Multiple Bonds Between Main Group Elements and Transition Metals. 151.1Trioxorhenium(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 [ReO 3 (OMe)(MeOH)] 2 ( 1 ), ReO 3 (OCMe 2 CMe 2 OMe) ( 2 ), ReO 3 (OCMe 2 CMe 2 OH) ( 3 ), and the glycolate complex (Me 3 SiO)ReO 2 (OCMe 2 CMe 2 O) ( 4 ), respectively. The alkoxides 1 − 4 have fluxional structures at room temperature in solution on the 17 O NMR time scale. The trigonal bipyramidal structure of 2, in the crystal, is static in solution only at −90 °C. The protic hydrogen of 3 can be abstracted by lithium 2,2,6,6-tetramethylpiperidinate to give the ionic complex Li[ReO 3 (OCMe 2 CMe 2 O)] ( 5 ). [ReO 3 (OMe)(MeOH)] 2 ( 1 ) crystallizes from dichloromethane in the space group P 1̄ with unit cell dimensions a = 6.276(3) Å, b = 6.720(3) Å, c = 8.005(4) Å, α = 109.39(3)°, β = 99.48(3)°, γ = 110.31(2)°, V = 238.3 Å 3, and Z = 1; the structure was refined to R = 0.050 and R w = 0.056. ReO 3 (OCMe 2 CMe 2 OMe) ( 2 ) crystallizes from toluene in the space group Pbca with unit cell dimensions a = 8.263(2) Å, b = 10.884(3) Å, c = 22.963(5) Å, V = 2065 Å 3, and Z = 8; the structure was refined to R = 0.044 and R w = 0.028. ReO 3 (OCMe 2 CMe 2 OH) ( 3 ) crystallizes from dichloromethane in the space group C 2/ c with unit cell dimensions a = 12.327(5) Å, b = 10.973(3) Å, c = 14.491(6) Å, β = 90.22(2)°, V = 1960 Å 3, and Z = 8; the structure was refined to R = 0.047 and R w = 0.030. (Me 3 SiO)ReO 2 (OCMe 2 CMe 2 O) ( 4 ) crystallizes from n -pentane in the space group P 2 1 / c with unit cell dimensions a = 12.042(8) Å, b = 10.782(2) Å, c = 12.485(9) Å, β = 117.44(3)°, V = 1439 Å 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)ReO 2 (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.