Chemistry of compounds containing sulphur-nitrogen bonds

Abstract

<p>The sulfur-nitrogen bonds in N,N'-monothiobisdialkylamines (N,N,N',N'-tetraalkylsulfoxylic diamides) and N,N'-dithiobisdialkyl-amines have been shown to undergo new reactions. The reaction of the former compounds with heptasulfurmide, (S₇NH), has led to the formation of the new compounds N,N-dialkyl-N,N'-cycloheptathiosul-foxylic diamides (S₇NSNR₂, R=CH₃, C₂H₅, CH(CH₃)₂, C₆H₁₁) in good yields. These compounds have been shown by NMR spectroscopy to have slow N-S bond rotation at room temperature. Structural studies suggested that the slow bond rotation is caused by strong pπ-dπ bonding in the single N-S bonds. The strengths of the π-interaction appears to be a function of the substituents of the and sulfur atoms. A synergic type of bonding is used to describe these saturated sulfur-nitrogen systems.</p> <p>The S-N bonds in the N,N'-thiobisdialkylamines have also been found to be very reactive towards chlorine substituted phosphorus compounds. The reaction proceeds via an electrophilic attack of phosphorus on sulfur with subsequent loss of chloride ion from the intermediate. This species then rapidly rearranges to give a product in which the phosphorus atom has inserted into the sulfur-nitrogen bond. The stability of this species has been found to be dependent on the number of phenyl group the insertion product loses N,N- dialkyl-N-sulfenyl chloride. Further reactions of these species are discussed. With two phenyl groups, the insertion product is quite stable. It, however, has been found to be susceptible to attack by another mole of (C₆H₅)₂PCl to give further products. A discussion of the mechanisms of reactions in this system is given.</p> <p>The sulfur-nitrogen bonds in the N,N'-dithiobisdialkylamines are considerably more stable towards these phosphorus compounds. The reactions that these compounds undergo suggest that the initial reaction involves fission of the sulfur-sulfur bond rather than N-S bond insertion. The reaction of (C₆H₅)₃P with these compounds to produce (C₆H₅)₃PS and the N,N'-thiobisamine offers a convenient method of purifying this latter compound from its major contaminant, the former compound. The reactions with (C₆H₅)PCl₂ and PCl₃ offer convenient methods of preparation of the compounds (C₆H₅)P(S)(Cl)(N(CH₃)₂) and ((CH₃)N₂)P(S)Cl₂ which have applications as insecticides. (C₆H₅)₂PCl and ((CH₃)₂N)₂S₂ have been shown to form a more complicated system in which reactions analogous to the two systems just discussed, occur. A discussion of the mechanisms of these reactions is presented. The chemical behaviour of these compounds suggests that the N-S bonds is the N,N'-dithiobisdialkylamines are considerably less reactive towards chlorine substituted phosphorus compounds than those in the monothio analogues.</p>