Synthesis and Properties of Phenyl Phosphines with Meta-Positioned Methyl Groups and the X-ray Structure of Tris(3,5-dimethyl-4-methoxyphenyl)phosphine

Nine phosphines, Phx(3,5-dimethyl-4-R-phenyl)3-x where R = H, F or OCH3, have been synthesized, and the donor properties of the P(III) centers have been evaluated by measuring the A1 ν(CO) frequencies of the Ni(CO)3L complexes. These data indicate that, compared to hydrogen, the methyl groups are electron donating, the fluoro groups are electron withdrawing, and the methoxy groups have little effect. The X-ray structure of tris(3,5-dimethyl-4-methoxyphenyl)phosphine has been obtained, and a prominent feature of the structure is that the methoxy groups are perpendicular to the phenyl ring faces and folded toward the ring faces adjacent to the phosphorus lone pair.