STRUCTURE OF THE NEW ELECTROPHILIC FLUORINATING AGENT 1-CHLOROMETHYL-4-FLUORO-1,4-DIAZONIABICYCLO[2.2.2]OCTANE BIS(TETRAFLUOROBORATE) AND 2 OF ITS MONOQUATERNARY ANALOGS

1-Chloromethyl-4-fluoro-1,4-diazoniabi-cyclo[2.2.2]octane bis(tetrafluoroborate) (1), C7H14ClFN22+.2BF4-, M(r) = 354.26, orthorhombic, Pnma, a = 12.599 (6), b = 7.653 (3), c = 14.094 (7) angstrom, V = 1359 (2) angstrom3, Z = 4, D(x) = 1.731 Mg M-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 0.373 mm-1, F(000) = 712, T = 293 K, R = 0.091 (disordered tetrafluoroborate anions) for 500 unique reflexions [I greater-than-or-equal-to 2sigma(I)] and 106 variables. 1-Chloromethyl-4-aza-1-azoniabicyclo[2.2.2]octane tetrafluoroborate (2), C7H14ClN2+.BF4-, M(r) = 248.46, orthorhombic, P2(1)2(1)2(1), a = 8.106 (3), b = 18.786 (4), c = 7.076 (3) angstrom, V = 1077.5 (6) angstrom3, Z = 4, D(x) = 1.531 Mg M-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 0.375 mm-1, F(000) = 512, T = 293 K, R = 0.046 for 813 unique reflexions [I greater-than-or-equal-to 2sigma(I)] and 192 variables I-Chloromethyl-4-aza-1-azoniabicyclo[2.2.2]-octane trifluoromethanesulfonate (3), C7H14ClN2+.CF3SO3-, M(r) = 310.72, orthorhombic, Pnma, a = 19.877 (7), b = 8.769 (3), c = 7.138 (2) angstrom, V = 1244 (1) angstrom3, Z = 4, D(x) = 1.659 Mg M-3, lambda(Mo Kalpha) = 0.71069 angstrom, mu = 0.50 mm-1, F(000) = 640, T = 293 K, R = 0.064 for 657 unique reflexions [I greater-than-or-equal-to 2sigma(I)] and 97 variables. Monoquaternization of 1,4-diazabicyclo[2.2.2]octane expands the ring C-N bonds of the donor N atom (+NCH2Cl) to 1.485 (8)-1.52 (1) angstrom compared to 1.445 (9)-l.454 (9) angstrom for the other bridgehead N atom. Subsequent fluorination of the latter N atom removes this asymmetry and contracts the bridgehead N...N distance from 2.56 (1), to 2.48 (2) angstrom. The +N-F bond length of 1. 3 7 (2) angstrom is significantly longer than found in NF4+.BF4-[1.265 (9)-l.321 (10) angstrom; Christie, Lind, Thorup, Russell, Fawcett & Bau (1988). Inorg. Chem. 27, 2450-2454].