Cyclic arsenic - Nitrogen cations

Article abstract of DOI:10.1021/ic900821h

A series of different cyclo-diarsa-diazenium salts bearing several bulky groups such as supermesityl (Mes^* = 2,4,6-tBu₃C ₆H₂) and m-terphenyl (2,6-Mes₂-C ₆H₃, Mes = 2,4,6-Me

Full text of DOI:10.1021/ic900821h

Inorg. Chem. 2009, 48, 7359–7367 7359
DOI: 10.1021/ic900821h
Cyclic Arsenic-Nitrogen Cations
Axel Schulz*,†,‡ and Alexander Villinger*,†
::
::
::
::
‡
†Universitat Rostock Institut fur Chemie Albert-Einstein-Str.3a, 18059 Rostock, Germany, and Leibniz-Institut fur
Katalyse e.V. an der Universitat Rostock, Albert-Einstein-Str. 29a, 18059 Rostock, Germany
Received April 28, 2009
A series of different cyclo-diarsa-diazenium salts bearing several bulky groups such as supermesityl (Mes* = 2,4,6-
tBu3C6H2) and m-terphenyl (2,6-Mes2-C6H3, Mes = 2,4,6-Me3C6H2) and anions such as triflate (OTf = SO3CF3 =
trifluoromethylsulfonate) and tetrachloridogallate (GaCl4-) were synthesized and fully characterized. The novel
1-chloro-cyclo-1,3-diarsa-2,4-diazenium cation represents the first example of a binary cyclic As(III)/N four-membered
heterocyclic cation, with a di- and tricoordinated As atom and a delocalized π bond along the NAs(þ)N unit. The
addition of excess Me3SiN3 yields the fully characterized cationic arsenic azide, 1-azido-cyclo-1,3-diarsa-2,4-
diazenium-μ-azido-hexachlorido-digallate. The Cl-/N3- exchange is triggered by the action of the Lewis acid GaCl3.
Depending on the Me3SiN3 stoichiometry, different μ-azido-hexachlorido-digallate salts with either 1-chloro- or
1-azido-cyclo-1,3-diarsa-2,4-diazenium cations or even a mixture of both are observed. Moreover, it was of special
interest to study the distances between the cationic arsenic center and the anion in cyclo-diarsa-diazenium salts.
˚
A correlation between the color of the salt and the anion/cation distance, ranging between 2 and 8 A in cyclo-diarsa-
diazenium salts of the type [R2N2As2Y]þX- depending on the bulky group R (R=Mes*, Ter), the substituent Y (Y=Cl,
N3, OTf), and the anion X- (X = OTf, GaCl4, Cl3Ga-N3-GaCl3), was established.
Introduction
Cyclodipnictadiazanes (RENR0)2 are known for all pnic-
togens E from phosphorus to bismuth1-4 and represent
potential starting materials for, for example, cations, ring-
opening oligomerization, and polymerization.
As first discovered by Olah and Oswald for alkyl deriva-
tives, cyclodiarsadiazanes are readily prepared by the addi-
tion of excess primary amine to AsCl3.5 Burfurd et al. have
recently developed a high-yield ring expansion reaction for
cyclodiphosphadiazanes to give cyclotriphosphatriazanes by
means of Lewis acids such as GaCl3.6 Later, this process was
extrapolated to the analogous arsenic derivatives providing
high-yield preparations of trimers (RNAsCl)3 starting from
the dimer (RNAsCl)2 (R=2,6-dimethylphenyl (Dmp) and
2,6-diisopropylphenyl (Dipp)).7
In recent years (besides the ring expansion reaction),
Lewis-acid-assisted reactions such as [3þ2] cyclizations or
methyl/halogen exchange with nitrogen-pnictogen com-
pounds have attracted considerable interest. With the
help of such reactions, it was possible to generate a series of
low-coordinated P(III)/N and As(III)/N heterocycles and
cationic PN species bearing reactive multiple EN bonds
(E=P, As).6-16
*To whom correspondence should be addressed. E-mail: axel.schulz@
uni-rostock.de (A.S.).
(1) Phosphorus, for example: (a) Keat, R. Top. Curr. Chem. 1982, 102, 89–
116. (b) Chen, H.-J.; Haltiwanger, R. C.; Hill, T. G.; Thompson, M. L.; Coons,
D. E.; Norman, A. D. Inorg. Chem. 1985, 24, 4725–4730. (c) Stahl, L. Coord.
Chem. Rev. 2000, 210, 203–250. (d) Burford, N.; Cameron, T. S.; Lam, K.-C.;
LeBlanc, D. J.; Macdonald, C. L. B.; Phillips, A. D.; Rheingold, A. L.; Stark, L.;
Walsh, D. Can. J. Chem. 2001, 79, 342–348.
(2) Arsenic, for example: (a) Bohra, R.; Roesky, H. W.; Noltemeyer, M.;
Sheldrick, G. M. Acta Crystallogr. 1984, C40, 1150–1152. (b) Ahlemann, J.-T.;
Roesky, H. W.; Murugavel, R.; Parisini, E.; Noltemeyer, M.; Schmidt, H.-G.;
::
Muller, O.; Herbst-Irmer, R.; Markovskii, L. N.; Shermolovich, Y. G. Chem. Ber.
1997, 130, 1113–1121. (c) Avtomonov, E. V.; Megges, K.; Li, X.; Lorberth, J.;
Wocadlo, S.; Massa, W.; Harms, K.; Churakov, A. V.; Howard, J. A. K.
J. Organomet. Chem. 1997, 544, 79–89. (d) Raston, C. L.; Skelton, B. W.;
Tolhurst, V.-A.; White, A. H. Dalton Trans. 2000, 1279–1285.
(3) Antimony, for example: (a) Ross, B.; Belz, J.; Nieger, M. Chem. Ber.
1990, 123, 975–978. (b) Garbe, R.; Pebler, J.; Dehnicke, K.; Fenske, D.;
Goesmann, H.; Baum, G. Z. Anorg. Allg. Chem. 1994, 620, 592–598.
(c) Edwards, A. J.; Leadbeater, N. E.; Paver, M. A.; Raithby, P. R.; Russell,
C. A.; Wright, D. S. Dalton Trans. 1994, 1479–1482. (d) Edwards, A. J.; Paver,
M. A.; Rennie, M.-A.; Raithby, P. R.; Russell, C. A.; Wright, D. S. Dalton Trans.
1994, 2963–2966. (e) Beswick, M. A.; Harmer, C. N.; Hopkins, A. D.; Paver,
M. A.; Raithby, P. R.; Wright, D. S. Polyhedron 1998, 17, 745–748. (f) Bryant,
R.; James, S. C.; Jeffrey, J. C.; Norman, N. C.; Orpen, A. G.; Weckenmann, U.
Dalton Trans. 2000, 4007–4009. (g) Beswick, M. A.; Elvidge, B. R.; Feeder, N.;
Kidd, S. J.; Wright, D. S. Chem. Commun. 2001, 379–380. (h) Haagenson, D. C.;
Stahl, L.; Staples, R. J. Inorg. Chem. 2001, 40, 4491–4493.
(5) Olah, G. A.; Oswald, A. A. Can. J. Chem. 1960, 38, 1428–1430.
(6) Burford, N.; Conroy, K. D.; Landry, J. C.; Ragogna, P. J.; Ferguson,
M. J.; McDonald, R. Inorg. Chem. 2004, 43, 8245–8251.
(7) Burford, N.; Landry, J. C.; Ferguson, M. J.; McDonald, R. Inorg.
Chem. 2005, 44, 5897–5902.
(8) Herler, S.; Villinger, A.; Weigand, J.; Mayer, P.; Schulz, A.; Schmedt
::
auf der Gunne, J. Angew. Chem. 2005, 117, 7968–7971. Angew. Chem., Int.
Ed. 2005, 44, 7790-7793.
(4) Bismuth, for example: (a) Wirringa, U.; Roesky, H. W.; Noltemeyer,
M.; Schmidt, H. G. Inorg. Chem. 1994, 33, 4607–4608. (b) Briand, G. G.;
Chivers, T.; Parvez, M. Can. J. Chem. 2003, 81, 169–174.
(9) Mayer, P.; Schulz, A.; Villinger, A. Chem. Commun. 2006, 1236–1238.
(10) Mayer, P.; Schulz, A.; Villinger, A. J. Organomet. Chem. 2007, 692,
2839–2842.
r
2009 American Chemical Society
Published on Web 07/08/2009
pubs.acs.org/IC

7360 Inorganic Chemistry, Vol. 48, No. 15, 2009
Schulz and Villinger
Scheme 1. Known Cyclic As-N Cations (5: R=Dipp)7,17-20
Scheme 2. Synthesis of cyclo-1,3-Dipnicta-2,4-diazenium Cations
(E=P, As; Ter=2,6-Mes2-C6H3, Mes=2,4,6-Me3C6H2)
Figure 1. ORTEP drawing of the molecular structure of 6a in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen
˚
atoms omitted for clarity). Selected bond lengths [A] and angles [deg]:
As-Ni 1.862(1), As-N 1.871(1), As-Cl 2.2605(7), As-Asi 2.874(1),
N-C1 1.409(2); Ni-As-N 79.30(6), Ni-As-Cl 98.99(5), N-As-Cl
98.39(5), Asi-N-As 100.70(6), Ni-As-N-Asi 0.0.
Scheme 3. Synthesis of 1,3-Dichloro-cyclo-1,3-diarsa-2,4-diazanes (6:
R=Ter; 9: R=Mes*)
cationic phosphorous azide, a 1-azido-cyclo-1,3-diphospha-
2,4-diazenium cation. With the knowledge that it is possible
to prepare salts with a cyclo-1,3-diphospha-2,4-diazenium
cation bearing a covalently bound azide, it was our idea to
prepare the heavier arsenic analog (Scheme 2). To achieve
this goal, two problems had to be solved: (i) the synthesis of
a hitherto unknown cyclic binary As/N cation (7) with a
dicoordinatedAs centerand (ii)a chloride-azideexchange in
this cation. Reactive azido compounds with four-membered
cationic, binary As/N rings are particularly challenging
to synthesize. The introduction of bulky groups such as
m-terphenyl (Ter=2,6-Mes2-C6H3, Mes=2,4,6-Me3C6H2)23
and delocalization have been found to be the keys to
stabilizing heavy element double bonds in low coordinated
reactive species.10,11
We report here (i) the first structural characterization of
a 1-chloro-cyclo-1,3-diarsa-2,4-diazenium cation (7, E=As,
Scheme 2) as well as (ii) the formation and full characteriza-
tion of the intriguing 1-azido-cyclo-1,3-diarsa-2,4-diazenium-
μ-azido-hexachlorido-digallate (8) and different mixed salts
of 7 and 8 depending on the stoichiometry of Me3SiN3 added
(Scheme 2).
An interesting aspect of the chemistry of the heavier group
15 elements, in terms of both structure and reactivity, which
continues to receive significant attention, is the area of
cationic compounds with low coordination numbers.21 Espe-
cially in the case of arsenic, only a few cyclic As-N cations
with a dicoordinated cyclic As center are known (Scheme 1).
Recently, the synthesis and full characterization of a 1-
chloro-cyclo-1,3-diphospha-2,4-diazenium salt was reported.22
A chlorine-azide exchange in the 1-chloro-cyclo-1,3-dipho-
spha-2,4-diazenium salt led to the isolation of the first
(11) Kowalewski, M.; Krumm, B.; Mayer, P.; Schulz, A.; Villinger, A.
Eur. J. Inorg. Chem. 2007, 5319–5322.
(12) Brand, H.; Schulz, A.; Villinger, A. Z. Anorg. Allg. Chem. 2007, 633,
22–35.
(13) Meyer, P.; Schulz, A.; Villinger, A. Inorg. Chem. 2007, 46, 8316–8322.
(14) Schulz, A.; Villinger, A. Angew. Chem. 2008, 120, 614–617. Schulz,
A.; Villinger, A. Angew. Chem., Int. Ed. 2008, 47, 603–606.
(15) Burford, N.; Clyburne, J. A. C.; Chan, M. S. W. Inorg. Chem. 1997,
36, 3204–3206.
(16) Burford, N.; Cameron, T. S.; Conroy, K. D.; Ellis, B.; Lumsden,
M. D.; McDonald, C. L. B.; McDonald, R.; Phillips, A. D.; Ragogna, P. J.;
Schurko, R. W.; Walsh, D.; Wasylishen, R. E. J. Am. Chem. Soc. 2002, 124,
14012–14013.
(17) Reeske, G.; Cowley, A. H. Chem. Commun. 2006, 1784–1786.
(18) Burford, N.; Parks, T. M.; Royan, B. W.; Richardson, J. F.; White,
P. S. Can. J. Chem. 1992, 70, 703–709.
(19) Burford, N.; Parks, T. M.; Royan, B. W.; Borecka, B.; Cameron,
T. S.; Richardson, J. F.; Gabe, E. J.; Hynes, R. J. Am. Chem. Soc. 1992, 114,
8147–8153.
(20) Burford, N.; Macdonald, C. L. B.; Parks, T. M.; Wu, G.; Borecka, B.;
Kwiatkowski, W.; Cameron, T. S. Can. J. Chem. 1996, 74, 2209–2216.
(21) Carmalt, C. J.; Farrugia, L. J.; Norman, N. C. J. Chem. Soc., Dalton
Trans. 1996, 443–454.
(22) Michalik, D.; Schulz, A.; Villinger, A.; Weding, D. Angew. Chem.
2008, 120, 6565–6568. Michalik, D.; Schulz, A.; Villinger, A.; Weding, D.
Angew. Chem., Int. Ed. 2008, 47, 6465–6468.
Moreover, we report on the synthesis of a series of different
cyclo-diarsa-diazenium salts bearing several bulky groups
such as supermesityl (Mes*=2,4,6-tBu3C6H2) and m-terphe-
nyl and anions such as triflate (OTf = SO3CF3 = trifluor-
omethylsulfonate) and tetrachloridogallate (GaCl4-). In this
context, it is of special interest to study the distances between
the cationic arsenic center and the anion. According to the
(23) (a) Twamley, B.; Haubrich, S. T.; Power, P. P. Adv. Organomet.
Chem. 1999, 44, 1–65. (b) Clyburne, J. A. C.; McMullen, N. Coord. Chem. Rev.
2000, 210, 73–99. (c) Wright, R. J.; Steiner, J.; Beaini, S.; Power, P. P. Inorg.
Chim. Acta 2006, 359, 1939–1946.

Article
Inorganic Chemistry, Vol. 48, No. 15, 2009 7361
Table 1. Selected bond lengths and angles along with reported data of 5, and 9
compound
9 from ref 24
6
10a
11
7
12
8
5 from ref 7
crystal color
λexp(nm)b
colorless
c
yellow
yellow
orange
black
554
7.030(3)
2.182(5)
black
566
6.875(1)
2.178(7)
black
559
6.266(2)
1.938(2)
yellow
418(429)d
1.964(1)
1.964(1)
578(418)d
2.2242(9)
2.159(2)
dlong(As-X1)e
dshort(As-X2)f
2.235(4)
2.235(4)
2.2605(7)
2.2605(7)
2.708(1)
2.207(1)
2.209(1)
1.786(2)g
1.793(2)
1.881(2)g
1.864(2)
0.095
dshort(As-N)
dlong(As-N)
Δ(dlong - dshort
1.840(8)
1.855(7)
0.015
1.862(1)
1.871(1)
0.008
1.842(1)
1.844(1)
0.002
1.819(2)
1.830(2)
1.886(2)
1.886(2)
0.067
0.056
77.83(8)
77.83(8)
1.799(2)g
1.827(2)
1.928(2)g
1.901(2)
0.128
0.074
81.8(1)
76.6(1)
1.793(2)
1.825(2)
1.914(2)
1.911(2)
0.121
0.086
81.93(8)
76.65(8)
1.799(3)
1.812(2)
1.915(3)
1.901(3)
0.116
0.089
82.1(1)
76.8(1)
)
0.071
<(N-As-N)h
<(N-As-N)i
80.4(3)
80.4(3)
79.30(6)
79.30(6)
81.55(6)
81.55(6)
103.8(1)
99.1(1)
98.4(1)
a P21/c structure, data of the P21/n structure can be found in the Supporting Information. b UV-vis experiments in diluted CH2Cl2 solutions. c It
has been shown that 9 monomerizes in CH2Cl2 solution with a deep red color.14 d Values in parentheses were determined in toluene (non-polar solvent).
e X1=Cl for 5, 6, 7, 11, 12; X1=OTf for 10; X1=N3=8. f X2=OTf for 10 and 11; Cl for 5, 6, and 7. g for 5, 7, 8, and 12: dshort=Asdi-coordinated-N, dlong
=
Astri-coordinated-N. h Corresponds to<(N-Asdi-coordinated-N) in the cationic species. i Corresponds to<(N-Astri-coordinated-N) in the cationic species.
Table 2. Crystallographic Details of 6, 10, and 11
little published data, these distances vary between 2.0 and
˚
2.7 A. Here, we want to establish a clear correlation between
the color of the cation and the closest anion/cation distance
in cyclo-diarsa-diazenium salts of the type [R2N2As2Y]þX-
depending on the bulky group R (R=Mes*, Ter), the
substituent Y (Y=Cl, N3, OTf), and the anion X- (X =
OTf, GaCl4, Cl3Ga-N3-GaCl3).
6aa
10ab
11
chem. formula
C
48H50As2
Cl2N2
C38H58As2
F6N2O6S2
966.82
yellow
monoclinic
P21/c
11.289(2)
16.454(3)
16.409(5)
90.00
133.431(17)
90.00
C49H50As2Cl
F3N2O3S
989.26
orange
monoclinic
P21/c
13.742(3)
14.494(3)
23.784(5)
90.00
91.51(3)
90.00
fw [g mol-1
color
cryst syst
]
875.64
yellow
triclinic
P1
8.6360(17)
10.658(2)
11.458(2)
79.40(3)
86.56(3)
82.36(3)
space group
˚
Results and Discussion
a [A]
˚
b [A]
Synthesis of cyclo-1,3-Diarsa-2,4-diazanes and cyclo-
1,3-Diarsa-2,4-diazenium Cations. Reactions of bases
such as triethylamine or 1,8-diazabicyclo[5.4.0]undec-7-
ene (DBU) and aminodichloroarsanes of the type [RN-
(H)-AsCl2] (R=Mes* and Ter) readily provide access
to 1,3-dichloro-2,4-bis-(2,4,6-tri-tert-butylphenyl)-cyclo-
1,3-diarsa-2,4-diazane ([Mes*-N-AsCl]2; 9) and bis[2,4-
bis(2,4,6-trimethylphenyl)phenyl]-cyclo-1,3-diarsa-2,4-dia-
zane ([Ter-N-AsCl]2; 6), respectively (Scheme 3).14
Compound 6 crystallizes dependent on the solvent,
either without any solvent (from CH2Cl2, Figure 1, Tables 1
and 2) or with tetrahydrofurane (THF) or toluene
(Schemes S1-S3 and Tables S1, S4-6 in the Supporting
Information).
˚
c [A]
R [deg]
β [deg]
γ [deg]
3
˚
V [A ]
1026.7(3)
1
1.416
1.794
2213.4(11)
2
1.451
1.673
4735.6(16)
4
Z
F
calcd [g cm-3
]
1.388
1.566
μ [mm-1
]
˚
MoKR [A]
λ
T [K]
0.71073
173(2)
29442
7529
6134
0.0304
452
0.0331
0.0734
1.038
250
0.71073
173(2)
41726
7989
7006
0.0295
1000
0.0265
0.0602
1.041
263
0.71073
173(2)
68264
13675
9900
0.0448
2032
0.0462
0.1182
1.055
562
measured reflns
independent reflns
reflns with I > 2σ(I)
Rint
F(000)
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
GoF
params
Investigation of the equilibrium14 between cyclic dia-
rsadiazane [Mes*-N-AsCl]2 and its monomer, the imi-
noarsane, by means of temperature-dependent 1H NMR
techniques revealed the presence of such an equilibrium as
already proposed by Burford et al.20 The white crystalline
dimer [Mes*-N-AsCl]2 is readily dissolved in CH2Cl2,
but the colorless solution from the beginning becomes
red, the color of the monomeric species, Mes*NdAs-Cl.
It was of interest to study the effect of the bulky group on
both the synthetic routes and the dimer/monomer equi-
librium. Hence, instead of the supermesityl group (Mes*),
the m-terphenyl group was also used for kinetic stabiliza-
tion of the iminoarsane (R-NdAs-Cl), displaying an
astonishingly stable dimer [TerNAsCl]2 in solution and in
the solid phase, which has already been observed for the
analogous phosphorous compound.22 In contrast to [Mes*-
N-AsCl]2, the m-terphenyl-substituted analog does
not monomerize in solution, as shown by 1H NMR
techniques. No monomeric Ter-NdAs-Cl could be
detected.
a Two further structures of 6 have been determined (6a: solvent free,
6b: with toluene, 6c with Thf, see Supporting Information). b A second
data set (10b) was measured and can be found in the Supporting
Information.
Burford et al. assumed that, depending on the steric
strain in derivatives of [RENR0]2 (E = P, As; R = Cl,
R0=organic group), the dimer can be destabilized with respect
to the monomer.6,7,9 The addition of Lewis acids such
as GaCl3 or AlCl3 resulted in ring-opening oligomeriza-
tion, with 1-halo-2,4-di(aryl)-cyclo-1,3-dipnicta-2,4-diaze-
nium cations discussed as intermediates.6,7 The only
arsenic/nitrogen cation which could be isolated in such a
ring-opening oligomerization represents the trimer 5
(Scheme 1).7
(24) Burford, N.; Cameron, T. S.; Macdonald, Ch. L. B.; Robertson,
K. N.; Schurko, R.; Walsh, D. Inorg. Chem. 2005, 44, 8058–8064.

7362 Inorganic Chemistry, Vol. 48, No. 15, 2009
Schulz and Villinger
Figure 2. ORTEP drawing of the molecular structure of 10 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydrogen
Figure 3. ORTEPdrawingofthemolecularstructureof11 inthe crystal.
Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms
omitted for clarity). Selected bond lengths [A] and angles [deg]: As1-N1
1.819(2), As1-N2 1.830(2), As1-O1 2.159(2), As1-As2 2.8453(7),
As2-N1 1.886(2), As2-N2 1.886(2), As2-Cl 2.2242(9), N1-As1-N2
80.98(9), N1-As1-O1 93.56(9), N2-As1-O1 92.46(9), N1-As2-N2
77.83 (8), N1-As2-Cl 96.68(7), N2-As2-Cl 98.98(7), As1-N1-As2
100.34(9), As1-N2-As2 99.93(8), N2-As1-As2-N1 168.8(1).
˚
atoms omitted for clarity). Selected bond lengths [A] and angles [deg]:
As-N 1.842(1), As-Ni 1.844(1), As-O1 1.964(1), As-Asi 2.7918(5), N-
C1 1.452(2), N-Asi 1.844(1); N-As-Ni 81.55(6), N-As-O1 93.35(6),
Ni-As-O1 99.75(5), C1-N-Asi 140.1(1), As-N-Asi 98.45(6).
˚
Scheme 4. Reaction of 1,3-Dichloro-cyclo-1,3-diarsa-2,4-diazanes
(R=Ter, Mes*) with AgOTf and GaCl3
reaction between ([Ter-N-AsCl]2) (6) and 2 equiv of
AgOTf led only to the formation of the singly substituted
1-chloro-3-trifluoromethylsulfonato-2,4-bis[2,4-bis-(2,4,6-
trimethylphenyl)phenyl]-cyclo-1,3-diarsa-2,4-diazane (11;
Figure 3). Triflate-substituted cyclo-1,3-diarsa-2,4-diazanes
(10 and 11) are astonishingly thermally stable (10, 174°; 11,
252 °C decomposition) and moisture-sensitive but stable
under an argon atmosphere over a long period as a solid and
in polar solvents at ambient temperature. Both compounds
are easily prepared in bulk and are infinitely stable when
stored in a sealed tube. Interestingly, both compounds
dissolve in nonpolar solvents (e.g. toluene) with a yellow
color, while in a polar solvent such as CH2Cl2, compound 11
dissolves red-violet in contrast to compound 10, which still
exhibits a yellow color (see below).
A “true” salt with separated anions and cations repre-
sents the 1-chloro-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)
phenyl]-cyclo-1,3-diarsa-2,4-diazenium tetrachloridogal-
late (7), which was isolated in the reaction of 6 with GaCl3
(Scheme 4, Figure 4, see below). Crystals of cyclo-1,3-
diarsa-2,4-diazenium salt 7 are black and moisture-sensi-
tive but stable under an argon atmosphere over a long
period as a solid and in CH2Cl2 at ambient temperature.
The black appearance vanishes rapidly when traces of
H2O are present. Crystals of 7 dissolve with a deep red-
violet color in CH2Cl2. Compound 7 can be prepared in
bulk and is also infinitely stable when stored in a sealed
tube at ambient temperatures.
The first observation of a monochlorodiphosphadia-
zenium cation (R2N2P2Clþ, R=tBu) was reported by
Cowley et al. in the reaction of the corresponding cyclo-
diphosphadiazane with AlCl3, independent of reaction
stoichiometry, as displayed by a detailed 31P NMR
study.25 Recently, the isolation and full characterization
of the 1-azido- and 1-chloridodiphosphadiazenium ca-
tions was achieved by the introduction of the sterically
demanding m-terphenyl group. Thus, it seemed interest-
ing to study chloride abstraction in [Mes*-N-AsCl]2
and [Ter-N-AsCl]2 by means of silver triflate, AgOTf,
and gallium trichloride, GaCl3, in detail.
In a high-yield reaction, [Mes*-N-AsCl]2 (9) is trans-
formed into the yellow crystalline 1,3-bis-(trifluoro-
methylsulfonato)-2,4-bis-(2,4,6-tri-tert-butylphenyl)-cyclo-
1,3-diarsa-2,4-diazane (10) by the addition of 2 equiv of
AgOTf (Figure 2, Scheme 4). On the contrary, the same
Cationic Cyclic Arsenic(III) Azides. The reactions of
7 with 1 equiv, 2 equiv, and an excess of Me3SiN3 in
the presence of one additional equivalent of GaCl3 in
CH2Cl2 result in facile chloride-azide exchange. However,
depending on the stoichiometry, three different products
could be isolated (Scheme 5). The first equivalent of Me3-
SiN3 is only used to form a μ-azido-hexachlorido-digallate
-
anion (GaCl3 þ GaCl4 þ Me3SiN3 f [Cl3Ga-N3-
(25) Cowley, A. H.; Lattman, M.; Wilburn, J.C. Inorg. Chem. 1981, 20,
2916–2919.
GaCl3]-þMe3SiCl) within 2 h, while upon the addition

Article
Inorganic Chemistry, Vol. 48, No. 15, 2009 7363
In the past two decades, neutral, cationic, and anionic
binary arsenic(III,V) azide species such as As(N3)3,26 As
(N3)5,27 [As(N3)4]þ,28 [As(N3)4]-,29 and [As(N3)6]- 28,29
have been reported and the crystal structures of As
(N3)328 and [As(N3)6]- 28,29 determined.30 In addition, the
Lewis-base-stabilized species As(N3)5 LB (LB=pyridine,
3
quinoline, NH3, N2H4, NH2CN) are known.31
The chemistry of azides covalently bound to organoar-
senic(III) fragments was opened by Revitt and Sowerby.32
However, uptonow, onlytwomoleculararsenic(III)azides
have been structurally characterized: the perfluoro-
alkyl species bis(trifluoromethyl)arsenic azide, (CF3)2-
AsN3, and trifluoromethylarsenic diazide, CF3As(N3)2,
which were studied by gas-phase electron diffrac-
tion.33,34 To the best of our knowledge, cyclic cationic
arsenic azides are not known yet.
X-Ray Structure Analysis. The solid-state structures of
the cyclo-diarsa-diazane derivatives 6, 10, and 11 are
shown in Figures 1-3 and those of the cyclo-diarsa-
diazenium salts 7 and 8 in Figures 4 and 5. Selected bond
lengths and angles are listed in Table 1; crystallographic
details are given in Tables 2 and 3. More details are found
in the Supporting Information. X-ray-quality crystals of
all considered species were selected in Kel-F-oil (Riedel
deHaen) or Fomblin YR-1800 (Alfa Aesar) at ambient
temperatures. All samples were cooled to either 173(2) K
(compounds 6, 7, 10, 11, and 12) or 100(2) K (compounds
8 and 13) during the measurement. It is worth mentioning
that compound 10 crystallizes isotypically to the analo-
gous phosphorous and antimony species.7
Figure 4. Molecular structure of 7 in the crystal (hydrogen atoms
omitted for clarity). As1-Cl2 distance in angstroms. Selected bond
˚
˚
lengths [A] and angles [deg]: As1-N1 1.799(2), As1-N2 1.828(2), As1-
As2 2.872(1), As1 Cl2 7.030(3), As2-N2 1.901(2), As2-N1 1.9270(2),
3 3 3
As2-Cl1 2.1820(8), Ga-Cl2 2.1642(9), Ga-Cl3 2.1716(8), Ga-Cl5
2.1785(9), Ga-Cl4 2.1797(8), N1-C1 1.417(3); N1-As1-N2 81.77(8),
N2-As2-N1 76.66(8), N2-As2-Cl1 101.22(6), N1-As2-Cl1 91.86(6),
As1-N2-As2 100.76(8), C1-N1-As1 132.7(2).
1,3-Diarsa-2,4-diazenium Salts. X-ray elucidation of 7
and crystals from the reaction sequences, as illustrated in
Scheme 5 (8, 12, and 13, see the Supporting Information),
revealed novel 1,3-diarsa-2,4-diazenium salts with no
Figure 5. ORTEP drawing of the molecular structure of 8 in the crystal.
Thermal ellipsoids with 50% probability at 173 K (hydrogen atoms
omitted for clarity). Selected bond lengths (A) and angles (deg): As1-
N1 1.799(3), As1-N2 1.812(2), As2-N1 1.901(3), As2-N2 1.915(3),
As2-N3 1.938(3), N3-N4 1.216(4), N4-N5 1.131(4), Ga2-N6 1.978(3),
Ga2-Cl4 2.140(1), N6-N7 1.252(4), N7-N8 1.126(4), N1-As1-N2
82.1(1), N1-As2-N2 76.8(1), N1-As2-N3 92.2(1), N2-As2-N3 101.0
(1), As1-N1-As2 100.7(1), As1-N2-As2 99.7(1), N5-N4-N3 171.5
(4), Ga1-N6-Ga2 125.4(1), N8-N7-N6 178.8(3).
significant cation-anion contacts (closest As Cl con-
3 3 3
˚
˚
˚
tact 7.030(3) A in 7, 6.266(2) A in 8) and a dicoordinated
As(III) atom as part of an As2N2 ring, kinetically pro-
tected in the pocket formed by the m-terphenyl groups
(Figure 5). All 1,3-diarsa-2,4-diazenium salts 7, 8, 12, and
13 crystallize isotypically in black blocks in the mono-
clinic space group P21/c with four units per cell. In the
case of the azide-containing salts 8, 12, and 13, the cell
of a second equivalent of Me3SiN3, only a partial Cl-/
N3 exchange occurs in the cation (reaction time
˚
parameters are almost identical (axes, deviation<0.2 A;
angles, deviation<0.4°), which is the reason for the observed
-
16 h), resulting in mixed crystals with about 3/4 Cl and
1/4 N3 attached to the As2N2 ring. Only when a large
excess of Me3SiN3 is used and the reaction time is
increased (2 days instead of 2 h) is a complete chloride-
azide exchange observed and pure 8 formed (Figure 5).
Azide formation in the anion and cation can also easily be
observed by means of IR spectroscopy (anion: νas(N3)=
2157, cation: 2102 cm-1).
::
(26) (a) Klapotke, T. M.; Geissler, P. J. Chem. Soc. Dalton Trans. 1995,
::
3365–3366. (b) Geissler, P.; Klapotke, T. M.; Kroth, H.-J. Spectrochim. Acta
Part A 1995, 51, 1075–1078. (c) Haiges, R.; Vij, A.; Boatz, J. A.; Schneider, S.;
Schroer, T.; Gerken, M.; Christe, K. O. Chem.-Eur. J. 2004, 10, 508–517.
(27) Haiges, R.; Boatz, J. A.; Vij, A.; Vij, V.; Gerken, M.; Schneider, S.;
Schroer, T.; Yousufuddin, M.; Christe, K. O. Angew. Chem., Int. Ed. 2004,
43, 6676–6680.
::
::
::
(28) Karaghiosoff, K.; Klapotke, T. M.; Krumm, B.; Noth, H.; Schutt,
Crystals of 1,3-diarsa-2,4-diazenium azide salts are also
black and moisture-sensitive but stable under an argon
atmosphere over a long period as a solid and in CH2Cl2 at
ambient temperature. The black appearance vanishes
rapidly when traces of H2O are present. All azide salts
are easily prepared in bulk and are infinitely stable when
stored in a sealed tube and kept cool at -20 °C in the dark.
Albeit salts such as compounds 8, 12, and 13 are covalen-
tly bound azides, they are neither heat- nor shock-sensitive.
Decomposition starts above 142 °C in 8 and 179 °C in 12
(cf. 7: decomposition T>199 °C).
T.; Suter, M. Inorg. Chem. 2002, 41, 170–179.
::
::
::
(29) Klapotke, T. M.; Noth, H.; Schutt, T.; Warchhold, M. Angew.
Chem., Int. Ed. 2000, 39, 2108–2109.
(30) For reviews, see: (a) Fraenk, W.; Klapotke, T. M. In Inorganic
Chemistry Highlights; Meyer, G., Naumann, D., Wesemann, L., Eds.; Wiley-
::
VCH: Weinheim< Germany, 2002. (b) Kornath, A. Angew. Chem., Int. Ed. 2001,
::
40, 3135–3136. (c) Klapotke, T. M. Chem. Ber. 1997, 130, 443–451.
::
::
(31) Klapotke, T. M.; Schutt, T. J. Fluorine Chem. 2001, 109, 151–162.
(32) Revitt, D. M.; Sowerby, D. B. J. Chem. Soc., Dalton Trans. 1972, 7,
847–850.
(33) Ang, H. G.; Kwik, W. L.; Lee, Y, W.; Liedle, S.; Oberhammer, H. J.
Mol. Struct. 1992, 268, 389–394.
(34) Ang, H. G.; Kwik, W. L.; Lee, Y, W.; Oberhammer, H. Inorg. Chem.
1994, 33, 4425–4426.

7364 Inorganic Chemistry, Vol. 48, No. 15, 2009
Schulz and Villinger
Scheme 5. Synthesis of Azido-cyclo-1,3-diarsa-2,4-diazenium salts (Ter=2,6-Mes2-C6H3, Mes=2,4,6-Me3C6H2, X=3/4Cl, 1/4N3)
˚
Table 3. Crystallographic Details of Compounds 7 and 8
1.825(2); and 12, 1.793(2)/1.825(2) þA; cf. 1.793(2)/
-
˚
1.786(2) A in trimeric [Dipp3N3As3Cl3] [GaCl4] , Dipp=
7
8
2,6-diisopropylphenyl).7 The short Asdicoord-N distances
between 1.79 and 1.83 A are substantially shorter than
˚
chem. formula
C
48H50As2Cl5GaN2
C48H50As2Cl6Ga2N8
1240.94
black
monoclinic
P21/c
16.018(3)
15.075(3)
22.445(3)
90.00
103.922(14)
90.00
fw [g mol-1
color
cryst syst
]
1051.71
black
monoclinic
P21/c
14.932(3)
18.372(4)
18.318(4)
90.00
112.23(3)
90.00
the sum of the covalent radii (dcov(N-As) = 1.91 and
dcov(NdAs)=1.71 A),35 which indicates partial double-
˚
bond character for these As-N bonds, while Astricoord.-N
bond lengths are in the range expected for As-N single
bonds. The Asdicoord.-N distances in 7 (Figure 4) are
slightly longer than those in 5 (Scheme 1, Table 1), which
can be attributed to a larger steric strain in a four-
membered As2N2 ring compared to the six-membered
core in 5, resulting in a stronger repulsion and an elonga-
tion of the atomic distances.
So far, little is known about arsenic compounds
containing an As-N double bond.14,24,36 The first fully
characterized compound with an As-N double bond
(1.714(7) and 1.745(7) A) was (2,4,6-tri-tert-butyl-
phenylamino)(2,4,6-tri-tert-butylimino)arsane prepared
space group
˚
a [A]
˚
b [A]
˚
c [A]
R [deg]
β [deg]
γ [deg]
3
˚
V [A ]
4651.6(16)
4
1.502
2.326
5260.9(16)
4
1.567
2.619
Z
F
calcd [g cm-3
]
μ [mm-1
]
˚
MoKR [A]
λ
T [K]
0.71073
173(2)
60730
13091
9166
0.0508
2136
0.0374
0.0800
1.026
535
0.71073
100(2)
44226
13010
9051
0.0497
2496
0.0381
0.0911
1.020
607
˚
measured reflns
independent reflns
reflns with I > 2σ(I)
Rint
by Lappert et al. in 1986.37
As shown on numerous occasions,26-33,38 covalently
bound azide groups such as in 8 display a trans-bent
configuration (regarding the As atom, As-NNN) with
a N-N-N bond angle of 171.5(4)°, while the bridging
F(000)
R1 (R[F2 > 2σ(F2)])
wR2 (F2)
GoF
params
(35) Holleman, W. Lehrbuch der Anorganischen Chemie, 102. Aufl.; Walter
formation of mixed crystals in 13 (with 3/4 Cl and 1/4 N3
attached to the As2N2 ring, see the Supporting Infor-
mation). For all 1,3-diarsa-2,4-diazenium salts, several
relatively close contacts between the dicoordinated As
center and both terphenyl ligands can be detected. These
de Gruyter: Berlin, 2007; Anhang IV.
::
(36) For example: (a) Kruppa, Ch.; Nieger, M.; Ross, B.; Vath, I. Eur. J.
Inorg. Chem. 2000, 165–168. (b) Miqueu, K.; Sotiropoulos, J.-M.; Pfister-
Guillouzo, G.; Romanenko, V. D. New J. Chem. 2001, 25, 930–938. (c) Ahlmann,
J. T.; Kunzel, A.; Roesky, H. W.; Noltemeyer, M.; Markovskii, L.; Schmidt, H. G.
Inorg. Chem. 1996, 35, 6644–6645.
˚
short contacts amount to 2.76-3.6 A and are within the
(37) Hitchcock, P. B.; Lappert, M. F.; Rai, A. K.; Williams, H. D.
˚
sum of the van der Waals radii (dvdW: As C=3.7 A),
indicating stabilizing Asdicoordinated Cterphenyl interactions.
J. Chem. Soc., Chem. Commun. 1986, 1633–34.
3 3 3
::
(38) For example: (a) Muller, U. Chem. Ber. 1977, 110, 788–791.
3 3 3
(b) Roesky, H. W.; Noltemeyer, M.; Sheldrick, G. M. Z. Naturforsch., Teil B
1986, 41, 803–807. (c) Schomburg, D.; Wermuth, U.; Schmutzler, R. Chem. Ber.
1987, 120, 1713–1718. (d) Cowley, A. H.; Gabbai, F.; Schluter, R.; Atwood, D. J.
Am. Chem. Soc. 1992, 114, 3142–3144. (e) Englert, U.; Paetzold, P.; Eversheim,
E. Z. Kristallogr. 1993, 208, 307–309. (f) Cowley, A. H.; Gabbai, F. P.; Bertrand,
As depicted in Figures 4 and 5, the As2N2 rings are
almost planar (deviation from planarity: <N1-As1-
N2-As2=1.4° in 7, -6.2° in 8, and 5.0° in 12), but sli-
ghtly distorted with two longer Astricoord.-N bond
lengths (7: 1.927(2)/1.901(2), 8: 1.915(3)/1.901(3), and
G.; Carrano, C. J.; Bond, M. R. J. Organomet. Chem. 1995, 493, 95–99.
::
(g) Larbig, M.; Nieger, M.; v. d. Gonna, V.; Ruban, A. V.; Niecke, E. Angew.
˚
12: 1.911(2)/1.914(2) A) and two considerably shorter
Asdicoord.-N distances (7, 1.799(2)/1.827(2); 8, 1.812(3)/
Chem., Int. Ed. Engl 1995, 34, 460–462. (h) Schranz, I.; Grocholl, L. P.; Stahl, L.;
Staples, R. J.; Johnson, A. Inorg. Chem. 2000, 39, 3037–3041.

Article
Inorganic Chemistry, Vol. 48, No. 15, 2009 7365
azide group attached to both GaCl3 moieties is
almost linear (<N-N-N=178.8(2)° in 12 and 178.8(2)°
in 8).
Ga-Cl distance is found in the GaCl4- anion (2.2581(7)
˚
compared to 2.14-2.15 A for the other three Ga-Cl
distances). Only increased steric strain as found in 7 (or as
in the azides 8, 12, and 13) leads to cation-anion separa-
tion (closest contact 7.030(3) A in 7 as well as in all azide
General Structural Trends and Crystal Color. In all
considered cyclo-diarsa-diazane derivatives, 6, 10, and
11, and the cyclo-diarsa-diazenium salts, 7, 8, 12, and 13,
as expected, both nitrogen atoms of the As2N2 ring are
almost trigonal-planar and the tri-coordinated arsenic
atom trigonal-pyramidal. The sum of the bond angles at
the tri-coordinated arsenic atom ranges between 269 and
277°. Always, an anti configuration is found for the
exocyclic substituents of the arsenic centers. The sum of
the bond angles at the nitrogen atoms N is always very
close to 360°, indicating a planar environment and, hence,
a formal sp2 hybridization. Thus, the molecular struc-
tures of 6, 7, 10, and 11 have a square N2As2 core and, in
the cases of 6 ([Ter-NAs-Cl]2) and 10 ([Mes*-NAs-
OTf]2), with crystallographically indistinguishable As-N
distances that are in the typical range for derivatives of
cyclo-1,3-diarsa-2,4-diazanes.24 However, in contrast to
the (pale) yellow crystals of 10, the crystals of 11 are deep
orange. Although in both compounds (10 and 11) the
As-OTf bonds are highly polar (NBO analysis),39-42
neither 10 nor 11 can be considered as “true” salts with
separated anions and cations in the solid state (see As-X
distances in Table 1, X=Cl and O). However, the consi-
˚
salts) with no elongated Ga-Cl bond; all distances are
between 2.16 and 2.18 A) in the solid state, with no
˚
significant cation-anion interactions and a dicoordi-
nated As(III) atom as part of an As2N2 ring, embedded
in a pocket formed by the m-terphenyl groups (Figures 4
and 5). It is interesting to note that, in the case of cation-
anion separation, the color of the crystals dramatically
changes from yellow to a black appearance (in CH2Cl2
solution, red-violet, see UV-vis data in Table 1). Actu-
ally, the color seems to be a very good “macroscopic”
property to predict if cation-anion separation occurs
in solution as well as in the solid state. For instance,
the yellow compound 11 dissociates (ion formation) in
CH2Cl2, exhibiting a red-violet color, but upon crystal-
lization, the color changes back to yellow, which indicates
a molecular species, as shown by X-ray analysis. On the
contrary, compound 7 also forms ions in CH2Cl2 but
crystallizes in black crystals, which were shown to be
composed of separated ions.
Another interesting structural feature with respect to
the question of dicoordination versus tricoordination is
the As-N distance within the As2N2 core. As depicted in
Figures 3 and 5, the As2N2 rings of 7 and 11 are also
almost planar (deviation from planarity: <N1-As1-
N2-As2=1.3° in 7, 7.4° in 11) but distorted with two
longer Astri-coord-N bond lengths (7, 1.928(2)/1.901(2);
derably longer As-O distance in 11 as compared to that
35
˚
˚
in 10 (2.159(2) vs. 1.964(1) A; cf. dcov(As-O)=1.95 A)
indicates already the transition to separated ion pairs.
Interestingly, 11 displays a red-violet color (578 nm) in a
polar solvent such as CH2Cl2 and a yellow color (433 nm)
in a nonpolar solvent such as toluene, while 10 is yellow
in both solvents (427 nm), as studied by means of UV-
vis experiments (Table 1). For comparison, the “true”
salt 7 dissolves only in the polar solvent CH2Cl2 with
a red-violet color (554 nm). In the case of 11, it can
be assumed that the red-violet color indicates dissocia-
tion in the polar solvent, while the yellow color in non-
polar solvents can be attributed to dissolved molecules of
11 without any significant dissociation of the triflate
group.
˚
11, 1.886(2)/1.886(2) A) and two considerably shorter
Asdi-coord-N distances (7, 1.799(2)/1.827(2); 11, 1.819(2)/
˚
˚
1.830(2) A; cf. 1.793(2)/1.786(2) A in 5), again indicating
partial double-bond character for these As-N bonds (see
above). The difference between both As-N bond lengths
increases along 10<11<7, in accord with an increasing
closest cation-anion contact (Table 1).
Conclusions
The main difference between 10 and 11 is the steric
demand of the bulky group (Mes* vs m-terphenyl).
Obviously, the m-terphenyl group provides only enough
space for one OTf- anion with a long As-O bond length,
so that even with a large excess of AgOTf only mono-
substitution occurs, in contrast to the reaction of 9
with an excess of AgOTf, resulting in the doubly sub-
stituted species 10 ([Mes*-NAs-OTf]2). In trimeric yel-
low [Dipp3N3As3Cl3]þ[GaCl4]- (5),7 there is one strong
In conclusion, we present here the first examples of binary
cyclic As(III)/N four-membered heterocyclic cations, with a
di- and tricoordinated As atom and a delocalized π bond
along the NAs(þ)N unit. The addition of an excess of
Me3SiN3 yields the first fully characterized cyclic cationic
arsenic azide. The Cl-/N3 exchange is triggered by the
-
action of the Lewis acid GaCl3. The cation-anion contacts
are discussed on the basis of structural and UV-vis data. The
larger the distance between thecyclo-diarsa-diazenium cation
and the anion, the more red-shifted (and deeper) the color in
the solid state, while in solution a deep red-violet color is
observed. When no significant contacts are detected, the
cyclo-diarsa-diazenium salt displays a black appearance.
Strong cation-anion interactions (short distances) lead to
pale yellow crystals and yellow solutions in nonpolar and
polar solvents.
˚
As Cl contact with a distance of 2.708(1) A which still
3 3 3
seems to be too short to be considered as separated ions,
as illustrated by the afore-mentioned notation. As a con-
sequence of the strong interaction, a slightly elongated
(39) Glendening, E. D; Reed, A. E.; Carpenter, J. E.; Weinhold, F. NBO,
version 3.1; Theoretical Chemistry Institute, University of Wisconsin: Madison,
WI.
(40) Carpenter, J. E.; Weinhold, F. THEOCHEM 1988, 169, 41.
(41) Weinhold, F.; Carpenter, J. E. The Structure of Small Molecules and
Ions; Plenum Press: New York, 1988; p 227.
(42) Weinhold, F.; Landis, C. Valency and Bonding. A Natural Bond
Orbital Donor-Acceptor Perspective; Cambridge University Press: New York,
2005 and references therein.
Experimental Section
General Information. All manipulations were carried out
under oxygen- and moisture-free conditions under argon using
standard Schlenk or drybox techniques.

7366 Inorganic Chemistry, Vol. 48, No. 15, 2009
Schulz and Villinger
Dichloromethane was purified according to a literature pro-
cedure,43 dried over P4O10, and freshly distilled prior to use.
Toluene was dried over Na/K/benzophenone and freshly dis-
tilled prior to use. THF and 1,8-diazabicyclo[5.4.0]undec-7-en
(98%, Sigma-Aldrich) were dried over Na/benzophenone
and freshly distilled prior to use. n-Hexane was dried over Na/
benzophenone/tetraglyme and freshly distilled prior to use.
Trimethylsilylazide (95% Fluka) was distilled prior to use. N-[2,4-
bis-(2,4,6-trimethylphenyl)phenyl]amino(dichloro)arsane was
prepared according to a modified literature procedure.14 Tri-
methylsilylchloride (99%, Merck) was freshly distilled prior to
use. 2,4,6-Tri-tert-butylaniline (99%, Sigma-Aldrich), silver tri-
flate (99%, Fluka), and GaCl3 (99.999%, Sigma-Aldrich) were
used as received.
The occupancy of each part was refined freely (0.750(4) Cl/
0.250(4) N3).
Synthesis of 1,3-Dichloro-2,4-bis[2,4-bis-(2,4,6-trimethylphe-
nyl)phenyl]-cyclo-1,3-diarsa-2,4-diazane (6). To a stirred solu-
tion of N-[2,4-bis-(2,4,6-trimethylphenyl)phenyl]amino(dichloro)-
arsane (4.743 g, 10.0 mmol) in tetrahydrofurane (50 mL) was
added a solution of DBU (1.675 g, 11.0 mmol) in tetrahydrofur-
ane (15 mL) dropwise at -80 °C over a period of 15 min. The
resulting yellow suspension was warmed to ambient tempera-
tures over a period of 4 h. The solvent was removed in vacuo,
and the yellowish residue was extracted with benzene (40 mL)
and filtered (F4), resulting in a champagne-colored solution.
Removal of the solvent in vacuo resulted in a yellowish residue,
which was recrystallized from dichloromethane (25 mL) at -25 °C
over a period of 16 h. Removal of the supernatant by syringe
yields 2.285 g (5.22 mmol, 52%) of 6 as a yellowish crystalline
solid. Mp: 259 °C (dec.) Anal. Calcd % (found): C, 65.84 (65.79);
H, 5.76 (5.73); N, 3.20 (3.20). 1H NMR (25°C, CD2Cl2, 250.13
MHz): δ 1.92 (s, 6H, CH3), 2.00 (s, 6H, CH3), 2.44 (s, 6H, CH3),
6.65 (m, 2H, m-CH-Ph), 6.77 (s, 2H, m-CH-Mes), 6.83 (s, 2H,
m-CH-Mes), 6.91 (m, 1H, p-CH-Ph). 13C{1H} NMR (25°C,
CD2Cl2, 75.5 MHz): δ 20.8 (s, CH3), 21.9 (s, CH3), 22.0 (s, CH3),
122.5 (s, aryl-CH), 129.3 (s, aryl-CH), 129.7 (s, aryl-CH), 131.4
(s, aryl-CH), 131.5, 135.3, 138.2, 138.9, 138.9, 139.7. IR (ATR,
32 scans): 3063 (w), 3034 (w), 2975 (w), 2915 (m), 2853 (w), 2732
(w), 1610 (w), 1574 (w), 1481 (w), 1449 (m), 1402 (s), 1377 (m),
1225 (s), 1187 (m), 1097 (w), 1080 (m), 1032 (m), 1003 (m), 952
(w), 874 (s), 846 (s), 820 (s), 791 (s), 753 (s), 744 (s), 672 (m),
644 (m), 588 (m), 568 (m), 559 (m), 546 (m), 535 (m). Raman
(100 mW, 25 °C, 161 scans, cm-1): 3039 (5), 2982 (3), 2919 (10),
2859 (3), 2734 (2), 1611 (3), 1577 (3), 1477 (1), 1412 (3), 1377 (2),
1302 (3), 1267 (3), 1189 (1), 1160 (1), 1088 (1), 1031 (1), 1005 (1),
947 (1), 740 (1), 689 (1), 565 (2), 518 (1), 460 (1), 424 (2), 380 (1),
314 (3), 274 (1), 233 (1), 177 (2), 145 (2). MS (CI, m/z): 330
[Ter*NH3]þ, 708 [M - Cl - Mes - CH3 þ 2H], 804 [M - 2Cl]þ,
839 [M - Cl]þ, 876 [M þ H]þ.
NMR. 13C{1H}, 13C DEPT, and 1H NMR spectra were
obtained on a Bruker AVANCE 250 or 300 spectrometer and
were referenced internally to the deuterated solvent (13C,
CD2Cl2: δreference=54 ppm; toluene-d8: δreference=137.5 ppm)
or to protic impurities in the deuterated solvent (1H, CDHCl2:
δreference=5.31 ppm; C6D4HCD3: δreference=7.09 ppm). NMR
solvents were dried as depicted above for the undeuterated
solvents.
IR. A Nicolet 6700 FT-IR spectrometer with a Smart En-
durance ATR or a Nicolet 380 FT-IR with Smart Orbit ATR
device was used.
Raman. A Bruker VERTEX 70 FT-IR with a RAM II FT-
Raman module, equipped with a Nd:YAG laser (1064 nm), was
used.
MS. A Finnigan MAT 95-XP from Thermo Electron was
used.
CHN analyses. An Analysator Flash EA 1112 from Thermo
Quest was used. Pb3O4 was added.
Melting Points. Melting points are uncorrected (EZ-Melt,
Stanford Research Systems). The heating rate was 20 °C/min
(clearing points are reported).
DSC. A DSC 823e from Mettler-Toledo was used, with a
heating rate of 5 °C/min.
Synthesis of 1-Chloro-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)
phenyl]-cyclo-1,3-diarsa-2,4-diazenium Tetrachloridogallate (7).
To a stirred solution of 1,3-dichloro-2,4-bis[2,4-bis-(2,4,6-
trimethylphenyl)phenyl]-cyclo-1,3-diarsa-2,4-diazane (0.875g,
1.0 mmol) in toluene (20 mL) was added a solution of GaCl3
(0.194 g, 1.1 mmol) in toluene (5 mL) dropwise at -25 °C over a
period of 10 min. The resulting greenish-black suspension was
warmed to ambient temperatures over a period of 1 h. The
suspension was concentrated to a volume of 0.5 mL in vacuo
and was filtered (F4). Drying of the black residue in vacuo
yielded 1.003 g (0.95 mmol, 95%) of 2 as a black crystalline solid.
Mp: 199 °C (dec.) Anal. Calcd % (found): C, 54.81 (54.62);
H, 4.79 (4.71); N, 2.66 (2.47). 1H NMR (25°C, CD2Cl2, 300.13
MHz): δ 1.91 (s, 6H, CH3), 1.93 (s, 6H, CH3), 2.42 (s, 6H, CH3),
7.05 (s, 4H, m-CH-Mes), 7.08 (m, 2H, m-CH-Ph), 7.30 (dd, 1H,
p-CH-Ph, J(1H-1H) = 7.0 Hz, 8.0 Hz). 13C{1H} NMR (25°C,
CD2Cl2, 75.5 MHz): δ 20.9 (s, CH3), 21.6 (s, o-CH3-Mes),
21.9 (s, p-CH3-Mes), 127.6 (s, aryl-CH), 131.0 (s, aryl-CH),
131.3, 132.1 (s, aryl-CH), 132.3 (s, aryl-CH), 134.0, 138.1,
138.5, 138.7, 142.3. IR (ATR, 32 scans): 2973 (w), 2946 (w),
2917 (m), 2854 (w), 2735 (w), 1606 (m), 1465 (w), 1472 (m),
1454 (m), 1444 (m), 1404 (m), 1378 (m), 1323 (w), 1295 (w), 1249
(w), 1215 (s), 1188 (w), 1162 (w), 1125 (w), 1105 (w), 1073 (m),
1028 (m), 1004 (m), 939 (w), 910 (w), 885 (s), 859 (s), 850 (s),
816 (s), 808 (s), 799 (s), 792 (s), 759 (s), 745 (s), 721 (s), 685 (m),
663 (m), 648 (m), 581 (m), 564 (m), 546 (m), 532 (m). Raman
(10 mW, 25 °C, 201 scans, cm-1): 3053 (1), 2919 (2), 2851 (1),
1608 (1), 1582 (3), 1479 (1), 1412 (6), 1305 (2), 1255 (10), 1082 (2),
1007 (1), 944 (1), 885 (1), 820 (1), 750 (1), 727 (1), 692 (1),
661 (1), 561 (1), 514 (1), 479 (1), 423 (1), 351 (2), 314 (1), 274 (1),
237 (1). MS (FABþ, Cs, 20 keV, p-NBA matrix, M =
Ter2N2As2Clþ): 402 [Ter - NAs]þ, 805 [M - Cl þ H]þ, 839
[M]þ, 874 [M þ Cl]þ.
UV-Vis. A Lambda 2 UV/VIS Spectrometer from Perkin
Elmer was used.
X-Ray Structure Determination. X-ray-quality crystals of 6,
6b, 6c, 7, 10a, 10b, and 11 were selected in Kel-F-oil (Riedel
deHaen). Crystals of 8, 12, and 13 were selected in Fomblin YR-
1800 (Alfa Aesar) at ambient temperatures. All samples were
cooled to 173(2) K (6, 6b, 6c, 7, 10a, 10b, 11, and 12) or 100 (2) K
(8 and 13) during measurement. The data were collected on a
Bruker-Nonius Apex X8 CCD diffractometer (6, 6b, 6c, 7, 10a,
10b, 11, and 12) or Bruker Kappa Apex II CCD diffractometer
(8 and 13) using graphite monochromated Mo Ka radiation
(λ=0.71073). The structures were solved by direct methods
(SHELXS-97)44 and refined by full-matrix least squares proce-
dures (SHELXL-97).45 Semiempirical absorption corrections
were applied (SADABS).46 All non-hydrogen atoms were re-
fined anisotropically; hydrogen atoms were included in the
refinement at calculated positions using a riding model.
The position of one of the two tetrahydrofurane molecules in
6c was found to be partially occupied. The occupancy was
refined freely (0.896(5)). The other tetrahydrofurane mole-
cule in 6c was found to be disordered and was split in two parts.
The occupancy of each part was refined freely (0.604(11)/
0.396(11)). The position of the Cl/azide group in 13 was
found to be partially occupied and was split in two parts.
(43) Fischer, C. B.; Xu, S.; Zipse, H. Chem.;Eur. J. 2006, 12, 5779–5784.
::
::
(44) Sheldrick, G. M.: SHELXS-97; University of Gottingen: Gottingen,
Germany, 1997.
::
::
(45) Sheldrick, G. M.: SHELXL-97; University of Gottingen: Gottingen,
Germany, 1997.
::
(46) Sheldrick, G. M.: SADABS, version 2; University of Gottingen:
::
Gottingen, Germany, 2004.

Article
Synthesis of 1-Azido-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)
Inorganic Chemistry, Vol. 48, No. 15, 2009 7367
resulting orange suspension was warmed to ambient tempera-
tures over a period of 3 h and was then filtered (F4), resulting in
an orange solution. Removal of the solvent in vacuo yielded
0.963 g (0.97 mmol, 97%) of 11 as an orange crystalline solid.
Mp: 253 °C (dec.) Anal. Calcd % (found): C, 59.49 (59.20); H,
phenyl]-cyclo-1,3-diarsa-2,4-diazenium μ-Azido-bis[hexachlori-
dogallium(III)] (8). To a stirred greenish-black solution of
1-chloro-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)phenyl]-cyclo-1,3-
diarsa-2,4-diazenium tetrachloridogallate (2; 1.052g, 1.0 mmol)
in CH2Cl2 (20 mL) was added a solution of (CH)3Si-N3 (1.152 g,
10 mmol) in CH2Cl2 (5 mL) dropwise at -10 °C over a period of
5 min. GaCl3 (0.194 g, 1.1 mmol) in CH2Cl2 (5 mL) was then
added dropwise at -10 °C over a period of 10 min. The resulting
greenish-black solution was warmed to ambient temperatures
and was stirred for two days. The solvent was removed in vacuo,
and the black residue was washed with n-hexane (10 mL) and
dried in vacuo. The residue was dissolved in CH2Cl2 (30 mL) and
filtered (F4), resulting in an brownish-black solution. Slow
removal of the solvent in vacuo yielded 1.209 g (0.97 mmol,
97%) of 3 as a black crystalline solid. Mp: 142 °C (dec.). Anal.
Calcd % (found): C, 46.46 (45.67); H, 4.06 (4.49); N, 9.03 (8.51).
1H NMR (25°C, CD2Cl2, 300.13 MHz): δ 1.91 (s, 12H, CH3),
2.44 (s, 6H, CH3), 7.04 (m, 2H, m-CH-Ph), 7.07 (s, 4H, m-CH-
Mes), 7.28 (m, 1H, p-CH-Ph). 13C{1H} NMR (25°C, CD2Cl2,
75.5 MHz): δ 20.9 (s, CH3), 21.9 (s, CH3), 127.6 (s, aryl-CH),
131.1 (s, aryl-CH), 131.4, 132.0 (s, aryl-CH), 134.0, 138.3, 138.5,
142.3. IR (ATR, 32 scans): 3052 (w), 2974 (w), 2943 (w), 2919
(m), 2854 (w), 2733 (w), 2155 (s), 2102 (s), 1635 (w), 1606 (m),
1562 (w), 1476 (m), 1455 (m), 1442 (m), 1405 (m), 1378 (m), 1297
(w), 1267 (w), 1218 (s), 1165 (m), 1105 (w), 1074 (m), 1021 (m),
940 (w), 885 (s), 860 (s), 825 (s), 813 (m), 799 (s), 768 (s), 748 (m),
728 (m), 686 (m), 667 (s). MS (FABþ, Cs, 20 keV, p-NBA
matrix, M = Ter2N2As2Clþ): 329 [Ter - NH2]þ, 330 [Ter -
NH3]þ, 402 [Ter - NAs]þ, 805 [M - N3 þH]þ, 839 [M þ Cl -
N3]þ, 956 [MþNBA - N3 - H]þ, 991 [M þ 2NBA þ Cl - N3 þ
H]þ, 1109 [M þ2NBA - N3 þH]þ.
1
5.09 (5.12); N, 2.83 (3.17). H NMR (25°C, toluene-d8, 250.13
MHz): δ 2.08 (s, 6H, CH3), 2.19 (s, 6H, CH3), 2.24 (s, 6H, CH3),
6.52 (d, 2H, m-CH-Ph), 6.63 (s, 2H, m-CH-Mes), 6.72 (dd, 1H,
p-CH-Ph, J(1H-1H) = 6.9 Hz, 7.9 Hz), 6.78 (s, 2H, m-CH-
Mes). 13C{1H} NMR (25°C, toluene-d8, 62.9 MHz): δ 20.6 (s,
CH3), 21.6 (s, CH3), 21.8 (s, CH3), 120.3 (q, CF3, 1J(13C-19F)=
320 Hz), 123.8 (s, aryl-CH), 129.6 (s, aryl-CH), 130.7 (s, aryl-
CH), 131.4 (s, aryl-CH), 131.0, 134.6, 136.7, 138.6, 139.3. 19F
{1H} NMR (25°C, toluene-d8, 235.5 MHz): δ -77.0 (s, CF3). IR
(ATR, 32 scans): 2974 (w), 2950 (w), 2919 (w), 2859 (w), 1612
(w), 1515 (w), 1446 (w), 1405 (w), 1381 (w), 1337 (w), 1263 (s),
1224 (s), 1174 (s), 1080 (w), 1024 (s), 951 (w), 876 (w), 850 (m),
806 (m), 762 (m), 745 (m), 672 (w), 632 (s), 577 (m), 549 (w).
Raman (150 mW, 25 °C, 204 scans, cm-1): 3051 (3), 3013 (3),
2923 (7), 2738 (3), 1611 (5), 1582 (7), 1481 (3), 1419 (7), 1382 (3),
1306 (6), 1262 (10), 1194 (2), 1163 (2). 1034 (2), 1006 (4), 950 (2),
851 (1), 824 (1), 762 (2), 741 (3), 692 (2), 674 (1), 650 (1), 574 (4),
561 (3), 524 (2), 514 (2), 482 (2), 463 (3), 427 (2), 353 (3), 336 (3),
312 (3), 283 (2), 268 (2), 254 (2), 234 (3), 172 (5), 141 (5), 126 (5).
MS (FABþ, Cs, 20 keV, p-NBA matrix, M = Ter2N2As2Cl-
(SO3CF3)): 330 [Ter - NH3]þ, 402 [Ter - NAs]þ, 805 [M - Cl -
SO3CF3 þ H]þ, 839 [M-SO3CF3]þ, 956 [M-Cl þ H]þ.
Synthesis of 1-Chloro-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)
phenyl]-cyclo-1,3-diarsa-2,4-diazenium μ-Azido-bis[hexachlori-
dogallium(III)] (12). To a stirred greenish-black solution of 1-
chloro-2,4-bis[2,4-bis-(2,4,6-trimethylphenyl)phenyl]-cyclo-1,3-dia-
rsa-2,4-diazenium tetrachloridogallate (7; 1.052g, 1.0 mmol) in
CH2Cl2 (30 mL) was added a solution of (CH)3Si-N3 (0.127 g,
1.1 mmol) in CH2Cl2 (5 mL) dropwise at -50 °C over a period of
5 min. GaCl3 (0.194 g, 1.1 mmol) in CH2Cl2 (5 mL) was then
added dropwise at -50 °C over a period of 10 min. The resulting
greenish-black solution was warmed to ambient temperatures
over a period of 2 h. The solvent was removed in vacuo, and the
black residue was washed with n-hexane (5 mL) and dried in
vacuo. The residue was dissolved in CH2Cl2 (30 mL) and filtered
(F4), resulting in a greenish-black solution. Slow removal of the
solvent in vacuo yielded 1.213 g (0.98 mmol, 98%) of 12 as
a black crystalline solid. Mp: 179 °C (dec.). Anal. Calcd %
(found): C, 46.70 (46.49); H, 4.08 (4.01); N, 5.67 (5.24). 1H NMR
(25°C, CD2Cl2, 250.13 MHz): δ 1.91 (s, 6H, CH3), 1.92 (s, 6H,
CH3), 2.42 (s, 6H, CH3), 7.04 (s, 4H, m-CH-Mes), 7.08 (m, 2H,
m-CH-Ph), 7.30 (m, 1H, p-CH-Ph). 13C{1H} NMR (25°C,
CD2Cl2, 62.9 MHz): δ 20.9 (s, CH3), 21.9 (s, CH3), 21.9
(s, CH3-Mes), 127.6 (s, aryl-CH), 130.6 (s, aryl-CH), 131.1,
132.1 (s, aryl-CH), 132.3 (s, aryl-CH), 134.0, 136.2, 138.1,
138.5, 138.8, 142.3. IR (ATR, 32 scans): 3053 (w), 2975 (w),
2943 (w), 2918 (m), 2854 (w), 2733 (w), 2157 (s), 1607 (m), 1561
(w), 1474 (m), 1454 (m), 1378 (m), 1323 (w), 1298 (w), 1267 (w),
1255 (w), 1213 (s), 1166 (w), 1125 (w), 1105 (w), 1092 (w),
1074 (m), 1062 (w), 1030 (m), 1012 (w), 1004 (w), 941 (w),
884 (s), 860 (s), 821 (s), 811 (m), 799 (s), 766 (s), 749 (m), 722 (s),
685 (m), 661 (m). MS (FABþ, Cs, 20 keV, p-NBA matrix,
M=Ter2N2As2Clþ): 329 [Ter - NH2]þ, 402 [Ter - NAs]þ, 805
[M-Cl þ H]þ, 839 [M]þ, 956 [MþNBA - Cl - H]þ, 991 [Mþ
2NBA-Cl þ H]þ, 1109 [M þ2NBA -Cl þ H]þ.
Synthesis of 1,3-Bis-(trifluoromethylsulfonato)-2,4-bis-(2,4,6-
tri-tert-butylphenyl)-cyclo-1,3-diarsa-2,4-diazane (10). To a stir-
red solution of Ag(SO3CF3) (0.549 g, 2.1 mmol) in toluene
(10 mL) was added a solution of 1,3-dichloro-2,4-bis-(2,4,6-tri-
tert-butylphenyl)-cyclo-1,3-diarsa-2,4-diazane (9; 0.740g, 1.0 mmol)
in toluene (10 mL) dropwise at -60 °C over a period of 15 min under
exclusion of light. The resulting orange suspension is warmed to
ambient temperatures over a period of 1 h and was then filtered (F4),
resulting in an orange solution. Removal of the solvent in vacuo
yielded 0.952 g (0.98 mmol, 98%) of 10 as a yellow crystalline solid.
Mp: 174 °C (dec.) Anal. Calcd % (found): C, 47.21 (46.78); H, 6.05
(6.12); N, 2.90 (2.72). 1H NMR(25°C, CD2Cl2, 250.13MHz):δ1.32
(s, 9H, p-C(CH3)3), 1.56 (s, 18H, o-C(CH3)3), 7.52 (s, 2H, aryl-CH).
13C{1H} NMR (25°C, CD2Cl2, 62.9 MHz): δ 31.6 (s, p-C(CH3)3),
34.3 (s, o-C(CH3)3), 35.6 (s, p-C(CH3)3), 37.4 (s, o-C(CH3)3), 120.2
(q, CF3, 1J(13C-19F) = 319 Hz), 124.4 (s, aryl-CH), 132.3, 148.4,
151.7. 19F{1H} NMR (25°C, CD2Cl2, 235.5 MHz): δ-78.3 (s, CF3).
IR (ATR, 32 scans): 3024 (w), 2958 (m), 2872 (w), 1464 (w), 1423 (w),
1397(w), 1377 (w), 1362 (m), 1292 (m), 1266 (m), 1227 (s), 1205 (s),
1153 (s), 1107 (m), 1020 (s), 926 (m), 879 (m), 856 (m), 820 (m), 783
(m), 757 (m), 734 (m), 658 (m), 633 (s), 593 (m), 574 (m). Raman
(75 mW, 25 °C, 200 scans, cm-1): 3058 (2), 2968 (9), 2916 (10), 2790
(2), 2753 (2), 2720 (2), 1596 (4), 1520 (2), 1448 (3), 1414 (2), 1372 (2),
1290 (2), 1240 (4), 1213 (3), 1145 (3), 1113 (2), 1030 (3), 990 (1),
919 (2), 887 (2), 822 (2), 789 (1), 762 (2), 705 (1), 629 (1), 705 (1),
629 (1), 594 (1), 565 (2), 526 (1), 436 (1), 358 (2), 328 (2), 247 (2),
212 (2), 141.5 (2). MS (EI, m/z, >10 %): 43 (22) [C3H7]þ, 57 (43)
[C4H9]þ, 69 (22) [CF3]þ, 83 (17), 97 (13), 246 (100) [Mes*H]þ, 261
(45) [Mes*NH2]þ, 329 (12) [Mes*NH þ CF3]þ. MS (FABþ, Cs, 20
keV, p-NBA matrix): 262 [Mes*-NH3]þ, 334 [Mes* - NAs]þ.
Synthesis of 1-Chloro-3-trifluoromethylsulfonato-2,4-bis[2,4-
bis-(2,4,6-trimethylphenyl)phenyl]-cyclo-1,3-diarsa-2,4-diazane (11).
To a stirred solution of 1,3-dichloro-2,4-bis[2,4-bis-(2,4,6-tri-
methylphenyl)phenyl]-cyclo-1,3-diarsa-2,4-diazane (6; 0.875g,
1.0 mmol) in toluene (20 mL) was added a solution of Ag-
(SO3CF3) (0.549 g, 1.1 mmol) in toluene (20 mL) dropwise at -
70 °C over a period of 10 min under exclusion of light. The
Acknowledgment. Financial support by the Deutsche
Forschungsgemeinschaft (SCHU 1170/4-1) is gratefully ac-
knowledged.
Supporting Information Available: Crystallographic data of
6a-c, 7, 8, 9, 10a-b, 11, 12, and 13 (CIF); experimental details
(PDF). This material is available free of charge via the Internet
at http://pubs.acs.org.