Tetrasulfur tetranitride



Tetrasulfur tetranitride
General
Systematic name Tetranitrogen tetrasulfide
tetrasulfur nitride
Molecular formula S4N4
Molar mass 184.29 g/mol
Appearance Orange solid
CAS number [28950-34-7]
Properties
water Insoluble
Solubility in other solvents benzene
Melting point 187 °C (460 K)
IR 928 768 727 700
630 553 548 and 529 cm-1
NMR 15N NMR: δ -246
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Tetrasulfur tetranitride is an nitrogen. It is a precursor to many S-N compounds and has attracted wide interest for its unusual structure and bonding.[1][2]

Nitrogen and sulfur have similar covalently bonded structures. Indeed, a large number of S-N and S-NH compounds are known with S4N4 as their parent.

Structure

S4N4 adopts an unusual “extreme cradle” structure, with D2d point group symmetry. It can be viewed as a derivative of a hypothetical eight-membered ring of alternating sulfur and nitrogen atoms. The pairs of sulfur atoms across the ring are further bonded, resulting in a cage-like structure with pentagonal S3N2 rings. The nature of the "transannular" S-S interactions is a matter of debate and computational investigation[3] but has been explained in the context of molecular orbital theory.[1] The bonding in S4N4 is considered to be delocalized, which is indicated by the fact that the bond distances between neighboring sulfur and nitrogen atoms are almost the same.

Properties

S4N4 is stable to endothermic heat of formation anticipates its inherent instability, and originates in the difference in energy of S4N4 compared to its highly stable decomposition products:

S4N4 → 2 N2 + 0.5 S8

It is not really very unusual for complex molecules to be unstable in a thermodynamic sense yet stable kinetically; this situation describes many compounds. This combination of kinetic stability and thermodynamic instability is, however, uncommon for very simple compositions, such as sulfur nitride. Because one of its decomposition products is a gas, S4N4 is an explosive.[1] Purer samples tend to be more explosive. Small samples can be detonated by striking with a hammer.

S4N4 is thermochromic, changing from pale yellow below -30 °C to orange at room temperature to deep red above 100 °C.[1]

Synthesis

Until recently, S4N4 was prepared by the reaction of dioxane.[4]

6 SCl2 + 16 NH3 → S4N4 + S8 + 12 NH4Cl

A related synthesis employs NH4Cl in place of ammonia:[1]

4 NH4Cl + 6 S2Cl2 → S4N4 + 16 HCl + S8

A more recent synthesis entails the use of {[Me3Si)2N]2S} as a precursor with pre-formed S-N bonds. {[Me3Si)2N]2S} is prepared by the reaction of lithium bis(trimethylsilyl)amide and SCl2.

2 [(CH3)3Si]2NLi + SCl2 → [(CH3)3Si)2N]2S + 2 LiCl

The {[(CH3)3Si)2N]2S} reacts with the combination of SCl2 and SO2Cl2 to form S4N4.[5]

[(CH3)3Si)2N]2S + SCl2 + SO2

Acid-base reactions

S4N4 serves as a Lewis base by binding through nitrogen to strongly electrons may be disrupted.[1]

S4N4 + SbCl5 → S4N4.SbCl5
S4N4 + SO3 → S4N4.SO3

The reaction of [Pt2Cl4(PMe2Ph)2] with S4N4 is reported to form a complex where a sulfur forms a dative bond to the metal, this compound upon standing is isomerised to a complex in which a nitrogen atom forms the additional bond to the metal centre.

It is protonated by HBF4:

S4N4 + HBF4 → S4N4H+BF4

The soft Lewis acid ligands:[1]

nS4N4 + nCuCl → (S4N4)n-μ-(-Cu-Cl-)n

S4N4 is sensitive to NaOH hydrolyzes S4N4 as follows:[1]

2S4N4 + 6 OH- + 9 H2O → S2O32- + 2 S3O62- + 8 NH3

Whereas more concentrated base yields sulfite:

S4N4 + 6 OH- + 3 H2O → S2O32- + 2 SO32- + 4 NH3

Reactions with metal complexes

This area has been reviewed.[6][2]

Reactions of S4N4 where the ring remains intact

S4N4 reacts with Zeise's salt.


Reactions of S4N4 where the ring does not remain intact

The reaction of S4N4 with the [Pd2Cl6]2- anion forms a series of three palladium complexes in which the S4N4 ring has been fragmented.

S4N4 as a precursor to other S-N compounds

Many important S-N compounds are prepared from S4N4.[7] Reaction with piperidine generates [S4N5]−:

3 S4N4 + 4 C5H10NH → (C5H10NH2)+[S4N5]- + (C5H10N)2S + 3/8 S8 + N2

It is indicative of the richness of this area that a related cation is also known, i.e. [S4N5]+.

Treatment with tetramethylammonium azide produces the heterocycle [S3N3]-:

S4N4 + 4 NMe4N3 → NMe4[S3N3] + 1/8 S8 + 2 N2

In the language of electron counting, [S3N3]- has 10 pi-electrons: 2e-/S plus 1e-/N plus 1e- for the negative charge.

In an apparently related reaction, the use of PPN+N3 gives the blue perthionitrite salt:

2 S4N4 + PPN(N3) → PPN[NS3] + 1/2 S8 + 5 N2

The anion NS3- is a chain described often as S=N-S-S-.

Reaction with acetylenes

S4N4 reacts with electron poor acetylenes.[8]

"SNx"

Passing gaseous S4N4 over polymerizes.[1]

S4N4 + 8 Ag → 4 Ag2S + 2 N2
S4N4 → (SN)x

Miscellaneous facts

S4N4 has been shown to co-crystallize with C60.[10]

Se4N4

The aluminium chloride with Se2N2 have been isolated, this is formed from Se4N4.[13]

Safety

S4N4 is shock-sensitive, thus grinding solid samples should be avoided. Purer samples are reportedly more sensitive than those contaminated with elemental sulfur.


References

  1. ^ a b c d e f g h i Greenwood, N. N.; Earnshaw, A. Chemical Elements; 2nd edition; Butterworth-Heinemann: Boston, MA, 1997, pp 721-725.
  2. ^ a b Chivers, T. “A Guide To Chalcogen-Nitrogen Chemistry” World Scientific Publishing Company: Singapore; 2004. ISBN 981-256-095-5
  3. ^ "A PM3 SCF-MO Study of the Structure and Bonding in the Cage Systems S4N4 and S4N4X (X=N [+], N[-], S, N2S, P[+], C, Si, B[-] and Al[-])." H. S. Rzepa and J. D.Woollins, Polyhedron 1990, volume 9, p. 107.
  4. ^ Villena-Blanco, M.; Jolly, W.L.; Tyree, S.Y. Ed.: Inorganic synthesis; Wiley: New York, NY, 1967; Vol. 9, pp. 98-102
  5. ^ Maaninen, A.; Shvari, J.; Laitinen, R.S.; Chivers, T; Inorganic Synthesis; (2002) Vol. 33, pp. 196-199
  6. ^ Paul. F. Kelly, Alexandra. M.Z. Slawin, David J. Williams and J. Derek Woollins, Chemical Society Reviews, 1992, 245
  7. ^ Bojes, J.; Chivers, T; Oakley, R. D. "Binary Cyclic Nitrogen-Sulfur Anions" Inorganic Synthesis (1989) Volume 25, pp. 30-40. DOS 0-471-61874-8
  8. ^ The Reaction between Tetrasulphur Tetranitride (S4N4) and Electron-deficient Alkynes. A Molecular Orbital Study" P. J. Dunn and H. S. Rzepa, Journal of the Chemical Society, Perkin Transactions 2 , 1987, 1669-1670.
  9. ^ R. L. Greene, G. B. Street and L. J. Suter, Superconductivity in Polysulfur Nitride (SN)x, Phys. Rev. Lett. 34, 577–579 (1975) doi:10.1103/PhysRevLett.34.577
  10. ^ Konarev, D.V. et al. "Donor-acceptor Complexes of Fullerene C60 with Organic and Organometallic Donors" Journal of Materials Chemistry (2000) Volume 10, pages 803-818.
  11. ^ Kelly, P.F. and Woollins, J.D., The Reactivity of Se4N4 in Liquid Ammonia, Polyhedron, 1993, volume 12, pp 1129-1133.
  12. ^ Kelly, P.F., Slawin, A.M.Z. and Soriano-Rama, A., Use of Se4N4 and Se(NSO)2 in the preparation of palladium adducts of diselenium dinitride, Se2N2; crystal structure of [PPh4]2[Pd2Br6(Se2N2), Journal of the Chemical Society, Dalton Transactions, 1997, pp 559-562
  13. ^ Kelly, P.F. and Slawin, A.M.Z., Preparation and crystal structure of [(AlBr3)2(Se2N2)], the first example of a main-group element adduct of diselenium dinitride, Journal of the Chemical Society, Dalton Transactions, 1996, pp 4029-4030
 
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