(000)
1168
h range (°)
No. of reflections
Rint
3.20–25.50
20745 (3725 unique)
0.090
R1/wR2
0.0534/0.0945
0.1103/0.1315
1.373 and –1.278
1.047
R1/wR2 (all data)
Largest diff. peak and hole (eÅÀ3
Goodness-of-fit
)
allows the closest approach of pairing molecules. However, the
presence of a parallel ring results in an increase in steric conges-
tion, as the cone angle rises from 145° to 149°. This results in a
longer P–I and shorter I–I bond length than observed for the other
molecule in 7b, and for the monoclinic form 7a.
The cone angles for all of the Ar3PI2 structures reported in this
paper fall over a relatively small region, varying between 145.0°
and 154.6°, suggesting that whilst the P–I bond may be affected
by a ring which becomes too close to parallel with it, the overall
steric ‘‘footprint’’ of the Ar3P group is moderated by the other
rings twisting such that the overall steric repulsion does not be-
come too great. However, the case of 7b shows that changes in
the conformation of the aryl rings can affect the P–I and I–I bond
lengths.
The structures of most of these adducts have been obtained, and
shown to be R3PI2 charge-transfer systems of the D–IÁ Á ÁI type, with
short P–I bonds and long I–I bonds. In contrast, the structure of (o-
SCH3C6H4)3PI2 (where suitable crystals could not be grown due to
poor solubility) may be a (10–I–2) type of CT adduct, on the basis of
the Raman spectrum and dark red colour of the adduct. An exam-
ination of P–I and I–I bond lengths in the structurally characterized
adducts show that electronic effects are primarily responsible for
differences in the bond lengths in m- and p-substituted Ar3PI2 ad-
ducts (unlike o-substituted adducts where steric effects are also
important). The adduct (p-FC6H4)3PI2 forms two polymorphs 7a
and 7b, the presence of which may be a consequence of the possi-
bility of either FÁ Á ÁF contacts (as in 7a) or FÁ Á ÁH contacts (as in 7b)
being able to link pairs of molecules into chains. Between the two
polymorphs there are a total of three crystallographically unique
molecules. Differences are observed in the ring conformations be-
tween these molecules, with one exhibiting a ring which is close to
parallel with respect to the P–I bond, resulting in steric congestion,
a lengthening of the P–I bond and concomitant shortening of the I–
I bond.
3. Conclusion
A series of Ar3PI2 adducts have been synthesized via the 1:1
reactions of Ar3P with di-iodine in anhydrous diethyl ether. The
31P{1H} NMR spectra of these adducts has been examined to re-
solve the conflicting data previously reported. We find no evidence
for ionization of Ar3PI2 adducts in CDCl3 solution (in contrast to re-
lated tri-alkyl adducts), and resonances previously assigned as
[Ar3PI]I are have been shown in most cases to be due to hydrolyzed
species such as [Ar3POH]+ or [{Ar3PO}2H]+. In many cases the Ar3PI2
adducts show reasonable stability towards hydrolysis (although
this is highly dependent on the nature of R), with slow hydrolysis
often producing [Ar3PH]I species.
4. Experimental
4.1. Reagents and physical measurements
The synthesis of the di-iodide adducts described herein was
undertaken using standard Schlenk techniques under anhydrous
and anaerobic conditions with all solvents being rigorously dried

N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
45
before use. (o-OCH3C6H4)3P, (m-OCH3C6H4)3P and (p-OCH3C6H4)3P
were purchased commercially (Alfa Aesar), as were (m-FC6H4)3P
(Apollo Scientific), (p-FC6H4)3P, (p-ClC6H4)3P and iodine (all Al-
drich). (o-SCH3C6H4)3P was synthesized as previously described
[12], and (p-SCH3C6H4)3P by a modification of the literature prep-
aration [56], as outlined below. Elemental analyses were per-
formed by the University of Manchester School of Chemistry
Microanalytical service. Raman spectra were recorded as solid
samples on a Nicolet–Nexus combined FT-IR/FT-Raman spectrom-
eter. 1H, 13C{1H}, 31P{1H} and 19F NMR spectra were recorded on a
Bruker AVANCE III 400 spectrometer operating at 400.1 (1H), 100.6
broad]. Raman: (cmÀ1): 3051, 2920, 1587, 1565, 1203, 1047, 800,
661, 559, 516, 463, 400, 273, 213, 155.
4.3.2. (m-OCH3C6H4)3PI2 (2)
Yield: 0.602 g (75.9%). Yellow solid. Anal. Calc. for C21H21O3PI2:
C, 41.5; H, 3.4. Found: C, 41.4; H, 3.4%. 1H NMR (CDCl3): 3.85 [s,
OCH3, 9H], 6.98–7.39 [m, aromatic, 6H], 7.44–7.64 [m, aromatic,
6H]. 13C{1H} NMR (CDCl3): 55.8 [s, OCH3], 118.9 [d, Co,
2J(PC) = 11.9 Hz], 119.7 [s, Cp], 125.5 [d, Cm, 3J(PC) = 9.9 Hz], 131.7
[d, Co, 2J(PC) = 13.7 Hz], 160.2 [d, Cm(bound
,
to
methoxy)
3J(PC) = 13.8 Hz]. 31P{1H} NMR (CDCl3): À18.5 [s, broad]. Raman:
(cmÀ1): 3064, 2835, 1588, 1493, 1308, 1292, 1267, 1181, 1121,
795, 675, 572, 545, 512, 454, 272, 154.
(
13C), 162.0 (31P) and 376.5 (19F) MHz, respectively. Peak positions
are quoted relative to TMS (1H/13C), 85% H3PO4 31P) or CFCl3 19F)
(
(
using the high frequency positive convention throughout.
4.3.3. (p-OCH3C6H4)3PI2 (3)
4.2. Synthesis of (p-SCH3C6H4)3P
Yield: 0.766 g (82.0%). Yellow solid. Anal. Calc. for C21H21O3PI2:
C, 41.5; H, 3.4; P, 5.1. Found: C, 41.1; H, 3.2; P, 4.8%. 1H NMR
(CDCl3): 3.85 [s, OCH3, 9H], 6.96–7.04 [m, aromatic, 6H], 7.36–
7.47 [m, aromatic, 6H]. 13C{1H} NMR (CDCl3): 56.0 [s, OCH3],
113.1 [d, Ci, 1J(PC) = 76.2 Hz], 115.7 [d, Cm, 3J(PC) = 14.5 Hz], 135.4
[d, Co, 2J(PC) = 12.4 Hz], 164.5 [d, Cp, 4J(PC) = 2.8 Hz]. 31P{1H} NMR
(CDCl3): À12.7 [s, broad]. Raman: (cmÀ1): 3063, 2829, 1589,
1103, 795, 613, 534, 503, 490, 463, 272, 207, 157.
4-Bromothioanisole (12.55 g, 0.062 mol) was dissolved in anhy-
drous THF (80 mL) in a 500 mL three-necked round bottomed flask
equipped with a stirrer bar and nitrogen inlet/outlet. To this was
slowly added dried magnesium turnings (1.54 g, 0.063 mol) over
15 min. The reaction was initiated with two drops of 1,2-dibromo-
ethane and heated gently with a heat gun until reaction com-
menced. A cloudy grey solution was formed after 30 min which
was allowed to stir for 2 h until all the magnesium had been con-
sumed. The reaction was then cooled to À78 °C (acetone slush
bath) and a solution of phosphorus(III) chloride (1.80 mL, 2.83 g,
0.021 mmol) in 50 mL of THF was added dropwise over 2 h. The
reaction was then allowed to warm up to room temperature over-
night. Any residual Grignard was destroyed by careful shaking of
the solution with an aqueous solution. The solution was then re-
duced in volume by half, and 50 mL each of dichloromethane and
water were added. The layers were shaken and the organic layer
separated off. The aqueous layer was then shaken with further
2 Â 30 mL portions of dichloromethane. The organic extracts were
combined, dried (MgSO4), filtered and the solvent removed to yield
(p-SCH3C6H4)3P as a white solid, which was re-crystallized from
dichloromethane/40:60 petroleum ether. Spectroscopic data is as
follows: 1H NMR (CDCl3): 2.40 [s, SCH3, 9H], 7.15–7.18 [m, aro-
matic]. 13C{1H} NMR (CDCl3): 15.3 [s, SCH3], 126.0 [d, Cm,
3J(PC) = 8.5 Hz], 133.0 [d, Ci, 1J(PC) = 10.3 Hz], 133.9 [d, Co,
2J(PC) = 19.8 Hz], 139.9 [s, Cp]. 31P{1H} NMR (CDCl3): À8.3 [s].
4.3.4. (o-SCH3C6H4)3PI2 (4)
Yield: 0.637 g (68.6%). Red solid. Anal. Calc. for C21H21S3PI2: C,
38.5; H, 3.2; P, 4.7; I, 38.8. Found: C, 38.1; H, 2.9; P, 4.6; I, 38.6%.
1H NMR (CDCl3): 2.38 [s, SCH3, 9H], 6.76–7.15 [m, aromatic, 6H],
7.18–7.57 [m, aromatic, 6H]. 13C{1H} NMR (CDCl3): 17.8 [s, SCH3],
125.9 [d, J(PC) = 13.6 Hz], 128.1 [d, J(PC) = 7.4 Hz], 130.5 [d,
J(PC) = 12.9 Hz], 133.6 [s, Cp], 144.2 [d, Co(bound
,
2J(PC) =
to SCH3)
23.2 Hz]. 31P{1H} NMR (CDCl3): À31.4 [s, vbroad]. Raman:
(cmÀ1): 3048, 2984, 2915, 1569, 1268, 1103, 1036, 698, 365, 160.
4.3.5. (p-SCH3C6H4)3PI2 (5)
Yield: 0.444 g (72.0%). Yellow solid. Anal. Calc. for C21H21S3PI2:
C, 38.5; H, 3.2; S, 14.7. Found: C, 37.9; H, 2.9; S, 14.6%. 1H NMR
(CDCl3): 2.59 [s, SCH3, 9H], 7.27–7.58 [m, aromatic, 6H], 7.70–
7.81 [m, aromatic, 6H]. 13C{1H} NMR (CDCl3): 14.9 [s, SCH3],
126.0 [d, Cm, 3J(PC) = 15.0 Hz], 133.1 [d, Co, 2J(PC) = 12.8 Hz].
31P{1H} NMR (CDCl3): À18.5 [s, broad]. Raman: (cmÀ1): sample
decomposes in the laser beam.
4.3. Synthesis of Ar3PI2 adducts 1–8
4.3.6. (m-FC6H4)3PI2 (6)
Yield: 0.493 g (83.8%). Yellow solid. Anal. Calc. for C18H12F3PI2:
C, 37.9; H, 2.1; I, 44.5. Found: C, 37.8; H, 1.8; I, 45.0%. 1H NMR
(CDCl3): 7.22–7.34 [m, aromatic, 3H], 7.39–7.54 [m, aromatic,
6H], 7.66–7.78 [m, aromatic, 3H]. 13C{1H} NMR (CDCl3): 120.2
[dd, Co, 2J(CF) = 11.1 Hz, 2J(PC) = 23.1 Hz], 121.8 [dd, Co,
4J(CF) = 3.0 Hz, 2J(PC) = 21.1 Hz], 124.6 [dd, Ci, 1J(PC) = 53.3 Hz,
3J(CF) = 6.0 Hz], 129.5 [dd, Cp, 4J(PC) = 4.0 Hz, 2J(CF) = 10.1 Hz],
132.4 [dd, Cm, 3J(CF) = 8.0 Hz, 3J(PC) = 15.1 Hz], 162.8 [dd, Cm,
3J(PC) = 17.1 Hz, 1J(CF) = 255.5 Hz]. 19F NMR (CDCl3): À106.9 [m,
broad]. 31P{1H} NMR (CDCl3): À29.8 [s, broad]. Raman: (cmÀ1):
sample decomposes in the laser beam.
The series of Ar3PI2 adducts were all prepared by reaction of the
aryl phosphine with I2 in anhydrous diethyl ether in a 1:1 ratio.
The synthesis of 1 is typical: 40 mL of diethyl ether was freshly dis-
tilled into a pre-dried rotaflo tube. To this solution was added
0.650 g, (1.85 mmol) of (o-OCH3C6H4)3P, followed by 0.469 g,
(1.85 mmol) of I2. A yellow solid rapidly formed and the reaction
was left to stir for ca. 48 h. The solid was isolated using standard
Schlenk techniques, and dried in vacuo for 2 h, before being trans-
ferred to pre-dried argon filled ampoules. Characterising data for 1
is given below, along with the other adducts 2–8 which were syn-
thesised via the same method. Raman spectroscopic data for 7 and
8 has been previously reported [27].
4.3.7. (p-FC6H4)3PI2 (7)
4.3.1. (o-OCH3C6H4)3PI2 (1)
Yield: 0.728 g (74.4%). Olive-green solid. Anal. Calc. for
Yield: 0.886 g (79.2%). Yellow solid. Anal. Calc. for C21H21O3PI2:
C, 41.5; H, 3.4; P, 5.1; I, 41.8. Found: C, 42.0; H, 3.4; P, 5.1; I, 41.3%.
1H NMR (CDCl3): 3.75 [s, OCH3, 9H], 6.89–7.40 [m, aromatic, 6H],
7.56–7.73 [m, aromatic, 6H]. 13C{1H} NMR (CDCl3): 55.0 [s,
OCH3], 108.8 [d, Ci, 1J(PC) = 71.2 Hz], 112.5 [d, Cm, 3J(PC) = 6.5 Hz],
121.3 [d, Co, 2J(PC) = 12.9 Hz], 134.9 [d, Cm, 3J(PC) = 7.4 Hz], 136.2
[s, Cp], 161.3 [s, Co(bound to methoxy)]. 31P{1H} NMR (CDCl3): À34.6 [s,
C18H12F3PI2: C, 37.9; H, 2.1; I, 44.5. Found: C, 37.6; H, 2.2; I,
44.2%. 1H NMR (CDCl3): 7.31–7.46 [m, aromatic, 6H], 7.69–7.97
[m, aromatic, 6H]. 13C{1H} NMR (CDCl3): 118.1 [dd, Cm,
2J(CF) = 14.1 Hz, 3J(PC) = 22.1 Hz], 126.2 [d, Ci, 1J(PC) = 73.4 Hz],
136.4 [dd, Co, 3J(CF) = 9.1 Hz, 2J(PC) = 11.1 Hz], 166.4 [d, Cp,
1J(CF) = 258.6 Hz]. 19F NMR (CDCl3): À100.6 [m, broad]. 31P{1H}
NMR (CDCl3): À20.2 [s, broad].

46
N.A. Barnes et al. / Polyhedron 35 (2012) 31–46
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4.3.8. (p-ClC6H4)3PI2 (8)
Chem. 626 (2000) 1105.
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Yield: 0.686 g (78.4%). Yellow solid. Anal. Calc. for C18H12Cl3PI2:
C, 36.5; H, 2.0; I, 42.9. Found: C, 36.3; H, 1.9; I, 42.4%. 1H NMR
(CDCl3): 7.18–7.50 [m, aromatic, 6H], 7.62–7.96 [m, aromatic,
6H]. 13C{1H} NMR (CDCl3): 130.1 [d, Cm, 3J(PC) = 11.1 Hz], 135.0
[d, Co, 2J(PC) = 16.1 Hz], 139.7 [d, Cp, 4J(PC) = 3.0 Hz]. 31P{1H} NMR
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(SHELXL97) [57]. Absorption corrections were carried out on all
structures via the multiscan method, and applied with the SORTAV
program [58]. Non-hydrogen atoms were refined with anisotropic
thermal parameters, whilst all hydrogen atoms were modeled in
ideal positions. In the structure of 6 the fluorine atoms exhibit par-
tial occupancy, F(3):F(3b) = 0.65(2):0.35(2) in one independent
molecule, and F(5):F(5b) = 0.56(3):0.44(3) in the other. Problems
with the crystal cooling systems prevented complete data-sets
being collected for compounds 3 and 6. As a result, completeness
to theta is low (92.8% for 3 and 95.0% for 6). All thermal ellipsoid
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Acknowledgements
The authors would like to thank EPSRC (Engineering and Phys-
ical Sciences Research Council) for support of the departmental FT
IR-Raman (Grant No: GR/M30135), NMR (Grant No: GR/L52246)
and X-ray (Research Initiative Grant) facilities.
Appendix A. Supplementary data
CCDC 843214–843220 contain the supplementary crystallo-
graphic data for compounds 2, 3, 5, 6, 7a, 7b and 8. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223
336 033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online version, at
doi:10.1016/j.poly.2011.12.023.
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