Formation of the Novel Six-Coordinate Atrane Cation in [FMeSn(HMeNCH₂CH₂)₂N(CH₂CH₂NMe)]BF₄

The reaction of the azastannatranes RSn(NMeCH₂CH₂)₃N 1 (R = Me), 2 (R = n-Bu), and 3 (R = Ph) with BF₃·Et₂O in THF gave the novel six-coordinate tin compounds 4−6, respectively, in which BF₃ adds across one of the three covalent Sn−N bonds to give a F−Sn←NMe(BF₂) linkage. The tricyclic atrane framework retained in the reaction with BF₃·Et₂O is preserved under hydrolysis conditions with substoichiometric amounts of water. A hydrolysis product of 4 is the new fluorotin salt [FMeSn(HMeNCH₂CH₂)₂N(CH₂CH₂NMe)]BF₄ [7(BF₄)] whose structure, determined by X-ray analysis, also features a six-coordinate tin atom. The IR and NMR spectra of 4−6 confirm their six-coordinate nature. The ¹H and ¹³C NMR spectra are assigned using COSY, NOESY, and selectively proton decoupled ¹³C NMR spectral techniques. Crystallographic parameters for 7(BF₄) are as follows:  triclinic space group P1̄, a = 8.295(2) Å, b = 8.924(2) Å, c = 13.639(2) Å, α = 88.59(2)°, β = 74.83(2)°, γ = 79.99(2)°, and Z = 2.