Email (record): Crystal structure of catena-poly[[[di­aqua­[1,2-bis(pyridin-4-yl)ethene]{4-[2-(pyridin-4-yl)ethen­yl]pyridinium}gold(I)iron(II)]-di-μ-cyanido] bis­[dicyanido­gold(I)] 1,2-bis­(pyridin-4-yl)ethene dihydrate]