Reactions Between Aminophosphinyl-Substituted Sulfur Diimides and Amino-Imino-Thiophosphoranes. Cycloaddition or Exchange

Abstract

Reactions between N,N′-di-tert-butyl sulfur diimide, ^tBu(NSN)^tBu (1), and the amino-imino-thiophosphoranes Me₃Si(R)NP(S)═N^tBu [R = ^tBu (6a), SiMe₃ (6b)] afforded the 1,2,4,3-thiadiazaphosphetidines 7a,b via [2+2]cycloaddition. The corresponding products 8a,b were obtained when one ^tBu group in 1 was replaced by a 2-(1,3-di-tert-butyl-1,3,2-diazaphosphoridinyl) group (2). In contrast, the reactions between 6a and the three different 2-(1,3-di-tert-butyl-1,3,2-diazaphospholidinyl)-substituted sulfur diimides [CH₂(N^tBu)]₂P(NSN)R¹ [R¹ = ^tBu (3), Me₃Si (4), [CH₂(N^tBu)]₂P (5)] gave the same phosphorus compound 9 which was identified as a zwitterionic bicyclic amino-imino-thiophosphorane. Exchange between imino groups at phosphorus and sulfur is the first step in this reaction, followed by 1,3-shifts of Me₃Si and phosphinyl groups and the final intramolecular N—P coordinative stabilization. The products were characterized by multinuclear NMR (¹H-, ¹³C-, ¹⁵N-, ²⁹Si- and ³¹P NMR). The molecular structures of the cycloadduct 8a and the zwitterionic compound 9 were determined by single crystal X-ray analyses. In solution, NMR spectra show that 8a is present as a single isomer in solution, whereas NMR spectra of 9 at 218 K indicate the presence of two isomers (86:14).

Key Words:

• Sulfur diimides
• amino-imino-thiophosphoranes
• [2 + 2]cycloaddition
• multinuclear NMR
• X-ray analyses.