98778-23-5Relevant articles and documents
Low-valent rhenium-oxo-alkoxide complexes: Synthesis, characterization, structure, and ligand exchange and carbon monoxide insertion reactions
Erikson, Torsten K. G.,Bryan, Jeffrey C.,Mayer, James M.
, p. 1930 - 1938 (2008/10/08)
A series of rhenium(III)-oxo-alkoxide-bis(acetylene) complexes of the form Re(O)(OR)(R′C≡CR′)2 have been prepared by reaction of the iodide derivatives Re(O)I(R′C≡CR′)2 with thallium alkoxides. An X-ray crystal structure of the phenoxide complex 7 a shows the pseudotetrahedral coordination geometry typical of Re(O)X(RC≡CR)2 compounds, with a short rhenium-oxo bond of 1.712 (13) ? and a longer Re-OPh distance of 1.966 (14) ?. The alkoxide complexes decompose in solution at less than 100°C by a number of pathways including β-hydrogen elimination. The complexes react rapidly with protic reagents such as alcohols, water, amines, acids, etc. with displacement of alcohol. Reactions of the tert-butoxide complex with ammonia or methylamine yield the corresponding amide complexes, and H2S gives the hydrosulfide species. Many of these ligand exchange reactions give equilibrium mixtures, indicating that the Re-X bond strengths in general parallel H-X bond strengths. The methylamide complex is fluxional on the NMR time scale, with a ground state that places the methyl group pointing at one of the acetylene ligands. The phenoxide ligand in the X-ray structure is approximately in the same sterically encumbered orientation. This orientation is preferred because it favors π-bonding and minimizes π-antibonding interactions of the π-donor orbital of the amide or phenoxide ligand. The ethoxide complex readily inserts carbon monoxide and isopropyl isocyanide to give Re(O)[C(O)OEt](MeC≡CMe)2 and Re(O)[C(N-i-Pr)OEt](MeC≡CMe)2, respectively. Crystal data for 7a: Pna21, a = 18.620 (7) ?, b = 7.2389 (9) ?, c = 10.552 (3) ?, Z = 4, refined to R = 0.044, Rw = 0.044.
