Bridged bis(amidinate) lanthanide aryloxides: Syntheses, structures, and catalytic activity for addition of amines to carbodiimides

Article abstract of DOI:10.1039/c3dt33069a

Various lanthanide aryloxide complexes supported by bridged bis(amidinate) ligand L, LLnOAr(DME) (L = Me₃SiNC(Ph)N(CH₂) ₃NC(Ph)NSiMe₃, DME = dimethoxyethane, Ln = Y, Ar = 2,6-(Me)₂C₆H₃

Full text of DOI:10.1039/c3dt33069a

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Bridged bis(amidinate) lanthanide aryloxides:
syntheses, structures, and catalytic activity for addition
Cite this: Dalton Trans., 2013, 42, 5890
of amines to carbodiimides†
Jing Tu, Wenbo Li, Mingqiang Xue,* Yong Zhang and Qi Shen*
Various lanthanide aryloxide complexes supported by bridged bis(amidinate) ligand L, LLnOAr(DME) (L =
Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3, DME = dimethoxyethane, Ln = Y, Ar = 2,6-(Me)2C6H3 (1), 2,6-
(iPr)2C6H3 (2), 2,6-(tBu)2-4-(Me)C6H2 (3); Ar = 2,6-(tBu)2-4-(Me)C6H2, Ln = Nd (4), Sm (5), Yb (6)) were
synthesized, and complexes 1, 2 and 4–6 were characterized by single crystal X-ray diffraction. All the
complexes are efficient precatalysts for catalytic addition of amines to carbodiimides. The catalytic activity
is influenced by lanthanide metals and the aryloxide groups (Nd (4) ∼ Sm (5) < Y (3) ∼ Yb (6) and -2,6-
(Me)2C6H3 < -2,6-(iPr)2C6H3 < -2,6-(tBu)2-4-(Me)C6H2). The catalytic addition reaction with 3 showed a
good scope of substrates. The mechanism investigation revealed the real active intermediate being the
monoguanidinate complexes supported by an aryloxide and an amidine-functionalized amidinate group,
L’Ln[O2,6-(tBu)2-4-(Me)C6H2][RNCNHRN(Ar’)] (L’ = Me3SiNHC(Ph)N(CH2)3NC(Ph)NSiMe3, R = iPr, Ar’ =
Received 21st December 2012,
Accepted 1st February 2013
i
phenyl, Ln = Yb (8), Y (11); R = Cy, Ar’ = phenyl, Ln = Yb (10), Y (12); R = Pr, Ar’ = 4-ClC6H4, Ln = Yb (9)),
which were isolated from the reactions of 6 (or 3) with amine and carbodiimide in a molar ratio of
1 : 1 : 1 and structurally characterized. The Ln-active group in the present precatalyst is a Ln–amidinate
species, not the Ln–OAr group.
DOI: 10.1039/c3dt33069a
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divalent lanthanide complexes7f,g as well as lanthanide tri-
Introduction
flates7h,i have been explored to be efficient catalysts for this
The catalytic formation of the C–N bond by metal complexes is process and the real active intermediate, lanthanide–guanidi-
an active subject in organic synthesis and organometallic nate species has been well documented.7j,k Very recently, we
chemistry of main, transition and lanthanide metals.1,2 Guani- have reported lanthanide trisaryloxides, Ln(OAr)3(THF)2 can
dines are the important structural motifs found in many bio- act as efficient catalyst precursors for the catalytic addition of
logically and pharmaceutically active compounds,3 and amines to carbodiimides yielding multi-substituted guani-
catalytic addition reaction of the amine N–H bond to carbodi- dines, which represents the first example of metal catalyst con-
imide provides a straightforward and atom-economical route taining metal–aryloxide (alkoxide) moiety. The detailed
for the preparation of multi-substituted guanidines.4 However, mechanism study revealed the Ln–OAr group is an active
this addition reaction without a catalyst requires harsh con- group and the corresponding monoguanidinate species
ditions.5 Therefore, exploring efficient metal catalysts for cata- formed via protonation of OAr group by in situ formed guanidi-
lytic addition of amines to carbodiimides has received much ne.8a In comparison with lanthanide alkyl and amide com-
current interest.6 Particularly, the utility of lanthanide com- plexes lanthanide aryloxides are easier to access and less
plexes as precatalysts has attracted much attention. A variety of sensitive to air and moisture. Thus, investigation of the influ-
lanthanide complexes containing M–C,7a,b M–N bond,6h,7c–e ence of ancillary ligands on the reactivity of Ln–aryloxide
species may be rewarding, as the ancillary ligands around the
center metal may play a key role in modification of the catalytic
behavior of the Ln–OAr active group. Bridged bis(amidinate) L
Key Laboratory of Organic Synthesis of Jiangsu Province, Department of Chemistry
(L = Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3) ligand has shown the
ability to provide a suitable coordination environment, which
allows the synthesis of various isolable lanthanide complexes
containing Ln–BH4,9a Ln–N9b–d and Ln–O9e bonds. These com-
plexes serve as well-defined single-site catalysts for polymeriz-
ation of ε-caprolactone and L-lactide in a living fashion and
and Chemical Engineering, Dushu Lake CampusSoochow University, Suzhou 215123,
People’s Republic of China. E-mail: qshen@suda.edu.cn, xuemingqiang@suda.edu.cn;
Fax: +(86) 512-65880305; Tel: +(86) 512-65882806
†Electronic supplementary information (ESI) available. CCDC 915745 (for 1),
915744 (for 2), 915746 (for 4), 915747 (for 5), 915748 (for 6), 915741 (for 7),
915742 (for 8) and 915743 (for 9). For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c3dt33069a
5890 | Dalton Trans., 2013, 42, 5890–5901
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the amide complexes are efficient catalysts for catalytic atoms from one OAr group and one DME molecule. The
addition of amines to aromatic nitriles to monosubstituted coordination geometry around each metal center can be
amidines.9 Ligand L in all these catalytic reactions serves as a described as a distorted trigonal bipyramid, when each amidi-
spectator ligand and does not participate in the transform- nate ligand is considered to be point donors located at the
ations. Therefore, we tried to synthesize a series of lanthanide central carbon atoms. Each center carbon atom (C1 and C2) of
aryloxides with different sized aryloxide groups and lanthanide the two amidinate groups and one oxygen atom (O3) occupy
metals using L as the ancillary ligand, LLn(OAr), and assessed equatorial positions, while two oxygen atoms (O1 and O2)
their activity for catalytic addition of amines to carbodiimides locate on axial sites with the angle of O(1)–Ln(1)–O(2) of
to guanidinates. It was found that the target complexes LLn- 157.32(9)° for 6, (154.65(16)° for 1, 149.68(9)° for 2, 142.66(7)°
(OAr)(DME) (Ln = Y, Ar = 2,6-(Me)2C6H3 (1); Ar = 2,6-(iPr)2C6H3 for 4 and 143.37(6)° for 5). The molecular structures of 1, 2
(2); Ar = 2,6-(tBu)2-4-(Me)C6H2 (3) and Ar = 2,6-(tBu)2-4-(Me)- and 4–6 are quite similar to that of LYb[O2,6-(iPr)2C6H3](DME)
C6H2, Ln = Nd (4); Sm (5); Yb (6)) could be prepared in high reported previously.9e
yields and all these complexes show higher activity for
The C–N bond distances in the chelating N–C–N unit are
addition of amines to carbodiimides than the corresponding nearly equal and the average value, 1.33 Å, indicates the de-
Ln(OAr)3(THF)2. A detailed investigation of the mechanism localization of the π bond in the N–C–N unit. The bond para-
revealed the active group here is the Ln–amidinate species of meters within the two amidinate ligands and within the Yb–
the L, not the Ln–OAr species as the cases with Ln N–C–N units compare well with those found in LYb[O2,6-
(OAr)3(THF)2. Here we report the results. The isolation and (iPr)2C6H3](DME) and the related complexes reported.9,11
characterization, as well as the activities of the real active inter-
mediates L′Ln[RNCNHRN(Ar′)](OAr) are also presented.
The Ln–O(OAr) bond distance in 6 is 2.110(2) Å and the
value is almost consistent with those found in 1, 2, 4 and 5
(Table 1), when the differences in the ionic radii among these
metals are considered (2.105(4) Å for 1, 2.095(2) Å for 2, 2.212(2)
Å for 4 and 2.189(2) Å for 5). The value is comparable to
those of the analogue LYb[O2,6-(iPr)2C6H3](DME) and the
lanthanide aryloxides.8
Results and discussion
Synthesis of bis(amidinate) lanthanide aryloxides
The ytterbium aryloxide complex bearing the bridged bis(ami-
dinate) ligand L, LYb[O2,6-(iPr)2C6H3](DME) (L = Me3SiNC(Ph)-
N(CH2)3NC(Ph)NSiMe3), has been reported previously.9e The
Catalytic activity of 1–6 for catalytic additions of amines to
carbodiimides
analogous aryloxide complexes LY[O2,6-(Me)2C6H3](DME) (1); The catalytic activity of 1–6 in the addition of PhNH2 to N,N′-
LY[O2,6-(iPr)2C6H3](DME) (2) and LLn[O2,6-(tBu)2-4-(Me)C6H2]- diisopropylcarbodiimide (iPrNCNiPr) was assessed under the
(DME) (Ln = Y (3); Nd (4); Sm (5); Yb (6)) were prepared simi- conditions as shown in Table 2. All complexes were found to
larly in high yields by the reaction of LLnCl(THF)2 with NaOAr be efficient precatalysts. However, the differences in the
in THF and followed by treatment with toluene and DME activity among them were observed. The activities of Y (3) and
(Scheme 1).
Yb (6) complexes are higher than those of Nd (4) and Sm (5)
Complexes 1–6 were characterized by elemental analysis, IR complexes (Table 2, entries 3–6). The aryloxide group also has
and NMR spectroscopy for Y complexes 1–3. The molecular a great influence on the activity with the activity trend of -2,6-
structures of 1, 2 and 4–6 were determined. X-ray single-crystal (Me)2C6H3 < -2,6-(iPr)2C6H3 < -2,6-(tBu)2-4-(Me)C6H2 (Table 2,
structure analyses revealed that complexes 1, 2 and 4–6 are iso- entries 1–3), which is consistent with the size of the aryloxide
structural and isomorphous. Their selected bond lengths and groups. Such an active sequence is as same as that reported
angles are summarized in Table 1, and only the ORTEP for the systems with Ln(OAr)3(THF)2.8a Thus, complexes 3 and
drawing of 6 is shown in Fig. 1. The ORTEP drawing of com- 6 show the highest activity, while complex 1 has the lowest one
plexes 1, 2, 4 and 5 are given in the ESI (Fig. S20–S23†).
among the six complexes.
The central metal in each complex coordinates to four
To compare the model, reactions with Y[O2,6-
nitrogen atoms from the bis(amidinate) ligand, three oxygen (Me)2C6H3]3(THF)2, Y[O2,6-(iPr)2C6H3]3(THF)2 and Y[O2,6-
Scheme 1 Preparations of LLn(OAr)(DME).
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Table 1 Selected bond distances (Å) and angles (°) for 1, 2 and 4–6
Bond lengths
1
2
4
5
6
Ln(1)–N(1)
Ln(1)–N(2)
Ln(1)–N(3)
Ln(1)–N(4)
Ln(1)–C(1)
Ln(1)–O(1)
Ln(1)–C(2)
N(1)–C(1)
N(2)–C(1)
N(3)–C(2)
N(4)–C(2)
2.516(5)
2.319(5)
2.524(5)
2.317(6)
2.832(6)
2.105(4)
2.820(7)
1.330(8)
1.318(8)
1.335(8)
1.296(8)
2.509(3)
2.328(3)
2.488(3)
2.382(3)
2.839(4)
2.095(2)
2.819(4)
1.341(5)
1.314(5)
1.341(5)
1.337(5)
2.559(2)
2.443(3)
2.674(3)
2.422(3)
2.911(3)
2.212(2)
2.974(3)
1.339(4)
1.307(4)
1.338(4)
1.314(4)
2.541(2)
2.415(2)
2.652(2)
2.399(2)
2.884(2)
2.189(2)
2.946(2)
1.336(3)
1.311(3)
1.331(3)
1.312(3)
2.586(3)
2.263(3)
2.510(3)
2.290(3)
2.860(4)
2.110(2)
2.794(4)
1.333(4)
1.325(5)
1.328(5)
1.306(5)
Bond angles
O(3)–Ln(1)–C(1)
O(3)–Ln(1)–C(2)
C(2)–Ln(1)–C(1)
O(2)–Ln(1)–C(1)
O(2)–Ln(1)–C(2)
O(3)–Ln(1)–O(2)
O(1)–Ln(1)–O(2)
N(2)–Ln(1)–N(1)
N(4)–Ln(1)–N(3)
116.88(17)
113.62(17)
124.07(19)
90.93(17)
88.1(2)
66.42(14)
154.65(16)
55.32(19)
54.77(17)
116.33(10)
116.60(10)
119.50(11)
88.60(12)
88.10(12)
65.48(8)
149.68(9)
55.41(11)
55.56(11)
128.22(7)
110.99(8)
112.50(8)
90.02(8)
92.65(8)
61.18(6)
142.66(7)
53.57(8)
52.33(8)
127.39(6)
111.09(7)
113.23(7)
89.97(6)
91.55(7)
61.81(6)
143.37(6)
54.13(7)
52.68(7)
110.30(10)
115.84(10)
119.88(12)
81.45(10)
83.30(11)
66.83(9)
157.32(9)
54.62(10)
55.50(11)
Table 2 Addition of PhNH2 to iPrNCNiPr by complexes 1–6, 8 and 11a
Entry Cat
Temp/°C Time/h Yieldb(%)
1
2
3
4
5
6
7
8
1
2
3
4
5
6
3
3
60
60
60
60
60
60
60
r.t.
60
60
60
0.25
0.25
0.25
0.25
0.25
0.25
0.5
2
24
4
0.5
78
87
95
67
69
92
>99
92
13
58
98
9
10
11
Y[O2,6-(Me)2C6H3]3(THF)2
Y[O2,6-(iPr)2C6H3]3(THF)2
Y[O2,6-(tBu)2-4-(Me)
C6H2]3(THF)2
8
11
Fig. 1 ORTEP diagram of the molecular structure of 6. Thermal ellipsoids are
12
13
60
60
0.25
0.25
97
99
drawn at 30% probability level. All hydrogen atoms are omitted for clarity.
a 1 mmol of aniline,
b Isolated yields.
1 mmol of N,N′-diisopropylcarbodiimide.
(tBu)2-4-(Me)C6H2]3(THF)2, respectively, were also conducted. It
is worth noting that the complexes with L ligand show higher
activity in comparison with the corresponding aryloxides com- C6H2]3(THF)2 was used (Table 2, entries 1–3 and 9–11). The
plexes without the L ligand. For example, the model reactions reaction with 3 can even proceed at room temperature and the
with Y[O2,6-(Me)2C6H3]3(THF)2 and Y[O2,6-(iPr)2C6H3]3(THF)2 yield of the product is as high as 92% after 2 h at the catalyst
afforded the guanidine in 13% yield after 24 h and 58% yield loading of 0.5 mol% (Table 2, entry 8).
after 4 h, respectively, while the yields increased to 78% and
Complex 3 was chosen as a catalyst precursor for the cata-
87% after 0.25 h when 1 and 2 were used instead. Also, the lytic addition of various primary and secondary amines to carbo-
same reaction with complex 3 yielded the product in 95% yield diimides. Representative results are summarized in Table 3. As
after 0.25 h, while to get the same yield the reaction time shown in Table 3, complex 3 is an efficient catalyst precursor
needed to be extended to 0.5 h, when Y[O2,6-(tBu)2-4-(Me)- with a wide scope of amines and it is robust. The reaction is
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Table 3 Catalytic additions of amines to carbodiimidesa
Entry
R
R1R2NH
Time/h
Product
Yieldb(%)
1
2
iPr
Cy
iPr
Cy
0.5
0.5
13
14
>99
99
3
4
0.5
0.5
15
16
>99
>99
5
6
iPr
Cy
0.5
0.5
17
18
93
96
7
8
iPr
Cy
0.5
0.5
19
20
90
93
9
10
iPr
Cy
0.5
0.5
21
22
92
98
11
12
13
14
15
iPr
iPr
iPr
iPr
iPr
0.5
0.5
0.5
2
23
24
25
26
27
>99
>99
>99
95
24
98
16
17
iPr
iPr
24
24
28
29
80
95
18
19
iPr
iPr
24
24
30
31
92
91
a The reaction was performed by treating 1 equiv. of amines with 1 equiv. of carbodiimides at 60 °C. b Isolated yields.
not influenced by either electron-withdrawing or electron- information about the real active species and the reaction
donating substituents at the phenyl ring of aromatic amines. pathways.
Primary and secondary amines both could be used for this
reaction. However, the reaction with a bulky amine, 2,6-diiso-
propylaniline, is less active, this may be attributed to the steric
Reaction of 6 with iPrNCNiPr
The coordination of carbodiimide to the center metal of
Ln(OAr)3(THF)2 is known to be the first key step in the catalytic
hindrance. The same phenomenon has also been observed for
the systems with other lanthanide catalysts reported.7d,10
addition of amine to carbodiimide using Ln(OAr)3(THF)2 as a
precatalyst.8a Therefore, the reaction of 6 with PrNCNiPr in a
i
1 : 1 molar ratio was firstly carried out in toluene at 60 °C to
Mechanistic studies
see whether the coordinated DME molecule in 6 could be
i
i
The stoichiometric reactions of 6 with PrNCNiPr and PhNH2, replaced by a PrNCNiPr molecule. However, after stirring for
and the reaction of 6 (or 3) with a mixture of amine and carbo- 24 h, no reaction was observed and complex 6 was recovered
diimide, respectively, were conducted in order to gain completely from the reaction solution.
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Scheme 2 Reaction of 6 with PhNH2.
Reaction of 6 with PhNH2
The reaction of 6 with PhNH2 at a molar ratio of 1 : 1 was then
carried out in toluene at 60 °C. The reaction took place
smoothly to afford a pale yellow solution, from which light
yellow crystals were isolated in 42% yield. The crystals were
characterized by elemental analysis, IR and X-ray crystal struc-
ture determination to be the bis-aryloxide complex supported
by a newly formed amidine-functionalized monoamidinate
ligand L′, L′Yb[O2,6-(tBu)2-4-(Me)C6H2]2 (7) (L′ = Me3SiNHC-
(Ph)N(CH2)3NC(Ph)NSiMe3) (Scheme 2).
The formation of 7 is unexpected, probably due to the dis-
proportionation of the in situ formed monoamide complex {L′-
Yb(NHC6H5)[O2,6-(tBu)2-4-(Me)C6H2]} via the protonation of
one amidinate group of L in 6 by PhNH2 (Scheme 2), as the
protonation of an amidinate group in lanthanide amidinate
complex by amine to the corresponding amide complex has
been documented.9d Probing the reaction of 3 with PhNH2 in
1 : 1 molar ratio at room temperature by NMR revealed the for-
mation of the Y-NHPh species (ESI: Fig. S25–S26†). However,
efforts to isolate the bisamido complex have not been
successful.
The molecular structure of 7 is shown in Fig. 2 and the
selective bond distances and angles are given in Table 4.
Complex 7 is a monomer. The bond parameters in the part
of Yb–N1–C1–N2 (Table 4) are comparable with those found in
complexes 1, 2 and 4–6 and the related bridged amidinate
complexes reported.7 Whilst, the distances of the C2–N3 bond
(1.415(14) Å) and the C2–N4 bond (1.321(14) Å) fall in the
range of C–N single and CvN double bonds, respectively, and
the bond distance of Yb–N4 of 2.416(8) Å is indicative of a
donating bonding, the N3 atom is out of the coordination
sphere. The bond parameters of the YbL′ unit, which is quite
different from those in 6, indicates the L′ in 7 is a newly
formed monoanionic amidine-functionalized amidinate
group. Thus, the Yb center in 7 is five-coordinate and bound
to two aryloxide ligands and three N atoms of the amidinate
fragment. The coordinated geometry around the center Yb
metal can be described as a distorted trigonal pyramid, when
the amidinate ligand is considered to be point donor located
at the central carbon atom (C1). The distances of two Ln–O
Fig. 2 Molecular structure of 7. Thermal ellipsoids are drawn at 30% prob-
ability level. All hydrogen atoms are omitted for clarity.
Table 4 Selected bond distances (Å) and angles (°) for 7
Bond lengths
Ln(1)–N(1)
Ln(1)–N(2)
Ln(1)–N(4)
Ln(1)–C(1)
Ln(1)–O(1)
2.415(8)
2.260(9)
2.416(8)
2.777(10)
2.066(7)
Ln(1)–O(2)
N(1)–C(1)
N(2)–C(1)
N(3)–C(2)
N(4)–C(2)
2.069(6)
1.358(13)
1.345(13)
1.415(14)
1.321(14)
Bond angles
O(1)–Ln(1)–O(2)
O(1)–Ln(1)–C(1)
O(2)–Ln(1)–C(1)
O(1)–Ln(1)–N(4)
126.7(3)
114.7(3)
114.2(3)
94.0(3)
O(2)–Ln(1)–N(4)
N(1)–Ln(1)–N(2)
N(2)–C(1)–N(1)
91.8(3)
58.0(3)
114.2(9)
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Scheme 3 Reactions of 6 (or 3) with amines and carbodiimides.
bonds, 2.066(7) and 2.069(6) Å, are almost equivalent and the corresponding Y-guanidinate species was formed (ESI:
i
values are comparable with those in complexes 1, 2 and 4–6.
Fig. S27–S29†). Then, the reaction of 6 with PhNH2 and PrNC-
NiPr in a molar ratio of 1 : 1 : 1 at 60 °C in toluene was tested.
The reaction went easily to give a light yellow solution, from
which yellow crystals were isolated upon crystallization from a
mixture of THF and hexane in high yield. The crystals were
characterized by X-ray crystal structure determination to be the
expected monoguanidinate complex supported by the L′ and
the -O2,6-(tBu)2-4-(Me)C6H2 ligands, L′Yb[O2,6-(tBu)2-4-(Me)-
C6H2][iPrNCNHiPrN(Ph)] (8) (Scheme 3). Treatments of 6 with
Reactions of 6 (or 3) with a mixture of amine and
carbodiimide
The Ln–guanidinate species has proven to be the real active
intermediate for addition of amines to carbodiimides.7j,k
Thus, the reaction of 6 (or 3) with equivalents of amine and
carbodiimide was conducted in an attempt to see whether the
monoguanidinate complex, the real active intermediate for
this catalytic reaction, could be isolated via the insertion of a
carbodiimide into the in situ formed monoamide complex
mentioned above. NMR experiments for the reaction of 3 with
PhNH2 and iPrNCNiPr at room temperature indicated the
either 4-ClC6H4NH2 and PrNCNiPr or PhNH2 and CyNCNCy
i
both afforded the corresponding monoguanidinate complexes
L′Yb[O2,6-(tBu)2-4-(Me)C6H2][iPrNCNHiPrN(4-ClC6H4)] (9) and
L′Yb[O2,6-(tBu)2-4-(Me)C6H2][CyNCNHCyN(Ph)] (10). Also, the
analogous Y complexes L′Y[O2,6-(tBu)2-4-(Me)C6H2][iPrNCN-
HiPrN(Ph)] (11) and L′Y[O2,6-(tBu)2-4-(Me)C6H2][CyNCNHCy-
N(Ph)] (12) could be prepared similarly by reactions of 3 with
PhNH2 and carbodiimides as shown in Scheme 3.
Table 5 Selected bond distances (Å) and angles (°) for 8 and 9
According to the NMR experiments (both for the reactions
i
of 3 with PhNH2 and with PhNH2 and PrNCNiPr) the pathway
8
9
8
9
for the preparations of monoguanidinate complexes of 8–12
could be proposed as follows: 3 (or 6) reacted firstly with
amine to yield the monoamide complex, which added immedi-
ately to carbodiimide affording the monoguanidinate complex
(Scheme 3).
The molecular structures of complexes 8–12 were deter-
mined by X-ray crystal structure analyses. The results revealed
that 9–12 and 8 are isostructural, although the detailed
bond parameters for complexes 11 and 12 could not be given
due to the poor quality of their single crystals. The selective
bond distances and angles for complexes 8 and 9 are given in
Table 5 and only the ORTEP drawing of 8 is shown in Fig. 3.
The ORTEP drawing of 9 is given in the ESI (Fig. S24†).
Complex 8 is a monomer. The center metal Yb coordi-
nates to one L′, one guanidinate ligand, and one OAr group.
The coordination number of the center metal is 6 and the
coordination geometry around the center metal can be
Bond lengths
Ln(1)–N(1) 2.384(7) 2.423(6)
Ln(1)–N(2) 2.300(7) 2.287(6)
Ln(1)–N(4) 2.419(7) 2.459(5)
Ln(1)–N(5) 2.328(7) 2.343(5)
Ln(1)–N(6) 2.384(8) 2.368(5)
Ln(1)–O(1) 2.083(6) 2.086(4)
N(1)–C(1)
N(2)–C(1)
N(3)–C(2)
N(4)–C(2)
N(5)–C(45) 1.340(11) 1.349(8)
N(6)–C(45) 1.350(12) 1.339(8)
1.345(11) 1.339(9)
1.324(11) 1.321(9)
1.372(12) 1.355(9)
1.320(11) 1.290(8)
Bond angles
O(1)–Ln(1)– 110.3(3) 112.06(19) N(4)–Ln(1)– 89.8(2)
C(1) O(1)
O(1)–Ln(1)– 126.2(3) 120.00(18) N(2)–C(1)– 113.7(8) 114.7(6)
C(45) N(1)
N(5)–Ln(1)– 56.8(3) 56.80(18) N(4)–C(2)– 120.2(9) 120.7(6)
91.26(18)
N(6)
N(3)
N(1)–Ln(1)– 57.0(2) 56.7(2)
N(2)
C(1)–Ln(1)– 110.8(3) 116.21(19)
C(45)
N(5)–C(45)– 112.9(9) 113.0(6)
N(6)
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errors. The bond angles around C45 are consistent with sp2
hybridization. The bond distances of C45–N5 (1.340(11) Å)
and C45–N6 (1.350(12) Å) are almost equivalent and signifi-
cantly shorter than the C–N single-bond distances, indicating
that the electrons are delocalized over the N–C–N unit. The
bond parameters of Yb–guanidinate unit (Table 5) are com-
pared to those in the related guanidinate Yb complexes
reported.7k,8a
As it stated that no reaction was observed between PhNH2
i
and PrNCNiPr at 60 °C for 24 h. In contrast, addition of
0.25 mol% of 8 led to rapid addition of PhNH2 to iPrNCNiPr to
give the guanidine in 92% yield. The activities of the inter-
mediates of 8 and 11 were found to be the same as those of
the catalyst precursors 6 and 3 (Table 2, entries 12–13 and 6).
According to the above results, a possible reaction pathway for
the catalytic addition of amines to carbodiimides by LLn(OAr)-
(DME) could be proposed in Scheme 4. The protonation reac-
tion between LLn(OAr)(DME) and an amine should simply
yield an amido species A. Nucleophilic addition of the amido
Fig. 3 ORTEP diagram of the molecular structure of 8. Thermal ellipsoids are
drawn at the 30% probability level. All hydrogen atoms and lattice solvent mole- species A to a carbodiimide would afford directly the guanidi-
cules are omitted for clarity.
nate species B. Protonation of B by another molecule of amine
would regenerate the amido species
guanidine.
A and release the
Thus, the active group in the precatalysts 1–6 is the amidi-
nate group of L ligand, not the OAr group as the systems with
Ln(OAr)3(THF)2. This may be because the Ln–amidinate bond is
more reactive than the Ln–OAr bond for the protonation reac-
tion, even the amidinate group is from a bridged bis(amidinate)
ligand. To the best of our knowledge this is the first example of
a catalytic addition of amines to carbodiimides by a precatalyst
containing the Ln-bridged amidinate active group.
described as a distorted trigonal pyramid when the amidinate
and the guanidinate ligands both are considered to be point
donors located at the central carbon atoms (C1 and C45,
respectively). The bond parameters of the unit of YbL′ and
the distance of Yb–O1 bond (Table 5) are well comparable
with those in complex 7 (Table 4). As expected, the coordi-
nated guanidinate group forms essentially a planar four-
member ring with the metal atom within experimental
Scheme 4 Mechanism for addition of amines to carbodiimides catalyzed by LLn(OAr)DME.
5896 | Dalton Trans., 2013, 42, 5890–5901
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Paper
–OC6H3(CH3)2), 0.07 (18 H, m, –SiMe3). IR (KBr, cm−1): 3648
(m), 3338 (m), 3062 (m), 2953 (m), 2872 (m), 1605 (s), 1540
Conclusion
A series of bridged bis(amidinate) lanthanide aryloxides, LLn (m), 1432 (m), 1360 (m), 1280 (m), 1233 (m), 1158 (s), 1053
(OAr)(DME) (1–6) can be easily prepared by the reaction of (m), 998 (s), 887 (w), 777 (m), 750 (m), 701 (m), 553 (m). Calcd
LLnCl(THF)2 with the corresponding sodium aryloxide in high for C42H61N4O3Si2Y (815.04): C, 61.89; H, 7.54; N, 6.87;
yields. All the complexes can serve as efficient catalyst precur- Y, 10.91. Found: C, 61.67; H, 7.38; N, 6.92; Y, 11.03.
sors for addition of amines to carbodiimides to multi-substi-
Synthesis of LY[O2,6-(iPr)2C6H3](DME) (2)
tuted guanidines in excellent yields with a wide range of
amines. The study on the isolation and structure characteriz- By the procedure described for 1, reaction of Na[O2,6-
ation of guanidinate complexes of 8–12 and their activity for (iPr)2C6H3] (0.70 g, 3.5 mmol) with a solution of LYCl(THF)2
catalytic addition of amines to carbodiimides revealed that the (2.43 g, 3.5 mmol) gave 2 as colorless crystals. Yield: 2.26 g
1
present catalytic reaction proceeds through the protonation of (83%). M.p.: 126–127 °C (decomp.). H NMR (400 MHz, C6D6):
an amidinate group of the precatalyst (1–6) by amine, then the δ = 7.33 (2 H, d, J = 7.5 Hz, –ArH), 7.21 (5 H, m, –ArH), 7.07
nucleophilic addition of the formed amide species to a carbo- (6 H, m, –ArH), 3.83 (8 H, s, –CH3OC2H4OCH3), 3.00 (2 H, s,
diimide, followed by amine protonolysis of the resultant guani- –CH3OC2H4OCH3), 1.54 (8 H, d, J = 6.8 Hz, –CH2 and –CH
dinate species.
(CH3)2), 1.38 (12 H, m, –OC6H3[CH(CH3)2]2), 0.06 (18 H, m,
–SiMe3). 13C NMR (101 MHz, C6D6): δ = 128.3, 127.9, 122.9,
116.4, 69.5, 48.2, 33.0, 25.4, 25.2, 24.6. IR (KBr, cm−1): 3690
(m), 3352 (m), 3060 (m), 2955 (m), 1609 (s), 1572 (m), 1540
(m), 1432 (m), 1343 (m), 1280 (m), 1239 (m), 1157 (s), 1043
(m), 998 (s), 887 (w), 833 (m), 778 (m), 751 (m), 701 (m), 555
(m). Calcd for C39H61N4O3Si2Y (779.01): C, 60.13; H, 7.89;
N, 7.19; Y, 11.41. Found: C, 59.89; H, 7.64; N, 7.12; Y, 11.21.
Experimental section
All preparations and manipulations involving air- and moist-
ure-sensitive complexes were carried out under an inert atmos-
phere of purified argon using standard Schlenk techniques.
The solvents of THF, DME (dimethoxyethane), toluene and n-
hexane were dried and distilled from sodium/benzophenone
ketal prior to use. [D6]Benzene was dried over fresh Na chips
in a glovebox for NMR reactions. Carbodiimides and amines
were purchased from TCI and were used as supplied. The
ligand precursor LH2 (LH2 = Me3SiNHC(Ph)N(CH2)3NC(Ph)-
NHSiMe3) and LLnCl(THF)2 were prepared according to the lit-
erature procedure.11 1H NMR and 13C NMR spectra were run
on a Bruker DPX-300 or a Unity Inova-400 spectrometer.
Lanthanide analyses were performed by EDTA titration with a
xylenol orange indicator and a hexamine buffer. Elemental
analyses were performed by direct combustion using a Carlo-
Erba EA 1110 instrument. The Infrared spectra were recorded
on a Magna-IR 550 spectrometer as KBr pellets.
Synthesis of LY[O2,6-(tBu)2-4-(Me)C6H2](DME) (3)
By the procedure described for 1, reaction of Na[O2,6-(tBu)2-
4-(Me)C6H2] (0.75 g, 3.1 mmol) with a solution of LYCl(THF)2
(2.15 g, 3.1 mmol) gave 3 as colorless crystals. Yield: 2.24 g
1
(88%). M.p.: 120–121 °C (decomp.). H NMR (400 MHz, C6D6):
δ = 7.35 (4 H, m, –ArH), 7.04 (12 H, s, –ArH), 3.32 (10 H, m,
–CH3OC2H4OCH3), 2.46 (3 H, m, –CH2), 2.13 (3 H, s, –CH2),
1.88 (21 H, m, –OC6H2[C(CH3)3]2CH3), 0.07 (18 H, m, –SiMe3).
IR (KBr, cm−1): 3647 (m), 3414 (m), 3326 (m), 2954 (m), 1645
(w), 1603 (s), 1569 (m), 1490 (m), 1431 (m), 1384 (m), 1362 (m),
1233 (m), 1216 (m), 1158 (s), 1073 (m), 957 (s), 832 (w), 776
(m), 701 (m), 503 (m). Calcd for C42H67N4O3Si2Y (821.08):
C, 61.44; H, 8.22; N, 6.82; Y, 10.83. Found: C, 61.19; H, 8.41;
N, 6.68; Y, 10.56.
Synthesis of LY[O2,6-(Me)2C6H3](DME) (1)
Following modified literature routes,9e a solution of Na[O2,6-
Synthesis of LNd[O2,6-(tBu)2-4-(Me)C6H2](DME) (4)
(Me)2C6H3] (0.48 g, 3.0 mmol) in THF (30 mL) was slowly By the procedure described for 1, reaction of Na[O2,6-(tBu)2-
added to a stirring solution of LYCl(THF)2 (2.08 g, 3.0 mmol) 4-(Me)C6H2] (0.85 g, 3.5 mmol) with a solution of LNdCl(THF)2
in a Schlenk flask. The reaction mixture was stirred at room (2.61 g, 3.5 mmol) gave 4 as light purple crystals. Yield: 2.39 g
temperature overnight. The residual NaCl was removed by cen- (78%). M.p.: 121–122 °C (decomp.). IR (KBr, cm−1): 3648 (m),
trifugation, the solvent evaporated in vacuo, and the solid 3415 (m), 3338 (m), 2957 (m), 1669 (m), 1646 (w), 1607 (s),
residue extracted with toluene (30 mL). The resulting pale 1569 (m), 1490 (m), 1433 (m), 1384 (m), 1363 (m), 1231 (m),
yellow solution was concentrated and a small amount of DME 1216 (m), 1158 (s), 1120 (m), 1028 (s), 860 (w), 777 (m), 701
was added. Then the mixture was filtered, and the solution (m), 504 (m). Calcd for C42H67N4O3Si2Nd (876.42): C, 57.56;
was slowly concentrated at room temperature, cooled to H, 7.71; N, 6.39; Nd, 16.46. Found: C, 57.39; H, 7.81; N, 6.68;
−30 °C, and left overnight. The crystalline precipitate was Nd, 16.65.
washed with cold hexane and dried in vacuo at room tempera-
Synthesis of LSm[O2,6-(tBu)2-4-(Me)C6H2](DME) (5)
ture. Complex 1 was obtained as colorless crystals. Yield:
1
1.85 g (85%). M.p.: 125–127 °C (decomp.). H NMR (400 MHz, By the procedure described for 1, reaction of Na[O2,6-(tBu)2-
C6D6): δ = 7.36 (2 H, d, J = 7.3 Hz, –ArH), 7.21 (7 H, d, J = 12.9 4-(Me)C6H2] (0.94 g, 3.9 mmol) with a solution of LSmCl(THF)2
Hz, –ArH), 7.08 (4 H, m, –ArH), 3.28 (10 H, m, (2.93 g, 3.9 mmol) gave 5 as pale yellow crystals. Yield: 2.79 g
–CH3OC2H4OCH3), 3.03 (6 H, s, –CH2), 2.77 (6 H, s, (81%). M.p.: 119–120 °C (decomp.). IR (KBr, cm−1): 3429 (m),
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Dalton Transactions
2957 (m), 1636 (w), 1607 (s), 1540 (m), 1490 (m), 1431 (m), pale yellow crystals. Yield: 3.27 g (82%). M.p.: 104–105 °C
1384 (m), 1363 (m), 1231 (m), 1215 (m), 1157 (s), 1120 (m), 860 (decomp.). IR (KBr, cm−1): 3456 (m), 2968 (m), 2869 (w), 2363
(w), 779 (m), 701 (m), 504 (m). Calcd for C42H67N4O3Si2Sm (m), 1637 (w), 1608 (s), 1491 (m), 1384 (w), 1243 (m), 1155 (s),
(882.54): C, 57.16; H, 7.65; N, 6.35; Sm, 17.04. Found: C, 57.19; 1090 (s), 859 (w), 836 (w), 639 (w), 555 (w), 504 (m). Calcd for
H, 8.41; N, 6.58; Sm, 17.26.
C55H85ClN7O2Si2Yb (1140.97): C, 57.89; H, 6.98; N, 8.59;
Yb, 15.17. Found: C, 57.54; H, 7.32; N, 9.01; Yb, 15.59.
Synthesis of LYb[O2,6-(tBu)2-4-(Me)C6H2](DME) (6)
By the procedure described for 1, reaction of Na[O2,6-(tBu)2-
Synthesis of L′Yb[O2,6-(tBu)2-4-(Me)C6H2][(C6H5N)C(NHCy)-
NCy](THF) (10)
4-(Me)C6H2] (0.73 g, 3.0 mmol) with a solution of LYbCl(THF)2
(2.32 g, 3.0 mmol) gave 6 as pale yellow crystals. Yield: 2.31 g By the procedure described for 8, reaction of 6 (3.50 g,
(85%). M.p.: 130–133 °C (decomp.). IR (KBr, cm−1): 3648 (m), 4.0 mmol) with CyNCNCy (2.38 ml, 1.677 M, 4.0 mmol) and
3422 (m), 3334 (m), 2955 (m), 1646 (w), 1603 (s), 1569 (m), aniline (0.36 ml, 10.96 M, 4.0 mmol) in toluene (20 mL) gave
1490 (m), 1431 (m), 1384 (m), 1363 (m), 1232 (m), 1216 (m), 10 as pale yellow crystals. Yield: 4.04 g (85%). M.p.: 117–118 °C
1158 (s), 1120 (m), 968 (s), 860 (w), 747 (m), 701 (m), 505 (m). (decomp.). IR (KBr, cm−1): 3424 (m), 2935 (m), 2869 (w), 1613
Calcd for C42H67N4O3Si2Yb (905.22): C, 55.73; H, 7.46; N, 6.19; (s), 1358 (w), 1164 (s), 1062 (s), 837 (w), 755 (m), 700 (m), 630
Yb, 19.12. Found: C, 55.67; H, 7.64; N, 6.12; Yb, 19.21.
(w), 500 (m). Calcd for C61H94N7O2Si2Yb (1186.66): C, 61.74;
H, 7.98; N, 8.26; Yb, 14.58. Found: C, 61.62; H, 8.12; N, 8.26;
Yb, 14.75.
Synthesis of L′Yb[O2,6-(tBu)2-4-(Me)C6H2]2 (7)
A certain amount of aniline (0.32 ml, 10.96 M, 3.5 mmol) was
added to a solution of 6 (3.06 g, 3.5 mmol) in toluene (30 mL),
which was stirred at 100 °C for 12 h. After the solvent was
Synthesis of L′Y[O2,6-(tBu)2-4-(Me)C6H2][(C6H5N)C(NHiPr)-
NiPr](THF) (11)
removed under reduced pressure, and the residue was To expand the scope and elucidate the mechanistic details for
extracted with hot THF. The resulting pale yellow solution was these transformations, we examined other potential catalyst
concentrated and a certain amount of hexane was added. Then precursors using the same method for 8. Reaction of 3 (3.28 g,
i
the mixture was filtered, and the solution was slowly concen- 4.0 mmol) with PrNCNiPr (0.62 ml, 6.418 M, 4.0 mmol) and
trated at room temperature. Single crystals of 7 suitable for aniline (0.36 ml, 10.96 M, 4.0 mmol) in toluene (20 mL) gave
X-ray analysis were obtained after about one day. Yield: 1.54 g 11 as colorless crystals. Yield: 3.19 g (80%). M.p.: 102–103 °C
1
(42%). M.p.: 109–110 °C (decomp.). IR (KBr, cm−1): 3443 (m), (decomp.). H NMR (300 MHz, C6D6): δ = 7.36 (2 H, s, –ArH),
2958 (m), 2361 (m), 1637 (w), 1436 (m), 1384 (w), 1232 (m), 7.29 (6 H, m, –ArH), 6.93 (9 H, m, –ArH), 3.56 (4 H, s, –OC4H8),
1155 (s), 1068 (s), 700 (m), 639 (m), 555 (w), 503 (m). Calcd for 3.39 (4 H, m, –CH2N), 2.86 (2 H, s, –NH), 2.43 (3 H, s,
C53H81N4O2Si2Yb (1035.44): C, 61.48; H, 7.88; N, 5.41; –OC6H2[C(CH3)3]2CH3), 1.82 (18 H, s, –OC6H2[C(CH3)3]2CH3),
Yb, 16.71. Found: C, 61.78; H, 7.64; N, 5.64; Yb, 16.57.
1.39 (4 H, s, –OC4H8), 1.22 (2 H, s, –NCH), 1.10 (2 H, s, –CHH),
0.87 (12 H, s, –NCH(CH3)2), 0.18 (18 H, m, –SiMe3). 13C NMR
Synthesis of L′Yb[O2,6-(tBu)2-4-(Me)C6H2][(C6H5N)C(NHiPr)-
(75 MHz, C6D6):
δ = 179.4, 167.4, 164.3, 161.6, 151.7,
NiPr](THF) (8)
150.8,149.5, 139.5,137.6, 135.1, 129.6, 128.3, 128.0, 127.7,
A certain amount of aniline (0.27 ml, 10.96 M, 3.0 mmol) was 125.9, 67.8, 46.5, 44.8, 43.2, 35.4, 32.8, 25.8, 23.2, 21.7. IR
added to a solution of 6 (2.63 g, 3.0 mmol) in toluene (20 mL). (KBr, cm−1): 3648 (m), 2957 (m), 2871 (w), 2360 (m), 1645 (w),
i
Then PrNCNiPr (0.47 ml, 6.418 M, 3.0 mmol) was added to 1615 (s), 1439 (m), 1386 (w), 1239 (m), 1155 (s), 1123 (s), 1071
the mixture. The mixture was stirred at 60 °C for 12 h. After (s), 1003 (w), 859 (w), 836 (w), 750 (m), 699 (m), 500 (m). Calcd
the solvent was removed under reduced pressure, the residue for C55H86N7O2Si2Y (1022.39): C, 64.61; H, 8.48; N, 9.59;
was washed by hexane twice then extracted with THF to give a Y, 8.70. Found: C, 64.48; H, 8.51; N, 9.63; Y, 8.86.
yellow solution, in which a certain amount of hexane was
Synthesis of L′Y[O2,6-(tBu)2-4-(Me)C6H2][(C6H5N)C(NHCy)NCy]-
(THF) (12)
added. The mixture was allowed to crystallize at room temp-
erature and light yellow crystals were obtained after about one
day (2.95 g, 89% yields). M.p.: 111–113 °C (decomp.). IR (KBr, Reaction of 3 (3.69 g, 4.5 mmol) with CyNCNCy (2.68 ml, 1.677
cm−1): 3646 (m), 2961 (m), 2866 (w), 2355 (m), 1645 (w), 1615 M, 4.5 mmol) and aniline (0.41 ml, 10.96 M, 4.5 mmol) in
(s), 1441 (m), 1383 (w), 1247 (m), 1156 (s), 1122 (s), 1068 (s), toluene (20 mL) gave 12 as colorless crystals. Yield: 4.07 g
1
1003 (w), 862 (w), 836 (w), 751 (m), 695 (m), 500 (m). Calcd for (82%). M.p.: 116–117 °C (decomp.). H NMR (300 MHz, C6D6):
C55H86N7O2Si2Yb (1106.53): C, 59.69; H, 7.28; N, 8.86; δ = 7.22 (6 H, d, J = 7.4 Hz, –ArH), 7.12 (6 H, d, J = 3.0 Hz,
Yb, 15.64. Found: C, 59.39; H, 7.38; N, 8.99; Yb, 16.01.
–ArH), 6.89 (5 H, s, –ArH), 4.00 (1 H, s, –NH), 3.56 (4 H, s,
–OC4H8), 3.36 (4 H, s, –CH2N), 2.83 (1 H, s, –NH), 2.40 (3 H, s,
–OC6H2[C(CH3)3]2CH3), 1.79 (18 H, s, –OC6H2[C(CH3)3]2CH3),
1.43 (4 H, d, J = 10.2 Hz, –OC4H8), 1.35 (2 H, s, –NCH), 1.10
Synthesis of L′Yb[O2,6-(tBu)2-4-(Me)C6H2][(4-Cl-C6H4N)C-
(NHiPr)NiPr](THF) (9)
By the procedure described for 8, reaction of 6 (3.06 g, (2 H, d, J = 11.1 Hz, –CHH), 0.85 (20 H, d, J = 0.9 Hz, –NC6H11),
i
3.5 mmol) with PrNCNiPr (0.54 ml, 6.418 M, 3.5 mmol) and 0.16 (18 H, m, –Si(CH3)3). 13C NMR (75 MHz, C6D6): δ = 179.0,
4-chloroaniline (0.37 g, 3.5 mmol) in toluene (20 mL) gave 9 as 167.3, 163.4, 161.3, 151.5, 150.2, 149.0, 139.2, 137.3, 134.8,
5898 | Dalton Trans., 2013, 42, 5890–5901
This journal is © The Royal Society of Chemistry 2013

Table 6 Crystallographic data for complexes 1, 2 and 4–9
Compound
1 (toluene)
2
4
5
6
7
8·(THF)
9·(THF)
Formula
Fw
T/K
C42H61N4O3Si2Y
815.04
200(2)
C39H61N4O3Si2Y
779.01
100(2)
C42H67N4O3Si2Nd
876.42
200(2)
C42H67N4O3Si2Sm
882.53
173(2)
C42H67N4O3Si2Yb
905.22
223(2)
C53H81N4O2Si2Yb
1035.44
223(2)
C55H86N7O2Si2Yb
1106.53
223(2)
C55H85ClN7O2Si2Yb
1140.97
223(2)
λ/Å
0.7107
Orthorhombic
Pcab
0.80 × 0.40 × 0.30
8.6929(2)
52.4298(17)
19.5627(7)
90
0.71070
Monoclinic
P21/c
0.60 × 0.20 × 0.20
24.6655(11)
8.6830(3)
20.0629(7)
90
0.71070
Monoclinic
P21/n
0.30 × 0.16 × 0.15
9.0793(2)
14.3645(3)
33.6538(8)
90
0.71073
Monoclinic
P21/n
0.70 × 0.25 × 0.20
9.0917(4)
14.3482(7)
33.7910(17)
90
0.71075
Monoclinic
P21/c
0.50 × 0.40 × 0.30
22.7177(9)
9.1356(3)
21.8886(9)
90
0.71075
Orthorhombic
P212121
0.80 × 0.60 × 0.40
13.244(4)
19.003(6)
21.832(6)
90
0.71075
Monoclinic
P21/n
0.40 × 0.20 × 0.10
13.980(2)
26.110(3)
17.139(3)
90
0.71075
Monoclinic
P21/c
0.80 × 0.30 × 0.10
18.079(2)
18.777(2)
18.448(2)
90
Crystal system
Space group
Crystal size/mm
a/Å
b/Å
c/Å
α (°)
β(°)
90
90
8916.0(5)
8
1.214
1.40
3456
106.124(4)
90
4127.9(3)
4
1.254
1.510
95.124(2)
90
4371.59(17)
4
1.332
1.283
95.344(2)
90
4388.9(4)
4
1.336
1.433
91.3490(10)
90
4541.5(3)
4
1.324
2.151
90
90
5495(3)
4
1.252
1.785
2164
111.891(4)
90
5804.8(14)
4
1.266
1.696
109.725(3)
90
5895.1(13)
4
1.286
1.716
γ(°)
V/Å3
Z/Å3
Dcalcd/g cm−3
μ/mm−1
F(000)
1656
1836
1844
1876
2316
2380
θrange/°
2.82–25.50
84 018
8290
2.84–25.50
28 966
7688
2.81–25.50
29 627
8114
2.27–25.50
131 137
8156
3.02–27.48
32 573
10 281
3.00–25.50
19 391
9737
3.02–25.50
28 075
10 714
3.12–25.50
29 491
10 935
Total no. of rflns
No. of indep rflns
Rint
0.1233
0.0408
0.0479
0.0448
0.0303
0.0475
0.1050
0.0817
GOF
R [I > 2σ(I)]
wR
1.193
0.0986
0.1725
1.072
0.0515
0.1216
1.032
0.0335
0.0620
1.129
0.0254
0.0607
1.072
0.0375
0.0827
1.094
0.0585
0.1428
1.188
0.0984
0.1410
1.173
0.0705
0.1494
Largest diff. peak
1.012, −1.904
1.551, −1.507
0.612, −0.574
1.404, −0.412
1.553, −0.930
2.888, −1.122
0.644, −0.903
1.906, −1.601
and hole/e Å−3

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Dalton Transactions
129.3, 128.0, 127.7, 123.5, 122.7, 121.0, 67.8, 56.0, 51.5, 49.2,
47.8, 35.6, 33.6, 32.4, 26.0, 24.9, 21.3. IR (KBr, cm−1): 3432 (m),
2941 (m), 2870 (w), 1615 (s), 1355 (w), 1158 (s), 1067 (s), 837
(w), 750 (m), 700 (m), 639 (w), 504 (m). Calcd for
C61H94N7O2Si2Y (1102.52): C, 66.45; H, 8.59; N, 8.89; Y, 8.06.
Found: C, 66.28; H, 8.64; N, 8.95; Y, 8.32.
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Acknowledgements
We are grateful to the National Natural Science Foundation of
China (Grants No. 21132002, 20972107), a project funded by
the Priority Academic Program Development of Jiangsu Higher
Education Institutions for financial support.
5900 | Dalton Trans., 2013, 42, 5890–5901
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