Synthesis and structural characterization of carbons-adjacent stannacarboranes of the C2B10 system

Article abstract of DOI:10.1021/om020984w

The chemistry of p-block metallacarboranes of the C₂B₁₀ systems is largely unexplored in comparison with that of s-, d-, and f-block metallacarboranes. This article reports several carbons-adjacent stannacarboranes of the C₂

Full text of DOI:10.1021/om020984w

Organometallics 2003, 22, 1775-1778
1775
Syn th esis a n d Str u ctu r a l Ch a r a cter iza tion of
Ca r bon s-Ad ja cen t Sta n n a ca r bor a n es of th e C B System
2
10
Kit-Hung Wong, Hoi-Shan Chan, and Zuowei Xie*
Department of Chemistry, The Chinese University of Hong Kong,
Shatin, New Territories, Hong Kong, China
Received December 3, 2002
Summary: The chemistry of p-block metallacarboranes
of the C2B10 systems is largely unexplored in comparison
with that of s-, d-, and f-block metallacarboranes. This
article reports several carbons-adjacent stannacarbo-
ranes of the C2B10 system and their chemical properties
for the first time. Reaction of SnCl2 with [{µ-1,2-[o-C6H4-
hedral p-block metallacarboranes are the very recently
reported carbons-apart stannacarboranes of the C2B10
system.
We have recently developed a methodology to prepare
carbons-adjacent carborane anions of the C2B10 system
1
7
by linking the cage carbon atoms together via a short
(
CH2)2]-1,2-C2B10H10}2Na4(THF)6]n gave the Lewis base
18-20
bridge.
The alkali-metal salts of the dianion [{µ-
free stannacarborane {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}-
Sn (1). Recrystallization of 1 from MeCN, THF, and
DME afforded the corresponding Lewis base coordinated
stannacarboranes {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}-
Sn(MeCN) (2), {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}Sn-
1
,2-[o-C6H4(CH2)2]-1,2-C2B10H10}2M4(THF)6]n are useful
synthons for the production of carbons-adjacent lantha-
21
nacarboranes. We have extended our research to
include p-block elements and report herein the synthe-
sis, structural characterization, and Lewis acid proper-
ties of carbons-adjacent stannacarboranes of the C2B10
system.
(
THF)‚THF (3‚THF), and {µ-1,2-[o-C6H4(CH2)2]-1,2-
C2B10H10}Sn(DME) (4), respectively. They were fully
characterized by various spectroscopic data and elemen-
tal analyses. Complexes 2-4 were further confirmed by
single-crystal X-ray analyses.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were performed
under an atmosphere of dry dinitrogen with the rigid exclusion
of air and moisture using standard Schlenk or cannula
techniques, or in a glovebox. THF and n-hexane were freshly
distilled from sodium benzophenone ketyl immediately prior
In tr od u ction
The incorporation of p-block elements in the carbo-
rane cages has been documented. A number of stan-
nacarboranes with or without Lewis base coordination
have been prepared and structurally characterized, in
which the carboranyl ligands are either the C2B4
1
to use. CH
and P , respectively, immediately prior to use. [{µ-1,2-[o-
(CH ]-1,2-C Na (THF) was prepared accord-
3 2 2 2
CN and CH Cl were freshly distilled from CaH
2
O
5
C
6
H
4
2
)
2
2
B
10
H
10
}
2
4
6 n
]
1
-11
or
19
ing to the literature method. All other chemicals were
purchased from either Aldrich or Acros Chemical Co. and used
as received unless otherwise noted. Infrared spectra were
obtained from KBr pellets prepared in the glovebox on a
1
,2,12-15
C2B9
systems. In sharp contrast, the chemistry
of p-block metallacarboranes of the large C2B10 systems
has been virtually unexplored, although the 13-vertex
metallacarboranes of s-, d- and f-block elements are
1
Perkin-Elmer 1600 Fourier transform spectrometer. H and
1
3
1
,16
C NMR spectra were recorded on a Bruker DPX 300
well-known.
The only examples of the supericosa-
1
1
spectrometer at 300.13 and 75.47 MHz, respectively. B and
1
19
Sn NMR spectra were recorded on a Varian Inova 400
*
To whom correspondence should be addressed. Fax: (852)-
6035057. Tel: (852)26096269. E-mail: zxie@cuhk.edu.hk.
1) For reviews, see: (a) Grimes, R. N. In Comprehensive Organo-
metallic Chemistry II; Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.;
Pergamon: New York, 1995; Vol. 1, p 373. (b) Saxena, A. K.; Maguire,
J . A.; Hosmane, N. S. Chem. Rev. 1997, 97, 2421.
2) Cowley, A. H.; Galow, P.; Hosmane, N. S.; J utzi, P.; Norman, N.
C. J . Chem. Soc., Chem. Commun. 1984, 1564.
3) Hosmane, N. S.; Sirmokadam, N. N. Organometallics 1984, 3,
665.
4) Hosmane, N. S.; de Meester, P.; Maldar, N. N.; Potts, S. B.; Chu,
S. S. C. Organometallics 1986, 5, 772.
5) Hosmane, N. S.; Islam, M. S.; Siriwardane, U.; Maguire, J . A.
Organometallics 1987, 6, 2447.
6) Barreto, R. D.; Fehlner, T. P.; Hosmane, N. S. Inorg. Chem. 1988,
7, 453.
7) Siriwardane, U.; Maguire, J . A.; Banewicz, J . J .; Hosmane, N.
S. Organometallics 1989, 8, 2792.
8) Hosmane, N. S.; Fagner, J . S.; Zhu, H.; Siriwardane, U.; Maguire,
J . A.; Zhang, G.; Pinkston, B. S. Organometallics 1989, 8, 1769.
spectrometer at 128.32 and 149.11 MHz, respectively. All
chemical shifts are reported in δ units with references to the
residual protons of the deuterated solvents for proton and
2
(
carbon chemical shifts, to external BF
boron chemical shifts, and to external Me
3
‚OEt
4
2
(0.0 ppm) for
Sn (0.0 ppm) for tin
(
(
(12) Voorhees, R. L.; Rudolph, R. W. J . Am. Chem. Soc. 1969, 91,
2173.
(13) Rudolph, R. W.; Voorhees, R. L.; Cochoy, R. E. J . Am. Chem.
Soc. 1970, 92, 3351.
(14) Chowdhry, V.; Pretzer, W. R.; Rai, D. N.; Rudolph, R. W. J .
Am. Chem. Soc. 1973, 95, 4560.
(15) J utzi, P.; Galow, P.; Abu-Orabi, S.; Arif, A. M.; Cowley, A. H.;
Norman, N. C. Organometallics 1987, 6, 1024.
(16) For reviews, see: (a) Grimes, R. N. Coord. Chem. Rev. 2000,
200/ 202, 773. (b) Saxena, A. K.; Hosmane, N. S. Chem. Rev. 1993, 93,
1081. (c) Xie, Z. Coord. Chem. Rev. 2002, 231, 23. (d) Xie, Z. Acc. Chem.
Res. 2003, 36, 1.
1
(
(
(
2
(
(
(
(
9) Brown, L. D.; Lipscomb, W. N. Inorg. Chem. 1977, 16, 2989.
10) (a) Hosmane, N. S.; J ia, L.; Zhang, H.; Maguire, J . A. Organo-
(17) Wilson, N. M. M.; Ellis, D.; Buoyd, A. S. F.; Giles, B. T.;
Macgregor, S. A.; Rosair, G. M.; Welch, A. J . Chem. Commun. 2002,
464.
(18) Zi, G.; Li, H. W.; Xie, Z. Chem. Commun. 2001, 1110.
(19) Zi, G.; Li, H. W.; Xie, Z. Organometallics 2001, 20, 3836.
(20) Zi, G.; Li, H. W.; Xie, Z. Organometallics 2002, 21, 5415.
(21) Zi, G.; Li, H. W.; Xie, Z. Organometallics 2002, 21, 3470.
metallics 1994, 13, 1411. (b) J ia, L.; Zhang, H.; Hosmane, N. S.
Organometallics 1992, 11, 2957.
(
11) Hosmane, N. S.; Zhang, H.; Maguire, J . A.; Demissie, T.; Oki,
A. R.; Saxena, A.; Lipscomb, W. N. Main Group Met. Chem. 2001, 24,
89.
5
1
0.1021/om020984w CCC: $25.00 © 2003 American Chemical Society
Publication on Web 03/07/2003

1
776 Organometallics, Vol. 22, No. 8, 2003
Notes
Ta ble 1. Cr ysta l Da ta a n d Su m m a r y of Da ta Collection a n d Refin em en t Deta ils for 2-4
2
3‚THF
4
formula
cryst size, mm
fw
C12H21B10NSn
0.40 × 0.35 × 0.20
406.1
C18H34B10O2Sn
0.35 × 0.25 × 0.20
509.2
C14H28B10O2Sn
0.63 × 0.18 × 0.13
455.2
cryst syst
space group
a, Å
b, Å
c, Å
monoclinic
Pn
monoclinic
P21/n
monoclinic
P21/n
7.161(1)
9.514(2)
13.892(3)
97.32(3)
938.7(3)
2
10.298(2)
14.631(3)
16.924(3)
105.80(3)
2453.6(9)
4
10.807(1)
16.965(1)
12.397(1)
105.54(1)
2189.9(2)
4
â, deg
3
V, Å
Z
Dcalcd, Mg/m3
radiation (λ, Å)
θ range, deg
1.437
1.379
1.381
Mo KR (0.710 73)
1.87-25.67
1.055
2.14-25.65
1.352
400
2.09-28.03
1.173
912
-
1
µ, mm
F(000)
1032
no. of obsd rflns
no. of params refnd
goodness of fit
R1
1786
219
1.021
0.034
0.087
3822
282
1.105
0.047
5276
244
0.909
0.048
0.107
wR2
0.141
chemical shifts. Elemental analyses were performed by ME-
DAC Ltd., Brunel University, Middlesex, U.K.
P r ep a r a tion of {µ-1,2-[o-C
(DME) (4). Recrystallization of 1 (203 mg, 0.50 mmol) from
6
H
4
(CH
2
)
2
]-1,2-C
2
B
10
H
10}Sn -
DME (10 mL) afforded 4 as pale yellow crystals (209 mg, 92%).
P r ep a r a t ion of {µ-1,2-[o-C
1). To a clear colorless THF (20 mL) solution of anhydrous
SnCl (189 mg, 1.00 mmol) was slowly added a THF (25 mL)
solution of [{µ-1,2-[o-C (CH ]-1,2-C Na (THF)
508 mg, 0.50 mmol) at -78 °C with stirring. The reaction
mixture was slowly warmed to room temperature and then
stirred overnight. After removal of the dark precipitate, the
clear pale yellow solution was concentrated to give a yellow
6 4 2 2 2 10
H (CH ) ]-1,2-C B H 10}Sn
1
H NMR (CD
5.9 Hz, C
Hz, C (CH
28.5, 126.8 (aryl C), 72.1 (DME), 59.1 (DME), 50.9 (C
CH Cl
); cage carbons were not observed. 11B NMR (CD
δ 8.67 (2), 6.83 (2), 6.20 (2), 2.59 (1), -2.01 (3). Sn NMR
): δ -380.5. IR (KBr, cm ): ν 3010 (w), 2958 (m), 2542
s), 2395 (s), 1608 (s), 1447 (m), 1260 (m), 1018 (s), 803 (s).
Sn: C, 36.94; H, 6.20. Found: C,
2
Cl
(CH
), 3.35 (s, 6H, DME). C NMR (CD
2
): δ 7.26 (m, 4H, aryl H), 4.17 (d, 2H, J )
(
1
6
H
4
2 2
)
), 3.51 (s, 4H, DME), 3.49 (d, 2H, J ) 15.9
2
1
3
6
H
4
2
)
2
2 2
Cl ): δ
6
H
4
2
)
2
2
B
10
H
10
}
2
4
6 n
]
1
6 4
H -
(
(
2
)
2
2
2
):
1
19
-1
2 2
(CD Cl
(
solid, which was extracted with CH
Cl solutions were combined and concentrated to about 10 mL.
was isolated as pale yellow crystals, after the solution stood
2
Cl
2
(8 mL × 3). The CH
2
-
Anal. Calcd for C14
6.72; H, 6.02.
X-r a y Str u ctu r e Deter m in a tion . All single crystals were
immersed in Paratone-N oil and sealed under N in thin-walled
28 10 2
H B O
2
3
1
1
at 20 °C for 1 week (171 mg, 42%). H NMR (CD
2
Cl
(CH
Cl ): δ 135.5,
2 2
) ); cage carbons were not
2
): δ 7.29
(
m, 4H, aryl H), 4.23 (d, 2H, J ) 15.9 Hz, C
6
H
2
4
2 2
)
), 3.46
2
1
3
glass capillaries. Data were collected at 293 K on a Bruker
SMART 1000 CCD diffractometer using Mo KR radiation. An
empirical absorption correction was applied using the SADABS
program.22 All structures were solved by direct methods and
subsequent Fourier difference techniques and refined aniso-
tropically for all non-hydrogen atoms by full-matrix least
(d, 2H, J ) 15.9 Hz, C
6
H
4
(CH
2
)
4
2
). C NMR (CD
(CH
): δ 9.25 (2), 7.28 (4), 3.75 (1), -0.63
2
1
28.8, 126.8 (aryl C), 50.8 (C
6
H
1
1
observed. B NMR (CD
2
Cl
2
1
19
-1
(
2 2
3). Sn NMR (CD Cl ): δ -363.8. IR (KBr, cm ): ν 3006
(w), 2952 (w), 2529 (s), 2395 (m), 1596 (m), 1448 (w), 1260 (m),
011 (m). Anal. Calcd for C10 18Sn: C, 32.90; H, 4.97.
1
10
B H
2
squares calculations on F using the SHELXTL program
Found: C, 33.28; H, 5.29.
package.23 For the noncentrosymmetric structure 2, the Flack
6 4 2 2 2 10
P r ep a r a tion of {µ-1,2-[o-C H (CH ) ]-1,2-C B H10}Sn -
MeCN) (2). Recrystallization of 1 (203 mg, 0.50 mmol) from
2
4
parameter x ) 0.45(8) after refinement. Most of the carborane
hydrogen atoms were located from difference Fourier synthe-
ses. All other hydrogen atoms were geometrically fixed using
the riding model. Crystal data and details of data collection
and structure refinements are given in Table 1. Further details
are included in the Supporting Information.
(
MeCN (10 mL) at 20 °C afforded 2 as pale yellow crystals (181
1
mg, 89%). H NMR (CD
(CH
), 1.60 (s, 3H, CH
28.8, 126.9 (aryl C), 120.5 (CH
2
Cl
2
2
): δ 7.29 (m, 4H, aryl H), 4.23 (d,
2
H, J ) 15.9 Hz, C
6
H
4
)
2
), 3.45 (d, 2H, J ) 15.9 Hz, C H -
6 4
1
3
(CH
2
)
2
3
CN). C NMR (CD
2
Cl
2
): δ 135.5,
(CH ), 1.3
Cl ):
δ 8.85 (2), 6.77 (4), 3.22 (1), -0.56 (1), -1.69 (2). Sn NMR
1
3
CN), 50.8 (C
6
H
4
2 2
)
1
1
(CH
3
CN); cage carbons were not observed. B NMR (CD
2
2
1
19
Resu lts a n d Discu ssion
-
1
(CD
2 2
Cl ): δ -364.2. IR (KBr, cm ): ν 3010 (w), 2959 (m), 2529
s), 2395 (s), 2307 (m), 1608 (m), 1260 (s), 1098 (s), 1024 (s),
Syn th esis. Salt metathesis is a general method for
the production of metallacarboranes. Treatment of
SnCl2 with 0.5 equiv of [{µ-1,2-[o-C6H4(CH2)2]-1,2-
C2B10H10}2Na4(THF)6]n in THF in the temperature
range -78 to 0 °C gave, after recrystallization from CH2-
Cl2, an unsolvated carbons-adjacent stannacarborane of
the C B system, {µ-1,2-[o-C H (CH ) ]-1,2-C B H }-
(
8
3
03 (s). Anal. Calcd for C12
.45. Found: C, 35.23; H, 5.01; N, 3.65.
P r ep a r a tion of {µ-1,2-[o-C (CH
THF )‚THF (3‚THF ). Recrystallization of 1 (203 mg, 0.50
mmol) from THF (10 mL) at 20 °C afforded 3‚THF as pale
21
H B10NSn: C, 35.49; H, 5.21; N,
6
H
4
2 2 2 10
) ]-1,2-C B H10}Sn -
(
1
yellow crystals (219 mg, 86%). H NMR (CD
4
8
2
Cl
(CH
(CH ), 1.83 (m, 8H,
): δ 135.5, 128.7, 126.8 (aryl C), 68.4
2 2
) ), 26.1 (THF); cage carbons were not
2
): δ 7.29 (m,
2
10
6
4
2 2
2
10 10
H, aryl H), 4.21 (d, 2H, J ) 15.9 Hz, C
H, THF), 3.47 (d, 2H, J ) 15.9 Hz, C
6
H
4
2
)
2
), 3.69 (m,
Sn, in 42% isolated yield. Temperature control is very
important to this reaction. Otherwise, a redox reaction
6
H
4
2 2
)
1
3
THF). C NMR (CD
THF), 50.9 (C (CH
observed. B NMR (CD
2 2
Cl
(
6
H
4
(22) Sheldrick, G. M. SADABS: Program for Empirical Absorption
1
1
2
Cl
2
): δ 8.93 (2), 7.03 (2), 6.55 (2), 3.38
Correction of Area Detector Data; University of G o¨ ttingen, G o¨ ttingen,
Germany, 1996.
1), -1.14 (3). 1 Sn NMR (CD
19
-1
(
2 2
Cl ): δ -364.4. IR (KBr, cm ):
(23) Sheldrick, G. M. SHELXTL 5.10 for Windows NT: Structure
ν 3020 (w), 2959 (m), 2529 (s), 2395 (m), 1622 (m), 1253 (s),
098 (m), 1025 (s), 803 (s). Anal. Calcd for C16
0.5 THF): C, 40.61; H, 6.39. Found: C, 40.57; H, 6.03.
Determination Software Programs; Bruker Analytical X-ray Systems,
Inc., Madison, WI, 1997.
(24) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
1
10 30
B H O1.5Sn (3
+

Notes
Organometallics, Vol. 22, No. 8, 2003 1777
Sch em e 1
F igu r e 1. Molecular structure of {µ-1,2-[o-C
,2-C 10}Sn(MeCN) (2).
6
H
4
(CH
2
)
2
]-
1
2 10
B H
occurred leading to the formation of the neutral cage
carbons-linked o-carborane µ-1,2-[o-C6H4(CH2)2]-1,2-
C2B10H10 and tin metal, since {µ-1,2-[o-C6H4(CH2)2]-1,2-
C2B10H10}2 is known to be a strong reducing agent.
-
21
1
1
This process can be closely monitored by B NMR
spectroscopy.
Complex 1 is a Lewis acid which can accept lone pairs
from various donor solvents to form Lewis acid-base
adducts. Recrystallization of 1 from MeCN, THF, and
DME afforded the corresponding Lewis base coordinated
stannacarboranes {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}-
Sn(MeCN) (2), {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}Sn-
F igu r e 2. Molecular structure of {µ-1,2-[o-C
,2-C 10}Sn(THF) (3).
6 4 2 2
H (CH ) ]-
1
2 10
B H
(
(
THF) (3), and {µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}Sn-
DME) (4), respectively. Scheme 1 outlines the trans-
formations mentioned above.
Complexes 1-4 are sensitive to moisture and air. The
B NMR data indicate that they slowly decompose into
1
1
the neutral carborane µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10
and tin metal upon heating in solution.
The composition and the carborane-to-solvent ratio
1
13
of complexes 1-4 are supported by the H and C NMR
spectroscopic data. Their 11B NMR spectra are very
similar and exhibit a 2:2:2:1:3 splitting pattern. The
solid-state IR spectra all show a strong broad absorption
-
1
119
at ∼2530 cm . The Sn chemical shifts in CD2Cl2 are
-
363.8, -364.2, -364.4, and -380.5 ppm for 1-4,
F igu r e 3. Molecular structure of {µ-1,2-[o-C
1,2-C 10}Sn(DME) (4).
6 4 2 2
H (CH ) ]-
respectively. This trend is consistent with the increasing
donor ability of the solvents going from CH2Cl2 through
MeCN and THF to DME, although the differences are
not very significant. These measured data can be
2 10
B H
Na4(THF)6]n.19 These structures show an increased slip
distortion of tin toward the boron side of the C2B4
6
7
compared to the value of -431 ppm reported for (η -
bonding face on complexation with the stronger base,
C2B10H12)Sn.17
119
which is consistent with the
Sn NMR data. It is
Cr ysta l Str u ctu r es. The solid-state structures of
-4 have been confirmed by single-crystal X-ray analy-
reasonable to suggest that the unsolvated stannacar-
2
borane 1 may adopt a more symmetric structure, like
6
17
ses and are shown in Figures 1-3, respectively. They
all adopt monomeric structures, and 3 shows one THF
of solvation. The selected bond distances are compiled
in Table 2.
The geometries of the carboranyl ligands in 2-4 are
very similar. The bond distances and angles are very
close to those in [{µ-1,2-[o-C6H4(CH2)2]-1,2-C2B10H10}2-
the carbons-apart (η -Me2C2B10H10)Sn.
The Sn-cage atom distances (see Table 2) fall in the
range 2.4-2.8 Å, which is normally observed in stanna-
1
b
carboranes. To make a comparison between carbons-
apart and carbons-adjacent stannacarboranes of the
C2B10 systems, the value of the longest Sn-cage atom
6
distance of 2.68 Å in (η -Me2C2B10H10)Sn is taken as a

1
778 Organometallics, Vol. 22, No. 8, 2003
Notes
Ta ble 2. Selected Bon d Len gth sa
Con clu sion
2
3‚THF
4
Several carbons-adjacent stannacarboranes of the
C2B10 system have been prepared and structurally
characterized. They represent the first examples of
carbons-adjacent p-block metallacarboranes of the C2B10
system. The interactions between the tin atom and
carborane are very diverse and dependent upon the
basicity of the coordinated bases. A stronger base leads
to an increased slip distortion of the tin from the center
of the C2B4 bonding face of the carboranyl ligand.
Sn(1)-C(1)
Sn(1)-C(2)
Sn(1)-B(3)
Sn(1)-B(4)
Sn(1)-B(5)
Sn(1)-B(6)
Sn(1)-X(N,O)
2.668(6)
2.680(6)
2.676(7)
2.431(7)
2.450(8)
2.680(9)
2.623(8)
2.745(5)
2.705(5)
2.658(5)
2.407(5)
2.506(5)
2.795(5)
2.439(3)
2.745(5)
2.692(5)
2.697(5)
2.455(5)
2.456(5)
2.756(5)
2.716(5)
2
.660(5)
a
All distances are in Å.
Ack n ow led gm en t. The work described in this paper
was supported by a grant from the Research Grants
Council of the Hong Kong Special Administration
Region (Project No. CUHK 4026/02P).
cutoff point.17 Dashed lines are drawn in Figures 1-3
when the Sn-cage atom distances are longer than 2.68
Å. One might suggest that the apical tin atom could be
6
considered as η bonded to the C2B4 face of the carbo-
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal-
lographic data and data collection details, atomic coordinates,
bond distances and angles, anisotropic thermal parameters,
and hydrogen atom coordinates and figures giving atom-
numbering schemes for complexes 2-4; data are also available
as CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
3
2
rane fragment in 2, whereas the tin is η and η bonded
to the carborane in 3 and 4, respectively; these notions
are supported by the 1 Sn NMR data. Similar results
19
1
have also been observed in the C2B4 and C2B9 systems.
These results show that the Lewis acid properties of the
tin atom in stannacarboranes of the C2B4, C2B9, and
C2B10 systems are very similar.
OM020984W