Two-coordinate Group 14 Element(ii) Hydrides As Reagents for the Facile, and Sometimes Reversible, Hydrogermylation/hydrostannylation of Unactivated Alkenes and Alkynes

Reactions of the solution stable, two-coordinate hydrido-tetrylenes, :E(H)(L) (E = Ge or Sn; L = -N(Ar)(SiPr ); Ar = CH{C(H)Ph}Pr-2,6,4), with a variety of unactivated cyclic and acyclic alkenes, and one internal alkyne, lead to the rapid and regiospecific hydrometallation of the unsaturated substrate at ambient temperature. The products of the reactions, [LE(CHR)] (E = Ge or Sn, R = H, Ph or Bu ), [LE{CH(CH)(CH) }] (E = Ge, = 1, 2 or 3; E = Sn, = 1) and [LE{C(Ph)[double bond, length as m-dash]C(H)(Me)}], include the first structurally characterised examples of two-coordinate amido/alkyl germylenes and stannylenes. The cycloalkene hydrometallation reactions are cleanly reversible under ambient conditions, a process which computational and experimental van't Hoff analyses suggest proceeds β-hydride elimination from the metal coordinated cycloalkyl ligand. Similarly, the reactions of :Ge(H)(L) with 1,5-cyclooctadiene and 2-methyl-2-butene, both likely proceed β-hydride elimination processes, leading to the clean isomerisation of the alkene involved, and its subsequent hydrogermylation, to give [LGe(2-cyclooctenyl)] and [LGe{CHC(H)Me}], respectively. Reactions of [LGeEt] and [LGe(CH)] with the protic reagents, HCl, NH and EtOH, lead to oxidative addition to the germanium(ii) centre, and formation of the stable chiral germanium(iv) complexes, [LGe(CH)(H)Cl] and [LGe(Et)(H)R] (R = NH or OEt). In contrast, related reactions between [LSnEt] and Bu OH or TEMPOH (TEMP = 2,2,6,6-tetramethylpiperidinyl) proceed ethane elimination, affording the tin(ii) products, [LSnR] (R = OBu or OTEMP). In addition, the oxidation of [LGe(CH)] and [LSn(CHBu )] with O yields the oxo-bridged metal(iv) dimers, [{L(CH)Ge(μ-O)}] and [{L(Bu CH)Sn(μ-O)}], respectively.