Copper(I) and silver(I) ions in unusual poly donor-atom environments; X-ray crystal and molecular structures of [M{( R)( S)-1,2-(5-Me-thiophene-2-CHz.dbnd;N) 2-cyclohexane} 2](O 3SCF 3), M = Cu I or Ag I

Abstract

Coordination properties of 0.t’ and Cu’ with ligand systems containing N and S donor atoms as potential coordinating sites continue to be of interest as models for the redox active sites in the ‘blue’ proteins [ 1] . The conformation and rigidity of the carbon skeleton connecting the hetero-atoms, as well as the types and number of hetero-atoms in the model ligand systems, are important with respect to both the number of metal atoms which can be bonded and the ultimate configuration at the metal centres. Recently we have shown that the quadridentate N-donor ligands (R)(S)-1 ,2-(6-R-py-2-CH=N)Z-cyclohexane (R = H or Me), in which the inner two N-donor sites are connected by the (R)(S)-1,2cyclohexanediyl ring, act as di-bidentate ligands binding two Cur or Ag’ atoms (see Fig. 1) [2]. The application of INEPT “N and ro9Ag NMR spectroscopy revealed that the structural features found for the silver(I) complex [Ag,{(R@)-1,2(py-2-CH=N)z-cyclohexane),l(03SCF3)2 in the solid, with characteristic alternating two short and two long Ag-N distances around the distorted tetrahedral silver centres [2], are retained in solution [3] . Attempts to form mononuclear Cu’ or Ag’ complexes with these N4donor ligands, using ‘A Curor Agr-to-ligand ratios were unsuccessful. Interpretation of these results requires more information concerning the influence of the donor sites on the coordination properties of these types of potentially quadridentate ligands. For this purpose we have now investigated the bonding features of the N2S, ligand system (R)(S)-1,2-(5-R-thiophene-