Crystal structure of 4-(5,5-difluoro-1,3,7,9-tetramethyl-3H,5H-5λ4-dipyrrolo[1,2-c:2′,1′-f][1,3,2]diazaborinin-10-yl)pyridin-1-ium tetraiodidoferrate(III), C18H19BF2FeI4N3