Synthesis, molecular structure, and reactions of bis(tetraphenylphosphonium) hexakis(.mu.-thiophenolato)-tetrachlorotetraferrate(II), (Ph4P)2[Fe4(SPh)6Cl4]. Its reactions with dibenzyl trisulfide and the synthesis of the [Fe4S4Cl4]2- and [Fe4S4(Cl)2(SC6H5)2]2- "Cubane"-type clusters