کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1307462 | 975140 | 2008 | 19 صفحه PDF | دانلود رایگان |

Reaction of SNSSbF6 and DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone (1)) in SO2 solution in a 2:1 ratio afforded the dicycloaddition product 1(SNS)2(SbF6)2 · SO2 in 85% isolated yield. The dicycloaddition product 1(SNS)2(SbF6)2 · SO2 was fully characterized by IR, Raman, NMR, elemental analysis, and single crystal X-ray crystallography. The product of the site selective dicycloaddition of SNS+ at the nitrile functionalities of 1 represents the first structurally characterized ortho-bis-1,3,2,4-dithiadiazolylium salt which adopts a conformation that utilizes the intramolecular Sδ+–Oδ− electrostatic interactions. The reaction of 1 and SNS[Al(OC(CF3)4] in a 1:1 ratio yielded only the monocycloaddition product 1(SNS)[Al(OC(CF3)3)4] indentified by multinuclear 13C, 14N, 19F, 27Al NMR in SO2 solution. The assignment of the 13C NMR of 1(SNS)+ in SO2 solution, were supported by comparison of the calculated (MPW1PW91/6-31G∗) 13C NMR and experimental chemical shifts, and by comparison of the observed chemical shifts of the related 2(SNS)+ produced on reacting the mono-nitrile CDMQ (2-cyano-5,6-dichloro-3-methoxy-1,4-benzoquinone (2)) with SNS+ (as the SbF6- salt). The reaction of SNSSbF6 with TCNE (1,1,2,2-tetracyanoethylene (3)) gave the tri-cycloaddition product 3(SNS)3(SbF6)3 · SO2 (IR, Raman microscopy and X-ray crystallography) in 40% yield.The energetics of the cycloaddition reactions of SNS+ with 1–3 and other multifunctional unsaturated centers (e.g. HCC–CN, NC–CN, C(CN)3-, o,m,p-(CN)2C6H4, 1,3,5-(NC)3C6H3, 4–10, previously reported, see Chart 1), were estimated in the gas phase (MPW1PW91/6-31G∗), solution (PBE0/6-311G∗) and in the solid state by the ‘volume based thermodynamics’ (VBT) approach. The general thermodynamic trends associated with the stepwise cycloaddition of SNS+ with multifunctional nitriles were established. The 1:1 cycloaddition products were calculated to be stable in the gas phase and solution, while in the solid state the larger lattice enthalpy of the 1:2 salt, relative to twice that of the 1:1 salt, favored the 1:2 cycloaddition product.
This work shows that the extensive and general cycloaddition chemistry of SNS+ as MF6− (M = As, Sb) salts with multifunctional nitrile can be expalined by a simple thermodynamic model, employing gas-phase and solution quantum chemical calculations and solid state estimates using the ‘volume based thermodynamic’ approach. Both our results and previous experimental results can be accounted for using this model. The cycloaddition chemistry of SNS+ provides access to a variety of thiazyl heterocycles that are not typically available by other synthetic methods, and herein we extend the cycloaddition chemistry to prepare a new class of redox active, hybrid-dithiadiazolylium salts.Figure optionsDownload as PowerPoint slide
Journal: Inorganica Chimica Acta - Volume 361, Issue 2, 15 January 2008, Pages 521–539