Stannylenes based on alkyl- and aryl-substituted diethylenetriamines: synthesis, structure, and catalytic activity

The reaction of 1,4,7-trisubstituted 1,4,7-triazaheptane derivatives RN(CH₂CH₂NHR′)₂ with one equivalent of Lappert’s stannylene Sn[N(SiMe₃)₂]₂ afforded the corresponding stannylenes RN(CH₂CH₂NR)₂Sn (R′ = Bn, R = Et (1h), Bn (1i); R′ = Et, R = Et (1j), Bn (1k); R′ = Ph, R = Et (1l), Bu^t (1m)) in satisfactory yields. According to the ¹H, ¹³C (for 1h—m), and ¹¹⁹Sn (for 1i,k—m) NMR data and the X-ray diffraction data (for stannylenes 1h—m are monomeric; the coordination number of the tin atom is 3. Stannylenes 1h—m were tested as initiators for the ε-caprolactone polymerization. The highest activity was shown by derivatives 1l,m containing phenyl groups at the terminal nitrogen atoms of the ligand. Stannylenes 1h—k containing ethyl and benzyl substituents are less active in the ring-opening polymerization of ε-caprolactone.