The Slow Isomerization of 2-(CF3SPCF3)B5H8; Other New Phosphinopentaboranes.

Abstract : Four new phosphinopentaborane (9) compounds have been made. The new reaction 4(CF3S)2 + (CF3P)4 yielding 4(CF3S)2PCF3 (quantitative at 200C.) provided the new compound (CF3S)2PCF3 for reaction with LiB5H8 to make 2-(CF3SPCF3)B5H8. This isomerized slowly at 25C. to 1-(CF3SPCF3)B5H8. With more strongly basic phosphine units, P-bridging of the 2 and 3 B atoms was retained: the new compound 2,3-mu-(C6H5)2PB5H8 showed an atypical 2,3-BH NMR doublet with B-P coupling evidently too small to be resolved; whereas 2,3-mu-(CH3PCl)B5H8 showed the pseudo-triplet typical of the 2,3-B signal of other 2,3-mu-R2PB5H8 compounds. This methylchloro-phosphinopentaborane proved to be unstable at 25C., converting slowly to resinous material. (Author)