Dilithium tetra(t-butylimido)-molybdate(VI) and -tungstate(VI) and some reactions thereof. X-Ray crystal structures of W[(µ-NBut)2AlX2]2(X = Cl or Me), [W(NBut)2(NH2But)Cl(µ-Cl)]2, and [W2Cu5(NBut)2(µ-NBut)6(NHBut)2]BF4

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Abstract
The compounds Li2M(NBut)4(M = Mo or W) have been made by deprotonation of M(NBut)2(NHBut)2 in diethyl ether by methyl-lithium. Interaction of Li2M(NBut)4 with AlCl3, GaCl3, and AlMe3 gives rise to compounds of the type M[(µ-NBut)2M′X2]2 and the crystal structures of compounds where M = W, M′= Al, X = Cl and Me have been determined. The Li2M(NBut)4 compounds are readily protonated by weak acids such as water or MeOH. Interaction with strong acids gives initially M(NBut)2(NHBut)2 and further protonation of the amido compound by CF3SO3H or CF3CO2H gives octahedral neutral species such as M(NBut)2(NH2But)2(OSO2CF3)2; W(NBut)2(NHBut)2 with HBF4 gives only monoprotonation forming two species, [W(NBut)2(NHBut)(NH2But)]BF4 and W(NBut)2(NHBut)(NH2But)(F2BF2), depending on the conditions; HCl gives [W(NBut)2(NH2But)Cl(µ-Cl)]2. Interaction of Li2W(NBut)4 with [Cu(MeCN)4]BF4 gives a remarkable cation of stoicheiometry [WVI 2CuI 5(NBut)2(µ-NBut)6(NHBut)2]+ in which each W has one linear terminal NBut group and three NBut groups bridging to three copper(I) atoms in a triangle; two of these NBut groups are also bound to a CuI(NHBut) unit thus being µ3.

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