A COMPARATIVE-STUDY OF 1,7-OCTADIENE AND 1,7-OCTADIYNE COMPLEXES OF COPPER(I) CHLORIDE - PREPARATION AND MOLECULAR-STRUCTURES

Polymeric complexes, [Cu2Cl2(C8H14)] (1) and [Cu2Cl2(C8H10)] (2), prepared by direct reaction between copper(I) chloride and 1,7-octadiene and 1,7-octadiyne, respectively, have been between characterized by crystal-structure determinations and IR spectroscopy. In both structures the organic ligands act as bridges between copper(I). In 1, there are two crystallographically independent copper(I) centres, one of which is three coordinated by C = C and two chloride ligands, the olefin being twisted 4-degrees out of the coordination plane. The other copper(I) centre is (3 + 1) coordinated and exhibits a larger olefin twist (10-degrees from the trigonal plane). The Cu-C bond lengths lie in the range 2.036(4) - 2.100(4) angstrom, and the C = C bond lengths are 1.353(6) and 1.356(6) angstrom. In 2, copper(I) is trigonally pyramidally coordinated, with the C = C linkage in the trigonal plane; Cu-C = 2.029(6) and 2.053(6) angstrom and C = C = 1.196(9) angstrom. The nu(C = C) and nu(C = C) frequencies are lowered by ca. 98 cm-1 and 135 cm-1. respectively, on complexation. In contrast to nu(C(sp)2-H), which remains virtually unchanged, nu(C(sp)-H) is lowered by 117 cm-1, indicating activation of the acetylenic C-H bond; this feature is, however, not paralleled by a significant lengthening of the C-H bond or bending back of the acetylenic hydrogen atom in the crystal structure.