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

Abstract

The compounds Li₂M(NBu^t)₄(M = Mo or W) have been made by deprotonation of M(NBu^t)₂(NHBu^t)₂ in diethyl ether by methyl-lithium. Interaction of Li₂M(NBu^t)₄ with AlCl₃, GaCl₃, and AlMe₃ gives rise to compounds of the type M[(µ-NBu^t)₂M′X₂]₂ and the crystal structures of compounds where M = W, M′= Al, X = Cl and Me have been determined. The Li₂M(NBu^t)₄ compounds are readily protonated by weak acids such as water or MeOH. Interaction with strong acids gives initially M(NBu^t)₂(NHBu^t)₂ and further protonation of the amido compound by CF₃SO₃H or CF₃CO₂H gives octahedral neutral species such as M(NBu^t)₂(NH₂Bu^t)₂(OSO₂CF₃)₂; W(NBu^t)₂(NHBu^t)₂ with HBF₄ gives only monoprotonation forming two species, [W(NBu^t)₂(NHBu^t)(NH₂Bu^t)]BF₄ and W(NBu^t)₂(NHBu^t)(NH₂Bu^t)(F₂BF₂), depending on the conditions; HCl gives [W(NBu^t)₂(NH₂Bu^t)Cl(µ-Cl)]₂. Interaction of Li₂W(NBu^t)₄ with [Cu(MeCN)₄]BF₄ gives a remarkable cation of stoicheiometry [W^VI₂Cu^I₅(NBu^t)₂(µ-NBu^t)₆(NHBu^t)₂]⁺ in which each W has one linear terminal NBu^t group and three NBu^t groups bridging to three copper(I) atoms in a triangle; two of these NBu^t groups are also bound to a Cu^I(NHBu^t) unit thus being µ₃.