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.