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

Abstract

The Staudinger reactions of SP(N3)3 (1) with 1, 2 and 3 equiv. of triphenylphosphane PPh3 and (TMS)2N-(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(N3)(NPPh 3)2 (4), but not the triple, while the reaction with 2 results only in the formation of the single Staudinger product SP(N 3)2NPPh2[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°C while 3 and 4 are stable only up to 96°C. However, when a solution of 5 is heated, a new surprising eight-membered ring (6) is formed in an intermolecular TMS-N3 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). © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.