On the staudinger reaction of SP(N3)3 with PPh3 and (Me3Si)2N-(Me3Si)N-PPh2

The Staudinger reactions of SP(N-3)(3) (1) with 1, 2 and 3 equiv. of triphenylphosphane PPh3 and (TMS)(2)N-(TMS)N-PPh2 (2) have been investigated (TMS = Me3Si). Reaction with PPh3 yields the single and double Staudinger products SP(N-3)(2)-NPPh3 (3) and SP(N-3)(NPPh3)(2) (4), but not the triple, while the reaction with 2 results only in the formation of the single Staudinger product SP(N-3)(2)NPPh2[N(TMS)N(TMS)](2) (5). Compound 5 is air- and moisture-sensitive but stable under argon over a long period in the solid state and in common organic solvents. Although there are covalently bound azide groups in 3, 4 and 5, these Staudinger products are neither shock- nor heat-sensitive in contrast to 1. Furthermore 3, 4 and 5 are easily prepared in bulk (yield > 95%), and unlimitedly stable when cooled and stored in the dark. Compound 5 is thermally stable up to over 150 degrees C while 3 and 4 are stable only up to 96 degrees C. However, when a solution of 5 is heated, a new surprising eight-membered ring (6) is formed in an intermolecular TMS-N-3 elimination reaction. The structure and bonding is discussed on the basis of experimental X-ray data and theoretical B3LYP calculations (thermodynamics, energy landscape and charge distribution). (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.