SYNTHESIS, CHARACTERIZATION AND CRYSTAL-STRUCTURE OF ETRAKIS(1'-(DIPHENYLPHOSPHINO)FERROCENE-CARBOXYLIC ACID-P)TETRACOPPER(I)]-ACETIC ACID (1 2)/

The title compound was prepared by the reaction of 1'-(diphenylphosphi no)ferrocenecarboxylic acid with copper(I) iodide in acetic acid. It h as the tetrameric structure of the heterocubane type and all four mono meric units are crystallographically independent. The central Cu(4)l(4 ) core is severely distorted from the O-h symmetry as a consequence of disparate radii of the atoms; however, this does not lead to transfor mation of the core into a stepped arrangement, the feature otherwise c ommon for similar tetrameric structures. The ligand behaves as a monod entate phosphine and completes the approximately tetrahedral coordinat ion polyhedron around copper(T). The carboxyl groups remain undissocia ted and uncoordinated but participate in intermolecular hydrogen bondi ng. Two carboxyl groups link the molecules of the tetramer into a zig- zag chain; the remaining two are bonded to molecules of solvating acet ic acid which act as spacers between the chains. As; expected, the geo metry of the flexible ligand is remarkably influenced by the hydrogen bonding, the main conformation changes taking place at the P-C bonds a nd in the mutual arrangement of the cyclopentadienyl rings.