THE SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF MESITYLDIPHENYLPHOSPHINE, DIMESITYLPHENYLPHOSPHINE AND TRIMESITYLPHOSPHINE

The synthesis and structural characterization of the tertiary phosphines mesityldiphenylphosphine [PPh2(mes)], dimesitylphenylphosphine [PPh(mes)2] and a new phase of trimesitylphosphine [P(mes)3] have been carried out. Crystals of PPh2(Mes) are monoclinic, space group P 2(1)/c, with a 10.252(10), b 9.847(11), c 17.444(7) angstrom, beta 99.78(6)-degrees, Z 4; R 0.059 for 2102 'observed' reflections. Crystals of PPh(mes)2 are also monoclinic, space group P 2(1)/c, with a 8.964(9), b 22.99(1), c 10.228(4) angstrom, beta 107.98(5)-degrees, Z4; R 0.058 for 2350 'observed' reflections. The new phase of P(mes)3 is monoclinic, Cc, a 11.390(5), b 12.034(4), c 17.564(9) angstrom, beta 104.22(4)-degrees, Z 4 (R 0.060 for 1046 'observed' reflections), in which the molecule is disordered. A full report is given for the phase previously studied (triclinic), P1BAR, a 8.191(3), b 16.447(5), c 18.667(6) angstrom, alpha 104.82(3), beta 97.74(3), gamma 100.07(3)-degrees, Z 4; R 0.065 for 4964 'observed' reflections. The P-C bond distances are similar for the whole series of compounds with an average value of 1.833(1) angstrom. introduction of the mesityl groups results in an increase of the C-P-C angles from c. 103 to c. 110-degrees with a concomitant flattening of the PC3 pyramid.