{μ-trans-N,N′-Bis[(diphenylphosphanyl)methyl]benzene-1,4-diamine-κ2 P:P′}bis{(acetonitrile-κN)[dipyrido[3,2-a:2′,3′-c]phenazine-κ2 N 4,N 5]copper(I)} bis(tetrafluoridoborate)