Structural investigations of silver(I) and copper(I) complexes with neutral N4 donor ligands; the X-ray crystal and molecular structure of the dimer [Ag2{m-(R,S)-1,2-(py-2-CH=N)2cyclohexane}2][O3SCF3]2 and 1H and 13C and INEPT 109Ag and 15N NMR solution studies