Propargyl calix[4]arenes and their complexes with silver(I) and gold(I)

A calix[4]arene 1b has been substituted at the lower rim by reaction with propargyl bromide to give either the 1,3- bis(propargyl) derivative 26, which is formed regioselectively, or the tetrakis(O-propargyl)calix[4]arene 3 under different reaction conditions. The molecular structure of 2b has been characterized by X-ray analysis (monoclinic, space group P2₁/c, Z = 4, a = 10.960(1), b = 24.302(3), c = 10.673(1) Å, β = 112.99(8)°, R = 0.0516). The molecules of 2b in the crystal are arranged in a "head-to-head, tail-to-tail" manner with a phenyl substituent of one molecule partly enclosed in the bowlic cavity of another. Since the two OCH₂C≡CH groups are accessible, 2b can be polymerized by heating to 250°C and the polymerized propargyl calix[4]arene derivatives are stable up to 460°C. Compound 3 exists as a mixture of conformers, the ratio of partial cone to 1,3-alternate conformations being 4:1 or 2:1, dependent on the preparative conditions. These propargyl calix[4]arene derivatives can be further derivatized to form silver(I) or gold(I) alkynyl units by reaction with AgNO₃ or [AuCl(SMe₂)], respectively, and base. Further reaction of these transition metal complexes with phosphines yields calixarene derivatives with two metalphosphine units at the lower rim of the calix[4]arene bowl.