Comparison of twists in isosteric propellers: X-ray structures of tris(2,6-dimethoxyphenyl)borane, tris(2,6-dimethoxyphenyl)methyl cation and tris(2,6-dimethoxyphenyl)methyl radical

Abstract

The X-ray structures of three per-o-methoxytriphenyl-X molecules were determined by direct methods. Tris(2,6-dimethoxyphenyl)borane (1), C24H27BO6, Mr=422.3, monoclinic, C2/e, a = 11.076(5), b=20.839(8), c=9.944(4) A, /3= 98.40 (3) °, V = 2271 (1) ]k 3, Z = 4, Dx = 1.24 gcm -3, A(Mo Ka) = 0.71073 A, ~ = 0.8 cm-1, F(000) = 896, T=295K. Refinement based on 926 unique observed reflections and 170 parameters gave a final R(Fo)=0.045. The tetrafluoroborate salt of the isoelectronic tris(2,6-dimethoxyphenyl)methyl cation (2), CEsH270~.BF4, Mr = 510.3, triclinic, P1, a = 7.214(5), b= 12.931 (4), c = 13.633 (3)A, a = 83.13 (2), /3 = 77.70 (3), y = 80.56 (4) °, v=