Yttrium Dihydride Cation [YH₂(THF)₂]⁺_<i>n</i>: Aggregate Formation and Reaction with (NNNN)-Type Macrocycles

Monocationic bis­(hydrocarbyl)­yttrium
complexes [YR2(THF)2]­[A] (R = CH2SiMe3, CH2C6H4-o-NMe2; A = weakly coordinating anion)
underwent hydrogenolysis using dihydrogen or phenylsilane to give
a mixture of polynuclear solvent-stabilized dihydride cations [YH2(THF)2]n[A]n. The mixture composition as well as the nuclearity n depended on the starting material, solvent, and reaction
conditions. NMR spectroscopic data in solution and X-ray diffraction
data suggested that the main product was tetranuclear, although conclusive
structural data were not obtained. DFT calculations supported a closo-type tetrahedral [YH2(THF)2]44+ core. The hydridic character of these cations
was revealed by their reaction with benzophenone to give the bis­(diphenylmethoxy)
cation [Y­(OCHPh2)2(THF)4]­[AlR4]. The reaction of this cluster with the (NNNN)-type macrocycle
Me4TACD under dihydrogen gave the dinuclear tetrahydride
dication with quadruply bridging hydride ligands, [Y2(μ-H)4(Me4TACD)2]­[A]2, analogous
to the previously characterized lutetium derivative. NH-acidic (Me3TACD)H gave the dinuclear dihydride dication [Y2(μ-H)2(Me3TACD)2(THF)2]­[A]2.