Synthesis and structure of sterically crowded triarylphosphine bearing 4-bromo-2,6-bis(4-tert-butylphenyl)phenyl group

A novel sterically crowded triarylphosphine bearing a 2,6-diaryl-4-bromophenyl group, [4-bromo-2,6-bis(4-tert-butylphenyl)phenyl]bis(2,4,6-triisopropylphenyl)phosphine (1), was synthesized. The X-ray crystallography revealed that the bond angles and lengths around the phosphorus atom (110.9°, 1.846 Å) are comparable to those of tris(2,4,6-triisopropylphenyl)phosphine and its derivatives. Triarylphosphine 1 is reversibly oxidized to the radical cation at the potential close to that of the typical sterically crowded (bromoaryl)phosphine, (4-bromo-2,6-diisopropylphenyl)bis(2,4,6-triisopropylphenyl)phosphine, and exhibits the UV absorption at long wavelength (_max 332 nm) characteristic of the sterically crowded triarylphosphines. Thus, triarylphosphine 1 can be regarded to be a promising candidate for the key synthetic intermediate or building block to the functional molecules bearing sterically crowded triarylphosphine moieties.