Facile activation of dihydrogen by an unsaturated heavier main group compound

The germanium alkyne analogue Ar-GeGeAr- (1, Ar- = C6H3-2,6(C6H3-2,6-Pri2)2) reacts with 1, 2, or 3 equiv of dihydrogen at room temperature, and at 1 atm pressure, to afford a mixture of the products Ar-HGeGeHAr- (2), Ar-H2GeGeH2Ar- (3), or Ar-GeH3 (4). The relative amounts of each product are governed by the number of equivalents of hydrogen used. A mechanism for the initial step in the reaction is proposed. The appearance of 4 among the reaction products was accounted for in terms of either its dissociation to monomers or isomerization to the bridged Ar-Ge(μ-H)2GeAr-. The reactions were monitored by 1H NMR spectroscopy. The products 2, 3, and 4 were characterized by X-ray crystallography, and 4 was synthesized independently by the reduction of Ar-Ge(OMe)3. These reactions represent the first direct addition of hydrogen to a closed shell unsaturated main group compound under ambient conditions. Copyright © 2005 American Chemical Society.