Pnictides as symmetrically bridging ligands in novel neutral complexes

The reaction of [LWCl] (3) [L = N(CH2CH2NiPr)(3)] with LiE(SiMe3)(2) (E=P, As, Sb) yields the novel, neutral pnictido-bridged complexes [LW=E=WL] (5-7 ). By following the reaction, which starts from the LiP(SiMe3)(2) derivativ e, by P-31 NMR spectroscopy, the formation of an intermediate with a termin al pnictido ligand can be ruled out. The paramagnetic complexes 5-7 are com prehensively spectroscopically characterised. The X-ray structure analysis of the heterocumulenes 5-7 reveals a linear structure in which the two W-"t ren" units bind to the central pnictido atom in a staggered conformation [" tren" = tren-based ligand; tren = tris(2-aminoethyl)amine. When N-2 is used as the inert gas in the synthesis of the starting material [(N(CH2CH2NNp)( 3)}WCl] [Np= CH2C-(CH3)(3)], the complex: [{[N(CH2CH2NNp)(3)]W}(2)(mu,eta(1 ):eta(1)-N-2)] (4) is formed as a side product, Complex 4 possesses a hydra zido(4 -) (N-2(4-)) ligand connected by two tungsten-"tren" moieties.