STERICLY SHIELDED NITRIDO COMPLEXES OF MOLYBDENUM AND TUNGSTEN - THE CRYSTAL-STRUCTURES OF [MON(NPH2)3] AND [W4N4(NPH2)6(ONC4H9)2]

The reactions of MoNCl3 and WNCl3, respectively, with lithium diphenylamide in tetrahydrofurane produce the monomeric nitrido complexes MN(NPh2)3 with CN = 4 at the metal atoms. In the presence of lithium-n-butyl LiNPh2 and WNCl3 also form the tetrameric nitrido complex [W4N4(NPh2)6(O(n)C4H9)2] which contains W(V) and W(VI). The compounds are characterized by their i.r. spectra, by X-ray structural analysis, and, partially, by H-1 and C-13 n.m.r. spectroscopy. MoN(NPh2)3: Space group P1BAR, Z = 2, 4060 observed independent reflexions, R = 0.031. Lattice dimensions at 20-degrees-C: a = 956.2(4) pm, b = 1015.9(2) pm, c = 1598.1(3) pm; alpha = 79.06(2)-degrees, beta = 85.67(3)-degrees, gamma = 82.57(3)-degrees. The compound forms monomeric molecules with Mo = N and lengths of 163.4 pm and mean Mo-NPh2 distances of 199.2 pm. [W4N4(NPh2)6(O(n)C4H9)2]: Space group P2(1)/n, Z = 2, 1903 observed independent reflexions, R = 0.039. Lattice parameters at 19-degrees-C: a = 1582.2(3) pm, b = 1182.4(2) pm, c = 2053.3(4) pm; beta = 103.77(2)-degrees. The compound forms centrosymmetric molecules, in which the central W-W dumb-bell (bond length 253.5 pm) is linked by the nitrido ligands of two WN2(NPh2)2-units in a T shaped order of the N-atoms.