Novel molecular organotin oxides derived from alkylidene bridged ditin precursors: Syntheses and structures

Article abstract of DOI:10.1021/om980369l

New diorganotin compounds (RCl₂Sn)₂(CR′₂)_n, [R = (SiMe₃)₂CH; R′ = Me, H; n = 1-3] linked by various spacers have been synthesized. These react with sodium hydroxide or (t-Bu₂SnO)₃ to give (R(O)Sn)₂(CR′₂)_n. Compounds 8 (R′ = Me, n = 1), 9 (R′ = H, n = 2), and 10 (R′ = H, n = 3) contain four-coordinate tin atoms. Compound 9 undergoes a reversible hydrolysis reaction from which a solid containing three ditin units has been isolated. Evidence is presented for the existence in solution of monomeric four-coordinate tin compounds (RXSn)₂(CH₂)₃O [R = (SiMe₃)₂CH, X = Cl, OH]. Crystal structures for monomeric ditin precursors 2,2-bis[bis(trimethylsilyl)methyldichlorostannyl]propane (3) and 1,2-bis-[bis(trimethylsilyl)methyldichlorostannyl]ethane (6), for dimeric units 1,3,5,7-tetrakis[bis-(trimethylsilyl)methyl]-9,9,10,10-tetramethyl-2,4,6,8- tetraoxa-1,3,5,7-tetrastannaadamantane (8), 1,3,7,9-tetrakis[bis(trimethylsilyl)methyl]-2,8,13,14-tetraoxatricyclo[7.3.1.13. 7]-1,3,7,9-tetrastannatetradecane (10), and 2,6-difluoro-2,6-bis[bis(trimethylsilyl)methyl]-1-oxa2,6-distannacyclohexane dimer (12), and for trimeric units {O[(RSn(CH₂)₂SnR)OH]OH}₃· 2H₂O (9a) are reported.

Full text of DOI:10.1021/om980369l

4096
Organometallics 1998, 17, 4096-4104
Novel Molecu la r Or ga n otin Oxid es Der ived fr om
Alk ylid en e Br id ged Ditin P r ecu r sor s: Syn th eses a n d
Str u ctu r es†,‡
Bernhard Zobel, Markus Schu¨rmann, and Klaus J urkschat*
Lehrstuhl fu¨r Anorganische Chemie II der Universita¨t Dortmund,
D-44221 Dortmund, Germany
Dainis Dakternieks* and Andrew Duthie
School of Biological and Chemical Sciences, Deakin University, Geelong,
Victoria 3217, Australia
Received May 11, 1998
New diorganotin compounds (RCl2Sn)2(CR′2)n [R ) (SiMe3)2CH; R′ ) Me, H; n ) 1-3]
linked by various spacers have been synthesized. These react with sodium hydroxide or
(t-Bu2SnO)3 to give (R(O)Sn)2(CR′2)n. Compounds 8 (R′ ) Me, n ) 1), 9 (R′ ) H, n ) 2), and
10 (R′ ) H, n ) 3) contain four-coordinate tin atoms. Compound 9 undergoes a reversible
hydrolysis reaction from which a solid containing three ditin units has been isolated.
Evidence is presented for the existence in solution of monomeric four-coordinate tin
compounds (RXSn)2(CH2)3O [R ) (SiMe3)2CH, X ) Cl, OH]. Crystal structures for monomeric
ditin precursors 2,2-bis[bis(trimethylsilyl)methyldichlorostannyl]propane (3) and 1,2-bis-
[bis(trimethylsilyl)methyldichlorostannyl]ethane (6), for dimeric units 1,3,5,7-tetrakis[bis-
(trimethylsilyl)methyl]-9,9,10,10-tetramethyl-2,4,6,8-tetraoxa-1,3,5,7-tetrastannaadaman-
tane (8), 1,3,7,9-tetrakis[bis(trimethylsilyl)methyl]-2,8,13,14-tetraoxatricyclo[7.3.1.13.7]-
1,3,7,9-tetrastannatetradecane (10), and 2,6-difluoro-2,6-bis[bis(trimethylsilyl)methyl]-1-oxa-
2,6-distannacyclohexane dimer (12), and for trimeric units {O[(RSn(CH2)2SnR)OH]OH}3‚
2H2O (9a ) are reported.
In tr od u ction
We have been interested for some time in bridged
ditin compounds containing various spacers, (RCl2Sn)-
(CH2)n (R ) Me3SiCH2, Ph; n ) 1-4).4 On reaction with
sulfide, selenide, or telluride, these derivatives provided
well-defined molecular organotin chalcogenides with
adamantane-type and tricyclic ring structures.4b,5
Reaction of [Me3SiCH2(Cl2)Sn]2(CH2)3 with (t-Bu2-
The structure and, hence, the properties of diorgano-
tin oxides (R2SnO)n essentially depend on the nature of
the organic substituent R. Insoluble polymers (n ) ∞)1
are observed for sterically nondemanding R groups such
as Me, Et, n-Bu, or Ph as a result of intramolecular
cross-linking2 brought about by Sn-O Lewis acid-base
interactions. Bulky substituents such as bis(trimeth-
ylsilyl)methyl, tris(trimethylsilyl)methyl, tert-butyl, tert-
amyl, 2,6-diethylphenyl, 2,4,6-trimethylphenyl, or 2,4,6-
tris(trifluoromethyl)phenyl inhibit cross-linking, and,
consequently, well-defined molecular organotin oxides
are formed, such as {[(Me3Si)2CH]2SnO}2,3a {(Me3-
Si)2CH(Me)Sn[OSn(Me)C(SiMe3)3]2O},3b (t-Bu2SnO)3,3c
[(t-C5H11)2SnO]3,3c [(2,6-Et2C6H3)2SnO]3,3d [(2,4,6-Me3C6-
H2)2SnO]3,3e and {[2,4,6-(CF3)3C6H2]2SnO}3.3f
1
SnO)3 or with /n{[Me3SiCH2(O)Sn]2(CH2)3}n gave {[Me3-
SiCH2(Cl)Sn(CH2)3Sn(Cl)CH2SiMe3]O}4, the first tet-
raorganodistannoxane with a double ladder structure
of type A4c,6 (see Chart 1). It is interesting to note that
alternative ditin and tetratin structures of types B and
C were not observed.
The reactions of [Me3SiCH2(Cl2)Sn]2(CH2)3 with so-
dium hydroxide and of (PhCl2Sn)2CH2 with (t-Bu2SnO)3
resulted in insoluble organotin oxides of unknown
structures.4b,6 As part of our systematic study of the
influence of both R and the spacer on the structure of
organotin oxides [(R(O)Sn)2(CR′2)n], we now report the
syntheses and structures of the representatives with R
) (Me3Si)2CH, R′ ) Me, n ) 1, and R ) (Me3Si)2CH, R′
) H, n ) 2, 3.
† Dedicated to Professor R. R. Holmes on the occasion of his 70th
birthday.
‡This paper includes part of the Ph.D. thesis of B. Zobel, Dortmund
University, 1997.
(1) Harrison, P. G., Ed. Chemistry of Tin; Blackie & Son: London,
1983.
(2) Harris, R. K.; Sebald, A. J . Organomet. Chem. 1987, 331, C9.
(3) (a) Edelman, M. A.; Hitchcock, P. B.; Lappert, M. F. J . Chem.
Soc., Chem. Commun. 1990, 1116. (b) Belsky, K. K.; Zemlyansky, N.
N.; Borisova, I. V.; Kolosova, N. D.; Beletskaya, I. P. J . Organomet.
Chem. 1983, 254, 189. (c) Puff, H.; Schuh, W.; Sievers, R.; Wald, W.;
Zimmer, R. J . Organomet. Chem. 1984, 260, 271. (d) Masamune, S.;
Sita, C. R.; Williams, D. J . J . Am. Chem. Soc. 1983, 105, 630. (e) Weber,
U.; Pauls, N.; Winter, W.; Stegmann, H. B. Z. Naturforsch., B 1982,
37, 1316. (f) Gru¨tzmacher, H.; Pritzkow, H. Chem. Ber. 1993, 126, 2409.
(4) (a) Gielen, M.; J urkschat, K. J . Organomet. Chem. 1984, 273,
303. (b) Dakternieks, D.; J urkschat, K.; Wu, H.; Tiekink, E. R. T.
Organometallics 1993, 12, 8. (c) Dakternieks, D.; J urkschat, K.;
Schollmeyer, D.; Wu, H. Organometallics 1994, 13, 4121. (d) Tsa-
gatakis, J . K.; Chaniotakis, N. A.; J urkschat, K. Helv. Chim. Acta 1994,
77, 2191.
(5) Dakternieks, D.; J urkschat, K.; Schollmeyer, D.; Wu, H. J .
Organomet. Chem. 1995, 492, 145.
(6) Mehring, M.; J urkschat, K. Unpublished results.
S0276-7333(98)00369-0 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 08/06/1998

Organotin Oxides from Ditin Precursors
Organometallics, Vol. 17, No. 18, 1998 4097
2J (117/119Sn-13C) ) 19 Hz, 2C, CH3). 29Si{1H} NMR (79.49
MHz, CDCl3): δ 1.37 (s, 2J (117/119Sn-29Si) ) 27/29 Hz, 1J (13C-
Ch a r t 1
29Si) ) 51 Hz). 119Sn{1H} NMR (111.92 MHz, CHCl3/D2OCap.):
2
δ 32.6 (s, J (117Sn-119Sn) ) 127 Hz). Anal. Calcd for C21H56
-
Si4Sn2: C, 38.30; H, 8.57. Found: C, 38.2; H, 8.8.
Syn th esis of 2,2-Bis[bis(tr im eth ylsilyl)m eth yldich lor o-
sta n n yl]p r op a n e (3). A mixture of 1 (10.71 g, 16.3 mmol)
and Me2SnCl2 (7.90 g, 36.0 mmol) was heated (110-120 °C)
for 30 h to give a clear melt. The resulting Me3SnCl was
removed by sublimation (3 h, 10-3 mmHg, 80-90 °C) to give
11.37
g (100% yield) of 2,2-bis[bis(trimethylsilyl)methyl-
chloromethylstannyl]propane (2) as a beige solid, which was
used for the synthesis of 3 without further purification.
Compound 2 consists of two diastereomers which were detected
by NMR spectroscopy. However, no effort was made to assign
the NMR signals to the diastereomers. 1H NMR (400.13 MHz,
CDCl3): δ 0.14, 0.142, 0.185, 0.195 (4×s, 36H, SiMe3); 0.256,
0.281 (2×s, 2J (117/119Sn-1H) ) 85/90 Hz, 2H, CH); 0.743, 0.753
(2×s, 2J (117/119Sn-1H) ) 48/50 Hz, 6H, SnMe); 1.710, 1.725,
1.740 (3×s, 3J (117/119Sn-1H) ) 100/115 Hz, 6H, C(CH3)2). 13C-
{1H} NMR (100.62 MHz, CDCl3): δ 3.33, 3.35, 3.53, 3.62 (s,
Exp er im en ta l Section
All solvents were dried and purified by standard procedures.
Bruker DPX-300 and DRX-400 spectrometers were used to
1
1
12C, SiMe3); 8.12 (s, J (117/119Sn-13C) ) 131/137 Hz, J (29Si-
1
13C) ) 37 Hz, 1C, CH(a)); 8.26 (s, J (117/119Sn-13C) ) 130/136
obtain H, 13C, 29Si, and 119Sn NMR spectra. 1H, 13C, 29Si, and
1
Hz, 1J (29Si-13C) ) 37 Hz, 1C, CH(b)); 2.83 (s, 1J (117/119Sn-13C)
119Sn chemical shifts δ are given in ppm and are referenced
against Me4Si and Me4Sn, respectively. 119Sn MAS spectra
were obtained from a Bruker MSL 400 spectrometer using
cross-polarization and high-power proton decoupling. Cy4Sn
was used as a secondary reference (δ -97.35 ppm).
1
) 309/322 Hz, 1C, SnMe(a)); 2.94 (s, J (117/119Sn-13C) ) 312/
325 Hz, 1C, SnMe(b)); 25.41, 25.69, 25.71, 25.77 (4×s, 2J -
(
117/119Sn-13C) ) 15 Hz, 2J (117/119Sn-13C) ) 16 Hz, 2J (117/119Sn-
13C) ) 16 Hz, 2J (117/119Sn-13C) ) 19 Hz, 2C, CH3); 34.98 (s,
1J (117/119Sn-13C) ) 333/349 Hz, C(a)); 35.04 (s, 1J (117/119Sn-
13C) ) 336/352 Hz, C(b)). 29Si{1H} NMR (79.49 MHz, CDCl3):
δ 0.80 (s, 2J (117/119Sn-29Si) ) 21/22 Hz, 1Si); 0.88 (s, 2J -
The electrospray mass spectra were recorded with a Plat-
form II single-quadrupole mass spectrometer (Micromass,
Altrincham, UK) using an acetonitrile mobile phase. Aceto-
nitrile solutions of the compounds were injected directly into
the spectrometer via a Rheodyne injector equipped with a 50-
µL loop. A Harvard 22 syringe pump delivered the solutions
to the vaporization nozzle of the electrospray ion source at a
flow rate of 10 µL min-1. Nitrogen was used both as a drying
gas and for nebulization with flow rates of approximately 200
and 20 mL min-1, respectively. Pressure in the mass analyzer
region was usually about 4 × 10-5 mbar. Typically, 10 signal-
averaged spectra were collected.
(
117/119Sn-29Si) ) 21/22 Hz, 1Si); 2.00 (s, 2J (117/119Sn-29Si) )
40/42 Hz, 1Si); 2.07 (s, 2J (117/119Sn-29Si) ) 40/42 Hz, 1Si).
119Sn{1H} NMR (149.21 MHz, CDCl3): δ 151.2 (s, 1 Sn); 151.7
(s, 1 Sn).
A mixture of 2 (11.37 g 16.3 mmol) and SnCl4 (8.50 g 32.6
mmol) was heated (60-70 °C) for 12 h. The resulting Me2-
SnCl2 was removed by sublimation (3-4 h, 10-3 mmHg, 80-
90 °C), and the residual solid was recrystallized from hexane
1
to give 8.9 g (74% yield) of crystalline 3, mp. 113-114 °C. H
NMR (400.13 MHz, CDCl3): δ 0.25 (s, 18H, SiMe3); 0.98 (s,
2J (117/119Sn-1H) ) 90/94 Hz, 1H, CH); 1.97 (s, 3J (117/119Sn-1H)
) 128/134 Hz, 3H, C(CH3)2). 13C{1H} NMR (100.62 MHz,
Molecular weight determinations were performed on a
Knaur osmometer. TGA measurements were made on a
Mettler instrument equipped with a PID module 200.
The density of the single crystals was determined using a
Micromeritics Accu Pyc 1330.
1
3
CDCl3): δ 3.1 (s, J (29Si-13C) ) 52 Hz, J (117/119Sn-13C) ) 26
1
1
Hz, 12C, SiMe3); δ 21.4 (s, J (117/119Sn-13C) ) 154/160 Hz, J -
(29Si-13C) ) 34 Hz, 2C, CH); 25.0 (s, 2J (117/119Sn-13C) ) 21
Compounds (Me3Si)2CHLi,7 (Me2ClSn)2CMe2,8 and (Ph2-
FSn)2(CH2)n (n ) 2, 3)9 were prepared according to the
literature.
Hz, 2C, CH3); 60.2 (s, J (117/119Sn-13C) ) 412/431 Hz, 1C, C).
1
29Si{1H} NMR (79.49 MHz, CDCl3): δ 1.89 (s, 2J (117/119Sn-
29Si) ) 48/50 Hz, 1J (13C-29Si) ) 52 Hz). 119Sn{1H} NMR
(149.21 MHz, CDCl3): δ 78.7 (s, 2J (117Sn-119Sn) ) 599 Hz).
Anal. Calcd for C17H44Cl4Si4Sn2: C, 27.59; H, 5.99. Found:
C, 27.5; H, 6.1.
Syn th esis of 2,2-Bis[bis(tr im eth ylsilyl)m eth yld im eth -
ylsta n n yl]p r op a n e (1). To a magnetically stirred solution
of (Me3Si)2CHLi (8.64 g, 52.0 mmol) in 500 mL of pentane was
added in small portions at room temperature (Me2ClSn)2CMe2
(10.00 g, 24.4 mmol). The reaction mixture was stirred
overnight, and resulting LiCl was filtered off. Removing the
solvent by rotary evaporation resulted in 15.38 g (96% yield)
of crude product, which was recrystallized from CH2Cl2 to give
13.10 g (yield 82%, mp 103-104 °C) of colorless crystals. 1H
NMR (400.13 MHz, CDCl3): δ -0.49 (s, 2J (117/119Sn-1H) ) 75/
Syn th esis of 1,2-Bis[bis(tr im eth ylsilyl)m eth yldich lor o-
sta n n yl]eth a n e (6) a n d 1,3-Bis[bis(tr im eth ylsilyl)m eth -
yld ich lor osta n n yl]p r op a n e (7). To a magnetically stirred
suspension of (Me3Si)2CHLi (5.00 g, 30.1 mmol) in 500 mL of
pentane was added in small portions at room temperature
(Ph2FSn)2(CH2)2 (9.00 g, 14.7 mmol) or (Ph2FSn)2(CH2)3 (9.10
g, 14.6 mmol). The reaction mixture was stirred overnight,
and the LiF was filtered. The solvent was removed in vacuo
togive11.60gof1,2-bis[bis(trimethylsilyl)methyldiphenylstannyl]-
ethane (4) or 10.80 g of 1,3-bis[bis(trimethylsilyl)methyl-
diphenylstannyl]propane (5), respectively, which were used
for the synthesis of 6 and 7, respectively, without further
purification. 13C{1H} NMR (100.62 MHz, CDCl3): 4, δ 0.71
2
78 Hz, 1H, CH); 0.06 (s, 18H, SiMe3); 0.17 (s, J (117/119Sn-1H)
) 46 Hz, 6H, SnMe2); 1.43 (s, 3J (117/119Sn-1H) ) 76/80 Hz, 6H,
C(CH3)2). 13C{1H} NMR (100.62 MHz, CDCl3): δ -4.9 (s,
1J (117/119Sn-13C) ) 274/286 Hz, 4C, SnMe); 3.76 (s, 1J -
1
(
117/119Sn-13C) ) 124/129 Hz, J (29Si-13C) ) 39 Hz, 2C, CH);
3.7 (s, 1J (29Si-13C) ) 51 Hz, 3J (117/119Sn-13C) ) 14 Hz, 12C,
SiMe3); 14.7 (s, 1J (117/119Sn-13C) ) 309/327 Hz, 1C, C); 27.7 (s,
1
3
(s, 1C, CH); 3.34 (s, J (29Si-13C) ) 52 Hz, J (117/119Sn-13C) )
16 Hz, 6C, SiMe3); 11.16 (s, 1J (117/119Sn-13C) ) 329/344 Hz,
2J (117/119Sn-13C) ) 43 Hz, 1C, SnCH2); 128.20 (s, 4C, Cm);
128.40 (s, 2C, Cp); 137.10 (s, 2J (117/119Sn-13C) ) 34 Hz, 4C, Co);
141.16 (s, 1J (117/119Sn-13C) ) 421/440 Hz, 2C, Ci). 29Si{1H}
(7) Davidson, P. J .; Harris, D. H.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1976, 2268.
(8) Karol, T. J .; Hutchinson, J . P.; Hyde, J . R.; Kuivila, H. G.;
Zubieta, J . A. Organometallics 1983, 2, 106.
(9) Dakternieks, D.; J urkschat, K.; Zhu, H.; Tiekink, E. R. T.
Organometallics 1995, 14, 2512.
2
NMR (79.49 MHz, CDCl3): 4, δ 1.5 (s, J (117/119Sn-29Si) ) 29/

4098 Organometallics, Vol. 17, No. 18, 1998
Zobel et al.
1
2
3
31 Hz, J (13C-29Si) ) 52 Hz); 5, δ 1.3 (s, J (117/119Sn-29Si) )
1J (29Si-13C) ) 52 Hz, J (117/119Sn-13C) ) 19 Hz, 12C, SiMe3);
9.17 (s, J (117/119Sn-13C) ) 198/208 Hz, J (29Si-13C) ) 38 Hz,
2C, CH); 24.83 (s, 2J (117/119Sn-13C) ) 16 Hz, 2C, CH3); 47.1 (s,
1J (117/119Sn-13C) ) 416/433 Hz, 1C, C); 9, δ 7.05 (s, 1J (29Si-
1
1
1
30 Hz, J (13C-29Si) ) 51 Hz). 119Sn{1H} NMR (111.92 MHz,
CHCl3/D2OCap.): 4, δ -62.0 (s, J (117Sn-119Sn) ) 1332 Hz); 5,
3
δ -69.0 (s, J (117Sn-119Sn) ) 99 Hz, J (13C-119Sn) ) 449 Hz).
4
1
13C) ) 49 Hz, J (117/119Sn-13C) ) 20 Hz, 6C, SiMe3); 15.30 (s,
3
To a magnetically stirred ice-cooled solution of 4 (10.00 g,
11.2 mmol) or 5 (10.16 g, 11.2 mmol) in 100 mL of acetone
was added dropwise a solution of HgCl2 (12.17 g, 44.9 mmol)
in 40 mL of acetone during 1 h. The resulting white suspen-
sion was stirred overnight at room temperature. The precipi-
tate of PhHgCl was filtered, and the solvent was removed in
vacuo. The resulting residue was extracted with hexane in a
Soxhlet apparatus over a period of 16 h. The hexane was
removed in vacuo, and the remaining crude product was
recrystallized from diethyl ether to give 5.94 g (73%) of 6 of
mp 115-117 °C or 7.17 g (86.5%) of 7 of mp 85-91 °C,
respectively. 1H NMR (400.13 MHz, CDCl3): 6, δ 0.23 (s, 18H,
SiMe3); 0.7 (s, 2J (117/119Sn-1H) ) 101/105 Hz, 1H, CH); 2.15
1J (117/119Sn-13C) ) 221/232 Hz, 1J (29Si-13C) ) 37 Hz, 1C, CH);
21.94 (s, 1J (117/119Sn-13C) ) 473/496 Hz, 2J (117/119Sn-13C) ) 30
Hz, 1C, SnCH2); 10, δ 3.21 (s, 1J (29Si-13C) ) 51 Hz, 3J -
1
(
117/119Sn-13C) ) 21 Hz, 6C, SiMe3(a)); 3.24 (s, J (29Si-13C) )
51 Hz, 3J (117/119Sn-13C) ) 18 Hz, 6C, SiMe3(b)); 12.34 (s,
1J (117/119Sn-13C) ) 237/249 Hz, 1J (29Si-13C) ) 39 Hz, 2C,
CH(a,b)); 20.54 (s, 2J (117/119Sn-13C) ) 42 Hz, 1C, CH2(a,b));
26.61 (s, 1J (117/119Sn-13C) ) 472/493 Hz, 3J (117/119Sn-13C) ) 19
Hz, 2C, SnCH2(a,b)). 29Si{1H} NMR (79.49 MHz, CDCl3): 8,
δ 1.23 (s, J (117/119Sn-29Si) ) 42/44 Hz, J (13C-29Si) ) 51 Hz);
2
1
9, δ 0.67 (s, 2J (117/119Sn-29Si) ) 37/39 Hz, 1J (13C-29Si) ) 51
Hz); 10, δ -0.08 (s, J (117/119Sn-29Si) ) 30/31 Hz, J (13C-29Si)
2
1
) 51 Hz, 1Si, SiMe3(a)); 0.68 (s, J (117/119Sn-29Si) ) 47/49 Hz,
2
(s, 2H, SnCH2); 7, δ 0.22 (s, 18H, SiMe3); 0.56 (s, J (117/119Sn-
2
1J (13C-29Si) ) 51 Hz, 1Si, SiMe3(b)). 119Sn{1H} NMR (149.21
1H) ) 103/108 Hz, 1H, CH); 1.81 (t, 3J (1H-1H) ) 8 Hz, 2J -
MHz, CDCl3.): 8, δ 23.8 (s, J (117Sn-O-119Sn) ) 390 Hz, J -
2
2
3
(
117/119Sn-1H) ) 48 Hz, 2H, SnCH2); 2.35 (quint, J (1H-1H) )
(
117Sn-119Sn) ) 740 Hz); 9, δ 24.7 (s, 2J (117Sn-O-119Sn) ) 520
8 Hz, 3J (117/119Sn-1H) ) 90 Hz, 1H, CH2). 13C{1H} NMR
(100.62 MHz, CDCl3): 6, δ 2.71 (s, 1J (29Si-13C) ) 53 Hz,
3J (117/119Sn-13C) ) 27 Hz, 6C, SiMe3); 19.05 (s, 1J (117/119Sn-
13C) ) 154/161 Hz, 1J (29Si-13C) ) 36 Hz, 1C, CH); 24.65 (s,
Hz, 3J (117Sn-119Sn) ) 205 Hz); 10, δ 24.9, W1/2 ) 1.2 Hz (s,
2J (117Sn-119Sn) ) 381 Hz, 2J (117Sn-119Sn) ) 495 Hz). 119Sn
MAS NMR (149.21 MHz): 8, δ 24.4; 9a , δ -163.4; -168.5;
10, δ 34.3 (s,2J (117Sn-119Sn) ) 436 Hz, 1Sn); 24.0 (s, 2J -
1J (117/119Sn-13C) ) 424/444 Hz, J (117/119Sn-13C) ) 58 Hz, 1C,
2
(
117Sn-119Sn) ) 436 Hz, 1Sn). Anal. Calcd for C34H88O4Si8-
SnCH2); 7, δ 2.64 (s, J (29Si-13C) ) 52 Hz, J (117/119Sn-13C) )
1
3
Sn4 (8): C, 32.39; H, 7.04. Found: C, 32.4; H, 7.2. Anal.
Calcd for C48H136O11Si12Sn6 (9a ): C, 29.73; H, 7.07. Found:
C, 30.02; H, 7.31. Anal. Calcd for C34H88O4Si8Sn4 (10): C,
32.39; H, 7.04. Found: C, 32.51; H, 7.22. Molecular mass
(found in CH2Cl2): 8, 1185; 9a , 1272 (fits for 9 in solution);
10, 1208 g/mol. DTA: 9a , 95-155 °C, loss of 5 H2O.
26 Hz, 12C, SiMe3); 18.1 (s, 1J (117/119Sn-13C) ) 160/168 Hz,
1J (29Si-13C) ) 36 Hz, 2C, CH); 20.7 (s, J (117/119Sn-13C) ) 37
2
Hz, 1C, CH2); 31.2 (s, 1J (117/119Sn-13C) ) 424/444 Hz, 3J -
(
117/119Sn-13C) ) 95/100 Hz, 2C, SnCH2). 29Si{1H} NMR (79.49
MHz, CDCl3): 6, δ 1.9 (s, 2J (117/119Sn-29Si) ) 43/45 Hz, 1J (13C-
29Si) ) 52 Hz); 7, δ 1.8 (s, 2J (117/119Sn-29Si) ) 40/42 Hz, 1J (13C-
29Si) ) 52 Hz). 119Sn{1H} NMR (149.21 MHz, CDCl3): 6, δ
Syn th esis of 2,6-Dich lor o-2,6-bis[bis(tr im eth ylsilyl)-
m eth yl]-1-oxa -2,6-d ista n n a cyloh exa n e (11). Meth od A.
Compounds 10 (50 mg, 0.040 mmol) and 7 (59 mg, 0.080 mmol)
were dissolved in CDCl3. After 24 h, the precipitate (95 mg,
87%) of colorless crystals of 11 was collected, mp 113-122 °C.
112.3 (s, J (117Sn-119Sn) ) 2010 Hz); 7, δ 118.6. Anal. Calcd
3
for C16H42Cl4Si4Sn2 (6): C, 26.47; H, 5.83. Found: C, 26.4; H,
6.0. Anal. Calcd for C17H44Cl4Si2Sn2 (7): C, 29.85; H, 6.48.
Found: C, 29.20; H, 6.30.
13C{1H} NMR (100.62 MHz, CDCl3): δ 2.77 (s, J (29Si-13C) )
1
52 Hz, 3J (117/119Sn-13C) ) 25 Hz, 12C, SiMe3); 16.94 (s, 2C,
CH); 21.48 (s, 2J (117/119Sn-13C) ) 46 Hz, 1C, CH2); 29.18 (s,
2C, SnCH2). 119Sn{1H} NMR (149.21 MHz,CDCl3): δ 86.4 (s,
14%); 78.97 (s, 86%). Anal. Calcd for C17H44Cl2OSi4Sn2: C,
29.80; H, 6.47. Found: C, 29.83; H, 6.71. Molecular weight
found in CH2Cl2: 687.
Syn th esis of 1,3,5,7-Tetr akis[bis(tr im eth ylsilyl)m eth yl]-
9,9,10,10-t et r a m et h yl-2,4,6,8-t et r a oxa -1,3,5,7-t et r a st a n -
n a a d a m a n ta n e (8), 1,3,6,8-Tetr a k is[bis(tr im eth ylsilyl)-
m et h yl]-2,7,11,12-t et r a oxa -1,3,6,8-t et r a st a n n a t r icyclo-
[4.4.1.13,8]dodecane (9), and 1,3,7,9-Tetrakis[bis(trimethylsilyl)-
methyl]-2,8,13,14-tetraoxa-tricyclo[7.3.-1.13,7]-1,3,7,9-tetrastannate-
tr a d eca n e (10). Meth od A. To a magnetically stirred sol-
ution of 3 (1.00 g, 1.35 mmol), 6 (1.00 g, 1.35 mmol), or 7 (1.00
g, 1.35 mmol) in 5 mL of toluene was added at 80 °C a solution
of NaOH (0.75 g, 18.75 mmol) in 5 mL of water, and the
reaction mixture was stirred overnight. The organic layer was
separated, and the toluene was removed in vacuo. The crude
product was recrystallized from toluene (8 and 10) to give 570
mg (67%) 8 of mp 227-229 °C and 750 mg (79%) 10 of mp
166-172 °C, respectively. Compound 9 could be isolated only
as its hydrolysis product (9a ) when recrystallized from CH2-
Cl2 (750 mg (88%), mp 165 °C).
Meth od B (in situ gen er a tion of 11). 12 (89 mg, 0.12
mmol) and (t-Bu2SnO)3 (30 mg, 0.04 mmol) were dissolved in
CDCl3, and the resulting clear solution was examined by
119Sn NMR spectroscopy. 119Sn{1H} NMR (149.21 MHz,
CDCl3): δ 86.1 (s, 15%); 71.6 (s, 85%); 54.6 (s, t-Bu2SnCl2).
Syn th esis of 2,6-Diflu or o-2,6-bis[bis(tr im eth ylsilyl)-
m eth yl]-1-oxa -2,6-d ista n n a cycloh exa n e Dim er (12). To
a magnetically stirred solution of 7 (0.61 g, 0.82 mmol) in 10
mL of diethyl ether was added excess potassium fluoride (3.00
g, 61.0 mmol), dissolved in 10 mL of water. The reaction
mixture was stirred for 5 d at room temperature. The ether
was removed in vacuo, and the resulting precipitate was
filtered and washed three times with water in order to remove
traces of KF and KCl. Recrystallization from chloroform
afforded colorless crystals of 12 (0.52 g, 89%) of mp 294-298
°C. Anal. Calcd for C34H88F4O2Si8Sn4: C, 31.30; H, 6.80.
Found: C, 31.21; H, 7.52. There are two sets of NMR signals.
Set 1. 19F NMR (282.4 MHz, CDCl3): δ 19Fa -134.3 ppm,
Meth od B. 3, 6, or 7 (0.10 mmol) and (tBu2SnO)3 (50 mg,
0.20 mmol) were dissolved in CDCl3, and, when examined, by
119Sn NMR spectroscopy, gave the same resonances as were
observed for the isolated solid samples prepared from Method
A.
1H NMR (400.13 MHz, CDCl3): 8, δ 0.01 (s, 2J (117/119Sn-
1H) ) 90/94 Hz, 1H, CH); 0.16 (s, 18H, SiMe3); 1.66 (s, 3J -
d, J (19Fa-19Fb) ) 59 Hz, J (117/119Sn-19Fa) ) 2643/2762 Hz; δ
19Fb -85.5 ppm, d, 2J (19Fa-19Fb) ) 59 Hz, 1J (117/119Sn-19Fb)
1270 Hz. 119Sn{1H} NMR (149.21 MHz, CDCl3): δ 119Sn(I)
2
1
(
(
117/119Sn-1H) ) 106/111 Hz, 3H, C(CH3)2); 9, δ -0.1 (s, 2J -
117/119Sn-1H) ) 102/107 Hz, 1H, CH); 0.14 (s, 18H, SiMe3);
1.49 (s, 2H, SnCH2); 10, δ -0.23 (s, J (117/119Sn-1H) ) 96/100
Hz, 2H, CH); 0.108 (s, 18H, SiMe3(a)); 0.116 (s, 18H, SiMe3(b));
1.08 (m, 2J (117/119Sn-1H) ) 170 Hz, 2H, SnCHH); 1.35 (m,
2
-153.8 ppm, dd J (119Sn(I)-19Fa) ) 2765 Hz, 1J (119Sn(I)-19Fb)
1
) 1255 Hz, 2J (119Sn(I)-117/119Sn(II)) ) 215 Hz; δ 119Sn(II) -115.1
ppm, ddd, 1J (119Sn(II)-19Fb) ) 1483 Hz, 3J (119Sn(II)-19Fa) )
33 Hz, J (119Sn(II)-19Fb′) ) 19 Hz.
3
2J (117/119Sn-1H) ) 80 Hz, 2H, SnCHH); 2.30 (m, J (117/119Sn-
3
1H) ) 200 Hz, 1H, CHH); 2.86 (m, J (117/119Sn-1H) ) 90 Hz,
3
Set 2. 19F NMR (282.4 MHz, CDCl3): δ 19Fa -133.8 ppm,
1H, CHH). 13C{1H} NMR (100.62 MHz, CDCl3): 8, δ 3.19 (s,
d, J (19Fa-19Fb) ) 62 Hz, J (117/119Sn-19Fa) ) 2700/2825 Hz; δ
2
1

Organotin Oxides from Ditin Precursors
Organometallics, Vol. 17, No. 18, 1998 4099
Ta ble 1. Cr ysta llogr a p h ic Da ta for 2, 6, 8, 9a , 10, a n d 12
3
6
8
9a
10
12
formula
fw
cryst syst
cryst size, mm
space group
a, Å
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
C
17H44Cl4Si4Sn2
C16H42Cl4Si4Sn2
726.04
monoclinic
C34H88O4Si8Sn4
1260.52
tetragonal
C48H132O9Si12Sn6‚2H2O C34H88O4Si8Sn4
C34H88O4Si8Sn4‚3CHCl3
1662.63
monoclinic
740.06
monoclinic
1938.79
triclinic
1260.52
monoclinic
0.25 × 0.20 × 0.20 0.23 × 0.20 × 0.20 0.28 × 0.28 × 0.25 0.12 × 0.10 × 0.10
0.20 × 0.15 × 0.12 0.40 × 0.20 × 0.20
P21/c
P21/c
P43212
16.044(2)
16.044(2)
22.914(3)
90
90
90
5897.3(13)
4
1.419
1.419(5)
1.865
2544
P-1
P21/n
C2/c
19.288(1)
12.703(1)
13.592(1)
90
101.517(1)
90
3263.2(4)
4
1.506
12.043(1)
17.284(1)
15.578(1)
90
107.817(1)
90
3087.1(4)
4
1.562
9.233(1)
17.048(1)
29.144(1)
87.050(1)
87.601(1)
77.645(1)
4473.0(6)
2
12.335(2)
16.616(2)
14.535(2)
90
99.58(1)
90
2935.7(9)
2
1.426
32.423(1)
9.723(1)
26.891(1)
90
123.038(1)
90
7097.1(8)
4
Z
F
F
calcd, Mg/m3
meas, Mg/m3
1.440
1.556
1.510(3)
2.010
1480
1.557(3)
2.123
1448
1.456(3)
1.850
1960
1.431(4)
1.873
1272
nma
µ, mm-1
1.556
3320
F(000)
θ range, deg
4.43-25.64
-20 e h e 20
-15 e k e 15
-16 e l e 16
4.61-25.66
-14 e h e 14
-21 e k e 21
-18 e l e 18
42 766
3.10-27.47
-2 e h e 20
-2 e k e 20
-2 e l e 29
10 357
100.0
4.80-24.72
-10 e h e 10
-15 e k e 20
-33 e l e 34
12 590
3.10-24.97
-1 e h e 14
-1 e k e 19
-17 e l e 17
6364
2.23-26.36
-38 e h e 38
-10 e k e 10
-31 e l e 26
47 422
index ranges
no. of reflns collctd 45 282
completeness to
θmax
no. of indep reflns/ 5749/0.036
Rint
93.1
100.0
45.1
100.0
87.9
5799/0.042
3883
6752/0.094
2549
6819/0.050
3728
5159/0.043
2965
6373/0.035
4354
no. of reflns obsd 3925
with (I > 2σ(I))
absorpn correction none
none
Psi-Scan
1.000/0.919
241
none
Psi-Scan
1.000/0.874
239
none
T
max/Tmin
no. of refined
245
248
732
370
params
GooF (F2)
0.912
0.905
0.991
1.048
1.012
0.942
R1 (F) (I > 2σ(I)) 0.0265
0.0292
0.0571
0.0729
0.1089
0.0585
0.1207
0.0458
0.1065
0.0309
0.0683
wR2 (F2) (all data) 0.0574
(∆/σ)max
0.001
0.311/-0.401
0.001
0.381/-0.621
<0.001
0.484/-0.512
0.001
0.367/-0.339
<0.001
0.967/-0.497
0.001
0.556/-0.726
largest diff
peak/hole, e/Å3
a
Not measured.
19Fb -71.9 ppm, broad, 1J (117/119Sn-19Fb) ) 1360 Hz. 119Sn-
{1H} NMR (149.21 MHz, CDCl3): δ 119Sn(I) -153.7 ppm, dd,
1J (119Sn(I)-19Fa) ) 2820 Hz, 1J (119Sn(I)-19Fb) ) 1190 Hz 2J -
Atomic scattering factors for neutral atoms and real and
imaginary dispersion terms were taken from ref 10d. Figures
were created by SHELXTL-Plus.10e Crystallographic data are
given in Table 1, while selected bond distances and bond angles
are listed in Tables 2 (3, 6), 3 (8, 10), 4 (9a ), and 5 (12).
(
119Sn(I)-117/119Sn(II)) ) 215 Hz; δ 119Sn(II) -108.4 ppm, dd,
3
1J (119Sn(II)-19Fb) ) 1537 Hz J (119Sn(II)-19Fa) ) 33 Hz.
Cr ysta llogr a p h y. Intensity data for the colorless crystals
were collected on Nonius MACH3 (8, 10) and KappaCCD (3,
6, 9a , 12) diffractometers with graphite-monochromated Mo
KR radiation (0.710 69 Å) at 291 (3, 6, 8, 9a , 10) and 200 K
(12). Three standard reflections were recorded every 60 min
(8, 10), and anisotropic intensity losses up to 28.6% (8) and
14.3% (10) were detected during X-ray exposure. The data
collections for (3, 6, 9a , 12) covered the sphere of reciprocal
space with 360 frames via ω-rotation (∆/ω ) 1°) (3, 6, 12) and
with 720 frames via ω-rotation (∆/ω ) 0.5°) (9a ) at two times
5s (6), 8s (12), and 10s (3, 9a ) per frame. The crystal-to-
detector distance was 2.6 (5, 10), 2.7 (9a ), and 2.9 cm (12).
Crystal decay was monitored by repeating the initial frames
at the end of data collection. On analyzing the duplicate
reflections, there was no indication for any decay (3, 6, 9a ,
12). The structures were solved by direct methods SHELXS8610a
and successive difference Fourier syntheses. Refinement
applied full-matrix least-squares methods SHELXL93.10b
The H atoms were placed in geometrically calculated
positions using a riding model and refined with a common
isotropic temperature factor (Cprim.-H 0.96, Csec.-H 0.97, and
Ctert.-H 0.98 Å; Uiso ) 0.119(2) (3), 0.088(2) (6), 0.0152(9) (8),
0.118(6) (9a ), 0.127(6) (10), 0.110(3) (12) Å2).
Resu lts a n d Discu ssion
Syn th esis of th e Sp a cer -Br id ged Ditin Com -
p ou n d s 1-7 a n d Molecu la r Str u ctu r es of th e Bis-
(or ga n od ich lor osta n n yl)a lk a n es 3 a n d 6. The re-
action of (Me2ClSn)2CMe28 with (Me3Si)2CHLi7 afforded
{Me2[(Me3Si)2CH]Sn}2CMe2 (1, eq 1), which was con-
verted into its tetrachloro derivative {[(Me3Si)2CH]Cl2-
Sn}2CMe2 (3) by stepwise reaction with Me2SnCl2 and
SnCl4 (eqs 2 and 3).
(SnMe2Cl)2CMe2 + 2(Me3Si)2CHLi pentane, 20 °C, 12 h8
-2LiCl
{SnMe2[CH(SiMe3)2]}2CMe2
(1)
(2)
(3)
1
1 + 2Me2SnCl2 30 h, 110-120 °C8
-2Me3SnCl
{SnMe(Cl)[CH(SiMe3)2]}2CMe2
2
The absolute configuration for 8 was confirmed by refine-
12 h, 60-70 °C
ment of the Flack10c parameter, 0.04(5).
{[(Me Si) CH]Cl Sn} CMe
8
2 + SnCl4
3
2
2
2
2
-Me2SnCl2
3
(10) (a) Sheldrick, G. M. Acta Crystallogr. 1990 A46, 467-473. (b)
Sheldrick, G. M. University of Go¨ttingen, 1993. (c) Flack, H. D. Acta
Crystallogr. 1983 A39, 876-881. (d) International Tables for Crystal-
lography; Kluwer Academic Publishers: Dordrecht, 1992; Vol. C. (e)
Sheldrick, G. M. SHELXTL-Plus, Release 4.1; Siemens Analytical
X-ray Instruments Inc., Madison, WI, 1991.
The di- and trimethylene bridged ditin compounds, 6
and 7, respectively, were prepared by reaction of (Ph2-
FSn)2(CH2)n (n ) 2, 3)9 with (Me3Si)2CHLi7 (eq 4),

4100 Organometallics, Vol. 17, No. 18, 1998
Ta ble 2. Selected In ter a tom ic Bon d Dista n ces (Å) a n d An gles (d eg) for 3 a n d 6
Zobel et al.
3
6
3
6
Bond Distances
Sn(1)-C(1)
Sn(1)-C(2)
Sn(1)-Cl(1)
Sn(1)-Cl(2)
Sn(1)-Cl(4)
Sn(2)-Cl(2)
2.125(3)
2.167(3)
2.3562(9)
2.3593(9)
3.637(1)
3.467(1)
2.132(3)
2.146(3)
2.356(1)
2.3460(9)
Sn(2)-C(2)
Sn(2)-C(3)
Sn(2)-C(4)
Sn(2)-C(5)
Sn(2)-Cl(3)
Sn(2)-Cl(4)
2.177(3)
2.151(3)
2.123(3)
2.125(3)
2.359(1)
2.357(1)
2.334(1)
2.355(1)
Bond Angles
C(1)-Sn(1)-C(2)
C(1)-Sn(1)-Cl(1)
C(1)-Sn(1)-Cl(2)
C(2)-Sn(1)-Cl(1)
C(2)-Sn(1)-Cl(2)
Cl(1)-Sn(1)-Cl(2)
C(2)-Sn(2)-C(5)
C(2)-Sn(2)-Cl(3)
C(2)-Sn(2)-Cl(4)
124.0(1)
124.3(1)
C(5)-Sn(2)-Cl(3)
C(5)-Sn(2)-Cl(4)
Cl(3)-Sn(2)-Cl(4)
C(3)-Sn(2)-C(4)
C(3)-Sn(2)-Cl(3)
C(3)-Sn(2)-Cl(4)
C(4)-Sn(2)-Cl(3
C(4)-Sn(2)-Cl(4)
107.0(1)
114.63(9)
100.77(4)
108.30(9)
114.57(9)
107.07(9)
102.16(9)
97.33(3)
131.2(1)
102.06(9)
96.2(1)
107.38(9)
111.90(8)
105.7(1)
104.5(1)
100.40(4)
101.11(4)
124.6(1)
103.3(1)
105.7(1)
111.50(9)
108.05(9)
Ta ble 3. Selected In ter a tom ic Bon d Dista n ces (Å) a n d An gles (d eg) for 8 a n d 10a
8
10
8
10
Bond Distances
Sn(1)-O(1)
Sn(1)-O(2)
Sn(1)-C(1)
Sn(1)-C(1a)
Sn(1)-C(10)
Sn(2)-O(1)
1.963(5)
1.973(7)
1.971(4)
1.961(4)
2.144(7)
Sn(2)-O(2a)
Sn(2)-O(2)
Sn(2)-O(3)
Sn(2)-C(1)
Sn(2)-C(3)
Sn(2)-C(20)
1.955(4)
1.982(7)
1.950(5)
2.14(1)
2.18(1)
2.15(1)
2.133(6)
1.970(4)
2.141(7)
2.143(6)
2.17(1)
Bond Angles
O(1)-Sn(1)-O(2)
O(1)-Sn(1)-C(1a)
O(1)-Sn(1)-C(10)
O(2)-Sn(1)-C(1a)
O(2)-Sn(1)-C(10)
O(1)-Sn(1)-C(1)
O(2)-Sn(1)-C(1)
C(1)-Sn(1)-C(10)
C(1a)-Sn(1)-C(10)
O(1)-Sn(2)-O(2a)
O(1)-Sn(2)-C(3)
O(2)-Sn(2)-O(3)
O(2)-Sn(2)-C(1)
103.0(2)
104.7(2)
O(2)-Sn(2)-C(20)
O(3)-Sn(2)-C(1)
O(3)-Sn(2)-C(20)
C(1)-Sn(1)-C(20)
O(1)-Sn(2)-C(20)
O(2a)-Sn(2)-C(3)
O(2a)-Sn(2)-C(20)
C(3)-Sn(2)-C(20)
Sn(1)-O(1)-Sn(2)
Sn(1)-O(2)-Sn(2a)
Sn(1)-O(2)-Sn(1a)
Sn(2)-O(3)-Sn(2a)
Sn(2)-C(1)-Sn(1a)
112.7(4)
108.6(3)
109.8(4)
103.6(3)
111.6(4)
107.7(3)
112.7(4)
114.4(4)
110.0(2)
107.3(2)
106.7(2)
107.9(3)
119.2(3)
107.6(2)
108.1(3)
108.1(2)
120.0(3)
122.1(2)
128.5(2)
118.9(4)
124.0(4)
105.6(2)
106.6(3)
121.3(5)
121.9(5)
106.9(4)
101.8(2)
106.5(4)
a
a ) -X, -Y, -Z + 0.5 (8); a ) -X, -Y, -Z + 1 (10).
followed by treatment with mercuric chloride (eq 5).
the van der Waals radii of tin (2.20 Å)11 and chlorine
(1.70-1.90 Å)11 and are made possible by opening of the
C(1)-Sn(1)-C(2) and C(2)-Sn(2)-C(5) angles to 123.4-
(4) and 133.2(4)°, respectively. A quantitative measure
of the position of a real structure along the path
tetrahedron-trigonal bipyramid is the difference of the
sums of the equatorial and axial angles, ∑ϑeq - ∑ϑax;12
it amounts to 26.1° for Sn(1) and 32.44 for Sn(2). In
the dimethylene-bridged compound 6, both tin atoms
are essentially tetracoordinate, there being no intra- or
intermolecular Sn‚‚‚Cl interactions. The Sn-C and
Sn-Cl bond lengths in both 3 and 6 are as expected
and comparable with those of related compounds.13
Syn th eses of th e Molecu la r Or ga n otin Oxid es
8-10 a n d Molecu la r Str u ctu r es of 8 a n d 10. Com-
pounds 3, 6, and 7 are easily transformed into the
corresponding diorganotin oxides 8, 9, and 10, respec-
tively (Scheme 1).
(Ph2FSn)2(CH2)n + 2(Me3Si)2CHLi pentane, 20 °C, 12 h8
-2LiF
{Ph2[(Me3Si)2CH]Sn}2(CH2)n
4, n ) 2; 5, n ) 3
(4)
{Ph2[(Me3Si)2CH]Sn}2(CH2)n 4HgCl , acetone, 12 h8
2
-4PhHgCl
{[(Me3Si)2CH](Cl2)Sn}2(CH2)n
6, n ) 2; 7, n ) 3
(5)
Compounds 1-7 are colorless crystalline solids which
are very soluble in organic solvents. As expected, 2
consists of a mixture of diastereomers, as was evidenced
by the observation of two almost equally intense 119Sn
NMR resonances at 151.2 and 151.7 ppm. No attempt
was made to separate these diastereomers.
The molecular structures of 3 and 6 are shown in
Figures 1 and 2, respectively. Selected bond lengths and
bond angles are listed in Table 2. In 3, both Sn(1) and
Sn(2) show geometries along the path tetrahedron-
trigonal bipyramid induced by weak intramolecular Sn-
(1)‚‚‚Cl(4) and Sn(2)‚‚‚Cl(2) contacts of 3.630(3) and
3.456(3) Å. These contacts are shorter than the sum of
(11) Huheey, J . E.; Keiter, E. A.; Keiter, R. L. Anorganische
Chemie: Prinzipien von Struktur und Reaktivita¨t, 2nd ed.; de
Gruyter: Berlin, New York, 1995; p 335.
(12) (a) Kolb, U.; Dra¨ger, M.; J ousseaume, B. Organometallics 1991,
10, 2737. (b) Kolb, U.; Beuter, M.; Dra¨ger, M. Inorg. Chem. 1994, 33,
4522.
(13) Dakternieks, D.; J urkschat, K.; Tiekink, E. R. T. Main Group
Metal Chem. 1994, 17, 471 and references cited.

Organotin Oxides from Ditin Precursors
Organometallics, Vol. 17, No. 18, 1998 4101
Ta ble 4. Selected In ter a tom ic Bon d Dista n ces (Å) a n d An gles (d eg) for 9a
Bond Distances
Sn(3)-O(2′)
1.98(1)
2.195(9)
2.15(1)
2.13(2)
3.251(2)
2.157(8)
2.244(9)
1.98(1)
2.13(1)
2.14(2)
2.23(1)
1.987(9)
2.15(1)
Sn(5)-C(5)
Sn(5)-C(5′)
Sn(6)-O(5)
Sn(6)-O(6)
Sn(6)-O(6′)
Sn(6)-C(6)
Sn(6)-C(6′)
O(1)...O(7)
O(2′)...O(7)
O(4′)...O(8)
O(5)...O(8)
2.15(2)
2.14(1)
2.19(1)
2.26(1)
1.994(8)
2.17(1)
2.13(2)
2.77(2)
2.79(2)
2.84(2)
2.98(2)
2.71(2)
2.78(2)
Sn(1)-O(1)
Sn(1)-O(6)
Sn(1)-O(6′)
Sn(1)-C(1)
Sn(1)-C(1′)
Sn(2)-Sn(3)
Sn(2)-O(1)
Sn(2)-O(2)
Sn(2)-O(2′)
Sn(2)-C(2)
Sn(2)-C(2′)
Sn(3)-O(2)
2.22(1)
2.193(9)
1.980(9)
2.15(2)
2.19(2)
3.261(2)
2.15(1)
2.26(1)
1.98(1)
2.15(2)
2.14(1)
2.19(1)
Sn(3)-O(3)
Sn(3)-C(3)
Sn(3)-C(3′)
Sn(4)-Sn(5)
Sn(4)-O(3)
Sn(4)-O(4)
Sn(4)-O(4′)
Sn(4)-C(4)
Sn(4)-C(4′)
Sn(5)-O(4)
Sn(5)-O(4′)
Sn(5)-O(5)
O(6′)...O(7)
O(7)...O(8)
Bond Angles
O(6′)-Sn(1)-C(1)
O(6′)-Sn(1)-C(1′)
C(1)-Sn(1)-C(1′)
O(6′)-Sn(1)-O(6)
C(1)-Sn(1)-O(6)
C(1′)-Sn(1)-O(6)
O(6′)-Sn(1)-O(1)
C(1)-Sn(1)-O(1)
C(1′)-Sn(1)-O(1)
O(6)-Sn(1)-O(1)
O(2′)-Sn(2)-C(2′)
O(2′)-Sn(2)-C(2)
C(2′)-Sn(2)-C(2)
O(2′)-Sn(2)-O(1)
C(2′)-Sn(2)-O(1)
C(2)-Sn(2)-O(1)
O(2′)-Sn(2)-O(2)
C(2′)-Sn(2)-O(2)
C(2)-Sn(2)-O(2)
O(1)-Sn(2)-O(2)
O(2′)-Sn(3)-C(3′)
O(2′)-Sn(3)-C(3)
C(3′)-Sn(3)-C(3)
O(2′)-Sn(3)-O(2)
C(3′)-Sn(3)-O(2)
C(3)-Sn(3)-O(2)
O(2′)-Sn(3)-O(3)
C(3′)-Sn(3)-O(3)
C(3)-Sn(3)-O(3)
107.3(5)
O(2)-Sn(3)-O(3)
O(4′)-Sn(4)-C(4)
O(4′)-Sn(4)-C(4′)
C(4)-Sn(4)-C(4′)
O(4′)-Sn(4)-O(3)
C(4)-Sn(4)-O(3)
C(4′)-Sn(4)-O(3)
O(4′)-Sn(4)-O(4)
C(4)-Sn(4)-O(4)
C(4′)-Sn(4)-O(4)
O(3)-Sn(4)-O(4)
O(4′)-Sn(5)-C(5′)
O(4′)-Sn(5)-C(5)
C(5′)-Sn(5)-C(5)
O(4′)-Sn(5)-O(5)
C(5′)-Sn(5)-O(5)
C(5)-Sn(5)-O(5)
O(4′)-Sn(5)-O(4)
C(5′)-Sn(5)-O(4)
C(5)-Sn(5)-O(4)
O(5)-Sn(5)-O(4)
O(6′)-Sn(6)-C(6′)
O(6′)-Sn(6)-C(6)
C(6′)-Sn(6)-C(6)
O(6′)-Sn(6)-O(5)
C(6′)-Sn(6)-O(5)
C(6)-Sn(6)-O(5)
O(6′)-Sn(6)-O(6)
C(6′)-Sn(6)-O(6)
166.0(4)
C(6)-Sn(6)-O(6)
O(5)-Sn(6)-O(6)
Sn(1)-O(1)-O(7)
Sn(3)-O(2)-Sn(2)
Sn(3)-O(2′)-Sn(2)
Sn(3)-O(2′)-O(7)
Sn(2)-O(2′)-O(7)
Sn(4)-O(3)-Sn(3)
Sn(5)-O(4)-Sn(4)
Sn(4)-O(4′)-Sn(5)
Sn(4)-O(4′)-O(8)
Sn(5)-O(4′)-O(8)
Sn(5)-O(5)-Sn(6)
Sn(5)-O(5)-O(8)
Sn(6)-O(5)-O(8)
Sn(1)-O(6)-Sn(6)
Sn(1)-O(6′)-Sn(6)
Sn(1)-O(6′)-O(7)
Sn(6)-O(6′)-O(7)
O(6′)-O(7)-O(1)
O(6′)-O(7)-O(8)
O(1)-O(7)-O(8)
O(6′)-O(7)-O(2′)
O(1)-O(7)-O(2′)
O(8)-O(7)-O(2′)
O(7)-O(8)-O(4′)
O(7)-O(8)-O(5)
O(4′)-O(8)-O(5)
90.1(5)
162.3(4)
99.4(4)
124.6(4)
128.1(5)
77.0(4)
94.8(5)
96.4(5)
87.4(4)
87.8(5)
94.1(4)
164.2(4)
114.7(5)
117.7(5)
126.7(6)
90.2(4)
100.6(5)
88.5(5)
75.1(4)
94.6(5)
89.6(5)
162.3(3)
124.3(5)
108.6(6)
127.0(7)
76.8(4)
96.7(5)
92.8(4)
89.5(4)
93.4(5)
88.8(4)
122.7(6)
115.8(5)
121.1(7)
88.3(4)
87.4(5)
100.8(5)
75.8(4)
92.2(5)
96.0(5)
160.7(4)
122.7(5)
109.7(5)
127.6(6)
89.1(4)
94.3(5)
87.5(6)
76.0(4)
97.1(5)
93.6(6)
164.6(3)
115.4(5)
120.2(5)
123.8(6)
91.1(4)
99.7(5)
87.1(6)
75.2(4)
96.3(5)
94.2(3)
110.7(4)
136.8(5)
105.1(5)
118.1(4)
93.3(3)
110.0(4)
143.5(5)
106.5(5)
117.5(4)
97.8(6)
126.7(5)
93.9(4)
109.9(5)
108.4(4)
133.9(5)
64.0(4)
95.5(5)
159.1(6)
105.6(5)
63.6(4)
122.6(7)
88.5(5)
86.1(5)
59.9(4)
Ta ble 5. Selected In ter a tom ic Bon d Dista n ces (Å) a n d An gles (d eg) for 12a
Bond Distances
Sn(1)-O(1a)
Sn(1)-C(1)
Sn(1)-C(11)
Sn(2)-F(1)
2.127(2)
2.147(3)
2.131(3)
2.235(2)
Sn(2)-F(2)
Sn(2)-O(1)
Sn(2)-C(3)
Sn(2)-C(21)
1.993(2)
2.038(2)
2.126(4)
2.132(3)
Sn(1)-F(1)
Sn(1)-F(2a)
Sn(1)-O(1)
2.141(2)
3.830(2)
2.076(2)
Bond Angles
O(1)-Sn(1)-F(1)
O(1a)-Sn(1)-F(1)
O(1)-Sn(1a)-F(2)
O(1)-Sn(1)-F(2a)
O(1)-Sn(1)-O(1a)
O(1)-Sn(1)-C(11)
O(1a)-Sn(1)-C(11)
O(1a)-Sn(1)-C(1)
O(1)-Sn(1)-C(1)
F(1)-Sn(1)-F(2a)
74.59(8)
150.34(9)
48.08(7)
117.00(7)
75.8(1)
124.8(1)
105.2(1)
97.8(1)
F(1)-Sn(1)-C(1)
F(1)-Sn(1)-C(11)
F(2a)-Sn(1)-C(1)
F(2a)-Sn(1)-C(11)
C(1)-Sn(1)-C(11)
O(1)-Sn(2)-F(1)
O(1)-Sn(2)-F(2)
O(1)-Sn(2)-C(3)
O(1)-Sn(2)-C(21)
F(1)-Sn(2)-F(2)
89.4(1)
91.0(1)
110.3(1)
62.0(1)
131.2(2)
73.30(8)
91.28(9)
101.8(1)
120.6(1)
164.55(8)
F(1)-Sn(2)-C(3)
F(1)-Sn(2)-C(21)
F(2)-Sn(2)-C(3)
F(2)-Sn(2)-C(21)
C(3)-Sn(2)-C(21)
Sn(1)-O(1)-Sn(2)
Sn(1)-O(1)-Sn(1a)
Sn(2)-O(1)-Sn(1a)
Sn(1)-F(1)-Sn(2)
87.2(1)
88.0(1)
97.0(1)
99.6(1)
133.7(2)
104.5(1)
104.2(1)
141.1(1)
96.03(8)
102.1(1)
152.85(6)
a
a ) -X + 0.5, -Y + 0.5, -Z.
These compounds are colorless, crystalline solids
which have sharp melting points. They are very soluble
in common organic solvents such as chloroform. Their
structure in solution follows from 13C and 119Sn NMR
ratios4b,15,16 proves unambiguously the connectivity of
the carbon, oxygen, and tin atoms in 8-10. For
2
instance, in 8 and 9, the J (119Sn-O-117Sn) satellites
2
3
are twice as intense as the J (119Sn-C-117Sn) and J -
1
spectroscopy. Both 119Sn chemical shifts and J (119Sn-
(
119Sn-C-C-117Sn) satellites, respectively. In 10, how-
13C) couplings are indicative of tetracoordinate tin atoms
with a C2SnO2 substituent pattern.14 The satellite
pattern as well as the satellite-to-signal integral
ever, there are two J (119Sn-O-117Sn) satellites, and
2
both are of the same integral ratio.
(15) Berwe, H.; Haas, A. Chem. Ber. 1987, 120, 1175.
(16) Masamune, S.; Sita, L. R. J . Am. Chem. Soc. 1985, 107, 6390.
(14) Kennedy, J . D. J . Chem. Soc., Perkin Trans. 2 1977, 242.

4102 Organometallics, Vol. 17, No. 18, 1998
Zobel et al.
F igu r e 1. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering for 3.
F igu r e 3. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering (symmetry transformations used to gen-
erate equivalent atoms: a ) -X, -Y, -Z + 0.5) for 8.
F igu r e 2. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering scheme for 6.
Sch em e 1
The solution-state structures of 8 and 10 are retained
in the solid state, as shown by X-ray crystallography
(see below) and also by the 119Sn CP MAS NMR
F igu r e 4. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering (symmetry transformations used to gen-
erate equivalent atoms: a ) -X, -Y, -Z + 1) for 10.
chemical shifts (8, δ 24.4 ppm; 10, δ 24.0 ppm, 2J -
2
(
119Sn-O-117Sn) ) 436 Hz, δ 34.3 ppm, J (119Sn-O-
117Sn) ) 436 Hz), being almost identical with the 119Sn
chemical shifts measured in solution. The observation
of two equally intense signals in the 119Sn CP MAS
spectrum of 10 reflects the nonequivalence of Sn(1) and
Sn(2) within one molecule of 10, as was shown by its
crystal structure (see below).
Selected bond lengths and bond angles are listed in
Table 3. Compound 8 shows an adamantane-type
structure with distorted tetrahedral tin atoms. The
deviation from the ideal geometry is especially mani-
fested in large Sn-O-Sn (121.4(5)-124.0(4)°), C(1)-
Sn(2)-C(20) (114.4(4)°), and C(1a)-Sn(1)-C(10) (118.9-
(4)°) angles and results from the bulky (Me3Si)2CH and
bridging CMe2 groups.
The molecular structures of the organotin oxides 8
and 10 are shown in Figures 3 and 4, respectively.

Organotin Oxides from Ditin Precursors
Organometallics, Vol. 17, No. 18, 1998 4103
Sch em e 2
Ch a r t 2
Sch em e 3
F igu r e 5. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering scheme for 9a .
The structure of 10 is comparable to those of related
siloxanes17 and to [Ph(S)Sn(CH2)3Sn(S)Ph]2.5 The C3-
OSn2 six-membered rings are mutually trans. The tin
atoms are of distorted tetrahedral configuration, with
the greatest deviations found for the C(1)-Sn(1)-C(10)
and C(3)-Sn(2)-C(20) angles of 119.3(3) and 120.0(3)°,
respectively. In both 8 and 10, the Sn-O and Sn-C
bond lengths are comparable to those of related dior-
ganotin oxides.3
angles exhibit values between 121.4(7) and 128.1(5)° as
well as 114.8(5) and 124.5(4)°, while the C-Sn-O
angles vary between 107.4(5) and 122.4(6)°.
A stabilizing factor in the structure of 9a seems to be
the two water molecules O(7) and O(8), which show
strong to moderate hydrogen bridges of 2.71(2)-2.98-
(2) Å to O(1), O(2′), O(4′), O(5), and O(6′) and among
each other. The bulky (Me3Si)2CH groups show a
clockwise orientation and prevent any intermolecular
interactions.
Attempts to grow single crystals of 9 under water-
free conditions failed.
Dissolving single crystalline 9a in CDCl3 resulted in
reformation of 9 and water, as was evidenced by a single
119Sn NMR resonance at 24.7 ppm, with 2J (119Sn-O-
Un exp ected F or m a tion of th e Hexa n u clea r Or -
ga n otin oxo Clu ster 9a . Compound 9 reacts with air
moisture to provide {O[(RSn(CH2)2SnR)OH]OH}3‚2H2O
(9a ) as a colorless crystalline solid. The 119Sn CP MAS
NMR spectrum of 9a displayed two resonances at
-163.4 and -168.5 ppm, with an integral ratio of about
1:2. The chemical shifts are in line with pentacoordi-
nation at tin. DTA studies of 9a revealed loss of 5 mole
equiv of water between 95 and 155 °C.
The molecular structure of 9a is shown in Figure 5.
Selected bond lengths and bond angles are listed in
Table 4. Compound 9a consists of six tin atoms, which
are connected by a combination of dimethylene, oxygen
(O(2′), O(4′), O(6′)), and hydroxo (O(1)-O(6)) bridges,
resulting in an alternating connection of four- (Sn2O2)
and five- (Sn2C2O) membered rings. Each tin atom has
a trigonal bipyramidal configuration with two carbons
(C(1), C(1′); C(2), C(2′); C(3), C(3′); C(4), C(4′); C(5), C(5′);
C(6), C(6′)) and one oxygen (O(2′), O(4′), O(6′)) in
equatorial and two OH groups (O(1), O(2), O(3), O(4),
O(5), O(6)) in axial positions. The bond angles about
the tin atoms show slight to moderate differences.
Thus, the axial O-Sn-O angles vary between 160.7(4)
and 166.0(4)°. The two sets of equatorial C-Sn-C
3
117Sn) and J (119Sn-C-C-117Sn) satellites of 520 and
205 Hz, respectively.
The molecular weight determination also shows that
9a easily loses water to give 9 in solution. These
observations are consistent with the equilibrium shown
in Scheme 2.
Such an equilibrium could be achieved by the exist-
ence of the monomeric ditin species 9b (Chart 2).
The existence of monomeric ditin species is strongly
implicated in the reaction between 7 and 10, which
yields 11. Solutions of 11 display two 119Sn NMR
signals at 86.4 and 79.0 ppm, with an integral ratio of
about 14:86. Interestingly, the chemical shifts are near
the average of the chemical shifts of 118.6 and 24.9 ppm
found for 10 and 7, respectively. This indicates that
the tin atoms in 11 are tetracoordinate, with a C2SnClO
substituent pattern. The molecular mass of 11 (687
g/mol in CH2Cl2) is also consistent with a monomeric
ditin species (Scheme 3). We tentatively assign the
major 119Sn signal at 79.0 ppm to the trans isomer of
11.
The monomeric nature of 11 is also supported by
electrospray studies. In the positive mode, a cluster was
detected at m/e 685 corresponding to [11 + H]+, whereas
in the negative mode, clusters were observed at m/e 719
and 755 representing [11 + Cl]- and [11 + H + 2Cl]-,
respectively.
(17) (a) Gar, T. K.; Buyakov, A. A.; Gusev, A. I.; Los, M. G.; Kisin,
A. V.; Mironov, V. F. Zh. Obshch. Khim. 1976, 46, 837. (b) Dubchak,
I. L.; Shklover, V. E.; Timofeeva, T. V.; Struchkov, Yu. T.; Zhdanov,
A. A.; Kashutina, E. A.; Shchegolikhina, O. I. Zh. Strukt. Khim. 1981,
22, 147.

4104 Organometallics, Vol. 17, No. 18, 1998
Zobel et al.
Ch a r t 3
distannoxanes, with the difference that, as result of the
C(1)-C(2)-C(3) bridge, the Sn(2)/Sn(2a) atoms are
strongly displaced by (0.905(3) Å from the F(1)Sn(1)O-
(1)Sn(1a)O(1a)F(1a) plane. The planarity of the latter
amounts to (0.010(1) Å. The intramolecular Sn(1)‚‚‚
Sn(2) distance within the four-membered Sn2O2 ring is
3.2536(4) Å.
Each tin atom exhibits a distorted trigonal bipyra-
midal geometry (geometrical goodness12b ∆∑ϑ 79.3°
(Sn1), 68.2° (Sn2); ∆Sn (plane) 0.161(2) Å (Sn1), 0.234-
(2) Å (Sn2)). Sn(1) is coordinated by C(1), C(11), and
O(1) in equatorial and by F(1) and O(1a) in axial
positions. Sn(2) is coordinated by C(3), C(21), and O(1)
in equatorial and by F(1) and F(2) in axial positions. In
contrast to [(t-Bu2FSn)2O]2,19 the Sn(1)-F(1)-Sn(2)
bridge in 12 is asymmetric, but the Sn-F distances are
of the same order of magnitude as those found for
[(Ph2XSn)2(CH2)n‚F]-Et4N+ (X ) F, Cl, Br, I; n ) 1, 2).9
The terminal Sn-F distance of 1.993(2) Å is almost
identical to the corresponding distance (1.981(7) Å) in
19
[(t-Bu2FSn)2O]2 and very close to a Sn-F single bond
length (1.96 Å).12a The Sn(1)‚‚‚F(2a) distance of 3.830-
(2) Å is too large to be considered as an interaction. As
a consequence of their equatorial and axial positions
within the trigonal bipyramidal Sn configuration, the
Sn(1)-O(1) (2.076(2) Å) and Sn(2)-O(1) (2.038(2) Å)
distances are shorter than the Sn(1)-O(1a) distance of
2.127(2) Å. The Sn-C distances are as expected and
comparable to those of related compounds.3a,b,20
F igu r e 6. General view (SHELXTL-PLUS) of a molecule
showing 30% probability displacement ellipsoids and the
atom numbering (symmetry transformations used to gen-
erate equivalent atoms: a ) -X + 0.5, -Y + 0.5, -Z) for
12.
Con clu sion
Unfortunately, it was not possible to grow single
crystals of 11 suitable for X-ray analysis. However, we
were able to exchange chloride by fluoride in order to
better characterize these systems.
Rea ction of 7 w ith KF /H2O a n d Molecu la r Str u c-
tu r e of th e F lu or in e-Con ta in in g Tetr a or ga n od is-
ta n n oxa n e 12. The reaction of 7 with a large excess
of potassium fluoride in water/diethyl ether afforded 1,3-
bis[bis(trimethylsilyl)methyl]-1,3-difluoro-1,3-distanna-
2-oxacyclohexane dimer (12) as colorless crystals (eq 6)
which have the trans molecular structure in the solid
state (see below).
It is apparent that both the nature of the spacer
linking the ditin precursors and the organo substituent
at tin have a profound influence on the hydrolysis/
oxygen transfer products. For simple precursors such
as RCl2Sn(CH2)3SnCl2R, where R is a sterically nonde-
manding group, the products are double ladders based
on tetrameric aggregation of the ditin precursors. Hy-
drolysis of precursors containing more demanding sub-
stituents such as R ) (SiMe3)2CH leads to equilibria
between monomeric, dimeric, and trimeric aggregates.
Ack n ow led gm en t. We are grateful to the Deutsche
Forschungsgemeinschaft and the Fonds der Chemischen
Industrie for financial support. We thank Mr. J ens
Beckmann for recording the 119Sn MAS spectra. The
Dortmunder Gambrinus Foundation is acknowledged
for making possible a visit of D.D. at Dortmund Uni-
versity.
KF, H O, Et O, 5 d8
2
2
(RCl2Sn)2(CH2)3
-KCl, -HCl
7
{[R(F)Sn(CH2)3Sn(F)R]O}2
(6)
12, R ) (Me3Si)2CH
The 19F and 119Sn NMR spectra of 12 in CDCl3 are
consistent with the presence in solution of both trans
and cis isomers (Chart 3). The ratio of the isomers is
approximately 2:1, but the data do not uniquely identify
each isomer.
Su p p or tin g In for m a tion Ava ila ble: Tables of all coor-
dinates, anisotropic displacement parameters, and geometric
data for 3, 6, 8, 9a , 10, and 12 (29 pages). Ordering informa-
tion is given on any current masthead page.
OM980369L
The positive ion ESMS of 12 in acetonitrile/dichlo-
romethane shows the presence of [12 + H]+ and [12 -
F]+, confirming that the tetratin units are retained in
solution.
The molecular structure of 12 (trans isomer) is shown
in Figure 6. Selected bond lengths and bond angles are
listed in Table 5. Compound 12 is a centrosymmetric
dimer with a center of inversion at (1/4, 1/4, 0). It shows
a ladder-type arrangement comparable with those of
[(R2ClSn)2O]2 (R ) alkyl, aryl)18 and [(tBu2FSn)2O]2,19
the only other known fluoride-containing tetraorgano-
(18) (a) Alleston, D. L.; Davies, A. G.; Hancock, M.; White, R. F. M.
J . Chem. Soc. 1963, 5469. (b) Harrison, P. G.; Begley, M. J .; Molloy,
K. C. J . Organomet. Chem. 1980, 186, 213. (c) Graziani, R.; Casellato,
U.; Plazzogna, G. Acta Crystallogr., Sect. C 1983, C39, 1188. (d) Puff,
H.; Friedrichs, E.; Visel, F. Z. Anorg. Allg. Chem. 1981, 477, 50. (e)
Dakternieks, D.; Gable, R.; Hoskins, B. F. Inorg. Chim. Acta 1984,
85, L43. (f) Vollano, J . F.; Day, R. O.; Holmes, R. R. Organometallics
1984, 3, 745. (g) Dakternieks, D.; J urkschat, K.; van Dreumel, S.;
Tiekink, E. R. T. Inorg. Chem. 1997, 36, 6, 2023.
(19) Beckmann, J .; Biesemans, M.; Hassler, K.; J urkschat, K.;
Martins, J . C., Schu¨rmann, M.; Willem, R. Inorg. Chem., in press.
(20) Raharinirina, A.; Boese, R.; Schmid, G. J . Organomet. Chem.
1990, 395, 39.