Thermodynamic investigations of the staudinger reaction of trialkylphosphines with 1-adamantyl azide and the isolation of an unusual s-cis phosphazide.
The reaction of PR(3) (R = Cy, (i)Pr) with 1-adamantyl azide (N(3)Ad) in benzene results in an equilibrium of the starting material and the phosphazide R(3)PN(3)Ad. Thermodynamic and kinetic measurements were taken of the reaction of P(i)Pr(3) with N(3)Ad and yielded DeltaH = -18.7 +/- 1.0 kcal mol(-1), DeltaS = -52.5 +/- 2.0 cal mol(-1) K(-1), DeltaH() = +12.0 +/- 1.0 kcal mol(-1), and DeltaS() = -25.3 +/- 1.2 cal mol(-1) K(-1). The phosphazides, R(3)PN(3)Ad, do not readily lose N(2) for R = Cy and (i)Pr; however, the reaction of PMe(3) with N(3)Ad results in a smooth formation of the phosphazene Me(3)PNAd with N(2) loss. Calorimetric investigations of this reaction led to an estimation of DeltaH = -40 +/- 3 kcal mol(-1) for the loss of N(2) from the intermediate phosphazide R(3)PN(3)Ad and also yield an estimation of 72 +/- 5 kcal mol(-1) for the bond dissociation energy of the PN bond in R(3)PNAd. The X-ray crystal structure of Cy(3)PN(3)Ad is reported.
Fortman
George C
GC
Department of Chemistry, University of Miami, Coral Gables, Florida 33146, USA.
Captain
Burjor
B
Hoff
Carl D
CD