The synthesis and structure of sterically encumbered terphenyl tin(II) halide derivatives: Simultaneous existence of monomers and dimers in the crystalline phase

Article abstract of DOI:10.1016/S0277-5387(00)00661-6

The reaction of Et₂O·LiC₆H₃-2,6-Trip₂ (Trip = C₆H²-2,4,6-i-Pr₃) with SnCl₂ afforded the two coordinate monomer Sn(Cl)C₆H₃-2,6-Trip₂ (1), and its dimer {Sn(μ-Cl)C₆H₃-2,6-Trip₂}₂ (2), as orange and yellow crystals, respectively. Solution ¹¹⁹Sn NMR spectroscopy of 2 in C₆D₆ solution showed that it dissociated readily to give 1. The addition of pyridine (py) to a solution of 1 yielded the adduct py·Sn(Cl)C₆H₃-2,6-Trip₂ (3) which featured tin in a three coordinate pyramidal environment. The reaction of the closely related bulky terphenyl lithium reagent LiC₆H₃-2,6-Dipp₂ (Dipp = C₆H₃-2,6-i-Pr₂ with SnCl₂ afforded the mixed halide species {Sn(μ-Cl)_0.35(μ-I)_0.65C₆H₃ -2,6-Dipp₂}₂ (4). This arose from the preparation of the lithium aryl precursor in situ from IC₆H₃-2,6-Dipp₂ and n-BuLi. The monomeric nature of 1, and the weak association of 2 and 4, were attributed to the large size of the terphenyl ligands. All compounds were characterized by X-ray crystallography, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, and IR and UV-Vis spectroscopy.

Full text of DOI:10.1016/S0277-5387(00)00661-6

Polyhedron 20 (2001) 551–556
www.elsevier.nl/locate/poly
The synthesis and structure of sterically encumbered terphenyl
tin(II) halide derivatives: simultaneous existence of monomers and
dimers in the crystalline phase
Barrett E. Eichler, Lihung Pu, Matthias Stender, Philip P. Power *
Department of Chemistry, Uni6ersity of California, Da6is, One Shields A6enue, Da6is, CA, 95616, USA
Received 5 September 2000; accepted 4 December 2000
Abstract
The reaction of Et2O·LiC6H3-2,6–Trip2 (Trip=C6H2–2,4,6-i-Pr3) with SnCl2 afforded the two coordinate monomer
Sn(Cl)C6H3-2,6–Trip2 (1), and its dimer {Sn(m-Cl)C6H3–2,6-Trip2}2 (2), as orange and yellow crystals, respectively. Solution 119Sn
NMR spectroscopy of 2 in C6D6 solution showed that it dissociated readily to give 1. The addition of pyridine (py) to a solution
of 1 yielded the adduct py·Sn(Cl)C6H3–2,6-Trip2 (3) which featured tin in a three coordinate pyramidal environment. The reaction
of the closely related bulky terphenyl lithium reagent LiC6H3–2,6-Dipp2 (Dipp=C6H3–2,6-i-Pr2) with SnCl2 afforded the mixed
halide species {Sn(m-Cl)0.35(m-I)0.65C6H3–2,6-Dipp2}2 (4). This arose from the preparation of the lithium aryl precursor in situ
from IC6H3–2,6-Dipp2 and n-BuLi. The monomeric nature of 1, and the weak association of 2 and 4, were attributed to the large
1
size of the terphenyl ligands. All compounds were characterized by X-ray crystallography, H, 13C and 119Sn NMR spectroscopy,
and IR and UV–Vis spectroscopy. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Terphenyl; Organotin(II) compounds; Bulky ligands; Stannanediyls
the lithium terphenyl and the metal dihalide. These
precursors, however, are also of interest in their own
right for several reasons; (i) well characterized com-
pounds of the general formula M(X)R are relatively
rare, especially when the organic group (R) is
monodentate, (ii) M(X)R species display a variety of
structures; e.g. halide bridged dimer [5,8], monomer
[6,7] and metal–metal bonded dimer [5]. The latter two
structural types have not been observed in the solid
state with other monodentate ligands. In previous pub-
lications it has been shown that, when the less crowding
–C6H3–2,6-Mes2 (Ar%) substitutent is used, the germa-
nium species has the unique Ge–Ge bonded
Ar%(Cl)GeGe(Cl)Ar% structure [5], whereas the tin ana-
logue has the halide bridged arrangement Ar%Sn(m-
Cl)2SnAr% [5]. For the bulkier –C6H3–2,6-Trip2 (Ar)
substituent a V-shaped monomeric structure was ob-
served for the orange germanium derivative Ge(Cl)Ar
[6]. However, the structure of the corresponding tin
species, Sn(Cl)Ar, which has been employed extensively
as a starting material, was unknown. It is generally
obtained as orange crystals from the reaction of SnCl2
1. Introduction
The use of sterically crowding, meta-terphenyl sub-
stituents has enabled the synthesis and characterization
of several new compound types throughout the periodic
table which were previously unavailable as stable spe-
cies [1]. In the case of the heavier Group 14 elements
the employment of these ligands has led to the isolation
of the first compounds with triple bonding to germa-
nium [2], the first diplumbyne valence isomer of an
alkyne [3], as well as the novel doubly bonded dianions
of formula [ArMMAr]2− (Ar=C6H3–2,6-Trip2, M=
Ge or Sn) [4]. The key starting materials for the synthe-
sis of these compounds are the terphenyl element halide
species M(X)Ar or M(X)Ar% (M=Ge, Sn or Pb; X=
Cl, Br or I; Ar=C6H3–2,6-Trip2; Ar%=C6H3–2,6-
Mes2; Trip=C6H2–2,4,6-i-Pr3; Mes=C6H2–2,4,6-
Me3) [5–7], which were synthesized by the reaction of
* Corresponding author. Tel.: +1-530-752-6913; fax: +1-530-752-
8995.
E-mail address: pppower@ucdavis.edu (P.P. Power).
0277-5387/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0277-5387(00)00661-6

552
B.E. Eichler et al. / Polyhedron 20 (2001) 551–556
3
and Et2O·LiAr in diethyl ether and subsequent crystal-
lization from hexane [9]. During the course of several
recrystallizations it was observed that two different
crystalline materials (one having an orange, the other a
yellow color) were obtained. At first, it was assumed
that the yellow crystals were an impurity (possibly the
hydroxide Sn(OH)Ar), formed as a result of moisture
contamination. However, further examination showed
that solutions of the orange or yellow crystals had
CH(CH3)2) JHH=6.6 Hz, 1.39 (d, 12H, o-CH(CH3)2)
3JHH=6.9 Hz, 2.81 (sept, 2H, p-CH(CH3)2) JHH=6.9
Hz, 3.15 (sept, 4H, o-CH(CH3)2) JHH=6.9 Hz, 7.19
3
3
(s, 4H, m-Trip) 7.22-7.31 (mult, 3H, o, p-C6H3),
13C{1H} NMR (C6H6): l 23.12 (o-CH(CH3)2), 24.26
(p-CH(CH3)2), 26.43 (o-CH(CH3)2), 31.07 (o-
CH(CH3)2), 34.75 (p-CH(CH3)2), 121.68 (m-Trip),
130.68 (m-C6H3), 135.01 (p-C6H3), 145.38 (o-C6H3),
146.79 (i-Trip), 147.57 (p-Trip), 149.53 (o-Trip), 181.86
(i-C6H3). UV–Vis (hexane) umax (nm), m=(mol−1
1
identical H, 13C and 119Sn NMR spectra. In this paper
the structural and spectroscopic characterization of
these crystals are reported, together with their interac-
tion with the Lewis bases THF and pyridine. The
spectroscopic structural characterization of a related
derivative involving the terphenyl ligand –C6H3–2,6-
Dipp2 (Dipp= –C6H3–2,6-i-Pr2) is also given.
cm−1): 284 (sh), 330; 395, 1040. IR (Nujol mull, cm−1
)
w: 1765(vw), 1730(w), 1600(m), 1550(m), 1310(w),
1175(vw), 1170(m), 1150(vw), 1110(w), 1090(vw),
1070(w), 1050(w), 1020(w), 1010(w), 955(w), 940(m),
920(vw), 880(s), 850(vw), 820(vw), 800(s), 770(m),
750(vw), 735(s), 720(vw), 695(vw), 650(m), 625(vw),
600(vw), 575(vw), 530(w), 465(vw), 395(vw), 300(s),
240(m).
2. Experimental
2.1. General procedures
2.3. py·Sn(Cl)C6H3–2,6-Trip2 (3)
All manipulations were carried out by using modified
Schlenk techniques under an atmosphere of N2 or in a
Vacuum Atmospheres HE-43 drybox. All solvents were
distilled from Na/K alloy, and degassed twice immedi-
ately before use. The compounds Et2O·LiC6H3–2,6-
Trip2 [10] and LiC6H3–2,6-Dipp2 [11] were prepared
according to literature procedures. Anhydrous SnCl2,
was purchased commercially and purified by sublima-
tion under reduced pressure. Pyridine (py) was dried by
Pyridine (0.37 ml, 4.6 mmol) was added to a rapidly
stirred orange solution of Sn(Cl)C6H3–2,6-Trip2 (2.91
g, 4.58 mmol) in hexane (80 ml) at ca. 25°C. The
reaction mixture became a yellow color and stirring was
continued for a further 1 h. The yellow solution was
separated from the small amount of white precipitate
by decanting. The volume was reduced to incipient
crystallization under reduced pressure and stored in a
ca. 5°C refrigerator for 2 days to afford 3 as yellow
crystals. Yield 2.67 g, 81%. M.p.: 140–142°C dec.
1
distillation from CaH2. H, 13C{1H}, and 119Sn {1H}
NMR spectra were recorded on a Bruker 300 MHz or
Varian 400 Hz instrument and referenced to the deuter-
ated solvent in the case of the 1H and 13C NMR
spectra. The 119Sn NMR spectra were referenced to
SnMe4. Infrared and UV–Vis spectra were recorded on
a Perkin PE-1430 and a Hitachi-1200 spectrometer.
1
119Sn{1H}(C6D6): l 264. H NMR (C6D6): l 1.13 (12H,
o-CH(CH3)2), 3JHH=6.9 Hz; 1.20 (d, 12H, o-
3
CH(CH3)2), JHH=6.9 Hz; 1.41 (d, 12H, p-CH(CH3)2),
3JHH=6.9 Hz; 2.74 (sept, 2H, p-CH(CH3)2), 3JHH=6.9
3
Hz; 3.34 (sept, 4H, o-CH(CH3)2), JHH=6.9 Hz; 6.26
3
(d of d, 2H, m-C5H5N), JHH=6.0 Hz; 6.59 (t of t, 1H,
3
4
2.2. Sn(Cl){C6H3–2,6-Trip2} (1) and
[Sn(v-Cl){C6H3–2,6-Trip2}]2 (2)
p-C5H5N), JHH =.75 Hz, JHH=1.2 Hz; 7.19 (s, 4H,
3
m-Trip); 7.26 (tr, 1H, p-C6H3), JHH=7.6 Hz; 7.93 (d
3
4
of d, 2H, m-C6H3), JHH=6.0 Hz; JHH=1.2 Hz; 7.98
(br, 2H, o-C5H5N); 13C{1H} NMR (C6H6): l 23.18
(o-CH(CH3)2); 24.28 (o-CH(CH3)2); 26.22 (p-
CH(CH3)2); 30.96 (o-CH(CH3)2); 34.52 (p-CH(CH3)2);
120.85 (m-Trip); 124.15 (m-C5H5N); 126.45 (p-C6H3);
130.86 (p-C5H5N); 137.43 (m-C6H3); 138.60 (i-Trip);
146.34 (p-Trip); 147.69 (o-Trip); 148.50 (o-C6H3);
148.55 (o-C5H5N); 175.77 (i-C6H3). UV–Vis (hexane):
umax (nm) 391; 750. IR (Nujol mull, cm−1) w: 1760(vw),
1640(vw), 1600(s), 1560(m), 1550(m) 1360(s), 1320(m),
1260(w), 1240(w), 1215(s), 1185(vw), 1170(m), 1150(m),
1100(s), 1070(s), 1035(s), 1010(s), 955(w), 940(m),
920(w), 880(s), 850(vw), 835(vw), 820(vw), 800(s),
775(m), 745(m), 740(m), 720(w), 690(s), 645(m), 625(s),
580(vw), 530(vw), 410(w), 270(s), 240(m).
(Et2O)LiC6H3–2,6-Trip2 (2.81 g, 5.0 mmol) in Et2O
(30 ml) was added dropwise to a stirred suspension of
SnCl2 (0.95 g, 5.0 mmol) in Et2O (10 ml) with cooling
in an ice bath. The orange solution was warmed to
room temperature, and stirred for a further 15 h. The
solvent was removed under reduced pressure, and the
orange residue was extracted with hexane (70 ml) and
filtered through Celite. Reduction in the volume to
incipient crystallization under reduced pressure, and
storage in a ca. −20°C freezer afforded the products 1
and 2 as orange and yellow crystals, respectively. Yield
1.91 g, 60.6%. M.p.: 220–223°C. 119Sn{1H} NMR
(C6D6): l 793.4. 1H NMR (C6D6): l 1.08 (d, 12H,
p-CH(CH3)2) 3JHH=6.6 Hz, 1.21 (d, 12H, o-

B.E. Eichler et al. / Polyhedron 20 (2001) 551–556
553
2.4. Sn(I)C6H3–2,6-Dipp2 (4)
90 K using a Bruker SMART 1000 system (Mo Ka
,
radiation, u=0.71073 A and a CCD area detector).
LiC6H3–2,6-Dipp2 (1.38 g, 3.40 mmol), generated in
situ from 2,6–Dipp2H3C6I and n-BuLi, in Et2O (30 ml)
was added dropwise to a stirred suspension of SnCl2
(0.65 g, 3.43 mmol) in Et2O (10 ml) with cooling in an
ice bath. The solution was stirred for ca. 15 h. The
solvent was removed under reduced pressure, and the
residue was extracted with hexane (70 ml). Filtration
through Celite, and reduction in the volume to incipient
crystallization, and storage in a −20°C freezer af-
forded the product 4 as orange crystals. Yield 1.35 g,
The Bruker SHELXTL 5.11 program package was used
for the structure solutions and refinement [13]. An
absorption correction was applied using the program
SADABS [14]. Data for 3 were obtained on Siemens R3
diffractometer at 140 K. An absorption correction was
applied using program XABS2 [15]. All structures were
solved by direct methods, and refined by full-matrix
least square refinement. All non-hydrogen atoms were
refined anisotropically. Anomalous electron densities
were observed in the neighborhood of tin in both 1 and
2, which were attributed to uncorrected absorption
effects. Some details of the data collection and refine-
ment are given in Tables 1 and 2.
1
72.2% mp: 185°C. 119Sn {1H} NMR (C6D6): l 1042. H
3
NMR (C6D6): l 1.02 (d, 12H, o-CH(CH3)2), JHH
=
6.8, 1.33 (d, 12H, o-CH(CH3)2), 3JHH=6.8 Hz, 3.09
(sept, 4H, o-CH(CH3)2) 3JHH=6.8 Hz, 7.12–7.30(mult,
9H, aromatic region), 13C{1H} NMR (C6H6): l 22.97
(o-CH(CH3)2), 26.41 (o-CH(CH3)2), 30.96 (o-
CH(CH3)2), 124.04 (m-Trip), 129.59 (p-Trip), 130.56
(m-C6H3), 136.44 (p-C6H3), 144.76 (o-C6H3), 146.83
(i-Trip), 147.49 (o-Trip), 181.17 (i-C6H3). UV–Vis
3. Results and discussion
3.1. Synthesis and spectroscopy
(hexane) umax (nm)=391, 420. IR (Nujol mull, cm−1
)
The compounds 1 and 2 were obtained in moderate
to good yields by the reaction of one equiv. of the
lithium reagent (Et2O)LiC6H3–2,6-Trip2 [10] and SnCl2
in diethyl ether. In several preparations it was found
that 1 and 2 were always obtained but the formation of
2 was favored by slower cooling rates and lower tem-
peratures. In hexane or benzene solutions an intense
orange color was observed, which corresponded to the
presence of the monomer 1. However, the orange color
was bleached to a pale yellow in donor solvents such as
THF (see below). The presence of monomeric 1 in
solution was confirmed by 119Sn NMR spectroscopy in
w: 1590(vw), 1570(vw), 1550(vw), 1360(vw), 1320(vw),
1310(w), 1260(w), 1170(vw), 1090(m), 1060(w),
1010(vw), 970(vw), 955(vw), 930(vw), 815(w), 800(s),
790(m), 750(s), 740(s), 720(w), 685(vw), 670(vw),
580(w), 450(vw), 300(w), 240(m).
2.5. X-ray crystallographic studies
Crystals of 1, 2 and 4 were coated with hydrocarbon
oil, mounted on a glass fiber and quickly placed in a N2
cold stream [12]. Data for 1, 2 and 4 were collected at
Table 1
Crystal and experimental data for compounds 1–4
1
2·hexane
3·0.5 methylcyclopenane 0.25 hexane
44.5H54ClNSn
4
Formula
C36H49ClSn
635.89
C78H112Cl2Sn2
1357.96
C
C30H35Cl0.35 0.65
595.45
I
Sn
FW
777.61
Color, habit
Crystal system
Space group
orange, prism
orthorhombic
Pnma
8.0503(3)
25.2002(10)
16.4070(6)
yellow, block
triclinic
pale yellow, block
monoclinic
P21/c
17.315(9)
14.508(6)
17.292(4)
orange, block
monoclinic
P21/n
13.3362(6)
14.1592(7)
14.4803(7)
(
P1
,
a (A)
9.6955(12)
13.2479(16)
13.9837(17)
93.306(2)
93.801(2)
94.092(2)
1784.1(4)
1
,
b (A)
,
c (A)
h (°)
i (°)
97.83(3)
97.422(1)
k (°)
3
,
V (A )
Z
3328.5(2)
4
1.269
1.48–31.51
0.869
4303(3)
4
1.200
1.19–26.00
0.684
2711.4(2)
4
1.459
1.95–31.44
1.576
Dcalc (mg m−3
q Range (°)
)
1.264
2.06–31.48
0.815
v (mm−1
)
Observed data, I\2|(I)
4530
8218
6525
7185
R1
wR2
0.0368
0.1001
0.0417
0.0907
0.0554
0.1621
0.0280
0.0913

554
B.E. Eichler et al. / Polyhedron 20 (2001) 551–556
Table 2
,
Selected bond lengths (A) and bond angles (°) for compounds 1–4
Compound 1
Compound 2
Compound 3
Compound 4
Bond lengths
Sn(1)–C(1)
Sn(1)–Cl(1)
C(1)–C(2)
2.180(2)
2.4088(8)
1.4013(17)
Sn(1)–C(1)
Sn(1)–Cl(1)
Sn(1)–Cl(1A)
C(1)–C(2)
2.214(2)
2.5768(6)
2.5978(7)
1.408(3)
Sn(1)–C(1)
Sn(1)–Cl(1)
N(1)–C(41)
Sn(1)–N(1)
N(1)–C(37)
2.229(4)
2.4478(19)
1.337(6)
2.369(4)
1.331(6)
Sn(1)–C(1)
Sn(1)–Cl(1)
Sn(1)–Cl(1A)
Sn(1)–I(1A)
Sn(1)–I(1A)
2.2303(18)
2.6061(13)
2.8430(12)
2.7700(5)
3.1227(5)
Bond angles
C(1)–Sn(1)–Cl(1)
C(2)–C(1)–Sn(1)
C(2)–C(1)–C(2A) 120.03(18)
99.67(6)
119.67(9)
C(1)–Sn(1)–Cl(1)
C(1)–Sn(1)–Cl(1A)
C(2)–C(1)–C(6)
Cl(1)–Sn(1)–Cl(1A)
Sn(1)–Cl(1)–Sn(1A)
92.61(6)
98.21(6)
118.9(2)
81.21(2)
98.79(2)
C(1)–Sn(1)–N(1)
N(1)–Sn(1)–Cl(1)
C(1)–Sn(1)–Cl(1)
C(37)–N(1)–Sn(1) 127.9(3)
C(41)–N(1)–Sn(1) 112.6(4)
104.02(14)
89.21(10)
93.14(11)
C(1)–Sn(1)–Cl(1)
C(1)–Sn(1)–I(1)
C(1)–Sn(1)–I(1)
Cl(1)–Sn(1)–Cl(1A)
I(1)–Sn(1)–I(1A)
Sn(1)–Cl(1)–Sn(1A)
Sn(1)–I(1)–Sn(1A)
92.42(6)
90.92(5)
90.92(5)
81.64(4)
91.309(12)
98.36(4)
88.69(12)
Sn(1)–C(1)–C(2)
Sn(1)–C(1)–C(6)
130.7(3)
111.3(3)
C6D6 solution which displayed a single resonance at
l=793.4. It is notable that this value is close to the
l=777 measured for the dimer {Sn(Cl)C(SiMe2Ph)3}2
[8] in C6D6 which supports the suggestion [8] that this
compound is also dissociated in solution. Both values
are upfield of the 119Sn NMR shifts measured for
Sn(I)C6H3–2,6-Trip2 (l=1140), or 4 Sn(I)C6H3–2,6-
Dipp2 (l=1042). This is opposite to what is expected
on the basis of inductive effects since the electronegativ-
ity of chlorine is significantly greater than that of
iodine. This apparent anomaly can be explained on the
basis that the paramagnetic shielding (a reflection of the
mixing of the ground and excited states) is decreased by
the more electronegative substituent leading (since
paramagnetic effects augment the applied field) to an
upfield shift [16].
Sn(I)C6H3–2,6-Dipp2 rather than the expected product
Sn(Cl)C6H3–2,6-Dipp2. The presence of iodine arises
from the synthetic method in which the lithium reagent
was prepared in situ by the reaction of LiBu with
IC6H3–2,6-Dipp2.
The addition of pyridine to solutions of 1 afforded
yellow crystals of the pyridine complex 3 in good yield.
The H NMR spectrum confirmed the presence of a 1:1
Fig. 1. Thermal ellipsoid (30%) drawing of 1 (H atoms are not
shown). Selected bond lengths and angles are given in Table 2.
1
ratio of pyridine and the terphenyl ligand. The 119Sn
NMR spectrum displayed a single peak at l=264. The
\500 ppm upfield shift in comparison to 1 is indicative
of a higher coordination and increased shielding of the
tin center. A ca. 300 ppm upfield shift was observed for
solutions of 1 in THF (l=456) where it has a pale
yellow color. Both the color and the upfield shift are
consistent with the formation of a THF complex of 1 in
this solvent. Attempts to isolate and characterize this
complex have been unsuccessful so far. The upfield shift
of 3 is also consistent with the l=350.6 observed for
the chelated species Sn(Cl)C(SiMe3)2(2-NC5H4) [17] or
the l=155.6 observed for the five-coordinate chelated
complex Sn(Cl){C6H3–2,6-(CH2NMe2)2} [18].
The reaction of LiC6H3–2,6-Dipp2 [11] with SnCl2
Fig. 2. Thermal ellipsoid (30%) drawing of 2 (H atoms are not
shown). Selected bond lengths and angles are given in Table 2.
produced
4 which contains a major portion of

B.E. Eichler et al. / Polyhedron 20 (2001) 551–556
555
the lower coordination of tin in comparison to the four
and five coordination of the tins in these complexes.
This view is supported by the Sn–Cl distance of
,
2.440(5) A observed in Sn(Cl)C(SiMe3)2(2-NC6H4) [17]
which has three coordinate tin and a slightly longer
metal halogen bond.
The structure of 2, a dimer of 1, features chlorides
bridging between the two tin atoms. The enthalpy of
association cannot be very large, however, since 2 dis-
sociates to 1 in hydrocarbon solvents. The molecule
possesses a center of symmetry in the middle of the
Sn2Cl2 core which has a planar geometry. There are
internal angles of 81.21(2)° at tin and 98.79(2)° at
Fig. 3. Thermal ellipsoid (30%) drawing of 3 (H atoms are not
shown). Selected bond lengths and angles are given in Table 2.
,
chloride. The Sn–C distance, 2.214(2) A, is slightly
longer than that in 1 which is probably due to the
increase in the metal coordination number from two to
three. The Sn–Cl distances are almost equal, and have
,
an average value of 2.587(11) A, which is comparable
to the shorter of the two bridging Sn–Cl distances
,
(2.596(3) and 2.779(3) A) in {Sn(Cl)C(SiMe2Ph)3}2 [8]
and {Sn(Cl)C6H3–2,6-Mes2}2 [5] (2.600(2) and 2.685(2)
,
A). The structural data for these three compounds are
consistent with the fact that they are dissociated in
solution as suggested previously by 119Sn NMR data
[8].
The addition of pyridine to 1 affords the monomeric
1:1 adduct 3 which has a three coordinate Sn(II) center.
The tin has an extremely pyramidal coordination with
S°Sn=286.37°. The coordination of the pyridine is
almost perpendicular to the Cl(1)–C(1)–Sn(1) plane,
although the plane of the pyridine ring deviates from
the Sn(1)–N(1) line by 12° towards the less crowded
side of the molecule. The Sn–C and Sn–Cl bond
Fig. 4. Thermal ellipsoid (30%) drawing of 4 (H atoms are not
shown). Selected bond lengths and angles are given in Table 2.
3.2. Structures
,
lengths, 2.229(4) and 2.4478(19) A are both about 0.04
,
A longer than those observed in 1 as a result of the
The structures of 1–4 are illustrated by the thermal
ellipsoid plots in Figs. 1–4. It can be clearly seen that 1
is a monomer with V-shaped geometry at tin. The
monomeric structure is a consequence of the very large
size of the terphenyl ligand [1]. It is a very rare example
of an unassociated, two-coordinate organotin(II)halide
structure in the solid state, and it is only preceded by
the monomeric iodide species Sn(I)C6H3–2,6-Trip2 [6].
All other examples of such compounds are associated
through halide bridging [5,8]. The geometry at tin is
characterized by Sn(1)–C(1) and Sn(1)–Cl(1) distances
increase in the tin coordination number. The Sn–N
,
distance, 2.364(4) A, is slightly shorter than the calcu-
lated distance for H2SnNH3 [21], or the average values
,
(ca. 2.39 A) observed [20] for the complexes SnCl2(2,2%-
bipyridine) and SnCl2(1,10-phenanthroline) which have
higher metal coordination numbers. However, much
shorter Sn–N distances were observed in the complexes
,
Sn(Cl){C(SiMe3)2(2-NC5H4)} (Sn–N=2.37(2) A) [17]
,
and (t-Bu)2(py)SnCr(CO)5 (Sn–N=2.29(1)
A [22]
which have three and four coordinate tins, respectively.
Perhaps, the chelating character of the former complex,
and the less crowded nature of the latter species, ac-
count for the large differences in the Sn–N bond
lengths.
,
of 2.180(2) and 2.4088(8) A and an interligand angle of
99.67(6)°. The Sn–C distance and C(1)–Sn(1)–Cl(1)
,
angle are very similar to the 2.213(13) A and 102.6(3)°
observed for Sn(I)C6H3–2,6-Trip2 [6]. The Sn–Cl bond
is slightly longer than the sum of the radii [19] of Sn
The structure of 4 is dimeric, and is similar to 2.
However, the crystalline sample selected for measure-
ment contains a mixture of chloride and iodide at the
halide positions. The optimum refinement was obtained
at an Cl:I ratio of 0.35:0.65. Like 2, the structure is
characterized by the presence of an inversion center.
,
,
(1.40 A) and chlorine (0.99 A). However, it is consider-
,
ably shorter than 2.565(2) and 2.539(1) A observed [20]
for the terminal Sn–Cl distances in the SnCl2 com-
plexes SnCl2(2,2%-dipyridine) and SnCl2(1,10-phenan-
throline). The shorter values in 1 can be attributed to
,
The Sn–C bond length 2.2303(18) A is similar to that

556
B.E. Eichler et al. / Polyhedron 20 (2001) 551–556
elements see: G.W. Rabe, C.S. Steissel, L.M. Liable-Sands, T.E.
Concolino, A.L. Rheingold. Inorg. Chem. 38 (1999) 3445. (c) G.
Heckmann, M. Niemeyer. J. Am. Chem. Soc. 122 (2000) 4227.
[2] (a) R.S. Simons, P.P. Power J. Am. Chem. Soc. 118 (1996)
11966. (b) L. Pu, B. Twamley, S.T. Haubrich, M.M. Olmstead,
B.V. Mork, R.S. Simons, P.P. Power J. Am. Chem. Soc. 122
(2000) 650.
[3] L. Pu, B.T. Twamley, P.P. Power, J. Am. Chem. Soc. 122 (2000)
3524.
[4] L. Pu, M.O. Senge, M.M. Olmstead, P.P. Power, J. Am. Chem.
Soc. 120 (1998) 12682.
in 2. The structure features two Sn–Cl (2.6061(13) and
,
2.8430(12) A) and two Sn–I (2.7700(5) and 3.1227(5)
,
A) distances. The former pair are very similar to the
,
2.596(3) and 2.779(3)
(SiMe2Ph)3}2 [17]. The iodine distances are 0.17–0.28 A
longer, although this is less than the almost 0.35 A
A reported for {Sn(Cl)C-
,
,
difference between the Sn–Cl bond in 1 and the corre-
sponding Sn–I bond in Sn(I)C6H3–2,6-Trip2. The latter
,
features on Sn–I bond length of 2.766(2)A — very
close to the shorter Sn–I bond length observed in 4.
[5] R.S. Simons, L. Pu, M.M. Olmstead, P.P. Power, Organometal-
lics 16 (1997) 1920.
[6] L. Pu, M.M. Olmstead, P.P. Power, B. Schiemenz, Organometal-
lics 17 (1998) 5602.
[7] L. Pu, B. Twamley, P.P. Power, Organometallics 19 (2000) 2874.
[8] C. Eaborn, P.B. Hitchcock, J.D. Smith, S.E. So¨zerli,
Organometallics 16 (1997) 5653.
[9] M.M. Olmstead, R.S. Simons, P.P. Power, J. Am. Chem. Soc.
119 (1997) 11705.
[10] B. Schiemenz, P.P. Power, Organometallics 15 (1996) 964.
[11] B. Schiemenz, P.P. Power, Angew. Chem. Int. Ed. Engl. 35
(1996) 2150.
[12] H. Hope, Prog. Inorg. Chem. 41 (1995) 1.
[13] SHELXTL version 5.1: Bruker AXS, Madison, WI, 1998.
[14] SADABS an empirical absorption correction program part of the
SAINT PLUS NT version 5.0 package Bruker AXS, Madison, WI,
1998.
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 149413–149416 for com-
pounds 1–4. Copies of this information may be ob-
tained from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44-1233-336033;
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
[15] S.R. Parkin, B. Moezzi, H. Hope, J. Appl. Crystallogr. 3 (1997)
1418.
Acknowledgements
[16] B. Wrackmeyer, Annu. Rep. NMR Spectr. 38 (1999) 203.
[17] L.M. Engelhardt, B.S. Jolly, M.F. Lappert, C.L. Raston, A.H.
White. J. Chem. Soc., Chem. Commun. (1988) 336.
[18] J.T.B.H. Jastrzebski, P.A. van der Schaaf, J. Boersma, G. van
Koten, M.C. Zoutberg, D. Heijderijk, Organometallics 8 (1989)
1373.
We are grateful to the National Science Foundation
and the Petroleum Research Fund administered by the
American Chemical Society for financial support and
Cornel Stanciu and Dr Marilyn Olmstead for experi-
mental assistance.
[19] A.F. Wells, Structural Inorganic Chemistry, 5th edn., Clarendon,
Oxford, 1984, pp. 388 and 1279.
[20] S.J. Archer, K.R. Koch, S. Schmidt, Inorg. Chim. Acta 126
(1987) 209.
References
[21] W.W. Schoeller, R. Schneider, Chem. Ber./Receuil. 130 (1997)
1013.
[22] M.D. Brice, F.A. Cotton, J. Am. Chem. Soc. 95 (1973) 4529.
[1] (a) B. Twamley, S.T. Haubrich, P.P. Power Adv. Organomet.
Chem. 41 (1999) 1. (b) For recent extensions to the lanthanide
.