Two-Coordinate Group 14 Element(II) Hydrides as Reagents for the Facile, and Sometimes Reversible, Hydrogermylation/Hydrostannylation of Unactivated Alkenes and Alkynes
Journal Article - Open Access
MONASH UNIV VICTORIA (AUSTRALIA) VICTORIA Australia
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Reactions of the solution stable, two-coordinate hydrido-tetrylenes, EHL E Ge or Sn L NArSiPri3 Ar C6H2CHPh22Pri-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, LEC2H4R E Ge or Sn, R H, Ph or But, LECHCH23CH2n E Ge, n 1, 2 or 3 E Sn, n 1 and LECPhdouble bond, length as m-dashCHMe, include the first structurally characterised examples of two-coordinate amidoalkyl germylenes and stannylenes. The cycloalkene hydrometallation reactions are cleanly reversible under ambient conditions, a process which computational and experimental vant Hoff analyses suggest proceeds via -hydride elimination from the metal coordinated cycloalkyl ligand. Similarly, the reactions of GeHL with 1,5-cyclooctadiene and 2-methyl-2-butene, both likely proceed via -hydride elimination processes, leading to the clean isomerisation of the alkene involved, and its subsequent hydrogermylation, to give LGe2-cyclooctenyl and LGeC2H4CHMe2, respectively. Reactions of LGeEt and LGeC5H9 with the protic reagents, HCl, NH3 and EtOH, lead to oxidative addition to the germaniumII centre, and formation of the stable chiral germaniumIV complexes, LGeC5H9HCl and LGeEtHR R NH2 or OEt. In contrast, related reactions between LSnEt and But OH or TEMPOH TEMP 2,2,6,6-tetramethylpiperidinyl proceed via ethane elimination, affording the tinII products, LSnR R OBut or OTEMP. In addition, the oxidation of LGeC6H11 and LSnC2H4But with O2 yields the oxo-bridged metalIV dimers, LC6H11Ge-O2 and LButC2H4Sn-O2, respectively.
- Organic Chemistry