Reactions of mTerphenyl-Stabilized Germylene and Stannylene with Water and Methanol: Oxidative Addition versus Arene Elimination and Different Reaction Pathways for Alkyl- and Aryl-Substituted Species [component]

Reactions of the divalent germylene Ge(Ar Me 6 )2 (Ar Me 6 = C6H3-2,6-{C6H2-2,4,6-(CH3)3}2) with water or methanol gave the Ge(IV) insertion products (Ar Me 6 )2Ge(H)OH (1) or (Ar Me 6 )2Ge(H)OMe (2), respectively. In contrast, its stannylene congener Sn(Ar Me 6 )2 reacted with water or methanol to produce the Sn(II) species {Ar Me 6 Sn(μ-OH)}2 (3) or {Ar Me 6 Sn(μ-OMe)}2 (4), respectively, with elimination of Ar Me 6 H. Compounds 1-4 were characterized by IR and NMR spectroscopy as well as by
more » ... copy as well as by X-ray crystallography. Density functional theory calculations yielded mechanistic insight into the formation of (Ar Me 6 )2Ge(H)OH and {Ar Me 6 Sn(μ-OH)}2. The insertion of an m-terphenyl stabilized germylene into the O-H bond was found to be catalytic, aided by a second molecule of water. The lowest energy pathway for the elimination of arene from the corresponding stannylene involved sigma-bond metathesis rather than separate oxidative addition and reductive elimination steps. The reactivity of Sn(Ar Me 6 )2 with water or methanol contrasts with that of Sn{(CH(SiMe3)2}2 which affords the Sn(IV) insertion products {(Me3Si)2CH}2Sn(H)OH or {(Me3Si)2CH}2Sn(H)OMe. The differences were tentatively ascribed to the Lewis basicity of the employed solvent (Et2O vs. THF) and the use of molar vs. millimolar concentrations of the substrate.
doi:10.1021/acs.organomet.5b00884.s002 fatcat:pq5ml45kk5hhlonj4ev3fzh4u4