Synthesis and characterization of some organotin(IV) adducts containing a related series of pyridines: Crystal structure of [SnMe2Cl2(bu2bpy)]

Article abstract of DOI:10.1016/j.poly.2010.01.025

Organotin(IV) complexes of [SnR_(4-n)Cl_n] (n = 2, R = Me, ⁿBu; n = 1, R = Ph) react with the bidentate pyridyl ligand 4,4′-di-tert-butyl-2,2′-bipyridine (bu₂bpy) to give hexa-coordinated adducts with the general formula [SnR_(4-n)Cl_n(bu₂b py)]. However, the reaction of these organotin(IV) complexes with the corresponding monodentate ligand 4-tert-butylpyridine (bupy) resulted in the formation of the hexa-coordinated complex [SnMe₂Cl₂(bupy)₂] and the penta-coordinated complexes [SnR_(4-n)Cl_n(bupy)] (n = 2, R = ⁿBu; n = 1, R = Ph). Moreover, the reaction of the above organotin(IV) complexes with 4,4′-trimethylenedipyridine (tmdp) yields hexa-coordinated adducts with the general formula [SnR₂Cl₂(tmdp)] (R = Me, ⁿBu) and the penta-coordinated complex [ClPh₃Sn-μ-(tmdp)SnPh₃Cl] in the solid state. The resulting complexes have been characterized by multinuclear NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and elemental analysis. NMR data shows that the triphenyltin(IV) adducts are not stable in solution and dissociate to give tetra-coordinated tin(IV) complexes. The X-ray crystal structure determination of [SnMe₂Cl₂(bu₂bpy)] reveals that the tin atom is hexa-coordinated in an octahedral geometry with a trans-[SnMe₂] configuration.

Full text of DOI:10.1016/j.poly.2010.01.025

Polyhedron 29 (2010) 1393–1398
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis and characterization of some organotin(IV) adducts containing a
related series of pyridines: Crystal structure of [SnMe2Cl2(bu2bpy)]
a
b
Badri Z. Momeni a, , Soheila Shahbazi , Hamid Reza Khavasi
*
a Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran 15418, Iran
b Department of Chemistry, Shahid Beheshti University, G. C., Evin, Tehran 1983963113, Iran
a r t i c l e i n f o
a b s t r a c t
Organotin(IV) complexes of [SnR(4ꢀn)Cln] (n = 2, R = Me, nBu; n = 1, R = Ph) react with the bidentate pyridyl
ligand 4,40-di-tert-butyl-2,20-bipyridine (bu2bpy) to give hexa-coordinated adducts with the general for-
mula [SnR(4ꢀn)Cln(bu2bpy)]. However, the reaction of these organotin(IV) complexes with the corre-
sponding monodentate ligand 4-tert-butylpyridine (bupy) resulted in the formation of the hexa-
coordinated complex [SnMe2Cl2(bupy)2] and the penta-coordinated complexes [SnR(4ꢀn)Cln(bupy)]
(n = 2, R = nBu; n = 1, R = Ph). Moreover, the reaction of the above organotin(IV) complexes with 4,40-
trimethylenedipyridine (tmdp) yields hexa-coordinated adducts with the general formula
Article history:
Received 12 December 2009
Accepted 4 January 2010
Available online 25 January 2010
Keywords:
Organotin
Adduct
Spectroscopy
Crystal structure
Geometry
[SnR2Cl2(tmdp)] (R = Me, nBu) and the penta-coordinated complex [ClPh3Sn-
l-(tmdp)SnPh3Cl] in the
solid state. The resulting complexes have been characterized by multinuclear NMR (1H, 13C, 119Sn) spec-
troscopy and elemental analysis. NMR data shows that the triphenyltin(IV) adducts are not stable in solu-
tion and dissociate to give tetra-coordinated tin(IV) complexes. The X-ray crystal structure determination
of [SnMe2Cl2(bu2bpy)] reveals that the tin atom is hexa-coordinated in an octahedral geometry with a
trans-[SnMe2] configuration.
Ó 2010 Published by Elsevier Ltd.
1. Introduction
For example, SnMe2Cl2 reacts with 2,20-bipyridine (bpy) or pyri-
dine (py) to form the 1:1 complex of [SnMe2Cl2(bpy)] or the 1:2
It has long been known that tin(IV) compounds are one of the
most convenient systems for the investigation of Lewis acid–base
interactions [1–4]. They usually form 1:1 and 1:2 adducts, and
the resulting adducts exist in trigonal bipyramidal or octahedral
geometries [5]. The formation of adducts depends upon the nature
of the organic group R on the organotin compounds, nature of the
donor ligand, donor ratio, halide or pseudohalide, reaction temper-
ature and solvent [5]. The organotin halides have a tendency to
form 1:1 adducts with monodentate ligands in solution. The equi-
librium constants for the formation of 1:1 adducts are strongly
dependent upon the size of the substituents. The greater insolubil-
ity of 1:2 adducts and an excess of base can result in the formation
of 1:2 adducts in the solid state [6]. Many organotin(IV) adducts
dissociate in solution and the behavior in solution is dependent
upon the organotin(IV) acceptor and solvent [7]. There are many
complexes of organotin halides with ligands such as sulfoxides,
phosphines, phosphine oxides and phosphine sulfides, and their
structure and stability have been investigated [5–7]. Monodentate
or bidentate pyridyl ligands are one of the strongest bases towards
organotin(IV) halides and form both stable 1:1 and 1:2 complexes.
complex of [SnMe2Cl2(py)2] [2]. These complexes have been shown
to exhibit anti-tumor activity. There is a relation between the Sn–N
bond length and the anti-cancer activity [8,9].
Herein, we report on the preparation and NMR data of some
organotin(IV) complexes with a related series of the monodentate
pyridyl ligand 4-tert-butylpyridine (bupy) and the corresponding
bidentate ligand 4,40-di-tert-butyl-2,20-bipyridine (bu2bpy). Also,
the reactions of the organotin(IV) complexes with the 4,40-trime-
thylenedipyridine (tmdp) ligand were investigated, where the li-
gand can act as a monodentate ligand or bridge two tin atoms
(Scheme 1). We used these three nitrogen-donor ligands to obtain
more information about the relative reactivities of organotin(IV)
complexes. The molecular structure of [SnMe2Cl2(bu2bpy)] was
determined by X-ray crystallography and is discussed.
2. Experimental
2.1. General remarks
Dimethyltin dichloride, dibutyltin dichloride and triphenyltin
chloride were purchased from Merck. 4,40-Di-tert-butyl-2,20-bipyr-
idine, 4-tert-butylpyridine and 4,40-trimethylenedipyridine were
purchased from Aldrich and were used without further purifica-
* Corresponding author. Tel.: +98 21 22850266; fax +98 21 22853650.
E-mail address: momeni@kntu.ac.ir (B.Z. Momeni).
0277-5387/$ - see front matter Ó 2010 Published by Elsevier Ltd.
doi:10.1016/j.poly.2010.01.025

1394
B.Z. Momeni et al. / Polyhedron 29 (2010) 1393–1398
2.5. Preparation of [SnMe2Cl2(bupy)2], 1b
4-tert-Butyl pyridine (0.07 mL, 0.46 mmol) was added to a solu-
tion of SnMe2Cl2 (50 mg, 0.23 mmol) in diethyl ether (5 mL). The
solution was stirred for 15 h, during which time a white solid
was formed. The solid was filtered and washed with diethyl ether
and air dried. Yield: 77%; m.p. 133–135 °C. Anal. Calc. for
C20H32Cl2N2Sn: C, 48.99; H, 6.58; N, 5.72. Found: C, 49.18; H,
6.76; N, 5.62%. NMR data in CDCl3: d (1H) 1.32 [s, 6H, 2J(119/
117Sn–H) = 100.8 Hz, Sn–Me], 1.33 [s, 18H, tBu], (bupy groups)
7.46 [d, 4H, 3J(HH) = 5.0 Hz, H3], 8.85 [d, 4H, H2]; d (13C) 29.2 [s, ter-
minal C atoms of tBu groups], 34.2 [s, central C atom of tBu groups],
20.4 [s, 1J(119/117Sn–C) = 1087 Hz, Sn–Me], (bupy groups) C2
(146.3), C3 (121.0), C4(162.7); d (119Sn) ꢀ217 (br).
N
N
(CH2)3
N
N
N
tmdp
bupy
bu2bpy
Scheme 1.
tion. Diethyl ether was distilled from sodium/benzophenone ketyl
and dichloromethane was distilled from P2O5. Elemental analyses
were performed on a Perkin–Elmer 2400 II elemental analyzer.
NMR data were recorded using Bruker Avance DRX 500 or DPX
250 MHz spectrometers. 1H and 13C NMR chemical shifts are re-
ported relative to the residual solvent signal, and 119Sn NMR chem-
ical shifts are reported relative to SnMe4. All the chemical shifts
and coupling constants are reported in ppm and Hz, respectively.
2.6. Preparation of [SnnBu2Cl2(bupy)], 2b
To a solution of SnnBu2Cl2 (60 mg, 0.20 mmol) in diethyl ether
(5 mL) was added 4-tert-butyl pyridine (0.06 mL, 0.40 mmol). The
resultant solution was stirred for 24 h. The solvent was evaporated
and a white solid was produced. Then, the solid was filtered off and
washed with diethyl ether and air dried. Yield: 75%; m.p. 67–69 °C.
Anal. Calc. for C17H31Cl2NSn: C, 46.48; H, 7.12; N, 3.19. Found: C,
47.38; H, 7.27; N, 3.95%. NMR data in CDCl3: d(1H) 1.32 [s, 9H,
tBu], 1.80 [m, 4H, SnCH2], 1.61 [q, 4H, 3J(HH) = 7.2 Hz, SnCH2CH2],
1.26 [m, 4H, 3J(HH) = 7.4 Hz, CH2CH3], 0.79 [t, 6H, 3J(HH) = 7.3 Hz,
CH3], (bupy group) 7.43 [d, 2H, 3J(HH) = 6.4 Hz, H3], 8.78 [d, 2H,
H2]; d (13C) 30.3 [s, terminal C atoms of tBu group], 35.6 [s, central
2.2. Preparation of [SnMe2Cl2(bu2bpy)], 1a
A
solution of 4,40-di-tert-butyl-2,20-bipyridine (61 mg,
0.23 mmol) in diethyl ether (5 mL) was added to a solution of
SnMe2Cl2 (50 mg, 0.23 mmol) in diethyl ether (5 mL) to afford a
white crystalline solid. The product was then filtered off and
washed with diethyl ether and air dried. Yield: 85%; m.p. 235–
236 °C. Anal. Calc. for C20H30Cl2N2Sn: C, 49.20; H, 6.20; N, 5.74.
Found: C, 49.93; H, 6.35; N, 5.83%. NMR data in CDCl3: d(1H) 1.06
[s, 6H, 2J(119/117Sn–H) = 106.4 Hz, Sn–Me], 1.48 [s, 18H, tBu], (bu2b-
t
C atom of Bu group], 32.8 [s, 1J(119/117Sn–C) not resolved, SnCH2],
0
0
py group) 7.67 [d, 2H, 3J(HH) = 5.6 Hz, H5,5 ], 8.23 [s, 2H, H3,3 ], 9.40
27.8 [s, 2J(119/117Sn–C) = 41 Hz, SnCH2CH2], 26.1 [s, 3J(119/117Sn–
C) = 131 Hz, CH2CH3], 13.5 [s, CH3], (bupy group) 147.7 (C2),
120.1 (C3), 160.4 (C4); d(119Sn) ꢀ84 (br), ꢀ90 (sh), ꢀ137 (sh).
0
[d, 2H, 3J(HH) = 5.4 Hz, H6,6 ]; d (13C) 25.3 [s, 1J(119Sn–C) = 1092 Hz,
1J(117Sn–C) = 1043 Hz, Sn–Me], 30.4 [s, terminal C atoms of tBu
t
groups], 35.7 [s, central C atoms of Bu groups], (bu2bpy group)
165.4 (C2), 118.9 (C3), 148.7 (C4), 123.8 (C5), 148.0 (C6); d(119Sn)
ꢀ251 (sh). Crystals suitable for X-ray structure determination were
grown from a chloroform solution.
2.7. Preparation of [SnPh3Cl(bupy)], 3b
2.3. Preparation of [SnnBu2Cl2(bu2bpy)], 2a
To a solution of SnPh3Cl (100 mg, 0.26 mmol) in dichlorometh-
ane (10 mL) was added 4-tert-butyl pyridine (0.04 mL, 0.26 mmol).
The solution was stirred for 48 h and then the solvent was evapo-
rated to afford a white solid. This was recrystallized from CH2Cl2/n-
hexane and air dried. Yield: 85%; m.p. 66–68 °C. Anal. Calc. for
C27H28ClNSn: C, 62.26; H, 5.42; N, 2.69. Found: C, 61.43; H, 5.25;
N, 2.44%. NMR data in CDCl3: d (13C) 30.5 [s, terminal C atoms of
tBu group], (bupy group) 149.4 (C2), 120.9 (C3), (Ph groups) 137.9
[s, C1], 136.2 [s, 2J(119/117Sn–C) = 48 Hz, C2], 129.1 [s, 3J(119/117Sn–
C) = 64 Hz, C3], 130.3 [s, 4J(119/117Sn–C) = 14 Hz, C4 ]; d (119Sn) in
CH2Cl2/CDCl3: ꢀ71 (sh).
Following the same procedure as for the preparation of 1a, a
solution of 4,40-di-tert-butyl-2,20-bipyridine (44 mg, 0.16 mmol)
in diethyl ether (5 mL) was added to a solution of SnnBu2Cl2
(50 mg, 0.16 mmol) in diethyl ether (5 mL) to give a white solid.
Yield: 81%; m.p. 188–190 °C. Anal. Calc. for C26H42Cl2N2Sn: C,
54.55; H, 7.40; N, 4.90. Found: C, 54.69; H, 7.59; N, 4.81%. NMR
t
data in CDCl3: d (1H) 1.47 [s, 18H, Bu], 1.58 [m, 4H, SnCH2], 1.41
[m, 4H, SnCH2CH2], 1.14 [m, 4H, 3J(HH) = 7.2 Hz, CH2CH3], 0.71 [t,
6H, 3J(HH) = 7.2 Hz, CH3], (bu2bpy group) 7.61 [dd, 2H,
0
3J(HH) = 5.5 Hz, 4J(HH) = 1.5 Hz, H5,5 ], 8.19 [d, 2H, 4J(HH) = 1.2 Hz,
0
0
H
3,3 ], 9.31 [d, 2H ,3J(HH) = 5.5 Hz, H6,6 ]; d (13C) 29.4 [s, terminal
t
t
C atoms of Bu groups], 34.6 [s, central C atoms of Bu groups],
40.2 [s, 1J(119/117Sn–C) not resolved, SnCH2], 27.0 [s, SnCH2CH2],
24.9 [s, CH2CH3], 12.5 [s, CH3], (bu2bpy group) 164.1 (C2), 117.5
(C3), 148.6 (C4), 122.4 (C5), 147.6 (C6); d(119Sn) ꢀ232 (br).
2.8. Preparation of [SnMe2Cl2(tmdp)], 1c
Following the same procedure as for the preparation of 1a, a
solution of 4,40-trimethylenedipyridine (45 mg, 0.23 mmol) in
diethyl ether (5 mL) was added to a solution of Me2SnCl2 (50 mg,
0.23 mmol) in diethyl ether (5 mL) to give a white solid. Yield:
87%; m.p. 174–176 °C. Anal. Calc. for C15H20Cl2N2Sn: C, 43.12; H,
4.78; N, 6.71. Found: C, 43.06; H, 4.69; N, 6.64%. NMR data in
CD2Cl2: d(1H) 2.73 [t, 4H ,3J(HH) = 7.8 Hz, terminal CH2 of tmdp],
2.03 [q, 2H, 3J(HH) = 4.6 Hz, central CH2 of tmdp], 1.26 [t, 6H,
2J(119/117Sn–H) = 84.1, Sn–Me], (tmdp group) 8.62 [d, 4H,
3J(HH) = 5.9 Hz, H2], 7.26 [d, 4H, 3J(HH) = 6.0 Hz, H3]; d (13C) 38.1
[s, terminal C atoms of tmdp], 34.1 [s, central C atom of tmdp],
24.1 [s, 1J(119/117Sn–C) not resolved, Sn–Me], (tmdp group) 152.9
(C2), 127.8 (C3), 155.0 (C4); d(119Sn) ꢀ66 (sh), ꢀ116 (sh).
2.4. Preparation of [SnPh3Cl(bu2bpy)], 3a
A
solution of 4,40-di- tert-butyl-2,20-bipyridine (50 mg,
0.19 mmol) in diethyl ether (5 mL) was added to a solution of
SnPh3Cl (72 mg, 0.19 mmol) in diethyl ether (5 mL). The solution
was stirred for 10 hours. The resultant colorless solution was evap-
orated to dryness to afford a white solid, which was filtered off. The
solid was washed with diethyl ether and air dried. Yield: 85%; m.p.
83–85 °C. Anal. Calc. for C36H39ClN2Sn: C, 66.11; H, 6.02; N, 4.29.
Found: C, 66.09; H, 5.77; N, 4.32%.

B.Z. Momeni et al. / Polyhedron 29 (2010) 1393–1398
1395
2.9. Preparation of [SnnBu2Cl2(tmdp)], 2c
Table 1
Experimental details, crystal data and refinement parameters for complex 1a.
Following the same procedure as for the preparation of 1a, a
Empirical formula
Formula weight (g/mol)
Crystal size (mm)
Crystal system
Space group
h range (°)
a (Å)
C20H30Cl2N2Snꢂ0.5CHCl3
1095.47
0.32 ꢁ 0.38 ꢁ 0.40
monoclinic
C2/c
solution of 4,40-trimethylenedipyridine (65 mg, 0.33 mmol) in
diethylether (5 mL) was added to
a
solution of SnnBu2Cl2
(100 mg, 0.33 mmol) in diethyl ether (5 mL) to afford a white solid.
The product was filtered off and then washed with ether and dried
in air. Yield: 82%; m.p. 137–139 °C. Anal. Calc. for C21H32Cl2N2Sn: C,
50.21; H, 6.43; N, 5.58. Found: C, 50.64; H, 6.56; N, 5.59%. NMR
data in CDCl3: d (1H) 2.70 [t, 4H ,3J(HH) = 7.8 Hz, terminal CH2 of
tmdp], 2.02 [q, 2H, 3J(HH) = 7.8 Hz, central CH2 of tmdp], 1.80 [m,
4H, SnCH2], 1.76 [m, 4H, SnCH2CH2], 1.60 [m, 4H, 3J(HH) = 7.0 Hz,
CH2CH3], 0.93 [t, 6H, 3J(HH) = 7.9 Hz, CH3], (tmdp group) 8.59 [d,
4H ,3J(HH) = 5.8 Hz, H2], 7.18 [d, 4H , 3J(HH) = 6.0 Hz, H3]; d (13C)
35.3 [s, terminal C atoms of tmdp], 34.6 [s, central C atom of tmdp],
30.2 [s, 1J(119/117Sn–C) not resolved, SnCH2], 27.7 [s, 2J(119/117Sn–
C) = 41 Hz, SnCH2CH2], 26.1 [s, 3J(119/117Sn–C) = 131 Hz, CH2CH3],
13.5 [s, CH3], (tmdp group) 148.4 (C2), 124.6 (C3), 153.0 (C4); d
29.2
33.560(2)
11.5983(5)
11.5983(5)
90.556(6)
5113.9(5)
4
1.423
1.373
2216
b (Å)
c (Å)
b (°)
Volume (Å3)
Z
Dcalc (g/cm3)
l
(mmꢀ1
)
F (0 0 0)
Index ranges
ꢀ46 6 h 6 46, ꢀ15 6 k 6 15, ꢀ15 6 l 6 17
Reflections collected
Independent reflections [Rint
Observed reflections
Parameters/restraints
Goodness-of-fit (GOF)
R1 (observed data)
wR2 (all data)a
19 478
]
6841 [0.057]
5875 (I > 2
279/24
1.11
r(I))
(
119Sn) ꢀ90 (sh),-105 (br), ꢀ137 (sh).
0.0459
0.1206
2.10. Preparation of [ClPh3Sn-l-(tmdp)SnPh3Cl], 3c
w = 1/[r
2(Fo2) + (0.0531P)2 + 7.039P], where P = (Fo2 + 2F2c )/3.
a
A solution of 4,40-trimethylenedipyridine (51 mg, 0.26 mmol) in
dichloromethane (3 mL) was added to a solution of SnPh3Cl
(200 mg, 0.52 mmol) in dichloromethane (10 mL) and stirred for
48 h. The solvent was evaporated to afford a white solid. The solid
was filtered off and air dried. Yield: 81%; m.p. 119–120 °C. Anal.
Calc. for C49H44Cl2N2Sn2: C, 60.70; H, 4.58; N, 2.89. Found: C,
60.39; H, 4.39; N, 2.66%. NMR data in CDCl3: d (1H) 2.64 [t, 4H
,3J(HH) = 8.0 Hz, terminal CH2 of tmdp], 1.98 [q, 2H,
3J(HH) = 7.8 Hz, central CH2 of tmdp], 8.48 [d, 4H ,3J(HH) = 4.3 Hz,
H2], 7.10 [d, 4H ,3J(HH) = 5.8 Hz, H3], 7.46, 7.68 [m, Ph groups]; d
data, experimental details and refinement parameters is given in
Table 1.
3. Results and discussion
3.1. Solution studies
The reactions of organotin(IV) chlorides [SnR(4ꢀn)Cln] (n = 2,
R = Me, nBu; n = 1, R = Ph) with the bidentate pyridyl ligand bu2bpy
gave the hexa-coordinated complexes [SnR(4ꢀn)Cln(bu2bpy)] (1a–
3a), as shown in Scheme 2. Moreover, the above organotin(IV)
chlorides reacted with the corresponding monodentate pyridyl li-
gand bupy to afford hexa- or penta-coordinated organotin(IV)
complexes 1b–3b (Scheme 2). These complexes were typically pre-
pared by mixing a diethyl ether or dichloromethane solution of the
appropriate organotin chloride with the ligands in a 1:1 or 1:2
mole ratio.
(
13C) 34.4 [s, terminal C atoms of tmdp], 30.4 [s, central C atom
of tmdp], (tmdp group) 149.6 (C2), 123.9 (C3), 150.9 (C4), (Ph
groups) 137.9 [s, C1], 136.2 [s, 2J(119/117Sn–C) = 49 Hz, C2], 129.1
[s, 3J(119/117Sn–C) = 65 Hz, C3 ], 130.3 [s, 4J(119/117Sn–C) = 14 Hz,
C4]; d (119Sn) in CH2Cl2/CDCl3: ꢀ80 (sh).
2.11. X-ray crystal structure determination
The X-ray diffraction measurements were made on a STOE
The reaction of dimethyltin(IV) dichloride with bu2bpy in a 1:1
mole ratio in diethyl ether yields the white complex [SnMe2Cl2-
(bu2bpy)], 1a, which was fully characterized by 1H, 13C and 119Sn
NMR spectroscopy. The 1H NMR spectrum of complex 1a in CDCl3
shows a signal at d 1.06 with 2J(119/117Sn–H) = 106.4 Hz, different
from that of the starting complex SnMe2Cl2 which has 2J(119Sn–
H) = 68.6 Hz and 2J(117Sn–H) = 65.7 Hz in CDCl3 [16]. It is well-
known that the magnitude of the magnetic coupling constant of
the methyl protons with 119Sn is a useful guide for the determining
the geometry of the tin atom. This coupling constant is in the range
of other hexacoordinate dimethyltin(IV) complexes [16,17]. The
13C NMR spectrum of 1a in CDCl3 displayed a signal at d = 25.3 with
1J(119Sn–C) = 1092 Hz and 1J(117Sn–C) = 1043 Hz, which were used
to calculate h (C–Sn–C) by the Lockhart and Manders equation
(Eq. (1)), giving a value of 172.54° [18]. The magnitude of h is very
close to the observed value in the solid state from analysis of the X-
ray crystallography data (174.22°).
IPDS-II diffractometer with graphite monochromated Mo Ka radi-
ation. The colorless block crystal with dimensions of
0.40 ꢁ 0.38 ꢁ 0.32 mm was mounted on a glass fiber and used
for data collection. Cell constants and an orientation matrix for
data collection were obtained by least-squares refinement of dif-
fraction data from 6841 unique reflections. Data were collected
at a temperature of 298(2) K to a maximum 2h value of 58.48°
and in a series of
the STOE X-AREA [10] software package. The numerical absorption
coefficient, , for Mo-K
radiation is 1.373 mmꢀ1 for 1a. A numer-
x scans with 1° oscillations and integrated using
l
a
ical absorption correction was applied using X-RED [11] and X-SHAPE
[12] software. The data were corrected for Lorentz and Polarizing
effects. The structure was solved by direct methods and subse-
quent difference Fourier map and then refined by a full-matrix
least-squares on F2 [13]. All of the H atoms except H21 were posi-
tioned geometrically, with C–H = 0.93 and 0.96 Å for aromatic and
methyl H atoms, respectively, and constrained to ride on their par-
ent atoms with Uiso(H) = 1.2Ueq(C). H21 was located in a differ-
ence Fourier map and then refined isotropically. Subsequent
refinement then converged with R factors and parameter errors
significantly better than for all attempts to model the solvent dis-
order. Atomic factors are from International Tables for X-ray Crys-
tallography [14]. All refinements were performed using the SHELXTL
crystallographic software package [15]. A summary of the crystal
1Jð119Sn—13CÞ ¼ 11:4h ꢀ 875
ð1Þ
The 119Sn NMR spectrum of complex 1a showed a sharp signal
at d = ꢀ251. A range of d values from +200 to ꢀ60 have been re-
ported for four-coordinated, ꢀ90 to ꢀ190 for five-coordinated
and ꢀ210 to ꢀ400 for six-coordinated diorganotin(IV) complexes
in solution [19]. Thus, the signal at ꢀ251 is consistent with those

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B.Z. Momeni et al. / Polyhedron 29 (2010) 1393–1398
[SnR(4-n)Cln(bupy)2]
n=2, R= Me 1b
bu2bpy
bupy
[SnR(4-n)Cln]
[SnR(4-n)Cln(bu2bpy)]
n=2, R= Me 1a
n=2, R= nBu 2a
n=1, R= Ph
3a
[SnR(4-n)Cln(bupy)]
n=2, R= nBu 2b
n=1, R= Ph
3b
Scheme 2.
reported for other hexa-coordinated diorganotin(IV) complexes.
The chemical shift of 1a is significantly more upfield than that
for the starting complex SnMe2Cl2 (d = 137.2 in CDCl3) [20], result-
ing from the coordination of two N atoms to the tin center. These
data, in combination with the spin–spin coupling constants, indi-
cate that the hexa-coordinated geometry persists in solution. In
addition, the reaction of dibutyltin(IV) dichloride with bu2bpy re-
sulted in the formation of the complex [Sn(nBu)2Cl2(bu2bpy)]
(2a). The 119Sn NMR spectrum of 2a in CDCl3 shows a signal at
d = ꢀ231, which indicates the presence of a hexa-coordinated ad-
duct of tin(IV) in solution [19].
The elemental analysis data show a ligand to metal ratio of 1:1
for complexes 1c and 2c, whereas a 1:2 ligand to metal ratio is ob-
served for 3c. The 119Sn NMR spectrum of 1c showed a signal at
d = ꢀ116 (in CDCl3), and three signals at d = ꢀ90, ꢀ105 and ꢀ137
(in CDCl3) were observed for 2c, typical for five-coordinated dior-
ganotin(IV) adducts (d = ꢀ90 to ꢀ190 ppm) [19]. Therefore, pen-
ta-coordinated diorganotin(IV) adducts are present in solutions of
1c and 2c. Moreover, the 119Sn NMR spectrum of 3c displayed a sig-
nal at d = ꢀ80 (in CH2Cl2/CDCl3) in the region of four-coordinated
triphenyltin(IV) compounds (d = ꢀ40 to ꢀ120 ppm for four-coordi-
nated and d = ꢀ180 to ꢀ260 ppm for five-coordinated triphenyl-
tin(IV) compounds) [23]. Therefore, a tetra-coordinated tin(IV)
compound persists in the solution of 3c. On the basis of combined
analytical data and spectral data, we suggest a penta-coordinated
geometry in the solid state for the organotin(IV) adduct of
The 119Sn NMR spectrum of the complex [SnPh3Cl(bu2bpy)], 3a,
in CDCl3 displayed a sharp signal at d = ꢀ46, which is in agreement
with the reported value for free SnPh3Cl (d = ꢀ44.7) [21]. These
data indicate that the interaction between SnPh3Cl and bu2bpy is
not maintained in solution and it strongly dissociates in chloro-
form solution to give triphenyltin chloride. This is consistent with
other triphenyltin(IV) adducts which are not stable in solution [7].
Therefore, the assignment of the stoichiometry of complex 3a was
based on the elemental analysis.
Additionally, SnMe2Cl2 reacts with bupy in a mole ratio of 1:2 to
give the hexa-coordinated complex [SnMe2Cl2(bupy)2], 1b. How-
ever, the reaction of SnBu2Cl2 with bupy in a mole ratio of 1:2 af-
fords the penta-coordinated complex [SnBu2Cl2(bupy)], 2b
(Scheme 2). The 119Sn spectrum of 2b in CDCl3 shows a broad sig-
nal at d = ꢀ84 and two sharp signals at d = ꢀ89 and ꢀ137, which
are more upfield than the starting complex SnBu2Cl2 (d = 126 in
CDCl3) [21]. The presence of several signals indicates the presence
of geometric isomers [22]. In the case of [SnPh3Cl], a penta-coordi-
nated crystalline tin complex of [SnPh3Cl(bupy)], 3b, could be iso-
lated. The 119Sn NMR spectrum of 3b in dichloromethane shows a
signal at d = ꢀ71, which is in the observed range of tetra-coordi-
nated triphenyltin compounds (d = ꢀ40 to ꢀ120 ppm) [23]. It
should be mentioned that the formation of an adduct between
[SnPh3Cl] and pyridine has been observed only in solution [24].
We attribute it to the increased basicity of bupy relative to that
pyridine, which can form a stable adduct in the solid state. The for-
mation of stronger complexes results in higher formation con-
stants of the complexes [24,25].
[ClPh3Sn-l-(tmdp)SnPh3Cl], 3c, which dissociates in solution to af-
ford a tetra-coordinated compound of tin(IV). However, a hexa-
coordinated solid state structure is reasonably assumed for 1c
and 2c, which is probably a polymeric chain of ꢂ ꢂ ꢂSn–tmdp–Sn–
tmdpꢂ ꢂ ꢂ which dissociates in solution to give the penta-coordi-
nated complexes of [SnR2Cl2(tmdp-j
1N)] (R = Me, nBu). It should
be mentioned that in the case of 1c, a signal at d = ꢀ66 was also ob-
served, and this value is ‘‘unnatural” [19]. It can be assigned to the
equilibrium of the four-coordinated complex [SnMe2Cl2] and the
five-coordinated complex SnMe2Cl2.tmdp.
The 1H and 13C NMR assignments for the butyl moiety in 2a–c,
the phenyl groups in 1–3c and the bu2bpy ligand were made
according to literature data [23,26,27].
The 1H NMR spectrum of 1c in CDCl3 solution and in the pres-
ence of a few drops of DMSO showed a singlet at d = 1.18 with
2J(Sn–H) = 102.8 Hz. The magnitude of the observed coupling con-
stant is consistent with an octahedral structure for the SnMe2Cl2
adduct, which is likely to be [SnMe2Cl2(tmdp-j
1N)(DMSO)]. Addi-
tionally, the 119Sn NMR spectrum of complex 1c in CDCl3/DMSO
showed a broad signal at d = ꢀ155, in the range of other penta-
coordinated complexes [19]. This indicates that the proposed com-
plex [SnMe2Cl2(tmdp-j
1N)(DMSO)] is not stable in solution for a
long time and dissociates to give a penta-coordinated complex.
It is also interesting to note that the reaction of triphenyltin(IV)
chloride with these nitrogen-donor ligands requires a longer reac-
tion time than the corresponding reaction of diorganotin(IV) chlo-
rides, which is consistent with a previous observation [7].
The preparation of all the complexes were attempted with
different stoichiometries in order to determine if more than
one kind of complex can be formed between a particular organo-
tin(IV) halide and ligand. It can be seen that the formation of
penta- or hexa-coordinated species is influenced by the nature
of alkyl groups R on the organotin(IV) compounds as well as
the nature of the ligand. They are more significant factors than
the ratio of the ligand to metal for the formation of adducts in
the solid state.
The organotin(IV) chlorides [SnR(4ꢀn)Cln] reacted with tmdp to
give the complexes [SnR(4ꢀn)Cln(tmdp)] (n = 2; R = Me, nBu) (1c–
2c) or [ClPh3Sn-
l-(tmdp)SnPh3Cl] (3c) in the solid state (Eqs. (2
and 3)).
[SnR2Cl2] + tmdp
[SnR2Cl2(tmdp)]
ð2Þ
R = Me
R = nBu
1c
2c
2[SnPh3Cl] + tmdp
[ClPh3Sn-µ-(tmdp)SnPh3Cl]
ð3Þ
3c

B.Z. Momeni et al. / Polyhedron 29 (2010) 1393–1398
1397
Table 2
Selected bond lengths (Å) and angles (°) for complex 1a.
Sn(1)–C(2)
Sn(1)–C(1)
Sn(1)–N(2)
Sn(1)–N(1)
2.126(4)
2.127(4)
2.379(2)
2.405(2)
Sn(1)–Cl(2)
Sn(1)–Cl(1)
N(1)–C(3)
2.4971(11)
2.5538(10)
1.336(4)
174.22(19)
86.43(14)
89.97(15)
89.20(16)
85.28(14)
68.66(8)
93.97(16)
90.75(14)
93.56(6)
161.74(7)
89.90(14)
91.97(14)
160.15(6)
91.81(6)
106.16(4)
123.1(2)
118.32(18)
117.9(3)
122.5(2)
118.84(18)
109.5
C(2)–Sn(1)–C(1)
C(2)–Sn(1)–N(2)
C(1)–Sn(1)–N(2)
C(2)–Sn(1)–N(1)
C(1)–Sn(1)–N(1)
N(2)–Sn(1)–N(1)
C(2)–Sn(1)–Cl(2)
C(1)–Sn(1)–Cl(2)
N(2)–Sn(1)–Cl(2)
N(1)–Sn(1)–Cl(2)
C(2)–Sn(1)–Cl(1)
C(1)–Sn(1)–Cl(1)
N(2)–Sn(1)–Cl(1)
N(1)–Sn(1)–Cl(1)
Cl(2)–Sn(1)–Cl(1)
C(3)–N(1)–Sn(1)
C(11)–N(1)–Sn(1)
C(20)–N(2)–C(12)
C(20)–N(2)–Sn(1)
C(12)–N(2)–Sn(1)
Sn(1)–C(1)–H(1A)
Sn(1)–C(1)–H(1B)
Sn(1)–C(1)–H(1C)
N(1)–C(3)–C(4)
N(1)–C(3)–H(3)
C(11)–C(10)–C(5)
N(1)–C(11)–C(10)
N(1)–C(11)–C(12)
Fig. 1. The molecular structure of complex 1a, showing 30% probability displace-
ment ellipsoids and the atomic numbering. The hydrogen atoms (except for the
solvent) are omitted for clarity. The open bonds show the minor component.
3.2. Description and discussion of the crystal structure of 1a
The molecular structure of [SnMe2Cl2(bu2bpy)] (1a) is shown in
Fig. 1. Selected bond distances and angles are given in Table 2.
Complex 1a was crystallized as the chloroform solvate [SnMe2Cl2-
(bu2bpy)]ꢂ0.5CHCl3. One of the tert-butyl groups of the bu2bpy li-
gand is disordered rotationally over two positions with a refined
site-occupancy ratio of 0.58(2)/0.42(2). In addition, the chloroform
solvent of crystallization is also disordered along the crystallo-
graphic twofold rotation axis which passes through the Cl3 atom.
The coordination geometry about the Sn(IV) atom is octahedral,
as revealed by the C(1)–Sn–C(2) angle which deviates insignifi-
cantly from linearity (174.22(19)°). The chlorine atoms are cis to
each other, while the methyl groups are trans. Bu2bpy acts in a
109.5
109.5
123.5(3)
118.2
120.7(3)
121.6(2)
116.1(2)
Symmetry transformations used to generate equivalent atoms: #1 ꢀx, y,ꢀz + 1/2.
bidentate manner through N(1) and N(2), adopting a cis conforma-
tion. The Sn–C bond distances are not equal (2.126 and 2.127 Å).
Fig. 2. The crystal packing of complex 1a, viewed down the c-axis, showing linking of the neighboring molecules through intermolecular C–Hꢂ ꢂ ꢂCl interactions along the a-
axis. The H-atoms except those involved in interactions are omitted for clarity. Intermolecular interactions are shown as dashed lines.

1398
B.Z. Momeni et al. / Polyhedron 29 (2010) 1393–1398
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CCDC 746807 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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Acknowledgment
We thank the Science Research Council of K.N. Toosi University
of Technology for financial support.
[22] C.H. Yoder, L.A. Margolis, J.M. Horne, J. Organomet. Chem. 633 (2001) 33.
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