New convenient procedures for the preparation of ammonia monochloroborane (NH3BH2Cl) and cyclotriborazane [(BH2NH2)(3)] are described. Crystal structures have been determined by single-crystal X-ray diffraction. Strong H center dot center dot center dot Cl center dot center dot center dot H bifurcated hydrogen bonding and weak N-H center dot center dot center dot H dihydrogen bonding are observed in the crystal structure of ammonia monochloroborane. When heated at 50 degrees C or under vacuum, ammonia monochloroborane decomposes to (NH2BHCl)(x), which was characterized by NMR, elemental analysis, and powder X-ray diffraction. Redetermination of the crystal structure of cyclotriborazane at low temperature by single-crystal X-ray diffraction analysis provides accurate hydrogen positions. Similar to ammonia borane, cyclotriborazane shows extensive dihydrogen bonding of N-H center dot center dot center dot H and B-H center dot center dot center dot H bonds with H delta+center dot center dot center dot H delta- interactions in the range of 2.00-2.34 angstrom.