2-Amino-substituted 1,3,2-diazaphospholenes

Abstract

2-Amino-substituted 1,3,2-diazaphospholenes 2-4 were synthesised by treatment of 1,3-dimesityl-2-chloro-1,3,2-diazaphospholene with one equivalent of lithium N,N′-dimesityl-2,4-pentanedioniminate, sodium amide, or a mixture of 3,5-diphenylpyrazole and NEt 3. In contrast, 1,3-di-tert.butyl-1,3,2-diazaphospholene reacted with sodium amide in a 2:1 molar ratio to afford the bis-diazaphospholenyl-imine 5. All products were characterised by spectroscopic data and single-crystal X-ray diffraction studies. Evaluation of trends in bond lengths suggest the presence of similar residual π-delocalisation effects as had previously established in P-Cl or P-H substituted diazaphospholenes but disclosed that 2-5 differ from these compounds in lacking all signs for a concomitant lengthening of the exocyclic P-X bonds. The results of computational studies allowed to conclude that the deviating behaviour of diazaphospholenes with differentP-X substituents is attributable to a shift in the balance between n(N)→σ*(P-X)- and n(X)→σ* (P-N)-hyperconjugation interactions. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.