Alternative methods of modifying the calixarene conformation. The synthesis and molecular structures oft-butylcalix[4]arene methyl ether complexed with aluminum alkyl species

Abstract

The configurations of calix[4]arenes may be modified by the formation of donor-acceptor complexes which make use of the basicity of the oxygen atoms of the macrocycle. The complex [t-butylcalix[4]arene methyl ether][AlMe₃]₂,2, exhibits the previously unseen ‘1,2-alternate’ geometry, while [t-butylcalix[4]arene methyl ether][MeAlCl₂]₂,3, and [t-butylcalix[4]arene methyl ether][EtAlCl₂]₂,4, show the ‘1,3-alternate’ configuration.2 crystallizes in the triclinic space groupPl witha=11.14(1),b=11.60(1),c=12.02(1) Å, α=77.32(8), β=67.91(8), and γ=69.34(8)^o withD _c =1.06 g cm⁻³ forZ=1. Refinement based on 1270 observed reflections led toR=0.106.3 as the benzene solvate belongs to the monoclinic space groupC2/c witha=12.116(2),b=21.557(7),c=23.470(6) Å, and β=104.05(2)^o withD _c =1.13 g cm⁻³ forZ=4. Refinement based on 2335 observed reflections led toR=0.075.4 crystallizes in the monoclinic space groupC2/c witha=12.062(4),b=21.175(6),c=21.596(5) Å, and β=100.78(4)^o withD _c =1.18 g cm⁻³ forZ=4. Refinement based on 2529 observed reflections gaveR=0.082. The Al-O lengths in all three complexes are normal for donor-acceptor interactions.