Reactions of MoNCl3 and WNCL(3) with elemental fluorine. Crystal structures of [MoO2F2(THF)(2)] and [WF4(NCl)(CH3CN)]

The nitrido chlorides MoNCl3 and WNCl3 as well as WCl4(NCl) react with elemental fluorine forming the N-chloro imido complexes MoF4(NCl) and WF4(NCl), which were characterized by IR spectroscopy. With tetrahydrofurane MoF4(NCl) reacts to give [MoF4(NCl)(THF)], which in THF solution slowly converts into [MoO2F2(THF)(2)]. From WF4(NCl) with acetonitrile the complex [WF4(NCl)(CH3CN)] is obtained. Both donor acceptor complexes were characterized by crystal structure determinations. [MoO2F2(THF)(2)]: Space group P2(1)/n, Z = 4, structure solution with 1823 unique reflections, R = 0.033 for reflections with I > 2 sigma(I). Lattice dimensions at -40 degrees C: a = 636.2, b = 1119.5, c = 1625.2 pm; beta = 93.92(1)degrees. The compound has a monomeric molecular structure with the fluorine atoms in trans-position to one another and with the oxygen atoms of the THF molecules in trans to the oxo ligands. [WF4(NCI)(CH3CN)]: Space group P2(1)/m, Z = 2, structure solution with 1119 unique reflections, R = 0.038 for reflections with I > 2 sigma(I). Lattice dimensions at 20 degrees C: a = 511.7, b = 714.9, c = 1002.5 pm; alpha = 102.59(10)degrees. The compound has a monomeric molecular structure in which the nitrogen atom of the acetonitrile molecule coordinates in trans-position to the N-chloro imido group W=N-Cl. The structural parameters of this group are WN = 172.2 pm, NCl = 161.1 pm, WNCl = 178.6 degrees.