Phosphinopentaboranes

Article abstract of DOI:10.1021/ic50063a037

Phosphine derivatives of the type R₂PCl react with LiB₅H₈ in ether to form 2,3-μ-(CH₃)₂PB₅H₈ (mp 17°; bp estd 191°), 2,3-μ-CH₃CF₃PB₅H₈-A (mp 14°; 1 mm at 25°) which isomerizes irreversibly by an apparently first-order rate process to 2,3-μ-CH₃CF₃PB₅H₈-B (mp - 28°; 9 mm at 25°; bp estd 137°), and 1-(CF₃)₂PB₅H₈ (mp - 42°; bp estd 184°). The bridging vs. peak positions of phosphorus are proved by the B, F, and H nmr spectra and understood in terms of different phosphine-base strengths. The phosphorus nmr spectra show an interesting dectet for 1-(CF₃)₂PB₅H₈ but no resolution for the B-P-B bridged compounds. Both infrared and nmr results indicate weaker-than-normal terminal B-H bonds (with more than normal B_2p character) adjacent to bridging P atoms. The CH₃CF₃PB₅H₈ isomers show no discernible B-F coupling, whereas 1-(CF₃)₂PB₅H₈ shows J_B-F = 6.0 cps.