A new route to iminoarsanes

Article abstract of DOI:10.1002/(sici)1099-0682(200001)2000:1<165::aid-ejic165>3.0.co;2-i

Dehydrohalogenation of (2,4,6-tri-tert- butylphenylamino)chloro[tris(trimethylsilyl)hydrazino]arsane (3) or [tert- butyl(trimethylsilyl)amino]chloro(2,4,6-tri-tert-butylphenylamino)arsane (4) with DBU yields novel stable compounds containing an As-N doubl

Full text of DOI:10.1002/(sici)1099-0682(200001)2000:1<165::aid-ejic165>3.0.co;2-i

FULL PAPER
A New Route to Iminoarsanes
Christian Kruppa,[a] Martin Nieger,[a] Bernd Ross,*[a] and Inka Väth[a]
Keywords: Arsenic / Imino compound / Hydrazinoiminoarsane / Aminoiminoarsane
Dehydrohalogenation of (2,4,6-tri-tert-butylphenylamino)chlo-
ro[tris(trimethylsilyl)hydrazino]arsane (3) or [tert-butyl(trimeth-
N double bond, (2,4,6-tri-tert-butylphenylimino)[tris(trimethyl-
silylhydrazino]arsane) (5) and [tert-butyl(trimethylsilyl)amino]-
ylsilyl)amino]chloro(2,4,6-tri-tert-butylphenylamino)arsane (4) (2,4,6-tri-tert-butylphenylimino)arsane (6). The structure of 5
with DBU yields novel stable compounds containing an As–
was confirmed by an X-ray structure determination.
Treatment of AsCl3 with lithium tris(trimethylsilyl)hydra-
zide or lithium trimethylsilyl(tert-butyl)amide, yielded the
hydrazinodichloroarsane 1 or the aminodichloroarsane 2,
respectively. These compounds react with lithium (2,4,6-tri-
tert-butylphenyl)amide to give the hydrazinoaminochlo-
roarsane 3 and the bisaminochloroarsane 4. All precursors
were isolated in good yield and have not yet been described,
except for compound 1.[4b] Compounds 3 and 4 were de-
hydrohalogenated by reaction with 1,8-diazabicy-
clo(5.4.0)undec-7-ene (DBU) to give the hydrazinoiminoar-
sane 5 and the aminoiminoarsane 6 in good yields. Com-
pound 6 is a red-orange amorphous solid and compound 5
is a red crystalline solid from which crystals suitable for X-
ray structural analysis could be isolated. Under dry, oxygen-
free argon both these novel compounds are stable indefi-
nitely.
Introduction
In contrast to the well-known iminophosphanes[1] little
is known about the corresponding compounds containing
an AsϪN double bond.[2Ϫ4] The first compound in which
an AsϪN double bond was clearly proven by X-ray struc-
tural analysis was (2,4,6-tri-tert-butylphenylamino)(2,4,6-
tri-tert-butylphenylimino)arsane prepared by Lappert et al.
in 1986.[5] It is an example for an aminoiminoarsane, in
which the AsϪN (p-p)π-bond is stabilized by both steric
and electronic effects. Ten years later Roesky et al. described
the synthesis and X-ray structural characterization of As,N-
bis[2,4,6-tris(trifluoromethyl)phenyl]iminoarsane,[6] an im-
inoarsane which is only kinetically stabilized by its bulky
organyl groups. Herein we report the preparation of hy-
drazino- and aminoiminoarsanes using a new method to
generate the AsϪN (p-p)π-bond.
X-ray Crystal Structure of 5
Results and Discussion
Synthesis
A suitable crystal for data collection was obtained from
toluene at room temperature. The molecular structure is
shown in Figure 1 and selected bond lengths and angles are
given in the legend. The AsϪN double bond of compound
5 has an (E)-configuration and a bond length of 170.8(3)
pm. This bond length is comparable to those found for the
aminoiminoarsane [171.4(7) pm] synthesized by Lappert et
al.[5] and the iminoarsane [170.7(2) pm] prepared by Roesky
et al.[6] The As1ϪN2 distance [182.2(2) pm] is shorter than
the calculated value (187 pm) for an AsϪN single bond.[7]
Therefore it is likely that there is some conjugation of the
hydrazino nitrogen (N2) lone pair with the AsϪN (p-p)π-
bond system, which one would expect because of the sp2-
hybridization of the planar coordinated N2 atom (sum of
angles at N2 ϭ 360°). The N2ϪN3 distance of 148.0(3) pm
lies within the range expected for NϪN single bonds (147
pm).[8] The nitrogen (N3) lone pair is not available for con-
jugation effects because of the perpendicular arrangement
of the nitrogen lone pairs at N2 and N3. The plane formed
by the phenyl ring occupies a vertical position to the central
π-system. For that reason there is no conjugation between
the two π-systems.
The Lappert and Roesky methods for the synthesis of
iminoarsanes are based on generation of the AsϪN (p-p)π-
bond by alkali metal chloride elimination from N-metalated
aminochloroarsanes, produced by substituting an H-atom
of the amino group with lithium or potassium amide. Our
method of synthesis is distinct from these syntheses as it
uses the principle of direct base-induced dehydrohalogen-
ation of aminochloroarsanes to iminoarsanes. Bisamino-
chloroarsanes suitable for the dehydrohalogenation to ami-
noiminoarsanes were obtained by successively substituting
two chlorine atoms of AsCl3 by treatment with lithium or-
ganyl amides. The introduction of two amino groups in a
stepwise sequence with isolation of the primary formed
aminodichloroarsane allows the synthesis of bisamino-
chloroarsanes and corresponding aminoiminoarsanes with
differently substituted N atoms (Scheme 1).
[a]
Institut für Anorganische Chemie der Universität Bonn,
Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
E-mail: ross@snchemie1.chemie.uni-bonn.de
Eur. J. Inorg. Chem. 2000, 165Ϫ168
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0101Ϫ0165 $ 17.50ϩ.50/0
165

C. Kruppa, M. Nieger, B. Ross, I. Väth
FULL PAPER
Scheme 1. Synthesis of aminoiminoarsanes
Figure 1. Moleculare structure of 5 (50% probabillity level, only one orientation of the disordered group is shown); selected bond
lengths [pm], angles [°] and torsion angles [°]: As(1)ϪN(1) 170.8(3), As(1)ϪN(2) 182.3(2), N(2)ϪN(3) 147.9(4), N(1)ϪC(1) 144.5(4);
As(1)ϪN(1)ϪC(1) 111.9(2), N(1)ϪAs(1)ϪN(2) 104.0(1); C(1)ϪN(1)ϪAs(1)ϪN(2) Ϫ178.5(2)
Bandorf. Ϫ Trimethylsilyl(tert-butyl)amine[9] and tris(trimethylsi-
Experimental Section
lyl)hydrazine[10] were prepared as reported in the literature.
General Remarks: All investigations were carried out in the absence
of air and moisture under dry, oxygen-free argon. Ϫ 1H NMR:
Dichloro[tris(trimethylsilyl)hydrazino]arsane (1): Tris(trimethylsi-
Varian EM 360 (60 MHz) or Bruker WH 90 (90 MHz), standards lyl)hydrazine (13 g, 52.4 mmol), dissolved in diethyl ether (120 mL),
used: residual solvent or TMS. Ϫ 13C NMR: Bruker WH 90
was treated with nBuLi (34 mL of a 1.6  solution in n-hexane,
52.4 mmol) at room temperature and stirred for 1 h. This solution
(22 MHz), standard used: solvent. Ϫ 29Si NMR: Bruker AMX 300
(59.63 MHz), external standard TMS. Ϫ Mass spectra: Kratos MS was then added dropwise at Ϫ78°C to AsCl3 (9.5 g, 52.4 mmol),
50. Ϫ IR spectra: Bruker FT IR IFS 113 V. Ϫ Microanalyses were
performed by the microanalytical laboratory E. Pascher, Remagen-
dissolved in diethyl ether (40 mL). Stirring was continued for an-
other hour whilst allowing the mixture to warm to room tempera-
166
Eur. J. Inorg. Chem. 2000, 165Ϫ168

A New Route to Iminoarsanes
FULL PAPER
ture. Thereafter the solvent was removed under reduced pressure,
and the residue was extracted with n-hexane (40 mL). Lithium
δ ϭ 6.26 [s, Si(CH3)3], 30.41 [s, p-C(CH3)3], 31.58 [s, p-C(CH3)3],
33.78 [s, NC(CH3)3], 34.10 [s, o-C(CH3)3], 36.82 [s, o-C(CH3)3],
chloride was filtered off and cooling at Ϫ24°C over two days 59.54 [s, NC(CH3)3], 124.05 [s, C3, C5], 138.20 [s, C4], 144.67 [s,
yielded 1. Yield: 14.4 g (70%), colourless solid, M.p. 130°C (slow C1], 145.03 [s, C2, C6]. Ϫ MS (EI): m/z (%) ϭ 514 (6) [Mϩ], 479
1
decomposition). Ϫ H NMR (C6D6): δ ϭ 0.13 [s, 18 H, N(Tms)2],
(2) [Mϩ Ϫ Cl], 260 (90) [Mes*NHϩ], 254 (20) [Mϩ Ϫ Mes*NH],
0.41 [s, 9 H, NTms]. Ϫ 13C NMR (C6D6): δ ϭ 2.51 [s, N(Tms)2], 246 (100) [Mes*Hϩ], 198 (84) [TmsNHAsClϩ] and other fragments.
2.70 [s, NTms]. Ϫ MS (EI): m/z (%) ϭ 392 (0.1) [Mϩ], 377 (3) [Mϩ
(2,4,6-Tri-tert-butylphenylimino)[tris(trimethylsilyl)hydrazino]-
Ϫ CH3], 357 (10) [Mϩ Ϫ Cl], 247 (100) [Mϩ Ϫ AsCl2], 73 (95)
arsane (5): DBU (0.39 g, 2.55 mmol), dissolved in n-hexane (5 mL),
was added dropwise to (2,4,6-tri-tert-butylphenylamino)chloro[tris-
[Tmsϩ] and other fragments.
[tert-Butyl(trimethylsilyl)amino]dichloroarsane (2): Trimethylsi-
lyl(tert-butyl)amine (7.25 g, 50 mmol), dissolved in diethyl ether
(20 mL), was mixed with nBuLi (31.5 mL of a 1.6  solution in n-
hexane, 50 mmol) at 0°C. Following 1 h stirring at room tempera-
ture the solution of the lithium salt was added dropwise to AsCl3
(9.1 g, 50 mmol), dissolved in diethyl ether (20 mL), at Ϫ78°C dur-
ing 30 mins. The mixture was then warmed slowly to room tem-
perature, lithium chloride was filtered off and the solvent was re-
moved under reduced pressure. Distillation of the remaining yel-
low-brown oil yielded 2. Yield: 11.79 g (81%), Bp. 78°C/1 mbar. Ϫ
(trimethylsilyl)hydrazino]arsane (3) (1.5 g, 2.43 mmol), dissolved in
n-hexane (10 mL), at room temperature. The solution immediately
turned red. Stirring was continued for 1 h, DBU·HCl was filtered
off and crystallization from the filtrate at Ϫ26°C yielded 5. Yield:
1.08 g (77%), red crystalline solid, M.p. 164Ϫ170°C. Ϫ 1H NMR
(CCl4/TMS): δ ϭ 0.2 [s, 18 H, N(Tms)2], 0.5 [s, 9 H, NTms], 1.34
[s, 9 H, p-tBu], 1.44 [s, 18 H, o-tBu], 7.27 [s, 2 H, Aryl]. Ϫ 13C
NMR (C6D6): δ ϭ 2.67 [s, Si(CH3)3], 30.41 [s, p-C(CH3)3], 32.06
[s, p-C(CH3)3], 33.82 [s, o-C(CH3)3], 36.73 [s, o-C(CH3)3], 121.77 [s.
C3, C5], 137.05 [s, C2, C6], 142.20 [s, C4], 149.29 [s, C1]. Ϫ 29Si
1H NMR (CDCl3): δ ϭ 0.43 [s, 9 H, Tms], 1.53 [s, 9 H, tBu]. Ϫ (C6D6): δ ϭ 10.96 [N(Tms)2], 15.68 [NTms]. Ϫ MS (EI): m/z (%) ϭ
13C NMR (CDCl3): δ ϭ 6.05 [s, Si(CH3)3], 33.86 [s, C(CH3)3], 61.92 581 (52) [Mϩ], 566 (5) [Mϩ Ϫ CH3], 334 (100) [Mϩ Ϫ N2(Tms)3],
[s, C(CH3)3]. Ϫ MS (EI): m/z (%) ϭ 289 (1) [Mϩ], 274 (33) [Mϩ
Ϫ
247 (92) [(Tms)3N2ϩ], 73 (65) [Tmsϩ], 57 (28) [tBuϩ] and other
CH3], 254 (5) [Mϩ Ϫ Cl], 218 (15) [Mϩ Ϫ CH3 Ϫ isobutene], 198 fragments. Ϫ IR (KBr): ν˜ ϭ 2956 (vs), 2904 (s), 2856 (s), 1595 (m),
(21) [Mϩ Ϫ Cl Ϫ isobutene], 166 (100) [Mϩ Ϫ TmsCl Ϫ CH3], 73
(80) [Tmsϩ], 57 (92) [tBuϩ] and other fragments.
1478 (m), 1460 (m), 1413 (s), 1389 (m), 1360 (s), 1253 (vs), 1213(s),
1191 (m), 1146 (m), 1021 (m), 925 (vs), 880 (vs), 842 (vs), 768 (s),
747 (m), 681 (m), 655 (m), 640 (w), 610 (w), 572 (m) cmϪ1. Ϫ
C27H56AsN3Si3 (581.94): calcd. C 55.73 H 9.70 N 7.22; found C
56.22 H 9.81 N 7.01
(2,4,6-Tri-tert-butylphenylamino)chloro[tris(trimethylsilyl)hydra-
zino]arsane (3): 2,4,6-Tri-tert-butylphenylamine (1.25 g, 4.8 mmol),
dissolved in diethyl ether (10 mL), was treated with nBuLi (3 mL
of a 1.6  solution in n-hexane) at room temperature. After stirring
for 30 mins. the solution of the lithium salt was added dropwise to
dichloro[tris(trimethylsilyl)hydrazino]arsane (1) (1.88 g, 4.8 mmol),
dissolved in diethyl ether (50 mL). Stirring was continued for 30
mins. and the solvent was removed under reduced pressure. The
residue was extracted with n-hexane (10 mL) and lithium chloride
was filtered off. Crystallization from the filtrate at Ϫ78°C yielded
[tert-Butyl(trimethylsilyl)amino](2,4,6-tri-tert-butylphen-
ylimino)arsane (6): [tert-Butyl(trimethylsilyl)amino]chloro(2,4,6-tri-
tert-butylphenylamino)arsane (4) (1.6 g, 3.1 mmol), dissolved in n-
hexane (10 mL), was treated with DBU (0.5 g, 3.3 mmol), dissolved
in n-hexane (3 mL). The solution immediately turned red. Stirring
was continued for 1 h, DBU·HCL was filtered off and cooling of
the filtrate at Ϫ26°C yielded 6. Yield: 1.1 g (75%), red solid, M.p.
1
1
3. Yield: 1.5 g (50%), light rose solid, M.p. 81Ϫ83°C. Ϫ H NMR
87Ϫ90°C. Ϫ H NMR (CCl4/TMS): δ ϭ 0.39 [s, 9 H, Tms], 1.32
(C6D6): δ ϭ 0.26 [s, 9 H, N(Tms)2], 0.34 [s, 9 H, N(Tms)2], 0.42 [s, [s, 9 H, p-tBu], 1.37 [s, 18 H, o-tBu], 1.80 [s, 9 H, NϪtBu], 7.24 [s,
9 H, AsNTms], 1.28 [s, 9 H, p-tBu], 1.56 [s, 18 H, o-tBu], 5.82 [s, 1 2 H, Aryl]. Ϫ 13C NMR (C6D6): δ ϭ 5.93 [s, Si(CH3)3], 30.48 [s,
H, NH], 7.49 [s, 2 H, Aryl]. Ϫ 13C NMR (C6D6): δ ϭ 3.80 [s,
N{Si(CH3)3}2], 3.86 [s, N{Si(CH3)3}2], 3.98 [s, AsNSi(CH3)3], 30.48
[s, p-C(CH3)3], 31.71 [s, p-C(CH3)3], 34.55 [s, o-C(CH3)3], 36.71 [s,
o-C(CH3)3], 124.08 [s, C3, C5], 138.13 [s, C4], 141.02 [s, C2, C6],
p-C(CH3)3], 32.10 [s, p-C(CH3)3], 33.31 [s, o-C(CH3)3], 33.47 [s,
NC(CH3)3], 36.63 [s, o-C(CH3)3], 60.97 [s, NC(CH3)3], 121.63 [s,
C3, C5], 138.23 [s, C2, C6] 142.17 [s, C4], 150.16 [s, C1]. Ϫ 29Si
NMR (C6D6): δ ϭ 5.99. Ϫ MS (EI): m/z (%) ϭ 478 (30) [Mϩ], 463
143.19 [s, C1]. Ϫ 29Si NMR (C6D6): δ ϭ 11.37 [N(Tms)2], 12.37 (6) [Mϩ Ϫ CH3], 421 (12) [Mϩ Ϫ tBu], 334 (100) [Mϩ
Ϫ
[N(Tms)2], 16.06 [NTms]. Ϫ MS (EI): m/z (%) ϭ 617 (2) [Mϩ], 602
N(Tms)tBu], 278 (50) [Mϩ Ϫ N(Tms)tBu Ϫ isobutene], 73 (90)
(0.4) [Mϩ Ϫ CH3], 581 (5) [Mϩ Ϫ HCl], 509 (0.4) [Mϩ Ϫ TmsCl], [Tmsϩ], 57 (50) [tBuϩ] and other fragments. Ϫ IR (KBr): ν˜ ϭ 2963
357 (100) [Mϩ Ϫ Mes*NH], 334 (54) [Mϩ Ϫ HCl Ϫ N2Tms3], 247 (vs), 2903 (m), 2864 (m), 1621 (w), 1596 (w), 1479 (m), 1436 (m),
(75) [Tms3N2ϩ], 73 (82) [Tmsϩ], 57 (20) [tBuϩ] and other fragments. 1409 (s), 1388 (m), 1360 (s), 1253 (s) 1234 (w), 1215 (s) 1179 (m),
1116 (s), 1034 (m), 958 (s), 917 (w), 847 (vs), 761 (m), 739 (m), 678
[tert-Butyl(trimethylsilyl)amino]chloro(2,4,6-tri-tert-butyl-
(s), 632 (m), 534 (w), 485 (m), 416 (w) cmϪ1
.
phenylamino)arsane (4): 2,4,6-Tri-tert-butylphenylamine (3 g,
11.5 mmol), dissolved in diethyl ether (130 mL), was treated with Crystal Data for 5: C27H56AsN3Si3, M ϭ 581.9, monoclinic, space
nBuLi (9.3 mL of a 1.6  solution in n-hexane) at room tempera-
ture. After stirring for 30 mins. the solution of the lithium salt was mm, a ϭ 9.865(3), b ϭ 34.578(2), c ϭ 10.035(1) A, β ϭ 98.80(2)°,
group P21/n (No. 14), red crystals, dimensions 0.10 ϫ 0.15 ϫ 0.35
˚
3
V ϭ 3.383(1) A , Dc ϭ 1.14 Mg mϪ3, Z ϭ 4, µ (CuKα) ϭ 2.5
˚
added dropwise at Ϫ78°C to [tert-butyl(trimethylsilyl)amino]di-
chloroarsane (2) (3.32 g, 11.5 mmol), dissolved in diethyl ether mmϪ1, T ϭ 208(2) K, F(000) ϭ 1256; 5328 reflection were collected
(20 mL). The mixture was warmed slowly to room temperature and
stirring was continued for 1 h. The solvent was removed under
on an EnrafϪNonius CAD4 diffractometer (2θmax ϭ 120°, Ϫ11 Յ
h Յ 0, 0 Յ k Յ 38, Ϫ11 Յ l Յ 11), 5008 symmetry independent
reduced pressure and the residue was extracted with n-hexane reflections (Rint ϭ 0.027) were used for the structure solution (di-
(15 mL). Lithium chloride was filtered off and cooling of the fil-
rect methods)[11] and refinement (full matrix least-squares on F2,[12]
trate at Ϫ78°C for three weeks yielded 4. Yield: 3.6 g (60%), colour- 302 parameters, 60 restraints), non-hydrogen atoms were refined
less solid, M.p. 90Ϫ92°C. Ϫ 1H NMR (C6D6): δ ϭ 0.47 [s, 9 H,
Tms], 1.33 [s, 9 H, p-tBu], 1.40 [s, 9 H, NϪtBu], 1.66 [s, 18 H, o-
tBu], 6.03 [s, 1 H, NH], 7.55 [s, 2 H, Aryl]. Ϫ 13C NMR (C6D6):
anisotropically, H atoms localized by difference electron density
and refined using a riding model; wR2 ϭ 0.108 [R1 ϭ 0.039 for
3969 I > 2σ(I)]. An empirical absorption correction on the basis of
Eur. J. Inorg. Chem. 2000, 165Ϫ168
167

C. Kruppa, M. Nieger, B. Ross, I. Väth
FULL PAPER
[4b]
Phosphorus, Sulfur, Silicon 1990, 47, 349Ϫ355. Ϫ
S. K. Vas-
isht, T. P. Kaur, K. Usha, J. Kaushal, K. Bandhu, Phosphorus,
Sulfur, Silicon 1995, 107, 189Ϫ195.
ψ-scans was applied (min./max. transmission 0.190/0.764). The p-
tBu-group is disordered.
[5]
[6]
P. B. Hitchcock, M. F. Lappert, A. K. Rai, H. D. Williams, J.
Chem. Soc., Chem. Commun. 1986, 1633Ϫ34.
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Data Centre as supplementary publication no. CCDC-132004.
Copies of the data can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [Fax: (in-
ternat.) ϩ 44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
J.-T. Ahlemann, A. Künzel, H. W. Roesky, M. Noltemeyer, L.
Markovskii, H.-G. Schmidt, Inorg Chem 1996, 35, 6644Ϫ6645.
V. Schomaker, D. P. Stevenson, J. Am. Chem. Soc. 1941, 63,
37Ϫ49.
[7]
[8]
`
P. A. Giguere, V. Schomaker, J. Am. Chem. Soc 1943, 65,
2025Ϫ2029.
[9]
I. Schumann-Ruidisch, W. Kalk, R. Brüning, Z. Naturforsch.
[1]
1968, B 23, 307Ϫ312
E. Niecke, D. Gudat, Angew. Chem. 1991, 103, 251Ϫ270; An-
[10]
[11]
[12]
K. Witke, P. Reich, H. Kriegsmann, J. Organomet. Chem. 1968,
gew. Chem. Int. Ed. Engl. 1991, 30, 217
[2]
15, 37Ϫ41
G. I. Kokorev, F. D. Yambushev, Sh. Kh. Badrutdinov, Zh.
Obshch. Khim. 1986, 56(9), 2058Ϫ2061 Chem. Abstr. 1987,
107, 59134c.
G. M. Sheldrick, SHELXS-86, Acta Crystallogr. 1990, A46,
467Ϫ473.
[3] [3a]
G. M. Sheldrick, SHELXL-97, University of Göttingen, 1997.
H. G. Ang, F. K. Lee, Polyhedron 1989, 8, 1461Ϫ1462. Ϫ
[3b]
H. G. Ang, F. K. Lee, Polyhedron 1989, 8, 2331Ϫ2332.
Received July 20, 1999
[I99268]
[4] [4a]
S. K. Vasisht, M. Sood, P. K. Verma, T. Kaur, K. Usha,
168
Eur. J. Inorg. Chem. 2000, 165Ϫ168