X-RAY CRYSTALLOGRAPHIC STUDIES OF TRICARBONYLCHROMIUM COMPLEXES OF CALIX[4]ARENE CONFORMERS - ON AN UNUSUAL CONFORMATION WHICH APPEARS IN CONE CONFORMERS

The structures of three arene-tricarbonylchromium complexes prepared from cone and 1,3-alternate-25,26,27,28-tetrapropoxycalix[4]arene(1) and Cr(CO)(6) were determined by single crystal X-ray studies. Crystal data for 1,3-alternate-1.Cr(CO)(3) are space group P2(1)/a, a=19.496(3)Angstrom, b=11.118(2)Angstrom, c=19.121(2)Angstrom, beta=109.95 degrees(1) and V=3895 Angstrom(3). The structure was refined to Rw=0.068. Crystal data for cone-1.Cr(CO)(3) are space group P2(1)/a, a=21.457(4)Angstrom, b=12.184(1)Angstrom, c=14.816(2)Angstrom, beta=91.61 degrees(1) and V=3872 Angstrom(3). The structure was refined to Rw=0.077. Crystal data for cone-1.2Cr(CO)(3) are space group P2(1)/a, a=18.019(3)Angstrom, b=41.347(4)Angstrom, c=11.743(2)Angstrom, beta=97.39 degrees(1) and V=8676 Angstrom(3). The single crystal included two similar but slightly different structures but the data were successfully refined to Rw=0.092. The structure of 1,3-alternate-1.Cr(CO)(3) differs only slightly from that of the regular 1,3-alternate calix[4]arene. In contrast, cone-1.Cr(CO)(3) and cone-1.2Cr(CO)(3) show an unusual conformation with a pair of faced gable-like roofs, which is considerably distorted from the regular cone calix[4]arene. The origin of this distortion is discussed in combination with the spectral studies.