Dinuclear Elimination from Rhenium Hydrides and AlMe3: Rhenium/Aluminum Polyhydrides

Article abstract of DOI:10.1021/ja00338a021

Reaction of Al2Me6 with ReH7P2 and with ReH5P3 (P = PMe2Ph and PMePh2) in benzene occurs with methane elimination to give ReH6AlMe2P2 and ReH4AlMe2P3, respectively.Each bimetallic compound is fluxional and shows evidence for both bridging and terminal hydride ligands.The X-ray crystal structure of ReH6AlMe2(PMePh2)2 shows it to be based on a ReH6P2 dodecahedron with AlMe2 bound to two hydride ligands, forming a η²-H2AlMe2 unit.Crystallographic data (-162 deg C): triclinic, P<*> with Z = 2 and a = 17.815(8) Angstroem, b = 10.386(4) Angstroem, c = 11.094(4) Angstroem, α = 111.47(2) deg, β = 86.08(2) deg, γ = 95.78(2) deg.The X-ray crystal structure of ReH4AlMe2(PMePh2)3 shows a ReH4P3 pentagonal bipyramid (one P axial and two equatorial) with AlMe2 attached through three hydride ligands, one axial and two equatorial on Re, forming a H3AlMe2^2- unit.Crystallographic data (-164 deg C): monoclinic, P2₁/a with Z = 4 and a = 15.053(4) Angstroem, b = 15.900(4) Angstroem, c = 11.705(2) Angstroem, and β = 92.59(1) deg.Evidence for the mechanism of these reactions is presented, and the trend for aluminum to achieve a coordination number greater than 4 is surveyed.