(O→Si)-Chelate difluorides R 3 R 2 NCH(R 1 )C(O)N(CH 2 SiMe 2 F) 2 ( 9a–c , R 1 R 2 = (CH 2 ) 3 , R 3 = Ms (a), Ts (b); R 1 = H, R 2 = Me, R 3 = Ms (c)), containing one penta- and one tetracoordinate silicon atoms were synthesized by silylmethylation of amides R 3 R 2 NCH(R 1 )C(O)NH 2 , subsequent hydrolysis of unstable intermediates R 3 R 2 NCH(R 1 )C(O)N(CH 2 SiMe 2 Cl) 2 ( 7a–c ) into 4-acyl-2,6-disilamorpholines R 3 R 2 NCH(R 1 )C(O)N(CH 2 SiMe 2 O) 2 ( 8a–c ) and the reaction of the latter compounds with BF 3 ·Et 2 O. The structures of disilamorpholines 8a , c and difluoride 9a were confirmed by an X-ray diffraction study. According to the IR and NMR data, the O→Si coordination in solutions of these compounds was weaker than that in the solid state due to effective solvation of the Si–F bond. A permutational isomerisation involving an exchange of equatorial Me groups at the pentacoordinate Si atom in complexes 9a–c was detected, and its activational parameters were determined by 1 H DNMR. In silico estimation of possible pharmacological effects and acute rat toxicity by PASS Online and GUSAR Online services showed a potential for their further pharmacological study.