N(2)S(2) is a four-membered-ring system with 6pi electrons. While earlier proposals considered N(2)S(2) to be aromatic, recent electronic structure calculations claimed that N(2)S(2) is a singlet diradical. Our careful reexamination does not support this assertion. N(2)S(2) is closed shell and aromatic since it satisfies all three generally accepted criteria for aromaticity: energetic (stability), structural (planarity with equal bond lengths), and magnetic (negative nucleus-independent chemical shift due to the pi electrons). These characteristics as well as the electronic structure of N(2)S(2) are compared with those for an isoelectronic pi system, Li(2)C(4)H(4), motivated by theoretical and recent experimental investigations that confirmed its aromaticity. However, N(2)S(2) and Li(2)C(4)H(4) are both essentially 2pi-electron aromatic systems with a formal N-S (C-C) bond order of 1.25 even though they both have 6pi electrons. This is because four of the six pi electrons occupy the nonbonding pi HOMOs and only two electrons participate effectively in the aromatic stabilization. However, wave function analysis shows relatively large LUMO occupation numbers; this antibonding effect can be said to reduce the aromatic character by approximately 7% and 4% for N(2)S(2) and Li(2)C(4)H(4), respectively.

Aromaticity of four-membered-ring 6pi-electron systems: N2S2 and Li2C4H4.

Publisher Summary In the following article an attempt has been made to bring together recent data on cyclic sulfur-nitrogen compounds The major sections of the review are organized on the basis of ring size Within each section the versatility of the sulfur-nitrogen compounds is simplified by using coordination numbers In other words, the focal point is the sulfur atom, which can be classified on the basis of the number of surrounding substituents In addition, the coordination numbers two and three at the nitrogen atoms will also be taken in account for the ordering principle Finally, sulfur-nitrogen compounds that contain one other element will be discussed in each section The numerous reports, wherein three- or four-membered rings are formulated as intermediates, will not be considered The literature has been surveyed up to the end of 1977 In many cases, the examples cited are meant to be representative and indicative rather than to be all-inclusive In general, for the cohesion of this article the alphabetical order was used for writing the formulas

Cyclic Sulfur-Nitrogen Compounds

The results of the thermal decomposition at low pressure of Cl3P NPCl2 ; NSO2Cl, Cl3P NPCl2 NPCl2 NSO2Cl and mixtures of these compounds with Cl3P NSO2Cl, are reported. In all cases inorganic heterocycli, containing nitrogen phosphorus and/or sulfur atoms, were obtained. The isolation of the hitherto unknown compound (NPCl2)2 NSOCl is described.



A short discussion of the I.R. spectra of α-(NSOCl)3, NPCl2(NSOCl)2, (NPCl2)2 NSOCl and (NPCl2)3 is given.

The preparation of a new inorganic ring system containing one sulfur, two phosphorus and three nitrogen atoms in the ring

The 35Cl NQR frequencies from 11 organic molecules and 3 inorganic molecules are given for 77°K. The frequencies are discussed in terms of σ and π inductive and conjugative effects of groups relative to the chlorine and compared to frequencies in analogous molecules. In [PCl4]+[BCl4]−, frequencies from both ions have been detected, and in [SCl3]+[SbCl6]− the first frequencies to date from [SCl3]+ have been measured.

35Cl NQR of 11 Organic and 3 Inorganic Molecules

Die Titelverbindung 1 reagiert mit Aminen HNRR′ im Molverhaltnis 1:2 zu 2, 3, 4, 5, 6 und 7. Aus 1 und Fluorierungsmitteln wie SbF3 und AgF2 ist die Verbindung 8 als cis, trans-Isomerengemisch zuganglich. – Die Raumgruppe und Gitterkonstanten von 8 sowie die IR-, Massen-, 1H-, 19F- und 31P-NMR-Spektren der Verbindungen werden mitgeteilt.



On the Reaction of 3,3-Dichloro-1,5,2,4,6,3-dithiatriazaphosphor(V)in-bis(oxidchloride), a Dioxodichlorocyclodithiazaphosphazen



The title compound 1 reacts with amines like HNRR′ in a molratio 1:2 to form 2, 3, 4, 5 6 and 7. The compound 8 is formed as a mixture of cis, trans-isomers from 1 and fluorinating agens like SbF3 and AgF2. The space group and lattice parameters of 8, as well as the i.r.-, mass-, 1H-, 10F- and 31P-n.m.r. spectra of the compounds are reported.

R. M. Hart

Papers

Preparation and nuclear quadrupole resonance interpretation of the structure of cyclo-tri-.mu.-nitrido-dichlorophosphorusbis(oxochlorosulfur