Syntheses, properties, and x-ray crystal structures of stable methylidene complexes of the formula [(.eta.-C5Me5)Re(NO)(L)(:CH2)]+ PF6-
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Reaction of Re2(CO)10 with pentamethylcyclopentadiene at 150-210 °C yields (η-C5Me5)Re(CO)3 (6). Treatment of 6 with [formula-ommited] gives [formula-ommited] (7). Reaction of 7 with C6H5I+-O-/CH3CN yields [formula-ommited] (8), which is subsequently treated with L (a, L = PPH3; b, L = P(OPh)3) to give [formula-ommited] (9a, 9b). Reduction of 9a and 9b with Li(C2H5)3BH/BH3 and NaBH4, respectively, yields (p-C5Me5)Re(NO)(L)(CH3) (10a, 10b). When 10a and 10b are treated with [formula-ommited], the stable (>100 °C as solids) methylidene complexes [formula-ommited] (4) and [formula-ommited] (5) form. Properties of the =CH2 ligands in 4 and 5 are studied in detail: ΔG*rot, (~114 °C)≳ 19 kcal/mol; IR v=CH2: 4, 2987/2972 and 2922 cm-1; 5, 2987/2976 and 2920 cm-1; v=CD2: 4-d2, 2246/2239 and 2181 cm-1; 5-d2, 2245/2238 and 2187 cm-1; NMR 1J13C-1H(5) = 154 and 143 Hz. The -160 °C X-ray crystal structure of 4 shows =CH2/NO disorder. The room-temperature X-ray crystal structure of 5 indicates space group P21/c, a = 8.666 (3) A,b= 12.387 (5) Å, c = 34.90 (1) Å, β = 102.34 (3)°, V = 3360 (2) Å3, Z = 4, ρcalcd = 1.82 g cm-3. For 3038 reflections (I0 3.0σ[formula-ommited], R = 0.057 and Rw = 0.064. The Re=CH2 bond length is 1.898 (18) A, and the =CH2 plane is essentially parallel to the Re-NO bond. This provides optimal overlap with the d orbital HOMO on rhenium. © 1983, American Chemical Society. All rights reserved.
author list (cited authors)
Patton, A. T., Strouse, C. E., Knobler, C. B., & Gladysz, J. A.