Molecular studies of the initiation and termination steps of the anionic polymerization of P=C bonds

Article abstract of DOI:10.1139/V07-121

The initiation and termination steps of the anionic polymerization of P=C bonds have been modeled. The initiation step was investigated through the stoichiometric reaction of MesP=CPh₂ (1) with RLi (R = Me or n-Bu). In each case, the addition w

Full text of DOI:10.1139/V07-121

1045
Molecular studies of the initiation and termination
steps of the anionic polymerization of P=C bonds
Bronwyn H. Gillon, Kevin J.T. Noonan, Bastian Feldscher, Jennifer M. Wissenz,
Zhi Ming Kam, Tom Hsieh, Justin J. Kingsley, Joshua I. Bates, and
Derek P. Gates
Abstract: The initiation and termination steps of the anionic polymerization of P=C bonds have been modeled. The
initiation step was investigated through the stoichiometric reaction of MesP=CPh2 (1) with RLi (R = Me or n-Bu). In
each case, the addition was highly regioselective with the formal attack of R– at phosphorus to give the carbanion
Li[Mes(R)P–CPh2] (3a, R = Me; 3b, R = n-Bu). To simulate the termination step in the anionic polymerization of 1,
carbanions 3a and 3b were quenched in situ with various electrophiles. Through these reactions, several new tertiary
phosphines have been prepared, namely, Mes(Me)P–CPh2H (4a), Mes(n-Bu)P-CPh2H (4b), Mes(Me)P–CPh2Me (6a),
Mes(Me)P–CPh2–P(NEt2)2 (7a), Mes(Me)P–CPh2–SiMe2H (8a), and Mes(Me)P–CPh2–SiMe3 (9a). In addition, com-
pounds 4a, 7a, 8a, and 9a were characterized by X-ray crystallography. Most of the metrical parameters are typical of
tertiary phosphines; however, the P–CPh2H bonds were elongated in all cases reflecting the considerable steric bulk
surrounding this bond. Unexpectedly, an unusually large 31P–31P coupling constant (2JPP > 200 Hz) was observed for
7a both in solution and the solid state. This observation may be rationalized by a through space PLP interaction. This
rationale is further supported by the short PLP distance [P(1)—P(2) = 2.966(1) Å; cf. Σ rvdw = 3.7 Å] and a small P–
C–P bond angle for 7a [P(1)–C(11)–P(1) = 99.17(9)°].
Key words: phosphaalkenes, phosphorus polymers, phosphines, anionic polymerization.
Résumé : On a développé un modèle pour les étapes d’initiation et de terminaison de la polymérisation anionique des
liaisons P=C. On a étudié l’étape d’initiation par le biais de la réaction stoechiométrique du MesP=CPh2 (1) avec du
RLi (R = Me ou Bu). Dans chacun des cas, l’addition est très régiosélective avec une attaque formelle du R– sur le
phosphore pour conduire à la formation du carbanion Li[Mes(R)P–CPh2] (3a, R = Me; 3b, R = Bu). Dans le but de si-
muler l’étape de terminaison de la polymérisation du composé 1, les carbanions 3a et 3b ont été piégés in situ avec di-
vers électrophiles. Par le biais de ces réactions, on a obtenu plusieurs nouvelles phosphines tertiaires, soit: Mes(Me)P–
CPh2H (4a); Mes(Bu)P–CPh2H (4b); Mes(Me)P–CPh2Me (6a); Mes(Me)P–CPh2–P(NEt2) (7a); Mes(Me)P–CPh2–
SiMe2H (8a) et Mes(Me)P–CPh2–SiMe3 (9a). De plus, on a caractérisé les composés 4a, 7a, 8a et 9a par diffraction
des rayons X. La plupart des paramètres métriques sont typiques des phosphines tertiaires; toutefois, dans tous les cas,
les liaisons P–CPh2H sont allongées et cette caractéristique reflète l’encombrement stérique important aux abords de
cette liaison. D’une façon inattendue, on a observé une constante de couplage 31P–31P exceptionnellement élevée (2JPP
> 200 Hz) avec le composé 7a, tant à l’état solide qu’en solution. On peut rationaliser cette observation à l’aide d’une
interaction PLP à travers l’espace. Ce raisonnement est supporté par la courte distance PLP [P(1)—P(2) = 2,966(1) Å;
cf. Σ rvdw = 3,7 Å] et un faible angle P–C–P pour le composé 7a [P(1)–C(11)–P(1) = 99,17(9)°].
Mots-clés : phosphaalcènes, polymères du phosphore, phosphines, polymérisation anionique.
[Traduit par la Rédaction] Gillon et al. 1052
Introduction
in the late 1970s, interest in phosphaalkenes continues to
grow because of their parallelism to the chemistry of C=C
bonds and their potential applications (1–3). For example,
compounds with P=C bonds are being explored as ligands in
transition-metal-catalyzed reactions (4–7) and in polymer
science (8–13).
Recently, we reported the polymerization of phos-
phaalkene 1 to afford poly(methylenephosphine) 2, a new
functional phosphine polymer with alternating phosphorus
and carbon atoms in the main chain (see Scheme 1) (12).
Our initial studies suggested that the polymerization of 1 re-
quired high temperatures (>150 °C), long reaction times, and
high concentrations, even in the presence of radical or an-
ionic initiators. We subsequently showed that short-chain
oligomers could be obtained when 1 is treated with anionic
Phosphaalkenes, compounds with genuine (2p–3p) π
bonds, are an intriguing class of low-coordinate phosphorus
species. Although the first stable derivatives were reported
Received 23 July 2007. Accepted 12 September 2007.
Published on the NRC Research Press Web site at
canjchem.nrc.ca on 22 November 2007.
B.H. Gillon, K.J.T. Noonan, B. Feldscher, J.M. Wissenz,
Z.M. Kam, T. Hsieh, J.J. Kingsley, J.I. Bates, and
D.P. Gates.1 Department of Chemistry, University of British
Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1,
Canada.
1Corresponding author (e-mail: dgates@chem.ubc.ca).
Can. J. Chem. 85: 1045–1052 (2007)
doi:10.1139/V07-121
© 2007 NRC Canada

1046
Can. J. Chem. Vol. 85, 2007
Scheme 1.
tures, resulting in an immediate color change to deep red.
Analysis of the reaction mixture using 31P{1H} NMR spec-
troscopy confirmed the complete conversion of 1 to the
carbanion 3a (δ = −44.3) or to 3b (δ = –31.1). These inter-
mediates are believed to be related to the active species in
the anionic polymerization of 1.
Ph
C
Ph
Ph
Radical or Anionic
Initiator
P
P
C
Mes
Mes Ph
n
2
1
Carbanion 3a was quenched by addition of water or meth-
anol to afford model compound 4a (δ
= –24.0). Addi-
31 P
initiators (i.e., MeLi) in THF solution at ambient tempera-
ture (14). This solution oligomerization has now been ex-
tended to the living anionic polymerization of monomer 1 to
afford homopolymer 2 and block copolymers with controlla-
ble architectures (11). To further develop the living anionic
polymerization of P=C bonds and to prepare end-
functionalized polymers, it is necessary to fully understand
the mechanism of anionic chain growth for 1.
To our knowledge, there is little previous work on the
reaction of P=C bonds with typical anionic initiators. Of par-
ticular relevance to our studies is the synthesis of phosphine
oxide 5a from phosphaalkene 1 (15) (see Scheme 2). Spe-
cifically, treating 1 with MeLi followed by MeOH and air
oxidation afforded 5a. Both the carbanion (3a) and the
phosphine (4a) were the proposed intermediates in this
reaction. In a separate study, the addition of MeLi to
RP=C(SiMe3)2 (R = Mes, t-Bu) afforded Li[MeRPC(SiMe3)2],
which was characterized spectroscopically (16–18). In sev-
eral other studies, the addition of alkyllithium reagents
across the P=C bond in phosphinines and triphosphafulvenes
similarly afforded only the P-alkyl products (19). These
regioselective additions are consistent with the predicted po-
larity of the P=C bond, based on the electronegativities of
phosphorus (δ+) and carbon (δ–). Interestingly, alkyllithium
reagents can also react with phosphaalkenes with preserva-
tion of the P=C bond (20).
In this paper, we disclose our molecular-model studies of
the initiation and termination steps of the anionic polymer-
ization of 1. Two initiators were chosen for the present studies:
MeLi and n-BuLi. Although n-BuLi is a better initiator for
the anionic polymerization of 1 (11, 12), MeLi is optimal in
molecular-model studies, since the small Me substituent is
more likely to afford crystalline products. The new com-
pounds obtained may be utilized as molecular models for the
development of the coordination chemistry of polymer 2.
Moreover, the development of methods to end-functionalize
poly(methylenephosphine)s will afford telechelic polymers,
which may function as precursors to novel block copoly-
mers.
1
tionally, 13C{1H}, H NMR spectroscopy, and low resolution
EI-MS (M+, m/z = 332) were consistent with the proposed
1
structure. The H NMR spectrum of 4a shows a notably
downfield doublet resonance at δ = 4.87 (2JHP = 5 Hz),
which is assigned to the benzylic proton. Importantly, a dou-
blet resonance is observed in the alkyl region (δ = 1.31,
2JHP = 6 Hz), which is attributed to the P-CH3 protons.
Clearly, addition of the methyl anion occurs regioselectively
at the phosphorus atom of the P=C bond. Also found in the
alkyl region are sharp singlets at 2.52 and 2.21 ppm that are
assigned to the ortho- and para-methyl protons of the
mesityl group, respectively.
Clear, colorless crystals suitable for X-ray diffraction
were obtained from the slow evaporation of a concentrated
solution of 4a in hexanes. The molecular structure and the
crystallographic data appear in Fig. 1, Table 1, and the Sup-
plementary data.2 The molecular structure provides insight
into the steric nature of the substituents around the P atom.
Importantly, the cone angle of the model compound 4a was
estimated to be roughly 140°, which is comparable to that of
triphenylphosphine (145°) (23).3 The P—C bond lengths (Å)
fall into the typical range for P—C single bonds [P(1)—C(1) =
1.852(1), P(1)—C(10) = 1.840(2), P(1)—C(11) = 1.882(1)]
(24). Presumably, steric repulsion is responsible for the
slight elongation of P(1)—C(11). For comparison, related
P—C bonds where the carbon atom has two aryl substituents
(i.e., RArP–CHPh2) are ~1.90 Å in length (25, 26).
Using n-BuLi as the initiator for 1, the related compound
4b, was prepared by terminating carbanion 3b with water.
Again, the reaction was quantitative as suggested by 31P{1H}
NMR spectroscopy (δ = –12.4). Upon workup, analytically
pure 4b was isolated in good yield (85%) as a yellow oil.
1
Akin to the Me-initiated 4a, the H NMR spectrum of n-Bu-
initiated 4b showed a characteristic doublet resonance at
4.91 ppm (2JHP = 5 Hz), which is assigned to the benzylic
proton. A sharp singlet at 2.20 ppm is assigned to the para-
methyl mesityl protons. In contrast to the sharp signals ob-
served for 4a, the ortho-methyl mesityl protons in 4b exhibit
a broad signal centred at 2.56 ppm. The broadening may be
a consequence of restricted rotation about the P—C
(ipso-mesityl) bond. Additionally, there is considerable
broadening of the resonance assigned to the ortho-methyl
mesityl carbon (δ = 23.8) in the 13C{1H} NMR spectrum.
Another interesting feature in the 1H NMR spectrum of 4b is
Results and discussion
The phosphaalkene 1 was prepared according to literature
methods (21, 22). A pale-yellow solution of 1 in THF was
treated with a slight excess of alkyllithium at low tempera-
2 Supplementary data for this article are available on the journal Web site (canjchem.nrc.ca) or may be purchased from the Depository of Un-
published Data, Document Delivery, CISTI, National Research Council Canada, Ottawa, ON K1A 0R6, Canada. DUD 5227. For more in-
formation on obtaining material, refer to cisti-icist.nrc-cnrc.gc.ca/irm/unpub_e.shtml. CCDC 655085 (4a), 655086 (7a), 655087 (8a), and
655088 (9a) contain the crystallographic data for this manuscript. These data can be obtained, free of charge, via
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax +44 1223 336033; or deposit@ccdc.cam.ac.uk).
3 The ligand cone angle θ was estimated according to Tolman’s method for an unsymmetrical phosphine (PR1R2R3) ligand. The cone angle is
the apex angle of a cylindrical cone centrally positioned 2.28 Å away from the P. The edges of the cylindrical cone encompassed the van
der Waals radii of the outermost atoms on each substituent on P. Using X-ray crystallographic data for 4a, θ was estimated to be ~140°.
© 2007 NRC Canada

Gillon et al.
1047
Scheme 2. Initiation of 1 with alkyllithium reagents and subsequent termination with electrophiles.
Ph
Ph
R
H
P
C
P
C
Mes
Ph
Mes Ph
n
2
1
RLi
Ph
C
1. (n–1)1
2. MeOH
–LiOMe
R
P
Li
Ph
Mes
R = Me 3a
R = n-Bu 3b
H2O or
MeOH
MeI
ClP(NEt2)2 Me2R'SiCl
–LiCl –LiCl
Ph
–LiOH
–LiI
Ph
C
Ph Me
Si R'
Mes Ph Me
R = Me; R' = H 8a
Ph
C
R
P
H
R
P
C
P
NEt2
R
P
C
R
P
Me
Mes Ph
Mes Ph NEt2
Mes Ph
R = Me 6a
R = Me 4a
R = n-Bu 4b
R = Me 7a
R = R' = Me 9a
H2O2 or
air
O
P
Ph
C
R
H
Mes Ph
R = Me 5a
the diastereotopic protons adjacent to the stereogenic phos-
phorus atom. In particular, they give rise to two sets of
multiplets (δ = 2.02 and 1.55). Assignments were made with
the help of 1H–1H COSY, HMQC, and HMBC experiments.
To model the end-functionalization of polymer 2, we in-
vestigated the termination of the methyl-initiated species 3a
with different electrophiles. These end-functionalized prod-
ucts are envisaged as model systems for the heretofore-
unknown telechelic polymers.
with cold hexanes (–78 °C). As expected, the 31P{1H} NMR
spectrum of the product showed that the phosphorus atoms
are inequivalent and are observed as two doublets (P2: δ =
2
105.3, P1: δ = –9.4; Jpp = 205 Hz). The observed coupling
constant is considerably larger than in a related asymmetric
2
diphosphine [Ph2PCH2P(NC4H4)2, JPP = 147 Hz] (27) and
suggests some direct P–P interaction. In contrast to the
broadened signals observed in 4b and 6a, the ortho-methyl
1
mesityl groups in 7a are inequivalent in both the H and
13C{1H} NMR spectra. Presumably, this results from re-
To obtain Me-terminated 6a, carbanion 3a was quenched
stricted rotation due to the increased steric bulk in 7a.
with neat methyl iodide, affording an orange solution (δ
=
31 P
1
–13.5). Model compound 6a was characterized by H, 13C{1H},
and 31P NMR spectroscopy and low resolution EI-MS (M+,
m/z = 346). Although analytically pure material could not be
isolated, analysis by NMR spectroscopy suggests 95% or
higher purity. As with butyl-initiated 4b, the signal assigned
X-ray-quality crystals of 7a were grown from toluene.
Crystallographic data are shown in Fig. 2, Table 1, and the
Supplementary data.2 Interestingly, the P(1)–C(11)–P(2)
bond angle (99.17(9)°) is more acute than a typical sp3-
hybridized C atom. This small bond angle, combined with
1
to the ortho-methyl mesityl protons in the H NMR spec-
the short PLP distance [P(1)—P(2) = 2.966(1) Å, cf. Σ rvdw
=
3.7 Å], may account for the large coupling constant (2JPP)
observed in solution. To confirm that the structure observed
in solution is the same as that in the solid state, a solid-state
31P NMR spectrum was recorded, which revealed a similarly
large coupling constant (2JPP = 255 Hz). Surprisingly, both
nitrogen atoms are planar with the sum of the bond angles at
nitrogen totaling 360°. Likely, the planarity is due to dona-
tion of nitrogen electron density into P(2), and this notion is
trum (δ = 1.87) is broad. Two doublets are observed in the
2
3
alkyl region (1.70 ppm, JPH = 13 Hz; 1.39 ppm, JPH
=
7 Hz). The resonance with the larger P–H coupling constant
is assigned to the P-CH3 group whilst the other signal is at-
tributed to the quenching methyl group.
Phosphine end-functionalized 7a was prepared by quench-
ing 3a with a solution of ClP(NEt2)2 (1.1 equiv.) in THF.
The crude diphosphine was purified by washing the solid
© 2007 NRC Canada

1048
Can. J. Chem. Vol. 85, 2007
Table 1. X-ray crystallographic data of 4a, 7a, 8a, and 9a.
Crystal
4a
7a
8a
9a
Formula
C23H25P
C31H44N2P2
C25H31PSi
C26H33PSi
Formula weight
Crystal system
Space group
332.40
monoclinic
P21/c
506.62
monoclinic
P21/n
390.56
monoclinic
C2/c
404.58
triclinic
P1
Color
a (Å)
b (Å)
c (Å)
colorless
18.867(2)
6.1290(5)
16.618(2)
90
92.401(3)
90
1919.9(3)
4
colorless
9.528(5)
15.614(5)
18.935(5)
90
94.828(5)
90
2807.0(19)
4
colorless
20.677(5)
8.955(5)
23.987(5)
90
101.555(5)
90
4351(3)
8
colorless
9.165(5)
10.757(5)
12.689(5)
79.511(5)
71.398(5)
75.169(5)
1143.3(9)
2
α (°)
β (°)
γ (°)
V (Å3)
Z
T (K)
173(2)
1.44
0.2 × 0.2 × 0.1
1.150
173(2)
1.77
1.4 × 0.6 × 0.4
1.199
173(2)
1.89
1.4 × 1.2 × 1.0
1.192
173(2)
1.82
1.0 × 1.0 × 0.5
1.175
µ(Mo Kα) (cm–1)
Crystal size (mm)
Dcalcd. (g cm–3)
2θ(max) (°)
56.02
26221
4580
56.04
27995
6560
56.36
54740
5281
55.66
27579
5333
No. of reflections
No. of unique data
Rint
0.040
0.050
0.033
0.024
Reflections/parameters ratio
20.82
0.0388, 0.0925
12.84
0.0418, 0.0944
14.35
0.0350, 0.0883
13.85
0.0306, 0.0820
R1, wR2 [I > 2σ(I)]a
R1, wR2 (all data)a
0.0662, 0.1015
0.0787, 0.1149
1.017
0.0446, 0.0950
1.029
0.0354, 0.0862
1.054
GOF
1.053
aR1 = Σ*(*Fo* – *Fc*)*/Σ*Fo*. wR2 = [Σ(Fo – Fc2)2/Σw(Fo )2]1/2
.
2
2
Fig. 1. Molecular structure of 4a (50% probability ellipsoids).
Hydrogen atoms are omitted for clarity. Selected bond lengths (Å):
P(1)—C(1) = 1.852(1); P(1)—C(10) = 1.840(2); P(1)—C(11) =
1.882(1). Selected bond angles (°): C(10)–P(1)–C(1) = 107.34(7);
C(10)–P(1)–C(11) = 100.51(7); C(1)–P(1)–C(11) = 100.18(6).
Fig. 2. Molecular structure of 7a (50% probability ellipsoids).
Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å): P(1)—C(1) = 1.851(2); P(1)—C(10) = 1.843(2); P(1)—
C(11) = 1.942(2); P(2)—C(11) = 1.951(2); P(2)—N(1) =
1.678(2); P(2)—N(2) = 1.689(2); P(1)LP(2) = 2.966(1). Selected
bond angles (°): C(1)–P(1)–C(10) = 105.1(1); C(1)–P(1)–C(11) =
110.05(9); C(10)–P(1)–C(11) = 101.5(1); P(1)–C(11)–P(2) =
99.17(9); C(11)–P(2)–N(1) = 103.87(8); C(11)–P(2)–N(2) =
105.97(9); N(1)–P(2)–N(2) = 107.80(9); Σ angles about N(1)
atom = 359.7(3)°; Σ angles about N(2) atom = 359.4(3)°.
reinforced by the short P—N distances; P(2)—N(1) =
1.678(2) and P(2)—N(2) = 1.689(2) Å (28). In related
bis(amino)phosphines, the P—N bonds are often shortened
to 1.6–1.7 Å, which is accompanied by planarity at the nitrogen
(29–32). Also, addition of the functional end-group length-
ens the backbone P—C bonds to beyond typical single bonds
[P(1)—C(11) = 1.942(2) and P(2)—C(11) = 1.951(2) Å]
(28).
© 2007 NRC Canada

Gillon et al.
1049
Fig. 3. Molecular structure of 8a (50% probability ellipsoids).
Hydrogen atoms are omitted for clarity except for H(1). Selected
bond lengths (Å): P(1)—C(1) = 1.834(2); P(1)—C(10) =
1.824(2); P(1)—C(11) = 1.902(1); Si(1)—C(11) = 1.910(2);
Si(1)—C(24) = 1.855(2); Si(1)—C(25) = 1.849(2); Si(1)—H(1) =
1.36(2). Selected bond angles (°): C(1)–P(1)–C(10) = 107.39(7);
C(1)–P(1)–C(11) = 106.61(6); C(10)–P(1)–C(11) = 102.33(7);
P(1)–C(11)–Si(1) = 106.57(6).
Addition of Me2HSiCl or Me3SiCl to carbanion 3a pro-
duced silane end-functionalized 8a and 9a, respectively.
These compounds formed quantitatively from 3a according
to the 31P NMR spectra of the reaction mixtures (8a: δ =
–23.9, 9a: δ = –25.4); however, their high solubility resulted
in low isolated yields of pure product after recrystallization
(8a: 50%, 9a: 14%). Analogous to that mentioned previously
1
for 7a, the H NMR signals for the ortho-methyl protons of
the mesityl group were inequivalent, and two broad signals
were observed (8a: δ = 3.1 and 1.1, 9a: δ = 2.8 and 0.9). Im-
portantly, for 8a, a singlet resonance is observed at
4.58 ppm, which is assigned to the Si–H proton. Although
the methyl protons of the SiMe3 moiety are equivalent in 9a,
the methyl protons of the SiMe2H moiety are inequivalent in
8a. In particular, the SiHMe2 group in 8a shows two sets of
doublets at 0.10 ppm (3JHH = 3 Hz) and 0.05 ppm (3JHH
=
3 Hz). Both 8a and 9a were also characterized by low reso-
lution EI-MS (M+: m/z = 390 for 8a and 404 for 9a), ele-
mental analysis (8a only), and X-ray crystallography.
Crystals of 8a and 9a were obtained from hexanes. The
molecular structures and important lengths and angles are
given in Figs. 3 and 4, and additional data is provided in
Table 1 and the Supplementary data.2 As with the other
model compounds, 4a and 7a, the P—CPh2H bond lengths
[8a: P(1)—C(11) = 1.902(1), 9a: P(1)—C(1) = 1.920(1) Å]
are significantly longer than the two other P—C bonds [avg.
for 8a and 9a = 1.835(5) Å]. Similar to that discussed previ-
ously, this elongation may be attributed to steric congestion.
The small size of the SiMe2H moiety compared with the
SiMe3 moiety is reflected by the smaller P–C–Si bond an-
gles in 8a [8a: P(1)–C(11)–Si(1) = 106.57(6)°, 9a: P(1)–
C(1)–Si(1) = 111.52(6)°]. Remarkably, these angles are
much larger than the the analogous angle in diphosphine 7a
[P(1)–C(11)–P(2) = 99.17(9)°] in which we speculate there
is a weak PLP interaction.
Fig. 4. Molecular structure of 9a (50% probability ellipsoids).
Hydrogen atoms are omitted for clarity. Selected bond lengths
(Å): P(1)—C(1) = 1.920(1); P(1)—C(2) = 1.839(2); P(1)—
C(3) = 1.844(1); C(1)—Si(1) = 1.944(1). Selected bond angles
(°): C(1)–P(1)–C(2) = 101.38(6); C(2)–P(1)–C(3) 106.97(7);
C(1)–P(1)–C(3) = 107.53(5); P(1)–C(1)–Si(1) = 111.52(6).
Summary
In closing, the initiation and termination steps in the an-
ionic polymerization of P=C bonds have been modeled. The
initiation step was investigated through the stoichiometric
reaction of MesP=CPh2 (1) with RLi (R = Me or n-Bu). In
all cases, the addition was highly regioselective with the for-
mal attack of R– at phosphorus to give the carbanion
Li[Mes(R)P–CPh2] (3a/3b). To simulate the termination step
in the anionic polymerization of 1, carbanions 3a and 3b
were quenched in situ with electrophiles such as a proton
(from H2O or MeOH), a methyl cation (from MeI), a
phosphenium moiety (from ClP(NEt2)2), or a silylium moi-
ety (from Me2HSiCl or Me3SiCl). In this way, five new ter-
tiary phosphines and one diphosphine were accessed and
will function as models for poly(methylenephosphine)s.
Four of these molecules were characterized crystallographi-
cally.
In future, we will extend this chemistry to the polymer 2
with the goal of preparing end-functional telechelic poly-
mers that can be employed in the synthesis of novel block
copolymers. In addition, these new compounds will be used
to prepare molecular complexes that will serve as models for
macromolecular coordination complexes of poly(methyl-
enephosphine)s.
Experimental
Materials and general procedure
All manipulations of oxygen- and (or) moisture-sensitive
compounds were performed under a nitrogen atmosphere us-
ing standard Schlenk and (or) glovebox techniques. Hex-
anes, diethyl ether, and dichloromethane were deoxygenated
with nitrogen and dried by passing through a column con-
taining activated alumina. THF was freshly distilled from so-
dium/benzophenone ketyl. Distilled water and methanol
were degassed prior to use. CDCl3 was distilled from P2O5
and degassed. CD2Cl2 and C6D6 were purchased from Cam-
bridge Isotope Laboratories and were dried over molecular
© 2007 NRC Canada

1050
Can. J. Chem. Vol. 85, 2007
sieves (3 Å). PCl3, HNEt2, MeI, MeLi (1.6 mol/L in Et2O),
and n-BuLi (1.6 mol/L in hexanes) were purchased from
Aldrich and used as received. Alkyllithium reagents were ti-
trated prior to use. Me2SiHCl and Me3SiCl were distilled
over CaH2 and degassed prior to use. MesP=CPh2, 1, was
prepared following literature procedures (21, 22).
ClP(NEt2)2 was prepared from an adaptation of a literature
method (33). A solution of HNEt2 (190 mL, 1.84 mol) and
CH2Cl2 (300 mL) was added slowly to a cooled (–78 °C) so-
lution of PCl3 (40 mL, 0.46 mol) in CH2Cl2 (250 mL). The
reaction mixture was slowly warmed to room temperature
and stirred for 1 h, and the solvent was removed in vacuo.
The resulting solid was extracted with hexanes (3 × 150 mL)
and filtered. Hexanes was removed in vacuo. The resulting
oil was distilled under vacuum, yielding a colorless liquid
(89 g, 92%). 31P{1H} NMR (C6D6, 121.5 MHz): δ = 154.8.
1H NMR (C6D6, 300 MHz): δ = 2.9–3.1 (m, 8H, CH2); 0.94
Preparation of Mes(Me)P–CPh2H (4a)
To a stirred red solution of 3a in THF (150 mL,
0.043 mol/L, 6.4 mmol) was added degassed MeOH
(0.4 mL). From the resultant colorless solution, THF was re-
moved in vacuo, affording a white solid residue. The soluble
fraction was extracted into hexanes (3 × 50 mL), and the re-
sultant solution was evaporated to dryness, affording a yel-
low oil. The oil was dissolved in minimal hexanes at reflux
(~5 mL). The solution was slowly cooled to room tempera-
ture to afford colorless crystals suitable for X-ray diffrac-
tion.
Yield: 0.50
g
(24%). 31P{1H} NMR (CD2Cl2,
1
121.5 MHz): δ = –24.0 (s). H NMR (CD2Cl2, 300 MHz):
δ = 7.58 – 7.10 (m, 10H, Ph–H), 6.77 (s, 2H, m-Mes–H),
4.87 (d, 2JHP = 5 Hz, 1H, CPh2H), 2.52 (s, 6H, o-Mes–CH3),
2.21 (s, 3H, p-Mes–CH3), 1.31 (d, 2JHP = 6 Hz, 3H, P–CH3).
13C{1H} NMR (CD2Cl2, 75.5 MHz) (unassigned): δ = 146.0
(d, JCP = 15 Hz), 144.3, 144.1, 144.0, 143.8 (4 × s or 2 × d),
3
(t, 12H, JHH = 7 Hz, CH3).
31P, 1H, and 13C{1H} NMR spectra were recorded on
Bruker AV300 or AV400 spectrometers at room temperature.
Solid-state NMR experiments were performed on a Bruker
Avance DSX400 spectrometer operating at frequencies of
1
140.4 (s), 131.4–127.4 (m), 52.8 (d, JCP = 16 Hz), 24.6,
1
24.4 (2 × s or 1 × d), 10.8 (d, JCP = 18 Hz, P–CH3). MS
+
(EI, 70 eV) m/z (%): 332 (28) [M+], 167 (100) [CHPh2 ],
165 (44) [M+ – CHPh2], 119 (12) [Mes+].
1
400.13 MHz and 161.98 MHz for H and 31P respectively,
using a Bruker triple resonance 4mm MAS probe. Chemical
shifts for 31P NMR spectra are reported relative to H3PO4 as
an external standard (85% in H2O, δ = 0). Chemical shifts
for 13C{1H} NMR spectra are reported relative to CD2Cl2
Preparation of Mes(n-Bu)P–CPh2H (4b)
To a stirred solution of carbanion 3b in Et2O (2.0 mmol)
was added dropwise degassed H2O until the reaction mixture
turned pale yellow (several drops). The mixture was then
dried with MgSO4, filtered, and the soluble fraction was ex-
tracted with Et2O (2 × 10 mL). The solvent was removed in
vacuo at 60 °C to afford pure 4b as a pale yellow oil.
1
(δ = 54.0) or CDCl3 (δ = 77.2). Chemical shifts for H NMR
spectra are reported relative to residual CHDCl2 (δ = 5.32)
or CHCl3 (δ = 7.27) or C6HD5 (δ = 7.16). Mass spectra were
recorded on a Kratos MS 50 instrument. Elemental analyses
were performed by Mr. Minaz Lakha in the Departmental
Microanalysis Facility.
Yield: 0.65 g (85 %). 31P NMR (CD2Cl2, 121.5 MHz): δ =
1
–12.4 (s). H NMR (CD2Cl2, 400 MHz) (assignments made
3
with the aid of a COSY experiment): δ = 7.57 (d, JHH
=
8 Hz, 2H, Ph–H), 7.36 (m, 4H, Ph–H), 7.24 (m, 1H, Ph–H),
7.15 (m, 2H, Ph–H), 7.06 (m, 1H, Ph–H), 6.77 (br s, 2H, m-
Preparation of Mes(Me)P–CPh2Li (3a)
2
Mes–H), 4.91 (d, JPH = 5 Hz, 1H, CPh2H), 2.56 (br s, 6H,
Typical procedure
o-Mes–CH3), 2.20 (s, 3H, p-Mes–CH3), 2.02 (m, 1H, P–
CHH), 1.55 (m, 1H, P–CHH), 1.22 (m, 2H, CH2CH2CH3),
1.08 (m, 2H, PCH2CH2), 0.74 (t, 3JHH = 7 Hz, 3H, CH2CH3).
13C{1H} NMR (CD2Cl2, 100.6 MHz) (assignments made
with the aid of HMQC/HMBC experiments): δ = 143.6 (d,
To a cooled (–78 °C) solution of phosphaalkene 1 (2.06 g,
6.5 mmol) in THF or Et2O (~150 mL) was slowly added
MeLi in Et2O (5.2 mL, 1.5 mol/L, 7.8 mmol). Upon addi-
tion, there was an immediate color change from yellow to
dark red. The cooled solution was stirred for 1 h and then
warmed to room temperature where it was stirred for an ad-
ditional 1 h. The concentration for use in subsequent steps
was 0.043 mol/L (see preparation of 4a). 31P{1H} NMR
spectroscopy of an aliquot removed from the reaction mix-
ture showed a single signal (δ = −42.0 in THF, −44.3 in
Et2O).
2
2JCP = 12 Hz, i-Ph–C), 143.4 (d, JCP = 13 Hz, i-Ph–C),
1
139.5 (s, p-Mes–C), 130.2 (br, m-Mes–C), 129.7 (d, JCP
=
3
26 Hz, i-Mes–C), 129.5 (d, JCP = 9 Hz, o-Ph–C), 129.1 (s,
3
o-Mes–C), 128.9 (d, JCP = 9 Hz, o-Ph–C), 128.6 (s, p-Ph–
4
4
C), 127.1 (d, JCP = 2 Hz, m-Ph–C), 126.5 (d, JCP = 2 Hz,
1
2
m-Ph–C), 51.6 (d, JCP = 16 Hz, CHPh2), 30.2 (d, JCP
=
1
20 Hz, P–CH2CH2), 25.5 (d, JCP = 16 Hz, P–CH2), 24.7 (d,
3JCP = 13 Hz, CH2CH2CH3), 23.8 (v br, o-Mes–CH3), 21.2
(s, p-Mes–CH3), 14.1 (s, CH2CH3). MS (EI, 70 eV) m/z (%):
374 (29) [M+], 167 (100) [CPh2H+], 151 (24) [PMes+].
Found (calcd.) (%): C, 83.81 (83.39); H, 8.55 (8.34).
Preparation of Mes(n-Bu)P–CPh2Li (3b)
To a stirred yellow solution of 1 (0.64 g, 2.0 mmol) in
Et2O (~30 mL) at –78 °C, a solution of n-BuLi in hexanes
(3.0 mL, 1.4 mol/L, 4.2 mmol) was added rapidly. The mix-
ture turned bright orange upon addition and was stirred at
–78 °C for 30 min. Subsequently, the solution was warmed
to room temperature where it was stirred for an additional
1 h. Over this time, the solution turned from bright orange to
red. The reaction was monitored by 31P{1H} NMR spectros-
copy, affording a single signal for 3b (δ = –31.1). This solu-
tion was used in the preparation of 4b.
Synthesis of Mes(Me)P–CPh2Me (6a)
MeI (1.6 mL, 26 mmol) was added dropwise to a solution
of 3a in Et2O (160 mL, 0.16 mol/L, 26 mmol). The solution
was stirred for 30 min over which time its color changed
from red to orange. The solvent was removed in vacuo, the
soluble fraction was extracted with hexanes, and evaporated
© 2007 NRC Canada

Gillon et al.
1051
to dryness. The product was purified by sublimation
(140 °C, 0.1 mmHg).
H), 3.1 (br s, 3H, o-Mes–CH3), 2.18 (s, 3H, p-Mes–CH3),
1.45 (d, JPH = 8 Hz, 3H, P–CH3), 1.1 (br s, 3H, o-Mes–
2
3
3
Yield = 5.7 g (64 %). 31P NMR (CDCl3, 121.5 MHz): δ =
CH3), 0.10 (d, JHH = 3 Hz, 3H, Si–CH3), 0.05 (d, JHH
=
3 Hz, 3H, Si–CH3). 13C{1H} NMR (CD2Cl2, 75.5 MHz) (as-
signments made with the aid of HMQC/HMBC experi-
ments): δ = 147.6 (s, Mes–C), 147.3 (s, Mes–C), 142.5 (s,
Mes–C), 142.1 (d, 1JPC = 7 Hz, i-Mes–C), 139.5 (s, Mes–C),
131–128 (m, Ph–C), 125.7 (s, Ph–C), 45.7 (d, JPC = 45 Hz,
PCPh2), 21.2 (s, p-Mes–CH3), 7.81 (d, JPC = 23 Hz, PCH3),
1
–13.5 (s). H NMR (CDCl3, 300 MHz): δ = 7.47 (m, 2H,
Ph–H), 7.21 (m, 6H, Ph–H), 7.01 (m, 2H, Ph–H), 6.74 (s,
2H, Mes–H), 2.23 (s, 3H, p-Mes–CH3), 1.87 (br, 6H, o-
2
Mes–CH3), 1.70 (d, JPH = 13 Hz, 3H, P–CH3), 1.39 (d,
1
3JPH = 7 Hz, 3H, CPh2CH3). 13C{1H} NMR (CDCl3,
75.5 MHz,) (unassigned): δ = 148.3 (d, JCP = 14 Hz), 146.3
(d, JCP = 16 Hz), 144.7 (s), 138.8 (s), 129.9 (s), 128.7–127.4
1
3
3
–3.96 (d, JPC = 5 Hz, SiCH3), –5.66 (d, JPC = 6 Hz,
SiCH3). MS (EI, 70 eV) m/z (%): 390 (38) [M+], 375 (17)
(m), 125.8 (s), 125.4 (s), 49.1 (d, JCP = 24 Hz), 28.8 (d,
[M+ – CH3], 332 (45) [M+ – SiMe2], 223 (69) [M+
–
1
JCP = 15 Hz), 23.5 (d, JCP = 18 Hz), 20.8 (s), 9.0 (d, JCP
=
+
21 Hz, P–CH3). MS (EI, 70 eV) m/z (%): 346 (7) [M+], 181
(100) [M+ – P(Mes)(CH3)], 165 (16) [M+ – CPh2(CH3)], 119
(5) [Mes+].
PMesMe], 167 (100) [CPh2 ]. Found (calcd.) (%): C, 77.20
(76.88); H, 7.64 (8.00).
Preparation of Mes(Me)P–CPh2–SiMe3 (9a)
Preparation of Mes(Me)P–CPh2–P(NEt2)2 (7a)
To the red solution of 3a in Et2O (22 mL, 0.14 mol/L,
3.2 mmol), neat Me3SiCl (0.4 mL, 3.2 mmol) was added. An
immediate color change to yellow was observed accompa-
nied by the formation of a white precipitate. The solution
was filtered, the solvent was removed in vacuo, and the solu-
ble fraction was extracted into Et2O (3 × 15 mL). The Et2O
was removed in vacuo. The crude product was dissolved in a
minimal amount of hexanes, and slow evaporation afforded
colorless crystals suitable for X-ray crystallography.
To a cooled (0 °C) solution of 3a in THF (20 mL,
0.32 mol/L, 6.4 mmol) was slowly added a solution of
ClP(NEt2)2 (1.50 g, 7.1 mmol) in THF (20 mL). An aliquot
was removed from the yellow reaction mixture for 31P NMR
spectroscopic analysis. After evaporation of the volatiles in
vacuo, the soluble fraction was extracted into toluene
(30 mL). Removal of the toluene in vacuo afforded the crude
product, which was washed with hexanes at –78 °C two
times. Crystals suitable for X-ray diffraction were obtained
from slow evaporation of a saturated toluene solution.
Yield: 1.73 g (54%). 31P NMR (CDCl3, 121.5 MHz): δ =
Yield = 0.18 g (14%). 31P NMR (CDCl3, 121.5 MHz): δ =
1
–25.4 (s). H NMR (CDCl3, 300 MHz): δ = 7.6 (br s, 2H,
Ph), 7.3–7.1 (m, 8H, Ph), 6.8 (br s, 2H, m-Mes–H), 2.8 (br s,
2
2
105.3 (d, JPP = 205 Hz, PN2), –9.4 (d, JPP = 205 Hz,
2
o-Mes–CH3), 2.22 (s, 3H, p-Mes–CH3), 1.33 (d, JPH
=
PMes). 31P MAS NMR (8.5 kHz, recycle delay of 20 s,
8 Hz, 3H, P–CH3), 0.9 (br s, 3H, o-Mes–CH3), –0.02 (s, 9H,
Si(CH3)3). MS (EI, 70 eV) m/z (%): 404 (100) [M+], 389
(26) [M+ – CH3], 331 (44) [M+ – SiMe3], 167 (39) [M+ –
CPh2SiMe3], 73 (34) [M+ – MesMePCPh2].
2
162.0 MHz): δ = 108.3 (d, JPP = 255 Hz, PN2), –7.9 (d,
2JPP = 255 Hz, PMes). 1H NMR (CDCl3, 400 MHz) δ = 7.79
(br, 2H, Ph–H), 7.43 (br, 2H, Ph–H), 7.28–7.14 (m, 6H, Ph–
H), 6.90 (br, 1H, m-Mes–H), 6.55 (br, 1H, m-Mes–H), 3.01–
2.52 (m, 11H, NCH2 and o-Mes–CH3), 2.25 (s, 3H, p-Mes–
2
CH3), 1.38 (d, JPH = 9 Hz, 3H, P–CH3), 0.97 (m, 9H,
X-ray crystallography
3
NCH2CH3 and o-Mes–CH3), 0.84 (t, 6H, JHH = 7 Hz,
Crystal data and refinement parameters are listed in Ta-
ble 1. Additional data are available in the Supplementary
data.2 All single crystals were immersed in oil and mounted
on a glass fiber. Data for 4a were collected on a Bruker X8
APEX diffractometer with graphite-monochromated Mo Kα
radiation. Data for 7a, 8a, and 9a were collected on a Bruker
X8 APEX II diffractometer. Data were collected and inte-
grated using the Bruker SAINT software package (34). All
structures were solved by direct methods and subsequent
Fourier difference techniques and were refined
anisotropically for all non-hydrogen atoms. Hydrogen atoms
were included in idealized positions and refined isotropically
except in 4a where they were not refined. All data sets were
corrected for Lorentz and polarization effects. All calcula-
tions were performed using the SHELXTL crystallographic
software package from Bruker-AXS (35).
Compounds 4a, 8a, and 9a did not show any crystallo-
graphic complexity. Compound 7a was a split crystal, and
cell_now (within SAINT) was used to determine that the
second domain was rotated from the first domain by 4.4°.
Only the first domain was integrated because there was little
or no overlap between the two lattices. One of the ethyl
groups was disordered at C(28) and C(29). The disorder at
carbon was modeled by including two additional carbon at-
NCH2CH3). 13C{1H} NMR (CDCl3, 100.6 MHz) (assign-
ments made with the aid of HMQC/HMBC experiments):
δ = 147.7 (s, o-Mes–C), 141.3 (br, Ar–C), 141.0 (t, JPC
=
5 Hz, Ar–C), 138.6 (s, p-Mes–C), 131.9–127.6 (m, Ar–C),
126.9 (s, Ar–C), 126.4 (s, Ar–C), 124.8 (d, JPC = 4 Hz, Ar–
1
C), 63.9 (dd, JPC = 46 and 34 Hz, P–CPh2–P), 44.5 (d,
2
2JPC = 21 Hz, N–CH2), 44.0 (d, JPC = 20 Hz, N–CH2), 26.2
(br s, o-Mes–CH3), 21.6 (br s, o-Mes–CH3), 21.0 (s, p-Mes–
CH3), 14.5 (d, 3JPC = 3 Hz, NCH2CH3), 14.0 (d, 3JPC = 5 Hz,
1
NCH2CH3), 9.7 (t, JPC = 22 Hz, P–CH3).
Preparation of Mes(Me)P–CPh2–SiMe2H (8a)
To the red solution of 3a (40 mL, 0.079 mol/L, 3.2 mmol)
in THF (40 mL), neat Me2HSiCl (0.5 mL, 4.6 mmol) was
added. An immediate color change to yellow was observed.
The solvent was removed in vacuo, and the residue was dis-
solved in hexanes (3 × 5 mL). Following solvent evapora-
tion, the crude product was recrystallized from a minimal
amount of hot hexanes in an inert atmosphere to afford large
colorless crystals.
Yield: 0.62 g (50%). 31P NMR (C6D6, 121.5 MHz): δ =
1
–23.9 (s). H NMR (C6D6, 300 MHz): δ = 7.70 (br s, 2H,
Ph), 7.3–6.5 (m, 10H, Ph and m-Mes–H), 4.58 (br s, 1H, Si–
© 2007 NRC Canada

1052
Can. J. Chem. Vol. 85, 2007
18. R. Appel, C. Casser, and F. Knoch. Chem. Ber. 119, 2609
(1986).
oms [C(28b) and C(29b)] and refining their respective popu-
lations [occupancy: 0.78(2) and 0.22(2)].
19. For examples, see: (a) S. Ito, H. Miyake, M. Yoshifuji, T.
Höltzl, and T. Veszprémi. Chem. Eur. J. 11, 5960 (2005);
(b) S. Ito, H. Miyake, H. Sugiyama, and M. Yoshifuji. Tetrahe-
dron Lett. 45, 7019 (2004); (c) A. Moores, L. Ricard, and P.
Le Floch. Angew. Chem., Int. Ed. 42, 4940 (2003); (d) G.
Märkl and A. Merz. Tetrahedron Lett. 32, 3611 (1968); (e) G.
Märkl, F. Lieb, and A. Merz. Angew. Chem., Int. Ed. 6, 87
(1967).
20. For examples, see: (a) S. Ito, M. Freytag, and M. Yoshifuji.
Dalton Trans. 710 (2006); (b) S. Ito, K. Toyota, and M.
Yoshifuji. Chem. Commun. 1637 (1997); (c) M. Yoshifuji, H.
Kawanami, Y. Kawai, K. Toyota, M. Yasunami, T. Niitsu, and
N. Inamoto. Chem. Lett. 1053 (1992); (d) S. J. Goede, and F.
Bickelhaupt. Chem. Ber. 124, 2677 (1991).
Acknowledgement
This work was supported by the Natural Sciences and En-
gineering Research Council (NSERC) of Canada. The Can-
ada Foundation for Innovation (CFI) and The British
Columbia Knowledge Development Fund (BCKDF) are
gratefully acknowledged for infrastructure support. The au-
thors wish to thank to Dr. Brian O. Patrick for assistance
with X-ray crystallography and Dr. Richard Darton and Pro-
fessor Colin Fyfe for acquiring the solid-state NMR spec-
trum of 7a.
21. G. Becker, W. Uhl, and H.-J. Wessely. Z. Anorg. Allg. Chem.
479, 41, (1981).
22. M. Yam, J.H. Chong, C.W. Tsang, B.O. Patrick, A.E. Lam,
and D.P. Gates. Inorg. Chem. 45, 5225 (2006).
23. For details of the Tolman method, see: C.A. Tolman. Chem.
Rev. 77, 313 (1977).
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© 2007 NRC Canada