1,3,5-Triazapentadienyltin(II) complexes and the additional reaction of phenylamine with N,N’-diisopropylcarbodiimide

Article abstract of DOI:10.1016/j.poly.2018.05.016

A series of tin(II) complexes 2–5 bearing 1,3,5-triazapentadienyl ligands are reported: Sn[N(Ph)C(R′)NC(R′)N(SiMe₃)]₂ [R′ = 1-piperidino, 2; NMe₂, 3], [N(Ph)C(NMe₂)NC(NMe₂)N(H)]SnCl (4) and [{N(SiMe

Full text of DOI:10.1016/j.poly.2018.05.016

Polyhedron 151 (2018) 273–278
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Polyhedron
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1,3,5-Triazapentadienyltin(II) complexes and the additional reaction of
phenylamine with N,N’-diisopropylcarbodiimide
Zeling Guo a,b, Fang Liu , Hongbo Tong , Jianbin Chao , Huan Wang , Meisu Zhou
a
a
c
a
a,
⇑
a
Institute of Applied Chemistry, Shanxi University, Taiyuan 030006, People’s Republic of China
Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
Scientific Instrument Center, Shanxi University, Taiyuan 030006, People’s Republic of China
b
c
a r t i c l e i n f o
a b s t r a c t
0
Article history:
A series of tin(II) complexes 2–5 bearing 1,3,5-triazapentadienyl ligands are reported: Sn[N(Ph)C(R )
Received 11 April 2018
Accepted 6 May 2018
Available online 23 May 2018
0
0
NC(R )N(SiMe
3
)]
Sn
2
[R = 1-piperidino, 2; NMe
2
, 3], [N(Ph)C(NMe
2
)NC(NMe
2
)N(H)]SnCl (4) and [{N(SiMe
3
)
0
0
0
C(R )NC(R )N}
2
2
]
2
(R = 1-piperidino) (5). Their single-crystal X-ray diffraction studies are presented.
Compounds 3 and 4 are efficient catalysts for the catalytic addition of phenylamine to N,N’-diisopropyl-
carbodiimide giving guanidine.
Keywords:
Synthesis
Ó 2018 Elsevier Ltd. All rights reserved.
Crystal structures
Triazapentadienyl ligands
Tin(II) complexes
Catalytic addition
1
. Introduction
As the counterparts of b-diketimate anions, 1, 3, 5-triazapenta-
Construction of CAN bonds and formation of guanidines by cat-
alytic addition of amines and carbodiimides have been paid a great
attention for the straightforward and atom-economic preparation
of substituted guanidines, which represent an essential functional-
ity in many biologically and pharmaceutically relevant compounds
[31,32]. Some divalent lanthanide complexes and half-sandwich
yttrium complex were proved to be excellent catalysts for this
transformation [33,34]. The lanthanide aryloxides supported by a
bridged-amidinate [35], or by a b-diketimate ligand [36], as well
as the phenylene-bridged b-ketoiminate dilanthanide aryloxides
[32] are also efficient catalysts for this purposes. Herein we
describe the isolation of a novel group of tin(II) 1,3,5-triazapenta-
dienyl anions, as ancillary ligands in organometallic chemistry,
also own similar attractive features [1–6]. Their transition metal
complexes [7–15], some main group lithium, thallium [16–18]
metal complexes and silicon fluoride LSiF
2
(L = NC(NMe
) [19] have been reported.
Tin(II) complexes with nitrogen ligands have been prepared, e.g.
b-N-functionalized tin(II) alkyls SnRX (R = C(SiMe N-2, and
X = R, Cl or N(SiMe [20], the tin(II) primary amido derivatives
Sn {N(H)Dipp} and Sn {N(H)Dipp} Cl [21], chloro- and azido-
2
)NC
i
(
2 2 6 3
NMe )NAr, Ar = 2,6- Pr C H
3 2 5 4
) C H
3 2
)
2
4
2
3
0
0
0
tin(II) 1,5-diazapentadienyls [22,23], tin(II) 1-azaallyls [24], and
tin(II) benzamidinates [25–27]. The tin(II) poly(pyrazolyl)borates
3 2
dienyl complexes: Sn[N(Ph)C(R )NC(R )N(SiMe [R = 1-piperi-
)]
)N(H)]SnCl (4), and
(R = 1-piperidino) (5). The catalytic
dino, 2; NMe
2
, 3], [N(Ph)C(NMe
2
)NC(NMe
2
0
0
0
[
H
2
B(pz)
2
]SnCl and [B(pz)
4
]
2
Sn have also been reported [28]. How-
[{N(SiMe
3
)C(R )NC(R )N}
Sn
2 2
]
2
ever, tin(II) 1, 3, 5-triazapentadienyl complexes have not been
involved.
activity of 3 and 4 as catalysts in the addition reaction of pheny-
lamine to N,N’-diisopropylcarbodiimide has been evaluated.
Our group presented the synthesis and characterization of mag-
nesium(II) and aluminum complexes supported by 1,3,5-triaza-
pentadienyl ligands [29,30], and their zinc complexes could be
used as catalyst in the ring-opening polymerization of rac-lactide
2
. Experimental
2.1. General procedures
[
30]. As a continuation, exploitation of other metal complexes
including tin(II) complexes of these ligands and their application
is certainly required.
All manipulations were carried out under an atmosphere of
argon using standard Schlenk techniques. Solvents were purchased
from commercial sources. Deuterated solvent CDCl was dried over
3
activated molecular sieves (4 Å) and vacuum transferred before
use. Diethyl ether was dried and distilled from sodium/benzophe-
none and stored over a sodium mirror under argon. Glassware was
⇑
Corresponding author.
E-mail address: mszhou@sxu.edu.cn (M. Zhou).
https://doi.org/10.1016/j.poly.2018.05.016
277-5387/Ó 2018 Elsevier Ltd. All rights reserved.
0

2
74
Z. Guo et al. / Polyhedron 151 (2018) 273–278
0
0
0
oven-dried at 150 °C overnight. The NMR spectra were recorded on
Bruker DRX-300 spectrometer and recorded in CDCl . The chemical
shifts are reported in d values in ppm relative to external SiMe for
Sn. Melting points were measured in
sealed capillaries and are uncorrected. Elemental analyses were
carried out using a Vario EL-III analyzer (Germany).
2.2.5. [{N(SiMe
1-Piperidinecarbonitrile (0.46 mL, 4.00 mmol) was added to a
solution of LiN(SiMe (0.334 g, 2.00 mmol) in Et O(30 mL) at
ꢀ78 °C. The resulting mixture was warmed to ca.25 °C and stirred
overnight. SnCl
3 2 2 2
)C(R )NC(R )NH} Sn ] (R = 1-piperidino) (5)
3
4
3
)
2
2
1
13
119
4
H and C and SnMe for
2
(0.20 g, 1.06 mmol) was added at ꢀ78 °C. The
resulting mixture was warmed to ca. 25 °C and stirred for 24 h,
then filtered. The filtrate was concentrated to give colorless crys-
2
2
.2. Synthesis and characterization
tals of 5 (0.19 g, 42%). Mp:113–115 °C. Anal. Calc. for C60
Si Sn : C, 42.27; H, 6.86; N, 16.43. Found: C, 41.97; H, 6.65; N,
16.22%. H NMR (CDCl
(m, 48H, (CH ), 3.13–3.67 (t, 32H, NCH
1.97–3.49 (SiMe ), 25.13 ((CH ), 27.61 ((CH
49.29 (NCH ), 159.48 (NCN), 164.19 (NCN).
116 20
H N -
4
4
0
0
0
1
.2.1. Sn[N(Ph)C(R )NC(R )N(SiMe
-Piperidinocarbonitrile (0.57 mL, 4.9 mmol) was added to a
solution of PhN(Li)SiMe (0.42 g, 2.45 mmol) in Et O (30 mL) at –
8 °C. The resulting mixture was warmed to ca. 25 °C and stirred
3
)]
2
(R = 1-piperidino) (2)
3
): d 0.02–0.25 (m, 36H, SiMe
3
), 1.16–1.56
). C NMR (CDCl ): d
), 46.26 (NCH ),
1
3
1
2
)
3
2
3
3
2
3
3
)
2
3
)
2
2
7
2
2
overnight. SnCl (0.23 g, 1.22 mmol) was added at –78 °C. The
resulting mixture was warmed to ca. 25 °C and stirred for 24 h
and filtered. The filtrate was concentrated in vacuo to ca. 20 mL
and cooled at ꢀ25 °C for 1 d, yielding colorless crystals of 2
2.2.6. X-ray crystallography
Data collection of 2–5 was performed with Mo-K
a
radiation (k
(
0.52 g, 48%). MP:126–128 °C. Anal. Calc. for C42
H
68
N
10Si
2
Sn: C,
= 0.71073 Å) on a Bruker Smart Apex CCD diffractometer using the
omega scan mode yielding a total of N reflections. Crystals were
coated in oil and then directly mounted on the diffractometer
under a stream of cold nitrogen gas. Corrections were applied for
Lorentz and polarization effects as well as absorption using
multi-scans (SADABS) [37]. The structure was solved by the direct
method (SHELXS-97) [38]. The remaining non-hydrogen atoms
were obtained from the successive difference Fourier map. All
non-H atoms were refined with anisotropic displacement parame-
ters, while the H atoms were constrained to parent sites, using rid-
ing modes (SHELXTL) [39]. Crystal data and details of data
collection and refinements for 2–5 are summarized in Table 1.
Selected bond distances and bond angles are listed in Tables 2–4.
CCDC (reference numbers 791258-2, 791257-3, 816129-4,
1
5
6.81; H, 7.72; N, 15.77. Found: C, 57.03; H, 7.80; N, 15.61%. H
NMR (CDCl
3
): d ꢀ0.06, ꢀ0.01, 0.09 (3s, 18H, SiMe
), 2.75–3.48 (m, 16H, CH ), 6.82–7.30 (m, 10H, Ph).
C NMR (CDCl ): d 1.09, 2.66, 3.34 (SiMe ), 25.2, 26.2, 26.6
CH ), 46.8, 49.3 (NCH ), 120.6 (p-CPh), 123.1, 123.7 (m-CPh),
28.6, 129.0 (o-CPh), 151.9 (Cipso-Ph), 156.4, 158.0 (NCN).
): d ꢀ593.5.
3
), 1.16–1.58
(
m, 24H, CH
2
2
1
3
3
3
(
2
2
1
19
1
Sn
NMR (CDCl
3
2 2 3 2
2.2.2. Sn[N(Ph)C(NMe )NC(NMe )N(SiMe )] (3)
(
CH NCN (0.44 mL, 5.48 mmol) was added to a solution of
PhN(Li)SiMe (0.47 g, 2.74 mmol) in Et
O (30 mL) at ꢀ78 °C. The
resulting mixture was warmed to ca. 25 °C and stirred overnight.
SnCl
3 2
)
3
2
2
(0.26 g, 1.37 mmol) was added at ꢀ78 °C. The resulting mix-
0
ture was warmed to ca. 25 °C and stirred for 24 h and filtered. The
filtrate was concentrated in vacuo to ca. 15 mL and cooled at ꢀ25
1059848-4 , 816128-5) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/datarequest/cif.
°
C for 1 d, yielding colorless crystals of 3 (0.52 g, 52%). Mp:100–
1
02 °C. Anal. Calc. for C30
Found: C, 49.88; H, 7.65; N, 19.02%. H NMR (CDCl
.41, 0.45 (3s, 18H, SiMe ), 2.68, 2.99, 3.25, 3.41 (4s, 24H, N
CH ), 6.98–7.54 (m, 10H, Ph). C NMR (CDCl
.03 (SiMe ), 39.0, 39.8, 40.5, 41.1 (NMe), 122.4 (p-CPh), 124.7,
24.9 (m-CPh), 129.8, 130.6 (o-CPh), 151.4 (Cipso-Ph), 160.7,
52 2
H N10Si Sn: C, 49.52; H, 7.20; N, 19.25.
1
3
): d 0.26,
0
(
3
1
1
3
13
)
3 2
3
): d ꢀ0.69, 1.48,
3. Results and discussion
3
The 1,3,5-triazapentadienyl ligands were prepared according to
the literature procedures [14,29]. The reactions of corresponding
1
19
64.3 (NCN).
Sn NMR (CDCl
3
): d ꢀ561.1.
ligands and anhydrous SnCl
2
at the ratio of 2:1 at low temperature
2 2
2.2.3. [N(Ph)C(NMe )NC(NMe )N(H)]SnCl (4)
led to the formation of 2 and 3. Compound 4 was obtained by treat-
(
CH
3
)
2
NCN (0.38 mL, 4.67 mmol) was added to a solution of
PhN(Li)SiMe (0.40 g, 2.34 mmol) in Et
O (30 mL) at ꢀ78 °C. The
resulting mixture was warmed to ca. 25 °C and stirred overnight.
SnCl .2H
ment of the ligand with SnCl
ether. Small amount of crystals of 4 , a polymorph of 4 were iso-
2
∙2H
2
O at the ratio of 1:1 in diethyl
0
3
2
lated in the related 1: 1 reaction of ligand: SnCl
2
carried out in
0
2
2
O (0.53 g, 2.34 mmol) was added at ꢀ78 °C. The resulting
Et
2
O. 4 was identified solely by its X-ray structure. Reaction of a
mixture was warmed to ca. 25 °C and stirred for 12 h. The pale yel-
low mixture was filtered. The filtrate was concentrated in vacuo to
ca. 10 mL and left at room temperature for several days to give col-
orless block crystals of 4 (0.89 g, 79%). Mp: 136–138 °C. Anal. Calc.
1:1 ratio of the ligand with SnCl
5, with the elimination of LiCl and Me
the 1,3,5-triazapentadienate ligand in 5 is dianionic; because of
the absence of one SiMe group, the ligands formed aggregates
2
in diethyl ether solution yielded
3
SiCl. It is noteworthy that
3
for C12
H
18ClN
5
Sn: C, 37.29; H, 4.69; N, 18.12. Found: C, 37.01; H,
leading to the tetramer 5. The dianionic feature of the 1,3,5-triaza-
pentadienate ligand was also found in its silicon fluorides [29]
(Scheme 1).
1
4
5
4
1
.65; N, 17.98%. H NMR (CDCl
3
): d 2.77, 3.04 (d, 12H, N(CH
3
)
2
),
): d 38.9,
), 122.1 (p-CPh, m-CPh), 130.3 (o-CPh), 149.3 (Cipso),
1
13
.3 (s, H, NH), 6.87–7.22 (m, 5H, Ph). C NMR (CDCl
0.2 (d, N(CH
59.1, 161.2 (NCN).
3
)
2
The 1H NMR spectrum of 3 in CDCl
3
at ambient temperature
as four singlets at d =
.68, 2.99, 3.25, 3.41, and the corresponding carbon atoms caused
3
1
19
3
Sn NMR (CDCl ): d ꢀ258.6.
3 2
shows the methyl protons of the N(CH )
2
0
2
.2.4. [N(Ph)C(NMe
CH
PhN(Li)SiMe
resulting mixture was warmed to ca. 25 °C and stirred overnight.
SnCl
2
)NC(NMe
2
)N(H)]SnCl (4 )
the appearance of four signals at d = 39.0, 39.8, 40.5, 41.1. The phe-
nyl carbon atoms showed six signals at d = 122.4, 124.7, 124.9,
129.8, 130.6 and 151.4. The methylsilyl protons gave rise to three
distinct signals at d = 0.26, 0.41 and 0.45, corresponding to the
(
3
)
2
NCN (0.45 mL, 5.60 mmol) was added to a solution of
(0.49 g, 2.80 mmol) in Et
O (30 mL) at ꢀ78 °C. The
3
2
1
3
1
2
(0.53 g, 2.80 mmol) was added at ꢀ78 °C. The resulting mix-
three C{ H} NMR signals of the methylsilyl carbon atoms at
1
13
ture was warmed to ca. 25 °C and stirred for 12 h, and then filtered.
The filtrate was concentrated in vacuo and left at room tempera-
ꢀ0.69, 1.48, 3.03. The H NMR and C NMR spectra of 2 were
essentially similar to those of 3, suggesting very similar solution
0
ture for four days to give colorless block crystals of 4 (0.36 g,
structures. The shielding of Si(CH
by restricted rotation of Si(CH
3
) groups may have been caused
due to the neighboring NMe or
3
3%). Mp: 132–134 °C.
3
)
3
2

Z. Guo et al. / Polyhedron 151 (2018) 273–278
275
Table 1
Crystal and refinement data for 2–5.
0
Compound
2
3
4
4
5
Formula
M
Crystal system
Space group
Unit cell dimensions
a (Å)
C
42
H
68
N
10Si
2
Sn
C
30
H
52
N
10Si
2
Sn
C
12
H
18ClN
5
Sn
C
12
H
18ClN
386.45
Monoclinic
P2 /c (No. 14)
5
Sn
C
60
H
116
N
20Si
4
Sn
4
887.93
Monoclinic
C2/c (No. 15)
727.69
Monoclinic
P2 /n (No. 14)
386.45
Monoclinic
P2 /n (No. 14)
1704.85
Monoclinic
C2/c (No. 15)
1
1
1
28.147(4)
10.6529(14)
19.384(3)
9.8407(19)
36.392(7)
11.094(2)
9.827(3)
8.634(2)
18.700(5)
18.366(3)
5.9413(9)
15.478(2)
26.825(3)
12.4290(13)
25.314(3)
b (Å)
c (Å)
a
(°)
b (°)
(°)
129.183(2)
110.759(3)
90.00(2)
113.286(2)
113.556(2)
c
3
V (Å )
4505.2(10)
4
0.662
3715.2(12)
4
0.786
1586.7(7)
4
1.774
1551.3(4)
4
1.814
7736.5(14)
4
1.387
Z
Absorption coeff. (mmꢀ1)
Unique reflections (Rint
Reflections with
)
3877, 0.0497
3649
6414, 0.0791
5668
2819, 0.0602
2527
2734, 0.0463
2337
6643, 0.0345
6178
I > 2
Final R indices
I > 2 (I)] R
R indices (all data) R
r(I)
0.0780, 0.2016
0.0853, 0.2162
0.1027, 0.2274
0.1173, 0.2356
0.0235, 0.0585
0.0278, 0.0614
0.0340, 0.0836
0.0414, 0.0888
0.0579, 0.1512
0.0639, 0.1625
[
r
1 2
, wR
, wR
1 2
Table 2
Table 3
0
Selected bond lengths (Å) and angles (°) for 2 and 3.
Selected bond lengths (Å) and angles (°) for 4 and 4 .
2
4
Sn1–N1
Sn1–N5
N1–C7
N2–C7
2.376(5)
2.193(5)
1.319(9)
1.400(9)
1.350 (8)
75.30(19)
121.5(4)
119.0(4)
125.8(6)
128.7(6)
N1–C1
N5–Si1
N3–C13
N4–C13
1.421(9)
1.748(6)
1.318(9)
1.371 (9)
1.356(9)
121.8(6)
154.8(3)
95.9(3)
Sn–N1
Sn–N3
Sn–Cl
C1–N1
2.166 (2)
2.132(2)
2.5097(9)
1.403(3)
1.375(3)
89.40(6)
92.73(6)
82.67(8)
117.21(16)
C7–N2
C7–N4
C8–N2
C8–N3
1.319(3)
1.355(3)
1.359(3)
1.322(3)
1.350(3)
125.69(17)
124.7(2)
123.2(2)
123.8(2)
N3–C7
N5–C13
C7–N1
C8–N5
N1–Sn1–N5
Sn–N1–C7
Sn–N5–C13
N1–C7–N3
N3–C13–N5
C7–N3–C13
N1–Sn1–N1A
N5–Sn1–N5A
N1–Sn1–N5A
N5–Sn1–N1A
Cl–Sn–N1
Cl–Sn–N3
N1–Sn–N3
Sn–N1–C7
Sn–N3–C8
N1–C7–N2
N2–C8–N3
C7–N2–C8
87.83(19)
87.83(19)
0
4
3
Sn–N1
Sn–N5
Sn–Cl
C7–N1
2.143 (3)
2.114 (3)
2.5065(11)
1.351(5)
1.361(5)
91.97(9)
92.75(9)
82.98(11)
C7–N3
1.320(4)
1.359(5)
1.348(4)
1.323(4)
Sn1–N1
Sn1–N5
Sn1–N6
Sn1–N10
N1–Si1
2.181(8)
2.389(7)
2.383(7)
2.191(7)
1.742(8)
1.446(11)
76.0(3)
N1–C1
N2–C1
N3–C1
N3–C2
N4–C2
N5–C2
N1–Sn1–N10
N1–Sn1–N6
N5–Sn1–N6
N5–Sn1–N10
C1–N3–C2
1.349(12)
1.390(12)
1.344(12)
1.350(12)
1.344(12)
1.336 (11)
97.3(3)
84.3(3)
151.8(2)
85.9(3)
C10–N3
C10–N4
C10–N5
C7–N2
Cl–Sn–N1
Cl–Sn–N5
N1–Sn–N5
Sn–N5–C10
N1–C7–N3
N3–C10–N5
126.2(2)
126.5(3)
125.2(3)
N5–C10
N1–Sn1–N5
N6–Sn1–N10
Sn1–N1–C1
Sn1–N5–C2
N1–C1–N3
N3–C2–N5
76.7(2)
117.1(6)
121.1(6)
129.4(8)
124.4(9)
Table 4
Selected bond lengths (Å) and angles (°) for 5.
122.1(8)
Sn1–N1
Sn1–N5
Sn1–N10
Sn2–N5
Sn2–N6
Sn2–N10
N1–C1
2.210(5)
2.152(5)
2.186(5)
2.179(5)
2.211(5)
2.154(5)
1.380(9)
1.371(9)
1.287(9)
86.4(2)
N3–C2
N4–C2
N5–C2
N6–C16
N7–C16
N8–C16
N8–C17
N9–C17
N10–C17
N1–C1–N3
C1–N3–C2
C16–N8–C17
Sn2–N6–C16
N6–C16–N8
1.363(9)
1.383(8)
1.323(8)
1.381(9)
1.346(9)
1.309(9)
1.381(9)
1.369(9)
1.320(8)
125.4(6)
124.6(6)
123.1(6)
112.2(4)
125.2(6)
0
the bulky 1-piperidino, and the even closer phenyl group of the
trigonal bipyramidal structure.
The 119Sn NMR spectra of 2 and 3 showed sharp signals at d
ꢀ
593.5 and ꢀ561.1, respectively. These resonances appeared at
the region expected for four-coordinate tin(II) atoms, as in, the
four-coordinate chlorotin complexes [HB(Pz)
]SnCl (d = ꢀ569)
and [HB(3,5-Me Pz)
]SnCl (d = ꢀ567) [28], which are ca. 300 ppm
upfield from the value of the four-coordinate tin(II) amidinate
N2–C1
N3–C1
N1–Sn1–N5
N6–Sn2–N10
Sn1–N5–Sn2
N5–Sn2–N10
Sn1–N1–C1
3
87.5(2)
121.0(2)
94.5(2)
2
3
2
119
[
Sn{
NMR spectrum of the three-coordination 4 displayed a signal d =
258.6 which is upfield of those previously for the three-coordi-
nate complexes [(i-Pr) ATI]SnCl ([(i-Pr) ATI] = N-isopropyl-2-(iso-
propylamino)troponimine, d = –68) [40], and was at much higher
j
3 6 4 2
-N(SiMe )C(C H Me-4)NPh} ] (d = ꢀ228.3) [25]. The
Sn
112.8(4)
ꢀ
2
2
lone pair on tin occupying an equatorial site. The bond distances
Sn1–N1 and Sn1–N5 are 2.376(5) Å and 2.193(5) Å. In complex 2,
a C -axis is present across Sn1 and the center point of N1–N1A;
2
the two 1,3,5-triazapentadieno ligands in 2 are equivalent. In the
molecule, all of the four ligating N atoms lie to one side of a plane
normal to the twofold axis, suggestive of the presence of a steri-
cally active lone pair which must lie to the other side. In the triaza-
+
field than in the two-coordinate tin(II) complex {[(i-Pr)
d = 734) [40].
The molecular structure of complex 2 (Fig. 1) shows that it is
2
ATI]Sn}
(
monomeric in the solid state. The geometry about the tin atom is
best described as a highly distorted trigonal bipyramid with the

2
76
Z. Guo et al. / Polyhedron 151 (2018) 273–278
Scheme 1. Synthetic routes to complexes 2–5.
Fig. 2. Molecular structure of 3.
Fig. 1. Molecular structure of 2.
cules in 2 or 3 (the closest Sn. . .Sn separation is 9.92 Å for 2 and
pentadieno ligand NCNCN backbone, the two terminal N atoms and
the adjacent C atoms N1, C7, C13 and N5 are almost coplanar with
mean deviation of 0.0599 Å, and only the central N atom of the
ligand is situated slightly above the plane with a dihedral angle
of ca. 16.5°. Therefore, the six-membered metallacycle NCNCNM
adopts boat conformation, and the distances from Sn1 and N3 to
the N1C7C13N5 plane are ca. 1.10 and 0.18 Å, respectively.
The molecule of 3 (Fig. 2), comprising the asymmetric unit of
the structure, is devoid of intrinsic or crystallographic symmetry.
Similar to complex 2, crowding of the ligating atoms to one side
of the tin suggests a sterically active lone pair. The tin-ligand dis-
tances [from 2.181(8) to 2.389(7) Å] are comparable to those in
1
0.62 Å for 3).
In 2 and 3, the dihedral angles between the two NSnN planes
are 84.3 and 96.4°, respectively. The dihedral angles between the
CNC plane of the 1-piperidino or dimethylamido group and its
adjacent NCN plane of the 1,3,5-triazapentadienyl ligand are 20.9
and 21.9° in 2, and 13.0 and 21.4° in 3. The sum of the three bond
angles around N2 or N4 of 2 (359.9°), or N2 and N4 of 3 (359.9° and
2
3
59.8°, respectively) are consistent with the sp hybridization nec-
essary for conjugation.
The molecular structure of crystalline 4 is illustrated in Fig. 3,
0
with selected geometric parameters listed in Table 3; data for 4
are closely similar. The tin center is three-coordinate, bonding to
two nitrogen atoms from the triazapentadienyl ligand and a chlo-
ride atom in a pyramidal manner, which is fairly common in Sn(II)
chemistry [21]. Its core is a twisted boat-shaped ring. Atoms N1,
C7, N2, C8 are almost planar with mean deviation of 0.0014 Å.
The dihedral angle between N1C7N2C8 and the adjacent
N1SnN3C8 (0.0604 Å) plane is 141.8°. The endocyclic bond lengths
compound 2 and those in the b-diiminatotin or b-dialdiminatotin
0
complexes [(Mes)
2
DAP]SnN
3
2
([(Mes) DAP] = 2,4-dimethyl-N, N -
bis(2,4,6-trimethylphenyl)-1,5-diazapentadienyl) [2.177(4) and
i
2
.210(4) Å] [23] or SnCl[{N(C
and 2.182(2) Å] [22], and are shorter than those in homoleptic tin
II) 1-azaallyls [2.510(2) Å] [24]. The Sn1–C distances in 2 [3.265
and 3.087 Å] and 3 [3.043 and 3.285 Å] are much longer than those
in SnCp [Sn-Cav 2.71 Å] [41]. The tin atom and central nitrogen atom
6 3 2 2
H Pr -2,6)C(H)} CPh [Sn–N: 2.190(2)
(
indicate that there is substantial
p-delocalisation over the
2
N1C7N2C8N3 moiety, the pairs of bond lengths Sn–N1/Sn–N3,
C7–N1/C8–N3 and C7–N2/C8–N2 differ by ca. 0.03, 0.05 and 0.04
Å, respectively. Likewise, the endocyclic bond angles subtended
at N1/N3 and C7/C8 differ by ca. 8.48° and 1.5°, respectively.
N3 in 3 deviates from the N1C1C2N5 plane by 1.13 and 0.18 Å,
respectively. The six-membered SnNCNCN ring is arranged in a boat
configuration with the Sn1-N3 distance of 3.470 Å. There is no inter-
molecular interaction between the Sn atoms of neighboring mole-

Z. Guo et al. / Polyhedron 151 (2018) 273–278
277
0
Fig. 3. Molecular structures of 4 and 4 .
The Sn–Cl bond distance is 2.5097(9) Å, which is (i) shorter than
the 2.542(2) Å in the 10- -electron [(i-Pr) ATI]SnCl ([(i-Pr) ATI] =
N-isopropyl-2-(isopropylamino)troponimine) [40], and the 2.68 Å
the tin atom of its neighbouring unit, leading to the tetrameric
structure of 5 having a central eight-membered boat (Fig. 4(b)).
The three-coordinate tin atom is located in a pyramidal environ-
ment. The sum of the three angles around Sn is 277.5°; the lone
pair on tin is stereochemically active.
p
2
2
in [C
5
H
5
]SnCl [42]; but (ii) longer than in the isoelectronic b-dike-
0
timinate [(Mes)
2
DAP]SnCl ([(Mes)
2
DAP] = 2,4-dimethyl-N, N -bis
(
2,4,6-trimethylphenyl)-1,5-diazapentadienyl) [2.468(1) Å] [23]
The NCNCN moiety in 5 shows a short–long–short–long pattern
of CAN bond distances beginning at N5. The closest Sn. . .Sn sepa-
ration is 3.768 Å, which is slightly longer than the reported weak
tin–tin bonding (Sn–Sn = 3.68 Å) [44].
Catalytic activity of selected complexes 3 and 4 for catalytic
2
addition of PhNH to N, N’-diisopropylcarbodiimide to guanidine,
as the model reaction, was evaluated (Table 5). Phenylamine did
not react with diisopropylcarbodiimide under solvent free condi-
tion for 24 h even with raised reaction temperature to 80 °C with-
out a catalyst (Table 5, entries 1 and 2). When 0.5 mol% of complex
3 was added, at 25 °C, the reaction went faster under solvent free
i
and the b-dialdiminatotin(II) chloride SnCl[{N(C
C(H)} CPh] [2.457(1) Å] [22]. These Sn–N bond lengths of 4 are com-
parable to those in the three-coordinate tin(II) complexes [(i-Pr) ATI]
SnCl [2.164(5) Å] [40] and [(Mes) DAP]SnCl [2.162(3) Å] [23], but
shorter than those in [H B(Pz) ]SnCl [2.243(7), 2.302(8) Å] [28];
and much longer than those in the two-coordinate tin(II) amide such
as [(Me Si) N] Sn [2.096(1), 2.088(6)] [43]. The NASnAN bond angle
of 82.67(8)° in 4 can be compared with the 73.9(2)° in [(i-Pr) ATI]
SnCl and the 87.38(17)° in [(Mes) DAP]SnCl. There was neither
6 3 2
H Pr -2,6)
2
2
2
2
2
3
2
2
2
2
SnꢁꢁꢁSn nor SnꢁꢁꢁCl intermolecular interactions (the closest SnꢁꢁꢁSn
and SnꢁꢁꢁCl separation are ca. 5.22 Å and 4.14 Å).
2
condition than that in Et O or Hexane solvent (Table 5, entries
The molecular structure of crystalline 5 is shown in Fig. 4(a);
selected values for bond lengths and angles are shown in Table 4.
3–5). The reaction went much faster with the increase of the reac-
tion time (Table 5, entries 5–7), and afforded the guanidine in 96%
yield for 1 h (Table 5, entry 7). However, the increased reaction
temperature resulted in decrease of the yield (Table 5, entries 8
and 9). For complex 4, the reaction time affected the reaction
3
The tin atom bound to the N,N-chelating dianionic ligand N(SiMe )
C(R )NC(R )N (R = 1-piperidino). The terminal nitrogen atom free
from a substituent of each monomeric fragment is coordinated to
0
0
0
4
Fig. 4. Molecular structure of 5 (a) and its boat (SnN) ring (b).

2
78
Z. Guo et al. / Polyhedron 151 (2018) 273–278
Table 5
Acknowledgments
i
i
a
2
Addition of PhNH to PrNCN Pr by complexes 3 and 4.
We thank the Natural Science Foundation of China (No.
2
0
1371111) and Shanxi Scholarship Council of China (No. 2017-
25) for funding. We acknowledge the Scientific Instrument Center
of Shanxi University for the NMR and crystallography service.
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Entry
Cat.b
Temp./°C
Time/h
Solvent
Yield/%c
[
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1
2
3
4
5
6
7
8
9
–
–
3
3
3
3
3
3
3
4
4
4
4
4
4
25
80
25
25
25
25
25
60
80
25
25
25
25
60
80
24
24
1/6
1/6
1/6
0.5
1
1/6
1/6
1
20
36
48
1/6
1/6
–
–
0
0
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Et O
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11
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75
96
87
94
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13
14
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[
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c
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[
(
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greatly. At 25 °C, the yields increased with an increase of the reac-
tion time (Table 5, entries 10–13), and in 48 h led to addition of
[
i
i
PhNH
2
to PrNCN Pr to give the guanidine in 97% yield (Table 5,
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(Table 5, entries 14 and 15).
The catalytic behavior of 3 (96%, entry 7) and 4 (97%, entry 13)
can be well comparable to the reported systems with lanthanide
aryloxide such as b-ketoiminate L[Yb(OAr) (THF)] , (L = p-OC(Me)
CHC(Me)N-C -p-NC(Me)CHC(Me)O) (98%, 60 °C, 0.25 h) [32], b-
diketimate LYb(OAr )
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(L = [N(2,6-Me
]) (91%, 60 °C, 0.25 h) [36], and amidinate com-
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2
C
6
H
3
)C(Me)]
2
CH , Ar =
t
[
2,6- Bu
plex LY[O2,6-( Bu)
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2 6 2
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In summary, a series of 1,3,5-triazapentadienyltin(II) complexes
were synthesized. These novel complexes exhibit good activity for
the catalytic addition of phenylamine to N,N’-diisopropylcarbodi-
imide. Developing new catalysts, elucidating the catalytic
mechanism, and processing extensive researches on the range of
substrates of amines and carbodiimides are the focus of our future
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on tin(II) suggesting their use in the preparation of a wide range of
heteroleptic organotin(II) complexes and low- valence tin
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