6533b83afe1ef96bd12a70c7

RESEARCH PRODUCT

Interaction Between Amines and N-Haloimides: a New Motif for Unprecedentedly Short Br...N and I...N Halogen Bonds

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The complexes of N-bromosuccinimide or N-iodosuccinimide with a halogen bond acceptor, either 1,4-diazabicyclo[2.2.2]octane (DABCO), hexamethylenetetramine (HMTA) or 1,3,5-triazine (TRZ), led to an unprecedentedly strong (CO)2N–X⋯N halogen bond synthon (X = Br or I) determined from crystal structures of [DABCO]·[NBS]22, [HMTA]·[NBS]22, [TRZ]·[NIS]22 and [HMTA]·[NIS]44. The Br⋯N distances with DABCO and with HMTA donors were 2.347 A and 2.414 A being remarkably shorter (31% and 29%) than the sum of the VDW radii of nitrogen and bromide atoms, respectively. The corresponding I⋯N distances with HMTA and TRZ were 2.549 A and 2.596 A (27.8% and 26.4% less than the sum of the VDW radii of N and I). Moreover, the tetrahedral complex of [HMTA]·[NIS]44 forms a stable halogen bond based organic framework structure (XBOF) with 7.31 A × 6.74 A diameter channels filled with disordered acetonitrile solvent. The total volume of the channels, four in each unit cell, was 1130.5 A3 which covers 28% of the unit cell volume.