X-Ray Structural Studies of Green and Brown Crystals of trans-[CoCl2(N48)]X (N48=1,4,7,10-Tetraazacyclopentadecane, X=NO3−, BF4−, and ClO4−)

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Abstract
Crystal structures of green (X=NO3−(1), BF4−(2)) and brown (X=BF4−(3) and ClO4−(4)) salts of trans-[CoCl2(N48)]X (N48=1,4,7,10-tetraazacyclopentadecane) were determined by an X-ray diffraction method. The complex cation is a RSSR(SRRS) isomer for the four chiral nitrogen atoms and has approximate C2 symmetry. Green crystals 1 and 2 are monoclinic and have the chiral space group P21, comprising one antipode of the complex ion by spontaneous resolution, whereas brown crystals 3 and 4 are orthorhombic and a racemate. The eight-membered chelate ring formed by the N48 ligand and the Co atom takes a distorted boat–boat (BB) form in 1 and 2, whereas the conformation is disordered in 3 and 4 with BB (40%) and distorted twist–boat-chair (TBC; 60%) forms at room temperature. At 113 K, the eight-membered chelate ring in 4 takes exclusively the TBC form. The crystal data are as follows: [CoCl2(C11H26N4)]X, monoclinic NO3 salt, 1, P21, a=9.672(3), b=12.285(5), c=7.051(2) Å, β=94.70(3)°, V=835.0(5) Å3, Z=2, T=300(1) K, final R=0.037 for 2381 reflections. Monoclinic BF4 salt, 2, 2, P21, a=9.857(2), b=12.694(2), c=7.065(1) Å, β=94.34(2)°, V=881.5(2) Å3, Z=2, T=300(1) K, final R=0.031 for 1880 reflections. Orthorhombic BF4 salt, 3, Pcab, a=12.816(1), b=22.359(2), c=12.388(1) Å, V=3549.8(5) Å3, Z=8, T=300(1) K, final R=0.095 for 2086 reflections. Orthorhombic ClO4 salt at 300(1) K, 4a, Pcab, a=12.829(1), b=22.376(2), c=12.425(1) Å, V=3566.7(6) Å3, Z=8, final R=0.070 for 1764 reflections; orthorhombic ClO4 salt at 113(2) K, 4b, a=12.630(2), b=22.276(5), c=12.354(2) Å, V=3475.7(11) Å3, final R=0.109 for 2215 reflections.

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