Reactions of bis[bis(trimethylsilyl)amido] zinc with amides of sulfonimidic acids. Crystal structure and NMR studies of bischelate zinc complex

Article abstract of DOI:10.1016/j.molstruc.2005.11.021

Reactions of bis[bis(trimethylsilyl)amido] zinc with amides of sulfonimidic acids are leading to the corresponding bischelate complexes 1-3. Compounds 1-3 were characterized by means of NMR spectroscopy and elemental analysis. The X-ray analysis of [p-MeC₆H₄S(O)(Nt-Bu)₂]₂Zn (3) demonstrates a tetrahedral environment of the Zn atom in the solid state and dynamic ¹H NMR studies showed interconvention between two conformers in solution at high temperatures.

Full text of DOI:10.1016/j.molstruc.2005.11.021

Journal of Molecular Structure 788 (2006) 89–92
www.elsevier.com/locate/molstruc
Reactions of bis[bis(trimethylsilyl)amido] zinc with amides
of sulfonimidic acids. Crystal structure and NMR studies
of bischelate zinc complex
b
b
c
Olexandr I. Guzyr a, , Leonid N. Markovskii , Mark I. Povolotskii , Herbert W. Roesky ,
*
Alexander N. Chernega b, Eduard B. Rusanov b
a
`
Institut de Ciencia de Materials de Barcelona, Campus U.A.B. 08193 Bellaterra, Spain
b Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Murmanskaya str.5, 02094 Kiev, Ukraine
c
¨ ¨ ¨ ¨
Institut fur Anorganische Chemie der Universitat Gottingen, Tammannstrabe 4, D-37077 Gottingen, Germany
Received 23 May 2005; received in revised form 17 November 2005; accepted 18 November 2005
Available online 18 January 2006
Abstract
Reactions of bis[bis(trimethylsilyl)amido] zinc with amides of sulfonimidic acids are leading to the corresponding bischelate complexes 1–3.
Compounds 1–3 were characterized by means of NMR spectroscopy and elemental analysis. The X-ray analysis of [p-MeC6H4S(O)(Nt-Bu)2]2Zn
(3) demonstrates a tetrahedral environment of the Zn atom in the solid state and dynamic 1H NMR studies showed interconvention between two
conformers in solution at high temperatures.
q 2005 Elsevier B.V. All rights reserved.
Keywords: Complexes; Sulfur; Zinc; N ligands; Solid-state structures
1. Introduction
complexes containing one metal cation and the
[RNS(O)(R0)NR]K monoanions as bischelating ligands are
unknown.
The chemistry of main group and transition metal
complexes containing sulfur–nitrogen multiple bonded
systems as ligands has been widely investigated since the
preparation of the first adducts with tetrasulfur tetranitride
[1–3]. Such complexes are attracting attention due to their
structural peculiarities, such as the coordination fashion of a
metal to the ligand, as well as a possible stabilization route for
non-isolable under normal conditions intermediates. Among
them, compounds containing the NSN fragment as a ligand are
of particular interest. Diimides are known to function as mono
or bidentante ligands in main group and transition metal
complexes [1–5]. Reactions of sulfur diimides with main group
metal alkyls, alkoxides or Grignard reagents are leading to a
nucleophilic addition to NaS bond, and formation of
complexes with the [RNS(R0)NR]K ligand [6–9], which
subsequently are bonded to transition metals via metathesis
reactions [7,10,11]. However, to the best of our knowledge,
One of the synthetic routes for the preparation of main group
and transition metal complexes are the reactions, involving the
metal alkyls or amides, and compounds containing donor atoms
and protic moieties [12]. Among the available reagents main
group and transition metals bis(trimethylsilyl) amides are of
particular interest due to their high reactivity combined with
stability, solubility and easy availability from simple starting
materials [13,14]. For instance, it was shown that the reaction of
bis[bis(trimethylsilyl)] amides of Zn2C and Cd2C with (E–NH)2
(EZAs, P) four-membered ring systems resulted in the
deprotonation of the NH moiety, ring opening, and formation
of bischelate complexes with low coordination numbers of As
andP(2)respectively[15–17]. Thus, thismethodwasshowntobe
generally suitable for the synthesis of metal chelate complexes.
Due to our broad interest in the chemistry of compounds
containing sulfur–nitrogen multiple bonds [18–20], we decided
to study the possibility for the preparation of bischelate metal
complexes, containing RNS(O)(Ar)NR fragment as a bidentate
ligand. As a synthetic route to such type of compounds, we
reacted amides of sulfonimidic acids with bis[bis(trimethyl-
silyl)] amido zinc. The results of our investigation are
presented in the current paper.
*
Corresponding author. Tel.: C34 93 580 1853x255; fax: C34 93 580 5729.
E-mail address: aguzyr@icmab.es (O.I. Guzyr).
0022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.11.021

90
O.I. Guzyr et al. / Journal of Molecular Structure 788 (2006) 89–92
2. Experimental
2.4. Preparation of [p-MeC6H4S(O)N(t-Bu)N(t-Bu)]2Zn (3)
2.1. General methods and materials
Zn[N(SiMe3)2] (0.77 g, 2.00 mmol) was added via syringe at
room temperature to the solution of p-MeC6H4S(O)
[N(t-Bu)]NH(t-Bu) (1.13 g, 4.00 mmol) in dry benzene
(10 mL). The reaction mixture was stirred for an additional
15 h, and refluxed for 1 h. All volatiles were removed in vacuum,
and the residue recrystallized from dry acetonitrile (20 mL),
All reactions were performed in deoxygenated argon or
dinitrogen atmosphere using high vacuum techniques.
Aromatic, hydrocarbon, and etherated solvents were distilled
over P4O10 and stored over sodium wire. Acetonitrile,
trichloromethane, and dichloromethane were dried over
P4O10. NMR spectra were recorded on a Bruker AM-200,
Bruker WP-200, and Variant VXR-300 instruments. Chemical
shifts are reported in d scale with reference to SiMe4. Melting
points were measured on Nagema melting-point apparatus and
are uncorrected. Elemental analyses were performed by the
Analytical Laboratory of the Institute of Organic Chemistry,
National Academy of Sciences of Ukraine.
1
resulting in compound 3. Yield: 1.01 g (80%). Mp: 237 8C. H
NMR (200 MHz, CDCl3, 25 8C): 1.18 [s, 18H, C(CH3)3], 1.19 [s,
18H, C(CH3)3], 2.40(s, 6H, CH3), 7.21[d, 4H, J2(HH)Z8.10 Hz,
aromatH], 7.84[d, 4H, J2(HH)Z8.10 Hz, aromatH]. Anal. calcd
for C36H50N4O2S2Zn: C 57.35, H 8.02, N 8.92, S 10.21. Found: C
57.30, H 8.10, N 8.94, S 10.65.
2.5. Crystal structure determination
The starting materials were prepared according to literature
methods [21–25] and were purified prior to use. Compound
p-MeC6H4S(O)[N(t-Bu)]NH(t-Bu) have not been reported in
literature. A few data are given here.
Single crystals of 3 were grown by slow evaporation of its
acetonitrile–benzene solution at room temperature. Crystal
data for 3: C30H50N4O2S2Zn, MZ628.20, monoclinic, aZ
˚
˚
˚
p-MeC6H4S(O)[N(t-Bu)]NH(t-Bu). Yield: 2.88 g (36%).
Mp: 162 8C. 1H NMR (300 MHz, CDCl3, 25 8C): 1.25 [s,
18H, C(CH3)3], 2.37 (s, 3H, CH3), 3.95 (s, 1H, NH), 7.19 (d,
2H, aromat H), 7.77 (d, 2H, aromat H). Anal. calcd for
C15H26N2OS: C 63.78, H 9.30, N 9.92, S 11.35. Found: C
63.88, H 9.98, N 9.87, S 11.57.
11.274(8) A, bZ19.205(5) A, cZ16.047(6) A, bZ91.33(5)8,
3
3
˚
VZ3473.5 A , ZZ4, dZ1.20 Mg/m , space group P21/c,
F(000)Z1344, crystal size 0.34!0.44!0.53 mm.
All crystallographic measurements were performed at
293 K on a CAD-4-Enraf-Nonius diffractometer operating in
the u/2q scan mode (the ratio of the scanning rates u/2qZ1.2).
The intensity data were collected within the range 3!q!638
(0!h!11, 0!k!22, K18!l!18) using graphite mono-
2.2. Preparation of [p-MeC6H4S(O)N(n-Bu)NPh]2Zn (1)
˚
chromated Cu-Ka radiation (lZ1.54184 A). Unit cell par-
ameters were calculated from the setting angles of 24 strong,
carefully centered reflections.
Zn[N(SiMe3)2] (1.00 g, 2.60 mmol) was added dropwise via
syringe at room temperature to the suspension of p-MeC6H4
S(O)[N(n-Bu)]NHPh (1.57 g, 5.19 mmol) in dry benzene
(30 mL). The reaction mixture was stirred for an additional
15 h. All volatiles were removed in vacuum, and the residue
treated with dry hexane (10 mL). The precipitate was filtered
off, and dried in vacuum, resulting in compound 1. Yield:
1.72 g (99%). Mp: 160 8C. 1H NMR (200 MHz, CDCl3, 25 8C):
0.73 [m, 6H, n-C4H9, C(4)–H], 1.13 [br, 4H, n-C4H9, C(3)–H],
1.35 [br, 4H, n-C4H9, C(2)–H], 2.35 (s, 6H, CH3), 2.92 [br, 4H,
n-C4H9, C(1)–H], 6.84–7.69 (br, mult, 9H, aromat H). Anal.
calcd for C34H42N4O2S2Zn: C 61.12, H 6.34, N 8.38, S 9.59.
Found: C 61.08, H 6.35, N 8.39, S 9.42.
Intensities of 6022 reflections (5496 unique reflections,
RintZ0.026) were measured. The structure was solved by
direct methods [26] and refined against F2 by full-matrix least-
squares technique in the anisotropic approximation [27]. In the
refinement 5496 independent reflections [4480 reflections with
IO2s(I)] were used. Convergence was obtained at R(F)Z
0.040, wR2Z0.120 GOFZ1.022 [IO2s(I)]; RZ0.052, wR2Z
0.1286 for all data (461 refined parameters; obs/variabl., 8.1;
the largest and minimal peaks in the final difference map, 0.39
3
and K0.32 e/A ). The weighting scheme wK1 Zs2ðF02ÞC
˚
2
ð0:0752PÞ C2:4171P, with PZðF02 C2Fc2Þ=3 was used.
Corrections for Lorentz and polarization effects but not for
absorption were applied. Positions of hydrogen atoms were
calculated according to an ideal geometry and refined riding
their supporting carbon atoms.
2.3. Preparation of [PhS(O)N(SO2Ph)NPh]2Zn (2)
Zn[N(SiMe3)2] (0.52 g, 1.34 mmol) was added via syringe
at room temperature to the suspension of PhS(O)(NSO2
Ph)NHPh (1.00 g, 2.68 mmol) in dry benzene (30 mL). The
reaction mixture was stirred for an additional 15 h. All volatiles
were removed in vacuum, and the residue treated with dry
hexane (10 mL). The precipitate was filtered off, dried in
vacuum, and finally recrystallized from dry benzene (10 mL),
resulting in compound 2. Yield: 0.36 g (33%). Mp: 225 8C. 1H
NMR (200 MHz, hexametapole-d18, 25 8C): 6.75–7.75 (br,
mult, 30H, aromat H). Anal. calcd for C36H30N4O6S4Zn: C
53.49, H 3.74, N 6.93, S 15.87. Found: C 53.55, H 3.76, N 6.68,
S 15.85.
3. Results and discussion
3.1. Reactions of bis[bis(trimethylsilyl)]amido zinc with
amides of sulfonimidic acids
We found that the reactions of bis[bis(trimethylsilyl)]amido
zinc with amides of sulfonimidic acids are taking place at room
temperature with elimination of 2 equiv. of hexamethyldisila-
sane and formation of the corresponding bischelate complexes
1–3 in analytically pure state (Scheme 1).

O.I. Guzyr et al. / Journal of Molecular Structure 788 (2006) 89–92
91
technique allowed to study the kinetics ofinversion processes and
was pioneered by Ernst et al. on bischelate aminopropenethionate
complexes of Zn (II) and Cd (II) [30,31].
R
N
R
N
R
N
O
S
O
S
O
S
Zn[N(SiMe3)2]2
- 2HN(SiMe3)2
2Ar
Ar
Ar
Zn
NH
R'
N
N
One of the stabilization routes for the conformation of non-
rigid molecules is the introduction of bulky substituents [32].
With this aim we performed the synthesis of compound 3,
containing tert-butyl groups attached to the nitrogen atoms. 1H
NMR spectrum of compound 3 at room temperature in CDCl3
showed sharp resonances: two singlets for the protons of tert-
butyl groups (1.18 and 1.19 ppm), a singlet (2.40 ppm, methyl
protons), and a characteristic AB system at low field (7.21–
7.84 ppm, aromatic protons of p-MeC6H4 groups), with the
correct integration 36:6:8. The presence of two resonances for
the protons of t-Bu groups is in a good agreement with the
solid-state structure of compound 3 (vide infra), which shows
different environment for tert-butyl groups in the solid state.
Thus, compound 3 exists in solution as a mixture of two
conformers. The frequency separation Dn for the protons of the
t-Bu groups at room temperature was found to be solvent
dependent, and varies from 2.00 Hz (CDCl3), and 3.17 Hz
(toluene-d8), to 3.40 Hz (DMSO-d6).
R'
R'
1 Ar = p-MeC6H4, R = n-Bu, R' = Ph
2 Ar = Ph, R = SO2Ph, R' = Ph
3 Ar = p-MeC6H4, R = t-Bu,
R' = t-Bu
Scheme 1.
No reaction with zinc bis[bis(trimethylsilyl)]amide was
observed when p-MeC6H4S(O)NHt-Bu and p-MeC6H4
S(O)NHPh were used as reagents. In both cases the starting
materials were recovered unchanged even after refluxing the
reaction mixture for several hours. This observation indicates
that although acidity of the hydrogen atom is high enough to
eliminate HN(SiMe3)2, the main driving force for the
formation of chelating complexes seems to be coordination
of the Zn atom by the lone pair of the nitrogen atom of SaN
bond, which appears to be an energetically unfavourable
process due to the lower donor ability of the lone pair of the
oxygen atom in the case of the SaO bond. Although dimeric
complexes {Me2Al[MeS(O)(NR)]}2 containing the RNS(R0)O
fragment as a ligand are known [8], their preparation involves
the addition reaction of trimethylalane to sulfinylanilines.
The spectral and analytical data for the obtained complexes
are summarized in Section 2. Compounds 1–3 are colorless or
pale yellow air-sensitive solids good soluble in trichlorometh-
ane or aromatic solvents.
Compound 3 was studied in the solution by means of dynamic
1H NMR spectroscopy. The 1H NMR spectrum of 3 was studied
in DMSO-d6 at different temperatures. Resonances for the
protons of the tert-butyl groups appeared as two separated
singlets at 295 K. They are broadened with increasing
temperature and coalesce at ca. 360 K as a result of the inversion
of the tetrahedral core. This observation indicates stereochemical
non-rigidity of 3 in solution and also explains the broad
1
resonances in the H NMR spectra observed for compounds 1
and 2 at room temperature. As it was expected for 3, introduction
of bulky substituents on nitrogen atoms increases the energetical
barrier of inversion and allowed to observe separated resonances
for the organic groups at room temperature.
3.2. Spectroscopic studies
1H NMR spectra of compounds 1 and 2 at room temperature
showed broad resonancesfor the protons of groups attachedtothe
nitrogenatomsaswellasforthesubstituentsonsulfuratoms.This
fact can be explained taking into account that the main group and
transition metal bischelate complexes are stereochemically non-
rigid and exhibiting fast isomerisation in solution via different
possible mechanisms [28,29]. Application of dynamic NMR
3.3. X-ray single crystal structure of 3
General view of the molecule is shown in Fig. 1; selected
bond lengths and angles are listed in Table 1.
Fig. 1. Molecular structure of [p-MeC6H4S(O)N(t-Bu)N(t-Bu)]2Zn (3) in the solid state.

92
O.I. Guzyr et al. / Journal of Molecular Structure 788 (2006) 89–92
Table 1
˚
Selected bond lengths (A) and angles (8) for 3
Acknowledgements
We are grateful to the Deutsche Forschungsgemeinschaft
for partial support of this research.
Zn–N(1)
2.023(3)
2.014(3)
2.002(3)
2.033(3)
2.665(2)
2.669(2)
1.571(3)
71.0(1)
S(1)–N(2)
S(1)–O(1)
S(1)–C(1)
S(2)–N(3)
S(2)–N(4)
S(2)–O(2)
S(2)–C(16)
ZnN(1)S(1)
ZnN(2)S(1)
ZnN(3)S(2)
ZnN(4)S(2)
1.571(2)
1.444(2)
1.778(3)
1.573(3)
1.566(3)
1.445(3)
1.782(3)
94.9(1)
Zn–N(2)
Zn–N(3)
Zn–N(4)
References
Zn/S(1)
Zn/S(2)
[1] R. Fleischer, D. Stalke, Coord. Chem. Rev. 176 (1998) 431.
[2] P.F. Kelly, J.D. Woollins, Polyhedron 5 (1986) 607.
[3] T. Chivers, F. Edelmann, Polyhedron 5 (1986) 1661.
[4] R. Fleischer, A. Rothenberger, D. Stalke, Angew. Chem. 109 (1997) 2075
(Angew. Chem. Int. Ed. Engl. 36 (1997) 1105).
S(1)–N(1)
N(1)ZnN(2)
N(3)ZnN(4)
N(1)S(1)N(2)
N(3)S(2)N(4)
71.2(1)
95.2(1)
96.5(1)
95.8(1)
96.9(2)
94.8(1)
[5] J.K. Brask, T. Chivers, M. Parvez, G. Schatte, Angew. Chem. 109 (1997)
2075 (Angew. Chem. Int. Ed. Engl. 36 (1997) 1986).
[6] J. Kuyper, K. Vrieze, J. Chem. Soc. Chem. Commun. 64 (1976) 64.
[7] J. Kuyper, P.C. Keijzer, K. Vrieze, J. Organomet. Chem. 116 (1976) 1.
[8] J.M. Klerks, R. Van Vliet, G. Van Koten, K. Vrieze, J. Organomet. Chem.
214 (1981) 1.
Compound 3 crystallizes in the monoclinic space group
(P21/c). In the X-ray structure the two ZnN2S four-membered
rings are interconnected by a common zinc atom and are
mutually orthogonal (interplane angle ZnN(1)N(2)S(1)/ZnN
(3)N(4)S(2) 89.68). The central Zn atom as well as the S(1) and
S(2) atoms adopt significantly distorted tetrahedral coordination
geometry. The bond configuration for all N atoms is trigonal
planar (sum of the bond angles 356–3588). Both four-membered
heterocycles are slightly non-planar (max. deviation from the
[9] H.W. Roesky, W. Schmieder, W. Isenberg, W.S. Sheldrick,
G.M. Sheldrick, Chem. Ber. 115 (1982) 2714.
[10] H. Van de Meer, D. Heijdenrijk, Cryst. Struct. Commun. 5 (1976) 401.
[11] P. Hendriks, J. Kuyper, K. Vrieze, J. Organomet. Chem. 120 (1976) 285.
[12] M. Veith, Chem. Rev. 90 (1990) 3.
[13] M. Westerhausen, Coord. Chem. Rev. 176 (1998) 157.
[14] M.F. Lappert, Metal and Metalloid Amides, Ellis Horwood, Chichester,
1979.
˚
least-square plane is 0.107 and 0.075 A, respectively) and
˚
folded by 16.1 and 11.2 A about N–N axis. Due to the steric
[15] U. Wirringa, Dissertation, Goettingen, 1994.
repulsions the C(1–6) and C(16–21) benzene rings attached to
the four-membered heterocycles showing substantial twisting
around the S(1)–C(1) and S(2)–C(16) bonds (corresponding
dihedral angles are 87.7 and 86.08).
[16] U. Wirringa, H.W. Roesky, M. Noltemeyer, H.-G. Schmidt, Angew.
Chem. 105 (1993) 1680 (Angew. Chem. Int. Ed. Engl. 32 (1993) 1628).
[17] U. Wirringa, H. Voelker, H.W. Roesky, Y. Shermolovich, L. Markovski,
I. Uson, M. Noltemeyer, H.-G. Schmidt, J. Chem. Soc. Dalton Trans. 12
(1995) 1951.
˚
˚
The Zn–N distances (2.002–2.033(3) A, av. 2.018 A) are in
the normal range [33,34]. The important feature of the structure
is the considerable electron density delocalisation in the N(1)–
S(1)–N(2) and N(3)–S(2)–N(4) linkages: the S–N bond lengths
[18] L.N. Markovskii, V.M. Timoshenko, Yu.G. Shermolovich, Zh. Org.
Khim. 31 (1995) 161.
[19] E.S. Levchenko, L.N. Markovskii, Yu.G. Shermolovich, Zh. Org. Khim.
32 (1996) 1447.
[20] E.S. Levchenko, L.N. Markovskii, Yu.G. Shermolovich, Russ. J. Org.
Chem. 36 (2000) 143.
˚
[1.566–1.573(3) A, av. 1.570 A] are significantly shortened in
˚
˚
comparison with that for a S–N single bond (1.65 A [35,36]),
reflecting the multiple bond character. The SaO and S–C bond
[21] E.S. Levchenko, N.Ya. Derkach, A.V. Kirsanov, Zh. Obshch. Khim. 32
(1962) 1208.
˚
lengths in 3 [1.444(3) and 1.770(12) A] are comparable with
those in MeS(O)Ph [37].
[22] E.S. Levchenko, L.N. Markovskii, A.V. Kirsanov, Zh. Org. Khim. 3
(1967) 1273.
[23] L. Markovskii, E.S. Levchenko, A.A. Kisilenko, A.V. Kirsanov, Zh. Org.
Khim. 3 (1967) 2218.
[24] K. Akutagava, N. Furukawa, S. Oae, Bull. Chem. Soc. Jpn 57 (1984) 518.
[25] H. Bu¨rger, W. Sawodny, U. Wannagat, J. Organomet. Chem. 3 (1965)
113.
4. Conclusions
We found that the reactions of bis[bis(trimethylsilyl)amido]
zinc with amides of sulfonimidic acids are taking place at mild
conditions and are leading to the formation of corresponding
bischelate complexes 1–3. NMR spectroscopic studies of
compounds 1–3 showed non-rigidity of the bischelate
complexes in the solution. Single crystal X-ray analysis of
compound 3 showed the tetrahedral environment of the Zn
atom in the solid state.
[26] G.M. Sheldrick, SHELXSK86, Program for the Solution of Crystal
¨ ¨
Structures, University of Gottingen, Gottingen, Germany, 1986.
[27] G.M. Sheldrick, SHELXS-93, Program for the Refinement of Crystal
¨
¨
Structures, University of Gottingen, Gottingen, Germany, 1993.
[28] V.I. Minkin, L.E. Nivorozhkin, M.S. Korobov, Usp. Khim. 63 (1994) 303.
[29] V.I. Minkin, L.E. Nivorozhkin, L.E. Konstantinovskii, M.S. Korobov,
Koord. Khim. 3 (1977) 174.
[30] R.E. Ernst, M.J. O’Connor, R.H. Holm, J. Am. Chem. Soc. 89 (1967)
6104.
[31] S.S. Eaton, R.H. Holm, Inorg. Chem. 10 (1971) 1146.
[32] D.L. Kepert, Inorganic Stereochemistry, Springer, Berlin, 1982.
[33] N.A. Bell, P.T. Moseley, H.M.M. Shearer, C.B. Spencer, Acta Crystal-
logr. Sect. B B36 (1980) 2950.
5. Supplementary material
[34] H. Albrich, H. Vahrenkamp, Chem. Ber. 127 (1994) 1223.
[35] I. Hargittai, E. Vajda, A. Szoke, J. Mol. Struct. 18 (1973) 381.
[36] V.A. Naumov, R.N. Garaeva, G.G. Butenko, Zh. Strukt. Khim. 20 (1979)
1110.
CCDC-220873 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB2 1EZ, UK; Fax: C44 1223 336033).
[37] J. Brunvoll, O. Exner, I. Hargittai, M. Kolonits, P. Scharfenberg, J. Mol.
Struct. 117 (1984) 317.