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T.C. thanks the NSERC (Canada) for continuing funding. J.D.W. is grateful to the University of St Andrews for support. A.N. thanks the EPSRC for financial support.

Review: [fundamental concepts necessary for an understanding of the unique structures and reactivities of tellurium compounds; 50 refs.

The trisulfur radical anion [S3]˙− is well-known from inorganic chemistry textbooks as the blue chromophore in ultramarine blues in which this highly reactive species is trapped in a zeolitic framework. Recent findings have revealed that [S3]˙− has a multi-faceted role in a variety of media, including alkali metal–sulfur batteries, aqueous solutions at high temperatures and pressures, and ionic liquids; it has also been used to detect trace amounts of water in organic solvents. This tutorial review illustrates how various physical techniques are used to identify a reactive species in solution and shows how elucidation of electronic structures can be used to explain spectroscopic and structural properties. Examples of the function of [S3]˙− in materials science, electrochemistry, analytical chemistry and geochemistry are used to illustrate the widespread influence of this fundamentally important triatomic sulfur species.

Diphosphadiselenatetrazocines, 1,5-R4P2Se2(R = Me, Et, Ph) and 1,3-R4P2N4Se2 (R = Me, Et), have been prepared in good combined yields from the cyclocondensation of R2PN2(SiMe3) with ‘SeCl3’. The compound 1,5-Ph4P2N4Se2 dissociates into Ph PN2Se radicals identified by ESR spectroscopy. Metal complexes (Ph3P2) (M = Pt, Pd) have been prepared from the reaction of 1,5-Ph4P2N4Se2 with (Ph3P)2PtC2H4 and (Ph3),Pd, respectively. The Se,Se'-dialkyl denvatives 1,5-Ph4P2N4Se2R2 undergo isomerization to produce 1,3-Ph4P2N4 2 in the solid-state (R = Me, Et) or, more rapidly, in solution (R = Me, Et, Ph).

The reaction of the Ph 2 PN 2 (SiMe 3 ) 3 with organoselenium trichlorides RSeCl 3 in acetonitrile at 23 o C produces high yields of 1,5-Ph 4 P 2 N 4 Se 2 R 2 (1a, R=Me; 1b, R=Et; 1c, R=Ph) and, for 1a,b, small amounts of 1,5-Ph 4 P 2 N 4 Se 2 . These heterocycles were characterized by 1 H, 31 P, and 77 Se NMR, IR, and mass spectroscopies and, in the case of 1a, by X-ray crystallography, which showed that the eight-membered P 2 N 4 Se 4 ring adopts a chair conformation.

The cyclocondensation of R 2 PN 2 (SiMe 3 ) 3 (R=Me, Et, Ph) with a mixture of selenium monochloride and selenium tetrachloride that gives a Se:Cl ratio of 1:3 in acetonitrile at 23 o C produces 1,5-Ph 4 P 2 N 4 Se 2 , 2a, in 85% yield by mixtures of 1,5- and 1,3-R 4 P 2 N 4 Se 2 in combined isolated yields of 79% (R=Me) or 96% (R=Et). The heterocycles 1,3-Me 4 P 2 N 4 Se 2 , 4b, and 1,5-Et 4 P 2 N 4 Se 2 , 2c, were separated from these mixtures by fractional crystallization and gel permeation chromatography, respectively.

The composition of sulfur-rich molten mixtures of sulfur, selenium, and tellurium has been studied by using 125 Te and 77 Se NMR spectroscopy at 145 o C. The spectral assignments and the identification of the molecular species were made on the basis of combined information from the natural abundance and from the 77 Se- and 125 Te-enriched samples.

The explosive black solid 3-chloro-1,3,4,2,5-triselenadiazolium chloride, Se 3 N 2 Cl 2 , has been prepared in high yield by three different reactions: (a) from [(Me 3 Si) 2 N] 2 Se and a mixture of SeCl 4 and Se 2 Cl 2 designed to give a Se:Cl ratio of 1:3, (b) from [(Me 3 Si) 2 N] 2 Se and SeOCl 2 in a 1:2 molar ratio, and (c) from Me 3 SiN 3 and Se 2 Cl 2 in a 2:3 molar ratio

The methods available for the synthesis of selenium-nitrogen (Se-N) heterocycles are discussed. The chemistry of phosphorus-containing Se-N and Te-N ring systems is described and compared with that of the corresponding S-N heterocycles. The P2N4Se2 ring is a versatile ligand in transition-metal complexes. The use of 77Se NMR and ESR spectroscopy in the characterization of cyclic Se-N systems is also presented.

This review is primarily concerned with the synthesis, structure and fluxional behaviour of cyclic and acyclic chalcogen-nitrogen systems containing phosphorus (V) or phosphorus (III). The cyclic Ph 4 P 2 N 4 S 2 R − and Ph 4 P 2 N 4 S 2− 2 anions (and their selenium analogues) are versatile ligands for both early and late transition metals. Mono-, di-, tri- and tetradentate bonding modes have been established for the eight-membered P 2 N 4 S 2 ring in these inorganic heterocycles. Ligation occurs through sulphur (or selenium) and/or nitrogen, while the coordinatively saturated phosphorus (V) centres serve as an informative probe of fluxional processes. By contrast, coordination occurs exclusively through phosphorus in both the cyclic and acyclic phosphorus (III) systems. In order to provide a background for the discussion of the coordination chemistry of hybrid PN/SN systems, the review begins with a short account of N-bonded complexes of cyclophosphazenes and S 4 N 4 , which is followed by a discussion of metal complexes of the S 4 N 2− 4 dianion. The concluding section of the review describes metal complexes of some related anionic SN ligands. In particular, the alkali metal derivatives of the acyclic [RNS(R′)NR″] − anions and transition metal complexes of the cyclic radical PhCN 2 S 2 are discussed.

NSERC ; U.S.A. by NSF [CHE-0716718]; Institute for Functional Nanomaterials [0701525]; U.S. Environmental Protection Agency [RD-83385601]; NSFC [20973137, 20721002, 20423002]; 973 program [2007CB815307]

Pentafluorophenyl substituted boranes and borates are important as co-catalysts in metallocene-based industrial processes for the homogeneous polymerization of olefins. Although first prepared in the early 1960s, the remarkable properties of tris(pentafluorophenyl)borane have only recently been exploited for applications in catalysis. Spurred by these developments, the related compounds bis(pentafluorophenyl)borane and salts of the tetrakis(pentafluorophenyl)borate anion have also found application in olefin polymerization and other fields. In this article, we trace the rise of pentafluorophenyl boron compounds from curiosities to important commodities.

The reaction of [(Me3Si)2N]2S with equimolar amounts of SCl2 and SO2Cl2 produces S4N4 in a good yield. The new chalcogen nitride 1,5-Se2S2N4 has been prepared in high yield by two different reactions: (a) from [(Me3Si)2N]2S and SeCl4 and (b) from [(Me3Si)2N]2Se with equimolar amounts of SCl2 and SO2Cl2. 1,5-Se2S2N4 has a cage structure similar to those of S4N4 and Se4N4. 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 Se2SN2+ as the fragment with highest mass. Both the 14N and 77Se 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 S4N4 and Se4N4 and imply the presence of 1,5-Se2S2N4. This deduction was further verified by Raman spectroscopy and vibrational analysis.

Weakly bonding interactions are a subject of interest for many areas of chemistry. For example, these interatomic forces are central in the association processes that lead to molecular recognition, self-assembly of supramolecular structures, crystal packing and crystal growth. The activity of biological macromolecules is determined by the structures they adopt as a result of such forces and the interaction with their substrates. The useful macroscopic properties (electric, optical or magnetic) of some materials depend on organization at a molecular level and electronic communication between neighboring molecules.

This paper summarizes developments in the synthesis, structural characterization and reactions of tellurium-nitrogen compounds that have occurred during the last five years.

Since the development of the laddering principle in the mid-1980s, it has become a useful concept for describing structural features in a wide variety of organoalkali metal (particularly organolithium) and other main-group element oligomers. Here a brief account of the laddering principle is given, and a two-stage approach to understanding structural diversity is described for several lithium heterocarboxylates. “Primary laddering” describes the initial aggregation of monomeric units, whereas “secondary laddering” deals with the assembly of these primary laddered units into larger structures. Both homo- and heteromolecular clusters can be formed by these processes. In this context, several examples are discussed, with particular emphasis on the effects of solvation and heteroatoms.

The dilithio boraamidinates {Li2[RB(NtBu)2]}x (R = Me, nBu) are obtained by the reaction of B[N(H)tBu]3 with 3 equivalents of LiR. The X-ray structures of the dimer (R = nBu) and trimer (R = Me) consist of distorted Li4N4 cubes or Li6N6 hexagonal prisms capped by two or three BR groups, respectively. The lithiation of the dimers {M[N(H)tBu]3}2 (M = Al, Ga) with LiR (R = tBu, Me) gives rise to complexes of the type {Li[Al(NtBu)(NHtBu)2]}2(LiR) [R = tBu, N(H)tBu] in which monomeric LitBu or LiN(H)tBu units are trapped by the dilithiated M2N6 template. The centrosymmetric dimer {THF Li3[Si(NiPr)3(NHiPr)]}2, formed by trilithiation of Si[N(H)iPr]4 with LinBu, forms a bicapped hexagonal prism. The tetraazasilicate (Et2O-Li)4[Si(Nnaph)4] is prepared by the reaction of SiCl4 with 4 equiv. of Li2(Nnaph). Treatment of OP[N(H)tBu]3 with an excess of LinBu yields the dilithiated derivative {(THF)Li2[OP(NtBu)2(NHtBu)]}2 with a box-shaped structure.

Oxo anions of p- and d-block elements, for example, SiO(4)(4-), PO(4)(3-), SO(4)(2-), and CrO(4)(2-), are commonly encountered species. The full or partial replacement of the oxo ligands by isoelectronic imido (NR) groups generates homoleptic polyimido anions of the type [E(NR)(x)](z-) or heteroleptic imidooxo anions with the general formula [O(y)E(NR)(x-y)](z-) (where E=main group element or transition metal). The alkali metal derivatives of this new class of anions form ternary or quaternary cluster systems, respectively. The structures of these clusters can be rationalized in terms of the self-assembly of fundamental building blocks. An understanding of the factors that control this process may allow the design of functional materials with specific properties. In addition, these anions are attracting attention as multidentate ligands with unique electronic and stereochemical properties that may engender novel metal-centered chemistry.

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).

Voltammetric studies of S2N2 employing both cyclic voltammetry (CV) and rotating disk electrode (RDE) methods on GC electrodes at room temperature (RT) revealed two irreversible reduction processes at about −1.4 V and −2.2 V in CH3CN, CH2Cl2, and tetrahydrofuran (vs ferrocene) and no observable oxidation processes up to the solvent limit when the scan is initially anodic. However, after cycling the potential through −1.4 V, two new couples appear near −0.3 V and −1.0 V due to [S3N3]−/0 and [S4N4]−/0 respectively. The diffusion coefficient D for S2N2 was determined to be 9.13 × 10−6 cm2 s−1 in CH2Cl2 and 7.65 × 10−6 cm2 s−1 in CH3CN. Digital modeling of CVs fits well to a mechanism in which [S2N2]−• couples rapidly with S2N2 to form [S4N4]−•, which then decomposes to [S3N3]−. In situ electron paramagnetic resonance (EPR) spectroelectrochemical studies of S2N2 in both CH2Cl2 and CH3CN resulted in the detection of strong EPR signals from [S4N4]−• when electrolysis is conducted at −1.4 V; at more negative vol...

Chalcogen-transfer reagents? The bonding in the dicationic rings C2N2E2+ (see picture) differs from that in N-heterocyclic carbenes and their isovalent p-block analogues in accommodating a lone pair of electrons with π symmetry, as well as σ symmetry, on the chalcogen center. The labile electrophilic chalcogenium dications (E2+) are potentially versatile chalcogen-transfer reagents in reactions with a variety of inorganic and organic substrates.

Tetrasulfur tetranitride and tellurium tetrachloride react in dichloromethane to form a 1:1 adduct TeCl4·S4N4 (1). The crystal structure of 1 shows that TeCl4 is bonded to the S4N4 ring through a Te–N linkage. As a consequence, the transannular S···S bonds in S4N4 are broken and the molecule assumes an open, monocyclic conformation. The Te–N bond of 2.16(1) A is slightly longer than the single bond. The S–N bonds span a range of 1.55(1)–1.67(1) A. The adduct 1 was also characterized by mass spectrometry and Raman spectroscopy. The bonding and spectroscopic properties of 1 are compared by DFT calculations at the B3PW91/(RLC ECP) level of theory with those of BF3·S4N4 (2), SO3·S4N4 (3), AsF5·S4N4 (4), SbCl5·S4N4 (5) for which experimental structural information is available. The structural and bonding trends in TeF4·S4N4 (6), TeBr4·S4N4 (7), and SeX4·S4N4 [X = F (8), Cl (9), Br (10)] are also discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The reaction of (Me3SiNSN)2S with TeCl4 in CH2Cl2 affords Cl2TeS2N2 (1) and that of (Me3SiNSN)2Se with TeCl4 produces Cl2TeSeSN2 (2) in good yields. The products were characterized by X-ray crystallography, as well as by NMR and vibrational spectroscopy and EI mass spectrometry. The Raman spectra were assigned by utilizing DFT molecular orbital calculations. The pathway of the formation of five-membered Cl2TeESN2 rings by the reactions of (Me3SiNSN)2E with TeCl4 (E = S, Se) is discussed. The reaction of (Me3SiNSN)2Se with [PPh4]2[Pd2X6] yields [PPh4]2[Pd2(μ-Se2N2S)X4] (X = Cl, 4a; Br, 4b), the first examples of complexes of the (Se2N2S)2- ligand. In both cases, this ligand bridges the two palladium centers through the selenium atoms.

The use of the tris(alkylamido)phosphate OP[N(H)tBu]3 as an in situ source of the templating agent [tBuNH3]+ produces the copper halide chain {[tBuNH3]2[Cu3(μ3-OH)(μ2-H2O)Cl7]}n (1) in a solvothermal process; the novel antiferromagnetically coupled trinuclear fragment Cu3(OH)(H2O)Cl7 is the building block in the polymeric anion in 1.

Monomeric complexes with two or three terminal M=Se bonds, Sn4Se2(NtBu)4 or Ge4Se3(NtBu)4, respectively, are produced by oxidation of (MNtBu)4 (M = Sn, Ge) with selenium in hot toluene. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Solutions of (NSCl)3 in the presence of excess SO2Cl2 behave as a source of the synthetic equivalent "NSCl3" in reactions with methacrylonitrile or thioacetamide to give 4-cyanoisothiazole (78%) or 5-methyl-1,3,2,4-dithiadiazolium chloride (63%), respectively. In the reaction of this reagent with thiobenzamide both 5-phenyl-1,3,2,4-dithiadiazolium chloride (42%) and 3,5-diphenyl-1,2,4-thiadiazole (51%) are produced. The treatment of the (NSCl)3-SO2Cl2 system with 2-aminobenzenethiol yields 2,4-C6H3Cl2NSCl2, which is converted to 2,4-(C6H3Cl2N)2S upon heating at 80 °C in toluene or by reduction with Ph3Sb or mercury. The reaction of 2-aminobenzenethiol with excess SO2Cl2, in the absence of (NSCl)3, produces 2,4,6-C6H2Cl3NSCl2. Attempts to characterize the active species in the (NSCl)3-SO2Cl2 system by 14N and 33S nmr, Raman and infrared spectroscopy are also described. Keywords: cyclotrithiazyl chloride, isothiazole, dithiadiazolium, arylimidosulfurous dichloride, 14N nmr.