Phosphinoborine Compounds: Mass Spectra and Pyrolysis

The mass spectra of tetramethylphosphinoborine trimer, [P(CH(3))(2)B(CH(3))(2)](3) (I) and a a compound, P(5)(CH(3))(9)B(5)H(9), (II) prepared from dimethylphosphinoborine were observed, and the compounds were pyrolyzed at 300 to 500° C. Most peaks in the spectrum of (I) came from the P—B, B—C, and P—C cleavages. The mass spectrum of (II) was much more complicated with evidence for methyl group redistribution. The pyrolysis of both compounds indicates a very complicated mechanism with many unidentifiable compounds. Trends in the formation of volatile products indicate that both compounds are completely decomposed in 4 hr at 450° C. Compound (I) produces trimethylboron, which disappears rapidly above 400° C. Neither (I) nor (II) formed ethane or elemental phosphorus.