BIMETALLIC HYDRAZIDO(3-AND4-) AND NITRIDO COMPLEXES OF TUNGSTEN CONTAINING THE W(ETA-5-C5ME5)ME3 CORE

Cp*Me3W = NNH2 (1) is successively deprotonated by Li-n-Bu to yield [Cp*Me3W = NNHLi]x (2) and then [Cp*Me3 W = NNLi2]x (3). Water reacts with 2 or 3 to re-form 1. SiMe3Cl reacts with 2 or 3 to give Cp*Me3W = NNH(SiMe3) or Cp*Me3W = NN(SiMe3)2, respectively. Reaction of 0.5 equiv of MgNp2(TMEDA) with 1 yields [Cp*Me3W = NNH]2[mu-Mg(TMEDA)], which can be recrystallized from THF to yield structurally characterized [Cp*Me3W = NNH]2[mu-Mg(THF)4] (6-(THF)4; space group P2(1)/n (No. 14), a = 12.380 (6) angstrom, b = 15.252 (6) angstrom, c = 30.618 (8) angstrom, beta = 97.91 (3)-degrees, V = 5726 (7) angstrom 3, MW = 1099.14, rho(calcd) = 1.275 g/cm3, Z = 4, R = 0.082, R(w) = 0.132). Cp*Me3W = NNH[MgNp(TMEDA)] (7) is obtained upon treating 1 with 1 equiv of MgNp2(TMEDA) at -40-degrees-C; warming 7 to room temperature yields [Cp*Me3W = NN]2[mu-Mg(TMEDA)]2 (8). Cp*Me3W = N - N = TaCp*Me2 (9) has been prepared by treating Cp*TaMe3Cl with 6 or Cp*TaMe4 with 1. Complexes of the type Cp*Me3W = NNH(ZrCp2R) (R = Me (10a), CH2Ph (10b)) are the products of the reactions between 1 and Cp2ZrR2, but they do not readily eliminate methane or toluene to generate a hydrazido(4-) complex. 10a and 10b react slowly with 1 to form [Cp*Me3W = NNH]2ZrCp2 (11). The tantalum and zirconium complexes react readily with water to re-form 1. Reaction of [Cp*Me3W = NLi]x (12) with Cp*WMe3(OTf) yields the symmetric, mixed-valent bridging nitride [Cp*Me3W]2(mu-N) (13a), which has been characterized crystallographically (space group P2(1)/c (No. 14), a = 8.390 (4) angstrom, b = 20.341 (6) angstrom, c = 8.733 (4) angstrom, beta = 117.83 (2)-degrees, V = 1318 (2) angstrom 3, MW = 742.37, rho(calcd) = 1.870 g/cm3, Z = 2, R = 0.057, R(w) = 0.063). The geometry about the tungsten in 13a is square pyramidal, a center of inversion defines a linear W-N-W backbone that has a W-N distance of 1.8475 (8) angstrom. 13a can be oxidized to yield {[Cp*Me3W]2(mu-N)}+ (13b). 12 also reacts with Cp*TaMe3X (X = Cl, OTf] or Cp*TaMe2(OTf)2 to give the unsymmetrical "metalloimido" complex Cp*Me3W = N-TaCp*Me3 (15) or the bridging nitride Cp*Me3W = N = TaCp*Me2(OTf) (14), respectively.