S-N bond distances

The calculated barrier to dissociation of the [S3N2] dication into [SN]" and [S2N] in the gas phase is 10.9 kcal mof . However, lattice-stabilization effects allow the isolation of [MEg] salts (M = As, Sb) of this six r-electron system in the solid state from the cycloaddition of [SN] and [S2N] cations in SO2 (Eq. 5.11)."° The S-S and S-N bond distances in the planar, monomeric dication are shorter than those in the... 

The S-N bond in [SO2N3] is much weaker than that in [SO3N3] as reflected in an increase in the S-N bond distance by 0.23 A in the Cs " salts.The S-N bond length in [Me4N][S02N3] is 2.00 A. " This marked difference can be attributed to the much weaker Lewis acidity of SO2 compared to that of SO3 which also results in lower thermal stability for the [SO2N3] anion. 

The eight-membered rings 13.14 normally adopt boat conformations in the solid state with short S=N bond distances (1.51-1.52 A) that are typical of sulfur diimides. There are no transannular S S contacts. The sole exception is the antimony derivative BuSb(NSN)2Sb Bu, which is a planar eight-membered ring. 

The [S2N]+ cation is an important reagent in S-N chemistry,63 especially in thermally allowed cycloaddition reactions with organic nitriles and alkynes, which give quantitative yields of heterocyclic cations (Scheme 3). It is conveniently prepared by reaction of S3N2C12 with AsF5 and S8 in liquid S02.63b The [SNS]+ cation is linear with S-N bond distances in the range indicating a bond order of two, i.e., S=N+=S. 

The pale yellow salt K2[SN2] is prepared from (Me3SiN)2S and K(OtBu).70 The dilithium salt is generated from (Me3SnN)2S and MeLi.71 The S=N bond distances in the [K(18-crown-6)]+ salt are ca. 0.05 A longer than the S=0 bonds in S02.72... 

The series E(NSO)2 (39a-c E=S, Se, Te) exhibit planar, acyclic structures with a cis arrangement about the two S=N bonds. The central E-N bonds are essentially single bonds. The S=N bond distances fall in the double bond range with a significant shortening of this bond along the series. 

X-ray structural determinations of the salts n-Bu. N SjNj and PPN SjNj show that the anion is an essentially planar, 6-membered ring with bond angles at nitrogen of ca. 123° and at sulfur ca. 117° (7). The S—N bond distances fall... 

Early studies on benzo[l,2-r 3,4-f ]bisthiadiazoles found S-N bond distances to be of the order of 1.620A <1996CHEC-II(7)841>, and subsequent analysis has revealed that benzobisthiadiazoles adopt planar conformations <1996CM570>. Additional studies have shown that benzo[l,2-r 4,5-f ]bisthiadiazole 17 has S-N bond lengths of approximately 1.601 A <1997T10169> and benzo [1,2- 4,5-,7 ]bisthiadiazole 18 has S-N bond lengths of 1.638 A <1997JA12136>. 

Nucleophilic substitution of fluorine in perfluorinated sulfonium ions yields the corresponding aminosulfonium ions when reacted with Me3SiNMe2 [Eq. (4.66)]. Crystal structure analysis of CF3S(NMe2)2+, (CF3)2SNMe2+, and F2SNMe2+ hexa-fluoroarsenates gives similar S—N bond distances (1.605, 1.578, and 1.535 A, respectively) 215,244... 

Little data has been reported on x-ray structural methods. In a study of benzo[l,2-c 3,4-c ]bis-thiadiazole and a monoselenium analogue, S—N bond distances of the order of 1.62 A were found and attributed to the heterocyclic rings being quasi aromatic, but with severe distortion of the aromatic character of the carbocyclic ring <84ZN(B)485>. 

The SNS+ cation is a linear species isoelectronic with CS2. The S-N bond distances are 146-147pm. The NS2+ cation exhibits a very narrow " N NMR resonance at —91 ppm (y /2= 8Hz) in SO2 and this technique is useful for monitoring reactions of the cation. ... 

The crystal and molecular structures of 5-chloro-2,l-benzisothiazole have been determined.115 The C—S and S—N bond distances are 1.664 and... 

The S-N bond distances exhibited are 2.10-2.50 A, which are within the sum of the van der Waals radii of nitrogen and sulfur (3.35 A). A linear relationship is observed between the and 13C NMR chemical shifts of the N-methyl group and the Hammett <7m-substituent constants. 

The thermal stability of substituted thiatriazines depends highly on the symmetry of substitution in the 3- and 5-positions. Identical substituents in the 3- and 5-position lead to a shortened exocyclic S-N bond distance in the 1-position.29... 

For the cation, the calculated bond distances and angles differ quite markedly from the X-ray data [85JCS(D)1405] (Section XV, Table XI). However, partial occupancy of the predominantly antibonding 3+ LUMO (Section XIII) should lead to an increase in C—S and S—N bond distances. Although there are no X-ray structural data available for any mono-1,3,2,4-dithiadiazolyls, the crystal structure of the diradical [p-C6H4(CNSNS)2] (Section XXIII.E) shows that these distances do indeed increase, compared to the dication, but appreciable discrepancies still exist between theoretical and experimental data sets. 

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