Theoretical and Experimental Studies of Six-Membered Selenium-Sulfur Nitrides Se(x)()S(4)(-)(x)()N(2) (x = 0-4). Preparation of S(4)N(2) and SeS(3)N(2) by the Reaction of Bis[bis(trimethylsilyl)amino]sulfane with Chalcogen Chlorides

Neutral binary chalcogen-nitrogen and ternary S,N,P molecules: new structures, bonding insights and potential applications

Early theoretical and experimental investigations of inorganic sulfur-nitrogen compounds were dominated by (a) assessments of the purported aromatic character of cyclic, binary S,N molecules and ions, (b) the unpredictable reactions of the fascinating cage compound S4N4, and (c) the unique structure and properties of the conducting polymer (SN)x. In the last few years, in addition to unexpected developments in the chemistry of well-known sulfur nitrides, the emphasis of these studies has changed to include nitrogen-rich species formed under high pressures, as well as the selenium analogues of well-known S,N compounds. Novel applications have been established or predicted for many binary S/Se,N molecules, including their use for fingerprint detection, in optoelectronic devices, as high energy-density compounds or as hydrogen-storage materials. The purpose of this perspective is to evaluate critically these new aspects of the chemistry of neutral, binary chalcogen-nitrogen molecules and to suggest experimental approaches to the synthesis of target compounds. Recently identified ternary S,N,P compounds will also be considered in light of their isoelectronic relationship with binary S,N cations.

Selenium– and tellurium–nitrogen reagents

The reactivity of the chalcogen–nitrogen bond toward main-group element or transition-metal halides, as well as electrophilic and nucleophilic reagents, is the source of a variety of applications of Se–N and Te–N compounds in both inorganic or organic chemistry. The thermal lability of Se–N compounds also engenders useful transformations including the formation of radicals via homolytic Se–N bond cleavage. These aspects of Se–N and Te–N chemistry will be illustrated with examples from the reactions of the binary selenium nitride Se4N4, selenium–nitrogen halides [N(SeCln)2]+ (n = 1, 2), the synthons E(NSO)2 (E = Se, Te), chalcogen–nitrogen–silicon reagents, chalcogen(IV) diimides RN=E=NR, the triimidotellurite dianion [Te(NtBu)3]2−, chalcogen(II) amides and diamides E(NR2)2 (E = Se, Te; R = alkyl, SiMe3), and heterocyclic systems.

Identification of mixed bromidochloridotellurate anions in disordered crystal structures of (bdmim)2[TeX2Y4] (X, Y=Br, Cl; bdmim=1-butyl-2,3-dimethylimidazolium) by combined application of Raman spectroscopy and solid-state DFT calculations

The discrete mixed [TeBrxCl6-x](2-) anions in their disordered crystal structures have been identified by using the phases prepared by the reaction of 1-butyl-2,3-dimethylimidazolium halogenides (bdmim)X with tellurium tetrahalogenides TeX4 (X=Cl, Br) as examples. Homoleptic (bdmim)2[TeX6] [X=Cl (1), Br (2)] and mixed (bdmim)2[TeBr2Cl4] (3), and (bdmim)2[TeBr4Cl2] (4) are formed depending on the choice of the reagents, and their crystal structures have been determined by single-crystal X-ray diffraction. The coordination environments of tellurium in all hexahalogenidotellurates are almost octahedral. Because of the crystallographic disorder, the mixed [TeBr2Cl4](2-) and [TeBr4Cl2](2-) anions in 3 and 4 cannot be identified in their crystal structures. Pawley refinement of the X-ray powder diffraction patterns of 1-4 indicates the presence of single phases in all four products. The solid state Raman spectra of 1-4 were assigned with help of DFT calculations that were performed both for the discrete anions in vacuum and for the complete crystal structures employing periodic boundary conditions. The fundamental vibrations of the homoleptic [TeX6](2-) (X=Cl, Br) anions could be well reproduced by the solid-state DFT computations and enabled a complete assignment of the Raman spectra. While the presence of cis-isomers in both [TeBr2Cl4](2-) and [TeBr4Cl2](2-) could be inferred by the computed fundamental vibrations, that of trans-isomers among the reaction products is, however, also possible. The pathway of the formation of [TeX4Y2](2-) isomers from TeX4 and Y(-) (X, Y=Cl, Br) was also explored by DFT calculations both in vacuum and in solution and indicated that both reactions afforded 80 mol% of cis-isomers and 20 mol% of trans-isomers.

Preparation and structural characterization of (Me(3)SiNSN)(2)Se, a new synthon for sulfur-selenium nitrides

The reaction of (Me(3)SiN)(2)S with SeCl(2) (2:1 ratio) in CH(2)Cl(2) at -70 degrees C provides a route to the novel mixed selenium-sulfur-nitrogen compound (Me(3)SiNSN)(2)Se (1). Crystals of 1 are monoclinic and belong the space group P2(1)/c, with a = 7.236(1) A, b = 19.260(4) A, c = 11.436(2) A, beta = 92.05(3) degrees, V = 1592.7(5) A(3), Z = 4, and T = -155(2) degrees C. The NSNSeNSN chain in 1 consists of Se-N single bonds (1.844(3) A) and S=N double bonds (1.521(3)-1.548(3) A) with syn and anti geometry at the N=S=N units. The N-Se-N bond angle is 91.8(1) degrees. The EI mass spectrum shows a molecular ion with good agreement between the observed and calculated isotopic distributions. The (14)N NMR spectrum exhibits two resonances at -65 and -77 ppm. Both (13)C and (77)Se NMR spectra show single resonances at 0.83 and 1433 ppm, respectively. The reaction of 1 with an equimolar amount of SeCl(2) produces 1,5-Se(2)S(2)N(4) (2) in a good yield, and that of (Me(3)SiNSN)(2)S with SCl(2) affords S(4)N(4) (3), but the reactions of (Me(3)SiNSN)(2)Se with SCl(2) and (Me(3)SiNSN)(2)S with SeCl(2) result in the formation of a mixture of 2 and 3. A likely reaction pathway involves the intermediate formation of E(2)N(2) fragments (E = S, Se).

Preparation, crystal structure, and spectroscopic characterization of [(Se(2)SN(2)Cl](2)

The reaction of [(Me(3)Si)(2)N](2)S with an equimolar amount of SeCl(4) in dioxane at 50 degrees C affords [(Se(2)SN(2))Cl](2) (1) in excellent yield. Crystals of 1 are orthorhombic, space group Pbca, with a = 8.5721(7) A, b = 7.8336(6) A, c = 15.228(1) A, and Z = 8. The crystal structure contains two planar Se(2)SN(2)(*)(+) rings which are linked by intermolecular Se.Se interactions [d(Se-Se) = 3.0690(7) A]. The EI mass spectrum shows Se(2)SN(2)(*)(+) as the fragment of highest mass. Both the (14)N and (77)Se NMR spectra show a single resonance (-52 and 1394 ppm, respectively). The solid [(Se(2)SN(2))Cl](2) gives a strong ESR signal indicating the presence of a Se(2)SN(2)(*)(+) radical. The Raman spectrum was assigned through normal coordinate treatment involving a general valence force field. The vibrational analysis yielded a good agreement between the observed and calculated wavenumbers.

Preparation, X-ray Structure, and Spectroscopic Characterization of 1,5-Se(2)S(2)N(4)

The reaction of [(Me(3)Si)(2)N](2)S with equimolar amounts of SCl(2) and SO(2)Cl(2) produces S(4)N(4) in a good yield. The new chalcogen nitride 1,5-Se(2)S(2)N(4) has been prepared in high yield by two different reactions: (a) from [(Me(3)Si)(2)N](2)S and SeCl(4) and (b) from [(Me(3)Si)(2)N](2)Se with equimolar amounts of SCl(2) and SO(2)Cl(2). 1,5-Se(2)S(2)N(4) has a cage structure similar to those of S(4)N(4) and Se(4)N(4). The crystal structure is disordered with site occupation factors ca. 50% for selenium in each chalcogen atom position. The 12 eV EI mass spectrum shows Se(2)SN(2)(+) as the fragment with highest mass. Both the (14)N and (77)Se NMR spectra show a single resonance (-238 and 1418 ppm, respectively). These data rule out the possibility that the crystalline sample is a solid solution of S(4)N(4) and Se(4)N(4) and imply the presence of 1,5-Se(2)S(2)N(4). This deduction was further verified by Raman spectroscopy and vibrational analysis.