SYNTHESIS AND SOLID-STATE STRUCTURE OF SUBSTITUTED ARYLPHOSPHINE OXIDES

We describe the preparation and characterization of several new arylphosphine oxides, which are of interest as second-order nonlinear optical materials, (4-Aminophenyl)diphenylphosphine oxide (la), bis(4-aminophenyl)phenylphosphine oxide (2a), and (4-aminophenyl)bis[4'-(trifluoromethyl)phenyl]phosphine oxide (5) were prepared by addition of aryl Grignard and organolithium reagents containing protected amines to phosphorus oxyhalides. Alternatively, 1a was prepared by treatment of (4-bromophenyl)diphenylphosphine oxide with azidomethyl phenyl sulfide, followed by hydrolysis. (4-Aminophenyl)(4'-nitrophenyl)phenylphosphine oxide (6) was prepared by nucleophilic aromatic substitution of bis(4-fluorophenyl)phenylphosphine oxide to give the corresponding dinitro compound, followed by selective mono-reduction. The X-ray crystal structure of (4-aminophenyl)diphenylphosphine oxide (1a), along with those of mono-, di-, and trihydroxy triphenylphosphine oxides 1b, 2b, and 3b, exhibit extensive intermolecular hydrogen bonding. The hydrogen bonding in 1a and 1b produces chains of arylphosphine oxide molecules with a head-to-tail alignment; the chains pack in an antiparallel manner to produce solid-state structures that display only slight deviations from centrosymmetry.