Names | |||
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Preferred IUPAC name sulfur mononitride | |||
Systematic IUPAC name Azaniumylsulfanidylidyne | |||
Other names
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Identifiers | |||
3D model (JSmol) | |||
Abbreviations | (NS)(.) | ||
ChEBI | |||
ChemSpider | |||
660 | |||
PubChem CID | |||
CompTox Dashboard (EPA) | |||
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Properties | |||
NS | |||
Molar mass | 46.07 g·mol−1 | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Sulfur mononitride is an inorganic compound with the molecular formula SN. It is the sulfur analogue of and isoelectronic to the radical nitric oxide, NO. It was initially detected in 1975, in outer space in giant molecular clouds and later the coma of comets. [1] This spurred further laboratory studies of the compound. Synthetically, it is produced by electric discharge in mixtures of nitrogen and sulfur compounds, or combustion in the gas phase and by photolysis in solution. [2]
The NS radical is a highly transient species, with a lifetime on the order of milliseconds, but it can be observed spectroscopically over short periods of time through several methods of generation. NS is too reactive to isolate as a solid or liquid, and has only been prepared as a vapor in low pressure or low-temperature matrices due to its tendency to rapidly oligomerize to more stable, diamagnetic species. [3]
Transmission of electric discharge through a glass tube with quartz windows containing a mixture of nitrogen and sulfur vapor (rigorously free of oxygen) results in the spectrum of emitted light gaining bands consistent with the formation of NS. [4]
Passing a mixture of gaseous N2 and S2Cl2 through the side arm of an absorption cell undergoing microwave discharge produces NS. Infrared diode laser spectroscopy taken using this method allowed for derivation of the equilibrium rotational constant, and therefore calculation of the equilibrium bond length as 1.4940 Å. [5]
With low pressure microwave discharge of elemental nitrogen and sulfur, followed by low temperature trapping in argon matrices, one obtains a mixture of products including NS, NNS, SNS, and NSS. By adding excess sulfur, SSNS is also produced. [6]
Methane was premixed with fuel in the form of either O2, N2O, or air and burned at ambient pressure. The source of nitrogen was introduced by addition of 1-5 mole% NH3 gas and sulfur by 0.01-0.5 mol% H2S or SF6 gas. A steady state concentration of NS within the flame front is observed by laser-induced fluorescence (LIF) spectrum. [7]
The NS radical was detected by LIF spectrum as the product of photolysis of tetranitrogen tetrasulfide (N4S4) gas by a 248 nm laser. [8]
Aerated solutions of Cr(CH3CN)5(NS)2+ are highly photoactive and prone to rapid decomposition. Deaerated solutions of Cr(CH3CN)5(NS)2+ in acetonitrile are stable as long as they are kept in the dark. Continuous photolysis using 366 nm light is slow, while using a 355 nm pulsed laser results in faster labilization of NS. [9]
Evidence suggests that NS can react with itself to reach N2S2, N4S4, and polymers of the form (NS)x. (NS)x forms from polymerization of cyclo-N2S2. [3]
Trans-NSSN results from direct dimerization of NS. [3]
N3S3 has been observed through photoelectron spectroscopy of vapors of the (SN)x, polymer, but has not yet been characterized further. Attempts to produce N3S3 by oxidation of [PPN] [S3N3] were unsuccessful. [10] Its theorized that rapid dimerization to (N3S3)2 will disproportionate irreversibly to N4S4 and N2S2. [3]
The radical decay time of NS alone is on the order of 1-3 ms. As evident by no change to this decay time upon addition of NO or O2 at ambient temperatures, the NS radical is unreactive with NO and O2. However, rapid, first-order decay is observed with the addition of NO2. This reaction is proposed to proceed through various intermediates, ultimately reaching final products of N2 and SO2. [8] This rapid reaction occurs with a rate constant of k = (2.54 ± 0.12) × 10−11 cm3 molecules−1 s−1 at 295 K. By use of Density Functional Theory based computational calculations, the minima and transition states of the potential energy surface of this reaction have been predicted. [8]
Within the inner coma of comets, many reactions are theorized to be relevant to the formation and reactivity of the NS radical. [11]
As a ligand, NS acts as a σ-donor and π-acceptor, forming metal-thionitrosyl complexes. Transition-metal thionitrosyl complexes have been prepared by the following procedures: [12]
From X-ray crystallography of many of such metal-thionitrosyl complexes, one can observe that the M-N-S bond angle is nearly linear, suggesting sp hybridization about N. Short M-N distances and long N-S distances reflect the resonance structure of M=N=S having greater contribution than M-N≡S. [12]
Typical v(NS) IR stretching frequencies are approximately 1065 cm−1 for low-valent transition metal complexes and around 1390 cm−1 in the high valent cases, whereas the free gas-phase radical exhibits a 1204 cm−1 signal. [3]
The electronic structures of Fe(S2CNMe2)2(NE), where E=O, S, or Se were calculated using Density Functional Theory methods. It was found that the large Mulliken spin density remained concentrated on the Fe(NE) core and Fe-N distances experienced little change from the chalcogen atom used. The HOMO of both nitrosyl and thionitrosyl complexes retained 1a1 (dz2) character. The small changes in the energies of the spin orbitals of the complexes, particularly the decreased energetic gap between 2b2 and 1b1 and 2b1 and 1b1 orbitals is attributed to NS being a weaker π-acceptor than NO. [9]
When a spin-trapping agent, such as Fe(S2CNEt2)2 is present during the photolysis of Cr(CH3CN)5(NS)2+, new S=1/2 EPR bands are observed, attributed to the formation of Fe(S2CNEt2)2(NS), and the signal from Cr(CH3CN)5(NS)2+ disappears. This suggests that the NS radical has transferred from the chromium complex to the iron complex. [9]
This was particularly significant as it was the first controlled and well-characterized reactivity of NS in solution. Further, it showed the potential for similar reactivity in known reactions with NO, such as use of this iron dithiocarbamate complex. [3]
The valence electrons of this compound match those of nitric oxide. Sulfur mononitride can be described as some average of a set of resonance structures. The singly bonded structure (first resonance structure shown) has little contribution. The formal bond order is considered to be 2.5.
The decreasing electronegativity with increasingly heavy chalcogenides leads to a reversal of the dipole. In NO, oxygen is the more electronegative element. In NS, nitrogen is more electronegative. The NS radical is significantly more unstable and prone to catenation than NO. [3]
NO | NS | NSe | |
---|---|---|---|
△fH°, kJ·mol−1 | +90.24 | +283.4 | - |
△fG°, kJ·mol−1 | +86.57 | +217.2 | - |
S° 273, J/deg | +207.5/273 K | +222.093/298 K | - |
B.D.E. | 627.6 | 463±24 | 370 Cal |
d(N-E), Å | 1.1517 | 1.4938 | 1.6634 |
Bond order | 2.5 | 2.5 | 2.5 |
Molecules in distant astronomical regions can be identified based on their unique rotational transitions, of which the corresponding microwave frequencies are detectable by antennae on Earth. The presence of interstellar sulfur mononitride was first reported in 1975 by back to back letters published in the Astrophysical Journal.
Interstellar NS was first identified in the giant molecular cloud Sagittarius B2 (Sgr B2). Its presence was reported in two concurrent articles. Measurements conducted with the National Radio Astronomy Observatory telescope at Kitt Peak, Arizona, picked up millimeter-wavelength radiation in Sgr B2 attributed to c-state transitions of NS in the 2Π1/2 state from J=5/2 to J=3/2 at 115.16 GHz. [15] This assignment was confirmed by measurements conducted at University of Texas Millimeter Wave Observatory on Mount Locke as well, demonstrating J=5/2 to J=3/2 c-state and d-state transitions at 115.16 GHz and 115.6 GHz, respectively. Hyperfine interactions arise from 14N magnetic and electric-quadrupole moments. [16]
NS has been detected in regions responsible for forming massive stars, such as giant molecular clouds like Sg B2 and cold, dark clouds such as L134N and TMC-1. One survey found NS in 12 out of 14 GMC studied, additionally observing the J=7/2 to J=5/2 and J=3/2 to J=1/2 transitions at 161 and 69 GHz, respectively. The abundance of NS in these regions was approximated based on the ratio of observed to intrinsic hyperfine line strengths as well as modeling using a statistical equilibrium program, finding low abundance in all except the Orion molecular cloud. [17]
NS was also observed in the coma of the comets Hyakutake and Hale-Bopp. It's believed that the observed abundance is higher than gas-phase, ion-molecule models due to an unidentified species X-NS photo-dissociating to release NS. [11]
Detection of NS at steady state concentration in the reaction zone of the combustion of methane doped with ammonia and a fuel sulfur such as H2S suggests that NS may be an important reactive intermediate in burning of hydrocarbon flames in a reducing atmosphere, which is relevant to coal pyrolysis and combustion. [7]
Fossil fuels contain bound nitrogen, which releases elevated levels of nitric oxide emissions during combustion. NOx emissions can be controlled by denitrification of the fuel source, combustion chamber modification, or both. One developing technique is the reburning of NOx, which is reduced to N2. These fuels also contain variable amounts of sulfur, which is oxidized to SO2. Therefore, understanding the reactivity of NO and SO2 is crucial to the process of reburning. The experimental apparatus to test this involved a primary flame for producing combustion products, which were mixed with NO and SO2 to mimic coal burning byproducts. This mixture was fed into the burner at atmospheric pressure. 1-2% decrease in NOx concentration is observed at various percentages of total fuel inlet (reburn ratio) in the presence of 0.1% SO2, which is attributed to the formation of H2S, HS, and the resulting reaction with NO, giving rise to NS. Reaction: HS + NO > NS + OH. [18]
A metallocene is a compound typically consisting of two cyclopentadienyl anions (C
5H−
5, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to [Cp2ZrCH3]+ catalyze olefin polymerization.
An oxide is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– ion with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 that protects the foil from further oxidation.
Sulfur monoxide is an inorganic compound with formula SO. It is only found as a dilute gas phase. When concentrated or condensed, it converts to S2O2 (disulfur dioxide). It has been detected in space but is rarely encountered intact otherwise.
In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.
Chromocene is the organochromium compound with the formula [Cr(C5H5)2]. Like structurally related metallocenes, chromocene readily sublimes in a vacuum and is soluble in non-polar organic solvents. It is more formally known as bis(η5-cyclopentadienyl)chromium(II).
Metal nitrosyl complexes are complexes that contain nitric oxide, NO, bonded to a transition metal. Many kinds of nitrosyl complexes are known, which vary both in structure and coligand.
Hexafluorophosphate is an anion with chemical formula of [PF6]−. It is an octahedral species that imparts no color to its salts. [PF6]− is isoelectronic with sulfur hexafluoride, SF6, and the hexafluorosilicate dianion, [SiF6]2−, and hexafluoroantimonate [SbF6]−. In this anion, phosphorus has a valence of 5. Being poorly nucleophilic, hexafluorophosphate is classified as a non-coordinating anion.
Silver hexafluorophosphate, sometimes referred to "silver PF-6," is an inorganic compound with the chemical formula AgPF6.
In organometallic chemistry, a transition metal indenyl complex is a coordination compound that contains one or more indenyl ligands. The indenyl ligand is formally the anion derived from deprotonation of indene. The η5-indenyl ligand is related to the η5cyclopentadienyl anion (Cp), thus indenyl analogues of many cyclopentadienyl complexes are known. Indenyl ligands lack the 5-fold symmetry of Cp, so they exhibit more complicated geometries. Furthermore, some indenyl complexes also exist with only η3-bonding mode. The η5- and η3-bonding modes sometimes interconvert.
Rhodocene is a chemical compound with the formula [Rh(C5H5)2]. Each molecule contains an atom of rhodium bound between two planar aromatic systems of five carbon atoms known as cyclopentadienyl rings in a sandwich arrangement. It is an organometallic compound as it has (haptic) covalent rhodium–carbon bonds. The [Rh(C5H5)2] radical is found above 150 °C (302 °F) or when trapped by cooling to liquid nitrogen temperatures (−196 °C [−321 °F]). At room temperature, pairs of these radicals join via their cyclopentadienyl rings to form a dimer, a yellow solid.
Disulfur monoxide or sulfur suboxide is an inorganic compound with the formula S2O, one of the lower sulfur oxides. It is a colourless gas and condenses to give a roughly dark red coloured solid that is unstable at room temperature.
In organometallic chemistry, metal sulfur dioxide complexes are complexes that contain sulfur dioxide, SO2, bonded to a transition metal. Such compounds are common but are mainly of theoretical interest. Historically, the study of these compounds has provided insights into the mechanisms of migratory insertion reactions.
Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur with the formula S2O2. The solid is unstable with a lifetime of a few seconds at room temperature.
Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.
In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOmXn, where X is a halogen. Known oxohalides have fluorine (F), chlorine (Cl), bromine (Br), and/or iodine (I) in their molecules. The element A may be a main group element, a transition element, a rare earth element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure.
Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula [(η5-C5H5)Fe(CO)2]2, often abbreviated to Cp2Fe2(CO)4, [CpFe(CO)2]2 or even Fp2, with the colloquial name "fip dimer". It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but less soluble in carbon tetrachloride and carbon disulfide. Cp2Fe2(CO)4 is insoluble in but stable toward water. Cp2Fe2(CO)4 is reasonably stable to storage under air and serves as a convenient starting material for accessing other Fp (CpFe(CO)2) derivatives (described below).
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Transition metal thiolate complexes are metal complexes containing thiolate ligands. Thiolates are ligands that can be classified as soft Lewis bases. Therefore, thiolate ligands coordinate most strongly to metals that behave as soft Lewis acids as opposed to those that behave as hard Lewis acids. Most complexes contain other ligands in addition to thiolate, but many homoleptic complexes are known with only thiolate ligands. The amino acid cysteine has a thiol functional group, consequently many cofactors in proteins and enzymes feature cysteinate-metal cofactors.
(Cyclopentadienyl)titanium trichloride is an organotitanium compound with the formula (C5H5)TiCl3. It is a moisture sensitive orange solid. The compound adopts a piano stool geometry.
Germyl, trihydridogermanate(1-), trihydrogermanide, trihydridogermyl or according to IUPAC Red Book: germanide is an anion containing germanium bounded with three hydrogens, with formula GeH−3. Germyl is the IUPAC term for the –GeH3 group. For less electropositive elements the bond can be considered covalent rather than ionic as "germanide" indicates. Germanide is the base for germane when it loses a proton.