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, Ph-x(3,5-dimethyl-4-R-phenyl)-(3-x) where R = N, F or OCH3 , have been synthesized, and the donor properties of the P(III) centers hav e been evaluated by measuring the A(1) nu(CO) frequencies of the Ni(CO)(3)L complexes. These data indicate that, compared to hydrogen, the methyl grou ps are electron donating, the fluoro groups are electron withdrawing, and t he methoxy groups have little effect. The X-ray structure of tris(3,5-dimet hyl-4-methoxyphenyl)phosphine has been obtained, and a prominent feature of the structure is that the methoxy groups are perpendicular to the phenyl r ing faces and folded toward the ring faces adjacent to the phosphorus lone pair.