Title:  Pentaborane(9) 
CAS Registry Number:  19624-22-7 
Additional Names:  Pentaboron nonahydride 
Molecular Formula:  B5H9 
Molecular Weight:  63.13 
Percent Composition:  B 85.62%, H 14.37% 
Literature References:  Prepd from diborane:  Stock, Mathing, Ber. 69B, 1456 (1936); Schlesinger, Burg, J. Am. Chem. Soc. 53, 4321 (1931); 55, 4009 (1933).  Molecular structure determination by rotational spectroscopy:  D. Schwoch et al., Inorg. Chem. 16, 3219 (1977).  Review of toxicity:  see Decaborane(14).  Review:  Greenwood in Comprehensive Inorganic Chemistry vol. 1, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 792-801. 
Properties:  Liquid.  mp -46.6°; bp 60°.  d40 0.61; vp 66 mm Hg at 0°.  Dec very slowly at 150°.  Ignites spontaneously in air.  Hydrolyzes in water after long heating.  Reacts with ammonia to form a diammoniate. 
Melting point:  mp -46.6° 
Boiling point:  bp 60° 
Density:  d40 0.61 
CAUTION:  Potential symptoms of overexposure are dizziness, headache, drowsiness and lightheadedness; incoordination, tremor, convulsions, behavioral changes; tonic spasms of face, neck, abdomen and limbs; irritation of eyes and skin.  See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 242.   |