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Cleavage of S4N4 to S2N2 at Room Temperature Formation and Structure of (AlCl3)2S2N2.

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H
S-N,
H
/N-S
N--s/
I
M\S-N I
1, M
= C o , Ni, Pd,
K
[
[4] Monoclinic, P2,/n, a = 1035.9(3), b = 1630.2(5), c = 1450.2(4) pm,
@=90.55(4)", Z = 2 . 880 reflections with I (hkf)>2.5u((1) Syntex R3, 8-28
scan, MoKa radiation. R,=0.054 (phenyl groups, including the H atoms,
were refined as rigid groups, C, H, and N of the cyanide groups isotropically, and the other atoms anisotropically).
Pt
N-S
I
H
NC'
Nc\Ni/N-T]
'S-N
I
Cleavage of S,N, to S2N2at Room Temperature:
Formation and Structure of (AIC13)2S2N2**
Kz
I
I
S-N
2
L
3
J
produced'31. The potassium salt of the novel dinuclear
complex 3, which was characterized by elemental analysis
and IR spectroscopy, is insoluble in nonpolar but soluble
in polar organic solvents: aqueous solutions decompose
slowly.
An X-ray crystal structure analysis was carried out on
the tetraphenylarsonium salt [Ph4As12[Ni2(N2S2)2(CN)21
3a['] which crystallizes more readilyL4].
By Urf TheWalt* and Maria Burger
The smallest cyclic (SN), compound, which is readily
accessible by thermolysis of S4N4vapor over a catalyst, is
S2N2,whose solid-state polymerization leads to metal-like
(SN)x''J. It is well known that reaction of S2N2with Lewis
or BC13[2'1 affords isolable S2N2acids such as SbC1s[2a.b1
adducts. Surprisingly, we have now been able to obtain an
S2N2/AIC13adduct by reaction of S4N4with AIC13 at room
temperature.
When a mixture of solid A1Cl3 and S4N4is covered by a
layer of CH2Clz and allowed to stand for a few days,
(AIC13)2S2N21 is formed, along with other products, as
colorless crystalline needlesI3]. On contact with water or
even on exposure to air the compound 1 decomposes with
separation of black insoluble products. On reaction of
A n 3 and S4N4 under conditions other than those given
here, Chan and Olsen[41obtained the S4N4-complex
(AlC13)S4N4as sole product.
The result of an X-ray structure analysis carried out for
the unequivocal characterization of 1 is presented in Figure lIs1.As in (SbC1s)2S2N2L2b1
and in free S2N2[6a1,
the central S2N2-ringin 1 is completely planar. (At its center there
is a crystallographic center of symmetry.) The S-N distances hardly differ from those in free S2N2(1.657(1) and
1.651(1)
Noteworthy are the relatively short S ...C1
contacts.
c12
N(2)
Fig. 1. Structure of the anion of 3a. Distances in pm. The ion has a center of
symmetry. All atoms, which the exception of C and N of the cyanide groups
are almost coplanar; deviations of the atoms of the cyanide group from this
plane: C 17 pm, N(3) 22 pm. NiNi distance 286.2(7) pm.
CI 1
Received: September 16, 1981,
revised: June 14, 1982 [Z 150a IE]
German version: Angew. Chem. 94 (1982) 645
Fig. 1. S p c t u r e of the (AIC13)2S2N2complex in the crystal, with bond
lengths [A] and angles ["I. Errors in the S-N, AI-N, and AI-CI bond
respectively; errors in the bond angles at
lengths: 0.003,0.003, and 0.002
S, N, and Al: 0.2,0.2, and 0.1". respectively. Deviations from the S2Nzplane:
A1 0.004 A, CI2 -0.087
A,
[I] J. Weiss, Top. Curr. Chem. 5 (1966) 635, and references cited therein K. F.
Mayer, J. Weiss, Acfa Cysfallogr. B 34 (1978) 1999; J. D. Woollins, R.
Crinter, M. K. Johnson, A. J. Thomson, J. Chem. SOC.Dalton Trans. 1980,
1910; S. Millefiori, A. Millefiori, G. Granozzi, Inorg. Chim. Acfa 48
(1981) 233.
(21 Procedure: 1 (490 mg, 2 mmol), KCN (260 mg, 4 mmol), and KHCO,
(200 mg, 2 mmol) are refluxed for 2 h in 100 mL of methanol. The redviolet solution is filtered, concentrated, the residue dissolved in 50 mL of
acetone and added slowly with stirring to 450 mL of benzene. The precipitate is filtered off and washed with benzene. Further purification was
carried out by taking up the precipitate on the filter in a little methanol
(-20 mL) and treating the solution with ca. 200 mL of ether. The intensely violet precipitate is filtered off, washed with ether, and dried in
uacuo. Yield 30 mg 3. No definite melting point is observed. and the
compound explodes at 239 "C. - A solution of [(C6H5)~As]CI.H20 (150
mg) in 4 mL of ethanol is added to a solution of 3 (75 mg) in 40 mL of
acetone. After 2 h, KCI is filtered off and the solution slowly evaporated.
Violet-black, strongly intergrown crystals of 3a, m. p.=276 "C, are
formed.
131 J. Weiss, Z. Nafurforsch. B 12 (1957) 481; Acfa Cysfallogr. B 34 (1978)
1997.
634
Q Verlag Chemie GmbH, 6940 Weinheim, 1982
A.
Symmetrical cleavage of the S4N4 cage with formation
of neutral S2N2rings evidently proceeds quite readily and
can be preparatively exploited if-firstly-a
Lewis acid
which has the ability to combine with both S4N, as well as
S2N2is present and-secondly-if
the solubilities of the
individual compounds are such that the S2N2-adductcrystallizes out. These prerequisites are fulfilled in the case of
AIC13 in CH2C12.The same applies for the system CuC12/
S4N4 in acetonitrile; in this case the polymeric complex
[*I
[**I
Prof. Dr. U. Thewalt, M. Burger
Sektion fur Rijntgen- und Elektronenbeugung der Universitit
Oberer Eselsberg, D-7900 Ulm (Germany)
This work was supported by the Fonds der Chemischen Industrie.
0570-0833/82/0808-0634 $02.50/0
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 8
[Cu(CH3CN)CI2l2S2N2
can be isolated, which likewise contains neutral S2N2groups as bridging ligands[6bJ.
Received: December 18, 1980 [Z 150b IE]
revised: October 19, 1981
German version: Angew. Chem. 94 (1982) 646
[ I ] M. M. Labes, P. Love, L. F. Nichols, Chem. Rev. 79 (1979) 1.
121 a) R. L. Patton, W. L. Jolly, Inorg. Chem. 8 (1969) 1389; b) R. L. Patton,
K. N. Raymond, ibid. 8 (1969) 2426; c) R. L. Patton, W.L. Jolly, ibid. 8
(1969) 1392.
(31 One of the other products characterized by X-ray structure analysis is
S2N"AIChe.
[4] C. H. Chan, F. P. Olsen, Inorg. Chem. I1 (1972) 2836.
[S] Crystallographic data: P2,/n with 2 = 2 ; lattice constants: a = 8.964(4),
b=9.636(7), c=7.309(4) A,fl= 110.45(3)". Measurement with MoKa radiation, h=0.71069 A;structure refined to R=0.042 using all 1030 reflections obtained for 8525"; unit weights.
16) a) M. J. Cohen, A. F. Garito, A. J. Heeger, A. G. MacDiarmid, C. M. MiI
Am.
. Chem. Soc. 98 (1976) 3844; b)
kulski, M. S . Saran, J. Kleppinger, .
U. Thewalt, B. Miiller, 2. Anorg. Allg. Chem. 462 (1980) 214.
Electrochemical Oxidation of Croconate Salts ;
Evidence of the Chemical Equivalence of the
Carbonyl Oxygen Atom
and the Dicyanomethylene Group**
By Lawrence M. Doane and Alexander J. Fatiadi*
We have found that dicyanomethylene derivatives of
croconates [pseudooxocarbon compounds of general formula C,O,[C(CN),]',r,]~'l
are excellent models for testing
the concept of Wallenfeld2'on the chemical equivalence of
carbonyl oxygen and the dicyanomethylene group. Several
electrochemical studies have been carried out on aromatic
ox~carbon[~"'
and pseudooxocarbon compounds[3b1,but,
as yet, no reversible electron transfer reactions have been
reported for croconates. We report here: (i) on some cyclovoltammetric and ESR investigations of salts of the oxocarbon dianion, croconate 1, and the pseudooxocarbon
dianions[", 3-(dicyanomethylene)croconate 2, 3,5-bis(dicyanomethy1ene)croconate [croconate violet] 3, and 3,4,5tris(dicyanomethy1ene)croconate [croconate blue] 4 ;(ii) on
the first supporting electrochemical evidence for the postulated chemical equivalence of =O and =C(CN)2.
These results suggest a reversible one-electron oxidation of
the dianion to a stable radical anion followed by a reversible one-electron oxidation of the radical anion to the neutral molecule. At scan rates less than 20 mV/s, the more
positive cathodic wave of the dianion of 4 is very small, indicating a fast chemical reaction following the electron
transfer.
Thin-layer cyclic voltammetry provides further evidence
of the electrochemical reversibility and the stability of the
components of the redox couple[51.If scan reversal occurs
immediately after the first oxidation wave, essentially
equal anodic peak and reversal cathodic peak currents are
obtained for all dianions. The stability of the radical anion
is therefore no less than several minutes. Equal anodic and
cathodic peak currents are obtained at the second redox
couple of the dianion of 1. However, for dianions of 3 and
4, scan reversal after the second oxidation wave gives no
cathodic wave where reversible reduction of the neutral
species and the radical anion should each occur. For the
dianion of 2, three cathodic waves appear on reversal after
the second oxidation wave. Despite the results of cyclic
voltammetry this indicates that the neutral species [except
in the case of 11 undergo chemical transformations that
alter their cathodic waves.
E vs SCE
E vs SCE
1 2 . 5 pA
E''= 0.45
E Q =0.87
c
E''= 0.91
Fig. 1. Cyclovoltammograms of the dianions 1-4. For conditions see Table
1.
Table 1. Cyclovoltammometric data for the oxidation of croconates in DMF
us. SCE.-In the case of 1-4 two reduction steps were observed in
[a]. E
[Vl us. SCE): 1: -0.78, -1.21; 2 : -0.68, -0.88; 3:
each case (Epc,,Epc2
- 1.48, - 1.73; 4 : - 1.05, - 1.40. Except in the case of 4, the reductions were
reversible.
[v
~~~
D ia nion
1. Peak [b]
2. Peak [b]
1, R 1 = R 2 = R 3 = 0
2, R'=R'=O, R2=C(CN)2
of
Epa
E,
AE,
Em
Epc
3, R'=O, R'=R3=C(CN)2
4, R' = R2= R3=C(CN)2
1
0.26
0.36
0.48
0.58
0.20
0.06
0.06
0.07
0.07
0.51
0.72
0.90
1.00
0.44
0.66
0.83
0.94 [c]
2
Figure 1 shows cyclic voltammograms of the salts of 1-4
in N,N-dimethylformamide (DMF) containing 0.5 mol/L
tetraethylammonium perchlorate (TEAP); the peak potentials are given in Table 1. The general behavior of dianions of 1-4 is similar and is characterized by essentially
equal anodic and reversal cathodic peak currents and a
V.
peak potential separation (Ep,-Epc) of 0.06-0.07
[*I Dr. A. J. Fatiadi, Dr. L. M. Doane
[*'I
Organic Analytical Research Division, National Bureau of Standards
Washington, DC 20234 (USA)
We thank Dr. Ts-Tse Chang for assistance with the ESR experiments.
Angew. Chem. Inr. Ed. Engl. 21 (1982) NO. 8
3
4
0.30
0.41
0.51
0.07
0.06
0.07
0.06
[a] Concentration of TEAP 0.5 mol/L. Working electrode: gold disk with surface area of 0.079 cm' (in the case of 3: 0.051 cm'), sweep rate 0.05 V/s. [b]
E , and Epc are the anodic and cathodic peak potentials, respectively. [c]
Weak current on scan reversal.
Evidence of radical anion formation was obtained from
ESR spectra of dianion solutions electrooxidized in
DMSO at a potential approximately 100 mV more positive
than the peak potential of the first oxidation wave. The
ESR spectrum of the electrooxidized solution of the salt 3
shows a 9-line pattern, which possibly indicates interac-
0 Verlag Chemie GmbH, 6940 Weinheim. 1982
0570-0833/82/0808-0635 $02.50/0
635
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alcl, structure, 2s2n2, cleavage, s2n2, temperature, formation, s4n4, room
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