Preparation and Photophysical Properties of Phosphino- and Phosphine Oxide-Linked Siloles

1,1-dimethyl-2,5-disubstituted-3,4-diphenylsiloles terminated at the 2,5-positions with a phosphino or phosphine oxide group were prepared. All reactions were carried out under an inert atmosphere of argon or nitrogen using standard Schlenk techniques or a drybox using solvents dried by standard procedures. The phosphine oxide-linked silole was prepared in 17% yield from the reaction of 1,1-dimethyl-2,5-bis(4-bromophenyl)-3,4-diphenylsilole with diphenyl(4-ethynyl phenyl)-phosphine oxide in the presence of CuI, Pd(PPh 3)4, and NEt3. The 13C{ 1H} NMR spectra for the siloles 1-5 and 9 all exhibit resonances generally above about 135 ppm for the silole ring carbons, and the Si{ 1H} resonances were generally observed near 8-9 ppm except for siloles 1a and 1b, which were shifted slightly downfield at 15 and 20 ppm.