Reactions of 3-(diethylboryl)stannoles with isocyanates

Article abstract of DOI:10.1002/ejic.200900061

Diethynyl(diphenyl)stannane was prepared, fully characterised in solution and in the solid state, and its reaction with triethylborane, BEt₃, afforded 3-(diethylboryl)-4-ethyl-1,1-di-phenyl-stannole in essentially quantitative yield. Treatment with isocyanates converted this stannole and the known analogous 1,1-dimethyl derivative into novel bicyclic compounds containing an aminoborane unit. These reactions were found to proceed diastereoselectively, again in essentially quantitative yield. The bicyclic compounds react with methanol through rearrangement and elimination of ethyl-(dimethoxy)borane to give novel 1-stannacyclopent-3-ene derivatives, one of which could be structurally characterised by X-ray analysis. All final products and intermediates were studied in solution by multinuclear NMR spectroscopy (1H, ¹¹B, ¹³C, ¹¹⁹Sn NMR). Wiley-VCH Verlag GmbH and Co. KGaA, 69451 Weinheim, Germany, 2009).

Full text of DOI:10.1002/ejic.200900061

FULL PAPER
DOI: 10.1002/ejic.200900061
Reactions of 3-(Diethylboryl)stannoles with Isocyanates
Bernd Wrackmeyer,*[a] Peter Thoma,[a] and Rhett Kempe[a]
Keywords: Organotin compounds / Alkynes / Stannoles / Organoboration / Isocyanates / NMR
Diethynyl(diphenyl)stannane was prepared, fully character-
ised in solution and in the solid state, and its reaction with
triethylborane, BEt3, afforded 3-(diethylboryl)-4-ethyl-1,1-di-
phenyl-stannole in essentially quantitative yield. Treatment
with isocyanates converted this stannole and the known
analogous 1,1-dimethyl derivative into novel bicyclic com-
pounds containing an aminoborane unit. These reactions
were found to proceed diastereoselectively, again in essen-
tially quantitative yield. The bicyclic compounds react with
methanol through rearrangement and elimination of ethyl-
(dimethoxy)borane to give novel 1-stannacyclopent-3-ene
derivatives, one of which could be structurally characterised
by X-ray analysis. All final products and intermediates were
studied in solution by multinuclear NMR spectroscopy (1H,
11B, 13C, 119Sn NMR).
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
viously in low yield[10] and its reaction with dicobaltocta-
carbonyl Co2(CO)8 has been studied.[10,11] Here, we report
that 1b reacts with BEt3 to afford the stannole 2b. Reactions
of the stannoles 2a and 2b with isocyanates were explored
and some properties of the products were studied.
Introduction
Little is known about stannoles without alkyl or aryl
substituents in the 2,5-positions[1] and the molecular struc-
ture of only a single example has been determined so far.[2]
Indeed, it appears that 1,1-organoboration[3] of diethynyltin
compounds provides the only convenient route to such
stannoles. In contrast with numerous other (alkyn-1-yl)tin
compounds,[4,5] ethynylstannanes are somewhat more diffi-
cult to prepare and less easy to handle. Therefore, they have
received less attention and the synthesis and properties of
some rather simple derivatives have not been described in
Results and Discussion
Diethynyl(diphenyl)stannane 1b
As reported earlier,[10] diethynyl(diphenyl)stannane 1b
detail. We have shown that diethynyl(dimethyl)stannane, can be prepared from the reaction of the diphenyltin dichlo-
Me2Sn(CϵC–H)2 1a, reacts with triethylborane, BEt3, be- ride with two equiv. of ethynylmagnesium bromide in thf
low room temperature by consecutive 1,1-ethylboration and (Scheme 2). One of the side products is the reported con-
1,1-vinylboration[3] to give the stannole derivative 2a densed compound A. We have found that 1b can be purified
(Scheme 1).[6] The stannole 2a cannot be stored for pro- by distillation at reduced pressure and stored for prolonged
longed periods of time and it decomposes by at least 50% periods of time in the refrigerator at –20 °C (see Table 1 for
during distillation at reduced pressure. Thus, only a few as- NMR spectroscopic data of 1a and 1b). The condensation
pects of its chemistry have been so far addressed.[6–9]
of 1b by elimination of ethyne appears to occur in the reac-
tion solutions in an unpredictable way, most likely catalysed
by the magnesium salts in thf. In order to obtain more
NMR spectroscopic data of the condensation products
(Table 2), a concentrated solution of 1b in [D8]toluene was
prepared, heated at 60 °C for 60 h and changes were moni-
tored by 119Sn NMR spectroscopy. Indeed, A was formed
along with several higher condensation products (Figure 1).
The 119Sn NMR signals for tin atoms bearing both a ter-
minal and a bridging CϵC unit may be observed in the
typical range,[12] slightly shifted by about 7.2 ppm to higher
field in comparison with the signals of 1b, whereas the same
effect is about doubled for tin atoms bearing solely bridging
CϵC units in addition to the phenyl groups. The respective
assignments (see expansions in Figure 1) can be ac-
complished by comparing the different signal intensities.
Scheme 1.
In the present work, we report on the synthesis and mo-
lecular structure of diethynyl(diphenyl)stannane, Ph2Sn-
(CϵC–H)2 1b. This compound has been obtained pre-
[a] Anorganische Chemie II, Universität Bayreuth,
95440 Bayreuth, Germany
Fax: +49-921-552157
E-mail: b.wrack@uni-bayreuth.de
Eur. J. Inorg. Chem. 2009, 1469–1476
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1469

B. Wrackmeyer, P. Thoma, R. Kempe
FULL PAPER
Scheme 2. Synthesis of diethynyl(diphenyl)stannane 1b and its decomposition by elimination of ethyne.
1
Table 1. 119Sn 13C and H NMR spectroscopic data[a] of 1a and 1b.
1
δ H
δ
13C
δ
119Sn
R1
ϵC–H
R1
SnCϵ
ϵC
1a
1b
0.51 [70.5]
2.29 [36.0]
–6.5 [503.0][b]
85.4 [576.2][b]
97.6 [122.0]
–153.8[b]
{16.0} (Me)
{–27.0} (Cϵ)
–229.6
{16.9} (C-i)
{–17.3} (Cϵ)
7.39–7.50 (m)
7.63–7.70 [67.0] (m)
2.45 [39.1] (s)
134.3 [757.2] (i)
136.1 [51.1] (o)
129.0 [70.7] (m)
130.2 [14.4] (p)
83.8 [675.0]
99.0 [134.5]
n
1
[a] In CH2Cl2 at 299 K (1a)[6] and in CDCl3 at 296 K (1b); J119Sn,13C in Hz in brackets; isotope-induced chemical shifts ∆12/13C(119Sn)
in ppb in braces with a negative sign for the shift of the more heavy isotopomer to lower frequency.[24] [b] Taken from ref.[24] (in CDCl3).
The complementary information is gained from the 13C
NMR signals for the alkynyl carbon atoms (Figure 2). As
expected, there are three different regions for alkynyl car-
bons, two of which are located near those which give rise
to the relevant 13C NMR signals of 1b. The third region is
typical of SnϪCϵCϪSn moieties.[13] The magnitude of the
1,2
coupling constants
J
of the terminal alkynyl
119Sn,13Cϵ
carbon atoms are similar to 1b and the coupling constants
1J119Sn,13Cϵ of the bridging CϵC units are somewhat
smaller than for terminal ethynyl groups.[13b] Severely over-
lapping 13C NMR signals prevented the complete assign-
2
ment and also some 117/119Sn satellites for J119Sn,13C could
not be observed.
Table 2. 119Sn and 13C (alkyne) NMR spectroscopic data[a] of 1b
and the condensation products A, B, C and D.
δ 13
C
δ 119Sn
inner
–
SnCϵ ϵC
CϵC Bridging
outer
Figure 1. 149.2 MHz 119Sn{1H} NMR spectrum (INEPT, refo-
cused) of 1b in toluene after 60 h at 60 °C. Prominent signals in the
expanded sections belong to the condensation products A, B, C
and D, assigned by their relative intensities and on the basis of
information from 13C NMR spectra (see Figure 2).
1b 83.8
99.5
–
–228.2
[681.3] [135.6]
A
B
C
D
84.1
[672.2] [134.3]
84.2
[669.8]
84.2
99.5
113.6 [599.0]
–
–235.5
–235.3
–235.2
n.o.
n.o.
n.o.
113.6 [600.1]
114.0 [586.8]
113.5, 114.0, 114.1
–242.7
–242.4
[671.4]
n.o.
The molecular structure of 1b is shown in Figure 3. To
the best of our knowledge this is the first structurally char-
acterised ethynyltin compound. Intermolecular interactions
113.5, 113.9, 114.1, 114.2 –242.4, –242.3 –235.2
n
[a] In [D8]toluene at 296 K; J119Sn,13C in Hz in brackets.
1470
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1469–1476

3-(Diethylboryl)stannoles
Figure 2. 100.5 MHz 13C{1H} NMR spectrum of 1b in toluene after 60 h at 60 °C. Prominent signals in the expanded regions belong to
1
the condensation products A, B, and C, as marked. Some 117/119Sn satellites belonging to J117/119Sn,13C are also marked.
appear to be negligible. The surroundings of the tin atom [115.55(11)°] is smaller than the respective one in dichloro-
correspond to a distorted tetrahedron. All bond lengths and (diphenyl)tin (123.9° and 127.0°) but larger than that in tet-
angles are close to the expected values when compared with raphenyltin (108.9° and 110.5°). The other bond angles at
those of other alkynes or phenyl tin compounds. The the tin atom in 1b are close to the tetrahedral bond angle.
SnϪC(Ph) bond lengths are 211.9 pm (Sn–C5) and The deviations of the SnϪCϵC units from a linear geome-
211.8 pm for (Sn–C11), slightly shorter than in tetraphen- try are small [174.8°(C2–C1–Sn1) and 172.0(3)° (C4–C3–
yltin (214.3 pm)[14a] and close to the value for dichloro(di- Sn1)].
phenyl)tin (211.4 pm)[14b] and several other chloro(phenyl)-
tin compounds.[14c,14d] As expected, the SnϪC(ethynyl)
3-(Diethylboryl)-4-ethyl-1,1-diphenylstannole 2b
bond lengths [209.4(3) (Sn–C1) and 212.3(3) (Sn–C3)] are
somewhat shorter. According to other alkyn-1-yl group 14
compounds,[15] the CϵC bonds (114.0 and 115.4 pm) ap-
pear to be rather short. The bond angle C11–Sn–C5
The reaction of 1b with BEt3 selectively affords the stan-
nole 2b in essentially quantitative yield (Scheme 3). The
stannole 2b is a yellowish air- and moisture-sensitive oil
which can be kept under argon in the refrigerator for pro-
longed periods of time. All relevant NMR spectroscopic
data (Table 3) of 2a and 2b are, as expected, analogous.
Scheme 3. Synthesis of the stannole 2b.
Reactions of the Stannoles 2 with Isocyanates
In addition to the well known reactivity of the cyclic
diene system of metalloles[1,16] the presence of the dieth-
ylboryl group in the 3-position of the stannoles 2 opens the
way to further attractive transformations. Thus, any reagent
containing a nucleophilic centre will be attracted by the
electrophilic boron atom. If this reagent also contains an
electrophilic centre, further intramolecular reactions, e.g. at
Figure 3. Molecular structure of 1b (ORTEP, 40% probability; hy-
dogen atoms have been omitted). Selected bond lengths [pm] and
angles [°]: Sn1–C1 209.4(3), Sn1–C3 212.3(3), Sn1–C5 211.9(2),
Sn1–C11 211.8(3), C1–C2 115.4(5), C3–C4 114.0(5), C1–Sn1–C11
108.84(13), C1–Sn1–C5 109.17(11), C11–Sn1–C5 115.55(11), C1–
Sn1–C3 107.59(12), C11–Sn1–C3 107.01(11), C5–Sn1–C3
108.39(11), C2–C1–Sn1 174.8(3), C4–C3–Sn1 172.0(3).
Eur. J. Inorg. Chem. 2009, 1469–1476
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1471

B. Wrackmeyer, P. Thoma, R. Kempe
FULL PAPER
Table 3. 119Sn, 13C and 11B NMR spectroscopic data[a] of the stannoles 2a and 2b.
δ
13C
δ
119Sn
δ
11B
R1
C-2
C-3
C-4
C-5
BEt2
Et
(h1/2 in Hz)
(h1/2 in Hz)
2a
2b
–9.3 [329.7]
127.8
[410.4]
124.8
175.3
(br)
176.5
(br)
162.7
[89.9]
164.7
[99.6]
121.0
[484.4]
118.4
21.4 (br), 9.2
30.9
[62.6], 13.2
30.5
19.5
85.0
138.5 [506.5] (i)
137.1 [40.0] (o)
128.6 [51.8] (m)
129.0 [11.4] (p)
21.1 (br), 8.9
–46.9
(23.4)
84.5
(1340)
[441.1]
[517.7]
[67.6], 12.7
[a] In CD2Cl2 (2a) at 299 K[19] and in CDCl3 (2b) at 296 K. 13C NMR signals for carbon atoms linked to boron are broad (br) owing to
partially relaxed 13C-11B spin-spin coupling;[25] nJ119Sn,13C in Hz in brackets.
the adjacent C=C bond, may be readily induced. This be- the reaction times were about 12 h at room temperature or
haviour has already been observed for alkenes bearing stan- 4 h at 60 °C. It should be noted that BEt3 does not react
nyl and boryl groups in vicinal positions at the C=C with isocyanates under these conditions. The stereochemis-
1
bond[17a,17b] and is explored here for the stannoles of type try of 4–6 follows conclusively from H/1H NOE difference
2 using isocyanates as reagents. In isocyanates, nitrogen and spectra[20] and the consistent NMR spectroscopic data set
the carbonyl carbon atoms serve as nucleophilic and elec- (Table 4) supports the proposed structure. The δ11B data
trophilic centres, respectively (Scheme 4).
are typical of amino(dialkyl)boranes, in which the nitrogen
The intermediates 3 were not observed. In the case of atoms bear a substituent competing for the nitrogen π elec-
ethylisocyanate, the reaction was complete after 30–60 min tron density.[21] An inspection of the 119Sn-13C coupling
at room temperature, whereas in the case of arylisocynates, constants reveals the rather small magnitude of the coup-
Scheme 4. Reactions of the stannoles 2 with isocyanates.
Table 4. 119Sn, 13C and 11B NMR spectroscopic data[a] of 4a, 4b, 5a, 5b and 6b.
δ
13C
δ
119Sn
δ
11B
R1
C-2
C-3
C-4
C-5
C=O BEt
Et(3)
Et(4)
NR
(h1/2 in Hz)
4a
–6.9 [350.4]
–9.3 [344.0]
118.5 167.8 54.0 (br)
[464.9] [51.6]
42.4
[209.6]
188.9 7.3 (br)
[15.0] 7.9
27.3
[16.0]
12.9
27.5
[20.1]
13.1
27.7
[15.7]
13.1
27.1
[78.8]
9.6
27.7
[84.4]
9.8
27.4
[79.3]
9.9
35.0
16.2
77.7
–8.2
83.5
56.5
(907)
4b[b] 137.1 [524.9]
116.0 171.6 53.9 (br)
[499.8] [59.2] [26.7]
43.6
[230.1]
187.8 7.3 (br)
[15.3] 8.0
35.1
15.3
57.0
(1330)
138.5 [540.6]
5a
–6.5 [353.8]
–8.7 [341.5]
119.1 168.0 54.6 (br)
[466.3] [50.8]
42.8
[199.9]
188.0 7.8 (br)
[14.8] 7.7
126.8
127.4
128.8
138.7
127.1
128.5
129.4
138.3
20.7
125.6
126.5
136.0
141.4
56.5
(1020)
5b[c] 137.1 [520.1]
116.0 171.8 54.3 (br)
[501.8] [57.1] [29.4]
44.0
[218.1]
186.7 7.5 (br)
[15.6] 7.7
27.8
[21.2]
13.1
27.9
[84.6]
9.9
–6.5
–6.7
60.0
(1600)
138.1 [548.2]
6b[d] 136.9 [519.5]
115.8 171.7 54.1 (br)
[501.0] [56.8] [28.3]
43.9
[219.0]
186.7 7.4 (br)
[15.4] 7.6
27.6
[21.4]
13.0
27.7
[83.3]
9.8
58.0
(1619)
138.0 [549.9]
[a] In CDCl3 at 296 K. 13C NMR signals for carbon atoms linked to boron are broad (br) owing to partially relaxed 13C-11B spin-spin
coupling;[25] nJ119Sn,13C in Hz in brackets. [b] Other δ13C(Ph) data: 128.3 [54.0], 128.7 [55.8], 129.1 [12.1], 129.2 [12.6], 136.5 [41.2], 136.9
[39.1]. [c] Other δ13C(Ph) data: 128.6 [57.0], 128.7 [53.0], 129.3 [12.1], 129.4 [13.9], 136.5 [42.6], 137.1 [39.4]. [d] Other δ13C values: 128.0
[52.3], 128.2 [55.4], 129.3 [n.o.], 129.4 [n.o.], 136.3 [42.0], 137.0 [39.2] ppm.
1472
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1469–1476

3-(Diethylboryl)stannoles
1
ling constant J119Sn,13C(5) when compared with other val- necessary for the complete conversion of the bicyclic com-
ues for 1J119Sn,13C found here and elsewhere.[12] The reduced pounds. Elimination of ethyl(dimethoxy)borane was found
1
magnitude of J119Sn,13C(5) is in agreement with σ-π hyper- and a rearrangement takes place into the new 1-stannacy-
conjugative effects[18] between the Sn–C(5) bond and the
carbonyl carbon.
Methanolysis of the 1-Stannacyclopent-2-ene Derivatives
The new bicyclic compounds possess numerous reactive
bonds, inviting further reactions. Here we report the reac-
tion with methanol (Scheme 5). Two equiv. of methanol are Scheme 5. Methanolysis of the bicyclic compounds 4.
Table 5. 119Sn and 13C NMR spectroscopic data[a] of 7a and 7b.
δ
13C
R1
δ
119Sn
C-2
C-3
C-4
C-5
C=O
Et(3)
Et(4)
NR
7a
–8.8 [328.4] 44.1
–10.1 [335.4] [211.3]
144.1
[10.7]
143.6
[13.9]
136.1
[20.7]
170.1
[12.4]
18.4 [323.9] 174.9
[15.5]
28.0 [57.5]
13.4
28.0 [61.3]
13.4
25.8 [38.8] 34.0, 15.5 72.6
13.3
7b[b] 137.2 [543.5] 44.5
17.7
173.6
[15.1]
25.6 [43.2] 34.0
13.2 15.3
–25.9
137.9 [500.5] [236.4]
[348.1]
n
[a] In CDCl3 at 296 K; J119Sn,13C in Hz in brackets. [b] Other δ13C(Ph) data: 128.4 [53.3], 128.6 [53.1], 129.1 [11.4], 129.3 [12.3], 136.3
[37.5], 136.8 [38.8] ppm.
Figure 4. 100.5 MHz 13C{1H} NMR spectrum of the stannol-3-ene 7a. 117/119Sn satellites in the expanded regions are marked by asterisks.
Eur. J. Inorg. Chem. 2009, 1469–1476
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1473

B. Wrackmeyer, P. Thoma, R. Kempe
FULL PAPER
clopent-3-ene derivatives 7a,b containing an acylamide reagents such as isocyanates which also contain an electro-
group in the 2-position. philic centre for further intramolecular rearrangements. The
The solution state structures of 7a,b were deduced from novel bicyclic products, thus obtained, react readily with
1
the diagnostic H, 13C and 119Sn NMR spectroscopic data methanol to give stannole-3-enes which possess an unprece-
(Table 5) and single crystals of compound 7a were studied dented pattern of substituents.
by X-ray diffraction. An example of a representative 13C
NMR spectrum is shown in Figure 4 and the straightfor-
ward assignment is indicated.
Experimental Section
The molecular structure of 7a is shown in Figure 5. The
molecules are associated by hydrogen bridges, indicated by
the distance between N and O (288 pm).[22] The two
enantiomers are present in an alternative way in the crystal
structure. The SnϪC(Me) bond lengths [211.8(10) and
212.9(12) pm] are in the normal range for methyltin com-
pounds[23a,23b,23c] and the Sn1–C3 [216.1(11) pm] and Sn1–
C6 [217.9(9) pm] bonds are slightly elongated compared
with many other Sn–C bonds. The endocyclic C–C bond
lengths correspond to the literature values of single bonds
[151.1(15) pm (C3–C4) and 151.0(13) pm (C6–C5)] or
double bonds, respectively [133.8(15) pm (C5–C4)]. All
angles at the tin atom are enlarged with respect to the tetra-
hedral angle, except for the endocyclic angle C6–Sn1–C3
[85.6(4)°] which is acute as expected. The angles at the C=C
bond are close to the expected 120° [C6–C5–C4 121.9(9)°
and C5–C4–C3 122.5(9)°].
General: All preparative work as well as handling of the samples
was carried out observing strict precautions to exclude traces of air
and moisture. Carefully dried solvents and oven-dried glassware
were used throughout. Diphenyltin dichloride, dimethyltin dichlo-
ride, triethylborane, ethynylmagnesium bromide and the isocyan-
ates were commercial products. Diethynyl(dimethyl)stannane was
prepared as described.[6] NMR measurements in CDCl3 or [D8]-
toluene (concentration ca. 5–10%) were carried out for samples
in 5 mm tubes at 23Ϯ1 °C using Varian Inova 300 and 400 MHz
spectrometers for 1H, 11B, 13C and 119Sn NMR. Chemical shifts
are given relative to Me4Si, δ1H (CHCl3) = 7.24; δ1H (C6D5CD2H)
= 2.03; δ13C (CDCl3) = 77.0; δ13C (C6D5CD3) = 20.4; external
Me4Sn [δ119Sn = 0 for Ξ(119Sn) = 37.290665 MHz]; external BF3–
OEt2 [δ11B = 0 for Ξ(11B) = 32.083971 MHz]. Chemical shifts are
given to Ϯ 0.1 for 13C and 119Sn, spectra and Ϯ0.4 ppm for 11B.
Coupling constants are given to Ϯ 0.4 Hz for J119Sn,13C.
119Sn
NMR spectra were measured by using the refocused INEPT pulse
2
sequence[26] based on J119Sn,1H (50 –100 Hz) after optimising the
delay times in the pulse sequence. IR spectra were recorded with a
Perkin–Elmer Spectrum 100 FTR spectrophotometer equipped
with an ATR sampling unit. The melting points (uncorrected) were
determined using a Büchi 510 melting point apparatus.
Synthesis of Diethynyl(diphenyl)stannane 1b: A two-necked Schlenk
flask equipped with magnetic stirring bar and dropping funnel was
charged with thf (230 mL) and diphenyltin dichloride (16.556 g,
48.15 mmol), and cooled whilst stirring to –78 °C. With vigorous
stirring, ethynylmagnesium bromide (101 mmol) in thf (202.2 mL)
was then added drop wise from the dropping funnel. The reaction
mixture was allowed to reach room temperature and stirring was
maintained for 12 h. Most of the thf was removed in vacuo and
the residue was suspended in hexane (100 mL). Insoluble materials
were filtered off, washed four times with hexane (4ϫ50 mL) and
the combined hexane solutions were evaporated. This left a colour-
less oil which could be distilled under reduced pressure (113 °C/7.5
10–3 Torr) to give pure 1b (6.9 g, 44%) as an oil. After storage in
the refrigerator, 1b solidified and remained solid (m.p. 52–55 °C).
Repeated crystallisation from its melt finally gave single crystals
suitable for X-ray structural analysis. Compound 1b can be stored
at –20 °C for prolonged periods of time (Ͼ 1 year) without decom-
position.
Figure 5. Molecular structure of 7a (ORTEP, 40% probability; hy-
drogen atoms have been omitted; the O·H·N hydrogen bond to the
next molecule is indicated). Selected bond lengths [pm] and angles
[°]: Sn1–C1 211.8(12), Sn1–C2 212.9(10), Sn1–C3 216.1(11), Sn1–
C6 217.9(9), C3–C4 151.1(15), C5–C4 133.8(15), C6–C5 151.0(13),
N–H–O 288.0, C2–Sn1–C1 113.8(5), C6–Sn1–C2 113.8(4), C6–
Sn1–C1 111.8(4), C3–Sn1–C2 116.7(5), C3–Sn1–C1 112.1(4), C6–
Sn1–C3 85.6(4), Sn1–C6–C5 103.1(6), C6–C5–C4 121.9(9), C5–
C4–C3 122.5(9), C4–C3–Sn1 102. 9(7).
1b: 1H NMR (400 MHz): δ = 2.45 (s, J119Sn,H = 39.1 Hz, 2 H,
ϵCϪH), 7.39–7.50 (m, 6 H, SnPh2-meta, para), 7.63–7.70 (m,
J119Sn,H = 66.8 Hz, 4 H, SnPh -ortho) ppm. IR (ATR): ν = 3262,
˜
2
3251 [ν(ϵC–H)], 3067, 3047, 3022, 2995 [ν(C–Hphenyl)], 2012
[ν(CϵC)] cm–1.
Conclusions
Observation of the Condensation Products of 1b (A, B, C, etc.): Di-
ethynyl(diphenyl)stannane 1b [0.25 g, (0.774 mmol)] was dissolved
in [D8]toluene (0.6 mL). The sample was kept in an oil bath at
60 °C for 60 h and changes were monitored by 119Sn NMR spec-
troscopy. After this time, when almost all material was in solution,
the reaction was stopped and the mixture was analysed by 13C and
The straightforward synthesis of stannoles by 1,1-organo-
boration can be extended to diphenyltin derivatives, using
diethynyl(diphenyl)stannane which is available in a highly
pure state in reasonable yield. The diethylboryl group in the
3-position at the stannole ring serves to attract nucleophilic 119Sn NMR spectroscopy (see Figures 1 and 2).
1474
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1469–1476

3-(Diethylboryl)stannoles
Synthesis of 3-(Diethylboryl)-3-ethyl-1,1-diphenyl-stannole 2b: In a
two-necked flask equipped with a magnetic stirring bar, the dieth-
ynylstannane 1b (0.43 g, 1.331 mmol) was dissolved in hexane
(10 mL) and cooled to –78 °C. A slight excess of BEt3 (0.2 mL,
1.382 mmol) was added in one portion. The mixture was warmed
to room temperature and stirred for 30 min. Then the solvent was
removed in vacuo and the pure stannole 2b was left as a yellowish
5 H, BEt), 1.66–1.76/1.76–1.87, 1.11 (m, m, t, 5 H, 3-Et), 2.61 [s,
J119Sn,H = 67.2 Hz, 1 H, 2-CH(2)], 5.99 (s, J119Sn,H = 144.8 Hz, 1
H, 5-H), 6.90–7.35 (m, 5 H, NPh).
1
5b: H NMR (400 MHz): δ = 2.38–2.49/2.49–2.62, 0.71 (m, m, t, 5
H, 4-Et), 0.85–0.93/1.01–1.11, 0.96 (m, m, t, 5 H, BEt), 1.75–1.86/
1.93–2.06, 1.28 (m, m, t, 5 H, 3-Et), 3.02 (s, J119Sn,H = 69.2 Hz,1
H, 2-H), 6.21 (s, J119Sn,H = 142.9 Hz, 1 H, 5-H), 6.94–7.77 (m, 15
H, SnPh2/NPh).
1
oil (Ͼ 98% by H NMR).
2b: 1H NMR (400 MHz): δ = 1.26, 0.88 (q, t, 10 H, BEt2), 2.21,
1.01 (q, t, 5 H, 4-Et), 6.04 (s, J119Sn,H = 163.5 Hz, 1 H, 5-H), 6.11
(s, J119Sn,H = 162.2 Hz, 1 H, 2-H), 7.15–7.27 (m, 6 H, SnPh2), 7.42–
7.50 (m, 4 H, SnPh2) ppm.
1
6b: H NMR (400 MHz): δ = 2.45–2.57/2.57–2.70, 0.79 (m, m, t, 5
H, 4-Et), 0.91–1.01/1.05–1.16, 1.07 (m, m, t, 5 H, BEt), 1.83–1.93/
2.01–2.12, 1.35 (m, m, t, 5 H, 3-Et), 2.31 [s, 3 H, CH3(tol)], 3.09
(s, J119Sn,1H = 67.9 Hz,1 H, 2-H), 6.28 (s, J119Sn,H = 143.1 Hz,1 H,
5-H), 6.82–7.82 (m, 14 H, SnPh2/Ntol).
Reactions of the Stannoles 2a and 2b with Isocyanates: General pro-
cedure: The respective isocyanate (one equiv.) was added in one
portion to a solution of the freshly prepared stannole 2a or 2b
(≈ 1.2–1.5 mmol) in hexane (10 mL) at room temperature. In the
case of EtNCO, the reaction mixture was stirred for 1 h. In the
case of the aromatic isocyanates, the reaction mixtures were stirred
for 12 h at room temperature (or 4 h at 60 °C) in the absence of
light. The solvent was removed in vacuo and the products were left
in essentially quantitative yield (NMR) as yellow oils. They can be
used without further purification.
Stannacyclopent-3-ene Derivatives 7a and 7b by Methanolysis: A
solution of the bicyclic compound 4a or 4b (1.2 mmol) as obtained
(vide supra) in CH2Cl2 (10 mL) was kept stirring at room tempera-
ture and methanol (2.5 mmol) was injected. After stirring for 3 h,
all volatiles were removed in vacuo and the residues were washed
several times with small amounts of hexane (2–4 mL). In the case
of R1 = Me (7a), a white powder precipitated at room temperature
and the supernatant liquid was decanted. In the case of R1 = Ph
(7b), the product was purified by washing with cold hexane
4a: 1H NMR (400 MHz): δ = 0.09 (s, J119Sn,H = 55.2 Hz, 6 H, (–20 °C) upon which it precipitated as a colourless powder (48%)
SnMe2), 0.29 (s, J119Sn,H = 58.2 Hz, 6 H, SnMe2), 1.02–1.09/1.12–
1.22, 0.84 (m, m, t, 5 H, BEt), 1.37–1.52/1.63–1.76, 1.03 (m, m, t,
which turns into an oil at room temperature. Pure 7a can be ob-
tained in 61% yield as a white powder (m.p. 63–67 °C, decomp.)
5 H, 3-Et), 2.07–2.19/2.19–2.32, 0.64 (m, m, t, 5 H, 4-Et), 2.39 (s, which was recrystallised from hexane/diethyl ether (1:1) to yield
J119Sn,H = 67.0 Hz, 1 H, 2-H), 3.05–3.18/3.24–3.26, 0.98 (m, m, t.
5 H, NEt), 5.86 (s, J119Sn,H = 140.2 Hz,1 H, 5-H) ppm.
single crystals for X-ray analysis.
7a: 1H NMR (400 MHz): δ = 0.29 (s, J119Sn,H = 56.4 Hz, 6 H,
SnMe2), 0.33 (s, J119Sn,H = 56.9 Hz , 6 H, SnMe2), 1.90–2.02/2.23–
2.33, 0.93 (m, m, t, 5 H, 4-Et), 2.13–2.23, 1.02 (m, t, 5 H, 3-Et),
1
4b: H NMR (400 MHz): δ = 2.13–2.26/2.26–2.39, 0.43 (m, m, t, 5
H, 4-Et), 0.82–0.92/0.95–1.04, 0.64 (m, m, t. 5 H, BEt), 1.34–1.46/
1.66–1.79, 1.05 (m, m, t, 5 H, 3-Et), 2.65 (s, J119Sn,H = 71.1 Hz, 1
H, 2-H), 2.71 –2.82/2.96–3.08, 0.76 (m, m, t, 5 H, NEt), 5.93 (s, J119Sn,H = 33.2 Hz, JH,H = 16.3 Hz, 2 H, 5-H2,], 3.06 (s, J119Sn,H
2
1.55 [d, J119Sn, H = 43.4 Hz, JH,H = 16.3 Hz, 2 H, 5-H2,], 1.83 [d,
2
J119Sn,H = 141.7 Hz, 1 H, 5-H), 7.05–7.08 (m, 10 H, SnPh2).
= 52.8 Hz,1 H, 2-H), 3.10–3.32, 1.03 (m, t, 5 H, NEt), 5.24 (br. s,
1 H, NH).
5a: 1H NMR (400 MHz): δ = 0.26 (s, J119Sn,H = 56.4 Hz, 6 H,
SnMe2), 0.39 (s, J119Sn,H = 58.8.4 Hz, 6 H, SnMe2), 2.18–2.28/2.28–
2.40, 0.65 (m, m, t, 5 H, 4-Et), 0.86–0.92/0.94–1.02, 0.81 (m, m, t,
7b: 1H NMR (400 MHz): δ = 2.27–2.36, 0.83 (m, t, 5 H, 4-Et),
2.36–2.45, 1.02 (m, t, 5 H, 3-Et), 1.98 (d, J119Sn,H = 45.3 Hz, JH,H
2
Table 6. Data pertinent to the crystal structure determinations[26] of 1b and 7a.
1b
7a
Chemical formula
Fw [gmolϪ1
Diffractometer
Crystal description
Dimensions [mm]
Crystal system
Space group
C16H12Sn
322.95
C13H25NOSn
]
330.03
STOE IPDS II, Mo-Kα, λ = 71.069 pm, graphite monochromator
colourless plates
colourless prism
0.28ϫ0.12ϫ0.10
orthorhombic
P212121
0.18ϫ0.17ϫ0.06
orthorhombic
Pbca
a = 781.80(5) Å
b = 993.90(7) Å
c = 1813.00(13) Å
4
1.523
632
α = 90°
β = 90°
γ = 90°
a = 1733.3(2) Å
b = 949.60(14) Å
c = 1861.5(3) Å
8
1.431
1344
α = 90°
β = 90°
γ = 90°
Lattice parameters
Z
density (calculated) [gcmϪ3
F000
]
θ measuring range [°]
1.66–26.05
1.789
133(2)
2.05–26.13
1.652
133(2)
Absorption coefficient µ [mm–1]
T [K]
Reflections collected
19011
2522
numerical
154
8450
1708
numerical
145
Observed reflections I Ͼ 2σ(I)
Absorption correction
Refined parameters
R1[I Ͼ 2σ(I)]; wR2 (all data)
0.0209; 0.0479
0.0778; 0.1367
0.133/–1.302
Max./min. residual electron density 0.827/–0.316
[e·m–3 ϫ10–6]
Eur. J. Inorg. Chem. 2009, 1469–1476
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1475

B. Wrackmeyer, P. Thoma, R. Kempe
FULL PAPER
= 16.3 Hz, 2 H, 5-H2), 2.28 (d, J119Sn,H = 33.7 Hz, 2JH,H = 16.3 Hz,
[13] a) B. Wrackmeyer, J. Organomet. Chem. 1978, 145, 183–188; b)
B. Wrackmeyer, J. Organomet. Chem. 1979, 166, 353–363.
[14] a) L. Engelhardt, W. P. Leung, C. L. Raston, A. H. White,
Aust. J. Chem. 1982, 35, 2383–2384; b) R. F. Bryan, P. T.
Greene, J. Chem. Soc. A 1971, 16, 2549–2554; c) J. S. Tse, F. L.
Lee, E. J. Gabe, Acta Crystallogr., Sect. C 1986, 42, 1876–1878;
d) P. Apodaca, F. Cervantes-Lee, K. H. Pannell, Main Group
Met. Chem. 2001, 24, 597–601.
[15] B. Wrackmeyer, B. H. Kenner-Hofmann, W. Milius, P. Thoma,
O. L. Tok, M. Herberhold, Eur. J. Inorg. Chem. 2006, 101–108.
[16] J. Dubac, A. Laporterie, G. Manuel, Chem. Rev. 1990, 90, 215–
263.
2 H, 5-H2), 2.94–3.12, 1.14 (m, t, 5 H, NEt), 3.45 (s, J119Sn,H
=
56.6 Hz,1 H, 2-H), 5.33 (br. s, 1 H, NH), 7.18–7.78 (m, 10 H,
SnPh2).
Crystal Structure Determinations of the 1b and 7a: Details pertinent
to the crystal structure determinations are listed in Table 6.[27]
Crystals of appropriate size were selected (in perfluorinated oil[28]
at room temperature) and the data collections were carried out at
133 K using a STOE IPDS II system equipped with an Oxford
Cryostream low-temperature unit. Structure solutions and refine-
ments were accomplished using SIR97,[29] SHELXL-97[30] and
WinGX.[31]
[17] a) B. Wrackmeyer, H. E. Maisel, K. Wagner, Chem. Heterocycl.
Compd. 2001, 1526–1534; b) B. Wrackmeyer, K. Wagner, R.
Boese, Chem. Ber. 1993, 126, 595–599.
[18] a) M. J. S. Dewar, Hyperconjugation, Ronald Press, New York,
1962; b) G. A. Olah, J. Org. Chem. 2001, 66, 5943–5957; c) I. V.
Alabugin, T. A. Zeidan, J. Am. Chem. Soc. 2002, 124, 3175–
3185; d) P. Buzek, P. v. R. Schleyer, S. Sieber, Chem. Unserer
Zeit 1992, 26, 116–128.
Acknowledgments
This work was supported by the Deutsche Forschungsgemein-
schaft.
[19] B. Wrackmeyer, S. Kundler, R. Boese, Chem. Ber. 1993, 126,
1361–1370.
[20] a) K. Stott, J. Keeler, Q. N. Van, A. J. Shaka, J. Magn. Reson.
1997, 125, 302; b) A. E. Derome, Modern NMR Techniques for
Chemistry in Research, Pergaon, Oxford, 1987, pp. 188–190.
[21] H. Nöth, B. Wrackmeyer, in P. Diehl, E. Fluck, R. Kosfeld
(Eds.), NMR - Basic Principles and Progress – Nuclear Mag-
netic Resonance Spectroscopy of Boron Compounds, vol. 14,
Springer, Berlin, 1978.
[22] G. A. Jeffrey, An Introduction to Hydrogen Bonding, chapter
2.1, pp. 11–12, Oxford University Press, Oxford, 1997.
[23] a) B. Krebs, G. Henkel, M. Dartmann, Acta Crystallogr., Sect.
C 1989, 45, 1010–1012; b) H. Reuter, R. Pawlak, Z. Kristallogr.
2001, 216, 56–59; c) J. L. Lefferts, K. C. Molloy, M. B. Hos-
sain, D. van der Helm, J. J. Zuckerman, J. Organomet. Chem.
1982, 240, 349–361.
[1] a) B. Wrackmeyer, O. L. Tok, Comprehensive Heterocyclic
Chemistry III (Eds.: A. R. Katritzky, C. A. Ramsden, E. F. V.
Scriven, R. J. K. Taylor), chapter 3.17, pp. 1181–1223; Elsevier,
Oxford, 2008; b) B. Wrackmeyer, Heteroat. Chem. 2006, 17,
188–206.
[2] B. Wrackmeyer, U. Klaus, W. Milius, E. Klaus, T. Schaller, J.
Organomet. Chem. 1996, 517, 235–242.
[3] B. Wrackmeyer, Coord. Chem. Rev. 1995, 145, 125–156.
[4] a) W. E. Davidsohn, M. C. Henry, Chem. Rev. 1967, 67, 73–
106; b) C. Cauletti, C. Furlani, A. Sebald, Gazz. Chim. Ital.
1988, 118, 1–23; c) L. Brandsma, Preparative Acetylenic Chem-
istry, 2nd ed. Elsevier, Amsterdam, 1988; d) L. Brandsma, Syn-
thesis of Acetylenes, Allenes, and Cumulenes – Methods and
Techniques, 2nd ed., Elsevier, Amsterdam, 2004.
[5] a) P. Jaumier, B. Jousseaume, M. Lahcini, Phosphorus, Sulfur,
Silicon, Relat. Elem. 1999, 150–151, 117–127; b) B. Wrackme-
yer, Rev. Silicon, Germanium, Tin Lead Compd. 1982, 6, 75–
148.
[24] S. Kerschl, A. Sebald, B. Wrackmeyer, Magn. Reson. Chem.
1985, 23, 514–520.
[25] B. Wrackmeyer, Prog. Nucl. Magn. Reson. Spectrosc. 1979, 12,
227–259.
[26] a) G. A. Morris, R. Freeman, J. Am. Chem. Soc. 1979, 101,
760–762; b) G. A. Morris, J. Am. Chem. Soc. 1980, 102, 428–
429; c) G. A. Morris, J. Magn. Reson. 1980, 41, 185–188; d)
D. P. Burum, R. R. Ernst, J. Magn. Reson. 1980, 39, 163–168.
[27] CCDC-716371 (for 1b) and -716370 (for 7a) contain the sup-
plementary crystallographic data for this paper. These data can
be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[28] T. Kottke, D. Stalke, J. Appl. Crystallogr. 1993, 26, 615–619.
[29] A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano, C.
Giacovazzo, A. Guagliardi, A. G. G. Moliterni, G. Polidori, R.
Spagna, J. Appl. Crystallogr. 1999, 32, 115–119.
[6] L. Killian, B. Wrackmeyer, J. Organomet. Chem. 1977, 132,
213–221.
[7] H. O. Berger, H. Nöth, B. Wrackmeyer, Chem. Ber. 1979, 112,
2884–2893.
[8] B. Wrackmeyer, U. Klaus, J. Organomet. Chem. 1996, 520, 211–
226.
[9] a) B. Wrackmeyer, U. Klaus, W. Milius, Chem. Ber. 1995, 128,
679–687; b) B. Wrackmeyer, J. Organomet. Chem. 1981, 205,
1–14.
[10] P. Galow, A. Sebald, B. Wrackmeyer, J. Organomet. Chem.
1983, 259, 253–268.
[11] B. Wrackmeyer, H. E. Maisel, G. Kehr, H. Nöth, J. Organomet.
Chem. 1997, 532, 201–206.
[12] a) B. Wrackmeyer, Annu. Rep. NMR Spectrosc. 1999, 38, 203–
264; b) B. Wrackmeyer, in A. Davies, M. Gielen, K. Pannell,
E. Tiekink (Eds.), Tin Chemistry – Fundamentals, Frontiers and
Applications, Wiley, Chichester, 2008, pp. 17–52.
[30] G. M. Sheldrick, SHELX-97, Program for Crystal Structure
Analysis (release 97-2), Institut für Anorganische Chemie der
Universität, Göttingen, Germany, 1998.
[31] L. J. Farrugia, J. Appl. Crystallogr. 1999, 32, 837–838.
Received: January 16, 2009
Published Online: March 12, 2009
1476
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 1469–1476