Ferrocenylethynyltin compounds - Characterization and reactivity towards triethylborane

Article abstract of DOI:10.1002/ejic.200500602

Ferrocenylethynyl(trimethyl)tin (1), bis(ferrocenylethynyl)dimethyltin (2), tetrakis(ferrocenylethynyl)tin (3), and chloro(ferrocenylethynyl)dimethyltin (4) have been prepared and characterized in solution by ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. Solid-state MAS ¹³C and ¹¹⁹Sn NMR spectra were measured for 2 and 3, and the molecular structure of one of the modifications of 2 was determined by X-ray analysis. The reactivity of 1-4 towards triethylborane has been explored. 1,1-Organoboration takes place in all cases, and the reactions are stereoselective for 1 and 4 to give the alkenes 5 and 6, respectively, in which the stannyl and the boryl groups are in cis-positions at the C=C bond. In the case of 2, the final products are the 1-stannacyclopenta-2,4-diene 7a and the 1-stanna-4-boracyclohexa-2,5-diene 8a, whereas the reaction of 2 with triisopropylborane leads selectively to the six-membered ring 8b. Zwitterionic intermediates 9a,b, in which the tin atom is coordinated side-on to the C≡C bond of an alkynylborate, have been detected by NMR spectroscopy. Compound 3 reacts with triethylborane to give a mixture of three spirotin compounds 10-12 as the final products, where the tin atom connects five- and six-membered rings. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200500602

FULL PAPER
DOI: 10.1002/ejic.200500602
Ferrocenylethynyltin Compounds – Characterization and Reactivity towards
Triethylborane
Bernd Wrackmeyer,*[a] Barbara H. Kenner-Hofmann,[a] Wolfgang Milius,[a] Peter Thoma,[a]
Oleg L. Tok,[a] and Max Herberhold*[a]
Dedicated to Professor Henri Brunner on the occasion of his 70th birthday
Keywords: Alkynes / Boranes / Ferrocenes / NMR spectroscopy / Tin
Ferrocenylethynyl(trimethyl)tin (1), bis(ferrocenylethynyl)di-
methyltin (2), tetrakis(ferrocenylethynyl)tin (3), and chloro-
(ferrocenylethynyl)dimethyltin (4) have been prepared and
characterized in solution by 1H, 13C, and 119Sn NMR spec-
troscopy. Solid-state MAS 13C and 119Sn NMR spectra were
measured for 2 and 3, and the molecular structure of one of
the modifications of 2 was determined by X-ray analysis. The
reactivity of 1–4 towards triethylborane has been explored.
1,1-Organoboration takes place in all cases, and the reac-
tions are stereoselective for 1 and 4 to give the alkenes 5 and
6, respectively, in which the stannyl and the boryl groups are
in cis-positions at the C=C bond. In the case of 2, the final
products are the 1-stannacyclopenta-2,4-diene 7a and the 1-
stanna-4-boracyclohexa-2,5-diene 8a, whereas the reaction
of 2 with triisopropylborane leads selectively to the six-mem-
bered ring 8b. Zwitterionic intermediates 9a,b, in which the
tin atom is coordinated side-on to the CϵC bond of an alkyn-
ylborate, have been detected by NMR spectroscopy. Com-
pound 3 reacts with triethylborane to give a mixture of three
spirotin compounds 10–12 as the final products, where the
tin atom connects five- and six-membered rings.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
at the tin atom and also by the second substituent at the
CϵC bond, which may be hydrogen, an alkyl or aryl group,
or another organometallic substituent. In the present work,
we describe the synthesis and characterization of the ferro-
cenylethynyltin compounds 1–4 (Scheme 1) and report their
reactivity towards triethylborane (BEt3) and, in the case of
2, triisopropylborane (BiPr3).
Introduction
The synthetic potential of the CϵC bond in alkynes can
be further enhanced by organometallic substituents.[1] This
is well known for stannyl groups,[2] and the polar Sn–Cϵ
bonds in alkyn-1-yltin compounds are useful for various
transformations. The reactivity of such alkyn-1-yltin com-
pounds can be modified by the nature of other substituents
Results and Discussion
Synthesis and NMR Spectroscopic Characterization of the
Ferrocenylethynyltin Compounds
The most convenient synthesis of 1–3 starts from ethynyl-
ferrocene,[3] which is first converted into the alkynyllithium
reagent and then treated with tin halides. (Scheme 2). Alter-
natively, the reaction of ethynylferrocene with the respective
tin amides[4] [e.g. Me3SnNEt2, Me2Sn(NEt2)2 and Sn-
(NEt2)4] can be used to obtain 1–3. The reaction of 2 with
one equivalent of dimethyltin dichloride at 110 °C in the
presence of a small amount of toluene leads to 4. A slight
excess (10%) of Me2SnCl2 helps to convert 2 into 4 quanti-
tatively. Compounds 1–4 are orange-red solids that are well
soluble (1, 2, 4) or rather insoluble (3) in hydrocarbons. Sin-
gle crystals of complex 2 suitable for X-ray structural analy-
sis were isolated after recrystallization from hexane. The
Scheme 1. The ferrocenylethynyltin compounds studied.
[a] Laboratorium für Anorganische Chemie, Universität Bayreuth,
95440 Bayreuth, Germany
Fax: +49-921-552-157
E-mail: b.wrack@uni-bayreuth.de
max.herberhold@uni-bayreuth.de
Eur. J. Inorg. Chem. 2006, 101–108
© 2006 Wiley-VCH Verlag GmbH & Co. KgaA, Weinheim
101

B. Wrackmeyer, M. Herberhold et al.
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Scheme 2. Synthesis of the ferrocenylethynyltin compounds (Fc = Ferrocenyl).
Table 1. 13C and 119Sn NMR spectroscopic data[a] of the ferrocenylethynyltin compounds 1–4.
13
δ
13
δ
13
δ
13
δ
13
δ
13
δ
C
C
13C1
δ
C
C
C
C
Me
119Sn
δ
2,5
3,4
Cp
ϵC–Sn
ϵC–Fc
1[b]
71.6
68.4
65.6
[12.8]
70.1
89.3
107.6
[94.4]
{–14.1}
109.6
[134.3]
{–2.2}
109.8
[241.8]
111.3
–7.4
[404.6]
{+2.7}
–5.7
[495.1]
{+20.2}
–-
–65.4
[433.2]
{–58.5}
87.8
[625.9]
{–26.7}
82.7
[1167.3]
89.7
[563.6]
2
72.6
[5.0]
69.5
66.3
[15.5]
71.0
–152.8[c]
3
4
72.4
69.7
69.9
63.5
[23.4]
65.0
70.7
71.1
–342.2
72.8
[5.0]
–0.1
[493.4]
+21.7
[133.3]
119Sn,13
[a] In CD2Cl2 at 296 K; coupling constants
J
0.5 Hz are given in brackets; isotope-induced chemical shifts
12/13C(119Sn) 0.5 ppb in braces with a negative sign for Cthe shift of the more heavy isotopomer to lower frequency. [b] In CDCl3
n
∆
119
119
at 296 K. [c] Solid-state MAS Sn NMR: δ
= –144.0 (minor) and –150.5 ppm (major).
Sn
identity of the compounds 1–4 in solution follows from a compounds.[5–7] This indicates that the ferrocenyl group
consistent set of NMR parameters (Table 1). Even in the does not exert a special influence on the bonding situation
case of the sparingly soluble complex 3, the 13C NMR spec- in the Sn–CϵC–Fc fragment.
117/119Sn,13
C
tra could be recorded for determination of the J
coupling constants (Figure 1). The large magnitude of the
nJ
coupling constants is typical of tetraalkyn-1-yltin
119Sn,13
C
derivatives.[5,6] In the cases of 1 and 2, the 119Sn NMR spec-
tra were recorded in order to measure isotope-induced
n
chemical shifts
∆
12/13C(119Sn) (Figure 2). Both the
nJ
coupling constants and isotope-induced chemical
119Sn,13
C
shifts ∆12/13C(119Sn) are observed in the expected ranges
n
of the data previously determined for other alkyn-1-yltin
Figure 2. 119Sn{1H} NMR spectrum (refocused INEPT[25]
;
186.5 MHz) of ferrocenylethynyl(trimethyl)tin (1; 5% in CDCl3 at
296 K; acquisition time 5 s, repetition delay 2.5 s; 64 transients).
The 13C satellites are marked, and coupling constants and isotope-
induced chemical shifts ∆12/13C(119Sn) are given. The 13C satellites
3
119Sn,13CFc
indicated by asterisks correspond to J
= 12.8 Hz.
Structural Studies of Bis(Ferrocenylethynyl)Dimethyltin (2)
and Tetrakis(Ferrocenylethynyl)tin (3)
Figure 1. 13C{1H} NMR spectrum (100.5 MHz) of tetrakis(ferro-
cenylethynyl)tin (3; saturated solution in CD2Cl2) showing the
117/119Sn satellites (marked by asterisks) for spin-spin coupling ac-
ross one, two, three, and four bonds.
The molecular structure of 2 in the solid state, deter-
mined by X-ray analysis, is shown in Figure 3. All bond
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Ferrocenylethynyltin Compounds
FULL PAPER
lengths and angles are close to the expected values, when are two sites for tin with rather similar isotropic 119Sn
compared with other alkynes[1a] or ferrocenyl derivatives.[8,9] chemical shifts, close to the value for solutions of 2. The
The cyclopentadienyl rings are almost exactly parallel to solid-state MAS 13C NMR spectrum reveals one set of al-
each other, and deviate by 6.3° from the eclipsed positions. kynyl 13C resonances, corresponding to the symmetric mol-
The C2–C3 bond forms an angle of 2.7° (pointing away ecular structure found by X-ray analysis, and there are two
from the iron atom) with the C5H4 plane. There are no ap- additional sets of alkynyl 13C resonances which can be ex-
preciable intermolecular interactions (dFe···Fe = 956.6 pm). pected for a less symmetric arrangement of the ferrocenyl-
The literature does not contain structural data on compar- ethynyl units in the second crystalline modification.
able di(alkyn-1-yl)dimethyltin compounds.
In the case of 3, we have not been able to obtain single
crystals so far. Only one tin site was detected in the solid-
state MAS 119Sn NMR of the microcrystalline powder of
3, and this site shows an expectedly small chemical shift
anisotropy.[10] Similarly, only one set of alkynyl 13C reso-
nances is observed in the solid-state MAS 13C NMR spec-
trum. If there are several modifications of 3 present, it can
be assumed that their structures are very similar.
Reactivity of the Ferrocenylethynyltin Compounds Towards
Triethylborane
The reactivity of Sn–Cϵ bonds in alkyn-1-yltin com-
pounds towards triorganoboranes is well documented.[11,12]
The results of the reactions of 1 and 4 with triethylborane
(BEt3) are fully consistent with previous observations for
1,1-organoboration reactions, all of which proceed by cleav-
age of the Sn–Cϵ bond via a borate-like zwitterionic inter-
mediate.[12] The 1,1-ethylboration is regio- and stereospec-
ific, and affords the alkenyltin compounds 5 and 6 in essen-
tially quantitative yield (Scheme 3). The proposed struc-
tures follow from the NMR spectroscopic data (Table 2),
and the cis-positions of the stannyl and boryl groups are
Figure 3. ORTEP representation (50% probability; hydrogen atoms
have been omitted) of the molecular structure of bis(ferrocenyl-
ethynyl)dimethyltin (2). Selected bond lengths [pm] and angles [°]:
Sn–C1 211.3(8), Sn–C13 211.3(12), Sn–C14 210.0 (12), C1–C2
119.0(9), C2–C3 141.3(9), C3–C4 143.0(8)m, C3–C7 142.2(9), C4–
C5 146.1(8), C5–C6 149.2(9), Fe–centroid(C5H4) 165.6, Fe–
centroid(C5H5) 164.4; C1–Sn–C1A 107.0(4), C1–Sn–C13 108.5(3),
C1–Sn–C14 109.2(3), C13–SnC14 114.3(5), Sn–C1–C2 174.0(6),
C1–C2–C3 177.1(7), centroid–Fe–centroid 178.7.
1
confirmed by selective H/1H NOE experiments.[13]
The symmetry in the solid-state structure of 2 is remark-
The reaction of 2 with BEt3 leads to a mixture of the
able, and would be somewhat surprising if this structure is stannacyclopenta-2,4-diene 7a and the 1-stanna-4-boracy-
the sole modification of 2. Therefore, solid-state MAS clohexa-2,5-diene 8a in a ratio close to 1:2. This ratio was
13C{1H} and 119Sn{1H} NMR spectra were recorded (Fig- reproduced in several experiments in different solvents (tol-
ure 4). These measurements clearly show that the bulk ma- uene or CH2Cl2). The structural assignment follows conclu-
terial of crystalline 2 contains a second modification. There sively from the NMR spectroscopic data (Table 3 and
Figure 4. Solid-state VACP[27] MAS 13C{1H} (100.5 MHz) and 119Sn{1H} (149.1 MHz) NMR spectra of 2, showing the presence of two
values are marked by filled circles. The alkynyl 13C NMR signals
119
modifications in the crystalline state. The signals for the isotropic δ
Sn
for the modification that is not represented by the crystal structure (Figure 3) are marked by arrows.
Eur. J. Inorg. Chem. 2006, 101–108
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103

B. Wrackmeyer, M. Herberhold et al.
FULL PAPER
Table 4), and in particular from the 119Sn and 13C NMR
spectra (Figure 5).
The formation of a mixture is reminiscent of the results
of the 1,1-ethylboration of bis(phenylethynyl)dimeth-
yltin.[14] Monitoring of the reaction of 2 with BEt3 by NMR
spectroscopy shows that there is a fairly stable intermediate
9a which must be regarded as the immediate precursor of
the heterocycles. Zwitterionic complexes similar to 9a have
been observed before,[12] and they have been fully charac-
terized by NMR spectroscopic data in solution,[15] in the
Scheme 3. 1,1-Ethylboration of the (ferrocenlyethynyl)tin com-
pounds 1 and 4.
Table 2. 11B, 13C, and 119Sn NMR spectroscopic data[a] of the alkenyltin compounds 5 and 6.
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
119Sn
δ
11B
δ
(Sn–C=)
(B–C=)
(Et)
(SnMe)
(BEt2)
5[b]
134.1
[543.5]
165.3 (br)
29,7
[87.3]
14.0
[10.2]
26.4
[104.7]
14.6
–5.7
[321.6]
21.9 (br),
9.2
–54.1
82.0
76.0
6[c]
136.0
[650.1]
170.0 (br)
[65.0]
2.4
[348.4]
21.8 (br)
10.7
+46.4
[12.9]
119Sn,13
[a] In CD2Cl2 at 296 K; coupling constants J
0.5 Hz are given in brackets; br. denotes 13C NMR signals of carbon atoms bonded
to boron. [b] Other 13C NMR spectroscopic dataC: δ = 90.5 [64.9] (C1), 70.0 (C2,5), 67.4 (C3,4), 69.2 ppm (C5H5). [c] Other 13C NMR
spectroscopic data: δ = 90.1 [98.3] (C1), 68.9 [5.0], 70.0 (C5H4), 68.4 ppm (C5H5).
Table 3. 11B, 13C, and 119Sn NMR spectroscopic data[a] of the intermediates 9a and 9b.
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
11B
δ
119Sn
δ
(B–Cϵ)
(Fc-Cϵ)
(Sn–C=)
(B–C=)
(R)
(SnMe)
(BR2)
9a[b] 103.6
128.2
[21.7]
134.5
[679.1]
183.9
(br)
27.5
[137.8]
16.1
1.4
[264.7]
20,5
(br)
13.5
+0.2
147.0
(br)
[16.1]
34.4 (CH)
[145.4]
9b[b,c] 106.7
127.4
[21.4]
134.7
[708.5]
192.7
(br)
1.9
[272.8]
[c]
+34
66.0
(br)
119Sn,13
[a] In CD2Cl2 at 296 K; coupling constants J
0.5 Hz are given in brackets; br. denotes 13C NMR signals of carbon atoms bonded
to boron. [b] Other 13C NMR spectroscopic data:Cδ = 69.0–75.0 ppm (numerous overlapping signals, not assigned, for C5H5 and C5H4).
[c] Other 13C NMR signals were not assigned.
Table 4. 11B, 13C, and 119Sn NMR spectroscopic data[a] of the stannacyclopenta-3,5-diene 7a and the 1-stanna-4-boracyclohexa-2,5-dienes
8.
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
13C
δ
119Sn
δ
11B
δ
[Sn–C(2)]
[Sn–C(5)]
(B–C=)
(=C-Et)
(R)
(SnMe)
(BR)
7a[b] 138.1
136.2
[489.0]
165.8
(br)
152.5
[115.8]
28.7
[55.9]
14.7
[9.5]
27.9
[63.5]
16.2
[9.5]
–5.5
[302.1]
22.7 (br)
10.3
+11.7
–145.7
–131.7
82.0
71.4
76.0
[446.0]
8a[c] 147.7
–
–
165.7
(br)
[33.8]
–
–
–3.9
[327.7]
18.1 (br)
10.4
[472.0]
8b[d] 133.6
174.9
(br)
32.9
–3.8
[313.7]
[d]
[452.2]
(CH)[d]
[66.1]
119Sn,13
[a] In CD2Cl2 at 296 K; coupling constants J
0.5 Hz are given in brackets; br. denotes 13C NMR signals of carbon atoms bonded
to boron. [b] Other 13C NMR signals: δ = 91.1 [7C1.6], 88.3 [69.0] (C1), 68–75 ppm (numerous overlapping signals for C5H4 und C5H5).
[c] δ = 89.3 [58.9], 68–75 ppm (numerous overlapping signals for C5H4 und C5H5). [d] Other signals were not assigned owing to strong
overlap.
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Ferrocenylethynyltin Compounds
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Figure 5. 13C{1H} NMR spectrum (100.5 MHz) of the mixture of products 7a and 8a showing the assigned 13C NMR signals in the
ranges expected for the olefinic and the aliphatic carbon atoms. 117/119Sn satellites are indicated and J
119Sn,13
C coupling constants are given
in brackets.
solid state,[16] and also by X-ray analysis.[15,17,18] In such and 11B NMR spectroscopic data for 9b at room tempera-
related derivatives, with alkyl instead of the ferrocenyl ture (δ +66 ppm and δ +34 ppm) indicate that the
119Sn
11B
groups, the 119Sn resonances[15] (δ119Sn = +160 to +215 ppm) equilibrium is shifted towards the nonbridged species.
are found at slightly higher frequencies than for 9a (δ The reaction of 3 with BEt3 proceeds slowly to give a
119Sn
=
+147 ppm at 23 °C and +159 ppm at –20 °C). It is known, mixture of three final products, the spirotin compounds 10–
that the ferrocenyl group can stabilize a vinyl-cationic struc- 12 (in a ratio of 45:50:5). When the progress of the reaction
ture,[19] which may be considered for 9a as an extreme case was monitored by 119Sn NMR spectroscopy (see Figure 6),
of unsymmetrical bridging. It should also be noted that the 119Sn NMR signals for various intermediates were ob-
triorganostannyl groups in the β-position to the carbo- served. In analogy to previous work,[17,21] these were as-
cationic center exert a stabilizing effect.[20] The NMR spec- signed to the zwitterionic intermediates 13–15, which have
troscopic evidence indicates that the ferrocenyl group stabi- to be considered as precursors of the final products
lizes the bridged structure in 9a much better than a phenyl (Scheme 5). The structural assignment of the final products
119Sn
group. In previous work, where the ferrocenyl was replaced is based on the δ
values together with the observation
with phenyl groups, the equilibrium shown for the interme- of relevant 13C NMR signals in the olefinic region. The
diate 9a in Scheme 4 was found, even at –10 °C, to be much latter correspond closely to those for compounds 7a and
more on the side of the nonbridged species[15] (cf. δ
=
=
8a (see Figure 5). The 119Sn resonances differ significantly,
depending on whether the tin atom is part of a five- or six-
membered ring. 119Sn nuclei as part of five-membered rings
are typically deshielded.[22]
119Sn
+11.6 ppm and δ = +33.3 ppm at –10 °C[15] with δ
11B
119Sn
11B
+147 ppm and δ = +0.2 ppm for 9a at 23 °C).
Scheme 4. 1,1-Organoboration of the bis(ferrocenylethynyl)dimeth-
yltin (2).
When the reaction of 2 with triisopropylborane (BiPr3)
was studied under similar conditions, the formation of the
intermediate 9b took place more slowly than that of 9a. The
rearrangement of 9b was also slow (several days at room
temperature); however, in contrast to the behavior of 9a,
Figure 6. 119Sn{1H-inverse-gated} NMR spectra (149.1 MHz) of
the CD2Cl2 solution from the reaction of tetrakis(ferrocenylethy-
nyl)tin (3) with an excess of BEt3. 119Sn NMR signals of the zwit-
terionic intermediates 13–15 are observed in the beginning, and
after 10 h at room temperature only 119Sn NMR signals of the spi-
the six-membered ring 8b was formed selectively. The 119Sn rotin compounds 10, 11 and 12 (ratio 45:50:5) are left.
Eur. J. Inorg. Chem. 2006, 101–108
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B. Wrackmeyer, M. Herberhold et al.
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Scheme 5. 1,1-Ethylboration of tetrakis(ferrocenylethynyl)tin (3).
NMR spectra of solutions were measured by using the refocused
Conclusions
1
INEPT pulse sequence[25] for methyltin compounds, and by H in-
All structural and spectroscopic data indicate that the
ferrocenyl group does not exert any special effects on the
CϵC bond in ferrocenylethynyltin compounds. This is also
supported by the results of the 1,1-organoboration reac-
tions. Novel organometallic-substituted alkenes with stan-
nyl and boryl groups in cis-positions are accessible by 1,1-
ethylboration of the mono(ferrocenylethynyl)tin com-
pounds 1 and 4. Fairly stable zwitterionic intermediates
were detected in the course of 1,1-organoboration reactions
of bis(ferrocenylethynyl)dimethyltin (2) and tetrakis(ferro-
cenylethylnyl)tin (4). These reactions give access to 1-stan-
nacyclopenta-2,4-diene or 1-stanna-4-boracyclohexa-2,5-
diene derivatives and the corresponding spirotin com-
pounds. The product distribution is apparently dependent
on the nature of the trialkylborane.
verse-gated decoupling for all other cases. The chemical shifts are
given relative to SiMe4 [δ1H(C6D5H) = 7.15 ppm; δ1H(CHCl3)/
13C
CDCl3 = 7.23 ppm; δ1H(CHDCl2/CD2Cl2) = 5.33 ppm; δ (C6D6)
13C
13C
= 128.0 ppm; δ (CDCl3) = 77.0 ppm; δ (CD2Cl2) = 53.8 ppm],
0 ppm for Ξ(119Sn)
=
37.290665 MHz], or
119Sn
SnMe4 [δ
=
BF3·OEt2 [δ = 0 ppm for Ξ(11B) = 32.083971 MHz]. For solid-
11B
13C
119Sn
NMR spectroscopic
state MAS NMR spectra, the δ and δ
data are given relative to external adamantane and Sn(chex)4,
respectively, and recalculated to the SiMe4 and SnMe4 scales.
[26]
Ferrocenylethynyltrimethyltin (1):
1H NMR (250 MHz,
CD2Cl2): δ [J119Sn,1H] = 0.31 [60.0] (s, 9 H, SnMe3), 3.39, 4.13 [2m,
2×2 H, H(3,4,2,5)], 4.11 (s, 5 H, Cp) ppm. MS: m/z (%) = 374
(100) [M+], 344 (82) [M+ – 2Me], 329 (19) [M+ – 3Me].
Bis(ferrocenylethynyl)dimethyltin (2): A THF (5 mL) solution of
Me2SnCl2 (0.98 g, 4.46 mmol) was added, at 0 °C, to a solution
of the Li salt of Fc-CϵC–H [prepared from 1.87 g of Fc-CϵC–H
(8.92 mmol and an equimolar amount of BuLi (1.6  in hexane)]
in THF (15 mL). The mixture was kept stirring overnight, THF
was removed under reduced pressure, and the residue was taken up
in hexane (15 mL). After filtration, the product 2 was crystallized
at –30 °C to give 1.21 g (48%) of orange crystals (m.p. 140–144 °C).
1H NMR (400 MHz, C6D6, 296 K): δ [J119Sn,1H] = 0.30 [68.6] (s, 6
H, Me2Sn), 3.84 (m, 4 H, C5H4), 4.05 (s, 10 H, C5H5), 4.41 (m, 4
Experimental Section
General Procedures: All reactions were carried out using the usual
techniques to exclude oxygen and moisture. The starting materials
ethynylferrocene,[3] tin amides,[23] and triisopropylborane[24] were
prepared following literature procedures. BuLi, tin chlorides, and
triethylborane were used as commercial products without further
purification. Melting points were measured (Büchi 510 melting
point apparatus) in sealed capillaries under argon and are uncor-
rected. Mass spectra (EI ionization, 70 eV) were obtained using a
Finnigan MAT 8500 spectrometer with direct inlet. IR spectra: Per-
kin–Elmer, Spectrum 2000 FTIR instrument. NMR spectra:
Bruker ARX 250, Bruker DRX 500 (both for 1H, 11B, 13C and
119Sn NMR spectra of solutions), and Varian Inova 400 (for solu-
tions and for solid-state MAS 13C and 119Sn NMR spectra). 119Sn
H, C H ) ppm. IR (toluene): ν = 2140, 2114 cm–1 (CϵC). MS:
˜
5
4
m/z (%) = 598 (80) [M+], 418 (100) [M+ – SnMe2].
Tetrakis(ferrocenylethynyl)tin (3): A hexane (5 mL) solution of
SnCl4 (0.205 g, 1.74 mmol) was added, at 0 °C, to a solution of the
Li salt of Fc-CϵC–H (prepared as above; 1.46 g, 6.94 mmol) in
THF (15 mL). After stirring for 12 h at room temperature, insolu-
ble materials were filtered off, and the solid was washed with tolu-
ene and dried to give the product 3 as an orange-yellow powder
(0.877 g, 52%; m.p. 210–214 °C). 1H NMR (400 MHz, CD2Cl2,
106
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 101–108

Ferrocenylethynyltin Compounds
296 K): δ = 4.26 (m, 8 H, C5H4), 4.27 (s, 20 H, C5H5), 4.56 (m, 8 fractometer at 293(2) K with Mo-Kα radiation (graphite monochro-
FULL PAPER
H, C H ) ppm. IR (toluene): ν = 2147 cm–1 (CϵC).
mator). The structure was solved by direct methods and refined by
a full-matrix least-squares procedure. A numerical absorption was
carried out. The positions of the hydrogen atoms were calculated
and refined isotropically by applying the riding model. All non-
hydrogen atoms were refined anisotropically revealing wR2 = 0.124
and R1 = 0.056 as final R values. The final difference map had no
peaks of chemical significance (min./max. residual electron den-
sity –0.76/0.62 e10–6 pm–3).
CCDC-275737 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
˜
5
4
Chloro(ferrocenylethynyl)dimethyltin (4): A mixture of the stannane
2 (213 mg, 0.376 mmol) and Me2SnCl2 (90.1 mg, 0.414 mmol) in
toluene (1 mL) was heated at for 1 h. After removal of the solvent
and the excess of Me2SnCl2 in vacuo, the tin chloride 4 was left as
a brownish-red solid that could be used without additional purifi-
cation. The purity of 4 (according to NMR spectroscopic data) was
Ն 95%. 1H NMR (400 MHz, C6D6, 296 K): δ [J119Sn,1H] = 0.55
[69.1] (s, 6 H, Me2Sn); 4.20 (m, 2 H, C5H4); 4.22 (s, 5 H, C5H5);
4.45 (m, 2 H, C5H4) ppm.
Organoboration the of Stannanes 1–4 with Triethylborane (General
Procedure): A twofold excess of BEt3 (four equivalents were used
in the case of 3) was added, at –78 °C, to a solution of the respec-
tive alkyn-1-yltin compound 1–4 (0.2–0.4 mmol) in CH2Cl2 and the
reactions were monitored by 119Sn NMR spectroscopy. For multi-
nuclear NMR characterization of the zwitterionic intermediates 9a
and 9b the same reactions were carried out with 0.1 mmol of 2 in
CD2Cl2. The reaction of 2 with BiPr3 was also done on a small
scale (0.05 mmol) in CD2Cl2 for NMR studies.
5: Orange-red oil. 1H NMR (500.1 MHz. CDCl3, 296 K): δ
[J119Sn,1H] = 0.05 [53.0] (s, 9 H, Me3Sn), 2.19, 0.85 (q and t, 2 H
and 3 H, =C-Et), 1.30, 1.11 (m and t, 10 H, BEt2), 3.85–4.00 (m,
4 H. C5H4), 3.83 (s, 5 H, C5H5) ppm.
Acknowledgments
This work was supported by the Deutsche Forschungsgemein-
schaft.
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6: Orange-red, waxy solid.: H NMR (400 MHz, 296 K, CD2Cl2):
δ [J119Sn,1H] = 0.59 [55.0] (s, 6 H, Me2Sn); 2.21 [8.5], 0.86 (q and t,
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7a: Obtained as a mixture with 8a. 1H NMR (400 MHz, 296 K,
CD2Cl2): δ [J119Sn,1H] = 0.73 [52.6] (s, 6 H, Me2Sn), 0.9 1.1 (m, 9 H,
Et, BEt2), 1.5 (q, 3J
= 7.6 Hz, 4 H, BEt2), 2.2 (q, 3J
119Sn,1H
119Sn,1H
=
7.6 Hz, 2 H, Et), 4.18 (s, 10 H, C5H5), 4.1–4.3 (m, 8 H, C5H4) ppm.
8a: Obtained as a mixture with 7a. 1H NMR (CD2Cl2, 296 K): δ
[J119Sn,1H] = 0.53 [52.6] (s, 6 H, Me2Sn), 0.9–1.1 (m, 9 H, Et, BEt),
1.5 (q, 2 H, BEt), 2.2 (q, 4 H, Et), 4.18 (s, 10 H, C5H5), 4.1–4.3
(m, 8 H, C5H4) ppm.
10: Obtained as a mixture with 11 and 12. 13C{1H} NMR
(125.8 MHz, CD2Cl2, 296 K): δ [J
28.3 [67.3], 16.2 [9.6] (Et), 68.9–69.9 (overlapping signals for C5H4
and C5H5), 87.6 [71.4] [C5H4-(1)], 89.9 [72.8] [C5H4-(1)], 134.2
[454.7] (C-1), 165.3 [43.6] (br) (C-2), 152.3 [117.8] (C-3), 139.0
[473.8] (C-4) ppm. 119Sn{1H inverse-gated} NMR (149.1 MHz,
CD2Cl2, 296 K): δ = 10.3 ppm.
11: Obtained as a mixture with 10 and 12. 13C{1H} NMR
(125.8 MHz, CD2Cl2, 296 K): δ [J
18.4 (br), 8.3 (BEt); 28.5 [57.6], 13.6 [10.1] (3-Et), 28.4 [56.4], 14.4
[9.5] (7-Et), 68.9–69.9 (overlapping signals for C5H4 and C5H5),
87.5 [79.7], 88.2 [71.0] [1,4-C5H4-(1)], 89.7 [76.1] [6-C5H4-(1)], 137.1
[409.0] (C-1), 164.5 [44.4] (br) (C-2), 153.7 [117.6] (C-3), 141.1
[428.8] (C-4), 150.0 [441.5] (C-6), 167.3 [36.6] (br) (C-7) ppm.
119Sn{1H inverse-gated} NMR (149.1 MHz, CD2Cl2, 296 K): δ =
–139.6 ppm.
12: A small amount as a mixture with 10 and 11. 13C NMR
(125.8 MHz, CD2Cl2, 296 K): δ = 18.6 (br), 8.2 (BEt), 28.5, 14.3
(2-Et), 68.9–69.9 (overlapping signals for C5H4 and C5H5), 87.9
[1-C5H4-(1)], 152.4 (C-1), 166.1 (br) (C-2) ppm. 119Sn{1H} NMR
(149.1 MHz, CD2Cl2, 296 K): δ = –275.7 ppm.
119Sn,13
C] = 22.9 (br), 9.9 (BEt2).
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Received: July 6, 2005
Published Online: November 11, 2005
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