Gravar-mail: Bis(μ-4,4′′-difluoro-1,1′:3′,1′′-terphenyl-2′-carboxylato-κ(2) O:O′)bis[aqua(4,4′′-di­fluoro-1,1′:3′,1′′-terphenyl-2′-carboxyl­ato-κO)(pyridine-κN)cobalt(II)] diethyl ether disolvate