Dimethylaluminium iminophosphoranylenamides and iminophosphoranylanilides: Synthesis, characterisation, and their controlled ring-opening polymerisation of ε-caprolactone

Article abstract of DOI:10.1039/c0dt01713b

A series of aluminium iminophosphoranylenamide complexes, [Me ₂Al{N(Ar)C(Ph)CHP(Ph₂)N-Ar¹}] (Ar = Ph, Ar ¹ = p-MeC₆H₄ (9); Ar = Ph, Ar¹ = o-ClC₆H₄ (10); Ar

Full text of DOI:10.1039/c0dt01713b

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PAPER
Dimethylaluminium iminophosphoranylenamides and
iminophosphoranylanilides: Synthesis, characterisation, and their controlled
ring-opening polymerisation of e-caprolactone†
Wen-An Ma, Li Wang and Zhong-Xia Wang*
Received 7th December 2010, Accepted 4th February 2011
DOI: 10.1039/c0dt01713b
A series of aluminium iminophosphoranylenamide complexes,
[Me2Al{N(Ar)C(Ph) CHP(Ph2) N-Ar1}] (Ar = Ph, Ar1 = p-MeC6H4 (9); Ar = Ph, Ar1 = o-ClC6H4
(10); Ar = Ph, Ar1 = o-FC6H4 (11); Ar = p-MeC6H4, Ar1 = o-FC6H4 (12)), were synthesised by the
reactions of ArN C(Ph)CH2P(Ph2) NAr1 (5–8) with AlMe3 in toluene. Similar reactions between
o-{ArN P(Ph2)}C6H4NHC(Ph) CHP(Ph2) NAr (Ar = p-MeC6H4, 13), and AlMe3 in toluene
generates aluminium iminophosphoranylanilide, 14. All new compounds were characterised by NMR
spectroscopy and elemental analysis. The molecular structures of complexes 9 and 14 were further
characterised by single-crystal X-ray structure determination. In the presence of benzyl alcohol
(BnOH) each of the complexes is catalytically active for the ring-opening polymerisation (ROP) of
e-caprolactone (e-CL), and complex 14 has the highest activity among them.
Introduction
Synthetic polyesters such as poly(e-caprolactone) (PCL),
poly(lactide) (PLA), poly(glycolide) (PGA) and their copolymers
have found wide applications in the biomedical and pharma-
ceutical fields due to their biodegradable, biocompatible, and
permeability properties.1–3 Among the polymers, PCL shows
specific advantages such as its miscibility with different com-
mercial polymers,4 its adhesive properties at low temperature,4c
the complexes showed relatively low activity and poor control
Chart 1
esters.3,8g–p Recently, aluminium b-diketiminate complexes were
reported to be active catalysts for the ROP of e-CL. However,
and its ability to disperse pigments.1h,5 It is also ideally suited
for long-term drug delivery due to its slow degradation in
comparison to other polymers.2a An efficient way to synthesise
the polyesters is the ROP of cyclic esters catalysed/initiated
by metal complexes. This polymerisation method allows good
control on the molecular weight, molecular weight distribution,
polymer architecture and end functionality.6 So far, a number
of metal catalysts or initiators have been reported, including
magnesium, aluminium, zinc, tin, and rare earth metal complexes
supported by various ligands.3,7 On the other hand, ancillary
ligands play important roles in stabilising central metal ions
and tuning the catalytic properties of the complexes. Nitrogen-
based polydentate ligands such as b-diketiminate ligands (A,
Chart 1) have attracted considerable attention.3,8 For example,
magnesium, zinc, and tin(II) complexes bearing b-diketiminate
ligands exhibit excellent catalytic properties in the ROP of cyclic
in the polymerisation.9 We intend to devise ligands that offer
a steric environment similar to diimines, while the electronic
characteristics are different, improving the catalytic properties
of the aluminium complexes. Bis(iminophosphoranyl)methanides
and iminophosphoranylenamides (B and C, Chart 1) are good
candidates for such a study. Iminophosphoranes essentially be-
have as strong p and s donor ligands and do not exhibit p-
accepting capacity in contrast to imines.10 These properties of
iminophosphoranes in the ancillary ligands may provide a proper
electronic environment at the metal centre for the catalysis. As
a first step, we synthesised aluminium complexes supported by
iminophosphoranylenamides and studied their catalytic behaviour
in the ROP of e-CL. A structurally related aluminium iminophos-
phoranylanilide complex was also studied. Here we report the
results.
Results and discussion
CAS Key Laboratory of Soft Matter Chemistry, Joint laboratory of Green
Synthetic Chemistry and Department of Chemistry, University of Science
and Technology of China, Hefei, Anhui, 230026, People’s Republic of China.
E-mail: zxwang@ustc.edu.cn; Fax: 86 551 3601592; Tel: 86 551 3603043
† CCDC reference numbers 803993–803994. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/c0dt01713b
Synthesis and characterisation of compounds 3–12 and 14
Synthesis of compounds 3–12 is illustrated in Scheme 1. a-
(Diphenylphosphino)imine 3 and 4 were synthesised by lithiation
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1H NMR spectrum of each of compounds 5–8 displays a singlet
at about 11 ppm, which is assigned to an NH group. This means
that each of 5–8 exists in an enamine form and the high frequency
chemical shifts indicate the presence of hydrogen bonds in the
molecules. Meanwhile, we also observed trace amounts of imine
isomer in each case from their respective 1H and 31P NMR spectra.
These phenomena are consistent with those observed by us and
other groups previously.11
Complexes 9–12 gave satisfactory elemental analytical results.
1H NMR spectra of each of complexes 9, 11, and 12 exhibits
only one Al–Me signal, showing the two methyl groups to be
chemically equivalent. 1H NMR spectrum of complex 10 exhibits
two Al–Me signals (d -0.09 and 0.01 ppm, respectively). This
was further confirmed by its 13C NMR spectrum in which two
Al–Me signals appear at d -8.01 and -7.73 ppm, respectively.
31P NMR spectra of each of complexes 9–12 exhibits one signal
as a multiplet. The structure of complex 9 was also determined
by single-crystal X-ray diffraction analysis. The ORTEP drawing
is shown in Fig. 1, along with selected bond lengths and
angles. The central aluminium atom has a distorted tetrahedral
geometry with the N1–Al–N2 angle [99.34(11)◦] narrower than
the C35–Al–C35 angle [118.67(16)◦]. The six-membered chelate
ring adopts a twist conformation. Each of the N1 and N2
atoms is approximately in a planar environment. The C1–C2–
C3–N1 atoms also lie on a plane. The Al–N bond distances of
Scheme 1 Synthesis of aluminium complexes 9–12.
of 1 or 2 with lithium diisopropylamide and the lithiated species
were then treated with chlorodiphenylphosphine in THF. Treat-
ment of 3 and 4 with aryl azides in dichloromethane at room
temperature for 4 h generated iminophosphoranylenamines 5–
8. Compound 5 was purified by washing with n-hexane after
removing the solvent from the reaction mixture, while compounds
6–8 were re-crystallised from diethyl ether. Reaction of 5–8 with
AlMe3 in toluene at room temperature for 16 h afforded complexes
9–12 as yellow crystalline solids. Complexes 9–12 were purified by
re-crystallising from diethyl ether (9 and 12) or a mixed solvent of
diethyl ether and n-hexane (10 and 11).
˚
˚
1.901(3) A and 1.925(2) A are shorter than the corresponding
distances in [Me2Al{N(2,6-Pri2C6H3)C(Me) CHP(Ph2) N(2,6-
i
11c
˚
Pr 2C6H3)}] (∫ LAlMe2) [1.932(2) and 1.943(2) A, respectively].
˚
The C2–N1 distance of 1.382(4) A is longer than the corresponding
˚
distance in [LAlMe2] [1.353(3) A], while the C1–C2 distance of
1
Each of compounds 3–12 were characterised by H, 13C, and
˚
1.362(4) A in complex 9 is shorter than the corresponding distance
31P NMR spectroscopy and elemental analysis. NMR spectra
of 3 indicate the presence of four isomers in CDCl3 at room
temperature. The 1H NMR spectrum exhibits four sets of signals at
d 3.50–3.66, 3.66–6.74, 5.56–5.66, and 5.72–5.76 ppm, respectively,
in the ratio of 17 : 2 : 3 : 1. This is attributed to the presence of the
imine (d 3.50–3.66 and 3.66–6.74 ppm) and enamine (d 5.56–5.66
and 5.72–5.76 ppm) isomers. Both imine and enamine have E
and Z isomers. Hence compound 3 has four isomers (D–G, Chart
2) and the ratio of the enamine to the imine is about 1 : 5. Four
signals of the 31P NMR of compound 3 at d -17.03, -22.85, -26.56,
and -36.32 ppm are also consistent with the four isomers. NMR
spectra of compound 4 also show the presence of four isomers and
the ratio of the enamine to the imine is about 1 : 4 based on the 1H
NMR spectrum.
11c
˚
˚
in [LAlMe2] [1.383(4) A]. The P–N distance of 1.622(2) A is
longer than a formal double bond and is normal for a coordinated
˚
iminophosphorane, while the P–C1 distance of 1.741(3) A is in
between that of a formal single and double bond.12,13
Fig. 1 Molecular structure of complex 9 shown with 30% probability
◦
˚
thermal ellipsoids. Selected bond lengths (A) and angles ( ): Al(1)–N(1)
1.901(3), Al(1)–N(2) 1.925(2), Al(1)–C(34) 1.947(4), Al(1)–C(35)
1.961(3), P(1)–N(2) 1.622(2), P(1)–C(1) 1.741(3), N(1)–C(2) 1.382(4),
C(1)–C(2) 1.362(4), N(1)–Al(1)–N(2) 99.34(11), N(1)–Al(1)–C(34)
108.33(14), C(34)–Al(1)–C(35) 118.67(16), P(1)–N(2)–Al(1) 116.51(13),
C(2)–N(1)–Al(1) 119.1(2), N(2)–P(1)–C(1) 110.35(14), C(2)–C(1)–P(1)
122.4(2), C(2)–N(1)–Al(1) 119.1(2), C(1)–C(2)–N(1) 119.9(3).
Chart 2 The isomers of 3 (Ar = Ph) and 4 (Ar = p-MeC6H4).
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Complex 14 was synthesised from 13 and AlMe3 as shown in
Scheme 2. Compound 13 was prepared according to the procedure
1
we reported previously14 and characterised by H, 13C and 31P
NMR spectroscopy and elemental analysis. Both 1H and 31P NMR
spectra show that 13 exists in three isomers with a ratio of 3 : 2 : 2.
Among the isomers the imine isomer accounts for about 30% and
the two enamine isomers account for about 70%. Treatment of 13
with AlMe3 in toluene at room temperature for 16 h and then at
110 ◦C for 8 h afforded, after re-crystallisation using diethyl ether,
a yellow crystalline complex, 14, in 63% yield. Complex 14 gave
1
satisfactory elemental analytical results. Its H NMR spectrum
exhibits a single Al–Me signal, indicating the two methyl groups
to be at the same chemical environment. The 31P NMR spectrum
displays two signals, being consistent with its molecular structure.
Fig. 2 Molecular structure of complex 14 shown with 30% probability
◦
˚
thermal ellipsoids. Selected bond lengths (A) and angles ( ): Al(1)–N(1)
1.946(2), Al(1)–N(2) 1.906(2), Al(1)–C(53) 1.962(3), Al(1)–C(54) 1.978(3),
P(1)–N(1) 1.623(2), P(1)–C(20) 1.792(3), N(2)–C(25) 1.394(3), P(2)–N(3)
1.569(2), P(2)–C(27) 1.795(3), C(26)–C(27) 1.354(4), N(1)–Al(1)–N(2)
98.39(10), N(2)–Al(1)–C(53) 110.66(13), N(1)–Al(1)–C(53) 109.91(13),
C(53)–Al(1)–C(54) 119.76(15), P(1)–N(1)–Al(1) 118.09(12), C(25)–
N(2)–Al(1) 121.37(17), N(1)–P(1)–C(20) 109.81(12).
Scheme 2 Synthesis of complex 14.
The structure of complex 14 was also determined by single-
crystal X-ray diffraction techniques and the ORTEP drawing is
presented in Fig. 2, along with selected bond lengths and angles. In
the solid state, the nitrogen atom of one of the iminophosphoranyls
(that attached on the C C double bond) does not coordinate to
the central metal. The aluminium atom is four coordinate and the
geometry at the aluminium atom is a distorted tetrahedron. The
chelate metal ring adopts a twist conformation, which is different
from that of [Me2Al{N(Dipp)C6H4(2-{P(Ph2) NMes}}]. The
structure of the latter reveals that the Al atom protrudes from
an idealized plane in the chelate metal ring.15 The N–Al–N angle
of 98.39(10)◦ is close to that reported [98.39(10)◦], but the C–Al–C
angle of 119.76(15)◦ is markedly wider than the corresponding◦an-
gle in [Me2Al{N(Dipp)C6H4(2-{P(Ph2) N-Mes}}] [113.7(2) ].15
{P(Ph2) NMes}}] [1.926(3) A and 1.891(3) A]15 and the distances
˚
˚
˚
˚
in complex 9 [1.925(2) A and 1.901(3) A]. The P1–N1 distance of
1.623(2) A is almost the same as that in complex 9 [1.622(2) A]. The
P2–N3 distance of 1.569(2) A is shorter than the P1–N1 distance
and is indicative of a P N double bond.13
˚
˚
˚
Ring-opening polymerisation of e-caprolactone
The ROPs of e-CL in toluene using 9–12 and 14 as the catalysts,
in the presence of BnOH at various temperatures, have been
systematically conducted as shown in Table 1. Thus, an aluminium
complex was treated with 1 equiv of BnOH in toluene at room
temperature for 1 h and then 200 equiv of e-CL was added into
the mixture at a preset temperature. The data in Table 1 show
that in the presence of benzyl alcohol all the complexes are active
˚
˚
The Al–N distances of 1.946(2) A and 1.906(2) A are longer
than the corresponding distances in [Me2Al{N(Dipp)C6H4(2-
Table 1 Ring-opening polymerisation of e-CL catalysed by organoaluminium complexes (9–12 and 14) in the presence of benzyl alcohola
Entry
Cat.
Temp. (◦C)
Time (min)
Conversion (%)b
Mn (GPC)c
Mn (Calcd)d
Yield (%)
PDIe
1
2
3
4
5
6
7
8
9
110
90
70
110
90
70
50
90
70
110
90
11
60
210
15
40
90
210
45
76
20
99
100
99
98
98
99
77
96
97
19 200
18 600
17 700
18 000
18 600
14 200
13 100
18 100
18 300
18 700
22 500
19 900
31 400
26 500
19 814
19 070
18 082
21 405
19 596
19 104
14 646
17 832
17 931
18 115
19 900
16 835
34 996
25 220
95
94
94
95
93
94
72
92
93
99
96
95
90
74
1.24
1.27
1.20
1.21
1.19
1.18
1.11
1.14
1.19
1.23
1.25
1.22
1.21
1.21
9
9
10
10
10
10
11
11
12
12
12
14
14
9
10
11
12
13
14
99
60
210
25
100
100
94
70
70
50
42
78
a All polymerisations were carried out in toluene; [CL]0 : [Al]0 : [BnOH]0 = 200 : 1 : 1, [CL]0 = 2 M. b Measured by 1H NMR spectra. c Calculated from the
molecular weight of e-CL, times the conversion of monomer and the ratio of [CL]0/[BnOH]0, plus the molecular weight of BnOH. d Obtained from GPC
analysis and calibrated against polystyrene standard, multiplied by 0.56.16 e Obtained from GPC analysis, PDI = polydispersity index.
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for the ROP of e-CL. GPC (Gel Permeation Chromatography)
analysis shows that the molecular weights of the polymers match
the calculated values very well. The polydispersities are also
very narrow, ranging from 1.11 to 1.27. These results imply
that the catalytically active species are quite stable during the
reaction process even at 110 ◦C and the polymerisations are well
controlled (see below on kinetic studies). Each of complexes 9–12
and 14 exhibits higher catalytic activity than the aluminium b-
diketiminate complexes.9 This is ascribed to the stronger electron-
donating effect of iminophosphorane than imine. In order to
establish reaction order in monomer and metal concentration, and
compare the catalytic activity of the complexes, kinetic studies of
e-CL polymerisation catalysed by the complexes in the presence
of BnOH were performed. Plots of ln([e-CL]0/[e-CL]) versus time
using 9–12 and 14 are shown in Fig. 3. Each of the plots exhibit
a good linear relationship, indicating the polymerisation reaction
proceeds with first-order dependence on monomer concentration.
The first-order kinetics implies that the concentration of active
species remains unchanged. The plots also reveal that each of
the polymerisations catalysed by 9–12 has an induction period
under the polymerisation conditions. At first we guessed that
formation of catalytically active species requires a period of time
at the reaction temperature. In order to verify our guess we mixed
complex 10 and an equiv. of BnOH in toluene and stirred the
of the Ar1 group also reduces the catalytic activity. These facts
seem contradictory with the inference mentioned above. However,
although a stronger donor capability of iminophosphorane than
imine may lead to a higher catalytic activity of complexes 9–12
than aluminium b-diketiminate complexes, a proper electronic
environment at the metal centre is critical for the catalysis. An
electron-withdrawing group on the phenyl ring of the ligands
in complexes 9–12 may tune the whole electron effect of the
ligand to a more proper condition for the catalysis. Complex 14
displays the highest catalytic activity among the complexes. This
result is also a sharp contrast to that of anilidoiminophosphorane
aluminium complexes (H in Chart 3). The latter showed poor
catalytic activity and gave polymers with much lower molecular
weights than calculated ones.8e The reason for the higher activity of
14 may be that an additional nitrogen atom of iminophosphoranyl
coordinates to the aluminium atom of the active catalyst during
the polymerisation process, which stabilises the central metal ion
and changes the electronic environment of the central metal.
◦
solution at 60 C for 60 min. The polymerisation of e-CL using
the mixture mentioned above as catalyst displayed an induction
period of about 50 min, shorter than that previous (about 80 min).
Hence it seems that the induction period is partially caused by
the reaction of the complex with BnOH. It was also noted that
the induction period changes with polymerisation temperatures.
For example, the induction period of the polymerisation catalysed
by 12 at 70 ◦C is about 20 min, while at 60 ◦C it is about
110 min. From Fig. 3 we can obtain a catalytic activity order
of 14 > 11 ≥ 10 > 12 > 9 at 60 ◦C. The higher activity of
complex 11 than complex 12 means that an electron-donating
group on the phenyl ring of the Ar group decreases the catalytic
activity. Higher activity of both complexes 10 and 11 compared
to 9 implies that an electron-donating group on the phenyl ring
Chart 3
Plots of the number-average molecular weights (Mn) of the
PCL catalysed by 10, 12 and 14 in the presence of BnOH,
and the polydispersities as functions of monomer conversions,
are shown in Fig. 4–6, respectively. In each case, the number-
average molecular weight follows a linear relationship in monomer
conversion and polydispersity values remain low, further proving
the controlled character of the polymerisations.
Fig. 4 Plots of PCL Mn (ꢀ obtained from GPC analysis) and polydis-
persity (᭡, Mw/Mn) as a function of e-CL conversion using complex 10
at 60 ◦C. [M]0 : [Al]0 : [BnOH]0 = 200 : 1 : 1, [M]0 = 2 M.
To understand the polymerisation process, we attempted to
Fig. 3 Plots of ln([M]0/[M]) versus time for the polymerisation of e-CL
catalysed by 9 ( , 60 ◦C), 10 ( , 60 ◦C), 11 (ꢀ, 60 ◦C), 12 (᭡, 60 ◦C;
isolate the reaction product of 14 with 1 equiv of BnOH. However,
᭹
᭺
1
ꢀ,70 ◦C) and 14 (ꢁ, 40 ◦C; ᭢, 60 ◦C). Conditions: Solvent: toluene;
a mixture identified by H NMR spectroscopy was always ob-
[M]0/[Al]/[BnOH]0 = 200 : 1 : 1, [M]0 = 2 M.
tained. We guess that the obtained alkoxyaluminium compounds
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Fig. 5 Plots of PCL Mn (ꢀ obtained from GPC analysis) and polydis-
persity (᭡, Mw/Mn) as a function of e-CL conversion using complex 12
at 70 ◦C. [M]0 : [Al] : [BnOH] = 200 : 1 : 1, [M]0 = 2 M.
Fig. 7 1H NMR spectrum of PCL (entry 3 in Table 1) in CDCl3.
on the phenyl rings attached to coordinated nitrogen atoms
affect the catalytic activity remarkably through electronic effects.
Kinetic studies reveal that each of the polymerisation reactions
catalysed by 10, 12, and 14 follows the first-order kinetics in
the concentration of monomer and the number-average molecular
weight follows a linear relationship in monomer conversion. These
results show that the polymerisations proceed in a controlled
manner.
Experimental
General
Fig. 6 Plots of PCL Mn (ꢀ obtained from GPC analysis) and polydis-
persity (᭡, Mw/Mn) as a function of e-CL conversion using complex 14
at 40 ◦C. [M]0 : [Al] : [BnOH] = 200 : 1 : 1, [M]0 = 2 M.
All air- or moisture-sensitive manipulations were performed under
nitrogen atmosphere using standard Schlenk and vacuum line
techniques. Solvents were distilled under nitrogen over sodium
(toluene), sodium/benzophenone (n-hexane, THF and Et2O)
or CaH2(CH2Cl2) and degassed prior to use. Compounds 1,
may have different structures in solution and they exist in an
equilibrium. One of the equilibrium components is an active
catalyst for the ROP and its concentration remains constant.
Hence, although the reaction between the complexes and BnOH
forms a mixture, the catalysed polymerisation still proceeds in an
almost living manner. The end group analysis of the PCL (entry
3 in Table 1), using 1H NMR spectrum as shown in Fig. 7, proves
that the PCL is capped with a benzyloxy group (Hg) on one end
and a hydroxymethyl group (Hf) on the other end. Further more,
the integration ratio between He and Hg is about 174, which is
to say the molecular weight of PCL is about 19 814 g mol-1 and
this value is close to the calculated value. This implies that the
polymerisation may be initiated through insertion of the benzyl
alkoxyl group to e-CL followed by ring opening via acyl-oxygen
cleavage.
217 and 2-(Ph2P)C6H4N C(Ph)CH2PPh2 were prepared using
14
the procedure described in literature. Chlorodiphenylphosphine
was purchased from Acros Organics and distilled prior to use.
Diisopropylamine was dried with NaOH and distilled prior to
use. n-BuLi was purchased from Acros Organics and used as
received. AlMe3 was purchased from Alfa-Aesar and used as
received. CDCl3 and C6D6, purchased from Cambridge Isotope
˚
Laboratories, were de-gassed and stored over 4 A molecular sieves
(CDCl3) or Na/K alloy (C6D6). e-Caprolactone, purchased from
Acros Organics, was stirred over CaH2 for 24 h and distilled
under vacuum. NMR spectra were recorded on a Bruker av300
spectrometer at ambient temperature. The chemical shifts of
1H and 13C NMR spectra were referenced to internal solvent
resonances or TMS; the 31P NMR spectra were referenced to
external 85% H3PO4. Elemental analysis was performed by the
Analytical Center of University of Science and Technology of
China. Gel permeation chromatography (GPC) measurements
were performed on a Waters 150C instrument equipped with
Conclusions
We have synthesised and characterised a series of dimethyla-
luminium complexes supported by iminophosphoranylenamide
ligands (9–12) or iminohosphoranylanilide ligand (14). In the
presence of BnOH each of the complexes is an efficient catalyst for
the ROP of e-CL. Complex 14 shows the highest catalytic activity
among the complexes, and in complexes 9–12 the substituents
˚
UltraStyragel columns (103, 104, and 105 A) and a 410 refractive
index detector, using monodispersed polystyrene as the calibration
standard. THF was used as the eluent at a flow rate of 1 cm3 min-1.
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Synthesis of PhC( NAr)CH2PPh2 (Ar = Ph, 3; Ar = p-MeC6H4,
4)
Ph), 11.44 (broad, 1H, NH). 13C NMR (CDCl3): d 20.64, 86.80 (d,
J = 49 Hz), 115.36, 120.81, 121.23, 121.45, 121.83, 122.38, 122.62,
128.25, 128.42, 128.60, 128.66, 128.75, 129.43, 129.36, 129.44 (d,
J = 1.3 Hz), 130.96 (d, J = 10.6 Hz), 131.39 (d, J = 2.7 Hz), 131.85,
131.98, 138.21, 141.84, 147.96 (d, J = 4.8 Hz), 159.63. 31P NMR
(CDCl3): d 2.42 (m).
A solution of 1 (4.00 g, 20.9 mmol) in THF (20 cm3) was added
dropwise to a stirred THF solution of i-Pr2NLi (22.5 mmol,
prepared in situ from n-BuLi and i-Pr2NH in THF) at 0 ◦C. The
◦
stirring continued at 0 C for 4 h and then a solution of Ph2PCl
(4.97 g, 22.5 mmol) in THF (20 cm3) was transferred to the
reaction mixture. The resultant mixture was stirred for 16 h at
room temperature. Volatiles were removed from the mixture under
reduced pressure and the yellow residue was extracted with CH2Cl2
(60 cm3). The extract was distilled to dryness under reduced
pressure. The residual solid was re-crystallised from a mixed
solvent of diethyl ether and n-hexane to afford yellow crystals
of 1 (4.51 g, 58%), (Found: C, 82.11, H, 5.80, N, 3.50. C26H22NP
requires C, 82.30, H, 5.84, N, 3.69). mp 100–102 C. H NMR
(CDCl3): d 3.50–3.66 (m, CH2), 3.66–3.74 (m, CH2), 5.56–5.66
(m, CH), 5.72–5.86 (m, CH), 6.28–6.68 (m, Ar), 6.70–7.64
(m, Ar), 7.74–7.95 (m, Ar). 13C NMR (CDCl3): d 31.46 (d, J =
23 Hz), 42.67 (d, J = 16.2 Hz), 106.05 (d, J = 4.5 Hz), 119.32,
119.49, 120.79, 123.05, 127.81, 128.13, 128.16, 128.36, 128.54,
128.64, 128.78, 128.90, 129.06, 130.46, 132.56, 132.81, 132.93,
133.05, 133.20, 133.31, 137.12, 137.33, 138.88, 150.83, 165.47,
165.60. 31P NMR (CDCl3): d -17.03 (m), -22.85 (m), -26.56 (m),
-36.32 (m).
By using the same procedure as for synthesis of 3, compound
4 was obtained in 58% yield, (Found: C, 82.24, H, 6.10, N, 3.38;
C27H24NP requires C, 82.42, H, 6.15, N, 3.56). mp 108–110 ◦C. 1H
NMR (CDCl3): d 2.17 (s, Me), 2.29 (s, Me), 3.56 (s, CH2), 3.64 (s,
CH2), 5.51 (t, J = 1.8 Hz, CH), 5.64 (d, J = 4.4 Hz, CH), 6.27
(d, J = 6.9 Hz, Ar), 6.34 (d, J = 6.9 Hz, Ar), 6.49 (d, J = 7.2 Hz,
Ar), 6.85 (d, J = 7.7 Hz, Ar), 6.96 (d, J = 7.7 Hz, Ar), 7.15–7.52
(m, Ar), 7.82 (d, J = 7.8 Hz, Ar). 13C NMR (CDCl3): d 17.39,
20.65, 20.95, 31.30 (d, J = 22.8 Hz), 42.79 (d, J = 16.2 Hz), 87.21,
88.64, 104.80, 119.45, 119.77, 120.78, 121.47, 127.26, 127.90,
128.02, 128.09, 128.12, 128.30, 128.45, 128.50, 128.58, 128.66,
128.82, 128.99, 129.07, 129.16, 129.35, 129.39, 129.48, 129.62,
129.72, 129.85, 130.29, 130.44, 130.89, 131.03, 131.36, 131.48,
131.56, 132.28, 132.37, 132.54, 132.69, 132.79, 132.95, 133.06,
133.21, 133.31, 135.33 (d, J = 7.1 Hz), 135.59 (d, J = 7.1 Hz),
137.40 (d, J = 16.2 Hz), 139.15, 148.33, 160.82, 165.61 (d, J =
9.7 Hz). 31P NMR (CDCl3): d -16.91 (m), -22.90 (m), -26.55 (m),
-36.71 (m).
Synthesis of o-ClC6H4N P(Ph2)CH C(Ph)NHPh (6)
A solution of o-chlorophenyl azide (0.97 g, 6.32 mmol) in CH2Cl2
(10 cm3) was added dropwise to a stirred solution of 3 (2.00 g,
◦
5.27 mmol) in CH2Cl2 (30 cm3) at 0 C. The mixture was stirred
at 0 ◦C for 10 min. and then at room temperature for 4 h. Solvent
was removed in vacuo. The residual solid was washed with n-
hexane and dried under vacuum to give a yellow powder of 6
(2.05 g, 77%). The compound was pure enough for the next step.
Further purification was carried out by re-crystallisation of the
crude product from diethyl ether. (Found: C, 76.03, H, 5.17, N,
5.28; C32H26ClN2P requires C, 76.11, H, 5.19, N, 5.55). mp 150–
◦
1
◦
1
152 C. H NMR (CDCl3): d 4.55 (d, J = 23.4 Hz, 1H, CH),
6.49–6.57 (m, 2H, Ar), 6.71–6.75 (m, 3H, Ar), 6.83 (t, J = 6.9 Hz,
1H, Ar), 7.03 (t, J = 7.8 Hz, 2H, Ar), 7.20–7.34 (m, 4H, Ar),
7.37–7.52 (m, 8H, Ar), 7.79 (d, J = 8.1 Hz, 2H, Ar), 7.83 (d, J =
8.1 Hz, 2H, Ar), 11.09 (s, 1H, NH). 13C NMR (CDCl3): d 86.18
(d, J = 129.6 Hz), 117.79, 121.42 (d, J = 12.3 Hz), 122.15, 122.75,
126.63, 128.31, 128.39, 128.46, 128.74 (d, J = 11.5 Hz), 129.38 (d,
J = 20.7 Hz), 131.60, 131.94 (d, J = 9.8 Hz), 132.85, 138.25 (d, J =
15.9 Hz), 141.81, 147.93, 160.23. 31P NMR (CDCl3): d 4.31 (m).
Synthesis of o-FC6H4N P(Ph2)CH C(Ph)NHPh (7)
Compound 7 was synthesised using the same procedure as for 6.
Thus, the reaction of 3 (2.00 g, 5.27 mmol) with o-fluorophenyl
azide (0.80 g, 5.80 mmol) in CH2Cl2 (40 cm3) gave, after work-up,
compound 7 (2.06 g, 80%), (Found: C, 78.41, H, 5.34, N, 5.59;
C32H26FN2P requires C, 78.67, H, 5.36, N, 5.73). mp 184–186 ◦C.
1H NMR (CDCl3): d 4.46 (d, J = 23.7 Hz, 1H, CH), 6.50–6.73 (m,
5H, Ar), 6.82 (t, J = 7.2 Hz, 1H, Ar), 6.92–6.98 (m, 1H, Ar), 7.06
(t, J = 7.8 Hz, 2H, Ar), 7.22–7.33 (m, 3H, Ar), 7.37–7.52 (m, 8H,
Ar), 7.76–7.83 (m, 4H, Ar), 11.66 (s, 1H, NH). 13C NMR (CDCl3):
d 86.06 (d, J = 130.8 Hz), 115.22 (d, J = 20.8 Hz), 117.47 (d, J =
7.4 Hz), 121.44, 121.46, 121.58, 122.68 (d, J = 2.6 Hz), 122.86
(d, J = 2.6 Hz), 123.68 (d, J = 3.4 Hz), 128.24, 128.36, 128.45,
128.55, 128.66, 128.81, 129.34, 131.60 (d, J = 2.2 Hz), 131.94 (d,
J = 10 Hz), 133.10, 138.33 (d, J = 16.2 Hz), 141.82, 160.09. 31P
NMR (CDCl3): d 5.97 (m).
Synthesis of p-MeC6H4N P(Ph2)CH C(Ph)NHPh (5)
A solution of p-methylphenyl azide (0.77 g, 5.80 mmol) in CH2Cl2
(10 cm3) was added dropwise to a stirred solution of 3 (2.00 g,
Synthesis of o-FC6H4N P(Ph2)CH C(Ph)NH(p-MeC6H4) (8)
◦
5.27 mmol) in CH2Cl2 (30 cm3) at 0 C. The mixture was stirred
A solution of o-fluorophenyl azide (0.77 g, 5.6 mmol) in CH2Cl2
(10 cm3) was added dropwise to a◦stirred solution of 4 (2.00 g,
5.08 mmol) in CH2Cl2 (30 cm3) at 0 C. The mixture was stirred at
0 ◦C for 10 min. and then at room temperature for 4 h. The solvent
was removed under vacuum. The residual solid was washed with
n-hexane and dried under vacuum to give a yellow powder of 8
(1.94 g, 76%). The compound was pure enough for the next step.
Further purification was carried out by re-crystallisation of the
crude product from diethyl ether. (Found: C, 77.66, H, 6.10, N,
5.10; C33H28FN2P·0.6Et2O requires C, 77.72, H, 6.26, N, 5.12). mp
136–138 ◦C. 1H NMR (CDCl3): d 1.21 (t, J = 6.9 Hz, Et2O), 2.19
at 0 ◦C for 10 min. and then at room temperature for 4 h. The
solvent was removed under reduced pressure and the residue was
washed with n-hexane and dried under vacuum to give a yellow
powder of 5 (2.12 g, 83%), (Found: C, 81.05, H, 6.03, N, 5.72;
C33H29N2P·0.06CH2Cl2 requires C, 81.09, H, 5.99, N, 5.72). mp 98–
100 ◦C. 1H NMR (CDCl3): d 2.18 (s, 3H, Me), 4.57 (d, J = 22.5 Hz,
1H, CH), 6.60 (d, J = 8.4 Hz, 2H, C6H4), 6.73 (d, J = 8.1 Hz, 2H,
Ar), 6.79 (d, J = 7.8 Hz, 1H, Ph), 6.83 (d, J = 7.8 Hz, 2H, Ph), 7.04
(t, J = 7.8 Hz, 2H, Ph), 7.21–7.33 (m, 4H, Ph), 7.36–7.49 (m, 7H,
Ph+C6H4), 7.78 (d, J = 7.5 Hz, 2H, Ph), 7.81 (d, J = 7.2 Hz, 2H,
4674 | Dalton Trans., 2011, 40, 4669–4677
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(s, 3H, Me), 3.47 (q, J = 6.9 Hz, Et2O), 4.40 (d, J = 24 Hz, 1H,
CH), 6.51–6.68 (m, 5H, Ar), 6.87 (d, J = 8.4 Hz, 2H, Ar), 6.90–6.98
(m, 1H, Ar), 7.20–7.34 (m, 3H, Ar), 7.21–7.32 (m, 3H, Ar), 7.40–
7.52 (m, 8H, Ar), 7.76–7.82 (m, 8H, Ar), 11.58 (s, 1H, NH). 13C
NMR (CDCl3): d 15.40 (Et2O), 20.74, 65.96 (Et2O), 84.98 (d, J =
131.1 Hz), 115.18 (d, J = 20.7 Hz), 117.39 (d, J = 7.2 Hz), 121.57,
122.76 (d, J = 13.1 Hz), 123.63 (d, J = 3.5 Hz), 128.38, 128.61,
128.77, 129.14, 129.22, 131.06, 131.53 (d, J = 2.3 Hz), 131.91 (d,
J = 10 Hz), 132.07, 133.22, 138.44 (d, J = 16.3 Hz), 139.27, 160.36.
31P NMR (CDCl3): d 6.03 (m).
25.5 Hz, 1H, CH), 6.63–6.73 (m, 2H, Ar), 6.75–6.84 (m, 2H, Ar),
6.96–7.23 (m, 14H, Ar), 7.56–7.60 (m, 2H, Ar), 7.86–7.93 (m, 4H,
Ar). 13C NMR (C6D6): d -8.23, 82.31 (d, J = 120.6 Hz), 116.49 (d,
J = 21.4 Hz), 122.54, 124.40, 125.21 (d, J = 7.4 Hz), 126.55, 128.65,
128.83, 128.99, 129.31, 130.26, 130.40 (d, J = 7.9 Hz), 132.54 (d,
J = 2.1 Hz), 133.29 (d, J = 10.2 Hz), 141.66 (d, J = 15.2 Hz),
150.11, 173.00. 31P NMR (C6D6): d 22.88 (m).
Synthesis of [Me2Al{N(p-MeC6H4)C(Ph) CHP(Ph2) N(o-
FC6H4)}] (12)
Synthesis of [Me2Al{N(Ph)C(Ph) CHP(Ph2) N(p-MeC6H4)}]
Synthesis of complex 12 follows the same procedure as for 9.
Reaction of 8 (0.30 g, 0.60 mmol) with AlMe3 (0.29 cm3, 2.3 M
solution in hexane, 0.667 mmol) in toluene (30 cm3) afforded a
yellow crystalline solid of 12 (0.22 g, 67%), (Found: C, 75.19, H,
5.97, N, 4.92; C35H33AlFN2P requires C, 75.25, H, 5.95, N, 5.01).
(9)
AlMe3 (0.50 cm3, 2.3 M solution in hexane, 1.15 mmol) was added
dropwise to a stirred solution of 5 (0.50 g, 1.03 mmol) in toluene
(30 cm3) at room temperature. The mixture was stirred at room
temperature for 16 h. Solvents were removed under vacuum and
the residue was dissolved in diethyl ether. The solution was filtered
and the filtrate was concentrated to generate yellow crystals of 9
(0.42 g, 75%), (Found: C, 77.43, H, 6.28, N, 5.16;◦C35H34AlN2P
◦
1
mp 146–148 C. H NMR (C6D6): d 0.04 (s, 6H, AlMe), 1.89 (s,
3H, Me), 4.59 (d, J = 25.8 Hz, 1H, CH), 6.45–6.55 (m, 2H, Ar),
6.62 (t, J = 7.8 Hz, 1H, Ar), 6.69–6.76 (m, 4H, Ar), 6.85–7.08 (m,
10H, Ar), 7.43 (d, J = 7.2 Hz, 2H, Ar), 7.70 (d, J = 8.4 Hz, 2H, Ar),
7.74 (d, J = 8.1 Hz, 2H, Ar). 13C NMR (C6D6): d -8.22, 21.06,
81.37 (d, J = 121 Hz), 116.52 (d, J = 24.5 Hz), 124.39, 125.15
(d, J = 7.3 Hz), 126.52, 128.79, 128.95, 129.25, 130.29, 130.44,
131.66, 132.45 (d, J = 2.3 Hz), 133.34 (d, J = 10.2 Hz), 141.87 (d,
J = 14.8 Hz), 147.49, 173.14. 31P NMR (C6D6): d 22.91 (m).
1
requires C, 77.76, H, 6.34, N, 5.18). mp 228–230 C. H NMR
(C6D6): d 0.05 (s, 6H, AlMe), 1.91 (s, 3H, Me), 4.65 (d, J = 25.2 Hz,
1H, CH), 6.62 (t, J = 7.2 Hz, 1H, Ar) 6.69 (d, J = 8.4 Hz, 2H, Ar),
6.78–7.03 (m, 15H, Ar), 7.37–7.40 (m, 2H, Ar), 7.66–7.73 (m, 4H,
Ar). 13C NMR (C6D6): d -7.65, 21.00, 83.20 (d J = 121 Hz), 122.54,
126.65, 127.26 (d, J = 33.54 Hz), 128.39, 128.64, 128.95, 129.11,
129.27, 130.05, 130.27, 132.51, 133.44 (d, J = 10.1 Hz), 142.38,
142.46, 142.42 (d, J = 6.1 Hz), 150.30, 172.70. 31P NMR (C6D6):
d 20.59 (m).
Synthesis of 2-{p-MeC6H4N P(Ph2)}C6H4N C(Ph)-
CH2P(Ph2) N(p-MeC6H4) (13)
Synthesis of complex 13 follows a similar procedure to 2-
{PhN P(Ph2)}C6H4N C(Ph)CH2P(Pri2) NPh.17 To a solution
of 2-(Ph2P)C6H4N C(Ph)CH2PPh2 (1.05 g, 1.863 mmol) in
CH2Cl2 (40 cm3) was added p-MeC6H4N3 (0.57 g, 4.28 mmol) at
room temperature and the mixture was stirred overnight. Volatiles
were removed in vacuo and the residue was dissolved in Et2O. The
solution was filtered and the filtrate was concentrated to give
yellow crystals of 13·0.5Et2O (1.31 g, 87%), (Found: C, 79.84,
H, 6.28, N, 5.25. C52H45N3P2·0.5Et2O requires C, 79.98, H, 6.21,
N, 5.18.), mp 182–184 ◦C. 1H NMR (CDCl3): d 1.20 (t, J =
7.2 Hz, Et2O), 2.06, 2.10, 2.13, 2.17, 2.20, 2.25 (Me), 3.27 (d,
J = 12.4 Hz,CH2), 3.47 (q, J = 7.2 Hz, Et2O), 5.23 (d, J = 15.6 Hz,
CH), 5.80 (dd, J = 4.4, 8 Hz, Ar), 5.85 (d, J = 14 Hz, CH), 5.95
(b, Ar), 6.21 (d, J = 8 Hz, Ar), 6.37 (d, J = 6.8 Hz, Ar), 6.60–6.76
(m, Ar), 6.80 (d, J = 8 Hz, Ar), 6.86–6.98 (m, Ar), 7.05–7.26 (m,
Ar), 7.31–7.46 (m, Ar), 7.48–7.60 (m, Ar), 7.62–7.67 (m, Ar), 7.73
(dd, J = 7.2, 11.6 Hz, Ar), 7.87 (dd, J = 7.2, 12 Hz, Ar), 10.78 (s,
NH). 13C NMR (CDCl3): d 15.40, 20.60, 20.65, 20.75, 65.96, 98.47
(d, J = 93.6 Hz), 118.73 (d, J = 21.1 Hz), 120.17, 120.31, 121.69
(d, J = 14.1 Hz), 122.37, 122.62 (d, J = 13.1 Hz), 122.82 (d, J =
11.1 Hz), 123.10, 123.36, 123.37 (d, J = 18.1 Hz), 123.59 (d, J =
10.1 Hz), 127.05, 127.36, 127.56, 128.02 (d, J = 12.1 Hz), 128.18,
128.33 (d, J = 4.4 Hz), 128.54 (d, J = 12.1 Hz), 128.74 (d, J =
12.1 Hz), 128.95, 129.06, 129.35, 129.57, 130.23, 130.95, 131.22,
131.65 (d, J = 9 Hz), 131.98, 132.09, 132.19, 132.24, 132.55, 132.83
(d, J = 9.6 Hz), 133.25 (d, J = 9.2 Hz), 133.35, 134.92, 135.81 (d,
J = 3.8 Hz), 146.29, 146.99, 148.21 (d, J = 11 Hz), 149.17, 149.56,
153.94, 156.57. 31P NMR (CDCl3): d -3.22, -0.34, 1.04, 1.86, 9.22,
11.91.
Synthesis of [Me2Al{N(Ph)C(Ph) CHP(Ph2) N(o-ClC6H4)}]
(10)
Synthesis of complex 10 follows the same procedure as for
9. Reaction of AlMe3 (0.29 cm3, 2.3 M solution in hexane,
0.667 mmol) with 6 (0.30 g, 0.594 mmol) in toluene (30 cm3)
afforded, after re-crystallisation from a mixed solvent of diethyl
ether and n-hexane, yellow crystals of 10 (0.24 g, 71%), (Found:
C, 72.53, H, 5.59, N, 4.87; C34H31AlClN2P requires C, 72.79, H,
5.57, N, 4.99). mp 138–140 ◦C. 1H NMR (C6D6): d -0.09 (s, 3H,
AlMe), 0.01 (s, 3H, AlMe), 4.46 (d, J = 24 Hz, 1H, CH), 6.44–6.54
(m, 1H, Ar), 6.58–6.73 (m, 2H, Ar), 6.82–7.10 (m, 14H, Ar), 7.13–
7.23 (m, 1H, Ar), 7.42–7.50 (m, 2H, Ar), 7.55–7.65 (m, 2H, Ar),
7.72–7.82 (m, 2H, Ar). 13C NMR (C6D6): d -8.01, -7.73, 77.94 (d,
J = 120.4 Hz), 122.65, 126.06 (d, J = 3 Hz), 126.74, 127.36 (d, J =
2.7 Hz), 128.58, 128.70, 128.95, 129.01, 129.16, 130.21, 130.68 (d,
J = 2.4 Hz), 131.83 (d, J = 4.9 Hz), 132.30, 132.58, 132.87 (d, J =
10.3 Hz), 133.58 (d, J = 9.7 Hz), 142.17 (d, J = 7.6 Hz), 142.32,
142.52, 150.09, 173.20. 31P NMR (C6D6): d 22.64 (m).
Synthesis of [Me2Al{N(Ph)C(Ph) CHP(Ph2) N(o-FC6H4)}]
(11)
Synthesis of complex 11 follows the same procedure as for 9.
Treatment of 7 (0.30 g, 0.62 mmol) with AlMe3 (0.3 cm3, 2.3 M
solution in hexane, 0.69 mmol) in toluene (30 cm3) yielded a yellow
crystalline solid of 11 (0.18 g, 53%), (Found: C, 74.86, H, 5.66, N,
5.22; C34H31AlFN2P requires C, 74.99, H, 5.74, N, 5.14). mp 180–
◦
1
182 C. H NMR (C6D6): d 0.19 (s, 6H, AlMe2), 4.82 (d, J =
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Table 2 Details of the X-ray structure determinations of complexes 9 and 14
9
14·0.13C8H16O2
empirical formula
fw
C35H34AlN2P
540.59
298(2)
0.71073
monoclinic
C54H50AlN3P2·0.13C8H16O2
848.67
294(2)
T (K)
˚
l (A)
0.71070
triclinic
crystal system
space group
¯
P21/c
P1
˚
a (A)
12.3833(13)
13.9861(14)
18.4732(18)
90
90.1360(10)
90
3199.4(6)
4
1.122
1144
0.138
1.64 to 25.02
16 587
10.7891(12)
15.4618(14)
17.1493(18)
63.402(8)
72.448(9)
89.894(9)
2409.0(4)
2
1.169
896
˚
b (A)
˚
c (A)
a (deg)
b (deg)
g (deg)
3
˚
V (A )
Z
Dcalcd (g cm-3)
F(000)
m (mm-1)
0.148
1.50 to 27.80
20 945
q range for data collecn (deg)
no. of reflns collected
no. of indep reflns (Rint
)
5650 (0.1109)
0/355
1.046
R1 = 0.0612 wR2 = 0.1311
R1 = 0.1220, wR2 = 0.1503
0.297 and -0.350
11 148 (0.0435)
10/566
1.010
R1 = 0.0631, wR2 = 0.1794
R1 = 0.1033, wR2 = 0.2035
0.739 and -0.368
restraints/params
goodness of fit on F2
final R indicesa [I > 2s(I)]
R indices (all data)
-3
˚
largest diff peak and hole [e A ]
ꢀ
ꢀ
ꢀ
ꢀ
1
2
a R1 =
ꢀFoꢀ - |Fcꢀ/ |Fo|; wR2 = [ w(Fo - Fc2)2/ w(Fo )]
2
4
collected on a Bruker Smart CCD area-detector or a Rigaku
Saturn CCD area detector with graphite-monochromated Mo Ka
radiation. Unit-cell dimensions were obtained with least squares
refinement. Data collection and reduction were performed using
the SMART (for 9)18 or CrystalClear (Rigaku Corporation,
2005) software (for 14). Absorption corrections were applied
using the SADABS19 (for 9) or REQAB program20 (for 14). The
structures were solved by direct methods using SHELXS-9721 and
refined against F2 by full-matrix least-squares using SHELXL-
97.22 Hydrogen atoms were placed in calculated positions. The
co-crystallised THF molecule in 14·0.13C8H16O2 disordered over
an inversion centre was refined with geometrical restraints. Crystal
data and experimental details of the structure determinations are
listed in Table 2.
Synthesis of [Me2Al{N{2-(p-MeC6H4N P(Ph2))C6H4}-
C(Ph) CHP(Ph2) N(p-MeC6H4)}] (14)
AlMe3 (0.31 cm3, 2.3 M solution in hexane, 0.713 mmol) was
added dropwise to a stirred solution of 13 (0.50 g, 0.646 mmol) in
toluene (20 cm3) at room temperature. The mixture was then stirred
at room temperature for 16 h and then again at 110 ◦C for 8 h. The
resulting solution was cooled back to room temperature and the
solvent was removed in vacuo. The residue was dissolved in diethyl
ether and filtered. The filtrate was concentrated under reduced
pressure to form yellow crystals of 14 (0.34 g, 63%), (Found: C,
77.06, H, 5.99, N, 4.96; C54H50AlN3P2·0.6Et2O requires C, 77.47,
◦
1
H, 6.46, N, 4.81). mp 238–240 C. H NMR (C6D6): d -0.13 (s,
6H, AlMe), 1.85 (s, 3H, Me), 2.33 (s, 3H, Me), 6.22 (d, J = 16.5 Hz,
1H, CH), 6.29–6.35 (m, 1H, Ar), 6.64–6.73 (m, 5H, Ar), 6.79–7.16
(m, 20H, Ar), 7.30 (d, J = 8.1 Hz, 2H, Ar), 7.36–7.40 (m, 1H, Ar),
7.47–7.54 (m, 4H, Ar), 8.04–8.11 (m, 4H, Ar). 13C NMR (C6D6): d
-6.74, 20.87, 21.40, 101.55 (d, J = 89.3 Hz), 119.57 (d, J = 14 Hz),
124.22 (d, J = 20.2 Hz), 124.93, 125.22, 126.20, 126.23 (d, J =
9.7 Hz), 127.51, 127.85 (d, J = 8.7 Hz), 128.36, 128.51, 129.02,
129.43 (d, J = 12.4 Hz), 130.04, 130.26 (d, J = 1.8 Hz), 130.49
(d, J = 2.7 Hz), 131.28, 131.70 (d, J = 12.1 Hz), 132.42 (d, J =
9 Hz), 133.47 (d, J = 2.9 Hz), 134.45 (d, J = 10.3 Hz), 134.60 (d,
J = 2 Hz), 135.19, 136.64, 139.50 (d, J = 3.3 Hz), 142.72 (d, J =
5.2 Hz), 150.98 (d, J = 2.1 Hz), 157.73 (d, J = 3.9 Hz), 168.56 (d,
J = 8.3 Hz). 31P NMR (CDCl3): d -12.58 (m), 29.12 (m).
Polymerisation of e-CL catalysed by complexes 9–12 and 14
A typical polymerisation procedure is exemplified by the synthesis
of PCL using complex 9 as a catalyst in the presence of benzyl
alcohol (Table 1, entry 1). Complex 9 (0.0122 g, 0.0226 mmol)
and toluene (2 cm3) were added successively into a Schlenk tube.
After the complex dissolved, benzyl alcohol (0.2 cm3, 0.1128 M
in toluene, 0.0226 mmol) was added at room temperature. The
mixture was stirred at room temperature for 1 h. The Schlenk
◦
tube was put into an oil bath which was preset at 110 C. After
Single crystals of complex 14 suitable for X-ray diffraction
10 min. e-CL (0.515 g, 4.512 mmol) was added via a syringe. After
the solution was stirred for 11 min. the polymerisation reaction
was terminated by addition of several drops of glacial acetic
acid. After stirring at room temperature for 0.5 h, the resulting
viscous solution was diluted with THF and then dropped into
cool methanol with stirring. The white precipitate was collected by
analysis were grown from a mixed solvent of THF and n-hexane.
X-ray crystallography
Single crystals of complexes 9 and 14·0.13C8H16O2 were mounted
in Lindemann capillaries under nitrogen. Diffraction data were
4676 | Dalton Trans., 2011, 40, 4669–4677
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filtration under reduced pressure and washed with cool methanol
and dried under vacuum, giving a white solid (0.4907 g, 95%).
For the GPC analysis, the sample was dissolved in
dichloromethane, passed through a short neutral aluminium oxide
column, precipitated in methanol and dried under vacuum.
For the kinetic studies, samples were taken from the reaction
mixture using a syringe at a desired time interval.
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Acknowledgements
We thank the National Natural Science Foundation of China
(Grant No. 20972146) and the Foundation for Talents of Anhui
Province (Grant No. 2008Z011) for financial support. We also
thank Prof. D.-Q. Wang and Prof. H.-B. Song for the crystal
structure determination and Prof. S.-Y. Liu for the GPC analysis.
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The Royal Society of Chemistry 2011
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