Synthesis and structures of some trisorganylstannyl boranes and triorganylstannyl borates

Article abstract of DOI:10.1002/1521-3749(200104)627:4<789::AID-ZAAC789>3.0.CO;2-U

New stannylboranes were prepared from tetramethylpiperidino dichloroborane or B-bromo-pentamethylborazine with lithium triorganylstannides LiSnR₃. Only double stannylation was possible with tmpBCl₂ and LiSnMe₃, while tmpBCl(SnPh₃) was obtained by employing LiSnPh₃. This chloride reacted with LiGePh₃ to the stannyl germyl borane tmpB(GePh₃)(SnPh₃). On the other hand, PhMeNBCl₂ and an excess of LiSnMe₃ gave the borate Li[B(NMePh)(SnMe₃)₃], which was isolated as a solvate with 4 molecules of THF. The compound is present in the solid state as a solvent separated ion pair. The borate Li(H₃BSnMe₃) · 2 THF is dimeric in the solid state. Dimerization occurs via two single Li-H-B bridges and a Li-H(B)-Li bridge. The B-Sn bonds in the borates are practically of the same lengths as those in the boranes. In solution all BH bonds of this trihydridoborate are equivalent. Wiley-VCH Verlag GmbH, 2001.

Full text of DOI:10.1002/1521-3749(200104)627:4<789::AID-ZAAC789>3.0.CO;2-U

Synthesis and Structures of some Trisorganylstannyl Boranes
and Triorganylstannyl Borates [1]
Tassilo Habereder und Heinrich NoÈth*
MuÈnchen, Department of Chemistry der UniversitaÈt
Received January 10th, 2001.
Professor Josef Goubeau in memoriam
Abstract. New stannylboranes were prepared from tetra-
methylpiperidino dichloroborane or B-bromo-pentamethyl-
borazine with lithium triorganylstannides LiSnR3. Only doub-
le stannylation was possible with tmpBCl2 and LiSnMe3,
while tmpBCl,SnPh3) was obtained by employing LiSnPh3.
This chloride reacted with LiGePh3 to the stannyl germyl
borane tmpB,GePh3),SnPh3). On the other hand,
PhMeNBCl2 and an excess of LiSnMe3 gave the borate
Li[B,NMePh),SnMe3)3], which was isolated as a solvate
with 4 molecules of THF. The compound is present in the
solid state as a solvent separated ion pair. The borate
Li,H3BSnMe3) ´ 2 THF is dimeric in the solid state.
Dimerization occurs via two single Li±H±B bridges and a
Li±H,B)±Li bridge. The B±Sn bonds in the borates are prac-
tically of the same lengths as those in the boranes. In solu-
tion all BH bonds of this trihydridoborate are equivalent.
Keywords: Boron; Tin; Stannyl boranes; NMR spectroscopy;
Crystal structures
Synthese und Strukturen einiger Triorganylstannylborane
und Triorganylstannylborate
InhaltsuÈbersicht. Neue Stannylborane wurden aus Tetra-
methylpiperidino-dichlorboran oder B-Bromopentamethyl-
borazin mit Lithium-Triorganylstanniden LiSnR3 hergestellt.
Doppelte Stannylierung war nur mit tmpBCl2 und LiSnMe3
moÈglich, waÈhrend tmpBCl,SnPh3) mit LiSnPh3 zugaÈnglich
war. Dieses Chlorid reagierte mit LiGePh3 zu dem Stannyl-
Germyl-Boran tmpB,GePh3),SnPh3). Andererseits ergab
die Reaktion von PhMeNBCl2 mit uÈberschuÈssigem LiSnMe3
das Borat Li[B,NMePh),SnMe3)3], das als Solvat mit vier
MolekuÈlen THF isoliert wurde. Die Verbindung liegt im fe-
sten Zustand als Salz vor. Das Borat Li,H3BSnMe3) ´ 2 THF
ist im festen Zustand dimer. Die Dimerisierung erfolgt uÈber
zwei Li±H±B- und eine Li±H,B)±Li-BruÈcke. Die B±Sn-Bin-
dungen in den Boraten sind praktisch genauso lang wie in
den Boranen. In LoÈsung sind alle B±H-Bindungen des Tri-
hydridoborats aÈquivalent.
Introduction
distance with increasing coordination number at the
boron atom. In attempts to check this observation we
decided to study the molecular structures of additional
stannylboranes and stannylborates by X-ray crystallo-
graphy in order to obtain more molecular parameters
for comparison.
In spite of their favorable synthetic potential [2], stan-
nylboranes have been rather poorly investigated so
far, especially concerning their molecular structures.
Although stannylboranes are known since 1964 [3] the
first structurally characterized stannylborane was 1,2-
bis[,diisopropylamino-trimethylstannyl)boryl]ethene
which was described by Siebert et al. in 1994 [4]. It
was obtained from lithium trimethylstannide and 1,2-
bis,diisopropylamino-chloro-boryl)ethene. Recently, we
described the molecular structures of several bis-
,amino)stannylboranes [5] as well those of stannyl-
diboranes,4) and stannyl-triboranes,5) [6]. In this con-
text we observed an unusual shortening of the B±Sn
Results and Discussion
The most straightforward pathway for building B±Sn
bonds are salt elimination reactions between boron
halides and alkali metal organylstannides. As the lat-
ter compounds have to be prepared in ether as sol-
vents particularly in THF [7] only boron compounds
can be employed, which will not induce ether cleavage
reactions, at least not at low temperatures. In order to
prevent ether cleavage we used mainly boron com-
pounds of low Lewis acidity, e. g. aminoboron chlor-
ides. For a successful synthesis not only the appro-
priate boron compound had to be selected but also
the proper alkali metal triorganylstannide. Thus,
* Prof. Dr. H. NoÈth,
Department of Chemistry, University of Munich,
Butenandtstr. 5±13,
D-81377 MuÈnchen
E-mail: H.Noeth@lrz.uni-muenchen.de
Z. Anorg. Allg. Chem. 2001, 627, 789±796
Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0044±2313/01/627789±796 $ 17.50+.50/0
789

T. Habereder, H. NoÈth
Me3SnLi was found to be much more reactive than
Ph3SnLi. For example the reaction of the bromo-bora-
zines 1 a and 1 b [8] yielded the stannyl-borazines 2 a
and 2 b, whereas no reaction occurred with Ph3SnLi
,s. Equ. ,1)).
boranes. For example, the reaction of 4 with Ph3GeLi
allows the synthesis of the stannyl-germyl-substituted
borane 5. This compound is the first borane, which
carries two different heavier elements of the 14th-main
group. On the other hand, the analogous reaction of 4
with Ph3SnLi failed to generate tmpB,SnPh3)2. This
result provides evidence that steric factors play an im-
portant role in these substitution reactions.
Compounds 4 and 5 were isolated as single crystals.
Their molecular structures could be determined by X-
ray structure analysis. Compound 3 was obtained as a
crystalline material too, but the crystals were not
suitable for an X-ray structure analysis.
The higher reactivity of Me3SnLi was further de-
monstrated by the reaction of Me3SnLi with the steri-
cally less crowded aminoborane Ph,Me)NBCl2 [11].
This time, not only the expected double substitution
by a stannyl group occurred, but even a third
equivalent of Me3SnLi was added and the borate
Li[Ph,Me)NB,SnMe3)3], 6, generated. Compounds si-
The different reactivity of Ph3SnLi compared to
Me3SnLi becomes also apparent in their reactions
with tmpBCl2 ,tmp = 2,2,6,6-tetramethylpiperidino
group) [9]. When Me3SnLi was used the bisstannyl
compound 3 was formed as a single product [10]. At-
tempts to synthesize the monostannyl derivative
tmpB,Cl)SnMe3 failed. Even by slowly adding Me3SnLi
to an excess of tmpBCl2 at low temperatures, 3 is
the only product. In contrast, the preparation of
the triphenylstannyl-substituted borane 4 was easily
achieved regardless of the reaction conditions. We ob-
tained 4 even when we added tmpBCl2 to Ph3SnLi at
ambient temperature. The stannylborane 4 bears a re-
active halide substituent and is, therefore, itself a suit-
able starting material for preparing still other stannyl-
ꢀ1†
ꢀ2†
ꢀ3†
790
Z. Anorg. Allg. Chem. 2001, 627, 789±796

Synthesis and Structures of some Trisorganylstannylboranes and Triorganylstannyl-borates
milar to 6 are scarce. That closest to 6 are the alkali
metal triorganylamidoborates M,R3BNR'2) ,N R'2 =
NH2, NHEt) [12]. Only few other monoalkylaminobo-
rates have been reported to our knowledge [13] while
dialkylamino and particularly pyrazolylborates are
well investigated [14]. The latter are much more stable
than the tris,stannylamino)borate 6. Decomposition
was observed on redissolving 6 in hexane as well as on
gentle heating. Among other compounds, the bis,stan-
nyl)aminoborane 7 was generated. Obviously, one
Me3Sn group is bound rather weakly to the boron
moiety ,s. Equ. ,2), ,3)).
the proposed structures. Once again these resonances
are at lower field compared with analogous silicon
and germanium compounds [18]. For the bis,stannyl)-
borane 3, a 11B NMR signal at d = 68.4 and a
119Sn NMR signal at d = ±146 was found. The
11B NMR signal is deshielded with respect to amino-
diorganyl boranes [16]. The symmetry of compound 3
1
allowed the determination of the JBSn coupling con-
stant [1JBSn = 650 Hz]. The NMR data for compound 7
are very similar to those of 3: the 11B signal appears
1
at d = 71.6 ,d, JBSn = 650 Hz).
Of special interest are the NMR data for the tris-
A
stannylborate which decomposes on gentle
,stannyl)borate 6. Its 11B NMR shows a quartet at
1
warming is Li,H3BSnMe3) which is readily formed in
the reaction of Me3SnLi with BH3*THF [15]. As no
X-ray structure of this borate is known, we repro-
duced the synthesis. However, we isolated the com-
pound as the bis-THF adduct [16] and not as the re-
ported mono-THF adduct [15]. The trihydridoborate 8
was crystallized from hexane, and completely charac-
terized. To investigate, whether the Me3Sn group of 8
or its hydrides are more reactive we treated 8 with
bromocatecholatoborane CatBBr ,Cat = catecholate2±).
Only the formation of CatBH was observed but no
CatBSnMe3. On the other hand we found no evidence
in the 11B NMR spectrum for the formation of a tri-
methylstannyl borane 9. This compound may de-
compose with formation of trimethylstannane and a
polyboron hydride. Because we did not record the
119Sn NMR spectrum we have no evidence for the
presence of Me3SnH in the solution. Thus, the borate
8 can be regarded as a hydride-transfer agent. As 8 is
highly reactive and soluble in hexane one can imagine
that 8 may find applications in organic synthesis.
d11B = ±13.1 ,d, JBSn = 580 Hz). The 119Sn NMR sig-
nal appears as a 1 : 1 : 1 : 1 quartet at d119Sn = ±42
,1JBSn = 580 Hz). The value of the coupling-constant is
smaller than observed for those of stannylboranes
with tricoordinated boron atoms. This can be ex-
plained by a decreased s-orbital participation of the
B±Sn bonds. Informative is also the 13C NMR spec-
trum: the C atoms of the Me3Sn-groups not only show
1JCSn-coupling ,250 Hz), but also that the nine methyl
groups attached to the three tin atoms are chemically
equivalent. For the PhNgroup five different signals
1
were found in the H and the 13C NMR spectra indi-
cating hindered rotation about the N±C,Ph) bond.
This is caused by a strong p-interaction between the N
atom and the Ph group.
The 11B NMR spectrum of compound 8 [d11B =
42.0] is almost identical to the monosilyl and mono-
germyl trihydridoborates Li,Me3EBH3) [15]. The
observed coupling patterns and coupling constants ±
1
1
doublet of quartet with JBSn = 598 Hz and JBH
=
84 Hz ± correspond fairly well with previous data [19].
In solution, all hydrogen atoms bound to the boron
atom are magnetically and chemically equivalent, in
spite of the fact that this is not the case in the solid
state ,v. i.). The IR spectrum of 8 shows two strong
BH3 stretching bands at 2293 ,vst) and 2267 ,vst) cm±1
for the antisymmetric and the symmetric stretching BH3
vibrations. The IR spectrum, therefore, is consistent
with local C3V symmetry for the Me3SnBH3 anion.
NMR and IR Spectra
The 11B NMR spectra of the two borazines 2 a and 2 b
are practically identical. For both compounds two sets
of signals in a 2 : 1 ratio were found [2 a: d11B = 37.4,
1
2 B), 44.7 ,d, JB,Sn = 950 Hz, 1 B), 2 b: d11B = 37.8
1
,2 B), 44.7 ,d, JB,Sn = 960 Hz)]. The resonances of the
boron atoms attached to the Me3Sn-groups appear as
doublets due to B, Sn coupling, and this proves the
presence of B±Sn bonds. These boron nuclei are sig-
nificantly deshielded compared with the boron atoms
in hexaorganylborazines ,d = 35.8 for ,MeBNMe)3
and 36.0 for ,MeBNiPr)3 [17], even more than the
analogous Ph3Ge-substitued borazines [18], where sig-
nals at d11B = 39.3 ,R = Me) and d11B = 41.4 ,R = iPr)
were found.
Molecular Structures in the Solid State
The structures of compound 4 and 5 are both influ-
enced by the presence of the bulky tmp ligand ,Fig-
ures 1 and 2). To meet with the steric requirements in
these compounds, the tmp ligands are twisted about
the BNbonds. This results in interplanar angles of
22.4° ,4) and 33.5° ,5) for the planes C2N/BClSn and
Due to the low symmetry of the aminoboranes 4
C2N/BGeSn, respectively. The B±N distances in 4 and
1
Ê
and 5, we were unable to determine the JBSn coupling
5
are of equal lengths [4: 1.387,4) A and 5:
Ê
constants for these compounds neither from the
11B NMR spectrum nor from the 119Sn NMR spec-
trum. Nevertheless, the observed 11B NMR chemical
shifts [4: d11B = 50.1, 5: d11B = 70.0] are consistent with
1.387,5) A]. They are rather short in spite of the non-
coplanar orientation of the boron and the nitrogen
bonding planes. Therefore, the B±Nbonds have still
considerable double bond character. The steric de-
Z. Anorg. Allg. Chem. 2001, 627, 789±796
791

T. Habereder, H. NoÈth
mand of the tmp group can also be derived from
the wide bond angles found at the boron atoms: [5:
N,1)±B,1)±Ge,1) = 129.8,3), N,1)±B,1)±Sn,1) = 124.9,3)
and Ge,1)±B,1)±Sn,1) = 105.3,2)]. Especially the
small Ge±B±Sn angle is striking. The smaller N±B±Sn
bond angle compared with the wider N±B±Ge bond
angle is indicative for the greater steric effect of the
triphenylgermyl group which is due to the shorter me-
tal boron distance compared to the Sn±B bond. To
cope with the space available and in order to mini-
mize the steric interactions between the substituent
the phenyls of the Ph3Ge-group and the Ph3Sn-group
are arranged in a type of staggered conformation ,see
Fig. 3 Molecular structure of 6 in the crystal; thermal ellip-
soids are shown at a 25% probability level. The carbon
atoms of the THF molecules and all hydrogen atoms are
Ê
omitted for clarity. Selected atom distances/A and bond an-
gles/°:
Sn1±B1 2.289,7), Sn2±B1 2.296,6), Sn3±B1 2.291,8), N1±B1 1.545,8),
N1±C1 1.442 ,7), N1±C2 1.379,7), Sn1±B1±Sn2 100.8,3), Sn1±B1±Sn3
107.6,3), Sn2±B1±Sn3 104.9,3), N1±B1±Sn1 121.8,5), N1±B1±Sn2
111.6,4), N1±B1±Sn3 108.7,4), C1±N1±C3 114.3,5), C1±N1±B1 120.2,5),
C1±N1±B2 124.6,5).
Fig. 1 Molecular structure of 4 in the crystal; thermal ellip-
soids are shown on a 25% probability level. Hydrogen atoms
Ê
are omitted for clarity. Selected atom distances/A and bond
angles/°:
Sn1±B1 2.277,4), Cl1±B1 1.834,3), N1±B1 1.387,4), N1±B1±Cl1 121.4,2),
N1±B1±Sn1 136.9,2), Cl1±B1±Sn1 101.7,2).
Fig. 4 Molecular structure of 8 in the crystal; thermal ellip-
soids are shown at a 25% probabilty level. One of the two
independent molecules is depicted. All hydrogen atoms at-
tached to carbon atoms are omitted for clarity. Selected
Fig. 2 Molecular structure of 5 in the crystal; thermal ellip-
soids are shown at a 25% probability level. Hydrogen atoms
Ê
are omitted for clarity. Selected atom distances/A and bond
angles/°:
Ê
atom distances/A and bond angles/°:
Sn1±B1 2.316,5), Ge1±B1 2.143,4), N1±B1 1.387,5), C10±Sn1±C22 102.1,1),
C10±Sn1±C16 100.7,2), C22±Sn1±C16 103.8,2), C10±C34±Ge1±C28
102.8,2), C40±Ge1±B1 111.4,2), C34±Ge1±B1 99.5,2), C28±Ge1±B1
124.4,2), N1±B1±Ge1 129.8,3), N1±B1±Sn1 124.9,3), Ge1±B1±Sn1 105.3,2).
Sn1±B1 2.254,6), Sn2±B2 2.246,5), B1±H1 1.15,2), B1±H2 1.13,3), B1±H3
1.32,3), B1±Li1 2.46,1), Li1±O2 1.93,1). Land the Li1±O2 1.92,1),
Sn1±B1±Li1 125.3,3).
792
Z. Anorg. Allg. Chem. 2001, 627, 789±796

Synthesis and Structures of some Trisorganylstannylboranes and Triorganylstannyl-borates
Table 1 Crystallographic data and data referring to data collection and refinement
Compound
4
5
6
8
Chem. formula
Form. wght.
C45H48BGeNSn
804.93
C27H33BClNSn
536.49
C32H59BLiNO4Sn3
895.62
C30H78B2Li2O6Sn2
807.80
Cryst. size/mm
Cryst. system
Space group
0.20 ´ 0.20 ´ 0.30
triclinic
P1
0.05 ´ 0.20 ´ 0.20
monoclinic
P2,1)/c
8.68180,10)
15.8320,2)
18.8794,2)
90.00
96.63
90.00
2577.62,5)
4
1.382
0.30 ´ 0.30 ´ 0.30
monoclinic
P2,1)/n
18.3180,13)
12.8073,10)
18.5683,13)
90.00
101.197,2)
90.00
4273.3,5)
4
0.20 ´ 0.20 ´ 0.30
monoclinic
P2,1)/n
16.5711,13)
12.4142,9)
17.4044,13)
90.00
108.443,1)
90.00
3396.5,4)
4
Ê
a/A
10.6028,3)
12.7814,3)
15.4537,4)
90.790,1)
90.504,1)
110.120,1)
1966.07,9)
2
Ê
b/A
Ê
c/A
a/°
b/°
c/°
3
Ê
V/A
Z
q,calcd.)/Mg/m3
l/mm±1
1.360
1.431
1.392
1.769
1.580
1.511
1.109
F,000)
824
1096
1792
1688
Index range
±13 £ h £ 13
±17 £ k £ 12
±19 £ l £ 19
58.22
±10 £ h £ 10
±18 £ k £ 18
±22 £ l £ 18
49.42
±23 £ h £ 23
±15 £ k £ 16
±23 £ l £ 23
57.64
±21 £ h £ 21
±15 £ k £ 15
±22 £ l £ 22
58.54
2 h/°
Temp/K
193
193
183,2)
183
Refl. collected
Refl. unique
Refl. observed ,4 s)
R ,int.)
11151
6039
5320
0.0153
12129
3998
3349
0.0249
24371
7484
5294
0.0312
19140
6675
4889
0.0756
No. variables
Weighting schemea) x/y
GOOF
446
0.0615/4.0935
1.006
284
0.0130/2.2452
1.096
408
0.081/3.989
1.029
301
0.065/4.304
1.133
Final R ,4r)
0.0355
0.0281
0.0463
0.0495
Final wR2
Larg. res. peak/e/A
0.1002
1.168
0.0529
0.355
0.1264
0.920
0.1421
0.846
3
Ê
a)
w±1 = s2F2o + ,xP)2 + yP; P = ,Fo2 + 2 F2c)/3
Ê
figure 2). The Sn±B-bond in 4 is 2.277,4) A long and
nated boron atoms. The B±Nbond length ,B1±N1 =
1.545,8) A) is consistent with a B±Nsingle bond to a
Ê
Ê
increases to 2.316,5) A in 5. These values correspond
well with those determined by Siebert et al. [4] for al-
tetracoordinated boron atom. The missing p-interac-
tion between the boron and the nitrogen atom is com-
pensated by a strong p-interaction between the Nand
the ipso-C atom of the phenyl group. This can be
readily seen from the short N1±C2 bond length
,1.379,7) A) as well as from the almost planar coordi-
nation at the Natom ,angle sum = 359.1 °).
Ê
kyl substituted amino,stannyl)boranes [2.27,2) A±
Ê
2.323,7) A]. The shorter B±Sn bond lengths in 4 can
be explained by the inductive effect of the Cl atom to
which a steric relief may contribute. Compound 5
shares three space demanding groups around its boron
atom. The B±Ge distance in 5 comprises a fairly long
Ê
Ê
B±Ge bond [2.143,4) A] similar to the B±Ge-bond
The stannyltrihydridoborate 8 is dimeric in the solid
state as two molecules are connected via Li±H±B-
bridges ,Fig. 4). Two independent molecules were
found in the unit cell. However, the structural para-
meter of the two molecules are not distinctively differ-
ent. Therefore, only one molecule will be described
length found for tmpB,GePh3)2 [18].
The tristannylborate 6 which was isolated as
[Li,THF)]4 [,Me3Sn)3BNMePh] is present as a solvent
separated ion pair ,see figure 3). The Li cation is al-
most perfectly surrounded tetrahedrally by the oxygen
atoms of the THF molecules. Its structures fits with
those reported in the literature [20]. More interesting
is the anionic part. The boron atom resides in a slightly
distorted tetrahedral environment. The Sn±B±Sn bond
angles show an average value of 104.4,3)°, whereas
the average N±B±Sn angle is 114.0,3)°. This indicates,
that the methylanilino ligand demands more space
than the trimethylstannyl groups, a result of the com-
parably short B±Nbond. The B±Sn bond is on aver-
1
2
here. The BH3 groups show a 2 l1 , l1 -coordination,
e. g. two hydrogen bridges to two different Li ions and
one H atom bridging to two Li atoms. This coordina-
tion type is also realized for the analogous germanium
compound [Li,py)2,H3BGePh3)]2 [18]. Consistent with
the coordination type of the BH3 group the B±Li dis-
Ê
tance is short with 2.46,1) A and the Li±B±Sn angle
quite open with 125.3,3)°. The Li atoms are hexacoor-
dinated by two oxygen atoms and by four hydrogen
atoms. The hydrogen atoms attached to the boron
atom were located in the Fourier map. Due to the
high electron density at the Sn atom, the determina-
tion of these hydrogen positions is not very accurate.
Ê
age 2.293,6) A long. In spite of the tetracoordination
of the boron atom and the presence of three tri-
methylstannyl groups the Sn±B bonds in 6 are not
longer than those found for 4 and 5 with its tricoordi-
Z. Anorg. Allg. Chem. 2001, 627, 789±796
793

T. Habereder, H. NoÈth
Reaction of triphenylstannyl lithium with B-bromo-penta-
methylborazine: Ph3SnLi [23] ,1.2 mmol) was prepared in
50 ml of THF. The solution was cooled to ±78 °C and slowly
treated with a solution of B-bromo-pentamethylborazine
,0.28 g, 1.2 mmol) in hexane ,50 ml). Then the solution was
allowed to attain ambient temperature. Its 11B NMR spec-
trum revealed only the presence of the starting borazine
The B±H and Li±H bond distances have, therefore,
rather large standard deviations. The B±Sn bond
Ê
lengths in 8 were determined as 2.254,6) A and
Ê
2.244,6) A, respectively. These B±Sn bonds are signifi-
cantly different and shorter than those of 4 and 5.
Therefore, this is another example that bonds of the
boron atom to electropositive elements such as tin
tend to shrink in length when the coordination num-
ber increases [21].
,d11B = 31.9 ,1 B, h1/2 = 180 Hz), d11B = 37.4 ,2 B, h1/2
=
130 Hz)). After stirring for 24 h at 40 °C the spectrum
showed no changes.
Bisꢀtrimethylstannyl)-ꢀ2,2,6,6-tetramethylpiperidino)borane,
ꢀ3) [10]: A stirred solution of Me3SnLi ,42.2. mmol) in THF
was cooled to ±78 °C and slowly treated with a solution of
dichloro,2,2,6,6-tetramethylpiperidino)borane [9] ,0.28 g,
1.2 mmol) in hexane ,50 ml). After stirring for 1 h at ambi-
ent temperature, all volatile components were removed in
vacuo, and the solid residue was then treated with 60 ml of
hexane. Insoluble products were removed by decantation.
Cooling the solution to ±30 °C afforded 5.8 g ,64%) of 3 as
yellow crystals; mp.: 105 °C. C15H36NBSn2 ,478.65), calcd.:
C 37.64, H 7.58, N2.93, found.: C 37.19, H 7.43, N2.82%.
Experimental
General: All experimental manipulations were conducted in
an dry atmosphere of dinitrogen or argon employing stan-
dard Schlenk and vacuum line techniques. Solvents were
dried by conventional methods. Starting materials were pre-
pared by literature methods. ± NMR: Jeol 270 and 400 as
well as Bruker 200 spectrometers [standards: TMS ,1H, 13C),
external BF3*OEt2 ,11B), external SnMe4,119Sn)] ± X-ray
structure determination: Siemens P4.
2
1H NMR ,400 MHz, C6D6): d = 0.37 ,d, JHSn = 40.0 Hz, 18 H, Sn,CH3)3),
1.26 ,s, 12 H, C,CH3)2), 1.46 ,s, 6 H, CCH2CH2 and CCH2) ± 13C N MR
B-ꢀtrimethylstannyl)-pentamethyl-borazine ꢀ2 a): A stirred so-
lution of Me3SnLi [22] ,6.4 mmol) in THF was cooled to
0 °C and slowly treated with a solution of B-bromo-penta-
methylborazine [8 b] ,1.4 g, 6.1 mmol) dissolved in ether
,25 ml). After stirring for 1 h at ambient temperature, all vol-
atile components were removed in vacuo and the solid resi-
due was treated with hexane ,60 ml). The hexane solution
was then decanted. Analysis by 11B NMR spectroscopy re-
vealed the presence of 2 a as the sole product. Attempts of
crystallization did not afford analytically pure samples as 2 a
decomposes slowly, and only oily samples were obtained.
Decomposition of 2 a produces hexamethylborazine
,d11B = 35.5 ,h1/2 = 190 Hz) [16]) within a few days.
1
1
,100 MHz, C6D6): d = ±5.5 ,m, JC117Sn = 216.8, JC119Sn = 227.3 Hz,
3JCSn = 15.6 Hz, Sn,CH3)3), 14.1 ,CH2CH2CH2), 33.9,C4CH3)2), 35.2
,C4CH3)2), 59.7 ,C4CH3)2) ± 11B NMR ,64 MHz, C6D6): d = 68.4 ,d, 1.3 d,
1JBSn = 650 Hz, h1/2 = 250 Hz) ± 119Sn NMR ,149 MHz, C6D6): ±146 ,q,
1JBSn = 650 Hz).
Chloroꢀtriphenylstannyl)ꢀ2,2,6,6-tetramethylpiperidino)borane
ꢀ4): A stirred solution of Ph3SnLi ,2.6 mmol) in THF was
cooled to 0 °C and slowly treated with dichloro,2,2,6,6-tetra-
methylpiperidino)borane ,0.29 g, 1.3 mmol) dissolved in hex-
ane ,20 ml). After stirring for 1 h at ambient temperature, all
volatile components were removed in vacuo. The solid resi-
due was treated with hexane ,40 ml) and the suspension fil-
tered. The filtrate was then reduced in volume to 20 ml and
kept at ±78 °C. Within 5 days 0.42 g ,60%) of 4 were obtained
as colorless prisms, mp.: 184 °C. C27H33NClBSn ,537.14),
calcd.: C 60.44, H 6.20, N2.61, Cl 6.61, found: C 59.94, H 6.35,
N2.36, Cl 6.73.
2 a: 1H NMR ,400 MHz, C6D6): d = 0.34 ,d, JHSn = 48.8 Hz, 9 H,
2
Sn,CH3)3), 0.39 ,s, 6 H, BCH3), 2.70 ,s, 3 H, NCH3), 2.89 ,s, 6 H, NCH3) ±
13C NMR ,100 MHz, C6D6): d = ±8.4 ,m, Sn,CH3)3), ±0.5 ,broad, BCH3),
34.2 ,NCH3), 39.2 ,NCH3)
±
11B NMR ,64 MHz, hexane): d = 37.4
1
,h1/2 = 160 Hz, 2 B), 44.7 ,d, JB, Sn = 950 Hz, h1/2 = 165 Hz, 1 B)
±
1H NMR ,270 MHz, C6D6): d = 1.31 ,s, 6 H, CCH2 and CCH2CH2), 1.40
,s, 12 H, CH3), 7.08±7.22 ,m, 9 H, m-Ph±H and p-Ph±H), 7.86 ,m, 6 H, o-
Ph±H) ± 13C NMR ,100 MHz, C6D6): d = 14.0 ,CCH2CH2), 33.0 ,CH3),
119Sn NMR ,149 MHz, C6D6): d = ±153.1 ,q, JB, Sn = 950 Hz).
B-ꢀtrimethylstannyl)-B',B@-dimethyl-N,N',N@-triisopropyl-bo-
35.5 ,CCH2), 58.3 ,C4CH3)2), 128.4, 136.2, 138.0, 142,4 ,C-arom) ±
11B NMR ,64 MHz, C6D6): d = 50.1 ,h1/2 = 480 Hz)
,149 MHz, C6D6): no signal observed.
±
119Sn NMR
razine ꢀ2 b): 10.0 mmol of Me3SnLi were prepared in ~40 ml
of THF. The stirred solution was cooled to ±78 °C and slowly
treated with a solution of B-bromo-B',B@-dimethyl-N,N',N@-
triisisopropyl-borazine [8 c] ,3.0 g, 9.5 mmol) in ether
,25 ml). After stirring for 1 h at ambient temperature, all vol-
atile components were removed in vacuo. The solid residue
was treated with hexane ,60 ml) and the suspension filtered.
The filtrate was cooled to 5 °C. Within 5 months 1.2 g ,31%)
of 2 b separated as colorless prisms, mp.: 20 °C.
C14H36B3N3Sn ,399.2), calcd.: C 42.29, H 9.13, N10.57,
found: C 43.08, H 9.33, N10.86%.
Triphenylgermylꢀtriphenylstannyl)ꢀ2,2,6,6-tetramethylpiperidi-
no)borane ꢀ5): 1.3 mmol of Ph3GeLi [23] were prepared
freshly in app. 50 ml of diethyl ether. The solution was
cooled to 0 °C and slowly treated with a solution of 0.50 g
,1.3 mmol) 4. After stirring for 5 h at ambient temperature,
all volatile components were removed in vacuo, the solid
residue was treated with 50 ml of toluene and filtered. The
solution was then reduced in volume to 20 ml and layered
with 20 ml of hexane. This afforded 0.82 g ,72%) 5 as color-
less crystals; map.: 189 °C. C45H48NBSnGe ,804.9), calcd.:
C 67.14, H 6.01, N1.74, found: C 64.25, H 5.37, N1.25%.
2
1H NMR ,400 MHz, C6D6): d = 0.34 ,d, JHSn = 42.3 Hz, 9 H, Sn,CH3)3),
3
0.72 ,s, 6 H, BCH3), 1.24 ,d, 6 H, JHH = 7.0 Hz, CH,CH3)2), 1.30 ,d,
3
3JHH = 7.1 Hz, 12 H, CH,CH3)2), 3.95 ,m, JHH = 7.0 Hz, 1 H, CH,CH3)2),
1H NMR ,400 MHz, C7D8, ±40 °C): d = 1.25 ,s, 6 H, CH3), 1.33 ,m, 4 H,
CCH2), 1.39 ,m, 2 H, CCH2CH2), 1.50 ,s, 6 H, CH3), 6.99 ,s, broad, 2 H,
pH-H), 7.07 ,m, broad, 9 H, pH-H), 7.10 ,m, broad, 5 H, pH-H), 7.14 ,s,
broad, 2 H, pH-H), 7.41 ,m, broad, 4 H, pH-H), 7.41 ,m, broad, 4 H, pH-
H), 7.54 ,m, broad, 6 H, pH-H), 7.65 ,m, broad, 2 H, pH-H) ± 13C N MR
,100 MHz, C6D6): d = 13.9 ,CCH2CH2), 31.8 ,CCH2), 33.8 ,broad, CH3),
3
4.10 ,m, JHH = 7.1 Hz, 2 H, CH,CH3)2) ± 13C NMR ,100 MHz, C6D6):
d = ±7.7 ,m, Sn,CH3)3), 5.0 ,broad, BC), 23.3 ,CH,CH3)2), 23.7
,CH,CH3)2), 47.2 ,CH,CH3)2), 54.8 ,CH,CH3)2) ± 11B NMR ,64 MHz,
1
hexane): d = 37.8 ,h1/2 = 235 Hz, 2 B), 44.7 ,d, JBSn = 960 Hz, h1/2
=
1
260 Hz, 1 B) ± 119Sn NMR ,149 MHz, C6D6): ±153.6 ,q, JBSn = 960 Hz).
794
Z. Anorg. Allg. Chem. 2001, 627, 789±796

Synthesis and Structures of some Trisorganylstannylboranes and Triorganylstannyl-borates
35.9 ,CCH2CH2), 60.7 ,broad, C,CH3)2), 127.2, 128.2, 128.±128.9 ,m),
the program SAINT [26] was used. For absorption correc-
135.2±138.0 ,m), 142.2, 143.0, 145.7 ,all C-aroma.) ± 11B NMR ,64 MHz,
C6D6): d = 70.0 ,h1/2 = 500 Hz).
tion the program SADABS was used [27]. The structures
were solved by direct or Patterson methods using
SHELX97 [28] programs for structure solution and refine-
ment. All non hydrogen atoms were refined anisotropically.
Hydrogen atoms were placed in calculated positions and in-
cluded in the refinement by applying a riding model. The hy-
drogen atoms attached to the boron were found by differ-
ence Fourier map and were refined freely. Relevant data are
presented in table 1. Additional information on the structure
solution are deposited with the Cambridge Crystallographic
Data Center as supplementary publication numbers
CCDC 155709±155712. Copies of the data can be obtained
free of charge on application to the CCDC, 12 Union Road,
Cambridge CN2 1EZ, U.K. [Fax: ,int,) # +44-12 23/3 36-0 33;
E-mail: deposit@ccdc.cam.uk]
Lithiumꢀtetrakis-tetrahydrofuran)ꢀtris-trimethylstannyl)-
[N-ꢀmethyl)anilino]borate ꢀ6): A stirred solution of Me3SnLi
,21.1 mmol) in THF was cooled to ±70 °C and a solution of
dichloro,N-methylanilino) borane [11] ,1.2 g, 6.2 mmol) in
hexane ,25 ml) was rapidly added. The resulting solution
showed only a single 11B resonance at ±13.2 ppm ,d,
1JBSn = 580 Hz). After stirring for 1 h at ambient tempera-
ture, all volatile components were removed in vacuo. The
black oily residue was extracted twice with 50 ml of diethyl
ether. Then the filtrates were unified. The yellow solution
was then cooled to ±78 °C. Colorless prisms of 6 separated
within two days. Yield: 2.9 g ,52%) of 6. The crystals decom-
posed within a few hours at ambient temperature. They are
also not stable in the presence of noncoordinating solvents.
Therefore, attempts to recrystallize 6 from hexane failed.
After several hours a hexane solution showed no longer
Acknowledgement. We thank Fonds der Chemischen Indus-
trie and Chemetall GmbH, both at Frankfurt/Main, for val-
uable support, Dr. W. Storch for helpful discussions, and
Dr. U. Braun and Mr. P. Mayer for the recording of many
NMR spectra.
the signal for 6 in its 11B NMR-spectrum but signals at
1
d11B = 71.6 ,d, JBSn = 650 Hz, h1/2 = 150 Hz) and 30.0 ,h1/2
=
150 Hz), for non-identified decomposition products. Two
days later only a signal at 30 ppm remained. In ether solu-
tion, however, 6 remains rather stable. C32H67NBLiO4Sn3
,907.2), calcd.: C 42.53, H 7.47, N1.55, found: C 38.52,
H 6.20, 1.98%. ,The large errors are due to decomposition
during the handling of the compound).
References
[1] Contribution to the Chemistry of Boron, 246. Contribu-
tion 245: R. Littger, J. Knizek, H. NoÈth, Eur. J. Inorg.
Chem. 2000, 1571.
[2] a) S. Onozawa, Y. Hatanaka, T. Sakakura, S. Shimada,
M. Tanaka, Organometallics, 1996, 15, 5450; b) S. Ono-
zawa, Y. Hatanaka, M. Tanaka, Tetrahedron Lett. 1998,
39, 9043; c) S. Onozawa, Y. Hatanaka, N. Choi, M. Tana-
ka, Organometallics 1997, 16, 5389.
2
1H NMR ,400 MHz, C6D6, Et2O): d = 0.43 ,d, JSnH = 32.3 Hz, 27 H,
Sn,CH3)3), 2.52 ,m, 16 H, OCH2CH2), 3.75 ,broad, 3 H, NCH3), 4.36 ,m,
16 H, OCH2CH2), 6.82 ,m, 1 H, Ph±H), 7.50 ,m, 2 H, Ph±H), 7.67 ,m, 1 H,
Ph±H), 7.81 ,m, 1 H, Ph±H) ± 13C NMR ,100 MHz, C6D6): d = ±10.6 ,m,
1JCSn = 250 Hz, JCSn = 59 Hz, Sn,CH3)3), 26.0 ,OCH2CH2), 45.9 ,broad,
3
NCH3), 68.6 ,OCH2), 111.6, ,C±Ph), 115.9 ,broad, C±Ph) 122.5, 122.8,
127.4, 128.9 ,all C-arom.) ± 11B NMR ,64 MHz, C6D6): d = ±13.1 ,d,
1JBSn = 580 Hz, h1/2 = 30 Hz)
±
119Sn NMR ,149 MHz, C6D6): d = ±42
,1JBSn = 580 Hz).
[3] H. NoÈth, K.-H. HermannsdoÈrfer, Angew. Chem. 1964,
76, 377; Angew. Chem. Int. Edit. Engl. 1964, 3, 377.
[4] P. Frankhauser, H. Pritzkow, W. Siebert, Z. Naturforsch.
1994, 49 b, 250.
[5] T. Habereder, H. NoÈth, submitted to Eur. J. Inorg.
Chem.; T. Habereder, PhD Thesis, Univ. of Munich,
2000.
Bisꢀtetrahydrofuran)lithium trimethylstannyltrihydridoborate,
8 was prepared according to literature [15]. The crystals that
separated from the THF solution at ±20 °C were removed
from the solution and covered at ±40 °C with perfluoroether
oil. NMR data were obtained for the THF solution and cor-
respond fairly well with those reported.
Reaction between 8 and catecholatobromoborane: Catechol-
bromoborane ,0.32 g, 1.6 mmol) was dissolved in 20 ml of
toluene and the stirred solution treated slowly with a solution
of 8 ,0.52 g, 1.6 mmol) in hexane ,20 ml). Immediately the
formation of a colorless precipitate ,LiBr) was observed.
After filtration the filtrate was cooled to ±30 °C. This caused
the precipitation of catecholatoborane as a crystalline mate-
[6] T. Habereder, H. NoÈth, submitted to Eur. J. Inorg.
Chem.
[7] W. L. Wells, T. L. Brown, J. Organometal. Chem. 1968,
11, 271.
[8] a) J. Bai, K. Niedenzu, Inorg. Chem. 1991, 30, 4631;
b) A. Meller, H. Marecek, Monatsh. Chem. 1968, 99,
1666; c) H. Schwenk-Kirchner, PhD Thesis, Univ. of
Munich, 1997; d) K. Anton, PhD Thesis, Univ. of Mu-
nich, 1982.
1
rial ,d11B = 27.9 ,d, JBH = 129 Hz, h1/2 = 240 Hz)). No other
product could be isolated or characterized.
[9] H. NoÈth, S. Weber, Z. Naturforsch. 1983, 38 b, 1460.
[10] K. Horchler, Diploma thesis, Univ. Munich, 1987.
[11] J. C. Lockart, J. R. Blackborow, J. E. Blackmore, J. Am.
Chem. Soc. 1971, 93, 49.
[12] Gmelin, Handbuch der Anorganischen Chemie, ErgaÈn-
zungswerk zur 8. Auflage, 1976, Vol. 33, Borverbindun-
gen, Teil 8, 150.
[13] H. NoÈth, H. Vahrenkamp, Chem. Ber. 1966, 69, 1049;
P. C. Keller, J. Am. Chem. Soc. 1969, 91, 1231.
[14] J. Trofimenko, J. Amer. Chem. Soc. 1967, 89, 3170;
H. NoÈth, S. Thomas, M. Schmidt, Chem. Ber. 1996, 129,
451.
X-Ray-structure-determinations
Single crystals were covered with perfluoropolyether oil,
suitable specimens were selected and mounted on the tip of
a glass fiber, placed on the goniometer head of the diffracto-
meter, and cooled to 193 K under a flow of N2. Preliminary
dimensions of the unit cells were calculated from the reflec-
tions on 15 frames each at four different v and w settings by
changing w by 0.3° per frame. Data collection was performed
in the hemisphere mode of the SMART program [25] at
193 K by collecting a total of 1264 frames. For data reduction
Z. Anorg. Allg. Chem. 2001, 627, 789±796
795

T. Habereder, H. NoÈth
[15] W. Biffar, H. NoÈth, H. Pommering, R. SchwerthoÈffer,
W. Storch, B. Wrackmeyer, Chem. Ber. 1981, 114, 49.
[16] The mono-THF adduct was obatined after drying
Li,H3BSnMe3) ´ n THF while compound 8 was isolated
from the solution at ±30 °C.
[17] H. NoÈth, B. Wrackmeyer, NMR Basic Priciples and
Progress, Editors: P. Diehl, E. Fluck, R. Kosfeld,
Springer Verlag, Berlin, Heidelberg, New York, 1978
,see Table XXXII).
D. A. Atwood, Main Group Chem. 1998, 12, 285 and
others.
[21] W. Lippert, PhD Thesis, Univ. of Munich, 1999; W. Lip-
pert, H. NoÈth, W. Ponikwar, T. Seifert, Eur. J. Inorg.
Chem. 1999, 817.
[22] G. Wittig, F. J. Meyer, G. Lange, Liebigs Ann. Chem.
1951, 571, 167.
[23] W. Still, J. Amer. Chem. Soc. 1978, 100, 1481.
[24] C. Tamborski, F. Ford, E. Soloski, J. Org. Chem. 1963,
28, 237.
[18] T. Habereder, PhD Thesis, Univ. of Munich, 2000.
1
[19] Previous values ,see [14]) are d11B = ±43.7, JBSn
=
[25] SMART, Bruker Analytical X-ray Instruments, Maison,
1998, Version 5.1.
1
±554 Hz, JBH = 91 Hz.
[20] S. S. Al-Juaaid, C. Eaborn, I. B. Goprrell, S. A. Hawkes,
P. B. Hitchcock, J. D. Smith, J. Chem. Soc. Dalton 1998,
2411; A. Heine, D. Stalke, Angew. Chem. Int. Ed, Engl.
1993, 32, 121; A. Dashti-Mommertrz, B. NeumuÈller,
Z. Anorg. Allg. Chem. 1999, 625, 954; M. S. Hill,
[26] SAINT, SHELXTL, Siemens Analytical Instruments,
Madison, 1995, Version 4.01.
[27] SADABS, G. M. Sheldrick, GoÈttingen, 1996.
[28] SHELX97, G. W. Sheldrick, University of GoÈttingen,
1993.
796
Z. Anorg. Allg. Chem. 2001, 627, 789±796