Chemical functionality of poly(methylenephosphine): Phosphine-borane adducts and methylphosphonium ionomers

Article abstract of DOI:10.1039/b718140j

The chemical functionality of poly(methylenephosphine) n-Bu[MesP-CPh ₂]_nH (2) is examined in reactions with two isoelectronic species, namely BH₃ and CH₃⁺. The potential reactivity of polymer 2 is mod

Full text of DOI:10.1039/b718140j

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PAPER
www.rsc.org/dalton | Dalton Transactions
Chemical functionality of poly(methylenephosphine): phosphine–borane
adducts and methylphosphonium ionomers†‡
Kevin J. T. Noonan, Bastian Feldscher, Joshua I. Bates, Justin J. Kingsley, Mandy Yam and Derek P. Gates*
Received 23rd November 2007, Accepted 4th February 2008
First published as an Advance Article on the web 29th July 2008
DOI: 10.1039/b718140j
The chemical functionality of poly(methylenephosphine) n-Bu[MesP–CPh2]nH (2) is examined in
+
reactions with two isoelectronic species, namely BH3 and CH3 . The potential reactivity of polymer 2 is
modelled by examining the reactivity of molecular phosphines bearing similar substituents as the
polymer. In particular, the phosphine–borane adducts Mes(Me)P(BH3)–CPh2H (4a) and Mes(Me)-
P(BH3)–CPh2SiMe2H (4b) are prepared from the reaction of BH3·SMe2 with Mes(Me)P–CPh2H (3a) or
Mes(Me)P–CPh2SiMe2H (3b), respectively. Treating 3a with MeOTf affords the methylated model
compound, [Mes(Me)2P–CPh2H]OTf (5). X-Ray crystal structures are reported for each model
compound. The reaction of n-Bu[MesP–CPh2]nH (Mn = 3.89 × 104, PDI = 1.34) with BH3·SMe2
affords the phosphine–borane polymer n-Bu[MesP(BH3)–CPh2]nH (6) (Mn = 4.13 × 104, PDI = 1.26).
In contrast, methylation of phosphine polymer 2 gives n-Bu[MesP–CPh2]x–/–[MesP(Me)–CPh2]yH·
(OTf)y (7) where approximately 50% of the phosphine moieties are methylated (from 31P NMR).
Introduction
Recent advances in the development of main-group-element-
containing macromolecules have played a major role in the
renaissance that is underway in main group chemistry.1,2 The
prospect of finding materials with unique properties imparted by
p-block elements is the impetus for the current widespread interest
Scheme 1
in this area. A principle barrier to the development of inorganic
polymerization route affords phosphine polymers in high yield and
with controllable molecular weights under mild conditions.
Although macromolecules possessing trivalent phosphorus
atoms in the main chain are common,7 polymer 2 is the only
alternating phosphorus–carbon polymer. The phosphine moieties
in 2 provide a unique opportunity for facile post-polymerization
modifications to tailor the polymer properties. With the exception
of oxidation and sulfurization, the chemical functionality of
poly(methylenephosphine)s has remained virtually unexplored.4
Although well-defined metal complexes have not yet been isolated,
we have illustrated that random copolymers of 1 and styrene are
effective supports for Pd-catalyzd Suzuki cross-coupling.8 Simple
main group complexes such as phosphine–borane adducts are
of interest as potential protecting groups for the slightly air-
sensitive phosphine environments in 2 and for their potential use
as pre-ceramic materials.9 In addition, alkylation of the phosphine
moieties would provide a convenient route to novel phosphonium
ionomers.10 Ionomers, or polymers with ionic groups, are of
interest in applications ranging from drug delivery to fuel cell
membranes.11 The successful methylation of 2 would provide
access to polymers with a high ion density in the main chain due
to the close proximity of phosphorus atoms.
macromolecules is the lack of general synthetic methods to link
inorganic elements into long chains. Most work has focused on
using ring-opening and condensation polymerization techniques.
We are interested in expanding addition polymerization, the most
commonly used method in organic polymer synthesis, to inorganic
multiple bonds.
=
Given their close analogy to C C bonds, we chose to begin
=
our investigations with P C bonds. Phosphaalkenes were first
synthesized thirty years ago and their chemistry closely parallels
that of alkenes. We have discovered that P C bonds can be poly-
3
=
merized to afford a new class of phosphorus containing polymer,
poly(methylenephosphine).4 When phosphaalkene 1, originally
reported by Bickelhaupt,5 is distilled or heated in the presence
of radical initiators a polymer with an alternating phosphorus-
carbon backbone is obtained in low isolated yield. Recently,
we improved upon the synthesis of poly(methylenephosphine)
with the development of the room temperature living anionic
polymerization of 1.6 Specifically, treating monomer 1 with n-BuLi
(1–4%) in glyme at 25 ◦C affords polymer 2 (Scheme 1). This living
Department of Chemistry, University of British Columbia, 2036 Main
Mall, Vancouver, British Columbia, Canada V6T 1Z1. E-mail: dgates@
chem.ubc.ca; Fax: +1 604 822 2847; Tel: +1 604 822 9117
† Based on the presentation given at Dalton Discussion No. 11, 23–25 June
2008, University of California, Berkeley, USA.
Herein, we describe our work on the chemical functionalization
of phosphine polymer 2 through boronation and methylation
reactions. To simplify polymer characterization, the potential
reactivity of the high polymer is first assessed by comparison to
molecular model systems. Although borane functionalities may
‡ CCDC reference numbers 668085–668087. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b718140j
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4451–4457 | 4451
©

be incorporated at every atom along the main chain in 2, only ca.
50% of the phosphine units were methylated by MeOTf.
Results and discussion
Synthesis of molecular model compounds
Phosphines 3a and 3b were prepared from 1 following the
literature procedures.12 These molecular compounds function as
useful models to evaluate the chemical functionality of polymer
2. In an attempt to form a phosphine–borane adduct, a pale
yellow solution of 3a in THF was treated with BH3·SMe2 in
Et2O at −78 ◦C (Scheme 2). Analysis of the reaction mixture
using 31P NMR spectroscopy revealed that the signal for free
phosphine 3a (d = −24.0) was replaced by a new signal (d = 18.3).
Likewise, treating silyl-terminated 3b with BH3·SMe2 affords a
single product as judged by its 31P NMR spectrum (d = 24.8 cf.
3b: d = −23.9). Crystals of each product were obtained directly
from the reaction solutions. Analysis of the crystals by X-ray
crystallography confirmed that phosphine–boranes 4a and 4b had
been formed successfully (see Fig. 1 and 2). Compounds 4a and 4b
were further characterized using 1H and 13C NMR spectroscopy.
Interestingly, the borane can conveniently be removed to regen-
erate 3 by treating either phosphine–borane with amines such as
diethylamine.
Fig. 2 Solid-state molecular structure of 4b. Thermal ellipsoids at
50% probability; hydrogen atoms are omitted for clarity. Selected bond
◦
˚
lengths (A) and angles ( ). P(1)–C(1) = 1.846(2), P(1)–C(10) = 1.819(2),
P(1)–C(11) = 1.894(2), P(1)–B(1) = 1.977(2), C(11)–Si(1) = 1.941(2),
C(24)–Si(1) = 1.857(2); C(1)–P(1)–C(11) = 107.8(1), C(2)–C(1)–P(1) =
117.6(1), C(8)–C(1)–P(1) = 124.1(1), C(12)–C(11)–P(1) = 106.6(1), C(18)–
C(11)–P(1) = 112.0(1), C(10)–P(1)–B(1) = 100.7(1), C(11)–P(1)–B(1) =
122.9(1), C(1)–P(1)–B(1) = 110.6(1).
We are also interested in the functionalization of
+
poly(methylenephosphine) with CH3 which is isoelectronic to
BH3. From a polymer perspective, this would provide access to
novel methylphosphonium polyelectrolytes. We chose MeOTf as
the methylating agent rather than milder agents due to the an-
ticipated difficulty fully alkylating the closely spaced phosphorus
atoms in 2. Thus, a solution of 3a in CH2Cl2 was treated with
excess MeOTf to give compound 5 (d 31P = 29.8) (Scheme 3). Slow
evaporation of the solvent afforded large crystals of the air-stable
phosphonium salt 5 which were analyzed using X-ray diffraction
(Fig. 3). The analytically pure crystals were further characterized
by 31P, 1H, 13C and 19F NMR spectroscopy and by elemental
analysis. The 1H NMR spectrum for compound 5 (in DMSO-d6) is
consistent with the proposed product, although it is not possible to
assign the overlapping signals for the methyl protons (i.e. P-CH3,
o-CH3 and p-CH3). In the 19F NMR spectrum, a sharp signal is
observed at −77.5 ppm which is characteristic of free triflate.
Fig. 1 Solid-state molecular structure of 4a. Thermal ellipsoids at
50% probability; hydrogen at◦oms are omitted for clarity. Selected
˚
bond lengths (A) and angles ( ). P(1)–C(1) = 1.814(4), P(1)–C(10) =
1.795(5), P(1)–C(11) = 1.837(4), P(1)–B(1) = 1.831(6); C(1)–P(1)–C(11) =
105.0(2), C(2)–C(1)–P(1) = 120.4(4), C(8)–C(1)–P(1) = 121.0(3), C(12)–
C(11)–P(1) = 111.6(3), C(18)–C(11)–P(1) = 112.0(3), C(10)–P(1)–B(1) =
102.6(3), B(1)–P(1)–C(11) = 115.1(3), C(1)–P(1)–B(1) = 121.1(3).
Scheme 3
X-Ray crystallography‡
Compounds 4a, 4b and 5 were characterized crystallographically
and the molecular structures are shown in Fig. 1, 2 and 3, re-
spectively. Important metrical parameters are found in the Figure
captions and details of the structure solution and refinement are
˚
given in Table 1. Interestingly, the P(1)–B(1) bond [1.831(6) A]
˚
Scheme 2
in 4a is shorter than the analogous bond in 4b [1.977(2) A].
4452 | Dalton Trans., 2008, 4451–4457
This journal is The Royal Society of Chemistry 2008
©

Table 1 X-Ray crystallographic data of 4a, 4b and 5
Crystal
4a
4b
5
Formula
C23H28PB
346.23
Monoclinic
C25H34PBSi
404.39
C25H28PSO3F3
496.50
Monoclinic
Formula weight
Crystal system
Space group
Color
Triclinic
¯
P 21/n
P1
P21/n
Colourless
8.342(2)
13.896(3)
16.931(3)
90
Colourless
10.128(1)
10.750(1)
12.890(1)
108.324(4)
93.499(3)
117.089(4)
1151.0(2)
2
Colourless
10.118(1)
17.583(1)
13.314(1)
90
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
99.909(11)
90
1933.4(10)
4
173(2)
1.45
98.166(1)
90
2344.6(2)
4
173(2)
2.56
3
˚
V/A
Z
T/K
173(2)
1.80
l(Mo Ka)/cm−1
Crystal size/mm
0.90 × 0.60 × 0.20
0.40 × 0.20 × 0.10
0.45 × 0.40 × 0.20
D
calcd/g cm−3
1.189
1.167
1.407
2h (max)/◦
47.3
56.0
55.8
No. of reflections
No. of unique data
Rint
Reflections/parameters ratio
R1, wR2[I > 2r(I)]a
R1, wR2 (all data)a
GOF
26 106
2889
0.077
12.45
0.073; 0.190
0.110; 0.222
1.10
23 770
5485
0.029
14.10
0.036; 0.091
0.045; 0.097
1.04
40 481
5623
0.055
18.56
0.044; 0.094
0.075; 0.108
1.00
ꢀ
ꢀ
ꢀ
ꢀ
2
a R1 =
ꢀFo| − |Fcꢀ/ |Fo|. wR2 = [ (w (Fo − Fc2)2)/ w(Fo2)2]1/2
.
than providing chemical insight into the bonding in 4a (see
Experimental for details).
The P–C bonds in 4a [avg. 1.815(8) A] and 4b [avg. 1.853(3) A]
are in the range typical for P–C bonds (1.85–1.90 A). For
˚
˚
13
˚
comparison, the analogous bonds in 3a [avg. 1.858(2)] and 3b [avg.
˚
1.853(3) A] are similar in length to those in 4a and 4b. Interestingly,
the longest P–C bond is the P–CPh2R bond [4a: P(1)–C(11) =
˚
˚
1.837(4) A, 4b: P(1)–C(11) = 1.894(1) A]. These P–CPh2R bonds
˚
in 4a and 4b are shorter than in the free phosphines [3a: 1.882(1) A,
3b: 1.902(1) A].12 The shortening is less significant between 3b and
˚
4b than between 3a and 4a. Presumably, this reflects the increased
steric congestion in the former [–CPh2(SiMe2H) vs. –CPh2(H)].
˚
Similarly, in methylphosphonium 5 the P–Me (avg. 1.794(3) A] and
˚
P–Mes [P(1)–C(1) = 1.809(2) A] bonds are significantly shorter
˚
than the P–CPh2H bond [P(1)–C(12) = 1.854(2) A]. The P–C
bonds in 5 are all shortened considerably with respect to the
analogous bonds in 3a [P–Me: D(P–C) = 0.046(3); P–Mes: D(P–
˚
C) = 0.043(2); P–CPh2H: D(P–C) = 0.030(2) A].
For the most part, the bond angles in compounds 4a, 4b and 5
are unremarkable with the exception of the Mes–P–CPh2R angles.
In particular, this angle is found to expand significantly upon
coordination. For example, Mes–P–CPh2R angle is between 105
and 108◦ in 4a, 4b and 5 whereas the analogous angle in 3a is just
100◦. This is likely a consequence of increased s-character in the
phosphorus bonds upon quaternization of the phosphorus lone
pair.
Fig. 3 Solid-state molecular structure of 5. Thermal ellipsoids at 50%
probability; hydrogen atoms are omitted for clarity. Selected bond
◦
˚
lengths (A) and angles ( ). P(1)–C(1) = 1.809(2), P(1)–C(10) = 1.797(2),
P(1)–C(11) = 1.790(2), P(1)–C(12) = 1.854(2); C(1)–P(1)–C(12) =
107.2(1), C(2)–C(1)–P(1) = 124.1(2), C(8)–C(1)–P(1) = 116.5(2), C(12)–
P(1)–C(11) = 109.0(1), C(12)–P(1)–C(10) = 110.6(1).
For comparison, the typical range for P–B bonds is 1.90 to
Chemical functionalization of poly(methylenephosphine)
13
14
˚
˚
1.95 A and the bond length in Ph3P–BH3 [1.917 A]. We
speculate that the apparent shortening of the P–B bond in 4a
results from difficulty modelling the disorder in the crystal rather
Following the synthesis and characterization of the model
compounds, the preparation of phosphine–borane and methyl
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4451–4457 | 4453
©

phosphonium polymers was attempted. The anionic polymer-
ization of 1 in glyme using nBuLi as the initiator afforded
poly(methylenephosphine) 2 (Mn of 3.89 × 104 g mol−1; PDI =
1.34).6 The polymerization was not conducted using the rigorous
standards required for a living polymerization and, consequently,
the molecular weight distribution (PDI) is greater than 1.1.
In an attempt to prepare poly(methylenephosphine borane) 6,
the phosphine polymer 2 was treated with BH3·SMe2 (1.4 equiv)
(Scheme 4). Polymer 6 was isolated as a colorless solid after the
volatiles were removed in vacuo. The 31P NMR spectrum of 6 is
shown in Fig. 4(b) and the chemical shift for the borane polymer
is similar to models 4a and 4b (d = 18.3 and 24.8, respectively).
The spectrum shows no evidence for the presence of uncoordi-
nated phosphine moieties [cf. Fig 4(a)]. Interestingly, the signals
observed for 6 are much sharper and are better resolved than those
observed for 2. For example, the 31P NMR spectrum of phosphine–
borane polymer 6 exhibits two signals at 32.4 ppm (minor) and
26.8 ppm (major). In addition, a small shoulder is observed on the
high field end of the signal at 26.8 ppm. In contrast, uncomplexed
poly(methylenephosphine) 2 shows broad unresolved signals that
likely encompass the different environments which are resolved
in 6. We speculate that the observation of multiple signals in the
31P NMR spectrum of macromolecule 6 may be an indication
of the tacticity in poly(methylenephosphine)s. Alternatively, the
minor signal at 32.4 ppm may be attributed to polymer end-groups,
however, the integrated ratios are not consistent with the degree
of polymerization (DPn ≈ 125) determined using GPC.
moieties in the main chain with the GPC columns which has been
observed previously for phosphine polymers.15 The reaction of
polymer 6 with excess amine such as NEt3 results in the clean
deprotection of the BH3 group to form poly(methylenephosphine)
2. The reformation of 2 was confirmed by 31P NMR spectroscopy
and GPC analysis (Mn = 3.71 × 104 g mol−1; PDI = 1.36). Thus,
borane may prove to be a useful protecting group for the mildly
air-sensitive polymer.
The synthesis of poly(methylenephosphonium triflate) proved
to be more difficult than the borane polymer. A solution of
2 in CH2Cl2 was treated with MeOTf (excess) and was heated
to 50 ◦C. The reaction mixture was monitored by 31P NMR
spectroscopy and signals for free phosphine were still observed
even after several days. The 31P NMR spectrum of the product after
precipitation is shown in Fig. 4(c). Importantly, a signal is observed
at 31 ppm which is consistent with methylphosphonium moieties
by comparison to the chemical shift of 5 (d = 29.8). Integrating the
signals for the methylated (d = 31) and unmethylated (d = −10)
phosphorus atoms in 7 suggests that approximately 50% of the
phosphorus atoms are methylated (Scheme 5). This experiment
was repeated several times and, even after several days of heating
2 with excess MeOTf, the degree of methylation never exceeded
50%. Complete methylation would require a formal positive charge
at every second atom in the polymer backbone. We speculate
that phosphorus atoms are methylated in a roughly alternating
fashion rather than in a completely random fashion as shown in
Fig. 5. For both steric and electronic (i.e. repulsive) reasons the
alternating addition would be favourable and would lead to ca.
50% methylation.
Scheme 4
Scheme 5
Fig. 5 Depictions of possible methylation patterns for methylated
poly(methylenephosphine) 7: (top) alternating positive charge, (bottom)
random distribution of positive charge.
Fig. 4 Stack plot showing the 31P NMR spectra (121.5 MHz) of:
(a) poly(methylenephosphine) 2 in THF, (b) poly(methylenephosphine
borane) 6 in CDCl3, and (c) poly(methylene phosphonium triflate) 7 in
DMSO-d6.
Polymer 7 was characterized by 1H, 31P, 19F and 13C NMR spec-
troscopy. The 13C NMR spectrum of poly(methylenephosphonium
triflate) 7 in DMSO-d6 is shown in Fig. 6 (bottom) and, although
the signals are broadened significantly, the spectrum shows signals
in the same regions with that for model compound 5 [Fig. 6 (top)].
Of note, are the signals assigned to P-CH3 (d = 13.2) and O3SCF3
The absolute number average molecular weight (Mn) of 6 was
determined using triple detection GPC (Mn = 4.13 × 104 g mol−1;
PDI = 1.26) which showed a slight increase over that for 2 (Mn =
3.89 × 104 g mol−1; PDI = 1.34). The similarity in the molecular
weights of 2 and 6 confirms that no backbone degradation
occurs during the BH3 protection. Notably, the molecular weight
distribution is much narrower for 6 than for 2. We postulate that
the larger PDI for 2 is due to some interaction of the phosphine
1
(d = 120.7, q, JCF = 322 Hz). Macromolecule 7 is not soluble
in THF and, consequently GPC analysis in THF could not be
obtained. Static light scattering experiments were attempted with
this ionic polymer but reliable molecular weight data could not be
attained.
4454 | Dalton Trans., 2008, 4451–4457
This journal is
The Royal Society of Chemistry 2008
©

from sodium/benzophenone ketyl. CDCl3 was distilled from
P2O5 and degassed. CD2Cl2 and DMSO–d6 were purchased from
Cambridge Isotope Laboratories and were used as received.
Methanol was degassed prior to use. NEt3, HNEt2, DBU, MeLi
(1.6 M in Et2O) n-BuLi (1.6 M in hexanes), BH3·SMe2 (2 M
in Et2O) and MeOTf were purchased from Aldrich and used
as received. Alkyllithium reagents were titrated prior to use.
MesP CPh2 (1),16,17 Me(Mes)P–CPh2(H) (3a) and Me(Mes)P–
=
CPh2(SiMe2H) (3b) were prepared using literature methods.12
Polymer 2 was prepared according to literature procedure.6
1H, 13C, 19F and 31P NMR spectra were recorded on a Bruker
Avance 300 MHz spectrometer. Chemical shifts are reported
relative to residual CHCl3 (d = 7.26 for 1H and and 77.23 for 13C),
1
CHDCl2 (d = 5.32 for H and and 54.00 for 13C) and DMSO-d5
(d = 2.50 for 1H and 39.52 for 13C). CFCl3 was used as an external
standard d = 0.0 for 19F. 85% H3PO4 was used as an external
standard d = 0.0 for 31P. Molecular weights were determined
by triple detection gel permeation chromatography (GPC–LLS)
using a Waters liquid chromatograph equipped with a Waters
515 HPLC pump, Waters 717 plus autosampler, Waters Styragel
columns (4.6 × 300 mm; HR5E, HR4 and HR2), Waters 2410
differential refractometer, Wyatt tristar miniDAWN (laser light
scattering detector-690 nm) and a Wyatt ViscoStar viscometer. A
flow rate of 0.5 mL min−1 was used and samples were dissolved in
THF (ca. 2 mg mL−1).
Fig. 6 13C NMR spectra (75.5 MHz, DMSO-d6) of compound 5 (top)
and macromolecule 7 (bottom). * DMSO–d6.
Summary
Preparation of Mes(Me)P(BH3)–CHPh2 (4a)
In closing, we have investigated the chemical functionality of
poly(methylenephosphine) 2 through phosphine coordination to
main group Lewis acids. The chemical functionality of 2 was
examined by reacting Mes(Me)P–CPh2R [R = H (3a) or SiMe2H
(3b)], molecular model compounds for the high polymer, with
BH3·SMe2 or MeOTf. Three new functionalized model systems
were prepared and characterized crystallographically; namely,
Mes(Me)P(BH3)–CPh2H (4a), Mes(Me)P(BH3)–CPh2H (4b) and
Mes(Me)2P–CPh2H (5). The analogous reactions were success-
ful when polymer 2 was used. Specifically, we report a new
phosphine–borane polymer n-Bu[MesP(BH3)–CPh2]nH (6) and a
methylphosphonium polymer n-Bu[MesP–CPh2]x–/–[MesP(Me)–
CPh2]yH·(OTf)y (7: x:y = ca. 1:1). These new polymers were fully
characterized spectroscopically and absolute molecular weights
were determined for 6.
An ethereal solution of BH3·SMe2 (1.4 ml, 2 M, 2.8 mmol) was
added dropwise by syringe to a cooled solution (−78 ◦C) of
compound 3a (0.94 g, 2.8 mmol) in THF (40 ml). The reaction
mixture was allowed to warm slowly to room temperature and
an aliquot was removed for analysis by 31P NMR spectroscopy
(d = 18.3, br). After removal of the volatiles in vacuo, an oil
was obtained which crystallized slowly over a period of 10 h.
Yield: 0.72 g, 74%. dP(121.5 MHz; CDCl3; H3PO4) 18.3 (br s).
dH(300.1 MHz, CDCl3; SiMe4) 7.69–7.17 (10 H, m, aryl H), 6.86
2
(2 H, s, m–H of Mes), 4.86 (1 H, d, JPH = 17 Hz, CHPh2), 2.40
(6 H, s, o–CH3), 2.27 (3 H, s, p–CH3), 2.0–0.5 (3H, br q, BH3),
2
1.69 (3 H, d, JPH = 9 Hz, PCH3). dC(75.5 MHz; CDCl3;SiMe4)
unassigned) 143.9 (d, JPC = 9 Hz), 140.9 (d, JPC = 2 Hz), 137.2 (d,
JPC = 3 Hz), 131.1 (d, JPC = 9 Hz), 129.9 (d, JPC = 5 Hz), 129.4
(d, JPC = 5 Hz), 128.6 (s), 128.1 (d, JPC = 2 Hz), 127.4 (d, JPC = 2
Future work will focus on studying the properties of the
phosphine–borane and methylphosphonium polymers reported
herein. The prospect of preparing water soluble phosphorus
homo- or co-polymers by post-polymerization modification of 2
is an exciting synthetic target.
Hz), 127.1 (d, JPC = 3 Hz), 123.4 (d, JPC = 46 Hz), 51.8 (d, JPC
26 Hz), 24.4 (d, JPC = 4 Hz), 20.8 (s), 15.7 (d, JPC = 39 Hz).
=
Reaction of 4a with Et2NH
A solution of compound 4a (0.72 g, 2.1 mmol) in THF (5 mL)
was combined with Et2NH (7 ml). The reaction mixture was
stirred for 4 h and an aliquot was removed for analysis by 31P
NMR spectroscopy. Complete conversion to 3a (−24 ppm) was
observed and the solvent was removed in vacuo. The resultant oil
was dissolved in CH2Cl2 and washed with water. The aqueous
phase was then extracted with CH2Cl2 (3 × 20 mL). The colleted
extracts were combined and dried over MgSO4. Filtration of the
CH2Cl2 solution and removal of the solvents in vacuo afforded 3a
as an oil. Yield: 0.22 g, 31%.
Experimental
Materials and general procedures
All manipulations of air- and/or water-sensitive compounds were
performed under pre-purified nitrogen (Praxair, 99.998%) using
standard high vacuum or Schlenk techniques or in an Innovative
Technology Inc. glovebox. Hexanes, and dichloromethane were
deoxygenated with nitrogen and dried by passing through a
column containing activated alumina. THF was freshly distilled
This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4451–4457 | 4455
©

Preparation of Mes(Me)P(BH3)–CPh2SiMe2H (4b)
in CH2Cl2 (15 ml) and washed with degassed water (2 × 5 ml).
The organic layer was dried over MgSO4 and solvent was removed
in vacuo affording 2. Yield: 0.22 g, 91%. Mn = 3.71 × 104 g/mol,
PDI = 1.36.
An ethereal solution of BH3·SMe2 (0.6 ml, 2 M, 1.2 mmol) was
added dropwise to a cooled solution (−78 ◦C) of phosphine
3b (0.47 g, 1.2 mmol) in THF (20 mL). The reaction mixture
was slowly warmed to room temperature. After evaporation of
the solvent in vacuo a white solid was obtained. The solid was
recrystallized by slow evaporation in an inert atmosphere from a
concentrated THF solution. Yield: 0.11 g, 22%. dP(121.5 MHz;
CDCl3; H3PO4) 24.8 (br s). dH(300.1 MHz, CDCl3; SiMe4) 7.6–7.2
(10 H, m, aryl H), 6.69 (2 H, br s, m-Mes), 4.77 (1 H, m, Si–H),
2.5–0.5 (3H, br q, BH3), 2.37 (6 H, br, o-CH3), 2.22 (3 H, s, p-CH3),
1.88 (3 H, d, 2JPH = 8 Hz, PCH3), 0.12 (3 H, d, J = 3 Hz, SiCH3),
0.0 (3 H, d, J = 3 Hz, SiCH3). dC(75.5 MHz, CD2Cl2: SiMe4) 145.2
(s), 140.4 (d, JPC = 2 Hz), 139.0 (d, JPC = 4 Hz), 138.4 (d, JPC = 4
Hz), 131.9 (s), 131.8 (s), 131.1 (d, JPC = 9 Hz), 127.8 (s), 127.5 (s),
126.7 (s), 125.7 (d, JPC = 47 Hz), 48.4 (s), 25.4 (br s), 20.8 (s), 16.8
(d, JPC = 39 Hz), −3.5 (s), −3.6 (s).
Preparation of n-Bu[MesP–CPh2]x–/–[MesP(Me)–CPh2]yH (7)
To a solution of polymer 2 (0.40 g, 1.3 mmol) in CH2Cl2 (10 ml)
was added excess methyl triflate (10 eq.). The reaction mixture
was stirred overnight. Analysis of the mixture by 31P NMR
spectroscopy exhibited two broad singlets with one signal at
31 ppm and the other at −7 ppm. Integration of the two signals
revealed an approximate 1:1 ratio of the two signals. The polymer
was isolated by concentrating the reaction mixture (ca. 1 mL) and
precipitating with hexanes (20 mL). The yellow solid was dried
in vacuo at 80 ◦C overnight. Yield: 0.23 g, 46%. dP(121.5 MHz;
DMSO-d6; H3PO4) 31 (br s, ca. 50%), −10 (br s, ca. 50%).
dH(300.1 MHz, DMSO-d6; SiMe4) 7.2 (12 H, br, m-Mes-H, Ph-
H), 2.2 (15H, o,p-CH3, P-CH3); dC(75.5 MHz; DMSO-d6;SiMe4)
(unassigned), 145 (s), 140 (s), 133 (s), 129 (s), 120.7 (q, 1JCF = 320
Hz), 114 (s), 49 (s), 23 (s), 20 (s), 12 (s); dF(282.4 MHz; DMSO-
d6;CFCl3) −78.7 (s, CF3).
Preparation of [Mes(Me)2P–CPh2H]OTf (5)
To a solution of compound 1 (2.00 g, 6.3 mmol) in THF (20 ml)
was added MeLi (5.4 mL, 1.4 M, 7.6 mmol). The reaction mixture
was stirred for 1 h and then solvent was removed in vacuo.
Extraction of the reaction mixture with hexanes (3 × 10 mL)
provided compound 3a as an oil. This yellow oil was dissolved in
CH2Cl2 and added to MeOTF (2 eq.) in the glovebox. The reaction
mixture was placed in a vial and the salt crystallized overnight.
The crystals were dried for 72 h. Yield: 0.60 g, 19%. dP(121.5 MHz;
DMSO-d6; H3PO4) 29.8 (s). dH(300.1 MHz, DMSO-d6; SiMe4)
7.57–7.39 (10 H, m, aryl H), 7.06 (2 H, s, m–H of Mes), 5.68 (1
H, d, 2JPH = 18 Hz, CHPh2) 2.33–2.27 (15 H, m, o–CH3, p–CH3,
P–CH3). dC(75.5 MHz; DMSO-d6;SiMe4) (unassigned) 144.0 (d,
JPC = 3 Hz), 143.6 (d, JPC = 10 Hz), 133.4 (d, JPC = 4 Hz), 131.8
X-Ray crystallography
Crystal data and refinement parameters are listed in Table 1.
Additional information can be obtained in the supplementary
data.‡ All single crystal were immersed in oil and mounted
on a glass fiber. Data were collected at 173.0
0.1K on a
Bruker X8 APEX 2 diffractometer with graphite-monochromated
Mo Ka radiation. Data was collected and integrated using the
Bruker SAINT18 software package. All structures were solved by
direct methods19 and subsequent Fourier difference techniques
and refined anisotropically for all non-hydrogen atoms using
the SHELXTL20 crystallographic software package from Bruker-
AXS. All data sets were corrected for Lorentz and polarization
effects. Cif files are available as supplementary data.‡
All single crystals were immersed in Paratone-N oil and were
mounted on a glass fiber. Compounds 4b and 5 did not exhibit any
crystallographic complexity. Data collection for compound 4a was
attempted to 2h = 56◦, however no significant reflections were ob-
served beyond 2h ≈ 46◦, which may be a consequence of disorder
in the crystal lattice. In particular, we speculate that the apparent
shortening of the P(1)–B(1) bond is due to disorder in these atom
positions, however, we have been unable to model this satisfacto-
rily. For the final refinement, only data below 47.2◦ was included.
(d, JPC = 12 Hz), 129.7 (d, JPC = 6 Hz), 129.2 (d, JPC = 2 Hz),
1
128.6 (d, JPC = 2 Hz), 120.7 (q, JFC = 322 Hz), 114.7 (d, JPC
=
77 Hz), 49.1 (d, JPC = 43 Hz), 23.7(d, JPC = 4 Hz), 20.4 (s), 13.2
(d, JPC = 52 Hz): dF(282.4 MHz; DMSO-d6;CFCl3) −77.5 (s, CF3).
Anal. calcd for C25H28PSO3F3: C, 60.47; H, 5.68. Found: C, 60.41;
H, 5.66.
Preparation of n-Bu[MesP(BH3)–CPh2]nH (6)
Poly(methylenephosphine) 2 (0.35 g, 1.1 mmol) (Mn = 3.89 ×
104 g/mol, PDI = 1.34) was dissolved in THF (20 ml) and
BH3·SMe2 (0.75 ml, 2 M, 1.5 mmol) was added dropwise via sy-
ringe at −78 ◦C. The reaction mixture was allowed to slowly warm
up to room temperature. After evaporation of the volatiles in vacuo
a solid was obtained. Yield: 0.25 g, 68%. GPC (THF): Mn = 4.13 ×
104 g/mol, PDI = 1.26. dP(121.5 MHz; CDCl3; H3PO4) 32.4 (br s,
ca. 10%), 26.8 (br s, ca. 90%). dC(75.5 MHz; CDCl3;SiMe4) (unas-
signed) 143–137 (br m), 132–122 (br m), 53 (br s), 26 (br s), 21 (br s).
Acknowledgements
We are grateful to the Natural Sciences and Engineering Research
Council (NSERC) of Canada for Discovery and Tools grants (DG)
and for PGS M and D scholarships (KJTN, JIB). We also thank
the Canada Foundation for Innovation (CFI) and the British
Columbia Knowledge Development Fund (BCKDF) for funding.
Reaction of 6 with amines
A solution of the poly(methylenephosphine–borane) 6 (0.25 g) in
THF was treated with excess amine (DBU, NEt3, NEt2H). The
reaction was stirred for 12 h and an aliquot of the reaction was
removed and analyzed using 31P NMR spectroscopy (d = −10, br).
Upon removal of the solvent in vacuo, the polymer was dissolved
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This journal is
The Royal Society of Chemistry 2008
Dalton Trans., 2008, 4451–4457 | 4457
©