Nitridokomplexe von Molybdän(V); Synthesen, IR- und EPR-Spektren. Die Kristallstruktur von [Na(15-Krone-5)Na(THF)]2[MoNCl3 ·THF]4·2THF / Nitrido Complexes of Molybdenum(V); Syntheses, IR, and EPR Spectra. Crystal Structure of [Na(15-Crown-5)Na(THF)]2[MoNCl3·THF]4·2THF