Gravar-mail: [μ-Bis(diphenyl­arsino)methane-1:2κ(2) As:As′]nona­carbonyl-1κ(3) C,2κ(3) C,3κ(3) C-[tris­(4-fluoro­phen­yl)phosphine-3κP]-triangulo-triruthenium(0)