Synthesis and Characterization of a Bis(μ-β-diketonato)bis((1,2,5,6-η)-1,5-dimethyl-1,5- cyclooctadiene)disilver Complex. An Intermediate in the Synthesis of an Isomerically Pure (β-Diketonato)((1,2,5,6-η)-1,5-dimethyl-1,5-cyclooctadiene)copper(I) Complex

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Abstract
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 1H and 13C NMR and IR spectroscopy. X-ray crystallography revealed a dinuclear complex with a short Ag−Ag spacing (3.0134(3) Å at −150 °C and 3.0278(5) Å at −20 °C) and bridging hfac ligands (μ2 bonding). The overall geometry around the Ag atoms is a deformed tetrahedron with two short Ag−O bonds (2.375 Å 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 1H and 13C NMR and IR spectroscopy and is a useful liquid precursor for Cu CVD. Crystallographic data: C30H34Ag2F12O4, monoclinic, P21/c (No. 14), Z = 4; at −150 °C, a = 12.428(1) Å, b = 11.071(1) Å, c = 24.520(2) Å, β = 101.98(1)°; at −20 °C, a = 12.597(1) Å, b = 11.191(1) Å, c = 24.641(2) Å, β = 102.08(1)°.
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