Synthesis, Properties, and Bishomoaromaticity of the First Tetrahalogenated Derivative of a 1, 5-Diphosphadithiatetrazocine: A Combined Experimental and Computational Investigation

• Published in: Inorganic chemistry 2010-04, Vol.49 (8), p.3810-3815
• Main Authors: Chivers, Tristram, Hilts, Robert W, Jin, Peng, Chen, Zhongfang, Lu, Xin
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic902428j

The first example of a tetrahalogenated derivative of a diphosphadithiatetrazocine, 1,5-Cl2P(NSN)2PCl2 (3), was synthesized by cyclocondensation of a 2:1 mixture of SCl2 and SO2Cl2 with Cl2P(NSiMe3)N(SiMe3)2 in CH2Cl2. The heterocycle 3 was isolated as an orange, moisture-sensitive, thermally labile solid and characterized by mass spectrometry, 31P NMR, and UV−visible spectroscopy. The low-field 31P NMR chemical shift (93.7 ppm) is indicative of a cross-ring S---S interaction in the eight-membered P2N4S2 ring, and this conclusion is supported by density-functional computations. Compound 3 exhibits unusual physical properties compared with those of the known tetraalkyl or aryl derivatives; mild heating (90 °C) produces an orange rubbery material. The bishomoaromatic character of the diphosphadithiatetrazocine 1,5-R2P(NSN)2PR2 (R = Me, Cl, F) is evinced by the negative nucleus-independent chemical shift (NICS) values, and the through-space bishomoconjugation in the eight-membered ring decreases with increasing electronegativity of the substituents attached to the P atoms.