Dimethyl-1,5-cyclooctadiene (DMCOD) is synthesized by the Ni-catalyzed dimerization of isoprene and consists of 80% 1,5-dimethyl-1,5-cyclooctadiene (1,5-DMCOD) and 20% 1,6-dimethyl-1,5-cyclooctadiene (1,6-DMCOD). Reaction of Hhfac (1,1,1,5,5,5-hexafluoro-2,4-pentanedione) with Ag2O in the presence of DMCOD results in the formation of isomeric Ag(I) species. Repeated recrystallizations yield an isomerically pure compound ((1,5-DMCOD)Ag(hfac))(2) that was characterized by X-ray crystallography and H-1 and C-13 NMR and IR spectroscopy. X-ray crystallography revealed a dinuclear complex with a short Ag-Ag spacing (3.0134(3) Angstrom at -150 degrees C and 3.0278(5) Angstrom at -20 degrees C) and bridging hfac ligands (mu(2) bonding). The overall geometry around the Ag atoms is a deformed tetrahedron with two short Ag-O bonds (2.375 Angstrom average) and two Ag-diene bonds. The methyl groups of the 1,5-DMCOD ligand are pointed toward the center of the molecule. Decomposition of the silver complex in a biphasic HCl (1 M)/CH2Cl2 mixture liberates isomerially pure 1,5-DMCOD; this diene is subsequently used to synthesize isomerically pure (1,5-DMCOD)Cu(hfac). The latter compound was characterized by H-1 and C-13 NMR and IR spectroscopy and is a useful liquid precursor for Cu CVD. Crystallographic data : C30H34- Ag2F12O4, monoclinic, P2(1)/(c) (No. 14), Z = 4; at -150 degrees C, a = 12.428(1) Angstrom, b = 11.071(1) Angstrom, c = 24.520(2) Angstrom, beta = 101.98(1)degrees; at -20 degrees C, a = 12.597(1) Angstrom, b = 11.191(1) Angstrom, c = 24.641(2) Angstrom, beta = 102.08(1)degrees.