Synthesis and structural characterization of β-diketiminato yttrium complexes and their application in epoxide/CO2-copolymerization

Article abstract of DOI:10.1002/zaac.200700246

The β-diketiminato yttrium complexes [(BDI^ph) ₂Y{N(SiHMe₂)₂}] (1, BDI^ph = [PhNC(Me)CHC(Me)NPh]), [(BDI^ph)₃Y] (2), and [(C ₅Me₅)(BDI^Ph)Y{N(SiHMe₂) ₂}] (4) are available via amine elimination starting from (BDI ^ph)H and either [Y{N(SiHMe₂)₂} ₃(THF)₂] or [(C₅Me₅)Y{N(SiHMe ₂)₂}₂(THF)] (3). X-ray crystallographic analysis of complexes 1 and 4 revealed a η⁵ coordination mode for the β-diketiminato ligand, whereas the distorted octahedral complex 2 displayed pure K² coordination. Complex 3 was also structurally characterized. 1, 3, and 4 are mo-derately active catalysts in the copolymerization of cyclohexene oxide and CO₂. Complex 3 was the most active system (TOF up to 33 h^-1 at 75 °C, 8.5 atm CO ₂) and gave the highest molecular weight and narrowest polydispersity (M_n = 12600 g mol^-1, M_w/M_n = 1.6).

Full text of DOI:10.1002/zaac.200700246

DOI: 10.1002/zaac.200700246
Synthesis and Structural Characterization of β-Diketiminato Yttrium Complexes
and their Application in Epoxide/CO2-Copolymerization
Boyan B. Lazarov, Frank Hampel, Kai C. Hultzsch*
Erlangen, Institut für Organische Chemie, Friedrich Alexander-Universität Erlangen-Nürnberg
Received April 15th, 2007.
Dedicated to Professor Dieter Fenske on the Occasion of his 65th Birthday
Abstract. The β-diketiminato yttrium complexes [(BDIPh)2Y-
{N(SiHMe2)2}] (1, BDIPh ϭ [PhNC(Me)CHC(Me)NPh]Ϫ), [(BDI-
Ph)3Y] (2), and [(C5Me5)(BDIPh)Y{N(SiHMe2)2}] (4) are available
via amine elimination starting from (BDIPh)H and either
[Y{N(SiHMe2)2}3(THF)2] or [(C5Me5)Y{N(SiHMe2)2}2(THF)]
(3). X-ray crystallographic analysis of complexes 1 and 4 revealed
a η5 coordination mode for the β-diketiminato ligand, whereas the
distorted octahedral complex 2 displayed pure κ2 coordination.
Complex 3 was also structurally characterized. 1, 3, and 4 are mo-
derately active catalysts in the copolymerization of cyclohexene
oxide and CO2. Complex 3 was the most active system (TOF up
to 33 hϪ1 at 75 °C, 8.5 atm CO2) and gave the highest molecular
weight and narrowest polydispersity (Mn
Mw/Mn ϭ 1.6).
ϭ ,
12600 g molϪ1
Keywords: β-Diketiminato complexes; Yttrium; Amine elimination;
Epoxide/CO2 Copolymerization
Introduction
mono(cyclopentadienyl) rare earth metal complexes in
epoxide/CO2 copolymerization [9]. In continuation of our
studies we report herein the synthesis and structural charac-
terization of mono-, bis- and tris(β-diketiminato) [10]
yttrium complexes and their catalytic activity in the copoly-
merization of cyclohexene oxide and CO2.
The organometallic chemistry of the rare earth elements has
attracted significant attention in particular due to their high
catalytic activity for a wide range of organic transform-
ations [1] and polymerizations [2]. An increasingly import-
ant field of research focuses on the development of non-
metallocene catalyst systems [3]. Non-cyclopentadienyl
ligands can be easily modified in their electronic and steric
properties, allowing facile catalyst tuning.
Results and Discussion
β-Diketiminato rare earth metal complexes have been pre-
pared via salt metathesis [11]. However, for practical syn-
thetic reasons we decided to utilize the more convenient
single-step amine elimination route [8, 12].
The utilization of CO2 as a C1 feedstock is an appealing
goal in contemporary catalysis research, because CO2 is
naturally abundant, inexpensive, nontoxic and nonflam-
mable [4]. In particular, the metal-catalyzed copolymeriz-
ation of CO2 and epoxides has been studied extensively, be-
cause the resulting polycarbonates are biodegradable poly-
mers with attractive material properties [5]. Homogeneous
catalyst systems based on β-diketiminato zinc [5d, 6] and
salen chromium [5b, 7] complexes are most prominent ex-
amples of recent developments.
Reaction
of
the trisamido
yttrium complex
[Y{N(SiHMe2)2}3(THF)2] with two equiv of the sterically
undemanding phenyl-substituted β-diketiminato ligand
(BDIPh)H at 70 °C produced the bis(β-diketiminato) yt-
trium complex 1 in 4 h (Scheme 1). Complex 1 was poorly
soluble in toluene and precipitated as slightly yellow crys-
tals suitable for X-ray diffraction (vide infra) in 73 % yield
from the reaction mixture. Attempts to perform the
reaction at elevated temperatures (100 °C) resulted in the
formation of the tris(β-diketiminato) yttrium complex
[(BDIPh)3Y] (2) as a by-product. Complex 2 could be ob-
tained selectively by heating [Y{N(SiHMe2)2}3(THF)2] with
three equiv of (BDIPh)H to 100 °C for 24 h to give 2 in
good yield. Interestingly, complex 2 was better soluble in
toluene than 1.
We have recently reported the application of mono(β-di-
ketiminato) and linked bis(β-diketiminato) rare earth metal
complexes as catalysts in the epoxide/CO2 copolymerization
[8]. Parallel to our study Hou reported the application of
* Priv.-Doz. Dr. K. C. Hultzsch
Institut für Organische Chemie
Friedrich Alexander-Universität Erlangen-Nürnberg
D-91054 Erlangen
Fax: ϩ49-9131-8526865
E-mail: hultzsch@chemie.uni-erlangen.de
While the NMR spectra of complex 1 do not show any
unusual behavior, the 1H NMR spectrum of complex 2
shows 5 distinct, though slightly broadened signals for the
Z. Anorg. Allg. Chem. 2007, 633, 2367Ϫ2373
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B. B. Lazarov, F. Hampel, K. C. Hultzsch
Scheme 1
aromatic ring protons at 25 °C, one of which is significantly
shifted to higher field and resonates at 5.23 ppm in C6D6
solution. This unusual feature can be readily rationalized
by an interaction of a phenyl ring proton with the ring cur-
rent of an aromatic substituent of a neighboring β-diketimi-
nato ligand. This proposal is supported by a crystallograph-
ically observed close proximity of one of the ortho-protons
in each phenyl substituent to a phenyl substituent of a se-
cond β-diketiminato ligand (vide infra).
Recrystallization of 2 from toluene afforded single crys-
tals suitable for a X-ray diffraction study. ORTEP diagrams
of 1 and 2 are depicted in Figures 1 and 2, while Table 1
and Table 2 give selected metrical parameters.
Fig. 1 ORTEP diagram of [(BDIPh)2Y{N(SiHMe2)2}] (1) a) view
from top b) view from the side. Thermal ellipsoids are drawn at the
50 % probability level. All hydrogen atoms, except those attached
to silicon, are omitted for clarity.
˚
Table 1 Selected Bond lengths /A and angles /° of
[(BDIPh)2Y{N(SiHMe2)2}] (1).
Y1-N1
Y1-N2
Y1-N3
Y1···Si1
Y1···CBDI
distance of Y from N2C3
N1-Y1-N1Ј
2.3591(18)
2.3169(19)
2.209(3)
3.3309(7)
3.17Ϫ3.42
1.20
N2-Y1-N2Ј
N1-Y1-N2
N1-Y1-N2Ј
N1-Y1-N3
N2-Y1-N3
Si1-N3-Si1Ј
Y1-N3-Si1
110.22(9)
77.80(6)
90.97(6)
99.79(5)
124.89(5)
127.54(17)
116.23(8)
160.42(9)
Table 2 Selected Bond lengths /A and angles /° of [(BDIPh)3Y] (2).
˚
Y1-N1
Y1-N5
Y1-N6
Y1-N10
Y1-N11
Y1-N15
Y1···CBDI
distance of Y from N2C3
N1-Y1-N5
N1-Y1-N6
N1-Y1-N10
N1-Y1-N11
2.406(4)
2.404(3)
2.397(4)
2.404(4)
2.388(4)
2.404(4)
3.41Ϫ3.77
0.10Ϫ0.11
78.14(12)
174.59(12)
99.36(12)
86.27(12)
N1-Y1-N15
N5-Y1-N6
96.66(12)
97.17(12)
88.11(12)
96.05(12)
172.64(12)
77.63(12)
96.99(12)
88.25(12)
173.61(13)
97.94(13)
78.29(12)
N5-Y1-N10
N5-Y1-N11
N5-Y1-N15
N6-Y1-N10
N6-Y1-N11
N6-Y1-N15
N10-Y1-N11
N10-Y1-N15
N11-Y1-N15
Fig. 2 ORTEP diagram of [(BDIPh)3Y] (2). Thermal ellipsoids are
drawn at the 30 % probability level. All hydrogen atoms are omitted
for clarity.
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β-Diketiminato Yttrium Complexes
The structure of 1 shows similar features as observed
in
the
bis(β-diketiminato)
neodymium
complex
[{Me3SiNC(Ph)CHC(Ph)NSiMe3}2NdCl] [11d]. The yt-
trium atom is coordinated in a distorted trigonal bipyrami-
dal fashion by two β-diketiminato and one amido ligand.
One nitrogen atom of each β-diketiminate (N1 and N1Ј)
occupies an axial position, while the other nitrogen atoms
(N2 and N2’) and the amido ligand (N3) are placed in
equatorial positions. Overall, complex 1 has C2-symmetry
in the solid state. The β-diketiminato ligands are bound in
the η5 bonding mode with the yttrium atom being displaced
˚
by 1.20 A out of the N2C3 planes and relative short Y···C
˚
contacts (3.17Ϫ3.41 A). The β-diketiminato ligand is
slightly puckered with C3 being placed slightly out of the
N2C3 plane by 0.175 A. The planes of the β-diketiminato
Scheme 2
˚
ligands have a dihedral angle of 33.9° and the aromatic sub-
stituents are oriented perpendicular to these planes. The β-
diketiminato ligands are bound slightly unsymmetrical with
˚
˚
the axial Y1-N1 bond (2.3591(18) A) being 0.04 A longer
˚
than the equatorial Y1-N2 bond (2.3169(19) A). Both bond
lengths exceed the typical range for Y-N bonds
˚
(2.18Ϫ2.32 A [13]), but are comparable to other β-diketimi-
nato rare earth metal complexes [8, 11], when considering
the ionic radius of yttrium. The Y-N bond to the bis(dime-
˚
thylsilyl)amido ligand is significant shorter (2.209(3) A) and
falls at the lower limit of the typical range of Y-N bonds.
The amido ligand shows a weak diagostic β-SiH interaction
[14], with a relative close contact to the silicon atoms
˚
(3.3309(7) A), concomitant with a decreased Y-N-Si angle
(116.23(8)°) and
(127.54(17)°).
a
slightly widened Si-N-Si angle
Complex 2 adopts a slightly distorted octahedral coordi-
nation which can be best compared with related tris(β-di-
ketiminato) samarium and gadolinium complexes
[{BDIPh}3Ln] (Ln ϭ Sm, Gd) [11a]. The β-diketiminato li-
gands are coordinated in a κ2-fashion, as indicated by long
Fig. 3 ORTEP diagram of [(C5Me5)Y{N(SiHMe2)2}2(THF)] (3).
Thermal ellipsoids are drawn at the 50 % probability level. All
hydrogen atoms, except those attached to silicon, are omitted for
clarity.
˚
yttrium-carbon distances (3.41Ϫ3.77 A). The yttrium atom
is situated close to the N2C3 plane of the β-diketiminato
˚
ligands (ca. 0.1 A) and the β-diketiminato ligands are
essentially planar. The Y-N bond lengths to the β-diketimi-
˚
nato ligands (2.39Ϫ2.41 A) are slightly longer than those in
complex 1, in agreement with the higher coordination num-
ber in complex 2. As indicated by NMR spectroscopic
evidence (vide supra), the protons attached to the aromatic
ortho-ring carbons C26, C36, C46, C56, C66 and C76 are
situated in close proximity (2.56Ϫ2.69 A) above the ring
plane of one of a neighboring β-diketiminato phenyl sub-
stituent.
We then began to investigate the synthesis of half-sand-
wich complexes containing one β-diketiminato and one
cyclopentadienyl ligand. A convenient precursor for the
synthesis are mono(cyclopentadienyl) yttrium diamido
complexes reported by Anwander and co-workers [15] as
base-free species, though no crystallographic data is avail-
able. However, we were able to obtain single crystals of the
THF-adduct 3 suitable for a X-ray diffraction study
(Scheme 2, Figure 3, Table 3).
˚
Table 3 Selected Bond lengths /A and angles /° of
[(C5Me5)Y{N(SiHMe2)2}2(THF)] (3).
Y1-N1
Y1-N2
2.264(2)
2.281(2)
2.3623(19)
3.636(1)
3.0929(8)
3.3247(8)
3.572(1)
N2-Y1-O10
Cpcent-Y1-N1
Cpcent-Y1-N2
Cpcent-Y1-O10
Si1-N1-Si2
Si3-N2-Si4
Y1-N1-Si1
Y1-N1-Si2
Y1-N2-Si3
Y1-N2-Si4
97.24(7)
˚
116.88(8)
114.99(8)
116.64(7)
125.39(13)
120.84(13)
132.44(12)
102.15(10)
112.57(11)
126.52(12)
Y1-O10
Y1···Si1
Y1···Si2
Y1···Si3
Y1···Si4
Y1-Cpcent
Y1···CCp
N1-Y1-N2
N1-Y1-O10
2.367(2)
2.647(3)Ϫ2.662(3)
120.05(8)
84.95(7)
Complex 3 adopts a three-legged piano stool arrange-
ment. The Y-N bonds (2.264(2) and 2.281(2) A) and the
˚
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2369

B. B. Lazarov, F. Hampel, K. C. Hultzsch
˚
Y-O bond (2.3623(19) A) fall within the usual range found
in other amido and THF containing yttrium complexes
˚
˚
(Y-N ϭ 2.18Ϫ2.32 A, Y-O ϭ 2.35Ϫ2.45 A [13]), likewise
the Y-CCp and Y-Cpcent distances are quite typical [16].
The geometry of the amido ligands are unsymmetric, in-
dicative of monoagostic β-SiH interactions similar to that
found in [(C5HPh4)2La{N(SiHMe2)2}] [14c] or (R,S)-
[Y(Biphen){N(SiHMe2)2}(THF)]2 [17]. This interaction is
most prominent in the amido ligand containing N1, in
˚
which Si2 is in close contact with yttrium (3.0929(8) A) con-
comitant with a decreased Y-N-Si angle (Y1-N1-Si2 ϭ
102.15(10)° vs. Y1-N1-Si1 ϭ 132.44(12)°), while the Si1-
N1-Si2 angle (125.39(13)°) remains typical. This agostic in-
teraction is less pronounced in the other amido ligand
˚
(Y1···Si3
ϭ
3.3247(8) A, Y1-N2-Si3
ϭ
112.57(11)°,
Y1-N2-Si4 ϭ 126.52(12)°, Si3-N2-Si4 ϭ 120.84(13)°).
The mono(cyclopentadienyl) yttrium diamido complex 3
1
reacted cleanly and quantitatively according to H NMR
Fig. 4 ORTEP diagram of [(C5Me5)(BDIPh)Y{N(SiHMe2)2}] (4).
Thermal ellipsoids are drawn at the 30 % probability level. All
hydrogen atoms, except those attached to silicon, are omitted for
clarity.
spectroscopy with the β-diketiminato ligand (BDIPh)H at
45 °C within 20 h to give the THF-free half-sandwich com-
plex 4 in good yield (Scheme 2).
X-ray crystallographic analysis of the half-sandwich
complex 4 (Figure 4, Table 4) revealed a three-legged piano
stool coordination geometry around yttrium and can be
compared to previously characterized [(C5H4CH3)-
(BDIDIPPh)YbR] (R ϭ Cl, NPh2) [11f]. Most noteworthy
seems to be the η5 binding mode of the β-diketiminato li-
gand, which is comparable to the chloro complex
[(C5H4CH3)(BDIDIPPh)YbCl], but significantly more pro-
nounced than in the corresponding diphenylamido complex
[(C5H4CH3)(BDIDIPPh)YbNPh2] [11f]. The N2C3 plane is
oriented perpendicular (88°) to the plane of the cyclopen-
tadienyl ligand, while the two phenyl rings are almost co-
planar (dihedral angle 20.4 and 21.9°) to the cyclopen-
tadienyl ring. The β-diketiminato chelating ring is slightly
˚
Table 4 Selected Bond lengths /A and angles /° of
[(C5Me5)(BDIPh)Y{N(SiHMe2)2}] (4).
Y1-N1
Y1-N2
Y1-N3
Y1···Si1
Y1···Si2
Y1···CCp
Y1-Cpcent
Y1···CBDI
2.3012(18)
2.3236(17)
2.2472(18)
3.493(1)
Cpcent-Y1-N1 117.37(6)
Cpcent-Y1-N2 119.88(7)
Cpcent-Y1-N3 119.00(7)
N1-Y1-N2
N1-Y1-N3
80.53(6)
3.1486(7)
103.21(7)
109.66(7)
129.98(11)
124.12(10)
105.68(9)
2.633(2)Ϫ2.690(2) N2-Y1-N3
2.373(2)
3.04Ϫ3.21
Si1-N3-Si2
Y1-N3-Si1
Y1-N3-Si2
distance of Y from N2C3 1.39
˚
more puckered (C12 is 0.19 A out of the N2C3 plane) than
those in the bis(β-diketiminato) complex 1. Furthermore,
˚
the Y···C contacts are shorter (3.04 Ϫ 3.21 A) and the yt-
˚
trium to N2C3 plane distance (1.39 A) is larger than in com-
catalyst system (Table 5, entries 6 and 8) and produced the
polymer with the highest molecular weight (Table 5, entry
7) and narrowest molecular weight distribution. Polymers
obtained with the bis(β-diketiminato) complex 1 generally
had lower molecular weights and broader molecular weight
distributions, but produced the polycarbonate with the
highest content in carbonate linkages (93 %, see Table 5,
entry 2) in this series. Formation of the cyclic carbonate by-
product was largely suppressed (Յ 2 %) under the optim-
ized polymerization conditions; only at higher reaction tem-
peratures (110 °C, Table 5, entry 3) a significant increase to
20 % was observed.
For comparison we also investigated the catalytic activity
of the yttrocene [Cp*2Y{N(SiHMe2)2}] [14c] in the epoxide/
CO2 copolymerization. Although the catalytic activity of
the yttrocene is at the lower end of the catalytic activities
observed herein, the resulting polycarbonate possessed the
highest percentage of carbonate linkages (95 %, Table 5, en-
try 11).
plex 1. The Y-CCp and Y-Cpcent distances are comparable
to those of complex 3 and all Y-N bond lengths fall within
the typical range (vide supra). Interestingly, the Y-N bonds
of the β-diketiminato ligand mark the lower end of the
range of Y-N(BDI) bond lengths observed in complexes 1,
2
and
the
linked
bis(β-diketiminato)
complex
[{C2H4(BDIMes)2}YN(SiMe3)2] [8b]. The amido ligand dis-
plays a monoagostic β-SiH interaction similar to that of
complex 3.
Complexes 1, 3 and 4 were tested as catalysts in the co-
polymerization of cyclohexene oxide and CO2 (Table 5). All
complexes showed moderate activity [5d] at 75 °C and
8 atm CO2 comparable in magnitude to linked bis(β-diketi-
minato) lanthanum complexes [8]. The best results were ob-
tained when the reactions were performed in a 1:1 (v:v) mix-
ture of cyclohexene oxide and toluene. All catalysts pro-
duced polycarbonate with carbonate linkages exceeding
80 %. The half-sandwich complex 3 was the most active
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β-Diketiminato Yttrium Complexes
Table 5 Rare earth metal catalyzed copolymerization of CO2 and cyclohexene oxide.
b)
b)
a)
Entry cat.
[M]/[cat.] CHO/toluene p(CO2) T (°C) t (h) TON TOF % cyclic
% carbonate Mn
Mw
Mw/Mn
v:v
atm
hϪ1
carbonatea) linkagesa)
g molϪ1 g molϪ1
1
2
3
4
5
6
7
8
1
1
1
1
1
3
3
3
3
4
1000
1000
1000
1000
1000
500
1:1
1:1
1:1
1:2
2:1
1:1
1:1
1:1
1:1
1:1
1:1
8
8
8
8
50
75
110
75
75
75
75
75
75
75
75
48
48
48
48
48
82
1.7
7.3
3.9
3
4.2
33
12.5
33
11.5
7.2
3.4
1
1
20
2
2
2
2
2
2
2
2
87
93
80
91
83
88
88
85
86
88
95
3500
7460
2430
2400
3190
6670
12600
5170
6700
nd
7600
2.2
2.3
5.4
5.0
2.8
1.8
1.6
1.4
1.9
nd
356
187
145
200
17200
13200
12000
8900
12000
20000
7400
12600
nd
19000
8
8.5
8.5
8.5
8.5
8
3.5 115
24 301
3.5 117
24
24
48
500
1000
1000
1000
9
10
11
276
173
163
[Cp*2Y{N(SiHMe2)2}] 1000
8.5
7400
2.6
a) Determined by 1H NMR spectroscopy. b) Determined by gel permeation chromatography relative to polystyrene standards.
m/z ϭ 719 ([M]ϩ, 46 %), 642 ([M-Ph]ϩ, 15 %), 587 ([(BDIPh)2Y]ϩ, 100 %),
Experimental Part
470 ([(BDIPh)Y(NSiHMe2)2]ϩ, 49 %), 337 ([(BDIPh)Y-H]ϩ, 26 %).
All operations were performed under an inert atmosphere of argon
using standard Schlenk-line or glovebox techniques. All solvents
were purified by distillation from sodium/triglyme benzophenone
ketyl under nitrogen. (BDIPh)H [18] [Y{N(SiHMe2)2}3(THF)n]
(n ϭ 1 [14a], n ϭ 2 [19]) and [Cp*2Y{N(SiHMe2)2}] [14c] were
prepared according to published procedures. Cyclohexene oxide
was dried by distillation from CaH2. NMR spectra were recorded
on a Bruker Avance 400 spectrometer (1H, 400.1 MHz; 13C,
100.6 MHz) at 25 °C. Chemical shifts were referenced internally
using the residual solvent resonances and reported relative to tetra-
methylsilane. Mass spectra (EI, 70 eV) were obtained using a Finni-
gan MAT 8200 instrument. Elemental analyses were performed by
the Microanalytical Laboratory of this department. Although me-
tal complexes were combusted with V2O5 as burning aid, some
analyses gave low carbon content repeatedly, presumably due to
carbide formation. Molecular weights of the polycarbonates were
determined by GPC (Agilent 1100 Series using RI detector, 3 SDV
Linear M 5µ columns with 8 ϫ 50 mm, 8 ϫ 300 mm and
8 ϫ 600 mm dimensions) versus polystyrene standards using THF
at 35 °C as eluent.
[(BDIPh)3Y] (2)
(BDIPh)H (188 mg, 0.75 mmol) and [Y{N(SiHMe2)2}3(THF)2]
(157 mg, 0.25 mmol) were dissolved in toluene (2 mL) and the reac-
tion mixture was heated to 100 °C for 24 h. All volatiles were re-
moved in vacuo to afford 205 mg (98 %) of 2 as a yellow powder.
This material is pure according to NMR spectroscopic analysis.
Crystals suitable for X-ray crystallographic analysis were obtained
from a concentrated toluene solution at room temperature. Melting
point: 353 °C dec. C51H51N6Y (837.52): C 72.35 % (calc. 73.19); H
5.85 (6.14); N 10.78 (10.04) %.
1H NMR (C6D6): δ ϭ 7.39 (br d, 6H, aryl-H), 7.26 (br t, 6H, aryl-H), 7.09
(br t, 6H, aryl-H), 7.01 (br t, 6H, aryl-H), 5.23 (br d, 6H, aryl-H), 4.84 (s,
3H, β-CH), 1.47 (s, 18H, CH3). 13C{1H} NMR (C6D6): δ ϭ 164.5 (CH3CN),
150.8 (aryl), 128.6 (aryl, 2C), 127.8, 127.1, 124.0 (aryl), 98.7 (β-CH), 24.9
(CH3). MS (70 eV): m/z ϭ 836 ([M]ϩ, 14 %), 587 ([(BDIPh)2Y]ϩ, 100 %), 337
([(BDIPh)Y-H]ϩ, 10 %).
[(C5Me5)Y{N(SiHMe2)2}2(THF)] (3)
C5Me5H (150 mg, 1.10 mmol) and [Y{N(SiHMe2)2}3(THF)]
(558 mg, 1.00 mmol) were dissolved in toluene (10 mL) in a round
bottom Schlenk-flask and the solution was heated with stirring to
160 °C for 1.5 h. All volatiles were removed in vacuo and the prod-
uct was crystallized from a concentrated pentane solution at
Ϫ78 °C to give 309 mg (55 %) of 3 as colorless crystals. Melting
point: 104 °C.
[(BDIPh)2Y{N(SiHMe2)2}] (1)
[Y{N(SiHMe2)2}3(THF)2] (670 mg, 1.06 mmol) and (BDIPh)H
(533 mg, 2.12 mmol) were dissolved in toluene (10 mL) and the
mixture was heated to 70 °C for 4 h. The resulting precipitate was
filtered, washed with pentane (3 ϫ 6 mL) and dried in vacuo to
give 560 mg (73 %) of 1 as a slight yellow microcrystalline powder.
Melting point: 262 °C dec. C38H48N5Si2Y (719.91): C 63.84 (calc.
63.40); H 6.76 (6.72); N 9.58 (9.73) %.
1H NMR (C6D6): δ ϭ 4.61 (m, 4H, SiH), 3.65 (br m, 4H, THF), 2.14 (s,
15H, C5Me5), 1.32 (br m, 4H, THF), 0.31 (d, 3JH,H ϭ 2.8 Hz, 24H, SiCH3).
13C{1H} NMR (C6D6): δ ϭ 119.2 (C5Me5), 71.0 (THF), 25.3 (THF), 11.8
(C5Me5), 3.6 (SiCH3). MS (70 eV): m/z ϭ 488 ([M-THF]ϩ, 12 %), 355
([(C5Me5)Y{N(SiHMe2)2}-H]ϩ, 100 %), 132 ([N(SiHMe2)2]ϩ, 7 %).
3
1H NMR (400 MHz, C6D6): δ ϭ 7.07 (pt, 8H, aryl-H), 6.91 (t, JH,H
ϭ
7.4 Hz, 4H, aryl-H), 6.73 (d, 3JH,H ϭ 8.3 Hz, 6H, aryl-H), 5.07 (sept, 3JH,H ϭ
2.9 Hz, 2H, SiH), 4.94 (s, 2H, β-CH), 1.80 (s, 12H, CH3), Ϫ0.09 (d, 3JH,H ϭ
2.9 Hz, 12H, SiCH3). 13C{1H} NMR (C6D6): δ ϭ 164.6 (CH3CN), 150.0,
128.9, 125.8, 124.2 (aryl), 97.9 (β-CH), 24.2 (CH3), 2.8 (SiCH3). MS (70 eV):
[(C5Me5)(BDIPh)Y{N(SiHMe2)2}] (4)
To a round bottom Schlenk flask were added 3 (280.4 mg,
0.50 mmol), (BDIPh)H (125.2 mg, 0.50 mmol) and toluene (5 mL).
Z. Anorg. Allg. Chem. 2007, 2367Ϫ2373
 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2371

B. B. Lazarov, F. Hampel, K. C. Hultzsch
The reaction mixture was stirred at 45 °C for 20 h. All volatiles
were removed in vacuo. The product was crystallized at Ϫ25 °C
from pentane to give 224 mg (74 %) of 4 as yellow crystals. Melting
point: 120 °C.
The space groups were determined from systematic absences and
subsequent least-squares refinement. The structures were solved by
direct methods. The parameters were refined with all data by full-
matrix-least-squares on F2 using SHELXL-97 [20c]. Non-hydrogen
atoms in complex 1Ϫ4 were refined anisotropically. The methyl
group of the toluene solvate in 1 was disordered and was refined
with two independent positions (occupation ratio 50 : 50 % by sym-
metry). The pentane solvate in 4 was split over 6 positions and
C103 was set manually to 50 % occupation. Hydrogen atoms were
fixed in idealized positions using a riding model, except hydrogen
atoms attached to silicon in complex 1 and 3, which were localized
and free isotropically refined. Scattering factors, and ∆fЈ and ∆fЉ
values, were taken from the literature [20d].
C31H46N3Si2Y (605.80): C 60.58 (calc. 61.46); H 7.16 (7.65); N
7.46 (6.94) %.
1H NMR (C6D6): δ ϭ 7.17 (m, 4H, aryl-H), 7.01 (m, 6H, aryl-H), 4.87 (s,
1H, β-CH), 4.69 (br m, 2H, SiH), 1.85 (s, 15H, C5Me5), 1.68 (s, 6H, CH3,
3
BDIPh), 0.26 (d, JH,H ϭ 2.9 Hz, 12H, SiCH3). 13C{1H} NMR (C6D6): δ ϭ
165.7 (CH3CN), 150.6, 129.1, 125.6, 124.9 (aryl), 118.9 (C5Me5), 96.4
(β-CH), 24.9 (CH3, BDIPh), 11.8 (C5Me5), 4.0 (SiCH3). MS (70 eV): m/z ϭ
605 ([M]ϩ, 4 %), 470 ([M-C5Me5]ϩ, 100 %), 337 ([(BDIPh)Y-H]ϩ, 10 %).
Crystal structure determination of 1-4
Crystallographic data for the structures (1: CCDC-642078, 2:
CCDC-642080, 3: CCDC-642081, 4: CCDC-642079) have been
deposited with the Cambridge Data Centre. Copies of the data
can be obtained free of charge on application to The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: int.code
ϩ(1223)336-033; e-mail for inquiry: fileserv@ccdc.cam.ac.uk).
Slight yellow crystals of [(BDIPh)2Y{N(SiHMe2)2}]·C7H8 (1·C7H8),
C45H55N5Si2Y, 811.03 g·molϪ1, were obtained from toluene solu-
tion at 25 °C. Crystal size 0.15 ϫ 0.15 ϫ 0.10 mm, monoclinic,
˚
˚
˚
P2/c, a ϭ 12.1244(2) A, b ϭ 11.3924(3) A, c ϭ 15.5232(4) A, β ϭ
96.030(2)°, V ϭ 2132.29(9) A , Z ϭ 2, ρcalcd ϭ 1.263 g cmϪ3, µ ϭ
3
˚
1.460 mmϪ1, F(000) ϭ 854. Data were collected on a Nonius Kap-
paCCD area detector at 173(2) K up to 2θmax ϭ 55.0° (Mo-KͰ
radiation). 9530 reflections were collected, 4897 were unique
[R(int) ϭ 0.0327] of which 3848 were observed [I > 2σ(I)].
R1 ϭ 0.0407, wR2 ϭ 0.1070 (obsd. data), goodness-of-fit on
F2 ϭ 1.040; residual electron density (max/min) 0.547/Ϫ0.481 e
Typical procedure for the copolymerization of
cyclohexene oxide and CO2
The copolymerization reactions were performed in a Buchi tiny-
clave reactor. Cyclohexene oxide (3.92 g, 40 mmol) and toluene
(4 mL) were added to the reactor in the glovebox under an inert
atmosphere of argon. The catalyst (20 µmol) was placed on a glass
boat in order to prevent premature mixing. Then the reactor was
closed and transferred to a Schlenk-line where the atmosphere was
exchanged for 8 atm CO2. After saturation of the solution with
CO2 was complete, the catalyst was dissolved by tilting the reactor.
The system was then heated to the desired temperature. The press-
ure of CO2 was maintained at 8 atm. After the specified reaction
time the heating was discontinued and the reactor was cooled in an
ice bath to 5-10 °C, then the pressure was released and the reaction
mixture was quenched by addition of CH2Cl2 and MeOH. All vol-
atiles were evaporated in vacuo at 80 °C to obtain the polymer prod-
uct as a crispy solid. The carbonate linkage contents were deter-
mined from the intensity of the cyclohexyl methyne proton signals
(4.6 ppm for carbonate linkages, 3.3 ppm for ether linkages) in the
1H NMR spectrum of the polymer.
Ϫ3
A
.
Yellow crystals of [(BDIPh)3Y] (2), C51H54N6Y,
˚
839.91 g·molϪ1, were obtained from toluene solution at 25 °C.
Crystal size 0.10 ϫ 0.10 ϫ 0.10 mm, monoclinic, P21/c, a ϭ
˚
˚
˚
18.5156(9) A,
b
ϭ
10.5296(3) A,
c
ϭ
22.8784(11) A,
β
ϭ
103.895(2)°, V ϭ 4329.9(3) A , Z ϭ 4, ρcalcd ϭ 1.288 g cmϪ3, µ ϭ
1.389 mmϪ1, F(000) ϭ 1764. Data were collected on a Nonius
KappaCCD area detector at 173(2) K up to 2θmax ϭ 50.0° (Mo-
KͰ radiation). 13443 reflections were collected, 7630 were unique
3
˚
[R(int) ϭ 0.0674] of which 4301 were observed [I > 2σ(I)]. R1
ϭ
0.0505, wR2 ϭ 0.1421 (obsd. data), goodness-of-fit on F2 ϭ 0.891;
residual electron density (max/min) 0.424/Ϫ0.583 e AϪ3. Colorless
˚
crystals of [(C5Me5)Y{N(SiHMe2)2}2(THF)] (3), C22H51N2OSi4Y,
560.92 g·molϪ1, were obtained from pentane solution at Ϫ35 °C.
Crystal size 0.20 ϫ 0.20 ϫ 0.20 mm, monoclinic, P21/n, a ϭ
˚
˚
˚
10.2388(2) A, b ϭ 21.0111(5) A, c ϭ 14.4477(3) A, β ϭ 96.780(2)°,
V
1.207 g cmϪ3, µ
˚
ϭ 3086.38(11) A , Z ϭ 4, ρcalcd ϭ ϭ
3
2.060 mmϪ1, F(000) ϭ 1200. Data were collected on a Nonius
KappaCCD area detector at 173(2) K up to 2θmax ϭ 55.0°
(Mo-KͰ radiation). 12327 reflections were collected, 7055 were
unique [R(int) ϭ 0.0255] of which 5479 were observed [I > 2σ(I)].
R1 ϭ 0.0395, wR2 ϭ 0.1055 (obsd. data), goodness-of-fit on F2 ϭ
Acknowledgement. Generous financial support by the Deutsche
Forschungsgemeinschaft (DFG SPP 1166) is gratefully acknowl-
edged. K.C.H. was a DFG Emmy Noether fellow (2001Ϫ2007) and
thanks Professor John A. Gladysz for his continual support. We
are indebted to Prof. J. Okuda and Dr. K. Beckerle (RWTH
Aachen) for GPC measurements and Dr. H. Luftmann and
J. Paweletz (WWU Münster) for obtaining Mass spectra.
Ϫ3
˚
1.027; residual electron density (max/min) 0.420/Ϫ0.444 e A
.
Yellow crystals of [(C5Me5)(BDIPh)Y{N(SiHMe2)2}]·1/2C5H12
(4·1/2C5H12), C33.5H51.5N3Si2Y, 641.37 g·molϪ1, were obtained from
pentane solution at Ϫ78 °C. Crystal size 0.25 ϫ 0.15 ϫ 0.15 mm,
˚
˚
˚
3
¯
triclinic, P1, a ϭ 9.6017(2) A, b ϭ 10.0017(4) A, c ϭ 20.4827(4) A,
˚
Ͱ ϭ 80.177(1)°, β ϭ 76.882(1)°, γ ϭ 69.695(1)°, V ϭ 1787.54(9) A ,
Z ϭ 2, ρcalcd ϭ 1.192 g cmϪ3, µ ϭ 1.723 mmϪ1, F(000) ϭ 681. Data
were collected on a Nonius KappaCCD area detector at 173(2) K
up to 2θmax ϭ 55.0° (Mo-KͰ radiation). 15491 reflections were col-
lected, 8181 were unique [R(int) ϭ 0.0263] of which 6713 were ob-
served [I > 2σ(I)]. R1 ϭ 0.0368, wR2 ϭ 0.0992 (obsd. data), good-
ness-of-fit on F2 ϭ 0.950; residual electron density (max/min)
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