The ambient temperature hydrometallations of a variety of unactivated alkene and alkyne substrates using two-coordinate hydrido-tetrylenes, :E(H)(L†) (E = Ge or Sn; L† = extremely bulky amide), are reported.

Reactions of two sterically hindered amidodigermynes, L*GeGeL* (1; L* = −N(Ar*)(SiMe 3 ); Ar* = C 6 H 2 Me{C(H)Ph 2 } 2 -4,2,6) and L † GeGeL † (2; L † = −N(Ar † )-(SiPr i3 ); Ar † = C 6 H 2 Pr i {C(H)Ph 2 } 2 -4,2,6), with a variety of olefins and related molecules are investigated. These lead to the facile reduction, C−H activation, dehydrogenation, and/or cycloaddition of the unsaturated substrate. Specifically, reaction of L † GeGeL † with ethylene proceeds via a formal [2 + 2 + 2] cycloaddition to give the digermabicyclo[2.2.0]hexane L † Ge(μ-C 2 H 4 ) 2 GeL † (3). In contrast, treating L † GeGeL † with norbornadiene proceeds via reductive insertion of one olefin moiety of the organic substrate into the Ge−Ge bond of 1, yielding the norbornenediyl-bridged bis(germylene) L † Ge(μ-C 7 H 8 )GeL † (4). Similarly, L*GeGeL* doubly reduces cyclooctatetraene (COT) to give the planar cyclooctateraenediyl inverse sandwich complex L*Ge(μ-η 2 ,η 2 -COT)GeL* ( 5). An indication that this reaction occurs via an initial formal [2 + 2] cycloaddition intermediate comes from the reaction of L † GeGeL † with 1,5-cyclooctadiene (COD). This affords the [2 + 2] cycloaddition product L † Ge(COD)GeL † (6), which exists in solution in equilibrium with 2 and free COD. A computational study indicates that 6 readily dissociates, as the reaction that gave it is close to thermoneutral. Reaction of 1,3-cyclohexadiene (1,3-CHD) with L † GeGeL † yields the 1,4-bis(germylene) substituted cyclohex-2-enediyl L † Ge(μ-C 6 H 8 )GeL † (7), which is an isolated intermediate in the transfer hydrogenation, or C−H activation, reaction between L † GeGeL † and 1,3-CHD. Heating 7 gives benzene and the known digermene L † (H)GeGe(H)L † . Reactions of 1 or 2 with propyne, bis(trimethylsilyl)butadiyne, and azobenzene all lead to reductive insertion of the unsaturated substrate into the Ge−Ge bond of the digermyne and formation of L † Ge{μ-HCC(Me)}GeL † (8), L*Ge{μ-(Me 3 Si)CC(CCSiMe 3 )}GeL* (9), and L*Ge{μ-(Ph)NN(Ph)}GeL* (10), respectively. The reaction of 4-dimethylaminopyridine (DMAP) with L*GeGeL* gives the adduct complex L*(DMAP)GeGe(DMAP)L* (11). Taken as a whole, this study highlights both similarities and significant differences between the reactivities of the amido-digermynes 1 and 2 and those of their previously described terphenyl-substituted counterparts.