Lithium, magnesium, and zinc iminophosphorano(8-quinolyl)methanide complexes: Syntheses, characterization, and activity in ε-caprolactone polymerization

Article abstract of DOI:10.1021/om0610400

Lithiation of R₂P(CH₂C₉H ₆N-8)=NBu^t (R = Ph, 3; R = Prⁱ, 4) with an equivalent of BuⁿLi afforded lithium itninophosphorano(8-quinolyl) methanide [Li{CH(8-C₉H₆

Full text of DOI:10.1021/om0610400

Organometallics 2007, 26, 2243-2251
2243
Lithium, Magnesium, and Zinc
Iminophosphorano(8-quinolyl)methanide Complexes: Syntheses,
Characterization, and Activity in E-Caprolactone Polymerization
Zhong-Xia Wang* and Chun-Yan Qi
Department of Chemistry, UniVersity of Science and Technology of China, Hefei, Anhui 230026,
People’s Republic of China
ReceiVed NoVember 12, 2006
Lithiation of R2P(CH2C9H6N-8)dNBut (R ) Ph, 3; R ) Pri, 4) with an equivalent of BunLi afforded
lithium iminophosphorano(8-quinolyl)methanide [Li{CH(8-C9H6N)P(Ph2)dNBut}(THF)] (5) and [Li-
{CH(8-C9H6N)P(Pri2)dNBut}]2 (6), respectively. Reaction of 4 with Et2Mg yielded magnesium
iminophosphorano(8-quinolyl)methanide complex (7). Treatment of 6 with ZnCl2 gave [Zn(Cl){CH(8-
C9H6N)P(Pri2)dNBut}] (8), which was transformed into alkylated zinc complexes [Zn(R1){CH(8-C9H6N)P-
(Pri2)dNBut}] (R1 ) Ph, 9; R1 ) Me, 10) by treating with R1Li or R1MgX. Ethylzinc complexes
[Zn(Et){CH(8-C9H6N)P(R2)dNBut}] (R ) Ph, 11; R ) Pri, 12) were obtained by reaction of 3 or 4 with
an equivalent of Et2Zn. Compounds 2 and 4-12 were characterized by 1H, 13C{1H}, and 31P{1H} NMR
spectroscopy and elemental analyses. Structures of complexes 6-8 and 10 were further characterized by
single-crystal X-ray diffraction techniques. The catalytic behaviors of complexes 7 and 9-12 in the
ring-opening polymerization of ꢀ-caprolactone was studied. Complex 7 exhibited high catalytic activity
in the presence or absence of benzyl alcohol. Complexes 9-12 catalyzed the ring-opening polymerization
of ꢀ-CL in the presence of benzyl alcohol and exhibited first-order dependence on monomer concentration.
ior.11 Among the nitrogen based ligands, iminophosphorano
ligands have attracted considerable attention recently. A range
of complexes supported by iminophosphorano ligands has been
synthesized and characterized.12 Some of them exhibited good
catalytic activity in the ROP of cyclic esters.13 We previously
reported synthesis of aluminum complexes bearing iminophos-
phorano ligands [CH(8-C9H6N){P(Ph2)dNBut}]- and [C(8-
Introduction
Poly(ꢀ-caprolactone) (PCL), polylactide (PLA), and their
copolymers are important materials for biomedical, pharma-
ceutical, and agricultural applications due to their biodegradable,
biocompatible, and permeable properties.1,2 The major method
to synthesize the polymers is ring-opening polymerization (ROP)
of lactones or lactides by a coordination, anoinic or cationic
initiator.3 Metal-complex-catalyzed ROP of cyclic esters is one
of the promising methodologies because it provides control on
molecular weight, molecular weight distribution, polymer
architecture, and end functionality.4 Some excellent metal
catalysts or initiators have been reported, including aluminum,5
tin,6 magnesium,7 zinc,8 transition metal,9 and rare earth metal10
complexes supported by various ligands. Nitrogen based ligand-
metal complexes are widely applied as catalysts/initiators for
ring-opening polymerization of cyclic esters. For example, some
of the â-diketiminate complexes of zinc and magnesium
demonstrated excellent catalytic lactide polymerization behav-
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J. Inorg. Chem. 2000, 441. (b) Chisholm, M. H.; Patmore, N. J.; Zhou, Z.
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* To whom correspondence should be addressed. E-mail: zxwang@
ustc.edu.cn.
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Macromolecules 1990, 23, 1640. (c) Ko, B. T.; Lin, C. C. Macromolecules
1999, 32, 8296.
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147, 1. (b) Stridsberg, K. M.; Ryner, M.; Albertsson, A.-C. AdV. Polym.
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10.1021/om0610400 CCC: $37.00 © 2007 American Chemical Society
Publication on Web 03/23/2007

2244 Organometallics, Vol. 26, No. 9, 2007
Wang and Qi
Scheme 1. Synthesis of Compounds 1-6a
C9H6N){P(Ph2)dNBut}]2- through reaction of Ph2P(CH2C9H6N-
8)dNBut with AlMe3.12h We now describe synthesis and
characterization of Li, Mg, and Zn complexes supported by [CH-
(8-C9H6N){P(R2)dNBut}]- (R ) Ph, Pri) ligands and the use
of the Mg and Zn complexes in the ring-opening polymerization
of ꢀ-caprolactone.
Results and Discussion
Syntheses and Characterization of Compounds 2 and
4-12. Syntheses of compounds 1-6 have been summarized in
Scheme 1. Compounds 1 and 3 were prepared according to our
previously reported methods.12h Compound 2 was prepared in
quantitative yield by a similar procedure through reaction of
8-(bromomethyl)quinoline with Pri2PNHBut. Treatment of 2
with excess NaH afforded Pri2P(CH2C9H6N-8)dNBut (4).
Compound 2 was almost insoluble in toluene, benzene, hexane,
and Et2O and soluble in CH2Cl2 and CHCl3, while 4 was soluble
in hexane and very soluble in toluene and Et2O. Both 2 and 4
were characterized by 1H, 13C, and 31P NMR spectroscopy and
elemental analyses. Reaction of 3 or 4 with an equivalent of
BunLi in tetrahydrofuran (THF) formed lithiated products 5 and
6, respectively, as red crystalline solids. Complex 5 was
crystallized from THF, and complex 6 was crystallized from
1
Et2O. Complexes 5 and 6 were characterized by H, 13C, and
31P NMR spectroscopy and elemental analyses. The variable-
temperature 1H NMR spectra of 5 in C6D6 (until 333 K) showed
no changes compared with that at room temperature, proving
its coordination mode to be kept at higher temperature. The 1H
NMR spectrum of complex 6 gave broad signals in the region
of Pri groups. Two CH signals of Pri were attributed to the
presence of diastereotopic Pri in the enantiomeric dimeric
structures of 6 (on the basis of the single-crystal X-ray
diffraction result; see below). The variable-temperature 1H NMR
spectra of 6 in C6D6 showed that the two broad CH signals of
Pri coalesced into a very broad signal at 313 K and became a
broad signal centered at δ 2.30 ppm at 323 K. The aromatic
proton signals also became broad at higher temperature. These
are attributed to the dissociation and recombination of the
dimeric structures at elevated temperature. The solid structure
of complex 6 was characterized by single-crystal X-ray dif-
fraction techniques. Complex 6 is dimeric in the solid state and
a Reagents and conditions: i, CH2Cl2, room temperature, 15 h.; ii,
NaH, THF, room temperature, 2 h. and then reflux for 4 h.; iii, BunLi,
THF, -80 °C to room temperature, 15 h., crystallized from THF; iv,
BunLi, THF, -80 °C to room temperature, 15 h., crystallized from
Et2O.
Scheme 2. Synthesis of Complexes 7-12a
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Macromolecules 1996, 29, 3332. (b) Stevels, W. M.; Ankone´, M. J. K.;
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Soc. 2001, 123, 3229.
a Reagents and Conditions: i, Et2Mg, THF, -80 °C to room
temperature, 15 h. and then reflux for 4 h.; ii, ZnCl2, Et2O, -80 °C to
room temperature, 15 h.; iii, R1Li or R1MgX, toluene, -80 °C to room
temperature, 15 h.; iv, Et2Zn, toluene, -80 °C to room temperature,
15 h. and then reflux for 7 h.
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2001, 617-618, 158. (b) Steiner, A.; Zacchini, S.; Richards, P. I. Coord.
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metallics 2004, 23, 1811. (e) Wei, P.; Stephan, D. W. Organometallics 2003,
22, 601. (f) Qi, C.-H.; Zhang, S.-B.; Sun, J.-H. J. Organomet. Chem. 2005,
690, 3946. (g) Masuda, J. D.; Wei, P.; Stephan, D. W. Dalton Trans. 2003,
3500. (h) Wang, Z.-X.; Li, Y.-X. Organometallics 2003, 22, 4900. (i) Jones,
N. D.; Cavell, R. G. J. Organomet. Chem. 2005, 690, 5485. (j) Hitchcock,
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44, 4621.
consists of two enantiomers (6a,b, Figure 1). It crystallizes with
three independent molecules in the asymmetric unit, two 6a and
one 6b. For each of the enantiomers 6a,b, the two lithium atoms
are bridged by two carbon atoms, forming a 1,3-Li2C2 four-
membered ring. With the 1,3-Li2C2 ring as the base, the CPNLi
and C3NLi rings form the flaps of an “open box”-like structure

ROP of ꢀ-CL and Mg and Zn Complexes
Organometallics, Vol. 26, No. 9, 2007 2245
Figure 1. ORTEP drawings of 6a,b shown with 20% thermal ellipsoids.
Table 1. Selected Bond Distances (Å) and Angles (deg) of 6a,b
compound 6a
Li1-N1
1.966(8)
2.410(9)
2.856(11)
1.585(4)
128.0(4)
75.3(3)
Li1-N4
2.101(8)
Li2-N2
2.058(9)
2.355(8)
1.584(4)
1.439(6)
126.8(4)
127.5(4)
126.2(4)
124.1(3)
Li2-N3
Li2-C21
P2-C21
1.946(8)
2.432(9)
1.753(4)
Li1-C1
Li1-C21
2.417(8)
1.739(4)
1.446(6)
73.6(3)
106.2(3)
74.1(3)
72.2(3)
Li2-C1
Li1‚‚‚Li2
P2-N3
N1-Li1-N4
N4-Li1-C21
N2-Li2-C1
Li1-C1-Li2
P1-C1
C1-C2
N1-Li1-C1
C1-Li1-C21
N3-Li2-C21
Li1-C21-Li2
P1-N1
C21-C22
N4-Li1-C1
N2-Li2-N3
N2-Li2-C2 1
C2-C1-P1
N1-Li1-C21
N3-Li2-C1
C1-Li2-C21
C22-C21-P2
152.0(4)
149.4(4)
107.5(3)
124.9(3)
77.2(3)
73.6(3)
compound 6b
Li3-N5
1.924(9)
1.734(5)
108.4(4)
71.6(4)
Li3-N6′
2.078(10)
1.437(6)
134.2(5)
79.5(3)
Li3-C41
2.443(11)
2.782(17)
124.5(5)
87.0(4)
Li3-C41′
2.311(10)
1.585(4)
78.2(3)
P3-C41
C41-C42
Li3‚‚‚Li3′
P3-Ν5
C41-Li3-C41′
Li3-C41-Li3′
P3-C41-C42
N5-Li3-C6′
Li3-C41-P3
Li3′-C41-C42
C41-Li3-N6′
Li3-C41-C42
C41′-Li3-N6′
Li3′-C41-P3
127.1(3)
126.5(4)
95.6(4)
framework. The two Pri2PdNBut groups lie on one side of the
base, and the two quinolyl groups lie on the other side of the
base. Each of the four-coordinated lithium centers adopts a very
distorted tetrahedral geometry. The average distance of 2.079
Å between the lithium atoms and the quinolyl nitrogen atoms
(Table 1) is longer than those between the lithium atoms and
the imino nitrogen atoms (average, 1.940 Å), and both lie
within the normal range as observed for lithiated iminophos-
phoranes, amidolithium, and diketiminatolithium complexes.14
The Li-C distances ranging from 2.311(10) to 2.443(11) Å
(average, 2.390 Å) are similar to those in the dilithium cluster
[Li2C(PPh2dNSiMe3)2]2 [2.312(9)-2.45(1) Å],15 but longer than
those in [Li(CH(SiMe3){Ph(1,2-C6H4)PdNSiMe2})]2 [2.232-
(6) Å]16 and [Li{CH(SiMe3)PPh2dNSiMe3}]2 [2.122(9) and
2.190(9) Å, respectively],17 and shorter than those found in [Li-
{CH(PPh2dNSiMe3)2}]2 (average, 2.615 Å)18 and [Li{CH-
(PR2dNSiMe3)2}(L)] (R ) Ph, L ) THF; R ) Cy, L ) Et2O)
[2.560(8), 2.622(9), and 2.633(7) Å, respectively].19
Syntheses of magnesium and zinc iminophosphorano(8-
quinolyl)methanide complexes are presented in Scheme 2.
Treatment of 4 with Et2Mg in THF afforded dark-red magne-
sium complex 7. Reaction of complex 6 with ZnCl2 in Et2O
gave yellow [Zn(Cl){CH(8-C9H6N)P(Pri2)dNBut}] (8) in rela-
tively low yield. Compound 8 was transformed into phenylated
or methylated zinc complexes [Zn(R1){CH(8-C9H6N)P(Pri2)d
NBut}] (R1 ) Ph, 9; R1 ) Me, 10) by treating with R1Li or
R1MgX (R1 ) Ph or Me). Ethyl zinc iminophosphorano(8-
quinolyl)methanide complexes 11 and 12 were obtained by
reaction of 3 or 4 with Et2Zn in toluene under reflux conditions.
Each of the complexes 7-12 was an air-sensitive crystalline
solid and was characterized by 1H, 13C, and 31P NMR
spectroscopy and elemental analyses. The data were consistent
with their respective structure. In addition, the variable-
(14) (a) Wang, Z.-X.; Li, Y.-X. Organometallics 2002, 21, 4641. (b)
Wang, Z.-X.; Qi, C.-Y. Dalton Trans. 2005, 996. (c) Hill, M. S.; Hitchcock,
P. B.; Karagouni, S. M. A. J. Organomet. Chem. 2004, 689, 722. (d) Said,
M.; Thornton-Pett, M.; Bochmann, M. Organometallics 2001, 20, 5629.
(e) Kocher, N.; Leusser, D.; Murso, A.; Stalke, D. Chem. Eur. J. 2004, 10,
3622. (f) Engelhardt, L. M.; Jacobsen, G. E.; Junk, P. C.; Raston, C. L.;
Skelton, B. W. J. Chem. Soc., Dalton Trans. 1988, 1011, and references
therein. (g) Deelman, B.-J.; Lappert, M. F.; Lee, H.-K.; Mak, T. C. W.;
Leung, W.-P.; Wei, P.-R. Organometallics 1997, 16, 1247. (h) Hitchcock,
P. B.; Liu, D.-S. J. Chem. Soc., Chem. Commun. 1994, 1699.
(15) (a) Kasani, A.; Babu, R. P. K.; McDonald, R.; Cavell, R. G. Angew.
Chem., Int. Ed. 1999, 38, 1483. (b) Ong, C. M.; Stephan, D. W. J. Am.
Chem. Soc. 1999, 121, 2939.
1
temperature H NMR spectra of complexes 7, 11, and 12 (7,
11, and 12 in C6D6 and 12 in C5D5N) proved that the
coordination mode of each of the complexes was retained at
higher temperature (until 333 K in C6D6 and 353 K in C5D5N).
The single-crystal X-ray diffraction structure of complex 7
is displayed in Figure 2; selected bond distances and bond angles
are listed in Table 2. Complex 7 is monomeric in the solid state.
The four-coordinated Mg is bonded to the methanide carbon
atom C1, ethyl carbon atom C21, quinolyl nitrogen atom N1,
and imino nitrogen atom N2 to form two metallacycles sharing
(16) Hitchcock, P. B.; Lappert, M. F.; Wang, Z.-X. J. Chem. Soc., Chem.
Commun. 1997, 1113.
(17) Hitchcock, P. B.; Lappert, M. F.; Uiterweerd, P. G. H.; Wang, Z.-
X. J. Chem. Soc., Dalton Trans. 1999, 3413.
(18) Babu, R. P. K.; Aparna, K.; McDonald, R.; Cavell, R. G. Inorg.
Chem. 2000, 39, 4981.
(19) (a) Gamer, M. T.; Roesky, P. W. Z. Anorg. Allg. Chem. 2001, 627,
877. (b) Leung, W.-P.; So, C.-W.; Wang, Z.-X.; Wang, J.-Z.; Mak, T. C.
W. Organometallics 2003, 22, 4305. (c) Babu, R. P. K.; Aparna, K.;
McDonald, R.; Cavell, R. G. Organometallics 2001, 20, 1451.

2246 Organometallics, Vol. 26, No. 9, 2007
Wang and Qi
Figure 3. ORTEP drawing of complex 8 shown with 30% thermal
ellipsoids.
Table 3. Selected Bond Distances (Å) and Angles (deg) of 8
Figure 2. ORTEP drawing of complex 7 shown with 30% thermal
ellipsoids.
Zn1-N1
2.076(4)
2.122(4)
1.601(4)
1.499(6)
102.90(15)
78.71(14)
126.88(11)
101.28(19)
104.3(3)
Zn1-N2
Zn1-Cl1
P1-C10
2.011(4)
2.1913(15)
1.787(4)
Zn1-C10
Table 2. Selected Bond Distances (Å) and Angles (deg) of 7
P1-N2
C8-C10
Mg1-C1
2.339(4)
2.187(3)
1.804(3)
1.515(4)
80.51(12)
101.45(12)
127.4(2)
103.70(19)
95.39(12)
121.5(2)
Mg1-C21
Mg1-N2
P1-N2
2.183(14)
2.108(3)
1.633(3)
N1-Zn1-N2
N2-Zn1-C10
N2-Zn1-Cl1
N2-P1-C10
C8-C10-Zn1
P1-N2-Zn1
N1-Zn1-C10
N1-Zn1-Cl1
C10-Zn1-Cl1
C8-C10-P1
P1-C10-Zn1
84.71(16)
110.02(12)
143.17(13)
122.2(3)
Mg1-N1
P1-C1
C1-C2
C1-Mg1-N1
N1-Mg1-N2
N2-Μg1-C21′
C2-C1-Μg1
P1-Ν2-Μg1
C2-C1-P1
C1-Mg1-N2
N1-Mg1-C21′
C1-Μg1-C21′
P1-C1-Μg1
C10-Ν1-Μg1
75.43(11)
114.7(3)
144.6(3)
83.43(12)
114.0(2)
84.50(17)
93.23(17)
Complex 8 is monomeric and crystallizes with two molecules
in the unit cell. An ORTEP structural drawing of a single
molecule is shown in Figure 3, and selected bond distances and
bond angles are listed in Table 3. The skeletal structure of
complex 8 is similar to that of complex 7. The Zn1-N1 distance
of 2.076(4) Å is slightly longer than the Zn1-N2 distance
[2.011(4) Å], and the latter represents a relatively short
interaction when compared with the corresponding distances
for other dative zinc-nitrogen bonds [2.070(4)-2.191(2)
Å].23a,26 The Zn1-C10 distance of 2.122(4) Å is longer than
the Zn-C σ-bond distances seen in [Zn(Br){C(SiMe3)2-
(SiMe2C5H4N-2)}]2 [2.037(4) Å],26c [Zn(Br){C(SiMe3)2(SiMe2-
NMe2)}]2 [2.045(3) Å],27 and [Zn(o-C6H4PPh2NSiMe3)2] [2.008-
(5) Å].28 Both P1-N2 and P1-C10 distances [1.601(4) and
1.787(4) Å, respectively] are shorter than those in complex 7.
The ORTEP drawing of complex 10 is presented in Figure
4. Selected bond distances and bond angles are listed in Table
4. Complex 10 is a monomer in the solid state. It has similar
structural skeleton to complex 8. However, the two structures
show some differences in bond lengths and angles. For example,
each of the N1-Zn1-N2, C3-Zn1-N1, C3-Zn1-N2, and
P1-C3-C9 bond angles in complex 10 is narrower than that
in complex 8. The Zn-N distances in complex 10 are longer
than those in complex 8. The Zn1-C3 distance of 2.172(2) Å
in complex 10 is also slightly longer than that in complex 8
[2.122(4) Å], and the former is comparable to the Zn-C distance
the Mg1-C1 edge. The magnesium atom exhibits a distorted
tetrahedral geometry. The Mg1-C21 distance of 2.183(14) Å
is slightly longer than those found in [Mg(CH2Ph){[N(2,6-
Pri2C6H3)C(Me)]2CH}(THF)] [2.1325(18) Å],20 [Mg(Et)-
{PhTpBut}] (PhTpBut ) phenyltris(3-tert-butylpyrazolyl)borato)
[2.163(2) Å],21 and [Mg(R){N(R)C5H3[ArNdC(Me)]2-2,6}] (R
) Me, Et, Pri) [2.122(2)-2.157(2) Å].22 The Mg1-C1 distance
of 2.339(4) Å is significantly longer than that of Mg1-C21.
This is probably a consequence of ring strain. A similar
structural feature is also found in [Mg(Cl){CH(P(Ph2)d
NSiMe3)2}]2 in which the Mg-C distance is 2.460(8) Å.12e The
Mg1-N1 distance of 2.187(3) Å is slightly longer than that of
Mg1-N2 [2.108(3) Å], and both are comparable to the dative
Mg-N bond distances in quinolyl, pyridyl, and iminophospho-
rane nitrogen atom coordinated magnesium complexes such as
[Mg{8-N(SiMe3)C9H6N}2], [Mg{2-C(SiMe3)2(C5H5N)}(Cl)]2,
[Mg2{{N(SiMe3)C(But)C(H)}2C4H2N2-2,3}Br2(THF)4], and [Mg-
{(Me3SiNdPPri2CH)2C5H3N-2,6}THF] [2.061(19)-2.220(2) Å].23
The phosphorus atom adopts a distorted tetrahedral geometry.
The P1-N2 diatance of 1.633(3) Å is normal for a coordinated
iminophosphorane24 and shows that the P-N bond has a bond
order that is larger than unity.25 The P1-C1 distance of 1.804-
(3) Å is indicative of a P-C single bond.
(20) Bailey, P. J.; Coxall, R. A.; Dick, C. M.; Fabre, S.; Henderson, L.
C.; Herber, C.; Liddle, S. T.; Loronn˜o-Gonza´lez, D.; Parkin, A.; Parsons,
S. Chem. Eur. J. 2003, 9, 4820.
(21) Kisko, J. L.; Fillebeeen, T.; Hascall, T.; Parkin, G. J. Organomet.
Chem. 2000, 596, 22.
(22) Blackmore, I. J.; Gibson, V. C.; Hitchcock, P. B.; Rees, C. W.;
Williams, D. J.; White, A. J. P. J. Am. Chem. Soc. 2005, 127, 6012.
(23) (a) Englehardt, L. M.; Junk, P. C.; Patalinghug, W. C.; Sue, R. E.;
Raston, C. L.; Skelton, B. W.; White, A. H. J. Chem. Soc., Chem. Commun.
1991, 930. (b) Andrews, P. C.; Brym, M.; Jones, C.; Junk, P. C.; Kloth, M.
Inorg. Chim. Acta 2006, 359, 355. (c) Leung, W.-P.; Ip, Q. W.-Y.; Lam,
T.-W.; Mak, T. C. W. Organometallics 2004, 23, 1284.
(24) Imhoff, P.; Nefkins, S. C. A.; Elsevier, C. J. Organometallics 1991,
10, 1421.
(25) (a) Corbridge, D. E. C. Phosphorus; Elsevier: Amsterdam, 1985;
p 38. (b) Imhoff, P.; van Asselt, R.; Elsevier, C. J.; Goubitz, K.; van Malssen,
K. F.; Stam, C. H. Phosphorus Sulfur 1990, 47, 401.
(26) (a) Tandon, S. S.; Chander, S.; Thompson, L. K.; Bridson, J. N.;
McKee, V. Inorg. Chim. Acta 1994, 219, 55. (b) Westerhausen, M.;
Bollwein, T.; Makropoulos, N.; Rotter, T. M.; Habereder, T.; Suter, M.;
No¨th, H. Eur. J. Inorg. Chem. 2001, 851. (c) Eaborn, C.; Hill, M. S.;
Hitchcock, P. B.; Smith, J. D. J. Chem. Soc., Dalton Trans. 2002, 2467.
(d) Kasani, A.; McDonald, R.; Cavell, R. G. Organometallics 1999, 18,
3775.
(27) Azarifar, D.; Coles, M. P.; El-Hamruni, S. M.; Eaborn, C.;
Hitchcock, P. B.; Smith, J. D. J. Organomet. Chem. 2004, 689, 1718.
(28) Wingerter, S.; Gornitzka, H.; Bertrand, G.; Stalke, D. Eur. J. Inorg.
Chem. 1999, 173.

ROP of ꢀ-CL and Mg and Zn Complexes
Organometallics, Vol. 26, No. 9, 2007 2247
8). In 70 mL of toluene, the polymerization gave 100%
conversion and 97% yield with wider PDI. When the molar
ratio of ꢀ-CL to 7 was 99, the polymerization could go to
completion within 3 min in 30 mL of toluene at 0 °C. The
molecular weights (Mn) determined by GPC are much higher
than the calculated Mn (based on the hypothesis of “living”
polymerization). This may be due to the presence of transes-
terifications in the process of reaction. The intermolecular chain-
transfer (via transesterification) results in formation of higher
molecular weights. A similar situation was also observed in the
ROP of ꢀ-CL catalyzed by [Mg(1,2-{N(PPh2)}2C6H4-κ2N,N′)-
(THF)2] and [ZnPr{1-N(PMes2)-2-N(PHMes2)C6H4-κ2N,N′}].31
1
The active catalyst was studied by H NMR spectroscopy.
To the solution of complex 7 in toluene was added dropwise
an equivalent of BnOH at 0 °C, and the mixture was stirred for
10 min 1H NMR spectrum showed that the reaction was
complete and the product formed was Ia (eq 1). The reason
that the reaction occurred on CH rather than CH2CH3 is probably
due to the existence of a strong ring strain in 7.
Figure 4. ORTEP drawing of complex 10 shown with 30% thermal
ellipsoids.
Table 4. Selected Bond Distances (Å) and Angles (deg) of 10
Zn1-N1
2.0584(15)
2.172(2)
1.5853(16)
1.477(3)
96.15(6)
80.97(7)
115.49(10)
103.04(9)
105.90(15)
93.65(7)
Zn1-N2
Zn1-C20
P1-C3
2.1651(17)
1.975(2)
1.7737(19)
Zn1-C3
P1-N1
C3-C9
N1-Zn1-N2
N2-Zn1-C3
N2-Zn1-C20
N1-P1-C3
C9-C3-Zn1
P1-N1-Zn1
N1-Zn1-C3
N1-Zn1-C20
C3-Zn1-C20
C9-C3-P1
76.90(6)
128.44(10)
143.99(11)
120.51(14)
84.80(8)
P1-C3-Zn1
for the η1-ring of [Zn(Pri4C5H)2] [(2.223(4) Å)].29 The Zn1-
C20 distance of 1.975(2) Å in complex 10 is in the expected
range for terminal zinc alkyl complexes.22,30
Complex 7 was also effective for the ROP of ꢀ-CL in the
absence of benzyl alcohol. A 100% conversion was achieved
within 3 min at a [CL]0/7 ratio of 200 in toluene at 0 °C. This
gave PCL with high Mn and narrow PDI (Table 5, entry 10).
From the 1H NMR spectrum of PCL we cannot judge which of
the CH and CH2CH3 groups inserts to ꢀ-CL due to the high
molecular weight of the PCL obtained.
Ring-Opening Polymerization of ꢀ-CL Catalyzed by 7 and
9-12. Organomagnesium complex 7 was highly active for the
ring-opening polymerization of ꢀ-CL in the presence or absence
of benzyl alcohol (BnOH) in toluene or THF. In the presence
of BnOH, the polymerization was found to be an exothermic
reaction and proceeded extremely fast. When polymerization
was performed at a [CL]0/7 ratio of 200:1 in 7 mL of toluene
at 25 °C, the lactone became gum rapidly during the period of
dropwise addition. This led to the catalyst being wrapped, and
the polymerization reaction could not go to completion. The
Complexes 9-12 were also investigated on their catalytic
behavior in the ROP of ꢀ-CL in the presence of benzyl alcohol.
Experimental results indicated that each of the complexes 9-12
had lower activity than the 7/BnOH system. The reactions were
carried out at 60 °C, and more than 90% conversions were
achieved in 60-156 min (Table 6, entries 1-7). These reactions
1
conversion of the monomer stopped at 67%, indicated by H
NMR spectrum. The poly(ꢀ-caprolactone) was identified by gel
permeation chromatography (GPC) with Mn ) 213 399 kg/mol
and polydispersity indice (PDI) ) 1.30 (Table 5, entry 1). To
reduce the reaction rate, we performed the polymerization at 0
°C in 20 mL of toluene or THF and the results are listed in
Table 5 (entries 2 and 3, respectively). Under these conditions,
the polymerization could achieve completion and gave high
yields of polymers. If the reaction was carried out in 40 mL of
toluene at 0 °C, the reaction proceeded more smoothly and
formed polymer with higher molecular weight (Table 5, entry
4). We further tried the polymerization reactions with a different
ratio of ꢀ-CL to 7. When the molar ratio of ꢀ-CL to 7 was about
500, the reaction in 20 mL of toluene at 0 °C or in 30 mL of
toluene at -25 °C gave gum, which resulted in low conversion
of monomer and low yields of polymers but much larger
molecular weights (determined by GPC) (Table 5, entries 7 and
gave PCLs with relatively low molecular weights (Mn
)
26 200-39 321) and narrow PDIs (1.01-1.09). The catalytic
active species of complex 12 in the presence of BnOH was
1
studied by H NMR spectroscopy, and the result proved to be
Ib (eq 1), similar to that of complex 7. Due to the catalytic
reactions run at 60 °C, we carried out a variable-temperature
1H NMR spectral study in C6D6 for Ib to see if the structure
was retained at higher temperature. The result revealed that the
structure was unchanged until 333 K.
The catalytic behavior of complex 12 was also studied in
the absence of benzyl alcohol, and the results showed that it
had very low catalytic activity in the ROP of ꢀ-CL (Table 6,
entry 8).
The kinetics of the ROPs catalyzed by 9-12 in the presence
of BnOH was determined in toluene. Plots of ln([M]0/[M]) vs
time are shown in Figure 5. For each of complexes 9-12 the
plot of ln([M]0/[M]) vs time exhibited well a linear relationship,
which indicated that the polymerization proceeded with first-
order dependence on the monomer concentration. The first-order
kinetics implied that the concentration of active species remained
unchanged, or, in other words, the growing polymer chain
(29) Burkey, D. J.; Hanusa, T. P. J. Organomet. Chem. 1996, 512, 165.
(30) (a) Westerhausen, M.; Bollwein, T.; Makropoulos, N.; Rotter, T.
M.; Habereder, T.; Suter, M.; No¨th, H. Eur. J. Inorg. Chem. 2001, 851. (b)
Dove, A. P.; Gibson, V. C.; Marshall, E. L.; White, A. J. P.; Williams, D.
J. Dalton Trans. 2004, 570. (c) Kasani, A.; McDonald, R.; Cavell, R. G.
Organometallics 1999, 18, 3775. (d) Coles, M. P.; Hitchcock, P. B. Eur. J.
Inorg. Chem. 2004, 2662. (e) Hannant, M. D.; Schormann, M.; Bochmann,
M. J. Chem. Soc., Dalton Trans. 2002, 4071. (f) Allen, S. D.; Moore, D.
R.; Lobkovsky, E. B.; Coates, G. W. J. Organomet. Chem. 2003, 683, 137.
(31) Mjaoumo-Mbe, F.; Smolensky, E.; Lo¨nnecke, P.; Shpasser, D.;
Eisen, M. S.; Hey-Hawkins, E. J. Mol. Catal. A: Chem. 2005, 240, 91.

2248 Organometallics, Vol. 26, No. 9, 2007
Table 5. Ring-Opening Polymerization of E-CL Catalyzed by Complex 7a
entry temp (°C) cat. (mmol) BnOH (mmol) [M]0/[BnOH]0 solvent vol (mL) time (min) conv. (%) Mn b (GPC) yield (%)
Wang and Qi
PDI
1c
2
3
4
5
25
0
0
0
0
0
0
0.104
0.104
0.104
0.102
0.105
0.099
0.099
0.101
0.102
0.107
0.104
0.104
0.104
0.103
0.104
0.099
0.1
199
201
199
203
99
400
498
506
488
7
20
20d
40
30
60
20
30
70
30
<1
4
<1
4
67
100
93
100
100
99
66
57
100
100
213 399
121 800
141 839
196 000
91 162
151 311
314 093
303 203
209 889
255 200
62
87
91
93
93
97
65
54
97
95
1.30
1.32
1.26
1.04
1.16
1.14
1.03
1.88
1.54
1.16
3
6
10
<1
<1
7
7c
8c
9
-25
0.1
0.104
0
0
10
3
a Catalytic polymerization was carried out in toluene except entry 3. b Obtained from GPC analysis and calibrated polystyrene standard. c Gum was
formed during the period of addition of ꢀ-caprolactone. d THF solvent.
Table 6. Ring-Opening Polymerization of E-CL Catalyzed by Complexes 9-12 in the Presence of Benzyl Alcohol at 60 °C
entry cat. (mmol) BnOH (mmol) [M]0/[BnOH]0 solvent vol. (mL) time (min) conv. (%) Mn a (calcd) Mn b (NMR) Mn c (GPC) yield (%) PDI
1
2
3
4
5
6
7
8
9 (0.105)
10 (0.105)
10 (0.107)
11 (0.105)
11 (0.101)
12 (0.104)
12 (0106)
12 (0.105)
0.105
0.105
0.104
0.105
0.102
0.104
0.107
198
199
200
202
202
200
197
12
7
12
7
12
7
12
30
156
61
89
34
60
47
120
57
90
71
92
67
100
74
20 400
16 200
21 100
15 500
23 100
16 800
22 500
22 200
19 100
22 200
20 100
22 800
24 300
26 100
26 200
28 114
35 300
29 620
39 121
33 410
34 036
30 415
82
67
88
62
96
65
92
13
1.01
1.03
1.01
1.03
1.09
1.05
1.01
1.92
100
20
a Calculated from the molecular weight of ꢀ-caprolactone times the conversion of monomer and the ratio of [M]0/[BnOH]0 plus the molecular weight of
1
BnOH. b Obtained from the H NMR spectral analysis. c Obtained from GPC analysis and calibrated polystyrene standard.
Figure 6. Plot of PCL Mn (9) and polydispersity (b) as a function
Figure 5. Plots of ln([M]0/[M]) vs time for the polymerization of
of conversion with ꢀ-caprolactone and 12 in the presence of an
equivalent of BnOH in toluene at 60 °C.
ꢀ-caprolactone catalyzed by (9) 9, (b) 10, (f) 11, and (2) 12 in
toluene in the presence of an equivalent of BnOH at 60 °C.
1
The H NMR spectral studies of the PCLs revealed that the
polymer chains were capped with one benzyl ester (δ 7.28 and
remained alive during the entire polymerization. The plot also
revealed that there was an induction period before each of 10-
5.05 ppm, respectively, for OCH2Ph) and one hydroxyl end (δ
12 initiated the ROP reaction, while 9 did not require an
3.58 ppm for CH2OH). This indicated that the polymerization
induction period. The lack of an induction period for 9 may be
mainly related to the electronic effect of the phenyl group on
the central metal because a more sterically hindered phenyl
group should lead to a longer induction period based on the
reaction was initiated through the insertion of the benzyl alkoxyl
group to ꢀ-CL followed by ring opening via acyl-oxygen
cleavage.
tendency seen in complexes 10 and 12. The plots also showed
that the two lines of ln([M]0/[M]) vs time for the ROP catalyzed
Conclusion
by 11 and 12 are almost parallel. This indicated that the
substisuents on the phosphorus atom affected mainly the
induction period rather than reaction rates.
We have synthesized and characterized lithium, magnesium,
and zinc iminophosphorano(8-quinolyl)methanide complexes.
The single-crystal X-ray diffraction result shows that lithium
The relationship between the number average molecular
weight and ꢀ-CL conversion was also studied for the complex
12/BnOH system (Figure 6). The linear relationship of Mn vs
ꢀ-CL conversion and the low polydispersities of the PCLs
obtained (1.02-1.05) showed that the polymerization proceeded
in a living fashion.
complex 6 is dimeric and consists of two enantiomers. The
magnesium complex exhibited excellent catalytic activity
in the ROP of ꢀ-CL in the presence or absence of BnOH,
yielding PCL with high molecular weights. The zinc complexes
also showed good catalytic activity in the ROP of ꢀ-CL in the
presence of BnOH. The kinetic studies revealed that the

ROP of ꢀ-CL and Mg and Zn Complexes
Organometallics, Vol. 26, No. 9, 2007 2249
1.68-1.85 (m, 2H, CHMe2), 3.83 (d, J ) 12.4 Hz, 2H, CH2), 6.68
(dd, J ) 4.1, 8.2 Hz, 1H, C9H6N), 7.19-7.22 (m, 2H, C9H6N),
7.45 (dd, J ) 1.8, 8.4 Hz, 1H, C9H6N), 8.25-8.29 (m, 1H, C9H6N),
8.60-8.62 (m, 1H, C9H6N). 13C{1H} NMR (CDCl3): δ 16.90 (d,
J ) 2.4 Hz, CHMe2), 17.33 (d, J ) 2.8 Hz, CHMe2), 27.17 (d, J
) 63.1 Hz, CHMe2), 27.93 (d, J ) 57.7 Hz, PCH2), 36.67 (d, J )
7.1 Hz, CMe3), 50.55 (d, J ) 3.7 Hz, CMe3), 120.72 (C9H6N),
125.94 (d, J ) 2.5 Hz, C9H6N), 126.28 (d, J ) 2.7 Hz, C9H6N),
128.64 (d, J ) 1.5 Hz, C9H6N), 131.49 (d, J ) 4 Hz, C9H6N),
135.39 (d, J ) 7.7 Hz, C9H6N), 136.28 (C9H6N), 147.35 (d, J )
4.7 Hz, C9H6N), 149.10 (C9H6N). 31P{1H} NMR (CDCl3): δ 9.34.
Anal. Calcd for C20H31N2P: C, 72.69; H, 9.46; N, 8.48. Found:
C, 72.64; H, 9.42; N, 8.38.
Preparation of [Li{CH(8-C9H6N)(R2PdNBut)}(L)] (R ) Ph,
L ) THF, 5; R ) Pri, L ) Absent, 6). BunLi (0.51 mL, 2.89 M
solution in hexanes, 1.47 mmol) was added dropwise to a stirred
solution of 3 (0.58 g, 1.46 mmol) in THF (10 mL) at about -80
°C. The mixture was warmed to room temperature and stirred
overnight. The solution was filtered, and then the filtrate was
concentrated under vacuum to give red crystalline 5 (0.46 g, 66.3%),
mp 132-136 °C. 1H NMR (C6D6): δ 1.40-1.44 (m, 4H, C4H8O),
1.51 (s, 9H, CMe3), 3.55-3.59 (m, 5H, CH + C4H8O), 6.02 (b,
1H, C9H6N + Ph), 6.22 (b, 1H, C9H6N + Ph), 6.67 (dd, J ) 4.5,
8.1 Hz, 1H, C9H6N + Ph), 6.96-7.33 (m, 8H, C9H6N + Ph), 7.99
(b, 4H, C9H6N + Ph), 8.49 (d, J ) 2.7 Hz,1H, C9H6N + Ph). 13C-
{1H} NMR (C6D6): δ 25.82 (THF), 35.91 (d, J ) 10.3 Hz, PCH),
51.50 (d, J ) 8.1 Hz, CMe3), 67.84 (THF), 112.94 (C9H6N), 114.8
(C9H6N), 120.28 (C9H6N), 127.19 (C9H6N), 127.86 (C9H6N), 127.92
(C9H6N), 128.17, 128.23, 129.33, 129.74, 130.11, 132.39 (d, J )
9.3 Hz), 132.91, 137.34 (C9H6N), 145.79 (C9H6N). 31P{1H} NMR
(C6D6): δ 6.00. Anal. Calcd for C26H26N2PLi‚THF: C, 75.62; H,
7.19; N, 5.88. Found: C, 75.29; H, 7.00; N, 6.17.
catalytic reactions were first-order-dependent on monomer
concentration and showed “living” characters. Investigation
by H NMR spectroscopy showed that the active species of
1
the Mg and Zn complexes in the presence of BnOH were
[M(R1)OCH2Ph{N(But)dP(R2)CH2(8-C9H6N)}] (M ) Mg, Zn).
Experimental Section
General Procedures. All reactions were performed under
nitrogen atmosphere using standard Schlenk and vacuum line
techniques. Solvents were distilled under nitrogen over sodium
(toluene, dioxane), sodium/benzophenone (THF, Et2O, and n-
hexane) or CaH2 (CH2Cl2) and degassed prior to use. PhLi, Et2-
Mg, Pri2PNHBut, and 8-bromomethylquinoline were prepared
according to literature methods.32-35 Compounds 1 and 3 were
prepared according to our previously reported methods.12h BunLi,
MeLi, and Et2Zn were purchased from Alfa Aesar and used as
received. CDCl3 and C6D6, purchased from Acros Organics, were
degassed and stored over 4A molecular sieves (CDCl3) or Na/K
alloy (C6D6). ꢀ-Caprolactone, purchased from Acros Organics, was
dried over 4A molecular sieves. NMR spectra were recorded on a
Bruker av300 spectrometer at ambient temperature. The chemical
1
shifts of the H and 13C NMR spectra were referenced to internal
solvent resonances; the 31P NMR spectra were referenced to external
85% H3PO4. Elemental analyses were performed by the Analytical
Center of the University of Science and Technology of China. Gel
permeation chromatography (GPC) measurements were performed
on a Waters 150C instrument equipped with UltraStyragel columns
(103, 104, and 105 Å) and 410 refractive index detector, using
monodispersed polystyrene as calibration standard. THF (HPLC
grade) was used as eluent at a flow rate of 1 mL/min.
Preparation of [Pri2P(CH2C9H6N-8)NHBut]+Br- (2). A solu-
tion of 8-bromomethylquinoline (7.88 g, 35.5 mmol) in CH2Cl2
(30 mL) was added dropwise to a solution of Pri2PNHBut (6.72 g,
35.50 mmol) in CH2Cl2 (40 mL) at room temperature with stirring.
Stirring of the mixture was continued overnight, and then the solvent
was removed under vacuum. The residue was washed with benzene
and dried under vacuum to give white powder 2 (14.57 g, 99.8%),
mp 194-196 °C. 1H NMR (CDCl3): δ 1.13 (dd, J ) 7.5, 17.1 Hz,
6H, CHMe2), 1.31 (dd, J ) 6.9, 17.7 Hz, 6H, CHMe2), 1.37 (s,
9H, CMe3), 2.89-3.02 (m, 2H, CHMe2), 4.65 (d, J ) 14.1 Hz,
2H, CH2), 6.64 (s, 1H, NH), 7.47-7.57 (m, 2H, C9H6N) 7.79 (d,
J ) 8.1 Hz, 1H, C9H6N), 8.23 (dd, J ) 1.5 Hz, J ) 8.4 Hz, 1H,
C9H6N), 8.46 (d, J ) 6.9 Hz, 1H, C9H6N), 8.84-8.86 (m, 1H,
C9H6N). 13C{1H} NMR (CDCl3): δ 15.96 (CHMe2), 16.10 (CHMe2),
23.41 (d, J ) 58.9 Hz, CHMe2), 24.87 (d, J ) 51.8 Hz, CHMe2),
32.22 (CMe3), 53.59 (d, J ) 5.1 Hz, CMe3), 121.74 (C9H6N), 126.90
(C9H6N), 128.33 (d, J ) 3 Hz, C9H6N), 128.42 (d, J ) 1.7 Hz,
C9H6N), 128.70 (d, J ) 8.7 Hz, C9H6N), 133.28 (d, J ) 6.6 Hz,
C9H6N), 137.45 (C9H6N), 145.88 (C9H6N), 149.41 (C9H6N). 31P-
{1H} NMR (CDCl3): δ 58.56. Anal. Calcd for C20H32N2PBr: C,
58.40; H, 7.84; N, 6.81. Found: C, 58.58; H, 7.61; N, 6.80.
Preparation of Pri2P(CH2C9H6N-8)dNBut (4). A mixture of
2 (3.58 g, 8.7 mmol), NaH (1 g, 57-63%, 23-26 mmol), and THF
(30 mL) was stirred for 2 h at room temperature and then refluxed
for 4 h. The mixture was filtered, and the solvent was removed
from the filtrate under vacuum. The residue was dissolved in
hexane, concentrated under vacuum, and stored at 0 °C to form
Complex 6 was prepared using similar procedure. Thus, treatment
of the solution of 4 (1.38 g, 4.18 mmol) in THF (15 mL) with
BunLi (1.45 mL, 2.89 M solution in hexanes, 4.19 mmol) gave,
after crystallizing from Et2O, red crystalline solid 6 (1.11 g, 79%),
mp 138-142 °C. 1H NMR (C6D6): δ 0.88-1.30 (m, 12H, CHMe2),
1.66 (s, 9H, CMe3), 1.98-2.21 (b, 1H, CHMe2), 2.49-2.77 (b, 1H,
CHMe2), 3.16 (d, J ) 11.7 Hz, 1H, CH), 6.02 (d, J ) 7.5 Hz, 1H,
C9H6N), 6.29 (t, J ) 7.5 Hz, 1H, C9H6N), 6.66 (d, J ) 7.2 Hz, 1H,
C9H6N), 6.73-6.77 (m,1H, C9H6N), 7.39 (d, J ) 8.1 Hz, 1H,
C9H6N), 8.53 (s, 1H, C9H6N). 13C{1H} NMR (C6D6): δ 18.44
(CHMe2), 20.48 (CHMe2), 28.01 (d, J ) 57.9 Hz, CHMe2), 30.21
(CMe3), 35.84 (d, J ) 9.1 Hz, PCH), 51.17 (d, J ) 7.2 Hz, CMe3),
111.37 (C9H6N), 113.02 (d, J ) 2.5 Hz, C9H6N), 120.22 (C9H6N),
127.24 (C9H6N), 127.85 (C9H6N), 128.17 (C9H6N), 137.34 (C9H6N),
145.14 (C9H6N), 146.59 (C9H6N). 31P{1H} NMR (C6D6): δ 31.34.
Anal. Calcd for C20H30N2PLi: C, 71.41; H, 8.99; N, 8.33. Found:
C, 71.31; H, 9.00; N, 8.15.
Preparation of [Mg(Et){CH(8-C9H6N)(Pri2PdNBut)}] (7).
MgEt2 (0.14 g, 1.70 mmol) was dissolved in THF (5 mL), and the
resulting solution was transferred into a stirred solution of 4 (0.28
g, 0.85 mmol) in THF (10 mL) at about -80 °C. Stirring of the
mixture was continued overnight at room temperature, and then it
was refluxed for 4 h. Solvents were removed under vacuum. The
residue was dissolved in hexane and then filtered. Concentration
of the filtrate afforded dark-red crystals of 7 (0.22 g, 67.8%), mp
1
98-100 °C. H NMR (C6D6): δ 0.14 (dd, J ) 7.2, 13.5 Hz, 3H,
1
CHMe2), 0.41 (q, J ) 8.4 Hz, 2H, CH2CH3), 0.71 (dd, J ) 6.9,
15.6 Hz, 3H, CHMe2), 1.00 (dd, J ) 7.2, 14.7 Hz, 3H, CHMe2),
1.30 (dd, J ) 6.9, 13.8 Hz, 3H, CHMe2), 1.34 (s, 9H, CMe3), 1.70-
1.94 (m, 2H, CHMe2), 2.07 (t, J ) 8.1 Hz, 3H, CH2CH3), 2.33 (d,
J ) 2.4 Hz, 1H, CH), 6.61 (dd, J ) 4.5, 8.4 Hz, 1H, C9H6N),
7.04-7.08 (m, 1H, C9H6N), 7.21-7.27 (m, 1H, C9H6N), 7.36-
7.39 (m, 1H, C9H6N), 7.56 (dd, J ) 1.5, 8.4 Hz, 1H, C9H6N), 8.38
(dd, J ) 1.2, 4.2 Hz, 1H, C9H6N). 13C{1H} NMR (C6D6): δ -1.87
(CH2CH3), 14.59 (CH2CH3), 16.21 (d, J ) 2.6 Hz, CHMe2), 16.39
yellowish crystals of 4 (2.31 g, 80.5%), mp 58-60 °C. H NMR
(CDCl3): δ 0.78 (dd, J ) 7.2, 14.6 Hz, 6H, CHMe2), 0.92 (dd, J
) 7.1, 14.3 Hz, 6H, CHMe2), 1.40 (d, J ) 0.9 Hz, 9H, CMe3),
(32) Wakefield, B. J. Organolithium Methods; Academic Press: London,
1988; p 24.
(33) Salinger, R. M.; Mosher, H. S. J. Am. Chem. Soc. 1964, 86, 1782.
(34) Sisler, H. R.; Smith, N. L. J. Org. Chem. 1961, 26, 611.
(35) Dupont, J.; Halfen, R. A. P.; Zinn, F. K.; Pfeffer, M. J. Organomet.
Chem. 1994, 484, C8.

2250 Organometallics, Vol. 26, No. 9, 2007
Wang and Qi
(CHMe2), 16.61 (d, J ) 3.2 Hz, CHMe2), 16.83 (d, J ) 2.1 Hz,
CHMe2), 28.01 (d, J ) 74.8 Hz, PCH), 28.37 (d, J ) 51 Hz,
CHMe2), 28.45 (d, J ) 41.4 Hz, CHMe2), 35.46 (d, J ) 7.4 Hz,
CMe3), 50.75 (d, J ) 7.2 Hz, CMe3), 119.69 (d, J ) 4.3 Hz,
C9H6N), 120.75 (C9H6N), 127.89 (d, J ) 3.6 Hz, C9H6N), 129.86
(d, J ) 2.9 Hz, C9H6N), 131.17 (d, J ) 8.4 Hz, C9H6N), 138.36
(C9H6N), 146.51 (C9H6N), 148.41 (d, J ) 1.3 Hz, C9H6N), 148.44
(d, J ) 4.3 Hz, C9H6N). 31P{1H} NMR (C6D6): δ 34.61. Anal.
Calcd for C22H35N2PMg: C, 69.03; H, 9.22; N, 7.32. Found: C,
68.17; H, 9.28; N, 7.42.
filtration, concentration of the filtrate afforded orange crystals of
10 (0.30 g, 76.8%), mp 82-86 °C. H NMR (C6D6): δ 0.12 (s,
1
3H, Me), 0.14 (dd, J ) 7.5, 13.5 Hz, 3H, CHMe2), 0.70 (dd, J )
6.9, 15 Hz, 3H, CHMe2), 1.02 (dd, J ) 7.2, 14.4 Hz, 3H, CHMe2),
1.34 (s, 9H, CMe3), 1.36 (dd, J ) 6.9, 13.8 Hz, 3H, CHMe2), 1.71-
1.87 (m, 2H, CHMe2), 2.60 (s, 1H, CH), 6.64 (dd, J ) 4.5, 8.4 Hz,
1H, C9H6N), 7.03-7.07 (m, 1H, C9H6N), 7.15-7.21 (m, 1H,
C9H6N), 7.31-7.34 (m, 1H, C9H6N), 7.48 (dd, J ) 1.6, 8.2 Hz,
1H, C9H6N), 8.39-8.41 (m, 1H, C9H6N). 13C{1H} NMR (C6D6):
δ -13.20 (Me), 16.08 (d, J ) 2 Hz, CHMe2), 16.50 (CHMe2), 16.90
(CHMe2), 16.92 (d, J ) 3.3 Hz, CHMe2), 28.22 (d, J ) 48.8 Hz,
CHMe2), 28.38 (d, J ) 38 Hz, CHMe2), 29.14 (d, J ) 81.8 Hz,
PCH), 35.17 (d, J ) 7.5 Hz, CMe3), 50.99 (d, J ) 7.1 Hz, CMe3),
120.89 (d, J ) 4.5 Hz, C9H6N), 120.02 (C9H6N), 127.53 (d, J )
3.8 Hz, C9H6N), 129.53 (d, J ) 2.6 Hz, C9H6N), 131.20 (d, J )
8.2 Hz, C9H6N), 137.38 (C9H6N), 146.87 (C9H6N), 147.83 (d, J )
5.6 Hz, C9H6N), 148.27 (d, J ) 3.5 Hz, C9H6N). 31P{1H} NMR
(C6D6): δ 44.12. Anal. Calcd for C21H33N2PZn: C, 61.54; H, 8.12;
N, 6.83. Found: C, 60.83; H, 8.05; N, 6.72.
Preparation of [Zn(Cl){CH(8-C9H6N)(Pri2PdNBut)}] (8). A
solution of 6 prepared from 4 (2.18 g, 6.60 mmol) and LiBun (2.3
mL, 2.89 M solution in hexanes, 6.65 mmol) in Et2O (30 mL) was
added into a stirred suspension of ZnCl2 (0.99 g, 7.26 mmol) in
Et2O (10 mL) at about -80 °C. The mixture was stirred overnight
at room temperature and then filtered. The residual solid was dried
under vacuum and then extracted with toluene (2 × 30 mL). The
extract was concentrated to afford yellow crystals of 8 (1.41 g,
1
49.7%), mp 156-160 °C. H NMR (C6D6): δ 0.24 (dd, J ) 7.4,
13.7 Hz, 3H, CHMe2), 0.78 (dd, J ) 7.1, 15.6 Hz, 3H, CHMe2),
1.16 (dd, J ) 7.3, 15 Hz, 3H, CHMe2), 1.50 (dd, J ) 6.9, 14.2 Hz,
3H, CHMe2), 1.54 (s, 9H, CMe3), 1.84-2.04 (m, 2H, CHMe2), 2.83
(s, 1H, CH), 6.81 (dd, J ) 4.5, 8.3 Hz, 1H, C9H6N), 7.25-7.36
(m, 2H, C9H6N), 7.45-7.49 (m, 1H, C9H6N), 7.66 (dd, J ) 1.6,
8.3 Hz, 1H, C9H6N), 8.77-8.79 (m, 1H, C9H6N). 13C{1H} NMR
(C6D6): δ 15.82 (d, J ) 2.9 Hz, CHMe2), 16.37 (d, J ) 1 Hz,
CHMe2), 16.65 (d, J ) 2.6 Hz, CHMe2), 16.81 (d, J ) 3.1 Hz,
CHMe2), 27.34 (d, J ) 65.1 Hz, CHMe2), 27.92 (d, J ) 73.1 Hz,
CHMe2), 29.32 (d, J ) 77.6 Hz, PCH), 34.96 (d, J ) 7.2 Hz, CMe3),
51.56 (d, J ) 7.5 Hz, CMe3), 121.35 (d, J ) 1 Hz, C9H6N), 122.66
(d, J ) 4.2 Hz, C9H6N), 127.52 (d, J ) 3.9 Hz, C9H6N), 129.22
(d, J ) 2.6 Hz, C9H6N), 132.73 (d, J ) 7.5 Hz, C9H6N), 138.70
(C9H6N), 144.52 (d, J ) 5.9 Hz, C9H6N), 147.22 (d, J ) 3.9 Hz,
C9H6N), 147.79 (C9H6N). 31P {1H} NMR (C6D6): δ 82.67. Anal.
Calcd for C20H30N2PZnCl: C, 55.83; H, 7.03; N, 6.51. Found: C,
55.66; H, 6.97; N, 6.38.
Preparation of [Zn(Ph){CH(8-C9H6N)(Pri2PdNBut)}] (9).
LiPh (2.45 mL, 0.48 M solution in Et2O, 1.18 mmol) was added
dropwise to a stirred solution of 8 (0.49 g, 1.14 mmol) in toluene
(10 mL) at about -80 °C. The reaction mixture was allowed to
warm to room temperature and stirred overnight. The precipitate
was filtered off, and the solvent was removed from the filtrate under
vacuum. The residue was dissolved in Et2O, and the solution was
concentrated to form orange crystals of 9 (0.35 g, 65.1%), mp 136-
140 °C. 1H NMR (C6D6): δ 0.19 (dd, J ) 7.2, 13.2 Hz, 3H,
CHMe2), 0.78 (dd, J ) 6.9, 15.3 Hz, 3H, CHMe2), 1.09 (dd, J )
6.9, 14.4 Hz, 3H, CHMe2), 1.48 (dd, J ) 6.9, 13.8 Hz, 3H, CHMe2),
1.41 (s, 9H, CMe3), 1.78-1.98 (m, 2H, CHMe2), 2.74 (s, 1H, CH),
6.72 (dd, J ) 4.2, 7.8 Hz, 1H, C9H6N), 7.14-7.29 (m, 2H, C9H6N),
7.41-7.48 (m, 2H, C9H6N), 7.55-7.63 (m, 3H, Ph), 8.18 (d, J )
7.2 Hz, 2H, Ph), 8.58 (d, J ) 3.9 Hz, 1H, C9H6N). 13C{1H} NMR
(C6D6): δ 16.01 (d, J ) 2.5 Hz, CHMe2), 16.46 (CHMe2), 16.81
(d, J ) 2 Hz, CHMe2), 16.96 (d, J ) 3 Hz, CHMe2), 28.26 (d, J )
33.1 Hz, CHMe2), 28.33 (d, J ) 54.2 Hz, CHMe2), 28.70 (d, J )
80.6 Hz, PCH), 35.31 (d, J ) 7.4 Hz, CMe3), 51.05 (d, J ) 6.9
Hz, CMe3), 121.04 (C9H6N), 121.26 (d, J ) 4.4 Hz, C9H6N), 125.80
(C9H6N), 127.38 (Ph), 127.59 (Ph), 127.64 (Ph), 127.91 (Ph),
128.59 (C9H6N), 131.66 (d, J ) 8.1 Hz, C9H6N), 137.71 (C9H6N),
139.85 (C9H6N), 147.52 (C9H6N), 157.65 (C9H6N). 31P{1H} NMR
(C6D6): δ 47.66. Anal. Calcd for C26H35N2PZn: C, 66.17; H, 7.48;
N, 5.94. Found: C, 65.99; H, 7.51; N, 5.71.
Preparation of [Zn(Et){CH(8-C9H6N)(R2PdNBut)}] (R ) Ph,
11; R ) Pri, 12). ZnEt2 (4.9 mL, 0.882 M solution in hexane,
4.32 mmol) was added dropwise to a stirred solution of 3 (0.85 g,
2.13 mmol) in toluene (30 mL) at about -80 °C. The mixture was
stirred overnight at room temperature and then refluxed for 7 h.
Solvents were removed under vacuum. The residue was dissolved
in hexane and filtered. Concentration of the filtrate afforded yellow
crystals of 11 (0.94 g, 89.6%), mp 128-134 °C. 1H NMR (C6D6):
δ 1.21 (dq, J ) 1.8, 8.1 Hz, CH2CH3), 1.38 (s, 9H, CMe3), 2.07 (t,
J ) 8.1 Hz, 3H, CH2CH3), 3.27 (d, J ) 2.4 Hz, 1H, CH), 6.74-
6.88 (m, 4H, C9H6N + Ph), 7.01-7.14 (m, 5H, C9H6N + Ph),
7.26-7.28 (m, 3H, C9H6N + Ph), 7.53 (dd, J ) 1.2, 8.1 Hz, 1H,
C9H6N + Ph), 8.07-8.14 (m, 2H, C9H6N + Ph), 8.61-8.64 (m,
1H, C9H6N + Ph). 13C{1H} NMR (C6D6): δ 1.16 (CH2CH3), 14.47
(CH2CH3), 34.53 (d, J ) 9.3 Hz, CMe3), 36.36 (d, J ) 84.2 Hz,
PCH), 51.66 (d, J ) 7.7 Hz, CMe3), 120.78 (C9H6N), 121.47 (d, J
) 5.3 Hz, C9H6N), 127.15 (d, J ) 10.5 Hz, Ph), 128.53 (Ph), 129.28
(d, J ) 3.4 Hz, C9H6N), 129.46 (d, J ) 2.9 Hz, Ph), 130.53 (d, J
) 2.6 Hz, Ph), 131.73 (d, J ) 8.7 Hz, C9H6N), 131.88 (d, J ) 9.2
Hz, Ph), 132.24 (d, J ) 8.6 Hz, Ph), 134.58 (d, J ) 68.4 Hz, Ph),
137.11 (C9H6N), 137.61 (C9H6N), 138.09 (Ph), 145.81 (d, J ) 5.5
Hz, C9H6N), 147.23 (C9H6N), 148.05 (d, J ) 4.3 Hz, C9H6N). 31P-
{1H} NMR (C6D6): δ 20.04. Anal. Calcd for C28H31N2PZn: C,
68.36; H, 6.35; N, 5.69. Found: C, 68.03; H, 6.35; N, 5.61.
Complex 12 was prepared using a similar procedure. Thus, ZnEt2
(4.23 mL, 0.882 M solution in hexane, 3.73 mmol) was reacted
with a solution of 4 (0.62 g, 1.88 mmol) in toluene (30 mL),
affording, after similar workup, yellow crystals of 12 (0.58 g,
1
72.9%), mp 118-121 °C. H NMR (C6D6): δ 0.23 (dd, J ) 7.2,
13.2 Hz, 3H, CHMe2), 0.80 (dd, J ) 6.9, 15 Hz, 3H, CHMe2),
1.05-1.16 (m, 5H, CHMe2 + CH2CH3), 1.44 (d, J ) 0.6 Hz, 9H,
CMe3), 1.46 (dd, J ) 6.9, 13.8 Hz, 3H, CHMe2), 1.84-1.95 (m,
2H, CHMe2), 2.03 (t, J ) 8.1 Hz, 3H, CH2CH3), 2.71 (s, 1H, CH),
6.75 (dd, J ) 4.5, 8.4 Hz, 1H, C9H6N), 7.12-7.16 (m, 1H, C9H6N),
7.25-7.30 (m, 1H, C9H6N), 7.41-7.45 (m, 1H, C9H6N), 7.58 (dd,
J ) 1.5 Hz, J ) 8.1 Hz, 1H, C9H6N), 8.54-8.56 (m, 1H, C9H6N).
13C{1H} NMR (C6D6): δ 0.66 (CH2CH3), 1.44 (CH2CH3), 14.62
(CHMe2), 16.06 (d, J ) 2.3 Hz, CHMe2), 16.47 (CHMe2), 16.83
(CHMe2), 28.24 (d, J ) 49.1 Hz, CHMe2), 28.41 (d, J ) 38 Hz,
CHMe2), 29.16 (d, J ) 82.3 Hz, PCH), 35.27 (d, J ) 7.5 Hz, CMe3),
50.82 (d, J ) 6.9 Hz, CMe3), 120.75 (d, J ) 4.4 Hz, C9H6N), 120.89
(C9H6N), 127.53 (d, J ) 3.8 Hz, C9H6N), 129.66 (d, J ) 2.9 Hz,
C9H6N) 131.10 (d, J ) 8.3 Hz, C9H6N), 137.36 (C9H6N), 147.00
(C9H6N), 147.93 (d, J ) 5.5 Hz), 148.38 (d, J ) 3.4 Hz). 31P{1H}
NMR (C6D6): δ 38.63. Anal. Calcd for C22H35N2PZn: C, 62.34;
H, 8.32; N, 6.61. Found: C, 61.61; H, 8.31; N, 6.48.
Preparation of [Zn(Me){CH(8-C9H6N)(Pri2PdNBut)}] (10).
MeLi (0.6 mL, 1.6 M solution in Et2O, 0.96 mmol) was added
dropwise to a stirred solution of 8 (0.41 g, 0.95 mmol) in toluene
(10 mL) at about -80 °C. The mixture was warmed to room
trmperature and stirred overnight. Solvents were removed under
reduced pressure, and the residue was dissolved in Et2O. After
Reaction of Complexes 7 and 12 with BnOH. To a solution
of complex 7 (0.0693 g, 0.181 mmol) in toluene (2 mL) was added

ROP of ꢀ-CL and Mg and Zn Complexes
Organometallics, Vol. 26, No. 9, 2007 2251
Table 7. Details of the X-ray Structure Determinations of Complexes 6-8 and 10
6
7
8
10
empirical formula
fw
C20H30LiN2P
336.37
C22H35MgN2P
382.80
C40H60Cl2N4P2Zn2
860.50
C21H33N2PZn
409.83
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
monoclinic
C2/c
33.885(6)
12.122(2)
31.117(6)
90
110.123(2)
90
12001(4)
24
triclinic
P1h
monoclinic
P21/n
21.705(5)
9.564(2)
21.744(6)
90
99.302(4)
90
4454.5(19)
4
orthorhombic
P212121
9.5809(8)
14.2373(12)
16.3071(14)
90
90
90
2224.4(3)
4
1.224
7.951(9)
9.184(11)
16.791(19)
95.46(2)
91.680(19)
94.724(19)
1216(2)
2
Z
D
calcd (g cm-3
)
1.117
1.046
1.283
F(000)
4368
0.140
416
0.146
1808
1.300
872
1.182
(mm-1
)
θ range for data collecn (deg)
no. of reflns collected
1.80-25.00
32157
2.24-25.01
6220
1.23-26.76
24826
1.90-27.89
15005
no. of indep reflns (Rint
)
10566 (0.1102)
10566/11/690
0.988
4237 (0.0291)
4237/27/263
1.024
9361 (0.0493)
9361/0/465
1.054
5270 (0.0198)
5270/0/234
1.010
no. of data/restraints/params
goodness of fit on F2
final R indicesa [I > 2σ(I)]
R1
Rw2
0.0695
0.1544
0.0522
0.1221
0.0490
0.1220
0.0279
0.0670
R indices (all data)
R1
0.1894
0.0974
0.0968
0.0362
Rw2
0.2052
0.543 and -0.388
0.1466
0.240 and -0.204
0.1502
0.354 and -0.486
0.0700
0.331 and -0.173
largest diff peak and hole (e‚Å-3
)
2
2
4
a R1 ) Σ|Fo| - |Fc|/Σ|Fo|; Rw2 ) [Σw(Fo - Fc )2/Σw(Fo )]1/2
.
listed in Table 7. The R indices (for all data) of complex 6 are
relatively high. This is due to poor crystal quality resulting in weak
diffraction data.
dropwise a solution of BnOH (0.0193 g, 0.179 mmol) in toluene
(0.3 mL) at 0 °C with stirring. Stirring of the mixture was continued
for 10 min at 0 °C. Solvent was removed under vacuum. The residue
was used to determine the NMR spectrum without further purifica-
tion. 1H NMR (C6D6): δ 0.36-0.45 (m, 2H, CH2, CH2CH3), 0.91
(dd, J ) 7.2, 14.6 Hz, 6H, CHMe2), 1.05 (dd, J ) 7.1, 14.4 Hz,
6H, CHMe2), 1.12 (t, J ) 7.2 Hz, 3H, CH2CH3), 1.55 (s, 9H, CMe3),
1.83-1.96 (m, 2H, CHMe2), 3.97 (d, J ) 12.4 Hz, 2H, PCH2),
4.29-5.34 (b, 2H, OCH2), 6.79 (dd, J ) 4.1, 8.2 Hz, 1H, Ar),
6.96-7.14 (m, 5H, Ar), 7.32 (d, J ) 4. 2 Hz, 3H, Ar), 7.56 (d, J
) 8.4 Hz, 1H, Ar), 8.42-8.44 (m, 1H, Ar).
Reaction of complex 12 with BnOH was carried out in a NMR
tube. Thus, to a solution of complex 12 (0.0553 g, 0.130 mmol) in
C6D6 (0.7 mL) in a NMR tube was added BnOH (0.0139 g, 0.128
mmol) at 0 °C. The reactants were fully mixed by shaking for a
few minutes. After 10 min, the NMR spectrum of the sample was
determined and the result showed that the reaction was complete.
1H NMR (C6D6): δ 0.27 (q, J ) 8.1 Hz, 2H, CH2CH3), 0.91 (dd,
J ) 7.2, 14.5 Hz, 6H, CHMe2), 1.05 (dd, J ) 7.1, 14.3 Hz, 6H,
CHMe2), 1.28 (t, J ) 8.1 Hz, 3H, CH2CH3), 1.54 (s, 9H, CMe3),
1.81-1.98 (m, 2H, CHMe2), 3.96 (d, J ) 12.4 Hz, 2H, PCH2),
4.76 (s, 2H, OCH2), 6.81 (dd, J ) 4.1, 8.2 Hz, 1H, Ar), 7.14-7.22
(m, 5H, Ar), 7.29-7.33 (m, 2H, Ar), 7.57 (d, J ) 8.1 Hz, 1H, Ar),
8.42 (b, 1H, Ar), 8.74 (d, J ) 2.4 Hz, 1H, Ar).
Polymerization of ꢀ-Caprolactone Catalyzed by Complexes
7 and 9-12. A typical polymerization procedure was exemplified
by the synthesis of PCL catalyzed by complex 9 in the presence of
BnOH. Complex 9 (0.0496 g, 0.105 mmol) was added into a
Schlenk tube and followed by injection of toluene (2 mL) via a
syringe. After the complex dissolved, an equivalent of BnOH
(0.0114 g, 0.105 mmol) was added at room temperature. The
mixture was stirred for 2 h, and then ꢀ-caprolactone (2.38 g, 20.85
mmol) diluted with toluene (10 mL) was added. The flask was put
into an oil bath which was preset at 60 °C. The mixture was stirred
at 60 °C for 2.6 h during which an increase in viscosity was
observed. The polymerization was quenched by addition of an
excess of glacial acetic acid (0.2 mL) into the solution. After stirring
for 0.5 h at room temperature, the resulting viscous solution was
poured into methanol with stirring. The white precipitate was
washed with hexane three times and dried under vacuum, giving a
white solid (1.95 g, 82%).
Acknowledgment. This work was supported by the National
Natural Science Foundation of China (Grant No. 20572106).
The authors thank Professors H.-G. Wang and H.-B. Song for
determining the crystal structures.
X-ray Crystallography. Single crystals were mounted in Lin-
demann capillaries under nitrogen. Diffraction data were collected
on a Bruker Smart CCD area detector (for 7 and 8) or a Bruker
APEX II CCD area detector (for 6 and 10) with graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å) at 293(2) K.
The structures were solved by direct methods using SHELXS-9736
and refined against F2 by full-matrix least-squares using SHELXL-
97.37 Hydrogen atoms were placed in calculated positions. Crystal
data and experimental details of the structure determinations are
Supporting Information Available: X-ray crystallographic files
reported in this paper in CIF format for the structure determinations
of 6-8 and 10. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0610400
(37) Sheldrick, G. M. SHELXL97, Programs for Structure Refinement;
Universita¨t Go¨ttingen: Go¨ttingen, Germany, 1997.
(36) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.