Cis versus Trans: The Coordination Environment about the Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives

Article abstract of DOI:10.1002/chem.201803952

The syntheses of amino alcohols MeN(CH₂CH₂CMe₂OH)₂ (1), MeN(CMe₂CH₂OH)(CH₂CMe₂OH) (2), MeN(CH₂CH₂CH₂OH)(CH₂CMe₂OH) (3), MeN(CH₂CH₂CMe₂OH)(CH₂CMe₂OH) (4), MeN(CH₂CH₂CMe₂OH)(CH₂CH₂OH) (5), and MeN(CH₂CH₂OH) (CH₂CH₂CH₂OH) (6) as well as spirocyclic tin(IV) alkoxides spiro-[nBuN(CH₂CMe₂O)₂]₂Sn (7), spiro-[MeN(CH₂CH₂CMe₂O)₂]₂Sn (8), spiro-[para-FC₆H₄N (CH₂CMe₂O)₂]₂Sn (9), spiro-[MeN(CMe₂CH₂O)(CH₂CMe₂O)]₂Sn (10), spiro-[MeN(CH₂CH₂CH₂O)(CH₂CMe₂O)]₂Sn (11), spiro-[MeN(CH₂CH₂CMe₂O)(CH₂CMe₂O)]₂Sn (12), spiro-[MeN(CH₂CH₂CMe₂O)(CH₂CH₂O)]₂Sn (13) and spiro-[MeN(CH₂CH₂O)(CH₂CH₂CH₂O)]₂Sn (14) are reported. The compounds were characterized by ¹H, ¹³C (1–14) and ¹¹⁹Sn (7–14) NMR and IR spectroscopy, EIMS and single-crystal XRD (2, 7–10 and 13, 14). Graph-set analyses were performed for compounds [(MeNH(CMe₂CH₂OH)(CH₂CMe₂OH)][HC(O)O] (2 a) and 2. The coordination environment about the tin(IV) centre of the spirocyclic compounds and their possible stereoisomers were analysed by DFT calculations (spiro-[MeN(CH₂CMe₂O)₂]₂Sn, 8–10 and 13).

Full text of DOI:10.1002/chem.201803952

A Journal of
Accepted Article
Title: Cis versus Trans: The Coordination Environment About the
Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives
Authors: Britta Glowacki, Roman Pallach, Michael Lutter, Fabian
Roesler, Hazem Alnasr, Cederic Thomas, Dieter Schollmeyer,
and Klaus Jurkschat
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To be cited as: Chem. Eur. J. 10.1002/chem.201803952
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Cis versus Trans: The Coordination Environment About the
Tin(IV) Atom in Spirocyclic Amino Alcohol Derivatives
Britta Glowackia, Roman Pallacha, Michael Luttera∆, Fabian Roeslera, Hazem Alnasra∆, Cedreric
Thomasa, Dieter Schollmeyerb∆, Klaus Jurkschat*a
Abstract: The syntheses of the novel amino alcohols
MeN(CH2CH2CMe2OH)2
(CH2CMe2OH) (2), MeN(CH2CH2CH2OH)(CH2CMe2OH) (3),
MeN(CH2CH2CMe2OH)(CH2CMe2OH) (4), MeN
(1),
MeN(CMe2CH2OH)
Introduction
(CH2CH2CMe2OH)(CH2CH2OH) (5) and MeN(CH2CH2OH)
(CH2CH2CH2OH) (6) as well as of the spirocyclic tin (IV)
alkoxides spiro-[n-BuN(CH2CMe2O)2]2Sn (7), spiro-[MeN
Amino alcohol derivatives of tin (II) and tin (IV) have been
known for a long time.[1] First investigations focused on
organotin derivatives such as organostannatranes,
(CH2CH2CMe2O)2]2Sn
(CH2CMe2O)2]2Sn
(CH2CMe2O)]2Sn
(CH2CMe2O)]2Sn
(CH2CMe2O)]2Sn
(CH2CH2O)]2Sn
(8,
spiro-[para-FC6H4N
spiro-[MeN(CMe2CH2O)
N(CH2CH2O)3SnR,
and
stannabicyclooctanes,
(9),
(10),
(11),
(12),
(13)
R’N(CH2CH2O)2SnR2 (R, R’ = alkyl, aryl). Especially the
coordination mode about the tin atom and the strength of
the intramolecular NSn coordination as a function of the
identity of the substituents R and R’ were studied .[2] With
the growing of environmental awareness, nontoxic
inorganic tin compounds[3] lacking any tin-carbon bonds
are in the focus of research.[4,5–9] Amino alcoholate
derivatives of tin are such inorganic compounds. They are
of commercial interest as they are delayed action catalysts
for polyurethane formation.[10,11,12]
In continuation of our systematic studies on amino alcohol
derivatives of tin, herein we report in a combined
experimental and theoretical approach on symmetrical
and unsymmetrical spirocyclic tin(IV) amino alcoholates
and study in detail the factors that control the coordination
environment about the central tin atoms. In all spirocyclic
tin compounds published so far, as for example spiro-
[MeN(CH2CMe2O)2]2Sn[6], the nitrogen atoms are cis.
spiro-[MeN
spiro-[MeN(CH2CH2CMe2O)
spiro-[MeN(CH2CH2CMe2O)
(CH2CH2CH2O)
and
spiro-[MeN(CH2CH2O)
(CH2CH2CH2O)]2Sn (14) are reported. The compounds
were characterized by 1H, 13C (1–14), 119Sn (7–14) NMR
and IR spectroscopy, electrospray ionization mass
spectrometry, and single crystal X-ray diffraction analysis (2,
7–10 and 13, 14). Graphset analyses were performed for
compounds
2a
[(MeNH(CMe2CH2OH)(CH2CMe2OH)]
[HC(O)O] and 2. The coordination environment about the
tin(IV) center of the spirocyclic compounds and their
possible stereoisomers were analysed by DFT calculations
(spiro-[MeN(CH2CMe2O)2]2Sn, 8–10 and 13).
Results and Discussion
I. Novel symmetrically and unsymmetrically substituted
amino alcohols
In analogy to the synthesis of similar compounds,[7,8] the
symmetrical amino dialcohol 4,4'-(methylazanediyl)bis(2-
methylbutane-2-ol), MeN(CH2CH2CMe2OH)2 (1) was prepared via
two reaction steps (Scheme 1). The reaction of methylamine and
two molar equiv methyl acrylate gave 3-methyl-[(3-methoxy-3-
oxopropyl)-methylamino]propanoate (1a). The reaction of 1a with
methylmagnesium chloride gave compound 1 as dark brown oil.
It is hydroscopic and soluble in dichloromethane and methanol
but less soluble in toluene, iso-hexane and ethylacetate.
The compounds 1a and 1 were characterized by 1H, 13C NMR
spectroscopy (see experimental section). An IR spectrum of 1
shows a broad OH at 3332 cm-1.
[a]
Dr. Britta Glowacki, M. Sc. Roman Pallach, Dr. Michael Lutter,
M. Sc. Fabian Roesler, Dr. Hazem Alnasr, B. Sc. Cederic
Thomas, Prof. Dr. Klaus Jurkschat.
Fakultät für Chemie und Chemische Biologie,
Technische Universität Dortmund
Otto-Hahn-Straße 6
44227 Dortmund, Germany
E-mail: klaus.jurkschat@tu-dortmund.de
Dr. Dieter Schollmeyer,
[b]
Institut für Organische Chemie,
Johannes Gutenberg-Universität Mainz,
55099 Mainz, Germany

Crystallography
Supporting information for this article is given via a link at the
end of the document.
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MeNH2 + 2 CH2CHCOOMe
MeOH
1. 4.2 eq. MeMgCl
2. H2O/NaOH
MeN(CH2CH2COOMe)2
1a
MeN(CH2CH2CMe2OH)2
1
2 MgCl(OMe)

Scheme 1. Synthesis of the amino alcohol 1.
The unsymmetrically substituted amino alcohol 2-[(2-hydroxy-2-
methylpropyl)(methyl)amino]-2-methylpropane-1-ol,
MeN(CMe2CH2OH)(CH2CMe2OH) (2), was obtained according to
Scheme
2
from
the
reaction
of
2-[(2-hydroxy-2-
methylpropyl)amino]-2-methylpropane-1-ol[5] with formic acid and
formaldehyde solution in an Eschweiler-Clark reaction[13]
.
Figure 1. Molecular structure of compound 2 in the solid state (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Symmetry transformations used to generate equivalent atoms: (i) 1 -
x+1,y+1/2,-z.+1/2.
Me Me
H
N
Me
Me
CH2O,
CHOOH
H
Me
N
[CHO2]
HO
OH
HO
Me
OH
Me
Me
The reaction of 1,1-dimethyloxirane with an excess of
methylamine in an ultrasonic bath gave (2-methyl-2-
hydroxypropyl)(methyl)amine MeN(H)(CH2CMe2OH) (3a) in good
yield. The precursor compounds (methyl 3-((2-hydroxy-2-
methylpropyl)(methyl)amino)propanoate) MeN(CH2CH2COOMe)
(CH2CMe2OH) (3b) and methyl 3-((2-hydroxyethyl)(methyl)
amino)propanoate MeN(CH2CH2COOMe)(CH2CH2OH) (5a) were
prepared in quantitative yield by the reaction of 3a respectively 2-
(methylamino)ethanol with methyl acrylate in an ultrasonic bath.
Reduction of compounds 3b and 5a with lithium aluminium
hydride respectively methyllithium provided the amino alcohols
Me
2a
2O
H
,
/
3
O
C
H
2
O
C
K
Me Me
Me

H
2C
O
K
N

HO
Me
OH
Me
2
Scheme 2. Synthesis of the amino alcohol 2.
The intermediate ammonium formate 2a was obtained as
crystalline material which shows good solubility in water. The
Supporting Information contains its molecular structure (Figure
S1) as determined by single crystal X-ray diffraction analysis, and
(3-hydroxypropyl)(2-hydroxy-2-dimethylpropyl)(methyl)
amine
MeN(CH2CH2CH2OH)(CH2CMe2OH) (A-3), (2-hydroxy-2-
methylbutyl)(2-hydroxy-2-methylpropyl)(methyl)amine
MeN(CH2CH2CMe2OH)(CH2CMe2OH) (4), and (2-hydroxy-2-
methylbutyl)(2-hydroxyethyl)(methyl)amine
a
detailed discussion including graph set analysis.[14,15]
Compound 2 shows good solubility in common organic solvents
such as dichloromethane, tetrahydrofuran and hot toluene.
Figure 1 shows the molecular structure of compound 2 in the solid
state.
MeN(CH2CH2CMe2OH)(CH2CH2OH) (5) (Scheme 3).
O
Me
Me
Compound 2 crystallized in the monoclinic space group P21/c with
four molecules in the unit cell. Table 1 contains selected
interatomic distances and angles involving hydrogen bonds. The
Proton H(17) is involved in an intramolecular hydrogen bond, b
(O(17)–H(17)···O(11) 2.7276(15) Å) and Proton H(11) is involved
in an intermolecular hydrogen bond, a (O(11)–H(11)···O(17)(i)
2.7298(16) Å). The interatomic <(DHA) angles in compound 2 are
171(2) and 160(2)° The hydrogen bond types a and b (Table 1)
were analysed by graph set analysis.[14,15] The unitary motif N1
contains one chain a N1 = ꢀꢁ8ꢂ and one hydrogen-bonded pattern
b N1 = ꢃꢁ8ꢂ. An IR spectrum of 2 shows a broad OH at 3294 cm-1.
MeNH2
Me
OH
H
N
Me
OH
N
Me
Me
H
3a
O
Me
O
Cl
OH
Me
N
Me
N
Table 1. Selected interatomic distances [Å] and angles [deg] of the hydrogen
bonds in compound 2 and unitary graph sets motifs (on diagonal) and basic
binary graph set (off diagonal). Symmetry transformations used to generate
equivalent atoms: (i) 1 -x+1,y+1/2,-z.+1/2.
Me
Me
HO
HO
O
O
O
O
Me
3b
Me
5a
hydrogen
D-H···A
d(D···A)
<(DHA)
a
b
bonds
MeLi
MeLi
LiAlH4
O(11)–H(11)···O(17)(i) 2.7300(15) 171(2)
a
b
ꢀꢁ8ꢂ,
a
Me
N
Me
N
Me
N
Me
N
O(17)–H(17)···O(11)
2.7274(14) 160(2)
ꢃꢁ8ꢂ
Me
Me
Me
Me
Me
Me
Me
Me
HO
HO
OH
HO
HO
OH
aNo link at binary level.
OH
OH
3
4
5
6
Scheme 3. Synthesis of the unsymmetrical amino alcohols 3–6 via the
precursors 3a, 3b and 5a.
Compounds 3–5 were obtained as yellowish oils which are
soluble in common organic solvents such as toluene,
tetrahydrofuran, dichloromethane, ethyl acetate or diethyl ether.
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The
amino
alcohol
(2-hydroxypropyl)(2-hydroxyethyl)
Compound 8 crystallized in the triclinic space group P1 (Z=1). The
tin atom has a nearly ideal octahedral coordination environment.
Remarkably, the nitrogen atoms are trans. This is the first case
for such an arrangement and a significant difference to the
structure of compound D, in which these atoms are cis.[6] In 8 the
Sn(1)–O(11) and Sn(1)–O(17) distances are 2.0134(12) and
2.0177(12) Å, respectively. They are comparable to the Sn–O
distances in 7. In compound 8 the Sn(1)–N(14) of 2.2843(15) Å is
significantly shorter than the corresponding distances in 7
(2.379(3), 2.340(3) Å) and D[6] (2.392(2) and 2.350(2) Å).
(methyl)amine MeN(CH2CH2OH)(CH2)3OH (6) was prepared by
the reaction of (2-hydroxyethyl)(methyl)amine with one molar
equiv of 3-chloro-1-propanol in the presence of ammonium
chloride (Scheme 3). Compound 6 is a colourless oil. It is soluble
in common organic solvents such as those mentioned above.
II. Spirocyclic tin(IV) compounds derived from symmetrically
substituted amino alcohols
The reaction of tin(tetra-tert-butoxide), Sn(Ot-Bu)4, with the
symmetrically substituted amino alcohols n-BuN(CH2CMe2OH)2
(B),[12,11] p-FC6H4N(CH2CMe2OH)2 (C)[9] as well as the amino
alcohol
1
gave the novel spirocyclic compounds 7[11]-9,
respectively (Scheme 4). These compounds are colourless
crystalline materials that show good solubility in common organic
solvents such as toluene, dichloromethane, and tetrahydrofuran.
Single crystals suitable for X-ray diffraction analysis of 7, 8, and 9
were obtained from their concentrated toluene solutions. Figures
2 – 4 show the molecular structures. The figure captions contain
selected interatomic distances and angles.
n-Bu
Me
Bu
n-
N
Me
Me
Me
N
Sn(Ot-Bu)4
4 t-BuOH
O
O
Me
Me
2 n-BuN(CH2CMe2OH)2
Sn
O
cis
O
B
Me
Me
7
Me
N
Figure 2. Molecular structure in the solid state of compound 7 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)–O(11) 2.001(3), Sn(1)–
O(17) 2.018(3), Sn(1)–O(31) 2.004(2), Sn(1)–O(37) 2.002(2), Sn(1)–N(14)
2.379(3), Sn(1)–N(34) 2.340(3), Sn(2)–O(61) 2.001(3), Sn(2)–O(67) 2.005(3),
Sn(2)–O(81) 2.007(3), Sn(2)–O(87) 2.006(3), Sn(2)–N(64) 2.389(3), Sn(2)–
N(84) 2.374(3). Selected interatomic angles [deg]: O(11)–Sn(1)–N(34)
165.63(11), O(37)–Sn(1)–N(14) 165.55(10), N(14)–Sn(1)–N(34) 113.80(11),
O(61)–Sn(2)–N(84) 162.59(11), O(87)–Sn(2)–N(64) 163.49(11), N(64)–Sn(2)–
N(84) 118.24(11).
Me
Me
Me
Me
Sn(O Bu)
t-
O
O
O
O
4
Sn
2 MeN(CH2CH2CMe2OH)2
1
4
BuOH
 t-
Me
Me
Me
Me
N
Me
8
Me
Me
trans
F
Me
Me
O
N
O
Sn(O Bu)
t-
4
2 p-F-C6H4N(CH2CMe2OH)2
Sn
O
4
BuOH
 t-
O
N
Me
Me
C
F
Me
Me
9
Scheme 4. Synthesis of the spirocyclic compounds 7-9. In compound 7 the
nitrogen atoms are cis and in compounds 8 and 9 the nitrogen atoms are trans,
as found in the solid state.
Compound 7 crystallized in the orthorhombic space group
P212121 (Z=4). The tin atom shows a strongly distorted octahedral
coordination environment with O(11)–Sn(1)–N(34) and O(37)–
Sn(1)–N(14) angles of 165.63(11) and 165.55(10)°, respectively.
The nitrogen atoms are cis (N(14)–Sn(1)–N(34) 113.80(11)°,
N(64)–Sn(2)–N(84) 118.24(11)°). This is in accordance with the
molecular
structures
of
the
compounds
spiro-[MeN
(CH2CMe2O)2]2Sn (D)[6], spiro-[n-BuN(CH2CMe2O)2]2Sn (E)[11]
and spiro-[Me2NCH2CH2N(CH2CMe2O)2]2Sn (F).[16]
Figure 3. Molecular structure in the solid state of compound 8 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)–O(11) 2.0134(12), Sn(1)–
O(17) 2.0177(12), Sn(1)–N(14) 2.2843(15). Selected interatomic angles [deg]:
O(11)(i)–Sn(1)–O(11) 180.00(2), O(17)–Sn(1)–O(17)(i) 180.0, N(14)(i)–Sn(1)–
N(14) 180.0. Symmetry transformations used to generate equivalent atoms:
(i) -x+1,-y,-z+1.
The Sn–O distances range between 2.001(3) Å (Sn(1)–O(11) )
and 2.018(3)Å (Sn(1)–O(17)). They are slightly longer as
compared to the corresponding distances in compound D
(1.982(2)-1.994(2)). The Sn(1)–N(34) (2.340(4) Å) and Sn(2)–
N(64) (2.389(4) Å) distances are similar to those found for D
(2.393(2), 2.350(2)). IR experiments under non-inert conditions
reveal that compound 7 is hygroscopic and sensitive towards
hydrolysis (see Supporting Information, Figure S15).
Compound 9 crystallized in the monoclinic space group P21/cwith
four molecules in the unit cell (Z = 4). In this compound the
nitrogen atoms are trans, although the amino alcoholate chains
are equal to the chains in D and 7. Apparently, the p-FC6H4-
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A
119Sn NMR spectrum shows two resonances at δ 402 ppm
substituent at the nitrogen atom in 9 is responsible for this change
of structure. The Sn(1) atom has a distorted octahedral
coordination environment with N(14)–Sn(1)–N(34), O(11)–Sn(1)–
O(17), and O(31)–Sn(1)–O(37) angles of 165.53(16)°, 153.74(16),
and 153.94(16)°, respectively. The Sn–O distances are
comparable to those of the spirocyclic compounds D[6], 7 and 8,
and range from 1.990(4) Å (Sn(1)–O(37)) to 2.025(4) Å (Sn(1)–
O(17)). The Sn(1)–N(14) and Sn(1)–N(34) distances of 2.321(4)
and 2.306(4) Å, respectively, are longer than the corresponding
(integral 23%) and δ 447 ppm (integral 77%), which are assigned
to compound 9a and the spirocyclic compound 9, respectively.
A 19F NMR spectrum of the same sample shows two signals at δ
113.6 ppm (9) and δ 116.4 ppm (9a), respectively.
distances in the trans configured spiro-compound
8
(2.2843(15) Å).
Figure 5. Molecular structure in the solid state of compound 9a (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)–O(3) 1.937(3), Sn(1)–O(4)
1.967(3), Sn(1)–O(11) 1.977(3), Sn(1)–O(17) 1.970(3), Sn(1)–N(14) 2.521(3),
Selected interatomic angles [deg]: O(3)–Sn(1)–O(4) 100.28(11), O(3)–Sn(1)–
O(11) 111.78(12), O(3)–Sn(1)–O(17) 118.98(12), O(4)–Sn(1)–O(11) 97.73(12),
O(4)–Sn(1)–O(17) 102.39(11), O(11)–Sn(1)–O(17) 120.02(12), O(3)–Sn(1)–
N(14) 87.06(11), O(4)–Sn(1)–N(14) 171.67(11), O(11)–Sn(1)–N(14) 75.71(11),
O(17)–Sn(1)–N(14) 77.09(11).
Figure 4. Molecular structure in the solid state of compound 9 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)–O(11) 2.012(4), Sn(1)–
O(17)
2.025(4),
Sn(1)–O(31)
2.021(4),
Sn(1)–O(37)
1.990(4), Sn(1)–N(14) 2.321(4), Sn(1)–N(34) 2.306(4). Selected interatomic
angles [deg]: O(11)–Sn(1)–O(17) 153.74(16), O(11)-Sn(1)-O(31) 93.96(15),
O(11)-Sn(1)-O(37) 87.91(15), O(17)-Sn(1)-O(31) 94.54(17), O(17)-Sn(1)-O(37)
95.14(17), O(31)–Sn(1)–O(37) 153.94(16), N(14)–Sn(1)–N(34) 165.53(16).
III. Spirocyclic tin compounds derived from unsymmetrically
substituted amino alcohols
To figure out whether the position of the methyl substituents at the
amino alcoholate chains has an influence concerning cis or trans
position of the nitrogen atoms in spirocyclic tin (IV) compounds,
compound 10 was synthesized by the reaction of Sn(Ot-Bu)4 with
the unsymmetrical amino alcohol 2 (Scheme 5). It was obtained
as a colourless crystalline material.
A 119Sn{1H} NMR Spectrum of a solution of 7 in C6D6 shows one
single resonance at δ –437 ppm. For compound 8 (in C6D6
solution) a single resonance at δ –603 ppm was observed. A
119Sn{1H} NMR spectrum of 9 (in C6D6 solution) shows a single
resonance at δ –447 ppm and a 19F{1H} NMR spectrum reveals a
single resonance at δ –113.6 ppm.
Me Me
An ESI MS spectrum (positive mode) of a solution of 7 in
acetonitrile showed a mass cluster centred at m/z = 218.1 which
is assigned to the protonated ligand [B+H]+, and mass clusters
centred at m/z = 551.3 [7 +H]+, 573.4 [7+Na]+, 589.4 [7+K]+, 614.4
[7+MeCN + H]+ assigned to the protonated spirocyclic compound,
the sodium- and potassium adducts and a protonated MeCN-
adduct, respectively. The compounds 8 and 9 are not stable under
ESI MS conditions.
Me
Me
Me
Me
Me Me
Me
N
Sn
O
Sn(Ot-Bu)4
BuOH
Me
Me
O
N
N
HO
Me
OH
 t-
O
O
Me
Me
Me
2
10
Scheme 5. Synthesis of the spirocyclic compound 10.
The reaction of Sn(Ot-Bu)4 with the symmetrically substituted
amino alcohol p-FC6H4N(CH2CMe2OH)2 (C)[9] gave, as a by-
product, a small amount of p-FC6H4N(CH2CMe2O)2Sn(Ot-Bu)2
(9a) as colourless crystalline material. It shows similar solubility in
organic solvents as compound 9. It crystallized in the monoclinic
space group I2/a, with eight molecules in the unit cell. Figure 5
shows the molecular structure of 9a. The figure caption contains
selected interatomic distances and angles.
The Sn(1) atom in compound 9a is five-coordinated by one
nitrogen and four oxygen atoms and shows a distorted trigonal
bipyramidal environment (geometric goodness (ϑ) = 50 °)[17]
with N(1) and O(4) occupying the axial and O(1), O(2) and O(3)
occupying the equatorial positions. The Sn–O distances vary
between 1.937(3) (Sn(1)–O(3)) and 1.977(3) Å (Sn(1)–O(11)).
The Sn(1)–N(14) distance of 2.521(3) Å is significantly longer than
the corresponding distances in the spirocyclic compound 9
(Sn(1)–N(14) 2.321(4) Å, Sn(1)–N(34) 2.306(4) Å). The trans
O(4)–Sn(1)–N(14) angle in 9a is 171.67(11) °.
Single crystals of 10 suitable for X-ray diffraction analysis were
obtained from its toluene solution. Figure 6 shows the molecular
structure of 10. The figure caption contains selected interatomic
distances and angles. Compound 10 crystallized in the
orthorhombic space group Pbca with eight molecules in the unit
cell. The nitrogen atoms are stereogenic centres in which the
coordinating lone electron pair is assigned the lowest priority. As
a consequence, there are four pairs of enantiomers with R,R and
S,S configuration.
The Sn(1) atom shows a distorted octahedral environment with
O(11)–Sn(11)–N(36), O(31)–Sn(11)–N(16), and O(22)–Sn(11)–
O(42) trans angles of 161.81(8), 159.10(8)°, and 136.38(9)°,
respectively. The N(16) and N(36) atoms are cis with an N(16)–
Sn(1)–N(36) angle of 121.72(8)°. This angle is slightly bigger than
those in compounds D (119.41(9)) and 7 (118.24(13)). The Sn–O
distances are very similar to compound D and fall in the narrow
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range between 1.9903(19) Å (Sn(11)–O(31)) and 2.002(2) Å
(Sn(11)–O(22)). However, the Sn(11)–N(16) (2.543(2) Å) and
Sn(11)–N(36) (2.461(2) Å) distances in 10 are significantly longer
as compared to those measured for D (2.392(2) Å, 2.350(2) Å).
cleavage/re-formation (traces of protons are rather difficult to
exclude experimentally), or (iii) a Ray-Dutt-twist- or Bailar-twist-
mechanism.[20]
119Sn NMR spectrum (in C6D6) of the crude reaction mixture
Me
Me
Me
Me
A
Me
Me
N
Sn
O
N
Sn
O
N
Sn
O
O
O
N
O
N
O
O
N
shows a total of five resonances at δ 398 ppm (integral 36%),
437 ppm (integral 23%), 443 ppm (integral 35%) and 460 ppm
(integral 3%), 500 ppm (integral 3%). The resonance at δ 398
O
O
O
O
10a
10b
10c
ppm
is
assigned
to
the
intermediate
MeN(CH2CMe2O)(CMe2CH2O)Sn(Ot-Bu)2. Because of the two
different amino alcoholate chains, for compound 10 three cis (10a
– 10c) and two trans (10d and 10e) isomers are possible (see
Figure 7).
cis
Me
Me
N
N
O
O
O
O
O
Sn
N
Sn
N
O
O
O
Me
10d
Me
10e
trans
Figure 7. Three possible cis isomers 10a, 10b, 10c (top) and two possible trans
isomers 10d and 10e (bottom). The methyl substituents are omitted for clarity.
The red amino alcoholate chain symbolizes NCH2CMe2O and the blue one
NCMe2CH2O.
An ESI MS spectrum (positive mode) of 10 shows a major mass
cluster centred at m/z = 467.2 which is assigned to the protonated
species of spirocyclic compound [10 + H]+.
A further alternative of generating unsymmetrical spirocyclic
tin(IV) compounds involves amino dialcohols containing two side
chains of different length. Accordingly, the reaction of Sn(Ot-Bu)4
with the unsymmetrically substituted amino dialcohols 3 – 6 gave
the novel spiro-type compounds 11 – 14 (Scheme 6).
Figure 6. Molecular structure in the solid state of compound 10 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(11)–O(11) 1.9954(19),
Sn(11)–O(22) 2.002(2), Sn(11)–O(31) 1.9903(19), Sn(11)–O(42) 1.998(2),
Sn(11)–N(16) 2.543(2), Sn(11)–N(36) 2.461(2). Selected interatomic angles
[deg]: O(22)–Sn(11)–O(42) 136.38(9), O(11)–Sn(11)–N(36) 161.81(8), O(31)–
Sn(11)–N(16) 159.10(8), N(36)–Sn(11)–N(16) 121.72(8).
A 119Sn NMR spectrum of a solution of the crystalline material in
C6D6 reveals two resonances at δ 437 ppm (integral 40%) and
443 ppm (integral 60%), respectively. A powder diffraction
analysis of the crystalline material was performed. A comparison
with the parameters obtained from the single crystal X-ray
analysis via Pawley fit[18] showed the homogeneity of the bulk
material and its identity with the structure established by single
crystal X-ray diffraction analysis. Evidently, only one isomer
crystallized. 119Sn NMR spectra of the crystalline material
dissolved in tetrachlorethane-d2, acetone-d6, acetonitrile-d3,
dichloromethane-d2 and chloroform-d1, respectively, were
collected (see Sporting Information Figure S21). The spectra in
acetonitrile-d3 (δ 438 ppm (1/2 = 134 Hz, integral 45%), δ
443 ppm (integral 55%)) and dichloromethane-d2 (δ 438 ppm
(1/2 = 150 Hz, integral 38%), δ 443 ppm (integral 62%)),
respectively, show each two resonances. Only one signal (δ
445 ppm) was observed in both acetone-d6 and chloroform-d1
whereas the spectrum in tetrachlorethane-d2 shows a total of
three resonances (δ 446 ppm (integral 70%), δ 443 ppm
(integral 18%), δ 454 ppm (integral 12%)). Apparently, in solution
several isomers exist. The population of these isomers depend on
the identity of the solvent. The interconversion of the isomers into
each other is slow on the 119Sn NMR time scale. No detailed
studies concerning the mechanism of the isomerization process
were performed. Possible mechanisms include (i) a combined
SnN dissociation followed by a Berry pseudorotation[19] and
SnN re-coordination, or (ii) protonation/de-protonation of a tin-
bound oxygen atom accompanied with tin-oxygen bond
Scheme 6. Synthesis of the spiro-cyclic compounds 11–14.
Compounds 13 and 14 are colourless crystalline materials,
whereas compounds 11 and 12 were isolated as waxy-type
residues.
Compounds 11 – 14 show good solubility in common organic
solvents such as toluene, tetrahydrofuran or dichloromethane.
The Figures 8 and 9 show the molecular structures of compounds
13 and 14, respectively, as determined by single-crystal X-ray
diffraction analysis. The Figure captions contain selected
interatomic distances and angles. The Supporting Information
(Figure S39) contains the molecular structure of the toluene
solvate 13·C7H8. In both the molecular structures of the spirocyclic
compounds 13 and 14 the nitrogen atoms are trans.
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Compound 13 crystallized in the orthorhombic space group Pbca
with four crystallographic independent molecules in the
asymmetric unit of the unit cell and 13·C7H8 crystallized in the
triclinic space group P1 with Z=1. In both 13 and 13·C7H8 the
Sn(1) atoms have an all-trans octahedral coordination sphere. In
both structures, the SnO distances are slightly longer
(Sn(1)O(11) 2.0337(11), 13; Sn(1)O(11) 2.0249(16), 13·C7H8)
when the shorter amino alcoholate chain -CH2CH2O is involved
than in the case when the longer amino alcoholate
chain -CH2CH2CMe2O is involved (Sn(1)–O(18) 2.0206(12) Å,
and Sn(1)O(17) 2.0216(15) Å, respectively). The Sn(1)–N(14)
distance in 13 is longer (2.2543(14) Å) than in 13·C7H8
(2.236(2) Å). A similarity of both structures is that in each
molecule one nitrogen atom shows a (R) and the other one a (S)
configuration.
in one molecule are both (R) or both (S) configured, giving again
four pairs of enantiomers in the unit cell.
In 13 the oxygen atoms of a given amino alcoholate chain are cis
(Figure 10, type I). Interestingly, 14 is the first example wherein
the corresponding oxygen atoms of a given amino dialcoholate
are trans (compare Figure 10, type II). This phenomenon was
already reported by Zaitsev et al[21] for related spirocyclic titan(IV)
compounds.
cis
trans
Me
Me
N
N
Sn
N
O
O
O
O
O
O
O
O
Sn
N
Me
Me
type I
type II
Figure 10. Coordination sphere of the tin atom in spirocyclic trans isomers.
Type I: the oxygen atoms of a given amino alcoholate chain are cis. Type II: the
oxygen atoms of a given amino alcoholate chain are trans.
The 119Sn NMR spectra of compounds 11–14 show respectively
two or three signals (11: δ –512 ppm (integral 48%), –512 ppm
(integral 46%) and –515 ppm (integral 6%); 12: δ 529 ppm
(integral 66%), 532 ppm (integral 13%) and 555 ppm (integral
21%); 13: δ 513 ppm (integral 25%), 536 ppm (integral 65%,
v1/2 = 150 Hz); 14: δ –516 ppm (integral 47%), –524 ppm (integral
30%) and –525 ppm (integral 23%)) which are assigned with
caution to different stereoisomers of these compounds.
Figure 8. Molecular structure in the solid state of compound 13 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)–O(11) 2.0337(11), Sn(1)–
O(18) 2.0206(12), Sn(1)–N(14) 2.2543(14). Selected interatomic angles [deg]:
O(11)–Sn(1)–O(11)(i) 180.00(7), O(18)(i)–Sn(1)–O(18) 180.0, N(14)(i)–Sn(1)–
N(14) 180.0. Symmetry transformations used to generate equivalent atoms:
(i) -x+1,-y,-z+1.
Comparing the 119Sn NMR spectra of the spirocyclic compounds
D and 7-14 (Figures 11, 12; see experimental section) reveals a
clear correlation between the 119Sn chemical shifts and the amino
alcoholate chain length and ring size associated with the latter.
The compounds D, 7, 9 and 10, exclusively containing five-
membered rings, show resonances between δ 437 (7) and 447
ppm (9). The compounds 11–14) consisting of five- and six-
membered rings high field shifts between δ 512 (11) and 556
ppm (13) are observed. A 119Sn NMR spectrum of compound 8
exclusively consisting of six-membered rings shows a high field
shifted resonance at δ –603 ppm. A correlation between ring size
and 119Sn NMR chemical shift has been reported for
stannacycloalkanes as well as for diorganodithiostannolanes.[22]
Figure 9. Molecular structure in the solid state of compound 14 (ORTEP
presentation at 30% probability of the depicted atoms and atom numbering
scheme). Selected interatomic distances [Å]: Sn(1)-O(12) 2.030(4), Sn(1)–
Figure 12. Trends for the 119Sn NMR chemical shifts for compounds D and 7–
14. Red colour: compounds crystallized as cis isomers; blue colour:
compounds crystallized as trans isomers; black colour: no solid-state structure
was obtained so far.
O(18)
2.014(4),
Sn(1)–O(21)
2.029(4),
Sn(1)–O(28)
2.011(4), Sn(1)–N(14) 2.249(5), Sn(1)–N(24) 2.261(5), Selected interatomic
angles [deg]: O(12)–Sn(1)–O(18), 167.75(17), O(21)–Sn(1)–O(28) 166.38(18),
N(14)–Sn(1)–N(24) 173.39(19).
Compound 14 crystallized in orthorhombic space group Pbca with
8 molecules per unit cell. The Sn(1) atom has a slightly distorted
octahedral coordination sphere with O(12)–Sn(1)–O(18), O(21)–
Sn(1)–O(28), and N(14)–Sn(1)–N(24) angles of 167.75(17)°,
166.38(18)°, and 173.39(19)°, respectively. The Sn(1)–N(14) and
Sn(1)–N(24) distances of 2.249(5) and 2.261(5) Å, respectively,
are comparable to those of 13 (2.2543(14) Å) and 13·C7H8
(2.236(2) Å). In the molecular structure of 14, the nitrogen atoms
Notably, the Sn–N distances in the spirocyclic compounds
reported herein vary between 2.249(5) (14) and 2.543(2) (10)
(Figure 11), although given the SnO4 substituent pattern the Lewis
acidity of the Sn(IV) atoms should be the same for all compounds.
The Sn–N distances are longer in the compounds D, 7, 9
consisting of five-membered rings only than in the spirocyclic
compounds consisting of both five- and six-membered rings (13,
14) or only-six membered rings (8). This phenomenon is
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explained by the different angles in five- and six-membered rings.
D
7
8
9
119Sn{1H} NMR [δ]
SnO [Å]
442
437
603
2.0134(12), 2.0177(12)
2.2843(15)
447
1.982(2)  1.996(2)
2.392(2)  2.350(2)
119.41(9)
2.001(3)  2.018(3)
2.340(3)  2.389(3)
113.80(11), 118.24(11)
1.990(4)  2.025(4)
2.306(4), 2.321(4)
165.53(16)
SnN [Å]
NSnN [°]
180.00
O
O
O
Me
N
Sn
N
Me
O
10
11
12
529 (66%),
13
14
437 (40%),
443 (60%)
512 (48%),
512 (46%), 515 (6%)
516 (47%),
119Sn{1H} NMR [δ]
513 (35%), 556 (65%)
532 (13%), 555 (21%)
524 (30%), 525 (23%)
2.011(4)  2.030(4)
2.249(5), 2.261(5)
173.39(19)
SnO [Å]
SnN [Å]
1.9903(19)  2.002(2)
2.461(2), 2.543(2)
121.72(8)
-
-
-
-
-
-
2.0337(11), 2.0206(12)
2.2543(14)
NSnN [°]
180.00
Figure 11. Selected experimental data of the spirocyclic tin compounds D[6]
7-14.
,
BP86/def2-TZVP
wB97xD/def2-TZVP
B3LYP/def2-TZVP
Me
Me
Me
Me
N
Me
O
O
O
O
Sn
kJ/mol
Me
Me
Me
Me
N
IV. DFT-Calculations:
Me
To investigate the coordination environment of the tin atoms in
selected spirocyclic compounds and to compare cis and trans
isomers as well as the corresponding stereoisomers, DFT
calculations with the program Gaussian09[23] were performed.
Me
Me
40
Me
N
Me
O
O
N
Sn
O
Me
Me
O
Me
Me
Me
The hybrid functional B3LYP[24–26], the pure functional BP86[24,27]
,
30
20
10
0
Me
Me
Me
N
Me
N
Me
Me
N
and the dispersive functional wB97xD[28] with the basis set def2-
TZVP[29,30], which includes the effective core potential on tin, were
used for geometry optimization and frequency analysis.
O
O
Me
Me
Me
Me
Me
Me
Me
Me
Sn
O
O
O
O
O
O
Sn
Me
Me
Me
Me
Me
Me
N
As shown above, the identity/length of the amino alcoholate chain
controls the formation of cis (D and 7) or trans isomers (8, 13, 14)
in the solid state. For the geometry optimizations, the molecular
structures of D (cis) and 8 (trans) were used. Also, the geometries
of the corresponding trans– (for D) and cis– (for 8) isomers were
calculated. Tables S2 and S3 in the Supporting Information
contain selected interatomic distances and angles. For both
structures D (cis) and 8 (trans) the calculated interatomic
distances fit best to the corresponding molecular structure in the
solid state when using the dispersive wB97xD functional.
The relative zero point-corrected energies are visualized in
Figure 13. Therein, the relative energies of the only calculated
structures are compared to the geometry optimized isomer which
was found in the solid state. The calculated relative energy levels
of D (trans) compared to D (cis) are: 39 kJ/mol (with B3LYP),
34 kJ/mol (with BP86), and 36 kJ/mol (with wB97xD), indicating
unambiguously for D the trans–isomer to be significantly higher in
energy than the cis–isomer. The trans–isomer is not preferred.
For compound 8 the case is different as the energy differences
are smaller. The relative energy levels of 8 (cis) compared to 8
(trans) are: 2 kJ/mol (with B3LYP), 9 kJ/mol (with BP86), and 15
kJ/mol (with wB97xD).
Me
D (cis)
D (trans )
8 (trans )
8 (cis)
Figure 13. Visualized relative zero point-corrected energies of the calculated
structures of the cis and the trans isomers of compounds D and 8. The relative
energy levels of D (trans) compared to D (cis) are: 39 kJ/mol (with B3LYP),
34 kJ/mol (with BP86), and 36 kJ/mol (with wB97xD) and the relative energy
levels of 8 (cis) compared to 9 (trans) are: 2 kJ/mol (with B3LYP), 9 kJ/mol (with
BP86), and 15kJ/mol (with wB97xD).
Analogously, the energy differences of the cis and the
corresponding trans isomers of compound 9 were calculated.
Furthermore, the geometry of a hypothetic pentacoordinated
species (9penta) was calculated in order to evaluate whether a
NSn dissociation might be a meaningful/reasonable step in an
isomerization process. Therein, one nitrogen atom is coordinating
the tin atom and the second nitrogen atom is not coordinating.
The geometry optimization of 9 (trans) based on the geometry as
found in solid state. Table S4 in the Supporting Information
contains selected interatomic distances and angles, and Figure
14 visualizes the resulting zero point-corrected energies.
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The N(14)–Sn(1)–N(34) angle in the molecular structure of 9 is
165.65(16)°. The DFT calculations describe this angle very well.
It varies between 164.82 and 168.26° (Supporting Information,
Table S4). For the hypothetic cis isomer the calculated N–Sn–N
angle ranges between 128.75 and 131.56°. This angle is bigger
than that measured for D (119.41(9)°) and calculated for 8
(108.66° (B3LYP)).
of 10e is likely the result of steric repulsion of the methyl
substituents of the NCH2CMe2O chain.
The energy differences between 9(cis) and 9(trans) are very small
(1 kJ/mol (with B3LYP), 3 kJ/mol (with BP86), and 6 kJ/mol (with
wB97xD)), indicating that both isomers have rather similar
probability to be formed in the reaction, but only the trans isomer
was found in the solid state. The situation is similar to that
discussed for 8, but even more pronounced. In accordance with
the fact that so far in the solid state no pentacoordinated species
was found for such spirocyclic compounds, the energy differences
between the hypothetic pentacoordinated species and the trans
isomer are significantly higher (38 kJ/mol (with B3LYP), 40 kJ/mol
(with BP86), and 67 kJ/mol (with wB97xD)).
Figure 15. Visualized relative zero point corrected energies of the calculated
structures of the cis and the trans isomers of compound 10. The methyl
substituents at the side chains are omitted for clarity. The red-coloured chain
refers to CH2CMe2O and the blue-coloured one to CMe2CH2O.
The position of the methyl groups in the amino alcoholate chains
is not decisive for a cis or a trans position of the nitrogen atoms in
such spirocyclic compounds, because in 10 the cis position is
preferred, like it is in D.
For each of the spirocyclic compounds 13 and 14, three trans
isomers a–c and three cis isomers d–f are possible. Exemplarily,
DFT calculations were performed for compound 13. The
calculations for the 13a (type I, Figure 10) and the 13b (type II,
Figure 10) isomers are based on the corresponding molecular
structures in the solid state. The molecular structure of 14, after
having artificially added four methyl moieties, was used as the
basis for the simulation of 13b. In the trans isomer 13c
the -CH2CH2CMe2O chains are cis. The cis isomers are
comparable to the calculated isomers 10a–10c. For the
calculations including toluene as solvent the IEFPCM solvent
model was used.[31–35] The Tables S8 and S9 in the Supporting
Information contain the calculated intramolecular distances and
angles and the relative zero point-corrected energies. Figure 16
visualizes the latter.
All energies are given in relation to 13a. The energy of 13b is
slightly lower with B3LYP (–2, –4 (toluene) kJ/mol), and with BP86
(2, 0 (toluene) kJ/mol) but similar to 13a when wB97xD (5, 3
(toluene) kJ/mol) is used 13b is slightly higher in energy.
Generally, the trans isomers 13a and 13b have the lowest energy
level, which is consistent with the corresponding molecular
structures as found in the solid state. Because of steric
interactions of the CH3-substituents in 13c, this trans isomer is
higher in energy (B3LYP: 13, 16 (toluene) kJ/mol; BP86: 19, 19
(toluene) kJ/mol; wB97xD: 15, 15 (toluene) kJ/mol). Generally, all
cis isomers 13d-f are higher in energy than the trans isomers 13a
and 13b. The isomer 13d is the lowest in energy of the cis isomers
(B3LYP: 9, 10 (with toluene) kJ/mol; BP86: 14, 15 (with toluene)
kJ/mol; wB97xD: 17, 17 (with toluene) kJ/mol B3LYP). The next
Figure 14. Visualized relative zero point-corrected energies for the calculated
cis and trans isomers of compound 9 and for a pentacoordinated species
9penta(cis). The relative energy levels of 9(cis) compared to 9(trans) are not
significant: 1 kJ/mol (with B3LYP), 3 kJ/mol (with BP86), and 6 kJ/mol (with
wB97xD). The relative energy levels of 9penta(cis) compared to 9(trans) are:
38 kJ/mol (with B3LYP), 40 kJ/mol (with BP86), and 67 kJ/mol (with wB97xD).
To estimate the relative energy differences between the five
possible isomers of 10 mentioned above (Figure 15), DFT
calculations were performed. Tables S5 and S6 in the Supporting
Information contain selected interatomic distances and angles.
The calculations for 10a are based on the molecular structure of
10 as found in solid state. The Sn–O distances are best described
with wB97xD/def2-TZVP. The calculated interatomic trans angles
are in good agreement with the molecular structure obtained
experimentally. The calculated trans angles for the trans isomers
10d an 10e vary between 164.23° and 176.11°. In both trans
isomers the tin atom has a distorted octahedral coordination
environment which is similar to the situation in D and 7 but
different to 8.
Generally, the isomer 10a, which is identical to the molecular
structure of 10, has the lowest energy. Table S7 in the Supporting
Information contains the relative energies of the other isomers
10b–10e compared to 10a. Figure 15 visualizes the relative zero
point-corrected energies. The energy levels of the cis isomers 10b
and 10c are very similar (31 kJ/mol for 10b and 28 kJ/mol for 10c).
Both trans isomers 10d (45 kJ/mol (B3LYP), 38 kJ/mol (BP86) 35
kJ/mol (wB97xD)) and 10e (50 kJ/mol (B3LYP), 59 kJ/mol (BP86
and wB97xD)) are higher in energy. The highest relative energy
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in energy is 13f (B3LYP: 16, 16 (with toluene) kJ/mol; BP86: 20,
21 (with toluene) kJ/mol; wB97xD: 31, 28 (with toluene) kJ/mol
B3LYP) and 13e is the highest in energy (B3LYP: 30, 30 (with
toluene) kJ/mol; BP86: 36, 34 (with toluene) kJ/mol; wB97xD: 45,
42 (with toluene) kJ/mol B3LYP).
Experimental Section
General aspects. All solvents, including deuterated solvents for
NMR experiments, were dried and purified by standard
procedures. All reactions were carried out under an atmosphere
of dry argon using Schlenk techniques. Varian Mercury Vx 200
MHz (4-nucleus probehead), Bruker DPX-300 (5 mm WBSO
probehead), Bruker Avance III HD 400 MHz, Bruker Avance III
HD 500 MHz, (with Prodigy-probehead), Bruker Avance III HD
600 MHz, (with Cryo-probehead) and Agilent DD2 500 MHz
spectrometers were used to obtain 1H, 13C NMR and the 119Sn-
NMR spectra as well as the 2D spectra. 1H, 13C, and 119Sn-NMR
chemical shifts are given in ppm and were referenced to SiMe4
(1H, 13C) and SnMe4 (119Sn).
Melting points are uncorrected and were measured on a Büchi
MP-560 device.
The electrospray ionization mass spectra were recorded on a
Thermoquest-Finnigan instrument using MeOH, CH2Cl2 or
MeCN as the mobile phase. The samples were introduced as
solution via a syringe pump operating at a rate of 0.5 μL/min.
The capillary voltage was 4.5 kV while the cone skimmer
voltage varied between 50 and 250 kV. Identification of the
expected ions was assisted by comparison of experimental and
calculated isotope distribution patterns. The m/z values reported
correspond to those of the most intense peak in the
corresponding isotope pattern.
Elemental analyses were performed on a LECO-CHNS-932
analyzer under non-inert conditions.
The infrared spectra were recorded with a Perkin Elmer Two
(ATR) spectrometer under non-inert conditions.
Crystallography:
Intensity data for 2, 2a, 8, 9, 9a, 10, 13·C7H8 and 14 were
collected on an XcaliburS CCD diffractometer (Oxford Diffraction) using
Mo-Kα radiation at 173(2) K with an Oxford Cryostream. Intensity data for
7 were collected on an APEX-II CCD diffractometer (Bruker Corporation)
using Mo-Kα radiation at 100 K. Intensity data for 13 were collected on an
APEX-II CCD diffractometer (Bruker Corporation) using Mo-Kα radiation
at 190 K.
Figure 16. Visualized relative zero point-corrected energies of compound 13 for
the cis and the trans isomers 13a–13f in the gas phase, and with the solvent
model IEF/PCM (toluene).
The structures were solved with direct methods using SHELXS-97[36] (2a,
8, 9, 10, 13, 13·C7H8, 14), SIR-2004[37] (2), SHELXT-2014/7[38] (7, 9a) and
refinements were carried out against F2 by using SHELXL-2018/1.[36,38]
The C–H hydrogen atoms were positioned with idealized geometry and
refined using a riding model. All non-hydrogen atoms were refined using
anisotropic displacement parameters.
Conclusion
Herein, we report in a combined experimental and theoretical
study how the coordination environment of spirocyclic tin (IV)
compounds can be influenced.
The protons of compounds 2 (OH) and 2a (OH and NH) are located in the
difference Fourier map and refined freely, distances are restrained to a fix
General observations for symmetrically substituted spirocyclic
compounds are: (i) With alkyl substituents such as methyl or n-
butyl at the nitrogen atoms the cis isomer is preferred in the solid
state. (ii) A lengthening of both alcoholate side chains by one CH2
moiety results in the nitrogen atoms being trans. The DFT
calculations show only rather small energy differences between
the isomers. (iii) The replacement of the aliphatic substituent at
the nitrogen atoms by an aromatic one such as p-FC6H4 provokes
the crystallization of the trans isomer in the solid state as well. (iv)
A pentacoordinated species such as 9 is not preferred.
The observations for unsymmetrically substituted spirocyclic
compounds are: (i) If both amino alcoholate side chains are short,
the position of the methyl substituents is not decisive for a cis or
a trans position of the nitrogen atoms. (ii) The lengthening of only
one alcoholate side chain by a CH2 moiety causes crystallization
of the trans isomer in solid state. (iii) For the trans isomers, type I
and type II coordination modes of the amino alcoholates are
observed in solid state and approved by DFT calculations. Given
the high economic potential of amino alcohol derivatives of tin as
delayed action catalysts for polyurethane formation, detailed
studies of the mechanism according to which the isomerization
takes place is of interest.
value. The studied crystal of compound
9 was of poor quality.
Consequently, the measured data set has a high Rint (0.1301) and in its
solution the tin atom is surrounded by large residual density maxima. In
the solution of the studied crystal of compound 9a a short contact between
the protons H6A and H15B is reported (1.88 Å). Since the protons are in
correct calculated positions the short contact may be arised due to packing
effects. In the solution of the studied crystal of compound 14 larger than
expected residual density maxima outside metal atom locations are
detected. To the best of our knowledge the possibilities for twinning,
wrongly assigned atom types, unaccounted solvents and other model
errors were eliminated.
CCDC-1858288 (2), CCDC-1858289 (2a), CCDC-1858290 (7), CCDC-
1858291 (8), CCDC-1858292 (9), CCDC-1858293 (9a), CCDC-1858294
(10), CCDC-1858295 (13·C7H8), CCDC-1858296 (13) and CCDC-
1858297 (14) contain the supplementary crystallographic data for this
paper. This data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
For decimal rounding of numerical parameters and su values the rules of
IUCr have been employed.[39]
All figures were generated using ORTEP III visualization software.[41]
Synthesis of 3-methyl[(3-methoxy-3-oxopropyl)-
methylamino]propanoate MeN(CH2CH2COOMe)2 (1a)
Methylamine (13.90 g, 447.52 mmol) was added to a solution of freshly
distilled methyl acrylate (30.48 g, 354.05 mmol) in methanol (90 ml) over
30 min at 0 °C. The reaction mixture was stirred over night at ambient
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10.1002/chem.201803952
Chemistry - A European Journal
FULL PAPER
temperature. The remaining volatiles were removed under reduced
pressure and the compound 1a was purified by distillation (125 °C, 6.8·10-
1 mbar) and obtained as colourless oil (46.88 g, 181.58 mmol, 51%).
1H NMR (500.13 MHz, CDCl3, 25 °C): δ 3.56 (s, 6H, OCH3), 2.57 (t, 3J(1H–
1H) = 7.2 Hz, 4H, NCH2), 2.34 (t, 3J(1H–1H) =7.2 Hz, 4H, CH2CH2C(O)O),
2.11 (s, 3H, N-CH3).
1H NMR (499.78 MHz, CDCl3, 25 °C): δ 3.70 (s, 3H, CH3O), 2.84 (t, 3J(1H–
1H) = 7 Hz, 2H, CH2CH2), 2.49 (t, 3J(1H–1H) = 7 Hz, 2H, NCH2), 2.36 (s,
5H, NCH3/NCH2), 1.15 (s, 6 H, CCH3).
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): δ 173.1 (s, COOCH3), 69.9
(s, COOCH3), 68.5 (s, NCH2CH2), 55.2 (s, NCH2), 51.5 (s, NCH3), 44.5 (s,
NCH2), 32.7 (s, C(CH3)2), 27.4 (s, CCH3),
13C{1H} NMR (125.77 MHz, CDCl3, 25 °C): δ 172.5 (s, C(O)O), 52.2 (s,
NCH2), 51.1 (s, OCH3), 41.4 (s, NCH3), 32.1 (s, NCH2CH2).
MS (ESI +) in CH3CN: m/z 204.1 [1a+H]+, 226.1 [1a+Na]+.
MS (ESI +) in CH3CN: m/z 172.1 [3b - H2O + H]+, 190.1 [3b + H]+, 212.1
[3b + Na]+.
Synthesis of 3-[(2-hydroxy-2-methylpropyl)(methyl)amino]propan-1-
ol MeN(CH2CMe2OH)(CH2)3OH (3)
Synthesis of 4,4'-(methylazanediyl)bis(2-methylbutane-2-ol)
MeN(CH2CH2CMe2OH)2 (1)
To a stirred suspension of lithium aluminium hydride (1.19 g, 31.4 mmol)
in dry THF (100 mL) was added within 15 min at 0 °C a solution of 3b (3.09
g, 16.3 mmol) in dry THF (10 mL). After further stirring at room temperature
for 3 d the solvent was removed under reduced pressure followed by
addition of Et2O (75 mL). At 0 °C H2O (1.2 mL), 15% aqueous solution of
NaOH (1.2 mL), and H2O (3.6 mL) were subsequently added. The resulting
solution was stirred for 1 h, dried with MgSO4, and filtered. The solvent of
the filtrate was removed under reduced pressure. Compound 3 (2.60 g,
16.08 mmol, 98%) was obtained as a colourless oil.
Compound 1a (15.00 g, 73.81 mmol) was added dropwise to MeMgCl
(23.19 g, 309.96 mmol, 4.2 eq.) in diethyl ether (500 ml) at 0 °C. Than the
mixture was heated at 35 °C for 3 h, followed by subsequent addition at
0 °C of water (10.60 mL) and sodium hydroxide solution (15%, 10.60 mL).
Then the mixture was stirred for 2 hat ambient temperature. The solid
material that had been formed was separated by filtration and extracted
with CH2Cl2 using a Soxhlet apparatus. The volatiles of the filtrate were
removed under reduced pressure. The residue thus obtained was
combined with the product obtained from the soxhlet extraction. Distillation
in vacuo gave compound 1 as colourless oil (125 °C, 5.6·10-1 mbar, 8.96 g,
44.07 mmol, 60%).
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 3.82 (t, 3J(1H–1H) = 6 Hz, 2H,
CH2OH), 2.72 (t, 3J(1H–1H) = 6 Hz, 2H, NCH2CH2), 2.40 (s, 2H,
NCH2C(CH3)2), 2.38 (s, 3H, NCH3), 1.72 (q, 3J(1H–1H) = 6 Hz, 2H,
CH2CH2CH2), 1.20 (s, 6H, CCH3).
1H NMR (500.13 MHz, C6D6, 25 °C): δ 2.41 (t, 3J(1H-1H) = 6.9 Hz, 4H
CH2CH2), 2.00 (s, 3H NCH3), 1.49 (t,3J(1H-1H)=6.9 Hz,4H, NCH2), 1.21 (s,
12 H, CCH3).
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): δ 70.7 (s, C(CH3)2OH), 69.4 (s,
NCH2CMe2), 63.2 (s, CH2OH), 59.5 (s, NCH2CH2), 45.0 (s, NCH3), 28.8 (s,
CH2CH2CH2), 27.8 (s, C(CH3)2).
13C{1H} NMR (125.75 MHz, C6D6, 25 °C):δ 70.4 (s, CCH3), 54.3 (s, NCH2),
42.3 (s, NCH3), 39.7 (s, NCH2CH2), 30.2 (s, CCH3).
MS (ESI +) in CH3CN: m/z 144.2 [3 – H2O + H]+, 162.2 [3 + H]+.
MS (ESI +) in CH3CN: m/z 204.1 [1+H]+, 186.[1-H2O +H]+.
IR spectroscopy (cm-1): 3332 (OH).
Synthesis
of
4-[(2-hydroxy-2-methylpropyl)(methyl)amino]-2-
methylbutan-2-ol MeN(CH2CMe2OH)CH2CH2CMe2OH (4)
To a solution of 3b (2.9 g, 15.5 mmol) in diethyl ether (10 mL) was added
within 10 min at – 60 °C a 1.4 molar solution of methyl lithium in diethyl
ether (15 mL). After the reaction mixture had been warmed to room
temperature (within 20 h), the solvent was removed under reduced
pressure. Water (1.5 mL) and dichloromethane (10 mL) was added. After
stirring of the solution for 1 h, drying of the latter with MgSO4 and
subsequent filtration, the reaction mixture was extracted with
dichloromethane (250 mL). Distillation under reduced pressure (90 °C,
4·10-2 mbar) gave compound 4 (1.97 g, 10.4 mmol, 67%) as a light
yellowish oil.
Synthesis
of
2-[(2-hydroxy-2-methylpropyl)(methyl)amino]-2-
methylpropane-1-ol MeN(CMe2CH2OH)(CH2CMe2OH) (2)
2-[(2-hydroxy-2-methylpropyl)amino]-2-methylpropan-1-ol
(25
g,
156 mmol) was mixed with formic acid (21.56 g, 468 mmol,17.67 mL, 3
eq.) and formaldehyde solution (18.93 g (w = 40%), 234 mmol, 1.5 eq.)
and heated at reflux for 24 h. The volatiles were removed under reduced
pressure giving the ammonium formate 2a as solid material (mp. 56 °C). It
was dissolved in dichloromethane (50 mL), extracted with potassium
carbonate solution (3 times 20 ml), and washed with water (20 mL). The
collected organic layers were dried over sodium sulphate and filtrated. The
volatiles of the filtrate were removed under reduced pressure giving 2-[(2-
hydroxy-2-methylpropyl)(methyl)amino]-2-methylpropan-1-ol (22.27 g,
127.06 mmol, 81.44%) as colourless oil, which crystallized after a few days.
Single crystals (mp. 53-55 °C) were obtained from its iso-hexane solution.
1H-NMR-(2a, 300.13 MHz, CDCl3, 21 °C): δ 3.37 (s, 2H, CH2OH), 3.01 (s,
2H, NCH2), 2.95 (s, 3H, NCH3), 1.40 (s, 6H, C(CH3)2OH), 1.36 (s, , 6H,
NC(CH3)2).
1H NMR (500.13 MHz, CDCl3, 25°C): δ 2.77 (t, 3J(1H–1H) = 5 Hz, 2H,
NCH2CH2), 2.43 (s, 2H, NCH2C(CH3)2), 2.40 (s, 3H, NCH3), 1.65 (t, 3J(1H–
1H) = 5 Hz, 2H, NCH2CH2), 1.25 (s, 6H, NCH2CH2C(CH3)2), 1.20 (s, 6H,
NCH2C(CH3)2).
13C{1H} NMR
(125.77
MHz,
CDCl3,
25°C):
δ
71.6
(s,
NCH2CH2C(CH3)2OH), 70.6 (s, NCH2C(CH3)2OH), 69.7 (s, NCH2(CH3)2),
57.2 (s, NCH2CH2), 45.5 (s, NCH3), 38.0 (s, NCH2CH2), 29.8 (s,
CH2CH2C(CH3)2), 27.8 (s, NCH2C(CH3)2).
1H NMR (2, 200.13 MHz, C6D6, 25 °C): δ 3.32 (s, 2H, CH2OH), 2.39 (s, 2H,
NCH2), 2.36. (s, 3H, NCH3), 1.21 (s, 6H, C(CH3)2OH), 1.02 (s, 6H,
NC(CH3)2).
MS (ESI +) in CH3CN: m/z 172.2 [4 – H2O + H]+, 190.2 [4 + H]+.
13C{1H} NMR-(2, 150.94 MHz, CDCl3, 25 °C): δ 70.5 (s, C(CH3)2OH), 69.1
(s, CH2OH), 60.9 (s, NCH2), 58.2 (s, NC(CH3)2), 38.68 (s, NCH3), 28.50 (s,
C(CH3)2OH), 20.6 (s, NC(CH3)2).
Synthesis
of
3-[(2-hydroxyethyl)(methyl)amino]propanoate
MeN(CH2CH2OH)CH2CH2COOMe (5a)
A mixture of 2-methylaminoethanol (17.6 g, 234.5 mmol) and methyl
acrylate (20.2 g, 234.2 mmol) was treated in an ultrasonic bath for 3 h.
Compound 5a was obtained as a colourless oil in almost quantitative yield.
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 3.68 (s, 3 H, COOCH3), 3.58 (t,
3J(1H–1H) = 6 Hz, 2H, CH2CH2OH), 2.73 (t, 3J(1H–1H) = 6 Hz, 2H,
NCH2CH2COO), 2.53 (t, 3J(1H–1H) = 5 Hz, 4H, NCH2CH2OH), 2.48 (t,
3J(1H–1H) = 7 Hz, 2H, NCH2CH2COO), 2.26 (s, 3 H, NCH3).
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): δ 173.0 (s, COOCH3), 58.7 (s,
COOCH3), 58.4 (s, CH2OH), 52.3 (s, NCH2), 51.6 (s, NCH2), 41.6 (s,
NCH3), 32.4 (s, CH2COOCH3),
MS (ESI +) in CH3CN: m/z 176.1 [2 + H]+.
Elemental analysis (%) calcd for C9H21NO2 (175.27 g/mol) C 61.7, H 12.1,
N 8.0. Found C 61.6, H 12.1, N: 7.7.
IR spectroscopy (cm-1): 3294 (OH).
Synthesis
MeN(H)CH2CMe2OH (3a)
of
2-methyl-1-(methylamino)propane-2-ol
A mixture of methylamine (3.89 g, 41.33 mmol, 33% in ethanol) and
isobutylene oxide (1.00 g, 13.87 mmol) was treated for a period of 2 h in
an ultrasonic bath. The remaining volatiles were removed under reduced
pressure. Compound 3a was obtained as a colourless liquid (0.78 g, 7.56
mmol, 55%, b.p.: 85 °C (27 mbar)).
MS (ESI +) in CH3CN: m/z 144.1 [5a + H2O + H]+, 162.1 [5a + H]+, 184.0
[5a + Na]+.
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 2.51 (s, 3H, NCH3), 2.49 (s, 2H,
NCH2), 1.85–2.33 (br. s, 2H, OH/NH), 1.18 (s, 6 H, CCH3).
13C{1H} NMR (125.68 MHz, CDCl3, 25 °C): δ 69.33 (s, NCH2C(CH3)2),
62.69 (s, NCH2), 37.23 (s, NCH3), 27.42 (s, NCH2C(CH3)2).
MS (ESI +) in CH3CN: m/z 86.2 [3a – H2O + H]+, 104.1 [3a + H]+, 145.1 [3a
+ CH3CN + H]+.
Synthesis of 4-[(2-hydroxyethyl)(methyl)amino]-2-methylbutan-2-ol
(5)
To a solution of 5a (2.2 g, 13.6 mmol) in diethylether (20 mL) was added
within 10 min at – 60 °C of a 1.4 molar solution of methyl lithium in
diethylether (30 mL). After the reaction mixture had been warmed to room
temperature (within 20 h), the solvent was removed under reduced
pressure. Water (1.5 mL) and dichloromethane (10 mL) were added. After
stirring of the solution for 1 h, drying of the latter with MgSO4 and
subsequent filtration, the reaction mixture was extracted with
dichloromethane (250 mL). Distillation under reduced pressure (90 °C,
4·10-2 mbar) gave compound 5 (0.26 g, 1.59 mmol, 24%) as a light
yellowish oil.
Synthesis
of
3-[(2-hydroxy-2-methylpropyl)(methyl)amino]
propanoate MeN(CH2CH2COOMe)CH2CMe2OH (3b)
A mixture of 2-methyl-1-(methylamino)propan-2-ol (3a, 5.9 g, 57.6 mmol)
and methyl acrylate (4.9 g, 57.6 mmol) was treated in an ultrasonic bath
for 3 h. Compound 3b was obtained as a colourless oil in quantitative yield.
This article is protected by copyright. All rights reserved.

10.1002/chem.201803952
Chemistry - A European Journal
FULL PAPER
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 3.70 (t, 3J(1H–1H) = 6 Hz, 2H,
NCH2CH2OH), 2.5 – 2.7 (not resolved, 4H, NCH2), 2.32 (s, 3H, NCH3),
1.64 (t, 3J(1H–1H) = 6 Hz, 2H, CH2C(CH3)2OH), 1.24 (s, 6H, C(CH3)2),
13C{1H} NMR (125.68 MHz, CDCl3, 25 °C): δ 71.26 (s, NCH2CH2CMe2OH),
59.75 (s, NCH2CH2OH), 59.55 (s, NCH2CH2OH), 54.52 (s,
NCH2CH2C(CH3)2), 42.39 (s, NCH3), 37.74 (s, NCH2CH2C(CH3)2), 29.63
(s, C(CH3)2).
13C{1H} NMR (150.94 MHz, C6D6, 25 °C): δ 163.0, 161.3 (s, CF), 146.70,
146.68 (s, CN), 129.81, 129.76 (s, HCCF), 116.6, 116.5 (s, HCCN), 71.9,
71.1 (s, CH2), 68.9, 68.4 (s, COSn), 33.8, 33.5, 31.4, 31.2 (s, CH3).
19F NMR (376.61 MHz, C6D6, 25 °C): δ –113.62.
119Sn{1H} NMR (149.26 MHz, C6D6, 25 °C): δ –447.
9 is not stable under ESI MS conditions.
Elemental analysis (%) calcd for C28H40F2N2O4Sn2 + 0.5 H2O (633.3
g/mol): C 53.0, H 6.5, N 4.4. Found: 53.0, 6.5, 4.2. The measurement was
performed under non-inert conditions. Partial hydrolysis took place.
MS (ESI +) in CH3CN: m/z 146.1 [5 – H2O + H]+, 162.1 [5 + H]+, 198.1 [5
+ 2 H2O + H]+.
Synthesis of 3-[(2-hydroxyethyl)(methyl)amino]propan-1-ol
MeN(CH2CH2OH)(CH2)3OH (6)
p-FC6H4N(CH2CMe2O)2Sn(Ot-Bu)2 9a
Compound 9a was obtained as by-product in the synthesis of 9.
19F NMR (376.61 MHz, C6D6, 25 °C): δ –116.42.
119Sn{1H} NMR (149.26 MHz, C6D6, 25 °C): δ –402 (23%), –447 (9,
77%).
A magnetically stirred suspension of 2-methylaminoethanol (5.0 g, 66.6
mmol), 3-chloro-1-propanol (6.3 g, 66.6 mmol) and potassium carbonate
(9.2 g, 66.6 mmol) in acetonitrile (40 mL) was heated at reflux for a period
of 5 d. The reaction mixture was filtrated, and the volatiles of the filtrate
were removed under reduced pressure. Compound 6 was obtained as a
colourless oil (7.5 g, 56.3 mmol, 85%, b.p.: 140 °C (27 mbar)).
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 3.85 (t, 3J(1H–1H) = 6 Hz, 2H,
CH2OH), 3.68 (t, 3J(1H–1H) = 6 Hz, 2H, CH2OH), 3.23 (br. s, 2H, OH), 2.63
(t, 3J(1H–1H) = 6 Hz, 2H, NCH2), 2.56 (t, 3J(1H–1H) = 6 Hz, 2H, NCH2), 2.30
(s, 3H, NCH3), 1.69–1.77 (m, 2H, CH2CH2CH2).
Synthesis of spiro–[MeN(CH2CMe2O)(CMe2CH2O)]2Sn (10)
Sn(Ot-Bu)4 (2.60 g, 6.33 mmol) was dissolved in toluene (150 mL) and a
solution of MeN(CH2CMe2OH)(CMe2CH2OH), 2, (2.16 g, 12.34 mmol,) in
toluene (50 mL) was added dropwise over a period of 15 min. The reaction
mixture was heated to reflux for 1 h, and the toluene/tert-butanol azeotrope
was removed by distillation. The reaction mixture was concentrated to a
volume of approximately 50 mL and stored at 4 °C. Colourless crystals of
10 (2.17 g, 4.66 mmol, 74%) were obtained (mp. 186 °C).
1H-NMR (400.25 MHz, C6D6, 25 °C): δ 3.69 and 3.47 (AX, 3J(1H–1H) =
10.8 Hz, 2H, OCH2), 3.68 and 3.51 (AX, 3J(1H–1H) = 11.3 Hz, 2H, OCH2),
2.38 and 1.77 (AX, 3J(1H–1H) = 12.7 Hz, 2H, NCH2), 2.37 and 1.72 (AX,
3J(1H–1H) = 12.7 Hz, 2H, NCH2), 2.27 and 2.26 (s, 6H each, NCH3), 1.53,
1.36, 1.30 and 1.27 (s, 6H each, OC(CH3)2), 1.19, 1.04, 0.61 and 0.58 (s,
6H each, NC(CH3)2). Two Isomers in solution.
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): δ 62.8 (s, NCH2), 59.5 (s,
CH2OH), 59.1 (s, CH2OH), 56.7 (s, NCH2), 42.1 (s, NCH3), 28.4 (s,
CH2CH2CH2).
MS (ESI +) in CH3CN: m/z 134.1 [6 + H]+, 156.0 [6 + Na]+, 192.1 [6 +
CH3CN + H3O]+.
Synthesis of spiro-[nBuN(CH2CMe2O)2]2Sn (7)
Sn(Ot-Bu)4 (30.02 g, 73.00 mmol) was dissolved in toluene (900 mL) and
a solution of n-BuMeN(CH2CMe2OH)2, B, (30.15 g, 130.70 mmol) in
toluene (200 mL) was added dropwise over a period of 15 min. The
reaction mixture was heated to reflux for 2 h, and the toluene/tert-butanol
azeotrope was removed by distillation. Colourless crystals of 7 (40.00 g,
72.81 mmol, 99.7%, mp: 180 °C) were obtained from its concentrated
toluene solution.
13C{1H}-NMR (100.64 MHz, C6D6, 25 °C) δ 70. 1 (s, J(117/119Sn) = 23 Hz,
C(CH3)2), 69.6 (s, J(117/119Sn) = 27 Hz, C(CH3)2), 67.6 (s, OCH2), 67.5 (s,
OCH2), 61.3 (s, J(117/119Sn) = 48 Hz, NCH2), 61.1 (s, J(117/119Sn) = 52 Hz,
NCH2), 40.0 (s, NCH3), 39.4 (s, NCH3), 34.1, 33.8, 32.0 and 31.1 (s,
OC(CH3)2), 24.9, 24.7, 18.1 and 17.6 (s, NC(CH3)2).
119Sn{1H}-NMR (sample from the crude reaction mixture, 194.26 MHz,
C6D6, 22 °C)  = –398, –437, –443, –460, –500.
1H NMR (600.29 MHz, C6D6, 22 °C): δ 2.43 (s, 8H, NCH2C(CH3)2), 2.35
(m, 4H, NCH2), 1.31, 1.26, 1.18 and 1.10 (m, 8H, CH2), 1.14 (s, 24H,
CCH3), 0.87 and 0.84 (t, 3J(1H–1H) 7.33 Hz, 6H, CH2CH3).
13C{1H} NMR (150.94 MHz, C6D6, 25 °C): δ 71.3 (s, C(CH3)2), 69.1 (s,
NCH2C(CH3)2), 60.6 (s, NCH2), 33.9 (s, CH2), 28.6 (s, C(CH3)2), 25.4 (s,
CH2), 21.4, 21.22 (s, CH2CH3). Tin satellites are not resolved.
119Sn{1H} NMR (149.26 MHz, C6D6, 25 °C): δ –437.
119Sn{1H}-NMR (149.26 MHz, C6D6, 25 °C): δ –437 (40%), –443 (60%).
119Sn{1H}-NMR (149.26 MHz, CDCl3, 25 °C): δ –445.
119Sn{1H}-NMR (149.26 MHz, CD2Cl2, 25 °C): δ –438 (br.1/2 = 150 Hz,
38%), –443 (62%).
119Sn{1H}-NMR (149.26 MHz, CH3CN, 25 °C): δ –438 (br.1/2 = 134 Hz,
45%), –443 (55%).
MS (ESI +) in CH3CN: m/z = 218.1 [B+H]+, 551.3 [7 +H]+, 573.4 [7+Na]+,
119Sn{1H}-NMR (149.26 MHz, acetone–d8, 25 °C): δ –445.
119Sn{1H}-NMR (149.26 MHz, tetracholormethane-d2, 25 °C): δ –446
(70%), –443 (18%), -454 (12%).
589.4 [7+K]+, 614.4 [7+MeCN + H]+.
Elemental analysis (%) calcd for C24H50N2O4Sn + 0.5·H2O(558.78 g/mol)
C 51.6, H 9.2, N 5.0. Found C 51.4, H 9.0, N: 5.0. Because the
measurement was performed under non-inert conditions, the compound
partially hydrolysed.
MS (ESI +) in CH3CN: m/z 467.2 [10 + H]+.
Elemental analysis (%) calcd for C18H38N2O4Sn + 1H2O (483.2 g/mol): C
44.7, H 8.3, N 5.8. Found: 44.5, 7.9, 6.6. The measurement was performed
under non-inert conditions. Partial hydrolysis took place.
Synthesis of spiro-[MeN(CH2CH2CMe2O)2]2Sn (8)
Sn(Ot-Bu)4 (1.03 g, 2.51 mmol) was dissolved in toluene (150 mL) and a
solution of 1, MeN(CH2CH2CMe2OH)2, (1.00 g, 4.92 mmol) in toluene (30
mL) was added dropwise over a period of 5 min. The reaction mixture was
heated to reflux for 1 h, and the toluene/tert-butanol azeotrope was
removed by distillation. Colourless crystals of 8 (mp: 180 °C, 1.60 g, 3.07
mmol, 31%) were obtained from its concentrated toluene solution at 4 °C.
1H NMR (400.25 MHz, C6D6, 25 °C): δ 2.39 (t, 3J(1H-1H)= 6.6 Hz, 8H,
NCH2), 1.99 (s, 6H, NCH3), 1.47 (t, 3J(1H-1H)= 6.8 Hz, 8H, NCH2CH2), 1.19
(s, 24H, C(CH3)2).
Synthesis of spiro–[MeN(CH2CH2CH2O)(CH2CMe2O)]2Sn (11)
To a stirred solution of Sn(Ot-Bu)4 (1.9 g, 4.55 mmol) in dry toluene
(75 mL) was added within 10 min at room temperature a solution of 3 (1.5
g, 9.1 mmol) in 25 mL dry toluene. The solution was stirred for 30 min
followed by distillation of the toluene/tert-butanol azeotrope and complete
removal in vacuo of all volatiles Compound 11 (1.2 g, 2.7 mmol, 59%) was
obtained as a waxy residue.
1H NMR (300.13 MHz, C6D6, 25 °C): δ 5.04–4.94 (m), 4.69 – 4.80 (m),
3.83 (t, 3J = 6 Hz), 3.31 – 3.47 (m), 2.47 – 2.70 (m), 2.44 (s), 2.32 – 2.42
(m), 2.22 (s), 2.17 (s), 2.11 (s), 1.81 – 1.94 (m), 1.43 (s), 1.60 (q, J = 6 Hz),
1.37 (s), 1.33 (s), 1.30 (s), 1.29 (s), 1.22 (s). Given the existence of several
isomers in solution, no assignment of the resonances was done.
13C{1H} NMR (75.47 MHz, CDCl3): δ 70.9 (s), 70.5 (s), 69.3 (s), 67.1 (s),
66.3 (s), 65.8 (s), 62.7 (s), 59.1 (s), 44.9 (s), 42.0 (s), 34.2 (s), 33.7 (s),
32.2 (s), 29.1 (s), 29.0 (s), 27.8 (s). Given the existence of several isomers
in solution, no assignment of the resonances was done.
13C{1H} NMR-(100.46 MHz, , C6D6, 25 °C): δ 70,5 (s, C(CH3)2), 54.5 (s,
NCH2), 42.4 (s, NCH3), 39.8 (s, NCH2CH2), 30.4 (s, C(CH3)2).
119Sn{1H} NMR-(150.94 MHz, CD2Cl2, 25 °C): δ –603.
MS (ESI –) in CH3CN: m/z 138.0 [8 + Cl]–.
Synthesis of spiro-[p-FC6H4N(CH2CMe2O)2]2Sn (9)
Sn(Ot-Bu)4 (2.01 g, 4.86 mmol) was dissolved in toluene (100 mL) and a
solution of p-FC6H4N(CH2CMe2OH)2, C, (2.42 g, 9.49 mmol) in toluene
(50 mL) was added dropwise over a period of 10 min. The reaction mixture
was heated to reflux for 1 h, and the toluene/tert-butanol azeotrope was
removed by distillation. After filtration the filtrate was concentrated to a
volume of approximately 50 mL and stored at 4 °C. Yellow crystals of 9
(1.88 g, 3.19 mmol, 65%) were obtained (mp.: 193-194 °C).
119Sn{1H} NMR (111.92 MHz, C6D6, 25 °C): δ (ppm) = –512 (s, Integral
48%), –512 (s, Integral 46%), –515 (s, Integral 6 %).
Elemental analysis (%) calcd for C16H34N2O4Sn + H2O (455.18 g/mol): C,
42.2; H, 8.0; N, 6.2. Found: C, 42.7; H, 8.1; N, 6.0.
MS (ESI+) (CH3CN, m/z): 162.1 [3 + H]+, 439.1 [11 + H]+.
1H NMR (600.29 MHz, C6D6, 25 °C): δ 7.91–7.87(m, 4H, FC(CH)2), 6.77–
6.72 (m, 4H, NC(CH)2), 3.37, 2.97 (d, 4J(1H–1H) = 11.74 Hz, 2H, NCH2),
3.07, (s, 4H, 2 x NCH2), 1.55, 1.30 (s, 6H, CH3), 0.78 (s, 12H, CH3).
Synthesis of spiro-[MeN(CH2CH2CMe2O) (CH2CMe2O)]2Sn (12)
To a stirred solution of Sn(Ot-Bu)4 (1.5 g, 3.6 mmol) in dry toluene (100
mL) was added within 10 min at room temperature a solution of 4 (1.4 g,
7.1 mmol) in 20 ml dry toluene. The solution was stirred for 30 min followed
by distillation of the toluene/tert-butanol azeotrope and complete removal
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10.1002/chem.201803952
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in vacuo of all volatiles. Compound 12 (1.2 g, 2.3 mmol, 65%) was
obtained as a waxy residue.
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 7.12 – 7.24 (m), 3.49 – 3.73 (m),
3.12 – 3.36 (m), 2.54 – 2.85 (m), 2.50 (s), 2.41 (s), 2.03 – 2.39 (m), 1.88
(t, 3J = 15 Hz), 1.09 – 1.57 (m), 0.80 – 0.91 (m). Given the existence of
several isomers in solution, no assignment of the resonances was done.
13C{1H} NMR (75.47 MHz, CDCl3, 25 °C): δ 129.0 (s), 128.2 (s), 125.3 (s),
74.6 (s), 69.6 (s), 67.6 (s), 67.5 (s), 57.9 (s), 42.3 (s), 37.2 (s), 35.9 (s),
34.8 (s), 32.7 (s), 30.2 (s), 29.8 (s), 27.8 (s), 21.4 (s). Given the existence
of several isomers in solution, no assignment of the resonances was done.
119Sn{1H} NMR (111.92 MHz, CDCl3, 25 °C): δ –529 (s, Integral 66%), –
532 (s, Integral 13%), –555 (s, Integral 21%).
Elemental analysis (%) calcd for C20H42N2O4Sn (493.27 g/mol): C, 48.7;
H, 8.6; N, 5.7. Found: C, 43.0; H, 8.1; N, 4.5. The measurement was done
under non-inert conditions. Apparantly, partial hydrolysis has taken place.
MS (ESI+) (CH3CN, m/z): 190.1 [4 + H]+. 12 is not stable under ESI-MS
conditions.
Acknowledgements
We thank Mrs. S. Marzian for recording the ESI mass spectra, Mr.
M. Hüffner for performing the elemental analyses, and Mrs. H.
Schulte for conducting powder XRD measurements.
This work contains part of the PhD thesis of Britta Glowacki, TU
Dortmund 2018.
Keywords: tin • amino alcohol • DFT calculation • X-ray
crystallography • 119Sn NMR spectroscopy
Synthesis of spiro-[MeN(CH2CH2CMe2O)(CH2CH2O)]2Sn (13)
To a stirred solution of Sn(Ot-Bu)4 (1.6 g, 4.55 mmol) in dry toluene
(100 mL) was added within 15 min at room temperature a solution of 5
(1.3 g, 8.1 mmol) in dry toluene (25 mL). The solution was stirred for 30
min followed by distillation of the toluene/tert-butanol azeotrope and
complete removal in vacuo of all volatiles Compound 13 (0.5 g, 1.1 mmol,
29%) was obtained as colourless solid. Single crystals were obtained from
its toluene solution at – 10 °C.
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H, 7.8; N, 6.4. Found: C, 43.6; H, 7.7; N, 6.3.
MS (ESI+) (CH3CN, m/z): 162.1 [5 + H]+, 539.2 [13 + 2 CH3CN + H2O + H]+.
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Synthesis of spiro-[MeN(CH2CH2O) (CH2CH2CH2O)]2Sn (14)
To a stirred solution of Sn(Ot-Bu)4 (2.6 g, 6.4 mmol) in dry toluene (80 mL)
was added within 15 min at room temperature a solution of 6 (1.7 g, 12.8
mmol) in 40 ml dry toluene. The solution was stirred for 30 min followed by
distillation of the toluene/tert-butanol azeotrope and complete removal in
vacuo of all volatiles. Compound 14 (1.11 g, 2.9 mmol, 45%) was obtained
as colourless solid. Single crystals were obtained from its toluene solution
at –10 °C.
1H NMR (300.13 MHz, CDCl3, 25 °C): δ 7.08 – 7.23 (m), 4.24 – 4.45 (m),
4.02 – 4.23 (m), 3.63 – 4.00 (m), 3.32 – 3.56 (m), 2.80 – 3.11 (m), 2.64 (s),
2.62 (s), 2.59 (s), 2.56 (s), 2.11 – 2.52 (m), 1.35 – 1.50 (m), 1.20 (s). Given
the existence of several isomers in solution, no assignment of the
resonances was done.
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MS (ESI+) (CH3CN, m/z): 134.1 [6 + H]+, 383.1 [14 + H] +.
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Entry for the Table of Contents (Please choose one layout)
Layout 1:
FULL PAPER
The length of the amino alcoholate
chains as well as the identity of the
substituents at the side chains and the
nitrogen atoms control the geometrical
environment about the tin atom in
spirocyclic amino alcohol derivatives
of the latter.
Britta Glowackia, Roman Pallacha,
Michael Luttera, Fabian Roeslera, Hazem
Alnasra, Cedreric Thomasa, Dieter
Schollmeyerb, Klaus Jurkschata
*
Page No. – Page No.
Cis versus Trans: The Coordination
Environment About the Tin(IV) Atom
in Spirocyclic Amino Alcohol
Derivatives
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