Synthesis and structures of three, four, and six-coordinate monomeric tin(II) and tin(IV) compounds containing η2-ketiminate ligands

Article abstract of DOI:10.1016/j.ica.2008.02.002

A series of Sn(II) and Sn(IV) compounds containing ketiminate ligands were synthesized. Reactions of SnCl₂ with 1 or 2 equiv. Li[OCMeCHCMeNAr] (where Ar = 2,6-diisopropylphenyl) generate [OCMeCHCMeNAr]SnCl (1) and [OCMeCHCMeNAr]₂Sn (2) in moderate yield, respectively. Similarly, reacting SnCl₄ with 2 equiv. Li[OCMeCHCMeNAr] yields a six-coordinated [OCMeCHCMeNAr]₂SnCl₂ (3). Divalent tin compound 2 can be oxidized with I₂ in diethyl ether to generate tetravalent tin compound [OCMeCHCMeNAr]₂SnI₂ (4) in moderate yield. Compounds 1-4 have been characterized by ¹H and ¹³C NMR spectroscopy and have been analyzed by X-ray crystallography. Theoretical calculation found that the bonding of ketiminate ligands and tin atom in compound 2 has a strong ionic character.

Full text of DOI:10.1016/j.ica.2008.02.002

Available online at www.sciencedirect.com
Inorganica Chimica Acta 361 (2008) 2792–2798
www.elsevier.com/locate/ica
Synthesis and structures of three, four, and six-coordinate monomeric
tin(II) and tin(IV) compounds containing g2-ketiminate ligands
Hung-Ming Kao a, Shih-Mao Ho a, I-Chun Chen a, Pei-Cheng Kuo a, Che-Yu Lin a,
a
a
a,
b
*
Cheng-Yi Tu , Ching-Han Hu , Jui-Hsien Huang , Gene-Hsiang Lee
a Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan
b Department of Chemistry and Instrumentation Center, National Taiwan University, Taipei 10764, Taiwan
Received 21 June 2007; received in revised form 28 January 2008; accepted 4 February 2008
Available online 8 February 2008
Abstract
A series of Sn(II) and Sn(IV) compounds containing ketiminate ligands were synthesized. Reactions of SnCl2 with 1 or 2 equiv.
Li[OCMeCHCMeNAr] (where Ar = 2,6-diisopropylphenyl) generate [OCMeCHCMeNAr]SnCl (1) and [OCMeCHCMeNAr]2Sn (2)
in moderate yield, respectively. Similarly, reacting SnCl4 with 2 equiv. Li[OCMeCHCMeNAr] yields a six-coordinated [OCMeCHC-
MeNAr]2SnCl2 (3). Divalent tin compound 2 can be oxidized with I2 in diethyl ether to generate tetravalent tin compound [OCMeCHC-
MeNAr]2SnI2 (4) in moderate yield. Compounds 1–4 have been characterized by 1H and 13C NMR spectroscopy and have been analyzed
by X-ray crystallography. Theoretical calculation found that the bonding of ketiminate ligands and tin atom in compound 2 has a strong
ionic character.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Tin; Ketiminate; Oxidative addition
1. Introduction
for synthesizing a monomeric organotin compound is
increasing the bulkiness of ligands which results the stabil-
ity of the tin metal coordination sphere. The strategy was
to use bidentate ligands with bulky substituents on one side
to protect the metal centers and open ends on the other side
to increase the activity of the metal complexes. We are
interested in using substituted ketiminate as ancillary
ligands in chelating to group 13 and early transition metals
[10] and we studied their reactivities towards small organic
molecules. Here, we report the synthesis and characteriza-
tion of a series of Sn(II) and Sn(IV) monomeric com-
pounds incorporating ketiminate ligands.
Organotin compounds have been widely used in many
fields such as organic synthesis and catalysis [1]. High
valent tin(IV) compounds have long been used as biocides
[2] and as homogeneous catalysts in industries [3]. More-
over, di- and tri-organotin compounds have been found
to have in vitro activity against a large variety of tumor cell
lines [4]. Therefore, the versatility of applications, oxida-
tion states, and molecular structures for the tin metals
has been attracting much attention. The structural diversity
of organotin compounds is of interest and is reviewed peri-
odically [5]. The molecular structures of these organotin
compounds can be formed as monomers [6], dimers [7], tri-
mers [8], or even oligomers [6b,9] depending on the steric
bulkiness of coordinating ligands. The general method
2. Results and discussion
2.1. Synthesis and characterization of tin compounds
A series of tin(II) and tin(IV) complexes containing
mono-anionic ketiminate ligand, [OCMeCHCMeNAr]ꢀ,
*
Corresponding author. Tel.: +886 4 7232105x3531; fax: +886 4
7211190.
E-mail address: juihuang@cc.ncue.edu.tw (J.-H. Huang).
has been synthesized as shown in Scheme 1. A
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.02.002

H.-M. Kao et al. / Inorganica Chimica Acta 361 (2008) 2792–2798
2793
NMR data, and the methine carbon of the ketiminate back-
bone was observed at d 101.3.
Similarly, while 2 equiv. of Li[OCMeCHCMeNAr] was
used to react with SnCl2 in THF solution, compound 2,
[OCMeCHCMeNAr]2Sn, can be obtained in 68% yield
(Scheme 1). Pure white crystals of 2 were obtained by
recrystallization from a methylene chloride solution at
N
Cl
Cl
O
N
O
1/2 SnCl4
SnCl2
Sn
Sn
Cl
O
N
O
Li
N
1
1/2 SnCl2
1
ꢀ20 °C. The H NMR spectrum of 2 was very similar to
that of 1. The methine protons of the ketiminate backbones
showed a singlet at d 5.06 and the methyl fragments
appeared at d 1.96 and 1.65. It is also worth noting that
the methine protons of the isopropyl groups on the phenyl
rings appeared as two septet at d 3.58 and 2.81, indicating
the slow rotation of the N–C (phenyl) bonds of the ketimi-
nate ligands. Again, the methyl groups of isopropyl showed
four doublets at d 1.03, 1.06, and 1.19 (where two doublets
accidentally overlapped; however, two doublets can be
observed when the d 1.19 resonances were expanded). This
indicates the slow rotation of C–C (isopropyl–phenyl)
bonds. The 13C NMR resonances for the methyl groups
of the isopropyl fragments and the ketiminate backbone
3
O
N
Sn
O
N
2
Scheme 1.
three-coordinated tin compound 1, [OCMeCHCMeNAr]-
SnCl, was isolated as a white solid in moderate yield from
the metathesis reaction of SnCl2 with 1 equiv. of Li-
[OCMeCHCMeNAr] in diethyl ether. A small amount of
ketimine ligand was presented in compound 1 even repeating
recrystallization from a methylene chloride solution. The 1H
NMR spectra of 1 in CDCl3 consisted of two singlet reso-
nances at d 2.32 and 1.80, indicating the existence of the keti-
minate ligands. The resonance for the methine proton of
ketiminate backbone was seen at d 5.46 and the two methine
protons of the isopropyl were found at d 2.98 as a multiplet.
1
were verified by the H–13C 2D HSQC (heteronuclear sin-
gle quantum correlation) NMR spectrum which is shown
in Fig. 1.
Similarly, reacting tetravalent SnCl4 with 2 equiv. of
ketiminate lithium salts in methylene chloride yielded a
six-coordinate Sn(IV) compound [OCMeCHCMeNAr]2-
1
SnCl2 (3) in 72% yield. The patterns of H and 13C NMR
spectra for 3 were similar to those of 2. The methine groups
The 13C NMR spectrum of 1 was consistent with the H
1
1
of the ketiminate backbones show their H and 13C NMR
Fig. 1. The 1H–13C 2D HSQC NMR spectrum for the range of isopropyl and methyl fragment of the ketiminate backbone.

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H.-M. Kao et al. / Inorganica Chimica Acta 361 (2008) 2792–2798
signal at d 5.19 and 98.3, respectively. However, due to the
sterically crowded of 3, the isopropyl–phenyl bonds rotated
slowly, causing the methyl groups of isopropyl fragments
to exhibit four distinguished doublets at d 1.02, 1.08,
1.16, and 1.33.
upfield shifted in comparison to those of compound 3 due
to the less electronegative and more electron donating abil-
ity of iodine. It is worthy to note that the carbon reso-
nances of methyl groups are all appearing within the
range of d 25.1–29.0 and some of them are overlapping.
However, the assignment for all carbon atoms can be com-
pleted by using 2D HSQC NMR spectra (see Section 4).
119Sn NMR spectra in a CDCl3 solution at room tem-
perature have been measured for compounds 1–4 which
show a resonance at d ꢀ590.6, ꢀ587.4, ꢀ626.9, and
ꢀ916.5, respectively. The 119Sn chemical shifts agree with
those reported in the literature [11]. However, the chemical
shift for compound 4 is in a much higher field than that for
compounds 1–3, presumably due to the iodide atoms con-
tributing a large amount of electron density to shield the tin
metal.
The divalent tin compound 2 reacted with 1 equiv. of
iodine to generate tetravalent cis-diiodo-diketiminate–tin
compound [OCMeCHCMeNAr]2SnI2 (4) in 73% yields
through oxidative addition (Scheme 2). Compound 4 has
been characterized by 1D 1H and 13C NMR and 2D HSQC
1
NMR spectroscopy and elemental analysis. Again, the H
and 13C NMR spectra of 4 were similar to those of 3; how-
ever, the 1H NMR spectra show that all the resonances are
2.2. Molecular structures of compounds 1–4
N
I
I
O
The molecular structures of 1–4 have been characterized
by single crystal X-ray diffraction analyses. The summary
of data collections and the selected bond lengths and angles
for compounds 1–4 are listed in Tables 1 and 2, respec-
tively. The molecular structures of 1–4 are shown in Figs.
2–5. The ketiminate backbone of the chelating ligands for
compounds 1–4 is essentially planar and the tin is out of
I2
N
Sn
N
Sn
O
O
O
N
2
4
˚
˚
˚
Scheme 2.
the plane at 0.6684 A for 1, 0.6891 A for 2, 0.1128 A for
Table 1
The summary of crystallographic data for compounds 1–4
1
2
3
4
Formula
C
412.51
150
17H24ClNOSn
C34H48N2O2Sn
635.43
150
monoclinic
C2/c
9.2184(4)
15.5961(4)
23.2357(11)
C34H48Cl2N2O2Sn
706.33
150
monoclinic
P21/c
11.9338(3)
16.7790(3)
16.9388(4)
C34H48I2N2O2Sn
889.23
150
monoclinic
P21/n
12.9602(4)
16.3356(5)
17.0852(5)
Formula weight
Temperature (K)
Crystal system
Space group
triclinic
ꢀ
P1
˚
a (A)
8.7981(4)
˚
b (A)
10.1224(4)
11.7124(5)
107.4765(14)
109.2478(15)
99.850(2)
896.08(7), 2
1.529
1.574
˚
c (A)
a (°)
b (°)
c (°)
Volume (A )/Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
91.5070(10)
99.9791(6)
103.6370(6)
3
˚
3339.5(3), 4
1.264
1.574
3339.5(3), 4
1.404
0.957
3515.18(18), 4
1.680
2.514
)
416
1328
1464
1752
Crystal size (mm)
h Range (°)
Number of reflections collected
Number of independent reflections [Rint
Maximum and minimum transmission
Number of data/restraints/parameters
Goodness-of-fit on F2
0.20 ꢁ 0.15 ꢁ 0.15
1.99–27.50
14565
4065 [0.0663]
0.775 and 0.630
4065/0/197
1.088
R1 = 0.0493
wR2 = 0.1096
R1 = 0.0874
wR2 = 0.1537
1.131 and ꢀ1.143
0.35 ꢁ 0.29 ꢁ 0.26
1.75–27.51
10477
3800 [0.0255]
0.9486 and 0.7580
3800/0/183
1.048
R1 = 0.0282
wR2 = 0.0738
R1 = 0.0316
wR2 = 0.0753
0.701 and ꢀ0.309
0.25 ꢁ 0.25 ꢁ 0.20
1.72–27.50
29864
7640 [0.0532]
0.859 and 0.663
7640/0/371
1.058
R1 = 0.0431
wR2 = 0.1072
R1 = 0.0663
wR2 = 0.1186
1. 729 and ꢀ0.821
0.45 ꢁ 0.41 ꢁ 0.30
1.75–29.05
39740
9378 [0.0193]
0.5192 and 0.3975
9378/0/382
1.073
R1 = 0.0246
wR2 = 0.0604
R1 = 0.0301
wR2 = 0.0618
1.109 and ꢀ1.576
]
a
Final R indices [I > 2r(I)], R1
wR2
b
a
R indices (all data), R1
b
wR2
ꢀ3
˚
Largest difference in peak and hole (e A
)
P
P
a
R1 = jFoj ꢀ jFcj/ jFoj.
P
P
2
2 1=2
b
wR2 ¼ ½ ½wðF 2o ꢀ F c2Þ ꢂ= ½wðF 2oÞ ꢂ
.

H.-M. Kao et al. / Inorganica Chimica Acta 361 (2008) 2792–2798
2795
Table 2
Selected bond lengths and angles for compounds 1–4
Compound 1
Sn(1)–O(1)
Sn(1)–Cl(1)
C(2)–C(3)
N(1)–C(4)
2.087(4)
2.4637(17)
1.359(9)
1.319(7)
Sn(1)–N(1)
O(1)–C(2)
C(3)–C(4)
2.227(5)
1.311(7)
1.419(8)
O(1)–Sn(1)–Cl(1)
O(1)–Sn(1)–N(1)
90.66(12)
84.63(16)
N(1)–Sn(1)–Cl(1)
93.92(12)
Compound 2
Sn(1)–O(1)
O(1)–C(2)
C(3)–C(4)
2.0944(15)
1.304(3)
1.426(2)
Sn(1)–N(1)
C(2)–C(3)
N(1)–C(4)
2.4092(15)
1.366(3)
1.303(3)
N(1)–Sn(1)–N(1A)
O(1)–Sn(1)–N(1)
152.38(8)
79.62(5)
O(1)–Sn(1)–O(1A)
O(1)–Sn(1)–N(1A)
91.16(9)
81.14(5)
Compound 3
Sn(1)–O(1)
Sn(1)–N(1)
Sn(1)–Cl(1)
O(1)–C(2)
2.074(2)
2.224(3)
2.3713(8)
1.281(4)
1.408(4)
1.292(4)
1.292(4)
1.413(4)
Sn(1)–O(2)
Sn(1)–N(2)
Sn(1)–Cl(2)
C(2)–C(3)
N(1)–C(4)
C(19)–C(20)
C(19)–C(20)
O(2)–C(19)
2.073(2)
2.224(3)
2.3708(8)
1.365(4)
1.324(4)
1.361(4)
1.361(4)
1.292(4)
Fig. 2. The molecular structure of compound 1, thermal ellipsoids drawn
at the 50% probability level.
C(3)–C(4)
O(2)–C(19)
O(2)–C(19)
C(20)–C(21)
N(2)–Sn(1)–N(1)
O(2)–Sn(1)–Cl(2)
O(2)–Sn(1)–N(2)
O(1)–Sn(1)–O(2)
Cl(1)–Sn(1)–Cl(2)
174.33(9)
173.11(7)
88.12(8)
83.61(11)
97.18(3)
O(1)–Sn(1)–Cl(1)
O(1)–Sn(1)–N(1)
O(2)–Sn(1)–Cl(1)
O(1)–Sn(1)–Cl(2)
172.80(7)
88.00(8)
89.50(8)
89.76(8)
Compound 4
Sn(1)–O(1)
Sn(1)–N(1)
Sn(1)–I(1)
O(1)–C(2)
C(3)–C(4)
2.0784(18)
2.246(2)
2.7683(2)
1.295(3)
1.420(4)
1.305(3)
1.422(4)
Sn(1)–O(2)
Sn(1)–N(2)
Sn(1)–I(2)
C(2)–C(3)
N(1)–C(4)
C(19)–C(20)
O(2)–C(19)
2.0650(18)
2.261(2)
2.7841(2)
1.370(4)
1.325(3)
1.359(4)
1.305(3)
O(2)–C(19)
C(20)–C(21)
N(1)–Sn(1)–N(2)
O(2)–Sn(1)–I(1)
O(2)–Sn(1)–N(2)
O(1)–Sn(1)–O(2)
O(1)–Sn(1)–I(1)
176.53(8)
167.93(5)
86.59(7)
78.90(7)
89.36(5)
O(1)–Sn(1)–I(2)
O(1)–Sn(1)–N(1)
O(2)–Sn(1)–I(2)
I(1)–Sn(1)–I(2)
164.46(5)
85.69(7)
85.81(5)
106.036(8)
Fig. 3. The molecular structure of compound 2, thermal ellipsoids drawn
at the 50% probability level.
˚
3, and 0.6450 A for 4. The geometry of 1 can be described
as a distorted three-coordinated tetrahedral with one apical
position filled with a pair of electrons. Due to the large lone
pair electrons repulsion with bonding electrons pushing the
coordinating atoms together, the bond angles around the
tin atom are close to 90°. The bond length of Sn–Cl
with the two oxygen atoms of the ketiminate ligands trans
to the two chloro atoms and the two nitrogen atoms of the
ketiminate ligands occupy opposite positions. The bond
˚
lengths of Sn–Cl in 3 (av. 2.37 A) are shorter than that of
1 due to the stronger interaction of high valent Sn(IV) with
chloro atoms. Similarly, the geometry of compound 4 is the
same as that of 3 with the two oxygen atoms of the ketimi-
nate ligands trans to the two iodo atoms and the two
nitrogen atoms of the ketiminate ligands occupy opposite
directions.
˚
2.4637(17) A is at the average length of normal Sn(II)-chlo-
ride. The geometry of 2 contains a C2 symmetry and can be
described as a distorted trigonal bipyramidal with lone pair
electrons occupying at equatorial position. The two nitro-
gen atoms from ketiminate ligands occupy the axial posi-
tions and again the bonding electrons are pushed away
from the lone pair electrons and the axial axis is bended
at 152.38(8)°. The ketiminate ligands bind to the central
tin atom with an acute angle of 79.62(5)°. The six-coordi-
nate compound 3 features a distorted octahedral geometry
2.3. Bonding models of the Sn(II)
It is interesting to compare the bonding nature of Sn(II)
in the complexes. For this purpose, we performed

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H.-M. Kao et al. / Inorganica Chimica Acta 361 (2008) 2792–2798
Table 3
The natural charges of Sn and its ligands, Wiber bond index, and natural
electron configurations of Sn
SnCl2
Sn(N–O)Cl
Sn(N–O)2
Natural charges 1.142 (Sn)
1.243 (Sn)
ꢀ0.643(Cl),
ꢀ0.600 (N–O)
0.582 (Sn–Cl)
0.680
1.428 (Sn)
ꢀ0.714 (N–O)
ꢀ0.570 (Cl)
Wiber bond
index
0.733 (Sn–Cl)
0.680
(Sn–(N–O))
(Sn–(N–O))
5s(1.80),
5p(0.94),
6s(0.01),
5d(0.01)
Natural electron 5s(1.89),
configuration 5p(0.93),
5s(1.79),
5p(0.77),
6s(0.01),
5d(0.01)
(Sn)
6s(0.01),
5d(0.01)
(N–O) = OCMeCHCMeN.
O
Cl
Cl
N
O
Cl
Sn
O
Sn
N
Sn
N
Fig. 4. The molecular structure of compound 3, thermal ellipsoids drawn
at the 50% probability level.
Fig. 6. DFT calculation depicted that the nonbonding Sn electrons of
SnCl2, Sn(N–O)Cl, and Sn(N–O)2 are all located in 5s orbitals forming the
geometries of V-shape, trigonal pyramidal, and sea-saw.
rized in Table 3. We can see that substitution of a chloride
ion from SnCl2 by the (N–O)ꢀ ligand increases the positive
charge on the Sn center. Natural electron configuration at
Sn shows that the valence electrons reside mostly on its 5s
orbital. A schematic drawing of the geometries of SnCl2,
Sn(N–O)Cl, and Sn(N–O)2 is depicted in Fig. 6 reveals
the nonbonding character of Sn. The tendency to place
nonbonding Sn electrons in 5s orbital has resulted the
geometries of SnCl2, Sn(N–O)Cl, and Sn(N–O)2 as V
shape, trigonal pyramid, and sea-saw, respectively. Natural
bond orbital analysis resolves Sn-natural bond orbitals
only in SnCl2, while for Sn(N–O)Cl and Sn(N–O)2 no nat-
ural bond involving Sn has been resolved. These observa-
tions suggest that Sn–(N–O) bond has a stronger ionic
character. Despite its ionic bonding nature, Sn(N–O)2 is
not a very polar compound, however. The dipole moments
of SnCl2, Sn(N–O)Cl and Sn(N–O)2 are 3.876, 5.972, and
2.559 Debyes, respectively. Despite the ionic character of
the Sn–(N–O) bond, an attempt to further study the reac-
tion of NaBPh4 and Sn(N–O)2 in d8-THF at 80 °C results
an decomposition.
Fig. 5. The molecular structure of compound 4, thermal ellipsoids drawn
at the 50% probability level.
theoretical studies on SnCl2, Sn(N–O)Cl, and Sn(N–O)2,
where (N–O) = OCMeCHCMeNAr. We used the gradi-
ent-corrected hybrid density functional theory (DFT),
B3LYP. The approach is a hybrid method, which consists
of the three-parameter mixing of gradient-corrected
exchange functional of Becke [12] and correlation func-
tional of Lee, Yang, and Parr [13]. For H, C, N, and O
atoms we used the 6-31G basis sets. For Sn, we used the
DGDZVP basis set [14]. At the optimized structure, natu-
ral bond orbital (NBO) analysis was performed [15]. All
calculations were carried out using the GAUSSIAN 03 pro-
gram [16].
3. Conclusions
In conclusion, we have synthesized a series of divalent
and tetravalent tin compounds containing mono-anionic
ketiminate ligands. The divalent tin compound 2 can be
easily oxidized with iodine to form a tetravalent tin com-
pound 4. DFT calculation shows that the nonbonding elec-
trons of Sn(II) are mainly localized on the 5s orbitals and
the Sn–(N–O) bond has strong ionic character. Further
study of the activity of these Sn compounds toward lactone
and lactide polymerization is undergoing.
The natural charge of Sn and its ligands, Wiber bond
index, and natural electron configuration of Sn are summa-

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2797
4. Experimental
13C NMR (CDCl3): 23.1 (q, JCH = 127 Hz, CHMe2), 23.8
(q, JCH = 126 Hz, CMe), 23.9 (q, JCH = 125 Hz, CHMe2),
24.6 (q, JCH = 127 Hz, CMe), 26.2 (q, JCH = 126 Hz,
CHMe2), 26.3 (q, JCH = 126 Hz, CHMe2), 27.1 (d,
JCH = 127 Hz, CHMe2), 28.0 (d, JCH = 127 Hz, CHMe2),
4.1. General procedure
All reactions were performed under a dry nitrogen
atmosphere using standard Schlenk techniques or in a
glove box. Toluene, diethyl ether, and tetrahydrofuran
were dried by refluxing over sodium benzophenone ketyl.
CH2Cl2 was dried over P2O5. All solvents were distilled
98.8 (d, JCH = 157 Hz, CMeCHCMe), 123.2 (d, JCH
=
156 Hz, phenyl CH), 123.8 (d, JCH = 157 Hz, phenyl
CH), 125.0 (d, JCH = 159 Hz, phenyl CH), 141.2 (s, phenyl
Cipso), 141.8 (s, phenyl Cipso), 143.6 (s, phenyl Cipso), 167.6
(s, CN), 175.3 (s, CO). 119Sn NMR (CDCl3): ꢀ587.4. Anal.
Calc. for C34H48N2O2Sn: C, 64.26; H, 7.61; N, 4.41.
Found: C, 64.06; H, 7.40; N, 4.18%.
˚
and stored in solvent reservoirs which contained 4 A
molecular sieves and were purged with nitrogen. H, 13C,
1
and 119Sn NMR spectra were recorded on a Bruker Avance
300 spectrometer. Chemical shifts for H and 13C spectra
1
were recorded in ppm relative to the residual protons and
13C of CDCl3 (d 7.24, 77.0) and C6D6 (d 7.15, 128.0).
119Sn chemical shifts are reported in ppm from an external
SnMe4 standard. Elemental analyses were performed on a
Heraeus CHN–OS Rapid Elemental Analyzer at the
Instrument Center, NCHU. OCMeCHCMeNHAr was
prepared according to a previously reported procedure.
SnCl2 and SnCl4 (Strem) were used as received.
4.4. Synthesis of (OCMeCHCMeNAr)2SnCl2 (3)
A solution of (OCMeCHCMeNAr)Li (1.00 g, 1.88
mmol) in CH2Cl2 (20 mL) was added dropwise to a stirred
solution of SnCl4 (0.49 g, 3.83 mmol) in CH2Cl2 (20 mL) at
0 °C. The reaction mixture was warmed to room tempera-
ture and was stirred for additional 12 h. The precipitate
was filtered, and the volatiles were removed to afford 3
(0.96 g, 72%). Colorless crystals were obtained from a sat-
1
4.2. Synthesis of (OCMeCHCMeNAr)SnCl (1)
urated THF solution of 3 at ꢀ20 °C. H NMR (CDCl3):
1.02 (d, 6H, CHMe2), 1.08 (d, 6H, CHMe2), 1.16 (d, 6H,
CHMe2), 1.33 (d, 6H, CHMe2),1.78 (s, 6H, CMe), 2.06
(s, 6H, CMe), 3.40 (m, 2H, CHMe2), 3.65 (m, 2H, CHMe2),
5.19 (s, 2H, CMeCHCMe), 7.12–7.24 (m, 6H, phenyl CH).
13C NMR (CDCl3): 25.1 (q, JCH = 126 Hz, CHMe2), 25.31
(q, JCH = 127 Hz, CHMe2), 25.34 (q, JCH = 127 Hz,
CHMe2), 25.4 (q, JCH = 127 Hz, CHMe2), 26.6 (q,
JCH = 128 Hz, CMe), 27.1 (q, JCH = 128 Hz, CMe), 27.2
(d, JCH = 128 Hz, CHMe2), 27.7 (d, JCH = 130 Hz,
CHMe2), 98.3 (d, JCH = 160 Hz, CMeCHCMe), 124.1 (d,
JCH = 156 Hz, phenyl CH), 124.5 (d, JCH = 156 Hz, phenyl
CH), 127.4 (d, JCH = 160 Hz, phenyl CH), 141.4 (s, phenyl
Cipso), 144.1 (s, phenyl Cipso), 144.3 (s, phenyl Cipso), 177.4
(s, CN), 181.1 (s, CO). 119Sn NMR (CDCl3): ꢀ626.9. Anal.
Calc. for C34H48N2O2SnCl2: C, 57.81; H, 6.85; N, 3.96.
Found: C, 58.00; H, 6.82; N, 4.87%.
A 50 mL Schlenk flask charged with (OCMeCHCMeN-
Ar)Li (0.50 g, 1.89 mmol) and SnCl2 (0.36 g, 1.90 mmol)
was cooled to ꢀ78 °C and CH2Cl2 (20 mL) was added.
The solution was then warmed to room temperature and
was stirred for 30 min. The solution was filtered through
Celite and the filtrate was dried under vacuum. The solid
was recrystallized from a saturated methylene chloride
solution to yield the final product. A small amount of com-
pound 2 and ketimine ligand was presented in the final
product even after repeating recrystallization. 1H NMR
(CDCl3):1.14 (d, 6H, Me), 1.19 (d, 6H, Me), 1.80 (s, 3H,
Me), 2.32 (s, 3H, Me), 2.93 (m, 2H, Me), 5.45 (s, 1H,
CMeCHCMe), 7.15–7.32 (m, 3H, phenyl CH). 13C NMR
(CDCl3): 23.5 (Me), 24.0 (Me), 25.0 (Me), 27.1 (Me), 28.5
(CHMe2), 101.3 (CMeCHCMe), 124.5 (phenyl), 127.1
(phenyl), 138.8 (phenyl), 167.0 (phenyl), 171.2 (s, CN),
179.7 (s, CO). 119Sn NMR (CDCl3): ꢀ590.6.
4.5. Synthesis of (OCMeCHCMeNAr)2SnI2 (4)
4.3. Synthesis of (OCMeCHCMeNAr)2Sn (2)
A solution of 2 (0.70 g, 1.10 mmol) in diethyl ether
(20 mL) was added dropwise to a stirred solution of I2
(0.28 g, 1.10 mmol) in diethyl ether (20 mL) at 0 °C. The
reaction mixture was warmed to room temperature and
was stirred for additional 2 h. Volatiles were removed
under vacuum and the resulting solid was recrystallized
from a saturated CH2Cl2 solution at ꢀ20 °C to afford yel-
low crystals of 4 (0.72 g, 73%). 1H NMR (CDCl3): 1.02 (d,
12H, CHMe2), 1.24 (d, 6H, CHMe2), 1.34 (d, 6H, CHMe2),
1.87 (s, 6H, CMe), 2.04 (s, 6H, CMe), 3.59 (m, 2H,
CHMe2), 3.72 (m, 2H, CHMe2), 5.29 (s, 2H,
CMeCHCMe),7.14–7.25 (m, 6H, phenyl CH). 13C NMR
A 100 mL Schlenk flask charged with SnCl2 (0.72 g,
3.79 mmol) and 20 mL THF was cooled to 0 °C. To the
SnCl2/THF solution, a solution of (OCMeCHCMeNAr)Li
(2.00 g, 7.55 mmol) in 20 mL THF was added and the solu-
tion was stirred at room temperature for 8 h. Volatiles were
removed under vacuum and the resulting solid was
extracted with 40 mL CH2Cl2 in three portions. The extrac-
tion was filtered through Celite and the solvent was
removed to yield 1.47 g of 2 (68% yield). 1H NMR
(CDCl3):1.03 (d, 6H, CHMe2), 1.06 (d, 6H, CHMe2),
1.19 (d, 12H, CHMe2), 1.65 (s, 6H, CMe), 1.96 (s, 6H,
CMe), 2.81 (m, 2H, CHMe2), 3.58 (m, 2H, CHMe2), 5.06
(s, 2H, CMeCHCMe), 7.10–7.18 (m, 6H, phenyl CH).
(CDCl3): 25.1 (q, JCH = 121 Hz, CHMe2), 25.2 (q, JCH
=
121 Hz, CMe), 25.3 (q, JCH = 121 Hz, CHMe2), 27.1 (q,
JCH = 127 Hz, CMe), 27.1 (d, JCH = 126 Hz, CHMe2)

2798
H.-M. Kao et al. / Inorganica Chimica Acta 361 (2008) 2792–2798
(d) R. Willem, H. Dalil, P. Broekaert, M. Biesemans, L. Gyhs, K.
Nooter, D. de Vos, F. Ribot, M. Gielen, Main Group Met. Chem. 20
(1997) 535.
(Two peaks are overlapped. This can be differentiated by
2D HSQC NMR spectra), 27.3 (q, JCH = 126 Hz, CHMe2),
28.2 (d, JCH = 130 Hz, CHMe2), 29.0 (q, JCH = 128 Hz,
CHMe2), 97.7 (d, JCH = 160 Hz, CMeCHCMe), 124.1 (d,
JCH = 165 Hz, phenyl CH), 124.8 (d, JCH = 153 Hz, phenyl
CH), 127.5 (d, JCH = 160 Hz, phenyl CH), 142.0 (s, phenyl
Cipso), 144.4 (s, phenyl Cipso), 145.4 (s, phenyl Cipso), 175.7
(s, CN), 180.0 (s, CO). 119Sn NMR (CDCl3): ꢀ916.5. Anal.
Calc. for C34H48N2O2SnI2: C, 45.92; H, 5.44; N, 3.15.
Found: C, 45.93; H, 5.53; N, 3.13%.
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Crystal data collection, refinement parameter and bond
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We are grateful to the National Science Council of Tai-
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the X-ray facility.
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