Acyclic Sulfur−Nitrogen Compounds. Syntheses and Crystal and Molecular Structures of Bis((trifluoromethyl)sulfonyl)amine ((CF₃SO₂)₂NH), Magnesium Hexaaquo Bis((trifluoromethyl)sulfonyl)amide Dihydrate ([Mg(H₂O)₆][(CF₃SO₂)₂N]₂·2H₂O), and Bis(bis(fluorosulfonyl)amino)sulfur ((FSO₂)₂NSN(SO₂F)₂)

Abstract

The syntheses of three acyclic (fluorosulfonyl)− or ((trifluoromethyl)sulfonyl)−nitrogen derivatives and their crystal and molecular structures are reported. The structures of bis((trifluoromethyl)sulfonyl)amine (1; (CF3SO2)2NH) and the corresponding anion in magnesium hexaaquo bis((trifluoromethyl)sulfonyl)amide dihydrate (2; [Mg(H2O)6][(CF3SO2)2N]2·2H2O) shed some light on the observed high gas-phase acidity of (CF3SO2)2NH. Extensive electron delocalization in the anion [(CF3SO)2N]- from planar, sp2-hybridized nitrogen into 3d orbitals of sulfur results in a noticeable shortening of the S−N bond on deprotonation. Similar electron delocalization is observed for the third compound, bis(bis(fluorosulfonyl)amino)sulfur (3; (FSO2)2NSN(SO2F)2), which features planar nitrogens with nearly six equidistant S−N bonds and extremely short S−O and S−F bonds. Compounds 2 and 3 have not been reported previously. Their unexpected, accidental formation and their characterization will be discussed. Compound 1 crystallizes in the space group Pccn (No. 56) with a = 16.404(3) Å, b = 5.535(1) Å, c = 9.557(2) Å, and Z = 4. Compound 2 crystallizes in the space group P21/n (No. 14) with a = 6.400(1) Å, b = 14.300(1) Å, c = 14.421(1) Å, β = 97.45(1)°, and Z = 2. Compound 3 crystallizes in the space group P21/c (No. 14) with a = 12.762(1) Å, b = 6.744(1) Å, c = 13.627(1) Å, β = 91.42(1)°, and Z = 4.