Crystal and molecular structure of [n-Bu4N+][S3N3-] and the vibrational assignments and electronic structure of the planar six-membered ring of the trisulfur trinitride anion

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Crystallographic evidence indicates that the structure of the trisulfur trinitride anion, S3N,-, is planar with cqual S N bond lengths. Although the recent literature contains a number of molecular orbital calculations of D,,, symmetry there arc also calculations which indicate inequivalent nitrogens, suggesting broken symmetry. The results of an investigation of Hartree-Fock instabilities of the ab initio molecular orbital description of this system are reported. The D3,, solution is indeed singlet stable but there are relatively close-lying C?,. broken-symmetry solutions. In the broken-symmetry solutions the n electron network encompasses only five centres; the sixth centre, essentially free of a charge, may be either a sulphur or a nitrogen, thus yielding two distinct broken-symmetry solutions.M. BENARD, W. G. LAIDLAW et J. PALDUS. Can. J. Chem. 63, 1797 (1985.Les donnkes cristallographiques indiqucnt que I'anion trinitrurc de soufre, S,N3-, a une structure plane avec des longueurs de liaisons SN qui sont Cgales. Quoique I'on retrouve dans la littkrature rCcente un certain nombre de calculs d'orbitales molCculaires de symCtrie D,,,, on y trouve Cgalement des calculs qui indiquent des azotes non equivalents et ceci suggkre une rupture de la symCtrie. On rapporte les rtsultats d'une Ctude des instabilitks de Hartree-Fock pour la description ab ini~io de l'orbitale molCculaire de ce systkme. La solution D3,, est effectivement stable pour le singulet mais il y a des solutions de symCtrie rompue C?, qui y sont assez Ctroitement associCes. Dans les solutions de symCtrie rompue, le rCseau d'tlectrons n entoure seulemcnt cinq centres; le sixicme centre qui est essentiellement dkpourvue de charges n pourrait etre soit le soufre soit I'azote et ceci conduit donc B deux solutions distinctes de symktrie rompue.[Traduit par lc journal]I. Introduction There has been considerable interest in unsaturated SN compounds as the recent reviews by Roesky (1), Chivers and Oakley (2), and Gleiter (3) attest. There are rings, cages, chains, cations, anions, and neutral species; many of these were made in the last 10 years. The particular focus of this work is the planar S 3 N 3 anion first prepared by Bojes and Chivers in 1977 (4). The tetrabutylammonium salt yields stable yellow crystals which have been analyzed structurally by X-ray diffraction to yield the ~esults depicted in Fig. 1. The bond lengths are 1.60 ? 0.02 A and the system is planar to within lo. A similar structure has been reported for this anion in (Tit)? (S,N3-) (S,N5-) ( 5 ) . Consequently a reasonable representation of the ~o l e c u l a r framework is a "hexagon" with bond lengths of 1.60 A and internal angles of 120°, i.e., the symmetry point group of the nuclei is D,,,. The S3N,-anion has 34 valence electrons and, using a Hartree-Fock-Slater (HFS) single determinant wavefunction, Bojes et al. reported (6) that 10 of these were .rr electrons. Thus, the S3N1-anion is a .rr "electron-rich" system (7). The essential features of the eigenvalue manifold are given in ...

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Hartree–Fock instabilities in the trisulphur–trinitride anion

Bénard¹,

Laidlaw²,

Paldus³

1985

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“…AD iniiio Hartree-Fock-Slater SCF calculations show that it is a six orbital 107-electron system in which the degenerate T:* levels are fully occupied (1,4) and this view of the electronic structure has been confirmed by experiment (2). Some It has been claimed that the dark red amorphous solid which prccipitates when S2N2 reacts with I, in boiling inert solvents is S,N,I (8c).…”

Section: \ @ ?mentioning

confidence: 80%

“…The trisulfur trinitride anion, SIN,-, has been thoroughly I characterized both structurally ( 1 ) and spectroscopically (ir and…”

Section: Introduction Omentioning

confidence: 99%

Reactions of the trisulfur trinitride anion, S₃N₃⁻, with halogens and other electrophilic substrates

Chivers¹,

Rao²

1983

The reactions of the trisulfur trinitride anion, S3N3−, with halogens (Cl2, Br2, l2), AsF5, SOCl2, SO2Cl2, S2Cl2, COCl2, CS2, Me3SiCl, and Ph2PCl have been investigated. In all cases these reactions gave mixtures of known sulfur–nitrogen compounds. Thus the halogens react with S3N3−.to give mainly S4N4, S4N3+X− (X = Br, Cl), (SN)x, and S3N3X3 (X = Cl), while AsF5 oxidizes S3N3− to S4N4•AsF5. The major products of the reaction of S3N3− with SOCl2 or SO2O2 were S4N4, S4N3+Cl−, and (for SOCl2 only) S3N2O2•S3N2Cl was the main product of the reaction of S3N3− with S2Cl2, whereas COCl2 yielded (SN)x in addition to S3N2Cl and S4N4. Carbon disulfide reacts with S3N3− to give S4N2, S4N4, and CNS−. The cyclophosphathiazenes, (Ph2PN)(SN)2, 1,3- and 1,5-(Ph2PN)2(SN)2, in addition to (Ph2PN)x (x = 3, 4), (Ph2PN)3•HCl and (Ph2PN)2NSCl were isolated from the reactions of Ph2PCl with S3N3− in various molar ratios. The latter reaction represents a useful alternative synthesis of the 1,5-isomer of the eight-membered ring (Ph2PN)2(SN)2.

“…Similar ideas took root in cyclothiazene chemistry in the 1970s, with seminal papers by Gleiter (7) and Banister (8). The structural stability associated with aromatic (4nf2) T-electron counts was recognized, and important examples of new aromatic systems, e.g., the binary rings S , N , (9) and s,N,' + (10) and heterocyclic dithiatetrazocines R2C2N,S2 (1 l ) , were identified. The electron richness of these heterocycles, coupled with the differing electronegativities of their constituent atoms (S and N), leads to highly polarizable T-systems (12).…”

Section: Aromatic and Anti-aromatic Ringsmentioning

confidence: 86%

1993 ALCAN Award Lecture Chemical binding within and between inorganic rings; the design and synthesis of molecular conductors

Oakley¹

1993

For a given number of skeletal atoms, the π-electron count of an unsaturated heterocycle can be modified by the incorporation of heteroatoms from different periodic groups. Sulfur and nitrogen are particularly effective in this regard, as their high electronegativity can stabilize electron-rich π-systems. A variety of aromatic, anti-aromatic, and radical systems can be prepared from admixtures of these elements. While the properties of these ring systems are interesting in their own right, the compounds are not without relevance in the design of new materials. The strong interannular interactions that are developed between these rings in the solid state makes them ideal candidates for the fabrication of molecular conductors. The origins and development of this area of research are the subjects of this presentation.