Activation of E-Cl bonds (E = C, Si, Ge and Sn) by a C,N-chelated stannylene

Article abstract of DOI:10.1039/c3dt50278c

The reactivity of (L^CN)₂Sn (1) (where L^CN is 2-(N,N-dimethylaminomethyl)phenyl-) towards various substrates containing E-Cl bond(s) has been studied (E = C, Si, Ge and Sn). Alkyl chlorides like chloroform or dichloromethane reacts with 1 to form (L^CN) ₂SnCl₂ and unidentified by-products in poor yields. The reaction of benzoyl chloride with 1 at low temperature yielded a thermally unstable product (L^CN)₂Sn(Cl)C(O)Ph (2) which was isolated and characterized by both multinuclear NMR spectroscopy and X-ray diffraction techniques. The vicinity of the central tin atom in 2 reveals trigonal bipyramidal geometry. Attempts to oxidize 2 by dioxygen to give the corresponding organotin(iv) benzoate failed. On the other hand, the reaction of the in situ prepared (L^CN)₂SnO (synthesized by the reaction of 1 with dioxygen) with PhCOCl resulted in the formation of the desired organotin(iv) benzoate (L^CN)₂Sn(Cl)C(O)OPh (3). The reaction of 1 with Ph₃GeCl yielded triphenylgermyl-substituted diorganotin(iv) chloride (L^CN)₂Sn(Cl)GePh₃ (4) which subsequently gave mixed diorganotin(iv) chloride-oxide [(L ^CN)₂SnCl]₂O (5) upon loss of the GePh ₃ moiety in the air. When the same reaction was carried out in benzene instead of chloroform a unique [Ph₃Ge]₄[Sn ₆O₈] cluster (6) was obtained. Similarly, the reaction of 1 with Ph₃SiCl provided triphenylsilyl-substituted diorganotin(iv) chloride (L^CN)₂Sn(Cl)SiPh₃ (7) which was then oxidized to (L^CN)₂Sn(Cl)OSiPh₃ (8). The unprecedented reaction of 1 with (n-Bu)₃SnCl provided the distannane (L^CN)₂Sn(Cl)SnBu₃ (9) which could be oxidized by dioxygen to a distannoxane (L^CN)₂Sn(Cl)OSnBu ₃ (10). In addition, the solid-state structures of 3, 5, 6 and 8 were determined by the X-ray diffraction techniques. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3dt50278c

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Activation of E–Cl bonds (E = C, Si, Ge and Sn) by a
C,N-chelated stannylene†‡
Cite this: Dalton Trans., 2013, 42, 7660
Zdeňka Padělková,*a Petr Švec,a Vladimír Pejchalb and Aleš Růžičkaa
The reactivity of (LCN)2Sn (1) (where LCN is 2-(N,N-dimethylaminomethyl)phenyl-) towards various sub-
strates containing E–Cl bond(s) has been studied (E = C, Si, Ge and Sn). Alkyl chlorides like chloroform or
dichloromethane reacts with 1 to form (LCN)2SnCl2 and unidentified by-products in poor yields. The reac-
tion of benzoyl chloride with 1 at low temperature yielded a thermally unstable product (LCN)2Sn(Cl)-
C(vO)Ph (2) which was isolated and characterized by both multinuclear NMR spectroscopy and X-ray
diffraction techniques. The vicinity of the central tin atom in 2 reveals trigonal bipyramidal geometry.
Attempts to oxidize 2 by dioxygen to give the corresponding organotin(IV) benzoate failed. On the other
hand, the reaction of the in situ prepared (LCN)2SnvO (synthesized by the reaction of 1 with dioxygen)
with PhCOCl resulted in the formation of the desired organotin(IV) benzoate (LCN)2Sn(Cl)C(vO)OPh (3).
The reaction of 1 with Ph3GeCl yielded triphenylgermyl-substituted diorganotin(IV) chloride (LCN)2Sn(Cl)-
GePh3 (4) which subsequently gave mixed diorganotin(IV) chloride-oxide [(LCN)2SnCl]2O (5) upon loss of
the GePh3 moiety in the air. When the same reaction was carried out in benzene instead of chloroform a
unique [Ph3Ge]4[Sn6O8] cluster (6) was obtained. Similarly, the reaction of 1 with Ph3SiCl provided triphe-
nylsilyl-substituted diorganotin(IV) chloride (LCN)2Sn(Cl)SiPh3 (7) which was then oxidized to (LCN)2Sn(Cl)-
OSiPh3 (8). The unprecedented reaction of 1 with (n-Bu)3SnCl provided the distannane (LCN)2Sn(Cl)SnBu3
(9) which could be oxidized by dioxygen to a distannoxane (LCN)2Sn(Cl)OSnBu3 (10). In addition, the
solid-state structures of 3, 5, 6 and 8 were determined by the X-ray diffraction techniques.
Received 27th January 2013,
Accepted 14th March 2013
DOI: 10.1039/c3dt50278c
www.rsc.org/dalton
hand, tin(II) compounds are widely used for example for ring
opening polymerization of biodegradable polymers.7 In the
1. Introduction
In early 1974, directly after its breakthrough discovery by last few years, a renaissance of low valent germanium and tin
Lappert, thermally robust higher congeners of carbenes – ger- chemistry is taking place mainly thanks to discoveries of new
mylenes and stannylenes – attracted considerable attention.1 reactivity of low valent germanium and tin compounds by
Much attention has been paid to the oxidation reactions,2 Bannaszak-Holl and Power, where the first one used Lappert
complexation to various transition metals3 and photolysis.4 germylenes and stannylenes for activation of C–H bonds in
The prominent reactivity issues have been studied also in the alkanes, alkenes and alkynes8 or one-pot coupling reactions,9
area of the oxidative addition reactions of alkyl- or arylhalides and the second one is successful in activation of various small
to dialkyl- or bis-amidogermylenes and stannylenes.5 The tin molecules such as for example dihydrogen or ammonia.10
halide promoted C–H bond activation as well as the addition
It is a well known fact that common stannylenes5b,d (Fig. 1A
of tin compounds to the unsaturated systems is also described and B) or tin(II) halides11 can undergo an oxidative addition
but the number of papers is rather limited.6 On the other using appropriate reagents, usually of the R–X type (R = alkyl
or aryl, X = Cl, Br, I), as stated above. The proper choice of the
aDepartment of General and Inorganic Chemistry, Faculty of Chemical Technology,
University of Pardubice, Studentská 573, CZ-532 10, Pardubice, Czech Republic.
E-mail: zdenka.padelkova@upce.cz; Fax: +420 466037068
bInstitute of Organic Chemistry and Technology, Faculty of Chemical Technology,
University of Pardubice, Studentská 573, CZ-532 10, Pardubice, Czech Republic
†This paper is dedicated to Professor Dr Jaroslav Holeček on the occasion of his
80th birthday on February 6th 2013 and for his enormous contribution to the
chemistry of coordination and organometallic compounds, NMR spectroscopy
as well as to the development of his parent faculty.
‡CCDC 921170–921174. For crystallographic data in CIF or other electronic
Fig. 1 Schematic drawings of Lappert stannylenes (A, B) and doubly C,N-
format see DOI: 10.1039/c3dt50278c
chelated stannylene (C) used by us for its reactivity studies.
7660 | Dalton Trans., 2013, 42, 7660–7671
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unsuccessful results were obtained when the reactivity of 1
towards alkyl chlorides (such as CH2Cl2 and (Me3Si)2CHCl)
and aryl iodide (9-isopropyl-6-iodopurine) was investigated.
The presumed oxidative addition reactions did not proceed as
one would expect, and only the slow formation of the corres-
Scheme 1 Solvent participation in oxidative reactions affects the formation of ponding diorganotin(IV) dihalides of the (LCN)2SnX2 type was
products (the scheme is adopted from the literature5d).
confirmed by the multinuclear NMR measurements. The pro-
ducts of the C–C coupling reactions were probably formed as
corresponding by-products but we did not even try to identify
them. Identically, (LCN)2SnI2 was the product of the reaction of
solvent plays a key role since different products can be thus
obtained as shown in Scheme 1. An important issue of these
reactions is also the possibility of oxidative coupling to give
R–R species which was reported in mid-seventies of the last
century.12
1 with [(Me3Si)2CH]3SnI. On the other hand, the reaction of 1
with benzoyl chloride provided novel organotin(IV) species as a
product of oxidative addition when carried out at proper con-
ditions as discussed below.
To the best of our knowledge, nobody has investigated the
reactivity of the C,N-chelated stannylene 1 (Fig. 1C) towards
group 14 species containing the E–X (where E = C, Si, Ge and
Sn; and X = Cl, Br and I) bond(s) yet. Recently only one paper
dealt with the oxidative additions of the RnPCl3−n (where n =
1–2) compounds towards the cyclic and acyclic germanium
and tin heterocarbenoids.13 The other two papers by Lappert
describe14 the reactivity of homoleptic aromatic amino-stabil-
ized germylene and stannylene (E{C6H3(NMe2)2-2,6}2), respect-
ively, with SiCl4, MeSiCl3, XeF2, HgCl2, TeCl4, dabco·2Br2, I2, or
SiMe3N3. Mixed species with a direct Sn–E (where E = Si, Ge
and Sn) bond are usually prepared from hydrido15 and
lithium16 compounds or by a Wurtz type coupling17 but the
direct and clean procedure using low valent compounds is still
elusive.
In this paper we explore the reactivity of coordinationally
saturated bis-C,N-chelated stannylene 1 (for the numbering of
the LCN ligand see Fig. 2), first prepared by Angermund,18 and
try to compare it with the first Lappert V-shaped stannylenes.
We have already described the C,N-chelated stannylene
oxidation by chalcogenes,19 the reactivity with azobenzene,20
molybdenum and tungsten carbonyls21 and Negishi reagent
analogs.22 Now we decided to investigate the reactivity of
C,N-chelated stannylene (Fig. 1C) towards various E–X (where
E = C, Si, Ge and Sn; X = Cl, I) bond containing species.
2.2. Reactivity of (LCN)2Sn (1) towards benzoyl chloride
The reaction of doubly C,N-chelated stannylene 1 with benzoyl
chloride, which has been also reported to be a successful one
by Lappert, was chosen for the purpose of this work as a paral-
lel for both types of stannylenes comparison, and also due to
the facile availability of both reagents. This reaction could be
taken as an alternative of conventional acyl stannanes success-
fully used for the acylation of dienes or allylic esters.23 More-
over, the desired product of the oxidative addition 2 can be
isolated in a moderate yield of 42% (Scheme 2).
Single crystals of 2 (Fig. 3) suitable for X-ray diffraction
analysis grew overnight in the NMR tube containing the satu-
rated benzene-d6 solution of 2. The central tin atom in 2 is
five-coordinated and reveals distorted trigonal bipyramidal
geometry. According to Bent’s rule,24 both electronegative
atoms X (X = N and Cl) occupy axial positions while all three
carbon atoms originating from organic ligands lie in the equa-
torial plane of the trigonal bipyramid. It is clearly seen that
only one of the ligands is bidentately bound to the tin
atom (the interatomic distance Sn1–N1 being 2.447(2) Å). This
connection can be considered as a strong intramolecular N→Sn
interaction. The second ligand behaves as a monodentate one.
This conclusion is based on the corresponding Sn1–N2 inter-
atomic distance (Sn1–N2 = 3.440(2) Å) found in the single
crystal of 2. The intramolecular N→Sn interaction causes a slight
elongation of the Sn–Cl bond to 2.508(3) Å which is in line
with the values found for similar C,N-chelated triorganotin(IV)
chlorides.25 The N1–Sn1–Cl1 interatomic angle being 170.88(5)°
is close to the ideal straight angle.
2. Results and discussion
2.1. Reactivity of (LCN)2Sn (1) towards alkyl chlorides and aryl
iodide
The chemical shift values, integral intensities and multi-
1
In general, and contrary to the reactivity described for the
Lappert stannylenes1c,5 as shown in Scheme 1, rather
plicity of each signal in the H NMR spectrum of 2 (recorded
in THF-d8) correspond well to the proposed molecular
Fig. 2 Schematic drawing of the C,N-chelating ligand and the numbering of its
atoms.
Scheme 2 Preparation of 2 and 3 from 1.
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Fig. 3 Molecular structure of 2 (ORTEP presentation, 50% probability level).
Hydrogen atoms are omitted for clarity. Selected interatomic distances [Å] and
angles [°]: Sn(1)–N(1) 2.447(2), Sn(1)–N(2) 3.440(2), Sn(1)–Cl(1) 2.5083(6), Sn(1)–
C(1) 2.129(2), Sn(1)–C(10) 2.140(2), Sn(1)–C(19) 2.220(3), O(1)–C(19) 1.218(3);
C(1)–Sn(1)–C(10) 132.28(9), C(1)–Sn(1)–C(19) 119.36(9), C(10)–Sn(1)–C(19)
106.55(9), C(1)–Sn(1)–N(1) 75.81(8), C(10)–Sn(1)–N(1) 93.35(8), C(19)–Sn(1)–N(1)
89.28(8), C(1)–Sn(1)–Cl(1) 95.30(7), C(10)–Sn(1)–Cl(1) 94.24(7), C(19)–Sn(1)–Cl(1)
93.40(7), N(1)–Sn(1)–Cl(1) 170.88(5).
Fig. 4 Molecular structure of 3 (ORTEP presentation, 30% probability level).
Hydrogen atoms and solvent molecules are omitted for clarity. Selected inter-
atomic distances [Å] and angles [°]: Sn(1)–N(1) 2.580(3), Sn(1)–N(2) 2.623(3),
Sn(1)–O(1) 2.071(3), Sn(1)–O(2) 3.189(3), Sn(1)–Cl(1) 2.4305(10), Sn(1)–C(1)
2.124(4), Sn(1)–C(10) 2.118(4), C(19)–O(1) 1.305(5), C(19)–O(2) 1.219(6), O(1)–
Sn(1)–N(1) 162.59(10), Cl(1)–Sn(1)–N2 168.75(8), O(1)–Sn(1)–C(10) 112.53(14),
O(1)–Sn(1)–C(1) 92.02(17), C(10)–Sn(1)–C(1) 146.53(18), O(1)–Sn(1)–Cl(1)
90.28(8), C(10)–Sn(1)–Cl(1) 101.25(10), C(1)–Sn(1)–Cl(1) 100.01(9).
structure. In general, the value of the 3J(119Sn, 1H) coupling
constant of satellites of the doublet of the H(6′) signal in 1H
NMR spectra is a very useful tool for the characterization of all
C,N-chelated organotin(IV) compounds.26 The observed value
of the coupling constant 3J(119Sn, 1H) being 72.7 Hz in the case
of 2 thus clearly matches with the typical values reported for
related triorganotin(IV) species.27 A typical AX spectral pattern
of the CH2N fragments is usually observed for doubly C,N-che-
lated organotin(IV) species25b,c in 1H NMR spectra and 2 makes
no exception (see the Experimental section). The only broad
resonance (δ(119Sn) = −319.6 ppm) observed in the 119Sn NMR
spectrum of 2 lies in the range of chemical shift values found
for six-coordinate organotin(IV) species in solution.25b,c Based
on the latter finding we assume that both ligands exhibit a
bidentate bonding fashion and thus the vicinity of the central
tin atom in solution reveals a distorted octahedral geometry.
Moreover, the 13C NMR spectrum of 2 was recorded. The
signal of the carbonyl fragment is significantly shifted down-
field to 238 ppm. Similar chemical shift values have already
been reported for compounds containing the E–C(vO)R (for
example E = Al, Mo, W, Pd, Ga, Pb, As, Sb and others)
moieties.28
carbon atoms in mutual trans positions. Contrary to 2, where
only one intramolecular N→Sn interaction was identified, in
this particular case both ligands are bound bidentately to the
tin atom. Nitrogen donor atoms are mutually in cis position
and the Sn–N interatomic distances (Sn1–N1 = 2.580(3) Å, Sn1–
N2 = 2.623(3) Å) reveal medium strength of the N→Sn intra-
molecular interaction. It is evident from the X-ray diffraction
analysis that the benzoate moiety exhibits a monodentate
bonding fashion with respect to the tin atom (Sn1–O1 2.071(3)
Å and Sn1–O2 3.189(3) Å) which is in accordance with
previously published results concerning the structure of doubly
C,N-chelated diorganotin(IV) carboxylates.29
1
The H NMR spectrum of 3 reveals similar spectral pattern
as observed for 2 (see the Experimental section). The 119Sn
NMR spectrum further supports the presumable formation of
3 because the observed chemical shift value (δ(119Sn) =
−372.5 ppm) is shifted by ca. 50 ppm upfield when compared
to 2 ((δ(119Sn) = −319.6 ppm)). Another proof of the formation
of 3 is based on the resonance of the OCvO moiety found at
161.9 ppm in the 13C NMR spectrum which is in the range
typical of related organotin(IV) carboxylates.29
Surprisingly, the air-stable diorganotin(IV) benzoate 3 could
not be prepared by the oxidation of 2 by bubbling dry dioxygen
into the diethyl ether/THF solution of 2. Nevertheless, the
desired organotin(IV) benzoate 3 was synthesized by the altera-
tion of the reaction procedure (Scheme 2) which is based first
on the oxidation of 1 by dioxygen and subsequent reaction of
2.3. Reactivity of (LCN)2Sn (1) towards triphenylgermyl
chloride
the in situ prepared (LCN)2SnvO19a with benzoyl chloride. Reaction of 1 with Ph3GeCl exclusively produced the triphenyl-
Since suitable single crystals of 3 were obtained the structure germyl-substituted doubly C,N-chelated diorganotin(IV) chlor-
of 3 in the solid state could be thus determined by X-ray crys- ide 4 (Scheme 3) in a reasonable yield. Since we isolated no
tallography techniques (Fig. 4). The tin atom is six-coordinated suitable single crystals of 4 this complex was characterized by
with a heavily distorted octahedral geometry having both multinuclear NMR spectroscopy only.
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Scheme 3 Preparation of 4 and its reactivity towards air.
1
The H NMR spectrum of 4 recorded in THF-d8 displays all
resonances at predictable positions which were assigned to
both LCN and –GePh3 substituents. The signal of the H(6′)
protons is somewhat broadened but still showing a readable
1
3J(119Sn, H) coupling constant of ca. 65 Hz which is close to
the typical values observed for related C,N-chelated triorgano-
Fig. 5 Molecular structure of 5 (ORTEP presentation, 40% probability level).
Hydrogen atoms are omitted for clarity. Selected interatomic distances [Å] and
angles [°]: Sn(1)–Cl(1) 2.4828(9), Sn(1)–O(1) 1.961(2), Sn(1)–C(1) 2.123(3), Sn(1)–
tin(IV) species. From this point of view one could say that the
3
1
–GePh3 substituent affects the J(119Sn, H) value in a similar
way as common organic substituents do. Unequivalent CH2N C(10) 2.142(3), Sn(2)–Cl(2) 2.4774(9), Sn(2)–O(1) 1.963(2), Sn(2)–C(19) 2.132(3),
Sn(2)–C(28) 2.119(3), Sn(1)–N(1) 2.560(3), Sn(1)–N(2) 2.804(3), Sn(2)–N(3)
protons resonate as doublets in the AX pattern at 3.78 and
2.94 ppm, respectively. The 119Sn NMR chemical shift value
2.607(3), Sn(2)–N(4) 2.910(3), O(1)–Sn(1)–C(1) 112.17(11), O(1)–Sn(1)–C(10)
97.78(11), C(1)–Sn(1)–C(10) 145.40(13), O(1)–Sn(1)–Cl(1) 96.99(7), C(1)–Sn(1)–
(δ(119Sn) = −167.7 ppm) of the resonance found for 4 indicates
Cl(1) 96.07(9), C(10)–Sn(1)–Cl(1) 97.10(8), O(1)–Sn(2)–C(28) 110.64(11), O(1)–
that the central tin atom is only five-coordinate in solution,
Sn(2)–C(19) 100.00(11), C(28)–Sn(2)–C(19) 143.02(13), O(1)–Sn(2)–Cl(2)
reflecting thus the presence of one monodentately and one 96.79(7), C(28)–Sn(2)–Cl(2) 97.29(9), C(19)–Sn(2)–Cl(2) 99.18(9), Sn(1)–O(1)–
bidentately bound C,N-ligands. A very close 119Sn NMR chemi-
Sn(2) 138.96(15), N(1)–Sn(1)–Cl(1) 169.76(6), N(3)–Sn(2)–Cl(2) 171.43(7).
cal shift value (δ(119Sn) = −163.4 ppm) was observed when the
same 119Sn NMR spectrum was recorded in benzene-d6 as a
non-coordinating solvent. Based on these measurements we
assume no coordination of the THF-d8 solvent to the tin
center in 4.
When chloroform solution of 4 is exposed to air for a long
period of time the Sn–Ge bond cleaves, forming thus novel
dinuclear doubly C,N-chelated organotin(IV) oxochloride 5 and
a hexaphenyldigermoxane which was confirmed by both multi-
with an integral intensity of four. The resonance observed in
the 119Sn NMR spectrum (δ(119Sn) = −278.8 ppm) can be thus
attributed to 5 since this chemical shift value is close to
that previously reported for doubly C,N-chelated organotin(IV)
halides.25b,c
On the other hand, surprisingly, if 4 is exposed to air in
benzene for several days it undergoes a hydrolysis giving thus
a unique germanium-substituted oxo-tin cluster and free
nuclear NMR spectroscopy and X-ray diffraction analysis
ligand as a by-product (Scheme 3). Unequivocal proof of struc-
(Scheme 3). Single crystals of 5 were isolated within several
ture 6 was provided by crystallographic analysis of single crys-
days from the diethyl ether/THF solution stored in a freezing
tals (Fig. 6). The structure of the [Sn6O8] core (Fig. 7) is
box (Fig. 5). The main feature of 5 is that the oxygen atom
bridges two tin-containing units (with interatomic Sn–O dis-
tances being 1.961(2) and 1.963(2) Å, respectively) each
identical with that prepared by the thermally-driven self-
condensation of the bis[bis(trimethylsilanolato)tin] reaction
differing only in the nature of substituents (–GePh3 instead of
bearing two C,N-chelating ligands and a terminal chlorine. A
–SiMe3).30 The Sn–O (2.08 Å on average) and Sn–O(Ge) (varying
detailed investigation revealed that only one of two ligands of
from 2.32 to 2.47 Å) interatomic distances are somewhat
each tin-containing unit exhibits intramolecular N→Sn inter-
action (Sn1–N1 = 2.560(3) Å and Sn2–N3 = 2.607(3) Å) of a
medium strength while the second one acts only as a mono-
dentate ligand since the interatomic Sn–N distances (Sn1–N2 =
longer than the corresponding distances found for similar
clusters bearing trimethylsilyl-substituents.30 Owing to the
presence of four Ph3Ge moieties, 6 is only sparingly soluble in
common organic solvents which was a limitation for us to
2.804(3) Å and Sn2–N4 = 2.910(3) Å) are too long to speculate
study the structure of 6 in solution by multinuclear NMR spec-
about coordination. From another point of view, one could say
that crystal structure of 5 is made up of two identical tin-
containing trigonal bipyramidal units which share one common
vertex represented by the O1 atom.
1
troscopy. Only the H NMR spectrum of 6 was recorded reveal-
ing resonances of Ph substituents at predictable positions.
2.4. Reactivity of (LCN)2Sn (1) towards triphenylsilyl and
trimethylsilyl chloride
Due to the limited solubility of 5 in common organic sol-
vents only 1H and 119Sn NMR spectra of poor quality were
1
recorded. Nevertheless, the H NMR spectrum of 5 measured Oxidative addition of Ph3SiCl to 1 gave triphenylsilyl substi-
in CDCl3 exhibited one set of broad signals attributable to the tuted diorganotin(IV) chloride 7 in a reasonable yield as
LCN ligands. A detailed interpretation further revealed the non- expected (Scheme 4). Unfortunately, we were not able to isolate
equivalency of the CH2N moieties which is represented by two single crystals of sufficient quality for the X-ray diffraction
very broad resonances at 3.81 and 3.42 ppm, respectively, each analysis and thus 7 was fully characterized by multinuclear
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Scheme 4 Preparation of 7 and its reactivity towards dioxygen.
positions. The only signal observed in the 119Sn NMR spec-
trum of 7 was found at 210.0 ppm (measured on two different
spectrometers) which is far away from the chemical shift value
found for 4 (δ(119Sn) = −167.7 ppm). This discrepancy has not
been rationally explained yet. To further support the suggested
presence of the silicon-tin bond we tried to read the 1J(29Si,
119Sn) value in the 119Sn NMR spectrum but no silicon satel-
lites were observed despite the long time of acquisition. The
explanation for this could be that the 1J(29Si, 119Sn) usually
exhibits a value of about 100 to 500 Hz (reported earlier in the
literature for compounds containing the Si–Sn bond(s))31 and
thus it is overlapped by the relatively broad resonance of the
tin atom. On the other hand, a similar chemical shift value
(δ(119Sn) = 192 ppm) was observed for tris(trimethylsilyl)silyl
substituted tin chloride.32 Downfield shift of the tin resonance
was reported for the 1,2-dichloro-1,1,2,2-tetrakis(di-tert-butyl-
methylsilyl)distannane (δ(119Sn) = 59 ppm), too.33 To the best
of our knowledge no more structurally relevant compounds
have been studied by 119Sn NMR spectroscopy and thus a more
detailed comparison with an observed chemical shift value
could not be made.
Fig. 6 Molecular structure of 6 (ORTEP presentation, 50% probability level).
Hydrogen atoms are omitted for clarity. Selected interatomic distances and
angles are given in Fig. 7 caption.
Amazingly, the analogous reaction of 1 with Me3SiCl did
not provide the target product of oxidative addition and only
pure unreacted 1 was recovered from the reaction mixture. The
possible explanation is that volatile Me3SiCl slowly evaporates
during the course of the reaction and thus becomes absent in
the solution.
In contrast to the unsuccessful oxidation of 2, the reaction
of 7 with oxygen gave presumably novel doubly C,N-chelated
diorganotin(IV) oxochloride 8 (Scheme 4). In other words, the
oxygen atom inserts into the original Sn–Si bond to form 8.
This species was structurally characterized by both multinuc-
lear NMR spectroscopy and X-ray diffraction techniques
(Fig. 8). In general, the vicinity of the tin atom in doubly C,N-
chelated diorganotin(IV) complexes usually exhibits a distorted
octahedral geometry with C,C-transoid arrangement and 8
makes no exception. Carbon atoms of the C,N-chelating
ligands are mutually in trans positions as well as the N2 and
O1 atoms are. The intramolecular N1→Sn1 interaction (Sn(1)–
N(1) = 2.582(6) Å) of medium strength causes the elongation of
the Sn–Cl bond to 2.4345(16) Å as in the case of 2 or 3. The
second N→Sn intramolecular interaction is significantly
Fig. 7 Detailed ORTEP presentation (50% probability level) of the oxo-tin core
of 6. All hydrogen and carbon atoms were omitted for clarity. Selected inter-
atomic distances [Å] and angles [°]: Sn(1)–O(1) 2.469(4), Sn(1)–O(2) 2.091(4),
Sn(1)–O(3) 2.0852(12), Sn(1)–O(1a) 2.324(4), Sn(2)–O(1) 2.421(4), Sn(2)–O(2)
2.062(4), Sn(2)–O(2b) 2.079(3), Sn(2)–O(4) 2.420(3), Ge(1)–O(1) 1.787(3), Ge(2)–
O(4) 1.792(5), Ge(1a)–O(1a) 1.787(4), Ge(1b)–O(1b) 1.787(3), Sn(1)–O(1)–Sn(2)
92.88(12), Sn(1)–O(3)–Sn(1a) 115.50(10), Sn(1)–O(3)–Sn(1b) 115.50(10),
Sn(1)–O(1a)–Sn(1a) 94.72(14), Sn(1)–O(3)–Sn(2a) 94.74(10), Sn(1)–O(2)–Sn(2)
117.18(17), Sn(1)–O(2)–Sn(2a) 113.75(16), Sn(1)–O(2)–Sn(2) 117.18(17), O(1)–
Sn(1)–O(1a) 135.31(12), O(1)–Sn(1)–O(2) 74.14(13), O(1)–Sn(1)–O(3) 73.19(8),
O(1)–Sn(1)–O(1a) 135.31(12), O(1)–Sn(1b)–O(1b) 135.31(13), O(1)–Sn(1b)–
O(2b) 135.31(13), O(1)–Sn(1b)–O(3) 76.39(10).
1
NMR spectroscopy in solution only. The H NMR spectrum of weaker (Sn(1)–N(2) = 2.714(3) Å) but still influences the vicinity
7 is in accordance with its proposed structure exhibiting very of the central tin atom.
broad resonances of both non-equivalent CH2N (δ(1H) = 4.25
The structure of 8 in solution was investigated with the
and 2.80 ppm, respectively, in C6D6) and NMe2 (δ(1H) = help of multinuclear NMR spectroscopy, too. The 1H NMR
1.80 ppm in C6D6) moieties. The resonance of the H(6′) is spectrum of 8 recorded in benzene-d6 exhibits all expected
somewhat broadened as well. The 13C NMR spectrum of 7 signals of both LCN ligands and Ph substituents. The reson-
displays somewhat broadened resonances at predictable ances of the H(6′) (with 3J(119Sn, 1H) being 94 Hz which is a
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and n-butyl substituents. The resonance of the H(6′) proton
(δ(1H) = 8.21 ppm) is extremely broad which makes it imposs-
3
1
ible to read the J(119Sn, H) coupling constant. The non-equi-
valence of the CH2N moieties is demonstrated by the presence
of the AX pattern (δ(1H) = 3.73 and 3.10 ppm, respectively) in
1
the H NMR spectrum of 9. Two sets of signals at predictable
positions were observed in the 13C NMR spectrum of 9 when
recorded at ambient temperature (see the Experimental
section). The 119Sn NMR spectrum displays two signals which
were assigned to both the (n-Bu)3Sn moiety (δ(119Sn) =
−46.3 ppm) and the (LCN)2SnCl fragment (extremely broad,
δ(119Sn) = −133.8 ppm). The direct and unambiguous proof of
the formation of the Sn–Sn bond is based on the observation
of the 1J(119Sn, 117/119Sn) coupling constant being 4532 Hz of
the resonance at −46.3 ppm. Unfortunately, the extremely
broad resonance of the (LCN)2SnCl fragment spoiled the
reading of the 1J(119Sn, 117/119Sn) coupling constant which
should have the same value. These extremely high values of
the Sn–Sn coupling constants are characteristic of the single
Sn–Sn bonds.34 According to the observed chemical shift
values we assume that the tin atom in the (n-Bu)3Sn moiety is
four-coordinate (as in the case of related Bu3SnSnBu3 which
resonates at −80 ppm in the 119Sn NMR spectrum34a,b). On the
other hand, the tin atom in the (LCN)2SnCl fragment is evi-
dently five-coordinate bearing thus one monodentately and
one bidentately bound LCN ligands. The direct proof of this
assignment is the 1H-119Sn HMBC NMR experiment where
appropriate cross-peaks were found.
Fig. 8 Molecular structure of 8 (ORTEP presentation, 50% probability level).
Hydrogen atoms are omitted for charity. Selected interatomic distances [Å] and
angles [°]: Sn(1)–N(1) 2.582(6), Sn(1)–N(2) 2.714(3), Sn(1)–Cl(1) 2.4345(16),
Sn(1)–N(O1) 1.999(3), Sn(1)–C(1) 2.112(5), Sn(1)–C(10) 2.127(4), Si(1)–O(1)
1.610(3), N(1)–Sn(1)–Cl(1) 168.45(12), O(1)–Sn(1)–N(2) 168.35(13), C(1)–Sn(1)–
C(10) 151.11(17), Sn(1)–O(1)–Si(1) 146.39(19).
typical value for C,N-chelated diorganotin(IV) species25,26) and
CH2N protons (3.61 and 2.83 ppm, respectively, AX pattern) are
narrow when compared to the 1H NMR spectrum of the pre-
cursor 7. Since the only resonance observed in the 119Sn NMR
spectrum is found at −355.5 ppm (in benzene-d6) it is evident
that the central tin atom is six-coordinated with a distorted
octahedral geometry which is in line with the solid state study.
Both ligands must be thus bound bidentately to the tin atom.
In addition, such a chemical shift value is close to that
observed for related diorganotin(IV) species bearing two highly
negative substituents.25,26
The facile oxidation of 9 to 10 was carried out directly in
the NMR tube containing the benzene-d6 solution of 9. The
oxidation yielded exclusively the distannoxane 10 and hexa-
butyldistannoxane34b,c as a minor product (less than 5% accord-
ing to 1H and 119Sn NMR spectroscopy). Contrary to the
situation described for 9 we found two sets of signals assigned
to the non-equivalently bound LCN ligands in the 1H NMR
spectrum of 10. Therefore, two doublets of the H(6′) protons
are found with two different (3J(119Sn, 1H) coupling constants –
one of ca. 114 Hz and the second being ca. 82 Hz. These
values can be attributed to the diorganotin(IV) species as
described earlier in the literature.26b In addition, four different
doublets (3.85, 3.72, 2.96, and 2.87 ppm, respectively, all with
a coupling constant of ca. 13 Hz), each with the integral inten-
sity of one, are displayed for the non-equivalent protons of the
CH2N moieties. There are two sets of broad resonances
assigned to the two LCN ligands and one set attributed to
n-butyl substituents in the 13C NMR spectrum of 10. This is in
good agreement with the observed 1H NMR spectral pattern.
The insertion of the oxygen atom to the original Sn–Sn bond
causes the downfield shift of the resonance of the Bu3Sn
moiety to 81.6 ppm. A low intense resonance attributed to the
2.5. Reactivity of (LCN)2Sn (1) towards tributyltin chloride
The reaction of 1 with (n-Bu)3SnCl provided exclusively a dis-
tannane of formula (LCN)2Sn(Cl)SnBu3 (9) as a product of a
Sn–Sn coupling reaction (Scheme 5). In other words, this
unprecedented reaction thus led to the formation of a dinuc-
lear complex containing the Sn–Sn single bond. 9 can be iso-
lated as an oily product in a nearly quantitative yield and can
be gently oxidized by oxygen to give distannoxane 10 similarly
as described for the oxidation of 7.
Due to the oily nature of 9 and 10 only multinuclear NMR
structural characterization was employed. The 1H NMR spec-
trum of 9 exhibits one set of signals attributable to LCN ligands
hexabutyldistannoxane is observed as well (δ(119Sn)
=
88.8 ppm34b,c) in the same region of the 119Sn NMR spectrum.
This species was formed as a minor product during the oxi-
dation of 9. On the other hand, the original resonance of the
(LCN)2SnCl fragment observed at −133.8 ppm in the 119Sn
NMR spectrum of 9 moves up to the −254.3 ppm in the case of
Scheme 5 Synthesis of a distannane 9 and its oxidation by dioxygen to 10.
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10. Based on these data we unequivocally assume the hexa-
4. Experimental
4.1. General methods
coordination of this tin atom bearing two bidentately bound
LCN ligands. Moreover, this chemical shift value is comparable
25b
with those observed for (LCN)2SnCl2
or 5 described above.
4.1.1. NMR spectroscopy. NMR spectra were recorded
Another direct proof of the oxygen insertion into the original from solutions in CDCl3, C6D6 and THF-d8 on a Bruker Avance
2
Sn–Sn bond is represented by the J(119Sn, 117/119Sn) coupling 500 spectrometer (equipped with a z-gradient 5 mm probe) at
constants both being 435 Hz which is in line with the corre- frequencies 500.13 MHz for 1H, 125.76 MHz for 13C{1H},
sponding values reported for structurally similar com- and 186.50 MHz for 119Sn{1H} at 295 K. Solutions were
pounds.19a,b,d According to the Lockhart equation19e the obtained by dissolving approximately 40 mg of each
1
magnitude of Sn–O–Sn angle could be calculated to be 137.4°.
compound in 0.6 mL of a deuterated solvent. The values of H
chemical shifts were calibrated to residual signals of chloro-
form (δ(1H) = 7.27 ppm), benzene (δ(1H) = 7.16 ppm) or THF
(δ(1H) = 3.57 ppm). The values of 13C{1H} chemical shifts were
calibrated to signals of C6D6 (δ(13C) = 128.4 ppm) and THF-d8
3. Conclusion
The unprecedented reactivity of the C,N-chelated stannylene 1 (δ(13C) = 67.4 ppm); due to insufficient solubility of 4–6, no 13
C
towards species containing the E–Cl bond(s) (E = C, Si, Ge, and NMR spectra for these compounds are reported. The 119Sn{1H}
Sn) has been exposed. In general, the corresponding products chemical shift values are referred to external neat tetramethyl-
of oxidative additions were achieved. Unique results described stannane (δ(119Sn) = 0.0 ppm). Positive chemical shift values
in this paper thus open an up-to-date unexplored field of denote shifts to the higher frequencies relative to the stan-
chemistry of stannylenes. Further reactivity studies of 1 dards. 119Sn{1H} NMR spectra were measured using the
towards other reagents containing group 14 elements, the inverse gated-decoupling mode.
triorganotin(IV) halides in particular, are under thorough inves-
4.1.2. Elemental analyses. The compositional analyses
tigation now. The mentioned Sn–Sn coupling reaction shall be were determined on the automatic analyzer EA 1108 by
a very powerful tool for accessing novel organotin(IV) com- FISONS Instruments.
pounds. Similar reactivity studies described here for 1 will
4.1.3. Crystallography. The X-ray data (Table 1) for colour-
follow using other available stannylenes (e.g. the Lappert stan- less crystals of all compounds were obtained at 150 K using an
nylenes). Moreover, we shall pay attention to the possible use Oxford Cryostream low-temperature device on a Nonius Kappa-
of other acyl chlorides or chloroformates instead of benzoyl CCD diffractometer with MoKα radiation (λ = 0.71073 Å), a
chloride within the reaction of 1.
graphite monochromator, and the ϕ and χ scan modes. Data
Table 1 Selected crystallographic data for compounds 2, 3, 5, 6 and 8
Compound
2
3·3(C6H6)
5
6·2(C6H6)
8
Empirical formula
C
25H29ClN2OSn
C43H47ClN2O2Sn
Monoclinic
P21/c
12.6721(5)
21.1300(18)
16.1630(9)
90
127.645(4)
90
4
C36H48Cl2N4OSn2
Triclinic
P1
9.5180(12)
9.5810(5)
23.3921(12)
78.972(4)
81.579(6)
60.585(7)
2
C84H72Ge4O8Sn6
Hexagonal
P63
16.0010
16.0010
17.4671(15)
90
90
120
2
C36H39ClN2OSiSn
Triclinic
P1
9.1550(6)
9.4191(5)
11.4639(9)
66.266(5)
79.640(5)
63.335(4)
1
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
Monoclinic
P21/c
12.7460(8)
9.9541(8)
18.3250(14)
90
94.748(5)
90
4
ˉ
γ (°)
Z
V (Å3)
2317.0(3)
1.513
3426.8(4)
1.508
1820.4(3)
1.571
3873.0(4)
1.897
808.70(9)
1.433
Dc (g cm−3
)
Crystal size (mm)
Crystal shape
0.24 × 0.20 × 0.10
Block
1.237
0.25 × 0.23 × 0.19
Block
0.866
0.27 × 0.24 × 0.15
Block
1.552
0.29 × 0.22 × 0.12
Plate
3.483
0.49 × 0.33 × 0.09
Plate
0.941
μ (mm−1
F(000)
)
1072
1608
868
2136
358
h; k; l Range
−16, 16; −11, 12;
−20, 23
2.78–27.50
18 190
−16, 16; −26, 27;
−12, 12; −12, 12;
−20, 17; −18, 17;
−22, 22
2.80–27.50
23 887
−11, 11; −12, 11;
−19, 20
−30, 30
−14, 14
θ Range (°)
Reflections measured
Independent (Rint
1.86–27.50
35 304
7488
1.78–27.50
34 529
8281
1.94–27.49
15 546
6923
a
)
5196
5856
Observed [I > 2σ(I)]
4335
271
0.668/−0.562
1.079
5186
388
0.428/−0.763
1.159
5607
406
0.520/−0.599
1.046
5053
271
0.472/−0.786
1.063
6852
379
0.684/−0.713
1.055
Parameters refined
Max/min τ (e Å−3
GOFb
)
Rc/wRc
0.0289/0.0544
0.0413/0.0775
0.0393/0.0535
0.0341/0.0643
0.0329/0.0802
a Rint = Σ|Fo2 − Fo,mean2|/ΣFo b S = [Σ(w(Fo2 − Fc2)2)/(Ndiffrs − Nparams)]1/2 c Weighting scheme: w = [σ2(Fo2) + (w1P)2 + w2P]−1, where P = [max(Fo2) +
, ,
2
2Fc2], R(F) = Σ||Fo| − |Fc||/Σ|Fo|, wR(F2) = [Σ(w(Fo2 − Fc2)2)/(Σw(Fo2)2)]1/2
.
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reductions were performed with DENZO-SMN.35 The absorp- 295 K, ppm): −319.6 (br). Elemental analysis (%): found: C
tion was corrected by integration methods.36 Structures were 57.1; H 5.8; N 5.1. Calcd (%) for C25H29ClN2OSn (527.67): C
solved by direct methods (Sir92)37 and refined by full matrix 56.91; H 5.54; N 5.31.
least-square based on F2 (SHELXL97).38 Hydrogen atoms were
4.2.3. Preparation of (LCN)2Sn(Cl)(OC(vO)Ph) (3). 1
mostly localized on a difference Fourier map; however, to (0.104 g, 0.27 mmol) was dissolved in an Et2O–THF mixture
ensure uniformity of the treatment of the crystal, all hydrogen (10/10 mL) and dry dioxygen was bubbled through the solution
atoms were recalculated into idealized positions (riding for 30 minutes. Afterwards the benzoyl chloride (99%, 32 μL,
model) and assigned temperature factors Hiso(H) = 1.2 Ueq- 0.27 mmol) was added drop-wise and the reaction mixture was
(pivot atom) or 1.5 Ueq for the methyl moiety with C–H = 0.96, stirred overnight at 30 °C. The clear pale yellow reaction
0.97, and 0.93 Å for methyl, methylene and hydrogen atoms in mixture was then concentrated. Crystals of pure 3 grew upon
aromatic rings, respectively. A disordered non-coordinated storing the saturated solution at −30 °C for several days.
solvent (benzene) was found in the structure of 6. Attempts Overall isolated yield was 0.072 g (49%). 3 can be handled in
were made to model this disorder or split into two positions, the air. Single crystals of 3 grew in the NMR tube containing
but were unsuccessful. PLATON/SQUEZZE39 was used to the C6D6 solution of 3. M.p. 210–211 °C. 1H NMR (C6D6,
correct the data for the presence of a disordered solvent. A 295 K, ppm): 8.61 (br, 2H, H(6′), 3J(119Sn, 1H) could not be
potential solvent volume of 528 Å3 was found. 196 electrons read); 7.99 (d, 2H, H(o-Ph), 3J(1H(m-Ph), 1H(o-Ph)) = 8.5 Hz);
per unit cell worth of scattering were located in the voids. The 7.30–7.00 (m, 7H, H(4′, 5′ and m, p-Ph)); 6.90 (m, 2H, H(3′));
calculated stoichiometry of the solvent was calculated to be 3.66 (br d, 2H, CH2N, J(1H(A), H(X)) ≈ 13 Hz); 2.99 (br, 2H,
2
1
four additional molecules of benzene per unit cell.
CH2N); 1.82 (br, 12H, NMe2). 13C NMR (C6D6, 295 K, ppm):
161.9 (OCvO); 143.6 (C(2′), 2J(119Sn, 13C) was not observed);
4.2. Synthesis
1
136.2 (br, C(1′), J(119Sn, 13C) could not be read); 135.4 (C(6′));
4.2.1. General remarks. All solvents and starting materials 134.3 (CAr); 130.2 (CAr); 129.7 (CAr); 128.8 (CAr); 128.0 (CAr);
such as SnCl2, n-BuLi, benzoyl chloride, dimethylbenzylamine 127.4 (CAr); 126.9 (CAr); 68.0 (anisochronous CH2N); 63.5
etc. were purchased from commercial sources (Sigma-Aldrich) (anisochronous CH2N); 46.1 (br, N(CH3)2); resonance of the
and used without further purification. (LCN)2Sn (1) was syn- i-Ph was not observed. 119Sn NMR (C6D6, 295 K, ppm):
thesized according to the procedure described in the litera- −372.5. Elemental analysis (%): found: C 55.5; H 5.7; N 5.0.
ture.18 Solvents were distilled from a K/Na alloy and stored Calcd (%) for C25H29ClN2O2Sn (543.67): C 55.23; H 5.38;
over a potassium mirror under an argon atmosphere or dried N 5.15.
and degassed using a commercial drying collumn apparatus
4.2.4. Preparation of (LCN)2Sn(Cl)GePh3 (4). 1 (0.379 g,
(Innovative Technology Inc., USA). Compounds 2, 4, 7 and 9 0.98 mmol) was dissolved in benzene (10 mL) and a benzene
should be stored in a fridge or better in a freezing box in order solution of Ph3GeCl (99%, 0.336 g, 0.98 mmol) was added in
to avoid the slow decomposition of samples which was one portion. The reaction mixture was tempered to 30 °C and
observed even in the cases of vacuo sealed samples at room stirred overnight. Afterwards the volatiles were removed
temperature.
in vacuo giving crude 4 which was washed with pentane (2 ×
4.2.2. Preparation of (LCN)2Sn(Cl)C(vO)Ph (2). 1 (0.505 g, 5 mL). Off-white crystalline 4 was then dried in vacuo and crys-
1.30 mmol) was dissolved in toluene (10 mL) and a solution of tallized from toluene. Isolated yield was 0.513 g (72%). M.p.
benzoyl chloride (99%, 153 μL; 1.30 mmol) in toluene (5 mL) 170–173 °C. 1H NMR (THF-d8, 295 K, ppm): 8.04 (br, 2H, H(6′),
was added drop-wise at −50 °C. The yellow reaction mixture 3J(119Sn, 1H) ≈ 65 Hz); 7.64 (m, 6H, H(o-Ph)); 7.53 (m, 2H,
was then stirred for 10 minutes at room temperature. Within H(5′)); 7.24 (m, 2H, H(4′)); 7.18–7.08 (m, 11H, H(3′ and m,
several minutes a yellow precipitate of the desired product p-Ph)); 3.78 (br d, 2H, CH2N, 2J(1H(A), 1H(X)) ≈ 13 Hz); 2.94 (d,
sedimented. The supernatant yellow solution was removed and 2H, CH2N, 2J(1H(A), 1H(X)) ≈ 13 Hz); 1.55 (s, 12H, NMe2). 119Sn
the yellow precipitate of 2 was dried in vacuo. Isolated yield NMR (THF-d8, 295 K, ppm): −167.7. 119Sn NMR (C6D6, 295 K,
was 0.288 g (42%). Single crystals of 2 suitable for the X-ray ppm): −163.4. Elemental analysis (%): found: C 59.8; H 5.7;
diffraction analysis grew overnight in the NMR tube containing N 3.7. Calcd (%) for C36H39ClGeN2Sn (726.46): C 59.52; H 5.41;
the saturated benzene-d6 solution of 2. M.p. 160–161 °C. N 3.86.
1H NMR (THF-d8, 295 K, ppm): 8.34 (d, 2H, H(6′), 3J(1H(5′),
4.2.5. Preparation of [(LCN)2SnCl]2O (5). A stirred chloro-
3
1
1H(6′)) = 6.4 Hz, J(119Sn, H) = 72.7 Hz); 7.98 (d, 2H, H(o-Ph), form solution of 4 was exposed to moist air for one day giving
1
3J(1H(m-Ph), H(o-Ph)) = 8.4 Hz); 7.47 (m, 2H, H(5′)); 7.40–7.30 dinuclear complex 5 which was isolated by fractional crystalli-
(m, 5H, H(4′ and m, p-Ph)); 7.18 (d, 2H, H(3′), 3J(1H(4′), zation from CH2Cl2/hexane. M.p. 250–251 °C. 1H NMR (CDCl3,
2
1
1H(3′)) = 7.2 Hz); 3.86 (d, 2H, CH2N, J(1H(A), H(X)) ≈ 13 Hz); 295 K, ppm): 8.14 (br, 4H, H(6′), 3J(119Sn, 1H) could not be
3.23 (br, 2H, CH2N); 1.92 (br, 12H, NMe2). 13C NMR (THF-d8, read); 7.36 (m, 8H, H(5′ and 4′)); 7.14 (d, 4H, H(3′), 3J(1H(4′),
2
295 K, ppm): 238.0 (br, CvO); 144.7 (C(2′), J(119Sn, 13C) was 1H(3′)) = 7.7 Hz)); 3.81 (very broad, 4H, CH2N); 3.42 (very
not observed); 143.9 (C(1′), 1J(119Sn, 13C) was not observed); broad, 4H, CH2N); 2.09 (very broad, 24H, NMe2). 119Sn NMR
140.0 (i-Ph); 138.0 (br, C(6′)); 133.8 (CAr); 130.0 (CAr); 129.8 (CDCl3, 295 K, ppm): −278.8. Elemental analysis (%): found:
(CAr); 129.4 (CAr); 128.0 (CAr); 127.1 (CAr); 126.9 (CAr); 125.0 C 50.5; H 5.9; N 6.3. Calcd (%) for C36H48Cl2N4OSn2 (861.10):
(CAr); 65.9 (br, CH2N); 46.1 (br, N(CH3)2). 119Sn NMR (THF-d8, C 50.22; H 5.62; N 6.51.
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1
4.2.6. Preparation of [Ph3Ge]4[Sn6O8] (6). A stirred ben- observed); 141.6 (br, anisochronous C(1′), J(119Sn, 13C) could
zene solution of 4 was exposed to moist air for two days giving not be read); 137.6 (anisochronous C(6′)); 137.4 (anisochro-
a unique oxo-tin cluster species 6 which precipitated as the nous C(6′)); 129.1 (CAr); 128.9 (CAr); 128.8 (CAr); 128.3 (CAr);
most insoluble product. Single crystals of 6 were obtained 127.4 (CAr); 126.7 (CAr); 65.9 (anisochronous CH2N); 65.6 (an-
from the benzene solution via slow evaporation of benzene at isochronous CH2N); 46.0 (br, N(CH3)2, 3J(119Sn, 13C) ≈ 117 Hz);
2
3
ambient temperature. M.p. 176 °C. 1H NMR (C6D6, 295 K, 30.2 (n-Bu(Cβ), J(119Sn, 13C) = 20 Hz); 27.7 (n-Bu(Cγ), J(119Sn,
ppm): 7.85 (m, 24H, H(o-Ph)); 7.12–7.02 (m, 36H, H(m, p-Ph)). 13C) = 59 Hz); 16.0 (n-Bu(Cα), J(119Sn, 13C) = 340 Hz, J(119Sn,
1
2
Elemental analysis (%): found: C 42.3; H 3.1. Calcd (%) for 13C) = 197 Hz); 13.7 (br, n-Bu(Cδ)). 119Sn NMR (C6D6, 295 K,
C72H60Ge4O8Sn6 (2055.76): C 42.07; H 2.94.
ppm): −46.3 ((n-Bu)3Sn moiety, 1J(119Sn, 117/119) = 4532 Hz);
4.2.7. Preparation of (LCN)2Sn(Cl)SiPh3 (7). Synthesis of 7 −133.8 (extremely broad, (LCN)2SnCl fragment, 1J(119Sn,
was carried out similarly as for 4 starting from 1 (0.441 g, 117/119Sn) could not be read). Elemental analysis (%): found:
1.14 mmol) and Ph3SiCl (99%, 0.339 g, 1.14 mmol). Isolated C 50.8; H 7.3; N 3.9. Calcd (%) for C30H51ClN2Sn2 (712.59):
1
yield 0.552 g (71%). H NMR (C6D6, 295 K, ppm): 7.87 (br, 2H, C 50.57; H 7.21; N 3.93.
H(6′), J(119Sn, H) could not be read); 7.64 (br d, 6H, H(o-Ph),
4.2.10. Conversion of 9 to (LCN)2Sn(Cl)OSnBu3 (10). Oxygen
3
1
3J(1H(m-Ph), H(o-Ph)) ≈ 8 Hz); 7.19–7.01 (m, 13H, H(LCN and was passed through the NMR tube containing the benzene-d6
1
m, p-Ph)); 6.90 (d, 2H, H(3′), J(1H(4′), H(3′)) = 7.0 Hz)); 4.25 solution of 9 for 30 minutes resulting in the formation of oily
(br, 2H, CH2N); 2.80 (br, 2H, CH2N); 1.80 (br, 12H, NMe2). 13C 10. [(n-Bu)3Sn]2O was also formed as a minor by-product (less
NMR (C6D6, 295 K, ppm): 146.7 (C(2′), 2J(119Sn, 13C) was not than 5%). 1H NMR (C6D6, 295 K, ppm): 8.39 (d, 1H, anisochro-
3
1
observed); 143.1 (br, C(1′), 1J(119Sn, 13C) could not be read); nous H(6′), J(1H(5′), H(6′)) = 6.8 Hz, J(119Sn, H) ≈ 114 Hz);
3
1
3
1
140.6 (br, i-Ph); 138.1 (br, C(6′)); 135.6 (br, m-Ph); 129.5 (CAr); 8.24 (d, 1H, anisochronous H(6′), 3J(1H(5′), 1H(6′)) = 6.7 Hz,
129.1 (CAr); 128.5 (CAr); 128.4 (CAr); 127.4 (CAr); 127.3 (CAr); 3J(119Sn, H) ≈ 82 Hz); 7.25 (m, 2H, H(4′)); 7.14 (m, 2H, H(5′));
1
124.9 (CAr); 68.8 (anisochronous CH2N); 63.8 (anisochronous 6.92 (d, 1H, H(3′), 3J(1H(4′), 1H(3′)) = 7.1 Hz); 6.87 (d, 1H, aniso-
CH2N); 44.7 (br, N(CH3)2). 119Sn NMR (C6D6, 295 K, ppm): chronous H(3′), J(1H(4′), H(3′)) = 7.1 Hz); 3.85 (d, 1H, CH2N,
3
1
210.0. Elemental analysis (%): found: C 63.6; H 5.9; N 4.0. 2J(1H(A), H(X)) ≈ 13 Hz); 3.72 (d, 1H, CH2N, J(1H(A), 1H(X)) ≈
1
2
Calcd (%) for C36H39ClSiN2Sn (681.95): C 63.41; H 5.76; N 4.11. 13 Hz); 2.96 (d, 1H, CH2N, J(1H(A), H(X)) ≈ 13 Hz); 2.87 (d,
4.2.8. Preparation of (LCN)2Sn(Cl)OSiPh3 (8). Pure 8 was 1H, CH2N, 2J(1H(A), 1H(X)) ≈ 13 Hz); 1.88 (br s, 12H, NMe2);
prepared by the bubbling of dioxygen into the benzene solu- 1.61 (br m, 6H, H(n-Bu)); 1.33 (m, 12H, H(n-Bu)); 0.84 (t, 9H,
tion of 7 for ca. 30 minutes. All volatiles were then removed H(n-Bu), 3J (1H, 1H) = 8.0 Hz). 13C NMR (C6D6, 295 K, ppm):
in vacuo giving essentially pure 8 which was crystallized from 145.1 (br, anisochronous C(2′), 2J(119Sn, 13C) was not observed);
chloroform. M.p. 218–220 °C. 1H NMR (C6D6, 295 K, ppm): 144.4 (br, anisochronous C(2′), 1J(119Sn, 13C) could not be
8.45 (d, 1H, H(6′), 3J(1H(5′), 1H(6′)) = 5.2 Hz, 3J(119Sn, 1H) ≈ read); 143.8 (br, anisochronous C(1′), 2J(119Sn, 13C) was not
2
1
94 Hz); 8.44 (d, 1H, H(6′), J(1H(5′), H(6′)) = 5.2 Hz, J(119Sn, observed); 142.1 (br, anisochronous C(1′), J(119Sn, 13C) could
1H) ≈ 94 Hz); 7.75 (d, 6H, H(o-Ph), 3J(1H(m-Ph), 1H(o-Ph)) = not be read); 137.3 (br, anisochronous C(6′)); 136.5 (br, aniso-
8.2 Hz); 7.34–6.99 (m, 15H, H(3′, 4′, 5′ and m, p-Ph)); 3.61 chronous C(6′)); 129.0 (br, CAr); 128.7 (br, CAr); 127.8 (CAr);
3
1
3
1
(br d, 2H, CH2N, J(1H(A), H(X)) ≈ 13 Hz); 2.83 (d, 2H, CH2N, 127.6 (br, CAr); 127.2 (br, CAr); 65.4 (br, anisochronous CH2N);
2
1
2J(1H(A), H(X)) = 13 Hz); 1.50 (s, 12H, NMe2). 13C NMR (C6D6, 64.7 (br, anisochronous CH2N); 46.6 (extremely broad,
1
295 K, ppm): 143.2 (C(2′), 2J(119Sn, 13C) could not be read); N(CH3)2); 29.1 (n-Bu(Cβ), 2J(119Sn, 13C) = 20 Hz); 28.0 (n-Bu(Cγ),
143.0 (C(1′), J(119Sn, 13C) could not be read); 140.3 (br, i-Ph); 3J(119Sn, 13C) = 61 Hz); 17.7 (n-Bu(Cα), J(119Sn, 13C) = 368 Hz);
136.7 (C(6′)); 136.1 (o-Ph); 135.6 (CAr); 129.9 (CAr); 129.3 (CAr); 14.4 (n-Bu(Cδ)). 119Sn NMR (C6D6, 295 K, ppm): 81.6
128.9 (CAr); 128.5 (CAr); 127.6 (CAr); 127.3 (CAr); 64.5 (CH2N); ((n-Bu)3SnO moiety, 2J(119Sn, 117/119Sn) = 435 Hz); −254.3
46.1 (N(CH3)2). 119Sn NMR (C6D6, 295 K, ppm): −355.5. ((LCN)2Sn(Cl)O fragment, 2J(119Sn, 117/119Sn) = 435 Hz). Elemen-
Elemental analysis (%): found: C 62.2; H 5.9; N 3.9. Calcd (%) tal analysis (%): found: C 49.8; H 7.2; N 3.9. Calcd (%) for
1
1
for C36H39ClSiON2Sn (697.95): C 61.95; H 5.63; N 4.01.
C30H51ClON2Sn2 (728.59): C 49.46; H 7.06; N 3.84.
4.2.11. Reaction of towards Me3SiCl. 1 (0.097 g,
4.2.9. Preparation of (LCN)2Sn(Cl)SnBu3 (9). Synthesis of 9
1
was carried out similarly as for 4 starting from 1 (0.195 g, 0.25 mmol) was dissolved in toluene (10 mL) and Me3SiCl
0.50 mmol) and (n-Bu)3SnCl (97%, 0.169 g, 0.50 mmol). Nearly (98%, 32 μL, 0.25 mmol) was added drop-wise. The reaction
pure oily 9 was obtained after evaporation of all volatiles from mixture was stirred overnight. Multinuclear NMR spectroscopy
the reaction mixture. Isolated yield 0.552 g (88%). 1H NMR measurements of the sample prepared from the concentrated
3
(C6D6, 295 K, ppm): 8.21 (extremely broad, 2H, H(6′), J(119Sn, reaction mixture revealed only the presence of unreacted 1.18
1H) could not be read); 7.25–7.05 (br, 6H, H(3′, 4′, 5′); 3.73 (br,
4.2.12. Reaction of 1 towards CH2Cl2 (1 : 1). 1 (0.162 g,
2
1
2H, CH2N); 3.10 (d, 2H, CH2N, J(1H(A), H(X)) = 13 Hz); 1.84 0.42 mmol) was dissolved in toluene (20 mL) and dichloro-
(br, 12H, NMe2); 1.70 (m, 6H, H(n-Bu)); 1.38 (m, 12H, H(n-Bu)); methane (27 μL, 0.42 mmol) in toluene (5 mL) was added at
0.88 (t, 9H, H(n-Bu), 3J (1H, 1H) = 8.0 Hz). 13C NMR (C6D6, −30 °C. The reaction mixture was then stirred overnight at
2
295 K, ppm): 146.2 (anisochronous C(2′), J(119Sn, 13C) was not ambient temperature. The clear yellow solution was concen-
1
25b
observed); 145.2 (br, anisochronous C(2′), J(119Sn, 13C) could trated in order to prepare the NMR sample. (LCN)2SnCl2
2
not be read); 143.6 (anisochronous C(1′), J(119Sn, 13C) was not (minor product, ca. 15% mol Sn) and unreacted 118 (major,
7668 | Dalton Trans., 2013, 42, 7660–7671
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ca. 85% mol Sn) were identified as the tin-containing com-
ponents of the reaction mixture with the help of multinuclear
NMR spectroscopy.
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4.2.13. Reaction of 1 towards CH2Cl2 (2 : 1). Similarly as in
the case described above the reaction of 1 (0.228 g, 0.59 mmol)
with dichloromethane (19 μL, 0.29 mmol) in toluene resulted
25b
in the formation of (LCN)2SnCl2 (minor product, ca. 5% mol
Sn). Unreacted 118 (major, ca. 95% mol Sn) was identified as
well.
4.2.14. Reaction of 1 towards 9-isopropyl-6-iodopurine.
Similarly as in the case described above the reaction of 1
(0.081 g, 0.21 mmol) with 9-isopropyl-6-iodopurine (0.061 g,
25b
0.21 mmol) in toluene yielded (LCN)2SnI2
(ca. 40% mol Sn)
which was confirmed by multinuclear NMR spectroscopy.
Unreacted 118 (ca. 60% mol Sn) was identified as well.
4.2.15. Reaction of 1 towards (Me3Si)2CHCl. Similarly as in
the case described above, the reaction of
1 (0.090 g,
0.23 mmol) with (Me3Si)2CHCl (97%, 0.047 g, 0.23 mmol) in
toluene yielded (LCN)2SnCl2
(minor, ca. 11% mol Sn) and
25b
unreacted 118 (major, ca. 77% mol Sn) which was confirmed
by the multinuclear NMR spectroscopy. In addition, unidenti-
fied tin-containing species (ca. 11% mol Sn) was detected with
the help of multinuclear NMR spectroscopy.
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4.2.16. Reaction of 1 towards [(Me3Si)2CH]3SnI. 1 (0.078 g,
0.20 mmol) was dissolved in toluene (10 mL) and
[(Me3Si)2CH]3SnI (0.145 g, 0.20 mmol) in toluene (10 mL) was
added drop-wise. The reaction mixture was stirred overnight at
ambient temperature and then filtered. Colourless filtrate con-
25b
tained unreacted 118 (major, ca. 67% mol Sn) and (LCN)2SnI2
(ca. 22% mol Sn) which was confirmed by multinuclear NMR
spectroscopy.
Acknowledgements
The authors would like to thank the Czech Science Foundation
(grant no. P207/10/P092) for the financial support of this
work. Professor D. Dvořák from ICT Prague is acknowledged
for the gift of the iodopurine sample.
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