Polymorphism of crystalline poly(hydroxymethyl) compounds. VIII. Structures of the tris(hydroxymethyl)aminomethane hydrogenhalides, (HOH2C)3CNH3+.X− (X=F,Cl,Br,I)

Three of the title compounds, TrisH+.X - (X = F,CI,Br), are isostructural: rhombohedral, R3 (H), Z= 6. At 294 K the crystal data are: TrisH+.F-: M r= 141.2, a=7.123(6), c= 22.47 (2),/~, V= 987.3/~3, D x = 1.425, D m = 1.418 Mg m -3, /t(Cu Ka)= 1.21mm-1 (only crystal data were ob- tained for this compound). TrisH+.Cl-: Mr,= 157.6, a = 7.569 (1), c = 24.694 (4) A, V= 1225.2/k 3, D x= 1.278, D m= 1.275Mgm -3, g(CuKs)=3.78mm -l, F(000) = 504; final R = 0.072 for 266 unique reflec-