Multiple bonds between main group elements and transition metals .151. Trioxorhenium(VII) alkoxide complexes

The reaction of Me(3)SiOReO(3) with trimethylsilyl ethers Me(3)SiOR (R = Me, CMe(2)CMe(2)OMe, CMe(2)CMe(2)OH CMe(2)CMe(2)OSiMe(3)) yields the trioxorhenium(VII) alkoxide complexes [ReO3(OMe)(MeOH)](2) (1),ReO3(OCMe(2)CMe(2)OMe) (2), ReO3(OCMe(2)CMe(2)OH) (3), and the glycolate complex (Me(3)SiO)ReO2(OCMe(2)CMe(2)O) (4), respectively. The alkoxides 1-4 have fluxional structures at room temperature in solution on the O-17 NMR time scale. The trigonal bipyramidal structure of 2, in the crystal, is static in solution only at -90 degrees C. The protic hydrogen of 3 can be abstracted by lithium 2,2,6,6-tetramethylpiperidinate to give the ionic complex Li[ReO3(OCMe(2)CMe(2)O)] (5). [ReO3(OMe)(MeOH)](2) (1) crystallizes from dichloromethane in the space group Pi with unit cell dimensions a = 6.276(3) Angstrom, b = 6.720(3) Angstrom(3), c = 8.005(4) Angstrom, alpha = 109.39(3)degrees, beta = 99.48(3)degrees, gamma = 110.31(2)degrees, V = 238.3 Angstrom(3), and Z = 1; the structure was refined to R = 0.050 and R(w) = 0.056. ReO3(OCMe(2)CMe(2)OMe) (2) crystallizes from toluene in the space group Pbca with unit cell dimensions a = 8.263(2) Angstrom, b = 10.884(3) Angstrom, c = 22.963(5) Angstrom, V = 2065 Angstrom(3), and Z = 8; the structure was refined to R = 0.044 and R(w) = 0.028. ReO3(OCMe(2)CMe(2)OH) (3) crystallizes from dichloromethane in the space group C2/c with unit cell dimensions a = 12.327(5) Angstrom, b = 10.973(3) Angstrom, c = 14.491(6) Angstrom, beta = 90.22(2)degrees, V = 1960 Angstrom(3), and Z = 8; the structure was refined to R = 0.047 and R(w) = 0.030. (Me(3)SiO)ReO2(OCMe(2)CMe(2)O) (4) crystallizes from n-pentane in the space group P2(1)/c with unit cell dimensions a = 12.042(8) Angstrom, b = 10.782(2) Angstrom, c = 12.485(9) Angstrom, beta = 117.44(3)degrees, V = 1439 Angstrom(3), and Z = 4; the structure was refined to R = 0.044 and R(w) = 0.044. The edge-sharing bioctahedral complex 1 has bridging methoxy and terminal methanol ligands trans to rhenium-oxygen double bonds. The rhenium centers in compounds 2 and 3 are pentacoordinated and located in a distorted trigonal bipyramidal geometry. The alkoxy function of the alkoxy ligand -OCMe(2)CMe(2)OR (R = H, Me) is located in the equatorial plane, and the Lewis base (-OMe, -OH) is bonded trans to an oxygen atom in an axial coordination site. (Me(3)SiO)ReO2(OCMe(2)CMe(2)O) (4) has a similar geometry to 2 and 3 with a trimethylsiloxy ligand trans to an alkoxy function in an axial position.