Novel coordination isomerization in organotin(IV) compounds. Synthesis, molecular structures, and NMR studies of LSnPhX2 (X = Ph, Cl, Br, I, SPh), LCH2SnPhX2 (X = Ph, Cl, Br, I), and LSiPh3, where LH is (2-MeO-3-tBu-5-Me-C6H2)2CH 2

Article abstract of DOI:10.1021/om960956b

The series of complexes LSnPhX₂ (1, X = Ph; 3, X = Cl; 4, X= Br; 5, X - I; 6, X = SPh), LSiPh₃ (2), LSnCl₃ (7), LCH₂SnPhX₂ (9, X = Ph; 10, X = Cl; 11, X = Br; 12, X = I) and LCH₂SnCl₃ (13), where LH is bis(2-methoxy-3-tert-butyl-5-methylphenyl)methane (2-MeO-3^tBu-5-Me-C₆H₂)₂CH ₂), has been synthesised, and compounds 1-6 have been characterized in the solid state by X-ray crystallography. Distorted tetrahedral geometries are found in the structures of 1 and 2. By contrast, distorted trigonal bipyramidal geometries are found in the structures of 3-6, owing to the presence of significant intramolecular Sn?O interactions that lie in the range from 2.559(4) ? for 3 to 2.989(4) ? for 6; the magnitudes of the Sn?O interactions have been correlated with the Lewis acidity of the tin atoms in the PhSnX₂ entities. NMR spectroscopy indicates a similar correlation in solution. Compounds 1, 2, 6, and 9 are essentially four coordinate in solution between 30 and -100 °C. In compound 4, intramolecular coordination of one of the methoxy groups results in the novel situation where both four- and five-coordinate tin species exist simultaneously at low temperature. At higher temperature, an average of these two coordination states is observed. The remaining compounds also participate in intramolecular exchange equilibria, with the position of the equilibrium being affected by both the Lewis acidity at tin and by the ring size; the six-membered rings in 10-13 are more labile than the five-membered rings in 3-5 and 7. Adduct formation between tributylphosphine oxide, Bu₃PO, and compounds 3-5 is described.

Full text of DOI:10.1021/om960956b

3696
Organometallics 1997, 16, 3696-3706
Novel Coor d in a tion Isom er iza tion in Or ga n otin (IV)
Com p ou n d s. Syn th esis, Molecu la r Str u ctu r es, a n d NMR
Stu d ies of LSn P h X2 (X ) P h , Cl, Br , I, SP h ), LCH2Sn P h X2
(X ) P h , Cl, Br , I), a n d LSiP h 3, Wh er e LH Is
(2-MeO-3-tBu -5-Me-C6H2)2CH2
Dainis Dakternieks,* Klaus J urkschat,*,† and Ramon Tozer
School of Biological and Chemical Sciences, Deakin University, Geelong 3217, Australia
J ames Hook
NMR Facility, University of New South Wales, Sydney 2052, Australia
Edward R. T. Tiekink
Department of Chemistry, University of Adelaide, South Australia 5005, Australia
Received November 12, 1996X
The series of complexes LSnPhX2 (1, X ) Ph; 3, X ) Cl; 4, X) Br; 5, X ) I; 6, X ) SPh),
LSiPh3 (2), LSnCl3 (7), LCH2SnPhX2 (9, X ) Ph; 10, X ) Cl; 11, X ) Br; 12, X ) I) and
LCH2SnCl3 (13), where LH is bis(2-methoxy-3-tert-butyl-5-methylphenyl)methane (2-MeO-
3tBu-5-Me-C6H2)2CH2), has been synthesised, and compounds 1-6 have been characterized
in the solid state by X-ray crystallography. Distorted tetrahedral geometries are found in
the structures of 1 and 2. By contrast, distorted trigonal bipyramidal geometries are found
in the structures of 3-6, owing to the presence of significant intramolecular Sn‚‚‚O
interactions that lie in the range from 2.559(4) Å for 3 to 2.989(4) Å for 6; the magnitudes
of the Sn‚‚‚O interactions have been correlated with the Lewis acidity of the tin atoms in
the PhSnX2 entities. NMR spectroscopy indicates a similar correlation in solution.
Compounds 1, 2, 6, and 9 are essentially four coordinate in solution between 30 and -100
°C. In compound 4, intramolecular coordination of one of the methoxy groups results in the
novel situation where both four- and five-coordinate tin species exist simultaneously at low
temperature. At higher temperature, an average of these two coordination states is observed.
The remaining compounds also participate in intramolecular exchange equilibria, with the
position of the equilibrium being affected by both the Lewis acidity at tin and by the ring
size; the six-membered rings in 10-13 are more labile than the five-membered rings in
3-5 and 7. Adduct formation between tributylphosphine oxide, Bu3PO, and compounds
3-5 is described.
In tr od u ction
formation process. Given that tin-oxygen oligomers of
predetermined size may have use in industrial applica-
tions,7 the rational synthesis of such species remains
an important synthetic target.
Hydrolysis reactions of organotin(IV) halides have
been established as viable sources of oligomeric tin
clusters.1 Factors that determine the pathways of such
reactions are not yet fully understood, and consequently,
reaction products have been somewhat unpredictable.
In an attempt to develop such designer molecular
technology, we are interested in the effects of intramo-
lecular donors on the hydrolysis pathways of mono- and
diorganotin(IV) halides. Intramolecular donors may
allow specific control over the geometry of tin sites from
which additional linkages can form during hydrolysis.
Accordingly, the study of intramolecular donor atom f
Sn interactions has attracted some recent attention.
Notably, the work of Willem et al.8 has explored the
nature of intramolecular O f Sn interactions versus
i
For example, the partial hydrolysis of PrSnCl3 leads
to a variety of products including PrSn(OH)Cl2‚H2O,2
i
(iPrSn)9O8(OH)6Cl5‚DMSO,3 and [(iPrSn)12O14(OH)6]2+ 4
.
5
6
Hydrolysis of nBuSnCl3 or of nBuSn(OiPr)3 leads to
[(BuSn)12O14(OH)6]2+. Research to date has lacked a
synthetic strategy aimed at controlling the oligomer
† Present address: Fachbereich Chemie der Universita¨t, Lehrstuhl
fu¨r Anorganische Chemie II, D-44221 Dortmund, Germany.
X Abstract published in Advance ACS Abstracts, J uly 1, 1997.
(1) Chemistry of Tin; Harrison, P. G., Ed.; Blackie: London, 1989;
Chapter 2.
(2) Puff, H.; Reuter, H. J . Organomet. Chem. 1989, 364, 57.
(3) Puff, H.; Reuter, H. J . Organomet. Chem. 1989, 368, 173.
(4) Puff, H.; Reuter, H. J . Organomet. Chem. 1989, 373, 173.
(5) Dakternieks, D.; Zhu, H.; Colton R.; Tiekink, E. R. T. J .
Organomet. Chem. 1994, 476, 33.
(7) Pinnavaia, T. J . Science 1983, 220, 4595.
(8) (a) Willem, R.; Delmotte, A.; De Borger, I.; Biesemans, M.; Gielen,
M.; Kayser, F.; Tiekink, E. R. T. J . Organomet. Chem. 1994, 480, 255.
(b) Kayser, F.; Biesemans. M.; Delmotte, A.; Verbruggen, I.; De Borger,
I.; Gielen, M.; Willem, R.; Tiekink, E. R. T. Organometallics 1994, 13,
4026. (c) Fu, F.; Li, H.; Zhu, D.; Fang, Q.; Pan, H.; Tiekink, E. R. T.;
Kayser, F.; Biesemans, M.; Verbruggen, I.; Willem, R.; Gielen, M. J .
Organomet. Chem. 1995, 490, 163. (d) Biesemans, M.; Willem, R.;
Damoun, S.; Geerlings, P.; Lahcini, M.; J aumier, P.; J ousseaume, B.
Organometallics 1996, 15, 2237.
(6) Ribot, F. B. F.; Toledano, P.; Maquet, J .; Sanchez, C. Inorg. Chem.
1995, 34, 6371.
S0276-7333(96)00956-9 CCC: $14.00 © 1997 American Chemical Society

Isomerization in Organotin(IV) Compounds
Organometallics, Vol. 16, No. 16, 1997 3697
polarization (CP) experiments, except for those of the dibro-
mide, 4, and the diiodide, 5, which were also measured at 330
K. The following CP conditions were used: Solid state 119Sn
NMR pulse width, 4.0 ms (90° pulse); contact time, 1.2 ms;
recycle time, 10 s. Chemical shifts are reported with respect
to tetracyclohexyltin (δSn -97.4 ppm), which was used to set
up the CP conditions and as an external chemical shift
standard. The isotropic peak, δiso, in each spectrum was
identified by comparing spectra acquired at various speeds.
Acquisition of ca. 400-15000 scans was sufficient to obtain
spectra with a satisfactory signal to noise ratio. Solid state
13C NMR: pulse width, 4.0 ms (90° pulse 1H pulse); contact
time, 1 ms; recycle time 5 s. Chemical shifts are reported with
respect to adamantane (δC 37.8 ppm), which was used to set
up the CP conditions. Spectra were acquired at various MAS
speeds, usually 4-6 kHz, to distinguish signals from spinning
side bands arising from the aromatic carbon signals. From
600-3000 scans were sufficient to obtain spectra with a
satisfactory signal to noise ratio.
Lewis acidity of the organotin center, exploiting X-ray
crystallographic as well as solid and solution state NMR
methods. In this context, we now report on the syn-
thesis and characterisation of the polyfunctional ligand
systems LH, bis(2-methoxy-3-tert-butyl-5-methylphen-
yl)methane [(2-MeO-3-tBu-5-Me-C6H2)2CH2], and LCH2-
Br, as well as the series of compounds of type A and B.
Cr ysta llogr a p h y. Intensity data for the colorless crystals
were measured at room temperature (20 °C) on a Rigaku
AFC6R diffractometer fitted with graphite-monochromatized
Mo KR radiation, λ ) 0.710 73 Å. The ω:2θ scan technique (ω
technique for 2 and 3) was employed to measure data up to a
maximum Bragg angle of 25.0° (27.5° for 1 and 6). A 20%
decrease in the net intensity values of three standard reflec-
tions measured after every 400 data acquisitions was noted
for 4, and the data set was corrected for this variation
assuming a linear decrease. The data sets were corrected for
Lorentz and polarization effects,9 and an empirical absorption
correction was applied in each case.10 Relevant crystal data
are given in Table 1.
These series were chosen because of their comparative
ease of synthesis and because they contain two methoxy
moieties capable of intramolecular coordination. The
two ligands A and B allow study of the effect of
moderation of the Lewis acidity of the tin center on the
number and magnitude of the intramolecular tin-
oxygen interactions. Furthermore, the series also per-
mits comparison of the relative stability of five- and six-
membered ring systems containing tin. Finally, this
ligand design may eventually lead to octahedral tin
compounds which have a facial arrangement of halides.
Such an arrangement would give interesting polymeric
hydrolysis products. X-ray crystal structure determina-
tions of 1-6 are presented, as is a detailed NMR
description of these compounds in solution. The hy-
drolysis reactions of these compounds will be the subject
of a future paper.
The structures were solved by direct methods employing
SHELXS8611 for 1, 2, 4, and 5 and SIR12 for 3 and 6 and
refined by a full-matrix least-squares procedure based on F.9
Non-H atoms were refined with anisotropic displacement
parameters, and H atoms were included in the models in their
calculated positions (C-H 0.97 Å) with the following excep-
tions. In the refinements of 3 and 4, disorder was noted for
the C(13′) tert-butyl group; the C(13a) and C(13b) atoms in 3
were refined isotropically, and for 4, the methyl groups were
modeled over five sites, two with 50% site occupancy and three
with 67% site occupancy; these atoms were also refined
isotropically. The refinements were continued until conver-
gence employing σ weights; the analysis of variance showed
no special features, indicating that an appropriate weighting
scheme had been applied in each case. The absolute config-
uration of 6 was determined by reversing the signs of the
reflections in each data set and comparing the refinements;
final refinement details are given in Table 1. The numbering
schemes employed are shown in Figures 1-4 (drawn with
ORTEP13 at 20, 25, 35, and 30% probability ellipsoids, respec-
tively). The teXsan9 package, installed on an Iris Indigo
workstation, was employed for all calculations.
Exp er im en ta l Section
Gen er a l Met h od s. Solvents were dried by standard
methods and distilled prior to use. All moisture- and air-
sensitive reactions were performed under an argon atmo-
sphere. Elemental analyses were carried out by the Microan-
alytical Laboratory of the Australian National University,
Canberra. Solution NMR spectra were recorded on a J EOL
GX 270 FT NMR spectrometer at 270.17 (1H), 67.84 (13C),
100.75 (119Sn), and 53.68 (29Si) MHz. Chemical shifts are
relative to external Me4Si (1H, 13C, 29Si) and Me4Sn (119Sn).
Spectra recorded in D2O were referenced against internal
acetone at 2.1 (1H) and 30.3 (13C) ppm. 2-D correlation spectra
were acquired from a heteronuclear correlation experiment
using the standard J EOL pulse sequence VCHSHF. For
119Sn-1H correlation, a delay of 5 ms was used. Correlation
spectra were recorded with 2048 data points in F2 and 128
increments in F1 (64 scans per increment), using a relaxation
delay of 1 s. The sample contained tris(acetylacetonato)-
chromium(III) as a paramagnetic relaxation agent. A shifted
sinebell window function was applied in both dimensions. Solid
state 119Sn and 13C NMR spectra were measured on a Bruker
MSL-300S operating at 111.92 and 75.47 MHz, respectively.
Samples of the LSnX3 (ca. 110 mg) were packed into 4 mm
double air-bearing zirconia rotors and spun at the magic angle
at speeds up to 12 kHz. Spectra were usually obtained at
ambient probe temperature (292 K) from single contact cross-
Syn th esis of Bis(2-m eth oxy-3-ter t-bu tyl-5-m eth ylp h en -
yl)m eth a n e, LH. To a 250 mL round bottom flask was added
25.0 g (73.4 mmol) of bis(2-hydroxy-3-tert-butyl-5-methylphen-
yl)methane (Tokyo Kasei), 22.33 g (0.16 mol) of anhydrous K2-
CO3, 150 mL of dry acetone, and 4 mL of a 10% KOH/methanol
solution. The mixture was magnetically stirred, and Me2SO4
(15.32 mL, 0.16 mol) was added dropwise, after which the
mixture was heated at reflux for 18 h. The resulting solution
(9) teXsan: Structure Analysis Software; Molecular Structure Cor-
poration: The Woodlands, Texas.
(10) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39, 158.
(11) Sheldrick, G. M. SHELXS86, Program for the Automatic
Solution of Crystal Structure; University of Go¨ttingen: Go¨ttingen,
Germany, 1986.
(12) Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo, C.;
Polidori, G.; Spagna, R.; Viterbo, D. J . Appl. Crystallogr. 1989, 22, 389.
(13) J ohnson, C. K. ORTEP. Report ORNL-5138; Oak Ridge Na-
tional Laboratory: Oak Ridge, TN, 1976.

3698 Organometallics, Vol. 16, No. 16, 1997
Ta ble 1. Cr ysta llogr a p h ic Da ta for 1-6
Dakternieks et al.
1
2
3
4
5
6
formula
fw
C
717.6
43H50O2Sn
C43H50O2Si
627.0
C31H40Cl2O2Sn
634.3
C31H40Br2O2Sn
723.2
C31H40I2O2Sn
817.2
C43H50O2S2Sn
781.7
cryst size, mm
cryst syst
space group
a, Å
b, Å
c, Å
0.08 × 0.16 × 0.32 0.32 × 0.32 × 0.44 0.26 × 0.39 × 0.52 0.08 × 0.24 × 0.40 0.02x0.24 × 0.32 0.16 × 0.16 × 0.40
monoclinic
P21/n
monoclinic
P21/c
monoclinic
C2/c
monoclinic
P21/c
monoclinic
P21/c
monoclinic
P2/c
14.758(7)
16.000(5)
16.562(8)
105.00(4)
3777(2)
4
14.793(6)
9.926(5)
25.549(8)
91.38(3)
3750(2)
4
39.53(2)
10.103(6)
14.908(8)
94.83(5)
5931(6)
8
21.305(9)
10.170(2)
15.312(6)
107.26(3)
3168(1)
4
21.268(8)
10.127(8)
15.874(7)
106.51(3)
3278(5)
4
19.757(7)
9.238(7)
22.768(4)
102.86(2)
4051(3)
4
â, deg
V, Å3
Z
F
calcd, g cm-3
1.262
1.110
1.420
1.516
1.656
1.281
F(000)
1496
1352
2608
1448
1592
1624
µ, cm-1
7.09
0.96
10.67
33.60
26.87
7.66
transm factors
data collcd
no. of data collcd
0.893-1.112
+h, +k, (l
9691
0.979-1.013
+h,+k,(l
7334
0.955-1.019
+h,+k,(l
7381
0.787-1.064
(h,+k,+l
6197
0.935-1.070
(h,+k,+l
6375
0.961-1.025
+h,+k,(l
10214
θ
max, deg
no. of unique data
27.5
9345
25.0
7045
25.0
7274
25.0
5961
25.0
6144
27.5
9623
no. of unique data
3458
3341
4391
2343
2607
5133
with g 3.0σ(I)
R
Rw
0.048
0.041
0.053
0.053
0.31
0.049
0.057
1.52
0.050
0.046
1.05
0.045
0.042
0.60
0.051
0.050
1.36
residual density, e Å-3 0.38
F igu r e 1. Molecular structure and crystallographic num-
bering scheme for 1.
F igu r e 3. Molecular structure and crystallographic num-
bering scheme for 3 (X ) Cl), 4 (X ) Br), and 5 (X ) I).
further reactions. Passing a sample through a silica column
(hexane eluent) gave an analytically pure sample, mp 230-
232 °C. Anal. Calcd for C25H36O2 (MW 368.59): C, 81.47; H,
9.84. Found: C, 81.05; H, 9.69. 1H NMR (CDCl3): δ 1.39 (s,
t
18H, Bu), 2.26 (s, 6H, Me), 3.72 (s, 6H, OMe), 4.06 (s, 2H,
CH2), 6.74 (s, 2H, C6H2), 6.99 (s, 2H, C6H2). 13C NMR
(CDCl3): δ 21.0 (CH3), 30.3 (CH2), 31.0 (C(CH3)3), 34.8
(C(CH3)3), 61.2 (OCH3), C6H2 (not assigned), 125.8, 129.7,
132.0, 133.8, 142.0, 156.2.
Syn th esis of P h 3Sn L (1). To a two-necked 250 mL round
bottom flask was added 7.41 g (20.11 mmol) of LH and 80 mL
of dry THF. The solution was cooled to -20 °C, and 8.38 mL
of n-butyllithium (2.4 M) was added dropwise; the solution was
stirred at this temperature for a further 2.5 h. The deep red
mixture was cooled to -55 °C, followed by dropwise addition
of a 20 mL solution of THF containing 7.75 g (20.11 mmol)
Ph3SnCl. J ust prior to the final addition of the Ph3SnCl
solution, the now orange color faded to pale yellow. The
sample was stirred overnight at ambient temperature, the
THF was removed under vacuum, and 50 mL of diethyl ether
was added. This solution was hydrolyzed with 20 mL of water,
and the aqueous phase was washed with two 25 mL portions
of diethyl ether; all extracts were combined and dried over
anhydrous magnesium sulfate. The pale yellow solution was
filtered. Evaporation of the solvent gave a white solid, which
was dissolved in 150 mL of boiling hexane and cooled in a
F igu r e 2. Molecular structure and crystallographic num-
bering scheme for 2.
was filtered, the acetone filtrate was evaporated, and a pale
yellow oil remained, which was dissolved in hexane and then
placed in a freezer overnight. The solution was filtered again,
and the filtrate was evaporated to yield 20.56 g (76%) of bis-
(2-methoxy-3-tert-butyl-5-methylphenyl)methane (LH) as a
pale yellow viscous oil, which was sufficiently pure to use in

Isomerization in Organotin(IV) Compounds
Organometallics, Vol. 16, No. 16, 1997 3699
(MW 634.29): C, 58.71; H, 6.36; Cl, 11.19. Found: C, 58.21;
H, 6.51; Cl, 11.64. 1H NMR (CDCl3): δ 1.39 (s, 18H, tBu), 2.26
1
2
(s, 6H, Me), 3.50 (s, 6H, OMe), 4.64 (s, H, CH, J (119Sn-1H)
) 128 Hz), 6.79 (s, 2H, C6H2), 7.10 (s, 2H, C6H2), 7.3-8.0
(complex pattern, 5H, SnPh). 13C NMR (CDCl3): δ 21.2 (CH3),
1
31.8 (C(CH3)3), 35.4 (C(CH3)3), 44.5 (CH, J (119Sn-13C) ) 673
Hz), 64.7 (OCH3), C6H2 (not assigned), 128.7, 130.1, 130.7,
134.3, 142.4, 154.1; SnPh 142.9 (Ci), 135.4 (Co), 129.9 (Cm),
127.7 (Cp).
Syn th esis of P h Br 2Sn L (4). To a 25 mL toluene solution
of 1 (1.0 g, 1.39 mmol) at -78 °C was added 0.446 g (2.78
mmol) of Br2 in 10 mL of methanol. The solution was stirred
at -78 °C for 25 min and then stirred for further 2 h at
ambient temperature. The clear colorless solution was evapo-
rated under vacuum to give a pale yellow solid, which was
recrystallized from hexane to yield 0.76 g (75%) of 4 as a white
solid, mp 134-136 °C. Anal. Calcd for C31H40O2SnBr2 (MW
723.20): C, 51.49; H, 5.58; Br, 22.10. Found: C, 51.71; H, 5.85;
Br, 22.24. 1H NMR (CDCl3): δ 1.41 (s, 18H, tBu), 2.26 (s, 6H,
Me), 3.59 (s, 6H, OMe), 5.00 (s, 1H, CH, 1J (119Sn-1H) ) 108
Hz), 6.87 (s, 2H, C6H2), 7.09 (s, 2H, C6H2), 7.3-8.0 (complex
pattern, 5H, SnPh). 13C NMR (CDCl3): δ 21.2 (CH3), 31.7
F igu r e 4. Molecular structure and crystallographic num-
bering scheme for 6.
1
(C(CH3)3), 35.4 (C(CH3)3), 44.8 (CH, J (119Sn-13C) ) 577 Hz),
63.6 (OCH3), C6H2 (not assigned), 128.8, 130.3, 132.8, 133.7,
1
refrigerator overnight to give 13.7 g (95%) of 1 as a white
crystaline solid, mp 187-190 °C. Anal. Calcd for C43H50O2-
Sn (MW 717.60): C, 71.98; H, 7.02. Found: C, 71.73; H, 6.97.
142.1, 154.7; SnPh 143.8 (Ci), J (119Sn-13C) ) 660 Hz), 134.8
(Co), 129.9 (Cm), 127.7 (Cp).
Syn th esis of P h I2Sn L (5). To a 100 mL round bottom
flask was added 50 mL of CH2Cl2 and 3.0 g (4.18 mmol) of 1;
2.12 g (8.36 mmol) of I2 was then added in small portions over
1 h. The pale yellow solution was stirred overnight, then
evaporated under vacuum to give a yellow oil. The oil was
then dissolved in hexane and placed in the refrigerator
overnight to yield 2.8 g (82%) of 5 as a pale yellow solid, mp
160-162 °C. Anal. Calcd for C31H40O2SnI2 (MW 817.19): C,
45.57; H, 4.93; I, 31.06. Found: C, 45.62; H, 4.83; I, 31.44. 1H
t
1H NMR (CDCl3): δ 1.28 (s, 18H, Bu), 2.02 (s, 6H, Me), 3.56
(s, 6H, OMe), 5.04 (s, 1H, CH, 2J (119Sn-1H) ) 101 Hz), 6.82
(2H, C6H2), 7.0-7.77 (complex pattern, 17H, C6H2, SnPh3). 13
C
NMR (CDCl3): δ 21.0 (CH3), 31.0 (C(CH3)3), 33.4 (CH,
1J (119Sn-13C) ) 380 Hz), 34.7 (C(CH3)3), 61.2 (OCH3), C6H2
(not assigned), 124.5, 130.1, 132.1, 135.2, 142.0, 155.1; Sn-
Ph3: 141.2 (Ci, 1J (119Sn-13C) ) 481 Hz), 136.7 (Co), 127.6 (Cm),
127.8 (Cp).
t
NMR (CDCl3): δ 1.43 (s, 18H, Bu), 2.28 (s, 6H, Me), 3.56 (s,
Syn th esis of P h 3SiL (2). To a two-necked 250 mL round
bottom flask was added 3.81 g (10.33 mmol) of LH and 60 mL
of dry THF. The solution was cooled to -20 °C, 4.40 mL of
n-butyllithium (2.35 M) was added dropwise, and the solution
was stirred at this temperature for 2.5 h. The deep red
mixture was cooled to -55 °C, followed by dropwise addition
of a THF solution of Ph3SiCl (3.05 g, 10.33 mmol in 20 mL).
The pale yellow solution was stirred overnight at ambient
temperature, the THF was then removed under vacuum, and
50 mL of diethyl ether was added. This solution was hydro-
lyzed with 20 mL of water, and the aqueous phase was washed
with two 25 mL portions of diethyl ether. The combined
diethyl ether extracts were dried over anhydrous magnesium
sulfate. Filtration and evaporation of the solution gave a white
solid. The solid was dissolved in 50 mL of hot hexane, which
upon cooling in a refrigerator overnight gave 4.67 g (72%) of 2
as a white crystalline solid, mp 193-195 °C. Anal. Calcd for
6H, OMe), 5.15 (s, 1H, CH, 1J (119Sn-1H) ) 88 Hz), 6.95 (s, 2H,
C6H2), 7.09 (s, 2H, C6H2), 7.00-7.70 (complex pattern, 5H,
SnPh). 13C NMR (CDCl3): δ 21.4 (CH3), 31.7 (C(CH3)3), 35.2
(C(CH3)3), 42.7 (CH, 1J (119Sn-13C) ) 476 Hz), 62.4 (OCH3),
C6H2 (not assigned), 129.8, 130.5, 133.3, 133.9, 142.5, 155.3;
SnPh 144.4 (Ci, 1J (119Sn-13C) ) 516 Hz), 134.8 (Co), 128.9 (Cm),
127.7 (Cp).
Syn th esis of P h (SP h )2Sn L (6). To 20 mL of dry MeOH
was added 0.0474 g (2.06 mmol) of Na, the solution was stirred
for 20 min, and 0.212 mL (2.06 mmol) of thiophenol was added
dropwise. After a further 20 min of stirring, a solution of 4
(0.747 g, 1.03 mmol in 15 mL of CHCl3) was added dropwise
and the resulting solution stirred overnight. The solvent was
removed under vacuum, and the resulting clear oil was
dissolved in hexane and placed in the refrigerator overnight
to yield 0.653 g (81%) of 6 as a white solid, mp 131-133 °C.
δ(119Sn MAS): 28 ppm. Anal. Calcd for C43H50O2S2Sn (MW
781.73): C, 66.07; H, 6.45. Found: C, 66.63; H, 6.69. 1H NMR
C
43H50O2Si (MW 627.00): C, 82.38; H, 8.04. Found: C, 82.00;
H, 7.89, 1H NMR (CDCl3): δ 1.29 (s, 18H, Bu), 2.10 (s, 6H,
Me), 3.49 (s, 6H, OMe), 5.38 (s, 1H, CH), 6.92 (2H, C6H2), 7.20-
7.77 (complex pattern, 17H, C6H2, SiPh3). 13C NMR (CDCl3):
δ 21.2 (CH3), 26.4 (CH), 31.3 (C(CH3)3), 35.1 (C(CH3)3), 61.9
(OCH3), C6H2 (not assigned), 125.6, 130.7, 131.5, 134.7, 135.0,
155.4 ppm; SiPh3 142.7 (Ci), 137.0 (Co), 127.1 (Cm), 129.0 (Cp).
29Si NMR (CH2Cl2): δ -22.7.
t
t
(CDCl3): δ 1.44 (s, 18H, Bu), 2.17 (s, 6H, Me), 3.53 (s, 6H,
OMe), 5.02 (s, 1H, CH, 2J (119Sn-1H) ) 104 Hz), 6.36 (2H, C6H2),
6.96 (2H, C6H2), 6.98-7.16 (complex pattern, 15H, SnPh, SPh).
13C NMR (CDCl3): δ 21.3 (CH3), 31.5 (C(CH3)3), 40.9 (CH,
1J (119Sn-13C) ) 430 Hz), 35.1 (C(CH3)3), 61.8 (OCH3); phenyl
carbons: δ/J (119Sn-13C) 155.3/45, 142.4/17, 142.0/526, 135.5/
43, 135.3/15, 133.3/43, 132.9/16, 132.5/22, 130.4/38, 128.9/15,
128.2/62, 128.1, 126.2/19, 126.0/8 Hz.
Syn th esis of P h Cl2Sn L (3). To a solution of 1 (4.0 g, 5.57
mmol) in 45 mL of acetone cooled to 0 °C was added, in small
portions, 3.48 g of HgCl2 (11.14 mmol). The solution was
stirred at this temperature for 15 min, after which it was left
to stir overnight at ambient temperature. The turbid liquid
was then evaporated under vacuum, and 20 mL of CH2Cl2 was
added. This solution was placed in the freezer overnight and
then filtered, and the volume was reduced to approximately
15 mL. The solution was placed in the freezer overnight,
filtered again, and evaporated under vacuum to yield a
colorless solid. Recrystallization from hexane afforded 3.1 g
(88%) of 3, mp 149-152 °C. Anal. Calcd for C31H40O2SnCl2
Syn th esis of Cl3Sn L (7). Dry HCl gas was bubbled for 30
min through a solution of 1 (1.0 g, 1.4 mmol) in 100 mL of
CHCl3 at 0 °C. The solution was then stirred at ambient
temperature for 5 days, after which evaporation of the CHCl3
afforded a purple oil. The oil was dissolved in hexane (10 mL)
and left to stand in a refrigerator overnight to yield 0.68 g
(82%) of 7 as a white solid, mp 155-156 °C. Anal. Calcd for
C
25H35O2SnCl3 (MW 592.63): C, 50.50; H, 6.27; Cl, 17.89.
Found: C, 50.24; H, 6.08; Cl, 18.07. 1H NMR (CDCl3): δ 1.43
t
1
(s, 18H, Bu), 2.28 (s, 6H, Me), 3.62 (s, 6H, OMe), 4.82 (s, H,

3700 Organometallics, Vol. 16, No. 16, 1997
Dakternieks et al.
1
CH, J (119Sn-1H) ) 127 Hz), 6.75 (s, 2H, C6H2), 7.20 (s, 2H,
filtered. The clear dichloromethane filtrate was reduced to
approximately 10 mL, and the solution was placed in the
freezer overnight. The solution was again filtered, the dichlo-
romethane filtrate was evaporated in vacuo, and the residue
was recrystallized from hexane to afford 0.52 g (84%) of 10,
C6H2). 13C NMR (CDCl3): δ 21.1 (CH3), 31.6 (C(CH3)3), 35.2
(C(CH3)3), 49.7 (CH, 1J (119Sn-13C) ) 860 Hz), 64.5 (OCH3),
C6H2 (not assigned), 129.1, 129.4, 131.1, 134.2, 142.7, 153.7.
Syn th esis of (2-MeO-3tBu -5-Me-C6H2)2CHCH2Br , (LCH2)-
Br (8). To a chilled solution (-20 °C) of (2-MeO-3tBu-5-
MeC6H2)2CH2 (10.82 g, 29.4 mmol) and 150 mL of dry THF,
n-butyllithium (16.32 mL, 1.8 M) was added dropwise. The
reaction mixture was maintained at -20 °C for 2 h and then
cooled to -55 °C. Formaldehyde gas, generated by heating
dry para-formaldehyde, was passed over the orange solution
until it faded to pale yellow. The reaction mixture was stirred
overnight at ambient temperature. Then the THF was
distilled off. Ether (100 mL) was added, and the solution was
hydrolyzed with 25 mL of 1.0 M HCl under ice cooling. The
organic layer was separated and washed with 20 mL of 1.0 M
HCl, 20 mL of H2O, and 20 mL of 10% K2CO3. The ether
solution was then dried over anhydrous potassium carbonate.
Evaporation of the ether gave a clear oil, which was dissolved
in hexane/ether (50:50) and placed in a refrigerator overnight
to afford 9.12 g (78%) of (2-MeO-3tBu-5-Me-C6H2)2CHCH2OH
as a colorless crystalline solid, mp 70-72 °C. 1H NMR
mp 125-127 °C. Anal. Calcd for
C32H42O2SnCl2 (MW
648.32): C, 59.29; H, 6.53; Cl, 10.94. Found: C, 59.03; H, 6.61;
Cl, 10.40. 1H NMR (CDCl3): δ 1.31 (s, 18H, Bu), 2.21 (s, 6H,
t
Me), 3.68 (s, 6H, OMe), 2.27 (δ, 2H, CH2, J (119Sn-1H) ) 74
2
Hz), 5.20 (t, 1H, CH), 6.92 (s, 2H, C6H2), 6.95 (s, 2H, C6H2),
7.28-7.60 (complex pattern, 5H, SnPh). 13C NMR (CDCl3): δ
21.2 (CH3), 37.1 (CH2, 1J (119Sn-13C) ) 542 Hz), 31.5 (C(CH3)3),
34.2 (CH), 35.2 (C(CH3)3), 62.7 (OMe), C6H2 (not assigned),
127.3, 127.9, 134.2, 138.0, 143.2, 154.8; SnPh 140.4 (Ci), 133.4
(Co), 130.7 (Cm), 128.9 (Cp).
Syn th esis of P h Br 2Sn (CH2L) (11). To a solution of 9 (0.4
g, 0.547 mmol) in 15 mL of toluene at -78 °C, bromine (0.175
g, 1.09 mmol) in 10 mL of methanol was added. The solution
was stirred at this temperature for 25 min and then stirred
for a further 2 h at ambient temperature. The solution was
evaporated in vacuo, and the residue was recrystallized from
hexane to yield 0.31 g (77%) of 11 as a colorless solid, mp 133-
135 °C. Anal. Calcd for C32H42O2SnBr2 (MW 737.23): C,
52.14; H, 5.74, Br 21.68. Found: C, 51.62; H, 5.73; Br, 21.91.
t
(CDCl3): δ 1.39 (s, 18H, Bu), 2.29 (s, 6H, Me), 3.78 (S, 6H,
OMe), 4.02 (δ, 2H, CH2), 5.02 (t, H, CH), 6.98 (s, H), 6.98 (s,
2H, C6H2), 7.02 (s, 2H, C6H2).
1
1
t
1H NMR (CDCl3): δ 1.33 (s, 18H, Bu), 2.14 (s, 6H, Me), 3.69
(s, 6H, OMe), 2.85 (δ, 2H, CH2, 2J (119Sn-1H) ) 65 Hz), 5.24 (t,
1H, CH), 6.89 (s, 2H, C6H2), 6.99 (s, 2H, C6H2), 7.13-7.50
(complex pattern, 5H, SnPh). 13C NMR (CDCl3): δ 21.2 (CH3),
38.4 (CH2, 1J (119Sn-13C) ) 484 Hz), 31.4 (C(CH3)3), 34.8 (CH),
35.2 (C(CH3)3), 62.5 (OMe), C6H2 (not assigned), 127.3, 128.7,
134.1, 137.8, 143.2, 155.2; SnPh 139.7 (Ci), 133.2 (Co), 130.6
(Cm), 127.6 (Cp).
A solution of (2-MeO-3tBu-5-Me-C6H2)2CHCH2OH (2.5 g,
6.72 mmol), PPh3 (1.65 g, 6.72 mmol), and CBr4 (2.08 g, 6.72
mmol) in toluene was prepared by adding each component in
small portions. The solution was heated at reflux overnight
and the resulting liquid was filtered. The toluene filtrate was
evaporated in vacuo and replaced with 25 mL of hexane, then
filtered once again. The resulting hexane filtrate was evapo-
rated in vacuo to leave an orange oil, which was dissolved in
methanol and placed in a refrigerator overnight to afford 2.38
g (83%) of 8 as a colorless crystalline solid, mp 94-96 °C. Anal.
Calcd for C26H37O2Br (MW 461.52): C, 67.66; H, 8.08; Br,
17.31. Found: C, 67.82; H, 7.89; Br, 17.22. 1H NMR
Syn th esis of P h I2Sn (CH2L) (12). To a solution of 9 (0.7
g, 0.957 mmol) in 25 mL of dichloromethane, iodine (0.493 g,
1.92 mmol) was added in portions over 15 min. After the
reaction mixture was stirred overnight, the solution was
evaporated in vacuo and the residue dissolved in hexane and
placed in a refrigerator to precipitate 0.63 g (79%) of 12 as an
orange oil. Anal. Calcd for C32H42O2SnI2 (MW 831.22): C,
46.24; H, 5.09; I, 30.54. Found: C, 46.12; H, 5.18; I, 30.65. 1H
t
(CDCl3): δ 1.41 (s, 18H, Bu), 2.25 (s, 6H, Me), 3.81 (s, 6H,
1
OMe), 3.88 (δ, 2H, CH2), 5.16 (t, H, CH), 6.83 (s, 2H, C6H2),
7.09 (s, 2H, C6H2). 13C NMR (CDCl3): δ 21.4 (CH3), 35.6 (CH2),
31.3 (C(CH3)3), 35.1 (CH), 40.8 (C(CH3)3), 62.2 (OMe), C6H2
(not assigned), 127.2, 127.4, 132.4, 134.5, 142.9, 156.4.
Syn th esis of P h 3Sn (CH2L) (9). To a solution of Ph3SnNa
in liquid ammonia at -78 °C, prepared from Ph3SnCl (3.34 g,
8.67 mmol) and sodium (0.398 g, 8.67 mmol), was added 8 (4.00
g, 8.67 mmol) dissolved in 40 mL of dry THF. After 30 min at
-78 °C, the reaction mixture was left to stir overnight at
ambient temperature. Then most of the THF was distilled off.
Ether (60 mL) was added, and the solution was hydrolyzed
with ice cooling. The organic layer was separated, and the
aqueous layer was extracted three times with 15 mL of ether.
The combined organic layers were dried over magnesium
sulfate. The ether was evaporated, and the clear oil was
dissolved in 50 mL of hexane, which upon cooling in a
refrigerator afforded 4.92 g (78%) of 9 as a colorless crystalline
solid, mp 135-137 °C. Anal. Calcd for C44H52O2Sn (MW
731.63): C, 72.24; H, 7.16. Found: C, 72.04; H, 7.19. 1H NMR
t
NMR (CDCl3): δ 1.49 (s, 18H, Bu), 2.20 (s, 6H, Me), 3.83 (s,
6H, OMe), 3.07 (δ, 2H, CH2, 2J (119Sn-1H) ) 54 Hz), 5.34 (t,
1H, CH), 6.99 (s, 2H, C6H2), 7.08 (s, 2H, C6H2), 7.21-7.64
(complex pattern, 5H, SnPh). 13C NMR (CDCl3): δ 21.3 (CH3),
38.1 (CH2, 1J (119Sn-13C) ) 392 Hz), 31.3 (C(CH3)3), 35.0 (CH),
35.7 (C(CH3)3), 62.3 (OMe), C6H2 (not assigned), 128.3, 134.1,
137.3, 143.0, 155.4; SnPh (not assigned due to overlapping)
127.2, 130.1, 132.8.
Syn th esis of Cl3Sn (CH2L) (13). To a solution of 9 (1.0 g,
1.37 mmol) in 100 mL of chloroform at 0 °C was bubbled dry
HCl gas for 30 min. The flask was removed from the cooling
bath and a stopper fixed securely. The solution was then
stirred at ambient temperature for 5 days, after which
evaporation of the chloroform afforded a clear oil. The oil was
dissolved in hexane and left to stand in a refrigerator overnight
to yield 0.62 g (75%) of 13 as a colorless solid, mp 187-189
°C. Anal. Calcd for C26H37O2SnCl3 (MW 606.66): C, 51.48;
H, 6.15; Cl, 17.53. Found: C, 51.14; H, 5.87, Cl, 17.52. 1H
t
(CDCl3): δ 1.34 (s, 18H, Bu), 2.07 (s, 6H, Me), 3.49 (s, 6H,
OMe), 2.27 (δ, 2H, CH2, 2J (119Sn-1H) ) 52 Hz), 5.13 (t, 1H,
CH), 6.92 (s, 2H, C6H2), 6.95 (s, 2H, C6H2), 7.18-7.51 (complex
pattern, 15H, SnPh). 13C NMR (CDCl3): δ 21.2 (CH3), 22.4
(CH2, 1J (119Sn-13C) ) 377 Hz), 31.4 (C(CH3)3), 34.8 (CH), 35.1
(C(CH3)3), 61.9 (OMe), C6H2 (not assigned), 126.4, 128.5, 132.4,
137.5, 142.6, 155.4; SnPh3 140.1 (Ci), 137.0 (Co), 128.5 (Cm),
128.1 (Cp).
t
NMR (CDCl3): δ 1.43 (s, 18H, Bu), 2.29 (s, 6H, Me), 3.77 (s,
6H, OMe), 2.82 (δ, 2H, CH2, 2J (119Sn-1H) ) 85 Hz), 5.16 (t,
1H, CH), 6.88 (s, 2H, C6H2), 7.15 (s, 2H, C6H2). 13C NMR
(CDCl3): δ 21.4 (CH3), 41.9 (CH2, 1J (119Sn-13C) ) 750 Hz),
31.7 (C(CH3)3), 34.6 (CH), 35.6 (C(CH3)3), 63.6 (OMe), C6H2
(not assigned), 127.6, 129.0, 134.1, 136.2, 143.3, 155.0.
Syn th esis of P h Cl2Sn (CH2L) (10). To a solution of 9 (0.7
g, 0.957 mmol) in 30 mL of acetone at 0 °C, HgCl2 (0.520 g,
1.92 mmol) was added in portions. The solution was stirred
at this temperature for 15 min and then stirred overnight at
ambient temperature. The reaction mixture was evaporated
in vacuo, and 20 mL of dichloromethane was added to the
residue. The solution was placed in the freezer overnight, then
Resu lts a n d Discu ssion
Syn th eses. Methylation of bis(2-hydroxy-3-tert-bu-
tyl-5-methylphenyl)methane, using Me2SO4/K2CO3 in
acetone solution affords bis(2-methoxy-3-tert-butyl-5-
methylphenyl)methane (LH) in good yield (eq 1).

Isomerization in Organotin(IV) Compounds
Organometallics, Vol. 16, No. 16, 1997 3701
2Me2SO4
K2CO3
(i) THF
L-Li + CH2O (ii) H O8 L-CH2OH + LiOH (7)
2
(2-HO-3-tBu-5-Me-C6H2)2CH2 -2KSO Me8
4
(2-MeO-3-tBu-5-Me-C6H2)2CH2 (1)
toluene,
reflux
L-CH2OH + CBr4 + Ph3P
8
L-CH Br
+ CHBr3 + Ph3PO (8)
2
8
was achieved by reaction of 8 with sodium triphenyl-
stannide, Ph3SnNa, in liquid ammonia (eq 9). Func-
L-CH2Br + Ph3SnNa NH , -78 °C8
3
Ph Sn(CH L)
+ NaBr (9)
3
2
9
Compounds 1 and 2 were prepared as white crystal-
line solids in good yield from reaction of LH with BuLi
followed by addition of Ph3SnCl and Ph3SiCl, respec-
tively, eq 2. Deuterium labeling experiments indicated
n
tionalization at tin was achieved in good yield by
reaction of 9 with HgCl2 or either Br2 or I2 (eqs 10 and
11), whereas treatment of 9 with excess HCl afforded
compound 13 (eq 12).
LH + n-BuLi THF/-20 °C8 L-Li Ph ECl8
3
acetone,
0 °C
-nBuH
THF
Ph3Sn(CH2L) + 2HgCl2
8
+ LiCl (2)
L-EPh3
PhCl Sn(CH L)
+ 2PhHgCl (10)
2
2
1, E ) Sn
10
2, E ) Si
MeOH or
CH2Cl2
that metalation of LH is best performed in THF at -20
°C (no attack of the solvent was observed at this
temperature, but at 0 °C rapid decomposition was
observed). Attempts to metalate diphenylmethane un-
der the same reaction conditions were not successful and
indicate that the methoxy groups in LH stabilize the
lithiated species, LiL.
Ph3Sn(CH2L) + 2X2
8
PhX Sn(CH L) + 2PhX
2
2
11, X ) Br
12, X ) I
(11)
HCl/CHCl3
Cl Sn(CH L)
Ph3Sn(CH2L)
8
+ 3PhCl (12)
3
2
13
Reaction of 1 with 2 equiv of HgCl2 cleaves two phenyl
groups to give 3 in high yield (eq 3). Compounds 4 and
Compounds 1-11 and 13 are colorless solids, whereas
12 is an oil. All compounds show good solubility in
common organic solvents, such as CH2Cl2, THF, and
toluene.
Acetone
PhCl SnL
1 + 2HgCl2
8
+ 2PhHgCl (3)
2
0 °C
3
Molecu la r Str u ctu r es of 1-6. The molecular struc-
tures of 1, 2, 3, and 6 are shown in Figures 1-4,
respectively, and selected interatomic parameters of all
structures are collected in Table 2; a common number-
ing scheme was employed for compounds 3-5. The
structures are molecular with no significant intermo-
lecular contacts in their respective crystal lattices. The
structures fall neatly into two categories with the first
featuring four-coordinate tin (or silicon) atom geom-
etries. The tin (silicon) atom in 1 (2) is coordinated by
three phenyl substituents and the tertiary carbon atom
of L with the Sn-C(1) (Si-C(1)) bond being significantly
longer at 2.182(6) Å (1.925(4) Å) than the Sn-C(Ph)
(Si-C(Ph)) bonds which lie in the range 2.102(7)-
2.122(7) Å (1.871(4)-1.884(4) Å). The angles subtended
at the tin (silicon) atom lie in the relatively narrow
range of 107.0(2)-112.9(2)° (107.3(2)-113.3(2)°), indi-
cating that any deviation from the ideal tetrahedral
geometry is small. The coordination environment about
the tin (silicon) atom is consistent with the absence of
a significant intramolecular interaction between the
methoxy oxygen atoms and the central atom. Thus, in
1 the Sn‚‚‚O(1) and Sn‚‚‚O(2) separations are 3.023(4)
and 4.406(5) Å, respectively, and the analogous separa-
tions in 2 are 4.442(3) and 3.857(3) Å, respectively. The
Sn‚‚‚O(1) separation is shorter than the sum of the van
der Waals radii for these atoms of 3.5 Å, and further
5 were prepared in excellent yields by reaction of 1 with
2 equiv of Br2 and I2, respectively (eq 4). The thiophe-
CH2Cl2 or MeOH
PhX SnL
1 + 2X2
8
+ 2PhX
(4)
2
25 or 0 °C
4, X ) Br
5, X ) I
nolate 6 was prepared by reaction of 4 with 2 equiv of
sodium thiolate (eq 5).
2PhSNa, MeOH
Ph(SPh) SnL
PhBr2SnL
8
(5)
2
-2NaBr
6
Attempts to cleave the remaining phenyl group from
compounds 3-5 using an additional equivalent of the
respective reagents were not successful. However,
cleavage of all three phenyl groups was achieved by
stirring 1 in a saturated solution of CHCl3/HCl for 5
days, producing 7 as a white solid (eq 6).
CHCl3
Cl SnL
1 + HCl (excess)
8
+ 3PhCl
(6)
3
0 °C
7
In order to synthesize a ligand which potentially
would give rise to a six-membered chelate L-Li was
reacted with formaldehyde followed by bromination to
give 8 (eqs 7 and 8). The formation of LCH2SnPh3 (9)

3702 Organometallics, Vol. 16, No. 16, 1997
Ta ble 2. Selected In ter a tom ic Bon d Dista n ces (Å) a n d An gles (d eg) for 1-6
Dakternieks et al.
1
2a
3
4
5
6b
X ) C(31)
Y ) C(51)
X ) C(31)
Y ) C(51)
X ) Cl(1)
Y ) Cl(2)
X ) Br(1)
Y ) Br(2)
X ) I(1)
Y ) I(2)
X ) S(1)
Y ) S(2)
Sn-X
2.122(7)
2.102(7)
2.182(6)
2.118(7)
1.873(4)
1.884(4)
1.925(4)
1.871(4)
2.321(2)
2.355(2)
2.164(5)
2.108(6)
2.559(4)
1.391(6)
1.392(6)
2.494(2)
2.526(2)
2.21(1)
2.15(1)
2.630(7)
1.41(1)
1.40(1)
2.702(1)
2.736(1)
2.23(1)
2.15(1)
2.684(7)
1.41(1)
1.39(1)
2.417(2)
2.419(2)
2.187(5)
2.135(6)
2.989(4)
1.395(7)
1.396(6)
Sn-Y
Sn-C(1)
Sn-C(41)
Sn-O(1)
O(1)-C(12)
O(2)-C(22)
1.378(7)
1.382(7)
1.396(4)
1.394(4)
X-Sn-Y
108.8(3)
107.0(2)
107.1(3)
107.3(2)
109.5(2)
108.7(2)
102.39(8)
105.1(2)
104.4(2)
87.5(1)
101.7(2)
99.9(2)
168.35(9)
138.4(2)
69.3(2)
104.13(6)
105.5(3)
105.2(3)
86.7(2)
101.2(3)
101.1(4)
167.3(2)
135.8(4)
69.1(3)
107.30(4)
107.3(3)
105.0(3)
88.4(1)
100.6(3)
100.8(3)
162.9(1)
133.5(4)
67.4(3)
109.22(7)
113.4(2)
101.6(2)
83.80(9)
103.5(1)
108.7(2)
164.56(8)
120.2(2)
62.7(2)
X-Sn-C(1)
X-Sn-C(41)
X-Sn-O(1)
Y-Sn-C(1)
111.6(2)
109.2(3)
108.5(2)
109.3(2)
Y-Sn-C(41)
Y-Sn-O(1)
C(1)-Sn-C(41)
C(1)-Sn-O(1)
C(41)-Sn-O(1)
Sn-C(1)-C(11)
Sn-C(1)-C(21)
C(11)-C(1)-C(21)
C(12)-O(1)-C(12′)
C(22)-O(2)-C(22′)
112.9(2)
113.3(2)
83.3(2)
81.9(4)
81.0(4)
75.5(2)
110.9(4)
109.5(4)
116.6(5)
115.3(5)
115.3(6)
114.0(2)
111.7(2)
112.7(3)
114.4(3)
115.4(3)
108.0(3)
110.1(3)
115.9(5)
113.5(5)
113.8(4)
107.7(7)
107.8(7)
119(1)
113.2(9)
113.3(8)
108.4(6)
107.7(7)
116.6(9)
112.2(8)
114.8(8)
111.5(3)
111.6(4)
114.9(4)
115.0(5)
114.5(5)
C(1)/C(11)/C(12)/O(1)
C(1)/C(21)/C(22)/O(2)
C(12)/C(11)/C(1)/C(21)
C(11)/C(1)/C(21)/C(22)
4.4(9)
5.4(5)
8.7(5)
100.5(4)
-140.0(3)
-4.2(6)
-4(2)
3(1)
7(1)
-165.0(9)
-129(1)
5.0(8)
-2.0(9)
179.6(6)
117.3(7)
6.8(7)
3(2)
-0.8(8)
178.0(5)
106.2(6)
-161.9(4)
-126.1(5)
-160(1)
-126(1)
a
b
For Sn read Si. For C(41) read C(51).
Ta ble 3. 119Sn NMR Da ta for Com p ou n d s 1 a n d
evidence for a weak interaction is found in the magni-
tude of the C(11)-C(12)-O(1) angle of 116.0(6)° (con-
comitantly, the C(13)-C(12)-O(1) angle is 119.8(6)°),
which is approximately 2° smaller than the C-C-O(2)
angles and the comparable angles in 2, and indicates
that the O(1) atom is being pulled toward the tin atom.
Such weak Sn‚‚‚O interactions have been described in
related studies on intramolecular Sn‚‚‚O in tetra-
organotin.8a In contrast to the structure of 1 (and of
2), generally significant intramolecular interactions are
found in the remaining structures where two of the tin-
bound phenyl groups have been substituted for X ) Cl
(3), Br (4), I (5), and SPh (6).
In each of the structures of 3-6 the tin atom is
coordinated by a phenyl substituent, two donor atoms
X, the C(1) atom, as well as the O(1) atom derived from
L. In each case, the Sn‚‚‚O(1) contact is longer than a
normal covalent Sn-O bond; however, the resulting tin
atom geometry, i.e., distorted trigonal bipyramidal,
clearly indicates the presence of a significant Sn‚‚‚O(1)
interaction. The O(1) and X(2) atoms define the axial
angle in this description, and the tin atom lies 0.4186(4),
0.4638(8), 0.4938(8), and 0.5279 (4) Å out of the trigonal
plane in the direction of the X(2) atom, respectively, for
3-6. The distortion from the ideal trigonal bipyramidal
geometry correlates with the magnitude of the Sn‚‚‚O-
(1) interaction, i.e., the weaker the interaction the
greater the distortion toward a tetrahedral geometry
about the tin atom. Thus, the length of the Sn‚‚‚O(1)
distance increases from 2.559(4) Å for 3, 2.630(7) Å for
4, 2.684(7) Å for 5 to a maximum of 2.989(4) Å for 6
and suggests an order for the Lewis acidity for the tin-
containing entities, i.e., PhSnCl2 > PhSnBr2 > PhSnI2
> PhSn(SPh)2. By contrast to the Sn‚‚‚O(1) contacts,
the Sn‚‚‚O(2) interactions are not significant at 4.344(4),
4.347(7), 4.365(7), and 4.621(4) Å for 3-6, respectively.
As a consequence of the diminished strength of the
Sn‚‚‚O(1) interaction in 3-6, there are other systematic
3-6
compd
T, °C
δ(119Sn), ppm
solvent
1
25
-80
+100
+25
-25
-55
-80
+100
+25
-25
-55
-100
+100
+75
+25
-90
+25
-55
-114.6
CH2Cl2
CH2Cl2
toluene
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
toluene
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
toluene
toluene
toluene
toluene
CH2Cl2
CH2Cl2
-114.0
3
-83.4
no signal
-69.5, -122.0
-71.0, -125.1
-132.4
4
-82.7
no signal
-60.2, -148.2
-59.8, -148.7
-63.8, -150.7
-153.9
5
6
-146.0
-129.3
-91.3
12.0
17.5
changes in the tin atom geometry, i.e., there is a general
increase in the X-Sn-Y and X-Sn-C(1) angles and a
general decrease in the C(1)-Sn-C(41), C(1)-Sn-O(1),
and C(41)-Sn-O(1) angles (see Table 2).
NMR Stu d ies. The 119Sn NMR (CH2Cl2) data for 1
indicate the tin atom is four-coordinate at room tem-
1
perature as well as at -80 °C (Table 3). The J (119Sn-
1
13CH) and J (119Sn-13Ci), couplings of 380 and 481 Hz,
respectively, also indicate four-coordinate tin. A com-
parable four coordinate species, Ph3SnCH3, has a δ(119Sn)
1
1
of -98.0 ppm,14 and J (119Sn-13C) and J (119Sn-13Ci)
couplings of 374 and 511 Hz, respectively.15 The
isotropic 119Sn chemical shift of 1 in the solid state, δiso
-101 ppm, indicates there is little difference between
the solution and solid state structures.
(14) Wrackmeyer, B. Ann. Rep. NMR Spectrosc. 1985, 16, 73.
(15) Mitchell, T. N.; Walter, G. J . Organomet. Chem. 1976, 121, 177.

Isomerization in Organotin(IV) Compounds
Organometallics, Vol. 16, No. 16, 1997 3703
1
At room temperature, the H and 13C NMR spectra
results in simultaneous observation of five- and six-
coordination states at low temperature.16 Examples of
temperature dependant coordination equilibria involv-
ing intramolecular coordination have also been reported,
but these all exhibit rapid exchange between two
coordination states at a given temperature. Such
equilibria give rise to a single 119Sn NMR resonance
which is an average of the population of the individual
coordination states.16 Unlike any previous examples,
compound 4 exhibits a unique temperature-dependant
equilibrium between two tin coordination states. At low
temperature, the exchange appears slow on the NMR
time scale and both coordination species are observed
simultaneously. The 119Sn NMR chemical shift values
of -59.8 and -148.7 ppm (-55 °C) for 4 are assigned
to four- and five-coordinate tin atoms, respectively,
while that of -82.7 ppm (100 °C) is assigned to an
average of both coordination states. Unfortunately, a
solid state 119Sn NMR spectrum could not resolve these
two species due to the very broad resonances (W1/2
approx 5 kHz, 45 ppm), although one isotropic peak
appeared to be at δiso -40 ppm.
of 1 show one resonance for the respective homologous
substituents on both ligand phenyl rings. On cooling
to -110 °C, the 13C NMR resonances become very broad.
The H NMR spectrum does show splitting at -110 °C,
indicating two types of methoxy groups (3.45, 3.55 ppm),
1
t
methyl groups (1.56, 2.15 ppm), and Bu groups (0.92,
1.32 ppm). Only one methine proton is present (4.89
ppm, 2J (119Sn-1H) ) 101 Hz), and a complex pattern is
observed in the aromatic region. These data are con-
sistent with rapid rotation of the ligand [MetBuOMeC6H2]
groups about their central methine carbon at room
temperature. Lowering the temperature slows this
rotation, and at -110 °C, the two ligand [MetBuO-
MeC6H2] groups in compound 1 become nonequivalent,
presumably adopting an orthogonal relationship as was
observed in the solid state structure. This was con-
firmed by the solid state 13C NMR of 1 which showed
two distinct signals for each of the substituents on the
aromatic ligand rings.
Interestingly, the 1H and 13C NMR spectra of LH and
of the silicon compound, 2, indicate free rotation of the
[MetBuOMeC6H2] down to -110 °C. This indicates that
the restricted rotation observed for 1 is a consequence
of the residual Lewis acidity at tin rather than of steric
hindrance.
The 1H-119Sn 2-D NMR spectrum shows that the
lower frequency tin resonance at -148.7 ppm correlates
to the methine proton resonance at 4.47 (correlation X)
and the higher frequency tin resonance at -59.8 ppm
to the methine proton resonance at 5.07 ppm (correla-
tion Y). The 1H-13C 2-D NMR spectrum shows that the
higher frequency methine carbon correlates to the lower
frequency methine proton (correlation X) and the lower
frequency methine carbon to the higher frequency
methine proton (correlation Y). It is concluded that X
and Y correlations represent resonances from the five-
and four-coordinate tin species, respectively, in com-
pound 4.
The 119Sn NMR spectrum of the analogous dichloro
compound, PhCl2SnL, 3, at -80 °C shows only one
resonance at -132.4 ppm. At -55 °C, two resonances
are observed at -71.0 and -125.1 ppm, the former
resonance being broad and of low intensity. The relative
intensities of the two 119Sn NMR signals observed at
-55 °C is approximately 1:8 in favor of the lower
frequency signal, this reduces to 1:5 at -25 °C. No 119Sn
NMR resonance is seen at 25 °C, but increasing the
temperature to 100 °C gives a single sharp resonance
at -83.4 ppm.
We conclude that compound 3 exhibits similar coor-
dination properties to that observed for 4; however, the
equilibrium involving 3 favors the five-coordinate tin
species. The 119Sn NMR resonance at -132.4 ppm (-80
°C) is assigned to the five-coordinate species. At -55
°C, both four- and five-coordinate tin species are ob-
served, with the major resonance at -125.1 ppm as-
signed to the five-coordinate tin species and that of the
minor signal at -71.0 ppm to the four-coordinate tin
species. The increased population of the five-coordinate
species for 3 compared to 4 results from an increase in
the Lewis acidity at the tin atom brought about by the
more electronegative chlorine substituents. The solid
state isotropic 119Sn NMR chemical shift of δiso -132
ppm fits well with the pentacoordinate structure ob-
served in the solid state for 3 and supports the inter-
pretation of the low-temperature solution NMR data.
The 119Sn NMR spectrum of PhBr2SnL, 4 (Table 3),
in toluene at 100 °C shows one resonance (-82.7 ppm),
which on cooling begins to broaden at 50 °C. No 119Sn
NMR resonance is observed at 25 °C, but at -25 °C two
broad signals appear at -60.2 and -148.2 ppm. At -55
°C these signals both sharpen (-59.8 and -148.7 ppm),
and at -100 °C the higher frequency signal becomes
very broad while the lower frequency signal remains
sharp. The relative intensities of the two 119Sn NMR
resonances vary with temperature. A ratio of 2:1 in
favor of the higher frequency peak is observed at -25
°C. This becomes a 1:1 ratio at -100 °C.
At 25 °C, the H and 13C NMR spectra of compound
1
4 show one resonance for each of the substituents of the
aromatic ligand rings. At -110 °C, the 1H NMR
spectrum shows two types of methine protons at 4.47
and 5.07 ppm, having 2J (119Sn-1H) couplings of 120 and
93 Hz, respectively. Additionally, four types of methoxy
protons, four types of methyl protons, and three types
of tert-butyl protons are observed. All signals are of
approximately equal intensity.
The 13C NMR spectrum of 4 at -80 °C shows two
types of methine carbons (42.33 and 44.31 ppm, having
1J (119Sn-13CH) couplings of 561 and 652 Hz, respec-
tively). Three types of methoxy carbons, two types of
methyl carbons, two types of tert-butyl carbons (C(CH3)3),
and three types of quaternary carbons are observed. The
aromatic region of the spectrum shows a complex set of
signals.
The 119Sn, 13C, and H NMR data indicate 4 exhibits
1
two coordination states simultaneously in solution at
low temperature, while at high temperature, an average
of these coordination states is observed. Previous
examples of two coordination states in organotin chem-
istry being observed simultaneously have been reported,
however, such examples result from the coordination of
an additional intermolecular donor molecule. For ex-
ample, addition of a 0.5 mol equiv of pyridine to
(2-[(dimethylamino)methyl]phenyl)phenyltin dichloride
(16) Van Koten, G.; J astrzebski, J . T. B. H.; Grove, D. M.; Boersma,
J .; Ernstinng, J . M. Magn. Reson. Chem. 1991, 29, 525.

3704 Organometallics, Vol. 16, No. 16, 1997
Dakternieks et al.
Room-temperature 1H and 13C NMR spectra of 3 show
equivalence of the respective ligand phenyl [MetBuO-
MeC6H2] groups about their central methine carbon at
room temperature. At low temperature, both the 1H
and 13C NMR spectra show the presence of both four-
and five-coordinate tin species, with the intensities of
the signals from the four-coordinate species being low.
set in the equatorial plane, in this case C2I, largely
determines the 119Sn chemical shift of five-coordinate
tin complexes.
Of the current series of 3-5, the tin atom in 5 has
the lowest Lewis acidity and is least likely to extend
its coordination number through intramolecular coor-
dination. This tendency is reflected in the X-ray crystal
structures where 5 exhibits the weakest intramolecular
Sn-O interaction (Table 2). Increasing the temperature
promotes a rapid exchange of the methoxy donors at the
tin atom, resulting in an essentially tetrahedral four-
coordinate geometry in which there is a C2I2 donor set
about the tin. Iodine is highly polarizable and produces
a very large shielding effect at tin.14 Usually a decrease
in coordination number is accompanied by 119Sn shifts
to higher frequency. However, in this particular case,
the change to lower coordination number which occurs
with increasing temperature results in greater influence
from the highly polarizable iodine atoms. The net result
of these circumstances is a 119Sn NMR signal which
shifts to lower frequency with a decrease in coordination
number at tin.
Rea ction of Com p ou n d s 3-5 w ith Tr ibu tylp h os-
p h in e Oxid e. In order to further examine the nature
of the coordination equilibrium involved in solution for
compounds 3-5, their reaction with the strong Lewis
base tributylphosphine oxide (Bu3PO) was studied. The
119Sn NMR spectrum (-80 °C, CH2Cl2) of a 1:1 mixture
of Bu3PO and 3 shows a doublet at -290.3 ppm
(2J (119Sn-31P) ) 205 Hz). The spectrum remains the
same when the ratio of Bu3PO is increased to 4:1. No
119Sn NMR signals were observed at higher tempera-
tures. These NMR data imply that 3 forms a 1:1 adduct
with Bu3PO (PhCl2SnL‚Bu3PO) in situ at low temper-
ature. The adduct is five-coordinate through intermo-
lecular coordination of the phosphorus oxygen. Its 119Sn
NMR chemical shift is consistent with other similar
pentacoordinated species,18,23,24 e.g., Ph2SnCl2‚Bu3PO
-276 ppm, 2J (119Sn-31P) ) 156 Hz.18 This result
indicates that the intramolecular coordination of the
methoxy group from the ligand has been replaced by a
stronger intermolecular coordination from Bu3PO.
Higher adducts are not observed, even when the amount
of Bu3PO is increased to 4:1, implying that the maxi-
mum coordination number possible for this system is
five. These data support the contention that the
equilibria observed for 3 and 4 are indeed between four-
and five- and not five- and six-coordinate tin species.
In order to confirm the interpretation of the NMR
results above and to exclude the existence of an ionic
equilibrium,17 such as PhCl2SnL h [PhClSn]+ Cl- an
equivalent molar ratio of 3 and 4 were dissolved in
CH2Cl2 and the 119Sn NMR spectrum of the resulting
solution recorded at -55 °C. The 119Sn NMR spectrum
contains seven signals (-64.1, -74.5, -85.3, -129.8,
-130.6, -146.9, and -148.1 ppm). This indicates that
ionic species are not present, since these could result
in only five species in the mixture, i.e., PhCl2SnL, PhBr2-
SnL, PhClBrSnL, [LSnPhCl]+X-, and [LSnPhBr]+X-
(where X ) Cl or Br). The 119Sn NMR experiment
confirmed the presence of both four- and five-coordinate
tin species with the above signals assigned as follows:
PhBr2SnL, PhBrClSnL, PhCl2SnL (four-coordinate),
PhClBrSnL (Br axial), PhCl2SnL, PhBrClSnL (Cl axial),
PhBr2SnL (five-coordinate), respectively. The 119Sn
NMR chemical shift assignments of the five-coordinate
species LSnPhClBr (Br axial) and SnPhBrCl (Cl axial)
were made on the basis that the isomer with the
strongest electron-donating group in the equatorial
plane, i.e., PhBrClSnL (Cl axial), would give rise to the
tin resonance at lower frequency.18
The 119Sn NMR spectrum of PhI2SnL, 5 (Table 3), at
100 °C consists of a single sharp resonance at -153.9
ppm. Lowering the temperature causes the signal to
shift progressively toward higher frequency (-146.0
ppm at 75 °C, -129.3 ppm at 25 °C, -91.3 ppm at -95
°C). The resonance begins to broaden below -95 °C.
Both 1H and 13C NMR spectra of 5 at 25 °C show
equivalence of the respective homologous substituents
on the ligand phenyl groups. The resonances in the low-
temperature 13C NMR spectrum are slightly broad.
However, the low-temperature 1H NMR spectrum shows
splitting of the resonances associated with the homolo-
gous ligand phenyl group substituents. As with com-
pound 4, the solid state 119Sn NMR spectrum of 5
showed very broad lines (W1/2 ≈ 9 khz, 80 ppm), with
one major species evident at δiso -72 ppm and both at
room temperature and at 330 K.
A 119Sn shift which moves to lower frequency with an
increase in temperature is unusual and requires com-
ment. It is likely that 5 adopts a five-coordinate
geometry at low temperature, similar to that observed
in the solid state i.e., an essentially trigonal bipyramidal
geometry in which one iodine atom occupies an axial
position and the other iodine atom occupies an equato-
rial position. It has been suggested earlier that penta-
coordinate tin(IV) complexes involve a secondary hy-
dridization such that the s-character electron density
is concentrated in the equatorial orbitals of the trigonal
bipyramid.18-22 Consequently, the nature of the donor
The 119Sn NMR spectrum (-80 °C, CH2Cl2) of a 1:1
mixture of Bu3PO and 4 shows a doublet at -275.7 ppm
(2J (119Sn-31P) ) 196 Hz). Increasing the ratio of Bu3PO
to 2:1 leaves the 119Sn NMR spectrum almost un-
changed, with a low-intensity triplet (1:7) also being
observed at -343.7 ppm (2J (119Sn-31P) ) 233 Hz). The
spectrum is unaffected by increasing the amount of
Bu3PO to 4:1. No 119Sn NMR signals are observed at
higher temperatures. Compound 4 also forms a 1:1
adduct with Bu3PO (PhBr2SnL‚Bu3PO) at low temper-
ature, having a similar 119Sn NMR chemical shift to the
(17) Van Koten, G.; J astrzebski, J . T. B. H.; Noltes, J . G.; Spek, A.
L.; Schoone, J . C. J . Organomet. Chem. 1978, 148, 233.
(18) Colton, R.; Dakternieks, D. Inorg. Chim. Acta. 1985, 102, L17.
(19) Petrosyan, V. S.; Permin, A. B.; Reutov, O. A.; Roberts, J . D. J .
Magn. Reson. 1980, 40, 511.
(20) Nadvornik, M.; Holecek, J .; Handlif, K.; Lycka, A. J . Organomet.
Chem. 1984, 275, 43.
(21) Bent, H. A. Chem. Rev. 1961, 61, 275.
(22) Van Der Berghe, E. V.; Verdonck, L.; Van Der Kelen, G. P. J .
Organomet. Chem. 1969, 16, 497.
(23) Smith, P. J .; Tupciauskas, A. P. Ann. Rep. NMR Spectrosc.
1978, 8, 291.
(24) NMR and the Periodic Table; Harris, R. K., Mann, B. E., Eds.;
Academic Press: London, 1978; Chapter 10.

Isomerization in Organotin(IV) Compounds
Organometallics, Vol. 16, No. 16, 1997 3705
Ta ble 4. 119Sn NMR (CH2Cl2) Da ta for Com p ou n d s
five-coordinate species Ph2SnBr2‚Bu3PO (-319 ppm,
2J (119Sn-31P) ) 166 Hz).25 The low-intensity triplet
observed when the ratio of Bu3PO is increased to 2:1
implies formation of an adduct containing two Bu3PO
groups. The 119Sn NMR chemical shift of this adduct
is to higher frequency compared with the similar six-
coordinate 1:2 adduct, Ph2SnBr2‚2Bu3PO (-479 ppm).25
Additionally, Ph2SnBr2‚2Bu3PO is known to undergo
halide displacement upon coordination of a third Bu3PO
donor, i.e., [Ph2SnBr‚3Bu3PO]+Br-.25 Thus, it is pro-
posed that when the ratio of Bu3PO is increased to 2:1,
an equilibrium is established between the 1:1 adduct
and a 1:2 adduct in which a bromo group has been
displaced (eq 13).
9-13
compd T, °C δ(119Sn), ppm compd T, °C δ(119Sn), ppm
9
+25
-80
+25
-55
-80
25
-109.8
-105.3
-4.7
-31.4
-40.7
-26.4
-53.0
-64.0
12
+25
-55
-80
+25
-55
-80
-163.3
-141.2
-133.7
-107.2
-142.6
-154.3
10
13
11
-55
-80
-80 °C shows only one signal (-205.3 ppm). At 25 °C,
1
the H and 13C NMR spectra of 7 show one resonance
for the respective homologous ligand phenyl group
substituents. At low temperature, they split into two
resonances of equal intensity.
PhBr2SnL‚Bu3PO + Bu3PO h
[PhBrSnL‚2Bu3PO]+Br- (13)
Compound 7 appears also to exhibit coordination
equilibria with the equilibrium favoring almost exclu-
sively the five-coordinate tin species as a result of the
higher Lewis acidity of the SnCl3 fragment. The low-
intensity 119Sn NMR signal at -25 °C (-159.7 ppm) is
assigned to the four-coordinate species, while the major
signal at -198.2 ppm is assigned to the five-coordinate
tin species. Lowering the temperature causes the 119Sn
NMR resonance of the four-coordinate species to broaden,
leaving only the resonance corresponding to the five-
coordinate species. The isotropic 119Sn NMR chemical
shift of δiso -176 ppm in the solid state is in agreement
with pentacoordination.
The 119Sn NMR spectrum (-80 °C, CH2Cl2) of a 1:1
mixture of Bu3PO and 5 shows a broad resonance at
2
-89.3 ppm, a doublet at -255.6 ppm, J (119Sn-31P) )
2
160 Hz, and a triplet at -326.3 ppm, J (119Sn-31P) )
244 Hz, all of approximately equal intensity. When the
ratio of Bu3PO is increased to 2:1, only the triplet at
-326.3 ppm remains, with further addition of Bu3PO
(4:1) not affecting the spectrum. No 119Sn NMR signals
are observed at higher temperatures. These NMR data
suggest that 5 undergoes halide displacement more
readily than 4. Thus, the three signals observed for the
1:1 mixture of 5 and Bu3PO result from PhI2SnL (5),
PhI2SnL‚Bu3PO, and [PhISnL‚2Bu3PO]+I-, respec-
tively. The addition of additional mole equivalents
of Bu3PO results in the exclusive formation of
[PhISnL‚2Bu3PO]+I-.
1
Both the H and 13C NMR spectra of 7 indicate that
only the five-coordinate species is present at low tem-
perature. The 2J (119Sn-1H) and 1J (119Sn-13CH) cou-
plings of 132 and 897 Hz observed at low temperature
are quite large compared to those for compounds 4 and
5 but are still within the expected range for five-
coordinate tin species of this class.27
These studies show that in the presence of a strong
intermolecular donor, the tin atoms in compounds 3-5
do not become six-coordinate. Instead, the added Lewis
base competes with the halide substituents for a coor-
dination site, compound 5 showing the least resistance
to halide displacement. It is well-known that diorga-
notin dihalides can form six-coordinate tin products
through intermolecular or intramolecular coordina-
tion.26 Consequently, the inability of compounds 3-5
to attain six-coordination through the interaction of an
intermolecular donor results from steric restraints
imposed around the tin atoms by the bulky ligand, L.
The almost temperature independent 119Sn NMR
chemical shift (Table 3) of Ph(SPh)2SnL, 6, in solution
is very close to its solid state isotropic 119Sn chemical
shift, δiso 28 ppm, indicating very similar structures in
solution and in the solid state. Thus, the tin atom in 6
has a distorted tetrahedral configuration.
In order to assess whether ring size affected the
ability of the methoxy groups to participate in intramo-
lecular coordination to tin, complexes based on LCH2-
Br, 8, were synthesised. This second ligand system
allows evaluation of any differences, which might be due
to ring size, i.e., five-membered rings with L and six-
membered rings with (LCH2H).
The almost temperature-independent 119Sn NMR
chemical shift, -109.8 ppm (Table 4), and 1J (119Sn-
13CH2) constant of 377 Hz indicate that the tin atom
1
in 9 is four coordinate. At room temperature, the H
and 13C NMR data of 9 show equivalence of the
homologous ligand phenyl group substituents. How-
ever, unlike 1, these signals only become broad at low
temperature and are not split. These results suggest
that rotation of the substituted ligand phenyl rings in
9 is less hindered compared with those in 1.
The 119Sn NMR (toluene) spectrum of 7, Cl3SnL, at
100 °C shows one resonance at -159.0 ppm. At 25 °C,
no 119Sn NMR (CH2Cl2) resonance is observed, but upon
cooling to -25 °C a low intensity resonance is observed
at -158.7 ppm along with a major signal at -198.2 ppm
(ratio 1:15, respectively). The 119Sn NMR spectrum at
The room-temperature 1H and 13C NMR data for
compounds PhCl2Sn(CH2L) (10), PhBr2Sn(CH2L), (11),
PhI2Sn(CH2L) (12), and Cl3Sn(CH2L) (13) show equiva-
lence of the respective homologous ligand phenyl group
substituents. At low temperature, compounds 10-12
1
exhibit broad resonances in the H NMR (CD2Cl2, -110
(25) Colton, R.; Dakternieks, D. Inorg. Chim. Acta. 1988, 148, 31.
(26) (a) Schollmeyer, D.; Hartung, H.; Klaus, C.; J urkschat, K. Main
Group Metal Chem. 1991, 14, 27 and references cited therein. (b) Van
Koten, G.; J astrzebski, J . T. B. H. J . Organomet. Chem. 1979, 177,
283. (c) Harrison, P. G.; King, T. J .; Healy, M. A. J . Organomet. Chem.
1979, 182, 17. (d) Hartung, H.; Krug, A.; Richter, F.; Weichmann, H.
Z. Anorg. Allg. Chem. 1993, 619, 859. (e) Van Koten, G.; J astrzebski,
J . T. B. H. Advances Organomet. Chem. 1993, 35, 241 and references
cited therein.
°C) spectra, whereas the spectrum of 13 shows two
peaks for C(CH3)3 (1.24, 1.35 ppm), Me (2.12, 2.27 ppm),
and OMe (3.19, 4.14 ppm). Broad peaks are observed
for the CH2 (no couplings visible), CH, and aromatic
(27) Fouquet, E.; J ousseaume, B.; Maillard, B.; and Perere, M. J .
Organomet. Chem. 1993, 453, C1.

3706 Organometallics, Vol. 16, No. 16, 1997
Dakternieks et al.
moieties (2.84, 4.93, and 6.82-7.24 ppm, respectively).
The resonances observed in the low-temperature 13C
NMR (CDCl2, -80 °C) spectra of compounds 10-13 are
all broad.
Con clu sion
The ability of intramolecular coordination to take
place in the two series of compounds 1, 3-7 and 9-13
depends both on the Lewis acidity at tin and the ring
size formed on intramolecular coordination. The Lewis
acidity is controlled by the nature of the ligands (in
addition to L or CH2L) attached to tin. The six-
membered rings in the series containing CH2L are more
labile than the five-membered rings possible in the
series containing L. In neither series (L or CH2L) was
there any evidence for intramolecular coordination of
both methoxy groups to tin and neither L nor CH2L are
suitable for synthesis of octahedral organotin trihalides
with a facial arrangement of halides.
Compounds 10, 11, and 13 show a progressive shift
to low frequency of their 119Sn NMR signals with a
decrease in temperature (Table 4). As was the case for
PhI2SnL, the behavior of PhI2Sn(CH2L) appears anoma-
lous, with a progressive shift to higher frequency of its
119Sn NMR signal with a decrease in temperature.
The NMR data for compounds 10-13 are explained
in terms of temperature-dependent equilibria between
four- and five-coordinate species. Unlike the five-
membered ring analogues 3, 4, and 7, the equilibria
involving compounds containing six-membered rings are
fast on the NMR time scale at all temperatures mea-
sured and only averaged signals are observed. The tin
centers in the six-membered ring compounds are ex-
pected to have almost the same Lewis acidity as those
in the five-membered ring systems 3-5 and 7. Conse-
quently, the greater rate constants for the equilibria
involving 10-13 result from greater lability imparted
by the larger ring size in these compounds 16.26e The
population of four- and five-coordinate species for 10,
11, and 13 is temperature dependent, with the higher
coordination again being favored at low temperature.
The equilibrium for 12 lies almost exclusively toward
four-coordinate tin.
Ack n ow led gm en t. We are grateful to the Austra-
lian Research Council (ARC) and the Stifterverband fu¨r
die Deutsche Wissenschaft for financial support and to
the Commonwealth of Australia for a Postgraduate
Research Scholarship (R.T.).
Su p p or tin g In for m a tion Ava ila ble: Tables of anisotro-
pic thermal parameters, hydrogen atom parameters, bond
distances, and bond angles for [Ph3SnL], [Ph3SiL], [PhSnCl2L],
[PhSnBr2L], [PhSnI2L], and [PhSn(SPh)2L] (34 pages). Order-
ing information is given on any current masthead page.
OM960956B