Crystal structure of (μ 2 -1,1′-bis(diphenylphosphino)ferrocene- P , P′ )-bis[( Z )- O -isopropyl N -(4-chlorophenyl)thiocarbamato- S ]-di-gold(I) acetonitrile di-solvate, C 54 H 50 Au 2 Cl 2 FeN 2 O 2 P 2 S 2 ⋅2(C 2 H 3 N)